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Sample records for anaphase

  1. The origins and processing of ultra fine anaphase DNA bridges

    DEFF Research Database (Denmark)

    Liu, Ying; Nielsen, Christian Thomas Friberg; Yao, Qi;

    2014-01-01

    and BLM. UFBs become visible in the anaphase of mitosis, and can persist into telophase in rare cases. There are at least three different types of UFBs that can be distinguished according to the chromosomal loci from which they originate. However, it remains largely unknown how these UFBs are...

  2. New insights into the formation and resolution of ultra-fine anaphase bridges

    DEFF Research Database (Denmark)

    Chan, Kok Lung; Hickson, Ian D

    2011-01-01

    that are important for preventing Fanconi anemia (FA) in man. As part of an analysis of the roles of these proteins in mitosis, we identified a novel class of anaphase bridge structure, called an ultra-fine anaphase bridge (UFB). These UFBs are also defined by the presence of a SNF2 family protein...

  3. Spindle checkpoint activation at meiosis I advances anaphase II onset via meiosis-specific APC/C regulation

    OpenAIRE

    Yamamoto, Ayumu; Kitamura, Kenji; Hihara, Daisuke; Hirose, Yukinobu; Katsuyama, Satoshi; Hiraoka, Yasushi

    2008-01-01

    During mitosis, the spindle assembly checkpoint (SAC) inhibits the Cdc20-activated anaphase-promoting complex/cyclosome (APC/CCdc20), which promotes protein degradation, and delays anaphase onset to ensure accurate chromosome segregation. However, the SAC function in meiotic anaphase regulation is poorly understood. Here, we examined the SAC function in fission yeast meiosis. As in mitosis, a SAC factor, Mad2, delayed anaphase onset via Slp1 (fission yeast Cdc20) when chromosomes attach to th...

  4. A decade of the anaphase-promoting complex in the nervous system.

    Science.gov (United States)

    Huang, Ju; Bonni, Azad

    2016-03-15

    Control of protein abundance by the ubiquitin-proteasome system is essential for normal brain development and function. Just over a decade ago, the first post-mitotic function of the anaphase-promoting complex, a major cell cycle-regulated E3 ubiquitin ligase, was discovered in the control of axon growth and patterning in the mammalian brain. Since then, a large number of studies have identified additional novel roles for the anaphase-promoting complex in diverse aspects of neuronal connectivity and plasticity in the developing and mature nervous system. In this review, we discuss the functions and mechanisms of the anaphase-promoting complex in neurogenesis, glial differentiation and migration, neuronal survival and metabolism, neuronal morphogenesis, synapse formation and plasticity, and learning and memory. We also provide a perspective on future investigations of the anaphase-promoting complex in neurobiology. PMID:26980187

  5. Processing, localization, and requirement of human separase for normal anaphase progression

    OpenAIRE

    Chestukhin, Anton; Pfeffer, Christian; Milligan, Scott; DeCaprio, James A.; Pellman, David

    2003-01-01

    In all eukaryotes, anaphase is triggered by the activation of a protease called separase. Once activated, separase cleaves a subunit of cohesin, a complex that links replicated chromatids before anaphase. Separase and cohesin are conserved from yeasts to humans. Although the machinery for dissolving sister cohesion is conserved, the regulation of this process appears to be more complex in higher eukaryotes than in yeast. Here we report the cloning of full-length human separase cDNA and the ch...

  6. Asymmetric division of cyst stem cells in Drosophila testis is ensured by anaphase spindle repositioning

    OpenAIRE

    Cheng, Jun; Tiyaboonchai, Amita; Yamashita, Yukiko M.; Hunt, Alan J.

    2011-01-01

    Many stem cells divide asymmetrically to balance self-renewal and differentiation. In Drosophila testes, two stem cell populations, germline stem cells (GSCs) and somatic cyst stem cells (CySCs), cohere and regulate one another. Here, we report that CySCs divide asymmetrically through repositioning the mitotic spindle around anaphase. CySC spindle repositioning requires functional centrosomes, Dynein and the actin-membrane linker Moesin. Anaphase spindle repositioning is required to achieve h...

  7. APC/C-Cdh1-dependent anaphase and telophase progression during mitotic slippage

    Directory of Open Access Journals (Sweden)

    Toda Kazuhiro

    2012-02-01

    Full Text Available Abstract Background The spindle assembly checkpoint (SAC inhibits anaphase progression in the presence of insufficient kinetochore-microtubule attachments, but cells can eventually override mitotic arrest by a process known as mitotic slippage or adaptation. This is a problem for cancer chemotherapy using microtubule poisons. Results Here we describe mitotic slippage in yeast bub2Δ mutant cells that are defective in the repression of precocious telophase onset (mitotic exit. Precocious activation of anaphase promoting complex/cyclosome (APC/C-Cdh1 caused mitotic slippage in the presence of nocodazole, while the SAC was still active. APC/C-Cdh1, but not APC/C-Cdc20, triggered anaphase progression (securin degradation, separase-mediated cohesin cleavage, sister-chromatid separation and chromosome missegregation, in addition to telophase onset (mitotic exit, during mitotic slippage. This demonstrates that an inhibitory system not only of APC/C-Cdc20 but also of APC/C-Cdh1 is critical for accurate chromosome segregation in the presence of insufficient kinetochore-microtubule attachments. Conclusions The sequential activation of APC/C-Cdc20 to APC/C-Cdh1 during mitosis is central to accurate mitosis. Precocious activation of APC/C-Cdh1 in metaphase (pre-anaphase causes mitotic slippage in SAC-activated cells. For the prevention of mitotic slippage, concomitant inhibition of APC/C-Cdh1 may be effective for tumor therapy with mitotic spindle poisons in humans.

  8. A driving and coupling “Pac-Man” mechanism for chromosome poleward translocation in anaphase A

    OpenAIRE

    Liu, Jian; Onuchic, José N.

    2006-01-01

    During mitosis, chromatid harnesses its kinetochore translocation at the depolymerizing microtubule ends for its poleward movement in anaphase A. The force generation mechanism for such movement remains unknown. Analysis of the current experimental results shows that the bending energy release from the bound tubulin subunits alone cannot provide sufficient driving force. Additional contribution from effective electrostatic attractions between the kinetochore and the microtubule is needed for ...

  9. The Giardia cell cycle progresses independently of the anaphase-promoting complex

    OpenAIRE

    Gourguechon, Stéphane; Holt, Liam J.; Cande, W. Zacheus

    2013-01-01

    Most cell cycle regulation research has been conducted in model organisms representing a very small part of the eukaryotic domain. The highly divergent human pathogen Giardia intestinalis is ideal for studying the conservation of eukaryotic pathways. Although Giardia has many cell cycle regulatory components, its genome lacks all anaphase-promoting complex (APC) components. In the present study, we show that a single mitotic cyclin in Giardia is essential for progression into mitosis. Strikin...

  10. Fin1-PP1 Helps Clear Spindle Assembly Checkpoint Protein Bub1 from Kinetochores in Anaphase.

    Science.gov (United States)

    Bokros, Michael; Gravenmier, Curtis; Jin, Fengzhi; Richmond, Daniel; Wang, Yanchang

    2016-02-01

    The spindle assembly checkpoint (SAC) monitors chromosome attachment defects, and the assembly of SAC proteins at kinetochores is essential for its activation, but the SAC disassembly process remains unknown. We found that deletion of a 14-3-3 protein, Bmh1, or hyperactivation of Cdc14 early anaphase release (FEAR) allows premature SAC silencing in budding yeast, which depends on a kinetochore protein Fin1 that forms a complex with protein phosphatase PP1. Previous works suggest that FEAR-dependent Fin1 dephosphorylation promotes Bmh1-Fin1 dissociation, which enables kinetochore recruitment of Fin1-PP1. We found persistent kinetochore association of SAC protein Bub1 in fin1Δ mutants after anaphase entry. Therefore, we revealed a mechanism that clears SAC proteins from kinetochores. After anaphase entry, FEAR activation promotes kinetochore enrichment of Fin1-PP1, resulting in SAC disassembly at kinetochores. This mechanism is required for efficient SAC silencing after SAC is challenged, and untimely Fin1-kinetochore association causes premature SAC silencing and chromosome missegregation. PMID:26832405

  11. Field applications of the piscine anaphase aberration test. Lessons from the Exxon Valdez oil spill

    International Nuclear Information System (INIS)

    Several large-scale genotoxicity assessments have been performed in coastal marine areas that have demonstrated either localized or widespread genetic effects resulting from human activity. One common assessment method is the anaphase aberration test, a measurement of abnormal chromosome division, using embryolarval fishes. It can be used to detect the presence of mutagens within a poorly characterized complex mixture or monitor specific genotoxins and is easily adapted for laboratory screening. One comprehensive marine genotoxicity assessment was conducted using Pacific herring (Clupea pallasi) following the Exxon Valdez oil spill (EVOS) in Prince William Sound (PWS), AK in late March 1989. In early May, genetic damage was detected at many sites within the oil trajectory and was correlated with concentrations of polycyclic aromatic hydrocarbons characteristic of Exxon Valdez oil (EVO) in intertidal mussels. Effects were related spatially and temporally to oil exposure. Anaphase aberration rates decreased throughout May and June 1989, and by 1991, genotoxicity was undetectable. The abundance of the 1989 herring year class in PWS is significantly reduced; this is the first reported example linking genotoxicity to subsequent population level effects. This review describes the methodology for the anaphase aberration test using fish eggs, its applications for large-scale assessments and supportive laboratory studies, and its limitations for prediction of higher level effects on populations

  12. Exocyst-Dependent Membrane Addition Is Required for Anaphase Cell Elongation and Cytokinesis in Drosophila.

    Directory of Open Access Journals (Sweden)

    Maria Grazia Giansanti

    2015-11-01

    Full Text Available Mitotic and cytokinetic processes harness cell machinery to drive chromosomal segregation and the physical separation of dividing cells. Here, we investigate the functional requirements for exocyst complex function during cell division in vivo, and demonstrate a common mechanism that directs anaphase cell elongation and cleavage furrow progression during cell division. We show that onion rings (onr and funnel cakes (fun encode the Drosophila homologs of the Exo84 and Sec8 exocyst subunits, respectively. In onr and fun mutant cells, contractile ring proteins are recruited to the equatorial region of dividing spermatocytes. However, cytokinesis is disrupted early in furrow ingression, leading to cytokinesis failure. We use high temporal and spatial resolution confocal imaging with automated computational analysis to quantitatively compare wild-type versus onr and fun mutant cells. These results demonstrate that anaphase cell elongation is grossly disrupted in cells that are compromised in exocyst complex function. Additionally, we observe that the increase in cell surface area in wild type peaks a few minutes into cytokinesis, and that onr and fun mutant cells have a greatly reduced rate of surface area growth specifically during cell division. Analysis by transmission electron microscopy reveals a massive build-up of cytoplasmic astral membrane and loss of normal Golgi architecture in onr and fun spermatocytes, suggesting that exocyst complex is required for proper vesicular trafficking through these compartments. Moreover, recruitment of the small GTPase Rab11 and the PITP Giotto to the cleavage site depends on wild-type function of the exocyst subunits Exo84 and Sec8. Finally, we show that the exocyst subunit Sec5 coimmunoprecipitates with Rab11. Our results are consistent with the exocyst complex mediating an essential, coordinated increase in cell surface area that potentiates anaphase cell elongation and cleavage furrow ingression.

  13. Exocyst-Dependent Membrane Addition Is Required for Anaphase Cell Elongation and Cytokinesis in Drosophila.

    Science.gov (United States)

    Giansanti, Maria Grazia; Vanderleest, Timothy E; Jewett, Cayla E; Sechi, Stefano; Frappaolo, Anna; Fabian, Lacramioara; Robinett, Carmen C; Brill, Julie A; Loerke, Dinah; Fuller, Margaret T; Blankenship, J Todd

    2015-11-01

    Mitotic and cytokinetic processes harness cell machinery to drive chromosomal segregation and the physical separation of dividing cells. Here, we investigate the functional requirements for exocyst complex function during cell division in vivo, and demonstrate a common mechanism that directs anaphase cell elongation and cleavage furrow progression during cell division. We show that onion rings (onr) and funnel cakes (fun) encode the Drosophila homologs of the Exo84 and Sec8 exocyst subunits, respectively. In onr and fun mutant cells, contractile ring proteins are recruited to the equatorial region of dividing spermatocytes. However, cytokinesis is disrupted early in furrow ingression, leading to cytokinesis failure. We use high temporal and spatial resolution confocal imaging with automated computational analysis to quantitatively compare wild-type versus onr and fun mutant cells. These results demonstrate that anaphase cell elongation is grossly disrupted in cells that are compromised in exocyst complex function. Additionally, we observe that the increase in cell surface area in wild type peaks a few minutes into cytokinesis, and that onr and fun mutant cells have a greatly reduced rate of surface area growth specifically during cell division. Analysis by transmission electron microscopy reveals a massive build-up of cytoplasmic astral membrane and loss of normal Golgi architecture in onr and fun spermatocytes, suggesting that exocyst complex is required for proper vesicular trafficking through these compartments. Moreover, recruitment of the small GTPase Rab11 and the PITP Giotto to the cleavage site depends on wild-type function of the exocyst subunits Exo84 and Sec8. Finally, we show that the exocyst subunit Sec5 coimmunoprecipitates with Rab11. Our results are consistent with the exocyst complex mediating an essential, coordinated increase in cell surface area that potentiates anaphase cell elongation and cleavage furrow ingression. PMID:26528720

  14. Augmin shapes the anaphase spindle for efficient cytokinetic furrow ingression and abscission.

    Science.gov (United States)

    Uehara, Ryota; Kamasaki, Tomoko; Hiruma, Shota; Poser, Ina; Yoda, Kinya; Yajima, Junichiro; Gerlich, Daniel W; Goshima, Gohta

    2016-03-01

    During anaphase, distinct populations of microtubules (MTs) form by either centrosome-dependent or augmin-dependent nucleation. It remains largely unknown whether these different MT populations contribute distinct functions to cytokinesis. Here we show that augmin-dependent MTs are required for the progression of both furrow ingression and abscission. Augmin depletion reduced the accumulation of anillin, a contractile ring regulator at the cell equator, yet centrosomal MTs were sufficient to mediate RhoA activation at the furrow. This defect in contractile ring organization, combined with incomplete spindle pole separation during anaphase, led to impaired furrow ingression. During the late stages of cytokinesis, astral MTs formed bundles in the intercellular bridge, but these failed to assemble a focused midbody structure and did not establish tight linkage to the plasma membrane, resulting in furrow regression. Thus augmin-dependent acentrosomal MTs and centrosomal MTs contribute to nonredundant targeting mechanisms of different cytokinesis factors, which are required for the formation of a functional contractile ring and midbody. PMID:26764096

  15. Kinetochore-Independent Chromosome Poleward Movement during Anaphase of Meiosis II in Mouse Eggs

    Science.gov (United States)

    Deng, Manqi; Gao, Juntao; Suraneni, Praveen; Li, Rong

    2009-01-01

    Kinetochores are considered to be the key structures that physically connect spindle microtubules to the chromosomes and play an important role in chromosome segregation during mitosis. Due to different mechanisms of spindle assembly between centrosome-containing mitotic cells and acentrosomal meiotic oocytes, it is unclear how a meiotic spindle generates the poleward forces to drive two rounds of meiotic chromosome segregation to achieve genome haploidization. We took advantage of the fact that DNA beads are able to induce bipolar spindle formation without kinetochores and studied the behavior of DNA beads in the induced spindle in mouse eggs during meiosis II. Interestingly, DNA beads underwent poleward movements that were similar in timing and speed to the meiotic chromosomes, although all the beads moved together to the same spindle pole. Disruption of dynein function abolished the poleward movements of DNA beads but not of the meiotic chromosomes, suggesting the existence of different dynein-dependent and dynein-independent force generation mechanisms for the chromosome poleward movement, and the latter may be dependent on the presence of kinetochores. Consistent with the observed DNA bead poleward movement, sperm haploid chromatin (which also induced bipolar spindle formation after injection to a metaphase egg without forming detectable kinetochore structures) also underwent similar poleward movement at anaphase as DNA beads. The results suggest that in the chromatin-induced meiotic spindles, kinetochore attachments to spindle microtubules are not absolutely required for chromatin poleward movements at anaphase. PMID:19365562

  16. Transcriptional intermediary factor 1γ binds to the anaphase-promoting complex/cyclosome and promotes mitosis

    DEFF Research Database (Denmark)

    Sedgwick, G.G.; Townsend, K.; Martin, A.;

    2013-01-01

    The anaphase-promoting complex/cyclosome (APC/C) is an ubiquitin ligase that functions during mitosis. Here we identify the transcriptional regulator, transcriptional intermediary factor 1γ, TIF1γ, as an APC/C-interacting protein that regulates APC/C function. TIF1γ is not a substrate for APC....../C-dependent ubiquitylation but instead, associates specifically with the APC/C holoenzyme and Cdc20 to affect APC/C activity and progression through mitosis. RNA interference studies indicate that TIF1γ knockdown results in a specific reduction in APC/C ubiquitin ligase activity, the stabilization of APC/C substrates, and...... an increase in the time taken for cells to progress through mitosis from nuclear envelope breakdown to anaphase. TIF1γ knockdown cells are also characterized by the inappropriate presence of cyclin A at metaphase, and an increase in the number of cells that fail to undergo metaphase...

  17. Multiple subunits of the Caenorhabditis elegans anaphase-promoting complex are required for chromosome segregation during meiosis I.

    OpenAIRE

    Davis, Edward S.; Wille, Lucia; Chestnut, Barry A.; Sadler, Penny L.; Shakes, Diane C; Golden, Andy

    2002-01-01

    Two genes, originally identified in genetic screens for Caenorhabditis elegans mutants that arrest in metaphase of meiosis I, prove to encode subunits of the anaphase-promoting complex or cyclosome (APC/C). RNA interference studies reveal that these and other APC/C subunits are essential for the segregation of chromosomal homologs during meiosis I. Further, chromosome segregation during meiosis I requires APC/C functions in addition to the release of sister chromatid cohesion.

  18. The Anaphase-Promoting Complex/Cyclosome in Control of Plant Development

    Institute of Scientific and Technical Information of China (English)

    Jefri Heyman; Lieven De Veylder

    2012-01-01

    Temporal controlled degradation of key cell division proteins ensures a correct onset of the different cell cycle phases and exit from the cell division program.In light of the cell cycle,the Anaphase-Promoting Complex/Cyclosome (APC/C) is an important conserved multi-subunit ubiquitin ligase,marking targets for degradation by the 26S proteasome.However,whereas the APC/C has been studied extensively in yeast and mammals,only in the last decade has the plant APC/C started to unveil its secrets.Research results have shown the importance of the APC/C core complex and its activators during gametogenesis,growth,hormone signaling,symbiotic interactions,and endoreduplication onset.In addition,recently,the first plant APC/C inhibitors have been reported,allowing a fine-tuning of APC/C activity during the cell cycle.Together with the identification of the first APC/C targets,a picture emerges of APC/C activity being essential for many different developmental processes.

  19. Nuclear pore protein NUP88 activates anaphase-promoting complex to promote aneuploidy.

    Science.gov (United States)

    Naylor, Ryan M; Jeganathan, Karthik B; Cao, Xiuqi; van Deursen, Jan M

    2016-02-01

    The nuclear pore complex protein NUP88 is frequently elevated in aggressive human cancers and correlates with reduced patient survival; however, it is unclear whether and how NUP88 overexpression drives tumorigenesis. Here, we show that mice overexpressing NUP88 are cancer prone and form intestinal tumors. To determine whether overexpression of NUP88 drives tumorigenesis, we engineered transgenic mice with doxycycline-inducible expression of Nup88. Surprisingly, NUP88 overexpression did not alter global nuclear transport, but was a potent inducer of aneuploidy and chromosomal instability. We determined that NUP88 and the nuclear transport factors NUP98 and RAE1 comprise a regulatory network that inhibits premitotic activity of the anaphase-promoting complex/cyclosome (APC/C). When overexpressed, NUP88 sequesters NUP98-RAE1 away from APC/CCDH1, triggering proteolysis of polo-like kinase 1 (PLK1), a tumor suppressor and multitasking mitotic kinase. Premitotic destruction of PLK1 disrupts centrosome separation, causing mitotic spindle asymmetry, merotelic microtubule-kinetochore attachments, lagging chromosomes, and aneuploidy. These effects were replicated by PLK1 insufficiency, indicating that PLK1 is responsible for the mitotic defects associated with NUP88 overexpression. These findings demonstrate that the NUP88-NUP98-RAE1-APC/CCDH1 axis contributes to aneuploidy and suggest that it may be deregulated in the initiating stages of a broad spectrum of human cancers. PMID:26731471

  20. Downregulation of Protein 4.1R impairs centrosome function,bipolar spindle organization and anaphase

    Energy Technology Data Exchange (ETDEWEB)

    Spence, Jeffrey R.; Go, Minjoung M.; Bahmanyar, S.; Barth,A.I.M.; Krauss, Sharon Wald

    2006-03-17

    Centrosomes nucleate and organize interphase MTs and areinstrumental in the assembly of the mitotic bipolar spindle. Here wereport that two members of the multifunctional protein 4.1 family havedistinct distributions at centrosomes. Protein 4.1R localizes to maturecentrioles whereas 4.1G is a component of the pericentriolar matrixsurrounding centrioles. To selectively probe 4.1R function, we used RNAinterference-mediated depletion of 4.1R without decreasing 4.1Gexpression. 4.1R downregulation reduces MT anchoring and organization atinterphase and impairs centrosome separation during prometaphase.Metaphase chromosomes fail to properly condense/align and spindleorganization is aberrant. Notably 4.1R depletion causes mislocalizationof its binding partner NuMA (Nuclear Mitotic Apparatus Protein),essential for spindle pole focusing, and disrupts ninein. Duringanaphase/telophase, 4.1R-depleted cells have lagging chromosomes andaberrant MT bridges. Our data provide functional evidence that 4.1R makescrucial contributions to centrosome integrity and to mitotic spindlestructure enabling mitosis and anaphase to proceed with the coordinatedprecision required to avoid pathological events.

  1. Smad3 recruits the anaphase-promoting complex for ubiquitination and degradation of SnoN

    Energy Technology Data Exchange (ETDEWEB)

    Stroschein, Shannon L.; Bonni, Shirin; Wrana, Jeffrey L.; Luo, Kunxin

    2001-09-11

    Smad proteins mediate transforming growth factor-b signaling to regulate cell growth and differentiation. SnoN is an important negative regulator of TGFb signaling that functions to maintain the repressed state of TGFb target genes in the absence of ligand. Upon TGFb stimulation, Smad3 and Smad2 translocate into the nucleus and induce a rapid degradation of SnoN, allowing activation of TGFb target genes. Here we show that Smad2- or Smad3-induced degradation of SnoN requires the ubiquitin-dependent proteasome and can be mediated by the anaphase promoting complex (APC) and the UbcH5 family of ubiquitin conjugating enzymes. Smad3 and to a lesser extent, Smad2, interact with both the APC and SnoN, resulting in the recruitment of the APC to SnoN and subsequent ubiquitination of SnoN in a destruction box-dependent manner. In addition to the destruction box, efficient degradation of SnoN also requires the Smad3 binding site in SnoN as well as key lysine residues necessary for ubiquitin attachment. Mutation of either the Smad3 binding site or lysine residues results in stabilization of SnoN and in enhanced antagonism of TGFb signaling. Our studies elucidate an important pathway for the degradation of SnoN and reveal a novel role of the APC in regulation of TGFb signaling.

  2. Building a pseudo-atomic model of the anaphase-promoting complex

    International Nuclear Information System (INIS)

    This article describes an example of molecular replacement in which atomic models are used to interpret electron-density maps determined using single-particle electron-microscopy data. The anaphase-promoting complex (APC/C) is a large E3 ubiquitin ligase that regulates progression through specific stages of the cell cycle by coordinating the ubiquitin-dependent degradation of cell-cycle regulatory proteins. Depending on the species, the active form of the APC/C consists of 14–15 different proteins that assemble into a 20-subunit complex with a mass of approximately 1.3 MDa. A hybrid approach of single-particle electron microscopy and protein crystallography of individual APC/C subunits has been applied to generate pseudo-atomic models of various functional states of the complex. Three approaches for assigning regions of the EM-derived APC/C density map to specific APC/C subunits are described. This information was used to dock atomic models of APC/C subunits, determined either by protein crystallography or homology modelling, to specific regions of the APC/C EM map, allowing the generation of a pseudo-atomic model corresponding to 80% of the entire complex

  3. Dose-response of x-ray-induced anaphase aberrations in the mitotic root tip chromosomes of allium

    International Nuclear Information System (INIS)

    A simplified Allium root mitotic chromosome aberration assay by using only the aberrant anaphases (fragments, laggards and bridges) as the end-points were developed by Rank and Nielsen (1993) for screening water soluble chemicals and complex mixtures. A dose-response curve was established by Meir et al., (1994) using a known clastogen, 4-nitroquinolene-N-oxide between the dose range of 0.1-0.5 ug/ml. In order to further validate this assay for clastogen detection, a series of X-ray dose response experiments was carried out. Allium roots were germinated in tapwater for 48 h and treated with a series of 10, 20, 30, 40, 50, 60 R (80 Kvp, 5 ma, dose rate 60 R/min) dosages. After an 18 hr recovery time, the root tips were hydrolyzed in 45% acetic and 1 N HC1 acid (9:1 ratio) solution under 50 degrees C for 5 min and stained with aceto-carmine. Each of the data points were derived from scoring 7-10 slides (15-50 anaphases/slide). The corrrelation coefficient, slope and intercept values of the dose-response curve are: 0.954, 0.515 and 1.155 respectively

  4. Allium cepa anaphase-telophase root tip chromosome aberration assay on N-methyl-N-nitrosourea, maleic hydrazide, sodium azide, and ethyl methanesulfonate.

    Science.gov (United States)

    Rank, J; Nielsen, M H

    1997-04-24

    The Allium anaphase-telophase assay was used to show genotoxicity of N-methyl-N-nitrosourea (MNU), maleic hydrazide (MH), sodium azide (NaN3) and ethyl methanesulfonate (EMS). All agents induced chromosome aberrations at statistically significant levels. The rank of the lowest doses with positive effect was as follows: NaN3 0.3 mg/l Allium test for NaN3 and EMS were in a lower range than that found for the other plant assays. EMS and MMS (methyl methanesulfonate), two chemicals used as positive controls in mutagenicity testing, were compared in the Allium test, and MMS was found to be about ten times more potent in inducing chromosome aberrations than EMS. Recording of micronuclei in interphase cells showed that this endpoint does not give more information of clastogenicity than recording of chromosome aberrations in anaphase-telophase cells. PMID:9150760

  5. Identification of the C. elegans anaphase promoting complex subunit Cdc26 by phenotypic profiling and functional rescue in yeast

    Directory of Open Access Journals (Sweden)

    Zachariae Wolfgang

    2007-03-01

    Full Text Available Abstract Background RNA interference coupled with videorecording of C. elegans embryos is a powerful method for identifying genes involved in cell division processes. Here we present a functional analysis of the gene B0511.9, previously identified as a candidate cell polarity gene in an RNAi videorecording screen of chromosome I embryonic lethal genes. Results Whereas weak RNAi inhibition of B0511.9 causes embryonic cell polarity defects, strong inhibition causes embryos to arrest in metaphase of meiosis I. The range of defects induced by RNAi of B0511.9 is strikingly similar to those displayed by mutants of anaphase-promoting complex/cyclosome (APC/C components. Although similarity searches did not reveal any obvious homologue of B0511.9 in the non-redundant protein database, we found that the N-terminus shares a conserved sequence pattern with the N-terminus of the small budding yeast APC/C subunit Cdc26 and its orthologues from a variety of other organisms. Furthermore, we show that B0511.9 robustly complements the temperature-sensitive growth defect of a yeast cdc26Δ mutant. Conclusion These data demonstrate that B0511.9 encodes the C. elegans APC/C subunit CDC-26.

  6. Dynein Light Intermediate Chain 2 Facilitates the Metaphase to Anaphase Transition by Inactivating the Spindle Assembly Checkpoint.

    Directory of Open Access Journals (Sweden)

    Sagar P Mahale

    Full Text Available The multi-functional molecular motor cytoplasmic dynein performs diverse essential roles during mitosis. The mechanistic importance of the dynein Light Intermediate Chain homologs, LIC1 and LIC2 is unappreciated, especially in the context of mitosis. LIC1 and LIC2 are believed to exist in distinct cytoplasmic dynein complexes as obligate subunits. LIC1 had earlier been reported to be required for metaphase to anaphase progression by inactivating the kinetochore-microtubule attachment-sensing arm of the spindle assembly checkpoint (SAC. However, the functional importance of LIC2 during mitosis remains elusive. Here we report prominent novel roles for the LIC2 subunit of cytoplasmic dynein in regulating the spindle assembly checkpoint. LIC2 depletion in mammalian cells led to prolonged metaphase arrest in the presence of an active SAC and also to stretched kinetochores, thus implicating it in SAC inactivation. Quantitative fluorescence microscopy of SAC components revealed accumulation of both attachment- and tension-sensing checkpoint proteins at metaphase kinetochores upon LIC2 depletion. These observations support a stronger and more diverse role in checkpoint inactivation for LIC2 in comparison to its close homolog LIC1. Our study uncovers a novel functional hierarchy during mitotic checkpoint inactivation between the closely related but homologous LIC subunits of cytoplasmic dynein. These subtle functional distinctions between dynein subpopulations could be exploited to study specific aspects of the spindle assembly checkpoint, which is a key mediator of fidelity in eukaryotic cell division.

  7. The anaphase inhibitor of Saccharomyces cerevisiae Pds1p is a target of the DNA damage checkpoint pathway

    International Nuclear Information System (INIS)

    Inhibition of DNA replication and physical DNA damage induce checkpoint responses that arrest cell cycle progression at two different stages. In Saccharomyces cerevisiae, the execution of both checkpoint responses requires the Mec1 and Rad53 proteins. This observation led to the suggestion that these checkpoint responses are mediated through a common signal transduction pathway. However, because the checkpoint-induced arrests occur at different cell cycle stages, the downstream effectors mediating these arrests are likely to be distinct. We have previously shown that the S. cerevisiae protein Pds1p is an anaphase inhibitor and is essential for cell cycle arrest in mitosis in the presence DNA damage. Herein we show that DNA damage, but not inhibition of DNA replication, induces the phosphorylation of Pds1p. Analyses of Pds1p phosphorylation in different checkpoint mutants reveal that in the presence of DNA damage, Pds1p is phosphorylated in a Mec1p- and Rad9p-dependent hut Rad53p-independent manner. Our data place Pds1p and Rad53p on parallel branches of the DNA damage checkpoint pathway. We suggest that Pds1p is a downstream target of the DNA damage checkpoint pathway and that it is involved in implementing the DNA damage checkpoint arrest specifically in mitosis

  8. Dynein Light Intermediate Chain 2 Facilitates the Metaphase to Anaphase Transition by Inactivating the Spindle Assembly Checkpoint

    Science.gov (United States)

    Mahale, Sagar P.; Sharma, Amit; Mylavarapu, Sivaram V. S.

    2016-01-01

    The multi-functional molecular motor cytoplasmic dynein performs diverse essential roles during mitosis. The mechanistic importance of the dynein Light Intermediate Chain homologs, LIC1 and LIC2 is unappreciated, especially in the context of mitosis. LIC1 and LIC2 are believed to exist in distinct cytoplasmic dynein complexes as obligate subunits. LIC1 had earlier been reported to be required for metaphase to anaphase progression by inactivating the kinetochore-microtubule attachment-sensing arm of the spindle assembly checkpoint (SAC). However, the functional importance of LIC2 during mitosis remains elusive. Here we report prominent novel roles for the LIC2 subunit of cytoplasmic dynein in regulating the spindle assembly checkpoint. LIC2 depletion in mammalian cells led to prolonged metaphase arrest in the presence of an active SAC and also to stretched kinetochores, thus implicating it in SAC inactivation. Quantitative fluorescence microscopy of SAC components revealed accumulation of both attachment- and tension-sensing checkpoint proteins at metaphase kinetochores upon LIC2 depletion. These observations support a stronger and more diverse role in checkpoint inactivation for LIC2 in comparison to its close homolog LIC1. Our study uncovers a novel functional hierarchy during mitotic checkpoint inactivation between the closely related but homologous LIC subunits of cytoplasmic dynein. These subtle functional distinctions between dynein subpopulations could be exploited to study specific aspects of the spindle assembly checkpoint, which is a key mediator of fidelity in eukaryotic cell division. PMID:27441562

  9. HTLV-1 Tax mutants that do not induce G1 arrest are disabled in activating the anaphase promoting complex

    Directory of Open Access Journals (Sweden)

    Kuo Yu-Liang

    2007-05-01

    Full Text Available Abstract HTLV-1 Tax is a potent activator of viral transcription and NF-κB. Recent data indicate that Tax activates the anaphase promoting complex/cyclosome (APC/C ahead of schedule, causing premature degradation of cyclin A, cyclin B1, securin, and Skp2. Premature loss of these mitotic regulators is accompanied by mitotic aberrations and leads to rapid senescence and cell cycle arrest in HeLa and S. cerevisiae cells. Tax-induced rapid senescence (tax-IRS of HeLa cells is mediated primarily by a dramatic stabilization of p27KIP and is also accompanied by a great surge in the level of p21CIP1mRNA and protein. Deficiencies in p27KIP prevent Tax-IRS. A collection of tax point mutants that permit normal growth of S. cerevisiae have been isolated. Like wild-type tax, many of them (C23W, A108T, L159F, and L235F transactivate both the HTLV-LTR and the NF-κB reporters. One of them, V19M, preferentially activates NF-κB, but is attenuated for LTR activation. None of the mutants significantly elevated the levels of p21CIP1and p27KIP1, indicating that the dramatic surge in p21CIP1/WAF1and p27KIP 1induced by Tax is brought about by a mechanism distinct from NF-κB or LTR activation. Importantly, the ability of these mutants to activate APC/C is attenuated or abrogated. These data indicate that Tax-induced rapid senescence is causally associated with APC/C activation.

  10. Intact Cohesion, Anaphase, and Chromosome Segregation in Human Cells Harboring Tumor-Derived Mutations in STAG2.

    Directory of Open Access Journals (Sweden)

    Jung-Sik Kim

    2016-02-01

    Full Text Available Somatic mutations of the cohesin complex subunit STAG2 are present in diverse tumor types. We and others have shown that STAG2 inactivation can lead to loss of sister chromatid cohesion and alterations in chromosome copy number in experimental systems. However, studies of naturally occurring human tumors have demonstrated little, if any, correlation between STAG2 mutational status and aneuploidy, and have further shown that STAG2-deficient tumors are often euploid. In an effort to provide insight into these discrepancies, here we analyze the effect of tumor-derived STAG2 mutations on the protein composition of cohesin and the expected mitotic phenotypes of STAG2 mutation. We find that many mutant STAG2 proteins retain their ability to interact with cohesin; however, the presence of mutant STAG2 resulted in a reduction in the ability of regulatory subunits WAPL, PDS5A, and PDS5B to interact with the core cohesin ring. Using AAV-mediated gene targeting, we then introduced nine tumor-derived mutations into the endogenous allele of STAG2 in cultured human cells. While all nonsense mutations led to defects in sister chromatid cohesion and a subset induced anaphase defects, missense mutations behaved like wild-type in these assays. Furthermore, only one of nine tumor-derived mutations tested induced overt alterations in chromosome counts. These data indicate that not all tumor-derived STAG2 mutations confer defects in cohesion, chromosome segregation, and ploidy, suggesting that there are likely to be other functional effects of STAG2 inactivation in human cancer cells that are relevant to cancer pathogenesis.

  11. Precocious anaphase and expression of Securin and p53 genes as candidate biomarkers for the early detection in areca nut-induced carcinogenesis.

    Science.gov (United States)

    Kurkalang, Sillarine; Banerjee, Atanu; Dkhar, Hughbert; Nongrum, Henry B; Ganguly, Buddha; Islam, Mohammad; Rangad, Gordon M; Chatterjee, Anupam

    2015-05-01

    Research over the years has generated enough evidence to implicate areca nut, as a carcinogen in humans. Besides oral, significant rise in the incidence of cancers of the oesophagus, liver and stomach was seen among areca nut chewers. Early diagnosis seems key to understand the initial processes of carcinogenesis which is highly curable. In North-East India, betel quid contains raw areca nut (RAN), lime and small portion of betel leaf without any other constituents. This study was not intended to isolate any active ingredients from the RAN and to look its action. The present objective is to validate the screening of precocious anaphase and analysis of expression of Securin and p53 in non-target cells like human peripheral blood lymphocytes (PBLs) and mouse bone marrow cells (BMCs) as early indicative parameters of RAN + lime-induced cancers. A total of 35 mice were examined at different time points for following ad libitum administration of RAN extract in drinking water with lime. Peripheral blood was collected from 32 human donors of which, 24 were RAN + lime heavy chewers. Expression of genes was assessed by immunoblotting and/or by immunohistochemistry. Histological preparation of stomach tissue of mice revealed that RAN + lime induced stomach cancer. A gradual increase in the frequency of precocious anaphases and aneuploid cells was observed in both RAN + lime-treated mouse BMC and human PBL of RAN heavy chewers. Levels of p53 and Securin were increased in these cells during early days of RAN + lime exposure. The level of Securin was significantly higher in human tumour samples than their adjacent normal counterpart. The expression of Securin was increased significantly in RAN + lime-administered mice as well as in stomach tumour. Present study revealed that precocious anaphase and expression of p53 and Securin in non-target cells are significantly associated with an increased risk of RAN-induced cancer and thus these parameters can be of early diagnostic value

  12. Anaphase-promoting complex/cyclosome protein Cdc27 is a target for curcumin-induced cell cycle arrest and apoptosis

    Directory of Open Access Journals (Sweden)

    Lee Seung Joon

    2012-01-01

    Full Text Available Abstract Background Curcumin (diferuloylmethane, the yellow pigment in the Asian spice turmeric, is a hydrophobic polyphenol from the rhizome of Curcuma longa. Because of its chemopreventive and chemotherapeutic potential with no discernable side effects, it has become one of the major natural agents being developed for cancer therapy. Accumulating evidence suggests that curcumin induces cell death through activation of apoptotic pathways and inhibition of cell growth and proliferation. The mitotic checkpoint, or spindle assembly checkpoint (SAC, is the major cell cycle control mechanism to delay the onset of anaphase during mitosis. One of the key regulators of the SAC is the anaphase promoting complex/cyclosome (APC/C which ubiquitinates cyclin B and securin and targets them for proteolysis. Because APC/C not only ensures cell cycle arrest upon spindle disruption but also promotes cell death in response to prolonged mitotic arrest, it has become an attractive drug target in cancer therapy. Methods Cell cycle profiles were determined in control and curcumin-treated medulloblastoma and various other cancer cell lines. Pull-down assays were used to confirm curcumin binding. APC/C activity was determined using an in vitro APC activity assay. Results We identified Cdc27/APC3, a component of the APC/C, as a novel molecular target of curcumin and showed that curcumin binds to and crosslinks Cdc27 to affect APC/C function. We further provide evidence that curcumin preferably induces apoptosis in cells expressing phosphorylated Cdc27 usually found in highly proliferating cells. Conclusions We report that curcumin directly targets the SAC to induce apoptosis preferably in cells with high levels of phosphorylated Cdc27. Our studies provide a possible molecular mechanism why curcumin induces apoptosis preferentially in cancer cells and suggest that phosphorylation of Cdc27 could be used as a biomarker to predict the therapeutic response of cancer cells to

  13. Anaphase-promoting complex/cyclosome protein Cdc27 is a target for curcumin-induced cell cycle arrest and apoptosis

    International Nuclear Information System (INIS)

    Curcumin (diferuloylmethane), the yellow pigment in the Asian spice turmeric, is a hydrophobic polyphenol from the rhizome of Curcuma longa. Because of its chemopreventive and chemotherapeutic potential with no discernable side effects, it has become one of the major natural agents being developed for cancer therapy. Accumulating evidence suggests that curcumin induces cell death through activation of apoptotic pathways and inhibition of cell growth and proliferation. The mitotic checkpoint, or spindle assembly checkpoint (SAC), is the major cell cycle control mechanism to delay the onset of anaphase during mitosis. One of the key regulators of the SAC is the anaphase promoting complex/cyclosome (APC/C) which ubiquitinates cyclin B and securin and targets them for proteolysis. Because APC/C not only ensures cell cycle arrest upon spindle disruption but also promotes cell death in response to prolonged mitotic arrest, it has become an attractive drug target in cancer therapy. Cell cycle profiles were determined in control and curcumin-treated medulloblastoma and various other cancer cell lines. Pull-down assays were used to confirm curcumin binding. APC/C activity was determined using an in vitro APC activity assay. We identified Cdc27/APC3, a component of the APC/C, as a novel molecular target of curcumin and showed that curcumin binds to and crosslinks Cdc27 to affect APC/C function. We further provide evidence that curcumin preferably induces apoptosis in cells expressing phosphorylated Cdc27 usually found in highly proliferating cells. We report that curcumin directly targets the SAC to induce apoptosis preferably in cells with high levels of phosphorylated Cdc27. Our studies provide a possible molecular mechanism why curcumin induces apoptosis preferentially in cancer cells and suggest that phosphorylation of Cdc27 could be used as a biomarker to predict the therapeutic response of cancer cells to curcumin

  14. In vivo dynamics and kinetics of pKi-67: Transition from a mobile to an immobile form at the onset of anaphase

    International Nuclear Information System (INIS)

    A cell proliferation marker protein, pKi-67, distributes to the chromosome periphery during mitosis and nucleolar heterochromatin in the interphase. We report here on the structural domains of pKi-67 that are required for its correct distribution. While both the LR domain and the conserved domain were involved in localization to the nucleolar heterochromatin, both the LR domain and the Ki-67 repeat domain were required for its distribution to the mitotic chromosome periphery. Using in vivo time-lapse microscopy, GFP-pKi-67 was dynamically tracked from the mitotic chromosome periphery to reforming nucleoli via prenucleolar bodies (PNBs). The signals in PNBs then moved towards and fused into the reforming nucleoli with a thin string-like fluorescence during early G1 phase. An analysis of the in vivo kinetics of pKi-67 using photobleaching indicated that the association of pKi-67 with chromatin was progressively altered from 'loose' to 'tight' after the onset of anaphase. These findings indicate that pKi-67 dynamically alters the nature of the interaction with chromatin structure during the cell cycle, which is closely related to the reformation process of the interphase nucleolar chromatin

  15. Structure of an APC3–APC16 Complex: Insights into Assembly of the Anaphase-Promoting Complex/Cyclosome

    Energy Technology Data Exchange (ETDEWEB)

    Yamaguchi, Masaya; Yu, Shanshan; Qiao, Renping; Weissmann, Florian; Miller, Darcie J.; VanderLinden, Ryan; Brown, Nicholas G.; Frye, Jeremiah J.; Peters, Jan-Michael; Schulman, Brenda A. (SJCH); (IMP)

    2015-08-21

    The anaphase-promoting complex/cyclosome (APC/C) is a massive E3 ligase that controls mitosis by catalyzing ubiquitination of key cell cycle regulatory proteins. The APC/C assembly contains two subcomplexes: the “Platform” centers around a cullin-RING-like E3 ligase catalytic core; the “Arc Lamp” is a hub that mediates transient association with regulators and ubiquitination substrates. The Arc Lamp contains the small subunits APC16, CDC26, and APC13, and tetratricopeptide repeat (TPR) proteins (APC7, APC3, APC6, and APC8) that homodimerize and stack with quasi-2-fold symmetry. Within the APC/C complex, APC3 serves as center for regulation. APC3's TPR motifs recruit substrate-binding coactivators, CDC20 and CDH1, via their C-terminal conserved Ile-Arg (IR) tail sequences. Human APC3 also binds APC16 and APC7 and contains a > 200-residue loop that is heavily phosphorylated during mitosis, although the basis for APC3 interactions and whether loop phosphorylation is required for ubiquitination are unclear. Here, we map the basis for human APC3 assembly with APC16 and APC7, report crystal structures of APC3Δloop alone and in complex with the C-terminal domain of APC16, and test roles of APC3's loop and IR tail binding surfaces in APC/C-catalyzed ubiquitination. The structures show how one APC16 binds asymmetrically to the symmetric APC3 dimer and, together with biochemistry and prior data, explain how APC16 recruits APC7 to APC3, show how APC3's C-terminal domain is rearranged in the full APC/C assembly, and visualize residues in the IR tail binding cleft important for coactivator-dependent ubiquitination. Overall, the results provide insights into assembly, regulation, and interactions of TPR proteins and the APC/C.

  16. A Research on the Diversification of the Anaphase Management Model of Indemnificatory housing%保障性住房后期管理模式的多元化

    Institute of Scientific and Technical Information of China (English)

    魏丽艳

    2012-01-01

      随着我国“十二五”期间3600万套保障性住房建设任务的不断完成,大量的保障性住房不断地投入使用,保障性住房的后期管理面临前所未有的挑战。政府、社区、物业企业等服务主体的管理模式亟待完善。因此,以提高保障性住房后期管理的有效性,实现中低收入家庭住有所居、乐有其所的幸福生活为目标,对相应主体管理模式的选择与应用问题的研究具有重要意义。%  Along with the task of constructing 36 million units of Indemnificatory housing during the 12th Five-Year-Plan period is completed continuously, and a large number of indemnificatory housing was put into use continuously, the anaphase management of indemnificatory housing is facing an unprecedented challenge. The management model of service principals such as governments, communities, property management companies needs to be perfected. Therefore, in order to improve the effectiveness of the anaphase management of indemnificatory housing, and achieve the objective of helping the low-and middle-income families to live a happy life that having their home to live, the study on the choice and application of the appropriate main management model is of important significance.

  17. Anaphase onset before complete DNA replication with intact checkpoint responses

    DEFF Research Database (Denmark)

    Torres-Rosell, Jordi; De Piccoli, Giacomo; Cordon-Preciado, Violeta;

    2007-01-01

    Cellular checkpoints prevent mitosis in the presence of stalled replication forks. Whether checkpoints also ensure the completion of DNA replication before mitosis is unknown. Here, we show that in yeast smc5-smc6 mutants, which are related to cohesin and condensin, replication is delayed, most...

  18. Timely anaphase onset requires a novel spindle and kinetochore complex comprising Ska1 and Ska2

    NARCIS (Netherlands)

    Hanisch, Anja; Silljé, Herman H W; Nigg, Erich A

    2006-01-01

    Chromosome segregation during mitosis requires chromosomes to undergo bipolar attachment on spindle microtubules (MTs) and subsequent silencing of the spindle checkpoint. Here, we describe the identification and characterisation of a novel spindle and kinetochore (KT)-associated complex that is requ

  19. Human Rif1 protein binds aberrant telomeres and aligns along anaphase midzone microtubules

    OpenAIRE

    Xu, Lifeng; Blackburn, Elizabeth H.

    2004-01-01

    We identified and characterized a human orthologue of Rif1 protein, which in budding yeast interacts in vivo with the major duplex telomeric DNA binding protein Rap1p and negatively regulates telomere length. Depletion of hRif1 by RNA interference in human cancer cells impaired cell growth but had no detectable effect on telomere length, although hRif1 overexpression in S. cerevisiae interfered with telomere length control, in a manner specifically dependent on the presence of yeast Rif1p. No...

  20. Cyc17, a meiosis-specific cyclin, is essential for anaphase initiation and chromosome segregation in Tetrahymena thermophila.

    Science.gov (United States)

    Yan, Guan-Xiong; Dang, Huai; Tian, Miao; Zhang, Jing; Shodhan, Anura; Ning, Ying-Zhi; Xiong, Jie; Miao, Wei

    2016-07-17

    Although the role of cyclins in controlling nuclear division is well established, their function in ciliate meiosis remains unknown. In ciliates, the cyclin family has undergone massive expansion which suggests that diverse cell cycle systems exist, and this warrants further investigation. A screen for cyclins in the model ciliate Tetrahymena thermophila showed that there are 34 cyclins in this organism. Only 1 cyclin, Cyc17, contains the complete cyclin core and is specifically expressed during meiosis. Deletion of CYC17 led to meiotic arrest at the diakinesis-like metaphase I stage. Expression of genes involved in DNA metabolism and chromosome organization (chromatin remodeling and basic chromosomal structure) was repressed in cyc17 knockout matings. Further investigation suggested that Cyc17 is involved in regulating spindle pole attachment, and is thus essential for chromosome segregation at meiosis. These findings suggest a simple model in which chromosome segregation is influenced by Cyc17. PMID:27192402

  1. Interaction of the anaphase-promoting complex/cyclosome and proteasome protein complexes with multiubiquitin chain-binding proteins

    DEFF Research Database (Denmark)

    Seeger, Michael; Hartmann-Petersen, Rasmus; Wilkinson, Caroline R M; Wallace, Mairi; Samejima, Itaru; Taylor, Martin S; Gordon, Colin

    2003-01-01

    Fission yeast Rhp23 and Pus1 represent two families of multiubiquitin chain-binding proteins that associate with the proteasome. We show that both proteins bind to different regions of the proteasome subunit Mts4. The binding site for Pus1 was mapped to a cluster of repetitive sequences also foun...

  2. A conserved cyclin-binding domain determines functional interplay between anaphase-promoting complex-Cdh1 and cyclin A-Cdk2 during cell cycle progression

    DEFF Research Database (Denmark)

    Lukas, C; Kramer, E R; Peters, J M;

    2001-01-01

    how cyclin-CDKs interact with APC subunits remains unresolved. Here we substantiate the evidence that mammalian cyclin A-Cdk2 prevents unscheduled APC reactivation during S phase by demonstrating its periodic interaction with Cdh1 at the level of endogenous proteins. Moreover, we identified a...... conserved cyclin-binding motif within the Cdh1 WD-40 domain and show that its disruption abolished the Cdh1-cyclin A-Cdk2 interaction, eliminated Cdh1-associated histone H1 kinase activity, and impaired Cdh1 phosphorylation by cyclin A-Cdk2 in vitro and in vivo. Overexpression of cyclin binding......, these data provide a mechanistic explanation for the mutual functional interplay between cyclin A-Cdk2 and APC-Cdh1 and the first evidence that Cdh1 may activate the APC by binding specific substrates....

  3. Nonperiodic activity of the human anaphase-promoting complex-Cdh1 ubiquitin ligase results in continuous DNA synthesis uncoupled from mitosis

    DEFF Research Database (Denmark)

    Lukas, C; Kramer, E R; Peters, J M;

    2000-01-01

    Saccharomyces cerevisiae and Drosophila spp., triggers exit from mitosis and during G(1) prevents unscheduled DNA replication. In this study we investigated the importance of periodic oscillation of the APC-Cdh1 activity for the cell cycle progression in human cells. We show that conditional interference with...

  4. Accumulation of cyclin B1 requires E2F and cyclin-A-dependent rearrangement of the anaphase-promoting complex

    DEFF Research Database (Denmark)

    Lukas, C; Sørensen, Claus Storgaard; Kramer, E;

    1999-01-01

    In mammalian somatic-cell cycles, progression through the G1-phase restriction point and initiation of DNA replication are controlled by the ability of the retinoblastoma tumour-suppressor protein (pRb) family to regulate the E2F/DP transcription factors. Continuing transcription of E2F target...

  5. AML1/RUNX1 Phosphorylation by Cyclin-Dependent Kinases Regulates the Degradation of AML1/RUNX1 by the Anaphase-Promoting Complex‡

    OpenAIRE

    Biggs, Joseph R.; Peterson, Luke F.; Zhang, Youhong; Kraft, Andrew S.; Zhang, Dong-Er

    2006-01-01

    AML1 (RUNX1) regulates hematopoiesis, angiogenesis, muscle function, and neurogenesis. Previous studies have shown that phosphorylation of AML1, particularly at serines 276 and 303, affects its transcriptional activation. Here, we report that phosphorylation of AML1 serines 276 and 303 can be blocked in vivo by inhibitors of the cyclin-dependent kinases (CDKs) Cdk1 and Cdk2. Furthermore, these residues can be phosphorylated in vitro by purified Cdk1/cyclin B and Cdk2/cyclin A. Mutant AML1 pro...

  6. Ipl1/Aurora-dependent phosphorylation of Sli15/INCENP regulates CPC–spindle interaction to ensure proper microtubule dynamics

    OpenAIRE

    Nakajima, Yuko; Cormier, Anthony; Tyers, Randall G.; Pigula, Adrianne; Peng, Yutian; Drubin, David G; Barnes, Georjana

    2011-01-01

    Dynamic microtubules facilitate chromosome arrangement before anaphase, whereas during anaphase microtubule stability assists chromosome separation. Changes in microtubule dynamics at the metaphase–anaphase transition are regulated by Cdk1. Cdk1-mediated phosphorylation of Sli15/INCENP promotes preanaphase microtubule dynamics by preventing chromosomal passenger complex (CPC; Sli15/INCENP, Bir1/Survivin, Nbl1/Borealin, Ipl1/Aurora) association with spindles. However, whether Cdk1 has sole con...

  7. Kinase signaling in the spindle checkpoint.

    Science.gov (United States)

    Kang, Jungseog; Yu, Hongtao

    2009-06-01

    The spindle checkpoint is a cell cycle surveillance system that ensures the fidelity of chromosome segregation. In mitosis, it elicits the "wait anaphase" signal to inhibit the anaphase-promoting complex or cyclosome until all chromosomes achieve bipolar microtubule attachment and align at the metaphase plate. Because a single kinetochore unattached to microtubules activates the checkpoint, the wait anaphase signal is thought to be generated by this kinetochore and is then amplified and distributed throughout the cell to inhibit the anaphase-promoting complex/cyclosome. Several spindle checkpoint kinases participate in the generation and amplification of this signal. Recent studies have begun to reveal the activation mechanisms of these checkpoint kinases. Increasing evidence also indicates that the checkpoint kinases not only help to generate the wait anaphase signal but also actively correct kinetochore-microtubule attachment defects. PMID:19228686

  8. Experimental Study onMalignant Transformation of Human Bronchial Epithelial CellsInduced by Glycidyl Methacrylate and Analysis on its Methylation

    Institute of Scientific and Technical Information of China (English)

    WANG An Na; WANG Quan Kai; YANG Min; HU Jie; DONG Lin; andXU Jian Ning

    2014-01-01

    ObjectiveTo establish the model of human bronchial epithelial cells(16HBE) malignant transformation induced by glycidyl methacrylate(GMA)and define the different methylation genes at different stages. MethodsDNA was extracted at different 16HBE malignant phasesandchanges of genes DNA methylation atdifferent stages weredetectedusing Methylation chip of‘NimbleGen HG18 CpG Promoter Microarray Methylation’. Methylation-specific PCR (MSP) was usedto observe the methylation status ofsome genes, and then compared with the control groups. ResultsThe resultshowed that GMA induced 16HBE morphorlogical transformation at the dose of 8µg/mL, and cell exposed to GMA had 1374 genes in protophase, 825 genes inmetaphase, 1149 genes in anaphase, respectively; 30 genes are all methylation in the 3 stages; 318 genes in protophase but not inmetaphase and anaphase; 272 genes in metaphase but not inprotophase and anaphase; 683 genes in anaphase but not inmetaphase and protophase; 73 genes inprotophase andmetaphase but not in anaphase; 67 genes in protophase and anaphase but not inmetaphase; 59 genes inmetaphase and anaphase but not in protophase. ConclusionThe pattern of DNA methylation could change in the process of 16HBEinduced by GMA.

  9. Mitotic Exit Function of Polo-like Kinase Cdc5 Is Dependent on Sequential Activation by Cdk1.

    Science.gov (United States)

    Rodriguez-Rodriguez, Jose-Antonio; Moyano, Yolanda; Játiva, Soraya; Queralt, Ethel

    2016-05-31

    To complete mitosis, Saccharomyces cerevisiae needs to activate the mitotic phosphatase Cdc14. Two pathways contribute to Cdc14 regulation: FEAR (Cdc14 early anaphase release) and MEN (mitotic exit network). Cdc5 polo-like kinase was found to be an important mitotic exit component. However, its specific role in mitotic exit regulation and its involvement in Cdc14 release remain unclear. Here, we provide insight into the mechanism by which Cdc5 contributes to the timely release of Cdc14. Our genetic and biochemical data indicate that Cdc5 acts in parallel with MEN during anaphase. This MEN-independent Cdc5 function requires active separase and activation by Cdk1-dependent phosphorylation. Cdk1 first phosphorylates Cdc5 to activate it in early anaphase, and then, in late anaphase, further phosphorylation of Cdc5 by Cdk1 is needed to promote its MEN-related functions. PMID:27210759

  10. The Functional Role of TopBP1 in DNA Maintenance at Mitosis

    DEFF Research Database (Denmark)

    Pedersen, Rune Troelsgaard

    When cells traverse mitosis, genome integrity of the emerging daughter cells is dependent on replication of the entire genome during the preceding S-phase and accurate chromosome segregation in mitosis. Replication stress may cause cells to enter mitosis with underreplicated loci, consisting of...... can lead to anaphase bridges that impair accurate chromosome segregation. The recent decade featured many advances in our understanding of how cells cope with underreplicated loci in mitosis. A major advance was the description of ultra-fine anaphase bridges (UFBs), a class of anaphase bridges that......-phase. We established Saccharomyces cerevisiae as a model organism to study anaphase bridges, and we identified Dpb11/TopBP1 as a novel UFB-associated protein in yeast and avian DT40 cells, respectively. TopBP1 localized to confined areas on replication-stress induced UFBs. Upon onset of mitosis we...

  11. Non-linear character of dose dependences of chromosome aberration frequency in radiation-damaged root

    International Nuclear Information System (INIS)

    The dose dependences of the aberrant anaphases in the root meristem in 48 hours after the irradiation have non-linear character and a plateau in the region about 6-8 Gy. The plateau indicates the activation of recovery processes. In the plateau range, the level of damages for this genotype is 33% for aberrant anaphases (FAA), 2.3 aberrations per aberrant anaphase (A/AC), and 0.74 aberrations for the total number of anaphases. At 10 Gy, the dose curve forms the exponential region caused by the involvement of the large number of new cells with unrepaired damages in the mutation process. The increase of A/AC to 1.1 indicate the ''criticality'' of the meristem radiation damage.

  12. Arabidopsis CDS blastp result: AK101105 [KOME

    Lifescience Database Archive (English)

    Full Text Available AK101105 J033025D11 At2g39090.1 tetratricopeptide repeat (TPR)-containing protein low similarity to prediabe...tic NOD sera-reactive autoantigen [Mus musculus] GI:6670773, anaphase-promoting com

  13. THE ROLE OF VALENCE AND METHYLATION STATE ON THE ACTIVITY OF ARSENIC DURING MITOSIS

    Science.gov (United States)

    Trivalent methylated arsenicals are much more potent DNA damaging agents, clastogens, and large deletion mutagens than are their inorganic and pentavalent counterparts. Previously we had noticed that many of the arsenicals induced "c-type" anaphases characteristic of spindle pois...

  14. Significance of elemental deposition in hair to internal contamination

    International Nuclear Information System (INIS)

    In standardized animal experiments the deposition of Cd, Hg and As in anaphase hair was studied. Due to rates of endogenous transfer observed hair analysis is considered less suitable as an indicator of endogenous ''contamination'' in the case of Cd than in Hg and As. Studies of the influence of a mild washing procedure recommended by IAEA/RL/41H on anaphase hair loaded with Cd or Hg demonstrated a heavy impact of washing on Cd but no influence on Hg. (author)

  15. CENP-A exceeds microtubule attachment sites in centromere clusters of both budding and fission yeast

    OpenAIRE

    Coffman, Valerie C.; Wu, Pengcheng; Parthun, Mark R.; Wu, Jian-Qiu

    2011-01-01

    The stoichiometries of kinetochores and their constituent proteins in yeast and vertebrate cells were determined using the histone H3 variant CENP-A, known as Cse4 in budding yeast, as a counting standard. One Cse4-containing nucleosome exists in the centromere (CEN) of each chromosome, so it has been assumed that each anaphase CEN/kinetochore cluster contains 32 Cse4 molecules. We report that anaphase CEN clusters instead contained approximately fourfold more Cse4 in Saccharomyces cerevisiae...

  16. The polo-like kinase Cdc5 interacts with FEAR network components and Cdc14

    OpenAIRE

    Rahal, Rami; Amon, Angelika

    2008-01-01

    Exit from mitosis in Saccharomyces cerevisiae is triggered by activation of the phosphatase Cdc14. Throughout interphase and early mitosis, Cdc14 is sequestered in the nucleolus by its inhibitor Cfi1/Net1. In anaphase, the Cdc Fourteen Early Anaphase Release (FEAR) network and the Mitotic Exit Network (MEN) coordinately trigger the release of Cdc14 from the nucleolus. Here we show that the FEAR network component Cdc5 physically associates with two other members of the pathway, the Separase Es...

  17. Positive feedback promotes mitotic exit via the APC/C-Cdh1-separase-Cdc14 axis in budding yeast.

    Science.gov (United States)

    Hatano, Yuhki; Naoki, Koike; Suzuki, Asuka; Ushimaru, Takashi

    2016-10-01

    The mitotic inhibitor securin is degraded via the ubiquitin ligase anaphase-promoting complex/cyclosome (APC/C)-Cdc20 after anaphase onset. This triggers activation of the mitotic protease separase and thereby sister chromatid separation. However, only a proportion of securin molecules are degraded at metaphase-anaphase transition and the remaining molecules are still present in anaphase. The roles of securin and separase in late mitosis remain elusive. Here, we show that securin still inhibits separase to repress mitotic exit in anaphase in budding yeast. APC/C-Cdh1-mediated securin degradation at telophase further liberated separase, which promotes Cdc14 release and mitotic exit. Separase executed these events via its proteolytic action and that in the Cdc14 early release (FEAR) network. Cdc14 release further activated APC/C-Cdh1 in the manner of a positive feedback loop. Thus, the positive feedback promotes mitotic exit via the APC/C-Cdh1-separase-Cdc14 axis. This study shows the importance of the two-step degradation mode of securin and the role of separase in mitotic exit. PMID:27418100

  18. Multipolar spindle pole coalescence is a major source of kinetochore mis-attachment and chromosome mis-segregation in cancer cells.

    Directory of Open Access Journals (Sweden)

    William T Silkworth

    Full Text Available Many cancer cells display a CIN (Chromosome Instability phenotype, by which they exhibit high rates of chromosome loss or gain at each cell cycle. Over the years, a number of different mechanisms, including mitotic spindle multipolarity, cytokinesis failure, and merotelic kinetochore orientation, have been proposed as causes of CIN. However, a comprehensive theory of how CIN is perpetuated is still lacking. We used CIN colorectal cancer cells as a model system to investigate the possible cellular mechanism(s underlying CIN. We found that CIN cells frequently assembled multipolar spindles in early mitosis. However, multipolar anaphase cells were very rare, and live-cell experiments showed that almost all CIN cells divided in a bipolar fashion. Moreover, fixed-cell analysis showed high frequencies of merotelically attached lagging chromosomes in bipolar anaphase CIN cells, and higher frequencies of merotelic attachments in multipolar vs. bipolar prometaphases. Finally, we found that multipolar CIN prometaphases typically possessed gamma-tubulin at all spindle poles, and that a significant fraction of bipolar metaphase/early anaphase CIN cells possessed more than one centrosome at a single spindle pole. Taken together, our data suggest a model by which merotelic kinetochore attachments can easily be established in multipolar prometaphases. Most of these multipolar prometaphase cells would then bi-polarize before anaphase onset, and the residual merotelic attachments would produce chromosome mis-segregation due to anaphase lagging chromosomes. We propose this spindle pole coalescence mechanism as a major contributor to chromosome instability in cancer cells.

  19. EMS induced mutagenicity in pollen mother cells of Sesbania Pea (Sesbania cannabina Poir.

    Directory of Open Access Journals (Sweden)

    Girjesh Kumar and Nitisha Srivastava

    2011-06-01

    Full Text Available Mutagenic effect of EMS on pollen mother cells of Sesbania cannabina has been investigated in the present cytogeneticalobservation. The progenies were obtained from seeds treated with four different time durations (1, 3, 5, and 7 hours of 0.5%solution of ethyl methane sulphonate (EMS. Study revealed various types of chromosomal aberrations at different doses ofEMS. Increase in chromosomal aberrations was dose dependent manner. Pollen mother cells of Sesbania cannabina exhibited anincreased incidence of chromosomal bridges, unorientation, laggards and precocious movement etc. at each dose of treatment.Anaphasic and telophasic bridges were major abnormalities and found to be highest at 3 hr dose of treatment. Anaphasic bridgeswere more prominent than telophasic bridges and percentages of different types of bridges at anaphase and telophase were alsostudied and scored.

  20. Budding yeast PAK kinases regulate mitotic exit by two different mechanisms

    OpenAIRE

    Chiroli, Elena; Fraschini, Roberta; Beretta, Alessia; Tonelli, Mariagrazia; Lucchini, Giovanna; Piatti, Simonetta

    2003-01-01

    We report the characterization of the dominant-negative CLA4t allele of the budding yeast CLA4 gene, encoding a member of the p21-activated kinase (PAK) family of protein kinases, which, together with its homologue STE20, plays an essential role in promoting budding and cytokinesis. Overproduction of the Cla4t protein likely inhibits both endogenous Cla4 and Ste20 and causes a delay in the onset of anaphase that correlates with inactivation of Cdc20/anaphase-promoting complex (APC)–dependent ...

  1. Protective effect of butylated hydroxytoluene (BHT) against the clastogenic acitivity of cadmium chloride and potassium dichromate in hamster ovary cells

    OpenAIRE

    Grillo Claudia A.; Seoane Analía I.; Dulout Fernando N.

    1999-01-01

    The effect of butylated hydroxytoluene (BHT), a widely used food additive, on chromosomal alterations induced by cadmium chloride (CC) and potassium dichromate (PD) in Chinese hamster ovary (CHO) cells was studied both at metaphase and anaphase-telophase. CHO cells were cultured for 15-16 h in the presence of PD (6.0, 9.0 or 12.0 mM), BHT (1.0 mg/ml), or PD plus BHT as well as CC (0.5, 1.0 and 2.0 mM), BHT or CC plus BHT for the analysis of chromosomal aberrations. To perform the anaphase-tel...

  2. Genotoxicity and toxicity evaluations of ECF cellulose bleaching effluents using the Allium cepa L. test.

    Science.gov (United States)

    Roa, O; Yeber, M C; Venegas, W

    2012-08-01

    Toxicity and genotoxicity tests were performed on root cells of Allium cepa in order to evaluate wastewater quality following an ECF cellulose bleaching process. The results revealed a toxic effect of the effluent, with inhibition of meristem growth and generally lower values of metaphase, anaphase and telophase indices at pH 10.5 than pH 7 for all effluent concentrations. The genotoxicity effect was different from the toxic effect given that the micronucleus and the chromosomal aberration tests in anaphase-telophase cells were low over all ranges of the studied effluent concentrations. PMID:22990817

  3. Human chromosome pellicle antibody recognizing centromere protein—C (CENP0C),the main component of the kinetochore

    Institute of Scientific and Technical Information of China (English)

    XIEYONG; ZUMEINI; 等

    1997-01-01

    Recently the antichromosome antisera from several sclerogerma patients have been found to recognize the pellicle of metaphase and anaphase chromosomes.In order to identify the pellicle components,we used these antichromosome antisera to screen a human embryonic cDNA library.The sequences of the positive clones are identical to the cDNA gene sequence of CENP-C (centromere protein C),a human centromere autoantigen.This result suggusts that CENP-C is a component of the pellicle of human metaphase and anaphase chromosomes.

  4. Dimethylsulfoxide reduces the x-ray-induced G2 delay in chinese hamster ovary cells

    International Nuclear Information System (INIS)

    The effects of dimethylsulfoxide (DMSO) on radiation-induced G2 delay and on each stage in mitotic phase were studied. The G2 delay was reduced by the postirradiation treatment of Chinese hamster ovary cells by over 2 %. DMSO at 2 % had no effect on the progression of the cells through metaphase, anaphase or telophase, when added after mechanical collection of cells at the mitotic phase. DMSO over 5 %, and particularly over 7 %, led to a retardation at metaphase, with little effect on anaphase or telophase. (author)

  5. INFLUENCE OF SODIUM METABISULPHITE (E 223) ON MITOTIC DIVISION IN CALENDULA OFFICINALIS L.s

    OpenAIRE

    Romeo-Cristian Marc; Gabriela Capraru

    2008-01-01

    This paper presents the cytogenetic effects induced by sodium metabisulphite (E 223) (a food additive used as preservative) in meristematic cells of Calendula officinalis L. root tips. The treatment has determined the lessening of the mitotic index (comparative with the control variant), until mitotic division total inhibition, as well as a growth frequency of division aberration in anaphase and telophase.

  6. A novel chromosome segregation mechanism during female meiosis.

    Science.gov (United States)

    McNally, Karen Perry; Panzica, Michelle T; Kim, Taekyung; Cortes, Daniel B; McNally, Francis J

    2016-08-15

    In a wide range of eukaryotes, chromosome segregation occurs through anaphase A, in which chromosomes move toward stationary spindle poles, anaphase B, in which chromosomes move at the same velocity as outwardly moving spindle poles, or both. In contrast, Caenorhabditis elegans female meiotic spindles initially shorten in the pole-to-pole axis such that spindle poles contact the outer kinetochore before the start of anaphase chromosome separation. Once the spindle pole-to-kinetochore contact has been made, the homologues of a 4-μm-long bivalent begin to separate. The spindle shortens an additional 0.5 μm until the chromosomes are embedded in the spindle poles. Chromosomes then separate at the same velocity as the spindle poles in an anaphase B-like movement. We conclude that the majority of meiotic chromosome movement is caused by shortening of the spindle to bring poles in contact with the chromosomes, followed by separation of chromosome-bound poles by outward sliding. PMID:27335123

  7. Fanconi anaemia proteins are associated with sister chromatid bridging in mitosis

    DEFF Research Database (Denmark)

    Ying, Songmin; Hickson, Ian D

    2011-01-01

    specifically occur during chromosome segregation in mitosis. The BS protein, BLM, was shown recently to define a novel class of anaphase DNA bridge structures that, in some cases, also contain FA proteins. We will discuss the possible source of these bridges and the role that FA proteins and BLM might play in...

  8. Cdc20 and Cks direct the spindle checkpoint-independent destruction of cyclin A

    NARCIS (Netherlands)

    Wolthuis, Rob; Clay-Farrace, Lori; van Zon, Wouter; Yekezare, Mona; Koop, Lars; Ogink, Janneke; Medema, Rene; Pines, Jonathon

    2008-01-01

    Successful mitosis requires the right protein be degraded at the right time. Central to this is the spindle checkpoint that prevents the destruction of securin and cyclin 131 when there are improperly attached chromosomes. The principal target of the checkpoint is Cdc20, which activates the anaphase

  9. PICH

    DEFF Research Database (Denmark)

    Biebricher, A.; Hirano, S.; Enzlin, J.;

    2013-01-01

    The Plk1-interacting checkpoint helicase (PICH) protein localizes to ultrafine anaphase bridges (UFBs) in mitosis alongside a complex of DNA repair proteins, including the Bloom's syndrome protein (BLM). However, very little is known about the function of PICH or how it is recruited to UFBs. Using...

  10. Parkin Regulates Mitosis and Genomic Stability through Cdc20/Cdh1

    NARCIS (Netherlands)

    Lee, S.B.; Kim, J.J.; Nam, H.J.; Gao, B.; Yin, P.; Qin, B.; Yi, S.Y.; Ham, H.; Evans, D.; Kim, S.H.; Zhang, Jun; Deng, M.; Liu, T.; Zhang, H.; Billadeau, D.D.; Wang, L.; Giaime, E.; Shen, J.; Pang, Y.P.; Jen, J.; Deursen, J.M.A. van; Lou, Z.

    2015-01-01

    Mutations in the E3 ubiquitin ligase Parkin have been linked to familial Parkinson's disease. Parkin has also been implicated in mitosis through mechanisms that are unclear. Here we show that Parkin interacts with anaphase promoting complex/cyclosome (APC/C) coactivators Cdc20 and Cdh1 to mediate th

  11. Structure of a Blinkin-BUBR1 complex reveals an interaction crucial for kinetochore-mitotic checkpoint regulation via an unanticipated binding Site

    DEFF Research Database (Denmark)

    Bolanos-Garcia, Victor M; Lischetti, Tiziana; Matak-Vinković, Dijana;

    2011-01-01

    The maintenance of genomic stability relies on the spindle assembly checkpoint (SAC), which ensures accurate chromosome segregation by delaying the onset of anaphase until all chromosomes are properly bioriented and attached to the mitotic spindle. BUB1 and BUBR1 kinases are central for this proc...

  12. Yeast Interacting Proteins Database: YMR294W, YLL049W [Yeast Interacting Proteins Database

    Lifescience Database Archive (English)

    Full Text Available YMR294W JNM1 Component of the yeast dynactin complex, consisting of Nip100p, Jnm1p, and Arp1p; r ... equired for proper nuclear migration ... and spindle partitioning during mitotic anaphase B ... Protein of unknown function; required for nuclear migration ; null mutant shows a reduced affinity for the alci ...

  13. Yeast Interacting Proteins Database: YLL049W, YMR294W [Yeast Interacting Proteins Database

    Lifescience Database Archive (English)

    Full Text Available YLL049W LDB18 Protein of unknown function; required for nuclear migration ; null mutant shows a r ... 00p, Jnm1p, and Arp1p; required for proper nuclear migration ... and spindle partitioning during mitotic anaphase B ... Protein of unknown function; required for nuclear migration ; null mutant shows a reduced affinity for the alci ...

  14. Microtubule flux mediates poleward motion of acentric chromosome fragments during meiosis in insect spermatocytes.

    Science.gov (United States)

    LaFountain, J R; Oldenbourg, R; Cole, R W; Rieder, C L

    2001-12-01

    We applied a combination of laser microsurgery and quantitative polarization microscopy to study kinetochore-independent forces that act on chromosome arms during meiosis in crane fly spermatocytes. When chromosome arms located within one of the half-spindles during prometa- or metaphase were cut with the laser, the acentric fragments (lacking kinetochores) that were generated moved poleward with velocities similar to those of anaphase chromosomes (approximately 0.5 microm/min). To determine the mechanism underlying this poleward motion of detached arms, we treated spermatocytes with the microtubule-stabilizing drug taxol. Spindles in taxol-treated cells were noticeably short, yet with polarized light, the distribution and densities of microtubules in domains where fragment movement occurred were not different from those in control cells. When acentric fragments were generated in taxol-treated spermatocytes, 22 of 24 fragments failed to exhibit poleward motion, and the two that did move had velocities attenuated by 80% (to approximately 0.1 microm/min). In these cells, taxol did not inhibit the disjunction of chromosomes nor prevent their poleward segregation during anaphase, but the velocity of anaphase was also decreased 80% (approximately 0.1 microm/min) relative to untreated controls. Together, these data reveal that microtubule flux exerts pole-directed forces on chromosome arms during meiosis in crane fly spermatocytes and strongly suggest that the mechanism underlying microtubule flux also is used in the anaphase motion of kinetochores in these cells. PMID:11739800

  15. Arabidopsis CDS blastp result: AK119376 [KOME

    Lifescience Database Archive (English)

    Full Text Available AK119376 001-132-A09 At2g39090.1 tetratricopeptide repeat (TPR)-containing protein low similarity to prediab...etic NOD sera-reactive autoantigen [Mus musculus] GI:6670773, anaphase-promoting co

  16. Arabidopsis CDS blastp result: AK105677 [KOME

    Lifescience Database Archive (English)

    Full Text Available AK105677 001-201-B01 At2g39090.1 tetratricopeptide repeat (TPR)-containing protein low similarity to prediab...etic NOD sera-reactive autoantigen [Mus musculus] GI:6670773, anaphase-promoting co

  17. Mechanisms controlling the temporal degradation of Nek2A and Kif18A by the APC/C-Cdc20 complex

    DEFF Research Database (Denmark)

    Sedgwick, G.G.; Hayward, D.G.; Nilsson, J.; Di Fiore, B.; Pines, J.; Pardo, Mercedes; Yu, L.

    2013-01-01

    The Anaphase Promoting Complex/Cyclosome (APC/C) in complex with its co-activator Cdc20 is responsible for targeting proteins for ubiquitin-mediated degradation during mitosis. The activity of APC/C-Cdc20 is inhibited during prometaphase by the Spindle Assembly Checkpoint (SAC) yet certain substr...

  18. DVC1 (C1orf124) is a DNA damage-targeting p97 adaptor that promotes ubiquitin-dependent responses to replication blocks

    DEFF Research Database (Denmark)

    Mosbech, Anna; Gibbs-Seymour, Ian; Kagias, Konstantinos;

    2012-01-01

    Ubiquitin-mediated processes orchestrate critical DNA-damage signaling and repair pathways. We identify human DVC1 (C1orf124; Spartan) as a cell cycle-regulated anaphase-promoting complex (APC) substrate that accumulates at stalled replication forks. DVC1 recruitment to sites of replication stress...

  19. Presenting Mitosis

    Science.gov (United States)

    Roche, Stephanie; Sterling, Donna R.

    2005-01-01

    When the topic of cell division is introduced in the classroom, students can showcase their interpretations of the stages of mitosis by creating a slide show illustrating prophase, metaphase, anaphase, and telophase (see samples in Figure 1). With the help of a computer, they can create a model of mitosis that will help them distinguish the…

  20. THE INFLUENCE OF CAFFEINE ON MITOTIC DIVISION AT CAPSICUM ANNUUM L.

    Directory of Open Access Journals (Sweden)

    Elena Rosu

    2006-08-01

    Full Text Available The paper presents, the caffeine effects in mitotic division at Capsicum annuum L.. The treatment has determined the lessening of the mitotic index (comparative with the control variant, until mitotic division total inhibition, as well as an growth frequency of division aberation in anaphase and telophase.

  1. Sequence Classification: 890645 [

    Lifescience Database Archive (English)

    Full Text Available tching on the kinase activity of Dbf2p; Cdc15p || http://www.ncbi.nlm.nih.gov/protein/6319328 ... ...nase of the Mitotic Exit Network that is localized to the spindle pole bodies at late anaphase; promotes mitotic exit by directly swi

  2. Attachment issues : kinetochore transformations and spindle checkpoint silencing

    NARCIS (Netherlands)

    Etemad, Banafsheh; Kops, Geert Jpl

    2016-01-01

    Cell division culminates in the segregation of duplicated chromosomes in opposite directions prior to cellular fission. This process is guarded by the spindle assembly checkpoint (SAC), which prevents the anaphase of cell division until stable connections between spindle microtubules and the kinetoc

  3. Chiasmata promote monopolar attachment of sister chromatids and their co-segregation toward the proper pole during meiosis I.

