Science.gov

Sample records for meiotic spatial chromosome

  1. Premeiotic events and meiotic chromosome pairing.

    PubMed

    Bennett, M D

    1984-01-01

    There is practical difficulty in identifying when meiosis begins. Moreover, because of contradictory definitions there is ambiguity and some confusion as to when, in terms of the cell cycle, premeiosis ends and meiosis begins. Nevertheless, results for several organisms show clearly that meiotic chromosome behaviour is affected by premeiotic events and especially by events during the final premeiotic mitosis and/or premeiotic interphase. This review considers only premeiotic events which do (or might) affect meiotic chromosome pairing by their effect on genomic characters, such as: chromosome number, homology, condition and position, with particular emphasis on the last. Interpreted in its widest sense 'premeiotic events affecting meiotic chromosome pairing' must include karyogamy. Moreover, while karyogamy is the normal means of achieving the diploid chromosome number and pairs of homologues essential for normal chromosome pairing, it is not the only way, as illustrated by the remarkable premeiotic adaptations seen in the apogamous ferns and the frog Rana esculenta. Little is known about the condition (including the molecular organization) of chromosomes during their approach and switch to meiosis. However, completion during premeiosis of some DNA synthesis may be essential for normal meiotic chromosome pairing. Various results (including different effects of colchicine given first at different premeiotic stages) have been claimed as evidence of one or other type of premeiotic spatial ordering of chromosomes which might favour, or be essential for, meiotic chromosome pairing. Chromosome placement has been studied recently using the electron microscope, serial thin-section, reconstruction technique. This has revealed clear evidence of non-random spatial placement of chromosomes in non-meiotic and premeiotic cells. For example, in root-tip cells of barley, Hordeum vulgare L. cv. Tuleen 346 (2n = 2x = 14), it showed: a significant spatial separation of two haploid

  2. Chromosome choreography: the meiotic ballet.

    PubMed

    Page, Scott L; Hawley, R Scott

    2003-08-01

    The separation of homologous chromosomes during meiosis in eukaryotes is the physical basis of Mendelian inheritance. The core of the meiotic process is a specialized nuclear division (meiosis I) in which homologs pair with each other, recombine, and then segregate from each other. The processes of chromosome alignment and pairing allow for homolog recognition. Reciprocal meiotic recombination ensures meiotic chromosome segregation by converting sister chromatid cohesion into mechanisms that hold homologous chromosomes together. Finally, the ability of sister kinetochores to orient to a single pole at metaphase I allows the separation of homologs to two different daughter cells. Failures to properly accomplish this elegant chromosome dance result in aneuploidy, a major cause of miscarriage and birth defects in human beings. PMID:12907787

  3. Meiotic chromosome structure and function in plants.

    PubMed

    Mainiero, Samantha; Pawlowski, Wojciech P

    2014-01-01

    Chromosome structure is important for many meiotic processes. Here, we outline 3 main determinants of chromosome structure and their effects on meiotic processes in plants. Cohesins are necessary to hold sister chromatids together until the first meiotic division, ensuring that homologous chromosomes and not sister chromatids separate during anaphase I. During meiosis in maize, Arabidopsis, and rice, cohesins are needed for establishing early prophase chromosome structure and recombination and for aligning bivalents at the metaphase plate. Condensin complexes play pivotal roles in controlling the packaging of chromatin into chromosomes through chromatin compaction and chromosome individualization. In animals and fungi, these complexes establish a meiotic chromosome structure that allows for proper recombination, pairing, and synapsis of homologous chromosomes. In plants, information on the role of condensins in meiosis is limited, but they are known to be required for successful completion of reproductive development. Therefore, we speculate that they play roles similar to animal and fungal condensins during meiosis. Plants generally have large and complex genomes due to frequent polyploidy events, and likely, condensins and cohesins organize chromosomes in such a way as to ensure genome stability. Hexaploid wheat has evolved a unique mechanism using a Ph1 locus-controlled chromosome organization to ensure proper chromosome pairing in meiosis. Altogether, studies on meiotic chromosome structure indicate that chromosome organization is not only important for chromatin packaging but also fulfills specific functions in facilitating chromosome interactions during meiosis, including pairing and recombination. PMID:25096046

  4. Meiotic segregation of a homeologous chromosome pair.

    PubMed

    Maxfield Boumil, R; Kemp, B; Angelichio, M; Nilsson-Tillgren, T; Dawson, D S

    2003-03-01

    During meiosis, the alignment of homologous chromosomes facilitates their subsequent migration away from one another to opposite spindle poles at anaphase I. Recombination is part of the mechanism by which chromosomes identify their homologous partners, and serves to link the homologs in a way that, in some organisms, has been shown to promote proper attachment to the meiotic spindle. We have built a diploid strain that contains a pair of homeologous chromosomes V': one is derived from Saccharomyces cerevisiae and one originates from S. carlsbergensis. Sequence analysis reveals that these chromosomes share 71% sequence identity. The homeologs experience high levels of meiotic double-stranded breaks. Despite their relatedness and their competence to initiate recombination, the meiotic segregation behavior of the homeologous chromosomes suggests that, in most meioses, they are partitioned by a meiotic segregation system that has been shown previously to partition non-exchange chromosomes and pairs with no homology. Though the homeologous chromosomes show a degree of meiotic segregation fidelity similar to that of other non-exchange pairs, our data provide evidence that their limited sequence homology may provide some bias in meiotic partner choice. PMID:12655401

  5. Female meiotic sex chromosome inactivation in chicken.

    PubMed

    Schoenmakers, Sam; Wassenaar, Evelyne; Hoogerbrugge, Jos W; Laven, Joop S E; Grootegoed, J Anton; Baarends, Willy M

    2009-05-01

    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. PMID:19461881

  6. Female Meiotic Sex Chromosome Inactivation in Chicken

    PubMed Central

    Schoenmakers, Sam; Wassenaar, Evelyne; Hoogerbrugge, Jos W.; Laven, Joop S. E.; Grootegoed, J. Anton; Baarends, Willy M.

    2009-01-01

    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, γH2AX, 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 γH2AX 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 γH2AX 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. PMID:19461881

  7. Cytological analysis of Arabidopsis thaliana meiotic chromosomes.

    PubMed

    Armstrong, Susan J; Sanchez-Moran, Eugenio; Franklin, F Chris H

    2009-01-01

    Advances in molecular biology and in the genetics of Arabidopsis thaliana have led to this organism becoming an important model for the analysis of meiosis in plants. Cytogenetic investigations are pivotal to meiotic studies and a number of technological improvements for Arabidopsis cytology have provided a range of tools to investigate chromosome behaviour during meiosis. This chapter includes protocols on basic cytology, FISH analysis, immunocytology, a procedure for a meiotic time course and electron microscopy.

  8. Meiotic drive of chromosomal knobs reshaped the maize genome.

    PubMed Central

    Buckler, E S; Phelps-Durr, T L; Buckler, C S; Dawe, R K; Doebley, J F; Holtsford, T P

    1999-01-01

    Meiotic drive is the subversion of meiosis so that particular genes are preferentially transmitted to the progeny. Meiotic drive generally causes the preferential segregation of small regions of the genome; however, in maize we propose that meiotic drive is responsible for the evolution of large repetitive DNA arrays on all chromosomes. A maize meiotic drive locus found on an uncommon form of chromosome 10 [abnormal 10 (Ab10)] may be largely responsible for the evolution of heterochromatic chromosomal knobs, which can confer meiotic drive potential to every maize chromosome. Simulations were used to illustrate the dynamics of this meiotic drive model and suggest knobs might be deleterious in the absence of Ab10. Chromosomal knob data from maize's wild relatives (Zea mays ssp. parviglumis and mexicana) and phylogenetic comparisons demonstrated that the evolution of knob size, frequency, and chromosomal position agreed with the meiotic drive hypothesis. Knob chromosomal position was incompatible with the hypothesis that knob repetitive DNA is neutral or slightly deleterious to the genome. We also show that environmental factors and transposition may play a role in the evolution of knobs. Because knobs occur at multiple locations on all maize chromosomes, the combined effects of meiotic drive and genetic linkage may have reshaped genetic diversity throughout the maize genome in response to the presence of Ab10. Meiotic drive may be a major force of genome evolution, allowing revolutionary changes in genome structure and diversity over short evolutionary periods. PMID:10471723

  9. Meiotic Crossing over between Nonhomologous Chromosomes Affects Chromosome Segregation in Yeast

    PubMed Central

    Jinks-Robertson, S.; Sayeed, S.; Murphy, T.

    1997-01-01

    Meiotic recombination between artificial repeats positioned on nonhomologous chromosomes occurs efficiently in the yeast Saccharomyces cerevisiae. Both gene conversion and crossover events have been observed, with crossovers yielding reciprocal translocations. In the current study, 5.5-kb ura3 repeats positioned on chromosomes V and XV were used to examine the effect of ectopic recombination on meiotic chromosome segregation. Ura(+) random spores were selected and gene conversion vs. crossover events were distinguished by Southern blot analysis. Approximately 15% of the crossover events between chromosomes V and XV were associated with missegregation of one of these chromosomes. The missegregation was manifest as hyperploid spores containing either both translocations plus a normal chromosome, or both normal chromosomes plus one of the translocations. In those cases where it could be analyzed, missegregation occurred at the first meiotic division. These data are discussed in terms of a model in which ectopic crossovers compete efficiently with normal allelic crossovers in directing meiotic chromosome segregation. PMID:9136001

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

    PubMed

    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.

  11. HIM-8 Binds to the X Chromosome Pairing Center and Mediates Chromosome-Specific Meiotic Synapsis

    PubMed Central

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

    2015-01-01

    SUMMARY The him-8 gene is essential for proper meiotic segregation of the X chromosomes in C. elegans. Here we show that loss of him-8 function causes profound X chromosome-specific defects in homolog pairing and synapsis. him-8 encodes a C2H2 zinc-finger protein that is expressed during meiosis and concentrates at a site on the X chromosome known as the meiotic pairing center (PC). A role for HIM-8 in PC function is supported by 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 that retains both chromosome binding and NE localization fails to stabilize pairing or promote synapsis. These observations indicate that stabilization of homolog pairing is an active process in which the tethering of chromosome sites to the NE may be necessary but is not sufficient. PMID:16360035

  12. Silencing of unsynapsed meiotic chromosomes in the mouse.

    PubMed

    Turner, James M A; Mahadevaiah, Shantha K; Fernandez-Capetillo, Oscar; Nussenzweig, André; Xu, Xiaoling; Deng, Chu-Xia; Burgoyne, Paul S

    2005-01-01

    In Neurospora, DNA unpaired in meiosis both is silenced and induces silencing of all DNA homologous to it. This process, called meiotic silencing by unpaired DNA, is thought to protect the host genome from invasion by transposable elements. We now show that silencing of unpaired (unsynapsed) chromosome regions also takes place in the mouse during both male and female meiosis. The tumor suppressor protein BRCA1 is implicated in this silencing, mirroring its role in the meiotic silencing of the X and Y chromosomes in normal male meiosis. These findings impact on the interpretation of the relationship between synaptic errors and sterility in mammals and extend our understanding of the biology of Brca1.

  13. Direct visualization reveals kinetics of meiotic chromosome synapsis

    SciTech Connect

    Rog, Ofer; Dernburg, Abby  F.

    2015-03-17

    The synaptonemal complex (SC) is a conserved protein complex that stabilizes interactions along homologous chromosomes (homologs) during meiosis. The SC regulates genetic exchanges between homologs, thereby enabling reductional division and the production of haploid gametes. Here, we directly observe SC assembly (synapsis) by optimizing methods for long-term fluorescence recording in C. elegans. We report that synapsis initiates independently on each chromosome pair at or near pairing centers—specialized regions required for homolog associations. Once initiated, the SC extends rapidly and mostly irreversibly to chromosome ends. Quantitation of SC initiation frequencies and extension rates reveals that initiation is a rate-limiting step in homolog interactions. Eliminating the dynein-driven chromosome movements that accompany synapsis severely retards SC extension, revealing a new role for these conserved motions. This work provides the first opportunity to directly observe and quantify key aspects of meiotic chromosome interactions and will enable future in vivo analysis of germline processes.

  14. Transcription dynamically patterns the meiotic chromosome-axis interface

    PubMed Central

    Sun, Xiaoji; Huang, Lingzhi; Markowitz, Tovah E; Blitzblau, Hannah G; Chen, Doris; Klein, Franz; Hochwagen, Andreas

    2015-01-01

    Meiotic chromosomes are highly compacted yet remain transcriptionally active. To understand how chromosome folding accommodates transcription, we investigated the assembly of the axial element, the proteinaceous structure that compacts meiotic chromosomes and promotes recombination and fertility. We found that the axial element proteins of budding yeast are flexibly anchored to chromatin by the ring-like cohesin complex. The ubiquitous presence of cohesin at sites of convergent transcription provides well-dispersed points for axis attachment and thus chromosome compaction. Axis protein enrichment at these sites directly correlates with the propensity for recombination initiation nearby. A separate modulating mechanism that requires the conserved axial-element component Hop1 biases axis protein binding towards small chromosomes. Importantly, axis anchoring by cohesin is adjustable and readily displaced in the direction of transcription by the transcriptional machinery. We propose that such robust but flexible tethering allows the axial element to promote recombination while easily adapting to changes in chromosome activity. DOI: http://dx.doi.org/10.7554/eLife.07424.001 PMID:26258962

  15. Meiotic chromosome pairing in triploid and tetraploid Saccharomyces cerevisiae

    SciTech Connect

    Loidl, J.

    1995-04-01

    Meiotic chromosome pairing in isogenic triploid and tetraploid strains of yeast and the consequences of polyploidy on meiotic chromosome segregation are studied. Synaptonemal complex formation at pachytene was found to be different in the triploid and in the tetraploid. In the triploid, triple-synapsis, that is, the connection of three homologues at a given site, is common. It can even extend all the way along the chromosomes. In the tetraploid, homologous chromosomes mostly come in pairs of synapsed bivalents. Multiple synapsis, that is, synapsis of more than two homologues in one and the same region, was virtually absent in the tetraploid. About five quadrivalents per cell occurred due to the switching of pairing partners. From the frequency of pairing partner switches it can be deduced that in most chromosomes synapsis is initiated primarily at one end, occasionally at both ends and rarely at an additional intercalary position. In contrast to a considerably reduced spore viability ({approximately}40%) in the triploid, spore viability is only mildly affected in the tetraploid. The good spore viability is presumably due to the low frequency of quadrivalents and to the highly regular 2:2 segregation of the few quadrivalents that do occur. Occasionally, however, quadrivalents appear to be subject to 3:1 nondisjunction that leads to spore death in the second generation. 29 refs., 6 figs., 4 tabs.

  16. Direct visualization reveals kinetics of meiotic chromosome synapsis

    DOE PAGES

    Rog, Ofer; Dernburg, Abby  F.

    2015-03-17

    The synaptonemal complex (SC) is a conserved protein complex that stabilizes interactions along homologous chromosomes (homologs) during meiosis. The SC regulates genetic exchanges between homologs, thereby enabling reductional division and the production of haploid gametes. Here, we directly observe SC assembly (synapsis) by optimizing methods for long-term fluorescence recording in C. elegans. We report that synapsis initiates independently on each chromosome pair at or near pairing centers—specialized regions required for homolog associations. Once initiated, the SC extends rapidly and mostly irreversibly to chromosome ends. Quantitation of SC initiation frequencies and extension rates reveals that initiation is a rate-limiting step inmore » homolog interactions. Eliminating the dynein-driven chromosome movements that accompany synapsis severely retards SC extension, revealing a new role for these conserved motions. This work provides the first opportunity to directly observe and quantify key aspects of meiotic chromosome interactions and will enable future in vivo analysis of germline processes.« less

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

    PubMed

    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. PMID:25790829

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

    PubMed

    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.

  19. A mammalian KASH domain protein coupling meiotic chromosomes to the cytoskeleton

    PubMed Central

    Horn, Henning F.; Kim, Dae In; Wright, Graham D.; Wong, Esther Sook Miin; Roux, Kyle J.

    2013-01-01

    Chromosome pairing is an essential meiotic event that ensures faithful haploidization and recombination of the genome. Pairing of homologous chromosomes is facilitated by telomere-led chromosome movements and formation of a meiotic bouquet, where telomeres cluster to one pole of the nucleus. In metazoans, telomere clustering is dynein and microtubule dependent and requires Sun1, an inner nuclear membrane protein. Here we provide a functional analysis of KASH5, a mammalian dynein-binding protein of the outer nuclear membrane that forms a meiotic complex with Sun1. This protein is related to zebrafish futile cycle (Fue), a nuclear envelope (NE) constituent required for pronuclear migration. Mice deficient in this Fue homologue are infertile. Males display meiotic arrest in which pairing of homologous chromosomes fails. These findings demonstrate that telomere attachment to the NE is insufficient to promote pairing and that telomere attachment sites must be coupled to cytoplasmic dynein and the microtubule system to ensure meiotic progression. PMID:24062341

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

    PubMed Central

    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

  1. Non-meiotic chromosome instability in human immature oocytes

    PubMed Central

    Daina, Gemma; Ramos, Laia; Rius, Mariona; Obradors, Albert; del Rey, Javier; Giralt, Magda; Campillo, Mercedes; Velilla, Esther; Pujol, Aïda; Martinez-Pasarell, Olga; Benet, Jordi; Navarro, Joaquima

    2014-01-01

    Aneuploidy has been a major issue in human gametes and is closely related to fertility problems, as it is known to be present in cleavage stage embryos and gestational losses. Pre-meiotic chromosome abnormalities in women have been previously described. The aim of this study is to assess the whole-chromosome complement in immature oocytes to find those abnormalities caused by mitotic instability. For this purpose, a total of 157 oocytes at the germinal vesicle or metaphase I stage, and discarded from IVF cycles, were analysed by CGH. Fifty-six women, between 18 and 45 years old (mean 32.5 years), including 32 IVF patients (25–45 years of age) and 24 IVF oocyte donors (18–33 years of age), were included in the study. A total of 25/157 (15.9%) of the oocytes analysed, obtained from three IVF clinics, contained chromosome abnormalities, including both aneuploidy (24/157) and structural aberrations (9/157). Independently of the maternal age, the incidence of abnormal oocytes which originated before meiosis is 15.9%, and these imbalances were found in 33.9% of the females studied. This work sheds light on the relevance of mitotic instability responsible for the generation of the abnormalities present in human oocytes. PMID:23695274

  2. The contribution of female meiotic drive to the evolution of neo-sex chromosomes.

    PubMed

    Yoshida, Kohta; Kitano, Jun

    2012-10-01

    Sex chromosomes undergo rapid turnover in certain taxonomic groups. One of the mechanisms of sex chromosome turnover involves fusions between sex chromosomes and autosomes. Sexual antagonism, heterozygote advantage, and genetic drift have been proposed as the drivers for the fixation of this evolutionary event. However, all empirical patterns of the prevalence of multiple sex chromosome systems across different taxa cannot be simply explained by these three mechanisms. In this study, we propose that female meiotic drive may contribute to the evolution of neo-sex chromosomes. The results of this study showed that in mammals, the XY(1) Y(2) sex chromosome system is more prevalent in species with karyotypes of more biarmed chromosomes, whereas the X(1) X(2) Y sex chromosome system is more prevalent in species with predominantly acrocentric chromosomes. In species where biarmed chromosomes are favored by female meiotic drive, X-autosome fusions (XY(1) Y(2) sex chromosome system) will be also favored by female meiotic drive. In contrast, in species with more acrocentric chromosomes, Y-autosome fusions (X(1) X(2) Y sex chromosome system) will be favored just because of the biased mutation rate toward chromosomal fusions. Further consideration should be given to female meiotic drive as a mechanism in the fixation of neo-sex chromosomes.

  3. A meiotic chromosomal core consisting of cohesin complex proteins recruits DNA recombination proteins and promotes synapsis in the absence of an axial element in mammalian meiotic cells.

    PubMed

    Pelttari, J; Hoja, M R; Yuan, L; Liu, J G; Brundell, E; Moens, P; Santucci-Darmanin, S; Jessberger, R; Barbero, J L; Heyting, C; Höög, C

    2001-08-01

    The behavior of meiotic chromosomes differs in several respects from that of their mitotic counterparts, resulting in the generation of genetically distinct haploid cells. This has been attributed in part to a meiosis-specific chromatin-associated protein structure, the synaptonemal complex. This complex consist of two parallel axial elements, each one associated with a pair of sister chromatids, and a transverse filament located between the synapsed homologous chromosomes. Recently, a different protein structure, the cohesin complex, was shown to be associated with meiotic chromosomes and to be required for chromosome segregation. To explore the functions of the two different protein structures, the synaptonemal complex and the cohesin complex, in mammalian male meiotic cells, we have analyzed how absence of the axial element affects early meiotic chromosome behavior. We find that the synaptonemal complex protein 3 (SCP3) is a main determinant of axial-element assembly and is required for attachment of this structure to meiotic chromosomes, whereas SCP2 helps shape the in vivo structure of the axial element. We also show that formation of a cohesin-containing chromosomal core in meiotic nuclei does not require SCP3 or SCP2. Our results also suggest that the cohesin core recruits recombination proteins and promotes synapsis between homologous chromosomes in the absence of an axial element. A model for early meiotic chromosome pairing and synapsis is proposed. PMID:11463847

  4. Double-strand break repair on sex chromosomes: challenges during male meiotic prophase

    PubMed Central

    Lu, Lin-Yu; Yu, Xiaochun

    2015-01-01

    During meiotic prophase, DNA double-strand break (DSB) repair-mediated homologous recombination (HR) occurs for exchange of genetic information between homologous chromosomes. Unlike autosomes or female sex chromosomes, human male sex chromosomes X and Y share little homology. Although DSBs are generated throughout male sex chromosomes, homologous recombination does not occur for most regions and DSB repair process is significantly prolonged. As a result, male sex chromosomes are coated with many DNA damage response proteins and form a unique chromatin structure known as the XY body. Interestingly, associated with the prolonged DSB repair, transcription is repressed in the XY body but not in autosomes, a phenomenon known as meiotic sex chromosome inactivation (MSCI), which is critical for male meiosis. Here using mice as model organisms, we briefly summarize recent progress on DSB repair in meiotic prophase and focus on the mechanism and function of DNA damage response in the XY body. PMID:25565522

  5. Rapid evolution of a Y-chromosome heterochromatin protein underlies sex chromosome meiotic drive.

    PubMed

    Helleu, Quentin; Gérard, Pierre R; Dubruille, Raphaëlle; Ogereau, David; Prud'homme, Benjamin; Loppin, Benjamin; Montchamp-Moreau, Catherine

    2016-04-12

    Sex chromosome meiotic drive, the non-Mendelian transmission of sex chromosomes, is the expression of an intragenomic conflict that can have extreme evolutionary consequences. However, the molecular bases of such conflicts remain poorly understood. Here, we show that a young and rapidly evolving X-linked heterochromatin protein 1 (HP1) gene, HP1D2, plays a key role in the classical Paris sex-ratio (SR) meiotic drive occurring in Drosophila simulans Driver HP1D2 alleles prevent the segregation of the Y chromatids during meiosis II, causing female-biased sex ratio in progeny. HP1D2 accumulates on the heterochromatic Y chromosome in male germ cells, strongly suggesting that it controls the segregation of sister chromatids through heterochromatin modification. We show that Paris SR drive is a consequence of dysfunctional HP1D2 alleles that fail to prepare the Y chromosome for meiosis, thus providing evidence that the rapid evolution of genes controlling the heterochromatin structure can be a significant source of intragenomic conflicts.

  6. Meiotic behavior and chromosome number of Urochloa adspersa (Trin.) R. D. Webster from the Brazilian Chaco.

    PubMed

    Felismino, M F; Maior, R L S; Damasceno, G A; Pott, A; Pagliarini, M S

    2015-01-01

    This is the first report of meiotic division in Uro-chloa adspersa (Trin.) collected from the Brazilian Chaco. Meiotic analyses were performed on three specimens of U. adspersa named G10, G15, and G16. Inflorescences were collected and fixed in a mixture of ethanol and acetic acid (3:1, v/v) for 24 h and then stored in 70% alcohol. Diakinesis revealed different chromosome numbers and ploidy levels. All three plants were polyploids: G10 and G15 exhibited 2n = 6x = 54 chromosomes (arranged in 27 bivalents), while G16 exhibited 2n = 4x = 36 chromosomes (18 bivalents). Meiotic behavior was mainly normal in the hexaploid G15 and the tetraploid G16 (5.3 and 6.2% of the cells were abnormal, respective-ly), revealing only a few meiotic abnormalities that are common to polyploids, i.e., those related to irregular chromosome segregation. G10 exhibited other meiotic abnormalities during meiosis II, such as chromosome stickiness, irregular spindle orientation, and irregular cytokinesis, which led to the formation of a few triads, resulting in 16.9% of the cells being abnormal. The origin of these abnormalities is discussed, and we suggest that the genes that control meiotic steps may be present in the Urochloa gene pool. PMID:26214424

  7. Meiotic chromosome mobility in fission yeast is resistant to environmental stress

    PubMed Central

    Illner, Doris; Lorenz, Alexander; Scherthan, Harry

    2016-01-01

    The formation of healthy gametes requires pairing of homologous chromosomes (homologs) as a prerequisite for their correct segregation during meiosis. Initially, homolog alignment is promoted by meiotic chromosome movements feeding into intimate homolog pairing by homologous recombination and/or synaptonemal complex formation. Meiotic chromosome movements in the fission yeast, Schizosaccharomyces pombe, depend on astral microtubule dynamics that drag the nucleus through the zygote; known as horsetail movement. The response of microtubule-led meiotic chromosome movements to environmental stresses such as ionizing irradiation (IR) and associated reactive oxygen species (ROS) is not known. Here, we show that, in contrast to budding yeast, the horsetail movement is largely radiation-resistant, which is likely mediated by a potent antioxidant defense. IR exposure of sporulating S. pombe cells induced misrepair and irreparable DNA double strand breaks causing chromosome fragmentation, missegregation and gamete death. Comparing radiation outcome in fission and budding yeast, and studying meiosis with poisoned microtubules indicates that the increased gamete death after IR is innate to fission yeast. Inhibition of meiotic chromosome mobility in the face of IR failed to influence the course of DSB repair, indicating that paralysis of meiotic chromosome mobility in a genotoxic environment is not a universal response among species. PMID:27074839

  8. Meiotic chromosome mobility in fission yeast is resistant to environmental stress.

    PubMed

    Illner, Doris; Lorenz, Alexander; Scherthan, Harry

    2016-01-01

    The formation of healthy gametes requires pairing of homologous chromosomes (homologs) as a prerequisite for their correct segregation during meiosis. Initially, homolog alignment is promoted by meiotic chromosome movements feeding into intimate homolog pairing by homologous recombination and/or synaptonemal complex formation. Meiotic chromosome movements in the fission yeast, Schizosaccharomyces pombe, depend on astral microtubule dynamics that drag the nucleus through the zygote; known as horsetail movement. The response of microtubule-led meiotic chromosome movements to environmental stresses such as ionizing irradiation (IR) and associated reactive oxygen species (ROS) is not known. Here, we show that, in contrast to budding yeast, the horsetail movement is largely radiation-resistant, which is likely mediated by a potent antioxidant defense. IR exposure of sporulating S. pombe cells induced misrepair and irreparable DNA double strand breaks causing chromosome fragmentation, missegregation and gamete death. Comparing radiation outcome in fission and budding yeast, and studying meiosis with poisoned microtubules indicates that the increased gamete death after IR is innate to fission yeast. Inhibition of meiotic chromosome mobility in the face of IR failed to influence the course of DSB repair, indicating that paralysis of meiotic chromosome mobility in a genotoxic environment is not a universal response among species. PMID:27074839

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

    PubMed Central

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

    2016-01-01

    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. PMID:27104744

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

    PubMed

    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.

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

    SciTech Connect

    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.

  12. Meiotic Recombination in Drosophila Females Depends on Chromosome Continuity Between Genetically Defined Boundaries

    PubMed Central

    Sherizen, Dalia; Jang, Janet K.; Bhagat, Rajal; Kato, Naohiro; McKim, Kim S.

    2005-01-01

    In the pairing-site model, specialized regions on each chromosome function to establish meiotic homolog pairing. Analysis of these sites could provide insights into the mechanism used by Drosophila females to form a synaptonemal complex (SC) in the absence of meiotic recombination. These specialized sites were first established on the X chromosome by noting that there were barriers to crossover suppression caused by translocation heterozygotes. These sites were genetically mapped and proposed to be pairing sites. By comparing the cytological breakpoints of third chromosome translocations to their patterns of crossover suppression, we have mapped two sites on chromosome 3R. We have performed experiments to determine if these sites have a role in meiotic homolog pairing and the initiation of recombination. Translocation heterozygotes exhibit reduced gene conversion within the crossover-suppressed region, consistent with an effect on the initiation of meiotic recombination. To determine if homolog pairing is disrupted in translocation heterozygotes, we used fluorescent in situ hybridization to measure the extent of homolog pairing. In wild-type oocytes, homologs are paired along their entire lengths prior to accumulation of the SC protein C(3)G. Surprisingly, translocation heterozygotes exhibited homolog pairing similar to wild type within the crossover-suppressed regions. This result contrasted with our observations of c(3)G mutant females, which were found to be defective in pairing. We propose that each Drosophila chromosome is divided into several domains by specialized sites. These sites are not required for homolog pairing. Instead, the initiation of meiotic recombination requires continuity of the meiotic chromosome structure within each of these domains. PMID:15545646

  13. Sex-specific differences in meiotic chromosome segregation revealed by dicentric bridge resolution in mice.

    PubMed Central

    Koehler, Kara E; Millie, Elise A; Cherry, Jonathan P; Burgoyne, Paul S; Evans, Edward P; Hunt, Patricia A; Hassold, Terry J

    2002-01-01

    The meiotic properties of paracentric inversion heterozygotes have been well studied in insects and plants, but not in mammalian species. In essence, a single meiotic recombination event within the inverted region results in the formation of a dicentric chromatid, which usually breaks or is stretched between the two daughter nuclei during the first meiotic anaphase. Here, we provide evidence that this is not the predominant mode of exchange resolution in female mice. In sharp contrast to previous observations in other organisms, we find that attempts to segregate the dicentric chromatid frequently result not in breakage, stretching, or loss, but instead in precocious separation of the sister centromeres of at least one homolog. This often further results in intact segregation of the dicentric into one of the meiotic products, where it can persist into the first few embryonic divisions. These novel observations point to an unusual mechanism for the processing of dicentric chromosomes in mammalian oogenesis. Furthermore, this mechanism is rare or nonexistent in mammalian spermatogenesis. Thus, our results provide additional evidence of sexual dimorphism in mammalian meiotic chromosome behavior; in "stressful" situations, meiotic sister chromatid cohesion is apparently handled differently in males than in females. PMID:12454080

  14. Dbl2 Regulates Rad51 and DNA Joint Molecule Metabolism to Ensure Proper Meiotic Chromosome Segregation

    PubMed Central

    Hyppa, Randy W.; Benko, Zsigmond; Misova, Ivana; Schleiffer, Alexander; Smith, Gerald R.; Gregan, Juraj

    2016-01-01

    To identify new proteins required for faithful meiotic chromosome segregation, we screened a Schizosaccharomyces pombe deletion mutant library and found that deletion of the dbl2 gene led to missegregation of chromosomes during meiosis. Analyses of both live and fixed cells showed that dbl2Δ mutant cells frequently failed to segregate homologous chromosomes to opposite poles during meiosis I. Removing Rec12 (Spo11 homolog) to eliminate meiotic DNA double-strand breaks (DSBs) suppressed the segregation defect in dbl2Δ cells, indicating that Dbl2 acts after the initiation of meiotic recombination. Analyses of DSBs and Holliday junctions revealed no significant defect in their formation or processing in dbl2Δ mutant cells, although some Rec12-dependent DNA joint molecules persisted late in meiosis. Failure to segregate chromosomes in the absence of Dbl2 correlated with persistent Rad51 foci, and deletion of rad51 or genes encoding Rad51 mediators also suppressed the segregation defect of dbl2Δ. Formation of foci of Fbh1, an F-box helicase that efficiently dismantles Rad51-DNA filaments, was impaired in dbl2Δ cells. Our results suggest that Dbl2 is a novel regulator of Fbh1 and thereby Rad51-dependent DSB repair required for proper meiotic chromosome segregation and viable sex cell formation. The wide conservation of these proteins suggests that our results apply to many species. PMID:27304859

  15. X Chromosome Control of Meiotic Chromosome Synapsis in Mouse Inter-Subspecific Hybrids

    PubMed Central

    Bhattacharyya, Tanmoy; Reifova, Radka; Gregorova, Sona; Simecek, Petr; Gergelits, Vaclav; Mistrik, Martin; Martincova, Iva; Pialek, Jaroslav; Forejt, Jiri

    2014-01-01

    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 Hstx2Mmm 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. PMID:24516397

  16. X chromosome control of meiotic chromosome synapsis in mouse inter-subspecific hybrids.

    PubMed

    Bhattacharyya, Tanmoy; Reifova, Radka; Gregorova, Sona; Simecek, Petr; Gergelits, Vaclav; Mistrik, Martin; Martincova, Iva; Pialek, Jaroslav; Forejt, Jiri

    2014-02-01

    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. PMID:24516397

  17. Translocations of chromosome end-segments and facultative heterochromatin promote meiotic ring formation in evening primroses.

    PubMed

    Golczyk, Hieronim; Massouh, Amid; Greiner, Stephan

    2014-03-01

    Due to reciprocal chromosomal translocations, many species of Oenothera (evening primrose) form permanent multichromosomal meiotic rings. However, regular bivalent pairing is also observed. Chiasmata are restricted to chromosomal ends, which makes homologous recombination virtually undetectable. Genetic diversity is achieved by changing linkage relations of chromosomes in rings and bivalents via hybridization and reciprocal translocations. Although the structural prerequisite for this system is enigmatic, whole-arm translocations are widely assumed to be the mechanistic driving force. We demonstrate that this prerequisite is genome compartmentation into two epigenetically defined chromatin fractions. The first one facultatively condenses in cycling cells into chromocenters negative both for histone H3 dimethylated at lysine 4 and for C-banding, and forms huge condensed middle chromosome regions on prophase chromosomes. Remarkably, it decondenses in differentiating cells. The second fraction is euchromatin confined to distal chromosome segments, positive for histone H3 lysine 4 dimethylation and for histone H3 lysine 27 trimethylation. The end-segments are deprived of canonical telomeres but capped with constitutive heterochromatin. This genomic organization promotes translocation breakpoints between the two chromatin fractions, thus facilitating exchanges of end-segments. We challenge the whole-arm translocation hypothesis by demonstrating why reciprocal translocations of chromosomal end-segments should strongly promote meiotic rings and evolution toward permanent translocation heterozygosity. Reshuffled end-segments, each possessing a major crossover hot spot, can furthermore explain meiotic compatibility between genomes with different translocation histories. PMID:24681616

  18. A Germline Clone Screen on the X Chromosome Reveals Novel Meiotic Mutants in Drosophila melanogaster

    PubMed Central

    Collins, Kimberly A.; Callicoat, Jonathon G.; Lake, Cathleen M.; McClurken, Cailey M.; Kohl, Kathryn P.; Hawley, R. Scott

    2012-01-01

    In an effort to isolate novel meiotic mutants that are severely defective in chromosome segregation and/or exchange, we employed a germline clone screen of the X chromosome of Drosophila melanogaster. We screened over 120,000 EMS-mutagenized chromosomes and isolated 19 mutants, which comprised nine complementation groups. Four of these complementation groups mapped to known meiotic genes, including mei-217, mei-218, mei-9, and nod. Importantly, we have identified two novel complementation groups with strong meiotic phenotypes, as assayed by X chromosome nondisjunction. One complementation group is defined by three alleles, and the second novel complementation group is defined by a single allele. All 19 mutants are homozygous viable, fertile, and fully recessive. Of the 9 mutants that have been molecularly characterized, 5 are canonical EMS-induced transitions, and the remaining 4 are transversions. In sum, we have identified two new genes that are defined by novel meiotic mutants, in addition to isolating new alleles of mei-217, mei-218, mei-9, and nod. PMID:23173088

  19. Proof that univalent chromosomes undergoing equational division at anaphase I are not lost during the second meiotic division

    SciTech Connect

    Weber, D. F.

    1980-01-01

    Monosomics in a diploid organism are ideal for characterizing the behavior of univalent chromosomes because each meiotic cell contains a univalent chromosome. We have isolated microsporocyte samples from all monosomic types except monosomics 3 and 5 and have carried out extensive analyses of the meiotic behavior in each of the different available monosomic types. It is demonstrated that univalent chromosomes can undergo equational division at the first anaphase and the resultant monads are not lost during the remainder of meiosis.

  20. Structural damage to meiotic chromosomes impairs DNA recombination and checkpoint control in mammalian oocytes.

    PubMed

    Wang, Hong; Höög, Christer

    2006-05-22

    Meiosis in human oocytes is a highly error-prone process with profound effects on germ cell and embryo development. The synaptonemal complex protein 3 (SYCP3) transiently supports the structural organization of the meiotic chromosome axis. Offspring derived from murine Sycp3(-)(/)(-) females die in utero as a result of aneuploidy. We studied the nature of the proximal chromosomal defects that give rise to aneuploidy in Sycp3(-)(/)(-) oocytes and how these errors evade meiotic quality control mechanisms. We show that DNA double-stranded breaks are inefficiently repaired in Sycp3(-)(/)(-) oocytes, thereby generating a temporal spectrum of recombination errors. This is indicated by a strong residual gammaH2AX labeling retained at late meiotic stages in mutant oocytes and an increased persistence of recombination-related proteins associated with meiotic chromosomes. Although a majority of the mutant oocytes are rapidly eliminated at early postnatal development, a subset with a small number of unfinished crossovers evades the DNA damage checkpoint, resulting in the formation of aneuploid gametes. PMID:16717125

  1. Meiotic crossing-over in nondisjoined chromosomes of children with trisomy 21 and a congenital heart defect

    SciTech Connect

    Howard, C.M.; Davis, G.E.; Farrer, M.J.; Cullen, L.M.; Coleman, M.M.; Williamson, R.; Wyse, R.K.H.; Palmer, R.; Kessling, A.M. )

    1993-08-01

    The authors have used DNA polymorphisms to study meiotic crossovers of chromosome 21q in 27 nuclear families. Each family had a child with Down syndrome and a congenital heart defect. Twenty DNA polymorphisms on chromosome 21 were used to determine parental and meiotic origin of nondisjunction and to identify crossovers. Twenty-four cases were of maternal origin, and three were of paternal origin. Twenty-two unequivocal crossover events were identified. Sixteen crossovers were observed in 22 chromosome pairs nondisjoining at the first meiotic division (MI), and six crossovers were observed in five chromosome pairs disjoining at the second meiotic division. Fifty percent of crossover events in MI nondisjunction are detectable by molecular genetic means. Thus, the results suggest that, in this sample, each nondisjoined chromosome 21 pair has been involved in at least one crossover event. 28 refs., 1 fig., 3 tabs.

  2. The condensin complexes play distinct roles to ensure normal chromosome morphogenesis during meiotic division in Arabidopsis.

    PubMed

    Smith, Sarah J; Osman, Kim; Franklin, F Christopher H

    2014-10-01

    Meiosis is a specialized cell division essential for sexual reproduction. During meiosis the chromosomes are highly organized, and correct chromosome architecture is required for faithful segregation of chromosomes at anaphase I and II. Condensin is involved in chromosome organization during meiotic and mitotic cell divisions. Three condensin subunits, AtSMC4 and the condensin I and II specific subunits AtCAP-D2 and AtCAP-D3, respectively, have been studied for their role in meiosis. This has revealed that both the condensin I and condensin II complexes are required to maintain normal structural integrity of the meiotic chromosomes during the two nuclear divisions. Their roles appear functionally distinct in that condensin I is required to maintain normal compaction of the centromeric repeats and 45S rDNA, whereas loss of condensin II was associated with extensive interchromosome connections at metaphase I. Depletion of condensin is also associated with a slight reduction in crossover formation, suggesting a role during meiotic prophase I. PMID:25065716

  3. How did the platypus get its sex chromosome chain? A comparison of meiotic multiples and sex chromosomes in plants and animals.

    PubMed

    Gruetzner, Frank; Ashley, Terry; Rowell, David M; Marshall Graves, Jennifer A

    2006-04-01

    The duck-billed platypus is an extraordinary mammal. Its chromosome complement is no less extraordinary, for it includes a system in which ten sex chromosomes form an extensive meiotic chain in males. Such meiotic multiples are unprecedented in vertebrates but occur sporadically in plant and invertebrate species. In this paper, we review the evolution and formation of meiotic multiples in plants and invertebrates to try to gain insights into the origin of the platypus meiotic multiple. We describe the meiotic hurdles that translocated mammalian chromosomes face, which make longer chains disadvantageous in mammals, and we discuss how sex chromosomes and dosage compensation might have affected the evolution of sex-linked meiotic multiples. We conclude that the evolutionary conservation of the chain in monotremes, the structural properties of the translocated chromosomes and the highly accurate segregation at meiosis make the platypus system remarkably different from meiotic multiples in other species. We discuss alternative evolutionary models, which fall broadly into two categories: either the chain is the result of a sequence of translocation events from an ancestral pair of sex chromosomes (Model I) or the entire chain came into being at once by hybridization of two populations with different chromosomal rearrangements sharing monobrachial homology (Model II).

  4. The fragile Y hypothesis: Y chromosome aneuploidy as a selective pressure in sex chromosome and meiotic mechanism evolution.

