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Sample records for tetrahymena meiotic nuclear

  1. Role of apoptosis-inducing factor (AIF in programmed nuclear death during conjugation in Tetrahymena thermophila

    Directory of Open Access Journals (Sweden)

    Endoh Hiroshi

    2010-02-01

    Full Text Available Abstract Background Programmed nuclear death (PND, which is also referred to as nuclear apoptosis, is a remarkable process that occurs in ciliates during sexual reproduction (conjugation. In Tetrahymena thermophila, when the new macronucleus differentiates, the parental macronucleus is selectively eliminated from the cytoplasm of the progeny, concomitant with apoptotic nuclear events. However, the molecular mechanisms underlying these events are not well understood. The parental macronucleus is engulfed by a large autophagosome, which contains numerous mitochondria that have lost their membrane potential. In animals, mitochondrial depolarization precedes apoptotic cell death, which involves DNA fragmentation and subsequent nuclear degradation. Results We focused on the role of mitochondrial apoptosis-inducing factor (AIF during PND in Tetrahymena. The disruption of AIF delays the normal progression of PND, specifically, nuclear condensation and kilobase-size DNA fragmentation. AIF is localized in Tetrahymena mitochondria and is released into the macronucleus prior to nuclear condensation. In addition, AIF associates and co-operates with the mitochondrial DNase to facilitate the degradation of kilobase-size DNA, which is followed by oligonucleosome-size DNA laddering. Conclusions Our results suggest that Tetrahymena AIF plays an important role in the degradation of DNA at an early stage of PND, which supports the notion that the mitochondrion-initiated apoptotic DNA degradation pathway is widely conserved among eukaryotes.

  2. Structural and functional adaptations of the mammalian nuclear envelope to meet the meiotic requirements.

    Science.gov (United States)

    Link, Jana; Jahn, Daniel; Alsheimer, Manfred

    2015-01-01

    Numerous studies in the past years provided definite evidence that the nuclear envelope is much more than just a simple barrier. It rather constitutes a multifunctional platform combining structural and dynamic features to fulfill many fundamental functions such as chromatin organization, regulation of transcription, signaling, but also structural duties like maintaining general nuclear architecture and shape. One additional and, without doubt, highly impressive aspect is the recently identified key function of selected nuclear envelope components in driving meiotic chromosome dynamics, which in turn is essential for accurate recombination and segregation of the homologous chromosomes. Here, we summarize the recent work identifying new key players in meiotic telomere attachment and movement and discuss the latest advances in our understanding of the actual function of the meiotic nuclear envelope.

  3. Depletion of UBC9 Causes Nuclear Defects during the Vegetative and Sexual Life Cycles in Tetrahymena thermophila

    OpenAIRE

    Yang, Qianyi; Nasir, Amjad M.; Coyne, Robert S.; Forney, James D.

    2015-01-01

    Ubc9p is the sole E2-conjugating enzyme for SUMOylation, and its proper function is required for regulating key nuclear events such as transcription, DNA repair, and mitosis. In Tetrahymena thermophila, the genome is separated into a diploid germ line micronucleus (MIC) that divides by mitosis and a polyploid somatic macronucleus (MAC) that divides amitotically. This unusual nuclear organization provides novel opportunities for the study of SUMOylation and Ubc9p function. We identified the UB...

  4. Csm4-dependent telomere movement on nuclear envelope promotes meiotic recombination.

    Directory of Open Access Journals (Sweden)

    Hiromichi Kosaka

    2008-09-01

    Full Text Available During meiotic prophase, chromosomes display rapid movement, and their telomeres attach to the nuclear envelope and cluster to form a "chromosomal bouquet." Little is known about the roles of the chromosome movement and telomere clustering in this phase. In budding yeast, telomere clustering is promoted by a meiosis-specific, telomere-binding protein, Ndj1. Here, we show that a meiosis-specific protein, Csm4, which forms a complex with Ndj1, facilitates bouquet formation. In the absence of Csm4, Ndj1-bound telomeres tether to nuclear envelopes but do not cluster, suggesting that telomere clustering in the meiotic prophase consists of at least two distinct steps: Ndj1-dependent tethering to the nuclear envelope and Csm4-dependent clustering/movement. Similar to Ndj1, Csm4 is required for several distinct steps during meiotic recombination. Our results suggest that Csm4 promotes efficient second-end capture of a double-strand break following a homology search, as well as resolution of the double-Holliday junction during crossover formation. We propose that chromosome movement and associated telomere dynamics at the nuclear envelope promotes the completion of key biochemical steps during meiotic recombination.

  5. Depletion of UBC9 Causes Nuclear Defects during the Vegetative and Sexual Life Cycles in Tetrahymena thermophila.

    Science.gov (United States)

    Yang, Qianyi; Nasir, Amjad M; Coyne, Robert S; Forney, James D

    2015-12-01

    Ubc9p is the sole E2-conjugating enzyme for SUMOylation, and its proper function is required for regulating key nuclear events such as transcription, DNA repair, and mitosis. In Tetrahymena thermophila, the genome is separated into a diploid germ line micronucleus (MIC) that divides by mitosis and a polyploid somatic macronucleus (MAC) that divides amitotically. This unusual nuclear organization provides novel opportunities for the study of SUMOylation and Ubc9p function. We identified the UBC9 gene and demonstrated that its complete deletion from both MIC and MAC genomes is lethal. Rescue of the lethal phenotype with a GFP-UBC9 fusion gene driven by a metallothionein promoter generated a cell line with CdCl2-dependent expression of green fluorescent protein (GFP)-Ubc9p. Depletion of Ubc9p in vegetative cells resulted in the loss of MICs, but MACs continued to divide. In contrast, expression of catalytically inactive Ubc9p resulted in the accumulation of multiple MICs. Critical roles for Ubc9p were also identified during the sexual life cycle of Tetrahymena. Cell lines that were depleted for Ubc9p did not form mating pairs and therefore could not complete any of the subsequent stages of conjugation, including meiosis and macronuclear development. Mating between cells expressing catalytically inactive Ubc9p resulted in arrest during macronuclear development, consistent with our observation that Ubc9p accumulates in the developing macronucleus. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

  6. The Nuclear Cap-Binding Complex Mediates Meiotic Silencing by Unpaired DNA

    Directory of Open Access Journals (Sweden)

    Logan M. Decker

    2017-04-01

    Full Text Available In the filamentous fungus Neurospora crassa, cross walls between individual cells are normally incomplete, making the entire fungal network vulnerable to attack by viruses and selfish DNAs. Accordingly, several genome surveillance mechanisms are maintained to help the fungus combat these repetitive elements. One of these defense mechanisms is called meiotic silencing by unpaired DNA (MSUD, which identifies and silences unpaired genes during meiosis. Utilizing common RNA interference (RNAi proteins, such as Dicer and Argonaute, MSUD targets mRNAs homologous to the unpaired sequence to achieve silencing. In this study, we have identified an additional silencing component, namely the cap-binding complex (CBC. Made up of cap-binding proteins CBP20 and CBP80, CBC associates with the 5′ cap of mRNA transcripts in eukaryotes. The loss of CBC leads to a deficiency in MSUD activity, suggesting its role in mediating silencing. As confirmed in this study, CBC is predominantly nuclear, although it is known to travel in and out of the nucleus to facilitate RNA transport. As seen in animals but not in plants, CBP20’s robust nuclear import depends on CBP80 in Neurospora. CBC interacts with a component (Argonaute of the perinuclear meiotic silencing complex (MSC, directly linking the two cellular factors.

  7. Spliceosomal small nuclear RNAs of Tetrahymena thermophila and some possible snRNA-snRNA base-pairing interactions

    DEFF Research Database (Denmark)

    Orum, H; Nielsen, Henrik; Engberg, J

    1991-01-01

    organisms. Furthermore, secondary structures closely similar to phylogenetically proven models can be inferred from the T. thermophila data. Analysis of the snRNA sequences identifies three potential snRNA-snRNA base-pairing interactions, all of which are consistent with available phylogenetic data. Two......We have identified and characterized the full set of spliceosomal small nuclear RNAs (snRNAs; U1, U2, U4, U5 and U6) from the ciliated protozoan Tetrahymena thermophila. With the exception of U4 snRNA, the sizes of the T. thermophila snRNAs are closely similar to their metazoan homologues. The T....... thermophila snRNAs all have unique 5' ends, which start with an adenine residue. In contrast, with the exception of U6, their 3' ends show some size heterogeneity. The primary sequences of the T. thermophila snRNAs contain the sequence motifs shown, or proposed, to be of functional importance in other...

  8. Structural organization of the genes encoding the small nuclear RNAs U1 to U6 of Tetrahymena thermophila is very similar to that of plant small nuclear RNA genes

    DEFF Research Database (Denmark)

    Orum, H; Nielsen, Henrik; Engberg, J

    1992-01-01

    We report the sequences of the genes encoding the small nuclear RNAs (snRNAs) U1 to U6 of the ciliate Tetrahymena thermophila. The genes of the individual snRNAs exist in two to six slightly different copies per haploid genome. Sequence analyses of the gene-flanking regions indicate that there ar......We report the sequences of the genes encoding the small nuclear RNAs (snRNAs) U1 to U6 of the ciliate Tetrahymena thermophila. The genes of the individual snRNAs exist in two to six slightly different copies per haploid genome. Sequence analyses of the gene-flanking regions indicate...

  9. A Pair of Maternal Chromosomes Derived from Meiotic Nondisjunction in Trisomy 21 Affects Nuclear Architecture and Transcriptional Regulation.

    Science.gov (United States)

    Omori, Sayaka; Tanabe, Hideyuki; Banno, Kimihiko; Tsuji, Ayumi; Nawa, Nobutoshi; Hirata, Katsuya; Kawatani, Keiji; Kokubu, Chikara; Takeda, Junji; Taniguchi, Hidetoshi; Arahori, Hitomi; Wada, Kazuko; Kitabatake, Yasuji; Ozono, Keiichi

    2017-04-10

    Eukaryotic genomes are organised into complex higher-order structures within the nucleus, and the three-dimensional arrangement of chromosomes is functionally important for global gene regulation. The existence of supernumerary chromosome 21 in Down syndrome may perturb the nuclear architecture at different levels, which is normally optimised to maintain the physiological balance of gene expression. However, it has not been clearly elucidated whether and how aberrant configuration of chromosomes affects gene activities. To investigate the effects of trisomy 21 on nuclear organisation and gene expression, we performed three-dimensional fluorescent imaging analysis of chromosome-edited human induced pluripotent stem cells (iPSCs), which enabled identification of the parental origin of the three copies of chromosome 21. We found that two copies of maternal chromosomes resulting from meiotic nondisjunction had a higher tendency to form an adjacent pair and were located relatively distant from the nuclear membrane, suggesting the conserved interaction between these homologous chromosomes. Transcriptional profiling of parental-origin-specific corrected disomy 21 iPSC lines indicated upregulated expression of the maternal alleles for a group of genes, which was accompanied by a fluctuating expression pattern. These results suggest the unique effects of a pair of maternal chromosomes in trisomy 21, which may contribute to the pathological phenotype.

  10. Meiotic abnormalities

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1993-12-31

    Chapter 19, describes meiotic abnormalities. These include nondisjunction of autosomes and sex chromosomes, genetic and environmental causes of nondisjunction, misdivision of the centromere, chromosomally abnormal human sperm, male infertility, parental age, and origin of diploid gametes. 57 refs., 2 figs., 1 tab.

  11. 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.

  12. Distinct functional roles of β-tubulin isotypes in microtubule arrays of Tetrahymena thermophila, a model single-celled organism.

    Science.gov (United States)

    Pucciarelli, Sandra; Ballarini, Patrizia; Sparvoli, Daniela; Barchetta, Sabrina; Yu, Ting; Detrich, H William; Miceli, Cristina

    2012-01-01

    The multi-tubulin hypothesis proposes that each tubulin isotype performs a unique role, or subset of roles, in the universe of microtubule function(s). To test this hypothesis, we are investigating the functions of the recently discovered, noncanonical β-like tubulins (BLTs) of the ciliate, Tetrahymena thermophila. Tetrahymena forms 17 distinct microtubular structures whose assembly had been thought to be based on single α- and β-isotypes. However, completion of the macronuclear genome sequence of Tetrahymena demonstrated that this ciliate possessed a β-tubulin multigene family: two synonymous genes (BTU1 and BTU2) encode the canonical β-tubulin, BTU2, and six genes (BLT1-6) yield five divergent β-tubulin isotypes. In this report, we examine the structural features and functions of two of the BLTs (BLT1 and BLT4) and compare them to those of BTU2. With respect to BTU2, BLT1 and BLT4 had multiple sequence substitutions in their GTP-binding sites, in their interaction surfaces, and in their microtubule-targeting motifs, which together suggest that they have specialized functions. To assess the roles of these tubulins in vivo, we transformed Tetrahymena with expression vectors that direct the synthesis of GFP-tagged versions of the isotypes. We show that GFP-BLT1 and GFP-BLT4 were not detectable in somatic cilia and basal bodies, whereas GFP-BTU2 strongly labeled these structures. During cell division, GFP-BLT1 and GFP-BLT4, but not GFP-BTU2, were incorporated into the microtubule arrays of the macronucleus and into the mitotic apparatus of the micronucleus. GFP-BLT1 also participated in formation of the microtubules of the meiotic apparatus of the micronucleus during conjugation. Partitioning of the isotypes between nuclear and ciliary microtubules was confirmed biochemically. We conclude that Tetrahymena uses a family of distinct β-tubulin isotypes to construct subsets of functionally different microtubules, a result that provides strong support for the multi

  13. Tetrahymena in the classroom.

    Science.gov (United States)

    Smith, Joshua J; Wiley, Emily A; Cassidy-Hanley, Donna M

    2012-01-01

    Tetrahymena has been a useful model in basic research in part due to the fact it is easy to grow in culture and exhibits a range of complex processes, all within a single cell. For these same reasons Tetrahymena has shown enormous potential as a teaching tool for fundamental principles of biology at multiple science education levels that can be integrated into K-12 classrooms and undergraduate and graduate college laboratory courses. These Tetrahymena-based teaching modules are inquiry-based experiences that are also effective at teaching scientific concepts, retaining students in science, and exciting students about the scientific process. Two learning communities have been developed that utilize Tetrahymena-based teaching modules. Advancing Secondary Science Education with Tetrahymena (ASSET) and the Ciliate Genomics Consortium (CGC) have developed modules for K-12 students and college-level curriculums, respectively. These modules range from addressing topics in ecology, taxonomy, and environmental toxicity to more advanced concepts in biochemistry, proteomics, bioinformatics, cell biology, and molecular biology. An overview of the current modules and their learning outcomes are discussed, as are assessment, dissemination, and sustainability strategies for K-12 and college-level curriculum. Copyright © 2012 Elsevier Inc. All rights reserved.

  14. Tetrahymena dynamin-related protein 6 self-assembles ...

    Indian Academy of Sciences (India)

    Usha P Kar

    2017-12-30

    Dec 30, 2017 ... Self-assembly on target membranes is one of the important properties of all dynamin family proteins. Drp6, a dynamin- related protein in Tetrahymena, controls nuclear remodelling and undergoes cycles of assembly/disassembly on the nuclear envelope. To elucidate the mechanism of Drp6 function, we ...

  15. Meiotic cytogenetics in Coprinus cinereus.

    Science.gov (United States)

    Zolan, Miriam E; Pukkila, Patricia J

    2009-01-01

    The basidiomycete fungus Coprinus cinereus has naturally synchronous meiosis and is amenable to analysis using an array of well-developed genetic and molecular tools. In this chapter, we explain in detail the two methods most commonly employed for C. cinereus, staining of intact gill segments and chromosome spreads, with an example of the application of each. We describe iron-hematoxylin staining of intact gill segments for the brightfield examination of meiotic progression, and the use of surface spreads and fluorescence in situ hybridization (FISH) to investigate meiotic chromosome pairing. Gill segments can alternatively be stained with DAPI for the determination of meiotic stage, or propidium iodide for the quantitation of nuclear DNA content, and the chromosome fixation and spreading techniques used for FISH are also suitable for immunolocalization studies of chromosomal proteins.

  16. Increased variability in nuclear DNA content of testis cells and spermatozoa from mice with irregular meiotic segregation

    Energy Technology Data Exchange (ETDEWEB)

    Meistrich, M.L. (Univ. of Texas, Houston); Lake, S.; Steinmetz, L.L.; Gledhill, B.L.

    1978-01-01

    Variability in DNA content of testis cells and sperm from F/sub 1/ hybrids between the laboratory mouse (M. musculus) and the tobacco mouse (M. poschiavinus), has been determined by flow cytometry (FCM). The F/sub 1/ hybrid mouse is known to be heterozygous for seven metacentric chromosomes produced by Robertsonian fusion. Enriched populations of nuclei from late pachytene spermatocytes and round spermatids were obtained by velocity sedimentation. These nuclei, as well as epididymal sperm nuclei and spleen cells, were stained by the acriflavine--Feulgen technique for DNA nd measured by FCM. Peaks in the fluorescence intensity frequency distributions resulting from these measurements were analyzed to determine their mean fluorescence intensities and their widths (coefficients of variation). Because mean intensities of corresponding cell types from M. musculus and the F/sub 1/ hybrids were identical, the average DNA contents were taken to be the same. The average coefficients of variation of the peaks of fluorescence from the pachytene, spermatid, and sperm nuclei and spleen cells from M. musculus animals were about 5%. While the peaks of fluorescence from spleen cells and pachytene nuclei from F/sub 1/ hybrids also had average coefficients of variation of 5%, post-meiotic nuclei from spermatids and spermatozoa had coefficients of variation of 8%. From these results we conclude that, these F/sub 1/ hybrids abnormal meiotic segregation causes an increased variability of 6% in the amount of DNA in the spermatozoa.

  17. LYSOSOMAL PHYSIOLOGY IN TETRAHYMENA

    Science.gov (United States)

    Rothstein, Thomas L.; Blum, J. J.

    1974-01-01

    The ingestion of 14C-labeled 9,10-dimethyl-1,2-benzanthracene particles, the extracellular release of acid phosphatase, ribonuclease, and α-glucosidase, and the egestion of preingested dimethylbenzanthracene particles by Tetrahymena taken from logarithmically growing cultures and resuspended in a dilute salt solution were followed in the presence of several pharmacologic agents. Serotonin, caffeine, and, to a lesser extent, dibutyryl cyclic AMP increased the rate of particle ingestion, but did not alter the rate of release of the three acid hydrolases studied. Added catecholamines did not affect either particle ingestion or acid hydrolase release, but particle ingestion was inhibited by the catecholamine antagonists, dichloroisoproterenol, desmethylimipramine, reserpine, and phenoxybenzamine. These drugs also increased the release of acid phosphatase and ribonuclease in 5-h incubations. Desmethylimipramine acted within 1 h to increase acid hydrolase release, but the effect of dichloroisoproterenol developed more slowly and was secondary to a change in cellular content of the hydrolases. Desmethylimipramine increased the energy of activation for the release of acid phosphatase, while dichloroisoproterenol did not. Both of these drugs enhanced the egestion of preingested dimethylbenzanthracene particles, supporting the view that acid hydrolase release occurs through a cytoproct egestion mechanism. Particle ingestion was also inhibited by colchicine, vinblastine, and cytochalasin B, but these agents had no effect on acid hydrolase release, thus further differentiating the properties of the ingestion mechanism from those of the egestion mechanism. It appears that both microtubules and microfilaments play a role in the ingestion process and that this process may be controlled in part by a cyclic AMP-mediated serotoninergic and adrenergic system. PMID:4152946

  18. Meiotic behavior and pollen fertility of five species in the genus ...

    African Journals Online (AJOL)

    fe

    2011-11-16

    Nov 16, 2011 ... frequency of meiotic abnormalities was recorded in five species. Chromosome bridges, laggards and ... was correlated with meiotic abnormality. Keywords: Epimedium, meiosis, chromosomal abnormality, pollen fertility. .... nuclear membranes reappeared and dyads were formed. In the second division, the ...

  19. Morphological apoptotic characteristics of the post-meiotic micronuclei in Paramecium caudatum.

    Science.gov (United States)

    Gao, Xin; Zhang, Xinjiong; Yang, Xianyu

    2010-08-01

    In a previous study, the apoptotic degeneration of meiotic products outside the paroral region of Paramecium caudatum was indirectly demonstrated by means of "apofluor" staining. In this experiment, conjugating pairs and exconjugants of P. caudatum were stained with either "apofluor" or carbol fuchsin or both to find some direct evidence to demonstrate the apoptotic characteristics of this process. As a result, asynchronous meiotic nuclear degeneration was observed. Furthermore, a number of additional meiotic nuclei were found. Disintegrating/dividing meiotic nuclei outside the paroral region were observed, which might be the origin of these additional meiotic nuclei. Condensed chromatin and disintegrated chromatin attached to the nuclear membrane were also observed in degenerating nuclei, which are the typical morphological characteristics of apoptosis. Comparison of the cells stained by the above two methods indicated that "apofluor"-stained meiotic nuclei could not be detected by carbol fuchsin in some cells, which suggests a time lag between meiotic nuclear DNA degradation and their eventual disappearance. In this study, some direct evidence was found to show that the meiotic nuclear degeneration in P. caudatum is of apoptotic nature, which further confirmed our previous study (Yang et al. 2007) and indicated that morphological apoptotic characteristics discovered in multicellular organisms do exist in unicellular eukaryotic ciliate protozoa. Copyright (c) 2010 Elsevier GmbH. All rights reserved.

  20. DSC1-MCB regulation of meiotic transcription in Schizosaccharomyces pombe.

    Science.gov (United States)

    Cunliffe, L; White, S; McInerny, C J

    2004-02-01

    Meiosis is initiated from the G1 phase of the mitotic cell cycle, and consists of pre-meiotic S-phase followed by two successive nuclear divisions. Here we show that control of gene expression during pre-meiotic S-phase in the fission yeast Schizosaccharomyces pombe is mediated by a DNA synthesis control-like transcription factor complex (DSC1), which acts upon M lu1 cell cycle box (MCB) promoter motifs. Several genes, including rec8+, rec11+, cdc18+, and cdc22+, which contain MCB motifs in their promoter regions, are found to be co-ordinately regulated during pre-meiotic S-phase. Both synthetic and native MCB motifs are shown to confer meiotic-specific transcription on a heterologous reporter gene. A DSC1-like transcription factor complex that binds to MCB motifs was also identified in meiotic cells. The effect of mutating and over-expressing individual components of DSC1 (cdc10+, res1+, res2+, rep1+ and rep2+) on the transcription of cdc22+, rec8+ and rec11+ during meiosis was examined. We found that cdc10+, res2+, rep1+ and rep2+ are required for correct meiotic transcription, while res1+ is not required for this process. This work demonstrates a role for MCB motifs and a DSC1-like transcription factor complex in controlling transcription during meiosis in fission yeast, and suggests a mechanism for how this specific expression occurs.

  1. Metabolism of extracellular phospholipids in Tetrahymena pyriformis

    National Research Council Canada - National Science Library

    Arai, H; Nishikawa, K; Inoue, K; Nozawa, Y; Nojima, S

    1987-01-01

    ...: Cytochalasin B, an inhibitor of endocytosis, suppressed the metabolism almost completely. Phospholipid vesicles were incorporated into a phagosome-like structure in Tetrahymena cells, as observed under an electron microscope...

  2. Regulation of Meiotic Recombination

    Energy Technology Data Exchange (ETDEWEB)

    Gregory p. Copenhaver

    2011-11-09

    Meiotic recombination results in the heritable rearrangement of DNA, primarily through reciprocal exchange between homologous chromosome or gene conversion. In plants these events are critical for ensuring proper chromosome segregation, facilitating DNA repair and providing a basis for genetic diversity. Understanding this fundamental biological mechanism will directly facilitate trait mapping, conventional plant breeding, and development of genetic engineering techniques that will help support the responsible production and conversion of renewable resources for fuels, chemicals, and the conservation of energy (1-3). Substantial progress has been made in understanding the basal recombination machinery, much of which is conserved in organisms as diverse as yeast, plants and mammals (4, 5). Significantly less is known about the factors that regulate how often and where that basal machinery acts on higher eukaryotic chromosomes. One important mechanism for regulating the frequency and distribution of meiotic recombination is crossover interference - or the ability of one recombination event to influence nearby events. The MUS81 gene is thought to play an important role in regulating the influence of interference on crossing over. The immediate goals of this project are to use reverse genetics to identify mutants in two putative MUS81 homologs in the model plant Arabidopsis thaliana, characterize those mutants and initiate a novel forward genetic screen for additional regulators of meiotic recombination. The long-term goal of the project is to understand how meiotic recombination is regulated in higher eukaryotes with an emphasis on the molecular basis of crossover interference. The ability to monitor recombination in all four meiotic products (tetrad analysis) has been a powerful tool in the arsenal of yeast geneticists. Previously, the qrt mutant of Arabidopsis, which causes the four pollen products of male meiosis to remain attached, was developed as a facile system

  3. Metabolism of extracellular phospholipids in Tetrahymena pyriformis.

    Science.gov (United States)

    Arai, H; Nishikawa, K; Inoue, K; Nozawa, Y; Nojima, S

    1987-05-01

    We studied the metabolism of phospholipids exogenously added to cultures of the protozoan, Tetrahymena pyriformis. Tetrahymena cells were found to metabolize the extracellular phospholipids and the fatty acyl chains of the latter were accumulated predominantly as a form of triacylglycerol in the cells. This metabolism was considered to be initiated via endocytosis of phospholipid vesicles, as judged from the following facts: Cytochalasin B, an inhibitor of endocytosis, suppressed the metabolism almost completely. Phospholipid vesicles were incorporated into a phagosome-like structure in Tetrahymena cells, as observed under an electron microscope. When phospholipids doubly labeled with 14C and 3H at the glycerol moiety and fatty acyl chain, respectively, were incubated with Tetrahymena cells, the glycerol moiety and fatty acyl chain at the sn-2-position of the exogenous phospholipids were incorporated into the cellular triacylglycerol fraction in a 1 to 1 ratio. Monoacylglycerol acyltransferase activity was detected in the microsomal fraction of Tetrahymena cells. From these results, together with those of our previous study on lysosomal phospholipid hydrolysis in Tetrahymena (J. Biochem. 99, 125-133 (1986)), it is suggested that the extracellular phospholipids which were taken up by the cells via endocytosis were hydrolyzed through the action of lysosomal phospholipases A1 and C, and also that one of the products, sn-2-monoacylglycerol, served as an acyl acceptor for the synthesis of triacylglycerol via the microsomal "monoacylglycerol pathway."

  4. Reduced meiotic fitness in hybrids with heterozygosity for ...

    Indian Academy of Sciences (India)

    Unknown

    hybrids between M. terricolor I and II have meiotic abnormalities as in the F1 male hybrids, though to a lesser extent. They show difference in pairing abnormalities in the different karyotypic forms; the backcross hybrids heterozygous for the .... Nuclear condensation in spermatocytes, coarse chromatin clumped and pycnotic ...

  5. A Link between Meiotic Prophase Progression and CrossoverControl

    Energy Technology Data Exchange (ETDEWEB)

    Carlton, Peter M.; Farruggio, Alfonso P.; Dernburg, Abby F.

    2005-07-06

    During meiosis, most organisms ensure that homologous chromosomes undergo at least one exchange of DNA, or crossover, to link chromosomes together and accomplish proper segregation. How each chromosome receives a minimum of one crossover is unknown. During early meiosis in Caenorhabditis elegans and many other species, chromosomes adopt a polarized organization within the nucleus, which normally disappears upon completion of homolog synapsis. Mutations that impair synapsis even between a single pair of chromosomes in C. elegans delay this nuclear reorganization. We quantified this delay by developing a classification scheme for discrete stages of meiosis. Immunofluorescence localization of RAD-51 protein revealed that delayed meiotic cells also contained persistent recombination intermediates. Through genetic analysis, we found that this cytological delay in meiotic progression requires double-strand breaks and the function of the crossover-promoting heteroduplex HIM-14 (Msh4) and MSH-5. Failure of X chromosome synapsis also resulted in impaired crossover control on autosomes, which may result from greater numbers and persistence of recombination intermediates in the delayed nuclei. We conclude that maturation of recombination events on chromosomes promotes meiotic progression, and is coupled to the regulation of crossover number and placement. Our results have broad implications for the interpretation of meiotic mutants, as we have shown that asynapsis of a single chromosome pair can exert global effects on meiotic progression and recombination frequency.

  6. The key role of CYC2 during meiosis in Tetrahymena thermophila.

    Science.gov (United States)

    Xu, Qianlan; Wang, Ruoyu; Ghanam, A R; Yan, Guanxiong; Miao, Wei; Song, Xiaoyuan

    2016-04-01

    Meiotic recombination is carried out through a specialized pathway for the formation and repair of DNA double-strand breaks (DSBs) made by the Spo11 protein. The present study shed light on the functional role of cyclin, CYC2, in Tetrahymena thermophila which has transcriptionally high expression level during meiosis process. Knocking out the CYC2 gene results in arrest of meiotic conjugation process at 2.5-3.5 h after conjugation initiation, before the meiosis division starts, and in company with the absence of DSBs. To investigate the underlying mechanism of this phenomenon, a complete transcriptome profile was performed between wild-type strain and CYC2 knock-out strain. Functional analysis of RNA-Seq results identifies related differentially expressed genes (DEGs) including SPO11 and these DEGs are enriched in DNA repair/mismatch repair (MMR) terms in homologous recombination (HR), which indicates that CYC2 could play a crucial role in meiosis by regulating SPO11 and participating in HR.

  7. Modules for C-terminal epitope tagging of Tetrahymena genes

    OpenAIRE

    Kataoka, Kensuke; Schoeberl, Ursula E.; Mochizuki, Kazufumi

    2010-01-01

    Although epitope tagging has been widely used for analyzing protein function in many organisms, there are few genetic tools for epitope tagging in Tetrahymena. In this study, we describe several C-terminal epitope tagging modules that can be used to express tagged proteins in Tetrahymena cells by both plasmid- and PCR-based strategies.

  8. Modules for C-terminal epitope tagging of Tetrahymena genes.

    Science.gov (United States)

    Kataoka, Kensuke; Schoeberl, Ursula E; Mochizuki, Kazufumi

    2010-09-01

    Although epitope tagging has been widely used for analyzing protein function in many organisms, there are few genetic tools for epitope tagging in Tetrahymena. In this study, we describe several C-terminal epitope tagging modules that can be used to express tagged proteins in Tetrahymena cells by both plasmid- and PCR-based strategies. (c) 2010 Elsevier B.V. All rights reserved.

  9. Meiotic behaviour of tetraploid wheats (Triticum turgidum L.) and ...

    Indian Academy of Sciences (India)

    Meiotic aberrations such as laggards, chromosome bridges, micronuclei, abnormal cytokines, chromatin pulling and meiotic restitution were observed and the studied genotypes were accordingly ranked as follows: triticale > synthetic hexaploid wheats > tetraploid wheats possessing meiotic restitution > tetraploid wheats ...

  10. Calcium Signaling and Meiotic Exit at Fertilization in Xenopus Egg

    Science.gov (United States)

    Tokmakov, Alexander A.; Stefanov, Vasily E.; Iwasaki, Tetsushi; Sato, Ken-Ichi; Fukami, Yasuo

    2014-01-01

    Calcium is a universal messenger that mediates egg activation at fertilization in all sexually reproducing species studied. However, signaling pathways leading to calcium generation and the mechanisms of calcium-induced exit from meiotic arrest vary substantially among species. Here, we review the pathways of calcium signaling and the mechanisms of meiotic exit at fertilization in the eggs of the established developmental model, African clawed frog, Xenopus laevis. We also discuss calcium involvement in the early fertilization-induced events in Xenopus egg, such as membrane depolarization, the increase in intracellular pH, cortical granule exocytosis, cortical contraction, contraction wave, cortical rotation, reformation of the nuclear envelope, sperm chromatin decondensation and sister chromatid segregation. PMID:25322156

  11. Analysis of the Basidiomycete Coprinopsis cinerea reveals conservation of the core meiotic expression program over half a billion years of evolution.

    Directory of Open Access Journals (Sweden)

    Claire Burns

    2010-09-01

    Full Text Available Coprinopsis cinerea (also known as Coprinus cinereus is a multicellular basidiomycete mushroom particularly suited to the study of meiosis due to its synchronous meiotic development and prolonged prophase. We examined the 15-hour meiotic transcriptional program of C. cinerea, encompassing time points prior to haploid nuclear fusion though tetrad formation, using a 70-mer oligonucleotide microarray. As with other organisms, a large proportion (∼20% of genes are differentially regulated during this developmental process, with successive waves of transcription apparent in nine transcriptional clusters, including one enriched for meiotic functions. C. cinerea and the fungi Saccharomyces cerevisiae and Schizosaccharomyces pombe diverged ∼500-900 million years ago, permitting a comparison of transcriptional programs across a broad evolutionary time scale. Previous studies of S. cerevisiae and S. pombe compared genes that were induced upon entry into meiosis; inclusion of C. cinerea data indicates that meiotic genes are more conserved in their patterns of induction across species than genes not known to be meiotic. In addition, we found that meiotic genes are significantly more conserved in their transcript profiles than genes not known to be meiotic, which indicates a remarkable conservation of the meiotic process across evolutionarily distant organisms. Overall, meiotic function genes are more conserved in both induction and transcript profile than genes not known to be meiotic. However, of 50 meiotic function genes that were co-induced in all three species, 41 transcript profiles were well-correlated in at least two of the three species, but only a single gene (rad50 exhibited coordinated induction and well-correlated transcript profiles in all three species, indicating that co-induction does not necessarily predict correlated expression or vice versa. Differences may reflect differences in meiotic mechanisms or new roles for paralogs

  12. The fission yeast MTREC and EJC orthologs ensure the maturation of meiotic transcripts during meiosis.

    Science.gov (United States)

    Marayati, Bahjat Fadi; Hoskins, Victoria; Boger, Robert W; Tucker, James F; Fishman, Emily S; Bray, Andrew S; Zhang, Ke

    2016-09-01

    Meiosis is a highly regulated process by which genetic information is transmitted through sexual reproduction. It encompasses unique mechanisms that do not occur in vegetative cells, producing a distinct, well-regulated meiotic transcriptome. During vegetative growth, many meiotic genes are constitutively transcribed, but most of the resulting mRNAs are rapidly eliminated by the Mmi1-MTREC (Mtl1-Red1 core) complex. While Mmi1-MTREC targets premature meiotic RNAs for degradation by the nuclear 3'-5' exoribonuclease exosome during mitotic growth, its role in meiotic gene expression during meiosis is not known. Here, we report that Red5, an essential MTREC component, interacts with pFal1, an ortholog of eukaryotic translation initiation factor eIF4aIII in the fission yeast Schizosaccharomyces pombe In mammals, together with MAGO (Mnh1), Rnps1, and Y14, elF4AIII (pFal1) forms the core of the exon junction complex (EJC), which is essential for transcriptional surveillance and localization of mature mRNAs. In fission yeast, two EJC orthologs, pFal1 and Mnh1, are functionally connected with MTREC, specifically in the process of meiotic gene expression during meiosis. Although pFal1 interacts with Mnh1, Y14, and Rnps1, its association with Mnh1 is not disrupted upon loss of Y14 or Rnps1. Mutations of Red1, Red5, pFal1, or Mnh1 produce severe meiotic defects; the abundance of meiotic transcripts during meiosis decreases; and mRNA maturation processes such as splicing are impaired. Since studying meiosis in mammalian germline cells is difficult, our findings in fission yeast may help to define the general mechanisms involved in accurate meiotic gene expression in higher eukaryotes. © 2016 Marayati et al.; Published by Cold Spring Harbor Laboratory Press for the RNA Society.

  13. MEIOTIC BEHAVIOUR OF ERAGROSTIS TEF AND ERAGROSTIS ...

    African Journals Online (AJOL)

    Administrator

    tillers than the parental lines which are the manifestation of meiotic stability in the hybrid and the subsequent generations. Pollen fertility test of the parental lines and selected recombinant inbred lines of E. tef and E. pilosa cross was also high (90 - 95%), which are an indication of regular meiotic chromosome division.

  14. Citrate synthase purified from Tetrahymena mitochondria is identical with Tetrahymena 14-nm filament protein.

    Science.gov (United States)

    Kojima, H; Chiba, J; Watanabe, Y; Numata, O

    1995-07-01

    A 14-nm filament protein (designated as 49K protein) was purified from a ciliated protozoan, Tetrahymena, using the polymerization and depolymerization procedure. Previous studies in our laboratory showed that its primary structure shared a high sequence identity with citrate synthases known so far and that the 49K protein possessed citrate synthase activity. To ascertain whether or not Tetrahymena's mitochondrial citrate synthase is identical to the 49K protein, citrate synthase was purified from Tetrahymena mitochondria using ammonium sulfate fractionation, Butyl-Toyopearl and SP-Toyopearl column chromatographies, based on monitoring of the enzymatic activity. The molecular weight of the purified citrate synthase was estimated to be 49 kDa, as was that of the 49K protein and the enzyme cross-reacted with an anti-49K protein antiserum. The purified citrate synthase showed much the same optimum pH, optimum KCl concentration, effects of substrate concentrations (acetyl-CoA and oxaloacetate), and inhibitory effect by ATP as those of purified 49K protein. Furthermore, an anti-49K protein monoclonal antibody strongly suppressed the enzymatic activity of the purified citrate synthase. Thus, we suggest that mitochondrial citrate synthase and the 49K protein are identical and that the 49K protein has dual functions in the cytoskeleton in cytoplasm and as a TCA cycle enzyme, citrate synthase, in mitochondria.

  15. Initiation of meiotic recombination in Ustilago maydis

    National Research Council Canada - National Science Library

    Kojic, Milorad; Sutherland, Jeanette H; Pérez-Martín, José; Holloman, William K

    2013-01-01

    .... Ustilago maydis, a biotrophic fungus that parasitizes maize, has long been utilized as an experimental system for studying recombination, but it has not been clear when in the life cycle meiotic recombination initiates. U...

  16. Transcriptional activation in Drosophila spermatogenesis involves the mutually dependent function of aly and a novel meiotic arrest gene cookie monster.

    Science.gov (United States)

    Jiang, Jianqiao; White-Cooper, Helen

    2003-02-01

    In Drosophila spermatogenesis, meiotic cell cycle progression and cellular differentiation are linked by the function of the meiotic arrest genes. The meiotic arrest genes control differentiation by regulating the transcriptional activation of many differentiation-specific genes. The meiotic arrest genes have been subdivided into aly and can classes, based on the mechanism by which they control cell cycle progression. aly has previously been shown to encode a chromatin-associated protein. We present the identification, cloning and characterisation of a novel Drosophila meiotic arrest gene, cookie monster (comr), that has a mutant phenotype indistinguishable from that of aly. A null mutant allele of comr is viable but male sterile. Mutant primary spermatocytes fail to initiate transcription of a large number of genes, and arrest before entry into the meiotic divisions. In adult males, expression of comr is testis specific, low levels of transcripts are detected at other stages of development. comr encodes a novel acidic protein, which is nuclear and primarily localised to regions of chromatin in primary spermatocytes. The nuclear localisation of Aly and Comr proteins are mutually dependent. Finally, we show that active RNA polymerase II is found in distinct domains in the nucleus that constitute a subset of the total Comr stained chromatin.

  17. Spermatogenesis-specific features of the meiotic program in Caenorhabditis elegans.

    Directory of Open Access Journals (Sweden)

    Diane C Shakes

    2009-08-01

    Full Text Available In most sexually reproducing organisms, the fundamental process of meiosis is implemented concurrently with two differentiation programs that occur at different rates and generate distinct cell types, sperm and oocytes. However, little is known about how the meiotic program is influenced by such contrasting developmental programs. Here we present a detailed timeline of late meiotic prophase during spermatogenesis in Caenorhabditis elegans using cytological and molecular landmarks to interrelate changes in chromosome dynamics with germ cell cellularization, spindle formation, and cell cycle transitions. This analysis expands our understanding C. elegans spermatogenesis, as it identifies multiple spermatogenesis-specific features of the meiotic program and provides a framework for comparative studies. Post-pachytene chromatin of spermatocytes is distinct from that of oocytes in both composition and morphology. Strikingly, C. elegans spermatogenesis includes a previously undescribed karyosome stage, a common but poorly understood feature of meiosis in many organisms. We find that karyosome formation, in which chromosomes form a constricted mass within an intact nuclear envelope, follows desynapsis, involves a global down-regulation of transcription, and may support the sequential activation of multiple kinases that prepare spermatocytes for meiotic divisions. In spermatocytes, the presence of centrioles alters both the relative timing of meiotic spindle assembly and its ultimate structure. These microtubule differences are accompanied by differences in kinetochores, which connect microtubules to chromosomes. The sperm-specific features of meiosis revealed here illuminate how the underlying molecular machinery required for meiosis is differentially regulated in each sex.

  18. Bovine oocyte vitrification before or after meiotic arrest: effects on ultrastructure and developmental ability

    OpenAIRE

    Díez, Carmen; Duque, Paloma; Gómez, Enrique; Hidalgo, C.O. (Carlos); Tamargo, Carolina; Rodríguez, Aida; Fernández, Lina; Varga, Santiago; Fernández, Alba; Facal, Nieves; Carbajo, Maite

    2011-01-01

    The nuclear stage at which oocytes are cryopreserved influences further development ability and cryopreservation affects ultrastructure of both cumulus cells and the oocyte. In this work, we analyze the effects of vitrification at different nuclear and cytoplasmic maturation stages on the oocyte ultrastructure and developmental ability. Culture in TCM199 + PVA with roscovitine 25 M during 24 h led to meiotic arrest (MA) in cumulus-oocyte complexes (COCs), while permissive in vitro...

  19. Biochemical and molecular characterisation of Tetrahymena thermophila extracellular cysteine proteases

    Directory of Open Access Journals (Sweden)

    Tiedtke Arno

    2006-02-01

    Full Text Available Abstract Background Over the last decades molecular biologic techniques have been developed to alter the genome and proteome of Tetrahymena thermophila thereby providing the basis for recombinant protein expression including functional human enzymes. The biotechnological potential of Tetrahymena has been proved in numerous publications, demonstrating fast growth, high biomass, fermentation in ordinary bacterial/yeast equipment, up-scalability, existence of cheap and chemical defined media. For these reasons Tetrahymena offers promising opportunities for the development of a high expression system. Yet optimised high yield strains with protease deficiency such as commonly used in yeast and bacterial systems are not available. Results This work presents the molecular identification of predominant proteases secreted into the medium by Tetrahymena thermophila. A one-step purification of the proteolytic enzymes is described. Conclusion The information provided will allow silencing of protease activity by either knock out methods or by Tetrahymena specific antisense-ribosome-techniques. This will facilitate the next step in the advancement of this exciting organism for recombinant protein production.

  20. Targeting of liposomes containing methotrexate towards Tetrahymena pyriformis cells.

    Science.gov (United States)

    Kotsifaki, H; Kapoulas, V; Deliconstantinos, G

    1985-01-01

    The uptake of liposomes containing methotrexate by Tetrahymena pyriformis cells was investigated with the aim of producing liposome-cell association enabling methotrexate to be introduced into the cytoplasm of intact cells. Incubation of liposomes containing methotrexate with tetrahymena pyriformis cells resulted in a time and concentration-dependent uptake of entrapped methotrexate by the cells. The uptake by Tetrahymena pyriformis cells (at 1 hr) of liposomes prepared by phospholipids and gangliosides extracted from Tetrahymena pyriformis cells was approximately three fold higher than that of liposomes prepared by commercial phospholipids. Approximately 90% of liposome uptake could be inhibited by cytochalasin B and also by NaN3 and 2-deoxyglucose. This was consistent with the uptake being the result of endocytosis. The remaining uptake was probably the result of adhesion of liposomes to the cell membrane. The rate of efflux vs time of methotrexate entrapped in liposomes was much slower than that of free methotrexate which reinforces the concept that endocytosis is the main mode of liposomes uptake by the cells. Liposomes containing methotrexate at concentrations as low as 4.5 microM effectively inhibited the activity of dihydrofolate reductase which was used as a function parameter in this study. Similar inhibition of the enzyme activity by free methotrexate was achieved only at concentrations as high as 880 microM. The influence of liposomes lipid composition on the targeting of liposomes to Tetrahymena pyriformis cells was discussed.

  1. Female meiotic sex chromosome inactivation in chicken.

    Directory of Open Access Journals (Sweden)

    Sam Schoenmakers

    2009-05-01

    Full Text Available During meiotic prophase in male mammals, the heterologous X and Y chromosomes remain largely unsynapsed, and meiotic sex chromosome inactivation (MSCI leads to formation of the transcriptionally silenced XY body. In birds, the heterogametic sex is female, carrying Z and W chromosomes (ZW, whereas males have the homogametic ZZ constitution. During chicken oogenesis, the heterologous ZW pair reaches a state of complete heterologous synapsis, and this might enable maintenance of transcription of Z- and W chromosomal genes during meiotic prophase. Herein, we show that the ZW pair is transiently silenced, from early pachytene to early diplotene using immunocytochemistry and gene expression analyses. We propose that ZW inactivation is most likely achieved via spreading of heterochromatin from the W on the Z chromosome. Also, persistent meiotic DNA double-strand breaks (DSBs may contribute to silencing of Z. Surprisingly, gammaH2AX, a marker of DSBs, and also the earliest histone modification that is associated with XY body formation in mammalian and marsupial spermatocytes, does not cover the ZW during the synapsed stage. However, when the ZW pair starts to desynapse, a second wave of gammaH2AX accumulates on the unsynapsed regions of Z, which also show a reappearance of the DSB repair protein RAD51. This indicates that repair of meiotic DSBs on the heterologous part of Z is postponed until late pachytene/diplotene, possibly to avoid recombination with regions on the heterologously synapsed W chromosome. Two days after entering diplotene, the Z looses gammaH2AX and shows reactivation. This is the first report of meiotic sex chromosome inactivation in a species with female heterogamety, providing evidence that this mechanism is not specific to spermatogenesis. It also indicates the presence of an evolutionary force that drives meiotic sex chromosome inactivation independent of the final achievement of synapsis.

  2. Chromosomal association of Ran during meiotic and mitotic divisions.

    Science.gov (United States)

    Hinkle, Beth; Slepchenko, Boris; Rolls, Melissa M; Walther, Tobias C; Stein, Pascal A; Mehlmann, Lisa M; Ellenberg, Jan; Terasaki, Mark

    2002-12-01

    Recent studies in Xenopus egg extracts indicate that the small G protein Ran has a central role in spindle assembly and nuclear envelope reformation. We determined Ran localization and dynamics in cells during M phase. By immunofluorescence, Ran is accumulated on the chromosomes of meiosis-II-arrested Xenopus eggs. In living cells, fluorescently labeled Ran associated with the chromosomes in Xenopus and remained associated during anaphase when eggs were artificially activated. Fluorescent Ran associated with chromosomes in mouse eggs, during meiotic maturation and early embryonic divisions in starfish, and to a lesser degree during mitosis of a cultured mammalian cell line. Chromosomal Ran undergoes constant flux. From photobleach experiments in immature starfish oocytes, chromosomal Ran has a k(off) of approximately 0.06 second(-1), and binding analysis suggests that there is a single major site. The chromosomal interactions may serve to keep Ran-GTP in the vicinity of the chromosomes for spindle assembly and nuclear envelope reformation.

  3. Induction of anti-actin drug resistance in Tetrahymena.

    Science.gov (United States)

    Zackroff, Robert V; Hufnagel, Linda A

    2002-01-01

    Both cytochalasin D and latrunculin B reversibly inhibited Tetrahymena phagocytosis at concentrations similar to those effective in mammalian systems, even though ciliate actins are known to be highly divergent from mammalian actins. Overnight exposure to relatively low (0.25 microM) concentrations of latrunculin B induced resistance in Tetrahymena to the inhibitory effects of that drug, as well as cross-resistance to cytochalasin D. However, much higher (> 30 microM) concentrations of cytochalasin D were required for induction of cross-resistance to latrunculin B. Anti-actin drug resistance in Tetrahymena may involve a general multidrug resistance mechanism and/or specific feedback regulation of F-actin assembly and stability.

  4. Epigenetic control of meiotic recombination in plants.

    Science.gov (United States)

    Yelina, Natasha; Diaz, Patrick; Lambing, Christophe; Henderson, Ian R

    2015-03-01

    Meiotic recombination is a deeply conserved process within eukaryotes that has a profound effect on patterns of natural genetic variation. During meiosis homologous chromosomes pair and undergo DNA double strand breaks generated by the Spo11 endonuclease. These breaks can be repaired as crossovers that result in reciprocal exchange between chromosomes. The frequency of recombination along chromosomes is highly variable, for example, crossovers are rarely observed in heterochromatin and the centromeric regions. Recent work in plants has shown that crossover hotspots occur in gene promoters and are associated with specific chromatin modifications, including H2A.Z. Meiotic chromosomes are also organized in loop-base arrays connected to an underlying chromosome axis, which likely interacts with chromatin to organize patterns of recombination. Therefore, epigenetic information exerts a major influence on patterns of meiotic recombination along chromosomes, genetic variation within populations and evolution of plant genomes.

  5. Initiation of Meiotic Recombination in Mammals

    Directory of Open Access Journals (Sweden)

    Rajeev Kumar

    2010-12-01

    Full Text Available Meiotic recombination is initiated by the induction of programmed DNA double strand breaks (DSBs. DSB repair promotes homologous interactions and pairing and leads to the formation of crossovers (COs, which are required for the proper reductional segregation at the first meiotic division. In mammals, several hundred DSBs are generated at the beginning of meiotic prophase by the catalytic activity of SPO11. Currently it is not well understood how the frequency and timing of DSB formation and their localization are regulated. Several approaches in humans and mice have provided an extensive description of the localization of initiation events based on CO mapping, leading to the identification and characterization of preferred sites (hotspots of initiation. This review presents the current knowledge about the proteins known to be involved in this process, the sites where initiation takes place, and the factors that control hotspot localization.

  6. Nuclear dimorphism: two peas in a pod.

    Science.gov (United States)

    Goldfarb, David S; Gorovsky, Martin A

    2009-06-09

    The macro- and micronuclei of Tetrahymena reside in the same cytoplasm but are about as different as night and day. This extreme case of nuclear dimorphism can now be partially attributed to differences in the subunit compositions of their nuclear pore complexes.

  7. Small phosphatidate phosphatase (TtPAH2) of Tetrahymena ...

    Indian Academy of Sciences (India)

    Phosphatidate phosphatases (PAH) play a central role in lipid metabolism and intracellular signaling. Herein, we report thepresence of a low-molecular-weight PAH homolog in the single-celled ciliate Tetrahymena thermophila. In vitro phosphataseassay showed that TtPAH2 belongs to the magnesium-dependent ...

  8. Human male meiotic sex chromosome inactivation.

    NARCIS (Netherlands)

    Vries, M. de; Vosters, S.; Merkx, G.F.M.; Hauwers, K.W.M. d'; Wansink, D.G.; Ramos, L.; Boer, P. de

    2012-01-01

    In mammalian male gametogenesis the sex chromosomes are distinctive in both gene activity and epigenetic strategy. At first meiotic prophase the heteromorphic X and Y chromosomes are placed in a separate chromatin domain called the XY body. In this process, X,Y chromatin becomes highly

  9. Initiation of meiotic recombination in Ustilago maydis.

    Science.gov (United States)

    Kojic, Milorad; Sutherland, Jeanette H; Pérez-Martín, José; Holloman, William K

    2013-12-01

    A central feature of meiosis is the pairing and recombination of homologous chromosomes. Ustilago maydis, a biotrophic fungus that parasitizes maize, has long been utilized as an experimental system for studying recombination, but it has not been clear when in the life cycle meiotic recombination initiates. U. maydis forms dormant diploid teliospores as the end product of the infection process. Upon germination, teliospores complete meiosis to produce four haploid basidiospores. Here we asked whether the meiotic process begins when teliospores germinate or at an earlier stage in development. When teliospores homozygous for a cdc45 mutation temperature sensitive for DNA synthesis were germinated at the restrictive temperature, four nuclei became visible. This implies that teliospores have already undergone premeiotic DNA synthesis and suggests that meiotic recombination initiates at a stage of infection before teliospores mature. Determination of homologous recombination in plant tissue infected with U. maydis strains heteroallelic for the nar1 gene revealed that Nar(+) recombinants were produced at a stage before teliospore maturation. Teliospores obtained from a spo11Δ cross were still able to germinate but the process was highly disturbed and the meiotic products were imbalanced in chromosomal complement. These results show that in U. maydis, homologous recombination initiates during the infection process and that meiosis can proceed even in the absence of Spo11, but with loss of genomic integrity.

  10. Polyploidization increases meiotic recombination frequency in Arabidopsis

    Directory of Open Access Journals (Sweden)

    Rehmsmeier Marc

    2011-04-01

    Full Text Available Abstract Background Polyploidization is the multiplication of the whole chromosome complement and has occurred frequently in vascular plants. Maintenance of stable polyploid state over generations requires special mechanisms to control pairing and distribution of more than two homologous chromosomes during meiosis. Since a minimal number of crossover events is essential for correct chromosome segregation, we investigated whether polyploidy has an influence on the frequency of meiotic recombination. Results Using two genetically linked transgenes providing seed-specific fluorescence, we compared a high number of progeny from diploid and tetraploid Arabidopsis plants. We show that rates of meiotic recombination in reciprocal crosses of genetically identical diploid and autotetraploid Arabidopsis plants were significantly higher in tetraploids compared to diploids. Although male and female gametogenesis differ substantially in meiotic recombination frequency, both rates were equally increased in tetraploids. To investigate whether multivalent formation in autotetraploids was responsible for the increased recombination rates, we also performed corresponding experiments with allotetraploid plants showing strict bivalent pairing. We found similarly increased rates in auto- and allotetraploids, suggesting that the ploidy effect is independent of chromosome pairing configurations. Conclusions The evolutionary success of polyploid plants in nature and under domestication has been attributed to buffering of mutations and sub- and neo-functionalization of duplicated genes. Should the data described here be representative for polyploid plants, enhanced meiotic recombination, and the resulting rapid creation of genetic diversity, could have also contributed to their prevalence.

  11. Homeostatic regulation of meiotic DSB formation by ATM/ATR

    Energy Technology Data Exchange (ETDEWEB)

    Cooper, Tim J.; Wardell, Kayleigh; Garcia, Valerie; Neale, Matthew J., E-mail: m.neale@sussex.ac.uk

    2014-11-15

    Ataxia–telangiectasia mutated (ATM) and RAD3-related (ATR) are widely known as being central players in the mitotic DNA damage response (DDR), mounting responses to DNA double-strand breaks (DSBs) and single-stranded DNA (ssDNA) respectively. The DDR signalling cascade couples cell cycle control to damage-sensing and repair processes in order to prevent untimely cell cycle progression while damage still persists [1]. Both ATM/ATR are, however, also emerging as essential factors in the process of meiosis; a specialised cell cycle programme responsible for the formation of haploid gametes via two sequential nuclear divisions. Central to achieving accurate meiotic chromosome segregation is the introduction of numerous DSBs spread across the genome by the evolutionarily conserved enzyme, Spo11. This review seeks to explore and address how cells utilise ATM/ATR pathways to regulate Spo11-DSB formation, establish DSB homeostasis and ensure meiosis is completed unperturbed.

  12. Transgenerational function of Tetrahymena Piwi protein Twi8p at distinctive noncoding RNA loci.

    Science.gov (United States)

    Farley, Brian M; Collins, Kathleen

    2017-04-01

    Transgenerational transmission of genome-regulatory epigenetic information can determine phenotypes in the progeny of sexual reproduction. Sequence specificity of transgenerational regulation derives from small RNAs assembled into Piwi-protein complexes. Known targets of transgenerational regulation are primarily transposons and transposon-derived sequences. Here, we extend the scope of Piwi-mediated transgenerational regulation to include unique noncoding RNA loci. Ciliates such as Tetrahymena have a phenotypically silent germline micronucleus and an expressed somatic macronucleus, which is differentiated anew from a germline genome copy in sexual reproduction. We show that the nuclear-localized Tetrahymena Piwi protein Twi8p shuttles from parental to zygotic macronuclei. Genetic elimination of Twi8p has no phenotype for cells in asexual growth. On the other hand, cells lacking Twi8p arrest in sexual reproduction with zygotic nuclei that retain the germline genome structure, without the DNA elimination and fragmentation required to generate a functional macronucleus. Twi8p-bound small RNAs originate from long-noncoding RNAs with a terminal hairpin, which become detectable in the absence of Twi8p. Curiously, the loci that generate Twi8p-bound small RNAs are essential for asexual cell growth, even though Twi8 RNPs are essential only in sexual reproduction. Our findings suggest the model that Twi8 RNPs act on silent germline chromosomes to permit their conversion to expressed macronuclear chromosomes. Overall this work reveals that a Piwi protein carrying small RNAs from long-noncoding RNA loci has transgenerational function in establishing zygotic nucleus competence for gene expression. © 2017 Farley and Collins; Published by Cold Spring Harbor Laboratory Press for the RNA Society.

  13. Human male meiotic sex chromosome inactivation.

    Directory of Open Access Journals (Sweden)

    Marieke de Vries

    Full Text Available In mammalian male gametogenesis the sex chromosomes are distinctive in both gene activity and epigenetic strategy. At first meiotic prophase the heteromorphic X and Y chromosomes are placed in a separate chromatin domain called the XY body. In this process, X,Y chromatin becomes highly phosphorylated at S139 of H2AX leading to the repression of gonosomal genes, a process known as meiotic sex chromosome inactivation (MSCI, which has been studied best in mice. Post-meiotically this repression is largely maintained. Disturbance of MSCI in mice leads to harmful X,Y gene expression, eventuating in spermatocyte death and sperm heterogeneity. Sperm heterogeneity is a characteristic of the human male. For this reason we were interested in the efficiency of MSCI in human primary spermatocytes. We investigated MSCI in pachytene spermatocytes of seven probands: four infertile men and three fertile controls, using direct and indirect in situ methods. A considerable degree of variation in the degree of MSCI was detected, both between and within probands. Moreover, in post-meiotic stages this variation was observed as well, indicating survival of spermatocytes with incompletely inactivated sex chromosomes. Furthermore, we investigated the presence of H3K9me3 posttranslational modifications on the X and Y chromatin. Contrary to constitutive centromeric heterochromatin, this heterochromatin marker did not specifically accumulate on the XY body, with the exception of the heterochromatic part of the Y chromosome. This may reflect the lower degree of MSCI in man compared to mouse. These results point at relaxation of MSCI, which can be explained by genetic changes in sex chromosome composition during evolution and candidates as a mechanism behind human sperm heterogeneity.

  14. Meiotic Recombination in the Giraffe (G. reticulata).

    Science.gov (United States)

    Vozdova, Miluse; Fröhlich, Jan; Kubickova, Svatava; Sebestova, Hana; Rubes, Jiri

    2017-01-01

    Recently, the reticulated giraffe (G. reticulata) was identified as a distinct species, which emphasized the need for intensive research in this interesting animal. To shed light on the meiotic process as a source of biodiversity, we analysed the frequency and distribution of meiotic recombination in 2 reticulated giraffe males. We used immunofluorescence detection of synaptonemal complex protein (SYCP3), meiotic double strand breaks (DSB, marked as RAD51 foci) in leptonema, and crossovers (COs, as MLH1 foci) in pachynema. The mean number of autosomal MLH1 foci per cell (27), which resulted from a single, distally located MLH1 focus observed on most chromosome arms, is one of the lowest among mammalian species analysed so far. The CO/DSB conversion ratio was 0.32. The pseudoautosomal region was localised in the Xq and Yp termini by FISH and showed an MLH1 focus in 83% of the pachytene cells. Chromatin structures corresponding to the nucleolus organiser regions were observed in the pachytene spermatocytes. The results are discussed in the context of known data on meiosis in Cetartiodactyla, depicting that the variation in CO frequency among species of this taxonomic group is mostly associated with their diploid chromosome number. © 2017 S. Karger AG, Basel.

  15. Inhibition of Tetrahymena pyriformis growth by Aliphatic Alcohols ...

    African Journals Online (AJOL)

    Une étude Relation Quantitative Structure- Activité (QSAR) a été réalisée pour évaluer la toxicité relative d'un mélange composé de 21 alcools (à chaînes linéaires et ramifiées) et 9 amines aliphatiques normales, en terme de concentration d'inhibition 50% de la croissance (IGC50) de Tetrahymena pyriformis . L'approche ...

  16. Comparative Proteome Bioinformatics: Identification of Phosphotyrosine Signaling Proteins in the Unicellular Protozoan Ciliate Tetrahymena

    DEFF Research Database (Denmark)

    Gammeltoft, Steen; Christensen, Søren Tvorup; Joachimiak, Marcin

    2005-01-01

    Tetrahymena, bioinformatics, cilia, evolution, signaling, TtPTK1, PTK, Grb2, SH-PTP 2, Plcy, Src, PTP, PI3K, SH2, SH3, PH......Tetrahymena, bioinformatics, cilia, evolution, signaling, TtPTK1, PTK, Grb2, SH-PTP 2, Plcy, Src, PTP, PI3K, SH2, SH3, PH...

  17. HIM-8 binds to the X chromosome pairing center and mediateschromosome-specific meiotic synapsis

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, Carolyn M.; Wong, Chihunt; Bhalla, Needhi; Carlton,Peter M.; Weiser, Pinky; Meneely, Philip M.; Dernburg, Abby F.

    2005-06-05

    The him-8 gene is essential for proper meiotic segregationof the X chromosomes in C. elegans. Herewe show that loss of him-8function causes profound X-chromosome-specific defects in homolog pairingand synapsis.him-8 encodes a C2H2 zinc finger protein that is expressedduring meiosis andconcentrates at a site on the X chromosome known as themeiotic Pairing Center (PC). A role for HIM-8 in PC function is supportedby genetic interactions between PC lesions and him-8 mutations.HIM-8-bound chromosome sites associate with the nuclear envelope (NE)throughout meiotic prophase. Surprisingly, a point mutation in him-8 thatretains both chromosome binding and NE localization fails to stabilizepairing or promote synapsis. These observations indicate thatstabilization of homolog pairing is an active process in which thetethering of chromosome sites to the NE may be necessary but is notsufficient.

  18. Meiotic chromosome behaviour and sexual sterility in two Nigerian ...

    African Journals Online (AJOL)

    The behaviour of meiotic chromosomes and the subsequent behaviour of the meiotic products were investigated in two Nigerian species of Aloe, namely Aloe keayi and Aloe macrocarpa var major with a view to uncovering the cause of their inability to reproduce sexually. The two plant materials used in this study were ...

  19. Comparative study of infection with Tetrahymena of different ornamental fish species.

    Science.gov (United States)

    Sharon, G; Pimenta Leibowitz, M; Chettri, J Kumar; Isakov, N; Zilberg, D

    2014-01-01

    Tetrahymena is a ciliated protozoan that can infect a wide range of fish species, although it is most commonly reported in guppies (Poecilia reticulata). The aim of this study was to compare the susceptibility to infection with Tetrahymena of five different ornamental fish species from two different super orders. The species examined were platy (Xiphophorus), molly (Poecilia sphenops) and angelfish (Pterophyllum scalare) of the Acanthopterygii super order (which also includes guppies) and goldfish (Carassius auratus auratus) and koi carp (Cyprinus carpio) of the Ostariophysi super order. These two super orders are phylogenetically distant from each other. Infection with Tetrahymena resulted in parasite invasion of internal organs, skin and muscle in all fish species. A relatively strong inflammatory response was observed in infected goldfish and koi, with negligible response in fish species of the Acanthopterygii super order. Guppies were the most susceptible to Tetrahymena infection, exhibiting a mortality rate of 87% and 100% in two separate experiments. A high mortality rate was also observed in platy (77%), while that of molly and angelfish was significantly lower (23% and 33%, respectively). Goldfish and koi carp were less susceptible to infection compared with guppies (24% and 59% mortality, respectively). Immunization studies revealed that the Tetrahymena are immunogenic, since infection of koi carp increased their Tetrahymena immobilization response by approximately three-fold at 3 weeks post infection, while immunization with Tetrahymena plus adjuvant increased their immobilization response by approximately 30-fold. Copyright © 2013 Elsevier Ltd. All rights reserved.

  20. Analysis of meiosis in SUN1 deficient mice reveals a distinct role of SUN2 in mammalian meiotic LINC complex formation and function.

    Directory of Open Access Journals (Sweden)

    Jana Link

    2014-02-01

    Full Text Available LINC complexes are evolutionarily conserved nuclear envelope bridges, composed of SUN (Sad-1/UNC-84 and KASH (Klarsicht/ANC-1/Syne/homology domain proteins. They are crucial for nuclear positioning and nuclear shape determination, and also mediate nuclear envelope (NE attachment of meiotic telomeres, essential for driving homolog synapsis and recombination. In mice, SUN1 and SUN2 are the only SUN domain proteins expressed during meiosis, sharing their localization with meiosis-specific KASH5. Recent studies have shown that loss of SUN1 severely interferes with meiotic processes. Absence of SUN1 provokes defective telomere attachment and causes infertility. Here, we report that meiotic telomere attachment is not entirely lost in mice deficient for SUN1, but numerous telomeres are still attached to the NE through SUN2/KASH5-LINC complexes. In Sun1(-/- meiocytes attached telomeres retained the capacity to form bouquet-like clusters. Furthermore, we could detect significant numbers of late meiotic recombination events in Sun1(-/- mice. Together, this indicates that even in the absence of SUN1 telomere attachment and their movement within the nuclear envelope per se can be functional.

  1. Protective immunization against Tetrahymena sp. infection in guppies (Poecilia reticulata).

    Science.gov (United States)

    Chettri, J Kumar; Leibowitz, M Pimenta; Ofir, R; Zilberg, D

    2009-08-01

    Systemic tetrahymenosis constitutes a serious problem in guppy (Poecilia reticulata) production worldwide and no therapeutic solution is available for this disease. Three immunization trials were conducted, testing the effectiveness of different Tetrahymena preparations applied by intraperitoneal injection (IP) with or without Freund's complete adjuvant (FCA) and with or without booster dose. In trial 1, immunization with the pathogenic Tet-NI 6 lysate and live attenuated Tet-NI 1 did not provide significant protection from infection, although infection rates were significantly lower in the Tet-NI 6-immunized group than in controls. In trial 2, mortality in Tet-NI 6 + FCA-immunized fish was 10%, significantly lower than in all other treatment groups, including Tet-NI 6 lysate, live attenuated Tet-NI 1 and controls (77, 67 and 73%, respectively). In trial 3, the lowest mortality rates were obtained in the Tet-NI 6 + FCA + booster-immunized group (15%). These levels were lower but not significantly different from the non-boostered Tet-NI 6-immunized group (28%) and the groups immunized with Tet-NI 1, with and without booster (32 and 34%, respectively). Mortality in these four groups was significantly lower than in controls, including adjuvant- and PBS-injected groups (72 and 81%, respectively). Body homogenates of immunized fish immobilized Tetrahymena in-vitro, as compared to no or very little immobilization in controls. Lysozyme levels in the Tet-NI 6 + FCA + booster group were significantly higher than in all other treatments in trial 2 and controls in trial 3. There was no significant difference in anti-protease activity among the differently immunized fish. We conclude that immunization with Tetrahymena lysates in FCA confers a high degree of protection from infection, suggesting this preparation as a basis for vaccine development.

  2. Radiation-induced inhibition of RNA synthesis in Tetrahymena pyriformis.

    Science.gov (United States)

    Ernst, S G; Rustad, R C; Oleinick, N L

    1975-07-01

    Radiation-induced disturbances in RNA synthesis were investigated in exponentially growing Tetrahymena. Sub-lethal doses of gamma-radiation lead to a transient, dose-dependent decrease in the rate of total RNA synthesis measured by 3H-uridine incorporation, without an alteration of 3H-uridine uptake by the cells. The rate of 3H-uridine incorporation decreases exponentially with dose. In contrast, the duration of inhibition of RNA synthesis is linearly dependent on dose. Target-theory calculations suggest that the sensitive molecule has a molecular weight of about 2 X 10(7) Daltons.

  3. Experimental identification and analysis of macronuclear non-coding RNAs from the ciliate Tetrahymena thermophila

    DEFF Research Database (Denmark)

    Andersen, Kasper Langebjerg; Nielsen, Henrik

    2012-01-01

    The ciliate Tetrahymena thermophila is an important eukaryotic model organism that has been used in pioneering studies of general phenomena, such as ribozymes, telomeres, chromatin structure and genome reorganization. Recent work has shown that Tetrahymena has many classes of small RNA molecules...... class was small nucleolar RNAs (snoRNAs), many of which are formed by an unusual maturation pathway. The modifications guided by the snoRNAs were analyzed bioinformatically and experimentally and many Tetrahymena-specific modifications were found, including several in an essential, but not conserved...

  4. Meiotic recombination, synapsis, meiotic inactivation and sperm aneuploidy in a chromosome 1 inversion carrier.

    Science.gov (United States)

    Kirkpatrick, Gordon; Chow, Victor; Ma, Sai

    2012-01-01

    Disrupted meiotic behaviour of inversion carriers may be responsible for suboptimal sperm parameters in these carriers. This study investigated meiotic recombination, synapsis, transcriptional silencing and chromosome segregation effects in a pericentric inv(1) carrier. Recombination (MLH1), synapsis (SYCP1, SYCP3) and transcriptional inactivation (γH2AX, BRCA1) were examined by fluorescence immunostaining. Chromosome specific rates of recombination were determined by fluorescence in-situ hybridization. Furthermore, testicular sperm was examined for aneuploidy and segregation of the inv(1). Our findings showed that global recombination rates were similar to controls. Recombination on the inv(1) and the sex chromosomes were reduced. The inv(1) associated with the XY body in 43.4% of cells, in which XY recombination was disproportionately absent, and 94.3% of cells displayed asynapsed regions which displayed meiotic silencing regardless of their association with the XY body. Furthermore, a low frequency of chromosomal imbalance was observed in spermatozoa (3.4%). Our results suggest that certain inversion carriers may display unimpaired global recombination and impaired recombination on the involved and the sex chromosomes during meiosis. Asynapsis or inversion-loop formation in the inverted region may be responsible for impaired spermatogenesis and may prevent sperm-chromosome imbalance. Copyright © 2011 Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved.

  5. Isolation and characterization of the actin gene from Tetrahymena thermophila

    Science.gov (United States)

    Cupples, Claire G.; Pearlman, Ronald E.

    1986-01-01

    The macronucleus of Tetrahymena thermophila contains a single actin gene. We have isolated this gene from a partial plasmid library by using the yeast actin gene as a probe. The nucleotide sequence of the gene has been determined and the amino acid sequence of the potential protein deduced. The encoded protein is 375 amino acids long, one amino acid longer than the yeast actin. It is one of the most divergent actins sequenced to date, being only 75% homologous to yeast actin. Unlike the actin genes from most other organisms, it does not contain introns. The coding region contains TAA and TAG codons; the translation termination codon is TGA. Comparison of the amino acid sequence of the Tetrahymena actin with that of actins from other organisms suggests that TAG may code for glutamic acid. The gene is transcribed from multiple initiation sites between 57 and 98 nucleotides upstream of the translation start codon. The 5′ flanking region is very A+T-rich and contains numerous “TATA-like” sequences upstream of the transcription start sites. Images PMID:16593729

  6. Netrin-1 Peptide Is a Chemorepellent in Tetrahymena thermophila

    Directory of Open Access Journals (Sweden)

    Heather Kuruvilla

    2016-01-01

    Full Text Available Netrin-1 is a highly conserved, pleiotropic signaling molecule that can serve as a neuronal chemorepellent during vertebrate development. In vertebrates, chemorepellent signaling is mediated through the tyrosine kinase, src-1, and the tyrosine phosphatase, shp-2. Tetrahymena thermophila has been used as a model system for chemorepellent signaling because its avoidance response is easily characterized under a light microscope. Our experiments showed that netrin-1 peptide is a chemorepellent in T. thermophila at micromolar concentrations. T. thermophila adapts to netrin-1 over a time course of about 10 minutes. Netrin-adapted cells still avoid GTP, PACAP-38, and nociceptin, suggesting that netrin does not use the same signaling machinery as any of these other repellents. Avoidance of netrin-1 peptide was effectively eliminated by the addition of the tyrosine kinase inhibitor, genistein, to the assay buffer; however, immunostaining using an anti-phosphotyrosine antibody showed similar fluorescence levels in control and netrin-1 exposed cells, suggesting that tyrosine phosphorylation is not required for signaling to occur. In addition, ELISA indicates that a netrin-like peptide is present in both whole cell extract and secreted protein obtained from Tetrahymena thermophila. Further study will be required in order to fully elucidate the signaling mechanism of netrin-1 peptide in this organism.

  7. Establishment of a Cre/loxP recombination system for N-terminal epitope tagging of genes in Tetrahymena.

    Science.gov (United States)

    Busch, Clara Jana-Lui; Vogt, Alexander; Mochizuki, Kazufumi

    2010-07-13

    Epitope tagging is a powerful strategy to study the function of proteins. Although tools for C-terminal protein tagging in the ciliated protozoan Tetrahymena thermophila have been developed, N-terminal protein tagging in this organism is still technically demanding. In this study, we have established a Cre/loxP recombination system in Tetrahymena and have applied this system for the N-terminal epitope tagging of Tetrahymena genes. Cre can be expressed in Tetrahymena and localizes to the macronucleus where it induces precise recombination at two loxP sequences in direct orientation in the Tetrahymena macronuclear chromosome. This Cre/loxP recombination can be used to remove a loxP-flanked drug-resistance marker from an N-terminal tagging construct after it is integrated into the macronucleus. The system established in this study allows us to express an N-terminal epitope tagged gene from its own endogenous promoter in Tetrahymena.

  8. Self-organization of dynein motors generates meiotic nuclear oscillations

    National Research Council Canada - National Science Library

    Vogel, Sven K; Pavin, Nenad; Maghelli, Nicola; Jülicher, Frank; Tolić-Nørrelykke, Iva M

    2009-01-01

    .... We report a mechanism of these oscillations on the basis of collective behavior of dynein motors linking the cell cortex and dynamic microtubules that extend from the spindle pole body in opposite directions...

  9. Establishment of a Cre/loxP recombination system for N-terminal epitope tagging of genes in Tetrahymena

    OpenAIRE

    Mochizuki Kazufumi; Vogt Alexander; Busch Clara

    2010-01-01

    Abstract Background Epitope tagging is a powerful strategy to study the function of proteins. Although tools for C-terminal protein tagging in the ciliated protozoan Tetrahymena thermophila have been developed, N-terminal protein tagging in this organism is still technically demanding. Results In this study, we have established a Cre/loxP recombination system in Tetrahymena and have applied this system for the N-terminal epitope tagging of Tetrahymena genes. Cre can be expressed in Tetrahymen...

  10. The role of meiotic drive in hybrid male sterility

    National Research Council Canada - National Science Library

    Shannon R. McDermott; Mohamed A. F. Noor

    2010-01-01

    .... Although the hypothesis that meiotic drive may contribute to hybrid sterility, and thus species formation, fell out of favour early in the 1990s, recent results showing an association between drive...

  11. Meiotic chromosome pairing is promoted by telomere-led chromosome movements independent of bouquet formation.

    Directory of Open Access Journals (Sweden)

    Chih-Ying Lee

    Full Text Available Chromosome pairing in meiotic prophase is a prerequisite for the high fidelity of chromosome segregation that haploidizes the genome prior to gamete formation. In the budding yeast Saccharomyces cerevisiae, as in most multicellular eukaryotes, homologous pairing at the cytological level reflects the contemporaneous search for homology at the molecular level, where DNA double-strand broken ends find and interact with templates for repair on homologous chromosomes. Synapsis (synaptonemal complex formation stabilizes pairing and supports DNA repair. The bouquet stage, where telomeres have formed a transient single cluster early in meiotic prophase, and telomere-promoted rapid meiotic prophase chromosome movements (RPMs are prominent temporal correlates of pairing and synapsis. The bouquet has long been thought to contribute to the kinetics of pairing, but the individual roles of bouquet and RPMs are difficult to assess because of common dependencies. For example, in budding yeast RPMs and bouquet both require the broadly conserved SUN protein Mps3 as well as Ndj1 and Csm4, which link telomeres to the cytoskeleton through the intact nuclear envelope. We find that mutants in these genes provide a graded series of RPM activity: wild-type>mps3-dCC>mps3-dAR>ndj1Δ>mps3-dNT = csm4Δ. Pairing rates are directly correlated with RPM activity even though only wild-type forms a bouquet, suggesting that RPMs promote homologous pairing directly while the bouquet plays at most a minor role in Saccharomyces cerevisiae. A new collision trap assay demonstrates that RPMs generate homologous and heterologous chromosome collisions in or before the earliest stages of prophase, suggesting that RPMs contribute to pairing by stirring the nuclear contents to aid the recombination-mediated homology search.

