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Sample records for axon guidance receptors

  1. Independent signaling by Drosophila insulin receptor for axon guidance and growth

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    Caroline Rita Li

    2014-01-01

    Full Text Available The Drosophila insulin receptor (DInR regulates a diverse array of biological processes including growth, axon guidance, and sugar homeostasis. Growth regulation by DInR is mediated by Chico, the Drosophila homolog of vertebrate insulin-receptor-substrate proteins IRS1-4. In contrast, DInR regulation of photoreceptor axon guidance in the developing visual system is mediated by the SH2-SH3 domain adaptor protein Dreadlocks (Dock. In vitro studies by others identified five NPXY motifs, one in the juxtamembrane region and four in the signaling C-terminal tail (C-tail, important for interaction with Chico. Here we used yeast two-hybrid assays to identify regions in the DInR C-tail that interact with Dock. These Dock-binding sites were in separate portions of the C-tail from the previously identified Chico-binding sites. To test whether these sites are required for growth or axon guidance in whole animals, a panel of DInR proteins, in which the putative Chico and Dock interaction sites had been mutated individually or in combination, were tested for their ability to rescue viability, growth, and axon guidance defects of dinr mutant flies. Sites required for viability were identified. Unexpectedly, mutation of both putative Dock binding sites, either individually or in combination, did not lead to defects in photoreceptor axon guidance. Thus, either sites also required for viability are necessary for DInR function in axon guidance and/or there is redundancy built into the DInR/Dock interaction such that Dock is able to interact with multiple regions of DInR. We also found that simultaneous mutation of all 5 NPXY motifs implicated in Chico interaction drastically decreased growth in both male and female adult flies. Mutation of these 5 NPXY motifs did not affect photoreceptor axon guidance, showing that different sites within DInR control growth and axon guidance.

  2. Independent signaling by Drosophila insulin receptor for axon guidance and growth.

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    Li, Caroline R; Guo, Dongyu; Pick, Leslie

    2013-01-01

    The Drosophila insulin receptor (DInR) regulates a diverse array of biological processes including growth, axon guidance, and sugar homeostasis. Growth regulation by DInR is mediated by Chico, the Drosophila homolog of vertebrate insulin receptor substrate proteins IRS1-4. In contrast, DInR regulation of photoreceptor axon guidance in the developing visual system is mediated by the SH2-SH3 domain adaptor protein Dreadlocks (Dock). In vitro studies by others identified five NPXY motifs, one in the juxtamembrane region and four in the signaling C-terminal tail (C-tail), important for interaction with Chico. Here we used yeast two-hybrid assays to identify regions in the DInR C-tail that interact with Dock. These Dock binding sites were in separate portions of the C-tail from the previously identified Chico binding sites. To test whether these sites are required for growth or axon guidance in whole animals, a panel of DInR proteins, in which the putative Chico and Dock interaction sites had been mutated individually or in combination, were tested for their ability to rescue viability, growth and axon guidance defects of dinr mutant flies. Sites required for viability were identified. Unexpectedly, mutation of both putative Dock binding sites, either individually or in combination, did not lead to defects in photoreceptor axon guidance. Thus, either sites also required for viability are necessary for DInR function in axon guidance and/or there is redundancy built into the DInR/Dock interaction such that Dock is able to interact with multiple regions of DInR. We also found that simultaneous mutation of all five NPXY motifs implicated in Chico interaction drastically decreased growth in both male and female adult flies. These animals resembled chico mutants, supporting the notion that DInR interacts directly with Chico in vivo to control body size. Mutation of these five NPXY motifs did not affect photoreceptor axon guidance, segregating the roles of DInR in the

  3. Cannabinoid receptor CB2 modulates axon guidance

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    Duff, Gabriel; Argaw, Anteneh; Cecyre, Bruno

    2013-01-01

    on axon guidance. These effects are specific to CB2R since no changes were observed in mice where the gene coding for this receptor was altered (cnr2 (-/-)). The CB2R induced morphological changes observed at the growth cone are PKA dependent and require the presence of the netrin-1 receptor, Deleted...... CB2R's implication in retinothalamic development. Overall, this study demonstrates that the contribution of endocannabinoids to brain development is not solely mediated by CB1R, but also involves CB2R....

  4. The axonal guidance receptor neogenin promotes acute inflammation.

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    Klemens König

    Full Text Available Neuronal guidance proteins (NGP were originally described in the context of axonal growth and migration. Yet recent work has demonstrated that NGPs also serve as guidance cues for immune competent cells. A crucial target receptor for NGPs during embryonic development is the neogenin receptor, however its role during acute inflammation is unknown. We report here that neogenin is abundantly expressed outside the nervous system and that animals with endogenous repression of neogenin (Neo1(-/- demonstrate attenuated changes of acute inflammation. Studies using functional inhibition of neogenin resulted in a significant attenuation of inflammatory peritonitis. In studies employing bone marrow chimeric animals we found the hematopoietic presence of Neo1(-/- to be responsible for the attenuated inflammatory response. Taken together our studies suggest that the guidance receptor neogenin holds crucial importance for the propagation of an acute inflammatory response and further define mechanisms shared between the nervous and the immune system.

  5. Meninges-derived cues control axon guidance.

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    Suter, Tracey A C S; DeLoughery, Zachary J; Jaworski, Alexander

    2017-10-01

    The axons of developing neurons travel long distances along stereotyped pathways under the direction of extracellular cues sensed by the axonal growth cone. Guidance cues are either secreted proteins that diffuse freely or bind the extracellular matrix, or membrane-anchored proteins. Different populations of axons express distinct sets of receptors for guidance cues, which results in differential responses to specific ligands. The full repertoire of axon guidance cues and receptors and the identity of the tissues producing these cues remain to be elucidated. The meninges are connective tissue layers enveloping the vertebrate brain and spinal cord that serve to protect the central nervous system (CNS). The meninges also instruct nervous system development by regulating the generation and migration of neural progenitors, but it has not been determined whether they help guide axons to their targets. Here, we investigate a possible role for the meninges in neuronal wiring. Using mouse neural tissue explants, we show that developing spinal cord meninges produce secreted attractive and repulsive cues that can guide multiple types of axons in vitro. We find that motor and sensory neurons, which project axons across the CNS-peripheral nervous system (PNS) boundary, are attracted by meninges. Conversely, axons of both ipsi- and contralaterally projecting dorsal spinal cord interneurons are repelled by meninges. The responses of these axonal populations to the meninges are consistent with their trajectories relative to meninges in vivo, suggesting that meningeal guidance factors contribute to nervous system wiring and control which axons are able to traverse the CNS-PNS boundary. Copyright © 2017 Elsevier Inc. All rights reserved.

  6. A developmental timing switch promotes axon outgrowth independent of known guidance receptors.

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    Katherine Olsson-Carter

    2010-08-01

    Full Text Available To form functional neuronal connections, axon outgrowth and guidance must be tightly regulated across space as well as time. While a number of genes and pathways have been shown to control spatial features of axon development, very little is known about the in vivo mechanisms that direct the timing of axon initiation and elongation. The Caenorhabditis elegans hermaphrodite specific motor neurons (HSNs extend a single axon ventrally and then anteriorly during the L4 larval stage. Here we show the lin-4 microRNA promotes HSN axon initiation after cell cycle withdrawal. Axons fail to form in lin-4 mutants, while they grow prematurely in lin-4-overexpressing animals. lin-4 is required to down-regulate two inhibitors of HSN differentiation--the transcriptional regulator LIN-14 and the "stemness" factor LIN-28--and it likely does so through a cell-autonomous mechanism. This developmental switch depends neither on the UNC-40/DCC and SAX-3/Robo receptors nor on the direction of axon growth, demonstrating that it acts independently of ventral guidance signals to control the timing of HSN axon elongation.

  7. Axon guidance molecules in vascular patterning.

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    Adams, Ralf H; Eichmann, Anne

    2010-05-01

    Endothelial cells (ECs) form extensive, highly branched and hierarchically organized tubular networks in vertebrates to ensure the proper distribution of molecular and cellular cargo in the vertebrate body. The growth of this vascular system during development, tissue repair or in disease conditions involves the sprouting, migration and proliferation of endothelial cells in a process termed angiogenesis. Surprisingly, specialized ECs, so-called tip cells, which lead and guide endothelial sprouts, share many feature with another guidance structure, the axonal growth cone. Tip cells are motile, invasive and extend numerous filopodial protrusions sensing growth factors, extracellular matrix and other attractive or repulsive cues in their tissue environment. Axonal growth cones and endothelial tip cells also respond to signals belonging to the same molecular families, such as Slits and Roundabouts, Netrins and UNC5 receptors, Semaphorins, Plexins and Neuropilins, and Eph receptors and ephrin ligands. Here we summarize fundamental principles of angiogenic growth, the selection and function of tip cells and the underlying regulation by guidance cues, the Notch pathway and vascular endothelial growth factor signaling.

  8. BmRobo2/3 is required for axon guidance in the silkworm Bombyx mori.

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    Li, Xiao-Tong; Yu, Qi; Zhou, Qi-Sheng; Zhao, Xiao; Liu, Zhao-Yang; Cui, Wei-Zheng; Liu, Qing-Xin

    2016-02-15

    Axon guidance is critical for proper wiring of the nervous system. During the neural development, the axon guidance molecules play a key role and direct axons to choose the correct way to reach the target. Robo, as the receptor of axon guidance molecule Slit, is evolutionarily conserved from planarians to humans. However, the function of Robo in the silkworm, Bombyx mori, remained unknown. In this study, we cloned robo2/3 from B. mori (Bmrobo2/3), a homologue of robo2/3 in Tribolium castaneum. Moreover, BmRobo2/3 was localized in the neuropil, and RNAi-mediated knockdown of Bmrobo2/3 resulted in the longitudinal connectives forming closer to the midline. These data demonstrate that BmRobo2/3 is required for axon guidance in the silkworm. Copyright © 2015 Elsevier B.V. All rights reserved.

  9. Highly effective photonic cue for repulsive axonal guidance.

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    Bryan J Black

    Full Text Available In vivo nerve repair requires not only the ability to regenerate damaged axons, but most importantly, the ability to guide developing or regenerating axons along paths that will result in functional connections. Furthermore, basic studies in neuroscience and neuro-electronic interface design require the ability to construct in vitro neural circuitry. Both these applications require the development of a noninvasive, highly effective tool for axonal growth-cone guidance. To date, a myriad of technologies have been introduced based on chemical, electrical, mechanical, and hybrid approaches (such as electro-chemical, optofluidic flow and photo-chemical methods. These methods are either lacking in desired spatial and temporal selectivity or require the introduction of invasive external factors. Within the last fifteen years however, several attractive guidance cues have been developed using purely light based cues to achieve axonal guidance. Here, we report a novel, purely optical repulsive guidance technique that uses low power, near infrared light, and demonstrates the guidance of primary goldfish retinal ganglion cell axons through turns of up to 120 degrees and over distances of ∼90 µm.

  10. The axon guidance receptor gene ROBO1 is a candidate gene for developmental dyslexia.

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    Katariina Hannula-Jouppi

    2005-10-01

    Full Text Available Dyslexia, or specific reading disability, is the most common learning disorder with a complex, partially genetic basis, but its biochemical mechanisms remain poorly understood. A locus on Chromosome 3, DYX5, has been linked to dyslexia in one large family and speech-sound disorder in a subset of small families. We found that the axon guidance receptor gene ROBO1, orthologous to the Drosophila roundabout gene, is disrupted by a chromosome translocation in a dyslexic individual. In a large pedigree with 21 dyslexic individuals genetically linked to a specific haplotype of ROBO1 (not found in any other chromosomes in our samples, the expression of ROBO1 from this haplotype was absent or attenuated in affected individuals. Sequencing of ROBO1 in apes revealed multiple coding differences, and the selection pressure was significantly different between the human, chimpanzee, and gorilla branch as compared to orangutan. We also identified novel exons and splice variants of ROBO1 that may explain the apparent phenotypic differences between human and mouse in heterozygous loss of ROBO1. We conclude that dyslexia may be caused by partial haplo-insufficiency for ROBO1 in rare families. Thus, our data suggest that a slight disturbance in neuronal axon crossing across the midline between brain hemispheres, dendrite guidance, or another function of ROBO1 may manifest as a specific reading disability in humans.

  11. The Axon Guidance Receptor Gene ROBO1 Is a Candidate Gene for Developmental Dyslexia.

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    2005-10-01

    Full Text Available Dyslexia, or specific reading disability, is the most common learning disorder with a complex, partially genetic basis, but its biochemical mechanisms remain poorly understood. A locus on Chromosome 3, DYX5, has been linked to dyslexia in one large family and speech-sound disorder in a subset of small families. We found that the axon guidance receptor gene ROBO1, orthologous to the Drosophila roundabout gene, is disrupted by a chromosome translocation in a dyslexic individual. In a large pedigree with 21 dyslexic individuals genetically linked to a specific haplotype of ROBO1 (not found in any other chromosomes in our samples, the expression of ROBO1 from this haplotype was absent or attenuated in affected individuals. Sequencing of ROBO1 in apes revealed multiple coding differences, and the selection pressure was significantly different between the human, chimpanzee, and gorilla branch as compared to orangutan. We also identified novel exons and splice variants of ROBO1 that may explain the apparent phenotypic differences between human and mouse in heterozygous loss of ROBO1. We conclude that dyslexia may be caused by partial haplo-insufficiency for ROBO1 in rare families. Thus, our data suggest that a slight disturbance in neuronal axon crossing across the midline between brain hemispheres, dendrite guidance, or another function of ROBO1 may manifest as a specific reading disability in humans.

  12. Piezoelectric ceramic (PZT) modulates axonal guidance growth of rat cortical neurons via RhoA, Rac1, and Cdc42 pathways.

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    Wen, Jianqiang; Liu, Meili

    2014-03-01

    Electrical stimulation is critical for axonal connection, which can stimulate axonal migration and deformation to promote axonal growth in the nervous system. Netrin-1, an axonal guidance cue, can also promote axonal guidance growth, but the molecular mechanism of axonal guidance growth under indirect electric stimulation is still unknown. We investigated the molecular mechanism of axonal guidance growth under piezoelectric ceramic lead zirconate titanate (PZT) stimulation in the primary cultured cortical neurons. PZT induced marked axonal elongation. Moreover, PZT activated the excitatory postsynaptic currents (EPSCs) by increasing the frequency and amplitude of EPSCs of the cortical neurons in patch clamp assay. PZT downregulated the expression of Netrin-1 and its receptor Deleted in Colorectal Cancer (DCC). Rho GTPase signaling is involved in interactions of Netrin-1 and DCC. PZT activated RhoA. Dramatic decrease of Cdc42 and Rac1 was also observed after PZT treatment. RhoA inhibitor Clostridium botulinum C3 exoenzyme (C3-Exo) prevented the PZT-induced downregulation of Netrin-1 and DCC. We suggest that PZT can promote axonal guidance growth by downregulation of Netrin-1 and DCC to mediate axonal repulsive responses via the Rho GTPase signaling pathway. Obviously, piezoelectric materials may provide a new approach for axonal recovery and be beneficial for clinical therapy in the future.

  13. Wnt5a regulates midbrain dopaminergic axon growth and guidance.

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    Brette D Blakely

    2011-03-01

    Full Text Available During development, precise temporal and spatial gradients are responsible for guiding axons to their appropriate targets. Within the developing ventral midbrain (VM the cues that guide dopaminergic (DA axons to their forebrain targets remain to be fully elucidated. Wnts are morphogens that have been identified as axon guidance molecules. Several Wnts are expressed in the VM where they regulate the birth of DA neurons. Here, we describe that a precise temporo-spatial expression of Wnt5a accompanies the development of nigrostriatal projections by VM DA neurons. In mice at E11.5, Wnt5a is expressed in the VM where it was found to promote DA neurite and axonal growth in VM primary cultures. By E14.5, when DA axons are approaching their striatal target, Wnt5a causes DA neurite retraction in primary cultures. Co-culture of VM explants with Wnt5a-overexpressing cell aggregates revealed that Wnt5a is capable of repelling DA neurites. Antagonism experiments revealed that the effects of Wnt5a are mediated by the Frizzled receptors and by the small GTPase, Rac1 (a component of the non-canonical Wnt planar cell polarity pathway. Moreover, the effects were specific as they could be blocked by Wnt5a antibody, sFRPs and RYK-Fc. The importance of Wnt5a in DA axon morphogenesis was further verified in Wnt5a-/- mice, where fasciculation of the medial forebrain bundle (MFB as well as the density of DA neurites in the MFB and striatal terminals were disrupted. Thus, our results identify a novel role of Wnt5a in DA axon growth and guidance.

  14. Axonal GABAA receptors.

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    Trigo, Federico F; Marty, Alain; Stell, Brandon M

    2008-09-01

    Type A GABA receptors (GABA(A)Rs) are well established as the main inhibitory receptors in the mature mammalian forebrain. In recent years, evidence has accumulated showing that GABA(A)Rs are prevalent not only in the somatodendritic compartment of CNS neurons, but also in their axonal compartment. Evidence for axonal GABA(A)Rs includes new immunohistochemical and immunogold data: direct recording from single axonal terminals; and effects of local applications of GABA(A)R modulators on action potential generation, on axonal calcium signalling, and on neurotransmitter release. Strikingly, whereas presynaptic GABA(A)Rs have long been considered inhibitory, the new studies in the mammalian brain mostly indicate an excitatory action. Depending on the neuron that is under study, axonal GABA(A)Rs can be activated by ambient GABA, by GABA spillover, or by an autocrine action, to increase either action potential firing and/or transmitter release. In certain neurons, the excitatory effects of axonal GABA(A)Rs persist into adulthood. Altogether, axonal GABA(A)Rs appear as potent neuronal modulators of the mammalian CNS.

  15. Guidance of retinal axons in mammals.

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    Herrera, Eloísa; Erskine, Lynda; Morenilla-Palao, Cruz

    2017-11-26

    In order to navigate through the surrounding environment many mammals, including humans, primarily rely on vision. The eye, composed of the choroid, sclera, retinal pigmented epithelium, cornea, lens, iris and retina, is the structure that receives the light and converts it into electrical impulses. The retina contains six major types of neurons involving in receiving and modifying visual information and passing it onto higher visual processing centres in the brain. Visual information is relayed to the brain via the axons of retinal ganglion cells (RGCs), a projection known as the optic pathway. The proper formation of this pathway during development is essential for normal vision in the adult individual. Along this pathway there are several points where visual axons face 'choices' in their direction of growth. Understanding how these choices are made has advanced significantly our knowledge of axon guidance mechanisms. Thus, the development of the visual pathway has served as an extremely useful model to reveal general principles of axon pathfinding throughout the nervous system. However, due to its particularities, some cellular and molecular mechanisms are specific for the visual circuit. Here we review both general and specific mechanisms involved in the guidance of mammalian RGC axons when they are traveling from the retina to the brain to establish precise and stereotyped connections that will sustain vision. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Axon guidance pathways served as common targets for human speech/language evolution and related disorders.

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    Lei, Huimeng; Yan, Zhangming; Sun, Xiaohong; Zhang, Yue; Wang, Jianhong; Ma, Caihong; Xu, Qunyuan; Wang, Rui; Jarvis, Erich D; Sun, Zhirong

    2017-11-01

    Human and several nonhuman species share the rare ability of modifying acoustic and/or syntactic features of sounds produced, i.e. vocal learning, which is the important neurobiological and behavioral substrate of human speech/language. This convergent trait was suggested to be associated with significant genomic convergence and best manifested at the ROBO-SLIT axon guidance pathway. Here we verified the significance of such genomic convergence and assessed its functional relevance to human speech/language using human genetic variation data. In normal human populations, we found the affected amino acid sites were well fixed and accompanied with significantly more associated protein-coding SNPs in the same genes than the rest genes. Diseased individuals with speech/language disorders have significant more low frequency protein coding SNPs but they preferentially occurred outside the affected genes. Such patients' SNPs were enriched in several functional categories including two axon guidance pathways (mediated by netrin and semaphorin) that interact with ROBO-SLITs. Four of the six patients have homozygous missense SNPs on PRAME gene family, one youngest gene family in human lineage, which possibly acts upon retinoic acid receptor signaling, similarly as FOXP2, to modulate axon guidance. Taken together, we suggest the axon guidance pathways (e.g. ROBO-SLIT, PRAME gene family) served as common targets for human speech/language evolution and related disorders. Copyright © 2017 Elsevier Inc. All rights reserved.

  17. The Molecular and Cellular Mechanisms of Axon Guidance in Mossy Fiber Sprouting

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    Ryuta Koyama

    2018-05-01

    Full Text Available The question of whether mossy fiber sprouting is epileptogenic has not been resolved; both sprouting-induced recurrent excitatory and inhibitory circuit hypotheses have been experimentally (but not fully supported. Therefore, whether mossy fiber sprouting is a potential therapeutic target for epilepsy remains under debate. Moreover, the axon guidance mechanisms of mossy fiber sprouting have attracted the interest of neuroscientists. Sprouting of mossy fibers exhibits several uncommon axonal growth features in the basically non-plastic adult brain. For example, robust branching of axonal collaterals arises from pre-existing primary mossy fiber axons. Understanding the branching mechanisms in adulthood may contribute to axonal regeneration therapies in neuroregenerative medicine in which robust axonal re-growth is essential. Additionally, because granule cells are produced throughout life in the neurogenic dentate gyrus, it is interesting to examine whether the mossy fibers of newly generated granule cells follow the pre-existing trajectories of sprouted mossy fibers in the epileptic brain. Understanding these axon guidance mechanisms may contribute to neuron transplantation therapies, for which the incorporation of transplanted neurons into pre-existing neural circuits is essential. Thus, clarifying the axon guidance mechanisms of mossy fiber sprouting could lead to an understanding of central nervous system (CNS network reorganization and plasticity. Here, we review the molecular and cellular mechanisms of axon guidance in mossy fiber sprouting by discussing mainly in vitro studies.

  18. Quantifying mechanical force in axonal growth and guidance

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    Ahmad Ibrahim Mahmoud Athamneh

    2015-09-01

    Full Text Available Mechanical force plays a fundamental role in neuronal development, physiology, and regeneration. In particular, research has shown that force is involved in growth cone-mediated axonal growth and guidance as well as stretch-induced elongation when an organism increases in size after forming initial synaptic connections. However, much of the details about the exact role of force in these fundamental processes remain unknown. In this review, we highlight (1 standing questions concerning the role of mechanical force in axonal growth and guidance and (2 different experimental techniques used to quantify forces in axons and growth cones. We believe that satisfying answers to these questions will require quantitative information about the relationship between elongation, forces, cytoskeletal dynamics, axonal transport, signaling, substrate adhesion, and stiffness contributing to directional growth advance. Furthermore, we address why a wide range of force values have been reported in the literature, and what these values mean in the context of neuronal mechanics. We hope that this review will provide a guide for those interested in studying the role of force in development and regeneration of neuronal networks.

  19. Optofluidic control of axonal guidance

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    Gu, Ling; Ordonez, Simon; Black, Bryan; Mohanty, Samarendra K.

    2013-03-01

    Significant efforts are being made for control on axonal guidance due to its importance in nerve regeneration and in the formation of functional neuronal circuitry in-vitro. These include several physical (topographic modification, optical force, and electric field), chemical (surface functionalization cues) and hybrid (electro-chemical, photochemical etc) methods. Here, we report comparison of the effect of linear flow versus microfluidic flow produced by an opticallydriven micromotor in guiding retinal ganglion axons. A circularly polarized laser tweezers was used to hold, position and spin birefringent calcite particle near growth cone, which in turn resulted in microfluidic flow. The flow rate and resulting shear-force on axons could be controlled by a varying the power of the laser tweezers beam. The calcite particles were placed separately in one chamber and single particle was transported through microfluidic channel to another chamber containing the retina explant. In presence of flow, the turning of axons was found to strongly correlate with the direction of flow. Turning angle as high as 90° was achieved. Optofluidic-manipulation can be applied to other types of mammalian neurons and also can be extended to stimulate mechano-sensing neurons.

  20. Caenorhabditis elegans VEM-1, a novel membrane protein, regulates the guidance of ventral nerve cord-associated axons.

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    Runko, Erik; Kaprielian, Zaven

    2004-10-13

    In the developing CNS, pathfinding growth cones use intermediate target- and pioneer axon-associated guidance cues to navigate along stereotypical trajectories. We previously showed that the novel membrane-associated protein Vema is localized to the floor plate and the optic chiasm, intermediate targets located at the ventral midline of the spinal cord and diencephalon in the developing rodent CNS, respectively. Here, we report that the Caenorhabditis elegans ortholog of vema, vem-1, is expressed by the AVG pioneer midline neuron and by several neurons that extend longitudinally projecting axons into the ventral nerve cord (VNC). In vem-1 mutants and vem-1 (RNAi) animals, a subset of posteriorly projecting interneuron axons either fail to extend ventrally to the VNC and, instead, assume aberrant lateral positions or are inappropriately located in the left tract of the VNC. In addition, ventral motor neuron axons exhibit pathfinding errors within the VNC and along the dorsoventral body axis. The conserved UNC-40/DCC and SAX-3-/Robo receptors mediate signaling events that regulate axon guidance in a wide variety of systems. Double-mutant analyses reveal that vem-1 genetically interacts with unc-40 and is likely to function in parallel with sax-3 to regulate the guidance of a subset of VNC-associated interneuron and motor neuron axons. Consistent with these genetic data, we also show that VEM-1 is capable of physically interacting with UNC-40 but not SAX-3.

  1. Chondroitin-4-sulfation negatively regulates axonal guidance and growth

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    Wang, Hang; Katagiri, Yasuhiro; McCann, Thomas E.; Unsworth, Edward; Goldsmith, Paul; Yu, Zu-Xi; Tan, Fei; Santiago, Lizzie; Mills, Edward M.; Wang, Yu; Symes, Aviva J.; Geller, Herbert M.

    2008-01-01

    Summary Glycosaminoglycan (GAG) side chains endow extracellular matrix proteoglycans with diversity and complexity based upon the length, composition, and charge distribution of the polysaccharide chain. Using cultured primary neurons, we show that specific sulfation in the GAG chains of chondroitin sulfate (CS) mediates neuronal guidance cues and axonal growth inhibition. Chondroitin-4-sulfate (CS-A), but not chondroitin-6-sulfate (CS-C), exhibits a strong negative guidance cue to mouse cerebellar granule neurons. Enzymatic and gene-based manipulations of 4-sulfation in the GAG side chains alter their ability to direct growing axons. Furthermore, 4-sulfated CS GAG chains are rapidly and significantly increased in regions that do not support axonal regeneration proximal to spinal cord lesions in mice. Thus, our findings provide the evidence showing that specific sulfation along the carbohydrate backbone carries instructions to regulate neuronal function. PMID:18768934

  2. TIPsy tour guides: How microtubule plus-end tracking proteins (+TIPs facilitate axon guidance

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    Elizabeth A Bearce

    2015-06-01

    Full Text Available The growth cone is a dynamic cytoskeletal vehicle, which drives the end of a developing axon. It serves to interpret and navigate through the complex landscape and guidance cues of the early nervous system. The growth cone’s distinctive cytoskeletal organization offers a fascinating platform to study how extracellular cues can be translated into mechanical outgrowth and turning behaviors. While many studies of cell motility highlight the importance of actin networks in signaling, adhesion, and propulsion, both seminal and emerging works in the field have highlighted a unique and necessary role for microtubules in growth cone navigation. Here, we focus on the role of singular pioneer microtubules, which extend into the growth cone periphery and are regulated by a diverse family of microtubule plus-end tracking proteins (+TIPs. These +TIPs accumulate at the dynamic ends of microtubules, where they are well-positioned to encounter and respond to key signaling events downstream of guidance receptors, catalyzing immediate changes in microtubule stability and actin cross-talk, that facilitate both axonal outgrowth and turning events.

  3. Effects of laminin blended with chitosan on axon guidance on patterned substrates

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    Zhu, N; Guan, Y J; Chen, X B [Division of Biomedical Engineering, University of Saskatchewan, Saskatoon S7N 5A9 (Canada); Li, M G [Department of Mechanical Engineering, University of Saskatchewan, Saskatoon S7N 5A9 (Canada); Schreyer, D J, E-mail: niz504@mail.usask.c [Department of Anatomy and Cell Biology, Cameco MS Neuroscience Research Center, University of Saskatchewan, Saskatoon, S7K 0M7 (Canada)

    2010-12-15

    Axon guidance is a crucial consideration in the design of tissue scaffolds used to promote nerve regeneration. Here we investigate the combined use of laminin (a putative axon adhesion and guidance molecule) and chitosan (a leading candidate base material for the construction of scaffolds) for promoting axon guidance in cultured adult dorsal root ganglion (DRG) neurons. Using a dispensing-based rapid prototyping (DBRP) technique, two-dimensional grid patterns were created by dispensing chitosan or laminin-blended chitosan substrate strands oriented in orthogonal directions. In vitro experiments illustrated DRG neurites on these patterns preferentially grew upon and followed the laminin-blended chitosan pathways. These results suggest that an orientation of neurite growth can be achieved in an artificially patterned substrate by creating selectively biofunctional pathways. The DBRP technique may provide improved strategies for the use of biofunctional pathways in the design of three-dimensional scaffolds for guidance of nerve repair.

  4. Effects of laminin blended with chitosan on axon guidance on patterned substrates

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    Zhu, N; Guan, Y J; Chen, X B; Li, M G; Schreyer, D J

    2010-01-01

    Axon guidance is a crucial consideration in the design of tissue scaffolds used to promote nerve regeneration. Here we investigate the combined use of laminin (a putative axon adhesion and guidance molecule) and chitosan (a leading candidate base material for the construction of scaffolds) for promoting axon guidance in cultured adult dorsal root ganglion (DRG) neurons. Using a dispensing-based rapid prototyping (DBRP) technique, two-dimensional grid patterns were created by dispensing chitosan or laminin-blended chitosan substrate strands oriented in orthogonal directions. In vitro experiments illustrated DRG neurites on these patterns preferentially grew upon and followed the laminin-blended chitosan pathways. These results suggest that an orientation of neurite growth can be achieved in an artificially patterned substrate by creating selectively biofunctional pathways. The DBRP technique may provide improved strategies for the use of biofunctional pathways in the design of three-dimensional scaffolds for guidance of nerve repair.

  5. Axon guidance in the developing ocular motor system and Duane retraction syndrome depends on Semaphorin signaling via alpha2-chimaerin

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    Ferrario, Juan E.; Baskaran, Pranetha; Clark, Christopher; Hendry, Aenea; Lerner, Oleg; Hintze, Mark; Allen, James; Chilton, John K.; Guthrie, Sarah

    2012-01-01

    Eye movements depend on correct patterns of connectivity between cranial motor axons and the extraocular muscles. Despite the clinical importance of the ocular motor system, little is known of the molecular mechanisms underlying its development. We have recently shown that mutations in the Chimaerin-1 gene encoding the signaling protein α2-chimaerin (α2-chn) perturb axon guidance in the ocular motor system and lead to the human eye movement disorder, Duane retraction syndrome (DRS). The axon guidance cues that lie upstream of α2-chn are unknown; here we identify candidates to be the Semaphorins (Sema) 3A and 3C, acting via the PlexinA receptors. Sema3A/C are expressed in and around the developing extraocular muscles and cause growth cone collapse of oculomotor neurons in vitro. Furthermore, RNAi knockdown of α2-chn or PlexinAs in oculomotor neurons abrogates Sema3A/C-dependent growth cone collapse. In vivo knockdown of endogenous PlexinAs or α2-chn function results in stereotypical oculomotor axon guidance defects, which are reminiscent of DRS, whereas expression of α2-chn gain-of-function constructs can rescue PlexinA loss of function. These data suggest that α2-chn mediates Sema3–PlexinA repellent signaling. We further show that α2-chn is required for oculomotor neurons to respond to CXCL12 and hepatocyte growth factor (HGF), which are growth promoting and chemoattractant during oculomotor axon guidance. α2-chn is therefore a potential integrator of different types of guidance information to orchestrate ocular motor pathfinding. DRS phenotypes can result from incorrect regulation of this signaling pathway. PMID:22912401

  6. Death Receptor 6 Promotes Wallerian Degeneration in Peripheral Axons.

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    Gamage, Kanchana K; Cheng, Irene; Park, Rachel E; Karim, Mardeen S; Edamura, Kazusa; Hughes, Christopher; Spano, Anthony J; Erisir, Alev; Deppmann, Christopher D

    2017-03-20

    Axon degeneration during development is required to sculpt a functional nervous system and is also a hallmark of pathological insult, such as injury [1, 2]. Despite similar morphological characteristics, very little overlap in molecular mechanisms has been reported between pathological and developmental degeneration [3-5]. In the peripheral nervous system (PNS), developmental axon pruning relies on receptor-mediated extrinsic degeneration mechanisms to determine which axons are maintained or degenerated [5-7]. Receptors have not been implicated in Wallerian axon degeneration; instead, axon autonomous, intrinsic mechanisms are thought to be the primary driver for this type of axon disintegration [8-10]. Here we survey the role of neuronally expressed, paralogous tumor necrosis factor receptor super family (TNFRSF) members in Wallerian degeneration. We find that an orphan receptor, death receptor 6 (DR6), is required to drive axon degeneration after axotomy in sympathetic and sensory neurons cultured in microfluidic devices. We sought to validate these in vitro findings in vivo using a transected sciatic nerve model. Consistent with the in vitro findings, DR6 -/- animals displayed preserved axons up to 4 weeks after injury. In contrast to phenotypes observed in Wld s and Sarm1 -/- mice, preserved axons in DR6 -/- animals display profound myelin remodeling. This indicates that deterioration of axons and myelin after axotomy are mechanistically distinct processes. Finally, we find that JNK signaling after injury requires DR6, suggesting a link between this novel extrinsic pathway and the axon autonomous, intrinsic pathways that have become established for Wallerian degeneration. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. Hindsight regulates photoreceptor axon targeting through transcriptional control of jitterbug/Filamin and multiple genes involved in axon guidance in Drosophila.

    Science.gov (United States)

    Oliva, Carlos; Molina-Fernandez, Claudia; Maureira, Miguel; Candia, Noemi; López, Estefanía; Hassan, Bassem; Aerts, Stein; Cánovas, José; Olguín, Patricio; Sierralta, Jimena

    2015-09-01

    During axon targeting, a stereotyped pattern of connectivity is achieved by the integration of intrinsic genetic programs and the response to extrinsic long and short-range directional cues. How this coordination occurs is the subject of intense study. Transcription factors play a central role due to their ability to regulate the expression of multiple genes required to sense and respond to these cues during development. Here we show that the transcription factor HNT regulates layer-specific photoreceptor axon targeting in Drosophila through transcriptional control of jbug/Filamin and multiple genes involved in axon guidance and cytoskeleton organization.Using a microarray analysis we identified 235 genes whose expression levels were changed by HNT overexpression in the eye primordia. We analyzed nine candidate genes involved in cytoskeleton regulation and axon guidance, six of which displayed significantly altered gene expression levels in hnt mutant retinas. Functional analysis confirmed the role of OTK/PTK7 in photoreceptor axon targeting and uncovered Tiggrin, an integrin ligand, and Jbug/Filamin, a conserved actin- binding protein, as new factors that participate of photoreceptor axon targeting. Moreover, we provided in silico and molecular evidence that supports jbug/Filamin as a direct transcriptional target of HNT and that HNT acts partially through Jbug/Filamin in vivo to regulate axon guidance. Our work broadens the understanding of how HNT regulates the coordinated expression of a group of genes to achieve the correct connectivity pattern in the Drosophila visual system. © 2015 Wiley Periodicals, Inc. Develop Neurobiol 75: 1018-1032, 2015. © 2015 Wiley Periodicals, Inc.

  8. Beyond Parkinson disease: amyotrophic lateral sclerosis and the axon guidance pathway.

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    Timothy G Lesnick

    2008-01-01

    Full Text Available We recently described a genomic pathway approach to study complex diseases. We demonstrated that models constructed using single nucleotide polymorphisms (SNPs within axon guidance pathway genes were highly predictive of Parkinson disease (PD susceptibility, survival free of PD, and age at onset of PD within two independent whole-genome association datasets. We also demonstrated that several axon guidance pathway genes represented by SNPs within our final models were differentially expressed in PD.Here we employed our genomic pathway approach to analyze data from a whole-genome association dataset of amyotrophic lateral sclerosis (ALS; and demonstrated that models constructed using SNPs within axon guidance pathway genes were highly predictive of ALS susceptibility (odds ratio = 1739.73, p = 2.92x10(-60, survival free of ALS (hazards ratio = 149.80, p = 1.25x10(-74, and age at onset of ALS (R(2 = 0.86, p = 5.96x10(-66. We also extended our analyses of a whole-genome association dataset of PD, which shared 320,202 genomic SNPs in common with the whole-genome association dataset of ALS. We compared for ALS and PD the genes represented by SNPs in the final models for susceptibility, survival free of disease, and age at onset of disease and noted that 52.2%, 37.8%, and 34.9% of the genes were shared respectively.Our findings for the axon guidance pathway and ALS have prior biological plausibility, overlap partially with PD, and may provide important insight into the causes of these and related neurodegenerative disorders.

  9. The Alzheimer's β-secretase enzyme BACE1 is required for accurate axon guidance of olfactory sensory neurons and normal glomerulus formation in the olfactory bulb

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    Rajapaksha Tharinda W

    2011-12-01

    Full Text Available Abstract Background The β-secretase, β-site amyloid precursor protein cleaving enzyme 1 (BACE1, is a prime therapeutic target for lowering cerebral β-amyloid (Aβ levels in Alzheimer's disease (AD. Clinical development of BACE1 inhibitors is being intensely pursued. However, little is known about the physiological functions of BACE1, and the possibility exists that BACE1 inhibition may cause mechanism-based side effects. Indeed, BACE1-/- mice exhibit a complex neurological phenotype. Interestingly, BACE1 co-localizes with presynaptic neuronal markers, indicating a role in axons and/or terminals. Moreover, recent studies suggest axon guidance molecules are potential BACE1 substrates. Here, we used a genetic approach to investigate the function of BACE1 in axon guidance of olfactory sensory neurons (OSNs, a well-studied model of axon targeting in vivo. Results We bred BACE1-/- mice with gene-targeted mice in which GFP is expressed from the loci of two odorant-receptors (ORs, MOR23 and M72, and olfactory marker protein (OMP to produce offspring that were heterozygous for MOR23-GFP, M72-GFP, or OMP-GFP and were either BACE1+/+ or BACE1-/-. BACE1-/- mice had olfactory bulbs (OBs that were smaller and weighed less than OBs of BACE1+/+ mice. In wild-type mice, BACE1 was present in OSN axon terminals in OB glomeruli. In whole-mount preparations and tissue sections, many OB glomeruli from OMP-GFP; BACE1-/- mice were malformed compared to wild-type glomeruli. MOR23-GFP; BACE1-/- mice had an irregular MOR23 glomerulus that was innervated by randomly oriented, poorly fasciculated OSN axons compared to BACE1+/+ mice. Most importantly, M72-GFP; BACE1-/- mice exhibited M72 OSN axons that were mis-targeted to ectopic glomeruli, indicating impaired axon guidance in BACE1-/- mice. Conclusions Our results demonstrate that BACE1 is required for the accurate targeting of OSN axons and the proper formation of glomeruli in the OB, suggesting a role for BACE1 in

  10. The transmembrane collagen COL-99 guides longitudinally extending axons in C. elegans.

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    Taylor, Jesse; Unsoeld, Thomas; Hutter, Harald

    2018-06-01

    We have identified the transmembrane collagen, COL-99, in a genetic screen for novel genes involved in axon guidance in the nematode C. elegans. COL-99 is similar to transmembrane collagens type XIII, XXIII and XXV in vertebrates. col-99 mutants exhibit guidance defects in axons extending along the major longitudinal axon tracts, most prominently the left ventral nerve cord (VNC). COL-99 is expressed in the hypodermis during the time of axon outgrowth. We provide evidence that a furin cleavage site in COL-99 is essential for function, suggesting that COL-99 is released from the cells producing it. Vertebrate homologs of COL-99 have been shown to be expressed in mammalian nervous systems and linked to various neurological disease but have not been associated with guidance of extending neurons. col-99 acts genetically with the discoidin domain receptors ddr-1 and ddr-2, which are expressed by neurons affected in col-99 mutants. Discoidin domain receptors are activated by collagens in vertebrates. DDR-1 and DDR-2 may function as receptors for COL-99. Our results establish a novel role for a transmembrane collagen in axonal guidance and asymmetry establishment of the VNC. Copyright © 2018 Elsevier Inc. All rights reserved.

  11. Fcγ receptor-mediated inflammation inhibits axon regeneration.

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    Gang Zhang

    Full Text Available Anti-glycan/ganglioside antibodies are the most common immune effectors found in patients with Guillain-Barré Syndrome, which is a peripheral autoimmune neuropathy. We previously reported that disease-relevant anti-glycan autoantibodies inhibited axon regeneration, which echo the clinical association of these antibodies and poor recovery in Guillain-Barré Syndrome. However, the specific molecular and cellular elements involved in this antibody-mediated inhibition of axon regeneration are not previously defined. This study examined the role of Fcγ receptors and macrophages in the antibody-mediated inhibition of axon regeneration. A well characterized antibody passive transfer sciatic nerve crush and transplant models were used to study the anti-ganglioside antibody-mediated inhibition of axon regeneration in wild type and various mutant and transgenic mice with altered expression of specific Fcγ receptors and macrophage/microglia populations. Outcome measures included behavior, electrophysiology, morphometry, immunocytochemistry, quantitative real-time PCR, and western blotting. We demonstrate that the presence of autoantibodies, directed against neuronal/axonal cell surface gangliosides, in the injured mammalian peripheral nerves switch the proregenerative inflammatory environment to growth inhibitory milieu by engaging specific activating Fcγ receptors on recruited monocyte-derived macrophages to cause severe inhibition of axon regeneration. Our data demonstrate that the antibody orchestrated Fcγ receptor-mediated switch in inflammation is one mechanism underlying inhibition of axon regeneration. These findings have clinical implications for nerve repair and recovery in antibody-mediated immune neuropathies. Our results add to the complexity of axon regeneration in injured peripheral and central nervous systems as adverse effects of B cells and autoantibodies on neural injury and repair are increasingly recognized.

  12. Formation of longitudinal axon pathways in Caenorhabditis elegans.

    Science.gov (United States)

    Hutter, Harald

    2017-11-18

    The small number of neurons and the simple architecture of the Caenorhabditis elegans (C. elegans) nervous system enables researchers to study axonal pathfinding at the level of individually identified axons. Axons in C. elegans extend predominantly along one of the two major body axes, the anterior-posterior axis and the dorso-ventral axis. This review will focus on axon navigation along the anterior-posterior axis, leading to the establishment of the longitudinal axon tracts, with a focus on the largest longitudinal axon tract, the ventral nerve cord (VNC). In the VNC, axons grow out in a stereotypic order, with early outgrowing axons (pioneers) playing an important role in guiding later outgrowing (follower) axons. Genetic screens have identified a number of genes specifically affecting the formation of longitudinal axon tracts. These genes include secreted proteins, putative receptors and adhesion molecules, as well as intracellular proteins regulating the cell's response to guidance cues. In contrast to dorso-ventral navigation, no major general guidance cues required for the establishment of longitudinal pathways have been identified so far. The limited penetrance of defects found in many mutants affecting longitudinal navigation suggests that guidance cues act redundantly in this process. The majority of the axon guidance genes identified in C. elegans are evolutionary conserved, i.e. have homologs in other animals, including vertebrates. For a number of these genes, a role in axon guidance has not been described outside C. elegans. Taken together, studies in C. elegans contribute to a fundamental understanding of the molecular basis of axonal navigation that can be extended to other animals, including vertebrates and probably humans as well. Copyright © 2017. Published by Elsevier Ltd.

  13. Regulation of Axonal Midline Guidance by Prolyl 4-Hydroxylation in Caenorhabditis elegans

    DEFF Research Database (Denmark)

    Torpe, Nanna; Pocock, Roger David John

    2014-01-01

    , little is known of its importance in the control of axon guidance. In a screen of prolyl 4-hydroxylase (P4H) mutants, we found that genetic removal of a specific P4H subunit, DPY-18, causes dramatic defects in C. elegans neuroanatomy. In dpy-18 mutant animals, the axons of specific ventral nerve cord......Neuronal wiring during development requires that the growth cones of axons and dendrites are correctly guided to their appropriate targets. As in other animals, axon growth cones in Caenorhabditis elegans integrate information in their extracellular environment via interactions among transiently...

  14. RGM is a repulsive guidance molecule for retinal axons

    DEFF Research Database (Denmark)

    Monnier, Philippe P; Sierra, Ana; Macchi, Paolo

    2002-01-01

    with known guidance cues, and its messenger RNA is distributed in a gradient with increasing concentration from the anterior to posterior pole of the embryonic tectum. Recombinant RGM at low nanomolar concentration induces collapse of temporal but not of nasal growth cones and guides temporal retinal axons...

  15. Slit stimulation recruits Dock and Pak to the roundabout receptor and increases Rac activity to regulate axon repulsion at the CNS midline.

    Science.gov (United States)

    Fan, Xueping; Labrador, Juan Pablo; Hing, Huey; Bashaw, Greg J

    2003-09-25

    Drosophila Roundabout (Robo) is the founding member of a conserved family of repulsive axon guidance receptors that respond to secreted Slit proteins. Here we present evidence that the SH3-SH2 adaptor protein Dreadlocks (Dock), the p21-activated serine-threonine kinase (Pak), and the Rac1/Rac2/Mtl small GTPases can function during Robo repulsion. Loss-of-function and genetic interaction experiments suggest that limiting the function of Dock, Pak, or Rac partially disrupts Robo repulsion. In addition, Dock can directly bind to Robo's cytoplasmic domain, and the association of Dock and Robo is enhanced by stimulation with Slit. Furthermore, Slit stimulation can recruit a complex of Dock and Pak to the Robo receptor and trigger an increase in Rac1 activity. These results provide a direct physical link between the Robo receptor and an important cytoskeletal regulatory protein complex and suggest that Rac can function in both attractive and repulsive axon guidance.

  16. A genomic pathway approach to a complex disease: axon guidance and Parkinson disease.

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    Timothy G Lesnick

    2007-06-01

    Full Text Available While major inroads have been made in identifying the genetic causes of rare Mendelian disorders, little progress has been made in the discovery of common gene variations that predispose to complex diseases. The single gene variants that have been shown to associate reproducibly with complex diseases typically have small effect sizes or attributable risks. However, the joint actions of common gene variants within pathways may play a major role in predisposing to complex diseases (the paradigm of complex genetics. The goal of this study was to determine whether polymorphism in a candidate pathway (axon guidance predisposed to a complex disease (Parkinson disease [PD]. We mined a whole-genome association dataset and identified single nucleotide polymorphisms (SNPs that were within axon-guidance pathway genes. We then constructed models of axon-guidance pathway SNPs that predicted three outcomes: PD susceptibility (odds ratio = 90.8, p = 4.64 x 10(-38, survival free of PD (hazards ratio = 19.0, p = 5.43 x 10(-48, and PD age at onset (R(2 = 0.68, p = 1.68 x 10(-51. By contrast, models constructed from thousands of random selections of genomic SNPs predicted the three PD outcomes poorly. Mining of a second whole-genome association dataset and mining of an expression profiling dataset also supported a role for many axon-guidance pathway genes in PD. These findings could have important implications regarding the pathogenesis of PD. This genomic pathway approach may also offer insights into other complex diseases such as Alzheimer disease, diabetes mellitus, nicotine and alcohol dependence, and several cancers.

  17. Synergistic Action of Presynaptic Muscarinic Acetylcholine Receptors and Adenosine Receptors in Developmental Axonal Competition at the Neuromuscular Junction.

    Science.gov (United States)

    Nadal, Laura; Garcia, Neus; Hurtado, Erica; Simó, Anna; Tomàs, Marta; Lanuza, Maria Angel; Cilleros, Victor; Tomàs, Josep Maria

    2016-01-01

    The development of the nervous system involves the initial overproduction of synapses, which promotes connectivity. Hebbian competition between axons with different activities leads to the loss of roughly half of the overproduced elements and this refines connectivity. We used quantitative immunohistochemistry to investigate, in the postnatal day 7 (P7) to P9 neuromuscular junctions, the involvement of muscarinic receptors (muscarinic acetylcholine autoreceptors and the M1, M2, and M4 subtypes) and adenosine receptors (A1 and A2A subtypes) in the control of axonal elimination after the mouse levator auris longus muscle had been exposed to selective antagonists in vivo. In a previous study we analyzed the role of each of the individual receptors. Here we investigate the additive or occlusive effects of their inhibitors and thus the existence of synergistic activity between the receptors. The main results show that the A2A, M1, M4, and A1 receptors (in this order of ability) delayed axonal elimination at P7. M4 produces some occlusion of the M1 pathway and some addition to the A1 pathway, which suggests that they cooperate. M2 receptors may modulate (by allowing a permissive action) the other receptors, mainly M4 and A1. The continued action of these receptors (now including M2 but not M4) finally promotes axonal loss at P9. All 4 receptors (M2, M1, A1, and A2A, in this order of ability) are necessary. The M4 receptor (which in itself does not affect axon loss) seems to modulate the other receptors. We found a synergistic action between the M1, A1, and A2A receptors, which show an additive effect, whereas the potent M2 effect is largely independent of the other receptors (though can be modulated by M4). At P9, there is a full mutual dependence between the A1 and A2A receptors in regulating axon loss. In summary, postnatal axonal elimination is a regulated multireceptor mechanism that involves the cooperation of several muscarinic and adenosine receptor subtypes.

  18. The axonal guidance cue semaphorin 3C contributes to alveolar growth and repair.

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    Arul Vadivel

    Full Text Available Lung diseases characterized by alveolar damage such as bronchopulmonary dysplasia (BPD in premature infants and emphysema lack efficient treatments. Understanding the mechanisms contributing to normal and impaired alveolar growth and repair may identify new therapeutic targets for these lung diseases. Axonal guidance cues are molecules that guide the outgrowth of axons. Amongst these axonal guidance cues, members of the Semaphorin family, in particular Semaphorin 3C (Sema3C, contribute to early lung branching morphogenesis. The role of Sema3C during alveolar growth and repair is unknown. We hypothesized that Sema3C promotes alveolar development and repair. In vivo Sema3C knock down using intranasal siRNA during the postnatal stage of alveolar development in rats caused significant air space enlargement reminiscent of BPD. Sema3C knock down was associated with increased TLR3 expression and lung inflammatory cells influx. In a model of O2-induced arrested alveolar growth in newborn rats mimicking BPD, air space enlargement was associated with decreased lung Sema3C mRNA expression. In vitro, Sema3C treatment preserved alveolar epithelial cell viability in hyperoxia and accelerated alveolar epithelial cell wound healing. Sema3C preserved lung microvascular endothelial cell vascular network formation in vitro under hyperoxic conditions. In vivo, Sema3C treatment of hyperoxic rats decreased lung neutrophil influx and preserved alveolar and lung vascular growth. Sema3C also preserved lung plexinA2 and Sema3C expression, alveolar epithelial cell proliferation and decreased lung apoptosis. In conclusion, the axonal guidance cue Sema3C promotes normal alveolar growth and may be worthwhile further investigating as a potential therapeutic target for lung repair.

  19. Precise Somatotopic Thalamocortical Axon Guidance Depends on LPA-Mediated PRG-2/Radixin Signaling

    DEFF Research Database (Denmark)

    Cheng, Jin; Sahani, Sadhna; Hausrat, Torben Johann

    2016-01-01

    Precise connection of thalamic barreloids with their corresponding cortical barrels is critical for processing of vibrissal sensory information. Here, we show that PRG-2, a phospholipid-interacting molecule, is important for thalamocortical axon guidance. Developing thalamocortical fibers both...

  20. Regulation of EphA4 kinase activity is required for a subset of axon guidance decisions suggesting a key role for receptor clustering in Eph function

    DEFF Research Database (Denmark)

    Egea, Joaquim; Nissen, Ulla Vig; Dufour, Audrey

    2005-01-01

    Signaling by receptor tyrosine kinases (RTKs) is mediated by their intrinsic kinase activity. Typically, kinase-activating mutations result in ligand-independent signaling and gain-of-function phenotypes. Like other RTKs, Ephs require kinase activity to signal, but signaling by Ephs in vitro also...... requires clustering by their membrane bound ephrin ligands. The relative importance of Eph kinase activity and clustering for in vivo functions is unknown. We find that knockin mice expressing a mutant form of EphA4 (EphA4 EE), whose kinase is constitutively activated in the absence of ephrinB ligands......, are deficient in the development of thalamocortical projections and some aspects of central pattern generator rhythmicity. Surprisingly, other functions of EphA4 were regulated normally by EphA4EE, including midline axon guidance, hindlimb locomotion, in vitro growth cone collapse, and phosphorylation...

  1. The discovery of the growth cone and its influence on the study of axon guidance

    Directory of Open Access Journals (Sweden)

    Elisa eTamariz

    2015-05-01

    Full Text Available For over a century, there has been a great deal of interest in understanding how neural connectivity is established during development and regeneration. Interest in the latter arises from the possibility that knowledge of this process can be used to reestablish lost connections after lesion or neurodegeneration. At the end of the XIX century, Santiago Ramón y Cajal discovered that the distal tip of growing axons contained a structure that he called the growth cone. He proposed that this structure enabled the axon’s oriented growth in response to attractants, now known as chemotropic molecules. He further proposed that the physical properties of the surrounding tissues could influence the growth cone and the direction of growth. This seminal discovery afforded a plausible explanation for directed axonal growth and has led to the discovery of axon guidance mechanisms that include diffusible attractants and repellants and guidance cues anchored to cell membranes or extracellular matrix. In this review the major events in the development of this field are discussed.

  2. Pancreatic cancer genomes reveal aberrations in axon guidance pathway genes.

    Science.gov (United States)

    Biankin, Andrew V; Waddell, Nicola; Kassahn, Karin S; Gingras, Marie-Claude; Muthuswamy, Lakshmi B; Johns, Amber L; Miller, David K; Wilson, Peter J; Patch, Ann-Marie; Wu, Jianmin; Chang, David K; Cowley, Mark J; Gardiner, Brooke B; Song, Sarah; Harliwong, Ivon; Idrisoglu, Senel; Nourse, Craig; Nourbakhsh, Ehsan; Manning, Suzanne; Wani, Shivangi; Gongora, Milena; Pajic, Marina; Scarlett, Christopher J; Gill, Anthony J; Pinho, Andreia V; Rooman, Ilse; Anderson, Matthew; Holmes, Oliver; Leonard, Conrad; Taylor, Darrin; Wood, Scott; Xu, Qinying; Nones, Katia; Fink, J Lynn; Christ, Angelika; Bruxner, Tim; Cloonan, Nicole; Kolle, Gabriel; Newell, Felicity; Pinese, Mark; Mead, R Scott; Humphris, Jeremy L; Kaplan, Warren; Jones, Marc D; Colvin, Emily K; Nagrial, Adnan M; Humphrey, Emily S; Chou, Angela; Chin, Venessa T; Chantrill, Lorraine A; Mawson, Amanda; Samra, Jaswinder S; Kench, James G; Lovell, Jessica A; Daly, Roger J; Merrett, Neil D; Toon, Christopher; Epari, Krishna; Nguyen, Nam Q; Barbour, Andrew; Zeps, Nikolajs; Kakkar, Nipun; Zhao, Fengmei; Wu, Yuan Qing; Wang, Min; Muzny, Donna M; Fisher, William E; Brunicardi, F Charles; Hodges, Sally E; Reid, Jeffrey G; Drummond, Jennifer; Chang, Kyle; Han, Yi; Lewis, Lora R; Dinh, Huyen; Buhay, Christian J; Beck, Timothy; Timms, Lee; Sam, Michelle; Begley, Kimberly; Brown, Andrew; Pai, Deepa; Panchal, Ami; Buchner, Nicholas; De Borja, Richard; Denroche, Robert E; Yung, Christina K; Serra, Stefano; Onetto, Nicole; Mukhopadhyay, Debabrata; Tsao, Ming-Sound; Shaw, Patricia A; Petersen, Gloria M; Gallinger, Steven; Hruban, Ralph H; Maitra, Anirban; Iacobuzio-Donahue, Christine A; Schulick, Richard D; Wolfgang, Christopher L; Morgan, Richard A; Lawlor, Rita T; Capelli, Paola; Corbo, Vincenzo; Scardoni, Maria; Tortora, Giampaolo; Tempero, Margaret A; Mann, Karen M; Jenkins, Nancy A; Perez-Mancera, Pedro A; Adams, David J; Largaespada, David A; Wessels, Lodewyk F A; Rust, Alistair G; Stein, Lincoln D; Tuveson, David A; Copeland, Neal G; Musgrove, Elizabeth A; Scarpa, Aldo; Eshleman, James R; Hudson, Thomas J; Sutherland, Robert L; Wheeler, David A; Pearson, John V; McPherson, John D; Gibbs, Richard A; Grimmond, Sean M

    2012-11-15

    Pancreatic cancer is a highly lethal malignancy with few effective therapies. We performed exome sequencing and copy number analysis to define genomic aberrations in a prospectively accrued clinical cohort (n = 142) of early (stage I and II) sporadic pancreatic ductal adenocarcinoma. Detailed analysis of 99 informative tumours identified substantial heterogeneity with 2,016 non-silent mutations and 1,628 copy-number variations. We define 16 significantly mutated genes, reaffirming known mutations (KRAS, TP53, CDKN2A, SMAD4, MLL3, TGFBR2, ARID1A and SF3B1), and uncover novel mutated genes including additional genes involved in chromatin modification (EPC1 and ARID2), DNA damage repair (ATM) and other mechanisms (ZIM2, MAP2K4, NALCN, SLC16A4 and MAGEA6). Integrative analysis with in vitro functional data and animal models provided supportive evidence for potential roles for these genetic aberrations in carcinogenesis. Pathway-based analysis of recurrently mutated genes recapitulated clustering in core signalling pathways in pancreatic ductal adenocarcinoma, and identified new mutated genes in each pathway. We also identified frequent and diverse somatic aberrations in genes described traditionally as embryonic regulators of axon guidance, particularly SLIT/ROBO signalling, which was also evident in murine Sleeping Beauty transposon-mediated somatic mutagenesis models of pancreatic cancer, providing further supportive evidence for the potential involvement of axon guidance genes in pancreatic carcinogenesis.

  3. DISCO Interacting Protein 2 regulates axonal bifurcation and guidance of Drosophila mushroom body neurons.

    Science.gov (United States)

    Nitta, Yohei; Yamazaki, Daisuke; Sugie, Atsushi; Hiroi, Makoto; Tabata, Tetsuya

    2017-01-15

    Axonal branching is one of the key processes within the enormous complexity of the nervous system to enable a single neuron to send information to multiple targets. However, the molecular mechanisms that control branch formation are poorly understood. In particular, previous studies have rarely addressed the mechanisms underlying axonal bifurcation, in which axons form new branches via splitting of the growth cone. We demonstrate that DISCO Interacting Protein 2 (DIP2) is required for precise axonal bifurcation in Drosophila mushroom body (MB) neurons by suppressing ectopic bifurcation and regulating the guidance of sister axons. We also found that DIP2 localize to the plasma membrane. Domain function analysis revealed that the AMP-synthetase domains of DIP2 are essential for its function, which may involve exerting a catalytic activity that modifies fatty acids. Genetic analysis and subsequent biochemical analysis suggested that DIP2 is involved in the fatty acid metabolization of acyl-CoA. Taken together, our results reveal a function of DIP2 in the developing nervous system and provide a potential functional relationship between fatty acid metabolism and axon morphogenesis. Copyright © 2016 Elsevier Inc. All rights reserved.

  4. BmRobo1a and BmRobo1b control axon repulsion in the silkworm Bombyx mori.

    Science.gov (United States)

    Li, Xiao-Tong; Yu, Qi; Zhou, Qi-Sheng; Zhao, Xiao; Liu, Zhao-Yang; Cui, Wei-Zheng; Liu, Qing-Xin

    2016-02-15

    The development of the nervous system is based on the growth and connection of axons, and axon guidance molecules are the dominant regulators during this course. Robo, as the receptor of axon guidance molecule Slit, plays a key role as a conserved repellent cue for axon guidance during the development of the central nervous system. However, the function of Robo in the silkworm Bombyx mori is unknown. In this study, we cloned two novel robo genes in B. mori (Bmrobo1a and Bmrobo1b). BmRobo1a and BmRobo1b lack an Ig and a FNIII domain in the extracellular region and the CC0 and CC2 motifs in the intracellular region. BmRobo1a and BmRobo1b were colocalized with BmSlit in the neuropil. Knock-down of Bmrobo1a and Bmrobo1b by RNA interference (RNAi) resulted in abnormal development of axons. Our results suggest that BmRobo1a and BmRobo1b have repulsive function in axon guidance, even though their structures are different from Robo1 of other species. Copyright © 2015 Elsevier B.V. All rights reserved.

  5. Anterograde axonal transport and intercellular transfer of WGA-HRP in trigeminal-innervated sensory receptors of rat incisive papilla.

    Science.gov (United States)

    Chan, K Y; Byers, M R

    1985-04-08

    The ultrastructure and identification of WGA-HRP-labeled sensory receptors in the rat incisive papilla (the most anterior part of hard palate) were studied using semiserial thin sections. Various sensory receptors were organized according to three locations: dome region (ventral), chemosensory corpuscle region (medial to orifice of incisive canal), and lateral labium (apposing the incisive canal). In the dome region, the sensory receptors were localized in three sensory zones that were associated with surface ridges (one medial and two lateral). In each of these zones, intraepithelial receptor axons and Merkel receptors occurred in the epithelium, while simple unencapsulated corpuscles, glomerular-Meissner corpuscles, and incisive (encapsulated) corpuscles occurred in the lamina propria. In the chemosensory corpuscle region, chemosensory corpuscles and intraepithelial receptor axons were located in the epithelium, and incisive corpuscles were present in the lamina propria. In the lateral labium, only intraepithelial receptor axons were prominent. In all these sensory receptors, the preterminal axons and axon terminals were labeled with the tracer protein. In addition, some nonneuronal cells closely associated with the axon terminals were selectively labeled, e.g., terminal Schwann cells, lamellar Schwann cells, Merkel cells, corpuscular basal cells and chemosensory cells. Other adjacent cells were not labeled, e.g., unspecialized epithelial cells, capsular cells, corpuscular sustentacular cells, and fibroblasts. In both labeled axons and cells, WGA-HRP was incorporated into vesicles, tubules, and vacuolar organelles. The specific intercellular transfer of tracer protein may indicate trophic interactions between axon terminals and support cells in sensory receptors. The specific organization of multiple sensory receptors in the rat incisive papilla may provide a useful alternative system for studying somatosensory physiology.

  6. MicroRNA-338 Attenuates Cortical Neuronal Outgrowth by Modulating the Expression of Axon Guidance Genes.

    Science.gov (United States)

    Kos, Aron; Klein-Gunnewiek, Teun; Meinhardt, Julia; Loohuis, Nikkie F M Olde; van Bokhoven, Hans; Kaplan, Barry B; Martens, Gerard J; Kolk, Sharon M; Aschrafi, Armaz

    2017-07-01

    MicroRNAs (miRs) are small non-coding RNAs that confer robustness to gene networks through post-transcriptional gene regulation. Previously, we identified miR-338 as a modulator of axonal outgrowth in sympathetic neurons. In the current study, we examined the role of miR-338 in the development of cortical neurons and uncovered its downstream mRNA targets. Long-term inhibition of miR-338 during neuronal differentiation resulted in reduced dendritic complexity and altered dendritic spine morphology. Furthermore, monitoring axon outgrowth in cortical cells revealed that miR-338 overexpression decreased, whereas inhibition of miR-338 increased axonal length. To identify gene targets mediating the observed phenotype, we inhibited miR-338 in cortical neurons and performed whole-transcriptome analysis. Pathway analysis revealed that miR-338 modulates a subset of transcripts involved in the axonal guidance machinery by means of direct and indirect gene targeting. Collectively, our results implicate miR-338 as a novel regulator of cortical neuronal maturation by fine-tuning the expression of gene networks governing cortical outgrowth.

  7. Son of sevenless directly links the Robo receptor to rac activation to control axon repulsion at the midline.

    Science.gov (United States)

    Yang, Long; Bashaw, Greg J

    2006-11-22

    Son of sevenless (Sos) is a dual specificity guanine nucleotide exchange factor (GEF) that regulates both Ras and Rho family GTPases and thus is uniquely poised to integrate signals that affect both gene expression and cytoskeletal reorganization. Here, using genetics, biochemistry, and cell biology, we demonstrate that Sos is recruited to the plasma membrane, where it forms a ternary complex with the Roundabout receptor and the SH3-SH2 adaptor protein Dreadlocks (Dock) to regulate Rac-dependent cytoskeletal rearrangement in response to the Slit ligand. Intriguingly, the Ras and Rac-GEF activities of Sos can be uncoupled during Robo-mediated axon repulsion; Sos axon guidance function depends on its Rac-GEF activity, but not its Ras-GEF activity. These results provide in vivo evidence that the Ras and RhoGEF domains of Sos are separable signaling modules and support a model in which Robo recruits Sos to the membrane via Dock to activate Rac during midline repulsion.

  8. Constitutively expressed Protocadherin-α regulates the coalescence and elimination of homotypic olfactory axons through its cytoplasmic region

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    Sonoko eHasegawa

    2012-10-01

    Full Text Available Olfactory sensory neuron (OSN axons coalesce into specific glomeruli in the olfactory bulb (OB according to their odorant receptor (OR expression. Several guidance molecules enhance the coalescence of homotypic OSN projections, in an OR-specific- and neural-activity-dependent manner. However, the mechanism by which homotypic OSN axons are organized into glomeruli is unsolved. We previously reported that the clustered protocadherin-α (Pcdh-α family of diverse cadherin-related molecules plays roles in the coalescence and elimination of homotypic OSN axons throughout development. Here we showed that the elimination of small ectopic homotypic glomeruli required the constitutive expression of a Pcdh-α isoform and Pcdh-α’s cytoplasmic region, but not OR specificity or neural activity. These results suggest that Pcdh-α proteins provide a cytoplasmic signal to regulate repulsive activity for homotypic OSN axons independently of OR expression and neural activity. The counterbalancing effect of Pcdh-α proteins for the axonal coalescence mechanisms mediated by other olfactory guidance molecules indicate a possible mechanism for the organization of homotypic OSN axons into glomeruli during development.

  9. Npn-1 contributes to axon-axon interactions that differentially control sensory and motor innervation of the limb.

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    Rosa-Eva Huettl

    2011-02-01

    Full Text Available The initiation, execution, and completion of complex locomotor behaviors are depending on precisely integrated neural circuitries consisting of motor pathways that activate muscles in the extremities and sensory afferents that deliver feedback to motoneurons. These projections form in tight temporal and spatial vicinities during development, yet the molecular mechanisms and cues coordinating these processes are not well understood. Using cell-type specific ablation of the axon guidance receptor Neuropilin-1 (Npn-1 in spinal motoneurons or in sensory neurons in the dorsal root ganglia (DRG, we have explored the contribution of this signaling pathway to correct innervation of the limb. We show that Npn-1 controls the fasciculation of both projections and mediates inter-axonal communication. Removal of Npn-1 from sensory neurons results in defasciculation of sensory axons and, surprisingly, also of motor axons. In addition, the tight coupling between these two heterotypic axonal populations is lifted with sensory fibers now leading the spinal nerve projection. These findings are corroborated by partial genetic elimination of sensory neurons, which causes defasciculation of motor projections to the limb. Deletion of Npn-1 from motoneurons leads to severe defasciculation of motor axons in the distal limb and dorsal-ventral pathfinding errors, while outgrowth and fasciculation of sensory trajectories into the limb remain unaffected. Genetic elimination of motoneurons, however, revealed that sensory axons need only minimal scaffolding by motor axons to establish their projections in the distal limb. Thus, motor and sensory axons are mutually dependent on each other for the generation of their trajectories and interact in part through Npn-1-mediated fasciculation before and within the plexus region of the limbs.

  10. Plexin A3 and turnout regulate motor axonal branch morphogenesis in zebrafish.

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    Rajiv Sainath

    Full Text Available During embryogenesis motor axons navigate to their target muscles, where individual motor axons develop complex branch morphologies. The mechanisms that control axonal branching morphogenesis have been studied intensively, yet it still remains unclear when branches begin to form or how branch locations are determined. Live cell imaging of individual zebrafish motor axons reveals that the first axonal branches are generated at the ventral extent of the myotome via bifurcation of the growth cone. Subsequent branches are generated by collateral branching restricted to their synaptic target field along the distal portion of the axon. This precisely timed and spatially restricted branching process is disrupted in turnout mutants we identified in a forward genetic screen. Molecular genetic mapping positioned the turnout mutation within a 300 kb region encompassing eight annotated genes, however sequence analysis of all eight open reading frames failed to unambiguously identify the turnout mutation. Chimeric analysis and single cell labeling reveal that turnout function is required cell non-autonomously for intraspinal motor axon guidance and peripheral branch formation. turnout mutant motor axons form the first branch on time via growth cone bifurcation, but unlike wild-type they form collateral branches precociously, when the growth cone is still navigating towards the ventral myotome. These precocious collateral branches emerge along the proximal region of the axon shaft typically devoid of branches, and they develop into stable, permanent branches. Furthermore, we find that null mutants of the guidance receptor plexin A3 display identical motor axon branching defects, and time lapse analysis reveals that precocious branch formation in turnout and plexin A3 mutants is due to increased stability of otherwise short-lived axonal protrusions. Thus, plexin A3 dependent intrinsic and turnout dependent extrinsic mechanisms suppress collateral branch

  11. Spatiotemporal expression of repulsive guidance molecules (RGMs and their receptor neogenin in the mouse brain.

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    Dianne M A van den Heuvel

    Full Text Available Neogenin has been implicated in a variety of developmental processes such as neurogenesis, neuronal differentiation, apoptosis, migration and axon guidance. Binding of repulsive guidance molecules (RGMs to Neogenin inhibits axon outgrowth of different neuronal populations. This effect requires Neogenin to interact with co-receptors of the uncoordinated locomotion-5 (Unc5 family to activate downstream Rho signaling. Although previous studies have reported RGM, Neogenin, and/or Unc5 expression, a systematic comparison of RGM and Neogenin expression in the developing nervous system is lacking, especially at later developmental stages. Furthermore, information on RGM and Neogenin expression at the protein level is limited. To fill this void and to gain further insight into the role of RGM-Neogenin signaling during mouse neural development, we studied the expression of RGMa, RGMb, Neogenin and Unc5A-D using in situ hybridization, immunohistochemistry and RGMa section binding. Expression patterns in the primary olfactory system, cortex, hippocampus, habenula, and cerebellum were studied in more detail. Characteristic cell layer-specific expression patterns were detected for RGMa, RGMb, Neogenin and Unc5A-D. Furthermore, strong expression of RGMa, RGMb and Neogenin protein was found on several major axon tracts such as the primary olfactory projections, anterior commissure and fasciculus retroflexus. These data not only hint at a role for RGM-Neogenin signaling during the development of different neuronal systems, but also suggest that Neogenin partners with different Unc5 family members in different systems. Overall, the results presented here will serve as a framework for further dissection of the role of RGM-Neogenin signaling during neural development.

  12. Drosophila photoreceptor axon guidance and targeting requires the dreadlocks SH2/SH3 adapter protein.

    Science.gov (United States)

    Garrity, P A; Rao, Y; Salecker, I; McGlade, J; Pawson, T; Zipursky, S L

    1996-05-31

    Mutations in the Drosophila gene dreadlocks (dock) disrupt photoreceptor cell (R cell) axon guidance and targeting. Genetic mosaic analysis and cell-type-specific expression of dock transgenes demonstrate dock is required in R cells for proper innervation. Dock protein contains one SH2 and three SH3 domains, implicating it in tyrosine kinase signaling, and is highly related to the human proto-oncogene Nck. Dock expression is detected in R cell growth cones in the target region. We propose Dock transmits signals in the growth cone in response to guidance and targeting cues. These findings provide an important step for dissection of signaling pathways regulating growth cone motility.

  13. Paired Immunoglobulin-like Receptor B Knockout Does Not Enhance Axonal Regeneration or Locomotor Recovery after Spinal Cord Injury*

    OpenAIRE

    Nakamura, Yuka; Fujita, Yuki; Ueno, Masaki; Takai, Toshiyuki; Yamashita, Toshihide

    2010-01-01

    Myelin components that inhibit axonal regeneration are believed to contribute significantly to the lack of axonal regeneration noted in the adult central nervous system. Three proteins found in myelin, Nogo, myelin-associated glycoprotein, and oligodendrocyte-myelin glycoprotein, inhibit neurite outgrowth in vitro. All of these proteins interact with the same receptors, namely, the Nogo receptor (NgR) and paired immunoglobulin-like receptor B (PIR-B). As per previous reports, corticospinal tr...

  14. A multi-protein receptor-ligand complex underlies combinatorial dendrite guidance choices in C. elegans

    Science.gov (United States)

    Zou, Wei; Shen, Ao; Dong, Xintong; Tugizova, Madina; Xiang, Yang K; Shen, Kang

    2016-01-01

    Ligand receptor interactions instruct axon guidance during development. How dendrites are guided to specific targets is less understood. The C. elegans PVD sensory neuron innervates muscle-skin interface with its elaborate dendritic branches. Here, we found that LECT-2, the ortholog of leukocyte cell-derived chemotaxin-2 (LECT2), is secreted from the muscles and required for muscle innervation by PVD. Mosaic analyses showed that LECT-2 acted locally to guide the growth of terminal branches. Ectopic expression of LECT-2 from seam cells is sufficient to redirect the PVD dendrites onto seam cells. LECT-2 functions in a multi-protein receptor-ligand complex that also contains two transmembrane ligands on the skin, SAX-7/L1CAM and MNR-1, and the neuronal transmembrane receptor DMA-1. LECT-2 greatly enhances the binding between SAX-7, MNR-1 and DMA-1. The activation of DMA-1 strictly requires all three ligands, which establishes a combinatorial code to precisely target and pattern dendritic arbors. DOI: http://dx.doi.org/10.7554/eLife.18345.001 PMID:27705746

  15. EphA4 blockers promote axonal regeneration and functional recovery following spinal cord injury in mice.

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    Yona Goldshmit

    Full Text Available Upregulation and activation of developmental axon guidance molecules, such as semaphorins and members of the Eph receptor tyrosine kinase family and their ligands, the ephrins, play a role in the inhibition of axonal regeneration following injury to the central nervous system. Previously we have demonstrated in a knockout model that axonal regeneration following spinal cord injury is promoted in the absence of the axon guidance protein EphA4. Antagonism of EphA4 was therefore proposed as a potential therapy to promote recovery from spinal cord injury. To further assess this potential, two soluble recombinant blockers of EphA4, unclustered ephrin-A5-Fc and EphA4-Fc, were examined for their ability to promote axonal regeneration and to improve functional outcome following spinal cord hemisection in wildtype mice. A 2-week administration of either of these blockers following spinal cord injury was sufficient to promote substantial axonal regeneration and functional recovery by 5 weeks following injury. Both inhibitors produced a moderate reduction in astrocytic gliosis, indicating that much of the effect of the blockers may be due to promotion of axon growth. These studies provide definitive evidence that soluble inhibitors of EphA4 function offer considerable therapeutic potential for the treatment of spinal cord injury and may have broader potential for the treatment of other central nervous system injuries.

  16. Hierarchical axon targeting of Drosophila olfactory receptor neurons specified by the proneural transcription factors Atonal and Amos.

    Science.gov (United States)

    Okumura, Misako; Kato, Tomoko; Miura, Masayuki; Chihara, Takahiro

    2016-01-01

    Sensory information is spatially represented in the brain to form a neural map. It has been suggested that axon-axon interactions are important for neural map formation; however, the underlying mechanisms are not fully understood. We used the Drosophila antennal lobe, the first olfactory center in the brain, as a model for studying neural map formation. Olfactory receptor neurons (ORNs) expressing the same odorant receptor target their axons to a single glomerulus out of approximately 50 glomeruli in the antennal lobe. Previous studies have showed that the axons of Atonal ORNs, specified by Atonal, a basic helix-loop-helix (bHLH) transcription factor, pioneer antennal lobe formation; however, the details remain to be elucidated. Here, we show that genetic ablation of Atonal ORNs affects antennal lobe structure and axon targeting of Amos ORNs, another type of ORN specified by the bHLH transcription factor Amos. During development, Atonal ORNs reach the antennal lobe and form the axon commissure before Amos ORNs. We also found that N-cadherin knockdown specifically in Atonal ORNs disrupts the glomerular boundary in the whole antennal lobe. Our results suggest that Atonal ORNs function as pioneer axons. Thus, correct axon targeting of Atonal ORNs is essential for formation of the whole antennal lobe. © 2015 The Molecular Biology Society of Japan and Wiley Publishing Asia Pty Ltd.

  17. Modulators of axonal growth and guidance at the brain midline with special reference to glial heparan sulfate proteoglycans

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    CAVALCANTE LENY A.

    2002-01-01

    Full Text Available Bilaterally symmetric organisms need to exchange information between the left and right sides of their bodies to integrate sensory input and to coordinate motor control. Thus, an important choice point for developing axons is the Central Nervous System (CNS midline. Crossing of this choice point is influenced by highly conserved, soluble or membrane-bound molecules such as the L1 subfamily, laminin, netrins, slits, semaphorins, Eph-receptors and ephrins, etc. Furthermore, there is much circumstantial evidence for a role of proteoglycans (PGs or their glycosaminoglycan (GAG moieties on axonal growth and guidance, most of which was derived from simplified models. A model of intermediate complexity is that of cocultures of young neurons and astroglial carpets (confluent cultures obtained from medial and lateral sectors of the embryonic rodent midbrain soon after formation of its commissures. Neurite production in these cocultures reveals that, irrespective of the previous location of neurons in the midbrain, medial astrocytes exerted an inhibitory or non-permissive effect on neuritic growth that was correlated to a higher content of both heparan and chondroitin sulfates (HS and CS. Treatment with GAG lyases shows minor effects of CS and discloses a major inhibitory or non-permissive role for HS. The results are discussed in terms of available knowledge on the binding of HSPGs to interative proteins and underscore the importance of understanding glial polysaccharide arrays in addition to its protein complement for a better understanding of neuron-glial interactions.

  18. Integration of shallow gradients of Shh and Netrin-1 guides commissural axons.

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    Sloan, Tyler F W; Qasaimeh, Mohammad A; Juncker, David; Yam, Patricia T; Charron, Frédéric

    2015-03-01

    During nervous system development, gradients of Sonic Hedgehog (Shh) and Netrin-1 attract growth cones of commissural axons toward the floor plate of the embryonic spinal cord. Mice defective for either Shh or Netrin-1 signaling have commissural axon guidance defects, suggesting that both Shh and Netrin-1 are required for correct axon guidance. However, how Shh and Netrin-1 collaborate to guide axons is not known. We first quantified the steepness of the Shh gradient in the spinal cord and found that it is mostly very shallow. We then developed an in vitro microfluidic guidance assay to simulate these shallow gradients. We found that axons of dissociated commissural neurons respond to steep but not shallow gradients of Shh or Netrin-1. However, when we presented axons with combined Shh and Netrin-1 gradients, they had heightened sensitivity to the guidance cues, turning in response to shallower gradients that were unable to guide axons when only one cue was present. Furthermore, these shallow gradients polarized growth cone Src-family kinase (SFK) activity only when Shh and Netrin-1 were combined, indicating that SFKs can integrate the two guidance cues. Together, our results indicate that Shh and Netrin-1 synergize to enable growth cones to sense shallow gradients in regions of the spinal cord where the steepness of a single guidance cue is insufficient to guide axons, and we identify a novel type of synergy that occurs when the steepness (and not the concentration) of a guidance cue is limiting.

  19. Distinct interneuron types express m2 muscarinic receptor immunoreactivity on their dendrites or axon terminals in the hippocampus.

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    Hájos, N; Papp, E C; Acsády, L; Levey, A I; Freund, T F

    1998-01-01

    In previous studies m2 muscarinic acetylcholine receptor-immunoreactive interneurons and various types of m2-positive axon terminals have been described in the hippocampal formation. The aim of the present study was to identify the types of interneurons expressing m2 receptor and to examine whether the somadendritic and axonal m2 immunostaining labels the same or distinct cell populations. In the CA1 subfield, neurons immunoreactive for m2 have horizontal dendrites, they are located at the stratum oriens/alveus border and have an axon that project to the dendritic region of pyramidal cells. In the CA3 subfield and the hilus, m2-positive neurons are multipolar and are scattered in all layers except stratum lacunosum-moleculare. In stratum pyramidale of the CA1 and CA3 regions, striking axon terminal staining for m2 was observed, surrounding the somata and axon initial segments of pyramidal cells in a basket-like manner. The co-localization of m2 with neurochemical markers and GABA was studied using the "mirror" technique and fluorescent double-immunostaining at the light microscopic level and with double-labelling using colloidal gold-conjugated antisera and immunoperoxidase reaction (diaminobenzidine) at the electron microscopic level. GABA was shown to be present in the somata of most m2-immunoreactive interneurons, as well as in the majority of m2-positive terminals in all layers. The calcium-binding protein parvalbumin was absent from practically all m2-immunoreactive cell bodies and dendrites. In contrast, many of the terminals synapsing on pyramidal cell somata and axon initial segments co-localized parvalbumin and m2, suggesting a differential distribution of m2 receptor immunoreactivity on the axonal and somadendritic membrane of parvalbumin-containing basket and axo-axonic cells. The co-existence of m2 receptors with the calcium-binding protein calbindin and the neuropeptides cholecystokinin and vasoactive intestinal polypeptide was rare throughout the

  20. Presynaptic Membrane Receptors Modulate ACh Release, Axonal Competition and Synapse Elimination during Neuromuscular Junction Development.

    Science.gov (United States)

    Tomàs, Josep; Garcia, Neus; Lanuza, Maria A; Santafé, Manel M; Tomàs, Marta; Nadal, Laura; Hurtado, Erica; Simó, Anna; Cilleros, Víctor

    2017-01-01

    During the histogenesis of the nervous system a lush production of neurons, which establish an excessive number of synapses, is followed by a drop in both neurons and synaptic contacts as maturation proceeds. Hebbian competition between axons with different activities leads to the loss of roughly half of the neurons initially produced so connectivity is refined and specificity gained. The skeletal muscle fibers in the newborn neuromuscular junction (NMJ) are polyinnervated but by the end of the competition, 2 weeks later, the NMJ are innervated by only one axon. This peripheral synapse has long been used as a convenient model for synapse development. In the last few years, we have studied transmitter release and the local involvement of the presynaptic muscarinic acetylcholine autoreceptors (mAChR), adenosine autoreceptors (AR) and trophic factor receptors (TFR, for neurotrophins and trophic cytokines) during the development of NMJ and in the adult. This review article brings together previously published data and proposes a molecular background for developmental axonal competition and loss. At the end of the first week postnatal, these receptors modulate transmitter release in the various nerve terminals on polyinnervated NMJ and contribute to axonal competition and synapse elimination.

  1. Presynaptic Membrane Receptors Modulate ACh Release, Axonal Competition and Synapse Elimination during Neuromuscular Junction Development

    Directory of Open Access Journals (Sweden)

    Josep Tomàs

    2017-05-01

    Full Text Available During the histogenesis of the nervous system a lush production of neurons, which establish an excessive number of synapses, is followed by a drop in both neurons and synaptic contacts as maturation proceeds. Hebbian competition between axons with different activities leads to the loss of roughly half of the neurons initially produced so connectivity is refined and specificity gained. The skeletal muscle fibers in the newborn neuromuscular junction (NMJ are polyinnervated but by the end of the competition, 2 weeks later, the NMJ are innervated by only one axon. This peripheral synapse has long been used as a convenient model for synapse development. In the last few years, we have studied transmitter release and the local involvement of the presynaptic muscarinic acetylcholine autoreceptors (mAChR, adenosine autoreceptors (AR and trophic factor receptors (TFR, for neurotrophins and trophic cytokines during the development of NMJ and in the adult. This review article brings together previously published data and proposes a molecular background for developmental axonal competition and loss. At the end of the first week postnatal, these receptors modulate transmitter release in the various nerve terminals on polyinnervated NMJ and contribute to axonal competition and synapse elimination.