    Directory of Open Access Journals (Sweden)

    Yukinobu Hirose

    2011-03-01

    Full Text Available The chiasma is a structure that forms between a pair of homologous chromosomes by crossover recombination and physically links the homologous chromosomes during meiosis. Chiasmata are essential for the attachment of the homologous chromosomes to opposite spindle poles (bipolar attachment and their subsequent segregation to the opposite poles during meiosis I. However, the overall function of chiasmata during meiosis is not fully understood. Here, we show that chiasmata also play a crucial role in the attachment of sister chromatids to the same spindle pole and in their co-segregation during meiosis I in fission yeast. Analysis of cells lacking chiasmata and the cohesin protector Sgo1 showed that loss of chiasmata causes frequent bipolar attachment of sister chromatids during anaphase. Furthermore, high time-resolution analysis of centromere dynamics in various types of chiasmate and achiasmate cells, including those lacking the DNA replication checkpoint factor Mrc1 or the meiotic centromere protein Moa1, showed the following three outcomes: (i during the pre-anaphase stage, the bipolar attachment of sister chromatids occurs irrespective of chiasma formation; (ii the chiasma contributes to the elimination of the pre-anaphase bipolar attachment; and (iii when the bipolar attachment remains during anaphase, the chiasmata generate a bias toward the proper pole during poleward chromosome pulling that results in appropriate chromosome segregation. Based on these results, we propose that chiasmata play a pivotal role in the selection of proper attachments and provide a backup mechanism that promotes correct chromosome segregation when improper attachments remain during anaphase I.

  4. Aberrant meiotic behavior in Agave tequilana Weber var. azul

    Directory of Open Access Journals (Sweden)

    Rodríguez-Garay Benjamin

    2002-10-01

    Full Text Available Abstract Background Agave tequilana Weber var. azul, is the only one variety permitted by federal law in México to be used for tequila production which is the most popular contemporary alcoholic beverage made from agave and recognized worldwide. Despite the economic, genetic, and ornamental value of the plant, it has not been subjected to detailed cytogenetic research, which could lead to a better understanding of its reproduction for future genetic improvement. The objective of this work was to study the meiotic behavior in pollen mother cells and its implications on the pollen viability in Agave tequilana Weber var. azul. Results The analysis of Pollen Mother Cells in anaphase I (A-I showed 82.56% of cells with a normal anaphase and, 17.44% with an irregular anaphase. In which 5.28% corresponded to cells with side arm bridges (SAB; 3.68% cells with one bridge and one fragment; 2.58% of irregular anaphase showed cells with one or two lagging chromosomes and 2.95% showed one acentric fragment; cells with two bridges and cells with two bridges and one acentric fragment were observed in frequencies of 1.60% and 1.35% respectively. In anaphase II some cells showed bridges and fragments too. Aberrant A-I cells had many shrunken or empty pollen grains (42.00% and 58.00 % viable pollen. Conclusion The observed meiotic irregularities suggest that structural chromosome aberrations have occurred, such as heterozygous inversions, sister chromatid exchanges, deletions and duplications which in turn are reflected in a low pollen viability.

  5. A descriptive mutagenicity assessment of tretinoin in Allium sativum

    International Nuclear Information System (INIS)

    This paper is primarily designed to assess the mutagenicity of tretinoin by applying the Allium test. Furthermore, it has the following objectives: to evaluate the macroscopic abnormalities caused by tretinoin based on root length and root form parameters; to investigate whether tretinoin can induce aberrances in cell division such as the formation of micronucleus, anaphase bridges, early anaphase, C-metaphase, sticky chromosome, stretched chromosome, vagrant chromosome and precocious chromosome; to determine the variation in the aberrations in the different concentration of tretinoin. Procedure: eight hundred equal-sized garlic bulbs were immersed in various concentrations of tretinoin and in tap water as control. These were divided into two groups. Six hundred bulbs were evaluated for macroscopic parameters while the remaining two hundred bulbs were fixed for microscopic observations. The Allium test set-ups were placed in the plant laboratory of UP-Manila. The were harvested on the third and on the fifth day. The fixed roots were examined in the Cytogenetics Laboratory of the Philippine Nuclear Research Institute. The data gathered for macroscopic parameter was statistically tested using Complete Randomized Design and the Tukey's Honestly Significant Difference. The microscopic abnormalities were determined descriptively for every concentration. Findings: analysis of macroscopic and microscopic parameters showed that: according to the analyses of variances, the number of roots, the root length and the number of root forms such as straight, bent, bulbous and tapered were not equal in all concentrations. However, the difference in the number of curled roots was not significant.; the root length distinctly showed the toxicity effect of tretinoin. The growth or the length of roots decreases as the tretinoin concentration increases; the mitotic abnormalities observed in the garlic cells include micronucleus, anaphase bridges, early anaphase. C-metaphase, sticky

  6. Automated three-dimensional single cell phenotyping of spindle dynamics, cell shape, and volume

    CERN Document Server

    Plumb, Kemp; Pelletier, Vincent; Kilfoil, Maria L

    2015-01-01

    We present feature finding and tracking algorithms in 3D in living cells, and demonstrate their utility to measure metrics important in cell biological processes. We developed a computational imaging hybrid approach that combines automated three-dimensional tracking of point-like features with surface determination from which cell (or nuclear) volume, shape, and planes of interest can be extracted. After validation, we applied the technique to real space context-rich dynamics of the mitotic spindle, and cell volume and its relationship to spindle length, in dividing living cells. These methods are additionally useful for automated segregation of pre-anaphase and anaphase spindle populations in budding yeast. We found that genetic deletion of the yeast kinesin-5 mitotic motor cin8 leads to large mother and daughter cells that were indistinguishable based on size, and that in those cells the spindle length becomes uncorrelated with cell size. The technique can be used to visualize and quantify tracked feature c...

  7. The distribution of α-kleisin during meiosis in the holocentromeric plant Luzula elegans.

    Science.gov (United States)

    Ma, Wei; Schubert, Veit; Martis, Mihaela Maria; Hause, Gerd; Liu, Zhaojun; Shen, Yi; Conrad, Udo; Shi, Wenqing; Scholz, Uwe; Taudien, Stefan; Cheng, Zhukuan; Houben, Andreas

    2016-09-01

    Holocentric chromosomes occur in a number of independent eukaryotic lineages, and they form holokinetic kinetochores along the entire poleward chromatid surfaces. Due to this alternative chromosome structure, Luzula elegans sister chromatids segregate already in anaphase I followed by the segregation of the homologues in anaphase II. However, not yet known is the localization and dynamics of cohesin and the structure of the synaptonemal complex (SC) during meiosis. We show here that the α-kleisin subunit of cohesin localizes at the centromeres of both mitotic and meiotic metaphase chromosomes and that it, thus, may contribute to assemble the centromere in L. elegans. This localization and the formation of a tripartite SC structure indicate that the prophase I behaviour of L. elegans is similar as in monocentric species. PMID:27294972

  8. F-actin distribution and function during sexual differentiation in Schizosaccharomyces pombe

    DEFF Research Database (Denmark)

    Petersen, J; Nielsen, O; Egel, R;

    1998-01-01

    accumulated towards the projection tip at one end of the cell. Following cell fusion, F-actin dots were randomly scattered during the horsetail movement that precedes meiosis I and remained scattered until prometaphase or metaphase of meiosis II, when they concentrated around the nucleus. F-actin was seen on...... the lagging face of the nuclei which faced the partner nucleus during anaphase B of meiosis II. Early on in this anaphase F-actin was also seen on the opposite side of the nucleus, near the spindle pole body. F-actin accumulated within the spores in the mature ascus. Treatment with the actin...... depolymerising drug Latrunculin A showed that F-actin is required for cell fusion and spore formation. Latrunculin A treatment extended all stages from karyogamy to meiosis I. The S. pombe homologue of the actin binding protein profilin, Cdc3, was shown to be required for conjugation. Cdc3 co-localized with the...

  9. ANALYSIS ON THE DYNAMICS OF SPATIAL DISTRIBUTION PATTERN OF MIXED SPIDER POPULATION IN RICE FIELD

    Institute of Scientific and Technical Information of China (English)

    ZhiWang; Zhe-mingYuan; Da-xiangSong; Ming-shengZhu

    2004-01-01

    The results make it clear that there are total 11 families, 29 genera and 43 species of spiders in the rice field of Dong Fang Hong Farm. Among them, there are 8 families, 19 genera and 28 species in the early rice field, and 10 families, 27 genera and 36 species in the late rice field. The spatial distribution pattern of mixed spider populations in rice fields was different during different development stages of rice plant. During the prophase, metaphase and anaphase of early rice plant development, the spatial distribution pattern of mixed spider populations was aggregative, random and aggregative respectively. During the prophase, metaphase and anaphase of late rice plant development, the spatial distribution pattern was uniform, aggregative and uniform respectively.

  10. Cohesin is needed for bipolar mitosis in human cells.

    Science.gov (United States)

    Díaz-Martínez, Laura A; Beauchene, Nicole A; Furniss, Katherine; Esponda, Pedro; Giménez-Abián, Juan F; Clarke, Duncan J

    2010-05-01

    Multi-polar mitosis is strongly linked with aggressive cancers and it is a histological diagnostic of tumor-grade. However, factors that cause chromosomes to segregate to more than two spindle poles are not well understood. Here we show that cohesins Rad21, Smc1 and Smc3 are required for bipolar mitosis in human cells. After Rad21 depletion, chromosomes align at the metaphase plate and bipolar spindles assemble in most cases, but in anaphase the separated chromatids segregate to multiple poles. Time-lapse microscopy revealed that the spindle poles often become split in Rad21-depleted metaphase cells. Interestingly, exogenous expression of non-cleavable Rad21 results in multi-polar anaphase. Since cohesins are present at the spindle poles in mitosis, these data are consistent with a non-chromosomal function of cohesin. PMID:20436271

  11. Meiosis I in Xenopus oocytes is not error-prone despite lacking spindle assembly checkpoint.

    Science.gov (United States)

    Liu, Dandan; Shao, Hua; Wang, Hongmei; Liu, X Johné

    2014-01-01

    The spindle assembly checkpoint, SAC, is a surveillance mechanism to control the onset of anaphase during cell division. SAC prevents anaphase initiation until all chromosome pairs have achieved bipolar attachment and aligned at the metaphase plate of the spindle. In doing so, SAC is thought to be the key mechanism to prevent chromosome nondisjunction in mitosis and meiosis. We have recently demonstrated that Xenopus oocyte meiosis lacks SAC control. This prompted the question of whether Xenopus oocyte meiosis is particularly error-prone. In this study, we have karyotyped a total of 313 Xenopus eggs following in vitro oocyte maturation. We found no hyperploid egg, out of 204 metaphase II eggs with countable chromosome spreads. Therefore, chromosome nondisjunction is very rare during Xenopus oocyte meiosis I, despite the lack of SAC. PMID:24646611

  12. Mechanisms of daughter cell-size control during cell division.

    Science.gov (United States)

    Kiyomitsu, Tomomi

    2015-05-01

    Daughter cell size is tightly regulated during cell division. In animal cells, the position of the anaphase spindle specifies the cell cleavage site to dictate the relative size of the daughter cells. Although spindle orientation is regulated by dynein-dependent cortical pulling forces exerted on astral microtubules in many cell types, it was unclear how these forces are precisely regulated to center or displace the spindle. Recently, intrinsic signals derived from chromosomes or spindle poles have been demonstrated to regulate dynein-dependent pulling forces in symmetrically dividing cells. Unexpectedly, myosin-dependent contractile forces have also been shown to control spindle position by altering the cellular boundaries during anaphase. In this review, I discuss how dynein- and myosin-dependent forces are coordinately regulated to control daughter cell size. PMID:25548067

  13. Attachment issues: kinetochore transformations and spindle checkpoint silencing.

    Science.gov (United States)

    Etemad, Banafsheh; Kops, Geert J P L

    2016-04-01

    Cell division culminates in the segregation of duplicated chromosomes in opposite directions prior to cellular fission. This process is guarded by the spindle assembly checkpoint (SAC), which prevents the anaphase of cell division until stable connections between spindle microtubules and the kinetochores of all chromosomes are established. The anaphase inhibitor is generated at unattached kinetochores and inhibitor production is prevented when microtubules are captured. Understanding the molecular changes in the kinetochore that are evoked by microtubule attachments is crucial for understanding the mechanisms of SAC signaling and silencing. Here, we highlight the most recent findings on these events, pinpoint some remaining mysteries, and argue for incorporating holistic views of kinetochore dynamics in order to understand SAC silencing. PMID:26947988

  14. The presence of synaptic and chromosome disjunction mutants in Cenchrus ciliaris (Poaceae: Paniceae

    Directory of Open Access Journals (Sweden)

    N. C. Visser

    1999-12-01

    Full Text Available Synaptic mutants are present in  Cenchrus ciliaris L This species, due to the presence of linear bivalents and occasion­al trivalents and quadrivalents, is an intermediate desynaptic species. In addition, geographical distribution and environmental factors, such as high temperatures and low humidity, could also have had an influence on the desynapsis observed.The disjunction of chromosomes during anaphase I was mostly abnormal in this desynaptic species. Precocious disjunction of chromosomes into chromatids occurred during anaphase I Due to the high incidence of this chromosome abnormality, a mutant gene,  'pc'  responsible for the disjunction of chromosomes, must be present. The absence of cytokinesis in one specimen indicates a recessive mutant gene,  'va' to be active in this species.

  15. Mad revival of cancer

    Institute of Scientific and Technical Information of China (English)

    Hong Liu; Hongtao Yu

    2010-01-01

    @@ Aneuploidy (wrong numbers of chromosomes) is a hallmark of cancer cells and arises from chromosome missegregation in mitosis. To prevent aneuploidy, cells employ surveillance systems to monitor mitosis. The spindle checkpoint (also known as the mitotic checkpoint) is one such surveillance system conserved from yeast to man [1, 2]. During each mitosis, this check-point detects aberrant kinetochore-microtubule attachments, inhibits the anaphase-promoting complex or cy-closome (APC/C), stabilizes cyclin B1 and securin, and delays anaphase onset until all sister chromatids reach proper microtubule attachment. Mad2 is a criti-cal player of the spindle checkpoint and contributes to the inhibition of APC/C directly [3].

  16. Activator-inhibitor coupling between Rho signalling and actin assembly makes the cell cortex an excitable medium.

    Science.gov (United States)

    Bement, William M; Leda, Marcin; Moe, Alison M; Kita, Angela M; Larson, Matthew E; Golding, Adriana E; Pfeuti, Courtney; Su, Kuan-Chung; Miller, Ann L; Goryachev, Andrew B; von Dassow, George

    2015-11-01

    Animal cell cytokinesis results from patterned activation of the small GTPase Rho, which directs assembly of actomyosin in the equatorial cortex. Cytokinesis is restricted to a portion of the cell cycle following anaphase onset in which the cortex is responsive to signals from the spindle. We show that shortly after anaphase onset oocytes and embryonic cells of frogs and echinoderms exhibit cortical waves of Rho activity and F-actin polymerization. The waves are modulated by cyclin-dependent kinase 1 (Cdk1) activity and require the Rho GEF (guanine nucleotide exchange factor), Ect2. Surprisingly, during wave propagation, although Rho activity elicits F-actin assembly, F-actin subsequently inactivates Rho. Experimental and modelling results show that waves represent excitable dynamics of a reaction-diffusion system with Rho as the activator and F-actin the inhibitor. We propose that cortical excitability explains fundamental features of cytokinesis including its cell cycle regulation. PMID:26479320

  17. Chromosomes Can Congress to the Metaphase Plate Before Biorientation

    OpenAIRE

    Kapoor, Tarun M.; Lampson, Michael A.; Hergert, Polla; Cameron, Lisa; Cimini, Daniela; Salmon, E. D.; McEwen, Bruce F.; Khodjakov, Alexey

    2006-01-01

    The stable propagation of genetic material during cell division depends on the congression of chromosomes to the spindle equator before the cell initiates anaphase. It is generally assumed that congression requires that chromosomes are connected to the opposite poles of the bipolar spindle (“bioriented”). In mammalian cells, we found that chromosomes can congress before becoming bioriented. By combining the use of reversible chemical inhibitors, live-cell light microscopy, and correlative ele...

  18. A Kinesin Mutant with an Atypical Bipolar Spindle Undergoes Normal Mitosis

    OpenAIRE

    Marcus, A. I.; Li, W.; Ma, H; Cyr, R. J.

    2003-01-01

    Motor proteins have been implicated in various aspects of mitosis, including spindle assembly and chromosome segregation. Here, we show that acentrosomal Arabidopsis cells that are mutant for the kinesin, ATK1, lack microtubule accumulation at the predicted spindle poles during prophase and have reduced spindle bipolarity during prometaphase. Nonetheless, all abnormalities are rectified by anaphase and chromosome segregation appears normal. We conclude that ATK1 is required for normal microtu...

  19. Cdc20 is critical for meiosis I and fertility of female mice.

    Directory of Open Access Journals (Sweden)

    Fang Jin

    2010-09-01

    Full Text Available Chromosome missegregation in germ cells is an important cause of unexplained infertility, miscarriages, and congenital birth defects in humans. However, the molecular defects that lead to production of aneuploid gametes are largely unknown. Cdc20, the activating subunit of the anaphase-promoting complex/cyclosome (APC/C, initiates sister-chromatid separation by ordering the destruction of two key anaphase inhibitors, cyclin B1 and securin, at the transition from metaphase to anaphase. The physiological significance and full repertoire of functions of mammalian Cdc20 are unclear at present, mainly because of the essential nature of this protein in cell cycle progression. To bypass this problem we generated hypomorphic mice that express low amounts of Cdc20. These mice are healthy and have a normal lifespan, but females produce either no or very few offspring, despite normal folliculogenesis and fertilization rates. When mated with wild-type males, hypomorphic females yield nearly normal numbers of fertilized eggs, but as these embryos develop, they become malformed and rarely reach the blastocyst stage. In exploring the underlying mechanism, we uncover that the vast majority of these embryos have abnormal chromosome numbers, primarily due to chromosome lagging and chromosome misalignment during meiosis I in the oocyte. Furthermore, cyclin B1, cyclin A2, and securin are inefficiently degraded in metaphase I; and anaphase I onset is markedly delayed. These results demonstrate that the physiologically effective threshold level of Cdc20 is high for female meiosis I and identify Cdc20 hypomorphism as a mechanism for chromosome missegregation and formation of aneuploid gametes.

  20. Monitoring of chromosomal aberrations in natural populations of Pinus pallasiana

    OpenAIRE

    V. P. Koba

    2012-01-01

    This paper presents the results of monitoring research of the chromosome aberrations at the stage of anaphase-telophase. The statistical characteristics of dynamics of chromosomal aberrations in populations of Pinus pallasiana D. Don across the high-altitude zones of the Mountain Crimea is given. It is established that on the southern macroslope of the Crimean Main Ridge the frequency of chromosomal aberrations in the P. pallasiana stands is higher in the lower zone in comparison with the mid...

  1. Centrioles in the cell cycle. I. Epithelial cells

    OpenAIRE

    1982-01-01

    A study was made of the structure of the centrosome in the cell cycle in a nonsynchronous culture of pig kidney embryo (PE) cells. In the spindle pole of the metaphase cell there are two mutually perpendicular centrioles (mother and daughter) which differ in their ultrastructure. An electron-dense halo, which surrounds only the mother centriole and is the site where spindle microtubules converge, disappears at the end of telophase. In metaphase and anaphase, the mother centriole is situated p...

  2. Microtubule Flux Mediates Poleward Motion of Acentric Chromosome Fragments during Meiosis in Insect SpermatocytesV⃞

    OpenAIRE

    LaFountain, James R.; Oldenbourg, Rudolf; Cole, Richard W.; Rieder, Conly L

    2001-01-01

    We applied a combination of laser microsurgery and quantitative polarization microscopy to study kinetochore-independent forces that act on chromosome arms during meiosis in crane fly spermatocytes. When chromosome arms located within one of the half-spindles during prometa- or metaphase were cut with the laser, the acentric fragments (lacking kinetochores) that were generated moved poleward with velocities similar to those of anaphase chromosomes (∼0.5 μm/min). To determine the mechanism und...

  3. Sequence Classification: 894237 [

    Lifescience Database Archive (English)

    Full Text Available amily of microtubule-associated proteins (MAPs) that function at the mitotic spindle midzone; required for spindle elongation; under...goes cell cycle-regulated degradation by anaphase promoting complex; potential Cdc28p substrate; Ase1p || http://www.ncbi.nlm.nih.gov/protein/14318440 ... ...Non-TMB Non-TMH TMB Non-TMB Non-TMB TMB >gi|14318440|ref|NP_116582.1| Member of a f

  4. Mcm10 proteolysis initiates before the onset of M-phase

    OpenAIRE

    Khan Muntaz; Sharma Aparna; Kaur Manpreet; Kar Ananya; Saxena Sandeep

    2010-01-01

    Abstract Background Mcm10 protein is essential for initiation and elongation phases of replication. Human cells proteolyze Mcm10 during mitosis, presumably to ensure a single round of replication. It has been proposed that anaphase promoting complex ubiquitinates Mcm10 in late M and early G1 phases. Results In contrast to the previous work, we report that the degradation of Mcm10 is initiated at the onset of mitosis. Immunoblotting and immunofluorescence assays display that Mcm10 levels are l...

  5. Visualizing the spindle checkpoint in Drosophila spermatocytes

    OpenAIRE

    Rebollo, Elena; González, Cayetano

    2000-01-01

    The spindle assembly checkpoint detects defects in spindle structure or in the alignment of the chromosomes on the metaphase plate and delays the onset of anaphase until defects are corrected. Thus far, the evidence regarding the presence of a spindle checkpoint during meiosis in male Drosophila has been indirect and contradictory. On the one hand, chromosomes without pairing partners do not prevent meiosis progression. On the other hand, some conserved components of the spindle checkpoint ma...

  6. A transmembrane inner nuclear membrane protein in the mitotic spindle

    OpenAIRE

    Figueroa, Ricardo; Gudise, Santhosh; Larsson, Veronica; Hallberg, Einar

    2010-01-01

    We have recently characterized a novel transmembrane protein of the inner nuclear membrane of mammalian cells. The protein has two very interesting features. First, despite being an integral membrane protein it is able to concentrate in the membranes colocalizing with the mitotic spindle in metaphase and anaphase. Hence, the protein was named Samp1, Spindle associated membrane protein 1. Secondly, it displays a functional connection to centrosomes. This article discusses various aspects of Sa...

  7. Ipl1p-dependent phosphorylation of Mad3p is required for the spindle checkpoint response to lack of tension at kinetochores

    OpenAIRE

    King, Emma M J; Rachidi, Najma; Morrice, Nick; Hardwick, Kevin G.; Stark, Michael J. R.

    2007-01-01

    The spindle checkpoint delays anaphase onset until all chromosomes are correctly attached to microtubules. Ipl1 protein kinase (Aurora B) is required to correct inappropriate kinetochore-microtubule attachments and for the response to lack of tension between sister kinetochores. Here we identify residues in the checkpoint protein Mad3p that are phosphorylated by Ipl1p. When phosphorylation of Mad3p at two sites is prevented, the cell's response to reduced kinetochore tension is dramatically c...

  8. Ipl1-dependent phosphorylation of Dam1 is reduced by tension applied on kinetochores

    OpenAIRE

    Keating, Patrick; Rachidi, Najma; Tanaka, Tomoyuki U.; Stark, Michael J. R.

    2009-01-01

    The conserved Aurora B protein kinase (Ipl1 in Saccharomyces cerevisiae) is essential for ensuring that sister kinetochores become attached to microtubules from opposite spindle poles (bi-orientation) before anaphase onset. When sister chromatids become attached to microtubules from a single pole, Aurora B/Ipl1 facilitates turnover of kinetochore-microtubule attachments. This process requires phosphorylation by Aurora B/Ipl1 of kinetochore components such as Dam1 in ye...

  9. Ipl1p-dependent phosphorylation of Mad3p is required for the spindle checkpoint response to lack of tension at kinetochores

    OpenAIRE

    King, Emma M J; Rachidi, Najma; Morrice, Nick; Hardwick, Kevin G.; Stark, Michael J. R.

    2007-01-01

    The spindle checkpoint delays anaphase onset until all chromosomes are correctly attached to microtubules. Ipl1 protein kinase (Aurora B) is required to correct inappropriate kinetochore–microtubule attachments and for the response to lack of tension between sister kinetochores. Here we identify residues in the checkpoint protein Mad3p that are phosphorylated by Ipl1p. When phosphorylation of Mad3p at two sites is prevented, the cell’s response to reduced kinetochore tension is dramatically c...

  10. Temperature-sensitive ipl1-2/Aurora B mutation is suppressed by mutations in TOR complex 1 via the Glc7/PP1 phosphatase

    OpenAIRE

    Tatchell, Kelly; Makrantoni, Vasso; Stark, Michael J. R.; Robinson, Lucy C.

    2011-01-01

    Ipl1/Aurora B is the catalytic subunit of a complex that is required for chromosome segregation and nuclear division. Before anaphase, Ipl1 localizes to kinetochores, where it is required to establish proper kinetochore–microtubule associations and regulate the spindle assembly checkpoint. The protein phosphatase Glc7/PP1 opposes Ipl1 for some of these activities. To more thoroughly characterize the Glc7 phosphatase that opposes Ipl1, we have identified mutations that suppress the thermosensi...

  11. Suppressors of ipl1-2 in Components of a Glc7 Phosphatase Complex, Cdc48 AAA ATPase, TORC1, and the Kinetochore

    OpenAIRE

    Robinson, Lucy C.; Phillips, Joshua; Brou, Lina; Boswell, Evan P.; Tatchell, Kelly

    2012-01-01

    Ipl1/Aurora B is the catalytic subunit of a protein kinase complex required for chromosome segregation and nuclear division. Before anaphase, Ipl1 is required to establish proper kinetochore-microtubule associations and to regulate the spindle assembly checkpoint (SAC). The phosphatase Glc7/PP1 opposes Ipl1 for these activities. To investigate Ipl1 and Glc7 regulation in more detail, we isolated and characterized mutations in the yeast Saccharomyces cerevisiae that raise the restrictive tempe...

  12. The use of Micronucleus Assay on Swiss-Webster Mice (Mus Musculus) Bone Marrow for the Mutagenicity Test of γ-Irradiation

    OpenAIRE

    R. Sofyan; Y. Sumpena; M. Lukita; A. Fitrisari

    2005-01-01

    Ionizing radiation is a potentially chromosomal damaging agent. The induction of chromosomal damage as well as the incidence of cell cycle disturbances may depend on the dose of irradiation. One of the indication of chromosomal damage is the formation of micronucleus (MN) during the anaphase of mitosis. This study deals with the MN assay on femur bone marrow polychromatic erythrocyte (PCE) cells of Swiss-Webster mice, for the mutagenicity test of g-irradiation. The study was conducted on fi...

  13. Basal aurora kinase B activity is sufficient for histone H3 phosphorylation in prophase

    Directory of Open Access Journals (Sweden)

    Ly-Thuy-Tram Le

    2013-02-01

    Histone H3 phosphorylation is the hallmark of mitosis deposited by aurora kinase B. Benzo[e]pyridoindoles are a family of potent, broad, ATP-competitive aurora kinase inhibitors. However, benzo[e]pyridoindole C4 only inhibits histone H3 phosphorylation in prophase but not in metaphase. Under the C4 treatment, the cells enter into mitosis with dephosphorylated histone H3, assemble chromosomes normally and progress to metaphase, and then to anaphase. C4 also induces lagging chromosome in anaphase but we demonstrated that these chromosome compaction defects are not related to the absence of H3 phosphorylation in prophase. As a result of C4 action, mitosis lasts longer and the cell cycle is slowed down. We reproduced the mitotic defects with reduced concentrations of potent pan aurora kinase as well as with a specific aurora B ATP-competitive inhibitor; we therefore propose that histone H3 phosphorylation and anaphase chromosome compaction involve the basal activity of aurora kinase B. Our data suggest that aurora kinase B is progressively activated at mitosis entry and at anaphase onset. The full activation of aurora kinase B by its partners, in prometaphase, induces a shift in the catalytic domain of aurora B that modifies its affinity for ATP. These waves of activation/deactivation of aurora B correspond to different conformations of the chromosomal complex revealed by FRAP. The presence of lagging chromosomes may have deleterious consequences on the daughter cells and, unfortunately, the situation may be encountered in patients receiving treatment with aurora kinase inhibitors.

  14. Regularity of mitosis in different varieties of winter bread wheat under the action of herbicides

    OpenAIRE

    Tatyana Eugenivna KOPYTCHUK; Alexander Lvovivh SECHNYAK

    2012-01-01

    The influence of the most widespread herbicides on winter wheat in Ukraine was studied by anaphase test. Treatment with herbicides reduced the germination of the seeds and disturbed the regularity of mitosis in all varieties of wheat. The range of violations of mitosis was demonstrated by the formation of chromosomal aberrations and dysfunctions of cell cytoskeleton which occurred while processing herbicides. Varietal differences between investigated wheat by sensitivity to herbicides were di...

  15. Meiotic behaviour and spermatogenesis in male mice heterozygous for translocation types also occurring in man

    International Nuclear Information System (INIS)

    In this thesis a start was made with meiotic observations of mouse translocation types - a Robertsonian translocation and a translocation between a metacentric and an acrocentric chromosome - which also occur in man. As an exogeneous factor of possible influence, the meiotic effects of two types of radiation (fission neutrons and X-rays) administered at relatively low doses 2 and 3 hours before prometaphase-metaphase II (probably during metaphase-anaphase I), were determined in Rb4Bnr/+-males. (Auth.)

  16. The E3 Ligase APC/C-Cdh1 Is Required for Associative Fear Memory and Long-Term Potentiation in the Amygdala of Adult Mice

    Science.gov (United States)

    Pick, Joseph E.; Malumbres, Marcos; Klann, Eric

    2013-01-01

    The anaphase promoting complex/cyclosome (APC/C) is an E3 ligase regulated by Cdh1. Beyond its role in controlling cell cycle progression, APC/C-Cdh1 has been detected in neurons and plays a role in long-lasting synaptic plasticity and long-term memory. Herein, we further examined the role of Cdh1 in synaptic plasticity and memory by generating…

  17. The Coordination of Centrosome Reproduction with Nuclear Events of the Cell Cycle in the Sea Urchin Zygote

    OpenAIRE

    Hinchcliffe, Edward H.; Cassels, Grizzel O.; Rieder, Conly L.; Sluder, Greenfield

    1998-01-01

    Centrosomes repeatedly reproduce in sea urchin zygotes arrested in S phase, whether cyclin-dependent kinase 1–cyclin B (Cdk1-B) activity remains at prefertilization levels or rises to mitotic values. In contrast, when zygotes are arrested in mitosis using cyclin B Δ-90, anaphase occurs at the normal time, yet centrosomes do not reproduce. Together, these results reveal the cell cycle stage specificity for centrosome reproduction and demonstrate that neither the level nor the cycling of Cdk1-B...

  18. Effect of polo-like kinase 1 gene silence on cell cycle and drug resistance in K562/A02 cell

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    @@ Polo-like kinase 1(PLK1) plays an important role in many cell-cycle-related events.1 At G2/M transition, PLK1 contributes to the activation of cyclinB/Cdc by phosphorylation of Cdc25C, centrosome functional maturation, bipolar spindle formation. In later stage of mitosis, PLK1 is involved in regulating components of the anaphase-promoting complex (APC) for mitotic exit and in the execution of cytokinesis.

  19. Focus on the centre: the role of chromatin on the regulation of centromere identity and function

    OpenAIRE

    Torras-Llort, Mònica; Moreno-Moreno, Olga; Azorín, Fernando

    2009-01-01

    The centromere is a specialised chromosomal structure that regulates faithful chromosome segregation during cell division, as it dictates the site of assembly of the kinetochore, a critical structure that mediates binding of chromosomes to the spindle, monitors bipolar attachment and pulls chromosomes to the poles during anaphase. Identified more than a century ago as the primary constriction of condensed metaphase chromosomes, the centromere remained elusive to molecular characterisation for...

  20. Cytology and palynology of the Clematis L. species (Ranunculaceae) in Iran

    OpenAIRE

    Sheidai, Masoud; Habibi, Meysam; Azizian, Dina; Khatamsaz, Mahboobeh

    2009-01-01

    Cytological and palynological studies were performed on Clematis L. species (Runanculaceae) of Iran indicating 2n = 2´ = 16 and 2n = 4´ = 32 in them. They formed only bivalents in metaphase of meiosis-I with some amount of chromosome stickiness and laggard formation in anaphase. The species possessed a symmetrical karyotype but differed in karyotypic formulae indicating the occurrence of structural changes in the chromosomes during species diversification. Clematis species usually possessed t...

  1. Chromosome orientation and sterility in gamma-ray induced interchanges in chili pepper (Capsicum annuum L.)

    International Nuclear Information System (INIS)

    After gamma irradiation (30 Kr) of seeds of Capsicum annuum cultivar cerasiformis (2 n = 24) two plants were recorded each carrying two interchanges. The nucleolus organiser chromosome appeared not to be involved. The interchange heterozygotes were weak and meiosis was irregular. At least one multivalent association per PMC was recorded. At metaphase I the predominant orientation was adjacent. The probable reasons for anaphase I and other meiotic irregularities and the incidence of high pollen sterility are discussed. (author)

  2. Determination of Some Cytological Characters of Wild Orchardgrass (Dactylis glomerata L.) Growing in Erzurum District

    OpenAIRE

    Tosun, Metin; Akgün, İlknur; SAĞSÖZ, Sevim

    1998-01-01

    In this study, some cytological characters of orchardgrass were examined naturally growing in Erzurum. Plants assessed for their chromosome number were tetraploid (2n=28). In metaphase I stage the most prevalent pairing was bivalents (avg. 8.37). This was followed by quadrivalent (avg. 2.81), univalent (avg. 0.04) and trivalent (avg. 0.015) pairings. All combinations of bivalents and quadrivalents were recorded. In most of anaphase l cells examined chromosomes distribution to poles were even ...

  3. When the genome plays dice: circumvention of the spindle assembly checkpoint and near-random chromosome segregation in multipolar cancer cell mitoses.

    Directory of Open Access Journals (Sweden)

    David Gisselsson

    Full Text Available BACKGROUND: Normal cell division is coordinated by a bipolar mitotic spindle, ensuring symmetrical segregation of chromosomes. Cancer cells, however, occasionally divide into three or more directions. Such multipolar mitoses have been proposed to generate genetic diversity and thereby contribute to clonal evolution. However, this notion has been little validated experimentally. PRINCIPAL FINDINGS: Chromosome segregation and DNA content in daughter cells from multipolar mitoses were assessed by multiphoton cross sectioning and fluorescence in situ hybridization in cancer cells and non-neoplastic transformed cells. The DNA distribution resulting from multipolar cell division was found to be highly variable, with frequent nullisomies in the daughter cells. Time-lapse imaging of H2B/GFP-labelled multipolar mitoses revealed that the time from the initiation of metaphase to the beginning of anaphase was prolonged and that the metaphase plates often switched polarity several times before metaphase-anaphase transition. The multipolar metaphase-anaphase transition was accompanied by a normal reduction of cellular cyclin B levels, but typically occurred before completion of the normal separase activity cycle. Centromeric AURKB and MAD2 foci were observed frequently to remain on the centromeres of multipolar ana-telophase chromosomes, indicating that multipolar mitoses were able to circumvent the spindle assembly checkpoint with some sister chromatids remaining unseparated after anaphase. Accordingly, scoring the distribution of individual chromosomes in multipolar daughter nuclei revealed a high frequency of nondisjunction events, resulting in a near-binomial allotment of sister chromatids to the daughter cells. CONCLUSION: The capability of multipolar mitoses to circumvent the spindle assembly checkpoint system typically results in a near-random distribution of chromosomes to daughter cells. Spindle multipolarity could thus be a highly efficient

  4. Mechanisms involved in the induction of aneuploidy: the significance of chromosome loss

    OpenAIRE

    A.I. Seoane; Güerci, A.M; F.N. Dulout

    2000-01-01

    The induction of aneuploidy by physical and chemical agents using different test systems was evaluated. The effect of X-rays, caffeine, acetaldehyde, ethanol, diethylstilbestrol, propionaldehyde, and chloral hydrate was studied by chromosome counting in Chinese hamster embryonic diploid cells. Aneugenic ability of cadmium chloride, cadmium sulfate, potassium dichromate, chromium chloride, nickel chloride, and nickel sulfate was assessed by means of anaphase-telophase analysis in Chinese hamst...

  5. The Mps1 Kinase Modulates the Recruitment and Activity of Cnn1CENP-T at Saccharomyces cerevisiae Kinetochores

    OpenAIRE

    Thapa, Kriti Shrestha; Oldani, Amanda; Pagliuca, Cinzia; De Wulf, Peter; Hazbun, Tony R.

    2015-01-01

    Kinetochores are conserved protein complexes that bind the replicated chromosomes to the mitotic spindle and then direct their segregation. To better comprehend Saccharomyces cerevisiae kinetochore function, we dissected the phospho-regulated dynamic interaction between conserved kinetochore protein Cnn1CENP-T, the centromere region, and the Ndc80 complex through the cell cycle. Cnn1 localizes to kinetochores at basal levels from G1 through metaphase but accumulates abruptly at anaphase onset...

  6. Structure-specific endonucleases

    DEFF Research Database (Denmark)

    Minocherhomji, Sheroy; Hickson, Ian D

    2014-01-01

    Fragile sites are conserved loci predisposed to form breaks in metaphase chromosomes. The inherent instability of these loci is associated with chromosomal rearrangements in cancers and is a feature of cells from patients with chromosomal instability syndromes. One class of fragile sites, the com......, leading to the formation of ultra-fine anaphase bridges (UFBs) and micronuclei. We discuss recent developments in the CFS field; in particular, the role of DNA structure-specific endonucleases in promoting cleavage at CFSs....

  7. The kinetochore proteins Pcs1 and Mde4 and heterochromatin are required to prevent merotelic orientation

    OpenAIRE

    Gregan, Juraj; Riedel, Christian G.; Pidoux, Alison L.; Katou, Yuki; Rumpf, Cornelia; Schleiffer, Alexander; Kearsey, Stephen E.; Shirahige, Katsuhiko; Allshire, Robin C.; Nasmyth, Kim

    2007-01-01

    Summary Background Accurate chromosome segregation depends on the establishment of correct—amphitelic—kinetochore orientation. Merotelic kinetochore orientation is an error that occurs when a single kinetochore attaches to microtubules emanating from opposite spindle poles, a condition that hinders segregation of the kinetochore to a spindle pole in anaphase. To avoid chromosome missegregation resulting from merotelic kinetochore orientation, cells have developed mechanisms to prevent or corr...

  8. The effect of the drug colchicine on the early life of fish

    OpenAIRE

    Aluko, P.O.

    1993-01-01

    The alkaloid drug colchicine is a mitotic inhibitor. The results of this study show that colchicine influence the normal functioning of the mitotic process in Sarotherodon galilaeus, S. melanotheron and the hybrid S. galilaeus, X S. melanotheron leading to the production of unusual chromosomal events such as anaphase bridges, laggards and polyploid cells. These unusual events could have serious genetic implications in the area of variability of the chromosome number. The use of colchicine als...

  9. Testing a Mathematical Model of the Yeast Cell Cycle

    OpenAIRE

    Cross, Frederick R.; Archambault, Vincent; Miller, Mary; Klovstad, Martha

    2002-01-01

    We derived novel, testable predictions from a mathematical model of the budding yeast cell cycle. A key qualitative prediction of bistability was confirmed in a strain simultaneously lacking cdc14 and G1 cyclins. The model correctly predicted quantitative dependence of cell size on gene dosage of the G1 cyclin CLN3, but it incorrectly predicted strong genetic interactions between G1 cyclins and the anaphase- promoting complex specificity factor Cdh1. To provide cons...

  10. Mouse Mos protooncogene product is present and functions during oogenesis.

    OpenAIRE

    Paules, R S; Buccione, R; Moschel, R C; Vande Woude, G F; Eppig, J.J.

    1989-01-01

    We have identified the mouse Mos-encoded protein product, p39mos, in maturing mouse oocytes and have shown that it is indistinguishable from the product expressed in Mos-transformed NIH 3T3 cells. p39mos is detected in oocytes arrested in the first meiotic prophase, during germinal-vesicle breakdown, metaphase I, anaphase I, and in ovulated eggs. We show that microinjection of three different Mos antisense (but not sense) oligodeoxyribonucleotides into germinal vesicle-stage oocytes prevents ...

  11. Protective Effects of Quercetin against Dimethoate-Induced Cytotoxicity and Genotoxicity in Allium sativum Test

    OpenAIRE

    Ahmad, Waseem; Shaikh, Sibhghatulla; Nazam, Nazia; Lone, Mohammad Iqbal

    2014-01-01

    The present investigation was directed to study the possible protective activity of quercetin—a natural antioxidant against dimethoate-induced cyto- and genotoxicity in meristematic cells of Allium sativum. So far there is no report on the biological properties of quercetin in plant test systems. Chromosome breaks, multipolar anaphase, stick chromosome, and mitotic activity were undertaken in the current study as markers of cyto- and genotoxicity. Untreated control, quercetin controls (@ 5, 1...

  12. Cytotoxicity of zinc nanoparticles fabricated by Justicia adhatoda L. on root tips of Allium cepa L.--a model approach.

    Science.gov (United States)

    Taranath, T C; Patil, Bheemanagouda N; Santosh, T U; Sharath, B S

    2015-06-01

    Zinc nanoparticles were synthesized using aqueous leaf extract of Justicia adhatoda L. The characterization of nanoparticles was done by ultraviolet-visible (UV-vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM), and high-resolution transmission electron microscopy (HR-TEM). The characteristic absorption peak of the UV spectrum was recorded at 379 nm. The FTIR data revealed the possible biomolecules involved in bioreduction and capping of zinc nanoparticles for efficient stabilization. AFM and HR-TEM images have shown that the size of zinc nanoparticles ranges from 55 to 83 nm and they are spherical in shape. The biogenic zinc nanoparticles were evaluated for their toxic effect on mitotic chromosomes of Allium cepa as a model system. Experiments were conducted in triplicate to assay the effect of 25, 50, 75, and 100 % of zinc nanoparticles on mitotic chromosomes at an interval of 6 h duration for 24 h. The investigation revealed that the mitotic index (MI) was decreased with increased concentration of zinc nanoparticles and exposure duration. The results revealed that zinc nanoparticles have induced abnormalities like anaphase bridge formation, diagonal anaphase, C-metaphase, sticky metaphase, laggards, and sticky anaphase at different percentages and times of exposure. It is evident from the observation that mitotic cell division becomes abortive at 100 % treatment of zinc nanoparticles. PMID:25586613

  13. 百合三倍体种间杂种花粉母细胞减数分裂行为观察%Meiosis Observation of Pollen Mother Cells of Triploid Interspecific Hybrids in Lily

    Institute of Scientific and Technical Information of China (English)

    雷家军; 梁印

    2012-01-01

    The meiosis process of the triploid interspecific hybrid derived from the cross of Lilium pumilum DC. (2n = 2x= 24) and Asiatic hybrids cv. Brunello (2n = 4x = 48) were observed. Some abnormal behaviors during meiosis were observed, including unequal bivalents in diplotene, chromosome bridges in anaphase IⅠand telophase Ⅰ , lagging chromosomes in anaphase Ⅰ, telophase I , metaphase Ⅱ and telophase Ⅱ , micronuclei in telophase I and dyad, unequal separation in telophase I and anaphase II and so on. These abnormal meiosis behaviors of microspore mother cells were responsible for pollen abortion.%对细叶百合(2x)×布鲁拉诺(4x)的三倍体种间杂种花粉母细胞减数分裂过程进行了观察,发现三倍体种间杂种减数分裂过程中出现较多异常现象,在双线期出现不等二价体;在后期I和末期工出现染色体桥;在后期Ⅰ、末期Ⅰ、中期Ⅱ和末期Ⅱ出现滞后染色体;在末期Ⅰ和二分体时期出现微核;在末期Ⅰ和后期Ⅱ出现不均等分离等.花粉母细胞减数分裂异常可能是导致花粉败育的主要原因.

  14. Protective effect of butylated hydroxytoluene (BHT against the clastogenic acitivity of cadmium chloride and potassium dichromate in hamster ovary cells

    Directory of Open Access Journals (Sweden)

    Grillo Claudia A.

    1999-01-01

    Full Text Available The effect of butylated hydroxytoluene (BHT, a widely used food additive, on chromosomal alterations induced by cadmium chloride (CC and potassium dichromate (PD in Chinese hamster ovary (CHO cells was studied both at metaphase and anaphase-telophase. CHO cells were cultured for 15-16 h in the presence of PD (6.0, 9.0 or 12.0 mM, BHT (1.0 mg/ml, or PD plus BHT as well as CC (0.5, 1.0 and 2.0 mM, BHT or CC plus BHT for the analysis of chromosomal aberrations. To perform the anaphase-telophase test, cells were cultured in cover glasses and treated 8 h before fixation with the same chemicals. An extra dose of CC (4 mM was used in this test. Both metal salts significantly increased chromosomal aberration frequencies in relation to untreated controls, and to DMSO- and BHT-treated cells. Post-treatment with BHT decreased the yield of chromosomal damage in relation to treatments performed with CC and PD. However, chromosomal aberration frequencies were significantly higher than those of the controls. In the anaphase-telophase test, CC significantly increased the yield of lagging chromosomes with the four doses employed and the frequency of lagging fragments with the highest dose. In combined treatments of CC and BHT, frequencies of the two types of alterations decreased significantly in relation to the cells treated with CC alone. No significant variation was found in the frequencies of chromatin bridges. Significant increases of numbers of chromatin bridges, lagging chromosomes and lagging fragments were found in cells treated with PD. The protective effect of BHT in combined treatments was evidenced by the significant decrease of chromatid bridges and lagging chromosomes in relation to PD-treated cells. Whereas BHT is able to induce chromosomal damage, it can also protect against oxidative damage induced by other genotoxicants.

  15. Physical and genetic mapping of maize chromosome 9S using mutations with terminal deficiencies

    International Nuclear Information System (INIS)

    Undoubtedly, cytogenetic materials containing chromosomal alterations, such as translocation, and inversions derived from X ray irradiation or other means have made a tremendous contribution to our understanding of chromosome behaviour in plants. In maize, such materials have been applied to gene mapping and linkage group assignment dating back to the 1930s. The fate of the chromosomes with broken ends has been examined and it was found that when a chromatid is broken at meiotic anaphase fusion will occur between the two sister halves of this chromatid and a bridge will re-form during the following mitotic anaphase. This process is referred to as the breakage-fusion-bridge cycle. It has also been demonstrated that this cycle will continue in all subsequent gametophytic and endosperm mitoses following its origin at meiotic anaphase. However, this cycle will cease when the broken chromosome enters the zygote. The broken end heals permanently, since no further fusion and breakage are found in sporophytic mitoses or any other tissues of later generations. A series of terminal deficient mutants involving the short arm of chromosome 9 derived from the breakage-fusion-bridge cycle has been used to determine the physical order of genes for pale yellow (pyd1), yellow-green (yg2) and while (wd1) seedlings. The purpose of this present study was to use a series of terminal deficient materials reported by McClintock in order to establish the physical order of six RFLP markers and five morphological markers located at the distal end of chromosome 9S. 13 refs

  16. Chromosomal Behavior during Meiosis in the Progeny of Triticum timopheevii × Hexaploid Wild Oat.

    Directory of Open Access Journals (Sweden)

    Hongzhou An

    Full Text Available The meiotic behavior of pollen mother cells (PMCs of the F2 and F3 progeny from Triticum timopheevii × hexaploid wild oat was investigated by cytological analysis and sequential C-banding-genomic in situ hybridization (GISH in the present study. A cytological analysis showed that the chromosome numbers of the F2 and F3 progeny ranged from 28 to 41. A large number of univalents, lagging chromosomes, chromosome bridges and micronuclei were found at the metaphase I, anaphase I, anaphase II and tetrad stages in the F2 and F3 progeny. The averages of univalents were 3.50 and 2.73 per cell, and those of lagging chromosomes were 3.37 and 1.87 in the F2 and F3 progeny, respectively. The PMC meiotic indices of the F2 and F3 progeny were 12.22 and 20.34, respectively, indicating considerable genetic instability. A sequential C-banding-GISH analysis revealed that some chromosomes and fragments from the hexaploid wild oat were detected at metaphase I and anaphase I in the progeny, showing that the progeny were of true intergeneric hybrid origin. The alien chromosomes 6A, 7A, 3C and 2D were lost during transmission from F2 to F3. In addition, partial T. timopheevii chromosomes appeared in the form of univalents or lagging chromosomes, which might result from large genome differences between the parents, and the wild oat chromosome introgression interfered with the wheat homologues' normally pairing.

  17. Immunogold electron microscopy and confocal analyses reveal distinctive patterns of histone H3 phosphorylation during mitosis in MCF-7 cells.

    Science.gov (United States)

    Yan, Yitang; Cummings, Connie A; Sutton, Deloris; Yu, Linda; Castro, Lysandra; Moore, Alicia B; Gao, Xiaohua; Dixon, Darlene

    2016-04-01

    Histone phosphorylation has a profound impact on epigenetic regulation of gene expression, chromosome condensation and segregation, and maintenance of genome integrity. Histone H3 Serine 10 is evolutionally conserved and heavily phosphorylated during mitosis. To examine Histone H3 Serine 10 phosphorylation (H3S10ph) dynamics in mitosis, we applied immunogold labeling and confocal microscopy to visualize H3S10ph expression in MCF-7 cells. Confocal observations showed that MCF-7 cells had abundant H3S10ph expression in prophase and metaphase. In anaphase, the H3S10ph expression was significantly decreased and displayed only sparsely localized staining that mainly associated with the chromatid tips. We showed that immunogold bead density distribution followed the H3S10ph expression patterns observed in confocal analysis. At a higher magnification in metaphase, the immunogold beads were readily visible and the bead distribution along the condensed chromosomes was distinctive, indicating the specificity and reliability of the immunogold staining procedure. In anaphase, the beads were found to distribute focally in specific regions of chromatids, reinforcing the confocal observations of differential H3 phosphorylation. To our knowledge, this is the first report to show the specific H3S10ph expression with an immunogold technique and transmission electron microscopy. Additionally, with confocal microscopy, we analyzed H3S10ph expression in an immortalized cell line derived from benign uterine smooth muscle tumor cells. H3S10ph epitope was expressed more abundantly during anaphase in the benign tumor cells, and there was no dramatic differential expression within the condensed chromatid clusters as observed in MCF-7 cells. The differences in H3S10ph expression pattern and dynamics may contribute to the differential proliferative potential between benign tumor cells and MCF-7 cells. Published 2016. This article is a U.S. Government work and is in the public domain in the

  18. Smurf2 as a novel mitotic regulator: From the spindle assembly checkpoint to tumorigenesis

    Directory of Open Access Journals (Sweden)

    Moore Finola E

    2009-07-01

    Full Text Available Abstract The execution of the mitotic program with high fidelity is dependent upon precise spatiotemporal regulation of posttranslational protein modifications. For example, the timely polyubiquitination of critical mitotic regulators by Anaphase Promoting Complex/Cyclosome (APC/C is essential for the metaphase to anaphase transition and mitotic exit. The spindle assembly checkpoint prevents unscheduled activity of APC/C-Cdc20 in early mitosis, allowing bipolar attachment of kinetochores to mitotic spindle and facilitating equal segregation of sister chromatids. The critical effector of the spindle checkpoint, Mitotic arrest deficient 2 (Mad2, is recruited to unattached kinetochores forming a complex with other regulatory proteins to efficiently and cooperatively inhibit APC/C-Cdc20. A weakened and/or dysfunctional spindle checkpoint has been linked to the development of genomic instability in both cell culture and animal models, and evidence suggests that aberrant regulation of the spindle checkpoint plays a critical role in human carcinogenesis. Recent studies have illuminated a network of both degradative and non-degradative ubiquitination events that regulate the metaphase to anaphase transition and mitotic exit. Within this context, our recent work showed that the HECT (Homologous to E6-AP C-terminus-family E3 ligase Smurf2 (Smad specific ubiquitin regulatory factor 2, known as a negative regulator of transforming growth factor-beta (TGF-β signaling, is required for a functional spindle checkpoint by promoting the functional localization and stability of Mad2. Here we discuss putative models explaining the role of Smurf2 as a new regulator in the spindle checkpoint. The dynamic mitotic localization of Smurf2 to the centrosome and other critical mitotic structures provides implications about mitotic checkpoint control dependent on various ubiquitination events. Finally, deregulated Smurf2 activity may contribute to carcinogenesis by

  19. Chromosomal Behavior during Meiosis in the Progeny of Triticum timopheevii × Hexaploid Wild Oat.

    Science.gov (United States)

    An, Hongzhou; Hu, Mei; Li, Pengfei; Geng, Guangdong; Zhang, Qingqin; Zhang, Suqin

    2015-01-01

    The meiotic behavior of pollen mother cells (PMCs) of the F2 and F3 progeny from Triticum timopheevii × hexaploid wild oat was investigated by cytological analysis and sequential C-banding-genomic in situ hybridization (GISH) in the present study. A cytological analysis showed that the chromosome numbers of the F2 and F3 progeny ranged from 28 to 41. A large number of univalents, lagging chromosomes, chromosome bridges and micronuclei were found at the metaphase I, anaphase I, anaphase II and tetrad stages in the F2 and F3 progeny. The averages of univalents were 3.50 and 2.73 per cell, and those of lagging chromosomes were 3.37 and 1.87 in the F2 and F3 progeny, respectively. The PMC meiotic indices of the F2 and F3 progeny were 12.22 and 20.34, respectively, indicating considerable genetic instability. A sequential C-banding-GISH analysis revealed that some chromosomes and fragments from the hexaploid wild oat were detected at metaphase I and anaphase I in the progeny, showing that the progeny were of true intergeneric hybrid origin. The alien chromosomes 6A, 7A, 3C and 2D were lost during transmission from F2 to F3. In addition, partial T. timopheevii chromosomes appeared in the form of univalents or lagging chromosomes, which might result from large genome differences between the parents, and the wild oat chromosome introgression interfered with the wheat homologues' normally pairing. PMID:25950431

  20. Yeast Interacting Proteins Database: YDL116W, YDR113C [Yeast Interacting Proteins Database

    Lifescience Database Archive (English)

    Full Text Available and mitotic exit, essential for meiotic progression and mitotic cell cycle arrest; localization is cell-cycle dep...arin Esp1p; blocks cyclin destruction and mitotic exit, essential for meiotic progression...fected by(YPD) - Interologs - Expression similarity (BRITE) - Alternative path with 1 intervening protein (Y... and mitotic cell cycle arrest; localization is cell-cycle dependent and regulated by Cdc28p phosphorylation...y gene name PDS1 Prey description Securin, inhibits anaphase by binding separin Esp1p; blocks cyclin destruction

  1. Chromosome numbers, meiotic behavior, and pollen viability of species of Vriesea and Aechmea genera (Bromeliaceae) native to Rio Grande do Sul, Brazil.

    Science.gov (United States)

    Palma-Silva, Clarisse; Dos Santos, Daniel G; Kaltchuk-Santos, Eliane; Bodanese-Zanettini, Maria H

    2004-06-01

    Chromosome number, meiotic behavior, and pollen viability were analyzed in 15 species of two genera, Vriesea and Aechmea, native to Rio Grande do Sul, Brazil. This study is the first cytogenetic analysis of these taxa. The chromosome numbers are all n = 25, consistent with the proposed base number of x = 25 for Bromeliaceae. All examined taxa displayed regular bivalent pairing and chromosome segregation at meiosis. Observed meiotic abnormalities include univalents in metaphase I; missing or extra chromosomes and precocious division of centromeres in metaphase II; laggards in telophase I and anaphase II/telophase II. The high pollen viability (>88%) reflects a regular meiosis. PMID:21653435

  2. Characterization of the NTPR and BD1 interacting domains of the human PICH-BEND3 complex

    DEFF Research Database (Denmark)

    Pitchai, Ganesha P; Hickson, Ian D; Streicher, Werner;

    2016-01-01

    Chromosome integrity depends on DNA structure-specific processing complexes that resolve DNA entanglement between sister chromatids. If left unresolved, these entanglements can generate either chromatin bridging or ultrafine DNA bridging in the anaphase of mitosis. These bridge structures are...... defined by the presence of the PICH protein, which interacts with the BEND3 protein in mitosis. To obtain structural insights into PICH-BEND3 complex formation at the atomic level, their respective NTPR and BD1 domains were cloned, overexpressed and crystallized using 1.56 M ammonium sulfate as a...

  3. A Putative Homologue of CDC20/CDH1 in the Malaria Parasite Is Essential for Male Gamete Development

    OpenAIRE

    Guttery, David S; Ferguson, David J. P.; Benoit Poulin; Zhengyao Xu; Ursula Straschil; Onny Klop; Lev Solyakov; Sandrini, Sara M.; Declan Brady; Nieduszynski, Conrad A.; Chris J. Janse; Holder, Anthony A.; Tobin, Andrew B.; Rita Tewari

    2012-01-01

    Cell-cycle progression is governed by a series of essential regulatory proteins. Two major regulators are cell-division cycle protein 20 (CDC20) and its homologue, CDC20 homologue 1 (CDH1), which activate the anaphase-promoting complex/cyclosome (APC/C) in mitosis, and facilitate degradation of mitotic APC/C substrates. The malaria parasite, Plasmodium, is a haploid organism which, during its life-cycle undergoes two stages of mitosis; one associated with asexual multiplication and the other ...

  4. Requirement of the SCFPop1/Pop2 Ubiquitin Ligase for Degradation of the Fission Yeast S Phase Cyclin Cig2

    OpenAIRE

    Yamano, H; Kominami, K; Harrison, C; Kitamura, K.; Katayama, S; Dhut, S.; Hunt, T; Toda, T.

    2004-01-01

    Two multiprotein E3 (ubiquitin-protein ligase) ubiquitin ligases, the SCF (Skp1-Cullin-1-F-box) and the APC/C (anaphase promoting complex/cyclosome), are vital in ensuring the temporal order of the cell cycle. Particularly, timely destruction of cyclins via these two E3s is essential for down-regulation of cyclin-dependent kinase. In general, G(1) and S phase cyclins are ubiquitylated by the SCF, whereas ubiquitylation of mitotic cyclins is catalyzed by the APC/C. Here we show that fission ye...

  5. Dual-mode regulation of the APC/C by CDK1 and MAPK controls meiosis I progression and fidelity

    OpenAIRE

    Nabti, Ibtissem; Marangos, Petros; Bormann, Jenny; Kudo, Nobuaki R; Carroll, John

    2014-01-01

    Female meiosis is driven by the activities of two major kinases, cyclin-dependent kinase 1 (Cdk1) and mitogen-activated protein kinase (MAPK). To date, the role of MAPK in control of meiosis is thought to be restricted to maintaining metaphase II arrest through stabilizing Cdk1 activity. In this paper, we find that MAPK and Cdk1 play compensatory roles to suppress the anaphase-promoting complex/cyclosome (APC/C) activity early in prometaphase, thereby allowing accumulation of APC/C substrates...

  6. Prometaphase APCcdh1 activity prevents non-disjunction in mammalian oocytes

    OpenAIRE

    Reis, Alexandra; Madgwick, Suzanne; Chang, Heng-Yu; Nabti, Ibtissem; Levasseur, Mark; Jones, Keith T

    2007-01-01

    The first female meiotic division (MI) is uniquely prone to chromosome segregation errors through non-disjunction, resulting in trisomies and early pregnancy loss1. Here, we show a fundamental difference in the control of mammalian meiosis which may underlie such susceptibility. It involved a reversal in the well-established timing of activation of the Anaphase-Promoting Complex (APC)2, 3 by its co-activators cdc20 and cdh1. APCcdh1 was active first, during prometaphase I, and was needed in o...

  7. Regularity of mitosis in different varieties of winter bread wheat under the action of herbicides

    Directory of Open Access Journals (Sweden)

    Tatyana Eugenivna KOPYTCHUK

    2012-05-01

    Full Text Available The influence of the most widespread herbicides on winter wheat in Ukraine was studied by anaphase test. Treatment with herbicides reduced the germination of the seeds and disturbed the regularity of mitosis in all varieties of wheat. The range of violations of mitosis was demonstrated by the formation of chromosomal aberrations and dysfunctions of cell cytoskeleton which occurred while processing herbicides. Varietal differences between investigated wheat by sensitivity to herbicides were discovered. The most resistant to herbicides was variety Fantasya Odesskaya, and the most sensitive – Nikoniya, while the most harmful herbicide for wheat was Napalm.

  8. Relative biological effectiveness of d(50)-Be neutrons determined for induction of chromosome aberrations in Allium cepa onion roots

    International Nuclear Information System (INIS)

    Relative biological effectiveness (RBE) of d(50)-Be neutrons, as a function of absorbed dose, was determined using as biological criterion induction of chromosome aberrations in Allium cepa onion roots. Two endpoints were used: mean number of aberrations per cell and percentage of intact cells, in anaphase and telophase. For both endpoints, RBE increases regularly from 7 to 12 when neutron absorbed dose decreases from 0.4 to 0.1 Gy. On the other hand, RBE/absorbed dose relationships are almost straight lines, in logarithmic coordinates, with a slope close to -1/2

  9. Emi1 is needed to couple DNA replication with mitosis but does not regulate activation of the mitotic APC/C

    OpenAIRE

    Di Fiore, Barbara; Pines, Jonathon

    2007-01-01

    Ubiquitin-mediated proteolysis is critical for the alternation between DNA replication and mitosis and for the key regulatory events in mitosis. The anaphase-promoting complex/cyclosome (APC/C) is a conserved ubiquitin ligase that has a fundamental role in regulating mitosis and the cell cycle in all eukaryotes. In vertebrate cells, early mitotic inhibitor 1 (Emi1) has been proposed as an important APC/C inhibitor whose destruction may trigger activation of the APC/C at mitosis. However, in t...

  10. Hypomorphic bimA(APC3) alleles cause errors in chromosome metabolism that activate the DNA damage checkpoint blocking cytokinesis in Aspergillus nidulans.

    OpenAIRE

    Wolkow, T D; Mirabito, P.M.; Venkatram, S; Hamer, J. E.

    2000-01-01

    The Aspergillus nidulans sepI(+) gene has been implicated in the coordination of septation with nuclear division and cell growth. We find that the temperature-sensitive (ts) sepI1 mutation represents a novel allele of bimA(APC3), which encodes a conserved component of the anaphase-promoting complex/cyclosome (APC/C). We have characterized the septation, nuclear division, cell-cycle checkpoint defects, and DNA sequence alterations of sepI1 (renamed bimA10) and two other ts lethal bimA(APC3) al...

  11. Resolution of Sister Centromeres Requires RanBP2-Mediated SUMOylation of Topoisomerase IIα

    OpenAIRE

    Dawlaty, Meelad M.; Malureanu, Liviu; Jeganathan, Karthik B.; Kao, Esther; Sustmann, Claudio; Tahk, Samuel; Shuai, Ke; Grosschedl, Rudolf; van Deursen, Jan M.

    2008-01-01

    RanBP2 is a nucleoporin with SUMO E3 ligase activity that functions in both nucleocytoplasmic transport and mitosis. However, the biological relevance of RanBP2 and the in vivo targets of its E3 ligase activity are unknown. Here we show that animals with low amounts of RanBP2 develop severe aneuploidy in the absence of overt transport defects. The main chromosome segregation defect in cells from these mice is anaphase-bridge formation. Topoisomerase IIα (Topo IIα), which decatenates sister ce...

  12. Changes in the architectonics of the root apical meristem at radiation mutagenesis

    International Nuclear Information System (INIS)

    Acute irradiation of pea germs induced an increase of the cell population polymorphism, vacuolation, and parenhimatization of individual cells and cell packets in the root meristem. The degree of topology disturbances is usually correlated with the dose of irradiation. Increasing the dose reduces the meristem size and increases the inactivation frequency of cells and the cell packet deformation. The structural architectonics of the meristem is deformed at the 33%-frequency of aberrant anaphases (FAA), but, nevertheless, it remains. At 50% FAA, the topology of cellular rows and the zoning of apex are destroyed, and sizes of the meristem are decreased to 'the critical' level.

  13. Fission Yeast Scm3: A CENP-A Receptor Required for Integrity of Subkinetochore Chromatin

    OpenAIRE

    Pidoux, Alison L.; Choi, Eun Shik; Abbott, Johanna K.R.; Liu, Xingkun; Kagansky, Alexander; Castillo, Araceli G.; Hamilton, Georgina L.; Richardson, William; Rappsilber, Juri; He, Xiangwei; Allshire, Robin C.

    2009-01-01

    Summary The mechanisms ensuring specific incorporation of CENP-A at centromeres are poorly understood. Mis16 and Mis18 are required for CENP-A localization at centromeres and form a complex that is conserved from fission yeast to human. Fission yeast sim1 mutants that alleviate kinetochore domain silencing are defective in Scm3Sp, the ortholog of budding yeast Scm3Sc. Scm3Sp depends on Mis16/18 for its centromere localization and like them is recruited to centromeres in late anaphase. Importa...

  14. Meiotic chromosomal variation resulting from irradiation of pollen in maize

    International Nuclear Information System (INIS)

    The objective of this study was to standardize an induction strategy of chromosome aberrations in maize inbred line L-869. Pollen grains irradiated with 0, 36 and 72 Gy were used for fertilization. Resulting seeds were planted in a greenhouse to assess the number of abnormal meiotic cells. Germination, height, sterility and mortality were verified. Cells with delayed separation of chromosomes, translocation, deficiency, abnormal pairing, later condensation and anaphase bridges were observed. The number of abnormalities increased as the dosage increased but chromosome aberration types were the same regardless of the dosages used. Various chromosome-altered plants were obtained without viability loss. (author)

  15. Postnatal telomere dysfunction induces cardiomyocyte cell-cycle arrest through p21 activation.

    Science.gov (United States)

    Aix, Esther; Gutiérrez-Gutiérrez, Óscar; Sánchez-Ferrer, Carlota; Aguado, Tania; Flores, Ignacio

    2016-06-01

    The molecular mechanisms that drive mammalian cardiomyocytes out of the cell cycle soon after birth remain largely unknown. Here, we identify telomere dysfunction as a critical physiological signal for cardiomyocyte cell-cycle arrest. We show that telomerase activity and cardiomyocyte telomere length decrease sharply in wild-type mouse hearts after birth, resulting in cardiomyocytes with dysfunctional telomeres and anaphase bridges and positive for the cell-cycle arrest protein p21. We further show that premature telomere dysfunction pushes cardiomyocytes out of the cell cycle. Cardiomyocytes from telomerase-deficient mice with dysfunctional telomeres (G3 Terc(-/-)) show precocious development of anaphase-bridge formation, p21 up-regulation, and binucleation. In line with these findings, the cardiomyocyte proliferative response after cardiac injury was lost in G3 Terc(-/-) newborns but rescued in G3 Terc(-/-)/p21(-/-) mice. These results reveal telomere dysfunction as a crucial signal for cardiomyocyte cell-cycle arrest after birth and suggest interventions to augment the regeneration capacity of mammalian hearts. PMID:27241915

  16. Using Photobleaching to Measure Spindle Microtubule Dynamics in Primary Cultures of Dividing Drosophila Meiotic Spermatocytes.

    Science.gov (United States)

    Savoian, Matthew S

    2015-07-01

    In dividing animal cells, a microtubule (MT)-based bipolar spindle governs chromosome movement. Current models propose that the spindle facilitates and/or generates translocating forces by regionally depolymerizing the kinetochore fibers (k-fibers) that bind each chromosome. It is unclear how conserved these sites and the resultant chromosome-moving mechanisms are between different dividing cell types because of the technical challenges of quantitatively studying MTs in many specimens. In particular, our knowledge of MT kinetics during the sperm-producing male meiotic divisions remains in its infancy. In this study, I use an easy-to-implement photobleaching-based assay for measuring spindle MT dynamics in primary cultures of meiotic spermatocytes isolated from the fruit fly Drosophila melanogaster. By use of standard scanning confocal microscopy features, fiducial marks were photobleached on fluorescent protein (FP)-tagged MTs. These were followed by time-lapse imaging during different division stages, and their displacement rates were calculated using public domain software. I find that k-fibers continually shorten at their poles during metaphase and anaphase A through the process of MT flux. Anaphase chromosome movement is complemented by Pac-Man, the shortening of the k-fiber at its chromosomal interface. Thus, Drosophila spermatocytes share the sites of spindle dynamism and mechanisms of chromosome movement with mitotic cells. The data reveal the applicability of the photobleaching assay for measuring MT dynamics in primary cultures. This approach can be readily applied to other systems. PMID:25802491

  17. Novel subcellular localization of the DNA helicase Twinkle at the kinetochore complex during mitosis in neuronal-like progenitor cells.

    Science.gov (United States)

    Uittenbogaard, Martine; Chiaramello, Anne

    2016-03-01

    During mitosis, the kinetochore, a multi-protein structure located on the centromeric DNA, is responsible for proper segregation of the replicated genome. More specifically, the outer kinetochore complex component Ndc80/Hec1 plays a critical role in regulating microtubule attachment to the spindle for accurate sister chromatid segregation. In addition, DNA helicases play a key contribution for precise and complete disjunction of sister chromatids held together through double-stranded DNA catenations until anaphase. In this study, we focused our attention on the nuclear-encoded DNA helicase Twinkle, which functions as an essential helicase for replication of mitochondrial DNA. It regulates the copy number of the mitochondrial genome, while maintaining its integrity, two processes essential for mitochondrial biogenesis and bioenergetic functions. Although the majority of the Twinkle protein is imported into mitochondria, a small fraction remains cytosolic with an unknown function. In this study, we report a novel expression pattern of Twinkle during chromosomal segregation at distinct mitotic phases. By immunofluorescence microscopy, we found that Twinkle protein colocalizes with the outer kinetochore protein HEC1 as early as prophase until late anaphase in neuronal-like progenitor cells. Thus, our collective results have revealed an unexpected cell cycle-regulated expression pattern of the DNA helicase Twinkle, known for its role in mtDNA replication. Therefore, its recruitment to the kinetochore suggests an evolutionary conserved function for both mitochondrial and nuclear genomic inheritance. PMID:26678504

  18. PTK2b function during fertilization of the mouse oocyte

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Jinping [Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, KS 66160 (United States); McGinnis, Lynda K. [Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, KS 66160 (United States); Carlton, Carol [Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, KS 66160 (United States); Beggs, Hilary E. [Department of Ophthalmology, University of California, San Francisco, CA (United States); Kinsey, William H., E-mail: wkinsey@kumc.edu [Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, KS 66160 (United States)

    2014-08-01

    Highlights: • PTK2b is expressed in oocytes and is activated following fertilization. • PTK2b suppression in oocytes prevents fertilization, but not parthenogenetic activation. • PTK2b suppression prevents the oocyte from fusing with or incorporating bound sperm. • PTK2b suppressed oocytes that fail to fertilize do not exhibit calcium oscillations. - Abstract: Fertilization triggers rapid changes in intracellular free calcium that serve to activate multiple signaling events critical to the initiation of successful development. Among the pathways downstream of the fertilization-induced calcium transient is the calcium-calmodulin dependent protein tyrosine kinase PTK2b or PYK2 kinase. PTK2b plays an important role in fertilization of the zebrafish oocyte and the objective of the present study was to establish whether PTK2b also functions in mammalian fertilization. PTK2b was activated during the first few hours after fertilization of the mouse oocyte during the period when anaphase resumption was underway and prior to the pronuclear stage. Suppression of PTK2b kinase activity in oocytes blocked sperm incorporation and egg activation although sperm-oocyte binding was not affected. Oocytes that failed to incorporate sperm after inhibitor treatment showed no evidence of a calcium transient and no evidence of anaphase resumption suggesting that egg activation did not occur. The results indicate that PTK2b functions during the sperm-egg fusion process or during the physical incorporation of sperm into the egg cytoplasm and is therefore critical for successful development.

  19. Mcm10 proteolysis initiates before the onset of M-phase

    Directory of Open Access Journals (Sweden)

    Khan Muntaz

    2010-10-01

    Full Text Available Abstract Background Mcm10 protein is essential for initiation and elongation phases of replication. Human cells proteolyze Mcm10 during mitosis, presumably to ensure a single round of replication. It has been proposed that anaphase promoting complex ubiquitinates Mcm10 in late M and early G1 phases. Results In contrast to the previous work, we report that the degradation of Mcm10 is initiated at the onset of mitosis. Immunoblotting and immunofluorescence assays display that Mcm10 levels are low in all phases of mitosis. We report that Mcm10 degradation is not dependent on anaphase promoting complex. Further, the proteolysis in M-phase can be independently mediated by non-overlapping regions of Mcm10, apparently employing a redundant mechanism to ensure downregulation. Conclusions It is believed that the proteolysis of Mcm10 during mitosis is a vital mechanism to prevent aberrant initiation of replication and the present study describes the regulation of Mcm10 during this phase of the cell-cycle.

  20. MICROTUBULE-ASSOCIATED PROTEIN65 is essential for maintenance of phragmoplast bipolarity and formation of the cell plate in Physcomitrella patens.

    Science.gov (United States)

    Kosetsu, Ken; de Keijzer, Jeroen; Janson, Marcel E; Goshima, Gohta

    2013-11-01

    The phragmoplast, a plant-specific apparatus that mediates cytokinesis, mainly consists of microtubules (MTs) arranged in a bipolar fashion, such that their plus ends interdigitate at the equator. Membrane vesicles are thought to move along the MTs toward the equator and fuse to form the cell plate. Although several genes required for phragmoplast MT organization have been identified, the mechanisms that maintain the bipolarity of phragmoplasts remain poorly understood. Here, we show that engaging phragmoplast MTs in a bipolar fashion in protonemal cells of the moss Physcomitrella patens requires the conserved MT cross-linking protein MICROTUBULE-ASSOCIATED PROTEIN65 (MAP65). Simultaneous knockdown of the three MAP65s expressed in those cells severely compromised MT interdigitation at the phragmoplast equator after anaphase onset, resulting in the collapse of the phragmoplast in telophase. Cytokinetic vesicles initially localized to the anaphase midzone as normal but failed to further accumulate in the next several minutes, although the bipolarity of the MT array was preserved. Our data indicate that the presence of bipolar MT arrays is insufficient for vesicle accumulation at the equator and further suggest that MAP65-mediated MT interdigitation is a prerequisite for maintenance of bipolarity of the phragmoplast and accumulation and/or fusion of cell plate-destined vesicles at the equatorial plane. PMID:24272487

  1. Visualizing the spindle checkpoint in Drosophila spermatocytes

    Science.gov (United States)

    Rebollo, Elena; González, Cayetano

    2000-01-01

    The spindle assembly checkpoint detects defects in spindle structure or in the alignment of the chromosomes on the metaphase plate and delays the onset of anaphase until defects are corrected. Thus far, the evidence regarding the presence of a spindle checkpoint during meiosis in male Drosophila has been indirect and contradictory. On the one hand, chromosomes without pairing partners do not prevent meiosis progression. On the other hand, some conserved components of the spindle checkpoint machinery are expressed in these cells and behave as their homologue proteins do in systems with an active spindle checkpoint. To establish whether the spindle checkpoint is active in Drosophila spermatocytes we have followed meiosis progression by time-lapse microscopy under conditions where the checkpoint is likely to be activated. We have found that the presence of a relatively high number of misaligned chromosomes or a severe disruption of the meiotic spindle results in a significant delay in the time of entry into anaphase. These observations provide the first direct evidence substantiating the activity of a meiotic spindle checkpoint in male Drosophila. PMID:11256627

  2. Virtual Nuclear Envelope Breakdown and Its Regulators in Fission Yeast Meiosis.

    Science.gov (United States)

    Asakawa, Haruhiko; Yang, Hui-Ju; Hiraoka, Yasushi; Haraguchi, Tokuko

    2016-01-01

    Ran, a small GTPase, is required for the spindle formation and nuclear envelope (NE) formation. After NE breakdown (NEBD) during mitosis in metazoan cells, the Ran-GTP gradient across the NE is lost and Ran-GTP becomes concentrated around chromatin, thus affecting the stability of microtubules and promoting the assembly of spindle microtubules and segregation of chromosomes. Mitosis in which chromosomes are segregated subsequent to NEBD is called "open mitosis." In contrast, many fungi undergo a process termed "closed mitosis" in which chromosome segregation and spindle formation occur without NEBD. Although the fission yeast Schizosaccharomyces pombe undergoes a closed mitosis, it exhibits a short period during meiosis (anaphase of the second meiosis; called "anaphase II") when nuclear and cytoplasmic proteins are mixed in the presence of intact NE and nuclear pore complexes (NPC). This "virtual" nuclear envelope breakdown (vNEBD) involves changes in the localization of RanGAP1, an activator of Ran-GTP hydrolysis. Recently, Nup132, a component of the structural core Nup107-160 subcomplex of the NPC, has been shown to be involved in the maintenance of the nuclear cytoplasmic barrier in yeast meiosis. In this review, we highlight the possible roles of RanGAP1 and Nup132 in vNEBD and discuss the biological significance of vNEBD in S. pombe meiosis. PMID:26870731

  3. Inter-domain Cooperation in INCENP Promotes Aurora B Relocation from Centromeres to Microtubules

    Directory of Open Access Journals (Sweden)

    Armando van der Horst

    2015-07-01

    Full Text Available The chromosomal passenger complex is essential for error-free chromosome segregation and proper execution of cytokinesis. To coordinate nuclear division with cytoplasmic division, its enzymatic subunit, Aurora B, relocalizes from centromeres in metaphase to the spindle midzone in anaphase. In budding yeast, this requires dephosphorylation of the microtubule-binding (MTB domain of the INCENP analog Sli15. The mechanistic basis for this relocalization in metazoans is incompletely understood. We demonstrate that the putative coiled-coil domain within INCENP drives midzone localization of Aurora B via a direct, electrostatic interaction with microtubules. Furthermore, we provide evidence that the CPC multimerizes via INCENP’s centromere-targeting domain (CEN box, which increases the MTB affinity of INCENP. In (prometaphase, the MTB affinity of INCENP is outcompeted by the affinity of its CEN box for centromeres, while at anaphase onset—when the histone mark H2AT120 is dephosphorylated—INCENP and Aurora B switch from centromere to microtubule localization.