  12. Cytological techniques to study human female meiotic prophase.

    Science.gov (United States)

    Roig, Ignasi; Garcia-Caldés, Montserrat

    2009-01-01

    Most of the human aneuploidies have a maternal origin. This feature makes the study of human female meiosis a fundamental topic to understand the reasons leading to this important social problem. Unfortunately, due to sample collection difficulties, not many studies have been performed on human female meiotic prophase. In this chapter we present a comprehensive collection of protocols that allows the study of human female meiotic prophase through different technical approaches using both spread and structurally preserved oocytes.

  13. pH-dependent effects of 2,4-dinitrophenol (DNP) on proliferation, endocytosis, fine structure and DNP resistance in Tetrahymena

    DEFF Research Database (Denmark)

    Nilsson, Jytte R.

    1995-01-01

    Biologi, 2,4-dinitrophenol, pH-dependence, fine structure, cell proliferation, phagocytosis, Tetrahymena pyriformis......Biologi, 2,4-dinitrophenol, pH-dependence, fine structure, cell proliferation, phagocytosis, Tetrahymena pyriformis...

  14. The zinc finger protein Zfr1p is localized specifically to conjugation junction and required for sexual development in Tetrahymena thermophila.

    Directory of Open Access Journals (Sweden)

    Jing Xu

    Full Text Available Conjugation in Tetrahymena thermophila involves a developmental program consisting of three prezygotic nuclear divisions, pronuclear exchange and fusion, and postzygotic and exconjugant stages. The conjugation junction structure appears during the initiation of conjugation development, and disappears during the exconjugant stage. Many structural and functional proteins are involved in the establishment and maintenance of the junction structure in T. thermophila. In the present study, a zinc finger protein-encoding gene ZFR1 was found to be expressed specifically during conjugation and to localize specifically to the conjugation junction region. Truncated Zfr1p localized at the plasma membrane in ordered arrays and decorated Golgi apparatus located adjacent to basal body. The N-terminal zinc finger and C-terminal hydrophobic domains of Zfr1p were found to be required for its specific conjugation junction localization. Conjugation development of ZFR1 somatic knockout cells was aborted at the pronuclear exchange and fusion conjugation stages. Furthermore, Zfr1p was found to be important for conjugation junction stability during the prezygotic nuclear division stage. Taken together, our data reveal that Zfr1p is required for the stability and integrity of the conjugation junction structure and essential for the sexual life cycle of the Tetrahymena cell.

  15. Bovine oocyte vitrification before or after meiotic arrest: effects on ultrastructure and developmental ability.

    Science.gov (United States)

    Diez, Carmen; Duque, Paloma; Gómez, Enrique; Hidalgo, Carlos O; Tamargo, Carolina; Rodríguez, Aida; Fernández, Lina; de la Varga, Santiago; Fernández, Alba; Facal, Nieves; Carbajo, Maite

    2005-07-15

    The nuclear stage at which oocytes are cryopreserved influences further development ability and cryopreservation affects ultrastructure of both cumulus cells and the oocyte. In this work, we analyze the effects of vitrification at different nuclear and cytoplasmic maturation stages on the oocyte ultrastructure and developmental ability. Culture in TCM199 + PVA with roscovitine 25 M during 24h led to meiotic arrest (MA) in cumulus-oocyte complexes (COCs), while permissive in vitro maturation (IVM) was performed in TCM199, 10% FCS, FSH-LH and 17beta-estradiol for 24 h. Oocytes were vitrified using the open pulled straw method (OPS) with minor modifications. Fresh and vitrified/warmed COCs were fixed as immature, after IVM, after meiotic arrest (MA) and after MA + IVM. Vitrification combined with MA followed by IVM produced the highest rates of degeneration, regardless of the vitrification time. As a consequence, lower proportions of embryos cleaved in these groups, although differences were eliminated at the five-eight cell stage. Development rates up to day 8 were similar in all experimental groups, being significantly lower than those in fresh controls. Only oocytes vitrified after IVM were able to give blastociysts. The morphological alterations observed can be responsible for compromised development. More research is needed to explain the low survival rates of the bovine oocyte after vitrification and warming.

  16. Biochanin a and Daidzein Influence Meiotic Maturation of Pig Oocytes in a Different Manner

    Directory of Open Access Journals (Sweden)

    Hošková K.

    2014-09-01

    Full Text Available The aim of the study was to determine the influence of different concentrations of phytoestrogens biochanin A (BIO A; 20, 40, 50μg ml-1 and daidzein (DAI; 10, 20, 40, 50μg ml-1 on the course of meiotic maturation of pig oocytes. After a 24-hour cultivation, a stage of nuclear maturation was achieved and the areas of cumulus-oocyte complexes (COCs, as an indicator of cumulus expansion, were evaluated. The effects of both contaminants on oocytes were mani - fested from the lowest concentration used. Nuclear maturation was inhibited in a dose-dependent manner in the case of BIO A. Effects of DAI reached a plateau at a concentration of 20μg ml-1.Possible relationship to limited solubility of DAI was excluded because limits of DAI solubility in culture medium were confirmed at 50 μg ml-1.The cumulus expansion was also influenced in a different manner - reduction of the COC’s area by BIO A was dose-dependent, whereas DAI had the strongest effect on CCs in the lowest and highest concentrations used. Both phytoestrogens negatively influence the meiotic maturation of porcine oocytes but there are significant differences in their concrete effects which could relate to the diverse mechanisms of their acting on target cells.

  17. A dynamic meiotic SUN belt includes the zygotene-stage telomere bouquet and is disrupted in chromosome segregation mutants of maize (Zea mays L..

    Directory of Open Access Journals (Sweden)

    Shaun Patrick Murphy

    2014-07-01

    Full Text Available The nuclear envelope (NE plays an essential role in meiotic telomere behavior and links the cytoplasm and nucleoplasm during homologous chromosome pairing and recombination in many eukaryotic species. Resident NE proteins including SUN (Sad-1/UNC-84 and KASH (Klarsicht/ANC-1/Syne-homology domain proteins are known to interact forming the Linker of Nucleoskeleton and Cytoskeleton (LINC complex that connects chromatin to the cytoskeleton. To investigate the possible cross-kingdom conservation of SUN protein functions in plant meiosis, we immunolocalized maize SUN2 using 3D microscopy of pollen mother cells from maize (Zea mays L., a large-genome plant model with a canonical NE zygotene-stage telomere bouquet. We detected SUN2 at the nuclear periphery and found that it exhibited a distinct belt-like structure that transitioned to a half-belt during the zygotene stage and back to a full belt during and beyond the pachytene stage. The zygotene-stage half-belt SUN structure was shown by 3D immuno-FISH to include the NE-associated telomere cluster that defines the bouquet stage and coincides with homologous chromosome synapsis. Microtubule and filamentous actin staining patterns did not show any obvious belt or a retracted-like structure other than a general enrichment of tubulin staining distributed widely around the nucleus and throughout the cytoplasm. Genetic disruption of the meiotic SUN belt staining patterns with three different meiosis-specific mutants, desynaptic (dy1, asynaptic1 (as1, and divergent spindle1 (dv1 provides additional evidence for the role of the nuclear envelope in meiotic chromosome behavior. Taking into account all of the observations from this study, we propose that the maize SUN belt is directly or indirectly involved in meiotic telomere dynamics, chromosome synapsis, and possibly integration of signals and forces across the meiotic prophase nuclear envelope.

  18. The incorporation of myo-inositol into phosphatidylinositol derivatives is stimulated during hormone-induced meiotic maturation of amphibian oocytes

    Energy Technology Data Exchange (ETDEWEB)

    Carrasco, D.; Allende, C.C.; Allende, J.E. (Universidad de Chile, Casilla, Santiago (Chile))

    1990-12-01

    The incorporation of myo-({sup 3}H)inositol into phosphatidylinositol and its phosphorylated derivatives was studied by microinjection of the radioactive precursor into Xenopus laevis oocytes. Induction of meiotic maturation of the oocytes by treatment with either progesterone one or insulin resulted in a significant increase in the incorporation of myo-({sup 3}H)inositol into the phospholipid fraction. This increase occurred 3-6 h after hormonal treatment, a time coincident with the start of the breakdown of the nuclear envelope, and requires protein synthesis. The effect of progesterone and insulin contrasts with the effect of acetylcholine, which acts through a muscarinic receptor causing the activation of phospholipase C, since the latter effector causes an increase in myo-({sup 3}H)inositol incorporation, which is more rapid and does not require protein synthesis. These results suggest that the meiotic maturation process is connected with changes in inositol metabolism in the amphibian oocyte.

  19. Suppression of Meiotic Recombination by CENP-B Homologs in Schizosaccharomyces pombe.

    Science.gov (United States)

    Johansen, Peter; Cam, Hugh P

    2015-11-01

    Meiotic homologous recombination (HR) is not uniform across eukaryotic genomes, creating regions of HR hot- and coldspots. Previous study reveals that the Spo11 homolog Rec12 responsible for initiation of meiotic double-strand breaks in the fission yeast Schizosaccharomyces pombe is not targeted to Tf2 retrotransposons. However, whether Tf2s are HR coldspots is not known. Here, we show that the rates of HR across Tf2s are similar to a genome average but substantially increase in mutants deficient for the CENP-B homologs. Abp1, which is the most prominent of the CENP-B family members and acts as the primary determinant of HR suppression at Tf2s, is required to prevent gene conversion and maintain proper recombination exchange of homologous alleles flanking Tf2s. In addition, Abp1-mediated suppression of HR at Tf2s requires all three of its domains with distinct functions in transcriptional repression and higher-order genome organization. We demonstrate that HR suppression of Tf2s can be robustly maintained despite disruption to chromatin factors essential for transcriptional repression and nuclear organization of Tf2s. Intriguingly, we uncover a surprising cooperation between the histone methyltransferase Set1 responsible for histone H3 lysine 4 methylation and the nonhomologous end joining pathway in ensuring the suppression of HR at Tf2s. Our study identifies a molecular pathway involving functional cooperation between a transcription factor with epigenetic regulators and a DNA repair pathway to regulate meiotic recombination at interspersed repeats. Copyright © 2015 by the Genetics Society of America.

  20. Meiotic analysis of interspecific hybrids between Capsicum frutescens and Capsicum chinense

    National Research Council Canada - National Science Library

    Nádia Fernandes Moreira; Telma Nair Santana Pereira; Kellen Coutinho Martins

    2017-01-01

    The aim of this study was to observe the genetic relationship between C. frutescens (UENF 1636) and C. chinense (UENF 1785) based on the meiotic behavior, on the meiotic index, and on pollen viability of their F1 hybrids...

  1. Meiotic recombination breakpoints are associated with open chromatin and enriched with repetitive DNA elements in potato

    Science.gov (United States)

    Meiotic recombination provides the framework for the genetic variation in natural and artificial populations of eukaryotes through the creation of novel haplotypes. Thus, determining the molecular characteristics of meiotic recombination remains essential for future plant breeding efforts, which hea...

  2. Mechanisms by which a lack of germinal vesicle (GV) material causes oocyte meiotic defects: a study using oocytes manipulated to replace GV with primary spermatocyte nuclei.

    Science.gov (United States)

    Zhang, Jie; Cui, Wei; Li, Qing; Wang, Tian-Yang; Sui, Hong-Shu; Wang, Jun-Zuo; Luo, Ming-Jiu; Tan, Jing-He

    2013-10-01

    Oocytes with germinal vesicles (GVs) replaced with somatic nuclei exhibit meiotic abnormalities. Although this suggests an exclusive role for GV material in meiosis, mechanisms by which a lack of GV material causes meiotic defects are unknown. Knowledge of these mechanisms will help us to understand meiotic control, nuclear-cytoplasmic interactions, and cellular reprogramming. This study showed that although oocytes with prometaphase I chromosomes replaced with primary spermatocyte nuclei (PSN) did not, oocytes with GV replaced with PSN (PSG oocytes) did display meiotic defects. Among the defects, insufficient chromosome condensation with chromosome bridges was associated with spindle abnormalities. Abnormal spindle migration, cortical nonpolarization, and the aberrant spindle caused randomly positioning of cleavage furrows, leading to large first polar bodies (PB1) and unequal allocation of chromosomes and mitogen-activated protein kinases (MAPK) between oocyte and PB1. Spindle assembly checkpoint was activated but did not stop the incorrect division. The unequal MAPK allocation resulted in differences in pronuclear formation and PB1 degeneration; oocytes receiving more MAPK were more capable of forming pronuclear rudiments, whereas PB1 receiving more MAPK degenerated sooner than those that received less. Because none of the PSG oocytes or the enucleated GV oocytes injected with sperm heads showed cortical polarization in spite of chromosome localization close to the oolemma and because the PSG oocytes receiving more MAPK could form only pronuclear rudiments and not normal pronuclei, we suggest that the GV material plays essential roles in polarization and pronuclear formation on top of those played by chromosomes or MAPK. In conclusion, using PSG oocytes as models, this study has revealed the primary pathways by which a lack of GV material cause meiotic defects, laying a foundation for future research on the role of GV material in oocyte meiotic control.

  3. Meiotic analysis in induced tetraploids of Brachiaria decumbens Stapf

    Directory of Open Access Journals (Sweden)

    Carine Simioni

    2011-01-01

    Full Text Available The meiotic behavior of three tetraploid plants (2n=4x=36 originated from somatic chromosome duplication ofsexually reproducing diploid plants of Brachiaria decumbens was evaluated. All the analyzed plants presented abnormalities relatedto polyploidy, such as irregular chromosome segregation, leading to precocious chromosome migration to the poles and micronucleiduring both meiotic divisions. However, the abnormalities observed did not compromise the meiotic products which were characterizedby regular tetrads and satisfactory pollen fertility varying from 61.36 to 64.86%. Chromosomes paired mostly as bivalents indiakinesis but univalents to tetravalents were also observed. These studies contributed to the choice of compatible fertile sexualgenitors to be crossed to natural tetraploid apomicts in the B. decumbens by identifying abnormalities and verifying pollen fertility.Intraespecific crosses should reduce sterility in the hybrids produced in the breeding program of Brachiaria, a problem observedwith the interspecific hybrids produced so far.

  4. Small phosphatidate phosphatase (TtPAH2) of Tetrahymena complements respiratory function and not membrane biogenesis function of yeast PAH1.

    Science.gov (United States)

    Pillai, Anoop Narayana; Shukla, Sushmita; Gautam, Sudhanshu; Rahaman, Abdur

    2017-12-01

    Phosphatidate phosphatases (PAH) play a central role in lipid metabolism and intracellular signaling. Herein, we report the presence of a low-molecular-weight PAH homolog in the single-celled ciliate Tetrahymena thermophila. In vitro phosphatase assay showed that TtPAH2 belongs to the magnesium-dependent phosphatidate phosphatase (PAP1) family. Loss of function of TtPAH2 did not affect the growth of Tetrahymena. Unlike other known PAH homologs, TtPAH2 did not regulate lipid droplet number and ER morphology. TtPAH2 did not rescue growth and ER/nuclear membrane defects of the pah1Δ yeast cells, suggesting that the phosphatidate phosphatase activity of the protein is not sufficient to perform these cellular functions. Surprisingly, TtPAH2 complemented the respiratory defect in the pah1Δ yeast cells indicating a specific role of TtPAH2 in respiration. Overall, our results indicate that TtPAH2 possesses the minimal function of PAH protein family in respiration. We suggest that the amino acid sequences absent from TtPAH2 but present in all other known PAH homologs are critical for lipid homeostasis and membrane biogenesis.

  5. Segregation for fertility and meiotic stability in novel Brassica allohexaploids.

    Science.gov (United States)

    Mwathi, Margaret W; Gupta, Mehak; Atri, Chaya; Banga, Surinder S; Batley, Jacqueline; Mason, Annaliese S

    2017-04-01

    Allohexaploid Brassica populations reveal ongoing segregation for fertility, while genotype influences fertility and meiotic stability. Creation of a new Brassica allohexaploid species is of interest for the development of a crop type with increased heterosis and adaptability. At present, no naturally occurring, meiotically stable Brassica allohexaploid exists, with little data available on chromosome behaviour and meiotic control in allohexaploid germplasm. In this study, 100 plants from the cross B. carinata × B. rapa (A2 allohexaploid population) and 69 plants from the cross (B. napus × B. carinata) × B. juncea (H2 allohexaploid population) were assessed for fertility and meiotic behaviour. Estimated pollen viability, self-pollinated seed set, number of seeds on the main shoot, number of pods on the main shoot, seeds per ten pods and plant height were measured for both the A2 and H2 populations and for a set of reference control cultivars. The H2 population had high segregation for pollen viability and meiotic stability, while the A2 population was characterised by low pollen fertility and a high level of chromosome loss. Both populations were taller, but had lower average fertility trait values than the control cultivar samples. The study also characterises fertility and meiotic chromosome behaviour in genotypes and progeny sets in heterozygous allotetraploid Brassica derived lines, and indicates that genotypes of the parents and H1 hybrids are affecting chromosome pairing and fertility phenotypes in the H2 population. The identification and characterisation of factors influencing stability in novel allohexaploid Brassica populations will assist in the development of this as a new crop species for food and agricultural benefit.

  6. The Phosphatase Dusp7 Drives Meiotic Resumption and Chromosome Alignment in Mouse Oocytes

    Directory of Open Access Journals (Sweden)

    Thomas Tischer

    2016-10-01

    Full Text Available Mammalian oocytes are stored in the ovary, where they are arrested in prophase for prolonged periods. The mechanisms that abrogate the prophase arrest in mammalian oocytes and reinitiate meiosis are not well understood. Here, we identify and characterize an essential pathway for the resumption of meiosis that relies on the protein phosphatase DUSP7. DUSP7-depleted oocytes either fail to resume meiosis or resume meiosis with a significant delay. In the absence of DUSP7, Cdk1/CycB activity drops below the critical level required to reinitiate meiosis, precluding or delaying nuclear envelope breakdown. Our data suggest that DUSP7 drives meiotic resumption by dephosphorylating and thereby inactivating cPKC isoforms. In addition to controlling meiotic resumption, DUSP7 has a second function in chromosome segregation: DUSP7-depleted oocytes that enter meiosis show severe chromosome alignment defects and progress into anaphase prematurely. Altogether, these findings establish the phosphatase DUSP7 as an essential regulator of multiple steps in oocyte meiosis.

  7. An RNA Recognition Motif-Containing Protein Functions in Meiotic Silencing by Unpaired DNA

    Directory of Open Access Journals (Sweden)

    Dilini A. Samarajeewa

    2017-08-01

    Full Text Available Meiotic silencing by unpaired DNA (MSUD is a biological process that searches pairs of homologous chromosomes (homologs for segments of DNA that are unpaired. Genes found within unpaired segments are silenced for the duration of meiosis. In this report, we describe the identification and characterization of Neurospora crassa sad-7, a gene that encodes a protein with an RNA recognition motif (RRM. Orthologs of sad-7 are found in a wide range of ascomycete fungi. In N. crassa, sad-7 is required for a fully efficient MSUD response to unpaired genes. Additionally, at least one parent must have a functional sad-7 allele for a cross to produce ascospores. Although sad-7-null crosses are barren, sad-7Δ strains grow at a wild-type (wt rate and appear normal under vegetative growth conditions. With respect to expression, sad-7 is transcribed at baseline levels in early vegetative cultures, at slightly higher levels in mating-competent cultures, and is at its highest level during mating. These findings suggest that SAD-7 is specific to mating-competent and sexual cultures. Although the role of SAD-7 in MSUD remains elusive, green fluorescent protein (GFP-based tagging studies place SAD-7 within nuclei, perinuclear regions, and cytoplasmic foci of meiotic cells. This localization pattern is unique among known MSUD proteins and raises the possibility that SAD-7 coordinates nuclear, perinuclear, and cytoplasmic aspects of MSUD.

  8. Dimethyl Sulfoxide Perturbs Cell Cycle Progression and Spindle Organization in Porcine Meiotic Oocytes.

    Directory of Open Access Journals (Sweden)

    Xuan Li

    Full Text Available Meiotic maturation of mammalian oocytes is a precisely orchestrated and complex process. Dimethyl sulfoxide (DMSO, a widely used solvent, drug, and cryoprotectant, is capable of disturbing asymmetric cytokinesis of oocyte meiosis in mice. However, in pigs, DMSO's effect on oocyte meiosis still remains unknown. We aimed to evaluate if DMSO treatment will affect porcine oocyte meiosis and the underlying molecular changes as well. Interestingly, we did not observe the formation of the large first polar body and symmetric division for porcine oocytes treated with DMSO, contrary to findings reported in mice. 3% DMSO treatment could inhibit cumulus expansion, increase nuclear abnormality, disturb spindle organization, decrease reactive oxygen species level, and elevate mitochondrial membrane potential of porcine oocytes. There was no effect on germinal vesicle breakdown rate regardless of DMSO concentration. 3% DMSO treatment did not affect expression of genes involved in spindle organization (Bub1 and Mad2 and apoptosis (NF-κB, Pten, Bcl2, Caspase3 and Caspase9, however, it significantly decreased expression levels of pluripotency genes (Oct4, Sox2 and Lin28 in mature oocytes. Therefore, we demonstrated that disturbed cumulus expansion, chromosome alignment, spindle organization and pluripotency gene expression could be responsible for DMSO-induced porcine oocyte meiotic arrest and the lower capacity of subsequent embryo development. Our results provide new insights on DMSO's effect on porcine oocyte meiosis and raise safety concerns over DMSO's usage on female reproduction in both farm animals and humans.

  9. Comparative study of infection with Tetrahymena of different ornamental fish species

    DEFF Research Database (Denmark)

    Sharon, G.; Leibowitz, M. Pimenta; Chettri, Jiwan Kumar

    2014-01-01

    Tetrahymena is a ciliated protozoan that can infect a wide range of fish species, although it is most commonly reported in guppies (Poecilia reticulata). The aim of this study was to compare the susceptibility to infection with Tetrahymena of five different ornamental fish species from two...... different super orders. The species examined were platy (Xiphophorus), molly (Poecilia sphenops) and angelfish (Pterophyllum scalare) of the Acanthopterygii super order (which also includes guppies) and goldfish (Carassius auratus auratus) and koi carp (Cyprinus carpio) of the Ostariophysi super order...... of the Acanthopterygii super order. Guppies were the most susceptible to Tetrahymena infection, exhibiting a mortality rate of 87% and 100% in two separate experiments. A high mortality rate was also observed in platy (77%), while that of molly and angelfish was significantly lower (23% and 33%, respectively). Goldfish...

  10. Environmental and physiological conditions affecting Tetrahymena sp. infection in guppies, Poecilia reticulata Peters.

    Science.gov (United States)

    Pimenta Leibowitz, M; Ariav, R; Zilberg, D

    2005-09-01

    Parasitic infections caused by Tetrahymena sp. constitute a serious problem in guppies, Poecilia reticulata. Tetrahymena was isolated from skin lesions of naturally infected guppies in a commercial aquaculture farm, cultured in vitro and used in subsequent experimental infections. In addition to guppies, angelfish, Pterophyllum scalare, platyfish, Xiphophorus maculates, and neontetra, Paracheirodon innesi, were susceptible, whereas tilapia (Oreochromis niloticus xO. aureus) was resistant. The ciliate had a high affinity for dead fish. Skin abrasion did not affect the infection, but fish with gas bubble disease exhibited a significantly higher infection than non-affected fish. Infection was significantly higher when fish were exposed to high levels of ammonia, high organic load and low water temperatures. Under shipment conditions, infection was significantly elevated. Full recovery was achieved at a low fish density. Results suggest that poor environmental and physiological conditions enhance infection with Tetrahymena sp.

  11. Distribution of meiotic recombination events: Talking to your neighbors

    Science.gov (United States)

    Martinez-Perez, Enrique; Colaiácovo, Monica P.

    2009-01-01

    Accurate chromosome segregation during meiosis is essential for a species' survival. Therefore, a series of events unfold during meiosis, including pairing, synapsis and recombination between homologous chromosomes, to ultimately ensure the successful completion of this task. This review will focus on how the regulation of crossover recombination events between homologous chromosomes plays a key role in promoting faithful segregation. Although our understanding of the molecular mechanisms by which crossovers are formed has increased significantly, the mechanisms governing the distribution of crossovers along meiotic chromosomes remain largely mysterious. Here, we review the different levels of apparent control of meiotic crossover formation and distribution. PMID:19328674

  12. Reduced meiotic fitness in hybrids with heterozygosity for ...

    Indian Academy of Sciences (India)

    ... the backcross hybrids heterozygous for the heterochromatic short arms have more anomalies compared to the homokaryotypic hybrids. This suggests a negative influence of the heterochromatin heterozygosity in meiotic pairing. The results indicate a role for heterochromatin variations in the development of a reproductive ...

  13. Bloom Syndrome Helicase Promotes Meiotic Crossover Patterning and Homolog Disjunction.

    Science.gov (United States)

    Hatkevich, Talia; Kohl, Kathryn P; McMahan, Susan; Hartmann, Michaelyn A; Williams, Andrew M; Sekelsky, Jeff

    2017-01-09

    In most sexually reproducing organisms, crossover formation between homologous chromosomes is necessary for proper chromosome disjunction during meiosis I. During meiotic recombination, a subset of programmed DNA double-strand breaks (DSBs) are repaired as crossovers, with the remainder becoming noncrossovers [1]. Whether a repair intermediate is designated to become a crossover is a highly regulated decision that integrates several crossover patterning processes, both along chromosome arms (interference and the centromere effect) and between chromosomes (crossover assurance) [2]. Because the mechanisms that generate crossover patterning have remained elusive for over a century, it has been difficult to assess the relationship between crossover patterning and meiotic chromosome behavior. We show here that meiotic crossover patterning is lost in Drosophila melanogaster mutants that lack the Bloom syndrome helicase. In the absence of interference and the centromere effect, crossovers are distributed more uniformly along chromosomes. Crossovers even occur on the small chromosome 4, which normally never has meiotic crossovers [3]. Regulated distribution of crossovers between chromosome pairs is also lost, resulting in an elevated frequency of homologs that do not receive a crossover, which in turn leads to elevated nondisjunction. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Genetic Analysis of Meiotic Recombination in Schizosaccharomyces pombe

    OpenAIRE

    Smith, Gerald R.

    2009-01-01

    The fission yeast Schizosaccharomyces pombe is well-suited for studying meiotic recombination. Methods are described here for culturing S. pombe and for genetic assays of intragenic recombination (gene conversion), intergenic recombination (crossing-over), and spore viability. Both random spore and tetrad analyses are described.

  15. [Meiotic chromosomes of the tree frog Smilisca baudinii (Anura: Hylidae)].

    Science.gov (United States)

    Hernández-Guzmán, Javier; Arias-Rodriguez, Lenin; Indy, Jeane Rimber

    2011-03-01

    The Mexican tree frog Smilisca baudinii, is a very common frog in Central America. In spite their importance to keep the ecological equilibrium of the rainforest, its biology and genetics are poorly known. In order to contribute with its biological knowledge, we described the typical meiotic karyotype based in standard cytogenetic protocols to specimens collected in Tabasco, Mexico. The study was centered in the analysis of 131 chromosome spreads at meiotic stage from two adults of the species (one female and one male). The metaphase analysis allowed the establishment of the modal haploid number of 1n = 12 bivalent chromosomes. The chromosomic formulae from the haploid bivalent karyotype was integrated by 12 biarmed chromosomes characterized by twelve pairs of metacentric-submetacentric (msm) chromosomes. The meiotic counting gives the idea that diploid chromosome number is integrated by a complement of 2n = 24 biarmed chromosomes. The presence of sex chromosomes from female and male meiotic spreads was not observed. Current results suggest that S. baudinii chromosome structure is well shared among Hylidae family and "B" chromosomes are particular structures that have very important evolutionary consequences in species diversification.

  16. Hed1 Promotes Meiotic Crossover Formation in Saccharomyces cerevisiae.

    Science.gov (United States)

    Kong, Yoon-Ju; Joo, Jeong-Hwan; Kim, Keun Pil; Hong, Soogil

    2017-02-28

    Homologous recombination occurs between homologous chromosomes and is significantly involved in programmed double-strand break (DSB) repair. Activation of two recombinases, Rad51 and Dmc1, is essential for an interhomolog bias during meiosis. Rad51 participates in both mitotic and meiotic recombination, and its strand exchange activity is regulated by an inhibitory factor during meiosis. Thus, activities of Rad51 and Dmc1 are coordinated to promote homolog bias. It has been reported that Hed1, a meiosis-specific protein in budding yeast, regulates Rad51-dependent recombination activity. Here, we investigated the role of Hed1 in meiotic recombination by ectopic expression of the protein after pre-meiotic replication in Saccharomyces cerevisiae. DNA physical analysis revealed that the overexpression of Hed1 delays the DSB-to-joint molecule (JM) transition and promotes interhomolog JM formation. The study indicates a possible role of Hed1 in controlling the strand exchange activity of Rad51 and, eventually, meiotic crossover formation.

  17. Highlights of meiotic genes in Arabidopsis thaliana | Consiglio ...

    African Journals Online (AJOL)

    Meiosis is a fascinating and complex phenomenon and, despite its central role in sexual plant reproduction, little is known on the molecular mechanisms involved in this process. We review the progress made in recent years using Arabidopsis thaliana mutants for isolating meiotic genes. In particular, emphasis is given on ...

  18. The nuclear exosome is active and important during budding yeast meiosis.

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    Stephen Frenk

    Full Text Available Nuclear RNA degradation pathways are highly conserved across eukaryotes and play important roles in RNA quality control. Key substrates for exosomal degradation include aberrant functional RNAs and cryptic unstable transcripts (CUTs. It has recently been reported that the nuclear exosome is inactivated during meiosis in budding yeast through degradation of the subunit Rrp6, leading to the stabilisation of a subset of meiotic unannotated transcripts (MUTs of unknown function. We have analysed the activity of the nuclear exosome during meiosis by deletion of TRF4, which encodes a key component of the exosome targeting complex TRAMP. We find that TRAMP mutants produce high levels of CUTs during meiosis that are undetectable in wild-type cells, showing that the nuclear exosome remains functional for CUT degradation, and we further report that the meiotic exosome complex contains Rrp6. Indeed Rrp6 over-expression is insufficient to suppress MUT transcripts, showing that the reduced amount of Rrp6 in meiotic cells does not directly cause MUT accumulation. Lack of TRAMP activity stabilises ∼ 1600 CUTs in meiotic cells, which occupy 40% of the binding capacity of the nuclear cap binding complex (CBC. CBC mutants display defects in the formation of meiotic double strand breaks (DSBs, and we see similar defects in TRAMP mutants, suggesting that a key function of the nuclear exosome is to prevent saturation of the CBC complex by CUTs. Together, our results show that the nuclear exosome remains active in meiosis and has an important role in facilitating meiotic recombination.

  19. Updating rDNA restriction enzyme maps of Tetrahymena reveals four new intron-containing species

    DEFF Research Database (Denmark)

    Nielsen, Henrik; Simon, E M; Engberg, J

    1985-01-01

    The extrachromosomal rDNA molecules from a number of Tetrahymena strains were characterized by restriction enzyme mapping using three different restriction enzymes combined with gel blotting and hybridization analysis. Strains from four out of six recently described species were found to contain...

  20. Poliovirus and echovirus survival in Tetrahymena pyriformis culture in vivo.

    Science.gov (United States)

    Danes, L; Cerva, L

    1984-01-01

    Axenic cultures of Tetrahymena pyriformis, strain I MT IV, grown in a defined medium at room temperature, were used to study interactions of these protozoa with vaccination strain L Sc 2ab of poliovirus type 1, vaccination strain P 712 of poliovirus type 2 and with type 30 echovirus, strain 480/78. T. pyriformis cultures in media containing 10(3.0) TCD50/1 ml of type poliovirus, 10(3.0) TCD50/1 ml of type 2 poliovirus or 10(2.5) TCD50/1 ml echovirus 30 and in virus-free medium did not differ one from another in their growth and die-away kinetics during the 21 days of observation. Two-day T. pyriformis cultures were infected with poliovirus 1 (initial concentration 10(3.2) TCD50/1 ml), and poliovirus 2 and echovirus 30 (initial concentrations 10(3.0) TCD50/1 ml). Viruses were titrated in test tube cultures of BGM cells. The supernatant fluid, standardized sediment and samples of control virus suspension free of protozoa were titrated after 0, 2, 6, 10, 13, 18, 28 and 30 days. Most of the virus in culture was found associated with the sediment, both in the period of active growth and during the die-away phase of T. pyriformis protozoa. The virus in sediment was present at higher titres and its survival time was longer than in virus in liquid phase. Thirteen days after the first contact between T. pyriformis and virus the sediment and supernatant fluid of the old protozoan culture and the T. pyriformis-free control viral suspension were taken and used as inocula for new two-day T. pyriformis cultures.(ABSTRACT TRUNCATED AT 250 WORDS)

  1. Meiotic faults as a major cause of offspring inviability

    DEFF Research Database (Denmark)

    Levitis, Daniel; Zimmerman, Kolea; Pringle, Anne

    2014-01-01

    , the most sex-like form of asex. Meiotic parthenogenesis does consistently achieve lower offspring viability than does sex. However when sexual reproduction is compared to forms of asex that don't involve meiosis, asex results in higher offspring viability. Combined with experimental and demographic data......, this result demonstrates that failures associated with meiosis are a major cause of offspring inviability not only for meiotic parthenogenesis, but for sexual reproducers such as humans. Meiosis is necessary for genetic recombination in eukaryotes, but is vestigial, and costly, in parthenogens. The question...... of why meiosis persists in parthenogens despite its clear fitness costs and lack of benefits for them is addressed in terms of mechanistic constraints upon what selection can achieve. This provides a clear example of evolutionary inertia having a major and maladaptive effect on the demography of a wide...

  2. Justified chauvinism: advances in defining meiotic recombination through sperm typing.

    Science.gov (United States)

    Carrington, Mary; Cullen, Michael

    2004-04-01

    Sperm typing offers an efficient means of studying the quantitative and qualitative aspects of meiotic recombination that are virtually unapproachable by pedigree analysis. Since the initial development of the technique >10 years ago, several salient findings based on empirically derived recombination data have been described. The precise rates and distributions of recombination have been reported for specific regions of the genome, serving as the prototype for high-resolution genome-wide recombination patterns. Identification and characterization of molecular genetic events, such as unequal crossing over, gene conversion and crossover asymmetry, are under close inspection for the first time as a result of this technology. The influence of these phenomena on the evolution of the genome is of primary interest from a scientific and medical perspective. In this article, we review the novel discoveries in mammalian meiotic recombination that have been revealed through sperm typing.

  3. Establishment of a Cre/loxP recombination system for N-terminal epitope tagging of genes in Tetrahymena

    Directory of Open Access Journals (Sweden)

    Mochizuki Kazufumi

    2010-07-01

    Full Text Available Abstract Background Epitope tagging is a powerful strategy to study the function of proteins. Although tools for C-terminal protein tagging in the ciliated protozoan Tetrahymena thermophila have been developed, N-terminal protein tagging in this organism is still technically demanding. Results In this study, we have established a Cre/loxP recombination system in Tetrahymena and have applied this system for the N-terminal epitope tagging of Tetrahymena genes. Cre can be expressed in Tetrahymena and localizes to the macronucleus where it induces precise recombination at two loxP sequences in direct orientation in the Tetrahymena macronuclear chromosome. This Cre/loxP recombination can be used to remove a loxP-flanked drug-resistance marker from an N-terminal tagging construct after it is integrated into the macronucleus. Conclusions The system established in this study allows us to express an N-terminal epitope tagged gene from its own endogenous promoter in Tetrahymena.

  4. TDM1 Regulation Determines the Number of Meiotic Divisions.

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    Marta Cifuentes

    2016-02-01

    Full Text Available 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.

  5. Effect of Cerophyl growth medium on exocytosis in Tetrahymena thermophila.

    Science.gov (United States)

    Pesciotta, D M; Satir, B H

    1985-10-01

    Culturing the ciliate Tetrahymena thermophila in Cerophyl has provided an opportunity for studying the assembly and/or synthesis of the intramembrane particle array, the rosette, which marks the site of exocytosis in these cells. Cultures grown in this medium cease cell division after only 12h and enter 'stationary phase' earlier (12h of growth) relative to growth in standard medium (proteose peptone). In addition, the cell changes from the normally observed pear-shaped body to a thinner more ellipsoid form. Despite the initial similarities to starving cells, several differences are observed in the Cerophyl-grown cells. One is that cell size remains constant for at least 72h in contrast to starved cells. Secondly, in spite of this block in cell division, results from freeze-fracture replicas of the cell membrane of these cells show that they continue to assemble rosettes, the number of which increases approximately six times, from 0.34 rosette/microgram2 to 2.1 rosettes/microgram2. Addition of the protein synthesis inhibitor, cycloheximide (6h exposure), during growth in Cerophyl shows that 70% of rosettes can be assembled, despite the blockage of translation, by using pre-existing component(s) from a pool. The remaining 30% must involve de novo synthesis of one or more components; this percentage can be increased with longer exposure to the drug. Thirdly, an apparent increase in the number of mucocysts is observed by thin-section electron microscopy. At first (12-24h) only docked mucocysts seem to accumulate in the cell. However, by 36h a considerable increase seems to have taken place, particularly in the number of mucocysts located in the cytoplasm. In the cycloheximide-treated cells this increase in mucocysts begins to be blocked after 6h of exposure to the drug. These observations are in agreement with the results obtained from the freeze-fracture data on the concomitant increase in number of rosettes. This system therefore offers the first possibility of

  6. Macronuclear genome sequence of the ciliate Tetrahymena thermophila, a model eukaryote.

    Directory of Open Access Journals (Sweden)

    Jonathan A Eisen

    2006-09-01

    Full Text Available The ciliate Tetrahymena thermophila is a model organism for molecular and cellular biology. Like other ciliates, this species has separate germline and soma functions that are embodied by distinct nuclei within a single cell. The germline-like micronucleus (MIC has its genome held in reserve for sexual reproduction. The soma-like macronucleus (MAC, which possesses a genome processed from that of the MIC, is the center of gene expression and does not directly contribute DNA to sexual progeny. We report here the shotgun sequencing, assembly, and analysis of the MAC genome of T. thermophila, which is approximately 104 Mb in length and composed of approximately 225 chromosomes. Overall, the gene set is robust, with more than 27,000 predicted protein-coding genes, 15,000 of which have strong matches to genes in other organisms. The functional diversity encoded by these genes is substantial and reflects the complexity of processes required for a free-living, predatory, single-celled organism. This is highlighted by the abundance of lineage-specific duplications of genes with predicted roles in sensing and responding to environmental conditions (e.g., kinases, using diverse resources (e.g., proteases and transporters, and generating structural complexity (e.g., kinesins and dyneins. In contrast to the other lineages of alveolates (apicomplexans and dinoflagellates, no compelling evidence could be found for plastid-derived genes in the genome. UGA, the only T. thermophila stop codon, is used in some genes to encode selenocysteine, thus making this organism the first known with the potential to translate all 64 codons in nuclear genes into amino acids. We present genomic evidence supporting the hypothesis that the excision of DNA from the MIC to generate the MAC specifically targets foreign DNA as a form of genome self-defense. The combination of the genome sequence, the functional diversity encoded therein, and the presence of some pathways missing from

  7. An expanded inventory of conserved meiotic genes provides evidence for sex in Trichomonas vaginalis.

    Directory of Open Access Journals (Sweden)

    Shehre-Banoo Malik

    Full Text Available Meiosis is a defining feature of eukaryotes but its phylogenetic distribution has not been broadly determined, especially among eukaryotic microorganisms (i.e. protists-which represent the majority of eukaryotic 'supergroups'. We surveyed genomes of animals, fungi, plants and protists for meiotic genes, focusing on the evolutionarily divergent parasitic protist Trichomonas vaginalis. We identified homologs of 29 components of the meiotic recombination machinery, as well as the synaptonemal and meiotic sister chromatid cohesion complexes. T. vaginalis has orthologs of 27 of 29 meiotic genes, including eight of nine genes that encode meiosis-specific proteins in model organisms. Although meiosis has not been observed in T. vaginalis, our findings suggest it is either currently sexual or a recent asexual, consistent with observed, albeit unusual, sexual cycles in their distant parabasalid relatives, the hypermastigotes. T. vaginalis may use meiotic gene homologs to mediate homologous recombination and genetic exchange. Overall, this expanded inventory of meiotic genes forms a useful "meiosis detection toolkit". Our analyses indicate that these meiotic genes arose, or were already present, early in eukaryotic evolution; thus, the eukaryotic cenancestor contained most or all components of this set and was likely capable of performing meiotic recombination using near-universal meiotic machinery.

  8. Involvement of a putative intercellular signal-recognizing G protein-coupled receptor in the engulfment of Salmonella by the protozoan Tetrahymena

    Directory of Open Access Journals (Sweden)

    P.N. Agbedanu

    2013-07-01

    Full Text Available In an effort to investigate the molecular basis of protozoa engulfment-mediated hypervirulence of Salmonella in cattle, we evaluated protozoan G protein-coupled receptors (GPCRs as transducers of Salmonella engulfment by the model protozoan Tetrahymena. Our laboratory previously demonstrated that non-pathogenic protozoa (including Tetrahymena engulf Salmonella and then exacerbate its virulence in cattle, but the mechanistic details of the phenomenon are not fully understood. GPCRs were investigated since these receptors facilitate phagocytosis of particulates by Tetrahymena, and a GPCR apparently modulates bacterial engulfment for the pathogenic protozoan Entamoeba histolytica. A database search identified three putative Tetrahymena GPCRs, based on sequence homologies and predicted transmembrane domains, that were the focus of this study. Salmonella engulfment by Tetrahymena was assessed in the presence of suramin, a non-specific GPCR inhibitor. Salmonella engulfment was also assessed in Tetrahymena in which expression of putative GPCRs was knocked-down using RNAi. A candidate GPCR was then expressed in a heterologous yeast expression system for further characterization. Our results revealed that Tetrahymena were less efficient at engulfing Salmonella in the presence of suramin. Engulfment was reduced concordantly with a reduction in the density of protozoa. RNAi-based studies revealed that knock-down of one the Tetrahymena GPCRs caused diminished engulfment of Salmonella. Tetrahymena lysates activated this receptor in the heterologous expression system. These data demonstrate that the Tetrahymena receptor is a putative GPCR that facilitates bacterial engulfment by Tetrahymena. Activation of the putative GPCR seemed to be related to protozoan cell density, suggesting that its cognate ligand is an intercellular signaling molecule.

  9. QSAR studies for the acute toxicity of nitrobenzenes to the Tetrahymena pyriformis

    Directory of Open Access Journals (Sweden)

    Wang Dan-Dan

    2014-01-01

    Full Text Available Quantitative structure-activity relationship (QSAR models play a key role in finding the relationship between molecular structures and the toxicity of nitrobenzenes to Tetrahymena pyriformis. In this work, genetic algorithm, along with partial least square (GA-PLS was employed to select optimal subset of descriptors that have significant contribution to the toxicity of nitrobenzenes to Tetrahymena pyriformis. A set of five descriptors, namely G2, HOMT, G(Cl…Cl, Mor03v and MAXDP, was used for the prediction of the toxicity of 45 nitrobenzene derivatives and then were used to build the model by multiple linear regression (MLR method. It turned out that the built model, whose stability was confirmed using the leave-one-out validation and external validation test, showed high statistical significance (R2=0.963, Q2LOO=0.944. Moreover, Y-scrambling test indicated there was no chance correlation in this model.

  10. Modeling the toxicity of chemicals to Tetrahymena pyriformis using molecular fragment descriptors and probabilistic neural networks.

    Science.gov (United States)

    Niculescu, S P; Kaiser, K L; Schultz, T W

    2000-10-01

    The results of an investigation into the use of a probabilistic neural network (PNN)-based methodology to model the 48-h ICG50 (inhibitory concentration for population growth) sublethal toxicity of 825 chemicals to the ciliate Tetrahymena pyriformis are presented. The information fed into the neural networks is solely based on simple molecular descriptors as can be derived from the chemical structure. In contrast to most other toxicological models, the octanol/water partition coefficient is not used as an input parameter, and no rules of thumb or other substance selection criteria are employed. The cross-validation and external validation experiments confirmed excellent recognitive and predictive capabilities of the resulting models and recommend their future use in evaluating the potential of most organic molecules to be toxic to Tetrahymena.

  11. Meiotic arrest maintained by cAMP during the initiation of maturation enhances meiotic potential and developmental competence and reduces polyspermy of IVM/IVF porcine oocytes.

    Science.gov (United States)

    Somfai, Tamás; Kikuchi, Kazuhiro; Onishi, Akira; Iwamoto, Masaki; Fuchimoto, Dai-ichiro; Papp, Agnes Bali; Sato, Eimei; Nagai, Takashi

    2003-08-01

    We investigated effects of invasive adenylate cyclase (iAC), 3-isobutyl-1-methylxanthine (IBMX) and dibutyryl cyclic AMP (dbcAMP) on porcine oocyte in vitro maturation (IVM), in vitro fertilisation (IVF) and subsequent embryonic development. Porcine oocytes were collected in Hepes-buffered NCSU-37 supplemented with or without 0.1 microg/ml iAC and 0.5 mM IBMX. IVM was performed in a modified NCSU-37 supplemented with or without 1 mM dbcAMP for 22 h and then without dbcAMP for an additional 24 h. After IVF, oocytes were cultured in vitro for 6 days. After 12 h of IVM, no difference in nuclear status was observed irrespective of supplementation with these chemicals during collection and IVM. At 22 h, most (95%) of the oocytes cultured with dbcAMP remained at the germinal vesicle (GV) stage, whereas 44.3% of the oocytes cultured without dbcAMP underwent GV breakdown. At 36 h, oocytes cultured with dbcAMP had progressed to prometaphase I or metaphase I (MI) (32.6% and 49.3%, respectively), whereas non-treated oocytes had progressed further to anaphase I, telophase I or metaphase II (MII) (13.6%, 14.3% and 38.0%, respectively). At 46 h, the rate of matured oocytes at MII was higher in oocytes cultured with dbcAMP (81%) than without dbcAMP (57%), while the proportion of oocytes arrested at MI was lower when cultured with dbcAMP (15%) than without dbcAMP (31%). The rate of monospermic fertilisation was higher when oocytes were cultured with dbcAMP (21%) than without dbcAMP (9%), with no difference in total penetration rates (58% and 52%, respectively). The blastocyst rate was higher in oocytes cultured with dbcAMP (32%) than without dbcAMP (19%). These results suggest that a change in intracellular level of cAMP during oocyte collection does not affect maturational and developmental competence of porcine oocytes and that synchronisation of meiotic maturation using dbcAMP enhances the meiotic potential of oocytes by promoting the MI to MII transition and results in high

  12. Cysteine proteases and acid phosphatases contribute to Tetrahymena spp. pathogenicity in guppies, Poecilia reticulata.

    Science.gov (United States)

    Leibowitz, M Pimenta; Ofir, R; Golan-Goldhirsh, A; Zilberg, D

    2009-12-03

    Systemic tetrahymenosis caused by the protozoan parasite Tetrahymena spp. is a serious problem in guppy (Poecilia reticulata) farms worldwide. There is no therapeutic solution for the systemic form of this disease. Guppies severely infected with Tetrahymena spp. were imported by a commercial ornamental fish farm and brought to our laboratory. Tetrahymena sp. (Tet-NI) was isolated and in vitro cultured. Isolates maintained in culture for different time periods (as reflected by different numbers of passages in culture) were analyzed-Tet-NI 1, 4, 5 and 6, with Tet-NI 1 being cultured for the longest period (about 15 months, 54 passages) and Tet-NI 6 for the shortest (2.5 months, 10 passages). Controlled internal infection was successfully achieved by IP injection with most isolates, except for Tet-NI 1 which produced no infection. The isolate Tet-NI 6 induced the highest infection rates in internal organs (80% vs. 50% and 64% for Tet-NI 4 and 5, respectively) and mortality rates (67% vs. 20% and 27% for Tet-NI 4 and 5, respectively, and 6.7% for Tet-NI 1). The correlation between pathogenicity and Tetrahymena enzymatic activity was studied. Electrophoretic analyses revealed at least two bands of gelanolytic activity in Tet-NI 4 and 5, three bands in Tet-NI 6, and no activity in Tet-NI 1. Total inhibition of gelanolytic activity was observed after pretreatment of Tet-NI 6 with E-64, a highly selective cysteine protease inhibitor. Using hemoglobin as a substrate, Tet-NI 6 had two bands of proteolytic activity and no bands were observed in Tet-NI 1. A correlation was observed between pathogenicity and acid phosphatase activities (analyzed by commercial fluorescence kit) for Tet-NI 1 and Tet-NI 6.

  13. Use of Tetrahymena thermophila To Study the Role of Protozoa in Inactivation of Viruses in Water▿

    OpenAIRE

    Pinheiro, Marcel D. O.; Power, Mary E.; Butler, Barbara J.; Dayeh, Vivian R.; Slawson, Robin; Lee, Lucy E. J.; Lynn, Denis H.; Bols, Niels C.

    2006-01-01

    The ability of a ciliate to inactivate bacteriophage was studied because these viruses are known to influence the size and diversity of bacterial populations, which affect nutrient cycling in natural waters and effluent quality in sewage treatment, and because ciliates are ubiquitous in aquatic environments, including sewage treatment plants. Tetrahymena thermophila was used as a representative ciliate; T4 was used as a model bacteriophage. The T4 titer was monitored on Escherichia coli B in ...

  14. Use of Tetrahymena thermophila to study the role of protozoa in inactivation of viruses in water.

    Science.gov (United States)

    Pinheiro, Marcel D O; Power, Mary E; Butler, Barbara J; Dayeh, Vivian R; Slawson, Robin; Lee, Lucy E J; Lynn, Denis H; Bols, Niels C

    2007-01-01

    The ability of a ciliate to inactivate bacteriophage was studied because these viruses are known to influence the size and diversity of bacterial populations, which affect nutrient cycling in natural waters and effluent quality in sewage treatment, and because ciliates are ubiquitous in aquatic environments, including sewage treatment plants. Tetrahymena thermophila was used as a representative ciliate; T4 was used as a model bacteriophage. The T4 titer was monitored on Escherichia coli B in a double-agar overlay assay. T4 and the ciliate were incubated together under different conditions and for various times, after which the mixture was centrifuged through a step gradient, producing a top layer free of ciliates. The T4 titer in this layer decreased as coincubation time increased, but no decrease was seen if phage were incubated with formalin-fixed Tetrahymena. The T4 titer associated with the pellet of living ciliates was very low, suggesting that removal of the phage by Tetrahymena inactivated T4. When Tetrahymena cells were incubated with SYBR gold-labeled phage, fluorescence was localized in structures that had the shape and position of food vacuoles. Incubation of the phage and ciliate with cytochalasin B or at 4 degrees C impaired T4 inactivation. These results suggest the active removal of T4 bacteriophage from fluid by macropinocytosis, followed by digestion in food vacuoles. Such ciliate virophagy may be a mechanism occurring in natural waters and sewage treatment, and the methods described here could be used to study the factors influencing inactivation and possibly water quality.

  15. Use of Tetrahymena thermophila To Study the Role of Protozoa in Inactivation of Viruses in Water▿

    Science.gov (United States)

    Pinheiro, Marcel D. O.; Power, Mary E.; Butler, Barbara J.; Dayeh, Vivian R.; Slawson, Robin; Lee, Lucy E. J.; Lynn, Denis H.; Bols, Niels C.

    2007-01-01

    The ability of a ciliate to inactivate bacteriophage was studied because these viruses are known to influence the size and diversity of bacterial populations, which affect nutrient cycling in natural waters and effluent quality in sewage treatment, and because ciliates are ubiquitous in aquatic environments, including sewage treatment plants. Tetrahymena thermophila was used as a representative ciliate; T4 was used as a model bacteriophage. The T4 titer was monitored on Escherichia coli B in a double-agar overlay assay. T4 and the ciliate were incubated together under different conditions and for various times, after which the mixture was centrifuged through a step gradient, producing a top layer free of ciliates. The T4 titer in this layer decreased as coincubation time increased, but no decrease was seen if phage were incubated with formalin-fixed Tetrahymena. The T4 titer associated with the pellet of living ciliates was very low, suggesting that removal of the phage by Tetrahymena inactivated T4. When Tetrahymena cells were incubated with SYBR gold-labeled phage, fluorescence was localized in structures that had the shape and position of food vacuoles. Incubation of the phage and ciliate with cytochalasin B or at 4°C impaired T4 inactivation. These results suggest the active removal of T4 bacteriophage from fluid by macropinocytosis, followed by digestion in food vacuoles. Such ciliate virophagy may be a mechanism occurring in natural waters and sewage treatment, and the methods described here could be used to study the factors influencing inactivation and possibly water quality. PMID:17114327

  16. Expression of a cell surface immobilization antigen during serotype transformation in Tetrahymena thermophila.

    OpenAIRE

    Williams, N. E.; Doerder, F. P.; Ron, A

    1985-01-01

    A temperature shift from 40 to 28 degrees C rapidly induced expression of a specific immobilization antigen at the cell surface in Tetrahymena thermophila. This transformation was inhibited by actinomycin D and cycloheximide but not by colchicine or cytochalasin B. The major surface antigen expressed at 28 degrees C in cells homozygous for the SerH3 allele was partially purified, and an antiserum against this preparation was raised in rabbits. Electrophoresis, immunoblot, and [35S]methionine ...

  17. Autophagy is required for efficient meiosis progression and proper meiotic chromosome segregation in fission yeast.

    Science.gov (United States)

    Matsuhara, Hirotada; Yamamoto, Ayumu

    2016-01-01

    Autophagy is a conserved intracellular degradation system, which contributes to development and differentiation of various organisms. Yeast cells undergo meiosis under nitrogen-starved conditions and require autophagy for meiosis initiation. However, the precise roles of autophagy in meiosis remain unclear. Here, we show that autophagy is required for efficient meiosis progression and proper meiotic chromosome segregation in fission yeast. Autophagy-defective strains bearing a mutation in the autophagy core factor gene atg1, atg7, or atg14 exhibit deformed nuclear structures during meiosis. These mutant cells require an extracellular nitrogen supply for meiosis progression following their entry into meiosis and show delayed meiosis progression even with a nitrogen supply. In addition, they show frequent chromosome dissociation from the spindle together with spindle overextension, forming extra nuclei. Furthermore, Aurora kinase, which regulates chromosome segregation and spindle elongation, is significantly increased at the centromere and spindle in the mutant cells. Aurora kinase down-regulation eliminated delayed initiation of meiosis I and II, chromosome dissociation, and spindle overextension, indicating that increased Aurora kinase activity may cause these aberrances in the mutant cells. Our findings show a hitherto unrecognized relationship of autophagy with the nuclear structure, regulation of cell cycle progression, and chromosome segregation in meiosis. © 2015 The Molecular Biology Society of Japan and Wiley Publishing Asia Pty Ltd.

  18. Treatment development for systemic Tetrahymena sp. infection in guppies, Poecilia reticulata Peters.

    Science.gov (United States)

    Leibowitz, M Pimenta; Chettri, J Kumar; Ofir, R; Zilberg, D

    2010-06-01

    Antibacterial and antiparasitic agents and a cysteine protease inhibitor (E-64) were tested against Tetrahymena infection, a serious problem in guppy production worldwide. Chemicals were tested in vitro by a colorimetric assay for Tetrahymena survival. The most effective were niclosamide, albendazole and chloroquine, with 23%, 35% and 60% survival, respectively, following 2-h exposure to 100 ppm. Longer incubation periods resulted in greater reductions in survival. Niclosamide was further studied in vivo at different dosages, administered orally to Tetrahymena-infected guppies. Mortality rates were significantly lower in all treatment groups; in trial I, 30% and 33% mortality in 5 and 40 mg kg(-1) niclosamide-fed fish vs. 59% mortality in controls; in trial II, 35%, 13% and 10% in 50, 100 and 200 mg kg(-1) niclosamide-fed fish vs. 64% in controls. The effect of the cysteine protease inhibitor E64 was tested in tissue culture, by measuring histolytic activity of the parasite (Tet-NI) on a guppy-fin cell line, based on cell depletion. Tet-NI feeding activity was significantly reduced following pretreatment with E-64 relative to non-treated Tet-NI. E-64-pretreated Tet-NI was injected i.p. into guppies: recorded mortality rates were significantly lower (35%) than that in non-treated Tet-NI (60%), suggesting inhibition of the parasite's cysteine protease as a possible therapeutic approach.

  19. The relationship between energy-dependent phagocytosis and the rate of oxygen consumption in Tetrahymena.

    Science.gov (United States)

    Skriver, L; Nilsson, J R

    1978-12-01

    The induction of high rates of food vacuole formation in Tetrahymena pyriformis increased the rate of respiration in exponentially growing cells by 17% and in starving cells by 47.5%. The increased rate of oxygen uptake was caused by phagocytosis itself, as shown by comparing the rates of respiration of a Tetrahymena mutant exposed to particles at the permissive or restrictive temperatures for food vacuole formation. During cell division, heat-synchronized cells in rich, particle-supplemented medium showed a significant decrease in the rate of respiration. Furthermore, dimethyl sulphoxide, in concentrations sufficient to block food vacuole formation, suppressed the rate of respiration to a level similar to that of starved cells. Cytochalasin B, fowever, did not reduce the rate of oxygen uptake despite the inability of the cells to complete the formation of food vacuoles during treatment; a possible explanation for this finding is discussed. There was a strong correlation between formation of food vacuoles and a high metabolic rate in Tetrahymena.

  20. Prevention of DNA Rereplication Through a Meiotic Recombination Checkpoint Response

    Directory of Open Access Journals (Sweden)

    Nicole A. Najor

    2016-12-01

    Full Text Available In the budding yeast Saccharomyces cerevisiae, unnatural stabilization of the cyclin-dependent kinase inhibitor Sic1 during meiosis can trigger extra rounds of DNA replication. When programmed DNA double-strand breaks (DSBs are generated but not repaired due to absence of DMC1, a pathway involving the checkpoint gene RAD17 prevents this DNA rereplication. Further genetic analysis has now revealed that prevention of DNA rereplication also requires MEC1, which encodes a protein kinase that serves as a central checkpoint regulator in several pathways including the meiotic recombination checkpoint response. Downstream of MEC1, MEK1 is required through its function to inhibit repair between sister chromatids. By contrast, meiotic recombination checkpoint effectors that regulate gene expression and cyclin-dependent kinase activity are not necessary. Phosphorylation of histone H2A, which is catalyzed by Mec1 and the related Tel1 protein kinase in response to DSBs, and can help coordinate activation of the Rad53 checkpoint protein kinase in the mitotic cell cycle, is required for the full checkpoint response. Phosphorylation sites that are targeted by Rad53 in a mitotic S phase checkpoint response are also involved, based on the behavior of cells containing mutations in the DBF4 and SLD3 DNA replication genes. However, RAD53 does not appear to be required, nor does RAD9, which encodes a mediator of Rad53, consistent with their lack of function in the recombination checkpoint pathway that prevents meiotic progression. While this response is similar to a checkpoint mechanism that inhibits initiation of DNA replication in the mitotic cell cycle, the evidence points to a new variation on DNA replication control.

  1. Cohesin SMC1 beta is required for meiotic chromosome dynamics, sister chromatid cohesion and DNA recombination

    NARCIS (Netherlands)

    Revenkova, E.; Eijpe, M.; Heyting, C.; Hodges, C.A.; Hunt, P.A.; Liebe, B.; Scherthan, H.; Jessberger, R.

    2004-01-01

    Sister chromatid cohesion ensures the faithful segregation of chromosomes in mitosis and in both meiotic divisions1, 2, 3, 4. Meiosis-specific components of the cohesin complex, including the recently described SMC1 isoform SMC15, were suggested to be required for meiotic sister chromatid cohesion

  2. Meiotic nondisjunction in the mouse: methodology for genetic testing and comparison with other methods

    Energy Technology Data Exchange (ETDEWEB)

    Russell, L. B.

    1978-01-01

    The following topics are discussed: genetic method for detecting sex-chromosome nondisjunction; events that can produce nondisjunction in mammals; biological parameters that may maximize induced meiotic ND; comparison with other measures of germline chromosomal damage in mammals; comparison with other methods for detecting meiotic nondisjunction in mammals; and application of the genetic method for detecting nondisjunction. (HLW)

  3. Meiotic silencing and fragmentation of the male germline restricted chromosome in zebra finch

    NARCIS (Netherlands)

    S. Schoenmakers (Sam); E. Wassenaar (Evelyne); J.S.E. Laven (Joop); J.A. Grootegoed (Anton); W.M. Baarends (Willy)

    2010-01-01

    textabstractDuring male meiotic prophase in mammals, X and Y are in a largely unsynapsed configuration, which is thought to trigger meiotic sex chromosome inactivation (MSCI). In avian species, females are ZW, and males ZZ. Although Z and W in chicken oocytes show complete, largely heterologous

  4. Chromosome numbers and meiotic analysis in the pre-breeding of ...

    Indian Academy of Sciences (India)

    The most common meiotic abnormalities were related to irregular chromosome segregation, but chromosome stickiness and abnormal cytokinesis were observed in low frequency. All abnormalities can compromise pollen viability by generating unbalanced gametes. Based on the chromosome number and meiotic stability, ...

  5. The microtubule-associated protein ASPM regulates spindle assembly and meiotic progression in mouse oocytes.

    Science.gov (United States)

    Xu, Xiao-Ling; Ma, Wei; Zhu, Yu-Bo; Wang, Chao; Wang, Bing-Yuan; An, Na; An, Lei; Liu, Yan; Wu, Zhong-Hong; Tian, Jian-Hui

    2012-01-01

    The microtubule-associated protein ASPM (abnormal spindle-like microcephaly-associated) plays an important role in spindle organization and cell division in mitosis and meiosis in lower animals, but its function in mouse oocyte meiosis has not been investigated. In this study, we characterized the localization and expression dynamics of ASPM during mouse oocyte meiotic maturation and analyzed the effects of the downregulation of ASPM expression on meiotic spindle assembly and meiotic progression. Immunofluorescence analysis showed that ASPM localized to the entire spindle at metaphase I (MI) and metaphase II (MII), colocalizing with the spindle microtubule protein acetylated tubulin (Ac-tubulin). In taxol-treated oocytes, ASPM colocalized with Ac-tubulin on the excessively polymerized microtubule fibers of enlarged spindles and the numerous asters in the cytoplasm. Nocodazole treatment induced the gradual disassembly of microtubule fibers, during which ASPM remained colocalized with the dynamic Ac-tubulin. The downregulation of ASPM expression by a gene-specific morpholino resulted in an abnormal meiotic spindle and inhibited meiotic progression; most of the treated oocytes were blocked in the MI stage with elongated meiotic spindles. Furthermore, coimmunoprecipitation combined with mass spectrometry and western blot analysis revealed that ASPM interacted with calmodulin in MI oocytes and that these proteins colocalized at the spindle. Our results provide strong evidence that ASPM plays a critical role in meiotic spindle assembly and meiotic progression in mouse oocytes.

  6. The microtubule-associated protein ASPM regulates spindle assembly and meiotic progression in mouse oocytes.

    Directory of Open Access Journals (Sweden)

    Xiao-Ling Xu

    Full Text Available The microtubule-associated protein ASPM (abnormal spindle-like microcephaly-associated plays an important role in spindle organization and cell division in mitosis and meiosis in lower animals, but its function in mouse oocyte meiosis has not been investigated. In this study, we characterized the localization and expression dynamics of ASPM during mouse oocyte meiotic maturation and analyzed the effects of the downregulation of ASPM expression on meiotic spindle assembly and meiotic progression. Immunofluorescence analysis showed that ASPM localized to the entire spindle at metaphase I (MI and metaphase II (MII, colocalizing with the spindle microtubule protein acetylated tubulin (Ac-tubulin. In taxol-treated oocytes, ASPM colocalized with Ac-tubulin on the excessively polymerized microtubule fibers of enlarged spindles and the numerous asters in the cytoplasm. Nocodazole treatment induced the gradual disassembly of microtubule fibers, during which ASPM remained colocalized with the dynamic Ac-tubulin. The downregulation of ASPM expression by a gene-specific morpholino resulted in an abnormal meiotic spindle and inhibited meiotic progression; most of the treated oocytes were blocked in the MI stage with elongated meiotic spindles. Furthermore, coimmunoprecipitation combined with mass spectrometry and western blot analysis revealed that ASPM interacted with calmodulin in MI oocytes and that these proteins colocalized at the spindle. Our results provide strong evidence that ASPM plays a critical role in meiotic spindle assembly and meiotic progression in mouse oocytes.

  7. Meiotic behavior and pollen fertility of five species in the genus ...

    African Journals Online (AJOL)

    Meiotic behavior and pollen fertility were analysed in five Epimedium species: Epimedium chlorandrum, Epimedium acuminatum, Epimedium davidii, Epimedium ecalcaratum and Epimedium pubescens. Chromosome numbers for five species were 2n = 2x = 12. All examined species displayed stable meiotic process and ...

  8. Meiotic analysis of interspecific hybrids between Capsicum frutescens and Capsicum chinense

    Directory of Open Access Journals (Sweden)

    Nádia Fernandes Moreira

    2017-04-01

    Full Text Available The aim of this study was to observe the genetic relationship between C. frutescens (UENF 1636 and C. chinense (UENF 1785 based on the meiotic behavior, on the meiotic index, and on pollen viability of their F1 hybrids. For meiotic analysis and meiotic index, flower buds were collected and fixed for 24 hours in ethanol: acetic acid (3:1, and then transferred to 70% ethanol, and stored in a freezer. Slides preparation for meiosis, meiotic index and pollen viability was carried out according to the laboratory’s protocol. Hybrid meiosis was regular, and 12 pairs of chromosomes were observed in diakinesis, as well as a few anomalies. The MI of 88.16%, as well as the pollen viability of 72.5%, were satisfactory. Given the results, it was confirmed the genetic proximity of these species, which are classified in the Capsicum annuum gene complex.

  9. Meiotic behavior of wild Caricaceae species potentially suitable for papaya improvement

    Directory of Open Access Journals (Sweden)

    Emanuelli Narducci da Silva

    2012-01-01

    Full Text Available The purpose of this study was to evaluate the meiotic behavior and determine the meiotic index and pollen viability of representative plants of the wild species V. goudotiana, V. quercifolia and J. spinosa. Meiotic analysis confirmed that the species are diploid and have 18 chromosomes. Meiosis was partially normal, since some abnormalities, e.g, sticky and lagging chromosomes, precocious segregation, lack of synchrony, and disturbances in the spindle fibers were observed. These abnormalities resulted in post-meiotic products (monads, dyads, triads, and polyads that probably contributed to the meiotic index of 85.7 % (V. goudotiana to 95.9 % (J. spinosa; significant variation was observed in the species V. goudotiana. The pollen viability of 68.0% (V. goudotiana to 96.0 % (J. spinosa was reasonably good in these wild species. Crossings in breeding programs involving V. goudotiana should therefore be carefully planned, since part of the gametes of this species is unviable.

  10. Meiotically stable natural epialleles of Sadhu, a novel Arabidopsis retroposon.

    Directory of Open Access Journals (Sweden)

    Sanjida H Rangwala

    2006-03-01

    Full Text Available Epigenetic variation is a potential source of genomic and phenotypic variation among different individuals in a population, and among different varieties within a species. We used a two-tiered approach to identify naturally occurring epigenetic alleles in the flowering plant Arabidopsis: a primary screen for transcript level polymorphisms among three strains (Col, Cvi, Ler, followed by a secondary screen for epigenetic alleles. Here, we describe the identification of stable, meiotically transmissible epigenetic alleles that correspond to one member of a previously uncharacterized non-LTR retroposon family, which we have designated Sadhu. The pericentromeric At2g10410 element is highly expressed in strain Col, but silenced in Ler and 18 other strains surveyed. Transcription of this locus is inversely correlated with cytosine methylation and both the expression and DNA methylation states map in a Mendelian manner to stable cis-acting variation. The silent Ler allele can be converted by the epigenetic modifier mutation ddm1 to a meiotically stable expressing allele with an identical primary nucleotide sequence, demonstrating that the variation responsible for transcript level polymorphism among Arabidopsis strains is epigenetic. We extended our characterization of the Sadhu family members and show that different elements are subject to both genetic and epigenetic variation in natural populations. These findings support the view that an important component of natural variation in retroelements is epigenetic.

  11. Inventory and phylogenetic analysis of meiotic genes in monogonont rotifers.

    Science.gov (United States)

    Hanson, Sara J; Schurko, Andrew M; Hecox-Lea, Bette; Welch, David B Mark; Stelzer, Claus-Peter; Logsdon, John M

    2013-01-01

    A long-standing question in evolutionary biology is how sexual reproduction has persisted in eukaryotic lineages. As cyclical parthenogens, monogonont rotifers are a powerful model for examining this question, yet the molecular nature of sexual reproduction in this lineage is currently understudied. To examine genes involved in meiosis, we generated partial genome assemblies for 2 distantly related monogonont species, Brachionus calyciflorus and B. manjavacas. Here we present an inventory of 89 meiotic genes, of which 80 homologs were identified and annotated from these assemblies. Using phylogenetic analysis, we show that several meiotic genes have undergone relatively recent duplication events that appear to be specific to the monogonont lineage. Further, we compare the expression of "meiosis-specific" genes involved in recombination and all annotated copies of the cell cycle regulatory gene CDC20 between obligate parthenogenetic (OP) and cyclical parthenogenetic (CP) strains of B. calyciflorus. We show that "meiosis-specific" genes are expressed in both CP and OP strains, whereas the expression of one of the CDC20 genes is specific to cyclical parthenogenesis. The data presented here provide insights into mechanisms of cyclical parthenogenesis and establish expectations for studies of obligate asexual relatives of monogononts, the bdelloid rotifer lineage.

  12. Meiotic cohesin-based chromosome structure is essential for homologous chromosome pairing in Schizosaccharomyces pombe.

    Science.gov (United States)

    Ding, Da-Qiao; Matsuda, Atsushi; Okamasa, Kasumi; Nagahama, Yuki; Haraguchi, Tokuko; Hiraoka, Yasushi

    2016-06-01

    Chromosome structure is dramatically altered upon entering meiosis to establish chromosomal architectures necessary for the successful progression of meiosis-specific events. An early meiotic event involves the replacement of the non-SMC mitotic cohesins with their meiotic equivalents in most part of the chromosome, forming an axis on meiotic chromosomes. We previously demonstrated that the meiotic cohesin complex is required for chromosome compaction during meiotic prophase in the fission yeast Schizosaccharomyces pombe. These studies revealed that chromosomes are elongated in the absence of the meiotic cohesin subunit Rec8 and shortened in the absence of the cohesin-associated protein Pds5. In this study, using super-resolution structured illumination microscopy, we found that Rec8 forms a linear axis on chromosomes, which is required for the organized axial structure of chromatin during meiotic prophase. In the absence of Pds5, the Rec8 axis is shortened whereas chromosomes are widened. In rec8 or pds5 mutants, the frequency of homologous chromosome pairing is reduced. Thus, Rec8 and Pds5 play an essential role in building a platform to support the chromosome architecture necessary for the spatial alignment of homologous chromosomes.

  13. Function of nuclear membrane proteins in shaping the nuclear envelope integrity during closed mitosis.

    Science.gov (United States)

    Yang, Hui-Ju; Iwamoto, Masaaki; Hiraoka, Yasushi; Haraguchi, Tokuko

    2017-06-01

    The nuclear envelope (NE) not only protects the genome from being directly accessed by detrimental agents but also regulates genome organization. Breaches in NE integrity threaten genome stability and impede cellular function. Nonetheless, the NE constantly remodels, and NE integrity is endangered in dividing or differentiating cells. Specifically, in unicellular eukaryotes undergoing closed mitosis, the NE expands instead of breaking down during chromosome segregation. The newly assembling nuclear pore complexes (NPCs) penetrate the existing NE in interphase. A peculiar example of NE remodelling during nuclear differentiation in Tetrahymena involves formation of the redundant NE and clustered NPCs. Even under these conditions, the NE remains intact. Many recent studies on unicellular organisms have revealed that nuclear membrane proteins, such as LEM-domain proteins, play a role in maintaining NE integrity. This review summarizes and discusses how nuclear membrane proteins participate in NE integrity. © The Authors 2017. Published by Oxford University Press on behalf of the Japanese Biochemical Society. All rights reserved.

  14. The effects of nucleoside analogs on telomerase and telomeres in Tetrahymena.

    Science.gov (United States)

    Strahl, C; Blackburn, E H

    1994-03-25

    The ribonucleoprotein enzyme telomerase is a specialized type of cellular reverse transcriptase which synthesizes one strand of telomeric DNA, using as the template a sequence in the RNA moiety of telomerase. We analyzed the effects of various nucleoside analogs, known to be chain-terminating inhibitors of retroviral reverse transcriptases, on Tetrahymena thermophila telomerase activity in vitro. We also analyzed the effects of such analogs on telomere length and maintenance in vivo, and on vegetative growth and mating of Tetrahymena cells. Arabinofuranyl-guanosine triphosphate (Ara-GTP) and ddGTP both efficiently inhibited telomerase activity in vitro, while azidothymidine triphosphate (AZT-TP), dideoxyinosine triphosphate (ddITP) or ddTTP were less efficient inhibitors. All of these nucleoside triphosphate analogs, however, produced analog-specific alterations of the normal banding patterns seen upon gel electrophoresis of the synthesis products of telomerase, suggesting that their chain terminating and/or competitive actions differ at different positions along the RNA template. The analogs AZT, 3'-deoxy-2',3'-didehydrothymidine (d4T) and Ara-G in nucleoside form caused consistent and rapid telomere shortening in vegetatively growing Tetrahymena. In contrast, ddG or ddI had no effect on telomere length or cell growth rates. AZT caused growth rates and viability to decrease in a fraction of cells, while Ara-G had no such effects even after several weeks in culture. Neither AZT, Ara-G, acycloguanosine (Acyclo-G), ddG nor ddI had any detectable effect on cell mating, as assayed by quantitation of the efficiency of formation of progeny from mated cells. However, AZT decreased the efficiency of programmed de novo telomere addition during macronuclear development in mating cells.

  15. Using Micromanipulation to Analyze Control of Vertebrate Meiotic Spindle Size

    Directory of Open Access Journals (Sweden)

    Jun Takagi

    2013-10-01

    Full Text Available The polymerization/depolymerization dynamics of microtubules (MTs have been reported to contribute to control of the size and shape of spindles, but quantitative analysis of how the size and shape correlate with the amount and density of MTs in the spindle remains incomplete. Here, we measured these parameters using 3D microscopy of meiotic spindles that self-organized in Xenopus egg extracts and presented a simple equation describing the relationship among these parameters. To examine the validity of the equation, we cut the spindle into two fragments along the pole-to-pole axis by micromanipulation techniques that rapidly decrease the amount of MTs. The spheroidal shape spontaneously recovered within 5 min, but the size of each fragment remained small. The equation we obtained quantitatively describes how the spindle size correlates with the amount of MTs while maintaining the shape and the MT density.

  16. Tetrahymena thermophila acidic ribosomal protein L37 contains an archaebacterial type of C-terminus

    DEFF Research Database (Denmark)

    Hansen, T S; Andreasen, P H; Dreisig, H

    1991-01-01

    We have cloned and characterized a Tetrahymena thermophila macronuclear gene (L37) encoding the acidic ribosomal protein (A-protein) L37. The gene contains a single intron located in the 3'-part of the coding region. Two major and three minor transcription start points (tsp) were mapped 39 to 63...... nucleotides upstream from the translational start codon. The uppermost tsp mapped to the first T in a putative T. thermophila RNA polymerase II initiator element, TATAA. The coding region of L37 predicts a protein of 109 amino acid (aa) residues. A substantial part of the deduced aa sequence was verified...

  17. Functional intron+ and intron- rDNA in the same macronucleus of the ciliate Tetrahymena pigmentosa

    DEFF Research Database (Denmark)

    Nielsen, Henrik; Engberg, J

    1985-01-01

    alleles was followed in the total culture and in single cells during their vegetative segregation and it was observed that replication was non-preferential with respect to the two alleles. The diallelic clones were also used to demonstrate that intron-containing rDNA was transcribed and the transcript......Diallelic clones of Tetrahymena pigmentosa containing equal amounts of intron+ and intron- rDNA in the macronucleus were constructed. The macronucleus of the resulting strains divides amitotically during vegetative growth and the diallelic genotype is therefore unstable. The coexistence of the two...

  18. 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.

  19. Ascospores of large-spored Metschnikowia species are genuine meiotic products of these yeasts

    DEFF Research Database (Denmark)

    Marinoni, G.; Piskur, Jure; Lachance, M.A.

    2003-01-01

    The asci of Metschnikowia species normally contain two ascospores (never more), raising the question of whether these spores are true meiotic products. We investigated this problem by crossing genetically-marked strains of the haploid, heterothallic taxa, Metschnikowia hawaiiensis, Metschnikowia...

  20. Phylogenetic evidence for the acquisition of ribosomal RNA introns subsequent to the divergence of some of the major Tetrahymena groups

    DEFF Research Database (Denmark)

    Sogin, M L; Ingold, A; Karlok, M

    1986-01-01

    . In an attempt to evaluate the evolutionary origins of the intervening sequences, we have now determined complete small subunit ribosomal RNA gene sequences from 13 species of Tetrahymena and the absolute number of nucleotide differences between the sequences was used to construct a phylogenetic tree...