  2. Axon guidance factor netrin-1 and its receptors regulate angiogenesis after cerebral ischemia

    OpenAIRE

    Ding, Qiao; Liao, Song-Jie; Yu, Jian

    2014-01-01

    Neurogenesis and angiogenesis play important roles in functional recovery after ischemic stroke. When cerebral ischemia occurs, axon regeneration can compensate for the loss of apoptotic neurons in the ischemic area. The formation of new blood vessels ameliorates the local decrease in blood supply, enhancing the supply of oxygen and nutrients to newly-formed neurons. New blood vessels also act as a scaffold for the migration of neuroblasts to the infarct area after ischemic stroke. In light o...

  3. beta(2)-ADRENERGIC RECEPTORS PROTECT AXONS DURING ENERGETIC STRESS BUT DO NOT INFLUENCE BASAL GLIO-AXONAL LACTATE SHUTTLING IN MOUSE WHITE MATTER

    NARCIS (Netherlands)

    Laureys, G.; Valentino, M.; Demol, F.; Zammit, C.; Muscat, R.; Cambron, M.; Kooijman, R.; De Keyser, J.

    2014-01-01

    In vitro studies have demonstrated that beta 2-adrenergic receptor activation stimulates glycogen degradation in astrocytes, generating lactate as a potential energy source for neurons. Using in vivo microdialysis in mouse cerebellar white matter we demonstrate continuous axonal lactate uptake and

  4. Paired immunoglobulin-like receptor B knockout does not enhance axonal regeneration or locomotor recovery after spinal cord injury.

    Science.gov (United States)

    Nakamura, Yuka; Fujita, Yuki; Ueno, Masaki; Takai, Toshiyuki; Yamashita, Toshihide

    2011-01-21

    Myelin components that inhibit axonal regeneration are believed to contribute significantly to the lack of axonal regeneration noted in the adult central nervous system. Three proteins found in myelin, Nogo, myelin-associated glycoprotein, and oligodendrocyte-myelin glycoprotein, inhibit neurite outgrowth in vitro. All of these proteins interact with the same receptors, namely, the Nogo receptor (NgR) and paired immunoglobulin-like receptor B (PIR-B). As per previous reports, corticospinal tract (CST) regeneration is not enhanced in NgR-knock-out mice after spinal cord injury. Therefore, we assessed CST regeneration in PIR-B-knock-out mice. We found that hindlimb motor function, as assessed using the Basso mouse scale, footprint test, inclined plane test, and beam walking test, did not differ between the PIR-B-knock-out and wild-type mice after dorsal hemisection of the spinal cord. Further, tracing of the CST fibers after injury did not reveal enhanced axonal regeneration or sprouting in the CST of the PIR-B-knock-out mice. Systemic administration of NEP1-40, a NgR antagonist, to PIR-B knock-out mice did not enhance the regenerative response. These results indicate that PIR-B knock-out is not sufficient to induce extensive axonal regeneration after spinal cord injury.

  5. A growing field: The regulation of axonal regeneration by Wnt signaling.

    Science.gov (United States)

    Garcia, Armando L; Udeh, Adanna; Kalahasty, Karthik; Hackam, Abigail S

    2018-01-01

    The canonical Wnt/β-catenin pathway is a highly conserved signaling cascade that plays critical roles during embryogenesis. Wnt ligands regulate axonal extension, growth cone guidance and synaptogenesis throughout the developing central nervous system (CNS). Recently, studies in mammalian and fish model systems have demonstrated that Wnt/β-catenin signaling also promotes axonal regeneration in the adult optic nerve and spinal cord after injury, raising the possibility that Wnt could be developed as a therapeutic strategy. In this review, we summarize experimental evidence that reveals novel roles for Wnt signaling in the injured CNS, and discuss possible mechanisms by which Wnt ligands could overcome molecular barriers inhibiting axonal growth to promote regeneration. A central challenge in the neuroscience field is developing therapeutic strategies that induce robust axonal regeneration. Although adult axons have the capacity to respond to axonal guidance molecules after injury, there are several major obstacles for axonal growth, including extensive neuronal death, glial scars at the injury site, and lack of axonal guidance signals. Research in rodents demonstrated that activation of Wnt/β-catenin signaling in retinal neurons and radial glia induced neuronal survival and axonal growth, but that activation within reactive glia at the injury site promoted proliferation and glial scar formation. Studies in zebrafish spinal cord injury models confirm an axonal regenerative role for Wnt/β-catenin signaling and identified the cell types responsible. Additionally, in vitro and in vivo studies demonstrated that Wnt induces axonal and neurite growth through transcription-dependent effects of its central mediator β-catenin, potentially by inducing regeneration-promoting genes. Canonical Wnt signaling may also function through transcription-independent interactions of β-catenin with cytoskeletal elements, which could stabilize growing axons and control growth cone

  6. Ascending Midbrain Dopaminergic Axons Require Descending GAD65 Axon Fascicles for Normal Pathfinding

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    Claudia Marcela Garcia-Peña

    2014-06-01

    Full Text Available The Nigrostriatal pathway (NSP is formed by dopaminergic axons that project from the ventral midbrain to the dorsolateral striatum as part of the medial forebrain bundle. Previous studies have implicated chemotropic proteins in the formation of the NSP during development but little is known of the role of substrate-anchored signals in this process. We observed in mouse and rat embryos that midbrain dopaminergic axons ascend in close apposition to descending GAD65-positive axon bundles throughout their trajectory to the striatum. To test whether such interaction is important for dopaminergic axon pathfinding, we analyzed transgenic mouse embryos in which the GAD65 axon bundle was reduced by the conditional expression of the diphtheria toxin. In these embryos we observed dopaminergic misprojection into the hypothalamic region and abnormal projection in the striatum. In addition, analysis of Robo1/2 and Slit1/2 knockout embryos revealed that the previously described dopaminergic misprojection in these embryos is accompanied by severe alterations in the GAD65 axon scaffold. Additional studies with cultured dopaminergic neurons and whole embryos suggest that NCAM and Robo proteins are involved in the interaction of GAD65 and dopaminergic axons. These results indicate that the fasciculation between descending GAD65 axon bundles and ascending dopaminergic axons is required for the stereotypical NSP formation during brain development and that known guidance cues may determine this projection indirectly by instructing the pathfinding of the axons that are part of the GAD65 axon scaffold.

  7. Nogo-66 receptor antagonist peptide (NEP1-40) administration promotes functional recovery and axonal growth after lateral funiculus injury in the adult rat

    NARCIS (Netherlands)

    Cao, Y.; Shumsky, J. S.; Sabol, M. A.; Kushner, R. A.; Strittmatter, S.; Hamers, F. P. T.; Lee, D. H. S.; Rabacchi, S. A.; Murray, M.

    2008-01-01

    Objective. The myelin protein Nogo inhibits axon regeneration by binding to its receptor (NgR) on axons. Intrathecal delivery of an NgR antagonist (NEP1-40) promotes growth of injured corticospinal axons and recovery of motor function following a dorsal hemisection. The authors used a similar design

  8. A Drosophila protein-tyrosine phosphatase associates with an adapter protein required for axonal guidance.

    Science.gov (United States)

    Clemens, J C; Ursuliak, Z; Clemens, K K; Price, J V; Dixon, J E

    1996-07-19

    We have used the yeast two-hybrid system to isolate a novel Drosophila adapter protein, which interacts with the Drosophila protein-tyrosine phosphatase (PTP) dPTP61F. Absence of this protein in Drosophila causes the mutant photoreceptor axon phenotype dreadlocks (dock) (Garrity, P. A., Rao, Y., Salecker, I., and Zipursky, S. L.(1996) Cell 85, 639-650). Dock is similar to the mammalian oncoprotein Nck and contains three Src homology 3 (SH3) domains and one Src homology 2 (SH2) domain. The interaction of dPTP61F with Dock was confirmed in vivo by immune precipitation experiments. A sequence containing five PXXP motifs from the non-catalytic domain of the PTP is sufficient for interaction with Dock. This suggests that binding to the PTP is mediated by one or more of the SH3 domains of Dock. Immune precipitations of Dock also co-precipitate two tyrosine-phosphorylated proteins having molecular masses of 190 and 145 kDa. Interactions between Dock and these tyrosine-phosphorylated proteins are likely mediated by the Dock SH2 domain. These findings identify potential signal-transducing partners of Dock and propose a role for dPTP61F and the unidentified phosphoproteins in axonal guidance.

  9. Phenotype of V2-derived interneurons and their relationship to the axon guidance molecule EphA4 in the developing mouse spinal cord

    DEFF Research Database (Denmark)

    Lundfald, Line; Restrepo, C. Ernesto; Butt, Simon J B

    2007-01-01

    , we demonstrated that a large proportion of V2 interneurons expressed the axon guidance molecule EphA4, a molecule previously shown to be important for correct organization of locomotor networks. We also showed that V2 interneurons and motor neurons alone did not account for all EphA4-expressing...

  10. Neurotrophin Signaling via Long-Distance Axonal Transport

    Science.gov (United States)

    Chowdary, Praveen D.; Che, Dung L.; Cui, Bianxiao

    2012-05-01

    Neurotrophins are a family of target-derived growth factors that support survival, development, and maintenance of innervating neurons. Owing to the unique architecture of neurons, neurotrophins that act locally on the axonal terminals must convey their signals across the entire axon for subsequent regulation of gene transcription in the cell nucleus. This long-distance retrograde signaling, a motor-driven process that can take hours or days, has been a subject of intense interest. In the last decade, live-cell imaging with high sensitivity has significantly increased our capability to track the transport of neurotrophins, their receptors, and subsequent signals in real time. This review summarizes recent research progress in understanding neurotrophin-receptor interactions at the axonal terminal and their transport dynamics along the axon. We emphasize high-resolution studies at the single-molecule level and also discuss recent technical advances in the field.

  11. The H3K4me3/2 histone demethylase RBR-2 controls axon guidance by repressing the actin-remodeling gene wsp-1

    DEFF Research Database (Denmark)

    Mariani, Luca; Lussi, Yvonne C.; Vandamme, Julien

    2016-01-01

    . Here, we show that RBR-2, the sole homolog of the KDM5 family of H3K4me3/2 demethylases in Caenorhabditis elegans, ensures correct axon guidance by controlling the expression of the actin regulator wsp-1. Loss of rbr-2 results in increased levels of H3K4me3 at the transcriptional start site of wsp-1...

  12. DISCO interacting protein 2 determines direction of axon projection under the regulation of c-Jun N-terminal kinase in the Drosophila mushroom body

    International Nuclear Information System (INIS)

    Nitta, Yohei; Sugie, Atsushi

    2017-01-01

    Precisely controlled axon guidance for complex neuronal wiring is essential for appropriate neuronal function. c-Jun N-terminal kinase (JNK) was found to play a role in axon guidance recently as well as in cell proliferation, protection and apoptosis. In spite of many genetic and molecular studies on these biological processes regulated by JNK, how JNK regulates axon guidance accurately has not been fully explained thus far. To address this question, we use the Drosophila mushroom body (MB) as a model since the α/β axons project in two distinct directions. Here we show that DISCO interacting protein 2 (DIP2) is required for the accurate direction of axonal guidance. DIP2 expression is under the regulation of Basket (Bsk), the Drosophila homologue of JNK. We additionally found that the Bsk/DIP2 pathway is independent from the AP-1 transcriptional factor complex pathway, which is directly activated by Bsk. In conclusion, our findings revealed DIP2 as a novel effector downstream of Bsk modulating the direction of axon projection. - Highlights: • DIP2 is required for accurate direction of axon guidance in Drosophila mushroom body. • DIP2 is a downstream of JNK in the axon guidance of Drosophila mushroom body neuron. • JNK/DIP2 pathway is independent from JNK/AP-1 transcriptional factor complex pathway.

  13. Current and calcium responses to local activation of axonal NMDA receptors in developing cerebellar molecular layer interneurons.

    Directory of Open Access Journals (Sweden)

    Bénédicte Rossi

    Full Text Available In developing cerebellar molecular layer interneurons (MLIs, NMDA increases spontaneous GABA release. This effect had been attributed to either direct activation of presynaptic NMDA receptors (preNMDARs or an indirect pathway involving activation of somato-dendritic NMDARs followed by passive spread of somatic depolarization along the axon and activation of axonal voltage dependent Ca(2+ channels (VDCCs. Using Ca(2+ imaging and electrophysiology, we searched for preNMDARs by uncaging NMDAR agonists either broadly throughout the whole field or locally at specific axonal locations. Releasing either NMDA or glutamate in the presence of NBQX using short laser pulses elicited current transients that were highly sensitive to the location of the spot and restricted to a small number of varicosities. The signal was abolished in the presence of high Mg(2+ or by the addition of APV. Similar paradigms yielded restricted Ca(2+ transients in interneurons loaded with a Ca(2+ indicator. We found that the synaptic effects of NMDA were not inhibited by blocking VDCCs but were impaired in the presence of the ryanodine receptor antagonist dantrolene. Furthermore, in voltage clamped cells, bath applied NMDA triggers Ca(2+ elevations and induces neurotransmitter release in the axonal compartment. Our results suggest the existence of preNMDARs in developing MLIs and propose their involvement in the NMDA-evoked increase in GABA release by triggering a Ca(2+-induced Ca(2+ release process mediated by presynaptic Ca(2+ stores. Such a mechanism is likely to exert a crucial role in various forms of Ca(2+-mediated synaptic plasticity.

  14. Co-immobilization of semaphorin3A and nerve growth factor to guide and pattern axons.

    Science.gov (United States)

    McCormick, Aleesha M; Jarmusik, Natalie A; Leipzig, Nic D

    2015-12-01

    Immobilization of axon guidance cues offers a powerful tissue regenerative strategy to control the presentation and spatial location of these biomolecules. We use our previously developed immobilization strategy to specifically tether recombinant biotinylated nerve growth factor (bNGF) and biotinylated semaphorin3A (bSema3A) to chitosan films as an outgrowth and guidance platform. DRG neurite length and number for a range of single cues of immobilized bNGF or bSema3A were examined to determine a concentration response. Next single and dual cues of bNGF and bSema3A were immobilized and DRG guidance was assessed in response to a step concentration change from zero. Overall, immobilized groups caused axon extension, retraction and turning depending on the ratio of bNGF and bSema3A immobilized in the encountered region. This response indicated the exquisite sensitivity of DRG axons to both attractive and repulsive tethered cues. bSema3A concentrations of 0.10 and 0.49 ng/mm(2), when co-immobilized with bNGF (at 0.86 and 0.43 ng/mm(2) respectively), caused axons to turn away from the co-immobilized region. Immunocytochemical analysis showed that at these bSema3A concentrations, axons inside the co-immobilized region display microtubule degradation and breakdown of actin filaments. At the lowest bSema3A concentration (0.01 ng/mm(2)) co-immobilized with a higher bNGF concentration (2.16 ng/mm(2)), neurite lengths are shorter in the immobilized area, but bNGF dominates the guidance mechanism as neurites are directed toward the immobilized region. Future applications can pattern these cues in various geometries and gradients in order to better modulate axon guidance in terms of polarity, extension and branching. Nervous system formation and regeneration requires key molecules for guiding the growth cone and nervous system patterning. In vivo these molecules work in conjunction with one another to modulate axon guidance, and often they are tethered to limit spatial

  15. Sigma-1 receptor agonist increases axon outgrowth of hippocampal neurons via voltage-gated calcium ions channels.

    Science.gov (United States)

    Li, Dong; Zhang, Shu-Zhuo; Yao, Yu-Hong; Xiang, Yun; Ma, Xiao-Yun; Wei, Xiao-Li; Yan, Hai-Tao; Liu, Xiao-Yan

    2017-12-01

    Sigma-1 receptors (Sig-1Rs) are unique endoplasmic reticulum proteins that have been implicated in both neurodegenerative and ischemic diseases, such as Alzheimer's disease and stroke. Accumulating evidence has suggested that Sig-1R plays a role in neuroprotection and axon outgrowth. The underlying mechanisms of Sig-1R-mediated neuroprotection have been well elucidated. However, the mechanisms underlying the effects of Sig-1R on axon outgrowth are not fully understood. To clarify this issue, we utilized immunofluorescence to compare the axon lengths of cultured naïve hippocampal neurons before and after the application of the Sig-1R agonist, SA4503. Then, electrophysiology and immunofluorescence were used to examine voltage-gated calcium ion channel (VGCCs) currents in the cell membranes and growth cones. We found that Sig-1R activation dramatically enhanced the axonal length of the naïve hippocampal neurons. Application of the Sig-1R antagonist NE100 and gene knockdown techniques both demonstrated the effects of Sig-1R. The growth-promoting effect of SA4503 was accompanied by the inhibition of voltage-gated Ca 2+ influx and was recapitulated by incubating the neurons with the L-type, N-type, and P/Q-type VGCC blockers, nimodipine, MVIIA and ω-agatoxin IVA, respectively. This effect was unrelated to glial cells. The application of SA4503 transformed the growth cone morphologies from complicated to simple, which favored axon outgrowth. Sig-1R activation can enhance axon outgrowth and may have a substantial influence on neurogenesis and neurodegenerative diseases. © 2017 John Wiley & Sons Ltd.

  16. Retinoic acid signaling in axonal regeneration

    Directory of Open Access Journals (Sweden)

    Radhika ePuttagunta

    2012-01-01

    Full Text Available Following an acute central nervous system injury, axonal regeneration and functional recovery are extremely limited. This is due to an extrinsic inhibitory growth environment and the lack of intrinsic growth competence. Retinoic acid (RA signaling, essential in developmental dorsoventral patterning and specification of spinal motor neurons, has been shown through its receptor, the transcription factor RA receptor β2 (RARß2, to induce axonal regeneration following spinal cord injury (SCI. Recently, it has been shown that in dorsal root ganglia neurons, cAMP levels were greatly increased by lentiviral RARβ2 expression and contributed to neurite outgrowth. Moreover, RARβ agonists, in cerebellar granule neurons and in the brain in vivo, induced phosphoinositide 3-kinase dependent phosphorylation of AKT that was involved in RARβ-dependent neurite outgrowth. More recently, RA-RARß pathways were shown to directly transcriptionally repress a member of the inhibitory Nogo receptor complex, Lingo-1, under an axonal growth inhibitory environment in vitro as well as following spinal injury in vivo. This perspective focuses on these newly discovered molecular mechanisms and future directions in the field.

  17. Post-guidance signaling by extracellular matrix-associated Slit/Slit-N maintains fasciculation and position of axon tracts in the nerve cord.

    Directory of Open Access Journals (Sweden)

    Krishna Moorthi Bhat

    2017-11-01

    Full Text Available Axon-guidance by Slit-Roundabout (Robo signaling at the midline initially guides growth cones to synaptic targets and positions longitudinal axon tracts in discrete bundles on either side of the midline. Following the formation of commissural tracts, Slit is found also in tracts of the commissures and longitudinal connectives, the purpose of which is not clear. The Slit protein is processed into a larger N-terminal peptide and a smaller C-terminal peptide. Here, I show that Slit and Slit-N in tracts interact with Robo to maintain the fasciculation, the inter-tract spacing between tracts and their position relative to the midline. Thus, in the absence of Slit in post-guidance tracts, tracts de-fasciculate, merge with one another and shift their position towards the midline. The Slit protein is proposed to function as a gradient. However, I show that Slit and Slit-N are not freely present in the extracellular milieu but associated with the extracellular matrix (ECM and both interact with Robo1. Slit-C is tightly associated with the ECM requiring collagenase treatment to release it, and it does not interact with Robo1. These results define a role for Slit and Slit-N in tracts for the maintenance and fasciculation of tracts, thus the maintenance of the hardwiring of the CNS.

  18. Axon tension regulates fasciculation/defasciculation through the control of axon shaft zippering

    Czech Academy of Sciences Publication Activity Database

    Šmít, Daniel; Fouquet, C.; Pincet, F.; Zápotocký, Martin; Trembleau, A.

    2017-01-01

    Roč. 6, Apr 19 (2017), č. článku e19907. ISSN 2050-084X R&D Projects: GA ČR(CZ) GA14-16755S; GA MŠk(CZ) 7AMB12FR002 Institutional support: RVO:67985823 Keywords : biophysics * cell adhesion * coarsening * developmental biology * mathematical model * mechanical tension * axon guidance Subject RIV: BO - Biophysics OBOR OECD: Biophysics Impact factor: 7.725, year: 2016

  19. Presynaptic type III neuregulin1-ErbB signaling targets {alpha}7 nicotinic acetylcholine receptors to axons.

    Science.gov (United States)

    Hancock, Melissa L; Canetta, Sarah E; Role, Lorna W; Talmage, David A

    2008-05-05

    Type III Neuregulin1 (Nrg1) isoforms are membrane-tethered proteins capable of participating in bidirectional juxtacrine signaling. Neuronal nicotinic acetylcholine receptors (nAChRs), which can modulate the release of a rich array of neurotransmitters, are differentially targeted to presynaptic sites. We demonstrate that Type III Nrg1 back signaling regulates the surface expression of alpha7 nAChRs along axons of sensory neurons. Stimulation of Type III Nrg1 back signaling induces an increase in axonal surface alpha7 nAChRs, which results from a redistribution of preexisting intracellular pools of alpha7 rather than from increased protein synthesis. We also demonstrate that Type III Nrg1 back signaling activates a phosphatidylinositol 3-kinase signaling pathway and that activation of this pathway is required for the insertion of preexisting alpha7 nAChRs into the axonal plasma membrane. These findings, in conjunction with prior results establishing that Type III Nrg1 back signaling controls gene transcription, demonstrate that Type III Nrg1 back signaling can regulate both short-and long-term changes in neuronal function.

  20. Presynaptic type III neuregulin1-ErbB signaling targets alpha7 nicotinic acetylcholine receptors to axons.

    Science.gov (United States)

    Hancock, Melissa L; Canetta, Sarah E; Role, Lorna W; Talmage, David A

    2008-06-01

    Type III Neuregulin1 (Nrg1) isoforms are membrane-tethered proteins capable of participating in bidirectional juxtacrine signaling. Neuronal nicotinic acetylcholine receptors (nAChRs), which can modulate the release of a rich array of neurotransmitters, are differentially targeted to presynaptic sites. We demonstrate that Type III Nrg1 back signaling regulates the surface expression of alpha7 nAChRs along axons of sensory neurons. Stimulation of Type III Nrg1 back signaling induces an increase in axonal surface alpha7 nAChRs, which results from a redistribution of preexisting intracellular pools of alpha7 rather than from increased protein synthesis. We also demonstrate that Type III Nrg1 back signaling activates a phosphatidylinositol 3-kinase signaling pathway and that activation of this pathway is required for the insertion of preexisting alpha7 nAChRs into the axonal plasma membrane. These findings, in conjunction with prior results establishing that Type III Nrg1 back signaling controls gene transcription, demonstrate that Type III Nrg1 back signaling can regulate both short-and long-term changes in neuronal function.

  1. Presynaptic Type III Neuregulin1-ErbB signaling targets α7 nicotinic acetylcholine receptors to axons

    Science.gov (United States)

    Hancock, Melissa L.; Canetta, Sarah E.; Role, Lorna W.; Talmage, David A.

    2008-01-01

    Type III Neuregulin1 (Nrg1) isoforms are membrane-tethered proteins capable of participating in bidirectional juxtacrine signaling. Neuronal nicotinic acetylcholine receptors (nAChRs), which can modulate the release of a rich array of neurotransmitters, are differentially targeted to presynaptic sites. We demonstrate that Type III Nrg1 back signaling regulates the surface expression of α7 nAChRs along axons of sensory neurons. Stimulation of Type III Nrg1 back signaling induces an increase in axonal surface α7 nAChRs, which results from a redistribution of preexisting intracellular pools of α7 rather than from increased protein synthesis. We also demonstrate that Type III Nrg1 back signaling activates a phosphatidylinositol 3-kinase signaling pathway and that activation of this pathway is required for the insertion of preexisting α7 nAChRs into the axonal plasma membrane. These findings, in conjunction with prior results establishing that Type III Nrg1 back signaling controls gene transcription, demonstrate that Type III Nrg1 back signaling can regulate both short-and long-term changes in neuronal function. PMID:18458158

  2. The Pseudopod System for Axon-Glia Interactions: Stimulation and Isolation of Schwann Cell Protrusions that Form in Response to Axonal Membranes.

    Science.gov (United States)

    Poitelon, Yannick; Feltri, M Laura

    2018-01-01

    In the peripheral nervous system, axons dictate the differentiation state of Schwann cells. Most of this axonal influence on Schwann cells is due to juxtacrine interactions between axonal transmembrane molecules (e.g., the neuregulin growth factor) and receptors on the Schwann cell (e.g., the ErbB2/ErbB3 receptor). The fleeting nature of this interaction together with the lack of synchronicity in the development of the Schwann cell population limits our capability to study this phenomenon in vivo. Here we present a simple Boyden Chamber-based method to study this important cell-cell interaction event. We isolate the early protrusions of Schwann cells that are generated in response to juxtacrine stimulation by sensory neuronal membranes. This method is compatible with a large array of current biochemical analyses and provides an effective approach to study biomolecules that are differentially localized in Schwann cell protrusions and cell bodies in response to axonal signals. A similar approach can be extended to different kinds of cell-cell interactions.

  3. The protection of acetylcholinesterase inhibitor on β-amyloid-induced injury of neurite outgrowth via regulating axon guidance related genes expression in neuronal cells

    OpenAIRE

    Shen, Jiao-Ning; Wang, Deng-Shun; Wang, Rui

    2012-01-01

    Cognitive deficits in AD correlate with progressive synaptic dysfunction and loss. The Rho family of small GTPases, including Rho, Rac, and Cdc42, has a central role in cellular motility and cytokinesis. Acetylcholinesterase inhibitor has been found to protect cells against a broad range of reagents-induced injuries. Present studies examined if the effect of HupA on neurite outgrowth in Aβ-treated neuronal cells executed via regulating Rho-GTPase mediated axon guidance relative gene expressio...

  4. Orexin A and Orexin Receptor 1 axonal traffic in dorsal roots at the CNS/PNS interface

    Directory of Open Access Journals (Sweden)

    Damien eColas

    2014-02-01

    Full Text Available Hypothalamic orexin/hypocretin neurons send long axonal projections through the dorsal spinal cord in lamina I-II of the dorsal horn at the interface with the peripheral nervous system (PNS. We show that in the dorsal horn OXA fibers colocalize with substance P (SP positive afferents of dorsal root ganglia (DRG neurons known to mediate sensory processing. Further, OR1 is expressed in p75NTR and SP positive DRG neurons, suggesting a potential signaling pathway between orexin and DRG neurons. Interestingly, DRG sensory neurons have a distinctive bifurcating axon where one branch innervates the periphery and the other one the spinal cord (pseudo-unipolar neurons, allowing for potential functional coupling of distinct targets. We observe that OR1 is transported selectively from DRG toward the spinal cord, while OXA is accumulated retrogradely toward the DRG. We hence report a rare situation of asymmetrical neuropeptide receptor distribution between axons projected by a single neuron. This molecular and cellular data are consistent with the role of OXA/OR1 in sensory processing, including DRG neuronal modulation, and support the potential existence of an OX/HCRT circuit between CNS and PNS.

  5. Guidance of vascular development: lessons from the nervous system.

    Science.gov (United States)

    Larrivée, Bruno; Freitas, Catarina; Suchting, Steven; Brunet, Isabelle; Eichmann, Anne

    2009-02-27

    The vascular system of vertebrates consists of an organized, branched network of arteries, veins, and capillaries that penetrates all the tissues of the body. One of the most striking features of the vascular system is that its branching pattern is highly stereotyped, with major and secondary branches forming at specific sites and developing highly conserved organ-specific vascular patterns. The factors controlling vascular patterning are not yet completely understood. Recent studies have highlighted the anatomic and structural similarities between blood vessels and nerves. The 2 networks are often aligned, with nerve fibers and blood vessels following parallel routes. Furthermore, both systems require precise control over their guidance and growth. Several molecules with attractive and repulsive properties have been found to modulate the proper guidance of both nerves and blood vessels. These include the Semaphorins, the Slits, and the Netrins and their receptors. In this review, we describe the molecular mechanisms by which blood vessels and axons achieve proper path finding and the molecular cues that are involved in their guidance.

  6. Vesicular glutamate release from central axons contributes to myelin damage.

    Science.gov (United States)

    Doyle, Sean; Hansen, Daniel Bloch; Vella, Jasmine; Bond, Peter; Harper, Glenn; Zammit, Christian; Valentino, Mario; Fern, Robert

    2018-03-12

    The axon myelin sheath is prone to injury associated with N-methyl-D-aspartate (NMDA)-type glutamate receptor activation but the source of glutamate in this context is unknown. Myelin damage results in permanent action potential loss and severe functional deficit in the white matter of the CNS, for example in ischemic stroke. Here, we show that in rats and mice, ischemic conditions trigger activation of myelinic NMDA receptors incorporating GluN2C/D subunits following release of axonal vesicular glutamate into the peri-axonal space under the myelin sheath. Glial sources of glutamate such as reverse transport did not contribute significantly to this phenomenon. We demonstrate selective myelin uptake and retention of a GluN2C/D NMDA receptor negative allosteric modulator that shields myelin from ischemic injury. The findings potentially support a rational approach toward a low-impact prophylactic therapy to protect patients at risk of stroke and other forms of excitotoxic injury.

  7. Evidence for a role of srGAP3 in the positioning of commissural axons within the ventrolateral funiculus of the mouse spinal cord.

    Directory of Open Access Journals (Sweden)

    Claire Bacon

    Full Text Available Slit-Robo signaling guides commissural axons away from the floor-plate of the spinal cord and into the longitudinal axis after crossing the midline. In this study we have evaluated the role of the Slit-Robo GTPase activating protein 3 (srGAP3 in commissural axon guidance using a knockout (KO mouse model. Co-immunoprecipitation experiments confirmed that srGAP3 interacts with the Slit receptors Robo1 and Robo2 and immunohistochemistry studies showed that srGAP3 co-localises with Robo1 in the ventral and lateral funiculus and with Robo2 in the lateral funiculus. Stalling axons have been reported in the floor-plate of Slit and Robo mutant spinal cords but our axon tracing experiments revealed no dorsal commissural axon stalling in the floor plate of the srGAP3 KO mouse. Interestingly we observed a significant thickening of the ventral funiculus and a thinning of the lateral funiculus in the srGAP3 KO spinal cord, which has also recently been reported in the Robo2 KO. However, axons in the enlarged ventral funiculus of the srGAP3 KO are Robo1 positive but do not express Robo2, indicating that the thickening of the ventral funiculus in the srGAP3 KO is not a Robo2 mediated effect. We suggest a role for srGAP3 in the lateral positioning of post crossing axons within the ventrolateral funiculus.

  8. Sigma-1 receptor regulates Tau phosphorylation and axon extension by shaping p35 turnover via myristic acid.

    Science.gov (United States)

    Tsai, Shang-Yi A; Pokrass, Michael J; Klauer, Neal R; Nohara, Hiroshi; Su, Tsung-Ping

    2015-05-26

    Dysregulation of cyclin-dependent kinase 5 (cdk5) per relative concentrations of its activators p35 and p25 is implicated in neurodegenerative diseases. P35 has a short t½ and undergoes rapid proteasomal degradation in its membrane-bound myristoylated form. P35 is converted by calpain to p25, which, along with an extended t½, promotes aberrant activation of cdk5 and causes abnormal hyperphosphorylation of tau, thus leading to the formation of neurofibrillary tangles. The sigma-1 receptor (Sig-1R) is an endoplasmic reticulum chaperone that is implicated in neuronal survival. However, the specific role of the Sig-1R in neurodegeneration is unclear. Here we found that Sig-1Rs regulate proper tau phosphorylation and axon extension by promoting p35 turnover through the receptor's interaction with myristic acid. In Sig-1R-KO neurons, a greater accumulation of p35 is seen, which results from neither elevated transcription of p35 nor disrupted calpain activity, but rather to the slower degradation of p35. In contrast, Sig-1R overexpression causes a decrease of p35. Sig-1R-KO neurons exhibit shorter axons with lower densities. Myristic acid is found here to bind Sig-1R as an agonist that causes the dissociation of Sig-1R from its cognate partner binding immunoglobulin protein. Remarkably, treatment of Sig-1R-KO neurons with exogenous myristic acid mitigates p35 accumulation, diminishes tau phosphorylation, and restores axon elongation. Our results define the involvement of Sig-1Rs in neurodegeneration and provide a mechanistic explanation that Sig-1Rs help maintain proper tau phosphorylation by potentially carrying and providing myristic acid to p35 for enhanced p35 degradation to circumvent the formation of overreactive cdk5/p25.

  9. Sugar Antennae for Guidance Signals: Syndecans and Glypicans Integrate Directional Cues for Navigating Neurons

    Directory of Open Access Journals (Sweden)

    Christa Rhiner

    2006-01-01

    Full Text Available Attractive and repulsive signals guide migrating nerve cells in all directions when the nervous system starts to form. The neurons extend thin processes, axons, that connect over wide distances with other brain cells to form a complicated neuronal network. One of the most fascinating questions in neuroscience is how the correct wiring of billions of nerve cells in our brain is controlled. Several protein families are known to serve as guidance cues for navigating neurons and axons. Nevertheless, the combinatorial potential of these proteins seems to be insufficient to sculpt the entire neuronal network and the appropriate formation of connections. Recently, heparan sulfate proteoglycans (HSPGs, which are present on the cell surface of neurons and in the extracellular matrix through which neurons and axons migrate, have been found to play a role in regulating cell migration and axon guidance. Intriguingly, the large number of distinct modifications that can be put onto the sugar side chains of these PGs would in principle allow for an enormous diversity of HSPGs, which could help in regulating the vast number of guidance choices taken by individual neurons. In this review, we will focus on the role of the cell surface HSPGs syndecan and glypican and specific HS modifications in promoting neuronal migration, axon guidance, and synapse formation.

  10. Brief electrical stimulation accelerates axon regeneration in the peripheral nervous system and promotes sensory axon regeneration in the central nervous system.

    Science.gov (United States)

    Gordon, Tessa; Udina, Esther; Verge, Valerie M K; de Chaves, Elena I Posse

    2009-10-01

    Injured peripheral but not central nerves regenerate their axons but functional recovery is often poor. We demonstrate that prolonged periods of axon separation from targets and Schwann cell denervation eliminate regenerative capacity in the peripheral nervous system (PNS). A substantial delay of 4 weeks for all regenerating axons to cross a site of repair of sectioned nerve contributes to the long period of separation. Findings that 1h 20Hz bipolar electrical stimulation accelerates axon outgrowth across the repair site and the downstream reinnervation of denervated muscles in rats and human patients, provides a new and exciting method to improve functional recovery after nerve injuries. Drugs that elevate neuronal cAMP and activate PKA promote axon outgrowth in vivo and in vitro, mimicking the electrical stimulation effect. Rapid expression of neurotrophic factors and their receptors and then of growth associated proteins thereafter via cAMP, is the likely mechanism by which electrical stimulation accelerates axon outgrowth from the site of injury in both peripheral and central nervous systems.

  11. The Influence of Glutamate on Axonal Compound Action Potential In Vitro.

    Science.gov (United States)

    Abouelela, Ahmed; Wieraszko, Andrzej

    2016-01-01

    Background  Our previous experiments demonstrated modulation of the amplitude of the axonal compound action potential (CAP) by electrical stimulation. To verify assumption that glutamate released from axons could be involved in this phenomenon, the modification of the axonal CAP induced by glutamate was investigated. Objectives  The major objective of this research is to verify the hypothesis that axonal activity would trigger the release of glutamate, which in turn would interact with specific axonal receptors modifying the amplitude of the action potential. Methods  Segments of the sciatic nerve were exposed to exogenous glutamate in vitro, and CAP was recorded before and after glutamate application. In some experiments, the release of radioactive glutamate analog from the sciatic nerve exposed to exogenous glutamate was also evaluated. Results  The glutamate-induced increase in CAP was blocked by different glutamate receptor antagonists. The effect of glutamate was not observed in Ca-free medium, and was blocked by antagonists of calcium channels. Exogenous glutamate, applied to the segments of sciatic nerve, induced the release of radioactive glutamate analog, demonstrating glutamate-induced glutamate release. Immunohistochemical examination revealed that axolemma contains components necessary for glutamatergic neurotransmission. Conclusion  The proteins of the axonal membrane can under the influence of electrical stimulation or exogenous glutamate change membrane permeability and ionic conductance, leading to a change in the amplitude of CAP. We suggest that increased axonal activity leads to the release of glutamate that results in changes in the amplitude of CAPs.

  12. Adenosine: an activity-dependent axonal signal regulating MAP kinase and proliferation in developing Schwann cells.

    Science.gov (United States)

    Stevens, Beth; Ishibashi, Tomoko; Chen, Jiang-Fan; Fields, R Douglas

    2004-02-01

    Nonsynaptic release of ATP from electrically stimulated dorsal root gangion (DRG) axons inhibits Schwann cell (SC) proliferation and arrests SC development at the premyelinating stage, but the specific types of purinergic receptor(s) and intracellular signaling pathways involved in this form of neuron-glia communication are not known. Recent research shows that adenosine is a neuron-glial transmitter between axons and myelinating glia of the CNS. The present study investigates the possibility that adenosine might have a similar function in communicating between axons and premyelinating SCs. Using a combination of pharmacological and molecular approaches, we found that mouse SCs in culture express functional adenosine receptors and ATP receptors, a far more complex array of purinergic receptors than thought previously. Adenosine, but not ATP, activates ERK/MAPK through stimulation of cAMP-linked A2(A) adenosine receptors. Both ATP and adenosine inhibit proliferation of SCs induced by platelet-derived growth factor (PDGF), via mechanisms that are partly independent. In contrast to ATP, adenosine failed to inhibit the differentiation of SCs to the O4+ stage. This indicates that, in addition to ATP, adenosine is an activity-dependent signaling molecule between axons and premyelinating Schwann cells, but that electrical activity, acting through adenosine, has opposite effects on the differentiation of myelinating glia in the PNS and CNS.

  13. Slit and Netrin-1 guide cranial motor axon pathfinding via Rho-kinase, myosin light chain kinase and myosin II

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    Drescher Uwe

    2010-06-01

    Full Text Available Abstract Background In the developing hindbrain, cranial motor axon guidance depends on diffusible repellent factors produced by the floor plate. Our previous studies have suggested that candidate molecules for mediating this effect are Slits, Netrin-1 and Semaphorin3A (Sema3A. It is unknown to what extent these factors contribute to floor plate-derived chemorepulsion of motor axons, and the downstream signalling pathways are largely unclear. Results In this study, we have used a combination of in vitro and in vivo approaches to identify the components of floor plate chemorepulsion and their downstream signalling pathways. Using in vitro motor axon deflection assays, we demonstrate that Slits and Netrin-1, but not Sema3A, contribute to floor plate repulsion. We also find that the axon pathways of dorsally projecting branchiomotor neurons are disrupted in Netrin-1 mutant mice and in chick embryos expressing dominant-negative Unc5a receptors, indicating an in vivo role for Netrin-1. We further demonstrate that Slit and Netrin-1 signalling are mediated by Rho-kinase (ROCK and myosin light chain kinase (MLCK, which regulate myosin II activity, controlling actin retrograde flow in the growth cone. We show that MLCK, ROCK and myosin II are required for Slit and Netrin-1-mediated growth cone collapse of cranial motor axons. Inhibition of these molecules in explant cultures, or genetic manipulation of RhoA or myosin II function in vivo causes characteristic cranial motor axon pathfinding errors, including the inability to exit the midline, and loss of turning towards exit points. Conclusions Our findings suggest that both Slits and Netrin-1 contribute to floor plate-derived chemorepulsion of cranial motor axons. They further indicate that RhoA/ROCK, MLCK and myosin II are components of Slit and Netrin-1 signalling pathways, and suggest that these pathways are of key importance in cranial motor axon navigation.

  14. Axonal Control of the Adult Neural Stem Cell Niche

    Science.gov (United States)

    Tong, Cheuk Ka; Chen, Jiadong; Cebrián-Silla, Arantxa; Mirzadeh, Zaman; Obernier, Kirsten; Guinto, Cristina D.; Tecott, Laurence H.; García-Verdugo, Jose Manuel; Kriegstein, Arnold; Alvarez-Buylla, Arturo

    2014-01-01

    SUMMARY The ventricular-subventricular zone (V-SVZ) is an extensive germinal niche containing neural stem cells (NSC) in the walls of the lateral ventricles of the adult brain. How the adult brain’s neural activity influences the behavior of adult NSCs remains largely unknown. We show that serotonergic (5HT) axons originating from a small group of neurons in the raphe form an extensive plexus on most of the ventricular walls. Electron microscopy revealed intimate contacts between 5HT axons and NSCs (B1) or ependymal cells (E1) and these cells were labeled by a transsynaptic viral tracer injected into the raphe. B1 cells express the 5HT receptors 2C and 5A. Electrophysiology showed that activation of these receptors in B1 cells induced small inward currents. Intraventricular infusion of 5HT2C agonist or antagonist increased or decreased V-SVZ proliferation, respectively. These results indicate that supraependymal 5HT axons directly interact with NSCs to regulate neurogenesis via 5HT2C. PMID:24561083

  15. Two Modes of the Axonal Interferon Response Limit Alphaherpesvirus Neuroinvasion

    Directory of Open Access Journals (Sweden)

    Ren Song

    2016-02-01

    Full Text Available Infection by alphaherpesviruses, including herpes simplex virus (HSV and pseudorabies virus (PRV, typically begins at epithelial surfaces and continues into the peripheral nervous system (PNS. Inflammatory responses are induced at the infected peripheral site prior to invasion of the PNS. When the peripheral tissue is first infected, only the innervating axons are exposed to this inflammatory milieu, which includes the interferons (IFNs. The fundamental question is how do PNS cell bodies respond to these distant, potentially damaging events experienced by axons. Using compartmented cultures that physically separate neuron axons from cell bodies, we found that pretreating isolated axons with beta interferon (IFN-β or gamma interferon (IFN-γ significantly diminished the number of herpes simplex virus 1 (HSV-1 and PRV particles moving in axons toward the cell bodies in a receptor-dependent manner. Exposing axons to IFN-β induced STAT1 phosphorylation (p-STAT1 only in axons, while exposure of axons to IFN-γ induced p-STAT1 accumulation in distant cell body nuclei. Blocking transcription in cell bodies eliminated antiviral effects induced by IFN-γ, but not those induced by IFN-β. Proteomic analysis of IFN-β- or IFN-γ-treated axons identified several differentially regulated proteins. Therefore, unlike treatment with IFN-γ, IFN-β induces a noncanonical, local antiviral response in axons. The activation of a local IFN response in axons represents a new paradigm for cytokine control of neuroinvasion.

  16. Pannexin 1 Modulates Axonal Growth in Mouse Peripheral Nerves

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    Steven M. Horton

    2017-11-01

    Full Text Available The pannexin family of channels consists of three members—pannexin-1 (Panx1, pannexin-2 (Panx2, and pannexin-3 (Panx3 that enable the exchange of metabolites and signaling molecules between intracellular and extracellular compartments. Pannexin-mediated release of intracellular ATP into the extracellular space has been tied to a number of cellular activities, primarily through the activity of type P2 purinergic receptors. Previous work indicates that the opening of Panx1 channels and activation of purinergic receptors by extracellular ATP may cause inflammation and apoptosis. In the CNS (central nervous system and PNS (peripheral nervous system, coupled pannexin, and P2 functions have been linked to peripheral sensitization (pain pathways. Purinergic pathways are also essential for other critical processes in the PNS, including myelination and neurite outgrowth. However, whether such pathways are pannexin-dependent remains to be determined. In this study, we use a Panx1 knockout mouse model and pharmacological inhibitors of the Panx1 and the ATP-mediated signaling pathway to fill gaps in our understanding of Panx1 localization in peripheral nerves, roles for Panx1 in axonal outgrowth and myelination, and neurite extension. Our data show that Panx1 is localized to axonal, myelin, and vascular compartments of the peripheral nerves. Knockout of Panx1 gene significantly increased axonal caliber in vivo and axonal growth rate in cultured dorsal root ganglia (DRG neurons. Furthermore, genetic knockout of Panx1 or inhibition of components of purinergic signaling, by treatment with probenecid and apyrase, resulted in denser axonal outgrowth from cultured DRG explants compared to untreated wild-types. Our findings suggest that Panx1 regulates axonal growth in the peripheral nervous system.

  17. Role of Netrin-1 Signaling in Nerve Regeneration

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    Xin-Peng Dun

    2017-02-01

    Full Text Available Netrin-1 was the first axon guidance molecule to be discovered in vertebrates and has a strong chemotropic function for axonal guidance, cell migration, morphogenesis and angiogenesis. It is a secreted axon guidance cue that can trigger attraction by binding to its canonical receptors Deleted in Colorectal Cancer (DCC and Neogenin or repulsion through binding the DCC/Uncoordinated (Unc5 A–D receptor complex. The crystal structures of Netrin-1/receptor complexes have recently been revealed. These studies have provided a structure based explanation of Netrin-1 bi-functionality. Netrin-1 and its receptor are continuously expressed in the adult nervous system and are differentially regulated after nerve injury. In the adult spinal cord and optic nerve, Netrin-1 has been considered as an inhibitor that contributes to axon regeneration failure after injury. In the peripheral nervous system, Netrin-1 receptors are expressed in Schwann cells, the cell bodies of sensory neurons and the axons of both motor and sensory neurons. Netrin-1 is expressed in Schwann cells and its expression is up-regulated after peripheral nerve transection injury. Recent studies indicated that Netrin-1 plays a positive role in promoting peripheral nerve regeneration, Schwann cell proliferation and migration. Targeting of the Netrin-1 signaling pathway could develop novel therapeutic strategies to promote peripheral nerve regeneration and functional recovery.

  18. Unc-51/ATG1 controls axonal and dendritic development via kinesin-mediated vesicle transport in the Drosophila brain.

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    Hiroaki Mochizuki

    2011-05-01

    Full Text Available Members of the evolutionary conserved Ser/Thr kinase Unc-51 family are key regulatory proteins that control neural development in both vertebrates and invertebrates. Previous studies have suggested diverse functions for the Unc-51 protein, including axonal elongation, growth cone guidance, and synaptic vesicle transport.In this work, we have investigated the functional significance of Unc-51-mediated vesicle transport in the development of complex brain structures in Drosophila. We show that Unc-51 preferentially accumulates in newly elongating axons of the mushroom body, a center of olfactory learning in flies. Mutations in unc-51 cause disintegration of the core of the developing mushroom body, with mislocalization of Fasciclin II (Fas II, an IgG-family cell adhesion molecule important for axonal guidance and fasciculation. In unc-51 mutants, Fas II accumulates in the cell bodies, calyx, and the proximal peduncle. Furthermore, we show that mutations in unc-51 cause aberrant overshooting of dendrites in the mushroom body and the antennal lobe. Loss of unc-51 function leads to marked accumulation of Rab5 and Golgi components, whereas the localization of dendrite-specific proteins, such as Down syndrome cell adhesion molecule (DSCAM and No distributive disjunction (Nod, remains unaltered. Genetic analyses of kinesin light chain (Klc and unc-51 double heterozygotes suggest the importance of kinesin-mediated membrane transport for axonal and dendritic development. Moreover, our data demonstrate that loss of Klc activity causes similar axonal and dendritic defects in mushroom body neurons, recapitulating the salient feature of the developmental abnormalities caused by unc-51 mutations.Unc-51 plays pivotal roles in the axonal and dendritic development of the Drosophila brain. Unc-51-mediated membrane vesicle transport is important in targeted localization of guidance molecules and organelles that regulate elongation and compartmentalization of

  19. Adenosine: an activity-dependent axonal signal regulating MAP kinase and proliferation in developing Schwann cells

    OpenAIRE

    Stevens, Beth; Ishibashi, Tomoko; Chen, Jiang-Fan; Fields, R. Douglas

    2004-01-01

    Nonsynaptic release of ATP from electrically stimulated dorsal root gangion (DRG) axons inhibits Schwann cell (SC) proliferation and arrests SC development at the premyelinating stage, but the specific types of purinergic receptor(s) and intracellular signaling pathways involved in this form of neuron–glia communication are not known. Recent research shows that adenosine is a neuron–glial transmitter between axons and myelinating glia of the CNS. The present study investigates the possibility...

  20. Possible Effects of Synaptic Imbalances on Oligodendrocyte-Axonic Interactions in Schizophrenia: a Hypothetical Model

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    Bernhard Joseph Mitterauer

    2011-04-01

    Full Text Available AbstractA model of glial-neuronal interactions is proposed that could be explanatory for the demyelination identified in brains with schizophrenia. According to this model, receptors on astrocytes in glial-neuronal synaptic units are not functional, loosing their modulatory influence on synaptic neurotransmission. Hence, an unconstrained neurotransmission flux occurs that hyperactivates the axon and floods the cognate receptors of neurotransmitters on oligodendrocytes. The excess of neurotransmitters may have a toxic effect on oligodendrocytes and myelin, causing demyelination. In parallel, an increasing impairment of axons may disconnect neuronal networks. It is formally shown how oligodendrocytes normally categorize axonic information processing via their processes. Demyelination decomposes the oligodendrocyte-axonic system making it incapable to generate categories of information. This incoherence may be responsible for symptoms of disorganization in schizophrenia, such as thought disorder, inappropriate affect and incommunicable motor behavior. In parallel, the loss of oligodendrocytes affects gap junctions in the panglial syncytium, presumably responsible for memory impairment in schizophrenia.

  1. Comparison of neurotrophin and repellent sensitivities of early embryonic geniculate and trigeminal axons

    NARCIS (Netherlands)

    Rochlin, M William; O'Connor, R.; Giger, Roman J; Verhaagen, J; Farbman, A I

    2000-01-01

    Geniculate (gustatory) and trigeminal (somatosensory) afferents take different routes to the tongue during rat embryonic development. To learn more about the mechanisms controlling neurite outgrowth and axon guidance, we are studying the roles of diffusible factors. We previously profiled the in

  2. Potential Involvement of Draxin in the Axonal Projection of Cranial Nerves, Especially Cranial Nerve X, in the Chick Hindbrain.

    Science.gov (United States)

    Zhang, Sanbing; Cui, Huixian; Wang, Lei; Kang, Lin; Huang, Guannan; Du, Juan; Li, Sha; Tanaka, Hideaki; Su, Yuhong

    2016-07-01

    The appropriate projection of axons within the nervous system is a crucial component of the establishment of neural circuitry. Draxin is a repulsive axon guidance protein. Draxin has important functions in the guidance of three commissures in the central nervous system and in the migration of neural crest cells and dI3 interneurons in the chick spinal cord. Here, we report that the distribution of the draxin protein and the location of 23C10-positive areas have a strong temporal and spatial correlation. The overexpression of draxin, especially transmembrane draxin, caused 23C10-positive axon bundles to misproject in the dorsal hindbrain. In addition, the overexpression of transmembrane draxin caused abnormal formation of the ganglion crest of the IX and X cranial nerves, misprojection of some anti-human natural killer-1 (HNK-1)-stained structures in the dorsal roof of the hindbrain, and a simultaneous reduction in the efferent nerves of some motoneuron axons inside the hindbrain. Our data reveal that draxin might be involved in the fascicular projection of cranial nerves in the hindbrain. © 2016 The Histochemical Society.

  3. Functional characterization and axonal transport of quantum dot labeled BDNF

    OpenAIRE

    Xie, Wenjun; Zhang, Kai; Cui, Bianxiao

    2012-01-01

    Brain derived neurotrophic factor (BDNF) plays a key role in the growth, development and maintenance of the central and peripheral nervous systems. Exogenous BDNF activates its membrane receptors at the axon terminal, and subsequently sends regulation signals to the cell body. To understand how BDNF signal propagates in neurons, it is important to follow the trafficking of BDNF after it is internalized at the axon terminal. Here we labeled BDNF with bright, photostable quantum dot (QD-BDNF) a...

  4. Presynaptic Muscarinic Acetylcholine Receptors and TrkB Receptor Cooperate in the Elimination of Redundant Motor Nerve Terminals during Development.

    Science.gov (United States)

    Nadal, Laura; Garcia, Neus; Hurtado, Erica; Simó, Anna; Tomàs, Marta; Lanuza, Maria A; Cilleros, Victor; Tomàs, Josep

    2017-01-01

    The development of the nervous system involves the overproduction of synapses but connectivity is refined by Hebbian activity-dependent axonal competition. The newborn skeletal muscle fibers are polyinnervated but, at the end of the competition process, some days later, become innervated by a single axon. We used quantitative confocal imaging of the autofluorescent axons from transgenic B6.Cg-Tg (Thy1-YFP)16 Jrs/J mice to investigate the possible cooperation of the muscarinic autoreceptors (mAChR, M 1 -, M 2 - and M 4 -subtypes) and the tyrosine kinase B (TrkB) receptor in the control of axonal elimination after the mice Levator auris longus (LAL) muscle had been exposed to several selective antagonist of the corresponding receptor pathways in vivo . Our previous results show that M 1 , M 2 and TrkB signaling individually increase axonal loss rate around P9. Here we show that although the M 1 and TrkB receptors cooperate and add their respective individual effects to increase axonal elimination rate even more, the effect of the M 2 receptor is largely independent of both M 1 and TrkB receptors. Thus both, cooperative and non-cooperative signaling mechanisms contribute to developmental synapse elimination.

  5. Abundant expression of guidance and synaptogenic molecules in the injured spinal cord.

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    Anne Jacobi

    Full Text Available BACKGROUND: Spinal interneurons have emerged as crucial targets of supraspinal input during post-injury axonal remodelling. For example, lesioned corticospinal projections use propriospinal neurons as relay stations to form intraspinal detour circuits that circumvent the lesion site and contribute to functional recovery. While a number of the molecules that determine the formation of neuronal circuits in the developing nervous system have been identified, it is much less understood which of these cues are also expressed in the injured spinal cord and can thus guide growing collaterals and initiate synaptogenesis during circuit remodelling. METHODOLOGY/PRINCIPAL FINDINGS: To address this question we characterized the expression profile of a number of guidance and synaptogenic molecules in the cervical spinal cord of healthy and spinal cord-injured mice by in situ hybridization. To assign the expression of these molecules to distinct populations of interneurons we labeled short and long propriospinal neurons by retrograde tracing and glycinergic neurons using a transgenically expressed fluorescent protein. Interestingly, we found that most of the molecules studied including members of slit-, semaphorin-, synCAM-, neuroligin- and ephrin- families as well as their receptors are also present in the adult CNS. While many of these molecules were abundantly expressed in all interneurons examined, some molecules including slits, semaphorin 7a, synCAM4 and neuroligin 1 showed preferential expression in propriospinal interneurons. Overall the expression pattern of guidance and synaptogenic molecules in the cervical spinal cord appeared to be stable over time and was not substantially altered following a midthoracic spinal cord injury. CONCLUSIONS: Taken together, our study indicates that many of the guidance and synaptogenic cues that regulate neuronal circuit formation in development are also present in the adult CNS and therefore likely contribute to the

  6. Conduction of impulses by axons regenerated in a Schwann cell graft in the transected adult rat thoracic spinal cord.

    Science.gov (United States)

    Pinzon, A; Calancie, B; Oudega, M; Noga, B R

    2001-06-01

    Central nervous system axons regenerate into a Schwann cell implant placed in the transected thoracic spinal cord of an adult rat. The present study was designed to test whether these regenerated axons are capable of conducting action potentials. Following the transection and removal of a 4- to 5-mm segment of the thoracic spinal cord (T8-T9), a polymer guidance channel filled with a mixture of adult rat Schwann cells and Matrigel was grafted into a 4- to 5-mm-long gap in the transected thoracic spinal cord. The two cut ends of the spinal cord were eased into the guidance channel openings. Transected control animals received a channel containing Matrigel only. Three months after implantation, electrophysiological studies were performed. Tungsten microelectrodes were used for monopolar stimulation of regenerated axons within the Schwann cell graft. Glass microelectrodes were used to record responses in the spinal cord rostral to the stimulation site. Evoked responses to electrical stimulation of the axon cable were found in two out of nine Schwann cell-grafted animals. These responses had approximate latencies in the range of those of myelinated axons. No responses were seen in any of the Matrigel-grafted animals. Histological analysis revealed that the two cases that showed evoked potentials had the largest number of myelinated axons present in the cable. This study demonstrates that axons regenerating through Schwann cell grafts in the complete transected spinal cord can produce measurable evoked responses following electrical stimulation. Copyright 2001 Wiley-Liss, Inc.

  7. Selective axonal growth of embryonic hippocampal neurons according to topographic features of various sizes and shapes

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    Christine E Schmidt

    2010-12-01

    Full Text Available David Y Fozdar1*, Jae Y Lee2*, Christine E Schmidt2–6, Shaochen Chen1,3–5,7,1Departments of Mechanical Engineering, 2Chemical Engineering, 3Biomedical Engineering; 4Center for Nano Molecular Science and Technology; 5Texas Materials Institute; 6Institute of Neuroscience; 7Microelectronics Research Center, The University of Texas at Austin, Austin, TX, USA *Contributed equally to this workPurpose: Understanding how surface features influence the establishment and outgrowth of the axon of developing neurons at the single cell level may aid in designing implantable scaffolds for the regeneration of damaged nerves. Past studies have shown that micropatterned ridge-groove structures not only instigate axon polarization, alignment, and extension, but are also preferred over smooth surfaces and even neurotrophic ligands.Methods: Here, we performed axonal-outgrowth competition assays using a proprietary four-quadrant topography grid to determine the capacity of various micropatterned topographies to act as stimuli sequestering axon extension. Each topography in the grid consisted of an array of microscale (approximately 2 µm or submicroscale (approximately 300 nm holes or lines with variable dimensions. Individual rat embryonic hippocampal cells were positioned either between two juxtaposing topographies or at the borders of individual topographies juxtaposing unpatterned smooth surface, cultured for 24 hours, and analyzed with respect to axonal selection using conventional imaging techniques.Results: Topography was found to influence axon formation and extension relative to smooth surface, and the distance of neurons relative to topography was found to impact whether the topography could serve as an effective cue. Neurons were also found to prefer submicroscale over microscale features and holes over lines for a given feature size.Conclusion: The results suggest that implementing physical cues of various shapes and sizes on nerve guidance conduits

  8. The ENU-3 protein family members function in the Wnt pathway parallel to UNC-6/Netrin to promote motor neuron axon outgrowth in C. elegans.

    Science.gov (United States)

    Florica, Roxana Oriana; Hipolito, Victoria; Bautista, Stephen; Anvari, Homa; Rapp, Chloe; El-Rass, Suzan; Asgharian, Alimohammad; Antonescu, Costin N; Killeen, Marie T

    2017-10-01

    The axons of the DA and DB classes of motor neurons fail to reach the dorsal cord in the absence of the guidance cue UNC-6/Netrin or its receptor UNC-5 in C. elegans. However, the axonal processes usually exit their cell bodies in the ventral cord in the absence of both molecules. Strains lacking functional versions of UNC-6 or UNC-5 have a low level of DA and DB motor neuron axon outgrowth defects. We found that mutations in the genes for all six of the ENU-3 proteins function to enhance the outgrowth defects of the DA and DB axons in strains lacking either UNC-6 or UNC-5. A mutation in the gene for the MIG-14/Wntless protein also enhances defects in a strain lacking either UNC-5 or UNC-6, suggesting that the ENU-3 and Wnt pathways function parallel to the Netrin pathway in directing motor neuron axon outgrowth. Our evidence suggests that the ENU-3 proteins are novel members of the Wnt pathway in nematodes. Five of the six members of the ENU-3 family are predicted to be single-pass trans-membrane proteins. The expression pattern of ENU-3.1 was consistent with plasma membrane localization. One family member, ENU-3.6, lacks the predicted signal peptide and the membrane-spanning domain. In HeLa cells ENU-3.6 had a cytoplasmic localization and caused actin dependent processes to appear. We conclude that the ENU-3 family proteins function in a pathway parallel to the UNC-6/Netrin pathway for motor neuron axon outgrowth, most likely in the Wnt pathway. Copyright © 2017 Elsevier Inc. All rights reserved.

  9. Central connectivity of transient receptor potential melastatin 8-expressing axons in the brain stem and spinal dorsal horn.

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    Yun Sook Kim

    Full Text Available Transient receptor potential melastatin 8 (TRPM8 ion channels mediate the detection of noxious and innocuous cold and are expressed by primary sensory neurons, but little is known about the processing of the TRPM8-mediated cold information within the trigeminal sensory nuclei (TSN and the spinal dorsal horn (DH. To address this issue, we characterized TRPM8-positive (+ neurons in the trigeminal ganglion and investigated the distribution of TRPM8+ axons and terminals, and their synaptic organization in the TSN and in the DH using light and electron microscopic immunohistochemistry in transgenic mice expressing a genetically encoded axonal tracer in TRPM8+ neurons. TRPM8 was expressed in a fraction of small myelinated primary afferent fibers (23.7% and unmyelinated fibers (76.3%, suggesting that TRPM8-mediated cold is conveyed via C and Aδ afferents. TRPM8+ axons were observed in all TSN, but at different densities in the dorsal and ventral areas of the rostral TSN, which dominantly receive sensory afferents from intra- and peri-oral structures and from the face, respectively. While synaptic boutons arising from Aδ and non-peptidergic C afferents usually receive many axoaxonic contacts and form complex synaptic arrangements, TRPM8+ boutons arising from afferents of the same classes of fibers showed a unique synaptic connectivity; simple synapses with one or two dendrites and sparse axoaxonic contacts. These findings suggest that TRPM8-mediated cold is conveyed via a specific subset of C and Aδ afferent neurons and is processed in a unique manner and differently in the TSN and DH.

  10. Large-scale Topographical Screen for Investigation of Physical Neural-Guidance Cues

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    Li, Wei; Tang, Qing Yuan; Jadhav, Amol D.; Narang, Ankit; Qian, Wei Xian; Shi, Peng; Pang, Stella W.

    2015-03-01

    A combinatorial approach was used to present primary neurons with a large library of topographical features in the form of micropatterned substrate for high-throughput screening of physical neural-guidance cues that can effectively promote different aspects of neuronal development, including axon and dendritic outgrowth. Notably, the neuronal-guidance capability of specific features was automatically identified using a customized image processing software, thus significantly increasing the screening throughput with minimal subjective bias. Our results indicate that the anisotropic topographies promote axonal and in some cases dendritic extension relative to the isotropic topographies, while dendritic branching showed preference to plain substrates over the microscale features. The results from this work can be readily applied towards engineering novel biomaterials with precise surface topography that can serve as guidance conduits for neuro-regenerative applications. This novel topographical screening strategy combined with the automated processing capability can also be used for high-throughput screening of chemical or genetic regulatory factors in primary neurons.

  11. Transcallosal Projections Require Glycoprotein M6-Dependent Neurite Growth and Guidance.

    Science.gov (United States)

    Mita, Sakura; de Monasterio-Schrader, Patricia; Fünfschilling, Ursula; Kawasaki, Takahiko; Mizuno, Hidenobu; Iwasato, Takuji; Nave, Klaus-Armin; Werner, Hauke B; Hirata, Tatsumi

    2015-11-01

    The function of mature neurons critically relies on the developmental outgrowth and projection of their cellular processes. It has long been postulated that the neuronal glycoproteins M6a and M6b are involved in axon growth because these four-transmembrane domain-proteins of the proteolipid protein family are highly enriched on growth cones, but in vivo evidence has been lacking. Here, we report that the function of M6 proteins is required for normal axonal extension and guidance in vivo. In mice lacking both M6a and M6b, a severe hypoplasia of axon tracts was manifested. Most strikingly, the corpus callosum was reduced in thickness despite normal densities of cortical projection neurons. In single neuron tracing, many axons appeared shorter and disorganized in the double-mutant cortex, and some of them were even misdirected laterally toward the subcortex. Probst bundles were not observed. Upon culturing, double-mutant cortical and cerebellar neurons displayed impaired neurite outgrowth, indicating a cell-intrinsic function of M6 proteins. A rescue experiment showed that the intracellular loop of M6a is essential for the support of neurite extension. We propose that M6 proteins are required for proper extension and guidance of callosal axons that follow one of the most complex trajectories in the mammalian nervous system. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  12. Slowing of axonal regeneration is correlated with increased axonal viscosity during aging

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    Heidemann Steven R

    2010-10-01

    Full Text Available Abstract Background As we age, the speed of axonal regeneration declines. At the biophysical level, why this occurs is not well understood. Results To investigate we first measured the rate of axonal elongation of sensory neurons cultured from neonatal and adult rats. We found that neonatal axons grew 40% faster than adult axons (11.5 µm/hour vs. 8.2 µm/hour. To determine how the mechanical properties of axons change during maturation, we used force calibrated towing needles to measure the viscosity (stiffness and strength of substrate adhesion of neonatal and adult sensory axons. We found no significant difference in the strength of adhesions, but did find that adult axons were 3 times intrinsically stiffer than neonatal axons. Conclusions Taken together, our results suggest decreasing axonal stiffness may be part of an effective strategy to accelerate the regeneration of axons in the adult peripheral nervous system.

  13. Tyrosine phosphorylation and proteolytic cleavage of Notch are required for non-canonical Notch/Abl signaling in Drosophila axon guidance.

    Science.gov (United States)

    Kannan, Ramakrishnan; Cox, Eric; Wang, Lei; Kuzina, Irina; Gu, Qun; Giniger, Edward

    2018-01-17

    Notch signaling is required for the development and physiology of nearly every tissue in metazoans. Much of Notch signaling is mediated by transcriptional regulation of downstream target genes, but Notch controls axon patterning in Drosophila by local modulation of Abl tyrosine kinase signaling, via direct interactions with the Abl co-factors Disabled and Trio. Here, we show that Notch-Abl axonal signaling requires both of the proteolytic cleavage events that initiate canonical Notch signaling. We further show that some Notch protein is tyrosine phosphorylated in Drosophila , that this form of the protein is selectively associated with Disabled and Trio, and that relevant tyrosines are essential for Notch-dependent axon patterning but not for canonical Notch-dependent regulation of cell fate. Based on these data, we propose a model for the molecular mechanism by which Notch controls Abl signaling in Drosophila axons. © 2018. Published by The Company of Biologists Ltd.

  14. Dynamics of target recognition by interstitial axon branching along developing cortical axons.

    Science.gov (United States)

    Bastmeyer, M; O'Leary, D D

    1996-02-15

    Corticospinal axons innervate their midbrain, hindbrain, and spinal targets by extending collateral branches interstitially along their length. To establish that the axon shaft rather than the axonal growth cone is responsible for target recognition in this system, and to characterize the dynamics of interstitial branch formation, we have studied this process in an in vivo-like setting using slice cultures from neonatal mice containing the entire pathway of corticospinal axons. Corticospinal axons labeled with the dye 1,1'-dioctodecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (or Dil) were imaged using time-lapse video microscopy of their pathway overlying the basilar pons, their major hindbrain target. The axon shaft millimeters behind the growth cone exhibits several dynamic behaviors, including the de novo formation of varicosities and filopodia-like extensions, and a behavior that we term "pulsation," which is characterized by a variable thickening and thining of short segments of the axon. An individual axon can have multiple sites of branching activity, with many of the branches being transient. These dynamic behaviors occur along the portion of the axon shaft overlying the basilar pons, but not just caudal to it. Once the collaterals extend into the pontine neuropil, they branch further in the neuropil, while the parent axon becomes quiescent. Thus, the branching activity is spatially restricted to specific portions of the axon, as well as temporally restricted to a relatively brief time window. These findings provide definitive evidence that collateral branches form de novo along corticospinal axons and establish that the process of target recognition in this system is a property of the axon shaft rather than the leading growth cone.

  15. An in vitro study of peptide-loaded alginate nanospheres for antagonizing the inhibitory effect of Nogo-A protein on axonal growth

    International Nuclear Information System (INIS)

    Zhai, Peng; Chen, X B; Schreyer, David J

    2015-01-01

    The adult mammalian central nervous system has limited ability to regenerate after injury. This is due, in part, to the presence of myelin-associated axon growth inhibitory proteins such as Nogo-A that bind and activate the Nogo receptor, leading to profound inhibition of actin-based motility within the growing axon tip. This paper presents an in vitro study of the use of a Nogo receptor-blocking peptide to antagonize the inhibitory effect of Nogo-A on axon growth. Alginate nanospheres were fabricated using an emulsion technique and loaded with Nogo receptor-blocking peptide, or with other model proteins. Protein release profiles were studied, and retention of the bioactivity of released proteins was verified. Primary dorsal root ganglion neurons were cultured and their ability to grow neurites was challenged with Nogo-A chimeric protein in the absence or presence of Nogo receptor antagonist peptide-loaded alginate nanospheres. Our results demonstrate that peptide released from alginate nanospheres could overcome the growth inhibitory effect of Nogo-A, suggesting that a similar peptide delivery strategy using alginate nanospheres might be used to improve axon regeneration within the injured central nervous system. (paper)

  16. Vesicular trafficking of semaphorin 3A is activity-dependent and differs between axons and dendrites

    NARCIS (Netherlands)

    de Wit, Joris; Toonen, Ruud F; Verhaagen, J.; Verhage, Matthijs

    Secreted semaphorins act as guidance cues in the developing nervous system and may have additional functions in mature neurons. How semaphorins are transported and secreted by neurons is poorly understood. We find that endogenous semaphorin 3A (Sema3A) displays a punctate distribution in axons and

  17. Reph, a regulator of Eph receptor expression in the Drosophila melanogaster optic lobe.

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    Richard E Dearborn

    Full Text Available Receptors of the Eph family of tyrosine kinases and their Ephrin ligands are involved in developmental processes as diverse as angiogenesis, axon guidance and cell migration. However, our understanding of the Eph signaling pathway is incomplete, and could benefit from an analysis by genetic methods. To this end, we performed a genetic modifier screen for mutations that affect Eph signaling in Drosophila melanogaster. Several dozen loci were identified on the basis of their suppression or enhancement of an eye defect induced by the ectopic expression of Ephrin during development; many of these mutant loci were found to disrupt visual system development. One modifier locus, reph (regulator of eph expression, was characterized in molecular detail and found to encode a putative nuclear protein that interacts genetically with Eph signaling pathway mutations. Reph is an autonomous regulator of Eph receptor expression, required for the graded expression of Eph protein and the establishment of an optic lobe axonal topographic map. These results reveal a novel component of the regulatory pathway controlling expression of eph and identify reph as a novel factor in the developing visual system.

  18. Early development of the circumferential axonal pathway in mouse and chick spinal cord.

    Science.gov (United States)

    Holley, J A

    1982-03-10

    The early development of the circumferential axonal pathway in the brachial and lumbar spinal cord of mouse and chick embryos was studied by scanning and transmission electron microscopy. The cellular processes which comprise this pathway grow in the transverse plane and along the lateral margin of the marginal zone (i.e., circumferentially oriented), as typified by the early embryonic commissural axons. The first formative event observed was in the ventrolateral margin of the primitive spinal cord ventricular zone. Cellular processes were found near the external limiting membrane that appeared to grow a variable distance either dorsally or ventrally. Later in development, presumptive motor column neurons migrated into the ventrolateral region, distal to these early circumferentially oriented processes. Concurrently, other circumferentially oriented perikarya and processes appeared along the dorsolateral margin. Due to their aligned sites of origin and parallel growth, the circumferential processes formed a more or less continuous line or pathway, which in about 10% of the scanned specimens could be followed along the entire lateral margin of the embryonic spinal cord. Several specimens later in development had two sets of aligned circumferential processes in the ventral region. Large numbers of circumferential axons were then found to follow the preformed pathway by fasciculation, after the primitive motor column had become established. Since the earliest circumferential processes appeared to differentiate into axons and were found nearly 24 hours prior to growth of most circumferential axons, their role in guidance as pioneering axons was suggested.

  19. Dendrosomatic Sonic Hedgehog Signaling in Hippocampal Neurons Regulates Axon Elongation

    Science.gov (United States)

    Petralia, Ronald S.; Ott, Carolyn; Wang, Ya-Xian; Lippincott-Schwartz, Jennifer; Mattson, Mark P.

    2015-01-01

    The presence of Sonic Hedgehog (Shh) and its signaling components in the neurons of the hippocampus raises a question about what role the Shh signaling pathway may play in these neurons. We show here that activation of the Shh signaling pathway stimulates axon elongation in rat hippocampal neurons. This Shh-induced effect depends on the pathway transducer Smoothened (Smo) and the transcription factor Gli1. The axon itself does not respond directly to Shh; instead, the Shh signal transduction originates from the somatodendritic region of the neurons and occurs in neurons with and without detectable primary cilia. Upon Shh stimulation, Smo localization to dendrites increases significantly. Shh pathway activation results in increased levels of profilin1 (Pfn1), an actin-binding protein. Mutations in Pfn1's actin-binding sites or reduction of Pfn1 eliminate the Shh-induced axon elongation. These findings indicate that Shh can regulate axon growth, which may be critical for development of hippocampal neurons. SIGNIFICANCE STATEMENT Although numerous signaling mechanisms have been identified that act directly on axons to regulate their outgrowth, it is not known whether signals transduced in dendrites may also affect axon outgrowth. We describe here a transcellular signaling pathway in embryonic hippocampal neurons in which activation of Sonic Hedgehog (Shh) receptors in dendrites stimulates axon growth. The pathway involves the dendritic-membrane-associated Shh signal transducer Smoothened (Smo) and the transcription factor Gli, which induces the expression of the gene encoding the actin-binding protein profilin 1. Our findings suggest scenarios in which stimulation of Shh in dendrites results in accelerated outgrowth of the axon, which therefore reaches its presumptive postsynaptic target cell more quickly. By this mechanism, Shh may play critical roles in the development of hippocampal neuronal circuits. PMID:26658865

  20. Overexpression of Pax6 results in microphthalmia, retinal dysplasia and defective retinal ganglion cell axon guidance

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    Jeffery Glen

    2008-05-01

    Full Text Available Abstract Background The transcription factor Pax6 is expressed by many cell types in the developing eye. Eyes do not form in homozygous loss-of-function mouse mutants (Pax6Sey/Sey and are abnormally small in Pax6Sey/+ mutants. Eyes are also abnormally small in PAX77 mice expressing multiple copies of human PAX6 in addition to endogenous Pax6; protein sequences are identical in the two species. The developmental events that lead to microphthalmia in PAX77 mice are not well-characterised, so it is not clear whether over- and under-expression of Pax6/PAX6 cause microphthalmia through similar mechanisms. Here, we examined the consequences of over-expression for the eye and its axonal connections. Results Eyes form in PAX77+/+ embryos but subsequently degenerate. At E12.5, we found no abnormalities in ocular morphology, retinal cell cycle parameters and the incidence of retinal cell death. From E14.5 on, we observed malformations of the optic disc. From E16.5 into postnatal life there is progressively more severe retinal dysplasia and microphthalmia. Analyses of patterns of gene expression indicated that PAX77+/+ retinae produce a normal range of cell types, including retinal ganglion cells (RGCs. At E14.5 and E16.5, quantitative RT-PCR with probes for a range of molecules associated with retinal development showed only one significant change: a slight reduction in levels of mRNA encoding the secreted morphogen Shh at E16.5. At E16.5, tract-tracing with carbocyanine dyes in PAX77+/+ embryos revealed errors in intraretinal navigation by RGC axons, a decrease in the number of RGC axons reaching the thalamus and an increase in the proportion of ipsilateral projections among those RGC axons that do reach the thalamus. A survey of embryos with different Pax6/PAX6 gene dosage (Pax6Sey/+, Pax6+/+, PAX77+ and PAX77+/+ showed that (1 the total number of RGC axons projected by the retina and (2 the proportions that are sorted into the ipsilateral and

  1. Navigating neurites utilize cellular topography of Schwann cell somas and processes for optimal guidance

    Science.gov (United States)

    Lopez-Fagundo, Cristina; Mitchel, Jennifer A.; Ramchal, Talisha D.; Dingle, Yu-Ting L.; Hoffman-Kim, Diane

    2013-01-01

    The path created by aligned Schwann cells (SCs) after nerve injury underlies peripheral nerve regeneration. We developed geometric bioinspired substrates to extract key information needed for axon guidance by deconstructing the topographical cues presented by SCs. We have previously reported materials that directly replicate SC topography with micro- and nanoscale resolution, but a detailed explanation of the means of directed axon extension on SC topography has not yet been described. Here, using neurite tracing and time-lapse microscopy, we analyzed the SC features that influence axon guidance. Novel poly(dimethylsiloxane) materials, fabricated via photolithography, incorporated bioinspired topographical components with the shapes and sizes of aligned SCs, namely somas and processes, where the length of the processes were varied but the soma geometry and dimensions were kept constant. Rat dorsal root ganglia neurites aligned to all materials presenting bioinspired topography after a 5 days in culture and to bioinspired materials presenting soma and process features after only 17 hours in culture. Key findings of this study were: Neurite response to underlying bioinspired topographical features was time dependent, where at 5 days, neurites aligned most strongly to materials presenting combinations of soma and process features, with higher than average density of either process or soma features; but at 17 hours they aligned more strongly to materials presenting average densities of soma and process features and to materials presenting process features only. These studies elucidate the influence of SC topography on axon guidance in a time-dependent setting and have implications for the optimization of nerve regeneration strategies. PMID:23557939

  2. Organophosphate-Related Alterations in Myelin and Axonal Transport in the Living Mammalian Brain

    Science.gov (United States)

    2014-10-01

    stress, impairments of mitochondrial function, neuroinflammation, altered neurotrophin responses, etc. (reviewed, Soltaninejad and Abdollahi, 2009...Exposure to Chlorpyrifos in Rats: Protracted Effects on Axonal Transport, Neurotrophin Receptors, Cholinergic Markers, and Information Processing

  3. Dissecting Repulsive Guidance Molecule/Neogenin function and signaling during neural development

    NARCIS (Netherlands)

    van den Heuvel, D.M.A.

    2013-01-01

    During neural development a series of precisely ordered cellular processes acts to establish a functional brain comprising millions of neurons and many more neuronal connections. Neogenin and its repulsive guidance molecule (RGM) ligands contribute to neuronal network formation by inducing axon

  4. Accelerated axon outgrowth, guidance, and target reinnervation across nerve transection gaps following a brief electrical stimulation paradigm.

    Science.gov (United States)

    Singh, Bhagat; Xu, Qing-Gui; Franz, Colin K; Zhang, Rumi; Dalton, Colin; Gordon, Tessa; Verge, Valerie M K; Midha, Rajiv; Zochodne, Douglas W

    2012-03-01

    Regeneration of peripheral nerves is remarkably restrained across transection injuries, limiting recovery of function. Strategies to reverse this common and unfortunate outcome are limited. Remarkably, however, new evidence suggests that a brief extracellular electrical stimulation (ES), delivered at the time of injury, improves the regrowth of motor and sensory axons. In this work, the authors explored and tested this ES paradigm, which was applied proximal to transected sciatic nerves in mice, and identified several novel and compelling impacts of the approach. Using thy-1 yellow fluorescent protein mice with fluorescent axons that allow serial in vivo tracking of regeneration, the morphological, electrophysiological, and behavioral indices of nerve regrowth were measured. The authors show that ES is associated with a 30%-50% improvement in several indices of regeneration: regrowth of axons and their partnered Schwann cells across transection sites, maturation of regenerated fibers in gaps spanning transection zones, and entry of axons into their muscle and cutaneous target zones. In parallel studies, the authors analyzed adult sensory neurons and their response to extracellular ES while plated on a novel microelectrode array construct designed to deliver the identical ES paradigm used in vivo. The ES accelerated neurite outgrowth, supporting the concept of a neuron-autonomous mechanism of action. Taken together, these results support a robust role for brief ES following peripheral nerve injuries in promoting regeneration. Electrical stimulation has a wider repertoire of impact than previously recognized, and its impact in vitro supports the hypothesis that a neuron-specific reprogrammed injury response is recruited by the ES protocol.

  5. Action Potential Dynamics in Fine Axons Probed with an Axonally Targeted Optical Voltage Sensor.

    Science.gov (United States)

    Ma, Yihe; Bayguinov, Peter O; Jackson, Meyer B

    2017-01-01

    The complex and malleable conduction properties of axons determine how action potentials propagate through extensive axonal arbors to reach synaptic terminals. The excitability of axonal membranes plays a major role in neural circuit function, but because most axons are too thin for conventional electrical recording, their properties remain largely unexplored. To overcome this obstacle, we used a genetically encoded hybrid voltage sensor (hVOS) harboring an axonal targeting motif. Expressing this probe in transgenic mice enabled us to monitor voltage changes optically in two populations of axons in hippocampal slices, the large axons of dentate granule cells (mossy fibers) in the stratum lucidum of the CA3 region and the much finer axons of hilar mossy cells in the inner molecular layer of the dentate gyrus. Action potentials propagated with distinct velocities in each type of axon. Repetitive firing broadened action potentials in both populations, but at an intermediate frequency the degree of broadening differed. Repetitive firing also attenuated action potential amplitudes in both mossy cell and granule cell axons. These results indicate that the features of use-dependent action potential broadening, and possible failure, observed previously in large nerve terminals also appear in much finer unmyelinated axons. Subtle differences in the frequency dependences could influence the propagation of activity through different pathways to excite different populations of neurons. The axonally targeted hVOS probe used here opens up the diverse repertoire of neuronal processes to detailed biophysical study.

  6. Axon-Axon Interactions Regulate Topographic Optic Tract Sorting via CYFIP2-Dependent WAVE Complex Function.

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    Cioni, Jean-Michel; Wong, Hovy Ho-Wai; Bressan, Dario; Kodama, Lay; Harris, William A; Holt, Christine E

    2018-03-07

    The axons of retinal ganglion cells (RGCs) are topographically sorted before they arrive at the optic tectum. This pre-target sorting, typical of axon tracts throughout the brain, is poorly understood. Here, we show that cytoplasmic FMR1-interacting proteins (CYFIPs) fulfill non-redundant functions in RGCs, with CYFIP1 mediating axon growth and CYFIP2 specifically involved in axon sorting. We find that CYFIP2 mediates homotypic and heterotypic contact-triggered fasciculation and repulsion responses between dorsal and ventral axons. CYFIP2 associates with transporting ribonucleoprotein particles in axons and regulates translation. Axon-axon contact stimulates CYFIP2 to move into growth cones where it joins the actin nucleating WAVE regulatory complex (WRC) in the periphery and regulates actin remodeling and filopodial dynamics. CYFIP2's function in axon sorting is mediated by its binding to the WRC but not its translational regulation. Together, these findings uncover CYFIP2 as a key regulatory link between axon-axon interactions, filopodial dynamics, and optic tract sorting. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

  7. Effect of Long-Term Cannabis Use on Axonal Fibre Connectivity

    Science.gov (United States)

    Zalesky, Andrew; Solowij, Nadia; Yucel, Murat; Lubman, Dan I.; Takagi, Michael; Harding, Ian H.; Lorenzetti, Valentina; Wang, Ruopeng; Searle, Karissa; Pantelis, Christos; Seal, Marc

    2012-01-01

    Cannabis use typically begins during adolescence and early adulthood, a period when cannabinoid receptors are still abundant in white matter pathways across the brain. However, few studies to date have explored the impact of regular cannabis use on white matter structure, with no previous studies examining its impact on axonal connectivity. The…

  8. Dcc regulates asymmetric outgrowth of forebrain neurons in zebrafish.

    Directory of Open Access Journals (Sweden)

    Jingxia Gao

    Full Text Available The guidance receptor DCC (deleted in colorectal cancer ortholog UNC-40 regulates neuronal asymmetry development in Caenorhabditis elegans, but it is not known whether DCC plays a role in the specification of neuronal polarity in vertebrates. To examine the roles of DCC in neuronal asymmetry regulation in vertebrates, we studied zebrafish anterior dorsal telencephalon (ADt neuronal axons. We generated transgenic zebrafish animals expressing the photo-convertible fluorescent protein Kaede in ADt neurons and then photo-converted Kaede to label specifically the ADt neuron axons. We found that ADt axons normally project ventrally. Knock down of Dcc function by injecting antisense morpholino oligonucleotides caused the ADt neurons to project axons dorsally. To examine the axon projection pattern of individual ADt neurons, we labeled single ADt neurons using a forebrain-specific promoter to drive fluorescent protein expression. We found that individual ADt neurons projected axons dorsally or formed multiple processes after morpholino knock down of Dcc function. We further found that knock down of the Dcc ligand, Netrin1, also caused ADt neurons to project axons dorsally. Knockdown of Neogenin1, a guidance receptor closely related to Dcc, enhanced the formation of aberrant dorsal axons in embryos injected with Dcc morpholino. These experiments provide the first evidence that Dcc regulates polarized axon initiation and asymmetric outgrowth of forebrain neurons in vertebrates.