  4. RBE of d(50)-Be neutrons for induction of chromosome aberrations in Allium cepa onion roots

    International Nuclear Information System (INIS)

    RBE/absorbed dose relationship of d(50)-Be neutrons was determined for the induction of chromosome aberrations in Allium cepa onion roots. Neutrons are produced at the cyclotron 'Cyclone' by bombarding a thick beryllium target with 50 MeV deuterons. Two biological criteria were selected: (1) mean number of aberrations (mainly breaks) per cell in anaphase and telophase, (2) fraction of intact cells in anaphase and telophase. For the two criteria, RBE increases continuously from about 7 to 12 as the neutron absorbed dose decreases from 0.4 to 0.1 Gy. RBE values for the first criterion are slightly higher than for the second one. This observation is interpreted in terms of the analysis of the distribution of the aberrations in the cells. In logarithmic coordinates, RBE/absorbed dose relationships for the two criteria are almost linear with a slope close to - 1/2. RBE values observed for induction of chromosome aberrations in Allium cepa are higher than those generally observed for biological effects related to mammalian cell lethality. (orig.)

  5. RBE/dose relationship for neutrons produced by 50MeV deuterons determined by chromosome aberrations in Allium cepa

    International Nuclear Information System (INIS)

    RBE of neutrons produced at ''CYCLONE'' (Louvain-la-Neuve) was investigated for chromosome aberrations in onion roots (Allium Cepa). In experimental conditions, it was observed that the best criteria for evaluation of RBE were: criterion 1: the % of cells in anaphase or telophase showing at least one aberration or; criterion 2: the average number of aberrations per cell in anaphase or telophase. Five independent experiments were performed. For the first criterion, following RBE values were obtained as a function of the (neutron) absorbed dose; RBE=11, 8, 7 and 6.5 for 10, 20, 30 and 40 rad (neutron absorbed dose) respectively. RBE values obtained for the second criteria were somewhat higher: RBE=12, 10, 8 and 7 for 10, 20, 30 and 40 rad (neutron absorbed dose) respectively. When plotted in a logarithmic scale as a function of the neutron absorbed dose, RBE values obtained for the two criteria are situated on two rather parallel straight lines with a slope slightly less than -1/2

  6. Starvation effects on pathogenic Vibrio alginolyticus in natural seawater

    Institute of Scientific and Technical Information of China (English)

    YI Jiabo; CHEN Qiang; ZOU Wenzheng; YAN Qingpi; ZHUANG Zhixia; WANG Xiaoru

    2008-01-01

    To get a better understanding of the starvation survival strategy of pathogenic Vibrio alginolyticus,log-phase cells were inoculated into sterile natural seawater for starvation studies.The results showed that all of total bacteria number,viable bacteria number and CFU number of V. alginolyticus increased remarkably at the initial starvation stage;after reaching their peaks at 5 d,both total bacteria number and viable bacteria number of V. alginolyricus fell slowly,while the CFU number fell more quickly after reaching its peak at 10 d;V.alginolyticus elongated their cells at the porphase of starvation,and then shrunk their volume and turned their shapes into ovals from rods at the anaphase of starvation;starved cells showed more sensitivity to heating and UV;starved cells showed n0 significant difference from unstarved ones at the lowest detection limit determined by indirect enzyme-linked immu-nosorbent assay(ELISA);starred cells'ability to adhere to the skin mucus of large yellow croaker(Pseudosciaena crocea)shorwed a sharp decline as the starvation time increases;the cellular protein of V.alginotyticus increased remarkably at the ana-phase of starvation.The results indicated that pathogenic V. alginolyticus could survive in starvation for relatively long periods of time(≥2 months)in 28℃ natural seawater due to the morphological and physiological changes;however,starved V. alginolytic-us cells showed Iess virulence and higher sensitivity under environmental stresses.

  7. Dynamic distribution of Ser-10 phosphorylated histone H3 in cytoplasm of MCF-7 and CHO cells during mitosis

    Institute of Scientific and Technical Information of China (English)

    Deng Wen LI; Qin YANG; Jia Tong CHEN; Hao ZHOU; Ru Ming LIU; Xi Tai HUANG

    2005-01-01

    The dynamic distribution of phosphorylated Histone H3 on Ser10 (phospho-H3) in cells was investigated to determine its function during mitosis. Human breast adenocarcinoma cells MCF-7, and Chinese hamster cells CHO were analyzed by indirect immunofluorescence staining with an antibody against phospho-H3. We found that the phosphorylation begins at early prophase, and spreads throughout the chromosomes at late prophase. At metaphase, most of the phosphoH3 aggregates at the end of the condensed entity of chromosomes at equatorial plate. During anaphase and telophase,the fluorescent signal of phospho-H3 is detached from chromosomes into cytoplasm. At early anaphase, phospho-H3shows ladder bands between two sets of separated chromosome, and forms "sandwich-like structure" when the chromosomes condensed. With the cleavage progressing, the "ladders" of the histone contract into a bigger bright dot. Then the histone aggregates and some of compacted microtubules in the midbody region are composed into a "bar-like"complex to separate daughter cells. The daughter cells seal their plasma membrane along with the ends of the "bar",inside which locates microtubules and modified histones, to finish the cytokinesis and keep the "bar complex" out of the cells. The specific distribution and kinetics of phospho-H3 in cytoplasm suggest that the modified histones may take part in the formation of midbody and play a crucial role in cytokinesis.

  8. Genotoxicity and mutagenicity of water contaminated with tannery effluents, as evaluated by the micronucleus test and comet assay using the fish Oreochromis niloticus and chromosome aberrations in onion root-tips

    Directory of Open Access Journals (Sweden)

    Silvia Tamie Matsumoto

    2006-01-01

    Full Text Available Cytotoxicity of metals is important because some metals are potential mutagens able to induce tumors in humans and experimental animals. Chromium can damage DNA in several ways, including DNA double strand breaks (DSBs which generate chromosomal aberrations, micronucleus formation, sister chromatid exchange, formation of DNA adducts and alterations in DNA replication and transcription. In our study, water samples from three sites in the Córrego dos Bagres stream in the Franca municipality of the Brazilian state of São Paulo were subjected to the comet assay and micronucleus test using erythrocytes from the fish Oreochromis niloticus. Nuclear abnormalities of the erythrocytes included blebbed, notched and lobed nuclei, probably due to genotoxic chromium compounds. The greatest comet assay damage occurred with water from a chromium-containing tannery effluent discharge site, supporting the hypothesis that chromium residues can be genotoxic. The mutagenicity of the water samples was assessed using the onion root-tip cell assay, the most frequent chromosomal abnormalities observed being: c-metaphases, stick chromosome, chromosome breaks and losses, bridged anaphases, multipolar anaphases, and micronucleated and binucleated cells. Onion root-tip cell mutagenicity was highest for water samples containing the highest levels of chromium.

  9. Motile properties of the bi-directional kinesin-5 Cin8 are affected by phosphorylation in its motor domain

    Science.gov (United States)

    Shapira, Ofer; Gheber, Larisa

    2016-01-01

    The Saccharomyces cerevisiae kinesin-5 Cin8 performs essential mitotic functions in spindle assembly and anaphase B spindle elongation. Recent work has shown that Cin8 is a bi-directional motor which moves towards the minus-end of microtubules (MTs) under high ionic strength (IS) conditions and changes directionality in low IS conditions and when bound between anti-parallel microtubules. Previous work from our laboratory has also indicated that Cin8 is differentially phosphorylated during late anaphase at cyclin-dependent kinase 1 (Cdk1)-specific sites located in its motor domain. In vivo, such phosphorylation causes Cin8 detachment from spindles and reduces the spindle elongation rate, while maintaining proper spindle morphology. To study the effect of phosphorylation on Cin8 motor function, we examined in vitro motile properties of wild type Cin8, as well as its phosphorylation using phospho-deficient and phospho-mimic variants, in a single molecule fluorescence motility assay. Analysis was performed on whole cell extracts and on purified Cin8 samples. We found that addition of negative charges in the phospho-mimic mutant weakened the MT-motor interaction, increased motor velocity and promoted minus-end-directed motility. These results indicate that phosphorylation in the catalytic domain of Cin8 regulates its motor function. PMID:27216310

  10. Relocalization of human chromatin remodeling cofactor TIP48 in mitosis

    International Nuclear Information System (INIS)

    TIP48 is a highly conserved eukaryotic AAA+ protein which is an essential cofactor for several complexes involved in chromatin acetylation and remodeling, transcriptional and developmental regulation and nucleolar organization and trafficking. We show that TIP48 abundance in HeLa cells did not change during the cell cycle, nor did its distribution in various biochemical fractions. However, we observed distinct changes in the subcellular localization of TIP48 during M phase using immunofluorescence microscopy. Our studies demonstrate that in interphase cells TIP48 was found mainly in the nucleus and exhibited a distinct localization in the nuclear periphery. As the cells entered mitosis, TIP48 was excluded from the condensing chromosomes but showed association with the mitotic apparatus. During anaphase, some TIP48 was detected in the centrosome colocalizing with tubulin but the strongest staining appeared in the mitotic equator associated with the midzone central spindle. Accumulation of TIP48 in the midzone and the midbody was observed in late telophase and cytokinesis. This redeployment of TIP48 during anaphase and cytokinesis was independent of microtubule assembly. The relocation of endogenous TIP48 to the midzone/midbody under physiological conditions suggests a novel and distinct function for TIP48 in mitosis and possible involvement in the exit of mitosis

  11. A family of snail-related zinc finger proteins regulates two distinct and parallel mechanisms that mediate Drosophila neuroblast asymmetric divisions.

    Science.gov (United States)

    Cai, Y; Chia, W; Yang, X

    2001-04-01

    Three snail family genes snail, escargot and worniu, encode related zinc finger transcription factors that mediate Drosophila central nervous system (CNS) development. We show that simultaneous removal of all three genes causes defective neuroblast asymmetric divisions; inscuteable transcription/translation is delayed/suppressed in the segmented CNS. Further more, defects in localization of cell fate determinants and orientation of the mitotic spindle in dividing neuroblasts are much stronger than those associated with inscuteable loss of function. In inscuteable neuroblasts, cell fate determinants are mislocalized during prophase and metaphase, yet during anaphase and telophase the great majority of mutant neuroblasts localize these determinants as cortical crescents overlying one of the spindle poles. This phenomenon, known as 'telophase rescue', does not occur in the absence of the snail family genes; moreover, in contrast to inscuteable mutants, mitotic spindle orientation is completely randomized. Our data provide further evidence for the existence of two distinct asymmetry-controlling mechanisms in neuroblasts both of which require snail family gene function: an inscuteable-dependent mechanism that functions throughout mitosis and an inscuteable-independent mechanism that acts during anaphase/telophase. PMID:11285234

  12. CENP-A exceeds microtubule attachment sites in centromere clusters of both budding and fission yeast.

    Science.gov (United States)

    Coffman, Valerie C; Wu, Pengcheng; Parthun, Mark R; Wu, Jian-Qiu

    2011-11-14

    The stoichiometries of kinetochores and their constituent proteins in yeast and vertebrate cells were determined using the histone H3 variant CENP-A, known as Cse4 in budding yeast, as a counting standard. One Cse4-containing nucleosome exists in the centromere (CEN) of each chromosome, so it has been assumed that each anaphase CEN/kinetochore cluster contains 32 Cse4 molecules. We report that anaphase CEN clusters instead contained approximately fourfold more Cse4 in Saccharomyces cerevisiae and ~40-fold more CENP-A (Cnp1) in Schizosaccharomyces pombe than predicted. These results suggest that the number of CENP-A molecules exceeds the number of kinetochore-microtubule (MT) attachment sites on each chromosome and that CENP-A is not the sole determinant of kinetochore assembly sites in either yeast. In addition, we show that fission yeast has enough Dam1-DASH complex for ring formation around attached MTs. The results of this study suggest the need for significant revision of existing CEN/kinetochore architectural models. PMID:22084306

  13. The temporal and spatial pattern of histone H3 phosphorylation at serine 28 and serine 10 is similar in plants but differs between mono- and polycentric chromosomes.

    Science.gov (United States)

    Gernand, D; Demidov, D; Houben, A

    2003-01-01

    Immunolabeling using site-specific antibodies against phosphorylated histone H3 at serine 10 or serine 28 revealed in plants an almost similar temporal and spatial pattern of both post-translational modification sites at mitosis and meiosis. During the first meiotic division the entire chromosomes are highly H3 phosphorylated. In the second meiotic division, like in mitosis, the chromosomes contain high phosphorylation levels in the pericentromeric region and very little H3 phosphorylation along the arms of monocentric species. In the polycentric plant Luzula luzuloides phosphorylation at both serine positions occurs along the whole chromosomes, whereas in monocentric species, only the pericentromeric regions showed strong signals from mitotic prophase to telophase. No phosphorylated serine 10 or serine 28 was detectable on single chromatids at anaphase II resulting from equational segregation of rye B chromosome univalents during the preceding anaphase I. In addition, we found a high level of serine 28 as well as of serine 10 phosphorylation along the entire mitotic monocentric chromosomes after treatment of mitotic cells using the phosphatase inhibitor cantharidin. These observations suggest that histone H3 phosphorylation at serine 10 and 28 is an evolutionarily conserved event and both sites are likely to be involved in the same process, such as sister chromatid cohesion. PMID:14610360

  14. [Cytogenetic investigations of bone marrow cells from mice exposed onboard biosatellite "Bion-M1"].

    Science.gov (United States)

    Dorozhkina, O V; Ivanov, A A

    2015-01-01

    The results of studying the mitotic activities and chromosomal aberrations in bone marrow cells from C57/BL6N mice with the help of the anaphase technique in 12 hours after completion of the 30-day "Bion-M1" mission and ground-based experiment using flight equipment are presented. A statistically reliable decline of the mitotic activity (0.74%) was found in cells taken from the space flown animals. In the ground-based experiment, a statistically reliable downward trend in proliferative activity (1.37%) was revealed after the comparison with groups of vivarium control (1.46-1.53%). In both experiments mice increased the number of initial mitotic phases (prophase + metaphase) relative to the sum of anaphases and telophases. The number of aberrant mitoses grew reliably in the group of flight animals by 29.7%, whereas in the ground-based experiment an upward trend was insignificant as their number increased up to 2.3% only. In the vivarium controls aberrant mitoses constituted 1.75-1.8%. An increase in chromosomal aberrations was largely due to such abnormalities as fragments. These findings seem to have been a result of summation of the effects of radiation and other stressful factors in space flight. PMID:25958465

  15. The significance of cytogenetics for the study of karyotype evolution and taxonomy of water bugs (Heteroptera, Belostomatidae) native to Argentina

    Science.gov (United States)

    Gabriela, Chirino Mónica; Papeschi, Alba Graciela; Bressa, María José

    2013-01-01

    Abstract Male meiosis behaviour and heterochromatin characterization of three big water bug species were studied. Belostoma dentatum (Mayr, 1863), Belostoma elongatum Montandon, 1908 and Belostoma gestroi Montandon, 1903 possess 2n = 26 + X1X2Y (male). In these species, male meiosis is similar to that previously observed in Belostoma Latreille, 1807. In general, autosomal bivalents show a single chiasma terminally located and divide reductionally at anaphase I. On the other hand, sex chromosomes are achiasmatic, behave as univalents and segregate their chromatids equationally at anaphase I. The analysis of heterochromatin distribution and composition revealed a C-positive block at the terminal region of all autosomes in Belostoma dentatum, a C-positive block at the terminal region and C-positive interstitial dots on all autosomes in Belostoma elongatum, and a little C-positive band at the terminal region of autosomes in Belostoma gestroi. A C-positive band on one bivalent was DAPI negative/CMA3 positive in the three species. The CMA3-bright band, enriched in GC base pairs, was coincident with a NOR detected by FISH. The results obtained support the hypothesis that all species of Belostoma with multiple sex chromosome systems preserve NORs in autosomal bivalents. The karyotype analyses allow the cytogenetic characterization and identification of these species belonging to a difficult taxonomic group. Besides, the cytogenetic characterization will be useful in discussions about evolutionary trends of the genome organization and karyotype evolution in this genus. PMID:24260694

  16. PTK2b function during fertilization of the mouse oocyte

    International Nuclear Information System (INIS)

    Highlights: • PTK2b is expressed in oocytes and is activated following fertilization. • PTK2b suppression in oocytes prevents fertilization, but not parthenogenetic activation. • PTK2b suppression prevents the oocyte from fusing with or incorporating bound sperm. • PTK2b suppressed oocytes that fail to fertilize do not exhibit calcium oscillations. - Abstract: Fertilization triggers rapid changes in intracellular free calcium that serve to activate multiple signaling events critical to the initiation of successful development. Among the pathways downstream of the fertilization-induced calcium transient is the calcium-calmodulin dependent protein tyrosine kinase PTK2b or PYK2 kinase. PTK2b plays an important role in fertilization of the zebrafish oocyte and the objective of the present study was to establish whether PTK2b also functions in mammalian fertilization. PTK2b was activated during the first few hours after fertilization of the mouse oocyte during the period when anaphase resumption was underway and prior to the pronuclear stage. Suppression of PTK2b kinase activity in oocytes blocked sperm incorporation and egg activation although sperm-oocyte binding was not affected. Oocytes that failed to incorporate sperm after inhibitor treatment showed no evidence of a calcium transient and no evidence of anaphase resumption suggesting that egg activation did not occur. The results indicate that PTK2b functions during the sperm-egg fusion process or during the physical incorporation of sperm into the egg cytoplasm and is therefore critical for successful development

  17. In silico analysis of deleterious single nucleotide polymorphisms in human BUB1 mitotic checkpoint serine/threonine kinase B gene.

    Science.gov (United States)

    Akhoundi, Fatemeh; Parvaneh, Nikpour; Modjtaba, Emadi-Baygi

    2016-09-01

    One of the major challenges in the analysis of human genetic variation is to distinguish mutations that are functionally neutral from those that contribute to disease. BubR1 is a key protein mediating spindle-checkpoint activation that plays a role in the inhibition of the anaphase-promoting complex/cyclosome (APC/C), delaying the onset of anaphase and ensuring proper chromosome segregation. Owing to the importance of BUB1B gene in mitotic checkpoint a functional analysis using different in silico approaches was undertaken to explore the possible associations between genetic mutations and phenotypic variation. In this work we found that 3 nsSNPs I82N, P334L and R814H have a functional effect on protein function and stability. A literature search revealed that R814H was already implicated in human diseases. Additionally, 2 SNPs in the 5' UTR region was predicted to exhibit a pattern change in the internal ribosome entry site (IRES), and eight MicroRNA binding sites were found to be highly affected due to 3' UTR SNPs. These in silico predictions will provide useful information in selecting the target SNPs that are likely to have functional impact on the BUB1B gene. PMID:27331020

  18. The Ku70 DNA-repair protein is involved in centromere function in a grasshopper species.

    Science.gov (United States)

    Cabrero, Josefa; Bakkali, Mohammed; Navarro-Domínguez, Beatriz; Ruíz-Ruano, Francisco J; Martín-Blázquez, Rubén; López-León, María Dolores; Camacho, Juan Pedro M

    2013-06-25

    The Ku70 protein is involved in numerous cell functions, the nonhomologous end joining (NHEJ) DNA repair pathway being the best known. Here, we report a novel function for this protein in the grasshopper Eyprepocnemis plorans. We observed the presence of large Ku70 foci on the centromeres of meiotic and mitotic chromosomes during the cell cycle stages showing the highest centromeric activity (i.e., metaphase and anaphase). The fact that colchicine treatment prevented centromeric location of Ku70, suggests a microtubule-dependent centromeric function for Ku70. Likewise, the absence of Ku70 at metaphase-anaphase centromeres from three males whose Ku70 gene had been knocked down using interference RNA, and the dramatic increase in the frequency of polyploid spermatids observed in these males, suggest that the centromeric presence of Ku70 is required for normal cytokinesis in this species. The centromeric function of Ku70 was not observed in 14 other grasshopper and locust species, or in the mouse, thus suggesting that it is an autapomorphy in E. plorans. PMID:23797468

  19. The BTG4 and CAF1 complex prevents the spontaneous activation of eggs by deadenylating maternal mRNAs.

    Science.gov (United States)

    Pasternak, Michał; Pfender, Sybille; Santhanam, Balaji; Schuh, Melina

    2016-09-01

    Once every menstrual cycle, eggs are ovulated into the oviduct where they await fertilization. The ovulated eggs are arrested in metaphase of the second meiotic division, and only complete meiosis upon fertilization. It is crucial that the maintenance of metaphase arrest is tightly controlled, because the spontaneous activation of the egg would preclude the development of a viable embryo (Zhang et al. 2015 J. Genet. Genomics 42, 477-485. (doi:10.1016/j.jgg.2015.07.004); Combelles et al. 2011 Hum. Reprod. 26, 545-552. (doi:10.1093/humrep/deq363); Escrich et al. 2011 J. Assist. Reprod. Genet. 28, 111-117. (doi:10.1007/s10815-010-9493-5)). However, the mechanisms that control the meiotic arrest in mammalian eggs are only poorly understood. Here, we report that a complex of BTG4 and CAF1 safeguards metaphase II arrest in mammalian eggs by deadenylating maternal mRNAs. As a follow-up of our recent high content RNAi screen for meiotic genes (Pfender et al. 2015 Nature 524, 239-242. (doi:10.1038/nature14568)), we identified Btg4 as an essential regulator of metaphase II arrest. Btg4-depleted eggs progress into anaphase II spontaneously before fertilization. BTG4 prevents the progression into anaphase by ensuring that the anaphase-promoting complex/cyclosome (APC/C) is completely inhibited during the arrest. The inhibition of the APC/C relies on EMI2 (Tang et al. 2010 Mol. Biol. Cell 21, 2589-2597. (doi:10.1091/mbc.E09-08-0708); Ohe et al. 2010 Mol. Biol. Cell 21, 905-913. (doi:10.1091/mbc.E09-11-0974)), whose expression is perturbed in the absence of BTG4. BTG4 controls protein expression during metaphase II arrest by forming a complex with the CAF1 deadenylase and we hypothesize that this complex is recruited to the mRNA via interactions between BTG4 and poly(A)-binding proteins. The BTG4-CAF1 complex drives the shortening of the poly(A) tails of a large number of transcripts at the MI-MII transition, and this wave of deadenylation is essential for the arrest in

  20. Quantitative imaging of subcellular calcium stores in mammalian LLC-PK1 epithelial cells undergoing mitosis by SIMS ion microscopy.

    Science.gov (United States)

    Chandra, Subhash

    2005-09-01

    Quantitative 3-D total calcium gradients, representing subcellular stored calcium, were imaged with a CAMECA IMS-3f SIMS ion microscope in cryogenically prepared frozen freeze-dried LLC-PK1 cells captured in interphase and various stages of mitosis. 39K and 23Na concentrations were also measured in the same cells. Correlative optical (or SEM) and SIMS analysis of cells revealed a redistribution of the interphase Golgi calcium store in prophase and prometaphase cells. In metaphase cells, simultaneous SIMS imaging of total calcium in both the spindle and the non-spindle cytoplasm of individual cells revealed a gradual and dynamic alignment of calcium stores in both half-spindles prior to the onset of anaphase. The anaphase cells revealed the highest local total calcium concentrations in the spindle regions behind the daughter chromosomes and the lowest in the central spindle region. The pericentriolar material in telophase cells contained calcium stores. Quantitatively, a typical metaphase cell with well-aligned calcium stores in the spindle region contained 1.1 mM total calcium in each half-spindle, 0.8 mM total calcium in the non-spindle cytoplasm, and 0.5mM total calcium in the chromosomes. At the submicron scale, the distribution of total calcium was heterogeneous in the chromosomes, metaphase spindle, and non-spindle cytoplasm. An increased binding of calcium to chromosomes is not a physiological requirement for chromosomal condensation in mitosis, since interphase nuclei and mitotic chromosomes contained comparable total calcium concentrations measured per unit volume. A significant reduction of total calcium in the non-spindle cytoplasm was observed in the metaphase, anaphase, and telophase cells, which is indicative of the limited storage of the releasable calcium pool in these specific stages of mitosis. Direct total calcium measurements in subcellular regions confirmed that both the spindle and the non-spindle cytoplasm of metaphase cells contained inositol

  1. Shugoshin prevents dissociation of cohesin from centromeres during mitosis in vertebrate cells.

    Directory of Open Access Journals (Sweden)

    Barry E McGuinness

    2005-03-01

    Full Text Available Cohesion between sister chromatids is essential for their bi-orientation on mitotic spindles. It is mediated by a multisubunit complex called cohesin. In yeast, proteolytic cleavage of cohesin's alpha kleisin subunit at the onset of anaphase removes cohesin from both centromeres and chromosome arms and thus triggers sister chromatid separation. In animal cells, most cohesin is removed from chromosome arms during prophase via a separase-independent pathway involving phosphorylation of its Scc3-SA1/2 subunits. Cohesin at centromeres is refractory to this process and persists until metaphase, whereupon its alpha kleisin subunit is cleaved by separase, which is thought to trigger anaphase. What protects centromeric cohesin from the prophase pathway? Potential candidates are proteins, known as shugoshins, that are homologous to Drosophila MEI-S332 and yeast Sgo1 proteins, which prevent removal of meiotic cohesin complexes from centromeres at the first meiotic division. A vertebrate shugoshin-like protein associates with centromeres during prophase and disappears at the onset of anaphase. Its depletion by RNA interference causes HeLa cells to arrest in mitosis. Most chromosomes bi-orient on a metaphase plate, but precocious loss of centromeric cohesin from chromosomes is accompanied by loss of all sister chromatid cohesion, the departure of individual chromatids from the metaphase plate, and a permanent cell cycle arrest, presumably due to activation of the spindle checkpoint. Remarkably, expression of a version of Scc3-SA2 whose mitotic phosphorylation sites have been mutated to alanine alleviates the precocious loss of sister chromatid cohesion and the mitotic arrest of cells lacking shugoshin. These data suggest that shugoshin prevents phosphorylation of cohesin's Scc3-SA2 subunit at centromeres during mitosis. This ensures that cohesin persists at centromeres until activation of separase causes cleavage of its alpha kleisin subunit. Centromeric

  2. Dicty_cDB: Contig-U15249-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available xisomal targeting signal 2 receptor; ... 60 3e-07 ( P69103 ) RecName: Full=Guanine nucleotide-binding protein...281_1( AB089281 |pid:none) Mamestra brassicae mRNA for recept... 60 4e-07 ( P36408 ) RecName: Full=Guanine nucleotide-binding pro...peat-containing protein 38; &AK0072... 69 6e-10 AY737531_1( AY737531 |pid:none) Toxoptera citricida putati...-containing protein srw1; AltNam... 342 3e-92 (Q54MZ3) RecName: Full=Anaphase-promoting ...ne ZM... 286 2e-75 ( P78972 ) RecName: Full=WD repeat-containing protein slp1; &AL12... 286 3e-75 CU633438_4

  3. An Overview of Alternating Electric Fields Therapy (NovoTTF Therapy) for the Treatment of Malignant Glioma.

    Science.gov (United States)

    Swanson, Kenneth D; Lok, Edwin; Wong, Eric T

    2016-01-01

    As with many cancer treatments, tumor treating fields (TTFields) target rapidly dividing tumor cells. During mitosis, TTFields-exposed cells exhibit uncontrolled membrane blebbing at the onset of anaphase, resulting in aberrant mitotic exit. Based on these criteria, at least two protein complexes have been proposed as TTFields' molecular targets, including α/β-tubulin and the septin 2, 6, 7 heterotrimer. After aberrant mitotic exit, cells exhibited abnormal nuclei and signs of cellular stress, including decreased cellular proliferation and p53 dependence, and exhibit the hallmarks of immunogenic cell death, suggesting that TTFields treatment may induce an antitumor immune response. Clinical trials lead to Food and Drug Administration approval for their treatment of recurrent glioblastoma. Detailed modeling of TTFields within the brain suggests that the location of the tumor may affect treatment efficacy. These observations have a profound impact on the use of TTFields in the clinic, including what co-therapies may be best applied to boost its efficacy. PMID:26739692

  4. Traits and meiosis in mutant of impatiens balsamina induced by space treatment

    International Nuclear Information System (INIS)

    A mutant of Impatiens balsamina was obtained after space induction, and its traits and meiosis were investigated. Characters such as color and form of the mutant expressed great variation. Observation of meiosis showed that most of pollen mother cells were normal in meiosis phase I, except the disproportion of chromosomal segregation, lagging chromosome and dispersal chromosome in anaphase I. Most pollen mother cells developed into microspores tetrad after meiosis, but paraspores also appeared. The number of chromosome in microspore varied from 1 to 21, even more than 30. The shape and size of the microspores fluctuated apparently, and the size of the microspores was in positive correlation to chromosome number. When staining with iodic solution, most of the pollens showed sterility, which was in consistence with the low setting percentage of the mutant plant. It was thought that space induction caused the variation of size, fertility and the abnormal meiosis

  5. Autoradoigraphic study of 3H colchicine binding in synchronously dividing cells of antheridial filaments of Chara vulgaris L. during successive stages of development

    International Nuclear Information System (INIS)

    The intensity of 3H colchicine binding was investigated autoradiographically as a marker of an amount of the microtubule subunits during interphase and mitosis in synchronously dividing 4-, 8-, 16- and 32-celled antheridial filaments of Chara vulgaris. These cells were incubated with 3H colchicine in vivo or after fixation. The radioactivity of cells in the successive generations of antheridial filaments diminishes, similarly as the surface of cytoplasm and intensity of protein synthesis. During interphase the intensity of 3H colchicine binding is proportional to the increase of cytoplasmic surface. During mitosis the increase of radioactivity continues in prophase; the highest radioactivity was found in prophase and telophase cells, the lowest in anaphase cells; a comparatively pronounced radioactivity is visible in metaphase. Radioactivity in posttelophase, as estimated per one daughter cell, is approximately one half of that of the mother cells in telophase of the previous generation suggesting the reutilization of microtubule proteins in the next mitotic cycle. (author)

  6. Back to the roots: segregation of univalent sex chromosomes in meiosis.

    Science.gov (United States)

    Fabig, Gunar; Müller-Reichert, Thomas; Paliulis, Leocadia V

    2016-06-01

    In males of many taxa, univalent sex chromosomes normally segregate during the first meiotic division, and analysis of sex chromosome segregation was foundational for the chromosome theory of inheritance. Correct segregation of single or multiple univalent sex chromosomes occurs in a cellular environment where every other chromosome is a bivalent that is being partitioned into homologous chromosomes at anaphase I. The mechanics of univalent chromosome segregation vary among animal taxa. In some, univalents establish syntelic attachment of sister kinetochores to the spindle. In others, amphitelic attachment is established. Here, we review how this problem of segregation of unpaired chromosomes is solved in different animal systems. In addition, we give a short outlook of how mechanistic insights into this process could be gained by explicitly studying model organisms, such as Caenorhabditis elegans. PMID:26511278

  7. The effect of ionizing radiations on the genetic variability of hop (Humulus lupulus L.)

    International Nuclear Information System (INIS)

    The microlayers fashioned at two eyes were subjected to gamma rays treatment (Co60), in doses of 0,5-4,0 Kr. Observations and determinations were performed in order to render the phenotypical mutations in M1, their morphological variability and the chromosomal aberrations occurring in Mitosis. A specific, depression reaction on hop genotypes was observed, that might be taken into account for the breeding of the lowsized plants. The rise of the variability coefficient makes evident the genetic effects of the mutagenic factors as well as the possibility to fix by a vegetative way some favourable. At the cellular level, an increase of the frequency of the cells with chromosomal aberrations in anaphase was noticed, directly proportional to the radiation dosis

  8. Radiation-induced chromosome breakages in bread wheat (Triticum aestivum L.)

    International Nuclear Information System (INIS)

    Meiosis and pollen fertility were studied in the M2 generation in four varieties of hexaploid wheat. Meiosis was characterized by the formation of interchange configurations, such as rings and chains of four chromosomes in several cells. Chromosomal aberrations showed linear relationship with gamma irradiation; 45 kR dose induced the highest chromosomal abnormalities. Most multivalents were interchange rings of four chromosomes. Translocations involving two pairs of homologous or nonhomologous chromosomes seemed to be higher in frequency than those involving more than two pairs of chromosomes. Anaphase abnormalities, such as laggards, bridges and fragments and unequal segregation of chromosomes, were frequently observed. Pollen fertility was considerably reduced in the M2 plants arising form the treatments of higher doses of gamma rays because of the induced chromosome interchanges. (author)

  9. Aurora A's functions during mitotic exit: the Guess Who game

    Directory of Open Access Journals (Sweden)

    David eReboutier

    2015-12-01

    Full Text Available Until recently, the knowledge of Aurora A kinase functions during mitosis was limited to pre-metaphase events, particularly centrosome maturation, G2/M transition, and mitotic spindle assembly. However, an involvement of Aurora A in post-metaphase events was also suspected, but not clearly demonstrated due to the technical difficulty to perform the appropriate experiments. Recent developments of both an analog specific version of Aurora A, and of small molecule inhibitors have led to the first demonstration that Aurora A is required for the early steps of cytokinesis. As in pre-metaphase, Aurora A plays diverse functions during anaphase, essentially participating in astral microtubules dynamics and central spindle assembly and functioning. The present review describes the experimental systems used to decipher new functions of Aurora A during late mitosis and situate these functions into the context of cytokinesis mechanisms.

  10. Research on Modified Shifting Balance Genetic Algorithms

    Institute of Scientific and Technical Information of China (English)

    MA Hong-mei; GONG Dun-wei

    2007-01-01

    The increasing overlap of core and colony populations during the anaphase of evolution may limit the performance of shifting balance genetic algorithms. To decrease such overlapping, so as to increase the local search capability of the core population, the sub-space method was used to generate uniformly distributed initial colony populations over the decision variable space. The core population was also dynamically divided, making simultaneous searching in several local spaces possible. The algorithm proposed in this paper was compared to the original one by searching for the optimum of a complicated multi-modal function. The results indicate that the solutions obtained by the modified algorithm are better than those of the original algorithm.

  11. [CdCl2-induced morphogenetic variation of Triticum aestivum cultivars].

    Science.gov (United States)

    Chunetova, Zh Zh; Omirbekova, N Zh; Shulembaeva, K K

    2008-11-01

    The effect cadmium chloride on released local cultivars of soft spring wheat (Triticum aestivum) has been studied under laboratory and field conditions in order to widen the variation spectrum of this plant. It has been found that treatment of grains with a 0.01% aqueous solution of CdCl2 induces the appearance of tall, strong plants with productive bushiness in the M1 generation that are characterized by various morphological changes: elongated ears, scales, and grains; increased number of grains per ear and mass of 1000 grains; anthocyan pigmentation of the stem and leaf axil; etc. Study of meiosis showed chromosome aggregation, displacement of the mitotic spindle of the metaphase plate, and empty (sterile) cells in anaphases (AI and AII). The altered characters of M1 plants are preserved in the M2-M4 generations. PMID:19137733

  12. Mislocalization of the Drosophila centromere-specific histone CIDpromotes formation of functional ectopic kinetochores

    Energy Technology Data Exchange (ETDEWEB)

    Heun, Patrick; Erhardt, Sylvia; Blower, Michael D.; Weiss,Samara; Skora, Andrew D.; Karpen, Gary H.

    2006-01-30

    The centromere-specific histone variant CENP-A (CID in Drosophila) is a structural and functional foundation for kinetochore formation and chromosome segregation. Here, we show that overexpressed CID is mislocalized into normally non-centromeric regions in Drosophila tissue culture cells and animals. Analysis of mitoses in living and fixed cells reveals that mitotic delays, anaphase bridges, chromosome fragmentation, and cell and organismal lethality are all direct consequences of CID mislocalization. In addition, proteins that are normally restricted to endogenous kinetochores assemble at a subset of ectopic CID incorporation regions. The presence of microtubule motors and binding proteins, spindle attachments, and aberrant chromosome morphologies demonstrate that these ectopic kinetochores are functional. We conclude that CID mislocalization promotes formation of ectopic centromeres and multicentric chromosomes, which causes chromosome missegregation, aneuploidy, and growth defects. Thus, CENP-A mislocalization is one possible mechanism for genome instability during cancer progression, as well as centromere plasticity during evolution.

  13. Chromosome numbers, meiotic behavior and pollen fertility in a collection of Paspalum nicorae Parodi accessions

    Directory of Open Access Journals (Sweden)

    Camila Aparecida de Oliveira dos Reis

    2008-01-01

    Full Text Available Chromosome number, meiotic behavior and pollen viability were evaluated in a collection of 53 Paspalumnicorae Parodi accessions, which are part of a breeding project of the species. All accessions are tetraploid, with 2n=4x=40.Despite the invariable chromosome numbers, there was variation among accessions in the frequencies of different chromosomeconfigurations at diakinesis and metaphase I, such as univalents, trivalents and quadrivalents. Other abnormalities asbridges and laggards were also observed at anaphase and telophase I. Meiotic indexes ranged from 82.00 to 99.50% andpollen viability from 88.99 to 95.06%. As the species is pseudogamous apomictic, fertile pollen is necessary for endospermformation. Results show that all plants are meiotically stable and have enough fertile pollen to be used as male parents incontrolled crosses.

  14. Cytogenetic evidence for genome elimination during microsporogenesis in interspecific hybrid between Brachiaria ruziziensis and B. brizantha (Poaceae

    Directory of Open Access Journals (Sweden)

    Andréa Beatriz Mendes-Bonato

    2006-01-01

    Full Text Available Microsporogenesis was analyzed in an interspecific hybrid between an artificially tetraploidized sexual accession of Brachiaria ruziziensis (R genome and a natural apomictic tetraploid accession of B. brizantha (B genome. Chromosomes associated predominantly as bivalents. From this phase to the end of meiosis, chromosomes presented irregular segregation and abnormal arrangement in the metaphase plate. During metaphase I, in 27.8% of meiocytes, bivalents were distributed in two metaphase plates. In anaphase I, two distinct and typical bipolar spindles were formed. In 29.7% of pollen mother cells, one genome did not divide synchronically, with chromosomes lagging behind or not segregating at all. The second division was very irregular, resulting in polyads. Based on previous results from analysis of a triploid hybrid between these species, where the R genome was eliminated by asynchrony during meiosis, it is suggested that the laggard genome in this hybrid also belongs to B. ruziziensis.

  15. The equatorial position of the metaphase plate ensures symmetric cell divisions.

    Science.gov (United States)

    Tan, Chia Huei; Gasic, Ivana; Huber-Reggi, Sabina P; Dudka, Damian; Barisic, Marin; Maiato, Helder; Meraldi, Patrick

    2015-01-01

    Chromosome alignment in the middle of the bipolar spindle is a hallmark of metazoan cell divisions. When we offset the metaphase plate position by creating an asymmetric centriole distribution on each pole, we find that metaphase plates relocate to the middle of the spindle before anaphase. The spindle assembly checkpoint enables this centering mechanism by providing cells enough time to correct metaphase plate position. The checkpoint responds to unstable kinetochore-microtubule attachments resulting from an imbalance in microtubule stability between the two half-spindles in cells with an asymmetric centriole distribution. Inactivation of the checkpoint prior to metaphase plate centering leads to asymmetric cell divisions and daughter cells of unequal size; in contrast, if the checkpoint is inactivated after the metaphase plate has centered its position, symmetric cell divisions ensue. This indicates that the equatorial position of the metaphase plate is essential for symmetric cell divisions. PMID:26188083

  16. Aurora A's Functions During Mitotic Exit: The Guess Who Game.

    Science.gov (United States)

    Reboutier, David; Benaud, Christelle; Prigent, Claude

    2015-01-01

    Until recently, the knowledge of Aurora A kinase functions during mitosis was limited to pre-metaphase events, particularly centrosome maturation, G2/M transition, and mitotic spindle assembly. However, an involvement of Aurora A in post-metaphase events was also suspected, but not clearly demonstrated due to the technical difficulty to perform the appropriate experiments. Recent developments of both an analog-specific version of Aurora A and small molecule inhibitors have led to the first demonstration that Aurora A is required for the early steps of cytokinesis. As in pre-metaphase, Aurora A plays diverse functions during anaphase, essentially participating in astral microtubules dynamics and central spindle assembly and functioning. The present review describes the experimental systems used to decipher new functions of Aurora A during late mitosis and situate these functions into the context of cytokinesis mechanisms. PMID:26734572

  17. Role and regulation of kinesin-8 motors through the cell cycle.

    Science.gov (United States)

    Messin, Liam J; Millar, Jonathan B A

    2014-09-01

    Members of the kinesin-8 motor family play a central role in controlling microtubule length throughout the eukaryotic cell cycle. Inactivation of kinesin-8 causes defects in cell polarity during interphase and astral and mitotic spindle length, metaphase chromosome alignment, timing of anaphase onset and accuracy of chromosome segregation. Although the biophysical mechanism by which kinesin-8 molecules influence microtubule dynamics has been studied extensively in a variety of species, a consensus view has yet to emerge. One reason for this might be that some members of the kinesin-8 family can associate to other microtubule-associated proteins, cell cycle regulatory proteins and other kinesin family members. In this review we consider how cell cycle specific modification and its association to other regulatory proteins may modulate the function of kinesin-8 to enable it to function as a master regulator of microtubule dynamics. PMID:25136382

  18. Cytology and mating systems in the climbing cacti Hylocereus and Selenicereus.

    Science.gov (United States)

    Lichtenzveig, J; Abbo, S; Nerd, A; Tel-Zur, N; Mizrahi, Y

    2000-07-01

    Chromosome numbers and meiotic behavior are reported for the climbing cacti species Hylocereus undatus, Hylocereus polyrhizus, and Selenicereus megalanthus. The Hylocereus spp. are diploid (2n = 22), while S. megalanthus is a tetraploid (2n = 44). Irregular chromosome disjunction at anaphase I in pollen mother cells of S. megalanthus is probably the major cause of its reduced pollen viability and may contribute to low seed set, low number of viable seeds and, consequently, low fruit mass. A pollination study confirmed self-incompatibility in H. polyrhizus and a weakened incompatibility reaction in H. undatus and S. megalanthus. Major crossability barriers do not exist between the Hylocereus spp. investigated. Reciprocal intergeneric crosses were successful between Hylocereus spp. and S. megalanthus, suggesting that an Hylocereus sp. might be one of the diploid progenitors of the tetraploid S. megalanthus. The implications of the results on cacti nomenclature and systematics are briefly discussed. PMID:10898783

  19. Monitoring genetic damage to ecosystems from hazardous waste

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, S.L.

    1992-03-01

    Applications of ecological toxicity testing to hazardous waste management have increased dramatically over the last few years, resulting in a greater awareness of the need for improved biomonitoring techniques. Our laboratory is developing advanced techniques to assess the genotoxic effects of environmental contamination on ecosystems. We have developed a novel mutagenesis assay using the nematode Caenorhabditis elegans, which is potentially applicable for multimedia studies in soil, sediment, and water. In addition, we are conducting validation studies of a previously developed anaphase aberration test that utilizes sea urchin embryos. Other related efforts include field validation studies of the new tests, evaluation of their potential ecological relevance, and analysis of their sensitivity relative to that of existing toxicity tests that assess only lethal effects, rather than genetic damage.

  20. An Overview of the Spindle Assembly Checkpoint Status in Oral Cancer

    Science.gov (United States)

    Teixeira, José Henrique; Silva, Patrícia Manuela; Reis, Rita Margarida; Moura, Inês Moranguinho; Marques, Sandra; Fonseca, Joana; Monteiro, Luís Silva; Bousbaa, Hassan

    2014-01-01

    Abnormal chromosome number, or aneuploidy, is a common feature of human solid tumors, including oral cancer. Deregulated spindle assembly checkpoint (SAC) is thought as one of the mechanisms that drive aneuploidy. In normal cells, SAC prevents anaphase onset until all chromosomes are correctly aligned at the metaphase plate thereby ensuring genomic stability. Significantly, the activity of this checkpoint is compromised in many cancers. While mutations are rather rare, many tumors show altered expression levels of SAC components. Genomic alterations such as aneuploidy indicate a high risk of oral cancer and cancer-related mortality, and the molecular basis of these alterations is largely unknown. Yet, our knowledge on the status of SAC components in oral cancer remains sparse. In this review, we address the state of our knowledge regarding the SAC defects and the underlying molecular mechanisms in oral cancer, and discuss their therapeutic relevance, focusing our analysis on the core components of SAC and its target Cdc20. PMID:24995269

  1. Cell division control by the Chromosomal Passenger Complex

    Energy Technology Data Exchange (ETDEWEB)

    Waal, Maike S. van der; Hengeveld, Rutger C.C.; Horst, Armando van der; Lens, Susanne M.A., E-mail: s.m.a.lens@umcutrecht.nl

    2012-07-15

    The Chromosomal Passenger Complex (CPC) consisting of Aurora B kinase, INCENP, Survivin and Borealin, is essential for genomic stability by controlling multiple processes during both nuclear and cytoplasmic division. In mitosis it ensures accurate segregation of the duplicated chromosomes by regulating the mitotic checkpoint, destabilizing incorrectly attached spindle microtubules and by promoting the axial shortening of chromosomal arms in anaphase. During cytokinesis the CPC most likely prevents chromosome damage by imposing an abscission delay when a chromosome bridge connects the two daughter cells. Moreover, by controlling proper cytoplasmic division, the CPC averts tetraploidization. This review describes recent insights on how the CPC is capable of conducting its various functions in the dividing cell to ensure chromosomal stability.

  2. Improved mutagen-testing systems in mice. Progress report, 1 June 1976--31 August 1977

    International Nuclear Information System (INIS)

    Results are reported from studies on the production of chromosomal inversion by chemical treatment or irradiation of sperm in mice and to detect inversions by observing high frequencies of first meiotic anaphase bridges of their sons or by using chromosomal banding techniques to detect inverted segments cytologically. For each new inversion, which is either of considerable length or which has particularly useful experimental properties, we will determine its linkage group, mark it genetically, if possible, or place it with a genetically marked homologous chromosome, and study its cytological, physiological, and anatomical effects. The inversions are being used to construct recessive lethal testing systems for estimating mutational loads in populations exposed to radiation or either proved or potential chemical mutagens, to mark and maintain induced lethals for analysis of their potential dominant effects on fitness, and to study other basic problems in mammalian genetics

  3. Mitosis and microtubule organizational changes in rice root-tip cells

    Institute of Scientific and Technical Information of China (English)

    XUSHIXIONG(SYZEE); CHUNGUILI; CHENGZHU

    1993-01-01

    The pattern of change of the microtubule cytoskeleton of the root-tip cells of rice during mitosis was studied using immunofluorescence technic and confocal laser scanning microscopy. All the major stages of ceil division including preprophase, prophase, metaphase, anaphase and telophase were observed. The most significant finding was that in the preprophase cells microtubules radiating from the nuclear surface to the cortex were frequently seen. During development these microtubules became closely associated with the preprophase band and prophase spindie indicating that the microtubules radiating from the nuclear surface, the preprophase band and the prophazc spindle were structurally and functionally closely related to each other. Granule-like anchorage sites for the radiating microtubules at the muclear surface were often seen and the possibility that these gramle-like anchorage sites might represent the microtubule organizing centres was discussed.

  4. Genotoxicity evaluation of the insecticide endosulfan in the wetland macrophyte Bidens laevis L

    Energy Technology Data Exchange (ETDEWEB)

    Perez, Debora J. [Laboratorio de Genetica, Estacion Experimental Agropecuaria Balcarce INTA - Facultad de Ciencias Agrarias - UNMdP, CC 276, 7620 Balcarce (Argentina); Laboratorio de Ecotoxicologia, Departamento de Ciencias Marinas, Facultad de Ciencias Exactas y Naturales UNMdP, Funes 3350 (7600) Mar del Plata (Argentina); Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET), Rivadavia 1917, 1033, Buenos Aires (Argentina); Menone, Mirta L. [Laboratorio de Ecotoxicologia, Departamento de Ciencias Marinas, Facultad de Ciencias Exactas y Naturales UNMdP, Funes 3350 (7600) Mar del Plata (Argentina); Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET), Rivadavia 1917, 1033, Buenos Aires (Argentina)], E-mail: lujanm@mdp.edu.ar; Camadro, Elsa L. [Laboratorio de Genetica, Estacion Experimental Agropecuaria Balcarce INTA - Facultad de Ciencias Agrarias - UNMdP, CC 276, 7620 Balcarce (Argentina); Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET), Rivadavia 1917, 1033, Buenos Aires (Argentina); Moreno, Victor J. [Laboratorio de Ecotoxicologia, Departamento de Ciencias Marinas, Facultad de Ciencias Exactas y Naturales UNMdP, Funes 3350 (7600) Mar del Plata (Argentina)

    2008-06-15

    The frequency of micronuclei (MN) and chromosome aberrations in anaphase-telophase (CAAT) was determined in root tips of the wetland macrophyte Bidens laevis exposed to environmentally relevant concentrations of endosulfan (0.01, 0.02, 0.5 and 5 {mu}g/L) for 48 h. MN frequency varied from 0 in negative controls and plants exposed to 0.01 {mu}g/L endosulfan to 0-3 in plants exposed to 5 {mu}g/L. Moreover, a significant concentration-dependent increase of CAAT was observed. The higher proportion of laggards and vagrand chromosomes observed at 5 {mu}g/L would indicate that endosulfan interacts with the spindle interrupting normal chromosome migration. Endosulfan resulted genotoxic to B. laevis, a species of potential value for bioassays and in situ monitoring of environmental contamination by pesticides. - Endosulfan causes a concentration-dependent increase of chromosome aberrations in the macrophyte Bidens laevis.

  5. Genotoxicity evaluation of the insecticide endosulfan in the wetland macrophyte Bidens laevis L

    International Nuclear Information System (INIS)

    The frequency of micronuclei (MN) and chromosome aberrations in anaphase-telophase (CAAT) was determined in root tips of the wetland macrophyte Bidens laevis exposed to environmentally relevant concentrations of endosulfan (0.01, 0.02, 0.5 and 5 μg/L) for 48 h. MN frequency varied from 0 in negative controls and plants exposed to 0.01 μg/L endosulfan to 0-3 in plants exposed to 5 μg/L. Moreover, a significant concentration-dependent increase of CAAT was observed. The higher proportion of laggards and vagrand chromosomes observed at 5 μg/L would indicate that endosulfan interacts with the spindle interrupting normal chromosome migration. Endosulfan resulted genotoxic to B. laevis, a species of potential value for bioassays and in situ monitoring of environmental contamination by pesticides. - Endosulfan causes a concentration-dependent increase of chromosome aberrations in the macrophyte Bidens laevis

  6. Cytology of 2n Pollen Formation in Nonastringent Persimmon

    Institute of Scientific and Technical Information of China (English)

    TANG Xian-ying; LUO Zheng-rong

    2002-01-01

    Cytological mechanisms of 2n pollen formation in ‘Zenjimaru' nonastringent persimmon (Diospyros kaki L.f. ) were studied. The following abnormalities in meiosis were found to be responsible for the production of 2n pollens: (1) disoriented spindles, including parallel, fused and tripolar spindles, were formed at metaphase Ⅱ and anaphase Ⅱ; (2) the nuclei at telophase Ⅱ were arranged to two poles, each of which contained two nuclei, or to three poles, one of which contained two nuclei, the other two contained one nucleus respectively; (3) dyads and triads were produced at the tetrad stage. The dyad would develop into two 2n pollens, and the triad would develop into one 2n and two n pollens. The 2n pollens produced by this mechanism were genetically equivalent to FDR (first division restitution) gametes, thus providing a potential value for sexual polyploidization.

  7. Chromosome studies in the genus Jatropha L.

    Directory of Open Access Journals (Sweden)

    R.Sasikala and M.Paramathma

    2010-07-01

    Full Text Available The inflorescences of ten species of the genus Jatropha were fixed in Cornoy’s fluid (6:3:1. Acetocarmine stain (2% wasused for staining the pollen mother cells. Seven species exhibited 11 bivalents and 2n =22 and x=11. But the two otherspecies, J.villosa var. villosa and J.villosa var. ramnadensis showed only 10 bivalents and 2n number of 20 chromosomesand x=10. The study concluded the occurrence of two kinds of haploid chromosome numbers of n =10 and n =11. ExceptJatropha tanjorensis, cytological investigation in all species exhibited normal and complete pairing and bivalent formationin metaphase I and equal separation of chromosome in anaphase and indicated that the course of meiosis was normal.Jatropha tanjorensis did not exhibit normal course of meiosis and no proper count of chromosomes could be made. Presentchromosomal studies in Jatropha revealed the existence of two basic chromosomes numbers x = 5 and x = 6.

  8. Postirradiation bone marrow damage in chickens

    International Nuclear Information System (INIS)

    The frequency of bone marrow damage induced by the continuous gamma irradiation was studied. Effect of dose rate and level of cumulated doses of radiation was evaluated in clinical and hematological examinations and bone marrow damage was determined by chromosome aberrations in anaphase. The regulative ability of hematopoiesis of many cytokines are discussed. Positive regulators are inducers of cell proliferation, and negative regulators are inducers of apoptosis /programmed cell death/. Birds corresponding with similarities in thymus-T and bursal-B cells appear to be an interesting model for studying the possible participation of apoptosis in radiation disease. Our recent experimental studies continue to progress in this direction. (author) 17 refs.; 3 figs.; 2 tabs

  9. Syncytes with premeiotic mitotic and cytomictic comportment in opium poppy (Papaver somniferum L.)

    International Nuclear Information System (INIS)

    Variations in terms of mitosis at premeiotic stage and cytomixis in multiploid microsporocytes have been recorded in mutagen treated and untreated populations raised from an inbred line S4I30 of Papaver sominiferum L. (2n = 22). In premeiotic mitosis all the chromosomes in syncytes were found to align on a single metaphase plate and separate normally in anaphase. Ploidy levels in premeiotic syncytes varied considerably from 2N to 4N in control, from 2N to 6N in 5kR-M1 and 2N to 10N in combined dose (5kR + 0.6% EMS) M1. Specific heterochromatic chromosomes were observed to be involved in cytomictic events suggesting thereby that cytomixis is a genetically manoeuvred process for the generation of syncytes. The results have been discussed from the point of view that higher ploidy level coupled with less sterility in gametes may be instrumental for variation and evolution in opium poppy

  10. Diving Into Cabazitaxel's Mode of Action: More Than a Taxane for the Treatment of Castration-Resistant Prostate Cancer Patients.

    Science.gov (United States)

    Mellado, Begoña; Jimenez, Natalia; Marin-Aguilera, Mercedes; Reig, Oscar

    2016-08-01

    Prostate cancer is a molecularly heterogeneous disease, and mechanisms of action of taxanes and potential mechanisms of resistance are not clearly defined. Taxanes are microtubule-stabilizing agents resulting in the slowing or blocking of mitosis at the metaphase-anaphase transition and induction of apoptotic cell death. Taxanes also can inhibit androgen receptor pathway. To date, several factors have been associated with taxane resistance, including alterations in tubulin, the effect of drug efflux pumps, and the dysfunctional regulation of signaling pathways that may be involved in resistance to therapy. Preclinical and clinical data support the distinct activity of cabazitaxel in prostate cancer that may overcome resistance to prior taxanes or hormonal therapies. It is challenging to define the most adequate therapeutic sequence for each patient. Moreover, the identification of molecular markers of resistance may help to select patients for specific therapies. PMID:26827258

  11. The syncytial Drosophila embryo as a mechanically excitable medium

    CERN Document Server

    Idema, Timon; Manning, M Lisa; Nelson, Philip C; Liu, Andrea J

    2013-01-01

    Mitosis in the early syncytial Drosophila embryo is highly correlated in space and time, as manifested in mitotic wavefronts that propagate across the embryo. In this paper we investigate the idea that the embryo can be considered a mechanically-excitable medium, and that mitotic wavefronts can be understood as nonlinear wavefronts that propagate through this medium. We study the wavefronts via both image analysis of confocal microscopy videos and theoretical models. We find that the mitotic wavefront can be resolved into two distinct wavefronts in each cycle, corresponding to metaphase and anaphase, respectively. The two wavefronts have the same speed and are separated by a time interval that is independent of cycle, supporting the idea that they are two different markers for the same process. To understand the wavefronts theoretically we analyze wavefront propagation in excitable media. We study two classes of models, one with biochemical signaling and one with mechanical signaling. We find that the depende...

  12. No neocentric activity on Aegilops markgrafii chromosome E.

    Science.gov (United States)

    Schubert, V

    2011-01-01

    Classical neocentromeres, proven mainly in Poaceae species, cause meiotic drive in higher plants. Here I present data indicating that the morphological stretching of a chromatin domain at the long arm of Aegilops markgrafii chromosome E during meiosis is not due to a supposed neocentric activity. The stretching is visible at the alien univalent in metaphase I and anaphase I pollen mother cells of Triticum aestivum--Ae. markgrafii monosomic addition line E and at one univalent of the 49-chromosome-containing plants containing the haploid Ae. markgrafii genome added to wheat. The absence of both centromeric histone variant CENH3 and attachment of spindle fibers, proven by immunostaining with antibodies against CENH3 and tubulin, respectively, revealed that the univalent elongation of chromosome E is not caused by a classical plant neocentromere. PMID:20720397

  13. Centromere structure and chromosome number in mitosis of the colourless phytoflagellate Polytoma papillatum (Chlorophyceae, Volvocales, Chlamydomonadaceae).

    Science.gov (United States)

    Wolf, K W

    1995-12-01

    Centromere structure is described in mitosis of the unicellular biflagellate alga Polytoma papillatum using transmission electron microscopy. The kinetochores are five-layered elements at the poleward surface of the chromosomes. The five layers consist of three dense plates interspersed by two transparent zones. The polemost dense layer serves as the attachment site for kinetochore microtubules and the innermost dense layer is intimately associated with the chromatin. The five-layered organization of the kinetochore in the alga is unusual. In animals, three-layered kinetochores are the rule. This type has also been found in some algae, while higher plants do not possess striated kinetochores. An attempt was made to determine the chromosome number of P. papillatum. Individual chromosomes could not be recognized with confidence, since there were numerous lateral contacts between the chromosomes throughout mitosis. An alternative approach, however, was successful. Counting the kinetochores in serial sections through mitotic metaphase and anaphase plates revealed a number of 15 chromosomes. PMID:18470243

  14. Peculiarities of the radioprotective effect of antioxidants during gamma irradiation of wheat seeds

    International Nuclear Information System (INIS)

    Bioantioxidant radioprotective action mechanism was studied using wheat seeds. Cobalt-60 was used as radiation source, phenosane potassium salt in aqueous solution in 0.1 and 0.25% concentrations possessing the maximum radioprotective effect - as an antioxidant. Dry seeds irradiated with 100 Gy dose were treated with fresh antioxidant solutions during 20 hours with 0.2, 4.6 an 8 hour interval at room temperature. The number of cells with aberrations at the anaphase stage in the main root apical meristem were counted in germinated seeds. A high radioprotective effect of phenosane antioxidant which represents space-complicated phenols is ascertained. Radioprotective effect is dependent on time interval between seed irradaition and germination and is maximal when this time makes up 4-8 hours

  15. Cytological Effects of Irradiated Guayabano Fruit Juice on Native Onion (Allium fistulosum L.

    Directory of Open Access Journals (Sweden)

    Milagros Serrana

    1993-06-01

    Full Text Available Thirty bottles of guayabano fruit juice were exposed to gamma ray doses of 0, 1, 2, 3 and 4 KGy. These bottles were then stored for 0, 4 and 8 days and used for treatment of Allium fistulosum L. root meristems. For each treatment, 2000 cells were scored to obtain data on mitotic index and types and frequency of cytological aberrations. The newly irradiated juice did not inhibit mitosis but storage showed marked effects on the mitotic index. Both irradiated or unirradiated juice stored for 8 days caused a significant inhibition of mitosis. The irradiated juice induced the production of anaphase bridges, binucleate cells, cells, cells with elongated nucleus and cells with obliquely oriented equatorial plate.

  16. The radioprotective effect of L-NAME inhibitor of NO-synthase in Chinese hamster cells in culture

    International Nuclear Information System (INIS)

    Radioprotective effect of L-NAME - one of the inhibitors of NO-synthase - was estimated by the yield of the aberrant anaphases after exposure of Chinese hamster cells to different doses of γ-rays and β-particles. Decrease of the frequency of radiation-induced chromosome aberrations was observed during LNAME cell treatment before irradiation (1-4 h) only. 3 Gy dose without LNAME and 6 Gy dose with L-NAME were equieffective ones. The treatment of cells with L-NAME decreased the level of SH-groups in cells and decreased fluorescence intensity of DNA-ethidium bromide complex during flow cytometry. Results obtained indicate the involvement of NO-dependent mechanism of the realization of the radiation-induced damage to the hereditary cell structure. Optimal conditions for the realization of the conceivable mechanism of radioprotective effect of L-NAME

  17. Assessment of genetic results of ionizing radiation effect on hydrobionts population

    International Nuclear Information System (INIS)

    The effect of dose value and rate on genetic results of chronic radiation with the low dose rate is estimated. At such irradiation the yield of abberant anaphases of embryos is determined by the dose value and it does not depend on the dose rate. The threshold radiation dose rate of the developing fish roe equals 2-3 cGy/h when ignoring the medium modifying factors. The estimation of possible limits of modification of genetic effects of radiation with the low rate when changing environmental factors is given. The model allowing to forecast the appearance of genetic effects of radiation with the low dose rate is constructed. The correspondence between the data obtained in laboratory experiments using organisms living in water reservoirs contaminated experimentally by radionuclides is marked

  18. The dynamics of signal amplification by macromolecular assemblies for the control of chromosome segregation

    Directory of Open Access Journals (Sweden)

    Semin eLee

    2014-09-01

    Full Text Available The control of chromosome segregation relies on the spindle assembly checkpoint (SAC, a complex regulatory system that ensures the high fidelity of chromosome segregation in higher organisms by delaying the onset of anaphase until each chromosome is properly bi-oriented on the mitotic spindle. Central to this process is the establishment of multiple yet specific protein-protein interactions in a narrow time-space window. Here we discuss the highly dynamic nature of multi-protein complexes that control chromosome segregation in which an intricate network of weak but cooperative interactions modulate signal amplification to ensure a proper SAC response. We also discuss the current structural understanding of the communication between the SAC and the kinetochore; how transient interactions can regulate the assembly and disassembly of the SAC as well as the challenges and opportunities for the definition and the manipulation of the flow of information in SAC signaling.

  19. Karyotypes, B-chromosomes and meiotic abnormalities in 13 populations of Alebra albostriella and A. wahlbergi (Hemiptera, Auchenorrhyncha, Cicadellidae from Greece

    Directory of Open Access Journals (Sweden)

    Valentina Kuznetsova

    2013-11-01

    Full Text Available In this work 13 populations of the leafhopper species Alebra albostriella (Fallén, 1826 (6 populations and A. wahlbergi (Boheman, 1845 (7 populations (Cicadellidae: Typhlocybinae from Greece were studied cytogenetically. We examined chromosomal complements and meiosis in 41 males of A. albostriella sampled from Castanea sativa, Fagus sylvatica and Quercus cerris and in 21 males of A. wahlbergi sampled from C. sativa, Acer opalus and Ulmus sp. The species were shown to share 2n = 22 + X(0 and male meiosis of the chiasmate preductional type typical for Auchenorrhyncha. In all populations of A. albostriella and in all but two populations of A. wahlbergi B chromosomes and/or different meiotic abnormalities including the end-to-end non-homologous chromosomal associations, translocation chains, univalents, anaphasic laggards besides aberrant sperms were encountered. This study represents the first chromosomal record for the genus Alebra and one of the few population-cytogenetic studies in the Auchenorrhyncha.

  20. Karyotypes, B-chromosomes and meiotic abnormalities in 13 populations of Alebra albostriella and A. wahlbergi (Hemiptera, Auchenorrhyncha, Cicadellidae) from Greece.

    Science.gov (United States)

    Kuznetsova, Valentina G; Golub, Natalia V; Aguin-Pombo, Dora

    2013-11-26

    In this work 13 populations of the leafhopper species Alebra albostriella (Fallén, 1826) (6 populations) and A. wahlbergi (Boheman, 1845) (7 populations) (Cicadellidae: Typhlocybinae) from Greece were studied cytogenetically. We examined chromosomal complements and meiosis in 41 males of A. albostriella sampled from Castanea sativa, Fagus sylvatica and Quercus cerris and in 21 males of A. wahlbergi sampled from C. sativa, Acer opalus and Ulmus sp. The species were shown to share 2n = 22 + X(0) and male meiosis of the chiasmate preductional type typical for Auchenorrhyncha. In all populations of A. albostriella and in all but two populations of A. wahlbergi B chromosomes and/or different meiotic abnormalities including the end-to-end non-homologous chromosomal associations, translocation chains, univalents, anaphasic laggards besides aberrant sperms were encountered. This study represents the first chromosomal record for the genus Alebra and one of the few population-cytogenetic studies in the Auchenorrhyncha. PMID:24455103

  1. Comparative Cytotoxicity of the Herbicide Atrazine to Four Inbred Maize Lines (Zea mays L.)

    International Nuclear Information System (INIS)

    Atrazine is one of the most widely used herbicides in the world. Recent reports have indicated that it has adverse impacts on the endocrine systems and on the early developments of wild animals and it has been banned in many European countries including Switzerland, the home of the manufacturing company. The genotoxic effects of Atrazine on four inbred lines of maize (Zea mays L.) were investigated. The herbicide showed mitoinhibition and clastogenic effects on the mitotic index of maize lines and they were proportional to the concentrations and time. The frequency of abnormality, chromosomal breakage, stickiness, lagging, C-metaphase and C-anaphase were observed at different stages of mitosis in treated cells. The harmful effect of this environmental pollutant proved that it may act as a strong mutagen. (author)

  2. PUL21a-Cyclin A2 interaction is required to protect human cytomegalovirus-infected cells from the deleterious consequences of mitotic entry.

    Directory of Open Access Journals (Sweden)

    Martin Eifler

    2014-10-01

    Full Text Available Entry into mitosis is accompanied by dramatic changes in cellular architecture, metabolism and gene expression. Many viruses have evolved cell cycle arrest strategies to prevent mitotic entry, presumably to ensure sustained, uninterrupted viral replication. Here we show for human cytomegalovirus (HCMV what happens if the viral cell cycle arrest mechanism is disabled and cells engaged in viral replication enter into unscheduled mitosis. We made use of an HCMV mutant that, due to a defective Cyclin A2 binding motif in its UL21a gene product (pUL21a, has lost its ability to down-regulate Cyclin A2 and, therefore, to arrest cells at the G1/S transition. Cyclin A2 up-regulation in infected cells not only triggered the onset of cellular DNA synthesis, but also promoted the accumulation and nuclear translocation of Cyclin B1-CDK1, premature chromatin condensation and mitotic entry. The infected cells were able to enter metaphase as shown by nuclear lamina disassembly and, often irregular, metaphase spindle formation. However, anaphase onset was blocked by the still intact anaphase promoting complex/cyclosome (APC/C inhibitory function of pUL21a. Remarkably, the essential viral IE2, but not the related chromosome-associated IE1 protein, disappeared upon mitotic entry, suggesting an inherent instability of IE2 under mitotic conditions. Viral DNA synthesis was impaired in mitosis, as demonstrated by the abnormal morphology and strongly reduced BrdU incorporation rates of viral replication compartments. The prolonged metaphase arrest in infected cells coincided with precocious sister chromatid separation and progressive fragmentation of the chromosomal material. We conclude that the Cyclin A2-binding function of pUL21a contributes to the maintenance of a cell cycle state conducive for the completion of the HCMV replication cycle. Unscheduled mitotic entry during the course of the HCMV replication has fatal consequences, leading to abortive infection and

  3. 稻田蜘蛛混合种群空间分布模式动态分析%ANALYSIS ON THE DYNAMICS OF SPATIAL DISTRIBUTION PATTERN OF MIXED SPIDER POPULATION IN RICE FIELD

    Institute of Scientific and Technical Information of China (English)

    王智; 袁哲明; 宋大祥; 朱明生

    2004-01-01

    The results make it clear that there are total 11 families, 29 genera and 43 species of spiders in the rice field of Dong Fang Hong Farm. Among them, there are 8 families, 19 genera and 28 species in the early rice field, and 10 families, 27 genera and 36 species in the late rice field. The spatial distribution pattern of mixed spider populations in rice fields was different during different development stages of rice plant. During the prophase, metaphase and anaphase of early rice plant development, the spatial distribution pattern of mixed spider populations was aggregative, random and aggregative respectively. During the prophase, metaphase and anaphase of late rice plant development, the spatial distribution pattern was uniform, aggregative and uniform respectively.%结果表明,在东方红农场稻田中总共有11科29属43种蜘蛛,其中早稻田中有8科19属43种,晚稻田中有10科27属36种.在水稻的不同发育阶段蜘蛛混合种群的空间分布模式存在差异.在早稻发育的前期、中期和后期,稻田蜘蛛混合种群的空间分布模式分别是聚集的、随机的和聚集的;在晚稻发育的前期、中期和后期,其空间分布模式依次是均匀的、聚集的和均匀的.同时,对其空间分布模式动态进行了初步分析.

  4. A single bivalent efficiently inhibits cyclin B1 degradation and polar body extrusion in mouse oocytes indicating robust SAC during female meiosis I.

    Directory of Open Access Journals (Sweden)

    Steffen Hoffmann

    Full Text Available The Spindle Assembly Checkpoint (SAC inhibits anaphase until microtubule-to-kinetochore attachments are formed, thus securing correct chromosome separation and preventing aneuploidy. Whereas in mitosis even a single unattached chromosome keeps the SAC active, the high incidence of aneuploidy related to maternal meiotic errors raises a concern about the lower efficiency of SAC in oocytes. Recently it was suggested that in mouse oocytes, contrary to somatic cells, not a single chromosome but a critical mass of chromosomes triggers efficient SAC pointing to the necessity of evaluating the robustness of SAC in oocytes. Two types of errors in chromosome segregation upon meiosis I related to SAC were envisaged: (1 SAC escape, when kinetochores emit SAC-activating signal unable to stop anaphase I; and (2 SAC deceive, when kinetochores do not emit the signal. Using micromanipulations and live imaging of the first polar body extrusion, as well as the dynamics of cyclin B1 degradation, here we show that in mouse oocytes a single bivalent keeps the SAC active. This is the first direct evaluation of SAC efficiency in mouse oocytes, which provides strong evidence that the robustness of SAC in mammalian oocytes is comparable to other cell types. Our data do not contradict the hypothesis of the critical mass of chromosomes necessary for SAC activation, but suggest that the same rule may govern SAC activity also in other cell types. We postulate that the innate susceptibility of oocytes to errors in chromosome segregation during the first meiotic division may not be caused by lower efficiency of SAC itself, but could be linked to high critical chromosome mass necessary to keep SAC active in oocyte of large size.

  5. 澳洲坚果花粉母细胞减数分裂观察%Microscopic Observation of Meiosis of Macadamia Pollen Mother Cells

    Institute of Scientific and Technical Information of China (English)

    孔广红; 柳觐; 倪书邦; 贺熙勇

    2013-01-01

    The complete process of meiosis of Macadamia pollen mother cells (PMC) was investigated, u-sing the squashing technique. Our results showed that meiosis of Macadamia started in December and the meiosis process was closely correlated with the bud length, and difference in the stages of meiosis was observed in same bud and in the same anther. Diplotene lasted for a long time and presented many shapes. The number and structure of Macadamia chromosome could be observed clearly in the stages of diakme-sis, metaphase Ⅰ, anaphase Ⅰ and anaphase Ⅱ. No variation in number and structure were detected of Macadamia chromosomes in meiosis, which was a typical division process of diploid species.%采用压片法观察了澳洲坚果花粉母细胞(PMC)减数分裂的完整过程,证实澳洲坚果PMC减数分裂始于12月份,其减数分裂进程与单花大小有密切关系,且同一花蕾甚至同一花药中表现不同步.减数分裂双线期历时时间长且形态多样,可于终变期、中期Ⅰ、后期Ⅰ以及后期Ⅱ观察到染色体数目和结构.澳洲坚果PMC减数分裂过程中无染色体结构和数目的变异,属二倍体的标准分裂进程.

  6. The breeding of two polyploid rice lines with the characteristic of polyploid meiosis stability

    Institute of Scientific and Technical Information of China (English)

    CAI DeTian; HE YuChi; ZHANG DaoSheng; HE GuangCun; ZHU YingGuo; CHEN JianGuo; CHEN DongLing; DAI BingCheng; ZHANG Wei; SONG ZhaoJian; YANG ZhiFan; DU ChaoQun; TANG ZhiQiang

    2007-01-01

    Polyploidization is a basic feature of plant evolution. Nearly all of the main food, cotton and oil crops are polyploid. When ploidy levels increase, yields double; this phenomenon suggested a new strategy of rice breeding that utilizes wide crosses and polyploidization dual advantages to breed super rice.Because low seed set rates in polyploid rice usually makes it difficult to breed, the selection of Ph-liked gene lines was emphasized. After progenies of indica-japonica were identified and selected, two polyploid lines, PMeS-1 and PMeS-2 with Polyploid Meiosis Stability (PMeS) genes were bred. The procedure included seven steps: selecting parents, crossing or multiple crossing, back-crossing, doubling chromosomes, identifying the polyploid, and choosing plants with high seed set rates that can breed themselves into stable lines. The characteristics of PMeS were determined by observing meiotic behaviors and by cross-identification of seed sets. PMeS-1 and PMeS-2, (japonica rice), have several characteristics different from other polyploid rice lines, including a higher rate of seed set (more than 65%, increasing to more than 70% in their F1 offspring); and stable meiotic behaviors (pairing with bivalents and quarivalents nearly without over-quarivalent in prophase, nearly without lagging chromosomes in metaphase and without micronuclei in anaphase and telophase). The latter was obviously different from control polyploid line Dure-4X, which displayed abnormal meiotic behaviors including a higher rate of multivalents, univalents and trivalents in prophase, lagging chromosomes in metaphase and micronuclei in anaphase and telophase. There were also three differences of the breeding method between PMeS lines and normal diploid lines: chromosomes doubling, polyploidism identifying and higher seed set testing. The selection of PMeS lines is the first step in polyploid rice breeding; their use will advance the progress of polyploid rice breeding, which will in turn offer

  7. The breeding of two polyploid rice lines with the characteristic of polyploid meiosis stability

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Polyploidization is a basic feature of plant evolution. Nearly all of the main food, cotton and oil crops are polyploid. When ploidy levels increase, yields double; this phenomenon suggested a new strategy of rice breeding that utilizes wide crosses and polyploidization dual advantages to breed super rice. Because low seed set rates in polyploid rice usually makes it difficult to breed, the selection of Ph-liked gene lines was emphasized. After progenies of indica-japonica were identified and selected, two poly- ploid lines, PMeS-1 and PMeS-2 with Polyploid Meiosis Stability (PMeS) genes were bred. The proce- dure included seven steps: selecting parents, crossing or multiple crossing, back-crossing, doubling chromosomes, identifying the polyploid, and choosing plants with high seed set rates that can breed themselves into stable lines. The characteristics of PMeS were determined by observing meiotic be- haviors and by cross-identification of seed sets. PMeS-1 and PMeS-2, (japonica rice), have several characteristics different from other polyploid rice lines, including a higher rate of seed set (more than 65%, increasing to more than 70% in their F1 offspring); and stable meiotic behaviors (pairing with bi- valents and quarivalents nearly without over-quarivalent in prophase, nearly without lagging chromo- somes in metaphase and without micronuclei in anaphase and telophase). The latter was obviously different from control polyploid line Dure-4X, which displayed abnormal meiotic behaviors including a higher rate of multivalents, univalents and trivalents in prophase, lagging chromosomes in metaphase and micronuclei in anaphase and telophase. There were also three differences of the breeding method between PMeS lines and normal diploid lines: chromosomes doubling, polyploidism identifying and higher seed set testing. The selection of PMeS lines is the first step in polyploid rice breeding; their use will advance the progress of polyploid rice breeding, which will in

  8. In-silico modeling of the mitotic spindle assembly checkpoint.

    Directory of Open Access Journals (Sweden)

    Bashar Ibrahim

    Full Text Available BACKGROUND: The Mitotic Spindle Assembly Checkpoint ((MSAC is an evolutionary conserved mechanism that ensures the correct segregation of chromosomes by restraining cell cycle progression from entering anaphase until all chromosomes have made proper bipolar attachments to the mitotic spindle. Its malfunction can lead to cancer. PRINCIPLE FINDINGS: We have constructed and validated for the human (MSAC mechanism an in silico dynamical model, integrating 11 proteins and complexes. The model incorporates the perspectives of three central control pathways, namely Mad1/Mad2 induced Cdc20 sequestering based on the Template Model, MCC formation, and APC inhibition. Originating from the biochemical reactions for the underlying molecular processes, non-linear ordinary differential equations for the concentrations of 11 proteins and complexes of the (MSAC are derived. Most of the kinetic constants are taken from literature, the remaining four unknown parameters are derived by an evolutionary optimization procedure for an objective function describing the dynamics of the APC:Cdc20 complex. MCC:APC dissociation is described by two alternatives, namely the "Dissociation" and the "Convey" model variants. The attachment of the kinetochore to microtubuli is simulated by a switching parameter silencing those reactions which are stopped by the attachment. For both, the Dissociation and the Convey variants, we compare two different scenarios concerning the microtubule attachment dependent control of the dissociation reaction. Our model is validated by simulation of ten perturbation experiments. CONCLUSION: Only in the controlled case, our models show (MSAC behaviour at meta- to anaphase transition in agreement with experimental observations. Our simulations revealed that for (MSAC activation, Cdc20 is not fully sequestered; instead APC is inhibited by MCC binding.