  1. Effects of protein kinase C activators and staurosporine on protein kinase activity, cell survival, and proliferation in Tetrahymena thermophila

    DEFF Research Database (Denmark)

    Straarup, EM; Schousboe, P; Hansen, HQ

    1997-01-01

    Autocrine factors prevent cell death in the ciliate Tetrahymena thermophila, a unicellular eukaryote, in a chemically defined medium. At certain growth conditions these factors are released at a sufficient concentration by > 500 cells ml-1 to support cell survival and proliferation. The protein k...

  2. Hybrid Sterility Locus on Chromosome X Controls Meiotic Recombination Rate in Mouse.

    Directory of Open Access Journals (Sweden)

    Maria Balcova

    2016-04-01

    Full Text Available Meiotic recombination safeguards proper segregation of homologous chromosomes into gametes, affects genetic variation within species, and contributes to meiotic chromosome recognition, pairing and synapsis. The Prdm9 gene has a dual role, it controls meiotic recombination by determining the genomic position of crossover hotspots and, in infertile hybrids of house mouse subspecies Mus m. musculus (Mmm and Mus m. domesticus (Mmd, it further functions as the major hybrid sterility gene. In the latter role Prdm9 interacts with the hybrid sterility X 2 (Hstx2 genomic locus on Chromosome X (Chr X by a still unknown mechanism. Here we investigated the meiotic recombination rate at the genome-wide level and its possible relation to hybrid sterility. Using immunofluorescence microscopy we quantified the foci of MLH1 DNA mismatch repair protein, the cytological counterparts of reciprocal crossovers, in a panel of inter-subspecific chromosome substitution strains. Two autosomes, Chr 7 and Chr 11, significantly modified the meiotic recombination rate, yet the strongest modifier, designated meiotic recombination 1, Meir1, emerged in the 4.7 Mb Hstx2 genomic locus on Chr X. The male-limited transgressive effect of Meir1 on recombination rate parallels the male-limited transgressive role of Hstx2 in hybrid male sterility. Thus, both genetic factors, the Prdm9 gene and the Hstx2/Meir1 genomic locus, indicate a link between meiotic recombination and hybrid sterility. A strong female-specific modifier of meiotic recombination rate with the effect opposite to Meir1 was localized on Chr X, distally to Meir1. Mapping Meir1 to a narrow candidate interval on Chr X is an important first step towards positional cloning of the respective gene(s responsible for variation in the global recombination rate between closely related mouse subspecies.

  3. Hybrid Sterility Locus on Chromosome X Controls Meiotic Recombination Rate in Mouse.

    Science.gov (United States)

    Balcova, Maria; Faltusova, Barbora; Gergelits, Vaclav; Bhattacharyya, Tanmoy; Mihola, Ondrej; Trachtulec, Zdenek; Knopf, Corinna; Fotopulosova, Vladana; Chvatalova, Irena; Gregorova, Sona; Forejt, Jiri

    2016-04-01

    Meiotic recombination safeguards proper segregation of homologous chromosomes into gametes, affects genetic variation within species, and contributes to meiotic chromosome recognition, pairing and synapsis. The Prdm9 gene has a dual role, it controls meiotic recombination by determining the genomic position of crossover hotspots and, in infertile hybrids of house mouse subspecies Mus m. musculus (Mmm) and Mus m. domesticus (Mmd), it further functions as the major hybrid sterility gene. In the latter role Prdm9 interacts with the hybrid sterility X 2 (Hstx2) genomic locus on Chromosome X (Chr X) by a still unknown mechanism. Here we investigated the meiotic recombination rate at the genome-wide level and its possible relation to hybrid sterility. Using immunofluorescence microscopy we quantified the foci of MLH1 DNA mismatch repair protein, the cytological counterparts of reciprocal crossovers, in a panel of inter-subspecific chromosome substitution strains. Two autosomes, Chr 7 and Chr 11, significantly modified the meiotic recombination rate, yet the strongest modifier, designated meiotic recombination 1, Meir1, emerged in the 4.7 Mb Hstx2 genomic locus on Chr X. The male-limited transgressive effect of Meir1 on recombination rate parallels the male-limited transgressive role of Hstx2 in hybrid male sterility. Thus, both genetic factors, the Prdm9 gene and the Hstx2/Meir1 genomic locus, indicate a link between meiotic recombination and hybrid sterility. A strong female-specific modifier of meiotic recombination rate with the effect opposite to Meir1 was localized on Chr X, distally to Meir1. Mapping Meir1 to a narrow candidate interval on Chr X is an important first step towards positional cloning of the respective gene(s) responsible for variation in the global recombination rate between closely related mouse subspecies.

  4. Elucidation of clathrin-mediated endocytosis in tetrahymena reveals an evolutionarily convergent recruitment of dynamin.

    Directory of Open Access Journals (Sweden)

    Nels C Elde

    2005-11-01

    Full Text Available Ciliates, although single-celled organisms, contain numerous subcellular structures and pathways usually associated with metazoans. How this cell biological complexity relates to the evolution of molecular elements is unclear, because features in these cells have been defined mainly at the morphological level. Among these ciliate features are structures resembling clathrin-coated, endocytic pits associated with plasma membrane invaginations called parasomal sacs. The combination of genome-wide sequencing in Tetrahymena thermophila with tools for gene expression and replacement has allowed us to examine this pathway in detail. Here we demonstrate that parasomal sacs are sites of clathrin-dependent endocytosis and that AP-2 localizes to these sites. Unexpectedly, endocytosis in Tetrahymena also involves a protein in the dynamin family, Drp1p (Dynamin-related protein 1. While phylogenetic analysis of AP subunits indicates a primitive origin for clathrin-mediated endocytosis, similar analysis of dynamin-related proteins suggests, strikingly, that the recruitment of dynamin-family proteins to the endocytic pathway occurred independently during the course of the ciliate and metazoan radiations. Consistent with this, our functional analysis suggests that the precise roles of dynamins in endocytosis, as well as the mechanisms of targeting, differ in metazoans and ciliates.

  5. Elucidation of Clathrin-Mediated Endocytosis in Tetrahymena Reveals an Evolutionarily Convergent Recruitment of Dynamin.

    Directory of Open Access Journals (Sweden)

    2005-11-01

    Full Text Available Ciliates, although single-celled organisms, contain numerous subcellular structures and pathways usually associated with metazoans. How this cell biological complexity relates to the evolution of molecular elements is unclear, because features in these cells have been defined mainly at the morphological level. Among these ciliate features are structures resembling clathrin-coated, endocytic pits associated with plasma membrane invaginations called parasomal sacs. The combination of genome-wide sequencing in Tetrahymena thermophila with tools for gene expression and replacement has allowed us to examine this pathway in detail. Here we demonstrate that parasomal sacs are sites of clathrin-dependent endocytosis and that AP-2 localizes to these sites. Unexpectedly, endocytosis in Tetrahymena also involves a protein in the dynamin family, Drp1p (Dynamin-related protein 1. While phylogenetic analysis of AP subunits indicates a primitive origin for clathrin-mediated endocytosis, similar analysis of dynamin-related proteins suggests, strikingly, that the recruitment of dynamin-family proteins to the endocytic pathway occurred independently during the course of the ciliate and metazoan radiations. Consistent with this, our functional analysis suggests that the precise roles of dynamins in endocytosis, as well as the mechanisms of targeting, differ in metazoans and ciliates.

  6. Developmental regulation of DNA replication: replication fork barriers and programmed gene amplification in Tetrahymena thermophila.

    Science.gov (United States)

    Zhang, Z; Macalpine, D M; Kapler, G M

    1997-01-01

    The palindromic Tetrahymena ribosomal DNA (rDNA) minichromosome is amplified 10,000-fold during development. Subsequent vegetative replication is cell cycle regulated. rDNA replication differs fundamentally in cycling vegetative and nondividing amplifying cells. Using two-dimensional gel electrophoresis, we show for the first time that replication origins that direct gene amplification also function in normal dividing cells. Two classes of amplification intermediates were identified. The first class is indistinguishable from vegetative rDNA, initiating in just one of the two 5' nontranscribed spacer (NTS) copies in the rDNA palindrome at either of two closely spaced origins. Thus, these origins are active throughout the life cycle and their regulation changes at different developmental stages. The second, novel class of amplification intermediates is generated by multiple initiation events. Intermediates with mass greater than fully replicated DNA were observed, suggesting that onionskin replication occurs at this stage. Unlike amplified rDNA in Xenopus laevis, the novel Tetrahymena species are not produced by random initiation; replication also initiates in the 5' NTS. Surprisingly, a replication fork barrier which is activated only in these amplifying molecules blocks the progression of forks near the center of the palindrome. Whereas barriers have been previously described, this is the first instance in which programmed regulation of replication fork progression has been demonstrated in a eukaryote. PMID:9315675

  7. Tetrahymena sp. infection in guppies, Poecilia reticulata Peters: parasite characterization and pathology of infected fish.

    Science.gov (United States)

    Leibowitz, M P; Zilberg, D

    2009-10-01

    Tetrahymena sp. infection was diagnosed in guppies imported from Singapore. The parasite was isolated (Tet-NI) and optimally cultured in vitro in RM-9 medium. Cytological analyses [silver-staining and scanning electron microscopy (SEM)] revealed a pyriform-shaped, 64 x 41-microm holotrich ciliate without caudal cilium, containing a macro-nucleus (18.25 x 16.83 microm) and micro-nucleus (5.73 x 5.40 microm). Wet-mount examination and histological analyses of fish exposed to the parasite by co-habitation, immersion and infection by i.p. (intra-peritoneal) and i.m. (intra-muscular) injection revealed numerous ciliates on the skin, and in the gill and caudal fin blood vessels. Ciliates surrounded internal organs, the peri-orbital region of the eye, and were observed inside developing guppy embryos. Some muscle necrosis was associated with infection, but little or no inflammatory response. Immersion, co-habitation and i.m. injection caused relatively high infection rates and levels in the skin and tail, and lower infection in the gill blood vessels and internal organs; i.p. injection caused higher infection in the gill blood vessels and internal organs. Co-habited fish had relatively high infection levels in the hind-gut sub-mucosa. This is the first report of controlled systemic infection by Tetrahymena sp.

  8. Sodium-dependent transport of [3H](1D)chiro-inositol by Tetrahymena.

    Science.gov (United States)

    Kersting, Michael C; Ryals, Phillip E

    2004-01-01

    The transport characteristics of (1D)chiro-inositol by the ciliate Tetrahymena were examined in competition studies employing [3H](1D)chiro-inositol. (1D)chiro-Inositol transport was competed by unlabeled (1D)chiro-inositol, myo-inositol, scyllo-inositol, and D-glucose in a concentration-dependent manner. Conversely, (1D)chiro-inositol competed for [3H]myo- and [3H]scyllo-inositol transport. Lineweaver-Burke analysis of the competition data indicated a Km of 10.3 mM and a Bmax of 4.7 nmol/min/mg for (1D)chiro-inositol. Transport of (1D)chiro-inositol was inhibited by cytochalasin B, an inhibitor of facilitated glucose transporters, and phlorizin, an inhibitor of sodium-dependent transporters. Removal of sodium from the radiolabeling buffer also inhibited uptake. The presence of 0.64 mM calcium or magnesium ions exerted negligible effects on transport, although potassium was inhibitory. [3H](1D)chiro-Inositol was shown to be incorporated into Tetrahymena phosphoinositides.

  9. Colocalization of somatic and meiotic double strand breaks near the Myc oncogene on mouse chromosome 15.

    Science.gov (United States)

    Ng, Siemon H; Maas, Sarah A; Petkov, Petko M; Mills, Kevin D; Paigen, Kenneth

    2009-10-01

    Both somatic and meiotic recombinations involve the repair of DNA double strand breaks (DSBs) that occur at preferred locations in the genome. Improper repair of DSBs during either mitosis or meiosis can lead to mutations, chromosomal aberration such as translocations, cancer, and/or cell death. Currently, no model exists that explains the locations of either spontaneous somatic DSBs or programmed meiotic DSBs or relates them to each other. One common class of tumorigenic translocations arising from DSBs is chromosomal rearrangements near the Myc oncogene. Myc translocations have been associated with Burkitt lymphoma in humans, plasmacytoma in mice, and immunocytoma in rats. Comparing the locations of somatic and meiotic DSBs near the mouse Myc oncogene, we demonstrated that the placement of these DSBs is not random and that both events clustered in the same short discrete region of the genome. Our work shows that both somatic and meiotic DSBs tend to occur in proximity to each other within the Myc region, suggesting that they share common originating features. It is likely that some regions of the genome are more susceptible to both somatic and meiotic DSBs, and the locations of meiotic hotspots may be an indicator of genomic regions more susceptible to DNA damage. (c) 2009 Wiley-Liss, Inc.

  10. The fission yeast RNA binding protein Mmi1 regulates meiotic genes by controlling intron specific splicing and polyadenylation coupled RNA turnover.

    Directory of Open Access Journals (Sweden)

    Huei-Mei Chen

    Full Text Available The polyA tails of mRNAs are monitored by the exosome as a quality control mechanism. We find that fission yeast, Schizosaccharomyces pombe, adopts this RNA quality control mechanism to regulate a group of 30 or more meiotic genes at the level of both splicing and RNA turnover. In vegetative cells the RNA binding protein Mmi1 binds to the primary transcripts of these genes. We find the novel motif U(U/C/GAAAC highly over-represented in targets of Mmi1. Mmi1 can specifically regulate the splicing of particular introns in a transcript: it inhibits the splicing of introns that are in the vicinity of putative Mmi1 binding sites, while allowing the splicing of other introns that are far from such sites. In addition, binding of Mmi1, particularly near the 3' end, alters 3' processing to promote extremely long polyA tails of up to a kilobase. The hyperadenylated transcripts are then targeted for degradation by the nuclear exonuclease Rrp6. The nuclear polyA binding protein Pab2 assists this hyperadenylation-mediated RNA decay. Rrp6 also targets other hyperadenylated transcripts, which become hyperadenylated in an unknown, but Mmi1-independent way. Thus, hyperadenylation may be a general signal for RNA degradation. In addition, binding of Mmi1 can affect the efficiency of 3' cleavage. Inactivation of Mmi1 in meiosis allows meiotic expression, through splicing and RNA stabilization, of at least 29 target genes, which are apparently constitutively transcribed.

  11. Selective Regulation of Oocyte Meiotic Events Enhances Progress in Fertility Preservation Methods

    Directory of Open Access Journals (Sweden)

    Onder Celik

    2015-01-01

    Full Text Available Following early embryonic germ cell migration, oocytes are surrounded by somatic cells and remain arrested at diplotene stage until luteinizing hormone (LH surge. Strict regulation of both meiotic arrest and meiotic resumption during dormant stage are critical for future fertility. Intercellular signaling system between the somatic compartment and oocyte regulates these meiotic events and determines the follicle quality. As well as the collected number of eggs, their qualities are also important for in vitro fertilization (IVF outcome. In spontaneous and IVF cycles, germinal vesicle (GV–stage oocytes, premature GV breakdown, and persistence of first meiotic arrest limit the reproductive performance. Likewise, both women with premature ovarian aging and young cancer women are undergoing chemoradiotherapy under the risk of follicle loss because of unregulated meiotic events. Understanding of oocyte meiotic events is therefore critical for the prevention of functional ovarian reserve. High levels of cyclic guanosine monophophate (cGMP, cyclic adenosine monophophate (cAMP and low phosphodiesterase (PDE 3A enzyme activity inside the oocyte are responsible for maintaining of meiotic arrest before the LH surge. cGMP is produced in the somatic compartment, and natriuretic peptide precursor C (Nppc and natriuretic peptide receptor 2 (Npr2 regulate its production. cGMP diffuses into the oocyte and reduces the PDE3A activity, which inhibits the conversion of cAMP to the 5′AMP, and cAMP levels are enhanced. In addition, oocyte itself has the ability to produce cAMP. Taken together, accumulation of cAMP inside the oocyte induces protein kinase activity, which leads to the inhibition of maturation-promoting factor and meiotic arrest also continues. By stimulating the expression of epidermal growth factor, LH inhibits the Nppc/Npr2 system, blocks cGMP synthesis, and initiates meiotic resumption. Oocytes lacking the functional of this pathway may lead to

  12. A yeast's eye view of mammalian reproduction: cross-species gene co-expression in meiotic prophase

    Directory of Open Access Journals (Sweden)

    Li Yunfei

    2010-09-01

    Full Text Available Abstract Background Meiotic prophase is a critical stage in sexual reproduction. Aberrant chromosome recombination during this stage is a leading cause of human miscarriages and birth defects. However, due to the experimental intractability of mammalian gonads, only a very limited number of meiotic genes have been characterized. Here we aim to identify novel meiotic genes important in human reproduction through computational mining of cross-species and cross-sex time-series expression data from budding yeast, mouse postnatal testis, mouse embryonic ovary, and human fetal ovary. Results Orthologous gene pairs were ranked by order statistics according to their co-expression profiles across species, allowing us to infer conserved meiotic genes despite obvious differences in cellular synchronicity and composition in organisms. We demonstrated that conserved co-expression networks could successfully recover known meiotic genes, including homologous recombination genes, chromatin cohesion genes, and genes regulating meiotic entry. We also showed that conserved co-expression pairs exhibit functional connections, as evidenced by the annotation similarity in Gene Ontology and overlap with physical interactions. More importantly, we predicted six new meiotic genes through their co-expression linkages with known meiotic genes, and subsequently used the genetically more amenable yeast system for experimental validation. The deletion mutants of all six genes showed sporulation defects, equivalent to a 100% validation rate. Conclusions We identified evolutionarily conserved gene modules in meiotic prophase by integrating cross-species and cross-sex expression profiles from budding yeast, mouse, and human. Our co-expression linkage analyses confirmed known meiotic genes and identified several novel genes that might be critical players in meiosis in multiple species. These results demonstrate that our approach is highly efficient to discover evolutionarily

  13. The evolution of meiotic sex and its alternatives.

    Science.gov (United States)

    Mirzaghaderi, Ghader; Hörandl, Elvira

    2016-09-14

    Meiosis is an ancestral, highly conserved process in eukaryotic life cycles, and for all eukaryotes the shared component of sexual reproduction. The benefits and functions of meiosis, however, are still under discussion, especially considering the costs of meiotic sex. To get a novel view on this old problem, we filter out the most conserved elements of meiosis itself by reviewing the various modifications and alterations of modes of reproduction. Our rationale is that the indispensable steps of meiosis for viability of offspring would be maintained by strong selection, while dispensable steps would be variable. We review evolutionary origin and processes in normal meiosis, restitutional meiosis, polyploidization and the alterations of meiosis in forms of uniparental reproduction (apomixis, apomictic parthenogenesis, automixis, selfing) with a focus on plants and animals. This overview suggests that homologue pairing, double-strand break formation and homologous recombinational repair at prophase I are the least dispensable elements, and they are more likely optimized for repair of oxidative DNA damage rather than for recombination. Segregation, ploidy reduction and also a biparental genome contribution can be skipped for many generations. The evidence supports the theory that the primary function of meiosis is DNA restoration rather than recombination. © 2016 The Authors.

  14. The equine oocyte: factors affecting meiotic and developmental competence.

    Science.gov (United States)

    Hinrichs, Katrin

    2010-08-01

    There is currently much interest in assisted reproduction techniques in the horse, however, many aspects of oocyte maturation, fertilization, and embryo development in the horse differ from those in other species. Because of the close attachment of the equine oocyte to the follicle wall, scraping of the follicle is the most effective method for oocyte recovery. A notable feature of equine oocytes is that those with expanded cumuli (Ex oocytes), which originate from atretic follicles, have higher meiotic competence (ability to mature to metaphase II in vitro) than do oocytes with compact cumuli (Cp oocytes). Cp oocytes originate in viable follicles but are largely juvenile. Recovery and culture of equine oocytes immediately after slaughter yields a higher maturation rate than that obtained from oocytes after ovary storage; this is related to damage to chromatin in Cp oocytes during storage. In contrast, developmental competence (rate of blastocyst development in vitro) is higher in oocytes recovered from the ovary after a delay. The optimum duration of maturation varies based on cumulus morphology and time of recovery from the ovary, but there is no difference in developmental competence between Ex and Cp oocytes. Because standard in vitro fertilization is not repeatable in the horse, oocyte transfer (surgical transfer of oocytes to the oviducts of inseminated mares) has been developed to allow fertilization of isolated oocytes. Fertilization in vitro may be achieved using intracytoplasmic sperm injection; culture of injected oocytes in a medium with high glucose can yield over 30% blastocyst development. (c) 2010 Wiley-Liss, Inc.

  15. Protein determinants of meiotic DNA break hot spots.

    Science.gov (United States)

    Fowler, Kyle R; Gutiérrez-Velasco, Susana; Martín-Castellanos, Cristina; Smith, Gerald R

    2013-03-07

    Meiotic recombination, crucial for proper chromosome segregation and genome evolution, is initiated by programmed DNA double-strand breaks (DSBs) in yeasts and likely all sexually reproducing species. In fission yeast, DSBs occur up to hundreds of times more frequently at special sites, called hot spots, than in other regions of the genome. What distinguishes hot spots from cold regions is an unsolved problem, although transcription factors determine some hot spots. We report the discovery that three coiled-coil proteins-Rec25, Rec27, and Mug20-bind essentially all hot spots with great specificity even without DSB formation. These small proteins are components of linear elements, are related to synaptonemal complex proteins, and are essential for nearly all DSBs at most hot spots. Our results indicate these hot spot determinants activate or stabilize the DSB-forming protein Rec12 (Spo11 homolog) rather than promote its binding to hot spots. We propose a paradigm for hot spot determination and crossover control by linear element proteins. Copyright © 2013 Elsevier Inc. All rights reserved.

  16. Holocentric chromosomes: convergent evolution, meiotic adaptations, and genomic analysis.

    Science.gov (United States)

    Melters, Daniël P; Paliulis, Leocadia V; Korf, Ian F; Chan, Simon W L

    2012-07-01

    In most eukaryotes, the kinetochore protein complex assembles at a single locus termed the centromere to attach chromosomes to spindle microtubules. Holocentric chromosomes have the unusual property of attaching to spindle microtubules along their entire length. Our mechanistic understanding of holocentric chromosome function is derived largely from studies in the nematode Caenorhabditis elegans, but holocentric chromosomes are found over a broad range of animal and plant species. In this review, we describe how holocentricity may be identified through cytological and molecular methods. By surveying the diversity of organisms with holocentric chromosomes, we estimate that the trait has arisen at least 13 independent times (four times in plants and at least nine times in animals). Holocentric chromosomes have inherent problems in meiosis because bivalents can attach to spindles in a random fashion. Interestingly, there are several solutions that have evolved to allow accurate meiotic segregation of holocentric chromosomes. Lastly, we describe how extensive genome sequencing and experiments in nonmodel organisms may allow holocentric chromosomes to shed light on general principles of chromosome segregation.

  17. A quality control mechanism coordinates meiotic prophase events to promote crossover assurance.

    Directory of Open Access Journals (Sweden)

    Alison J Deshong

    2014-04-01

    Full Text Available Meiotic chromosome segregation relies on homologous chromosomes being linked by at least one crossover, the obligate crossover. Homolog pairing, synapsis and meiosis specific DNA repair mechanisms are required for crossovers but how they are coordinated to promote the obligate crossover is not well understood. PCH-2 is a highly conserved meiotic AAA+-ATPase that has been assigned a variety of functions; whether these functions reflect its conserved role has been difficult to determine. We show that PCH-2 restrains pairing, synapsis and recombination in C. elegans. Loss of pch-2 results in the acceleration of synapsis and homolog-dependent meiotic DNA repair, producing a subtle increase in meiotic defects, and suppresses pairing, synapsis and recombination defects in some mutant backgrounds. Some defects in pch-2 mutants can be suppressed by incubation at lower temperature and these defects increase in frequency in wildtype worms grown at higher temperature, suggesting that PCH-2 introduces a kinetic barrier to the formation of intermediates that support pairing, synapsis or crossover recombination. We hypothesize that this kinetic barrier contributes to quality control during meiotic prophase. Consistent with this possibility, defects in pch-2 mutants become more severe when another quality control mechanism, germline apoptosis, is abrogated or meiotic DNA repair is mildly disrupted. PCH-2 is expressed in germline nuclei immediately preceding the onset of stable homolog pairing and synapsis. Once chromosomes are synapsed, PCH-2 localizes to the SC and is removed in late pachytene, prior to SC disassembly, correlating with when homolog-dependent DNA repair mechanisms predominate in the germline. Indeed, loss of pch-2 results in premature loss of homolog access. Altogether, our data indicate that PCH-2 coordinates pairing, synapsis and recombination to promote crossover assurance. Specifically, we propose that the conserved function of PCH-2 is to

  18. Sisters unbound is required for meiotic centromeric cohesion in Drosophila melanogaster.

    Science.gov (United States)

    Krishnan, Badri; Thomas, Sharon E; Yan, Rihui; Yamada, Hirotsugu; Zhulin, Igor B; McKee, Bruce D

    2014-11-01

    Regular meiotic chromosome segregation requires sister centromeres to mono-orient (orient to the same pole) during the first meiotic division (meiosis I) when homologous chromosomes segregate, and to bi-orient (orient to opposite poles) during the second meiotic division (meiosis II) when sister chromatids segregate. Both orientation patterns require cohesion between sister centromeres, which is established during meiotic DNA replication and persists until anaphase of meiosis II. Meiotic cohesion is mediated by a conserved four-protein complex called cohesin that includes two structural maintenance of chromosomes (SMC) subunits (SMC1 and SMC3) and two non-SMC subunits. In Drosophila melanogaster, however, the meiotic cohesion apparatus has not been fully characterized and the non-SMC subunits have not been identified. We have identified a novel Drosophila gene called sisters unbound (sunn), which is required for stable sister chromatid cohesion throughout meiosis. sunn mutations disrupt centromere cohesion during prophase I and cause high frequencies of non-disjunction (NDJ) at both meiotic divisions in both sexes. SUNN co-localizes at centromeres with the cohesion proteins SMC1 and SOLO in both sexes and is necessary for the recruitment of both proteins to centromeres. Although SUNN lacks sequence homology to cohesins, bioinformatic analysis indicates that SUNN may be a structural homolog of the non-SMC cohesin subunit stromalin (SA), suggesting that SUNN may serve as a meiosis-specific cohesin subunit. In conclusion, our data show that SUNN is an essential meiosis-specific Drosophila cohesion protein. Copyright © 2014 by the Genetics Society of America.

  19. Chapter 4. Stem cell proliferation versus meiotic fate decision in C. elegans

    Science.gov (United States)

    Schedl, Tim

    2013-01-01

    The C. elegans germ line has emerged as an important model for understanding how a stem cell population is maintained throughout the life of the animal while still producing the gametes necessary for propagation of the species. The stem cell population in the adult hermaphrodite is relatively large, with stem cells giving rise to daughters that appear intrinsically equivalent; however, some of the daughters retain the proliferative fate while others enter meiotic prophase. While machinery exists for cells to progress through the mitotic cell cycle and machinery exists for cells to progress through meiotic prophase, central to understanding germline development is identifying the genes and regulatory processes that determine whether the mitotic cell cycle or meiotic prophase machinery will be utilized; in other words, the genes that regulate the switch of germ cells from the proliferative stem cell fate to the meiotic development fate. Whether a germ cell self-renews or enters meiotic prophase is largely determined by its proximity to the distal tip cell (DTC), which is the somatic niche cell that caps the distal end of the gonad. Germ cells close to the DTC have high levels of GLP-1 Notch signaling, which promotes the proliferative fate, while cells further from the DTC have high activity levels of the GLD-1 and GLD-2 redundant RNA regulatory pathways, as well as a third uncharacterized pathway, each of which direct cells to enter meiotic prophase. Other factors and pathways modulate this core genetic pathway, or work in parallel to it, presumably to ensure that a tight balance is maintained between proliferation and meiotic entry. PMID:22872475

  20. Transcriptome analysis of the model protozoan, Tetrahymena thermophila, using Deep RNA sequencing.

    Directory of Open Access Journals (Sweden)

    Jie Xiong

    Full Text Available BACKGROUND: The ciliated protozoan Tetrahymena thermophila is a well-studied single-celled eukaryote model organism for cellular and molecular biology. However, the lack of extensive T. thermophila cDNA libraries or a large expressed sequence tag (EST database limited the quality of the original genome annotation. METHODOLOGY/PRINCIPAL FINDINGS: This RNA-seq study describes the first deep sequencing analysis of the T. thermophila transcriptome during the three major stages of the life cycle: growth, starvation and conjugation. Uniquely mapped reads covered more than 96% of the 24,725 predicted gene models in the somatic genome. More than 1,000 new transcribed regions were identified. The great dynamic range of RNA-seq allowed detection of a nearly six order-of-magnitude range of measurable gene expression orchestrated by this cell. RNA-seq also allowed the first prediction of transcript untranslated regions (UTRs and an updated (larger size estimate of the T. thermophila transcriptome: 57 Mb, or about 55% of the somatic genome. Our study identified nearly 1,500 alternative splicing (AS events distributed over 5.2% of T. thermophila genes. This percentage represents a two order-of-magnitude increase over previous EST-based estimates in Tetrahymena. Evidence of stage-specific regulation of alternative splicing was also obtained. Finally, our study allowed us to completely confirm about 26.8% of the genes originally predicted by the gene finder, to correct coding sequence boundaries and intron-exon junctions for about a third, and to reassign microarray probes and correct earlier microarray data. CONCLUSIONS/SIGNIFICANCE: RNA-seq data significantly improve the genome annotation and provide a fully comprehensive view of the global transcriptome of T. thermophila. To our knowledge, 5.2% of T. thermophila genes with AS is the highest percentage of genes showing AS reported in a unicellular eukaryote. Tetrahymena thus becomes an excellent unicellular

  1. A community model of ciliate Tetrahymena and bacteria E. coli. Part 1: Individual-based models of Tetrahymena and E. coli populations

    Energy Technology Data Exchange (ETDEWEB)

    Jaworska, J.S.; Hallam, T.G.; Schultz, T.W. [Univ. of Tennessee, Knoxville, TN (United States)

    1996-03-01

    The dynamics of a microbial community consisting of a eucaryotic ciliate Tetrahymena pyriformis and procaryotic. Escherichia coli in a batch culture is explored by employing an individual-based approach. In this portion of the article, Part 1, population models are presented. Because both models are individual-based, models of individual organisms are developed prior to construction of the population models. The individual models use an energy budget method in which growth depends on energy gain from feeding and energy sinks such as maintenance and reproduction. These models are not limited by simplifying assumptions about constant yield, constant energy sinks and Monod growth kinetics as are traditional models of microbial organisms. Population models are generated from individual models by creating distinct individual types and assigning to each type the number of real individuals they represent. A population is a compilation of individual types that vary in a phase of cell cycle and physiological parameters such as filtering rate for ciliates and maximum anabolic rate for bacteria. An advantage of the developed models is that they realistically describe the growth of the individual cells feeding on resource which varies in density and composition. Part 2, the core of the project, integrates models into a dynamic microbial community and provides model analysis based upon available data.

  2. An mre11 mutant of Coprinus cinereus has defects in meiotic chromosome pairing, condensation and synapsis.

    Science.gov (United States)

    Gerecke, E E; Zolan, M E

    2000-01-01

    The rad11 gene of the basidiomycete Coprinus cinereus is required for the completion of meiosis and for survival after gamma irradiation. We have cloned the rad11 gene and shown that it is a homolog of MRE11, a gene required for meiosis and DNA repair in numerous organisms. The expression of C. cinereus mre11 is induced during prophase I of meiosis and following gamma irradiation. The gene encodes a predicted polypeptide of 731 amino acids, and the mre11-1 (rad11-1) mutation is a single base pair change that results in a stop codon after amino acid 315. The mre11-1 mutant shows enhanced sensitivity to ionizing radiation, but no enhanced sensitivity to UV radiation. It shows a delay in fruitbody formation and a reduction in the number of mushrooms formed per dikaryon. The mre11-1 mutant also has several meiotic defects. Pachytene chromatin condensation is disrupted, and although some meiotic cells appear to achieve metaphase I condensation, no further meiotic progression is observed. The mre11-1 mutant also fails to undergo proper chromosome synapsis; neither axial elements nor mature synaptonemal complexes are complete. Finally, meiotic homolog pairing is reduced in the mre11-1 mutant. Thus, in C. cinereus, Mre11 is required for meiotic DNA metabolism. PMID:10757758

  3. Augmin promotes meiotic spindle formation and bipolarity in Xenopus egg extracts.

    Science.gov (United States)

    Petry, Sabine; Pugieux, Céline; Nédélec, François J; Vale, Ronald D

    2011-08-30

    Female meiotic spindles in many organisms form in the absence of centrosomes, the organelle typically associated with microtubule (MT) nucleation. Previous studies have proposed that these meiotic spindles arise from RanGTP-mediated MT nucleation in the vicinity of chromatin; however, whether this process is sufficient for spindle formation is unknown. Here, we investigated whether a recently proposed spindle-based MT nucleation pathway that involves augmin, an 8-subunit protein complex, also contributes to spindle morphogenesis. We used an assay system in which hundreds of meiotic spindles can be observed forming around chromatin-coated beads after introduction of Xenopus egg extracts. Spindles forming in augmin-depleted extracts showed reduced rates of MT formation and were predominantly multipolar, revealing a function of augmin in stabilizing the bipolar shape of the acentrosomal meiotic spindle. Our studies also have uncovered an apparent augmin-independent MT nucleation process from acentrosomal poles, which becomes increasingly active over time and appears to partially rescue the spindle defects that arise from augmin depletion. Our studies reveal that spatially and temporally distinct MT generation pathways from chromatin, spindle MTs, and acentrosomal poles all contribute to robust bipolar spindle formation in meiotic extracts.

  4. The chromatin remodeling complex Swi/Snf regulates splicing of meiotic transcripts in Saccharomyces cerevisiae.

    Science.gov (United States)

    Venkataramanan, Srivats; Douglass, Stephen; Galivanche, Anoop R; Johnson, Tracy L

    2017-07-27

    Despite its relatively streamlined genome, there are important examples of regulated RNA splicing in Saccharomyces cerevisiae, such as splicing of meiotic transcripts. Like other eukaryotes, S. cerevisiae undergoes a dramatic reprogramming of gene expression during meiosis, including regulated splicing of a number of crucial meiosis-specific RNAs. Splicing of a subset of these is dependent upon the splicing activator Mer1. Here we show a crucial role for the chromatin remodeler Swi/Snf in regulation of splicing of meiotic genes and find that the complex affects meiotic splicing in two ways. First, we show that Swi/Snf regulates nutrient-dependent downregulation of ribosomal protein encoding RNAs, leading to the redistribution of spliceosomes from this abundant class of intron-containing RNAs (the ribosomal protein genes) to Mer1-regulated transcripts. We also demonstrate that Mer1 expression is dependent on Snf2, its acetylation state and histone H3 lysine 9 acetylation at the MER1 locus. Hence, Snf2 exerts systems level control of meiotic gene expression through two temporally distinct mechanisms, demonstrating that it is a key regulator of meiotic splicing in S. cerevisiae. We also reveal an evolutionarily conserved mechanism whereby the cell redirects its energy from maintaining its translational capacity to the process of meiosis. © The Author(s) 2017. Published by Oxford University Press on behalf of Nucleic Acids Research.

  5. Meiotic behaviour and morpho-phenological variation in cut stock (Matthiola incana L. flower

    Directory of Open Access Journals (Sweden)

    Irani Sepideh Famil

    2017-06-01

    Full Text Available Morpho-phenological and meiotic studies were performed in twelve cultivars of Matthiola incana. All of the cultivars were diploid (2n = 2x = 14 with basic chromosome number x = 7. A number of aneuploid PMCs (n + 1 were observed in plants of two cultivars, named ‘Nobel’ (NB and ‘Goddess’ (GD, at the diakinesis stage. Trisomic individuals with the frequency of 20% and 5% and (2n + 1 = 15 somatic chromosomes were observed in seeds obtained from single-flowered plants of the cultivars NB and GD, respectively. An additional chromosome was mostly observed in the form of a chain trivalent or a rod univalent. Various meiotic abnormalities were found in all the cultivars to different degrees. In these cultivars, the percentage of cells with meiotic abnormalities was higher in anaphase I. Cytomixis was observed for the first time in Matthiola incana. ANOVA tests revealed significant differences in morpho-phenological characteristics. ‘Nobel’ differs from the others in all of the vegetative features investigated in this study. All the cultivars studied except ‘Nobel’ and ‘Pacific Crimson’ possessed high pollen fertility (> 90%. Five groups of the cultivars based on morpho-phenological features disagree with the clustering of cultivars based on meiotic traits. It is thought that the various morpho-phenological features observed among the cultivars could be due to their different genetic background and not only to meiotic anomalies.

  6. Mutation in mouse hei10, an e3 ubiquitin ligase, disrupts meiotic crossing over.

    Directory of Open Access Journals (Sweden)

    Jeremy O Ward

    2007-08-01

    Full Text Available Crossing over during meiotic prophase I is required for sexual reproduction in mice and contributes to genome-wide genetic diversity. Here we report on the characterization of an N-ethyl-N-nitrosourea-induced, recessive allele called mei4, which causes sterility in both sexes owing to meiotic defects. In mutant spermatocytes, chromosomes fail to congress properly at the metaphase plate, leading to arrest and apoptosis before the first meiotic division. Mutant oocytes have a similar chromosomal phenotype but in vitro can undergo meiotic divisions and fertilization before arresting. During late meiotic prophase in mei4 mutant males, absence of cyclin dependent kinase 2 and mismatch repair protein association from chromosome cores is correlated with the premature separation of bivalents at diplonema owing to lack of chiasmata. We have identified the causative mutation, a transversion in the 5' splice donor site of exon 1 in the mouse ortholog of Human Enhancer of Invasion 10 (Hei10; also known as Gm288 in mouse and CCNB1IP1 in human, a putative B-type cyclin E3 ubiquitin ligase. Importantly, orthologs of Hei10 are found exclusively in deuterostomes and not in more ancestral protostomes such as yeast, worms, or flies. The cloning and characterization of the mei4 allele of Hei10 demonstrates a novel link between cell cycle regulation and mismatch repair during prophase I.

  7. Histone H2AX phosphorylation is associated with most meiotic events in grasshopper.

    Science.gov (United States)

    Cabrero, J; Teruel, M; Carmona, F D; Camacho, J P M

    2007-01-01

    It is widely accepted that the H2AX histone in its phosphorylated form (gamma-H2AX) is related to the repair of DNA double-strand breaks (DSBs). In several organisms, gamma-H2AX presence has been demonstrated in meiotic processes such as recombination and sex chromosome inactivation during prophase I (from leptotene to pachytene). To test whether gamma-H2AX is present beyond pachytene, we have analysed the complete sequence of changes in H2AX phosphorylation during meiosis in grasshopper, a model organism for meiotic studies at the cytological level. We show the presence of phosphorylated H2AX during most of meiosis, with the exception only of diplotene and the end of each meiotic division. During the first meiotic division, gamma-H2AX is associated with i) recombination, as deduced from its presence in leptotene-zygotene over all chromosome length, ii) X chromosome inactivation, since at pachytene gamma-H2AX is present in the X chromosome only, and iii) chromosome segregation, as deduced from gamma-H2AX presence in centromere regions at first metaphase-anaphase. During second meiotic division, gamma-H2AX was very abundant at most chromosome lengths from metaphase to telophase, suggesting its possible association with the maintenance of chromosome condensation and segregation. Copyright 2007 S. Karger AG, Basel.

  8. Product analysis illuminates the final steps of IES deletion in Tetrahymena thermophila.

    Science.gov (United States)

    Saveliev, S V; Cox, M M

    2001-06-15

    DNA sequences (IES elements) eliminated from the developing macronucleus in the ciliate Tetrahymena thermophila are released as linear fragments, which have now been detected and isolated. A PCR-mediated examination of fragment end structures reveals three types of strand scission events, reflecting three steps in the deletion process. New evidence is provided for two steps proposed previously: an initiating double-stranded cleavage, and strand transfer to create a branched deletion intermediate. The fragment ends provide evidence for a previously uncharacterized third step: the branched DNA strand is cleaved at one of several defined sites located within 15-16 nucleotides of the IES boundary, liberating the deleted DNA in a linear form.

  9. Probabilistic neural network modeling of the toxicity of chemicals to Tetrahymena pyriformis with molecular fragment descriptors.

    Science.gov (United States)

    Kaiser, K L E; Niculescu, S P; Schultz, T W

    2002-03-01

    We present the results of an investigation into the use of a probabilistic neural network (PNN) based methodology to model the 48-60-h ICG50 (inhibitory concentration for population growth) sublethal toxicity to the ciliate Tetrahymena pyriformis. The information fed into the neural network is solely based on simple molecular descriptors as can be derived from the chemical structure. In contrast to most other toxicological models, the octanol/water partition coefficient is not used as an input parameter and no rules of thumb, or other substance selection-criteria, are involved. The model was trained on a 1,000 substances data set and validated using an 84 substances external test set. The associated analysis of errors confirms the excellent recognitive and predictive capabilities of the model.

  10. Fine structure and RNA synthesis of Tetrahymena during cytochalasin B inhibition of phagocytosis.

    Science.gov (United States)

    Nilsson, J R

    1977-01-01

    Cytochalasin B inhibits the formation of normal-sized food vacuoles in Tetrahymena but the cells do not starve. Treated cells differ from starved cells in that they retain a high rate of incorporation of tritiated uridine. Large numbers of smaller vacuoles, about 1 micrometer in diameter, are formed, presumably by pinocytic activity of the cytopharyngeal membrane. This effect may perhaps be due to interference with the mechanism by which food vacuoles are sealed off at the cytostome, in which microfilaments may participate. Inhibited organisms may form tubes continuous with the cytopharynx instead of separate food vacuoles. It is not clear, however, why the formation of the small vacuoles is resistant to the drug.

  11. Expression of a cell surface immobilization antigen during serotype transformation in Tetrahymena thermophila.

    Science.gov (United States)

    Williams, N E; Doerder, F P; Ron, A

    1985-08-01

    A temperature shift from 40 to 28 degrees C rapidly induced expression of a specific immobilization antigen at the cell surface in Tetrahymena thermophila. This transformation was inhibited by actinomycin D and cycloheximide but not by colchicine or cytochalasin B. The major surface antigen expressed at 28 degrees C in cells homozygous for the SerH3 allele was partially purified, and an antiserum against this preparation was raised in rabbits. Electrophoresis, immunoblot, and [35S]methionine incorporation studies are reported which support the conclusion that the H3 antigen is an acidic protein with an Mr of approximately 52,000 daltons. An induced synthesis of the H3 immobilization antigen was detected within 30 min after a shift from 40 to 28 degrees C. This protein appeared to be synthesized in the microsomal fraction and transferred without cleavage to the cell surface, where it was inserted first into nonciliated regions.

  12. Meiotic segregation and sperm DNA fragmentation in Tunisian men with dysplasia of the fibrous sheath (DFS) associated with head abnormalities.

    Science.gov (United States)

    Ghedir, H; Mehri, A; Mehdi, M; Brahem, S; Saad, A; Ibala-Romdhane, S

    2014-09-01

    Dysplasia of the Fibrous Sheath (DFS) is a primitive flagellar pathology for which a broad spectrum of ultrastructural flagellar abnormalities has been described responsible for a severe to total asthenozoospermia. To this phenotype other morphological abnormalities including cephalic and abnormalities in nuclear structure can be associated that could compromise embryonic development in case of use of Assisted Reproductive Technology (ART). The aim of this study was to evaluate the level of DNA fragmentation and aneuploidy rate in ejaculated spermatozoa of Tunisian men presented with DFS sperm defect associated to high percentage of head abnormalities and to compare the results with those from fertile men. Sperm DNA fragmentation was evaluated by the terminal desoxynucleotidyl transferase mediated deoxyuridine triphosphate biotin nick-end labelling (TUNEL) assay. The study of meiotic segregation was performed by Fluorescence in situ hybridization (FISH) for chromosomes X, Y and 18. The mean DNA fragmentation index was significantly higher in patients compared to the control group. FISH revealed a significantly higher incidence of sperm aneuploidies compared with controls. All patients showed elevated frequencies of sex chromosomes disomy, disomy 18 and diploidy. In some cases of syndromic teratozoospermia due to sperm tail structural abnormalities, such as DFS, other morphological cephalic abnormalities may be associated. In these cases we have demonstrated impaired sperm nuclear quality which will affect the results in ICSI. Hence the interest of a thorough study of the sperm nucleus in these forms of infertility in order to predict the chances of success in ART.

  13. The CAF-1 and Hir Histone Chaperones Associate with Sites of Meiotic Double-Strand Breaks in Budding Yeast: e0125965

    National Research Council Canada - National Science Library

    Elsa Brachet; Claire Béneut; Maria-Elisabetta Serrentino; Valérie Borde

    2015-01-01

    ... by stabilizing recombination intermediates. Here we show in budding yeast that nucleosomes flanking a meiotic DSB are transiently lost during recombination, and that specific histone H3 chaperones, CAF-1 and Hir, are mobilized at meiotic DSBs...

  14. Stra8 and its inducer, retinoic acid, regulate meiotic initiation in both spermatogenesis and oogenesis in mice

    NARCIS (Netherlands)

    Anderson, Ericka L.; Baltus, Andrew E.; Roepers-Gajadien, Hermien L.; Hassold, Terry J.; de Rooij, Dirk G.; van Pelt, Ans M. M.; Page, David C.

    2008-01-01

    In eukaryotes, diploid cells give rise to haploid cells via meiosis, a program of two cell divisions preceded by one round of DNA replication. Although key molecular components of the meiotic apparatus are highly conserved among eukaryotes, the mechanisms responsible for initiating the meiotic

  15. Characterization of wheat-Thinopyrum partial amphiploids by meiotic analysis and genomic in situ hybridization.

    Science.gov (United States)

    Fedak, G; Chen, Q; Conner, R L; Laroche, A; Petroski, R; Armstrong, K W

    2000-08-01

    A combination of genomic in situ hybridization (GISH) and meiotic pairing analysis of wheat-Thinopyrum partial amphiploids was employed to identify the genomic constitution and relationships between partial amphiploids derived from wheat and wheatgrass crosses. On the basis of similarities in the meiotic behavior and GISH patterns, the alien chromosomes of two of eight partial amphiploids, TAF46 and 'Otrastayuskaya 38', were judged to originate from Th. intermedium, whereas Th. ponticum was one of the parents of the other six partial amphiploids; PWM706, PWM206, PWM209, PWMIII, OK7211542, and Ag-wheat hybrid. Each of these partial amphiploids was found to contain a synthetic alien genome composed of different combinations of St-, J-, or Js-genome chromosomes. For relatedness of partial amphiploid lines, meiotic analysis of F1 hybrids and GISH results were generally complementary, but the latter offered greater precision in identifying constituent genomes.

  16. Altered cohesin gene dosage affects Mammalian meiotic chromosome structure and behavior.

    Directory of Open Access Journals (Sweden)

    Brenda Murdoch

    Full Text Available Based on studies in mice and humans, cohesin loss from chromosomes during the period of protracted meiotic arrest appears to play a major role in chromosome segregation errors during female meiosis. In mice, mutations in meiosis-specific cohesin genes cause meiotic disturbances and infertility. However, the more clinically relevant situation, heterozygosity for mutations in these genes, has not been evaluated. We report here evidence from the mouse that partial loss of gene function for either Smc1b or Rec8 causes perturbations in the formation of the synaptonemal complex (SC and affects both synapsis and recombination between homologs during meiotic prophase. Importantly, these defects increase the frequency of chromosomally abnormal eggs in the adult female. These findings have important implications for humans: they suggest that women who carry mutations or variants that affect cohesin function have an elevated risk of aneuploid pregnancies and may even be at increased risk of transmitting structural chromosome abnormalities.

  17. Meiotic versus Mitotic Recombination: Two Different Routes for Double-Strand Break Repair

    Science.gov (United States)

    Andersen, Sabrina L.; Sekelsky, Jeff

    2011-01-01

    Summary Studies in the yeast Saccharomyces cerevisiae have validated the major features of the double-strand break repair (DSBR) model as an accurate representation of the pathway through which meiotic crossovers are produced. This success has led to this model being invoked to explain double-strand break (DSB) repair in other contexts. However, most non-crossover recombinants generated during S. cerevisiae meiosis do not arise via a DSBR pathway. Furthermore, and it is becoming increasing clear that DSBR is a minor pathway for recombinational repair of DSBs that occur in mitotically proliferating cells; rather, the synthesis-dependent strand annealing (SDSA) model appears to describe mitotic DSB repair more accurately. Fundamental dissimilarities between meiotic and mitotic recombination are not unexpected, since meiotic recombination serves a very different purpose (accurate chromosome segregation, which requires crossovers) than mitotic recombination (repair of DNA damage, which typically generates non-crossovers). PMID:20967781

  18. Grazing of a Tetrahymena sp. on Adhered Bacteria in Percolated Columns Monitored by In Situ Hybridization with Fluorescent Oligonucleotide Probes

    OpenAIRE

    Eisenmann, Heinrich; Harms, Hauke; Meckenstock, Rainer; Meyer, Elisabeth I.; Zehnder, Alexander J. B.

    1998-01-01

    Predation of attached Pseudomonas putida mt2 by the small ciliate Tetrahymena sp. was investigated with a percolated column system. Grazing rates were examined under static and dynamic conditions and were compared to grazing rates in batch systems containing suspended prey. The prey densities were 2 × 108 bacteria per ml of pore space and 2 × 108 bacteria per ml of suspension, respectively. Postingestion in situ hybridization of bacteria with fluorescent oligonucleotide probes was used to qua...

  19. ADF/cofilin is not essential but is critically important for actin activities during phagocytosis in Tetrahymena thermophila.

    Science.gov (United States)

    Shiozaki, Nanami; Nakano, Kentaro; Kushida, Yasuharu; Noguchi, Taro Q P; Uyeda, Taro Q P; Wloga, Dorota; Dave, Drashti; Vasudevan, Krishna Kumar; Gaertig, Jacek; Numata, Osamu

    2013-08-01

    ADF/cofilin is a highly conserved actin-modulating protein. Reorganization of the actin cytoskeleton in vivo through severing and depolymerizing of F-actin by this protein is essential for various cellular events, such as endocytosis, phagocytosis, cytokinesis, and cell migration. We show that in the ciliate Tetrahymena thermophila, the ADF/cofilin homologue Adf73p associates with actin on nascent food vacuoles. Overexpression of Adf73p disrupted the proper localization of actin and inhibited the formation of food vacuoles. In vitro, recombinant Adf73p promoted the depolymerization of filaments made of T. thermophila actin (Act1p). Knockout cells lacking the ADF73 gene are viable but grow extremely slowly and have a severely decreased rate of food vacuole formation. Knockout cells have abnormal aggregates of actin in the cytoplasm. Surprisingly, unlike the case in animals and yeasts, in Tetrahymena, ADF/cofilin is not required for cytokinesis. Thus, the Tetrahymena model shows promise for future studies of the role of ADF/cofilin in vivo.

  20. Visualizing and Analyzing Branching Microtubule Nucleation Using Meiotic Xenopus Egg Extracts and TIRF Microscopy.

    Science.gov (United States)

    King, Matthew; Petry, Sabine

    2016-01-01

    Mitotic and meiotic spindles consist primarily of microtubules, which originate from centrosomes and within the vicinity of chromatin. Indirect evidence suggested that microtubules also originate throughout the spindle, but the high microtubule density within the spindle precludes the direct observation of this phenomenon. By using meiotic Xenopus laevis egg extract and employing total internal reflection (TIRF) microscopy, microtubule nucleation from preexisting microtubules could be demonstrated and analyzed. Branching microtubule nucleation is an ideal mechanism to assemble and maintain a mitotic spindle, because microtubule numbers are amplified while preserving their polarity. Here, we describe the assays that made these findings possible and the experiments that helped identify the key molecular players involved.

  1. A meiotic study of two translocations and a tertiary trisomic in the mouse (Mus musculus)

    NARCIS (Netherlands)

    Boer, de P.

    1975-01-01

    In this section, the order of the articles has not been closely followed. Each point ends with the number(s) of the article(s) (as given in the contents), where the conclusion is based on.

    1) Cytological meiotic studies of T(2;8)26H and T(1;13)70H heterozygotes and Ts(1

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

    NARCIS (Netherlands)

    Nijhoff, J.H.

    1981-01-01

    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. It is generally accepted that, when no chromosomal rearrangements are involved, man

  3. SPO11-Independent DNA Repair Foci and Their Role in Meiotic Silencing

    NARCIS (Netherlands)

    F. Carofiglio (Fabrizia); A. Inagaki (Akiko); S.I. de Vries (Sanne); E. Wassenaar (Evelyne); S. Schoenmakers (Sam); C.E. Vermeulen (Cindy); W.A. van Cappellen (Gert); E. Sleddens-Linkels (Esther); J.A. Grootegoed (Anton); H.P.J. te Riele (Hein); B. de Massy (Bernard); W.M. Baarends (Willy)

    2013-01-01

    textabstractIn mammalian meiotic prophase, the initial steps in repair of SPO11-induced DNA double-strand breaks (DSBs) are required to obtain stable homologous chromosome pairing and synapsis. The X and Y chromosomes pair and synapse only in the short pseudo-autosomal regions. The rest of the

  4. The epigenetic modifications and the anterior to posterior characterization of meiotic entry during mouse oogenesis.

    Science.gov (United States)

    Fu, Xia-Fei; Yang, Fan; Cheng, Shun-Feng; Feng, Yan-Ni; Li, Lan; Dyce, Paul W; Shen, Wei; Sun, Xiao-Feng

    2017-07-01

    The meiotic initiation of mammalian oogonia is a critical step during the development of primordial germ cells (PGCs) to mature oocytes. In this study, a systematic investigation of epigenetic modifications and DAZL gene expression during oogonia meiotic entry were performed. We found that the expression of DAZL was epigenetically regulated by DNA methylation of CpG islands within its promoter region. During meiotic entry, a continuously increasing level of 5hmC, a stable epigenetic marker usually associated with the activation of gene expression, was observed from 11.5 to 16.5 dpc (days post coitum). Meanwhile trimethylation of lysine 27 on histone3 (H3K27me3), usually associated with repression of gene expression, had a sustainable increase from 12.5 to 16.5 dpc. Finally, by equally dividing the ovaries into three regions representing the anterior, the middle, and the posterior of the ovary and performing immunofluorescence and qRT-PCR on the individual regions, we provided further evidences that the meiotic entry and progression of female germ cells is in an anterior to posterior pattern.

  5. Insulin alone can lead to a withdrawal of meiotic arrest in the carp ...

    Indian Academy of Sciences (India)

    Meiotic arrest of oocyte in an Indian carp, Labeo rohita Ham. has been found for the first time to be withdrawn by insulin only. Addition of insulin to oocytes in vitro caused germinal vesicle breakdown (GVBD), one of the first visual markers to determine initiation of the final maturational process. Under the influence of insulin ...

  6. Localized chiasmata and meiotic nodules in the tetraploid onion Allium porrum

    NARCIS (Netherlands)

    Stack, S M; Roelofs, D

    Allium porrum L. (cultivated leek) (2n = 4x = 32) is a fertile tetraploid that forms bivalents with pericentric chiasmata at metaphase I. To investigate the basis of this unusual behavior for a tetraploid, we describe the karyotype, axial cores, synaptonemal complexes (SCs), and meiotic nodules of

  7. Mouse Sycp1 functions in synaptonemal complex assembly, meiotic recombination., and XY body formation

    NARCIS (Netherlands)

    Vries, de F.A.T.; Boer, de E.; Bosch, M.; Baarends, W.M.; Ooms, M.; Yuan, L.; Liu, J.G.; Zeeland, van A.A.; Heyting, C.; Pastink, A.

    2005-01-01

    In meiotic prophase, synaptonemal complexes (SCs) closely appose homologous chromosomes (homologs) along their length. SCs are assembled from two axial elements (AEs), one along each homolog, which are connected by numerous transverse filaments (TFs). We disrupted the mouse gene encoding TF protein

  8. Meiotic behavior and pollen fertility of five species in the genus ...

    African Journals Online (AJOL)

    fe

    2011-11-16

    Nov 16, 2011 ... Meiotic behavior and pollen fertility were analysed in five Epimedium species: Epimedium chlorandrum,. Epimedium acuminatum, Epimedium davidii, Epimedium ecalcaratum and Epimedium pubescens. Chromosome numbers for five species were 2n = 2x = 12. All examined species displayed stable ...

  9. A quality control mechanism linking meiotic success to release of ascospores.

    Directory of Open Access Journals (Sweden)

    Haiyan Guo

    Full Text Available Eukaryotic organisms employ a variety of mechanisms during meiosis to assess and ensure the quality of their gametes. Defects or delays in successful meiotic recombination activate conserved mechanisms to delay the meiotic divisions, but many multicellular eukaryotes also induce cell death programs to eliminate gametes deemed to have failed during meiosis. It is generally thought that yeasts lack such mechanisms. Here, we show that in the fission yeast Schizosaccharomyces pombe, defects in meiotic recombination lead to the activation of a checkpoint that is linked to ascus wall endolysis--the process by which spores are released in response to nutritional cues for subsequent germination. Defects in meiotic recombination are sensed as unrepaired DNA damage through the canonical ATM and ATR DNA damage response kinases, and this information is communicated to the machinery that stimulates ascus wall breakdown. Viability of spores that undergo endolysis spontaneously is significantly higher than that seen upon chemical endolysis, demonstrating that this checkpoint contributes to a selective mechanism for the germination of high quality progeny. These results provide the first evidence for the existence of a checkpoint linking germination to meiosis and suggest that analysis solely based on artificial, enzymatic endolysis bypasses an important quality control mechanism in this organism and potentially other ascomycota, which are models widely used to study meiosis.

  10. Nested Inversion Polymorphisms Predispose Chromosome 22q11.2 to Meiotic Rearrangements

    NARCIS (Netherlands)

    Demaerel, Wolfram; Hestand, Matthew S.; Vergaelen, Elfi; Swillen, Ann; López-Sánchez, Marcos; Pérez-Jurado, Luis A.; McDonald-Mcginn, Donna M.; Zackai, Elaine; Emanuel, Beverly S.; Morrow, Bernice E.; Breckpot, Jeroen; Devriendt, Koenraad; Vermeesch, Joris R.; Antshel, Kevin M.; Arango, Celso; Armando, Marco; Bassett, Anne S.; Bearden, Carrie E.; Boot, Erik; Bravo-Sanchez, Marta; Breetvelt, Elemi|info:eu-repo/dai/nl/357937414; Busa, Tiffany; Butcher, Nancy J.; Campbell, Linda E.; Carmel, Miri; Chow, Eva W C; Crowley, T. Blaine; Cubells, Joseph; Cutler, David; Demaerel, Wolfram; Digilio, Maria Cristina; Duijff, Sasja|info:eu-repo/dai/nl/30481914X; Eliez, Stephan; Emanuel, Beverly S.; Epstein, Michael P.; Evers, Rens; Fernandez Garcia-Moya, Luis; Fiksinski, Ania; Fraguas, David; Fremont, Wanda; Fritsch, Rosemarie; Garcia-Minaur, Sixto; Golden, Aaron; Gothelf, Doron; Guo, Tingwei; Gur, Ruben C.; Gur, Raquel E.; Heine-Suner, Damian; Hestand, Matthew; Hooper, Stephen R.; Kates, Wendy R.; Kushan, Leila; Laorden-Nieto, Alejandra; Maeder, Johanna; Marino, Bruno; Marshall, Christian R.; McCabe, Kathryn; McDonald-Mcginn, Donna M.; Michaelovosky, Elena; Morrow, Bernice E.; Moss, Edward; Mulle, Jennifer; Murphy, Declan; Murphy, Kieran C.; Murphy, Clodagh M.; Niarchou, Maria; Ornstein, Claudia; Owen, Michael J; Philip, Nicole; Repetto, Gabriela M.; Schneider, Maude; Shashi, Vandana; Simon, Tony J.; Swillen, Ann; Tassone, Flora; Unolt, Marta; Van Amelsvoort, Therese; van den Bree, Marianne B M; Van Duin, Esther; Vergaelen, Elfi; Vermeesch, Joris R.; Vicari, Stefano; Vingerhoets, Claudia; Vorstman, Jacob|info:eu-repo/dai/nl/304817023; Warren, Steve; Weinberger, Ronnie; Weisman, Omri; Weizman, Abraham; Zackai, Elaine; Zhang, Zhengdong; Zwick, Michael

    2017-01-01

    Inversion polymorphisms between low-copy repeats (LCRs) might predispose chromosomes to meiotic non-allelic homologous recombination (NAHR) events and thus lead to genomic disorders. However, for the 22q11.2 deletion syndrome (22q11.2DS), the most common genomic disorder, no such inversions have

  11. Meiotic behaviour of Eragrostis tef and,i> Eragrostis Pilosa | Admas ...

    African Journals Online (AJOL)

    It also produced better seed and biomass yield and number of tillers than the parental lines which are the manifestation of meiotic stability in the hybrid and the subsequent generations. Pollen fertility test of the parental lines and selected recombinant inbred lines of E. tef and E. pilosa cross was also high (90 - 95%), which ...

  12. Meiotic homoeologous recombination-based alien gene introgression in the genomics era of wheat

    Science.gov (United States)

    Wheat (Triticum spp.) has a narrow genetic basis due to its allopolyploid origin. However, wheat has numerous wild relatives usable for expanding genetic variability of its genome through meiotic homoeologous recombination. Traditionally, laborious cytological analyses have been employed to detect h...

  13. Meiotic recombination breakpoints are associated with open chromatin and enriched with Stowaway transposons in potato

    Science.gov (United States)

    Meiotic recombination is the foundation for genetic variation in natural and artificial populations of eukaryotes. Although genetic recombination maps have been developed in numerous plant species since late the 1980s, very few of these maps have provided the necessary resolution needed to investiga...

  14. Light induced toxicity reduction of silver nanoparticles to Tetrahymena Pyriformis: Effect of particle size

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Junpeng; Xu, Bin; Sun, Xia; Ma, Chunyan; Yu, Changping [Institute of Urban Environment, Chinese Academy of Sciences, Jimei Road 1799, Xiamen 361021 (China); Zhang, Hongwu, E-mail: hwzhang@iue.ac.cn [Institute of Urban Environment, Chinese Academy of Sciences, Jimei Road 1799, Xiamen 361021 (China)

    2013-05-15

    Highlights: ► Small AgNPs had higher toxicity than large to Tetrahymena pyriformis under dark. ► AgNPs toxicity was decreased by light. ► The decrease of small AgNP toxicity induced by light was more notable than that of large AGNPs. ► Light can influence Ag{sup +} release from, particle size of, and aggregation of AgNPs. -- Abstract: As a result of the extensive application of silver nanoparticles (AgNPs), their potential hazards, once they are released into the natural environment, are of great concern to people. Since silver is very sensitive to light, the toxicity of AgNPs released into the natural environment will be inevitably affected by light. The aim of this study was to investigate the relationship between light, toxicity, and particle size of AgNPs and deduce the possible mechanism of any interaction. Our study revealed that there was negative correlation between the particle size and the toxicity: small AgNPs (5–10 nm) had higher toxicity than large AgNPs (15–25 nm) to Tetrahymena pyriformis (T. pyriformis) under dark condition. Comparing the size dependent AgNPs toxicity under dark and light conditions, the effect of light to size dependent AgNPs toxicity was ascertained. The results indicated that AgNPs toxicity was decreased by light and the most important discovery was that the change of size dependent AgNPs toxicity had significant difference under light irradiation. The decrease of small AgNPs toxicity induced by light was more notable than large AgNPs. The decreased level of cell toxicity for small AgNPs was 32 ± 0.7%, whereas it was only 10.6 ± 5.2% for large AgNPs kept 24 h under light irradiation. The further investigation indicated that the above changes induced by light can be attributed to the decrease of released silver ions, particle growth and aggregation of AgNPs under light irradiation. The obtained results showed that the light irradiation can promote the rapid growth of small AgNPs and result in the obvious increase of

  15. Modeling Meiotic Chromosomes Indicates a Size Dependent Contribution of Telomere Clustering and Chromosome Rigidity to Homologue Juxtaposition

    Science.gov (United States)

    Penfold, Christopher A.; Brown, Paul E.; Lawrence, Neil D.; Goldman, Alastair S. H.

    2012-01-01

    Meiosis is the cell division that halves the genetic component of diploid cells to form gametes or spores. To achieve this, meiotic cells undergo a radical spatial reorganisation of chromosomes. This reorganisation is a prerequisite for the pairing of parental homologous chromosomes and the reductional division, which halves the number of chromosomes in daughter cells. Of particular note is the change from a centromere clustered layout (Rabl configuration) to a telomere clustered conformation (bouquet stage). The contribution of the bouquet structure to homologous chromosome pairing is uncertain. We have developed a new in silico model to represent the chromosomes of Saccharomyces cerevisiae in space, based on a worm-like chain model constrained by attachment to the nuclear envelope and clustering forces. We have asked how these constraints could influence chromosome layout, with particular regard to the juxtaposition of homologous chromosomes and potential nonallelic, ectopic, interactions. The data support the view that the bouquet may be sufficient to bring short chromosomes together, but the contribution to long chromosomes is less. We also find that persistence length is critical to how much influence the bouquet structure could have, both on pairing of homologues and avoiding contacts with heterologues. This work represents an important development in computer modeling of chromosomes, and suggests new explanations for why elucidating the functional significance of the bouquet by genetics has been so difficult. PMID:22570605

  16. Unisexual Reproduction Drives Meiotic Recombination and Phenotypic and Karyotypic Plasticity in Cryptococcus neoformans

    Science.gov (United States)

    Sun, Sheng; Billmyre, R. Blake; Mieczkowski, Piotr A.; Heitman, Joseph

    2014-01-01

    In fungi, unisexual reproduction, where sexual development is initiated without the presence of two compatible mating type alleles, has been observed in several species that can also undergo traditional bisexual reproduction, including the important human fungal pathogens Cryptococcus neoformans and Candida albicans. While unisexual reproduction has been well characterized qualitatively, detailed quantifications are still lacking for aspects of this process, such as the frequency of recombination during unisexual reproduction, and how this compares with bisexual reproduction. Here, we analyzed meiotic recombination during α-α unisexual and a-α bisexual reproduction of C. neoformans. We found that meiotic recombination operates in a similar fashion during both modes of sexual reproduction. Specifically, we observed that in α-α unisexual reproduction, the numbers of crossovers along the chromosomes during meiosis, recombination frequencies at specific chromosomal regions, as well as meiotic recombination hot and cold spots, are all similar to those observed during a-α bisexual reproduction. The similarity in meiosis is also reflected by the fact that phenotypic segregation among progeny collected from the two modes of sexual reproduction is also similar, with transgressive segregation being observed in both. Additionally, we found diploid meiotic progeny were also produced at similar frequencies in the two modes of sexual reproduction, and transient chromosomal loss and duplication likely occurs frequently and results in aneuploidy and loss of heterozygosity that can span entire chromosomes. Furthermore, in both α-α unisexual and a-α bisexual reproduction, we observed biased allele inheritance in regions on chromosome 4, suggesting the presence of fragile chromosomal regions that might be vulnerable to mitotic recombination. Interestingly, we also observed a crossover event that occurred within the MAT locus during α-α unisexual reproduction. Our results

  17. The tension at the top of the animal pole decreases during meiotic cell division.

    Directory of Open Access Journals (Sweden)

    Setsuko K Satoh

    Full Text Available Meiotic maturation is essential for the reproduction procedure of many animals. During this process an oocyte produces a large egg cell and tiny polar bodies by highly asymmetric division. In this study, to fully understand the sophisticated spatiotemporal regulation of accurate oocyte meiotic division, we focused on the global and local changes in the tension at the surface of the starfish (Asterina pectinifera oocyte in relation to the surface actin remodeling. Before the onset of the bulge formation, the tension at the animal pole globally decreased, and started to increase after the onset of the bulge formation. Locally, at the onset of the bulge formation, tension at the top of the animal pole began to decrease, whereas that at the base of the bulge remarkably increased. As the bulge grew, the tension at the base of the bulge additionally increased. Such a change in the tension at the surface was similar to the changing pattern of actin distribution. Therefore, meiotic cell division was initiated by the bulging of the cortex, which had been weakened by actin reduction, and was followed by contraction at the base of the bulge, which had been reinforced by actin accumulation. The force generation system is assumed to allow the meiotic apparatus to move just under the membrane in the small polar body. Furthermore, a detailed comparison of the tension at the surface and the cortical actin distribution indicated another sophisticated feature, namely that the contraction at the base of the bulge was more vigorous than was presumed based on the actin distribution. These features of the force generation system will ensure the precise chromosome segregation necessary to produce a normal ovum with high accuracy in the meiotic maturation.

  18. Genome Dynamics of Hybrid Saccharomyces cerevisiae During Vegetative and Meiotic Divisions

    Directory of Open Access Journals (Sweden)

    Abhishek Dutta

    2017-11-01

    Full Text Available Mutation and recombination are the major sources of genetic diversity in all organisms. In the baker’s yeast, all mutation rate estimates are in homozygous background. We determined the extent of genetic change through mutation and loss of heterozygosity (LOH in a heterozygous Saccharomyces cerevisiae genome during successive vegetative and meiotic divisions. We measured genome-wide LOH and base mutation rates during vegetative and meiotic divisions in a hybrid (S288c/YJM789 S. cerevisiae strain. The S288c/YJM789 hybrid showed nearly complete reduction in heterozygosity within 31 generations of meioses and improved spore viability. LOH in the meiotic lines was driven primarily by the mating of spores within the tetrad. The S288c/YJM789 hybrid lines propagated vegetatively for the same duration as the meiotic lines, showed variable LOH (from 2 to 3% and up to 35%. Two of the vegetative lines with extensive LOH showed frequent and large internal LOH tracts that suggest a high frequency of recombination repair. These results suggest significant LOH can occur in the S288c/YJM789 hybrid during vegetative propagation presumably due to return to growth events. The average base substitution rates for the vegetative lines (1.82 × 10−10 per base per division and the meiotic lines (1.22 × 10−10 per base per division are the first genome-wide mutation rate estimates for a hybrid yeast. This study therefore provides a novel context for the analysis of mutation rates (especially in the context of detecting LOH during vegetative divisions, compared to previous mutation accumulation studies in yeast that used homozygous backgrounds.

  19. Ploidy-Dependent Unreductional Meiotic Cell Division in Polyploid Wheat

    Science.gov (United States)

    Meiosis includes one round of DNA replication and two successive nuclear divisions, i.e. meiosis I (reductional) and meiosis II (equational). This specialized cell division reduces chromosomes in half and generates haploid gametes in sexual reproduction of eukaryotes. It ensures faithful transmiss...

  20. Phosphoproteomic analysis of protein phosphorylation networks in Tetrahymena thermophila, a model single-celled organism.

    Science.gov (United States)

    Tian, Miao; Chen, Xiulan; Xiong, Qian; Xiong, Jie; Xiao, Chuanle; Ge, Feng; Yang, Fuquan; Miao, Wei

    2014-02-01

    Tetrahymena thermophila is a widely used unicellular eukaryotic model organism in biological research and contains more than 1000 protein kinases and phosphatases with specificity for Ser/Thr/Tyr residues. However, only a few dozen phosphorylation sites in T. thermophila are known, presenting a major obstacle to further understanding of the regulatory roles of reversible phosphorylation in this organism. In this study, we used high-accuracy mass-spectrometry-based proteomics to conduct global and site-specific phosphoproteome profiling of T. thermophila. In total, 1384 phosphopeptides and 2238 phosphorylation sites from 1008 T. thermophila proteins were identified through the combined use of peptide prefractionation, TiO2 enrichment, and two-dimensional LC-MS/MS analysis. The identified phosphoproteins are implicated in the regulation of various biological processes such as transport, gene expression, and mRNA metabolic process. Moreover, integrated analysis of the T. thermophila phosphoproteome and gene network revealed the potential biological functions of many previously unannotated proteins and predicted some putative kinase-substrate pairs. Our data provide the first global survey of phosphorylation in T. thermophila using a phosphoproteomic approach and suggest a wide-ranging regulatory scope of this modification. The provided dataset is a valuable resource for the future understanding of signaling pathways in this important model organism.

  1. Machine learning-based models to predict modes of toxic action of phenols to Tetrahymena pyriformis.

    Science.gov (United States)

    Castillo-Garit, J A; Casañola-Martin, G M; Barigye, S J; Pham-The, H; Torrens, F; Torreblanca, A

    2017-09-01

    The phenols are structurally heterogeneous pollutants and they present a variety of modes of toxic action (MOA), including polar narcotics, weak acid respiratory uncouplers, pro-electrophiles, and soft electrophiles. Because it is often difficult to determine correctly the mechanism of action of a compound, quantitative structure-activity relationship (QSAR) methods, which have proved their interest in toxicity prediction, can be used. In this work, several QSAR models for the prediction of MOA of 221 phenols to the ciliated protozoan Tetrahymena pyriformis, using Chemistry Development Kit descriptors, are reported. Four machine learning techniques (ML), k-nearest neighbours, support vector machine, classification trees, and artificial neural networks, have been used to develop several models with higher accuracies and predictive capabilities for distinguishing between four MOAs. They showed global accuracy values between 95.9% and 97.7% and area under Receiver Operator Curve values between 0.978 and 0.998; additionally, false alarm rate values were below 8.2% for training set. In order to validate our models, cross-validation (10-folds-out) and external test-set were performed with good behaviour in all cases. These models, obtained with ML techniques, were compared with others previously reported by other researchers, and the improvement was significant.

  2. Characterization of the Tetrahymena ribozyme folding pathway using the kinetic footprinting reagent peroxynitrous acid.

    Science.gov (United States)

    Chaulk, S G; MacMillan, A M

    2000-01-11

    Large RNAs fold into complex structures which determine their biological activities. A full understanding of both RNA structure and dynamics will include the description of the pathways by which these structures are formed. Kinetic footprinting [Sclavi, B., et al. (1997) J. Mol. Biol. 266, 144-159] has been shown to be a powerful method for the study of dynamic processes involving RNA. Here we describe the use of a readily available reagent, peroxynitrous acid, as a kinetic footprinting tool for the study of RNA folding. Hydroxyl radicals generated from this reagent were used to footprint the Tetrahymena ribozyme during its magnesium-dependent folding-in agreement with synchroton X-ray footprinting [Sclavi, B., et al. (1998) Science 279, 1940-1943] and oligonucleotide/hybridization cleavage experiments [Zarrinkar, P. P., and Williamson, J. R. (1994) Science 265, 918-924], this work suggests an ordered, hierarchical folding pathway for the ribozyme. Several slow steps in the folding pathway were observed in the peroxynitrous acid footprinting, but none of these corresponded to the rate-determining step of folding. This suggests that the formation of the global, protected structure is followed by one or more slow local rearrangements to yield the final active structure. These studies illustrate the utility of peroxynitrous acid as a reagent for the elucidation of RNA folding pathways and the study of RNA dynamics.

  3. Is Evolution of Mating Preferences Inevitable? Random Mating in the Multisex System of Tetrahymena thermophila

    Directory of Open Access Journals (Sweden)

    Sujal S. Phadke

    2012-01-01

    Full Text Available Ciliate mating systems are highly diversified, providing unique opportunities to study sexual differentiation and its implications for mating dynamics. Many species of ciliates have multiple (>2 sexes. More sexes may mean more choice and an opportunity for evolution of preferential mating. We asked if the multiple sexes of the ciliate Tetrahymena thermophila mate preferentially among each other. We quantified pairing frequencies among four sexes of T. thermophila using experiments that allowed the sexes to compete as mating partners. We found that all sexes mated equally frequently among each other, that is, we found no evidence of preferential mating with respect to sex. This suggests that the “mate choice” in this ciliate is binary, between whether to form a pair or not and, in this regard, sex facilitates only self-/non-self-distinction. Thus, presence of multiple sexes does not necessarily result in the evolution of mating bias, which could decrease the maximum amount of mating that would otherwise be possible in a population. Our result of random mating verifies a key assumption in the theoretical model of sex ratio evolution in T. thermophila. Investigation into molecular differences between the sexes will be necessary to reveal the mechanistic basis of random mating among them.