    PubMed

    Blackmon, Heath; Demuth, Jeffery P

    2015-09-01

    Loss of the Y-chromosome is a common feature of species with chromosomal sex determination. However, our understanding of why some lineages frequently lose Y-chromosomes while others do not is limited. The fragile Y hypothesis proposes that in species with chiasmatic meiosis the rate of Y-chromosome aneuploidy and the size of the recombining region have a negative correlation. The fragile Y hypothesis provides a number of novel insights not possible under traditional models. Specifically, increased rates of Y aneuploidy may impose positive selection for (i) gene movement off the Y; (ii) translocations and fusions which expand the recombining region; and (iii) alternative meiotic segregation mechanisms (achiasmatic or asynaptic). These insights as well as existing evidence for the frequency of Y-chromosome aneuploidy raise doubt about the prospects for long-term retention of the human Y-chromosome despite recent evidence for stable gene content in older non-recombining regions.

  5. Plasticity in the Meiotic Epigenetic Landscape of Sex Chromosomes in Caenorhabditis Species.

    PubMed

    Larson, Braden J; Van, Mike V; Nakayama, Taylor; Engebrecht, JoAnne

    2016-08-01

    During meiosis in the heterogametic sex in some species, sex chromosomes undergo meiotic sex chromosome inactivation (MSCI), which results in acquisition of repressive chromatin and transcriptional silencing. In Caenorhabditis elegans, MSCI is mediated by MET-2 methyltransferase deposition of histone H3 lysine 9 dimethylation. Here we examined the meiotic chromatin landscape in germ lines of four Caenorhabditis species; C. remanei and C. brenneri represent ancestral gonochorism, while C. briggsae and C. elegans are two lineages that independently evolved hermaphroditism. While MSCI is conserved across all four species, repressive chromatin modifications are distinct and do not correlate with reproductive mode. In contrast to C. elegans and C. remanei germ cells where X chromosomes are enriched for histone H3 lysine 9 dimethylation, X chromosomes in C. briggsae and C. brenneri germ cells are enriched for histone H3 lysine 9 trimethylation. Inactivation of C. briggsae MET-2 resulted in germ-line X chromosome transcription and checkpoint activation. Further, both histone H3 lysine 9 di- and trimethylation were reduced in Cbr-met-2 mutant germ lines, suggesting that in contrast to C. elegans, H3 lysine 9 di- and trimethylation are interdependent. C. briggsae H3 lysine 9 trimethylation was redistributed in the presence of asynapsed chromosomes in a sex-specific manner in the related process of meiotic silencing of unsynapsed chromatin. However, these repressive marks did not influence X chromosome replication timing. Examination of additional Caenorhabditis species revealed diverse H3 lysine 9 methylation patterns on the X, suggesting that the sex chromosome epigenome evolves rapidly. PMID:27280692

  6. Arabidopsis Cell Division Cycle 20.1 Is Required for Normal Meiotic Spindle Assembly and Chromosome Segregation[OPEN

    PubMed Central

    Niu, Baixiao; Wang, Liudan; Ren, Ding; Ren, Ren

    2015-01-01

    Cell division requires proper spindle assembly; a surveillance pathway, the spindle assembly checkpoint (SAC), monitors whether the spindle is normal and correctly attached to kinetochores. The SAC proteins regulate mitotic chromosome segregation by affecting CDC20 (Cell Division Cycle 20) function. However, it is unclear whether CDC20 regulates meiotic spindle assembly and proper homolog segregation. Here, we show that the Arabidopsis thaliana CDC20.1 gene is indispensable for meiosis and male fertility. We demonstrate that cdc20.1 meiotic chromosomes align asynchronously and segregate unequally and the metaphase I spindle has aberrant morphology. Comparison of the distribution of meiotic stages at different time points between the wild type and cdc20.1 reveals a delay of meiotic progression from diakinesis to anaphase I. Furthermore, cdc20.1 meiocytes exhibit an abnormal distribution of a histone H3 phosphorylation mark mediated by the Aurora kinase, providing evidence that CDC20.1 regulates Aurora localization for meiotic chromosome segregation. Further evidence that CDC20.1 and Aurora are functionally related was provided by meiosis-specific knockdown of At-Aurora1 expression, resulting in meiotic chromosome segregation defects similar to those of cdc20.1. Taken together, these results suggest a critical role for CDC20.1 in SAC-dependent meiotic chromosome segregation. PMID:26672070

  7. Dis1: A Yeast Gene Required for Proper Meiotic Chromosome Disjunction

    PubMed Central

    Rockmill, B.; Fogel, S.

    1988-01-01

    Mutants at a newly identified locus, DIS1 (disjunction), were detected by screening for mutants that generate aneuploid spores (chromosome VIII disomes) at an increased frequency. Strains carrying the partially dominant alleles, DIS1-1 or DIS1-2, generate disomes at rates up to 100 times the background level. Mitotic nondisjunction is also increased 10- to 50-fold over background. Half-tetrad analysis of disomes for a marked interval on chromosome VIII yields wild-type map distances, indicating that a general recombination deficiency is not the cause of nondisjuction. Meiotic nondisjunction in DIS1 mutants is not chromosome specific; 5% of the spores disomic for chromosome VIII are also disomic for chromosome III. Although only one disomic spore is found per exceptional ascus most of the disomes appear to be generated in the first meiotic division because recovered chromosome VIII disomes contain mostly nonsister chromosomes. We propose that disome generation in the DIS1 mutants results from precocious separation of sister centromeres. PMID:3294101

  8. The mismatch repair system reduces meiotic homeologous recombination and stimulates recombination-dependent chromosome loss.

    PubMed

    Chambers, S R; Hunter, N; Louis, E J; Borts, R H

    1996-11-01

    Efficient genetic recombination requires near-perfect homology between participating molecules. Sequence divergence reduces the frequency of recombination, a process that is dependent on the activity of the mismatch repair system. The effects of chromosomal divergence in diploids of Saccharomyces cerevisiae in which one copy of chromosome III is derived from a closely related species, Saccharomyces paradoxus, have been examined. Meiotic recombination between the diverged chromosomes is decreased by 25-fold. Spore viability is reduced with an observable increase in the number of tetrads with only two or three viable spores. Asci with only two viable spores are disomic for chromosome III, consistent with meiosis I nondisjunction of the homeologs. Asci with three viable spores are highly enriched for recombinants relative to tetrads with four viable spores. In 96% of the class with three viable spores, only one spore possesses a recombinant chromosome III, suggesting that the recombination process itself contributes to meiotic death. This phenomenon is dependent on the activities of the mismatch repair genes PMS1 and MSH2. A model of mismatch-stimulated chromosome loss is proposed to account for this observation. As expected, crossing over is increased in pms1 and msh2 mutants. Furthermore, genetic exchange in pms1 msh2 double mutants is affected to a greater extent than in either mutant alone, suggesting that the two proteins act independently to inhibit homeologous recombination. All mismatch repair-deficient strains exhibited reductions in the rate of chromosome III nondisjunction. PMID:8887641

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

    PubMed Central

    Cloutier, Jeffrey M.; Mahadevaiah, Shantha K.; ElInati, Elias; Nussenzweig, André; Tóth, Attila; Turner, James M. A.

    2015-01-01

    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. PMID:26509888

  10. Meiotic cohesin STAG3 is required for chromosome axis formation and sister chromatid cohesion.

    PubMed

    Winters, Tristan; McNicoll, Francois; Jessberger, Rolf

    2014-06-01

    The cohesin complex is essential for mitosis and meiosis. The specific meiotic roles of individual cohesin proteins are incompletely understood. We report in vivo functions of the only meiosis-specific STAG component of cohesin, STAG3. Newly generated STAG3-deficient mice of both sexes are sterile with meiotic arrest. In these mice, meiotic chromosome architecture is severely disrupted as no bona fide axial elements (AE) form and homologous chromosomes do not synapse. Axial element protein SYCP3 forms dot-like structures, many partially overlapping with centromeres. Asynapsis marker HORMAD1 is diffusely distributed throughout the chromatin, and SYCP1, which normally marks synapsed axes, is largely absent. Centromeric and telomeric sister chromatid cohesion are impaired. Centromere and telomere clustering occurs in the absence of STAG3, and telomere structure is not severely affected. Other cohesin proteins are present, localize throughout the STAG3-devoid chromatin, and form complexes with cohesin SMC1β. No other deficiency in a single meiosis-specific cohesin causes a phenotype as drastic as STAG3 deficiency. STAG3 emerges as the key STAG cohesin involved in major functions of meiotic cohesin. PMID:24797474

  11. Mechanism and regulation of rapid telomere prophase movements in mouse meiotic chromosomes

    PubMed Central

    Lee, Chih-Ying; Horn, Henning F.; Stewart, Colin L.; Burke, Brian; Bolcun-Filas, Ewelina; Schimenti, John C.; Dresser, Michael E.; Pezza, Roberto J.

    2015-01-01

    SUMMARY Telomere-led rapid prophase movements (RPMs) in meiotic prophase have been observed in diverse eukaryote species. A shared feature of RPMs is that the force that drives the chromosomal movements is transmitted from the cytoskeleton, through the nuclear envelope, to the telomeres. Studies in mice suggested that dynein movement along microtubules is transmitted to telomeres through SUN1/KASH5 nuclear envelope bridges to generate RPMs. We monitored RPMs in mouse seminiferous tubules using four-dimensional fluorescence imaging and quantitative motion analysis to characterize patterns of movement in the RPM process. We find that RPMs reflect a combination of nuclear rotation and individual chromosome movements. The telomeres move along microtubule tracks which are apparently continuous with the cytoskeletal network, and exhibit characteristic arrangements at different stages of prophase. Quantitative measurements confirmed that SUN1/KASH5, microtubules, and dynein but not actin were necessary for RPMs and that defects in meiotic recombination and synapsis resulted in altered RPMs. PMID:25892231

  12. Meiotic chromosome dynamics dependent upon the rec8(+), rec10(+) and rec11(+) genes of the fission yeast Schizosaccharomyces pombe.

    PubMed

    Krawchuk, M D; DeVeaux, L C; Wahls, W P

    1999-09-01

    During meiosis homologous chromosomes replicate once, pair, experience recombination, and undergo two rounds of segregation to produce haploid meiotic products. The rec8(+), rec10(+), and rec11(+) genes of the fission yeast Schizosaccharomyces pombe exhibit similar specificities for meiotic recombination and rec8(+) is required for sister chromatid cohesion and homolog pairing. We applied cytological and genetic approaches to identify potential genetic interactions and to gauge the fidelity of meiotic chromosome segregation in the mutants. The rec8(+) gene was epistatic to rec10(+) and to rec11(+), but there was no clear epistatic relationship between rec10(+) and rec11(+). Reciprocal (crossover) recombination in the central regions of all three chromosomes was compromised in the rec mutants, but recombination near the telomeres was nearly normal. Each of the mutants also exhibited a high rate of aberrant segregation for all three chromosomes. The rec8 mutations affected mainly meiosis I segregation. Remarkably, the rec10 and rec11 mutations, which compromised recombination during meiosis I, affected mainly meiosis II segregation. We propose that these genes encode regulators or components of a "meiotic chromatid cohesion" pathway involved in establishing, maintaining, and appropriately releasing meiotic interactions between chromosomes. A model of synergistic interactions between sister chromatid cohesion and crossover position suggests how crossovers and cohesion help ensure the proper segregation of chromosomes in each of the meiotic divisions. PMID:10471700

  13. Meiotic chromosome dynamics dependent upon the rec8(+), rec10(+) and rec11(+) genes of the fission yeast Schizosaccharomyces pombe.

    PubMed Central

    Krawchuk, M D; DeVeaux, L C; Wahls, W P

    1999-01-01

    During meiosis homologous chromosomes replicate once, pair, experience recombination, and undergo two rounds of segregation to produce haploid meiotic products. The rec8(+), rec10(+), and rec11(+) genes of the fission yeast Schizosaccharomyces pombe exhibit similar specificities for meiotic recombination and rec8(+) is required for sister chromatid cohesion and homolog pairing. We applied cytological and genetic approaches to identify potential genetic interactions and to gauge the fidelity of meiotic chromosome segregation in the mutants. The rec8(+) gene was epistatic to rec10(+) and to rec11(+), but there was no clear epistatic relationship between rec10(+) and rec11(+). Reciprocal (crossover) recombination in the central regions of all three chromosomes was compromised in the rec mutants, but recombination near the telomeres was nearly normal. Each of the mutants also exhibited a high rate of aberrant segregation for all three chromosomes. The rec8 mutations affected mainly meiosis I segregation. Remarkably, the rec10 and rec11 mutations, which compromised recombination during meiosis I, affected mainly meiosis II segregation. We propose that these genes encode regulators or components of a "meiotic chromatid cohesion" pathway involved in establishing, maintaining, and appropriately releasing meiotic interactions between chromosomes. A model of synergistic interactions between sister chromatid cohesion and crossover position suggests how crossovers and cohesion help ensure the proper segregation of chromosomes in each of the meiotic divisions. PMID:10471700

  14. A molecular model for the role of SYCP3 in meiotic chromosome organisation

    PubMed Central

    Syrjänen, Johanna Liinamaria; Pellegrini, Luca; Davies, Owen Richard

    2014-01-01

    The synaptonemal complex (SC) is an evolutionarily-conserved protein assembly that holds together homologous chromosomes during prophase of the first meiotic division. Whilst essential for meiosis and fertility, the molecular structure of the SC has proved resistant to elucidation. The SC protein SYCP3 has a crucial but poorly understood role in establishing the architecture of the meiotic chromosome. Here we show that human SYCP3 forms a highly-elongated helical tetramer of 20 nm length. N-terminal sequences extending from each end of the rod-like structure bind double-stranded DNA, enabling SYCP3 to link distant sites along the sister chromatid. We further find that SYCP3 self-assembles into regular filamentous structures that resemble the known morphology of the SC lateral element. Together, our data form the basis for a model in which SYCP3 binding and assembly on meiotic chromosomes leads to their organisation into compact structures compatible with recombination and crossover formation. DOI: http://dx.doi.org/10.7554/eLife.02963.001 PMID:24950965

  15. Molecular cell biology of male meiotic chromosomes and isolation of male meiocytes in Arabidopsis thaliana.

    PubMed

    Wang, Yingxiang; Cheng, Zhihao; Lu, Pingli; Timofejeva, Ljudmilla; Ma, Hong

    2014-01-01

    Plants typically produce numerous flowers whose meiotic chromosomes are relatively easy to observe, making them excellent structures for studying the cellular processes underlying meiosis. In recent years, breakthroughs in light and electron microscopic technologies for small chromosomes, combined with molecular genetic methods, have resulted in major advances in the understanding of meiosis in the model plant Arabidopsis thaliana. In this chapter, we summarize protocols for basic cytology, fluorescence in situ hybridization, immunofluorescence, electron microscopy, and isolation of male meiocytes for the analysis of Arabidopsis meiosis. PMID:24395259

  16. DNA methylation epigenetically silences crossover hot spots and controls chromosomal domains of meiotic recombination in Arabidopsis

    PubMed Central

    Yelina, Nataliya E.; Lambing, Christophe; Hardcastle, Thomas J.; Zhao, Xiaohui; Santos, Bruno; Henderson, Ian R.

    2015-01-01

    During meiosis, homologous chromosomes undergo crossover recombination, which is typically concentrated in narrow hot spots that are controlled by genetic and epigenetic information. Arabidopsis chromosomes are highly DNA methylated in the repetitive centromeres, which are also crossover-suppressed. Here we demonstrate that RNA-directed DNA methylation is sufficient to locally silence Arabidopsis euchromatic crossover hot spots and is associated with increased nucleosome density and H3K9me2. However, loss of CG DNA methylation maintenance in met1 triggers epigenetic crossover remodeling at the chromosome scale, with pericentromeric decreases and euchromatic increases in recombination. We used recombination mutants that alter interfering and noninterfering crossover repair pathways (fancm and zip4) to demonstrate that remodeling primarily involves redistribution of interfering crossovers. Using whole-genome bisulfite sequencing, we show that crossover remodeling is driven by loss of CG methylation within the centromeric regions. Using cytogenetics, we profiled meiotic DNA double-strand break (DSB) foci in met1 and found them unchanged relative to wild type. We propose that met1 chromosome structure is altered, causing centromere-proximal DSBs to be inhibited from maturation into interfering crossovers. These data demonstrate that DNA methylation is sufficient to silence crossover hot spots and plays a key role in establishing domains of meiotic recombination along chromosomes. PMID:26494791

  17. Modeling meiotic chromosome pairing: nuclear envelope attachment, telomere-led active random motion, and anomalous diffusion

    NASA Astrophysics Data System (ADS)

    Marshall, Wallace F.; Fung, Jennifer C.

    2016-04-01

    The recognition and pairing of homologous chromosomes during meiosis is a complex physical and molecular process involving a combination of polymer dynamics and molecular recognition events. Two highly conserved features of meiotic chromosome behavior are the attachment of telomeres to the nuclear envelope and the active random motion of telomeres driven by their interaction with cytoskeletal motor proteins. Both of these features have been proposed to facilitate the process of homolog pairing, but exactly what role these features play in meiosis remains poorly understood. Here we investigate the roles of active motion and nuclear envelope tethering using a Brownian dynamics simulation in which meiotic chromosomes are represented by a Rouse polymer model subjected to tethering and active forces at the telomeres. We find that tethering telomeres to the nuclear envelope slows down pairing relative to the rates achieved by unattached chromosomes, but that randomly directed active forces applied to the telomeres speed up pairing dramatically in a manner that depends on the statistical properties of the telomere force fluctuations. The increased rate of initial pairing cannot be explained by stretching out of the chromosome conformation but instead seems to correlate with anomalous diffusion of sub-telomeric regions.

  18. Meiotic chromosome synapsis and recombination in Arabidopsis thaliana: new ways of integrating cytological and molecular approaches.

    PubMed

    Sanchez-Moran, E; Armstrong, S J

    2014-06-01

    Meiosis is an evolutionary conserved mechanism that produces haploid gametes and is essential for the sexual reproduction of higher eukaryotes. Since the late nineteenth century, meiosis has been studied in plants due their large chromosomes compared with other organisms and due to advances in microscopy and cytological approaches. On the other hand, non-plant model organisms like budding yeast have been widely used recently in order to characterise the molecular and functional aspects of meiosis. Arabidopsis arose as a new meiotic model for plants during the last decade of the twentieth century. This emergence was sustained by different molecular and genetic advances, mainly by completing the full genome sequence in 2000. Since then, further development of molecular technologies and the cytological methodologies to analyse the meiotic dynamics in Arabidopsis have permitted researchers to establish plant meiosis at the forefront of international research. Some key plant meiotic recombination events have been established in Arabidopsis. These advances have placed researchers into the position to transfer their knowledge from this plant meiotic model to crops and are likely to have an impact on plant breeding and the development of agriculture in future years. PMID:24941912

  19. The Meiotic Nuclear Lamina Regulates Chromosome Dynamics and Promotes Efficient Homologous Recombination in the Mouse

    PubMed Central

    Schmitt, Johannes; Göb, Eva; Baar, Johannes; Ortega, Sagrario; Benavente, Ricardo; Alsheimer, Manfred

    2013-01-01

    The nuclear lamina is the structural scaffold of the nuclear envelope and is well known for its central role in nuclear organization and maintaining nuclear stability and shape. In the past, a number of severe human disorders have been identified to be associated with mutations in lamins. Extensive research on this topic has provided novel important clues about nuclear lamina function. These studies have contributed to the knowledge that the lamina constitutes a complex multifunctional platform combining both structural and regulatory functions. Here, we report that, in addition to the previously demonstrated significance for somatic cell differentiation and maintenance, the nuclear lamina is also an essential determinant for germ cell development. Both male and female mice lacking the short meiosis-specific A-type lamin C2 have a severely defective meiosis, which at least in the male results in infertility. Detailed analysis revealed that lamin C2 is required for telomere-driven dynamic repositioning of meiotic chromosomes. Loss of lamin C2 affects precise synapsis of the homologs and interferes with meiotic double-strand break repair. Taken together, our data explain how the nuclear lamina contributes to meiotic chromosome behaviour and accurate genome haploidization on a mechanistic level. PMID:23382700

  20. BRCA1, histone H2AX phosphorylation, and male meiotic sex chromosome inactivation.

    PubMed

    Turner, James M A; Aprelikova, Olga; Xu, Xiaoling; Wang, Ruihong; Kim, Sangsoo; Chandramouli, Gadisetti V R; Barrett, J Carl; Burgoyne, Paul S; Deng, Chu-Xia

    2004-12-14

    In mammalian spermatogenesis, the X and Y chromosomes are transcriptionally silenced during the pachytene stage of meiotic prophase (meiotic sex chromosome inactivation, MSCI), forming a condensed chromatin domain termed the sex or XY body. The nucleosomal core histone H2AX is phosphorylated within the XY chromatin domain just prior to MSCI, and it has been hypothesized that this triggers the chromatin condensation and transcriptional repression. Here, we show that the kinase ATR localizes to XY chromatin at the onset of MSCI and that this localization is disrupted in mice with a mutant form of the tumor suppressor protein BRCA1. In the mutant pachytene cells, ATR is usually present at nonsex chromosomal sites, where it colocalizes with aberrant sites of H2AX phosphorylation; in these cells, there is MSCI failure. In rare pachytene cells, ATR does locate to XY chromatin, H2AX is then phosphorylated, a sex body forms, and MSCI ensues. These observations highlight an important role for BRCA1 in recruiting the kinase ATR to XY chromatin at the onset of MSCI and provide compelling evidence that it is ATR that phosphorylates H2AX and triggers MSCI.

  1. Meiotic recombination at the Lmp2 hotspot tolerates minor sequence divergence between homologous chromosomes

    SciTech Connect

    Yoshino, Masayasu; Sagai, Tomoko; Shiroishi, Toshihiko

    1996-06-01

    Recombination is widely considered to linearly depend on the length of the homologous sequences. An 11% mismatch decreases the rate of phage-plasmid recombination 240-fold. Two single nucleotide mismatches, which reduce the longest uninterrupted stretch of similarity from 232 base pairs (bp) to 134 bp, reduce gene conversion in mouse L cells 20-fold. The efficiency of gene targeting through homologous recombination in mouse embryonic stem cells can be increased by using an isogenic, rather than a non-isogenic, DNA construct. In this study we asked whether a high degree of sequence identity between homologous mouse chromosomes enhances meiotic recombination at a hotspot. Sites of meiotic recombination in the mouse major histocompatibility complex (MHC) class II region are not randomly distributed but are almost all clustered within short segments known as recombinational hotspots. The wm7 MHC haplotype, derived from Japanese wild mice Mus musculus molossinus, enhances meiotic recombination at a hotspot near the Lmp2 gene. Heterozygotes between the wm7 haplotype and the b or k haplotypes have yielded a high frequency of recombination (2.1%) in 1.3 kilobase kb segment of this hotspot. 20 refs., 2 figs.

  2. Cytomixis and meiotic abnormalities during microsporogenesis are responsible for male sterility and chromosome variations in Houttuynia cordata.

    PubMed

    Guan, J-Z; Wang, J-J; Cheng, Z-H; Liu, Y; Li, Z-Y

    2012-01-01

    Houttuynia cordata (Saururaceae) is a leaf vegetable and a medicinal herb througout much of Asia. Cytomixis and meiotic abnormalities during microsporogenesis were found in two populations of H. cordata with different ploidy levels (2n = 38, 96). Cytomixis occurred in pollen mother cells during meiosis at high frequencies and with variable degrees of chromatin/chromosome transfer. Meiotic abnormalities, such as chromosome laggards, asymmetric segregation and polyads, also prevailed in pollen mother cells at metaphase of the first division and later stages. They were caused by cytomixis and resulted in very low pollen viability and male sterility. Pollen mother cells from the population with 2n = 38 showed only simultaneous cytokinesis, but most pollen mother cells from the population with 2n = 96 showed successive cytokinesis; a minority underwent simultaneous cytokinesis. Cytomixis and irregular meiotic divisions appear to be the origin of the intraspecific polyploidy in this species, which has large variations in chromosome numbers. PMID:22290472

  3. Homoeologous Chromosome Sorting and Progression of Meiotic Recombination in Brassica napus: Ploidy Does Matter!

    PubMed

    Grandont, Laurie; Cuñado, Nieves; Coriton, Olivier; Huteau, Virgine; Eber, Frédérique; Chèvre, Anne Marie; Grelon, Mathilde; Chelysheva, Liudmila; Jenczewski, Eric

    2014-04-15

    Meiotic recombination is the fundamental process that produces balanced gametes and generates diversity within species. For successful meiosis, crossovers must form between homologous chromosomes. This condition is more difficult to fulfill in allopolyploid species, which have more than two sets of related chromosomes (homoeologs). Here, we investigated the formation, progression, and completion of several key hallmarks of meiosis in Brassica napus (AACC), a young polyphyletic allotetraploid crop species with closely related homoeologous chromosomes. Altogether, our results demonstrate a precocious and efficient sorting of homologous versus homoeologous chromosomes during early prophase I in two representative B. napus accessions that otherwise show a genotypic difference in the progression of homologous recombination. More strikingly, our detailed comparison of meiosis in near isogenic allohaploid and euploid plants showed that the mechanism(s) promoting efficient chromosome sorting in euploids is adjusted to promote crossover formation between homoeologs in allohaploids. This suggests that, in contrast to other polyploid species, chromosome sorting is context dependent in B. napus. PMID:24737673

  4. Meiotic chromosome pairing behaviour of natural tetraploids and induced autotetraploids of Actinidia chinensis.

    PubMed

    Wu, Jin-Hu; Datson, Paul M; Manako, Kelvina I; Murray, Brian G

    2014-03-01

    Non-preferential chromosome pairing was identified in tetraploid Actinidia chinensis and a higher mean multivalent frequency in pollen mother cells was found in colchine-induced tetraploids of A. chinensis compared with naturally occurring tetraploids. Diploid and tetraploid Actinidia chinensis are used for the development of kiwifruit cultivars. Diploid germplasm can be exploited in a tetraploid breeding programme via unreduced (2n) gametes and chemical-induced chromosome doubling of diploid cultivars and selections. Meiotic chromosome behaviour in diploid A. chinensis 'Hort16A' and colchicine-induced tetraploids from 'Hort16A' was analysed and compared with that in a diploid male and tetraploid males of A. chinensis raised from seeds sourced from the wild in China. Both naturally occurring and induced tetraploids formed multivalents, but colchicine-induced tetraploids showed a higher mean multivalent frequency in the pollen mother cells. Lagging chromosomes at anaphase I and II were observed at low frequencies in the colchicine-induced tetraploids. To investigate whether preferential or non-preferential chromosome pairing occurs in tetraploid A. chinensis, the inheritance of microsatellite alleles was analysed in the tetraploid progeny of crosses between A. chinensis (4x) and A. arguta (4x). The frequencies of inherited microsatellite allelic combinations in the hybrids suggested that non-preferential chromosome pairing had occurred in the tetraploid A. chinensis parent. PMID:24306317

  5. Sexual antagonism and meiotic drive cause stable linkage disequilibrium and favour reduced recombination on the X chromosome.

    PubMed

    Rydzewski, W T; Carioscia, S A; Liévano, G; Lynch, V D; Patten, M M

    2016-06-01

    Sexual antagonism and meiotic drive are sex-specific evolutionary forces with the potential to shape genomic architecture. Previous theory has found that pairing two sexually antagonistic loci or combining sexual antagonism with meiotic drive at linked autosomal loci augments genetic variation, produces stable linkage disequilibrium (LD) and favours reduced recombination. However, the influence of these two forces has not been examined on the X chromosome, which is thought to be enriched for sexual antagonism and meiotic drive. We investigate the evolution of the X chromosome under both sexual antagonism and meiotic drive with two models: in one, both loci experience sexual antagonism; in the other, we pair a meiotic drive locus with a sexually antagonistic locus. We find that LD arises between the two loci in both models, even when the two loci freely recombine in females and that driving haplotypes will be enriched for male-beneficial alleles, further skewing sex ratios in these populations. We introduce a new measure of LD, Dz', which accounts for population allele frequencies and is appropriate for instances where these are sex specific. Both models demonstrate that natural selection favours modifiers that reduce the recombination rate. These results inform observed patterns of congealment found on driving X chromosomes and have implications for patterns of natural variation and the evolution of recombination rates on the X chromosome.

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

    PubMed Central

    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

  7. Kdm5/Lid Regulates Chromosome Architecture in Meiotic Prophase I Independently of Its Histone Demethylase Activity

    PubMed Central

    Zhaunova, Liudmila; Ohkura, Hiroyuki; Breuer, Manuel

    2016-01-01

    During prophase of the first meiotic division (prophase I), chromatin dynamically reorganises to recombine and prepare for chromosome segregation. Histone modifying enzymes are major regulators of chromatin structure, but our knowledge of their roles in prophase I is still limited. Here we report on crucial roles of Kdm5/Lid, one of two histone demethylases in Drosophila that remove one of the trimethyl groups at Lys4 of Histone 3 (H3K4me3). In the absence of Kdm5/Lid, the synaptonemal complex was only partially formed and failed to be maintained along chromosome arms, while localisation of its components at centromeres was unaffected. Kdm5/Lid was also required for karyosome formation and homologous centromere pairing in prophase I. Although loss of Kdm5/Lid dramatically increased the level of H3K4me3 in oocytes, catalytically inactive Kdm5/Lid can rescue the above cytological defects. Therefore Kdm5/Lid controls chromatin architecture in meiotic prophase I oocytes independently of its demethylase activity. PMID:27494704

  8. Lack of evidence for association of meiotic nondisjunction with particular DNA haplotypes on chromosome 21.

    PubMed Central

    Sacchi, N; Gusella, J F; Perroni, L; Bricarelli, F D; Papas, T S

    1988-01-01

    The hypothesis of a predisposition to meiotic nondisjunction for chromosome 21 carrying a specific molecular haplotype has been tested. The haplotype in question is defined by the restriction fragment length polymorphisms for the D21S1/D21S11 loci. Our results obtained on a sample of Northern Italian families with the occurrence of trisomy 21 (Down syndrome) failed to support this hypothesis, contradicting a previous study [Antonarakis, S. E., Kittur, S. D., Metaxotou, C., Watkins, P. C. & Patel, A. S. (1985) Proc. Natl. Acad. Sci. USA 82, 3360-3364]. These findings rule out an association between any specific D21S1/D21S11 haplotype (as well as other haplotypes for the D21S13, ETS2, and D21S23 loci) and a putative cis-acting genetic element favoring the meiotic missegregation of chromosome 21. For this reason, no preventive screening for couples at risk for trisomy 21 may be based on any of the haplotypes tested. Images PMID:2898783

  9. A Whole-Chromosome Analysis of Meiotic Recombination in Drosophila melanogaster.

    PubMed

    Miller, Danny E; Takeo, Satomi; Nandanan, Kavyasree; Paulson, Ariel; Gogol, Madelaine M; Noll, Aaron C; Perera, Anoja G; Walton, Kendra N; Gilliland, William D; Li, Hua; Staehling, Karen K; Blumenstiel, Justin P; Hawley, R Scott

    2012-02-01

    Although traditional genetic assays have characterized the pattern of crossing over across the genome in Drosophila melanogaster, these assays could not precisely define the location of crossovers. Even less is known about the frequency and distribution of noncrossover gene conversion events. To assess the specific number and positions of both meiotic gene conversion and crossover events, we sequenced the genomes of male progeny from females heterozygous for 93,538 X chromosomal single-nucleotide and InDel polymorphisms. From the analysis of the 30 F1 hemizygous X chromosomes, we detected 15 crossover and 5 noncrossover gene conversion events. Taking into account the nonuniform distribution of polymorphism along the chromosome arm, we estimate that most oocytes experience 1 crossover event and 1.6 gene conversion events per X chromosome pair per meiosis. An extrapolation to the entire genome would predict approximately 5 crossover events and 8.6 conversion events per meiosis. Mean gene conversion tract lengths were estimated to be 476 base pairs, yielding a per nucleotide conversion rate of 0.86 × 10(-5) per meiosis. Both of these values are consistent with estimates of conversion frequency and tract length obtained from studies of rosy, the only gene for which gene conversion has been studied extensively in Drosophila. Motif-enrichment analysis revealed a GTGGAAA motif that was enriched near crossovers but not near gene conversions. The low-complexity and frequent occurrence of this motif may in part explain why, in contrast to mammalian systems, no meiotic crossover hotspots have been found in Drosophila. PMID:22384403

  10. A Whole-Chromosome Analysis of Meiotic Recombination in Drosophila melanogaster

    PubMed Central

    Miller, Danny E.; Takeo, Satomi; Nandanan, Kavyasree; Paulson, Ariel; Gogol, Madelaine M.; Noll, Aaron C.; Perera, Anoja G.; Walton, Kendra N.; Gilliland, William D.; Li, Hua; Staehling, Karen K.; Blumenstiel, Justin P.; Hawley, R. Scott

    2012-01-01

    Although traditional genetic assays have characterized the pattern of crossing over across the genome in Drosophila melanogaster, these assays could not precisely define the location of crossovers. Even less is known about the frequency and distribution of noncrossover gene conversion events. To assess the specific number and positions of both meiotic gene conversion and crossover events, we sequenced the genomes of male progeny from females heterozygous for 93,538 X chromosomal single-nucleotide and InDel polymorphisms. From the analysis of the 30 F1 hemizygous X chromosomes, we detected 15 crossover and 5 noncrossover gene conversion events. Taking into account the nonuniform distribution of polymorphism along the chromosome arm, we estimate that most oocytes experience 1 crossover event and 1.6 gene conversion events per X chromosome pair per meiosis. An extrapolation to the entire genome would predict approximately 5 crossover events and 8.6 conversion events per meiosis. Mean gene conversion tract lengths were estimated to be 476 base pairs, yielding a per nucleotide conversion rate of 0.86 × 10−5 per meiosis. Both of these values are consistent with estimates of conversion frequency and tract length obtained from studies of rosy, the only gene for which gene conversion has been studied extensively in Drosophila. Motif-enrichment analysis revealed a GTGGAAA motif that was enriched near crossovers but not near gene conversions. The low-complexity and frequent occurrence of this motif may in part explain why, in contrast to mammalian systems, no meiotic crossover hotspots have been found in Drosophila. PMID:22384403

  11. Arabidopsis PCH2 Mediates Meiotic Chromosome Remodeling and Maturation of Crossovers.

    PubMed

    Lambing, Christophe; Osman, Kim; Nuntasoontorn, Komsun; West, Allan; Higgins, James D; Copenhaver, Gregory P; Yang, Jianhua; Armstrong, Susan J; Mechtler, Karl; Roitinger, Elisabeth; Franklin, F Chris H

    2015-07-01

    Meiotic chromosomes are organized into linear looped chromatin arrays by a protein axis localized along the loop-bases. Programmed remodelling of the axis occurs during prophase I of meiosis. Structured illumination microscopy (SIM) has revealed dynamic changes in the chromosome axis in Arabidopsis thaliana and Brassica oleracea. We show that the axis associated protein ASY1 is depleted during zygotene concomitant with synaptonemal complex (SC) formation. Study of an Atpch2 mutant demonstrates this requires the conserved AAA+ ATPase, PCH2, which localizes to the sites of axis remodelling. Loss of PCH2 leads to a failure to deplete ASY1 from the axes and compromizes SC polymerisation. Immunolocalization of recombination proteins in Atpch2 indicates that recombination initiation and CO designation during early prophase I occur normally. Evidence suggests that CO interference is initially functional in the mutant but there is a defect in CO maturation following designation. This leads to a reduction in COs and a failure to form COs between some homologous chromosome pairs leading to univalent chromosomes at metaphase I. Genetic analysis reveals that CO distribution is also affected in some chromosome regions. Together these data indicate that the axis remodelling defect in Atpch2 disrupts normal patterned formation of COs.

  12. Meiotic inheritance of a fungal supernumerary chromosome and its effect on sexual fertility in Nectria haematococca.

    PubMed

    Garmaroodi, Hamid S; Taga, Masatoki

    2015-10-01

    PDA1-conditionally dispensable chromosome (CDC) of Nectria haematococca MP VI has long served as a model of supernumerary chromosomes in plant pathogenic fungi because of pathogenicity-related genes located on it. In our previous study, we showed the dosage effects of PDA1-CDC on pathogenicity and homoserine utilization by exploiting tagged PDA1-CDC with a marker gene. CDC content of mating partners and progenies analyzed by PCR, PFGE combined with Southern analysis and chromosome painting via FISH. In this study, we analyzed mode of meiotic inheritance of PDA1-CDC in several mating patterns with regard to CDC content and found a correlation between CDC content of parental strains with fertility of crosses. The results showed non-Mendelian inheritance of this chromosome followed by duplication or loss of the CDC in haploid genome through meiosis that probably were due to premature centromere division, not by nondisjunction as reported for the supernumerary chromosomes in other species. Correlation of CDC with fertility is the first time to be examined in fungi in this study.

  13. Arabidopsis PCH2 Mediates Meiotic Chromosome Remodeling and Maturation of Crossovers.

    PubMed

    Lambing, Christophe; Osman, Kim; Nuntasoontorn, Komsun; West, Allan; Higgins, James D; Copenhaver, Gregory P; Yang, Jianhua; Armstrong, Susan J; Mechtler, Karl; Roitinger, Elisabeth; Franklin, F Chris H

    2015-07-01

    Meiotic chromosomes are organized into linear looped chromatin arrays by a protein axis localized along the loop-bases. Programmed remodelling of the axis occurs during prophase I of meiosis. Structured illumination microscopy (SIM) has revealed dynamic changes in the chromosome axis in Arabidopsis thaliana and Brassica oleracea. We show that the axis associated protein ASY1 is depleted during zygotene concomitant with synaptonemal complex (SC) formation. Study of an Atpch2 mutant demonstrates this requires the conserved AAA+ ATPase, PCH2, which localizes to the sites of axis remodelling. Loss of PCH2 leads to a failure to deplete ASY1 from the axes and compromizes SC polymerisation. Immunolocalization of recombination proteins in Atpch2 indicates that recombination initiation and CO designation during early prophase I occur normally. Evidence suggests that CO interference is initially functional in the mutant but there is a defect in CO maturation following designation. This leads to a reduction in COs and a failure to form COs between some homologous chromosome pairs leading to univalent chromosomes at metaphase I. Genetic analysis reveals that CO distribution is also affected in some chromosome regions. Together these data indicate that the axis remodelling defect in Atpch2 disrupts normal patterned formation of COs. PMID:26182244

  14. Arabidopsis PCH2 Mediates Meiotic Chromosome Remodeling and Maturation of Crossovers

    PubMed Central

    West, Allan; Higgins, James D.; Copenhaver, Gregory P.; Yang, Jianhua; Armstrong, Susan J.; Mechtler, Karl; Roitinger, Elisabeth; Franklin, F. Chris H.

    2015-01-01

    Meiotic chromosomes are organized into linear looped chromatin arrays by a protein axis localized along the loop-bases. Programmed remodelling of the axis occurs during prophase I of meiosis. Structured illumination microscopy (SIM) has revealed dynamic changes in the chromosome axis in Arabidopsis thaliana and Brassica oleracea. We show that the axis associated protein ASY1 is depleted during zygotene concomitant with synaptonemal complex (SC) formation. Study of an Atpch2 mutant demonstrates this requires the conserved AAA+ ATPase, PCH2, which localizes to the sites of axis remodelling. Loss of PCH2 leads to a failure to deplete ASY1 from the axes and compromizes SC polymerisation. Immunolocalization of recombination proteins in Atpch2 indicates that recombination initiation and CO designation during early prophase I occur normally. Evidence suggests that CO interference is initially functional in the mutant but there is a defect in CO maturation following designation. This leads to a reduction in COs and a failure to form COs between some homologous chromosome pairs leading to univalent chromosomes at metaphase I. Genetic analysis reveals that CO distribution is also affected in some chromosome regions. Together these data indicate that the axis remodelling defect in Atpch2 disrupts normal patterned formation of COs. PMID:26182244

  15. Meiotic inheritance of a fungal supernumerary chromosome and its effect on sexual fertility in Nectria haematococca.

    PubMed

    Garmaroodi, Hamid S; Taga, Masatoki

    2015-10-01

    PDA1-conditionally dispensable chromosome (CDC) of Nectria haematococca MP VI has long served as a model of supernumerary chromosomes in plant pathogenic fungi because of pathogenicity-related genes located on it. In our previous study, we showed the dosage effects of PDA1-CDC on pathogenicity and homoserine utilization by exploiting tagged PDA1-CDC with a marker gene. CDC content of mating partners and progenies analyzed by PCR, PFGE combined with Southern analysis and chromosome painting via FISH. In this study, we analyzed mode of meiotic inheritance of PDA1-CDC in several mating patterns with regard to CDC content and found a correlation between CDC content of parental strains with fertility of crosses. The results showed non-Mendelian inheritance of this chromosome followed by duplication or loss of the CDC in haploid genome through meiosis that probably were due to premature centromere division, not by nondisjunction as reported for the supernumerary chromosomes in other species. Correlation of CDC with fertility is the first time to be examined in fungi in this study. PMID:26399187

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

    PubMed

    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.