  9. Radioprotective and cytoprotective activity of Tinospora cordifolia stem enriched extract containing cordifolioside-A

    Directory of Open Access Journals (Sweden)

    Arti Patel

    2013-01-01

    Full Text Available Objectives: The present study was undertaken to evaluate the radioprotective and cytoprotective potential of cordifolioside-A, a primary active constituent of n-butanol fraction of Tinospora Cordifolia (NBTC against 4 Gy-γ radiation in mice and cyclophosphamide induced genotoxicity. Materials and Methods: Presence of cordifolioside-A in NBTC stem ethanolic extract was confirmed by high performance thin layer chromatography (HPTLC analysis. Radioprotective activity was evaluated at 80 and 120 mg/kg, intraperitoneal (i.p. dose of NBTC administered 15 days prior to whole body radiation exposure by observing survival rate, change in body weight, hematology, spleen colony forming unit (CFU, and micronucleus (MN expression. Cytoprotective activity of NBTC was evaluated at 5, 10, and 15 mg/ml concentrations on Allium cepa root meristem growth against cyclophosphamide. Results: HPTLC analysis of standard cordifolioside A, and NBTC confirmed the presence of cordifolioside-A in NBTC with the retention factor value of 0.86. Administration of NBTC (120 mg/kg, i.p. produced significant protection against radiation in terms of increased survival rate, body weight retention, hematological parameters, spleen CFU assay (P < 0.01, and decreased MN expression (P < 0.01. Cytoprotectivity was observed maximally at 10 mg/ml NBTC concentration with significant increase in root growth (P < 0.01, non-toxic mitotic index (MI (65.9% and lesser chromosomal aberrations (15.4%. NBTC at 10 mg/ml concentration showed very few C-anaphase compared to aberrations like fragmentation, C-anaphase, multipolarity and sticky chromosome in cyclophosphamide alone. Conclusion: The results suggest that enriched NBTC containing cordifolioside-A has a potential in vivo radioprotective effect as well as in vitro cytoprotective activity.

  10. Pre-therapeutic radiobiological experiments performed at Cyclone with d(50)-Be neutrons. Comparison of RBE/absorbed dose relationships obtained for several biological criteria

    International Nuclear Information System (INIS)

    The RBE/absorbed dose relationships for d(50)-Be neutrons were determined for several biological criteria. Irradiations were performed with the isochronous cyclotron Cyclone at Louvain-la-Neuve. Neutrons are produced by bombarding a thick beryllium target with 50MeV deuterons. This energy is to be used for the clinical applications. As first biological criterion, early intestinal tolerance was assessed in BALB/c mice from LD50 determination. Abdomen only was irradiated in order to avoid interference from the bone marrow syndrome. For single fraction irradiation, an RBE value of 1.8+-0.2 was observed (LD50 neutron absorbed dose: 525 rad). Fractionated irradiation had to be used to study smaller doses per fraction. The RBE increases progressively with decreasing dose and reaches 2.8 for a neutron absorbed dose of 80 rad (i.e. for a gamma absorbed dose of about 225 rad). A further RBE increase is unlikely since, for smaller absorbed doses, the survival curve for gamma rays nearly coincides with its initial tangent. The RBE/absorbed dose relationships observed for several mammalian cell lines in vitro, although they have a rather similar shape, show significant differences. For a neutron absorbed dose of 100 rad, the RBE is about 3 for EMT6 mouse cancer cells and 2 for HF19 human fibroblasts. For chromosome aberrations in Allium cepa onion roots, observed RBE values are much higher than for mammalian cell lethality. The RBE increases regularly from 7 to 12 with decreasing neutron dose from 40 to 10 rad. Two criteria were selected: (i) the mean number of aberrations (mainly breaks) per cell in anaphase and telophase, and (ii) the fraction of cells in anaphase and telophase having at least one aberration. For growth delay in Vicia faba, the RBE increases from 2.8 to 4.4 when the neutron absorbed dose decreases from 90 to 20 rad. (author)

  11. Microcystin-LR induces mitotic spindle assembly disorders in Vicia faba by protein phosphatase inhibition and not reactive oxygen species induction.

    Science.gov (United States)

    Garda, Tamás; Kónya, Zoltán; Tándor, Ildikó; Beyer, Dániel; Vasas, Gábor; Erdődi, Ferenc; Vereb, György; Papp, Georgina; Riba, Milán; M-Hamvas, Márta; Máthé, Csaba

    2016-07-20

    We aimed to reveal the mechanisms of mitotic spindle anomalies induced by microcystin-LR (MCY-LR), a cyanobacterial toxin in Vicia faba, a well-known model in plant cell and molecular biology. MCY-LR inhibits type 1 and 2A phosphoserine/threonine specific protein phosphatases (PP1 and PP2A) and induces reactive oxygen species (ROS) formation. The cytoskeleton is one of the main targets of the cyanotoxin during cytopathogenesis. Histochemical-immunohistochemical and biochemical methods were used. A significant number of MCY-LR induced spindle alterations are described for the first time. Disrupted, multipolar spindles and missing kinetochore fibers were detected both in metaphase and anaphase cells. Additional polar microtubule (MT) bundles, hyperbundling of spindle MTs, monopolar spindles, C-S- shaped, additional and asymmetric spindles were detected in metaphase, while midplane kinetochore fibers were detected in anaphase cells only. Several spindle anomalies induced mitotic disorders, i.e. they occurred concomitantly with altered sister chromatid separation. Alterations were dependent on the MCY-LR dose and exposure time. Under long-term (2 and mainly 6 days') exposure they were detected in the concentration range of 0.1-20μgmL(-1) MCY-LR that inhibited PP1 and PP2A significantly without significant ROS induction. Elevated peroxidase/catalase activities indicated that MCY-LR treated V. faba plants showed efficient defense against oxidative stress. Thus, although the elevation of ROS is known to induce cytoskeletal aberrations in general, this study shows that long-term protein phosphatase inhibition is the primary cause of MCY-LR induced spindle disorders. PMID:27186862

  12. Origin of nuclear buds and micronuclei in normal and folate-deprived human lymphocytes

    International Nuclear Information System (INIS)

    Micronuclei are formed from chromosomes and chromosomal fragments that lag behind in anaphase and are left outside daughter nuclei in telophase. They may also be derived from broken anaphase bridges. Nuclear buds, micronucleus-like bodies attached to the nucleus by a thin nucleoplasmic connection, have been proposed to be generated similarly to micronuclei during nuclear division or in S-phase as a stage in the extrusion of extra DNA, possibly giving rise to micronuclei. To better understand these phenomena, we have characterized the contents of 894 nuclear buds and 1392 micronuclei in normal and folate-deprived 9-day cultures of human lymphocytes using fluorescence in situ hybridization with pancentromeric and pantelomeric DNA probes. Such information has not earlier been available for human primary cells. Surprisingly, there appears to be no previous data on the occurrence of telomeres in micronuclei (or buds) of normal human cells in general. Our results suggest that nuclear buds and micronuclei have partly different mechanistic origin. Interstitial DNA without centromere or telomere label was clearly more prevalent in nuclear buds (43%) than in micronuclei (13%). DNA with only telomere label or with both centromere and telomere label was more frequent in micronuclei (62% and 22%, respectively) than in nuclear buds (44% and 10%, respectively). Folate deprivation especially increased the frequency of nuclear buds and micronuclei harboring telomeric DNA and nuclear buds harboring interstitial DNA but also buds and micronuclei with both centromeric and telomeric DNA. According to the model we propose, that micronuclei in binucleate lymphocytes primarily derive from lagging chromosomes and terminal acentric fragments during mitosis. Most nuclear buds, however, are suggested to originate from interstitial or terminal acentric fragments, possibly representing nuclear membrane entrapment of DNA that has been left in cytoplasm after nuclear division or excess DNA that

  13. Induced mutation and radiation sensitivity in vitro culture of soybean (Glycine Max L. Merrill)

    International Nuclear Information System (INIS)

    In our research, the seeds of J-357 soybean variety were irradiated with 50, 100, 200, 300 and 500 Gy of gamma rays. Callus and meristem cultures were established from the primary leaves and apical meristem of 5-day-old seeding from the irradiation seeds. The average callus fresh weight formed at the cultures were determined on the 30th day and GR50 dose which reduces the callus fresh weight at the rate 50% in accordance with control was found as 250 Gy. The regenerated plants from meristem cultures were determined on the 28th day and LD50 dose which decreases the regenerated plant percentage at the 50% in accordance with control was found as 220 Gy. Cytological investigation was done at the callus and meristem cultures obtained from both irradiated seeds and explants. At the seed and explant irradiations, gamma radiation dose between the ranges 50 to 200 Gy and 5 to 25 Gy; respectively were used. Observations were done at mitotic anaphase in the samples taken from meristem and callus cultures. In anaphase, two types of cytological aberrations, bridge and fragments were determined. The regenerated plants were grown in the climate chamber and the seeds were taken from each M1 plant and chlorophyll mutants were determined in M2 generation. The radiosensitivity of the meristem cultures established by irradiated seeds from view of plant regenerations and plant number which is taken seed was evaluated by comparing with the results of meristem cultures established from the irradiated explant from the point of in vitro mutation studies

  14. Pyrimidine Pool Disequilibrium Induced by a Cytidine Deaminase Deficiency Inhibits PARP-1 Activity, Leading to the Under Replication of DNA.

    Directory of Open Access Journals (Sweden)

    Simon Gemble

    2015-07-01

    Full Text Available Genome stability is jeopardized by imbalances of the dNTP pool; such imbalances affect the rate of fork progression. For example, cytidine deaminase (CDA deficiency leads to an excess of dCTP, slowing the replication fork. We describe here a novel mechanism by which pyrimidine pool disequilibrium compromises the completion of replication and chromosome segregation: the intracellular accumulation of dCTP inhibits PARP-1 activity. CDA deficiency results in incomplete DNA replication when cells enter mitosis, leading to the formation of ultrafine anaphase bridges between sister-chromatids at "difficult-to-replicate" sites such as centromeres and fragile sites. Using molecular combing, electron microscopy and a sensitive assay involving cell imaging to quantify steady-state PAR levels, we found that DNA replication was unsuccessful due to the partial inhibition of basal PARP-1 activity, rather than slower fork speed. The stimulation of PARP-1 activity in CDA-deficient cells restores replication and, thus, chromosome segregation. Moreover, increasing intracellular dCTP levels generates under-replication-induced sister-chromatid bridges as efficiently as PARP-1 knockdown. These results have direct implications for Bloom syndrome (BS, a rare genetic disease combining susceptibility to cancer and genomic instability. BS results from mutation of the BLM gene, encoding BLM, a RecQ 3'-5' DNA helicase, a deficiency of which leads to CDA downregulation. BS cells thus have a CDA defect, resulting in a high frequency of ultrafine anaphase bridges due entirely to dCTP-dependent PARP-1 inhibition and independent of BLM status. Our study describes previously unknown pathological consequences of the distortion of dNTP pools and reveals an unexpected role for PARP-1 in preventing DNA under-replication and chromosome segregation defects.

  15. Effects of sorghum (sorghum bicolor L. root exudates on the cell cycle of the bean plant (phaseolus vulgaris L. root

    Directory of Open Access Journals (Sweden)

    Hallak Angela Maria Gattás

    1999-01-01

    Full Text Available Two experiments were conducted to test the allelopathic effect of sorghum (Sorghum bicolor L. root exudates on bean (Phaseolus vulgaris L. cell division. Research was conducted in the greenhouse of the Wistock Agricultural Research Institute of Minas Gerais State (EPAMIG and in a laboratory of the Federal University of Lavras (UFLA. Sorghum variety BR-601 and bean variety Carioca MG were used. The exudate, called sorgoleone (SGL, was obtained by methylene chloride and acetic acid extraction from sorghum roots seven days after sowing on Petri dishes, and refrigerated until use. Solutions of 0.01, 0.05, 0.10, and 0.15 mM were prepared using Johanson solution as the SGL solvent. Seven-day-old bean seedlings grown in vermiculite in a greenhouse were transplanted to the solution. Seven days after transplantation, the beans did not show any sign of phytotoxicity; however, cytogenetic observations showed that SGL reduced the number of cells in prophase, metaphase, and anaphase stages. Colchicine effects were observed among cells in metaphase on the third and fifth days after treatments and varied with SGL concentrations. By the seventh day, the colchicine effects were inversely proportional to concentration, which varied from 34.3% for 0.01 mM to 6.6% for 0.15 mM. SGL acts as a mitotic inhibitor. It probably depolymerizes the microtubular proteins and induces the formation of colchicine metaphases causing polyploid nuclei. A largest period of SGL treatment also induced chromosome breaks and bridge formation in anaphase and telophase. Although SGL cannot be used as a herbicide for bean cultures, its allelochemical effects on other cultures are the factors that will define the use of sorghum as a natural herbicide.

  16. Radiation and chemotherapy bystander effects induce early genomic instability events: telomere shortening and bridge formation coupled with mitochondrial dysfunction.

    LENUS (Irish Health Repository)

    Gorman, Sheeona

    2012-02-01

    The bridge breakage fusion cycle is a chromosomal instability mechanism responsible for genomic changes. Radiation bystander effects induce genomic instability; however, the mechanism driving this instability is unknown. We examined if radiation and chemotherapy bystander effects induce early genomic instability events such as telomere shortening and bridge formation using a human colon cancer explant model. We assessed telomere lengths, bridge formations, mitochondrial membrane potential and levels of reactive oxygen species in bystander cells exposed to medium from irradiated and chemotherapy-treated explant tissues. Bystander cells exposed to media from 2Gy, 5Gy, FOLFOX treated tumor and matching normal tissue showed a significant reduction in telomere lengths (all p values <0.018) and an increase in bridge formations (all p values <0.017) compared to bystander cells treated with media from unirradiated tissue (0Gy) at 24h. There was no significant difference between 2Gy and 5Gy treatments, or between effects elicited by tumor versus matched normal tissue. Bystander cells exposed to media from 2Gy irradiated tumor tissue showed significant depolarisation of the mitochondrial membrane potential (p=0.012) and an increase in reactive oxygen species levels. We also used bystander cells overexpressing a mitochondrial antioxidant manganese superoxide dismutase (MnSOD) to examine if this antioxidant could rescue the mitochondrial changes and subsequently influence nuclear instability events. In MnSOD cells, ROS levels were reduced (p=0.02) and mitochondrial membrane potential increased (p=0.04). These events were coupled with a decrease in percentage of cells with anaphase bridges and a decrease in the number of cells undergoing telomere length shortening (p values 0.01 and 0.028 respectively). We demonstrate that radiation and chemotherapy bystander responses induce early genomic instability coupled with defects in mitochondrial function. Restoring mitochondrial

  17. Nicotine-induced Disturbances of Meiotic Maturation in Cultured Mouse Oocytes: Alterations of Spindle Integrity and Chromosome Alignment

    Directory of Open Access Journals (Sweden)

    Zenzes Maria

    2004-09-01

    Full Text Available Abstract We investigated whether nicotine exposure in vitro of mouse oocytes affects spindle and chromosome function during meiotic maturation (M-I and M-II. Oocytes in germinal vesicle (GV stage were cultured in nicotine for 8 h or for 16 h, to assess effects in M-I and in metaphase II (M-II. The latter culture setting used the three protocols: 8 h nicotine then 8 h medium (8N + 8M; 16 h nicotine (16N; 8 h medium then 8 h nicotine (8M + 8N. Non-toxic concentrations of nicotine at 1.0, 2.5, 5.0 and 10.0 mmol/L were used. Spindle-chromosome configurations were analyzed with wide-field optical sectioning microscopy. In 8 h cultures, nicotine exposure resulted in dose-related increased proportions of M-I oocytes with defective spindle-chromosome configurations. A dose-related delayed entry into anaphase I was also detected. In 16 h cultures, nicotine exposure for the first 8 h (8N + 8M, or for 16 h (16N, resulted in dose- and time-related increased proportions of oocytes arrested in M-I (10 mmol/L; 8 h: 53.2%, controls 9.6%; 16 h: 87.6%, controls 8.5%. Defects in M-I spindles and chromosomes caused M-I arrest leading to dose-related decreased proportions of oocytes that reached metaphase-II (10 mmol/L 8 h: 46.8%, controls 90.4%;16 h: 12.4%, controls 91.5%. A delayed anaphase-I affected the normal timing of M-II, leading to abnormal oocytes with dispersed chromosomes, or with double spindles and no polar body. Nicotine exposure during the second 8 h (8M + 8N resulted in dose-related, increased proportions of M-II oocytes with defective spindles and chromosomes (10 mmol/L: 42.9%, controls 2.0%. Nicotine has no adverse effects on GV break down, but induces spindle and chromosome defects compromising oocyte meiotic maturation and development.

  18. Induction of chromosome instability and stomach cancer by altering the expression pattern of mitotic checkpoint genes in mice exposed to areca-nut

    International Nuclear Information System (INIS)

    There are strong indications for a causal association between areca-nut consumption and cancers. In Meghalaya, India, the variety of areca-nut is used as raw and unprocessed form whose chemical composition and pharmacological actions have been reported. Yet we know little on the initial pathway involved in areca-nut associated carcinogenesis since it is difficult to assess its effects on genetic alterations without interference of other compounding factors. Therefore, present study was undertaken in mice to verify the ability of raw areca-nut (RAN) to induce cancer and to monitor the expression of certain genes involved in carcinogenesis. This study was not intended to isolate any active ingredients from the RAN and to look its action. Three groups of mice (n = 25 in each) were taken and used at different time-points for different experimental analysis. The other three groups of mice (n = 15 in each) were considered for tumor induction studies. In each set, two groups were administered RAN-extract ad libitum in drinking water with or without lime. The expression of certain genes was assessed by conventional RT-PCR and immunoblotting. The mice were given the whole RAN-extract with and without lime in order to mimic the human consumption style of RAN. Histological preparation of stomach tissue revealed that RAN induced stomach cancer. A gradual increase in the frequency of precocious anaphase and aneuploid cells was observed in the bone marrow cells with a greater increment following RAN + lime administeration. Levels of p53, Bax, Securin and p65 in esophageal and stomach cells were elevated during early days of RAN exposure while those of different mitotic checkpoint proteins were downregulated. Apoptotic cell death was detected in non-cancerous stomach cells but not in tumor cells which showed overexpression of Bax and absence of PARP. Present study suggested (a) RAN induces stomach cancer, however, presence of lime promoted higher cell transformation and thereby

  19. 二倍体和同源四倍体‘辣椒枣’减数分裂的比较%Meiotic Observations of Pollen Mother Cells in Diploid and Autotetraploid Ziziphus jujuba Mill.'Lajiaozao'

    Institute of Scientific and Technical Information of China (English)

    吴改娥; 刘平; 刘孟军; 刘冠楠

    2011-01-01

    Meiosis of pollen mother cells (PMCs) in diploid and autotetraploid ‘ Lajiaozao’ Chinese jujube were observed, and all stages of the meiosis were analyzed. The results showed that the behavior of meiosis in autotetraploid was much more complicated than that in diploid. Compared with meiosis in diploid, the behavior of meiosis in autotetraploid was much more complicated. Diakinesis, univalents,bivalents, trivalents and quadrivalents appeared in autotetraploid ‘Lajiaozao’, while two nuclei, including a large one and a small one, were observed. Some of the chromosomes were found not being arranged on equatorial plate at metaphase Ⅰ and metaphase Ⅱ followed by lagged chromosomes and chromosome bridges appeared at anaphase Ⅰ and anaphase Ⅱ in the autotetraploid. At tetrad stage, dyads, triads with micronucleus, tetrads with micronucleus appeared. In conclusion, abnormal meiosis of PMCs is the cytogenetic reason for fertility reduction in autotetraploid ‘Lajiaozao’%观察了‘辣椒枣’(Ziziphus jujuba Mill.‘Lajiaozao’)二倍体和四倍体花粉母细胞的减数分裂过程,并将其减数分裂的各个时期加以系统分析.结果表明,与二倍体相比,同源四倍体终变期染色体构型复杂,有单价体、二价体、三价体和四价体出现,并且此时期出现双核仁,且核仁一大一小;中期Ⅰ和中期Ⅱ有部分染色体游离于赤道板外:后期Ⅰ和后期Ⅱ出现落后染色体及染色体桥现象;四分体时期还出现了二分体、含微核的异常三分体和含微核的异常四分体;减数分裂行为异常是同源四倍体‘辣椒枣'育性降低的细胞学原因.

  20. lemmingA encodes the Apc11 subunit of the APC/C in Drosophila melanogaster that forms a ternary complex with the E2-C type ubiquitin conjugating enzyme, Vihar and Morula/Apc2

    Directory of Open Access Journals (Sweden)

    Nagy Olga

    2012-03-01

    Full Text Available Abstract Background Ubiquitin-dependent protein degradation is a critical step in key cell cycle events, such as metaphase-anaphase transition and mitotic exit. The anaphase promoting complex/cyclosome (APC/C plays a pivotal role in these transitions by recognizing and marking regulatory proteins for proteasomal degradation. Its overall structure and function has been elucidated mostly in yeasts and mammalian cell lines. The APC/C is, however, a multisubunit assembly with at least 13 subunits and their function and interaction within the complex is still relatively uncharacterized, particularly in metazoan systems. Here, lemming (lmg mutants were used to study the APC/C subunit, Apc11, and its interaction partners in Drosophila melanogaster. Results The lmg gene was initially identified through a pharate adult lethal P element insertion mutation expressing developmental abnormalities and widespread apoptosis in larval imaginal discs and pupal abdominal histoblasts. Larval neuroblasts were observed to arrest mitosis in a metaphase-like state with highly condensed, scattered chromosomes and frequent polyploidy. These neuroblasts contain high levels of both cyclin A and cyclin B. The lmg gene was cloned by virtue of the lmg03424 P element insertion which is located in the 5' untranslated region. The lemming locus is transcribed to give a 2.0 kb mRNA that contains two ORFs, lmgA and lmgB. The lmgA ORF codes for a putative protein with more than 80% sequence homology to the APC11 subunit of the human APC/C. The 85 amino acid protein also contains a RING-finger motif characteristic of known APC11 subunits. The lmgA ORF alone was sufficient to rescue the lethal and mitotic phenotypes of the lmg138 null allele and to complement the temperature sensitive lethal phenotype of the APC11-myc9 budding yeast mutant. The LmgA protein interacts with Mr/Apc2, and they together form a binding site for Vihar, the E2-C type ubiquitin conjugating enzyme. Despite

  1. Characterization of novel MPS1 inhibitors with preclinical anticancer activity.

    Science.gov (United States)

    Jemaà, M; Galluzzi, L; Kepp, O; Senovilla, L; Brands, M; Boemer, U; Koppitz, M; Lienau, P; Prechtl, S; Schulze, V; Siemeister, G; Wengner, A M; Mumberg, D; Ziegelbauer, K; Abrieu, A; Castedo, M; Vitale, I; Kroemer, G

    2013-11-01

    Monopolar spindle 1 (MPS1), a mitotic kinase that is overexpressed in several human cancers, contributes to the alignment of chromosomes to the metaphase plate as well as to the execution of the spindle assembly checkpoint (SAC). Here, we report the identification and functional characterization of three novel inhibitors of MPS1 of two independent structural classes, N-(4-{2-[(2-cyanophenyl)amino][1,2,4]triazolo[1,5-a]pyridin-6-yl}phenyl)-2-phenylacetamide (Mps-BAY1) (a triazolopyridine), N-cyclopropyl-4-{8-[(2-methylpropyl)amino]-6-(quinolin-5-yl)imidazo[1,2-a]pyrazin-3-yl}benzamide (Mps-BAY2a) and N-cyclopropyl-4-{8-(isobutylamino)imidazo[1,2-a]pyrazin-3-yl}benzamide (Mps-BAY2b) (two imidazopyrazines). By selectively inactivating MPS1, these small inhibitors can arrest the proliferation of cancer cells, causing their polyploidization and/or their demise. Cancer cells treated with Mps-BAY1 or Mps-BAY2a manifested multiple signs of mitotic perturbation including inefficient chromosomal congression during metaphase, unscheduled SAC inactivation and severe anaphase defects. Videomicroscopic cell fate profiling of histone 2B-green fluorescent protein-expressing cells revealed the capacity of MPS1 inhibitors to subvert the correct timing of mitosis as they induce a premature anaphase entry in the context of misaligned metaphase plates. Hence, in the presence of MPS1 inhibitors, cells either divided in a bipolar (but often asymmetric) manner or entered one or more rounds of abortive mitoses, generating gross aneuploidy and polyploidy, respectively. In both cases, cells ultimately succumbed to the mitotic catastrophe-induced activation of the mitochondrial pathway of apoptosis. Of note, low doses of MPS1 inhibitors and paclitaxel (a microtubular poison) synergized at increasing the frequency of chromosome misalignments and missegregations in the context of SAC inactivation. This resulted in massive polyploidization followed by the activation of mitotic catastrophe. A

  2. Genetic analysis of the spindle checkpoint genes san-1, mdf-2, bub-3 and the CENP-F homologues hcp-1 and hcp-2 in Caenorhabditis elegans

    Directory of Open Access Journals (Sweden)

    Moore Landon L

    2008-02-01

    Full Text Available Abstract Background The spindle checkpoint delays the onset of anaphase until all sister chromatids are aligned properly at the metaphase plate. To investigate the role san-1, the MAD3 homologue, has in Caenorhabditis elegans embryos we used RNA interference (RNAi to identify genes synthetic lethal with the viable san-1(ok1580 deletion mutant. Results The san-1(ok1580 animal has low penetrating phenotypes including an increased incidence of males, larvae arrest, slow growth, protruding vulva, and defects in vulva morphogenesis. We found that the viability of san-1(ok1580 embryos is significantly reduced when HCP-1 (CENP-F homologue, MDF-1 (MAD-1 homologue, MDF-2 (MAD-2 homologue or BUB-3 (predicted BUB-3 homologue are reduced by RNAi. Interestingly, the viability of san-1(ok1580 embryos is not significantly reduced when the paralog of HCP-1, HCP-2, is reduced. The phenotype of san-1(ok1580;hcp-1(RNAi embryos includes embryonic and larval lethality, abnormal organ development, and an increase in abnormal chromosome segregation (aberrant mitotic nuclei, anaphase bridging. Several of the san-1(ok1580;hcp-1(RNAi animals displayed abnormal kinetochore (detected by MPM-2 and microtubule structure. The survival of mdf-2(RNAi;hcp-1(RNAi embryos but not bub-3(RNAi;hcp-1(RNAi embryos was also compromised. Finally, we found that san-1(ok1580 and bub-3(RNAi, but not hcp-1(RNAi embryos, were sensitive to anoxia, suggesting that like SAN-1, BUB-3 has a functional role as a spindle checkpoint protein. Conclusion Together, these data suggest that in the C. elegans embryo, HCP-1 interacts with a subset of the spindle checkpoint pathway. Furthermore, the fact that san-1(ok1580;hcp-1(RNAi animals had a severe viability defect whereas in the san-1(ok1580;hcp-2(RNAi and san-1(ok1580;hcp-2(ok1757 animals the viability defect was not as severe suggesting that hcp-1 and hcp-2 are not completely redundant.

  3. Microcystin-LR induces abnormal root development by altering microtubule organization in tissue-cultured common reed (Phragmites australis) plantlets.

    Science.gov (United States)

    Máthé, Csaba; Beyer, Dániel; Erdodi, Ferenc; Serfozo, Zoltán; Székvölgyi, Lóránt; Vasas, Gábor; M-Hamvas, Márta; Jámbrik, Katalin; Gonda, Sándor; Kiss, Andrea; Szigeti, Zsuzsa M; Surányi, Gyula

    2009-05-01

    Microcystin-LR (MC-LR) is a heptapeptide cyanotoxin, known to be a potent inhibitor of type 1 and 2A protein phosphatases in eukaryotes. Our aim was to investigate the effect of MC-LR on the organization of microtubules and mitotic chromatin in relation to its possible effects on cell and whole organ morphology in roots of common reed (Phragmites australis). P. australis is a widespread freshwater and brackish water aquatic macrophyte, frequently exposed to phytotoxins in eutrophic waters. Reed plantlets regenerated from embryogenic calli were treated with 0.001-40 microg ml(-1) (0.001-40.2 microM) MC-LR for 2-20 days. At 0.5 microg ml(-1) MC-LR and at higher cyanotoxin concentrations, the inhibition of protein phosphatase activity by MC-LR induced alterations in reed root growth and morphology, including abnormal lateral root development and the radial swelling of cells in the elongation zone of primary and lateral roots. Both short-term (2-5 days) and long-term (10-20 days) of cyanotoxin treatment induced microtubule disruption in meristems and in the elongation and differentiation zones. Microtubule disruption was accompanied by root cell shape alteration. At concentrations of 0.5-5 microg ml(-1), MC-LR increased mitotic index at long-term exposure and induced the increase of the percentage of meristematic cells in prophase as well as telophase and cytokinesis of late mitosis. High cyanotoxin concentrations (10-40 microg ml(-1)) inhibited mitosis at as short as 2 days of exposure. The alteration of microtubule organization was observed in mitotic cells at all exposure periods studied, at cyanotoxin concentrations of 0.5-40 microg ml(-1). MC-LR induced spindle anomalies at the metaphase-anaphase transition, the formation of asymmetric anaphase spindles and abnormal sister chromatid separation. This paper reports for the first time that MC-LR induces cytoskeletal changes that lead to alterations of root architecture and development in common reed and generally, in

  4. Effects of Lead on the Morphology and Structure of the Nucleolus in the Root Tip Meristematic Cells of Allium cepa L.

    Directory of Open Access Journals (Sweden)

    Ze Jiang

    2014-07-01

    Full Text Available To study the toxic mechanisms of lead (Pb in plants, the effects of Pb on the morphology and structure of the nucleolus in root tip meristematic cells of Allium cepa var. agrogarum L. were investigated. Fluorescence labeling, silver-stained indirect immunofluorescent microscopy and western blotting were used. Fluorescence labeling showed that Pb ions were localized in the meristematic cells and the uptake and accumulation of Pb increased with treatment time. At low concentrations of Pb (1–10 μM there were persistent nucleoli in some cells during mitosis, and at high concentration (100 μM many of the nucleolar organizing regions were localized on sticky chromosomes in metaphase and anaphase cells. Pb induced the release of particles containing argyrophilic proteins to be released from the nucleus into the cytoplasm. These proteins contained nucleophosmin and nucleolin. Pb also caused the extrusion of fibrillarin from the nucleus into the cytoplasm. Western blotting demonstrated the increased expression of these three major nucleolar proteins under Pb stress.

  5. Quantitative phosphoproteomics reveals new roles for the protein phosphatase PP6 in mitotic cells.

    Science.gov (United States)

    Rusin, Scott F; Schlosser, Kate A; Adamo, Mark E; Kettenbach, Arminja N

    2015-10-13

    Protein phosphorylation is an important regulatory mechanism controlling mitotic progression. Protein phosphatase 6 (PP6) is an essential enzyme with conserved roles in chromosome segregation and spindle assembly from yeast to humans. We applied a baculovirus-mediated gene silencing approach to deplete HeLa cells of the catalytic subunit of PP6 (PP6c) and analyzed changes in the phosphoproteome and proteome in mitotic cells by quantitative mass spectrometry-based proteomics. We identified 408 phosphopeptides on 272 proteins that increased and 298 phosphopeptides on 220 proteins that decreased in phosphorylation upon PP6c depletion in mitotic cells. Motif analysis of the phosphorylated sites combined with bioinformatics pathway analysis revealed previously unknown PP6c-dependent regulatory pathways. Biochemical assays demonstrated that PP6c opposed casein kinase 2-dependent phosphorylation of the condensin I subunit NCAP-G, and cellular analysis showed that depletion of PP6c resulted in defects in chromosome condensation and segregation in anaphase, consistent with dysregulation of condensin I function in the absence of PP6 activity. PMID:26462736

  6. Carbamazepine induces mitotic arrest in mammalian Vero cells

    International Nuclear Information System (INIS)

    We reported recently that the anticonvulsant drug carbamazepine, at supratherapeutic concentrations, exerts antiproliferative effects in mammalian Vero cells, but the underlying mechanism has not been elucidated. This motivates us to examine rigorously whether growth arrest was associated with structural changes in cellular organization during mitosis. In the present work, we found that exposure of the cells to carbamazepine led to an increase in mitotic index, mainly due to the sustained block at the metaphase/anaphase boundary, with the consequent inhibition of cell proliferation. Indirect immunofluorescence, using antibodies directed against spindle apparatus proteins, revealed that mitotic arrest was associated with formation of monopolar spindles, caused by impairment of centrosome separation. The final consequence of the spindle defects induced by carbamazepine, depended on the duration of cell cycle arrest. Following the time course of accumulation of metaphase and apoptotic cells during carbamazepine treatments, we observed a causative relationship between mitotic arrest and induction of cell death. Conversely, cells released from the block of metaphase by removal of the drug, continued to progress through mitosis and resume normal proliferation. Our results show that carbamazepine shares a common antiproliferative mechanism with spindle-targeted drugs and contribute to a better understanding of the cytostatic activity previously described in Vero cells. Additional studies are in progress to extend these initial findings that define a novel mode of action of carbamazepine in cultured mammalian cells

  7. Is the LIM-domain protein HaWLIM1 associated with cortical microtubules in sunflower protoplasts?

    Science.gov (United States)

    Brière, Christian; Bordel, Anne-Claire; Barthou, Henri; Jauneau, Alain; Steinmetz, André; Alibert, Gilbert; Petitprez, Michel

    2003-10-01

    Flowering plants express several LIM-domain proteins related to the animal cystein-rich proteins. The expression of sunflower LIM genes was followed by RT-PCR in cultured sunflower protoplasts. A transcript was detected only for HaWLIM1, but not for the other two genes HaPLIM1 and HaPLIM2. Polyclonal antibodies raised against either full length recombinant HaWLIM1 protein or peptides recognized a 27 kDa polypeptide on Western blots. Immunocytolocalization studies showed that HaWLIM1 is located in the cytoplasm and in the nucleus. In the cytoplasm, HaWLIM1 is localized in punctate structures, distributed along microtubule bundles. Depolymerizing microtubules with oryzalin resulted in a strong modification of the HaWLIM1 cortical pattern. In contrast, treatment of protoplasts with latrunculin B, which disrupts actin filaments, had no effect on HaWLIM1 localization. HaWLIM1 was also located within the nucleus of interphase protoplasts. During mitosis, nuclear labelling was observed in prophase, which decreased in metaphase, disappeared in anaphase, and recovered in telophase. These results suggest a dual role for HaWLIM1: in the cytoplasm, as a component of molecular complexes which may interact with microtubules, and in the nucleus, as a partner of transcription factors during interphase. PMID:14581630

  8. Detection of potential genetic hazards in complex environmental mixtures using plant cytogenetics and microbial mutagenesis assays. [Arsenic-contaminated groundwater and power plant fly ash extract

    Energy Technology Data Exchange (ETDEWEB)

    Constantin, M J; Lowe, K; Rao, T K; Larimer, F W; Epler, J L

    1980-01-01

    Solid wastes have been characterized to determine their potential hazards to humans and the environment. An arsenic-contaminated ground water sample increased the frequency of histidine revertants in Salmonella typhimurium (TA-98) at 0.025 to 5.000 ..mu..l per plate with Aroclor-induced S-9 liver microsomes. When 2.5 to 75 ..mu..l of the XAD-2 concentrate (12.5-fold, v:v) were used, the mutant frequency was increased in strains TA-98, TA-100, and TA-1537; metabolic activation was not required. Only the XAD-2 concentrate was mutagenic in the Saccharomyces cerevisiae haploid strain XL-7-10B; metabolic activation was not required. The mutagenic principal, which is not known, appears to be at the limit of resolution; hence, the XAD-2 concentration is necessary to demonstrate mutagenic activity. The arsenic-contaminated ground water (0.0625 and 0.125 dilutions) and the power plant fly ash extract (undiluted) increased the frequency of bridges and fragements at anaphase in root tip cells of Hordeum. The fly ash sample was negative in the microbial assays. Results emphasize (1) the need for a battery of assays with different organisms and (2) the potential of a simple assay using plant root tip cells to detect mutagenic activity in complex environmental mixtures.

  9. Redistribution of the nuclear mitotic apparatus protein (NuMA) during mitosis and nuclear assembly. Properties of purified NuMA protein.

    Science.gov (United States)

    Price, C M; Pettijohn, D E

    1986-10-01

    Monoclonal antibodies and human autoimmune sera specific for the nuclear mitotic apparatus protein (NuMA protein) were applied to study the structure of this protein and its intracellular distribution. The NuMA protein was purified using immuno-affinity columns. Studies on this large (250 kD) nuclear protein indicated that it is a highly asymmetric phosphoprotein. It is present in all mammalian cells examined and in those of some non-mammals. Immunofluorescence studies on fixed cells demonstrated that its intracellular distribution is essentially the same in all species at all stages of the cell cycle. Immunoblot (western blot) analysis showed that the size of the NuMA protein varies slightly in different species. At the onset of mitosis the NuMA protein redistributes from the nucleus to two centrosomal structures that later will become part of the mitotic spindle pole. This occurs at the time of nuclear breakdown and eventually leads to an accumulation of the NuMA protein at the polar region of the mitotic spindle. After anaphase the protein redistributes from the spindle polar region into the reforming nucleus and concentrates initially at the site where nuclear lamins and perichomatin have been reported to assemble. Living cells microinjected with fluorescent anti-NuMA antibodies were studied to examine parameters that effect the redistribution of the NuMA protein in vivo. These experiments indicate that microtubule assembly is essential for the NuMA protein to accumulate in the polar region. PMID:3527729

  10. The effects of proteasome inhibitor lactacystin on mouse oocyte meiosis and first cleavage

    Institute of Scientific and Technical Information of China (English)

    TAN; Xin; PENG; An; WANG; Yongchao; TANG; Zuoqing

    2005-01-01

    In order to study the effects of ubiquitin-proteasome pathway (UPP) on mouse oocyte meiosis and cleavage, oocytes undergoing maturation and parthenogenetic activation and 1-cell embryos were treated with lactacystin, a specific inhibitor of proteasome. The results indicared that the rate of GVBD was not influenced by the treatment, but polar body extrusion, parthenogenesis and first cleavage were inhibited. Immunofluorescent staining using anti β-tubulin antibody indicated that the continuous treatment of lactacystin from GV stage disorganized microtubules and spindle assembly. When metaphase stage oocytes were treated with the drug,the already formed spindle structure was not affected, but the oocytes were arrested at metaphases. The 1-cell embryos were arrested at interphase or metaphase of first mitosis when they were incubated in the drug. Proteasome regulatory subunit PA700 was located in the spindle region, as indicated by immunofluorescence. These results suggest that UPP has effects on the process of oocyte meiosis and early cleavage in many aspects, including normal organization of spindle at prophase and segregation of chromosomes at anaphase for normal meiosis.

  11. PP2A(Cdc55)'s role in reductional chromosome segregation during achiasmate meiosis in budding yeast is independent of its FEAR function.

    Science.gov (United States)

    Kerr, Gary W; Wong, Jin Huei; Arumugam, Prakash

    2016-01-01

    PP2A(Cdc55) is a highly conserved serine-threonine protein phosphatase that is involved in diverse cellular processes. In budding yeast, meiotic cells lacking PP2A(Cdc55) activity undergo a premature exit from meiosis I which results in a failure to form bipolar spindles and divide nuclei. This defect is largely due to its role in negatively regulating the Cdc Fourteen Early Anaphase Release (FEAR) pathway. PP2A(Cdc55) prevents nucleolar release of the Cdk (Cyclin-dependent kinase)-antagonising phosphatase Cdc14 by counteracting phosphorylation of the nucleolar protein Net1 by Cdk. CDC55 was identified in a genetic screen for monopolins performed by isolating suppressors of spo11Δ spo12Δ lethality suggesting that Cdc55 might have a role in meiotic chromosome segregation. We investigated this possibility by isolating cdc55 alleles that suppress spo11Δ spo12Δ lethality and show that this suppression is independent of PP2A(Cdc55)'s FEAR function. Although the suppressor mutations in cdc55 affect reductional chromosome segregation in the absence of recombination, they have no effect on chromosome segregation during wild type meiosis. We suggest that Cdc55 is required for reductional chromosome segregation during achiasmate meiosis and this is independent of its FEAR function. PMID:27455870

  12. Meiosis, egg activation, and nuclear envelope breakdown are differentially reliant on Ca2+, whereas germinal vesicle breakdown is Ca2+ independent in the mouse oocyte

    Science.gov (United States)

    Tombes, R. M.; Simerly, C.; Borisy, G. G.; Schatten, G.

    1992-01-01

    During early development, intracellular Ca2+ mobilization is not only essential for fertilization, but has also been implicated during other meiotic and mitotic events, such as germinal vesicle breakdown (GVBD) and nuclear envelope breakdown (NEBD). In this study, the roles of intracellular and extracellular Ca2+ were examined during meiotic maturation and reinitiation at parthenogenetic activation and during first mitosis in a single species using the same methodologies. Cumulus-free metaphase II mouse oocytes immediately resumed anaphase upon the induction of a large, transient Ca2+ elevation. This resumption of meiosis and associated events, such as cortical granule discharge, were not sensitive to extracellular Ca2+ removal, but were blocked by intracellular Ca2+ chelators. In contrast, meiosis I was dependent on external Ca2+; in its absence, the formation and function of the first meiotic spindle was delayed, the first polar body did not form and an interphase-like state was induced. GVBD was not dependent on external Ca2+ and showed no associated Ca2+ changes. NEBD at first mitosis in fertilized eggs, on the other hand, was frequently, but not always associated with a brief Ca2+ transient and was dependent on Ca2+ mobilization. We conclude that GVBD is Ca2+ independent, but that the dependence of NEBD on Ca2+ suggests regulation by more than one pathway. As cells develop from Ca(2+)-independent germinal vesicle oocytes to internal Ca(2+)-dependent pronuclear eggs, internal Ca2+ pools increase by approximately fourfold.

  13. The role of meiotic cohesin REC8 in chromosome segregation in {gamma} irradiation-induced endopolyploid tumour cells

    Energy Technology Data Exchange (ETDEWEB)

    Erenpreisa, Jekaterina [Latvian Biomedicine Research and Study Centre, Riga, LV-1067 (Latvia); Cragg, Mark S. [Tenovus Laboratory, Cancer Sciences Division, Southampton University School of Medicine, General Hospital, Southampton SO16 6YD (United Kingdom); Salmina, Kristine [Latvian Biomedicine Research and Study Centre, Riga, LV-1067 (Latvia); Hausmann, Michael [Kirchhoff Inst. fuer Physik, Univ. of Heidelberg, D-69120 Heidelberg (Germany); Scherthan, Harry, E-mail: scherth@web.de [Inst. fuer Radiobiologie der Bundeswehr in Verbindung mit der Univ. Ulm, D-80937 Munich (Germany); MPI for Molec. Genetics, 14195 Berlin (Germany)

    2009-09-10

    Escape from mitotic catastrophe and generation of endopolyploid tumour cells (ETCs) represents a potential survival strategy of tumour cells in response to genotoxic treatments. ETCs that resume the mitotic cell cycle have reduced ploidy and are often resistant to these treatments. In search for a mechanism for genome reduction, we previously observed that ETCs express meiotic proteins among which REC8 (a meiotic cohesin component) is of particular interest, since it favours reductional cell division in meiosis. In the present investigation, we induced endopolyploidy in p53-dysfunctional human tumour cell lines (Namalwa, WI-L2-NS, HeLa) by gamma irradiation, and analysed the sub-cellular localisation of REC8 in the resulting ETCs. We observed by RT-PCR and Western blot that REC8 is constitutively expressed in these tumour cells, along with SGOL1 and SGOL2, and that REC8 becomes modified after irradiation. REC8 localised to paired sister centromeres in ETCs, the former co-segregating to opposite poles. Furthermore, REC8 localised to the centrosome of interphase ETCs and to the astral poles in anaphase cells where it colocalised with the microtubule-associated protein NuMA. Altogether, our observations indicate that radiation-induced ETCs express features of meiotic cell divisions and that these may facilitate chromosome segregation and genome reduction.

  14. PP2ACdc55’s role in reductional chromosome segregation during achiasmate meiosis in budding yeast is independent of its FEAR function

    Science.gov (United States)

    Kerr, Gary W.; Wong, Jin Huei; Arumugam, Prakash

    2016-01-01

    PP2ACdc55 is a highly conserved serine-threonine protein phosphatase that is involved in diverse cellular processes. In budding yeast, meiotic cells lacking PP2ACdc55 activity undergo a premature exit from meiosis I which results in a failure to form bipolar spindles and divide nuclei. This defect is largely due to its role in negatively regulating the Cdc Fourteen Early Anaphase Release (FEAR) pathway. PP2ACdc55 prevents nucleolar release of the Cdk (Cyclin-dependent kinase)-antagonising phosphatase Cdc14 by counteracting phosphorylation of the nucleolar protein Net1 by Cdk. CDC55 was identified in a genetic screen for monopolins performed by isolating suppressors of spo11Δ spo12Δ lethality suggesting that Cdc55 might have a role in meiotic chromosome segregation. We investigated this possibility by isolating cdc55 alleles that suppress spo11Δ spo12Δ lethality and show that this suppression is independent of PP2ACdc55’s FEAR function. Although the suppressor mutations in cdc55 affect reductional chromosome segregation in the absence of recombination, they have no effect on chromosome segregation during wild type meiosis. We suggest that Cdc55 is required for reductional chromosome segregation during achiasmate meiosis and this is independent of its FEAR function. PMID:27455870

  15. Early development of Drosophila embryos requires Smc5/6 function during oogenesis

    Directory of Open Access Journals (Sweden)

    Martin Tran

    2016-07-01

    Full Text Available Mutations in structural maintenance of chromosomes (Smc proteins are frequently associated with chromosomal abnormalities commonly observed in developmental disorders. However, the role of Smc proteins in development still remains elusive. To investigate Smc5/6 function during early embryogenesis we examined smc5 and smc6 mutants of the fruit fly Drosophila melanogaster using a combination of reverse genetics and microscopy approaches. Smc5/6 exhibited a maternally contributed function in maintaining chromosome stability during early embryo development, which manifested as female subfertility in its absence. Loss of Smc5/6 caused an arrest and a considerable delay in embryo development accompanied by fragmented nuclei and increased anaphase-bridge formation, respectively. Surprisingly, early embryonic arrest was attributable to the absence of Smc5/6 during oogenesis, which resulted in insufficient repair of pre-meiotic and meiotic DNA double-strand breaks. Thus, our findings contribute to the understanding of Smc proteins in higher eukaryotic development by highlighting a maternal function in chromosome maintenance and a link between oogenesis and early embryogenesis.

  16. Early development of Drosophila embryos requires Smc5/6 function during oogenesis.

    Science.gov (United States)

    Tran, Martin; Tsarouhas, Vasilios; Kegel, Andreas

    2016-01-01

    Mutations in structural maintenance of chromosomes (Smc) proteins are frequently associated with chromosomal abnormalities commonly observed in developmental disorders. However, the role of Smc proteins in development still remains elusive. To investigate Smc5/6 function during early embryogenesis we examined smc5 and smc6 mutants of the fruit fly Drosophila melanogaster using a combination of reverse genetics and microscopy approaches. Smc5/6 exhibited a maternally contributed function in maintaining chromosome stability during early embryo development, which manifested as female subfertility in its absence. Loss of Smc5/6 caused an arrest and a considerable delay in embryo development accompanied by fragmented nuclei and increased anaphase-bridge formation, respectively. Surprisingly, early embryonic arrest was attributable to the absence of Smc5/6 during oogenesis, which resulted in insufficient repair of pre-meiotic and meiotic DNA double-strand breaks. Thus, our findings contribute to the understanding of Smc proteins in higher eukaryotic development by highlighting a maternal function in chromosome maintenance and a link between oogenesis and early embryogenesis. PMID:27288507

  17. The Meiotic Behavior of an Alien Chromosome in Triticum aestivum-Haynaldia villosa Monosomic Addition Lines

    Institute of Scientific and Technical Information of China (English)

    LI Rui-fen; LIANG Hong-xia; ZHAO Mao-lin

    2002-01-01

    By the combination of cytological analysis and using genomic in situ hybridization technique to identify an alien chromosome in wheat-Haynaldia villosa monosomic addition lines, we studied the meiotic behavior of the alien chromosome. The results indicated that the frequency of bivalent pairing was lower than the value expected in PMCs of two monosomic addition lines, the frequency of wheat chromosomes unpairing increased, and the wheat homologous chromosome pairing was interfered with by the added chromosome 6V at metaphase I. The chromosome 6V lagged in 20.3% -29.3% of PMCs, sister chromatids 6V early divided in 29.0% - 34.1% of PMCs, the single chromosome 6V in 18.2% - 26.1% of PMCs went to a pole randomly,the breakage frequency of chromosome 6V was 1.2% - 2.9%. Meanwhile, it was also found that several wheat chromosomes showed earlier division, lagging and breakage in a few PMCs. It revealed that the added chromosome 6V influenced the behavior of wheat chromosomes at anaphase. It was also found that the translocation was produced between 6V and wheat chromosomes in 1.2% of PMCs. It offered evidence for translocation between wheat and Haynaldia villosa 6V chromosomes.

  18. Cytogenetic Effects of Low Dose Radiation in Mammalian Cells Analysis of the Phenomenon Hypersensitivity and Induced Radioresistence

    CERN Document Server

    Shmakova, N L; Nasonova, E A; Krasavin, E A; Rsjanina, A V

    2001-01-01

    The induction of cytogenetic damage after irradiation of chinese hamster cells and human melanoma cells within dose range 1-200 cGy was studied. The anaphase and metaphase analysis of chromosome damage and micronuclei test were applied. The hypersensitivity (HRS) at doses below 20 cGy and the increased radioresistence at higher doses (IR) were shown with all cytogenetic criteria for both cell lines. The phenomenon of HRS/IR was reproduced in synchronic as well as in asynchronic population of chinese hamster cells. This fact shows that HRS was caused by high radiosensitivity of all cells and can not be explained by any differential sensitivity of cells in different phases of the cell cycle. So it was supposed that the increasing radioresistence is determined by the inclusion of the inducible repair processes in all cells. This conclusion agress with the fact that there was no evidence of HRS on dose-effect curves and that some part of pre-existent damage was repaired after preliminary irradiation with low dose...

  19. Effects of varying doses of gamma radiation on locally adapted Tradescantia clone 02 (BNL) (Brookhaven National Laboratory)

    International Nuclear Information System (INIS)

    This study determined the effects of gamma radiation on the meiotic cells of Tradescantia bracteata clone 02 (BNL). The flower buds collected were exposed through dosages ranging from 1 Gy to 5 Gy using gamma cell 220 machine (AECL) in a central axis position (c/a) and grown in Peralta's solution for three days. Out of the twenty buds designated for each dosages, ten buds were treated with 0.05% colchicine solution. The occurrence of micronuclei among the irradiated pollen mother cells suggested a linear relation with the quantity of radiation dose. The occurrence of MN among cells increased linearly from 1 Gy until it reached 3 Gy and 4 Gy. Beyond this maximum dose, cells were less responsive to the dose caused by inhibition of cell division, as demonstrated in the buds exposed to 5 Gy. This result was validated through the kruskal-Wallis test, where the computed h value was 3.44 (critical region of X20.05 = 9.49) Experimental results also showed chromosomal breaks, sticky chromosomes, and anaphase bridges in the pollen mother cells of irradiated buds. A significant numbers of cells were also found to have micronuclei, which may vary from 1 to 6 per pollen mother cell, and this showed no relationship with radiation dose. (Author)

  20. Timely Closure of the Prospore Membrane Requires SPS1 and SPO77 in Saccharomyces cerevisiae.

    Science.gov (United States)

    Paulissen, Scott M; Slubowski, Christian J; Roesner, Joseph M; Huang, Linda S

    2016-07-01

    During sporulation in Saccharomyces cerevisiae, a double lipid bilayer called the prospore membrane is formed de novo, growing around each meiotic nucleus and ultimately closing to create four new cells within the mother cell. Here we show that SPS1, which encodes a kinase belonging to the germinal center kinase III family, is involved in prospore membrane development and is required for prospore membrane closure. We find that SPS1 genetically interacts with SPO77 and see that loss of either gene disrupts prospore membrane closure in a similar fashion. Specifically, cells lacking SPS1 and SPO77 produce hyperelongated prospore membranes from which the leading edge protein complex is not removed from the prospore membrane in a timely fashion. The SPS1/SPO77 pathway is required for the proper phosphorylation and stability of Ssp1, a member of the leading edge protein complex that is removed and degraded when the prospore membrane closes. Genetic dissection of prospore membrane closure finds SPS1 and SPO77 act in parallel to a previously described pathway of prospore membrane closure that involves AMA1, an activator of the meiotic anaphase promoting complex. PMID:27182947

  1. Study of Soil Seed Banks in Antaibao Opencast Mine

    Institute of Scientific and Technical Information of China (English)

    HAN Li-jun; BAI Zhong-ke; LI Jin-chuan

    2006-01-01

    A seed germinating method was used to study soil seed banks in dump sites of the Antaibao opencast mine for soil reclamation and ecological rehabilitation. Based on a richness index, a diversity index and an evenness index, the diversity of species of soil seed banks was studied. As well, the progress of vegetation succession in this thoroughly destroyed ecosystem is discussed and the self-renewal ability of the soil seed banks is analyzed. The results indicate that 1) there are 17 plant species belonging to five families with annuals as the dominant species; 2) the soil seed banks at the dump site show great temporal and spatial heterogeneity and 3) the model of Robinia pseudoacacia × Pinus tabulaeformis × Caragana korshinskii in the anaphase is the best among several reclamation models studied. Therefore, with the extension of reclamation time, the correct choice of a reclamation model is quite helpful for the improvement of the self-renewal ability of soil seed banks and for the stability of the ecosystem, which is very important for land reclamation and ecological rehabilitation of the dump sites of the ATB opencast coal mine.

  2. Low cdc27 and high securin expression predict short survival for breast cancer patients.

    Science.gov (United States)

    Talvinen, Kati; Karra, Henna; Pitkänen, Reino; Ahonen, Ilmari; Nykänen, Marjukka; Lintunen, Minnamaija; Söderström, Mirva; Kuopio, Teijo; Kronqvist, Pauliina

    2013-10-01

    Cell cycle regulators cdc27 and securin participate in control of the mitotic checkpoint and survey the mitotic spindle to maintain chromosomal integrity. This is achieved by their functions in metaphase-anaphase transition, DNA damage repair, enhancement of mitotic arrest and apoptosis. We report on the roles of cdc27 and securin in aneuploidy and prognosis of breast cancer. The study comprises 429 breast cancer patients with up to 22 years of follow-up. DNA content was determined by image cytometry, and immunopositivity for cdc27 and securin was based on tissue microarrays. An inverse association between cdc27 and securin expression was observed in both image cytometric and immunohistochemical analyses. Low cdc27 and high securin expression identified patients with significant difference in disease outcome. Cdc27 and securin immunoexpression identified patients at risk of early cancer death within five years from diagnosis. In multivariate analysis, the combination of cdc27 and securin immunohistochemistry was the strongest predictor of cancer death after lymph node status. We demonstrate, for the first time in human breast cancer, the prognostic value of cdc27 and securin immunohistochemistry. Cdc27 and securin appear promising biomarkers for applications in predicting disease progression, prognostication of individual patients and potential in anti-mitotic drug development. PMID:23755904

  3. Cdc20 and securin overexpression predict short-term breast cancer survival

    Science.gov (United States)

    Karra, H; Repo, H; Ahonen, I; Löyttyniemi, E; Pitkänen, R; Lintunen, M; Kuopio, T; Söderström, M; Kronqvist, P

    2014-01-01

    Background: Cdc20 is an essential component of cell division and responsible for anaphase initiation regulated by securin degradation. Cdc20 function is strongly regulated by the spindle assembly checkpoint to ensure the timely separation of sister chromatids and integrity of the genome. We present the first results on Cdc20 in a large clinical breast cancer material. Methods: The study was based on 445 breast cancer patients with up to 20 years of follow-up (mean 10.0 years). DNA content was determined by image cytometry on cell imprints, and Cdc20 and securin immunohistochemistry on tissue microarrays of breast cancer tissue. Results: In our results, high Cdc20 and securin expression was associated with aneuploid DNA content. In prognostic analyses, high Cdc20 immunoexpression alone and in combination with high securin immunoexpression indicated aggressive course of disease and up to 6.8-fold (P<0.001) risk of breast cancer death. Particularly, high Cdc20 and securin immunoexpression identified a patient subgroup with extremely short, on average 2.4 years, breast cancer survival and triple-negative breast cancer (TNBC) subtype. Conclusions: We report for the first time the association of high Cdc20 and securin immunoexpression with extremely poor outcome of breast cancer patients. Our experience indicates that Cdc20 and securin are promising candidates for clinical applications in breast cancer prognostication, especially in the challenging prognostic decisions of TNBC. PMID:24853182

  4. APC/C-Cdh1 coordinates neurogenesis and cortical size during development

    Science.gov (United States)

    Delgado-Esteban, Maria; García-Higuera, Irene; Maestre, Carolina; Moreno, Sergio; Almeida, Angeles

    2013-12-01

    The morphology of the adult brain is the result of a delicate balance between neural progenitor proliferation and the initiation of neurogenesis in the embryonic period. Here we assessed whether the anaphase-promoting complex/cyclosome (APC/C) cofactor, Cdh1—which regulates mitosis exit and G1-phase length in dividing cells—regulates neurogenesis in vivo. We use an embryo-restricted Cdh1 knockout mouse model and show that functional APC/C-Cdh1 ubiquitin ligase activity is required for both terminal differentiation of cortical neurons in vitro and neurogenesis in vivo. Further, genetic ablation of Cdh1 impairs the ability of APC/C to promote neurogenesis by delaying the exit of the progenitor cells from the cell cycle. This causes replicative stress and p53-mediated apoptotic death resulting in decreased number of cortical neurons and cortex size. These results demonstrate that APC/C-Cdh1 coordinates cortical neurogenesis and size, thus posing Cdh1 in the molecular pathogenesis of congenital neurodevelopmental disorders, such as microcephaly.

  5. Breakage-fusion-bridge cycles and de novo telomere formation on broken chromosomes in maize callus cultures.

    Science.gov (United States)

    Santos-Serejo, Janay A; Aguiar-Perecin, Margarida L R

    2016-06-01

    Breakpoints involved in chromosome alterations associated with heterochromatin have been detected in maize plants regenerated from callus culture. A cytogenetic analysis of plants regenerated from a maize callus was performed aiming to analyze the stability of a chromosome 7 bearing a deficiency-duplication (Df-Dp), which was interpreted as derived from a chromatid type breakage-fusion-bridge (BFB) cycle. The Df-Dp chromosome 7 was stable in mitotic and meiotic cells of the regenerated plants. Fluorescence in situ hybridization showed signals of telomeric sequences on the broken chromosome arm and provided evidence of de novo telomere formation. The stability of two types of altered chromosome 7 was investigated in C-banded metaphases from samples of the original callus that were collected during a period of 30-42 months after culture initiation. New alterations involving heterochromatic knobs of chromosomes 7 and 9 were observed. The aberrant chromosomes were stable in the subcultures, thus providing evidence of broken chromosome healing. The examination of anaphases showed the presence of bridges, which was consistent with the occurrence of BFB cycles. De novo telomere formation occurred in euchromatic and heterochromatic chromosome termini. The results point to events of chromosomal evolution that might occur in plants. PMID:27203556

  6. Pathologic mitoses and pathology of mitosis in tumorigenesis

    Directory of Open Access Journals (Sweden)

    RG Steinbeck

    2009-12-01

    Full Text Available The gist of my hypothesis (.. is a certain abnormal chromatin constitution. Each process, which brings about this chromatin constitution, would result in the origin of a malignant tumour. Certainly, I consider irregularities with mitosis as the normal mode of the origin of an incorrectly assembled nucleus. This statement by Boveri (1914 has considered earlier observations of asymmetric divisions in human cancers (Hansemann, 1890. The hypothesis is based on the understanding of mitosis as an equational bipartition of the hereditary substance (Flemming, 1879; Roux, 1883. Latest since it was known that genes are located on chromosomes (Sturtevant, 1913, their balanced transport in anaphase appeared as a condition of correct somatic proliferation. True mitoses guarantee the constancy of terminally differentiated tissues. Politzer (1934 has performed X-ray experiments to investigate abnormal karyokinesis with regard to anomalous chromatin condensation, chromosome breakage, spindle malformation, and failure in cytokinesis. On the basis of light microscopy, further significant progress in understanding the pathology of mitosis was not possible. Tumour cases with reduced chromosome numbers seduced to the idea that mitotic activity is rather under cytoplasmic than under nuclear control (Koller, 1947.

  7. New mitotic regulators released from chromatin

    Directory of Open Access Journals (Sweden)

    Hideki eYokoyama

    2013-12-01

    Full Text Available Faithful action of the mitotic spindle segregates duplicated chromosomes into daughter cells. Perturbations of this process result in chromosome mis-segregation, leading to chromosomal instability and cancer development. Chromosomes are not simply passengers segregated by spindle microtubules but rather play a major active role in spindle assembly. The GTP bound form of the Ran GTPase (RanGTP, produced around chromosomes, locally activates spindle assembly factors. Recent studies have uncovered that chromosomes organize mitosis beyond spindle formation. They distinctly regulate other mitotic events, such as spindle maintenance in anaphase, which is essential for chromosome segregation. Furthermore, the direct function of chromosomes is not only to produce RanGTP but, in addition, to release key mitotic regulators from chromatin. Chromatin-remodeling factors and nuclear pore complex proteins, which have established functions on chromatin in interphase, dissociate from mitotic chromatin and function in spindle assembly or maintenance. Thus, chromosomes actively organize their own segregation using chromatin-releasing mitotic regulators as well as RanGTP.

  8. P190B RhoGAP Regulates Chromosome Segregation in Cancer Cells

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Melissa [Department of Biochemistry and Molecular Biology and the Indiana University Simon Cancer Center, Indiana University School of Medicine, 1234 Notre Dame Avenue, South Bend, IN 46617 (United States); Peddibhotla, Sirisha [Department of Molecular and Human Genetics, Baylor College of Medicine, John P. McGovern Campus, NABS-0250, Houston, TX 77030 (United States); McHenry, Peter [Department of Biology, Southwestern Adventist University, 100 W. Hillcrest, Keene, TX 76059 (United States); Chang, Peggy; Yochum, Zachary; Park, Ko Un; Sears, James Cooper; Vargo-Gogola, Tracy, E-mail: vargo-gogola.1@nd.edu [Department of Biochemistry and Molecular Biology and the Indiana University Simon Cancer Center, Indiana University School of Medicine, 1234 Notre Dame Avenue, South Bend, IN 46617 (United States)

    2012-04-25

    Rho GTPases are overexpressed and hyperactivated in many cancers, including breast cancer. Rho proteins, as well as their regulators and effectors, have been implicated in mitosis, and their altered expression promotes mitotic defects and aneuploidy. Previously, we demonstrated that p190B Rho GTPase activating protein (RhoGAP) deficiency inhibits ErbB2-induced mammary tumor formation in mice. Here we describe a novel role for p190B as a regulator of mitosis. We found that p190B localized to centrosomes during interphase and mitosis, and that it is differentially phosphorylated during mitosis. Knockdown of p190B expression in MCF-7 and Hela cells increased the incidence of aberrant microtubule-kinetochore attachments at metaphase, lagging chromosomes at anaphase, and micronucleation, all of which are indicative of aneuploidy. Cell cycle analysis of p190B deficient MCF-7 cells revealed a significant increase in apoptotic cells with a concomitant decrease in cells in G1 and S phase, suggesting that p190B deficient cells die at the G1 to S transition. Chemical inhibition of the Rac GTPase during mitosis reduced the incidence of lagging chromosomes in p190B knockdown cells to levels detected in control cells, suggesting that aberrant Rac activity in the absence of p190B promotes chromosome segregation defects. Taken together, these data suggest that p190B regulates chromosome segregation and apoptosis in cancer cells. We propose that disruption of mitosis may be one mechanism by which p190B deficiency inhibits tumorigenesis.

  9. The flavonoid eupatorin inactivates the mitotic checkpoint leading to polyploidy and apoptosis

    Energy Technology Data Exchange (ETDEWEB)

    Salmela, Anna-Leena [VTT Technical Research Centre of Finland, Medical Biotechnology, P.O. Box 106, Turku (Finland); Turku Graduate School of Biomedical Sciences, Turku (Finland); Turku Centre for Biotechnology, P.O. Box 123, University of Turku (Finland); Pouwels, Jeroen; Kukkonen-Macchi, Anu [VTT Technical Research Centre of Finland, Medical Biotechnology, P.O. Box 106, Turku (Finland); Waris, Sinikka; Toivonen, Pauliina [Turku Centre for Biotechnology, P.O. Box 123, University of Turku (Finland); Jaakkola, Kimmo [VTT Technical Research Centre of Finland, Medical Biotechnology, P.O. Box 106, Turku (Finland); Maeki-Jouppila, Jenni [VTT Technical Research Centre of Finland, Medical Biotechnology, P.O. Box 106, Turku (Finland); Turku Centre for Biotechnology, P.O. Box 123, University of Turku (Finland); Drug Discovery Graduate School, University of Turku (Finland); Kallio, Lila, E-mail: lila.kallio@vtt.fi [VTT Technical Research Centre of Finland, Medical Biotechnology, P.O. Box 106, Turku (Finland); Kallio, Marko J. [VTT Technical Research Centre of Finland, Medical Biotechnology, P.O. Box 106, Turku (Finland); Turku Centre for Biotechnology, P.O. Box 123, University of Turku (Finland); Centre of Excellence for Translational Genome-Scale Biology, P.O. Box 106, Academy of Finland (Finland)

    2012-03-10

    The spindle assembly checkpoint (SAC) is a conserved mechanism that ensures the fidelity of chromosome distribution in mitosis by preventing anaphase onset until the correct bipolar microtubule-kinetochore attachments are formed. Errors in SAC function may contribute to tumorigenesis by inducing numerical chromosome anomalies (aneuploidy). On the other hand, total disruption of SAC can lead to massive genomic imbalance followed by cell death, a phenomena that has therapeutic potency. We performed a cell-based high-throughput screen with a compound library of 2000 bioactives for novel SAC inhibitors and discovered a plant-derived phenolic compound eupatorin (3 Prime ,5-dihydroxy-4 Prime ,6,7-trimethoxyflavone) as an anti-mitotic flavonoid. The premature override of the microtubule drug-imposed mitotic arrest by eupatorin is dependent on microtubule-kinetochore attachments but not interkinetochore tension. Aurora B kinase activity, which is essential for maintenance of normal SAC signaling, is diminished by eupatorin in cells and in vitro providing a mechanistic explanation for the observed forced mitotic exit. Eupatorin likely has additional targets since eupatorin treatment of pre-mitotic cells causes spindle anomalies triggering a transient M phase delay followed by impaired cytokinesis and polyploidy. Finally, eupatorin potently induces apoptosis in multiple cancer cell lines and suppresses cancer cell proliferation in organotypic 3D cell culture model.

  10. Relationship between plant growth and cytological effect in root apical meristem after exposure of wheat dry seeds to carbon ion beams

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Qingfang [Radiobiology Laboratory, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, Gansu Province 730000 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Wang, Zhuanzi; Zhou, Libin; Qu, Ying; Lu, Dong [Radiobiology Laboratory, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, Gansu Province 730000 (China); Yu, Lixia; Du, Yan [Radiobiology Laboratory, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, Gansu Province 730000 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Jin, Wenjie [Radiobiology Laboratory, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, Gansu Province 730000 (China); Li, Wenjian, E-mail: wjli@impcas.ac.cn [Radiobiology Laboratory, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, Gansu Province 730000 (China)

    2013-06-15

    In order to analyze the relationship between plant growth and cytological effects, wheat dry seeds were exposed to various doses of {sup 12}C{sup 6+} beams and the biological endpoints reflecting plant growth and root apical meristem (RAM) activities were investigated. The results showed that most of the seeds were able to germinate normally within all dose range, while the plant survival rate descended at higher doses. The seedling growth including root length and seedling height also decreased significantly at higher doses. Mitotic index (MI) in RAM had no changes at 10 and 20 Gy and decreased obviously at higher doses and the proportion of prophase cells had the same trend with MI. These data suggested that RAM cells experienced cell cycle arrest, which should be responsible for the inhibition of root growth after exposure to higher doses irradiation. Moreover, various types of chromosome aberrations (CAs) were observed in the mitotic cells. The frequencies of mitotic cells with lagging chromosomes and these with anaphase bridges peaked around 60 Gy, while the frequencies of these with fragments increased as the irradiation doses increased up to 200 Gy. The total frequencies of mitotic cells with CAs induced by irradiation increased significantly with the increasing doses. The serious damage of mitotic chromosomes maybe caused cell cycle arrest or cell death. These findings suggested that the influences of {sup 12}C{sup 6+} beams irradiation on plant growth were related to the alternation of mitotic activities and the chromosomal damages in RAM.

  11. Influence of the stage of the hair cycle on Cd deposition in hair

    International Nuclear Information System (INIS)

    Shortly after a single injection of Cd a much higher deposition of Cd was observed in growing hair (anaphase) than in resting hair (telophase). Shifting the time of the administration in a period ranging from 7 d before the onset of matrix production to full hair growth did not appreciably alter the initial deposition in spite of the rapid decline of Cd in blood plasma. After the initial deposition the concentration decreased in growing as well as in resting hair. In growing hair this is attributed to the addition of new matrix containing less Cd due to its declining supply via blood. In the resting hair it may reflect the decline of Cd in the follicular tissue adhering to the hair roots. The study demonstrates that the deposition of internal Cd in hair occurs mainly in those sections of hair growing at the time of the actual intake of Cd into the organism. The quantity of Cd found in a particular section of hair in the absence of external contamination, indicates first and foremost the quantity of Cd taken up into the blood stream - after ingestion or inhalation -at the time of the actual formation of this section notwithstanding the actual body burden at that time. (author)

  12. Visualization of the chromosome scaffold and intermediates of loop domain compaction in extracted mitotic cells.

    Science.gov (United States)

    Sheval, Eugene V; Polyakov, Vladimir Y

    2006-12-01

    A novel extraction protocol for cells cultured on coverslips is described. Observations of the extraction process in a perfusion chamber reveal that cells of all mitotic stages are not detached from coverslips during extraction, and all stages can be recognized using phase contrast images. We studied the extracted cell morphology and distribution of a major scaffold component - topoisomerase IIalpha, in extracted metaphase and anaphase cells. An extraction using 2M NaCl leads to destruction of chromosomes at the light microscope level. Immunogold studies demonstrate that the only residual structure observed is an axial chromosome scaffold that contains topoisomerase IIalpha. In contrast, mitotic chromosomes are swelled only partially after an extraction using dextran sulphate and heparin, and it appears that this treatment does not lead to total destruction of loop domains. In this case, the chromosome scaffold and numerous structures resembling small rosettes are revealed inside extracted cells. The rosettes observed condense after addition of Mg2+-ions and do not contain topoisomerase IIalpha suggesting that these structures correspond to intermediates of loop domain compaction. We propose a model of chromosome structure in which the loop domains are condensed into highly regular structures with rosette organization. PMID:17029868

  13. Stable kinetochore–microtubule attachment is sufficient to silence the spindle assembly checkpoint in human cells

    Science.gov (United States)

    Tauchman, Eric C.; Boehm, Frederick J.; DeLuca, Jennifer G.

    2015-01-01

    During mitosis, duplicated sister chromatids attach to microtubules emanating from opposing sides of the bipolar spindle through large protein complexes called kinetochores. In the absence of stable kinetochore–microtubule attachments, a cell surveillance mechanism known as the spindle assembly checkpoint (SAC) produces an inhibitory signal that prevents anaphase onset. Precisely how the inhibitory SAC signal is extinguished in response to microtubule attachment remains unresolved. To address this, we induced formation of hyper-stable kinetochore–microtubule attachments in human cells using a non-phosphorylatable version of the protein Hec1, a core component of the attachment machinery. We find that stable attachments are sufficient to silence the SAC in the absence of sister kinetochore bi-orientation and strikingly in the absence of detectable microtubule pulling forces or tension. Furthermore, we find that SAC satisfaction occurs despite the absence of large changes in intra-kinetochore distance, suggesting that substantial kinetochore stretching is not required for quenching the SAC signal. PMID:26620470

  14. The flavonoid eupatorin inactivates the mitotic checkpoint leading to polyploidy and apoptosis

    International Nuclear Information System (INIS)

    The spindle assembly checkpoint (SAC) is a conserved mechanism that ensures the fidelity of chromosome distribution in mitosis by preventing anaphase onset until the correct bipolar microtubule–kinetochore attachments are formed. Errors in SAC function may contribute to tumorigenesis by inducing numerical chromosome anomalies (aneuploidy). On the other hand, total disruption of SAC can lead to massive genomic imbalance followed by cell death, a phenomena that has therapeutic potency. We performed a cell-based high-throughput screen with a compound library of 2000 bioactives for novel SAC inhibitors and discovered a plant-derived phenolic compound eupatorin (3′,5-dihydroxy-4′,6,7-trimethoxyflavone) as an anti-mitotic flavonoid. The premature override of the microtubule drug-imposed mitotic arrest by eupatorin is dependent on microtubule–kinetochore attachments but not interkinetochore tension. Aurora B kinase activity, which is essential for maintenance of normal SAC signaling, is diminished by eupatorin in cells and in vitro providing a mechanistic explanation for the observed forced mitotic exit. Eupatorin likely has additional targets since eupatorin treatment of pre-mitotic cells causes spindle anomalies triggering a transient M phase delay followed by impaired cytokinesis and polyploidy. Finally, eupatorin potently induces apoptosis in multiple cancer cell lines and suppresses cancer cell proliferation in organotypic 3D cell culture model.

  15. Roles of protein kinase C in oocyte meiotic maturation and fertilization

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Protein kinase C (PKC) is a superfamily of Ser/Thr protein kinases that is distributed widely in eukaryotes. It plays key regulatory roles at multiple steps of oocyte meiotic maturation and fertilization. During the process of meiotic maturation, the activation of PKC in cumulus cells stimulates meiotic maturation, whereas the activation of PKC in oocytes results in the inhibition of germinal vesicle breakdown. PKC activity increases following the meiotic maturation, and decreases at the transition of metaphase/anaphase in meiosis I, so as to facilitate the release of the first polar body and the entry of meiosis II. In fertilization of mammalian oocytes, PKC may act as one of the downstream targets of Ca2+ to stimulate the cortical granule exocytosis, release the oocytes from MII arrest and to induce pronucleus formation. PKC is also involved in the regulation of maturation promoting factor (MPF) and mitogen-activated protein kinase (MAPK). Several PKC isoforms have been identified in mammalian oocytes, and there is evidence showing that classical PKCs may be the principal mediator of oocyte cortical reaction.

  16. Cdh1-APC/C, cyclin B-Cdc2, and Alzheimer's disease pathology

    International Nuclear Information System (INIS)

    The anaphase-promoting complex/cyclosome (APC/C) is a key E3 ubiquitin ligase complex that functions in regulating cell cycle transitions in proliferating cells and has, as revealed recently, novel roles in postmitotic neurons. Regulated by its activator Cdh1 (or Hct1), whose level is high in postmitotic neurons, APC/C seems to have multiple functions at different cellular locations, modulating diverse processes such as synaptic development and axonal growth. These processes do not, however, appear to be directly connected to cell cycle regulation. It is now shown that Cdh1-APC/C activity may also have a basic role in suppressing cyclin B levels, thus preventing terminally differentiated neurons from aberrantly re-entering the cell cycle. The result of an aberrant cyclin B-induced S-phase entry, at least for some of these neurons, would be death via apoptosis. Cdh1 thus play an active role in maintaining the terminally differentiated, non-cycling state of postmitotic neurons-a function that could become impaired in Alzheimer's and other neurodegenerative diseases

  17. Prometaphase APCcdh1 activity prevents non-disjunction in mammalian oocytes.

    Science.gov (United States)

    Reis, Alexandra; Madgwick, Suzanne; Chang, Heng-Yu; Nabti, Ibtissem; Levasseur, Mark; Jones, Keith T

    2007-10-01

    The first female meiotic division (meiosis I, MI) is uniquely prone to chromosome segregation errors through non-disjunction, resulting in trisomies and early pregnancy loss. Here, we show a fundamental difference in the control of mammalian meiosis that may underlie such susceptibility. It involves a reversal in the well-established timing of activation of the anaphase-promoting complex (APC) by its co-activators cdc20 and cdh1. APC(cdh1) was active first, during prometaphase I, and was needed in order to allow homologue congression, as loss of cdh1 speeded up MI, leading to premature chromosome segregation and a non-disjunction phenotype. APC(cdh1) targeted cdc20 for degradation, but did not target securin or cyclin B1. These were degraded later in MI through APC(cdc20), making cdc20 re-synthesis essential for successful meiotic progression. The switch from APC(cdh1) to APC(cdc20) activity was controlled by increasing CDK1 and cdh1 loss. These findings demonstrate a fundamentally different mechanism of control for the first meiotic division in mammalian oocytes that is not observed in meioses of other species. PMID:17891138

  18. Dual-mode regulation of the APC/C by CDK1 and MAPK controls meiosis I progression and fidelity.

    Science.gov (United States)

    Nabti, Ibtissem; Marangos, Petros; Bormann, Jenny; Kudo, Nobuaki R; Carroll, John

    2014-03-17

    Female meiosis is driven by the activities of two major kinases, cyclin-dependent kinase 1 (Cdk1) and mitogen-activated protein kinase (MAPK). To date, the role of MAPK in control of meiosis is thought to be restricted to maintaining metaphase II arrest through stabilizing Cdk1 activity. In this paper, we find that MAPK and Cdk1 play compensatory roles to suppress the anaphase-promoting complex/cyclosome (APC/C) activity early in prometaphase, thereby allowing accumulation of APC/C substrates essential for meiosis I. Furthermore, inhibition of MAPK around the onset of APC/C activity at the transition from meiosis I to meiosis II led to accelerated completion of meiosis I and an increase in aneuploidy at metaphase II. These effects appear to be mediated via a Cdk1/MAPK-dependent stabilization of the spindle assembly checkpoint, which when inhibited leads to increased APC/C activity. These findings demonstrate new roles for MAPK in the regulation of meiosis in mammalian oocytes. PMID:24637322

  19. Human chromokinesins promote chromosome congression and spindle microtubule dynamics during mitosis.

    Science.gov (United States)

    Wandke, Cornelia; Barisic, Marin; Sigl, Reinhard; Rauch, Veronika; Wolf, Frank; Amaro, Ana C; Tan, Chia H; Pereira, Antonio J; Kutay, Ulrike; Maiato, Helder; Meraldi, Patrick; Geley, Stephan

    2012-09-01

    Chromokinesins are microtubule plus end-directed motor proteins that bind to chromosome arms. In Xenopus egg cell-free extracts, Xkid and Xklp1 are essential for bipolar spindle formation but the functions of the human homologues, hKID (KIF22) and KIF4A, are poorly understood. By using RNAi-mediated protein knockdown in human cells, we find that only co-depletion delayed progression through mitosis in a Mad2-dependent manner. Depletion of hKID caused abnormal chromosome arm orientation, delayed chromosome congression, and sensitized cells to nocodazole. Knockdown of KIF4A increased the number and length of microtubules, altered kinetochore oscillations, and decreased kinetochore microtubule flux. These changes were associated with failures in establishing a tight metaphase plate and an increase in anaphase lagging chromosomes. Co-depletion of both chromokinesins aggravated chromosome attachment failures, which led to mitotic arrest. Thus, hKID and KIF4A contribute independently to the rapid and correct attachment of chromosomes by controlling the positioning of chromosome arms and the dynamics of microtubules, respectively. PMID:22945934

  20. CENP-32 is required to maintain centrosomal dominance in bipolar spindle assembly.

    Science.gov (United States)

    Ohta, Shinya; Wood, Laura; Toramoto, Iyo; Yagyu, Ken-Ichi; Fukagawa, Tatsuo; Earnshaw, William C

    2015-04-01

    Centrosomes nucleate spindle formation, direct spindle pole positioning, and are important for proper chromosome segregation during mitosis in most animal cells. We previously reported that centromere protein 32 (CENP-32) is required for centrosome association with spindle poles during metaphase. In this study, we show that CENP-32 depletion seems to release centrosomes from bipolar spindles whose assembly they had previously initiated. Remarkably, the resulting anastral spindles function normally, aligning the chromosomes to a metaphase plate and entering anaphase without detectable interference from the free centrosomes, which appear to behave as free asters in these cells. The free asters, which contain reduced but significant levels of CDK5RAP2, show weak interactions with spindle microtubules but do not seem to make productive attachments to kinetochores. Thus CENP-32 appears to be required for centrosomes to integrate into a fully functional spindle that not only nucleates astral microtubules, but also is able to nucleate and bind to kinetochore and central spindle microtubules. Additional data suggest that NuMA tethers microtubules at the anastral spindle poles and that augmin is required for centrosome detachment after CENP-32 depletion, possibly due to an imbalance of forces within the spindle. PMID:25657325

  1. The transforming parasite Theileria co-opts host cell mitotic and central spindles to persist in continuously dividing cells.