  4. Delineating cellular interactions between ciliates and fish by co-culturing Tetrahymena thermophila with fish cells.

    Science.gov (United States)

    Pinheiro, Marcel D O; Bols, Niels C

    2014-10-01

    Although several species of Tetrahymena are often described as histophagous and opportunistic pathogens of fish, little is known about ciliate/fish cell interactions, but one approach for studying these is in vitro with cell lines. In this study, T. thermophila, B1975 (wild type) and NP1 (temperature sensitive mutant for phagocytosis) were cultured on monolayers of 3 fish epithelial cell lines, CHSE-214, RTgill-W1, and ZEB2J, and the rabbit kidney epithelial cell line, RK-13. Generally the ciliates flourished, whereas the monolayers died, being completely consumed over several days. The destruction of monolayers required that the ciliates could make contact with the animal cells through swimming, which appeared to dislodge or loosen cells so that they could be phagocytosed. The ciliates internalized into food vacuoles ZEB2J from cell monolayers as well as from cell suspensions. Phagocytosis was essential for monolayer destruction as monolayers remained intact under conditions where phagocytosis was impeded, such as 37°C for NP1 and 4°C for B1975. Monolayers of fish cells supported the proliferation of ciliates. Thus T. thermophila can 'eat' animal cells or be histophagous in vitro, with the potential to be histophagous in vivo. © 2014 International Federation for Cell Biology.

  5. Negative Regulators of an RNAi-Heterochromatin Positive Feedback Loop Safeguard Somatic Genome Integrity in Tetrahymena.

    Science.gov (United States)

    Suhren, Jan H; Noto, Tomoko; Kataoka, Kensuke; Gao, Shan; Liu, Yifan; Mochizuki, Kazufumi

    2017-03-07

    RNAi-mediated positive feedback loops are pivotal for the maintenance of heterochromatin, but how they are downregulated at heterochromatin-euchromatin borders is not well understood. In the ciliated protozoan Tetrahymena, heterochromatin is formed exclusively on the sequences that are removed from the somatic genome by programmed DNA elimination, and an RNAi-mediated feedback loop is important for assembling heterochromatin on the eliminated sequences. In this study, we show that the heterochromatin protein 1 (HP1)-like protein Coi6p, its interaction partners Coi7p and Lia5p, and the histone demethylase Jmj1p are crucial for confining the production of small RNAs and the formation of heterochromatin to the eliminated sequences. The loss of Coi6p, Coi7p, or Jmj1p causes ectopic DNA elimination. The results provide direct evidence for the existence of a dedicated mechanism that counteracts a positive feedback loop between RNAi and heterochromatin at heterochromatin-euchromatin borders to maintain the integrity of the somatic genome. Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.

  6. In vivo synthesis of nano-selenium by Tetrahymena thermophila SB210.

    Science.gov (United States)

    Cui, Yin-Hua; Li, Ling-Li; Zhou, Nan-Qing; Liu, Jing-Hua; Huang, Qing; Wang, Hui-Juan; Tian, Jie; Yu, Han-Qing

    2016-12-01

    Nano-selenium has a great potential to be used in chemical, biological, medical and environmental fields. Biological methods for nano-selenium synthesis have attracted wide interests, because they can be operated at ambient temperature and pressure without complicated equipments. In this work, a protozoa, Tetrahymena thermophila (T. thermophila) SB210, was used to in vivo synthesize nano-selenium. The biosynthesized nano-selenium was characterized using transmission electron microscopy, energy dispersive X-ray spectroscopy and Raman spectroscopy. The synthesized amorphous spherical selenium nanoparticles had diameters of 50-500nm with the coexistence of irregular nano-selenium. The expressions of glutathione (GSH) synthesis related gene glutathione synthase, cysteine-rich protein metallothionein related gene metallothionein-1 and [2Fe-2S] cluster-binding protein related gene were up-regulated in the nano-selenium producing group. Also, the subsequent GSH detection and in vitro synthesis experimental results suggest the three proteins were likely to be involved in the nano-selenium synthesis process. Copyright © 2016 Elsevier Inc. All rights reserved.

  7. Distinct localization of a beta-tubulin epitope in the Tetrahymena thermophila and Paramecium caudatum cortex.

    Science.gov (United States)

    Libusová, L; Sulimenko, T; Sulimenko, V; Janisch, R; Hozák, P; Dráber, P

    2005-10-01

    Many of the highly organized microtubular arrangements in ciliates are located in the cortical area containing membrane vesicles and vacuoles. In Tetrahymena thermophila and Paramecium caudatum, immunofluorescence microscopy with the monoclonal antibody TU-06, directed against beta-tubulin, revealed distinct staining of this cortical region alone, while the cilia and other microtubular structures were unstained. The specificity of the antibody was confirmed by immunoblotting and by preabsorption of the antibody with purified tubulin. Double-label immunofluorescence with antibodies against gamma-tubulin, detyrosinated alpha-tubulin, and centrin showed that the TU-06 epitope is localized outside the basal body region. This was also confirmed by immunogold electron microscopy of thin sections. Proteolytic digestion of porcine brain beta-tubulin combined with a peptide scan of immobilized, overlapping peptides disclosed that the epitope was in the beta-tubulin region beta81-95, a region which is phylogenetically highly conserved. As known posttranslational modifications of beta-tubulin are located outside this area, the observed staining pattern cannot be interpreted as evidence of subcellular sequestration of modified tubulin. The limited distribution of the epitope could rather reflect the dependence of TU-06 epitope exposition on conformations of tubulin molecules in microtubule arrangements or on differential masking by interacting proteins.

  8. A model for endosymbiosis: interaction between Tetrahymena pyriformis and Escherichia coli.

    Science.gov (United States)

    Siegmund, Lisa; Burmester, Anke; Fischer, Martin S; Wöstemeyer, Johannes

    2013-11-01

    Endosymbiosis in ciliates is a common and highly diverse phenomenon in nature, but its development at the mechanistic level and the origins are not easy to understand, since these associations may have arisen at any time during evolution. Therefore a laboratory model is helpful. It could be provided by the interaction of Tetrahymena pyriformis and Escherichia coli. Microscopic analyses with a genetically manipulated fluorescent strain of E. coli show single bacteria leaving food vacuoles and escaping digestion, an important prerequisite for further experiments. Under selective conditions, beneficial for T. pyriformis, the ciliate was shown to internalize E. coli cells. After feeding, bacteria, transformed with the plasmids pBS-neoTet or pNeo4, provide T. pyriformis with the ability to handle toxic conditions, caused by the aminoglykoside antibiotic paromomycin. Axenic cultures or cocultures with untransformed bacteria show lower cell numbers and survival rates compared to cocultures with transformed bacteria after transfer to paromomycin containing media. PCR detects bacterial DNA inside T. pyriformis cells. Additionally, microscopical analysis of selectively grown cocultures reveals fluorescing particles in the cytoplasm of T. pyriformis containing DNA and lipids, corresponding in size to E. coli. This system could be a reasonable model for understanding mechanisms of endosymbiosis establishment in ciliates. Copyright © 2013 Elsevier GmbH. All rights reserved.

  9. QSAR analysis of nitroaromatics' toxicity in Tetrahymena pyriformis: structural factors and possible modes of action

    Science.gov (United States)

    Artemenko, A.G.; Muratov, E. N.; Kuz’min, V.E.; Muratov, N.N.; Varlamova, E.V.; Kuz'mina, A.V.; Gorb, L. G.; Golius, A.; Hill, F.C.; Leszczynski, J.; Tropsha, A.

    2012-01-01

    The Hierarchical Technology for Quantitative Structure - Activity Relationships (HiT QSAR) was applied to 95 diverse nitroaromatic compounds (including some widely known explosives) tested for their toxicity (50% inhibition growth concentration, IGC50) against the ciliate Tetrahymena pyriformis. The dataset was divided into subsets according to putative mechanisms of toxicity. Classification and Regression Trees (CART) approach implemented within HiT QSAR has been used for prediction of mechanism of toxicity for new compounds. The resulting models were shown to have ~80% accuracy for external datasets indicating that the mechanistic dataset division was sensible. Then, Partial Least Squares (PLS) statistical approach was used for the development of 2D QSAR models. Validated PLS models were explored to (i) elucidate the effects of different substituents in nitroaromatic compounds on toxicity; (ii) differentiate compounds by probable mechanisms of toxicity based on their structural descriptors; (iii) analyze the role of various physical-chemical factors responsible for compounds’ toxicity. Models were interpreted in terms of molecular fragments promoting or interfering with toxicity. It was also shown that mutual influence of substituents in benzene ring plays the determining role in toxicity variation. Although chemical mechanism based models were statistically significant and externally predictive (R2ext=0.64 for the external set of 63 nitroaromatics identified after all calculations have been completed), they were also shown to have limited coverage (57% for modeling and 76% for external set). PMID:21714735

  10. Epigenetic Control May Explain Large Within-Plant Heterogeneity of Meiotic Behavior in Telocentric Trisomics of Rye

    OpenAIRE

    Sybenga, J.; Verhaar, H.; Botje, D. G. A.

    2008-01-01

    In telocentric trisomics (telotrisomics) of organisms in which the chromosomes normally have two distinct arms, a single chromosome arm with a centromere is present in addition to a complete diploid set of chromosomes. It is the simplest form of polysomy and suitable for analyzing meiotic pairing and recombination patterns in situations where chromosomes compete for pairing. When no suitable meiotic chromosome markers are available, four metaphase I configurations can be distinguished. Their ...

  11. Reduced dosage of the chromosome axis factor Red1 selectively disrupts the meiotic recombination checkpoint in Saccharomyces cerevisiae.

    Directory of Open Access Journals (Sweden)

    Tovah E Markowitz

    2017-07-01

    Full Text Available Meiotic chromosomes assemble characteristic "axial element" structures that are essential for fertility and provide the chromosomal context for meiotic recombination, synapsis and checkpoint signaling. Whether these meiotic processes are equally dependent on axial element integrity has remained unclear. Here, we investigated this question in S. cerevisiae using the putative condensin allele ycs4S. We show that the severe axial element assembly defects of this allele are explained by a linked mutation in the promoter of the major axial element gene RED1 that reduces Red1 protein levels to 20-25% of wild type. Intriguingly, the Red1 levels of ycs4S mutants support meiotic processes linked to axis integrity, including DNA double-strand break formation and deposition of the synapsis protein Zip1, at levels that permit 70% gamete survival. By contrast, the ability to elicit a meiotic checkpoint arrest is completely eliminated. This selective loss of checkpoint function is supported by a RED1 dosage series and is associated with the loss of most of the cytologically detectable Red1 from the axial element. Our results indicate separable roles for Red1 in building the structural axis of meiotic chromosomes and mounting a sustained recombination checkpoint response.

  12. Analysis of self-fertilization and meiotic behavior of eleven Brazilian triticale cultivars at two sowing dates

    Directory of Open Access Journals (Sweden)

    Divanilde Guerra

    2011-01-01

    Full Text Available Eleven Brazilian hexaploid triticale cultivars (2n = 6x = 42, from three breeding programs, were evaluated for theirability of self-fertilization in 2006 and for meiotic behavior, meiotic index and pollen viability at two sowing dates in 2007. Highpotential of self-fertilization was observed, with values up to 89.52 %. Many irregularities were found in the meiotic analysis, suchas the presence of univalents, laggard chromosomes and micronuclei in tetrads, which compromised both meiotic behavior andmeiotic index. At the first sowing date, more suitable for normal plant development, overall mean values of 52.68 % for normal cellsand 64.95 % for meiotic index were observed. At the second sowing date, less appropriate for the crop, overall means of 52.23 %for normal cells and 58.24 % for meiotic index were obtained. Despite all the irregularities, considerable pollen viability wasobserved, reaching overall means of 92.08 % and 91.07 % for the first and second sowing dates, respectively.

  13. Co-Localization of Somatic and Meiotic Double Strand Breaks Near the Myc Oncogene on Mouse Chromosome 15

    Science.gov (United States)

    Ng, Siemon H.; Maas, Sarah A.; Petkov, Petko M.; Mills, Kevin D.; Paigen, Kenneth

    2010-01-01

    Both somatic and meiotic recombinations involve the repair of DNA double strand breaks (DSBs) that occur at preferred locations in the genome. Improper repair of DSBs during either mitosis or meiosis can lead to mutations, chromosomal aberration such as translocations, cancer and/or cell death. Currently, no model exists that explains the locations of either spontaneous somatic DSBs or programmed meiotic DSBs or relates them to each other. One common class of tumorigenic translocations arising from DSBs is chromosomal rearrangements near the Myc oncogene. Myc translocations have been associated with Burkitt lymphoma in humans, plasmacytoma in mice and immunocytoma in rats. Comparing the locations of somatic and meiotic DSBs near the mouse Myc oncogene, we demonstrated that the placement of these DSBs is not random and that both events clustered in the same short discrete region of the genome. Our work shows that both somatic and meiotic DSBs tend to occur in proximity to each other within the Myc region, suggesting that they share common originating features. It is likely that some regions of the genome are more susceptible to both somatic and meiotic DSBs, and the locations of meiotic hotspots may be an indicator of genomic regions more susceptible to DNA damage. PMID:19603522

  14. Correlation between induction of meiotic delay and aneuploidy in male mouse germ cells

    Energy Technology Data Exchange (ETDEWEB)

    Adler, I.D.; Gassner, P.; Schriever-Schwemmer, G.; Min, Zhou Ru [Institut fuer Sauugetiergenetik, Neuherberg (Germany)

    1993-12-31

    No aneuploidy assays are prescribed in any international guidelines for chemical safety testing up to now. The CEC-sponsored Aneuploidy Project has the aim to validate test methods for aneuploidy induction which could be used as screening tests. Furthermore, one of the major goals is to develop an understanding of mechanisms by which aneuploidy is induced. The present paper describes the investigation of meiotic delay and aneuploidy induction with the drug diazepam (DZ), the environmentally important mutagen acrylamide (AA) and the spindle poison colchicine (COL), which is used as a positive control. The time course of events was investigated. It is concluded that the assessment of meiotic delay can be used to preselect chemicals which require evaluation of aneuploidy induction during MMI in male germ cells.

  15. Meiotic behavior of two polyploid species of genus Pleurodema (Anura: Leiuperidae from central Argentina

    Directory of Open Access Journals (Sweden)

    Nancy E. Salas

    2014-06-01

    Full Text Available Polyploidy is an important evolutionary force but rare in vertebrates. However, in anurans, the genus Pleurodema has polyploid species, two of them tetraploid and one octoploid. The manner in which the chromosomes join in diakinesis can vary among species and, crucially, if they differ in their ploidy levels. In this work, we describe the meiotic configurations in two cryptic species from central Argentina, with different ploidy levels, Pleurodema kriegi (tetraploid and P. cordobae (octoploid. A total of 306 diakineses from 19 individuals were analyzed. In meiosis, P. kriegi form 22 bivalents, whereas P. cordobae exhibits variation in meiotic figures. We discuss the possible allo- and autopolyploid origin of these species, and we consider that the autopolyploid origin of P. cordobae from P. kriegi might be the most feasible.

  16. Meiotic behavior of a nonaploid accession endorses x = 6 for Brachiaria humidicola (Poaceae).

    Science.gov (United States)

    Boldrini, K R; Pagliarini, M S; Valle, C B

    2009-12-01

    Brachiaria humidicola (Poaceae), originally from Africa, is an economically important pasture plant in tropical South America. An accession of B. humidicola (H038) collected from the wild African savanna (Mbeya, Tanzania) showed irregular microsporogenesis. This meiotic behavior was consistent with an allopolyploid origin. Multivalent chromosome association at diakinesis gave tri- to octavalents, associated with two nucleoli in some cells. Six non-congregated univalents in metaphase I and anaphase I, along with previous lines of evidence for x = 6 in B. humidicola, confirm H038 as a nonaploid accession, 2n = 9x = 54. Asynchrony in the genome during microsporogenesis also corroborated this assumption. Its putative origin could be a cross between two related species with different rhythms in meiosis. The meiotic behavior of this accession reinforces the hypothesis of the existence of a new basic chromosome number (x = 6) for Brachiaria. The use of this accession in the breeding of this important forage grass for the tropics is discussed.

  17. Effects of Pluronic F-68 on Tetrahymena cells: protection against chemical and physical stress and prolongation of survival under toxic conditions

    DEFF Research Database (Denmark)

    Hellung-Larsen, P; Assaad, F; Pankratova, Stanislava

    2000-01-01

    The effects of the non-ionic surfactant Pluronic F-68 (0.01% w/v) on Tetrahymena cells have been studied. A marked protection against chemical and physical stress was observed. The chemical stress effects were studied in cells suspended in buffer (starvation) or in buffers with added ingredients ...

  18. Comparison of primary and secondary 26S rRNA structures in two Tetrahymena species: evidence for a strong evolutionary and structural constraint in expansion segments

    DEFF Research Database (Denmark)

    Engberg, J; Nielsen, Henrik; Lenaers, G

    1990-01-01

    We have determined the nucleotide sequence of the 26S large subunit (LSU) rRNA genes for two Tetrahymena species, T. thermophila and T. pyriformis. The inferred rRNA sequences are presented in their most probable secondary structures based on compensatory mutations, energy, and conservation...

  19. Meiotic genes and sexual reproduction in the green algal class Trebouxiophyceae (Chlorophyta)

    KAUST Repository

    Fučíková, Karolina

    2015-04-06

    © 2015 Phycological Society of America. Sexual reproduction is widespread in eukaryotes and is well documented in chlorophytan green algae. In this lineage, however, the Trebouxiophyceae represent a striking exception: in contrast to its relatives Chlorophyceae and Ulvophyceae this group appears to be mostly asexual, as fertilization has been rarely observed. Assessments of sexual reproduction in the Trebouxiophyceae have been based on microscopic observation of gametes fusing. New genomic data offer now the opportunity to check for the presence of meiotic genes, which represent an indirect evidence of a sexual life cycle. Using genomic and transcriptomic data for 12 taxa spanning the phylogenetic breadth of the class, we tried to clarify whether genuine asexuality or cryptic sexuality is the most likely case for the numerous putatively asexual trebouxiophytes. On the basis of these data and a bibliographic review, we conclude that the view of trebouxiophytes as primarily asexual is incorrect. In contrast to the limited number of reports of fertilization, meiotic genes were found in all genomes and transcriptomes examined, even in species presumed asexual. In the taxa examined the totality or majority of the genes were present, Helicosporidium and Auxenochlorella being the only partial exceptions (only four genes present). The evidence of sex provided by the meiotic genes is phylogenetically widespread in the class and indicates that sexual reproduction is not associated with any particular morphological or ecological trait. On the basis of the results, we expect that the existence of the meiotic genes will be documented in all trebouxiophycean genomes that will become available in the future.

  20. Maize germinal cell initials accommodate hypoxia and precociously express meiotic genes.

    Science.gov (United States)

    Kelliher, Timothy; Walbot, Virginia

    2014-02-01

    In flowering plants, anthers are the site of de novo germinal cell specification, male meiosis, and pollen development. Atypically, anthers lack a meristem. Instead, both germinal and somatic cell types differentiate from floral stem cells packed into anther lobes. To better understand anther cell fate specification and to provide a resource for the reproductive biology community, we isolated cohorts of germinal and somatic initials from maize anthers within 36 h of fate acquisition, identifying 815 specific and 1714 significantly enriched germinal transcripts, plus 2439 specific and 2112 significantly enriched somatic transcripts. To clarify transcripts involved in cell differentiation, we contrasted these profiles to anther primordia prior to fate specification and to msca1 anthers arrested in the first step of fate specification and hence lacking normal cell types. The refined cell-specific profiles demonstrated that both germinal and somatic cell populations differentiate quickly and express unique transcription factor sets; a subset of transcript localizations was validated by in situ hybridization. Surprisingly, germinal initials starting 5 days of mitotic divisions were enriched significantly in >100 transcripts classified in meiotic processes that included recombination and synapsis, along with gene sets involved in RNA metabolism, redox homeostasis, and cytoplasmic ATP generation. Enrichment of meiotic-specific genes in germinal initials challenges current dogma that the mitotic to meiotic transition occurs later in development during pre-meiotic S phase. Expression of cytoplasmic energy generation genes suggests that male germinal cells accommodate hypoxia by diverting carbon away from mitochondrial respiration into alternative pathways that avoid producing reactive oxygen species (ROS). © 2013 The Authors The Plant Journal © 2013 John Wiley & Sons Ltd.

  1. Unreduced Megagametophyte Production in Lemon Occurs via Three Meiotic Mechanisms, Predominantly Second-Division Restitution

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    Houssem Rouiss

    2017-07-01

    Full Text Available Unreduced (2n gametes have played a pivotal role in polyploid plant evolution and are useful for sexual polyploid breeding in various species, particularly for developing new seedless citrus varieties. The underlying mechanisms of 2n gamete formation were recently revealed for Citrus reticulata but remain poorly understood for other citrus species, including lemon (C. limon [L.] Burm. f.. Here, we investigated the frequency and causal meiotic mechanisms of 2n megagametophyte production in lemon. We genotyped 48progeny plants of two lemon genotypes, “Eureka Frost” and “Fino”, using 16 Simple Sequence Repeat (SSR and 18 Single Nucleotide Polymorphism (SNP markers to determine the genetic origin of the progenies and the underlying mechanisms for 2n gamete formation. We utilized a maximum-likelihood method based on parental heterozygosity restitution (PHR of centromeric markers and analysis of PHR patterns along the chromosome. The frequency of 2n gamete production was 4.9% for “Eureka Frost” and 8.3% for “Fino”, with three meiotic mechanisms leading to 2n gamete formation. We performed the maximum-likelihood method at the individual level via centromeric marker analysis, finding that 88% of the hybrids arose from second-division restitution (SDR, 7% from first-division restitution (FDR or pre-meiotic doubling (PRD, and 5% from post-meiotic genome doubling (PMD. The pattern of PHR along LG1 confirmed that SDR is the main mechanism for 2n gamete production. Recombination analysis between markers in this LG revealed partial chiasma interference on both arms. We discuss the implications of these restitution mechanisms for citrus breeding and lemon genetics.

  2. Expression of arf tumor suppressor in spermatogonia facilitates meiotic progression in male germ cells.

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    Michelle L Churchman

    2011-07-01

    Full Text Available The mammalian Cdkn2a (Ink4a-Arf locus encodes two tumor suppressor proteins (p16(Ink4a and p19(Arf that respectively enforce the anti-proliferative functions of the retinoblastoma protein (Rb and the p53 transcription factor in response to oncogenic stress. Although p19(Arf is not normally detected in tissues of young adult mice, a notable exception occurs in the male germ line, where Arf is expressed in spermatogonia, but not in meiotic spermatocytes arising from them. Unlike other contexts in which the induction of Arf potently inhibits cell proliferation, expression of p19(Arf in spermatogonia does not interfere with mitotic cell division. Instead, inactivation of Arf triggers germ cell-autonomous, p53-dependent apoptosis of primary spermatocytes in late meiotic prophase, resulting in reduced sperm production. Arf deficiency also causes premature, elevated, and persistent accumulation of the phosphorylated histone variant H2AX, reduces numbers of chromosome-associated complexes of Rad51 and Dmc1 recombinases during meiotic prophase, and yields incompletely synapsed autosomes during pachynema. Inactivation of Ink4a increases the fraction of spermatogonia in S-phase and restores sperm numbers in Ink4a-Arf doubly deficient mice but does not abrogate γ-H2AX accumulation in spermatocytes or p53-dependent apoptosis resulting from Arf inactivation. Thus, as opposed to its canonical role as a tumor suppressor in inducing p53-dependent senescence or apoptosis, Arf expression in spermatogonia instead initiates a salutary feed-forward program that prevents p53-dependent apoptosis, contributing to the survival of meiotic male germ cells.

  3. Unreduced Megagametophyte Production in Lemon Occurs via Three Meiotic Mechanisms, Predominantly Second-Division Restitution

    Science.gov (United States)

    Rouiss, Houssem; Cuenca, José; Navarro, Luis; Ollitrault, Patrick; Aleza, Pablo

    2017-01-01

    Unreduced (2n) gametes have played a pivotal role in polyploid plant evolution and are useful for sexual polyploid breeding in various species, particularly for developing new seedless citrus varieties. The underlying mechanisms of 2n gamete formation were recently revealed for Citrus reticulata but remain poorly understood for other citrus species, including lemon (C. limon [L.] Burm. f.). Here, we investigated the frequency and causal meiotic mechanisms of 2n megagametophyte production in lemon. We genotyped 48progeny plants of two lemon genotypes, “Eureka Frost” and “Fino”, using 16 Simple Sequence Repeat (SSR) and 18 Single Nucleotide Polymorphism (SNP) markers to determine the genetic origin of the progenies and the underlying mechanisms for 2n gamete formation. We utilized a maximum-likelihood method based on parental heterozygosity restitution (PHR) of centromeric markers and analysis of PHR patterns along the chromosome. The frequency of 2n gamete production was 4.9% for “Eureka Frost” and 8.3% for “Fino”, with three meiotic mechanisms leading to 2n gamete formation. We performed the maximum-likelihood method at the individual level via centromeric marker analysis, finding that 88% of the hybrids arose from second-division restitution (SDR), 7% from first-division restitution (FDR) or pre-meiotic doubling (PRD), and 5% from post-meiotic genome doubling (PMD). The pattern of PHR along LG1 confirmed that SDR is the main mechanism for 2n gamete production. Recombination analysis between markers in this LG revealed partial chiasma interference on both arms. We discuss the implications of these restitution mechanisms for citrus breeding and lemon genetics. PMID:28747921

  4. Lifespan extension in a semelparous chordate occurs via developmental growth arrest just prior to meiotic entry.

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    Gunasekaran Subramaniam

    Full Text Available It is proposed that the ageing process is linked to signaling from the germline such that the rate of ageing can be adjusted to the state of the reproductive system, allowing these two processes to co-evolve. Mechanistic insight into this link has been primarily derived from iteroparous reproductive models, the nematode C. elegans, and the arthropod Drosophila. Here, we examined to what extent these mechanisms are evolutionarily conserved in a semelparous chordate, Oikopleura dioica, where we identify a developmental growth arrest (GA in response to crowded, diet-restricted conditions, which can extend its lifespan at least three-fold. Under nutritional stress, the iteroparative models sacrifice germ cells that have entered meiosis, while maintaining a reduced pool of active germline stem cells (GSCs. In contrast, O. dioica only entered GA prior to meiotic entry. Stress conditions encountered after this point led to maturation in a normal time frame but with reduced reproductive output. During GA, TOR signaling was inhibited, whereas MAPK, ERK1/2 and p38 pathways were activated, and under such conditions, activation of these pathways was shown to be critical for survival. Direct inhibition of TOR signaling alone was sufficient to prevent meiotic entry and germline differentiation. This inhibition activated the p38 pathway, but did not activate the ERK1/2 pathway. Thus, the link between reproductive status and lifespan extension in response to nutrient-limited conditions is interpreted in a significantly different manner in these iteroparative versus semelparous models. In the latter case, meiotic entry is a definitive signal that lifespan extension can no longer occur, whereas in the former, meiotic entry is not a unique chronological event, and can be largely erased during lifespan extension in response to nutrient stress, and reactivated from a pool of maintained GSCs when conditions improve.

  5. Genomic features shaping the landscape of meiotic double-strand-break hotspots in maize.

    Science.gov (United States)

    He, Yan; Wang, Minghui; Dukowic-Schulze, Stefanie; Zhou, Adele; Tiang, Choon-Lin; Shilo, Shay; Sidhu, Gaganpreet K; Eichten, Steven; Bradbury, Peter; Springer, Nathan M; Buckler, Edward S; Levy, Avraham A; Sun, Qi; Pillardy, Jaroslaw; Kianian, Penny M A; Kianian, Shahryar F; Chen, Changbin; Pawlowski, Wojciech P

    2017-11-14

    Meiotic recombination is the most important source of genetic variation in higher eukaryotes. It is initiated by formation of double-strand breaks (DSBs) in chromosomal DNA in early meiotic prophase. The DSBs are subsequently repaired, resulting in crossovers (COs) and noncrossovers (NCOs). Recombination events are not distributed evenly along chromosomes but cluster at recombination hotspots. How specific sites become hotspots is poorly understood. Studies in yeast and mammals linked initiation of meiotic recombination to active chromatin features present upstream from genes, such as absence of nucleosomes and presence of trimethylation of lysine 4 in histone H3 (H3K4me3). Core recombination components are conserved among eukaryotes, but it is unclear whether this conservation results in universal characteristics of recombination landscapes shared by a wide range of species. To address this question, we mapped meiotic DSBs in maize, a higher eukaryote with a large genome that is rich in repetitive DNA. We found DSBs in maize to be frequent in all chromosome regions, including sites lacking COs, such as centromeres and pericentromeric regions. Furthermore, most DSBs are formed in repetitive DNA, predominantly Gypsy retrotransposons, and only one-quarter of DSB hotspots are near genes. Genic and nongenic hotspots differ in several characteristics, and only genic DSBs contribute to crossover formation. Maize hotspots overlap regions of low nucleosome occupancy but show only limited association with H3K4me3 sites. Overall, maize DSB hotspots exhibit distribution patterns and characteristics not reported previously in other species. Understanding recombination patterns in maize will shed light on mechanisms affecting dynamics of the plant genome.

  6. ATP-binding cassette transporter enhances tolerance to DDT in Tetrahymena.

    Science.gov (United States)

    Ning, YingZhi; Dang, Huai; Liu, GuangLong; Xiong, Jie; Yuan, DongXia; Feng, LiFang; Miao, Wei

    2015-03-01

    The reuse of dichlorodiphenyltrichloroethane (DDT) as an indoor residual spray was permitted by the World Health Organization in 2007, and approximately 14 countries still use DDT to control disease vectors. The extensive exposure of insects to DDT has resulted in the emergence of DDT resistance, especially in mosquitoes, and the mechanism for this resistance in mosquitoes has been widely reported. Spraying can also introduce DDT directly into surface water, and DDT can subsequently accumulate in microorganisms, but the mechanism for the resistance to DDT degradation in microorganisms is unclear. Using whole-genome microarray analysis, we detected an abcb15 gene that was up-regulated in a specific manner by DDT treatment in T. thermophile. The deduced ABCB15 peptide sequence had two transmembrane domains (TMDs) and two nucleotide-binding domains (NBDs) to form the structure TMD-NBD-TMD-NBD, and each NBD contained three conserved motifs: Walker-A, C-loop, and Walker-B, which indicated the T. thermophila abcb15 was a typical ABC transporter gene. The expression of ABCB15 fused with a C-terminal green fluorescent protein was found to be on the periphery of the cell, suggesting that ABCB15 was a membrane pump protein. In addition, cells with abcb15 partially knocked down (abcb15-KD) grew slower than wild-type cells in the presence of 256 mg L(-1) DDT, indicating the tolerance of abcb15-KD strain to DDT exposure was decreased. Thus, we suggest that in Tetrahymena, the membrane pump protein encoded by ABCT gene abcb15 can enhance the tolerance to DDT and protect cells from this exogenous toxin by efficiently pumping it to the extracellular space.

  7. Encystment/excystment response and serotypic variation in the gastropod parasite Tetrahymena rostrata (Ciliophora, Tetrahymenidae).

    Science.gov (United States)

    Segade, P; García, N; García Estévez, J M; Arias, C; Iglesias, R

    2016-02-01

    Tetrahymena rostrata, which is characterized by a particular encystment-excystment cycle involving autogamy, has been recently found infecting the kidney of edible Helix aspersa snails under farming conditions. In this work, the effects of several factors on its encystment/excystment behaviour and the occurrence of different serotypes were investigated. The encystment/excystment response under starvation conditions was seriously affected by temperature. While a peak of encystment at 48 h followed by a progressive spontaneous excystment was observed at 18 and 25 °C, the encystment response was practically inhibited at 5 °C and clearly slowed down at 10 °C. At 30 °C, most of surviving ciliates remained encysted throughout the experiment, with spontaneous excystment being detected only after switching the temperature to 18 °C. Soil components also affected the encystment/excystment behaviour at 18 °C, with spontaneous excystment occurring in the presence of a sterile-filtered soil extract or mineral water but being strongly minimized with a non-filtered soil extract. Resting cysts formed in the latter extract exhibited a 3–4 times thicker and ultrastructurally more complex wall than that formed in mineral water and retained the excystment ability for about 4 weeks. Incomplete desiccation did not affect significantly the encystment response, while the mucus and kidney extracts from snails as well as a ciliate extract strongly stimulated a rapid excystment. Finally, two different serotypes infecting H. aspersa in heliciculture farms of Galicia (NW Spain) were identified, but no differences were observed between the encystment/excystment responses exhibited by two isolates belonging to each serotype.

  8. MtnBD is a multifunctional fusion enzyme in the methionine salvage pathway of Tetrahymena thermophila.

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    Toshihiro Nakano

    Full Text Available To recycle reduced sulfur to methionine in the methionine salvage pathway (MSP, 5-methylthioribulose-1-phosphate is converted to 2-keto-4-methylthiobutyrate, the methionine precursor, by four steps; dehydratase, enolase, phosphatase, and dioxygenase reactions (catalyzed by MtnB, MtnW, MtnX and MtnD, respectively, in Bacillus subtilis. It has been proposed that the MtnBD fusion enzyme in Tetrahymena thermophila catalyzes four sequential reactions from the dehydratase to dioxygenase steps, based on the results of molecular biological analyses of mutant yeast strains with knocked-out MSP genes, suggesting that new catalytic function can be acquired by fusion of enzymes. This result raises the question of how the MtnBD fusion enzyme can catalyze four very different reactions, especially since there are no homologous domains for enolase and phosphatase (MtnW and MtnX, respectively, in B. subtilis in the peptide. Here, we tried to identify the domains responsible for catalyzing the four reactions using recombinant proteins of full-length MtnBD and each domain alone. UV-visible and ¹H-NMR spectral analyses of reaction products revealed that the MtnB domain catalyzes dehydration and enolization and the MtnD domain catalyzes dioxygenation. Contrary to a previous report, conversion of 5-methylthioribulose-1-phosphate to 2-keto-4-methylthiobutyrate was dependent on addition of an exogenous phosphatase from B. subtilis. This was observed for both the MtnB domain and full-length MtnBD, suggesting that MtnBD does not catalyze the phosphatase reaction. Our results suggest that the MtnB domain of T. thermophila MtnBD acquired the new function to catalyze both the dehydratase and enolase reactions through evolutionary gene mutations, rather than fusion of MSP genes.

  9. Loading and pre-loading processes generate a distinct siRNA population in Tetrahymena

    Energy Technology Data Exchange (ETDEWEB)

    Mochizuki, Kazufumi, E-mail: kazufumi.mochizuki@imba.oeaw.ac.at; Kurth, Henriette M.

    2013-07-05

    Highlights: •The Tetrahymena Argonaute protein Twi1p binds to ∼28–30-nt siRNAs called scnRNAs. •The size of scnRNAs is determined during a pre-loading process. •The 5′ uracil bias of scnRNAs is attributed to pre-loading and loading processes. •The thermodynamic asymmetry of scnRNA duplex doesnot affect the guide strand decision. •scnRNAs may be produced non-sequentially from dsRNA substrates by Dicer. -- Abstract: The various properties of small RNAs, such as length, terminal nucleotide, thermodynamic asymmetry and duplex mismatches, can impact their sorting into different Argonaute proteins in diverse eukaryotes. The developmentally regulated 26- to 32-nt siRNAs (scnRNAs) are loaded to the Argonaute protein Twi1p and display a strong bias for uracil at the 5′ end. In this study, we used deep sequencing to analyze loaded and unloaded populations of scnRNAs. We show that the size of the scnRNA is determined during a pre-loading process, whereas their 5′ uracil bias is attributed to both pre-loading and loading processes. We also demonstrate that scnRNAs have a strong bias for adenine at the third base from the 3′ terminus, suggesting that most scnRNAs are direct Dicer products. Furthermore, we show that the thermodynamic asymmetry of the scnRNA duplex does not affect the guide and passenger strand decision. Finally, we show that scnRNAs frequently have templated uracil at the last base without a strong bias for adenine at the second base indicating non-sequential production of scnRNAs from substrates. These findings provide a biochemical basis for the varying attributes of scnRNAs, which should help improve our understanding of the production and turnover of scnRNAs in vivo.

  10. AAA-ATPase FIDGETIN-LIKE 1 and Helicase FANCM Antagonize Meiotic Crossovers by Distinct Mechanisms.

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    Chloe Girard

    2015-07-01

    Full Text Available Meiotic crossovers (COs generate genetic diversity and are critical for the correct completion of meiosis in most species. Their occurrence is tightly constrained but the mechanisms underlying this limitation remain poorly understood. Here we identified the conserved AAA-ATPase FIDGETIN-LIKE-1 (FIGL1 as a negative regulator of meiotic CO formation. We show that Arabidopsis FIGL1 limits CO formation genome-wide, that FIGL1 controls dynamics of the two conserved recombinases DMC1 and RAD51 and that FIGL1 hinders the interaction between homologous chromosomes, suggesting that FIGL1 counteracts DMC1/RAD51-mediated inter-homologue strand invasion to limit CO formation. Further, depleting both FIGL1 and the previously identified anti-CO helicase FANCM synergistically increases crossover frequency. Additionally, we showed that the effect of mutating FANCM on recombination is much lower in F1 hybrids contrasting from the phenotype of inbred lines, while figl1 mutation equally increases crossovers in both contexts. This shows that the modes of action of FIGL1 and FANCM are differently affected by genomic contexts. We propose that FIGL1 and FANCM represent two successive barriers to CO formation, one limiting strand invasion, the other disassembling D-loops to promote SDSA, which when both lifted, leads to a large increase of crossovers, without impairing meiotic progression.

  11. Quantitative control of protein S-palmitoylation regulates meiotic entry in fission yeast.

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    Mingzi M Zhang

    2013-07-01

    Full Text Available Protein S-palmitoylation, a lipid modification mediated by members of the palmitoyltransferase family, serves as an important membrane-targeting mechanism in eukaryotes. Although changes in palmitoyltransferase expression are associated with various physiological and disease states, how these changes affect global protein palmitoylation and cellular function remains unknown. Using a bioorthogonal chemical reporter and labeling strategy to identify and analyze multiple cognate substrates of a single Erf2 palmitoyltransferase, we demonstrate that control of Erf2 activity levels underlies the differential modification of key substrates such as the Rho3 GTPase in vegetative and meiotic cells. We show further that modulation of Erf2 activity levels drives changes in the palmitoylome as cells enter meiosis and affects meiotic entry. Disruption of Erf2 function delays meiotic entry, while increasing Erf2 palmitoyltransferase activity triggers aberrant meiosis in sensitized cells. Erf2-induced meiosis requires the function of the Rho3 GTPase, which is regulated by its palmitoylation state. We propose that control of palmitoyltransferase activity levels provides a fundamental mechanism for modulating palmitoylomes and cellular functions.

  12. A dynamical model of oocyte maturation unveils precisely orchestrated meiotic decisions.

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    Benjamin Pfeuty

    2012-01-01

    Full Text Available Maturation of vertebrate oocytes into haploid gametes relies on two consecutive meioses without intervening DNA replication. The temporal sequence of cellular transitions driving eggs from G2 arrest to meiosis I (MI and then to meiosis II (MII is controlled by the interplay between cyclin-dependent and mitogen-activated protein kinases. In this paper, we propose a dynamical model of the molecular network that orchestrates maturation of Xenopus laevis oocytes. Our model reproduces the core features of maturation progression, including the characteristic non-monotonous time course of cyclin-Cdks, and unveils the network design principles underlying a precise sequence of meiotic decisions, as captured by bifurcation and sensitivity analyses. Firstly, a coherent and sharp meiotic resumption is triggered by the concerted action of positive feedback loops post-translationally activating cyclin-Cdks. Secondly, meiotic transition is driven by the dynamic antagonism between positive and negative feedback loops controlling cyclin turnover. Our findings reveal a highly modular network in which the coordination of distinct regulatory schemes ensures both reliable and flexible cell-cycle decisions.

  13. Population dynamics of a meiotic/mitotic expansion model for the fragile X syndrome

    Energy Technology Data Exchange (ETDEWEB)

    Ashley, A.E.; Sherman, S.L. [Emory Univ. School of Medicine, Atlanta, GA (United States)

    1995-12-01

    A model to explain the mutational process and population dynamics of the fragile X syndrome is presented. The mutational mechanism was assumed to be a multi-pathway, multistep process. Expansion of CGG repeats was based on an underlying biological process and was assumed to occur at two time points: meiosis and early embryonic development (mitosis). Meiotic expansion was assumed to occur equally in oogenesis and spermatogenesis, while mitotic expansion was restricted to somatic, or constitutional, alleles of maternal origin. Testable hypotheses were predicted by this meiotic/mitotic model. First, parental origin of mutation is predicted to be associated with the risk of a woman to have a full-mutation child. Second, {open_quotes}contractions{close_quotes} seen in premutation male transmissions are predicted not to be true contractions in repeat size, but a consequence of the lack of mitotic expansion in paternally derived alleles. Third, a portion of full-mutation males should have full-mutation alleles in their sperm, due to the lack of complete selection against the full-mutation female. Fourth, a specific premutation-allele frequency distribution is predicted and differs from that based on models assuming only meiotic expansion. Last, it is predicted that {approximately}65 generations are required to achieve equilibrium, but this depends greatly on the expansion probabilities. 42 refs., 4 figs., 4 tabs.

  14. Meiotic regulation of TPX2 protein levels governs cell cycle progression in mouse oocytes.

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    Stéphane Brunet

    Full Text Available Formation of female gametes requires acentriolar spindle assembly during meiosis. Mitotic spindles organize from centrosomes and via local activation of the RanGTPase on chromosomes. Vertebrate oocytes present a RanGTP gradient centred on chromatin at all stages of meiotic maturation. However, this gradient is dispensable for assembly of the first meiotic spindle. To understand this meiosis I peculiarity, we studied TPX2, a Ran target, in mouse oocytes. Strikingly, TPX2 activity is controlled at the protein level through its accumulation from meiosis I to II. By RNAi depletion and live imaging, we show that TPX2 is required for spindle assembly via two distinct functions. It controls microtubule assembly and spindle pole integrity via the phosphorylation of TACC3, a regulator of MTOCs activity. We show that meiotic spindle formation in vivo depends on the regulation of at least a target of Ran, TPX2, rather than on the regulation of the RanGTP gradient itself.

  15. Meiotic behavior in apomictic Brachiaria ruziziensis × B. brizantha (Poaceae progenies

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    Veridiana Aparecida Fuzinatto

    2012-12-01

    Full Text Available Hybrids combining desirable traits from divergent parents are the main objective of some Brachiaria (Syn. Urochloa P. Beauv. breeding programs. There is great interest in the development of apomictic hybrid cultivars that combine desirable genes such as resistance to spittlebugs, high nutritive value, and tolerance to acid soils. Microsporogenesis of six apomictic progenies resulting from a tetraploid (2n = 4x = 36 cross between B. ruziziensis × B. brizantha was evaluated under light microscopy. Genetic recombination, ensured by multivalent chromosome association and crossing-over at prophase occurred in low frequency among progenies, and in one, recombination was almost nonexistent. The percentage of meiocytes with meiotic abnormalities among progenies ranged from 16.6 % to 85.6 %. Besides an observed irregular chromosome segregation typical of polyploid hybrids in these five progenies, putative meiotic mutations characterized as desynapsis and divergent spindle organization occurred in three progenies. These anomalies caused frequent fractionation of the genome into several microspores of different sizes. In Brachiaria, new cultivars must be apomictic to fix the genotype. However, Brachiaria is a pseudogamous apomict, and viable gametes are necessary to produce viable seeds. Considering meiotic behavior, only two progenies are promising for advancement in the breeding program.

  16. Chromosome Synapsis Alleviates Mek1-Dependent Suppression of Meiotic DNA Repair.

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    Vijayalakshmi V Subramanian

    2016-02-01

    Full Text Available Faithful meiotic chromosome segregation and fertility require meiotic recombination between homologous chromosomes rather than the equally available sister chromatid, a bias that in Saccharomyces cerevisiae depends on the meiotic kinase, Mek1. Mek1 is thought to mediate repair template bias by specifically suppressing sister-directed repair. Instead, we found that when Mek1 persists on closely paired (synapsed homologues, DNA repair is severely delayed, suggesting that Mek1 suppresses any proximal repair template. Accordingly, Mek1 is excluded from synapsed homologues in wild-type cells. Exclusion requires the AAA+-ATPase Pch2 and is directly coupled to synaptonemal complex assembly. Stage-specific depletion experiments further demonstrate that DNA repair in the context of synapsed homologues requires Rad54, a repair factor inhibited by Mek1. These data indicate that the sister template is distinguished from the homologue primarily by its closer proximity to inhibitory Mek1 activity. We propose that once pairing or synapsis juxtaposes homologues, exclusion of Mek1 is necessary to avoid suppression of all templates and accelerate repair progression.

  17. Production and Characterization of Radiation-Sensitive Meiotic Mutants of Coprinus Cinereus

    Science.gov (United States)

    Zolan, M. E.; Tremel, C. J.; Pukkila, P. J.

    1988-01-01

    We have isolated four γ-ray-sensitive mutants of the basidiomycete Coprinus cinereus. When homozygous, two of these (rad 3-1 and rad 9-1) produce fruiting bodies with very few viable basidiospores, the products of meiosis in this organism. A less radiation-sensitive allele of RAD 3, rad 3-2, causes no apparent meiotic defect in homozygous strains. Quantitative measurements of oidial survival of rad 3-1;rad 9-1 double mutants compared to the single mutants indicated that rad 3-1 and rad 9-1 mutants are defective in the same DNA repair pathway. In the few viable basidiospores that are produced by these two strains, essentially normal levels of meiotic recombination can be detected. None of the mutants exhibits increased sensitivity to UV radiation. Cytological examination of meiotic chromosomes from mutant and wild-type fruiting bodies showed that rad 3-1 homozygous strains fail to condense and pair homologous chromosomes during prophase I. Although rad 9-1 strains are successful at chromosome pairing, meiosis is usually not completed in these mutants. PMID:3197952

  18. Post-meiotic intra-testicular sperm senescence in a wild vertebrate.

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    Attila Hettyey

    Full Text Available There is growing interest in sperm senescence, both in its underlying mechanisms and evolutionary consequences, because it can impact the evolution of numerous life history traits. Previous studies have documented various types of sperm senescence, but evidence of post-meiotic intra-testicular sperm senescence in wild animals is lacking. To assess such senescence, we studied within-season changes in sperm motility in the common toad (Bufo bufo, where males produce all sperm prior to the breeding season. We found that males exposed to experimentally induced re-hibernation at the start of the breeding season, that is to experimentally lowered metabolic rates, stored sperm of significantly higher motility than males that were kept under seminatural conditions without females throughout the breeding season. This finding indicates that re-hibernation slows normal rates of sperm ageing and constitutes the first evidence to our knowledge of post-meiotic intra-testicular sperm senescence in a wild vertebrate. We also found that in males kept in seminatural conditions, sperm motility was positively related to the number of matings a male achieved. Thus, our results suggest that post-meiotic intra-testicular sperm senescence does not have a genetically fixed rate and may be modulated by temperature and possibly by mating opportunities.

  19. Induction of meiotic gynogenesis in Atlantic cod (Gadus morhua L.) through pressure shock.

    Science.gov (United States)

    Ghigliotti, Laura; Bolla, Sylvie L; Duc, Michal; Ottesen, Oddvar H; Babiak, Igor

    2011-08-01

    The Atlantic cod, Gadus morhua, is one of the most important species for commercial fisheries and a promising candidate for aquaculture. Precocious sexual maturation of males is one of the major issues compromising large scale production. The potential approaches to this problem include production of all female populations. Consequently, the objective of this study was to develop an effective protocol to induce meiotic gynogenesis in the Atlantic cod by using hydrostatic pressure shock. Our first experiment tested the relevance of gamete quality on achievement of chromosome manipulation and identified the best time interval between fertilization and pressure shock. Our second experiment was designed to determine the optimal pressure value and duration of the pressure shock. Eight combinations of pressure values and durations were tested. Among them, the 34.47 MPa/6 min combination gave the best survival rate (23.6 ± 3.9%), the highest percentage of normal larvae (15.7 ± 3.6%), and the highest percentage of meiotic diploids (88.89%). In both experiments, haploid controls served as an indirect reference for paternal DNA inactivation. Chromosome counting confirmed the restoration of diploidy in gynogenetic fish. The present study optimizes a procedure for the induction of meiotic gynogenesis in the Atlantic cod, thus laying the basis for further applications towards producing monosex and defining the sex determination system. Copyright © 2011 Elsevier B.V. All rights reserved.

  20. AAA-ATPase FIDGETIN-LIKE 1 and Helicase FANCM Antagonize Meiotic Crossovers by Distinct Mechanisms.

    Science.gov (United States)

    Girard, Chloe; Chelysheva, Liudmila; Choinard, Sandrine; Froger, Nicole; Macaisne, Nicolas; Lemhemdi, Afef; Lehmemdi, Afef; Mazel, Julien; Crismani, Wayne; Mercier, Raphael

    2015-07-01

    Meiotic crossovers (COs) generate genetic diversity and are critical for the correct completion of meiosis in most species. Their occurrence is tightly constrained but the mechanisms underlying this limitation remain poorly understood. Here we identified the conserved AAA-ATPase FIDGETIN-LIKE-1 (FIGL1) as a negative regulator of meiotic CO formation. We show that Arabidopsis FIGL1 limits CO formation genome-wide, that FIGL1 controls dynamics of the two conserved recombinases DMC1 and RAD51 and that FIGL1 hinders the interaction between homologous chromosomes, suggesting that FIGL1 counteracts DMC1/RAD51-mediated inter-homologue strand invasion to limit CO formation. Further, depleting both FIGL1 and the previously identified anti-CO helicase FANCM synergistically increases crossover frequency. Additionally, we showed that the effect of mutating FANCM on recombination is much lower in F1 hybrids contrasting from the phenotype of inbred lines, while figl1 mutation equally increases crossovers in both contexts. This shows that the modes of action of FIGL1 and FANCM are differently affected by genomic contexts. We propose that FIGL1 and FANCM represent two successive barriers to CO formation, one limiting strand invasion, the other disassembling D-loops to promote SDSA, which when both lifted, leads to a large increase of crossovers, without impairing meiotic progression.

  1. Two genes required for meiotic recombination in Drosophila are expressed from a dicistronic message.

    Science.gov (United States)

    Liu, H; Jang, J K; Graham, J; Nycz, K; McKim, K S

    2000-04-01

    We have isolated two alleles of a previously unidentified meiotic recombination gene, mei-217. Genetic analysis of these mutants shows that mei-217 is a typical "precondition" gene. The phenotypes of the mutants are meiosis specific. The strongest allele has <10% of the normal level of crossing over, and the residual events are distributed abnormally. We have used double mutant analysis to position mei-217 in the meiotic recombination pathway. In general, mutations causing defects in the initiation of meiotic recombination are epistatic to mutations in mei-41 and spnB. These two mutations, however, are epistatic to mei-217, suggesting that recombination is initiated normally in mei-217 mutants. It is likely that mei-217 mutants are able to make Holliday junction intermediates but are defective in the production of crossovers. These phenotypes are most similar to mutants of the mei-218 gene. This is striking because mei-217 and mei-218 are part of the same transcription unit and are most likely produced from a dicistronic message.

  2. Shifting meiotic to mitotic spindle assembly in oocytes disrupts chromosome alignment.

    Science.gov (United States)

    Bennabi, Isma; Quéguiner, Isabelle; Kolano, Agnieszka; Boudier, Thomas; Mailly, Philippe; Verlhac, Marie-Hélène; Terret, Marie-Emilie

    2018-01-12

    Mitotic spindles assemble from two centrosomes, which are major microtubule-organizing centers (MTOCs) that contain centrioles. Meiotic spindles in oocytes, however, lack centrioles. In mouse oocytes, spindle microtubules are nucleated from multiple acentriolar MTOCs that are sorted and clustered prior to completion of spindle assembly in an "inside-out" mechanism, ending with establishment of the poles. We used HSET (kinesin-14) as a tool to shift meiotic spindle assembly toward a mitotic "outside-in" mode and analyzed the consequences on the fidelity of the division. We show that HSET levels must be tightly gated in meiosis I and that even slight overexpression of HSET forces spindle morphogenesis to become more mitotic-like: rapid spindle bipolarization and pole assembly coupled with focused poles. The unusual length of meiosis I is not sufficient to correct these early spindle morphogenesis defects, resulting in severe chromosome alignment abnormalities. Thus, the unique "inside-out" mechanism of meiotic spindle assembly is essential to prevent chromosomal misalignment and production of aneuploidy gametes. © 2018 The Authors. Published under the terms of the CC BY 4.0 license.

  3. Meiotic segregation and interchromosomal effect in the sperm of a double translocation carrier: a case report.

    Science.gov (United States)

    Juchniuk de Vozzi, Maria S; Santos, Silvio A; Pereira, Ciro S; Cuzzi, Juliana F; Laureano, Lucimar Af; Franco, José G; Martelli, Lucia

    2009-12-01

    Infertility is a natural mechanism of selection intended to prevent the delivery of a child with malformations or mental retardation. Male infertility is closely related to chromosomal abnormalities. This study was focused on the analysis of meiotic segregation involving a Robertsonian translocation, 45,XY,der(13;13) [56]/45,XY,der(13;14) [44] and the evaluation of possible interchromosomal effects. Hybridisation with LSI 13q14 and subtelomere 14q probes and WCP13 SpectrumGreen and WCP14 SpectrumOrange probes showed a high proportion of unbalanced gametes, corresponding to 71.2% of the spermatozoa. The disomic frequencies of the sexual chromosomes and chromosome 18 of the patient were higher (5.28% and 2.55%, respectively) than those of the control (0.6% and 0.59%, respectively). Meiotic segregation studies in sperm are an important tool for genetic counselling of chromosomal aberrations, allowing for a prediction of the risks and consequent implications for the reproductive life. The patient with this rare translocation exhibited meiotic segregation fidelity, and a high rate of unbalanced gametes with disomic spermatozoa.

  4. Meiotic segregation and interchromosomal effect in the sperm of a double translocation carrier: a case report

    Directory of Open Access Journals (Sweden)

    Laureano Lucimar AF

    2009-12-01

    Full Text Available Abstract Background Infertility is a natural mechanism of selection intended to prevent the delivery of a child with malformations or mental retardation. Male infertility is closely related to chromosomal abnormalities. This study was focused on the analysis of meiotic segregation involving a Robertsonian translocation, 45,XY,der(13;13 [56]/45,XY,der(13;14 [44] and the evaluation of possible interchromosomal effects. Results Hybridisation with LSI 13q14 and subtelomere 14q probes and WCP13 SpectrumGreen and WCP14 SpectrumOrange probes showed a high proportion of unbalanced gametes, corresponding to 71.2% of the spermatozoa. The disomic frequencies of the sexual chromosomes and chromosome 18 of the patient were higher (5.28% and 2.55%, respectively than those of the control (0.6% and 0.59%, respectively. Conclusion Meiotic segregation studies in sperm are an important tool for genetic counselling of chromosomal aberrations, allowing for a prediction of the risks and consequent implications for the reproductive life. The patient with this rare translocation exhibited meiotic segregation fidelity, and a high rate of unbalanced gametes with disomic spermatozoa.

  5. Divergent kleisin subunits of cohesin specify mechanisms to tether and release meiotic chromosomes.

    Science.gov (United States)

    Severson, Aaron F; Meyer, Barbara J

    2014-08-29

    We show that multiple, functionally specialized cohesin complexes mediate the establishment and two-step release of sister chromatid cohesion that underlies the production of haploid gametes. In C. elegans, the kleisin subunits REC-8 and COH-3/4 differ between meiotic cohesins and endow them with distinctive properties that specify how cohesins load onto chromosomes and then trigger and release cohesion. Unlike REC-8 cohesin, COH-3/4 cohesin becomes cohesive through a replication-independent mechanism initiated by the DNA double-stranded breaks that induce crossover recombination. Thus, break-induced cohesion also tethers replicated meiotic chromosomes. Later, recombination stimulates separase-independent removal of REC-8 and COH-3/4 cohesins from reciprocal chromosomal territories flanking the crossover site. This region-specific removal likely underlies the two-step separation of homologs and sisters. Unexpectedly, COH-3/4 performs cohesion-independent functions in synaptonemal complex assembly. This new model for cohesin function diverges from that established in yeast but likely applies directly to plants and mammals, which utilize similar meiotic kleisins.

  6. Effects of Tris(1,3-dichloro-2-propyl) Phosphate (TDCPP) in Tetrahymena Thermophila: Targeting the Ribosome

    Science.gov (United States)

    Li, Jing; Giesy, John P.; Yu, Liqin; Li, Guangyu; Liu, Chunsheng

    2015-05-01

    Tris(1,3-dichloro-2-propyl) phosphate (TDCPP) has been frequently detected in the environment, and exposure to TDCPP appears widespread. It has been implicated to cause toxicity in vertebrates, but its potential to affect lower-trophic-level species remains unknown. In the present study, the ciliated protozoan, Tetrahymena thermophila, was used as a model to evaluate toxic effects of TDCPP and explore molecular mechanisms by integrating phenotypic observation, RNA-Seq and transmission electron microscopy (TEM) Imaging technologies. Exposure to 0.01, 0.1 or 1 μM TDCPP for 5 days significantly decreased the relative biomass by reducing number of cells, size of cells and quantity of cilia in a dose-dependent manner. RNA-Seq analysis demonstrated that expression of twenty-one ribosome protein genes was down-regulated and these genes were enriched in “ribosome” term in KEGG pathway analysis. Furthermore, down-regulation of genes expressing ribosome proteins was accompanied by decreased ribosome quantity in rough endoplasmic reticulum and cytoplasm and enlarged ribosome size. Therefore, taken together, the data from the present study suggest that exposure to TDCPP affects growth and reproduction of Tetrahymena thermophila by targeting the ribosome. This information might provide insights into critical mechanisms of toxic action in other species and lead to useful bioindicators of exposure to TDCPP.

  7. Association of poly-purine/poly-pyrimidine sequences with meiotic recombination hot spots

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    Pitt Joel PW

    2006-07-01

    Full Text Available Abstract Background Meiotic recombination events have been found to concentrate in 1–2.5 kilo base regions, but these recombination hot spots do not share a consensus sequence and why they occur at specific sites is not fully understood. Some previous evidence suggests that poly-purine/poly-pyrimidine (poly-pu/py tracts (PPTs, a class of sequence with distinctive biochemical properties, could be involved in recombination, but no general association of PPTs with meiotic recombination hot spots has previously been reported. Results We used computational methods to investigate in detail the relationship between PPTs and hot spots. We show statistical associations of PPT frequency with hot spots of meiotic recombination initiating lesions, double-strand breaks, in the genome of the yeast S. cerevisiae and with experimentally well characterized human meiotic recombination hot spots. Supporting a possible role of poly-pu/py-rich sequences in hot spot recombination, we also found that all three single nucleotide polymorphisms previously shown to be associated with human hot spot activity changes occur within sequence contexts of 14 bp or longer that are 85% or more poly-pu/py and at least 70% G/C. These polymorphisms are all close to the hot spot mid points. Comparing the sequences of experimentally characterized human hot spots with the orthologous regions of the chimpanzee genome previously shown not to contain hot spots, we found that in all five cases in which comparisons for the hot spot central regions are possible with publicly available sequence data, there are differences near the human hot spot mid points within sequences 14 bp or longer consisting of more than 80% poly-pu/py and at least 50% G/C. Conclusion Our results, along with previous evidence for the unique biochemical properties and recombination-stimulating potential of poly-pu/py-rich sequences, suggest that the possible functional involvement of this type of sequence in meiotic

  8. Rejuvenation of meiotic cohesion in oocytes during prophase I is required for chiasma maintenance and accurate chromosome segregation.

    Science.gov (United States)

    Weng, Katherine A; Jeffreys, Charlotte A; Bickel, Sharon E

    2014-09-01

    Chromosome segregation errors in human oocytes are the leading cause of birth defects, and the risk of aneuploid pregnancy increases dramatically as women age. Accurate segregation demands that sister chromatid cohesion remain intact for decades in human oocytes, and gradual loss of the original cohesive linkages established in fetal oocytes is proposed to be a major cause of age-dependent segregation errors. Here we demonstrate that maintenance of meiotic cohesion in Drosophila oocytes during prophase I requires an active rejuvenation program, and provide mechanistic insight into the molecular events that underlie rejuvenation. Gal4/UAS inducible knockdown of the cohesion establishment factor Eco after meiotic S phase, but before oocyte maturation, causes premature loss of meiotic cohesion, resulting in destabilization of chiasmata and subsequent missegregation of recombinant homologs. Reduction of individual cohesin subunits or the cohesin loader Nipped B during prophase I leads to similar defects. These data indicate that loading of newly synthesized replacement cohesin rings by Nipped B and establishment of new cohesive linkages by the acetyltransferase Eco must occur during prophase I to maintain cohesion in oocytes. Moreover, we show that rejuvenation of meiotic cohesion does not depend on the programmed induction of meiotic double strand breaks that occurs during early prophase I, and is therefore mechanistically distinct from the DNA damage cohesion re-establishment pathway identified in G2 vegetative yeast cells. Our work provides the first evidence that new cohesive linkages are established in Drosophila oocytes after meiotic S phase, and that these are required for accurate chromosome segregation. If such a pathway also operates in human oocytes, meiotic cohesion defects may become pronounced in a woman's thirties, not because the original cohesive linkages finally give out, but because the rejuvenation program can no longer supply new cohesive linkages

  9. Meiotic aberrations during 2n pollen formation in Begonia.

    Science.gov (United States)

    Dewitte, A; Eeckhaut, T; Van Huylenbroeck, J; Van Bockstaele, E

    2010-02-01

    Unreduced gametes are the driving force for the polyploidization of plants in nature, and are also an important tool for ploidy breeding. The final heterozygosity of a 2n pollen grain depends on the cytological mechanism behind 2n pollen formation. In this study, chromosome pairing and chromosome segregation during the microsporogenesis of seven Begonia genotypes were analysed using fluorescent chromosome staining on (squashed) pollen mother cells. Among the seven genotypes, five genotypes produce 2n pollen (B. 'Bubbles', B. 'Florence Rita', B. 'Orococo', B. 'Tamo' and B276) and two genotypes produce only normal n pollen (B. fischeri and B243). All 2n pollen producers showed a mechanism equivalent to first division restitution (FDR), in which chromosomes did not segregate during meiosis I but only during meiosis II. This FDR was the result of (a) an irregular chromosome pairing in B. 'Tamo', (b) stickiness of chromosomes associated with numerous chromosome bridges in B. 'Florence Rita' and B276, and (c) a combination of irregular chromosome pairing and stickiness of chromosomes in B. 'Bubbles'. The exact mechanism of the nuclear restitution in B. 'Orococo' could not be determined. Other mechanisms, such as early asymmetric cytokinesis, omission of meiosis II, parallel or tripolar spindle formation, were rather uncommon. Unpaired chromosomes (univalents) were observed in all genotypes, but they had moved to one of the poles by the end of anaphase I or II. Only B. 'Tamo' formed a high number of micronuclei. Consequently, this genotype formed a large number of malformed pollen. Obviously, chromosome behaviour during meiosis in Begonia is very dynamic, which may have important consequences for chromosome evolution and biodiversity within the genus.

  10. Caenorhabditis elegans oocyte meiotic spindle pole assembly requires microtubule severing and the calponin homology domain protein ASPM-1.

    Science.gov (United States)

    Connolly, Amy A; Osterberg, Valerie; Christensen, Sara; Price, Meredith; Lu, Chenggang; Chicas-Cruz, Kathy; Lockery, Shawn; Mains, Paul E; Bowerman, Bruce

    2014-04-01

    In many animals, including vertebrates, oocyte meiotic spindles are bipolar but assemble in the absence of centrosomes. Although meiotic spindle positioning in oocytes has been investigated extensively, much less is known about their assembly. In Caenorhabditis elegans, three genes previously shown to contribute to oocyte meiotic spindle assembly are the calponin homology domain protein encoded by aspm-1, the katanin family member mei-1, and the kinesin-12 family member klp-18. We isolated temperature-sensitive alleles of all three and investigated their requirements using live-cell imaging to reveal previously undocumented requirements for aspm-1 and mei-1. Our results indicate that bipolar but abnormal oocyte meiotic spindles assemble in aspm-1(-) embryos, whereas klp-18(-) and mei-1(-) mutants assemble monopolar and apolar spindles, respectively. Furthermore, two MEI-1 functions--ASPM-1 recruitment to the spindle and microtubule severing--both contribute to monopolar spindle assembly in klp-18(-) mutants. We conclude that microtubule severing and ASPM-1 both promote meiotic spindle pole assembly in C. elegans oocytes, whereas the kinesin 12 family member KLP-18 promotes spindle bipolarity.

  11. The CAF-1 and Hir Histone Chaperones Associate with Sites of Meiotic Double-Strand Breaks in Budding Yeast.

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    Elsa Brachet

    Full Text Available In the meiotic prophase, programmed DNA double-strand breaks (DSB are introduced along chromosomes to promote homolog pairing and recombination. Although meiotic DSBs usually occur in nucleosome-depleted, accessible regions of chromatin, their repair by homologous recombination takes place in a nucleosomal environment. Nucleosomes may represent an obstacle for the recombination machinery and their timely eviction and reincorporation into chromatin may influence the outcome of recombination, for instance by stabilizing recombination intermediates. Here we show in budding yeast that nucleosomes flanking a meiotic DSB are transiently lost during recombination, and that specific histone H3 chaperones, CAF-1 and Hir, are mobilized at meiotic DSBs. However, the absence of these chaperones has no effect on meiotic recombination, suggesting that timely histone reincorporation following their eviction has no influence on the recombination outcome, or that redundant pathways are activated. This study is the first example of the involvement of histone H3 chaperones at naturally occurring, developmentally programmed DNA double-strand breaks.

  12. The CAF-1 and Hir Histone Chaperones Associate with Sites of Meiotic Double-Strand Breaks in Budding Yeast.

    Science.gov (United States)

    Brachet, Elsa; Béneut, Claire; Serrentino, Maria-Elisabetta; Borde, Valérie

    2015-01-01

    In the meiotic prophase, programmed DNA double-strand breaks (DSB) are introduced along chromosomes to promote homolog pairing and recombination. Although meiotic DSBs usually occur in nucleosome-depleted, accessible regions of chromatin, their repair by homologous recombination takes place in a nucleosomal environment. Nucleosomes may represent an obstacle for the recombination machinery and their timely eviction and reincorporation into chromatin may influence the outcome of recombination, for instance by stabilizing recombination intermediates. Here we show in budding yeast that nucleosomes flanking a meiotic DSB are transiently lost during recombination, and that specific histone H3 chaperones, CAF-1 and Hir, are mobilized at meiotic DSBs. However, the absence of these chaperones has no effect on meiotic recombination, suggesting that timely histone reincorporation following their eviction has no influence on the recombination outcome, or that redundant pathways are activated. This study is the first example of the involvement of histone H3 chaperones at naturally occurring, developmentally programmed DNA double-strand breaks.

  13. Caenorhabditis elegans oocyte meiotic spindle pole assembly requires microtubule severing and the calponin homology domain protein ASPM-1

    Science.gov (United States)

    Connolly, Amy A.; Osterberg, Valerie; Christensen, Sara; Price, Meredith; Lu, Chenggang; Chicas-Cruz, Kathy; Lockery, Shawn; Mains, Paul E.; Bowerman, Bruce

    2014-01-01

    In many animals, including vertebrates, oocyte meiotic spindles are bipolar but assemble in the absence of centrosomes. Although meiotic spindle positioning in oocytes has been investigated extensively, much less is known about their assembly. In Caenorhabditis elegans, three genes previously shown to contribute to oocyte meiotic spindle assembly are the calponin homology domain protein encoded by aspm-1, the katanin family member mei-1, and the kinesin-12 family member klp-18. We isolated temperature-sensitive alleles of all three and investigated their requirements using live-cell imaging to reveal previously undocumented requirements for aspm-1 and mei-1. Our results indicate that bipolar but abnormal oocyte meiotic spindles assemble in aspm-1(-) embryos, whereas klp-18(-) and mei-1(-) mutants assemble monopolar and apolar spindles, respectively. Furthermore, two MEI-1 functions—ASPM-1 recruitment to the spindle and microtubule severing—both contribute to monopolar spindle assembly in klp-18(-) mutants. We conclude that microtubule severing and ASPM-1 both promote meiotic spindle pole assembly in C. elegans oocytes, whereas the kinesin 12 family member KLP-18 promotes spindle bipolarity. PMID:24554763

  14. Meiotic versus mitotic recombination: two different routes for double-strand break repair: the different functions of meiotic versus mitotic DSB repair are reflected in different pathway usage and different outcomes.

    Science.gov (United States)

    Andersen, Sabrina L; Sekelsky, Jeff

    2010-12-01

    Studies in the yeast Saccharomyces cerevisiae have validated the major features of the double-strand break repair (DSBR) model as an accurate representation of the pathway through which meiotic crossovers (COs) are produced. This success has led to this model being invoked to explain double-strand break (DSB) repair in other contexts. However, most non-crossover (NCO) recombinants generated during S. cerevisiae meiosis do not arise via a DSBR pathway. Furthermore, it is becoming increasingly clear that DSBR is a minor pathway for recombinational repair of DSBs that occur in mitotically-proliferating cells and that the synthesis-dependent strand annealing (SDSA) model appears to describe mitotic DSB repair more accurately. Fundamental dissimilarities between meiotic and mitotic recombination are not unexpected, since meiotic recombination serves a very different purpose (accurate chromosome segregation, which requires COs) than mitotic recombination (repair of DNA damage, which typically generates NCOs). Copyright © 2010 WILEY Periodicals, Inc.

  15. Nuclear Medicine

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    ... Parents/Teachers Resource Links for Students Glossary Nuclear Medicine What is nuclear medicine? What are radioactive tracers? ... funded researchers advancing nuclear medicine? What is nuclear medicine? Nuclear medicine is a medical specialty that uses ...

  16. Implications of mitotic and meiotic irregularities in common beans (Phaseolus vulgaris L.).

    Science.gov (United States)

    Lima, D C; Braz, G T; Dos Reis, G B; Techio, V H; Davide, L C; de F B Abreu, A

    2016-05-23

    The common bean has great social and economic importance in Brazil and is the subject of a high number of publications, especially in the fields of genetics and breeding. Breeding programs aim to increase grain yield; however, mitosis and meiosis represent under explored research areas that have a direct impact on grain yield. Therefore, the study of cell division could be another tool available to bean geneticists and breeders. The aim of this study was to investigate irregularities occurring during the cell cycle and meiosis in common bean. The common bean cultivar used was BRSMG Talismã, which owing to its high yield and grain quality is recommended for cultivation in Brazil. We classified the interphase nuclei, estimated the mitotic and meiotic index, grain pollen viability, and percentage of abnormalities in both processes. The mitotic index was 4.1%, the interphase nucleus was non-reticulated, and 19% of dividing somatic cells showed abnormal behavior. Meiosis also presented irregularities resulting in a meiotic index of 44.6%. Viability of pollen grains was 94.3%. These results indicate that the common bean cultivar BRSMG Talismã possesses repair mechanisms that compensate for changes by producing a large number of pollen grains. Another important strategy adopted by bean plants to ensure stability is the elimination of abnormal cells by apoptosis. As the common bean cultivar BRSMG Talismã is recommended for cultivation because of its good agronomic performance, it can be concluded that mitotic and meiotic irregularities have no negative influence on its grain quality and yield.

  17. Escape of X-linked miRNA genes from meiotic sex chromosome inactivation.

    Science.gov (United States)

    Sosa, Enrique; Flores, Luis; Yan, Wei; McCarrey, John R

    2015-11-01

    Past studies have indicated that transcription of all X-linked genes is repressed by meiotic sex chromosome inactivation (MSCI) during the meiotic phase of spermatogenesis in mammals. However, more recent studies have shown an increase in steady-state levels of certain X-linked miRNAs in pachytene spermatocytes, suggesting that either synthesis of these miRNAs increases or that degradation of these miRNAs decreases dramatically in these cells. To distinguish between these possibilities, we performed RNA-FISH to detect nascent transcripts from multiple miRNA genes in various spermatogenic cell types. Our results show definitively that Type I X-linked miRNA genes are subject to MSCI, as are all or most X-linked mRNA genes, whereas Type II and III X-linked miRNA genes escape MSCI by continuing ongoing, active transcription in primary spermatocytes. We corroborated these results by co-localization of RNA-FISH signals with both a corresponding DNA-FISH signal and an immunofluorescence signal for RNA polymerase II. We also found that X-linked miRNA genes that escape MSCI locate non-randomly to the periphery of the XY body, whereas genes that are subject to MSCI remain located within the XY body in pachytene spermatocytes, suggesting that the mechanism of escape of X-linked miRNA genes from MSCI involves their relocation to a position outside of the repressive chromatin domain associated with the XY body. The fact that Type II and III X-linked miRNA genes escape MSCI suggests an immediacy of function of the encoded miRNAs specifically required during the meiotic stages of spermatogenesis. © 2015. Published by The Company of Biologists Ltd.

  18. Characterization of Schizosaccharomyces pombe copper transporter proteins in meiotic and sporulating cells.

    Science.gov (United States)

    Plante, Samuel; Ioannoni, Raphaël; Beaudoin, Jude; Labbé, Simon

    2014-04-04

    Meiosis requires copper to undertake its program in which haploid gametes are produced from diploid precursor cells. In Schizosaccharomyces pombe, copper is transported by three members of the copper transporter (Ctr) family, namely Ctr4, Ctr5, and Ctr6. Although central for sexual differentiation, very little is known about the expression profile, cellular localization, and physiological contribution of the Ctr proteins during meiosis. Analysis of gene expression of ctr4(+) and ctr5(+) revealed that they are primarily expressed in early meiosis under low copper conditions. In the case of ctr6(+), its expression is broader, being detected throughout the entire meiotic process with an increase during middle- and late-phase meiosis. Whereas the expression of ctr4(+) and ctr5(+) is exclusively dependent on the presence of Cuf1, ctr6(+) gene expression relies on two distinct regulators, Cuf1 and Mei4. Ctr4 and Ctr5 proteins co-localize at the plasma membrane shortly after meiotic induction, whereas Ctr6 is located on the membrane of vacuoles. After meiotic divisions, Ctr4 and Ctr5 disappear from the cell surface, whereas Ctr6 undergoes an intracellular re-location to co-localize with the forespore membrane. Under copper-limiting conditions, disruption of ctr4(+) and ctr6(+) results in altered SOD1 activity, whereas these mutant cells exhibit substantially decreased levels of CAO activity mostly in early- and middle-phase meiosis. Collectively, these results emphasize the notion that Ctr proteins exhibit differential expression, localization, and contribution in delivering copper to SOD1 and Cao1 proteins during meiosis.

  19. The bifunctional dihydrofolate reductase thymidylate synthase of Tetrahymena thermophila provides a tool for molecular and biotechnology applications

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    Tiedtke Arno

    2006-03-01

    Full Text Available Abstract Background Dihydrofolate reductase (DHFR and thymidylate synthase (TS are crucial enzymes in DNA synthesis. In alveolata both enzymes are expressed as one bifunctional enzyme. Results Loss of this essential enzyme activities after successful allelic assortment of knock out alleles yields an auxotrophic marker in ciliates. Here the cloning, characterisation and functional analysis of Tetrahymena thermophila's DHFR-TS is presented. A first aspect of the presented work relates to destruction of DHFR-TS enzyme function in an alveolate thereby causing an auxotrophy for thymidine. A second aspect is to knock in an expression cassette encoding for a foreign gene with subsequent expression of the target protein. Conclusion This system avoids the use of antibiotics or other drugs and therefore is of high interest for biotechnological applications.

  20. Germination, growth, and sporulation of Bacillus thuringiensis subsp. israelensis in excreted food vacuoles of the protozoan Tetrahymena pyriformis.

    Science.gov (United States)

    Manasherob, R; Ben-Dov, E; Zaritsky, A; Barak, Z

    1998-05-01

    Spores of Bacillus thuringiensis subsp. israelensis and their toxic crystals are bioencapsulated in the protozoan Tetrahymena pyriformis, in which the toxin remains stable. Each T. pyriformis cell concentrates the spores and crystals in its food vacuoles, thus delivering them to mosquito larvae, which rapidly die. Vacuoles containing undigested material are later excreted from the cells. The fate of spores and toxin inside the food vacuoles was determined at various times after excretion by phase-contrast and electron microscopy as well as by viable-cell counting. Excreted food vacuoles gradually aggregated, and vegetative growth of B. thuringiensis subsp. israelensis was observed after 7 h as filaments that stemmed from the aggregates. The outgrown cells sporulated between 27 and 42 h. The spore multiplication values in this system are low compared to those obtained in carcasses of B. thuringiensis subsp. israelensis-killed larvae and pupae, but this bioencapsulation represents a new possible mode of B. thuringiensis subsp. israelensis recycling in nontarget organisms.

  1. The oral apparatus of Tetrahymena pyriformis, strain WH-6. II. Cytochalasin B inhibition of oral apparatus morphogenesis.

    Science.gov (United States)

    Gavin, R H

    1976-07-01

    The effects of cytochalasin B on oral apparatus morphogenesis and cell division were studied in synchronized Tetrahymena pyriformis, strain WH-6 syngen 1. Cytochalasin B brought about the rapid arrest of oral apparatus primordium development when added prior to the completion of oral apparatus membranelle differentiation. Cells arrested in development did not divide. When cytochalasin B was added after this transition point, oral apparatus morphogenesis and cell division were completed. The effects of cytochalasin B could be reversed by washing it from the medium. Even though cytochalasin B (at 400 mug/ml) reduced protein synthesis by 30%, the data are consistent with the interpretation that cytochalasin B prevents an assembly process during the membranelle differentiation phase of oral apparatus development.