  17. Meiotic behavior and H3K4m distribution in B chromosomes of Characidium gomesi (Characiformes, Crenuchidae)

    PubMed Central

    Serrano, Érica Alves; Araya-Jaime, Cristian; Suárez-Villota, Elkin Y.; Oliveira, Claudio; Foresti, Fausto

    2016-01-01

    Abstract Characidium gomesi Travasso, 1956 specimens from the Pardo River have up to four heterochromatic supernumerary chromosomes, derived from the sex chromosomes. To access the meiotic behavior and distribution of an active chromatin marker, males and females of Characidium gomesi with two or three B chromosomes were analyzed. Mitotic chromosomes were characterized using C-banding and FISH with B chromosome probes. Meiocytes were subjected to immunofluorescence-FISH assay using anti-SYCP3, anti-H3K4m, and B chromosomes probes. Molecular homology of supernumeraries was confirmed by FISH and by its bivalent conformation in individuals with two of these chromosomes. In individuals with three Bs, these elements formed a bivalent and a univalent. Supernumerary and sex chromosomes exhibited H3K4m signals during pachytene contrasting with their heterochromatic and asynaptic nature, which suggest a more structural role than functional of this histone modification. The implications of this result are discussed in light of the homology, meiotic nuclear organization, and meiotic silencing of unsynapsed chomatin. PMID:27551347

  18. Meiotic behavior and H3K4m distribution in B chromosomes of Characidium gomesi (Characiformes, Crenuchidae).

    PubMed

    Serrano, Érica Alves; Araya-Jaime, Cristian; Suárez-Villota, Elkin Y; Oliveira, Claudio; Foresti, Fausto

    2016-01-01

    Characidium gomesi Travasso, 1956 specimens from the Pardo River have up to four heterochromatic supernumerary chromosomes, derived from the sex chromosomes. To access the meiotic behavior and distribution of an active chromatin marker, males and females of Characidium gomesi with two or three B chromosomes were analyzed. Mitotic chromosomes were characterized using C-banding and FISH with B chromosome probes. Meiocytes were subjected to immunofluorescence-FISH assay using anti-SYCP3, anti-H3K4m, and B chromosomes probes. Molecular homology of supernumeraries was confirmed by FISH and by its bivalent conformation in individuals with two of these chromosomes. In individuals with three Bs, these elements formed a bivalent and a univalent. Supernumerary and sex chromosomes exhibited H3K4m signals during pachytene contrasting with their heterochromatic and asynaptic nature, which suggest a more structural role than functional of this histone modification. The implications of this result are discussed in light of the homology, meiotic nuclear organization, and meiotic silencing of unsynapsed chomatin. PMID:27551347

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

    PubMed

    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. PMID:23760560

  20. The Dissection of Meiotic Chromosome Movement in Mice Using an In Vivo Electroporation Technique

    PubMed Central

    Shibuya, Hiroki; Morimoto, Akihiro; Watanabe, Yoshinori

    2014-01-01

    During meiosis, the rapid movement of telomeres along the nuclear envelope (NE) facilitates pairing/synapsis of homologous chromosomes. In mammals, the mechanical properties of chromosome movement and the cytoskeletal structures responsible for it remain poorly understood. Here, applying an in vivo electroporation (EP) technique in live mouse testis, we achieved the quick visualization of telomere, chromosome axis and microtubule organizing center (MTOC) movements. For the first time, we defined prophase sub-stages of live spermatocytes morphologically according to GFP-TRF1 and GFP-SCP3 signals. We show that rapid telomere movement and subsequent nuclear rotation persist from leptotene/zygotene to pachytene, and then decline in diplotene stage concomitant with the liberation of SUN1 from telomeres. Further, during bouquet stage, telomeres are constrained near the MTOC, resulting in the transient suppression of telomere mobility and nuclear rotation. MTs are responsible for these movements by forming cable-like structures on the NE, and, probably, by facilitating the rail-tacking movements of telomeres on the MT cables. In contrast, actin regulates the oscillatory changes in nuclear shape. Our data provide the mechanical scheme for meiotic chromosome movement throughout prophase I in mammals. PMID:25502938

  1. Reduced polymorphism associated with X chromosome meiotic drive in the stalk-eyed fly Teleopsis dalmanni.

    PubMed

    Christianson, Sarah J; Brand, Cara L; Wilkinson, Gerald S

    2011-01-01

    Sex chromosome meiotic drive has been suggested as a cause of several evolutionary genetic phenomena, including genomic conflicts that give rise to reproductive isolation between new species. In this paper we present a population genetic analysis of X chromosome drive in the stalk-eyed fly, Teleopsis dalmanni, to determine how this natural polymorphism influences genetic diversity. We analyzed patterns of DNA sequence variation at two X-linked regions (comprising 1325 bp) approximately 50 cM apart and one autosomal region (comprising 921 bp) for 50 males, half of which were collected in the field from one of two allopatric locations and the other half were derived from lab-reared individuals with known brood sex ratios. These two populations are recently diverged but exhibit partial postzygotic reproductive isolation, i.e. crosses produce sterile hybrid males and fertile females. We find no nucleotide or microsatellite variation on the drive X chromosome, whereas the same individuals show levels of variation at autosomal regions that are similar to field-collected flies. Furthermore, one field-caught individual collected 10 years previously had a nearly identical X haplotype to the drive X, and is over 2% divergent from other haplotypes sampled from the field. These results are consistent with a selective sweep that has removed genetic variation from much of the drive X chromosome. We discuss how this finding may relate to the rapid evolution of postzygotic reproductive isolation that has been documented for these flies.

  2. A model for chromosome structure during the mitotic and meiotic cell cycles.

    PubMed

    Stack, S M; Anderson, L K

    2001-01-01

    The chromosome scaffold model in which loops of chromatin are attached to a central, coiled chromosome core (scaffold) is the current paradigm for chromosome structure. Here we present a modified version of the chromosome scaffold model to describe chromosome structure and behavior through the mitotic and meiotic cell cycles. We suggest that a salient feature of chromosome structure is established during DNA replication when sister loops of DNA extend in opposite directions from replication sites on nuclear matrix strands. This orientation is maintained into prophase when the nuclear matrix strand is converted into two closely associated sister chromatid cores with sister DNA loops extending in opposite directions. We propose that chromatid cores are contractile and show, using a physical model, that contraction of cores during late prophase can result in coiled chromatids. Coiling accounts for the majority of chromosome shortening that is needed to separate sister chromatids within the confines of a cell. In early prophase I of meiosis, the orientation of sister DNA loops in opposite directions from axial elements assures that DNA loops interact preferentially with homologous DNA loops rather than with sister DNA loops. In this context, we propose a bar code model for homologous presynaptic chromosome alignment that involves weak paranemic interactions of homologous DNA loops. Opposite orientation of sister loops also suppresses crossing over between sister chromatids in favor of crossing over between homologous non-sister chromatids. After crossing over is completed in pachytene and the synaptonemal complex breaks down in early diplotene (= diffuse stage), new contractile cores are laid down along each chromatid. These chromatid cores are comparable to the chromatid cores in mitotic prophase chromosomes. As an aside, we propose that leptotene through early diplotene represent the 'missing' G2 period of the premeiotic interphase. The new chromosome cores, along

  3. Cohesin-interacting protein WAPL-1 regulates meiotic chromosome structure and cohesion by antagonizing specific cohesin complexes

    PubMed Central

    Crawley, Oliver; Barroso, Consuelo; Testori, Sarah; Ferrandiz, Nuria; Silva, Nicola; Castellano-Pozo, Maikel; Jaso-Tamame, Angel Luis; Martinez-Perez, Enrique

    2016-01-01

    Wapl induces cohesin dissociation from DNA throughout the mitotic cell cycle, modulating sister chromatid cohesion and higher-order chromatin structure. Cohesin complexes containing meiosis-specific kleisin subunits govern most aspects of meiotic chromosome function, but whether Wapl regulates these complexes remains unknown. We show that during C. elegans oogenesis WAPL-1 antagonizes binding of cohesin containing COH-3/4 kleisins, but not REC-8, demonstrating that sensitivity to WAPL-1 is dictated by kleisin identity. By restricting the amount of chromosome-associated COH-3/4 cohesin, WAPL-1 controls chromosome structure throughout meiotic prophase. In the absence of REC-8, WAPL-1 inhibits COH-3/4-mediated cohesion, which requires crossover-fated events formed during meiotic recombination. Thus, WAPL-1 promotes functional specialization of meiotic cohesin: WAPL-1-sensitive COH-3/4 complexes modulate higher-order chromosome structure, while WAPL-1-refractory REC-8 complexes provide stable cohesion. Surprisingly, a WAPL-1-independent mechanism removes cohesin before metaphase I. Our studies provide insight into how meiosis-specific cohesin complexes are regulated to ensure formation of euploid gametes. DOI: http://dx.doi.org/10.7554/eLife.10851.001 PMID:26841696

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

    PubMed Central

    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

  5. Rejuvenation of Meiotic Cohesion in Oocytes during Prophase I Is Required for Chiasma Maintenance and Accurate Chromosome Segregation

    PubMed Central

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

    2014-01-01

    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

  6. Platypus chain reaction: directional and ordered meiotic pairing of the multiple sex chromosome chain in Ornithorhynchus anatinus.

    PubMed

    Daish, Tasman; Casey, Aaron; Grützner, Frank

    2009-01-01

    Monotremes are phylogenetically and phenotypically unique animals with an unusually complex sex chromosome system that is composed of ten chromosomes in platypus and nine in echidna. These chromosomes are alternately linked (X1Y1, X2Y2, ...) at meiosis via pseudoautosomal regions and segregate to form spermatozoa containing either X or Y chromosomes. The physical and epigenetic mechanisms involved in pairing and assembly of the complex sex chromosome chain in early meiotic prophase I are completely unknown. We have analysed the pairing dynamics of specific sex chromosome pseudoautosomal regions in platypus spermatocytes during prophase of meiosis I. Our data show a highly coordinated pairing process that begins at the terminal Y5 chromosome and completes with the union of sex chromosomes X1Y1. The consistency of this ordered assembly of the chain is remarkable and raises questions about the mechanisms and factors that regulate the differential pairing of sex chromosomes and how this relates to potential meiotic silencing mechanisms and alternate segregation. PMID:19874721

  7. Meiotic sex chromosome inactivation is disrupted in sterile hybrid male house mice.

    PubMed

    Campbell, Polly; Good, Jeffrey M; Nachman, Michael W

    2013-03-01

    In male mammals, the X and Y chromosomes are transcriptionally silenced in primary spermatocytes by meiotic sex chromosome inactivation (MSCI) and remain repressed for the duration of spermatogenesis. Here, we test the longstanding hypothesis that disrupted MSCI might contribute to the preferential sterility of heterogametic hybrid males. We studied a cross between wild-derived inbred strains of Mus musculus musculus and M. m. domesticus in which sterility is asymmetric: F1 males with a M. m. musculus mother are sterile or nearly so while F1 males with a M. m. domesticus mother are normal. In previous work, we discovered widespread overexpression of X-linked genes in the testes of sterile but not fertile F1 males. Here, we ask whether this overexpression is specifically a result of disrupted MSCI. To do this, we isolated cells from different stages of spermatogenesis and measured the expression of several genes using quantitative PCR. We found that X overexpression in sterile F1 primary spermatocytes is coincident with the onset of MSCI and persists in postmeiotic spermatids. Using a series of recombinant X genotypes, we then asked whether X overexpression in hybrids is controlled by cis-acting loci across the X chromosome. We found that it is not. Instead, one large interval in the proximal portion of the M. m. musculus X chromosome is associated with both overexpression and the severity of sterility phenotypes in hybrids. These results demonstrate a strong association between X-linked hybrid male sterility and disruption of MSCI and suggest that trans-acting loci on the X are important for the transcriptional regulation of the X chromosome during spermatogenesis.

  8. Silencing of X-Linked MicroRNAs by Meiotic Sex Chromosome Inactivation.

    PubMed

    Royo, Hélène; Seitz, Hervé; ElInati, Elias; Peters, Antoine H F M; Stadler, Michael B; Turner, James M A

    2015-10-01

    During the pachytene stage of meiosis in male mammals, the X and Y chromosomes are transcriptionally silenced by Meiotic Sex Chromosome Inactivation (MSCI). MSCI is conserved in therian mammals and is essential for normal male fertility. Transcriptomics approaches have demonstrated that in mice, most or all protein-coding genes on the X chromosome are subject to MSCI. However, it is unclear whether X-linked non-coding RNAs behave in a similar manner. The X chromosome is enriched in microRNA (miRNA) genes, with many exhibiting testis-biased expression. Importantly, high expression levels of X-linked miRNAs (X-miRNAs) have been reported in pachytene spermatocytes, indicating that these genes may escape MSCI, and perhaps play a role in the XY-silencing process. Here we use RNA FISH to examine X-miRNA expression in the male germ line. We find that, like protein-coding X-genes, X-miRNAs are expressed prior to prophase I and are thereafter silenced during pachynema. X-miRNA silencing does not occur in mouse models with defective MSCI. Furthermore, X-miRNAs are expressed at pachynema when present as autosomally integrated transgenes. Thus, we conclude that silencing of X-miRNAs during pachynema in wild type males is MSCI-dependent. Importantly, misexpression of X-miRNAs during pachynema causes spermatogenic defects. We propose that MSCI represents a chromosomal mechanism by which X-miRNAs, and other potential X-encoded repressors, can be silenced, thereby regulating genes with critical late spermatogenic functions.

  9. 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.

    PubMed

    Wang, Jun; Niu, Baixiao; Huang, Jiyue; Wang, Hongkuan; Yang, Xiaohui; Dong, Aiwu; Makaroff, Christopher; Ma, Hong; Wang, Yingxiang

    2016-08-01

    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.

  10. 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.

    PubMed

    Wang, Jun; Niu, Baixiao; Huang, Jiyue; Wang, Hongkuan; Yang, Xiaohui; Dong, Aiwu; Makaroff, Christopher; Ma, Hong; Wang, Yingxiang

    2016-08-01

    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

  11. Meiotic abnormalities

    SciTech Connect

    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.

  12. Mps1 and Ipl1/Aurora B Act Sequentially to Correctly Orient Chromosomes on the Meiotic Spindle of Budding Yeast

    PubMed Central

    Meyer, Régis E.; Kim, Seoyoung; Obeso, David; Straight, Paul D.; Winey, Mark; Dawson, Dean S.

    2013-01-01

    The conserved kinases Mps1 and Ipl1/Aurora B are critical for enabling chromosomes to attach to microtubules such that partner chromosomes will be segregated correctly from each other, but the precise roles of these kinases have been unclear. Here, imaging of live yeast cells was performed to elucidate the stages of chromosome-microtubule interactions, and their regulation by Ipl1 and Mps1, through meiosis I. Ipl1 was found to release kinetochore-microtubule (kMT) associations following meiotic entry, liberating chromosomes to begin homologous pairing. Surprisingly, most chromosome pairs were found to begin their spindle interactions with incorrect kMT attachments. Ipl1 released these improper connections while Mps1 triggered the formation of new force-generating microtubule attachments. This microtubule release and reattachment cycle can prevent catastrophic chromosome segregation errors in meiosis. PMID:23371552

  13. Meiotic stability and polymorphism of CAG repeat in normal chromosome at SCA1 locus

    SciTech Connect

    Limprasert, P.; Nouri, N.; Keats, B.J.B.

    1994-09-01

    Spinocerebellar ataxia type 1 (SCA1) is an autosomal dominant neurodegenerative disorder associated with an unstable and expanded CAG repeat. We analyzed the CAG repeat in normal chromosomes from various sources including SCA1 and nonSCA1 families, and Caucasian, African American, Eskimo, South American Indian and Acadian populations. The range of CAG repeats is 10-37 in normal alleles while the disease allele contains 45-65 repeats in our studies. To determine unbiased normal allelic frequencies, we analyzed data from unrelated individuals in each group. The significance of differences in allelic frequencies among the groups was determined by a chi-square test. Caucasian and Acadian frequencies were similar (p = 0.23), but highly significant differences were found among the Caucasians, African Americans, Eskimos, and South American Indians (p < 0.0005), and the range of allele sizes was much narrower in Eskimos and South American Indians. To determine if the normal chromosome is susceptible to meiotic instability, we examined members of 19 Caucasian and 24 Acadian families. Normal sized CAG repeats were faithfully transmitted from parents to offspring without any alteration in CAG number in 236 meioses. Transmission of CAG repeats in normal alleles were also stable in our SCA1 family. However, the disease allele was associated with a significant degree of instability. Some patients showed 2 expanded bands in DNA prepared from untransformed blood cells. This finding suggest mitotic instability of the disease allele.

  14. Meiotic chromosome morphology and behavior in zip1 mutants of Saccharomyces cerevisiae.

    PubMed Central

    Tung, K S; Roeder, G S

    1998-01-01

    The yeast Zip1 protein (Zip1p) is a component of the central region of the synaptonemal complex (SC). Zip1p is predicted to form a dimer consisting of a coiled-coil domain flanked by globular domains. To analyze the organization of Zip1p within the SC, in-frame deletions of ZIP1 were constructed and analyzed. The results demonstrate that the C terminus but not the N terminus of Zip1p is required for its localization to chromosomes. Deletions in the carboxy half of the predicted coiled-coil region cause decreases in the width of the SC. Based on these results, a model for the organization of Zip1p within the SC is proposed. zip1 deletion mutations were also examined for their effects on sporulation, spore viability, crossing over, and crossover interference. The results demonstrate that the extent of synapsis is positively correlated with the levels of spore viability, crossing over, and crossover interference. In contrast, the role of Zip1p in synapsis is separable from its role in meiotic cell cycle progression. zip1 mutants display interval-specific effects on crossing over. PMID:9611194

  15. The SMC-5/6 Complex and the HIM-6 (BLM) Helicase Synergistically Promote Meiotic Recombination Intermediate Processing and Chromosome Maturation during Caenorhabditis elegans Meiosis.

    PubMed

    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.

  16. The SMC-5/6 Complex and the HIM-6 (BLM) Helicase Synergistically Promote Meiotic Recombination Intermediate Processing and Chromosome Maturation during Caenorhabditis elegans Meiosis

    PubMed Central

    Hong, Ye; Sonneville, Remi; Agostinho, Ana; Meier, Bettina; Wang, Bin; Blow, J. Julian; Gartner, Anton

    2016-01-01

    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. PMID:27010650

  17. The SMC-5/6 Complex and the HIM-6 (BLM) Helicase Synergistically Promote Meiotic Recombination Intermediate Processing and Chromosome Maturation during Caenorhabditis elegans Meiosis.

    PubMed

    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. PMID:27010650

  18. A Meiotic Drive Element in the Maize Pathogen Fusarium verticillioides Is Located Within a 102 kb Region of Chromosome V

    PubMed Central

    Pyle, Jay; Patel, Tejas; Merrill, Brianna; Nsokoshi, Chabu; McCall, Morgan; Proctor, Robert H.; Brown, Daren W.; Hammond, Thomas M.

    2016-01-01

    Fusarium verticillioides is an agriculturally important fungus because of its association with maize and its propensity to contaminate grain with toxic compounds. Some isolates of the fungus harbor a meiotic drive element known as Spore killer (SkK) that causes nearly all surviving meiotic progeny from an SkK × Spore killer-susceptible (SkS) cross to inherit the SkK allele. SkK has been mapped to chromosome V but the genetic element responsible for meiotic drive has yet to be identified. In this study, we used cleaved amplified polymorphic sequence markers to genotype individual progeny from an SkK × SkS mapping population. We also sequenced the genomes of three progeny from the mapping population to determine their single nucleotide polymorphisms. These techniques allowed us to refine the location of SkK to a contiguous 102 kb interval of chromosome V, herein referred to as the Sk region. Relative to SkS genotypes, SkK genotypes have one extra gene within this region for a total of 42 genes. The additional gene in SkK genotypes, herein named SKC1 for Spore Killer Candidate 1, is the most highly expressed gene from the Sk region during early stages of sexual development. The Sk region also has three hyper-variable regions, the longest of which includes SKC1. The possibility that SKC1, or another gene from the Sk region, is an essential component of meiotic drive and spore killing is discussed. PMID:27317777

  19. A Meiotic Drive Element in the Maize Pathogen Fusarium verticillioides Is Located Within a 102 kb Region of Chromosome V.

    PubMed

    Pyle, Jay; Patel, Tejas; Merrill, Brianna; Nsokoshi, Chabu; McCall, Morgan; Proctor, Robert H; Brown, Daren W; Hammond, Thomas M

    2016-08-09

    Fusarium verticillioides is an agriculturally important fungus because of its association with maize and its propensity to contaminate grain with toxic compounds. Some isolates of the fungus harbor a meiotic drive element known as Spore killer (Sk(K)) that causes nearly all surviving meiotic progeny from an Sk(K) × Spore killer-susceptible (Sk(S)) cross to inherit the Sk(K) allele. Sk(K) has been mapped to chromosome V but the genetic element responsible for meiotic drive has yet to be identified. In this study, we used cleaved amplified polymorphic sequence markers to genotype individual progeny from an Sk(K) × Sk(S) mapping population. We also sequenced the genomes of three progeny from the mapping population to determine their single nucleotide polymorphisms. These techniques allowed us to refine the location of Sk(K) to a contiguous 102 kb interval of chromosome V, herein referred to as the Sk region. Relative to Sk(S) genotypes, Sk(K) genotypes have one extra gene within this region for a total of 42 genes. The additional gene in Sk(K) genotypes, herein named SKC1 for Spore Killer Candidate 1, is the most highly expressed gene from the Sk region during early stages of sexual development. The Sk region also has three hyper-variable regions, the longest of which includes SKC1 The possibility that SKC1, or another gene from the Sk region, is an essential component of meiotic drive and spore killing is discussed.

  20. A Meiotic Drive Element in the Maize Pathogen Fusarium verticillioides Is Located Within a 102 kb Region of Chromosome V.

    PubMed

    Pyle, Jay; Patel, Tejas; Merrill, Brianna; Nsokoshi, Chabu; McCall, Morgan; Proctor, Robert H; Brown, Daren W; Hammond, Thomas M

    2016-01-01

    Fusarium verticillioides is an agriculturally important fungus because of its association with maize and its propensity to contaminate grain with toxic compounds. Some isolates of the fungus harbor a meiotic drive element known as Spore killer (Sk(K)) that causes nearly all surviving meiotic progeny from an Sk(K) × Spore killer-susceptible (Sk(S)) cross to inherit the Sk(K) allele. Sk(K) has been mapped to chromosome V but the genetic element responsible for meiotic drive has yet to be identified. In this study, we used cleaved amplified polymorphic sequence markers to genotype individual progeny from an Sk(K) × Sk(S) mapping population. We also sequenced the genomes of three progeny from the mapping population to determine their single nucleotide polymorphisms. These techniques allowed us to refine the location of Sk(K) to a contiguous 102 kb interval of chromosome V, herein referred to as the Sk region. Relative to Sk(S) genotypes, Sk(K) genotypes have one extra gene within this region for a total of 42 genes. The additional gene in Sk(K) genotypes, herein named SKC1 for Spore Killer Candidate 1, is the most highly expressed gene from the Sk region during early stages of sexual development. The Sk region also has three hyper-variable regions, the longest of which includes SKC1 The possibility that SKC1, or another gene from the Sk region, is an essential component of meiotic drive and spore killing is discussed. PMID:27317777

  1. Presence of an extra chromosome alters meiotic double-stranded break repair dynamics and MLH1 foci distribution in human oocytes.

    PubMed

    Robles, P; Roig, I; Garcia, R; Brieño-Enríquez, M; Martin, M; Cabero, Ll; Toran, N; Garcia Caldés, M

    2013-03-01

    Studies performed on human trisomic 21 oocytes have revealed that during meiosis, the three homologues 21 synapse and, in some cases, achieve what looks like a trivalent. This implies that meiotic recombination takes place among the three homologous chromosomes 21, and to some extent, crossovers form between them. To see how meiotic recombination is in the presence of an extra chromosome 21, we analyzed the distribution of three recombination markers (γH2AX, RPA, and MLH1) on trisomic 21 oocytes at pachynema and, in particular, on chromosomes 21. Results clearly show how the presence of an extra chromosome 21 alters meiotic recombination progression, leading to the presence of a higher number of early recombination markers at pachynema. Moreover, the distribution on these chromosomes 21 of some of these markers is different in aneuploid oocytes. Finally, there is a substantial increase in the number of MLH1 foci, a marker of most crossovers in mammals, which is related to the number of synapsed chromosomes in pachynema. Thus, bivalents 21 had fewer MLH1 foci than partial or total trivalents, suggesting a close relationship between synapsis and crossover designation. All of the data presented suggest that the presence of an extra chromosome alters meiotic recombination globally in aneuploid human oocytes. PMID:23283390

  2. Meiotic chromosome segregation mutants identified by insertional mutagenesis of fission yeast Schizosaccharomyces pombe; tandem-repeat, single-site integrations

    PubMed Central

    Davidson, Mari K.; Young, Nathan P.; Glick, Gloria G.; Wahls, Wayne P.

    2004-01-01

    Identification of genes required for segregation of chromosomes in meiosis (scm) is difficult because in most organisms high-fidelity chromosome segregation is essential to produce viable meiotic products. The biology of fission yeast Schizosaccharomyces pombe facilitates identification of such genes. Insertional mutagenesis was achieved by electroporation of linear ura4+ DNA into cells harboring a ura4 deletion. Approximately 1000 stable transformants were screened individually for the production of elevated frequencies of aneuploid spore colonies. Twenty-two candidates were subjected to a secondary screen for cytological defects. Five mutants exhibited significant levels of aberrant meiotic chromosome segregation, but were proficient for mating and completion of meiosis. Each mutant's phenotype cosegregated with its respective ura4+ transgene. The mutations were recessive and defined five complementation groups, revealing five distinct genes (scm1, scm2, scm3, scm4 and scm5). Southern blotting revealed single-site integration in each transformant, indicating that insertional mutagenesis is useful for generating single-locus scm mutations linked to a selectable marker. The transgene insertion points were refractory to analysis by inverse-PCR. Molecular and real-time PCR analyses revealed the presence of multiple, truncated copies of ura4+ at each integration site. Thus, electroporation-mediated insertional mutagenesis in S.pombe is preceded by exonucleolytic processing and concatomerization of the transforming DNA. PMID:15316103

  3. Meiotic chromosome segregation mutants identified by insertional mutagenesis of fission yeast Schizosaccharomyces pombe; tandem-repeat, single-site integrations.

    PubMed

    Davidson, Mari K; Young, Nathan P; Glick, Gloria G; Wahls, Wayne P

    2004-01-01

    Identification of genes required for segregation of chromosomes in meiosis (scm) is difficult because in most organisms high-fidelity chromosome segregation is essential to produce viable meiotic products. The biology of fission yeast Schizosaccharomyces pombe facilitates identification of such genes. Insertional mutagenesis was achieved by electroporation of linear ura4+ DNA into cells harboring a ura4 deletion. Approximately 1000 stable transformants were screened individually for the production of elevated frequencies of aneuploid spore colonies. Twenty-two candidates were subjected to a secondary screen for cytological defects. Five mutants exhibited significant levels of aberrant meiotic chromosome segregation, but were proficient for mating and completion of meiosis. Each mutant's phenotype cosegregated with its respective ura4+ transgene. The mutations were recessive and defined five complementation groups, revealing five distinct genes (scm1, scm2, scm3, scm4 and scm5). Southern blotting revealed single-site integration in each transformant, indicating that insertional mutagenesis is useful for generating single-locus scm mutations linked to a selectable marker. The transgene insertion points were refractory to analysis by inverse-PCR. Molecular and real-time PCR analyses revealed the presence of multiple, truncated copies of ura4+ at each integration site. Thus, electroporation-mediated insertional mutagenesis in S.pombe is preceded by exonucleolytic processing and concatomerization of the transforming DNA. PMID:15316103

  4. The rad9 gene of Coprinus cinereus encodes a proline-rich protein required for meiotic chromosome condensation and synapsis

    SciTech Connect

    Seitz, L.C.; Tang, Keliang; Cummings, W.J.; Zolan, M.E.

    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.

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

    SciTech Connect

    Erenpreisa, Jekaterina; Cragg, Mark S.; Salmina, Kristine; Hausmann, Michael; Scherthan, Harry

    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.

  6. Intriguing evidence of translocations in Discus fish (Symphysodon, Cichlidae) and a report of the largest meiotic chromosomal chain observed in vertebrates.

    PubMed

    Gross, M C; Feldberg, E; Cella, D M; Schneider, M C; Schneider, C H; Porto, J I R; Martins, C

    2009-05-01

    As part of a program to understand the genetics of Amazonian ornamental fish, classical cytogenetics was used to analyze Symphysodon aequifasciatus, S. discus and S. haraldi, popular and expensive aquarium fishes that are endemic to the Amazon basin. Mitotic analyses in Symphysodon have shown some odd patterns compared with other Neotropical cichlids. We have confirmed that Symphysodon species are characterized by chromosomal diversity and meiotic complexity despite the fact that species share the same diploid number 2n=60. An intriguing meiotic chromosomal chain, with up to 20 elements during diplotene/diakinesis, was observed in S. aequifasciatus and S. haraldi, whereas S. discus only contains typical bivalent chromosomes. Such chromosomal chains with a high number of elements have not been observed in any other vertebrates. We showed that the meiotic chromosomal chain was not sex related. This observation is unusual and we propose that the origin of meiotic multiples in males and females is based on a series of translocations that involved heterochromatic regions after hybridization of ancestor wild Discus species.

  7. Separable Roles for a Caenorhabditis elegans RMI1 Homolog in Promoting and Antagonizing Meiotic Crossovers Ensure Faithful Chromosome Inheritance

    PubMed Central

    Jagut, Marlène; Hamminger, Patricia; Woglar, Alexander; Millonigg, Sophia; Paulin, Luis; Mikl, Martin; Dello Stritto, Maria Rosaria; Tang, Lois; Habacher, Cornelia; Tam, Angela; Gallach, Miguel; von Haeseler, Arndt; Villeneuve, Anne M.; Jantsch, Verena

    2016-01-01

    During the first meiotic division, crossovers (COs) between homologous chromosomes ensure their correct segregation. COs are produced by homologous recombination (HR)-mediated repair of programmed DNA double strand breaks (DSBs). As more DSBs are induced than COs, mechanisms are required to establish a regulated number of COs and to repair remaining intermediates as non-crossovers (NCOs). We show that the Caenorhabditis elegans RMI1 homolog-1 (RMH-1) functions during meiosis to promote both CO and NCO HR at appropriate chromosomal sites. RMH-1 accumulates at CO sites, dependent on known pro-CO factors, and acts to promote CO designation and enforce the CO outcome of HR-intermediate resolution. RMH-1 also localizes at NCO sites and functions in parallel with SMC-5 to antagonize excess HR-based connections between chromosomes. Moreover, RMH-1 also has a major role in channeling DSBs into an NCO HR outcome near the centers of chromosomes, thereby ensuring that COs form predominantly at off-center positions. PMID:27011106

  8. Separable Roles for a Caenorhabditis elegans RMI1 Homolog in Promoting and Antagonizing Meiotic Crossovers Ensure Faithful Chromosome Inheritance.

    PubMed

    Jagut, Marlène; Hamminger, Patricia; Woglar, Alexander; Millonigg, Sophia; Paulin, Luis; Mikl, Martin; Dello Stritto, Maria Rosaria; Tang, Lois; Habacher, Cornelia; Tam, Angela; Gallach, Miguel; von Haeseler, Arndt; Villeneuve, Anne M; Jantsch, Verena

    2016-03-01

    During the first meiotic division, crossovers (COs) between homologous chromosomes ensure their correct segregation. COs are produced by homologous recombination (HR)-mediated repair of programmed DNA double strand breaks (DSBs). As more DSBs are induced than COs, mechanisms are required to establish a regulated number of COs and to repair remaining intermediates as non-crossovers (NCOs). We show that the Caenorhabditis elegans RMI1 homolog-1 (RMH-1) functions during meiosis to promote both CO and NCO HR at appropriate chromosomal sites. RMH-1 accumulates at CO sites, dependent on known pro-CO factors, and acts to promote CO designation and enforce the CO outcome of HR-intermediate resolution. RMH-1 also localizes at NCO sites and functions in parallel with SMC-5 to antagonize excess HR-based connections between chromosomes. Moreover, RMH-1 also has a major role in channeling DSBs into an NCO HR outcome near the centers of chromosomes, thereby ensuring that COs form predominantly at off-center positions.

  9. Nondisjunction of chromosome 21: Comparisons of cytogenetic and molecular studies of the meiotic stage and parent of origin

    SciTech Connect

    Lorber, B.J.; Grantham, M.; Peters, J.; Hassold, T.J. ); Willard, H.F. )

    1992-12-01

    In the present report, the authors summarize studies aimed at examining the reliability of chromosome heteromorphisms in analyses of chromosome 21, nondisjunction. They used two cytogenetic approaches - fluorescent in sity hybridization (FISH) to repetitive sequences on 21p and traditional Q-banding - to distinguish chromosome 21 homologues and then compared the results of these studies with those obtained by DNA markers. Using a conservative scoring system for Q-banding and FISH heteromorphisms, they were able to specify the parental origin of trisomy in 10% of cases, in contrast, DNA marker studies were informative for parental origin in almost all cases. The results of the molecular and cytogenetic studies of parental origin concurred in all cases in which assignments were made independently using both techniques. However, in 4 of 13 cases in which the molecular studies contributed to the interpretation of the cytogenetic findings, the two results did not agree with respect to the meiotic stage of nondisjunction. A relatively high frequency of crossing-over on either the short arm or proximal long arm of chromosome 21 could explain these results and may be a mechanism leading to nondisjunction. 20 refs., 2 figs., 4 tabs.

  10. Synaptonemal complex (SC) component Zip1 plays a role in meiotic recombination independent of SC polymerization along the chromosomes.

    PubMed Central

    Storlazzi, A; Xu, L; Schwacha, A; Kleckner, N

    1996-01-01

    Zip1 is a yeast synaptonemal complex (SC) central region component and is required for normal meiotic recombination and crossover interference. Physical analysis of meiotic recombination in a zip1 mutant reveals the following: Crossovers appear later than normal and at a reduced level. Noncrossover recombinants, in contrast, seem to appear in two phases: (i) a normal number appear with normal timing and (ii) then additional products appear late, at the same time as crossovers. Also, Holliday junctions are present at unusually late times, presumably as precursors to late-appearing products. Red1 is an axial structure component required for formation of cytologically discernible axial elements and SC and maximal levels of recombination. In a red1 mutant, crossovers and noncrossovers occur at coordinately reduced levels but with normal timing. If Zip1 affected recombination exclusively via SC polymerization, a zip1 mutation should confer no recombination defect in a red1 strain background. But a red1 zip1 double mutant exhibits the sum of the two single mutant phenotypes, including the specific deficit of crossovers seen in a zip1 strain. We infer that Zip1 plays at least one role in recombination that does not involve SC polymerization along the chromosomes. Perhaps some Zip1 molecules act first in or around the sites of recombinational interactions to influence the recombination process and thence nucleate SC formation. We propose that a Zip1-dependent, pre-SC transition early in the recombination reaction is an essential component of meiotic crossover control. A molecular basis for crossover/noncrossover differentiation is also suggested. Images Fig. 2 Fig. 3 Fig. 4 Fig. 5 PMID:8799151

  11. 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

    PubMed Central

    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

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

    PubMed

    Murphy, Shaun P; Gumber, Hardeep K; Mao, Yunyun; Bass, Hank W

    2014-01-01

    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. PMID:25071797

  13. Mitotic and meiotic behavior of rye chromosomes in wheat - Psathyrostachys huashanica amphiploid x triticale progeny.

    PubMed

    Xie, Q; Kang, H; Sparkes, D L; Tao, S; Fan, X M; Xu, L; Fan, X; Sha, L; Zhang, H; Wang, Y; Zeng, J; Zhou, Y

    2013-07-24

    The dynamics of rye chromosomes during mitosis and meiosis was analyzed in a subset comprising 33 F3 lines from the cross of wheat, Psathyrostachys huashanica amphiploid (AABBDDNsNs) and hexaploid triticale (AABBRR), as visualized by genomic in situ hybridization. The results indicated that 31 of the total lines contained 4-14 rye chromosomes. Twenty-eight combinations had more rye chromosomes than the F1 hybrids, suggesting the occurrence of spontaneous quantitative increment. No P. huashanica chromosomes were detected in all of the combinations tested. Mitotic analysis showed that rye chromosomes progressed normally with the wheat counterparts without loss. However, abnormal meiosis was found in almost all lines. Similar progression between wheat and rye genomes appeared from interphase to metaphase I. It was at anaphase I that many rye univalents lagged behind those of wheat, followed by equational division. This resulted in the formation of chromosomal segments and micronuclei at telophase I or II. Micronuclei could also be generated from the immobilized univalents in the periphery of cells. Synapsis and translocations between wheat and rye genomes, chromosome bridges, and unreduced gametes were detected. Therefore, it is proposed that rye chromosome elimination may involve chromatid lagging, fragmentation and micronucleation, or the immobilization of certain univalents during meiosis instead of mitosis in the relatively advanced generations. This mechanism, together with spontaneous incremental increase of rye chromosome number, permitted the generation of various germplasms for wheat improvement.

  14. Chromosomes carrying meiotic avoidance loci in three apomictic eudicot Hieracium subgenus Pilosella species share structural features with two monocot apomicts.

    PubMed

    Okada, Takashi; Ito, Kanae; Johnson, Susan D; Oelkers, Karsten; Suzuki, Go; Houben, Andreas; Mukai, Yasuhiko; Koltunow, Anna M

    2011-11-01

    The LOSS OF APOMEIOSIS (LOA) locus is one of two dominant loci known to control apomixis in the eudicot Hieracium praealtum. LOA stimulates the differentiation of somatic aposporous initial cells after the initiation of meiosis in ovules. Aposporous initial cells undergo nuclear proliferation close to sexual megaspores, forming unreduced aposporous embryo sacs, and the sexual program ceases. LOA-linked genetic markers were used to isolate 1.2 Mb of LOA-associated DNAs from H. praealtum. Physical mapping defined the genomic region essential for LOA function between two markers, flanking 400 kb of identified sequence and central unknown sequences. Cytogenetic and sequence analyses revealed that the LOA locus is located on a single chromosome near the tip of the long arm and surrounded by extensive, abundant complex repeat and transposon sequences. Chromosomal features and LOA-linked markers are conserved in aposporous Hieracium caespitosum and Hieracium piloselloides but absent in sexual Hieracium pilosella. Their absence in apomictic Hieracium aurantiacum suggests that meiotic avoidance may have evolved independently in aposporous subgenus Pilosella species. The structure of the hemizygous chromosomal region containing the LOA locus in the three Hieracium subgenus Pilosella species resembles that of the hemizygous apospory-specific genomic regions in monocot Pennisetum squamulatum and Cenchrus ciliaris. Analyses of partial DNA sequences at these loci show no obvious conservation, indicating that they are unlikely to share a common ancestral origin. This suggests convergent evolution of repeat-rich hemizygous chromosomal regions containing apospory loci in these monocot and eudicot species, which may be required for the function and maintenance of the trait. PMID:21896890

  15. Meiotic abnormalities in metaphase I human spermatocytes from infertile males: frequencies, chromosomes involved, and relationship with polymorphic karyotype and seminal parameters

    PubMed Central

    Sarrate, Zaida; Vidal, Francesca; Blanco, Joan

    2014-01-01

    The aim of this study was to look in depth at the relationship between meiotic anomalies and male infertility, such as the determination of the chromosomes involved or the correlation with patient features. For this purpose, a total of 31 testicular tissue samples from individuals consulting for fertility problems were analyzed. Metaphase I cells were evaluated using a sequential methodology combining Leishman stained procedures and multiplex fluorescence in situ hybridization protocols. The number of chromosomal units and chiasmata count per bivalent were established and a hierarchical cluster analysis of the individuals was performed. The relationship of the seminogram and the karyotype over recombination were evaluated using Poisson regression models. Results obtained in this study show a significant percentage of infertile individuals with altered meiotic behavior, mostly specified as a reduction in chiasmata count in medium and large chromosomes, the presence of univalents, and the observation of tetraploid metaphases. Moreover, the number and the type of anomalies were found to be different between cells of the same individual, suggesting the coexistence of cell lines with normal meiotic behavior and cell lines with abnormalities. In addition, chromosomal abnormalities in metaphase I are significantly associated with oligozoospermia and/or polymorphic karyotype variants. PMID:25080930

  16. Pulled Polymer Loops as a Model for the Alignment of Meiotic Chromosomes

    NASA Astrophysics Data System (ADS)

    Lin, Yen Ting; Frömberg, Daniela; Huang, Wenwen; Delivani, Petrina; Chacón, Mariola; Tolić, Iva M.; Jülicher, Frank; Zaburdaev, Vasily

    2015-11-01

    During recombination, the DNA of parents exchange their genetic information to give rise to a genetically unique offspring. For recombination to occur, homologous chromosomes need to find each other and align with high precision. Fission yeast solves this problem by folding chromosomes in loops and pulling them through the viscous nucleoplasm. We propose a theory of pulled polymer loops to quantify the effect of drag forces on the alignment of chromosomes. We introduce an external force field to the concept of a Brownian bridge and thus solve for the statistics of loop configurations in space.

  17. Pulled Polymer Loops as a Model for the Alignment of Meiotic Chromosomes.

    PubMed

    Lin, Yen Ting; Frömberg, Daniela; Huang, Wenwen; Delivani, Petrina; Chacón, Mariola; Tolić, Iva M; Jülicher, Frank; Zaburdaev, Vasily

    2015-11-13

    During recombination, the DNA of parents exchange their genetic information to give rise to a genetically unique offspring. For recombination to occur, homologous chromosomes need to find each other and align with high precision. Fission yeast solves this problem by folding chromosomes in loops and pulling them through the viscous nucleoplasm. We propose a theory of pulled polymer loops to quantify the effect of drag forces on the alignment of chromosomes. We introduce an external force field to the concept of a Brownian bridge and thus solve for the statistics of loop configurations in space. PMID:26613475

  18. Reciprocal translocations in man. 3:1 Meiotic disjunction resulting in 47- or 45-chromosome offspring.

    PubMed Central

    Lindenbaum, R H; Bobrow, M

    1975-01-01

    Five cases of chromosome imbalance resulting from 3:1 disjunction of reciprocal translocations are described. A review of the literature suggests this phenomenon is more common than has previously been recognized. Images PMID:123589

  19. A conserved checkpoint monitors meiotic chromosome synapsis inCaenorhabditis elegans

    SciTech Connect

    Bhalla, Needhi; Dernburg, Abby F.