  9. Delineating neurotrophin-3 dependent signaling pathways underlying sympathetic axon growth along intermediate targets.

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    Keeler, Austin B; Suo, Dong; Park, Juyeon; Deppmann, Christopher D

    2017-07-01

    Postganglionic sympathetic neurons detect vascular derived neurotrophin 3 (NT3) via the axonally expressed receptor tyrosine kinase, TrkA, to promote chemo-attraction along intermediate targets. Once axons arrive to their final target, a structurally related neurotrophic factor, nerve growth factor (NGF), also acts through TrkA to promote final target innervation. Does TrkA signal differently at these different locales? We previously found that Coronin-1 is upregulated in sympathetic neurons upon exposure to NGF, thereby endowing the NGF-TrkA complex with new signaling capabilities (i.e. calcium signaling), which dampens axon growth and branching. Based on the notion that axons do not express functional levels of Coronin-1 prior to final target innervation, we developed an in vitro model for axon growth and branching along intermediate targets using Coro1a -/- neurons grown in NT3. We found that, similar to NGF-TrkA, NT3-TrkA is capable of inducing MAPK and PI3K in the presence or absence of Coronin-1. However, unlike NGF, NT3 does not induce calcium release from intracellular stores. Using a combination of pharmacology, knockout neurons and in vitro functional assays, we suggest that the NT3-TrkA complex uses Ras/MAPK and/or PI3K-AKT signaling to induce axon growth and inhibit axon branching along intermediate targets. However, in the presence of Coronin-1, these signaling pathways lose their ability to impact NT3 dependent axon growth or branching. This is consistent with a role for Coronin-1 as a molecular switch for axon behavior and suggests that Coronin-1 suppresses NT3 dependent axon behavior. Copyright © 2017 Elsevier Inc. All rights reserved.

  10. Molecular Analysis of Sensory Axon Branching Unraveled a cGMP-Dependent Signaling Cascade.

    Science.gov (United States)

    Dumoulin, Alexandre; Ter-Avetisyan, Gohar; Schmidt, Hannes; Rathjen, Fritz G

    2018-04-24

    Axonal branching is a key process in the establishment of circuit connectivity within the nervous system. Molecular-genetic studies have shown that a specific form of axonal branching—the bifurcation of sensory neurons at the transition zone between the peripheral and the central nervous system—is regulated by a cyclic guanosine monophosphate (cGMP)-dependent signaling cascade which is composed of C-type natriuretic peptide (CNP), the receptor guanylyl cyclase Npr2, and cGMP-dependent protein kinase Iα (cGKIα). In the absence of any one of these components, neurons in dorsal root ganglia (DRG) and cranial sensory ganglia no longer bifurcate, and instead turn in either an ascending or a descending direction. In contrast, collateral axonal branch formation which represents a second type of axonal branch formation is not affected by inactivation of CNP, Npr2, or cGKI. Whereas axon bifurcation was lost in mouse mutants deficient for components of CNP-induced cGMP formation; the absence of the cGMP-degrading enzyme phosphodiesterase 2A had no effect on axon bifurcation. Adult mice that lack sensory axon bifurcation due to the conditional inactivation of Npr2-mediated cGMP signaling in DRG neurons demonstrated an altered shape of sensory axon terminal fields in the spinal cord, indicating that elaborate compensatory mechanisms reorganize neuronal circuits in the absence of bifurcation. On a functional level, these mice showed impaired heat sensation and nociception induced by chemical irritants, whereas responses to cold sensation, mechanical stimulation, and motor coordination are normal. These data point to a critical role of axon bifurcation for the processing of acute pain perception.

  11. Molecular Analysis of Sensory Axon Branching Unraveled a cGMP-Dependent Signaling Cascade

    Directory of Open Access Journals (Sweden)

    Alexandre Dumoulin

    2018-04-01

    Full Text Available Axonal branching is a key process in the establishment of circuit connectivity within the nervous system. Molecular-genetic studies have shown that a specific form of axonal branching—the bifurcation of sensory neurons at the transition zone between the peripheral and the central nervous system—is regulated by a cyclic guanosine monophosphate (cGMP-dependent signaling cascade which is composed of C-type natriuretic peptide (CNP, the receptor guanylyl cyclase Npr2, and cGMP-dependent protein kinase Iα (cGKIα. In the absence of any one of these components, neurons in dorsal root ganglia (DRG and cranial sensory ganglia no longer bifurcate, and instead turn in either an ascending or a descending direction. In contrast, collateral axonal branch formation which represents a second type of axonal branch formation is not affected by inactivation of CNP, Npr2, or cGKI. Whereas axon bifurcation was lost in mouse mutants deficient for components of CNP-induced cGMP formation; the absence of the cGMP-degrading enzyme phosphodiesterase 2A had no effect on axon bifurcation. Adult mice that lack sensory axon bifurcation due to the conditional inactivation of Npr2-mediated cGMP signaling in DRG neurons demonstrated an altered shape of sensory axon terminal fields in the spinal cord, indicating that elaborate compensatory mechanisms reorganize neuronal circuits in the absence of bifurcation. On a functional level, these mice showed impaired heat sensation and nociception induced by chemical irritants, whereas responses to cold sensation, mechanical stimulation, and motor coordination are normal. These data point to a critical role of axon bifurcation for the processing of acute pain perception.

  12. Glia to axon RNA transfer.

    Science.gov (United States)

    Sotelo, José Roberto; Canclini, Lucía; Kun, Alejandra; Sotelo-Silveira, José Roberto; Calliari, Aldo; Cal, Karina; Bresque, Mariana; Dipaolo, Andrés; Farias, Joaquina; Mercer, John A

    2014-03-01

    The existence of RNA in axons has been a matter of dispute for decades. Evidence for RNA and ribosomes has now accumulated to a point at which it is difficult to question, much of the disputes turned to the origin of these axonal RNAs. In this review, we focus on studies addressing the origin of axonal RNAs and ribosomes. The neuronal soma as the source of most axonal RNAs has been demonstrated and is indisputable. However, the surrounding glial cells may be a supplemental source of axonal RNAs, a matter scarcely investigated in the literature. Here, we review the few papers that have demonstrated that glial-to-axon RNA transfer is not only feasible, but likely. We describe this process in both invertebrate axons and vertebrate axons. Schwann cell to axon ribosomes transfer was conclusively demonstrated (Court et al. [2008]: J. Neurosci 28:11024-11029; Court et al. [2011]: Glia 59:1529-1539). However, mRNA transfer still remains to be demonstrated in a conclusive way. The intercellular transport of mRNA has interesting implications, particularly with respect to the integration of glial and axonal function. This evolving field is likely to impact our understanding of the cell biology of the axon in both normal and pathological conditions. Most importantly, if the synthesis of proteins in the axon can be controlled by interacting glia, the possibilities for clinical interventions in injury and neurodegeneration are greatly increased. Copyright © 2013 Wiley Periodicals, Inc.

  13. The genetics of axonal transport and axonal transport disorders.

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    Jason E Duncan

    2006-09-01

    Full Text Available Neurons are specialized cells with a complex architecture that includes elaborate dendritic branches and a long, narrow axon that extends from the cell body to the synaptic terminal. The organized transport of essential biological materials throughout the neuron is required to support its growth, function, and viability. In this review, we focus on insights that have emerged from the genetic analysis of long-distance axonal transport between the cell body and the synaptic terminal. We also discuss recent genetic evidence that supports the hypothesis that disruptions in axonal transport may cause or dramatically contribute to neurodegenerative diseases.

  14. Utilizing Combined Methodologies to Define the Role of Plasma Membrane Delivery During Axon Branching and Neuronal Morphogenesis.

    Science.gov (United States)

    Winkle, Cortney C; Hanlin, Christopher C; Gupton, Stephanie L

    2016-03-16

    During neural development, growing axons extend to multiple synaptic partners by elaborating axonal branches. Axon branching is promoted by extracellular guidance cues like netrin-1 and results in dramatic increases to the surface area of the axonal plasma membrane. Netrin-1-dependent axon branching likely involves temporal and spatial control of plasma membrane expansion, the components of which are supplied through exocytic vesicle fusion. These fusion events are preceded by formation of SNARE complexes, comprising a v-SNARE, such as VAMP2 (vesicle-associated membrane protein 2), and plasma membrane t-SNAREs, syntaxin-1 and SNAP25 (synaptosomal-associated protein 25). Detailed herein isa multi-pronged approach used to examine the role of SNARE mediated exocytosis in axon branching. The strength of the combined approach is data acquisition at a range of spatial and temporal resolutions, spanning from the dynamics of single vesicle fusion events in individual neurons to SNARE complex formation and axon branching in populations of cultured neurons. This protocol takes advantage of established biochemical approaches to assay levels of endogenous SNARE complexes and Total Internal Reflection Fluorescence (TIRF) microscopy of cortical neurons expressing VAMP2 tagged with a pH-sensitive GFP (VAMP2-pHlourin) to identify netrin-1 dependent changes in exocytic activity in individual neurons. To elucidate the timing of netrin-1-dependent branching, time-lapse differential interference contrast (DIC) microscopy of single neurons over the order of hours is utilized. Fixed cell immunofluorescence paired with botulinum neurotoxins that cleave SNARE machinery and block exocytosis demonstrates that netrin-1 dependent axon branching requires SNARE-mediated exocytic activity.

  15. hnRNP R and its main interactor, the noncoding RNA 7SK, coregulate the axonal transcriptome of motoneurons.

    Science.gov (United States)

    Briese, Michael; Saal-Bauernschubert, Lena; Ji, Changhe; Moradi, Mehri; Ghanawi, Hanaa; Uhl, Michael; Appenzeller, Silke; Backofen, Rolf; Sendtner, Michael

    2018-03-20

    Disturbed RNA processing and subcellular transport contribute to the pathomechanisms of motoneuron diseases such as amyotrophic lateral sclerosis and spinal muscular atrophy. RNA-binding proteins are involved in these processes, but the mechanisms by which they regulate the subcellular diversity of transcriptomes, particularly in axons, are not understood. Heterogeneous nuclear ribonucleoprotein R (hnRNP R) interacts with several proteins involved in motoneuron diseases. It is located in axons of developing motoneurons, and its depletion causes defects in axon growth. Here, we used individual nucleotide-resolution cross-linking and immunoprecipitation (iCLIP) to determine the RNA interactome of hnRNP R in motoneurons. We identified ∼3,500 RNA targets, predominantly with functions in synaptic transmission and axon guidance. Among the RNA targets identified by iCLIP, the noncoding RNA 7SK was the top interactor of hnRNP R. We detected 7SK in the nucleus and also in the cytosol of motoneurons. In axons, 7SK localized in close proximity to hnRNP R, and depletion of hnRNP R reduced axonal 7SK. Furthermore, suppression of 7SK led to defective axon growth that was accompanied by axonal transcriptome alterations similar to those caused by hnRNP R depletion. Using a series of 7SK-deletion mutants, we show that the function of 7SK in axon elongation depends on its interaction with hnRNP R but not with the PTEF-B complex involved in transcriptional regulation. These results propose a role for 7SK as an essential interactor of hnRNP R to regulate its function in axon maintenance. Copyright © 2018 the Author(s). Published by PNAS.

  16. A regulatory code for neuron-specific odor receptor expression.

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    Anandasankar Ray

    2008-05-01

    Full Text Available Olfactory receptor neurons (ORNs must select-from a large repertoire-which odor receptors to express. In Drosophila, most ORNs express one of 60 Or genes, and most Or genes are expressed in a single ORN class in a process that produces a stereotyped receptor-to-neuron map. The construction of this map poses a problem of receptor gene regulation that is remarkable in its dimension and about which little is known. By using a phylogenetic approach and the genome sequences of 12 Drosophila species, we systematically identified regulatory elements that are evolutionarily conserved and specific for individual Or genes of the maxillary palp. Genetic analysis of these elements supports a model in which each receptor gene contains a zip code, consisting of elements that act positively to promote expression in a subset of ORN classes, and elements that restrict expression to a single ORN class. We identified a transcription factor, Scalloped, that mediates repression. Some elements are used in other chemosensory organs, and some are conserved upstream of axon-guidance genes. Surprisingly, the odor response spectra and organization of maxillary palp ORNs have been extremely well-conserved for tens of millions of years, even though the amino acid sequences of the receptors are not highly conserved. These results, taken together, define the logic by which individual ORNs in the maxillary palp select which odor receptors to express.

  17. Differential expression of anti-angiogenic factors and guidance genes in the developing macula.

    Science.gov (United States)

    Kozulin, Peter; Natoli, Riccardo; O'Brien, Keely M Bumsted; Madigan, Michele C; Provis, Jan M

    2009-01-01

    The primate retina contains a specialized, cone-rich macula, which mediates high acuity and color vision. The spatial resolution provided by the neural retina at the macula is optimized by stereotyped retinal blood vessel and ganglion cell axon patterning, which radiate away from the macula and reduce shadowing of macular photoreceptors. However, the genes that mediate these specializations, and the reasons for the vulnerability of the macula to degenerative disease, remain obscure. The aim of this study was to identify novel genes that may influence retinal vascular patterning and definition of the foveal avascular area. We used RNA from human fetal retinas at 19-20 weeks of gestation (WG; n=4) to measure differential gene expression in the macula, a region nasal to disc (nasal) and in the surrounding retina (surround) by hybridization to 12 GeneChip microarrays (HG-U133 Plus 2.0). The raw data was subjected to quality control assessment and preprocessing, using GC-RMA. We then used ANOVA analysis (Partek) Genomic Suite 6.3) and clustering (DAVID website) to identify the most highly represented genes clustered according to "biological process." The neural retina is fully differentiated at the macula at 19-20 WG, while neuronal progenitor cells are present throughout the rest of the retina. We therefore excluded genes associated with the cell cycle, and markers of differentiated neurons, from further analyses. Significantly regulated genes (pmacula versus surround" and "macula versus nasal." KEGG pathway clustering of the filtered gene lists identified 25 axon guidance-related genes that are differentially regulated in the macula. Furthermore, we found significant upregulation of three anti-angiogenic factors in the macula: pigment epithelium derived factor (PEDF), natriuretic peptide precurusor B (NPPB), and collagen type IValpha2. Differential expression of several members of the ephrin and semaphorin axon guidance gene families, PEDF, and NPPB was verified by

  18. EGFR Activation Mediates Inhibition of Axon Regeneration by Myelin and Chondroitin Sulfate Proteoglycans

    Science.gov (United States)

    Koprivica, Vuk; Cho, Kin-Sang; Park, Jong Bae; Yiu, Glenn; Atwal, Jasvinder; Gore, Bryan; Kim, Jieun A.; Lin, Estelle; Tessier-Lavigne, Marc; Chen, Dong Feng; He, Zhigang

    2005-10-01

    Inhibitory molecules associated with myelin and the glial scar limit axon regeneration in the adult central nervous system (CNS), but the underlying signaling mechanisms of regeneration inhibition are not fully understood. Here, we show that suppressing the kinase function of the epidermal growth factor receptor (EGFR) blocks the activities of both myelin inhibitors and chondroitin sulfate proteoglycans in inhibiting neurite outgrowth. In addition, regeneration inhibitors trigger the phosphorylation of EGFR in a calcium-dependent manner. Local administration of EGFR inhibitors promotes significant regeneration of injured optic nerve fibers, pointing to a promising therapeutic avenue for enhancing axon regeneration after CNS injury.

  19. Interactions between entorhinal axons and target hippocampal neurons: a role for glutamate in the development of hippocampal circuitry.

    Science.gov (United States)

    Mattson, M P; Lee, R E; Adams, M E; Guthrie, P B; Kater, S B

    1988-11-01

    A coculture system consisting of input axons from entorhinal cortex explants and target hippocampal pyramidal neurons was used to demonstrate that glutamate, released spontaneously from afferent axons, can influence both dendritic geometry of target neurons and formation of presumptive synaptic sites. Dendritic outgrowth was reduced in hippocampal neurons growing on entorhinal axons when compared with neurons growing off the axons. Presumptive presynaptic sites were observed in association with hippocampal neuron dendrites and somas. HPLC analysis showed that glutamate was released from the explants in an activity- and Ca2(+)-dependent manner. The general glutamate receptor antagonist D-glutamylglycine significantly increased dendritic outgrowth in pyramidal neurons associated with entorhinal axons and reduced presumptive presynaptic sites. Tetrodotoxin and reduction of extracellular Ca2+ also promoted dendritic outgrowth and reduced the formation of presumptive synaptic sites. The results suggest that the neurotransmitter glutamate may play important roles in the development of hippocampal circuitry.

  20. NMDA Receptors Regulate the Structural Plasticity of Spines and Axonal Boutons in Hippocampal Interneurons

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    Marta Perez-Rando

    2017-06-01

    Full Text Available N-methyl-D-aspartate receptors (NMDARs are present in both pyramidal neurons and interneurons of the hippocampus. These receptors play an important role in the adult structural plasticity of excitatory neurons, but their impact on the remodeling of interneurons is unknown. Among hippocampal interneurons, somatostatin-expressing cells located in the stratum oriens are of special interest because of their functional importance and structural characteristics: they display dendritic spines, which change density in response to different stimuli. In order to understand the role of NMDARs on the structural plasticity of these interneurons, we have injected acutely MK-801, an NMDAR antagonist, to adult mice which constitutively express enhanced green fluorescent protein (EGFP in these cells. We have behaviorally tested the animals, confirming effects of the drug on locomotion and anxiety-related behaviors. NMDARs were expressed in the somata and dendritic spines of somatostatin-expressing interneurons. Twenty-four hours after the injection, the density of spines did not vary, but we found a significant increase in the density of their en passant boutons (EPB. We have also used entorhino-hippocampal organotypic cultures to study these interneurons in real-time. There was a rapid decrease in the apparition rate of spines after MK-801 administration, which persisted for 24 h and returned to basal levels afterwards. A similar reversible decrease was detected in spine density. Our results show that both spines and axons of interneurons can undergo remodeling and highlight NMDARs as regulators of this plasticity. These results are specially relevant given the importance of all these players on hippocampal physiology and the etiopathology of certain psychiatric disorders.

  1. Neuron-glia signaling and the protection of axon function by Schwann cells.

    Science.gov (United States)

    Quintes, Susanne; Goebbels, Sandra; Saher, Gesine; Schwab, Markus H; Nave, Klaus-Armin

    2010-03-01

    The interaction between neurons and glial cells is a feature of all higher nervous systems. In the vertebrate peripheral nervous system, Schwann cells ensheath and myelinate axons thereby allowing rapid saltatory conduction and ensuring axonal integrity. Recently, some of the key molecules in neuron-Schwann cell signaling have been identified. Neuregulin-1 (NRG1) type III presented on the axonal surface determines the myelination fate of axons and controls myelin sheath thickness. Recent observations suggest that NRG1 regulates myelination via the control of Schwann cell cholesterol biosynthesis. This concept is supported by the finding that high cholesterol levels in Schwann cells are a rate-limiting factor for myelin protein production and transport of the major myelin protein P0 from the endoplasmic reticulum into the growing myelin sheath. NRG1 type III activates ErbB receptors on the Schwann cell, which leads to an increase in intracellular PIP3 levels via the PI3-kinase pathway. Surprisingly, enforced elevation of PIP3 levels by inactivation of the phosphatase PTEN in developing and mature Schwann cells does not entirely mimic NRG1 type III stimulated myelin growth, but predominantly causes focal hypermyelination starting at Schmidt-Lanterman incisures and nodes of Ranvier. This indicates that the glial transduction of pro-myelinating signals has to be under tight and life-long control to preserve integrity of the myelinated axon. Understanding the cross talk between neurons and Schwann cells will help to further define the role of glia in preserving axonal integrity and to develop therapeutic strategies for peripheral neuropathies such as CMT1A.

  2. Improved axonal regeneration of transected spinal cord mediated by multichannel collagen conduits functionalized with neurotrophin-3 gene.

    Science.gov (United States)

    Yao, L; Daly, W; Newland, B; Yao, S; Wang, W; Chen, B K K; Madigan, N; Windebank, A; Pandit, A

    2013-12-01

    Functionalized biomaterial scaffolds targeted at improving axonal regeneration by enhancing guided axonal growth provide a promising approach for the repair of spinal cord injury. Collagen neural conduits provide structural guidance for neural tissue regeneration, and in this study it is shown that these conduits can also act as a reservoir for sustained gene delivery. Either a G-luciferase marker gene or a neurotrophin-3-encoding gene, complexed to a non-viral, cyclized, PEGylated transfection vector, was loaded within a multichannel collagen conduit. The complexed genes were then released in a controlled fashion using a dual release system both in vitro and in vivo. For evaluation of their biological performance, the loaded conduits were implanted into the completely transected rat thoracic spinal cord (T8-T10). Aligned axon regeneration through the channels of conduits was observed one month post-surgery. The conduits delivering neurotrophin-3 polyplexes resulted in significantly increased neurotrophin-3 levels in the surrounding tissue and a statistically higher number of regenerated axons versus the control conduits (P<0.05). This study suggests that collagen neural conduits delivering a highly effective non-viral therapeutic gene may hold promise for repair of the injured spinal cord.

  3. Acute ethanol exposure inhibits silencing of cerebellar Golgi cell firing induced by granule cell axon input

    Directory of Open Access Journals (Sweden)

    Paolo eBotta

    2014-02-01

    Full Text Available Golgi cells (GoCs are specialized interneurons that provide inhibitory input to granule cells in the cerebellar cortex. GoCs are pacemaker neurons that spontaneously fire action potentials, triggering spontaneous inhibitory postsynaptic currents in granule cells and also contributing to the generation tonic GABAA receptor-mediated currents in granule cells. In turn, granule cell axons provide feedback glutamatergic input to GoCs. It has been shown that high frequency stimulation of granule cell axons induces a transient pause in GoC firing in a type 2-metabotropic glutamate receptor (mGluR2-dependent manner. Here, we investigated the effect ethanol on the pause of GoC firing induced by high frequency stimulation of granule cell axons. GoC electrophysiological recordings were performed in parasagittal cerebellar vermis slices from postnatal day 23 to 26 rats. Loose-patch cell-attached recordings revealed that ethanol (40 mM reversibly decreases the pause duration. An antagonist of mGluR2 reduced the pause duration but did not affect the effect of ethanol. Whole-cell voltage-clamp recordings showed that currents evoked by an mGluR2 agonist were not significantly affected by ethanol. Perforated-patch experiments in which hyperpolarizing and depolarizing currents were injected into GoCs demonstrated that there is an inverse relationship between spontaneous firing and pause duration. Slight inhibition of the Na+/K+ pump mimicked the effect of ethanol on pause duration. In conclusion, ethanol reduces the granule cell axon-mediated feedback mechanism by reducing the input responsiveness of GoCs. This would result in a transient increase of GABAA receptor-mediated inhibition of granule cells, limiting information flow at the input stage of the cerebellar cortex.

  4. Signal propagation along the axon.

    Science.gov (United States)

    Rama, Sylvain; Zbili, Mickaël; Debanne, Dominique

    2018-03-08

    Axons link distant brain regions and are usually considered as simple transmission cables in which reliable propagation occurs once an action potential has been generated. Safe propagation of action potentials relies on specific ion channel expression at strategic points of the axon such as nodes of Ranvier or axonal branch points. However, while action potentials are generally considered as the quantum of neuronal information, their signaling is not entirely digital. In fact, both their shape and their conduction speed have been shown to be modulated by activity, leading to regulations of synaptic latency and synaptic strength. We report here newly identified mechanisms of (1) safe spike propagation along the axon, (2) compartmentalization of action potential shape in the axon, (3) analog modulation of spike-evoked synaptic transmission and (4) alteration in conduction time after persistent regulation of axon morphology in central neurons. We discuss the contribution of these regulations in information processing. Copyright © 2018 Elsevier Ltd. All rights reserved.

  5. The axon guidance molecule semaphorin 3F is a negative regulator of tumor progression and proliferation in ileal neuroendocrine tumors

    Science.gov (United States)

    Vercherat, Cécile; Blanc, Martine; Lepinasse, Florian; Gadot, Nicolas; Couderc, Christophe; Poncet, Gilles; Walter, Thomas; Joly, Marie-Odile; Hervieu, Valérie; Scoazec, Jean-Yves; Roche, Colette

    2015-01-01

    Gastro-intestinal neuroendocrine tumors (GI-NETs) are rare neoplasms, frequently metastatic, raising difficult clinical and therapeutic challenges due to a poor knowledge of their biology. As neuroendocrine cells express both epithelial and neural cell markers, we studied the possible involvement in GI-NETs of axon guidance molecules, which have been shown to decrease tumor cell proliferation and metastatic dissemination in several tumor types. We focused on the role of Semaphorin 3F (SEMA3F) in ileal NETs, one of the most frequent subtypes of GI-NETs. SEMA3F expression was detected in normal neuroendocrine cells but was lost in most of human primary tumors and all their metastases. SEMA3F loss of expression was associated with promoter gene methylation. After increasing endogenous SEMA3F levels through stable transfection, enteroendocrine cell lines STC-1 and GluTag showed a reduced proliferation rate in vitro. In two different xenograft mouse models, SEMA3F-overexpressing cells exhibited a reduced ability to form tumors and a hampered liver dissemination potential in vivo. This resulted, at least in part, from the inhibition of mTOR and MAPK signaling pathways. This study demonstrates an anti-tumoral role of SEMA3F in ileal NETs. We thus suggest that SEMA3F and/or its cellular signaling pathway could represent a target for ileal NET therapy. PMID:26447612

  6. Two classes of astrocytes in the adult human and pig retina in terms of their expression of high affinity NGF receptor (TrkA).

    Science.gov (United States)

    Ruiz-Ederra, Javier; Hitchcock, Peter F; Vecino, Elena

    2003-02-13

    Astrocytes have been implicated in axon guidance and synaptic regeneration in the retina and these processes involve activation of the high affinity nerve growth factor receptor, known as the tyrosine kinase A (TrkA) receptor. The purpose of the present study was to characterize the expression of TrkA in astrocytes of the adult pig and human retina. To this end, sections of human and pig retinas were immunolabeled with a combination of antibodies to glial fibrillary acidic protein (GFAP) and TrkA. Our study revealed that most of the GFAP-positive cells express TrkA, whereas a rare, novel subpopulation of astrocytes was found to be devoid of TrkA. Our results support the idea that astrocytes play an important neurotrophic role in the retina.

  7. Trends in the design of nerve guidance channels in peripheral nerve tissue engineering.

    Science.gov (United States)

    Chiono, Valeria; Tonda-Turo, Chiara

    2015-08-01

    The current trend of peripheral nerve tissue engineering is the design of advanced nerve guidance channels (NGCs) acting as physical guidance for regeneration of nerves across lesions. NGCs should present multifunctional properties aiming to direct the sprouting of axons from the proximal nerve end, to concentrate growth factors secreted by the injured nerve ends, and to reduce the ingrowth of scar tissue into the injury site. A critical aspect in the design of NGCs is conferring them the ability to provide topographic, chemotactic and haptotactic cues that lead to functional nerve regeneration thus increasing the axon growth rate and avoiding or minimizing end-organ (e.g. muscle) atrophy. The present work reviews the recent state of the art in NGCs engineering and defines the external guide and internal fillers structural and compositional requirements that should be satisfied to improve nerve regeneration, especially in the case of large gaps (>2 cm). Techniques for NGCs fabrication were described highlighting the innovative approaches direct to enhance the regeneration of axon stumps compared to current clinical treatments. Furthermore, the possibility to apply stem cells as internal cues to the NGCs was discussed focusing on scaffold properties necessary to ensure cell survival. Finally, the optimized features for NGCs design were summarized showing as multifunctional cues are needed to produce NGCs having improved results in clinics. Copyright © 2015 Elsevier Ltd. All rights reserved.

  8. Axons take a dive

    Science.gov (United States)

    Tong, Cheuk Ka; Cebrián-Silla, Arantxa; Paredes, Mercedes F; Huang, Eric J; García-Verdugo, Jose Manuel; Alvarez-Buylla, Arturo

    2015-01-01

    In the walls of the lateral ventricles of the adult mammalian brain, neural stem cells (NSCs) and ependymal (E1) cells share the apical surface of the ventricular–subventricular zone (V–SVZ). In a recent article, we show that supraependymal serotonergic (5HT) axons originating from the raphe nuclei in mice form an extensive plexus on the walls of the lateral ventricles where they contact E1 cells and NSCs. Here we further characterize the contacts between 5HT supraependymal axons and E1 cells in mice, and show that suprependymal axons tightly associated to E1 cells are also present in the walls of the human lateral ventricles. These observations raise interesting questions about the function of supraependymal axons in the regulation of E1 cells. PMID:26413556

  9. Axonal regeneration in zebrafish spinal cord

    Science.gov (United States)

    Hui, Subhra Prakash

    2018-01-01

    Abstract In the present review we discuss two interrelated events—axonal damage and repair—known to occur after spinal cord injury (SCI) in the zebrafish. Adult zebrafish are capable of regenerating axonal tracts and can restore full functionality after SCI. Unlike fish, axon regeneration in the adult mammalian central nervous system is extremely limited. As a consequence of an injury there is very little repair of disengaged axons and therefore functional deficit persists after SCI in adult mammals. In contrast, peripheral nervous system axons readily regenerate following injury and hence allow functional recovery both in mammals and fish. A better mechanistic understanding of these three scenarios could provide a more comprehensive insight into the success or failure of axonal regeneration after SCI. This review summarizes the present understanding of the cellular and molecular basis of axonal regeneration, in both the peripheral nervous system and the central nervous system, and large scale gene expression analysis is used to focus on different events during regeneration. The discovery and identification of genes involved in zebrafish spinal cord regeneration and subsequent functional experimentation will provide more insight into the endogenous mechanism of myelination and remyelination. Furthermore, precise knowledge of the mechanism underlying the extraordinary axonal regeneration process in zebrafish will also allow us to unravel the potential therapeutic strategies to be implemented for enhancing regrowth and remyelination of axons in mammals. PMID:29721326

  10. Immunohistochemical and transcriptome analyses indicate complex breakdown of axonal transport mechanisms in canine distemper leukoencephalitis.

    Science.gov (United States)

    Spitzbarth, Ingo; Lempp, Charlotte; Kegler, Kristel; Ulrich, Reiner; Kalkuhl, Arno; Deschl, Ulrich; Baumgärtner, Wolfgang; Seehusen, Frauke

    2016-07-01

    CDV-DL (Canine distemper virus-induced demyelinating leukoencephalitis) represents a spontaneously occurring animal model for demyelinating disorders. Axonopathy represents a key pathomechanism in this disease; however, its underlying pathogenesis has not been addressed in detail so far. This study aimed at the characterization of axonal cytoskeletal, transport, and potential regenerative changes with a parallel focus upon Schwann cell remyelination. Immunohistochemistry of canine cerebellar tissue as well as a comparative analysis of genes from an independent microarray study were performed. Increased axonal immunoreactivity for nonphosphorylated neurofilament was followed by loss of cytoskeletal and motor proteins. Interestingly, a subset of genes encoding for neurofilament subunits and motor proteins was up-regulated in the chronic stage compared to dogs with subacute CDV-DL. However, immunohistochemically, hints for axonal regeneration were restricted to up-regulated axonal positivity of hypoxia-inducible factor 1 alpha, while growth-associated protein 43, erythropoietin and its receptor were not or even down-regulated. Periaxin-positive structures, indicative of Schwann cell remyelination, were only detected within few advanced lesions. The present findings demonstrate a complex sequence of axonal cytoskeletal breakdown mechanisms. Moreover, though sparse, this is the first report of Schwann cell remyelination in CDV-DL. Facilitation of these very limited endogenous regenerative responses represents an important topic for future research.

  11. The influence of electrospun fibre size on Schwann cell behaviour and axonal outgrowth

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    Gnavi, S., E-mail: sara.gnavi@unito.it [Department of Clinical and Biological Sciences, University of Torino, Orbassano 10043 (Italy); Neuroscience Institute of the Cavalieri-Ottolenghi Foundation, University of Torino, Orbassano 10043 (Italy); Fornasari, B.E., E-mail: benedettaelena.fornasari@unito.it [Department of Clinical and Biological Sciences, University of Torino, Orbassano 10043 (Italy); Neuroscience Institute of the Cavalieri-Ottolenghi Foundation, University of Torino, Orbassano 10043 (Italy); Tonda-Turo, C., E-mail: chiara.tondaturo@polito.it [Politecnico di Torino, Department of Mechanical and Aerospace Engineering, Politecnico of Torino, Torino 10100 (Italy); Ciardelli, G., E-mail: gianluca.ciardelli@polito.it [Politecnico di Torino, Department of Mechanical and Aerospace Engineering, Politecnico of Torino, Torino 10100 (Italy); CNR-IPCF UOS, Pisa 56124 (Italy); Zanetti, M., E-mail: marco.zanetti@unito.it [Nanostructured Interfaces and Surfaces, Department of Chemistry, University of Torino, Torino 10100 (Italy); Geuna, S., E-mail: stefano.geuna@unito.it [Department of Clinical and Biological Sciences, University of Torino, Orbassano 10043 (Italy); Neuroscience Institute of the Cavalieri-Ottolenghi Foundation, University of Torino, Orbassano 10043 (Italy); Perroteau, I., E-mail: isabelle.perroteau@unito.it [Department of Clinical and Biological Sciences, University of Torino, Orbassano 10043 (Italy)

    2015-03-01

    Fibrous substrates functioning as temporary extracellular matrices can be prepared easily by electrospinning, yielding fibrous matrices suitable as internal fillers for nerve guidance channels. In this study, gelatin micro- or nano-fibres were prepared by electrospinning by tuning the gelatin concentration and solution flow rate. The effect of gelatin fibre diameter on cell adhesion and proliferation was tested in vitro using explant cultures of Schwann cells (SC) and dorsal root ganglia (DRG). Cell adhesion was assessed by quantifying the cell spreading area, actin cytoskeleton organization and focal adhesion complex formation. Nano-fibres promoted cell spreading and actin cytoskeleton organization, increasing cellular adhesion and the proliferation rate. However, both migration rate and motility, quantified by transwell and time lapse assays respectively, were greater in cells cultured on micro-fibres. Finally, there was more DRG axon outgrowth on micro-fibres. These data suggest that the topography of electrospun gelatin fibres can be adjusted to modulate SC and axon organization and that both nano- and micro-fibres are promising fillers for the design of devices for peripheral nerve repair. - Highlights: • Electrospinning used to produce gelatin nano- and micro-fibre matrices. • Nano-fibre matrices promote Schwann cell organization and increase proliferation rate. • Micro-fibre matrices promote Schwann cell migration. • Micro-fibre matrices promote axonal outgrowth.

  12. Pαx6 expression in postmitotic neurons mediates the growth of axons in response to SFRP1.

    Directory of Open Access Journals (Sweden)

    Alvaro Sebastián-Serrano

    Full Text Available During development, the mechanisms that specify neuronal subclasses are coupled to those that determine their axonal response to guidance cues. Pax6 is a homedomain transcription factor required for the specification of a variety of neural precursors. After cell cycle exit, Pax6 expression is often shut down in the precursor progeny and most postmitotic neurons no longer express detectable levels of the protein. There are however exceptions and high Pax6 protein levels are found, for example, in postmitotic retinal ganglion cells (RGCs, dopaminergic neurons of the olfactory bulb and the limbic system in the telencephalon. The function of Pax6 in these differentiating neurons remains mostly elusive. Here, we demonstrate that Pax6 mediates the response of growing axons to SFRP1, a secreted molecule expressed in several Pax6-positive forebrain territories. Forced expression of Pax6 in cultured postmitotic cortical neurons, which do not normally express Pax6, was sufficient to increment axonal length. Growth was blocked by the addition of anti-SFRP1 antibodies, whereas exogenously added SFRP1 increased axonal growth of Pax6-transfected neurons but not that of control or untransfected cortical neurons. In the reverse scenario, shRNA-mediated knock-down of Pax6 in mouse retinal explants specifically abolished RGCs axonal growth induced by SFRP1, but had no effect on RGCs differentiation and it did not modify the effect of Shh or Netrin on axon growth. Taken together these results demonstrate that expression of Pax6 is necessary and sufficient to render postmitotic neurons competent to respond to SFRP1. These results reveal a novel and unexpected function of Pax6 in postmitotic neurons and situate Pax6 and SFRP1 as pair regulators of axonal connectivity.

  13. Pathophysiologic insights into motor axonal function in Kennedy disease.

    Science.gov (United States)

    Vucic, Steve; Kiernan, Matthew C

    2007-11-06

    Kennedy disease (KD), or spinobulbomuscular atrophy, is a slowly progressive inherited neurodegenerative disorder, marked by prominent fasciculations that typically precede the development of other symptoms. Although the genetic basis of KD relates to triplet (CAG) repeat expansion in the androgen receptor (AR) gene on the X chromosome, the mechanisms underlying the clinical presentation in KD have yet to be established. Consequently, the present study applied axonal excitability techniques to investigate the pathophysiologic mechanisms associated with KD. Peripheral nerve excitability studies were undertaken in 7 patients with KD with compound muscle action potentials (CMAP) recorded from the right abductor pollicis brevis. Strength-duration time constant (KD 0.54 +/- 0.03 msec; controls, 0.41 +/- 0.02 msec, p TEd [90 to 100 msec], 50.75 +/- 1.98%; controls TEd [90 to 100 msec], 45.67 +/- 0.67%, p < 0.01) and hyperpolarizing (KD TEh [90 to 100 msec], 128.5 +/- 6.9%; controls TEh [90 to 100 msec], 120.5 +/- 2.4%) conditioning pulses. Measurements of refractoriness, superexcitability, and late subexcitability changed appropriately for axonal hyperpolarization, perhaps reflecting the effects of increased ectopic activity. In total, the increase in the strength-duration time constant may be the primary event, occurring early in course of the disease, contributing to the development of axonal hyperexcitability in Kennedy disease, and thereby to the generation of fasciculations, a characteristic hallmark of the disease.

  14. Histological methods for assessing myelin sheaths and axons in human nerve trunks.

    Science.gov (United States)

    Miko, T L; Gschmeissner, S E

    1994-03-01

    Although there are many histological techniques for assessing myelin sheaths and axons in paraffin embedded or frozen sections of the peripheral nervous system, modern approaches usually use plastic embedded material. Although plastic embedding is superior for small cutaneous branches, this method has limited value for histological assessment of nerve trunks. We report three methods which together yield a comprehensive approach for thorough and detailed investigation of human nerve trunks. The rapid osmication method permitted assessment of myelinated nerve fibers from frozen sections at operation, thus providing the surgeon with guidance on the extent of nerve resection. The modification presented here resulted in permanent slides, allowing comparison of results with those of the other two procedures. The new osmium-hematoxylin technique could be performed on paraffin embedded nerves. Paraffin, unlike plastic, permitted the study of the whole cross sectional area of the nerve in single sections. Moreover, the sharp image of the myelin permitted computerized morphometry. The significantly modified axonal silver impregnation technique was performed on frozen sections mounted on glass slides, as opposed to the time-consuming impregnation of free-floating sections. The latter technique had a high success rate and permitted semiquantitative assessment of axons in nerve trunks. These methods can be performed in any routine histology laboratory and resulted in greater accuracy compared to conventional methods.

  15. En masse in vitro functional profiling of the axonal mechanosensitivity of sensory neurons.

    Science.gov (United States)

    Usoskin, Dmitry; Zilberter, Misha; Linnarsson, Sten; Hjerling-Leffler, Jens; Uhlén, Per; Harkany, Tibor; Ernfors, Patrik

    2010-09-14

    Perception of the environment relies on somatosensory neurons. Mechanosensory, proprioceptor and many nociceptor subtypes of these neurons have specific mechanosensitivity profiles to adequately differentiate stimulus patterns. Nevertheless, the cellular basis of differential mechanosensation remains largely elusive. Successful transduction of sensory information relies on the recruitment of sensory neurons and mechanosensation occurring at their peripheral axonal endings in vivo. Conspicuously, existing in vitro models aimed to decipher molecular mechanisms of mechanosensation test single sensory neuron somata at any one time. Here, we introduce a compartmental in vitro chamber design to deliver precisely controlled mechanical stimulation of sensory axons with synchronous real-time imaging of Ca(2+) transients in neuronal somata that reliably reflect action potential firing patterns. We report of three previously not characterized types of mechanosensitive neuron subpopulations with distinct intrinsic axonal properties tuned specifically to static indentation or vibration stimuli, showing that different classes of sensory neurons are tuned to specific types of mechanical stimuli. Primary receptor currents of vibration neurons display rapidly adapting conductance reliably detected for every single stimulus during vibration and are consistently converted into action potentials. This result allows for the characterization of two critical steps of mechanosensation in vivo: primary signal detection and signal conversion into specific action potential firing patterns in axons.

  16. Regeneración axonal posterior a lesiones traumáticas de médula espinal: Papel crítico de galectina-1

    Directory of Open Access Journals (Sweden)

    Héctor R Quintá

    2014-08-01

    Full Text Available Al producirse una lesión de médula espinal (LME, un sinnúmero de proteínas inhibidoras de la regeneración axonal ocupan el sitio de lesión en forma secuencial. La primer proteína en llegar al mismo se conoce como semaforina 3A (Sema3A, siendo además una de las más potentes por su acción de inhibir la regeneración axonal. A nivel mecanístico la unión de esta proteína al complejo-receptor neuronal neuropilin-1 (NRP-1/PlexinA4 evita que se produzca regeneración axonal. En este trabajo de revisión se discutirá la acción de galectin-1 (Gal-1, una proteína endógena de unión a glicanos, que selectivamente se une al complejo-receptor NRP-1/PlexinA4 de las neuronas lesionadas a través de un mecanismo dependiente de interacciones lectina-glicano, interrumpiendo la señalización generada por Sema3A y permitiendo de esta manera la regeneración axonal y recuperación locomotora luego de producirse la LME. Mientras ambas formas de Gal-1 (monomérica y dimérica contribuyen a la inactivación de la microglia, solo la forma dimérica de Gal-1 es capaz de unirse al complejo-receptor NRP-1/PlexinA4 y promover regeneración axonal. Por lo tanto, Gal-1 dimérica produce recuperación de las lesiones espinales interfiriendo en la señalización de Sema3A a través de la unión al complejo-receptor NRP-1/PlexinA4, sugiriendo el uso de esta lectina en su forma dimérica para el tratamiento de pacientes con LME.

  17. Diversity of Internal Sensory Neuron Axon Projection Patterns Is Controlled by the POU-Domain Protein Pdm3 in Drosophila Larvae.

    Science.gov (United States)

    Qian, Cheng Sam; Kaplow, Margarita; Lee, Jennifer K; Grueber, Wesley B

    2018-02-21

    Internal sensory neurons innervate body organs and provide information about internal state to the CNS to maintain physiological homeostasis. Despite their conservation across species, the anatomy, circuitry, and development of internal sensory systems are still relatively poorly understood. A largely unstudied population of larval Drosophila sensory neurons, termed tracheal dendrite (td) neurons, innervate internal respiratory organs and may serve as a model for understanding the sensing of internal states. Here, we characterize the peripheral anatomy, central axon projection, and diversity of td sensory neurons. We provide evidence for prominent expression of specific gustatory receptor genes in distinct populations of td neurons, suggesting novel chemosensory functions. We identify two anatomically distinct classes of td neurons. The axons of one class project to the subesophageal zone (SEZ) in the brain, whereas the other terminates in the ventral nerve cord (VNC). We identify expression and a developmental role of the POU-homeodomain transcription factor Pdm3 in regulating the axon extension and terminal targeting of SEZ-projecting td neurons. Remarkably, ectopic Pdm3 expression is alone sufficient to switch VNC-targeting axons to SEZ targets, and to induce the formation of putative synapses in these ectopic target zones. Our data thus define distinct classes of td neurons, and identify a molecular factor that contributes to diversification of axon targeting. These results introduce a tractable model to elucidate molecular and circuit mechanisms underlying sensory processing of internal body status and physiological homeostasis. SIGNIFICANCE STATEMENT How interoceptive sensory circuits develop, including how sensory neurons diversify and target distinct central regions, is still poorly understood, despite the importance of these sensory systems for maintaining physiological homeostasis. Here, we characterize classes of Drosophila internal sensory neurons (td

  18. Studies of axon-glial cell interactions and periaxonal K+ homeostasis--II. The effect of axonal stimulation, cholinergic agents and transport inhibitors on the resistance in series with the axon membrane.

    Science.gov (United States)

    Hassan, S; Lieberman, E M

    1988-06-01

    The small electrical resistance in series with the axon membrane is generally modeled as the intercellular pathway for current flow through the periaxonal glial (Schwann cell) sheath. The series resistance of the medial giant axon of the crayfish, Procambarus clarkii, was found to vary with conditions known to affect the electrical properties of the periaxonal glia. Series resistance was estimated from computer analysed voltage waveforms generated by axial wire-constant current and space clamp techniques. The average series resistance for all axons was 6.2 +/- 0.5 omega cm2 (n = 128). Values ranged between 1 and 30 omega cm2. The series resistance of axons with low resting membrane resistance (less than 1500 omega cm2) increased an average of 30% when stimulated for 45 s to 7 min (50 Hz) whereas the series resistance of high membrane resistance (greater than 1500 omega cm2) axons decreased an average of 10%. Carbachol (10(-7) M) caused the series resistance of low membrane resistance axons to decrease during stimulation but had no effect on high membrane resistance axons. d-Tubocurare (10(-8) M) caused the series resistance of high membrane resistance axons to increase during stimulation but had no effect on low membrane resistance axons. Bumetanide, a Na-K-Cl cotransport inhibitor and low [K+]o, prevented the stimulation-induced increase in series resistance of low membrane resistance axons but had no effect on the high membrane resistance axons. The results suggest that the series resistance of axons varies in response to the activity of the glial K+ uptake mechanisms stimulated by the appearance of K+ in the periaxonal space during action potential generation.(ABSTRACT TRUNCATED AT 250 WORDS)

  19. Regulation of axonal development by the nuclear protein hindsight (pebbled) in the Drosophila visual system.

    Science.gov (United States)

    Oliva, Carlos; Sierralta, Jimena

    2010-08-15

    The molecules and networks involved in the process of acquisition and maintenance of the form of a mature neuron are not completely known. Using a misexpression screen we identified the gene hindsight as a gene involved in the process of acquisition of the neuronal morphogenesis in the Drosophila adult nervous system. hindsight encodes a transcription factor known for its role in early developmental processes such as embryonic germ band retraction and dorsal closure, as well as in the establishment of cell morphology, planar cell polarity, and epithelial integrity during retinal development. We describe here a novel function for HNT by showing that both loss and gain of function of HNT affects the pathfinding of the photoreceptors axons. By manipulating the timing and level of HNT expression, together with the number of cells manipulated we show here that the function of HNT in axonal guidance is independent of the HNT functions previously reported in retinal cells. Based on genetic interaction experiments we show that part of HNT function in axonal development is exerted through the regulation of genes involved in the dynamics of the actin cytoskeleton. Copyright 2010 Elsevier Inc. All rights reserved.

  20. Uncoupling nicotine mediated motoneuron axonal pathfinding errors and muscle degeneration in zebrafish

    International Nuclear Information System (INIS)

    Welsh, Lillian; Tanguay, Robert L.; Svoboda, Kurt R.

    2009-01-01

    Zebrafish embryos offer a unique opportunity to investigate the mechanisms by which nicotine exposure impacts early vertebrate development. Embryos exposed to nicotine become functionally paralyzed by 42 hpf suggesting that the neuromuscular system is compromised in exposed embryos. We previously demonstrated that secondary spinal motoneurons in nicotine-exposed embryos were delayed in development and that their axons made pathfinding errors (Svoboda, K.R., Vijayaraghaven, S., Tanguay, R.L., 2002. Nicotinic receptors mediate changes in spinal motoneuron development and axonal pathfinding in embryonic zebrafish exposed to nicotine. J. Neurosci. 22, 10731-10741). In that study, we did not consider the potential role that altered skeletal muscle development caused by nicotine exposure could play in contributing to the errors in spinal motoneuron axon pathfinding. In this study, we show that an alteration in skeletal muscle development occurs in tandem with alterations in spinal motoneuron development upon exposure to nicotine. The alteration in the muscle involves the binding of nicotine to the muscle-specific AChRs. The nicotine-induced alteration in muscle development does not occur in the zebrafish mutant (sofa potato, [sop]), which lacks muscle-specific AChRs. Even though muscle development is unaffected by nicotine exposure in sop mutants, motoneuron axonal pathfinding errors still occur in these mutants, indicating a direct effect of nicotine exposure on nervous system development.

  1. The netrin protein family.

    Science.gov (United States)

    Rajasekharan, Sathyanath; Kennedy, Timothy E

    2009-01-01

    The name netrin is derived from the Sanskrit Netr, meaning 'guide'. Netrins are a family of extracellular proteins that direct cell and axon migration during embryogenesis. Three secreted netrins (netrins 1, 3 and 4), and two glycosylphosphatidylinositol (GPI)-anchored membrane proteins, netrins G1 and G2, have been identified in mammals. The secreted netrins are bifunctional, acting as attractants for some cell types and repellents for others. Receptors for the secreted netrins include the Deleted in Colorectal Cancer (DCC) family, the Down's syndrome cell adhesion molecule (DSCAM), and the UNC-5 homolog family: Unc5A, B, C and D in mammals. Netrin Gs do not appear to interact with these receptors, but regulate synaptic interactions between neurons by binding to the transmembrane netrin G ligands NGL1 and 2. The chemotropic function of secreted netrins has been best characterized with regard to axon guidance during the development of the nervous system. Extending axons are tipped by a flattened, membranous structure called the growth cone. Multiple extracellular guidance cues direct axonal growth cones to their ultimate targets where synapses form. Such cues can be locally derived (short-range), or can be secreted diffusible cues that allow target cells to signal axons from a distance (long-range). The secreted netrins function as short-range and long-range guidance cues in different circumstances. In addition to directing cell migration, functional roles for netrins have been identified in the regulation of cell adhesion, the maturation of cell morphology, cell survival and tumorigenesis.

  2. Attenuated traumatic axonal injury and improved functional outcome after traumatic brain injury in mice lacking Sarm1.

    Science.gov (United States)

    Henninger, Nils; Bouley, James; Sikoglu, Elif M; An, Jiyan; Moore, Constance M; King, Jean A; Bowser, Robert; Freeman, Marc R; Brown, Robert H

    2016-04-01

    Axonal degeneration is a critical, early event in many acute and chronic neurological disorders. It has been consistently observed after traumatic brain injury, but whether axon degeneration is a driver of traumatic brain injury remains unclear. Molecular pathways underlying the pathology of traumatic brain injury have not been defined, and there is no efficacious treatment for traumatic brain injury. Here we show that mice lacking the mouse Toll receptor adaptor Sarm1 (sterile α/Armadillo/Toll-Interleukin receptor homology domain protein) gene, a key mediator of Wallerian degeneration, demonstrate multiple improved traumatic brain injury-associated phenotypes after injury in a closed-head mild traumatic brain injury model. Sarm1(-/-) mice developed fewer β-amyloid precursor protein aggregates in axons of the corpus callosum after traumatic brain injury as compared to Sarm1(+/+) mice. Furthermore, mice lacking Sarm1 had reduced plasma concentrations of the phophorylated axonal neurofilament subunit H, indicating that axonal integrity is maintained after traumatic brain injury. Strikingly, whereas wild-type mice exibited a number of behavioural deficits after traumatic brain injury, we observed a strong, early preservation of neurological function in Sarm1(-/-) animals. Finally, using in vivo proton magnetic resonance spectroscopy we found tissue signatures consistent with substantially preserved neuronal energy metabolism in Sarm1(-/-) mice compared to controls immediately following traumatic brain injury. Our results indicate that the SARM1-mediated prodegenerative pathway promotes pathogenesis in traumatic brain injury and suggest that anti-SARM1 therapeutics are a viable approach for preserving neurological function after traumatic brain injury. © The Author (2016). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  3. Acute nutritional axonal neuropathy.

    Science.gov (United States)

    Hamel, Johanna; Logigian, Eric L

    2018-01-01

    This study describes clinical, laboratory, and electrodiagnostic features of a severe acute axonal polyneuropathy common to patients with acute nutritional deficiency in the setting of alcoholism, bariatric surgery (BS), or anorexia. Retrospective analysis of clinical, electrodiagnostic, and laboratory data of patients with acute axonal neuropathy. Thirteen patients were identified with a severe, painful, sensory or sensorimotor axonal polyneuropathy that developed over 2-12 weeks with sensory ataxia, areflexia, variable muscle weakness, poor nutritional status, and weight loss, often with prolonged vomiting and normal cerebrospinal fluid protein. Vitamin B6 was low in half and thiamine was low in all patients when obtained before supplementation. Patients improved with weight gain and vitamin supplementation, with motor greater than sensory recovery. We suggest that acute or subacute axonal neuropathy in patients with weight loss or vomiting associated with alcohol abuse, BS, or dietary deficiency is one syndrome, caused by micronutrient deficiencies. Muscle Nerve 57: 33-39, 2018. © 2017 Wiley Periodicals, Inc.

  4. Axon Regeneration Is Regulated by Ets-C/EBP Transcription Complexes Generated by Activation of the cAMP/Ca2+ Signaling Pathways.

    Directory of Open Access Journals (Sweden)

    Chun Li

    2015-10-01

    Full Text Available The ability of specific neurons to regenerate their axons after injury is governed by cell-intrinsic regeneration pathways. In Caenorhabditis elegans, the JNK and p38 MAPK pathways are important for axon regeneration. Axonal injury induces expression of the svh-2 gene encoding a receptor tyrosine kinase, stimulation of which by the SVH-1 growth factor leads to activation of the JNK pathway. Here, we identify ETS-4 and CEBP-1, related to mammalian Ets and C/EBP, respectively, as transcriptional activators of svh-2 expression following axon injury. ETS-4 and CEBP-1 function downstream of the cAMP and Ca2+-p38 MAPK pathways, respectively. We show that PKA-dependent phosphorylation of ETS-4 promotes its complex formation with CEBP-1. Furthermore, activation of both cAMP and Ca2+ signaling is required for activation of svh-2 expression. Thus, the cAMP/Ca2+ signaling pathways cooperatively activate the JNK pathway, which then promotes axon regeneration.

  5. Axon degeneration: make the Schwann cell great again

    Directory of Open Access Journals (Sweden)

    Keit Men Wong

    2017-01-01

    Full Text Available Axonal degeneration is a pivotal feature of many neurodegenerative conditions and substantially accounts for neurological morbidity. A widely used experimental model to study the mechanisms of axonal degeneration is Wallerian degeneration (WD, which occurs after acute axonal injury. In the peripheral nervous system (PNS, WD is characterized by swift dismantling and clearance of injured axons with their myelin sheaths. This is a prerequisite for successful axonal regeneration. In the central nervous system (CNS, WD is much slower, which significantly contributes to failed axonal regeneration. Although it is well-documented that Schwann cells (SCs have a critical role in the regenerative potential of the PNS, to date we have only scarce knowledge as to how SCs 'sense' axonal injury and immediately respond to it. In this regard, it remains unknown as to whether SCs play the role of a passive bystander or an active director during the execution of the highly orchestrated disintegration program of axons. Older reports, together with more recent studies, suggest that SCs mount dynamic injury responses minutes after axonal injury, long before axonal breakdown occurs. The swift SC response to axonal injury could play either a pro-degenerative role, or alternatively a supportive role, to the integrity of distressed axons that have not yet committed to degenerate. Indeed, supporting the latter concept, recent findings in a chronic PNS neurodegeneration model indicate that deactivation of a key molecule promoting SC injury responses exacerbates axonal loss. If this holds true in a broader spectrum of conditions, it may provide the grounds for the development of new glia-centric therapeutic approaches to counteract axonal loss.

  6. Motor axon excitability during Wallerian degeneration

    DEFF Research Database (Denmark)

    Moldovan, Mihai; Alvarez, Susana; Krarup, Christian

    2008-01-01

    Axonal loss and degeneration are major factors in determining long-term outcome in patients with peripheral nerve disorders or injury. Following loss of axonal continuity, the isolated nerve stump distal to the lesion undergoes Wallerian degeneration in several phases. In the initial 'latent' phase......, action potential propagation and structural integrity of the distal segment are maintained. The aim of this study was to investigate in vivo the changes in membrane function of motor axons during the 'latent' phase of Wallerian degeneration. Multiple indices of axonal excitability of the tibial nerve...

  7. Serotonin induces memory-like, rapamycin-sensitive hyperexcitability in sensory axons of aplysia that contributes to injury responses.

    Science.gov (United States)

    Weragoda, Ramal M S; Walters, Edgar T

    2007-09-01

    The induction of long-term facilitation (LTF) of synapses of Aplysia sensory neurons (SNs) by serotonin (5-HT) has provided an important mechanistic model of memory, but little is known about other long-term effects of 5-HT on sensory properties. Here we show that crushing peripheral nerves results in long-term hyperexcitability (LTH) of the axons of these nociceptive SNs that requires 5-HT activity in the injured nerve. Serotonin application to a nerve segment induces local axonal (but not somal) LTH that is inhibited by 5-HT-receptor antagonists. Blockade of crush-induced axonal LTH by an antagonist, methiothepin, provides evidence for mediation of this injury response by 5-HT. This is the first demonstration in any axon of neuromodulator-induced LTH, a phenomenon potentially important for long-lasting pain. Methiothepin does not reduce axonal LTH induced by local depolarization, so 5-HT is not required for all forms of axonal LTH. Serotonin-induced axonal LTH is expressed as reduced spike threshold and increased repetitive firing, whereas depolarization-induced LTH involves only reduced threshold. Like crush- and depolarization-induced LTH, 5-HT-induced LTH is blocked by inhibiting protein synthesis. Blockade by rapamycin, which also blocks synaptic LTF, is interesting because the eukaryotic protein kinase that is the target of rapamycin (TOR) has a conserved role in promoting growth by stimulating translation of proteins required for translation. Rapamycin sensitivity suggests that localized increases in translation of proteins that promote axonal conduction and excitability at sites of nerve injury may be regulated by the same signals that increase translation of proteins that promote neuronal growth.

  8. EFA6 regulates selective polarised transport and axon regeneration from the axon initial segment

    Czech Academy of Sciences Publication Activity Database

    Eva, R.; Koseki, H.; Kanamarlapudi, V.; Fawcett, James

    2017-01-01

    Roč. 130, č. 21 (2017), s. 3663-3675 ISSN 0021-9533 Institutional support: RVO:68378041 Keywords : axon regeneration * axon transport * neuronal polarisation Subject RIV: FH - Neurology OBOR OECD: Neuroscience s (including psychophysiology Impact factor: 4.431, year: 2016

  9. Axo-Glia Interaction Preceding CNS Myelination Is Regulated by Bidirectional Eph-Ephrin Signaling

    Directory of Open Access Journals (Sweden)

    Cecilie Linneberg

    2015-09-01

    Full Text Available In the central nervous system, myelination of axons is required to ensure fast saltatory conduction and for survival of neurons. However, not all axons are myelinated, and the molecular mechanisms involved in guiding the oligodendrocyte processes toward the axons to be myelinated are not well understood. Only a few negative or positive guidance clues that are involved in regulating axo-glia interaction prior to myelination have been identified. One example is laminin, known to be required for early axo-glia interaction, which functions through α6β1 integrin. Here, we identify the Eph-ephrin family of guidance receptors as novel regulators of the initial axo-glia interaction, preceding myelination. We demonstrate that so-called forward and reverse signaling, mediated by members of both Eph and ephrin subfamilies, has distinct and opposing effects on processes extension and myelin sheet formation. EphA forward signaling inhibits oligodendrocyte process extension and myelin sheet formation, and blocking of bidirectional signaling through this receptor enhances myelination. Similarly, EphB forward signaling also reduces myelin membrane formation, but in contrast to EphA forward signaling, this occurs in an integrin-dependent manner, which can be reversed by overexpression of a constitutive active β1-integrin. Furthermore, ephrin-B reverse signaling induced by EphA4 or EphB1 enhances myelin sheet formation. Combined, this suggests that the Eph-ephrin receptors are important mediators of bidirectional signaling between axons and oligodendrocytes. It further implies that balancing Eph-ephrin forward and reverse signaling is important in the selection process of axons to be myelinated.

  10. Dynamics of mitochondrial transport in axons

    Directory of Open Access Journals (Sweden)

    Robert Francis Niescier

    2016-05-01

    Full Text Available The polarized structure and long neurites of neurons pose a unique challenge for proper mitochondrial distribution. It is widely accepted that mitochondria move from the cell body to axon ends and vice versa; however, we have found that mitochondria originating from the axon ends moving in the retrograde direction never reach to the cell body, and only a limited number of mitochondria moving in the anterograde direction from the cell body arrive at the axon ends of mouse hippocampal neurons. Furthermore, we have derived a mathematical formula using the Fokker-Planck equation to characterize features of mitochondrial transport, and the equation could determine altered mitochondrial transport in axons overexpressing parkin. Our analysis will provide new insights into the dynamics of mitochondrial transport in axons of normal and unhealthy neurons.

  11. Practical Guidance on Peptide Receptor Radionuclide Therapy (PRRNT) for Neuroendocrine Tumours

    International Nuclear Information System (INIS)

    2013-01-01

    Peptide receptor radionuclide therapy (PRRNT) using 90 Y-DOTATOC was first administered in 1996 in Basel, Switzerland, to a 40 year old patient with a gastroenteropancreatic neuroendocrine tumour (NET). The objective was to stabilize the progression of the tumour, which had proven refractory to conventional chemotherapy. The excellent subjective and objective responses after several treatment cycles prompted exhaustive pre-clinical and clinical research to explore the therapeutic potential of PRRNT for the treatment of NETs. Since then, PRRNT using 90 Y- or 177 Lu-DOTATOC has acquired wide acceptance and is now used in many medical centres in Europe and other parts of the world. NET is a unique subclass of cancer in which a good percentage of affected patients may experience disease control following several cycles of PRRNT, with improvement of symptoms and quality of life in the majority of cases. This book is a practical reference for specialists in clinical oncology and nuclear medicine embarking on deploying and executing a comprehensive programme for treating patients with NETs. It is part of a larger endeavour of the IAEA to enable medical centres in Member States to introduce therapeutic applications of unsealed radioisotopes in clinical routine practice. This publication provides comprehensive, multidisciplinary guidance on the use of PRRNT in order to enhance the effective, safe and standardized implementation of best practice for treating patients with NETs and gastroenteropancreatic cancers, with due regard to the recent international classifications of NETs. It provides comprehensive protocols for employing either 90 Y or 177 Lu tagged somatostatin receptor targeting peptides, as well as clinically assessed protocols for renal protection. It is a comprehensive compilation of clinically based evidence with input from experienced and renowned medical professionals in this field. The various sections cover clinical presentations, patient eligibility

  12. Practical Guidance on Peptide Receptor Radionuclide Therapy (PRRNT) for Neuroendocrine Tumours

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2013-03-15

    Peptide receptor radionuclide therapy (PRRNT) using {sup 90}Y-DOTATOC was first administered in 1996 in Basel, Switzerland, to a 40 year old patient with a gastroenteropancreatic neuroendocrine tumour (NET). The objective was to stabilize the progression of the tumour, which had proven refractory to conventional chemotherapy. The excellent subjective and objective responses after several treatment cycles prompted exhaustive pre-clinical and clinical research to explore the therapeutic potential of PRRNT for the treatment of NETs. Since then, PRRNT using {sup 90}Y- or {sup 177}Lu-DOTATOC has acquired wide acceptance and is now used in many medical centres in Europe and other parts of the world. NET is a unique subclass of cancer in which a good percentage of affected patients may experience disease control following several cycles of PRRNT, with improvement of symptoms and quality of life in the majority of cases. This book is a practical reference for specialists in clinical oncology and nuclear medicine embarking on deploying and executing a comprehensive programme for treating patients with NETs. It is part of a larger endeavour of the IAEA to enable medical centres in Member States to introduce therapeutic applications of unsealed radioisotopes in clinical routine practice. This publication provides comprehensive, multidisciplinary guidance on the use of PRRNT in order to enhance the effective, safe and standardized implementation of best practice for treating patients with NETs and gastroenteropancreatic cancers, with due regard to the recent international classifications of NETs. It provides comprehensive protocols for employing either {sup 90}Y or {sup 177}Lu tagged somatostatin receptor targeting peptides, as well as clinically assessed protocols for renal protection. It is a comprehensive compilation of clinically based evidence with input from experienced and renowned medical professionals in this field. The various sections cover clinical presentations

  13. Quantitative measurements and modeling of cargo–motor interactions during fast transport in the living axon

    International Nuclear Information System (INIS)

    Seamster, Pamela E; Loewenberg, Michael; Pascal, Jennifer; Chauviere, Arnaud; Gonzales, Aaron; Cristini, Vittorio; Bearer, Elaine L

    2012-01-01

    The kinesins have long been known to drive microtubule-based transport of sub-cellular components, yet the mechanisms of their attachment to cargo remain a mystery. Several different cargo-receptors have been proposed based on their in vitro binding affinities to kinesin-1. Only two of these—phosphatidyl inositol, a negatively charged lipid, and the carboxyl terminus of the amyloid precursor protein (APP-C), a trans-membrane protein—have been reported to mediate motility in living systems. A major question is how these many different cargo, receptors and motors interact to produce the complex choreography of vesicular transport within living cells. Here we describe an experimental assay that identifies cargo–motor receptors by their ability to recruit active motors and drive transport of exogenous cargo towards the synapse in living axons. Cargo is engineered by derivatizing the surface of polystyrene fluorescent nanospheres (100 nm diameter) with charged residues or with synthetic peptides derived from candidate motor receptor proteins, all designed to display a terminal COOH group. After injection into the squid giant axon, particle movements are imaged by laser-scanning confocal time-lapse microscopy. In this report we compare the motility of negatively charged beads with APP-C beads in the presence of glycine-conjugated non-motile beads using new strategies to measure bead movements. The ensuing quantitative analysis of time-lapse digital sequences reveals detailed information about bead movements: instantaneous and maximum velocities, run lengths, pause frequencies and pause durations. These measurements provide parameters for a mathematical model that predicts the spatiotemporal evolution of distribution of the two different types of bead cargo in the axon. The results reveal that negatively charged beads differ from APP-C beads in velocity and dispersion, and predict that at long time points APP-C will achieve greater progress towards the presynaptic

  14. Axonal Membranes and Their Domains: Assembly and Function of the Axon Initial Segment and Node of Ranvier

    Directory of Open Access Journals (Sweden)

    Andrew D. Nelson

    2017-05-01

    Full Text Available Neurons are highly specialized cells of the nervous system that receive, process and transmit electrical signals critical for normal brain function. Here, we review the intricate organization of axonal membrane domains that facilitate rapid action potential conduction underlying communication between complex neuronal circuits. Two critical excitable domains of vertebrate axons are the axon initial segment (AIS and the nodes of Ranvier, which are characterized by the high concentrations of voltage-gated ion channels, cell adhesion molecules and specialized cytoskeletal networks. The AIS is located at the proximal region of the axon and serves as the site of action potential initiation, while nodes of Ranvier, gaps between adjacent myelin sheaths, allow rapid propagation of the action potential through saltatory conduction. The AIS and nodes of Ranvier are assembled by ankyrins, spectrins and their associated binding partners through the clustering of membrane proteins and connection to the underlying cytoskeleton network. Although the AIS and nodes of Ranvier share similar protein composition, their mechanisms of assembly are strikingly different. Here we will cover the mechanisms of formation and maintenance of these axonal excitable membrane domains, specifically highlighting the similarities and differences between them. We will also discuss recent advances in super resolution fluorescence imaging which have elucidated the arrangement of the submembranous axonal cytoskeleton revealing a surprising structural organization necessary to maintain axonal organization and function. Finally, human mutations in axonal domain components have been associated with a growing number of neurological disorders including severe cognitive dysfunction, epilepsy, autism, neurodegenerative diseases and psychiatric disorders. Overall, this review highlights the assembly, maintenance and function of axonal excitable domains, particularly the AIS and nodes of

  15. Use of self-complementary adeno-associated virus serotype 2 as a tracer for labeling axons: implications for axon regeneration.

    Directory of Open Access Journals (Sweden)

    Yingpeng Liu

    Full Text Available Various types of tracers are available for use in axon regeneration, but they require an extra operational tracer injection, time-consuming immunohistochemical analysis and cause non-specific labeling. Considerable efforts over the past years have explored other methodologies, especially the use of viral vectors, to investigate axon regeneration after injury. Recent studies have demonstrated that self-complementary Adeno-Associated Virus (scAAV induced a high transduction efficiency and faster expression of transgenes. Here, we describe for the first time the use of scAAV2-GFP to label long-projection axons in the corticospinal tract (CST, rubrospinal tract (RST and the central axons of dorsal root ganglion (DRG in the normal and lesioned animal models. We found that scAAV2-GFP could efficiently transduce neurons in the sensorimotor cortex, red nucleus and DRG. Strong GFP expression could be transported anterogradely along the axon to label the numerous axon fibers from CST, RST and central axons of DRG separately. Comparison of the scAAV2 vector with single-stranded (ss AAV2 vector in co-labeled sections showed that the scAAV2 vector induced a faster and stronger transgene expression than the ssAAV2 vector in DRG neurons and their axons. In both spinal cord lesion and dorsal root crush injury models, scAAV-GFP could efficiently label the lesioned and regenerated axons around the lesion cavity and the dorsal root entry zone (DREZ respectively. Further, scAAV2-GFP vector could be combined with traditional tracer to specifically label sensory and motor axons after spinal cord lesion. Thus, we show that using scAAV2-GFP as a tracer is a more effective and efficient way to study axon regeneration following injury.

  16. Monocrotophos, an organophosphorus insecticide, disrupts the expression of HpNetrin and its receptor neogenin during early development in the sea urchin (Hemicentrotus pulcherrimus).

    Science.gov (United States)

    Zhang, Xiaona; Xu, Lei; Tian, Hua; Wang, Cuicui; Wang, Wei; Ru, Shaoguo

    2017-09-01

    Netrins, chemotropic guidance cues, can guide the extension of serotonergic axons by binding to netrin receptors during neural development. However, little is known about whether disruption of netrin signaling is involved in the mechanisms by which organophosphorus pesticides affect serotonergic nervous system (SNS) development. In this study, we evaluated the effects of the pesticide monocrotophos (MCP) on the expression patterns of HpNetrin and its receptor neogenin as well as on the intracellular calcium ion (Ca 2+ ) levels in Hemicentrotus pulcherrimus (sea urchin) by exposing fertilized embryos to 0, 0.01, 0.10, and 1.00mg/L MCP. The results showed that MCP disrupted HpNetrin and neogenin expression at different developmental stages in H. pulcherrimus and that Ca 2+ appeared to be involved in the MCP-induced developmental neurotoxicity. Specifically, the lower concentrations of MCP elevated HpNetrin and neogenin transcription, resulting in higher intracellular Ca 2+ levels during the early developmental stages in the sea urchin; this may affect netrin-directed cell migration/axon extension and subsequently disrupt serotonergic axon branching and synapse formation. In contrast, 1.00mg/L MCP exhibited an inhibitory effect on HpNetrin and neogenin transcription. This finding implies that the regulatory roles of these factors may be diminished during early development, thereby causing developmental defects in the sea urchin. Collectively, our results provide a basis for exploring the involvement of netrin and neogenin in the organophosphate-induced disruption of the SNS during development. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. The C. elegans histone deacetylase HDA-1 is required for cell migration and axon pathfinding.

    Science.gov (United States)

    Zinovyeva, Anna Y; Graham, Serena M; Cloud, Veronica J; Forrester, Wayne C

    2006-01-01

    Histone proteins play integral roles in chromatin structure and function. Histones are subject to several types of posttranslational modifications, including acetylation, which can produce transcriptional activation. The converse, histone deacetylation, is mediated by histone deacetylases (HDACs) and often is associated with transcriptional silencing. We identified a new mutation, cw2, in the Caenorhabditis elegans hda-1 gene, which encodes a histone deacetylase. Previous studies showed that a mutation in hda-1, e1795, or reduction of hda-1 RNA by RNAi causes defective vulval and gonadal development leading to sterility. The hda-1(cw2) mutation causes defective vulval development and reduced fertility, like hda-1(e1795), albeit with reduced severity. Unlike the previously reported hda-1 mutation, hda-1(cw2) mutants are viable as homozygotes, although many die as embryos or larvae, and are severely uncoordinated. Strikingly, in hda-1(cw2) mutants, axon pathfinding is defective; specific axons often appear to wander randomly or migrate in the wrong direction. In addition, the long range migrations of three neuron types and fasciculation of the ventral nerve cord are defective. Together, our studies define a new role for HDA-1 in nervous system development, and provide the first evidence for HDAC function in regulating neuronal axon guidance.

  18. Oxycodone Self-Administration Induces Alterations in Expression of Integrin, Semaphorin and Ephrin Genes in the Mouse Striatum

    Directory of Open Access Journals (Sweden)

    Vadim Yuferov

    2018-06-01

    Full Text Available Oxycodone is one a commonly used medication for pain, and is also a widely abused prescription opioid, like other short-acting MOPr agonists. Neurochemical and structural adaptations in brain following chronic MOPr-agonist administration are thought to underlie pathogenesis and persistence of opiate addiction. Many axon guidance molecules, such as integrins, semaphorins, and ephrins may contribute to oxycodone-induced neuroadaptations through alterations in axon-target connections and synaptogenesis, that may be implicated in the behaviors associated with opiate addiction. However, little is known about this important area. The aim of this study is to investigate alterations in expression of selected integrin, semaphorin, ephrins, netrin, and slit genes in the nucleus accumbens (NAc and caudate putamen (CPu of mice following extended 14-day oxycodone self-administration (SA, using RNAseq.Methods: Total RNA from the NAc and CPu were isolated from adult male C57BL/6J mice within 1 h after the last session of oxycodone in a 14-day self-administration paradigm (4h/day, 0.25 mg/kg/infusion, FR1 or from yoked saline controls. Gene expressions were examined using RNA sequencing (RNA-Seq technology. RNA-Seq libraries were prepared using Illumina's TruSeq® Stranded Total RNA LT kit. The reads were aligned to the mouse reference genome (version mm10 using STAR. DESeq2 was applied to the counts of protein coding genes to estimate the fold change between the treatment groups. False Discovery Rate (FDR q < 0.1 were used to select genes that have a significant expression change. For selection of a subset of genes related to axon guidance pathway, REACTOME was used.Results: Among 38 known genes of the integrin, semaphorin, and ephrin gene families, RNA-seq data revealed up-regulation of six genes in the NAc: heterodimer receptor, integrins Itgal, Itgb2, and Itgam, and its ligand semaphorin Sema7a, two semaphorin receptors, plexins Plxnd1 and Plxdc1. There was

  19. Distinct kinetics of inhibitory currents in thalamocortical neurons that arise from dendritic or axonal origin.

    Directory of Open Access Journals (Sweden)

    Sunggu Yang

    Full Text Available Thalamocortical neurons in the dorsal lateral geniculate nucleus (dLGN transfer visual information from retina to primary visual cortex. This information is modulated by inhibitory input arising from local interneurons and thalamic reticular nucleus (TRN neurons, leading to alterations of receptive field properties of thalamocortical neurons. Local GABAergic interneurons provide two distinct synaptic outputs: axonal (F1 terminals and dendritic (F2 terminals onto dLGN thalamocortical neurons. By contrast, TRN neurons provide only axonal output (F1 terminals onto dLGN thalamocortical neurons. It is unclear if GABAA receptor-mediated currents originating from F1 and F2 terminals have different characteristics. In the present study, we examined multiple characteristics (rise time, slope, halfwidth and decay τ of GABAA receptor-mediated miniature inhibitory postsynaptic synaptic currents (mIPSCs originating from F1 and F2 terminals. The mIPSCs arising from F2 terminals showed slower kinetics relative to those from F1 terminals. Such differential kinetics of GABAAR-mediated responses could be an important role in temporal coding of visual signals.

  20. Slow Muscle Precursors Lay Down a Collagen XV Matrix Fingerprint to Guide Motor Axon Navigation.

    Science.gov (United States)

    Guillon, Emilie; Bretaud, Sandrine; Ruggiero, Florence

    2016-03-02

    The extracellular matrix (ECM) provides local positional information to guide motoneuron axons toward their muscle target. Collagen XV is a basement membrane component mainly expressed in skeletal muscle. We have identified two zebrafish paralogs of the human COL15A1 gene, col15a1a and col15a1b, which display distinct expression patterns. Here we show that col15a1b is expressed and deposited in the motor path ECM by slow muscle precursors also called adaxial cells. We further demonstrate that collagen XV-B deposition is both temporally and spatially regulated before motor axon extension from the spinal cord in such a way that it remains in this region after the adaxial cells have migrated toward the periphery of the myotome. Loss- and gain-of-function experiments in zebrafish embryos demonstrate that col15a1b expression and subsequent collagen XV-B deposition and organization in the motor path ECM depend on a previously undescribed two-step mechanism involving Hedgehog/Gli and unplugged/MuSK signaling pathways. In silico analysis predicts a putative Gli binding site in the col15a1b proximal promoter. Using col15a1b promoter-reporter constructs, we demonstrate that col15a1b participates in the slow muscle genetic program as a direct target of Hedgehog/Gli signaling. Loss and gain of col15a1b function provoke pathfinding errors in primary and secondary motoneuron axons both at and beyond the choice point where axon pathway selection takes place. These defects result in muscle atrophy and compromised swimming behavior, a phenotype partially rescued by injection of a smyhc1:col15a1b construct. These reveal an unexpected and novel role for collagen XV in motor axon pathfinding and neuromuscular development. In addition to the archetypal axon guidance cues, the extracellular matrix provides local information that guides motor axons from the spinal cord to their muscle targets. Many of the proteins involved are unknown. Using the zebrafish model, we identified an

  1. Cargo distributions differentiate pathological axonal transport impairments.

    Science.gov (United States)

    Mitchell, Cassie S; Lee, Robert H

    2012-05-07

    Axonal transport is an essential process in neurons, analogous to shipping goods, by which energetic and cellular building supplies are carried downstream (anterogradely) and wastes are carried upstream (retrogradely) by molecular motors, which act as cargo porters. Impairments in axonal transport have been linked to devastating and often lethal neurodegenerative diseases, such as Amyotrophic Lateral Sclerosis, Huntington's, and Alzheimer's. Axonal transport impairment types include a decrease in available motors for cargo transport (motor depletion), the presence of defective or non-functional motors (motor dilution), and the presence of increased or larger cargos (protein aggregation). An impediment to potential treatment identification has been the inability to determine what type(s) of axonal transport impairment candidates that could be present in a given disease. In this study, we utilize a computational model and common axonal transport experimental metrics to reveal the axonal transport impairment general characteristics or "signatures" that result from three general defect types of motor depletion, motor dilution, and protein aggregation. Our results not only provide a means to discern these general impairments types, they also reveal key dynamic and emergent features of axonal transport, which potentially underlie multiple impairment types. The identified characteristics, as well as the analytical method, can be used to help elucidate the axonal transport impairments observed in experimental and clinical data. For example, using the model-predicted defect signatures, we identify the defect candidates, which are most likely to be responsible for the axonal transport impairments in the G93A SOD1 mouse model of ALS. Copyright © 2012 Elsevier Ltd. All rights reserved.

  2. Axon initial segment Kv1 channels control axonal action potential waveform and synaptic efficacy

    NARCIS (Netherlands)

    Kole, Maarten H. P.; Letzkus, Johannes J.; Stuart, Greg J.

    2007-01-01

    Action potentials are binary signals that transmit information via their rate and temporal pattern. In this context, the axon is thought of as a transmission line, devoid of a role in neuronal computation. Here, we show a highly localized role of axonal Kv1 potassium channels in shaping the action

  3. Elucidation of axonal transport by radioautography

    International Nuclear Information System (INIS)

    Droz, Bernard.

    1979-01-01

    Radioautography permits to distinguish various pathways within the axons: the axoplasm which includes soluble enzymes and constituents of the cytoskeleton moving with slow axoplasmic flow; the mitochondria which are conveyed as organelles; the smooth endoplasmic reticulum which ensures the fast axonal transport of membrane constituents delivered to axolemma, synaptic vesicles, presynaptic membranes or mitochondria. Furthermore radioautography makes it possible to visualize intercellular exchanges of molecules between axon and glia

  4. The axonal cytoskeleton : from organization to function

    NARCIS (Netherlands)

    Kevenaar, Josta T; Hoogenraad, Casper C

    The axon is the single long fiber that extends from the neuron and transmits electrical signals away from the cell body. The neuronal cytoskeleton, composed of microtubules (MTs), actin filaments and neurofilaments, is not only required for axon formation and axonal transport but also provides the

  5. Differential effects of myostatin deficiency on motor and sensory axons.

    Science.gov (United States)

    Jones, Maria R; Villalón, Eric; Northcutt, Adam J; Calcutt, Nigel A; Garcia, Michael L

    2017-12-01

    Deletion of myostatin in mice (MSTN -/- ) alters structural properties of peripheral axons. However, properties like axon diameter and myelin thickness were analyzed in mixed nerves, so it is unclear whether loss of myostatin affects motor, sensory, or both types of axons. Using the MSTN -/- mouse model, we analyzed the effects of increasing the number of muscle fibers on axon diameter, myelin thickness, and internode length in motor and sensory axons. Axon diameter and myelin thickness were increased in motor axons of MSTN -/- mice without affecting internode length or axon number. The number of sensory axons was increased without affecting their structural properties. These results suggest that motor and sensory axons establish structural properties by independent mechanisms. Moreover, in motor axons, instructive cues from the neuromuscular junction may play a role in co-regulating axon diameter and myelin thickness, whereas internode length is established independently. Muscle Nerve 56: E100-E107, 2017. © 2017 Wiley Periodicals, Inc.

  6. Slits Are Chemorepellents Endogenous to Hypothalamus and Steer Thalamocortical Axons into Ventral Telencephalon

    OpenAIRE

    Braisted, Janet E.; Ringstedt, Thomas; O'Leary, Dennis D. M.

    2009-01-01

    Thalamocortical axons (TCAs) originate in dorsal thalamus, extend ventrally along the lateral thalamic surface, and as they approach hypothalamus make a lateral turn into ventral telencephalon. In vitro studies show that hypothalamus releases a chemorepellent for TCAs, and analyses of knockout mice indicate that Slit chemorepellents and their receptor Robo2 influence TCA pathfinding. We show that Slit chemorepellents are the hypothalamic chemorepellent and act through Robos to steer TCAs into...

  7. Evidence that glutamate mediates axon-to-Schwann cell signaling in the squid.

    Science.gov (United States)

    Lieberman, E M; Abbott, N J; Hassan, S

    1989-01-01

    High-frequency stimulation (100 Hz) of isolated giant axons of the small squid Alloteuthis subulata and the large squid Loligo forbesi caused the periaxonal Schwann cell resting potential (Em = -40 mV) to hyperpolarize up to 11 mV in direct proportion to train duration and action potential amplitude. In both species, the Schwann cell also hyperpolarized up to 17 mV with the application of L-glutamate (10(-9) to 10(-6) M), in a dose-dependent manner. By contrast, in the presence of 10(-8) M d-tubocurarine (d-TC) to block the cholinergic component of the Schwann cell response, Schwann cells depolarized 8-9 mV during electrical stimulation of the axon or application of L-glutamate. In the presence of 10(-5) M 2-amino-4-phosphonobutyrate (2-APB), the hyperpolarization to glutamate and to axon stimulation was blocked, whereas the cholinergic (carbachol-induced) hyperpolarization was unaffected. In experiments with Alloteuthis, L-aspartate (10(-7) M) also caused a Schwann cell hyperpolarization, but this was not blocked by 2-APB. In tests with glutamate receptor agonists and antagonists, quisqualate (10(-5) M) produced a hyperpolarization blocked by 10(-4) M L-glutamic acid diethylester (GDEE), which also blocked the response to axonal stimulation. Kainic acid (10(-4) M) also caused a hyperpolarization, but n-methyl-D-aspartate (NMDA; 10(-4) M), ibotenate (10(-5) M), alpha-amino-3-hydroxy-5-methyl-isoxazole proprionate (AMPA; (10(-4) M), and isethionate (10(-5) M) had no effect.(ABSTRACT TRUNCATED AT 250 WORDS)

  8. The axon-protective WLD(S) protein partially rescues mitochondrial respiration and glycolysis after axonal injury.

    Science.gov (United States)

    Godzik, Katharina; Coleman, Michael P

    2015-04-01

    The axon-protective Wallerian degeneration slow (WLD(S)) protein can ameliorate the decline in axonal ATP levels after neurite transection. Here, we tested the hypothesis that this effect is associated with maintenance of mitochondrial respiration and/or glycolysis. We used isolated neurites of superior cervical ganglion (SCG) cultures in the Seahorse XF-24 Metabolic Flux Analyser to determine mitochondrial respiration and glycolysis under different conditions. We observed that both mitochondrial respiration and glycolysis declined significantly during the latent phase of Wallerian degeneration. WLD(S) partially reduced the decline both in glycolysis and in mitochondrial respiration. In addition, we found that depleting NAD levels in uncut cultures led to changes in mitochondrial respiration and glycolysis similar to those rescued by WLD(S) after cut, suggesting that the maintenance of NAD levels in Wld(S) neurites after axonal injury at least partially underlies the maintenance of ATP levels. However, by using another axon-protective mutation (Sarm1(-/-)), we could demonstrate that rescue of basal ECAR (and hence probably glycolysis) rather than basal OCR (mitochondrial respiration) may be part of the protective phenotype to delay Wallerian degeneration. These findings open new routes to study glycolysis and the connection between NAD and ATP levels in axon degeneration, which may help to eventually develop therapeutic strategies to treat neurodegenerative diseases.