    Directory of Open Access Journals (Sweden)

    Conrad von Schubert

    Full Text Available The protozoan parasite Theileria inhabits the host cell cytoplasm and possesses the unique capacity to transform the cells it infects, inducing continuous proliferation and protection against apoptosis. The transforming schizont is a multinucleated syncytium that resides free in the host cell cytoplasm and is strictly intracellular. To maintain transformation, it is crucial that this syncytium is divided over the two daughter cells at each host cell cytokinesis. This process was dissected using different cell cycle synchronization methods in combination with the targeted application of specific inhibitors. We found that Theileria schizonts associate with newly formed host cell microtubules that emanate from the spindle poles, positioning the parasite at the equatorial region of the mitotic cell where host cell chromosomes assemble during metaphase. During anaphase, the schizont interacts closely with host cell central spindle. As part of this process, the schizont recruits a host cell mitotic kinase, Polo-like kinase 1, and we established that parasite association with host cell central spindles requires Polo-like kinase 1 catalytic activity. Blocking the interaction between the schizont and astral as well as central spindle microtubules prevented parasite segregation between the daughter cells during cytokinesis. Our findings provide a striking example of how an intracellular eukaryotic pathogen that evolved ways to induce the uncontrolled proliferation of the cells it infects usurps the host cell mitotic machinery, including Polo-like kinase 1, one of the pivotal mitotic kinases, to ensure its own persistence and survival.

  2. An astral simulacrum of the central spindle accounts for normal, spindle-less, and anucleate cytokinesis in echinoderm embryos.

    Science.gov (United States)

    Su, Kuan-Chung; Bement, William M; Petronczki, Mark; von Dassow, George

    2014-12-15

    Cytokinesis in animal cells depends on spindle-derived spatial cues that culminate in Rho activation, and thereby actomyosin assembly, in a narrow equatorial band. Although the nature, origin, and variety of such cues have long been obscure, one component is certainly the Rho activator Ect2. Here we describe the behavior and function of Ect2 in echinoderm embryos, showing that Ect2 migrates from spindle midzone to astral microtubules in anaphase and that Ect2 shapes the pattern of Rho activation in incipient furrows. Our key finding is that Ect2 and its binding partner Cyk4 accumulate not only at normal furrows, but also at furrows that form in the absence of associated spindle, midzone, or chromosomes. In all these cases, the cell assembles essentially the same cytokinetic signaling ensemble—opposed astral microtubules decorated with Ect2 and Cyk4. We conclude that if multiple signals contribute to furrow induction in echinoderm embryos, they likely converge on the same signaling ensemble on an analogous cytoskeletal scaffold. PMID:25298401

  3. Cytogenetics of semi-fertile triploid and aneuploid intergeneric vine cacti hybrids.

    Science.gov (United States)

    Tel-Zur, N; Abbo, S; Mizrahi, Y

    2005-01-01

    Crosses between the diploid Hylocereus polyrhizus, as the female parent, and the tetraploid Selenicereus megalanthus, as the male parent, yielded triploid and aneuploid hybrids. The fruits of these hybrids combined the attractive appearance of Hylocereus fruits with the delicious taste of S. megalanthus fruits. The aim of this work was to assess the fertility and breeding potential of the triploid and aneuploid hybrids with a view to developing an improved vine cactus crop. Pollen mother cells at metaphase I revealed univalents, bivalents, trivalents, and occasionally quadrivalents. Chromosome distribution at anaphase I revealed different classes of chromosome segregation as well as lagging chromosomes. At metaphase II, parallel and tripolar spindles were observed. The occurrence of triads was frequent, whereas dyads were rarely observed. Pollen stainability varied among the clones studied ranging from 9.8% to 18.6%. The diameters of the stained pollen grains varied widely, probably as a result of the number of chromosomes. Despite the allotriploid origin of our hybrids, functional female and male gametes were produced in considerable proportions, most likely as a result of balanced chromosome segregation. The triploid and aneuploid clones studied yielded viable seeds whose number per fruit was strongly dependent on the pollen donor. PMID:15618308

  4. Low LET radiation dose rate effect and free radical production and survival

    International Nuclear Information System (INIS)

    The authors previously published the finding that LD-50/30 varied with the reciprocal cube root of x- or gamma-radiation dose rate in a number of studies by others in mice and rats. Human skin erythema also appeared to fit the relationship. Broyles subsequently employed a modification of the relationship with particular interest in dose rates of less than 6 rad per day. Having noted a deflection of actual data from reciprocal cube root- predicted values at higher dose rates in the earlier utilized studies, they modified the original relationship with the finding of a better fit of data from a broad variety of endpoints to predicted values. These end-points include E. Coli survival, murine lens opacification, spermatogonia depletion, and abnormal liver anaphases, skin erythema in man and swine, LD 50/4 in mice and rats, LD-50/30 in mice, rats, and swine, and LD-50/60 in sheep. ED-50 specific loss of dose-rate effect appears to occur with several of the quoted parameters at very high dose rates (greater than 1000 rad per minute). The possible role of oxygen depletion and free radical production and survival

  5. Mitotic effects of monochromatic ultraviolet radiation at 225, 265, and 280 nm on eleven stages of the cell cycle of the grasshopper neuroblast in culture. II. Changes in progression rate and cell sequence between the stage irradiated and nuclear membrane breakdown

    International Nuclear Information System (INIS)

    Portions of embryos of the grasshopper, Chortophaga viridifasciata (DeGeer), were cultured in hanging drops under quartz cover slips. Immediately after exposure to 225, 265, or 280 nm radiation, microscope observations at 380C were begun. The morphologically identified stage and the time after treatment of selected neuroblasts were recorded at short-time intervals until prometaphase was reached. Mitotic retardation induced by irradiation of prereplication stages (metaphase, anaphase, or early telophase) or S phase (middle or late telophase, interphase, or very early prophase) is greatest in postreplication stages (early, middle, and late prophase) and absent or minimal in stages morphologically identified as parts of S phase. Ultraviolet irradiation superimposes on the normal diversity of progression rates an additional variation factor, so that cells do not necessarily reach prometaphase in the order of their sequence at the time of treatment. This suggests the need for caution in ascribing particular radiosensitivities to substages of limited duration on the basis of the order in which they attain a subsequent stage

  6. The use of Micronucleus Assay on Swiss-Webster Mice (Mus Musculus Bone Marrow for the Mutagenicity Test of γ-Irradiation

    Directory of Open Access Journals (Sweden)

    R. Sofyan

    2005-07-01

    Full Text Available Ionizing radiation is a potentially chromosomal damaging agent. The induction of chromosomal damage as well as the incidence of cell cycle disturbances may depend on the dose of irradiation. One of the indication of chromosomal damage is the formation of micronucleus (MN during the anaphase of mitosis. This study deals with the MN assay on femur bone marrow polychromatic erythrocyte (PCE cells of Swiss-Webster mice, for the mutagenicity test of g-irradiation. The study was conducted on five groups of mice (each group consist of five mice that were irradiated at the doses of 0; 0,2; 0,4; 0,6 and 0,8 Gy respectively. One day after irradiation, the mice were killed by cervical dislocation. Furthermore the femur bone marrow was taken, the cells were then prepared by smear technique onto slides followed by Giemsa staining. The MN in PCE cells or MNPCE were examined microscopically by the magnification of 1000 and counted for every 1000 cells in each mice. The results showed that the MNPCE frequencies on the treatment groups were significantly higher than that of the control (P< 0,05. Further evaluation indicated that the MNPCE frequencies increased with the increase of irradiation dose.

  7. The effect of hypoxia on micronucleus expression

    International Nuclear Information System (INIS)

    The oxygen enhancement ratio (OER) for micronucleus (MN) induction in Chinese Hamster Ovary (CHO) cells was determined. CHO cells were irradiated in air or after being made hypoxic by a combination of vacuum formation and 3 hours of metabolic O/sub 2/ depletion. Clonogenic assays show that this treatment results in an OER of 3.0 at doses above 200 rad. However, when MN were used as the endpoint, radiation doses of 25 to 600 rad resulted in a constant OER of 5.9, an unrealistically high value for cell survival. Hypoxia alone did not influence the cell cycle kinetics, which would change MN expression. To further examine this problem, analysis of anaphases from cells attempting their first division after irradiation revealed that the expected number of acentric chromosome fragments were produced in hypoxic cells (assuming an OER of 3.0). However, the proportion of lagging fragments was reduced form 77% when irradiated in air to 45% when irradiated under hypoxia; lagging chromosome fragments become MN. In addition, the number of chromosome bridges was increased in cells irradiated under hypoxic conditions

  8. Evaluation of the genotoxicity of zinc oxide-eugenol cement to Allium cepa L. - doi: 10.4025/actascibiolsci.v35i4.17925

    Directory of Open Access Journals (Sweden)

    Elisângela de Fátima Rezende

    2013-07-01

    Full Text Available Evaluation of the Genotoxicity of Zinc Oxide-Eugenol Cement in Allium cepa L. Dental materials can induce local and systemic effects. The Allium cepa assay was used to evaluate the genotoxicity and/or cytotoxicity of zinc oxide and eugenol (ZOE at different proportions. The ZOE solution was tested at the concentration of 1 drop of eugenol (in each drop of liquid, the approximate concentration of eugenol is 85% and 1 portion of zinc oxide cement (treatment I, and twice the concentration of eugenol (treatment II. Treated roots appeared to be yellowish-brown, fewer in number, thicker and less turgid compared with the control, suggesting a cytotoxic activity of ZOE. A significant difference was found in the root size between the control and treatment II. This treatment reduced by 79% the size of the root compared with the control, and the mitotic index was 66%, indicating a 22.4% reduction relative to the control, which in turn evidenced the cytotoxicity of ZOE. The significant increase in anaphase bridges suggests a genotoxic effect.

  9. Studies on the mitotic chromosome scaffold of Allium sativum

    Institute of Scientific and Technical Information of China (English)

    ZHAOJIAN; SHAOBOJIN; 等

    1995-01-01

    An argentophilic structure is present in the metaphase chromosomes of garlic(Allium sativum),Cytochemical studies indicate that the main component of the structure is non-histone proteins(NHPs).The results of light and electron microscopic observations reveal that the chromosme NHP scaffold is a network which is composed of fibres and granules and distributed throughout the chromosomes.In the NHP network,there are many condensed regions that are connected by redlatively looser regions.The distribution of the condensed regions varies in individual chromosomes.In some of the chromosomes the condensed regions are lognitudinally situsted in the central part of a chromatid while in others these regions appear as coillike transverse bands.At early metaphase.scaffolds of the sister chromatids of a chromosome are linked to each other in the centromeric region,meanwhile,they are connected by scafold materials along the whole length of the chromosome.At late metaphase,however,the connective scaffold materials between the two sister chromatids disappear gradually and the chromatids begin to separate from one another at their ends.but the chromatids are linked together in the centromeric region until anaphase.This connection seems to be related to the special structure of the NHP scaffold formed in the centromeric region.The morphological features and dynamic changes of the chromosome scaffold are discussed.

  10. Recruitment of phosphorylated small heat shock protein Hsp27 to nuclear speckles without stress

    International Nuclear Information System (INIS)

    During stress, the mammalian small heat shock protein Hsp27 enters cell nuclei. The present study examines the requirements for entry of Hsp27 into nuclei of normal rat kidney (NRK) renal epithelial cells, and for its interactions with specific nuclear structures. We find that phosphorylation of Hsp27 is necessary for the efficient entry into nuclei during heat shock but not sufficient for efficient nuclear entry under control conditions. We further report that Hsp27 is recruited to an RNAse sensitive fraction of SC35 positive nuclear speckles, but not other intranuclear structures, in response to heat shock. Intriguingly, Hsp27 phosphorylation, in the absence of stress, is sufficient for recruitment to speckles found in post-anaphase stage mitotic cells. Additionally, pseudophosphorylated Hsp27 fused to a nuclear localization peptide (NLS) is recruited to nuclear speckles in unstressed interphase cells, but wildtype and nonphosphorylatable Hsp27 NLS fusion proteins are not. The expression of NLS-Hsp27 mutants does not enhance colony forming abilities of cells subjected to severe heat shock, but does regulate nuclear speckle morphology. These data demonstrate that phosphorylation, but not stress, mediates Hsp27 recruitment to an RNAse soluble fraction of nuclear speckles and support a site-specific role for Hsp27 within the nucleus

  11. [Prenatal diagnosis of five cases of monochorionic-diamniotic twins discordant for karyotype analysis].

    Science.gov (United States)

    Wu, Jianzhu; Zhou, Yi; Lin, Shaobin; Chen, Baojiang; Xie, Yingjun

    2015-10-01

    OBJECTIVE To explore the mechanism and diagnostic method for monochorionic-diamniotic twins discordant for karyotype analysis. METHODS Dual amniocentesis was performed on five pairs of monochorionic-diamniotic twins, which all consisted of a normal twin and one with multiple malformations revealed by ultrasound. Karyotype analysis was performed on amniocytes derived from each of the twins. Zygosity was also determined with DNA extracted from amniocytes with 16 polymorphic microsatellite markers. RESULTS Three cases of 45,X, one case of 47,XX,+9 and one case of 47,XY,+18 were detected among the abnormal twins, while the normal fetuses all had a normal karyotype. DNA analysis suggested that, in all cases, the twins have shared the 16 polymorphic microsatellite markers, which confirmed their monozygosity. CONCLUSION Monochorionic-diamniotic twins may be discordant for karyotyping, for which anaphase lagging, chromosomal non-disjunction and trisomy rescue may be the underlying reasons. As a simple method, dual amniocentesis can be used to obtain amniotic fluid samples for karyotype analysis and determination of zygosity for such twins. PMID:26418994

  12. Genotoxicity and cytotoxicity assay of water sampled from the underground nuclear explosion site in the north of the Perm region (Russia)

    International Nuclear Information System (INIS)

    The results of our study revealed a local biologically relevant surface water contamination in the radionuclide anomaly in the north of Russia (Perm region) by means of Allium schoenoprasum L. anaphase-telophase chromosome aberration assay. This radionuclide anomaly was formed in 1971 as a result of an underground nuclear explosion with soil excavation. Specific activities of main dose-forming radionuclides in all examined reservoirs are below intervention levels officially adopted in Russia for drinking water. We found that 90Sr significantly contributes to induction of cytogenetic disturbances. Our previous data and the data described here suggest that metal and radionuclide combined exposure (with the dose below permissible exposure limits for human) may cause substantial biological effects. These effects are in part due to synergic response. The findings described here indicated that development of a new concept of radiation protection for humans and biota should be based on the clear understanding of biological effects of low doses of radiation in chronic exposure to multi-pollutant mixtures

  13. Genotoxicity of hydrated sulfur dioxide on root tips of Allium sativum and Vicia faba.

    Science.gov (United States)

    Yi, Huilan; Meng, Ziqiang

    2003-05-01

    Genotoxicity of sulfur dioxide (SO(2)) and its hydrates (bisulfite and sulfite) in human lymphocytes and other mammalian cells have been found earlier in our laboratory. In the present studies, we used Allium stavium and Vicia faba cytogenetic tests, which are the highly sensitive and simple plant bioassays. A mixture of sodium bisulfite and sodium sulfite (1:3), at various concentrations from 1 x 10(-4) to 2 x 10(-3)M was used for the treatment. Genotoxicity was expressed in terms of anaphase aberration (AA) frequencies in the Vicia-AA test and in terms of micronuclei (MCN) frequencies in both Vicia-MCN test and Alllium-MCN test. On average, the results showed a 1.7-3.9-fold increase of AA frequencies and a 3.5-4.5-fold increase of MCN frequencies in Vicia root tips as compared with the negative control. Similarly, results of Allium-MCN test also showed a significant increase in MCN frequencies in the treated samples. In addition, pycnotic cells (PNC) appeared in Allium root tips of treated groups. The frequencies of MCN, AA and PNC increased dose-dependently and the cell cycle delayed at the same time in bisulfite treated samples. Results of the present study suggest that the Vicia and Allium cytogenetic bioassays are efficient, simple and reproducible in genotoxicity studies of bisulfite. PMID:12742512

  14. The chromosome passenger complex is required for fidelity of chromosome transmission and cytokinesis in meiosis of mouse oocytes.

    Science.gov (United States)

    Sharif, Bedra; Na, Jie; Lykke-Hartmann, Karin; McLaughlin, Stephen H; Laue, Ernest; Glover, David M; Zernicka-Goetz, Magdalena

    2010-12-15

    The existence of two forms of the chromosome passenger complex (CPC) in the mammalian oocyte has meant that its role in female meiosis has remained unclear. Here we use loss- and gain-of function approaches to assess the meiotic functions of one of the shared components of these complexes, INCENP, and of the variable kinase subunits, Aurora B or Aurora C. We show that either the depletion of INCENP or the combined inhibition of Aurora kinases B and C activates the anaphase-promoting complex or cyclosome (APC/C) before chromosomes have properly congressed in meiosis I and also prevents cytokinesis and hence extrusion of the first polar body. Overexpression of Aurora C also advances APC/C activation and results in cytokinesis failure in a high proportion of oocytes, indicative of a dominant effect on CPC function. Together, this points to roles for the meiotic CPC in functions similar to the mitotic roles of the complex: correcting chromosome attachment to microtubules, facilitating the spindle-assembly checkpoint (SAC) function and enabling cytokinesis. Surprisingly, overexpression of Aurora B leads to a failure of APC/C activation, stabilization of securin and consequently a failure of chiasmate chromosomes to resolve - a dominant phenotype that is completely suppressed by depletion of INCENP. Taken together with the differential distribution of Aurora proteins B and C on chiasmate chromosomes, this points to differential functions of the two forms of CPC in regulating the separation of homologous chromosomes in meiosis I. PMID:21123620

  15. The Induction of Chromosome Aberrations and Micronuclei in Human Peripheral Blood Lymphocytes at Low Doses of Radiation

    CERN Document Server

    Shmakova, N L; Krasavin, E A; Melnikova, L A; Fadeeva, T A

    2003-01-01

    The chromosome damage induced by the low doses of gamma-irradiation with ^{60}Co and X-rays in peripheral blood lymphocytes has been studied using different cytogenetic assays. Isolated lymphocytes were exposed to 0.01-1.0 Gy, simulated by PHA, and analysed for chromosome aberrations by the metaphase and the anaphase methods, by the micronucleus assay. Despite the quantitative differences in the amount of chromosome damage revealed by different methods, all of them demonstrated complex nonlinear dose dependence of the frequency of aberrant cells and aberrations. At the dose range of 0.01-0.05 Gy the cells showed the highest radiosensitivity; at 0.05-0.5 Gy the dose-independent induction of chromosome damage was revealed. At the doses of 0.5-1.0 Gy the dose-effect curves became linear with the decreased slope compared with the initial one (by a factor of 5 to 10 for different criteria) reflecting a higher radioresistance of the cells. These data confirm the idea that the direct linear extrapolation of high-dos...

  16. The MCM-binding protein ETG1 aids sister chromatid cohesion required for postreplicative homologous recombination repair.

    Directory of Open Access Journals (Sweden)

    Naoki Takahashi

    2010-01-01

    Full Text Available The DNA replication process represents a source of DNA stress that causes potentially spontaneous genome damage. This effect might be strengthened by mutations in crucial replication factors, requiring the activation of DNA damage checkpoints to enable DNA repair before anaphase onset. Here, we demonstrate that depletion of the evolutionarily conserved minichromosome maintenance helicase-binding protein ETG1 of Arabidopsis thaliana resulted in a stringent late G2 cell cycle arrest. This arrest correlated with a partial loss of sister chromatid cohesion. The lack-of-cohesion phenotype was intensified in plants without functional CTF18, a replication fork factor needed for cohesion establishment. The synergistic effect of the etg1 and ctf18 mutants on sister chromatid cohesion strengthened the impact on plant growth of the replication stress caused by ETG1 deficiency because of inefficient DNA repair. We conclude that the ETG1 replication factor is required for efficient cohesion and that cohesion establishment is essential for proper development of plants suffering from endogenous DNA stress. Cohesion defects observed upon knockdown of its human counterpart suggest an equally important developmental role for the orthologous mammalian ETG1 protein.

  17. Chromosomal and Nuclear Alterations in Root Tip Cells of Allium Cepa L. Induced by Alprazolam

    Science.gov (United States)

    Nefic, Hilada; Musanovic, Jasmin; Metovic, Azra; Kurteshi, Kemajl

    2013-01-01

    ABSTRACT Introduction: Alprazolam is a triazolobenzodiazepine used in panic disorders and other anxiety states. Target organ of Alprazolam is CNS, causing depression of respiration and consciousness. Aim: This study aimed to estimate the genotoxic potential of Alprazolam using Allium cepa test. Methods: Allium cepa is one of the most suitable plants for detecting different types of xenobiotics. The test enables the assessment of different genetic endpoints making possible damage to the DNA of humans to be predicted. Results: Alprazolam induced chromosomal (anaphase bridges, breaks, lagging and stickiness, abnormal spiralisation, multipolarity and polyploidy) and cytological aberrations, especially nuclear alterations (nuclear buds, fragmented nucleus and apoptotic bodies, cells without nucleus, binucleated and micronucleated cells), morphological alterations in shape and size of cells, spindle disturbance and polar deviation in root tip meristem cells of Allium cepa at all tested concentrations. Alprazolam also caused significant inhibition of mitotic index in these cells. Conclusion: These changes in cells are indicators of genotoxic potential of Alprazolam suggesting a need for further in vitro studies on animal and human lymphocytes as well as in vivo studies. PMID:25568504

  18. Concentration and toxicity of sea-surface contaminants in Puget Sound

    Energy Technology Data Exchange (ETDEWEB)

    Hardy, J.T.; Crecelius, E.A.; Kocan, R.

    1986-04-01

    The Marine Research Laboratory conducted studies during CY 1985 to evaluate the effects of sea-surface contamination on the reproductive success of a valued marine species. Microlayer and bulk water samples were collected from a rural bay, central Puget Sound, and three urban bays and analyzed for a number of metal and organic contaminants as well as for densities of neuston and plankton organisms. Fertilized neustonic eggs of sand sole (Psettichthys melanostictus) were exposed to the same microlayer samples during their first week of embryonic and larval development. Also, we evaluated the effects of microlayer extracts on the growth of trout cell cultures. Compared to rural sites, urban bays generally contained lower densities of neustonic flatfish eggs during the spawning season. Also, in contrast to the rural sites or the one central Puget Sound site, approximately half of the urban bay microlayer samples resulted in significant increases in embryo mortality (up to 100%), kyphosis (bent spine abnormalities) in hatched larvae, increased anaphase aberrations in developing embryos, and decreased trout cell growth. The toxic samples generally contained high concentrations of polycyclic aromatic and/or chlorinated hydrocarbons and/or potentially toxic metals. In some cases, concentrations of contaminants on the sea surface exceeded water-quality criteria by several orders of magnitude. Several samples of subsurface bulk water collected below highly contaminated surfaces showed no detectable contamination or toxicity.

  19. Prediction of solar cycle based on the invariant

    Institute of Scientific and Technical Information of China (English)

    LIU Shijun; YU Xiaoding; CHEN Yongyi

    2003-01-01

    A new method of predicting solar activities has been introduced in this paper. The method can predict both the occurrence time and the maximum number of sunspot at the same time. By studying the variation of sunspot, we find that the combination of the several variables was nearly invariable during the entire solar cycles, as called invariant. And just only by determining the start time of a cycle, we can predict the occurrence time of cycle's peak value accurately. Furthermore, according to observational data of the sunspot cycles, it showed that the sunspot maximum number has correlation not only with the prophase variety of the number in the cycle but also with the anaphase of the previous period. So we can introduce an equivalent regression coefficient, which can dynamically self-adapt to different cycle lengths, and effectively solve the inconsistency between the accuracy and the lead-time of the forecast. It can guarantee the satisfied accuracy and effectively increases the lead-time of the forecast. This method can predict the maximum sunspot number for solar cycle at the approximate half rise of the period. This method predicts that the occurrence time of the maximum sunspot number for cycle 24 will be in January 2011.

  20. Sensitivity of Bidens laevis L. to mutagenic compounds. Use of chromosomal aberrations as biomarkers of genotoxicity

    International Nuclear Information System (INIS)

    The wetland macrophyte Bidens laevis possesses suitable cytological characteristics for genotoxicity testing. To test its sensitivity as compared to terrestrial plants species currently in use in standardized assays, Methyl Methanesulfonate (MMS), N-ethyl-N-nitrosourea (ENU) and Maleic Hydrazide (HM) were used. On the other hand, the insecticide Endosulfan (ES) - an environmentally relevant contaminant - was assayed in seeds and two-month old plants. Mitotic Index (MI), frequency of Chromosome Aberrations in Anaphase-Telophase (CAAT) and frequency of Abnormal Metaphases (AM) were analyzed. MH, MMS and ENU caused a significant decrease of the MI. MMS was aneugenic whereas MH and ENU were both aneugenic and clastogenic. ES caused a significant concentration-dependent increase of total- and aneugenic-CAAT in roots and a significant high frequency of AM at high concentrations. Because of its sensitivity to mutagenic substances, B. laevis can be regarded as a reliable and convenient species for genotoxicity assays especially if aquatic contaminants are evaluated. - The wetland macrophyte Bidens laevis is sensitive to genotoxic compounds similarly to terrestrial standardized species.

  1. Study on Haploid Inducing and Its Meiotic Abnormality in Maize

    Institute of Scientific and Technical Information of China (English)

    TANG Qi-lin; FENG Yun-chao; HAN Xue-li; ZHENG Ming-min; RONG Ting-zhao

    2009-01-01

    The haploid-inducing line Stock 6 was used to produce haploid maize and expected to obtain maize haploid plants successfully. The detailed meiotic studies on selected haploid maize (n=x=10) were conducted. Cytogenetie analysis revealed a high frequency of meiotic abnormality occurred in both meiosis Ⅰ and meiosis Ⅱ. During the prophase I, univalents were common configurations, and there were bivalents or trivalents in some pollen mother cells, however, a few cells containing five bivalents were also observed. After prophase I, chromosomes did not congregate in a single metaphase plate but they were scattered in the cytoplasm. At anaphase I, the chromosome distribution was highly irregular with almost all possible combinations. In some cells, chromosomes were grouped into the three or four masses and several spindles appeared. At the tetrad stage of meiosis Ⅱ, cytokinesis splitting abnormality occurred, and a variety of diad, triad, tetrad, pentad, hexad, as well as decury microspores were easily observed. As a consequence of abnormalities of the two meiotic stages, various microspores and the pollen grains with different size were formed, and its pollen grains were almost completely sterile.

  2. Observation on Meiosis of Pollen Mother Cells in Apium graveolens%芹菜花粉母细胞减数分裂观察

    Institute of Scientific and Technical Information of China (English)

    赵冬; 张蜀宁; 张宇; 李俊星; 刘惠吉

    2011-01-01

    The flower buds of celery (Apium graveolens ) were used to study the mitosis in pollen mother cells with enzyme - dye -squash technique.The results showed that the pollen mother cells carried on their meiosis and cytokinesis simultaneously and their tetrads were tetrahedral or decussate type; at metaphases Ⅰ and Ⅱ there showed a small number of chromosomes scattered outside their equatorial plate; at anaphases Ⅰ and Ⅱ there appeared chromosome bridges and lagged chromosomes in some pollen mother cells.%以中国芹品种铁杆芹花蕾为材料,采用改良卡宝染色压片法对芹菜花粉母细胞减数分裂进行了细胞学研究.结果表明:花粉母细胞减数分裂为胞质同时型,四分体为正四面体型或十字交叉型,中期Ⅰ和中期Ⅱ细胞可见赤道板外染色体,后期Ⅰ和后期Ⅱ部分细胞出现染色体桥及落后染色体.

  3. Carbamazepine induces mitotic arrest in mammalian Vero cells

    Energy Technology Data Exchange (ETDEWEB)

    Perez Martin, J.M.; Fernandez Freire, P.; Labrador, V. [Departamento de Biologia, Facultad de Ciencias, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Hazen, M.J. [Departamento de Biologia, Facultad de Ciencias, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain)], E-mail: mariajose.hazen@uam.es

    2008-01-01

    We reported recently that the anticonvulsant drug carbamazepine, at supratherapeutic concentrations, exerts antiproliferative effects in mammalian Vero cells, but the underlying mechanism has not been elucidated. This motivates us to examine rigorously whether growth arrest was associated with structural changes in cellular organization during mitosis. In the present work, we found that exposure of the cells to carbamazepine led to an increase in mitotic index, mainly due to the sustained block at the metaphase/anaphase boundary, with the consequent inhibition of cell proliferation. Indirect immunofluorescence, using antibodies directed against spindle apparatus proteins, revealed that mitotic arrest was associated with formation of monopolar spindles, caused by impairment of centrosome separation. The final consequence of the spindle defects induced by carbamazepine, depended on the duration of cell cycle arrest. Following the time course of accumulation of metaphase and apoptotic cells during carbamazepine treatments, we observed a causative relationship between mitotic arrest and induction of cell death. Conversely, cells released from the block of metaphase by removal of the drug, continued to progress through mitosis and resume normal proliferation. Our results show that carbamazepine shares a common antiproliferative mechanism with spindle-targeted drugs and contribute to a better understanding of the cytostatic activity previously described in Vero cells. Additional studies are in progress to extend these initial findings that define a novel mode of action of carbamazepine in cultured mammalian cells.

  4. The characteristic analysis of the magnetic structure distribution in Xiangsan volcanic basin

    International Nuclear Information System (INIS)

    Basing on large-scale gravity and magnetic surveying result in Xiangsan area, the forward modeling were established in this paper. By using simulate annealing algorithm, the physical construction distribution at different depth in Xiangsan volcanic basic were calculated and the underground structure of the rock layers and variation trend of the interface were analyzed. According to the calculation results, we think that the magma activity and deepther structure of the basin were development, the local sub volcanic rocks trended deeper underground and trended expansile, the variation of the interface were relatively complex at the northeast parts and the buried depth of the magnetic rocks were larger than 800 meters, the variation of the interface were relatively smooth at the southeast parts and the buried depth of the magnetic rocks were less than 800 meters. There were the muti-channels of the magma, the magma activity of the anaphase structure were development at the southeast or south and east parts of the Xiangsan basin. This is the main reason why at this parts the uranium deposit were enrichment and the uranium were controlled by structure and the magnetic rocks were massive body. There is of great significant for guiding to find deeper underground uranium in Xiangsan areas. (authors)

  5. The radiosensitivity of some trisomic variants of a diploid mammalian cell line

    International Nuclear Information System (INIS)

    The radiosensitivity of trisomic cells from a diploid BHK21 Cl3 cell line was investigated. The technique used confined measurement of most of the established criteria to a single set of direct observations on one population of cells, and the results from this method were compared with those obtained from some more conventional techniques. Trisomic cells were isolated after a chronic treatment of the diploid cells with low doses of colcemid, which increased the incidence of nondisjunction at anaphase. Over several cell cycles the incidence of trisomy in the population increased to the extent where standard cloning techniques yielded a tolerably high proportion of trisomic clones. The radiosensitivity of one of these clones was examined in detail and the results compared with those obtained by other workers. Other trisomic clones were also assayed for the incidence of chromosome aberrations, post irradiation colony-forming ability and tumourigenicity to identify any which display markedly individual characteristics. These results and their implications in the radiobiology of mammalian cells are discussed. (author)

  6. Effect of anisotonic NaCl treatment on cellular ultrastructure of V79 Chinese hamster cells

    International Nuclear Information System (INIS)

    The ultrastructural modifications produced by anisotonic NaCl treatment of Chinese hamster mitotic cells were observed at three NaCl concentrations which have been frequently used in radiosensitization studies: 0.05, 0.5 and 1.5 M. After exposureto 0.05 M NaCl, many well-spread chromosomes are visible. The chromatin fibres are well dispersed and membraneous material is associated with the chromosomes. After hypertonic treatment with 0.5 M NaCl, the chromosomes have a uniform, structureless appearance with some coalescing into larger anaphase-like masses. At 1.5 M NaCl, large scale cellular dehydration is apparent, and filamentous structures such as microfilaments are tightly constricted. The degree of chromosome staining is also reduced below the level of the cytoplasm. After both hypo- and hypertonic NaCl treatment the chromosomes appear swollen relative to untreated cells, but hypertonic treatment causes chromosome clumping and dissociates chromatin. Conformational changes in the chromatin may restrict the capacity for DNA repair and be related to cellular radiosensitivity. (author)

  7. Meiosis in a triploid hybrid of Gossypium: high frequency of secondary bipolar spindles at metaphase II

    Indian Academy of Sciences (India)

    Mosareza Vafaie-Tabar; Shanti Chandrashekaran

    2007-01-01

    Studies on meiosis in pollen mother cells (PMCs) of a triploid interspecific hybrid ($3x = 39$ chromosomes, AAD) between tetraploid Gossypium hirsutum ($4n = 2x = 52$,AADD) and diploid G. arboreum ($2n = 2x = 26$,AA) are reported. During meiotic metaphase I, 13 AA bivalents and 13 D univalents are expected in the hybrid. However, only 28% of the PMCs had this expected configuration. The rest of the PMCs had between 8 and 12 bivalents and between 12 and 17 univalents. Univalents lagged at anaphase I, and at metaphase II one or a group of univalents remained scattered in the cytoplasm and failed to assemble at a single metaphase plate. Primary bipolar spindles organized around the bivalents and multivalents. In addition to the primary spindle, several secondary and smaller bipolar spindles organized themselves around individual univalents and groups of univalents. Almost all (97%) of the PMCs showed secondary spindles. Each spindle functioned independently and despite their multiple numbers in a cell, meiosis I proceeded normally, with polyad formation. These observations strongly support the view that in plant meiocytes bilateral kinetochore symmetry is not required for establishing a bipolar spindle and that single unpaired chromosomes can initiate and stabilize the formation of a functional bipolar spindle.

  8. Synchronizing Progression of Schizosaccharomyces pombe Cells from Prophase through Mitosis and into S Phase with nda3-KM311 Arrest Release.

    Science.gov (United States)

    Hagan, Iain M; Grallert, Agnes; Simanis, Viesturs

    2016-01-01

    Here, we describe how the rapid reversibility of the nda3-KM311 cold-sensitive β-tubulin mutation was optimized by Mitsuhiro Yanagida's laboratory to synchronize mitotic progression in an entire cell population. The inability to form microtubules following the loss of β-tubulin function at 20°C triggers the spindle assembly checkpoint, which arrests mitotic progression. Restoration of β-tubulin function by rewarming to 30°C (or higher) releases the arrest, generating a highly synchronous progression through mitosis. The viability of nda3-KM311 strains at 30°C makes it feasible to generate double mutants between nda3-KM311 and any temperature-sensitive mutant that can also grow at 30°C. These double mutants can be used in reciprocal shift analyses, in which cold-induced early mitotic arrest is relieved by a shift to 36°C, which then inactivates the product of the second mutant gene. The addition of microtubule depolymerizing drugs before the return to 36°C will maintain checkpoint signaling at 36°C transiently, permitting analysis of the impact of temperature-sensitive mutations on checkpoint function. Silencing the checkpoint of nda3-KM311-arrested cells at 20°C through chemical inhibition of aurora kinase is a powerful way to study checkpoint recovery pathways and mitotic exit without anaphase. PMID:27480719

  9. Characterization of the NTPR and BD1 interacting domains of the human PICH-BEND3 complex.

    Science.gov (United States)

    Pitchai, Ganesha P; Hickson, Ian D; Streicher, Werner; Montoya, Guillermo; Mesa, Pablo

    2016-08-01

    Chromosome integrity depends on DNA structure-specific processing complexes that resolve DNA entanglement between sister chromatids. If left unresolved, these entanglements can generate either chromatin bridging or ultrafine DNA bridging in the anaphase of mitosis. These bridge structures are defined by the presence of the PICH protein, which interacts with the BEND3 protein in mitosis. To obtain structural insights into PICH-BEND3 complex formation at the atomic level, their respective NTPR and BD1 domains were cloned, overexpressed and crystallized using 1.56 M ammonium sulfate as a precipitant at pH 7.0. The protein complex readily formed large hexagonal crystals belonging to space group P6122, with unit-cell parameters a = b = 47.28, c = 431.58 Å and with one heterodimer in the asymmetric unit. A complete multiwavelength anomalous dispersion (MAD) data set extending to 2.2 Å resolution was collected from a selenomethionine-labelled crystal at the Swiss Light Source. PMID:27487930

  10. Cyclin B1 is localized to unattached kinetochores and contributes to efficient microtubule attachment and proper chromosome alignment during mitosis

    Institute of Scientific and Technical Information of China (English)

    Qiang Chen; Xiaoyan Zhang; Qing Jiang; Paul R Clarke; Chuanmao Zhang

    2008-01-01

    Cyclin Bl is a key regulatory protein controlling cell cycle progression in vertebrates. Cyclin Bl binds CDK1, a cyclin-dependent kinase catalytic subunit, forming a complex that orchestrates mitosis through phosphorylation of key proteins. Cyclin Bl regulates both the activation of CDK1 and its subcellular localization, which may be critical for substrate selection. Here, we demonstrate that cyclin Bl is concentrated on the outer plate of the kinetochore during prometaphase. This localization requires the cyclin box region of the protein. Cyclin Bl is displaced from individual kinetochores to the spindle poles by microtubule attachment to the kinetochores, and this displacement is dependent on the dynein/dynactin complex. Depletion of cyclin Bl by vector-based siRNA causes inefficient attachment between kinetochores and microtubules, and chromosome alignment defects, and delays the onset of anaphase. We conclude that cyclin Bl accumulates at kinetochores during prometaphase, where it contributes to the correct attachment of microtubules to kinetochores and efficient alignment of the chromosomes, most likely through localized phosphorylation of specific substrates by cyclin B1-CDK1. Cyclin Bl is then transported from each kinetochore as microtubule attachment is completed, and this relocalization may redirect the activity of cyclin B1-CDK1 and contribute to inactivation of the spindle assembly checkpoint.

  11. Partitioning and Exocytosis of Secretory Granules during Division of PC12 Cells

    Directory of Open Access Journals (Sweden)

    Nickolay Vassilev Bukoreshtliev

    2012-01-01

    Full Text Available The biogenesis, maturation, and exocytosis of secretory granules in interphase cells have been well documented, whereas the distribution and exocytosis of these hormone-storing organelles during cell division have received little attention. By combining ultrastructural analyses and time-lapse microscopy, we here show that, in dividing PC12 cells, the prominent peripheral localization of secretory granules is retained during prophase but clearly reduced during prometaphase, ending up with only few peripherally localized secretory granules in metaphase cells. During anaphase and telophase, secretory granules exhibited a pronounced movement towards the cell midzone and, evidently, their tracks colocalized with spindle microtubules. During cytokinesis, secretory granules were excluded from the midbody and accumulated at the bases of the intercellular bridge. Furthermore, by measuring exocytosis at the single granule level, we showed, that during all stages of cell division, secretory granules were competent for regulated exocytosis. In conclusion, our data shed new light on the complex molecular machinery of secretory granule redistribution during cell division, which facilitates their release from the F-actin-rich cortex and active transport along spindle microtubules.

  12. Dendrite Development Regulated by the Schizophrenia-Associated Gene FEZ1 Involves the Ubiquitin Proteasome System

    Directory of Open Access Journals (Sweden)

    Yasuhito Watanabe

    2014-04-01

    Full Text Available Downregulation of the schizophrenia-associated gene DISC1 and its interacting protein FEZ1 positively regulates dendrite growth in young neurons. However, little is known about the mechanism that controls these molecules during neuronal development. Here, we identify several components of the ubiquitin proteasome system and the cell-cycle machinery that act upstream of FEZ1. We demonstrate that the ubiquitin ligase cell division cycle 20/anaphase-promoting complex (Cdc20/APC controls dendrite growth by regulating the degradation of FEZ1. Furthermore, dendrite growth is modulated by BubR1, whose known function so far has been restricted to control Cdc20/APC activity during the cell cycle. The modulatory function of BubR1 is dependent on its acetylation status. We show that BubR1 is deacetylated by Hdac11, thereby disinhibiting the Cdc20/APC complex. Because dendrite growth is affected both in hippocampal dentate granule cells and olfactory bulb neurons upon modifying expression of these genes, we conclude that the proposed mechanism governs neuronal development in a general fashion.

  13. Effects of the Food Additive Sodium Benzoate on Developing Chicken Liver

    Directory of Open Access Journals (Sweden)

    Feryal KARAKAHYA

    2016-04-01

    Full Text Available In this study, the effects of sodium benzoate (E-211 (SB on the liver tissues of chicken embryos which were exposed to different doses of SB and for different durations were histopathologically investigated. SB was injected into vitellus at three different doses (250, 500, 1000 mg/kg on the 5th day of the incubation. The embryos of the control and experimental groups were collected on the 7th day (stage 31 and 10th day (stage 36 of incubation and weighed. It was statistically detected that SB caused rise to a significant decrease (P<0.001 on the total weights of the embryos depending in the dose and duration. At microscopic level deterioration of vein structures, congestion, edema, sinusoidal dilation, deterioration of hepatocyte arrangements, swelling, vacuolization, chromatin condensation, karyolysis, shape deformation and eccentric located of the nuclei decrease in Nuclear Organization Regions (NOR and mitotic division, stickiness of chromosomes, anaphase bridge, nuclei budding and the formation of micronuclei were observed.

  14. Centromeric chromatin and its dynamics in plants.

    Science.gov (United States)

    Lermontova, Inna; Sandmann, Michael; Mascher, Martin; Schmit, Anne-Catherine; Chabouté, Marie-Edith

    2015-07-01

    Centromeres are chromatin structures that are required for proper separation of chromosomes during mitosis and meiosis. The centromere is composed of centromeric DNA, often enriched in satellite repeats, and kinetochore complex proteins. To date, over 100 kinetochore components have been identified in various eukaryotes. Kinetochore assembly begins with incorporation of centromeric histone H3 variant CENH3 into centromeric nucleosomes. Protein components of the kinetochore are either present at centromeres throughout the cell cycle or localize to centromeres transiently, prior to attachment of microtubules to each kinetochore in prometaphase of mitotic cells. This is the case for the spindle assembly checkpoint (SAC) proteins in animal cells. The SAC complex ensures equal separation of chromosomes between daughter nuclei by preventing anaphase onset before metaphase is complete, i.e. the sister kinetochores of all chromosomes are attached to spindle fibers from opposite poles. In this review, we focus on the organization of centromeric DNA and the kinetochore assembly in plants. We summarize recent advances regarding loading of CENH3 into the centromere, and the subcellular localization and protein-protein interactions of Arabidopsis thaliana proteins involved in kinetochore assembly and function. We describe the transcriptional activity of corresponding genes based on in silico analysis of their promoters and cell cycle-dependent expression. Additionally, barley homologs of all selected A. thaliana proteins have been identified in silico, and their sequences and domain structures are presented. PMID:25976696

  15. Genotoxicity and cytotoxicity assay of water sampled from the underground nuclear explosion site in the north of the Perm region (Russia)

    Energy Technology Data Exchange (ETDEWEB)

    Evseeva, Tatiana I. [Institute of Biology, Komi Scientific Center, Ural Division RAS, 167982, Syktyvkar, Kommunisticheskaya 28 (Russian Federation); Geras' kin, Stanislav A. [Russian Institute of Agricultural Radiology and Agroecology RAAS, 249020 Obninsk, Kaluga region (Russian Federation)]. E-mail: stgeraskin@list.ru; Shuktomova, Ida I. [Institute of Biology, Komi Scientific Center, Ural Division RAS, 167982, Syktyvkar, Kommunisticheskaya 28 (Russian Federation); Taskaev, Anatoliy I. [Institute of Biology, Komi Scientific Center, Ural Division RAS, 167982, Syktyvkar, Kommunisticheskaya 28 (Russian Federation)

    2005-07-01

    The results of our study revealed a local biologically relevant surface water contamination in the radionuclide anomaly in the north of Russia (Perm region) by means of Allium schoenoprasum L. anaphase-telophase chromosome aberration assay. This radionuclide anomaly was formed in 1971 as a result of an underground nuclear explosion with soil excavation. Specific activities of main dose-forming radionuclides in all examined reservoirs are below intervention levels officially adopted in Russia for drinking water. We found that {sup 90}Sr significantly contributes to induction of cytogenetic disturbances. Our previous data and the data described here suggest that metal and radionuclide combined exposure (with the dose below permissible exposure limits for human) may cause substantial biological effects. These effects are in part due to synergic response. The findings described here indicated that development of a new concept of radiation protection for humans and biota should be based on the clear understanding of biological effects of low doses of radiation in chronic exposure to multi-pollutant mixtures.

  16. Sensitivity of Bidens laevis L. to mutagenic compounds. Use of chromosomal aberrations as biomarkers of genotoxicity

    Energy Technology Data Exchange (ETDEWEB)

    Perez, D.J. [Laboratorio de Genetica, Estacion Experimental Agropecuaria Balcarce (INTA), Facultad de Ciencias Agrarias, UNMdP, CC 276, 7620 Balcarce (Argentina); Laboratorio de Ecotoxicologia, Departamento de Ciencias Marinas, Facultad de Ciencias Exactas y Naturales, UNMdP, Funes 3350, 7600 Mar del Plata (Argentina); Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET), Rivadavia 1917, 1033 Buenos Aires (Argentina); Lukaszewicz, G. [Laboratorio de Ecotoxicologia, Departamento de Ciencias Marinas, Facultad de Ciencias Exactas y Naturales, UNMdP, Funes 3350, 7600 Mar del Plata (Argentina); Menone, M.L., E-mail: lujanm@mdp.edu.a [Laboratorio de Ecotoxicologia, Departamento de Ciencias Marinas, Facultad de Ciencias Exactas y Naturales, UNMdP, Funes 3350, 7600 Mar del Plata (Argentina); Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET), Rivadavia 1917, 1033 Buenos Aires (Argentina); Camadro, E.L. [Laboratorio de Genetica, Estacion Experimental Agropecuaria Balcarce (INTA), Facultad de Ciencias Agrarias, UNMdP, CC 276, 7620 Balcarce (Argentina); Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET), Rivadavia 1917, 1033 Buenos Aires (Argentina)

    2011-01-15

    The wetland macrophyte Bidens laevis possesses suitable cytological characteristics for genotoxicity testing. To test its sensitivity as compared to terrestrial plants species currently in use in standardized assays, Methyl Methanesulfonate (MMS), N-ethyl-N-nitrosourea (ENU) and Maleic Hydrazide (HM) were used. On the other hand, the insecticide Endosulfan (ES) - an environmentally relevant contaminant - was assayed in seeds and two-month old plants. Mitotic Index (MI), frequency of Chromosome Aberrations in Anaphase-Telophase (CAAT) and frequency of Abnormal Metaphases (AM) were analyzed. MH, MMS and ENU caused a significant decrease of the MI. MMS was aneugenic whereas MH and ENU were both aneugenic and clastogenic. ES caused a significant concentration-dependent increase of total- and aneugenic-CAAT in roots and a significant high frequency of AM at high concentrations. Because of its sensitivity to mutagenic substances, B. laevis can be regarded as a reliable and convenient species for genotoxicity assays especially if aquatic contaminants are evaluated. - The wetland macrophyte Bidens laevis is sensitive to genotoxic compounds similarly to terrestrial standardized species.

  17. Analysis of the mitotic exit control system using locked levels of stable mitotic cyclin.

    Science.gov (United States)

    Drapkin, Benjamin J; Lu, Ying; Procko, Andrea L; Timney, Benjamin L; Cross, Frederick R

    2009-01-01

    Cyclin-dependent kinase (Cdk) both promotes mitotic entry (spindle assembly and anaphase) and inhibits mitotic exit (spindle disassembly and cytokinesis), leading to an elegant quantitative hypothesis that a single cyclin oscillation can function as a ratchet to order these events. This ratchet is at the core of a published ODE model for the yeast cell cycle. However, the ratchet model requires appropriate cyclin dose-response thresholds. Here, we test the inhibition of mitotic exit in budding yeast using graded levels of stable mitotic cyclin (Clb2). In opposition to the ratchet model, stable levels of Clb2 introduced dose-dependent delays, rather than hard thresholds, that varied by mitotic exit event. The ensuing cell cycle was highly abnormal, suggesting a novel reason for cyclin degradation. Cdc14 phosphatase antagonizes Clb2-Cdk, and Cdc14 is released from inhibitory nucleolar sequestration independently of stable Clb2. Thus, Cdc14/Clb2 balance may be the appropriate variable for mitotic regulation. Although our results are inconsistent with the aforementioned ODE model, revision of the model to allow Cdc14/Clb2 balance to control mitotic exit corrects these discrepancies, providing theoretical support for our conclusions. PMID:19920813

  18. Mutation in the bimD gene of Aspergillus nidulans confers a conditional mitotic block and sensitivity to DNA damaging agents

    International Nuclear Information System (INIS)

    Mutation in the bimD gene of Aspergillus nidulans results in a mitotic block in anaphase characterized by a defective mitosis. Mutation in bimD also confers, at temperatures permissive for the mitotic arrest phenotype, an increased sensitivity to DNA damaging agents, including methyl methanesulfonate and ultraviolet light. In order to better understand the relationship between DNA damage and mitotic progression, the authors cloned the bimD gene from Aspergillus. A cosmid containing the bimD gene was identified among pools of cosmids by cotransformation with the nutritional selective pyrG gene of a strain carrying the recessive, temperature-sensitive lethal bimD6 mutation. The bimD gene encodes a predicted polypeptide of 166,000 daltons in mass and contains amino acid sequence motifs similar to those found in some DNA-binding transcription factors. These sequences include a basic domain followed by a leucine zipper, which together are called a bZIP motif, and a carboxyl-terminal domain enriched in acidic amino acids. Overexpression of the wild-type bimD protein resulted in an arrest of the nuclear division cycle that was reversible and determined to be in either the G1 or S phase of the cell cycle. The data suggest that bimD may play an essential regulatory role relating to DNA metabolism which is required for a successful mitosis. 7l refs., 7 figs., 1 tab

  19. A simple and reliable in vitro test system for the analysis of induced aneuploidy as well as other cytogenetic end-points using Chinese hamster cells

    International Nuclear Information System (INIS)

    Although aneuploidy is a serious human health problem, the experimental methodology devised until now to study the mechanisms involved in the induction of aneuploidy and for the screening of aneuploidy-inducing agents has not been so much employed to have the necessary validation. A procedure using primary cell cultures of Chinese hamster embryo cells grown on cover glasses is described. To avoid the excessive scattering and subsequent loss of chromosomes, a hypotonic treatment with a 0.17% sodium chloride solution, at room temperature, followed by in situ fixation has been standardized. This procedure improves the method through the reduction of the spontaneous frequency of aneuploid cells. Experiments carried out with cells treated with X-rays, X-rays plus caffeine, and the synthetic estrogen diethylstilbestrol (DES) demonstrated the accuracy of the system since the average chromosome number remained constant in spite of the induction of high frequencies of aneuploid cells. Moreover, the method allows for the analysis of other cytogenetic endpoints such as anaphase-telophase alterations, structural chromosome aberrations or sister chromatid exchanges. (author)

  20. Visualization and Characterization of High-Order Chromatin Fibers under Light Microscope during Interphase and Mitotic Stages in Plants

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Using genomic in situ hybridization with genomic DNA.high-order chromatin fibers were successfully exhibited under a light microscope through the cell cycle in barley,rice,maize and field bean.From the interphase to prophase and metaphase of mitosis,the fibers were basically similar.Each was estimated to be around 200 nm in diameter,but the strength of signals was not the same along the fiber length.Through the cell cycle a series of dynamic distribution changes occurred in the fibers.In the interphase,they were unraveled.At the early prophase they were arranged with parallel and mirror symmetry.During late-prophase and metaphase,the fibers were bundled and became different visible chromosomes.The parallel coiling and mirror symmetry structures were visible clearly until the metaphase.In anaphase they disappeared.During telophase,in peripheral regions of congregated chromosome group,borderlines of the chromosomes disappeared and the fibers were unraveled.This demonstrated that mitotic chromosomes are assembled and organized by parallel and adjacent coiling of the fibers and the fibers should be the highest order structure for DNA coiling.

  1. Mechanism of the chromosome-induced polar body extrusion in mouse eggs

    Directory of Open Access Journals (Sweden)

    Racowsky Catherine

    2011-08-01

    Full Text Available Abstract Background An oocyte undergoes two rounds of asymmetric division to generate a haploid gamete and two small polar bodies designed for apoptosis. Chromosomes play important roles in specifying the asymmetric meiotic divisions in the oocytes but the underlying mechanism is poorly understood. Results Chromosomes independently induce spindle formation and cortical actomyosin assembly into special cap and ring structures in the cortex of the oocyte. The spindle and the cortical cap/ring interact to generate mechanical forces, leading to polar body extrusion. Two distinct force-driven membrane changes were observed during 2nd polar body extrusion: a protrusion of the cortical cap and a membrane invagination induced by an anaphase spindle midzone. The cortical cap protrusion and invagination help rotate the spindle perpendicularly so that the spindle midzone can induce bilateral furrows at the shoulder of the protruding cap, leading to an abscission of the polar body. It is interesting to note that while the mitotic spindle midzone induces bilateral furrowing, leading to efficient symmetric division in the zygote, the meiotic spindle midzone induced cytokinetic furrowing only locally. Conclusions Distinct forces driving cortical cap protrusion and membrane invagination are involved in spindle rotation and polar body extrusion during meiosis II in mouse oocytes.

  2. Occurrence of differential meiotic associations and additional chromosomes in the embryo-sac mother cells of Allium roylei Stearn

    Indian Academy of Sciences (India)

    Geeta Sharma; Ravinder N. Gohil

    2011-04-01

    A small population of complex translocation heterozygote plants of Allium roylei from the Bani region of Jammu Province was studied for meiosis in the female track. This study resulted in identification of two variants, having embryo-sac mother cells (EMCs) with more than 16 chromosomes. EMCs of the remaining plants invariably had diploid $(2n = 16)$ chromosome complement. Female meiosis, in general, was found to be abnormal, with nearly 23% and 11% chromosomes associating as quadrivalents or trivalents at prophase I and at metaphase I, respectively. This was followed by irregular segregation of chromosomes at anaphase I. Amongst the variants; one had 38% EMCs with eight bivalents plus two small sized chromosomes. Their small size, dispensable nature and tendency to affect the pairing behaviour of normal complement are some of the features that latter chromosomes share with the B chromosomes. Seventeen to nineteen chromosomes were observed in 35% EMCs of other variant; the remaining cells had 16 chromosomes. Chromosomal behaviour in both kind of cells (euploid and aneuploid) was more or less similar. Unlike female meiocytes, male meiocytes analysed earlier of this strain always had 16 chromosomes which paired to form extremely complex associations involving 3–16 chromosomes. The most likely cause of this asynchrony with regards to number of chromosomes involved in multivalent formation seems to be interaction of genes controlling chiasma formation with the different physiological conditions of male and female meiocytes.

  3. Effect of SPL (Spent Pot Liner) and its main components on root growth, mitotic activity and phosphorylation of Histone H3 in Lactuca sativa L.

    Science.gov (United States)

    Freitas, Aline Silva; Fontes Cunha, Isabela Martinez; Andrade-Vieira, Larissa Fonseca; Techio, Vânia Helena

    2016-02-01

    Spent Pot Liner (SPL) is a solid waste from the aluminum industry frequently disposed of in industrial landfills; it can be leached and contaminate the soil, sources of drinking water and plantations, and thus may pose a risk to human health and to ecosystems. Its composition is high variable, including cyanide, fluoride and aluminum salts, which are highly toxic and environmental pollutants. This study evaluated the effect of SPL and its main components on root growth and the mitosis of Lactuca sativa, by investigating the mechanisms of cellular and chromosomal alterations with the aid of immunolocalization. To this end, newly emerged roots of L. sativa were exposed to SPL and its main components (solutions of cyanide, fluoride and aluminum) and to calcium chloride (control) for 48h. After this, root length was measured and cell cycle was examined by means of conventional cytogenetics and immunolocalization. Root growth was inhibited in the treatments with SPL and aluminum; chromosomal and nuclear alterations were observed in all treatments. The immunolocalization evidenced normal dividing cells with regular temporal and spatial distribution of histone H3 phosphorylation at serine 10 (H3S10ph). However, SPL and its main components inhibited the phosphorylation of histone H3 at serine 10, inactivated pericentromeric regions and affected the cohesion of sister chromatids, thus affecting the arrangement of chromosomes in the metaphase plate and separation of chromatids in anaphase. In addition, these substances induced breaks in pericentromeric regions, characterized as fragile sites. PMID:26615478

  4. Cenp-meta is required for sustained spindle checkpoint

    Directory of Open Access Journals (Sweden)

    Thomas Rubin

    2014-05-01

    Full Text Available Cenp-E is a kinesin-like motor protein required for efficient end-on attachment of kinetochores to the spindle microtubules. Cenp-E immunodepletion in Xenopus mitotic extracts results in the loss of mitotic arrest and massive chromosome missegregation, whereas its depletion in mammalian cells leads to chromosome segregation defects despite the presence of a functional spindle assembly checkpoint (SAC. Cenp-meta has previously been reported to be the Drosophila homolog of vertebrate Cenp-E. In this study, we show that cenp-metaΔ mutant neuroblasts arrest in mitosis when treated with colchicine. cenp-metaΔ mutant cells display a mitotic delay. Yet, despite the persistence of the two checkpoint proteins Mad2 and BubR1 on unattached kinetochores, these cells eventually enter anaphase and give rise to highly aneuploid daughter cells. Indeed, we find that cenp-metaΔ mutant cells display a slow but continuous degradation of cyclin B, which eventually triggers the mitotic exit observed. Thus, our data provide evidence for a role of Cenp-meta in sustaining the SAC response.

  5. Mutations in Drosophila Greatwall/Scant reveal its roles in mitosis and meiosis and interdependence with Polo kinase.

    Directory of Open Access Journals (Sweden)

    Vincent Archambault

    2007-11-01

    Full Text Available Polo is a conserved kinase that coordinates many events of mitosis and meiosis, but how it is regulated remains unclear. Drosophila females having only one wild-type allele of the polo kinase gene and the dominant Scant mutation produce embryos in which one of the centrosomes detaches from the nuclear envelope in late prophase. We show that Scant creates a hyperactive form of Greatwall (Gwl with altered specificity in vitro, another protein kinase recently implicated in mitotic entry in Drosophila and Xenopus. Excess Gwl activity in embryos causes developmental failure that can be rescued by increasing maternal Polo dosage, indicating that coordination between the two mitotic kinases is crucial for mitotic progression. Revertant alleles of Scant that restore fertility to polo-Scant heterozygous females are recessive alleles or deficiencies of gwl; they show chromatin condensation defects and anaphase bridges in larval neuroblasts. One recessive mutant allele specifically disrupts a Gwl isoform strongly expressed during vitellogenesis. Females hemizygous for this allele are sterile, and their oocytes fail to arrest in metaphase I of meiosis; both homologues and sister chromatids separate on elongated meiotic spindles with little or no segregation. This allelic series of gwl mutants highlights the multiple roles of Gwl in both mitotic and meiotic progression. Our results indicate that Gwl activity antagonizes Polo and thus identify an important regulatory interaction of the cell cycle.

  6. Genotoxicity and cytotoxicity assay of water sampled from the underground nuclear explosion site in the north of the Perm region (Russia).

    Science.gov (United States)

    Evseeva, Tatiana I; Geras'kin, Stanislav A; Shuktomova, Ida I; Taskaev, Anatoliy I

    2005-01-01

    The results of our study revealed a local biologically relevant surface water contamination in the radionuclide anomaly in the north of Russia (Perm region) by means of Allium schoenoprasum L. anaphase-telophase chromosome aberration assay. This radionuclide anomaly was formed in 1971 as a result of an underground nuclear explosion with soil excavation. Specific activities of main dose-forming radionuclides in all examined reservoirs are below intervention levels officially adopted in Russia for drinking water. We found that (90)Sr significantly contributes to induction of cytogenetic disturbances. Our previous data and the data described here suggest that metal and radionuclide combined exposure (with the dose below permissible exposure limits for human) may cause substantial biological effects. These effects are in part due to synergic response. The findings described here indicated that development of a new concept of radiation protection for humans and biota should be based on the clear understanding of biological effects of low doses of radiation in chronic exposure to multi-pollutant mixtures. PMID:15653187

  7. [Genotoxicity and toxicity assay of water sampled from the underground nuclear explosion site in the north of the Perm region (Russia)].

    Science.gov (United States)

    Evseeva, T I; Geras'kin, S A; Shuktomova, I I; Taskaev, A I

    2004-01-01

    The results of our study revealed a local biologically relevant surface water contamination in the radionuclide anomaly in the north of Russia (Perm region) by means of Allium shoenoprasum L. the anaphase-telophase chromosome aberration assay. This radionuclide anomaly was formed in 1971 as a result of an underground nuclear explosion with soil excavation. Specific activities of main dose-forming radionuclides in all examined reservoirs are below intervention levels officially adopted in Russia for drinking water. We found that 90Sr significantly contribute to induction of cytogenetic disturbances. Our previous and described here data suggest that metal ions and radionuclides combined exposure on the various biota species (with the dose below permissible exposure limits for human) may cause substantial biological effects in part be due to synergic response. The findings described here indicated that development of a new concept of radiation protection for humans and biota should be based on the clear understanding of biological effects of low doses of radiation in chronic exposure to multi-pollutant mixtures. PMID:15700811

  8. Morphological Studies of Nucleologenesis in Giardia lamblia.

    Science.gov (United States)

    Lara-Martínez, Reyna; De Lourdes Segura-Valdez, María; De La Mora-De La Mora, Ignacio; López-Velázquez, Gabriel; JimÉnez-García, Luis Felipe

    2016-05-01

    The nucleolus is a nuclear organelle involved in ribosome biogenesis. In most eukaryotes this structure disperses during prophase through anaphase and reorganizes at telophase by a process known as nucleologenesis. This process involves new transcription of ribosomal DNA at the nucleolar organizer region and the formation of prenucleolar bodies fusing to it. In Giardia lamblia, for a long time considered the only anucleolated eukaryote, a very small nucleolus has been recently described. In order to evaluate whether nucleologenesis is also present in Giardia, we analyzed the distribution of nucleolar material during telophase using different light and electron microscopy techniques including silver staining for the nucleolar organizer. Results indicate that in G. lamblia, nucleolar elements persist mainly as an intranuclear peripheral organelle during all stages of division, including telophase, however, no prenucleolar bodies are detected in the nucleoplasm. Therefore, in the parasite, nucleolar material is present throughout cell division including telophase and formation of prenucleolar bodies may not be required for nucleologenesis. Anat Rec, 299:549-556, 2016. © 2016 Wiley Periodicals, Inc. PMID:26833978

  9. Relationship between plant growth and cytological effect in root apical meristem after exposure of wheat dry seeds to carbon ion beams

    International Nuclear Information System (INIS)

    In order to analyze the relationship between plant growth and cytological effects, wheat dry seeds were exposed to various doses of 12C6+ beams and the biological endpoints reflecting plant growth and root apical meristem (RAM) activities were investigated. The results showed that most of the seeds were able to germinate normally within all dose range, while the plant survival rate descended at higher doses. The seedling growth including root length and seedling height also decreased significantly at higher doses. Mitotic index (MI) in RAM had no changes at 10 and 20 Gy and decreased obviously at higher doses and the proportion of prophase cells had the same trend with MI. These data suggested that RAM cells experienced cell cycle arrest, which should be responsible for the inhibition of root growth after exposure to higher doses irradiation. Moreover, various types of chromosome aberrations (CAs) were observed in the mitotic cells. The frequencies of mitotic cells with lagging chromosomes and these with anaphase bridges peaked around 60 Gy, while the frequencies of these with fragments increased as the irradiation doses increased up to 200 Gy. The total frequencies of mitotic cells with CAs induced by irradiation increased significantly with the increasing doses. The serious damage of mitotic chromosomes maybe caused cell cycle arrest or cell death. These findings suggested that the influences of 12C6+ beams irradiation on plant growth were related to the alternation of mitotic activities and the chromosomal damages in RAM

  10. Relationship between plant growth and cytological effect in root apical meristem after exposure of wheat dry seeds to carbon ion beams

    Science.gov (United States)

    Liu, Qingfang; Wang, Zhuanzi; Zhou, Libin; Qu, Ying; Lu, Dong; Yu, Lixia; Du, Yan; Jin, Wenjie; Li, Wenjian

    2013-06-01

    In order to analyze the relationship between plant growth and cytological effects, wheat dry seeds were exposed to various doses of 12C6+ beams and the biological endpoints reflecting plant growth and root apical meristem (RAM) activities were investigated. The results showed that most of the seeds were able to germinate normally within all dose range, while the plant survival rate descended at higher doses. The seedling growth including root length and seedling height also decreased significantly at higher doses. Mitotic index (MI) in RAM had no changes at 10 and 20 Gy and decreased obviously at higher doses and the proportion of prophase cells had the same trend with MI. These data suggested that RAM cells experienced cell cycle arrest, which should be responsible for the inhibition of root growth after exposure to higher doses irradiation. Moreover, various types of chromosome aberrations (CAs) were observed in the mitotic cells. The frequencies of mitotic cells with lagging chromosomes and these with anaphase bridges peaked around 60 Gy, while the frequencies of these with fragments increased as the irradiation doses increased up to 200 Gy. The total frequencies of mitotic cells with CAs induced by irradiation increased significantly with the increasing doses. The serious damage of mitotic chromosomes maybe caused cell cycle arrest or cell death. These findings suggested that the influences of 12C6+ beams irradiation on plant growth were related to the alternation of mitotic activities and the chromosomal damages in RAM.

  11. Fission yeast Scm3: A CENP-A receptor required for integrity of subkinetochore chromatin.

    Science.gov (United States)

    Pidoux, Alison L; Choi, Eun Shik; Abbott, Johanna K R; Liu, Xingkun; Kagansky, Alexander; Castillo, Araceli G; Hamilton, Georgina L; Richardson, William; Rappsilber, Juri; He, Xiangwei; Allshire, Robin C

    2009-02-13

    The mechanisms ensuring specific incorporation of CENP-A at centromeres are poorly understood. Mis16 and Mis18 are required for CENP-A localization at centromeres and form a complex that is conserved from fission yeast to human. Fission yeast sim1 mutants that alleviate kinetochore domain silencing are defective in Scm3(Sp), the ortholog of budding yeast Scm3(Sc). Scm3(Sp) depends on Mis16/18 for its centromere localization and like them is recruited to centromeres in late anaphase. Importantly, Scm3(Sp) coaffinity purifies with CENP-A(Cnp1) and associates with CENP-A(Cnp1) in vitro, yet localizes independently of intact CENP-A(Cnp1) chromatin and is differentially released from chromatin. While Scm3(Sc) has been proposed to form a unique hexameric nucleosome with CENP-A(Cse4) and histone H4 at budding yeast point centromeres, we favor a model in which Scm3(Sp) acts as a CENP-A(Cnp1) receptor/assembly factor, cooperating with Mis16 and Mis18 to receive CENP-A(Cnp1) from the Sim3 escort and mediate assembly of CENP-A(Cnp1) into subkinetochore chromatin. PMID:19217404

  12. The DASH complex and Klp5/Klp6 kinesin coordinate bipolar chromosome attachment in fission yeast.

    Science.gov (United States)

    Sanchez-Perez, Isabel; Renwick, Steven J; Crawley, Karen; Karig, Inga; Buck, Vicky; Meadows, John C; Franco-Sanchez, Alejandro; Fleig, Ursula; Toda, Takashi; Millar, Jonathan B A

    2005-08-17

    We identified a truncated allele of dam1 as a multicopy suppressor of the sensitivity of cdc13-117 (cyclin B) and mal3-1 (EB-1) cells to thiabendazole, a microtubule poison. We find that Dam1 binds to the plus end of spindle microtubules and kinetochores as cells enter mitosis and this is dependent on other components of the fission yeast DASH complex, including Ask1, Duo1, Spc34 and Dad1. By contrast, Dad1 remains bound to kinetochores throughout the cell cycle and its association is dependent on the Mis6 and Mal2, but not Mis12, Nuf2 or Cnp1, kinetochore proteins. In cells lacking Dam1, or other components of the DASH complex, anaphase is delayed due to activation of the spindle assembly checkpoint and lagging sister chromatids are frequently observed and occasionally sister chromatid pairs segregate to the same spindle pole. We find that the mitotic centromere-associated Klp5/Klp6 kinesin complex is essential in cells lacking components of the DASH complex. Cells lacking both Dam1 and Klp5 undergo a first cell cycle arrest in mitosis due to a failure to establish bipolar chromosome attachment. PMID:16079915

  13. Early localization of NPA58, a rat nuclear pore-associated protein, to the reforming nuclear envelope during mitosis

    Indian Academy of Sciences (India)

    Radhika Ganeshan; Nandini Rangaraj; Veena K Parnaik

    2001-03-01

    We have studied the mitotic reassembly of the nuclear envelope, using antibodies to nuclear marker proteins and NPA58 in F-111 rat fibroblast cells. In earlier studies we have proposed that NPA58, a 58 kDa rat nuclear protein, is involved in nuclear protein import. In this report, NPA58 is shown to be localized on the cytoplasmic face of the envelope in interphase cells, in close association with nuclear pores. In mitotic cells NPA58 is dispersed in the cytoplasm till anaphase. The targeting of NPA58 to the reforming nuclear envelope in early telophase coincides with the recruitment of a well-characterized class of nuclear pore proteins recognized by the antibody mAb 414, and occurs prior to the incorporation of lamin B1 into the envelope. Significant protein import activity is detectable only after localization of NPA58 in the newly-formed envelope. The early targeting of NPA58 is consistent with its proposed role in nuclear transport.

  14. PTP-S2, a nuclear tyrosine phosphatase, is phosphorylated and excluded from condensed chromosomes during mitosis

    Indian Academy of Sciences (India)

    Sundaram Nambirajan; Vegesna Radha; Shubhangi Kamatkar; Ghanshyam Swarup

    2000-03-01

    PTP-S2 is a tyrosine specific protein phosphatase that binds to DNA and is localized to the nucleus in association with chromatin. It plays a role in the regulation of cell proliferation. Here we show that the subcellular distribution of this protein changes during cell division. While PTP-S2 was localized exclusively to the nucleus in interphase cells, during metaphase and anaphase it was distributed throughout the cytoplasm and excluded from condensed chromosomes. At telophase PTP-S2 began to associate with chromosomes and at cytokinesis it was associated with chromatin in the newly formed nucleus. It was hyperphosphorylated and showed retarded mobility in cells arrested in metaphase. In vitro experiments showed that it was phosphorylated by CK2 resulting in mobility shift. Using a deletion mutant we found that CK2 phosphorylated PTP-S2 in the C-terminal non-catalytic domain. A heparin sensitive kinase from mitotic cell extracts phosphorylated PTP-S2 resulting in mobility shift. These results are consistent with the suggestion that during metaphase PTP-S2 is phosphorylated (possibly by CK2 or a CK2-like enzyme), resulting in its dissociation from chromatin.

  15. The Cohesin Subunit Rad21 Is Required for Synaptonemal Complex Maintenance, but Not Sister Chromatid Cohesion, during Drosophila Female Meiosis

    Science.gov (United States)

    Lehner, Christian F.; Heidmann, Stefan K.

    2014-01-01

    Replicated sister chromatids are held in close association from the time of their synthesis until their separation during the next mitosis. This association is mediated by the ring-shaped cohesin complex that appears to embrace the sister chromatids. Upon proteolytic cleavage of the α-kleisin cohesin subunit at the metaphase-to-anaphase transition by separase, sister chromatids are separated and segregated onto the daughter nuclei. The more complex segregation of chromosomes during meiosis is thought to depend on the replacement of the mitotic α-kleisin cohesin subunit Rad21/Scc1/Mcd1 by the meiotic paralog Rec8. In Drosophila, however, no clear Rec8 homolog has been identified so far. Therefore, we have analyzed the role of the mitotic Drosophila α-kleisin Rad21 during female meiosis. Inactivation of an engineered Rad21 variant by premature, ectopic cleavage during oogenesis results not only in loss of cohesin from meiotic chromatin, but also in precocious disassembly of the synaptonemal complex (SC). We demonstrate that the lateral SC component C(2)M can interact directly with Rad21, potentially explaining why Rad21 is required for SC maintenance. Intriguingly, the experimentally induced premature Rad21 elimination, as well as the expression of a Rad21 variant with destroyed separase consensus cleavage sites, do not interfere with chromosome segregation during meiosis, while successful mitotic divisions are completely prevented. Thus, chromatid cohesion during female meiosis does not depend on Rad21-containing cohesin. PMID:25101996

  16. Sensitivity of Roberts Syndrome Cells to gamma radiation, mitomycin C, and protein synthesis inhibitors

    International Nuclear Information System (INIS)

    Roberts syndrome (RS) is a rare autosomal recessive disorder characterized by pre- and postnatal growth retardation, limb reduction abnormalities, and craniofacial anomalies. Mitotic chromosomes from RS individuals display repulsion of heterochromatin regions or centromere splitting, leading to a railroad-track appearance of mitotic chromosomes. Abnormalities in metaphase duration, anaphase progression, nuclear morphology, and increased frequency of micronucleation have been reported in RS cells. Cells from RS heterozygotes are normal in these respects, and in vitro complementation of the defects in somatic cell hybrids has been reported. Therefore, in preparation for the isolation of cDNAs that complement the RS defect, the authors investigated various drug treatments to identify an agent that specifically involves the growth of RS cells. Based on the cytogenetic and cell biologic findings, they chose agents that increase micronucleation or inhibit protein synthesis. They found that RS cells are hypersensitive to gamma radiation, mitomycin C, G418 and hygromycin B, but not to colcemid or streptonigrin when compared to normal cells. DNA content and cell viability analysis confirmed that the sensitivity to gamma irradiation was primarily due to increased cell death

  17. The Deadbeat Paternal Effect of Uncapped Sperm Telomeres on Cell Cycle Progression and Chromosome Behavior in Drosophila melanogaster.

    Science.gov (United States)

    Yamaki, Takuo; Yasuda, Glenn K; Wakimoto, Barbara T

    2016-06-01

    Telomere-capping complexes (TCCs) protect the ends of linear chromosomes from illegitimate repair and end-to-end fusions and are required for genome stability. The identity and assembly of TCC components have been extensively studied, but whether TCCs require active maintenance in nondividing cells remains an open question. Here we show that Drosophila melanogaster requires Deadbeat (Ddbt), a sperm nuclear basic protein (SNBP) that is recruited to the telomere by the TCC and is required for TCC maintenance during genome-wide chromatin remodeling, which transforms spermatids to mature sperm. Ddbt-deficient males produce sperm lacking TCCs. Their offspring delay the initiation of anaphase as early as cycle 1 but progress through the first two cycles. Persistence of uncapped paternal chromosomes induces arrest at or around cycle 3. This early arrest can be rescued by selective elimination of paternal chromosomes and production of gynogenetic haploid or haploid mosaics. Progression past cycle 3 can also occur if embryos have reduced levels of the maternally provided checkpoint kinase Chk2. The findings provide insights into how telomere integrity affects the regulation of the earliest embryonic cell cycles. They also suggest that other SNBPs, including those in humans, may have analogous roles and manifest as paternal effects on embryo quality. PMID:27029731

  18. Expression of BUB1 protein in gastric cancer correlates with the histological subtype, but not with DNA ploidy or microsatellite instability.