    2005-07-14

    We report the discovery of a checkpoint that monitorssynapsis between homologous chromosomes to ensure accurate meioticsegregation. Oocytes containing unsynapsed chromosomes selectivelyundergo apoptosis even if agermline DNA damage checkpoint is inactivated.This culling mechanism isspecifically activated by unsynapsed pairingcenters, cis-acting chromosomesites that are also required to promotesynapsis in Caenorhabditis elegans. Apoptosis due to synaptic failurealso requires the C. elegans homolog of PCH2,a budding yeast pachytenecheckpoint gene, which suggests that this surveillance mechanism iswidely conserved.

  20. Meiotic Recombination Analyses in Pigs Carrying Different Balanced Structural Chromosomal Rearrangements

    PubMed Central

    Mary, Nicolas; Barasc, Harmonie; Ferchaud, Stéphane; Priet, Aurélia; Calgaro, Anne; Loustau-Dudez, Anne-Marie; Bonnet, Nathalie; Yerle, Martine; Ducos, Alain; Pinton, Alain

    2016-01-01

    Correct pairing, synapsis and recombination between homologous chromosomes are essential for normal meiosis. All these events are strongly regulated, and our knowledge of the mechanisms involved in this regulation is increasing rapidly. Chromosomal rearrangements are known to disturb these processes. In the present paper, synapsis and recombination (number and distribution of MLH1 foci) were studied in three boars (Sus scrofa domestica) carrying different chromosomal rearrangements. One (T34he) was heterozygote for the t(3;4)(p1.3;q1.5) reciprocal translocation, one (T34ho) was homozygote for that translocation, while the third (T34Inv) was heterozygote for both the translocation and a pericentric inversion inv(4)(p1.4;q2.3). All three boars were normal for synapsis and sperm production. This particular situation allowed us to rigorously study the impact of rearrangements on recombination. Overall, the rearrangements induced only minor modifications of the number of MLH1 foci (per spermatocyte or per chromosome) and of the length of synaptonemal complexes for chromosomes 3 and 4. The distribution of MLH1 foci in T34he was comparable to that of the controls. Conversely, the distributions of MLH1 foci on chromosome 4 were strongly modified in boar T34Inv (lack of crossover in the heterosynaptic region of the quadrivalent, and crossover displaced to the chromosome extremities), and also in boar T34ho (two recombination peaks on the q-arms compared with one of higher magnitude in the controls). Analyses of boars T34he and T34Inv showed that the interference was propagated through the breakpoints. A different result was obtained for boar T34ho, in which the breakpoints (transition between SSC3 and SSC4 chromatin on the bivalents) seemed to alter the transmission of the interference signal. Our results suggest that the number of crossovers and crossover interference could be regulated by partially different mechanisms. PMID:27124413

  1. Sex Chromosome Meiotic Drive Systems in DROSOPHILA MELANOGASTER I. Abnormal Spermatid Development in Males with a Heterochromatin-Deficient X Chromosome (sc4sc8)

    PubMed Central

    Peacock, W. J.; Miklos, George L. Gabor; Goodchild, D. J.

    1975-01-01

    The meiotic drive characteristics of the In(1)sc4Lsc8R/Y system have been examined by genetic analysis and by light and electron microscopy. sc4sc8/Y males show a direct correlation between nondisjunction frequency and meiotic drive. Temperature-shift experiments reveal that the temperature-sensitive period for nondisjunction is at meiosis, whereas that for meiotic drive has both meiotic and post-meiotic components. Cytological analyses in the light and electron microscopes reveal failures in spermiogenesis in the testes of sc4sc8 males. The extent of abnormal spermatid development increases as nondisjunction becomes more extreme. PMID:805751

  2. Behavior of homologous chromosomes in early meiotic stages of human spermatocytes as revealed by FISH

    SciTech Connect

    Bar-Am, I.; Avivi, L.; Mukame, E.

    1994-09-01

    The process by which homologous chromosomes recognize each other at the beginning of meiosis, prior to synapsis, is poorly understood. To gain a better understanding as to when, where and how a given chromosome approaches its pairing partner, chromosome behavior at early stages of meiosis in human spermatocytes was studied. Using multi-color FISH with centromeric- and telomeric-specific probes, as well as with whole chromosome DNA libraries, it was clearly aligned. Rather, similarly to non-homologous chromosomes, they were well separated from each other. At the commencement of synapsis, during the process of homology search, homologues underwent a drastic conformational change, elongating into strands that approached each other by their telomeres. Just preceding the co-alignment of the homologous centromeres, telomeres changed their interphase random distribution and occupied a confined region of the nuclear periphery. Following synapsis, telomeres spread over the whole nuclear periphery. These dynamics in the telomeres distribution, which are unique to early stages of meiosis, are presumably related to the role that telomeres play in the process of homology search and the commencement of synapsis.

  3. Spatial organization of chromatin domains and compartments in single chromosomes.

    PubMed

    Wang, Siyuan; Su, Jun-Han; Beliveau, Brian J; Bintu, Bogdan; Moffitt, Jeffrey R; Wu, Chao-ting; Zhuang, Xiaowei

    2016-08-01

    The spatial organization of chromatin critically affects genome function. Recent chromosome-conformation-capture studies have revealed topologically associating domains (TADs) as a conserved feature of chromatin organization, but how TADs are spatially organized in individual chromosomes remains unknown. Here, we developed an imaging method for mapping the spatial positions of numerous genomic regions along individual chromosomes and traced the positions of TADs in human interphase autosomes and X chromosomes. We observed that chromosome folding deviates from the ideal fractal-globule model at large length scales and that TADs are largely organized into two compartments spatially arranged in a polarized manner in individual chromosomes. Active and inactive X chromosomes adopt different folding and compartmentalization configurations. These results suggest that the spatial organization of chromatin domains can change in response to regulation. PMID:27445307

  4. Spatial organization of chromatin domains and compartments in single chromosomes.

    PubMed

    Wang, Siyuan; Su, Jun-Han; Beliveau, Brian J; Bintu, Bogdan; Moffitt, Jeffrey R; Wu, Chao-ting; Zhuang, Xiaowei

    2016-08-01

    The spatial organization of chromatin critically affects genome function. Recent chromosome-conformation-capture studies have revealed topologically associating domains (TADs) as a conserved feature of chromatin organization, but how TADs are spatially organized in individual chromosomes remains unknown. Here, we developed an imaging method for mapping the spatial positions of numerous genomic regions along individual chromosomes and traced the positions of TADs in human interphase autosomes and X chromosomes. We observed that chromosome folding deviates from the ideal fractal-globule model at large length scales and that TADs are largely organized into two compartments spatially arranged in a polarized manner in individual chromosomes. Active and inactive X chromosomes adopt different folding and compartmentalization configurations. These results suggest that the spatial organization of chromatin domains can change in response to regulation.

  5. Evidence that meiotic pairing starts at the telomeres: Molecular analysis of recombination in a family with a pericentric X chromosome inversion

    SciTech Connect

    Shashi, V.; Allinson, P.S.; Golden, W.L.; Kelly, T.E.

    1994-09-01

    Recent studies in yeast have shown that telomeres rather than centromeres lead in chromosome movement just prior to meiosis and may have a role in recombination. Cytological studies of meiosis in Drosophila and mice have shown that in pericentric inversion heterozygotes there is lack of loop formation, with recobmination seen only outside the inversion. In a family with Duchenne muscular dystrophy (DMD) we recognized that only affected males and carrier females had a pericentric X chromosome inversion (inv X(p11.4;q26)). Since the short arm inversion breakpoint was proximal to the DMD locus, it could not be implicated in the mutational event causing DMD. There was no history of infertility, recurrent miscarriages or liveborn unbalanced females to suggest there was recombination within the inversion. We studied 22 members over three generations to understand the pattern of meiotic recombination between the normal and the inverted X chromosome. In total, 17 meioses involving the inverted X chromosome in females were studied by cytogenetic analysis and 16 CA repeat polymorphisms along the length of the X chromosome. Results: (a) There was complete concordance between the segregation of the DMD mutation and the inverted X chromosome. (b) On DNA analysis, there was complete absence of recombination within the inverted segment. We also found no recombination at the DMD locus. Recombination was seen only at Xp22 and Xq27-28. (c) Recombination was seen in the same individual at both Xp22 and Xq27-28 without recombination otherwise. Conclusions: (1) Pericentric X inversions reduce the genetic map length of the chromosome, with the physical map length being normal. (2) Meiotic X chromosome pairing in this family is initiated at the telomeres. (3) Following telomeric pairing in pericentric X chromosome inversions, there is inhibition of recombination within the inversion and adjacent regions.

  6. The behavior of the X- and Y-chromosomes in the oocyte during meiotic prophase in the B6.Y(TIR)sex-reversed mouse ovary.

    PubMed

    Alton, Michelle; Lau, Mau Pan; Villemure, Michele; Taketo, Teruko

    2008-02-01

    Sexual differentiation of the germ cells follows gonadal differentiation, which is determined by the presence or the absence of the Y-chromosome. Consequently, oogenesis and spermatogenesis take place in the germ cells with XX and XY sex chromosomal compositions respectively. It is unclear how sexual dimorphic regulation of meiosis is associated with the sex-chromosomal composition. In the present study, we examined the behavior of the sex chromosomes in the oocytes of the B6.Y(TIR) sex-reversed female mouse, in comparison with XO and XX females. As the sex chromosomes fail to pair in both XY and XO oocytes during meiotic prophase, we anticipated that the pairing failure may lead to excessive oocyte loss. However, the total number of germ cells, identified by immunolabeling of germ cell nuclear antigen 1 (GCNA1), did not differ between XY and XX ovaries or XO and XX ovaries up to the day of delivery. The progression of meiotic prophase, assessed by immunolabeling of synaptonemal complex components, was also similar between the two genotypes of ovaries. These observations suggest that the failure in sex-chromosome pairing is not sufficient to cause oocyte loss. On the other hand, labeling of phosphorylated histone gammaH2AX, known to be associated with asynapsis and transcriptional repression, was seen over the X-chromosome but not over the Y-chromosome in the majority of XY oocytes at the pachytene stage. For comparison, gammaH2AX labeling was seen only in the minority of XX oocytes at the same stage. We speculate that the transcriptional activity of sex chromosomes in the XY oocyte may be incompatible with ooplasmic maturation. PMID:18239052

  7. Meiotic chromosome configurations in triploid progeny from reciprocal crosses between wild-type diploid and natural tetraploid loach Misgurnus anguillicaudatus in China.

    PubMed

    Li, Ya-Juan; Gao, Yang-Chun; Zhou, He; Ma, Hai-Yan; Li, Jia-Qi; Arai, Katsutoshi

    2015-10-01

    Here, we showed meiotic chromosome configurations prepared from oocyte germinal vesicles and spermatocytes of triploid loaches produced from reciprocal crosses between wild-type diploids (2n = 50) obtained from Dalian, Liaoning Province, China and natural tetraploids (4n = 100) from Chibi, Hubei Province, China. Major meiotic cells in triploids comprised 25 bivalents and 25 univalents, but cells with one to five trivalents were also observed. When three homologous chromosomes bearing nucleolar organizing regions (NOR) were identified with the detection of signals or positive sites by silver staining, chromomycin A3 staining and fluorescence in situ hybridization with a 5.8S + 28S rDNA probe, two third of selected triploid cells gave a configuration including one bivalent with two NORs (association of two homologous chromosomes) and one univalent with one NOR. However, other triploid cells showed three univalent each of which had one NOR, suggesting a failure of synapsis between homologous chromosomes. These results suggested that triploid female and male should produce aneuploid gametes with the theoretical mode at 1.5n (37 or 38 chromosomes).

  8. Lsh is required for meiotic chromosome synapsis and retrotransposon silencing in female germ cells.

    PubMed

    De La Fuente, Rabindranath; Baumann, Claudia; Fan, Tao; Schmidtmann, Anja; Dobrinski, Ina; Muegge, Kathrin

    2006-12-01

    Lymphoid specific helicase (Lsh) is a major epigenetic regulator that is essential for DNA methylation and transcriptional silencing of parasitic elements in the mammalian genome. However, whether Lsh is involved in the regulation of chromatin-mediated processes during meiosis is not known. Here, we show that Lsh is essential for the completion of meiosis and transcriptional repression of repetitive elements in the female gonad. Oocytes from Lsh knockout mice exhibit demethylation of transposable elements and tandem repeats at pericentric heterochromatin, as well as incomplete chromosome synapsis associated with persistent RAD51 foci and gammaH2AX phosphorylation. Failure to load crossover-associated foci results in the generation of non-exchange chromosomes. The severe oocyte loss observed and lack of ovarian follicle formation, together with the patterns of Lsh nuclear compartmentalization in the germ line, demonstrate that Lsh has a critical and previously unidentified role in epigenetic gene silencing and maintenance of genomic stability during female meiosis. PMID:17115026

  9. A Nucleoporin Docks Protein Phosphatase 1 to Direct Meiotic Chromosome Segregation and Nuclear Assembly.

    PubMed

    Hattersley, Neil; Cheerambathur, Dhanya; Moyle, Mark; Stefanutti, Marine; Richardson, Amelia; Lee, Kian-Yong; Dumont, Julien; Oegema, Karen; Desai, Arshad

    2016-09-12

    During M-phase entry in metazoans with open mitosis, the concerted action of mitotic kinases disassembles nuclei and promotes assembly of kinetochores-the primary microtubule attachment sites on chromosomes. At M-phase exit, these major changes in cellular architecture must be reversed. Here, we show that the conserved kinetochore-localized nucleoporin MEL-28/ELYS docks the catalytic subunit of protein phosphatase 1 (PP1c) to direct kinetochore disassembly-dependent chromosome segregation during oocyte meiosis I and nuclear assembly during the transition from M phase to interphase. During oocyte meiosis I, MEL-28-PP1c disassembles kinetochores in a timely manner to promote elongation of the acentrosomal spindles that segregate homologous chromosomes. During nuclear assembly, MEL-28 recruits PP1c to the periphery of decondensed chromatin, where it directs formation of a functional nuclear compartment. Thus, a pool of phosphatase activity associated with a kinetochore-localized nucleoporin contributes to two key events that occur during M-phase exit in metazoans: kinetochore disassembly and nuclear reassembly. PMID:27623381

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

    PubMed Central

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

    2013-01-01

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

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

    PubMed

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

    2013-11-26

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

  12. A meiotic drive element in the maize pathogen Fusarium verticillioides is located within a 102-kb region of chromosome V

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Fusarium verticillioides is an agriculturally important fungus because of its association with maize and its propensity to contaminate grain with toxic compounds. Some isolates of the fungus harbor a meiotic drive element known as Spore killer (SkK) that causes nearly all surviving meiotic progeny f...

  13. CDC-48/p97 is required for proper meiotic chromosome segregation via controlling AIR-2/Aurora B kinase localization in Caenorhabditis elegans.

    PubMed

    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.

  14. The Opposing Actions of Arabidopsis CHROMOSOME TRANSMISSION FIDELITY7 and WINGS APART-LIKE1 and 2 Differ in Mitotic and Meiotic Cells.

    PubMed

    De, Kuntal; Bolaños-Villegas, Pablo; Mitra, Sayantan; Yang, Xiaohui; Homan, Garret; Jauh, Guang-Yuh; Makaroff, Christopher A

    2016-02-01

    Sister chromatid cohesion, which is mediated by the cohesin complex, is essential for the proper segregation of chromosomes during mitosis and meiosis. Stable binding of cohesin with chromosomes is regulated in part by the opposing actions of CTF7 (CHROMOSOME TRANSMISSION FIDELITY7) and WAPL (WINGS APART-LIKE). In this study, we characterized the interaction between Arabidopsis thaliana CTF7 and WAPL by conducting a detailed analysis of wapl1-1 wapl2 ctf7 plants. ctf7 plants exhibit major defects in vegetative growth and development and are completely sterile. Inactivation of WAPL restores normal growth, mitosis, and some fertility to ctf7 plants. This shows that the CTF7/WAPL cohesin system is not essential for mitosis in vegetative cells and suggests that plants may contain a second mechanism to regulate mitotic cohesin. WAPL inactivation restores cohesin binding and suppresses ctf7-associated meiotic cohesion defects, demonstrating that WAPL and CTF7 function as antagonists to regulate meiotic sister chromatid cohesion. The ctf7 mutation only had a minor effect on wapl-associated defects in chromosome condensation and centromere association. These results demonstrate that WAPL has additional roles that are independent of its role in regulating chromatin-bound cohesin. PMID:26813623

  15. Evidence for human meiotic recombination interference obtained through construction of a short tandem repeat-polymorphism linkage map of chromosome 19

    SciTech Connect

    Weber, J.L.; Wang, Z.; Hansen, K.; Stephenson, M.; Kappel, C.; Salzman, S.; Wilkie, P.J. ); Keats, B. ); Dracopoli, N.C. ); Brandriff, B.F.; Olsen, A.S. )

    1993-11-01

    An improved linkage map for human chromosome 19 containing 35 short tandem repeat polymorphisms (STRPs) and one VNTR (D19S20) was constructed. The map included 12 new (GATA)[sub n] tetranucleotide STRPs. Although total lengths of the male (114 cM) and female (128 cM) maps were similar, at both ends of the chromosome male recombination exceeded female recombination, while in the interior portion of the map female recombination was in excess. Cosmid clones containing the STRP sequences were identified and were positioned along the chromosome by fluorescent in situ hybridization. Four rounds of careful checking and removal of genotyping errors allowed biologically relevant conclusions to be made concerning the numbers and distributions of recombination events on chromosome 19. The average numbers of recombinations per chromosome matched closely the lengths of the genetic maps computed by using the program CRIMAP. Significant numbers of chromosomes with zero, one, two, or three recombinations were detected as products of both female and male meioses. On the basis of the total number of observed pairs of recombination events in which only a single informative marker was situated between the two recombinations, a maximal estimate for the rate of meiotic STRP [open quotes]gene[close quotes] conversion without recombination was calculated as 3 [times] 10[sup [minus]4]/meiosis. For distances up to 30 cM between recombinations, many fewer chromosomes which had undergone exactly two recombinations were observed than were expected on the basis of the assumption of independent recombination locations. This strong new evidence for human meiotic interference will help to improve the accuracy of interpretation of clinical DNA test results involving polymorphisms flanking a genetic abnormality. 61 refs., 2 figs., 5 tabs.

  16. Persistence of histone H2AX phosphorylation after meiotic chromosome synapsis and abnormal centromere cohesion in Poly (ADP-ribose) polymerase (Parp-1) null oocytes

    PubMed Central

    Yang, Feikun; Baumann, Claudia; De La Fuente, Rabindranath

    2009-01-01

    In spite of the impact of aneuploidy on human health little is known concerning the molecular mechanisms involved in the formation of structural or numerical chromosome abnormalities during meiosis. Here, we provide novel evidence indicating that lack of PARP-1 function during oogenesis predisposes the female gamete to genome instability. During prophase I of meiosis, a high proportion of Parp-1 (−/−) mouse oocytes exhibit a spectrum of meiotic defects including incomplete homologous chromosome synapsis or persistent histone H2AX phosphorylation in fully synapsed chromosomes at the late pachytene stage. Moreover, the X chromosome bivalent is also prone to exhibit persistent double strand DNA breaks (DSBs). In striking contrast, such defects were not detected in mutant pachytene spermatocytes. In fully-grown wild type oocytes at the germinal vesicle stage, PARP-1 protein associates with nuclear speckles and upon meiotic resumption, undergoes a striking re-localization towards spindle poles as well as pericentric heterochromatin domains at the metaphase II stage. Notably, a high proportion of in vivo matured Parp-1 (−/−) oocytes show lack of recruitment of the kinetochore-associated protein BUB3 to centromeric domains and fail to maintain metaphase II arrest. Defects in chromatin modifications in the form of persistent histone H2AX phosphorylation during prophase I of meiosis and deficient sister chromatid cohesion during metaphase II predispose mutant oocytes to premature anaphase II onset upon removal from the oviductal environment. Our results indicate that PARP-1 plays a critical role in the maintenance of chromosome stability at key stages of meiosis in the female germ line. Moreover, in the metaphase II stage oocyte PARP-1 is required for the regulation of centromere structure and function through a mechanism that involves the recruitment of BUB3 protein to centromeric domains. PMID:19463809

  17. Topoisomerase II Mediates Meiotic Crossover Interference

    PubMed Central

    Zhang, Liangran; Wang, Shunxin; Yin, Shen; Hong, Soogil; Kim, Keun P.; Kleckner, Nancy

    2014-01-01

    Summary Spatial patterning is a ubiquitous feature of biological systems. Meiotic crossovers provide an interesting example, defined by the classical phenomenon of crossover interference. Here, analysis of crossover patterns in budding yeast identifies a molecular pathway for interference. Topoisomerase II (Topo II) plays a central role, thus identifying a new function for this critical molecule. SUMOylation [of TopoII and axis component Red1] and ubiquitin-mediated removal of SUMOylated proteins are also required. These and other findings support the hypothesis that crossover interference involves accumulation, relief and redistribution of mechanical stress along the protein/DNA meshwork of meiotic chromosome axes, with TopoII required to adjust spatial relationships among DNA segments. PMID:25043020

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

    PubMed

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

    2014-04-01

    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

  19. Role of the pseudoautosomal region in sex-chromosome pairing during male meiosis: Meiotic studies in a man with a deletion of distal Xp

    SciTech Connect

    Mohandas, T.K.; Passage, M.B.; Yen, P.H.; Speed, R.M.; Chandley, A.C.; Shapiro, L.J. )

    1992-09-01

    Meiotic studies were undertaken in a 24-year-old male patient with short stature, chondrodysplasia punctata, ichthyosis, steroid sulfatase deficiency, and mild mental retardation with an inherited cytologically visible deletion of distal Xp. Molecular investigations showed that the pseudoautosomal region as well as the steroid sulfatase gene were deleted, but telomeric sequences were present at the pter on the deleted X chromosome. A complete failure of sex-chromosome pairing was observed in the primary spermatocytes of the patient. Telomeric approaches between the sex chromosomes were made at zygotene in some cells, but XY synaptonemal complex was formed. The sex chromosomes were present as univalents at metaphase I, and germ-cell development was arrested between metaphase I and metaphase II in the vast majority of cells, consistent with the azoospermia observed in the patient. The failure of XY pairing in this individual indicates that the pseudoautosomal sequences play an important role in initiating XY pairing and formation of synaptonemal complex at meiosis. 36 refs., 6 figs.

  20. The Double-Strand Break Landscape of Meiotic Chromosomes Is Shaped by the Paf1 Transcription Elongation Complex in Saccharomyces cerevisiae.

    PubMed

    Gothwal, Santosh K; Patel, Neem J; Colletti, Meaghan M; Sasanuma, Hiroyuki; Shinohara, Miki; Hochwagen, Andreas; Shinohara, Akira

    2016-02-01

    Histone modification is a critical determinant of the frequency and location of meiotic double-strand breaks (DSBs), and thus recombination. Set1-dependent histone H3K4 methylation and Dot1-dependent H3K79 methylation play important roles in this process in budding yeast. Given that the RNA polymerase II associated factor 1 complex, Paf1C, promotes both types of methylation, we addressed the role of the Paf1C component, Rtf1, in the regulation of meiotic DSB formation. Similar to a set1 mutation, disruption of RTF1 decreased the occurrence of DSBs in the genome. However, the rtf1 set1 double mutant exhibited a larger reduction in the levels of DSBs than either of the single mutants, indicating independent contributions of Rtf1 and Set1 to DSB formation. Importantly, the distribution of DSBs along chromosomes in the rtf1 mutant changed in a manner that was different from the distributions observed in both set1 and set1 dot1 mutants, including enhanced DSB formation at some DSB-cold regions that are occupied by nucleosomes in wild-type cells. These observations suggest that Rtf1, and by extension the Paf1C, modulate the genomic DSB landscape independently of H3K4 methylation. PMID:26627841

  1. Different timing and spatial separation of parental chromosomes in intergeneric somatic hybrids between Brassica napus and Orychophragmus violaceus.

    PubMed

    Ding, L; Zhao, Z G; Ge, X H; Li, Z Y

    2014-01-01

    Experimental and newly formed hybrids and polyploids generated by wide crosses usually show varying degrees of cytological instability. The spatial separation of parental genomes and uniparental chromosome elimination in hybrid cells has been reported in many hybrids from plants and animals. Herein, the behavior of parental genomes in intergeneric somatic hybrids between Brassica napus and Orychophragmus violaceus was analyzed using genomic in situ hybridization (GISH). In mitotic and meiotic cells, the chromosomes from O. violaceus were distinguished from B. napus by their larger size and staining patterns. In interphase nuclei of the hybrid, O. violaceus-labeled chromatin appeared as large heterochromatic blocks that were nonrandomly distributed at prophase, typically distributed toward one side of the nucleus. In pollen mother cells at prophase I of meiosis, O. violaceus chromosomes appeared as one or two deeply stained chromatin blocks that resolved into bivalents at a late stage, after bivalents from B. napus were visible. Thereafter, bivalents of O. violaceus congressed to the equatorial plate and segregated at anaphase I after those from B. napus. The different behavior of O. violaceus chromosomes in the hybrids indicates that they have differential condensation states at interphase and progress later through the cell cycle and meiosis than B. napus chromosomes. This difference in behavior may restrict or prevent the formation of bivalents of mixed genome origin. Differential gene expression of parental alleles including rDNA loci may contribute to their distinct cytological behavior and to the phenotype of hybrids. PMID:24782049

  2. Experimental Population Genetics of Meiotic Drive Systems I. Pseudo-Y Chromosomal Drive as a Means of Eliminating Cage Populations of DROSOPHILA MELANOGASTER

    PubMed Central

    Lyttle, Terrence W.

    1977-01-01

    The experimental population genetics of Y-chromosome drive in Drosophila melanogaster is approximated by studying the behavior of T(Y;2),SD lines. These exhibit "pseudo-Y" drive through the effective coupling of the Y chromosome to the second chromosome meiotic drive locus, Segregation distorter (SD). T(Y;2),SD males consequently produce only male offspring. When such lines are allowed to compete against structurally normal SD+ flies in population cages, T(Y;2),SD males increase in frequency according to the dynamics of a simple haploid selection model until the cage population is eliminated as a result of a deficiency in the number of adult females. Cage population extinction generally occurs within about seven generations.—Several conclusions can be drawn from these competition cage studies: (1) Fitness estimates for the T(Y;2),SD lines (relative to SD+ ) are generally in the range of 2–4, and these values are corroborated by independent estimates derived from studies of migration-selection equilibrium. (2) Fitness estimates are unaffected by cage replication, sample time, or the starting frequency of T(Y;2),SD males, indicating that data from diverse cages can be legitimately pooled to give an overall fitness estimate. (3) Partitioning of the T(Y;2),SD fitnesses into components of viability, fertility, and frequency of alternate segregation (Y + SD from X + SD+) suggests that most of the T(Y;2),SD advantage derives from the latter two components. Improvements in the system might involve increasing both the viability and the alternate segregation to increase the total fitness. While pseudo-Y drive operates quite effectively against laboratory stocks, it is less successful in eliminating wild-type populations which are already segregating for suppressors of SD action. This observation suggests that further studies into the origin and rate of accumulation of suppressors of meiotic drive are needed before an overall assessment can be made of the potential of Y-chromosome

  3. Meiotic chromosomes move by linkage to dynamic actin cables with transduction of force through the nuclear envelope.

    PubMed

    Koszul, R; Kim, K P; Prentiss, M; Kleckner, N; Kameoka, S

    2008-06-27

    Chromosome movement is prominent during meiosis. Here, using a combination of in vitro and in vivo approaches, we elucidate the basis for dynamic mid-prophase telomere-led chromosome motion in budding yeast. Diverse findings reveal a process in which, at the pachytene stage, individual telomere/nuclear envelope (NE) ensembles attach passively to, and then move in concert with, nucleus-hugging actin cables that are continuous with the global cytoskeletal actin network. Other chromosomes move in concert with lead chromosome(s). The same process, in modulated form, explains the zygotene "bouquet" configuration in which, immediately preceding pachytene, chromosome ends colocalize dynamically in a restricted region of the NE. Mechanical properties of the system and biological roles of mid-prophase movement for meiosis, including recombination, are discussed. PMID:18585353

  4. Identifying crossover-rich regions and their effect on meiotic homologous interactions by partitioning chromosome arms of wheat and rye.

    PubMed

    Valenzuela, Nohelia T; Perera, Esther; Naranjo, Tomás

    2013-08-01

    Chiasmata are usually formed in the distal half of cereal chromosomes. Previous studies showed that the crossover-rich region displays a more active role in homologous recognition at early meiosis than crossover-poor regions in the long arm of rye chromosome 1R, but not in the long arm of chromosome 5R. In order to determine what happens in other chromosomes of rye and wheat, we have partitioned, by wheat-rye translocations of variable-size, the distal fourth part of chromosome arms 1BS and 2BL of wheat and 1RS and 2RL of rye. Synapsis and chiasma formation in chromosome pairs with homologous (wheat-wheat or rye-rye) and homoeologous (wheat-rye) stretches, positioned distally and proximally, respectively, or vice versa, have been studied by rye chromatin labelling using fluorescence in situ hybridisation. Chromosome arm partitioning showed that the distal 12 % of 1BS form one crossover in 50 % of the cells, while the distal 6.7 % of 2RL and the distal 10.5 % of 2BL account for 94 % and 81 % of chiasmata formed in these arms. Distal homoeologous segments reduce the frequency of chiasmata and the possibility of interaction between the intercalary/proximal homologous segments. Such a reduction is related to the size of the homoeologous (translocated) segment. The effect on synapsis and chiasma formation was much lower in chromosome constructions with distal homology and proximal homoeology. All of these data support that among wheat and rye chromosomes, recombining regions are more often involved in homologous recognition and pairing than crossover-poor regions.

  5. Effect of oil of nutmeg on the fertility and induction of meiotic chromosome rearrangements in mice and their first generation.

    PubMed

    Pecevski, J; Savković, D; Radivojević, D; Vuksanović, L

    1981-01-01

    The dose-dependent effects of oil of nutmeg on the fertility and induction of chromosomal translocations in treated mice and their F1 males were examined. C3H male mice were treated with oil of nutmeg for 8 successive weeks at 60, 80, 100 and 400 mg/kg body weight. The greatest reduction of fertility occurred in the group treated with 400 mg/kg; chromosomal translocation in directly treated animals was not found. The chromosomal translocations in F1 males, derived from males treated with oil of nutmeg at dose levels of 60, 80 and 100 mg/kg. PMID:7194525

  6. Analysis of meiotic chromosome structure and behavior in Robertsonian heterozygotes of Ellobius tancrei (Rodentia, Cricetidae): a case of monobrachial homology

    PubMed Central

    Matveevsky, Sergey; Bakloushinskaya, Irina; Tambovtseva, Valentina; Romanenko, Svetlana; Kolomiets, Oxana

    2015-01-01

    Abstract Synaptonemal complex (SC) chains were revealed in semisterile intraspecific F1 hybrids of Ellobius tancrei Blasius, 1884 (2n = 49, NF=56 and 2n=50, NF=56), heterozygous for Robertsonian (Rb) translocations. Chains were formed by Rb submetacentrics with monobrachial homology. Chromosome synapsis in spermatocytes of these hybrids was disturbed, apparently because of the problematic release of the chromosomes from the SC chains. These hybrids suffer from low fertility, and our data support the opinion that this is because a formation of Rb metacentrics with monobrachial homology within different races of the same species might be an initial event for the divergence of chromosomal forms. PMID:26752380

  7. Meiotic Recombination: The Essence of Heredity.

    PubMed

    Hunter, Neil

    2015-10-28

    The study of homologous recombination has its historical roots in meiosis. In this context, recombination occurs as a programmed event that culminates in the formation of crossovers, which are essential for accurate chromosome segregation and create new combinations of parental alleles. Thus, meiotic recombination underlies both the independent assortment of parental chromosomes and genetic linkage. This review highlights the features of meiotic recombination that distinguish it from recombinational repair in somatic cells, and how the molecular processes of meiotic recombination are embedded and interdependent with the chromosome structures that characterize meiotic prophase. A more in-depth review presents our understanding of how crossover and noncrossover pathways of meiotic recombination are differentiated and regulated. The final section of this review summarizes the studies that have defined defective recombination as a leading cause of pregnancy loss and congenital disease in humans.

  8. Preparations of Meiotic Pachytene Chromosomes and Extended DNA Fibers from Cotton Suitable for Fluorescence In Situ Hybridization

    PubMed Central

    Liu, Fang; Ling, Jian; Wang, Chunying; Li, Shaohui; Zhang, Xiangdi; Wang, Yuhong; Wang, Kunbo

    2012-01-01

    Fluorescence in situ hybridization (FISH) has become one of the most important techniques applied in plant molecular cytogenetics. However, the application of this technique in cotton has lagged behind because of difficulties in chromosome preparation. The focus of this article was FISH performed not only on cotton pachytene chromosomes, but also on cotton extended DNA fibers. The cotton pollen mother cells (PMCs) instead of buds or anthers were directly digested in enzyme to completely breakdown the cell wall. Before the routine acetic acid treatment, PMCs were incubated in acetic acid and enzyme mixture to remove the cytoplasm and clear the background. The method of ice-cold Carnoy's solution spreading chromosome was adopted instead of nitrogen removed method to avoid chromosomes losing and fully stretch chromosome. With the above-improved steps, the high-quality well-differentiated pachytene chromosomes with clear background were obtained. FISH results demonstrated that a mature protocol of cotton pachytene chromosomes preparation was presented. Intact and no debris cotton nuclei were obtained by chopping from etiolation cotyledons instead of the conventional liquid nitrogen grinding method. After incubating the nuclei with nucleus lysis buffer on slide, the parallel and clear background DNA fibers were acquired along the slide. This method overcomes the twist, accumulation and fracture of DNA fibers compared with other methods. The entire process of DNA fibers preparation requires only 30 min, in contrast, it takes 3 h with routine nitrogen grinding method. The poisonous mercaptoethanol in nucleus lysis buffer is replaced by nonpoisonous dithiothreitol. PVP40 in nucleus isolation buffer is used to prevent oxidation. The probability of success in isolating nuclei for DNA fiber preparation is almost 100% tested with this method in cotton. So a rapid, safe, and efficient method for the preparation of cotton extended DNA fibers suitable for FISH was established

  9. Physical mapping of male fertility and meiotic drive quantitative trait loci in the mouse t complex using chromosome deficiencies.

    PubMed Central

    Planchart, A; You, Y; Schimenti, J C

    2000-01-01

    The t complex spans 20 cM of the proximal region of mouse chromosome 17. A variant form, the t haplotype (t), exists at significant frequencies in wild mouse populations and is characterized by the presence of inversions that suppress recombination with wild-type (+) chromosomes. Transmission ratio distortion and sterility are associated with t and affect males only. It is hypothesized that these phenomena are caused by trans-acting distorter/sterility factors that interact with a responder locus (Tcr(t)) and that the distorter and sterility factors are the same because homozygosity of the distorters causes male sterility. One factor, Tcd1, was previously shown to be amorphic using a chromosome deletion. To overcome limitations imposed by recombination suppression, we used a series of deletions within the t complex in trans to t chromosomes to characterize the Tcd1 region. We find that the distorter activity of Tcd1 is distinct from a linked sterility factor, originally called tcs1. YACs mapped with respect to deletion breakpoints localize tcs1 to a 1.1-Mb interval flanked by D17Aus9 and Tctex1. We present evidence for the existence of multiple proximal t complex regions that exhibit distorter activity. These studies demonstrate the utility of chromosome deletions for complex trait analysis. PMID:10835401

  10. Misregulation of the Kinesin-like Protein Subito Induces Meiotic Spindle Formation in the Absence of Chromosomes and Centrosomes

    PubMed Central

    Jang, Janet K.; Rahman, Taslima; Kober, Vanessa S.; Cesario, Jeffry; McKim, Kim S.

    2007-01-01

    Bipolar spindles assemble in the absence of centrosomes in the oocytes of many species. In Drosophila melanogaster oocytes, the chromosomes have been proposed to initiate spindle assembly by nucleating or capturing microtubules, although the mechanism is not understood. An important contributor to this process is Subito, which is a kinesin-6 protein that is required for bundling interpolar microtubules located within the central spindle at metaphase I. We have characterized the domains of Subito that regulate its activity and its specificity for antiparallel microtubules. This analysis has revealed that the C-terminal domain may interact independently with microtubules while the motor domain is required for maintaining the interaction with the antiparallel microtubules. Surprisingly, deletion of the N-terminal domain resulted in a Subito protein capable of promoting the assembly of bipolar spindles that do not include centrosomes or chromosomes. Bipolar acentrosomal spindle formation during meiosis in oocytes may be driven by the bundling of antiparallel microtubules. Furthermore, these experiments have revealed evidence of a nuclear- or chromosome-based signal that acts at a distance to activate Subito. Instead of the chromosomes directly capturing microtubules, signals released upon nuclear envelope breakdown may activate proteins like Subito, which in turn bundles together microtubules. PMID:17660552

  11. Analysis of four microsatellite markers on the long arm of chromosome 9 by meiotic recombination in flow-sorted single sperm

    SciTech Connect

    Furlong, R.A.; Goudie, D.R.; Carter, N.P.; Lyall, J.E.W.; Affara, N.A.; Ferguson-Smith, M.A. )

    1993-06-01

    Meiotic recombination in flow-sorted single sperm was used to analyze four highly polymorphic microsatellite markers on the long arm of chromosome 9. The microsatellites comprised three tightly linked markers: 9CMP1 (D9S109), 9CMP2 (D9S127), and D9S53, which map to 9q31, and a reference marker, ASS, which is located in 9q34.1. Haplotypes of single sperm were assessed by using PCR in a single-step multiplex reaction to amplify each locus. Recombinant haplotypes were identified by their relative infrequency and were analyzed using THREELOC, a maximum-likelihood-analysis program, and an adaptation of CRI-MAP. The most likely order of these markers was cen-D9S109-D9S127-D9S53-ASS-tel with D9S109, D9S127, and D9S53 being separated by a genetic distance of approximately 3%. The order of the latter three markers did not however achieve statistical significance using the THREELOC program. 21 refs., 2 figs., 4 tabs.

  12. Transillumination spatially modulated illumination microscopy for human chromosome imaging

    NASA Astrophysics Data System (ADS)

    Pitris, Costas; Heracleous, Peter; Patsalis, Philippos

    2005-03-01

    Human chromosome analysis is an essential task in cytogenetics, especially in prenatal screening, genetic syndrome diagnosis, cancer pathology research and mutagen dosimetry. Chromosomal analysis begins with the creation of a karyotype, which is a layout of chromosome images organized by decreasing size in pairs. Both manual and automatic classification of chromosomes are limited by the resolution of the microscope and imaging system used. One way to improve the results of classification and even detect subtleties now remaining undetected, is to enhance the resolution of the images. It is possible to achieve lateral resolution beyond the classical limit, by using spatially modulated illumination (SMI) in a wide-field, non-confocal microscope. In this case, the sample is illuminated with spatially modulated light, which makes normally inaccessible high-resolution information visible in the observed image by shifting higher frequencies within the OTF limits of the microscope. Although, SMI microscopes have been reported in the past, this manuscript reports the development of a transillumination microscope for opaque, non-fluorescent samples. The illumination path consisted of a light source illuminating a ruled grating which was subsequently imaged on the sample. The grating was mounted on a rotating and translating stage so that the magnification and rotation of the pattern could be adjusted. The imaging lens was a 1.25 NA oil immersion objective. Test samples showed resolution improvement, as judged from a comparison of the experimentally obtained FWHM. Further studies using smaller fringe distance or laser interference pattern illumination will be evaluated to further optimize the SMI results.

  13. Meiotic interstrand DNA damage escapes paternal repair and causes chromosomal aberrations in the zygote by maternal misrepair

    DOE PAGES

    Marchetti, Francesco; Bishop, Jack; Gingerich, John; Wyrobek, Andrew J.

    2015-01-08

    De novo point mutations and chromosomal structural aberrations (CSA) detected in offspring of unaffected parents show a preferential paternal origin with higher risk for older fathers. Studies in rodents suggest that heritable mutations transmitted from the father can arise from either paternal or maternal misrepair of damaged paternal DNA, and that the entire spermatogenic cycle can be at risk after mutagenic exposure. Understanding the susceptibility and mechanisms of transmission of paternal mutations is important in family planning after chemotherapy and donor selection for assisted reproduction. We report that treatment of male mice with melphalan (MLP), a bifunctional alkylating agent widelymore » used in chemotherapy, induces DNA lesions during male mouse meiosis that persist unrepaired as germ cells progress through DNA repair-competent phases of spermatogenic development. After fertilization, unrepaired sperm DNA lesions are mis-repaired into CSA by the egg's DNA repair machinery producing chromosomally abnormal offspring. In conclusion, these findings highlight the importance of both pre- and post-fertilization DNA repair in assuring the genomic integrity of the conceptus.« less

  14. Meiotic interstrand DNA damage escapes paternal repair and causes chromosomal aberrations in the zygote by maternal misrepair

    SciTech Connect

    Marchetti, Francesco; Bishop, Jack; Gingerich, John; Wyrobek, Andrew J.