  9. Increased mitochondrial content in remyelinated axons: implications for multiple sclerosis

    Science.gov (United States)

    Zambonin, Jessica L.; Zhao, Chao; Ohno, Nobuhiko; Campbell, Graham R.; Engeham, Sarah; Ziabreva, Iryna; Schwarz, Nadine; Lee, Sok Ee; Frischer, Josa M.; Turnbull, Doug M.; Trapp, Bruce D.; Lassmann, Hans; Franklin, Robin J. M.

    2011-01-01

    Mitochondrial content within axons increases following demyelination in the central nervous system, presumably as a response to the changes in energy needs of axons imposed by redistribution of sodium channels. Myelin sheaths can be restored in demyelinated axons and remyelination in some multiple sclerosis lesions is extensive, while in others it is incomplete or absent. The effects of remyelination on axonal mitochondrial content in multiple sclerosis, particularly whether remyelination completely reverses the mitochondrial changes that follow demyelination, are currently unknown. In this study, we analysed axonal mitochondria within demyelinated, remyelinated and myelinated axons in post-mortem tissue from patients with multiple sclerosis and controls, as well as in experimental models of demyelination and remyelination, in vivo and in vitro. Immunofluorescent labelling of mitochondria (porin, a voltage-dependent anion channel expressed on all mitochondria) and axons (neurofilament), and ultrastructural imaging showed that in both multiple sclerosis and experimental demyelination, mitochondrial content within remyelinated axons was significantly less than in acutely and chronically demyelinated axons but more numerous than in myelinated axons. The greater mitochondrial content within remyelinated, compared with myelinated, axons was due to an increase in density of porin elements whereas increase in size accounted for the change observed in demyelinated axons. The increase in mitochondrial content in remyelinated axons was associated with an increase in mitochondrial respiratory chain complex IV activity. In vitro studies showed a significant increase in the number of stationary mitochondria in remyelinated compared with myelinated and demyelinated axons. The number of mobile mitochondria in remyelinated axons did not significantly differ from myelinated axons, although significantly greater than in demyelinated axons. Our neuropathological data and findings in

  10. Creatine pretreatment protects cortical axons from energy depletion in vitro

    Science.gov (United States)

    Shen, Hua; Goldberg, Mark P.

    2012-01-01

    Creatine is a natural nitrogenous guanidino compound involved in bioenergy metabolism. Although creatine has been shown to protect neurons of the central nervous system (CNS) from experimental hypoxia/ischemia, it remains unclear if creatine may also protect CNS axons, and if the potential axonal protection depends on glial cells. To evaluate the direct impact of creatine on CNS axons, cortical axons were cultured in a separate compartment from their somas and proximal neurites using a modified two-compartment culture device. Axons in the axon compartment were subjected to acute energy depletion, an in vitro model of white matter ischemia, by exposure to 6 mM sodium azide for 30 min in the absence of glucose and pyruvate. Energy depletion reduced axonal ATP by 65%, depolarized axonal resting potential, and damaged 75% of axons. Application of creatine (10 mM) to both compartments of the culture at 24 h prior to energy depletion significantly reduced axonal damage by 50%. In line with the role of creatine in the bioenergy metabolism, this application also alleviated the axonal ATP loss and depolarization. Inhibition of axonal depolarization by blocking sodium influx with tetrodotoxin also effectively reduced the axonal damage caused by energy depletion. Further study revealed that the creatine effect was independent of glial cells, as axonal protection was sustained even when creatine was applied only to the axon compartment (free from somas and glial cells) for as little as 2 h. In contrast, application of creatine after energy depletion did not protect axons. The data provide the first evidence that creatine pretreatment may directly protect CNS axons from energy deficiency. PMID:22521466

  11. In vivo regulation of the serotonin-2 receptor in rat brain

    International Nuclear Information System (INIS)

    Stockmeier, C.A.; Kellar, K.J.

    1986-01-01

    Serotonin-2 (5-HT-2) receptors in brain were measured using ( 3 H)ketanserin. The authors examined the effects of amitriptyline, an anti-depressant drug, of electroconvulsive shock (ECS) and of drug-induced alterations in presynaptic 5-HT function on ( 3 H)ketanserin binding to 5-HT-2 receptors in rat brain. The importance of intact 5-HT axons to the up-regulation of 5-HT-2 receptors by ECS was also investigated, and an attempt was made to relate the ECS-induced increase in this receptor to changes in 5-HT presynaptic mechanisms. Twelve days of ECS increased the number of 5-HT-2 receptors in frontal cortex. Neither the IC 50 nor the Hill coefficient of 5-HT in competing for ( 3 H)ketanserin binding sites was altered by ECS. Repeated injections of amitriptyline reduced the number of 5-HT-2 receptors in frontal cortex. Reserpine, administered daily for 12 days, caused a significant increase in 5-HT-2 receptors, but neither daily injections of p-chlorophenylalanine (PCPA) nor lesions of 5-HT axons with 5,7-dihydroxytryptamine (5,7-DHT) affected 5-HT-2 receptors. However, regulation of 5-HT-2 receptors by ECS was dependent on intact 5-HT axons since ECS could not increase the number of 5-HT-2 receptors in rats previously lesioned with 5,7-DHT. Repeated ECS, however, does not appear to affect either the high-affinity uptake of ( 3 H)5-HT or ( 3 H)imipramine binding, two presynaptic markers of 5-HT neuronal function. 5-HT-2 receptors appear to be under complex control. ECS or drug treatments such as reserpine or amitriptyline, which affect several monoamine neurotransmission systems including 5-HT, can alter 5-HT-2 receptors. 28 references, 1 figure, 7 tables

  12. Axonal regeneration and development of de novo axons from distal dendrites of adult feline commissural interneurons after a proximal axotomy

    DEFF Research Database (Denmark)

    Fenrich, Keith K; Skelton, Nicole; MacDermid, Victoria E

    2007-01-01

    Following proximal axotomy, several types of neurons sprout de novo axons from distal dendrites. These processes may represent a means of forming new circuits following spinal cord injury. However, it is not know whether mammalian spinal interneurons, axotomized as a result of a spinal cord injury......, develop de novo axons. Our goal was to determine whether spinal commissural interneurons (CINs), axotomized by 3-4-mm midsagittal transection at C3, form de novo axons from distal dendrites. All experiments were performed on adult cats. CINs in C3 were stained with extracellular injections of Neurobiotin...... at 4-5 weeks post injury. The somata of axotomized CINs were identified by the presence of immunoreactivity for the axonal growth-associated protein-43 (GAP-43). Nearly half of the CINs had de novo axons that emerged from distal dendrites. These axons lacked immunoreactivity for the dendritic protein...

  13. Increased Cx32 expression in spinal cord TrkB oligodendrocytes following peripheral axon injury.

    Science.gov (United States)

    Coulibaly, Aminata P; Isaacson, Lori G

    2016-08-03

    Following injury to motor axons in the periphery, retrograde influences from the injury site lead to glial cell plasticity in the vicinity of the injured neurons. Following the transection of peripherally located preganglionic axons of the cervical sympathetic trunk (CST), a population of oligodendrocyte (OL) lineage cells expressing full length TrkB, the cognate receptor for brain derived neurotrophic factor (BDNF), is significantly increased in number in the spinal cord. Such robust plasticity in OL lineage cells in the spinal cord following peripheral axon transection led to the hypothesis that the gap junction communication protein connexin 32 (Cx32), which is specific to OL lineage cells, was influenced by the injury. Following CST transection, Cx32 expression in the spinal cord intermediolateral cell column (IML), the location of the parent cell bodies, was significantly increased. The increased Cx32 expression was localized specifically to TrkB OLs in the IML, rather than other cell types in the OL cell lineage, with the population of Cx32/TrkB cells increased by 59%. Cx32 expression in association with OPCs was significantly decreased at one week following the injury. The results of this study provide evidence that peripheral axon injury can differentially affect the gap junction protein expression in OL lineage cells in the adult rat spinal cord. We conclude that the retrograde influences originating from the peripheral injury site elicit dramatic changes in the CNS expression of Cx32, which in turn may mediate the plasticity of OL lineage cells observed in the spinal cord following peripheral axon injury. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  14. Modeling of axonal endoplasmic reticulum network by spastic paraplegia proteins.

    Science.gov (United States)

    Yalçın, Belgin; Zhao, Lu; Stofanko, Martin; O'Sullivan, Niamh C; Kang, Zi Han; Roost, Annika; Thomas, Matthew R; Zaessinger, Sophie; Blard, Olivier; Patto, Alex L; Sohail, Anood; Baena, Valentina; Terasaki, Mark; O'Kane, Cahir J

    2017-07-25

    Axons contain a smooth tubular endoplasmic reticulum (ER) network that is thought to be continuous with ER throughout the neuron; the mechanisms that form this axonal network are unknown. Mutations affecting reticulon or REEP proteins, with intramembrane hairpin domains that model ER membranes, cause an axon degenerative disease, hereditary spastic paraplegia (HSP). We show that Drosophila axons have a dynamic axonal ER network, which these proteins help to model. Loss of HSP hairpin proteins causes ER sheet expansion, partial loss of ER from distal motor axons, and occasional discontinuities in axonal ER. Ultrastructural analysis reveals an extensive ER network in axons, which shows larger and fewer tubules in larvae that lack reticulon and REEP proteins, consistent with loss of membrane curvature. Therefore HSP hairpin-containing proteins are required for shaping and continuity of axonal ER, thus suggesting roles for ER modeling in axon maintenance and function.

  15. Schwann Cell Glycogen Selectively Supports Myelinated Axon Function

    Science.gov (United States)

    Brown, Angus M; Evans, Richard D; Black, Joel; Ransom, Bruce R

    2012-01-01

    Objectives Interruption of energy supply to peripheral axons is a cause of axon loss. We determined if glycogen was present in mammalian peripheral nerve, and if it supported axon conduction during aglycemia. Methods We used biochemical assay and electron microscopy to determine the presence of glycogen, and electrophysiology to monitor axon function. Results Glycogen was present in sciatic nerve, its concentration varying directly with ambient [glucose]. Electron microscopy detected glycogen granules primarily in myelinating Schwann cell cytoplasm and these diminished after exposure to aglycemia. During aglycemia, conduction failure in large myelinated axons (A fibers) mirrored the time-course of glycogen loss. Latency to CAP failure was directly related to nerve glycogen content at aglycemia onset. Glycogen did not benefit the function of slow-conducting, small diameter unmyelinated axons (C fibers) during aglycemia. Blocking glycogen breakdown pharmacologically accelerated CAP failure during aglycemia in A fibers, but not in C fibers. Lactate was as effective as glucose in supporting sciatic nerve function, and was continuously released into the extracellular space in the presence of glucose and fell rapidly during aglycemia. Interpretation Our findings indicated that glycogen is present in peripheral nerve, primarily in myelinating Schwann cells, and exclusively supports large diameter, myelinated axon conduction during aglycemia. Available evidence suggests that peripheral nerve glycogen breaks down during aglycemia and is passed, probably as lactate, to myelinated axons to support function. Unmyelinated axons are not protected by glycogen and are more vulnerable to dysfunction during periods of hypoglycemia. PMID:23034913

  16. Activity-induced and developmental downregulation of the Nogo receptor

    DEFF Research Database (Denmark)

    Josephson, Anna; Trifunovski, Alexandra; Schéele, Camilla

    2003-01-01

    The three axon growth inhibitory proteins, myelin associated glycoprotein, oligodendrocyte-myelin glycoprotein and Nogo-A, can all bind to the Nogo-66 receptor (NgR). This receptor is expressed by neurons with high amounts in regions of high plasticity where Nogo expression is also high. We hypot...

  17. The Role of Rab Proteins in Neuronal Cells and in the Trafficking of Neurotrophin Receptors

    Directory of Open Access Journals (Sweden)

    Cecilia Bucci

    2014-10-01

    Full Text Available Neurotrophins are a family of proteins that are important for neuronal development, neuronal survival and neuronal functions. Neurotrophins exert their role by binding to their receptors, the Trk family of receptor tyrosine kinases (TrkA, TrkB, and TrkC and p75NTR, a member of the tumor necrosis factor (TNF receptor superfamily. Binding of neurotrophins to receptors triggers a complex series of signal transduction events, which are able to induce neuronal differentiation but are also responsible for neuronal maintenance and neuronal functions. Rab proteins are small GTPases localized to the cytosolic surface of specific intracellular compartments and are involved in controlling vesicular transport. Rab proteins, acting as master regulators of the membrane trafficking network, play a central role in both trafficking and signaling pathways of neurotrophin receptors. Axonal transport represents the Achilles' heel of neurons, due to the long-range distance that molecules, organelles and, in particular, neurotrophin-receptor complexes have to cover. Indeed, alterations of axonal transport and, specifically, of axonal trafficking of neurotrophin receptors are responsible for several human neurodegenerative diseases, such as Huntington’s disease, Alzheimer’s disease, amyotrophic lateral sclerosis and some forms of Charcot-Marie-Tooth disease. In this review, we will discuss the link between Rab proteins and neurotrophin receptor trafficking and their influence on downstream signaling pathways.

  18. The Role of Rab Proteins in Neuronal Cells and in the Trafficking of Neurotrophin Receptors

    Science.gov (United States)

    Bucci, Cecilia; Alifano, Pietro; Cogli, Laura

    2014-01-01

    Neurotrophins are a family of proteins that are important for neuronal development, neuronal survival and neuronal functions. Neurotrophins exert their role by binding to their receptors, the Trk family of receptor tyrosine kinases (TrkA, TrkB, and TrkC) and p75NTR, a member of the tumor necrosis factor (TNF) receptor superfamily. Binding of neurotrophins to receptors triggers a complex series of signal transduction events, which are able to induce neuronal differentiation but are also responsible for neuronal maintenance and neuronal functions. Rab proteins are small GTPases localized to the cytosolic surface of specific intracellular compartments and are involved in controlling vesicular transport. Rab proteins, acting as master regulators of the membrane trafficking network, play a central role in both trafficking and signaling pathways of neurotrophin receptors. Axonal transport represents the Achilles' heel of neurons, due to the long-range distance that molecules, organelles and, in particular, neurotrophin-receptor complexes have to cover. Indeed, alterations of axonal transport and, specifically, of axonal trafficking of neurotrophin receptors are responsible for several human neurodegenerative diseases, such as Huntington’s disease, Alzheimer’s disease, amyotrophic lateral sclerosis and some forms of Charcot-Marie-Tooth disease. In this review, we will discuss the link between Rab proteins and neurotrophin receptor trafficking and their influence on downstream signaling pathways. PMID:25295627

  19. Enlarging the nosological spectrum of hereditary diffuse leukoencephalopathy with axonal spheroids (HDLS).

    Science.gov (United States)

    Hoffmann, Sarah; Murrell, Jill; Harms, Lutz; Miller, Kelly; Meisel, Andreas; Brosch, Thomas; Scheel, Michael; Ghetti, Bernardino; Goebel, Hans-Hilmar; Stenzel, Werner

    2014-09-01

    Hereditary diffuse leukoencephalopathy with axonal spheroids (HDLS) is an autosomal dominant disease clinically characterized by cognitive decline, personality changes, motor impairment, parkinsonism and seizures. Recently, mutations in the colony-stimulating factor-1 receptor (CSF1R) gene have been shown to be associated with HDLS. We report clinical, neuropathological and molecular genetic findings of patients from a new family with a mutation in the CSF1R gene. Disease onset was earlier and disease progression was more rapid compared with previously reported patients. Psychiatric symptoms including personality changes, alcohol abuse and severe depression were the first symptoms in male patients. In the index, female patient, the initial symptom was cognitive decline. Magnetic resonance imaging (MRI) showed bilateral, confluent white matter lesions in the cerebrum. Stereotactic biopsy revealed loss of myelin and microglial activation as well as macrophage infiltration of the parenchyma. Numerous axonal swellings and spheroids were present. Ultrastructural analysis revealed pigment-containing macrophages. Axonal swellings were detected by electron microscopy not only in the central nervous system (CNS) but also in skin nerves. We identified a heterozygous mutation (c.2330G>A, p.R777Q) in the CSF1R gene. Through this report, we aim to enlarge the nosological spectrum of HDLS, providing new clinical descriptions as well as novel neuropathological findings from the peripheral nervous system. © 2014 International Society of Neuropathology.

  20. Electrophysiology of Axonal Constrictions

    Science.gov (United States)

    Johnson, Christopher; Jung, Peter; Brown, Anthony

    2013-03-01

    Axons of myelinated neurons are constricted at the nodes of Ranvier, where they are directly exposed to the extracellular space and where the vast majority of the ion channels are located. These constrictions are generated by local regulation of the kinetics of neurofilaments the most important cytoskeletal elements of the axon. In this paper we discuss how this shape affects the electrophysiological function of the neuron. Specifically, although the nodes are short (about 1 μm) in comparison to the distance between nodes (hundreds of μm) they have a substantial influence on the conduction velocity of neurons. We show through computational modeling that nodal constrictions (all other features such as numbers of ion channels left constant) reduce the required fiber diameter for a given target conduction velocity by up to 50% in comparison to an unconstricted axon. We further show that the predicted optimal fiber morphologies closely match reported fiber morphologies. Supported by The National Science Foundation (IOS 1146789)

  1. Internodal function in normal and regenerated mammalian axons

    DEFF Research Database (Denmark)

    Moldovan, M; Krarup, C

    2007-01-01

    AIM: Following Wallerian degeneration, peripheral myelinated axons have the ability to regenerate and, given a proper pathway, establish functional connections with targets. In spite of this capacity, the clinical outcome of nerve regeneration remains unsatisfactory. Early studies have found...... that regenerated internodes remain persistently short though this abnormality did not seem to influence recovery in conduction. It remains unclear to which extent abnormalities in axonal function itself may contribute to the poor outcome of nerve regeneration. METHODS: We review experimental evidence indicating...... that internodes play an active role in axonal function. RESULTS: By investigating internodal contribution to axonal excitability we have found evidence that axonal function may be permanently compromised in regenerated nerves. Furthermore, we illustrate that internodal function is also abnormal in regenerated...

  2. Can injured adult CNS axons regenerate by recapitulating development?

    Science.gov (United States)

    Hilton, Brett J; Bradke, Frank

    2017-10-01

    In the adult mammalian central nervous system (CNS), neurons typically fail to regenerate their axons after injury. During development, by contrast, neurons extend axons effectively. A variety of intracellular mechanisms mediate this difference, including changes in gene expression, the ability to form a growth cone, differences in mitochondrial function/axonal transport and the efficacy of synaptic transmission. In turn, these intracellular processes are linked to extracellular differences between the developing and adult CNS. During development, the extracellular environment directs axon growth and circuit formation. In adulthood, by contrast, extracellular factors, such as myelin and the extracellular matrix, restrict axon growth. Here, we discuss whether the reactivation of developmental processes can elicit axon regeneration in the injured CNS. © 2017. Published by The Company of Biologists Ltd.

  3. Dependence of regenerated sensory axons on continuous neurotrophin-3 delivery.

    Science.gov (United States)

    Hou, Shaoping; Nicholson, LaShae; van Niekerk, Erna; Motsch, Melanie; Blesch, Armin

    2012-09-19

    Previous studies have shown that injured dorsal column sensory axons extend across a spinal cord lesion site if axons are guided by a gradient of neurotrophin-3 (NT-3) rostral to the lesion. Here we examined whether continuous NT-3 delivery is necessary to sustain regenerated axons in the injured spinal cord. Using tetracycline-regulated (tet-off) lentiviral gene delivery, NT-3 expression was tightly controlled by doxycycline administration. To examine axon growth responses to regulated NT-3 expression, adult rats underwent a C3 dorsal funiculus lesion. The lesion site was filled with bone marrow stromal cells, tet-off-NT-3 virus was injected rostral to the lesion site, and the intrinsic growth capacity of sensory neurons was activated by a conditioning lesion. When NT-3 gene expression was turned on, cholera toxin β-subunit-labeled sensory axons regenerated into and beyond the lesion/graft site. Surprisingly, the number of regenerated axons significantly declined when NT-3 expression was turned off, whereas continued NT-3 expression sustained regenerated axons. Quantification of axon numbers beyond the lesion demonstrated a significant decline of axon growth in animals with transient NT-3 expression, only some axons that had regenerated over longer distance were sustained. Regenerated axons were located in white matter and did not form axodendritic synapses but expressed presynaptic markers when closely associated with NG2-labeled cells. A decline in axon density was also observed within cellular grafts after NT-3 expression was turned off possibly via reduction in L1 and laminin expression in Schwann cells. Thus, multiple mechanisms underlie the inability of transient NT-3 expression to fully sustain regenerated sensory axons.

  4. Receptor for Advanced Glycation End Products (RAGE and Its Ligands: Focus on Spinal Cord Injury

    Directory of Open Access Journals (Sweden)

    Juhyun Song

    2014-07-01

    Full Text Available Spinal cord injury (SCI results in neuronal and glial death and the loss of axons at the injury site. Inflammation after SCI leads to the inhibition of tissue regeneration and reduced neuronal survival. In addition, the loss of axons after SCI results in functional loss below the site of injury accompanied by neuronal cell body’s damage. Consequently, reducing inflammation and promoting axonal regeneration after SCI is a worthy therapeutic goal. The receptor for advanced glycation end products (RAGE is a transmembrane protein and receptor of the immunoglobulin superfamily. RAGE is implicated in inflammation and neurodegeneration. Several recent studies demonstrated an association between RAGE and central nervous system disorders through various mechanisms. However, the relationship between RAGE and SCI has not been shown. It is imperative to elucidate the association between RAGE and SCI, considering that RAGE relates to inflammation and axonal degeneration following SCI. Hence, the present review highlights recent research regarding RAGE as a compelling target for the treatment of SCI.

  5. A novel Drosophila injury model reveals severed axons are cleared through a Draper/MMP-1 signaling cascade

    Science.gov (United States)

    Purice, Maria D; Ray, Arpita; Münzel, Eva Jolanda; Pope, Bernard J; Park, Daniel J; Speese, Sean D; Logan, Mary A

    2017-01-01

    Neural injury triggers swift responses from glia, including glial migration and phagocytic clearance of damaged neurons. The transcriptional programs governing these complex innate glial immune responses are still unclear. Here, we describe a novel injury assay in adult Drosophila that elicits widespread glial responses in the ventral nerve cord (VNC). We profiled injury-induced changes in VNC gene expression by RNA sequencing (RNA-seq) and found that responsive genes fall into diverse signaling classes. One factor, matrix metalloproteinase-1 (MMP-1), is induced in Drosophila ensheathing glia responding to severed axons. Interestingly, glial induction of MMP-1 requires the highly conserved engulfment receptor Draper, as well as AP-1 and STAT92E. In MMP-1 depleted flies, glia do not properly infiltrate neuropil regions after axotomy and, as a consequence, fail to clear degenerating axonal debris. This work identifies Draper-dependent activation of MMP-1 as a novel cascade required for proper glial clearance of severed axons. DOI: http://dx.doi.org/10.7554/eLife.23611.001 PMID:28825401

  6. Cell intrinsic modulation of Wnt signaling controls neuroblast migration in C. elegans

    NARCIS (Netherlands)

    Mentink, Remco A; Middelkoop, Teije C; Rella, Lorenzo; Ji, Ni; Tang, Chung Yin; Betist, Marco C; van Oudenaarden, Alexander; Korswagen, Hendrik C

    2014-01-01

    Members of the Wnt family of secreted signaling proteins are key regulators of cell migration and axon guidance. In the nematode C. elegans, the migration of the QR neuroblast descendants requires multiple Wnt ligands and receptors. We found that the migration of the QR descendants is divided into

  7. Functional Impact of Corticotropin-Releasing Factor Exposure on Tau Phosphorylation and Axon Transport.

    Directory of Open Access Journals (Sweden)

    Michelle H Le

    Full Text Available Stress exposure or increased levels of corticotropin-releasing factor (CRF induce hippocampal tau phosphorylation (tau-P in rodent models, a process that is dependent on the type-1 CRF receptor (CRFR1. Although these preclinical studies on stress-induced tau-P provide mechanistic insight for epidemiological work that identifies stress as a risk factor for Alzheimer's disease (AD, the actual impact of stress-induced tau-P on neuronal function remains unclear. To determine the functional consequences of stress-induced tau-P, we developed a novel mouse neuronal cell culture system to explore the impact of acute (0.5hr and chronic (2hr CRF treatment on tau-P and integral cell processes such as axon transport. Consistent with in vivo reports, we found that chronic CRF treatment increased tau-P levels and caused globular accumulations of phosphorylated tau in dendritic and axonal processes. Furthermore, while both acute and chronic CRF treatment led to significant reduction in CREB activation and axon transport of brain-derived neurotrophic factor (BDNF, this was not the case with mitochondrial transport. Acute CRF treatment caused increased mitochondrial velocity and distance traveled in neurons, while chronic CRF treatment modestly decreased mitochondrial velocity and greatly increased distance traveled. These results suggest that transport of cellular energetics may take priority over growth factors during stress. Tau-P was required for these changes, as co-treatment of CRF with a GSK kinase inhibitor prevented CRF-induced tau-P and all axon transport changes. Collectively, our results provide mechanistic insight into the consequences of stress peptide-induced tau-P and provide an explanation for how chronic stress via CRF may lead to neuronal vulnerability in AD.

  8. 4S RNA is transported axonally in normal and regenerating axons of the sciatic nerves of rats

    Energy Technology Data Exchange (ETDEWEB)

    Lindquist, T D; Ingoglia, N A; Gould, R M [Departments of Physiology and Neuroscience, New Jersey Medical School, Newark, NJ, USA

    1982-12-28

    Experiments were designed to determine if following injection of (/sup 3/H)uridine into the lumbar spinal cord of the rat, (/sup 3/H)RNA could be demonstrated within axons of the sciatic nerve, and if 4S RNA is the predominant predominant RNA species present in these axons.

  9. Outer Electrospun Polycaprolactone Shell Induces Massive Foreign Body Reaction and Impairs Axonal Regeneration through 3D Multichannel Chitosan Nerve Guides

    OpenAIRE

    Duda, Sven; Dreyer, Lutz; Behrens, Peter; Wienecke, Soenke; Chakradeo, Tanmay; Glasmacher, Birgit; Haastert-Talini, Kirsten

    2014-01-01

    We report on the performance of composite nerve grafts with an inner 3D multichannel porous chitosan core and an outer electrospun polycaprolactone shell. The inner chitosan core provided multiple guidance channels for regrowing axons. To analyze the in vivo properties of the bare chitosan cores, we separately implanted them into an epineural sheath. The effects of both graft types on structural and functional regeneration across a 10 mm rat sciatic nerve gap were compared to autologous nerv...

  10. The Absence of Sensory Axon Bifurcation Affects Nociception and Termination Fields of Afferents in the Spinal Cord

    Directory of Open Access Journals (Sweden)

    Philip Tröster

    2018-02-01

    Full Text Available A cGMP signaling cascade composed of C-type natriuretic peptide, the guanylyl cyclase receptor Npr2 and cGMP-dependent protein kinase I (cGKI controls the bifurcation of sensory axons upon entering the spinal cord during embryonic development. However, the impact of axon bifurcation on sensory processing in adulthood remains poorly understood. To investigate the functional consequences of impaired axon bifurcation during adult stages we generated conditional mouse mutants of Npr2 and cGKI (Npr2fl/fl;Wnt1Cre and cGKIKO/fl;Wnt1Cre that lack sensory axon bifurcation in the absence of additional phenotypes observed in the global knockout mice. Cholera toxin labeling in digits of the hind paw demonstrated an altered shape of sensory neuron termination fields in the spinal cord of conditional Npr2 mouse mutants. Behavioral testing of both sexes indicated that noxious heat sensation and nociception induced by chemical irritants are impaired in the mutants, whereas responses to cold sensation, mechanical stimulation, and motor coordination are not affected. Recordings from C-fiber nociceptors in the hind limb skin showed that Npr2 function was not required to maintain normal heat sensitivity of peripheral nociceptors. Thus, the altered behavioral responses to noxious heat found in Npr2fl/fl;Wnt1Cre mice is not due to an impaired C-fiber function. Overall, these data point to a critical role of axonal bifurcation for the processing of pain induced by heat or chemical stimuli.

  11. Effects of cholinergic compounds on the axon-Schwann cell relationship in the squid nerve fiber.

    Science.gov (United States)

    Villegas, J

    1975-04-01

    The effects of acetylcholine, carbamylcholine, D-tubocurarine, eserine, and alpha-bungarotoxin on the Schwann cell electrical potential of resting and stimulated squid nerve fibers were studied. Acetylcholine (10-7 M) and barbamylcholine (10-6 M) induce a prolonged hyper polarization in the Schwann cells of the unstimulated nerve fiber. In the presence of carbamylcholine (10-6 M) the behavior of the Schwann cell membrane to changes in the external potassium concentration approximates the behavior of an ideal potassium electrode. D-Tubocurarine (10-9 M) blocks the hyperpolarizing effects of nerve impulse trains and carbamylcholine (10-6 M), whereas at the same concentration eserine prolongs the Schwann cell hyperpolarizations induced by axon stimulation or by acetylcholine (10-7 M). alpha-Bungarotoxin (10-9M) also blocks the hyperpolarizing effect of nerve impulse trains and of carbamylcholine. D-Tubocurarine (10-5M) protects the Schwann cells against the irreversible action of alpha-bungarotoxin. These results show the existence of acetylcholine receptors in the Schwann cell membrane. Preliminary measurements of the binding of 125I-alpha bungarotoxin to the plasma membranes isolated from squid nerves also indicate the presence of acetylcholine receptors. These findings support the involvement of cholinergic mechanisms in the axon-Schwann cell relationship previously described.

  12. Axonal Conduction Delays, Brain State, and Corticogeniculate Communication.

    Science.gov (United States)

    Stoelzel, Carl R; Bereshpolova, Yulia; Alonso, Jose-Manuel; Swadlow, Harvey A

    2017-06-28

    Thalamocortical conduction times are short, but layer 6 corticothalamic axons display an enormous range of conduction times, some exceeding 40-50 ms. Here, we investigate (1) how axonal conduction times of corticogeniculate (CG) neurons are related to the visual information conveyed to the thalamus, and (2) how alert versus nonalert awake brain states affect visual processing across the spectrum of CG conduction times. In awake female Dutch-Belted rabbits, we found 58% of CG neurons to be visually responsive, and 42% to be unresponsive. All responsive CG neurons had simple, orientation-selective receptive fields, and generated sustained responses to stationary stimuli. CG axonal conduction times were strongly related to modulated firing rates (F1 values) generated by drifting grating stimuli, and their associated interspike interval distributions, suggesting a continuum of visual responsiveness spanning the spectrum of axonal conduction times. CG conduction times were also significantly related to visual response latency, contrast sensitivity (C-50 values), directional selectivity, and optimal stimulus velocity. Increasing alertness did not cause visually unresponsive CG neurons to become responsive and did not change the response linearity (F1/F0 ratios) of visually responsive CG neurons. However, for visually responsive CG neurons, increased alertness nearly doubled the modulated response amplitude to optimal visual stimulation (F1 values), significantly shortened response latency, and dramatically increased response reliability. These effects of alertness were uniform across the broad spectrum of CG axonal conduction times. SIGNIFICANCE STATEMENT Corticothalamic neurons of layer 6 send a dense feedback projection to thalamic nuclei that provide input to sensory neocortex. While sensory information reaches the cortex after brief thalamocortical axonal delays, corticothalamic axons can exhibit conduction delays of <2 ms to 40-50 ms. Here, in the corticogeniculate

  13. Loss of Fractalkine Signaling Exacerbates Axon Transport Dysfunction in a Chronic Model of Glaucoma.

    Science.gov (United States)

    Breen, Kevin T; Anderson, Sarah R; Steele, Michael R; Calkins, David J; Bosco, Alejandra; Vetter, Monica L

    2016-01-01

    Neurodegeneration in glaucoma results in decline and loss of retinal ganglion cells (RGCs), and is associated with activation of myeloid cells such as microglia and macrophages. The chemokine fractalkine (FKN or Cx3cl1) mediates communication from neurons to myeloid cells. Signaling through its receptor Cx3cr1 has been implicated in multiple neurodegenerative diseases, but the effects on neuronal pathology are variable. Since it is unknown how FKN-mediated crosstalk influences RGC degeneration in glaucoma, we assessed this in a chronic mouse model, DBA/2J. We analyzed a DBA/2J substrain deficient in Cx3cr1, and compared compartmentalized RGC degeneration and myeloid cell responses to those in standard DBA/2J mice. We found that loss of FKN signaling exacerbates axon transport dysfunction, an early event in neurodegeneration, with a significant increase in RGCs with somal accumulation of the axonal protein phosphorylated neurofilament, and reduced retinal expression of genes involved in axon transport, Kif1b, and Atp8a2. There was no change in the loss of Brn3-positive RGCs, and no difference in the extent of damage to the proximal optic nerve, suggesting that the loss of fractalkine signaling primarily affects axon transport. Since Cx3cr1 is specifically expressed in myeloid cells, we assessed changes in retinal microglial number and activation, changes in gene expression, and the extent of macrophage infiltration. We found that loss of fractalkine signaling led to innate immune changes within the retina, including increased infiltration of peripheral macrophages and upregulated nitric oxide synthase-2 (Nos-2) expression in myeloid cells, which contributes to the production of NO and can promote axon transport deficits. In contrast, resident retinal microglia appeared unchanged either in number, morphology, or expression of the myeloid activation marker ionized calcium binding adaptor molecule 1 (Iba1). There was also no significant increase in the proinflammatory

  14. Modelling genetic reorganization in the mouse spinal cord affecting left-right coordination during locomotion

    DEFF Research Database (Denmark)

    Rybak, Ilya A.; Shevtsova, Natalia A.; Kiehn, Ole

    2013-01-01

    glutamatergic interneurons, whose axon guidance involves the EphA4 receptor. In EphA4 knockout (KO) and Netrin-1 KO mice, the normal left-right alternating pattern is replaced with a synchronized hopping gait, and the cord of DCC KO mice exhibits uncoordinated left and right oscillations. To investigate...

  15. Axonal inclusions in the crab Hemigrapsus nudus.

    Science.gov (United States)

    Smith, R S

    1978-10-01

    Light microscopic examination of living giant axons from the walking legs of Hemigrapsus nudus revealed intra-axonal inclusions which were usually several tens of micrometers long and about 5 micron wide. The inclusions were filled with small light-scattering particles. The inclusions were shown, by thin section electron microscopy, to be composed largely 68% by volume) of mitochondria. Each inclusion was surrounded by membrane bounded spaces which are presumed to represent a part of the smooth endoplasmic reticulum. Similar inclusions were not found in the leg axons of a variety of other decapod crustaceans.

  16. Con-nectin axons and dendrites.

    Science.gov (United States)

    Beaudoin, Gerard M J

    2006-07-03

    Unlike adherens junctions, synapses are asymmetric connections, usually between axons and dendrites, that rely on various cell adhesion molecules for structural stability and function. Two cell types of adhesion molecules found at adherens junctions, cadherins and nectins, are thought to mediate homophilic interaction between neighboring cells. In this issue, Togashi et al. (see p. 141) demonstrate that the differential localization of two heterophilic interacting nectins mediates the selective attraction of axons and dendrites in cooperation with cadherins.

  17. Mechanisms of Distal Axonal Degeneration in Peripheral Neuropathies

    Science.gov (United States)

    Cashman, Christopher R.; Höke, Ahmet

    2015-01-01

    Peripheral neuropathy is a common complication of a variety of diseases and treatments, including diabetes, cancer chemotherapy, and infectious causes (HIV, hepatitis C, and Campylobacter jejuni). Despite the fundamental difference between these insults, peripheral neuropathy develops as a combination of just six primary mechanisms: altered metabolism, covalent modification, altered organelle function and reactive oxygen species formation, altered intracellular and inflammatory signaling, slowed axonal transport, and altered ion channel dynamics and expression. All of these pathways converge to lead to axon dysfunction and symptoms of neuropathy. The detailed mechanisms of axon degeneration itself have begun to be elucidated with studies of animal models with altered degeneration kinetics, including the slowed Wallerian degeneration (Wlds) and Sarmknockout animal models. These studies have shown axonal degeneration to occur througha programmed pathway of injury signaling and cytoskeletal degradation. Insights into the common disease insults that converge on the axonal degeneration pathway promise to facilitate the development of therapeutics that may be effective against other mechanisms of neurodegeneration. PMID:25617478

  18. Oligodendrocyte Development in the Absence of Their Target Axons In Vivo.

    Directory of Open Access Journals (Sweden)

    Rafael Almeida

    Full Text Available Oligodendrocytes form myelin around axons of the central nervous system, enabling saltatory conduction. Recent work has established that axons can regulate certain aspects of oligodendrocyte development and myelination, yet remarkably oligodendrocytes in culture retain the ability to differentiate in the absence of axons and elaborate myelin sheaths around synthetic axon-like substrates. It remains unclear the extent to which the life-course of oligodendrocytes requires the presence of, or signals derived from axons in vivo. In particular, it is unclear whether the specific axons fated for myelination regulate the oligodendrocyte population in a living organism, and if so, which precise steps of oligodendrocyte-cell lineage progression are regulated by target axons. Here, we use live-imaging of zebrafish larvae carrying transgenic reporters that label oligodendrocyte-lineage cells to investigate which aspects of oligodendrocyte development, from specification to differentiation, are affected when we manipulate the target axonal environment. To drastically reduce the number of axons targeted for myelination, we use a previously identified kinesin-binding protein (kbp mutant, in which the first myelinated axons in the spinal cord, reticulospinal axons, do not fully grow in length, creating a region in the posterior spinal cord where most initial targets for myelination are absent. We find that a 73% reduction of reticulospinal axon surface in the posterior spinal cord of kbp mutants results in a 27% reduction in the number of oligodendrocytes. By time-lapse analysis of transgenic OPC reporters, we find that the reduction in oligodendrocyte number is explained by a reduction in OPC proliferation and survival. Interestingly, OPC specification and migration are unaltered in the near absence of normal axonal targets. Finally, we find that timely differentiation of OPCs into oligodendrocytes does not depend at all on the presence of target axons

  19. Robo4 maintains vessel integrity and inhibits angiogenesis by interacting with UNC5B.

    Science.gov (United States)

    Koch, Alexander W; Mathivet, Thomas; Larrivée, Bruno; Tong, Raymond K; Kowalski, Joe; Pibouin-Fragner, Laurence; Bouvrée, Karine; Stawicki, Scott; Nicholes, Katrina; Rathore, Nisha; Scales, Suzie J; Luis, Elizabeth; del Toro, Raquel; Freitas, Catarina; Bréant, Christiane; Michaud, Annie; Corvol, Pierre; Thomas, Jean-Léon; Wu, Yan; Peale, Franklin; Watts, Ryan J; Tessier-Lavigne, Marc; Bagri, Anil; Eichmann, Anne

    2011-01-18

    Robo4 is an endothelial cell-specific member of the Roundabout axon guidance receptor family. To identify Robo4 binding partners, we performed a protein-protein interaction screen with the Robo4 extracellular domain. We find that Robo4 specifically binds to UNC5B, a vascular Netrin receptor, revealing unexpected interactions between two endothelial guidance receptors. We show that Robo4 maintains vessel integrity by activating UNC5B, which inhibits signaling downstream of vascular endothelial growth factor (VEGF). Function-blocking monoclonal antibodies against Robo4 and UNC5B increase angiogenesis and disrupt vessel integrity. Soluble Robo4 protein inhibits VEGF-induced vessel permeability and rescues barrier defects in Robo4(-/-) mice, but not in mice treated with anti-UNC5B. Thus, Robo4-UNC5B signaling maintains vascular integrity by counteracting VEGF signaling in endothelial cells, identifying a novel function of guidance receptor interactions in the vasculature. Copyright © 2011 Elsevier Inc. All rights reserved.

  20. Type III Nrg1 back signaling enhances functional TRPV1 along sensory axons contributing to basal and inflammatory thermal pain sensation.

    Science.gov (United States)

    Canetta, Sarah E; Luca, Edlira; Pertot, Elyse; Role, Lorna W; Talmage, David A

    2011-01-01

    Type III Nrg1, a member of the Nrg1 family of signaling proteins, is expressed in sensory neurons, where it can signal in a bi-directional manner via interactions with the ErbB family of receptor tyrosine kinases (ErbB RTKs). Type III Nrg1 signaling as a receptor (Type III Nrg1 back signaling) can acutely activate phosphatidylinositol-3-kinase (PtdIns3K) signaling, as well as regulate levels of α7* nicotinic acetylcholine receptors, along sensory axons. Transient receptor potential vanilloid 1 (TRPV1) is a cation-permeable ion channel found in primary sensory neurons that is necessary for the detection of thermal pain and for the development of thermal hypersensitivity to pain under inflammatory conditions. Cell surface expression of TRPV1 can be enhanced by activation of PtdIns3K, making it a potential target for regulation by Type III Nrg1. We now show that Type III Nrg1 signaling in sensory neurons affects functional axonal TRPV1 in a PtdIns3K-dependent manner. Furthermore, mice heterozygous for Type III Nrg1 have specific deficits in their ability to respond to noxious thermal stimuli and to develop capsaicin-induced thermal hypersensitivity to pain. Cumulatively, these results implicate Type III Nrg1 as a novel regulator of TRPV1 and a molecular mediator of nociceptive function.

  1. Type III Nrg1 back signaling enhances functional TRPV1 along sensory axons contributing to basal and inflammatory thermal pain sensation.

    Directory of Open Access Journals (Sweden)

    Sarah E Canetta

    Full Text Available Type III Nrg1, a member of the Nrg1 family of signaling proteins, is expressed in sensory neurons, where it can signal in a bi-directional manner via interactions with the ErbB family of receptor tyrosine kinases (ErbB RTKs. Type III Nrg1 signaling as a receptor (Type III Nrg1 back signaling can acutely activate phosphatidylinositol-3-kinase (PtdIns3K signaling, as well as regulate levels of α7* nicotinic acetylcholine receptors, along sensory axons. Transient receptor potential vanilloid 1 (TRPV1 is a cation-permeable ion channel found in primary sensory neurons that is necessary for the detection of thermal pain and for the development of thermal hypersensitivity to pain under inflammatory conditions. Cell surface expression of TRPV1 can be enhanced by activation of PtdIns3K, making it a potential target for regulation by Type III Nrg1. We now show that Type III Nrg1 signaling in sensory neurons affects functional axonal TRPV1 in a PtdIns3K-dependent manner. Furthermore, mice heterozygous for Type III Nrg1 have specific deficits in their ability to respond to noxious thermal stimuli and to develop capsaicin-induced thermal hypersensitivity to pain. Cumulatively, these results implicate Type III Nrg1 as a novel regulator of TRPV1 and a molecular mediator of nociceptive function.

  2. Quantitative Study of NPY-Expressing GABAergic Neurons and Axons in Rat Spinal Dorsal Horn*

    OpenAIRE

    Polg?r, Erika; Sardella, Thomas CP; Watanabe, Masahiko; Todd, Andrew J

    2010-01-01

    Between 25?40% of neurons in laminae I?III are GABAergic, and some of these express neuropeptide Y (NPY). We previously reported that NPY-immunoreactive axons form numerous synapses on lamina III projection neurons that possess the neurokinin 1 receptor (NK1r). The aims of this study were to determine the proportion of neurons and GABAergic boutons in this region that contain NPY, and to look for evidence that they selectively innervate different neuronal populations. We found that 4?6% of ne...

  3. Axonal regeneration and neuronal function are preserved in motor neurons lacking ß-actin in vivo.

    Directory of Open Access Journals (Sweden)

    Thomas R Cheever

    2011-03-01

    Full Text Available The proper localization of ß-actin mRNA and protein is essential for growth cone guidance and axon elongation in cultured neurons. In addition, decreased levels of ß-actin mRNA and protein have been identified in the growth cones of motor neurons cultured from a mouse model of Spinal Muscular Atrophy (SMA, suggesting that ß-actin loss-of-function at growth cones or pre-synaptic nerve terminals could contribute to the pathogenesis of this disease. However, the role of ß-actin in motor neurons in vivo and its potential relevance to disease has yet to be examined. We therefore generated motor neuron specific ß-actin knock-out mice (Actb-MNsKO to investigate the function of ß-actin in motor neurons in vivo. Surprisingly, ß-actin was not required for motor neuron viability or neuromuscular junction maintenance. Skeletal muscle from Actb-MNsKO mice showed no histological indication of denervation and did not significantly differ from controls in several measurements of physiologic function. Finally, motor axon regeneration was unimpaired in Actb-MNsKO mice, suggesting that ß-actin is not required for motor neuron function or regeneration in vivo.

  4. Axonal loss in the multiple sclerosis spinal cord revisited.

    Science.gov (United States)

    Petrova, Natalia; Carassiti, Daniele; Altmann, Daniel R; Baker, David; Schmierer, Klaus

    2018-05-01

    Preventing chronic disease deterioration is an unmet need in people with multiple sclerosis, where axonal loss is considered a key substrate of disability. Clinically, chronic multiple sclerosis often presents as progressive myelopathy. Spinal cord cross-sectional area (CSA) assessed using MRI predicts increasing disability and has, by inference, been proposed as an indirect index of axonal degeneration. However, the association between CSA and axonal loss, and their correlation with demyelination, have never been systematically investigated using human post mortem tissue. We extensively sampled spinal cords of seven women and six men with multiple sclerosis (mean disease duration= 29 years) and five healthy controls to quantify axonal density and its association with demyelination and CSA. 396 tissue blocks were embedded in paraffin and immuno-stained for myelin basic protein and phosphorylated neurofilaments. Measurements included total CSA, areas of (i) lateral cortico-spinal tracts, (ii) gray matter, (iii) white matter, (iv) demyelination, and the number of axons within the lateral cortico-spinal tracts. Linear mixed models were used to analyze relationships. In multiple sclerosis CSA reduction at cervical, thoracic and lumbar levels ranged between 19 and 24% with white (19-24%) and gray (17-21%) matter atrophy contributing equally across levels. Axonal density in multiple sclerosis was lower by 57-62% across all levels and affected all fibers regardless of diameter. Demyelination affected 24-48% of the gray matter, most extensively at the thoracic level, and 11-13% of the white matter, with no significant differences across levels. Disease duration was associated with reduced axonal density, however not with any area index. Significant association was detected between focal demyelination and decreased axonal density. In conclusion, over nearly 30 years multiple sclerosis reduces axonal density by 60% throughout the spinal cord. Spinal cord cross sectional area

  5. Time course of ongoing activity during neuritis and following axonal transport disruption.

    Science.gov (United States)

    Satkeviciute, Ieva; Goodwin, George; Bove, Geoffrey M; Dilley, Andrew

    2018-05-01

    Local nerve inflammation (neuritis) leads to ongoing activity and axonal mechanical sensitivity (AMS) along intact nociceptor axons and disrupts axonal transport. This phenomenon forms the most feasible cause of radiating pain, such as sciatica. We have previously shown that axonal transport disruption without inflammation or degeneration also leads to AMS but does not cause ongoing activity at the time point when AMS occurs, despite causing cutaneous hypersensitivity. However, there have been no systematic studies of ongoing activity during neuritis or noninflammatory axonal transport disruption. In this study, we present the time course of ongoing activity from primary sensory neurons following neuritis and vinblastine-induced axonal transport disruption. Whereas 24% of C/slow Aδ-fiber neurons had ongoing activity during neuritis, few (disruption of axonal transport without inflammation does not lead to ongoing activity in sensory neurons, including nociceptors, but does cause a rapid and transient development of AMS. Because it is proposed that AMS underlies mechanically induced radiating pain, and a transient disruption of axonal transport (as previously reported) leads to transient AMS, it follows that processes that disrupt axonal transport, such as neuritis, must persist to maintain AMS and the associated symptoms. NEW & NOTEWORTHY Many patients with radiating pain lack signs of nerve injury on clinical examination but may have neuritis, which disrupts axonal transport. We have shown that axonal transport disruption does not induce ongoing activity in primary sensory neurons but does cause transient axonal mechanical sensitivity. The present data complete a profile of key axonal sensitivities following axonal transport disruption. Collectively, this profile supports that an active peripheral process is necessary for maintained axonal sensitivities.

  6. Epigenetic regulation of axon and dendrite growth

    Directory of Open Access Journals (Sweden)

    Ephraim F Trakhtenberg

    2012-03-01

    Full Text Available Neuroregenerative therapies for central nervous system (CNS injury, neurodegenerative disease, or stroke require axons of damaged neurons to grow and reinnervate their targets. However, mature mammalian CNS neurons do not regenerate their axons, limiting recovery in these diseases (Yiu and He, 2006. CNS’ regenerative failure may be attributable to the development of an inhibitory CNS environment by glial-associated inhibitory molecules (Yiu and He, 2006, and by various cell-autonomous factors (Sun and He, 2010. Intrinsic axon growth ability also declines developmentally (Li et al., 1995; Goldberg et al., 2002; Bouslama-Oueghlani et al., 2003; Blackmore and Letourneau, 2006 and is dependent on transcription (Moore et al., 2009. Although neurons’ intrinsic capacity for axon growth may depend in part on the panoply of expressed transcription factors (Moore and Goldberg, 2011, epigenetic factors such as the accessibility of DNA and organization of chromatin are required for downstream genes to be transcribed. Thus a potential approach to overcoming regenerative failure focuses on the epigenetic mechanisms regulating regenerative gene expression in the CNS. Here we review molecular mechanisms regulating the epigenetic state of DNA through chromatin modifications, their implications for regulating axon and dendrite growth, and important new directions for this field of study.

  7. Neuron-to-neuron transmission of α-synuclein fibrils through axonal transport

    Science.gov (United States)

    Freundt, Eric C.; Maynard, Nate; Clancy, Eileen K.; Roy, Shyamali; Bousset, Luc; Sourigues, Yannick; Covert, Markus; Melki, Ronald; Kirkegaard, Karla; Brahic, Michel

    2012-01-01

    Objective The lesions of Parkinson's disease spread through the brain in a characteristic pattern that corresponds to axonal projections. Previous observations suggest that misfolded α-synuclein could behave as a prion, moving from neuron to neuron and causing endogenous α-synuclein to misfold. Here, we characterized and quantified the axonal transport of α-synuclein fibrils and showed that fibrils could be transferred from axons to second-order neurons following anterograde transport. Methods We grew primary cortical mouse neurons in microfluidic devices to separate soma from axonal projections in fluidically isolated microenvironments. We used live-cell imaging and immunofluorescence to characterize the transport of fluorescent α-synuclein fibrils and their transfer to second-order neurons. Results Fibrillar α-synuclein was internalized by primary neurons and transported in axons with kinetics consistent with slow component-b of axonal transport (fast axonal transport with saltatory movement). Fibrillar α-synuclein was readily observed in the cell bodies of second-order neurons following anterograde axonal transport. Axon-to-soma transfer appeared not to require synaptic contacts. Interpretation These results support the hypothesis that the progression of Parkinson's disease can be caused by neuron-to-neuron spread of α-synuclein aggregates and that the anatomical pattern of progression of lesions between axonally connected areas results from the axonal transport of such aggregates. That the transfer did not appear to be transsynaptic gives hope that α-synuclein fibrils could be intercepted by drugs during the extra-cellular phase of their journey. PMID:23109146

  8. Axon density and axon orientation dispersion in children born preterm

    NARCIS (Netherlands)

    Kelly, Claire E.; Thompson, Deanne K.; Chen, Jian; Leemans, Alexander; Adamson, Christopher L.; Inder, Terrie E.; Cheong, Jeanie L Y; Doyle, Lex W.; Anderson, Peter J.

    2016-01-01

    Background Very preterm birth (VPT, <32 weeks' gestation) is associated with altered white matter fractional anisotropy (FA), the biological basis of which is uncertain but may relate to changes in axon density and/or dispersion, which can be measured using Neurite Orientation Dispersion and Density

  9. Axon-glia interaction and membrane traffic in myelin formation

    Directory of Open Access Journals (Sweden)

    Robin eWhite

    2014-01-01

    Full Text Available In vertebrate nervous systems myelination of neuronal axons has evolved to increase conduction velocity of electrical impulses with minimal space and energy requirements. Myelin is formed by specialised glial cells which ensheath axons with a lipid-rich insulating membrane. Myelination is a multi-step process initiated by axon-glia recognition triggering glial polarisation followed by targeted myelin membrane expansion and compaction. Thereby, a myelin sheath of complex subdomain structure is established. Continuous communication between neurons and glial cells is essential for myelin maintenance and axonal integrity. A diverse group of diseases, from multiple sclerosis to schizophrenia, have been linked to malfunction of myelinating cells reflecting the physiological importance of the axon-glial unit. This review describes the mechanisms of axonal signal integration by oligodendrocytes emphasising the central role of the Src-family kinase Fyn during CNS myelination. Furthermore, we discuss myelin membrane trafficking with particular focus on endocytic recycling and the control of PLP (proteolipid protein transport by SNARE proteins. Finally, PLP mistrafficking is considered in the context of myelin diseases.

  10. In vivo testing of a 3D bifurcating microchannel scaffold inducing separation of regenerating axon bundles in peripheral nerves

    Science.gov (United States)

    Stoyanova, Irina I.; van Wezel, Richard J. A.; Rutten, Wim L. C.

    2013-12-01

    Artificial nerve guidance channels enhance the regenerative effectiveness in an injured peripheral nerve but the existing design so far has been limited to basic straight tubes simply guiding the growth to bridge the gap. Hence, one of the goals in development of more effective neuroprostheses is to create bidirectional highly selective neuro-electronic interface between a prosthetic device and the severed nerve. A step towards improving selectivity for both recording and stimulation have been made with some recent in vitro studies which showed that three-dimensional (3D) bifurcating microchannels can separate neurites growing on a planar surface and bring them into contact with individual electrodes. Since the growing axons in vivo have the innate tendency to group in bundles surrounded by connective tissue, one of the big challenges in neuro-prosthetic interface design is how to overcome it. Therefore, we performed experiments with 3D bifurcating guidance scaffolds implanted in the sciatic nerve of rats to test if this new channel architecture could trigger separation pattern of ingrowth also in vivo. Our results showed that this new method enabled the re-growth of neurites into channels with gradually diminished width (80, 40 and 20 µm) and facilitated the separation of the axonal bundles with 91% success. It seems that the 3D bifurcating scaffold might contribute towards conveying detailed neural control and sensory feedback to users of prosthetic devices, and thus could improve the quality of their daily life.

  11. Axon diameter mapping in crossing fibers with diffusion MRI

    DEFF Research Database (Denmark)

    Zhang, Hui; Dyrby, Tim B; Alexander, Daniel C

    2011-01-01

    This paper proposes a technique for a previously unaddressed problem, namely, mapping axon diameter in crossing fiber regions, using diffusion MRI. Direct measurement of tissue microstructure of this kind using diffusion MRI offers a new class of biomarkers that give more specific information about...... tissue than measures derived from diffusion tensor imaging. Most existing techniques for axon diameter mapping assume a single axon orientation in the tissue model, which limits their application to only the most coherently oriented brain white matter, such as the corpus callosum, where the single...... model to enable axon diameter mapping in voxels with crossing fibers. We show in simulation that the technique can provide robust axon diameter estimates in a two-fiber crossing with the crossing angle as small as 45 degrees. Using ex vivo imaging data, we further demonstrate the feasibility...

  12. miR126-5p down-regulation facilitates axon degeneration and NMJ disruption via a non-cell-autonomous mechanism in ALS.

    Science.gov (United States)

    Maimon, Roy; Ionescu, Ariel; Bonnie, Avichai; Sweetat, Sahar; Wald-Altman, Shane; Inbar, Shani; Gradus, Tal; Trotti, Davide; Weil, Miguel; Behar, Oded; Perlson, Eran

    2018-05-17

    Axon degeneration and disruption of neuromuscular junctions (NMJs) are key events in Amyotrophic Lateral Sclerosis (ALS) pathology. Although the disease's etiology is not fully understood, it is thought to involve a non-cell-autonomous mechanism and alterations in RNA metabolism. Here, we identified reduced levels of miR-126-5p in pre-symptomatic ALS male mice models, and an increase in its targets: axon destabilizing type-3 Semaphorins and their co-receptor Neuropilins. Utilizing compartmentalized in vitro co-cultures, we demonstrated that myocytes expressing diverse ALS-causing mutations promote axon degeneration and NMJ dysfunction, which were inhibited by applying Neuropilin1 (NRP1) blocking antibody. Finally, overexpressing miR126-5p is sufficient to transiently rescue axon degeneration and NMJ disruption both in vitro and in vivo Thus, we demonstrate a novel mechanism underlying ALS pathology, in which alterations in miR126-5p facilitate a non-cell-autonomous mechanism of motor neuron degeneration in ALS. SIGNIFICANCE STATEMENT In spite of some progress, currently no effective treatment is available for ALS. We suggest a novel regulatory role for miR126-5p in ALS and demonstrate for the first time a mechanism by which alterations in miR126-5p contribute to axon degeneration and NMJ disruption observed in ALS. We show that miR126-5p is altered in ALS models and that it can modulate Sema3 and NRP protein expression. Furthermore, NRP1 elevations in motor neurons and muscle secretion of Sema3A contribute to axon degeneration and NMJ disruption in ALS. Finally, overexpressing miR126-5p is sufficient to transiently rescue NMJ disruption and axon degeneration both in vitro and in vivo. Copyright © 2018 Maimon et al.

  13. SnoN facilitates axonal regeneration after spinal cord injury.

    Directory of Open Access Journals (Sweden)

    Jiun L Do

    Full Text Available Adult CNS neurons exhibit a reduced capacity for growth compared to developing neurons, due in part to downregulation of growth-associated genes as development is completed. We tested the hypothesis that SnoN, an embryonically regulated transcription factor that specifies growth of the axonal compartment, can enhance growth in injured adult neurons. In vitro, SnoN overexpression in dissociated adult DRG neuronal cultures significantly enhanced neurite outgrowth. Moreover, TGF-β1, a negative regulator of SnoN, inhibited neurite outgrowth, and SnoN over-expression overcame this inhibition. We then examined whether SnoN influenced axonal regeneration in vivo: indeed, expression of a mutant form of SnoN resistant to degradation significantly enhanced axonal regeneration following cervical spinal cord injury, despite peri-lesional upregulation of TGF-β1. Thus, a developmental mechanism that specifies extension of the axonal compartment also promotes axonal regeneration after adult CNS injury.

  14. The cholinergic ligand binding material of axonal membranes

    International Nuclear Information System (INIS)

    Mautner, H.G.; Coronado, R.; Jumblatt, J.E.

    1986-01-01

    Choline acetyltransferase and acetylcholinesterase, the enzymes responsible for the synthesis and hydrolysis of ACh, are present in nerve fibers. In crustacean peripheral nerves, release of ACh from cut nerve fibers has been demonstrated. Previously closed membrane vesicles have been prepared from lobster walking leg nerve plasma membrane and saturable binding of cholinergic agonsist and antagonists to such membranes have been demonstrated. This paper studies this axonal cholinergic binding material, and elucidates its functions. The binding of tritium-nicotine to lobster nerve plasma membranes was antagonized by a series of cholinergic ligands as well as by a series of local anesthetics. This preparation was capable of binding I 125-alpha-bungarotoxin, a ligand widely believed to be a specific label for nicotinic ACh receptor. The labelling of 50 K petide band with tritium-MBTA following disulfide reduction is illustrated

  15. Development of raphe serotonin neurons from specification to guidance.

    Science.gov (United States)

    Kiyasova, Vera; Gaspar, Patricia

    2011-11-01

    The main features of the development of the serotonin (5-HT) raphe neurons have been known for many years but more recent molecular studies, using mouse genetics, have since unveiled several intriguing aspects of the specification of the raphe serotonergic system. These studies indicated that, although all 5-HT neurons in the raphe follow the same general program for their specification, there are also clear regional differences in the way that these neurons are specified and are guided towards different brain targets. Here we overview recent progress made in the understanding of the developmental programming of serotonergic neurons in the mouse raphe, emphasizing data showing how heterogeneous subsets of 5-HT neurons may be generated. Serotonergic progenitors are produced in the brainstem in different rhombomeres under the influence of a set of secreted factors, sonic hedgehog and fibroblast growth factors, which determine their position in the neural tube. Two main transcriptional gene networks are involved in the specification of 5-HT identity, with Lmx1b and Pet1 transcription factors as main players. A differential requirement for Pet1 was, however, revealed, which underlies an anatomical and functional diversity. Transcriptional programs controlling 5-HT identity could also impact axon guidance mechanisms directing 5-HT neurons to their targets. Although no direct links have yet been established, a large set of molecular determinants have already been shown to be involved in the growth, axon guidance and targeting of 5-HT raphe neurons, particularly within the forebrain. Alterations in the molecular mechanisms involved in 5-HT development are likely to have significant roles in mood disease predisposition. © 2011 The Authors. European Journal of Neuroscience © 2011 Federation of European Neuroscience Societies and Blackwell Publishing Ltd.

  16. N-docosahexaenoylethanolamine regulates Hedgehog signaling and promotes growth of cortical axons

    Directory of Open Access Journals (Sweden)

    Giorgi Kharebava

    2015-12-01

    Full Text Available Axonogenesis, a process for the establishment of neuron connectivity, is central to brain function. The role of metabolites derived from docosahexaenoic acid (DHA, 22:6n-3 that is specifically enriched in the brain, has not been addressed in axon development. In this study, we tested if synaptamide (N-docosahexaenoylethanolamine, an endogenous metabolite of DHA, affects axon growth in cultured cortical neurons. We found that synaptamide increased the average axon length, inhibited GLI family zinc finger 1 (GLI1 transcription and sonic hedgehog (Shh target gene expression while inducing cAMP elevation. Similar effects were produced by cyclopamine, a regulator of the Shh pathway. Conversely, Shh antagonized elevation of cAMP and blocked synaptamide-mediated increase in axon length. Activation of Shh pathway by a smoothened (SMO agonist (SAG or overexpression of SMO did not inhibit axon growth mediated by synaptamide or cyclopamine. Instead, adenylate cyclase inhibitor SQ22536 abolished synaptamide-mediated axon growth indicating requirement of cAMP elevation for this process. Our findings establish that synaptamide promotes axon growth while Shh antagonizes synaptamide-mediated cAMP elevation and axon growth by a SMO-independent, non-canonical pathway.

  17. Protein Prenylation Constitutes an Endogenous Brake on Axonal Growth

    Directory of Open Access Journals (Sweden)

    Hai Li

    2016-07-01

    Full Text Available Suboptimal axonal regeneration contributes to the consequences of nervous system trauma and neurodegenerative disease, but the intrinsic mechanisms that regulate axon growth remain unclear. We screened 50,400 small molecules for their ability to promote axon outgrowth on inhibitory substrata. The most potent hits were the statins, which stimulated growth of all mouse- and human-patient-derived neurons tested, both in vitro and in vivo, as did combined inhibition of the protein prenylation enzymes farnesyltransferase (PFT and geranylgeranyl transferase I (PGGT-1. Compensatory sprouting of motor axons may delay clinical onset of amyotrophic lateral sclerosis (ALS. Accordingly, elevated levels of PGGT1B, which would be predicted to reduce sprouting, were found in motor neurons of early- versus late-onset ALS patients postmortem. The mevalonate-prenylation pathway therefore constitutes an endogenous brake on axonal growth, and its inhibition provides a potential therapeutic approach to accelerate neuronal regeneration in humans.

  18. The protection of acetylcholinesterase inhibitor on β-amyloid-induced injury of neurite outgrowth via regulating axon guidance related genes expression in neuronal cells

    Science.gov (United States)

    Shen, Jiao-Ning; Wang, Deng-Shun; Wang, Rui

    2012-01-01

    Cognitive deficits in AD correlate with progressive synaptic dysfunction and loss. The Rho family of small GTPases, including Rho, Rac, and Cdc42, has a central role in cellular motility and cytokinesis. Acetylcholinesterase inhibitor has been found to protect cells against a broad range of reagents-induced injuries. Present studies examined if the effect of HupA on neurite outgrowth in Aβ-treated neuronal cells executed via regulating Rho-GTPase mediated axon guidance relative gene expression. Affymetrix cDNA microarray assay followed by real-time RT-PCR and Western Blotting analysis were used to elucidate and analyze the signaling pathway involved in Aβ and HupA’s effects. The effects of Aβ and HupA on the neurite outgrowth were further confirmed via immunofluorescence staining. Aβ up-regulated the mRNA expressions of NFAT5, LIMK1, EPHA1, NTN4 and RAC2 markedly in SH-SY5Y cells. Co-incubation of Aβ and HupA reversed or decreased the changes of NFAT5, NTN4, RAC2, CDC42 and SEMA4F. HupA treated alone increased NFAT5, LIMK1, NTN4 significantly. Following qRT-PCR validation showed that the correlation of the gene expression ratio between microarray and qRT-PCR is significant. Western blot result showed that the change of CDC42 protein is consistent with the mRNA level while RAC2 is not. The morphological results confirmed that HupA improved, or partly reversed, the Aβ-induced damage of neurite outgrowth. The protective effect of HupA from Aβ induced morphological injury might be correlative to, at least partially, regulating the network of neurite outgrowth related genes. PMID:23119107

  19. Modality-Specific Axonal Regeneration: Towards selective regenerative neural interfaces

    Directory of Open Access Journals (Sweden)

    Parisa eLotfi

    2011-10-01

    Full Text Available Regenerative peripheral nerve interfaces have been proposed as viable alternatives for the natural control of robotic prosthetic devices. However, sensory and motor axons at the neural interface are of mixed submodality types, which difficult the specific recording from motor axons and the eliciting of precise sensory modalities through selective stimulation. Here we evaluated the possibility of using type-specific neurotrophins to preferentially entice the regeneration of defined axonal populations from transected peripheral nerves into separate compartments. Segregation of mixed sensory fibers from dorsal root ganglion neurons was evaluated in vitro by compartmentalized diffusion delivery of nerve growth factor (NGF and neurotrophin-3 (NT-3, to preferentially entice the growth of TrkA+ nociceptive and TrkC+ proprioceptive subsets of sensory neurons, respectively. The average axon length in the NGF channel increased 2.5 fold compared to that in saline or NT-3, whereas the number of branches increased 3 fold in the NT-3 channels. These results were confirmed using a 3-D Y-shaped in vitro assay showing that the arm containing NGF was able to entice a 5-fold increase in axonal length of unbranched fibers. To address if such segregation can be enticed in vivo, a Y-shaped tubing was used to allow regeneration of the transected adult rat sciatic nerve into separate compartments filled with either NFG or NT-3. A significant increase in the number of CGRP+ pain fibers were attracted towards the sural nerve, while N-52+ large diameter axons were observed in the tibial and NT-3 compartments. This study demonstrates the guided enrichment of sensory axons in specific regenerative chambers, and supports the notion that neurotrophic factors can be used to segregate sensory and perhaps motor axons in separate peripheral interfaces.

  20. Localization of mRNA in vertebrate axonal compartments by in situ hybridization.

    Science.gov (United States)

    Sotelo-Silveira, José Roberto; Calliari, Aldo; Kun, Alejandra; Elizondo, Victoria; Canclini, Lucía; Sotelo, José Roberto

    2011-01-01

    The conclusive demonstration of RNA in vertebrate axons by in situ hybridization (ISH) has been elusive. We review the most important reasons for difficulties, including low concentration of axonal RNAs, localization in specific cortical domains, and the need to isolate axons. We demonstrate the importance of axon micro-dissection to obtain a whole mount perspective of mRNA distribution in the axonal territory. We describe a protocol to perform fluorescent ISH in isolated axons and guidelines for the preservation of structural and molecular integrity of cortical RNA-containing domains (e.g., Periaxoplasmic Ribosomal Plaques, or PARPs) in isolated axoplasm.

  1. An αII Spectrin-Based Cytoskeleton Protects Large-Diameter Myelinated Axons from Degeneration.

    Science.gov (United States)

    Huang, Claire Yu-Mei; Zhang, Chuansheng; Zollinger, Daniel R; Leterrier, Christophe; Rasband, Matthew N

    2017-11-22

    Axons must withstand mechanical forces, including tension, torsion, and compression. Spectrins and actin form a periodic cytoskeleton proposed to protect axons against these forces. However, because spectrins also participate in assembly of axon initial segments (AISs) and nodes of Ranvier, it is difficult to uncouple their roles in maintaining axon integrity from their functions at AIS and nodes. To overcome this problem and to determine the importance of spectrin cytoskeletons for axon integrity, we generated mice with αII spectrin-deficient peripheral sensory neurons. The axons of these neurons are very long and exposed to the mechanical forces associated with limb movement; most lack an AIS, and some are unmyelinated and have no nodes. We analyzed αII spectrin-deficient mice of both sexes and found that, in myelinated axons, αII spectrin forms a periodic cytoskeleton with βIV and βII spectrin at nodes of Ranvier and paranodes, respectively, but that loss of αII spectrin disrupts this organization. Avil-cre;Sptan1 f/f mice have reduced numbers of nodes, disrupted paranodal junctions, and mislocalized Kv1 K + channels. We show that the density of nodal βIV spectrin is constant among axons, but the density of nodal αII spectrin increases with axon diameter. Remarkably, Avil-cre;Sptan1 f/f mice have intact nociception and small-diameter axons, but severe ataxia due to preferential degeneration of large-diameter myelinated axons. Our results suggest that nodal αII spectrin helps resist the mechanical forces experienced by large-diameter axons, and that αII spectrin-dependent cytoskeletons are also required for assembly of nodes of Ranvier. SIGNIFICANCE STATEMENT A periodic axonal cytoskeleton consisting of actin and spectrin has been proposed to help axons resist the mechanical forces to which they are exposed (e.g., compression, torsion, and stretch). However, until now, no vertebrate animal model has tested the requirement of the spectrin cytoskeleton in

  2. Optogenetically enhanced axon regeneration: motor versus sensory neuron-specific stimulation.

    Science.gov (United States)

    Ward, Patricia J; Clanton, Scott L; English, Arthur W

    2018-02-01

    Brief neuronal activation in injured peripheral nerves is both necessary and sufficient to enhance motor axon regeneration, and this effect is specific to the activated motoneurons. It is less clear whether sensory neurons respond in a similar manner to neuronal activation following peripheral axotomy. Further, it is unknown to what extent enhancement of axon regeneration with increased neuronal activity relies on a reflexive interaction within the spinal circuitry. We used mouse genetics and optical tools to evaluate the precision and selectivity of system-specific neuronal activation to enhance axon regeneration in a mixed nerve. We evaluated sensory and motor axon regeneration in two different mouse models expressing the light-sensitive cation channel, channelrhodopsin (ChR2). We selectively activated either sensory or motor axons using light stimulation combined with transection and repair of the sciatic nerve. Regardless of genotype, the number of ChR2-positive neurons whose axons had regenerated successfully was greater following system-specific optical treatment, with no effect on the number of ChR2-negative neurons (whether motor or sensory neurons). We conclude that acute system-specific neuronal activation is sufficient to enhance both motor and sensory axon regeneration. This regeneration-enhancing effect is likely cell autonomous. © 2018 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

  3. α1b-Adrenergic Receptor Localization and Relationship to the D1-Dopamine Receptor in the Rat Nucleus Accumbens.

    Science.gov (United States)

    Mitrano, Darlene A; Jackson, Kelsey; Finley, Samantha; Seeley, Allison

    2018-02-10

    The α1-adrenergic receptors (α1ARs) have been implicated in numerous actions of the brain, including attention and wakefulness. Additionally, they have been identified as contributing to disorders of the brain, such as drug addiction, and recent work has shown a role of these receptors in relapse to psychostimulants. While some functionality is known, the actual subcellular localization of the subtypes of the α1ARs remains to be elucidated. Further, their anatomical relationship to receptors for other neurotransmitters, such as dopamine (DA), remains unclear. Therefore, using immunohistochemistry and electron microscopy techniques, this study describes the subcellular localization of the α1b-adrenergic receptor (α1bAR), the subtype most tied to relapse behaviors, as well as its relationship to the D1-dopamine receptor (D1R) in both the shell and core of the rat nucleus accumbens (NAc). Overall, α1bARs were found in unmyelinated axons and axon terminals with some labeling in dendrites. In accordance with other studies of the striatum, the D1R was found mainly in dendrites and spines; therefore, colocalization of the D1R with the α1bAR was rare postsynaptically. However, in the NAc shell, when the receptors were co-expressed in the same neuronal elements there was a trend for both receptors to be found on the plasma membrane, as opposed to the intracellular compartment. This study provides valuable anatomical information about the α1bAR and its relationship to the D1R and the regulation of DA and norepinephrine (NE) neurotransmission in the brain which have been examined previously. Published by Elsevier Ltd.

  4. Axon-somatic back-propagation in detailed models of spinal alpha motoneurons

    Directory of Open Access Journals (Sweden)

    Pietro eBalbi

    2015-02-01

    Full Text Available Antidromic action potentials following distal stimulation of motor axons occasionally fail to invade the soma of alpha motoneurons in spinal cord, due to their passing through regions of high non-uniformity.Morphologically detailed conductance-based models of cat spinal alpha motoneurons have been developed, with the aim to reproduce and clarify some aspects of the electrophysiological behavior of the antidromic axon-somatic spike propagation. Fourteen 3D morphologically detailed somata and dendrites of cat spinal alpha motoneurons have been imported from an open-access web-based database of neuronal morphologies, NeuroMorpho.org, and instantiated in neurocomputational models. An axon hillock, an axonal initial segment and a myelinated axon are added to each model.By sweeping the diameter of the axonal initial segment (AIS and the axon hillock, as well as the maximal conductances of sodium channels at the AIS and at the soma, the developed models are able to show the relationships between different geometric and electrophysiological configurations and the voltage attenuation of the antidromically travelling wave.In particular, a greater than usually admitted sodium conductance at AIS is necessary and sufficient to overcome the dramatic voltage attenuation occurring during antidromic spike propagation both at the myelinated axon-AIS and at the AIS-soma transitions.

  5. A Communication Theoretical Modeling of Axonal Propagation in Hippocampal Pyramidal Neurons.

    Science.gov (United States)

    Ramezani, Hamideh; Akan, Ozgur B

    2017-06-01

    Understanding the fundamentals of communication among neurons, known as neuro-spike communication, leads to reach bio-inspired nanoscale communication paradigms. In this paper, we focus on a part of neuro-spike communication, known as axonal transmission, and propose a realistic model for it. The shape of the spike during axonal transmission varies according to previously applied stimulations to the neuron, and these variations affect the amount of information communicated between neurons. Hence, to reach an accurate model for neuro-spike communication, the memory of axon and its effect on the axonal transmission should be considered, which are not studied in the existing literature. In this paper, we extract the important factors on the memory of axon and define memory states based on these factors. We also describe the transition among these states and the properties of axonal transmission in each of them. Finally, we demonstrate that the proposed model can follow changes in the axonal functionality properly by simulating the proposed model and reporting the root mean square error between simulation results and experimental data.

  6. Is action potential threshold lowest in the axon?

    NARCIS (Netherlands)

    Kole, Maarten H. P.; Stuart, Greg J.

    2008-01-01

    Action potential threshold is thought to be lowest in the axon, but when measured using conventional techniques, we found that action potential voltage threshold of rat cortical pyramidal neurons was higher in the axon than at other neuronal locations. In contrast, both current threshold and voltage

  7. Mechanistic logic underlying the axonal transport of cytosolic proteins

    Science.gov (United States)

    Scott, David A.; Das, Utpal; Tang, Yong; Roy, Subhojit

    2011-01-01

    Proteins vital to presynaptic function are synthesized in the neuronal perikarya and delivered into synapses via two modes of axonal transport. While membrane-anchoring proteins are conveyed in fast axonal transport via motor-driven vesicles, cytosolic proteins travel in slow axonal transport; via mechanisms that are poorly understood. We found that in cultured axons, populations of cytosolic proteins tagged to photoactivable-GFP (PA-GFP) move with a slow motor-dependent anterograde bias; distinct from vesicular-trafficking or diffusion of untagged PA-GFP. The overall bias is likely generated by an intricate particle-kinetics involving transient assembly and short-range vectorial spurts. In-vivo biochemical studies reveal that cytosolic proteins are organized into higher-order structures within axon-enriched fractions that are largely segregated from vesicles. Data-driven biophysical modeling best predicts a scenario where soluble molecules dynamically assemble into mobile supra-molecular structures. We propose a model where cytosolic proteins are transported by dynamically assembling into multi-protein complexes that are directly/indirectly conveyed by motors. PMID:21555071

  8. Presynaptic muscarinic acetylcholine autoreceptors (M1, M2 and M4 subtypes), adenosine receptors (A1 and A2A) and tropomyosin-related kinase B receptor (TrkB) modulate the developmental synapse elimination process at the neuromuscular junction.

    Science.gov (United States)

    Nadal, Laura; Garcia, Neus; Hurtado, Erica; Simó, Anna; Tomàs, Marta; Lanuza, Maria A; Santafé, Manel; Tomàs, Josep

    2016-06-23

    The development of the nervous system involves an initially exuberant production of neurons that make an excessive number of synaptic contacts. The initial overproduction of synapses promotes connectivity. Hebbian competition between axons with different activities (the least active are punished) leads to the loss of roughly half of the overproduced elements and this refines connectivity and increases specificity. The neuromuscular junction is innervated by a single axon at the end of the synapse elimination process and, because of its relative simplicity, has long been used as a model for studying the general principles of synapse development. The involvement of the presynaptic muscarinic ACh autoreceptors may allow for the direct competitive interaction between nerve endings through differential activity-dependent acetylcholine release in the synaptic cleft. Then, the most active ending may directly punish the less active ones. Our previous results indicate the existence in the weakest axons on the polyinnervated neonatal NMJ of an ACh release inhibition mechanism based on mAChR coupled to protein kinase C and voltage-dependent calcium channels. We suggest that this mechanism plays a role in the elimination of redundant neonatal synapses. Here we used confocal microscopy and quantitative morphological analysis to count the number of brightly fluorescent axons per endplate in P7, P9 and P15 transgenic B6.Cg-Tg (Thy1-YFP)16 Jrs/J mice. We investigate the involvement of individual mAChR M1-, M2- and M4-subtypes in the control of axonal elimination after the Levator auris longus muscle had been exposed to agonist and antagonist in vivo. We also analysed the role of adenosine receptor subtypes (A1 and A2A) and the tropomyosin-related kinase B receptor. The data show that postnatal axonal elimination is a regulated multireceptor mechanism that guaranteed the monoinnervation of the neuromuscular synapses. The three receptor sets considered (mAChR, AR and TrkB receptors

  9. Characterization of axon formation in the embryonic stem cell-derived motoneuron.

    Science.gov (United States)

    Pan, Hung-Chuan; Wu, Ya-Ting; Shen, Shih-Cheng; Wang, Chi-Chung; Tsai, Ming-Shiun; Cheng, Fu-Chou; Lin, Shinn-Zong; Chen, Ching-Wen; Liu, Ching-San; Su, Hong-Lin

    2011-01-01

    The developing neural cell must form a highly organized architecture to properly receive and transmit nerve signals. Neural formation from embryonic stem (ES) cells provides a novel system for studying axonogenesis, which are orchestrated by polarity-regulating molecules. Here the ES-derived motoneurons, identified by HB9 promoter-driven green fluorescent protein (GFP) expression, showed characteristics of motoneuron-specific gene expression. In the majority of motoneurons, one of the bilateral neurites developed into an axon that featured with axonal markers, including Tau1, vesicle acetylcholine transporter, and synaptophysin. Interestingly, one third of the motoneurons developed bi-axonal processes but no multiple axonal GFP cell was found. The neuronal polarity-regulating proteins, including the phosphorylated AKT and ERK, were compartmentalized into both of the bilateral axonal tips. Importantly, this aberrant axon morphology was still present after the engraftment of GFP(+) neurons into the spinal cord, suggesting that even a mature neural environment fails to provide a proper niche to guide normal axon formation. These findings underscore the necessity for evaluating the morphogenesis and functionality of neurons before the clinical trials using ES or somatic stem cells.

  10. Motor Axonal Regeneration After Partial and Complete Spinal Cord Transection

    Science.gov (United States)

    Lu, Paul; Blesch, Armin; Graham, Lori; Wang, Yaozhi; Samara, Ramsey; Banos, Karla; Haringer, Verena; Havton, Leif; Weishaupt, Nina; Bennett, David; Fouad, Karim; Tuszynski, Mark H.

    2012-01-01

    We subjected rats to either partial mid-cervical or complete upper thoracic spinal cord transections and examined whether combinatorial treatments support motor axonal regeneration into and beyond the lesion. Subjects received cAMP injections into brainstem reticular motor neurons to stimulate their endogenous growth state, bone marrow stromal cell grafts in lesion sites to provide permissive matrices for axonal growth, and brain-derived neurotrophic factor (BDNF) gradients beyond the lesion to stimulate distal growth of motor axons. Findings were compared to several control groups. Combinatorial treatment generated motor axon regeneration beyond both C5 hemisection and complete transection sites. Yet despite formation of synapses with neurons below the lesion, motor outcomes worsened after partial cervical lesions and spasticity worsened after complete transection. These findings highlight the complexity of spinal cord repair, and the need for additional control and shaping of axonal regeneration. PMID:22699902

  11. Blocking p75 (NTR) receptors alters polyinnervationz of neuromuscular synapses during development.

    Science.gov (United States)

    Garcia, Neus; Tomàs, Marta; Santafe, Manel M; Lanuza, Maria A; Besalduch, Nuria; Tomàs, Josep

    2011-09-01

    High-resolution immunohistochemistry shows that the receptor protein p75(NTR) is present in the nerve terminal, muscle cell, and glial Schwann cell at the neuromuscular junction (NMJ) of postnatal rats (P4-P6) during the synapse elimination period. Blocking the receptor with the antibody anti-p75-192-IgG (1-5 μg/ml, 1 hr) results in reduced endplate potentials (EPPs) in mono- and polyinnervated synapses ex vivo, but the mean number of functional inputs per NMJ does not change for as long as 3 hr. Incubation with exogenous brain-derived neurotrophic factor (BDNF) for 1 hr (50 nM) resulted in a significant increase in the size of the EPPs in all nerve terminals, and preincubation with anti-p75-192-IgG prevented this potentiation. Long exposure (24 hr) in vivo of the NMJs to the antibody anti-p75-192-IgG (1-2 μg/ml) results in a delay of postnatal synapse elimination and even some regrowth of previously withdrawn axons, but also in some acceleration of the morphologic maturation of the postsynaptic nicotinic acetylcholine receptor (nAChR) clusters. The results indicate that p75(NTR) is involved in both ACh release and axonal retraction during postnatal axonal competition and synapse elimination. Copyright © 2011 Wiley-Liss, Inc.

  12. The neuroprotection of cannabidiol against MPP⁺-induced toxicity in PC12 cells involves trkA receptors, upregulation of axonal and synaptic proteins, neuritogenesis, and might be relevant to Parkinson's disease.