    Science.gov (United States)

    Grabsch, Heike I; Askham, Jon M; Morrison, Ewan E; Pomjanski, Natalja; Lickvers, Kristina; Parsons, Wendy J; Boecking, Alfred; Gabbert, Helmut E; Mueller, Wolfram

    2004-02-01

    During mitosis, the spindle checkpoint delays the onset of anaphase until all chromosomes have attached properly to the mitotic spindle, preventing chromosome missegregation. BUB (budding uninhibited by benzimidazole) 1 is one of the key components of this checkpoint. BUB1 mutations are rare in cancer tissues and no mutations have been identified in gastric cancer. In mice, immunodepletion of BUB1 abolished the spindle checkpoint. Thus, aberrant expression of BUB1 protein could impair mitotic checkpoint function, resulting in aneuploidy, a common phenomenon in gastric cancer. In the present study, an antibody was generated against BUB1 and its expression was studied in gastric cancer tissue sections (n = 80) by immunohistochemistry. Nuclear BUB1 expression was found in all gastric cancer cases. The proportion of tumour cells expressing BUB1 was significantly greater in diffuse-type than in intestinal-type gastric carcinoma (p knowledge, this is the first study of BUB1 protein expression in gastric cancer tissues. Different BUB1 protein expression levels in intestinal- and diffuse-type gastric cancer may provide further evidence of a potential link between different genetic pathways and morphological phenotype in gastric carcinogenesis. However, further studies are needed to establish whether there is an association between BUB1 protein expression level and mitotic spindle checkpoint function in gastric cancer. PMID:14743503

  19. Cytological changes in meristematic cells of Allium cepa L. root tip treated with extracts from callus of Catharanthus roseus (L. G. Don

    Directory of Open Access Journals (Sweden)

    Agnieszka Pietrosiuk

    2014-02-01

    Full Text Available The effect of an ethanolic extract from callus of Catharanthus roseus on Allium cepa root cells divisions was investigated. Two lines: white and green callus, were established on solid B5 medium with IAA 1 mg/l and kinetin 0.1 mg/l. The HPLC analysis of callus extracts showed the presence of indole alkaloids, however not known pharmacologically active alkaloids or derivatives used in semisynthesis (vinblastine, ajmalicine, serpentine, yohimbine, vindoline and catharanthine have been found. The ethanolic extract of C. roseus callus inhibited the number of mitoses in Allium cepa root tip cells. Short (1-3 hours treatment resulted in an increase in the index of late prophases, with characteristic light spaces, and the index of metaphases with twisted chromosomes forming an equatorial plate or irregular structures of c-metaphases. At the same time, the percentage of anaphases and telophases decreased significantly. Longer treatment of the root tip inhibited mitotic activity, stopping it completely already after 12 hours. Interphase nuclei became at first denser and homogeneous, eventually their structure became , partitioned into zones and formation of chromatin territories, with distinct large nucleoli has been observed. Electron microscope observations revealed well developed rough endoplasmic reticulum and thick, invaginating cell membrane.

  20. Dynamics and roles of phragmoplast microfilaments in cell plate formation during cytokinesis of tobacco BY-2 cells

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yan; ZHANG WenJie; BALUSKA Frantisek; MENZEL Diedrik; REN HaiYun

    2009-01-01

    The phragmoplast is a special apparatus that functions in establishing a cell plate in dividing plant cells.It is known that microfilaments (MFs) are involved in constituting phragmoplast structure, but the dynamic distribution and role of phragmoplast MFs are far from being understood. In this study, the precise structure and dynamics of MFs during the initiation and the late lateral expansion of the phragmoplast were observed by using a tobacco BY-2 cell line stably expressing the microfilament reporter construct GFP-f ABD2. Three-dimensional imaging showed that the phragmoplast MFs were initiated by two populations of MFs emerging between the reconstituting daughter nuclei at anaphase, which migrated to the mid-zone and gave rise to two layers of microfilament arrays. FM4-64 stained vesicles accumulated and fused with the cell plate between the two populations of MFs. The two layers of microfilament arrays of phragmoplast with ends overlapped always surrounded the centrifugally expanding cell plate. Partial disruption of MFs at metaphase by low concentration of latrunculin B resulted in the inhibition of the cell plate consolidation and the blockage of cell plate lateral expansion,whereas high concentration of latrunculin B restrained the progression of the cell cycle. Treating the cell after the initiation of phragmoplast led to the cease of the expansion of the cell plate. Our observations provide new insights into the precise structure and dynamics of phragmoplast MFs during cytokinesis and suggest that dynamic phragmoplast MFs are important in cell plate formation.

  1. Idas, a novel phylogenetically conserved geminin-related protein, binds to geminin and is required for cell cycle progression.

    Science.gov (United States)

    Pefani, Dafni-Eleutheria; Dimaki, Maria; Spella, Magda; Karantzelis, Nickolas; Mitsiki, Eirini; Kyrousi, Christina; Symeonidou, Ioanna-Eleni; Perrakis, Anastassis; Taraviras, Stavros; Lygerou, Zoi

    2011-07-01

    Development and homeostasis of multicellular organisms relies on an intricate balance between cell proliferation and differentiation. Geminin regulates the cell cycle by directly binding and inhibiting the DNA replication licensing factor Cdt1. Geminin also interacts with transcriptional regulators of differentiation and chromatin remodelling factors, and its balanced interactions are implicated in proliferation-differentiation decisions during development. Here, we describe Idas (Idas being a cousin of the Gemini in Ancient Greek Mythology), a previously uncharacterised coiled-coil protein related to Geminin. We show that human Idas localizes to the nucleus, forms a complex with Geminin both in cells and in vitro through coiled-coil mediated interactions, and can change Geminin subcellular localization. Idas does not associate with Cdt1 and prevents Geminin from binding to Cdt1 in vitro. Idas depletion from cells affects cell cycle progression; cells accumulate in S phase and are unable to efficiently progress to mitosis. Idas protein levels decrease in anaphase, whereas its overexpression causes mitotic defects. During development, we show that Idas exhibits high level expression in the choroid plexus and the cortical hem of the mouse telencephalon. Our data highlight Idas as a novel Geminin binding partner, implicated in cell cycle progression, and a putative regulator of proliferation-differentiation decisions during development. PMID:21543332

  2. TDM1 Regulation Determines the Number of Meiotic Divisions

    Science.gov (United States)

    Cifuentes, Marta; Jolivet, Sylvie; Cromer, Laurence; Harashima, Hirofumi; Bulankova, Petra; Renne, Charlotte; Crismani, Wayne; Nomura, Yuko; Nakagami, Hirofumi; Sugimoto, Keiko; Schnittger, Arp; Riha, Karel; Mercier, Raphael

    2016-01-01

    Cell cycle control must be modified at meiosis to allow two divisions to follow a single round of DNA replication, resulting in ploidy reduction. The mechanisms that ensure meiosis termination at the end of the second and not at the end of first division are poorly understood. We show here that Arabidopsis thaliana TDM1, which has been previously shown to be essential for meiotic termination, interacts directly with the Anaphase-Promoting Complex. Further, mutations in TDM1 in a conserved putative Cyclin-Dependant Kinase (CDK) phosphorylation site (T16-P17) dominantly provoked premature meiosis termination after the first division, and the production of diploid spores and gametes. The CDKA;1-CYCA1.2/TAM complex, which is required to prevent premature meiotic exit, phosphorylated TDM1 at T16 in vitro. Finally, while CYCA1;2/TAM was previously shown to be expressed only at meiosis I, TDM1 is present throughout meiosis. These data, together with epistasis analysis, lead us to propose that TDM1 is an APC/C component whose function is to ensure meiosis termination at the end of meiosis II, and whose activity is inhibited at meiosis I by CDKA;1-TAM-mediated phosphorylation to prevent premature meiotic exit. This provides a molecular mechanism for the differential decision of performing an additional round of division, or not, at the end of meiosis I and II, respectively. PMID:26871453

  3. DVC1 (C1orf124) is a DNA damage-targeting p97 adaptor that promotes ubiquitin-dependent responses to replication blocks.

    Science.gov (United States)

    Mosbech, Anna; Gibbs-Seymour, Ian; Kagias, Konstantinos; Thorslund, Tina; Beli, Petra; Povlsen, Lou; Nielsen, Sofie Vincents; Smedegaard, Stine; Sedgwick, Garry; Lukas, Claudia; Hartmann-Petersen, Rasmus; Lukas, Jiri; Choudhary, Chunaram; Pocock, Roger; Bekker-Jensen, Simon; Mailand, Niels

    2012-11-01

    Ubiquitin-mediated processes orchestrate critical DNA-damage signaling and repair pathways. We identify human DVC1 (C1orf124; Spartan) as a cell cycle-regulated anaphase-promoting complex (APC) substrate that accumulates at stalled replication forks. DVC1 recruitment to sites of replication stress requires its ubiquitin-binding UBZ domain and PCNA-binding PIP box motif but is independent of RAD18-mediated PCNA monoubiquitylation. Via a conserved SHP box, DVC1 recruits the ubiquitin-selective chaperone p97 to blocked replication forks, which may facilitate p97-dependent removal of translesion synthesis (TLS) DNA polymerase η (Pol η) from monoubiquitylated PCNA. DVC1 knockdown enhances UV light-induced mutagenesis, and depletion of human DVC1 or the Caenorhabditis elegans ortholog DVC-1 causes hypersensitivity to replication stress-inducing agents. Our findings establish DVC1 as a DNA damage-targeting p97 adaptor that protects cells from deleterious consequences of replication blocks and suggest an important role of p97 in ubiquitin-dependent regulation of TLS. PMID:23042605

  4. Cytogenetic Effects of Ethanol Extract of Sun Dried Seeds of Soursop (Annona muricata on The Male Germ Line Cells of The African Pest Grasshopper Zonocerus variegatus L.

    Directory of Open Access Journals (Sweden)

    Seino RA

    2013-04-01

    Full Text Available This study was carried out to investigate the effect of Ethanol extract of the seeds of Annona muricata on some meiotic parameters in the pest grasshopper Zonocerus variegatus. Adult grasshoppers were treated with 28μl of the Ethanol extract of sun dry seeds of Annona muricata and absolute ethanol (control for 48 hours and all the parameters (chiasma frequency, formation of rod and ring shaped bivalents and meiotic anomalies were affected by the extract. Chiasma formation was observed to significantly (P<0.05 increase following treatment and this was correlated by a significant increase in the formation of ring shaped bivalents. The incidences of meiotic anomalies such as laggards and bridges at first and second meiotic Anaphases, second meiotic Metaphase as well as in first and second meiotic Telophases were observed to increase when insects were treated with the ethanol extract. These observations indicated that the Ethanol extract of the seeds of A. muricata contain substances that could induce cytotoxicity. The importance of such property in the formulation of grasshopper pest control measures cannot be overemphasized.

  5. Dichlorophen and Dichlorovos mediated genotoxic and cytotoxic assessment on root meristem cells of Allium cepa

    Directory of Open Access Journals (Sweden)

    Sibhghatulla Shaikh

    2012-06-01

    Full Text Available Plants are direct recipients of agro – toxics and therefore important materials for assessing environmental chemicals for genotoxicity. The meristematic mitotic cell of Allium cepa is an efficient cytogenetic material for chromosome aberration assay on environmental pollutants. Onion root tips were grown on moistened filter paper in petri dish at room temperature. Germinated root tips were then exposed to three concentrations of each pesticide for 24 h. About 1 – 2 mm length of root tip was cut, fixed in cornoy’s fixative, hydrolyzed in warm 1 N HCL, stained with acetocarmine and squashed on glass slide. About 3000 cells were scored and classified into interphase and normal or aberrant division stage. Cytotoxicity was determined by comparing the mitotic index (MI of treated cells with that of the negative control. The MI of cells treated with Dichlorophen and Dichlorovos at one or more concentration was half or less than that of control are said to be cytotoxic. Genotoxicity was measured by comparing the number of cells/1000 in aberrant division stages at each dose with the negative control using Mann – Whitney U test. Both Dichlorophen and Dichlorovos are genotoxic at higher concentrations i.e. 0.001%, 0.002% and 0.028%, 0.056% inducing chromosome fragment, chromosome lagging and bridges, stick chromosome and multipolar anaphase.

  6. CENP-C facilitates the recruitment of M18BP1 to centromeric chromatin.

    Science.gov (United States)

    Dambacher, Silvia; Deng, Wen; Hahn, Matthias; Sadic, Dennis; Fröhlich, Jonathan; Nuber, Alexander; Hoischen, Christian; Diekmann, Stephan; Leonhardt, Heinrich; Schotta, Gunnar

    2012-01-01

    Centromeres are important structural constituents of chromosomes that ensure proper chromosome segregation during mitosis by providing defined sites for kinetochore attachment. In higher eukaryotes, centromeres have no specific DNA sequence and thus, they are rather determined through epigenetic mechanisms. A fundamental process in centromere establishment is the incorporation of the histone variant CENP-A into centromeric chromatin, which provides a binding platform for the other centromeric proteins. The Mis18 complex, and, in particular, its member M18BP1 was shown to be essential for both incorporation and maintenance of CENP-A. Here we show that M18BP1 displays a cell cycle-regulated association with centromeric chromatin in mouse embryonic stem cells. M18BP1 is highly enriched at centromeric regions from late anaphase through to G1 phase. An interaction screen against 16 core centromeric proteins revealed a novel interaction of M18BP1 with CENP-C. We mapped the interaction domain in M18BP1 to a central region containing a conserved SANT domain and in CENP-C to the C-terminus. Knock-down of CENP-C leads to reduced M18BP1 association and lower CENP-A levels at centromeres, suggesting that CENP-C works as an important factor for centromeric M18BP1 recruitment and thus for maintaining centromeric CENP-A. PMID:22540025

  7. Influence of low-dose gamma-ray irradiation on mitosis and adaptive response of meristematic cells of pea rootlets

    International Nuclear Information System (INIS)

    Pea seeds (Pisum sativa) were exposed to gamma irradiation (60Co, dose 7 Gy) at different dose rates (from 0.3 cGy/h to 19.1 cGy/h). The beginning of irradiation coincided with the beginning of soaking. After the irradiation a fraction of the seeds was irradiated with 50 Gy (137Cs, dose rate 25 Gy/min) to examine the adaptive response. After 24 hours of soaking all the seeds were germinated at 25 deg C and rootlets were fixed. Mitotic index and the number of cells with chromosomal aberrations (CA) in first mitosis anaphases of the meristematic cells of rootlets were determined. After 7 cGy irradiation, judging by the above criteria, the radiation hormesis was identified at the dose rate 1.2 cGy/h. For 19.1 cGy/h damaging effect and decrease in the mitotic activity were observed. As the dose rate grows, the adaptive response is better expressed (by the analysis of CA). When the seeds are conserved at 13-14 % humidity, the CA level is higher and the adaptive response is better expressed compared to conserving at 10 % humidity. (author)

  8. Research on the human resource development of the Three Gorges Region, China

    Institute of Scientific and Technical Information of China (English)

    Zhou Yinzhen; Sun Dalin

    2008-01-01

    The Three Gorges Region (TGR) is an economic region of China, and lies in the western part of Yangtze economic belt. It takes the Three Gorges Project as leading, Chongqing and Yichang City as main body, the Three Gorges Reservoir as ligament. It covers about 700 km of the Yangtze River valley from Chongqing to Yichang, in- cluding Chongqing City, Yichang City and Enshi District of Hubei Province. Since the construction of Three Gorges Project and establishment of Chongqing as municipality directly under the Central Government, the regional econ-omy, culture, education, technology, etc., all developed harmoniously and rapidly, and the diathesis of the regional human resources also got an exaltation. While compared with the eastern region of China, the economy, science and technology in this region still fall behind, and the current situation is of no optimism. Based on the theory of human resources development, this paper analyzes current situation and problems in the human resources development of the TGR, and puts forward the countermeasures, such as planning human resources development program based on"anaphase support "policy, developing education and training business, reasonably organizing labor export, etc.

  9. Bio-efficacy of the essential oil of oregano (Origanum vulgare Lamiaceae. Ssp. Hirtum).

    Science.gov (United States)

    Grondona, Ezequiel; Gatti, Gerardo; López, Abel G; Sánchez, Leonardo Rodolfo; Rivero, Virginia; Pessah, Oscar; Zunino, María P; Ponce, Andrés A

    2014-12-01

    The aim of this study was to investigate the bioactivity of the essential oil isolated from Origanum vulgare L. (EOv). We analyzed the in vivo anti-inflammatory properties in a mouse-airway inflammation model and the in vitro antimicrobial activity, genotoxicity over the anaphase-telophase with the Allium cepa strain and its cytotoxicity/viability in A549 culture cells. In vivo, EOv modified the levels of tumor necrosis factor -α and viable activated macrophages and was capable to mitigate the effects of degradation of conjugated dienes. In vitro, EOv reduced the viability of cultured A549 cells as well as the mitotic index and a number of chromosomal aberrations; however, it did not change the number of phases. We found that EOv presents antimicrobial activity against different Gram (-) and (+) strains, measured by disc-diffusion test and confirmed with a more accurate method, the AutoCad software. We postulate that EOv presents antibacterial, antioxidant and chemopreventive properties and could be play an important role as bioprotector agent. PMID:25266989

  10. Centromere binding and a conserved role in chromosome stability for SUMO-dependent ubiquitin ligases.

    Directory of Open Access Journals (Sweden)

    Loes A L van de Pasch

    Full Text Available The Saccharomyces cerevisiae Slx5/8 complex is the founding member of a recently defined class of SUMO-targeted ubiquitin ligases (STUbLs. Slx5/8 has been implicated in genome stability and transcription, but the precise contribution is unclear. To characterise Slx5/8 function, we determined genome-wide changes in gene expression upon loss of either subunit. The majority of mRNA changes are part of a general stress response, also exhibited by mutants of other genome integrity pathways and therefore indicative of an indirect effect on transcription. Genome-wide binding analysis reveals a uniquely centromeric location for Slx5. Detailed phenotype analyses of slx5Δ and slx8Δ mutants show severe mitotic defects that include aneuploidy, spindle mispositioning, fish hooks and aberrant spindle kinetics. This is associated with accumulation of the PP2A regulatory subunit Rts1 at centromeres prior to entry into anaphase. Knockdown of the human STUbL orthologue RNF4 also results in chromosome segregation errors due to chromosome bridges. The study shows that STUbLs have a conserved role in maintenance of chromosome stability and links SUMO-dependent ubiquitination to a centromere-specific function during mitosis.

  11. P190B RhoGAP Regulates Chromosome Segregation in Cancer Cells

    International Nuclear Information System (INIS)

    Rho GTPases are overexpressed and hyperactivated in many cancers, including breast cancer. Rho proteins, as well as their regulators and effectors, have been implicated in mitosis, and their altered expression promotes mitotic defects and aneuploidy. Previously, we demonstrated that p190B Rho GTPase activating protein (RhoGAP) deficiency inhibits ErbB2-induced mammary tumor formation in mice. Here we describe a novel role for p190B as a regulator of mitosis. We found that p190B localized to centrosomes during interphase and mitosis, and that it is differentially phosphorylated during mitosis. Knockdown of p190B expression in MCF-7 and Hela cells increased the incidence of aberrant microtubule-kinetochore attachments at metaphase, lagging chromosomes at anaphase, and micronucleation, all of which are indicative of aneuploidy. Cell cycle analysis of p190B deficient MCF-7 cells revealed a significant increase in apoptotic cells with a concomitant decrease in cells in G1 and S phase, suggesting that p190B deficient cells die at the G1 to S transition. Chemical inhibition of the Rac GTPase during mitosis reduced the incidence of lagging chromosomes in p190B knockdown cells to levels detected in control cells, suggesting that aberrant Rac activity in the absence of p190B promotes chromosome segregation defects. Taken together, these data suggest that p190B regulates chromosome segregation and apoptosis in cancer cells. We propose that disruption of mitosis may be one mechanism by which p190B deficiency inhibits tumorigenesis

  12. Analysis of centromeres in radiation-induced micronuclei in human peripheral lymphocytes by means of Fish

    International Nuclear Information System (INIS)

    The micronucleus assay is frequently used in mutagenicity testing. Micronuclei can arise either from acentric fragments that fail to be incorporated into daughter nuclei or from whole chromosomes that lag in anaphase due to centromere dysfunction, defective spindle apparatus or complex chromosomal rearrangements. Several studies have shown that many micronuclei which arise spontaneously contain whole chromosomes. Relatively few data are available on the frequency of centromere positive micronuclei following exposure to ionizing radiation. In the present study we have analyzed the occurrence of centromere positive micronuclei in human peripheral lymphocytes of three donors following irradiation with X-rays. The centromeres were made visible with commercially available alpha-satellite probes labelled with biotin and detected with FITC-labelled avidin. Additionally, the micronucleus frequencies per bi-nucleated cells were estimated in Giemsa-stained slides. Our results show that the majority of control micronuclei contain whole chromosomes. With increasing dose the fraction of centromere positive micronuclei decreases indicating that the micronuclei contain predominantly acentric fragments. Individual differences in frequencies of centromere containing micronuclei were observed between the donors. There appears to be a negative correlation between the frequency of micronuclei and centromere within them. Further experiments with more donors are presently being carried out to substantiate this result. (authors)

  13. Casein Kinase 1δ Is an APC/CCdh1 Substrate that Regulates Cerebellar Granule Cell Neurogenesis

    Directory of Open Access Journals (Sweden)

    Clara Penas

    2015-04-01

    Full Text Available Although casein kinase 1δ (CK1δ is at the center of multiple signaling pathways, its role in the expansion of CNS progenitor cells is unknown. Using mouse cerebellar granule cell progenitors (GCPs as a model for brain neurogenesis, we demonstrate that the loss of CK1δ or treatment of GCPs with a highly selective small molecule inhibits GCP expansion. In contrast, CK1δ overexpression increases GCP proliferation. Thus, CK1δ appears to regulate GCP neurogenesis. CK1δ is targeted for proteolysis via the anaphase-promoting complex/cyclosome (APC/CCdh1 ubiquitin ligase, and conditional deletion of the APC/CCdh1 activator Cdh1 in cerebellar GCPs results in higher levels of CK1δ. APC/CCdh1 also downregulates CK1δ during cell-cycle exit. Therefore, we conclude that APC/CCdh1 controls CK1δ levels to balance proliferation and cell-cycle exit in the developing CNS. Similar studies in medulloblastoma cells showed that CK1δ holds promise as a therapeutic target.

  14. Dual RING E3 Architectures Regulate Multiubiquitination and Ubiquitin Chain Elongation by APC/C.

    Science.gov (United States)

    Brown, Nicholas G; VanderLinden, Ryan; Watson, Edmond R; Weissmann, Florian; Ordureau, Alban; Wu, Kuen-Phon; Zhang, Wei; Yu, Shanshan; Mercredi, Peter Y; Harrison, Joseph S; Davidson, Iain F; Qiao, Renping; Lu, Ying; Dube, Prakash; Brunner, Michael R; Grace, Christy R R; Miller, Darcie J; Haselbach, David; Jarvis, Marc A; Yamaguchi, Masaya; Yanishevski, David; Petzold, Georg; Sidhu, Sachdev S; Kuhlman, Brian; Kirschner, Marc W; Harper, J Wade; Peters, Jan-Michael; Stark, Holger; Schulman, Brenda A

    2016-06-01

    Protein ubiquitination involves E1, E2, and E3 trienzyme cascades. E2 and RING E3 enzymes often collaborate to first prime a substrate with a single ubiquitin (UB) and then achieve different forms of polyubiquitination: multiubiquitination of several sites and elongation of linkage-specific UB chains. Here, cryo-EM and biochemistry show that the human E3 anaphase-promoting complex/cyclosome (APC/C) and its two partner E2s, UBE2C (aka UBCH10) and UBE2S, adopt specialized catalytic architectures for these two distinct forms of polyubiquitination. The APC/C RING constrains UBE2C proximal to a substrate and simultaneously binds a substrate-linked UB to drive processive multiubiquitination. Alternatively, during UB chain elongation, the RING does not bind UBE2S but rather lures an evolving substrate-linked UB to UBE2S positioned through a cullin interaction to generate a Lys11-linked chain. Our findings define mechanisms of APC/C regulation, and establish principles by which specialized E3-E2-substrate-UB architectures control different forms of polyubiquitination. PMID:27259151

  15. Cryo-EM of Mitotic Checkpoint Complex-Bound APC/C Reveals Reciprocal and Conformational Regulation of Ubiquitin Ligation.

    Science.gov (United States)

    Yamaguchi, Masaya; VanderLinden, Ryan; Weissmann, Florian; Qiao, Renping; Dube, Prakash; Brown, Nicholas G; Haselbach, David; Zhang, Wei; Sidhu, Sachdev S; Peters, Jan-Michael; Stark, Holger; Schulman, Brenda A

    2016-08-18

    The mitotic checkpoint complex (MCC) coordinates proper chromosome biorientation on the spindle with ubiquitination activities of CDC20-activated anaphase-promoting complex/cyclosome (APC/C(CDC20)). APC/C(CDC20) and two E2s, UBE2C and UBE2S, catalyze ubiquitination through distinct architectures for linking ubiquitin (UB) to substrates and elongating polyUB chains, respectively. MCC, which contains a second molecule of CDC20, blocks APC/C(CDC20)-UBE2C-dependent ubiquitination of Securin and Cyclins, while differentially determining or inhibiting CDC20 ubiquitination to regulate spindle surveillance, checkpoint activation, and checkpoint termination. Here electron microscopy reveals conformational variation of APC/C(CDC20)-MCC underlying this multifaceted regulation. MCC binds APC/C-bound CDC20 to inhibit substrate access. However, rotation about the CDC20-MCC assembly and conformational variability of APC/C modulate UBE2C-catalyzed ubiquitination of MCC's CDC20 molecule. Access of UBE2C is limiting for subsequent polyubiquitination by UBE2S. We propose that conformational dynamics of APC/C(CDC20)-MCC modulate E2 activation and determine distinctive ubiquitination activities as part of a response mechanism ensuring accurate sister chromatid segregation. PMID:27522463

  16. biGBac enables rapid gene assembly for the expression of large multisubunit protein complexes.

    Science.gov (United States)

    Weissmann, Florian; Petzold, Georg; VanderLinden, Ryan; Huis In 't Veld, Pim J; Brown, Nicholas G; Lampert, Fabienne; Westermann, Stefan; Stark, Holger; Schulman, Brenda A; Peters, Jan-Michael

    2016-05-10

    Analyses of protein complexes are facilitated by methods that enable the generation of recombinant complexes via coexpression of their subunits from multigene DNA constructs. However, low experimental throughput limits the generation of such constructs in parallel. Here we describe a method that allows up to 25 cDNAs to be assembled into a single baculoviral expression vector in only two steps. This method, called biGBac, uses computationally optimized DNA linker sequences that enable the efficient assembly of linear DNA fragments, using reactions developed by Gibson for the generation of synthetic genomes. The biGBac method uses a flexible and modular "mix and match" approach and enables the generation of baculoviruses from DNA constructs at any assembly stage. Importantly, it is simple, efficient, and fast enough to allow the manual generation of many multigene expression constructs in parallel. We have used this method to generate and characterize recombinant forms of the anaphase-promoting complex/cyclosome, cohesin, and kinetochore complexes. PMID:27114506

  17. Abnormal meiosis in tetraploid genotypes of Brachiaria brizantha (Poaceae) induced by colchicine: its implications for breeding.

    Science.gov (United States)

    Mendes-Bonato, A B; Ferrari Felismino, M; Souza Kaneshima, A M; Pessim, C; Calisto, V; Suely Pagliarini, M; Borges do Valle, C

    2009-01-01

    Meiotic behavior was analyzed in 6 progenies from 3 artificially induced tetraploid (2n = 4x = 36) sexual genotypes (C31, C41, and C48) of the normally apomictic Brachiaria brizantha (Hochst. ex A. Rich.) Stapf., syn. Urochloa brizantha (Hochst. ex A. Rich.) R. Webster. These are key plants to allow intraspecific hybridization of this important forage species, widely used for pastures in the tropics. The percentage of abnormal cells among the plants ranged from 39.8% to 63.2%. In the single plant derived from C48, only the common meiotic abnormalities typical of polyploids were observed, while in plants derived from C31 and C41, a distinct behavior was found. In the majority of cells of those plants, the chromosomes remained scattered in the cytoplasm in the first division, without forming a metaphase plate. This abnormality blocked chromosome movements at anaphase I. Several micronuclei of various sizes were formed and, after the occurrence of an irregular first cytokinesis, the meiocytes progressed normally to the second division, generating polyads with unbalanced microspores. Pollen viability was not correlated with meiotic abnormalities. The importance of these findings to the Brachiaria breeding program is discussed. The sexual progeny of C48 seems most suitable as female parents to be used in intra- and interspecific hybridization. PMID:19433904

  18. The APC/C Ubiquitin Ligase: from Cell Biology to Tumorigenesis

    Directory of Open Access Journals (Sweden)

    NagiGeorgeAyad

    2012-01-01

    Full Text Available The ubiquitin proteasome system (UPS is required for normal cell proliferation, vertebrate development, and cancer cell transformation. The UPS consists of multiple proteins that work in concert to target a protein for degradation via the 26S proteasome. Chains of an 8.5 kDa protein called ubiquitin are attached to substrates, thus allowing recognition by the 26S proteasome. Enzymes called ubiquitin ligases or E3s mediate specific attachment to substrates. Although there are over 600 different ubiquitin ligases, the Skp1-Cullin-F-box proteins (SCF ubiquitin ligases and the Anaphase Promoting Complex/cyclosome (APC/C are the most studied. SCF involvement in cancer has been known for some time while APC/C’s cancer role has recently emerged. In this review we will discuss the importance of APC/C to normal cell proliferation and development, thus underscoring its possible contribution to transformation. We will also put forth the hypothesis that modulating a specific interaction of the APC/C may be therapeutically attractive in specific cancer subtypes. Finally, given that the APC/C pathway is relatively new as a cancer target, therapeutic interventions affecting APC/C activity may be beneficial in cancers that are resistant to classical chemotherapy.

  19. Centromere binding and a conserved role in chromosome stability for SUMO-dependent ubiquitin ligases.

    Science.gov (United States)

    van de Pasch, Loes A L; Miles, Antony J; Nijenhuis, Wilco; Brabers, Nathalie A C H; van Leenen, Dik; Lijnzaad, Philip; Brown, Markus K; Ouellet, Jimmy; Barral, Yves; Kops, Geert J P L; Holstege, Frank C P

    2013-01-01

    The Saccharomyces cerevisiae Slx5/8 complex is the founding member of a recently defined class of SUMO-targeted ubiquitin ligases (STUbLs). Slx5/8 has been implicated in genome stability and transcription, but the precise contribution is unclear. To characterise Slx5/8 function, we determined genome-wide changes in gene expression upon loss of either subunit. The majority of mRNA changes are part of a general stress response, also exhibited by mutants of other genome integrity pathways and therefore indicative of an indirect effect on transcription. Genome-wide binding analysis reveals a uniquely centromeric location for Slx5. Detailed phenotype analyses of slx5Δ and slx8Δ mutants show severe mitotic defects that include aneuploidy, spindle mispositioning, fish hooks and aberrant spindle kinetics. This is associated with accumulation of the PP2A regulatory subunit Rts1 at centromeres prior to entry into anaphase. Knockdown of the human STUbL orthologue RNF4 also results in chromosome segregation errors due to chromosome bridges. The study shows that STUbLs have a conserved role in maintenance of chromosome stability and links SUMO-dependent ubiquitination to a centromere-specific function during mitosis. PMID:23785440

  20. SUMO-targeted ubiquitin ligase RNF4 plays a critical role in preventing chromosome loss.

    Science.gov (United States)

    Hirota, Kouji; Tsuda, Masataka; Murai, Junko; Takagi, Tokiyo; Keka, Islam Shamima; Narita, Takeo; Fujita, Mari; Sasanuma, Hiroyuki; Kobayashi, Junya; Takeda, Shunichi

    2014-10-01

    RING finger protein 4 (RNF4) represents a subclass of ubiquitin ligases that target proteins modified by the small ubiquitin-like modifier (SUMO) for ubiquitin-mediated degradation. We disrupted the RNF4 gene in chicken DT40 cells and found that the resulting RNF4(-/-) cells gradually lost proliferation capability. Strikingly, this compromised proliferation was associated with an unprecedented cellular effect: the gradual decrease in the number of intact chromosomes. In the 6 weeks after gene targeting, there was a 25% reduction in the DNA content of the RNF4(-/-) cells. Regarding trisomic chromosome 2, 60% of the RNF4(-/-) cells lost one homologue, suggesting that DNA loss was mediated by whole chromosome loss. To determine the cause of this chromosome loss, we examined cell-cycle checkpoint pathways. RNF4(-/-) cells showed a partial defect in the spindle assembly checkpoint, premature dissociation of sister chromatids, and a marked increase in the number of lagging chromosomes at anaphase. Thus, combined defects in SAC and sister chromatid cohesion may result in increased lagging chromosomes, leading to chromosome loss without accompanying chromosome gain in RNF4(-/-) cells. We therefore propose that RNF4 plays a novel role in preventing the loss of intact chromosomes and ensures the maintenance of chromosome integrity. PMID:25205350

  1. Analysis of F1 hybrid and BC1 monosomic alien addition line plants from Brassica oleracea × Sinapis alba by GISH

    Institute of Scientific and Technical Information of China (English)

    WEI Wenhui; ZHANG Sufeng; LI Jun; WANG Lijun; CHEN Bo; FANG Xiaoping; WANG Zhuan; LUO Lixia

    2006-01-01

    Sterile and semi-fertile F1 plants were obtained by intergeneric sexual hybridization between paternal Brassica oleracea var. alboglabra (genome CC, 2n=18) and maternal Sinapis alba (genome SS, 2n=24), BC1 plants were obtained by backcrossing between paternal B. oleracea and maternal semi-fertile F1 plants. Genomic in situ hybridization (GISH) combined with dual-colour fluorescence in situ hybridization (dcFISH) showed that sterile F1 plants contained 21 chromosomes consisting of one B. oleracea chromosome set and one S.alba chromosome set, belonging to expected hybrids,and semi-fertile F1 plants contained 30 chromosomes consisting of two B. oleracea chromosome sets and one S. alba chromosome set. It is obvious that the semi-fertile F1 plants belong to unexpected hybrids.1 -3 trivalents were detected at meiotic metaphase I of semi-fertile F1 pollen mother cells (PMCs). Different separation ratios of S chromosomes were detected at anaphase I. A monosomic alien addition line(MAAL) was identified by GISH-dcFISH from BC1plants; it contained 19 chromosomes consisting of 18 C chromosomes and 1 S chromosome. At meiotic metaphase I, 9 divalents from B. oleracea and one univalent from S. alba could be detected. Sometimes,one putative C-S trivalent could also be detected.The achievement of B. oleracea-S, alba monosomic alien addition lines lays a foundation for gene introgression, location and cloning.

  2. DNA damage response during mitosis induces whole chromosome mis-segregation

    Science.gov (United States)

    Bakhoum, Samuel F.; Kabeche, Lilian; Murnane, John P.; Zaki, Bassem I.; Compton, Duane A.

    2014-01-01

    Many cancers display both structural (s-CIN) and numerical (w-CIN) chromosomal instabilities. Defective chromosome segregation during mitosis has been shown to cause DNA damage that induces structural rearrangements of chromosomes (s-CIN). In contrast, whether DNA damage can disrupt mitotic processes to generate whole chromosomal instability (w-CIN) is unknown. Here we show that activation of the DNA damage response (DDR) during mitosis selectively stabilizes kinetochore-microtubule (k-MT) attachments to chromosomes through Aurora-A and Plk1 kinases, thereby increasing the frequency of lagging chromosomes during anaphase. Inhibition of DDR proteins, ATM or Chk2, abolishes the effect of DNA damage on k-MTs and chromosome segregation, whereas activation of the DDR in the absence of DNA damage is sufficient to induce chromosome segregation errors. Finally, inhibiting the DDR during mitosis in cancer cells with persistent DNA damage suppresses inherent chromosome segregation defects. Thus, DDR during mitosis inappropriately stabilizes k-MTs creating a link between s-CIN and w-CIN. PMID:25107667

  3. Microsporogênese de Coffea canephora Pierre ex Froehner com número duplicado de cromossomos Microsporogenesis in a tetraploid plant of Coffea canephora Pierre ex Froehner

    Directory of Open Access Journals (Sweden)

    Yone M. Sellito Boaventura

    1990-01-01

    Full Text Available Realizou-se o estudo do comportamento meiótico de C. canephora tetraplóide com 2n =44 cromossomos por tratar-se de uma espécie considerada possível ancestral de C. arabica (2n = 44: constatou-se, em 92,0% das células-mães de pólen, em todas as fases da microsporogênese estudada, 2n = 44 cromossomos. Em diacinese os cromossomos se apresentaram na forma de mono-, bi-, tri- e tetravalentes. Em metáfase 1, somente 13,16% das células apresentaram 22II sendo a seguinte a fórmula média do pareamento: 3,61I; 15,21II 0,71III e 1,93IV. As irregularidades anafásicas resumiram-se praticamente na disjunção desigual dos cromossomos para os pólos de 21-23, 20-24 e 19-25. Somente 37,65% das células apresentaram segregação normal de 22 cromossomos para cada pólo. Em anáfase II, observaram-se sete tipos diferentes de distribuição cromatídica e, também, somente em 26,0% das células foi encontrada distribuição normal dos cromossomos. Após a citocinese, foram observadas tríades (1,6%, tétrades (77,0% e políades (21,4%. A inviabilidade dos grãos de pólen foi alta, 79,0%. Observações em cortes transversais medianos de frutos mostraram 43,4% do tipo normal, sendo 11,0% do tipo moca e 32,4% do chato. Em 56,6% dos frutos, não houve desenvolvimento de sementes, formando-se apenas perisperma.Cytological investigations in a tetraploid plant of Coffea canephora with 2n =44 chromosomes were performed, In every meiosis phase studied, 92.0% of lhe pollen mother cells were found as 2n =44 chromosomes. In dia kinesis, lhe chromosomes were found as univalents, bivalents, trivalents and quadrivalents-At first metaphase, only 13.16% were 22II The average chromosomic associations were 3.61I, 15.21II, 0.71III, and 1.93IV- Irregular chromosomic distribution to the poles included 21-23, 20-24 and 19-25, while only 37.65% of the cells exhibited normal segregations of 22 chromosomes to each pole at first anaphase. At second anaphase, seven different

  4. Meiose e viabilidade polínica na família Araceae Meiosis and pollen viability in Araceae family

    Directory of Open Access Journals (Sweden)

    Maria Goreti Senna Corrêa

    2005-06-01

    Full Text Available O objetivo deste trabalho foi analisar a microsporogênese e a viabilidade dos grãos de pólen em 17 espécies de aráceas coletadas no Rio Grande do Sul, Brasil. Nove espécies foram analisadas quanto à ocorrência de células mãe de pólen (CMP normais e anormais nas fases de metáfase, anáfase e telófase, tanto da meiose I (M I como da meiose II (M II; 10 espécies foram estudadas quanto à presença de tétrades com número normal ou anormal de micrósporos e 17 espécies quanto à viabilidade dos grãos de pólen. As CMP anormais apresentaram, tanto em M I quanto em M II, cromossomos fora da placa metafásica ou cromossomos retardatários em anáfase e/ou telófase. As freqüências de CMP normais/anormais encontradas na microsporogênese salientam a grande variação existente entre as espécies. Ressalta-se a ausência de CMP com anomalias na microsporogênese de Monstera deliciosa Adans., assim como em M I de Anthurium scandens (Aubl Engl. e em M II de Caladium hortulanum Birdsey. O número observado de CMP anômalas, em M I e M II, nas espécies Syngonium podophyllum Schott e Zantedeschia aethiopica Spreng, foi maior que o esperado. A freqüência média de tétrades normais em dez espécies de aráceas, assim como a de grãos de pólen viáveis em 17 espécies, foi significativamente superior à freqüência média de anormais e de inviáveis, respectivamente.The objective of this work was to analyze microsporogenesis and pollen viability in 17 species of the Araceae family collected at Rio Grande do Sul, Brazil. Occurrence of normal and abnormal pollen mother cells (PMC was analyzed in metaphase, anaphase and telophase, in meiosis I (M I and meiosis II (M II of nine species; tetrads with normal or abnormal number of microspores was observed in 10 species, and pollen grain viability, in 17 species. Abnormal PMC presented chromosomes outside the metaphasic plate or laggard chromosomes in anaphase and/or telophase in both M I and M

  5. Sôbre a meiose de Dysdercus mendesi bloete (1937 - Hemiptera, pyrrhocoridæ

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    Luiz O. T. Mendes

    1947-01-01

    Full Text Available 1 - The spermatogonia of Dysdercus mendesi Bloete have 16 chromosomes : 7 pairs of autosomes and 2 sex-chromosomes. 2 - After the last spermatogonia! division, the chromatin of the autosomes diffuses and the nucleoplasm assumes an uniform granulai- aspect ; each sex-chromosome is involved by a vesicle and stands well colored. 3 - While the chromatin of the autosomes starts to condense again, to form the long threads (that finnally are seen in a paired condition the cycle of the sex-chromosomes is as follows : a yet contained in the vesicles, they grow in size and become long rods ; b the vesicles disappear, the sex-chromosomes move inside the nucleoplasm and come to be disposed longitudinally, close together. c they touch each other, become fissured, and a tetradlike chromatic element is formed, which contracts itself, remaining always well colored. 4 - The hetero-pycnosis of the sex-chromosomes is observed through the whole grow phase of the spermatocyte I. 5 - The separation of the sex-chromosome tetrad, originating two independent sex-chromosomes, is observed in the early grow phase of the spermatocyte as well as during any other period of this phase. The latest separation is observed during the diffuse stage of the nucleus. 6 - When the autosomes are in diakinesis, the sex-chromosomes assume the aspect of chromosomes in pachytene. 7 - In metaphase I the autosomic tetrads are in a more condensed and colored condition than the sex-chromosomes. The sex-chromosomes move to the center of the autosome-forming circle, but there is no contact between them. 8 - In anaphase I it is observed 2 interzonal connections between each autosomic dyad ; some exceptions are observed. Only one interzonal connection is observed between the separating sex-chromosomes. Moving to the poles the sex-chromosomes also approximate one to the other. 9 - In telophase I the sex-chromosome touch each other, and fuse side-by-side, forming only one chromatic element. The line

  6. Mechanisms involved in the induction of aneuploidy: the significance of chromosome loss

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    A.I. Seoane

    2000-12-01

    Full Text Available The induction of aneuploidy by physical and chemical agents using different test systems was evaluated. The effect of X-rays, caffeine, acetaldehyde, ethanol, diethylstilbestrol, propionaldehyde, and chloral hydrate was studied by chromosome counting in Chinese hamster embryonic diploid cells. Aneugenic ability of cadmium chloride, cadmium sulfate, potassium dichromate, chromium chloride, nickel chloride, and nickel sulfate was assessed by means of anaphase-telophase analysis in Chinese hamster ovary cells. Chromosome counting in human fibroblasts (MRC-5 cell line was employed to evaluate the effect of cacodilic acid, cadmium chloride, cadmium sulfate, and potassium dichromate. Finally, the induction of kinetochore-positive and kinetochore negative micronuclei by cadmium chloride, cadmium sulfate, potassium dichromate, chromium chloride, and nickel chloride was studied using CREST antibodies. When the effect of different agents was determined by chromosome counting, an increase of hypoploid but not of hyperploid cells was observed. Anaphase-telophase analysis showed that metal salts increased the frequency of lagging chromosomes. This finding has been confirmed by the increment of kinetochore-positive micronuclei using CREST antibodies. Therefore, chromosome loss could be considered as the main cause of induced aneuploidy.A indução de aneuploidia por agentes físicos e químicos usando diferentes sistemas de teste foi avaliada. O efeito de raios-X, cafeína, acetaldeído, etanol, dietilestilbestrol, propionaldeído e hidrato de cloral foi estudado por contagem cromossômica em células diplóides embriônicas de hamster chinês. A habilidade aneugênica de cloreto de cádmio, sulfato de cádmio, dicromato de potássio, cloreto de crômio, cloreto de níquel e sulfato de níquel foi avaliada por meio de análise de anáfase-telófase em células de ovário de hamster chinês. A contagem cromossômica em fibroblastos humanos (linhagem celular

  7. 超表达Cdc20基因不影响牛卵母细胞第一极体排出%Over-expression of Cdc20 Gene Has No Effect on Bovine Oocytes First Polar Body Extrusion

    Institute of Scientific and Technical Information of China (English)

    杨文琳; 安鹏; 李伟; 赵贵民; 史芸安; 雷安民

    2012-01-01

    As one of the co-activator of anaphase-promoting complex ( APC) , cell division cycle 20 (CDC20) protein also functions as the target of the spindle assembly checkpoint ( SAC), which is essential for the cell cycle regulation. To investigate the function of Cdc20 during the first polar body extrusion ( PBE I) , Cdc20 CDS was cloned and eukaryotic expression vector pCdc20-Venus was constructed. Using the linear pCdc20-Venus as template, the capped Cdc20-Venus mRNA was synthesized via T7 Mmessage Mmachine Kit ( Ambion). Cdc20 over-expression was performed by microinjection of Cdc20-Venus mRNA into the cytoplasm of bovine oocytes. The results showed that Venus tagged Cdc20 dispersed around the nucleus in HeLa cells. In bovine oocytes, the fluorescence appeared in the whole cytoplasm. However, the PBE I rate in over-expressed group (48. 9% ) is not significant, compared to Venus mRNA injection group (50.9%) and non-injection group (51.1%). Our study demonstrated that the over-expression of Cdc20 in bovine oocytes does not affect the PBE I rate ( P > 0.05).%CDC20(cell division cycle 20)是后期促进复合物(anaphase-promoting complex,APC)的共激活剂之一,也是纺锤体组装检查点(spindle assembly checkpoint,SAC)的靶点,在细胞周期调控中扮演重要角色.为探讨Cdc20在第一极体排出(first polar body extrusion,PBE I)中的作用,Cdc20基因被成功克隆并构建了真核表达载体pCdc20-Venus,随后用T7 Mmessage Mmachine Kit(Ambion)以线性化pCdc20-Venus为模板体外转录(in vitro transcription)获得带帽的Cdc20-Venus mRNA,将Ccdc20-Venus mRNA显微注射到体外培养的牛卵母细胞胞质中进行超量表达.结果表明,真核表达载体pCdc20-Venus转染HeLa细胞后能够正常表达,绿色荧光在细胞核周围呈弥散状分布;将Cdc20-Venus mRNA注射到牛卵母细胞胞质后,胞质内有绿色荧光出现.Cdc20-Venus mRNA注射组卵母细胞的PBE I率(48.9%)与Venus mRNA注射组卵母细胞的PBE I率(50

  8. 笼养大鸨繁殖不同时期行为时间分配及活动节律%Time Budget of Behaviors and Activity Rhytinn of Great Bustard in Captivity During Different Breeding Periods

    Institute of Scientific and Technical Information of China (English)

    卢小琴; 田秀华

    2011-01-01

    The instantaneous scan method was used to study the time budget of breeding behaviors and activity rhythm of Great Bustards in Changchun Zoological and Botanical Gardens during April-August in 2010. The differences in time budget of behaviors of Great Bustards in the same breeding period between male and female and of the same sex between different breeding periods were analyzed by independent sample T-test. Results show that the time budget of behaviors and activity rhythm of the Great bustards are regular to some degree. Feeding mostly occurs in the middle of the morning and the afternoon, flaunting and hatching mostly in the morning and evening, and resting mostly occurs at noon. During the prophase of breeding, the Great bustards spend their time mainly in standing, lying and walking, and the male and the female spend 80.63% and 66.34% of their time on the three behaviors, respectively. The time budget of the male changes greatly during the anaphase of breeding. They spend 90.41% of their time in incubating in the nest, and incubating, feeding and alerting behaviors have an obvious rhythm; however, the male still spend 59.23% of their time mainly in standing, lying and walking. The time budget of behaviors of Great Bustards exhibits differences not only between the male and the female, but also between the prophase and anaphase of breeding.%2010年4月到8月,采用瞬时扫描法对长春动植物公园两对繁殖良好的大鸨的繁殖行为时间分配和活动节律进行了研究,并利用独立样本T检验分析了不同性别大鸨繁殖前后期行为的性别差异,以及相同性别的大鸨在繁殖的不同时期的行为差异.结果表示:大鸨繁殖期的各种行为活动具有一定的时间分配和日节律,取食行为多发生在上午和下午的中间时段,炫耀、孵化多在早晨和傍晚,而中午的大部分时间处于休息状态.繁殖前期,大鸨的行为主要表现为静立、趴卧和游走,雌雄大鸨的这3

  9. Microsporogênese em Coffea stenophylla G. Don e C. salvatrix Swynn et Phil Microsporogenesis in Coffea stenophylla G. Don and C. salvatrix Swynn et. Phil

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    Dixier M. Medina

    1969-01-01

    Full Text Available Estudou-se a microsporogênese de Coffea stenophylla,G. Don e de C. salvatrixSwynn et Phil, espécies diplóides de Coffea, introduzidas respectivamente da Guatemala e da Colômbia e mantidas em coleção no Instituto Agronômico de Campinas. O aspecto dos cromossomos é semelhante ao já descrito para outras espécies do gênero. O emparelhamento ocorre em todos os cromossomos, desde os estádios iniciais da prófase até a primeira metáfase; os 11 bivalentes formados separam-se normalmente nas anáfases, e os micróspores resultantes são haplóides, com n= 11 cromossomos. O comportamento cromossômico nas diversas fases da meiose é regular na maioria das células mães. O número de bivalentes com três, dois e um quiasma é, em média, 1, 4 e 6 para C. stenophyllae 1, 3 e 7 para C. salvatrix, num total de 16 e 17 quiasmas por célula, respectivamente. Parece haver em C. stenophyllavariação maior nos tipos de distribuição dos quiasmas pelos bivalentes. As irregularidades encontradas referem-se principalmente à ocorrência de monovalentes, de retardatários nas anáfases e à distribuição desigual dos cromossomos para os pólos. Discute-se a possibilidade de formação de gametas com números de cromossomos diferentes de 11 e de gametas com conjuntos não balanceados, além dos haplóides normais.Studies on the microsporogenesis in Coffea stenophylla and C. salvatrix demonstrated that the meiotic chromosomes of both species resemble those of the other diploid species of the genus Coffea. Complete chromosome pairing was observed from early prophase till first metaphase, "with 11 bivalents being formed in most of the cells. These bivalents fall apart in a quite regular manner at the two anaphases. The average numbers of bivalents with three, two and one chiasma at first metaphase are 1, 4 and 6 por C. stenophylla and 1, 3 and 7 for C. salvatrix, the mean number of chiasmata per cell being 17 and 16 respectively. Despite of the very

  10. CENPA overexpression promotes genome instability in pRb-depleted human cells

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    Lentini Laura

    2009-12-01

    Full Text Available Abstract Background Aneuploidy is a hallmark of most human cancers that arises as a consequence of chromosomal instability and it is frequently associated with centrosome amplification. Functional inactivation of the Retinoblastoma protein (pRb has been indicated as a cause promoting chromosomal instability as well centrosome amplification. However, the underlying molecular mechanism still remains to be clarified. Results Here we show that pRb depletion both in wild type and p53 knockout HCT116 cells was associated with the presence of multipolar spindles, anaphase bridges, lagging chromosomes and micronuclei harbouring whole chromosomes. In addition aneuploidy caused by pRb acute loss was not affected by p53 loss. Quantitative real-time RT-PCR showed that pRB depletion altered expression of genes involved in centrosome duplication, kinetochore assembly and in the Spindle Assembly Checkpoint (SAC. However, despite MAD2 up-regulation pRb-depleted cells seemed to have a functional SAC since they arrested in mitosis after treatments with mitotic poisons. Moreover pRb-depleted HCT116 cells showed BRCA1 overexpression that seemed responsible for MAD2 up-regulation. Post-transcriptional silencing of CENPA by RNA interference, resulting in CENP-A protein levels similar to those present in control cells greatly reduced aneuploid cell numbers in pRb-depleted cells. Conclusion Altogether our findings indicate a novel aspect of pRb acute loss that promotes aneuploidy mainly by inducing CENPA overexpression that in turn might induce micronuclei by affecting the correct attachment of spindle microtubules to kinetochores.

  11. Radiation-modulated gene expression in C. elegans

    International Nuclear Information System (INIS)

    Full text: We use the nematode C. elegans to characterize the genotoxic and cytotoxic effects of ionizing radiation with emphasis effects of charged particle radiation and have described the fluence vs. response relationships for mutation, chromosome aberration and certain developmental errors. These endpoints quantify the biological after repair and compensation pathways have completed their work. In order to address the control of these reactions we have turned to gene expression profiling to identify genes that uniquely respond to high LET species or respond differentially as a function of radiation properties. We have employed whole genome microarray methods to map gene expression following exposure to gamma rays, protons and accelerated iron ions. We found that 599 of 17871 genes analyzed showed differential expression 3 hrs after exposure to 3 Gy of at least one radiation types. 193 were up-regulated, 406 were down-regulated, and 90% were affected by only one species of radiation. Genes whose transcription levels responded significantly mapped to definite statistical clusters that were unique for each radiation type. We are now trying to establish the functional relationships of the genes their relevance to mitigation of radiation-induced damage. Three approaches are being used. First, bioinformatics tools are being used to determine the roles of genes in co-regulated gene sets. Second, we are applying the technique of RNA interference to determine whether our radiation-induced genes affect cell survival (measured in terms of embryo survival) and chromosome aberration (intestinal anaphase bridges). Finally we are focussing on the response of the most strongly-regulated gene in our data set. This is the autosomal gene, F36D3.9, whose predicted structure is that of a cysteine protease resembling cathepsin B. An enzymological approach is being used to characterize this gene at the protein level. This work was supported by NASA Cooperative Agreement NCC9-149

  12. The Pleiomorphic Plant MTOC: An Evolutionary Perspective

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    γ-Tubulin is an essential component of the microtubule organizing center (MTOC) responsible for nucleating microtubules In both plants and animals. Whereas γ-tubulin is tightly associated with centrosomes that are inheritable organelles in cells of animals and most algae, it appears at different times and places to organize the myriad specialized microtubule systems that characterize plant cells. We have traced the distribution of γ-tubulin through the cell cycle in representative land plants (embryophytes) and herein present data that have led to a concept of the pleiomorphic and migratory MTOC.The many forms of the plant MTOC at spindle organization constitute pleiomorphism, and stage-specific "migration" is suggested by the consistent pattern of redistribution of γ-tubulin during mitosis. Mitotic spindles may be organized at centriolar centrosomes (only in final divisions of spermatogenesis), polar organizers (POs), plastid MTOCs, or nuclear envelope MTOCs (NE-MTOCs). In all cases, with the possible exception of centrosomes in spermatogenesis, the γ-tubulin migrates to broad polar regions and along the spindle fibers, even when it is initially a discrete polar entity. At anaphase it moves poleward, and subsequently migrates from polar regions (distal nuclear surfaces) into the interzone (proximal nuclear surfaces) where interzonal microtubule arrays and phragmoplasts are organized. Following cytokinesis, γ-tubulin becomes associated with nuclear envelopes and organizes radial microtubule systems (RMSs). These may exist only briefly, before establishment of hoop-like cortical arrays in vegetative tissues, or they may be characteristic of interphase in syncytial systems where they serve to organize the common cytoplasm into nuclear cytoplasmic domains (NCDs).

  13. Sequential phosphorylation of GRASP65 during mitotic Golgi disassembly

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    Danming Tang

    2012-09-01

    GRASP65 phosphorylation during mitosis and dephosphorylation after mitosis are required for Golgi disassembly and reassembly during the cell cycle. At least eight phosphorylation sites on GRASP65 have been identified, but whether they are modified in a coordinated fashion during mitosis is so far unknown. In this study, we raised phospho-specific antibodies that recognize phosphorylated T220/T224, S277 and S376 residues of GRASP65, respectively. Biochemical analysis showed that cdc2 phosphorylates all three sites, while plk1 enhances the phosphorylation. Microscopic studies using these antibodies for double and triple labeling demonstrate sequential phosphorylation and dephosphorylation during the cell cycle. S277 and S376 are phosphorylated from late G2 phase through metaphase until telophase when the new Golgi is reassembled. T220/224 is not modified until prophase, but is highly modified from prometaphase to anaphase. In metaphase, phospho-T220/224 signal localizes on both Golgi haze and mitotic Golgi clusters that represent dispersed Golgi vesicles and Golgi remnants, respectively, while phospho-S277 and S376 labeling is more concentrated on mitotic Golgi clusters. Expression of a phosphorylation-resistant GRASP65 mutant T220A/T224A inhibited mitotic Golgi fragmentation to a much larger extent than the expression of the S277A and S376A mutants. In cytokinesis, T220/224 dephosphorylation occurs prior to that of S277, but after S376. This study provides evidence that GRASP65 is sequentially phosphorylated and dephosphorylated during mitosis at different sites to orchestrate Golgi disassembly and reassembly during cell division, with phosphorylation of the T220/224 site being most critical in the process.

  14. The evaluation of waste, surface and ground water quality using the Allium test procedure.

    Science.gov (United States)

    Smaka-Kincl, V; Stegnar, P; Lovka, M; Toman, M J

    1996-07-01

    The bulbs of Allium cepa were grown in test liquids of various pollution levels as follows: undiluted industrial and municipal waste water; biological treatment plant output water; water from the Drava river upstream and downstream of the city of Maribor; and non-chlorinated drinking water as a negative control test. The paper presents the response of the Allium cepa genetic material to the presence of potential cytotoxic and genotoxic substances in test liquids and the suitability of the Allium cepa testing procedure as a method for short-term determination of water pollution level. The suitability of the Allium test procedure as a system for environmental monitoring is presented. The influence of water pollution on macroscopic and cytologic parameters of the common onion by application of the biological testing method was examined. The macroscopic parameter was inhibition of root growth. The cytological parameters were: aberrant cells in metaphase and anaphase, index of micronuclei appearance and inhibition of cell division. The possibility of categorization the different polluted test liquids into quality classes is presented according to the influence of the test liquids on macroscopic and cytologic parameters. Test liquids are divided into 8 quality classes: the first class is the least polluted surface waters, the second and the third classes are more polluted surface water, the fourth and the fifth classes are biological treatment plant output waters, the sixth till the eighth quality classes are untreated waste waters. The most polluted test liquids (untreated industrial and municipal waste waters) caused sublethal and even lethal effects. The most polluted tested liquids cause the inhibition of root growth over 50% (even up to 74%), decrease of mitotic index over 36% (even up to 66%), increase of presence of interphase cells with micronuclei over 3% and increase of presence of aberrant cells for more than 10 times in comparison to control test. PMID

  15. 太行菊和芙蓉菊花粉母细胞减数分裂过程%Meiosis process of pollen mother cells in Opisthopappus taihangensis (Ling)Shih and Crossostephium chinense(L.)Makino

    Institute of Scientific and Technical Information of China (English)

    李健; 陈发棣; 陈素梅; 房伟民

    2009-01-01

    对太行菊和芙蓉菊花粉母细胞减数分裂过程进行了研究.结果表明:太行菊和芙蓉菊减数分裂过程基本正常,为同时型胞质分裂.减数分裂中期Ⅰ染色体基本构型为9个二价体,其中太行菊和芙蓉菊每个花粉母细胞(PMC)平均染色体配对构型分别为005Ⅰ+892Ⅱ+003Ⅳ和004Ⅰ+861Ⅱ+002Ⅲ+017Ⅳ;部分花粉母细胞后期Ⅰ和后期Ⅱ及末期Ⅰ和末期Ⅱ发现有染色体桥、落后染色体、微核及不同步分裂等减数分裂异常现象.%Meiosis behaviors in the Opisthopappus taihangensis (Ling) Shih and Crossostephium chinense (L. ) Makino were investigated for the first time. The results showed that meiosis of pollen mother cell ( PMC) was overall normal and simultaneous cytokinesis. The chromosome pairing configurations at meiotic metaphase Ⅰ per PMC in Opisthopappus taihangensis (Ling) Shih and Crossostephium chinense (L. ) Makino, with the commonest configurations of 9 bivalents (9Ⅱ ), were 0. 05 Ⅰ +8. 92 Ⅱ +0. 03Ⅳ and 0. 04Ⅰ +8. 61 Ⅱ +0. 02Ⅲ+0. 17Ⅳ , respectively. A few of chromosome bridges and laggard chromosomes were found in some PMCs at anaphase Ⅰ and Ⅱ ; moreover, micronucleus and nonsynchronous division were also observed in several cells at telophase land Ⅱ.

  16. Mitotic defects lead to pervasive aneuploidy and accompany loss of RB1 activity in mouse LmnaDhe dermal fibroblasts.

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    C Herbert Pratt

    Full Text Available BACKGROUND: Lamin A (LMNA is a component of the nuclear lamina and is mutated in several human diseases, including Emery-Dreifuss muscular dystrophy (EDMD; OMIM ID# 181350 and the premature aging syndrome Hutchinson-Gilford progeria syndrome (HGPS; OMIM ID# 176670. Cells from progeria patients exhibit cell cycle defects in both interphase and mitosis. Mouse models with loss of LMNA function have reduced Retinoblastoma protein (RB1 activity, leading to aberrant cell cycle control in interphase, but how mitosis is affected by LMNA is not well understood. RESULTS: We examined the cell cycle and structural phenotypes of cells from mice with the Lmna allele, Disheveled hair and ears (Lmna(Dhe. We found that dermal fibroblasts from heterozygous Lmna(Dhe (Lmna(Dhe/+ mice exhibit many phenotypes of human laminopathy cells. These include severe perturbations to the nuclear shape and lamina, increased DNA damage, and slow growth rates due to mitotic delay. Interestingly, Lmna(Dhe/+ fibroblasts also had reduced levels of hypophosphorylated RB1 and the non-SMC condensin II-subunit D3 (NCAP-D3, a mitosis specific centromere condensin subunit that depends on RB1 activity. Mitotic check point control by mitotic arrest deficient-like 1 (MAD2L1 also was perturbed in Lmna(Dhe/+ cells. Lmna(Dhe/+ fibroblasts were consistently aneuploid and had higher levels of micronuclei and anaphase bridges than normal fibroblasts, consistent with chromosome segregation defects. CONCLUSIONS: These data indicate that RB1 may be a key regulator of cellular phenotype in laminopathy-related cells, and suggest that the effects of LMNA on RB1 include both interphase and mitotic cell cycle control.

  17. Observações citológicas em Coffea: XVI - Microsporogênese em Coffea canephora Pierre ex Froehner

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    Cândida H. T. Mendes

    1950-04-01

    Full Text Available This paper presents the results of cytological observations on microsporogenesis in the self-sterile species Coffea canephora. It was found difficult to study chromosome structure in the first stages of meiosis because the chromosomes do not stain well with aceto carmine and could be seen only as long faintly threads with some heteropycnotic regions. In many observations of the pachytene stage it was possible to observe and study a chromosome attached to the nucleolus. This chromosome characteristically had a visible centromere which divided it into two arms of different sizes. The short arm was attached to the nucleolus and had several heteropycnotic regions. In the long arm the heteropycnotic regions were observed to be close to the centromere ; the distal portion of this arm was only faintly stained. Other chromosomes in the pachytene stage were found to have a conspicuous centromere located between two highly heteropycnotic regions. The heteropycnotic regions in some chromosomes were located near the centromere while in others they were observed to be scattered throughout the chromosome. In diakinesis the chiasmata were counted and there were found seven chromosomes with one chiasma, three chromosomes with two chiasmata and one chromosome with three chiasmata. The average number of chiasmata per cell was 15.88. In metaphase the average number of chiasmata per cell was found to be 14.57, which is less than the average per cell in diakinesis. Anaphase I appeared normal as did all subsequent phases of meiosis, that resulted finally in the development of four microspores with eleven chromosomes each. Very few pollen mother cells with abnormal numbers of chromosomes were observed. On the basis of this study, it is concluded that microsporogenesis in Coffea canephora is normal.

  18. Perturbing microtubule integrity blocks AMP-activated protein kinase-induced meiotic resumption in cultured mouse oocytes.

    Science.gov (United States)

    Ya, Ru; Downs, Stephen M

    2014-02-01

    The oocyte meiotic spindle is comprised of microtubules (MT) that bind chromatin and regulate both metaphase plate formation and karyokinesis during meiotic maturation; however, little information is known about their role in meiosis reinitiation. This study was conducted to determine if microtubule integrity is required for meiotic induction and to ascertain how it affects activation of AMP-activated protein kinase (AMPK), an important participant in the meiotic induction process. Treatment with microtubule-disrupting agents nocodazole and vinblastine suppressed meiotic resumption in a dose-dependent manner in both arrested cumulus cell-enclosed oocytes (CEO) stimulated with follicle-stimulating hormone (FSH) and arrested denuded oocytes (DO) stimulated with the AMPK activator, 5-aminoimidazole-4-carboxamide-1-beta-4-ribofuranoside (AICAR). This effect coincided with suppression of AMPK activation as determined by western blotting and germinal vesicle immunostaining. Treatment with the MT stabilizer paclitaxel also suppressed meiotic induction. Targeting actin filament polymerization had only a marginal effect on meiotic induction. Immunolocalization experiments revealed that active AMPK colocalized with γ-tubulin during metaphase I and II stages, while it localized at the spindle midzone during anaphase. This discrete localization pattern was dependent on MT integrity. Treatment with nocodazole led to disruption of proper spindle pole localization of active AMPK, while paclitaxel induced excessive polymerization of spindle MT and formation of ectopic asters with accentuated AMPK colocalization. Although stimulation of AMPK increased the rate of germinal vesicle breakdown (GVB), spindle formation and polar body (PB) extrusion, the kinase had no effect on peripheral movement of the spindle. These data suggest that the meiosis-inducing action and localization of AMPK are regulated by MT spindle integrity during mouse oocyte maturation. PMID:23199370

  19. Loss of centromeric histone H2AT120 phosphorylation accompanies somatic chromosomes inactivation in the aberrant spermatocytes of Acricotopus lucidus (Diptera, Chironomidae).

    Science.gov (United States)

    Staiber, Wolfgang

    2016-01-01

    In the germ line of the chironomid Acricotopus lucidus, two cells with quite different chromosome constitutions result from the last unequal gonial mitosis. In the male, the future primary spermatocyte receives all the germ line-limited chromosomes (=Ks) together with somatic chromosomes (=Ss), and later on undergoes meiotic divisions, while the connected aberrant spermatocyte gets only Ss and remains undivided with chromosomes inactivated in a metaphase-like condensed state. This raises the question whether the centromeres of the permanently condensed Ss of the aberrant spermatocyte remain active during meiosis of the connected regular spermatocyte. Active centromeres exhibit an epigenetic phosphorylation mark at threonine 120 of histone H2A. To visualise the centromeric H2A phosphorylation of the Ss in the aberrant spermatocyte, meiotic stages were immunostained with different anti-phospho histone H2AT120 antibodies. Clear H2AT120ph signals appear at the centromeres of the Ss during prophase, persist on the metaphase-like condensed Ss during meiosis I of the connected primary spermatocyte and disappear during transition to meiosis II. The centromeres of the Ss and Ks of the regular spermatocytes display H2AT120ph signals from prophase I to anaphase II. The loss of the H2AT120 phosphorylation detected on the centromeres of the Ss of the aberrant spermatocyte indicating their deactivation supports the idea of a programmed inactivation of the Ss to block the entry of the germ line-derived aberrant spermatocyte, lacking Ks, into meiosis, and thus to prevent the generation of sperms possessing only Ss. This mechanism would ensure the presence of the Ks in the germ line. PMID:25820679

  20. Mitotic chromosomal abnormalities in diploid and colchicine-induced tetraploid jute (Corchorus capsularis L.) following gamma-rays treatment

    International Nuclear Information System (INIS)

    The purpose of the present study was to detect and explain the various types of chromosomal abnormalities resulting from seed irradiation and to evaluate the frequency of abnormal cells in different doses and thereby establish the relative radiosensitivity between the 2x (2n = 14) and c-4x (2n = 28) (colchicine-induced) Corchorus capsularis. Air-dried seeds of the two ploidy levels were exposed to 60, 70 and 80 KR gamma-rays (60Co) and different stages of the mitotic division of the treated and control root tips were studied. There was no chromosomal abnormality in the untreated root-tip cells of both the types. The aberrations in the irradiated samples included: a) only bridges, b) only laggards and c) both bridges and laggards in the anaphase of root-tip cells of both the ploidy levels, d) much more variation in length of metaphase chromosomes in c-4x capsularis. Plausible causes of the origin and occurrence of the abnormalities have been discussed in the light of the findings of other workers in the field. There was increase in the frequency of abnormal cells with the increase in radiation dose in both the ploidy levels but at a given dose c-4x capsularis produced more aberrations than the 2x diploid. It was concluded that the artificially induced autotetoraploid was more radio-sensitive than the 2x type. This perhaps, was due to the artificial nature of origin of the autotetraploid and its lack of sufficient adaptation to protect itself from radiation effect. (author)

  1. Measurement of separase proteolytic activity in single living cells by a fluorogenic flow cytometry assay.

    Directory of Open Access Journals (Sweden)

    Wiltrud Haaß

    Full Text Available ESPL1/Separase, an endopeptidase, is required for centrosome duplication and separation of sister-chromatides in anaphase of mitosis. Overexpression and deregulated proteolytic activity of Separase as frequently observed in human cancers is associated with the occurrence of supernumerary centrosomes, chromosomal missegregation and aneuploidy. Recently, we have hypothesized that increased Separase proteolytic activity in a small subpopulation of tumor cells may serve as driver of tumor heterogeneity and clonal evolution in chronic myeloid leukemia (CML. Currently, there is no quantitative assay to measure Separase activity levels in single cells. Therefore, we have designed a flow cytometry-based assay that utilizes a Cy5- and rhodamine 110 (Rh110-biconjugated Rad21 cleavage site peptide ([Cy5-D-R-E-I-M-R]2-Rh110 as smart probe and intracellular substrate for detection of Separase enzyme activity in living cells. As measured by Cy5 fluorescence the cellular uptake of the fluorogenic peptide was fast and reached saturation after 210 min of incubation in human histiocytic lymphoma U937 cells. Separase activity was recorded as the intensity of Rh110 fluorescence released after intracellular peptide cleavage providing a linear signal gain within a 90-180 min time slot. Compared to conventional cell extract-based methods the flow cytometric assay delivers equivalent results but is more reliable, bypasses the problem of vague loading controls and unspecific proteolysis associated with whole cell extracts. Especially suited for the investigaton of blood- and bone marrow-derived hematopoietic cells the flow cytometric Separase assay allows generation of Separase activity profiles that tell about the number of Separase positive cells within a sample i.e. cells that currently progress through mitosis and about the range of intercellular variation in Separase activity levels within a cell population. The assay was used to quantify Separase proteolytic

  2. Immobility, inheritance and plasticity of shape of the yeast nucleus

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    Andrulis Erik D

    2007-11-01

    Full Text Available Abstract Background Since S. cerevisiae undergoes closed mitosis, the nuclear envelope of the daughter nucleus is continuous with that of the maternal nucleus at anaphase. Nevertheless, several constitutents of the maternal nucleus are not present in the daughter nucleus. The present study aims to identify proteins which impact the shape of the yeast nucleus and to learn whether modifications of shape are passed on to the next mitotic generation. The Esc1p protein of S. cerevisiae localizes to the periphery of the nucleoplasm, can anchor chromatin, and has been implicated in targeted silencing both at telomeres and at HMR. Results Upon increased Esc1p expression, cell division continues and dramatic elaborations of the nuclear envelope extend into the cytoplasm. These "escapades" include nuclear pores and associate with the nucleolus, but exclude chromatin. Escapades are not inherited by daughter nuclei. This exclusion reflects their relative immobility, which we document in studies of prezygotes. Moreover, excess Esc1p affects the levels of multiple transcripts, not all of which originate at telomere-proximal loci. Unlike Esc1p and the colocalizing protein, Mlp1p, overexpression of selected proteins of the inner nuclear membrane is toxic. Conclusion Esc1p is the first non-membrane protein of the nuclear periphery which – like proteins of the nuclear lamina of higher eukaryotes – can modify the shape of the yeast nucleus. The elaborations of the nuclear envelope ("escapades" which appear upon induction of excess Esc1p are not inherited during mitotic growth. The lack of inheritance of such components could help sustain cell growth when parental nuclei have acquired potentially deleterious characteristics.

  3. Cytokinesis-block micronucleus assay evolves into a 'cytome' assay of chromosomal instability, mitotic dysfunction and cell death

    International Nuclear Information System (INIS)

    The cytokinesis-block micronucleus (CBMN) assay was originally developed as an ideal system for measuring micronuclei (MNi) however it can also be used to measure nucleoplasmic bridges (NPBs), nuclear buds (NBUDs), cell death (necrosis or apoptosis) and nuclear division rate. Current evidence suggests that (a) NPBs originate from dicentric chromosomes in which the centromeres have been pulled to the opposite poles of the cell at anaphase and are therefore indicative of DNA mis-repair, chromosome rearrangement or telomere end-fusions, (b) NPBs may break to form MNi, (c) the nuclear budding process is the mechanism by which cells remove amplified and/or excess DNA and is therefore a marker of gene amplification and/or altered gene dosage, (d) cell cycle checkpoint defects result in micronucleus formation and (e) hypomethylation of DNA, induced nutritionally or by inhibition of DNA methyl transferase can lead to micronucleus formation either via chromosome loss or chromosome breakage. The strong correlation between micronucleus formation, nuclear budding and NPBs (r = 0.75-0.77, P < 0.001) induced by either folic acid deficiency or exposure to ionising radiation is supportive of the hypothesis that folic acid deficiency and/or ionising radiation cause genomic instability and gene amplification by the initiation of breakage-fusion-bridge cycles. In its comprehensive mode, the CBMN assay measures all cells including necrotic and apoptotic cells as well as number of nuclei per cell to provide a measure of cytotoxicity and mitotic activity. The CBMN assay has in fact evolved into a 'cytome' method for measuring comprehensively chromosomal instability phenotype and altered cellular viability caused by genetic defects and/or nutrional deficiencies and/or exogenous genotoxins thus opening up an exciting future for the use of this methodology in the emerging fields of nutrigenomics and toxicogenomics and their combinations

  4. The multiple roles of Bub1 in chromosome segregation during mitosis and meiosis

    Energy Technology Data Exchange (ETDEWEB)

    Marchetti, Francesco; Venkatachalam, Sundaresan

    2009-06-19

    Aneuploidy, any deviation from an exact multiple of the haploid number of chromosomes, is a common occurrence in cancer and represents the most frequent chromosomal disorder in newborns. Eukaryotes have evolved mechanisms to assure the fidelity of chromosome segregation during cell division that include a multiplicity of checks and controls. One of the main cell division control mechanisms is the spindle assembly checkpoint (SAC) that monitors the proper attachment of chromosomes to spindle fibers and prevents anaphase until all kinetochores are properly attached. The mammalian SAC is composed by at least 14 evolutionary-conserved proteins that work in a coordinated fashion to monitor the establishment of amphitelic attachment of all chromosomes before allowing cell division to occur. Among the SAC proteins, the budding uninhibited by benzimidazole protein 1 (Bub1), is a highly conserved protein of prominent importance for the proper functioning of the SAC. Studies have revealed many roles for Bub1 in both mitosis and meiosis, including the localization of other SAC proteins to the kinetochore, SAC signaling, metaphase congression and the protection of the sister chromatid cohesion. Recent data show striking sex specific differences in the response to alterations in Bub1 activity. Proper Bub1 functioning is particularly important during oogenesis in preventing the generation of aneuploid gametes that can have detrimental effects on the health status of the fetus and the newborn. These data suggest that Bub1 is a master regulator of SAC and chromosomal segregation in both mitosis and meiosis. Elucidating its many essential functions in regulating proper chromosome segregation can have important consequences for preventing tumorigenesis and developmental abnormalities.

  5. Centromere-tethered Mps1 pombe homolog (Mph1) kinase is a sufficient marker for recruitment of the spindle checkpoint protein Bub1, but not Mad1.

    Science.gov (United States)

    Ito, Daisuke; Saito, Yu; Matsumoto, Tomohiro

    2012-01-01

    The spindle checkpoint delays the onset of anaphase until all of the chromosomes properly achieve bipolar attachment to the spindle. It has been shown that unattached kinetochores are the site that emits a signal for activation of the checkpoint. Although the components of the checkpoint such as Bub1, Mad1 and Mad2 selectively accumulate at unattached kinetochores, the answer to how they recognize unattached kinetochores has remained elusive. Mps1 pombe homolog (Mph1) kinase has been shown to function upstream of most of the components of the checkpoint and thus it is thought to recognize unattached kinetochores by itself and recruit other components. In this study we have expressed a fusion protein of Mph1 and Ndc80 (a kinetochore protein of the outer plate) and shown that the fusion protein arrests cell cycle progression in a spindle-checkpoint\\x{2013}dependent manner in fission yeast. When expression of Mad2 is turned off, the cells grow normally with Mph1 constitutively localized at centromeres/kinetochores. Under this condition, Bub1 can be found with Mph1 throughout the cell cycle, indicating that localization of Mph1 at centromeres/kinetochores is sufficient to recruit Bub1. In contrast, Mad1 is found to transiently localize at kinetochores, which are presumably unattached to the spindle, but soon it dissociates from kinetochores. We propose that Mph1 is a sufficient marker for recruitment of Bub1. Mad1, in contrast, requires an additional condition/component for stable association with kinetochores. PMID:22184248

  6. EB1 is required for spindle symmetry in mammalian mitosis.

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    Anke Brüning-Richardson

    Full Text Available Most information about the roles of the adenomatous polyposis coli protein (APC and its binding partner EB1 in mitotic cells has come from siRNA studies. These suggest functions in chromosomal segregation and spindle positioning whose loss might contribute to tumourigenesis in cancers initiated by APC mutation. However, siRNA-based approaches have drawbacks associated with the time taken to achieve significant expression knockdown and the pleiotropic effects of EB1 and APC gene knockdown. Here we describe the effects of microinjecting APC- or EB1- specific monoclonal antibodies and a dominant-negative EB1 protein fragment into mammalian mitotic cells. The phenotypes observed were consistent with the roles proposed for EB1 and APC in chromosomal segregation in previous work. However, EB1 antibody injection also revealed two novel mitotic phenotypes, anaphase-specific cortical blebbing and asymmetric spindle pole movement. The daughters of microinjected cells displayed inequalities in microtubule content, with the greatest differences seen in the products of mitoses that showed the severest asymmetry in spindle pole movement. Daughters that inherited the least mobile pole contained the fewest microtubules, consistent with a role for EB1 in processes that promote equality of astral microtubule function at both poles in a spindle. We propose that these novel phenotypes represent APC-independent roles for EB1 in spindle pole function and the regulation of cortical contractility in the later stages of mitosis. Our work confirms that EB1 and APC have important mitotic roles, the loss of which could contribute to CIN in colorectal tumour cells.