  2. Mitotic and meiotic chromosomes of a southern Brazilian population of Boophilus microplus (Acari, Ixodidae

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    Rosane Nunes Garcia

    Full Text Available Using conventional staining with acetic orcein and C-banding techniques it was investigated constitutive heterochromatin chromosomal polymorphisms and the mitotic and the meiotic behavior of male and female chromosomes of Boophilus microplus (Canestrini, 1887. Some differences were detected in the population of southern Brazil as compared to the data of other authors for populations in other latitudes. The differences being mainly concerned with the distribution of constitutive centromeric heterochromatin and variation in the length of heterochromatic blocks in the pericentromeric regions of some chromosome pairs.

  3. Physical Lengths of Meiotic and Mitotic Gene Conversion Tracts in Saccharomyces Cerevisiae

    OpenAIRE

    Judd, S. R.; Petes, T D

    1988-01-01

    Physical lengths of gene conversion tracts for meiotic and mitotic conversions were examined, using the same diploid yeast strain in all experiments. This strain is heterozygous for a mutation in the URA3 gene as well as closely linked restriction site markers. In cells that had a gene conversion event at the URA3 locus, it was determined by Southern analysis which of the flanking heterozygous restriction sites had co-converted. It was found that mitotic conversion tracts were longer on the a...

  4. Direct and indirect control of the initiation of meiotic recombination by DNA damage checkpoint mechanisms in budding yeast.

    Directory of Open Access Journals (Sweden)

    Bilge Argunhan

    Full Text Available Meiotic recombination plays an essential role in the proper segregation of chromosomes at meiosis I in many sexually reproducing organisms. Meiotic recombination is initiated by the scheduled formation of genome-wide DNA double-strand breaks (DSBs. The timing of DSB formation is strictly controlled because unscheduled DSB formation is detrimental to genome integrity. Here, we investigated the role of DNA damage checkpoint mechanisms in the control of meiotic DSB formation using budding yeast. By using recombination defective mutants in which meiotic DSBs are not repaired, the effect of DNA damage checkpoint mutations on DSB formation was evaluated. The Tel1 (ATM pathway mainly responds to unresected DSB ends, thus the sae2 mutant background in which DSB ends remain intact was employed. On the other hand, the Mec1 (ATR pathway is primarily used when DSB ends are resected, thus the rad51 dmc1 double mutant background was employed in which highly resected DSBs accumulate. In order to separate the effect caused by unscheduled cell cycle progression, which is often associated with DNA damage checkpoint defects, we also employed the ndt80 mutation which permanently arrests the meiotic cell cycle at prophase I. In the absence of Tel1, DSB formation was reduced in larger chromosomes (IV, VII, II and XI whereas no significant reduction was found in smaller chromosomes (III and VI. On the other hand, the absence of Rad17 (a critical component of the ATR pathway lead to an increase in DSB formation (chromosomes VII and II were tested. We propose that, within prophase I, the Tel1 pathway facilitates DSB formation, especially in bigger chromosomes, while the Mec1 pathway negatively regulates DSB formation. We also identified prophase I exit, which is under the control of the DNA damage checkpoint machinery, to be a critical event associated with down-regulating meiotic DSB formation.

  5. A primer on meiotic resumption in starfish oocytes: the proposed signaling pathway triggered by maturation-inducing hormone.

    Science.gov (United States)

    Kishimoto, Takeo

    2011-01-01

    This short review updates the maturation-inducing hormonal signaling in starfish oocytes. In this system, the activation of cyclin B-Cdc2 kinase (Cdk1) that leads to meiotic resumption does not require new protein synthesis. The key intracellular mediator after hormonal stimulation by 1-methyladenine is the protein kinase Akt/PKB, which in turn directly downregulates Myt1 and upregulates Cdc25 toward the activation of cyclin B-Cdc2. Mitotic kinases including Aurora, Plk1 and Greatwall are activated downstream of cyclin B-Cdc2. The starfish oocyte thus provides a simple model system for the study of meiotic resumption. Copyright © 2011 Wiley Periodicals, Inc.

  6. Preferential accumulation of sex and Bs chromosomes in biarmed karyotypes by meiotic drive and rates of chromosomal changes in fishes.

    Science.gov (United States)

    Molina, Wagner F; Martinez, Pablo A; Bertollo, Luiz A C; Bidau, Claudio J

    2014-12-01

    Mechanisms of accumulation based on typical centromeric drive or of chromosomes carrying pericentric inversions are adjusted to the general karyotype differentiation in the principal Actinopterygii orders. Here, we show that meiotic drive in fish is also supported by preferential establishment of sex chromosome systems and B chromosomes in orders with predominantly bi-brachial chromosomes. The mosaic of trends acting at an infra-familiar level in fish could be explained as the interaction of the directional process of meiotic drive as background, modulated on a smaller scale by adaptive factors or specific karyotypic properties of each group, as proposed for the orthoselection model.

  7. Confocal Analysis of Nuclear Lamina Behavior during Male Meiosis and Spermatogenesis in Drosophila melanogaster.

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    Fabiana Fabbretti

    Full Text Available Lamin family proteins are structural components of a filamentous framework, the nuclear lamina (NL, underlying the inner membrane of nuclear envelope. The NL not only plays a role in nucleus mechanical support and nuclear shaping, but is also involved in many cellular processes including DNA replication, gene expression and chromatin positioning. Spermatogenesis is a very complex differentiation process in which each stage is characterized by nuclear architecture dramatic changes, from the early mitotic stage to the sperm differentiation final stage. Nevertheless, very few data are present in the literature on the NL behavior during this process. Here we show the first and complete description of NL behavior during meiosis and spermatogenesis in Drosophila melanogaster. By confocal imaging, we characterized the NL modifications from mitotic stages, through meiotic divisions to sperm differentiation with an anti-laminDm0 antibody against the major component of the Drosophila NL. We observed that continuous changes in the NL structure occurred in parallel with chromatin reorganization throughout the whole process and that meiotic divisions occurred in a closed context. Finally, we analyzed NL in solofuso meiotic mutant, where chromatin segregation is severely affected, and found the strict correlation between the presence of chromatin and that of NL.

  8. Senataxin plays an essential role with DNA damage response proteins in meiotic recombination and gene silencing.

    Directory of Open Access Journals (Sweden)

    Olivier J Becherel

    2013-04-01

    Full Text Available Senataxin, mutated in the human genetic disorder ataxia with oculomotor apraxia type 2 (AOA2, plays an important role in maintaining genome integrity by coordination of transcription, DNA replication, and the DNA damage response. We demonstrate that senataxin is essential for spermatogenesis and that it functions at two stages in meiosis during crossing-over in homologous recombination and in meiotic sex chromosome inactivation (MSCI. Disruption of the Setx gene caused persistence of DNA double-strand breaks, a defect in disassembly of Rad51 filaments, accumulation of DNA:RNA hybrids (R-loops, and ultimately a failure of crossing-over. Senataxin localised to the XY body in a Brca1-dependent manner, and in its absence there was incomplete localisation of DNA damage response proteins to the XY chromosomes and ATR was retained on the axial elements of these chromosomes, failing to diffuse out into chromatin. Furthermore persistence of RNA polymerase II activity, altered ubH2A distribution, and abnormal XY-linked gene expression in Setx⁻/⁻ revealed an essential role for senataxin in MSCI. These data support key roles for senataxin in coordinating meiotic crossing-over with transcription and in gene silencing to protect the integrity of the genome.

  9. Repetitive DNA and meiotic behavior of sex chromosomes in Gymnotus pantanal (Gymnotiformes, Gymnotidae).

    Science.gov (United States)

    da Silva, M; Matoso, D A; Vicari, M R; de Almeida, M C; Margarido, V P; Artoni, R F

    2011-01-01

    Neotropical fishes have a low rate of chromosome differentiation between sexes. The present study characterizes the first meiotic analysis of sex chromosomes in the order Gymnotiformes. Gymnotus pantanal - females had 40 chromosomes (14m/sm, 26st/a) and males had 39 chromosomes (15m/sm, 24st/a), with a fundamental number of 54 - showed a multiple sexual determination chromosome system of the type X(1)X(1)X(2)X(2)/X(1)X(2)Y. The heterochromatin is restricted to centromeres of all chromosomes of the karyotype. The meiotic behavior of sex chromosomes involved in this system in males is from a trivalent totally pared in the pachytene stage, with a high degree of similarity. The cells of metaphase II exhibit 19 and 20 chromosomes, normal disjunction of sex chromosomes and the formation of balanced gametes with 18 + Y and 18 + X(1)X(2) chromosomes, respectively. The small amount of heterochromatin and repetitive DNA involved in this system and the high degree of chromosome similarity indicated a recent origin of the X(1)X(1)X(2)X(2)/X(1)X(2)Y system in G. pantanal and suggests the existence of a simple ancestral system with morphologically undifferentiated chromosomes. Copyright © 2011 S. Karger AG, Basel.

  10. DAF-2 and ERK couple nutrient availability to meiotic progression during Caenorhabditis elegans oogenesis.

    Science.gov (United States)

    Lopez, Andrew L; Chen, Jessica; Joo, Hyoe-Jin; Drake, Melanie; Shidate, Miri; Kseib, Cedric; Arur, Swathi

    2013-10-28

    Coupling the production of mature gametes and fertilized zygotes to favorable nutritional conditions improves reproductive success. In invertebrates, the proliferation of female germline stem cells is regulated by nutritional status. However, in mammals, the number of female germline stem cells is set early in development, with oocytes progressing through meiosis later in life. Mechanisms that couple later steps of oogenesis to environmental conditions remain largely undefined. We show that, in the presence of food, the DAF-2 insulin-like receptor signals through the RAS-ERK pathway to drive meiotic prophase I progression and oogenesis; in the absence of food, the resultant inactivation of insulin-like signaling leads to downregulation of the RAS-ERK pathway, and oogenesis is stalled. Thus, the insulin-like signaling pathway couples nutrient sensing to meiotic I progression and oocyte production in C. elegans, ensuring that oocytes are only produced under conditions favorable for the survival of the resulting zygotes. Copyright © 2013 Elsevier Inc. All rights reserved.

  11. Signaling-Mediated Regulation of Meiotic Prophase I and Transition During Oogenesis.

    Science.gov (United States)

    Arur, Swathi

    2017-01-01

    Generation of healthy oocytes requires coordinated regulation of multiple cellular events and signaling pathways. Oocytes undergo a unique developmental growth and differentiation pattern interspersed with long periods of arrest. Oocytes from almost all species arrest in prophase I of oogenesis that allows for long period of growth and differentiation essential for normal oocyte development. Depending on species, oocytes that transit from prophase I to meiosis I also arrest at meiosis I for fairly long periods of time and then undergo a second arrest at meiosis II that is completed upon fertilization. While there are species-specific differences in C. elegans, D. melanogaster, and mammalian oocytes in stages of prophase I, meiosis I, or meiosis II arrest, in all cases cell signaling pathways coordinate the developmental events controlling oocyte growth and differentiation to regulate these crucial phases of transition. In particular, the ERK MAP kinase signaling pathway, cyclic AMP second messengers, and the cell cycle regulators CDK1/cyclin B are key signaling pathways that seem evolutionarily conserved in their control of oocyte growth and meiotic maturation across species. Here, I identify the common themes and differences in the regulation of key meiotic events during oocyte growth and maturation.

  12. Brain abnormalities, defective meiotic chromosome synapsis and female subfertility in HSF2 null mice

    Science.gov (United States)

    Kallio, Marko; Chang, Yunhua; Manuel, Martine; Alastalo, Tero-Pekka; Rallu, Murielle; Gitton, Yorick; Pirkkala, Lila; Loones, Marie-Thérèse; Paslaru, Liliana; Larney, Severine; Hiard, Sophie; Morange, Michel; Sistonen, Lea; Mezger, Valérie

    2002-01-01

    Heat shock factor 2, one of the four vertebrate HSFs, transcriptional regulators of heat shock gene expression, is active during embryogenesis and spermatogenesis, with unknown functions and targets. By disrupting the Hsf2 gene, we show that, although the lack of HSF2 is not embryonic lethal, Hsf2–/– mice suffer from brain abnormalities, and meiotic and gameto genesis defects in both genders. The disturbances in brain are characterized by the enlargement of lateral and third ventricles and the reduction of hippocampus and striatum, in correlation with HSF2 expression in proliferative cells of the neuroepithelium and in some ependymal cells in adults. Many developing spermatocytes are eliminated via apoptosis in a stage-specific manner in Hsf2–/– males, and pachytene spermatocytes also display structural defects in the synaptonemal complexes between homologous chromosomes. Hsf2–/– females suffer from multiple fertility defects: the production of abnormal eggs, the reduction in ovarian follicle number and the presence of hemorrhagic cystic follicles are consistent with meiotic defects. Hsf2–/– females also display hormone response defects, that can be rescued by superovulation treatment, and exhibit abnormal rates of luteinizing hormone receptor mRNAs. PMID:12032072

  13. Signaling-Mediated Regulation of Meiotic Prophase I and Transition During Oogenesis

    Science.gov (United States)

    2017-01-01

    Generation of healthy oocytes requires coordinated regulation of multiple cellular events and signaling pathways. Oocytes undergo a unique developmental growth and differentiation pattern interspersed with long periods of arrest. Oocytes from almost all species arrest in prophase I of oogenesis that allows for long period of growth and differentiation essential for normal oocyte development. Depending on species, oocytes that transit from prophase I to meiosis I also arrest at meiosis I for fairly long periods of time and then undergo a second arrest at meiosis II that is completed upon fertilization. While there are species-specific differences in C. elegans, D. melanogaster, and mammalian oocytes in stages of prophase I, meiosis I, or meiosis II arrest, in all cases cell signaling pathways coordinate the developmental events controlling oocyte growth and differentiation to regulate these crucial phases of transition. In particular, the ERK MAP kinase signaling pathway, cyclic AMP second messengers, and the cell cycle regulators CDK1/cyclin B are key signaling pathways that seem evolutionarily conserved in their control of oocyte growth and meiotic maturation across species. Here, I identify the common themes and differences in the regulation of key meiotic events during oocyte growth and maturation. PMID:28247047

  14. The impact of Zearalenone on the meiotic progression and primordial follicle assembly during early oogenesis.

    Science.gov (United States)

    Liu, Ke-Han; Sun, Xiao-Feng; Feng, Yan-Zhong; Cheng, Shun-Feng; Li, Bo; Li, Ya-Peng; Shen, Wei; Li, Lan

    2017-08-15

    Zearalenone (ZEA) is a mycotoxin produced by fusarium graminearum. It can cause abnormal reproductive function by acting as an environmental estrogen. Research has traditionally focused on acute and chronic injury on mammalian reproductive capacity after ZEA treatment. Little research has been done studying the effects of ZEA exposure on early oogenesis. In this study, we investigate the effects of ZEA exposure on meiotic entry, DNA double-strand breaks (DSBs), and primordial follicle assembly during murine early oogenesis. The results show that ZEA exposure significantly decreased the percentage of diplotene stage germ cells, and made more germ cells remain at zygotene or pachytene stages. Moreover, the mRNA expression level of meiosis-related genes was significantly reduced after ZEA treatment. ZEA exposure significantly increased DNA-DSBs at the diplotene stage. Meanwhile, DNA damage repair genes such as RAD51 and BRCA1 were activated. Furthermore, maternal exposure to ZEA significantly decreased the number of primordial follicles in newborn mouse ovaries. In conclusion, ZEA exposure impairs mouse female germ cell meiotic progression, DNA-DSBs, and primordial follicle assembly. Copyright © 2017 Elsevier Inc. All rights reserved.

  15. Immunocytological analysis of meiotic recombination in two anole lizards (Squamata, Dactyloidae).

    Science.gov (United States)

    Lisachov, Artem P; Trifonov, Vladimir A; Giovannotti, Massimo; Ferguson-Smith, Malcolm A; Borodin, Pavel M

    2017-01-01

    Although the evolutionary importance of meiotic recombination is not disputed, the significance of interspecies differences in the recombination rates and recombination landscapes remains under-appreciated. Recombination rates and distribution of chiasmata have been examined cytologically in many mammalian species, whereas data on other vertebrates are scarce. Immunolocalization of the protein of the synaptonemal complex (SYCP3), centromere proteins and the mismatch-repair protein MLH1 was used, which is associated with the most common type of recombination nodules, to analyze the pattern of meiotic recombination in the male of two species of iguanian lizards, Anolis carolinensis Voigt, 1832 and Deiroptyx coelestinus (Cope, 1862). These species are separated by a relatively long evolutionary history although they retain the ancestral iguanian karyotype. In both species similar and extremely uneven distributions of MLH1 foci along the macrochromosome bivalents were detected: approximately 90% of crossovers were located at the distal 20% of the chromosome arm length. Almost total suppression of recombination in the intermediate and proximal regions of the chromosome arms contradicts the hypothesis that "homogenous recombination" is responsible for the low variation in GC content across the anole genome. It also leads to strong linkage disequilibrium between the genes located in these regions, which may benefit conservation of co-adaptive gene arrays responsible for the ecological adaptations of the anoles.

  16. Two X family DNA polymerases, lambda and mu, in meiotic tissues of the basidiomycete, Coprinus cinereus.

    Science.gov (United States)

    Sakamoto, Aiko; Iwabata, Kazuki; Koshiyama, Akiyo; Sugawara, Hiroko; Yanai, Takuro; Kanai, Yoshihiro; Takeuchi, Ryo; Daikuhara, Yoko; Takakusagi, Yoichi; Sakaguchi, Kengo

    2007-12-01

    The X family DNA polymerases lambda (CcPollambda) and mu (CcPolmu) were shown to be expressed during meiotic prophase in the basidiomycete, Coprinus cinereus. These two polymerases are the only members of the X family in the C. cinereus genome. The open reading frame of CcPollambda encoded a predicted product of 800 amino acid residues and that of CcPolmicro of 621 amino acid residues. Both CcPollambda and CcPolmicro required Mn(2+) ions for activity, and both were strongly inhibited by dideoxythymidine triphosphate. Unlike their mammalian counterparts, CcPollambda and CcPolmicro had no terminal deoxynucleotidyl transferase activity. Immunostaining analysis revealed that CcPollambda was present at meiotic prophase nuclei in zygotene and pachytene cells, which is the period when homologous chromosomes pair and recombine. CcPolmicro was present in a slightly wider range of cell stages, zygotene to diplotene. In analyses using D-loop recombination intermediate substrates, we found that both CcPollambda and CcPolmicro could promote primer extension of an invading strand in a D-loop structure. Moreover, both polymerases could fully extend the primer in the D-loop substrate, suggesting that D-loop extension is an activity intrinsic to CcPollambda and CcPolmicro. Based on these data, we discuss the possible roles of these polymerases in meiosis.

  17. A discrete class of intergenic DNA dictates meiotic DNA break hotspots in fission yeast.

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    Gareth A Cromie

    2007-08-01

    Full Text Available Meiotic recombination is initiated by DNA double-strand breaks (DSBs made by Spo11 (Rec12 in fission yeast, which becomes covalently linked to the DSB ends. Like recombination events, DSBs occur at hotspots in the genome, but the genetic factors responsible for most hotspots have remained elusive. Here we describe in fission yeast the genome-wide distribution of meiosis-specific Rec12-DNA linkages, which closely parallel DSBs measured by conventional Southern blot hybridization. Prominent DSB hotspots are located approximately 65 kb apart, separated by intervals with little or no detectable breakage. Most hotspots lie within exceptionally large intergenic regions. Thus, the chromosomal architecture responsible for hotspots in fission yeast is markedly different from that of budding yeast, in which DSB hotspots are much more closely spaced and, in many regions of the genome, occur at each promoter. Our analysis in fission yeast reveals a clearly identifiable chromosomal feature that can predict the majority of recombination hotspots across a whole genome and provides a basis for searching for the chromosomal features that dictate hotspots of meiotic recombination in other organisms, including humans.

  18. Xenopus laevis Kif18A is a highly processive kinesin required for meiotic spindle integrity

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    Martin M. Möckel

    2017-04-01

    Full Text Available The assembly and functionality of the mitotic spindle depends on the coordinated activities of microtubule-associated motor proteins of the dynein and kinesin superfamily. Our current understanding of the function of motor proteins is significantly shaped by studies using Xenopus laevis egg extract as its open structure allows complex experimental manipulations hardly feasible in other model systems. Yet, the Kinesin-8 orthologue of human Kif18A has not been described in Xenopus laevis so far. Here, we report the cloning and characterization of Xenopus laevis (Xl Kif18A. Xenopus Kif18A is expressed during oocyte maturation and its depletion from meiotic egg extract results in severe spindle defects. These defects can be rescued by wild-type Kif18A, but not Kif18A lacking motor activity or the C-terminus. Single-molecule microscopy assays revealed that Xl_Kif18A possesses high processivity, which depends on an additional C-terminal microtubule-binding site. Human tissue culture cells depleted of endogenous Kif18A display mitotic defects, which can be rescued by wild-type, but not tail-less Xl_Kif18A. Thus, Xl_Kif18A is the functional orthologue of human Kif18A whose activity is essential for the correct function of meiotic spindles in Xenopus oocytes.

  19. Histone H2AFX Links Meiotic Chromosome Asynapsis to Prophase I Oocyte Loss in Mammals.

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    Jeffrey M Cloutier

    2015-10-01

    Full Text Available Chromosome abnormalities are common in the human population, causing germ cell loss at meiotic prophase I and infertility. The mechanisms driving this loss are unknown, but persistent meiotic DNA damage and asynapsis may be triggers. Here we investigate the contribution of these lesions to oocyte elimination in mice with chromosome abnormalities, e.g. Turner syndrome (XO and translocations. We show that asynapsed chromosomes trigger oocyte elimination at diplonema, which is linked to the presence of phosphorylated H2AFX (γH2AFX. We find that DNA double-strand break (DSB foci disappear on asynapsed chromosomes during pachynema, excluding persistent DNA damage as a likely cause, and demonstrating the existence in mammalian oocytes of a repair pathway for asynapsis-associated DNA DSBs. Importantly, deletion or point mutation of H2afx restores oocyte numbers in XO females to wild type (XX levels. Unexpectedly, we find that asynapsed supernumerary chromosomes do not elicit prophase I loss, despite being enriched for γH2AFX and other checkpoint proteins. These results suggest that oocyte loss cannot be explained simply by asynapsis checkpoint models, but is related to the gene content of asynapsed chromosomes. A similar mechanistic basis for oocyte loss may operate in humans with chromosome abnormalities.

  20. CDK-1 inhibits meiotic spindle shortening and dynein-dependent spindle rotation in C. elegans

    Science.gov (United States)

    Ellefson, Marina L.

    2011-01-01

    In animals, the female meiotic spindle is positioned at the egg cortex in a perpendicular orientation to facilitate the disposal of half of the chromosomes into a polar body. In Caenorhabditis elegans, the metaphase spindle lies parallel to the cortex, dynein is dispersed on the spindle, and the dynein activators ASPM-1 and LIN-5 are concentrated at spindle poles. Anaphase-promoting complex (APC) activation results in dynein accumulation at spindle poles and dynein-dependent rotation of one spindle pole to the cortex, resulting in perpendicular orientation. To test whether the APC initiates spindle rotation through cyclin B–CDK-1 inactivation, separase activation, or degradation of an unknown dynein inhibitor, CDK-1 was inhibited with purvalanol A in metaphase-I–arrested, APC-depleted embryos. CDK-1 inhibition resulted in the accumulation of dynein at spindle poles and dynein-dependent spindle rotation without chromosome separation. These results suggest that CDK-1 blocks rotation by inhibiting dynein association with microtubules and with LIN-5–ASPM-1 at meiotic spindle poles and that the APC promotes spindle rotation by inhibiting CDK-1. PMID:21690306

  1. Distinct regulators for Plk1 activation in starfish meiotic and early embryonic cycles

    Science.gov (United States)

    Okano-Uchida, Takayuki; Okumura, Eiichi; Iwashita, Motoko; Yoshida, Hitoshi; Tachibana, Kazunori; Kishimoto, Takeo

    2003-01-01

    The Polo-like kinase, Plk, has multiple roles in regulating mitosis. In particular, Plk1 has been postulated to function as a trigger kinase that phosphorylates and activates Cdc25C prior to the activation of cyclin B–Cdc2 and thereby initiates its activation. However, the upstream regulation of Plk1 activation remains unclear. Here we have studied the interplay between Plk1 and Cdc2 through meiotic and early embryonic cycles in starfish. Distinct kinases, cyclin B–Cdc2, MAPK along with cyclin B– and/or cyclin A–Cdc2 and cyclin A–Cdc2, were unique upstream regulators for Plk1 activation at meiosis I, meiosis II and embryonic M-phase, respectively, indicating that Plk1 is not the trigger kinase at meiotic reinitiation. When Plk1 was required for cyclin B–Cdc2 activation, the action of Plk1 was mediated primarily through suppression of Myt1 rather than through activation of Cdc25. We propose that Plk1 can be activated by either cyclin A– or cyclin B–Cdc2, and its primary target is Myt1. PMID:14532135

  2. The Chromosomal Passenger Complex Is Required for Meiotic Acentrosomal Spindle Assembly and Chromosome Biorientation

    Science.gov (United States)

    Radford, Sarah J.; Jang, Janet K.; McKim, Kim S.

    2012-01-01

    DURING meiosis in the females of many species, spindle assembly occurs in the absence of the microtubule-organizing centers called centrosomes. In the absence of centrosomes, the nature of the chromosome-based signal that recruits microtubules to promote spindle assembly as well as how spindle bipolarity is established and the chromosomes orient correctly toward the poles is not known. To address these questions, we focused on the chromosomal passenger complex (CPC). We have found that the CPC localizes in a ring around the meiotic chromosomes that is aligned with the axis of the spindle at all stages. Using new methods that dramatically increase the effectiveness of RNA interference in the germline, we show that the CPC interacts with Drosophila oocyte chromosomes and is required for the assembly of spindle microtubules. Furthermore, chromosome biorientation and the localization of the central spindle kinesin-6 protein Subito, which is required for spindle bipolarity, depend on the CPC components Aurora B and Incenp. Based on these data we propose that the ring of CPC around the chromosomes regulates multiple aspects of meiotic cell division including spindle assembly, the establishment of bipolarity, the recruitment of important spindle organization factors, and the biorientation of homologous chromosomes. PMID:22865736

  3. The RTR complex as caretaker of genome stability and its unique meiotic function in plants

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    Alexander eKnoll

    2014-02-01

    Full Text Available The RTR complex consisting of a RecQ helicase, a type IA topoisomerase and the structural protein RMI1 is involved in the processing of DNA recombination intermediates in all eukaryotes. In Arabidopsis thaliana the complex partners RECQ4A, topoisomerase 3α and RMI1 have been shown to be involved in DNA repair and in the suppression of homologous recombination (HR in somatic cells. Interestingly, mutants of AtTOP3A and AtRMI1 are also sterile due to extensive chromosome breakage in meiosis I, a phenotype that seems to be specific for plants. Although both proteins are essential for meiotic recombination it is still elusive on what kind of intermediates they are acting on. Recent data indicate that the pattern of non-crossover (NCO-associated meiotic gene conversion (GC differs between plants and other eukaryotes, as less NCOs in comparison to crossovers (CO could be detected in Arabidopsis. This indicates that NCOs happen either more rarely in plants or that the conversion tract length is significantly shorter than in other organisms. As the TOP3α/RMI1-mediated dissolution of recombination intermediates results exclusively in NCOs, we suggest that the peculiar GC pattern found in plants is connected to the unique role, members of the RTR complex play in plant meiosis.

  4. Molecular Basis for Enhancement of the Meiotic DMCI Recombinase by RAD51AP1

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    Dray, Eloise; Dunlop, Myun Hwa; Kauppi, Liisa; San Filippo, Joseph San; Wiese, Claudia; Tsai, Miaw-Sheue; Begovic, Sead; Schild, David; Jasin, Maria; Keeney, Scott; Sung, Patrick

    2010-11-05

    Homologous recombination is needed for meiotic chromosome segregation, genome maintenance, and tumor suppression. RAD51AP1 (RAD51 Associated Protein 1) has been shown to interact with and enhance the recombinase activity of RAD51. Accordingly, genetic ablation of RAD51AP1 leads to enhanced sensitivity to and also chromosome aberrations upon DNA damage, demonstrating a role for RAD51AP1 in mitotic homologous recombination. Here we show physical association of RAD51AP1 with the meiosis-specific recombinase DMC1 and a stimulatory effect of RAD51AP1 on the DMC1-mediated D-loop reaction. Mechanistic studies have revealed that RAD51AP1 enhances the ability of the DMC1 presynaptic filament to capture the duplex DNA partner and to assemble the synaptic complex, in which the recombining DNA strands are homologously aligned. We also provide evidence that functional co-operation is dependent on complex formation between DMC1 and RAD51AP1, and that distinct epitopes in RAD51AP1 mediate interactions with RAD51 and DMC1. Finally, we show that RAD51AP1 is expressed in mouse testes, and that RAD51AP1 foci co-localize with a subset of DMC1 foci in spermatocytes. These results suggest that RAD51AP1 also serves an important role in meiotic homologous recombination.

  5. Immunocytological analysis of meiotic recombination in two anole lizards (Squamata, Dactyloidae

    Directory of Open Access Journals (Sweden)

    Artem P. Lisachov

    2017-03-01

    Full Text Available Although the evolutionary importance of meiotic recombination is not disputed, the significance of interspecies differences in the recombination rates and recombination landscapes remains under-appreciated. Recombination rates and distribution of chiasmata have been examined cytologically in many mammalian species, whereas data on other vertebrates are scarce. Immunolocalization of the protein of the synaptonemal complex (SYCP3, centromere proteins and the mismatch-repair protein MLH1 was used, which is associated with the most common type of recombination nodules, to analyze the pattern of meiotic recombination in the male of two species of iguanian lizards, Anolis carolinensis Voigt, 1832 and Deiroptyx coelestinus (Cope, 1862. These species are separated by a relatively long evolutionary history although they retain the ancestral iguanian karyotype. In both species similar and extremely uneven distributions of MLH1 foci along the macrochromosome bivalents were detected: approximately 90% of crossovers were located at the distal 20% of the chromosome arm length. Almost total suppression of recombination in the intermediate and proximal regions of the chromosome arms contradicts the hypothesis that “homogenous recombination” is responsible for the low variation in GC content across the anole genome. It also leads to strong linkage disequilibrium between the genes located in these regions, which may benefit conservation of co-adaptive gene arrays responsible for the ecological adaptations of the anoles.

  6. Nested Inversion Polymorphisms Predispose Chromosome 22q11.2 to Meiotic Rearrangements.

    Science.gov (United States)

    Demaerel, Wolfram; Hestand, Matthew S; Vergaelen, Elfi; Swillen, Ann; López-Sánchez, Marcos; Pérez-Jurado, Luis A; McDonald-McGinn, Donna M; Zackai, Elaine; Emanuel, Beverly S; Morrow, Bernice E; Breckpot, Jeroen; Devriendt, Koenraad; Vermeesch, Joris R

    2017-10-05

    Inversion polymorphisms between low-copy repeats (LCRs) might predispose chromosomes to meiotic non-allelic homologous recombination (NAHR) events and thus lead to genomic disorders. However, for the 22q11.2 deletion syndrome (22q11.2DS), the most common genomic disorder, no such inversions have been uncovered as of yet. Using fiber-FISH, we demonstrate that parents transmitting the de novo 3 Mb LCR22A-D 22q11.2 deletion, the reciprocal duplication, and the smaller 1.5 Mb LCR22A-B 22q11.2 deletion carry inversions of LCR22B-D or LCR22C-D. Hence, the inversions predispose chromosome 22q11.2 to meiotic rearrangements and increase the individual risk for transmitting rearrangements. Interestingly, the inversions are nested or flanking rather than coinciding with the deletion or duplication sizes. This finding raises the possibility that inversions are a prerequisite not only for 22q11.2 rearrangements but also for all NAHR-mediated genomic disorders. Copyright © 2017. Published by Elsevier Inc.

  7. Location of 45S Ribosomal Genes in Mitotic and Meiotic Chromosomes of Buthid Scorpions.

    Science.gov (United States)

    Mattos, Viviane Fagundes; Carvalho, Leonardo Sousa; Cella, Doralice Maria; Schneider, Marielle Cristina

    2014-09-01

    Buthid scorpions exhibit a high variability in diploid number within genera and even within species. Cytogenetically, Buthidae differs from other families of Scorpiones based on its low diploid numbers, holocentric chromosomes, and complex chromosomal chains, which form during meiosis. In this study, we analyzed the distribution of the 45S ribosomal DNA (rDNA) genes in the mitotic and meiotic chromosomes of seven buthid species belonging to the genera Rhopalurus and Tityus with the ultimate goal of elucidating the chromosome organization in these scorpions. The chromosome number ranged from 2n=6 to 2n=28. Despite the high variance in diploid number, all species examined carried their 45S rDNA sites in the terminal region of exactly two chromosomes. Analyses of meiotic cells revealed 45S rDNA clusters in the chromosomal chains of Rhopalurus agamemnon, Tityus bahiensis, Tityus confluens, and Tityus martinpaechi, or in bivalent-like configuration in Rhopalurus rochai, Tityus bahiensis, Tityus confluens, Tityus fasciolatus, and Tityus paraguayensis. In the species examined, the 45S rDNA sites colocalized with constitutive heterochromatin regions. In light of the high chromosome variability and maintenance of number and terminal position of 45S rDNA sites in buthids, the heterochromatin may act to conserve the integrity of the ribosomal genes.

  8. Meiotic pairing as an indicator of genome composition in polyploid prairie cordgrass (Spartina pectinata Link).

    Science.gov (United States)

    Bishop, Jeffrey W; Kim, Sumin; Villamil, María B; Lee, D K; Rayburn, A Lane

    2017-04-01

    The existence of neopolyploidy in prairie cordgrass (Spartina pectinata Link) has been documented. The neohexaploid was discovered coexisting with tetraploids in central Illinois, and has been reported to exhibit competitiveness in the natural environment. It is hypothesized that the natural tetraploid cytotype produced the hexaploid cytotype via production of unreduced gametes. Meiosis I chromosome pairing was observed in tetraploid (2n = 4x = 40), hexaploid (2n = 6x = 60), and octoploid (2n = 8x = 80) accessions and the percentage of meiotic abnormality was determined. Significant differences in meiotic abnormality exist between tetraploid, hexaploid, and octoploid cytotypes. An elevated incidence of abnormal, predominantly trivalent pairing in the neohexaploid suggests that it may possess homologous chromosomes in sets of three, in contrast to the tetraploid and octoploid cytotypes, which likely possess homologous chromosomes in sets of two. Abnormal chromosome pairing in the hexaploid may result in unequal allocation of chromosomes to daughter cells during later stages of meiosis. Chromosome pairing patterns in tetraploid, hexaploid, and octoploid cytotypes indicate genome compositions of AABB, AAABBB, and AABBA'A'B'B', respectively.

  9. Phosphorylation of the synaptonemal complex protein SYP-1 promotes meiotic chromosome segregation.

    Science.gov (United States)

    Sato-Carlton, Aya; Nakamura-Tabuchi, Chihiro; Chartrand, Stephane Kazuki; Uchino, Tomoki; Carlton, Peter Mark

    2017-12-08

    Chromosomes that have undergone crossing over in meiotic prophase must maintain sister chromatid cohesion somewhere along their length between the first and second meiotic divisions. Although many eukaryotes use the centromere as a site to maintain cohesion, the holocentric organism Caenorhabditis elegans instead creates two chromosome domains of unequal length termed the short arm and long arm, which become the first and second site of cohesion loss at meiosis I and II. The mechanisms that confer distinct functions to the short and long arm domains remain poorly understood. Here, we show that phosphorylation of the synaptonemal complex protein SYP-1 is required to create these domains. Once crossover sites are designated, phosphorylated SYP-1 and PLK-2 become cooperatively confined to short arms and guide phosphorylated histone H3 and the chromosomal passenger complex to the site of meiosis I cohesion loss. Our results show that PLK-2 and phosphorylated SYP-1 ensure creation of the short arm subdomain, promoting disjunction of chromosomes in meiosis I. © 2018 Sato-Carlton et al.

  10. Expression of Tetrahymena snRNA gene variants including a U1 gene with mutations in the 5' splice site recognition sequence

    DEFF Research Database (Denmark)

    Eugen-Olsen, J; Hagemeister, J J; Hellung-Larsen, P

    1997-01-01

    The expression of U1, U2 and U5 snRNA gene variants has been studied under different physiological states of Tetrahymena. Variants of all three snRNA genes are expressed. Among the snRNAs detected is U1-3, a variant with 66 mutations compared to the normal U1 snRNA. Three of these mutations affec...... the 5' splice site recognition sequence. The U1-3 snRNA is present in a few hundred copies per cell. The expression of Tetrahymena snRNA genes is independent of the physiological state of the cell.......The expression of U1, U2 and U5 snRNA gene variants has been studied under different physiological states of Tetrahymena. Variants of all three snRNA genes are expressed. Among the snRNAs detected is U1-3, a variant with 66 mutations compared to the normal U1 snRNA. Three of these mutations affect...

  11. Hormone-induced cortical maturation ensures the slow block to polyspermy and does not couple with meiotic maturation in starfish.

    Science.gov (United States)

    Hirohashi, Noritaka; Harada, Kaori; Chiba, Kazuyoshi

    2008-06-01

    Meiotic progression in starfish oocytes is reinitiated by a maturation-inducing hormone called 1-methyladenine (1-MeAde). In addition to meiotic maturation, 1-MeAde induces cortical maturation in which cortical granules become competent to discharge in response to fusion of a single sperm, which results in the formation of the fertilization envelope. We found that subthreshold concentrations of 1-MeAde induce cortical maturation without germinal vesicle breakdown (GVBD). During cortical maturation, the IP3 sensitivity of calcium stores was increased as well as during meiotic maturation. When oocytes were exposed with 1-MeAde only on a hemisphere of oocytes, the IP3 sensitivity of the cortical region was increased only in the exposed hemisphere, suggesting that signals and components involved in cortical maturation do not readily spread in the cytoplasm. Although a specific inhibitor of phosphatidylinositol-3 kinase, LY294002 blocked both GVBD and cortical maturation, a Cdc2 kinase inhibitor, roscovitine did not block cortical maturation. Inhibition of Akt activation by injecting the competitors for Akt phosphorylation and membrane recruitment also blocked cortical maturation. These results suggest that the signaling pathway leading to Akt activation is common in cortical maturation and meiotic maturation, and Cdc2 activation was not required for cortical maturation.

  12. Comparative Meiotic Studies in Triatoma sordida (Stål and T. guasayana Wygodzinsky & Abalos (Reduviidae, Heteroptera

    Directory of Open Access Journals (Sweden)

    P Rebagliati

    1998-05-01

    Full Text Available Triatoma sordida and T. guasayana are competent Trypanosoma cruzi vectors, with overlapping distribution areas in Argentina. Both species are morphologically similar, and their immature stages are hard to discriminate. Cytogenetic studies in the genus Triatoma reveal scarce karyotypic variations, being 2n= 20 + XY the most frequent diploid number in males. In the present work the meiotic behaviour of different Argentinian populations of T. sordida and T. guasayana has been analyzed; the meiotic karyotype of both species has also been compared. The species differ in total chromosome area and in the relative area of the sex chromosomes. These meiotic karyotypic differences constitute an additional tool for the taxonomic characterization of T. sordida and T. guasayana. The analysis of an interpopulation hybrid of T. sordida (Brazil x Argentina reveals a regular meiotic behaviour, despite the presence of heteromorphic bivalents. Our observations support the hypothesis that karyotype variations through the gain or loss of heterochromatin can not be considered as a primary mechanism of reproductive isolation in Triatoma.

  13. Katanin maintains meiotic metaphase chromosome alignment and spindle structure in vivo and has multiple effects on microtubules in vitro

    Science.gov (United States)

    McNally, Karen; Berg, Evan; Cortes, Daniel B.; Hernandez, Veronica; Mains, Paul E.; McNally, Francis J.

    2014-01-01

    Assembly of Caenorhabditis elegans female meiotic spindles requires both MEI-1 and MEI-2 subunits of the microtubule-severing ATPase katanin. Strong loss-of-function mutants assemble apolar intersecting microtubule arrays, whereas weaker mutants assemble bipolar meiotic spindles that are longer than wild type. To determine whether katanin is also required for spindle maintenance, we monitored metaphase I spindles after a fast-acting mei-1(ts) mutant was shifted to a nonpermissive temperature. Within 4 min of temperature shift, bivalents moved off the metaphase plate, and microtubule bundles within the spindle lengthened and developed a high degree of curvature. Spindles eventually lost bipolar structure. Immunofluorescence of embryos fixed at increasing temperature indicated that MEI-1 was lost from spindle microtubules before loss of ASPM-1, indicating that MEI-1 and ASPM-1 act independently at spindle poles. We quantified the microtubule-severing activity of purified MEI-1/MEI-2 complexes corresponding to six different point mutations and found a linear relationship between microtubule disassembly rate and meiotic spindle length. Previous work showed that katanin is required for severing at points where two microtubules intersect in vivo. We show that purified MEI-1/MEI-2 complexes preferentially sever at intersections between two microtubules and directly bundle microtubules in vitro. These activities could promote parallel/antiparallel microtubule organization in meiotic spindles. PMID:24501424

  14. The Chromatin Protein DUET/MMD1 Controls Expression of the Meiotic Gene TDM1 during Male Meiosis in Arabidopsis.

    Science.gov (United States)

    Andreuzza, Sébastien; Nishal, Bindu; Singh, Aparna; Siddiqi, Imran

    2015-09-01

    Meiosis produces haploid cells essential for sexual reproduction. In yeast, entry into meiosis activates transcription factors which trigger a transcriptional cascade that results in sequential co-expression of early, middle and late meiotic genes. However, these factors are not conserved, and the factors and regulatory mechanisms that ensure proper meiotic gene expression in multicellular eukaryotes are poorly understood. Here, we report that DUET/MMD1, a PHD finger protein essential for Arabidopsis male meiosis, functions as a transcriptional regulator in plant meiosis. We find that DUET-PHD binds H3K4me2 in vitro, and show that this interaction is critical for function during meiosis. We also show that DUET is required for proper microtubule organization during meiosis II, independently of its function in meiosis I. Remarkably, DUET protein shows stage-specific expression, confined to diplotene. We identify two genes TDM1 and JAS with critical functions in cell cycle transitions and spindle organization in male meiosis, as DUET targets, with TDM1 being a direct target. Thus, DUET is required to regulate microtubule organization and cell cycle transitions during male meiosis, and functions as a direct transcription activator of the meiotic gene TDM1. Expression profiling showed reduced expression of a subset comprising about 12% of a known set of meiosis preferred genes in the duet mutant. Our results reveal the action of DUET as a transcriptional regulator during male meiosis in plants, and suggest that transcription of meiotic genes is under stagewise control in plants as in yeast.

  15. Meiotic behaviour and sperm aneuploidy in an infertile man with a mosaic 45,X/46,XY karyotype.

    Science.gov (United States)

    Ren, He; Chow, Victor; Ma, Sai

    2015-12-01

    The meiotic behaviour of the germ cells in 45,X/46,XY men has not been extensively studied. This study investigated the meiotic events and sperm aneuploidy in an azoospermic man with a 45,X/46,XY (50/50) mosaic karyotype to better understand the fate of the 45,X cells and the production of chromosomally abnormal spermatozoa. Combining immunofluorescence techniques and fluorescence in-situ hybridization, meiotic recombination, synapsis, meiotic sex chromosome inactivation (MSCI) and configuration were analysed, as well as sperm aneuploidy in the patient and 10 normal, fertile men. Despite the 50:50 somatic mosaicism in the patient, 25% of pachytene cells analysed were 45,X. Furthermore, 63% of pachytene cells were 46,XY with paired sex chromosomes, and 12% were 46,XY with unpaired sex chromosomes, which displayed abnormal MCSI patterns. Although the patient's testicular spermatozoa showed increased aneuploidy, the majority were of normal constitution. The X:Y sperm ratio was significantly increased compared with the controls (P XY cells in meiosis, supporting the hypothesis that stringent checkpoints ensure the favourable production of spermatozoa with normal chromosomal constitution despite an individual's abnormal karyotype. Copyright © 2015 Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved.

  16. Genetic probing of homologous recombination and non-homologous end joining during meiotic prophase in irradiated mouse spermatocytes.

    NARCIS (Netherlands)

    Ahmed, E.A.; Philippens, M.E.P.; Kal, H.B.; Rooij, D.G. de; Boer, P. de

    2010-01-01

    This study was designed to obtain a better insight into the relative contribution of homologous recombination (HR) and non-homologous end joining (NHEJ) to the repair of radiation-induced DNA double-strand breaks (DSBs) at first meiotic prophase. Early and late pachytene and early diplotene

  17. Depletion of Key Meiotic Genes and Transcriptome-Wide Abiotic Stress Reprogramming Mark Early Preparatory Events Ahead of Apomeiotic Transition

    Science.gov (United States)

    Shah, Jubin N.; Kirioukhova, Olga; Pawar, Pallavi; Tayyab, Muhammad; Mateo, Juan L.; Johnston, Amal J.

    2016-01-01

    Molecular dissection of apomixis – an asexual reproductive mode – is anticipated to solve the enigma of loss of meiotic sex, and to help fixing elite agronomic traits. The Brassicaceae genus Boechera comprises of both sexual and apomictic species, permitting comparative analyses of meiotic circumvention (apomeiosis) and parthenogenesis. Whereas previous studies reported local transcriptome changes during these events, it remained unclear whether global changes associated with hybridization, polyploidy and environmental adaptation that arose during evolution of Boechera might serve as (epi)genetic regulators of early development prior apomictic initiation. To identify these signatures during vegetative stages, we compared seedling RNA-seq transcriptomes of an obligate triploid apomict and a diploid sexual, both isolated from a drought-prone habitat. Uncovered were several genes differentially expressed between sexual and apomictic seedlings, including homologs of meiotic genes ASYNAPTIC 1 (ASY1) and MULTIPOLAR SPINDLE 1 (MPS1) that were down-regulated in apomicts. An intriguing class of apomict-specific deregulated genes included several NAC transcription factors, homologs of which are known to be transcriptionally reprogrammed during abiotic stress in other plants. Deregulation of both meiotic and stress-response genes during seedling stages might possibly be important in preparation for meiotic circumvention, as similar transcriptional alteration was discernible in apomeiotic floral buds too. Furthermore, we noted that the apomict showed better tolerance to osmotic stress in vitro than the sexual, in conjunction with significant upregulation of a subset of NAC genes. In support of the current model that DNA methylation epigenetically regulates stress, ploidy, hybridization and apomixis, we noted that ASY1, MPS1 and NAC019 homologs were deregulated in Boechera seedlings upon DNA demethylation, and ASY1 in particular seems to be repressed by global DNA

  18. Depletion of Key Meiotic Genes and Transcriptome-Wide Abiotic Stress Reprogramming Mark Early Preparatory Events Ahead of Apomeiotic Transition

    Directory of Open Access Journals (Sweden)

    Jubin N Shah

    2016-10-01

    Full Text Available Molecular dissection of apomixis - an asexual reproductive mode - is anticipated to solve the enigma of loss of meiotic sex, and to help fixing elite agronomic traits. The Brassicaceae genus Boechera comprises of both sexual and apomictic species, permitting comparative analyses of meiotic circumvention (apomeiosis and parthenogenesis. Whereas previous studies reported local transcriptome changes during these events, it remained unclear whether global changes associated with hybridization, polyploidy and environmental adaptation that arose during evolution of Boechera might hint as (epigenetic regulators of early development prior apomictic initiation. To identify these signatures during vegetative stages, we compared seedling RNA-seq transcriptomes of an obligate triploid apomict and a diploid sexual, both isolated from a drought-prone habitat. Uncovered were several genes differentially expressed between sexual and apomictic seedlings, including homologues of meiotic genes ASYNAPTIC 1 (ASY1 and MULTIPOLAR SPINDLE 1 (MPS1 that were down-regulated in apomicts. An intriguing class of apomict-specific deregulated genes included several NAC transcription factors, homologues of which are known to be transcriptionally reprogrammed during abiotic stress in other plants. Deregulation of both meiotic and stress-response genes during seedling stages might possibly be important in preparation for meiotic circumvention, as similar transcriptional alteration was discernible in apomeiotic floral buds too. Furthermore, we noted that the apomict showed better tolerance to osmotic stress in vitro than the sexual, in conjunction with significant upregulation of a subset of NAC genes. In support of the current model that DNA methylation epigenetically regulates stress, ploidy, hybridization and apomixis, we noted that ASY1, MPS1 and NAC019 homologues were deregulated in Boechera seedlings upon DNA demethylation, and ASY1 in particular seems to be repressed by

  19. Chromosomes in the porcine first polar body possess competence of second meiotic division within enucleated MII stage oocytes.

    Directory of Open Access Journals (Sweden)

    Tao Lin

    Full Text Available To determine whether chromosomes in the porcine first polar body (PB1 can complete the second meiotic division and subsequently undergo normal pre-implantation embryonic development, we examined the developmental competence of PB1 chromosomes injected into enucleated MII stage oocytes by nuclear transfer method (chromosome replacement group, CR group. After parthenogenetic activation (PA or in vitro fertilization (IVF, the cleavage rate of reconstructed oocytes in the IVF group (CR-IVF group, 36.4 ± 3.2% and PA group (CR-PA group, 50.8 ± 4.2% were significantly lower than that of control groups in which normal MII oocytes were subjected to IVF (MII-IVF group, 75.8 ± 1.5% and PA (MII-PA group, 86.9 ± 3.7%. Unfertilized rates was significantly higher in the CR-IVF group (48.6 ± 3.3% than in the MII-IVF group (13.1 ± 3.4%. The blastocyst formation rate was 8.3 ± 1.9% in the CR-PA group, whereas no blastocyst formation was observed in the CR-IVF group. To produce tetraploid parthenogenetic embryos, intact MII stage oocytes injected with PB1 chromosomes were electrically stimulated, treated with 7.5 μg/mL cytochalasin B for 3 h (MII oocyte + PB1 + CB group, and then cultured without cytochalasin B. The average cleavage rate of reconstructed oocytes was 72.5% (48 of 66, and the blastocyst formation rate was 18.7% (9 of 48. Chromosome analysis showed similar proportions of haploid and diploid cells in the control (normal MII oocytes and CR groups after PA; overall, 23.6% of blastocysts were tetraploid in the MII oocyte + PB1 + CB group. These results demonstrate that chromosomes in PB1 can participate in normal pre-implantation embryonic development when injected into enucleated MII stage oocytes, and that tetraploid PA blastocysts are produced (although at a low proportion when PB1 chromosomes are injected into intact MII stage oocytes.

  20. Oocyte heterogeneity with respect to the meiotic silencing of unsynapsed X chromosomes in the XY female mouse.

    Science.gov (United States)

    Taketo, Teruko; Naumova, Anna K

    2013-10-01

    In the XY pachytene spermatocyte, the sex chromosomes do not synapse except for the pseudoautosomal region and become transcriptionally silenced. It has been suggested that the meiotic silencing of unsynapsed chromatin (MSUC) also occurs in oocytes. In the XY sex-reversed female mouse, the sex chromosomes fail to pair in the majority of oocytes and a greater number of oocytes are eliminated during the meiotic prophase compared to the XX female. Yet, many XY oocytes survive to reach the second meiotic metaphase. The goal of our current study was to determine whether the single X chromosome shows the characteristics of asynapsis and meiotic silencing in a proportion of XY oocytes, which can explain the survival of the remaining oocytes. We first examined the accumulation of markers associated with asynapsis or transcriptional silencing, i.e., BRCA1, γH2AX, H3K9me3, and H3K27me3, at the single X chromosome in the XY oocyte. We found that γH2AX and BRCA1 were enriched on the single X chromosome whereas H3K9me3 was not, and H3K27me3 was enriched at all chromosomes in the majority of XY oocytes. We next examined the meiotic silencing of the single X chromosome using enrichment of the X-encoded ATRX protein. On average, ATRX enrichment was lower in XY oocytes than in XX oocytes as expected from its half gene dosage. However, the intensity of ATRX staining in XY oocytes harboring γH2AX domains showed a remarkable heterogeneity. We conclude that MSUC occurs with varying consequences, resulting in a heterogeneous population of oocytes with respect to protein enrichment in the XY female mouse.

  1. Fine-scale variation in meiotic recombination in Mimulus inferred from population shotgun sequencing

    Energy Technology Data Exchange (ETDEWEB)

    Hellsten, Uffe [USDOE Joint Genome Inst., Walnut Creek, CA (United States); Wright, Kevin M. [Harvard Univ., Cambridge, MA (United States); Jenkins, Jerry [USDOE Joint Genome Inst., Walnut Creek, CA (United States); HudsonAlpha Inst. of Biotechnology, Huntsville, AL (United States); Shu, Shengqiang [USDOE Joint Genome Inst., Walnut Creek, CA (United States); Yuan, Yao-Wu [Univ. of Connecticut, Storrs, CT (United States); Wessler, Susan R. [Univ. of California, Riverside, CA (United States); Schmutz, Jeremy [USDOE Joint Genome Inst., Walnut Creek, CA (United States); HudsonAlpha Inst. of Biotechnology, Huntsville, AL (United States); Willis, John H. [Duke Univ., Durham, NC (United States); Rokhsar, Daniel S. [USDOE Joint Genome Inst., Walnut Creek, CA (United States); Univ. of California, Berkeley, CA (United States)

    2013-11-13

    Meiotic recombination rates can vary widely across genomes, with hotspots of intense activity interspersed among cold regions. In yeast, hotspots tend to occur in promoter regions of genes, whereas in humans and mice hotspots are largely defined by binding sites of the PRDM9 protein. To investigate the detailed recombination pattern in a flowering plant we use shotgun resequencing of a wild population of the monkeyflower Mimulus guttatus to precisely locate over 400,000 boundaries of historic crossovers or gene conversion tracts. Their distribution defines some 13,000 hotspots of varying strengths, interspersed with cold regions of undetectably low recombination. Average recombination rates peak near starts of genes and fall off sharply, exhibiting polarity. Within genes, recombination tracts are more likely to terminate in exons than in introns. The general pattern is similar to that observed in yeast, as well as in PRDM9-knockout mice, suggesting that recombination initiation described here in Mimulus may reflect ancient and conserved eukaryotic mechanisms

  2. Pre-meiotic transformation of germplasm-related structures during male gamete differentiation in Xenopus laevis.

    Science.gov (United States)

    Reunov, Arkadiy A; Reunova, Yulia A

    2016-02-01

    To highlight the ultrastructural features of transformation occurring with germplasm-related structures (GPRS), the spermatogenic cells of Xenopus laevis were studied by transmission electron microscopy and quantitative analysis. It was determined that in spermatogonia and spermatocytes, the compact germinal granules underwent fragmentation into particles comparable with inter-mitochondrial cement (IMC). Fragments of IMC agglutinated some cell mitochondria and resulted in the creation of mitochondrial clusters. Clustered mitochondria responded with loss of their membranes that occurred by the twisting of membranous protrusions around themselves until multi-layered membranes were formed. The mitochondrial affinity of multi-layered membranes was proven by an immunopositive test for mitochondrial dihydrolipoamide acetyltransferase. As a consequence of mitochondrial membrane twisting, the naked mitochondrial cores appeared and presumably underwent dispersion, which is the terminal stage of GPRS transformation. As no GPRS were observed in spermatids and sperm, it was assumed that these structures are functionally assigned to early stages of meiotic differentiation.

  3. Selective microspore abortion correlated with aneuploidy: an indication of meiotic drive.

    Science.gov (United States)

    Furness, Carol A; Rudall, Paula J

    2011-03-01

    Selective megaspore abortion (monomegaspory) probably arose once in seed plants and occurs routinely in more than 70% of angiosperm species, representing one of the key characters of a heterosporous life history. In contrast, selective microspore abortion leading to pollen dispersal as pseudomonads (here termed monomicrospory) apparently arose at least twice independently within angiosperms, though it occurs in a limited number of taxa. Remarkably, similar examples of monomicrospory occur in members of two distantly related angiosperm families: the sedge family (Cyperaceae) and the epacrid subfamily (Styphelioideae) of the eudicot family Ericaceae. In sedges, monomicrospory is derived directly from normal tetrads, whereas epacrid pseudomonads apparently evolved via an intermediate stage, in which variable sterility occurs in a single tetrad. Our comparison of these two examples of selective microspore abortion highlights a correlation with aneuploidy, indicating that non-random chromosome segregation caused by monomicrospory could drive chromosomal mutations to rapid fixation through meiotic drive.

  4. Cis- and trans-acting elements regulate the mouse Psmb9 meiotic recombination hotspot.

    Directory of Open Access Journals (Sweden)

    Frédéric Baudat

    2007-06-01

    Full Text Available In most eukaryotes, the prophase of the first meiotic division is characterized by a high level of homologous recombination between homologous chromosomes. Recombination events are not distributed evenly within the genome, but vary both locally and at large scale. Locally, most recombination events are clustered in short intervals (a few kilobases called hotspots, separated by large intervening regions with no or very little recombination. Despite the importance of regulating both the frequency and the distribution of recombination events, the genetic factors controlling the activity of the recombination hotspots in mammals are still poorly understood. We previously characterized a recombination hotspot located close to the Psmb9 gene in the mouse major histocompatibility complex by sperm typing, demonstrating that it is a site of recombination initiation. With the goal of uncovering some of the genetic factors controlling the activity of this initiation site, we analyzed this hotspot in both male and female germ lines and compared the level of recombination in different hybrid mice. We show that a haplotype-specific element acts at distance and in trans to activate about 2,000-fold the recombination activity at Psmb9. Another haplotype-specific element acts in cis to repress initiation of recombination, and we propose this control to be due to polymorphisms located within the initiation zone. In addition, we describe subtle variations in the frequency and distribution of recombination events related to strain and sex differences. These findings show that most regulations observed act at the level of initiation and provide the first analysis of the control of the activity of a meiotic recombination hotspot in the mouse genome that reveals the interactions of elements located both in and outside the hotspot.

  5. Mitotic and Meiotic Behavior of B Chromosomes in Crenicichla lepidota: New Report in the Family Cichlidae.

    Science.gov (United States)

    Pires, Larissa B; Sampaio, Tatiane R; Dias, Ana Lucia

    2015-01-01

    B chromosomes are additional genetic elements to the standard complement. They display distinctive features and have been found in 15% of eukaryote species. In this study, we analyzed 4 populations of Crenicichla lepidota from hydrographic system of Laguna dos Patos/RS (Brazil). All specimens showed 2n = 48 with 6m + 42st - a, FN = 54, with a secondary constriction on the first pair of the complement. Among the 18 samples analyzed, 6 individuals belonging to the Gasômetro and Saco da Alemoa populations presented 1-3 small-sized heterochromatic B chromosomes, with intra- and interindividual variation. Simple AgNORs coincident with 18S rDNA and CMA3 positive/DAPI negative sites were present in all populations. The extra chromosomes did not exhibit any 18S rDNA sites. The meiotic analyses showed heteropycnotic regions in leptotene and zygotene stages, which may be related to the presence of B chromosomes. During pachytene were found 24 bivalents and 1 spatially separated, as well as during metaphases I and diplotene, indicating that there is no association between B chromosomes and those of the A complement. During diakinesis, an unusual meiotic configuration was observed, revealing a proximity between the bivalent and chromosome B (univalent), that might be the result of a heterochromatin affinity between these chromosomes. In anaphase I, late migration of B chromosomes was detected. The low frequency of B chromosomes in the Cichlidae family and in Crenicichla suggests its recent origin in this group and may be ascribable to animal exposure to deleterious effects under certain environmental conditions. Moreover, this is the first report in C. lepidota. © The American Genetic Association 2015. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  6. Oocyte Polarization Is Coupled to the Chromosomal Bouquet, a Conserved Polarized Nuclear Configuration in Meiosis.

    Science.gov (United States)

    Elkouby, Yaniv M; Jamieson-Lucy, Allison; Mullins, Mary C

    2016-01-01

    The source of symmetry breaking in vertebrate oocytes is unknown. Animal-vegetal oocyte polarity is established by the Balbiani body (Bb), a conserved structure found in all animals examined that contains an aggregate of specific mRNAs, proteins, and organelles. The Bb specifies the oocyte vegetal pole, which is key to forming the embryonic body axes as well as the germline in most vertebrates. How Bb formation is regulated and how its asymmetric position is established are unknown. Using quantitative image analysis, we trace oocyte symmetry breaking in zebrafish to a nuclear asymmetry at the onset of meiosis called the chromosomal bouquet. The bouquet is a universal feature of meiosis where all telomeres cluster to one pole on the nuclear envelope, facilitating chromosomal pairing and meiotic recombination. We show that Bb precursor components first localize with the centrosome to the cytoplasm adjacent to the telomere cluster of the bouquet. They then aggregate around the centrosome in a specialized nuclear cleft that we identified, assembling the early Bb. We show that the bouquet nuclear events and the cytoplasmic Bb precursor localization are mechanistically coordinated by microtubules. Thus the animal-vegetal axis of the oocyte is aligned to the nuclear axis of the bouquet. We further show that the symmetry breaking events lay upstream to the only known regulator of Bb formation, the Bucky ball protein. Our findings link two universal features of oogenesis, the Bb and the chromosomal bouquet, to oocyte polarization. We propose that a meiotic-vegetal center couples meiosis and oocyte patterning. Our findings reveal a novel mode of cellular polarization in meiotic cells whereby cellular and nuclear polarity are aligned. We further reveal that in zygotene nests, intercellular cytoplasmic bridges remain between oocytes and that the position of the cytoplasmic bridge coincides with the location of the centrosome meiotic-vegetal organizing center. These results

  7. Oocyte Polarization Is Coupled to the Chromosomal Bouquet, a Conserved Polarized Nuclear Configuration in Meiosis.

    Directory of Open Access Journals (Sweden)

    Yaniv M Elkouby

    2016-01-01

    Full Text Available The source of symmetry breaking in vertebrate oocytes is unknown. Animal-vegetal oocyte polarity is established by the Balbiani body (Bb, a conserved structure found in all animals examined that contains an aggregate of specific mRNAs, proteins, and organelles. The Bb specifies the oocyte vegetal pole, which is key to forming the embryonic body axes as well as the germline in most vertebrates. How Bb formation is regulated and how its asymmetric position is established are unknown. Using quantitative image analysis, we trace oocyte symmetry breaking in zebrafish to a nuclear asymmetry at the onset of meiosis called the chromosomal bouquet. The bouquet is a universal feature of meiosis where all telomeres cluster to one pole on the nuclear envelope, facilitating chromosomal pairing and meiotic recombination. We show that Bb precursor components first localize with the centrosome to the cytoplasm adjacent to the telomere cluster of the bouquet. They then aggregate around the centrosome in a specialized nuclear cleft that we identified, assembling the early Bb. We show that the bouquet nuclear events and the cytoplasmic Bb precursor localization are mechanistically coordinated by microtubules. Thus the animal-vegetal axis of the oocyte is aligned to the nuclear axis of the bouquet. We further show that the symmetry breaking events lay upstream to the only known regulator of Bb formation, the Bucky ball protein. Our findings link two universal features of oogenesis, the Bb and the chromosomal bouquet, to oocyte polarization. We propose that a meiotic-vegetal center couples meiosis and oocyte patterning. Our findings reveal a novel mode of cellular polarization in meiotic cells whereby cellular and nuclear polarity are aligned. We further reveal that in zygotene nests, intercellular cytoplasmic bridges remain between oocytes and that the position of the cytoplasmic bridge coincides with the location of the centrosome meiotic-vegetal organizing center

  8. Progesterone-induced changes in the phosphoryl potential during the meiotic divisions in amphibian oocytes: Role of Na/K-ATPase

    National Research Council Canada - National Science Library

    Gene A Morrill; Terry L Dowd; Adele B Kostellow; Raj K Gupta

    2011-01-01

      Abstract Background: Progesterone triggers resumption of the first meiotic division in the Rana pipiens oocyte by binding to the N-terminal external loop of the catalytic subunit of Na/K-ATPase, releasing a cascade...

  9. Usual and unusual biochemical properties of ADF/cofilin-like protein Adf73p in ciliate Tetrahymena thermophila.

    Science.gov (United States)

    Shiozaki, Nanami; Nakano, Kentaro; Takaine, Masak; Abe, Hiroshi; Numata, Osamu

    2009-12-04

    Actin-depolymerizing factor (ADF)/cofilin is a well-conserved actin-modulating protein, which induces reorganization of the actin cytoskeleton by severing and depolymerizing F-actin. ADF/cofilin also binds to G-actin and inhibits nucleotide exchange, and hence, is supposed to regulate the nucleotide-bound state of the cellular G-actin pool cooperating with profilin, another well-conserved G-actin-binding protein that promotes nucleotide exchange. In this report, we investigated the biochemical properties of the ADF/cofilin-like protein Adf73p from ciliate Tetrahymena thermophila. Adf73p also binds to both G- and F-actin and severs and depolymerizes F-actin. Unlike canonical ADF/cofilin, however, Adf73p accelerates nucleotide exchange on actin and allows repolymerization of disassembled actin. These results suggest that the actin cytoskeleton of T. thermophila is regulated by Adf73p in a different way from those of mammals, plants, and yeasts.

  10. Heteroagglomeration of zinc oxide nanoparticles with clay mineral modulates the bioavailability and toxicity of nanoparticle in Tetrahymena pyriformis.

    Science.gov (United States)

    Gupta, Govind Sharan; Senapati, Violet Aileen; Dhawan, Alok; Shanker, Rishi

    2017-06-01

    The extensive use of zinc oxide nanoparticles (ZnO NPs) in cosmetics, sunscreens and healthcare products increases their release in the aquatic environment. The present study explored the possible interaction of ZnO NPs with montmorillonite clay minerals in aqueous conditions. An addition of ZnO NPs on clay suspension significantly (pclay particles from 1652±90nm to 2158±13nm due to heteroagglomeration. The electrokinetic measurements showed a significant (pclay association (-1.37±0.03μmcm/Vs) that results to the electrostatic interaction between ZnO NPs and clay particles. The attenuated total reflectance Fourier transform infrared spectroscopy analysis of ZnO NPs-clay association demonstrated the binding of ZnO NPs with the Si-O-Al region on the edges of clay particles. The increase in size of ZnO NPs-clay heteroagglomerates further leads to their sedimentation at 24h. Although, the stability of ZnO NPs in the clay suspension was decreased due to heteroagglomeration, but the bioavailability and toxicity of ZnO NPs-clay heteroagglomerates in Tetrahymena pyriformis was enhanced. These observations provide an evidence on possible mechanisms available in natural environment that can facilitate nanoparticles entry into the organisms present in lower trophic levels of the food web. Copyright © 2017 Elsevier Inc. All rights reserved.

  11. Genome-wide prediction of the polymorphic Ser gene family in Tetrahymena thermophila based on motif analysis.

    Science.gov (United States)

    Ponsuwanna, Patrath; Kümpornsin, Krittikorn; Chookajorn, Thanat

    2014-01-01

    Even though antigenic variation is employed among parasitic protozoa for host immune evasion, Tetrahymena thermophila, a free-living ciliate, can also change its surface protein antigens. These cysteine-rich glycosylphosphatidylinositol (GPI)-linked surface proteins are encoded by a family of polymorphic Ser genes. Despite the availability of T. thermophila genome, a comprehensive analysis of the Ser family is limited by its high degree of polymorphism. In order to overcome this problem, a new approach was adopted by searching for Ser candidates with common motif sequences, namely length-specific repetitive cysteine pattern and GPI anchor site. The candidate genes were phylogenetically compared with the previously identified Ser genes and classified into subtypes. Ser candidates were often found to be located as tandem arrays of the same subtypes on several chromosomal scaffolds. Certain Ser candidates located in the same chromosomal arrays were transcriptionally expressed at specific T. thermophila developmental stages. These Ser candidates selected by the motif analysis approach can form the foundation for a systematic identification of the entire Ser gene family, which will contribute to the understanding of their function and the basis of T. thermophila antigenic variation.

  12. Ecological Traits of the Algae-Bearing Tetrahymena utriculariae (Ciliophora) from Traps of the Aquatic Carnivorous Plant Utricularia reflexa.

    Science.gov (United States)

    Šimek, Karel; Pitsch, Gianna; Salcher, Michaela M; Sirová, Dagmara; Shabarova, Tanja; Adamec, Lubomír; Posch, Thomas

    2017-05-01

    Trap fluid of aquatic carnivorous plants of the genus Utricularia hosts specific microbiomes consisting of commensal pro- and eukaryotes of largely unknown ecology. We examined the characteristics and dynamics of bacteria and the three dominant eukaryotes, i.e. the algae-bearing ciliate Tetrahymena utriculariae (Ciliophora), a green flagellate Euglena agilis (Euglenophyta), and the alga Scenedesmus alternans (Chlorophyta), associated with the traps of Utricularia reflexa. Our study focused on ecological traits and life strategies of the highly abundant ciliate whose biomass by far exceeds that of other eukaryotes and bacteria independent of the trap age. The ciliate was the only bacterivore in the traps, driving rapid turnover of bacterial standing stock. However, given the large size of the ciliate and the cell-specific uptake rates of bacteria we estimated that bacterivory alone would likely be insufficient to support its apparent rapid growth in traps. We suggest that mixotrophy based on algal symbionts contributes significantly to the diet and survival strategy of the ciliate in the extreme (anaerobic, low pH) trap-fluid environment. We propose a revised concept of major microbial interactions in the trap fluid where ciliate bacterivory plays a central role in regeneration of nutrients bound in rapidly growing bacterial biomass. © 2016 The Author(s) Journal of Eukaryotic Microbiology © 2016 International Society of Protistologists.

  13. A Comparative Study of Two Quantum Chemical Descriptors in Predicting Toxicity of Aliphatic Compounds towards Tetrahymena pyriformis

    Directory of Open Access Journals (Sweden)

    Altaf Hussain Pandith

    2010-01-01

    Full Text Available Quantum chemical parameters such as LUMO energy, HOMO energy, ionization energy (I, electron affinity (A, chemical potential (μ, hardness (η electronegativity (χ, philicity (ωα, and electrophilicity (ω of a series of aliphatic compounds are calculated at the B3LYP/6-31G(d level of theory. Quantitative structure-activity relationship (QSAR models are developed for predicting the toxicity (pIGC50 of 13 classes of aliphatic compounds, including 171 electron acceptors and 81 electron donors, towards Tetrahymena pyriformis. The multiple linear regression modeling of toxicity of these compounds is performed by using the molecular descriptor log P (1-octanol/water partition coefficient in conjunction with two other quantum chemical descriptors, electrophilicity (ω and energy of the lowest unoccupied molecular orbital (ELUMO. A comparison is made towards the toxicity predicting the ability of electrophilicity (ω versus ELUMO as a global chemical reactivity descriptor in addition to log P. The former works marginally better in most cases. There is a slight improvement in the quality of regression by changing the unit of IGC50 from mg/L to molarity and by removing the racemates and the diastereoisomers from the data set.

  14. DNA content alterations in Tetrahymena pyriformis macronucleus after exposure to food preservatives sodium nitrate and sodium benzoate.

    Science.gov (United States)

    Loutsidou, Ariadni C; Hatzi, Vasiliki I; Chasapis, C T; Terzoudi, Georgia I; Spiliopoulou, Chara A; Stefanidou, Maria E

    2012-12-01

    The toxicity, in terms of changes in the DNA content, of two food preservatives, sodium nitrate and sodium benzoate was studied on the protozoan Tetrahymena pyriformis using DNA image analysis technology. For this purpose, selected doses of both food additives were administered for 2 h to protozoa cultures and DNA image analysis of T. pyriformis nuclei was performed. The analysis was based on the measurement of the Mean Optical Density which represents the cellular DNA content. The results have shown that after exposure of the protozoan cultures to doses equivalent to ADI, a statistically significant increase in the macronuclear DNA content compared to the unexposed control samples was observed. The observed increase in the macronuclear DNA content is indicative of the stimulation of the mitotic process and the observed increase in MOD, accompanied by a stimulation of the protozoan proliferation activity is in consistence with this assumption. Since alterations at the DNA level such as DNA content and uncontrolled mitogenic stimulation have been linked with chemical carcinogenesis, the results of the present study add information on the toxicogenomic profile of the selected chemicals and may potentially lead to reconsideration of the excessive use of nitrates aiming to protect public health.

  15. The C-terminal domain of Tetrahymena thermophila telomerase holoenzyme protein p65 induces multiple structural changes in telomerase RNA

    Science.gov (United States)

    Akiyama, Benjamin M.; Loper, John; Najarro, Kevin; Stone, Michael D.

    2012-01-01

    The unique cellular activity of the telomerase reverse transcriptase ribonucleoprotein (RNP) requires proper assembly of protein and RNA components into a functional complex. In the ciliate model organism Tetrahymena thermophila, the La-domain protein p65 is required for in vivo assembly of telomerase. Single-molecule and biochemical studies have shown that p65 promotes efficient RNA assembly with the telomerase reverse transcriptase (TERT) protein, in part by inducing a bend in the conserved stem IV region of telomerase RNA (TER). The domain architecture of p65 consists of an N-terminal domain, a La-RRM motif, and a C-terminal domain (CTD). Using single-molecule Förster resonance energy transfer (smFRET), we demonstrate the p65CTD is necessary for the RNA remodeling activity of the protein and is sufficient to induce a substantial conformational change in stem IV of TER. Moreover, nuclease protection assays directly map the site of p65CTD interaction to stem IV and reveal that, in addition to bending stem IV, p65 binding reorganizes nucleotides that comprise the low-affinity TERT binding site within stem–loop IV. PMID:22315458

  16. Number and nuclear localisation of nucleoli in mammalian spermatocytes.

    Science.gov (United States)

    Berríos, Soledad; Fernández-Donoso, Raúl; Pincheira, Juana; Page, Jesús; Manterola, Marcia; Cerda, M Cristina

    2004-07-01

    In seven mammalian species, including man, the position and number of nucleoli in pachytene spermatocyte nuclei were studied from electron microscope (EM) nuclear sections or bivalent microspreads. The number and position of the nucleolar organiser regions (NORs) in mitotic and meiotic chromosomes were also analysed, using silver staining techniques and in situ hybridisation protocols. The general organisation of pachytene spermatocyte nucleoli was almost the same, with only minor morphological differences between species. The terminal NORs of Thylamys elegans (Didelphoidea, Marsupialia), Dromiciops gliroides (Microbiotheridae, Marsupialia), Phyllotys osgoodi (Rodentia, Muridae) and man, always gave rise to peripheral nucleoli in the spermatocyte nucleus. In turn, the intercalated NORs from Octodon degus, Ctenomys opimus (Rodentia, Octodontidae) and Chinchilla lanigera (Rodentia, Cavidae), gave rise to central nucleoli. In species with a single nucleolar bivalent, just one nucleolus is formed, while in those with multiple nucleolar bivalents a variable number of nucleoli are formed by association of different nucleolar bivalents or NORs that occupy the same nuclear peripheral space (Phyllotis and man). It can be concluded that the position of each nucleolus within the spermatocyte nucleus is mainly dependent upon: (1) the position of the NOR in the nucleolar bivalent synaptonemal complex (SC), (2) the nuclear pathway of the nucleolar bivalent SC, being both telomeric ends attached to the nuclear envelope, and (3) the association between nucleolar bivalents by means of their NOR-nucleolar domains that occupy the same nuclear space. Thus, the distribution of nucleoli within the nuclear space of spermatocytes is non-random and it is consistent with the existence of a species-specific meiotic nuclear architecture.

  17. LINCing the nuclear envelope to gametogenesis.

    Science.gov (United States)

    Kracklauer, Martin P; Link, Jana; Alsheimer, Manfred

    2013-01-01

    Gametogenesis combines two important features: reduction of the genome content from diploid to haploid by carefully partitioning chromosomes, and the subsequent differentiation into fertilization-competent gametes, which in males is characterized by profound nuclear restructuring. These are quite difficult tasks and require a tight coordination of different cellular mechanisms. Recent studies in the field established a key role for LINC complexes in both meiosis and sperm head formation. LINC complexes comprise SUN and KASH domain proteins that form nuclear envelope (NE) bridges, linking the nucleoskeleton to the cytoskeleton. They are well known for their crucial roles in diverse cellular and developmental processes, such as nuclear positioning and cell polarization. In this review, we highlight key roles ascribed to LINC complexes and to the nucleocytoskeletal connection in gametogenesis. First, we give a short overview about the general features of LINC components and the profound reorganization of the NE in germ cells. We then focus on specific roles of LINC complexes in meiotic chromosome dynamics and their impact on pairing, synapsis, and recombination. Finally, we provide an update of the mechanisms controlling sperm head formation and discuss the role of sperm-specific LINC complexes in nuclear shaping and their relation to specialized cytoskeletal structures that form concurrently with nuclear restructuring and sperm elongation. Copyright © 2013 Elsevier Inc. All rights reserved.