    2015-01-08

    De novo point mutations and chromosomal structural aberrations (CSA) detected in offspring of unaffected parents show a preferential paternal origin with higher risk for older fathers. Studies in rodents suggest that heritable mutations transmitted from the father can arise from either paternal or maternal misrepair of damaged paternal DNA, and that the entire spermatogenic cycle can be at risk after mutagenic exposure. Understanding the susceptibility and mechanisms of transmission of paternal mutations is important in family planning after chemotherapy and donor selection for assisted reproduction. We report that treatment of male mice with melphalan (MLP), a bifunctional alkylating agent widely used in chemotherapy, induces DNA lesions during male mouse meiosis that persist unrepaired as germ cells progress through DNA repair-competent phases of spermatogenic development. After fertilization, unrepaired sperm DNA lesions are mis-repaired into CSA by the egg's DNA repair machinery producing chromosomally abnormal offspring. In conclusion, these findings highlight the importance of both pre- and post-fertilization DNA repair in assuring the genomic integrity of the conceptus.

  15. Meiotic interstrand DNA damage escapes paternal repair and causes chromosomal aberrations in the zygote by maternal misrepair

    PubMed Central

    Marchetti, Francesco; Bishop, Jack; Gingerich, John; Wyrobek, Andrew J.

    2015-01-01

    De novo point mutations and chromosomal structural aberrations (CSA) detected in offspring of unaffected parents show a preferential paternal origin with higher risk for older fathers. Studies in rodents suggest that heritable mutations transmitted from the father can arise from either paternal or maternal misrepair of damaged paternal DNA, and that the entire spermatogenic cycle can be at risk after mutagenic exposure. Understanding the susceptibility and mechanisms of transmission of paternal mutations is important in family planning after chemotherapy and donor selection for assisted reproduction. We report that treatment of male mice with melphalan (MLP), a bifunctional alkylating agent widely used in chemotherapy, induces DNA lesions during male mouse meiosis that persist unrepaired as germ cells progress through DNA repair-competent phases of spermatogenic development. After fertilization, unrepaired sperm DNA lesions are mis-repaired into CSA by the egg's DNA repair machinery producing chromosomally abnormal offspring. These findings highlight the importance of both pre- and post-fertilization DNA repair in assuring the genomic integrity of the conceptus. PMID:25567288

  16. Meiotic recombination mechanisms.

    PubMed

    Grelon, Mathilde

    2016-01-01

    Meiosis is a specialized cell division at the origin of the haploid cells that eventually develop into the gametes. It therefore lies at the heart of Mendelian heredity. Recombination and redistribution of the homologous chromosomes arising during meiosis constitute an important source of genetic diversity, conferring to meiosis a particularly important place in the evolution and the diversification of the species. Our understanding of the molecular mechanisms governing meiotic recombination has considerably progressed these last decades, benefiting from complementary approaches led on various model species. An overview of these mechanisms will be provided as well as a discussion on the implications of these recent discoveries. PMID:27180110

  17. The osmium tetroxide-p-phenylenediamine procedure reveals the chromatid cores and kinetochores of meiotic chromosomes by light and electron microscopy.

    PubMed

    Antonio, C; González-García, J M; Page, J; Suja, J A; Stockert, J C; Rufas, J S

    1996-11-01

    We analyzed first-metaphase meiotic chromosomes of the grasshopper Chorthippus jucundus by two different methods, i.e., a silver impregnation technique and the osmium tetroxide-p-phenylenediamine (Os-PPD) procedure. The former was applied on squashed testes previously fixed in ethanol-acetic acid, whereas for Os-PPD the material was not subjected to any previous extraction treatment but was fixed in OsO4, treated with PPD, and embedded in Epon 812. Both techniques revealed chromatid cores and kinetochores regardless of the processing of the material (squashed or sectioned). Unstained Os-PPD sections were analyzed by light microscopy and transmission electron microscopy (TEM). The Os-PPD technique provided a high contrast of chromatid cores and kinetochores in relation to the chromatin, which revealed a low electron density. To determine the Os-PPD reaction mechanism, the PAS procedure, as well as scanning electron microscopy (SEM) backscattering and SEM X-ray microanalysis, was performed on sections. By use of the Os-PPD-PAS procedure, glycol groups formed by oxidation of osmium bound to aromatic substrates were detected in chromatid cores and kinetochores by brightfield and fluorescence microscopy. A high Z contrast was detected in these structures by backscattered electron imaging. SEM X-ray microanalysis showed osmium and phosphorus to be the main elements present on the chromatid cores. Taking into account the known reactivity of OsO4 and the present results, the possible participation of nucleic acids as well as proteins in the Os-PPD reaction mechanism and in the composition of chromatid cores and kinetochores is discussed.

  18. Advanced maternal age and the risk of Down syndrome characterized by the meiotic stage of the chromosomal error: A population-based study

    SciTech Connect

    Yoon, P.W.; Khoury, M.J.; Freeman, S.B.

    1996-03-01

    The identification of DNA polymorphisms makes it possible to classify trisomy 21 according to the parental origin and stage (meiosis I [MI], meiosis II [MII], or postzygotic mitotic) of the chromosomal error. Studying the effect of parental age on these subgroups could shed light on parental exposures and their timing. From 1989 through 1993, 170 infants with trisomy 21 and 267 randomly selected control infants were ascertained in a population-based, case-control study in metropolitan Atlanta. Blood samples for genetic studies were obtained from case infants and their parents. Using logistic regression, we independently examined the association between maternal and paternal age and subgroups of trisomy 21 defined by parental origin and meiotic stage. The distribution of trisomy 21 by origin was 86% maternal (75% MI and 25% MII), 9% paternal (50% MI and 50% MII), and 5% mitotic. Compared with women <25 years of age, women {>=}40 years old had an odds ratio of 5.2 (95% confidence interval, 1.0-27.4) for maternal MI (MMI) errors and 51.4 (95% confidence interval, 2.3-999.0) for maternal MII (MMII) errors. Birth-prevalence rates for women {>=}40 years old were 4.2/1,000 births for MMI errors and 1.9/1,000 births for MMII errors. These results support an association between advanced maternal age and both MMI and MMII errors. The association with MI does not pinpoint the timing of the error; however, the association with MII implies that there is at least one maternal age-related mechanism acting around the time of conception. 16 refs., 1 fig., 2 tabs.

  19. Regulation of Meiotic Recombination

    SciTech Connect

    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

  20. The role of chromatin modifications in progression through mouse meiotic prophase.

    PubMed

    Crichton, James H; Playfoot, Christopher J; Adams, Ian R

    2014-03-20

    Meiosis is a key event in gametogenesis that generates new combinations of genetic information and is required to reduce the chromosome content of the gametes. Meiotic chromosomes undergo a number of specialised events during prophase to allow meiotic recombination, homologous chromosome synapsis and reductional chromosome segregation to occur. In mammalian cells, DNA physically associates with histones to form chromatin, which can be modified by methylation, phosphorylation, ubiquitination and acetylation to help regulate higher order chromatin structure, gene expression, and chromosome organisation. Recent studies have identified some of the enzymes responsible for generating chromatin modifications in meiotic mammalian cells, and shown that these chromatin modifying enzymes are required for key meiosis-specific events that occur during meiotic prophase. This review will discuss the role of chromatin modifications in meiotic recombination, homologous chromosome synapsis and regulation of meiotic gene expression in mammals. PMID:24656230

  1. Meiotic process and aneuploidy

    SciTech Connect

    Grell, R.F.

    1985-01-01

    The process of meiosis is analyzed by dissecting it into its component parts using the early oocyte of Drosophila as a model. Entrance of the oocytes into premeiotic interphase signals initiation of DNA replication which continues for 30 h. Coincidentally, extensive synaptonemal complexes appear, averaging 50 ..mu..m (132 h), peaking at 75 ..mu..m (144 h) and continuing into early vitellarial stages. Recombinational response to heat, evidenced by enhancement or induction of exchange, is limited to the S-phase with a peak at 144 h coinciding with maximal extension of the SC. Coincidence of synapsis and recombination response with S at premeiotic interphase is contrary to their conventional localization at meiotic prophase. The interrelationship between exchange and nondisjunction has been clarified by the Distributive Pairing Model of meiosis. Originally revealed through high frequencies of nonrandom assortment of nonhomologous chromosomes, distributive pairing has been shown to follow and to be noncompetitive with exchange, to be based on size-recognition, not homology, and as a raison d'etre, to provide a segregational mechanism for noncrossover homologues. Rearrangements, recombination mutants and aneuploids may contribute noncrossover chromosomes to the distributive pool and so promote the nonhomologous associations responsible for nondisjunction of homologues and regular segregation of nonhomologues. 38 references, 15 figures. (ACR)

  2. Complex elaboration: making sense of meiotic cohesin dynamics

    PubMed Central

    Rankin, Susannah

    2015-01-01

    In mitotically dividing cells, the cohesin complex tethers sister chromatids, the products of DNA replication, together from the time they are generated during S phase until anaphase. Cohesion between sister chromatids ensures accurate chromosome segregation, and promotes normal gene regulation and certain kinds of DNA repair. In somatic cells, the core cohesin complex is composed of four subunits: Smc1, Smc3, Rad21 and an SA subunit. During meiotic cell divisions meiosis-specific isoforms of several of the cohesin subunits are also expressed and incorporated into distinct meiotic cohesin complexes. The relative contributions of these meiosis-specific forms of cohesin to chromosome dynamics during meiotic progression have not been fully worked out. However, the localization of these proteins during chromosome pairing and synapsis, and their unique loss-of-function phenotypes, suggest non-overlapping roles in controlling meiotic chromosome behavior. Many of the proteins that regulate cohesin function during mitosis also appear to regulate cohesin during meiosis. Here we review how cohesin contributes to meiotic chromosome dynamics, and explore similarities and differences between cohesin regulation during the mitotic cell cycle and meiotic progression. A deeper understanding of the regulation and function of cohesin in meiosis will provide important new insights into how the cohesin complex is able to promote distinct kinds of chromosome interactions under diverse conditions. PMID:25895170

  3. Entropy-driven spatial organization of highly confined polymers: Lessons for the bacterial chromosome

    NASA Astrophysics Data System (ADS)

    Jun, Suckjoon; Mulder, Bela

    2006-08-01

    Despite recent progress in visualization experiments, the mechanism underlying chromosome segregation in bacteria still remains elusive. Here we address a basic physical issue associated with bacterial chromosome segregation, namely the spatial organization of highly confined, self-avoiding polymers (of nontrivial topology) in a rod-shaped cell-like geometry. Through computer simulations, we present evidence that, under strong confinement conditions, topologically distinct domains of a polymer complex effectively repel each other to maximize their conformational entropy, suggesting that duplicated circular chromosomes could partition spontaneously. This mechanism not only is able to account for the spatial separation per se but also captures the major features of the spatiotemporal organization of the duplicating chromosomes observed in Escherichia coli and Caulobacter crescentus. bacterial chromosome segregation | Caulobacter crescentus | Escherichia coli | polymer physics

  4. Self-Organization of Meiotic Recombination Initiation: General Principles and Molecular Pathways

    PubMed Central

    Keeney, Scott; Lange, Julian; Mohibullah, Neeman

    2015-01-01

    Recombination in meiosis is a fascinating case study for the coordination of chromosomal duplication, repair, and segregation with each other and with progression through a cell-division cycle. Meiotic recombination initiates with formation of developmentally programmed DNA double-strand breaks (DSBs) at many places across the genome. DSBs are important for successful meiosis but are also dangerous lesions that can mutate or kill, so cells ensure that DSBs are made only at the right times, places, and amounts. This review examines the complex web of pathways that accomplish this control. We explore how chromosome breakage is integrated with meiotic progression and how feedback mechanisms spatially pattern DSB formation and make it homeostatic, robust, and error-correcting. Common regulatory themes recur in different organisms or in different contexts in the same organism. We review this evolutionary and mechanistic conservation but also highlight where control modules have diverged. The framework that emerges helps explain how meiotic chromosomes behave as a self-organizing system. PMID:25421598

  5. Self-organization of meiotic recombination initiation: general principles and molecular pathways.

    PubMed

    Keeney, Scott; Lange, Julian; Mohibullah, Neeman

    2014-01-01

    Recombination in meiosis is a fascinating case study for the coordination of chromosomal duplication, repair, and segregation with each other and with progression through a cell-division cycle. Meiotic recombination initiates with formation of developmentally programmed DNA double-strand breaks (DSBs) at many places across the genome. DSBs are important for successful meiosis but are also dangerous lesions that can mutate or kill, so cells ensure that DSBs are made only at the right times, places, and amounts. This review examines the complex web of pathways that accomplish this control. We explore how chromosome breakage is integrated with meiotic progression and how feedback mechanisms spatially pattern DSB formation and make it homeostatic, robust, and error correcting. Common regulatory themes recur in different organisms or in different contexts in the same organism. We review this evolutionary and mechanistic conservation but also highlight where control modules have diverged. The framework that emerges helps explain how meiotic chromosomes behave as a self-organizing system.

  6. A Link between Meiotic Prophase Progression and CrossoverControl

    SciTech Connect

    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.

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

    PubMed Central

    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

  8. Modeling and Experimental Methods to Probe the Link between Global Transcription and Spatial Organization of Chromosomes

    PubMed Central

    Gupta, Soumya; Libchaber, Albert; Tlusty, Tsvi; Shivashankar, G. V.

    2012-01-01

    Genomes are spatially assembled into chromosome territories (CT) within the nucleus of living cells. Recent evidences have suggested associations between three-dimensional organization of CTs and the active gene clusters within neighboring CTs. These gene clusters are part of signaling networks sharing similar transcription factor or other downstream transcription machineries. Hence, presence of such gene clusters of active signaling networks in a cell type may regulate the spatial organization of chromosomes in the nucleus. However, given the probabilistic nature of chromosome positions and complex transcription factor networks (TFNs), quantitative methods to establish their correlation is lacking. In this paper, we use chromosome positions and gene expression profiles in interphase fibroblasts and describe methods to capture the correspondence between their spatial position and expression. In addition, numerical simulations designed to incorporate the interacting TFNs, reveal that the chromosome positions are also optimized for the activity of these networks. These methods were validated for specific chromosome pairs mapped in two distinct transcriptional states of T-Cells (naïve and activated). Taken together, our methods highlight the functional coupling between topology of chromosomes and their respective gene expression patterns. PMID:23049710

  9. Spatial control of chromosomal location in a live cell with functionalized magnetic particles

    NASA Astrophysics Data System (ADS)

    Hong, Juhee; Purwar, Prashant; Cha, Misun; Lee, Junghoon

    2015-11-01

    Long-range chromosomal travel is a phenomenon unique to cell division. Methods for non-invasive, artificial manipulation of chromosomes, such as optical or magnetic tweezers, have difficulty in producing the motion of whole chromosomes in live cells. Here, we report the spatial control of chromosomes over 10 μm in a live mouse oocyte using magnetic particles driven by an external magnetic field. Selective capture of the chromosomes was achieved using antibodies specific for histone H1 in the chromosome that were conjugated to magnetic particles (H1-BMPs). When an external magnetic field was applied, the chromosomes captured by the H1-BMPs traveled through the cytosol and accumulated near the cell membrane though the movement of the chromosomes captured by H1-BMPs was strongly disturbed by the distribution of the cytoskeleton (e.g. actin filaments). Being non-invasive in nature, our approach will enable new opportunities in the remote manipulation of subcellular elements.Long-range chromosomal travel is a phenomenon unique to cell division. Methods for non-invasive, artificial manipulation of chromosomes, such as optical or magnetic tweezers, have difficulty in producing the motion of whole chromosomes in live cells. Here, we report the spatial control of chromosomes over 10 μm in a live mouse oocyte using magnetic particles driven by an external magnetic field. Selective capture of the chromosomes was achieved using antibodies specific for histone H1 in the chromosome that were conjugated to magnetic particles (H1-BMPs). When an external magnetic field was applied, the chromosomes captured by the H1-BMPs traveled through the cytosol and accumulated near the cell membrane though the movement of the chromosomes captured by H1-BMPs was strongly disturbed by the distribution of the cytoskeleton (e.g. actin filaments). Being non-invasive in nature, our approach will enable new opportunities in the remote manipulation of subcellular elements. Electronic supplementary

  10. Linear and spatial organization of polytene chromosomes of the African malaria mosquito Anopheles funestus.

    PubMed Central

    Sharakhov, I V; Sharakhova, M V; Mbogo, C M; Koekemoer, L L; Yan, G

    2001-01-01

    Anopheles funestus Giles is one of the major malaria vectors in Africa, but little is known about its genetics. Lack of a cytogenetic map characterized by regions has hindered the progress of genetic research with this important species. This study developed a cytogenetic map of An. funestus using ovarian nurse cell polytene chromosomes. We demonstrate an important application with the cytogenetic map for characterizing various chromosomal inversions for specimens collected from coastal Kenya. The linear and spatial organization of An. funestus polytene chromosomes was compared with the best-studied malaria mosquito, An. gambiae Giles. Comparisons of chromosome morphology between the two species have revealed that the most extensive chromosomal rearrangement occurs in pericentromeric heterochromatin of autosomes. Differences in pericentromeric heterochromatin types correlate with nuclear organization differences between An. funestus and An. gambiae. Attachments of chromosomes to the nuclear envelope strongly depend on the presence of diffusive beta-heterochromatin. Thus, An. funestus and An. gambiae exhibit species-specific characteristics in chromosome-linear and -spatial organizations. PMID:11560898

  11. Chromosome

    MedlinePlus

    Chromosomes are structures found in the center (nucleus) of cells that carry long pieces of DNA. DNA ... is the building block of the human body. Chromosomes also contain proteins that help DNA exist in ...

  12. History of chromosome rearrangements reflects the spatial organization of yeast chromosomes.

    PubMed

    Khrameeva, Ekaterina E; Fudenberg, Geoffrey; Gelfand, Mikhail S; Mirny, Leonid A

    2016-04-01

    Three-dimensional (3D) organization of genomes affects critical cellular processes such as transcription, replication, and deoxyribo nucleic acid (DNA) repair. While previous studies have investigated the natural role, the 3D organization plays in limiting a possible set of genomic rearrangements following DNA repair, the influence of specific organizational principles on this process, particularly over longer evolutionary time scales, remains relatively unexplored. In budding yeast S.cerevisiae, chromosomes are organized into a Rabl-like configuration, with clustered centromeres and telomeres tethered to the nuclear periphery. Hi-C data for S.cerevisiae show that a consequence of this Rabl-like organization is that regions equally distant from centromeres are more frequently in contact with each other, between arms of both the same and different chromosomes. Here, we detect rearrangement events in Saccharomyces species using an automatic approach, and observe increased rearrangement frequency between regions with higher contact frequencies. Together, our results underscore how specific principles of 3D chromosomal organization can influence evolutionary events.

  13. Multimodality hard-x-ray imaging of a chromosome with nanoscale spatial resolution

    DOE PAGES

    Yan, Hanfei; Nazaretski, Evgeny; Lauer, Kenneth R.; Huang, Xiaojing; Wagner, Ulrich; Rau, Christoph; Yusuf, Mohammed; Robinson, Ian K.; Kalbfleisch, Sebastian; Li, Li; et al

    2016-02-05

    Here, we developed a scanning hard x-ray microscope using a new class of x-ray nano-focusing optic called a multilayer Laue lens and imaged a chromosome with nanoscale spatial resolution. The combination of the hard x-ray's superior penetration power, high sensitivity to elemental composition, high spatial-resolution and quantitative analysis creates a unique tool with capabilities that other microscopy techniques cannot provide. Using this microscope, we simultaneously obtained absorption-, phase-, and fluorescence-contrast images of Pt-stained human chromosome samples. The high spatial-resolution of the microscope and its multi-modality imaging capabilities enabled us to observe the internal ultra-structures of a thick chromosome without sectioningmore » it.« less

  14. Multimodality hard-x-ray imaging of a chromosome with nanoscale spatial resolution

    NASA Astrophysics Data System (ADS)

    Yan, Hanfei; Nazaretski, Evgeny; Lauer, Kenneth; Huang, Xiaojing; Wagner, Ulrich; Rau, Christoph; Yusuf, Mohammed; Robinson, Ian; Kalbfleisch, Sebastian; Li, Li; Bouet, Nathalie; Zhou, Juan; Conley, Ray; Chu, Yong S.

    2016-02-01

    We developed a scanning hard x-ray microscope using a new class of x-ray nano-focusing optic called a multilayer Laue lens and imaged a chromosome with nanoscale spatial resolution. The combination of the hard x-ray’s superior penetration power, high sensitivity to elemental composition, high spatial-resolution and quantitative analysis creates a unique tool with capabilities that other microscopy techniques cannot provide. Using this microscope, we simultaneously obtained absorption-, phase-, and fluorescence-contrast images of Pt-stained human chromosome samples. The high spatial-resolution of the microscope and its multi-modality imaging capabilities enabled us to observe the internal ultra-structures of a thick chromosome without sectioning it.

  15. Multimodality hard-x-ray imaging of a chromosome with nanoscale spatial resolution

    PubMed Central

    Yan, Hanfei; Nazaretski, Evgeny; Lauer, Kenneth; Huang, Xiaojing; Wagner, Ulrich; Rau, Christoph; Yusuf, Mohammed; Robinson, Ian; Kalbfleisch, Sebastian; Li, Li; Bouet, Nathalie; Zhou, Juan; Conley, Ray; Chu, Yong S.

    2016-01-01

    We developed a scanning hard x-ray microscope using a new class of x-ray nano-focusing optic called a multilayer Laue lens and imaged a chromosome with nanoscale spatial resolution. The combination of the hard x-ray’s superior penetration power, high sensitivity to elemental composition, high spatial-resolution and quantitative analysis creates a unique tool with capabilities that other microscopy techniques cannot provide. Using this microscope, we simultaneously obtained absorption-, phase-, and fluorescence-contrast images of Pt-stained human chromosome samples. The high spatial-resolution of the microscope and its multi-modality imaging capabilities enabled us to observe the internal ultra-structures of a thick chromosome without sectioning it. PMID:26846188

  16. Sister cohesion and structural axis components mediate homolog bias of meiotic recombination

    PubMed Central

    Kim, Keun P.; Weiner, Beth M.; Zhang, Liangran; Jordan, Amy; Dekker, Job; Kleckner, Nancy

    2010-01-01

    SUMMARY Meiotic recombination occurs between one chromatid of each maternal and paternal homolog (homolog bias) versus between sister chromatids (sister bias). Physical DNA analysis reveals that meiotic cohesin/axis component Rec8 promotes sister bias, likely via its cohesion activity. Two meiosis-specific axis components, Red1/Mek1kinase, counteract this effect. With this precondition satisfied, other molecules directly specify homolog bias per se. Rec8 also acts positively to maintain homolog bias during crossover recombination. These observations point to sequential release of double-strand break ends from association with their sister. Red1 and Rec8 are found to play distinct roles for sister cohesion, DSB formation and recombination progression kinetics. Also, the two components are enriched in spatially distinct domains of axial structure that develop prior to DSB formation. We propose that Red1 and Rec8 domains provide functionally complementary environments whereby inputs evolved from DSB repair and late-stage chromosome morphogenesis are integrated to give the complete meiotic chromosomal program. PMID:21145459

  17. Immunolocalization of meiotic proteins in Arabidopsis thaliana: method 2.

    PubMed

    Armstrong, Susan; Osman, Kim

    2013-01-01

    Advances in the molecular biology and genetics of Arabidopsis thaliana have led to it becoming an important model for the analysis of meiosis in plants. Cytogenetic investigations are pivotal to meiotic studies and a number of technological improvements for Arabidopsis cytology have provided a range of tools to investigate chromosome behavior during meiosis (Jones et al. Chromosome Res 11:205-215, 2003). This chapter contains a detailed description of an immunological technique currently used in our lab for the preparation of meiotic chromosomes for immunolocalization.

  18. Coevolutionary dynamics of polyandry and sex-linked meiotic drive.

    PubMed

    Holman, Luke; Price, Thomas A R; Wedell, Nina; Kokko, Hanna

    2015-03-01

    Segregation distorters located on sex chromosomes are predicted to sweep to fixation and cause extinction via a shortage of one sex, but in nature they are often found at low, stable frequencies. One potential resolution to this longstanding puzzle involves female multiple mating (polyandry). Because many meiotic drivers severely reduce the sperm competitive ability of their male carriers, females are predicted to evolve more frequent polyandry and thereby promote sperm competition when a meiotic driver invades. Consequently, the driving chromosome's relative fitness should decline, halting or reversing its spread. We used formal modeling to show that this initially appealing hypothesis cannot resolve the puzzle alone: other selective pressures (e.g., low fitness of drive homozygotes) are required to establish a stable meiotic drive polymorphism. However, polyandry and meiotic drive can strongly affect one another's frequency, and polyandrous populations may be resistant to the invasion of rare drive mutants.

  19. Initiation of meiotic recombination in Ustilago maydis.

    PubMed

    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.

  20. Children with Chromosome 22q11.2 Deletion Syndrome Exhibit Impaired Spatial Working Memory

    ERIC Educational Resources Information Center

    Wong, Ling M.; Riggins, Tracy; Harvey, Danielle; Cabaral, Margarita; Simon, Tony J.

    2014-01-01

    Individuals with chromosome 22q11.2 deletion syndrome (22q11.2DS) have been shown to have impairments in processing spatiotemporal information. The authors examined whether children with 22q11.2DS exhibit impairments in spatial working memory performance due to these weaknesses, even when controlling for maintenance of attention. Children with…

  1. High-resolution meiotic and physical mapping of the Best`s vitelliform macular dystrophy (VMD2) locus to pericentromeric chromosome 11

    SciTech Connect

    Weber, B.H.F.; Vogt, G.; Walker, D.

    1994-09-01

    Vitelliform macular dystrophy, also known as Best`s disease, is a juvenile-onset macular degeneration with autosomal dominant inheritance. It is characterized by well-demarcated accumulation of lipofuscin-like material within and beneath the retinal pigment epithelium (RPE) and classically results in an egg yolk-like appearance of the macula. Typically, carriers of the disease gene show a specific electrophysiological sign which can be detected by electrooculography (EOG). The EOG measures a standing potential between the cornea and the retina which is primarily generated by the RPE. The histopathological findings as well as the EOG abnormalities suggest that Best`s disease is a generalized disorder of the RPE. The basic biochemical defect is still unknown. As a first step in the positional cloning of the defective gene, the Best`s disease locus was mapped to chromosome 11 between markers at D11S871 and INT2. Subsequently, his region was refined to a 3.7 cM interval flanked by loci D11S903 and PYGM. To further narrow the D11S903-PYGM interval and to obtain an estimate of the physical size of the minimal candidate region, we used a combination of high-resolution PCR hybrid mapping and analysis of recombinant Best`s disease chromosomes. We identified six markers from within the D11S903-PYGM interval that show no recombination with the defective gene in three multigeneration Best`s disease pedigrees. Our hybrid panel localizes these markers on either side of the centromere on chromosome 11. The closest markers flanking the disease gene are at D11S986 in band p12-11.22 and at D11S480 in band q13.2-13.3. Our study demonstrates that the physical size of the Best`s disease region is exceedingly larger than was previously estimated from the genetic data due to the proximity of the defective gene to the centromere of chromosome 11.

  2. Tissue-specific differences in the spatial interposition of X-chromosome and 3R chromosome regions in the malaria mosquito Anopheles messeae Fall.

    PubMed

    Artemov, Gleb; Bondarenko, Semen; Sapunov, Gleb; Stegniy, Vladimir

    2015-01-01

    Spatial organization of a chromosome in a nucleus is very important in biology but many aspects of it are still generally unresolved. We focused on tissue-specific features of chromosome architecture in closely related malaria mosquitoes, which have essential inter-specific differences in polytene chromosome attachments in nurse cells. We showed that the region responsible for X-chromosome attachment interacts with nuclear lamina stronger in nurse cells, then in salivary glands cells in Anopheles messeae Fall. The inter-tissue differences were demonstrated more convincingly in an experiment of two distinct chromosomes interposition in the nucleus space of cells from four tissues. Microdissected DNA-probes from nurse cells X-chromosome (2BC) and 3R chromosomes (32D) attachment regions were hybridized with intact nuclei of nurse cells, salivary gland cells, follicle epithelium cells and imaginal disсs cells in 3D-FISH experiments. We showed that only salivary gland cells and follicle epithelium cells have no statistical differences in the interposition of 2BC and 32D. Generally, the X-chromosome and 3R chromosome are located closer to each other in cells of the somatic system in comparison with nurse cells on average. The imaginal disсs cell nuclei have an intermediate arrangement of chromosome interposition, similar to other somatic cells and nurse cells. In spite of species-specific chromosome attachments there are no differences in interposition of nurse cells chromosomes in An. messeae and An. atroparvus Thiel. Nurse cells have an unusual chromosome arrangement without a chromocenter, which could be due to the special mission of generative system cells in ontogenesis and evolution.

  3. Meiotic chromosomes and nucleolar behavior in testicular cells of the grassland spittlebugs Deois flavopicta, Mahanarva fimbriolata and Notozulia entreriana (Hemiptera, Auchenorrhyncha)

    PubMed Central

    2010-01-01

    Spittlebugs annually infest pastures and cause severe damage, representing a serious problem for the tropical American beef cattle industry. Spittlebugs are an important biotic constraint to forage production and there is a lack of cytogenetic data for this group of insects. For these reasons, we conducted this work, in which the spermatogenesis and nucleolar behavior of Deois flavopicta, Mahanarva fimbriolata and Notozulia entreriana were studied. The males possessed testes in the shape of a “bunch of grapes”; a variable number of testicular lobes per individual and polyploid nuclei composed of several heteropycnotic bodies. A heteropycnotic area was located in the periphery of the nucleus (prophase I); the chiasmata were terminal or interstitial; metaphases I were circular or linear and anaphase showed late migration of the sex chromosome. The chromosome complement had 2n = 19, except for N. entreriana (2n = 15); the spermatids were round with heteropycnotic material in the center and elongated with conspicuos chromatin. The analysis of testes after silver nitrate staining showed polyploid nuclei with three large and three smaller nucleolar bodies. Early prophase cells had an intensely stained nucleolar body located close to the chromatin and another less evident body located away from the chromatin. The nucleolar bodies disintegrated during diplotene. Silver staining occurred in two autosomes, in terminal and subterminal locations, the latter probably corresponding to the nucleolus organizer regions (NORs). The spermatids were round with a round nucleolar body and silver staining was observed in the medial and posterior region of the elongated part of the spermatid head. PMID:21637477

  4. Chromosomal G-dark Bands Determine the Spatial Organization of Centromeric Heterochromatin in the Nucleus

    PubMed Central

    Carvalho, Célia; Pereira, Henrique M.; Ferreira, João; Pina, Cristina; Mendonça, Denise; Rosa, Agostinho C.; Carmo-Fonseca, Maria

    2001-01-01

    Gene expression can be silenced by proximity to heterochromatin blocks containing centromeric α-satellite DNA. This has been shown experimentally through cis-acting chromosome rearrangements resulting in linear genomic proximity, or through trans-acting changes resulting in intranuclear spatial proximity. Although it has long been been established that centromeres are nonrandomly distributed during interphase, little is known of what determines the three-dimensional organization of these silencing domains in the nucleus. Here, we propose a model that predicts the intranuclear positioning of centromeric heterochromatin for each individual chromosome. With the use of fluorescence in situ hybridization and confocal microscopy, we show that the distribution of centromeric α-satellite DNA in human lymphoid cells synchronized at G0/G1 is unique for most individual chromosomes. Regression analysis reveals a tight correlation between nuclear distribution of centromeric α-satellite DNA and the presence of G-dark bands in the corresponding chromosome. Centromeres surrounded by G-dark bands are preferentially located at the nuclear periphery, whereas centromeres of chromosomes with a lower content of G-dark bands tend to be localized at the nucleolus. Consistent with the model, a t(11; 14) translocation that removes G-dark bands from chromosome 11 causes a repositioning of the centromere, which becomes less frequently localized at the nuclear periphery and more frequently associated with the nucleolus. The data suggest that “chromosomal environment” plays a key role in the intranuclear organization of centromeric heterochromatin. Our model further predicts that facultative heterochromatinization of distinct genomic regions may contribute to cell-type specific patterns of centromere localization. PMID:11694589

  5. Spatial Dynamics of Evolving Dosage Compensation in a Young Sex Chromosome System

    PubMed Central

    Schultheiß, Roland; Viitaniemi, Heidi M.; Leder, Erica H.

    2015-01-01

    The loss of Y-linked genes during sex chromosome evolution creates a potentially deleterious low gene dosage in males. Recent studies have reported different strategies of dosage compensation. Unfortunately, most of these studies investigated taxa with comparatively old sex chromosome systems, which may limit insights into the evolution of dosage compensation and thus into the causes of different compensation strategies. Using deep RNA sequencing, we investigate differential expression patterns along the young XY chromosomes of threespine sticklebacks. Our strata-specific analyses provide new insights into the spatial patterns during the early stages of the evolution of dosage compensation. In particular, our results indicate systematic upregulation of male gene expression in stratum II, which in turn causes female hypertranscription in the same stratum. These findings are consistent with theoretical predictions that selection during early stages of sex chromosome evolution is stronger for a compensating upregulation in males than for the countercompensation of female hyperexpression. In contrast, no elevated gene expression is detectable in stratum I. We argue that strata-specific differences in compensating male gene expression may evolve in response to differences in the prevailing mechanism of Y chromosome degeneration. PMID:25618140

  6. Spatial relationship between chromosomal domains in diploid and autotetraploid Arabidopsis thaliana nuclei.

    PubMed

    Sas-Nowosielska, H; Bernas, T

    2016-04-25

    Polyploids constitute more than 80% of angiosperm plant species. Their DNA content is often further increased by endoreplication, which occurs as a part of cell differentiation. Here, we explore the relationship between 3D chromatin architecture, number of genome copies and their origin in the model plant, Arabidopsis thaliana. Spatial proximity between pericentromeric, interstitial and subtelomeric domains of chromosomes 1 and 4 was quantified over a range of distances. The results indicate that average nuclear volume as well as chromatin density increase with the genome copy number. Similar dependence is observed when association of homologous chromosomes (in 2C/ endopolyploid nuclei) and sister chromatid separation (in endopolyploid nuclei) is studied. Moreover, clusters of chromosomal domains are detectable at the spatial scale above microscopy resolution. Subtelomeric, interstitial and pericentromeric chromosomal domains are affected to different extent by these processes, which are modulated by endopolyploidy. This factor influences fusion of heterochromatin as well. Nonetheless, local chromatin architecture of Arabidopsis thaliana depends mainly on endopolyploidy level, and to lesser extend on polyploidy. PMID:27310308

  7. Control of Oocyte Growth and Meiotic Maturation in C. elegans

    PubMed Central

    Kim, Seongseop; Spike, Caroline; Greenstein, David

    2013-01-01

    In sexually reproducing animals, oocytes arrest at diplotene or diakinesis and resume meiosis (meiotic maturation) in response to hormones. Chromosome segregation errors in female meiosis I are the leading cause of human birth defects, and age-related changes in the hormonal environment of the ovary are a suggested cause. C. elegans is emerging as a genetic paradigm for studying hormonal control of meiotic maturation. The meiotic maturation processes in C. elegans and mammals share a number of biological and molecular similarities. Major sperm protein (MSP) and luteinizing hormone (LH), though unrelated in sequence, both trigger meiotic resumption using somatic Gαs-adenylate cyclase pathways and soma-germline gap-junctional communication. At a molecular level, the oocyte responses apparently involve the control of conserved protein kinase pathways and post-transcriptional gene regulation in the oocyte. At a cellular level, the responses include cortical cytoskeletal rearrangement, nuclear envelope breakdown, assembly of the acentriolar meiotic spindle, chromosome segregation, and likely changes important for fertilization and the oocyte-to-embryo transition. This chapter focuses on signaling mechanisms required for oocyte growth and meiotic maturation in C. elegans and discusses how these mechanisms coordinate the completion of meiosis and the oocyte-to-embryo transition. PMID:22872481

  8. Spatial positioning of all 24 chromosomes in the lymphocytes of six subjects: evidence of reproducible positioning and spatial repositioning following DNA damage with hydrogen peroxide and ultraviolet B.

    PubMed

    Ioannou, Dimitrios; Kandukuri, Lakshmi; Quadri, Ameer; Becerra, Victor; Simpson, Joe Leigh; Tempest, Helen G

    2015-01-01

    The higher-order organization of chromatin is well-established, with chromosomes occupying distinct positions within the interphase nucleus. Chromatin is susceptible to, and constantly assaulted by both endogenous and exogenous threats. However, the effects of DNA damage on the spatial topology of chromosomes are hitherto, poorly understood. This study investigates the organization of all 24 human chromosomes in lymphocytes from six individuals prior to- and following in-vitro exposure to genotoxic agents: hydrogen peroxide and ultraviolet B. This study is the first to report reproducible distinct hierarchical radial organization of chromosomes with little inter-individual differences between subjects. Perturbed nuclear organization was observed following genotoxic exposure for both agents; however a greater effect was observed for hydrogen peroxide including: 1) More peripheral radial organization; 2) Alterations in the global distribution of chromosomes; and 3) More events of chromosome repositioning (18 events involving 10 chromosomes vs. 11 events involving 9 chromosomes for hydrogen peroxide and ultraviolet B respectively). Evidence is provided of chromosome repositioning and altered nuclear organization following in-vitro exposure to genotoxic agents, with notable differences observed between the two investigated agents. Repositioning of chromosomes following genotoxicity involved recurrent chromosomes and is most likely part of the genomes inherent response to DNA damage. The variances in nuclear organization observed between the two agents likely reflects differences in mobility and/or decondensation of chromatin as a result of differences in the type of DNA damage induced, chromatin regions targeted, and DNA repair mechanisms. PMID:25756782

  9. Spatial Positioning of All 24 Chromosomes in the Lymphocytes of Six Subjects: Evidence of Reproducible Positioning and Spatial Repositioning following DNA Damage with Hydrogen Peroxide and Ultraviolet B

    PubMed Central

    Kandukuri, Lakshmi; Quadri, Ameer; Becerra, Victor; Simpson, Joe Leigh

    2015-01-01

    The higher-order organization of chromatin is well-established, with chromosomes occupying distinct positions within the interphase nucleus. Chromatin is susceptible to, and constantly assaulted by both endogenous and exogenous threats. However, the effects of DNA damage on the spatial topology of chromosomes are hitherto, poorly understood. This study investigates the organization of all 24 human chromosomes in lymphocytes from six individuals prior to- and following in-vitro exposure to genotoxic agents: hydrogen peroxide and ultraviolet B. This study is the first to report reproducible distinct hierarchical radial organization of chromosomes with little inter-individual differences between subjects. Perturbed nuclear organization was observed following genotoxic exposure for both agents; however a greater effect was observed for hydrogen peroxide including: 1) More peripheral radial organization; 2) Alterations in the global distribution of chromosomes; and 3) More events of chromosome repositioning (18 events involving 10 chromosomes vs. 11 events involving 9 chromosomes for hydrogen peroxide and ultraviolet B respectively). Evidence is provided of chromosome repositioning and altered nuclear organization following in-vitro exposure to genotoxic agents, with notable differences observed between the two investigated agents. Repositioning of chromosomes following genotoxicity involved recurrent chromosomes and is most likely part of the genomes inherent response to DNA damage. The variances in nuclear organization observed between the two agents likely reflects differences in mobility and/or decondensation of chromatin as a result of differences in the type of DNA damage induced, chromatin regions targeted, and DNA repair mechanisms. PMID:25756782

  10. Spatiotemporal regulation of meiotic recombination by Liaisonin.

    PubMed

    Miyoshi, Tomoichiro; Ito, Masaru; Ohta, Kunihiro

    2013-01-01

    Sexual reproduction involves diversification of genetic information in successive generations. Meiotic recombination, which substantially contributes to the increase in genetic diversity, is initiated by programmed DNA double-strand breaks (DSBs) catalyzed by the evolutionarily conserved Spo11 protein. Spo11 requires additional partner proteins for its DNA cleavage reaction. DSBs are preferentially introduced at defined chromosomal sites called "recombination hotspots." Recent studies have revealed that meiotically established higher-order chromosome structures, such as chromosome axes and loops, are also crucial in the control of DSB formation. Most of the DSB sites are located within chromatin loop regions, while many of the proteins involved in DSB formation reside on chromosomal axes. Hence, DSB proteins and DSB sites seem to be distantly located. To resolve this paradox, we conducted comprehensive proteomics and ChIP-chip analyses on Spo11 partners in Schizosaccharomyces pombe, in combination with mutant studies. We identified two distinct DSB complexes, the "DSBC (DSB Catalytic core)" and "SFT (Seven-Fifteen-Twenty four; Rec7-Rec15-Rec24)" subcomplexes. The DSBC subcomplex contains Spo11 and functions as the catalytic core for the DNA cleavage reaction. The SFT subcomplex is assumed to execute regulatory functions. To activate the DSBC subcomplex, the SFT subcomplex tethers hotspots to axes via its interaction with Mde2, which can interact with proteins in both DSBC and SFT subcomplexes. Thus, Mde2 is likely to bridge these two subcomplexes, forming a "tethered loop-axis complex." It should be noted that Mde2 expression is strictly regulated by S phase checkpoint monitoring of the completion of DNA replication. From these observations, we proposed that Mde2 is a central coupler for meiotic recombination initiation to establish a tethered loop-axis complex in liaison with the S phase checkpoint.

  11. Meiotic recombination initiated by a double-strand break in rad50{Delta} yeast cells otherwise unable to initiate meiotic recombination

    SciTech Connect

    Malkova, A.; Haber, J.E.; Dawson, D.