  7. Characteristics of Cd uptake and accumulation in two Cd accumulator oilseed rape species

    Institute of Scientific and Technical Information of China (English)

    RU Shu-hua; WANG Ji-qing; SU De-chun

    2004-01-01

    Two pot experiments were conducted under greenhouse conditions to investigate the characteristics of Cd uptake and accumulation by two Cd accumulator oilseed rape varieties and one Indian mustard grown on a loamy soil that had been artificially contaminated by different amounts of CdSO4 (0, 20, 40, 60, 80, 100 mg/kg soil). The relationship between shoot Cd uptake of the two oilseed rape cultivars and the soil Cd concentrations could be simulated via quadratic equations. The curve showed that maximum shoot Cd uptake of Indian mustard was 314.7μg/pot at soil Cd concentration of 87.8 mg/kg, while maximum uptake of the variety Xikou Huazi was 543.3μg/pot at soil Cd concentration of 69.1 mg/kg and that of the variety Zhongyou Za-1hao was 576.7μg/pot at soil Cd concentration of 84.0 mg/kg, suggesting that shoot Cd uptake ability of the two Cd accumulator oilseed rapes was significantly higher than that of the Indian mustard. Xikou Huazi had higher phytoremediation potential for Cd contaminated soil. Shoot Cd accumulation ability of the two Cd accumulator oilseed rapes was correspond and Cd was easier translocated to the shoot than hyperaccumulator Indian mustard as comparation plant. Shoot Cd distribution pattern showed consistent and significant reduction from older leaves to younger ones of two oilseed rapes and Indian mustard. Cd uptake by oilseed rapes in growth prophase was higher than that of growth anaphase.

  8. A cell cycle timer for asymmetric spindle positioning.

    Directory of Open Access Journals (Sweden)

    Erin K McCarthy Campbell

    2009-04-01

    Full Text Available The displacement of the mitotic spindle to one side of a cell is important for many cells to divide unequally. While recent progress has begun to unveil some of the molecular mechanisms of mitotic spindle displacement, far less is known about how spindle displacement is precisely timed. A conserved mitotic progression mechanism is known to time events in dividing cells, although this has never been linked to spindle displacement. This mechanism involves the anaphase-promoting complex (APC, its activator Cdc20/Fizzy, its degradation target cyclin, and cyclin-dependent kinase (CDK. Here we show that these components comprise a previously unrecognized timer for spindle displacement. In the Caenorhabditis elegans zygote, mitotic spindle displacement begins at a precise time, soon after chromosomes congress to the metaphase plate. We found that reducing the function of the proteasome, the APC, or Cdc20/Fizzy delayed spindle displacement. Conversely, inactivating CDK in prometaphase caused the spindle to displace early. The consequence of experimentally unlinking spindle displacement from this timing mechanism was the premature displacement of incompletely assembled components of the mitotic spindle. We conclude that in this system, asymmetric positioning of the mitotic spindle is normally delayed for a short time until the APC inactivates CDK, and that this delay ensures that the spindle does not begin to move until it is fully assembled. To our knowledge, this is the first demonstration that mitotic progression times spindle displacement in the asymmetric division of an animal cell. We speculate that this link between the cell cycle and asymmetric cell division might be evolutionarily conserved, because the mitotic spindle is displaced at a similar stage of mitosis during asymmetric cell divisions in diverse systems.

  9. The centenary of Janssens's chiasmatype theory.

    Science.gov (United States)

    Koszul, Romain; Meselson, Matthew; Van Doninck, Karine; Vandenhaute, Jean; Zickler, Denise

    2012-06-01

    The segregation and random assortment of characters observed by Mendel have their basis in the behavior of chromosomes in meiosis. But showing this actually to be the case requires a correct understanding of the meiotic behavior of chromosomes. This was achieved only gradually, over several decades, with much dispute and confusion along the way. One crucial step in the understanding of meiosis was provided in 1909 by Frans Alfons Janssens who published in La Cellule an article entitled "La théorie de la Chiasmatypie. Nouvelle interprétation des cinèses de maturation," which contains the first description of the chiasma structure. He observed that, of the four chromatids present at the connection sites (chiasmata sites) at diplotene or anaphase of the first meiotic division, two crossed each other and two did not. He therefore postulated that the maternal and paternal chromatids that crossed penetrated the other until they broke and rejoined in maternal and paternal segments new ways; the other two chromatids remained free and thus intact. This allowed him also to propose that the chromatids distributed in the four nuclei issued from the second meiotic division had various combinations of maternal and paternal segments of each chromosome. And conversely, permitted the appreciation that the laws of Mendelian segregation required breakage and joining (crossing over) between homologous non-sister chromatids. Although Janssens's article found a broad appreciative audience and had a large influence on the chromosomal theory at that time, his theory was resisted by both geneticists and cytologists for several decades. This Perspectives aims to highlight the novelty of Janssens's chiasmatype theory by examining the historical background and our actual understanding of meiotic recombination. PMID:22701050

  10. P190B RhoGAP Regulates Chromosome Segregation in Cancer Cells

    Directory of Open Access Journals (Sweden)

    Tracy Vargo-Gogola

    2012-04-01

    Full Text Available Rho GTPases are overexpressed and hyperactivated in many cancers, including breast cancer. Rho proteins, as well as their regulators and effectors, have been implicated in mitosis, and their altered expression promotes mitotic defects and aneuploidy. Previously, we demonstrated that p190B Rho GTPase activating protein (RhoGAP deficiency inhibits ErbB2-induced mammary tumor formation in mice. Here we describe a novel role for p190B as a regulator of mitosis. We found that p190B localized to centrosomes during interphase and mitosis, and that it is differentially phosphorylated during mitosis. Knockdown of p190B expression in MCF-7 and Hela cells increased the incidence of aberrant microtubule-kinetochore attachments at metaphase, lagging chromosomes at anaphase, and micronucleation, all of which are indicative of aneuploidy. Cell cycle analysis of p190B deficient MCF-7 cells revealed a significant increase in apoptotic cells with a concomitant decrease in cells in G1 and S phase, suggesting that p190B deficient cells die at the G1 to S transition. Chemical inhibition of the Rac GTPase during mitosis reduced the incidence of lagging chromosomes in p190B knockdown cells to levels detected in control cells, suggesting that aberrant Rac activity in the absence of p190B promotes chromosome segregation defects. Taken together, these data suggest that p190B regulates chromosome segregation and apoptosis in cancer cells. We propose that disruption of mitosis may be one mechanism by which p190B deficiency inhibits tumorigenesis.

  11. Phosphoproteomic Profiling Reveals Epstein-Barr Virus Protein Kinase Integration of DNA Damage Response and Mitotic Signaling.

    Science.gov (United States)

    Li, Renfeng; Liao, Gangling; Nirujogi, Raja Sekhar; Pinto, Sneha M; Shaw, Patrick G; Huang, Tai-Chung; Wan, Jun; Qian, Jiang; Gowda, Harsha; Wu, Xinyan; Lv, Dong-Wen; Zhang, Kun; Manda, Srikanth S; Pandey, Akhilesh; Hayward, S Diane

    2015-12-01

    Epstein-Barr virus (EBV) is etiologically linked to infectious mononucleosis and several human cancers. EBV encodes a conserved protein kinase BGLF4 that plays a key role in the viral life cycle. To provide new insight into the host proteins regulated by BGLF4, we utilized stable isotope labeling by amino acids in cell culture (SILAC)-based quantitative proteomics to compare site-specific phosphorylation in BGLF4-expressing Akata B cells. Our analysis revealed BGLF4-mediated hyperphosphorylation of 3,046 unique sites corresponding to 1,328 proteins. Frequency analysis of these phosphosites revealed a proline-rich motif signature downstream of BGLF4, indicating a broader substrate recognition for BGLF4 than its cellular ortholog cyclin-dependent kinase 1 (CDK1). Further, motif analysis of the hyperphosphorylated sites revealed enrichment in ATM, ATR and Aurora kinase substrates while functional analyses revealed significant enrichment of pathways related to the DNA damage response (DDR), mitosis and cell cycle. Phosphorylation of proteins associated with the mitotic spindle assembly checkpoint (SAC) indicated checkpoint activation, an event that inactivates the anaphase promoting complex/cyclosome, APC/C. Furthermore, we demonstrated that BGLF4 binds to and directly phosphorylates the key cellular proteins PP1, MPS1 and CDC20 that lie upstream of SAC activation and APC/C inhibition. Consistent with APC/C inactivation, we found that BGLF4 stabilizes the expression of many known APC/C substrates. We also noted hyperphosphorylation of 22 proteins associated the nuclear pore complex, which may contribute to nuclear pore disassembly and SAC activation. A drug that inhibits mitotic checkpoint activation also suppressed the accumulation of extracellular EBV virus. Taken together, our data reveal that, in addition to the DDR, manipulation of mitotic kinase signaling and SAC activation are mechanisms associated with lytic EBV replication. All MS data have been deposited in

  12. Cytological Analyses on Development of Male and Female Gametophytes in an Interspecific Hybrid F1 from Cucumis hystrix Chakr. × Cucumis sativus L.

    Institute of Scientific and Technical Information of China (English)

    LUO Xiang-dong; DAI Liang-fang; QIAN Chun-tao; CHEN Jin-feng

    2006-01-01

    An interspecific hybrid F1 of Cucumis hystrix Chakr. × Cucumis sativus L. (NC4406) was used to establish the developmental sequence and to characterize the male and female gametophytes at cytological level for further understanding of the phylogenic relationship and the mechanism of fertility or sterility in the interspecific hybrid F1. The development of male and female gametophytes was studied through meiotic analysis and paraffin section observation technique, respectively.Meanwhile, the fertility level was assessed through hybrid F1 backcrossing to cultivated cucumber 4406. Variable chromosome confgurations were observed in the pollen mother cells (PMCs) of hybrid F1 at metaphase Ⅰ, e.g., univalents,bivalents, trivalents, quadravalents, etc. At anaphase Ⅰ and Ⅱ, chromosome lagging and bridges were frequently observed as well, which led to the formation of polyads and only a partial number of microspores could develop into fertile pollen grains (about 23.3%). Observations of the paraffin sections showed numerous degenerated and abnormal embryo sacs during the development of female gametophytes, and only 40% of the female gametophytes could develop into normal eight-nuclear megaspore. On an average, 22.8 and 6.3 seeds per fruit could be obtained from the reciprocal backcross. The interspecific hybrid F1 of C. hystrix × NC4406 was partially fertile; however, the meiotic behaviors of hybrid F1 showed a high level of intergenomic recombination between C. hystrix and C. sativus chromosomes, which indicated that it plays an important role for introgression of useful traits from C. hystrix into C. sativus.

  13. Genotoxicity of industrial wastewaters obtained from two different pollution sources in northern India: a comparison of three bioassays.

    Science.gov (United States)

    Fatima, Riffat A; Ahmad, Masood

    2006-10-10

    The genotoxicity of industrial wastewater samples from Aligarh and Ghaziabad cities was compared using the Ames plate incorporation test, the Ames fluctuation test and the Allium cepa test. While TA102 and TA104 strains exhibited the highest sensitivity against the Aligarh sample (AWW) in terms of the slope (m) of the dose-response curve in the plate incorporation assay, TA98 and TA97a were the most sensitive strains based on the induction factor, Mi(p). TA98 once again, was the most sensitive strain against the test sample from Ghaziabad (GWW) in terms of 'Mi(p)' while TA102 was the most sensitive strain on the basis of the slope (m). TA100 displayed the highest susceptibility towards the samples from Aligarh in the fluctuation test. However, TA102 and TA98 responded maximally to GWW in this bioassay. The mutagenicity of the test samples seemed to be partly mediated by reactive oxygen species (ROS) as evidenced by the use of free radical scavengers. Mannitol brought about the maximum decline in the number of revertants of TA102 by the Aligarh sample, whereas such a reduction in case of Ghaziabad sample was exhibited with superoxide dismutase. Both the test water samples induced various anaphase aberrations in the root cells of Allium cepa. Fragmentation of the chromosome was the predominant effect of the Aligarh water sample while the Ghaziabad sample induced chromosome stickiness. The crucial roles of heavy metals and pesticides in the genotoxicity of AWW and GWW, respectively, have been suggested. In view of the problem associated with the interpretations of data, we recommend that all the test bioassays should be carried out in the presence of ROS scavengers for the fool proof evaluation of the genotoxicity of water samples. PMID:16887378

  14. The role of p53 in the response to mitotic spindle damage

    International Nuclear Information System (INIS)

    The p53 tumour suppressor protein has defined roles in G1/S and G2/M cell cycle checkpoint in response to a range of cellular stresses including DNA damage, dominant oncogene expression, hypoxia, metabolic changes and viral infection. In addition to these responses, p53 can also be activated when damage occurs to the mitotic spindle. Initially, spindle damage activates a p53-independent checkpoint which functions at the metaphase-anaphase transition and prevents cells from progressing through mitosis until the completion of spindle formation. Cells eventually escape from this block (a process termed 'mitotic slippage'), and an aberrant mitosis ensues in which sister chromatids fail to segregate properly. After a delay period, p53 responds to this mitotic failure by instituting a G1-like growth arrest, with an intact nucleus containing 4N DNA, but without the cells undergoing division. Cells lacking wild-type p53 are still able to arrest transiently at mitosis, and also fail to undergo division, underscoring that the delay in mitosis is p53-independent. However, these cells are not prevented from re-entering the cell cycle and can reduplicate their DNA unchecked, leading to polyploidy. Additionally, p53-null cells which experience spindle failure often show the appearance of micronuclei arising from poorly segregated chromosomes which have de-condensed and been enclosed in a nuclear envelope. The ability of p53 to prevent their formation suggests an additional G2 involvement which prevents nuclear breakdown prior to mitosis. The molecular mechanism by which p53 is able to sense mitotic failure is still unknown, but may be linked to the ability of p53 to regulate duplication of the centrosome, the organelle which nucleates spindle formation. (authors)

  15. Photoreactivation of developmental abnormality in sea urchin embryos induced by UV-irradiated sperm

    International Nuclear Information System (INIS)

    The effects of UV-irradiation of sperm on the embryonic development of sea urchins (H. pulcherrimus, Anthocidaris crassispina, Pseudocentrotus depressus, and C. japonicus) were studied. Eggs inseminated with UV-irradiated sperm developed almost normally into blastulae without arrest of cleavage or hatching, even though they showed some division delay. Morphogenesis was disturbed in and after the gastrula stage, and the formation of normal pluteus larvae was inhibited depending on the UV dose (5 - 30 J/m2) given to the sperm. Morphological abnormalities observed were as follows: inhibition of gastrulation; abnormal delamination and random arrangement of primary mesenchymal cells onto the ectodermal wall; abnormal localization or an excess number of spicules; malformed skeletons. These developmental abnormalities were photoreactivated with high efficiency. Inhibition of pluteus formation to less than 5% by the UV-irradiation with 20 J/m2 completely recovered under fluorescent light illumination with 10 klux. By treating the eggs with brief illumination at various times after insemination, a stage-dependent change of the photoreactivation (PR) efficiency was found. PR treatment after the insemination up to the onset of the first DNA synthesizing phase was highly effective for the recovery, while the PR efficiency began to decrease during the S phase, becoming zero on and after the end of the phase. In eggs fertilized with UV-irradiated sperm, mitoses were abnormal and shromosomal bridges were formed at the anaphase of the first mitosis. Their frequency increased depending on the UV dose. The mitotic abnormality was also photoreactivated with visible light treatment after fertilization. The change in PR efficiency of the illumination was very similar to that of morphological abnormality. (Author)

  16. Arsenite-induced mitotic death involves stress response and is independent of tubulin polymerization

    International Nuclear Information System (INIS)

    Arsenite, a known mitotic disruptor, causes cell cycle arrest and cell death at anaphase. The mechanism causing mitotic arrest is highly disputed. We compared arsenite to the spindle poisons nocodazole and paclitaxel. Immunofluorescence analysis of α-tubulin in interphase cells demonstrated that, while nocodazole and paclitaxel disrupt microtubule polymerization through destabilization and hyperpolymerization, respectively, microtubules in arsenite-treated cells remain comparable to untreated cells even at supra-therapeutic concentrations. Immunofluorescence analysis of α-tubulin in mitotic cells showed spindle formation in arsenite- and paclitaxel-treated cells but not in nocodazole-treated cells. Spindle formation in arsenite-treated cells appeared irregular and multi-polar. γ-tubulin staining showed that cells treated with nocodazole and therapeutic concentrations of paclitaxel contained two centrosomes. In contrast, most arsenite-treated mitotic cells contained more than two centrosomes, similar to centrosome abnormalities induced by heat shock. Of the three drugs tested, only arsenite treatment increased expression of the inducible isoform of heat shock protein 70 (HSP70i). HSP70 and HSP90 proteins are intimately involved in centrosome regulation and mitotic spindle formation. HSP90 inhibitor 17-DMAG sensitized cells to arsenite treatment and increased arsenite-induced centrosome abnormalities. Combined treatment of 17-DMAG and arsenite resulted in a supra-additive effect on viability, mitotic arrest, and centrosome abnormalities. Thus, arsenite-induced abnormal centrosome amplification and subsequent mitotic arrest is independent of effects on tubulin polymerization and may be due to specific stresses that are protected against by HSP90 and HSP70

  17. Cytogenetic comparison of restorers TP-4 and Dminghui63 with maintainer D46B of autotetraploid rice

    Institute of Scientific and Technical Information of China (English)

    Wenbo LONG; Li LUAN; Xing WANG; Yuhua LIU; Shengbin TU; Fanlun KONG; Tao HE

    2008-01-01

    Cytogenetical comparison was made between high seed setting restorers TP-4 and Dminghui63 with eminent maintainer line D46B of autotetraploid rice. The meiosis observation demonstrated that the genomes of our autotetraploid materials were all 2n = 48, which was the same as those in mitosis observation. Low percentages of univalent and trivalent in diakinesis-metaphase I (MI) of restorers TP-4 and Dminghui63 as well as maintainer line D46B of autotetraploid rice were observed. And the percent-ages of chromosome pairing were all over 99%, showing eminent cytological character. The frequency of TP-4 and Dminghui63 in diakinesis-metaphase I was 2.00/PMC (pollen mother cell) and 2.26/PMC, respectively. However, the frequency of D46B was 6.00/PMC, significantly higher than those of TP-4 and Dminghui63. It indicated that the maintainer D46B had better chromosome pairing capability in diakinesis-metaphase. While, the frequency of lagging chromosomes of the maintainer D46B in anaphase I (AI) was 10.62%, significantly lower than that of TP-4 (19.44%) or Dminghui63 (23.14%), and close to the level of diploid con-trol (7.30%). In telophase I (TI), maintainer D46B exhibited lower frequency of microkernel, and in telophase Ⅱ (TII) the frequency of normal quartered microspore of maintainer D46B was not only higher than that of TP-4 or Dminghui63 but also than that of diploid control. The percentage of the cell observed chromosome lagging in AI and the percentage of abnormal cell in TI showed a greatly significant positive cor-relation. That may demonstrate that chromosome separation in AI and microkernel formation in TI are controlled by the same dominant single gene or the major gene of a QTL.

  18. Syncytes during male meiosis resulting in 2n pollen grain formation in Lindelofia longiflora var.falconeri

    Institute of Scientific and Technical Information of China (English)

    Vijay Kumar SINGHAL; Pawan Kumar RANA; Puneet KUMAR

    2011-01-01

    Lindelofia longiflora (Royle ex Benth.) Baill.var.falconeri (Cl.) Brand (Family:Boraginaceae) is investigated cytologically (n =12) for the first time from the cold deserts of Pangi Valley,Chamba District (Himachal Pradesh) in India.We report the formation of syncytes and 2n pollen grains in the species.During meiosis,the majority of the pollen mother cells (PMCs) exhibited 12 bivalents,equal segregation of chromosomes during anaphases,regular tetrads,and normal-sized pollen grain formation.Occasionally,two proximate PMCs fused during the early stages ofprophase-I and resulted in the formation of syncytes.The frequency of syncytes in the accession is rather low,at 25 out of 1866 (1.33%).Such syncyte PMCs are detectable during meiosis due to their larger size compared to typical PMCs.The syncytes or polyploid cells showed normal 24 bivalents and depicted perfectly regular meiotic course.But the products of such PMCs yield 2n or larger sized pollen grains that are almost double the size of typical normal or n pollen grains.The origin of syncytes as a consequence of the fusion of meiocytes during the early stages of meiosis-I could be attributed to low temperature stress conditions prevailing in the Pangi Valley,where temperature during May and June dip to below freezing,the time the plants enters the reproductive/flowering bud stage.It is possible that such apparently fertile 2n pollen grains originating from syncytes might play a role in the origin of intraspecific polyploids in the species.

  19. Phosphorylation of HPV-16 E2 at serine 243 enables binding to Brd4 and mitotic chromosomes.

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    Szu-Wei Chang

    Full Text Available The papillomavirus E2 protein is involved in the maintenance of persistent infection and known to bind either to cellular factors or directly to mitotic chromosomes in order to partition the viral genome into the daughter cells. However, how the HPV-16 E2 protein acts to facilitate partitioning of the viral genome remains unclear. In this study, we found that serine 243 of HPV-16 E2, located in the hinge region, is crucial for chromosome binding during mitosis. Bromodomain protein 4 (Brd4 has been identified as a cellular binding target through which the E2 protein of bovine papillomavirus type 1 (BPV-1 tethers the viral genome to mitotic chromosomes. Mutation analysis showed that, when the residue serine 243 was substituted by glutamic acid or aspartic acid, whose negative charges mimic the effect of constitutive phosphorylation, the protein still can interact with Brd4 and colocalize with Brd4 in condensed metaphase and anaphase chromosomes. However, substitution by the polar uncharged residues asparagine or glutamine abrogated Brd4 and mitotic chromosome binding. Moreover, following treatment with the inhibitor JQ1 to release Brd4 from the chromosomes, Brd4 and E2 formed punctate foci separate from the chromosomes, further supporting the hypothesis that the association of the HPV-16 E2 protein with the chromosomes is Brd4-dependent. In addition, the S243A E2 protein has a shorter half-life than the wild type, indicating that phosphorylation of the HPV-16 E2 protein at serine 243 also increases its half-life. Thus, phosphorylation of serine 243 in the hinge region of HPV-16 E2 is essential for interaction with Brd4 and required for host chromosome binding.

  20. Cyclin A degradation by primate cytomegalovirus protein pUL21a counters its innate restriction of virus replication.

    Directory of Open Access Journals (Sweden)

    Nicolas Caffarelli

    Full Text Available Cyclin A is critical for cellular DNA synthesis and S phase progression of the cell cycle. Human cytomegalovirus (HCMV can reduce cyclin A levels and block cellular DNA synthesis, and cyclin A overexpression can repress HCMV replication. This interaction has only been previously observed in HCMV as murine CMV does not downregulate cyclin A, and the responsible viral factor has not been identified. We previously reported that the HCMV protein pUL21a disrupted the anaphase-promoting complex (APC, but a point mutant abrogating this activity did not phenocopy a UL21a-deficient virus, suggesting that pUL21a has an additional function. Here we identified a conserved arginine-x-leucine (RxL cyclin-binding domain within pUL21a, which allowed pUL21a to interact with cyclin A and target it for proteasome degradation. Homologous pUL21a proteins from both chimpanzee and rhesus CMVs also contained the RxL domain and similarly degraded cyclin A, indicating that this function is conserved in primate CMVs. The RxL point mutation disabled the virus' ability to block cellular DNA synthesis and resulted in a growth defect similar to pUL21a-deficient virus. Importantly, knockdown of cyclin A rescued growth of UL21a-deficient virus. Together, these data show that during evolution, the pUL21a family proteins of primate CMVs have acquired a cyclin-binding domain that targets cyclin A for degradation, thus neutralizing its restriction on virus replication. Finally, the combined proteasome-dependent degradation of pUL21a and its cellular targets suggests that pUL21a may act as a novel suicide protein, targeting its protein cargos for destruction.

  1. Radmis, a novel mitotic spindle protein that functions in cell division of neural progenitors.

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    Takahito Yumoto

    Full Text Available Developmental dynamics of neural stem/progenitor cells (NSPCs are crucial for embryonic and adult neurogenesis, but its regulatory factors are not fully understood. By differential subtractive screening with NSPCs versus their differentiated progenies, we identified the radmis (radial fiber and mitotic spindle/ckap2l gene, a novel microtubule-associated protein (MAP enriched in NSPCs. Radmis is a putative substrate for the E3-ubiquitin ligase, anaphase promoting complex/cyclosome (APC/C, and is degraded via the KEN box. Radmis was highly expressed in regions of active neurogenesis throughout life, and its distribution was dynamically regulated during NSPC division. In embryonic and perinatal brains, radmis localized to bipolar mitotic spindles and radial fibers (basal processes of dividing NSPCs. As central nervous system development proceeded, radmis expression was lost in most brain regions, except for several neurogenic regions. In adult brain, radmis expression persisted in the mitotic spindles of both slowly-dividing stem cells and rapid amplifying progenitors. Overexpression of radmis in vitro induced hyper-stabilization of microtubules, severe defects in mitotic spindle formation, and mitotic arrest. In vivo gain-of-function using in utero electroporation revealed that radmis directed a reduction in NSPC proliferation and a concomitant increase in cell cycle exit, causing a reduction in the Tbr2-positive basal progenitor population and shrinkage of the embryonic subventricular zone. Besides, radmis loss-of-function by shRNAs induced the multipolar mitotic spindle structure, accompanied with the catastrophe of chromosome segregation including the long chromosome bridge between two separating daughter nuclei. These findings uncover the indispensable role of radmis in mitotic spindle formation and cell-cycle progression of NSPCs.

  2. Genotoxic assessment and optimization of pressmud with the help of exotic earthworm Eisenia fetida.

    Science.gov (United States)

    Bhat, Sartaj Ahmad; Singh, Jaswinder; Vig, Adarsh Pal

    2014-01-01

    Genotoxicity of pressmud (PM) to Allium cepa was investigated to assess its toxic potential and to elucidate the effect of vermicomposting to reduce its toxicity. The PM produced as a waste by product of the sugar cane industry was mixed with cow dung (CD) at different ratios of 0:100 (V₀), 25:75 (V₂₅), 50:50 (V₅₀), 75:25 (V₇₅) and 100:0 (V100) (PM:CD) on a dry weight basis for vermicomposting with Eisenia fetida. Different concentrations of 100% PM sludge extract (10%, 20%, 40%, 60%, 80% and 100%) and negative control (distilled water) and positive control (maleic hydrazide) were analyzed with A. cepa assay to evaluate frequency of chromosomal aberrations before and after vermicomposting. Percent aberration was greatest (30.8%) after exposure to 100% PM extract after 6 h but was reduced to 20.3% after vermicomposting. Exposure to the extract induced c-mitosis, delayed anaphase, laggards, stickiness and vagrant aberrations. Microscopic examination of root meristem exposed to PM sludge extract showed significant inhibition of mitotic index. Also, the mitotic index decreased with increase in concentration of PM sludge extract. After vermicomposting the mitotic index was increased. However, increasing percentages of PM significantly affected the growth and fecundity of the worms and maximum population size was reached in the 25:75 (PM:CD) feed mixture. Nitrogen, phosphorus, sodium, electrical conductivity (EC) and pH increased from initial feed mixture to the final products (i.e., vermicompost), while organic carbon, C/N ratio and potassium declined in all products of vermicomposting. Scanning electron microscopy (SEM) was recorded to identify the changes in texture with numerous surface irregularities and high porosity that proves to be good vermicompost manure. It could be concluded that vermicomposting could be an important tool to reduce the toxicity of PM as evidenced by the results of genotoxicity. PMID:24671397

  3. Chromothripsis and epigenomics complete causality criteria for cannabis- and addiction-connected carcinogenicity, congenital toxicity and heritable genotoxicity.

    Science.gov (United States)

    Reece, Albert Stuart; Hulse, Gary Kenneth

    2016-07-01

    The recent demonstration that massive scale chromosomal shattering or pulverization can occur abruptly due to errors induced by interference with the microtubule machinery of the mitotic spindle followed by haphazard chromosomal annealing, together with sophisticated insights from epigenetics, provide profound mechanistic insights into some of the most perplexing classical observations of addiction medicine, including cancerogenesis, the younger and aggressive onset of addiction-related carcinogenesis, the heritability of addictive neurocircuitry and cancers, and foetal malformations. Tetrahydrocannabinol (THC) and other addictive agents have been shown to inhibit tubulin polymerization which perturbs the formation and function of the microtubules of the mitotic spindle. This disruption of the mitotic machinery perturbs proper chromosomal segregation during anaphase and causes micronucleus formation which is the primary locus and cause of the chromosomal pulverization of chromothripsis and downstream genotoxic events including oncogene induction and tumour suppressor silencing. Moreover the complementation of multiple positive cannabis-cancer epidemiological studies, and replicated dose-response relationships with established mechanisms fulfils causal criteria. This information is also consistent with data showing acceleration of the aging process by drugs of addiction including alcohol, tobacco, cannabis, stimulants and opioids. THC shows a non-linear sigmoidal dose-response relationship in multiple pertinent in vitro and preclinical genotoxicity assays, and in this respect is similar to the serious major human mutagen thalidomide. Rising community exposure, tissue storage of cannabinoids, and increasingly potent phytocannabinoid sources, suggests that the threshold mutagenic dose for cancerogenesis will increasingly be crossed beyond the developing world, and raise transgenerational transmission of teratogenicity as an increasing concern. PMID:27208973

  4. Meiose e viabilidade polínica em acessos de Capsicum annuum e Capsicum baccatum Meiosis and pollen viability in accessions of Capsicum annuum and Capsicum baccatum

    Directory of Open Access Journals (Sweden)

    Kellen Coutinho Martins

    2010-08-01

    Full Text Available O objetivo deste trabalho foi estudar o comportamento meiótico e a viabilidade polínica em quatro acessos das espécies Capsicum annuum e Capsicum baccatum. Em todos os acessos, foram observados 12 bivalentes, confirmando o número e nível de ploidia relatados na literatura para essas espécies. Os resultados mostraram uma divisão celular normal, porém algumas anormalidades foram detectadas, tais como migração precoce dos cromossomos em metáfases I e II, cromossomos retardatários em anáfase I e divisão assincrônica. Os acessos estudados apresentaram um índice meiótico variando de 75,6 a 93,6%, e a viabilidade polínica em todos os acessos foi superior a 90%, demonstrando que as irregularidades meióticas observadas não comprometeram a viabilidade destes.The objective of this research was to study the meiotic behavior and pollen viability in four accessions of species Capsicum annuum and Capsicum baccatum. In all accessions, twelve bivalents were observed, confirming the number and ploidy level reported in the literature for these species. The results showed a normal cell division although some abnormalities had been detected, as early chromosome migration at metaphases I and II, later chromosomes at anaphase I and asynchronous division. The studied accessions presented a meiotic index (MI that varied from 75.6 to 93.6% and the pollen viability in all accessions was higher than 90%, demonstrating that the meiotic irregularities observed didn't affect their viability.

  5. Ground and surface water for drinking: a laboratory study on genotoxicity using plant tests

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    Donatella Feretti

    2012-02-01

    Full Text Available Surface waters are increasingly utilized for drinking water because groundwater sources are often polluted. Several monitoring studies have detected the presence of mutagenicity in drinking water, especially from surface sources due to the reaction of natural organic matter with disinfectant. The study aimed to investigate the genotoxic potential of the products of reaction between humic substances, which are naturally present in surface water, and three disinfectants: chlorine dioxide, sodium hypochlorite and peracetic acid. Commercial humic acids dissolved in distilled water at different total organic carbon (TOC concentrations were studied in order to simulate natural conditions of both ground water (TOC=2.5 mg/L and surface water (TOC=7.5 mg/L. These solutions were treated with the biocides at a 1:1 molar ratio of C:disinfectant and tested for genotoxicity using the anaphase chromosomal aberration and micronucleus tests in Allium cepa, and the Vicia faba and Tradescantia micronucleus tests. The tests were carried out after different times and with different modes of exposure, and at 1:1 and 1:10 dilutions of disinfected and undisinfected humic acid solutions. A genotoxic effect was found for sodium hypochlorite in all plant tests, at both TOCs considered, while chlorine dioxide gave positive results only with the A.cepa tests. Some positive effects were also detected for PAA (A.cepa and Tradescantia. No relevant differences were found in samples with different TOC values. The significant increase in all genotoxicity end-points induced by all tested disinfectants indicates that a genotoxic potential is exerted even in the presence of organic substances at similar concentrations to those frequently present in drinking water.

  6. Meiotic behaviour in three interspecific three-way hybrids between Brachiaria ruziziensis and B. brizantha (Poaceae: Paniceae)

    Indian Academy of Sciences (India)

    Eleniza De Victor Adamowski; Maria Suely Pagliarini; Cacilda Borges Do Valle

    2008-04-01

    The meiotic behaviour of three three-way interspecific promising hybrids (H17, H27, and H34) was evaluated. These hybrids resulted from the crosses between B. ruziziensis × B. brizantha and crossed to another B. brizantha. Two half-sib hybrids (H27 and H34) presented an aneuploid chromosome number ($2n = 4x = 33$), whereas hybrid H17 was a tetraploid ($2n = 4x = 36$), as expected. Chromosome paired predominantly as multivalents suggesting that genetic recombination and introgression of specific target genes from B. brizantha into B. ruziziensis can be expected. Arrangement of parental genomes in distinct metaphase plates was observed in H27 and H34, which have different male genitors. Hybrids H17 and H34 have the same male genitor, but did not display this abnormality. In H17, abnormalities were more frequent from anaphase II, when many laggard chromosomes appeared, suggesting that each genome presented a different genetic control for meiotic phase timing. Despite the phylogenetic proximity among these two species, these three hybrids presented a high frequency of meiotic abnormalities, mainly those related to irregular chromosome segregation typical of polyploids, H34, 69.1%; H27, 56.1% and H17, 44.9%. From the accumulated results obtained through cytological studies in Brachiaria hybrids, it is evident that cytogenetical analysis is of prime importance in determining which genotypes can continue in the process of cultivar development and which can be successfully used in the breeding. Hybrids with high frequency of meiotic abnormalities can seriously compromise seed production, a key trait in assuring adoption of a new apomictic cultivar of Brachiaria for pasture formation.

  7. Drosophila MOF controls Checkpoint protein2 and regulates genomic stability during early embryogenesis

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    Pushpavalli Sreerangam NCVL

    2013-01-01

    Full Text Available Abstract Background In Drosophila embryos, checkpoints maintain genome stability by delaying cell cycle progression that allows time for damage repair or to complete DNA synthesis. Drosophila MOF, a member of MYST histone acetyl transferase is an essential component of male X hyperactivation process. Until recently its involvement in G2/M cell cycle arrest and defects in ionizing radiation induced DNA damage pathways was not well established. Results Drosophila MOF is highly expressed during early embryogenesis. In the present study we show that haplo-insufficiency of maternal MOF leads to spontaneous mitotic defects like mitotic asynchrony, mitotic catastrophe and chromatid bridges in the syncytial embryos. Such abnormal nuclei are eliminated and digested in the yolk tissues by nuclear fall out mechanism. MOF negatively regulates Drosophila checkpoint kinase 2 tumor suppressor homologue. In response to DNA damage the checkpoint gene Chk2 (Drosophila mnk is activated in the mof mutants, there by causing centrosomal inactivation suggesting its role in response to genotoxic stress. A drastic decrease in the fall out nuclei in the syncytial embryos derived from mof1/+; mnkp6/+ females further confirms the role of DNA damage response gene Chk2 to ensure the removal of abnormal nuclei from the embryonic precursor pool and maintain genome stability. The fact that mof mutants undergo DNA damage has been further elucidated by the increased number of single and double stranded DNA breaks. Conclusion mof mutants exhibited genomic instability as evidenced by the occurance of frequent mitotic bridges in anaphase, asynchronous nuclear divisions, disruption of cytoskeleton, inactivation of centrosomes finally leading to DNA damage. Our findings are consistent to what has been reported earlier in mammals that; reduced levels of MOF resulted in increased genomic instability while total loss resulted in lethality. The study can be further extended using

  8. Automated high-throughput quantification of mitotic spindle positioning from DIC movies of Caenorhabditis embryos.

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    David Cluet

    Full Text Available The mitotic spindle is a microtubule-based structure that elongates to accurately segregate chromosomes during anaphase. Its position within the cell also dictates the future cell cleavage plan, thereby determining daughter cell orientation within a tissue or cell fate adoption for polarized cells. Therefore, the mitotic spindle ensures at the same time proper cell division and developmental precision. Consequently, spindle dynamics is the matter of intensive research. Among the different cellular models that have been explored, the one-cell stage C. elegans embryo has been an essential and powerful system to dissect the molecular and biophysical basis of spindle elongation and positioning. Indeed, in this large and transparent cell, spindle poles (or centrosomes can be easily detected from simple DIC microscopy by human eyes. To perform quantitative and high-throughput analysis of spindle motion, we developed a computer program ACT for Automated-Centrosome-Tracking from DIC movies of C. elegans embryos. We therefore offer an alternative to the image acquisition and processing of transgenic lines expressing fluorescent spindle markers. Consequently, experiments on large sets of cells can be performed with a simple setup using inexpensive microscopes. Moreover, analysis of any mutant or wild-type backgrounds is accessible because laborious rounds of crosses with transgenic lines become unnecessary. Last, our program allows spindle detection in other nematode species, offering the same quality of DIC images but for which techniques of transgenesis are not accessible. Thus, our program also opens the way towards a quantitative evolutionary approach of spindle dynamics. Overall, our computer program is a unique macro for the image- and movie-processing platform ImageJ. It is user-friendly and freely available under an open-source licence. ACT allows batch-wise analysis of large sets of mitosis events. Within 2 minutes, a single movie is processed

  9. Cohesin without cohesion: a novel role for Pds5 in Saccharomyces cerevisiae.

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    Kevin Tong

    Full Text Available High fidelity chromosome segregation during mitosis requires that cells identify the products of DNA replication during S-phase and then maintain that identity until anaphase onset. Sister chromatid identity is achieved through cohesin complexes (Smc1, Smc3, and Mcd1 and Irr1/Scc3, but the structure through which cohesins perform this task remains enigmatic. In the absence of unambiguous data, a popular model is that a subset of cohesin subunits form a huge ring-like structure that embraces both sister chromatids. This 'one-ring two-sister chromatid embrace' model makes clear predictions--including that premature cohesion loss in mitotic cells must occur through a substantial reduction in cohesin-DNA associations. We used chromatin immunoprecipitation to directly test for cohesin dissociation from well-established cohesin binding sites in mitotic cells inactivated for Pds5--a key cohesin regulatory protein. The results reveal little if any chromatin dissociation from cohesins, despite a regimen that produces both massive loss of sister chromatid tethering and cell inviability. We further excluded models that cohesion loss in mitotic cells inactivated for Pds5 arises through either cohesin subunit degradation, premature Hos1-dependent Smc3 de-acetylation or Rad61/WAPL-dependent regulation of cohesin dynamics. In combination, our findings support a model that cohesin complexes associate with each sister and that sister chromatid cohesion likely results from cohesin-cohesin interactions. We further assessed the role that Pds5 plays in cohesion establishment during S-phase. The results show that Pds5 inactivation can result in establishment defects despite normal cohesion loading and Smc3 acetylation, revealing a novel establishment role for Pds5 that is independent of these processes. The combination of findings provides important new insights that significantly impact current models of both cohesion establishment reactions and maintenance.

  10. An anillin-Ect2 complex stabilizes central spindle microtubules at the cortex during cytokinesis.

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    Paul Frenette

    Full Text Available Cytokinesis occurs due to the RhoA-dependent ingression of an actomyosin ring. During anaphase, the Rho GEF (guanine nucleotide exchange factor Ect2 is recruited to the central spindle via its interaction with MgcRacGAP/Cyk-4, and activates RhoA in the central plane of the cell. Ect2 also localizes to the cortex, where it has access to RhoA. The N-terminus of Ect2 binds to Cyk-4, and the C-terminus contains conserved DH (Dbl homologous and PH (Pleckstrin Homology domains with GEF activity. The PH domain is required for Ect2's cortical localization, but its molecular function is not known. In cultured human cells, we found that the PH domain interacts with anillin, a contractile ring protein that scaffolds actin and myosin and interacts with RhoA. The anillin-Ect2 interaction may require Ect2's association with lipids, since a novel mutation in the PH domain, which disrupts phospholipid association, weakens their interaction. An anillin-RacGAP50C (homologue of Cyk-4 complex was previously described in Drosophila, which may crosslink the central spindle to the cortex to stabilize the position of the contractile ring. Our data supports an analogous function for the anillin-Ect2 complex in human cells and one hypothesis is that this complex has functionally replaced the Drosophila anillin-RacGAP50C complex. Complexes between central spindle proteins and cortical proteins could regulate the position of the contractile ring by stabilizing microtubule-cortical interactions at the division plane to ensure the generation of active RhoA in a discrete zone.

  11. Dynamics of response to asynapsis and meiotic silencing in spermatocytes from Robertsonian translocation carriers.

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    Anna K Naumova

    Full Text Available Failure of homologous synapsis during meiotic prophase triggers transcriptional repression. Asynapsis of the X and Y chromosomes and their consequent silencing is essential for spermatogenesis. However, asynapsis of portions of autosomes in heterozygous translocation carriers may be detrimental for meiotic progression. In fact, a wide range of phenotypic outcomes from meiotic arrest to normal spermatogenesis have been described and the causes of such a variation remain elusive. To better understand the consequences of asynapsis in male carriers of Robertsonian translocations, we focused on the dynamics of recruitment of markers of asynapsis and meiotic silencing at unsynapsed autosomal trivalents in the spermatocytes of Robertsonian translocation carrier mice. Here we report that the enrichment of breast cancer 1 (BRCA1 and histone γH2AX at unsynapsed trivalents declines during the pachytene stage of meiosis and differs from that observed in the sex body. Furthermore, histone variant H3.3S31, which associates with the sex chromosomes in metaphase I/anaphase I spermatocytes, localizes to autosomes in 12% and 31% of nuclei from carriers of one and three translocations, respectively. These data suggest that the proportion of spermatocytes with markers of meiotic silencing of unsynapsed chromatin (MSUC at trivalents depends on both, the stage of meiosis and the number of translocations. This may explain some of the variability in phenotypic outcomes associated with Robertsonian translocations. In addition our data suggest that the dynamics of response to asynapsis in Robertsonian translocations differs from the response to sex chromosomal asynapsis in the male germ line.

  12. Separase Is Required for Homolog and Sister Disjunction during Drosophila melanogaster Male Meiosis, but Not for Biorientation of Sister Centromeres.

    Science.gov (United States)

    Blattner, Ariane C; Chaurasia, Soumya; McKee, Bruce D; Lehner, Christian F

    2016-04-01

    Spatially controlled release of sister chromatid cohesion during progression through the meiotic divisions is of paramount importance for error-free chromosome segregation during meiosis. Cohesion is mediated by the cohesin protein complex and cleavage of one of its subunits by the endoprotease separase removes cohesin first from chromosome arms during exit from meiosis I and later from the pericentromeric region during exit from meiosis II. At the onset of the meiotic divisions, cohesin has also been proposed to be present within the centromeric region for the unification of sister centromeres into a single functional entity, allowing bipolar orientation of paired homologs within the meiosis I spindle. Separase-mediated removal of centromeric cohesin during exit from meiosis I might explain sister centromere individualization which is essential for subsequent biorientation of sister centromeres during meiosis II. To characterize a potential involvement of separase in sister centromere individualization before meiosis II, we have studied meiosis in Drosophila melanogaster males where homologs are not paired in the canonical manner. Meiosis does not include meiotic recombination and synaptonemal complex formation in these males. Instead, an alternative homolog conjunction system keeps homologous chromosomes in pairs. Using independent strategies for spermatocyte-specific depletion of separase complex subunits in combination with time-lapse imaging, we demonstrate that separase is required for the inactivation of this alternative conjunction at anaphase I onset. Mutations that abolish alternative homolog conjunction therefore result in random segregation of univalents during meiosis I also after separase depletion. Interestingly, these univalents become bioriented during meiosis II, suggesting that sister centromere individualization before meiosis II does not require separase. PMID:27120695

  13. Synthetic lethality of cohesins with PARPs and replication fork mediators.

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    Jessica L McLellan

    Full Text Available Synthetic lethality has been proposed as a way to leverage the genetic differences found in tumor cells to affect their selective killing. Cohesins, which tether sister chromatids together until anaphase onset, are mutated in a variety of tumor types. The elucidation of synthetic lethal interactions with cohesin mutants therefore identifies potential therapeutic targets. We used a cross-species approach to identify robust negative genetic interactions with cohesin mutants. Utilizing essential and non-essential mutant synthetic genetic arrays in Saccharomyces cerevisiae, we screened genome-wide for genetic interactions with hypomorphic mutations in cohesin genes. A somatic cell proliferation assay in Caenorhabditis elegans demonstrated that the majority of interactions were conserved. Analysis of the interactions found that cohesin mutants require the function of genes that mediate replication fork progression. Conservation of these interactions between replication fork mediators and cohesin in both yeast and C. elegans prompted us to test whether other replication fork mediators not found in the yeast were required for viability in cohesin mutants. PARP1 has roles in the DNA damage response but also in the restart of stalled replication forks. We found that a hypomorphic allele of the C. elegans SMC1 orthologue, him-1(e879, genetically interacted with mutations in the orthologues of PAR metabolism genes resulting in a reduced brood size and somatic cell defects. We then demonstrated that this interaction is conserved in human cells by showing that PARP inhibitors reduce the viability of cultured human cells depleted for cohesin components. This work demonstrates that large-scale genetic interaction screening in yeast can identify clinically relevant genetic interactions and suggests that PARP inhibitors, which are currently undergoing clinical trials as a treatment of homologous recombination-deficient cancers, may be effective in treating

  14. Comparative Study of Domoic Acid and Okadaic Acid Induced - Chromosomal Abnormalities in the CACO-2 Cell Line

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    Edmond E. Creppy

    2006-03-01

    Full Text Available Okadaic Acid (OA the major diarrheic shellfish poisoning (DSP toxin is known as a tumor promoter and seems likely implicated in the genesis of digestive cancer. Little is known regarding genotoxicity and carcinogenicity of Domoic Acid (DA, the major Amnesic Shellfish Poisoning (ASP toxin. Both OA and DA occur in seafood and are of human health concerns. Micronuclei (MN arise from abnormalities in nuclear division during mitosis due to a failure of the mitotic spindle or by complex chromosomal configurations that pose problems during anaphase. In order to evaluate the ability of okadaic acid (OA and domoic acid (DA to induce DNA damage we performed the micronucleus assay using the Caco-2 cell line. To discriminate between a clastogenic or aneugenic effect of OA and DA, the micronucleus assay was conducted by cytokinesis-block micronucleus assay using cytochalasin B with Giemsa staining and/or acridine orange staining, in parallel to fluorescence in situ hybridization (FISH using a concentrated human pan-centromeric chromosome paint probe. Our results showed that OA and DA significantly increased the frequency of MN in Caco-2 cells. The MN caused by OA are found in mononucleated cells and binucleated cells, whereas those caused by DA are mainly in binucleated cells. The results of FISH analysis showed that OA induced centromere-positive micronuclei and DA increased the percentage of MN without a centromeric signal. In conclusion, both OA and DA bear mutagenic potential as revealed in Caco-2 cells by induction of MN formation. Moreover, OA induced whole chromosome loss suggesting a specific aneugenic potential, whereas DA seems simply clastogenic. At present, one cannot rule out possible DNA damage of intestinal cells if concentrations studied are reached in vivo, since this may happen with concentrations of toxins just below regulatory limits in case of frequent consumption of contaminated shell fishes.

  15. Overexpression of UbcH10 alternates the cell cycle profile and accelerate the tumor proliferation in colon cancer

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    Hatoh Shinji

    2009-03-01

    Full Text Available Abstract Background UbcH10 participates in proper metaphase to anaphase transition, and abrogation of UbcH10 results in the premature separation of sister chromatids. To assess the potential role of UbcH10 in colon cancer progression, we analyzed the clinicopathological relevance of UbcH10 in colon cancer. Methods We firstly screened the expression profile of UbcH10 in various types of cancer tissues as well as cell lines. Thereafter, using the colon cancer cells line, we manipulated the expression of UbcH10 and evaluated the cell cycle profile and cellular proliferations. Furthermore, the clinicopathological significance of UbcH10 was immunohistologically evaluated in patients with colon cancer. Statistical analysis was performed using the student's t-test and Chi-square test. Results Using the colon cancer cells, depletion of UbcH10 resulted in suppression of cellular growth whereas overexpression of UbcH10 promoted the cellular growth and oncogenic cellular growth. Mitotic population was markedly alternated by the manipulation of UbcH10 expression. Immunohistochemical analysis indicated that UbcH10 was significantly higher in colon cancer tissue compared with normal colon epithelia. Furthermore, the clinicopathological evaluation revealed that UbcH10 was associated with high-grade histological tumors. Conclusion The results show the clinicopathological significance of UbcH10 in the progression of colon cancer. Thus UbcH10 may act as a novel biomarker in patients with colon cancer.

  16. Structural Basis for the Catalytic Activity of Human Serine/Threonine Protein Phosphatase type 5 (PP5)

    Science.gov (United States)

    Swingle, Mark R.; Ciszak, Ewa M.; Honkanen, Richard E.

    2004-01-01

    Serine/threonine protein phosphatase-5 (PP5) is a member of the PPP-gene family of protein phosphatases that is widely expressed in mammalian tissues and is highly conserved among eukaryotes. PP5 associates with several proteins that affect signal transduction networks, including the glucocorticoid receptor (GR)-heat shock protein-90 (Hsp90)-heterocomplex, the CDC16 and CDC27 subunits of the anaphase-promoting complex, elF2alpha kinase, the A subunit of PP2A, the G12-alpha / G13-alpha subunits of heterotrimeric G proteins and DNA-PK. The catalytic domain of PP5 (PP5c) shares 35-45% sequence identity with the catalytic domains of other PPP-phosphatases, including protein phosphatase-1 (PP1), -2A (PP2A), -2B / calcineurin (PP2B), -4 (PP4), -6 (PP6), and -7 (PP7). Like PP1, PP2A and PP4, PP5 is also sensitive to inhibition by okadaic acid, microcystin, cantharidin, tautomycin, and calyculin A. Here we report the crystal structure of the PP5 catalytic domain (PP5c) at a resolution of 1.6 angstroms. From this structure we propose a mechanism for PP5-mediated hydrolysis of phosphoprotein substrates, which requires the precise positioning of two metal ions within a conserved Asp(sup 271)-M(sub 1):M(sub 2)-W(sup 1)-His(sup 304)-Asp(sup 274) catalytic motif. The structure of PP5c provides a possible structural basis for explaining the exceptional catalytic proficiency of protein phosphatases, which are among the most powerful known catalysts. Resolution of the entire C-terminus revealed a novel subdomain, and the structure of the PP5c should also aid development of type-specific inhibitors.

  17. Multi-SNP analysis of GWAS data identifies pathways associated with nonalcoholic fatty liver disease.

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    Qing-Rong Chen

    Full Text Available Non-alcoholic fatty liver disease (NAFLD is a common liver disease; the histological spectrum of which ranges from steatosis to steatohepatitis. Nonalcoholic steatohepatitis (NASH often leads to cirrhosis and development of hepatocellular carcinoma. To better understand pathogenesis of NAFLD, we performed the pathway of distinction analysis (PoDA on a genome-wide association study dataset of 250 non-Hispanic white female adult patients with NAFLD, who were enrolled in the NASH Clinical Research Network (CRN Database Study, to investigate whether biologic process variation measured through genomic variation of genes within these pathways was related to the development of steatohepatitis or cirrhosis. Pathways such as Recycling of eIF2:GDP, biosynthesis of steroids, Terpenoid biosynthesis and Cholesterol biosynthesis were found to be significantly associated with NASH. SNP variants in Terpenoid synthesis, Cholesterol biosynthesis and biosynthesis of steroids were associated with lobular inflammation and cytologic ballooning while those in Terpenoid synthesis were also associated with fibrosis and cirrhosis. These were also related to the NAFLD activity score (NAS which is derived from the histological severity of steatosis, inflammation and ballooning degeneration. Eukaryotic protein translation and recycling of eIF2:GDP related SNP variants were associated with ballooning, steatohepatitis and cirrhosis. Il2 signaling events mediated by PI3K, Mitotic metaphase/anaphase transition, and Prostanoid ligand receptors were also significantly associated with cirrhosis. Taken together, the results provide evidence for additional ways, beyond the effects of single SNPs, by which genetic factors might contribute to the susceptibility to develop a particular phenotype of NAFLD and then progress to cirrhosis. Further studies are warranted to explain potential important genetic roles of these biological processes in NAFLD.

  18. Mechanism of APC/CCDC20 activation by mitotic phosphorylation.

    Science.gov (United States)

    Qiao, Renping; Weissmann, Florian; Yamaguchi, Masaya; Brown, Nicholas G; VanderLinden, Ryan; Imre, Richard; Jarvis, Marc A; Brunner, Michael R; Davidson, Iain F; Litos, Gabriele; Haselbach, David; Mechtler, Karl; Stark, Holger; Schulman, Brenda A; Peters, Jan-Michael

    2016-05-10

    Chromosome segregation and mitotic exit are initiated by the 1.2-MDa ubiquitin ligase APC/C (anaphase-promoting complex/cyclosome) and its coactivator CDC20 (cell division cycle 20). To avoid chromosome missegregation, APC/C(CDC20) activation is tightly controlled. CDC20 only associates with APC/C in mitosis when APC/C has become phosphorylated and is further inhibited by a mitotic checkpoint complex until all chromosomes are bioriented on the spindle. APC/C contains 14 different types of subunits, most of which are phosphorylated in mitosis on multiple sites. However, it is unknown which of these phospho-sites enable APC/C(CDC20) activation and by which mechanism. Here we have identified 68 evolutionarily conserved mitotic phospho-sites on human APC/C bound to CDC20 and have used the biGBac technique to generate 47 APC/C mutants in which either all 68 sites or subsets of them were replaced by nonphosphorylatable or phospho-mimicking residues. The characterization of these complexes in substrate ubiquitination and degradation assays indicates that phosphorylation of an N-terminal loop region in APC1 is sufficient for binding and activation of APC/C by CDC20. Deletion of the N-terminal APC1 loop enables APC/C(CDC20) activation in the absence of mitotic phosphorylation or phospho-mimicking mutations. These results indicate that binding of CDC20 to APC/C is normally prevented by an autoinhibitory loop in APC1 and that its mitotic phosphorylation relieves this inhibition. The predicted location of the N-terminal APC1 loop implies that this loop controls interactions between the N-terminal domain of CDC20 and APC1 and APC8. These results reveal how APC/C phosphorylation enables CDC20 to bind and activate the APC/C in mitosis. PMID:27114510

  19. Identification of Quantitative Trait Loci and Water Environmental Interactions for Developmental Behaviors of Leaf Greenness in Wheat.

    Science.gov (United States)

    Yang, Delong; Li, Mengfei; Liu, Yuan; Chang, Lei; Cheng, Hongbo; Chen, Jingjing; Chai, Shouxi

    2016-01-01

    The maintenance of leaf greenness in wheat, highly responsible for yield potential and resistance to drought stress, has been proved to be quantitatively inherited and susceptible to interact with environments by traditional genetic analysis. In order to further dissect the developmental genetic behaviors of flag leaf greenness under terminal drought, unconditional and conditional QTL mapping strategies were performed with a mixed linear model in 120 F8-derived recombinant inbred lines (RILs) from two Chinese common wheat cultivars (Longjian 19 × Q9086) in different water environments. A total of 65 additive QTLs (A-QTLs) and 42 pairs of epistatic QTLs (AA-QTLs) were identified as distribution on almost all 21 chromosomes except 5A, explaining from 0.24 to 3.29 % of the phenotypic variation. Of these, 22 A-QTLs and 25 pairs of AA-QTLs were common in two sets of mapping methods but the others differed. These putative QTLs were essentially characteristic of time- and environmentally-dependent expression patterns. Indeed some loci were expressed at two or more stages, while no single QTL was continually active through whole measuring duration. More loci were detected in early growth periods but most of QTL × water environment interactions (QEIs) happened in mid-anaphase, where drought stress was more conducted with negative regulation on QTL expressions. Compared to other genetic components, epistatic effects and additive QEIs effects could be predominant in regulating phenotypic variations during the ontogeny of leaf greenness. Several QTL cluster regions were suggestive of tight linkage or expression pleiotropy in the inheritance of these traits. Some reproducibly-expressed QTLs or common loci consistent with previously detected would be useful to the genetic improvement of staygreen types in wheat through MAS, especially in water-deficit environments. PMID:27014298

  20. Rab11-FIP3 is a cell cycle-regulated phosphoprotein

    Directory of Open Access Journals (Sweden)

    Collins Louise L

    2012-03-01

    Full Text Available Abstract Background Rab11 and its effector molecule, Rab11-FIP3 (FIP3, associate with recycling endosomes and traffic into the furrow and midbody of cells during cytokinesis. FIP3 also controls recycling endosome distribution during interphase. Here, we examine whether phosphorylation of FIP3 is involved in these activities. Results We identify four sites of phosphorylation of FIP3 in vivo, S-102, S-280, S-347 and S-450 and identify S-102 as a target for Cdk1-cyclin B in vitro. Of these, we show that S-102 is phosphorylated in metaphase and is dephosphorylated as cells enter telophase. Over-expression of FIP3-S102D increased the frequency of binucleate cells consistent with a role for this phospho-acceptor site in cytokinesis. Mutation of S-280, S-347 or S-450 or other previously identified phospho-acceptor sites (S-488, S-538, S-647 and S-648 was without effect on binucleate cell formation and did not modulate the distribution of FIP3 during the cell cycle. In an attempt to identify a functional role for FIP3 phosphorylation, we report that the change in FIP3 distribution from cytosolic to membrane-associated observed during progression from anaphase to telophase is accompanied by a concomitant dephosphorylation of FIP3. However, the phospho-acceptor sites identified here did not control this change in distribution. Conclusions Our data thus identify FIP3 as a cell cycle regulated phosphoprotein and suggest dephosphorylation of FIP3 accompanies its translocation from the cytosol to membranes during telophase. S102 is dephosphorylated during telophase; mutation of S102 exerts a modest effect on cytokinesis. Finally, we show that de/phosphorylation of the phospho-acceptor sites identified here (S-102, S-280, S-347 and S-450 is not required for the spatial control of recycling endosome distribution or function.

  1. High telomerase activity and long telomeres in advanced hepatocellular carcinomas with poor prognosis.

    Science.gov (United States)

    Oh, Bong-Kyeong; Kim, Haeryoung; Park, Young Nyun; Yoo, Jeong Eun; Choi, Jinsub; Kim, Kyung-Sik; Lee, Jae Jung; Park, Chanil

    2008-02-01

    Telomerase reactivation and telomere maintenance are crucial in carcinogenesis and tumor progression. In this study, the relationships between telomere parameters, chromosomal instability and clinicopathological features were evaluated in hepatocellular carcinomas (HCCs). Telomere length (TL), telomerase activity (TA) and human telomerase reverse transcriptase (hTERT) mRNA levels were measured in 49 hepatitis B virus (HBV)-related HCCs and corresponding non-tumorous tissues. The results were compared with clinicopathological data, including differentiation, multipolar mitosis (MM), anaphase bridge, immunohistochemical stain results for cytokeratin 19 (CK19) and patient outcome. TL of HCCs ranged from 4.7 to 13.1 kb, and 44.4% of HCCs showed telomere lengthening. hTERT mRNA levels and TA were closely related (P=0.008), and were significantly higher in HCCs than non-tumorous tissues. TL was significantly higher in HCCs with strong TA (P=0.048), high hTERT mRNA levels (P=0.001) and poor differentiation (P=0.041). Frequent MM was associated with poor differentiation (P=0.007) and advanced stage (Ptelomeres than CK19- HCCs (P=0.046). Overall survival was poor in HCCs with MM >0.4 per field (P=0.016), high TA (P=0.009) and high TL ratio (HCC/non-HCC) >0.8 (P=0.044). Our results show that long telomeres, high TA and high mitotic instability are poor prognostic markers for HBV-related HCCs and their close association suggests that telomere maintenance may be important for the progression of HCCs with high chromosomal instability to more aggressive ones. PMID:18158557

  2. SAP-like domain in nucleolar spindle associated protein mediates mitotic chromosome loading as well as interphase chromatin interaction

    International Nuclear Information System (INIS)

    Highlights: → The SAP-like domain in NuSAP is a functional DNA-binding domain with preference for dsDNA. → This SAP-like domain is essential for chromosome loading during early mitosis. → NuSAP is highly dynamic on mitotic chromatin, as evident from photobleaching experiments. → The SAP-like domain also mediates NuSAP-chromatin interaction in interphase nucleoplasm. -- Abstract: Nucleolar spindle associated protein (NuSAP) is a microtubule-stabilizing protein that localizes to chromosome arms and chromosome-proximal microtubules during mitosis and to the nucleus, with enrichment in the nucleoli, during interphase. The critical function of NuSAP is underscored by the finding that its depletion in HeLa cells results in various mitotic defects. Moreover, NuSAP is found overexpressed in multiple cancers and its expression levels often correlate with the aggressiveness of cancer. Due to its localization on chromosome arms and combination of microtubule-stabilizing and DNA-binding properties, NuSAP takes a special place within the extensive group of spindle assembly factors. In this study, we identify a SAP-like domain that shows DNA binding in vitro with a preference for dsDNA. Deletion of the SAP-like domain abolishes chromosome arm binding of NuSAP during mitosis, but is not sufficient to abrogate its chromosome-proximal localization after anaphase onset. Fluorescence recovery after photobleaching experiments revealed the highly dynamic nature of this NuSAP-chromatin interaction during mitosis. In interphase cells, NuSAP also interacts with chromatin through its SAP-like domain, as evident from its enrichment on dense chromatin regions and intranuclear mobility, measured by fluorescence correlation spectroscopy. The obtained results are in agreement with a model where NuSAP dynamically stabilizes newly formed microtubules on mitotic chromosomes to enhance chromosome positioning without immobilizing these microtubules. Interphase NuSAP-chromatin interaction

  3. APC/C-mediated degradation of dsRNA-binding protein 4 (DRB4 involved in RNA silencing.

    Directory of Open Access Journals (Sweden)

    Katia Marrocco

    Full Text Available BACKGROUND: Selective protein degradation via the ubiquitin-26S proteasome is a major mechanism underlying DNA replication and cell division in all Eukaryotes. In particular, the APC/C (Anaphase Promoting Complex or Cyclosome is a master ubiquitin protein ligase (E3 that targets regulatory proteins for degradation allowing sister chromatid separation and exit from mitosis. Interestingly, recent work also indicates that the APC/C remains active in differentiated animal and plant cells. However, its role in post-mitotic cells remains elusive and only a few substrates have been characterized. METHODOLOGY/PRINCIPAL FINDINGS: In order to identify novel APC/C substrates, we performed a yeast two-hybrid screen using as the bait Arabidopsis APC10/DOC1, one core subunit of the APC/C, which is required for substrate recruitment. This screen identified DRB4, a double-stranded RNA binding protein involved in the biogenesis of different classes of small RNA (sRNA. This protein interaction was further confirmed in vitro and in plant cells. Moreover, APC10 interacts with DRB4 through the second dsRNA binding motif (dsRBD2 of DRB4, which is also required for its homodimerization and binding to its Dicer partner DCL4. We further showed that DRB4 protein accumulates when the proteasome is inactivated and, most importantly, we found that DRB4 stability depends on APC/C activity. Hence, depletion of Arabidopsis APC/C activity by RNAi leads to a strong accumulation of endogenous DRB4, far beyond its normal level of accumulation. However, we could not detect any defects in sRNA production in lines where DRB4 was overexpressed. CONCLUSIONS/SIGNIFICANCE: Our work identified a first plant substrate of the APC/C, which is not a regulator of the cell cycle. Though we cannot exclude that APC/C-dependent degradation of DRB4 has some regulatory roles under specific growth conditions, our work rather points to a housekeeping function of APC/C in maintaining precise cellular

  4. Development of Triticum aestivum-Leymus racemosus ditelosomic substitution line 7Lr#1S(7A) with resistance to wheat scab and its meiotic behavior analysis

    Institute of Scientific and Technical Information of China (English)

    WANG LinSheng; CHEN PeiDu

    2008-01-01

    Leymus racemosus is highly resistant to wheat scab (Fusarum head bright). The transfer of scab re-sistant gene from L. racemosus to Triticum aestivum is of great significance for broadening the base of wheat resistance. In the present study, the pollen of T. aestivum-L, racemosus monosomic addition linewith scab resistance was treated by irradiation with 1200 R 60Co-γ-rays prior to pollinating to emasculated wheat cv. Mianyang 85-45. Nine plants with a telocentric chromosome 7Lr#1S were observed in M1,and one ditelosomic substitution line 7Lr#1S was selected from selfcrossing progenies and confirmed by chromosome C-banding and GISH. Furthermore, a co-dominant EST-SSR marker CINAU 31 was em-ployed to identify this substitution line. A pair of chromosome 7A of common wheat were found to be replaced by a pair of telocentric chromosome 7Lr#1S, and further investigation showed that chromo-some configuration of the substitution line at MI of PMCs after GISH was 17.50(Ⅱ) w + 2.19 (Ⅱ)w +0.42 (Ⅱ)7Lr#1S + 1.08 Ⅰ7Lr#1S + 0.69 Ⅰw. Two telocentric chromosomes paired as a bivalent in 59.7% of PMCs.Abnormal chromosome behaviors of telocentric chromosomes were observed in part of PMCs at ana-phase Ⅰ and telophase Ⅰ, including the moving of two telocentric chromosomes to the same pole, lag-ging and earlier separation of their sister chromatid. All these abnormal behaviors can be grouped into three distinct types of tetrads according to different numbers of 7Lr#1S in their daughter cells and various micronucieus in some tetrads. However, due to the high transmission frequency of the female and male gametes with a 7Lr#1S, 84% of the selfcrossing progeny plants had ditelosomic substitution. The substitution line showed high resistance to wheat scab in a successive two-year test both in the greenhouse and field; hence, the line will be particularly valuable for alien gene mapping, small frag-ment translocation induction and telosomic cytological behavior analysis.

  5. Analysis of the meiosis in the F1 hybrids of Longiflorum x Asiatic(LA) of lilies (Lilium) using genomic in situ hybridization

    Institute of Scientific and Technical Information of China (English)

    Shujun Zhou; Munikote S. Ramanna; Richard G.F.Visser; Jaap M. van Tuyl

    2008-01-01

    Longiflorum and Asiatic lilies of the genus Lilium of the family Liliaeeae are two important groups of modern lily eultivars. One of the main trends of lily breeding is to realize introgression between these groups. With cut style pollination and embryo rescue, distant hybrids between the two groups have been obtained. However, the F1hybrids are highly sterile or some of them could produce a small number of 2n gametes, and their BC1 progenies are usually triploids. Dutch lily breeders have selected many cultivars from these BC1 progenies based on their variation. It is presumably suggested that such variation could be caused by intergenomic recombination and abnormal meiosis during gamete formation in F1 hybrids of Longiflorum x Asiatic (LA) hybrids in Lilium. Therefore, the meiotic process of ten F1 LA hybrids was cytologically investigated using genomic in situ hybridization and traditional cytological methods in the present research.The results showed that: at metaphase I, the homoeologous chromosome pairing among different F1hybrids ranged from 2.0 to 11.4 bi-valents formed by homoeologous chromosomes per pollen mother cell (PMC), and very few multivalents, and even very few bivalents were formed by two chromosomes within one genome rather than homoeologous chromosomes in some PMCs; at anaphase I, all biva-lents were disjoined and most univalents were divided. Both the disjoined bivalents (half-bivalents) and the divided univalents (sister chromatids) moved to the opposite poles, and then formed two groups of chromosomes; because the two resulting half-bivalents retained their axes in the cell undisturbed, many crossover types, including single crossovers, three strand double crossovers, four strand double crossovers, four strand triple crossovers, and four strand multiple crossovers between the non-sister chromatids in the tetrads of bivalents,were clearly inferred by analyzing the breakpoints on the disjoined bivalents. The present investigation not only

  6. 烟草小孢子母细胞减数分裂过程中微管分布变化%Microtubule Distribution and Change during Meiosis of Microspore Mother Cells of Nicotiana tabacum L.

    Institute of Scientific and Technical Information of China (English)

    王雅英; 张亚楠; 王宏毅; 林石明; 田惠桥

    2011-01-01

    The organization of microtubule cytoskeleton during tobacco microsporogenesis was observed.At the prophase of meiosis Ⅰ of microspore mother cell (MMC), the microtubules in the cell are short and dispersive in cytoplasm. At the metaphase of meiosis Ⅰ, the microtubules in the cell set up a spindle which makes chromosomes move at equatorial plate. When MMCs enter the anaphase of meiosis Ⅰ, the spindle microtubules break. At the metaphase of meiosis Ⅱ, the microtubules form two spindles in the same cytoplasm. In the telophase of meiosis Ⅱ,spindle microtubules depolymerize and change from short segment to tubulin. Then the MMC begins to cytokinesis by cytoplasmic constriction to form contractile furrows, which separate four nuclei into four microspores. There was not evidence to show that microtubules participate in the cytokinesis directly.%应用间接免疫荧光标记技术和激光共聚焦扫描显微镜成像技术观察了烟草小孢子母细胞减数分裂过程中微管的分布变化.在减数分裂前期,小孢子母细胞中的微管较短,随机分散在细胞质中.在减数分裂中期,细胞质中微管形成纺锤体,控制染色体的分布.进入减数分裂Ⅰ后期,部分纺锤体微管将两组染色体拉向两级.在减数分裂Ⅱ中期,细胞中的微管又形成两个纺锤体.在减数分裂Ⅱ后期,纺锤体微管解聚为微管蛋白分散在细胞质中.胞质分裂发生在四个细胞核形成之后.通过细胞核之间的质膜向内缢缩分隔四个细胞核,产生四个小孢子.

  7. Sequential loading of cohesin subunits during the first meiotic prophase of grasshoppers.

    Directory of Open Access Journals (Sweden)

    Ana M Valdeolmillos

    2007-02-01

    Full Text Available The cohesin complexes play a key role in chromosome segregation during both mitosis and meiosis. They establish sister chromatid cohesion between duplicating DNA molecules during S-phase, but they also have an important role during postreplicative double-strand break repair in mitosis, as well as during recombination between homologous chromosomes in meiosis. An additional function in meiosis is related to the sister kinetochore cohesion, so they can be pulled by microtubules to the same pole at anaphase I. Data about the dynamics of cohesin subunits during meiosis are scarce; therefore, it is of great interest to characterize how the formation of the cohesin complexes is achieved in order to understand the roles of the different subunits within them. We have investigated the spatio-temporal distribution of three different cohesin subunits in prophase I grasshopper spermatocytes. We found that structural maintenance of chromosome protein 3 (SMC3 appears as early as preleptotene, and its localization resembles the location of the unsynapsed axial elements, whereas radiation-sensitive mutant 21 (RAD21 (sister chromatid cohesion protein 1, SCC1 and stromal antigen protein 1 (SA1 (sister chromatid cohesion protein 3, SCC3 are not visualized until zygotene, since they are located in the synapsed regions of the bivalents. During pachytene, the distribution of the three cohesin subunits is very similar and all appear along the trajectories of the lateral elements of the autosomal synaptonemal complexes. However, whereas SMC3 also appears over the single and unsynapsed X chromosome, RAD21 and SA1 do not. We conclude that the loading of SMC3 and the non-SMC subunits, RAD21 and SA1, occurs in different steps throughout prophase I grasshopper meiosis. These results strongly suggest the participation of SMC3 in the initial cohesin axis formation as early as preleptotene, thus contributing to sister chromatid cohesion, with a later association of both RAD21

  8. Cdc20 mediates D-box-dependent degradation of Sp100

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Ran; Li, Ke-min; Zhou, Cai-hong; Xue, Jing-lun [State Key Laboratory of Genetic Engineering, Institute of Genetics, School of Life Science, Fudan University, Shanghai (China); Ji, Chao-neng, E-mail: Chnji@fudan.edu.cn [State Key Laboratory of Genetic Engineering, Institute of Genetics, School of Life Science, Fudan University, Shanghai (China); Chen, Jin-zhong, E-mail: kingbellchen@fudan.edu.cn [State Key Laboratory of Genetic Engineering, Institute of Genetics, School of Life Science, Fudan University, Shanghai (China)

    2011-12-02

    Highlights: Black-Right-Pointing-Pointer Cdc20 is a co-activator of APC/C complex. Black-Right-Pointing-Pointer Cdc20 recruits Sp100 and mediates its degradation. Black-Right-Pointing-Pointer The D-box of Sp100 is required for Cdc20-mediated degradation. Black-Right-Pointing-Pointer Sp100 expresses consistently at both the mRNA and protein levels in cell cycle. -- Abstract: Cdc20 is a co-activator of the anaphase-promoting complex/cyclosome (APC/C complex), which recruits substrates at particular phases of the cell cycle and mediates their degradation. Sp100 is a PML-NB scaffold protein, which localizes to nuclear particles during interphase and disperses from them during mitosis, participates in viral resistance, transcriptional regulation, and apoptosis. However, its metabolism during the cell cycle has not yet been fully characterized. We found a putative D-box in Sp100 using the Eukaryotic Linear Motif (ELM) predictor database. The putative D-box of Sp100 was verified by mutational analysis. Overexpression of Cdc20 resulted in decreased levels of both endogenous Sp100 protein and overexpressed Sp100 mRNA in HEK 293 cells. Only an overexpressed D-box deletion mutant of Sp100 accumulated in HEK293 cells that also overexpressed Cdc20. Cdc20 knockdown by cdc20 specific siRNA resulted in increased Sp100 protein levels in cells. Furthermore, we discovered that the Cdc20 mediated degradation of Sp100 is diminished by the proteasome inhibitor MG132, which suggests that the ubiquitination pathway is involved in this process. However, unlike the other Cdc20 substrates, which display oscillating protein levels, the level of Sp100 protein remains constant throughout the cell cycle. Additionally, both overexpression and knockdown of endogenous Sp100 had no effect on the cell cycle. Our results suggested that sp100 is a novel substrate of Cdc20 and it is degraded by the ubiquitination pathway. The intact D-box of Sp100 was necessary for this process. These findings expand

  9. Combinatorial regulation of meiotic holliday junction resolution in C. elegans by HIM-6 (BLM helicase, SLX-4, and the SLX-1, MUS-81 and XPF-1 nucleases.