  18. Sterility in hybrid cattle. I. Distribution of constitutive heterochromatin and nucleolus organizer regions in somatic and meiotic chromosomes.

    Science.gov (United States)

    Pathak, S; Kieffer, N M

    1979-01-01

    The distribution of constitutive heterochromatin and nucleolus organizer regions (NOR's) in somatic as well as in meiotic chromosomes of Bos taurus, Bos banteng, Bison bison, and their hybrids are analyzed. C-bands are present in the centromeric regions of every autosome. The X chromosome does not show a distinct C-band in the centromeric region, whereas the Y chromosome contains an appreciable amount of C-band material. In somatic metaphases, NOR's are present on the telomeric ends of five pairs of autosomes. During pachytene, five autosomal bivalents contain NOR's on their terminal ends. Meiotic preparations made from sterile bulls did not contain stages beyond the degenerating pachytene, which are C-banding, more frequently showed clustering of heterochromatin than did the pachytene stage in normal bulls.

  19. HURP permits MTOC sorting for robust meiotic spindle bipolarity, similar to extra centrosome clustering in cancer cells.

    Science.gov (United States)

    Breuer, Manuel; Kolano, Agnieszka; Kwon, Mijung; Li, Chao-Chin; Tsai, Ting-Fen; Pellman, David; Brunet, Stéphane; Verlhac, Marie-Hélène

    2010-12-27

    In contrast to somatic cells, formation of acentriolar meiotic spindles relies on the organization of microtubules (MTs) and MT-organizing centers (MTOCs) into a stable bipolar structure. The underlying mechanisms are still unknown. We show that this process is impaired in hepatoma up-regulated protein (Hurp) knockout mice, which are viable but female sterile, showing defective oocyte divisions. HURP accumulates on interpolar MTs in the vicinity of chromosomes via Kinesin-5 activity. By promoting MT stability in the spindle central domain, HURP allows efficient MTOC sorting into distinct poles, providing bipolarity establishment and maintenance. Our results support a new model for meiotic spindle assembly in which HURP ensures assembly of a central MT array, which serves as a scaffold for the genesis of a robust bipolar structure supporting efficient chromosome congression. Furthermore, HURP is also required for the clustering of extra centrosomes before division, arguing for a shared molecular requirement of MTOC sorting in mammalian meiosis and cancer cell division.

  20. Pollen viability and meiotic analysis of Solanum commersonii commersonii Dun., Solanum commersonii malmeanum Bitt. and Solanum tuberosum L.

    Directory of Open Access Journals (Sweden)

    Alexandre Alonso Alves

    2007-01-01

    Full Text Available Meiotic abnormalities in potato hamper sexual recombination, due to their influence on pollen production andviability rate. In this study we evaluated pollen viability and meiosis of three clones of Solanum commersonii commersoniiDun. (SCC, two of Solanum commersonii malmeanum Bitt. (SCM and seven clones and four cultivars of Solanum tuberosumL., with the purpose of indicating promising genotypes for genetic breeding of potato. Early chromosome migration atmetaphases I and II and chromosome pairing anomalies were the main causes of pollen inviability in the evaluated genotypes.Clones SCC 07 and SCM 60 are the most suitable for sexual recombination, owing to the high percentage of viable pollengrains and low frequencies of meiotic abnormalities.

  1. Xp38gamma/SAPK3 promotes meiotic G(2)/M transition in Xenopus oocytes and activates Cdc25C

    DEFF Research Database (Denmark)

    Perdiguero, Eusebio; Pillaire, Marie-Jeanne; Bodart, Jean-Francois

    2003-01-01

    /SAPK3 is the major p38 activated by MKK6 in the oocytes. We have cloned Xenopus p38gamma (Xp38gamma) and show that co-expression of active MKK6 with Xp38gamma induces oocyte maturation in the absence of progesterone. The maturation induced by Xp38gamma requires neither protein synthesis nor activation...... for the meiotic G(2)/M progression of Xenopus oocytes....

  2. BRIT1/MCPH1 is essential for mitotic and meiotic recombination DNA repair and maintaining genomic stability in mice.

    Directory of Open Access Journals (Sweden)

    Yulong Liang

    2010-01-01

    Full Text Available BRIT1 protein (also known as MCPH1 contains 3 BRCT domains which are conserved in BRCA1, BRCA2, and other important molecules involved in DNA damage signaling, DNA repair, and tumor suppression. BRIT1 mutations or aberrant expression are found in primary microcephaly patients as well as in cancer patients. Recent in vitro studies suggest that BRIT1/MCPH1 functions as a novel key regulator in the DNA damage response pathways. To investigate its physiological role and dissect the underlying mechanisms, we generated BRIT1(-/- mice and identified its essential roles in mitotic and meiotic recombination DNA repair and in maintaining genomic stability. Both BRIT1(-/- mice and mouse embryonic fibroblasts (MEFs were hypersensitive to gamma-irradiation. BRIT1(-/- MEFs and T lymphocytes exhibited severe chromatid breaks and reduced RAD51 foci formation after irradiation. Notably, BRIT1(-/- mice were infertile and meiotic homologous recombination was impaired. BRIT1-deficient spermatocytes exhibited a failure of chromosomal synapsis, and meiosis was arrested at late zygotene of prophase I accompanied by apoptosis. In mutant spermatocytes, DNA double-strand breaks (DSBs were formed, but localization of RAD51 or BRCA2 to meiotic chromosomes was severely impaired. In addition, we found that BRIT1 could bind to RAD51/BRCA2 complexes and that, in the absence of BRIT1, recruitment of RAD51 and BRCA2 to chromatin was reduced while their protein levels were not altered, indicating that BRIT1 is involved in mediating recruitment of RAD51/BRCA2 to the damage site. Collectively, our BRIT1-null mouse model demonstrates that BRIT1 is essential for maintaining genomic stability in vivo to protect the hosts from both programmed and irradiation-induced DNA damages, and its depletion causes a failure in both mitotic and meiotic recombination DNA repair via impairing RAD51/BRCA2's function and as a result leads to infertility and genomic instability in mice.

  3. Nitric oxide donor s-nitroso-n-acetyl penicillamine (SNAP) alters meiotic spindle morphogenesis in Xenopus oocytes.

    Science.gov (United States)

    Gelaude, Armance; Marin, Matthieu; Cailliau, Katia; Jeseta, Michal; Lescuyer-Rousseau, Arlette; Vandame, Pauline; Nevoral, Jan; Sedmikova, Marketa; Martoriati, Alain; Bodart, Jean-François

    2015-11-01

    Nitric Oxide (NO) has been involved in both intra- and extra-cellular signaling pathways in a wide range of organisms, and can be detected in some reproductive tissues. Based upon previous results reporting that NO-donor SNAP (s-nitroso-n-acetyl penicillamine) promoted the release from the metaphase II-anaphase II block in amphibian eggs, the aim of the present study was to assess the influence of SNAP on the activation of the molecular mechanisms triggering meiotic resumption of Xenopus oocytes, analogous to G2/M transition of the cell cycle. A high concentration of SNAP (2.5 mM) was found to inhibit the appearance of the white spot (meiotic resumption) and promoted alteration of spindle morphogenesis leading to atypical structures lacking bipolarity and correct chromosomes equatorial alignment. The medium acidification (pH = 4) promoted by SNAP specifically impacted the white spot occurrence. However, even when pH was restored to 7.4 in SNAP medium, observed spindles remained atypical (microtubule disorganization), suggesting SNAP impacted spindle assembly regardless of the pH. n-Acetyl-d,l-penicillamine disulfide, a degradation product of SNAP with the same molecular characteristics, albeit without release of NO, yielded spindle assemblies typical of metaphase II suggesting the specificity of NO action on meiotic spindle morphogenesis in Xenopus oocytes. © 2015 Wiley Periodicals, Inc.

  4. Quantitative Genome-Wide Measurements of Meiotic DNA Double-Strand Breaks and Protein Binding in S. pombe.

    Science.gov (United States)

    Hyppa, Randy W; Fowler, Kyle R; Smith, Gerald R

    2017-01-01

    The fission yeast Schizosaccharomyces pombe is especially well suited for studying meiosis in molecular detail. Experiments with S. pombe strains that undergo a nearly synchronous meiosis-at variable temperatures-have elucidated the mechanisms of meiotic progression and the proteins that are involved. For example, studies focused on the initiation of meiotic recombination by programmed DNA double-strand breaks (DSBs) have proven exceptionally informative. In meiosis, some regions of DNA have more frequent DSBs than the surrounding regions. These DSB hotspots can be visualized by Southern blot hybridization of restriction fragments ranging from kilobases (kb) to megabases (Mb) in size. More recently, the benefits of genome-wide analysis to map the distribution and frequency of meiotic DSBs have been attained, with resolution down to the nucleotide level. Infrequent, non-hotspot DSBs previously not detectable have been observed, creating a better understanding of how recombination is regulated. Additional genome-wide analyses have shown proteins that bind specifically to DSB hotspots, providing insight into how the DSB initiation complex functions. We describe here detailed methods for achieving these results.

  5. Meiotic behaviour and its implication on species inter-relationship in the genus Curcuma (Linnaeus, 1753 (Zingiberaceae

    Directory of Open Access Journals (Sweden)

    Judith Mary Lamo

    2017-10-01

    Full Text Available In this paper, detailed meiotic analysis was investigated in seven species of Curcuma (Linnaeus, 1753 which can contribute significantly to our understanding about species inter-relationship, speciation and evolution. The species were divided into two groups viz., Group I having 2n = 42 (C. comosa Roxburgh, 1810, C. haritha Mangaly & M.Sabu, 1993, C. mangga Valeton & Zijp, 1917, and C. motana Roxburgh, 1800 and Group II with 2n = 63 (C. caesia Roxburgh, 1810, C. longa Linnaeus, 1753 and C. sylvatica Valeton, 1918. Both groups display varying degree of chromosome associations. Group I species showed the prevalence of bivalents, however occasional quadrivalents besides univalents were also encountered. About 48% of the PMCs analyzed in C. mangga showed 21 bivalents (II meiotic configurations, 32% in C. comosa and 16% in C. haritha. Group II species as expected showed the presence of trivalents besides bivalents, univalents and quadrivalents. About 32% of the PMCs analyzed at MI in C. sylvatica showed 21 trivalents (III meiotic configurations, 24% in C. longa and 8% in C. caesia. Overall, low frequency of multivalent associations as compared to bivalents indicates that Curcuma is an allopolyploid complex. Moreover, x = 21 is too high a basic number, therefore, we suggest that the genus Curcuma has evolved by hybridization of species with different chromosome numbers of 2n = 24 and 18, resulting in a dibasic amphidiploid species.

  6. KLP-7 acts through the Ndc80 complex to limit pole number in C. elegans oocyte meiotic spindle assembly

    Science.gov (United States)

    Connolly, Amy A.; Sugioka, Kenji; Chuang, Chien-Hui; Lowry, Joshua B.

    2015-01-01

    During oocyte meiotic cell division in many animals, bipolar spindles assemble in the absence of centrosomes, but the mechanisms that restrict pole assembly to a bipolar state are unknown. We show that KLP-7, the single mitotic centromere–associated kinesin (MCAK)/kinesin-13 in Caenorhabditis elegans, is required for bipolar oocyte meiotic spindle assembly. In klp-7(−) mutants, extra microtubules accumulated, extra functional spindle poles assembled, and chromosomes frequently segregated as three distinct masses during meiosis I anaphase. Moreover, reducing KLP-7 function in monopolar klp-18(−) mutants often restored spindle bipolarity and chromosome segregation. MCAKs act at kinetochores to correct improper kinetochore–microtubule (k–MT) attachments, and depletion of the Ndc-80 kinetochore complex, which binds microtubules to mediate kinetochore attachment, restored bipolarity in klp-7(−) mutant oocytes. We propose a model in which KLP-7/MCAK regulates k–MT attachment and spindle tension to promote the coalescence of early spindle pole foci that produces a bipolar structure during the acentrosomal process of oocyte meiotic spindle assembly. PMID:26370499

  7. 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.

  8. New elements in the C-type natriuretic peptide signaling pathway inhibiting swine in vitro oocyte meiotic resumption.

    Science.gov (United States)

    Santiquet, Nicolas; Papillon-Dion, Emilie; Djender, Nadjib; Guillemette, Christine; Richard, François J

    2014-07-01

    C-type natriuretic peptide (CNP) and its cognate receptor, natriuretic peptide receptor (NPR) B, have been shown to promote cGMP production in granulosa/cumulus cells. Once transferred to the oocyte through the gap junctions, the cGMP inhibits oocyte meiotic resumption. CNP has been shown to bind another natriuretic receptor, NPR-C. NPR-C is known to interact with and degrade bound CNP, and has been reported to possess signaling functions. Therefore, NPR-C could participate in the control of oocyte maturation during swine in vitro maturation (IVM). Here, we examine the effect of CNP signaling on meiotic resumption, the amount of cGMP and gap junctional communication (GJC) regulation during swine IVM. The results show an inhibitory effect of CNP in inhibiting oocyte meiotic resumption in follicle-stimulating hormone (FSH)-stimulated IVM. We also found that an NPR-C-specific agonist (cANP([4-23])) is likely to play a role in maintaining meiotic arrest during porcine IVM when in the presence of a suboptimal dose of CNP. Moreover, we show that, even if CNP can increase intracellular concentration of cGMP in cumulus-oocyte complexes, cANP((4-23)) had no impact on cGMP concentration, suggesting a potential cGMP-independent signaling pathway related to NPR-C activation. These data support a potential involvement of cANP((4-23)) through NPR-C in inhibiting oocyte meiotic resumption while in the presence of a suboptimal dose of CNP. The regulation of GJC was not altered by CNP, cANP((4-23)), or the combination of CNP and cANP((4-23)), supporting their potential contribution in sending signals to the oocytes. These findings offer promising insights in to new elements of the signaling pathways that may be involved in inhibiting resumption of meiosis during FSH-stimulated swine IVM. © 2014 by the Society for the Study of Reproduction, Inc.

  9. Toxicity of Nine (Doped) Rare Earth Metal Oxides and Respective Individual Metals to Aquatic Microorganisms Vibrio fischeri and Tetrahymena thermophila.

    Science.gov (United States)

    Kurvet, Imbi; Juganson, Katre; Vija, Heiki; Sihtmäe, Mariliis; Blinova, Irina; Syvertsen-Wiig, Guttorm; Kahru, Anne

    2017-07-05

    Despite the increasing use of rare earth elements (REEs) and oxides (REOs) in various technologies, the information on their ecotoxicological hazard is scarce. Here, the effects of La(3+), Ce(3+), Pr(3+), Nd(3+), Gd(3+), CeO₂, and eight doped REOs to marine bacteria Vibrio fischeri and freshwater protozoa Tetrahymena thermophila were studied in parallel with REO dopant metals (Co(2+), Fe(3+), Mn(2+), Ni(2+), Sr(2+)). The highest concentrations of REOs tested were 100 mg/L with protozoa in deionized water and 500 mg/L with bacteria in 2% NaCl. Although (i) most REOs produced reactive oxygen species; (ii) all studied soluble REEs were toxic to bacteria (half-effective concentration, EC50 3.5-21 mg metal/L; minimal bactericidal concentration, MBC 6.3-63 mg/L) and to protozoa (EC50 28-42 mg/L); and (iii) also some dopant metals (Ni(2+), Fe(3+)) proved toxic (EC50 ≤ 3 mg/L), no toxicity of REOs to protozoa (EC50 > 100 mg/L) and bacteria (EC50 > 500 mg/L; MBC > 500 mg/L) was observed except for La₂NiO₄ (MBC 25 mg/L). According to kinetics of V. fischeri bioluminescence, the toxicity of REEs was triggered by disturbing cellular membrane integrity. Fortunately, as REEs and REOs are currently produced in moderate amounts and form in the environment insoluble salts and/or oxides, they apparently present no harm to aquatic bacteria and protozoa.

  10. Lysosomal physiology in Tetrahymena. 3. Pharmacological studies on acid hydrolase release and the ingestion and egestion of dimethylbenzanthracene particles.

    Science.gov (United States)

    Rothstein, T L; Blum, J J

    1974-09-01

    The ingestion of (14)C-labeled 9,10-dimethyl-1,2-benzanthracene particles, the extracellular release of acid phosphatase, ribonuclease, and alpha-glucosidase, and the egestion of preingested dimethylbenzanthracene particles by Tetrahymena taken from logarithmically growing cultures and resuspended in a dilute salt solution were followed in the presence of several pharmacologic agents. Serotonin, caffeine, and, to a lesser extent, dibutyryl cyclic AMP increased the rate of particle ingestion, but did not alter the rate of release of the three acid hydrolases studied. Added catecholamines did not affect either particle ingestion or acid hydrolase release, but particle ingestion was inhibited by the catecholamine antagonists, dichloroisoproterenol, desmethylimipramine, reserpine, and phenoxybenzamine. These drugs also increased the release of acid phosphatase and ribonuclease in 5-h incubations. Desmethylimipramine acted within 1 h to increase acid hydrolase release, but the effect of dichloroisoproterenol developed more slowly and was secondary to a change in cellular content of the hydrolases. Desmethylimipramine increased the energy of activation for the release of acid phosphatase, while dichloroisoproterenol did not. Both of these drugs enhanced the egestion of preingested dimethylbenzanthracene particles, supporting the view that acid hydrolase release occurs through a cytoproct egestion mechanism. Particle ingestion was also inhibited by colchicine, vinblastine, and cytochalasin B, but these agents had no effect on acid hydrolase release, thus further differentiating the properties of the ingestion mechanism from those of the egestion mechanism. It appears that both microtubules and microfilaments play a role in the ingestion process and that this process may be controlled in part by a cyclic AMP-mediated serotoninergic and adrenergic system.

  11. Meiotic drive influences the outcome of sexually antagonistic selection at a linked locus.

    Science.gov (United States)

    Patten, M M

    2014-11-01

    Most meiotic drivers, such as the t-haplotype in Mus and the segregation distorter (SD) in Drosophila, act in a sex-specific manner, gaining a transmission advantage through one sex although suffering only the fitness costs associated with the driver in the other. Their inheritance is thus more likely through one of the two sexes, a property they share with sexually antagonistic alleles. Previous theory has shown that pairs of linked loci segregating for sexually antagonistic alleles are more likely to remain polymorphic and that linkage disequilibrium accrues between them. I probe this similarity between drive and sexual antagonism and examine the evolution of chromosomes experiencing these selection pressures simultaneously. Reminiscent of previous theory, I find that: the opportunity for polymorphism increases for a sexually antagonistic locus that is physically linked to a driving locus; the opportunity for polymorphism at a driving locus also increases when linked to a sexually antagonistic locus; and stable linkage disequilibrium accompanies any polymorphic equilibrium. Additionally, I find that drive at a linked locus favours the fixation of sexually antagonistic alleles that benefit the sex in which drive occurs. Further, I show that under certain conditions reduced recombination between these two loci is selectively favoured. These theoretical results provide clear, testable predictions about the nature of sexually antagonistic variation on driving chromosomes and have implications for the evolution of genomic architecture. © 2014 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2014 European Society For Evolutionary Biology.

  12. Centromere strength provides the cell biological basis for meiotic drive and karyotype evolution in mice.

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    Chmátal, Lukáš; Gabriel, Sofia I; Mitsainas, George P; Martínez-Vargas, Jessica; Ventura, Jacint; Searle, Jeremy B; Schultz, Richard M; Lampson, Michael A

    2014-10-06

    Mammalian karyotypes (number and structure of chromosomes) can vary dramatically over short evolutionary time frames. There are examples of massive karyotype conversion, from mostly telocentric (centromere terminal) to mostly metacentric (centromere internal), in 10(2)-10(5) years. These changes typically reflect rapid fixation of Robertsonian (Rb) fusions, a common chromosomal rearrangement that joins two telocentric chromosomes at their centromeres to create one metacentric. Fixation of Rb fusions can be explained by meiotic drive: biased chromosome segregation during female meiosis in violation of Mendel's first law. However, there is no mechanistic explanation of why fusions would preferentially segregate to the egg in some populations, leading to fixation and karyotype change, while other populations preferentially eliminate the fusions and maintain a telocentric karyotype. Here we show, using both laboratory models and wild mice, that differences in centromere strength predict the direction of drive. Stronger centromeres, manifested by increased kinetochore protein levels and altered interactions with spindle microtubules, are preferentially retained in the egg. We find that fusions preferentially segregate to the polar body in laboratory mouse strains when the fusion centromeres are weaker than those of telocentrics. Conversely, fusion centromeres are stronger relative to telocentrics in natural house mouse populations that have changed karyotype by accumulating metacentric fusions. Our findings suggest that natural variation in centromere strength explains how the direction of drive can switch between populations. They also provide a cell biological basis of centromere drive and karyotype evolution. Copyright © 2014 Elsevier Ltd. All rights reserved.

  13. Somatic transposition and meiotically driven elimination of an active helitron family in Pleurotus ostreatus.

    Science.gov (United States)

    Borgognone, Alessandra; Castanera, Raúl; Muguerza, Elaia; Pisabarro, Antonio G; Ramírez, Lucía

    2017-04-01

    Helitrons constitute a superfamily of DNA transposons that were discovered in silico and are widespread in most eukaryotic genomes. They are postulated to mobilize through a "rolling-circle" mechanism, but the experimental evidence of their transposition has been described only recently. Here, we present the inheritance patterns of HELPO1 and HELPO2 helitron families in meiotically derived progeny of the basidiomycete Pleurotus ostreatus. We found distorted segregation patterns of HELPO2 helitrons that led to a strong under-representation of these elements in the progeny. Further investigation of HELPO2 flanking sites showed that gene conversion may contribute to the elimination of such repetitive elements in meiosis, favouring the presence of HELPO2 vacant loci. In addition, the analysis of HELPO2 content in a reconstructed pedigree of subclones maintained under different culture conditions revealed an event of helitron somatic transposition. Additional analyses of genome and transcriptome data indicated that P. ostreatus carries active RNAi machinery that could be involved in the control of transposable element proliferation. Our results provide the first evidence of helitron mobilization in the fungal kingdom and highlight the interaction between genome defence mechanisms and invasive DNA. © The Author 2017. Published by Oxford University Press on behalf of Kazusa DNA Research Institute.

  14. A sex-ratio meiotic drive system in Drosophila simulans. I: an autosomal suppressor.

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    Yun Tao

    2007-11-01

    Full Text Available Sex ratio distortion (sex-ratio for short has been reported in numerous species such as Drosophila, where distortion can readily be detected in experimental crosses, but the molecular mechanisms remain elusive. Here we characterize an autosomal sex-ratio suppressor from D. simulans that we designate as not much yang (nmy, polytene chromosome position 87F3. Nmy suppresses an X-linked sex-ratio distorter, contains a pair of near-perfect inverted repeats of 345 bp, and evidently originated through retrotransposition from the distorter itself. The suppression is likely mediated by sequence homology between the suppressor and distorter. The strength of sex-ratio is greatly enhanced by lower temperature. This temperature sensitivity was used to assign the sex-ratio etiology to the maturation process of the Y-bearing sperm, a hypothesis corroborated by both light microscope observations and ultrastructural studies. It has long been suggested that an X-linked sex-ratio distorter can evolve by exploiting loopholes in the meiotic machinery for its own transmission advantage, which may be offset by other changes in the genome that control the selfish distorter. Data obtained in this study help to understand this evolutionary mechanism in molecular detail and provide insight regarding its evolutionary impact on genomic architecture and speciation.

  15. Downregulation of surface sodium pumps by endocytosis during meiotic maturation of Xenopus laevis oocytes

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    Schmalzing, G.; Eckard, P.; Kroener, S.P.; Passow, H. (Max-Planck-Institut fuer Biophysik, Frankfurt (Germany, F.R.))

    1990-01-01

    During meiotic maturation, plasma membranes of Xenopus laevis oocytes completely lose the capacity to transport Na and K and to bind ouabain. To explore whether the downregulation might be due to an internalization of the sodium pump molecules, the intracellular binding of ouabain was determined. Selective permeabilization of the plasma membrane of mature oocytes (eggs) by digitonin almost failed to disclose ouabain binding sites. However, when the eggs were additionally treated with 0.02% sodium dodecyl sulfate (SDS) to permeabilize inner membranes, all sodium pumps present before maturation were recovered. Phosphorylation by (gamma-32P)ATP combined with SDS-polyacrylamide gel electrophoresis (PAGE) and autoradiography showed that sodium pumps were greatly reduced in isolated plasma membranes of eggs. According to sucrose gradient fractionation, maturation induced a shift of sodium pumps from the plasma membrane fraction to membranes of lower buoyant density with a protein composition different from that of the plasma membrane. Endocytosed sodium pumps identified on the sucrose gradient from (3H)ouabain bound to the cell surface before maturation could be phosphorylated with inorganic (32P)phosphate. The findings suggest that downregulation of sodium pumps during maturation is brought about by translocation of surface sodium pumps to an intracellular compartment, presumably endosomes. This contrasts the mechanism of downregulation of Na-dependent cotransport systems, the activities of which are reduced as a consequence of a maturation-induced depolarization of the membrane without a removal of the corresponding transporter from the plasma membrane.

  16. Meiotic changes in Vicia faba L. subsequent to treatments of hydrazine hydrate and maleic hydrazide

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    Shaheen Husain

    2013-01-01

    Full Text Available Assessing the impact of mutagens for creating variations in crops like faba bean (Vicia faba L. is an important criterion in the contemporary world where food insecurity and malnutrition is alarming at the doors of various nations. Impact of two chemical mutagens viz. hydrazine hydrate (HZ and maleic hydrazide (MH on the two varieties (NDF-1 and HB-405 of Vicia faba were analysed in terms of meiotic behavior and pollen sterility. Since there are not enough data about the effect of these mutagens on the chromosomal behaviors of Vicia faba, this study presents the role of hydrazine hydrate and maleic hydrazide as well as various types of chromosomal aberrations in crop improvement. The lower concentration of mutagens showed less pollen sterility compared to the higher concentrations. Manipulation of plant structural component to induce desirable alternations provides valuable material for the breeders and could be used favorably for increasing mutation rate and obtaining a desirable spectrum of mutation in faba beans based on preliminary studies of cell division.

  17. Double trouble: combined action of meiotic drive and Wolbachia feminization in Eurema butterflies.

    Science.gov (United States)

    Kern, Peter; Cook, James M; Kageyama, Daisuke; Riegler, Markus

    2015-05-01

    Arthropod sex ratios can be manipulated by a diverse range of selfish genetic elements, including maternally inherited Wolbachia bacteria. Feminization by Wolbachia is rare but has been described for Eurema mandarina butterflies. In this species, some phenotypic and functional females, thought to be ZZ genetic males, are infected with a feminizing Wolbachia strain, wFem. Meanwhile, heterogametic WZ females are not infected with wFem. Here, we establish a quantitative PCR assay allowing reliable sexing in three Eurema species. Against expectation, all E. mandarina females, including wFem females, had only one Z chromosome that was paternally inherited. Observation of somatic interphase nuclei confirmed that W chromatin was absent in wFem females, but present in females without wFem. We conclude that the sex bias in wFem lines is due to meiotic drive (MD) that excludes the maternal Z and thus prevents formation of ZZ males. Furthermore, wFem lines may have lost the W chromosome or harbour a dysfunctional version, yet rely on wFem for female development; removal of wFem results in all-male offspring. This is the first study that demonstrates an interaction between MD and Wolbachia feminization, and it highlights endosymbionts as potentially confounding factors in MD of sex chromosomes. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  18. Ubc9 sumoylation controls SUMO chain formation and meiotic synapsis in Saccharomyces cerevisiae.

    Science.gov (United States)

    Klug, Helene; Xaver, Martin; Chaugule, Viduth K; Koidl, Stefanie; Mittler, Gerhard; Klein, Franz; Pichler, Andrea

    2013-06-06

    Posttranslational modification with the small ubiquitin-related modifier SUMO depends on the sequential activities of E1, E2, and E3 enzymes. While regulation by E3 ligases and SUMO proteases is well understood, current knowledge of E2 regulation is very limited. Here, we describe modification of the budding yeast E2 enzyme Ubc9 by sumoylation (Ubc9(*)SUMO). Although less than 1% of Ubc9 is sumoylated at Lys153 at steady state, a sumoylation-deficient mutant showed significantly reduced meiotic SUMO conjugates and abrogates synaptonemal complex formation. Biochemical analysis revealed that Ubc9(*)SUMO is severely impaired in its classical activity but promoted SUMO chain assembly in the presence of Ubc9. Ubc9(*)SUMO cooperates with charged Ubc9 (Ubc9~SUMO) by noncovalent backside SUMO binding and by positioning the donor SUMO for optimal transfer. Thus, sumoylation of Ubc9 converts an active enzyme into a cofactor and reveals a mechanism for E2 regulation that orchestrates catalytic (Ubc9~SUMO) and noncatalytic (Ubc9(*)SUMO) functions of Ubc9. Copyright © 2013 Elsevier Inc. All rights reserved.

  19. Localized chiasmata and meiotic nodules in the tetraploid onion Allium porrum.

    Science.gov (United States)

    Stack, S M; Roelofs, D

    1996-08-01

    Allium porrum L. (cultivated leek) (2n = 4x = 32) is a fertile tetraploid that forms bivalents with pericentric chiasmata at metaphase I. To investigate the basis of this unusual behavior for a tetraploid, we describe the karyotype, axial cores, synaptonemal complexes (SCs), and meiotic nodules of A. porrum. The karyotype appears to be autotetraploid. This conclusion is also supported by presynaptic alignment of axial cores in groups of four and partner trades between pairs of SCs. Numerous early nodules are distributed all along axial cores and SCs during zygonema, but they are lost by late zygonema - early pachynema. Late (recombination) nodules (RNs) are present on SCs near kinetochores throughout the remainder of pachynema. This pattern of RNs corresponds to the pattern of pericentric chiasmata. Pachytene quadrivalents usually are resolved into bivalents because partner trades between SC lateral elements rarely occur between RNs on the same segment of SC. Thus, the patterns of crossing-over and partner trades promote balanced disjunction and high fertility in autotetraploid A. porrum. Rare quadrivalents observed at metaphase I must be due to infrequent partner trades between RNs. Polycomplexes, unusual in their number and size, were observed during zygonema. Key words : synaptonemal complex, recombination nodules, localized chiasmata, polycomplex, Allium porrum.

  20. Effects of Mild and Severe Vitamin B Deficiencies on the Meiotic Maturation of Mice Oocytes

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    Ai Tsuji

    2017-03-01

    Full Text Available We investigated the effects of vitamin B 1 deficiency on the meiosis maturation of oocytes. Female Crl:CD1 (ICR mice were fed a 20% casein diet (control group or a vitamin B 1 –free diet (test group. The vitamin B 1 concentration in ovary was approximately 30% lower in the test group than in the control group. Oocyte meiosis was not affected by vitamin B 1 deficiency when the deficiency was not accompanied by body weight loss. On the contrary, frequency of abnormal oocyte was increased by vitamin B 1 deficiency when deficiency was accompanied by body weight loss (referred to as severe vitamin B 1 deficiency; frequency of abnormal oocyte, 13.8% vs 43.7%, P  = .0071. The frequency of abnormal oocytes was decreased by refeeding of a vitamin B 1 –containing diet (13.9% vs 22.9%, P  = .503. These results suggest that severe vitamin B 1 deficiency inhibited meiotic maturation of oocytes but did not damage immature oocytes.

  1. Complex History and Differentiation Patterns of the t-Haplotype, a Mouse Meiotic Driver.

    Science.gov (United States)

    Kelemen, Reka K; Vicoso, Beatriz

    2017-11-14

    The t-haplotype, a mouse meiotic driver found on chromosome 17, has been a model for autosomal segregation distortion for close to a century, but several questions remain regarding its biology and evolutionary history. A recently published set of population genomics resources for wild mice includes several individuals heterozygous for the t-haplotype, which we use to characterize this selfish element at the genomic and transcriptomic level. Our results show that large sections of the t-haplotype have been replaced by standard homologous sequences, possibly due to occasional events of recombination, and that this complicates the inference of its history. As expected for a long genomic segment of very low recombination, the t-haplotype carries an excess of fixed nonsynonymous mutations compared to the standard chromosome. This excess is stronger for regions that have not undergone recent recombination, suggesting that occasional gene flow between the t and the standard chromosome may provide a mechanism to regenerate coding sequences that have accumulated deleterious mutations. Finally, we find that t-complex genes with altered expression largely overlap with deleted or amplified regions, and that carrying a t-haplotype alters the testis expression of genes outside of the t-complex, providing new leads into the pathways involved in the biology of this segregation distorter. Copyright © 2017, Genetics.

  2. Meiotic recombination analyses of individual chromosomes in male domestic pigs (Sus scrofa domestica).

    Science.gov (United States)

    Mary, Nicolas; Barasc, Harmonie; Ferchaud, Stéphane; Billon, Yvon; Meslier, Frédéric; Robelin, David; Calgaro, Anne; Loustau-Dudez, Anne-Marie; Bonnet, Nathalie; Yerle, Martine; Acloque, Hervé; Ducos, Alain; Pinton, Alain

    2014-01-01

    For the first time in the domestic pig, meiotic recombination along the 18 porcine autosomes was directly studied by immunolocalization of MLH1 protein. In total, 7,848 synaptonemal complexes from 436 spermatocytes were analyzed, and 13,969 recombination sites were mapped. Individual chromosomes for 113 of the 436 cells (representing 2,034 synaptonemal complexes) were identified by immunostaining and fluorescence in situ hybridization (FISH). The average total length of autosomal synaptonemal complexes per cell was 190.3 µm, with 32.0 recombination sites (crossovers), on average, per cell. The number of crossovers and the lengths of the autosomal synaptonemal complexes showed significant intra- (i.e. between cells) and inter-individual variations. The distributions of recombination sites within each chromosomal category were similar: crossovers in metacentric and submetacentric chromosomes were concentrated in the telomeric regions of the p- and q-arms, whereas two hotspots were located near the centromere and in the telomeric region of acrocentrics. Lack of MLH1 foci was mainly observed in the smaller chromosomes, particularly chromosome 18 (SSC18) and the sex chromosomes. All autosomes displayed positive interference, with a large variability between the chromosomes.

  3. The SMC-5/6 Complex and the HIM-6 (BLM) Helicase Synergistically Promote Meiotic Recombination Intermediate Processing and Chromosome Maturation during Caenorhabditis elegans Meiosis.

    Science.gov (United States)

    Hong, Ye; Sonneville, Remi; Agostinho, Ana; Meier, Bettina; Wang, Bin; Blow, J Julian; Gartner, Anton

    2016-03-01

    Meiotic recombination is essential for the repair of programmed double strand breaks (DSBs) to generate crossovers (COs) during meiosis. The efficient processing of meiotic recombination intermediates not only needs various resolvases but also requires proper meiotic chromosome structure. The Smc5/6 complex belongs to the structural maintenance of chromosome (SMC) family and is closely related to cohesin and condensin. Although the Smc5/6 complex has been implicated in the processing of recombination intermediates during meiosis, it is not known how Smc5/6 controls meiotic DSB repair. Here, using Caenorhabditis elegans we show that the SMC-5/6 complex acts synergistically with HIM-6, an ortholog of the human Bloom syndrome helicase (BLM) during meiotic recombination. The concerted action of the SMC-5/6 complex and HIM-6 is important for processing recombination intermediates, CO regulation and bivalent maturation. Careful examination of meiotic chromosomal morphology reveals an accumulation of inter-chromosomal bridges in smc-5; him-6 double mutants, leading to compromised chromosome segregation during meiotic cell divisions. Interestingly, we found that the lethality of smc-5; him-6 can be rescued by loss of the conserved BRCA1 ortholog BRC-1. Furthermore, the combined deletion of smc-5 and him-6 leads to an irregular distribution of condensin and to chromosome decondensation defects reminiscent of condensin depletion. Lethality conferred by condensin depletion can also be rescued by BRC-1 depletion. Our results suggest that SMC-5/6 and HIM-6 can synergistically regulate recombination intermediate metabolism and suppress ectopic recombination by controlling chromosome architecture during meiosis.

  4. The SMC-5/6 Complex and the HIM-6 (BLM Helicase Synergistically Promote Meiotic Recombination Intermediate Processing and Chromosome Maturation during Caenorhabditis elegans Meiosis.

    Directory of Open Access Journals (Sweden)

    Ye Hong

    2016-03-01

    Full Text Available Meiotic recombination is essential for the repair of programmed double strand breaks (DSBs to generate crossovers (COs during meiosis. The efficient processing of meiotic recombination intermediates not only needs various resolvases but also requires proper meiotic chromosome structure. The Smc5/6 complex belongs to the structural maintenance of chromosome (SMC family and is closely related to cohesin and condensin. Although the Smc5/6 complex has been implicated in the processing of recombination intermediates during meiosis, it is not known how Smc5/6 controls meiotic DSB repair. Here, using Caenorhabditis elegans we show that the SMC-5/6 complex acts synergistically with HIM-6, an ortholog of the human Bloom syndrome helicase (BLM during meiotic recombination. The concerted action of the SMC-5/6 complex and HIM-6 is important for processing recombination intermediates, CO regulation and bivalent maturation. Careful examination of meiotic chromosomal morphology reveals an accumulation of inter-chromosomal bridges in smc-5; him-6 double mutants, leading to compromised chromosome segregation during meiotic cell divisions. Interestingly, we found that the lethality of smc-5; him-6 can be rescued by loss of the conserved BRCA1 ortholog BRC-1. Furthermore, the combined deletion of smc-5 and him-6 leads to an irregular distribution of condensin and to chromosome decondensation defects reminiscent of condensin depletion. Lethality conferred by condensin depletion can also be rescued by BRC-1 depletion. Our results suggest that SMC-5/6 and HIM-6 can synergistically regulate recombination intermediate metabolism and suppress ectopic recombination by controlling chromosome architecture during meiosis.

  5. Meiotic Progression in Arabidopsis Is Governed by Complex Regulatory Interactions between SMG7, TDM1, and the Meiosis I–Specific Cyclin TAM[W][OA

    Science.gov (United States)

    Bulankova, Petra; Riehs-Kearnan, Nina; Nowack, Moritz K.; Schnittger, Arp; Riha, Karel

    2010-01-01

    Meiosis is a modified cell division that produces four haploid nuclei from a single diploid cell in two rounds of chromosome segregation. Here, we analyze the role of Arabidopsis thaliana SUPPRESSOR WITH MORPHOGENETIC EFFECTS ON GENITALIA7 (SMG7), THREE DIVISION MUTANT1 (TDM1), and TARDY ASYNCHRONOUS MEIOSIS (TAM) in meiotic progression. SMG7 is a conserved nonsense-mediated mRNA decay factor that is also, in Arabidopsis, essential for completion of meiosis. Examination of activating CYCLIN DEPENDENT KINASE A;1 phosophorylation at Thr-161 suggests that the meiotic arrest observed in smg7 mutants is likely caused by a failure to downregulate cyclin-dependent kinase (CDK) activity at the end of the second meiotic division. Genetic analysis indicates that SMG7 and TDM1 act in the same pathway to facilitate exit from meiosis. We further demonstrate that the cyclin TAM is specifically expressed in meiosis I and has both stimulatory and inhibitory effects on progression to meiosis II. TAM knockouts skip the second meiotic division producing unreduced gametes, but inactivation of SMG7 or TDM1 alleviates TAM’s requirement for entry into meiosis II. We propose a model that meiotic progression in Arabidopsis pollen mother cells is driven by a yet to be identified cyclin-CDK activity that is modulated by regulatory interactions between TDM1, SMG7, and TAM. PMID:21119056

  6. Cytostatic factor proteins are present in male meiotic cells and beta-nerve growth factor increases mos levels in rat late spermatocytes.

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    Marie-Hélène Perrard

    Full Text Available BACKGROUND: In co-cultures of pachytene spermatocytes with Sertoli cells, beta-NGF regulates the second meiotic division by blocking secondary spermatocytes in metaphase (metaphase II, and thereby lowers round spermatid formation. In vertebrates, mature oocytes are arrested at metaphase II until fertilization, because of the presence of cytostatic factor (CSF in their cytoplasm. By analogy, we hypothesized the presence of CSF in male germ cells. METHODOLOGY/PRINCIPAL FINDINGS: We show here, that Mos, Emi2, cyclin E and Cdk2, the four proteins of CSF, and their respective mRNAs, are present in male rat meiotic cells; this was assessed by using Western blotting, immunocytochemistry and reverse transcriptase PCR. We measured the relative cellular levels of Mos, Emi2, Cyclin E and Cdk2 in the meiotic cells by flow cytometry and found that the four proteins increased throughout the first meiotic prophase, reaching their highest levels in middle to late pachytene spermatocytes, then decreased following the meiotic divisions. In co-cultures of pachytene spermatocytes with Sertoli cells, beta-NGF increased the number of metaphases II, while enhancing Mos and Emi2 levels in middle to late pachytene spermatocytes, pachytene spermatocytes in division and secondary spermatocytes. CONCLUSION/SIGNIFICANCE: Our results suggest that CSF is not restricted to the oocyte. In addition, they reinforce the view that NGF, by enhancing Mos in late spermatocytes, is one of the intra-testicular factors which adjusts the number of round spermatids that can be supported by Sertoli cells.

  7. Meiotic behavior of economically important plant species: the relationship between fertility and male sterility

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    Maria Suely Pagliarini

    2000-12-01

    Full Text Available Meiosis is an event of high evolutionary stability which culminates in a reduction of chromosome number. The normal and harmonious course of meiosis ensures gamete viability. The cytologic events of gametogenesis are controlled by a large number of genes that act from premeiotic to postmeiotic mitosis. Mutations in these genes cause anomalies that may impair fertility, and many abnormalities affecting plant fertility or causing total male sterility have been detected during the evaluation of meiotic behavior in some species. Some of these abnormalities have been frequently described in the literature, while others have not been previously reported. The most frequent abnormalities found in the species analyzed were irregular chromosome segregation, cytomixis, chromosome stickiness, mixoploidy, chromosome fragmentation, syncyte formation, abnormal spindles, and failure of cytokinesis. Uncommon abnormalities, such as chromosome elimination during microsporogenesis, were found in one species. Original meiotic mutations affecting different steps of meiosis were also observed in these species, especially in maize, Paspalum and soybean. Some mutants present characteristics that may be exploited successfully in breeding programs because they cause total male sterility.A meiose é um evento de alta estabilidade evolucionária que culmina na redução do número de cromossomos. O curso normal e harmonioso da meiose garante a viabilidade gamética. Os eventos citológicos da gametogênese são controlados por um grande número de genes que atuam desde as mitoses pré-meióticas até as pós-meióticas. Mutações nestes genes causam anomalias que podem afetar a fertilidade. Durante a avaliação do comportamento meiótico em algumas espécies de plantas, muitas anormalidades que afetaram a fertilidade ou causaram total macho-esterilidade foram detectadas. Algumas das anormalidades encontradas já eram descritas na literatura, enquanto outras eram

  8. Nuclear Chemistry.

    Science.gov (United States)

    Chemical and Engineering News, 1979

    1979-01-01

    Provides a brief review of the latest developments in nuclear chemistry. Nuclear research today is directed toward increased activity in radiopharmaceuticals and formation of new isotopes by high-energy, heavy-ion collisions. (Author/BB)

  9. Nuclear Scans

    Science.gov (United States)

    Nuclear scans use radioactive substances to see structures and functions inside your body. They use a special ... images. Most scans take 20 to 45 minutes. Nuclear scans can help doctors diagnose many conditions, including ...

  10. Interpopulation hybridization generates meiotically stable rDNA epigenetic variants in allotetraploid Tragopogon mirus.

    Science.gov (United States)

    Matyášek, Roman; Dobešová, Eva; Húska, Dalibor; Ježková, Ivana; Soltis, Pamela S; Soltis, Douglas E; Kovařík, Aleš

    2016-02-01

    Uniparental silencing of 35S rRNA genes (rDNA), known as nucleolar dominance (ND), is common in interspecific hybrids. Allotetraploid Tragopogon mirus composed of Tragopogon dubius (d) and Tragopogon porrifolius (p) genomes shows highly variable ND. To examine the molecular basis of such variation, we studied the genetic and epigenetic features of rDNA homeologs in several lines derived from recently and independently formed natural populations. Inbred lines derived from T. mirus with a dominant d-rDNA homeolog transmitted this expression pattern over generations, which may explain why it is prevalent among natural populations. In contrast, lines derived from the p-rDNA dominant progenitor were meiotically unstable, frequently switching to co-dominance. Interpopulation crosses between progenitors displaying reciprocal ND resulted in d-rDNA dominance, indicating immediate suppression of p-homeologs in F1 hybrids. Original p-rDNA dominance was not restored in later generations, even in those segregants that inherited the corresponding parental rDNA genotype, thus indicating the generation of additional p-rDNA and d-rDNA epigenetic variants. Despite preserved intergenic spacer (IGS) structure, they showed altered cytosine methylation and chromatin condensation patterns, and a correlation between expression, hypomethylation of RNA Pol I promoters and chromatin decondensation was apparent. Reversion of such epigenetic variants occurred rarely, resulting in co-dominance maintained in individuals with distinct genotypes. Generally, interpopulation crosses may generate epialleles that are not present in natural populations, underlying epigenetic dynamics in young allopolyploids. We hypothesize that highly expressed variants with distinct IGS features may induce heritable epigenetic reprogramming of the partner rDNA arrays, harmonizing the expression of thousands of genes in allopolyploids. © 2015 The Authors The Plant Journal © 2015 John Wiley & Sons Ltd.

  11. X chromosome control of meiotic chromosome synapsis in mouse inter-subspecific hybrids.

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    Tanmoy Bhattacharyya

    2014-02-01

    Full Text Available Hybrid sterility (HS belongs to reproductive isolation barriers that safeguard the integrity of species in statu nascendi. Although hybrid sterility occurs almost universally among animal and plant species, most of our current knowledge comes from the classical genetic studies on Drosophila interspecific crosses or introgressions. With the house mouse subspecies Mus m. musculus and Mus m. domesticus as a model, new research tools have become available for studies of the molecular mechanisms and genetic networks underlying HS. Here we used QTL analysis and intersubspecific chromosome substitution strains to identify a 4.7 Mb critical region on Chromosome X (Chr X harboring the Hstx2 HS locus, which causes asymmetrical spermatogenic arrest in reciprocal intersubspecific F1 hybrids. Subsequently, we mapped autosomal loci on Chrs 3, 9 and 13 that can abolish this asymmetry. Combination of immunofluorescent visualization of the proteins of synaptonemal complexes with whole-chromosome DNA FISH on pachytene spreads revealed that heterosubspecific, unlike consubspecific, homologous chromosomes are predisposed to asynapsis in F1 hybrid male and female meiosis. The asynapsis is under the trans- control of Hstx2 and Hst1/Prdm9 hybrid sterility genes in pachynemas of male but not female hybrids. The finding concurred with the fertility of intersubpecific F1 hybrid females homozygous for the Hstx2(Mmm allele and resolved the apparent conflict with the dominance theory of Haldane's rule. We propose that meiotic asynapsis in intersubspecific hybrids is a consequence of cis-acting mismatch between homologous chromosomes modulated by the trans-acting Hstx2 and Prdm9 hybrid male sterility genes.

  12. Nuclear weapons, nuclear effects, nuclear war

    Energy Technology Data Exchange (ETDEWEB)

    Bing, G.F.

    1991-08-20

    This paper provides a brief and mostly non-technical description of the militarily important features of nuclear weapons, of the physical phenomena associated with individual explosions, and of the expected or possible results of the use of many weapons in a nuclear war. Most emphasis is on the effects of so-called ``strategic exchanges.``

  13. JPRS Report, Nuclear Developments

    National Research Council Canada - National Science Library

    1989-01-01

    Partial Contents: Nuclear Weapons, Nuclear Development, Nuclear Power Plant, Uranium, Missiles, Space Firm Protested, Satellite, Rocket Launching, Nuclear Submarine, Environmental, Radioactivity, Nuclear Plant...

  14. Dicer1 depletion in male germ cells leads to infertility due to cumulative meiotic and spermiogenic defects.

    Directory of Open Access Journals (Sweden)

    Yannick Romero

    Full Text Available BACKGROUND: Spermatogenesis is a complex biological process that requires a highly specialized control of gene expression. In the past decade, small non-coding RNAs have emerged as critical regulators of gene expression both at the transcriptional and post-transcriptional level. DICER1, an RNAse III endonuclease, is essential for the biogenesis of several classes of small RNAs, including microRNAs (miRNAs and endogenous small interfering RNAs (endo-siRNAs, but is also critical for the degradation of toxic transposable elements. In this study, we investigated to which extent DICER1 is required for germ cell development and the progress of spermatogenesis in mice. PRINCIPAL FINDINGS: We show that the selective ablation of Dicer1 at the early onset of male germ cell development leads to infertility, due to multiple cumulative defects at the meiotic and post-meiotic stages culminating with the absence of functional spermatozoa. Alterations were observed in the first spermatogenic wave and include delayed progression of spermatocytes to prophase I and increased apoptosis, resulting in a reduced number of round spermatids. The transition from round to mature spermatozoa was also severely affected, since the few spermatozoa formed in mutant animals were immobile and misshapen, exhibiting morphological defects of the head and flagellum. We also found evidence that the expression of transposable elements of the SINE family is up-regulated in Dicer1-depleted spermatocytes. CONCLUSIONS/SIGNIFICANCE: Our findings indicate that DICER1 is dispensable for spermatogonial stem cell renewal and mitotic proliferation, but is required for germ cell differentiation through the meiotic and haploid phases of spermatogenesis.

  15. Support vector machine for classification of meiotic recombination hotspots and coldspots in Saccharomyces cerevisiae based on codon composition

    Directory of Open Access Journals (Sweden)

    Sun Xiao

    2006-04-01

    Full Text Available Abstract Background Meiotic double-strand breaks occur at relatively high frequencies in some genomic regions (hotspots and relatively low frequencies in others (coldspots. Hotspots and coldspots are receiving increasing attention in research into the mechanism of meiotic recombination. However, predicting hotspots and coldspots from DNA sequence information is still a challenging task. Results We present a novel method for classification of hot and cold ORFs located in hotspots and coldspots respectively in Saccharomyces cerevisiae, using support vector machine (SVM, which relies on codon composition differences. This method has achieved a high classification accuracy of 85.0%. Since codon composition is a fusion of codon usage bias and amino acid composition signals, the ability of these two kinds of sequence attributes to discriminate hot ORFs from cold ORFs was also investigated separately. Our results indicate that neither codon usage bias nor amino acid composition taken separately performed as well as codon composition. Moreover, our SVM based method was applied to the full genome: We predicted the hot/cold ORFs from the yeast genome by using cutoffs of recombination rate. We found that the performance of our method for predicting cold ORFs is not as good as that for predicting hot ORFs. Besides, we also observed a considerable correlation between meiotic recombination rate and amino acid composition of certain residues, which probably reflects the structural and functional dissimilarity between the hot and cold groups. Conclusion We have introduced a SVM-based novel method to discriminate hot ORFs from cold ones. Applying codon composition as sequence attributes, we have achieved a high classification accuracy, which suggests that codon composition has strong potential to be used as sequence attributes in the prediction of hot and cold ORFs.

  16. Epigenetic control may explain large within-plant heterogeneity of meiotic behavior in telocentric trisomics of rye.

    Science.gov (United States)

    Sybenga, J; Verhaar, H; Botje, D G A

    2008-04-01

    In telocentric trisomics (telotrisomics) of organisms in which the chromosomes normally have two distinct arms, a single chromosome arm with a centromere is present in addition to a complete diploid set of chromosomes. It is the simplest form of polysomy and suitable for analyzing meiotic pairing and recombination patterns in situations where chromosomes compete for pairing. When no suitable meiotic chromosome markers are available, four metaphase I configurations can be distinguished. Their relative frequencies are indicative of the pairing and recombination patterns. In short arm (1RS) telotrisomics of chromosome 1R of rye (Secale cereale) we observed great differences in pairing and recombination patterns among spikes from different tillers and clones of the same plants. Anthers within spikes were only very rarely different. We analyzed a large number of genotypes, including inbreds as well as hybrids. The effects of genetic and environmental conditions on heterogeneity, if any, were limited. Considering that the reproductive tissue of a spike is derived from one primordial cell, it seems that at the start of sexual differentiation there was variation among cells in chromosomal control, which at meiosis determines pairing and crossing-over competence. We suggest that it is an epigenetic system that rigidly maintains this pattern through generative differentiation. In competitive situations the combination most competent for pairing will pair preferentially, forming specific meiotic configurations with different frequencies for different spikes of the same plant. This would explain the heterogeneity between spikes and the homogeneity within spikes. The epigenetic system could involve chromatin conformation or DNA methylation. There were no signs of heterochromatinization.

  17. Hints for Metal-Preference Protein Sequence Determinants: Different Metal Binding Features of the Five Tetrahymena thermophila Metallothioneins

    Science.gov (United States)

    Espart, Anna; Marín, Maribel; Gil-Moreno, Selene; Palacios, Òscar; Amaro, Francisco; Martín-González, Ana; Gutiérrez, Juan C.; Capdevila, Mercè; Atrian, Sílvia

    2015-01-01

    The metal binding preference of metallothioneins (MTs) groups them in two extreme subsets, the Zn/Cd- and the Cu-thioneins. Ciliates harbor the largest MT gene/protein family reported so far, including 5 paralogs that exhibit relatively low sequence similarity, excepting MTT2 and MTT4. In Tetrahymena thermophila, three MTs (MTT1, MTT3 and MTT5) were considered Cd-thioneins and two (MTT2 and MTT4) Cu-thioneins, according to gene expression inducibility and phylogenetic analysis. In this study, the metal-binding abilities of the five MTT proteins were characterized, to obtain information about the folding and stability of their cognate- and non-cognate metal complexes, and to characterize the T. thermophila MT system at protein level. Hence, the five MTTs were recombinantly synthesized as Zn2+-, Cd2+- or Cu+-complexes, which were analyzed by electrospray mass spectrometry (ESI-MS), circular dichroism (CD), and UV-vis spectrophotometry. Among the Cd-thioneins, MTT1 and MTT5 were optimal for Cd2+ coordination, yielding unique Cd17- and Cd8- complexes, respectively. When binding Zn2+, they rendered a mixture of Zn-species. Only MTT5 was capable to coordinate Cu+, although yielding heteronuclear Zn-, Cu-species or highly unstable Cu-homometallic species. MTT3 exhibited poor binding abilities both for Cd2+ and for Cu+, and although not optimally, it yielded the best result when coordinating Zn2+. The two Cu-thioneins, MTT2 and MTT4 isoforms formed homometallic Cu-complexes (major Cu20-MTT) upon synthesis in Cu-supplemented hosts. Contrarily, they were unable to fold into stable Cd-complexes, while Zn-MTT species were only recovered for MTT4 (major Zn10-MTT4). Thus, the metal binding preferences of the five T. thermophila MTs correlate well with their previous classification as Cd- and Cu-thioneins, and globally, they can be classified from Zn/Cd- to Cu-thioneins according to the gradation: MTT1>MTT5>MTT3>MTT4>MTT2. The main mechanisms underlying the evolution and

  18. Comportamiento meiótico de diferentes especies de lulo, Solanum sp Meiotic behavior of lulo species, Solanum sp

    Directory of Open Access Journals (Sweden)

    Nancy Maricela Pareja Ordóñez

    2010-10-01

    Full Text Available Se realizó un análisis del comportamiento meiótico de las especies de lulo S. hirtum, S. quitoense y S. sessiliflorum, siguiendo la metodología convencional para los estudios de microsporogénesis. Se tomaron botones florales en diferentes estados de desarrollo, fijándolos por 24 horas en una solución de tres partes de etanol por una parte de ácido acético, saturada con trazas de cristales de cloruro férrico. Para la preparación de las placas se siguió la técnica de aplastamiento, se liberaron las células madres del grano de polen y finalmente se hicieron las observaciones bajo microscopía de luz. El análisis mostró que la meiosis se presenta en longitudes de antera que van desde los 2,79 mm hasta los 4,45 mm. La normalidad meiótica fue del 100%, tanto para meiosis I, como para la meiosis II. El índice meiótico en las tres especies fue del 99,98% lo cual indica que son buenos parentales y que pueden utilizarse en programas de cruzamiento. Las tres especies evaluadas tienen igual número de cromosomas (2n=2X=24. La frecuencia de anormalidades durante el proceso meiótico fue baja para S. hirtum, y alta para S. quitoense; sin embargo, la viabilidad polínica fue de gran magnitud (91,2-97,3%.An analysis of meiotic behavior of lulo species S. hirtum, S. quitoense and S. sessiliflorum, following the conventional methodology for studies of microsporogenesis was realized. Flower buds were taken at different stages of development, fixing them for 24 hours in a solution of three parts of ethanol per one part of acetic acid, saturated with traces of ferric chloride crystals. For the preparation of the slides following the technique of squash, releasing pollen mother cells and finally made the observations under light microscopy. The analysis showed that meiosis occurs in anther ranging from 2.79 to 4.45 mm. Meiotic normality was 100% for both meiosis I and II. The meiotic index in all three species was 99,98% indicating that they are

  19. Reproductive Performance of Holstein Dairy Cows Grazing in Dry-summer Subtropical Climatic Conditions: Effect of Heat Stress and Heat Shock on Meiotic Competence and Fertilization

    Directory of Open Access Journals (Sweden)

    Krishna Pavani

    2015-03-01

    Full Text Available The present study was designed to evaluate how environmental factors in a dry-summer subtropical climate in Terceira-Azores (situated in the North Atlantic Ocean: 38° 43′ N 27° 12′ W can affect dairy cow (Holstein fertility, as well as seasonal influence on in vitro oocytes maturation and embryos development. Impact of heat shock (HS effects on in vitro oocyte’s maturation and further embryo development after in vitro fertilization (IVF was also evaluated. For such purpose the result of the first artificial insemination (AI performed 60 to 90 days after calving of 6,300 cows were recorded for one year. In parallel, climatic data was obtained at different elevation points (n = 5 from 0 to 1,000 m and grazing points from 0 to 500 m, in Terceira island, and the temperature humidity index (THI was calculated. For in vitro experiments, oocytes (n = 706 were collected weekly during all year, for meiotic maturation and IVF. Further, to evaluate HS effect, 891 oocytes were collected in the cold moths (December, January, February and March and divided in three groups treated to HS for 24 h during in vitro maturation at: C (Control = 38.5°C, HS1 (39.5°C and HS2 (40.5°C. Oocytes from each group were used for meiotic assessment and IVF. Cleavage, morula and blastocyst development were evaluated respectively on day 2, 6, and 9 after IVF. A negative correlation between cow’s conception rate (CR and THI in grazing points (−91.3%; p<0.001 was observed. Mean THI in warmer months (June, July, August and September was 71.7±0.7 and the CR (40.2±1.5% while in cold months THI was 62.8±0.2 and CR was 63.8±0.4%. A similar impact was obtained with in vitro results in which nuclear maturation rate (NMR ranged from 78.4% (±8.0 to 44.3% (±8.1, while embryos development ranged from 53.8% (±5.8 to 36.3% (±3.3 in cold and warmer months respectively. In vitro HS results showed a significant decline (p<0.05 on NMR of oocytes for every 1°C rising

  20. In the polymorphic ciliate Tetrahymena vorax, the non-selective phagocytosis seen in microstomes changes to a highly selective process in macrostomes.

    Science.gov (United States)

    Grønlien, Heidi K; Berg, Trond; Løvlie, Arne M

    2002-07-01

    Ciliates use phagocytosis to acquire edible particles. The polymorphic ciliate Tetrahymena vorax appears in two forms ('microstomes' and 'macrostomes'). Transformation of microstomes into macrostomes takes place in the presence of the ciliate Tetrahymena thermophila and enables the macrostome to phagocytose the latter species. The non-specific, constitutive phagocytosis in microstomes thereby changes into a specific inducible process in macrostomes. The purpose of this study was to determine whether the phagocytotic process in macrostomes is specifically aimed at catching T. thermophila. The two forms of phagocytosis represent an interesting model system for studying the mechanism whereby phagosomes are formed. The macrostomal form capture deciliated and ciliated Tetrahymena thermophila, latex beads with diameters of 20.3 and 30.0 microm and small microstomal cells. However, the macrostomes select T. thermophila as a prey when they have the opportunity to choose between deciliated T. thermophila and latex beads and between T. thermophila and microstomes. The non-selective formation of phagosomes seen in microstomes changes to a highly selective process during the transformation to macrostomes. Unlike microstomes, macrostomes do not form a closed vacuole after capturing a latex bead, indicating that mechanical stimulation by the prey does not in itself trigger phagocytosis in the macrostomal form of T. vorax. Although macrostomes captured T. thermophila in preference to microstomes, phagocytosis of microstomes started immediately following capture, indicating that the substance/molecule that triggers the formation of the phagosome is not specific for T. thermophila cells. After capturing a T. thermophila cell, the macrostomal cell, which normally swims in a forward direction, reverses direction and swims backwards for a short time before starting to rotate. Macrostomal cells did not change their swimming pattern after capturing a latex bead. We believe, therefore

  1. Nuclear spectroscopy

    CERN Document Server

    Ajzenberg-Selove, Fay

    1960-01-01

    Nuclear Spectroscopy, Part B focuses on the ways in which experimental data may be analyzed to furnish information about nuclear parameters and nuclear models in terms of which the data are interpreted.This book discusses the elastic and inelastic potential scattering amplitudes, role of beta decay in nuclear physics, and general selection rules for electromagnetic transitions. The nuclear shell model, fundamental coupling procedure, vibrational spectra, and empirical determination of the complex potential are also covered. This publication is suitable for graduate students preparing for exper

  2. Human Chorionic Gonadotropin Mediated Generation of Reactive Oxygen Species Is Sufficient to Induce Meiotic Exit but Not Apoptosis in Rat Oocytes

    Directory of Open Access Journals (Sweden)

    Meenakshi Tiwari

    2017-09-01

    Full Text Available Generation of reactive oxygen species (ROS is associated with final stages of follicular development and ovulation in mammals. The human chorionic gonadotropin (hCG mimics the action of luteinizing hormone and triggers follicular development and ovulation. However, it remains unclear whether hCG induces generation of ROS, if yes, whether hCG-mediated increased level of ROS could induce meiotic exit and/or apoptosis in rat oocytes. For this purpose, cumulus–oocyte complexes (COCs were collected from ovary of experimental rats injected with 20 IU pregnant mare's serum gonadotropin for 48 h followed by 20 IU hCG for 0, 7, 14, and 21 h. The morphological changes in COCs, meiotic status of oocyte, total ROS, hydrogen peroxide (H2O2, inducible nitric oxide synthase (iNOS, nitric oxide (NO, Bax, Bcl-2, cytochrome c, telomerase reverse transcriptase (TERT expression levels, and DNA fragmentation were analyzed in COCs. Our data suggest that hCG surge increased total ROS as well as H2O2 levels but decreased iNOS expression and total NO level in oocytes. The hCG-mediated increased level of ROS was sufficient to induce meiotic cell cycle resumption in majority of oocytes as evidenced by meiotic exit from diplotene as well as metaphase-II (M-II arrest and their meiotic status. However, increase of ROS level due to hCG surge was not sufficient to trigger Bax and cytochrome c expression levels and DNA fragmentation in COCs. In addition, increased TERT activity was observed in oocytes collected 21 h post-hCG surge showing onset of oocyte aging. Taken together, these results suggest that hCG induces generation of ROS sufficient to trigger meiotic exit from diplotene, as well as M-II arrest, but not good enough to induce apoptosis in rat oocytes.

  3. Nuclear networking.

    Science.gov (United States)

    Xie, Wei; Burke, Brian

    2017-07-04

    Nuclear lamins are intermediate filament proteins that represent important structural components of metazoan nuclear envelopes (NEs). By combining proteomics and superresolution microscopy, we recently reported that both A- and B-type nuclear lamins form spatially distinct filament networks at the nuclear periphery of mouse fibroblasts. In particular, A-type lamins exhibit differential association with nuclear pore complexes (NPCs). Our studies reveal that the nuclear lamina network in mammalian somatic cells is less ordered and more complex than that of amphibian oocytes, the only other system in which the lamina has been visualized at high resolution. In addition, the NPC component Tpr likely links NPCs to the A-type lamin network, an association that appears to be regulated by C-terminal modification of various A-type lamin isoforms. Many questions remain, however, concerning the structure and assembly of lamin filaments, as well as with their mode of association with other nuclear components such as peripheral chromatin.

  4. TGN38 is required for the metaphase I/anaphase I transition and asymmetric cell division during mouse oocyte meiotic maturation

    OpenAIRE

    Chen, Lei; Ge, Zhao-Jia; Wang, Zhen-Bo; Sun, Tianyi; Ouyang, Ying-Chun; Sun, Qing-Yuan; Sun, Ying-Pu

    2014-01-01

    The cellular functions of the trans-Golgi network protein TGN38 remain unknown. In this research, we studied the expression, localization and functions of TGN38 in the meiotic maturation of mouse oocytes. TGN38 was expressed at every stage of oocyte meiotic maturation and colocalized with γ-tubulin at metaphase I and metaphase II. The spindle microtubule disturbing agents nocodazole and taxol did not affect the colocalization of TGN38 and γ-tubulin. Depletion of TGN38 with specific siRNAs res...

  5. Comparison of primary and secondary 26S rRNA structures in two Tetrahymena species: evidence for a strong evolutionary and structural constraint in expansion segments

    DEFF Research Database (Denmark)

    Engberg, J; Nielsen, Henrik; Lenaers, G

    1990-01-01

    . These are regions within the common core of secondary structure where expansions have taken place during the evolution of the rRNA of higher eukaryotes. The dispensable nature of some of the expansion segments has been taken as evidence of their non-functionality. However, our data show that a considerable......We have determined the nucleotide sequence of the 26S large subunit (LSU) rRNA genes for two Tetrahymena species, T. thermophila and T. pyriformis. The inferred rRNA sequences are presented in their most probable secondary structures based on compensatory mutations, energy, and conservation...... selective constraint has operated to preserve the secondary structure of these segments. Especially in the case of the D2 and D8 segments, the presence of a considerable number of compensatory base changes suggests that the secondary structure of these regions is of functional importance. Alternatively...

  6. Bee algorithm and adaptive neuro-fuzzy inference system as tools for QSAR study toxicity of substituted benzenes to Tetrahymena pyriformis.

    Science.gov (United States)

    Zarei, Kobra; Atabati, Morteza; Kor, Kamalodin

    2014-06-01

    A quantitative structure-activity relationship (QSAR) was developed to predict the toxicity of substituted benzenes to Tetrahymena pyriformis. A set of 1,497 zero- to three-dimensional descriptors were used for each molecule in the data set. A major problem of QSAR is the high dimensionality of the descriptor space; therefore, descriptor selection is one of the most important steps. In this paper, bee algorithm was used to select the best descriptors. Three descriptors were selected and used as inputs for adaptive neuro-fuzzy inference system (ANFIS). Then the model was corrected for unstable compounds (the compounds that can be ionized in the aqueous solutions or can easily metabolize under some conditions). Finally squared correlation coefficients were obtained as 0.8769, 0.8649 and 0.8301 for training, test and validation sets, respectively. The results showed bee-ANFIS can be used as a powerful model for prediction of toxicity of substituted benzenes to T. pyriformis.

  7. 8-Methoxypsoralen DNA interstrand cross-linking of the ribosomal RNA genes in Tetrahymena thermophila. Distribution, repair and effect on rRNA synthesis

    DEFF Research Database (Denmark)

    Fengquin, X; Nielsen, Henrik; Zhen, W

    1993-01-01

    The distribution and repair of 8-methoxypsoralen-DNA interstrand cross-links in the ribosomal RNA genes (rDNA) in Tetrahymena thermophila have been studied in vivo by Southern blot analysis. It is found that the cross-links at a density of ... between three domains (terminal spacer, transcribed region and central spacer) as defined by restriction enzyme analysis (BamHI and ClaI). It is furthermore shown that a dosage resulting in approximately one cross-link per rDNA molecule (21 kbp, two genes) is sufficient to block RNA synthesis. Finally......, it is shown that the cross-links in the rDNA molecules are repaired at equal rate in all three domains within 24 h and that RNA synthesis is partly restored during this repair period. The majority of the cells also go through one to two cell divisions in this period but do not survive....

  8. Sodium-dependent uptake of [3H]scyllo-inositol by Tetrahymena: incorporation into phosphatidylinositol, phosphatidylinositol-linked glycans, and polyphosphoinositols.

    Science.gov (United States)

    Ryals, P E; Kersting, M C

    1999-06-15

    [3H]Scyllo-inositol was taken up by Tetrahymena cells through a sodium-dependent pathway wherein unlabeled scyllo- and myo-inositol competed for uptake. d-Glucose was a competitor of [3H]myo-inositol uptake, but did not appear to compete for [3H]scyllo-inositol uptake. Transport of [3H]scyllo- and [3H]myo-inositol was inhibited when sodium was removed from the labeling buffer and by phlorizin, an inhibitor of sodium-dependent transporters. Cytochalasin B, an inhibitor of facilitated glucose transporters, had no significant effect on inositol transport. Internalized [3H]scyllo-inositol was readily incorporated intact into phosphatidylinositol, phosphatidylinositol-linked glycans, and polyphosphoinositols. Distribution of [3H]scyllo- and [3H]myo-inositol radioactivity into individual polyphosphoinositols was found to differ. Copyright 1999 Academic Press.

  9. The oral apparatus of Tetrahymena pyriformis, strain WH-6. III. The binding of 3H-cytochalasin B by the isolated oral apparatus.

    Science.gov (United States)

    Gavin, R H

    1976-07-01

    The binding of tritium-labelled cytochalasin B by the isolated oral apparatus of Tetrahymena pyriformis, strain WH-6, syngen 1, was investigated. Equilibrium binding studies revealed approximately 1.4 x 10(5) cytochalasin B binding sites per oral apparatus. A Scatchard plot indicates a single class of binding affinities with an association constant of 10(5) liters/mole. Rapid release of oral apparatus-bound cytochalasin B occurred when oral apparatuses were washed and resuspended in 1 mM TRIS without cytochalasin B. Because cytochalasin B binding to oral apparatus microtubular protein was not detected, microtubules are probably not the cytochalasin B binding site. The probable nature of the cytochalasin B binding site within the oral apparatus is discussed.

  10. Sperm DNA Integrity and Meiotic Behavior Assessment in an Infertile Male Carrier of a 9qh+++ Polymorphism

    Directory of Open Access Journals (Sweden)

    A. García-Peiró

    2011-01-01

    Full Text Available Although several reports on male infertility suggest a relationship between chromosome 9 polymorphisms and infertility, the effects on the phenotype have not been extensively reported. In this study, an infertile patient was found to carry a 9qh+++ chromosome. The flow cytometric TUNEL assay and SCD test have been applied to characterize sperm DNA integrity. In order to assess its meiotic behaviour, synapsis, recombination, and aneuploidy, analyses have been also performed. Sperm DNA fragmentation (SDF was 77.81% and 87% for the TUNEL and SCD tests, respectively. Ninety-two percent of pachytene cells analyzed showed meiotic abnormalities. The mean number of MLH1 foci per pachytene in the control group was higher (49 than the mean found in the 9qh+++ patient (38 (P<.0001. In spermatozoa, significant increases of disomy rates were observed for chromosome 18 and for the sex chromosomes (P<.0001. These disturbances could be present in other male carriers of a less marked 9qh+.

  11. The p53-like Protein CEP-1 Is Required for Meiotic Fidelity in C. elegans.

    Science.gov (United States)

    Mateo, Abigail-Rachele F; Kessler, Zebulin; Jolliffe, Anita Kristine; McGovern, Olivia; Yu, Bin; Nicolucci, Alissa; Yanowitz, Judith L; Derry, W Brent

    2016-05-09

    The passage of genetic information during meiosis requires exceptionally high fidelity to prevent birth defects and infertility. Accurate chromosome segregation during the first meiotic division relies on the formation of crossovers between homologous chromosomes and a series of precisely controlled steps to exchange genetic information. Many studies have hinted at a role for p53 in meiosis, but how it functions in this process is poorly understood. Here, we have identified a cooperative role for the p53-like protein CEP-1 and the meiotic protein HIM-5 in maintaining genome stability in the C. elegans germline. Loss of cep-1 and him-5 results in synthetic lethality that is dependent on the upstream DNA damage checkpoint but independent of the downstream core apoptotic pathway. We show that this synthetic lethality is the result of defective crossover formation due to reduced SPO-11-dependent double-strand breaks. Using cep-1 separation-of-function alleles, we show that cep-1 and him-5 also suppress inappropriate activation of the nonhomologous end joining (NHEJ) pathway. This work reveals an ancestral function for the p53 family in ensuring the fidelity of meiosis and establishes CEP-1 as a critical determinant of repair pathway choice. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. PRDM9 drives evolutionary erosion of hotspots in Mus musculus through haplotype-specific initiation of meiotic recombination.

    Directory of Open Access Journals (Sweden)

    Christopher L Baker

    2015-01-01

    Full Text Available Meiotic recombination generates new genetic variation and assures the proper segregation of chromosomes in gametes. PRDM9, a zinc finger protein with histone methyltransferase activity, initiates meiotic recombination by binding DNA at recombination hotspots and directing the position of DNA double-strand breaks (DSB. The DSB repair mechanism suggests that hotspots should eventually self-destruct, yet genome-wide recombination levels remain constant, a conundrum known as the hotspot paradox. To test if PRDM9 drives this evolutionary erosion, we measured activity of the Prdm9Cst allele in two Mus musculus subspecies, M.m. castaneus, in which Prdm9Cst arose, and M.m. domesticus, into which Prdm9Cst was introduced experimentally. Comparing these two strains, we find that haplotype differences at hotspots lead to qualitative and quantitative changes in PRDM9 binding and activity. Using Mus spretus as an outlier, we found most variants affecting PRDM9Cst binding arose and were fixed in M.m. castaneus, suppressing hotspot activity. Furthermore, M.m. castaneus×M.m. domesticus F1 hybrids exhibit novel hotspots, with large haplotype biases in both PRDM9 binding and chromatin modification. These novel hotspots represent sites of historic evolutionary erosion that become activated in hybrids due to crosstalk between one parent's Prdm9 allele and the opposite parent's chromosome. Together these data support a model where haplotype-specific PRDM9 binding directs biased gene conversion at hotspots, ultimately leading to hotspot erosion.

  13. The rad9 gene of Coprinus cinereus encodes a proline-rich protein required for meiotic chromosome condensation and synapsis

    Energy Technology Data Exchange (ETDEWEB)

    Seitz, L.C.; Tang, Keliang; Cummings, W.J.; Zolan, M.E. [Indiana Univ., Bloomington, IN (United States)

    1996-04-01

    The rad9 gene of Coprinus cinereus is essential for the normal completion of meiosis. We examined surface-spread preparations of wild-type and rad9-1 nuclei from the meiotic stages of karyogamy through metaphase I, and we determined the primary sequence, structure, and meiotic expression of the rad9 gene. In wild-type C. cinereus, karyogamy is followed by condensation and alignment of homologous chromosomes. Condensation and axial core development largely precede synapsis, which often initiates at telomeres. A diffuse diplotene phase coincides with dissolution of the synaptonemal complex, and subsequently chromosomes further condense as the cells progress into metaphase I. In contrast, although karyogamy and nucleolar fusion are apparently normal in rad9-1 basidia, only short stretches of synaptonemal complex form. These correlate with stretches of condensed chromatin, mostly at apparent chromosome ends, and regions of presumptive triple synapsis are numerous. rad9-1 basidia enter the diffuse stages of early diplotene, and then 50% of these cells enter metaphase I by the criteria of nucleolar elimination and at least some chromatin condensation. rad9 gene expression is induced after gamma irradiation and during meiosis. The gene has 27 exons and encodes a predicted protein of 2157 amino acids, with a proline-rich amino terminus. 62 refs., 10 figs.

  14. The Rad9 Gene of Coprinus Cinereus Encodes a Proline-Rich Protein Required for Meiotic Chromosome Condensation and Synapsis

    Science.gov (United States)

    Seitz, L. C.; Tang, K.; Cummings, W. J.; Zolan, M. E.

    1996-01-01

    The rad9 gene of Coprinus cinereus is essential for the normal completion of meiosis. We examined surface-spread preparations of wild-type and rad9-1 nuclei from the meiotic stages of karyogamy through metaphase I, and we determined the primary sequence, structure, and meiotic expression of the rad9 gene. In wild-type C. cinereus, karyogamy is followed by condensation and alignment of homologous chromosomes. Condensation and axial core development largely precede synapsis, which often initiates at telomeres. A diffuse diplotene phase coincides with dissolution of the synaptonemal complex, and subsequently chromosomes further condense as the cells progress into metaphase I. In contrast, although karyogamy and nucleolar fusion are apparently normal in rad9-1 basidia, only short stretches of synaptonemal complex form. These correlate with stretches of condensed chromatin, mostly at apparent chromosome ends, and regions of presumptive triple synapsis are numerous. rad9-1 basidia enter the diffuse stage of early diplotene, and then 50% of these cells enter metaphase I by the criteria of nucleolar elimination and at least some chromatin condensation. rad9 gene expression is induced after gamma irradiation and during meiosis. The gene has 27 exons and encodes a predicted protein of 2157 amino acids, with a proline-rich amino terminus. PMID:8846891

  15. PRDM9 drives evolutionary erosion of hotspots in Mus musculus through haplotype-specific initiation of meiotic recombination.