    Science.gov (United States)

    Santos, Neife Aparecida Guinaim; Martins, Nádia Maria; Sisti, Flávia Malvestio; Fernandes, Laís Silva; Ferreira, Rafaela Scalco; Queiroz, Regina Helena Costa; Santos, Antônio Cardozo

    2015-12-25

    Cannabidiol (CBD) is a non-psychoactive constituent of Cannabis sativa with potential to treat neurodegenerative diseases. Its neuroprotection has been mainly associated with anti-inflammatory and antioxidant events; however, other mechanisms might be involved. We investigated the involvement of neuritogenesis, NGF receptors (trkA), NGF, and neuronal proteins in the mechanism of neuroprotection of CBD against MPP(+) toxicity in PC12 cells. CBD increased cell viability, differentiation, and the expression of axonal (GAP-43) and synaptic (synaptophysin and synapsin I) proteins. Its neuritogenic effect was not dependent or additive to NGF, but it was inhibited by K252a (trkA inhibitor). CBD did not increase the expression of NGF, but protected against its decrease induced by MPP(+), probably by an indirect mechanism. We also evaluated the neuritogenesis in SH-SY5Y cells, which do not express trkA receptors. CBD did not induce neuritogenesis in this cellular model, which supports the involvement of trkA receptors. This is the first study to report the involvement of neuronal proteins and trkA in the neuroprotection of CBD. Our findings suggest that CBD has a neurorestorative potential independent of NGF that might contribute to its neuroprotection against MPP(+), a neurotoxin relevant to Parkinson's disease. Copyright © 2015 Elsevier B.V. All rights reserved.

  13. Acutely damaged axons are remyelinated in multiple sclerosis and experimental models of demyelination.

    Science.gov (United States)

    Schultz, Verena; van der Meer, Franziska; Wrzos, Claudia; Scheidt, Uta; Bahn, Erik; Stadelmann, Christine; Brück, Wolfgang; Junker, Andreas

    2017-08-01

    Remyelination is in the center of new therapies for the treatment of multiple sclerosis to resolve and improve disease symptoms and protect axons from further damage. Although remyelination is considered beneficial in the long term, it is not known, whether this is also the case early in lesion formation. Additionally, the precise timing of acute axonal damage and remyelination has not been assessed so far. To shed light onto the interrelation between axons and the myelin sheath during de- and remyelination, we employed cuprizone- and focal lysolecithin-induced demyelination and performed time course experiments assessing the evolution of early and late stage remyelination and axonal damage. We observed damaged axons with signs of remyelination after cuprizone diet cessation and lysolecithin injection. Similar observations were made in early multiple sclerosis lesions. To assess the correlation of remyelination and axonal damage in multiple sclerosis lesions, we took advantage of a cohort of patients with early and late stage remyelinated lesions and assessed the number of APP- and SMI32- positive damaged axons and the density of SMI31-positive and silver impregnated preserved axons. Early de- and remyelinating lesions did not differ with respect to axonal density and axonal damage, but we observed a lower axonal density in late stage demyelinated multiple sclerosis lesions than in remyelinated multiple sclerosis lesions. Our findings suggest that remyelination may not only be protective over a long period of time, but may play an important role in the immediate axonal recuperation after a demyelinating insult. © 2017 The Authors GLIA Published by Wiley Periodicals, Inc.

  14. Poliovirus trafficking toward central nervous system via human poliovirus receptor-dependent and -independent pathway.

    Directory of Open Access Journals (Sweden)

    Seii eOHKA

    2012-04-01

    Full Text Available In humans, paralytic poliomyelitis results from the invasion of the central nervous system by circulating poliovirus (PV via the blood-brain barrier (BBB. After the virus enters the central nervous system (CNS, it replicates in neurons, especially in motor neurons (MNs, inducing the cell death that causes paralytic poliomyelitis. Along with this route of dissemination, neural pathway has been reported in humans, monkeys, and PV-sensitive human PV receptor (hPVR/CD155-transgenic (Tg mice. We demonstrated that a fast retrograde axonal transport process is required for PV dissemination through the sciatic nerve of hPVR-Tg mice and that intramuscularly inoculated PV causes paralysis in a hPVR-dependent manner. We also showed that hPVR-independent axonal transport of PV exists in hPVR-Tg and non-Tg mice, indicating that several different pathways for PV axonal transport exist in these mice. Circulating PV after intravenous inoculation in mice cross the BBB at a high rate in a hPVR-independent manner. Recently, we identified transferrin receptor 1 (TfR1 of mouse brain capillary endothelial cells as a binding protein to PV, implicating that TfR1 is a possible receptor for PV to permeate the BBB.

  15. The protection of acetylcholinesterase inhibitor on β-amyloid-induced the injury of neurite outgrowth via regulating axon guidance related genes expression in neuronal cells.

    Science.gov (United States)

    Shen, Jiao-Ning; Wang, Deng-Shun; Wang, Rui

    2012-01-01

    Cognitive deficits in AD correlate with progressive synaptic dysfunction and loss. The Rho family of small GTPases, including Rho, Rac, and Cdc42, has a central role in cellular motility and cytokinesis. Acetylcholinesterase inhibitor has been found to protect cells against a broad range of reagents-induced injuries. Present studies examined if the effect of HupA on neurite outgrowth in Aβ-treated neuronal cells executed via regulating Rho-GTPase mediated axon guidance relative gene expression. Affymetrix cDNA microarray assay followed by real-time RT-PCR and Western Blotting analysis were used to elucidate and analyze the signaling pathway involved in Aβ and HupA's effects. The effects of Aβ and HupA on the neurite outgrowth were further confirmed via immunofluorescence staining. Aβ up-regulated the mRNA expressions of NFAT5, LIMK1, EPHA1, NTN4 and RAC2 markedly in SH-SY5Y cells. Co-incubation of Aβ and HupA reversed or decreased the changes of NFAT5, NTN4, RAC2, CDC42 and SEMA4F. HupA treated alone increased NFAT5, LIMK1, NTN4 significantly. Following qRT-PCR validation showed that the correlation of the gene expression ratio between microarray and qRT-PCR is significant. Western blot result showed that the change of CDC42 protein is consistent with the mRNA level while RAC2 is not. The morphological results confirmed that HupA improved, or partly reversed, the Aβ-induced damage of neurite outgrowth. The protective effect of HupA from Aβ induced morphological injury might be correlative to, at least partially, regulating the network of neurite outgrowth related genes.

  16. A high mitochondrial transport rate characterizes CNS neurons with high axonal regeneration capacity.

    Directory of Open Access Journals (Sweden)

    Romain Cartoni

    Full Text Available Improving axonal transport in the injured and diseased central nervous system has been proposed as a promising strategy to improve neuronal repair. However, the contribution of each cargo to the repair mechanism is unknown. DRG neurons globally increase axonal transport during regeneration. Because the transport of specific cargos after axonal insult has not been examined systematically in a model of enhanced regenerative capacity, it is unknown whether the transport of all cargos would be modulated equally in injured central nervous system neurons. Here, using a microfluidic culture system we compared neurons co-deleted for PTEN and SOCS3, an established model of high axonal regeneration capacity, to control neurons. We measured the axonal transport of three cargos (mitochondria, synaptic vesicles and late endosomes in regenerating axons and found that the transport of mitochondria, but not the other cargos, was increased in PTEN/SOCS3 co-deleted axons relative to controls. The results reported here suggest a pivotal role for this organelle during axonal regeneration.

  17. Ephrin-B3 is the midline barrier that prevents corticospinal tract axons from recrossing, allowing for unilateral motor control.

    Science.gov (United States)

    Kullander, K; Croll, S D; Zimmer, M; Pan, L; McClain, J; Hughes, V; Zabski, S; DeChiara, T M; Klein, R; Yancopoulos, G D; Gale, N W

    2001-04-01

    Growing axons follow highly stereotypical pathways, guided by a variety of attractive and repulsive cues, before establishing specific connections with distant targets. A particularly well-known example that illustrates the complexity of axonal migration pathways involves the axonal projections of motor neurons located in the motor cortex. These projections take a complex route during which they first cross the midline, then form the corticospinal tract, and ultimately connect with motor neurons in the contralateral side of the spinal cord. These obligatory contralateral connections account for why one side of the brain controls movement on the opposing side of the body. The netrins and slits provide well-known midline signals that regulate axonal crossings at the midline. Herein we report that a member of the ephrin family, ephrin-B3, also plays a key role at the midline to regulate axonal crossing. In particular, we show that ephrin-B3 acts as the midline barrier that prevents corticospinal tract projections from recrossing when they enter the spinal gray matter. We report that in ephrin-B3(-/-) mice, corticospinal tract projections freely recross in the spinal gray matter, such that the motor cortex on one side of the brain now provides bilateral input to the spinal cord. This neuroanatomical abnormality in ephrin-B3(-/-) mice correlates with loss of unilateral motor control, yielding mice that simultaneously move their right and left limbs and thus have a peculiar hopping gait quite unlike the alternate step gait displayed by normal mice. The corticospinal and walking defects in ephrin-B3(-/-) mice resemble those recently reported for mice lacking the EphA4 receptor, which binds ephrin-B3 as well as other ephrins, suggesting that the binding of EphA4-bearing axonal processes to ephrin-B3 at the midline provides the repulsive signal that prevents corticospinal tract projections from recrossing the midline in the developing spinal cord.

  18. Role of motoneuron-derived neurotrophin 3 in survival and axonal projection of sensory neurons during neural circuit formation.

    Science.gov (United States)

    Usui, Noriyoshi; Watanabe, Keisuke; Ono, Katsuhiko; Tomita, Koichi; Tamamaki, Nobuaki; Ikenaka, Kazuhiro; Takebayashi, Hirohide

    2012-03-01

    Sensory neurons possess the central and peripheral branches and they form unique spinal neural circuits with motoneurons during development. Peripheral branches of sensory axons fasciculate with the motor axons that extend toward the peripheral muscles from the central nervous system (CNS), whereas the central branches of proprioceptive sensory neurons directly innervate motoneurons. Although anatomically well documented, the molecular mechanism underlying sensory-motor interaction during neural circuit formation is not fully understood. To investigate the role of motoneuron on sensory neuron development, we analyzed sensory neuron phenotypes in the dorsal root ganglia (DRG) of Olig2 knockout (KO) mouse embryos, which lack motoneurons. We found an increased number of apoptotic cells in the DRG of Olig2 KO embryos at embryonic day (E) 10.5. Furthermore, abnormal axonal projections of sensory neurons were observed in both the peripheral branches at E10.5 and central branches at E15.5. To understand the motoneuron-derived factor that regulates sensory neuron development, we focused on neurotrophin 3 (Ntf3; NT-3), because Ntf3 and its receptors (Trk) are strongly expressed in motoneurons and sensory neurons, respectively. The significance of motoneuron-derived Ntf3 was analyzed using Ntf3 conditional knockout (cKO) embryos, in which we observed increased apoptosis and abnormal projection of the central branch innervating motoneuron, the phenotypes being apparently comparable with that of Olig2 KO embryos. Taken together, we show that the motoneuron is a functional source of Ntf3 and motoneuron-derived Ntf3 is an essential pre-target neurotrophin for survival and axonal projection of sensory neurons.

  19. The nano-architecture of the axonal cytoskeleton.

    Science.gov (United States)

    Leterrier, Christophe; Dubey, Pankaj; Roy, Subhojit

    2017-12-01

    The corporeal beauty of the neuronal cytoskeleton has captured the imagination of generations of scientists. One of the easiest cellular structures to visualize by light microscopy, its existence has been known for well over 100 years, yet we have only recently begun to fully appreciate its intricacy and diversity. Recent studies combining new probes with super-resolution microscopy and live imaging have revealed surprising details about the axonal cytoskeleton and, in particular, have discovered previously unknown actin-based structures. Along with traditional electron microscopy, these newer techniques offer a nanoscale view of the axonal cytoskeleton, which is important for our understanding of neuronal form and function, and lay the foundation for future studies. In this Review, we summarize existing concepts in the field and highlight contemporary discoveries that have fundamentally altered our perception of the axonal cytoskeleton.

  20. GSK3 controls axon growth via CLASP-mediated regulation of growth cone microtubules

    Science.gov (United States)

    Hur, Eun-Mi; Saijilafu; Lee, Byoung Dae; Kim, Seong-Jin; Xu, Wen-Lin; Zhou, Feng-Quan

    2011-01-01

    Suppression of glycogen synthase kinase 3 (GSK3) activity in neurons yields pleiotropic outcomes, causing both axon growth promotion and inhibition. Previous studies have suggested that specific GSK3 substrates, such as adenomatous polyposis coli (APC) and collapsin response mediator protein 2 (CRMP2), support axon growth by regulating the stability of axonal microtubules (MTs), but the substrate(s) and mechanisms conveying axon growth inhibition remain elusive. Here we show that CLIP (cytoplasmic linker protein)-associated protein (CLASP), originally identified as a MT plus end-binding protein, displays both plus end-binding and lattice-binding activities in nerve growth cones, and reveal that the two MT-binding activities regulate axon growth in an opposing manner: The lattice-binding activity mediates axon growth inhibition induced by suppression of GSK3 activity via preventing MT protrusion into the growth cone periphery, whereas the plus end-binding property supports axon extension via stabilizing the growing ends of axonal MTs. We propose a model in which CLASP transduces GSK3 activity levels to differentially control axon growth by coordinating the stability and configuration of growth cone MTs. PMID:21937714

  1. Parallel simulation of axon growth in the nervous system

    NARCIS (Netherlands)

    J. Wensch; B.P. Sommeijer (Ben)

    2002-01-01

    textabstractIn this paper we discuss a model from neurobiology, which describes theoutgrowth of axons from neurons in the nervous system. The model combines ordinary differential equations, defining the movement of the axons, with parabolic partial differential equations. The parabolic equations

  2. Golgi bypass for local delivery of axonal proteins, fact or fiction?

    Science.gov (United States)

    González, Carolina; Cornejo, Víctor Hugo; Couve, Andrés

    2018-04-06

    Although translation of cytosolic proteins is well described in axons, much less is known about the synthesis, processing and trafficking of transmembrane and secreted proteins. A canonical rough endoplasmic reticulum or a stacked Golgi apparatus has not been detected in axons, generating doubts about the functionality of a local route. However, axons contain mRNAs for membrane and secreted proteins, translation factors, ribosomal components, smooth endoplasmic reticulum and post-endoplasmic reticulum elements that may contribute to local biosynthesis and plasma membrane delivery. Here we consider the evidence supporting a local secretory system in axons. We discuss exocytic elements and examples of autonomous axonal trafficking that impact development and maintenance. We also examine whether unconventional post-endoplasmic reticulum pathways may replace the canonical Golgi apparatus. Copyright © 2018. Published by Elsevier Ltd.

  3. Structure and Function of an Actin-Based Filter in the Proximal Axon

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    Varuzhan Balasanyan

    2017-12-01

    Full Text Available Summary: The essential organization of microtubules within neurons has been described; however, less is known about how neuronal actin is arranged and the functional implications of its arrangement. Here, we describe, in live cells, an actin-based structure in the proximal axon that selectively prevents some proteins from entering the axon while allowing the passage of others. Concentrated patches of actin in proximal axons are present shortly after axonal specification in rat and zebrafish neurons imaged live, and they mark positions where anterogradely traveling vesicles carrying dendritic proteins halt and reverse. Patches colocalize with the ARP2/3 complex, and when ARP2/3-mediated nucleation is blocked, a dendritic protein mislocalizes to the axon. Patches are highly dynamic, with few persisting longer than 30 min. In neurons in culture and in vivo, actin appears to form a contiguous, semipermeable barrier, despite its apparently sparse distribution, preventing axonal localization of constitutively active myosin Va but not myosin VI. : Balasanyan et al. find dynamic patches of actin in proximal axons of live neurons, mature and newly differentiated, in culture and in vivo. Patches contribute to a filter that sequesters some proteins within the somatodendritic domain while allowing others to pass into the axon, leading to polarized localization of proteins.

  4. GABA and its B-receptor are present at the node of Ranvier in a small population of sensory fibers, implicating a role in myelination

    DEFF Research Database (Denmark)

    Corell, Mikael; Wicher, Grzegorz; Radomska, Katarzyna J

    2015-01-01

    throughout development and after injury. A small population of myelinated sensory fibers displayed all of these molecules at the node of Ranvier, indicating a role in axon-glia communication. Functional studies using GABAB receptor agonists and antagonists were performed in fetal DRG primary cultures...... to study the function of this receptor during development. The results show that GABA, via its B receptor, is involved in the myelination process but not in Schwann cell proliferation. The data from adult nerves suggest additional roles in axon-glia communication after injury.......The γ-aminobutyric acid (GABA) type B receptor has been implicated in glial cell development in the peripheral nervous system (PNS), although the exact function of GABA signaling is not known. To investigate GABA and its B receptor in PNS development and degeneration, we studied the expression...

  5. Differential Axonal Projection of Mitral and Tufted Cells in the Mouse Main Olfactory System

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    Shin Nagayama

    2010-09-01

    Full Text Available In the past decade, much has been elucidated regarding the functional organization of the axonal connection of olfactory sensory neurons to olfactory bulb (OB glomeruli. However, the manner in which projection neurons of the OB process odorant input and send this information to higher brain centers remains unclear. Here, we report long-range, large-scale tracing of the axonal projection patterns of OB neurons using two-photon microscopy. Tracer injection into a single glomerulus demonstrated widely distributed mitral/tufted cell axonal projections on the lateroventral surface of the mouse brain, including the anterior/posterior piriform cortex (PC and olfactory tubercle (OT. We noted two distinct groups of labeled axons: PC-orienting axons and OT-orienting axons. Each group occupied distinct parts of the lateral olfactory tract. PC-orienting axons projected axon collaterals to a wide area of the PC but only a few collaterals to the OT. OT-orienting axons densely projected axon collaterals primarily to the anterolateral OT (alOT. Different colored dye injections into the superficial and deep portions of the OB external plexiform layer revealed that the PC-orienting axon populations originated in presumed mitral cells and the OT-orienting axons in presumed tufted cells. These data suggest that although mitral and tufted cells receive similar odor signals from a shared glomerulus, they process the odor information in different ways and send their output to different higher brain centers via the PC and alOT.

  6. Membrane Receptor-Induced Changes of the Protein Kinases A and C Activity May Play a Leading Role in Promoting Developmental Synapse Elimination at the Neuromuscular Junction.

    Science.gov (United States)

    Tomàs, Josep M; Garcia, Neus; Lanuza, Maria A; Nadal, Laura; Tomàs, Marta; Hurtado, Erica; Simó, Anna; Cilleros, Víctor

    2017-01-01

    Synapses that are overproduced during histogenesis in the nervous system are eventually lost and connectivity is refined. Membrane receptor signaling leads to activity-dependent mutual influence and competition between axons directly or with the involvement of the postsynaptic cell and the associated glial cell/s. Presynaptic muscarinic acetylcholine (ACh) receptors (subtypes mAChR; M 1 , M 2 and M 4 ), adenosine receptors (AR; A 1 and A 2A ) and the tropomyosin-related kinase B receptor (TrkB), among others, all cooperate in synapse elimination. Between these receptors there are several synergistic, antagonic and modulatory relations that clearly affect synapse elimination. Metabotropic receptors converge in a limited repertoire of intracellular effector kinases, particularly serine protein kinases A and C (PKA and PKC), to phosphorylate protein targets and bring about structural and functional changes leading to axon loss. In most cells A 1 , M 1 and TrkB operate mainly by stimulating PKC whereas A 2A , M 2 and M 4 inhibit PKA. We hypothesize that a membrane receptor-induced shifting in the protein kinases A and C activity (inhibition of PKA and/or stimulation of PKC) in some nerve endings may play an important role in promoting developmental synapse elimination at the neuromuscular junction (NMJ). This hypothesis is supported by: (i) the tonic effect (shown by using selective inhibitors) of several membrane receptors that accelerates axon loss between postnatal days P5-P9; (ii) the synergistic, antagonic and modulatory effects (shown by paired inhibition) of the receptors on axonal loss; (iii) the fact that the coupling of these receptors activates/inhibits the intracellular serine kinases; and (iv) the increase of the PKA activity, the reduction of the PKC activity or, in most cases, both situations simultaneously that presumably occurs in all the situations of singly and paired inhibition of the mAChR, AR and TrkB receptors. The use of transgenic animals and

  7. Membrane Receptor-Induced Changes of the Protein Kinases A and C Activity May Play a Leading Role in Promoting Developmental Synapse Elimination at the Neuromuscular Junction

    Directory of Open Access Journals (Sweden)

    Josep M. Tomàs

    2017-08-01

    Full Text Available Synapses that are overproduced during histogenesis in the nervous system are eventually lost and connectivity is refined. Membrane receptor signaling leads to activity-dependent mutual influence and competition between axons directly or with the involvement of the postsynaptic cell and the associated glial cell/s. Presynaptic muscarinic acetylcholine (ACh receptors (subtypes mAChR; M1, M2 and M4, adenosine receptors (AR; A1 and A2A and the tropomyosin-related kinase B receptor (TrkB, among others, all cooperate in synapse elimination. Between these receptors there are several synergistic, antagonic and modulatory relations that clearly affect synapse elimination. Metabotropic receptors converge in a limited repertoire of intracellular effector kinases, particularly serine protein kinases A and C (PKA and PKC, to phosphorylate protein targets and bring about structural and functional changes leading to axon loss. In most cells A1, M1 and TrkB operate mainly by stimulating PKC whereas A2A, M2 and M4 inhibit PKA. We hypothesize that a membrane receptor-induced shifting in the protein kinases A and C activity (inhibition of PKA and/or stimulation of PKC in some nerve endings may play an important role in promoting developmental synapse elimination at the neuromuscular junction (NMJ. This hypothesis is supported by: (i the tonic effect (shown by using selective inhibitors of several membrane receptors that accelerates axon loss between postnatal days P5–P9; (ii the synergistic, antagonic and modulatory effects (shown by paired inhibition of the receptors on axonal loss; (iii the fact that the coupling of these receptors activates/inhibits the intracellular serine kinases; and (iv the increase of the PKA activity, the reduction of the PKC activity or, in most cases, both situations simultaneously that presumably occurs in all the situations of singly and paired inhibition of the mAChR, AR and TrkB receptors. The use of transgenic animals and various

  8. Cortical Interneuron Subtypes Vary in Their Axonal Action Potential Properties.

    Science.gov (United States)

    Casale, Amanda E; Foust, Amanda J; Bal, Thierry; McCormick, David A

    2015-11-25

    The role of interneurons in cortical microcircuits is strongly influenced by their passive and active electrical properties. Although different types of interneurons exhibit unique electrophysiological properties recorded at the soma, it is not yet clear whether these differences are also manifested in other neuronal compartments. To address this question, we have used voltage-sensitive dye to image the propagation of action potentials into the fine collaterals of axons and dendrites in two of the largest cortical interneuron subtypes in the mouse: fast-spiking interneurons, which are typically basket or chandelier neurons; and somatostatin containing interneurons, which are typically regular spiking Martinotti cells. We found that fast-spiking and somatostatin-expressing interneurons differed in their electrophysiological characteristics along their entire dendrosomatoaxonal extent. The action potentials generated in the somata and axons, including axon collaterals, of somatostatin-expressing interneurons are significantly broader than those generated in the same compartments of fast-spiking inhibitory interneurons. In addition, action potentials back-propagated into the dendrites of somatostatin-expressing interneurons much more readily than fast-spiking interneurons. Pharmacological investigations suggested that axonal action potential repolarization in both cell types depends critically upon Kv1 channels, whereas the axonal and somatic action potentials of somatostatin-expressing interneurons also depend on BK Ca(2+)-activated K(+) channels. These results indicate that the two broad classes of interneurons studied here have expressly different subcellular physiological properties, allowing them to perform unique computational roles in cortical circuit operations. Neurons in the cerebral cortex are of two major types: excitatory and inhibitory. The proper balance of excitation and inhibition in the brain is critical for its operation. Neurons contain three main

  9. Current Opportunities for Clinical Monitoring of Axonal Pathology in Traumatic Brain Injury

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    Parmenion P. Tsitsopoulos

    2017-11-01

    Full Text Available Traumatic brain injury (TBI is a multidimensional and highly complex disease commonly resulting in widespread injury to axons, due to rapid inertial acceleration/deceleration forces transmitted to the brain during impact. Axonal injury leads to brain network dysfunction, significantly contributing to cognitive and functional impairments frequently observed in TBI survivors. Diffuse axonal injury (DAI is a clinical entity suggested by impaired level of consciousness and coma on clinical examination and characterized by widespread injury to the hemispheric white matter tracts, the corpus callosum and the brain stem. The clinical course of DAI is commonly unpredictable and it remains a challenging entity with limited therapeutic options, to date. Although axonal integrity may be disrupted at impact, the majority of axonal pathology evolves over time, resulting from delayed activation of complex intracellular biochemical cascades. Activation of these secondary biochemical pathways may lead to axonal transection, named secondary axotomy, and be responsible for the clinical decline of DAI patients. Advances in the neurocritical care of TBI patients have been achieved by refinements in multimodality monitoring for prevention and early detection of secondary injury factors, which can be applied also to DAI. There is an emerging role for biomarkers in blood, cerebrospinal fluid, and interstitial fluid using microdialysis in the evaluation of axonal injury in TBI. These biomarker studies have assessed various axonal and neuroglial markers as well as inflammatory mediators, such as cytokines and chemokines. Moreover, modern neuroimaging can detect subtle or overt DAI/white matter changes in diffuse TBI patients across all injury severities using magnetic resonance spectroscopy, diffusion tensor imaging, and positron emission tomography. Importantly, serial neuroimaging studies provide evidence for evolving axonal injury. Since axonal injury may be a key

  10. The lactate receptor HCAR1 promotes neuronal development and protects axons and myelin during hypoglycemia

    DEFF Research Database (Denmark)

    Kennedy, L. H.; Andersson, K. A.; Haugen, O. P.

    2017-01-01

    Lactate plays a significant role as an energy supply for neurons and has a neuroprotective effect in hypoglycemia and ischemia (1±5). Further, oligodendrocytes can use lactate for myelination when glucose levels are low. New studies suggest that lactate is not only a metabolic fuel but also...... in the development and survival of neurons and oligodendrocytes in normal conditions and hypoglycemia. We show that young HCAR1 KO mice have a reduced number of neural progenitor cells in the hippocampus and the cerebral cortex, and the average size of cortical axons is smaller in KO compared with WT mice...

  11. Mecanismos involucrados en la promoción de crecimiento axonal por la glia envolvente del bulbo olfatorio

    Directory of Open Access Journals (Sweden)

    Vilma C. Muñetón-Gómez

    2001-06-01

    Full Text Available La actividad que promueve el crecimiento de axones por la glia envolvente (GE del bulbo olfatorio depende de la expresión de diversas moléculas durante el desarrollo, la vida adulta y la reparación de lesiones nerviosas. Diversas moléculas tales como las neurotrofinas y sus receptores, los factores de crecimiento, las moléculas de adhesión celular, las moléculas de matriz extracelular y las moléculas asociadas con la mielinización son producidas por la glia del sistema olfatorio durante el desarrollo. Su expresión sostenida durante la vida adulta parece estar asociada con el reemplazo celular y la alta plasticidad de este sistema. A su vez, su expresión se involucra en procesos de reparación de lesiones mediados por trasplantes de glia. La migración de la GE, que acompaña axones en crecimiento, se observa durante el desarrollo y en procesos de regeneración luego de una lesión. Los trasplantes de,GE permiten la navegación de brotes regenerantes a través del tejido gliótico inhibidor formado luego de una lesión del sistema nervioso central. El propósito de esta revisión es profundizar en los mecanismos de actividad promotora de crecimiento axonal.

  12. A dam for retrograde axonal degeneration in multiple sclerosis?

    NARCIS (Netherlands)

    Balk, L.J.; Twisk, J.W.R.; Steenwijk, M.D.; Daams, M.; Tewarie, P.; Killestein, J.; Uitdehaag, B.M.J.; Polman, C.H.; Petzold, A.F.S.

    2014-01-01

    Objective: Trans-synaptic axonal degeneration is a mechanism by which neurodegeneration can spread from a sick to a healthy neuron in the central nervous system. This study investigated to what extent trans-synaptic axonal degeneration takes place within the visual pathway in multiple sclerosis

  13. Calpain Inhibition Reduces Axolemmal Leakage in Traumatic Axonal Injury

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    János Sándor

    2009-12-01

    Full Text Available Calcium-induced, calpain-mediated proteolysis (CMSP has recently been implicated to the pathogenesis of diffuse (traumatic axonal injury (TAI. Some studies suggested that subaxolemmal CMSP may contribute to axolemmal permeability (AP alterations observed in TAI. Seeking direct evidence for this premise we investigated whether subaxolemmal CMSP may contribute to axolemmal permeability alterations (APA and pre-injury calpain-inhibition could reduce AP in a rat model of TAI. Horseradish peroxidase (HRP, a tracer that accumulates in axons with APA was administered one hour prior to injury into the lateral ventricle; 30 min preinjury a single tail vein bolus injection of 30 mg/kg MDL-28170 (a calpain inhibitor or its vehicle was applied in Wistar rats exposed to impact acceleration brain injury. Histological detection of traumatically injured axonal segments accumulating HRP and statistical analysis revealed that pre-injury administration of the calpain inhibitor MDL-28170 significantly reduced the average length of HRP-labeled axonal segments. The axono-protective effect of pre-injury calpain inhibition recently demonstrated with classical immunohistochemical markers of TAI was further corroborated in this experiment; significant reduction of the length of labeled axons in the drug-treated rats implicate CMSP in the progression of altered AP in TAI.

  14. Subtypes of GABAergic neurons project axons in the neocortex

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    Shigeyoshi Higo

    2009-11-01

    Full Text Available γ-aminobutyric acid (GABAergic neurons in the neocortex have been regarded as interneurons and speculated to modulate the activity of neurons locally. Recently, however, several experiments revealed that neuronal nitric oxide synthase (nNOS-positive GABAergic neurons project cortico-cortically with long axons. In this study, we illustrate Golgi-like images of the nNOS-positive GABAergic neurons using a nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d reaction and follow the emanating axon branches in cat brain sections. These axon branches projected cortico-cortically with other non-labeled arcuate fibers, contra-laterally via the corpus callosum and anterior commissure. The labeled fibers were not limited to the neocortex but found also in the fimbria of the hippocampus. In order to have additional information on these GABAergic neuron projections, we investigated green fluorescent protein (GFP-labeled GABAergic neurons in GAD67-Cre knock-in / GFP Cre-reporter mice. GFP-labeled axons emanate densely, especially in the fimbria, a small number in the anterior commissure, and very sparsely in the corpus callosum. These two different approaches confirm that not only nNOS-positive GABAergic neurons but also other subtypes of GABAergic neurons project long axons in the cerebral cortex and are in a position to be involved in information processing.

  15. Target-Derived Neurotrophins Coordinate Transcription and Transport of Bclw to Prevent Axonal Degeneration

    Science.gov (United States)

    Cosker, Katharina E.; Pazyra-Murphy, Maria F.; Fenstermacher, Sara J.

    2013-01-01

    Establishment of neuronal circuitry depends on both formation and refinement of neural connections. During this process, target-derived neurotrophins regulate both transcription and translation to enable selective axon survival or elimination. However, it is not known whether retrograde signaling pathways that control transcription are coordinated with neurotrophin-regulated actions that transpire in the axon. Here we report that target-derived neurotrophins coordinate transcription of the antiapoptotic gene bclw with transport of bclw mRNA to the axon, and thereby prevent axonal degeneration in rat and mouse sensory neurons. We show that neurotrophin stimulation of nerve terminals elicits new bclw transcripts that are immediately transported to the axons and translated into protein. Bclw interacts with Bax and suppresses the caspase6 apoptotic cascade that fosters axonal degeneration. The scope of bclw regulation at the levels of transcription, transport, and translation provides a mechanism whereby sustained neurotrophin stimulation can be integrated over time, so that axonal survival is restricted to neurons connected within a stable circuit. PMID:23516285

  16. N-Propionylmannosamine stimulates axonal elongation in a murine model of sciatic nerve injury

    Directory of Open Access Journals (Sweden)

    Christian Witzel

    2015-01-01

    Full Text Available Increasing evidence indicates that sialic acid plays an important role during nerve regeneration. Sialic acids can be modified in vitro as well as in vivo using metabolic oligosaccharide engineering of the N-acyl side chain. N-Propionylmannosamine (ManNProp increases neurite outgrowth and accelerates the reestablishment of functional synapses in vitro. We investigated the influence of systemic ManNProp application using a specific in vivo mouse model. Using mice expressing axonal fluorescent proteins, we quantified the extension of regenerating axons, the number of regenerating axons, the number of arborising axons and the number of branches per axon 5 days after injury. Sciatic nerves from non-expressing mice were grafted into those expressing yellow fluorescent protein. We began a twice-daily intraperitoneal application of either peracetylated ManNProp (200 mg/kg or saline solution 5 days before injury, and continued it until nerve harvest (5 days after transection. ManNProp significantly increased the mean distance of axonal regeneration (2.49 mm vs. 1.53 mm; P < 0.005 and the number of arborizing axons (21% vs. 16% P = 0.008 5 days after sciatic nerve grafting. ManNProp did not affect the number of regenerating axons or the number of branches per arborizing axon. The biochemical glycoengineering of the N-acyl side chain of sialic acid might be a promising approach for improving peripheral nerve regeneration.

  17. Spontaneous axonal regeneration in rodent spinal cord after ischemic injury

    DEFF Research Database (Denmark)

    von Euler, Mia; Janson, A M; Larsen, Jytte Overgaard

    2002-01-01

    cells, while other fibers were unmyelinated. Immunohistochemistry demonstrated that some of the regenerated fibers were tyrosine hydroxylase- or serotonin-immunoreactive, indicating a central origin. These findings suggest that there is a considerable amount of spontaneous regeneration after spinal cord......Here we present evidence for spontaneous and long-lasting regeneration of CNS axons after spinal cord lesions in adult rats. The length of 200 kD neurofilament (NF)-immunolabeled axons was estimated after photochemically induced ischemic spinal cord lesions using a stereological tool. The total...... length of all NF-immunolabeled axons within the lesion cavities was increased 6- to 10-fold at 5, 10, and 15 wk post-lesion compared with 1 wk post-surgery. In ultrastructural studies we found the putatively regenerating axons within the lesion to be associated either with oligodendrocytes or Schwann...

  18. The disruption of mitochondrial axonal transport is an early event in neuroinflammation

    DEFF Research Database (Denmark)

    Errea, Oihana; Moreno, Beatriz; Gonzalez-Franquesa, Alba

    2015-01-01

    in the cerebellar slice cultures was analyzed through high-resolution respirometry assays and quantification of adenosine triphosphate (ATP) production. RESULTS: Both conditions promoted an increase in the size and complexity of axonal mitochondria evident in electron microscopy images, suggesting a compensatory...... acutely impairs axonal mitochondrial transportation, which would promote an inappropriate delivery of energy throughout axons and, by this way, contribute to axonal damage. Thus, preserving axonal mitochondrial transport might represent a promising avenue to exploit as a therapeutic target...... response. Such compensation was reflected at the tissue level as increased respiratory activity of complexes I and IV and as a transient increase in ATP production in response to acute inflammation. Notably, time-lapse microscopy indicated that mitochondrial transport (mean velocity) was severely impaired...

  19. Axonal sprouting regulates myelin basic protein gene expression in denervated mouse hippocampus

    DEFF Research Database (Denmark)

    Jensen, M B; Poulsen, F R; Finsen, B

    2000-01-01

    to 35 days after transection of the entorhino-hippocampal perforant path axonal projection. In situ hybridization analysis showed that anterograde axonal and terminal degeneration lead to upregulated oligodendrocyte MBP mRNA expression starting between day 2 and day 4, in (1) the deep part of stratum...... axonal and terminal degeneration, myelin degenerative changes, microglial activation and axotomi-induced axonal sprouting. Oligodendrocyte MBP mRNA expression reached maximum in both these areas at day 7. MBP gene transcription remained constant in stratum radiatum, stratum pyramidale and stratum oriens...... of CA1, areas that were unaffected by perforant path transection. These results provide strong evidence that oligodendrocyte MBP gene expression can be regulated by axonal sprouting independently of microglial activation in the injured adult CNS....

  20. Neurokinin-1 Receptor Immunoreactive Neuronal Elements in the Superficial Dorsal Horn of the Chicken Spinal Cord: With Special Reference to Their Relationship with the Tachykinin-containing Central Axon Terminals in Synaptic Glomeruli

    International Nuclear Information System (INIS)

    Sakamoto, Hiroshi; Kawate, Toyoko; Li, Yongnan; Atsumi, Saoko

    2009-01-01

    Synaptic glomeruli that involve tachykinin-containing primary afferent central terminals are numerous in lamina II of the chicken spinal cord. Therefore, a certain amount of noxious information is likely to be modulated in these structures in chickens. In this study, we used immunohistochemistry with confocal and electron microscopy to investigate whether neurokinin-1 receptor (NK-1R)-expressing neuronal elements are in contact with the central primary afferent terminals in synaptic glomeruli of the chicken spinal cord. We also investigated which neuronal elements (axon terminals, dendrites, cell bodies) and which neurons in the spinal cord possess NK-1R, and are possibly influenced by tachykinin in the glomeruli. By confocal microscopy, NK-1R immunoreactivities were seen in a variety of neuronal cell bodies, their dendrites and smaller fibers of unknown origin. Some of the NK-1R immunoreactive profiles also expressed GABA immunoreactivities. A close association was observed between the NK-1R-immunoreactive neurons and tachykinin-immunoreactive axonal varicosities. By electron microscopy, NK-1R immunoreactivity was seen in cell bodies, conventional dendrites and vesicle-containing dendrites in laminae I and II. Among these elements, dendrites and vesicle-containing dendrites made contact with tachykinin-containing central terminals in the synaptic glomeruli. These results indicate that tachykinin-containing central terminals in the chicken spinal cord can modulate second-order neuronal elements in the synaptic glomeruli

  1. Blast overpressure induced axonal injury changes in rat brainstem and spinal cord

    Directory of Open Access Journals (Sweden)

    Srinivasu Kallakuri

    2015-01-01

    Full Text Available Introduction: Blast induced neurotrauma has been the signature wound in returning soldiers from the ongoing wars in Iraq and Afghanistan. Of importance is understanding the pathomechansim(s of blast overpressure (OP induced axonal injury. Although several recent animal models of blast injury indicate the neuronal and axonal injury in various brain regions, animal studies related to axonal injury in the white matter (WM tracts of cervical spinal cord are limited. Objective: The purpose of this study was to assess the extent of axonal injury in WM tracts of cervical spinal cord in male Sprague Dawley rats subjected to a single insult of blast OP. Materials and Methods: Sagittal brainstem sections and horizontal cervical spinal cord sections from blast and sham animals were stained by neurofilament light (NF-L chain and beta amyloid precursor protein immunocytochemistry and observed for axonal injury changes. Results: Observations from this preliminary study demonstrate axonal injury changes in the form of prominent swellings, retraction bulbs, and putative signs of membrane disruptions in the brainstem and cervical spinal cord WM tracts of rats subjected to blast OP. Conclusions: Prominent axonal injury changes following the blast OP exposure in brainstem and cervical spinal WM tracts underscores the need for careful evaluation of blast induced injury changes and associated symptoms. NF-L immunocytochemistry can be considered as an additional tool to assess the blast OP induced axonal injury.

  2. Modelling in vivo action potential propagation along a giant axon.

    Science.gov (United States)

    George, Stuart; Foster, Jamie M; Richardson, Giles

    2015-01-01

    A partial differential equation model for the three-dimensional current flow in an excitable, unmyelinated axon is considered. Where the axon radius is significantly below a critical value R(crit) (that depends upon intra- and extra-cellular conductivity and ion channel conductance) the resistance of the intracellular space is significantly higher than that of the extracellular space, such that the potential outside the axon is uniformly small whilst the intracellular potential is approximated by the transmembrane potential. In turn, since the current flow is predominantly axial, it can be shown that the transmembrane potential is approximated by a solution to the one-dimensional cable equation. It is noted that the radius of the squid giant axon, investigated by (Hodgkin and Huxley 1952e), lies close to R(crit). This motivates us to apply the three-dimensional model to the squid giant axon and compare the results thus found to those obtained using the cable equation. In the context of the in vitro experiments conducted in (Hodgkin and Huxley 1952e) we find only a small difference between the wave profiles determined using these two different approaches and little difference between the speeds of action potential propagation predicted. This suggests that the cable equation approximation is accurate in this scenario. However when applied to the it in vivo setting, in which the conductivity of the surrounding tissue is considerably lower than that of the axoplasm, there are marked differences in both wave profile and speed of action potential propagation calculated using the two approaches. In particular, the cable equation significantly over predicts the increase in the velocity of propagation as axon radius increases. The consequences of these results are discussed in terms of the evolutionary costs associated with increasing the speed of action potential propagation by increasing axon radius.

  3. Regional Retinal Ganglion Cell Axon Loss in a Murine Glaucoma Model.

    Science.gov (United States)

    Schaub, Julie A; Kimball, Elizabeth C; Steinhart, Matthew R; Nguyen, Cathy; Pease, Mary E; Oglesby, Ericka N; Jefferys, Joan L; Quigley, Harry A

    2017-05-01

    To determine if retinal ganglion cell (RGC) axon loss in experimental mouse glaucoma is uniform in the optic nerve. Experimental glaucoma was induced for 6 weeks with a microbead injection model in CD1 (n = 78) and C57BL/6 (B6, n = 68) mice. From epoxy-embedded sections of optic nerve 1 to 2 mm posterior to the globe, total nerve area and regional axon density (axons/1600 μm2) were measured in superior, inferior, nasal, and temporal zones. Control eyes of CD1 mice have higher axon density and more total RGCs than control B6 mice eyes. There were no significant differences in control regional axon density in all mice or by strain (all P > 0.2, mixed model). Exposure to elevated IOP caused loss of RGC in both strains. In CD1 mice, axon density declined without significant loss of nerve area, while B6 mice had less density loss, but greater decrease in nerve area. Axon density loss in glaucoma eyes was not significantly greater in any region in either mouse strain (both P > 0.2, mixed model). In moderately damaged CD1 glaucoma eyes, and CD1 eyes with the greatest IOP elevation exposure, density loss differed by region (P = 0.05, P = 0.03, mixed model) with the greatest loss in the temporal and superior regions, while in severely injured B6 nerves superior loss was greater than inferior loss (P = 0.01, mixed model, Bonferroni corrected). There was selectively greater loss of superior and temporal optic nerve axons of RGCs in mouse glaucoma at certain stages of damage. Differences in nerve area change suggest non-RGC responses differ between mouse strains.

  4. Developmental time windows for axon growth influence neuronal network topology.

    Science.gov (United States)

    Lim, Sol; Kaiser, Marcus

    2015-04-01

    Early brain connectivity development consists of multiple stages: birth of neurons, their migration and the subsequent growth of axons and dendrites. Each stage occurs within a certain period of time depending on types of neurons and cortical layers. Forming synapses between neurons either by growing axons starting at similar times for all neurons (much-overlapped time windows) or at different time points (less-overlapped) may affect the topological and spatial properties of neuronal networks. Here, we explore the extreme cases of axon formation during early development, either starting at the same time for all neurons (parallel, i.e., maximally overlapped time windows) or occurring for each neuron separately one neuron after another (serial, i.e., no overlaps in time windows). For both cases, the number of potential and established synapses remained comparable. Topological and spatial properties, however, differed: Neurons that started axon growth early on in serial growth achieved higher out-degrees, higher local efficiency and longer axon lengths while neurons demonstrated more homogeneous connectivity patterns for parallel growth. Second, connection probability decreased more rapidly with distance between neurons for parallel growth than for serial growth. Third, bidirectional connections were more numerous for parallel growth. Finally, we tested our predictions with C. elegans data. Together, this indicates that time windows for axon growth influence the topological and spatial properties of neuronal networks opening up the possibility to a posteriori estimate developmental mechanisms based on network properties of a developed network.

  5. Parametric Probability Distribution Functions for Axon Diameters of Corpus Callosum

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    Farshid eSepehrband

    2016-05-01

    Full Text Available Axon diameter is an important neuroanatomical characteristic of the nervous system that alters in the course of neurological disorders such as multiple sclerosis. Axon diameters vary, even within a fiber bundle, and are not normally distributed. An accurate distribution function is therefore beneficial, either to describe axon diameters that are obtained from a direct measurement technique (e.g., microscopy, or to infer them indirectly (e.g., using diffusion-weighted MRI. The gamma distribution is a common choice for this purpose (particularly for the inferential approach because it resembles the distribution profile of measured axon diameters which has been consistently shown to be non-negative and right-skewed. In this study we compared a wide range of parametric probability distribution functions against empirical data obtained from electron microscopy images. We observed that the gamma distribution fails to accurately describe the main characteristics of the axon diameter distribution, such as location and scale of the mode and the profile of distribution tails. We also found that the generalized extreme value distribution consistently fitted the measured distribution better than other distribution functions. This suggests that there may be distinct subpopulations of axons in the corpus callosum, each with their own distribution profiles. In addition, we observed that several other distributions outperformed the gamma distribution, yet had the same number of unknown parameters; these were the inverse Gaussian, log normal, log logistic and Birnbaum-Saunders distributions.

  6. Transient developmental Purkinje cell axonal torpedoes in healthy and ataxic mouse cerebellum

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    Lovisa Ljungberg

    2016-11-01

    Full Text Available Information is carried out of the cerebellar cortical microcircuit via action potentials propagated along Purkinje cell axons. In several human neurodegenerative diseases, focal axonal swellings on Purkinje cells – known as torpedoes – have been associated with Purkinje cell loss. Interestingly, torpedoes are also reported to appear transiently during development in rat cerebellum. The function of Purkinje cell axonal torpedoes in health as well as in disease is poorly understood. We investigated the properties of developmental torpedoes in the postnatal mouse cerebellum of wildtype and transgenic mice. We found that Purkinje cell axonal torpedoes transiently appeared on axons of Purkinje neurons, with the largest number of torpedoes observed at postnatal day 11 (P11. This was after peak developmental apoptosis had occurred, when Purkinje cell counts in a lobule were static, suggesting that most developmental torpedoes appear on axons of neurons that persist into adulthood. We found that developmental torpedoes were not associated with a presynaptic GABAergic marker, indicating that they are not synapses. They were seldom found at axonal collateral branch points, and lacked microglia enrichment, suggesting that they are unlikely to be involved in axonal refinement. Interestingly, we found several differences between developmental torpedoes and disease-related torpedoes: developmental torpedoes occured largely on myelinated axons, and were not associated with changes in basket cell innervation on their parent soma. Disease-related torpedoes are typically reported to contain neurofilament; while the majority of developmental torpedoes did as well, a fraction of smaller developmental torpedoes did not. These differences indicate that developmental torpedoes may not be functionally identical to disease-related torpedoes. To study this further, we used a mouse model of spinocerebellar ataxia type 6 (SCA6, and found elevated disease

  7. Bridging the gap: axonal fusion drives rapid functional recovery of the nervous system

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    Jean-Sébastien Teoh

    2018-01-01

    Full Text Available Injuries to the central or peripheral nervous system frequently cause long-term disabilities because damaged neurons are unable to efficiently self-repair. This inherent deficiency necessitates the need for new treatment options aimed at restoring lost function to patients. Compared to humans, a number of species possess far greater regenerative capabilities, and can therefore provide important insights into how our own nervous systems can be repaired. In particular, several invertebrate species have been shown to rapidly initiate regeneration post-injury, allowing separated axon segments to re-join. This process, known as axonal fusion, represents a highly efficient repair mechanism as a regrowing axon needs to only bridge the site of damage and fuse with its separated counterpart in order to re-establish its original structure. Our recent findings in the nematode Caenorhabditis elegans have expanded the promise of axonal fusion by demonstrating that it can restore complete function to damaged neurons. Moreover, we revealed the importance of injury-induced changes in the composition of the axonal membrane for mediating axonal fusion, and discovered that the level of axonal fusion can be enhanced by promoting a neuron's intrinsic growth potential. A complete understanding of the molecular mechanisms controlling axonal fusion may permit similar approaches to be applied in a clinical setting.

  8. MuSC is involved in regulating axonal fasciculation of mouse primary vestibular afferents.

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    Kawauchi, Daisuke; Kobayashi, Hiroaki; Sekine-Aizawa, Yoko; Fujita, Shinobu C; Murakami, Fujio

    2003-10-01

    Regulation of axonal fasciculation plays an important role in the precise patterning of neural circuits. Selective fasciculation contributes to the sorting of different types of axons and prevents the misrouting of axons. However, axons must defasciculate once they reach the target area. To study the regulation of fasciculation, we focused on the primary vestibulo-cerebellar afferents (PVAs), which show a dramatic change from fasciculated axon bundles to defasciculated individual axons at their target region, the cerebellar primordium. To understand how fasciculation and defasciculation are regulated in this system, we investigated the roles of murine SC1-related protein (MuSC), a molecule belonging to the immunoglobulin superfamily. We show: (i) by comparing 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (Dil) labelling and anti-MuSC immunohistochemistry, that downregulation of MuSC in PVAs during development is concomitant with the defasciculation of PVA axons; (ii) in a binding assay with cells expressing MuSC, that MuSC has cell-adhesive activity via a homophilic binding mechanism, and this activity is increased by multimerization; and (iii) that MuSC also displays neurite outgrowth-promoting activity in vestibular ganglion cultures. These findings suggest that MuSC is involved in axonal fasciculation and its downregulation may help to initiate the defasciculation of PVAs.

  9. Alterations in a Unique Class of Cortical Chandelier Cell Axon Cartridges in Schizophrenia.

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    Rocco, Brad R; DeDionisio, Adam M; Lewis, David A; Fish, Kenneth N

    2017-07-01

    The axons of chandelier cells (ChCs) target the axon initial segment of pyramidal neurons, forming an array of boutons termed a cartridge. In schizophrenia, the density of cartridges detectable by gamma-aminobutyric acid (GABA) membrane transporter 1 immunoreactivity is lower, whereas the density of axon initial segments detectable by immunoreactivity for the α2 subunit of the GABA A receptor is higher in layers 2/superficial 3 of the prefrontal cortex. These findings were interpreted as compensatory responses to lower GABA levels in ChCs. However, we recently found that in schizophrenia, ChC cartridge boutons contain normal levels of the 67 kDa isoform of glutamic acid decarboxylase (GAD67) protein, the enzyme responsible for GABA synthesis in these boutons. To understand these findings we quantified the densities of ChC cartridges immunoreactive for vesicular GABA transporter (vGAT+), which is present in all cartridge boutons, and the subset of cartridges that contain calbindin (CB+). Prefrontal cortex tissue sections from 20 matched pairs of schizophrenia and unaffected comparison subjects were immunolabeled for vGAT, GAD67, and CB. The mean density of vGAT+/CB+ cartridges was 2.7-fold higher, exclusively in layer 2 of schizophrenia subjects, whereas the density of vGAT+/CB- cartridges did not differ between subject groups. Neither vGAT, CB, or GAD67 protein levels per ChC bouton nor the number of boutons per cartridge differed between subject groups. Our findings of a greater density of CB+ ChC cartridges in prefrontal cortex layer 2 from schizophrenia subjects suggests that the normal developmental pruning of these cartridges is blunted in the illness. Copyright © 2016 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

  10. Evidence that the EphA2 receptor exacerbates ischemic brain injury.

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    John Thundyil

    Full Text Available Ephrin (Eph signaling within the central nervous system is known to modulate axon guidance, synaptic plasticity, and to promote long-term potentiation. We investigated the potential involvement of EphA2 receptors in ischemic stroke-induced brain inflammation in a mouse model of focal stroke. Cerebral ischemia was induced in male C57Bl6/J wild-type (WT and EphA2-deficient (EphA2(-/- mice by middle cerebral artery occlusion (MCAO; 60 min, followed by reperfusion (24 or 72 h. Brain infarction was measured using triphenyltetrazolium chloride staining. Neurological deficit scores and brain infarct volumes were significantly less in EphA2(-/- mice compared with WT controls. This protection by EphA2 deletion was associated with a comparative decrease in brain edema, blood-brain barrier damage, MMP-9 expression and leukocyte infiltration, and higher expression levels of the tight junction protein, zona occludens-1. Moreover, EphA2(-/- brains had significantly lower levels of the pro-apoptotic proteins, cleaved caspase-3 and BAX, and higher levels of the anti-apoptotic protein, Bcl-2 as compared to WT group. We confirmed that isolated WT cortical neurons express the EphA2 receptor and its ligands (ephrin-A1-A3. Furthermore, expression of all four proteins was increased in WT primary cortical neurons following 24 h of glucose deprivation, and in the brains of WT mice following stroke. Glucose deprivation induced less cell death in primary neurons from EphA2(-/- compared with WT mice. In conclusion, our data provide the first evidence that the EphA2 receptor directly contributes to blood-brain barrier damage and neuronal death following ischemic stroke.

  11. Sodium Channel β2 Subunits Prevent Action Potential Propagation Failures at Axonal Branch Points.

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    Cho, In Ha; Panzera, Lauren C; Chin, Morven; Hoppa, Michael B

    2017-09-27

    Neurotransmitter release depends on voltage-gated Na + channels (Na v s) to propagate an action potential (AP) successfully from the axon hillock to a synaptic terminal. Unmyelinated sections of axon are very diverse structures encompassing branch points and numerous presynaptic terminals with undefined molecular partners of Na + channels. Using optical recordings of Ca 2+ and membrane voltage, we demonstrate here that Na + channel β2 subunits (Na v β2s) are required to prevent AP propagation failures across the axonal arborization of cultured rat hippocampal neurons (mixed male and female). When Na v β2 expression was reduced, we identified two specific phenotypes: (1) membrane excitability and AP-evoked Ca 2+ entry were impaired at synapses and (2) AP propagation was severely compromised with >40% of axonal branches no longer responding to AP-stimulation. We went on to show that a great deal of electrical signaling heterogeneity exists in AP waveforms across the axonal arborization independent of axon morphology. Therefore, Na v β2 is a critical regulator of axonal excitability and synaptic function in unmyelinated axons. SIGNIFICANCE STATEMENT Voltage-gated Ca 2+ channels are fulcrums of neurotransmission that convert electrical inputs into chemical outputs in the form of vesicle fusion at synaptic terminals. However, the role of the electrical signal, the presynaptic action potential (AP), in modulating synaptic transmission is less clear. What is the fidelity of a propagating AP waveform in the axon and what molecules shape it throughout the axonal arborization? Our work identifies several new features of AP propagation in unmyelinated axons: (1) branches of a single axonal arborization have variable AP waveforms independent of morphology, (2) Na + channel β2 subunits modulate AP-evoked Ca 2+ -influx, and (3) β2 subunits maintain successful AP propagation across the axonal arbor. These findings are relevant to understanding the flow of excitation in the

  12. Modifying Lipid Rafts Promotes Regeneration and Functional Recovery

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    Nardos G. Tassew

    2014-08-01

    Full Text Available Ideal strategies to ameliorate CNS damage should promote both neuronal survival and axon regeneration. The receptor Neogenin promotes neuronal apoptosis. Its ligand prevents death, but the resulting repulsive guidance molecule a (RGMa-Neogenin interaction also inhibits axonal growth, countering any prosurvival benefits. Here, we explore strategies to inhibit Neogenin, thus simultaneously enhancing survival and regeneration. We show that bone morphogenetic protein (BMP and RGMa-dependent recruitment of Neogenin into lipid rafts requires an interaction between RGMa and Neogenin subdomains. RGMa or Neogenin peptides that prevent this interaction, BMP inhibition by Noggin, or reduction of membrane cholesterol all block Neogenin raft localization, promote axon outgrowth, and prevent neuronal apoptosis. Blocking Neogenin raft association influences axonal pathfinding, enhances survival in the developing CNS, and promotes survival and regeneration in the injured adult optic nerve and spinal cord. Moreover, lowering cholesterol disrupts rafts and restores locomotor function after spinal cord injury. These data reveal a unified strategy to promote both survival and regeneration in the CNS.

  13. Oligodendroglial MCT1 and Metabolic Support of Axons in Multiple Sclerosis

    Science.gov (United States)

    2015-10-01

    AWARD NUMBER: W81XWH-14-1-0524 TITLE:Oligodendroglial MCT1 and Metabolic Support of Axons in Multiple Sclerosis PRINCIPAL INVESTIGATOR: Jeffrey D...29 Sep 2015 4. TITLE AND SUBTITLE Oligodendroglial MCT1 and Metabolic Support of Axons in Multiple Sclerosis 5a. CONTRACT NUMBER W81XWH-14-1-0524...MCT1 in injured oligodendroglia of multiple sclerosis patients contributes to axon neurodegeneration and that increasing MCT1 will be protective in the

  14. Study of the Peripheral Nerve Fibers Myelin Structure Changes during Activation of Schwann Cell Acetylcholine Receptors.

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    Ekaterina E Verdiyan

    Full Text Available In the present paper we consider a new type of mechanism by which neurotransmitter acetylcholine (ACh regulates the properties of peripheral nerve fibers myelin. Our data show the importance of the relationship between the changes in the number of Schwann cell (SC acetylcholine receptors (AChRs and the axon excitation (different intervals between action potentials (APs. Using Raman spectroscopy, an effect of activation of SC AChRs on the myelin membrane fluidity was investigated. It was found, that ACh stimulates an increase in lipid ordering degree of the myelin lipids, thus providing evidence for specific role of the "axon-SC" interactions at the axon excitation. It was proposed, that during the axon excitation, the SC membrane K+- depolarization and the Ca2+-influx led to phospholipase activation or exocytosis of intracellular membrane vesicles and myelin structure reorganization.

  15. Motoneuron axon pathfinding errors in zebrafish: Differential effects related to concentration and timing of nicotine exposure

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    Menelaou, Evdokia; Paul, Latoya T.; Perera, Surangi N.; Svoboda, Kurt R.

    2015-01-01

    Nicotine exposure during embryonic stages of development can affect many neurodevelopmental processes. In the developing zebrafish, exposure to nicotine was reported to cause axonal pathfinding errors in the later born secondary motoneurons (SMNs). These alterations in SMN axon morphology coincided with muscle degeneration at high nicotine concentrations (15–30 μM). Previous work showed that the paralytic mutant zebrafish known as sofa potato exhibited nicotine-induced effects onto SMN axons at these high concentrations but in the absence of any muscle deficits, indicating that pathfinding errors could occur independent of muscle effects. In this study, we used varying concentrations of nicotine at different developmental windows of exposure to specifically isolate its effects onto subpopulations of motoneuron axons. We found that nicotine exposure can affect SMN axon morphology in a dose-dependent manner. At low concentrations of nicotine, SMN axons exhibited pathfinding errors, in the absence of any nicotine-induced muscle abnormalities. Moreover, the nicotine exposure paradigms used affected the 3 subpopulations of SMN axons differently, but the dorsal projecting SMN axons were primarily affected. We then identified morphologically distinct pathfinding errors that best described the nicotine-induced effects on dorsal projecting SMN axons. To test whether SMN pathfinding was potentially influenced by alterations in the early born primary motoneuron (PMN), we performed dual labeling studies, where both PMN and SMN axons were simultaneously labeled with antibodies. We show that only a subset of the SMN axon pathfinding errors coincided with abnormal PMN axonal targeting in nicotine-exposed zebrafish. We conclude that nicotine exposure can exert differential effects depending on the levels of nicotine and developmental exposure window. - Highlights: • Embryonic nicotine exposure can specifically affect secondary motoneuron axons in a dose-dependent manner.

  16. Motoneuron axon pathfinding errors in zebrafish: Differential effects related to concentration and timing of nicotine exposure

    Energy Technology Data Exchange (ETDEWEB)

    Menelaou, Evdokia; Paul, Latoya T. [Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803 (United States); Perera, Surangi N. [Joseph J. Zilber School of Public Health, University of Wisconsin — Milwaukee, Milwaukee, WI 53205 (United States); Svoboda, Kurt R., E-mail: svobodak@uwm.edu [Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803 (United States); Joseph J. Zilber School of Public Health, University of Wisconsin — Milwaukee, Milwaukee, WI 53205 (United States)

    2015-04-01

    Nicotine exposure during embryonic stages of development can affect many neurodevelopmental processes. In the developing zebrafish, exposure to nicotine was reported to cause axonal pathfinding errors in the later born secondary motoneurons (SMNs). These alterations in SMN axon morphology coincided with muscle degeneration at high nicotine concentrations (15–30 μM). Previous work showed that the paralytic mutant zebrafish known as sofa potato exhibited nicotine-induced effects onto SMN axons at these high concentrations but in the absence of any muscle deficits, indicating that pathfinding errors could occur independent of muscle effects. In this study, we used varying concentrations of nicotine at different developmental windows of exposure to specifically isolate its effects onto subpopulations of motoneuron axons. We found that nicotine exposure can affect SMN axon morphology in a dose-dependent manner. At low concentrations of nicotine, SMN axons exhibited pathfinding errors, in the absence of any nicotine-induced muscle abnormalities. Moreover, the nicotine exposure paradigms used affected the 3 subpopulations of SMN axons differently, but the dorsal projecting SMN axons were primarily affected. We then identified morphologically distinct pathfinding errors that best described the nicotine-induced effects on dorsal projecting SMN axons. To test whether SMN pathfinding was potentially influenced by alterations in the early born primary motoneuron (PMN), we performed dual labeling studies, where both PMN and SMN axons were simultaneously labeled with antibodies. We show that only a subset of the SMN axon pathfinding errors coincided with abnormal PMN axonal targeting in nicotine-exposed zebrafish. We conclude that nicotine exposure can exert differential effects depending on the levels of nicotine and developmental exposure window. - Highlights: • Embryonic nicotine exposure can specifically affect secondary motoneuron axons in a dose-dependent manner.

  17. Effects of X-irradiation on axonal sprouting induced by botulinum toxin

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    Gomez, S; Duchen, L W [National Hospital, London (UK); Hornsey, S [Hammersmith Hospital, London (UK). M.R.C. Cyclotron Unit

    1982-01-01

    The effect of X-irradiation on axonal sprouting of motor nerves induced by botulinum toxin was examined. Muscles of one leg in the mouse were X-irradiated (15Gy) prior to the injection of a locally paralysing dose of botulinum toxin. It was found that axonal sprouting occurred as expected, but the sprouts remained unmyelinated and many degenerated. Fewer new end-plates were formed, muscles remained more severely atrophied and supersensitive to acetylcholine and recovery of neuromuscular transmission was greatly delayed when compared with the effects of botulinum toxin alone. X-irradiation did not prevent sprouting but, probably by impairing Schwann cell proliferation, altered axon-Schwann cell relationships and prevented the maturation of newly-formed axons and the differentiation of new end-plates.

  18. Modeling of the axon membrane skeleton structure and implications for its mechanical properties.

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    Yihao Zhang

    2017-02-01

    Full Text Available Super-resolution microscopy recently revealed that, unlike the soma and dendrites, the axon membrane skeleton is structured as a series of actin rings connected by spectrin filaments that are held under tension. Currently, the structure-function relationship of the axonal structure is unclear. Here, we used atomic force microscopy (AFM to show that the stiffness of the axon plasma membrane is significantly higher than the stiffnesses of dendrites and somata. To examine whether the structure of the axon plasma membrane determines its overall stiffness, we introduced a coarse-grain molecular dynamics model of the axon membrane skeleton that reproduces the structure identified by super-resolution microscopy. Our proposed computational model accurately simulates the median value of the Young's modulus of the axon plasma membrane determined by atomic force microscopy. It also predicts that because the spectrin filaments are under entropic tension, the thermal random motion of the voltage-gated sodium channels (Nav, which are bound to ankyrin particles, a critical axonal protein, is reduced compared to the thermal motion when spectrin filaments are held at equilibrium. Lastly, our model predicts that because spectrin filaments are under tension, any axonal injuries that lacerate spectrin filaments will likely lead to a permanent disruption of the membrane skeleton due to the inability of spectrin filaments to spontaneously form their initial under-tension configuration.

  19. Modeling of the axon membrane skeleton structure and implications for its mechanical properties.

    Science.gov (United States)

    Zhang, Yihao; Abiraman, Krithika; Li, He; Pierce, David M; Tzingounis, Anastasios V; Lykotrafitis, George

    2017-02-01

    Super-resolution microscopy recently revealed that, unlike the soma and dendrites, the axon membrane skeleton is structured as a series of actin rings connected by spectrin filaments that are held under tension. Currently, the structure-function relationship of the axonal structure is unclear. Here, we used atomic force microscopy (AFM) to show that the stiffness of the axon plasma membrane is significantly higher than the stiffnesses of dendrites and somata. To examine whether the structure of the axon plasma membrane determines its overall stiffness, we introduced a coarse-grain molecular dynamics model of the axon membrane skeleton that reproduces the structure identified by super-resolution microscopy. Our proposed computational model accurately simulates the median value of the Young's modulus of the axon plasma membrane determined by atomic force microscopy. It also predicts that because the spectrin filaments are under entropic tension, the thermal random motion of the voltage-gated sodium channels (Nav), which are bound to ankyrin particles, a critical axonal protein, is reduced compared to the thermal motion when spectrin filaments are held at equilibrium. Lastly, our model predicts that because spectrin filaments are under tension, any axonal injuries that lacerate spectrin filaments will likely lead to a permanent disruption of the membrane skeleton due to the inability of spectrin filaments to spontaneously form their initial under-tension configuration.

  20. Electrically conductive biodegradable polymer composite for nerve regeneration: electricity-stimulated neurite outgrowth and axon regeneration.

    Science.gov (United States)

    Zhang, Ze; Rouabhia, Mahmoud; Wang, Zhaoxu; Roberge, Christophe; Shi, Guixin; Roche, Phillippe; Li, Jiangming; Dao, Lê H

    2007-01-01

    Normal and electrically stimulated PC12 cell cultures and the implantation of nerve guidance channels were performed to evaluate newly developed electrically conductive biodegradable polymer composites. Polypyrrole (PPy) doped by butane sulfonic acid showed a significantly higher number of viable cells compared with PPy doped by polystyrenesulfonate after a 6-day culture. The PC12 cells were left to proliferate for 6 days, and the PPy-coated membranes, showing less initial cell adherence, recorded the same proliferation rate as did the noncoated membranes. Direct current electricity at various intensities was applied to the PC12 cell-cultured conductive membranes. After 7 days, the greatest number of neurites appeared on the membranes with a current intensity approximating 1.7-8.4 microA/cm. Nerve guidance channels made of conductive biodegradable composite were implanted into rats to replace 8 mm of sciatic nerve. The implants were harvested after 2 months and analyzed with immunohistochemistry and transmission electron microscopy. The regenerated nerve tissue displayed myelinated axons and Schwann cells that were similar to those in the native nerve. Electrical stimulation applied through the electrically conductive biodegradable polymers therefore enhanced neurite outgrowth in a current-dependent fashion. The conductive polymers also supported sciatic nerve regeneration in rats.

  1. Sim1 is required for the migration and axonal projections of V3 interneurons in the developing mouse spinal cord.

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    Blacklaws, Jake; Deska-Gauthier, Dylan; Jones, Christopher T; Petracca, Yanina L; Liu, Mingwei; Zhang, Han; Fawcett, James P; Glover, Joel C; Lanuza, Guillermo M; Zhang, Ying

    2015-09-01

    V3 spinal interneurons (INs) are a group of excitatory INs that play a crucial role in producing balanced and stable gaits in vertebrate animals. In the developing mouse spinal cord, V3 INs arise from the most ventral progenitor domain and form anatomically distinctive subpopulations in adult spinal cords. They are marked by the expression of transcription factor Sim1 postmitotically, but the function of Sim1 in V3 development remains unknown. Here, we used Sim1(Cre) ;tdTomato mice to trace the fate of V3 INs in a Sim1 mutant versus control genetic background during development. In Sim1 mutants, V3 INs are produced normally and maintain a similar position and organization as in wild types before E12.5. Further temporal analysis revealed that the V3 INs in the mutants failed to migrate properly to form V3 subgroups along the dorsoventral axis of the spinal cord. At birth, in the Sim1 mutant the number of V3 INs in the ventral subgroup was normal, but they were significantly reduced in the dorsal subgroup with a concomitant increase in the intermediate subgroup. Retrograde labeling at lumbar level revealed that loss of Sim1 led to a reduction in extension of contralateral axon projections both at E14.5 and P0 without affecting ipsilateral axon projections. These results demonstrate that Sim1 is essential for proper migration and the guidance of commissural axons of the spinal V3 INs. © 2015 Wiley Periodicals, Inc.

  2. Microtubule-targeting drugs rescue axonal swellings in cortical neurons from spastin knockout mice

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    Coralie Fassier

    2013-01-01

    Mutations in SPG4, encoding the microtubule-severing protein spastin, are responsible for the most frequent form of hereditary spastic paraplegia (HSP, a heterogeneous group of genetic diseases characterized by degeneration of the corticospinal tracts. We previously reported that mice harboring a deletion in Spg4, generating a premature stop codon, develop progressive axonal degeneration characterized by focal axonal swellings associated with impaired axonal transport. To further characterize the molecular and cellular mechanisms underlying this mutant phenotype, we have assessed microtubule dynamics and axonal transport in primary cultures of cortical neurons from spastin-mutant mice. We show an early and marked impairment of microtubule dynamics all along the axons of spastin-deficient cortical neurons, which is likely to be responsible for the occurrence of axonal swellings and cargo stalling. Our analysis also reveals that a modulation of microtubule dynamics by microtubule-targeting drugs rescues the mutant phenotype of cortical neurons. Together, these results contribute to a better understanding of the pathogenesis of SPG4-linked HSP and ascertain the influence of microtubule-targeted drugs on the early axonal phenotype in a mouse model of the disease.

  3. In vivo imaging reveals mitophagy independence in the maintenance of axonal mitochondria during normal aging.

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    Cao, Xu; Wang, Haiqiong; Wang, Zhao; Wang, Qingyao; Zhang, Shuang; Deng, Yuanping; Fang, Yanshan

    2017-10-01

    Mitophagy is thought to be a critical mitochondrial quality control mechanism in neurons and has been extensively studied in neurological disorders such as Parkinson's disease. However, little is known about how mitochondria are maintained in the lengthy neuronal axons in the context of physiological aging. Here, we utilized the unique Drosophila wing nerve model and in vivo imaging to rigorously profile changes in axonal mitochondria during aging. We revealed that mitochondria became fragmented and accumulated in aged axons. However, lack of Pink1 or Parkin did not lead to the accumulation of axonal mitochondria or axonal degeneration. Further, unlike in in vitro cultured neurons, we found that mitophagy rarely occurred in intact axons in vivo, even in aged animals. Furthermore, blocking overall mitophagy by knockdown of the core autophagy genes Atg12 or Atg17 had little effect on the turnover of axonal mitochondria or axonal integrity, suggesting that mitophagy is not required for axonal maintenance; this is regardless of whether the mitophagy is PINK1-Parkin dependent or independent. In contrast, downregulation of mitochondrial fission-fusion genes caused age-dependent axonal degeneration. Moreover, Opa1 expression in the fly head was significantly decreased with age, which may underlie the accumulation of fragmented mitochondria in aged axons. Finally, we showed that adult-onset, neuronal downregulation of the fission-fusion, but not mitophagy genes, dramatically accelerated features of aging. We propose that axonal mitochondria are maintained independently of mitophagy and that mitophagy-independent mechanisms such as fission-fusion may be central to the maintenance of axonal mitochondria and neural integrity during normal aging. © 2017 The Authors. Aging Cell published by the Anatomical Society and John Wiley & Sons Ltd.

  4. Synaptic Democracy and Vesicular Transport in Axons

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    Bressloff, Paul C.; Levien, Ethan

    2015-04-01

    Synaptic democracy concerns the general problem of how regions of an axon or dendrite far from the cell body (soma) of a neuron can play an effective role in neuronal function. For example, stimulated synapses far from the soma are unlikely to influence the firing of a neuron unless some sort of active dendritic processing occurs. Analogously, the motor-driven transport of newly synthesized proteins from the soma to presynaptic targets along the axon tends to favor the delivery of resources to proximal synapses. Both of these phenomena reflect fundamental limitations of transport processes based on a localized source. In this Letter, we show that a more democratic distribution of proteins along an axon can be achieved by making the transport process less efficient. This involves two components: bidirectional or "stop-and-go" motor transport (which can be modeled in terms of advection-diffusion), and reversible interactions between motor-cargo complexes and synaptic targets. Both of these features have recently been observed experimentally. Our model suggests that, just as in human societies, there needs to be a balance between "efficiency" and "equality".

  5. Characterization of patients with head trauma and traumatic axonal injury

    International Nuclear Information System (INIS)

    Mosquera Betancourt, Dra.C. Gretel; Van Duc, Dr. Hanh; Casares Delgado, Dr. Jorge Alejandro; Hernández González, Dr. Erick Héctor

    2016-01-01

    Background: traumatic axonal injury is characterized by multifocal lesions, consequences of primary, secondary and tertiary damage which is able to cause varying degrees of disability. Objective: to characterize patients with traumatic axonal injury. Methods: a cross-sectional analytical study was conducted from January 2014 to December 2015. The target population was composed of 35 patients over age 18 whose diagnosis was traumatic axonal injury type I and IV of the Marshall computed tomographic (CT) classification. With the data collected from medical records revisions and direct observation, a database was created in SPSS for its processing through univariate and multivariate techniques. Results: male patients between 18 and 30 years old without bad habits prevailed. Most of the patients survived and death was associated with the presence of severe traumatic axonal injury, Marshall computed tomographic (CT) classification degree III, complications and presence of trauma in thorax, abdomen and cervical spine. Conclusions: diagnosis of traumatic axonal injury is based on the clinical radiological correlation based on images from tomography and it is confirmed by Magnetic resonance imaging (MRI). Histological study shows injuries that are not demonstrated in the most advanced radiological studies. Its prevention is the most fundamental base in medical assistance, followed by neurocritical attention oriented by neuromonitoring. (author)

  6. Functional complexity of the axonal growth cone: a proteomic analysis.

    Directory of Open Access Journals (Sweden)

    Adriana Estrada-Bernal

    Full Text Available The growth cone, the tip of the emerging neurite, plays a crucial role in establishing the wiring of the developing nervous system. We performed an extensive proteomic analysis of axonal growth cones isolated from the brains of fetal Sprague-Dawley rats. Approximately 2000 proteins were identified at ≥ 99% confidence level. Using informatics, including functional annotation cluster and KEGG pathway analysis, we found great diversity of proteins involved in axonal pathfinding, cytoskeletal remodeling, vesicular traffic and carbohydrate metabolism, as expected. We also found a large and complex array of proteins involved in translation, protein folding, posttranslational processing, and proteasome/ubiquitination-dependent degradation. Immunofluorescence studies performed on hippocampal neurons in culture confirmed the presence in the axonal growth cone of proteins representative of these processes. These analyses also provide evidence for rough endoplasmic reticulum and reveal a reticular structure equipped with Golgi-like functions in the axonal growth cone. Furthermore, Western blot revealed the growth cone enrichment, relative to fetal brain homogenate, of some of the proteins involved in protein synthesis, folding and catabolism. Our study provides a resource for further research and amplifies the relatively recently developed concept that the axonal growth cone is equipped with proteins capable of performing a highly diverse range of functions.

  7. Wnt3 and Gata4 regulate axon regeneration in adult mouse DRG neurons.

    Science.gov (United States)

    Duan, Run-Shan; Liu, Pei-Pei; Xi, Feng; Wang, Wei-Hua; Tang, Gang-Bin; Wang, Rui-Ying; Saijilafu; Liu, Chang-Mei

    2018-05-05

    Neurons in the adult central nervous system (CNS) have a poor intrinsic axon growth potential after injury, but the underlying mechanisms are largely unknown. Wingless-related mouse mammary tumor virus integration site (WNT) family members regulate neural stem cell proliferation, axon tract and forebrain development in the nervous system. Here we report that Wnt3 is an important modulator of axon regeneration. Downregulation or overexpression of Wnt3 in adult dorsal root ganglion (DRG) neurons enhances or inhibits their axon regeneration ability respectively in vitro and in vivo. Especially, we show that Wnt3 modulates axon regeneration by repressing mRNA translation of the important transcription factor Gata4 via binding to the three prime untranslated region (3'UTR). Downregulation of Gata4 could restore the phenotype exhibited by Wnt3 downregulation in DRG neurons. Taken together, these data indicate that Wnt3 is a key intrinsic regulator of axon growth ability of the nervous system. Copyright © 2018 Elsevier Inc. All rights reserved.

  8. Phospholipid synthesis in the squid giant axon: incorporation of lipid precursors

    Energy Technology Data Exchange (ETDEWEB)

    Gould, R.M.; Pant, H.; Gainer, H.; Tytell, M.

    1983-05-01

    The squid giant axon and extruded axoplasm from the giant axon were used to study the capacity of axoplasm for phospholipid synthesis. Extruded axoplasm, suspended in chemically defined media, catalyzed the synthesis of phospholipids from all of the precursors tested. /sup 32/P-Labeled inorganic phosphate and gamma-labeled ATP were actively incorporated into phosphatidylinositol phosphate, while (2-/sup 3/H)myo-inositol and L-(/sup 3/H(G))serine were actively incorporated into phosphatidylinositol and phosphatidylserine, respectively. Though less well utilized. (2-/sup 3/H)glycerol was incorporated into phosphatidic acid, phosphatidylinositol, and triglyceride, and methyl-3H)choline and (1-/sup 3/H)ethanolamine were incorporated into phosphatidylcholine and phosphatidylethanolamine, respectively. Isolated squid giant axons were incubated in artificial seawater containing the above precursors. The axoplasm was extruded following the incubations. Although most of the product lipids were recovered in the sheath (composed of cortical axoplasm, axolemma, and surrounding satellite cells), significant amounts (4-20%) were present in the extruded axoplasm. With tritiated choline and myo-inositol, the major labeled phospholipids found in both the extruded axoplasm and the sheath were phosphatidylcholine and phosphatidylinositol, respectively. With both glycerol and phosphate, phosphatidylethanolamine was a major labeled lipid in both axoplasm and sheath. These findings demonstrate that all classes of phospholipids are formed by endogenous synthetic enzymes in axoplasm. In addition, we feel that the different patterns of incorporation by intact axons and extruded axoplasm indicate that surrounding sheath cells contribute lipids to axoplasm. A comprehensive picture of axonal lipid metabolism should include axoplasmic synthesis and glial-axon transfer as pathways complementing the axonal transport of perikaryally formed lipids.

  9. Perilesional edema in radiation necrosis reflects axonal degeneration

    International Nuclear Information System (INIS)

    Perez-Torres, Carlos J; Yuan, Liya; Schmidt, Robert E; Rich, Keith M; Ackerman, Joseph JH; Garbow, Joel R

    2015-01-01

    Recently, we characterized a Gamma Knife® radiation necrosis mouse model with various magnetic resonance imaging (MRI) protocols to identify biomarkers useful in differentiation from tumors. Though the irradiation was focal to one hemisphere, a contralateral injury was observed that appeared to be localized in the white matter only. Interestingly, this injury was identifiable in T2-weighted images, apparent diffusion coefficient (ADC), and magnetization transfer ratio (MTR) maps, but not on post-contrast T1-weighted images. This observation of edema independent of vascular changes is akin to the perilesional edema seen in clinical radiation necrosis. The pathology underlying the observed white-matter MRI changes was explored by performing immunohistochemistry for healthy axons and myelin. The presence of both healthy axons and myelin was reduced in the contralateral white-matter lesion. Based on our immunohistochemical findings, the contralateral white-matter injury is most likely due to axonal degeneration

  10. Dynamic Changes of Neuroskeletal Proteins in DRGs Underlie Impaired Axonal Maturation and Progressive Axonal Degeneration in Type 1 Diabetes

    Directory of Open Access Journals (Sweden)

    Hideki Kamiya

    2009-01-01

    Full Text Available We investigated mechanisms underlying progressive axonal dysfunction and structural deficits in type 1 BB/Wor-rats from 1 week to 10 month diabetes duration. Motor and sensory conduction velocities were decreased after 4 and 6 weeks of diabetes and declined further over the remaining 9 months. Myelinated sural nerve fibers showed progressive deficits in fiber numbers and sizes. Structural deficits in unmyelinated axonal size were evident at 2 month and deficits in number were present at 4 mo. These changes were preceded by decreased availability of insulin, C-peptide and IGF-1 and decreased expression of neurofilaments and β-III-tubulin. Upregulation of phosphorylating stress kinases like Cdk5, p-GSK-3β, and p42/44 resulted in increased phosphorylation of neurofilaments. Increasing activity of p-GSK-3β correlated with increasing phosphorylation of NFH, whereas decreasing Cdk5 correlated with diminishing phosphorylation of NFM. The data suggest that impaired neurotrophic support results in sequentially impaired synthesis and postranslational modifications of neuroskeletal proteins, resulting in progressive deficits in axonal function, maturation and size.

  11. Chronic severe axonal polyneuropathy associated with hyperthyroidism and multivitamin deficiency.

    Science.gov (United States)

    Sugie, Kazuma; Umehara, Fujio; Kataoka, Hiroshi; Kumazawa, Aya; Ueno, Satoshi

    2012-01-01

    Hyperthyroidism is often associated with various neuromuscular disorders, most commonly proximal myopathy. Peripheral nerve involvement in hyperthyroidism is very uncommon and has rarely been reported. We describe a 29-year-old woman with untreated hyperthyroidism who presented with chronic severe axonal sensory-motor polyneuropathy. Peripheral nerve involvement developed together with other symptoms of hyperthyroidism 2 years before presentation. She also had anorexia nervosa for the past 6 months, resulting in multivitamin deficiency. Electrophysiological and pathological findings as well as clinical manifestations confirmed the diagnosis of severe axonal polyneuropathy. Anorexia nervosa has been considered a manifestation of untreated hyperthyroidism. We considered hyperthyroidism to be an important causal factor in the polyneuropathy in our patient, although peripheral nerve involvement in hyperthyroidism is rare. To our knowledge, this is the first documented case of chronic severe axonal polyneuropathy ascribed to both hyperthyroidism and multivitamin deficiency. Our findings strongly suggest that not only multivitamin deficiency, but also hyperthyroidism can cause axonal polyneuropathy, thus expanding the clinical spectrum of hyperthyroidism.

  12. The MADD-3 LAMMER Kinase Interacts with a p38 MAP Kinase Pathway to Regulate the Display of the EVA-1 Guidance Receptor in Caenorhabditis elegans.

    Directory of Open Access Journals (Sweden)

    Serena A D'Souza

    2016-04-01

    Full Text Available The proper display of transmembrane receptors on the leading edge of migrating cells and cell extensions is essential for their response to guidance cues. We previously discovered that MADD-4, which is an ADAMTSL secreted by motor neurons in Caenorhabditis elegans, interacts with an UNC-40/EVA-1 co-receptor complex on muscles to attract plasma membrane extensions called muscle arms. In nematodes, the muscle arm termini harbor the post-synaptic elements of the neuromuscular junction. Through a forward genetic screen for mutants with disrupted muscle arm extension, we discovered that a LAMMER kinase, which we call MADD-3, is required for the proper display of the EVA-1 receptor on the muscle's plasma membrane. Without MADD-3, EVA-1 levels decrease concomitantly with a reduction of the late-endosomal marker RAB-7. Through a genetic suppressor screen, we found that the levels of EVA-1 and RAB-7 can be restored in madd-3 mutants by eliminating the function of a p38 MAP kinase pathway. We also found that EVA-1 and RAB-7 will accumulate in madd-3 mutants upon disrupting CUP-5, which is a mucolipin ortholog required for proper lysosome function. Together, our data suggests that the MADD-3 LAMMER kinase antagonizes the p38-mediated endosomal trafficking of EVA-1 to the lysosome. In this way, MADD-3 ensures that sufficient levels of EVA-1 are present to guide muscle arm extension towards the source of the MADD-4 guidance cue.

  13. Uncovering sensory axonal dysfunction in asymptomatic type 2 diabetic neuropathy.

    Directory of Open Access Journals (Sweden)

    Jia-Ying Sung

    Full Text Available This study investigated sensory and motor nerve excitability properties to elucidate the development of diabetic neuropathy. A total of 109 type 2 diabetes patients were recruited, and 106 were analyzed. According to neuropathy severity, patients were categorized into G0, G1, and G2+3 groups using the total neuropathy score-reduced (TNSr. Patients in the G0 group were asymptomatic and had a TNSr score of 0. Sensory and motor nerve excitability data from diabetic patients were compared with data from 33 healthy controls. Clinical assessment, nerve conduction studies, and sensory and motor nerve excitability testing data were analyzed to determine axonal dysfunction in diabetic neuropathy. In the G0 group, sensory excitability testing revealed increased stimulus for the 50% sensory nerve action potential (P<0.05, shortened strength-duration time constant (P<0.01, increased superexcitability (P<0.01, decreased subexcitability (P<0.05, decreased accommodation to depolarizing current (P<0.01, and a trend of decreased accommodation to hyperpolarizing current in threshold electrotonus. All the changes progressed into G1 (TNSr 1-8 and G2+3 (TNSr 9-24 groups. In contrast, motor excitability only had significantly increased stimulus for the 50% compound motor nerve action potential (P<0.01 in the G0 group. This study revealed that the development of axonal dysfunction in sensory axons occurred prior to and in a different fashion from motor axons. Additionally, sensory nerve excitability tests can detect axonal dysfunction even in asymptomatic patients. These insights further our understanding of diabetic neuropathy and enable the early detection of sensory axonal abnormalities, which may provide a basis for neuroprotective therapeutic approaches.