    1996-06-01

    Meiotic recombination in Saccharomyces cerevisiae is initiated by double-strand breaks (DSBs). We have developed a system to compare the properties of meiotic DSBs with those created by the site-specific HO endonuclease. HO endonuclease was expressed under the control of the meiotic-specific SPO13 promoter, creating a DSB at a single site on one of yeast`s 16 chromosomes. In Rad{sup +} strains the times of appearance of the HO-induced DSBs and of subsequent recombinants are coincident with those induced by normal meiotic DSBs. Physical monitoring of DNA showed that SPO13::HO induced gene conversions both in Rad{sup +} and in rad50{Delta} cells that cannot initiate normal meiotic DSBs. We find that the RAD50 gene is important, but not essential, for recombination even after a DSB has been created in a meiotic cell. In rad50{Delta} cells, some DSBs are not repaired until a broken chromosome has been packaged into a spore and is subsequently germinated. This suggests that a broken chromosome does not signal an arrest of progression through meiosis. The recombination defect in rad50{Delta} diploids is not, however, meiotic specific, as mitotic rad50 diploids, experiencing an HO-induced DSB, exhibit similar departures from wild-type recombination. 57 refs., 5 figs., 3 tabs.

  12. Children with Chromosome 22q11.2 Deletion Syndrome Exhibit Impaired Spatial Working Memory

    PubMed Central

    Wong, Ling M; Riggins, Tracy; Harvey, Danielle; Cabaral, Margarita; Simon, Tony J.

    2014-01-01

    Individuals with chromosome 22q11.2 deletion syndrome (22q11.2DS) have been shown to have impairments in processing spatiotemporal information. We examined whether children with 22q11.2DS exhibit impairments in spatial working memory performance due to these weaknesses, even when controlling for maintenance of attention. Children with 22q11.2DS (n = 47) and typically developing controls (n = 49) ages 6–15 years saw images within a grid and after a delay, then indicated the positions of the images in the correct temporal order. Children with 22q11.2DS made more spatial and temporal errors than controls. Females with 22q11.2DS made more spatial and temporal errors than males. These results extend findings of impaired spatiotemporal processing into the memory domain in 22q11.2DS by documenting their influence on working memory performance. PMID:24679349

  13. Kinetochore Fibers Are Not Involved in the Formation of the First Meiotic Spindle in Mouse Oocytes, but Control the Exit from the First Meiotic M Phase

    PubMed Central

    Brunet, Stéphane; Maria, Angélica Santa; Guillaud, Philippe; Dujardin, Denis; Kubiak, Jacek Z.; Maro, Bernard

    1999-01-01

    During meiosis, two successive divisions occur without any intermediate S phase to produce haploid gametes. The first meiotic division is unique in that homologous chromosomes are segregated while the cohesion between sister chromatids is maintained, resulting in a reductional division. Moreover, the duration of the first meiotic M phase is usually prolonged when compared with mitotic M phases lasting 8 h in mouse oocytes. We investigated the spindle assembly pathway and its role in the progression of the first meiotic M phase in mouse oocytes. During the first 4 h, a bipolar spindle forms and the chromosomes congress near the equatorial plane of the spindle without stable kinetochore– microtubule end interactions. This late prometaphase spindle is then maintained for 4 h with chromosomes oscillating in the central region of the spindle. The kinetochore–microtubule end interactions are set up at the end of the first meiotic M phase (8 h after entry into M phase). This event allows the final alignment of the chromosomes and exit from metaphase. The continuous presence of the prometaphase spindle is not required for progression of the first meiotic M phase. Finally, the ability of kinetochores to interact with microtubules is acquired at the end of the first meiotic M phase and determines the timing of polar body extrusion. PMID:10402455

  14. Analysis of Yeast Sporulation Efficiency, Spore Viability, and Meiotic Recombination on Solid Medium.

    PubMed

    Börner, G Valentin; Cha, Rita S

    2015-11-01

    Under conditions of nutrient deprivation, yeast cells initiate a differentiation program in which meiosis is induced and spores are formed. During meiosis, one round of genome duplication is followed by two rounds of chromosome segregation (meiosis I and meiosis II) to generate four haploid nuclei. Meiotic recombination occurs during prophase I. During sporogenesis, each nucleus becomes surrounded by an individual spore wall, and all four haploid spores become contained as a tetrad within an ascus. Important insights into the meiotic function(s) of a gene of interest can be gained by observing the effects of gene mutations on spore viability and viability patterns among tetrads. Moreover, recombination frequencies among viable spores can reveal potential involvement of the gene during meiotic exchange between homologous chromosomes. Here, we describe methods for inducing spore formation on solid medium, determining spore viability, and measuring, via tetrad analysis, frequencies of crossing over and gene conversion as indicators of meiotic chromosome exchange. PMID:26527763

  15. Effect of the topoisomerase-II inhibitor etoposide on meiotic recombination in male mice.

    PubMed

    Russell, L B; Hunsicker, P R; Hack, A M; Ashley, T

    2000-01-24

    Unlike other chemicals that have been tested in mammalian germ cells, the type-II topoisomerase inhibitor etoposide exhibits significant mutagenicity in primary spermatocytes. Because this is the cell stage during which meiotic recombination normally occurs, and because topoisomerases play a role in recombination, we studied the effect of etoposide on crossing-over in male mice. Exposure to those meiotic prophase stages (probably early to mid-pachytene) during which specific-locus deletion mutations can be induced resulted in decreased crossing-over in the p-Tyr(c) interval of mouse chromosome 7. Accompanying cytological studies with fluorescent antibodies indicated that while there was no detectable effect on the number of recombination nodules (MLH1 foci), there were marked changes in the stage of appearance and localization of RAD51 and RPA proteins. These temporal and spatial protein patterns suggest the formation of multiple lesions in the DNA after MLH1 has already disappeared from spermatocytes. Since etoposide blocks religation of the cut made by type II topoisomerases, repair of DNA damage may result in rejoining of the original DNA strands, undoing the reciprocal exchange that had already occurred and resulting in reduced crossing-over despite a normal frequency of MLH1 foci. Crossing-over could conceivably be affected differentially in different chromosomal regions. If, however, the predominant action of etoposide is to decrease homologous meiotic recombination, the chemical could be expected to increase nondisjunction, an event associated with human genetic risk. Three periods in spermatogenesis respond to etoposide in different ways. Exposure of (a) late differentiating spermatogonia (and, possibly, preleptotene spermatocytes) results in cell death; (b) early- to mid-pachytene induces specific-locus deletions and crossover reduction; and, (c) late pachytene-through-diakinesis leads to genetically unbalanced conceptuses as a result of clastogenic damage.

  16. Connecting by breaking and repairing: mechanisms of DNA strand exchange in meiotic recombination.

    PubMed

    Sansam, Christopher L; Pezza, Roberto J

    2015-07-01

    During prophase of meiosis I, homologous chromosomes interact and undergo recombination. Successful completion of these processes is required in order for the homologous chromosomes to mount the meiotic spindle as a pair. The organization of the chromosomes into pairs ensures orderly segregation to opposite poles of the dividing cell, such that each gamete receives one copy of each chromosome. Chiasmata, the cytological manifestation of crossover products of recombination, physically connect the homologs in pairs, providing a linkage that facilitates their segregation. Consequently, mutations that reduce the level of recombination are invariably associated with increased errors in meiotic chromosome segregation. In this review, we focus on recent biochemical and genetic advances in elucidating the mechanisms of meiotic DNA strand exchange catalyzed by the Dmc1 protein. We also discuss the mode by which two recombination mediators, Hop2 and Mnd1, facilitate rate-limiting steps of DNA strand exchange catalyzed by Dmc1.

  17. RPA homologs and ssDNA processing during meiotic recombination.

    PubMed

    Ribeiro, Jonathan; Abby, Emilie; Livera, Gabriel; Martini, Emmanuelle

    2016-06-01

    Meiotic homologous recombination is a specialized process that involves homologous chromosome pairing and strand exchange to guarantee proper chromosome segregation and genetic diversity. The formation and repair of DNA double-strand breaks (DSBs) during meiotic recombination differs from those during mitotic recombination in that the homologous chromosome rather than the sister chromatid is the preferred repair template. The processing of single-stranded DNA (ssDNA) formed on intermediate recombination structures is central to driving the specific outcomes of DSB repair during meiosis. Replication protein A (RPA) is the main ssDNA-binding protein complex involved in DNA metabolism. However, the existence of RPA orthologs in plants and the recent discovery of meiosis specific with OB domains (MEIOB), a widely conserved meiosis-specific RPA1 paralog, strongly suggest that multiple RPA complexes evolved and specialized to subdivide their roles during DNA metabolism. Here we review ssDNA formation and maturation during mitotic and meiotic recombination underlying the meiotic specific features. We describe and discuss the existence and properties of MEIOB and multiple RPA subunits in plants and highlight how they can provide meiosis-specific fates to ssDNA processing during homologous recombination. Understanding the functions of these RPA homologs and how they interact with the canonical RPA subunits is of major interest in the fields of meiosis and DNA repair.

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

    PubMed

    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. PMID:25194162

  19. Sisters Unbound Is Required for Meiotic Centromeric Cohesion in Drosophila melanogaster

    PubMed Central

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

    2014-01-01

    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. PMID:25194162

  20. Multiple Meiotic Drive Systems in the DROSOPHILA MELANOGASTER Male

    PubMed Central

    Miklos, George L. Gabor; Yanders, Armon F.; Peacock, W. J.

    1972-01-01

    The behaviour of two "meiotic drive" systems, Segregation-Distorter (SD) and the sex chromosome sc4sc8 has been examined in the same meiocyte. It has been found that the two systems interact in a specific way. When the distorting effects of SD and sc4sc8 are against each other, there is no detectable interaction. Each system is apparently oblivious to the presence of the other, gametes being produced according to independence expectations. However when the affected chromosomes are at the same meiotic pole an interaction occurs; the survival probability of the gamete containing both distorted chromosomal products is increased, rather than being decreased by the combined action of two systems. PMID:4627460

  1. MEI4 – a central player in the regulation of meiotic DNA double-strand break formation in the mouse

    PubMed Central

    Kumar, Rajeev; Ghyselinck, Norbert; Ishiguro, Kei-ichiro; Watanabe, Yoshinori; Kouznetsova, Anna; Höög, Christer; Strong, Edward; Schimenti, John; Daniel, Katrin; Toth, Attila; de Massy, Bernard

    2015-01-01

    The formation of programmed DNA double-strand breaks (DSBs) at the beginning of meiotic prophase marks the initiation of meiotic recombination. Meiotic DSB formation is catalyzed by SPO11 and their repair takes place on meiotic chromosome axes. The evolutionarily conserved MEI4 protein is required for meiotic DSB formation and is localized on chromosome axes. Here, we show that HORMAD1, one of the meiotic chromosome axis components, is required for MEI4 localization. Importantly, the quantitative correlation between the level of axis-associated MEI4 and DSB formation suggests that axis-associated MEI4 could be a limiting factor for DSB formation. We also show that MEI1, REC8 and RAD21L are important for proper MEI4 localization. These findings on MEI4 dynamics during meiotic prophase suggest that the association of MEI4 to chromosome axes is required for DSB formation, and that the loss of this association upon DSB repair could contribute to turning off meiotic DSB formation. PMID:25795304

  2. Meiotic behaviour of evolutionary sex-autosome translocations in Bovidae.

    PubMed

    Vozdova, Miluse; Ruiz-Herrera, Aurora; Fernandez, Jonathan; Cernohorska, Halina; Frohlich, Jan; Sebestova, Hana; Kubickova, Svatava; Rubes, Jiri

    2016-09-01

    The recurrent occurrence of sex-autosome translocations during mammalian evolution suggests common mechanisms enabling a precise control of meiotic synapsis, recombination and inactivation of sex chromosomes. We used immunofluorescence and FISH to study the meiotic behaviour of sex chromosomes in six species of Bovidae with evolutionary sex-autosome translocations (Tragelaphus strepsiceros, Taurotragus oryx, Tragelaphus imberbis, Tragelaphus spekii, Gazella leptoceros and Nanger dama ruficollis). The autosomal regions of fused sex chromosomes showed normal synapsis with their homologous counterparts. Synapsis in the pseudoautosomal region (PAR) leads to the formation of characteristic bivalent (in T. imberbis and T. spekii with X;BTA13/Y;BTA13), trivalent (in T. strepsiceros and T. oryx with X/Y;BTA13 and G. leptoceros with X;BTA5/Y) and quadrivalent (in N. dama ruficollis with X;BTA5/Y;BTA16) structures at pachynema. However, when compared with other mammals, the number of pachynema lacking MLH1 foci in the PAR was relatively high, especially in T. imberbis and T. spekii, species with both sex chromosomes involved in sex autosome translocations. Meiotic transcriptional inactivation of the sex-autosome translocations assessed by γH2AX staining was restricted to their gonosomal regions. Despite intraspecies differences, the evolutionary fixation of sex-autosome translocations among bovids appears to involve general mechanisms ensuring sex chromosome pairing, synapsis, recombination and inactivation. PMID:27136937

  3. Meiotic behaviour of evolutionary sex-autosome translocations in Bovidae.

    PubMed

    Vozdova, Miluse; Ruiz-Herrera, Aurora; Fernandez, Jonathan; Cernohorska, Halina; Frohlich, Jan; Sebestova, Hana; Kubickova, Svatava; Rubes, Jiri

    2016-09-01

    The recurrent occurrence of sex-autosome translocations during mammalian evolution suggests common mechanisms enabling a precise control of meiotic synapsis, recombination and inactivation of sex chromosomes. We used immunofluorescence and FISH to study the meiotic behaviour of sex chromosomes in six species of Bovidae with evolutionary sex-autosome translocations (Tragelaphus strepsiceros, Taurotragus oryx, Tragelaphus imberbis, Tragelaphus spekii, Gazella leptoceros and Nanger dama ruficollis). The autosomal regions of fused sex chromosomes showed normal synapsis with their homologous counterparts. Synapsis in the pseudoautosomal region (PAR) leads to the formation of characteristic bivalent (in T. imberbis and T. spekii with X;BTA13/Y;BTA13), trivalent (in T. strepsiceros and T. oryx with X/Y;BTA13 and G. leptoceros with X;BTA5/Y) and quadrivalent (in N. dama ruficollis with X;BTA5/Y;BTA16) structures at pachynema. However, when compared with other mammals, the number of pachynema lacking MLH1 foci in the PAR was relatively high, especially in T. imberbis and T. spekii, species with both sex chromosomes involved in sex autosome translocations. Meiotic transcriptional inactivation of the sex-autosome translocations assessed by γH2AX staining was restricted to their gonosomal regions. Despite intraspecies differences, the evolutionary fixation of sex-autosome translocations among bovids appears to involve general mechanisms ensuring sex chromosome pairing, synapsis, recombination and inactivation.

  4. Heteroduplex DNA in Meiotic Recombination in Drosophila mei-9 Mutants

    PubMed Central

    Radford, Sarah J.; McMahan, Susan; Blanton, Hunter L.; Sekelsky, Jeff

    2007-01-01

    Meiotic recombination gives rise to crossovers, which are required in most organisms for the faithful segregation of homologous chromosomes during meiotic cell division. Characterization of crossover-defective mutants has contributed much to our understanding of the molecular mechanism of crossover formation. We report here a molecular analysis of recombination in a Drosophila melanogaster crossover-defective mutant, mei-9. In the absence of mei-9 activity, postmeiotic segregation associated with noncrossovers occurs at the expense of crossover products, suggesting that the underlying meiotic function for MEI-9 is in crossover formation rather than mismatch repair. In support of this, analysis of the arrangement of heteroduplex DNA in the postmeiotic segregation products reveals different patterns from those observed in Drosophila Msh6 mutants, which are mismatch-repair defective. This analysis also provides evidence that the double-strand break repair model applies to meiotic recombination in Drosophila. Our results support a model in which MEI-9 nicks Holliday junctions to generate crossovers during meiotic recombination, and, in the absence of MEI-9 activity, the double Holliday junction intermediate instead undergoes dissolution to generate noncrossover products in which heteroduplex is unrepaired. PMID:17339219

  5. ATM controls meiotic double-strand break formation

    PubMed Central

    Lange, Julian; Pan, Jing; Cole, Francesca; Thelen, Michael P.; Jasin, Maria; Keeney, Scott

    2011-01-01

    In many organisms, developmentally programmed double-strand breaks (DSBs) formed by the SPO11 transesterase initiate meiotic recombination, which promotes pairing and segregation of homologous chromosomes1. Because every chromosome must receive a minimum number of DSBs, attention has focused on factors that support DSB formation2. However, improperly repaired DSBs can cause meiotic arrest or mutation3,4, thus having too many DSBs is likely as deleterious as having too few. Only a small fraction of SPO11 protein ever makes a DSB in yeast or mouse5, and SPO11 and its accessory factors remain abundant long after most DSB formation ceases1, implying the existence of mechanisms that restrain SPO11 activity to limit DSB numbers. Here we report that the number of meiotic DSBs in mouse is controlled by ATM, a kinase activated by DNA damage to trigger checkpoint signaling and promote DSB repair. Levels of SPO11-oligonucleotide complexes, by-products of meiotic DSB formation, are elevated at least ten-fold in spermatocytes lacking ATM. Moreover, Atm mutation renders SPO11-oligonucleotide levels sensitive to genetic manipulations that modulate SPO11 protein levels. We propose that ATM restrains SPO11 via a negative feedback loop in which kinase activation by DSBs suppresses further DSB formation. Our findings explain previously puzzling phenotypes of Atm-null mice and provide a molecular basis for the gonadal dysgenesis observed in ataxia telangiectasia, the human syndrome caused by ATM deficiency. PMID:22002603

  6. Formation of interference-sensitive meiotic cross-overs requires sufficient DNA leading-strand elongation.

    PubMed

    Huang, Jiyue; Cheng, Zhihao; Wang, Cong; Hong, Yue; Su, Hang; Wang, Jun; Copenhaver, Gregory P; Ma, Hong; Wang, Yingxiang

    2015-10-01

    Meiosis halves diploid genomes to haploid and is essential for sexual reproduction in eukaryotes. Meiotic recombination ensures physical association of homologs and their subsequent accurate segregation and results in the redistribution of genetic variations among progeny. Most organisms have two classes of cross-overs (COs): interference-sensitive (type I) and -insensitive (type II) COs. DNA synthesis is essential for meiotic recombination, but whether DNA synthesis has a role in differentiating meiotic CO pathways is unknown. Here, we show that Arabidopsis POL2A, the homolog of the yeast DNA polymerase-ε (a leading-strand DNA polymerase), is required for plant fertility and meiosis. Mutations in POL2A cause reduced fertility and meiotic defects, including abnormal chromosome association, improper chromosome segregation, and fragmentation. Observation of prophase I cell distribution suggests that pol2a mutants likely delay progression of meiotic recombination. In addition, the residual COs in pol2a have reduced CO interference, and the double mutant of pol2a with mus81, which affects type II COs, displayed more severe defects than either single mutant, indicating that POL2A functions in the type I pathway. We hypothesize that sufficient leading-strand DNA elongation promotes formation of some type I COs. Given that meiotic recombination and DNA synthesis are conserved in divergent eukaryotes, this study and our previous study suggest a novel role for DNA synthesis in the differentiation of meiotic recombination pathways. PMID:26392549

  7. Formation of interference-sensitive meiotic cross-overs requires sufficient DNA leading-strand elongation

    PubMed Central

    Huang, Jiyue; Cheng, Zhihao; Wang, Cong; Hong, Yue; Su, Hang; Wang, Jun; Copenhaver, Gregory P.; Ma, Hong; Wang, Yingxiang

    2015-01-01

    Meiosis halves diploid genomes to haploid and is essential for sexual reproduction in eukaryotes. Meiotic recombination ensures physical association of homologs and their subsequent accurate segregation and results in the redistribution of genetic variations among progeny. Most organisms have two classes of cross-overs (COs): interference-sensitive (type I) and -insensitive (type II) COs. DNA synthesis is essential for meiotic recombination, but whether DNA synthesis has a role in differentiating meiotic CO pathways is unknown. Here, we show that Arabidopsis POL2A, the homolog of the yeast DNA polymerase-ε (a leading-strand DNA polymerase), is required for plant fertility and meiosis. Mutations in POL2A cause reduced fertility and meiotic defects, including abnormal chromosome association, improper chromosome segregation, and fragmentation. Observation of prophase I cell distribution suggests that pol2a mutants likely delay progression of meiotic recombination. In addition, the residual COs in pol2a have reduced CO interference, and the double mutant of pol2a with mus81, which affects type II COs, displayed more severe defects than either single mutant, indicating that POL2A functions in the type I pathway. We hypothesize that sufficient leading-strand DNA elongation promotes formation of some type I COs. Given that meiotic recombination and DNA synthesis are conserved in divergent eukaryotes, this study and our previous study suggest a novel role for DNA synthesis in the differentiation of meiotic recombination pathways. PMID:26392549

  8. Roles for mismatch repair family proteins in promoting meiotic crossing over.

    PubMed

    Manhart, Carol M; Alani, Eric

    2016-02-01

    The mismatch repair (MMR) family complexes Msh4-Msh5 and Mlh1-Mlh3 act with Exo1 and Sgs1-Top3-Rmi1 in a meiotic double strand break repair pathway that results in the asymmetric cleavage of double Holliday junctions (dHJ) to form crossovers. This review discusses how meiotic roles for Msh4-Msh5 and Mlh1-Mlh3 do not fit paradigms established for post-replicative MMR. We also outline models used to explain how these factors promote the formation of meiotic crossovers required for the accurate segregation of chromosome homologs during the Meiosis I division.

  9. A sex-ratio Meiotic Drive System in Drosophila simulans. II: An X-linked Distorter

    PubMed Central

    Tao, Yun; Araripe, Luciana; Kingan, Sarah B; Ke, Yeyan; Xiao, Hailian; Hartl, Daniel L

    2007-01-01

    The evolution of heteromorphic sex chromosomes creates a genetic condition favoring the invasion of sex-ratio meiotic drive elements, resulting in the biased transmission of one sex chromosome over the other, in violation of Mendel's first law. The molecular mechanisms of sex-ratio meiotic drive may therefore help us to understand the evolutionary forces shaping the meiotic behavior of the sex chromosomes. Here we characterize a sex-ratio distorter on the X chromosome (Dox) in Drosophila simulans by genetic and molecular means. Intriguingly, Dox has very limited coding capacity. It evolved from another X-linked gene, which also evolved de nova. Through retrotransposition, Dox also gave rise to an autosomal suppressor, not much yang (Nmy). An RNA interference mechanism seems to be involved in the suppression of the Dox distorter by the Nmy suppressor. Double mutant males of the genotype dox; nmy are normal for both sex-ratio and spermatogenesis. We postulate that recurrent bouts of sex-ratio meiotic drive and its subsequent suppression might underlie several common features observed in the heterogametic sex, including meiotic sex chromosome inactivation and achiasmy. PMID:17988173

  10. Meiotic failure in male mice lacking an X-linked factor

    PubMed Central

    Yang, Fang; Gell, Katarina; van der Heijden, Godfried W.; Eckardt, Sigrid; Leu, N. Adrian; Page, David C.; Benavente, Ricardo; Her, Chengtao; Höög, Christer; McLaughlin, K. John; Wang, Peijing Jeremy

    2008-01-01

    Meiotic silencing of sex chromosomes may cause their depletion of meiosis-specific genes during evolution. Here, we challenge this hypothesis by reporting the identification of TEX11 as the first X-encoded meiosis-specific factor in mice. TEX11 forms discrete foci on synapsed regions of meiotic chromosomes and appears to be a novel constituent of meiotic nodules involved in recombination. Loss of TEX11 function causes chromosomal asynapsis and reduced crossover formation, leading to elimination of spermatocytes, respectively, at the pachytene and anaphase I stages. Specifically, TEX11-deficient spermatocytes with asynapsed autosomes undergo apoptosis at the pachytene stage, while those with only asynapsed sex chromosomes progress. However, cells that survive the pachytene stage display chromosome nondisjunction at the first meiotic division, resulting in cell death and male infertility. TEX11 interacts with SYCP2, which is an integral component of the synaptonemal complex lateral elements. Thus, TEX11 promotes initiation and/or maintenance of synapsis and formation of crossovers, and may provide a physical link between these two meiotic processes. PMID:18316482

  11. Meiotic failure in male mice lacking an X-linked factor.

    PubMed

    Yang, Fang; Gell, Katarina; van der Heijden, Godfried W; Eckardt, Sigrid; Leu, N Adrian; Page, David C; Benavente, Ricardo; Her, Chengtao; Höög, Christer; McLaughlin, K John; Wang, Peijing Jeremy

    2008-03-01

    Meiotic silencing of sex chromosomes may cause their depletion of meiosis-specific genes during evolution. Here, we challenge this hypothesis by reporting the identification of TEX11 as the first X-encoded meiosis-specific factor in mice. TEX11 forms discrete foci on synapsed regions of meiotic chromosomes and appears to be a novel constituent of meiotic nodules involved in recombination. Loss of TEX11 function causes chromosomal asynapsis and reduced crossover formation, leading to elimination of spermatocytes, respectively, at the pachytene and anaphase I stages. Specifically, TEX11-deficient spermatocytes with asynapsed autosomes undergo apoptosis at the pachytene stage, while those with only asynapsed sex chromosomes progress. However, cells that survive the pachytene stage display chromosome nondisjunction at the first meiotic division, resulting in cell death and male infertility. TEX11 interacts with SYCP2, which is an integral component of the synaptonemal complex lateral elements. Thus, TEX11 promotes initiation and/or maintenance of synapsis and formation of crossovers, and may provide a physical link between these two meiotic processes.

  12. Cohesin in determining chromosome architecture

    SciTech Connect

    Haering, Christian H.; Jessberger, Rolf

    2012-07-15

    Cells use ring-like structured protein complexes for various tasks in DNA dynamics. The tripartite cohesin ring is particularly suited to determine chromosome architecture, for it is large and dynamic, may acquire different forms, and is involved in several distinct nuclear processes. This review focuses on cohesin's role in structuring chromosomes during mitotic and meiotic cell divisions and during interphase.

  13. Contribution of Structural Chromosome Mutants to the Study of Meiosis in Plants.

    PubMed

    Naranjo, Tomás

    2015-01-01

    Dissection of the molecular mechanisms underlying the transition through the complex events of the meiotic process requires the use of gene mutants or RNAi-mediated gene silencing. A considerable number of meiotic mutants have been isolated in plant species such as Arabidopsis thaliana, maize or rice. However, structural chromosome mutants are also important for the identification of the role developed by different chromosome domains in the meiotic process. This review summarizes the contribution of studies carried out in plants using structural chromosome variations. Meiotic events concerning the search of the homologous partner, the control of number and distribution of chiasmata, the mechanism of pairing correction, and chromosome segregation are considered. PMID:26658116

  14. Meiotic recombination errors, the origin of sperm aneuploidy and clinical recommendations.

    PubMed

    Tempest, Helen G

    2011-02-01

    Since the early 1990s male infertility has successfully been treated by intracytoplasmic sperm injection (ICSI), nevertheless concerns have been raised regarding the genetic risk of ICSI. Chromosome aneuploidy (the presence of extra or missing chromosomes) is the leading cause of pregnancy loss and mental retardation in humans. While the majority of chromosome aneuploidies are maternal in origin, the paternal contribution to aneuploidy is clinically relevant particularly for the sex chromosomes. Given that it is difficult to study female gametes investigations are predominantly conducted in male meiotic recombination and sperm aneuploidy. Research suggests that infertile men have increased levels of sperm aneuploidy and that this is likely due to increased errors in meiotic recombination and chromosome synapsis within these individuals. It is perhaps counterintuitive but there appears to be no selection against chromosomally aneuploid sperm at fertilization. In fact the frequency of aneuploidy in sperm appears to be mirrored in conceptions. Given this information this review will cover our current understanding of errors in meiotic recombination and chromosome synapsis and how these may contribute to increased sperm aneuploidy. Frequencies of sperm aneuploidy in infertile men and individuals with constitutional karyotypic abnormalities are reviewed, and based on these findings, indications for clinical testing of sperm aneuploidy are discussed. In addition, the application of single nucleotide arrays for the analysis of meiotic recombination and identification of parental origin of aneuploidy are considered.

  15. Meiotic recombination errors, the origin of sperm aneuploidy and clinical recommendations.

    PubMed

    Tempest, Helen G

    2011-02-01

    Since the early 1990s male infertility has successfully been treated by intracytoplasmic sperm injection (ICSI), nevertheless concerns have been raised regarding the genetic risk of ICSI. Chromosome aneuploidy (the presence of extra or missing chromosomes) is the leading cause of pregnancy loss and mental retardation in humans. While the majority of chromosome aneuploidies are maternal in origin, the paternal contribution to aneuploidy is clinically relevant particularly for the sex chromosomes. Given that it is difficult to study female gametes investigations are predominantly conducted in male meiotic recombination and sperm aneuploidy. Research suggests that infertile men have increased levels of sperm aneuploidy and that this is likely due to increased errors in meiotic recombination and chromosome synapsis within these individuals. It is perhaps counterintuitive but there appears to be no selection against chromosomally aneuploid sperm at fertilization. In fact the frequency of aneuploidy in sperm appears to be mirrored in conceptions. Given this information this review will cover our current understanding of errors in meiotic recombination and chromosome synapsis and how these may contribute to increased sperm aneuploidy. Frequencies of sperm aneuploidy in infertile men and individuals with constitutional karyotypic abnormalities are reviewed, and based on these findings, indications for clinical testing of sperm aneuploidy are discussed. In addition, the application of single nucleotide arrays for the analysis of meiotic recombination and identification of parental origin of aneuploidy are considered. PMID:21204593

  16. REC-1 and HIM-5 distribute meiotic crossovers and function redundantly in meiotic double-strand break formation in Caenorhabditis elegans.

    PubMed

    Chung, George; Rose, Ann M; Petalcorin, Mark I R; Martin, Julie S; Kessler, Zebulin; Sanchez-Pulido, Luis; Ponting, Chris P; Yanowitz, Judith L; Boulton, Simon J

    2015-09-15

    The Caenorhabditis elegans gene rec-1 was the first genetic locus identified in metazoa to affect the distribution of meiotic crossovers along the chromosome. We report that rec-1 encodes a distant paralog of HIM-5, which was discovered by whole-genome sequencing and confirmed by multiple genome-edited alleles. REC-1 is phosphorylated by cyclin-dependent kinase (CDK) in vitro, and mutation of the CDK consensus sites in REC-1 compromises meiotic crossover distribution in vivo. Unexpectedly, rec-1; him-5 double mutants are synthetic-lethal due to a defect in meiotic double-strand break formation. Thus, we uncovered an unexpected robustness to meiotic DSB formation and crossover positioning that is executed by HIM-5 and REC-1 and regulated by phosphorylation.

  17. REC-1 and HIM-5 distribute meiotic crossovers and function redundantly in meiotic double-strand break formation in Caenorhabditis elegans

    PubMed Central

    Chung, George; Rose, Ann M.; Petalcorin, Mark I.R.; Martin, Julie S.; Kessler, Zebulin; Sanchez-Pulido, Luis; Ponting, Chris P.; Yanowitz, Judith L.; Boulton, Simon J.

    2015-01-01

    The Caenorhabditis elegans gene rec-1 was the first genetic locus identified in metazoa to affect the distribution of meiotic crossovers along the chromosome. We report that rec-1 encodes a distant paralog of HIM-5, which was discovered by whole-genome sequencing and confirmed by multiple genome-edited alleles. REC-1 is phosphorylated by cyclin-dependent kinase (CDK) in vitro, and mutation of the CDK consensus sites in REC-1 compromises meiotic crossover distribution in vivo. Unexpectedly, rec-1; him-5 double mutants are synthetic-lethal due to a defect in meiotic double-strand break formation. Thus, we uncovered an unexpected robustness to meiotic DSB formation and crossover positioning that is executed by HIM-5 and REC-1 and regulated by phosphorylation. PMID:26385965

  18. Specific features in linear and spatial organizations of pericentromeric heterochromatin regions in polytene chromosomes of the closely related species Drosophila virilis and D. kanekoi (Diptera: Drosophilidae).

    PubMed

    Wasserlauf, Irina; Usov, Konstantin; Artemov, Gleb; Anan'ina, Tatyana; Stegniy, Vladimir

    2015-06-01

    Heterochromatin plays an important role in the spatial arrangement and evolution of the eukaryotic genetic apparatus. The closely related species Drosophila virilis (phyla virilis) and D. kanekoi (phyla montana) differ in the amount of heterochromatin along the chromosomes as well as by the presence of the metacentric chromosome 2, which emerged as a result of a pericentric inversion during speciation, in the D. kanekoi karyotype. The purpose of this study was to establish if chromosome rearrangements have any influence on the linear redistribution of centromeric heterochromatin in polytene chromosomes and the spatial organization of chromosomes in the nuclei of nurse cell. We have microdissected the chromocenter of D. virilis salivary gland polytene chromosomes; obtained a DNA library of this region (DvirIII); and hybridized (FISH) DvirIII to the salivary gland and nurse cell polytene chromosomes of D. virilis and D. kanekoi. We demonstrated that DvirIII localizes to the pericentromeric heterochromatin regions of all chromosomes and peritelomeric region of chromosome 5 in both species. Unlike D. virilis, the DvirIII signal in D. kanekoi chromosomes is detectable in the telomeric region of chromosome 2. We have also conducted a 3D FISH of DvirIII probe to the D. virilis and D. kanekoi nurse cell chromosomes. In particular, the DvirIII signal in D. virilis was observed in the local chromocenter at one pole of the nucleus, while the signal belonging to the telomeric region of chromosome 5 was detectable at the other pole. In contrast, in D. kanekoi there exist two separate DvirIII-positive regions. One of these regions belongs to the pericentromeric region of chromosome 2 and the other, to pericentromeric regions of the remaining chromosomes. These results suggest that chromosome rearrangements play an important role in the redistribution of heterochromatin DNA sequences in the genome, representing a speciation mechanism, which, in general, could also affect the

  19. A cohesin-based structural platform supporting homologous chromosome pairing in meiosis.

    PubMed

    Ding, Da-Qiao; Haraguchi, Tokuko; Hiraoka, Yasushi

    2016-08-01

    The pairing and recombination of homologous chromosomes during the meiotic prophase is necessary for the accurate segregation of chromosomes in meiosis. However, the mechanism by which homologous chromosomes achieve this pairing has remained an open question. Meiotic cohesins have been shown to affect chromatin compaction; however, the impact of meiotic cohesins on homologous pairing and the fine structures of cohesion-based chromatin remain to be determined. A recent report using live-cell imaging and super-resolution microscopy demonstrated that the lack of meiotic cohesins alters the chromosome axis structures and impairs the pairing of homologous chromosomes. These results suggest that meiotic cohesin-based chromosome axis structures are crucial for the pairing of homologous chromosomes.

  20. Abnormal chromosome behavior in human oocytes which remained unfertilized during human in vitro fertilization.

    PubMed

    Spielmann, H; Krüger, C; Stauber, M; Vogel, R

    1985-09-01

    Chromosomal abnormalities and abnormal embryonic development have previously been observed after human in vitro fertilization (IVF). Chromosomal abnormalities may arise not only after fertilization but even earlier during meiotic maturation of human oocytes in culture. Since chromosomal analysis is simple in oocytes during meiotic maturation, the chromosomal status was analyzed in oocytes which remained unfertilized in a human in vitro fertilization program. In 50 fertilization attempts the chromosomes of 62 unfertilized oocytes could be analyzed; 45 of them were in the process of meiotic maturation. In three oocytes two small polar bodies were observed 16-18 hr after insemination in the absence of fertilization. In one oocyte abnormal chromosome behavior was found during the first meiotic division, and in four oocytes during metaphase of the second meiotic division. These data suggest that chromosomal analysis of unfertilized oocytes in human IVF may improve the understanding human oocyte maturation and fertilization.

  1. OsHUS1 facilitates accurate meiotic recombination in rice.

    PubMed

    Che, Lixiao; Wang, Kejian; Tang, Ding; Liu, Qiaoquan; Chen, Xiaojun; Li, Yafei; Hu, Qing; Shen, Yi; Yu, Hengxiu; Gu, Minghong; Cheng, Zhukuan

    2014-06-01

    Meiotic recombination normally takes place between allelic sequences on homologs. This process can also occur between non-allelic homologous sequences. Such ectopic interaction events can lead to chromosome rearrangements and are normally avoided. However, much remains unknown about how these ectopic interaction events are sensed and eliminated. In this study, using a screen in rice, we characterized a homolog of HUS1 and explored its function in meiotic recombination. In Oshus1 mutants, in conjunction with nearly normal homologous pairing and synapsis, vigorous, aberrant ectopic interactions occurred between nonhomologous chromosomes, leading to multivalent formation and subsequent chromosome fragmentation. These ectopic interactions relied on programmed meiotic double strand breaks and were formed in a manner independent of the OsMER3-mediated interference-sensitive crossover pathway. Although early homologous recombination events occurred normally, the number of interference-sensitive crossovers was reduced in the absence of OsHUS1. Together, our results indicate that OsHUS1 might be involved in regulating ectopic interactions during meiosis, probably by forming the canonical RAD9-RAD1-HUS1 (9-1-1) complex. PMID:24901798

  2. Sex-ratio meiotic drive and Y-linked resistance in Drosophila affinis.

    PubMed

    Unckless, Robert L; Larracuente, Amanda M; Clark, Andrew G

    2015-03-01

    Genetic elements that cheat Mendelian segregation by biasing transmission in their favor gain a significant fitness benefit. Several examples of sex-ratio meiotic drive, where one sex chromosome biases its own transmission at the cost of the opposite sex chromosome, exist in animals and plants. While the distorting sex chromosome gains a significant advantage by biasing sex ratio, the autosomes, and especially the opposite sex chromosome, experience strong selection to resist this transmission bias. In most well-studied sex-ratio meiotic drive systems, autosomal and/or Y-linked resistance has been identified. We specifically surveyed for Y-linked resistance to sex-ratio meiotic drive in Drosophila affinis by scoring the sex ratio of offspring sired by males with a driving X and one of several Y chromosomes. Two distinct types of resistance were identified: a restoration to 50/50 sex ratios and a complete reversal of sex ratio to all sons. We confirmed that fathers siring all sons lacked a Y chromosome, consistent with previously published work. Considerable variation in Y-chromosome morphology exists in D. affinis, but we showed that morphology does not appear to be associated with resistance to sex-ratio meiotic drive. We then used two X chromosomes (driving and standard) and three Y chromosomes (susceptible, resistant, and lacking) to examine fertility effects of all possible combinations. We find that both the driving X and resistant and lacking Y have significant fertility defects manifested in microscopic examination of testes and a 48-hr sperm depletion assay. Maintenance of variation in this sex-ratio meiotic drive system, including both the X-linked distorter and the Y-resistant effects, appear to be mediated by a complex interaction between fertility fitness and transmission dynamics.

  3. Spatial arrangement of chromosomes in oocytes and spermatocytes of malaria mosquitoes

    SciTech Connect

    Stegnii, V.N.; Vasserlauf, I.E.

    1995-02-01

    It is shown that prophase chromosomes of oocytes in Anopheles messeae ovaries do not form local chromocenters, unlike spermatocytes, in which chromosomes fuse in a joint centromeric assembly. This fact reflects the dynamic nature of the system of chromocenter formation in generative tissues. During analysis of interspecific hybrids F{sub 1} A. maculipennis x A. subalpinus, no conjunction of homeologous chromosomes was observed, and the latter remained separated from one another. 6 refs., 1 fig.

  4. Volume increase and spatial shifts of chromosome territories in nuclei of radiation-induced polyploidizing tumour cells.