    Science.gov (United States)

    Baker, Christopher L; Kajita, Shimpei; Walker, Michael; Saxl, Ruth L; Raghupathy, Narayanan; Choi, Kwangbom; Petkov, Petko M; Paigen, Kenneth

    2015-01-01

    Meiotic recombination generates new genetic variation and assures the proper segregation of chromosomes in gametes. PRDM9, a zinc finger protein with histone methyltransferase activity, initiates meiotic recombination by binding DNA at recombination hotspots and directing the position of DNA double-strand breaks (DSB). The DSB repair mechanism suggests that hotspots should eventually self-destruct, yet genome-wide recombination levels remain constant, a conundrum known as the hotspot paradox. To test if PRDM9 drives this evolutionary erosion, we measured activity of the Prdm9Cst allele in two Mus musculus subspecies, M.m. castaneus, in which Prdm9Cst arose, and M.m. domesticus, into which Prdm9Cst was introduced experimentally. Comparing these two strains, we find that haplotype differences at hotspots lead to qualitative and quantitative changes in PRDM9 binding and activity. Using Mus spretus as an outlier, we found most variants affecting PRDM9Cst binding arose and were fixed in M.m. castaneus, suppressing hotspot activity. Furthermore, M.m. castaneus×M.m. domesticus F1 hybrids exhibit novel hotspots, with large haplotype biases in both PRDM9 binding and chromatin modification. These novel hotspots represent sites of historic evolutionary erosion that become activated in hybrids due to crosstalk between one parent's Prdm9 allele and the opposite parent's chromosome. Together these data support a model where haplotype-specific PRDM9 binding directs biased gene conversion at hotspots, ultimately leading to hotspot erosion.

  16. Cytoplasmic and Genomic Effects on Meiotic Pairing in Brassica Hybrids and Allotetraploids from Pair Crosses of Three Cultivated Diploids

    Science.gov (United States)

    Cui, Cheng; Ge, Xianhong; Gautam, Mayank; Kang, Lei; Li, Zaiyun

    2012-01-01

    Interspecific hybridization and allopolyploidization contribute to the origin of many important crops. Synthetic Brassica is a widely used model for the study of genetic recombination and “fixed heterosis” in allopolyploids. To investigate the effects of the cytoplasm and genome combinations on meiotic recombination, we produced digenomic diploid and triploid hybrids and trigenomic triploid hybrids from the reciprocal crosses of three Brassica diploids (B. rapa, AA; B. nigra, BB; B. oleracea, CC). The chromosomes in the resultant hybrids were doubled to obtain three allotetraploids (B. juncea, AA.BB; B. napus, AA.CC; B. carinata, BB.CC). Intra- and intergenomic chromosome pairings in these hybrids were quantified using genomic in situ hybridization and BAC-FISH. The level of intra- and intergenomic pairings varied significantly, depending on the genome combinations and the cytoplasmic background and/or their interaction. The extent of intragenomic pairing was less than that of intergenomic pairing within each genome. The extent of pairing variations within the B genome was less than that within the A and C genomes, each of which had a similar extent of pairing. Synthetic allotetraploids exhibited nondiploidized meiotic behavior, and their chromosomal instabilities were correlated with the relationship of the genomes and cytoplasmic background. Our results highlight the specific roles of the cytoplasm and genome to the chromosomal behaviors of hybrids and allopolyploids. PMID:22505621

  17. Sex chromosome-specific regulation in the Drosophila male germline but little evidence for chromosomal dosage compensation or meiotic inactivation.

    Directory of Open Access Journals (Sweden)

    Colin D Meiklejohn

    2011-08-01

    Full Text Available The evolution of heteromorphic sex chromosomes (e.g., XY in males or ZW in females has repeatedly elicited the evolution of two kinds of chromosome-specific regulation: dosage compensation--the equalization of X chromosome gene expression in males and females--and meiotic sex chromosome inactivation (MSCI--the transcriptional silencing and heterochromatinization of the X during meiosis in the male (or Z in the female germline. How the X chromosome is regulated in the Drosophila melanogaster male germline is unclear. Here we report three new findings concerning gene expression from the X in Drosophila testes. First, X chromosome-wide dosage compensation appears to be absent from most of the Drosophila male germline. Second, microarray analysis provides no evidence for X chromosome-specific inactivation during meiosis. Third, we confirm the previous discovery that the expression of transgene reporters driven by autosomal spermatogenesis-specific promoters is strongly reduced when inserted on the X chromosome versus the autosomes; but we show that this chromosomal difference in expression is established in premeiotic cells and persists in meiotic cells. The magnitude of the X-autosome difference in transgene expression cannot be explained by the absence of dosage compensation, suggesting that a previously unrecognized mechanism limits expression from the X during spermatogenesis in Drosophila. These findings help to resolve several previously conflicting reports and have implications for patterns of genome evolution and speciation in Drosophila.

  18. Conditional ablation of Raptor in the male germline causes infertility due to meiotic arrest and impaired inactivation of sex chromosomes.

    Science.gov (United States)

    Xiong, Mengneng; Zhu, Zhiping; Tian, Suwen; Zhu, Ruping; Bai, Shun; Fu, Kaiqiang; Davis, James G; Sun, Zheng; Baur, Joseph A; Zheng, Ke; Ye, Lan

    2017-09-01

    Rapamycin is a clinically important drug that is used in transplantation and cancer therapy but which causes a number of side effects, including male infertility. Its canonical target, mammalian target of rapamycin complex 1 (mTORC1), plays a key role in metabolism and binds chromatin; however, its precise role in the male germline has not been elucidated. Here, we inactivate the core component, Raptor, to show that mTORC1 function is critical for male meiosis and the inactivation of sex chromosomes. Disruption of the Raptor gene impairs chromosomal synapsis and prevents the efficient spreading of silencing factors into the XY chromatin. Accordingly, mRNA for XY-linked genes remains inappropriately expressed in Raptor-deficient mice. Molecularly, the failure to suppress gene expression corresponded with deficiencies in 2 repressive chromatin markers, H3K9 dimethylation and H3K9 trimethylation, in the XY body. Together, these results demonstrate that mTORC1 has an essential role in the meiotic progression and silencing of sex chromosomes in the male germline, which may explain the infertility that has been associated with such inhibitors as rapamycin.-Xiong, M., Zhu, Z., Tian, S., Zhu, R., Bai, S., Fu, K., Davis, J. G., Sun, Z., Baur, J. A., Zheng, K., Ye, L. Conditional ablation of Raptor in the male germline causes infertility due to meiotic arrest and impaired inactivation of sex chromosomes. © FASEB.

  19. Fitness Costs and Variation in Transmission Distortion Associated with the Abnormal Chromosome 10 Meiotic Drive System in Maize.

    Science.gov (United States)

    Higgins, David M; Lowry, Elizabeth G; Kanizay, Lisa B; Becraft, Philip W; Hall, David W; Dawe, R Kelly

    2017-11-09

    Meiotic drive describes a process whereby selfish genetic elements are transmitted at levels greater than Mendelian expectations. Maize abnormal chromosome 10 (Ab10) encodes a meiotic drive system that exhibits strong preferential segregation through female gametes. We performed transmission assays of nine Ab10 chromosomes from landraces and teosinte lines and found a transmission advantage of 62% to 79% in heterozygotes. Despite this transmission advantage, Ab10 is present at low frequencies in natural populations, suggesting that it carries large negative fitness consequences. We measured pollen transmission, percentage of live pollen, seed production, and seed size to estimate several of the possible fitness effects of Ab10. We found no evidence that Ab10 affects pollen transmission, i.e. Ab10 and N10 pollen are transmitted equally from heterozygous fathers. However, at the diploid (sporophyte) level, both heterozygous and homozygous Ab10-I-MMR individuals show decreased pollen viability, decreased seed set, and decreased seed weight. The observed fitness costs can nearly but not entirely account for the observed frequencies of Ab10. Sequence analysis shows a surprising amount of molecular variation among Ab10 haplotypes, suggesting that there may be other phenotypic variables that contribute to the low but stable equilibrium frequencies. Copyright © 2017, Genetics.

  20. Origin of triploid Arachis pintoi (Leguminosae) by autopolyploidy evidenced by FISH and meiotic behaviour

    Science.gov (United States)

    Lavia, Graciela Inés; Ortiz, Alejandra Marcela; Robledo, Germán; Fernández, Aveliano; Seijo, Guillermo

    2011-01-01

    Background and Aims Polyploidy is a dominant feature of flowering-plant genomes, including those of many important crop species. Arachis is a largely diploid genus with just four polyploid species. Two of them are economically important: the cultivated peanut and A. glabrata, a tropical forage crop. Even though it is usually accepted that polyploids within papilionoid legumes have arisen via hybridization and further chromosome doubling, it has been recently suggested that peanut arose through bilateral sexual polyploidization. In this paper, the polyploid nature of the recent, spontaneously originated triploid cytotype of the tropical lucerne, A. pintoi, was analysed, and thereby the mechanism by which polyploids may arise in the genus. Methods Chromosome morphology of 2x and 3x A. pintoi was determined by the Feulgeńs technique and the rDNA sites were mapped by FISH. To investigate whether polyploidization occurred by means of unreduced gametes, a detailed analysis of the microsporogenesis and pollen grains was made. Key Results The 2x and 3x plants presented 9m + 1sm and a satellited chromosome type 2 in each haploid genome. Physical mapping revealed a cluster of 18S–26S rDNA, proximally located on chromosome 6, and two 5S rDNA loci on chromosomes 3 and 5. Diploid plants presented 10II in meiosis while trivalents were observed in all triploids, with a maximum of 10III by cell. Diploid A. pintoi produced normal tetrads, but also triads, dyads and monads. Two types of pollen grains were detected: (1) normal-sized with a prolate shape and (2) large ones with a tetrahedral morphology. Conclusions Karyotype and meiotic analysis demonstrate that the 3x clone of A. pintoi arose by autopolyploidy. The occurrence of unreduced gametes strongly supports unilateral sexual polyploidization as the most probable mechanism that could have led to the origin of the triploid cytotype. This mechanism of polyploidization would probably be one of the most important mechanisms

  1. Meiotic behavior of 18 species from eight families of terrestrial heteroptera.

    Science.gov (United States)

    De Souza, Hederson Vinicius; Castanhole, Márcia Maria Urbanin; Gomes, Mariana Oliveira; Murakami, Aline Sumitani; De Souza Firmino, Tatiani Seni; Saran, Priscila Samara; Banho, Cecilia Artico; Monteiro, Letícia Da Silva; Da Silva, Jocielly Cristina Pereira; Itoyama, Mary Massumi

    2014-10-15

    study extends the knowledge of these characteristics, such as the variations related to chromosome complements, sex chromosome systems, and meiotic behavior. © The Author 2014. Published by Oxford University Press on behalf of the Entomological Society of America.

  2. Cloning and characterization of the major histone H2A genes completes the cloning and sequencing of known histone genes of Tetrahymena thermophila.

    Science.gov (United States)

    Liu, X; Gorovsky, M A

    1996-01-01

    A truncated cDNA clone encoding Tetrahymena thermophila histone H2A2 was isolated using synthetic degenerate oligonucleotide probes derived from H2A protein sequences of Tetrahymena pyriformis. The cDNA clone was used as a homologous probe to isolate a truncated genomic clone encoding H2A1. The remaining regions of the genes for H2A1 (HTA1) and H2A2 (HTA2) were then isolated using inverse PCR on circularized genomic DNA fragments. These partial clones were assembled into intact HTA1 and HTA2 clones. Nucleotide sequences of the two genes were highly homologous within the coding region but not in the noncoding regions. Comparison of the deduced amino acid sequences with protein sequences of T. pyriformis H2As showed only two and three differences respectively, in a total of 137 amino acids for H2A1, and 132 amino acids for H2A2, indicating the two genes arose before the divergence of these two species. The HTA2 gene contains a TAA triplet within the coding region, encoding a glutamine residue. In contrast with the T. thermophila HHO and HTA3 genes, no introns were identified within the two genes. The 5'- and 3'-ends of the histone H2A mRNAs; were determined by RNase protection and by PCR mapping using RACE and RLM-RACE methods. Both genes encode polyadenylated mRNAs and are highly expressed in vegetatively growing cells but only weakly expressed in starved cultures. With the inclusion of these two genes, T. thermophila is the first organism whose entire complement of known core and linker histones, including replication-dependent and basal variants, has been cloned and sequenced. PMID:8760889

  3. Genome-wide identification and evolution of ATP-binding cassette transporters in the ciliate Tetrahymena thermophila: A case of functional divergence in a multigene family

    Directory of Open Access Journals (Sweden)

    Yuan Dongxia

    2010-10-01

    Full Text Available Abstract Background In eukaryotes, ABC transporters that utilize the energy of ATP hydrolysis to expel cellular substrates into the environment are responsible for most of the efflux from cells. Many members of the superfamily of ABC transporters have been linked with resistance to multiple drugs or toxins. Owing to their medical and toxicological importance, members of the ABC superfamily have been studied in several model organisms and warrant examination in newly sequenced genomes. Results A total of 165 ABC transporter genes, constituting a highly expanded superfamily relative to its size in other eukaryotes, were identified in the macronuclear genome of the ciliate Tetrahymena thermophila. Based on ortholog comparisons, phylogenetic topologies and intron characterizations, each highly expanded ABC transporter family of T. thermophila was classified into several distinct groups, and hypotheses about their evolutionary relationships are presented. A comprehensive microarray analysis revealed divergent expression patterns among the members of the ABC transporter superfamily during different states of physiology and development. Many of the relatively recently formed duplicate pairs within individual ABC transporter families exhibit significantly different expression patterns. Further analysis showed that multiple mechanisms have led to functional divergence that is responsible for the preservation of duplicated genes. Conclusion Gene duplications have resulted in an extensive expansion of the superfamily of ABC transporters in the Tetrahymena genome, making it the largest example of its kind reported in any organism to date. Multiple independent duplications and subsequent divergence contributed to the formation of different families of ABC transporter genes. Many of the members within a gene family exhibit different expression patterns. The combination of gene duplication followed by both sequence divergence and acquisition of new patterns of

  4. Nuclear astrophysics

    Energy Technology Data Exchange (ETDEWEB)

    Haxton, W.C.

    1992-01-01

    The problem of core-collapse supernovae is used to illustrate the many connections between nuclear astrophysics and the problems nuclear physicists study in terrestrial laboratories. Efforts to better understand the collapse and mantle ejection are also motivated by a variety of interdisciplinary issues in nuclear, particle, and astrophysics, including galactic chemical evolution, neutrino masses and mixing, and stellar cooling by the emission of new particles. The current status of theory and observations is summarized.

  5. Nuclear astrophysics

    Energy Technology Data Exchange (ETDEWEB)

    Haxton, W.C.

    1992-12-31

    The problem of core-collapse supernovae is used to illustrate the many connections between nuclear astrophysics and the problems nuclear physicists study in terrestrial laboratories. Efforts to better understand the collapse and mantle ejection are also motivated by a variety of interdisciplinary issues in nuclear, particle, and astrophysics, including galactic chemical evolution, neutrino masses and mixing, and stellar cooling by the emission of new particles. The current status of theory and observations is summarized.

  6. Nuclear Safety

    Energy Technology Data Exchange (ETDEWEB)

    Silver, E G [ed.

    1989-01-01

    This document is a review journal that covers significant developments in the field of nuclear safety. Its scope includes the analysis and control of hazards associated with nuclear energy, operations involving fissionable materials, and the products of nuclear fission and their effects on the environment. Primary emphasis is on safety in reactor design, construction, and operation; however, the safety aspects of the entire fuel cycle, including fuel fabrication, spent-fuel processing, nuclear waste disposal, handling of radioisotopes, and environmental effects of these operations, are also treated.

  7. Specific deletion of Cdc42 does not affect meiotic spindle organization/migration and homologous chromosome segregation but disrupts polarity establishment and cytokinesis in mouse oocytes

    DEFF Research Database (Denmark)

    Wang, Zhen-Bo; Jiang, Zong-Zhe; Zhang, Qing-Hua

    2013-01-01

    Mammalian oocyte maturation is distinguished by highly asymmetric meiotic divisions during which a haploid female gamete is produced and almost all the cytoplasm is maintained in the egg for embryo development. Actin-dependent meiosis I spindle positioning to the cortex induces the formation...

  8. A Taz1- and Microtubule-Dependent Regulatory Relationship between Telomere and Centromere Positions in Bouquet Formation Secures Proper Meiotic Divisions.

    Directory of Open Access Journals (Sweden)

    Kazuhiro Katsumata

    2016-09-01

    Full Text Available During meiotic prophase, telomeres cluster, forming the bouquet chromosome arrangement, and facilitate homologous chromosome pairing. In fission yeast, bouquet formation requires switching of telomere and centromere positions. Centromeres are located at the spindle pole body (SPB during mitotic interphase, and upon entering meiosis, telomeres cluster at the SPB, followed by centromere detachment from the SPB. Telomere clustering depends on the formation of the microtubule-organizing center at telomeres by the linker of nucleoskeleton and cytoskeleton complex (LINC, while centromere detachment depends on disassembly of kinetochores, which induces meiotic centromere formation. However, how the switching of telomere and centromere positions occurs during bouquet formation is not fully understood. Here, we show that, when impaired telomere interaction with the LINC or microtubule disruption inhibited telomere clustering, kinetochore disassembly-dependent centromere detachment and accompanying meiotic centromere formation were also inhibited. Efficient centromere detachment required telomere clustering-dependent SPB recruitment of a conserved telomere component, Taz1, and microtubules. Furthermore, when artificial SPB recruitment of Taz1 induced centromere detachment in telomere clustering-defective cells, spindle formation was impaired. Thus, detachment of centromeres from the SPB without telomere clustering causes spindle impairment. These findings establish novel regulatory mechanisms, which prevent concurrent detachment of telomeres and centromeres from the SPB during bouquet formation and secure proper meiotic divisions.

  9. EZH2 is required for mouse oocyte meiotic maturation by interacting with and stabilizing spindle assembly checkpoint protein BubRI

    Science.gov (United States)

    Qu, Yi; Lu, Danyu; Jiang, Hao; Chi, Xiaochun; Zhang, Hongquan

    2016-01-01

    Enhancer of zeste homolog 2 (EZH2) trimethylates histone H3 Lys 27 and plays key roles in a variety of biological processes. Stability of spindle assembly checkpoint protein BubR1 is essential for mitosis in somatic cells and for meiosis in oocytes. However, the role of EZH2 in oocyte meiotic maturation was unknown. Here, we presented a mechanism underlying EZH2 control of BubR1 stability in the meiosis of mouse oocytes. We identified a methyltransferase activity-independent function of EZH2 by demonstrating that EZH2 regulates spindle assembly and the polar body I extrusion. EZH2 was increased with the oocyte progression from GVBD to MII, while EZH2 was concentrated on the chromosomes. Interestingly, inhibition of EZH2 methyltranferase activity by DZNep or GSK343 did not affect oocyte meiotic maturation. However, depletion of EZH2 by morpholino led to chromosome misalignment and abnormal spindle assembly. Furthermore, ectopic expression of EZH2 led to oocyte meiotic maturation arrested at the MI stage followed by chromosome misalignment and aneuploidy. Mechanistically, EZH2 directly interacted with and stabilized BubR1, an effect driving EZH2 into the concert of meiosis regulation. Collectively, we provided a paradigm that EZH2 is required for mouse oocyte meiotic maturation. PMID:27226494

  10. Human somatic cells subjected to genetic induction with six germ line-related factors display meiotic germ cell-like features

    Science.gov (United States)

    Medrano, Jose V.; Martínez-Arroyo, Ana M.; Míguez, Jose M.; Moreno, Inmaculada; Martínez, Sebastián; Quiñonero, Alicia; Díaz-Gimeno, Patricia; Marqués-Marí, Ana I.; Pellicer, Antonio; Remohí, Jose; Simón, Carlos

    2016-01-01

    The in vitro derivation of human germ cells has attracted interest in the last years, but their direct conversion from human somatic cells has not yet been reported. Here we tested the ability of human male somatic cells to directly convert into a meiotic germ cell-like phenotype by inducing them with a combination of selected key germ cell developmental factors. We started with a pool of 12 candidates that were reduced to 6, demonstrating that ectopic expression of the germ line-related genes PRDM1, PRDM14, LIN28A, DAZL, VASA and SYCP3 induced direct conversion of somatic cells (hFSK (46, XY), and hMSC (46, XY)) into a germ cell-like phenotype in vitro. Induced germ cell-like cells showed a marked switch in their transcriptomic profile and expressed several post-meiotic germ line related markers, showed meiotic progression, evidence of epigenetic reprogramming, and approximately 1% were able to complete meiosis as demonstrated by their haploid status and the expression of several post-meiotic markers. Furthermore, xenotransplantation assays demonstrated that a subset of induced cells properly colonize the spermatogonial niche. Knowledge obtained from this work can be used to create in vitro models to study gamete-related diseases in humans. PMID:27112843

  11. Nuclear Astrophysics

    Science.gov (United States)

    Drago, Alessandro

    2005-04-01

    The activity of the Italian nuclear physicists community in the field of Nuclear Astrophysics is reported. The researches here described have been performed within the project "Fisica teorica del nucleo e dei sistemi a multi corpi", supported by the Ministero dell'Istruzione, dell'Università e della Ricerca.

  12. Nuclear Astrophysics

    CERN Document Server

    Langanke, K

    1999-01-01

    The manuscript reviews progress achieved in recent years in various aspects of nuclear astrophysics, including stellar nucleosynthesis, nuclear aspects of supernova collapse and explosion, neutrino-induced reactions and their possible role in the supernova mechanism and nucleosynthesis, explosive hydrogen burning in binary systems, and finally the observation of gamma-rays from supernova remnants.

  13. Assessing fluctuating evolutionary pressure in yeast and mammal evolutionary rate covariation using bioinformatics of meiotic protein genetic sequences

    Science.gov (United States)

    Dehipawala, Sunil; Nguyen, A.; Tremberger, G.; Cheung, E.; Holden, T.; Lieberman, D.; Cheung, T.

    2013-09-01

    The evolutionary rate co-variation in meiotic proteins has been reported for yeast and mammal using phylogenic branch lengths which assess retention, duplication and mutation. The bioinformatics of the corresponding DNA sequences could be classified as a diagram of fractal dimension and Shannon entropy. Results from biomedical gene research provide examples on the diagram methodology. The identification of adaptive selection using entropy marker and functional-structural diversity using fractal dimension would support a regression analysis where the coefficient of determination would serve as evolutionary pathway marker for DNA sequences and be an important component in the astrobiology community. Comparisons between biomedical genes such as EEF2 (elongation factor 2 human, mouse, etc), WDR85 in epigenetics, HAR1 in human specificity, clinical trial targeted cancer gene CD47, SIRT6 in spermatogenesis, and HLA-C in mosquito bite immunology demonstrate the diagram classification methodology. Comparisons to the SEPT4-XIAP pair in stem cell apoptosis, testesexpressed taste genes TAS1R3-GNAT3 pair, and amyloid beta APLP1-APLP2 pair with the yeast-mammal DNA sequences for meiotic proteins RAD50-MRE11 pair and NCAPD2-ICK pair have accounted for the observed fluctuating evolutionary pressure systematically. Regression with high R-sq values or a triangular-like cluster pattern for concordant pairs in co-variation among the studied species could serve as evidences for the possible location of common ancestors in the entropy-fractal dimension diagram, consistent with an example of the human-chimp common ancestor study using the FOXP2 regulated genes reported in human fetal brain study. The Deinococcus radiodurans R1 Rad-A could be viewed as an outlier in the RAD50 diagram and also in the free energy versus fractal dimension regression Cook's distance, consistent with a non-Earth source for this radiation resistant bacterium. Convergent and divergent fluctuating evolutionary

  14. Parp2 is required for the differentiation of post-meiotic germ cells: Identification of a spermatid-specific complex containing Parp1, Parp2, TP2 and HSPA2

    Energy Technology Data Exchange (ETDEWEB)

    Quenet, Delphine [IREBS-FRE 3211, Ecole Superieure de Biotechnologie de Strasbourg, F-67412 Illkirch cedex (France); Mark, Manuel [Institut de Genetique et de Biologie Moleculaire et Cellulaire (IGBMC), Institut Clinique de la souris (ICS), F-67404 Illkirch cedex (France); Govin, Jerome [INSERM, U823, Grenoble, F-38706 (France); Universite Joseph Fourier, Institut Albert Bonniot, Grenoble, F-38706 (France); Dorsselear, A. van [Laboratoire de Spectrometrie de Masse Bio-organique, UMR7178, Ecole de Chimie, Polymeres et Materiaux, Strasbourg (France); Schreiber, Valerie [IREBS-FRE 3211, Ecole Superieure de Biotechnologie de Strasbourg, F-67412 Illkirch cedex (France); Khochbin, Saadi [INSERM, U823, Grenoble, F-38706 (France); Universite Joseph Fourier, Institut Albert Bonniot, Grenoble, F-38706 (France); Dantzer, Francoise, E-mail: francoise.dantzer@unistra.fr [IREBS-FRE 3211, Ecole Superieure de Biotechnologie de Strasbourg, F-67412 Illkirch cedex (France)

    2009-10-01

    Spermiogenesis is a complex male germ cell post-meiotic differentiation process characterized by dramatic changes in chromatin structure and function, including chromatin condensation, transcriptional inhibition and the sequential replacement of histones by transition proteins and protamines. Recent advances, in mammalian cells, suggest a possible role of poly(ADP-ribosyl)ation catalyzed by Parp1 and/or Parp2 in this process. We have recently reported severely compromised spermiogenesis in Parp2-deficient mice characterized by a marked delay in nuclear elongation whose molecular mechanisms remain however unknown. Here, using in vitro protein-protein interaction assays, we show that Parp2 interacts significantly with both the transition protein TP2 and the transition chaperone HSPA2, whereas Parp1 binds weakly to HSPA2. Parp2-TP2 interaction is partly mediated by poly(ADP-ribosyl)ation. Only Parp1 poly(ADP-ribosyl)ates HSPA2. In addition, a detailed analysis of spermatid maturation in Parp2-deficient mice, combining immunohistochemistry and electron microscopic approaches, reveals a loss of spermatids expressing TP2, a defect in chromatin condensation and abnormal formation of the manchette microtubules that, together, contribute to spermatid-specific cell death. In conclusion, we propose both Parps as new participants of a spermatid-specific protein complex involved in genome reorganization throughout spermiogenesis.

  15. Nuclear stress test

    Science.gov (United States)

    ... Persantine stress test; Thallium stress test; Stress test - nuclear; Adenosine stress test; Regadenoson stress test; CAD - nuclear stress; Coronary artery disease - nuclear stress; Angina - nuclear ...

  16. MCM8 is required for a pathway of meiotic double-strand break repair independent of DMC1 in Arabidopsis thaliana.

    Science.gov (United States)

    Crismani, Wayne; Portemer, Virginie; Froger, Nicole; Chelysheva, Liudmila; Horlow, Christine; Vrielynck, Nathalie; Mercier, Raphaël

    2013-01-01

    Mini-chromosome maintenance (MCM) 2-9 proteins are related helicases. The first six, MCM2-7, are essential for DNA replication in all eukaryotes. In contrast, MCM8 is not always conserved in eukaryotes but is present in Arabidopsis thaliana. MCM8 is required for 95% of meiotic crossovers (COs) in Drosophila and is essential for meiosis completion in mouse, prompting us to study this gene in Arabidopsis meiosis. Three allelic Atmcm8 mutants showed a limited level of chromosome fragmentation at meiosis. This defect was dependent on programmed meiotic double-strand break (DSB) formation, revealing a role for AtMCM8 in meiotic DSB repair. In contrast, CO formation was not affected, as shown both genetically and cytologically. The Atmcm8 DSB repair defect was greatly amplified in the absence of the DMC1 recombinase or in mutants affected in DMC1 dynamics (sds, asy1). The Atmcm8 fragmentation defect was also amplified in plants heterozygous for a mutation in either recombinase, DMC1 or RAD51. Finally, in the context of absence of homologous chromosomes (i.e. haploid), mutation of AtMCM8 also provoked a low level of chromosome fragmentation. This fragmentation was amplified by the absence of DMC1 showing that both MCM8 and DMC1 can promote repair on the sister chromatid in Arabidopsis haploids. Altogether, this establishes a role for AtMCM8 in meiotic DSB repair, in parallel to DMC1. We propose that MCM8 is involved with RAD51 in a backup pathway that repairs meiotic DSB without giving CO when the major pathway, which relies on DMC1, fails.

  17. MCM8 is required for a pathway of meiotic double-strand break repair independent of DMC1 in Arabidopsis thaliana.

    Directory of Open Access Journals (Sweden)

    Wayne Crismani

    Full Text Available Mini-chromosome maintenance (MCM 2-9 proteins are related helicases. The first six, MCM2-7, are essential for DNA replication in all eukaryotes. In contrast, MCM8 is not always conserved in eukaryotes but is present in Arabidopsis thaliana. MCM8 is required for 95% of meiotic crossovers (COs in Drosophila and is essential for meiosis completion in mouse, prompting us to study this gene in Arabidopsis meiosis. Three allelic Atmcm8 mutants showed a limited level of chromosome fragmentation at meiosis. This defect was dependent on programmed meiotic double-strand break (DSB formation, revealing a role for AtMCM8 in meiotic DSB repair. In contrast, CO formation was not affected, as shown both genetically and cytologically. The Atmcm8 DSB repair defect was greatly amplified in the absence of the DMC1 recombinase or in mutants affected in DMC1 dynamics (sds, asy1. The Atmcm8 fragmentation defect was also amplified in plants heterozygous for a mutation in either recombinase, DMC1 or RAD51. Finally, in the context of absence of homologous chromosomes (i.e. haploid, mutation of AtMCM8 also provoked a low level of chromosome fragmentation. This fragmentation was amplified by the absence of DMC1 showing that both MCM8 and DMC1 can promote repair on the sister chromatid in Arabidopsis haploids. Altogether, this establishes a role for AtMCM8 in meiotic DSB repair, in parallel to DMC1. We propose that MCM8 is involved with RAD51 in a backup pathway that repairs meiotic DSB without giving CO when the major pathway, which relies on DMC1, fails.

  18. Nuclear questions

    Energy Technology Data Exchange (ETDEWEB)

    Durrani, M. [Physics World (United Kingdom)

    2006-01-01

    The future of nuclear power has returned to centre stage. Freezing weather on both sides of the Atlantic and last month's climate-change talks in Montreal have helped to put energy and the future of nuclear power right back on the political agenda. The issue is particularly pressing for those countries where existing nuclear stations are reaching the end of their lives. In the UK, prime minister Tony Blair has commissioned a review of energy, with a view to deciding later this year whether to build new nuclear power plants. The review comes just four years after the Labour government published a White Paper on energy that said the country should keep the nuclear option open but did not follow this up with any concrete action. In Germany, new chancellor and former physicist Angela Merkel is a fan of nuclear energy and had said she would extend the lifetime of its nuclear plants beyond 2020, when they are due to close. However, that commitment has had to be abandoned, at least for the time being, following negotiations with her left-wing coalition partners. The arguments in favour of nuclear power will be familiar to all physicists - it emits almost no carbon dioxide and can play a vital role in maintaining a diverse energy supply. To over-rely on imported supplies of oil and gas can leave a nation hostage to fortune. The arguments against are equally easy to list - the public is scared of nuclear power, it generates dangerous waste with potentially huge clean-up costs, and it is not necessarily cheap. Nuclear plants could also be a target for terrorist attacks. Given political will, many of these problems can be resolved, or at least tackled. China certainly sees the benefits of nuclear power, as does Finland, which is building a new 1600 MW station - the world's most powerful - that is set to open in 2009. Physicists, of course, are essential to such developments. They play a vital role in ensuring the safety of such plants and developing new types of

  19. Nuclear war and nuclear peace

    Energy Technology Data Exchange (ETDEWEB)

    Segal, G.; Moreton, E.; Freedman, L.; Baylis, J.

    1983-01-01

    This book is an in-depth examination of East-West tactical and strategic nuclear weapons policy. The contributors explore such issues as the history and implications of tactical weapons in Europe, the general conflicts that have characterized US and Soviet interaction, the development of British nuclear weapons policy, and arms control including SALT I and II and the START talks.

  20. Nuclear Physics

    CERN Document Server

    Savage, Martin J

    2016-01-01

    Lattice QCD is making good progress toward calculating the structure and properties of light nuclei and the forces between nucleons. These calculations will ultimately refine the nuclear forces, particularly in the three- and four-nucleon sector and the short-distance interactions of nucleons with electroweak currents, and allow for a reduction of uncertainties in nuclear many-body calculations of nuclei and their reactions. After highlighting their importance, particularly to the Nuclear Physics and High-Energy Physics experimental programs, I discuss the progress that has been made toward achieving these goals and the challenges that remain.

  1. Meiotic recombination dramatically decreased in thelytokous queens of the little fire ant and their sexually produced workers.

    Science.gov (United States)

    Rey, Olivier; Loiseau, Anne; Facon, Benoit; Foucaud, Julien; Orivel, Jérôme; Cornuet, Jean-Marie; Robert, Stéphanie; Dobigny, Gauthier; Delabie, Jacques Hubert Charles; Mariano, Cléa Dos Santos Ferreria; Estoup, Arnaud

    2011-09-01

    The little fire ant, Wasmannia auropunctata, displays a peculiar breeding system polymorphism. Classical haplo-diploid sexual reproduction between reproductive individuals occurs in some populations, whereas, in others, queens and males reproduce clonally. Workers are produced sexually and are sterile in both clonal and sexual populations. The evolutionary fate of the clonal lineages depends strongly on the underlying mechanisms allowing reproductive individuals to transmit their genomes to subsequent generations. We used several queen-offspring data sets to estimate the rate of transition from heterozygosity to homozygosity associated with recombination events at 33 microsatellite loci in thelytokous parthenogenetic queen lineages and compared these rates with theoretical expectations under various parthenogenesis mechanisms. We then used sexually produced worker families to define linkage groups for these 33 loci and to compare meiotic recombination rates in sexual and parthenogenetic queens. Our results demonstrate that queens from clonal populations reproduce by automictic parthenogenesis with central fusion. These same parthenogenetic queens produce normally segregating meiotic oocytes for workers, which display much lower rates of recombination (by a factor of 45) than workers produced by sexual queens. These low recombination rates also concern the parthenogenetic production of queen offspring, as indicated by the very low rates of transition from heterozygosity to homozygosity observed (from 0% to 2.8%). We suggest that the combination of automixis with central fusion and a major decrease in recombination rates allows clonal queens to benefit from thelytoky while avoiding the potential inbreeding depression resulting from the loss of heterozygosity during automixis. In sterile workers, the strong decrease of recombination rates may also facilitate the conservation over time of some coadapted allelic interactions within chromosomes that might confer an

  2. The Caenorhabditis elegans Ste20 kinase, GCK-3, is essential for postembryonic developmental timing and regulates meiotic chromosome segregation.

    Science.gov (United States)

    Kupinski, Adam P; Müller-Reichert, Thomas; Eckmann, Christian R

    2010-08-15

    Ste20 kinases constitute a large family of serine/threonine kinases with a plethora of biological functions. Members of the GCK-VI subfamily have been identified as important regulators of osmohomeostasis across species functioning upstream of ion channels. Although the expression of the two highly similar mammalian GCK-VI kinases is eminent in a wide variety of tissues, which includes also the testis, their potential roles in development remain elusive. Caenorhabditis elegans contains a single ancestral ortholog termed GCK-3. Here, we report a comprehensive analysis of gck-3 function and demonstrate its requirement for several developmental processes independent of ion homeostasis, i.e., larval progression, vulva, and germ line formation. Consistent with a wide range of gck-3 function we find that endogenous GCK-3 is expressed ubiquitously. The serine/threonine kinase activity of GCK-3, but not its presumed C-terminal substrate interaction domain, is essential for gck-3 gene function. Although expressed in female germ cells, we find GCK-3 progressively accumulating during spermatogenesis where it promotes the first meiotic cell division and facilitates faithful chromosome segregation. In particular, we find that different levels of gck-3 activity appear to be important for various aspects of germ line development. Taken together, our findings suggest that members of the GCK-VI kinase subfamily may act as key regulators of many developmental processes and that this newly described role in meiotic progression might be conserved and an important part of sexual reproduction. Copyright 2010 Elsevier Inc. All rights reserved.

  3. Error-prone ZW pairing and no evidence for meiotic sex chromosome inactivation in the chicken germ line.

    Directory of Open Access Journals (Sweden)

    Silvana Guioli

    Full Text Available In the male mouse the X and Y chromosomes pair and recombine within the small pseudoautosomal region. Genes located on the unsynapsed segments of the X and Y are transcriptionally silenced at pachytene by Meiotic Sex Chromosome Inactivation (MSCI. The degree to which MSCI is conserved in other vertebrates is currently unclear. In the female chicken the ZW bivalent is thought to undergo a transient phase of full synapsis at pachytene, starting from the homologous ends and spreading through the heterologous regions. It has been proposed that the repair of the ZW DNA double-strand breaks (DSBs is postponed until diplotene and that the ZW bivalent is subject to MSCI, which is independent of its synaptic status. Here we present a distinct model of meiotic pairing and silencing of the ZW pair during chicken oogenesis. We show that, in most oocytes, DNA DSB foci on the ZW are resolved by the end of pachytene and that the ZW desynapses in broad synchrony with the autosomes. We unexpectedly find that ZW pairing is highly error prone, with many oocytes failing to engage in ZW synapsis and crossover formation. Oocytes with unsynapsed Z and W chromosomes nevertheless progress to the diplotene stage, suggesting that a checkpoint does not operate during pachytene in the chicken germ line. Using a combination of epigenetic profiling and RNA-FISH analysis, we find no evidence for MSCI, associated with neither the asynaptic ZW, as described in mammals, nor the synaptic ZW. The lack of conservation of MSCI in the chicken reopens the debate about the evolution of MSCI and its driving forces.

  4. Guanine Nucleotides in the Meiotic Maturation of Starfish Oocytes: Regulation of the Actin Cytoskeleton and of Ca2+ Signaling

    Science.gov (United States)

    Kyozuka, Keiichiro; Chun, Jong T.; Puppo, Agostina; Gragnaniello, Gianni; Garante, Ezio; Santella, Luigia

    2009-01-01

    Background Starfish oocytes are arrested at the first prophase of meiosis until they are stimulated by 1-methyladenine (1-MA). The two most immediate responses to the maturation-inducing hormone are the quick release of intracellular Ca2+ and the accelerated changes of the actin cytoskeleton in the cortex. Compared with the later events of oocyte maturation such as germinal vesicle breakdown, the molecular mechanisms underlying the early events involving Ca2+ signaling and actin changes are poorly understood. Herein, we have studied the roles of G-proteins in the early stage of meiotic maturation. Methodology/Principal Findings By microinjecting starfish oocytes with nonhydrolyzable nucleotides that stabilize either active (GTPγS) or inactive (GDPβS) forms of G-proteins, we have demonstrated that: i) GTPγS induces Ca2+ release that mimics the effect of 1-MA; ii) GDPβS completely blocks 1-MA-induced Ca2+; iii) GDPβS has little effect on the amplitude of the Ca2+ peak, but significantly expedites the initial Ca2+ waves induced by InsP3 photoactivation, iv) GDPβS induces unexpectedly striking modification of the cortical actin networks, suggesting a link between the cytoskeletal change and the modulation of the Ca2+ release kinetics; v) alteration of cortical actin networks with jasplakinolide, GDPβS, or actinase E, all led to significant changes of 1-MA-induced Ca2+ signaling. Conclusions/Significance Taken together, these results indicate that G-proteins are implicated in the early events of meiotic maturation and support our previous proposal that the dynamic change of the actin cytoskeleton may play a regulatory role in modulating intracellular Ca2+ release. PMID:19617909

  5. Guanine nucleotides in the meiotic maturation of starfish oocytes: regulation of the actin cytoskeleton and of Ca(2+ signaling.

    Directory of Open Access Journals (Sweden)

    Keiichiro Kyozuka

    Full Text Available BACKGROUND: Starfish oocytes are arrested at the first prophase of meiosis until they are stimulated by 1-methyladenine (1-MA. The two most immediate responses to the maturation-inducing hormone are the quick release of intracellular Ca(2+ and the accelerated changes of the actin cytoskeleton in the cortex. Compared with the later events of oocyte maturation such as germinal vesicle breakdown, the molecular mechanisms underlying the early events involving Ca(2+ signaling and actin changes are poorly understood. Herein, we have studied the roles of G-proteins in the early stage of meiotic maturation. METHODOLOGY/PRINCIPAL FINDINGS: By microinjecting starfish oocytes with nonhydrolyzable nucleotides that stabilize either active (GTPgammaS or inactive (GDPbetaS forms of G-proteins, we have demonstrated that: i GTPgammaS induces Ca(2+ release that mimics the effect of 1-MA; ii GDPbetaS completely blocks 1-MA-induced Ca(2+; iii GDPbetaS has little effect on the amplitude of the Ca(2+ peak, but significantly expedites the initial Ca(2+ waves induced by InsP(3 photoactivation, iv GDPbetaS induces unexpectedly striking modification of the cortical actin networks, suggesting a link between the cytoskeletal change and the modulation of the Ca(2+ release kinetics; v alteration of cortical actin networks with jasplakinolide, GDPbetaS, or actinase E, all led to significant changes of 1-MA-induced Ca(2+ signaling. CONCLUSIONS/SIGNIFICANCE: Taken together, these results indicate that G-proteins are implicated in the early events of meiotic maturation and support our previous proposal that the dynamic change of the actin cytoskeleton may play a regulatory role in modulating intracellular Ca(2+ release.

  6. High fat diet induced developmental defects in the mouse: oocyte meiotic aneuploidy and fetal growth retardation/brain defects.

    Directory of Open Access Journals (Sweden)

    Kerri M Luzzo

    Full Text Available BACKGROUND: Maternal obesity is associated with poor outcomes across the reproductive spectrum including infertility, increased time to pregnancy, early pregnancy loss, fetal loss, congenital abnormalities and neonatal conditions. Furthermore, the proportion of reproductive-aged woman that are obese in the population is increasing sharply. From current studies it is not clear if the origin of the reproductive complications is attributable to problems that arise in the oocyte or the uterine environment. METHODOLOGY/PRINCIPAL FINDINGS: We examined the developmental basis of the reproductive phenotypes in obese animals by employing a high fat diet mouse model of obesity. We analyzed very early embryonic and fetal phenotypes, which can be parsed into three abnormal developmental processes that occur in obese mothers. The first is oocyte meiotic aneuploidy that then leads to early embryonic loss. The second is an abnormal process distinct from meiotic aneuploidy that also leads to early embryonic loss. The third is fetal growth retardation and brain developmental abnormalities, which based on embryo transfer experiments are not due to the obese uterine environment but instead must be from a defect that arises prior to the blastocyst stage. CONCLUSIONS/SIGNIFICANCE: Our results suggest that reproductive complications in obese females are, at least in part, from oocyte maternal effects. This conclusion is consistent with IVF studies where the increased pregnancy failure rate in obese women returns to the normal rate if donor oocytes are used instead of autologous oocytes. We postulate that preconceptional weight gain adversely affects pregnancy outcomes and fetal development. In light of our findings, preconceptional counseling may be indicated as the preferable, earlier target for intervention in obese women desiring pregnancy and healthy outcomes.

  7. Genetic probing of homologous recombination and non-homologous end joining during meiotic prophase in irradiated mouse spermatocytes

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, Emad A. [Department of Endocrinology and Metabolism, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht (Netherlands); Department of Zoology, Faculty of Science, Assiut University, 71516 Assiut (Egypt); Philippens, Marielle E.P.; Kal, Henk B. [Department of Radiotherapy, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht (Netherlands); Rooij, Dirk G. de, E-mail: d.g.derooij@uu.nl [Department of Endocrinology and Metabolism, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht (Netherlands); Center for Reproductive Medicine, Academic Medical Center, University of Amsterdam, 1105 AZ Amsterdam (Netherlands); Boer, Peter de [Department of Obstetrics and Gynaecology, Radboud University Nijmegen Medical Centre, 6500 HB Nijmegen (Netherlands)

    2010-06-01

    This study was designed to obtain a better insight into the relative contribution of homologous recombination (HR) and non-homologous end joining (NHEJ) to the repair of radiation-induced DNA double-strand breaks (DSBs) at first meiotic prophase. Early and late pachytene and early diplotene spermatocytes that had completed crossing over were sampled. We studied the kinetics of {gamma}-H2AX chromatin foci removal after irradiation of mice deficient for HR and mice deficient for NHEJ. Analyzing {gamma}-H2AX signals in unirradiated RAD54/RAD54B deficient spermatocytes indicated incomplete meiotic recombination repair due to the pronounced increase of {gamma}-H2AX foci in late prophase primary spermatocytes. In these mice, 8 h after irradiation, early pachytene spermatocytes showed a reduction of the numbers of {gamma}-H2AX foci by 52% compared to 82% in the wild type, the difference being significant. However, after crossing over (in late pachytene and early diplotene), no effect of RAD54/RAD54B deficiency on the reduction of irradiation-induced foci was observed. In NHEJ deficient SCID mice, repair kinetics in early spermatocytes were similar to those in wild type mice. However, 1 h after irradiation in late pachytene and early diplotene spermatocytes 1.7 times more foci were found than in wild type mice. This difference might be related to the absence of a DNA-PKcs dependent fast repair component in SCID mice. As subsequent repair is normal, HR likely is taking over. Taken together, the results obtained in RAD54/RAD54B deficient mice and in SCID mice indicate that DSB repair in early pachytene spermatocytes is mainly carried out through HR. In late spermatocytes (late pachytenes and early diplotenes) NHEJ is active. However, probably there is an interplay between these repair pathways and when in late spermatocytes the NHEJ pathway is compromised HR may take over.

  8. (Nuclear theory). [Research in nuclear physics

    Energy Technology Data Exchange (ETDEWEB)

    Haxton, W.

    1990-01-01

    This report discusses research in nuclear physics. Topics covered in this paper are: symmetry principles; nuclear astrophysics; nuclear structure; quark-gluon plasma; quantum chromodynamics; symmetry breaking; nuclear deformation; and cold fusion. (LSP)

  9. The ability to form full-length intron RNA circles is a general property of nuclear group I introns

    DEFF Research Database (Denmark)

    Nielsen, Henrik; Fiskaa, Tonje; Birgisdottir, Asa Birna

    2003-01-01

    In addition to splicing, group I intron RNA is capable of an alternative two-step processing pathway that results in the formation of full-length intron circular RNA. The circularization pathway is initiated by hydrolytic cleavage at the 3' splice site and followed by a transesterification reaction...... in which the intron terminal guanosine attacks the 5' splice site presented in a structure analogous to that of the first step of splicing. The products of the reactions are full-length circular intron and unligated exons. For this reason, the circularization reaction is to the benefit of the intron...... at the expense of the host. The circularization pathway has distinct structural requirements that differ from those of splicing and appears to be specifically suppressed in vivo. The ability to form full-length circles is found in all types of nuclear group I introns, including those from the Tetrahymena...

  10. Nuclear reaction

    CERN Multimedia

    Penwarden, C

    2001-01-01

    At the European Research Organization for Nuclear Research, Nobel laureates delve into the mysteries of particle physics. But when they invited artists from across the continent to visit their site in Geneva, they wanted a new kind of experiment.

  11. Nuclear Fusion

    National Research Council Canada - National Science Library

    Ghoranneviss, Mahmood; Parashar, S. K. S; Aslan, Necdet; Aslaninejad, Morteza; Salar Elahi, A

    2014-01-01

    ... in both inertial and magnetic confinement fusion, with attendees from major fusion energy research centers worldwide. It is one of the most important issues in this field. Nuclear fusion continues t...

  12. Nuclear Structure

    Science.gov (United States)

    Gargano, Angela

    2003-04-01

    An account of recent studies in the field of theoretical nuclear structure is reported. These studies concern essentially research activities performed under the Italian project "Fisica Teorica del Nucleo e dei Sistemi a Molti Corpi". Special attention is addressed to results obtained during the last two years as regards the development of new many-body techniques as well as the interpretation of new experimental aspects of nuclear structure.

  13. Nuclear Data

    Energy Technology Data Exchange (ETDEWEB)

    White, Morgan C. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2014-01-23

    PowerPoint presentation targeted for educational use. Nuclear data comes from a variety of sources and in many flavors. Understanding where the data you use comes from and what flavor it is can be essential to understand and interpret your results. This talk will discuss the nuclear data pipeline with particular emphasis on providing links to additional resources that can be used to explore the issues you will encounter.

  14. Dm nxf1/sbr gene affects the formation of meiotic spindle in female Drosophila melanogaster.

    Science.gov (United States)

    Golubkova, Elena V; Markova, Ekaterina G; Markov, Anton V; Avanesyan, Elina O; Nokkala, Seppo; Mamon, Ludmila A

    2009-01-01

    The small bristles (sbr) gene of Drosophila melanogaster belongs to the family of nuclear export factor (NXF) genes that participate in mRNA nuclear export. During meiosis, females of Drosophila melanogaster that carry various combinations of mutant alleles of the Dm nxf1/sbr gene exhibit disruption of the division spindle and misalignment of chromosomes at the metaphase plate. Meiosis of sbr ( 5 ) /+ females is characterized by the formation of tripolar spindles during the first cell division. According to the sequencing results, the sbr ( 5 ) (l(1)K4) lethal allele is a deletion of 492 nucleotides. In SBR(5) protein, 57 of the 146 amino acids that have been lost by deletion belong to the NTF2-like domain.

  15. Nuclear safety

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2014-07-01

    The Program on Nuclear Safety comprehends Radioprotection, Radioactive Waste Management and Nuclear Material Control. These activities are developed at the Nuclear Safety Directory. The Radioactive Waste Management Department (GRR) was formally created in 1983, to promote research and development, teaching and service activities in the field of radioactive waste. Its mission is to develop and employ technologies to manage safely the radioactive wastes generated at IPEN and at its customer’s facilities all over the country, in order to protect the health and the environment of today's and future generations. The Radioprotection Service (GRP) aims primarily to establish requirements for the protection of people, as workers, contractors, students, members of the general public and the environment from harmful effects of ionizing radiation. Furthermore, it also aims to establish the primary criteria for the safety of radiation sources at IPEN and planning and preparing for response to nuclear and radiological emergencies. The procedures about the management and the control of exposures to ionizing radiation are in compliance with national standards and international recommendations. Research related to the main activities is also performed. The Nuclear Material Control has been performed by the Safeguard Service team, which manages the accountability and the control of nuclear material at IPEN facilities and provides information related to these activities to ABACC and IAEA. (author)

  16. TBP dynamics during mouse oocyte meiotic maturation and early embryo development.

    Science.gov (United States)

    Sun, Shao-Chen; Wang, Xu-Guang; Ma, Xue-Shan; Huang, Xian-Ju; Li, Juan; Liu, Hong-Lin

    2013-01-01

    To maintain cell lineage, cells develop a mechanism which can transmit the gene activity information to the daughter cells. In mitosis, TBP (TATA-binding protein), a transcription factor which belongs to TFIID was associated with M phase chromosomes and was proved to be a bookmark for cellular memory. Although previous work showed that TBP was dispensable for mouse oocyte maturation and early embryo development, exogenous TBP protein was detected in the nuclear of oocytes and early embryos. It is still unknown whether exogenous TBP can associate with condensed chromosomes during meiosis and mouse early embryo development. In present study by the injection of GFP-tagged TBP mRNA we for the first time investigated TBP dynamics in mouse early embryos and confirmed its localization pattern in oocytes. The exogenous TBP enriched at germinal vesicle at GV stage but disappeared from the chromosomes after GVBD. Moreover, exogenous TBP was still dispersed from the chromosomes of somatic donor nuclear in oocytes by nuclear transfer (NT), further proving that oocyte has some mechanism to remove TBP. During mouse embryo development, the exogenous TBP was removed from the chromosomes of M phase zygotes, but was found to express weakly at the M phase of 2-cell. Moreover, in the blastocyst TBP was also detected at the M phase chromosomes. Overexpression of TBP caused the failure of oocyte maturation and embryo development. Our results supported the idea that TBP might be a marker for transmitting cellular memory to daughter cells.

  17. In vitro and in vivo studies reveal that hamster oocyte meiotic arrest is maintained only transiently by follicular fluid, but persistently by membrana/cumulus granulosa cell contact.

    Science.gov (United States)

    Racowsky, C; Baldwin, K V

    1989-08-01

    Studies were carried out with the golden Syrian hamster to investigate the capacity of follicular fluid to maintain oocyte meiotic arrest and to determine the importance of cumulus-membrana granulosa cell contact in the regulation of meiotic status. The follicular fluid studies were conducted by cytological assessment of meiotic stage up to 6 hr after transferring cumulus-free oocytes into antra of explanted "host" follicles in vitro or into follicles of anesthetized animals prior to the gonadotropin surge at proestrus in vivo. The cumulus-membrana granulosa contact studies were undertaken with explanted follicles in which the oocyte-cumulus complex was dislodged from the underlying membrana granulosa, released into the antrum, and subsequently allowed to reestablish contact during 6 hr of incubation within the follicle. The extent of recontact of the dislodged complex with the underlying membrana granulosa was assessed visually at the end of incubation and was classified as close, moderate, or none. These various degrees of contact typically involved the following number of cumulus cells, as determined by serial sectioning of a representative sample of follicles after dislodgement and subsequent incubation: close, 32.7 +/- 1.78; moderate, 9.0 +/- 2.1; and no contact, 0. After 6 hr of incubation either in vitro or in vivo, few transferred oocytes remained at the germinal vesicle (GV) stage (18.8 +/- 8.7 and 17.3 +/- 4.0% GV, respectively). However, time course experiments revealed that meiotic resumption was significantly delayed in transferred oocytes compared with either liberated oocytes, spontaneously maturing oocytes, or follicle-enclosed oocytes induced to mature by luteinizing hormone in vitro (after 4 hr, transferred, 31.3 +/- 6.0% GV; liberated, 0% GV; follicle-enclosed, 0% GV; after 6 hr, 0% transferred oocytes exhibited a GV). In the dislodgement studies, after 6 hr of incubation, 26% of complexes reestablished close contact with the underlying membrana

  18. Children's (Pediatric) Nuclear Medicine

    Medline Plus

    Full Text Available ... News Physician Resources Professions Site Index A-Z Children's (Pediatric) Nuclear Medicine Children’s (pediatric) nuclear medicine imaging ... the limitations of Children's Nuclear Medicine? What is Children's (Pediatric) Nuclear Medicine? Nuclear medicine is a branch ...

  19. Children's (Pediatric) Nuclear Medicine

    Science.gov (United States)

    ... Professions Site Index A-Z Children's (Pediatric) Nuclear Medicine Children’s (pediatric) nuclear medicine imaging uses small amounts ... Children's Nuclear Medicine? What is Children's (Pediatric) Nuclear Medicine? Nuclear medicine is a branch of medical imaging ...

  20. Children's (Pediatric) Nuclear Medicine

    Medline Plus

    Full Text Available ... Professions Site Index A-Z Children's (Pediatric) Nuclear Medicine Children’s (pediatric) nuclear medicine imaging uses small amounts ... Children's Nuclear Medicine? What is Children's (Pediatric) Nuclear Medicine? Nuclear medicine is a branch of medical imaging ...

  1. General Nuclear Medicine

    Science.gov (United States)

    ... Resources Professions Site Index A-Z General Nuclear Medicine Nuclear medicine imaging uses small amounts of radioactive ... of General Nuclear Medicine? What is General Nuclear Medicine? Nuclear medicine is a branch of medical imaging ...

  2. Children's (Pediatric) Nuclear Medicine

    Medline Plus

    Full Text Available ... Physician Resources Professions Site Index A-Z Children's (Pediatric) Nuclear Medicine Children’s (pediatric) nuclear medicine imaging uses ... limitations of Children's Nuclear Medicine? What is Children's (Pediatric) Nuclear Medicine? Nuclear medicine is a branch of ...

  3. Children's (Pediatric) Nuclear Medicine

    Medline Plus

    Full Text Available ... Resources Professions Site Index A-Z Children's (Pediatric) Nuclear Medicine Children’s (pediatric) nuclear medicine imaging uses small ... of Children's Nuclear Medicine? What is Children's (Pediatric) Nuclear Medicine? Nuclear medicine is a branch of medical ...

  4. Nuclear scales

    Energy Technology Data Exchange (ETDEWEB)

    Friar, J.L.

    1998-12-01

    Nuclear scales are discussed from the nuclear physics viewpoint. The conventional nuclear potential is characterized as a black box that interpolates nucleon-nucleon (NN) data, while being constrained by the best possible theoretical input. The latter consists of the longer-range parts of the NN force (e.g., OPEP, TPEP, the {pi}-{gamma} force), which can be calculated using chiral perturbation theory and gauged using modern phase-shift analyses. The shorter-range parts of the force are effectively parameterized by moments of the interaction that are independent of the details of the force model, in analogy to chiral perturbation theory. Results of GFMC calculations in light nuclei are interpreted in terms of fundamental scales, which are in good agreement with expectations from chiral effective field theories. Problems with spin-orbit-type observables are noted.

  5. Nuclear astrophysics

    Science.gov (United States)

    Penionzhkevich, Yu. E.

    2010-08-01

    The International Year of Astronomy 2009 (IYA2009) was declared by the 62nd General Assembly of the United Nations and was also endorsed by UNESCO. Investigations in the realms of particle and nuclear physicsmake a large contribution in the development of our ideas of the properties of the Universe. The present article discusses some problems of the evolution of the Universe, nucleosyntheses, and cosmochronology from the point of view of nuclear and particle physics. Processes occurring in the Universe are compared with the mechanisms of the production and decay of nuclei, as well as with the mechanisms of their interaction at high energies. Examples that demonstrate the potential of nuclearphysics methods for studying cosmic objects and the properties of the Universe are given. The results that come from investigations into nuclear reactions induced by beams of radioactive nuclei and which make it possible to take a fresh look at the nucleosynthesis scenario in the range at light nuclei are presented.

  6. Nuclear enthalpies

    Directory of Open Access Journals (Sweden)

    Rozynek Jacek

    2015-01-01

    Full Text Available Even small departures from a nuclear equilibrium density with constant nucleon masses require an increase of a nucleon enthalpy. This process can be described as volume corrections to a nucleon rest energy, which are proportional to pressure and absent in a standard Relativistic Mean Field (RMF with point-like nucleons. Bag model and RMF calculations show the modifications of nucleon mass, nucleon radius and a Parton Distribution Function (PDF of Nuclear Matter (NM above the saturation point originated from the pressure correction.

  7. Nuclear spectroscopy

    CERN Document Server

    Ajzenberg-Selove, Fay

    1960-01-01

    Nuclear Spectroscopy, Part A deals with the experimental and theoretical techniques involved in nuclear spectroscopy.This book discusses the interactions of charged particles with matter, gaseous ionization detectors, and particular mass attenuation coefficients. The magnetic gamma-ray spectrometers for photo or internal-conversion electrons, general characteristics of cross-section variation with energy, and measurement of fast neutron spectra are also elaborated. This text likewise covers the elastic scattering of photons by nuclei and measurement of widths of gamma-radiating levels.This pub

  8. Localization and Dynamics of Cdc2-Cyclin B during Meiotic Reinitiation in Starfish OocytesV⃞

    Science.gov (United States)

    Terasaki, Mark; Okumura, Ei-ichi; Hinkle, Beth; Kishimoto, Takeo

    2003-01-01

    The Cdc2-cyclin B kinase has a central role in regulating the onset of M phase. In starfish oocytes, Cdc2-cyclin B begins to be activated ∼10 min after application of maturation hormone, followed by accumulation in the nucleus then nuclear envelope breakdown. By immunofluorescence and by expressing a green fluorescent (GFP) chimera of cyclin B, we find that cyclin B is present in aggregates in the cytoplasm of immature oocytes. The aggregates disperse at ∼10 min, suggesting that the dispersal is closely related to the activation of the kinase. Using cyclin B-GFP, the dispersion begins from the region containing the centrosomes. Extractability of Cdc2-cyclin B changes with similar kinetics during maturation. Active Cdc25 phosphatase released Cdc2-cyclin B from the detergent-insoluble fraction independently of its phosphatase activity. Live cell imaging also showed that Cdc2-cyclin B begins to accumulate in the nucleus before changes in nuclear pore permeability, consistent with Cdc2-cyclin B-induced disassembly of the pores. PMID:14551249

  9. Prediction of acute toxicity of phenol derivatives using multiple linear regression approach for Tetrahymena pyriformis contaminant identification in a median-size database.

    Science.gov (United States)

    Dieguez-Santana, Karel; Pham-The, Hai; Villegas-Aguilar, Pedro J; Le-Thi-Thu, Huong; Castillo-Garit, Juan A; Casañola-Martin, Gerardo M

    2016-12-01

    In this article, the modeling of inhibitory grown activity against Tetrahymena pyriformis is described. The 0-2D Dragon descriptors based on structural aspects to gain some knowledge of factors influencing aquatic toxicity are mainly used. Besides, it is done by some enlarged data of phenol derivatives described for the first time and composed of 358 chemicals. It overcomes the previous datasets with about one hundred compounds. Moreover, the results of the model evaluation by the parameters in the training, prediction and validation give adequate results comparable with those of the previous works. The more influential descriptors included in the model are: X3A, MWC02, MWC10 and piPC03 with positive contributions to the dependent variable; and MWC09, piPC02 and TPC with negative contributions. In a next step, a median-size database of nearly 8000 phenolic compounds extracted from ChEMBL was evaluated with the quantitative-structure toxicity relationship (QSTR) model developed providing some clues (SARs) for identification of ecotoxicological compounds. The outcome of this report is very useful to screen chemical databases for finding the compounds responsible of aquatic contamination in the biomarker used in the current work. Copyright © 2016 Elsevier Ltd. All rights reserved.

  10. Cows are not mice: the role of cyclic AMP, phosphodiesterases, and adenosine monophosphate-activated protein kinase in the maintenance of meiotic arrest in bovine oocytes.

    Science.gov (United States)

    Bilodeau-Goeseels, Sylvie

    2011-01-01

    Meiotic maturation in mammalian oocytes is initiated during fetal development, and is then arrested at the dictyate stage - possibly for several years. Oocyte meiosis resumes in preovulatory follicles in response to the lutenizing hormone (LH) surge or spontaneously when competent oocytes are removed from follicles and cultured. The mechanisms involved in meiotic arrest and resumption in bovine oocytes are not fully understood, and several studies point to important differences between oocytes from rodent and livestock species. This paper reviews earlier and contemporary studies on the effects of cAMP-elevating agents and phosphodiesterase (PDE) enzyme inhibitors on the maintenance of meiotic arrest in bovine oocytes in vitro. Contrary to results obtained with mouse oocytes, bovine oocyte meiosis is inhibited by activators of the energy sensor adenosine monophosphate-activated protein kinase (AMPK, mammalian gene PRKA), which is activated by AMP, the degradation product of cAMP. It is not clear whether or not the effects were due to AMPK activation, and they may depend on culture conditions. Evidence suggests that other signaling pathways (for example, the cGMP/nitric oxide pathway) are involved in bovine oocyte meiotic arrest, but further studies are needed to understand the interactions between the signaling pathways that lead to maturation promoting factor (MPF) being inactive or active. An improved understanding of the mechanisms involved in the control of bovine oocyte meiosis will facilitate better control of the process in vitro, resulting in increased developmental competence and increased efficiency of in vitro embryo production procedures. Copyright © 2011 Wiley Periodicals, Inc.

  11. Meiotic localization of Mre11 and Rad50 in wild type, spo11-1, and MRN complex mutants of Coprinus cinereus.

    Science.gov (United States)

    Many, Alexander M; Melki, Christina S; Savytskyy, Oleksandr P; Maillet, Daniel S; Acharya, Sonia N; Zolan, Miriam E

    2009-08-01

    The Mre11-Rad50-Nbs1 (MRN) complex is required for numerous cellular processes that involve interactions with DNA double-strand breaks. For the majority of these processes, the MRN complex is thought to act as a unit, with each protein aiding the activity of the others. We have examined the relationship between Mre11 and Rad50 during meiosis in the basidiomycete Coprinus cinereus (Coprinopsis cinerea), investigating to what extent activities of Mre11 and Rad50 are interdependent. We showed that mre11-1 is epistatic to rad50-1 with respect to the time of meiotic arrest, indicating that Mre11 activity facilitates the diffuse diplotene arrest of rad50 mutants. Anti-Mre11 and anti-Rad50 antibodies were used to examine MRN complex localization in a wild-type strain and in spo11, mre11, and rad50 mutants. In wild type, numbers of Mre11 and Rad50 foci peaked at time points corresponding to leptotene and early zygotene. In the spo11-1 mutant, which is defective in meiotic double-strand break formation, foci accumulated throughout prophase I. Of seven MRN mutants examined, only two rad50 strains exhibited Mre11 and Rad50 foci that localized to chromatin, although Mre11 protein was found in the cell for all of them. Analysis of predicted mutant structures showed that stable localization of Mre11 and Rad50 does not depend upon a wild-type hook-proximal coiled coil, but does require the presence of the Rad50 ATPase/adenylate cyclase domains. We found that Mre11 and Rad50 were interdependent for binding to meiotic chromosomes. However, the majority of foci observed apparently contained only one of the two proteins. Independent Mre11 and Rad50 foci might indicate disassociation of the complex during meiosis or could reflect independent structural roles for the two proteins in meiotic chromatin.

  12. A high incidence of meiotic silencing of unsynapsed chromatin is not associated with substantial pachytene loss in heterozygous male mice carrying multiple simple robertsonian translocations.

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    Marcia Manterola

    2009-08-01

    Full Text Available Meiosis is a complex type of cell division that involves homologous chromosome pairing, synapsis, recombination, and segregation. When any of these processes is altered, cellular checkpoints arrest meiosis progression and induce cell elimination. Meiotic impairment is particularly frequent in organisms bearing chromosomal translocations. When chromosomal translocations appear in heterozygosis, the chromosomes involved may not correctly complete synapsis, recombination, and/or segregation, thus promoting the activation of checkpoints that lead to the death of the meiocytes. In mammals and other organisms, the unsynapsed chromosomal regions are subject to a process called meiotic silencing of unsynapsed chromatin (MSUC. Different degrees of asynapsis could contribute to disturb the normal loading of MSUC proteins, interfering with autosome and sex chromosome gene expression and triggering a massive pachytene cell death. We report that in mice that are heterozygous for eight multiple simple Robertsonian translocations, most pachytene spermatocytes bear trivalents with unsynapsed regions that incorporate, in a stage-dependent manner, proteins involved in MSUC (e.g., gammaH2AX, ATR, ubiquitinated-H2A, SUMO-1, and XMR. These spermatocytes have a correct MSUC response and are not eliminated during pachytene and most of them proceed into diplotene. However, we found a high incidence of apoptotic spermatocytes at the metaphase stage. These results suggest that in Robertsonian heterozygous mice synapsis defects on most pachytene cells do not trigger a prophase-I checkpoint. Instead, meiotic impairment seems to mainly rely on the action of a checkpoint acting at the metaphase stage. We propose that a low stringency of the pachytene checkpoint could help to increase the chances that spermatocytes with synaptic defects will complete meiotic divisions and differentiate into viable gametes. This scenario, despite a reduction of fertility, allows the spreading

  13. A High Incidence of Meiotic Silencing of Unsynapsed Chromatin Is Not Associated with Substantial Pachytene Loss in Heterozygous Male Mice Carrying Multiple Simple Robertsonian Translocations

    Science.gov (United States)

    Vasco, Chiara; Berríos, Soledad; Parra, María Teresa; Viera, Alberto; Rufas, Julio S.; Zuccotti, Maurizio; Garagna, Silvia; Fernández-Donoso, Raúl

    2009-01-01

    Meiosis is a complex type of cell division that involves homologous chromosome pairing, synapsis, recombination, and segregation. When any of these processes is altered, cellular checkpoints arrest meiosis progression and induce cell elimination. Meiotic impairment is particularly frequent in organisms bearing chromosomal translocations. When chromosomal translocations appear in heterozygosis, the chromosomes involved may not correctly complete synapsis, recombination, and/or segregation, thus promoting the activation of checkpoints that lead to the death of the meiocytes. In mammals and other organisms, the unsynapsed chromosomal regions are subject to a process called meiotic silencing of unsynapsed chromatin (MSUC). Different degrees of asynapsis could contribute to disturb the normal loading of MSUC proteins, interfering with autosome and sex chromosome gene expression and triggering a massive pachytene cell death. We report that in mice that are heterozygous for eight multiple simple Robertsonian translocations, most pachytene spermatocytes bear trivalents with unsynapsed regions that incorporate, in a stage-dependent manner, proteins involved in MSUC (e.g., γH2AX, ATR, ubiquitinated-H2A, SUMO-1, and XMR). These spermatocytes have a correct MSUC response and are not eliminated during pachytene and most of them proceed into diplotene. However, we found a high incidence of apoptotic spermatocytes at the metaphase stage. These results suggest that in Robertsonian heterozygous mice synapsis defects on most pachytene cells do not trigger a prophase-I checkpoint. Instead, meiotic impairment seems to mainly rely on the action of a checkpoint acting at the metaphase stage. We propose that a low stringency of the pachytene checkpoint could help to increase the chances that spermatocytes with synaptic defects will complete meiotic divisions and differentiate into viable gametes. This scenario, despite a reduction of fertility, allows the spreading of Robertsonian

  14. A C. elegans eIF4E-family member upregulates translation at elevated temperatures of mRNAs encoding MSH-5 and other meiotic crossover proteins

    Science.gov (United States)

    Song, Anren; Labella, Sara; Korneeva, Nadejda L.; Keiper, Brett D.; Aamodt, Eric J.; Zetka, Monique; Rhoads, Robert E.

    2010-01-01

    Caenorhabditis elegans expresses five family members of the translation initiation factor eIF4E whose individual physiological roles are only partially understood. We report a specific role for IFE-2 in a conserved temperature-sensitive meiotic process. ife-2 deletion mutants have severe temperature-sensitive chromosome-segregation defects. Mutant germ cells contain the normal six bivalents at diakinesis at 20°C but 12 univalents at 25°C, indicating a defect in crossover formation. Analysis of chromosome pairing in ife-2 mutants at the permissive and restrictive temperatures reveals no defects. The presence of RAD-51-marked early recombination intermediates and 12 well condensed univalents indicate that IFE-2 is not essential for formation of meiotic double-strand breaks or their repair through homologous recombination but is required for crossover formation. However, RAD-51 foci in ife-2 mutants persist into inappropriately late stages of meiotic prophase at 25°C, similar to mutants defective in MSH-4/HIM-14 and MSH-5, which stabilize a critical intermediate in crossover formation. In wild-type worms, mRNAs for msh-4/him-14 and msh-5 shift from free messenger ribonucleoproteins to polysomes at 25°C but not in ife-2 mutants, suggesting that IFE-2 translationally upregulates synthesis of MSH-4/HIM-14 and MSH-5 at elevated temperatures to stabilize Holliday junctions. This is confirmed by an IFE-2-dependent increase in MSH-5 protein levels. PMID:20530576

  15. mus309 mutation, defective in DNA double-strand break repair, affects intergenic but not intragenic meiotic recombination in Drosophila melanogaster.

    Science.gov (United States)

    Portin, Petter

    2005-12-01

    The effect was investigated of the hypomorphic DNA double-strand break repair, notably synthesis-dependent strand annealing, deficient mutation mus309 on the third chromosome of Drosophila melanogaster on intergenic and intragenic meiotic recombination in the X chromosome. The results showed that the mutation significantly increases the frequency of intergenic crossing over in two of three gene intervals of the X chromosome studied. Interestingly the increase was most prevalent in the tip of the X chromosome where crossovers normally are least frequent per physical map unit length. In particular crossing over interference was also affected, indicating that the effect of the mus309 mutation involves preconditions of crossing over but not the event of crossing over itself. On the other hand, the results also show that most probably the mutation does not have any effect on intragenic recombination, i.e. gene conversion. These results are fully consistent with the present molecular models of meiotic crossing over initiated by double-strand breaks of DNA followed by formation of a single-end-invasion intermediate, or D-loop, which is subsequently processed to generate either crossover or non-crossover products involving formation of a double Holliday junction. In particular the results suggest that the mus309 gene is involved in resolution of the D-loop, thereby affecting the choice between double-strand-break repair (DSBR) and synthesis-dependent strand annealing (SDSA) pathways of meiotic recombination.

  16. The conserved histone deacetylase Rpd3 and the DNA binding regulator Ume6 repress BOI1's meiotic transcript isoform during vegetative growth in Saccharomyces cerevisiae.

    Science.gov (United States)

    Liu, Yuchen; Stuparevic, Igor; Xie, Bingning; Becker, Emmanuelle; Law, Michael J; Primig, Michael

    2015-05-01

    BOI1 and BOI2 are paralogs important for the actin cytoskeleton and polar growth. BOI1 encodes a meiotic transcript isoform with an extended 5'-untranslated region predicted to impair protein translation. It is, however, unknown how the isoform is repressed during mitosis, and if Boi1 is present during sporulation. By interpreting microarray data from MATa cells, MATa/α cells, a starving MATα/α control, and a meiosis-impaired rrp6 mutant, we classified BOI1's extended isoform as early meiosis-specific. These results were confirmed by RNA-Sequencing, and extended by a 5'-RACE assay and Northern blotting, showing that meiotic cells induce the long isoform while the mitotic isoform remains detectable during meiosis. We provide evidence via motif predictions, an in vivo binding assay and genetic experiments that the Rpd3/Sin3/Ume6 histone deacetylase complex, which represses meiotic genes during mitosis, also prevents the induction of BOI1's 5'-extended isoform in mitosis by direct binding of Ume6 to its URS1 target. Finally, we find that Boi1 protein levels decline when cells switch from fermentation to respiration and sporulation. The histone deacetylase Rpd3 is conserved, and eukaryotic genes frequently encode transcripts with variable 5'-UTRs. Our findings are therefore relevant for regulatory mechanisms involved in the control of transcript isoforms in multi-cellular organisms. © 2015 John Wiley & Sons Ltd.

  17. Multicolor Spectral Analyses of Mitotic and Meiotic Mouse Chromosomes Involved in Multiple Robertsonian Translocations. II. The NMRI/CD and CD/TA Hybrid Strains.

    Science.gov (United States)

    Schmid, Michael; Steinlein, Claus; Winking, Heinz

    2017-01-01

    Multicolor spectral analyses (spectral karyotyping) were performed on mitotic chromosomes of NMRI, CD, and TA mice and on male meiotic chromosomes (diakineses) of NMRI/CD and CD/TA hybrids. All chromosomes, including the various centric (robertsonian) fusions, could be unequivocally identified. Apart from the robertsonian translocations, which were previously detected by conventional banding analyses, no other interchromosomal rearrangements were found in these mice. In both the CD and TA mice, the autosomes 19 and the XY sex chromosomes are not involved in robertsonian translocations. In diakineses of male meiosis of the NMRI/CD hybrid, the 9 expected trivalents were present, whereas in those of the CD/TA hybrids a stable large meiotic multivalent, formed by 15 robertsonian fusion chromosomes and 2 terminally located normal chromosomes, was observed. The specific sequential order of the robertsonian fusion chromosomes found within this meiotic chain was as theoretically predicted. In the majority of diakineses of the NMRI/CD and CD/TA hybrids, the free autosomal bivalent 19 and the XY sex bivalent formed noticeable tight spatial associations. © 2017 S. Karger AG, Basel.

  18. Nuclear energy.

    Science.gov (United States)

    Wilson, Peter D

    2010-01-01

    The technical principles and practices of the civil nuclear industry are described with particular reference to fission and its products, natural and artificial radioactivity elements principally concerned and their relationships, main types of reactor, safety issues, the fuel cycle, waste management, issues related to weapon proliferation, environmental considerations and possible future developments.