  14. NMNAT1 inhibits axon degeneration via blockade of SARM1-mediated NAD+ depletion

    Science.gov (United States)

    Sasaki, Yo; Nakagawa, Takashi; Mao, Xianrong; DiAntonio, Aaron; Milbrandt, Jeffrey

    2016-01-01

    Overexpression of the NAD+ biosynthetic enzyme NMNAT1 leads to preservation of injured axons. While increased NAD+ or decreased NMN levels are thought to be critical to this process, the mechanism(s) of this axon protection remain obscure. Using steady-state and flux analysis of NAD+ metabolites in healthy and injured mouse dorsal root ganglion axons, we find that rather than altering NAD+ synthesis, NMNAT1 instead blocks the injury-induced, SARM1-dependent NAD+ consumption that is central to axon degeneration. DOI: http://dx.doi.org/10.7554/eLife.19749.001 PMID:27735788

  15. Reversible Axonal Dystrophy by Calcium Modulation in Frataxin-Deficient Sensory Neurons of YG8R Mice

    Directory of Open Access Journals (Sweden)

    Belén Mollá

    2017-08-01

    Full Text Available Friedreich’s ataxia (FRDA is a peripheral neuropathy involving a loss of proprioceptive sensory neurons. Studies of biopsies from patients suggest that axonal dysfunction precedes the death of proprioceptive neurons in a dying-back process. We observed that the deficiency of frataxin in sensory neurons of dorsal root ganglia (DRG of the YG8R mouse model causes the formation of axonal spheroids which retain dysfunctional mitochondria, shows alterations in the cytoskeleton and it produces impairment of axonal transport and autophagic flux. The homogenous distribution of axonal spheroids along the neurites supports the existence of continues focal damages. This lead us to propose for FRDA a model of distal axonopathy based on axonal focal damages. In addition, we observed the involvement of oxidative stress and dyshomeostasis of calcium in axonal spheroid formation generating axonal injury as a primary cause of pathophysiology. Axonal spheroids may be a consequence of calcium imbalance, thus we propose the quenching or removal extracellular Ca2+ to prevent spheroids formation. In our neuronal model, treatments with BAPTA and o-phenanthroline reverted the axonal dystrophy and the mitochondrial dysmorphic parameters. These results support the hypothesis that axonal pathology is reversible in FRDA by pharmacological manipulation of intracellular Ca2+ with Ca2+ chelators or metalloprotease inhibitors, preventing Ca2+-mediated axonal injury. Thus, the modulation of Ca2+ levels may be a relevant therapeutic target to develop early axonal protection and prevent dying-back neurodegeneration.

  16. Role of calpains in the injury-induced dysfunction and degeneration of the mammalian axon.

    Science.gov (United States)

    Ma, Marek

    2013-12-01

    Axonal injury and degeneration, whether primary or secondary, contribute to the morbidity and mortality seen in many acquired and inherited central nervous system (CNS) and peripheral nervous system (PNS) disorders, such as traumatic brain injury, spinal cord injury, cerebral ischemia, neurodegenerative diseases, and peripheral neuropathies. The calpain family of proteases has been mechanistically linked to the dysfunction and degeneration of axons. While the direct mechanisms by which transection, mechanical strain, ischemia, or complement activation trigger intra-axonal calpain activity are likely different, the downstream effects of unregulated calpain activity may be similar in seemingly disparate diseases. In this review, a brief examination of axonal structure is followed by a focused overview of the calpain family. Finally, the mechanisms by which calpains may disrupt the axonal cytoskeleton, transport, and specialized domains (axon initial segment, nodes, and terminals) are discussed. © 2013.

  17. Hydrogels as scaffolds and delivery systems to enhance axonal regeneration after injuries

    Directory of Open Access Journals (Sweden)

    Oscar A. Carballo-Molina

    2015-02-01

    Full Text Available Damage caused to neural tissue by disease or injury frequently produces a discontinuity in the nervous system. Such damage generates diverse alterations that are commonly permanent, due to the limited regeneration capacity of the adult nervous system, particularly the Central Nervous System (CNS. The cellular reaction to noxious stimulus leads to several events such as the formation of glial and fibrous scars, which inhibit axonal regeneration in both the CNS and the Peripheral Nervous System (PNS. Although in the PNS there is some degree of nerve regeneration, it is common that the growing axons reinnervate incorrect areas, causing mismatches. Providing a permissive substrate for axonal regeneration in combination with delivery systems for the release of molecules, which enhances axonal growth, could increase regeneration and the recovery of functions in the CNS or the PNS. Currently, there are no effective vehicles to supply growth factors or cells to the damaged/diseased nervous system. Hydrogels are polymers that are biodegradable, biocompatible and have the capacity to deliver a large range of molecules in situ. The inclusion of cultured neural cells into hydrogels forming three-dimensional structures allows the formation of synapses and neuronal survival. There is also evidence showing that hydrogels constitute an amenable substrate for axonal growth of endogenous or grafted cells, overcoming the presence of axonal regeneration inhibitory molecules, in both the central and peripheral nervous systems. Recent experiments suggest that hydrogels can carry and deliver several proteins relevant for improving neuronal survival and axonal growth. Although the use of hydrogels is appealing, its effectiveness is still a matter of discussion, and more results are needed to achieve consistent recovery using different parameters. This review also discusses areas of opportunity where hydrogels can be applied, in order to promote axonal regeneration of

  18. Mice with GFAP-targeted loss of neurofibromin demonstrate increased axonal MET expression with aging.

    Science.gov (United States)

    Su, Weiping; Xing, Rubing; Guha, Abhijit; Gutmann, David H; Sherman, Larry S

    2007-05-01

    Neurofibromatosis 1 (NF1) is a common genetic disease that predisposes patients to peripheral nerve tumors and central nervous system (CNS) abnormalities including low-grade astrocytomas and cognitive disabilities. Using mice with glial fibrillary acidic protein (GFAP)-targeted Nf1 loss (Nf1(GFAP)CKO mice), we found that Nf1(-/-) astrocytes proliferate faster and are more invasive than wild-type astrocytes. In light of our previous finding that aberrant expression of the MET receptor tyrosine kinase contributes to the invasiveness of human NF1-associated malignant peripheral nerve sheath tumors, we sought to determine whether MET expression is aberrant in the brains of Nf1 mutant mice. We found that Nf1(-/-) astrocytes express slightly more MET than wild-type cells in vitro, but do not express elevated MET in situ. However, fiber tracts containing myelinated axons in the hippocampus, midbrain, cerebral cortex, and cerebellum express higher than normal levels of MET in older (> or =6 months) Nf1(GFAP)CKO mice. Both Nf1(GFAP)CKO and wild-type astrocytes induced MET expression in neurites of wild-type hippocampal neurons in vitro, suggesting that astrocyte-derived signals may induce MET in Nf1 mutant mice. Because the Nf1 gene product functions as a RAS GTPase, we examined MET expression in the brains of mice with GFAP-targeted constitutively active forms of RAS. MET was elevated in axonal fiber tracts in mice with active K-RAS but not H-RAS. Collectively, these data suggest that loss of Nf1 in either astrocytes or GFAP(+) neural progenitor cells results in increased axonal MET expression, which may contribute to the CNS abnormalities in children and adults with NF1. (c) 2007 Wiley-Liss, Inc.

  19. Nuclear-Encoded Mitochondrial mRNAs: A Powerful Force in Axonal Growth and Development.

    Science.gov (United States)

    Gale, Jenna R; Aschrafi, Armaz; Gioio, Anthony E; Kaplan, Barry B

    2018-04-01

    Axons, their growth cones, and synaptic nerve terminals are neuronal subcompartments that have high energetic needs. As such, they are enriched in mitochondria, which supply the ATP necessary to meet these demands. To date, a heterogeneous population of nuclear-encoded mitochondrial mRNAs has been identified in distal axons and growth cones. Accumulating evidence suggests that the local translation of these mRNAs is required for mitochondrial maintenance and axonal viability. Here, we review evidence that suggests a critical role for axonal translation of nuclear-encoded mitochondrial mRNAs in axonal growth and development. Additionally, we explore the role that site-specific translation at the mitochondria itself may play in this process. Finally, we briefly review the clinical implications of dysregulation of local translation of mitochondrial-related mRNAs in neurodevelopmental disorders.

  20. Growing axons analysis by using Granulometric Size Distribution

    International Nuclear Information System (INIS)

    Gonzalez, Mariela A; Ballarin, Virginia L; Rapacioli, Melina; CelIn, A R; Sanchez, V; Flores, V

    2011-01-01

    Neurite growth (neuritogenesis) in vitro is a common methodology in the field of developmental neurobiology. Morphological analyses of growing neurites are usually difficult because their thinness and low contrast usually prevent to observe clearly their shape, number, length and spatial orientation. This paper presents the use of the granulometric size distribution in order to automatically obtain information about the shape, size and spatial orientation of growing axons in tissue cultures. The results here presented show that the granulometric size distribution results in a very useful morphological tool since it allows the automatic detection of growing axons and the precise characterization of a relevant parameter indicative of the axonal growth spatial orientation such as the quantification of the angle of deviation of the growing direction. The developed algorithms automatically quantify this orientation by facilitating the analysis of these images, which is important given the large number of images that need to be processed for this type of study.

  1. Axonal plasticity elicits long-term changes in oligodendroglia and myelinated fibers

    DEFF Research Database (Denmark)

    Drøjdahl, Nina; Nielsen, Helle Hvilsted; Gardi, Jonathan E

    2010-01-01

    Axons are linked to induction of myelination during development and to the maintenance of myelin and myelinated tracts in the adult CNS. Currently, it is unknown whether and how axonal plasticity in adult CNS impacts the myelinating cells and their precursors. In this article, we report that newly...... formed axonal sprouts are able to induce a protracted myelination response in adult CNS. We show that newly formed axonal sprouts, induced by lesion of the entorhino-hippocampal perforant pathway, have the ability to induce a myelination response in stratum radiatum and lucidum CA3. The lesion resulted...... in significant recruitment of newly formed myelinating cells, documented by incorporation of the proliferation marker bromodeoxyuridine into chondroitin sulphate NG2 expressing cells in stratum radiatum and lucidum CA3 early after lesion, and the occurrence of a 28% increase in the number of oligodendrocytes...

  2. Axonal excitability properties in amyotrophic lateral sclerosis.

    Science.gov (United States)

    Vucic, Steve; Kiernan, Matthew C

    2006-07-01

    To investigate axolemmal ion channel function in patients diagnosed with sporadic amyotrophic lateral sclerosis (ALS). A recently described threshold tracking protocol was implemented to measure multiple indices of axonal excitability in 26 ALS patients by stimulating the median motor nerve at the wrist. The excitability indices studied included: stimulus-response curve (SR); strength-duration time constant (tauSD); current/threshold relationship; threshold electrotonus to a 100 ms polarizing current; and recovery curves to a supramaximal stimulus. Compound muscle action potential (CMAP) amplitudes were significantly reduced in ALS patients (ALS, 2.84+/-1.17 mV; controls, 8.27+/-1.09 mV, P<0.0005) and the SR curves for both 0.2 and 1 ms pulse widths were shifted in a hyperpolarized direction. Threshold electrotonus revealed a greater threshold change to both depolarizing and hyperpolarizing conditioning stimuli, similar to the 'fanned out' appearance that occurs with membrane hyperpolarization. The tauSD was significantly increased in ALS patients (ALS, 0.50+/-0.03 ms; controls, 0.42+/-0.02 ms, P<0.05). The recovery cycle of excitability following a conditioning supramaximal stimulus revealed increased superexcitability in ALS patients (ALS, 29.63+/-1.25%; controls, 25.11+/-1.01%, P<0.01). Threshold tracking studies revealed changes indicative of widespread dysfunction in axonal ion channel conduction, including increased persistent Na+ channel conduction, and abnormalities of fast paranodal K+ and internodal slow K+ channel function, in ALS patients. An increase in persistent Na+ conductances coupled with reduction in K+ currents would predispose axons of ALS patients to generation of fasciculations and cramps. Axonal excitability studies may provide insight into mechanisms responsible for motor neuron loss in ALS.

  3. Mapping axonal density and average diameter using non-monotonic time-dependent gradient-echo MRI

    DEFF Research Database (Denmark)

    Nunes, Daniel; Cruz, Tomás L; Jespersen, Sune N

    2017-01-01

    available in the clinic, or extremely long acquisition schemes to extract information from parameter-intensive models. In this study, we suggest that simple and time-efficient multi-gradient-echo (MGE) MRI can be used to extract the axon density from susceptibility-driven non-monotonic decay in the time...... the quantitative results are compared against ground-truth histology, they seem to reflect the axonal fraction (though with a bias, as evident from Bland-Altman analysis). As well, the extra-axonal fraction can be estimated. The results suggest that our model is oversimplified, yet at the same time evidencing......-dependent signal. We show, both theoretically and with simulations, that a non-monotonic signal decay will occur for multi-compartmental microstructures – such as axons and extra-axonal spaces, which we here used in a simple model for the microstructure – and that, for axons parallel to the main magnetic field...

  4. Detection of axonal synapses in 3D two-photon images.

    Directory of Open Access Journals (Sweden)

    Cher Bass

    Full Text Available Studies of structural plasticity in the brain often require the detection and analysis of axonal synapses (boutons. To date, bouton detection has been largely manual or semi-automated, relying on a step that traces the axons before detection the boutons. If tracing the axon fails, the accuracy of bouton detection is compromised. In this paper, we propose a new algorithm that does not require tracing the axon to detect axonal boutons in 3D two-photon images taken from the mouse cortex. To find the most appropriate techniques for this task, we compared several well-known algorithms for interest point detection and feature descriptor generation. The final algorithm proposed has the following main steps: (1 a Laplacian of Gaussian (LoG based feature enhancement module to accentuate the appearance of boutons; (2 a Speeded Up Robust Features (SURF interest point detector to find candidate locations for feature extraction; (3 non-maximum suppression to eliminate candidates that were detected more than once in the same local region; (4 generation of feature descriptors based on Gabor filters; (5 a Support Vector Machine (SVM classifier, trained on features from labelled data, and was used to distinguish between bouton and non-bouton candidates. We found that our method achieved a Recall of 95%, Precision of 76%, and F1 score of 84% within a new dataset that we make available for accessing bouton detection. On average, Recall and F1 score were significantly better than the current state-of-the-art method, while Precision was not significantly different. In conclusion, in this article we demonstrate that our approach, which is independent of axon tracing, can detect boutons to a high level of accuracy, and improves on the detection performance of existing approaches. The data and code (with an easy to use GUI used in this article are available from open source repositories.

  5. Computed tomography in diagnosis of diffuse axonal injury

    International Nuclear Information System (INIS)

    Iwadate, Yasuo; Ono, Juniti; Okimura, Yoshitaka; Suda, Sumio; Isobe, Katsumi; Yamaura, Akira.

    1990-01-01

    Diffuse axonal injury (DAI) has been described in instances of prolonged traumatic coma on the basis of the neuropathological findings, but the same findings are also found in patients with cerebral concussion. Experimental studies confirm that the quality of survivors following trauma is directly proportional to the amount of primarily injured-axon. When the injured axon lies in a widespread area of the brain, outcome for the patient is always poor. In a series of 260 severely head-injured patients, based on their poor outcome, 69 (27%) were diagnosed as DAI. Because of their relatively good outcome, eighty-two patients (32%) were classified into non-DAI group. The predominant CT finding of DAI patients was intraparenchymal deep-seated hemorrhagic lesion. This was observed in 28 patients (41%). Normal CT was also observed in 11 patients (16%). On the other hand, 8 of the non-DAI group (10%) manifested deep-seated lesions. Diffuse cerebral swelling (DCS) appeared in both groups in the same incidence. Subarachnoid hematoma in the perimesencephalic cistern (SAH (PMC)) and intraventricular hematoma (IVH) were observed in 64% of the DAI group, and in 23% of the non-DAI group. The available evidence indicates that various types of hematoma seen in the deep-seated structures of the brain do not have an absolute diagnostic value, but the frequency of hematoma is thought to increase in proportion to the amount of injured-axon. (author)

  6. A Combinatorial Approach to Induce Sensory Axon Regeneration into the Dorsal Root Avulsed Spinal Cord

    DEFF Research Database (Denmark)

    Hoeber, Jan; Konig, Niclas; Trolle, Carl

    2017-01-01

    Spinal root injuries result in newly formed glial scar formation, which prevents regeneration of sensory axons causing permanent sensory loss. Previous studies showed that delivery of trophic factors or implantation of human neural progenitor cells supports sensory axon regeneration and partly......MIM), supported sensory axon regeneration. However, when hscNSPC and MesoMIM were combined, sensory axon regeneration failed. Morphological and tracing analysis showed that sensory axons grow through the newly established glial scar along “bridges” formed by migrating stem cells. Coimplantation of Meso...... their level of differentiation. Our data show that (1) the ability of stem cells to migrate into the spinal cord and organize cellular “bridges” in the newly formed interface is crucial for successful sensory axon regeneration, (2) trophic factor mimetics delivered by mesoporous silica may be a convenient...

  7. Partial Denervation of Subbasal Axons Persists Following Debridement Wounds to the Mouse Cornea

    Science.gov (United States)

    Pajoohesh-Ganji, Ahdeah; Pal-Ghosh, Sonali; Tadvalkar, Gauri; Kyne, Briana M.; Saban, Daniel R.; Stepp, Mary Ann

    2015-01-01

    Although sensory reinnervation occurs after injury in the PNS, poor reinnervation in the elderly and those with diabetes often leads to pathology. Here we quantify subbasal axon density in the central and peripheral mouse cornea over time after three different types of injury. The mouse cornea is highly innervated with a dense array of subbasal nerves that form a spiral called the vortex at the corneal center or apex; these nerves are readily detected within flat mounted corneas. After anesthesia, corneal epithelial cells were removed using either a dulled blade or a rotating burr within an area demarcated centrally with a 1.5 mm trephine. A third wound type, superficial trephination, involved demarcating the area with the 1.5 mm trephine but not removing cells. By 7d after superficial trephination, subbasal axon density returns to control levels; by 28d the vortex reforms. Although axon density is similar to control 14d after dulled blade and rotating burr wounding, defects in axon morphology at the corneal apex remain. After 14d, axons retract from the center leaving the subbasal axon density reduced by 37.2% and 36.8% at 28d after dulled blade and rotating burr wounding, respectively, compared to control. Assessment of inflammation using flow cytometry shows that persistent inflammation is not a factor in the incomplete reinnervation. Expression of mRNAs encoding 22 regeneration associated genes (RAGs) involved in axon targeting assessed by QPCR reveals that netrin-1 and ephrin signaling are altered after wounding. Subpopulations of corneal epithelial basal cells at the corneal apex stop expressing ki67 as early as 7d after injury and by 14d and 28d after wounding, many of these basal cells undergo apoptosis and die. While subbasal axons are restored to their normal density and morphology after superficial trephination, subbasal axon recovery is partial after debridement wounds. The increase in corneal epithelial basal cell apoptosis at the apex observed at 14d

  8. Self-amplifying autocrine actions of BDNF in axon development

    OpenAIRE

    Cheng, Pei-Lin; Song, Ai-Hong; Wong, Yu-Hui; Wang, Sheng; Zhang, Xiang; Poo, Mu-Ming

    2011-01-01

    A critical step in neuronal development is the formation of axon/dendrite polarity, a process involving symmetry breaking in the newborn neuron. Local self-amplifying processes could enhance and stabilize the initial asymmetry in the distribution of axon/dendrite determinants, but the identity of these processes remains elusive. We here report that BDNF, a secreted neurotrophin essential for the survival and differentiation of many neuronal populations, serves as a self-amplifying autocrine f...

  9. Slit-Robo signalling in heart development

    OpenAIRE

    Zhao, J; Mommersteeg, MTM

    2018-01-01

    The Slit ligands and their Robo receptors are well-known for their roles during axon guidance in the central nervous system, but are still relatively unknown in the cardiac field. However, data from different animal models suggest a broad involvement of the pathway in many aspects of heart development, from cardiac cell migration and alignment, lumen formation, chamber formation, to the formation of the ventricular septum, semilunar and atrioventricular valves, caval veins and pericardium. Ab...

  10. Outer Electrospun Polycaprolactone Shell Induces Massive Foreign Body Reaction and Impairs Axonal Regeneration through 3D Multichannel Chitosan Nerve Guides

    Directory of Open Access Journals (Sweden)

    Sven Duda

    2014-01-01

    Full Text Available We report on the performance of composite nerve grafts with an inner 3D multichannel porous chitosan core and an outer electrospun polycaprolactone shell. The inner chitosan core provided multiple guidance channels for regrowing axons. To analyze the in vivo properties of the bare chitosan cores, we separately implanted them into an epineural sheath. The effects of both graft types on structural and functional regeneration across a 10 mm rat sciatic nerve gap were compared to autologous nerve transplantation (ANT. The mechanical biomaterial properties and the immunological impact of the grafts were assessed with histological techniques before and after transplantation in vivo. Furthermore during a 13-week examination period functional tests and electrophysiological recordings were performed and supplemented by nerve morphometry. The sheathing of the chitosan core with a polycaprolactone shell induced massive foreign body reaction and impairment of nerve regeneration. Although the isolated novel chitosan core did allow regeneration of axons in a similar size distribution as the ANT, the ANT was superior in terms of functional regeneration. We conclude that an outer polycaprolactone shell should not be used for the purpose of bioartificial nerve grafting, while 3D multichannel porous chitosan cores could be candidate scaffolds for structured nerve grafts.

  11. Outer electrospun polycaprolactone shell induces massive foreign body reaction and impairs axonal regeneration through 3D multichannel chitosan nerve guides.

    Science.gov (United States)

    Duda, Sven; Dreyer, Lutz; Behrens, Peter; Wienecke, Soenke; Chakradeo, Tanmay; Glasmacher, Birgit; Haastert-Talini, Kirsten

    2014-01-01

    We report on the performance of composite nerve grafts with an inner 3D multichannel porous chitosan core and an outer electrospun polycaprolactone shell. The inner chitosan core provided multiple guidance channels for regrowing axons. To analyze the in vivo properties of the bare chitosan cores, we separately implanted them into an epineural sheath. The effects of both graft types on structural and functional regeneration across a 10 mm rat sciatic nerve gap were compared to autologous nerve transplantation (ANT). The mechanical biomaterial properties and the immunological impact of the grafts were assessed with histological techniques before and after transplantation in vivo. Furthermore during a 13-week examination period functional tests and electrophysiological recordings were performed and supplemented by nerve morphometry. The sheathing of the chitosan core with a polycaprolactone shell induced massive foreign body reaction and impairment of nerve regeneration. Although the isolated novel chitosan core did allow regeneration of axons in a similar size distribution as the ANT, the ANT was superior in terms of functional regeneration. We conclude that an outer polycaprolactone shell should not be used for the purpose of bioartificial nerve grafting, while 3D multichannel porous chitosan cores could be candidate scaffolds for structured nerve grafts.

  12. BORC/kinesin-1 ensemble drives polarized transport of lysosomes into the axon.

    Science.gov (United States)

    Farías, Ginny G; Guardia, Carlos M; De Pace, Raffaella; Britt, Dylan J; Bonifacino, Juan S

    2017-04-04

    The ability of lysosomes to move within the cytoplasm is important for many cellular functions. This ability is particularly critical in neurons, which comprise vast, highly differentiated domains such as the axon and dendrites. The mechanisms that control lysosome movement in these domains, however, remain poorly understood. Here we show that an ensemble of BORC, Arl8, SKIP, and kinesin-1, previously shown to mediate centrifugal transport of lysosomes in nonneuronal cells, specifically drives lysosome transport into the axon, and not the dendrites, in cultured rat hippocampal neurons. This transport is essential for maintenance of axonal growth-cone dynamics and autophagosome turnover. Our findings illustrate how a general mechanism for lysosome dispersal in nonneuronal cells is adapted to drive polarized transport in neurons, and emphasize the importance of this mechanism for critical axonal processes.

  13. Live Imaging of Calcium Dynamics during Axon Degeneration Reveals Two Functionally Distinct Phases of Calcium Influx

    Science.gov (United States)

    Yamagishi, Yuya; Tessier-Lavigne, Marc

    2015-01-01

    Calcium is a key regulator of axon degeneration caused by trauma and disease, but its specific spatial and temporal dynamics in injured axons remain unclear. To clarify the function of calcium in axon degeneration, we observed calcium dynamics in single injured neurons in live zebrafish larvae and tested the temporal requirement for calcium in zebrafish neurons and cultured mouse DRG neurons. Using laser axotomy to induce Wallerian degeneration (WD) in zebrafish peripheral sensory axons, we monitored calcium dynamics from injury to fragmentation, revealing two stereotyped phases of axonal calcium influx. First, axotomy triggered a transient local calcium wave originating at the injury site. This initial calcium wave only disrupted mitochondria near the injury site and was not altered by expression of the protective WD slow (WldS) protein. Inducing multiple waves with additional axotomies did not change the kinetics of degeneration. In contrast, a second phase of calcium influx occurring minutes before fragmentation spread as a wave throughout the axon, entered mitochondria, and was abolished by WldS expression. In live zebrafish, chelating calcium after the first wave, but before the second wave, delayed the progress of fragmentation. In cultured DRG neurons, chelating calcium early in the process of WD did not alter degeneration, but chelating calcium late in WD delayed fragmentation. We propose that a terminal calcium wave is a key instructive component of the axon degeneration program. SIGNIFICANCE STATEMENT Axon degeneration resulting from trauma or neurodegenerative disease can cause devastating deficits in neural function. Understanding the molecular and cellular events that execute axon degeneration is essential for developing treatments to address these conditions. Calcium is known to contribute to axon degeneration, but its temporal requirements in this process have been unclear. Live calcium imaging in severed zebrafish neurons and temporally controlled

  14. Environmental Subconcussive Injury, Axonal Injury, and Chronic Traumatic Encephalopathy

    Directory of Open Access Journals (Sweden)

    Wendy A. Morley

    2018-03-01

    Full Text Available Brain injury occurs in two phases: the initial injury itself and a secondary cascade of precise immune-based neurochemical events. The secondary phase is typically functional in nature and characterized by delayed axonal injury with more axonal disconnections occurring than in the initial phase. Axonal injury occurs across the spectrum of disease severity, with subconcussive injury, especially when repetitive, now considered capable of producing significant neurological damage consistent with axonal injury seen in clinically evident concussion, despite no observable symptoms. This review is the first to introduce the concept of environmental subconcussive injury (ESCI and sets out how secondary brain damage from ESCI once past the juncture of microglial activation appears to follow the same neuron-damaging pathway as secondary brain damage from conventional brain injury. The immune response associated with ESCI is strikingly similar to that mounted after conventional concussion. Specifically, microglial activation is followed closely by glutamate and calcium flux, excitotoxicity, reactive oxygen species and reactive nitrogen species (RNS generation, lipid peroxidation, and mitochondrial dysfunction and energy crisis. ESCI damage also occurs in two phases, with the primary damage coming from microbiome injury (due to microbiome-altering events and secondary damage (axonal injury from progressive secondary neurochemical events. The concept of ESCI and the underlying mechanisms have profound implications for the understanding of chronic traumatic encephalopathy (CTE etiology because it has previously been suggested that repetitive axonal injury may be the primary CTE pathogenesis in susceptible individuals and it is best correlated with lifetime brain trauma load. Taken together, it appears that susceptibility to brain injury and downstream neurodegenerative diseases, such as CTE, can be conceptualized as a continuum of brain resilience. At one end

  15. The toll-like receptor 2 agonist Pam3CSK4 is neuroprotective after spinal cord injury.

    Science.gov (United States)

    Stivers, Nicole S; Pelisch, Nicolas; Orem, Ben C; Williams, Joshua; Nally, Jacqueline M; Stirling, David P

    2017-08-01

    Microglia/macrophage activation and recruitment following spinal cord injury (SCI) is associated with both detrimental and reparative functions. Stimulation of the innate immune receptor Toll-like receptor-2 (TLR2) has shown to be beneficial following SCI, and it increases axonal regeneration following optic nerve crush. However, the mechanism(s) remain unclear. As microglia express high levels of TLR2, we hypothesized that modulating the microglial response to injury using a specific TLR2 agonist, Pam3CSK4, would prevent secondary-mediated white matter degeneration following SCI. To test this hypothesis, we documented acute changes in microglia, axons, and oligodendroglia over time using two-photon excitation and an ex vivo laser-induced SCI (LiSCI) model. We utilized double transgenic mice that express GFP in either microglia or oligodendroglia, and YFP in axons, and we applied the lipophilic fluorescent dye (Nile Red) to visualize myelin. We found that treatment with Pam3CSK4 initiated one hour after injury induced a significant increase in the extent and timing of the microglial response to injury compared to vehicle controls. This enhanced response was observed 2 to 4h following SCI and was most prominent in areas closer to the ablation site. In addition, Pam3CSK4 treatment significantly reduced axonal dieback rostral and caudal to the ablation at 6h post-SCI. This protective effect of Pam3CSK4 was also mirrored when assessing secondary bystander axonal damage (i.e., axons spared by the primary injury that then succumb to secondary degeneration), and when assessing the survival of oligodendroglia. Following these imaging experiments, custom microarray analysis of the ex vivo spinal cord preparations revealed that Pam3CSK4-treatment induced an alternative (mixed M1:M2) microglial activation profile. In summary, our data suggest that by providing a second "sterile" activation signal to microglia through TLR2/TLR1 signaling, the microglial response to injury can

  16. Multiple sclerosis and anterograde axonal degeneration study by magnetic resonance

    International Nuclear Information System (INIS)

    Martinez Pardo, P.; Capdevila Cirera, A.; Sanz Marin, P.M.; Gili Planas, J.

    1993-01-01

    Multiple sclerosis (MS) is a disease of the central nervous system that affects specifically the myelin. Its diagnosis by imaging techniques is, since the development of magnetic resonance (MR), relatively simple, and its occasional association with anterograde axonal degeneration (WD) has been reported. In both disorders, there is a lengthening of the T1 and T2 relaxation times. In the present report, 76 patients with MS with less than 4 plaques in the typical periventricular position were studied retrospectively, resulting in a rate of association with anterograde axonal degeneration of 8%. We consider that in spite of their same behavior in MR,MS and WD, with moreover represent completely different pathologies, are perfectly differential by MR. The S-E images with longer repetition and echo times in the axial and coronal planes have proved to be those most sensitive for this differentiation. Given that MS is specific pathology of then myelin, the axonal damages in delayed until several plaques adjacent to an axon affect it. We consider that this, added to the restriction of our study group (less than 4 plaques), is the cause of the pow percentage of the MS-WD association in our study. (Author)

  17. Noninvasive Detection and Differentiation of Axonal Injury/Loss, Demyelination, and Inflammation

    Science.gov (United States)

    2014-10-01

    phosphorylated neurofilament primary antibody (SMI-31; 1:1000, Covance , US) to stain non-injured axons, and in rabbit anti-myelin basic protein (MBP) primary...neurofilament antibody (SMI- 31; 1:1000, Covance , US) to stain non-injured axons or with rabbit anti-myelin basic protein (MBP) antibody (1:1000, Sigma Inc

  18. Assessing the direct effects of deep brain stimulation using embedded axon models

    Science.gov (United States)

    Sotiropoulos, Stamatios N.; Steinmetz, Peter N.

    2007-06-01

    To better understand the spatial extent of the direct effects of deep brain stimulation (DBS) on neurons, we implemented a geometrically realistic finite element electrical model incorporating anisotropic and inhomogenous conductivities. The model included the subthalamic nucleus (STN), substantia nigra (SN), zona incerta (ZI), fields of Forel H2 (FF), internal capsule (IC) and Medtronic 3387/3389 electrode. To quantify the effects of stimulation, we extended previous studies by using multi-compartment axon models with geometry and orientation consistent with anatomical features of the brain regions of interest. Simulation of axonal firing produced a map of relative changes in axonal activation. Voltage-controlled stimulation, with clinically typical parameters at the dorso-lateral STN, caused axon activation up to 4 mm from the target. This activation occurred within the FF, IC, SN and ZI with current intensities close to the average injected during DBS (3 mA). A sensitivity analysis of model parameters (fiber size, fiber orientation, degree of inhomogeneity, degree of anisotropy, electrode configuration) revealed that the FF and IC were consistently activated. Direct activation of axons outside the STN suggests that other brain regions may be involved in the beneficial effects of DBS when treating Parkinsonian symptoms.

  19. Formation of compact myelin is required for maturation of the axonal cytoskeleton

    Science.gov (United States)

    Brady, S. T.; Witt, A. S.; Kirkpatrick, L. L.; de Waegh, S. M.; Readhead, C.; Tu, P. H.; Lee, V. M.

    1999-01-01

    Although traditional roles ascribed to myelinating glial cells are structural and supportive, the importance of compact myelin for proper functioning of the nervous system can be inferred from mutations in myelin proteins and neuropathologies associated with loss of myelin. Myelinating Schwann cells are known to affect local properties of peripheral axons (de Waegh et al., 1992), but little is known about effects of oligodendrocytes on CNS axons. The shiverer mutant mouse has a deletion in the myelin basic protein gene that eliminates compact myelin in the CNS. In shiverer mice, both local axonal features like phosphorylation of cytoskeletal proteins and neuronal perikaryon functions like cytoskeletal gene expression are altered. This leads to changes in the organization and composition of the axonal cytoskeleton in shiverer unmyelinated axons relative to age-matched wild-type myelinated fibers, although connectivity and patterns of neuronal activity are comparable. Remarkably, transgenic shiverer mice with thin myelin sheaths display an intermediate phenotype indicating that CNS neurons are sensitive to myelin sheath thickness. These results indicate that formation of a normal compact myelin sheath is required for normal maturation of the neuronal cytoskeleton in large CNS neurons.

  20. Developmental plasticity of ascending spinal axons studies using the North American opossum, Didelphis virginiana.

    Science.gov (United States)

    Terman, J R; Wang, X M; Martin, G F

    1999-01-11

    The objectives of the present study were to determine if axons of all ascending tracts grow through the lesion after transection of the thoracic spinal cord during development in the North American opossum, and if so, whether they reach regions of the brain they normally innervate. Opossum pups were subjected to transection of the mid-thoracic cord at PD5, PD8, PD12, PD20, or PD26 and injections of Fast Blue (FB) into the lower thoracic or upper lumbar cord 30-40 days or 6 months later. In the PD5 transected cases, labeled axons were present in all of the supraspinal areas labeled by comparable injections in unlesioned, age-matched controls. In the experimental cases, however, labeled axons appeared to be fewer in number and in some areas more restricted in location than in the controls. When lesions were made at PD8, labeled axons were present in the brain of animals allowed to survive 30-40 days prior to FB injections but they were not observed in those allowed to survive 6 months. When lesions were made at PD12 or later, labeled axons were never found rostral to the lesion. It appears, therefore, that axons of all ascending spinal pathways grow though the lesion after transection of the thoracic cord in developing opossums and that they innervate appropriate areas of the brain. Interestingly, the critical period for such growth is shorter than that for most descending axons, suggesting that factors which influence loss of developmental plasticity are not the same for all axons.

  1. BORC/kinesin-1 ensemble drives polarized transport of lysosomes into the axon

    Science.gov (United States)

    Farías, Ginny G.; Guardia, Carlos M.; De Pace, Raffaella; Britt, Dylan J.; Bonifacino, Juan S.

    2017-01-01

    The ability of lysosomes to move within the cytoplasm is important for many cellular functions. This ability is particularly critical in neurons, which comprise vast, highly differentiated domains such as the axon and dendrites. The mechanisms that control lysosome movement in these domains, however, remain poorly understood. Here we show that an ensemble of BORC, Arl8, SKIP, and kinesin-1, previously shown to mediate centrifugal transport of lysosomes in nonneuronal cells, specifically drives lysosome transport into the axon, and not the dendrites, in cultured rat hippocampal neurons. This transport is essential for maintenance of axonal growth-cone dynamics and autophagosome turnover. Our findings illustrate how a general mechanism for lysosome dispersal in nonneuronal cells is adapted to drive polarized transport in neurons, and emphasize the importance of this mechanism for critical axonal processes. PMID:28320970

  2. In silico modeling of axonal reconnection within a discrete fiber tract after spinal cord injury.

    Science.gov (United States)

    Woolfe, Franco; Waxman, Stephen G; Hains, Bryan C

    2007-02-01

    Following spinal cord injury (SCI), descending axons that carry motor commands from the brain to the spinal cord are injured or transected, producing chronic motor dysfunction and paralysis. Reconnection of these axons is a major prerequisite for restoration of function after SCI. Thus far, only modest gains in motor function have been achieved experimentally or in the clinic after SCI, identifying the practical limitations of current treatment approaches. In this paper, we use an ordinary differential equation (ODE) to simulate the relative and synergistic contributions of several experimentally-established biological factors related to inhibition or promotion of axonal repair and restoration of function after SCI. The factors were mathematically modeled by the ODE. The results of our simulation show that in a model system, many factors influenced the achievability of axonal reconnection. Certain factors more strongly affected axonal reconnection in isolation, and some factors interacted in a synergistic fashion to produce further improvements in axonal reconnection. Our data suggest that mathematical modeling may be useful in evaluating the complex interactions of discrete therapeutic factors not possible in experimental preparations, and highlight the benefit of a combinatorial therapeutic approach focused on promoting axonal sprouting, attraction of cut ends, and removal of growth inhibition for achieving axonal reconnection. Predictions of this simulation may be of utility in guiding future experiments aimed at restoring function after SCI.

  3. Sensory axon-derived neuregulin-1 is required for axoglial signaling and normal sensory function but not for long-term axon maintenance

    DEFF Research Database (Denmark)

    Fricker, F.R.; Zhu, N.; Tsantoulas, C.

    2009-01-01

    " pockets. The total number of axons in the sural nerve was unchanged, but a greater proportion was unmyelinated. In addition, we observed large-diameter axons that were in a 1:1 relationship with Schwann cells, surrounded by a basal lamina but not myelinated. There was no evidence of DRG or Schwann cell...... death; the markers of different DRG cell populations and cutaneous innervation were unchanged. These anatomical changes were reflected in a slowing of conduction velocity at the lower end of the A-fiber conduction velocity range and a new population of more rapidly conducting C-fibers that are likely...

  4. Dorsal column sensory axons degenerate due to impaired microvascular perfusion after spinal cord injury in rats

    Science.gov (United States)

    Muradov, Johongir M.; Ewan, Eric E.; Hagg, Theo

    2013-01-01

    The mechanisms contributing to axon loss after spinal cord injury (SCI) are largely unknown but may involve microvascular loss as we have previously suggested. Here, we used a mild contusive injury (120 kdyn IH impactor) at T9 in rats focusing on ascending primary sensory dorsal column axons, anterogradely traced from the sciatic nerves. The injury caused a rapid and progressive loss of dorsal column microvasculature and oligodendrocytes at the injury site and penumbra and a ~70% loss of the sensory axons, by 24 hours. To model the microvascular loss, focal ischemia of the T9 dorsal columns was achieved via phototoxic activation of intravenously injected rose bengal. This caused an ~53% loss of sensory axons and an ~80% loss of dorsal column oligodendrocytes by 24 hours. Axon loss correlated with the extent and axial length of microvessel and oligodendrocyte loss along the dorsal column. To determine if oligodendrocyte loss contributes to axon loss, the glial toxin ethidium bromide (EB; 0.3 µg/µl) was microinjected into the T9 dorsal columns, and resulted in an ~88% loss of dorsal column oligodendrocytes and an ~56% loss of sensory axons after 72 hours. EB also caused an ~72% loss of microvessels. Lower concentrations of EB resulted in less axon, oligodendrocyte and microvessel loss, which were highly correlated (R2 = 0.81). These data suggest that focal spinal cord ischemia causes both oligodendrocyte and axon degeneration, which are perhaps linked. Importantly, they highlight the need of limiting the penumbral spread of ischemia and oligodendrocyte loss after SCI in order to protect axons. PMID:23978615

  5. Glia-axon interactions and the regulation of the extracellular K+ in the peripheral nerve.

    Science.gov (United States)

    Jirounek, P; Robert, A; Kindler, E; Blazek, T

    1998-01-01

    Changes in membrane potential of both axons and Schwann cells were measured simultaneously during electrical activity and during the period of recovery in the rabbit vagus nerve by the use of the sucrose-gap apparatus. During low-frequency stimulation (0.5-1 Hz) the preparation developed a ouabain-sensitive hyperpolarization. This hyperpolarization increased when the inwardly rectifying K+ channels in Schwann cells were blocked with Ba2+, indicating that the hyperpolarization was generated by the electrogenic glial Na(+)-K+ pump. During trains at higher frequencies (15 Hz), the preparation depolarized, but after cessation of the stimulation it developed a posttetanic hyperpolarization (PTH). The PTH was also ouabain-sensitive and was strongly enhanced by Cs+ which is known to block the hyperpolarization-activated inward current (Ih) in axons but not in glial cells. These results show that the PTH reflects mainly the axonal electrogenic pump. Our results indicate that during activity the K+ released from the firing axons is removed from the extracellular space by Schwann cells and that after cessation of the stimulation the K+ surplus returns from Schwann cells back to axons. Both the glial and axonal K+ uptake is mediated by successive activation of the glial and axonal Na(+)-K+ pump. The nature of the signalling mechanisms that control the pumping rates of the respective pumps remain unknown.

  6. In vivo electrophysiological measurement of the rat ulnar nerve with axonal excitability testing

    DEFF Research Database (Denmark)

    Wild, Brandon M.; Morris, Renée; Moldovan, Mihai

    2018-01-01

    Electrophysiology enables the objective assessment of peripheral nerve function in vivo. Traditional nerve conduction measures such as amplitude and latency detect chronic axon loss and demyelination, respectively. Axonal excitability techniques "by threshold tracking" expand upon these measures...... by providing information regarding the activity of ion channels, pumps and exchangers that relate to acute function and may precede degenerative events. As such, the use of axonal excitability in animal models of neurological disorders may provide a useful in vivo measure to assess novel therapeutic...... interventions. Here we describe an experimental setup for multiple measures of motor axonal excitability techniques in the rat ulnar nerve. The animals are anesthetized with isoflurane and carefully monitored to ensure constant and adequate depth of anesthesia. Body temperature, respiration rate, heart rate...

  7. Adenosine Receptors in Developing and Adult Mouse Neuromuscular Junctions and Functional Links With Other Metabotropic Receptor Pathways.

    Science.gov (United States)

    Tomàs, Josep; Garcia, Neus; Lanuza, Maria A; Santafé, Manel M; Tomàs, Marta; Nadal, Laura; Hurtado, Erica; Simó-Ollé, Anna; Cilleros-Mañé, Víctor; Just-Borràs, Laia

    2018-01-01

    In the last few years, we have studied the presence and involvement in synaptogenesis and mature transmitter release of the adenosine autoreceptors (AR) in the mammalian neuromuscular junction (NMJ). Here, we review and bring together the previously published data to emphasize the relevance of these receptors for developmental axonal competition, synaptic loss and mature NMJ functional modulation. However, in addition to AR, activity-dependent mediators originating from any of the three cells that make the synapse (nerve, muscle, and glial cells) cross the extracellular cleft to generate signals in target metabotropic receptors. Thus, the integrated interpretation of the complementary function of all these receptors is needed. We previously studied, in the NMJ, the links of AR with mAChR and the neurotrophin receptor TrkB in the control of synapse elimination and transmitter release. We conclude that AR cooperate with these receptors through synergistic and antagonistic effects in the developmental synapse elimination process. In the adult NMJ, this cooperation is manifested so as that the functional integrity of a given receptor group depends on the other receptors operating normally (i.e., the functional integrity of mAChR depends on AR operating normally). These observations underlie the relevance of AR in the NMJ function.

  8. Adenosine Receptors in Developing and Adult Mouse Neuromuscular Junctions and Functional Links With Other Metabotropic Receptor Pathways

    Directory of Open Access Journals (Sweden)

    Josep Tomàs

    2018-04-01

    Full Text Available In the last few years, we have studied the presence and involvement in synaptogenesis and mature transmitter release of the adenosine autoreceptors (AR in the mammalian neuromuscular junction (NMJ. Here, we review and bring together the previously published data to emphasize the relevance of these receptors for developmental axonal competition, synaptic loss and mature NMJ functional modulation. However, in addition to AR, activity-dependent mediators originating from any of the three cells that make the synapse (nerve, muscle, and glial cells cross the extracellular cleft to generate signals in target metabotropic receptors. Thus, the integrated interpretation of the complementary function of all these receptors is needed. We previously studied, in the NMJ, the links of AR with mAChR and the neurotrophin receptor TrkB in the control of synapse elimination and transmitter release. We conclude that AR cooperate with these receptors through synergistic and antagonistic effects in the developmental synapse elimination process. In the adult NMJ, this cooperation is manifested so as that the functional integrity of a given receptor group depends on the other receptors operating normally (i.e., the functional integrity of mAChR depends on AR operating normally. These observations underlie the relevance of AR in the NMJ function.

  9. Axon-Sorting Multifunctional Nerve Guides: Accelerating Restoration of Nerve Function

    Science.gov (United States)

    2014-10-01

    factor (singly & in selected combinations) in the organotypic model system for preferential sensory or motor axon extension. Use confocal microscopy to...track axon extension of labeled sensory or motor neurons from spinal cord slices (motor) or dorsal root ganglia ( DRG ) (sensory). 20 Thy1-YFP mice...RESEARCH ACCOMPLISHMENTS: • Established a system of color-coded mixed nerve tracking using GFP and RFP expressing motor and sensory neurons (Figure 1

  10. Depth-sensing nano-indentation on a myelinated axon at various stages

    International Nuclear Information System (INIS)

    Huang, Wei-Chin; Liao, Jiunn-Der; Lin, Chou-Ching K; Ju, Ming-Shaung

    2011-01-01

    A nano-mechanical characterization of a multi-layered myelin sheath structure, which enfolds an axon and plays a critical role in the transmission of nerve impulses, is conducted. Schwann cells co-cultured in vitro with PC12 cells for various co-culture times are differentiated to form a myelinated axon, which is then observed using a transmission electron microscope. Three major myelination stages, with distinct structural characteristics and thicknesses around the axon, can be produced by varying the co-culture time. A dynamic contact module and continuous depth-sensing nano-indentation are used on the myelinated structure to obtain the load-on-sample versus measured displacement curve of a multi-layered myelin sheath, which is used to determine the work required for the nano-indentation tip to penetrate the myelin sheath. By analyzing the harmonic contact stiffness versus the measured displacement profile, the results can be used to estimate the three stages of the multi-layered structure on a myelinated axon. The method can also be used to evaluate the development stages of myelination or demyelination during nerve regeneration.

  11. Axonal propagation of simple and complex spikes in cerebellar Purkinje neurons.

    Science.gov (United States)

    Khaliq, Zayd M; Raman, Indira M

    2005-01-12

    In cerebellar Purkinje neurons, the reliability of propagation of high-frequency simple spikes and spikelets of complex spikes is likely to regulate inhibition of Purkinje target neurons. To test the extent to which a one-to-one correspondence exists between somatic and axonal spikes, we made dual somatic and axonal recordings from Purkinje neurons in mouse cerebellar slices. Somatic action potentials were recorded with a whole-cell pipette, and the corresponding axonal signals were recorded extracellularly with a loose-patch pipette. Propagation of spontaneous and evoked simple spikes was highly reliable. At somatic firing rates of approximately 200 spikes/sec, 375 Hz during somatic hyperpolarizations that silenced spontaneous firing to approximately 150 Hz during spontaneous activity. The probability of propagation of individual spikelets could be described quantitatively as a saturating function of spikelet amplitude, rate of rise, or preceding interspike interval. The results suggest that ion channels of Purkinje axons are adapted to produce extremely short refractory periods and that brief bursts of forward-propagating action potentials generated by complex spikes may contribute transiently to inhibition of postsynaptic neurons.

  12. Partial denervation of sub-basal axons persists following debridement wounds to the mouse cornea.

    Science.gov (United States)

    Pajoohesh-Ganji, Ahdeah; Pal-Ghosh, Sonali; Tadvalkar, Gauri; Kyne, Briana M; Saban, Daniel R; Stepp, Mary Ann

    2015-11-01

    Although sensory reinnervation occurs after injury in the peripheral nervous system, poor reinnervation in the elderly and those with diabetes often leads to pathology. Here we quantify sub-basal axon density in the central and peripheral mouse cornea over time after three different types of injury. The mouse cornea is highly innervated with a dense array of sub-basal nerves that form a spiral called the vortex at the corneal center or apex; these nerves are readily detected within flat mounted corneas. After anesthesia, corneal epithelial cells were removed using either a dulled blade or a rotating burr within an area demarcated centrally with a 1.5 mm trephine. A third wound type, superficial trephination, involved demarcating the area with the 1.5 mm trephine but not removing cells. By 7 days after superficial trephination, sub-basal axon density returns to control levels; by 28 days the vortex reforms. Although axon density is similar to control 14 days after dulled blade and rotating burr wounding, defects in axon morphology at the corneal apex remain. After 14 days, axons retract from the center leaving the sub-basal axon density reduced by 37.2 and 36.8% at 28 days after dulled blade and rotating burr wounding, respectively, compared with control. Assessment of inflammation using flow cytometry shows that persistent inflammation is not a factor in the incomplete reinnervation. Expression of mRNAs encoding 22 regeneration-associated genes involved in axon targeting assessed by QPCR reveals that netrin-1 and ephrin signaling are altered after wounding. Subpopulations of corneal epithelial basal cells at the corneal apex stop expressing ki67 as early as 7 days after injury and by 14 and 28 days after wounding, many of these basal cells undergo apoptosis and die. Although sub-basal axons are restored to their normal density and morphology after superficial trephination, sub-basal axon recovery is partial after debridement wounds. The increase in corneal

  13. Retinal glia promote dorsal root ganglion axon regeneration.

    Directory of Open Access Journals (Sweden)

    Barbara Lorber

    Full Text Available Axon regeneration in the adult central nervous system (CNS is limited by several factors including a lack of neurotrophic support. Recent studies have shown that glia from the adult rat CNS, specifically retinal astrocytes and Müller glia, can promote regeneration of retinal ganglion cell axons. In the present study we investigated whether retinal glia also exert a growth promoting effect outside the visual system. We found that retinal glial conditioned medium significantly enhanced neurite growth and branching of adult rat dorsal root ganglion neurons (DRG in culture. Furthermore, transplantation of retinal glia significantly enhanced regeneration of DRG axons past the dorsal root entry zone after root crush in adult rats. To identify the factors that mediate the growth promoting effects of retinal glia, mass spectrometric analysis of retinal glial conditioned medium was performed. Apolipoprotein E and secreted protein acidic and rich in cysteine (SPARC were found to be present in high abundance, a finding further confirmed by western blotting. Inhibition of Apolipoprotein E and SPARC significantly reduced the neuritogenic effects of retinal glial conditioned medium on DRG in culture, suggesting that Apolipoprotein E and SPARC are the major mediators of this regenerative response.

  14. Botulinum toxin's axonal transport from periphery to the spinal cord.

    Science.gov (United States)

    Matak, Ivica; Riederer, Peter; Lacković, Zdravko

    2012-07-01

    Axonal transport of enzymatically active botulinum toxin A (BTX-A) from periphery to the CNS has been described in facial and trigeminal nerve, leading to cleavage of synaptosomal-associated protein 25 (SNAP-25) in central nuclei. Aim of present study was to examine the existence of axonal transport of peripherally applied BTX-A to spinal cord via sciatic nerve. We employed BTX-A-cleaved SNAP-25 immunohistochemistry of lumbar spinal cord after intramuscular and subcutaneous hind limb injections, and intraneural BTX-A sciatic nerve injections. Truncated SNAP-25 in ipsilateral spinal cord ventral horns and dorsal horns appeared after single peripheral BTX-A administrations, even at low intramuscular dose applied (5 U/kg). Cleaved SNAP-25 appearance in the spinal cord after BTX-A injection into the sciatic nerve was prevented by proximal intrasciatic injection of colchicine (5 mM, 2 μl). Cleaved SNAP-25 in ventral horn, using choline-acetyltransferase (ChAT) double labeling, was localized within cholinergic neurons. These results extend the recent findings on BTX-A retrograde axonal transport in facial and trigeminal nerve. Appearance of truncated SNAP-25 in spinal cord following low-dose peripheral BTX-A suggest that the axonal transport of BTX-A occurs commonly following peripheral application. Copyright © 2012 Elsevier Ltd. All rights reserved.

  15. Axonal degeneration in association with carpal tunnel syndrome Degeneração axonal na síndrome do túnel do carpo

    Directory of Open Access Journals (Sweden)

    Marcelo Ribeiro Caetano

    2003-03-01

    Full Text Available Median nerve entrapment in the palm to wrist segment is known as carpal tunnel syndrome (CTS. Electromyography is the best evaluation test to confirm the disease, as it shows a median reduced conduction velocity and/or conduction block; however, the usual CTS electrodiagnostic tests do not separate segmental demyelination alone from segmental demyelination plus secondary axonal degeneration. We studied 100 hands from CTS patients (classified as mild, moderate, and severe, and 50 hands from normal subjects. The median palmar sensory nerve action potential (SNAP amplitude was measured and compared between the two groups. It would be expected that SNAP was normal if no axonal degeneration had occurred. The results showed that in mild CTS group and part of moderate CTS group SNAP amplitude was normal, whereas in severe CTS group, and part of moderate group SNAP amplitude was reduced, proving that axonal degeneration was involved. As it is well stated that axonal lesions have worse prognosis than segmental demyelinating ones, this simple test may help to preditic the CTS outcome and treatment.A compressão do nervo mediano no segmento punho-palma produz uma entidade clínica conhecida como síndrome do túnel do carpo (STC. A eletroneuromiografia é o exame de escolha para o diagnóstico da STC, através da identificação de diminuição de velocidade e/ou bloqueio de condução quando estudamos a neurocondução do nervo mediano, no trecho do punho. Entretanto, as técnicas comumente usadas não conseguem separar a lesão em mielínica focal com ou sem degeneração axonal secundária. Avaliamos 100 mãos de pacientes com STC e comparamos com 50 mãos de um grupo controle. Medimos a amplitude do potencial de ação do nervo sensitivo do mediano, com estímulo na palma e captação no dedo, e comparamos entre os grupos controle e de pacientes (o grupo de STC foi subdividido em leve, moderado e grave. Era esperado que a amplitude do potencial

  16. Fisiopatología del síndrome de Guillain Barré axonal Physiopathology of axonal acute Guillain Barré syndrome

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    Juan Guillermo Montoya Ch.

    2002-02-01

    Full Text Available Se describe la fisiopatología del síndrome de Guillain Barré axonal. Se consideran especialmente cinco aspectos: 1 Agentes etiológicos, específicamente el Campylobacter jejuni. 2 Susceptibilidad genética humana. 3 Mimetismo molecular entre lipopolisacáridos y lipoproteínas. 4 Mecanismo de acción de los anticuerpos antigangliósidos y 5 Hallazgos patológicos. The physiopathology of axonal acute Guillain Barré syndrome is described. Five aspects are considered, namely: 1 Etiologic agents emphasizing on Campylobacter jejuni. 2 Human genetic predisposition. 3 Molecular mimicry between lipopolysaccharides and gangliosides. 4 Mechanisms of action of antiganglioside antibodies and, 5 Pathologic findings.

  17. The Actin-Binding Protein α-Adducin Is Required for Maintaining Axon Diameter

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    Sérgio Carvalho Leite

    2016-04-01

    Full Text Available The actin-binding protein adducin was recently identified as a component of the neuronal subcortical cytoskeleton. Here, we analyzed mice lacking adducin to uncover the function of this protein in actin rings. α-adducin knockout mice presented progressive axon enlargement in the spinal cord and optic and sciatic nerves, followed by axon degeneration and loss. Using stimulated emission depletion super-resolution microscopy, we show that a periodic subcortical actin cytoskeleton is assembled in every neuron type inspected including retinal ganglion cells and dorsal root ganglia neurons. In neurons devoid of adducin, the actin ring diameter increased, although the inter-ring periodicity was maintained. In vitro, the actin ring diameter adjusted as axons grew, suggesting the lattice is dynamic. Our data support a model in which adducin activity is not essential for actin ring assembly and periodicity but is necessary to control the diameter of both actin rings and axons and actin filament growth within rings.

  18. The Actin-Binding Protein α-Adducin Is Required for Maintaining Axon Diameter.

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    Leite, Sérgio Carvalho; Sampaio, Paula; Sousa, Vera Filipe; Nogueira-Rodrigues, Joana; Pinto-Costa, Rita; Peters, Luanne Laurel; Brites, Pedro; Sousa, Mónica Mendes

    2016-04-19

    The actin-binding protein adducin was recently identified as a component of the neuronal subcortical cytoskeleton. Here, we analyzed mice lacking adducin to uncover the function of this protein in actin rings. α-adducin knockout mice presented progressive axon enlargement in the spinal cord and optic and sciatic nerves, followed by axon degeneration and loss. Using stimulated emission depletion super-resolution microscopy, we show that a periodic subcortical actin cytoskeleton is assembled in every neuron type inspected including retinal ganglion cells and dorsal root ganglia neurons. In neurons devoid of adducin, the actin ring diameter increased, although the inter-ring periodicity was maintained. In vitro, the actin ring diameter adjusted as axons grew, suggesting the lattice is dynamic. Our data support a model in which adducin activity is not essential for actin ring assembly and periodicity but is necessary to control the diameter of both actin rings and axons and actin filament growth within rings. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  19. Intra-axonal Synthesis of SNAP25 Is Required for the Formation of Presynaptic Terminals

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    Andreia F.R. Batista

    2017-09-01

    Full Text Available Localized protein synthesis is a mechanism for developing axons to react acutely and in a spatially restricted manner to extracellular signals. As such, it is important for many aspects of axonal development, but its role in the formation of presynapses remains poorly understood. We found that the induced assembly of presynaptic terminals required local protein synthesis. Newly synthesized proteins were detectable at nascent presynapses within 15 min of inducing synapse formation in isolated axons. The transcript for the t-SNARE protein SNAP25, which is required for the fusion of synaptic vesicles with the plasma membrane, was recruited to presynaptic sites and locally translated. Inhibition of intra-axonal SNAP25 synthesis affected the clustering of SNAP25 and other presynaptic proteins and interfered with the release of synaptic vesicles from presynaptic sites. This study reveals a critical role for the axonal synthesis of SNAP25 in the assembly of presynaptic terminals.

  20. Transfer of vesicles from Schwann cell to axon: a novel mechanism of communication in the peripheral nervous system

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    María Alejandra eLopez-Verrilli

    2012-06-01

    Full Text Available Schwann cells (SCs are the glial component of the peripheral nervous system, with essential roles during development and maintenance of axons, as well as during regenerative processes after nerve injury. SCs increase conduction velocities by myelinating axons, regulate synaptic activity at presynaptic nerve terminals and are a source of trophic factors to neurons. Thus, development and maintenance of peripheral nerves are crucially dependent on local signalling between SCs and axons. In addition to the classic mechanisms of intercellular signalling, the possibility of communication through secreted vesicles has been poorly explored to date. Interesting recent findings suggest the occurrence of lateral transfer mediated by vesicles from glial cells to axons that could have important roles in axonal growth and axonal regeneration. Here, we review the role of vesicular transfer from SCs to axons and propose the benefits of this means in supporting neuronal and axonal maintenance and regeneration after nerve damage.

  1. Trafficking of cholesterol from cell bodies to distal axons in Niemann Pick C1-deficient neurons.

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    Karten, Barbara; Vance, Dennis E; Campenot, Robert B; Vance, Jean E

    2003-02-07

    Niemann Pick type C (NPC) disease is a progressive neurodegenerative disorder. In cells lacking functional NPC1 protein, endocytosed cholesterol accumulates in late endosomes/lysosomes. We utilized primary neuronal cultures in which cell bodies and distal axons reside in separate compartments to investigate the requirement of NPC1 protein for transport of cholesterol from cell bodies to distal axons. We have recently observed that in NPC1-deficient neurons compared with wild-type neurons, cholesterol accumulates in cell bodies but is reduced in distal axons (Karten, B., Vance, D. E., Campenot, R. B., and Vance, J. E. (2002) J. Neurochem. 83, 1154-1163). We now show that NPC1 protein is expressed in both cell bodies and distal axons. In NPC1-deficient neurons, cholesterol delivered to cell bodies from low density lipoproteins (LDLs), high density lipoproteins, or cyclodextrin complexes was transported into axons in normal amounts, whereas transport of endogenously synthesized cholesterol was impaired. Inhibition of cholesterol synthesis with pravastatin in wild-type and NPC1-deficient neurons reduced axonal growth. However, LDLs restored a normal rate of growth to wild-type but not NPC1-deficient neurons treated with pravastatin. Thus, although LDL cholesterol is transported into axons of NPC1-deficient neurons, this source of cholesterol does not sustain normal axonal growth. Over the lifespan of NPC1-deficient neurons, these defects in cholesterol transport might be responsible for the observed altered distribution of cholesterol between cell bodies and axons and, consequently, might contribute to the neurological dysfunction in NPC disease.

  2. Bergmann glia and the recognition molecule CHL1 organize GABAergic axons and direct innervation of Purkinje cell dendrites.

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    Fabrice Ango

    2008-04-01

    Full Text Available The geometric and subcellular organization of axon arbors distributes and regulates electrical signaling in neurons and networks, but the underlying mechanisms have remained elusive. In rodent cerebellar cortex, stellate interneurons elaborate characteristic axon arbors that selectively innervate Purkinje cell dendrites and likely regulate dendritic integration. We used GFP BAC transgenic reporter mice to examine the cellular processes and molecular mechanisms underlying the development of stellate cell axons and their innervation pattern. We show that stellate axons are organized and guided towards Purkinje cell dendrites by an intermediate scaffold of Bergmann glial (BG fibers. The L1 family immunoglobulin protein Close Homologue of L1 (CHL1 is localized to apical BG fibers and stellate cells during the development of stellate axon arbors. In the absence of CHL1, stellate axons deviate from BG fibers and show aberrant branching and orientation. Furthermore, synapse formation between aberrant stellate axons and Purkinje dendrites is reduced and cannot be maintained, leading to progressive atrophy of axon terminals. These results establish BG fibers as a guiding scaffold and CHL1 a molecular signal in the organization of stellate axon arbors and in directing their dendritic innervation.

  3. Axons Pull on the Brain, But Tension Does Not Drive Cortical Folding

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    Xu, Gang; Knutsen, Andrew K.; Dikranian, Krikor; Kroenke, Christopher D.; Bayly, Philip V.; Taber, Larry A.

    2011-01-01

    During human brain development, the cerebral cortex undergoes substantial folding, leading to its characteristic highly convoluted form. Folding is necessary to accommodate the expansion of the cerbral cortex; abnormal cortical folding is linked to various neurological disorders, including schizophrenia, epilepsy, autism and mental retardation. Although this process requires mechanical forces, the specific force-generating mechanisms that drive folding remain unclear. The two most widely accepted hypotheses are (1) folding is caused by differential growth of the cortex and (2) folding is caused by mechanical tension generated in axons. Direct evidence supporting either theory, however, is lacking. Here we show that axons are indeed under considerable tension in the developing ferret brain, but the patterns of tissue stress are not consistent with a causal role for axonal tension. In particular, microdissection assays reveal that significant tension exists along axons aligned circumferentially in subcortical white matter tracts, as well as those aligned radially inside developing gyri (outward folds). Contrary to previous speculation, however, axonal tension is not directed across developing gyri, suggesting that axon tension does not drive folding. On the other hand, using computational (finite element) models, we show that differential cortical growth accompanied by remodeling of the subplate leads to outward folds and stress fields that are consistent with our microdissection experiments, supporting a mechanism involving differential growth. Local perturbations, such as temporal differences in the initiation of cortical growth, can ensure consistent folding patterns. This study shows that a combination of experimental and computational mechanics can be used to evaluate competing hypotheses of morphogenesis, and illuminate the biomechanics of cortical folding. PMID:20590291

  4. The Kinesin Adaptor Calsyntenin-1 Organizes Microtubule Polarity and Regulates Dynamics during Sensory Axon Arbor Development

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    Mary C. Halloran

    2017-04-01

    Full Text Available Axon growth and branching, and development of neuronal polarity are critically dependent on proper organization and dynamics of the microtubule (MT cytoskeleton. MTs must organize with correct polarity for delivery of diverse cargos to appropriate subcellular locations, yet the molecular mechanisms regulating MT polarity remain poorly understood. Moreover, how an actively branching axon reorganizes MTs to direct their plus ends distally at branch points is unknown. We used high-speed, in vivo imaging of polymerizing MT plus ends to characterize MT dynamics in developing sensory axon arbors in zebrafish embryos. We find that axonal MTs are highly dynamic throughout development, and that the peripheral and central axons of sensory neurons show differences in MT behaviors. Furthermore, we show that Calsyntenin-1 (Clstn-1, a kinesin adaptor required for sensory axon branching, also regulates MT polarity in developing axon arbors. In wild type neurons the vast majority of MTs are directed in the correct plus-end-distal orientation from early stages of development. Loss of Clstn-1 causes an increase in MTs polymerizing in the retrograde direction. These misoriented MTs most often are found near growth cones and branch points, suggesting Clstn-1 is particularly important for organizing MT polarity at these locations. Together, our results suggest that Clstn-1, in addition to regulating kinesin-mediated cargo transport, also organizes the underlying MT highway during axon arbor development.

  5. Vesicular Axonal Transport is Modified In Vivo by Tau Deletion or Overexpression in Drosophila

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    Yasmina Talmat-Amar

    2018-03-01

    Full Text Available Structural microtubule associated protein Tau is found in high amount in axons and is involved in several neurodegenerative diseases. Although many studies have highlighted the toxicity of an excess of Tau in neurons, the in vivo understanding of the endogenous role of Tau in axon morphology and physiology is poor. Indeed, knock-out mice display no strong cytoskeleton or axonal transport phenotype, probably because of some important functional redundancy with other microtubule-associated proteins (MAPs. Here, we took advantage of the model organism Drosophila, which genome contains only one homologue of the Tau/MAP2/MAP4 family to decipher (endogenous Tau functions. We found that Tau depletion leads to a decrease in microtubule number and microtubule density within axons, while Tau excess leads to the opposite phenotypes. Analysis of vesicular transport in tau mutants showed altered mobility of vesicles, but no change in the total amount of putatively mobile vesicles, whereas both aspects were affected when Tau was overexpressed. In conclusion, we show that loss of Tau in tau mutants not only leads to a decrease in axonal microtubule density, but also impairs axonal vesicular transport, albeit to a lesser extent compared to the effects of an excess of Tau.

  6. Chemokines and Chemokine Receptors in Multiple Sclerosis

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    Wenjing Cheng

    2014-01-01

    Full Text Available Multiple sclerosis is an autoimmune disease with classical traits of demyelination, axonal damage, and neurodegeneration. The migration of autoimmune T cells and macrophages from blood to central nervous system as well as the destruction of blood brain barrier are thought to be the major processes in the development of this disease. Chemokines, which are small peptide mediators, can attract pathogenic cells to the sites of inflammation. Each helper T cell subset expresses different chemokine receptors so as to exert their different functions in the pathogenesis of MS. Recently published results have shown that the levels of some chemokines and chemokine receptors are increased in blood and cerebrospinal fluid of MS patients. This review describes the advanced researches on the role of chemokines and chemokine receptors in the development of MS and discusses the potential therapy of this disease targeting the chemokine network.

  7. A phantom axon setup for validating models of action potential recordings.

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    Rossel, Olivier; Soulier, Fabien; Bernard, Serge; Guiraud, David; Cathébras, Guy

    2016-08-01

    Electrode designs and strategies for electroneurogram recordings are often tested first by computer simulations and then by animal models, but they are rarely implanted for long-term evaluation in humans. The models show that the amplitude of the potential at the surface of an axon is higher in front of the nodes of Ranvier than at the internodes; however, this has not been investigated through in vivo measurements. An original experimental method is presented to emulate a single fiber action potential in an infinite conductive volume, allowing the potential of an axon to be recorded at both the nodes of Ranvier and the internodes, for a wide range of electrode-to-fiber radial distances. The paper particularly investigates the differences in the action potential amplitude along the longitudinal axis of an axon. At a short radial distance, the action potential amplitude measured in front of a node of Ranvier is two times larger than in the middle of two nodes. Moreover, farther from the phantom axon, the measured action potential amplitude is almost constant along the longitudinal axis. The results of this new method confirm the computer simulations, with a correlation of 97.6 %.

  8. The Drosophila HEM-2/NAP1 homolog KETTE controls axonal pathfinding and cytoskeletal organization.

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    Hummel, T; Leifker, K; Klämbt, C

    2000-04-01

    In Drosophila, the correct formation of the segmental commissures depends on neuron-glial interactions at the midline. The VUM midline neurons extend axons along which glial cells migrate in between anterior and posterior commissures. Here, we show that the gene kette is required for the normal projection of the VUM axons and subsequently disrupts glial migration. Axonal projection defects are also found for many other moto- and interneurons. In addition, kette affects the cell morphology of mesodermal and epidermal derivatives, which show an abnormal actin cytoskeleton. The KETTE protein is homologous to the transmembrane protein HEM-2/NAP1 evolutionary conserved from worms to vertebrates. In vitro analysis has shown a specific interaction of the vertebrate HEM-2/NAP1 with the SH2-SH3 adapter protein NCK and the small GTPase RAC1, which both have been implicated in regulating cytoskeleton organization and axonal growth. Hypomorphic kette mutations lead to axonal defects similar to mutations in the Drosophila NCK homolog dreadlocks. Furthermore, we show that kette and dock mutants genetically interact. NCK is thought to interact with the small G proteins RAC1 and CDC42, which play a role in axonal growth. In line with these observations, a kette phenocopy can be obtained following directed expression of mutant DCDC42 or DRAC1 in the CNS midline. In addition, the kette mutant phenotype can be partially rescued by expression of an activated DRAC1 transgene. Our data suggest an important role of the HEM-2 protein in cytoskeletal organization during axonal pathfinding.

  9. Axonal Spheroid Accumulation In the Brainstem and Spinal Cord of A Young Angus Cow with Ataxia.

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    Hanshaw, D M; Finnie, J W; Manavis, J; Kessell, A E

    2015-08-01

    An 18-month-old Angus cow presented with rapidly developing ataxia and subsequently died. The finding of large numbers of axonal spheroids in brainstem nuclei and spinal cord grey matter, bilaterally symmetrical in distribution, was consistent with a histopathological diagnosis of neuroaxonal dystrophy (NAD). Most of the axonal swellings were immunopositive to amyloid precursor protein, suggesting that interruption to axonal flow was important in their genesis. The topographical distribution of axonal spheroids in the brain and spinal cord in this bovine case closely resembled that found in the ovine neurodegenerative disorder termed NAD, in which axonal swellings are the major pathological feature. This appears to be the first reported case of this type of NAD in cattle. The aetiology of the spheroidal aggregations in this case was not determined. There was no evidence from the case history or neuropathology to indicate whether the axonal spheroids in this case involved an acquired or heritable aetiology. © 2015 Australian Veterinary Association.

  10. Repulsive guidance molecule a blockade exerts the immunoregulatory function in DCs stimulated with ABP and LPS.

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    Xu, Xuxu; Gao, Yan; Zhai, Zhiyong; Zhang, Shuo; Shan, Fengping; Feng, Juan

    2016-08-02

    Repulsive guidance molecule a (RGMa) is an axonal guidance molecule that has recently found to exert function in immune system. This study evaluated the function of RGMa in modulation of dendritic cells (DCs) function stimulated with Achyranthes bidentata polysaccharide (ABP) and lipopolysaccharide (LPS) using a RGMa-neutralizing antibody. Compared with the Control-IgG/ABP and Control-IgG/LPS groups, DCs in the Anti-RGMa/ABP and Anti-RGMa/LPS groups 1) showed small, round cells with a few cell processes and organelles, and many pinocytotic vesicles; 2) had decreased MHC II, CD86, CD80, and CD40 expression; 3) displayed the decreased IL-12p70, IL-1β and TNF-α levels and increased IL-10 secretion; 4) had a high percentage of FITC-dextran uptake; and 5) displayed a reduced ability to drive T cell proliferation and reinforced T cell polarization toward a Th2 cytokine pattern. We conclude that DCs treated with RGMa-neutralizing antibodies present with tolerogenic and immunoregulatory characteristics, which provides new insights into further understanding of the function of RGMa.

  11. Chondroitin sulfates do not impede axonal regeneration in goldfish spinal cord.

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    Takeda, Akihito; Okada, Soichiro; Funakoshi, Kengo

    2017-10-15

    Chondroitin sulfate proteoglycans produced in glial scar tissue are a major inhibitory factor for axonal regeneration after central nervous system injury in mammals. The inhibition is largely due to chondroitin sulfates, whose effects differ according to the sulfation pattern. In contrast to mammals, fish nerves spontaneously regenerate beyond the scar tissue after spinal cord injury, although the mechanisms that allow for axons to pass through the scar are unclear. Here, we used immunohistochemistry to examine the expression of two chondroitin sulfates with different sulfation variants at the lesion site in goldfish spinal cord. The intact spinal cord was immunoreactive for both chondroitin sulfate-A (CS-A) and chondroitin sulfate-C (CS-C), and CS-A immunoreactivity overlapped extensively with glial processes positive for glial fibrillary acidic protein. At 1week after inducing the spinal lesion, CS-A immunoreactivity was observed in the cell bodies and extracellular matrix, as well as in glial processes surrounding the lesion center. At 2weeks after the spinal lesion, regenerating axons entering the lesion center overtook the CS-A abundant area. In contrast, at 1week after lesion induction, CS-C immunoreactivity was significantly decreased, and at 2weeks after lesion induction, CS-C immunoreactivity was observed along the regenerating axons entering the lesion center. The present findings suggest that after spinal cord injury in goldfish, chondroitin sulfate proteoglycans are deposited in the extracellular matrix at the lesion site but do not form an impenetrable barrier to the growth of regenerating axons. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Investigation on the mechanism of peripheral axonal injury in glaucoma

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    Jun- Hong Zhao

    2013-05-01

    Full Text Available AIM: To compare the angles of longitudinal section of sclera around optic nerve heads and the never fiber layer changes in healthy adults and patients with glaucoma, and to investigate the mechanism of peripheral retinal axonal injury, with the combined knowledge of biomechanics. METHODS: The optical nerves and their peripheral tissue specimen in the 12 eyes from health adult donators and 12 eyes from glaucoma patient donators were dyed by Glees' method to compare the angles of longitudinal section of sclera around optic nerve heads(through optic nerve center, and to observe the anatomical features of the peripheral retinal axons. RESULTS: The mean angle of longitudinal section of sclera around optic nerve in healthy adults was 73.3°, while that in patients with absolute glaucoma was 75.6°. The difference showed no significance(t=1.44, P>0.05. There was a sharp bend in the course of peripheral optical fiber in healthy adults. However, the optic nerve fiber disappeared completely in patients with glaucoma end stage. CONCLUSION: The angle between the medial edge and leading edge of sclera(around optic nerve headsis an acute angle. The optical fiber in glaucoma end stage disappeared completely. The phenomenon may be related to high intraocular pressure, the sclera shape, the shear modulus of sclera and axons, and “axonal bending-injury” mechanism.

  13. Impaired Mitochondrial Dynamics Underlie Axonal Defects in Hereditary Spastic Paraplegias.

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    Denton, Kyle; Mou, Yongchao; Xu, Chong-Chong; Shah, Dhruvi; Chang, Jaerak; Blackstone, Craig; Li, Xue-Jun

    2018-05-02

    Mechanisms by which long corticospinal axons degenerate in hereditary spastic paraplegia (HSP) are largely unknown. Here, we have generated induced pluripotent stem cells (iPSCs) from patients with two autosomal recessive forms of HSP, SPG15 and SPG48, which are caused by mutations in the ZFYVE26 and AP5Z1 genes encoding proteins in the same complex, the spastizin and AP5Z1 proteins, respectively. In patient iPSC-derived telencephalic glutamatergic and midbrain dopaminergic neurons, neurite number, length and branching are significantly reduced, recapitulating disease-specific phenotypes. We analyzed mitochondrial morphology and noted a significant reduction in both mitochondrial length and their densities within axons of these HSP neurons. Mitochondrial membrane potential was also decreased, confirming functional mitochondrial defects. Notably, mdivi-1, an inhibitor of the mitochondrial fission GTPase DRP1, rescues mitochondrial morphology defects and suppresses the impairment in neurite outgrowth and late-onset apoptosis in HSP neurons. Furthermore, knockdown of these HSP genes causes similar axonal defects, also mitigated by treatment with mdivi-1. Finally, neurite outgrowth defects in SPG15 and SPG48 cortical neurons can be rescued by knocking down DRP1 directly. Thus, abnormal mitochondrial morphology caused by an imbalance of mitochondrial fission and fusion underlies specific axonal defects and serves as a potential therapeutic target for SPG15 and SPG48.

  14. Tri-partite complex for axonal transport drug delivery achieves pharmacological effect

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    Frederickson Martyn

    2010-01-01

    Full Text Available Abstract Background Targeted delivery of pharmaceutical agents into selected populations of CNS (Central Nervous System neurons is an extremely compelling goal. Currently, systemic methods are generally used for delivery of pain medications, anti-virals for treatment of dermatomal infections, anti-spasmodics, and neuroprotectants. Systemic side effects or undesirable effects on parts of the CNS that are not involved in the pathology limit efficacy and limit clinical utility for many classes of pharmaceuticals. Axonal transport from the periphery offers a possible selective route, but there has been little progress towards design of agents that can accomplish targeted delivery via this intraneural route. To achieve this goal, we developed a tripartite molecular construction concept involving an axonal transport facilitator molecule, a polymer linker, and a large number of drug molecules conjugated to the linker, then sought to evaluate its neurobiology and pharmacological behavior. Results We developed chemical synthesis methodologies for assembling these tripartite complexes using a variety of axonal transport facilitators including nerve growth factor, wheat germ agglutinin, and synthetic facilitators derived from phage display work. Loading of up to 100 drug molecules per complex was achieved. Conjugation methods were used that allowed the drugs to be released in active form inside the cell body after transport. Intramuscular and intradermal injection proved effective for introducing pharmacologically effective doses into selected populations of CNS neurons. Pharmacological efficacy with gabapentin in a paw withdrawal latency model revealed a ten fold increase in half life and a 300 fold decrease in necessary dose relative to systemic administration for gabapentin when the drug was delivered by axonal transport using the tripartite vehicle. Conclusion Specific targeting of selected subpopulations of CNS neurons for drug delivery by axonal

  15. Polarized axonal surface expression of neuronal KCNQ potassium channels is regulated by calmodulin interaction with KCNQ2 subunit.

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    John P Cavaretta

    Full Text Available KCNQ potassium channels composed of KCNQ2 and KCNQ3 subunits give rise to the M-current, a slow-activating and non-inactivating voltage-dependent potassium current that limits repetitive firing of action potentials. KCNQ channels are enriched at the surface of axons and axonal initial segments, the sites for action potential generation and modulation. Their enrichment at the axonal surface is impaired by mutations in KCNQ2 carboxy-terminal tail that cause benign familial neonatal convulsion and myokymia, suggesting that their correct surface distribution and density at the axon is crucial for control of neuronal excitability. However, the molecular mechanisms responsible for regulating enrichment of KCNQ channels at the neuronal axon remain elusive. Here, we show that enrichment of KCNQ channels at the axonal surface of dissociated rat hippocampal cultured neurons is regulated by ubiquitous calcium sensor calmodulin. Using immunocytochemistry and the cluster of differentiation 4 (CD4 membrane protein as a trafficking reporter, we demonstrate that fusion of KCNQ2 carboxy-terminal tail is sufficient to target CD4 protein to the axonal surface whereas inhibition of calmodulin binding to KCNQ2 abolishes axonal surface expression of CD4 fusion proteins by retaining them in the endoplasmic reticulum. Disruption of calmodulin binding to KCNQ2 also impairs enrichment of heteromeric KCNQ2/KCNQ3 channels at the axonal surface by blocking their trafficking from the endoplasmic reticulum to the axon. Consistently, hippocampal neuronal excitability is dampened by transient expression of wild-type KCNQ2 but not mutant KCNQ2 deficient in calmodulin binding. Furthermore, coexpression of mutant calmodulin, which can interact with KCNQ2/KCNQ3 channels but not calcium, reduces but does not abolish their enrichment at the axonal surface, suggesting that apo calmodulin but not calcium-bound calmodulin is necessary for their preferential targeting to the axonal

  16. Wnt Signalling Promotes Actin Dynamics during Axon Remodelling through the Actin-Binding Protein Eps8.

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    Eleanna Stamatakou

    Full Text Available Upon arrival at their synaptic targets, axons slow down their growth and extensively remodel before the assembly of presynaptic boutons. Wnt proteins are target-derived secreted factors that promote axonal remodelling and synaptic assembly. In the developing spinal cord, Wnts secreted by motor neurons promote axonal remodelling of NT-3 responsive dorsal root ganglia neurons. Axon remodelling induced by Wnts is characterised by growth cone pausing and enlargement, processes that depend on the re-organisation of microtubules. However, the contribution of the actin cytoskeleton has remained unexplored. Here, we demonstrate that Wnt3a regulates the actin cytoskeleton by rapidly inducing F-actin accumulation in growth cones from rodent DRG neurons through the scaffold protein Dishevelled-1 (Dvl1 and the serine-threonine kinase Gsk3β. Importantly, these changes in actin cytoskeleton occurs before enlargement of the growth cones is evident. Time-lapse imaging shows that Wnt3a increases lamellar protrusion and filopodia velocity. In addition, pharmacological inhibition of actin assembly demonstrates that Wnt3a increases actin dynamics. Through a yeast-two hybrid screen, we identified the actin-binding protein Eps8 as a direct interactor of Dvl1, a scaffold protein crucial for the Wnt signalling pathway. Gain of function of Eps8 mimics Wnt-mediated axon remodelling, whereas Eps8 silencing blocks the axon remodelling activity of Wnt3a. Importantly, blockade of the Dvl1-Eps8 interaction completely abolishes Wnt3a-mediated axonal remodelling. These findings demonstrate a novel role for Wnt-Dvl1 signalling through Eps8 in the regulation of axonal remodeling.

  17. Developmental axon stretch stimulates neuron growth while maintaining normal electrical activity, intracellular calcium flux, and somatic morphology.

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    Loverde, Joseph R; Pfister, Bryan J

    2015-01-01

    Elongation of nerve fibers intuitively occurs throughout mammalian development, and is synchronized with expansion of the growing body. While most tissue systems enlarge through mitosis and differentiation, elongation of nerve fibers is remarkably unique. The emerging paradigm suggests that axons undergo stretch as contiguous tissues enlarge between the proximal and distal segments of spanning nerve fibers. While stretch is distinct from growth, tension is a known stimulus which regulates the growth of axons. Here, we hypothesized that the axon stretch-growth process may be a natural form of injury, whereby regenerative processes fortify elongating axons in order to prevent disconnection. Harnessing the live imaging capability of our axon stretch-growth bioreactors, we assessed neurons both during and following stretch for biomarkers associated with injury. Utilizing whole-cell patch clamp recording, we found no evidence of changes in spontaneous action potential activity or degradation of elicited action potentials during real-time axon stretch at strains of up to 18% applied over 5 min. Unlike traumatic axonal injury, functional calcium imaging of the soma revealed no shifts in free intracellular calcium during axon stretch. Finally, the cross-sectional areas of nuclei and cytoplasms were normal, with no evidence of chromatolysis following week-long stretch-growth limited to the lower of 25% strain or 3 mm total daily stretch. The neuronal growth cascade coupled to stretch was concluded to be independent of the changes in membrane potential, action potential generation, or calcium flux associated with traumatic injury. While axon stretch-growth is likely to share overlap with regenerative processes, we conclude that developmental stretch is a distinct stimulus from traumatic axon injury.