    PubMed

    Schwarz-Finsterle, Jutta; Scherthan, Harry; Huna, Anda; González, Paula; Mueller, Patrick; Schmitt, Eberhard; Erenpreisa, Jekaterina; Hausmann, Michael

    2013-08-30

    The exposure of tumour cells to high doses of ionizing radiation can induce endopolyploidization as an escape route from cell death. This strategy generally results in mitotic catastrophe during the first few days after irradiation. However, some cells escape mitotic catastrophe, polyploidize and attempt to undergo genome reduction and de-polyploidization in order to create new, viable para-diploid tumour cell sub-clones. In search for the consequences of ionizing radiation induced endopolyploidization, genome and chromosome architecture in nuclei of polyploid tumour cells, and sub-nuclei after division of bi- or multi-nucleated cells were investigated during 7 days following irradiation. Polyploidization was induced in p53-function deficient HeLa cells by exposure to 10Gy of X-irradiation. Chromosome territories #1, #4, #12 and centromeres of chromosomes #6, #10, #X were labelled by FISH and analysed for chromosome numbers, volumes and spatial distribution during 7 days post irradiation. The numbers of interphase chromosome territories or centromeres, respectively, the positions of the most peripherally and centrally located chromosome territories, and the territory volumes were compared to non-irradiated controls over this time course. Nuclei with three copies of several chromosomes (#1, #6, #10, #12, #X) were found in the irradiated as well as non-irradiated specimens. From day 2 to day 5 post irradiation, chromosome territories (#1, #4, #12) shifted towards the nuclear periphery and their volumes increased 16- to 25-fold. Consequently, chromosome territories returned towards the nuclear centre during day 6 and 7 post irradiation. In comparison to non-irradiated cells (∼500μm(3)), the nuclear volume of irradiated cells was increased 8-fold (to ∼4000μm(3)) at day 7 post irradiation. Additionally, smaller cell nuclei with an average volume of about ∼255μm(3) were detected on day 7. The data suggest a radiation-induced generation of large intra

  5. Two statistical tests for meiotic breakpoint analysis.

    PubMed Central

    Plaetke, R; Schachtel, G A

    1995-01-01

    Meiotic breakpoint analysis (BPA), a statistical method for ordering genetic markers, is increasing in importance as a method for building genetic maps of human chromosomes. Although BPA does not provide estimates of genetic distances between markers, it efficiently locates new markers on already defined dense maps, when likelihood analysis becomes cumbersome or the sample size is small. However, until now no assessments of statistical significance have been available for evaluating the possibility that the results of a BPA were produced by chance. In this paper, we propose two statistical tests to determine whether the size of a sample and its genetic information content are sufficient to distinguish between "no linkage" and "linkage" of a marker mapped by BPA to a certain region. Both tests are exact and should be conducted after a BPA has assigned the marker to an interval on the map. Applications of the new tests are demonstrated by three examples: (1) a synthetic data set, (2) a data set of five markers on human chromosome 8p, and (3) a data set of four markers on human chromosome 17q. PMID:7847387

  6. Nuclear Localization of PRDM9 and Its Role in Meiotic Chromatin Modifications and Homologous Synapsis

    PubMed Central

    Sun, Fengyun; Fujiwara, Yasuhiro; Reinholdt, Laura G.; Hu, Jianjun; Saxl, Ruth L.; Baker, Christopher L.; Petkov, Petko M.; Paigen, Kenneth; Handel, Mary Ann

    2015-01-01

    Developmental progress of germ cells through meiotic phases is closely tied to ongoing meiotic recombination. In mammals, recombination preferentially occurs in genomic regions known as hotspots; the protein that activates these hotspots is PRDM9, containing a genetically variable zinc-finger domain and a PR-SET domain with histone H3K4 trimethyltransferase activity. PRDM9 is required for fertility in mice, but little is known about its localization and developmental dynamics. Application of spermatogenic stage-specific markers demonstrates that PRDM9 accumulates in male germ-cell nuclei at pre-leptonema to early leptonema, but is no longer detectable in nuclei by late zygonema. By the pachytene stage, PRDM9-dependent histone H3K4 trimethyl marks on hotspots also disappear. PRDM9 localizes to nuclei concurrently with the deposition of meiotic cohesin complexes, but is not required for incorporation of cohesin complex proteins into chromosomal axial elements, or accumulation of normal numbers of RAD51 foci on meiotic chromatin by late zygonema. Germ cells lacking PRDM9 exhibit inefficient homology recognition and synapsis, with aberrant repair of meiotic DNA double-strand breaks and transcriptional abnormalities characteristic of meiotic silencing of unsynapsed chromatin. Together, these results on the developmental time course for nuclear localization of PRDM9 establish its direct window of function, and demonstrate the independence of chromosome axial element formation from the concurrent PRDM9-mediated activation of recombination hotspots. PMID:25894966

  7. MEIOTIC F-BOX Is Essential for Male Meiotic DNA Double-Strand Break Repair in Rice[OPEN

    PubMed Central

    Wang, Chong; Yu, Junping; Zong, Jie; Lu, Pingli

    2016-01-01

    F-box proteins constitute a large superfamily in plants and play important roles in controlling many biological processes, but the roles of F-box proteins in male meiosis in plants remain unclear. Here, we identify the rice (Oryza sativa) F-box gene MEIOTIC F-BOX (MOF), which is essential for male meiotic progression. MOF belongs to the FBX subfamily and is predominantly active during leptotene to pachytene of prophase I. mof meiocytes display disrupted telomere bouquet formation, impaired pairing and synapsis of homologous chromosomes, and arrested meiocytes at late prophase I, followed by apoptosis. Although normal, programmed double-stranded DNA breaks (DSBs) form in mof mutants, foci of the phosphorylated histone variant γH2AX, a marker for DSBs, persist in the mutant, indicating that many of the DSBs remained unrepaired. The recruitment of Completion of meiosis I (COM1) and Radiation sensitive51C (RAD51C) to DSBs is severely compromised in mutant meiocytes, indicating that MOF is crucial for DSB end-processing and repair. Further analyses showed that MOF could physically interact with the rice SKP1-like Protein1 (OSK1), indicating that MOF functions as a component of the SCF E3 ligase to regulate meiotic progression in rice. Thus, this study reveals the essential role of an F-box protein in plant meiosis and provides helpful information for elucidating the roles of the ubiquitin proteasome system in plant meiotic progression. PMID:27436711

  8. MEIOTIC F-BOX Is Essential for Male Meiotic DNA Double-Strand Break Repair in Rice.

    PubMed

    He, Yi; Wang, Chong; Higgins, James D; Yu, Junping; Zong, Jie; Lu, Pingli; Zhang, Dabing; Liang, Wanqi

    2016-08-01

    F-box proteins constitute a large superfamily in plants and play important roles in controlling many biological processes, but the roles of F-box proteins in male meiosis in plants remain unclear. Here, we identify the rice (Oryza sativa) F-box gene MEIOTIC F-BOX (MOF), which is essential for male meiotic progression. MOF belongs to the FBX subfamily and is predominantly active during leptotene to pachytene of prophase I. mof meiocytes display disrupted telomere bouquet formation, impaired pairing and synapsis of homologous chromosomes, and arrested meiocytes at late prophase I, followed by apoptosis. Although normal, programmed double-stranded DNA breaks (DSBs) form in mof mutants, foci of the phosphorylated histone variant γH2AX, a marker for DSBs, persist in the mutant, indicating that many of the DSBs remained unrepaired. The recruitment of Completion of meiosis I (COM1) and Radiation sensitive51C (RAD51C) to DSBs is severely compromised in mutant meiocytes, indicating that MOF is crucial for DSB end-processing and repair. Further analyses showed that MOF could physically interact with the rice SKP1-like Protein1 (OSK1), indicating that MOF functions as a component of the SCF E3 ligase to regulate meiotic progression in rice. Thus, this study reveals the essential role of an F-box protein in plant meiosis and provides helpful information for elucidating the roles of the ubiquitin proteasome system in plant meiotic progression. PMID:27436711

  9. Spatial coordination between chromosomes and cell division proteins in Escherichia coli.

    PubMed

    Männik, Jaan; Bailey, Matthew W

    2015-01-01

    To successfully propagate, cells need to coordinate chromosomal replication and segregation with cell division to prevent formation of DNA-less cells and cells with damaged DNA. Here, we review molecular systems in Escherichia coli that are known to be involved in positioning the divisome and chromosome relative to each other. Interestingly, this well-studied micro-organism has several partially redundant mechanisms to achieve this task; none of which are essential. Some of these systems determine the localization of the divisome relative to chromosomes such as SlmA-dependent nucleoid occlusion, some localize the chromosome relative to the divisome such as DNA translocation by FtsK, and some are likely to act on both systems such as the Min system and newly described Ter linkage. Moreover, there is evidence that E. coli harbors other divisome-chromosome coordination systems in addition to those known. The review also discusses the minimal requirements of coordination between chromosomes and cell division proteins needed for cell viability. Arguments are presented that cells can propagate without any dedicated coordination between their chromosomes and cell division machinery at the expense of lowered fitness. PMID:25926826

  10. Spatial coordination between chromosomes and cell division proteins in Escherichia coli

    PubMed Central

    Männik, Jaan; Bailey, Matthew W.

    2015-01-01

    To successfully propagate, cells need to coordinate chromosomal replication and segregation with cell division to prevent formation of DNA-less cells and cells with damaged DNA. Here, we review molecular systems in Escherichia coli that are known to be involved in positioning the divisome and chromosome relative to each other. Interestingly, this well-studied micro-organism has several partially redundant mechanisms to achieve this task; none of which are essential. Some of these systems determine the localization of the divisome relative to chromosomes such as SlmA-dependent nucleoid occlusion, some localize the chromosome relative to the divisome such as DNA translocation by FtsK, and some are likely to act on both systems such as the Min system and newly described Ter linkage. Moreover, there is evidence that E. coli harbors other divisome-chromosome coordination systems in addition to those known. The review also discusses the minimal requirements of coordination between chromosomes and cell division proteins needed for cell viability. Arguments are presented that cells can propagate without any dedicated coordination between their chromosomes and cell division machinery at the expense of lowered fitness. PMID:25926826

  11. Alternative Induction of Meiotic Recombination From Single-Base Lesions of DNA Deaminases

    PubMed Central

    Pauklin, Siim; Burkert, Julia S.; Martin, Julie; Osman, Fekret; Weller, Sandra; Boulton, Simon J.; Whitby, Matthew C.; Petersen-Mahrt, Svend K.

    2009-01-01

    Meiotic recombination enhances genetic diversity as well as ensures proper segregation of homologous chromosomes, requiring Spo11-initiated double-strand breaks (DSBs). DNA deaminases act on regions of single-stranded DNA and deaminate cytosine to uracil (dU). In the immunoglobulin locus, this lesion will initiate point mutations, gene conversion, and DNA recombination. To begin to delineate the effect of induced base lesions on meiosis, we analyzed the effect of expressing DNA deaminases (activation-induced deaminase, AID, and APOBEC3C) in germ cells. We show that meiotic dU:dG lesions can partially rescue a spo11Δ phenotype in yeast and worm. In rec12 Schizosaccharomyces pombe, AID expression increased proper chromosome segregation, thereby enhancing spore viability, and induced low-frequency meiotic crossovers. Expression of AID in the germ cells of Caenorhabditis elegans spo-11 induced meiotic RAD-51 foci formation and chromosomal bivalency and segregation, as well as an increase in viability. RNAi experiments showed that this rescue was dependent on uracil DNA-glycosylase (Ung). Furthermore, unlike ionizing radiation-induced spo-11 rescue, AID expression did not induce large numbers of DSBs during the rescue. This suggests that the products of DNA deamination and base excision repair, such as uracil, an abasic site, or a single-stranded nick, are sufficient to initiate and alter meiotic recombination in uni- and multicellular organisms. PMID:19237686

  12. Temporal and spatial regulation of translation in the mammalian oocyte via the mTOR-eIF4F pathway.

    PubMed

    Susor, Andrej; Jansova, Denisa; Cerna, Renata; Danylevska, Anna; Anger, Martin; Toralova, Tereza; Malik, Radek; Supolikova, Jaroslava; Cook, Matthew S; Oh, Jeong Su; Kubelka, Michal

    2015-01-28

    The fully grown mammalian oocyte is transcriptionally quiescent and utilizes only transcripts synthesized and stored during early development. However, we find that an abundant RNA population is retained in the oocyte nucleus and contains specific mRNAs important for meiotic progression. Here we show that during the first meiotic division, shortly after nuclear envelope breakdown, translational hotspots develop in the chromosomal area and in a region that was previously surrounded the nucleus. These distinct translational hotspots are separated by endoplasmic reticulum and Lamin, and disappear following polar body extrusion. Chromosomal translational hotspots are controlled by the activity of the mTOR-eIF4F pathway. Here we reveal a mechanism that-following the resumption of meiosis-controls the temporal and spatial translation of a specific set of transcripts required for normal spindle assembly, chromosome alignment and segregation.

  13. Temporal and spatial regulation of translation in the mammalian oocyte via the mTOR–eIF4F pathway

    PubMed Central

    Susor, Andrej; Jansova, Denisa; Cerna, Renata; Danylevska, Anna; Anger, Martin; Toralova, Tereza; Malik, Radek; Supolikova, Jaroslava; Cook, Matthew S.; Oh, Jeong Su; Kubelka, Michal

    2015-01-01

    The fully grown mammalian oocyte is transcriptionally quiescent and utilizes only transcripts synthesized and stored during early development. However, we find that an abundant RNA population is retained in the oocyte nucleus and contains specific mRNAs important for meiotic progression. Here we show that during the first meiotic division, shortly after nuclear envelope breakdown, translational hotspots develop in the chromosomal area and in a region that was previously surrounded the nucleus. These distinct translational hotspots are separated by endoplasmic reticulum and Lamin, and disappear following polar body extrusion. Chromosomal translational hotspots are controlled by the activity of the mTOR–eIF4F pathway. Here we reveal a mechanism that—following the resumption of meiosis—controls the temporal and spatial translation of a specific set of transcripts required for normal spindle assembly, chromosome alignment and segregation. PMID:25629602

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

    PubMed Central

    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. PMID:25674669

  15. [Value of a meiotic study of male sterility].

    PubMed

    Carré-Pigeon, F; Teyssier, J R; Gaillard, D; Bajolle, F; Melin, M C

    1987-01-01

    Both in men where the somatic karyotype is abnormal as well as in cases where it is normal, it is worth while studying meiosis in the male. The picture of meiosis has been studied in the main from testicular biopsies and also partly from spermatic line cells found in sperm. Studying the haploid portion of the male pronucleus using the hamster test reflects the process of meiosis. In this way it has been possible to individualise different pathological entities such as asynapsis or desynapsis, alterations in synaptic complexes, the presence of several nucleoli or micronucleoli in the pachytene stage, hyper or hypo polidies, the presence of univalents and the breakdown of bivalents, oligochiasmatasis, chain or ring pictures or early desynapsis of the sexual vesicle in the diacinesis and in the first metaphase stage. Aneuploidies have been found in the second metaphase stage or when carrying out chromosome analysis on the male pronucleus. The abnormalities in the number of chromosomes which are found with the formula 47,XXY, may be due to faults in spermatogenesis, but in the case of the double Y in 47,XYY the extra Y will rarely be found during meiotic divisions. The Robertsonian translocations causing abnormalities in structure are due to the formation of trivalents whereas reciprocal translocations give rise to the idea of quadrivalent pictures mainly associated with faults in spermatogenesis. Finally, autosomal chromosome translocations seem to have more severe meiotic repercussions, particularly in cases where the inactive autosomal X chromosome is involved. Even where a somatic karyotype is normal in a fertile subject that does not mean that there is no meiotic abnormality present, because 8-10% of the cells that were studied showed such an abnormality.

  16. Evidence for meiotic drive at the myotonic dystrophy locus

    SciTech Connect

    Shaw, A.M.; Barnetson, R.A.; Phillips, M.F.

    1994-09-01

    Myotonic dystrophy (DM), an autosomal dominant disorder, is the most common form of adult muscular dystrophy, affecting at least 1 in 8000 of the population. It is a multisystemic disorder, primarily characterized by myotonia, muscle wasting and cataract. The molecular basis of DM is an expanded CTG repeat located within the 3{prime} untranslated region of a putative serine-threonine protein kinase on chromosome 19q13.3. DM exhibits anticipation, that is, with successive generations there is increasing disease severity and earlier age of onset. This mechanism and the fact that the origin of the disease has been attributed to one or a small number of founder chromosomes suggests that, in time, DM should die out. Meiotic drive has been described as a way in which certain alleles are transmitted to succeeding generations in preference to others: preferential transmission of large CTG alleles may account for their continued existence in the gene pool. There is evidence that a CTG allele with > 19 repeats may gradually increase in repeat number over many generations until it is sufficiently large to give a DM phenotype. We report a study of 495 transmissions from individuals heterozygous for the CTG repeat and with repeat numbers within the normal range (5-30). Alleles were simply classified as large or small relative to the other allele in an individual. Of 242 male meioses, 126 transmissions from parent to child were of the larger allele to their offspring (57.7%, p=0.014). This shows that there is strong evidence for meiotic drive favoring the transmission of the larger DM allele in unaffected individuals. Contrary to a previous report of meiotic drive in the male, we have shown that females preferentially transmit the larger DM allele. Taken together, the data suggest the occurrence of meiotic drive in both males and females in this locus.

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

    PubMed Central

    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

  18. Aging predisposes oocytes to meiotic nondisjunction when the cohesin subunit SMC1 is reduced.

    PubMed

    Subramanian, Vijayalakshmi V; Bickel, Sharon E

    2008-11-01

    In humans, meiotic chromosome segregation errors increase dramatically as women age, but the molecular defects responsible are largely unknown. Cohesion along the arms of meiotic sister chromatids provides an evolutionarily conserved mechanism to keep recombinant chromosomes associated until anaphase I. One attractive hypothesis to explain age-dependent nondisjunction (NDJ) is that loss of cohesion over time causes recombinant homologues to dissociate prematurely and segregate randomly during the first meiotic division. Using Drosophila as a model system, we have tested this hypothesis and observe a significant increase in meiosis I NDJ in experimentally aged Drosophila oocytes when the cohesin protein SMC1 is reduced. Our finding that missegregation of recombinant homologues increases with age supports the model that chiasmata are destabilized by gradual loss of cohesion over time. Moreover, the stage at which Drosophila oocytes are most vulnerable to age-related defects is analogous to that at which human oocytes remain arrested for decades. Our data provide the first demonstration in any organism that, when meiotic cohesion begins intact, the aging process can weaken it sufficiently and cause missegregation of recombinant chromosomes. One major advantage of these studies is that we have reduced but not eliminated the SMC1 subunit. Therefore, we have been able to investigate how aging affects normal meiotic cohesion. Our findings that recombinant chromosomes are at highest risk for loss of chiasmata during diplotene argue that human oocytes are most vulnerable to age-induced loss of meiotic cohesion at the stage at which they remain arrested for several years. PMID:19008956

  19. Aging Predisposes Oocytes to Meiotic Nondisjunction When the Cohesin Subunit SMC1 Is Reduced

    PubMed Central

    Subramanian, Vijayalakshmi V.; Bickel, Sharon E.

    2008-01-01

    In humans, meiotic chromosome segregation errors increase dramatically as women age, but the molecular defects responsible are largely unknown. Cohesion along the arms of meiotic sister chromatids provides an evolutionarily conserved mechanism to keep recombinant chromosomes associated until anaphase I. One attractive hypothesis to explain age-dependent nondisjunction (NDJ) is that loss of cohesion over time causes recombinant homologues to dissociate prematurely and segregate randomly during the first meiotic division. Using Drosophila as a model system, we have tested this hypothesis and observe a significant increase in meiosis I NDJ in experimentally aged Drosophila oocytes when the cohesin protein SMC1 is reduced. Our finding that missegregation of recombinant homologues increases with age supports the model that chiasmata are destabilized by gradual loss of cohesion over time. Moreover, the stage at which Drosophila oocytes are most vulnerable to age-related defects is analogous to that at which human oocytes remain arrested for decades. Our data provide the first demonstration in any organism that, when meiotic cohesion begins intact, the aging process can weaken it sufficiently and cause missegregation of recombinant chromosomes. One major advantage of these studies is that we have reduced but not eliminated the SMC1 subunit. Therefore, we have been able to investigate how aging affects normal meiotic cohesion. Our findings that recombinant chromosomes are at highest risk for loss of chiasmata during diplotene argue that human oocytes are most vulnerable to age-induced loss of meiotic cohesion at the stage at which they remain arrested for several years. PMID:19008956

  20. Analysis of meiotic segregation, using single-sperm typing: Meiotic drive at the myotonic dystrophy locus

    SciTech Connect

    Leeflang, E.P.; Arnheim, N.; McPeek, M.S.

    1996-10-01

    Meiotic drive at the myotonic dystrophy (DM) locus has recently been suggested as being responsible for maintaining the frequency, in the human population, of DM chromosomes capable of expansion to the disease state. In order to test this hypothesis, we have studied samples of single sperm from three individuals heterozygous at the DM locus, each with one allele larger and one allele smaller than 19 CTG repeats. To guard against the possible problem of differential PCR amplification rates based on the lengths of the alleles, the sperm were also typed at another closely linked marker whose allele size was unrelated to the allele size at the DM locus. Using statistical models specifically designed to study single-sperm segregation data, we find no evidence of meiotic segregation distortion. The upper limit of the two-sided 95% confidence interval for the estimate of the common segregation probability for the three donors is at or below .515 for all models considered, and no statistically significant difference from .5 is detected in any of the models. This suggests that any greater amount of segregation distortion at the myotonic dystrophy locus must result from events following sperm ejaculation. The mathematical models developed make it possible to study segregation distortion with high resolution by using sperm-typing data from any locus. 26 refs., 1 fig., 8 tabs.

  1. Meiotic studies in some species of tribe Cichorieae (Asteraceae) from Western Himalayas.

    PubMed

    Gupta, Raghbir Chand; Goyal, Henna; Singh, Vijay; Goel, Rajesh Kumar

    2014-01-01

    The present paper deals with meiotic studies in 15 species belonging to 6 genera of the tribe Cichorieae from various localities of Western Himalayas. The chromosome number has been reported for the first time in Hieracium crocatum (2n = 10) and Lactuca lessertiana (2n = 2x = 16). Further, intraspecific variability has been reported for the first time in H. umbellatum (2n = 2x = 10 and 2n = 6x = 54), Tragopogon dubius (2n = 2x = 14 and 2n = 4x = 28), and T. gracilis (2n = 2x = 14). The chromosome report of 2n = 2x = 10 in Youngia tenuifolia is made for the first time in India. Maximum numbers of the populations show laggards, chromosome stickiness, and cytomixis from early prophase to telophase-II, leading to the formation of aneuploid cells or meiocytes with double chromosome number. Such meiotic abnormalities produce unreduced pollen grains and the reduced pollen viability. PMID:25489603

  2. Identification of novel Drosophila meiotic genes recovered in a P-element screen.

    PubMed Central

    Sekelsky, J J; McKim, K S; Messina, L; French, R L; Hurley, W D; Arbel, T; Chin, G M; Deneen, B; Force, S J; Hari, K L; Jang, J K; Laurençon, A C; Madden, L D; Matthies, H J; Milliken, D B; Page, S L; Ring, A D; Wayson, S M; Zimmerman, C C; Hawley, R S

    1999-01-01

    The segregation of homologous chromosomes from one another is the essence of meiosis. In many organisms, accurate segregation is ensured by the formation of chiasmata resulting from crossing over. Drosophila melanogaster females use this type of recombination-based system, but they also have mechanisms for segregating achiasmate chromosomes with high fidelity. We describe a P-element mutagenesis and screen in a sensitized genetic background to detect mutations that impair meiotic chromosome pairing, recombination, or segregation. Our screen identified two new recombination-deficient mutations: mei-P22, which fully eliminates meiotic recombination, and mei-P26, which decreases meiotic exchange by 70% in a polar fashion. We also recovered an unusual allele of the ncd gene, whose wild-type product is required for proper structure and function of the meiotic spindle. However, the screen yielded primarily mutants specifically defective in the segregation of achiasmate chromosomes. Although most of these are alleles of previously undescribed genes, five were in the known genes alphaTubulin67C, CycE, push, and Trl. The five mutations in known genes produce novel phenotypes for those genes. PMID:10353897

  3. Purification, folding, and characterization of Rec12 (Spo11) meiotic recombinase of fission yeast

    PubMed Central

    Wu, Heng; Gao, Jun; Sharif, Wallace D.; Davidson, Mari K.; Wahls, Wayne P.

    2011-01-01

    Meiotic recombination is initiated by controlled dsDNA breaks (DSBs). Rec12 (Spo11) protein of fission yeast is essential for the formation of meiotic DSBs in vivo, for meiotic recombination, and for segregation of chromosomes during meiosis I. Rec12 is orthologous to Top6A topoisomerase of Archaea and is likely the catalytic subunit of a meiotic recombinase that introduces recombinogenic DSBs. However, despite intensive effort, it has not been possible to produce Rec12 protein in a soluble form required to permit biochemical analyses of function. To obtain purified Rec12 protein for in vitro studies, a rec12+ cDNA was generated, cloned into vector pET15b(+), and expressed in Escherichia coli. Rec12 protein was produced at moderate levels and it partitioned into insoluble fractions of whole-cell extracts. The protein was enriched based upon its differential solubility in two different denaturants and was further purified by column chromatography. A combinatorial, fractional, factorial approach was used to identify conditions under which Rec12 protein could be refolded. Four parameters were most important and, following optimization, soluble Rec12 protein was obtained. Gel filtration demonstrated that refolded Rec12 protein exists as a monomer in solution, suggesting that additional proteins may be required to assemble biologically-active Rec12 dimers, as inferred previously from genetic data [Cell Chromosome 1 (2002) 1]. The production of refolded Rec12 in a soluble form will allow for characterization in vitro of this key meiotic recombination enzyme. PMID:15477092

  4. Purification, folding, and characterization of Rec12 (Spo11) meiotic recombinase of fission yeast.

    PubMed

    Wu, Heng; Gao, Jun; Sharif, Wallace D; Davidson, Mari K; Wahls, Wayne P

    2004-11-01

    Meiotic recombination is initiated by controlled dsDNA breaks (DSBs). Rec12 (Spo11) protein of fission yeast is essential for the formation of meiotic DSBs in vivo, for meiotic recombination, and for segregation of chromosomes during meiosis I. Rec12 is orthologous to Top6A topoisomerase of Archaea and is likely the catalytic subunit of a meiotic recombinase that introduces recombinogenic DSBs. However, despite intensive effort, it has not been possible to produce Rec12 protein in a soluble form required to permit biochemical analyses of function. To obtain purified Rec12 protein for in vitro studies, a rec12(+) cDNA was generated, cloned into vector pET15b(+), and expressed in Escherichia coli. Rec12 protein was produced at moderate levels and it partitioned into insoluble fractions of whole-cell extracts. The protein was enriched based upon its differential solubility in two different denaturants and was further purified by column chromatography. A combinatorial, fractional, factorial approach was used to identify conditions under which Rec12 protein could be refolded. Four parameters were most important and, following optimization, soluble Rec12 protein was obtained. Gel filtration demonstrated that refolded Rec12 protein exists as a monomer in solution, suggesting that additional proteins may be required to assemble biologically-active Rec12 dimers, as inferred previously from genetic data [Cell Chromosome 1 (2002) 1]. The production of refolded Rec12 in a soluble form will allow for characterization in vitro of this key meiotic recombination enzyme. PMID:15477092

  5. DNA methylation restrains transposons from adopting a chromatin signature permissive for meiotic recombination

    PubMed Central

    Zamudio, Natasha; Barau, Joan; Teissandier, Aurélie; Walter, Marius; Borsos, Maté; Servant, Nicolas; Bourc'his, Déborah

    2015-01-01

    DNA methylation is essential for protecting the mammalian germline against transposons. When DNA methylation-based transposon control is defective, meiotic chromosome pairing is consistently impaired during spermatogenesis: How and why meiosis is vulnerable to transposon activity is unknown. Using two DNA methylation-deficient backgrounds, the Dnmt3L and Miwi2 mutant mice, we reveal that DNA methylation is largely dispensable for silencing transposons before meiosis onset. After this, it becomes crucial to back up to a developmentally programmed H3K9me2 loss. Massive retrotransposition does not occur following transposon derepression, but the meiotic chromatin landscape is profoundly affected. Indeed, H3K4me3 marks gained over transcriptionally active transposons correlate with formation of SPO11-dependent double-strand breaks and recruitment of the DMC1 repair enzyme in Dnmt3L−/− meiotic cells, whereas these features are normally exclusive to meiotic recombination hot spots. Here, we demonstrate that DNA methylation restrains transposons from adopting chromatin characteristics amenable to meiotic recombination, which we propose prevents the occurrence of erratic chromosomal events. PMID:26109049

  6. Global Patterns in Human Mitochondrial DNA and Y-Chromosome Variation Caused by Spatial Instability of the Local Cultural Processes

    PubMed Central

    Kumar, Vikrant; Langstieh, Banrida T; Madhavi, Komal V; Naidu, Vegi M; Singh, Hardeep Pal; Biswas, Silpak; Thangaraj, Kumarasamy; Singh, Lalji; Reddy, B. Mohan

    2006-01-01

    Because of the widespread phenomenon of patrilocality, it is hypothesized that Y-chromosome variants tend to be more localized geographically than those of mitochondrial DNA (mtDNA). Empirical evidence confirmatory to this hypothesis was subsequently provided among certain patrilocal and matrilocal groups of Thailand, which conforms to the isolation by distance mode of gene diffusion. However, we expect intuitively that the patterns of genetic variability may not be consistent with the above hypothesis among populations with different social norms governing the institution of marriage, particularly among those that adhere to strict endogamy rules. We test the universality of this hypothesis by analyzing Y-chromosome and mtDNA data in three different sets of Indian populations that follow endogamy rules to varying degrees. Our analysis of the Indian patrilocal and the matrilocal groups is not confirmatory to the sex-specific variation observed among the tribes of Thailand. Our results indicate spatial instability of the impact of different cultural processes on the genetic variability, resulting in the lack of universality of the hypothesized pattern of greater Y-chromosome variation when compared to that of mtDNA among the patrilocal populations. PMID:16617372

  7. A single internal telomere tract ensures meiotic spindle formation

    PubMed Central

    Tomita, Kazunori; Bez, Cécile; Fennell, Alex; Cooper, Julia Promisel

    2013-01-01

    Contact between telomeres and the fission yeast spindle pole body during meiotic prophase is crucial for subsequent spindle assembly, but the feature of telomeres that confers their ability to promote spindle formation remains mysterious. Here we show that while strains harbouring circular chromosomes devoid of telomere repeat tracts undergo aberrant meiosis with defective spindles, the insertion of a single internal telomere repeat stretch rescues the spindle defects. Moreover, the telomeric overhang-binding protein Pot1 is dispensable for rescue of spindle formation. Hence, an inherent feature of the double-strand telomeric region endows telomeres with the capacity to promote spindle formation. PMID:23295325

  8. The Pch2 AAA+ ATPase promotes phosphorylation of the Hop1 meiotic checkpoint adaptor in response to synaptonemal complex defects.

    PubMed

    Herruzo, Esther; Ontoso, David; González-Arranz, Sara; Cavero, Santiago; Lechuga, Ana; San-Segundo, Pedro A

    2016-09-19

    Meiotic cells possess surveillance mechanisms that monitor critical events such as recombination and chromosome synapsis. Meiotic defects resulting from the absence of the synaptonemal complex component Zip1 activate a meiosis-specific checkpoint network resulting in delayed or arrested meiotic progression. Pch2 is an evolutionarily conserved AAA+ ATPase required for the checkpoint-induced meiotic block in the zip1 mutant, where Pch2 is only detectable at the ribosomal DNA array (nucleolus). We describe here that high levels of the Hop1 protein, a checkpoint adaptor that localizes to chromosome axes, suppress the checkpoint defect of a zip1 pch2 mutant restoring Mek1 activity and meiotic cell cycle delay. We demonstrate that the critical role of Pch2 in this synapsis checkpoint is to sustain Mec1-dependent phosphorylation of Hop1 at threonine 318. We also show that the ATPase activity of Pch2 is essential for its checkpoint function and that ATP binding to Pch2 is required for its localization. Previous work has shown that Pch2 negatively regulates Hop1 chromosome abundance during unchallenged meiosis. Based on our results, we propose that, under checkpoint-inducing conditions, Pch2 also possesses a positive action on Hop1 promoting its phosphorylation and its proper distribution on unsynapsed chromosome axes. PMID:27257060

  9. The Pch2 AAA+ ATPase promotes phosphorylation of the Hop1 meiotic checkpoint adaptor in response to synaptonemal complex defects

    PubMed Central

    Herruzo, Esther; Ontoso, David; González-Arranz, Sara; Cavero, Santiago; Lechuga, Ana; San-Segundo, Pedro A.

    2016-01-01

    Meiotic cells possess surveillance mechanisms that monitor critical events such as recombination and chromosome synapsis. Meiotic defects resulting from the absence of the synaptonemal complex component Zip1 activate a meiosis-specific checkpoint network resulting in delayed or arrested meiotic progression. Pch2 is an evolutionarily conserved AAA+ ATPase required for the checkpoint-induced meiotic block in the zip1 mutant, where Pch2 is only detectable at the ribosomal DNA array (nucleolus). We describe here that high levels of the Hop1 protein, a checkpoint adaptor that localizes to chromosome axes, suppress the checkpoint defect of a zip1 pch2 mutant restoring Mek1 activity and meiotic cell cycle delay. We demonstrate that the critical role of Pch2 in this synapsis checkpoint is to sustain Mec1-dependent phosphorylation of Hop1 at threonine 318. We also show that the ATPase activity of Pch2 is essential for its checkpoint function and that ATP binding to Pch2 is required for its localization. Previous work has shown that Pch2 negatively regulates Hop1 chromosome abundance during unchallenged meiosis. Based on our results, we propose that, under checkpoint-inducing conditions, Pch2 also possesses a positive action on Hop1 promoting its phosphorylation and its proper distribution on unsynapsed chromosome axes. PMID:27257060

  10. The Pch2 AAA+ ATPase promotes phosphorylation of the Hop1 meiotic checkpoint adaptor in response to synaptonemal complex defects.

    PubMed

    Herruzo, Esther; Ontoso, David; González-Arranz, Sara; Cavero, Santiago; Lechuga, Ana; San-Segundo, Pedro A

    2016-09-19

    Meiotic cells possess surveillance mechanisms that monitor critical events such as recombination and chromosome synapsis. Meiotic defects resulting from the absence of the synaptonemal complex component Zip1 activate a meiosis-specific checkpoint network resulting in delayed or arrested meiotic progression. Pch2 is an evolutionarily conserved AAA+ ATPase required for the checkpoint-induced meiotic block in the zip1 mutant, where Pch2 is only detectable at the ribosomal DNA array (nucleolus). We describe here that high levels of the Hop1 protein, a checkpoint adaptor that localizes to chromosome axes, suppress the checkpoint defect of a zip1 pch2 mutant restoring Mek1 activity and meiotic cell cycle delay. We demonstrate that the critical role of Pch2 in this synapsis checkpoint is to sustain Mec1-dependent phosphorylation of Hop1 at threonine 318. We also show that the ATPase activity of Pch2 is essential for its checkpoint function and that ATP binding to Pch2 is required for its localization. Previous work has shown that Pch2 negatively regulates Hop1 chromosome abundance during unchallenged meiosis. Based on our results, we propose that, under checkpoint-inducing conditions, Pch2 also possesses a positive action on Hop1 promoting its phosphorylation and its proper distribution on unsynapsed chromosome axes.

  11. Discovery of Supernumerary B Chromosomes in Drosophila melanogaster

    PubMed Central

    Bauerly, Elisabeth; Hughes, Stacie E.; Vietti, Dana R.; Miller, Danny E.; McDowell, William; Hawley, R. Scott

    2014-01-01

    B chromosomes are small, heterochromatic chromosomes that are transmitted in a non-Mendelian manner. We have identified a stock of Drosophila melanogaster that recently (within the last decade) acquired an average of 10 B chromosomes per fly. These B chromosomes are transmitted by both males and females and can be maintained for multiple generations in a wild-type genetic background despite the fact that they cause high levels of 4th chromosome meiotic nondisjunction in females. Most curiously, these B chromosomes are mitotically unstable, suggesting either the absence of critical chromosomal sites or the inability of the meiotic or mitotic systems to cope with many additional chromosomes. These B chromosomes also contain centromeres and are primarily composed of the heterochromatic AATAT satellite sequence. Although the AATAT sequence comprises the majority of the 4th chromosome heterochromatin, the B chromosomes lack most, if not all, 4th chromosome euchromatin. Presumably as a consequence of their heterochromatic content, these B chromosomes significantly modify position-effect variegation in two separate reporter systems, acting as enhancers of variegation in one case and suppressors in the other. The identification of B chromosomes in a genetically tractable organism like D. melanogaster will facilitate studies of chromosome evolution and the analysis of the mechanisms by which meiotic and mitotic processes cope with additional chromosomes. PMID:24478336

  12. Identification of DSB-1, a Protein Required for Initiation of Meiotic Recombination in Caenorhabditis elegans, Illuminates a Crossover Assurance Checkpoint

    PubMed Central

    Stamper, Ericca L.; Rodenbusch, Stacia E.; Rosu, Simona; Ahringer, Julie; Villeneuve, Anne M.; Dernburg, Abby F.

    2013-01-01

    Meiotic recombination, an essential aspect of sexual reproduction, is initiated by programmed DNA double-strand breaks (DSBs). DSBs are catalyzed by the widely-conserved Spo11 enzyme; however, the activity of Spo11 is regulated by additional factors that are poorly conserved through evolution. To expand our understanding of meiotic regulation, we have characterized a novel gene, dsb-1, that is specifically required for meiotic DSB formation in the nematode Caenorhabditis elegans. DSB-1 localizes to chromosomes during early meiotic prophase, coincident with the timing of DSB formation. DSB-1 also promotes normal protein levels and chromosome localization of DSB-2, a paralogous protein that plays a related role in initiating recombination. Mutations that disrupt crossover formation result in prolonged DSB-1 association with chromosomes, suggesting that nuclei may remain in a DSB-permissive state. Extended DSB-1 localization is seen even in mutants with defects in early recombination steps, including spo-11, suggesting that the absence of crossover precursors triggers the extension. Strikingly, failure to form a crossover precursor on a single chromosome pair is sufficient to extend the localization of DSB-1 on all chromosomes in the same nucleus. Based on these observations we propose a model for crossover assurance that acts through DSB-1 to maintain a DSB-permissive state until all chromosome pairs acquire crossover precursors. This work identifies a novel component of the DSB machinery in C. elegans, and sheds light on an important pathway that regulates DSB formation for crossover assurance. PMID:23990794

  13. Live Imaging of Intracellular Dynamics During Meiotic Maturation in Mouse Oocytes.

    PubMed

    Yoshida, Shuhei; Sakakibara, Yogo; Kitajima, Tomoya S

    2016-01-01

    Fluorescence live imaging is a powerful approach to study intracellular dynamics during cellular events such as cell division. By applying automated confocal live imaging to mouse oocytes, in which meiotic maturation can be induced in vitro after the introduction of fluorescent proteins through microinjection, the meiotic dynamics of intracellular structures, such as chromosomes, can be monitored at high resolution. A combination of this method with approaches for the perturbation of specific proteins opens up opportunities for understanding the molecular and intracellular basis of mammalian meiosis. PMID:27557586

  14. Ten years of gene discovery for meiotic event control in rice.

    PubMed

    Luo, Qiong; Li, Yafei; Shen, Yi; Cheng, Zhukuan

    2014-03-20

    Meiosis is the crucial process by which sexually propagating eukaryotes give rise to haploid gametes from diploid cells. Several key processes, like homologous chromosomes pairing, synapsis, recombination, and segregation, sequentially take place in meiosis. Although these widely conserved events are under both genetic and epigenetic control, the accurate details of molecular mechanisms are continuing to investigate. Rice is a good model organism for exploring the molecular mechanisms of meiosis in higher plants. So far, 28 rice meiotic genes have been characterized. In this review, we give an overview of the discovery of rice meiotic genes in the last ten years, with a particular focus on their functions in meiosis. PMID:24656233

  15. Pre-meiotic bands and novel meiotic spindle ontogeny in quadrilobed sporocytes of leafy liverworts (Jungermannidae, Bryophyta).

    PubMed

    Brown, Roy C; Lemmon, Betty E

    2009-10-01

    Indirect immunofluorescence and confocal microscopy were used to study the nucleation and organization of microtubules during meiosis in two species of leafy liverworts, Cephalozia macrostachya and Telaranea longifolia. This is the first such study of sporogenesis in the largest group of liverworts important as living representatives of some of the first land plant lineages. These studies show that cytoplasmic quadrilobing of pre-meiotic sporocytes into future spore domains is initiated by girdling bands of gamma-tubulin and microtubules similar to those recently described in lobed sporocytes of simple thalloid liverworts. However, spindle ontogeny is not like other liverworts studied and is, in fact, probably unique among bryophytes. Following the establishment of quadrilobing, numerous microtubules diverge from the bands and extend into the enlarging lobes. The bands disappear and are replaced by microtubules that arise from gamma-tubulin associated with the nuclear envelope. This microtubule system extends into the four lobes and is gradually reorganized into a quadripolar spindle, each half spindle consisting of a pair of poles straddling opposite cleavage furrows. Chromosomes move on this spindle to the polar cleavage furrows. The reniform daughter nuclei, each curved over a cleavage furrow, immediately enter second meiotic division with spindles now terminating in the lobes. Phragmoplasts that develop in the interzones among the haploid tetrad nuclei guide deposition of cell plates that join with the pre-meiotic furrows resulting in cleavage of the tetrad of spores. These observations document a significant variation in the innovative process of sporogenesis evolved in early land plants.

  16. Evaluating the relationship between spermatogenic silencing of the X chromosome and evolution of the Y chromosome in chimpanzee and human.

    PubMed

    Mulugeta Achame, Eskeatnaf; Baarends, Willy M; Gribnau, Joost; Grootegoed, J Anton

    2010-12-14

    Chimpanzees and humans are genetically very similar, with the striking exception of their Y chromosomes, which have diverged tremendously. The male-specific region (MSY), representing the greater part of the Y chromosome, is inherited from father to son in a clonal fashion, with natural selection acting on the MSY as a unit. Positive selection might involve the performance of the MSY in spermatogenesis. Chimpanzees have a highly polygamous mating behavior, so that sperm competition is thought to provide a strong selective force acting on the Y chromosome in the chimpanzee lineage. In consequence of evolution of the heterologous sex chromosomes in mammals, meiotic sex chromosome inactivation (MSCI) results in a transcriptionally silenced XY body in male meiotic prophase, and subsequently also in postmeiotic repression of the sex chromosomes in haploid spermatids. This has evolved to a situation where MSCI has become a prerequisite for spermatogenesis. Here, by analysis of microarray testicular expression data representing a small number of male chimpanzees and men, we obtained information indicating that meiotic and postmeiotic X chromosome silencing might be more effective in chimpanzee than in human spermatogenesis. From this, we suggest that the remarkable reorganization of the chimpanzee Y chromosome, compared to the human Y chromosome, might have an impact on its meiotic interactions with the X chromosome and thereby on X chromosome silencing in spermatogenesis. Further studies will be required to address comparative functional aspects of MSCI in chimpanzee, human, and other placental mammals.