  19. Variation in genome-wide levels of meiotic recombination is established at the onset of prophase in mammalian males.

    Directory of Open Access Journals (Sweden)

    Brian Baier

    2014-01-01

    Full Text Available Segregation of chromosomes during the first meiotic division relies on crossovers established during prophase. Although crossovers are strictly regulated so that at least one occurs per chromosome, individual variation in crossover levels is not uncommon. In an analysis of different inbred strains of male mice, we identified among-strain variation in the number of foci for the crossover-associated protein MLH1. We report studies of strains with "low" (CAST/EiJ, "medium" (C3H/HeJ, and "high" (C57BL/6J genome-wide MLH1 values to define factors responsible for this variation. We utilized immunofluorescence to analyze the number and distribution of proteins that function at different stages in the recombination pathway: RAD51 and DMC1, strand invasion proteins acting shortly after double-strand break (DSB formation, MSH4, part of the complex stabilizing double Holliday junctions, and the Bloom helicase BLM, thought to have anti-crossover activity. For each protein, we identified strain-specific differences that mirrored the results for MLH1; i.e., CAST/EiJ mice had the lowest values, C3H/HeJ mice intermediate values, and C57BL/6J mice the highest values. This indicates that differences in the numbers of DSBs (as identified by RAD51 and DMC1 are translated into differences in the number of crossovers, suggesting that variation in crossover levels is established by the time of DSB formation. However, DSBs per se are unlikely to be the primary determinant, since allelic variation for the DSB-inducing locus Spo11 resulted in differences in the numbers of DSBs but not the number of MLH1 foci. Instead, chromatin conformation appears to be a more important contributor, since analysis of synaptonemal complex length and DNA loop size also identified consistent strain-specific differences; i.e., crossover frequency increased with synaptonemal complex length and was inversely related to chromatin loop size. This indicates a relationship between recombination

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

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    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.

  1. Microtubule assembly is required for the formation of the pronuclei, nuclear lamin acquisition, and DNA synthesis during mouse, but not sea urchin, fertilization.

    Science.gov (United States)

    Schatten, H; Simerly, C; Maul, G; Schatten, G

    1989-07-01

    Microtubule assembly is required for the formation of the male and female pronuclei during mouse, but not sea urchin, fertilization. In mouse oocytes, 50 microM colcemid prevents the decondensation of the maternal meiotic chromosomes and of the incorporated sperm nucleus during in vitro fertilization. Nuclear lamins do not associate with either of the parental chromatin sets although peripherin, the Pl nuclear peripheral antigen, appears on both. DNA synthesis does not occur in these fertilized, colcemid-arrested oocytes. This effect is limited to the first hours after ovulation, since colcemid added 4-6 hours later no longer prevents pronuclear development, lamin acquisition, or DNA synthesis. Neither microtubule stabilization with 10 microM taxol nor microfilament inhibition with 10 microM cytochalasin D or 2.2 micrograms/ml latrunculin A prevent these pronuclear events; these drugs will inhibit the apposition of the pronuclei at the egg center. In sea urchin eggs, colcemid or griseofulvin treatment does not result in the same effect and the male pronucleus forms with the attendant accumulation of the nuclear lamins. The differences in the requirement for microtubule assembly during pronucleus formation may be related to the cell cycle: In mice the sperm enters a meiotic cytoplasm, whereas in sea urchin eggs it enters an interphase cytoplasm. Refertilization of mitotic sea urchin eggs was performed to test the possibility that this phenomenon is related to whether the sperm enters a meiotic/mitotic cytoplasm or one at interphase; during refertilization at first mitosis, the incorporated sperm nucleus is unable to decondense and acquire lamins. These results indicate a requirement for microtubule assembly for the progression from meiosis to first interphase during mouse fertilization and suggest that the cytoskeleton is required for changes in nuclear architecture necessary during fertilization and the cell cycle.

  2. Sequencing of Single Pollen Nuclei Reveals Meiotic Recombination Events at Megabase Resolution and Circumvents Segregation Distortion Caused by Postmeiotic Processes

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    Steven Dreissig

    2017-09-01

    Full Text Available Meiotic recombination is a fundamental mechanism to generate novel allelic combinations which can be harnessed by breeders to achieve crop improvement. The recombination landscape of many crop species, including the major crop barley, is characterized by a dearth of recombination in 65% of the genome. In addition, segregation distortion caused by selection on genetically linked loci is a frequent and undesirable phenomenon in double haploid populations which hampers genetic mapping and breeding. Here, we present an approach to directly investigate recombination at the DNA sequence level by combining flow-sorting of haploid pollen nuclei of barley with single-cell genome sequencing. We confirm the skewed distribution of recombination events toward distal chromosomal regions at megabase resolution and show that segregation distortion is almost absent if directly measured in pollen. Furthermore, we show a bimodal distribution of inter-crossover distances, which supports the existence of two classes of crossovers which are sensitive or less sensitive to physical interference. We conclude that single pollen nuclei sequencing is an approach capable of revealing recombination patterns in the absence of segregation distortion.

  3. MAPK-activated protein kinase 2 is required for mouse meiotic spindle assembly and kinetochore-microtubule attachment.

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    Ju Yuan

    Full Text Available MAPK-activated protein kinase 2 (MK2, a direct substrate of p38 MAPK, plays key roles in multiple physiological functions in mitosis. Here, we show for the first time the unique distribution pattern of MK2 in meiosis. Phospho-MK2 was localized on bipolar spindle minus ends and along the interstitial axes of homologous chromosomes extending over centromere regions and arm regions at metaphase of first meiosis (MI stage in mouse oocytes. At metaphase of second meiosis (MII stage, p-MK2 was localized on the bipolar spindle minus ends and at the inner centromere region of sister chromatids as dots. Knockdown or inhibition of MK2 resulted in spindle defects. Spindles were surrounded by irregular nondisjunction chromosomes, which were arranged in an amphitelic or syntelic/monotelic manner, or chromosomes detached from the spindles. Kinetochore-microtubule attachments were impaired in MK2-deficient oocytes because spindle microtubules became unstable in response to cold treatment. In addition, homologous chromosome segregation and meiosis progression were inhibited in these oocytes. Our data suggest that MK2 may be essential for functional meiotic bipolar spindle formation, chromosome segregation and proper kinetochore-microtubule attachments.

  4. A rare Robertsonian translocation rob(14;22) carrier with azoospermia, meiotic defects, and testicular sperm aneuploidy.

    Science.gov (United States)

    Sobotka, Vladimir; Vozdova, Miluse; Heracek, Jiri; Rubes, Jiri

    2015-01-01

    Male infertility is a serious problem in an increasing number of couples. We report an infertile man with non-obstructive azoospermia and karyotype 45,XY,rob(14;22). The immunofluorescence analysis of his testicular tissue using antibodies to SYCP1, SYCP3, HORMAD2, MLH1, and centromeres showed delayed synapsis of the chromosomes involved in the translocation, a varying extent of trivalent asynapsis and its association with sex chromosomes. The mean frequency of meiotic recombination per cell was within the range of normal values. Fluorescence in situ hybridization (FISH) with probes for chromosomes 14 and 22 revealed 5.83% of chromosomally abnormal testicular spermatozoa. FISH with probes for chromosomes X, Y, and 21 showed frequencies of disomic and diploid testicular spermatozoa increased when compared to ejaculated sperm of healthy donors, but comparable with published results for azoospermic patients. PGD by FISH for the translocation and aneuploidy of chromosomes X, Y, 13, 18, and 21 showed a normal chromosomal complement in one out of three analyzed embryos. A healthy carrier girl was born after the embryo transfer. This study shows the benefits of preimplantation genetic diagnosis in a case of a rare Robertsonian translocation carrier with azoospermia and a relatively low frequency of chromosomally unbalanced testicular spermatozoa.

  5. Solution structure and DNA-binding properties of the winged helix domain of the meiotic recombination HOP2 protein.

    Science.gov (United States)

    Moktan, Hem; Guiraldelli, Michel F; Eyster, Craig A; Zhao, Weixing; Lee, Chih-Ying; Mather, Timothy; Camerini-Otero, R Daniel; Sung, Patrick; Zhou, Donghua H; Pezza, Roberto J

    2014-05-23

    The HOP2 protein is required for efficient double-strand break repair which ensures the proper synapsis of homologous chromosomes and normal meiotic progression. We previously showed that in vitro HOP2 shows two distinctive activities: when it is incorporated into a HOP2-MND1 heterodimer, it stimulates DMC1 and RAD51 recombination activities, and the purified HOP2 alone is proficient in promoting strand invasion. The structural and biochemical basis of HOP2 action in recombination are poorly understood; therefore, they are the focus of this work. Herein, we present the solution structure of the amino-terminal portion of mouse HOP2, which contains a typical winged helix DNA-binding domain. Together with NMR spectral changes in the presence of double-stranded DNA, protein docking on DNA, and mutation analysis to identify the amino acids involved in DNA coordination, our results on the three-dimensional structure of HOP2 provide key information on the fundamental structural and biochemical requirements directing the interaction of HOP2 with DNA. These results, in combination with mutational experiments showing the role of a coiled-coil structural feature involved in HOP2 self-association, allow us to explain important aspects of the function of HOP2 in recombination. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

  6. Meiotic maturation induces animal-vegetal asymmetric distribution of aPKC and ASIP/PAR-3 in Xenopus oocytes.

    Science.gov (United States)

    Nakaya, M; Fukui, A; Izumi, Y; Akimoto, K; Asashima, M; Ohno, S

    2000-12-01

    The asymmetric distribution of cellular components is an important clue for understanding cell fate decision during embryonic patterning and cell functioning after differentiation. In C. elegans embryos, PAR-3 and aPKC form a complex that colocalizes to the anterior periphery of the one-cell embryo, and are indispensable for anterior-posterior polarity that is formed prior to asymmetric cell division. In mammals, ASIP (PAR-3 homologue) and aPKCgamma form a complex and colocalize to the epithelial tight junctions, which play critical roles in epithelial cell polarity. Although the mechanism by which PAR-3/ASIP and aPKC regulate cell polarization remains to be clarified, evolutionary conservation of the PAR-3/ASIP-aPKC complex suggests their general role in cell polarity organization. Here, we show the presence of the protein complex in Xenopus laevis. In epithelial cells, XASIP and XaPKC colocalize to the cell-cell contact region. To our surprise, they also colocalize to the animal hemisphere of mature oocytes, whereas they localize uniformly in immature oocytes. Moreover, hormonal stimulation of immature oocytes results in a change in the distribution of XaPKC 2-3 hours after the completion of germinal vesicle breakdown, which requires the kinase activity of aPKC. These results suggest that meiotic maturation induces the animal-vegetal asymmetry of aPKC.

  7. Improving ethanol fermentation performance of Saccharomyces cerevisiae in very high-gravity fermentation through chemical mutagenesis and meiotic recombination

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jing-Jing; Ding, Wen-Tao; Zhang, Guo-Chang; Wang, Jing-Yu [Tianjin Univ. (China). Dept. of Biochemical Engineering

    2011-08-15

    Genome shuffling is an efficient way to improve complex phenotypes under the control of multiple genes. For the improvement of strain's performance in very high-gravity (VHG) fermentation, we developed a new method of genome shuffling. A diploid ste2/ste2 strain was subjected to EMS (ethyl methanesulfonate) mutagenesis followed by meiotic recombination-mediated genome shuffling. The resulting haploid progenies were intrapopulation sterile and therefore haploid recombinant cells with improved phenotypes were directly selected under selection condition. In VHG fermentation, strain WS1D and WS5D obtained by this approach exhibited remarkably enhanced tolerance to ethanol and osmolarity, increased metabolic rate, and 15.12% and 15.59% increased ethanol yield compared to the starting strain W303D, respectively. These results verified the feasibility of the strain improvement strategy and suggested that it is a powerful and high throughput method for development of Saccharomyces cerevisiae strains with desired phenotypes that is complex and cannot be addressed with rational approaches. (orig.)

  8. Intraspecific variability of the facultative meiotic parthenogenetic root-knot nematode (Meloidogyne graminicola) from rice fields in Vietnam.

    Science.gov (United States)

    Bellafiore, Stéphane; Jougla, Claire; Chapuis, Élodie; Besnard, Guillaume; Suong, Malyna; Vu, Phong Nguyen; De Waele, Dirk; Gantet, Pascal; Thi, Xuyen Ngo

    2015-07-01

    Twenty years ago, the facultative meiotic parthenogenetic root-knot nematode (RKN), Meloidogyne graminicola, was recognised as an important rice pathogen in South Vietnam. Although this country is one of the most important rice exporters worldwide, a comprehensive picture of the occurrence of M. graminicola in Vietnamese rice fields is still not available. Therefore a nematode survey was carried out with the aim of better understanding the geographical distribution, and the pathogenic and genetic variability of the RKN in Vietnam. From the fields surveyed in a range of ecosystems, 21 RKN populations were recovered from infected rice roots. A diagnostic SCAR marker was developed showing that all Vietnamese populations belong to M. graminicola. Furthermore, sequencing of the Internal Transcribed Spacer (ITS) of the rDNA genes confirmed this identification. These populations were then characterised using morphometrics and pathogenicity tests (host plant range diversity, reproduction and virulence diversity) revealing intraspecific variability. We showed that morphometric traits are mainly genetically heritable characters with significant differences among the studied populations. Finally, a distinctive trait signature was found for the populations isolated from the upland rice cultures. All together, our study reveals the prevalence of M. graminicola populations in Vietnamese rice. Further investigations need to be developed to explore the population dynamics and evolutionary history of this species in South East Asia. Copyright © 2015 Académie des sciences. Published by Elsevier SAS. All rights reserved.

  9. Incomplete pole orientation of kinetochores in complex meiotic metaphase I configurations delays metaphase-anaphase transition in Secale.

    Science.gov (United States)

    Sybenga, J

    2014-04-01

    To prevent unbalanced chromosome segregation, meiotic metaphase I - anaphase I transition is carefully regulated by delaying anaphase until all kinetochores are well oriented (anaphase checkpoint) in mammals and insects. In plants this has not yet been established. In heterozygotes of two reciprocal translocations of Secale cereale, with one chromosome replaced by its two telocentric arms, anaphase delay was correlated with the orientation of the kinetochores of the complex of five chromosomes. The terminal kinetochores of the half chromosomes were readily elongated and pole oriented. Chains of five chromosomes with all five kinetochores orienting on alternate poles where the first to start anaphase. Kinetochores of two adjacent chromosomes when oriented on the same pole were partly shielded and less well pole directed. Anaphase was delayed. Cells with this configuration accumulated during anther development. Kinetochores in metacentric chromosomes lacking chiasmata in one arm (in trivalents and bivalents) were slightly better pole oriented and delayed anaphase less. Release of chromatid cohesion as triggered by kinetochore stretch is apparently delayed by inadequate exposition and pole orientation of the kinetochores. It is a mild form of an anaphase checkpoint, in normal material synchronizing bivalent segregation.

  10. Nuclear politics

    Science.gov (United States)

    Ranson, John

    2009-04-01

    The sentiments expressed by Sidney Drell in his forum article "The nuclear threat: a new start" (February pp16-17) are laudable, but it was disappointing to find this almost entirely political story in isolation. The article, which outlined the prospects for reducing weapons stockpiles under the new US administration, would have been more pertinent as an introduction to a series describing the technology used in detecting nuclear-testing activity. It would have been interesting to discuss the specific equipment and methods used, together with the analysis and correlation techniques - along with an indication of how sensitive and reliable they are (if the information is not classified). It is far easier to detect an explosive event than it is to detect and quantify weapons stores, which is a key factor for any negotiated solution. Apart from deductions based on actual inspection and satellite surveillance, are there other techniques that can be applied to this issue?

  11. Children's (Pediatric) Nuclear Medicine

    Medline Plus

    Full Text Available ... are the limitations of Children's Nuclear Medicine? What is Children's (Pediatric) Nuclear Medicine? Nuclear medicine is a ... top of page What are some common uses of the procedure? Children's (pediatric) nuclear medicine imaging is ...

  12. NUCLEAR REACTOR

    Science.gov (United States)

    Grebe, J.J.

    1959-07-14

    High temperature reactors which are uniquely adapted to serve as the heat source for nuclear pcwered rockets are described. The reactor is comprised essentially of an outer tubular heat resistant casing which provides the main coolant passageway to and away from the reactor core within the casing and in which the working fluid is preferably hydrogen or helium gas which is permitted to vaporize from a liquid storage tank. The reactor core has a generally spherical shape formed entirely of an active material comprised of fissile material and a moderator material which serves as a diluent. The active material is fabricated as a gas permeable porous material and is interlaced in a random manner with very small inter-connecting bores or capillary tubes through which the coolant gas may flow. The entire reactor is divided into successive sections along the direction of the temperature gradient or coolant flow, each section utilizing materials of construction which are most advantageous from a nuclear standpoint and which at the same time can withstand the operating temperature of that particular zone. This design results in a nuclear reactor characterized simultaneously by a minimum critiral size and mass and by the ability to heat a working fluid to an extremely high temperature.

  13. 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.

  14. Time-Lapse Dynamics of the Mouse Oocyte Chromatin Organisation during Meiotic Resumption

    Directory of Open Access Journals (Sweden)

    Martina Belli

    2014-01-01

    Full Text Available In the mammalian oocyte, distinct patterns of centromeres and pericentromeric heterochromatin localisation correlate with the gamete’s developmental competence. Mouse antral oocytes display two main types of chromatin organisation: SN oocytes, with a ring of Hoechst-positive chromatin surrounding the nucleolus, and NSN oocytes lacking this ring. When matured to MII and fertilised, only SN oocytes develop beyond the 2-cell, and reach full term. To give detailed information on the dynamics of the SN or NSN chromatin during meiosis resumption, we performed a 9 hr time-lapse observation. The main significant differences recorded are: (1 reduction of the nuclear area only in SN oocytes; (2 ~17 min delay of GVBD in NSN oocytes; (3 chromatin condensation, after GVBD, in SN oocytes; (4 formation of 4-5 CHCs in SN oocytes; (5 increase of the perivitelline space, ~57 min later in NSN oocytes; (6 formation of a rosette-like disposition of CHCs, ~84 min later in SN oocytes; (7 appearance of the MI plate ~40 min later in NSN oocytes. Overall, we described a pathway of transition from the GV to the MII stage that is punctuated of discrete recordable events showing their specificity and occurring with different time kinetics in the two types of oocytes.

  15. Nuclear photonics

    Science.gov (United States)

    Habs, D.; Günther, M. M.; Jentschel, M.; Thirolf, P. G.

    2012-07-01

    With the planned new γ-beam facilities like MEGa-ray at LLNL (USA) or ELI-NP at Bucharest (Romania) with 1013 γ/s and a band width of ΔEγ/Eγ≈10-3, a new era of γ beams with energies up to 20MeV comes into operation, compared to the present world-leading HIγS facility at Duke University (USA) with 108 γ/s and ΔEγ/Eγ≈3ṡ10-2. In the long run even a seeded quantum FEL for γ beams may become possible, with much higher brilliance and spectral flux. At the same time new exciting possibilities open up for focused γ beams. Here we describe a new experiment at the γ beam of the ILL reactor (Grenoble, France), where we observed for the first time that the index of refraction for γ beams is determined by virtual pair creation. Using a combination of refractive and reflective optics, efficient monochromators for γ beams are being developed. Thus, we have to optimize the total system: the γ-beam facility, the γ-beam optics and γ detectors. We can trade γ intensity for band width, going down to ΔEγ/Eγ≈10-6 and address individual nuclear levels. The term "nuclear photonics" stresses the importance of nuclear applications. We can address with γ-beams individual nuclear isotopes and not just elements like with X-ray beams. Compared to X rays, γ beams can penetrate much deeper into big samples like radioactive waste barrels, motors or batteries. We can perform tomography and microscopy studies by focusing down to μm resolution using Nuclear Resonance Fluorescence (NRF) for detection with eV resolution and high spatial resolution at the same time. We discuss the dominating M1 and E1 excitations like the scissors mode, two-phonon quadrupole octupole excitations, pygmy dipole excitations or giant dipole excitations under the new facet of applications. We find many new applications in biomedicine, green energy, radioactive waste management or homeland security. Also more brilliant secondary beams of neutrons and positrons can be produced.

  16. Nuclear tele medicine; Telemedicina nuclear

    Energy Technology Data Exchange (ETDEWEB)

    Vargas, L.; Hernandez, F.; Fernandez, R. [Departamento de Medicina Nuclear, Imagenologia Diagnostica, Xalapa, Veracruz (Mexico)

    2005-07-01

    The great majority of the digital images of nuclear medicine are susceptible of being sent through internet. This has allowed that the work in diagnosis cabinets by image it can benefit of this modern technology. We have presented in previous congresses works related with tele medicine, however, due to the speed in the evolution of the computer programs and the internet, becomes necessary to make a current position in this modality of work. (Author)

  17. In silico prediction of toxicity of phenols to Tetrahymena pyriformis by using genetic algorithm and decision tree-based modeling approach.

    Science.gov (United States)

    Abbasitabar, Fatemeh; Zare-Shahabadi, Vahid

    2017-04-01

    Risk assessment of chemicals is an important issue in environmental protection; however, there is a huge lack of experimental data for a large number of end-points. The experimental determination of toxicity of chemicals involves high costs and time-consuming process. In silico tools such as quantitative structure-toxicity relationship (QSTR) models, which are constructed on the basis of computational molecular descriptors, can predict missing data for toxic end-points for existing or even not yet synthesized chemicals. Phenol derivatives are known to be aquatic pollutants. With this background, we aimed to develop an accurate and reliable QSTR model for the prediction of toxicity of 206 phenols to Tetrahymena pyriformis. A multiple linear regression (MLR)-based QSTR was obtained using a powerful descriptor selection tool named Memorized_ACO algorithm. Statistical parameters of the model were 0.72 and 0.68 for R training 2 and R test 2 , respectively. To develop a high-quality QSTR model, classification and regression tree (CART) was employed. Two approaches were considered: (1) phenols were classified into different modes of action using CART and (2) the phenols in the training set were partitioned to several subsets by a tree in such a manner that in each subset, a high-quality MLR could be developed. For the first approach, the statistical parameters of the resultant QSTR model were improved to 0.83 and 0.75 for R training 2 and R test 2 , respectively. Genetic algorithm was employed in the second approach to obtain an optimal tree, and it was shown that the final QSTR model provided excellent prediction accuracy for the training and test sets (R training 2 and R test 2 were 0.91 and 0.93, respectively). The mean absolute error for the test set was computed as 0.1615. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. Gravity-dependent changes in bioconvection of Tetrahymena and Chlamydomonas during parabolic flight: increases in wave number induced by pre- and post-parabola hypergravity.

    Science.gov (United States)

    Kage, Azusa; Asato, Eriko; Chiba, Yoko; Wada, Yuuko; Katsu-Kimura, Yumiko; Kubota, Ayami; Sawai, Satoe; Niihori, Maki; Baba, Shoji A; Mogami, Yoshihiro

    2011-03-01

    Bioconvection emerges in a dense suspension of swimming protists as a consequence of their negative-gravitactic upward migration and later settling as a blob of density greater than that of water. Thus, gravity is an important parameter governing bioconvective pattern formation. However, inconsistencies are found in previous studies dealing with the response of bioconvection patterns to increased gravity acceleration (hypergravity); the wave number of the patterns has been reported to decrease during the hypergravity phases of parabolic aircraft flight, while it increases in centrifugal hypergravity. In this paper, we reassess the responses of bioconvection to altered gravity during parabolic flight on the basis of vertical and horizontal observations of the patterns formed by Tetrahymena thermophila and Chlamydomonas reinhardtii. Spatiotemporal analyses of the horizontal patterns revealed an increase in the pattern wave number in both pre- and post-parabola hypergravity. Vertical pattern analysis was generally in line with the horizontal pattern analysis, and further revealed that hypergravity-induced changes preceded at the top layer of the suspensions while microgravity-induced changes appeared to occur from the bottom part of the settling blobs. The responses to altered gravity were rather different between the two sample species: T. thermophila tended to drastically modify its bioconvection patterns in response to changes in gravity level, while the patterns of C. reinhardtii responded to a much lesser extent. This difference can be attributed to the distinct physical and physiological properties of the individual organisms, suggesting a significant contribution of the gyrotactic property to the swimming behavior of some protists.

  19. Efficient expression of codon-adapted affinity tagged super folder green fluorescent protein for synchronous protein localization and affinity purification studies in Tetrahymena thermophila.

    Science.gov (United States)

    Yilmaz, Gürkan; Arslanyolu, Muhittin

    2015-03-25

    A superior Green Fluorescent Protein (GFP) mutant, known as superfolder GFP (sfGFP), is more soluble, faster folding, and is the brightest of the known GFP mutants. This study aimed to create a codon-adapted sfGFP tag (TtsfGFP) for simultaneous protein localization and affinity purification in Tetrahymena thermophila. In vivo fluorescence spectroscopic analyses of clones carrying a codon-adapted and 6 × His tagged TtsfGFP cassette showed approximately 2-4-fold increased fluorescence emission compared with the control groups at 3 h. Fluorescence microscopy also revealed that TtsfGFP reached its emission maxima at 100 min, which was much earlier than controls expressing EGFP and sfGFP (240 min). A T. thermophila ATP-dependent DNA ligase domain containing hypothetical gene (H) was cloned into the 3' end of 6 × His-TtsfGFP to assess the affinity/localization dual tag feature. Fluorescence microscopy of the 6 × His-TtsfGFP-H clone confirmed its localization in the macro- and micronucleus of vegetative T. thermophila. Simultaneous affinity purification of TtsfGFP and TtsfGFP-H with Ni-NTA beads was feasible, as shown by Ni-NTA purified proteins analysis by SDS-PAGE and western blotting. We successfully codon adapted the N-terminal 6 × His-TtsfGFP tag and showed that it could be used for protein localization and affinity purification simultaneously in T. thermophila. We believe that this dual tag will advance T. thermophila studies by providing strong visual traceability of the target protein in vivo and in vitro during recombinant production of heterologous and homologous proteins.

  20. The plant nuclear envelope as a multifunctional platform LINCed by SUN and KASH.

    Science.gov (United States)

    Zhou, Xiao; Graumann, Katja; Meier, Iris

    2015-03-01

    The nuclear envelope (NE) is a double membrane system enclosing the genome of eukaryotes. Besides nuclear pore proteins, which form channels at the NE, nuclear membranes are populated by a collection of NE proteins that perform various cellular functions. However, in contrast to well-conserved nuclear pore proteins, known NE proteins share little homology between opisthokonts and plants. Recent studies on NE protein complexes formed by Sad1/UNC-84 (SUN) and Klarsicht/ANC-1/Syne-1 Homology (KASH) proteins have advanced our understanding of plant NE proteins and revealed their function in anchoring other proteins at the NE, nuclear shape determination, nuclear positioning, anti-pathogen defence, root development, and meiotic chromosome organization. In this review, we discuss the current understanding of plant SUN, KASH, and other related NE proteins, and compare their function with the opisthokont counterparts. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

  1. The PHD Finger Protein MMD1/DUET Ensures the Progression of Male Meiotic Chromosome Condensation and Directly Regulates the Expression of the Condensin Gene CAP-D3[OPEN

    Science.gov (United States)

    Wang, Jun; Niu, Baixiao; Huang, Jiyue; Wang, Hongkuan; Yang, Xiaohui; Dong, Aiwu

    2016-01-01

    Chromosome condensation, a process mediated by the condensin complex, is essential for proper chromosome segregation during cell division. Unlike rapid mitotic chromosome condensation, meiotic chromosome condensation occurs over a relatively long prophase I and is unusually complex due to the coordination with chromosome axis formation and homolog interaction. The molecular mechanisms that regulate meiotic chromosome condensation progression from prophase I to metaphase I are unclear. Here, we show that the Arabidopsis thaliana meiotic PHD-finger protein MMD1/DUET is required for progressive compaction of prophase I chromosomes to metaphase I bivalents. The MMD1 PHD domain is required for its function in chromosome condensation and binds to methylated histone tails. Transcriptome analysis and qRT-PCR showed that several condensin genes exhibit significantly reduced expression in mmd1 meiocytes. Furthermore, MMD1 specifically binds to the promoter region of the condensin subunit gene CAP-D3 to enhance its expression. Moreover, cap-d3 mutants exhibit similar chromosome condensation defects, revealing an MMD1-dependent mechanism for regulating meiotic chromosome condensation, which functions in part by promoting condensin gene expression. Together, these discoveries provide strong evidence that the histone reader MMD1/DUET defines an important step for regulating the progression of meiotic prophase I chromosome condensation. PMID:27385818

  2. Applications of nuclear physics

    Science.gov (United States)

    Hayes, A. C.

    2017-02-01

    Today the applications of nuclear physics span a very broad range of topics and fields. This review discusses a number of aspects of these applications, including selected topics and concepts in nuclear reactor physics, nuclear fusion, nuclear non-proliferation, nuclear-geophysics, and nuclear medicine. The review begins with a historic summary of the early years in applied nuclear physics, with an emphasis on the huge developments that took place around the time of World War II, and that underlie the physics involved in designs of nuclear explosions, controlled nuclear energy, and nuclear fusion. The review then moves to focus on modern applications of these concepts, including the basic concepts and diagnostics developed for the forensics of nuclear explosions, the nuclear diagnostics at the National Ignition Facility, nuclear reactor safeguards, and the detection of nuclear material production and trafficking. The review also summarizes recent developments in nuclear geophysics and nuclear medicine. The nuclear geophysics areas discussed include geo-chronology, nuclear logging for industry, the Oklo reactor, and geo-neutrinos. The section on nuclear medicine summarizes the critical advances in nuclear imaging, including PET and SPECT imaging, targeted radionuclide therapy, and the nuclear physics of medical isotope production. Each subfield discussed requires a review article unto itself, which is not the intention of the current review; rather, the current review is intended for readers who wish to get a broad understanding of applied nuclear physics.

  3. Applications of nuclear physics.

    Science.gov (United States)

    Hayes, A C

    2017-02-01

    Today the applications of nuclear physics span a very broad range of topics and fields. This review discusses a number of aspects of these applications, including selected topics and concepts in nuclear reactor physics, nuclear fusion, nuclear non-proliferation, nuclear-geophysics, and nuclear medicine. The review begins with a historic summary of the early years in applied nuclear physics, with an emphasis on the huge developments that took place around the time of World War II, and that underlie the physics involved in designs of nuclear explosions, controlled nuclear energy, and nuclear fusion. The review then moves to focus on modern applications of these concepts, including the basic concepts and diagnostics developed for the forensics of nuclear explosions, the nuclear diagnostics at the National Ignition Facility, nuclear reactor safeguards, and the detection of nuclear material production and trafficking. The review also summarizes recent developments in nuclear geophysics and nuclear medicine. The nuclear geophysics areas discussed include geo-chronology, nuclear logging for industry, the Oklo reactor, and geo-neutrinos. The section on nuclear medicine summarizes the critical advances in nuclear imaging, including PET and SPECT imaging, targeted radionuclide therapy, and the nuclear physics of medical isotope production. Each subfield discussed requires a review article unto itself, which is not the intention of the current review; rather, the current review is intended for readers who wish to get a broad understanding of applied nuclear physics.

  4. Development of the competence of bovine oocytes to release cortical granules and block polyspermy after meiotic maturation.

    Science.gov (United States)

    Wang, W; Hosoe, M; Li, R; Shioya, Y

    1997-10-01

    Bovine immature oocytes do not have the ability to block polyspermic penetration. The present study was conducted to determine whether this is correlated to cortical granule (CG) distribution and the competence of oocytes to release CG upon sperm penetration, and whether the ability of bovine oocytes to release CG develops during in vitro maturation. Fluorescein isothiocyanate-conjugated Lens culinaris agglutinin was used for detecting CG in immature and mature oocytes before and after sperm penetration and electric stimulation. The labeled oocytes were examined with laser confocal and fluorescent microscopes. The results show that CG exist as clusters in all immature oocytes. The CG were not released from immature oocytes exposed to electric pulse or penetrated by spermatozoa, resulting in 94% of oocytes being polyspermic. When immature oocytes were cultured for 22 h in vitro, 81% extruded the first polar body and reached metaphase II. In mature oocytes, 25% of oocytes showed CG clusters, 42% and 33% of oocytes showed partial and complete CG dispersion, respectively. When mature oocytes were inseminated in vitro, only 15% of oocytes were polyspermic. Cortical granule exocytosis occurred in 97% of oocytes after sperm penetration and 84% of oocytes released all of the CG 18 h after insemination. Electric pulse induced all of the mature oocytes to release CG but only 55% released all of their CG 18 h post stimulation. These results indicate that polyspermy in immature bovine oocytes is the result of the complete failure of the oocyte to release CG after sperm penetration. Bovine oocytes became competent to release CG by sperm penetration and electric stimulation after meiotic maturation. These results provide evidence that CG exocytosis plays an important role(s) in the establishment of the block to polyspermy in bovine oocytes.

  5. Genome Evolution and Meiotic Maps by Massively Parallel DNA Sequencing: Spotted Gar, an Outgroup for the Teleost Genome Duplication

    Science.gov (United States)

    Amores, Angel; Catchen, Julian; Ferrara, Allyse; Fontenot, Quenton; Postlethwait, John H.

    2011-01-01

    Genomic resources for hundreds of species of evolutionary, agricultural, economic, and medical importance are unavailable due to the expense of well-assembled genome sequences and difficulties with multigenerational studies. Teleost fish provide many models for human disease but possess anciently duplicated genomes that sometimes obfuscate connectivity. Genomic information representing a fish lineage that diverged before the teleost genome duplication (TGD) would provide an outgroup for exploring the mechanisms of evolution after whole-genome duplication. We exploited massively parallel DNA sequencing to develop meiotic maps with thrift and speed by genotyping F1 offspring of a single female and a single male spotted gar (Lepisosteus oculatus) collected directly from nature utilizing only polymorphisms existing in these two wild individuals. Using Stacks, software that automates the calling of genotypes from polymorphisms assayed by Illumina sequencing, we constructed a map containing 8406 markers. RNA-seq on two map-cross larvae provided a reference transcriptome that identified nearly 1000 mapped protein-coding markers and allowed genome-wide analysis of conserved synteny. Results showed that the gar lineage diverged from teleosts before the TGD and its genome is organized more similarly to that of humans than teleosts. Thus, spotted gar provides a critical link between medical models in teleost fish, to which gar is biologically similar, and humans, to which gar is genomically similar. Application of our F1 dense mapping strategy to species with no prior genome information promises to facilitate comparative genomics and provide a scaffold for ordering the numerous contigs arising from next generation genome sequencing. PMID:21828280

  6. Dictionary of nuclear engineering

    Energy Technology Data Exchange (ETDEWEB)

    Sube, R.

    1985-01-01

    Ralf Sube, an experienced compiler of three wellknown four-language reference works has now prepared this glossary of nuclear engineering terms in English, German, French and Russian. Based on the proven lexicography of the Technik-Worterbuch series, it comprises about 30,000 terms in each language covering the following: Nuclear and Atomic Physics; Nuclear Radiation and Isotopes; Nuclear Materials; Nuclear Facilties; Nuclear Power Industry; Nuclear Weapons.

  7. Applications of Nuclear Physics

    OpenAIRE

    Hayes, Anna C.

    2017-01-01

    Today the applications of nuclear physics span a very broad range of topics and fields. This review discusses a number of aspects of these applications, including selected topics and concepts in nuclear reactor physics, nuclear fusion, nuclear non-proliferation, nuclear-geophysics, and nuclear medicine. The review begins with a historic summary of the early years in applied nuclear physics, with an emphasis on the huge developments that took place around the time of World War II, and that und...

  8. Differences in meiotic recombination rates in childhood acute lymphoblastic leukemia at an MHC class II hotspot close to disease associated haplotypes.

    Directory of Open Access Journals (Sweden)

    Pamela Thompson

    Full Text Available Childhood Acute Lymphoblastic Leukemia (ALL is a malignant lymphoid disease of which B-cell precursor- (BCP and T-cell- (T ALL are subtypes. The role of alleles encoded by major histocompatibility loci (MHC have been examined in a number of previous studies and results indicating weak, multi-allele associations between the HLA-DPB1 locus and BCP-ALL suggested a role for immunosusceptibility and possibly infection. Two independent SNP association studies of ALL identified loci approximately 37 kb from one another and flanking a strong meiotic recombination hotspot (DNA3, adjacent to HLA-DOA and centromeric of HLA-DPB1. To determine the relationship between this observation and HLA-DPB1 associations, we constructed high density SNP haplotypes of the 316 kb region from HLA-DMB to COL11A2 in childhood ALL and controls using a UK GWAS data subset and the software PHASE. Of four haplotype blocks identified, predicted haplotypes in Block 1 (centromeric of DNA3 differed significantly between BCP-ALL and controls (P = 0.002 and in Block 4 (including HLA-DPB1 between T-ALL and controls (P = 0.049. Of specific common (>5% haplotypes in Block 1, two were less frequent in BCP-ALL, and in Block 4 a single haplotype was more frequent in T-ALL, compared to controls. Unexpectedly, we also observed apparent differences in ancestral meiotic recombination rates at DNA3, with BCP-ALL showing increased and T-ALL decreased levels compared to controls. In silico analysis using LDsplit sotware indicated that recombination rates at DNA3 are influenced by flanking loci, including SNPs identified in childhood ALL association studies. The observed differences in rates of meiotic recombination at this hotspot, and potentially others, may be a characteristic of childhood leukemia and contribute to disease susceptibility, alternatively they may reflect interactions between ALL-associated haplotypes in this region.

  9. Supplementation with cumulus cell masses improves the in vitro meiotic competence of porcine cumulus-oocytes complexes derived from small follicles.

    Science.gov (United States)

    Matsunaga, R; Funahashi, H

    2017-08-01

    The present study was conducted to examine the supplemented effect of cumulus cell masses (CCMs) derived from middle follicle (MF; 3-6 mm diameter) on the morphology and the meiotic or developmental competence of oocytes from small follicles (SF; 1-2 mm diameter). The number of cumulus cells surrounding oocytes just after collection was also lower in cumulus-oocyte complexes (COCs) from SF than MF. The ooplasmic diameter of oocytes was significantly smaller in SF-derived oocytes than MF-derived ones before and after in vitro maturation (IVM), whereas the diameter significantly increased during the culture. Co-culture of SF-derived COCs with MF-derived CCMs during IVM significantly improved the meiotic competence of the oocytes to the metaphase-II stage. Furthermore, the ooplasmic diameter of SF-derived COCs during IVM was increased to the similar size of MF-derived those in the presence of MF-derived CCMs. The abilities of oocytes to be penetrated, to form male pronuclear formation and to cleave or develop to the blastocyst stage were not affected by the co-culture with CCMs. Electrophoretic analysis of CCM secretions clearly showed the presence of more protein(s) approximately 27.6 kDa in the conditioned medium when supplemented with MF-derived CCMs. In conclusion, we demonstrate that supplementation with MF-derived CCMs improves the ooplasmic diameter and meiotic competence of SF-derived oocytes. © 2017 Blackwell Verlag GmbH.

  10. RAD51AP2, a novel vertebrate- and meiotic-specific protein, sharesa conserved RAD51-interacting C-terminal domain with RAD51AP1/PIR51

    Energy Technology Data Exchange (ETDEWEB)

    Kovalenko, Oleg V.; Wiese, Claudia; Schild, David

    2006-07-25

    Many interacting proteins regulate and/or assist the activities of RAD51, a recombinase which plays a critical role in both DNA repair and meiotic recombination. Yeast two-hybrid screening of a human testis cDNA library revealed a new protein, RAD51AP2 (RAD51 Associated Protein 2), that interacts strongly with RAD51. A full-length cDNA clone predicts a novel vertebrate specific protein of 1159 residues, and the RAD51AP2 transcript was observed only in meiotic tissue (i.e. adult testis and fetal ovary), suggesting a meiotic-specific function for RAD51AP2. In HEK293 cells the interaction of RAD51 with an ectopically-expressed recombinant large fragment of RAD51AP2 requires the C-terminal 57 residues of RAD51AP2. This RAD51-binding region shows 81% homology to the C-terminus of RAD51AP1/PIR51, an otherwise totally unrelated RAD51-binding partner that is ubiquitously expressed. Analyses using truncations and point mutations in both RAD51AP1 and RAD51AP2 demonstrate that these proteins use the same structural motif for RAD51 binding. RAD54 shares some homology with this RAD51-binding motif, but this homologous region plays only an accessory role to the adjacent main RAD51-interacting region, which has been narrowed here to 40 amino acids. A novel protein, RAD51AP2, has been discovered that interacts with RAD51 through a C-terminal motif also present in RAD51AP1.

  11. Coprinus cinereus rad50 mutants reveal an essential structural role for Rad50 in axial element and synaptonemal complex formation, homolog pairing and meiotic recombination.

    Science.gov (United States)

    Acharya, Sonia N; Many, Alexander M; Schroeder, Andrew P; Kennedy, Felicia M; Savytskyy, Oleksandr P; Grubb, Jennifer T; Vincent, Jack A; Friedle, Elizabeth A; Celerin, Martina; Maillet, Daniel S; Palmerini, Heather J; Greischar, Megan A; Moncalian, Gabriel; Williams, R Scott; Tainer, John A; Zolan, Miriam E

    2008-12-01

    The Mre11/Rad50/Nbs1 (MRN) complex is required for eukaryotic DNA double-strand break (DSB) repair and meiotic recombination. We cloned the Coprinus cinereus rad50 gene and showed that it corresponds to the complementation group previously named rad12, identified mutations in 15 rad50 alleles, and mapped two of the mutations onto molecular models of Rad50 structure. We found that C. cinereus rad50 and mre11 mutants arrest in meiosis and that this arrest is Spo11 dependent. In addition, some rad50 alleles form inducible, Spo11-dependent Rad51 foci and therefore must be forming meiotic DSBs. Thus, we think it likely that arrest in both mre11-1 and the collection of rad50 mutants is the result of unrepaired or improperly processed DSBs in the genome and that Rad50 and Mre11 are dispensable in C. cinereus for DSB formation, but required for appropriate DSB processing. We found that the ability of rad50 mutant strains to form Rad51 foci correlates with their ability to promote synaptonemal complex formation and with levels of stable meiotic pairing and that partial pairing, recombination initiation, and synapsis occur in the absence of wild-type Rad50 catalytic domains. Examination of single- and double-mutant strains showed that a spo11 mutation that prevents DSB formation enhances axial element (AE) formation for rad50-4, an allele predicted to encode a protein with intact hook region and hook-proximal coiled coils, but not for rad50-1, an allele predicted to encode a severely truncated protein, or for rad50-5, which encodes a protein whose hook-proximal coiled-coil region is disrupted. Therefore, Rad50 has an essential structural role in the formation of AEs, separate from the DSB-processing activity of the MRN complex.

  12. Topoisomerase 3alpha and RMI1 suppress somatic crossovers and are essential for resolution of meiotic recombination intermediates in Arabidopsis thaliana.

    Directory of Open Access Journals (Sweden)

    Frank Hartung

    2008-12-01

    Full Text Available Topoisomerases are enzymes with crucial functions in DNA metabolism. They are ubiquitously present in prokaryotes and eukaryotes and modify the steady-state level of DNA supercoiling. Biochemical analyses indicate that Topoisomerase 3alpha (TOP3alpha functions together with a RecQ DNA helicase and a third partner, RMI1/BLAP75, in the resolution step of homologous recombination in a process called Holliday Junction dissolution in eukaryotes. Apart from that, little is known about the role of TOP3alpha in higher eukaryotes, as knockout mutants show early lethality or strong developmental defects. Using a hypomorphic insertion mutant of Arabidopsis thaliana (top3alpha-2, which is viable but completely sterile, we were able to define three different functions of the protein in mitosis and meiosis. The top3alpha-2 line exhibits fragmented chromosomes during mitosis and sensitivity to camptothecin, suggesting an important role in chromosome segregation partly overlapping with that of type IB topoisomerases. Furthermore, AtTOP3alpha, together with AtRECQ4A and AtRMI1, is involved in the suppression of crossover recombination in somatic cells as well as DNA repair in both mammals and A. thaliana. Surprisingly, AtTOP3alpha is also essential for meiosis. The phenotype of chromosome fragmentation, bridges, and telophase I arrest can be suppressed by AtSPO11 and AtRAD51 mutations, indicating that the protein is required for the resolution of recombination intermediates. As Atrmi1 mutants have a similar meiotic phenotype to Attop3alpha mutants, both proteins seem to be involved in a mechanism safeguarding the entangling of homologous chromosomes during meiosis. The requirement of AtTOP3alpha and AtRMI1 in a late step of meiotic recombination strongly hints at the possibility that the dissolution of double Holliday Junctions via a hemicatenane intermediate is indeed an indispensable step of meiotic recombination.

  13. Nuclear "waffles"

    Science.gov (United States)

    Schneider, A. S.; Berry, D. K.; Briggs, C. M.; Caplan, M. E.; Horowitz, C. J.

    2014-11-01

    Background: The dense neutron-rich matter found in supernovae and inside neutron stars is expected to form complex nonuniform phases, often referred to as nuclear pasta. The pasta shapes depend on density, temperature and proton fraction and determine many transport properties in supernovae and neutron star crusts. Purpose: To characterize the topology and compute two observables, the radial distribution function (RDF) g (r ) and the structure factor S (q ) , for systems with proton fractions Yp=0.10 ,0.20 ,0.30 , and 0.40 at about one-third of nuclear saturation density, n =0.050 fm-3 , and temperatures near k T =1 MeV . Methods: We use two recently developed hybrid CPU/GPU codes to perform large scale molecular dynamics (MD) simulations with 51 200 and 409 600 nucleons. From the output of the MD simulations we obtain the two desired observables. Results: We compute and discuss the differences in topology and observables for each simulation. We observe that the two lowest proton fraction systems simulated, Yp=0.10 and 0.20 , equilibrate quickly and form liquidlike structures. Meanwhile, the two higher proton fraction systems, Yp=0.30 and 0.40 , take a longer time to equilibrate and organize themselves in solidlike periodic structures. Furthermore, the Yp=0.40 system is made up of slabs, lasagna phase, interconnected by defects while the Yp=0.30 systems consist of a stack of perforated plates, the nuclear waffle phase. Conclusions: The periodic configurations observed in our MD simulations for proton fractions Yp≥0.30 have important consequences for the structure factors S (q ) of protons and neutrons, which relate to many transport properties of supernovae and neutron star crust. A detailed study of the waffle phase and how its structure depends on temperature, size of the simulation, and the screening length showed that finite-size effects appear to be under control and, also, that the plates in the waffle phase merge at temperatures slightly above 1.0 MeV and

  14. Effect of holding equine oocytes in meiosis inhibitor-free medium before in vitro maturation and of holding temperature on meiotic suppression and mitochondrial energy/redox potential.

    Science.gov (United States)

    Martino, Nicola A; Dell'Aquila, Maria E; Filioli Uranio, Manuel; Rutigliano, Lucia; Nicassio, Michele; Lacalandra, Giovanni M; Hinrichs, Katrin

    2014-10-11

    Evaluation of mitochondrial function offers an alternative to evaluate embryo development for assessment of oocyte viability, but little information is available on the relationship between mitochondrial and chromatin status in equine oocytes. We evaluated these parameters in immature equine oocytes either fixed immediately (IMM) or held overnight in an Earle's/Hank's' M199-based medium in the absence of meiotic inhibitors (EH treatment), and in mature oocytes. We hypothesized that EH holding may affect mitochondrial function and that holding temperature may affect the efficiency of meiotic suppression. Experiment 1 - Equine oocytes processed immediately or held in EH at uncontrolled temperature (22 to 27°C) were evaluated for initial chromatin configuration, in vitro maturation (IVM) rates and mitochondrial energy/redox potential. Experiment 2 - We then investigated the effect of holding temperature (25°C, 30°C, 38°C) on initial chromatin status of held oocytes, and subsequently repeated mitochondrial energy/redox assessment of oocytes held at 25°C vs. immediately-evaluated controls. EH holding at uncontrolled temperature was associated with advancement of germinal vesicle (GV) chromatin condensation and with meiotic resumption, as well as a lower maturation rate after IVM. Holding did not have a significant effect on mitochondrial distribution within chromatin configurations. Independent of treatment, oocytes having condensed chromatin had a significantly higher proportion of perinuclear/pericortical mitochondrial distribution than did other GV configurations. Holding did not detrimentally affect oocyte energy/redox parameters in viable GV-stage oocytes. There were no significant differences in chromatin configuration between oocytes held at 25°C and controls, whereas holding at higher temperature was associated with meiosis resumption and loss of oocytes having the condensed chromatin GV configuration. Holding at 25°C was not associated with progression

  15. EZH2 is required for mouse oocyte meiotic maturation by interacting with and stabilizing spindle assembly checkpoint protein BubRI

    OpenAIRE

    Qu, Yi; Lu, Danyu; Jiang, Hao; Chi, Xiaochun; Zhang, Hongquan

    2016-01-01

    Enhancer of zeste homolog 2 (EZH2) trimethylates histone H3 Lys 27 and plays key roles in a variety of biological processes. Stability of spindle assembly checkpoint protein BubR1 is essential for mitosis in somatic cells and for meiosis in oocytes. However, the role of EZH2 in oocyte meiotic maturation was unknown. Here, we presented a mechanism underlying EZH2 control of BubR1 stability in the meiosis of mouse oocytes. We identified a methyltransferase activity-independent function of EZH2 ...

  16. Abnormal meiotic behavior in three species of Crotalaria Comportamento meiótico anormal em três espécies de Crotalaria

    Directory of Open Access Journals (Sweden)

    Kátia Ferreira

    2009-12-01

    Full Text Available The objective of this work was to compare the meiotic behavior and pollen grain viability of three species of Crotalaria. Slides for meiotic analysis were prepared by the air-drying technique. Pollen grain viability was measured by three staining procedures (Alexander's solution, tetrazolium chloride and fluorescein diacetate and in vitro germination in a sucrose solution. Eight bivalents were observed, confirming previous reports on populations from other regions of Brazil, as well as from other countries. All species showed abnormal meiotic behavior as follows: in Crotalaria micans, cytomixis and abnormal chromosome pairing in diakinesis; in C. spectabilis, abnormal chromosome pairing in diplotene; in C. zanzibarica, shrunk nuclei in leptotene and zygotene. Pollen grains of all three species show low viability, which may be associated with the irregularities of the meiotic behavior.O objetivo deste trabalho foi comparar o comportamento meiótico e a viabilidade dos grãos de pólen de três espécies de Crotalaria. A análise meiótica foi realizada por meio da técnica de secagem ao ar. A viabilidade dos grãos de pólen foi avaliada por testes de coloração (corante de Alexander, cloreto de tetrazólio e diacetato de fluoresceína e por teste de germinação em solução de sacarose. Foram observados oito bivalentes, confirmando relatos prévios em populações de outras regiões do Brasil e de outros países. As três espécies apresentaram comportamento meiótico irregular: em Crotalaria micans, citomixia e pareamento irregular na diacinese; em C. spectabilis, pareamento irregular no diplóteno; e em C. zanzibarica, núcleo fortemente condensado nas fases de leptóteno e zigóteno. A viabilidade dos grãos de pólen das três espécies é baixa, o que pode estar associado às irregularidades do comportamento meiótico.

  17. NUCLEAR REACTOR

    Science.gov (United States)

    Miller, H.I.; Smith, R.C.

    1958-01-21

    This patent relates to nuclear reactors of the type which use a liquid fuel, such as a solution of uranyl sulfate in ordinary water which acts as the moderator. The reactor is comprised of a spherical vessel having a diameter of about 12 inches substantially surrounded by a reflector of beryllium oxide. Conventionnl control rods and safety rods are operated in slots in the reflector outside the vessel to control the operation of the reactor. An additional means for increasing the safety factor of the reactor by raising the ratio of delayed neutrons to prompt neutrons, is provided and consists of a soluble sulfate salt of beryllium dissolved in the liquid fuel in the proper proportion to obtain the result desired.

  18. On China's Nuclear Doctrine

    Directory of Open Access Journals (Sweden)

    Xia Liping

    2015-12-01

    Full Text Available Nuclear weapons have played an important role in China's national strategy. China’s nuclear doctrine has a very strong continuity. Nevertheless, China has made readjustments in its nuclear doctrine according to the changes of its internal and external situation and its general strategic threat perception. China’s nuclear doctrine has experienced a process of evolution from anti-nuclear blackmail to minimum deterrence. There are five major parts in China's nuclear doctrine: policy of declaration, nuclear development, nuclear deployment, nuclear employment, and nuclear disarmament. Because China is faced with a different situation from other nuclear powers and has its own strategic culture, China has a nuclear doctrine with its own characteristics. China’s nuclear doctrine has been affiliated with and has served the national development strategy, national security strategy, national defense policy and military strategy of China.

  19. Reconversion of nuclear weapons

    CERN Document Server

    Kapitza, Sergei P

    1992-01-01

    The nuclear predicament or nuclear option. Synopsis of three lectures : 1- The physical basis of nuclear technology. Physics of fission. Chain reaction in reactors and weapons. Fission fragments. Separration of isotopes. Radiochemistry.2- Nuclear reactors with slow and fast neutrons. Power, size, fuel and waste. Plutonium production. Dose rate, shielding and health hazard. The lessons of Chernobyl3- Nuclear weapons. Types, energy, blast and fallout. Fusion and hydrogen bombs. What to do with nuclear weapons when you cannot use them? Testing. Nonmilittary use. Can we get rid of the nuclear weapon? Nuclear proliferation. Is there a nuclear future?

  20. Nuclear fuels

    Energy Technology Data Exchange (ETDEWEB)

    Beauvy, M.; Berthoud, G.; Defranceschi, M.; Ducros, G.; Guerin, Y.; Limoge, Y.; Madic, Ch.; Santarini, G.; Seiler, J.M.; Sollogoub, P.; Vernaz, E.; Guillet, J.L.; Ballagny, A.; Bechade, J.L.; Bonin, B.; Brachet, J.Ch.; Delpech, M.; Dubois, S.; Ferry, C.; Freyss, M.; Gilbon, D.; Grouiller, J.P.; Iracane, D.; Lansiart, S.; Lemoine, P.; Lenain, R.; Marsault, Ph.; Michel, B.; Noirot, J.; Parrat, D.; Pelletier, M.; Perrais, Ch.; Phelip, M.; Pillon, S.; Poinssot, Ch.; Vallory, J.; Valot, C.; Pradel, Ph.; Bonin, B.; Bouquin, B.; Dozol, M.; Lecomte, M.; Vallee, A.; Bazile, F.; Parisot, J.F.; Finot, P.; Roberts, J.F

    2009-07-01

    Fuel is one of the essential components in a reactor. It is within that fuel that nuclear reactions take place, i.e. fission of heavy atoms, uranium and plutonium. Fuel is at the core of the reactor, but equally at the core of the nuclear system as a whole. Fuel design and properties influence reactor behavior, performance, and safety. Even though it only accounts for a small part of the cost per kilowatt-hour of power provided by current nuclear power plants, good utilization of fuel is a major economic issue. Major advances have yet to be achieved, to ensure longer in-reactor dwell-time, thus enabling fuel to yield more energy; and improve ruggedness. Aside from economics, and safety, such strategic issues as use of plutonium, conservation of resources, and nuclear waste management have to be addressed, and true technological challenges arise. This Monograph surveys current knowledge regarding in-reactor behavior, operating limits, and avenues for R and D. It also provides illustrations of ongoing research work, setting out a few noteworthy results recently achieved. Content: 1 - Introduction; 2 - Water reactor fuel: What are the features of water reactor fuel? 9 (What is the purpose of a nuclear fuel?, Ceramic fuel, Fuel rods, PWR fuel assemblies, BWR fuel assemblies); Fabrication of water reactor fuels (Fabrication of UO{sub 2} pellets, Fabrication of MOX (mixed uranium-plutonium oxide) pellets, Fabrication of claddings); In-reactor behavior of UO{sub 2} and MOX fuels (Irradiation conditions during nominal operation, Heat generation, and removal, The processes involved at the start of irradiation, Fission gas behavior, Microstructural changes); Water reactor fuel behavior in loss of tightness conditions (Cladding, the first containment barrier, Causes of failure, Consequences of a failure); Microscopic morphology of fuel ceramic and its evolution under irradiation; Migration and localization of fission products in UOX and MOX matrices (The ceramic under

  1. Trends in Nuclear Astrophysics

    OpenAIRE

    Schatz, Hendrik

    2016-01-01

    Nuclear Astrophysics is a vibrant field at the intersection of nuclear physics and astrophysics that encompasses research in nuclear physics, astrophysics, astronomy, and computational science. This paper is not a review. It is intended to provide an incomplete personal perspective on current trends in nuclear astrophysics and the specific role of nuclear physics in this field.

  2. Mouse Y-linked Zfy1 and Zfy2 are expressed during the male-specific interphase between meiosis I and meiosis II and promote the 2nd meiotic division.

    Science.gov (United States)

    Vernet, Nadège; Mahadevaiah, Shantha K; Yamauchi, Yasuhiro; Decarpentrie, Fanny; Mitchell, Michael J; Ward, Monika A; Burgoyne, Paul S

    2014-06-01

    Mouse Zfy1 and Zfy2 encode zinc finger transcription factors that map to the short arm of the Y chromosome (Yp). They have previously been shown to promote meiotic quality control during pachytene (Zfy1 and Zfy2) and at the first meiotic metaphase (Zfy2). However, from these previous studies additional roles for genes encoded on Yp during meiotic progression were inferred. In order to identify these genes and investigate their function in later stages of meiosis, we created three models with diminishing Yp and Zfy gene complements (but lacking the Y-long-arm). Since the Y-long-arm mediates pairing and exchange with the X via their pseudoautosomal regions (PARs) we added a minute PAR-bearing X chromosome derivative to enable formation of a sex bivalent, thus avoiding Zfy2-mediated meiotic metaphase I (MI) checkpoint responses to the unpaired (univalent) X chromosome. Using these models we obtained definitive evidence that genetic information on Yp promotes meiosis II, and by transgene addition identified Zfy1 and Zfy2 as the genes responsible. Zfy2 was substantially more effective and proved to have a much more potent transactivation domain than Zfy1. We previously established that only Zfy2 is required for the robust apoptotic elimination of MI spermatocytes in response to a univalent X; the finding that both genes potentiate meiosis II led us to ask whether there was de novo Zfy1 and Zfy2 transcription in the interphase between meiosis I and meiosis II, and this proved to be the case. X-encoded Zfx was also expressed at this stage and Zfx over-expression also potentiated meiosis II. An interphase between the meiotic divisions is male-specific and we previously hypothesised that this allows meiosis II critical X and Y gene reactivation following sex chromosome silencing in meiotic prophase. The interphase transcription and meiosis II function of Zfx, Zfy1 and Zfy2 validate this hypothesis.

  3. Germ cell nuclear factor regulates gametogenesis in developing gonads.

    Science.gov (United States)

    Sabour, Davood; Xu, Xueping; Chung, Arthur C K; Le Menuet, Damien; Ko, Kinarm; Tapia, Natalia; Araúzo-Bravo, Marcos J; Gentile, Luca; Greber, Boris; Hübner, Karin; Sebastiano, Vittorio; Wu, Guangming; Schöler, Hans R; Cooney, Austin J

    2014-01-01

    Expression of germ cell nuclear factor (GCNF; Nr6a1), an orphan member of the nuclear receptor gene family of transcription factors, during gastrulation and neurulation is critical for normal embryogenesis in mice. Gcnf represses the expression of the POU-domain transcription factor Oct4 (Pou5f1) during mouse post-implantation development. Although Gcnf expression is not critical for the embryonic segregation of the germ cell lineage, we found that sexually dimorphic expression of Gcnf in germ cells correlates with the expression of pluripotency-associated genes, such as Oct4, Sox2, and Nanog, as well as the early meiotic marker gene Stra8. To elucidate the role of Gcnf during mouse germ cell differentiation, we generated an ex vivo Gcnf-knockdown model in combination with a regulated CreLox mutation of Gcnf. Lack of Gcnf impairs normal spermatogenesis and oogenesis in vivo, as well as the derivation of germ cells from embryonic stem cells (ESCs) in vitro. Inactivation of the Gcnf gene in vivo leads to loss of repression of Oct4 expression in both male and female gonads.

  4. Children's (Pediatric) Nuclear Medicine

    Medline Plus

    Full Text Available ... What are the limitations of Children's Nuclear Medicine? What is Children's (Pediatric) Nuclear Medicine? Nuclear medicine is ... this time is PET/MRI. top of page What are some common uses of the procedure? Children's ( ...

  5. Children's (Pediatric) Nuclear Medicine

    Medline Plus

    Full Text Available ... previous nuclear medicine exam. top of page What are the limitations of Children's (Pediatric) Nuclear Medicine? Nuclear medicine procedures can be time consuming. It can take several hours to days ...

  6. Mean nuclear volume

    DEFF Research Database (Denmark)

    Mogensen, O.; Sørensen, Flemming Brandt; Bichel, P.

    1999-01-01

    We evaluated the following nine parameters with respect to their prognostic value in females with endometrial cancer: four stereologic parameters [mean nuclear volume (MNV), nuclear volume fraction, nuclear index and mitotic index], the immunohistochemical expression of cancer antigen (CA125...

  7. Nuclear Quadrupole Moments and Nuclear Shell Structure

    Science.gov (United States)

    Townes, C. H.; Foley, H. M.; Low, W.

    1950-06-23

    Describes a simple model, based on nuclear shell considerations, which leads to the proper behavior of known nuclear quadrupole moments, although predictions of the magnitudes of some quadrupole moments are seriously in error.

  8. Listeria monocytogenes virulence factor Listeriolysin O favors bacterial growth in co-culture with the ciliate Tetrahymena pyriformis, causes protozoan encystment and promotes bacterial survival inside cysts

    Directory of Open Access Journals (Sweden)

    Ermolaeva Svetlana A

    2010-01-01

    Full Text Available Abstract Background The gram-positive pathogenic bacterium Listeria monocytogenes is widely spread in the nature. L. monocytogenes was reported to be isolated from soil, water, sewage and sludge. Listeriolysin O (LLO is a L. monocytogenes major virulence factor. In the course of infection in mammals, LLO is required for intracellular survival and apoptosis induction in lymphocytes. In this study, we explored the potential of LLO to promote interactions between L. monocytogenes and the ubiquitous inhabitant of natural ecosystems bacteriovorous free-living ciliate Tetrahymena pyriformis. Results Wild type L. monocytogenes reduced T. pyriformis trophozoite counts and stimulated encystment. The effects were observed starting from 48 h of co-incubation. On the day 14, trophozoites were eliminated from the co-culture while about 5 × 104 cells/ml remained in the axenic T. pyriformis culture. The deficient in the LLO-encoding hly gene L. monocytogenes strain failed to cause mortality among protozoa and to trigger protozoan encystment. Replenishment of the hly gene in the mutant strain restored toxicity towards protozoa and induction of protozoan encystment. The saprophytic non-haemolytic species L. innocua transformed with the LLO-expressing plasmid caused extensive mortality and encystment in ciliates. During the first week of co-incubation, LLO-producing L. monocytogenes demonstrated higher growth rates in association with T. pyriformis than the LLO-deficient isogenic strain. At latter stages of co-incubation bacterial counts were similar for both strains. T. pyriformis cysts infected with wild type L. monocytogenes caused listerial infection in guinea pigs upon ocular and oral inoculation. The infection was proved by bacterial plating from the internal organs. Conclusions The L. monocytogenes virulence factor LLO promotes bacterial survival and growth in the presence of bacteriovorous ciliate T. pyriformis. LLO is responsible for L. monocytogenes

  9. Nuclear energy data 2010

    CERN Document Server

    2010-01-01

    This 2010 edition of Nuclear Energy Data , the OECD Nuclear Energy Agency's annual compilation of official statistics and country reports on nuclear energy, provides key information on plans for new nuclear plant construction, nuclear fuel cycle developments as well as current and projected nuclear generating capacity to 2035 in OECD member countries. This comprehensive overview provides authoritative information for policy makers, experts and other interested stakeholders.

  10. Nuclear Fuel Cycle & Vulnerabilities

    Energy Technology Data Exchange (ETDEWEB)

    Boyer, Brian D. [Los Alamos National Laboratory

    2012-06-18

    The objective of safeguards is the timely detection of diversion of significant quantities of nuclear material from peaceful nuclear activities to the manufacture of nuclear weapons or of other nuclear explosive devices or for purposes unknown, and deterrence of such diversion by the risk of early detection. The safeguards system should be designed to provide credible assurances that there has been no diversion of declared nuclear material and no undeclared nuclear material and activities.

  11. In vitro growth and maturation of isolated caprine preantral follicles: Influence of insulin and FSH concentration, culture dish, coculture, and oocyte size on meiotic resumption.

    Science.gov (United States)

    Silva, G M; Brito, I R; Sales, A D; Aguiar, F L N; Duarte, A B G; Araújo, V R; Vieira, L A; Magalhães-Padilha, D M; Lima, L F; Alves, B G; Silveira, L B R; Lo Turco, E G; Rodrigues, A P; Campello, C C; Wheeler, M B; Figueiredo, J R

    2017-03-01

    The aims of this study were: (1) to evaluate the effect of different insulin concentrations, alone or in combination with either a fixed FSH concentration or increasing FSH concentrations on the in vitro culture of isolated caprine preantral follicles and (2) to analyze the efficiency of two IVM media and maturation culture systems (with or without coculture with in vivo grown oocytes) on the meiosis resumption. Secondary follicles were cultured for 18 days in a basic medium supplemented with low- or high-insulin concentration alone or with a fixed FSH concentration or with increasing FSH concentrations. Oocytes grown in vivo or in vitro were matured alone or cocultured. The high-insulin concentration associated with fixed FSH treatment had higher meiotic resumption rate (P culture period improved meiotic resumption rate and produced MII oocytes from caprine preantral follicles cultured in vitro. The MII rate was similar between in vivo and in vitro grown oocytes ≥110 μm. Copyright © 2016 Elsevier Inc. All rights reserved.

  12. A mutation in the FHA domain of Coprinus cinereus Nbs1 Leads to Spo11-independent meiotic recombination and chromosome segregation.

    Science.gov (United States)

    Crown, K Nicole; Savytskyy, Oleksandr P; Malik, Shehre-Banoo; Logsdon, John; Williams, R Scott; Tainer, John A; Zolan, Miriam E

    2013-11-06

    Nbs1, a core component of the Mre11-Rad50-Nbs1 complex, plays an essential role in the cellular response to DNA double-strand breaks (DSBs) and poorly understood roles in meiosis. We used the basidiomycete Coprinus cinereus to examine the meiotic roles of Nbs1. We identified the C. cinereus nbs1 gene and demonstrated that it corresponds to a complementation group previously known as rad3. One allele, nbs1-2, harbors a point mutation in the Nbs1 FHA domain and has a mild spore viability defect, increased frequency of meiosis I nondisjunction, and an altered crossover distribution. The nbs1-2 strain enters meiosis with increased levels of phosphorylated H2AX, which we hypothesize represent unrepaired DSBs formed during premeiotic replication. In nbs1-2, there is no apparent induction of Spo11-dependent DSBs during prophase. We propose that replication-dependent DSBs, resulting from defective replication fork protection and processing by the Mre11-Rad50-Nbs1 complex, are competent to form meiotic crossovers in C. cinereus, and that these crossovers lead to high levels of faithful chromosome segregation. In addition, although crossover distribution is altered in nbs1-2, the majority of crossovers were found in subtelomeric regions, as in wild-type. Therefore, the location of crossovers in C. cinereus is maintained when DSBs are induced via a Spo11-independent mechanism.

  13. NuMA-related LIN-5, ASPM-1, calmodulin and dynein promote meiotic spindle rotation independently of cortical LIN-5/GPR/Galpha.

    Science.gov (United States)

    van der Voet, Monique; Berends, Christian W H; Perreault, Audrey; Nguyen-Ngoc, Tu; Gönczy, Pierre; Vidal, Marc; Boxem, Mike; van den Heuvel, Sander

    2009-03-01

    The spindle apparatus dictates the plane of cell cleavage, which is critical in the choice between symmetric or asymmetric division. Spindle positioning is controlled by an evolutionarily conserved pathway, which involves LIN-5/GPR-1/2/Galpha in Caenorhabditis elegans, Mud/Pins/Galpha in Drosophila and NuMA/LGN/Galpha in humans. GPR-1/2 and Galpha localize LIN-5 to the cell cortex, which engages dynein and controls the cleavage plane during early mitotic divisions in C. elegans. Here we identify ASPM-1 (abnormal spindle-like, microcephaly-associated) as a novel LIN-5 binding partner. ASPM-1, together with calmodulin (CMD-1), promotes meiotic spindle organization and the accumulation of LIN-5 at meiotic and mitotic spindle poles. Spindle rotation during maternal meiosis is independent of GPR-1/2 and Galpha, yet requires LIN-5, ASPM-1, CMD-1 and dynein. Our data support the existence of two distinct LIN-5 complexes that determine localized dynein function: LIN-5/GPR-1/2/Galpha at the cortex, and LIN-5/ASPM-1/CMD-1 at spindle poles. These functional interactions may be conserved in mammals, with implications for primary microcephaly.

  14. CDC-48/p97 is required for proper meiotic chromosome segregation via controlling AIR-2/Aurora B kinase localization in Caenorhabditis elegans.

    Science.gov (United States)

    Sasagawa, Yohei; Higashitani, Atsushi; Urano, Takeshi; Ogura, Teru; Yamanaka, Kunitoshi

    2012-08-01

    CDC-48/p97 is a AAA (ATPases associated with diverse cellular activities) chaperone involved in protein conformational changes such as the disassembly of protein complexes. We previously reported that Caenorhabditis elegans CDC-48.1 and CDC-48.2 (CDC-48s) are essential for the progression of meiosis I metaphase. Here, we report that CDC-48s are required for proper chromosome segregation during meiosis in C. elegans. In wild-type worms, at the diakinesis phase, phosphorylation of histone H3, one of the known substrates of aurora B kinase (AIR-2), on meiosis I chromatids correlated with AIR-2 localization at the cohesion sites of homologous chromatids. Conversely, depletion of CDC-48s resulted in a significant expansion of signals for AIR-2 and phosphorylated histone H3 over the entire length of meiotic chromosomes, leading to defective chromosome segregation, while the total amount of AIR-2 in lysates was not changed by the depletion of CDC-48s. The defective segregation of meiotic chromosomes caused by the depletion of CDC-48s was suppressed by the simultaneous depletion of AIR-2 and is similar to that observed following the depletion of protein phosphatase 1 (PP1) phosphatases. However, the amount and localization of PP1 were not changed by the depletion of CDC-48s. These results suggest that CDC-48s control the restricted localization of AIR-2 to the cohesion sites of homologous chromatids in meiosis I. Copyright © 2012 Elsevier Inc. All rights reserved.

  15. Cohesin Removal along the Chromosome Arms during the First Meiotic Division Depends on a NEK1-PP1γ-WAPL Axis in the Mouse

    Directory of Open Access Journals (Sweden)

    Miguel A. Brieño-Enríquez

    2016-10-01

    Full Text Available Mammalian NIMA-like kinase-1 (NEK1 is a dual-specificity kinase highly expressed in mouse germ cells during prophase I of meiosis. Loss of NEK1 induces retention of cohesin on chromosomes at meiotic prophase I. Timely deposition and removal of cohesin is essential for accurate chromosome segregation. Two processes regulate cohesin removal: a non-proteolytic mechanism involving WAPL, sororin, and PDS5B and direct cleavage by separase. Here, we demonstrate a role for NEK1 in the regulation of WAPL loading during meiotic prophase I, via an interaction between NEK1 and PDS5B. This regulation of WAPL by NEK1-PDS5B is mediated by protein phosphatase 1 gamma (PP1γ, which both interacts with and is a phosphotarget of NEK1. Taken together, our results reveal that NEK1 phosphorylates PP1γ, leading to the dephosphorylation of WAPL, which, in turn, results in its retention on chromosome cores to promote loss of cohesion at the end of prophase I in mammals.

  16. Temperature stress differentially modulates transcription in meiotic anthers of heat-tolerant and heat-sensitive tomato plants

    Directory of Open Access Journals (Sweden)

    Pezzotti Mario

    2011-07-01

    Full Text Available Abstract Background Fluctuations in temperature occur naturally during plant growth and reproduction. However, in the hot summers this variation may become stressful and damaging for the molecular mechanisms involved in proper cell growth, impairing thus plant development and particularly fruit-set in many crop plants. Tolerance to such a stress can be achieved by constitutive gene expression or by rapid changes in gene expression, which ultimately leads to protection against thermal damage. We have used cDNA-AFLP and microarray analyses to compare the early response of the tomato meiotic anther transcriptome to moderate heat stress conditions (32°C in a heat-tolerant and a heat-sensitive tomato genotype. In the light of the expected global temperature increases, elucidating such protective mechanisms and identifying candidate tolerance genes can be used to improve breeding strategies for crop tolerance to heat stress. Results The cDNA-AFLP analysis shows that 30 h of moderate heat stress (MHS alter the expression of approximately 1% of the studied transcript-derived fragments in a heat-sensitive genotype. The major effect is gene down-regulation after the first 2 h of stress. The microarray analysis subsequently applied to elucidate early responses of a heat-tolerant and a heat-sensitive tomato genotype, also shows about 1% of the genes having significant changes in expression after the 2 h of stress. The tolerant genotype not only reacts with moderate transcriptomic changes but also exhibits constitutively higher expression levels of genes involved in protection and thermotolerance. Conclusion In contrast to the heat-sensitive genotype, the heat-tolerant genotype exhibits moderate transcriptional changes under moderate heat stress. Moreover, the heat-tolerant genotype also shows a different constitutive gene expression profile compared to the heat-sensitive genotype, indicating genetic differences in adaptation to increased temperatures. In

  17. Nuclear weapons modernizations

    Energy Technology Data Exchange (ETDEWEB)

    Kristensen, Hans M. [Federation of American Scientists, Washington, DC (United States)

    2014-05-09

    This article reviews the nuclear weapons modernization programs underway in the world's nine nuclear weapons states. It concludes that despite significant reductions in overall weapons inventories since the end of the Cold War, the pace of reductions is slowing - four of the nuclear weapons states are even increasing their arsenals, and all the nuclear weapons states are busy modernizing their remaining arsenals in what appears to be a dynamic and counterproductive nuclear competition. The author questions whether perpetual modernization combined with no specific plan for the elimination of nuclear weapons is consistent with the nuclear Non-Proliferation Treaty and concludes that new limits on nuclear modernizations are needed.

  18. Nuclear energy data 2011

    CERN Document Server

    2011-01-01

     . Nuclear Energy Data, the OECD Nuclear Energy Agency's annual compilation of statistics and country reports on nuclear energy, contains official information provided by OECD member country governments on plans for new nuclear plant construction, nuclear fuel cycle developments as well as current and projected nuclear generating capacity to 2035. For the first time, it includes data for Chile, Estonia, Israel and Slovenia, which recently became OECD members. Key elements of this edition show a 2% increase in nuclear and total electricity production and a 0.5% increase in nuclear generating ca

  19. l-carnitine supplementation during vitrification of mouse germinal vesicle stage-oocytes and their subsequent in vitro maturation improves meiotic spindle configuration and mitochondrial distribution in metaphase II oocytes.

    Science.gov (United States)

    Moawad, Adel R; Xu, Baozeng; Tan, Seang Lin; Taketo, Teruko

    2014-10-10

    How does l-carnitine (LC) supplementation during vitrification and in vitro maturation (IVM) of germinal vesicle stage (GV)-oocytes improve the developmental competence of the resultant metaphase II (MII) oocytes? LC supplementation during both vitrification of GV-oocytes and their subsequent IVM improved nuclear maturation as well as meiotic spindle assembly and mitochondrial distribution in MII oocytes. Vitrification of GV-oocytes results in a lower success rate of blastocyst development compared with non-vitrified oocytes. LC supplementation during both vitrification and IVM of mouse GV-oocytes significantly improves embryonic development after IVF. GV-oocytes were collected from (B6.DBA)F1 and B6 mouse strains and subjected to vitrification and warming with or without 3.72 mM LC supplementation. After IVM with or without LC supplementation, the rate of nuclear maturation and the quality of MII oocytes were evaluated. At least 20 oocytes/group were examined, and each experiment was repeated at least three times. All experiments were conducted during 2013-2014. Extrusion of the first polar body in IVM oocytes was observed as an indication of nuclear maturation. Spindle assembly and chromosomal alignment were examined by immunostaining of α-tubulin and nuclear staining with 4,6-diamidino-2-phenylindole (DAPI). Mitochondrial distribution and oxidative activity were measured by staining with Mitotracker Green Fluorescence Mitochondria (Mitotracker Green FM) and chloromethyltetramethylrosamine (Mitotracker Orange CMTMRos), respectively. ATP levels were determined by using the Bioluminescent Somatic Cell Assay Kit. LC supplementation during both vitrification and IVM of GV-oocytes significantly increased the proportions of oocytes with normal MII spindles to the levels comparable with those of non-vitrified oocytes in both mouse strains. While vitrification of GV-oocytes lowered the proportions of MII oocytes with peripherally concentrated mitochondrial distribution

  20. Synaptonemal complexes , transverse filaments and interference in mouse meiotic recombination; an immunocytological study = Synaptonemale complexen, transversale filamenten en interferentie bij de meiotsche recombinatie bij de muis; een immuuncytologische studie

    NARCIS (Netherlands)

    Boer, de E.

    2007-01-01

    During the prophase of the first meiotic division, homologous chromosomes (homologs} recognize each other and form stable pairs (bivalents). Subsequently non-sister chromatids of homologous chromosomes exchange corresponding parts (crossing over). These events are accompanied by the formation of a