    Directory of Open Access Journals (Sweden)

    Ana Agostinho

    Full Text Available Holliday junctions (HJs are cruciform DNA structures that are created during recombination events. It is a matter of considerable importance to determine the resolvase(s that promote resolution of these structures. We previously reported that C. elegans GEN-1 is a symmetrically cleaving HJ resolving enzyme required for recombinational repair, but we could not find an overt role in meiotic recombination. Here we identify C. elegans proteins involved in resolving meiotic HJs. We found no evidence for a redundant meiotic function of GEN-1. In contrast, we discovered two redundant HJ resolution pathways likely coordinated by the SLX-4 scaffold protein and also involving the HIM-6/BLM helicase. SLX-4 associates with the SLX-1, MUS-81 and XPF-1 nucleases and has been implicated in meiotic recombination in C. elegans. We found that C. elegans [mus-81; xpf-1], [slx-1; xpf-1], [mus-81; him-6] and [slx-1; him-6] double mutants showed a similar reduction in survival rates as slx-4. Analysis of meiotic diakinesis chromosomes revealed a distinct phenotype in these double mutants. Instead of wild-type bivalent chromosomes, pairs of "univalents" linked by chromatin bridges occur. These linkages depend on the conserved meiosis-specific transesterase SPO-11 and can be restored by ionizing radiation, suggesting that they represent unresolved meiotic HJs. This suggests the existence of two major resolvase activities, one provided by XPF-1 and HIM-6, the other by SLX-1 and MUS-81. In all double mutants crossover (CO recombination is reduced but not abolished, indicative of further redundancy in meiotic HJ resolution. Real time imaging revealed extensive chromatin bridges during the first meiotic division that appear to be eventually resolved in meiosis II, suggesting back-up resolution activities acting at or after anaphase I. We also show that in HJ resolution mutants, the restructuring of chromosome arms distal and proximal to the CO still occurs, suggesting that

  10. Evidence of Allopolyploidy in Urochloa humidicola Based on Cytological Analysis and Genetic Linkage Mapping.

    Science.gov (United States)

    Vigna, Bianca B Z; Santos, Jean C S; Jungmann, Leticia; do Valle, Cacilda B; Mollinari, Marcelo; Pastina, Maria M; Pagliarini, Maria Suely; Garcia, Antonio A F; Souza, Anete P

    2016-01-01

    The African species Urochloa humidicola (Rendle) Morrone & Zuloaga (syn. Brachiaria humidicola (Rendle) Schweick.) is an important perennial forage grass found throughout the tropics. This species is polyploid, ranging from tetra to nonaploid, and apomictic, which makes genetic studies challenging; therefore, the number of currently available genetic resources is limited. The genomic architecture and evolution of U. humidicola and the molecular markers linked to apomixis were investigated in a full-sib F1 population obtained by crossing the sexual accession H031 and the apomictic cultivar U. humidicola cv. BRS Tupi, both of which are hexaploid. A simple sequence repeat (SSR)-based linkage map was constructed for the species from 102 polymorphic and specific SSR markers based on simplex and double-simplex markers. The map consisted of 49 linkage groups (LGs) and had a total length of 1702.82 cM, with 89 microsatellite loci and an average map density of 10.6 cM. Eight homology groups (HGs) were formed, comprising 22 LGs, and the other LGs remained ungrouped. The locus that controls apospory (apo-locus) was mapped in LG02 and was located 19.4 cM from the locus Bh027.c.D2. In the cytological analyses of some hybrids, bi- to hexavalents at diakinesis were observed, as well as two nucleoli in some meiocytes, smaller chromosomes with preferential allocation within the first metaphase plate and asynchronous chromosome migration to the poles during anaphase. The linkage map and the meiocyte analyses confirm previous reports of hybridization and suggest an allopolyploid origin of the hexaploid U. humidicola. This is the first linkage map of an Urochloa species, and it will be useful for future quantitative trait locus (QTL) analysis after saturation of the map and for genome assembly and evolutionary studies in Urochloa spp. Moreover, the results of the apomixis mapping are consistent with previous reports and confirm the need for additional studies to search for a co

  11. DNA polymerase ζ: new insight into eukaryotic mutagenesis and mammalian embryonic development

    Institute of Scientific and Technical Information of China (English)

    Feng Zhu; Ming Zhang

    2003-01-01

    Information about the mechanisms that generate mutationsin eukaryotes is likely to be useful for understanding humanhealth concerns, such as genotoxicity and cancer.Eukaryotic mutagenesis is largely the outcome of attacksby' endogenous and environmental agents. Except for DNArepair, cell cycle checkpoints and DNA damage avoidance,cells have also evolved DNA damage tolerance mechanism,by which lesion-targeted mutation might occur in thegenome during replication by specific DNA polymerases tobypass the lesions (translesion DNA synthesis, TLS), ormutation on undamaged DNA templates (untargetedmutation) might be induced. DNA polymerase ζ (poiζ),which was found firstly in budding yeast Saccharomycescerevisiae and consists of catalytic subunit scRev3 and stimulating subunit scRev7, has Received more attention in recent years. Poi ζ is a member of DNA polymerase δsubfamily, which belongs to DNA polymerase B family, and exists in almost all eukaryotes. Human homolog of the scRev3gene is located in chromosome region 6q21, and the mouse equivalent maps to chromosome 10, distal to the c-myb gene and close to the Macs gene. Alternative splicing, upstream out-of frame ATG can be found in yeast scRev3, mouse and human homologs. Furthermore, the sequence from 253-323 immediate upstream of the AUG initiator codon has the potential to form a stem-loop hairpin secondary structure in REV3 mRNA, suggesting that human REV3 protein may be expressed at low levels in human cells under normal growth conditions. The functional domain analysis showed that yeast Rev3-980 tyrosine in conserved region II is at the polymerase active site. Human REV3 amino acid residues 1 776-2 195 provide a REV7binding domain, and REV7 amino acid residues 1-211provide a bind domain for REV1, REV3 and REV7 itself.More interestingly, REV7 interacts with hMAD2 and therefore might function in the cell cycle control by affecting the activation of APC (anaphase promoting complex).Currently it has been known that

  12. Genome of crocodilepox virus.

    Science.gov (United States)

    Afonso, C L; Tulman, E R; Delhon, G; Lu, Z; Viljoen, G J; Wallace, D B; Kutish, G F; Rock, D L

    2006-05-01

    Here, we present the genome sequence, with analysis, of a poxvirus infecting Nile crocodiles (Crocodylus niloticus) (crocodilepox virus; CRV). The genome is 190,054 bp (62% G+C) and predicted to contain 173 genes encoding proteins of 53 to 1,941 amino acids. The central genomic region contains genes conserved and generally colinear with those of other chordopoxviruses (ChPVs). CRV is distinct, as the terminal 33-kbp (left) and 13-kbp (right) genomic regions are largely CRV specific, containing 48 unique genes which lack similarity to other poxvirus genes. Notably, CRV also contains 14 unique genes which disrupt ChPV gene colinearity within the central genomic region, including 7 genes encoding GyrB-like ATPase domains similar to those in cellular type IIA DNA topoisomerases, suggestive of novel ATP-dependent functions. The presence of 10 CRV proteins with similarity to components of cellular multisubunit E3 ubiquitin-protein ligase complexes, including 9 proteins containing F-box motifs and F-box-associated regions and a homologue of cellular anaphase-promoting complex subunit 11 (Apc11), suggests that modification of host ubiquitination pathways may be significant for CRV-host cell interaction. CRV encodes a novel complement of proteins potentially involved in DNA replication, including a NAD(+)-dependent DNA ligase and a protein with similarity to both vaccinia virus F16L and prokaryotic serine site-specific resolvase-invertases. CRV lacks genes encoding proteins for nucleotide metabolism. CRV shares notable genomic similarities with molluscum contagiosum virus, including genes found only in these two viruses. Phylogenetic analysis indicates that CRV is quite distinct from other ChPVs, representing a new genus within the subfamily Chordopoxvirinae, and it lacks recognizable homologues of most ChPV genes involved in virulence and host range, including those involving interferon response, intracellular signaling, and host immune response modulation. These data

  13. Centralspindlin in Rappaport's cleavage signaling.

    Science.gov (United States)

    Mishima, Masanori

    2016-05-01

    Cleavage furrow in animal cell cytokinesis is formed by cortical constriction driven by contraction of an actomyosin network activated by Rho GTPase. Although the role of the mitotic apparatus in furrow induction has been well established, there remain discussions about the detailed molecular mechanisms of the cleavage signaling. While experiments in large echinoderm embryos highlighted the role of astral microtubules, data in smaller cells indicate the role of central spindle. Centralspindlin is a constitutive heterotetramer of MKLP1 kinesin and the non-motor CYK4 subunit and plays crucial roles in formation of the central spindle and recruitment of the downstream cytokinesis factors including ECT2, the major activator of Rho during cytokinesis, to the site of division. Recent reports have revealed a role of this centralspindlin-ECT2 pathway in furrow induction both by the central spindle and by the astral microtubules. Here, a unified view of the stimulation of cortical contractility by this pathway is discussed. Cytokinesis, the division of the whole cytoplasm, is an essential process for cell proliferation and embryonic development. In animal cells, cytokinesis is executed using a contractile network of actin filaments driven by a myosin-II motor that constricts the cell cortex (cleavage furrow ingression) into a narrow channel between the two daughter cells, which is resolved by scission (abscission) [1-3]. The anaphase-specific organization of the mitotic apparatus (MA, spindle with chromosomes plus asters) positions the cleavage furrow and plays a major role in spatial coupling between mitosis and cytokinesis [4-6]. The nucleus and chromosomes are dispensable for furrow specification [7-10], although they contribute to persistent furrowing and robust completion in some cell types [11,12]. Likewise, centrosomes are not essential for cytokinesis, but they contribute to the general fidelity of cell division [10,13-15]. Here, classical models of cleavage furrow

  14. Conserved CDC20 cell cycle functions are carried out by two of the five isoforms in Arabidopsis thaliana.

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    Zoltán Kevei

    Full Text Available BACKGROUND: The CDC20 and Cdh1/CCS52 proteins are substrate determinants and activators of the Anaphase Promoting Complex/Cyclosome (APC/C E3 ubiquitin ligase and as such they control the mitotic cell cycle by targeting the degradation of various cell cycle regulators. In yeasts and animals the main CDC20 function is the destruction of securin and mitotic cyclins. Plants have multiple CDC20 gene copies whose functions have not been explored yet. In Arabidopsis thaliana there are five CDC20 isoforms and here we aimed at defining their contribution to cell cycle regulation, substrate selectivity and plant development. METHODOLOGY/PRINCIPAL FINDINGS: Studying the gene structure and phylogeny of plant CDC20s, the expression of the five AtCDC20 gene copies and their interactions with the APC/C subunit APC10, the CCS52 proteins, components of the mitotic checkpoint complex (MCC and mitotic cyclin substrates, conserved CDC20 functions could be assigned for AtCDC20.1 and AtCDC20.2. The other three intron-less genes were silent and specific for Arabidopsis. We show that AtCDC20.1 and AtCDC20.2 are components of the MCC and interact with mitotic cyclins with unexpected specificity. AtCDC20.1 and AtCDC20.2 are expressed in meristems, organ primordia and AtCDC20.1 also in pollen grains and developing seeds. Knocking down both genes simultaneously by RNAi resulted in severe delay in plant development and male sterility. In these lines, the meristem size was reduced while the cell size and ploidy levels were unaffected indicating that the lower cell number and likely slowdown of the cell cycle are the cause of reduced plant growth. CONCLUSIONS/SIGNIFICANCE: The intron-containing CDC20 gene copies provide conserved and redundant functions for cell cycle progression in plants and are required for meristem maintenance, plant growth and male gametophyte formation. The Arabidopsis-specific intron-less genes are possibly "retrogenes" and have hitherto undefined

  15. Effects of Chinese herbal formula Heat-stress-releasing on antioxidant function in dairy cows

    Institute of Scientific and Technical Information of China (English)

    ZHANG Qingru; NI Yaodi; GUO Hongbin; WANG Chunguang

    2007-01-01

    In order to investigate the effects of a Chinese herbal formula Heat-stress-releasing on the antioxidant function in dairy cows,ten dairy cows were randomly divided into the control group and the experimental group,with five cows in each group.All the cows were fed with a basal diet.The animals in the experimental group were given with 220 g of herbs per day in addition to the basal diet.The trial was conducted for 14 days.Blood samples were taken from the vena cava at day 0,day 7,and day 15,respectively.The antioxidant statuses were examined.The results are as follows.(1) Heat-Stress-releasing formula can significantly increase the milk yield of dairy cows under heat stress.Compared with the control group,the milk yield of the herb-treated group increased by 14.01% (P<0.05),14.32% (P<0.05) and 15.01% (P<0.05) in prophase,metaphase and anaphase of the test,respectively.(2) Heat-Stress-releasing formula can increase significantly the antioxidant status of the heat stressed dairy cows.Compared with the control group,the superoxide dismutase (SOD) activity increased by 45.93% (P<0.01) at day 7 and by 54.40% (P<0.01) at day 15.The Glutathione-peroxidase (GSH-PX) activity of the test group increased by 17.99% (P<0.05) at day 7 and 25.98% (P<0.01) at day 15.The total antioxidant capacity (T-AOC) of the test group increased by 43.64% (P<0.01) at day 7 and 46.35% (P<0.01)at day 15.The malondaldehyd (MDA) content of test group declined by 23.88% (P<0.01) at day 7 and 25.32% (P<0.01)at day 15.

  16. Genetic diversity and phylogenetic analysis of Citrus (L from north-east India as revealed by meiosis, and molecular analysis of internal transcribed spacer region of rDNA

    Directory of Open Access Journals (Sweden)

    Marlykynti Hynniewta

    2014-12-01

    Full Text Available The north-eastern region of India is reported to be the center of origin and rich in diversity of Citrus (L. species, where some wild and endangered species namely Citrus indica, Citrus macroptera, Citrus latipes, Citrus ichagensis and Citrus assamensis exist in their natural and undisturbed habitat. In order to have comprehensive information about the extent of genetic variability and the occurrence of cryptic genomic hybridity between and within various Citrus species, a combined approach involving morphological, cytogenetical and molecular approaches were adopted in the present study. Cytogenetic approaches are known to resolve taxonomic riddles in a more efficient manner, by clearly delineating taxa at species and sub species levels. Male meiotic studies revealed a gametic chromosome number of n = 9, without any evidence of numerical variations. Bivalents outnumbered all other types of associations in pollen mother cells (PMCs analyzed at diplotene, diakinesis and metaphase I. Univalents were frequently encountered in nine species presently studied, though their presence appropriately did not influence the distributional pattern of the chromosomes at anaphases I and II. The molecular approaches for phylogenetic analysis based on sequence data related to ITS 1, ITS 2 and ITS 1 + 5.8 s + ITS 2 of rDNA using maximum parsimony method and Bayesian inference have thrown light on species inter-relationship and evolution of Citrus species confirming our cytogenetical interpretations. The three true basic species i.e. Citrus medica, Citrus maxima and Citrus reticulata with their unique status have been resolved into distinct clades with molecular approaches as well. C. indica which occupies a unique position in the phylogenetic ladder of the genus Citrus has been resolved as a distinct clade and almost behaving as an out-group. The presences of quadrivalents in C. indica also echo and support its unique position. From our study it is amply

  17. SAP-like domain in nucleolar spindle associated protein mediates mitotic chromosome loading as well as interphase chromatin interaction

    Energy Technology Data Exchange (ETDEWEB)

    Verbakel, Werner, E-mail: werner.verbakel@chem.kuleuven.be [Laboratory of Biomolecular Dynamics, Katholieke Universiteit Leuven, Celestijnenlaan 200G, Bus 2403, 3001 Heverlee (Belgium); Carmeliet, Geert, E-mail: geert.carmeliet@med.kuleuven.be [Laboratory of Experimental Medicine and Endocrinology, Katholieke Universiteit Leuven, Herestraat 49, Bus 902, 3000 Leuven (Belgium); Engelborghs, Yves, E-mail: yves.engelborghs@fys.kuleuven.be [Laboratory of Biomolecular Dynamics, Katholieke Universiteit Leuven, Celestijnenlaan 200G, Bus 2403, 3001 Heverlee (Belgium)

    2011-08-12

    Highlights: {yields} The SAP-like domain in NuSAP is a functional DNA-binding domain with preference for dsDNA. {yields} This SAP-like domain is essential for chromosome loading during early mitosis. {yields} NuSAP is highly dynamic on mitotic chromatin, as evident from photobleaching experiments. {yields} The SAP-like domain also mediates NuSAP-chromatin interaction in interphase nucleoplasm. -- Abstract: Nucleolar spindle associated protein (NuSAP) is a microtubule-stabilizing protein that localizes to chromosome arms and chromosome-proximal microtubules during mitosis and to the nucleus, with enrichment in the nucleoli, during interphase. The critical function of NuSAP is underscored by the finding that its depletion in HeLa cells results in various mitotic defects. Moreover, NuSAP is found overexpressed in multiple cancers and its expression levels often correlate with the aggressiveness of cancer. Due to its localization on chromosome arms and combination of microtubule-stabilizing and DNA-binding properties, NuSAP takes a special place within the extensive group of spindle assembly factors. In this study, we identify a SAP-like domain that shows DNA binding in vitro with a preference for dsDNA. Deletion of the SAP-like domain abolishes chromosome arm binding of NuSAP during mitosis, but is not sufficient to abrogate its chromosome-proximal localization after anaphase onset. Fluorescence recovery after photobleaching experiments revealed the highly dynamic nature of this NuSAP-chromatin interaction during mitosis. In interphase cells, NuSAP also interacts with chromatin through its SAP-like domain, as evident from its enrichment on dense chromatin regions and intranuclear mobility, measured by fluorescence correlation spectroscopy. The obtained results are in agreement with a model where NuSAP dynamically stabilizes newly formed microtubules on mitotic chromosomes to enhance chromosome positioning without immobilizing these microtubules. Interphase Nu

  18. Crystal structure of the karyopherin Kap121p bound to the extreme C-terminus of the protein phosphatase Cdc14p

    Energy Technology Data Exchange (ETDEWEB)

    Kobayashi, Junya [Division of Biological Science, Graduate School of Science, Nagoya University (Japan); Hirano, Hidemi [Division of Biological Science, Graduate School of Science, Nagoya University (Japan); Structural Biology Research Center, Graduate School of Science, Nagoya University (Japan); Matsuura, Yoshiyuki, E-mail: matsuura.yoshiyuki@d.mbox.nagoya-u.ac.jp [Division of Biological Science, Graduate School of Science, Nagoya University (Japan); Structural Biology Research Center, Graduate School of Science, Nagoya University (Japan)

    2015-07-31

    In Saccharomyces cerevisiae, the protein phosphatase Cdc14p is an antagonist of mitotic cyclin-dependent kinases and is a key regulator of late mitotic events such as chromosome segregation, spindle disassembly and cytokinesis. The activity of Cdc14p is controlled by cell-cycle dependent changes in its association with its competitive inhibitor Net1p (also known as Cfi1p) in the nucleolus. For most of the cell cycle up to metaphase, Cdc14p is sequestered in the nucleolus in an inactive state. During anaphase, Cdc14p is released from Net1p, spreads into the nucleus and cytoplasm, and dephosphorylates key mitotic targets. Although regulated nucleocytoplasmic shuttling of Cdc14p has been suggested to be important for exit from mitosis, the mechanism underlying Cdc14p nuclear trafficking remains poorly understood. Here we show that the C-terminal region (residues 517–551) of Cdc14p can function as a nuclear localization signal (NLS) in vivo and also binds to Kap121p (also known as Pse1p), an essential nuclear import carrier in yeast, in a Gsp1p-GTP-dependent manner in vitro. Moreover we report a crystal structure, at 2.4 Å resolution, of Kap121p bound to the C-terminal region of Cdc14p. The structure and structure-based mutational analyses suggest that either the last five residues at the extreme C-terminus of Cdc14p (residues 547–551; Gly-Ser-Ile-Lys-Lys) or adjacent residues with similar sequence (residues 540–544; Gly-Gly-Ile-Arg-Lys) can bind to the NLS-binding site of Kap121p, with two residues (Ile in the middle and Lys at the end of the five residues) of Cdc14p making key contributions to the binding specificity. Based on comparison with other structures of Kap121p-ligand complexes, we propose “IK-NLS” as an appropriate term to refer to the Kap121p-specific NLS. - Highlights: • The C-terminus of Cdc14p binds to Kap121p in a Gsp1p-GTP-dependent manner. • The crystal structure of Kap121p-Cdc14p complex is determined. • The structure reveals how

  19. Hibridações entre Coffea arabica e C. kapakata. análise citológica de um híbrido triplóide Crossability between C. arabica and C. kapakata and cytological analysis of the hybrid

    Directory of Open Access Journals (Sweden)

    L. C. Mônaco

    1965-01-01

    Full Text Available Os cruzamentos realizados entre Coffea arabica e C. kapakata revelaram que há possibilidade de hibridação entre estas duas espécies e que o pegamento é bem mais elevado quando C. arabica é usada como planta feminina. Os resultados das hibridações realizadas, acrescidos aos já existentes sôbre a relação de compatibilidade de C. kapakata com outras espécies, vêm reforçar a sua inclusão dentro do gênero Coffea. As observações feitas na meiose de um híbrido triplóide entre C. arabica e C. kapakata demonstraram a formação de 1,33III 9,45II e 10,07I em média, para diacinese e primeira metáfase. As separações anafásicas são irregulares, bem como as tétrades produzidas. Os grãos de pólen contêm, em sua maioria, 13 a 17 cromossomos. Os híbridos triplóides são vigorosos e vêm sendo utilizados no melhoramento, visando introduzir nos cultivares de C. arabica a resistência à sêca presente em C. kapakata.The ability of C. kapakata to cross with C. arabica was analysed in the present paper. The ratios between seed-ovules, seedling-seeds and seedling-ovules were taken into account in order to evaluate the kinhood of the two species. It was found that the crossing rate was higher when C. arabica, the tetraploid species, was used as female. In the backcrosses it was found that the hybrid could not be crossed with C. kapakata, while C. arabica crosses in both directions with the F, hybrid. The hybrids were morphologically intermediate to both species. Observations were made about the meiosis of one of the hybrids. The chromosome associations were in average 1.33III 9.45II and 10.07I, for diakinesis and first metaphase. The distribution of the chromosomes during anaphase as well as the tetrades are abnormal. The pollen grains contain more frequently from 13 to 17 chromosomes. The hybrids between C. arabica and C. kapakata have been used as bridge for transferring drought resistance of C. kapakata to the cultivars of C

  20. Dietary Energy Level:Effects on Slaughter Performance and Body Composition of Luxi Game Chickens%饲粮能量水平对鲁西斗鸡屠宰性能和体成分的影响

    Institute of Scientific and Technical Information of China (English)

    姜淑贞; 窦文洁; 杨维仁; 张相伦; 杨在宾; 高翔; 牛群升

    2014-01-01

    This trial was conducted to study the effects of dietary energy level on slaughter performance and body composition of Luxi game chickens during growth prophase (1 to 42 days of age) and growth anaphase ( 43 to 140 days of age) , respectively. A total of 1-day-old 1 000 sex-mixed healthy Luxi game chickens were randomly divided into five treatments with four replicates per treatment and fifty birds per replicate. The levels of metabolizable energy (ME) were 11. 98, 12. 19, 12. 38, 12. 62 and 12. 81 MJ/kg of diets from 1 to 42 days of age, meanwhile, 11. 63, 11. 82, 12. 03, 12. 25 and 12. 45 MJ/kg of diets from 43 to 140 days of age. Results showed that different dietary ME levels had no significant effects on slaughter performance of part-empty thoracic cavity rate, empty thoracic cavity rate, breast muscle rate, leg muscle rate, and body composi-tion of moisture, crude protein ( CP) , ether extract ( EE) and ash contents, and net energy retained ( ER) of Luxi game chickens aged 42 and 140 days ( P>0 . 05 ) . Moisture content of Luxi game chickens aged 140 days significantly was lower than that of Luxi game chickens aged 1 and 42 days ( P0.05)。140日龄鲁西斗鸡水分含量显著低于1日龄和42日龄鲁西斗鸡( P<0.05);CP和CA含量随日龄增加显著升高( P<0.05);1日龄鲁西斗鸡EE含量显著高于42日龄和140日龄( P<0.05);42日龄鲁西斗鸡ER显著低于1日龄和140日龄( P <0.05)。本试验条件下,日龄对鲁西斗鸡水分、CP、EE、CA含量以及ER均有显著影响,EE含量随日龄增长呈现下降的趋势,反映了鲁西斗鸡的品种特性。

  1. Characterization of the interaction between the cohesin subunits Rad21 and SA1/2.

    Directory of Open Access Journals (Sweden)

    Nenggang Zhang

    Full Text Available The cohesin complex is responsible for the fidelity of chromosomal segregation during mitosis. It consists of four core subunits, namely Rad21/Mcd1/Scc1, Smc1, Smc3, and one of the yeast Scc3 orthologs SA1 or SA2. Sister chromatid cohesion is generated during DNA replication and maintained until the onset of anaphase. Among the many proposed models of the cohesin complex, the 'core' cohesin subunits Smc1, Smc3, and Rad21 are almost universally displayed as tripartite ring. However, other than its supportive role in the cohesin ring, little is known about the fourth core subunit SA1/SA2. To gain deeper insight into the function of SA1/SA2 in the cohesin complex, we have mapped the interactive regions of SA2 and Rad21 in vitro and ex vivo. Whereas SA2 interacts with Rad21 through a broad region (301-750 aa, Rad21 binds to SA proteins through two SA-binding motifs on Rad21, namely N-terminal (NT and middle part (MP SA-binding motif, located at 60-81 aa of the N-terminus and 383-392 aa of the MP of Rad21, respectively. The MP SA-binding motif is a 10 amino acid, α-helical motif. Deletion of these 10 amino acids or mutation of three conserved amino acids (L(385, F(389, and T(390 in this α-helical motif significantly hinders Rad21 from physically interacting with SA1/2. Besides the MP SA-binding motif, the NT SA-binding motif is also important for SA1/2 interaction. Although mutations on both SA-binding motifs disrupt Rad21-SA1/2 interaction, they had no apparent effect on the Smc1-Smc3-Rad21 interaction. However, the Rad21-Rad21 dimerization was reduced by the mutations, indicating potential involvement of the two SA-binding motifs in the formation of the two-ring handcuff for chromosomal cohesion. Furthermore, mutant Rad21 proteins failed to significantly rescue precocious chromosome separation caused by depletion of endogenous Rad21 in mitotic cells, further indicating the physiological significance of the two SA-binding motifs of Rad21.

  2. Effects of hydrostatic pressure on microtubule organization and nucleus changes in gynogenetically activated eggs of olive flounder (Paralichthys olivaceus).

    Science.gov (United States)

    Lin, Zhengmei; Zhu, Xiangping; Zhang, Tingrong; You, Feng; Wu, Zhihao; Cao, Yuanshui

    2016-06-01

    Fluorescent double-labeled technique was used to investigate the effects of hydrostatic pressure on microtubule organization and nucleus in gynogenetically activated eggs of olive flounder (Paralichthys olivaceus). The parameter of hydrostatic pressure treatment was 600 kg/cm(2) for 6 minutes at prometaphase of the first mitosis. The data showed that nucleus and microtubule changes of the diploid control were basically similar to those of the haploid one (5 minutes behind those of the diploid control). Nuclear diameter of the haploid embryo was significantly smaller than that of the diploid one (P < 0.01). The ploidy of chromosome set could be determined basing on nuclear diameter. The results of nuclear diameter measurement and the ratio of developmentally delayed embryo showed that the chromosome set was not doubled during the second cell cycle, the first cleavage proceeded normally; but that of about 80% treated embryo was doubled during the third cell cycle, the second cleavage was inhibited. Microtubules were disassembled, and nucleation capacity of centrosome was just temporarily inhibited by pressure treatment. Centrosome renucleated microtubule, and a bipolar spindle reassembled 15 minutes after treatment, leading to occurrence of the first cleavage. During the second cell cycle, about 80% treated embryo had a single centrosome and formed a unipolar spindle in both blastomeres. After prometaphase, chromosomes spread around for about 20 minutes instead of aligning on the equatorial plane, then assembled and formed one large nucleus without anaphase separation. The second cleavage was inhibited, and the chromosome set was doubled. The data indicated that the chromosome set doubling of mitogynogenetic diploid induced by hydrostatic pressure treatment, which performed at prometaphase of the first mitosis, mainly resulted from the inhibition of the second cleavage rather than the first one. This study is the first to adapt fluorescent double

  3. Crystal structure of the karyopherin Kap121p bound to the extreme C-terminus of the protein phosphatase Cdc14p

    International Nuclear Information System (INIS)

    In Saccharomyces cerevisiae, the protein phosphatase Cdc14p is an antagonist of mitotic cyclin-dependent kinases and is a key regulator of late mitotic events such as chromosome segregation, spindle disassembly and cytokinesis. The activity of Cdc14p is controlled by cell-cycle dependent changes in its association with its competitive inhibitor Net1p (also known as Cfi1p) in the nucleolus. For most of the cell cycle up to metaphase, Cdc14p is sequestered in the nucleolus in an inactive state. During anaphase, Cdc14p is released from Net1p, spreads into the nucleus and cytoplasm, and dephosphorylates key mitotic targets. Although regulated nucleocytoplasmic shuttling of Cdc14p has been suggested to be important for exit from mitosis, the mechanism underlying Cdc14p nuclear trafficking remains poorly understood. Here we show that the C-terminal region (residues 517–551) of Cdc14p can function as a nuclear localization signal (NLS) in vivo and also binds to Kap121p (also known as Pse1p), an essential nuclear import carrier in yeast, in a Gsp1p-GTP-dependent manner in vitro. Moreover we report a crystal structure, at 2.4 Å resolution, of Kap121p bound to the C-terminal region of Cdc14p. The structure and structure-based mutational analyses suggest that either the last five residues at the extreme C-terminus of Cdc14p (residues 547–551; Gly-Ser-Ile-Lys-Lys) or adjacent residues with similar sequence (residues 540–544; Gly-Gly-Ile-Arg-Lys) can bind to the NLS-binding site of Kap121p, with two residues (Ile in the middle and Lys at the end of the five residues) of Cdc14p making key contributions to the binding specificity. Based on comparison with other structures of Kap121p-ligand complexes, we propose “IK-NLS” as an appropriate term to refer to the Kap121p-specific NLS. - Highlights: • The C-terminus of Cdc14p binds to Kap121p in a Gsp1p-GTP-dependent manner. • The crystal structure of Kap121p-Cdc14p complex is determined. • The structure reveals how

  4. A Study on Affective Decision -making of Children with Different Aggression/Victim Groups by Gambling Task,%运用赌博任务测查不同攻击/受欺类别儿童的情感决策过程

    Institute of Scientific and Technical Information of China (English)

    李亚真; 桑标

    2012-01-01

    features of affective decision-making of the children belonging to different aggression/victim groups. The above is the innovation of this study. Gambling task consisted of 80 test items, each involving four doors A, B, C and D, from left to right. The net losses of A and B are equal in general. So are C and D. But A or C belongs to the high-frequency small punishment, while B or D belongs to the low-frequency big punishment. In the long term, it is disadvantageous to choose A and B, but advantageous to choose C and D. Using the method of companion nomination and scales compiled by Masten and Salmivalli, the authors first selected 262 subjects, who were classified according to the aggressors/victims and the non-involved types and by grade and gender. The results show that there were obvious differences among different groups of children, comprising net difference of advantage-disadvantage selection, decision-making difference (style) of advantage-disadvantage selection and frequency of rewards and punishment. The performance of children in each block reveals the following conclusions. First, in net difference of advantage-disadvantage selection, the overall behavior of the non-involved children is better than other groups of children, reflecting the learning effect of gradually improving their decision making in the process of experimentation. Aggressive/victim children's affective decision-making scores are worse than the noninvolved children's in improving prophase performance and unchanging anaphase performance. Indirect-aggressive children show strong learning effect during latter stage. The victim - children's and the direct-aggressive children's decision-making scores are the worst in the overall trials, the former displaying the course of upgrading in prophase then descending in anaphase, and the latter exhibiting a little ascending of learning effect. Secondly, in the acquirement style of the advantage-disadvantage selection, all kinds of children manifest finally

  5. Effect of phosphorylated Smad3 on expression of SnoN in the kidney of diabetic rats%磷酸化Smad3对糖尿病大鼠肾组织SnoN表达的影响

    Institute of Scientific and Technical Information of China (English)

    刘瑞霞; 郭兵; 肖瑛; 石明隽; 王圆圆; 桂华珍; 张国忠

    2011-01-01

    Objective To explore the effect of phosphorylated Sma and Mad Homologue 3 (Smad3) on expression of transcription co-repressor Ski-related protein N (SnoN) protein in the kidney of diabetes mellitus (DM) rats.Methods The DM rats were induced by intraperitoneal injection of streptozotocin (STZ).Rats in different groups were killed at 2, 4, 8, 12, 16 and 24 weeks, respectively, after inducing DM.Meanwhile, the rats in age-matched groups as normal control were treated at the same period.Glucose and protein in urine collected within 24 hours were measured by biochemistry methods.PAS staining was used to observe the renal pathological changes.The protein levels of phosphorylated Smad3, SnoN, transforming growth factor-β1 ( TGF-β1 ), Smad2/3 and anaphase promoting complex (APC) in renal tissues were examined by immunohistochemical staining and Western blotting.The RT-PCR was employed to determine the expression of SnoN mRNA in renal cortex.Results Levels of blood glucose and 24 h-urine protein were remarkably increased in DM rats as compared with controls.The protein levels of phosphorylated Smad3, TGF-β1 and Smad2/3 were significantly up-regulated in the kidney of DM rats.There was a significant decrease of SnoN protein from DM4 week, the SnoN mRNA levels was unchanged in each diabetes group.Conclusions Phosphorylated Smad3 and APC may play a key role in the ubiquitin of SnoN protein.%目的 探讨磷酸化Smad3(p-Smad3)在糖尿病(DM)大鼠肾组织SnoN蛋白表达的影响.方法 链脲佐菌素诱发大鼠DM模型,分为DM2、4、8、12、16和24 w组(n=6),每组均设鼠龄匹配的正常对照组(n=6).生化方法测血糖和24 h尿蛋白;PAS染色观察肾组织病理学改变;免疫组化检测肾组织SnoN、Smad2/3和E3泛素连接酶APC10蛋白的表达;Western印迹方法动态观察肾皮质SnoN、p-Smad3、转化生长因子-β1(TGF-β1)和Smad2/3蛋白的表达;RT-PCR检测SnoN mRNA.结果 DM各组大鼠血糖和24 h尿蛋白较

  6. Effect of microsporidia on adult Ancylis sativa Liu and Carposina nipponensis Matsmura%微孢子虫对枣镰翅小卷蛾和桃小食心虫成虫的影响

    Institute of Scientific and Technical Information of China (English)

    张晓; 李新岗; 张学武; 姬升; 王飞; 刘瑜

    2012-01-01

    [Objective] The study was conducted to identify that the effect of mierosporidia on adult Ancylis sativa Liu and Carposina nipponensis Matsmura was strong infectivity, and discuss the effect of microsporidia on controlling population growth and decline. [Method] Ordinary optics microscope was used to detect the levels of microsporidian infection in different years or different generations of adult A. sativa Liu and C. nipponensis Matsmura. Wing area was determined by ImageJ 1.41 (United States National In- stitutes of Health). [Result] The levels of microsporidian infection in adult A. sativa Liu increased strong- ly from overwintering to first-generation until second-generation. At the same time,body size(wing areas) of A. sativa Liu decreased significantly with the increasing infection levels. The levels of microsporidian in- fection in adult C. nipponensis Matsmura increased extremely significantly from prophase to metaphase to anaphase in both 2009 and 2010. There was no significant difference in the wing areas of C. nipponensis Matsmura between prophase and metaphase, but wing areas of metaphase were significantly bigger than an- aphase. [Conclusion] Microsporidia can strongly infect adult A. sativa Liu and C. nipponensis Matsmura. Microsporidian infection may cause death of A. sativa Liu and C. nipponensis Matsmura at the overwinte- ring stages or result in growth retardation and smaller individual,which means microsporidia has a signifi-cant effect on controlling population growth and decline.%【目的】研究微孢子虫对枣镰翅小卷蛾和桃小食心虫成虫的侵染作用,探讨微孢子虫在调控其种群消长方面的作用。【方法】采用光学显微镜镜检法检测年度或不同代间枣镰翅小卷蛾和桃小食心虫的微孢子虫感染水平;用ImageJ1.41图形处理软件测量其翅面积大小。【结果】枣镰翅小卷蛾雌雄蛾越冬代、第1代和第2代的微孢子虫感染水平逐渐上升,差异

  7. Gamma rays induced bold seeded high yielding mutant in chickpea

    International Nuclear Information System (INIS)

    (12.64±0.14g). This ultimately resulted in an increase in the overall yield of the mutant plant (38.86±1.69g) as compared to Pusa-212 (30.05±0.59g). Gamma ray induced bold seeded mutants have been reported earlier by different workers. The decrease in the number of seeds per pod and pods/plant and increase in seed weight is evidence of the fact that each trait is affected independently by the mutagenic treatment. Although the mutant was morphologically distinct, cytologically it was normal. There were 8 perfect bivalents at metaphase and the anaphase segregation was normal. It is concluded that bold seeded mutant may be utilized in various breeding programs as a donor parent for boldness character of the mutant. On the other hand the mutant may also itself be improved through crosses with other parents to accommodate more seeds in its large sized pod, which remained almost 50% empty

  8. Multicolor detection of every chromosome as a means of detecting mosaicism and nuclear organization in human embryonic nuclei.

    Science.gov (United States)

    Turner, Kara; Fowler, Katie; Fonseka, Gothami; Griffin, Darren; Ioannou, Dimitrios

    2016-06-01

    previously published studies and hitherto unreported data indicating that 24 chromosome FISH is a useful tool for studying chromosome mosaicism, one of the most hotly debated topics currently in preimplantation genetics. Our results suggest that mosaic embryo aneuploidy is not highly significantly correlated to maternal age, probably due, in part, to the large preponderance of post-zygotic (mitotic) errors. Chromosome loss (anaphase lag) appears to be the most common mechanism, followed by chromosome gain (endoreduplication), however 3:1 mitotic non-disjunction of chromosomes appears to be rare. Nuclear organization (i.e. the spatial and temporal topology of chromosomes or sub-chromosomal compartments) studies indicate that human morula or blastocyst embryos (days 4-5) appear to adopt a "chromocentric" pattern (i.e. almost all centromeric signals reside in the innermost regions of the nuclear volume). By the blastocyst stage however, a more ordered organization with spatial and temporal cues important for embryo development appears. We have however found no association between aneuploidy and nuclear organization using this approach despite our earlier studies. In conclusion, while FISH is mostly "dead and buried" for mainstream PGS, it still has a place for basic biology studies; the development of a 24 chromosome protocol extends the power of this analysis. PMID:26982524

  9. Chromosome stickiness during meiotic behavior analysis of Passiflora serrato-digitata L. (PassifloraCEAE Aderência cromossômica durante a análise do comportamento meiótico de Passiflora serrato-digitata L (PassifloraCEAE

    Directory of Open Access Journals (Sweden)

    Paulo Roberto Peres Kiihl

    2011-06-01

    Full Text Available Almost 90% of species of the genus Passiflora are native to the American continent, with high commercial value due to the fact that some species are used for human food while others have ornamental and medical qualities. Passiflora serrato-digitata is one of the species that integrates the Paraná Agronomic Institute germoplasm bank at its experimental base in Londrina, PR, Brazil. Collected flower buds were fixed in ethanol/acetic acid (3:1 v/v for 24h, transferred to 70% alcohol and stored under refrigeration. Slides were prepared by the squashing technique and stained with 1.0% propionic carmine; they were analyzed under an optic microscope. Irregularities in the chromosome segregation process of P. serrato-digitata have been verified by meiotic behavior analysis. These comprised precocious migration to poles in metaphase I and II, non-oriented chromosomes in metaphase plate in metaphase I and II, laggard chromosomes in anaphase I and II towards the formation of micronucleus in telophase I and II, and microspores in tetrads. Chromosome stickiness was another irregularity reported in the Passiflora genus for the first time. These irregularities which also contributed to the formation of monads, dyads and triads, resulted in normal imbalanced 2n and 4n microspores. According to the observed Meiotic Index of 71.83%, this species is not meiotically stable.Cerca de 90% das espécies do gênero Passiflora são nativas das Américas, sendo que aproximadamente 200 espécies são nativas do Brasil. Possuem grande importância comercial, pois algumas espécies são utilizadas na alimentação humana, outras apresentam propriedades medicinais e ornamentais. A espécie Passiflora serrato-digitata faz parte do banco de germoplasma do Instituto Agronômico do Paraná - IAPAR, estação experimental de Londrina, PR. Botões florais colhidos foram fixados em etanol/ácido acético (3:1 v/v por 24 horas, transferidos para álcool a 70% e acondicionado sob

  10. Bio-indication-based estimates as an integral part of the environment quality assessment on an example of allium-test application

    International Nuclear Information System (INIS)

    , there is a capability for a mutual intensification of the effects from environmental factors that actually occur in situations of low-level exposure, as demonstrated earlier (Evseeva et al., 2001; Geras kin et al., 2005). It is therefore impossible to estimate biological risk from combined action based on the only contaminants levels in the environment. This conclusion emphasizes the need to update some current principles of ecological standardization, which are still in use nowadays. Measurements of dose and concentrations of contaminants provide detailed information on the acting agents but only indirectly indicate potential biological consequences. A biological assay, in turn, provides an integrative estimation of toxicity and genotoxicity of environmental pollutants. A combination of these two techniques allows identifying the major sources of risk which require continuous biological monitoring. An adequate assessment of the risk to the environment from contamination needs to be based on the simultaneous use of toxicity and genotoxicity tests. As a genotoxicity test, the Allium-based assay of chromosome aberration in anaphase-telophase is for many reasons especially useful for the rapid screening of chemicals involved in environmental hazards. In addition,mitotic index is a good toxicity indicator as well. The high sensitivity of the Allium- test (Fiskesjo, 1985) ensures that contaminants will not be overlooked, which may be of special importance when complex mixtures are to be tested. Therefore, positive results in the Allium-test should be considered as a warning and also an indication that the tested compounds may cause a risk to human health and to our environment. Complex issues are involved in evaluating environmental risk, and an effectively linking of bio indication screening assays to the well-established environmental pollution monitoring system is a way of improving and upgrading an existing system of the public and the environment protection to meet

  11. Frequency of micronuclei in individuals from high level natural radiation areas of Kerala in India, as a function of age and gender

    International Nuclear Information System (INIS)

    by age (P=0.5) and residential area (NLNRA/HLNRA, P=0.24). A significant age related increase in the frequency of MN as seen in all subjects may be due to a reduction in DNA repair capacity and spindle disturbances resulting in chromosome lagging at anaphase. In our study, it seems more likely for female subjects to have higher DNA damage. Absence of the influence of age on the frequency of MN in female subjects may be because majority of female samples belonged to a narrow age range of 35-55. However, in this pilot study, we could not observe significant genotoxic effects of chronic low level radiation exposure with regard to the frequency of micronuclei in HLNRA subjects. (author)

  12. Bio-indication-based estimates as an integral part of the environment quality assessment on an example of allium-test application

    Energy Technology Data Exchange (ETDEWEB)

    Oudalova, A.; Geras' kin, S.; Dikarev, V.; Dikareva, N. [Russian Institute of Agricultural Radiology and Agroecology, Obninsk (Russian Federation); Michalik, B.; Chalupnik, S.; Wysocka, M. [Central Mining Institute, Katowice (Poland); Evseeva, T. [Institute of Biology, Komi Scientific Center, Syktyvkar (Russian Federation); Kozmin, G. [State Technical University of Atomic Energy, Obninsk (Russian Federation)

    2006-07-01

    , there is a capability for a mutual intensification of the effects from environmental factors that actually occur in situations of low-level exposure, as demonstrated earlier (Evseeva et al., 2001; Geras kin et al., 2005). It is therefore impossible to estimate biological risk from combined action based on the only contaminants levels in the environment. This conclusion emphasizes the need to update some current principles of ecological standardization, which are still in use nowadays. Measurements of dose and concentrations of contaminants provide detailed information on the acting agents but only indirectly indicate potential biological consequences. A biological assay, in turn, provides an integrative estimation of toxicity and genotoxicity of environmental pollutants. A combination of these two techniques allows identifying the major sources of risk which require continuous biological monitoring. An adequate assessment of the risk to the environment from contamination needs to be based on the simultaneous use of toxicity and genotoxicity tests. As a genotoxicity test, the Allium-based assay of chromosome aberration in anaphase-telophase is for many reasons especially useful for the rapid screening of chemicals involved in environmental hazards. In addition,mitotic index is a good toxicity indicator as well. The high sensitivity of the Allium- test (Fiskesjo, 1985) ensures that contaminants will not be overlooked, which may be of special importance when complex mixtures are to be tested. Therefore, positive results in the Allium-test should be considered as a warning and also an indication that the tested compounds may cause a risk to human health and to our environment. Complex issues are involved in evaluating environmental risk, and an effectively linking of bio indication screening assays to the well-established environmental pollution monitoring system is a way of improving and upgrading an existing system of the public and the environment protection to meet

  13. 微生态制剂对产蛋后期蛋鸡生产性能及饲料营养物质消化率的影响%Effect of Probiotics Supplementation in Laying Hens Diets on Performance and Nutrient Digestibility of hens at late Laying Stage

    Institute of Scientific and Technical Information of China (English)

    范彧; 李笑樱; 马秋刚; 陈余; 贾亚雄; 计成; 付国强; 王晓霞

    2012-01-01

    This experiment was conducted to evaluate the effect of Bacillus supplementation in laying hens diets on performance and nutrient apparent digestibility in the anaphase of laying production. A total of 864, 50 -week -old, healthy Hy-line brown laying hens were selected to carry out metabolize experiment using direct collection feces method. These layers were randomly divided into 4 groups with 8 repeats (3 layers in each repeat), included one control group fed a corn-soybean-cottonseed basal diet without any antibiotics and prebiotics and three experiment groups supplemented 0.01% Bacillus, 0.02% Bacillus and 0.02% compound probiotics, respectively. Pre-feeding period lasted 4 days for achieving the optimum performance. The feces from birds of each repeat were collected continuously for 3 days when birds fully adapted to the diets and showed the best production performance. The utilization efficiency of apparent digestibility of energy (AME), crude protein (CP), dry matter (DM), Ca, P and amino acid in diets supplemented with different probiotics were determined. The results showed that 0.02% Bacillus and 0.02% compound probiotics supplementation could significantly improve laying rate, egg production and feed intake (P<0.01). AME, DM and Ser, Glu, Thr, Gly, Arg, Ala, Pro, Val, Phe, He, Leu, His, Lys, Met, Cys in hens during the late laying period have been improved by 0.02% Bacillus and 0.02% compound probiotics supplementation (P<0.05), significantly. 0.02% compound probiotics supplementation could also significantly improve average egg weight (P<0.05), lower feed conversion efficiency and increase of CP, Ca, P (F<0.05). In conclusion, the both probiotics can significantly improve the performance and nutrient apparent digestibility of hens during the late laying period.%本试验选用864只健康海兰褐蛋鸡,随机分为4个处理,在基础日粮中分别添加0.01%、0.02%芽孢杆菌微生态制剂以及0.02%合生素类复合微生态制剂,研究

  14. Apoptin特写:新治疗展望%Apoptin Close-ups: Perspectives Towards Novel Therapies

    Institute of Scientific and Technical Information of China (English)

    章应慧; Olijslagers SJ; Backendorf C; Noteborn MHM

    2006-01-01

    Apoptin induces apoptosis in human transformed but not in normal cells. Apoptin senses and is activated by the cellular signals that are symptomatic only for transformed cells. These properties make apoptin a potential therapy for cell-transformation-related diseases such as cancer and related auto-immune diseases like rheumatoid arthritis (RA) . Several research groups reported and unraveled fragmentarily the transformation-specific processes involved in apoptin-induced apoptosis. For instance, activation of a cancer-specific kinase as well as the anaphase-promoting complex(APC) in a transformed-related p53-minus setting plays a crucial role. Various in vitro and/or in vivo preclinical gene therapy studies and protein delivery experiments have convincingly shown that apoptin is a potential effective and safe therapeutic agent. Chemotherapeutic agents such as etoposide,paclitaxel or methotrexate share with apoptin a cooperative cytotoxic effect on different human tumor cell types. Further research on apoptin-sensed cellular transformation processes will provide detailed insight into molecular mechanisms underlying cancer or rheumatoid arthritis diseases. Apoptin-therapy technology combined with other therapeutic elements will generate novel therapeutic strategies against transformation-related diseases.%Apoptin诱导人转化细胞而不是正常细胞的凋亡,特异性地感知转化细胞的信号并被激活.这些特性使得Apoptin成为一种用于与细胞转化相关的肿瘤以及自身免疫性疾病(如风湿性关节炎)的前景型制剂.不同研究小组相继报道了细胞转化特异性过程和Apoptin凋亡诱导的相关性,如肿瘤特异激酶激活以及p53阴性转化细胞中细胞分裂后期启动复合物(APC)即起关键作用.体内外前临床基因治疗研究和蛋白转导试验充分显示Apoptin作为治疗制剂的有效性和安全性.化疗药物,如etoposide、paclitaxel或methotrexate(甲氨蝶呤)与Apoptin的联合治

  15. Effects of Cordyceps power on growth performance and immune function of broilers%冬虫夏草菌粉对肉鸡生长性能和免疫功能的影响

    Institute of Scientific and Technical Information of China (English)

    邵紫培; 尹艳军; 袁洪水

    2016-01-01

    试验旨在研究冬虫夏草菌粉对肉鸡生长性能和免疫功能的影响。将200羽1日龄AA肉鸡随机分为5组,每组4个重复。空白对照组仅饲喂基础日粮;抗生素对照组在基础日粮中添加350 mg/kg金霉素;冬虫夏草菌粉试验组设低、中、高3个剂量,分别在基础日粮中添加0.05%、0.1%、0.2%冬虫夏草菌粉。试验周期42 d,分为前期(1~21 d)、后期(22~42 d)两个阶段。结果表明,与空白对照组相比,中、高剂量组在增加肉鸡均重、平均日增重,降低肉鸡料重比,提高肉鸡胸腺指数和脾脏指数,增加机体外周血T淋巴细胞的转化率、增强肉鸡白细胞吞噬能力方面均呈显著水平(P<0.05);与抗生素对照组相比,可降低腹泻发生率。由此可知,冬虫夏草菌粉可作为饲料添加剂用来提高肉鸡的生长性能和免疫功能,替代抗生素预防腹泻发生。%The aim of this experiment is to study the effects of Cordyceps power on growth performance and immune function of broiler chicken. 200 1-day-old Arbor Acres broilers were randomly divided into 5 groups with 5 repeats. The blank control group was fed basal diet and the antibiotics control group was supplemented with 350 mg/kg chlortetracycline, the experimental groups were supplemented with 0.05%, 0.1%, 0.2% Cordyceps power respectively. The cycle of test were 42 days, including pro⁃phase (1~21 d) and anaphase (22~42 d). The results showed that: compared with control group, middle and high dose groups increased average weigh, average daily gain and reduced feed gain ratio signifi⁃cantly (P<0.05); improved thymus index and spleen index dramatically (P<0.05); increased the quanti⁃ty of T lymphocyte (P<0.05) and enhanced phagocytic function of leukocyte remarkably (P<0.05). Com⁃pared with antibiotics control group, middle and high dose groups can reduce incidence of diarrhea. This research indicated that growth performance and

  16. Effect of malic acid on aluminum and silicon release from kaolinite%苹果酸对高岭石中铝和硅释放的影响

    Institute of Scientific and Technical Information of China (English)

    胡华锋; 王慧杰; 王兴祥; 介晓磊; 李清曼

    2013-01-01

    Experiment was conducted to investigate the long-time dissolution effects of water-eluviated and acid-eluviated kaolinite with batch method in malic acid solution. The results showed that malic acid significantly enhanced Al and Si release from kaolinite, and release of Al and Si from kaolinite increased with the increase of concentration of malic acid. Acid-eluviated kaolinite was more easily dissolved than that of water-eluviated kaolinite. When the concentration of malic acid was 20 mmol·L-1, after reaction for 936 hours, the release amount of Al and Si from water-eluviated kaolinite was 0.51 mmol·L-1 and 0.57 mmol·L-1, which were 86.44% and 83.82% of the release amount of Al and Si from acid-eluviated kaolinite. The preferential Si-release of kaolinite was observed initially, but at reaction anaphase, when the concentration of malic acid were less than 20 mmol/L, Al and Si showed stoichiometric release. Dissolution rate of kaolinite increased with the increase of concentration of malic acids, and dissolution rate of acid-eluviated kaolinite was higher than that of water-eluviated kaolinite; the dissolution rate didn't show the character of saturation, and the dissolution rate indiated the increasing character of linearity; malic acid significantly enhanced Al and Si release from kaolinite, and the acid-eluviated kaolinite was more easily dissolved than water-eluviated kaolinite in the malic acids reactive solution.%采用间歇法(batch method)模拟研究水洗和酸洗高岭石在苹果酸溶液中的长期溶解效应及其相对溶解能力.结果表明,水洗和酸水高岭石反应液中Al、Si离子浓度均随苹果酸浓度的增加而升高,且酸洗高岭石中Al、Si离子更易释放;当苹果酸浓度为20 mmol·L-1时,反应936h后,水洗高岭石Al、Si的释放量为0.51 mmol·L-1和0.57 mmol·L-1,分别是酸洗高岭石Al、Si释放量的86.44%和83.82%.高岭石反应前期表现为Si的优先释放,而在反

  17. Comparison of cytogenetic effects in bone marrow of mice after the flight on the biosatellite "BION-M1" and the ground-based radiobiological experiment

    Science.gov (United States)

    Dorozhkina, Olga; Vorozhtsova, Svetlana; Ivanov, Alexander

    2016-07-01

    During space flight, the astronauts are exposed to radiation exposure at low doses with low dose rates, so one of the actual areas of Radiobiology is research of action of ionizing radiation in low and ultra-low doses. Violation of the chromosome apparatus of living biosystems, ranging from viruses and bacteria to humans, is the most reliable evidence of exposure to ionizing radiation. In this regard, the study of cytogenetic damage in the cells of humans and animals is central to space radiobiology (Fedorenko B.S., 2006). In experiment "BION - M1" by anaphase method was determined level of chromosomal aberrations in bone marrow cells of tibia of mice. Flight duration biosatellite "BION - M1" (Sychev V.N. et al., 2014) was 30 days in Earth orbit. Euthanasia of experimental animals was carried out after 12 hours from the moment of landing satellite by method of cervical dislocation. The level of chromosomal aberrations in vivarium-housed control mice was 1,75 ± 0,6% and 1,8 ± 0,45%, while the mitotic index 1,46 ± 0,09% and 1,53 ± 0,05%. The content of animals in the experiment with onboard equipment led to some increase in aberrant mitosis (2,3 ± 0,4%) and reduction of the mitotic index (1,37 ± 0,02%). In the flight experiment "BION-M1" was a statistically significant increase in level of chromosome aberrations (29,7 ± 4,18%) and a decrease in the mitotic index (0,74 ± 0,07%). According to VA Shurshakova (2014), the radiation dose to mice ranged from 32 to 72 mGy and relate to a range of small doses (ICRP, 2012). In this connection we conducted a series of experiments in the ground conditions, the aim of which was the study of earliest effects of ionizing radiation in vivo in mice irradiated with low doses of γ-irradiation of 10 to 200 mGy in the first 24 hours after exposure, i.e. within the first post-radiation exposure cell cycle. Studies were carried out on adult female mice outbred ICR (CD-1) - SPF category at the age of 4-4.5 months with an average

  18. 黑腹果蝇dCAF-1-p55突变引起果蝇发育迟缓和染色体不稳定性%dCAF-1-p55 is Essential for Drosophila Development and Involved in The Maintenance of Chromosomal Stability

    Institute of Scientific and Technical Information of China (English)

    吴青华; 刘继勇; 陈毅序; 焦仁杰

    2012-01-01

    在真核生物中高度保守的染色质装配因子1 (chromatin assembly factor 1,CAF-1)是染色质装配过程中的组蛋白分子伴侣之一.dCAF-1-p55是果蝇中CAF-1复合物中的最小亚基,它与另外两个亚基dCAF- 1-p 180及dCAF-1-p105一起负责将组蛋白H3/H4组装到新合成的DNA上.除了CAF-1复合物,dCAF-1-p55还参与其他多个复合物的形成,如NURF、PRC2及Sin3-HDAC1.dCAF- 1-p55的这一广泛参与性提示了其功能的多样性和重要性.为了研究dCAF-1-p55的体内功能,我们利用基因靶向敲除技术制备了果蝇dCAF-1-p55突变体.实验结果表明,dCAF-1-p55的缺失导致果蝇发育迟缓并且最终致死.进一步研究发现,在dCA F-1-p55突变细胞中,中期染色体较为松散,姐妹染色单体连接异常,后期染色体不能正常分离.这些缺陷都是与癌症发生密切相关的染色体不稳定性(chromosome instability,CIN)的典型特征.综上所述,我们的研究表明了dCAF-1-p55在果蝇发育过程及维持染色体稳定性方面的重要作用,同时提示该基因具有保护细胞免遭CIN和癌变的潜在功能.%The chromatin assembly factor 1 (CAF-1) is a three-subunit protein complex that functions in chaperoning histone deposition.The smallest subunit of Drosophila CAF-1,dCAF-1-p55,together with the other two subunits dCAF-1-p180 and dCAF-1-p105,participates in the deposition of histone H3 and H4 onto the newly synthesized DNA.In addition to the CAF-1 complex,dCAF-1-p55 is also found in several other complexes such as NURF,PRC2 and Sin3-HDAC1 complex,suggesting that it plays multiple roles other than a histone chaperone.Here we report a new allele of dCA F-1-p55 generated by gene targeting.We show that dCAF-1-p55 loss-of-function led to developmental delay and lethality.Further investigations demonstrated that dCAF-1-p55 deficient cells exhibited defects in metaphase chromosome condensation,sister chromatids association and anaphase chromosomes segregation

  19. Male sterility associated with overexpression of the noncoding $hsr\\omega$ gene in cyst cells of testis of Drosophila melanogaster

    Indian Academy of Sciences (India)

    T. K. Rajendra; K. V. Prasanth; S. C. Lakhotia

    2001-08-01

    Of the several noncoding transcripts produced by the $hsr\\omega$ gene of Drosophila melanogaster, the nucleus-limited > 10-kb hsr-n transcript colocalizes with heterogeneous nuclear RNA binding proteins (hnRNPs) to form fine nucleoplasmic omega speckles. Our earlier studies suggested that the noncoding hsr-n transcripts dynamically regulate the distribution of hnRNPs in active (chromatin bound) and inactive (in omega speckles) compartments. Here we show that a P transposon insertion in this gene’s promoter (at – 130 bp) in the $hsr\\omega^{05241}$ enhancer-trap line had no effect on viability or phenotype of males or females, but the insertion-homozygous males were sterile. Testes of $hsr\\omega^{05241}$ homozygous flies contained nonmotile sperms while their seminal vesicles were empty. RNA : RNA in situ hybridization showed that the somatic cyst cells in testes of the mutant male flies contained significantly higher amounts of hsr-n transcripts, and unlike the characteristic fine omega speckles in other cell types they displayed large clusters of omega speckles as typically seen after heat shock. Two of the hnRNPs, viz. HRB87F and Hrp57A, which are expressed in cyst cells, also formed large clusters in these cells in parallel with the hsr-n transcripts. A complete excision of the P transposon insertion restored male fertility as well as the fine-speckled pattern of omega speckles in the cyst cells. The in situ distribution patterns of these two hnRNPs and several other RNA-binding proteins (Hrp40, Hrb57A, S5, Sxl, SRp55 and Rb97D) were not affected by $hsr\\omega$ mutation in any of the meiotic stages in adult testes. The present studies, however, revealed an unexpected presence (in wild-type as well as mutant) of the functional form of Sxl in primary spermatocytes and an unusual distribution of HRB87F along the retracting spindle during anaphase-telophase of the first meiotic division. It appears that the P transposon insertion in the promoter region causes

  20. Microsporogênese em clones normais e tetraplóides de Hevea brasiliensis Muell.-Arg Microsporo genesis in normal and tetraploid Hevea brasiliensis (Muell.-Arg.

    Directory of Open Access Journals (Sweden)

    Cândida H. T. M. Conagin

    1971-01-01

    in one plant showed a certain percentage of normal first meiotic division, without laggards in anaphase I, but it presented also abnormal sporads containing four microspores and one to four microcytes. It was also observed that pollen grains have four germinal pores and their development stopped at the one-nucleus stage. These observations suggest male sterility for this duplicated clone.

  1. Microsporogenesis in Brachiaria bovonei (Chiov. Robyns and B. subulifolia (Mez Clayton (Poaceae Microsporogênese em Brachiaria bovonei (Chiov. Robyns e B. subulifolia (Mez Clayton (Poaceae

    Directory of Open Access Journals (Sweden)

    Claudicéia Risso-Pascotto

    2009-10-01

    Full Text Available Some African species of Brachiaria have been introduced into the Americas and became the most important forage for pastures in the tropics. New cultivars can be obtained either from direct selections from the natural existing variability in the germplasm collections or from interspecific hybridizations. Polyploidy is predominant in the genus Brachiaria and correlated with apomixis which complicates hybridization. The objective of cytological studies underway on the Brachiaria germplasm collection at Embrapa Beef Cattle is to determine the chromosome number and meiotic behavior of accessions. For the breeding of Brachiaria species, compatible sexual and apomictic accessions need to be identified. Microsporogenesis was evaluated in two accessions of Brachiaria bovonei (BO01 and BO05 and one accession of B. subulifolia (SU01. BO01 is pentaploid (2n = 5x = 45, BO05 is tetraploid (2n = 4x = 36, and SU01 is hexaploid (2n = 6x = 54, derived from x = 9. Meiotic abnormalities typical of polyploids, characterized by precocious chromosome migration to the poles in metaphases, laggard chromosomes in anaphases, and micronuclei in telophases and tetrads, were recorded in high frequency in all the accessions generating unbalanced gametes. Both accessions of B. bovonei presented chromosome stickiness. The results are discussed in the view of the Brachiaria breeding program objectives.Algumas espécies africanas de Brachiaria foram introduzidas nas Américas e tornaram-se importantes pastagens nos trópicos. Novas cultivares podem ser obtidas por seleção direta da variabilidade genética existente na coleção de germoplasma ou por hibridização interespecífica. Poliploidia é predominante no gênero Brachiaria e correlacionada com apomixia, o que complica a hibridização. O objetivo dos estudos citogenéticos na coleção de germoplasma de Brachiaria da Embrapa Gado de Corte é determinar o número de cromossomos e o comportamento meiótico dos acessos. A

  2. 安徽沿江棉区控失型化肥施用技术研究%Research on the Application Technology of Controlled-release Chemical Fertilizer in the Cotton Area along Yangtze River in Anhui Province

    Institute of Scientific and Technical Information of China (English)

    余立祥; 邱冠男; 吴跃进

    2009-01-01

    [目的]研究控失肥在棉区的施用技术,验证控失肥的"控失"效果及其经济效益.[方法]以当地主要推广的抗虫棉品种为供试作物,通过在安徽省沿江棉田进行施肥试验研究了控失肥不同施用方式对棉花产量和效益的影响.[结果]与一次基施全部控失肥相比,将控失肥分3次施用使棉花产量增加了240 kg/hm~2,棉农的净收入增加了156元/hm~2;将控失肥基施,后期追施速效化肥使棉花产量增加了7.04%,棉农的净收入增加了833.4元/hm~2.施用减氮20%的控失肥的棉花的现蕾期提前了6 d,开花期提前了7 d,吐絮期提前了8 d,生育期短了8 d.与施用普通氮肥的棉花相比,施用控失氮肥的棉花的秋桃增加幅度为22.29%~36.31%,皮棉产量增加了27.78%.[结论]该研究为在安徽沿江棉区推广应用控失肥提供了科学依据.%[Objective] The purpose was to research the application technology of controlled-release fertilizer in cotton area and validate its controlled-release effect and economic benefit. [Method] With the insect-resistant cotton varieties mainly popularized in the local place as tested crops, the effect of different application methods of controlled-release fertilizer on the yield and benefit of cotton was researched through carrying out fertilization experiment in the cotton fields along Yangtze River in Anhui Province. [Result] Compared with applying all the controlled-release fertilizer as base fertilizer at the first fertilization, when the controlled-release fertilizer was applied 3 times separately, the cotton yield was increased for 240 kg/hm~2 and the net income of cotton farmers was increased for 156 yuan/hm~2; when the controlled-release fertilizer was applied as base fertilizer and the fast-available chemical fertilizer was dressed in the anaphase, the cotton yield was increased by 7.04% and the net income of cotton farmers was increased for 833.4 yuan/hm~2. The squaring period of cottons applied

  3. 顾客参与企业产品创新的文献回顾和未来展望%Customer Participation in Enterprise Product Innovation:Literature Review and Prospects

    Institute of Scientific and Technical Information of China (English)

    高海霞

    2014-01-01

    Based on the existing research of customer participation in the enterprise product innovation and development , customer participation motivation, participation performance, participation degree were reviewed. Participation motivation includes intrinsic motivation and extrinsic motivation. Participation performance includes time performance and innovation performance , customer participation can speed up new products to market, but the effect of customer participation on innovation performance is necessary to combine the specific industry analysis. Participation degree includes participation breadth , depth and intensity. Customer involvement in innovation process mainly includes the idea generation, product design and development and commercialization. In the early stage of product innovation, the degree of interaction between customers and businesses remain at a high level, in the metaphase and anaphase of product innovation, customer acting as co creators. From idea generation to commercialization, customer participation time, freque-ncy, quantity changes. Based on the above analysis, paper proposed the future research should focus on the integration form of participation, innovation risk, customer participation under network environment and customer citizenship behavior in the process.%文章基于国内外顾客参与企业产品创新的已有研究,对顾客参与产品创新的动机、参与绩效、参与程度进行了重点评述。参与动机既有需求满足等内在动机,又有对奖励的期望等外在动机;参与绩效表现在时间绩效和创新绩效两个维度,顾客参与可以加快新产品上市速度,但顾客参与对创新绩效的影响有必要结合具体的行业进行分析;参与程度分为参与广度、参与深度和参与强度三个方面,顾客参与创新过程主要包括了创意产生、产品设计开发和商业化三个阶段,产品创新前期,顾客与企业的互动程度保持在较高水

  4. 小白菜与大白菜亚种间杂交减数分裂染色体行为观察%Chromosome Behaviors in Meiotic of Pollen Mother Cells in Inter-subspecific Hybridization between Chinese Cabbage and Non-heading Chinese Cabbage

    Institute of Scientific and Technical Information of China (English)

    陈龙正; 徐海; 宋波; 樊小雪

    2015-01-01

    Meiotic behaviors of pollen mother cells ( PMCs) in inter-subspecific hybrid F1 and BC1-3 be⁃tween Chinese cabbage and non-heading Chinese cabbage were studied. It was observed that 90.7%of F1 pollen were stainable, indicating good fertility. The fertility of BC1-3 was gradually increased. 89.1%chro⁃mosome behavior in F1 meiotic PMCs was regular which could explain the good fertility. Abnormal chro⁃mosome behaviors such as double nucleoli, disordered paring in Prophase I, chromosome bridge in meta⁃phase I, segments loss in anaphase I were discovered which could explain the lower fertility of F1 hybrid than normal diploid. 14.3% abnormal chromosome behaviors were found in BC1 generation however very limited in BC2-3 which indicated that it was a repaid process for chromosome behavior of backcross genera⁃tion becoming normal;this result was consistent to phenotype and fertility investigation.%研究了小白菜与大白菜亚种间杂交及回交世代花粉母细胞减数分裂行为,发现杂种F1花粉可染率90.7%,表现出较好的育性;回交BC1-3花粉可染率升高,表明育性逐步提高.F1花粉母细胞减数分裂正常染色体行为细胞数占总观察数的89.1%,这解释了F1具有较好育性的原因.杂种F1减数分裂各个时期会出现不正常现象,如双核仁、配对紊乱、染色体桥、染色体片段丢失等,这在一定程度上可以说明杂种F1育性低于正常二倍体的原因.14.3%的BC1花粉母细胞会出现不正常现象,而BC2-3已经相对正常,极少观察到减数分裂不正常现象,表明在回交过程中染色体稳定是一个快速的过程,这与表型及育性调查结果相吻合.

  5. Observações citológicas em Coffea: XV - Microsporogênese em Coffea arabica L.

    Directory of Open Access Journals (Sweden)

    A. J. T. Mendes

    1950-03-01

    semperflorens and 1.67 in caturra. In anaphase I the 22 pairs of chromosomes were normally separated and in telophase I the chromosomes did not stain well, again making detailed observations difficult. Practically no interkinesis was observed. Following telophase I the chromosomes were observed to contract and entered into anaphase II, that was observed to be normal. The formation of microspores appeared to be normal. After separation of the microspores there occured a division of the nucleus giving origin to two nuclei with 22 chromosomes each. This was observed ot occur three to four days before opening of the flowers. The vegetative nucleus was observed to be large, round, homogeneous, and stain only faintly. The reproductive nucleus was observed to be small, reticulated ; it stained well, and was located at the periphery of the cell. The reproductive nucleus was usually found to be surrounded by a small amount of cytoplasm in a lenticular shape. The division of the reproductive nucleus usually takes place in the pollen tube. Both vegetative and reproductive nuclei were observed to occur in the extremity of pollen tube.

  6. 牦牛HSP27基因的克隆及其在雌性生殖器官中的表达%Cloning of Bos Grunniens HSP27 Gene and Its Expression in the Female Yak Reproductive Organs

    Institute of Scientific and Technical Information of China (English)

    何翃闳; 崔燕; 潘阳阳; 樊江峰; 胡威; 张译夫; 刘鹏刚; 李秦; 余四九

    2015-01-01

    巢、输卵管和子宫组织中均有表达,其中在卵泡期卵巢中的表达量最高,在黄体期子宫中的表达量最低;在不同繁殖周期,牦牛HSP27基因在卵巢中的表达均极显著大于在子宫中的表达,其在卵巢、输卵管和子宫的表达因妊娠而发生了显著变化。【结论】通过与其他物种HSP27基因的同源性对比分析,发现HSP27基因在进化中具有高度保守性,同时也存在种属特异性;通过对HSP27在繁殖周期母牦牛主要生殖器官中的表达情况分析,推测出HSP27可能参与了母牦牛妊娠的调控,为进一步探讨HSP27在牦牛生殖过程中发挥的作用提供了参考资料。%Objective]The objective of this study was carried out to study differences of the expression of Heat Shock Protein 27(HSP27) gene in the main reproductive organs of the female yak under normal physiological conditions by cloning the HSP27 gene and analyzing its biological characteristics.[Method] Samples from the tissues of ipsilateral Ovary, oviduct and uterus during follicular anaphase, luteal anaphase and early pregnancy phase were collected and cDNA were isolated from each of the collected tissues. RT-PCR was used to clone the HSP27 gene, and purified PCR products were cloned on pMDTM18-T Vector to detect the sequence. The genetic characteristics of HSP27 gene were then analyzed utilizing bioinformation software to predict its product protein structure and potential functions. Next, RT-qPCR was employed to reveal the relative expression of HSP27 gene in the main reproductive organ during the reproductive cycle of the yak. Statistical analysis was performed using the software program SPSS (version 19.0, SPSS).[Result]HSP27 gene sequence containing a complete coding sequence, with the coding region length of 450bp (GenBank accession No: KP716832), This length could encode 149 amino acids of which Leucine (10.7%) was the most, and Tryptophan (0.7%) the least abundant. We

  7. 小麦-黑麦1BL/1RS 易位染色体和外源染色体在两个三属杂种中的减数分裂行为%Meiotic Behavior of 1BL/1RS Translocation Chromosome and Alien Chromosome in Two Tri-genera Hybrids

    Institute of Scientific and Technical Information of China (English)

    李义文; 李振声; 贾旭

    2002-01-01

    The behavior of wheat-rye translocation chromosome and alien chromosome including Thinopyrum and Haynaldia chromosome at meiosis was investigated in two hybrids by fluorescence in situ hybridization (FISH). Misdivision of translocation chromosome at anaphase Ⅰ and rye chromatin micronucleus at tetrad stage were observed. A plant with one normal 1BL/1RS translocation chromosome and one 1BL/1RS translocation chromosome deleted about 1/3 of rye chromosome arm in length was identified. One plant with wheat-Thinopyrum non-Robertson translocation chromosome was also detected in the F2 population of Yi4212×Yi4095. That could be the results of unequal misdivision of wheat-rye 1BL/1RS translocation chromosome and Thinopyrum chromosome during meiosis. No interaction between translocation chromosome and alien chromosome at meiosis was supported by the data of the distribution frequencies of translocation chromosome and Thinopyrum or Haynaldia chromosome in the progeny of two hybrids. The results may be useful to cultivate new germplasms with different length of rye 1R short arm and wheat-alien non-Robertson translocation lines under wheat background.%利用荧光原位杂交技术分析了两个小麦-外源种杂种花粉母细胞中1BL/1RS 小麦-黑麦易位染色体和外源染色体包括中间偃麦草(Thinopyrum intermedium (Host) Barkworth & DR Dewey)、簇毛麦(Haynaldia villosa (L.) Schur)染色体的减数分裂行为. 我们首次发现:在减数分裂后期, 1BL/1RS 小麦-黑麦易位染色体发生错分裂,形成两个易位染色单体. 这种错分裂导致易位染色单体在末期Ⅰ分配到两个正在形成的细胞核内,错分裂的易位染色单体进一步形成微核,并在四分体期观察到黑麦的微核出现.从贵农22×遗4095 的F2代植株中检测到一个2n=41的植株,其含有一对1BL/1RS 小麦-黑麦易位染色体,核型分析表明,其中一条黑麦染色体臂比另一条的黑麦染色体臂短1/3左右.在遗4212

  8. 血管性痴呆大鼠认知障碍的N-甲基D-天冬氨酸受体机制%Relationship between hippocampal N - methyl - D - aspartate receptor and cognitive impairment of vascular dementia rat model

    Institute of Scientific and Technical Information of China (English)

    姚国恩; 王景周; 陈曼娥

    2003-01-01

    Aim By establishing a reliable vascular dementia (VD) rat model to study the changes of the N - methyl - D - aspartate receptor1 (NMDAR) mRNA expression in rat's hippocampus, and to provide the theoretical basis for the mechanism of NMDAR's effect on cognitive impairment of VD rat model.Methods The VD rat model was established by improved Pulsinelli's four - vessel occlusion(4VO) method.The changes of memory ability, long - term potentiation (LTP) in CA1 area and the NMDAR1mRNA expression in the hippocampus were examined by computerized shuttle - training case, extracorporeal hippocampal slices method and in situ hybridization. Results Compared with the control group,the (active avoidance response,AAR) in the VD model group was less in the 2nd week,the 4th week and the 2nd month(P< 0.05).It was more obviously at the later two time points (P< 0.01).In the slices of extracorporeal hippocampal CA1 region,LTP detection showed that its injury had happened clearly in VD model group at each time point of the 2nd week, the 4th week and the 2nd month.Compared with the control group, at the 2nd week the mean optical density(OD) of NMDAR1mRNA expression in pyramidal cell layer of hippocampus in the VD model group was increased in the CA1 and CA3 regions,but no changes were found in DG region;at the 4th week and the 2nd month,it was decreased in each region.Conclusion The hippocampal NMDA receptor is related to the cognitive impairment of VD rat model.In the early phase of the brain ischemic - reperfusion injury,the expression of NMDAR mRNA increases,which mediate the exitotoxicity, but it decreases in the anaphase,which might be correlated to the learning and memory impairment of VD.Therefore it supplies the foundation to use antagonist or agonist of EAAs receptor in the VD therapy.%目的观察四血管阻断( four - vessel occulusion,4VO)大鼠海马 N-甲基-D-天冬氨酸受体( N - methyl - D - aspartate receptor, NMDAR)的变化规

  9. 组蛋白H3K9me3在胆管癌发生机制中的作用%The role of histone H3 lysine 9 trimethylation modification on cholangiocarcinoma moleculor mechanism

    Institute of Scientific and Technical Information of China (English)

    李明岳; 鲍世韵; 刘嘉林; 郑锦锋; 许成裘; 余小舫

    2015-01-01

    differences were found in tumor cell compared with normal extrahepatic bile duct cell.In bile duct cancer tissues,six selected oncogenes [calcium binding protein A2 (S100A2),anaphase-promoting complex subunit 2 (ANAPC2),myeloid translocation gene on chromosome 16 (CBFA2T3),Rho GTPase activating protein 4 isoform 2 (ARHGAP),Rap guanine nucleotide exchange factor 3 isoform (RAPGEF3),protein kinase C alpha (PRKCA)] H3K9me3 modifications levelwere:(3.51±3.51) %,(8.45±0.16) %,(0.89 ±0.27) %,(0.66 ±0.22) %,(0.04± 0.01) %,(5.21 ± 1.53) %,there was a statistically significant difference compared with normal bile duct cells.It was the Pearson correlation between selected genes expression and H3K9Me3 modification (r =-0.539) in the turmor cell.Conclusion Compared with normal extrahepatic bile duct cell,there are significant changes in many genes of cholangiocarcinoma cell about histone H3K9Me3 profiling.And resulting in a number of related oncogenes and tumor suppressor genes expression change.

  10. 石油污染对海洋浮游植物群落生长的影响%The impact of oil pollution on marine phytoplankton community growth change

    Institute of Scientific and Technical Information of China (English)

    黄逸君; 陈全震; 曾江宁; 江志兵

    2011-01-01

    correlation between the chlorophyll a and cell density of phytoplankton (P <0.001 ). In addition, the impact of crude oil pollution on phytoplankton varies with time. The phytoplankton communities with low concentration crude oil pollution could recover to grow, as the oil hydrocarbons were decompounded in the anaphase of culture period.

  11. Robertsonian chromosome polymorphism of Akodon molinae (Rodentia: Sigmodontinae: analysis of trivalents in meiotic prophase Polimorfismo cromosómico Robertsoniano de Akodon molinae (Rodentia: Sigmodontinae

    Directory of Open Access Journals (Sweden)

    RAÚL FERNÁNDEZ-DONOSO

    2001-03-01

    association with the XY bivalent. In 70 % of spermatocytes studied, the XY bivalent showed complete pairing between X and Y, with SC formation along the whole length of the Y chromosome. The remaining 30 % showed partial pairing, with an SC length which varied from the common end. Based on these findings and those of previous studies, we discuss: 1.- that the obliged configuration of the trivalent, with SC formation between the short arms of 1a and 1b, helps to assure a quasi normal segregation between 1, 1a and 1b in anaphase I of Ht meiosis; and 2.- that co-existence in trivalents of chromosomes 1, 1a and 1b in Ht individuals, breaks down the structural and functional integrity of the short arms of 1a and 1b, producing an accumulative damage which would also explain the decreased viability of individuals bearing these chromosomesAkodon molinae con 2n = 42-43-44 y FN = 44 presenta un notable polimorfismo en el cromosoma 1 en poblaciones naturales y de laboratorio, los individuos 2n = 42 tienen un par 1 formado por dos cromosomas metacéntricos grandes y son denominados homocigotos simples (SH; los individuos 2n = 43, heterocigotos (Ht, presentan un cromosoma 1 y dos cromosomas subtelocéntricos de tamaño medio 1a and 1b, que son homólogos con los brazos largo y corto del 1, respectivamente; y los individuos 2n = 44 que son los doble homocigotos (DH y presentan dos pares de cromosomas subtelocéntricos 1a y 1b. Análisis de la metafases I y II meióticas han demostrado que se producen segregaciones anómalas con una alta frecuencia en los espermatocitos portadores de los cromosomas 1a and 1b. Ello alteraría a otros procesos, como la gametogénesis, la reproducción y el desarrollo, disminuyendo la viabilidad individual y poblacional de los DH. No ha habido una explicación satisfactoria para estos fenómenos. Para investigar elementos estructurales que pudiesen explicar tales alteraciones segregacionales, se estudió la sinapsis de bivalentes y trivalentes en

  12. 适当保水剂施用和覆盖促进旱作马铃薯生长发育和产量提高%Using water-retaining agent and mulch to improve growth and yield of potato under dry farming

    Institute of Scientific and Technical Information of China (English)

    李倩; 刘景辉; 张磊; 陈勤; 于健; SuryaN.Achary

    2013-01-01

    To explore drought resistant effects of water-retaining agent, straw mulch and plastic film mulch between lines on osmotic substances and plasmas membrane system and yield of potato under dry farming, potato variety ‘Shepody’was used, and totally six treatments such as straw mulch, plastic film mulch between lines, control group, and combined with water-retaining agent were set in the field experiment. The results showed that the value of plasmas membrane permeability was larger at seedling stage, then decreased and increased again from tuber bulking stage. Contents of proline and malonaldehyde presented a gradual increment trend in different growth stages, but content of soluble sugar showed a single-peak curve change. Lower contents of osmotic regulation substances and plasmas membrane permeability were observed in the treatments of plastic mulch between lines combined with water-retaining agent, water-retaining agent, straw mulch, and straw mulch combined with water-retaining agent, all these treatments released drought stress efficiently. Potato growth anaphase, till starch accumulation stage, proline content, soluble sugar content, plasma membrane permeability and malondialdehyde content changes were relatively stable. Compared with control group, the four indexes of plastic mulch between lines combined with water-retaining agent treatment decreased by 15.57%, 6.90%, 42.79%and 17.69%, respectively. The four indexes of water-retaining agent treatment decreased by 2.31%, 5.17%, 10.62% and 8.04%, respectively, which of straw mulch treatment decreased by 28.45%, 3.45%, 51.63% and 25.58%, respectively, and 25.14%, 12.07%, 49.17% and 22.58%, respectively for straw mulch combined with water-retaining agent treatment. At potato mature stage, soil moisture content under straw mulch combined with water-retaining agent treatments changed stably, 0-20 cm soil moisture content under water-retaining agent treatment was higher than that without water-retention agent