  18. Developmental Axon Stretch Stimulates Neuron Growth While Maintaining Normal Electrical Activity, Intracellular Calcium Flux, and Somatic Morphology

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    Joseph R Loverde

    2015-08-01

    Full Text Available Elongation of nerve fibers intuitively occurs throughout mammalian development, and is synchronized with expansion of the growing body. While most tissue systems enlarge through mitosis and differentiation, elongation of nerve fibers is remarkably unique. The emerging paradigm suggests that axons undergo stretch as contiguous tissues enlarge between the proximal and distal segments of spanning nerve fibers. While stretch is distinct from growth, tension is a known stimulus which regulates the growth of axons. Here, we hypothesized that the axon stretch-growth process may be a natural form of injury, whereby regenerative processes fortify elongating axons in order to prevent disconnection. Harnessing the live imaging capability of our axon stretch-growth bioreactors, we assessed neurons both during and following stretch for biomarkers associated with injury. Utilizing whole-cell patch clamp recording, we found no evidence of changes in spontaneous action potential activity or degradation of elicited action potentials during real-time axon stretch at strains of up to 18 % applied over 5 minutes. Unlike traumatic axonal injury, functional calcium imaging of the soma revealed no shifts in free intracellular calcium during axon stretch. Finally, the cross-sectional areas of nuclei and cytoplasms were normal, with no evidence of chromatolysis following week-long stretch-growth limited to the lower of 25 % strain or 3 mm total daily stretch. The neuronal growth cascade coupled to stretch was concluded to be independent of the changes in membrane potential, action potential generation, or calcium flux associated with traumatic injury. While axon stretch-growth is likely to share overlap with regenerative processes, we conclude that developmental stretch is a distinct stimulus from traumatic axon injury.

  19. Axon Termination, Pruning, and Synaptogenesis in the Giant Fiber System of Drosophila melanogaster Is Promoted by Highwire.

    Science.gov (United States)

    Borgen, Melissa; Rowland, Kimberly; Boerner, Jana; Lloyd, Brandon; Khan, Aruna; Murphey, Rodney

    2017-03-01

    The ubiquitin ligase Highwire has a conserved role in synapse formation. Here, we show that Highwire coordinates several facets of central synapse formation in the Drosophila melanogaster giant fiber system, including axon termination, axon pruning, and synaptic function. Despite the similarities to the fly neuromuscular junction, the role of Highwire and the underlying signaling pathways are distinct in the fly's giant fiber system. During development, branching of the giant fiber presynaptic terminal occurs and, normally, the transient branches are pruned away. However, in highwire mutants these ectopic branches persist, indicating that Highwire promotes axon pruning. highwire mutants also exhibit defects in synaptic function. Highwire promotes axon pruning and synaptic function cell-autonomously by attenuating a mitogen-activated protein kinase pathway including Wallenda, c-Jun N-terminal kinase/Basket, and the transcription factor Jun. We also show a novel role for Highwire in non-cell autonomous promotion of synaptic function from the midline glia. Highwire also regulates axon termination in the giant fibers, as highwire mutant axons exhibit severe overgrowth beyond the pruning defect. This excessive axon growth is increased by manipulating Fos expression in the cells surrounding the giant fiber terminal, suggesting that Fos regulates a trans -synaptic signal that promotes giant fiber axon growth. Copyright © 2017 by the Genetics Society of America.

  20. Drug therapy for chronic idiopathic axonal polyneuropathy

    NARCIS (Netherlands)

    Vrancken, A. F. J. E.; van Schaik, I. N.; Hughes, R. A. C.; Notermans, N. C.

    2004-01-01

    BACKGROUND: Chronic idiopathic axonal polyneuropathy is an insidiously progressive sensory or sensorimotor polyneuropathy that affects elderly people. Although severe disability or handicap does not occur, it reduces quality of life. OBJECTIVES: To assess whether drug therapy for chronic idiopathic

  1. p27Kip1 Modulates Axonal Transport by Regulating α-Tubulin Acetyltransferase 1 Stability

    Directory of Open Access Journals (Sweden)

    Giovanni Morelli

    2018-05-01

    Full Text Available Summary: The protein p27Kip1 plays roles that extend beyond cell-cycle regulation during cerebral cortex development, such as the regulation of neuronal migration and neurite branching via signaling pathways that converge on the actin and microtubule cytoskeletons. Microtubule-dependent transport is essential for the maturation of neurons and the establishment of neuronal connectivity though synapse formation and maintenance. Here, we show that p27Kip1 controls the transport of vesicles and organelles along the axon of mice cortical projection neurons in vitro. Moreover, suppression of the p27Kip1 ortholog, dacapo, in Drosophila melanogaster disrupts axonal transport in vivo, leading to the reduction of locomotor activity in third instar larvae and adult flies. At the molecular level, p27Kip1 stabilizes the α-tubulin acetyltransferase 1, thereby promoting the acetylation of microtubules, a post-translational modification required for proper axonal transport. : Morelli et al. report that p27Kip1/Dacapo modulates the acetylation of microtubules in axons via stabilization of ATAT1, the main α-tubulin acetyltransferase. Its conditional loss leads to the reduction of bidirectional axonal transport of vesicles and mitochondria in vitro in mice and in vivo in Drosophila. Keywords: p27Kip1, dacapo, acetylation, axonal transport, ATAT1, alpha-tubulin, HDAC6, Drosophila, mouse, cerebral cortex

  2. Mouse Intermittent Hypoxia Mimicking Apnea of Prematurity: Effects on Myelinogenesis and Axonal Maturation

    Science.gov (United States)

    CAI, JUN; TUONG, CHI MINH; ZHANG, YIPING; SHIELDS, CHRISTOPHER B.; GUO, GANG; FU, HUI; GOZAL, DAVID

    2014-01-01

    Premature babies are at high risk for both infantile apnea and long-term neurobehavioral deficits. Recent studies suggest that diffuse structural changes in brain white matter are a positive predictor of poor cognitive outcomes. Since oligodendrocyte maturation, myelination, axon development and synapse formation mainly occur in the 3rd trimester of gestation and 1st postnatal year, infantile apnea could lead to and/or exaggerate white matter impairments in preterm neonates. Therefore, we investigated oligodendroglia and axon development in a neonatal mouse model of intermittent hypoxia between postnatal days 2 to 10. During critical phases of central nervous system development, intermittent hypoxia induced hypomyelination in the corpus callosum, striatum, fornix and cerebellum, but not the pons or spinal cord. Intermittent hypoxia-elicited alterations in myelin-forming processes were reflected by decreased expression of myelin proteins, including MBP, PLP, MAG and CNPase, possibly due to arrested maturation of oligodendrocytes. Ultra-structural abnormalities were apparent in the myelin sheath and axon. Immature oligodendrocytes were more vulnerable to neonatal intermittent hypoxia exposures than developing axons, suggesting that hypomyelination may contribute, at least partially, to axonal deficits. Insufficient neurofilament synthesis with anomalous components of neurofilament subunits, β-tubulin and MAP2 isoforms indicated immaturity of axons in intermittent hypoxia-exposed mouse brains. In addition, down-regulation of Synapsin I, Synaptophysin and Gap-43 phosphorylation suggested a potential stunt in axonogenesis and synaptogenesis. The region-selective and complex impairment in brain white matter induced by intermittent hypoxia was further associated with electrophysiological changes that may underlie long-term neurobehavioral sequelae. PMID:21953180

  3. Current contribution of diffusion tensor imaging in the evaluation of diffuse axonal injury

    Directory of Open Access Journals (Sweden)

    Daphine Centola Grassi

    Full Text Available ABSTRACT Traumatic brain injury (TBI is the number one cause of death and morbidity among young adults. Moreover, survivors are frequently left with functional disabilities during the most productive years of their lives. One main aspect of TBI pathology is diffuse axonal injury, which is increasingly recognized due to its presence in 40% to 50% of all cases that require hospital admission. Diffuse axonal injury is defined as widespread axonal damage and is characterized by complete axotomy and secondary reactions due to overall axonopathy. These changes can be seen in neuroimaging studies as hemorrhagic focal areas and diffuse edema. However, the diffuse axonal injury findings are frequently under-recognized in conventional neuroimaging studies. In such scenarios, diffuse tensor imaging (DTI plays an important role because it provides further information on white matter integrity that is not obtained with standard magnetic resonance imaging sequences. Extensive reviews concerning the physics of DTI and its use in the context of TBI patients have been published, but these issues are still hazy for many allied-health professionals. Herein, we aim to review the current contribution of diverse state-of-the-art DTI analytical methods to the understanding of diffuse axonal injury pathophysiology and prognosis, to serve as a quick reference for those interested in planning new studies and who are involved in the care of TBI victims. For this purpose, a comprehensive search in Pubmed was performed using the following keywords: “traumatic brain injury”, “diffuse axonal injury”, and “diffusion tensor imaging”.

  4. Investigating the Slow Axonal Transport of Neurofilaments: A Precursor for Optimal Neuronal Signaling

    Science.gov (United States)

    Johnson, Christopher M.

    Neurofilaments are the intermediate filaments of neurons and are the most abundant structure of the neuronal cytoskeleton. Once synthesized within the cell body they are then transported throughout the axon along microtubule tracks, driven by the molecular motors kinesin and dynein. This movement is characterized by long pauses with no movement interrupted by infrequent bouts of rapid movement, resulting in an aggregate dense cytoskeletal structure, which serves to regulate an axon's shape and size. Curiously, the modulated kinetics of these polymers produces a very regular, yet non-uniform, morphology in myelinated axons which are composed of discretely spaced myelin-ensheathed segments that are separated by short constricted regions called "nodes of Ranvier". This unique design optimizes the conduction velocity of myelinated axons at minimal fiber size. Hence, neurofilaments regulate the axon caliber to optimize neuron function. The goal of this dissertation is to investigate the motile mechanism of neurofilament transport as well as the resulting electrophysiological effects that follow. We start by examining highly time-resolved kymograph images generated from recorded neurofilament movement via epifluorescence microscopy. Using kymograph analysis, edge detection algorithms, and pixel smoothing tactics, neurofilament trajectories are extracted and used to obtain statistical distributions for the characteristics of how these filaments move within cells. The results suggest that the observed intermittent and bidirectional motions of these filaments might be explained by a model in which dynein and kinesin motors attach to a single neurofilament cargo and interact through mechanical forces only (i.e. a "tug-of-war" model). We test this hypothesis by developing two discrete-state stochastic models for the kinetic cycles of kinesin and dynein, which are then incorporated into a separate stochastic model that represents the posed tug-of-war scenario. We then

  5. In vivo phosphorylation of axonal proteins in goldfish optic nerve during regeneration

    Energy Technology Data Exchange (ETDEWEB)

    Larrivee, D.C.; Grafstein, B.

    1987-01-01

    In vivo phosphorylation of axonal proteins was investigated in normal and regenerating optic nerves of goldfish by two-dimensional gel electrophoresis. By 6-24 h after intraocular injection of H/sub 3/(32)PO/sub 4/, approximately 20 optic nerve proteins ranging in size from 19 to 180 kilodaltons and in pI from 4.4 to 6.8 were seen to have incorporated radiolabel. Five of these proteins showed a robust increase in incorporation of phosphate during regeneration. Among the latter was an acidic (pI 4.5) 45-kilodalton protein, which has previously been shown to be conveyed by fast axonal transport and to increase dramatically in its rate of synthesis during regeneration of goldfish optic axons.

  6. Sustained maximal voluntary contraction produces independent changes in human motor axons and the muscle they innervate.

    Directory of Open Access Journals (Sweden)

    David A Milder

    Full Text Available The repetitive discharges required to produce a sustained muscle contraction results in activity-dependent hyperpolarization of the motor axons and a reduction in the force-generating capacity of the muscle. We investigated the relationship between these changes in the adductor pollicis muscle and the motor axons of its ulnar nerve supply, and the reproducibility of these changes. Ten subjects performed a 1-min maximal voluntary contraction. Activity-dependent changes in axonal excitability were measured using threshold tracking with electrical stimulation at the wrist; changes in the muscle were assessed as evoked and voluntary electromyography (EMG and isometric force. Separate components of axonal excitability and muscle properties were tested at 5 min intervals after the sustained contraction in 5 separate sessions. The current threshold required to produce the target muscle action potential increased immediately after the contraction by 14.8% (p<0.05, reflecting decreased axonal excitability secondary to hyperpolarization. This was not correlated with the decline in amplitude of muscle force or evoked EMG. A late reversal in threshold current after the initial recovery from hyperpolarization peaked at -5.9% at ∼35 min (p<0.05. This pattern was mirrored by other indices of axonal excitability revealing a previously unreported depolarization of motor axons in the late recovery period. Measures of axonal excitability were relatively stable at rest but less so after sustained activity. The coefficient of variation (CoV for threshold current increase was higher after activity (CoV 0.54, p<0.05 whereas changes in voluntary (CoV 0.12 and evoked twitch (CoV 0.15 force were relatively stable. These results demonstrate that activity-dependent changes in motor axon excitability are unlikely to contribute to concomitant changes in the muscle after sustained activity in healthy people. The variability in axonal excitability after sustained activity

  7. Macrophages Promote Axon Regeneration with Concurrent Neurotoxicity

    NARCIS (Netherlands)

    Gensel, J.C.; Nakamura, S.; Guan, Z.; Rooijen, van N.; Ankeny, D.P.; Popovich, P.G.

    2009-01-01

    Activated macrophages can promote regeneration of CNS axons. However, macrophages also release factors that kill neurons. These opposing functions are likely induced simultaneously but are rarely considered together in the same experimental preparation. A goal of this study was to unequivocally

  8. [Severe, subacute axonal polyneuropathy due to hypophosphatemia].

    NARCIS (Netherlands)

    Eijk, J.J.J. van; Abdo, W.F.; Deurwaarder, E. den; Zwarts, M.J.; Warrenburg, B.P.C. van de

    2010-01-01

    A 46-year-old man receiving tube feeding because of anorexia and weight loss developed progressive neurological symptoms initially resembling Guillain-Barre syndrome. Eventually axonal neuropathy due to severe hypophosphatemia was diagnosed. Hypophosphatemia can be caused by the so-called refeeding

  9. The Microtubule Regulatory Protein Stathmin Is Required to Maintain the Integrity of Axonal Microtubules in Drosophila

    Science.gov (United States)

    Duncan, Jason E.; Lytle, Nikki K.; Zuniga, Alfredo; Goldstein, Lawrence S. B.

    2013-01-01

    Axonal transport, a form of long-distance, bi-directional intracellular transport that occurs between the cell body and synaptic terminal, is critical in maintaining the function and viability of neurons. We have identified a requirement for the stathmin (stai) gene in the maintenance of axonal microtubules and regulation of axonal transport in Drosophila . The stai gene encodes a cytosolic phosphoprotein that regulates microtubule dynamics by partitioning tubulin dimers between pools of soluble tubulin and polymerized microtubules, and by directly binding to microtubules and promoting depolymerization. Analysis of stai function in Drosophila , which has a single stai gene, circumvents potential complications with studies performed in vertebrate systems in which mutant phenotypes may be compensated by genetic redundancy of other members of the stai gene family. This has allowed us to identify an essential function for stai in the maintenance of the integrity of axonal microtubules. In addition to the severe disruption in the abundance and architecture of microtubules in the axons of stai mutant Drosophila , we also observe additional neurological phenotypes associated with loss of stai function including a posterior paralysis and tail-flip phenotype in third instar larvae, aberrant accumulation of transported membranous organelles in stai deficient axons, a progressive bang-sensitive response to mechanical stimulation reminiscent of the class of Drosophila mutants used to model human epileptic seizures, and a reduced adult lifespan. Reductions in the levels of Kinesin-1, the primary anterograde motor in axonal transport, enhance these phenotypes. Collectively, our results indicate that stai has an important role in neuronal function, likely through the maintenance of microtubule integrity in the axons of nerves of the peripheral nervous system necessary to support and sustain long-distance axonal transport. PMID:23840848

  10. Profiling neurotransmitter receptor expression in the Ambystoma mexicanum brain.

    Science.gov (United States)

    Reyes-Ruiz, Jorge Mauricio; Limon, Agenor; Korn, Matthew J; Nakamura, Paul A; Shirkey, Nicole J; Wong, Jamie K; Miledi, Ricardo

    2013-03-22

    Ability to regenerate limbs and central nervous system (CNS) is unique to few vertebrates, most notably the axolotl (Ambystoma sp.). However, despite the fact the neurotransmitter receptors are involved in axonal regeneration, little is known regarding its expression profile. In this project, RT-PCR and qPCR were performed to gain insight into the neurotransmitter receptors present in Ambystoma. Its functional ability was studied by expressing axolotl receptors in Xenopus laevis oocytes by either injection of mRNA or by direct microtransplantation of brain membranes. Oocytes injected with axolotl mRNA expressed ionotropic receptors activated by GABA, aspartate+glycine and kainate, as well as metabotropic receptors activated by acetylcholine and glutamate. Interestingly, we did not see responses following the application of serotonin. Membranes from the axolotl brain were efficiently microtransplanted into Xenopus oocytes and two types of native GABA receptors that differed in the temporal course of their responses and affinities to GABA were observed. Results of this study are necessary for further characterization of axolotl neurotransmitter receptors and may be useful for guiding experiments aimed at understanding activity-dependant limb and CNS regeneration. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  11. Oxidative stress and proinflammatory cytokines contribute to demyelination and axonal damage in a cerebellar culture model of neuroinflammation.

    Science.gov (United States)

    di Penta, Alessandra; Moreno, Beatriz; Reix, Stephanie; Fernandez-Diez, Begoña; Villanueva, Maite; Errea, Oihana; Escala, Nagore; Vandenbroeck, Koen; Comella, Joan X; Villoslada, Pablo

    2013-01-01

    Demyelination and axonal damage are critical processes in the pathogenesis of multiple sclerosis (MS). Oxidative stress and pro-inflammatory cytokines elicited by inflammation mediates tissue damage. To monitor the demyelination and axonal injury associated with microglia activation we employed a model using cerebellar organotypic cultures stimulated with lipopolysaccharide (LPS). Microglia activated by LPS released pro-inflammatory cytokines (IL-1β, IL-6 and TNFα), and increased the expression of inducible nitric oxide synthase (iNOS) and production of reactive oxygen species (ROS). This activation was associated with demyelination and axonal damage in cerebellar cultures. Axonal damage, as revealed by the presence of non-phosphorylated neurofilaments, mitochondrial accumulation in axonal spheroids, and axonal transection, was associated with stronger iNOS expression and concomitant increases in ROS. Moreover, we analyzed the contribution of pro-inflammatory cytokines and oxidative stress in demyelination and axonal degeneration using the iNOS inhibitor ethyl pyruvate, a free-scavenger and xanthine oxidase inhibitor allopurinol, as well as via blockage of pro-inflammatory cytokines using a Fc-TNFR1 construct. We found that blocking microglia activation with ethyl pyruvate or allopurinol significantly decreased axonal damage, and to a lesser extent, demyelination. Blocking TNFα significantly decreased demyelination but did not prevented axonal damage. Moreover, the most common therapy for MS, interferon-beta, was used as an example of an immunomodulator compound that can be tested in this model. In vitro, interferon-beta treatment decreased oxidative stress (iNOS and ROS levels) and the release of pro-inflammatory cytokines after LPS stimulation, reducing axonal damage. The model of neuroinflammation using cerebellar culture stimulated with endotoxin mimicked myelin and axonal damage mediated by the combination of oxidative stress and pro-inflammatory cytokines

  12. Drug therapy for chronic idiopathic axonal polyneuropathy

    NARCIS (Netherlands)

    Warendorf, Janna; Vrancken, Alexander F.J.E.; van Schaik, Ivo N.; Hughes, Richard A.C.; Notermans, Nicolette C.

    2017-01-01

    Background: Chronic idiopathic axonal polyneuropathy (CIAP) is an insidiously progressive sensory or sensorimotor polyneuropathy that affects elderly people. Although severe disability or handicap does not occur, CIAP reduces quality of life. CIAP is diagnosed in 10% to 25% of people referred for

  13. Drug therapy for chronic idiopathic axonal polyneuropathy

    NARCIS (Netherlands)

    Warendorf, Janna; Vrancken, Alexander F. J. E.; van Schaik, Ivo N.; Hughes, Richard A. C.; Notermans, Nicolette C.

    2017-01-01

    Chronic idiopathic axonal polyneuropathy (CIAP) is an insidiously progressive sensory or sensorimotor polyneuropathy that affects elderly people. Although severe disability or handicap does not occur, CIAP reduces quality of life. CIAP is diagnosed in 10% to 25% of people referred for evaluation of

  14. Fractional cable equation for general geometry: A model of axons with swellings and anomalous diffusion

    Science.gov (United States)

    López-Sánchez, Erick J.; Romero, Juan M.; Yépez-Martínez, Huitzilin

    2017-09-01

    Different experimental studies have reported anomalous diffusion in brain tissues and notably this anomalous diffusion is expressed through fractional derivatives. Axons are important to understand neurodegenerative diseases such as multiple sclerosis, Alzheimer's disease, and Parkinson's disease. Indeed, abnormal accumulation of proteins and organelles in axons is a hallmark of these diseases. The diffusion in the axons can become anomalous as a result of this abnormality. In this case the voltage propagation in axons is affected. Another hallmark of different neurodegenerative diseases is given by discrete swellings along the axon. In order to model the voltage propagation in axons with anomalous diffusion and swellings, in this paper we propose a fractional cable equation for a general geometry. This generalized equation depends on fractional parameters and geometric quantities such as the curvature and torsion of the cable. For a cable with a constant radius we show that the voltage decreases when the fractional effect increases. In cables with swellings we find that when the fractional effect or the swelling radius increases, the voltage decreases. Similar behavior is obtained when the number of swellings and the fractional effect increase. Moreover, we find that when the radius swelling (or the number of swellings) and the fractional effect increase at the same time, the voltage dramatically decreases.

  15. Fiber Optic Detection of Action Potentials in Axons

    National Research Council Canada - National Science Library

    Smela, Elisabeth

    2006-01-01

    In prior exploratory research, we had designed a fiber optic sensor utilizing a long period Bragg grating for the purpose of detecting action potentials in axons optically, through a change in index...

  16. Regulated viral BDNF delivery in combination with Schwann cells promotes axonal regeneration through capillary alginate hydrogels after spinal cord injury.

    Science.gov (United States)

    Liu, Shengwen; Sandner, Beatrice; Schackel, Thomas; Nicholson, LaShae; Chtarto, Abdelwahed; Tenenbaum, Liliane; Puttagunta, Radhika; Müller, Rainer; Weidner, Norbert; Blesch, Armin

    2017-09-15

    Grafting of cell-seeded alginate capillary hydrogels into a spinal cord lesion site provides an axonal bridge while physically directing regenerating axonal growth in a linear pattern. However, without an additional growth stimulus, bridging axons fail to extend into the distal host spinal cord. Here we examined whether a combinatory strategy would support regeneration of descending axons across a cervical (C5) lateral hemisection lesion in the rat spinal cord. Following spinal cord transections, Schwann cell (SC)-seeded alginate hydrogels were grafted to the lesion site and AAV5 expressing brain-derived neurotrophic factor (BDNF) under control of a tetracycline-regulated promoter was injected caudally. In addition, we examined whether SC injection into the caudal spinal parenchyma would further enhance regeneration of descending axons to re-enter the host spinal cord. Our data show that both serotonergic and descending axons traced by biotinylated dextran amine (BDA) extend throughout the scaffolds. The number of regenerating axons is significantly increased when caudal BDNF expression is activated and transient BDNF delivery is able to sustain axons after gene expression is switched off. Descending axons are confined to the caudal graft/host interface even with continuous BDNF expression for 8weeks. Only with a caudal injection of SCs, a pathway facilitating axonal regeneration through the host/graft interface is generated allowing axons to successfully re-enter the caudal spinal cord. Recovery from spinal cord injury is poor due to the limited regeneration observed in the adult mammalian central nervous system. Biomaterials, cell transplantation and growth factors that can guide axons across a lesion site, provide a cellular substrate, stimulate axon growth and have shown some promise in increasing the growth distance of regenerating axons. In the present study, we combined an alginate biomaterial with linear channels with transplantation of Schwann cells within

  17. Chlorpyrifos and chlorpyrifos-oxon inhibit axonal growth by interfering with the morphogenic activity of acetylcholinesterase

    International Nuclear Information System (INIS)

    Yang Dongren; Howard, Angela; Bruun, Donald; Ajua-Alemanj, Mispa; Pickart, Cecile; Lein, Pamela J.

    2008-01-01

    A primary role of acetylcholinesterase (AChE) is regulation of cholinergic neurotransmission by hydrolysis of synaptic acetylcholine. In the developing nervous system, however, AChE also functions as a morphogenic factor to promote axonal growth. This raises the question of whether organophosphorus pesticides (OPs) that are known to selectively bind to and inactivate the enzymatic function of AChE also interfere with its morphogenic function to perturb axonogenesis. To test this hypothesis, we exposed primary cultures of sensory neurons derived from embryonic rat dorsal root ganglia (DRG) to chlorpyrifos (CPF) or its oxon metabolite (CPFO). Both OPs significantly decreased axonal length at concentrations that had no effect on cell viability, protein synthesis or the enzymatic activity of AChE. Comparative analyses of the effects of CPF and CPFO on axonal growth in DRG neurons cultured from AChE nullizygous (AChE -/- ) versus wild type (AChE +/+ ) mice indicated that while these OPs inhibited axonal growth in AChE +/+ DRG neurons, they had no effect on axonal growth in AChE -/- DRG neurons. However, transfection of AChE -/- DRG neurons with cDNA encoding full-length AChE restored the wild type response to the axon inhibitory effects of OPs. These data indicate that inhibition of axonal growth by OPs requires AChE, but the mechanism involves inhibition of the morphogenic rather than enzymatic activity of AChE. These findings suggest a novel mechanism for explaining not only the functional deficits observed in children and animals following developmental exposure to OPs, but also the increased vulnerability of the developing nervous system to OPs

  18. Axonal degeneration stimulates the formation of NG2+ cells and oligodendrocytes in the mouse

    DEFF Research Database (Denmark)

    Nielsen, Helle Hvilsted; Ladeby, Rune; Drøjdahl, Nina

    2006-01-01

    the response of the NG2+ cells to the different components of demyelinating pathology, we investigated the response of adult NG2+ cells to axonal degeneration in the absence of primary myelin or oligodendrocyte pathology. Axonal degeneration was induced in the hippocampal dentate gyrus of adult mice...... by transection of the entorhino-dentate perforant path projection. The acutely induced degeneration of axons and terminals resulted in a prompt response of NG2+ cells, consisting of morphological transformation, cellular proliferation, and upregulation of NG2 expression days 2-3 after surgery. This was followed...

  19. Diapause formation and downregulation of insulin-like signaling via DAF-16/FOXO delays axonal degeneration and neuronal loss.

    Directory of Open Access Journals (Sweden)

    Andrea Calixto

    Full Text Available Axonal degeneration is a key event in the pathogenesis of neurodegenerative conditions. We show here that mec-4d triggered axonal degeneration of Caenorhabditis elegans neurons and mammalian axons share mechanistical similarities, as both are rescued by inhibition of calcium increase, mitochondrial dysfunction, and NMNAT overexpression. We then explore whether reactive oxygen species (ROS participate in axonal degeneration and neuronal demise. C. elegans dauers have enhanced anti-ROS systems, and dauer mec-4d worms are completely protected from axonal degeneration and neuronal loss. Mechanistically, downregulation of the Insulin/IGF-1-like signaling (IIS pathway protects neurons from degenerating in a DAF-16/FOXO-dependent manner and is related to superoxide dismutase and catalase-increased expression. Caloric restriction and systemic antioxidant treatment, which decrease oxidative damage, protect C. elegans axons from mec-4d-mediated degeneration and delay Wallerian degeneration in mice. In summary, we show that the IIS pathway is essential in maintaining neuronal homeostasis under pro-degenerative stimuli and identify ROS as a key intermediate of neuronal degeneration in vivo. Since axonal degeneration represents an early pathological event in neurodegeneration, our work identifies potential targets for therapeutic intervention in several conditions characterized by axonal loss and functional impairment.

  20. Cross-talk between KLF4 and STAT3 regulates axon regeneration

    Science.gov (United States)

    Qin, Song; Zou, Yuhua; Zhang, Chun-Li

    2013-10-01

    Cytokine-induced activation of signal transducer and activator of transcription 3 (STAT3) promotes the regrowth of damaged axons in the adult central nervous system (CNS). Here we show that KLF4 physically interacts with STAT3 upon cytokine-induced phosphorylation of tyrosine 705 (Y705) on STAT3. This interaction suppresses STAT3-dependent gene expression by blocking its DNA-binding activity. The deletion of KLF4 in vivo induces axon regeneration of adult retinal ganglion cells (RGCs) via Janus kinase (JAK)-STAT3 signalling. This regeneration can be greatly enhanced by exogenous cytokine treatment, or removal of an endogenous JAK-STAT3 pathway inhibitor called suppressor of cytokine signalling 3 (SOCS3). These findings reveal an unexpected cross-talk between KLF4 and activated STAT3 in the regulation of axon regeneration that might have therapeutic implications in promoting repair of injured adult CNS.

  1. Neurofilament subunit (NFL) head domain phosphorylation regulates axonal transport of neurofilaments.

    LENUS (Irish Health Repository)

    Yates, Darran M

    2009-04-01

    Neurofilaments are the intermediate filaments of neurons and are synthesised in neuronal cell bodies and then transported through axons. Neurofilament light chain (NFL) is a principal component of neurofilaments, and phosphorylation of NFL head domain is believed to regulate the assembly of neurofilaments. However, the role that NFL phosphorylation has on transport of neurofilaments is poorly understood. To address this issue, we monitored axonal transport of phosphorylation mutants of NFL. We mutated four known phosphorylation sites in NFL head domain to either preclude phosphorylation, or mimic permanent phosphorylation. Mutation to preclude phosphorylation had no effect on transport but mutation of three sites to mimic permanent phosphorylation inhibited transport. Mutation of all four sites together to mimic permanent phosphorylation proved especially potent at inhibiting transport and also disrupted neurofilament assembly. Our results suggest that NFL head domain phosphorylation is a regulator of neurofilament axonal transport.

  2. Internalization and Axonal Transport of the HIV Glycoprotein gp120

    Science.gov (United States)

    Berth, Sarah; Caicedo, Hector Hugo; Sarma, Tulika; Morfini, Gerardo

    2015-01-01

    The HIV glycoprotein gp120, a neurotoxic HIV glycoprotein that is overproduced and shed by HIV-infected macrophages, is associated with neurological complications of HIV such as distal sensory polyneuropathy, but interactions of gp120 in the peripheral nervous system remain to be characterized. Here, we demonstrate internalization of extracellular gp120 in a manner partially independent of binding to its coreceptor CXCR4 by F11 neuroblastoma cells and cultured dorsal root ganglion neurons. Immunocytochemical and pharmacological experiments indicate that gp120 does not undergo trafficking through the endolysosomal pathway. Instead, gp120 is mainly internalized through lipid rafts in a cholesterol-dependent manner, with a minor fraction being internalized by fluid phase pinocytosis. Experiments using compartmentalized microfluidic chambers further indicate that, after internalization, endocytosed gp120 selectively undergoes retrograde but not anterograde axonal transport from axons to neuronal cell bodies. Collectively, these studies illuminate mechanisms of gp120 internalization and axonal transport in peripheral nervous system neurons, providing a novel framework for mechanisms for gp120 neurotoxicity. PMID:25636314

  3. Oxytocin and Estrogen Receptor β in the Brain: An Overview

    OpenAIRE

    Acevedo-Rodriguez, Alexandra; Mani, Shaila K.; Handa, Robert J.

    2015-01-01

    Oxytocin is a neuropeptide synthesized primarily by neurons of the paraventricular and supraoptic nuclei of the hypothalamus. These neurons have axons that project into the posterior pituitary and release oxytocin into the bloodstream to promote labor and lactation; however, oxytocin neurons also project to other brain areas where it plays a role in numerous brain functions. Oxytocin binds to the widely expressed oxytocin receptor, and, in doing so, it regulates homeostatic processes, social ...

  4. Schwann cell transplantation improves reticulospinal axon growth and forelimb strength after severe cervical spinal cord contusion.

    Science.gov (United States)

    Schaal, S M; Kitay, B M; Cho, K S; Lo, T P; Barakat, D J; Marcillo, A E; Sanchez, A R; Andrade, C M; Pearse, D D

    2007-01-01

    Schwann cell (SC) implantation alone has been shown to promote the growth of propriospinal and sensory axons, but not long-tract descending axons, after thoracic spinal cord injury (SCI). In the current study, we examined if an axotomy close to the cell body of origin (so as to enhance the intrinsic growth response) could permit supraspinal axons to grow onto SC grafts. Adult female Fischer rats received a severe (C5) cervical contusion (1.1 mm displacement, 3 KDyn). At 1 week postinjury, 2 million SCs ex vivo transduced with lentiviral vector encoding enhanced green fluorescent protein (EGFP) were implanted within media into the injury epicenter; injury-only animals served as controls. Animals were tested weekly using the BBB score for 7 weeks postimplantation and received at end point tests for upper body strength: self-supported forelimb hanging, forearm grip force, and the incline plane. Following behavioral assessment, animals were anterogradely traced bilaterally from the reticular formation using BDA-Texas Red. Stereological quantification revealed a twofold increase in the numbers of preserved NeuN+ neurons rostral and caudal to the injury/graft site in SC implanted animals, corroborating previous reports of their neuroprotective efficacy. Examination of labeled reticulospinal axon growth revealed that while rarely an axon was present within the lesion site of injury-only controls, numerous reticulospinal axons had penetrated the SC implant/lesion milieu. This has not been observed following implantation of SCs alone into the injured thoracic spinal cord. Significant behavioral improvements over injury-only controls in upper limb strength, including an enhanced grip strength (a 296% increase) and an increased self-supported forelimb hanging, accompanied SC-mediated neuroprotection and reticulospinal axon growth. The current study further supports the neuroprotective efficacy of SC implants after SCI and demonstrates that SCs alone are capable of supporting

  5. Craniocerebral trauma. Magnetic resonance imaging of diffuse axonal injury

    International Nuclear Information System (INIS)

    Mallouhi, A.

    2014-01-01

    Acceleration-deceleration rotational brain trauma is a common cause of disability or death in young adults and often leads to a focal destruction of axons. The resulting pathology, axonal shear injury is referred to as diffuse axonal injury (DAI). The DAI-associated lesions occur bilaterally, are widely dispersed and have been observed in the surface and deep white matter. They are found near to and far from the impact site. When DAI is clinically suspected, magnetic resonance imaging (MRI) is the method of choice for further clarification, especially in patients where cranial computed tomography (CT) is inconspicuous. To investigate the presence of DAI after traumatic brain injury (TBI), a multimodal MRI approach is applied including the common structural and also functional imaging sequences. For structural MRI, fluid-attenuated inversion recovery (FLAIR) weighted and susceptibility contrast imaging (SWI) are the sequences mainly used. The SWI technique is extremely sensitive to blood breakdown products, which appear as small signal voids at three locations, at the gray-white interface, in the corpus callosum and in the brain stem. Functional MRI comprises a group of constantly developing techniques that have great potential in optimal evaluation of the white matter in patients after craniocerebral trauma. These imaging techniques allow the visualization of changes associated with shear injuries, such as functional impairment of axons and decreased blood flow and abnormal metabolic activity of the brain parts affected. The multimodal MRI approach in patients with DAI results in a more detailed and differentiated representation of the underlying pathophysiological changes of the injured nerve tracts and helps to improve the diagnostic and prognostic accuracy of MRI. When DAI is suspected multimodal MRI should be performed as soon as possible after craniocerebral injury. (orig.) [de

  6. Polyethylene glycol restores axonal conduction after corpus callosum transection

    Directory of Open Access Journals (Sweden)

    Ravinder Bamba

    2017-01-01

    Full Text Available Polyethylene glycol (PEG has been shown to restore axonal continuity after peripheral nerve transection in animal models. We hypothesized that PEG can also restore axonal continuity in the central nervous system. In this current experiment, coronal sectioning of the brains of Sprague-Dawley rats was performed after animal sacrifice. 3Brain high-resolution microelectrode arrays (MEA were used to measure mean firing rate (MFR and peak amplitude across the corpus callosum of the ex-vivo brain slices. The corpus callosum was subsequently transected and repeated measurements were performed. The cut ends of the corpus callosum were still apposite at this time. A PEG solution was applied to the injury site and repeated measurements were performed. MEA measurements showed that PEG was capable of restoring electrophysiology signaling after transection of central nerves. Before injury, the average MFRs at the ipsilateral, midline, and contralateral corpus callosum were 0.76, 0.66, and 0.65 spikes/second, respectively, and the average peak amplitudes were 69.79, 58.68, and 49.60 μV, respectively. After injury, the average MFRs were 0.71, 0.14, and 0.25 spikes/second, respectively and peak amplitudes were 52.11, 8.98, and 16.09 μV, respectively. After application of PEG, there were spikes in MFR and peak amplitude at the injury site and contralaterally. The average MFRs were 0.75, 0.55, and 0.47 spikes/second at the ipsilateral, midline, and contralateral corpus callosum, respectively and peak amplitudes were 59.44, 45.33, 40.02 μV, respectively. There were statistically differences in the average MFRs and peak amplitudes between the midline and non-midline corpus callosum groups (P < 0.01, P < 0.05. These findings suggest that PEG restores axonal conduction between severed central nerves, potentially representing axonal fusion.

  7. Polyethylene glycol restores axonal conduction after corpus callosum transection.

    Science.gov (United States)

    Bamba, Ravinder; Riley, D Colton; Boyer, Richard B; Pollins, Alonda C; Shack, R Bruce; Thayer, Wesley P

    2017-05-01

    Polyethylene glycol (PEG) has been shown to restore axonal continuity after peripheral nerve transection in animal models. We hypothesized that PEG can also restore axonal continuity in the central nervous system. In this current experiment, coronal sectioning of the brains of Sprague-Dawley rats was performed after animal sacrifice. 3Brain high-resolution microelectrode arrays (MEA) were used to measure mean firing rate (MFR) and peak amplitude across the corpus callosum of the ex-vivo brain slices. The corpus callosum was subsequently transected and repeated measurements were performed. The cut ends of the corpus callosum were still apposite at this time. A PEG solution was applied to the injury site and repeated measurements were performed. MEA measurements showed that PEG was capable of restoring electrophysiology signaling after transection of central nerves. Before injury, the average MFRs at the ipsilateral, midline, and contralateral corpus callosum were 0.76, 0.66, and 0.65 spikes/second, respectively, and the average peak amplitudes were 69.79, 58.68, and 49.60 μV, respectively. After injury, the average MFRs were 0.71, 0.14, and 0.25 spikes/second, respectively and peak amplitudes were 52.11, 8.98, and 16.09 μV, respectively. After application of PEG, there were spikes in MFR and peak amplitude at the injury site and contralaterally. The average MFRs were 0.75, 0.55, and 0.47 spikes/second at the ipsilateral, midline, and contralateral corpus callosum, respectively and peak amplitudes were 59.44, 45.33, 40.02 μV, respectively. There were statistically differences in the average MFRs and peak amplitudes between the midline and non-midline corpus callosum groups ( P < 0.01, P < 0.05). These findings suggest that PEG restores axonal conduction between severed central nerves, potentially representing axonal fusion.

  8. PTEN deletion from adult-generated dentate granule cells disrupts granule cell mossy fiber axon structure.

    Science.gov (United States)

    LaSarge, Candi L; Santos, Victor R; Danzer, Steve C

    2015-03-01

    Dysregulation of the mTOR-signaling pathway is implicated in the development of temporal lobe epilepsy. In mice, deletion of PTEN from hippocampal dentate granule cells leads to mTOR hyperactivation and promotes the rapid onset of spontaneous seizures. The mechanism by which these abnormal cells initiate epileptogenesis, however, is unclear. PTEN-knockout granule cells develop abnormally, exhibiting morphological features indicative of increased excitatory input. If these cells are directly responsible for seizure genesis, it follows that they should also possess increased output. To test this prediction, dentate granule cell axon morphology was quantified in control and PTEN-knockout mice. Unexpectedly, PTEN deletion increased giant mossy fiber bouton spacing along the axon length, suggesting reduced innervation of CA3. Increased width of the mossy fiber axon pathway in stratum lucidum, however, which likely reflects an unusual increase in mossy fiber axon collateralization in this region, offsets the reduction in boutons per axon length. These morphological changes predict a net increase in granule cell innervation of CA3. Increased diameter of axons from PTEN-knockout cells would further enhance granule cell communication with CA3. Altogether, these findings suggest that amplified information flow through the hippocampal circuit contributes to seizure occurrence in the PTEN-knockout mouse model of temporal lobe epilepsy. Copyright © 2015 Elsevier Inc. All rights reserved.

  9. Cell intrinsic modulation of Wnt signaling controls neuroblast migration in C. elegans.

    Science.gov (United States)

    Mentink, Remco A; Middelkoop, Teije C; Rella, Lorenzo; Ji, Ni; Tang, Chung Yin; Betist, Marco C; van Oudenaarden, Alexander; Korswagen, Hendrik C

    2014-10-27

    Members of the Wnt family of secreted signaling proteins are key regulators of cell migration and axon guidance. In the nematode C. elegans, the migration of the QR neuroblast descendants requires multiple Wnt ligands and receptors. We found that the migration of the QR descendants is divided into three sequential phases that are each mediated by a distinct Wnt signaling mechanism. Importantly, the transition from the first to the second phase, which is the main determinant of the final position of the QR descendants along the anteroposterior body axis, is mediated through a cell-autonomous process in which the time-dependent expression of a Wnt receptor turns on the canonical Wnt/β-catenin signaling response that is required to terminate long-range anterior migration. Our results show that, in addition to direct guidance of cell migration by Wnt morphogenic gradients, cell migration can also be controlled indirectly through cell-intrinsic modulation of Wnt signaling responses.

  10. Oxidative Stress and Proinflammatory Cytokines Contribute to Demyelination and Axonal Damage in a Cerebellar Culture Model of Neuroinflammation

    Science.gov (United States)

    di Penta, Alessandra; Moreno, Beatriz; Reix, Stephanie; Fernandez-Diez, Begoña; Villanueva, Maite; Errea, Oihana; Escala, Nagore; Vandenbroeck, Koen; Comella, Joan X.; Villoslada, Pablo

    2013-01-01

    Background Demyelination and axonal damage are critical processes in the pathogenesis of multiple sclerosis (MS). Oxidative stress and pro-inflammatory cytokines elicited by inflammation mediates tissue damage. Methods/Principal Findings To monitor the demyelination and axonal injury associated with microglia activation we employed a model using cerebellar organotypic cultures stimulated with lipopolysaccharide (LPS). Microglia activated by LPS released pro-inflammatory cytokines (IL-1β, IL-6 and TNFα), and increased the expression of inducible nitric oxide synthase (iNOS) and production of reactive oxygen species (ROS). This activation was associated with demyelination and axonal damage in cerebellar cultures. Axonal damage, as revealed by the presence of non-phosphorylated neurofilaments, mitochondrial accumulation in axonal spheroids, and axonal transection, was associated with stronger iNOS expression and concomitant increases in ROS. Moreover, we analyzed the contribution of pro-inflammatory cytokines and oxidative stress in demyelination and axonal degeneration using the iNOS inhibitor ethyl pyruvate, a free-scavenger and xanthine oxidase inhibitor allopurinol, as well as via blockage of pro-inflammatory cytokines using a Fc-TNFR1 construct. We found that blocking microglia activation with ethyl pyruvate or allopurinol significantly decreased axonal damage, and to a lesser extent, demyelination. Blocking TNFα significantly decreased demyelination but did not prevented axonal damage. Moreover, the most common therapy for MS, interferon-beta, was used as an example of an immunomodulator compound that can be tested in this model. In vitro, interferon-beta treatment decreased oxidative stress (iNOS and ROS levels) and the release of pro-inflammatory cytokines after LPS stimulation, reducing axonal damage. Conclusion The model of neuroinflammation using cerebellar culture stimulated with endotoxin mimicked myelin and axonal damage mediated by the combination of

  11. Genetic dysfunction of MT-ATP6 causes axonal Charcot-Marie-Tooth disease.

    LENUS (Irish Health Repository)

    Pitceathly, Robert D S

    2012-09-11

    Charcot-Marie-Tooth (CMT) disease is the most common inherited neuromuscular disorder, affecting 1 in 2,500 individuals. Mitochondrial DNA (mtDNA) mutations are not generally considered within the differential diagnosis of patients with uncomplicated inherited neuropathy, despite the essential requirement of ATP for axonal function. We identified the mtDNA mutation m.9185T>C in MT-ATP6, encoding the ATP6 subunit of the mitochondrial ATP synthase (OXPHOS complex V), at homoplasmic levels in a family with mitochondrial disease in whom a severe motor axonal neuropathy was a striking feature. This led us to hypothesize that mutations in the 2 mtDNA complex V subunit encoding genes, MT-ATP6 and MT-ATP8, might be an unrecognized cause of isolated axonal CMT and distal hereditary motor neuropathy (dHMN).

  12. A novel ALS-associated variant in UBQLN4 regulates motor axon morphogenesis

    Science.gov (United States)

    Edens, Brittany M; Yan, Jianhua; Miller, Nimrod; Deng, Han-Xiang; Siddique, Teepu; Ma, Yongchao C

    2017-01-01

    The etiological underpinnings of amyotrophic lateral sclerosis (ALS) are complex and incompletely understood, although contributions to pathogenesis by regulators of proteolytic pathways have become increasingly apparent. Here, we present a novel variant in UBQLN4 that is associated with ALS and show that its expression compromises motor axon morphogenesis in mouse motor neurons and in zebrafish. We further demonstrate that the ALS-associated UBQLN4 variant impairs proteasomal function, and identify the Wnt signaling pathway effector beta-catenin as a UBQLN4 substrate. Inhibition of beta-catenin function rescues the UBQLN4 variant-induced motor axon phenotypes. These findings provide a strong link between the regulation of axonal morphogenesis and a new ALS-associated gene variant mediated by protein degradation pathways. DOI: http://dx.doi.org/10.7554/eLife.25453.001 PMID:28463112

  13. In Vitro Analysis of the Role of Schwann Cells on Axonal Degeneration and Regeneration Using Sensory Neurons from Dorsal Root Ganglia.

    Science.gov (United States)

    López-Leal, Rodrigo; Diaz, Paula; Court, Felipe A

    2018-01-01

    Sensory neurons from dorsal root ganglion efficiently regenerate after peripheral nerve injuries. These neurons are widely used as a model system to study degenerative mechanisms of the soma and axons, as well as regenerative axonal growth in the peripheral nervous system. This chapter describes techniques associated to the study of axonal degeneration and regeneration using explant cultures of dorsal root ganglion sensory neurons in vitro in the presence or absence of Schwann cells. Schwann cells are extremely important due to their involvement in tissue clearance during axonal degeneration as well as their known pro-regenerative effect during regeneration in the peripheral nervous system. We describe methods to induce and study axonal degeneration triggered by axotomy (mechanical separation of the axon from its soma) and treatment with vinblastine (which blocks axonal transport), which constitute clinically relevant mechanical and toxic models of axonal degeneration. In addition, we describe three different methods to evaluate axonal regeneration using quantitative methods. These protocols constitute a valuable tool to analyze in vitro mechanisms associated to axonal degeneration and regeneration of sensory neurons and the role of Schwann cells in these processes.

  14. Reduced axonal transport in Parkinson's disease cybrid neurites is restored by light therapy

    Directory of Open Access Journals (Sweden)

    De Taboada Luis

    2009-06-01

    Full Text Available Abstract Background It has been hypothesized that reduced axonal transport contributes to the degeneration of neuronal processes in Parkinson's disease (PD. Mitochondria supply the adenosine triphosphate (ATP needed to support axonal transport and contribute to many other cellular functions essential for the survival of neuronal cells. Furthermore, mitochondria in PD tissues are metabolically and functionally compromised. To address this hypothesis, we measured the velocity of mitochondrial movement in human transmitochondrial cybrid "cytoplasmic hybrid" neuronal cells bearing mitochondrial DNA from patients with sporadic PD and disease-free age-matched volunteer controls (CNT. The absorption of low level, near-infrared laser light by components of the mitochondrial electron transport chain (mtETC enhances mitochondrial metabolism, stimulates oxidative phosphorylation and improves redox capacity. PD and CNT cybrid neuronal cells were exposed to near-infrared laser light to determine if the velocity of mitochondrial movement can be restored by low level light therapy (LLLT. Axonal transport of labeled mitochondria was documented by time lapse microscopy in dopaminergic PD and CNT cybrid neuronal cells before and after illumination with an 810 nm diode laser (50 mW/cm2 for 40 seconds. Oxygen utilization and assembly of mtETC complexes were also determined. Results The velocity of mitochondrial movement in PD cybrid neuronal cells (0.175 +/- 0.005 SEM was significantly reduced (p Conclusion The results from this study support our proposal that axonal transport is reduced in sporadic PD and that a single, brief treatment with near-infrared light can restore axonal transport to control levels. These results are the first demonstration that LLLT can increase axonal transport in model human dopaminergic neuronal cells and they suggest that LLLT could be developed as a novel treatment to improve neuronal function in patients with PD.

  15. Drosophila growth cones: a genetically tractable platform for the analysis of axonal growth dynamics.

    Science.gov (United States)

    Sánchez-Soriano, Natalia; Gonçalves-Pimentel, Catarina; Beaven, Robin; Haessler, Ulrike; Ofner-Ziegenfuss, Lisa; Ballestrem, Christoph; Prokop, Andreas

    2010-01-01

    The formation of neuronal networks, during development and regeneration, requires outgrowth of axons along reproducible paths toward their appropriate postsynaptic target cells. Axonal extension occurs at growth cones (GCs) at the tips of axons. GC advance and navigation requires the activity of their cytoskeletal networks, comprising filamentous actin (F-actin) in lamellipodia and filopodia as well as dynamic microtubules (MTs) emanating from bundles of the axonal core. The molecular mechanisms governing these two cytoskeletal networks, their cross-talk, and their response to extracellular signaling cues are only partially understood, hindering our conceptual understanding of how regulated changes in GC behavior are controlled. Here, we introduce Drosophila GCs as a suitable model to address these mechanisms. Morphological and cytoskeletal readouts of Drosophila GCs are similar to those of other models, including mammals, as demonstrated here for MT and F-actin dynamics, axonal growth rates, filopodial structure and motility, organizational principles of MT networks, and subcellular marker localization. Therefore, we expect fundamental insights gained in Drosophila to be translatable into vertebrate biology. The advantage of the Drosophila model over others is its enormous amenability to combinatorial genetics as a powerful strategy to address the complexity of regulatory networks governing axonal growth. Thus, using pharmacological and genetic manipulations, we demonstrate a role of the actin cytoskeleton in a specific form of MT organization (loop formation), known to regulate GC pausing behavior. We demonstrate these events to be mediated by the actin-MT linking factor Short stop, thus identifying an essential molecular player in this context.

  16. γ-diketone central neuropathy: quantitative morphometric analysis of axons in rat spinal cord white matter regions and nerve roots

    International Nuclear Information System (INIS)

    LoPachin, Richard M.; Jortner, Bernard S.; Reid, Maria L.; Das, Soma

    2003-01-01

    A quantitative analytical method was used to measure myelinated axon morphometric parameters (e.g., axon area, ratio of axon area/fiber area, and index of circularity) in rat nervous tissue during intoxication with 2,5-hexanedione (HD). Parameters were assessed in nerve roots (dorsal and ventral) and in ascending (gracile fasciculus and spinocerebellar tract) and descending (corticospinal and rubrospinal tracts) spinal cord white matter tracts (L4-L5) of rats intoxicated with HD at two different daily dose-rates (175 or 400 mg HD/kg/day, gavage). For each dose-rate, tissue was sampled at four neurological endpoints: unaffected, slight, moderate, and severe toxicity, as determined by gait analysis and measurements of grip strength. Results indicate that, regardless of the HD dose-rate, axon atrophy (reduced axon area) was a widespread, abundant effect that developed in concert with neurological deficits. The atrophy response occurred contemporaneously in both ascending and descending spinal tracts, which suggests that loss of caliber developed simultaneously along the proximodistal axon axis. In contrast, swollen axons were a numerically small component and were present in nerve roots and spinal tracts only during subchronic intoxication at the lower HD dose-rate (i.e., 175 mg/kg/day). Intoxication at the higher dose-rate (400 mg/kg/day) produced neurological deficits in the absence of axonal swellings. These observations in conjunction with our previous studies of HD-induced peripheral neuropathy (Toxicol. Appl. Pharmacol. 135 (1995) 58; and Toxicol. Appl. Pharmacol. 165 (2000) 127) indicate that axon atrophy, and not axonal swelling, is a primary neuropathic phenomenon

  17. Muscarinic receptors modulate dendrodendritic inhibitory synapses to sculpt glomerular output.

    Science.gov (United States)

    Liu, Shaolin; Shao, Zuoyi; Puche, Adam; Wachowiak, Matt; Rothermel, Markus; Shipley, Michael T

    2015-04-08

    Cholinergic [acetylcholine (ACh)] axons from the basal forebrain innervate olfactory bulb glomeruli, the initial site of synaptic integration in the olfactory system. Both nicotinic acetylcholine receptors (nAChRs) and muscarinic acetylcholine receptors (mAChRs) are expressed in glomeruli. The activation of nAChRs directly excites both mitral/tufted cells (MTCs) and external tufted cells (ETCs), the two major excitatory neurons that transmit glomerular output. The functional roles of mAChRs in glomerular circuits are unknown. We show that the restricted glomerular application of ACh causes rapid, brief nAChR-mediated excitation of both MTCs and ETCs in the mouse olfactory bulb. This excitation is followed by mAChR-mediated inhibition, which is blocked by GABAA receptor antagonists, indicating the engagement of periglomerular cells (PGCs) and/or short axon cells (SACs), the two major glomerular inhibitory neurons. Indeed, selective activation of glomerular mAChRs, with ionotropic GluRs and nAChRs blocked, increased IPSCs in MTCs and ETCs, indicating that mAChRs recruit glomerular inhibitory circuits. Selective activation of glomerular mAChRs in the presence of tetrodotoxin increased IPSCs in all glomerular neurons, indicating action potential-independent enhancement of GABA release from PGC and/or SAC dendrodendritic synapses. mAChR-mediated enhancement of GABA release also presynaptically suppressed the first synapse of the olfactory system via GABAB receptors on sensory terminals. Together, these results indicate that cholinergic modulation of glomerular circuits is biphasic, involving an initial excitation of MTC/ETCs mediated by nAChRs followed by inhibition mediated directly by mAChRs on PGCs/SACs. This may phasically enhance the sensitivity of glomerular outputs to odorants, an action that is consistent with recent in vivo findings. Copyright © 2015 the authors 0270-6474/15/355680-13$15.00/0.

  18. 3Tesla magnetic resonance examination of a patient suffering from diffuse axonal injury

    International Nuclear Information System (INIS)

    Bonchev, S.; Zlatareva, D.; Hadjidekov, V.

    2016-01-01

    Diffuse axonal injury has been observed in traumatic brain injury. Both type of lesions - haemorrhagic and non-haemorrhagic, demonstrate on MRI. We would like to introduce you a 24 year old outpatient man, who was examined in our Department with a past medical history of severe traumatic brain injury, followed by two weeks of coma in Intensive care, discharged from hospital with good outcome. Subsequently cognitive impairments have developed and an episode of tonic-clonic seizure have been undergone by the patient. 3Tesla MRI was performed and lesions typical for diffuse axonal injury were found. MRI is the study of choice for demonstrating the lesions of diffuse axonal injury in the acute and chronic period

  19. Dendrites of cerebellar granule cells correctly recognize their target axons for synaptogenesis in vitro.

    Science.gov (United States)

    Ito, Shoko; Takeichi, Masatoshi

    2009-08-04

    Neural circuits are generated by precisely ordered synaptic connections among neurons, and this process is thought to rely on the ability of neurons to recognize specific partners. However, it is also known that neurons promiscuously form synapses with nonspecific partners, in particular when cultured in vitro, causing controversies about neural recognition mechanisms. Here we reexamined whether neurons can or cannot select particular partners in vitro. In the cerebellum, granule cell (GC) dendrites form synaptic connections specifically with mossy fibers, but not with climbing fibers. We cocultured GC neurons with pontine or inferior olivary axons, the major sources for mossy and climbing fibers, respectively, as well as with hippocampal axons as a control. The GC neurons formed synapses with pontine axons predominantly at the distal ends of their dendrites, reproducing the characteristic morphology of their synapses observed in vivo, whereas they failed to do so when combined with other axons. In the latter case, synaptic proteins could accumulate between axons and dendrites, but these synapses were randomly distributed throughout the contact sites, and also their synaptic vesicle recycling was anomalous. These observations suggest that GC dendrites can select their authentic partners for synaptogenesis even in vitro, forming the synapses with a GC-specific nature only with them.

  20. Sodium channels in axons and glial cells of the optic nerve of Necturus maculosa.

    Science.gov (United States)

    Tang, C M; Strichartz, G R; Orkand, R K

    1979-11-01

    Experiments investigating both the binding of radioactively labelled saxitoxin (STX) and the electrophysiological response to drugs that increase the sodium permeability of excitable membranes were conducted in an effort to detect sodium channels in glial cells of the optic nerve of Necturus maculosa, the mudpuppy. Glial cells in nerves from chronically enucleated animals, which lack optic nerve axons, show no saturable uptake of STX whereas a saturable uptake is clearly present in normal optic nerves. The normal nerve is depolarized by aconitine, batrachotoxin, and veratridine (10(-6)-10(-5) M), whereas the all-glial preparation is only depolarized by veratridine and at concentrations greater than 10(-3) M. Unlike the depolarization caused by veratridine in normal nerves, the response in the all-glial tissue is not blocked by tetrodotoxin nor enhanced by scorpion venom (Leiurus quinquestriatus). In glial cells of the normal nerve, where axons are also present, the addition of 10(-5) M veratridine does lead to a transient depolarization; however, it is much briefer than the axonal response to veratridine in this same tissue. This glial response to veratridine could be caused by the efflux of K+ from the drug-depolarized axons, and is similar to the glial response to extracellular K+ accumulation resulting from action potentials in the axon.

  1. Postnatal Development of CB1 Receptor Expression in Rodent Somatosensory Cortex

    Science.gov (United States)

    Deshmukh, Suvarna; Onozuka, Kaori; Bender, Kevin J.; Bender, Vanessa A.; Lutz, Beat; Mackie, Ken; Feldman, Daniel E.

    2007-01-01

    Endocannabinoids are powerful modulators of synaptic transmission that act on presynaptic cannabinoid receptors. Cannabinoid receptor type 1 (CB1) is the dominant receptor in the CNS, and is present in many brain regions, including sensory cortex. To investigate the potential role of CB1 receptors in cortical development, we examined the developmental expression of CB1 in rodent primary somatosensory (barrel) cortex, using immunohistochemistry with a CB1-specific antibody. We found that before postnatal day (P) 6, CB1 receptor staining was present exclusively in the cortical white matter, and that CB1 staining appeared in the grey matter between P6 and P20 in a specific laminar pattern. CB1 staining was confined to axons, and was most prominent in cortical layers 2/3, 5a, and 6. CB1 null (−/−) mice showed altered anatomical barrel maps in layer 4, with enlarged inter-barrel septa, but normal barrel size. These results indicate that CB1 receptors are present in early postnatal development and influence development of sensory maps. PMID:17210229

  2. A Novel Approach for Studying the Physiology and Pathophysiology of Myelinated and Non-Myelinated Axons in the CNS White Matter.

    Directory of Open Access Journals (Sweden)

    Lijun Li

    Full Text Available Advances in brain connectomics set the need for detailed knowledge of functional properties of myelinated and non-myelinated (if present axons in specific white matter pathways. The corpus callosum (CC, a major white matter structure interconnecting brain hemispheres, is extensively used for studying CNS axonal function. Unlike another widely used CNS white matter preparation, the optic nerve where all axons are myelinated, the CC contains also a large population of non-myelinated axons, making it particularly useful for studying both types of axons. Electrophysiological studies of optic nerve use suction electrodes on nerve ends to stimulate and record compound action potentials (CAPs that adequately represent its axonal population, whereas CC studies use microelectrodes (MEs, recording from a limited area within the CC. Here we introduce a novel robust isolated "whole" CC preparation comparable to optic nerve. Unlike ME recordings where the CC CAP peaks representing myelinated and non-myelinated axons vary broadly in size, "whole" CC CAPs show stable reproducible ratios of these two main peaks, and also reveal a third peak, suggesting a distinct group of smaller caliber non-myelinated axons. We provide detailed characterization of "whole" CC CAPs and conduction velocities of myelinated and non-myelinated axons along the rostro-caudal axis of CC body and show advantages of this preparation for comparing axonal function in wild type and dysmyelinated shiverer mice, studying the effects of temperature dependence, bath-applied drugs and ischemia modeled by oxygen-glucose deprivation. Due to the isolation from gray matter, our approach allows for studying CC axonal function without possible "contamination" by reverberating signals from gray matter. Our analysis of "whole" CC CAPs revealed higher complexity of myelinated and non-myelinated axonal populations, not noticed earlier. This preparation may have a broad range of applications as a robust

  3. Conduction velocity is regulated by sodium channel inactivation in unmyelinated axons innervating the rat cranial meninges.

    Science.gov (United States)

    De Col, Roberto; Messlinger, Karl; Carr, Richard W

    2008-02-15

    Axonal conduction velocity varies according to the level of preceding impulse activity. In unmyelinated axons this typically results in a slowing of conduction velocity and a parallel increase in threshold. It is currently held that Na(+)-K(+)-ATPase-dependent axonal hyperpolarization is responsible for this slowing but this has long been equivocal. We therefore examined conduction velocity changes during repetitive activation of single unmyelinated axons innervating the rat cranial meninges. In direct contradiction to the currently accepted postulate, Na(+)-K(+)-ATPase blockade actually enhanced activity-induced conduction velocity slowing, while the degree of velocity slowing was curtailed in the presence of lidocaine (10-300 microm) and carbamazepine (30-500 microm) but not tetrodotoxin (TTX, 10-80 nm). This suggests that a change in the number of available sodium channels is the most prominent factor responsible for activity-induced changes in conduction velocity in unmyelinated axons. At moderate stimulus frequencies, axonal conduction velocity is determined by an interaction between residual sodium channel inactivation following each impulse and the retrieval of channels from inactivation by a concomitant Na(+)-K(+)-ATPase-mediated hyperpolarization. Since the process is primarily dependent upon sodium channel availability, tracking conduction velocity provides a means of accessing relative changes in the excitability of nociceptive neurons.

  4. Diffuse axonal injury: detection of changes in anisotropy of water diffusion by diffusion-weighted imaging

    International Nuclear Information System (INIS)

    Chan, J.H.M.; Tsui, E.Y.K.; Yuen, M.K.; Peh, W.C.G.; Fong, D.; Fok, K.F.; Leung, K.M.; Fung, K.K.L.

    2003-01-01

    Myelinated axons of white matter demonstrate prominent directional differences in water diffusion. We performed diffusion-weighted imaging on ten patients with head injury to explore the feasibility of using water diffusion anisotropy for quantitating diffuse axonal injury. We showed significant decrease in diffusion anisotropy indices in areas with or without signal abnormality on T2 and T2*-weighted images. We conclude that the water diffusion anisotropy index a potentially useful, sensitive and quantitative way of diagnosing and assessing patients with diffuse axonal injury. (orig.)

  5. Extracellular matrix and its receptors in Drosophila neural development

    Science.gov (United States)

    Broadie, Kendal; Baumgartner, Stefan; Prokop, Andreas

    2011-01-01

    Extracellular matrix (ECM) and matrix receptors are intimately involved in most biological processes. The ECM plays fundamental developmental and physiological roles in health and disease, including processes underlying the development, maintenance and regeneration of the nervous system. To understand the principles of ECM-mediated functions in the nervous system, genetic model organisms like Drosophila provide simple, malleable and powerful experimental platforms. This article provides an overview of ECM proteins and receptors in Drosophila. It then focuses on their roles during three progressive phases of neural development: 1) neural progenitor proliferation, 2) axonal growth and pathfinding and 3) synapse formation and function. Each section highlights known ECM and ECM-receptor components and recent studies done in mutant conditions to reveal their in vivo functions, all illustrating the enormous opportunities provided when merging work on the nervous system with systematic research into ECM-related gene functions. PMID:21688401

  6. The L1-type cell adhesion molecule Neuroglian is necessary for maintenance of sensory axon advance in the Drosophila embryo

    Directory of Open Access Journals (Sweden)

    Martin Veronica

    2008-04-01

    Full Text Available Abstract Background Cell adhesion molecules have long been implicated in the regulation of axon growth, but the precise cellular roles played by individual cell adhesion molecules and the molecular basis for their action are still not well understood. We have used the sensory system of the Drosophila embryo to shed light on the mechanism by which the L1-type cell adhesion molecule Neuroglian regulates axon growth. Results We have found a highly penetrant sensory axon stalling phenotype in neuroglian mutant embryos. Axons stalled at a variety of positions along their normal trajectory, but most commonly in the periphery some distance along the peripheral nerve. All lateral and dorsal cluster sensory neurons examined, except for the dorsal cluster neuron dbd, showed stalling. Sensory axons were never seen to project along inappropriate pathways in neuroglian mutants and stalled axons showed normal patterns of fasciculation within nerves. The growth cones of stalled axons possessed a simple morphology, similar to their appearance in wild-type embryos when advancing along nerves. Driving expression of the wild-type form of Neuroglian in sensory neurons alone rescued the neuroglian mutant phenotype of both pioneering and follower neurons. A partial rescue was achieved by expressing the Neuroglian extracellular domain. Over/mis-expression of Neuroglian in all neurons, oenocytes or trachea had no apparent effect on sensory axon growth. Conclusion We conclude that Neuroglian is necessary to maintain axon advance along axonal substrates, but is not required for initiation of axon outgrowth, axon fasciculation or recognition of correct growth substrates. Expression of Neuroglian in sensory neurons alone is sufficient to promote axon advance and the intracellular region of the molecule is largely dispensable for this function. It is unlikely, therefore, that Nrg acts as a molecular 'clutch' to couple adhesion of F-actin within the growth cone to the

  7. Impaired axonal Na+ current by hindlimb unloading: implication for disuse neuromuscular atrophy

    Directory of Open Access Journals (Sweden)

    Chimeglkham eBanzrai

    2016-02-01

    Full Text Available This study aimed to characterize the excitability changes in peripheral motor axons caused by hindlimb unloading, which is a model of disuse neuromuscular atrophy. Hindlimb unloading was performed in normal 6-week-old male mice by fixing the proximal tail by a clip connected to the top of the animal’s cage for 3 weeks. Axonal excitability studies were performed by stimulating the sciatic nerve at the ankle and recording the compound muscle action potential from the foot. The amplitudes of the motor responses of the unloading group were 51% of the control amplitudes (2.2 ± 1.3 mV [HLU] vs. 4.3 ± 1.2 mV [Control], P = 0.03. Multiple axonal excitability analysis showed that the unloading group had a smaller strength-duration time constant (SDTC and late subexcitability (recovery cycle than the controls (0.075 ± 0.01 [HLU] vs. 0.12 ± 0.01 [Control], P < 0.01; 5.4 ± 1.0 [HLU] vs. 10.0 ± 1.3 % [Control], P = 0.01, respectively. Three weeks after releasing from HLU, the SDTC became comparable to the control range. Using a modeling study, the observed differences in the waveforms could be explained by reduced persistent Na+ currents along with parameters related to current leakage. Quantification of RNA of a SCA1A gene coding a voltage-gated Na+ channel tended to be decreased in the sciatic nerve in HLU. The present study suggested that axonal ion currents are altered in vivo by hindlimb unloading. It is still undetermined whether the dysfunctional axonal ion currents have any pathogenicity on neuromuscular atrophy or are the results of neural plasticity by atrophy.

  8. Cortical compression rapidly trimmed transcallosal projections and altered axonal anterograde transport machinery.

    Science.gov (United States)

    Chen, Li-Jin; Wang, Yueh-Jan; Tseng, Guo-Fang

    2017-10-24

    Trauma and tumor compressing the brain distort underlying cortical neurons. Compressed cortical neurons remodel their dendrites instantly. The effects on axons however remain unclear. Using a rat epidural bead implantation model, we studied the effects of unilateral somatosensory cortical compression on its transcallosal projection and the reversibility of the changes following decompression. Compression reduced the density, branching profuseness and boutons of the projection axons in the contralateral homotopic cortex 1week and 1month post-compression. Projection fiber density was higher 1-month than 1-week post-compression, suggesting adaptive temporal changes. Compression reduced contralateral cortical synaptophysin, vesicular glutamate transporter 1 (VGLUT1) and postsynaptic density protein-95 (PSD95) expressions in a week and the first two marker proteins further by 1month. βIII-tubulin and kinesin light chain (KLC) expressions in the corpus callosum (CC) where transcallosal axons traveled were also decreased. Kinesin heavy chain (KHC) level in CC was temporarily increased 1week after compression. Decompression increased transcallosal axon density and branching profuseness to higher than sham while bouton density returned to sham levels. This was accompanied by restoration of synaptophysin, VGLUT1 and PSD95 expressions in the contralateral cortex of the 1-week, but not the 1-month, compression rats. Decompression restored βIII-tubulin, but not KLC and KHC expressions in CC. However, KLC and KHC expressions in the cell bodies of the layer II/III pyramidal neurons partially recovered. Our results show cerebral compression compromised cortical axonal outputs and reduced transcallosal projection. Some of these changes did not recover in long-term decompression. Copyright © 2017 IBRO. Published by Elsevier Ltd. All rights reserved.

  9. Action potential propagation recorded from single axonal arbors using multi-electrode arrays.

    Science.gov (United States)

    Tovar, Kenneth R; Bridges, Daniel C; Wu, Bian; Randall, Connor; Audouard, Morgane; Jang, Jiwon; Hansma, Paul K; Kosik, Kenneth S

    2018-04-11

    We report the presence of co-occurring extracellular action potentials (eAPs) from cultured mouse hippocampal neurons among groups of planar electrodes on multi-electrode arrays (MEAs). The invariant sequences of eAPs among co-active electrode groups, repeated co-occurrences and short inter-electrode latencies are consistent with action potential propagation in unmyelinated axons. Repeated eAP co-detection by multiple electrodes was widespread in all our data records. Co-detection of eAPs confirms they result from the same neuron and allows these eAPs to be isolated from all other spikes independently of spike sorting algorithms. We averaged co-occurring events and revealed additional electrodes with eAPs that would otherwise be below detection threshold. We used these eAP cohorts to explore the temperature sensitivity of action potential propagation and the relationship between voltage-gated sodium channel density and propagation velocity. The sequence of eAPs among co-active electrodes 'fingerprints' neurons giving rise to these events and identifies them within neuronal ensembles. We used this property and the non-invasive nature of extracellular recording to monitor changes in excitability at multiple points in single axonal arbors simultaneously over several hours, demonstrating independence of axonal segments. Over several weeks, we recorded changes in inter-electrode propagation latencies and ongoing changes in excitability in different regions of single axonal arbors. Our work illustrates how repeated eAP co-occurrences can be used to extract physiological data from single axons with low electrode density MEAs. However, repeated eAP co-occurrences leads to over-sampling spikes from single neurons and thus can confound traditional spike-train analysis.

  10. Odorant responses of olfactory sensory neurons expressing the odorant receptor MOR23: A patch clamp analysis in gene-targeted mice

    OpenAIRE

    Grosmaitre, Xavier; Vassalli, Anne; Mombaerts, Peter; Shepherd, Gordon M.; Ma, Minghong

    2006-01-01

    A glomerulus in the mammalian olfactory bulb receives axonal inputs from olfactory sensory neurons (OSNs) that express the same odorant receptor (OR). Glomeruli are generally thought to represent functional units of olfactory coding, but there are no data on the electrophysiological properties of OSNs that express the same endogenous OR. Here, using patch clamp recordings in an intact epithelial preparation, we directly measured the transduction currents and receptor potentials from the dendr...

  11. Mitochondrial Dynamics Decrease Prior to Axon Degeneration Induced by Vincristine and are Partially Rescued by Overexpressed cytNmnat1.

    Directory of Open Access Journals (Sweden)

    Gregory Berbusse

    2016-07-01

    Full Text Available Axon degeneration is a prominent feature of various neurodegenerative diseases, such as Parkinson’s and Alzheimer’s, and is often characterized by aberrant mitochondrial dynamics. Mitochondrial fission, fusion, and motility have been shown to be particularly important in progressive neurodegeneration. Thus we investigated these imperative dynamics, as well as mitochondrial fragmentation in vincristine induced axon degradation in cultured DRG neurons. CytNmnat1 inhibits axon degeneration in various paradigms including vincristine toxicity. The mechanism of its protection is not yet fully understood; therefore, we also investigated the effect of cytNmnat1 on mitochondrial dynamics in vincristine treated neurons. We observed that vincristine treatment decreases the rate of mitochondrial fission, fusion and motility and induces mitochondrial fragmentation. These mitochondrial events precede visible axon degeneration. Overexpression of cytNmnat1 inhibits axon degeneration and preserves the normal mitochondrial dynamics and motility in vincristine treated neurons. We suggest the alterations in mitochondrial structure and dynamics are early events which lead to axon degeneration and cytNmnat1 blocks axon degeneration by halting the vincristine induced changes to mitochondrial structure and dynamics.

  12. Interaction between the soma and the axon terminal of horizontal cells in carp retina

    NARCIS (Netherlands)

    Kamermans, M.; van Dijk, B. W.; Spekreijse, H.

    1990-01-01

    In teleost retina, the receptive fields of horizontal cell axon terminals have a larger space constant than the receptive fields of the horizontal cell somata. Generally this difference in receptive field size is attributed to the cell coupling which is assumed to be stronger in the horizontal axon

  13. Specific effects of c-Jun NH2-terminal kinase-interacting protein 1 in neuronal axons

    Directory of Open Access Journals (Sweden)

    Shu Tang

    2016-01-01

    Full Text Available c-Jun NH2-terminal kinase (JNK-interacting protein 3 plays an important role in brain-derived neurotrophic factor/tropomyosin-related kinase B (TrkB anterograde axonal transport. It remains unclear whether JNK-interacting protein 1 mediates similar effects, or whether JNK-interacting protein 1 affects the regulation of TrkB anterograde axonal transport. In this study, we isolated rat embryonic hippocampus and cultured hippocampal neurons in vitro. Coimmunoprecipitation results demonstrated that JNK-interacting protein 1 formed TrkB complexes in vitro and in vivo. Immunocytochemistry results showed that when JNK-interacting protein 1 was highly expressed, the distribution of TrkB gradually increased in axon terminals. However, the distribution of TrkB reduced in axon terminals after knocking out JNK-interacting protein 1. In addition, there were differences in distribution of TrkB after JNK-interacting protein 1 was knocked out compared with not. However, knockout of JNK-interacting protein 1 did not affect the distribution of TrkB in dendrites. These findings confirm that JNK-interacting protein 1 can interact with TrkB in neuronal cells, and can regulate the transport of TrkB in axons, but not in dendrites.

  14. Histamine H3 Receptors Decrease Dopamine Release in the Ventral Striatum by Reducing the Activity of Striatal Cholinergic Interneurons.

    Science.gov (United States)

    Varaschin, Rafael Koerich; Osterstock, Guillaume; Ducrot, Charles; Leino, Sakari; Bourque, Marie-Josée; Prado, Marco A M; Prado, Vania Ferreira; Salminen, Outi; Rannanpää Née Nuutinen, Saara; Trudeau, Louis-Eric

    2018-04-15

    Histamine H 3 receptors are widely distributed G i -coupled receptors whose activation reduces neuronal activity and inhibits release of numerous neurotransmitters. Although these receptors are abundantly expressed in the striatum, their modulatory role on activity-dependent dopamine release is not well understood. Here, we observed that histamine H 3 receptor activation indirectly diminishes dopamine overflow in the ventral striatum by reducing cholinergic interneuron activity. Acute brain slices from C57BL/6 or channelrhodopsin-2-transfected DAT-cre mice were obtained, and dopamine transients evoked either electrically or optogenetically were measured by fast-scan cyclic voltammetry. The H 3 agonist α-methylhistamine significantly reduced electrically- evoked dopamine overflow, an effect blocked by the nicotinic acetylcholine receptor antagonist dihydro-β-erythroidine, suggesting involvement of cholinergic interneurons. None of the drug treatments targeting H 3 receptors affected optogenetically evoked dopamine overflow, indicating that direct H 3 -modulation of dopaminergic axons is unlikely. Next, we used qPCR and confirmed the expression of histamine H 3 receptor mRNA in cholinergic interneurons, both in ventral and dorsal striatum. Activation of H 3 receptors by α-methylhistamine reduced spontaneous firing of cholinergic interneurons in the ventral, but not in the dorsal striatum. Resting membrane potential and number of spontaneous action potentials in ventral-striatal cholinergic interneurons were significantly reduced by α-methylhistamine. Acetylcholine release from isolated striatal synaptosomes, however, was not altered by α-methylhistamine. Together, these results indicate that histamine H 3 receptors are important modulators of dopamine release, specifically in the ventral striatum, and that they do so by decreasing the firing rate of cholinergic neurons and, consequently, reducing cholinergic tone on dopaminergic axons. Copyright © 2018 IBRO

  15. Analysis of axonal regeneration in the central and peripheral nervous systems of the NG2-deficient mouse

    Directory of Open Access Journals (Sweden)

    Lieberman Alexander R

    2007-09-01

    Full Text Available Abstract Background The chondroitin sulphate proteoglycan NG2 blocks neurite outgrowth in vitro and has been proposed as a major inhibitor of axonal regeneration in the CNS. Although a substantial body of evidence underpins this hypothesis, it is challenged by recent findings including strong expression of NG2 in regenerating peripheral nerve. Results We studied axonal regeneration in the PNS and CNS of genetically engineered mice that do not express NG2, and in sex and age matched wild-type controls. In the CNS, we used anterograde tracing with BDA to study corticospinal tract (CST axons after spinal cord injury and transganglionic labelling with CT-HRP to trace ascending sensory dorsal column (DC axons after DC lesions and a conditioning lesion of the sciatic nerve. Injury to these fibre tracts resulted in no difference between knockout and wild-type mice in the ability of CST axons or DC axons to enter or cross the lesion site. Similarly, after dorsal root injury (with conditioning lesion, most regenerating dorsal root axons failed to grow across the dorsal root entry zone in both transgenic and wild-type mice. Following sciatic nerve injuries, functional recovery was assessed by analysis of the toe-spreading reflex and cutaneous sensitivity to Von Frey hairs. Anatomical correlates of regeneration were assessed by: retrograde labelling of regenerating dorsal root ganglion (DRG cells with DiAsp; immunostaining with PGP 9.5 to visualise sensory reinnervation of plantar hindpaws; electron microscopic analysis of regenerating axons in tibial and digital nerves; and by silver-cholinesterase histochemical study of motor end plate reinnervation. We also examined functional and anatomical correlates of regeneration after injury of the facial nerve by assessing the time taken for whisker movements and corneal reflexes to recover and by retrograde labelling of regenerated axons with Fluorogold and DiAsp. None of the anatomical or functional analyses

  16. Localization of brain-derived neurotrophic factor, neurotrophin-4, tropomyosin-related kinase b receptor, and p75 NTR receptor by high-resolution immunohistochemistry on the adult mouse neuromuscular junction.

    Science.gov (United States)

    Garcia, Neus; Tomàs, Marta; Santafe, Manel M; Lanuza, M Angel; Besalduch, Nuria; Tomàs, Josep

    2010-03-01

    Neurotrophins and their receptors, the trk receptor tyrosine kinases (trks) and p75(NTR), are differentially expressed among the cell types that make up synapses. It is important to determine the precise location of these molecules involved in neurotransmission. Here we use immunostaining and Western blotting to study the localization and expression of neurotrophin brain-derived neurotrophic factor (BDNF) and neurotrophin-4 (NT-4) and the receptors tropomyosin-related kinase b (trkB) and p75(NTR) at the adult neuromuscular junction. Our confocal immunofluorescence results on the whole mounts of the mouse Levator auris longus muscle and on semithin cross-sections showed that BDNF, NT-4, trkB, and p75(NTR) were localized on the three cells in the neuromuscular synapse (motor axons, post-synaptic muscle and Schwann cells).

  17. Variable laterality of corticospinal tract axons that regenerate after spinal cord injury as a result of PTEN deletion or knock-down

    Science.gov (United States)

    Willenberg, Rafer; Zukor, Katherine; Liu, Kai; He, Zhigang; Steward, Oswald

    2016-01-01

    Corticospinal tract (CST) axons from one hemisphere normally extend and terminate predominantly in the contralateral spinal cord. We previously showed that deleting PTEN in the sensorimotor cortex enables CST axons to regenerate after spinal cord injury and that some regenerating axons extend along the “wrong” side. Here, we characterize the degree of specificity of regrowth in terms of laterality. PTEN was selectively deleted via cortical AAV-Cre injections in neonatal PTEN-floxed mice. As adults, mice received dorsal hemisection injuries at T12 or complete crush injuries at T9. CST axons from one hemisphere were traced by unilateral BDA injections in PTEN-deleted mice with spinal cord injury and in non-injured PTEN-floxed mice that had not received AAV-Cre. In non-injured mice, 97.9 ± 0.7% of BDA-labeled axons in white matter and 88.5 ± 1.0% of BDA-labeled axons in grey matter were contralateral to the cortex of origin. In contrast, laterality of CST axons that extended past a lesion due to PTEN deletion varied across animals. In some cases, regenerated axons extended predominantly on the ipsilateral side, in other cases, axons extended predominantly contralaterally, and in others, axons were similar in numbers on both sides. Similar results were seen in analyses of cases from previous studies using shRNA-mediated PTEN knock-down. These results indicate that CST axons that extend past a lesion due to PTEN deletion or knock-down do not maintain the contralateral rule of the non-injured CST, highlighting one aspect for how resultant circuitry from regenerating axons may differ from that of the uninjured CST. PMID:26878190

  18. Defective Ca2+ channel clustering in axon terminals disturbs excitability in motoneurons in spinal muscular atrophy

    OpenAIRE

    Jablonka, Sibylle; Beck, Marcus; Lechner, Barbara Dorothea; Mayer, Christine; Sendtner, Michael

    2007-01-01

    Proximal spinal muscular atrophy (SMA) is a motoneuron disease for which there is currently no effective treatment. In animal models of SMA, spinal motoneurons exhibit reduced axon elongation and growth cone size. These defects correlate with reduced β-actin messenger RNA and protein levels in distal axons. We show that survival motoneuron gene (Smn)–deficient motoneurons exhibit severe defects in clustering Cav2.2 channels in axonal growth cones. These defects also correlate with a reduced f...

  19. REGENERATIVE GROWTH OF CORTICOSPINAL TRACT AXONS VIA THE VENTRAL COLUMN AFTER SPINAL CORD INJURY IN MICE

    OpenAIRE

    Steward, Oswald; Zheng, Binhai; Tessier-Lavigne, Marc; Hofstadter, Maura; Sharp, Kelli; Yee, Kelly Matsudaira

    2008-01-01

    Studies that have assessed regeneration of corticospinal tract (CST) axons in mice following genetic modifications or other treatments have tacitly assumed that there is little if any regeneration of CST axons in normal mice in the absence of some intervention. Here, we document a previously unrecognized capability for regenerative growth of CST axons in normal mice that involves growth past the lesion via the ventral column. Mice received dorsal hemisection injuries at thoracic level 6–7, wh...

  20. Varicose and cheerio collaborate with pebble to mediate semaphorin-1a reverse signaling in Drosophila.

    Science.gov (United States)

    Jeong, Sangyun; Yang, Da-Som; Hong, Young Gi; Mitchell, Sarah P; Brown, Matthew P; Kolodkin, Alex L

    2017-09-26

    The transmembrane semaphorin Sema-1a acts as both a ligand and a receptor to regulate axon-axon repulsion during neural development. Pebble (Pbl), a Rho guanine nucleotide exchange factor, mediates Sema-1a reverse signaling through association with the N-terminal region of the Sema-1a intracellular domain (ICD), resulting in cytoskeletal reorganization. Here, we uncover two additional Sema-1a interacting proteins, varicose (Vari) and cheerio (Cher), each with neuronal functions required for motor axon pathfinding. Vari is a member of the membrane-associated guanylate kinase (MAGUK) family of proteins, members of which can serve as scaffolds to organize signaling complexes. Cher is related to actin filament cross-linking proteins that regulate actin cytoskeleton dynamics. The PDZ domain binding motif found in the most C-terminal region of the Sema-1a ICD is necessary for interaction with Vari, but not Cher, indicative of distinct binding modalities. Pbl/Sema-1a-mediated repulsive guidance is potentiated by both vari and cher Genetic analyses further suggest that scaffolding functions of Vari and Cher play an important role in Pbl-mediated Sema-1a reverse signaling. These results define intracellular components critical for signal transduction from the Sema-1a receptor to the cytoskeleton and provide insight into mechanisms underlying semaphorin-induced localized changes in cytoskeletal organization.

  1. IFNgamma enhances microglial reactions to hippocampal axonal degeneration

    DEFF Research Database (Denmark)

    Jensen, M B; Hegelund, I V; Lomholt, N D

    2000-01-01

    periods. Message for the immune cytokine interferon-gamma (IFNgamma) was undetectable, and glial reactivity to axonal lesions occurred as normal in IFNgamma-deficient mice. Microglial responses to lesion-induced neuronal injury were markedly enhanced in myelin basic protein promoter-driven transgenic mice...

  2. Regeneration of supraspinal axons after transection of the thoracic spinal cord in the developing opossum, Didelphis virginiana.

    Science.gov (United States)

    Wang, X M; Terman, J R; Martin, G F

    1998-08-17

    When the thoracic spinal cord of the North American opossum is transected early in development, supraspinal axons grow through the lesion. In the experiments reported here, we asked whether regeneration of cut axons contributes to such growth. Fast Blue (FB) was injected into the lumbar cord on postnatal day (PD)5, 8, 15, or 20. Five days later, FB was removed by gentle suction, and the spinal cord was transected at thoracic levels. Fourteen days later, rhodamine B dextran was injected between the site of the FB injection and the lesion. The pups were maintained for an additional 7-10 days before killing and perfusion. We assumed that supraspinal neurons that contained FB survived axotomy and those that contained both FB and rhodamine B dextran supported regenerating axons. In the PD5 group (lesioned at PD10), regenerative growth was documented for axons originating in all of the supraspinal nuclei that innervate the lumbar cord by PD10. When the injections were made at the later ages, however, neurons that supported regenerative growth were fewer in number and regionally restricted. In some cases, they were limited primarily to the red nucleus, the medullary raphe, and the adjacent reticular formation. Our results show that regeneration of cut axons contributes to growth of supraspinal axons through the lesion after transection of the thoracic cord in developing opossums and that the critical period for regenerative growth is not the same for all axons.

  3. T-cell- and macrophage-mediated axon damage in the absence of a CNS-specific immune response: involvement of metalloproteinases.

    Science.gov (United States)

    Newman, T A; Woolley, S T; Hughes, P M; Sibson, N R; Anthony, D C; Perry, V H

    2001-11-01

    Recent evidence has highlighted the fact that axon injury is an important component of multiple sclerosis pathology. The issue of whether a CNS antigen-specific immune response is required to produce axon injury remains unresolved. We investigated the extent and time course of axon injury in a rodent model of a delayed-type hypersensitivity (DTH) reaction directed against the mycobacterium bacille Calmette-Guérin (BCG). Using MRI, we determined whether the ongoing axon injury is restricted to the period during which the blood-brain barrier is compromised. DTH lesions were initiated in adult rats by intracerebral injection of heat-killed BCG followed by a peripheral challenge with BCG. Our findings demonstrate that a DTH reaction to a non-CNS antigen within a CNS white matter tract leads to axon injury. Ongoing axon injury persisted throughout the 3-month period studied and was not restricted to the period of blood-brain barrier breakdown, as detected by MRI enhancing lesions. We have previously demonstrated that matrix metalloproteinases (MMPs) are upregulated in multiple sclerosis plaques and DTH lesions. In this study we demonstrated that microinjection of activated MMPs into the cortical white matter results in axon injury. Our results show that axon injury, possibly mediated by MMPs, is immunologically non-specific and may continue behind an intact blood-brain barrier.

  4. Massive accumulation of luminal protease-deficient axonal lysosomes at Alzheimer's disease amyloid plaques.

    Science.gov (United States)

    Gowrishankar, Swetha; Yuan, Peng; Wu, Yumei; Schrag, Matthew; Paradise, Summer; Grutzendler, Jaime; De Camilli, Pietro; Ferguson, Shawn M

    2015-07-14

    Through a comprehensive analysis of organellar markers in mouse models of Alzheimer's disease, we document a massive accumulation of lysosome-like organelles at amyloid plaques and establish that the majority of these organelles reside within swollen axons that contact the amyloid deposits. This close spatial relationship between axonal lysosome accumulation and extracellular amyloid aggregates was observed from the earliest stages of β-amyloid deposition. Notably, we discovered that lysosomes that accumulate in such axons are lacking in multiple soluble luminal proteases and thus are predicted to be unable to efficiently degrade proteinaceous cargos. Of relevance to Alzheimer's disease, β-secretase (BACE1), the protein that initiates amyloidogenic processing of the amyloid precursor protein and which is a substrate for these proteases, builds up at these sites. Furthermore, through a comparison between the axonal lysosome accumulations at amyloid plaques and neuronal lysosomes of the wild-type brain, we identified a similar, naturally occurring population of lysosome-like organelles in neuronal processes that is also defined by its low luminal protease content. In conjunction with emerging evidence that the lysosomal maturation of endosomes and autophagosomes is coupled to their retrograde transport, our results suggest that extracellular β-amyloid deposits cause a local impairment in the retrograde axonal transport of lysosome precursors, leading to their accumulation and a blockade in their further maturation. This study both advances understanding of Alzheimer's disease brain pathology and provides new insights into the subcellular organization of neuronal lysosomes that may have broader relevance to other neurodegenerative diseases with a lysosomal component to their pathology.

  5. ON Cone Bipolar Cell Axonal Synapses in the OFF Inner Plexiform Layer of the Rabbit Retina

    Science.gov (United States)

    Lauritzen, J. Scott; Anderson, James R.; Jones, Bryan W.; Watt, Carl B.; Mohammed, Shoeb; Hoang, John V.; Marc, Robert E.

    2012-01-01

    Analysis of the rabbit retinal connectome RC1 reveals that the division between the ON and OFF inner plexiform layer (IPL) is not structurally absolute. ON cone bipolar cells make non-canonical axonal synapses onto specific targets and receive amacrine cell synapses in the nominal OFF layer, creating novel motifs, including inhibitory crossover networks. Automated transmission electron microscope (ATEM) imaging, molecular tagging, tracing, and rendering of ≈ 400 bipolar cells reveals axonal ribbons in 36% of ON cone bipolar cells, throughout the OFF IPL. The targets include GABA-positive amacrine cells (γACs), glycine-positive amacrine cells (GACs) and ganglion cells. Most ON cone bipolar cell axonal contacts target GACs driven by OFF cone bipolar cells, forming new architectures for generating ON-OFF amacrine cells. Many of these ON-OFF GACs target ON cone bipolar cell axons, ON γACs and/or ON-OFF ganglion cells, representing widespread mechanisms for OFF to ON crossover inhibition. Other targets include OFF γACs presynaptic to OFF bipolar cells, forming γAC-mediated crossover motifs. ON cone bipolar cell axonal ribbons drive bistratified ON-OFF ganglion cells in the OFF layer and provide ON drive to polarity-appropriate targets such as bistratified diving ganglion cells (bsdGCs). The targeting precision of ON cone bipolar cell axonal synapses shows that this drive incidence is necessarily a joint distribution of cone bipolar cell axonal frequency and target cell trajectories through a given volume of the OFF layer. Such joint distribution sampling is likely common when targets are sparser than sources and when sources are coupled, as are ON cone bipolar cells. PMID:23042441

  6. Prediction of Functional Outcome in Axonal Guillain-Barre Syndrome.

    Science.gov (United States)

    Sung, Eun Jung; Kim, Dae Yul; Chang, Min Cheol; Ko, Eun Jae

    2016-06-01

    To identify the factors that could predict the functional outcome in patients with the axonal type of Guillain-Barre syndrome (GBS). Two hundred and two GBS patients admitted to our university hospital between 2003 and 2014 were reviewed retrospectively. We defined a good outcome as being "able to walk independently at 1 month after onset" and a poor outcome as being "unable to walk independently at 1 month after onset". We evaluated the factors that differed between the good and poor outcome groups. Twenty-four patients were classified into the acute motor axonal neuropathy type. There was a statistically significant difference between the good and poor outcome groups in terms of the GBS disability score at admission, and GBS disability score and Medical Research Council sum score at 1 month after admission. In an electrophysiologic analysis, the good outcome group showed greater amplitude of median, ulnar, deep peroneal, and posterior tibial nerve compound muscle action potentials (CMAP) and greater amplitude of median, ulnar, and superficial peroneal sensory nerve action potentials (SNAP) than the poor outcome group. A lower GBS disability score at admission, high amplitude of median, ulnar, deep peroneal, and posterior tibial CMAPs, and high amplitude of median, ulnar, and superficial peroneal SNAPs were associated with being able to walk at 1 month in patients with axonal GBS.

  7. The effects of voluntary running exercise coincidence with social isolation after early weaning on monoaminergic axonal development.

    Science.gov (United States)

    Ishikawa, J; Ishikawa, A

    2013-01-29

    The axonal development of serotonin (5-HT)-, noradrenaline (NA)-, or tyrosine hydroxylase (TH)-containing monoaminergic neurons is affected by rearing conditions during the juvenile period. Impaired monoaminergic axonal development is implicated in the pathophysiology of emotional and cognitive dysfunction. On the other hand, exercise may have beneficial effects on emotional and learning performance in adults. We have examined whether voluntary running exercise during social isolation after early weaning (early weaning/social isolation; EI) from postnatal day (PD) 14-28 could prevent the impaired monoaminergic axonal development associated with EI. Compared with control animals reared with their dam and siblings until PD28, the EI animals showed lower density of 5-HT and NA axons in the dorsal-medial prefrontal cortex (mPFC) and basolateral nucleus of the amygdala and of NA- and TH-containing axons in the ventral-mPFC. These adverse effects of EI were not observed in rats taking part in voluntary running (EI+R) when these animals were compared to controls. The 5-HT axon density in the ventral-mPFC was significantly higher in the EI+R rats than that in the EI rats, although both these values were significantly lower than those in the control rats. The density of monoaminergic axons in the dentate gyrus and CA3 of the hippocampus was not affected by either EI or EI+R. These results suggest that the beneficial effects of voluntary running may be because of the modulation of monoaminergic axonal morphology. Our findings will hopefully provide the basis for future research into the beneficial effects of voluntary exercise during the juvenile period on brain development and emotional and cognitive performance. Copyright © 2012 IBRO. Published by Elsevier Ltd. All rights reserved.

  8. Effects of p-xylene inhalation on axonal transport in the rat retinal ganglion cells

    Energy Technology Data Exchange (ETDEWEB)

    Padilla, S.S.; Lyerly, D.P. (Environmental Protection Agency, Research Triangle Park, NC (USA))

    1989-12-01

    Although the solvent xylene is suspected of producing nervous system dysfunction in animals and humans, little is known regarding the neurochemical consequences of xylene inhalation. The intent of this study was to determine the effect of intermittent, acute, and subchronic p-xylene exposure on the axonal transport of proteins and glycoproteins within the rat retinofugal tract. A number of different exposure regimens were tested ranging from 50 ppm for a single 6-hr exposure to 1600 ppm 6 hr/day, 5 days/week, for a total of 8 exposure days. Immediately following removal from the inhalation chambers rats were injected intraocularly with (35S)methionine and (3H)fucose (to label retinal proteins and glycoproteins, respectively) and the axonal transport of labeled macromolecules to axons (optic nerve and optic tract) and nerve endings (lateral geniculate body and superior colliculus) was examined 20 hr after precursor injection. Only relatively severe exposure regimens (i.e., 800 or 1600 ppm 6 hr/day, 5 days/week, for 1.5 weeks) produced significant reductions in axonal transport; there was a moderate reduction in the axonal transport of 35S-labeled proteins in the 800-ppm-treated group which was more widespread in the 1600 ppm-treated group. Transport of 3H-labeled glycoproteins was less affected. Assessment of retinal metabolism immediately after isotope injection indicated that the rate of precursor uptake was not reduced in either treatment group. Furthermore, rapid transport was still substantially reduced in animals exposed to 1600 ppm p-xylene and allowed a 13-day withdrawal period. These data indicate that p-xylene inhalation decreases rapid axonal transport supplied to the projections of the rat retinal ganglion cells immediately after cessation of inhalation exposure and that this decreased transport is still apparent 13 days after the last exposure.

  9. Effects of p-xylene inhalation on axonal transport in the rat retinal ganglion cells

    International Nuclear Information System (INIS)

    Padilla, S.S.; Lyerly, D.P.

    1989-01-01

    Although the solvent xylene is suspected of producing nervous system dysfunction in animals and humans, little is known regarding the neurochemical consequences of xylene inhalation. The intent of this study was to determine the effect of intermittent, acute, and subchronic p-xylene exposure on the axonal transport of proteins and glycoproteins within the rat retinofugal tract. A number of different exposure regimens were tested ranging from 50 ppm for a single 6-hr exposure to 1600 ppm 6 hr/day, 5 days/week, for a total of 8 exposure days. Immediately following removal from the inhalation chambers rats were injected intraocularly with [35S]methionine and [3H]fucose (to label retinal proteins and glycoproteins, respectively) and the axonal transport of labeled macromolecules to axons (optic nerve and optic tract) and nerve endings (lateral geniculate body and superior colliculus) was examined 20 hr after precursor injection. Only relatively severe exposure regimens (i.e., 800 or 1600 ppm 6 hr/day, 5 days/week, for 1.5 weeks) produced significant reductions in axonal transport; there was a moderate reduction in the axonal transport of 35S-labeled proteins in the 800-ppm-treated group which was more widespread in the 1600 ppm-treated group. Transport of 3H-labeled glycoproteins was less affected. Assessment of retinal metabolism immediately after isotope injection indicated that the rate of precursor uptake was not reduced in either treatment group. Furthermore, rapid transport was still substantially reduced in animals exposed to 1600 ppm p-xylene and allowed a 13-day withdrawal period. These data indicate that p-xylene inhalation decreases rapid axonal transport supplied to the projections of the rat retinal ganglion cells immediately after cessation of inhalation exposure and that this decreased transport is still apparent 13 days after the last exposure

  10. Optically-Induced Neuronal Activity Is Sufficient to Promote Functional Motor Axon Regeneration In Vivo.

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    Patricia J Ward

    Full Text Available Peripheral nerve injuries are common, and functional recovery is very poor. Beyond surgical repair of the nerve, there are currently no treatment options for these patients. In experimental models of nerve injury, interventions (such as exercise and electrical stimulation that increase neuronal activity of the injured neurons effectively enhance axon regeneration. Here, we utilized optogenetics to determine whether increased activity alone is sufficient to promote motor axon regeneration. In thy-1-ChR2/YFP transgenic mice in which a subset of motoneurons express the light-sensitive cation channel, channelrhodopsin (ChR2, we activated axons in the sciatic nerve using blue light immediately prior to transection and surgical repair of the sciatic nerve. At four weeks post-injury, direct muscle EMG responses evoked with both optical and electrical stimuli as well as the ratio of these optical/electrical evoked EMG responses were significantly greater in mice that received optical treatment. Thus, significantly more ChR2+ axons successfully re-innervated the gastrocnemius muscle in mice that received optical treatment. Sections of the gastrocnemius muscles were reacted with antibodies to Synaptic Vesicle Protein 2 (SV2 to quantify the number of re-occupied motor endplates. The number of SV2+ endplates was greater in mice that received optical treatment. The number of retrogradely-labeled motoneurons following intramuscular injection of cholera toxin subunit B (conjugated to Alexa Fluor 555 was greater in mice that received optical treatment. Thus, the acute (1 hour, one-time optical treatment resulted in robust, long-lasting effects compared to untreated animals as well as untreated axons (ChR2-. We conclude that neuronal activation is sufficient to promote motor axon regeneration, and this regenerative effect is specific to the activated neurons.

  11. A fast and robust method for automated analysis of axonal transport.

    Science.gov (United States)

    Welzel, Oliver; Knörr, Jutta; Stroebel, Armin M; Kornhuber, Johannes; Groemer, Teja W

    2011-09-01

    Cargo movement along axons and dendrites is indispensable for the survival and maintenance of neuronal networks. Key parameters of this transport such as particle velocities and pausing times are often studied using kymograph construction, which converts the transport along a line of interest from a time-lapse movie into a position versus time image. Here we present a method for the automatic analysis of such kymographs based on the Hough transform, which is a robust and fast technique to extract lines from images. The applicability of the method was tested on simulated kymograph images and real data from axonal transport of synaptophysin and tetanus toxin as well as the velocity analysis of synaptic vesicle sharing between adjacent synapses in hippocampal neurons. Efficiency analysis revealed that the algorithm is able to detect a wide range of velocities and can be used at low signal-to-noise ratios. The present work enables the quantification of axonal transport parameters with high throughput with no a priori assumptions and minimal human intervention.

  12. DRG axon elongation and growth cone collapse rate induced by Sema3A are differently dependent on NGF concentration.

    Science.gov (United States)

    Kaselis, Andrius; Treinys, Rimantas; Vosyliūtė, Rūta; Šatkauskas, Saulius

    2014-03-01

    Regeneration of embryonic and adult dorsal root ganglion (DRG) sensory axons is highly impeded when they encounter neuronal growth cone-collapsing factor semaphorin3A (Sema3A). On the other hand, increasing evidence shows that DRG axon's regeneration can be stimulated by nerve growth factor (NGF). In this study, we aimed to evaluate whether increased NGF concentrations can counterweight Sema3A-induced inhibitory responses in 15-day-old mouse embryo (E15) DRG axons. The DRG explants were grown in Neurobasal-based medium with different NGF concentrations ranging from 0 to 100 ng/mL and then treated with Sema3A at constant 10 ng/mL concentration. To evaluate interplay between NGF and Sema3A number of DRG axons, axon outgrowth distance and collapse rate were measured. We found that the increased NGF concentrations abolish Sema3A-induced inhibitory effect on axon outgrowth, while they have no effect on Sema3A-induced collapse rate.

  13. Origin, course, and laterality of spinocerebellar axons in the North American opossum, Didelphis virginiana.

    Science.gov (United States)

    Terman, J R; Wang, X M; Martin, G F

    1998-08-01

    Spinocerebellar axons have been studied extensively in placental mammals, but there have been no full reports on their origin, laterality, or spinal course in any marsupial. We have used the North American opossum (Didelphis virginiana) to obtain such information and to ask whether any spinocerebellar neurons innervate both the anterior and posterior lobes of the cerebellum through axonal collaterals. To identify spinal neurons that project to the cerebellum, we employed the retrograde transport of Fluoro-Gold (FG) from the anterior lobe, the main target of spinocerebellar axons. In some cases, cerebellar injections of FG were combined with hemisections of the rostral cervical or midthoracic spinal cord, so that laterality of spinocerebellar connections could be established. To determine whether single neurons project to both the anterior lobe and the posterior lobe, injections of Fast Blue (FB) into the anterior lobe were combined with injections of Diamidino yellow (DY) or rhodamine B dextran (RBD) into the posterior lobe, or vice versa. Following injections of FG into the anterior lobe, neurons were labeled throughout the length of the spinal cord, which differed in laminar distribution and laterality of their projections. Among other areas, neurons were labeled in the central cervical nucleus, the nucleus centrobasalis, Clarke's nucleus, the dorsal horn dorsal spinocerebellar tract area, the spinal border region, and Stilling's nucleus. When anterior lobe injections of FB were combined with injections of RBD or DY into the posterior lobe, or vice versa, some double-labeled neurons were present in all major spinocerebellar groups. Cerebellar injections of FG also retrogradely labeled spinocerebellar axons, allowing us to document their locations in the gray matter as well as within the periphery of the lateral and ventral funiculi at all spinal levels. A few spinocerebellar axons also were found in the dorsal funiculus (a dorsal column-spinocerebellar tract

  14. Polygalae Radix Extract Prevents Axonal Degeneration and Memory Deficits in a Transgenic Mouse Model of Alzheimer's Disease.

    Science.gov (United States)

    Kuboyama, Tomoharu; Hirotsu, Keisuke; Arai, Tetsuya; Yamasaki, Hiroo; Tohda, Chihiro

    2017-01-01

    Memory impairments in Alzheimer's disease (AD) occur due to degenerated axons and disrupted neural networks. Since only limited recovery is possible after the destruction of neural networks, preventing axonal degeneration during the early stages of disease progression is necessary to prevent AD. Polygalae Radix (roots of Polygala tenuifolia ; PR) is a traditional herbal medicine used for sedation and amnesia. In this study, we aimed to clarify and analyze the preventive effects of PR against memory deficits in a transgenic AD mouse model, 5XFAD. 5XFAD mice demonstrated memory deficits at the age of 5 months. Thus, the water extract of Polygalae Radix (PR extract) was orally administered to 4-month-old 5XFAD mice that did not show signs of memory impairment. After consecutive administrations for 56 days, the PR extract prevented cognitive deficit and axon degeneration associated with the accumulation of amyloid β (Aβ) plaques in the perirhinal cortex of the 5XFAD mice. PR extract did not influence the formation of Aβ plaques in the brain of the 5XFAD mice. In cultured neurons, the PR extract prevented axonal growth cone collapse and axonal atrophy induced by Aβ. Additionally, it prevented Aβ-induced endocytosis at the growth cone of cultured neurons. Our previous study reported that endocytosis inhibition was enough to prevent Aβ-induced growth cone collapse, axonal degeneration, and memory impairments. Therefore, the PR extract possibly prevented axonal degeneration and memory impairment by inhibiting endocytosis. PR is the first preventive drug candidate for AD that inhibits endocytosis in neurons.

  15. Neural cell adhesion molecule, NCAM, regulates thalamocortical axon pathfinding and the organization of the cortical somatosensory representation in mouse

    Science.gov (United States)

    Enriquez-Barreto, Lilian; Palazzetti, Cecilia; Brennaman, Leann H.; Maness, Patricia F.; Fairén, Alfonso

    2012-01-01

    To study the potential role of neural cell adhesion molecule (NCAM) in the development of thalamocortical (TC) axon topography, wild type, and NCAM null mutant mice were analyzed for NCAM expression, projection, and targeting of TC afferents within the somatosensory area of the neocortex. Here we report that NCAM and its α-2,8-linked polysialic acid (PSA) are expressed in developing TC axons during projection to the neocortex. Pathfinding of TC axons in wild type and null mutant mice was mapped using anterograde DiI labeling. At embryonic day E16.5, null mutant mice displayed misguided TC axons in the dorsal telencephalon, but not in the ventral telencephalon, an intermediate target that initially sorts TC axons toward correct neocortical areas. During the early postnatal period, rostrolateral TC axons within the internal capsule along the ventral telencephalon adopted distorted trajectories in the ventral telencephalon and failed to reach the neocortex in NCAM null mutant animals. NCAM null mutants showed abnormal segregation of layer IV barrels in a restricted portion of the somatosensory cortex. As shown by Nissl and cytochrome oxidase staining, barrels of the anterolateral barrel subfield (ALBSF) and the most distal barrels of the posteromedial barrel subfield (PMBSF) did not segregate properly in null mutant mice. These results indicate a novel role for NCAM in axonal pathfinding and topographic sorting of TC axons, which may be important for the function of specific territories of sensory representation in the somatosensory cortex. PMID:22723769

  16. Tissue-engineered spiral nerve guidance conduit for peripheral nerve regeneration.

    Science.gov (United States)

    Chang, Wei; Shah, Munish B; Lee, Paul; Yu, Xiaojun

    2018-06-01

    Recently in peripheral nerve regeneration, preclinical studies have shown that the use of nerve guidance conduits (NGCs) with multiple longitudinally channels and intra-luminal topography enhance the functional outcomes when bridging a nerve gap caused by traumatic injury. These features not only provide guidance cues for regenerating nerve, but also become the essential approaches for developing a novel NGC. In this study, a novel spiral NGC with aligned nanofibers and wrapped with an outer nanofibrous tube was first developed and investigated. Using the common rat sciatic 10-mm nerve defect model, the in vivo study showed that a novel spiral NGC (with and without inner nanofibers) increased the successful rate of nerve regeneration after 6 weeks recovery. Substantial improvements in nerve regeneration were achieved by combining the spiral NGC with inner nanofibers and outer nanofibrous tube, based on the results of walking track analysis, electrophysiology, nerve histological assessment, and gastrocnemius muscle measurement. This demonstrated that the novel spiral NGC with inner aligned nanofibers and wrapped with an outer nanofibrous tube provided a better environment for peripheral nerve regeneration than standard tubular NGCs. Results from this study will benefit for future NGC design to optimize tissue-engineering strategies for peripheral nerve regeneration. We developed a novel spiral nerve guidance conduit (NGC) with coated aligned nanofibers. The spiral structure increases surface area by 4.5 fold relative to a tubular NGC. Furthermore, the aligned nanofibers was coated on the spiral walls, providing cues for guiding neurite extension. Finally, the outside of spiral NGC was wrapped with randomly nanofibers to enhance mechanical strength that can stabilize the spiral NGC. Our nerve histological data have shown that the spiral NGC had 50% more myelinated axons than a tubular structure for nerve regeneration across a 10 mm gap in a rat sciatic nerve

  17. Axonal transport and secretion of fibrillar forms of α-synuclein, Aβ42 peptide and HTTExon 1.

    Science.gov (United States)

    Brahic, Michel; Bousset, Luc; Bieri, Gregor; Melki, Ronald; Gitler, Aaron D

    2016-04-01

    Accruing evidence suggests that prion-like behavior of fibrillar forms of α-synuclein, β-amyloid peptide and mutant huntingtin are responsible for the spread of the lesions that characterize Parkinson disease, Alzheimer disease and Huntington disease, respectively. It is unknown whether these distinct protein assemblies are transported within and between neurons by similar or distinct mechanisms. It is also unclear if neuronal death or injury is required for neuron-to-neuron transfer. To address these questions, we used mouse primary cortical neurons grown in microfluidic devices to measure the amounts of α-synuclein, Aβ42 and HTTExon1 fibrils transported by axons in both directions (anterograde and retrograde), as well as to examine the mechanism of their release from axons after anterograde transport. We observed that the three fibrils were transported in both anterograde and retrograde directions but with strikingly different efficiencies. The amount of Aβ42 fibrils transported was ten times higher than that of the other two fibrils. HTTExon1 was efficiently transported in the retrograde direction but only marginally in the anterograde direction. Finally, using neurons from two distinct mutant mouse strains whose axons are highly resistant to neurodegeneration (Wld(S) and Sarm1(-/-)), we found that the three different fibrils were secreted by axons after anterograde transport, in the absence of axonal lysis, indicating that trans-neuronal spread can occur in intact healthy neurons. In summary, fibrils of α-synuclein, Aβ42 and HTTExon1 are all transported in axons but in directions and amounts that are specific of each fibril. After anterograde transport, the three fibrils were secreted in the medium in the absence of axon lysis. Continuous secretion could play an important role in the spread of pathology between neurons but may be amenable to pharmacological intervention.

  18. Resolving the biophysics of axon transmembrane polarization in a single closed-form description

    Energy Technology Data Exchange (ETDEWEB)

    Melendy, Robert F., E-mail: rfmelendy@liberty.edu [School of Engineering and Computational Sciences, Liberty University, Lynchburg, Virginia 24515 (United States)

    2015-12-28

    When a depolarizing event occurs across a cell membrane there is a remarkable change in its electrical properties. A complete depolarization event produces a considerably rapid increase in voltage that propagates longitudinally along the axon and is accompanied by changes in axial conductance. A dynamically changing magnetic field is associated with the passage of the action potential down the axon. Over 75 years of research has gone into the quantification of this phenomenon. To date, no unified model exist that resolves transmembrane polarization in a closed-form description. Here, a simple but formative description of propagated signaling phenomena in the membrane of an axon is presented in closed-form. The focus is on using both biophysics and mathematical methods for elucidating the fundamental mechanisms governing transmembrane polarization. The results presented demonstrate how to resolve electromagnetic and thermodynamic factors that govern transmembrane potential. Computational results are supported by well-established quantitative descriptions of propagated signaling phenomena in the membrane of an axon. The findings demonstrate how intracellular conductance, the thermodynamics of magnetization, and current modulation function together in generating an action potential in a unified closed-form description. The work presented in this paper provides compelling evidence that three basic factors contribute to the propagated signaling in the membrane of an axon. It is anticipated this work will compel those in biophysics, physical biology, and in the computational neurosciences to probe deeper into the classical and quantum features of membrane magnetization and signaling. It is hoped that subsequent investigations of this sort will be advanced by the computational features of this model without having to resort to numerical methods of analysis.

  19. Nicotinamide mononucleotide adenylyltransferase 2 (Nmnat2 regulates axon integrity in the mouse embryo.

    Directory of Open Access Journals (Sweden)

    Amy N Hicks

    Full Text Available Using transposon-mediated gene-trap mutagenesis, we have generated a novel mouse mutant termed Blad (Bloated Bladder. Homozygous mutant mice die perinatally showing a greatly distended bladder, underdeveloped diaphragm and a reduction in total skeletal muscle mass. Wild type and heterozygote mice appear normal. Using PCR, we identified a transposon insertion site in the first intron of Nmnat2 (Nicotinamide mononucleotide adenyltransferase 2. Nmnat2 is expressed predominantly in the brain and nervous system and has been linked to the survival of axons. Expression of this gene is undetectable in Nmnat2(blad/blad mutants. Examination of the brains of E18.5 Nmnat2(blad/blad mutant embryos did not reveal any obvious morphological changes. In contrast, E18.5 Nmnat2(blad/blad homozygotes showed an approximate 60% reduction of spinal motoneurons in the lumbar region and a more than 80% reduction in the sensory neurons of the dorsal root ganglion (DRG. In addition, facial motoneuron numbers were severely reduced, and there was virtually a complete absence of axons in the hind limb. Our observations suggest that during embryogenesis, Nmnat2 plays an important role in axonal growth or maintenance. It appears that in the absence of Nmnat2, major target organs and tissues (e.g., muscle are not functionally innervated resulting in perinatal lethality. In addition, neither Nmnat1 nor 3 can compensate for the loss of Nmnat2. Whilst there have been recent suggestions that Nmnat2 may be an endogenous modulator of axon integrity, this work represents the first in vivo study demonstrating that Nmnat2 is involved in axon development or survival in a mammal.

  20. Cell-type specific expression of constitutively-active Rheb promotes regeneration of bulbospinal respiratory axons following cervical SCI.

    Science.gov (United States)

    Urban, Mark W; Ghosh, Biswarup; Strojny, Laura R; Block, Cole G; Blazejewski, Sara M; Wright, Megan C; Smith, George M; Lepore, Angelo C

    2018-05-01

    Damage to respiratory neural circuitry and consequent loss of diaphragm function is a major cause of morbidity and mortality in individuals suffering from traumatic cervical spinal cord injury (SCI). Repair of CNS axons after SCI remains a therapeutic challenge, despite current efforts. SCI disrupts inspiratory signals originating in the rostral ventral respiratory group (rVRG) of the medulla from their phrenic motor neuron (PhMN) targets, resulting in loss of diaphragm function. Using a rat model of cervical hemisection SCI, we aimed to restore rVRG-PhMN-diaphragm circuitry by stimulating regeneration of injured rVRG axons via targeted induction of Rheb (ras homolog enriched in brain), a signaling molecule that regulates neuronal-intrinsic axon growth potential. Following C2 hemisection, we performed intra-rVRG injection of an adeno-associated virus serotype-2 (AAV2) vector that drives expression of a constitutively-active form of Rheb (cRheb). rVRG neuron-specific cRheb expression robustly increased mTOR pathway activity within the transduced rVRG neuron population ipsilateral to the hemisection, as assessed by levels of phosphorylated ribosomal S6 kinase. By co-injecting our novel AAV2-mCherry/WGA anterograde/trans-synaptic axonal tracer into rVRG, we found that cRheb expression promoted regeneration of injured rVRG axons into the lesion site, while we observed no rVRG axon regrowth with AAV2-GFP control. AAV2-cRheb also significantly reduced rVRG axonal dieback within the intact spinal cord rostral to the lesion. However, cRheb expression did not promote any recovery of ipsilateral hemi-diaphragm function, as assessed by inspiratory electromyography (EMG) burst amplitudes. This lack of functional recovery was likely because regrowing rVRG fibers did not extend back into the caudal spinal cord to synaptically reinnervate PhMNs that we retrogradely-labeled with cholera toxin B from the ipsilateral hemi-diaphragm. Our findings demonstrate that enhancing neuronal

  1. Cellular and Axonal Diversity in Molecular Layer Heterotopia of the Rat Cerebellar Vermis

    Directory of Open Access Journals (Sweden)

    Sarah E. Van Dine

    2013-01-01

    Full Text Available Molecular layer heterotopia of the cerebellar primary fissure are a characteristic of many rat strains and are hypothesized to result from defect of granule cells exiting the external granule cell layer during cerebellar development. However, the cellular and axonal constituents of these malformations remain poorly understood. In the present report, we use histochemistry and immunocytochemistry to identify neuronal, glial, and axonal classes in molecular layer heterotopia. In particular, we identify parvalbumin-expressing molecular layer interneurons in heterotopia as well as three glial cell types including Bergmann glia, Olig2-expressing oligodendrocytes, and Iba1-expressing microglia. In addition, we document the presence of myelinated, serotonergic, catecholaminergic, and cholinergic axons in heterotopia indicating possible spinal and brainstem afferent projections to heterotopic cells. These findings are relevant toward understanding the mechanisms of normal and abnormal cerebellar development.

  2. PI3K-GSK3 signalling regulates mammalian axon regeneration by inducing the expression of Smad1

    Science.gov (United States)

    Saijilafu; Hur, Eun-Mi; Liu, Chang-Mei; Jiao, Zhongxian; Xu, Wen-Lin; Zhou, Feng-Quan

    2013-10-01

    In contrast to neurons in the central nervous system, mature neurons in the mammalian peripheral nervous system (PNS) can regenerate axons after injury, in part, by enhancing intrinsic growth competence. However, the signalling pathways that enhance the growth potential and induce spontaneous axon regeneration remain poorly understood. Here we reveal that phosphatidylinositol 3-kinase (PI3K) signalling is activated in response to peripheral axotomy and that PI3K pathway is required for sensory axon regeneration. Moreover, we show that glycogen synthase kinase 3 (GSK3), rather than mammalian target of rapamycin, mediates PI3K-dependent augmentation of the growth potential in the PNS. Furthermore, we show that PI3K-GSK3 signal is conveyed by the induction of a transcription factor Smad1 and that acute depletion of Smad1 in adult mice prevents axon regeneration in vivo. Together, these results suggest PI3K-GSK3-Smad1 signalling as a central module for promoting sensory axon regeneration in the mammalian nervous system.

  3. Oxytocin and Estrogen Receptor β in the Brain: An Overview

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    Alexandra eAcevedo-Rodriguez

    2015-10-01

    Full Text Available Oxytocin is a neuropeptide synthesized primarily by neurons of the paraventricular and supraoptic nuclei of the hypothalamus. These neurons have axons that project into the posterior pituitary and release oxytocin into the bloodstream to promote labor and lactation; however, oxytocin neurons also project to other brain areas where it plays a role in numerous brain functions. Oxytocin binds to the widely expressed oxytocin receptor, and, in doing so, it regulates homeostatic processes, social recognition and fear conditioning. In addition to these functions, oxytocin decreases neuroendocrine stress signaling and anxiety-related and depression-like behaviors. Steroid hormones differentially modulate stress responses and alter oxytocin receptor expression. In particular, estrogen receptor β activation has been found to both reduce anxiety-related behaviors and increase oxytocin peptide transcription, suggesting a role for oxytocin in this estrogen receptor β mediated anxiolytic effect. Further research is needed to identify modulators of oxytocin signaling and the pathways utilized and to elucidate molecular mechanisms controlling oxytocin expression to allow better therapeutic manipulations of this system in patient populations.

  4. Spinal muscular atrophy pathogenic mutations impair the axonogenic properties of axonal-survival of motor neuron.

    Science.gov (United States)

    Locatelli, Denise; d'Errico, Paolo; Capra, Silvia; Finardi, Adele; Colciaghi, Francesca; Setola, Veronica; Terao, Mineko; Garattini, Enrico; Battaglia, Giorgio

    2012-05-01

    The axonal survival of motor neuron (a-SMN) protein is a truncated isoform of SMN1, the spinal muscular atrophy (SMA) disease gene. a-SMN is selectively localized in axons and endowed with remarkable axonogenic properties. At present, the role of a-SMN in SMA is unknown. As a first step to verify a link between a-SMN and SMA, we investigated by means of over-expression experiments in neuroblastoma-spinal cord hybrid cell line (NSC34) whether SMA pathogenic mutations located in the N-terminal part of the protein affected a-SMN function. We demonstrated here that either SMN1 missense mutations or small intragenic re-arrangements located in the Tudor domain consistently altered the a-SMN capability of inducing axonal elongation in vitro. Mutated human a-SMN proteins determined in almost all NSC34 motor neurons the growth of short axons with prominent morphologic abnormalities. Our data indicate that the Tudor domain is critical in dictating a-SMN function possibly because it is an association domain for proteins involved in axon growth. They also indicate that Tudor domain mutations are functionally relevant not only for FL-SMN but also for a-SMN, raising the possibility that also a-SMN loss of function may contribute to the pathogenic steps leading to SMA. © 2012 The Authors. Journal of Neurochemistry © 2012 International Society for Neurochemistry.

  5. Antiretroviral Therapy-Associated Acute Motor and Sensory Axonal Neuropathy

    Directory of Open Access Journals (Sweden)

    Kimberly N. Capers

    2011-01-01

    Full Text Available Guillain-Barré syndrome (GBS has been reported in HIV-infected patients in association with the immune reconstitution syndrome whose symptoms can be mimicked by highly active antiretroviral therapy (HAART-mediated mitochondrial toxicity. We report a case of a 17-year-old, HIV-infected patient on HAART with a normal CD4 count and undetectable viral load, presenting with acute lower extremity weakness associated with lactatemia. Electromyography/nerve conduction studies revealed absent sensory potentials and decreased compound muscle action potentials, consistent with a diagnosis of acute motor and sensory axonal neuropathy. Lactatemia resolved following cessation of HAART; however, neurological deficits minimally improved over several months in spite of immune modulatory therapy. This case highlights the potential association between HAART, mitochondrial toxicity and acute axonal neuropathies in HIV-infected patients, distinct from the immune reconstitution syndrome.

  6. Calsyntenin-1 shelters APP from proteolytic processing during anterograde axonal transport

    Directory of Open Access Journals (Sweden)

    Martin Steuble

    2012-06-01

    Endocytosis of amyloid-β precursor protein (APP is thought to represent the major source of substrate for the production of the amyloidogenic Aβ peptide by the β-secretase BACE1. The irreversible nature of proteolytic cleavage implies the existence of an efficient replenishment route for APP from its sites of synthesis to the cell surface. We recently found that APP exits the trans-Golgi network in intimate association with calsyntenin-1, a transmembrane cargo-docking protein for Kinesin-1-mediated vesicular transport. Here we characterized the function of calsyntenin-1 in neuronal APP transport using selective immunoisolation of intracellular trafficking organelles, immunocytochemistry, live-imaging, and RNAi. We found that APP is co-transported with calsyntenin-1 along axons to early endosomes in the central region of growth cones in carriers that exclude the α-secretase ADAM10. Intriguingly, calsyntenin-1/APP organelles contained BACE1, suggesting premature cleavage of APP along its anterograde path. However, we found that APP contained in calsyntenin-1/APP organelles was stable. We further analyzed vesicular trafficking of APP in cultured hippocampal neurons, in which calsyntenin-1 was reduced by RNAi. We found a markedly increased co-localization of APP and ADAM10 in axons and growth cones, along with increased proteolytic processing of APP and Aβ secretion in these neurons. This suggested that the reduced capacity for calsyntenin-1-dependent APP transport resulted in mis-sorting of APP into additional axonal carriers and, therefore, the premature encounter of unprotected APP with its ectodomain proteases. In combination, our results characterize calsyntenin-1/APP organelles as carriers for sheltered anterograde axonal transport of APP.

  7. High-Frequency Stimulation of Dorsal Column Axons: Potential Underlying Mechanism of Paresthesia-Free Neuropathic Pain Relief.

    Science.gov (United States)

    Arle, Jeffrey E; Mei, Longzhi; Carlson, Kristen W; Shils, Jay L

    2016-06-01

    Spinal cord stimulation (SCS) treats neuropathic pain through retrograde stimulation of dorsal column axons and their inhibitory effects on wide dynamic range (WDR) neurons. Typical SCS uses frequencies from 50-100 Hz. Newer stimulation paradigms use high-frequency stimulation (HFS) up to 10 kHz and produce pain relief but without paresthesia. Our hypothesis is that HFS preferentially blocks larger diameter axons (12-15 µm) based on dynamics of ion channel gates and the electric potential gradient seen along the axon, resulting in inhibition of WDR cells without paresthesia. We input field potential values from a finite element model of SCS into an active axon model with ion channel subcomponents for fiber diameters 1-20 µm and simulated dynamics on a 0.001 msec time scale. Assuming some degree of wave rectification seen at the axon, action potential (AP) blockade occurs as hypothesized, preferentially in larger over smaller diameters with blockade in most medium and large diameters occurring between 4.5 and 10 kHz. Simulations show both ion channel gate and virtual anode dynamics are necessary. At clinical HFS frequencies and pulse widths, HFS preferentially blocks larger-diameter fibers and concomitantly recruits medium and smaller fibers. These effects are a result of interaction between ion gate dynamics and the "activating function" (AF) deriving from current distribution over the axon. The larger fibers that cause paresthesia in low-frequency simulation are blocked, while medium and smaller fibers are recruited, leading to paresthesia-free neuropathic pain relief by inhibiting WDR cells. © 2016 International Neuromodulation Society.

  8. Massive accumulation of luminal protease-deficient axonal lysosomes at Alzheimer’s disease amyloid plaques

    Science.gov (United States)

    Gowrishankar, Swetha; Yuan, Peng; Wu, Yumei; Schrag, Matthew; Paradise, Summer; Grutzendler, Jaime; De Camilli, Pietro; Ferguson, Shawn M.

    2015-01-01

    Through a comprehensive analysis of organellar markers in mouse models of Alzheimer’s disease, we document a massive accumulation of lysosome-like organelles at amyloid plaques and establish that the majority of these organelles reside within swollen axons that contact the amyloid deposits. This close spatial relationship between axonal lysosome accumulation and extracellular amyloid aggregates was observed from the earliest stages of β-amyloid deposition. Notably, we discovered that lysosomes that accumulate in such axons are lacking in multiple soluble luminal proteases and thus are predicted to be unable to efficiently degrade proteinaceous cargos. Of relevance to Alzheimer’s disease, β-secretase (BACE1), the protein that initiates amyloidogenic processing of the amyloid precursor protein and which is a substrate for these proteases, builds up at these sites. Furthermore, through a comparison between the axonal lysosome accumulations at amyloid plaques and neuronal lysosomes of the wild-type brain, we identified a similar, naturally occurring population of lysosome-like organelles in neuronal processes that is also defined by its low luminal protease content. In conjunction with emerging evidence that the lysosomal maturation of endosomes and autophagosomes is coupled to their retrograde transport, our results suggest that extracellular β-amyloid deposits cause a local impairment in the retrograde axonal transport of lysosome precursors, leading to their accumulation and a blockade in their further maturation. This study both advances understanding of Alzheimer’s disease brain pathology and provides new insights into the subcellular organization of neuronal lysosomes that may have broader relevance to other neurodegenerative diseases with a lysosomal component to their pathology. PMID:26124111

  9. Career guidance in communities

    DEFF Research Database (Denmark)

    Thomsen, Rie

    for the development of a critically reflexive career guidance practice. The considerations are organised around seven elements. 1. Creating opportunity, structure and access 2. Entering a community and increasing visibility 3. Providing guidance in communities 4. Exploring potentials in guidance situations 5...... in career guidance practices as well as in the lives of the people in the communities. This paper falls into two parts: The first part considers the collective as the starting point for the development of meaningful career guidance activities. Based on previous research on career guidance in communities......The aim of this paper is to inspire practitioners and professionals to leave their offices to bring career guidance into communities that might not identify with career guidance in the first instance. By making the effort to engage with communities, practitioners may bring about a critical change...

  10. High dendritic expression of Ih in the proximity of the axon origin controls the integrative properties of nigral dopamine neurons.

    Science.gov (United States)

    Engel, Dominique; Seutin, Vincent

    2015-11-15

    The hyperpolarization-activated cation current Ih is expressed in dopamine neurons of the substantia nigra, but the subcellular distribution of the current and its role in synaptic integration remain unknown. We used cell-attached patch recordings to determine the localization profile of Ih along the somatodendritic axis of nigral dopamine neurons in slices from young rats. Ih density is higher in axon-bearing dendrites, in a membrane area close to the axon origin, than in the soma and axon-lacking dendrites. Dual current-clamp recordings revealed a similar contribution of Ih to the waveform of single excitatory postsynaptic potentials throughout the somatodendritic domain. The Ih blocker ZD 7288 increased the temporal summation in all dendrites with a comparable effect in axon- and non-axon dendrites. The strategic position of Ih in the proximity of the axon may influence importantly transitions between pacemaker and bursting activities and consequently the downstream release of dopamine. Dendrites of most neurons express voltage-gated ion channels in their membrane. In combination with passive properties, active currents confer to dendrites a high computational potential. The hyperpolarization-activated cation current Ih present in the dendrites of some pyramidal neurons affects their membrane and integration properties, synaptic plasticity and higher functions such as memory. A gradient of increasing h-channel density towards distal dendrites has been found to be responsible for the location independence of excitatory postsynaptic potential (EPSP) waveform and temporal summation in cortical and hippocampal pyramidal cells. However, reports on other cell types revealed that smoother gradients or even linear distributions of Ih can achieve homogeneous temporal summation. Although the existence of a robust, slowly activating Ih current has been repeatedly demonstrated in nigral dopamine neurons, its subcellular distribution and precise role in synaptic integration

  11. Retinal ganglion cell survival and axon regeneration after optic nerve injury in naked mole-rats.

    Science.gov (United States)

    Park, Kevin K; Luo, Xueting; Mooney, Skyler J; Yungher, Benjamin J; Belin, Stephane; Wang, Chen; Holmes, Melissa M; He, Zhigang

    2017-02-01

    In the adult mammalian central nervous system (CNS), axonal damage often triggers neuronal cell death and glial activation, with very limited spontaneous axon regeneration. In this study, we performed optic nerve injury in adult naked mole-rats, the longest living rodent, with a maximum life span exceeding 30 years, and found that injury responses in this species are quite distinct from those in other mammalian species. In contrast to what is seen in other mammals, the majority of injured retinal ganglion cells (RGCs) survive with relatively high spontaneous axon regeneration. Furthermore, injured RGCs display activated signal transducer and activator of transcription-3 (STAT3), whereas astrocytes in the optic nerve robustly occupy and fill the lesion area days after injury. These neuron-intrinsic and -extrinsic injury responses are reminiscent of those in "cold-blooded" animals, such as fish and amphibians, suggesting that the naked mole-rat is a powerful model for exploring the mechanisms of neuronal injury responses and axon regeneration in mammals. J. Comp. Neurol. 525:380-388, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  12. Loss of Axon Bifurcation in Mesencephalic Trigeminal Neurons Impairs the Maximal Biting Force in Npr2-Deficient Mice

    Directory of Open Access Journals (Sweden)

    Gohar Ter-Avetisyan

    2018-06-01

    Full Text Available Bifurcation of axons from dorsal root ganglion (DRG and cranial sensory ganglion (CSG neurons is mediated by a cGMP-dependent signaling pathway composed of the ligand C-type natriuretic peptide (CNP, the receptor guanylyl cyclase Npr2 and the cGMP-dependent protein kinase I (cGKI. Here, we demonstrate that mesencephalic trigeminal neurons (MTN which are the only somatosensory neurons whose cell bodies are located within the CNS co-express Npr2 and cGKI. Afferents of MTNs form Y-shaped branches in rhombomere 2 where the ligand CNP is expressed. Analyzing mouse mutants deficient for CNP or Npr2 we found that in the absence of CNP-induced cGMP signaling MTN afferents no longer bifurcate and instead extend either into the trigeminal root or caudally in the hindbrain. Since MTNs provide sensory information from jaw closing muscles and periodontal ligaments we measured the bite force of conditional mouse mutants of Npr2 (Npr2flox/flox;Engr1Cre that lack bifurcation of MTN whereas the bifurcation of trigeminal afferents is normal. Our study revealed that the maximal biting force of both sexes is reduced in Npr2flox/flox;Engr1Cre mice as compared to their Npr2flox/flox littermate controls. In conclusion sensory feedback mechanisms from jaw closing muscles or periodontal ligaments might be impaired in the absence of MTN axon bifurcation.

  13. Polygalae Radix Extract Prevents Axonal Degeneration and Memory Deficits in a Transgenic Mouse Model of Alzheimer’s Disease

    Directory of Open Access Journals (Sweden)

    Tomoharu Kuboyama

    2017-11-01

    Full Text Available Memory impairments in Alzheimer’s disease (AD occur due to degenerated axons and disrupted neural networks. Since only limited recovery is possible after the destruction of neural networks, preventing axonal degeneration during the early stages of disease progression is necessary to prevent AD. Polygalae Radix (roots of Polygala tenuifolia; PR is a traditional herbal medicine used for sedation and amnesia. In this study, we aimed to clarify and analyze the preventive effects of PR against memory deficits in a transgenic AD mouse model, 5XFAD. 5XFAD mice demonstrated memory deficits at the age of 5 months. Thus, the water extract of Polygalae Radix (PR extract was orally administered to 4-month-old 5XFAD mice that did not show signs of memory impairment. After consecutive administrations for 56 days, the PR extract prevented cognitive deficit and axon degeneration associated with the accumulation of amyloid β (Aβ plaques in the perirhinal cortex of the 5XFAD mice. PR extract did not influence the formation of Aβ plaques in the brain of the 5XFAD mice. In cultured neurons, the PR extract prevented axonal growth cone collapse and axonal atrophy induced by Aβ. Additionally, it prevented Aβ-induced endocytosis at the growth cone of cultured neurons. Our previous study reported that endocytosis inhibition was enough to prevent Aβ-induced growth cone collapse, axonal degeneration, and memory impairments. Therefore, the PR extract possibly prevented axonal degeneration and memory impairment by inhibiting endocytosis. PR is the first preventive drug candidate for AD that inhibits endocytosis in neurons.

  14. Fibronectin type III (FN3) modules of the neuronal cell adhesion molecule L1 interact directly with the fibroblast growth factor (FGF) receptor

    DEFF Research Database (Denmark)

    Kulahin, Nikolaj; Li, Shizhong; Hinsby, Anders Mørkeberg

    2008-01-01

    The neuronal cell adhesion molecule (CAM) L1 promotes axonal outgrowth, presumably through an interaction with the fibroblast growth factor receptor (FGFR). The present study demonstrates a direct interaction between L1 fibronectin type III (FN3) modules I-V and FGFR1 immunoglobulin (Ig) modules II...

  15. Regeneration of Drosophila sensory neuron axons and dendrites is regulated by the Akt pathway involving Pten and microRNA bantam

    Science.gov (United States)

    Song, Yuanquan; Ori-McKenney, Kassandra M.; Zheng, Yi; Han, Chun; Jan, Lily Yeh; Jan, Yuh Nung

    2012-01-01

    Both cell-intrinsic and extrinsic pathways govern axon regeneration, but only a limited number of factors have been identified and it is not clear to what extent axon regeneration is evolutionarily conserved. Whether dendrites also regenerate is unknown. Here we report that, like the axons of mammalian sensory neurons, the axons of certain Drosophila dendritic arborization (da) neurons are capable of substantial regeneration in the periphery but not in the CNS, and activating the Akt pathway enhances axon regeneration in the CNS. Moreover, those da neurons capable of axon regeneration also display dendrite regeneration, which is cell type-specific, developmentally regulated, and associated with microtubule polarity reversal. Dendrite regeneration is restrained via inhibition of the Akt pathway in da neurons by the epithelial cell-derived microRNA bantam but is facilitated by cell-autonomous activation of the Akt pathway. Our study begins to reveal mechanisms for dendrite regeneration, which depends on both extrinsic and intrinsic factors, including the PTEN–Akt pathway that is also important for axon regeneration. We thus established an important new model system—the fly da neuron regeneration model that resembles the mammalian injury model—with which to study and gain novel insights into the regeneration machinery. PMID:22759636

  16. Sonic Hedgehog switches on Wnt/planar cell polarity signaling in commissural axon growth cones by reducing levels of Shisa2

    Science.gov (United States)

    Onishi, Keisuke

    2017-01-01

    Commissural axons switch on responsiveness to Wnt attraction during midline crossing and turn anteriorly only after exiting the floor plate. We report here that Sonic Hedgehog (Shh)-Smoothened signaling downregulates Shisa2, which inhibits the glycosylation and cell surface presentation of Frizzled3 in rodent commissural axon growth cones. Constitutive Shisa2 expression causes randomized turning of post-crossing commissural axons along the anterior–posterior (A–P) axis. Loss of Shisa2 led to precocious anterior turning of commissural axons before or during midline crossing. Post-crossing commissural axon turning is completely randomized along the A–P axis when Wntless, which is essential for Wnt secretion, is conditionally knocked out in the floor plate. This regulatory link between Shh and planar cell polarity (PCP) signaling may also occur in other developmental processes. PMID:28885142

  17. Hyaluronic acid hydrogels with IKVAV peptides for tissue repair and axonal regeneration in an injured rat brain

    International Nuclear Information System (INIS)

    Wei, Y T; Tian, W M; Yu, X; Cui, F Z; Hou, S P; Xu, Q Y; Lee, In-Seop

    2007-01-01

    A biocompatible hydrogel of hyaluronic acid with the neurite-promoting peptide sequence of IKVAV was synthesized. The characterization of the hydrogel shows an open porous structure and a large surface area available for cell interaction. Its ability to promote tissue repair and axonal regeneration in the lesioned rat cerebrum is also evaluated. After implantation, the polymer hydrogel repaired the tissue defect and formed a permissive interface with the host tissue. Axonal growth occurred within the microstructure of the network. Within 6 weeks the polymer implant was invaded by host-derived tissue, glial cells, blood vessels and axons. Such a hydrogel matrix showed the properties of neuron conduction. It has the potential to repair tissue defects in the central nervous system by promoting the formation of a tissue matrix and axonal growth by replacing the lost tissue

  18. Normal axonal ion channel function in large peripheral nerve fibers following chronic ciguatera sensitization.

    Science.gov (United States)

    Vucic, Steve; Kiernan, Matthew C

    2008-03-01

    Although the acute clinical effects of ciguatera poisoning, due to ingestion of ciguatoxin, are mediated by activation of transient Na+ channels, the mechanisms underlying ciguatera sensitization remain undefined. Axonal excitability studies were performed by stimulating the median motor and sensory nerves in two patients with ciguatera sensitization. Excitability parameters were all within normal limits, thereby arguing against dysfunction of axonal membrane ion channels in large-diameter fibers in ciguatera sensitization.

  19. Dynamics of oligodendrocyte responses to anterograde axonal (Wallerian) and terminal degeneration in normal and TNF-transgenic mice

    DEFF Research Database (Denmark)

    Drøjdahl, Nina; Fenger, Christina; Nielsen, Helle H

    2004-01-01

    degeneration and lesion-induced axonal sprouting in the hippocampal dentate gyrus in TNF-transgenic mice with the response in genetically normal mice. Transectioning of the entorhino-dentate perforant path axonal projection increased hippocampal TNF mRNA expression in both types of mice, but to significantly...... larger levels in the TNF-transgenics. At 5 days after axonal transection, numbers of oligodendrocytes and myelin basic protein (MBP) mRNA expression in the denervated dentate gyrus in TNF-transgenic mice had increased to the same extent as in nontransgenic littermates. At this time, transgenics showed...

  20. Axonal transport and incorporation of radioactivity after injection of N-[3H]acetyl-D-mannosamine into rat mesencephalon

    International Nuclear Information System (INIS)

    Loopuijt, L.D.

    1980-01-01

    A study has been performed to demonstrate the possibility of incorporation of sialic acid into nerve endings of the rubrospinal tract after antegrade axonal transport. Young adult rats received injections of N-[ 3 H]acetyl-D-mannosamine into the red nucleus and axonal transport of the tritiated compounds along the axons of afferent and efferent connections of the red nucleus was studied and the transported material was analysed. Light microscopic autoradiography and biochemical methods were used. (Auth./C.F.)

  1. Regulation of Adult CNS Axonal Regeneration by the Post-transcriptional Regulator Cpeb1

    Directory of Open Access Journals (Sweden)

    Wilson Pak-Kin Lou

    2018-01-01

    Full Text Available Adult mammalian central nervous system (CNS neurons are unable to regenerate following axonal injury, leading to permanent functional impairments. Yet, the reasons underlying this regeneration failure are not fully understood. Here, we studied the transcriptome and translatome shortly after spinal cord injury. Profiling of the total and ribosome-bound RNA in injured and naïve spinal cords identified a substantial post-transcriptional regulation of gene expression. In particular, transcripts associated with nervous system development were down-regulated in the total RNA fraction while remaining stably loaded onto ribosomes. Interestingly, motif association analysis of post-transcriptionally regulated transcripts identified the cytoplasmic polyadenylation element (CPE as enriched in a subset of these transcripts that was more resistant to injury-induced reduction at the transcriptome level. Modulation of these transcripts by overexpression of the CPE binding protein, Cpeb1, in mouse and Drosophila CNS neurons promoted axonal regeneration following injury. Our study uncovered a global evolutionarily conserved post-transcriptional mechanism enhancing regeneration of injured CNS axons.

  2. Na(v)1.8 channelopathy in mutant mice deficient for myelin protein zero is detrimental to motor axons

    DEFF Research Database (Denmark)

    Moldovan, Mihai; Alvarez Herrero, Susana; Pinchenko, Volodymyr

    2011-01-01

    Myelin protein zero mutations were found to produce Charcot-Marie-Tooth disease phenotypes with various degrees of myelin impairment and axonal loss, ranging from the mild 'demyelinating' adult form to severe and early onset forms. Protein zero deficient homozygous mice ( ) show a severe and prog......Myelin protein zero mutations were found to produce Charcot-Marie-Tooth disease phenotypes with various degrees of myelin impairment and axonal loss, ranging from the mild 'demyelinating' adult form to severe and early onset forms. Protein zero deficient homozygous mice ( ) show a severe...... and progressive dysmyelinating neuropathy from birth with compromised myelin compaction, hypomyelination and distal axonal degeneration. A previous study using immunofluorescence showed that motor nerves deficient of myelin protein zero upregulate the Na(V)1.8 voltage gated sodium channel isoform, which...... is normally present only in restricted populations of sensory axons. The aim of this study was to investigate the function of motor axons in protein zero-deficient mice with particular emphasis on ectopic Na(V)1.8 voltage gated sodium channel. We combined 'threshold tracking' excitability studies...

  3. Spider silk constructs enhance axonal regeneration and remyelination in long nerve defects in sheep.

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    Christine Radtke

    Full Text Available BACKGROUND: Surgical reapposition of peripheral nerve results in some axonal regeneration and functional recovery, but the clinical outcome in long distance nerve defects is disappointing and research continues to utilize further interventional approaches to optimize functional recovery. We describe the use of nerve constructs consisting of decellularized vein grafts filled with spider silk fibers as a guiding material to bridge a 6.0 cm tibial nerve defect in adult sheep. METHODOLOGY/PRINCIPAL FINDINGS: The nerve constructs were compared to autologous nerve grafts. Regeneration was evaluated for clinical, electrophysiological and histological outcome. Electrophysiological recordings were obtained at 6 months and 10 months post surgery in each group. Ten months later, the nerves were removed and prepared for immunostaining, electrophysiological and electron microscopy. Immunostaining for sodium channel (NaV 1.6 was used to define nodes of Ranvier on regenerated axons in combination with anti-S100 and neurofilament. Anti-S100 was used to identify Schwann cells. Axons regenerated through the constructs and were myelinated indicating migration of Schwann cells into the constructs. Nodes of Ranvier between myelin segments were observed and identified by intense sodium channel (NaV 1.6 staining on the regenerated axons. There was no significant difference in electrophysiological results between control autologous experimental and construct implantation indicating that our construct are an effective alternative to autologous nerve transplantation. CONCLUSIONS/SIGNIFICANCE: This study demonstrates that spider silk enhances Schwann cell migration, axonal regrowth and remyelination including electrophysiological recovery in a long-distance peripheral nerve gap model resulting in functional recovery. This improvement in nerve regeneration could have significant clinical implications for reconstructive nerve surgery.

  4. The age factor in axonal repair after spinal cord injury: A focus on neuron-intrinsic mechanisms.

    Science.gov (United States)

    Geoffroy, Cédric G; Meves, Jessica M; Zheng, Binhai

    2017-06-23

    Age is an important consideration for recovery and repair after spinal cord injury. Spinal cord injury is increasingly affecting the middle-aged and aging populations. Despite rapid progress in research to promote axonal regeneration and repair, our understanding of how age can modulate this repair is rather limited. In this review, we discuss the literature supporting the notion of an age-dependent decline in axonal growth after central nervous system (CNS) injury. While both neuron-intrinsic and extrinsic factors are involved in the control of axon growth after injury, here we focus on possible intrinsic mechanisms for this age-dependent decline. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  5. Direct transfer of viral and cellular proteins from varicella-zoster virus-infected non-neuronal cells to human axons.

    Science.gov (United States)

    Grigoryan, Sergei; Yee, Michael B; Glick, Yair; Gerber, Doron; Kepten, Eldad; Garini, Yuval; Yang, In Hong; Kinchington, Paul R; Goldstein, Ronald S

    2015-01-01

    Varicella Zoster Virus (VZV), the alphaherpesvirus that causes varicella upon primary infection and Herpes zoster (shingles) following reactivation in latently infected neurons, is known to be fusogenic. It forms polynuclear syncytia in culture, in varicella skin lesions and in infected fetal human ganglia xenografted to mice. After axonal infection using VZV expressing green fluorescent protein (GFP) in compartmentalized microfluidic cultures there is diffuse filling of axons with GFP as well as punctate fluorescence corresponding to capsids. Use of viruses with fluorescent fusions to VZV proteins reveals that both proteins encoded by VZV genes and those of the infecting cell are transferred in bulk from infecting non-neuronal cells to axons. Similar transfer of protein to axons was observed following cell associated HSV1 infection. Fluorescence recovery after photobleaching (FRAP) experiments provide evidence that this transfer is by diffusion of proteins from the infecting cells into axons. Time-lapse movies and immunocytochemical experiments in co-cultures demonstrate that non-neuronal cells fuse with neuronal somata and proteins from both cell types are present in the syncytia formed. The fusogenic nature of VZV therefore may enable not only conventional entry of virions and capsids into axonal endings in the skin by classical entry mechanisms, but also by cytoplasmic fusion that permits viral protein transfer to neurons in bulk.

  6. Cortical Divergent Projections in Mice Originate from Two Sequentially Generated, Distinct Populations of Excitatory Cortical Neurons with Different Initial Axonal Outgrowth Characteristics.

    Science.gov (United States)

    Hatanaka, Yumiko; Namikawa, Tomohiro; Yamauchi, Kenta; Kawaguchi, Yasuo

    2016-05-01

    Excitatory cortical neurons project to various subcortical and intracortical regions, and exhibit diversity in their axonal connections. Although this diversity may develop from primary axons, how many types of axons initially occur remains unknown. Using a sparse-labeling in utero electroporation method, we investigated the axonal outgrowth of these neurons in mice and correlated the data with axonal projections in adults. Examination of lateral cortex neurons labeled during the main period of cortical neurogenesis (E11.5-E15.5) indicated that axonal outgrowth commonly occurs in the intermediate zone. Conversely, the axonal direction varied; neurons labeled before E12.5 and the earliest cortical plate neurons labeled at E12.5 projected laterally, whereas neurons labeled thereafter projected medially. The expression of Ctip2 and Satb2 and the layer destinations of these neurons support the view that lateral and medial projection neurons are groups of prospective subcortical and callosal projection neurons, respectively. Consistently, birthdating experiments demonstrated that presumptive lateral projection neurons were generated earlier than medial projection neurons, even within the same layer. These results suggest that the divergent axonal connections of excitatory cortical neurons begin from two types of primary axons, which originate from two sequentially generated distinct subpopulations: early-born lateral (subcortical) and later-born medial (callosal) projection neuron groups. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  7. Nociceptive afferents to the premotor neurons that send axons simultaneously to the facial and hypoglossal motoneurons by means of axon collaterals.

    Directory of Open Access Journals (Sweden)

    Yulin Dong

    Full Text Available It is well known that the brainstem premotor neurons of the facial nucleus and hypoglossal nucleus coordinate orofacial nociceptive reflex (ONR responses. However, whether the brainstem PNs receive the nociceptive projection directly from the caudal spinal trigeminal nucleus is still kept unclear. Our present study focuses on the distribution of premotor neurons in the ONR pathways of rats and the collateral projection of the premotor neurons which are involved in the brainstem local pathways of the orofacial nociceptive reflexes of rat. Retrograde tracer Fluoro-gold (FG or FG/tetramethylrhodamine-dextran amine (TMR-DA were injected into the VII or/and XII, and anterograde tracer biotinylated dextran amine (BDA was injected into the caudal spinal trigeminal nucleus (Vc. The tracing studies indicated that FG-labeled neurons receiving BDA-labeled fibers from the Vc were mainly distributed bilaterally in the parvicellular reticular formation (PCRt, dorsal and ventral medullary reticular formation (MdD, MdV, supratrigeminal nucleus (Vsup and parabrachial nucleus (PBN with an ipsilateral dominance. Some FG/TMR-DA double-labeled premotor neurons, which were observed bilaterally in the PCRt, MdD, dorsal part of the MdV, peri-motor nucleus regions, contacted with BDA-labeled axonal terminals and expressed c-fos protein-like immunoreactivity which induced by subcutaneous injection of formalin into the lip. After retrograde tracer wheat germ agglutinated horseradish peroxidase (WGA-HRP was injected into VII or XII and BDA into Vc, electron microscopic study revealed that some BDA-labeled axonal terminals made mainly asymmetric synapses on the dendritic and somatic profiles of WGA-HRP-labeled premotor neurons. These data indicate that some premotor neurons could integrate the orofacial nociceptive input from the Vc and transfer these signals simultaneously to different brainstem motonuclei by axonal collaterals.

  8. [A study on toxic effects of sodium salicylate on rat cochlear spiral ganglion neurons: dopamine receptors mediate expressions of NMDA and GABAA receptors].

    Science.gov (United States)

    Wei, Ting-Jia; Chen, Hui-Ying; Huang, Xi; Weng, Jing-Jin; Qin, Jiang-Yuan; Su, Ji-Ping

    2017-06-25

    The aim of the present study was to observe whether dopamine receptor (DR) was involved in the effects of sodium salicylate (SS) on the expressions of N-methyl-D-aspartic acid (NMDA) and γ-aminobutyric acid (GABA) receptors in rat cochlear spiral ganglion neurons (SGNs). Forty-eight hours after primary culture of rat SGNs, immunofluorescence technique was applied to detect expressions of DR1 and DR2, the two subtypes of dopamine receptors. Western blot was performed to assess NMDA receptor NR1 subunit and GABA A receptor subunit α2 (GABRα2) protein expressions in the SGNs after the treatments of SS alone or in combination with DR antagonists. The results demonstrated that: (1) The DR1 and DR2 were expressed in the bodies and axons of the SGN; (2) After the treatment with SS, the surface protein expressions of GABRα2 and NR1 were decreased by 44.69% and 21.57%, respectively, while the total protein expressions showed no significant changes; (3) Neither SS + SCH23390 (DR1 antagonist) group nor SS + Eticlopride (DR2 antagonist) group showed significant differences in GABRα2 and NR1 surface protein expressions compared with the control group. These results suggest that SS regulates the surface GABA A and NMDA receptors trafficking on SGN, and the mechanism may involve DR mediation.

  9. Early Life Stress Effects on Glucocorticoid—BDNF Interplay in the Hippocampus

    Science.gov (United States)

    Daskalakis, Nikolaos P.; De Kloet, Edo Ronald; Yehuda, Rachel; Malaspina, Dolores; Kranz, Thorsten M.

    2015-01-01

    Early life stress (ELS) is implicated in the etiology of multiple psychiatric disorders. Important biological effects of ELS are manifested in stress-susceptible regions of the hippocampus and are partially mediated by long-term effects on glucocorticoid (GC) and/or neurotrophin signaling pathways. GC-signaling mediates the regulation of stress response to maintain homeostasis, while neurotrophin signaling plays a key role in neuronal outgrowth and is crucial for axonal guidance and synaptic integrity. The neurotrophin and GC-signaling pathways co-exist throughout the central nervous system (CNS), particularly in the hippocampus, which has high expression levels of glucocorticoid-receptors (GR) and mineralocorticoid-receptors (MR) as well as brain-derived neurotrophic factor (BDNF) and its receptor, tropomyosin-related kinase receptor B (TrkB). This review addresses the effects of ELS paradigms on GC- and BDNF-dependent mechanisms and their crosstalk in the hippocampus, including potential implications for the pathogenesis of common stress-related disorders. PMID:26635521

  10. Retention of retinal axon collateral is responsible for induced ipsilateral retinotectal projections in adult goldfish.

    Science.gov (United States)

    Sharma, S C; Tsai, C

    1991-01-01

    In normal goldfish, optic axons innervate only the contralateral optic tectum. When one eye was enucleated and the optic nerve of the other eye crushed, the regenerating optic axons innervated both optic tecta. We studied the presence of bilaterally projecting retinal ganglion cells by double retrograde cell labeling methods using Nuclear Yellow and True Blue dyes. About 10% of the retinal ganglion cells were double labeled and these cells were found throughout the retina. In addition, HRP application to the ipsilateral tectum revealed retrogradely-labeled retinal ganglion cells of all morphological types. These results suggest that induced ipsilateral projections are formed by regenerating axon collaterals and that all cell types are involved in the generation of normal mirror image typography.

  11. Loss of spastin function results in disease-specific axonal defects in human pluripotent stem cell-based models of hereditary spastic paraplegia

    Science.gov (United States)

    Denton, Kyle R.; Lei, Ling; Grenier, Jeremy; Rodionov, Vladimir; Blackstone, Craig; Li, Xue-Jun

    2013-01-01

    Human neuronal models of hereditary spastic paraplegias (HSP) that recapitulate disease-specific axonal pathology hold the key to understanding why certain axons degenerate in patients and to developing therapies. SPG4, the most common form of HSP, is caused by autosomal dominant mutations in the SPAST gene, which encodes the microtubule-severing ATPase spastin. Here, we have generated a human neuronal model of SPG4 by establishing induced pluripotent stem cells (iPSCs) from an SPG4 patient and differentiating these cells into telencephalic glutamatergic neurons. The SPG4 neurons displayed a significant increase in axonal swellings, which stained strongly for mitochondria and tau, indicating the accumulation of axonal transport cargoes. In addition, mitochondrial transport was decreased in SPG4 neurons, revealing that these patient iPSC-derived neurons recapitulate disease-specific axonal phenotypes. Interestingly, spastin protein levels were significantly decreased in SPG4 neurons, supporting a haploinsufficiency mechanism. Furthermore, cortical neurons derived from spastin-knockdown human embryonic stem cells (hESCs) exhibited similar axonal swellings, confirming that the axonal defects can be caused by loss of spastin function. These spastin-knockdown hESCs serve as an additional model for studying HSP. Finally, levels of stabilized acetylated-tubulin were significantly increased in SPG4 neurons. Vinblastine, a microtubule-destabilizing drug, rescued this axonal swelling phenotype in neurons derived from both SPG4 iPSCs and spastin-knockdown hESCs. Thus, this study demonstrates the successful establishment of human pluripotent stem cell-based neuronal models of SPG4, which will be valuable for dissecting the pathogenic cellular mechanisms and screening compounds to rescue the axonal degeneration in HSP. PMID:24123785

  12. ImagePAD, a novel counting application for the Apple iPad, used to quantify axons in the mouse optic nerve.

    Science.gov (United States)

    Templeton, Justin P; Struebing, Felix L; Lemmon, Andrew; Geisert, Eldon E

    2014-11-01

    The present article introduces a new and easy to use counting application for the Apple iPad. The application "ImagePAD" takes advantage of the advanced user interface features offered by the Apple iOS platform, simplifying the rather tedious task of quantifying features in anatomical studies. For example, the image under analysis can be easily panned and zoomed using iOS-supported multi-touch gestures without losing the spatial context of the counting task, which is extremely important for ensuring count accuracy. This application allows one to quantify up to 5 different types of objects in a single field and output the data in a tab-delimited format for subsequent analysis. We describe two examples of the use of the application: quantifying axons in the optic nerve of the C57BL/6J mouse and determining the percentage of cells labeled with NeuN or ChAT in the retinal ganglion cell layer. For the optic nerve, contiguous images at 60× magnification were taken and transferred onto an Apple iPad. Axons were counted by tapping on the touch-sensitive screen using ImagePAD. Nine optic nerves were sampled and the number of axons in the nerves ranged from 38,872 axons to 50,196 axons with an average of 44,846 axons per nerve (SD = 3980 axons). Copyright © 2014 Elsevier Ltd. All rights reserved.

  13. In vivo imaging reveals rapid astrocyte depletion and axon damage in a model of neuromyelitis optica-related pathology

    DEFF Research Database (Denmark)

    Herwerth, Marina; Kalluri, Sudhakar Reddy; Srivastava, Rajneesh

    2016-01-01

    IgG autoantibodies against aquaporin-4 (AQP4), an astrocytic water channel. Antibodies against AQP4 can damage astrocytes via complement, but NMO histopathology also shows demyelination, and - importantly - axon injury, which may determine permanent deficits following NMO relapses. The dynamics...... antibodies in mice. RESULTS: We found that human AQP4 antibodies caused acute astrocyte depletion with initial oligodendrocyte survival. Within two hours of antibody application, we observed secondary axon injury in the form of progressive swellings. Astrocyte toxicity and axon damage were dependent on AQP4...... antibody concentration and complement, specifically C1q. INTERPRETATION: In vivo imaging of the spinal cord reveals the swift development of NMO-related acute axon injury following AQP4 antibody-mediated astrocyte depletion. This approach will be useful in studying the mechanisms underlying the spread...

  14. Matrix metalloproteinase 2 and membrane type 1 matrix metalloproteinase co-regulate axonal outgrowth of mouse retinal ganglion cells

    DEFF Research Database (Denmark)

    Gaublomme, Djoere; Buyens, Tom; De Groef, Lies

    2014-01-01

    regenerative therapies, an improved understanding of axonal outgrowth and the various molecules influencing it, is highly needed. Matrix metalloproteinases (MMPs) constitute a family of zinc-dependent proteases that were sporadically reported to influence axon outgrowth. Using an ex vivo retinal explant model......, but not MMP-9, are involved in this process. Furthermore, administration of a novel antibody to MT1-MMP that selectively blocks pro-MMP-2 activation revealed a functional co-involvement of these proteinases in determining RGC axon outgrowth. Subsequent immunostainings showed expression of both MMP-2 and MT1...... nervous system is lacking in adult mammals, thereby impeding recovery from injury to the nervous system. Matrix metalloproteinases (MMPs) constitute a family of zinc-dependent proteases that were sporadically reported to influence axon outgrowth. Inhibition of specific MMPs reduced neurite outgrowth from...

  15. Acetylated tau destabilizes the cytoskeleton in the axon initial segment and is mislocalized to the somatodendritic compartment.

    Science.gov (United States)

    Sohn, Peter Dongmin; Tracy, Tara E; Son, Hye-In; Zhou, Yungui; Leite, Renata E P; Miller, Bruce L; Seeley, William W; Grinberg, Lea T; Gan, Li

    2016-06-29

    Neurons are highly polarized cells in which asymmetric axonal-dendritic distribution of proteins is crucial for neuronal function. Loss of polarized distribution of the axonal protein tau is an early sign of Alzheimer's disease (AD) and other neurodegenerative disorders. The cytoskeletal network in the axon initial segment (AIS) forms a barrier between the axon and the somatodentritic compartment, contributing to axonal retention of tau. Although perturbation of the AIS cytoskeleton has been implicated in neurological disorders, the molecular triggers and functional consequence of AIS perturbation are incompletely understood. Here we report that tau acetylation and consequent destabilization of the AIS cytoskeleton promote the somatodendritic mislocalization of tau. AIS cytoskeletal proteins, including ankyrin G and βIV-spectrin, were downregulated in AD brains and negatively correlated with an increase in tau acetylated at K274 and K281. AIS proteins were also diminished in transgenic mice expressing tauK274/281Q, a tau mutant that mimics K274 and K281 acetylation. In primary neuronal cultures, the tauK274/281Q mutant caused hyperdynamic microtubules (MTs) in the AIS, shown by live-imaging of MT mobility and fluorescence recovery after photobleaching. Using photoconvertible tau constructs, we found that axonal tauK274/281Q was missorted into the somatodendritic compartment. Stabilizing MTs with epothilone D to restore the cytoskeletal barrier in the AIS prevented tau mislocalization in primary neuronal cultures. Together, these findings demonstrate that tau acetylation contributes to the pathogenesis of neurodegenerative disease by compromising the cytoskeletal sorting machinery in the AIS.

  16. Axonal diameter and density estimated with 7-Tesla hybrid diffusion imaging in transgenic Alzheimer rats

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    Daianu, Madelaine; Jacobs, Russell E.; Town, Terrence; Thompson, Paul M.

    2016-03-01

    Diffusion-weighted MR imaging (DWI) is a powerful tool to study brain tissue microstructure. DWI is sensitive to subtle changes in the white matter (WM), and can provide insight into abnormal brain changes in diseases such as Alzheimer's disease (AD). In this study, we used 7-Tesla hybrid diffusion imaging (HYDI) to scan 3 transgenic rats (line TgF344-AD; that model the full clinico-pathological spectrum of the human disease) ex vivo at 10, 15 and 24 months. We acquired 300 DWI volumes across 5 q-sampling shells (b=1000, 3000, 4000, 8000, 12000 s/mm2). From the top three b-value shells with highest signal-to-noise ratios, we reconstructed markers of WM disease, including indices of axon density and diameter in the corpus callosum (CC) - directly quantifying processes that occur in AD. As expected, apparent anisotropy progressively decreased with age; there were also decreases in the intra- and extra-axonal MR signal along axons. Axonal diameters were larger in segments of the CC (splenium and body, but not genu), possibly indicating neuritic dystrophy - characterized by enlarged axons and dendrites as previously observed at the ultrastructural level (see Cohen et al., J. Neurosci. 2013). This was further supported by increases in MR signals trapped in glial cells, CSF and possibly other small compartments in WM structures. Finally, tractography detected fewer fibers in the CC at 10 versus 24 months of age. These novel findings offer great potential to provide technical and scientific insight into the biology of brain disease.

  17. Ion channel density regulates switches between regular and fast spiking in soma but not in axons.

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    Hugo Zeberg

    2010-04-01

    Full Text Available The threshold firing frequency of a neuron is a characterizing feature of its dynamical behaviour, in turn determining its role in the oscillatory activity of the brain. Two main types of dynamics have been identified in brain neurons. Type 1 dynamics (regular spiking shows a continuous relationship between frequency and stimulation current (f-I(stim and, thus, an arbitrarily low frequency at threshold current; Type 2 (fast spiking shows a discontinuous f-I(stim relationship and a minimum threshold frequency. In a previous study of a hippocampal neuron model, we demonstrated that its dynamics could be of both Type 1 and Type 2, depending on ion channel density. In the present study we analyse the effect of varying channel density on threshold firing frequency on two well-studied axon membranes, namely the frog myelinated axon and the squid giant axon. Moreover, we analyse the hippocampal neuron model in more detail. The models are all based on voltage-clamp studies, thus comprising experimentally measurable parameters. The choice of analysing effects of channel density modifications is due to their physiological and pharmacological relevance. We show, using bifurcation analysis, that both axon models display exclusively Type 2 dynamics, independently of ion channel density. Nevertheless, both models have a region in the channel-density plane characterized by an N-shaped steady-state current-voltage relationship (a prerequisite for Type 1 dynamics and associated with this type of dynamics in the hippocampal model. In summary, our results suggest that the hippocampal soma and the two axon membranes represent two distinct kinds of membranes; membranes with a channel-density dependent switching between Type 1 and 2 dynamics, and membranes with a channel-density independent dynamics. The difference between the two membrane types suggests functional differences, compatible with a more flexible role of the soma membrane than that of the axon membrane.

  18. Sensory-motor axonal polyneuropathy involving cranial nerves: An uncommon manifestation of disulfiram toxicity.

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    Santos, Telma; Martins Campos, António; Morais, Hugo

    2017-01-01

    Disulfiram (tetraethylthiuram disulfide) has been used for the treatment of alcohol dependence. An axonal sensory-motor polyneuropathy with involvement of cranial pairs due to disulfiram is exceedingly rare. The authors report a unique case of an extremely severe axonal polyneuropathy involving cranial nerves that developed within weeks after a regular dosage of 500mg/day disulfiram. To the authors best knowledge, such a severe and rapidly-progressive course has never been described with disulfiram dosages of only 500mg/day. Copyright © 2016 Elsevier B.V. All rights reserved.

  19. Adenosine A2B and A3 receptor location at the mouse neuromuscular junction.

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    Garcia, Neus; Priego, Mercedes; Hurtado, Erica; Obis, Teresa; Santafe, Manel M; Tomàs, Marta; Lanuza, Maria Angel; Tomàs, Josep

    2014-07-01

    To date, four subtypes of adenosine receptors have been cloned (A(1)R, A(2A)R, A(2B)R, and A(3)R). In a previous study we used confocal immunocytochemistry to identify A(1)R and A(2A)R receptors at mouse neuromuscular junctions (NMJs). The data shows that these receptors are localized differently in the three cells (muscle, nerve and glia) that configure the NMJs. A(1)R localizes in the terminal teloglial Schwann cell and nerve terminal, whereas A(2A)R localizes in the postsynaptic muscle and in the axon and nerve terminal. Here, we use Western blotting to investigate the presence of A(2B)R and A(3)R receptors in striated muscle and immunohistochemistry to localize them in the three cells of the adult neuromuscular synapse. The data show that A(2B)R and A(3)R receptors are present in the nerve terminal and muscle cells at the NMJs. Neither A(2B)R nor A(3)R receptors are localized in the Schwann cells. Thus, the four subtypes of adenosine receptors are present in the motor endings. The presence of these receptors in the neuromuscular synapse allows the receptors to be involved in the modulation of transmitter release. © 2014 Anatomical Society.

  20. Studies in the development of a bridging device for guiding regenerating axons

    Science.gov (United States)

    Wen, Xuejun

    At present there is no clinically effective treatment for injuries or pathological processes that disrupt the continuity of axons in the mature central nervous system. However, a number of studies suggest that a tremendous potential exists for developing therapies. In particular biomaterials in the form of bridging substrates been shown to support at least some level of axonal regeneration across the lesion site, but display a limited capacity for directing axons toward their targets. To influence the directionality of the regeneration process filaments and tubes appear promising but the technology is far from optimized. As a step toward optimization, we investigated various components of a tissue-engineered bridging device consisting of numerous filaments surrounded by a semipermeable biodegradable hollow fiber membrane (HFM). In the first part of the thesis, we studied the influence of filament diameter and various extracellular matrix coatings on neuron regeneration suing a dorsal root ganglion explant model. We found that laminin surface treated filaments that approached the size of spinal axons support significantly longer regenerative outgrowth than similarly treated filaments of larger diameter, and exceed outgrowth distance on similarly sized filaments treated with fibronectin. Such substrates also consistently supported the attachment and alignment of glial cells and directed the outgrowth of regenerating axons along the long axis of the filaments. In the last part of the thesis, biodegradable hollow fiber membranes were fabricated and their physical, chemical and degradation properties were analyzed. We found that it is possible to use phase inversion methods to fabricate hollow fiber membranes of widely varying properties that degrade of the course of several months. We then evaluated the biocompatibility of the new materials after implantation in the CNS using an adult rat model. We found that the implants were well tolerated and elicited a reaction