  17. Evolution of a MCM complex in flies promoting meiotic crossovers by blocking BLM helicase

    PubMed Central

    Kohl, Kathryn P.; Jones, Corbin D.; Sekelsky, Jeff

    2013-01-01

    Generation of meiotic crossovers in many eukaryotes requires the elimination of anti-crossover activities by utilizing the Msh4–Msh5 heterodimer to block helicases. Msh4 and Msh5 have been lost from the flies Drosophila and Glossina but we identified a complex of mini-chromosome maintenance (MCM) proteins that functionally replace Msh4–Msh5. REC, an ortholog of MCM8 that evolved under strong positive selection in flies, interacts with MEI-217 and MEI-218, which arose from a previously undescribed metazoan-specific MCM protein. Meiotic crossovers are reduced in Drosophila rec, mei-217, and mei-218 mutants; however, removal of the Bloom syndrome helicase ortholog restores crossovers. Thus, MCMs were co-opted into a novel complex that replaces the meiotic pro-crossover function of Msh4–Msh5 in flies. PMID:23224558

  18. Meiotic recombination in normal and clone bulls and their offspring.

    PubMed

    Hart, E J; Pinton, A; Powell, A; Wall, R; King, W A

    2008-01-01

    Homologous chromosome pairing and recombination are essential components of meiosis and sexual reproduction. The reshuffling of genetic material through breakage and reunion of chromatids ensure proper segregation of homologous chromosomes in reduction division and genetic diversity in the progeny. The advent of somatic cell nuclear transfer (SCNT) as a reproductive biotechnology for use in livestock industry has made it easy to bypass these vital steps. However, few studies have been carried out on the impact of SCNT on the reproductive characteristics of cloned animals and, none to date, on the meiotic processes in animals, which were created by circumventing meiosis. In an attempt to assess the impact of cloning by SCNT on the meiotic processes, we undertook an immunocytological comparison of recombination in normal and clone bulls using antibodies raised against the synaptonemal complex protein 3 (SCP3) to label the lateral elements and the mismatch repair protein 1 (MLH1) foci on bivalents as indicators of recombination events. Our studies involving five normal bulls of proven fertility, two SCNT-derived bulls, and four mature offspring of SCNT bulls showed that the mean number of crossing over per spermatocyte for normal bulls (42 +/- 4 SD; ranging from 33 to 56), was not significantly different from that of SCNT-derived bulls (43 +/- 5 SD; ranging from 35 to 56), and the offspring of SCNT-derived bulls (43 +/- 5 SD; ranging from 37 to 58). It would appear that circumventing meiosis to produce these animals does not influence the meiotic processes revealed by MLH1 foci detected in spermatocytes.

  19. REC, Drosophila MCM8, drives formation of meiotic crossovers.

    PubMed

    Blanton, Hunter L; Radford, Sarah J; McMahan, Susan; Kearney, Hutton M; Ibrahim, Joseph G; Sekelsky, Jeff

    2005-09-01

    Crossovers ensure the accurate segregation of homologous chromosomes from one another during meiosis. Here, we describe the identity and function of the Drosophila melanogaster gene recombination defective (rec), which is required for most meiotic crossing over. We show that rec encodes a member of the mini-chromosome maintenance (MCM) protein family. Six MCM proteins (MCM2-7) are essential for DNA replication and are found in all eukaryotes. REC is the Drosophila ortholog of the recently identified seventh member of this family, MCM8. Our phylogenetic analysis reveals the existence of yet another family member, MCM9, and shows that MCM8 and MCM9 arose early in eukaryotic evolution, though one or both have been lost in multiple eukaryotic lineages. Drosophila has lost MCM9 but retained MCM8, represented by REC. We used genetic and molecular methods to study the function of REC in meiotic recombination. Epistasis experiments suggest that REC acts after the Rad51 ortholog SPN-A but before the endonuclease MEI-9. Although crossovers are reduced by 95% in rec mutants, the frequency of noncrossover gene conversion is significantly increased. Interestingly, gene conversion tracts in rec mutants are about half the length of tracts in wild-type flies. To account for these phenotypes, we propose that REC facilitates repair synthesis during meiotic recombination. In the absence of REC, synthesis does not proceed far enough to allow formation of an intermediate that can give rise to crossovers, and recombination proceeds via synthesis-dependent strand annealing to generate only noncrossover products.

  20. Discrete DNA sites regulate global distribution of meiotic recombination.

    PubMed

    Wahls, Wayne P; Davidson, Mari K

    2010-05-01

    Homologous recombination is induced to high levels in meiosis, is initiated by Spo11-catalyzed DNA double-strand breaks (DSBs) and is clustered at hotspots that regulate its positioning in the genome. Recombination is required for proper chromosome segregation in meiosis and defects in its frequency or positioning cause chromosome mis-segregation and, consequently, congenital birth defects such as Down's syndrome. Therefore, elucidating how meiotic recombination is positioned is of fundamental and biomedical interest. Our integration of historical and contemporary advances in the field, plus the re-analysis of published microarray data on the genome-wide distribution of recombination supports a unifying model for such regulation. We posit that discrete DNA sequence motifs position and regulate essentially all recombination across the genome, in much the same way that DNA sites position and regulate transcription. Moreover, we illustrate the use of overlapping mechanisms for the regulation of transcription and meiotic recombination. Bound transcription factors induce histone modifications that position recombination at hotspots. PMID:20381894

  1. Discrete DNA sites regulate global distribution of meiotic recombination

    PubMed Central

    Wahls, Wayne P.; Davidson, Mari K.

    2010-01-01

    Homologous recombination is induced to high levels in meiosis, is initiated by Spo11-catalyzed DNA double-strand breaks (DSBs), and is clustered at hotspots that regulate its positioning in the genome. Recombination is required for proper chromosome segregation in meiosis; defects in its frequency or positioning cause chromosome mis-segregation and, consequently, congenital birth defects such as Down’s syndrome. Therefore elucidating how meiotic recombination is positioned is of fundamental and biomedical interest. Integration of historical and contemporary advances in the field, plus the re-analysis of published microarray data on the genome-wide distribution of recombination, support a unifying model for such regulation. We posit that discrete DNA sequence motifs position and regulate essentially all recombination across the genome, in much the same way that DNA sites position and regulate transcription. Moreover, we illustrate the use of overlapping mechanisms for the regulation of transcription and meiotic recombination. Bound transcription factors induce histone modifications that position recombination at hotspots. PMID:20381894

  2. Meiotic recombination analysis in female ducks (Anas platyrhynchos).

    PubMed

    Pigozzi, M I; Del Priore, L

    2016-06-01

    Meiotic recombination in female ducks was directly studied by immunolocalization of MLH1 protein, a mismatch repair protein of mature recombination nodules. In total, 6820 crossovers were scored along the autosomal synaptonemal complexes in 122 meiotic nuclei. From this analysis we predict that the female map length of the duck is 2845 cM, with a genome wide recombination rate of 2 cM/Mb. MLH1-focus mapping along the six largest bivalents shows regional variations of recombination frequencies that can be linked to differences in chromosome morphology. From this MLH1 mapping it can be inferred that distally located markers will appear more separated in genetic maps than physically equidistant markers located near the centromeres on bivalents 1 and 2. Instead, markers at interstitial positions on the acrocentric bivalents 3-6 will appear more tightly linked than expected on the basis of their physical distance because recombination is comparatively lower at the mid region of these chromosomes. The present results provide useful information to complement linkage mapping in ducks and extend previous knowledge about the variation of recombination rates among domestic Galloanserae.

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

    PubMed

    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 < 0.001), which may indicate that some 45,X cells gave rise to X-bearing spermatozoa. The findings provide insight into the fate of 45,X/46,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.

  4. Description of the pre-reductional sex chromosome during male meiosis of Pachylis laticornis (Heteroptera: Coreidae).

    PubMed

    Banho, C A; Alevi, K C C; Pereira, L L V; Souza-Firmino, T S; Itoyama, M M

    2016-04-28

    In Heteroptera, the division of sex chromosomes is well defined as post-reductional for most of species, i.e., the first meiotic division is equational and the second is reductional. However, in some species pre-reductional division has been observed, whereby the first meiotic division is reductional and the second is equational. These include Anisops fieberi (Notonectidae), Ectrychotes disparate (Reduviidae), Dictyonota tricornis (Tingidae), and Archimerus alternatus (Coreidae), as well as other species of the genus Pachylis, in the family Coreidae. Thus, this study aimed to characterize the meiotic behavior of Pachylis laticornis, in order to consider whether this species also undergoes pre-reduction division for the sex chromosomes. Cytogenetic analysis of meiosis in P. laticornis made it possible to characterize the holocentric nature of the chromosomes, the chromosome number of this species [2n = 15 (2m + 12A + X0)], the chromosomal system of sex X0 type, and the presence of m-chromosomes. Furthermore, the analysis of anaphase I, telophase I and II allowed pre-reductional meiotic behavior to be observed for this sex chromosome. Thus, this meiotic behavior was confirmed for another species of Heteroptera, stressing the importance of more cytogenetic studies of meiosis to increase our understanding of variation in the behavior of sex chromosomes during spermatogenesis in heteropterans. Therefore, the present study describes the chromosomal number, the system of sex determination, and meiotic behavior of P. laticornis, corroborating the relationship of this species with others of the same genus.

  5. Backcrossing to increase meiotic stability in triticale.

    PubMed

    Giacomin, R M; Assis, R; Brammer, S P; Nascimento Junior, A; Da-Silva, P R

    2015-01-01

    Triticale (X Triticosecale Wittmack) is an intergeneric hybrid derived from a cross between wheat and rye. As a newly created allopolyploid, the plant shows instabilities during the meiotic process, which may result in the loss of fertility. This genomic instability has hindered the success of triticale-breeding programs. Therefore, strategies should be developed to obtain stable triticale lines for use in breeding. In some species, backcrossing has been effective in increasing the meiotic stability of lineages. To assess whether backcrossing has the same effect in triticale, indices of meiotic abnormalities, meiotic index, and pollen viability were determined in genotypes from multiple generations of triticale (P1, P2, F1, F2, BC1a, and BC1b). All analyzed genotypes exhibited instability during meiosis, and their meiotic index values were all lower than normal. However, the backcrosses BC1a and BC1b showed the lowest mean meiotic abnormalities and the highest meiotic indices, demonstrating higher stability. All genotypes showed a high rate of pollen viability, with the backcrosses BC1a and BC1b again exhibiting the best values. Statistical analyses confirmed that backcrossing positively affects the meiotic stability of triticale. Our results show that backcrossing should be considered by breeders aiming to obtain triticale lines with improved genomic stability. PMID:26400358

  6. Holocentromere identity: from the typical mitotic linear structure to the great plasticity of meiotic holocentromeres.

    PubMed

    Marques, André; Pedrosa-Harand, Andrea

    2016-09-01

    The centromere is the chromosomal site of kinetochore assembly and is responsible for the correct chromosome segregation during mitosis and meiosis in eukaryotes. Contrary to monocentrics, holocentric chromosomes lack a primary constriction, what is attributed to a kinetochore activity along almost the entire chromosome length during mitosis. This extended centromere structure imposes a problem during meiosis, since sister holocentromeres are not co-oriented during first meiotic division. Thus, regardless of the relatively conserved somatic chromosome structure of holocentrics, during meiosis holocentric chromosomes show different adaptations to deal with this condition. Recent findings in holocentrics have brought back the discussion of the great centromere plasticity of eukaryotes, from the typical CENH3-based holocentromeres to CENH3-less holocentric organisms. Here, we summarize recent and former findings about centromere/kinetochore adaptations shown by holocentric organisms during mitosis and meiosis and discuss how these adaptations are related to the type of meiosis found. PMID:27530342

  7. Time-dependent effects of transcription- and translation-halting drugs on the spatial distributions of the Escherichia coli chromosome and ribosomes.

    PubMed

    Bakshi, Somenath; Choi, Heejun; Mondal, Jagannath; Weisshaar, James C

    2014-11-01

    Previously observed effects of rifampicin and chloramphenicol indicate that transcription and translation activity strongly affect the coarse spatial organization of the bacterial cytoplasm. Single-cell, time-resolved, quantitative imaging of chromosome and ribosome spatial distributions and ribosome diffusion in live Escherichia coli provides insight into the underlying mechanisms. Monte Carlo simulations of model DNA-ribosome mixtures support a novel nucleoid-ribosome mixing hypothesis. In normal conditions, 70S-polysomes and the chromosomal DNA segregate, while 30S and 50S ribosomal subunits are able to penetrate the nucleoids. Growth conditions and drug treatments determine the partitioning of ribosomes into 70S-polysomes versus free 30S and 50S subunits. Entropic and excluded volume effects then dictate the resulting chromosome and ribosome spatial distributions. Direct observation of radial contraction of the nucleoids 0-5 min after treatment with either transcription- or translation-halting drugs supports the hypothesis that simultaneous transcription, translation, and insertion of proteins into the membrane ('transertion') exerts an expanding force on the chromosomal DNA. Breaking of the DNA-RNA polymerase-mRNA-ribosome-membrane chain in either of two ways causes similar nucleoid contraction on a similar timescale. We suggest that chromosomal expansion due to transertion enables co-transcriptional translation throughout the nucleoids.

  8. Dynamic spatial organization of multi-protein complexes controlling microbial polar organization, chromosome replication, and cytokinesis

    SciTech Connect

    McAdams, Harley; Shapiro, Lucille; Horowitz, Mark; Andersen, Gary; Downing, Kenneth; Earnest, Thomas; Ellisman, Mark; Gitai, Zemer; Larabell, Carolyn; Viollier, Patrick

    2012-06-18

    This project was a program to develop high-throughput methods to identify and characterize spatially localized multiprotein complexes in bacterial cells. We applied a multidisciplinary systems engineering approach to the detailed characterization of localized multi-protein structures in vivo a problem that has previously been approached on a fragmented, piecemeal basis.

  9. Unique sex chromosome systems in Ellobius: How do male XX chromosomes recombine and undergo pachytene chromatin inactivation?

    PubMed Central

    Matveevsky, Sergey; Bakloushinskaya, Irina; Kolomiets, Oxana

    2016-01-01

    Most mammalian species have heteromorphic sex chromosomes in males, except for a few enigmatic groups such as the mole voles Ellobius, which do not have the Y chromosome and Sry gene. The Ellobius (XX ♀♂) system of sex chromosomes has no analogues among other animals. The structure and meiotic behaviour of the two X chromosomes were investigated for males of the sibling species Ellobius talpinus and Ellobius tancrei. Their sex chromosomes, despite their identical G-structure, demonstrate short synaptic fragments and crossover-associated MLH1 foci in both telomeric regions only. The chromatin undergoes modifications in the meiotic sex chromosomes. SUMO-1 marks a small nucleolus-like body of the meiotic XX. ATR and ubiH2A are localized in the asynaptic area and the histone γH2AFX covers the entire XX bivalent. The distribution of some markers of chromatin inactivation differentiates sex chromosomes of mole voles from those of other mammals. Sex chromosomes of both studied species have identical recombination and meiotic inactivation patterns. In Ellobius, similar chromosome morphology masks the functional heteromorphism of the male sex chromosomes, which can be seen at meiosis. PMID:27425629

  10. Unique sex chromosome systems in Ellobius: How do male XX chromosomes recombine and undergo pachytene chromatin inactivation?

    PubMed

    Matveevsky, Sergey; Bakloushinskaya, Irina; Kolomiets, Oxana

    2016-07-18

    Most mammalian species have heteromorphic sex chromosomes in males, except for a few enigmatic groups such as the mole voles Ellobius, which do not have the Y chromosome and Sry gene. The Ellobius (XX ♀♂) system of sex chromosomes has no analogues among other animals. The structure and meiotic behaviour of the two X chromosomes were investigated for males of the sibling species Ellobius talpinus and Ellobius tancrei. Their sex chromosomes, despite their identical G-structure, demonstrate short synaptic fragments and crossover-associated MLH1 foci in both telomeric regions only. The chromatin undergoes modifications in the meiotic sex chromosomes. SUMO-1 marks a small nucleolus-like body of the meiotic XX. ATR and ubiH2A are localized in the asynaptic area and the histone γH2AFX covers the entire XX bivalent. The distribution of some markers of chromatin inactivation differentiates sex chromosomes of mole voles from those of other mammals. Sex chromosomes of both studied species have identical recombination and meiotic inactivation patterns. In Ellobius, similar chromosome morphology masks the functional heteromorphism of the male sex chromosomes, which can be seen at meiosis.

  11. The role of centromere alignment in meiosis I segregation of homologous chromosomes in Saccharomyces cerevisiae.

    PubMed Central

    Guerra, C E; Kaback, D B

    1999-01-01

    During meiosis, homologous chromosomes pair and then segregate from each other at the first meiotic division. Homologous centromeres appear to be aligned when chromosomes are paired. The role of centromere alignment in meiotic chromosome segregation was investigated in Saccharomyces cerevisiae diploids that contained one intact copy of chromosome I and one copy bisected into two functional centromere-containing fragments. The centromere on one fragment was aligned with the centromere on the intact chromosome while the centromere on the other fragment was either aligned or misaligned. Fragments containing aligned centromeres segregated efficiently from the intact chromosome, while fragments containing misaligned centromeres segregated much less efficiently from the intact chromosome. Less efficient segregation was correlated with crossing over in the region between the misaligned centromeres. Models that suggest that these crossovers impede proper segregation by preventing either a segregation-promoting chromosome alignment on the meiotic spindle or some physical interaction between homologous centromeres are proposed. PMID:10581265

  12. HORMAD2 is essential for synapsis surveillance during meiotic prophase via the recruitment of ATR activity.

    PubMed

    Kogo, Hiroshi; Tsutsumi, Makiko; Inagaki, Hidehito; Ohye, Tamae; Kiyonari, Hiroshi; Kurahashi, Hiroki

    2012-11-01

    Meiotic chromosome segregation requires homologous pairing, synapsis and crossover recombination during meiotic prophase. The checkpoint kinase ATR has been proposed to be involved in the quality surveillance of these processes, although the underlying mechanisms remain largely unknown. In our present study, we generated mice lacking HORMAD2, a protein that localizes to unsynapsed meiotic chromosomes. We show that this Hormad2 deficiency hampers the proper recruitment of ATR activity to unsynapsed chromosomes. Male Hormad2-deficient mice are infertile due to spermatocyte loss as a result of characteristic impairment of sex body formation; an ATR- and γH2AX-enriched repressive chromatin domain is formed, but is partially dissociated from the elongated sex chromosome axes. In contrast to males, Hormad2-deficient females are fertile. However, our analysis of Hormad2/Spo11 double-mutant females shows that the oocyte number is negatively correlated with the frequency of pseudo-sex body formation in a Hormad2 gene dosage-dependent manner. This result suggests that the elimination of Spo11-deficient asynaptic oocytes is associated with the HORMAD2-dependent pseudo-sex body formation that is likely initiated by local concentration of ATR activity in the absence of double-strand breaks. Our results thus show a HORMAD2-dependent quality control mechanism that recognizes unsynapsis and recruits ATR activity during mammalian meiosis. PMID:23039116

  13. A single cohesin complex performs mitotic and meiotic functions in the protist tetrahymena.

    PubMed

    Howard-Till, Rachel A; Lukaszewicz, Agnieszka; Novatchkova, Maria; Loidl, Josef

    2013-03-01

    The cohesion of sister chromatids in the interval between chromosome replication and anaphase is important for preventing the precocious separation, and hence nondisjunction, of chromatids. Cohesion is accomplished by a ring-shaped protein complex, cohesin; and its release at anaphase occurs when separase cleaves the complex's α-kleisin subunit. Cohesin has additional roles in facilitating DNA damage repair from the sister chromatid and in regulating gene expression. We tested the universality of the present model of cohesion by studying cohesin in the evolutionarily distant protist Tetrahymena thermophila. Localization of tagged cohesin components Smc1p and Rec8p (the α-kleisin) showed that cohesin is abundant in mitotic and meiotic nuclei. RNAi knockdown experiments demonstrated that cohesin is crucial for normal chromosome segregation and meiotic DSB repair. Unexpectedly, cohesin does not detach from chromosome arms in anaphase, yet chromosome segregation depends on the activity of separase (Esp1p). When Esp1p is depleted by RNAi, chromosomes become polytenic as they undergo multiple rounds of replication, but fail to separate. The cohesion of such bundles of numerous chromatids suggests that chromatids may be connected by factors in addition to topological linkage by cohesin rings. Although cohesin is not detected in transcriptionally active somatic nuclei, its loss causes a slight defect in their amitotic division. Notably, Tetrahymena uses a single version of α-kleisin for both mitosis and meiosis. Therefore, we propose that the differentiation of mitotic and meiotic cohesins found in most other model systems is not due to the need of a specialized meiotic cohesin, but due to additional roles of mitotic cohesin.

  14. LSD1 is essential for oocyte meiotic progression by regulating CDC25B expression in mice

    PubMed Central

    Kim, Jeesun; Singh, Anup Kumar; Takata, Yoko; Lin, Kevin; Shen, Jianjun; Lu, Yue; Kerenyi, Marc A.; Orkin, Stuart H.; Chen, Taiping

    2015-01-01

    Mammalian oocytes are arrested at prophase I until puberty when hormonal signals induce the resumption of meiosis I and progression to meiosis II. Meiotic progression is controlled by CDK1 activity and is accompanied by dynamic epigenetic changes. Although the signalling pathways regulating CDK1 activity are well defined, the functional significance of epigenetic changes remains largely unknown. Here we show that LSD1, a lysine demethylase, regulates histone H3 lysine 4 di-methylation (H3K4me2) in mouse oocytes and is essential for meiotic progression. Conditional deletion of Lsd1 in growing oocytes results in precocious resumption of meiosis and spindle and chromosomal abnormalities. Consequently, most Lsd1-null oocytes fail to complete meiosis I and undergo apoptosis. Mechanistically, upregulation of CDC25B, a phosphatase that activates CDK1, is responsible for precocious meiotic resumption and also contributes to subsequent spindle and chromosomal defects. Our findings uncover a functional link between LSD1 and the major signalling pathway governing meiotic progression. PMID:26626423

  15. Homomorphic sex chromosomes and the intriguing Y chromosome of Ctenomys rodent species (Rodentia, Ctenomyidae).

    PubMed

    Suárez-Villota, Elkin Y; Pansonato-Alves, José C; Foresti, Fausto; Gallardo, Milton H

    2014-01-01

    Unlike the X chromosome, the mammalian Y chromosome undergoes evolutionary decay resulting in small size. This sex chromosomal heteromorphism, observed in most species of the fossorial rodent Ctenomys, contrasts with the medium-sized, homomorphic acrocentric sex chromosomes of closely related C. maulinus and C. sp. To characterize the sequence composition of these chromosomes, fluorescent banding, self-genomic in situ hybridization, and fluorescent in situ hybridization with an X painting probe were performed on mitotic and meiotic plates. High molecular homology between the sex chromosomes was detected on mitotic material as well as on meiotic plates immunodetected with anti-SYCP3 and anti-γH2AX. The Y chromosome is euchromatic, poor in repetitive sequences and differs from the X by the loss of a block of pericentromeric chromatin. Inferred from the G-banding pattern, an inversion and the concomitant prevention of recombination in a large asynaptic region seems to be crucial for meiotic X chromosome inactivation. These peculiar findings together with the homomorphism of Ctenomys sex chromosomes are discussed in the light of the regular purge that counteracts Muller's ratchet and the probable mechanisms accounting for their origin and molecular homology.

  16. Meiotic recombination and male infertility: from basic science to clinical reality?

    PubMed

    Hann, Michael C; Lau, Patricio E; Tempest, Helen G

    2011-03-01

    Infertility is a common problem that affects approximately 15% of the population. Although many advances have been made in the treatment of infertility, the molecular and genetic causes of male infertility remain largely elusive. This review will present a summary of our current knowledge on the genetic origin of male infertility and the key events of male meiosis. It focuses on chromosome synapsis and meiotic recombination and the problems that arise when errors in these processes occur, specifically meiotic arrest and chromosome aneuploidy, the leading cause of pregnancy loss in humans. In addition, meiosis-specific candidate genes will be discussed, including a discussion on why we have been largely unsuccessful at identifying disease-causing mutations in infertile men. Finally clinical applications of sperm aneuploidy screening will be touched upon along with future prospective clinical tests to better characterize male infertility in a move towards personalized medicine. PMID:21297654

  17. Association between Maternal Age and Meiotic Recombination for Trisomy 21

    PubMed Central

    Lamb, Neil E.; Yu, Kai; Shaffer, John; Feingold, Eleanor; Sherman, Stephanie L.

    2005-01-01

    Altered genetic recombination has been identified as the first molecular correlate of chromosome nondisjunction in both humans and model organisms. Little evidence has emerged to link maternal age—long recognized as the primary risk factor for nondisjunction—with altered recombination, although some studies have provided hints of such a relationship. To determine whether an association does exist, chromosome 21 recombination patterns were examined in 400 trisomy 21 cases of maternal meiosis I origin, grouped by maternal age. These recombination patterns were used to predict the chromosome 21 exchange patterns established during meiosis I. There was no statistically significant association between age and overall rate of exchange. The placement of meiotic exchange, however, differed significantly among the age groups. Susceptible patterns (pericentromeric and telomeric exchanges) accounted for 34% of all exchanges among the youngest class of women but only 10% of those among the oldest class. The pattern of exchanges among the oldest age group mimicked the pattern observed among normally disjoining chromosomes 21. These results suggest that the greatest risk factor for nondisjunction among younger women is the presence of a susceptible exchange pattern. We hypothesize that environmental and age-related insults accumulate in the ovary as a woman ages, leading to malsegregation of oocytes with stable exchange patterns. It is this risk, due to recombination-independent factors, that would be most influenced by increasing age, leading to the observed maternal age effect. PMID:15551222

  18. Spatial organisation and behaviour of the parental chromosome sets in the nuclei of Saccharomyces cerevisiae x S. paradoxus hybrids.

    PubMed

    Lorenz, Alexander; Fuchs, Jörg; Trelles-Sticken, Edgar; Scherthan, Harry; Loidl, Josef

    2002-10-01

    We demonstrate that the genomes of Saccharomyces cerevisiae and S. paradoxus are sufficiently divergent to allow their differential labeling by genomic in situ hybridisation (GISH). The cytological discrimination of the genomes allowed us to study the merging of the two genomes during hybrid mating. GISH revealed that in hybrid nuclei the two genomes are intermixed. In hybrid meiosis, extensive intraspectific nonhomologous pairing takes place. GISH on chromosome addition and substitution strains (with chromosomes of S. paradoxus added to or replacing the homoeologous chromosome of an otherwise S. cerevisiae background) was used to delineate individual chromosomes at interphase and to examine various aspects of chromosome structure and arrangement.

  19. Insights from Space: Potential Role of Diet in the Spatial Organization of Chromosomes

    PubMed Central

    O’Sullivan, Justin M.; Doynova, Malina D.; Antony, Jisha; Pichlmuller, Florian; Horsfield, Julia A.

    2014-01-01

    We can now sequence and identify genome wide epigenetic patterns and perform a variety of “genomic experiments” within relatively short periods of time—ranging from days to weeks. Yet, despite these technological advances, we have a poor understanding of the inter-relationships between epigenetics, genome structure-function, and nutrition. Perhaps this limitation lies, in part, in our propensity to study epigenetics in terms of the linear arrangement of elements and genes. Here we propose that a more complete understanding of how nutrition impacts on epigenetics and cellular development resides within the inter-relationships between DNA and histone modification patterns and genome function, in the context of spatial organization of chromatin and the epigenome. PMID:25514390

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

    PubMed Central

    2015-01-01

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

  1. MS5 Mediates Early Meiotic Progression and Its Natural Variants May Have Applications for Hybrid Production in Brassica napus.

    PubMed

    Xin, Qiang; Shen, Yi; Li, Xi; Lu, Wei; Wang, Xiang; Han, Xue; Dong, Faming; Wan, Lili; Yang, Guangsheng; Hong, Dengfeng; Cheng, Zhukuan

    2016-06-01

    During meiotic prophase I, chromatin undergoes dynamic changes to establish a structural basis for essential meiotic events. However, the mechanism that coordinates chromosome structure and meiotic progression remains poorly understood in plants. Here, we characterized a spontaneous sterile mutant MS5(b)MS5(b) in oilseed rape (Brassica napus) and found its meiotic chromosomes were arrested at leptotene. MS5 is preferentially expressed in reproductive organs and encodes a Brassica-specific protein carrying conserved coiled-coil and DUF626 domains with unknown function. MS5 is essential for pairing of homologs in meiosis, but not necessary for the initiation of DNA double-strand breaks. The distribution of the axis element-associated protein ASY1 occurs independently of MS5, but localization of the meiotic cohesion subunit SYN1 requires functional MS5. Furthermore, both the central element of the synaptonemal complex and the recombination element do not properly form in MS5(b)MS5(b) mutants. Our results demonstrate that MS5 participates in progression of meiosis during early prophase I and its allelic variants lead to differences in fertility, which may provide a promising strategy for pollination control for heterosis breeding. PMID:27194707

  2. Chiasmatic and achiasmatic inverted meiosis of plants with holocentric chromosomes.

    PubMed

    Cabral, Gabriela; Marques, André; Schubert, Veit; Pedrosa-Harand, Andrea; Schlögelhofer, Peter

    2014-01-01

    Meiosis is a specialized cell division in sexually reproducing organisms before gamete formation. Following DNA replication, the canonical sequence in species with monocentric chromosomes is characterized by reductional segregation of homologous chromosomes during the first and equational segregation of sister chromatids during the second meiotic division. Species with holocentric chromosomes employ specific adaptations to ensure regular disjunction during meiosis. Here we present the analysis of two closely related plant species with holocentric chromosomes that display an inversion of the canonical meiotic sequence, with the equational division preceding the reductional. In-depth analysis of the meiotic divisions of Rhynchospora pubera and R. tenuis reveals that during meiosis I sister chromatids are bi-oriented, display amphitelic attachment to the spindle and are subsequently separated. During prophase II, chromatids are connected by thin chromatin threads that appear instrumental for the regular disjunction of homologous non-sister chromatids in meiosis II. PMID:25295686

  3. Chiasmatic and achiasmatic inverted meiosis of plants with holocentric chromosomes.

    PubMed

    Cabral, Gabriela; Marques, André; Schubert, Veit; Pedrosa-Harand, Andrea; Schlögelhofer, Peter

    2014-10-08

    Meiosis is a specialized cell division in sexually reproducing organisms before gamete formation. Following DNA replication, the canonical sequence in species with monocentric chromosomes is characterized by reductional segregation of homologous chromosomes during the first and equational segregation of sister chromatids during the second meiotic division. Species with holocentric chromosomes employ specific adaptations to ensure regular disjunction during meiosis. Here we present the analysis of two closely related plant species with holocentric chromosomes that display an inversion of the canonical meiotic sequence, with the equational division preceding the reductional. In-depth analysis of the meiotic divisions of Rhynchospora pubera and R. tenuis reveals that during meiosis I sister chromatids are bi-oriented, display amphitelic attachment to the spindle and are subsequently separated. During prophase II, chromatids are connected by thin chromatin threads that appear instrumental for the regular disjunction of homologous non-sister chromatids in meiosis II.

  4. A high throughput genetic screen identifies new early meiotic recombination functions in Arabidopsis thaliana.

    PubMed

    De Muyt, Arnaud; Pereira, Lucie; Vezon, Daniel; Chelysheva, Liudmila; Gendrot, Ghislaine; Chambon, Aurélie; Lainé-Choinard, Sandrine; Pelletier, Georges; Mercier, Raphaël; Nogué, Fabien; Grelon, Mathilde

    2009-09-01

    Meiotic recombination is initiated by the formation of numerous DNA double-strand breaks (DSBs) catalysed by the widely conserved Spo11 protein. In Saccharomyces cerevisiae, Spo11 requires nine other proteins for meiotic DSB formation; however, unlike Spo11, few of these are conserved across kingdoms. In order to investigate this recombination step in higher eukaryotes, we took advantage of a high-throughput meiotic mutant screen carried out in the model plant Arabidopsis thaliana. A collection of 55,000 mutant lines was screened, and spo11-like mutations, characterised by a drastic decrease in chiasma formation at metaphase I associated with an absence of synapsis at prophase, were selected. This screen led to the identification of two populations of mutants classified according to their recombination defects: mutants that repair meiotic DSBs using the sister chromatid such as Atdmc1 or mutants that are unable to make DSBs like Atspo11-1. We found that in Arabidopsis thaliana at least four proteins are necessary for driving meiotic DSB repair via the homologous chromosomes. These include the previously characterised DMC1 and the Hop1-related ASY1 proteins, but also the meiotic specific cyclin SDS as well as the Hop2 Arabidopsis homologue AHP2. Analysing the mutants defective in DSB formation, we identified the previously characterised AtSPO11-1, AtSPO11-2, and AtPRD1 as well as two new genes, AtPRD2 and AtPRD3. Our data thus increase the number of proteins necessary for DSB formation in Arabidopsis thaliana to five. Unlike SPO11 and (to a minor extent) PRD1, these two new proteins are poorly conserved among species, suggesting that the DSB formation mechanism, but not its regulation, is conserved among eukaryotes.

  5. Genome rearrangements and pervasive meiotic drive cause hybrid infertility in fission yeast

    PubMed Central

    Zanders, Sarah E; Eickbush, Michael T; Yu, Jonathan S; Kang, Ji-Won; Fowler, Kyle R; Smith, Gerald R; Malik, Harmit Singh

    2014-01-01

    Hybrid sterility is one of the earliest postzygotic isolating mechanisms to evolve between two recently diverged species. Here we identify causes underlying hybrid infertility of two recently diverged fission yeast species Schizosaccharomyces pombe and S. kambucha, which mate to form viable hybrid diploids that efficiently complete meiosis, but generate few viable gametes. We find that chromosomal rearrangements and related recombination defects are major but not sole causes of hybrid infertility. At least three distinct meiotic drive alleles, one on each S. kambucha chromosome, independently contribute to hybrid infertility by causing nonrandom spore death. Two of these driving loci are linked by a chromosomal translocation and thus constitute a novel type of paired meiotic drive complex. Our study reveals how quickly multiple barriers to fertility can arise. In addition, it provides further support for models in which genetic conflicts, such as those caused by meiotic drive alleles, can drive speciation. DOI: http://dx.doi.org/10.7554/eLife.02630.001 PMID:24963140

  6. SLX2 interacting with BLOS2 is differentially expressed during mouse oocyte meiotic maturation.

    PubMed

    Zhuang, Xin-Jie; Shi, Yu-Qiang; Xu, Bo; Chen, Lei; Tang, Wen-Hao; Huang, Jin; Lian, Ying; Liu, Ping; Qiao, Jie

    2014-01-01

    Gametogenesis is a complex biological process of producing cells for sexual reproduction. Xlr super family members containing a conserved COR1 domain play essential roles in gametogenesis. In the present study, we identified that Slx2, a novel member of Xlr super family, is specifically expressed in the meiotic oocytes, which is demonstrated by western blotting and immunohistochemistry studies. In the first meiotic prophase, SLX2 is unevenly distributed in the nuclei of oocytes, during which phase SLX2 is partly co-localized with SYCP3 in synaptonemal complex and γH2AX in the nucleus of oocytes. Interestingly, the localization of SLX2 was found to be switched into the cytoplasm of oocytes after prometaphase I during oocyte maturation. Furthermore, yeast two-hybrid and coimmunoprecipitation studies demonstrated that SLX2 interacts with BLOS2, which is a novel centrosome-associated protein, and co-localized with γ-Tubulin, which is a protein marker of chromosome segregation in meiosis. These results indicated that SLX2 might get involved in chromosomes segregation during meiosis by interaction with BLOS2. In conclusion, SLX2 might be a novel gametogenesis-related protein that could play multiple roles in regulation of meiotic processes including synaptonemal complex assembly and chromosome segregation. PMID:24870619

  7. A Maternal Screen for Genes Regulating Drosophila Oocyte Polarity Uncovers New Steps in Meiotic Progression

    PubMed Central

    Barbosa, Vitor; Kimm, Naomi; Lehmann, Ruth

    2007-01-01

    Meiotic checkpoints monitor chromosome status to ensure correct homologous recombination, genomic integrity, and chromosome segregation. In Drosophila, the persistent presence of double-strand DNA breaks (DSB) activates the ATR/Mei-41 checkpoint, delays progression through meiosis, and causes defects in DNA condensation of the oocyte nucleus, the karyosome. Checkpoint activation has also been linked to decreased levels of the TGFα-like molecule Gurken, which controls normal eggshell patterning. We used this easy-to-score eggshell phenotype in a germ-line mosaic screen in Drosophila to identify new genes affecting meiotic progression, DNA condensation, and Gurken signaling. One hundred eighteen new ventralizing mutants on the second chromosome fell into 17 complementation groups. Here we describe the analysis of 8 complementation groups, including Kinesin heavy chain, the SR protein kinase cuaba, the cohesin-related gene dPds5/cohiba, and the Tudor-domain gene montecristo. Our findings challenge the hypothesis that checkpoint activation upon persistent DSBs is exclusively mediated by ATR/Mei-41 kinase and instead reveal a more complex network of interactions that link DSB formation, checkpoint activation, meiotic delay, DNA condensation, and Gurken protein synthesis. PMID:17507684

  8. Genome rearrangements and pervasive meiotic drive cause hybrid infertility in fission yeast.

    PubMed

    Zanders, Sarah E; Eickbush, Michael T; Yu, Jonathan S; Kang, Ji-Won; Fowler, Kyle R; Smith, Gerald R; Malik, Harmit Singh

    2014-06-24

    Hybrid sterility is one of the earliest postzygotic isolating mechanisms to evolve between two recently diverged species. Here we identify causes underlying hybrid infertility of two recently diverged fission yeast species Schizosaccharomyces pombe and S. kambucha, which mate to form viable hybrid diploids that efficiently complete meiosis, but generate few viable gametes. We find that chromosomal rearrangements and related recombination defects are major but not sole causes of hybrid infertility. At least three distinct meiotic drive alleles, one on each S. kambucha chromosome, independently contribute to hybrid infertility by causing nonrandom spore death. Two of these driving loci are linked by a chromosomal translocation and thus constitute a novel type of paired meiotic drive complex. Our study reveals how quickly multiple barriers to fertility can arise. In addition, it provides further support for models in which genetic conflicts, such as those caused by meiotic drive alleles, can drive speciation.DOI: http://dx.doi.org/10.7554/eLife.02630.001.

  9. Php4 Is a Key Player for Iron Economy in Meiotic and Sporulating Cells

    PubMed Central

    Brault, Ariane; Rallis, Charalampos; Normant, Vincent; Garant, Jean-Michel; Bähler, Jürg; Labbé, Simon

    2016-01-01

    Meiosis is essential for sexually reproducing organisms, including the fission yeast Schizosaccharomyces pombe. In meiosis, chromosomes replicate once in a diploid precursor cell (zygote), and then segregate twice to generate four haploid meiotic products, named spores in yeast. In S. pombe, Php4 is responsible for the transcriptional repression capability of the heteromeric CCAAT-binding factor to negatively regulate genes encoding iron-using proteins under low-iron conditions. Here, we show that the CCAAT-regulatory subunit Php4 is required for normal progression of meiosis under iron-limiting conditions. Cells lacking Php4 exhibit a meiotic arrest at metaphase I. Microscopic analyses of cells expressing functional GFP-Php4 show that it colocalizes with chromosomal material at every stage of meiosis under low concentrations of iron. In contrast, GFP-Php4 fluorescence signal is lost when cells undergo meiosis under iron-replete conditions. Global gene expression analysis of meiotic cells using DNA microarrays identified 137 genes that are regulated in an iron- and Php4-dependent manner. Among them, 18 genes are expressed exclusively during meiosis and constitute new putative Php4 target genes, which include hry1+ and mug14+. Further analysis validates that Php4 is required for maximal and timely repression of hry1+ and mug14+ genes. Using a chromatin immunoprecipitation approach, we show that Php4 specifically associates with hry1+ and mug14+ promoters in vivo. Taken together, the results reveal that in iron-starved meiotic cells, Php4 is essential for completion of the meiotic program since it participates in global gene expression reprogramming to optimize the use of limited available iron. PMID:27466270

  10. Meiotic recombination counteracts male-biased mutation (male-driven evolution).

    PubMed

    Mawaribuchi, Shuuji; Ito, Michihiko; Ogata, Mitsuaki; Oota, Hiroki; Katsumura, Takafumi; Takamatsu, Nobuhiko; Miura, Ikuo

    2016-01-27

    Meiotic recombination is believed to produce greater genetic variation despite the fact that deoxyribonucleic acid (DNA)-replication errors are a major source of mutations. In some vertebrates, mutation rates are higher in males than in females, which developed the theory of male-driven evolution (male-biased mutation). However, there is little molecular evidence regarding the relationships between meiotic recombination and male-biased mutation. Here we tested the theory using the frog Rana rugosa, which has both XX/XY- and ZZ/ZW-type sex-determining systems within the species. The male-to-female mutation-rate ratio (α) was calculated from homologous sequences on the X/Y or Z/W sex chromosomes, which supported male-driven evolution. Surprisingly, each α value was notably higher in the XX/XY-type group than in the ZZ/ZW-type group, although α should have similar values within a species. Interestingly, meiotic recombination between homologous chromosomes did not occur except at terminal regions in males of this species. Then, by subdividing α into two new factors, a replication-based male-to-female mutation-rate ratio (β) and a meiotic recombination-based XX-to-XY/ZZ-to-ZW mutation-rate ratio (γ), we constructed a formula describing the relationship among a nucleotide-substitution rate and the two factors, β and γ. Intriguingly, the β- and γ-values were larger and smaller than 1, respectively, indicating that meiotic recombination might reduce male-biased mutations.

  11. Senataxin controls meiotic silencing through ATR activation and chromatin remodeling.

    PubMed

    Yeo, Abrey J; Becherel, Olivier J; Luff, John E; Graham, Mark E; Richard, Derek; Lavin, Martin F

    2015-01-01

    Senataxin, defective in ataxia oculomotor apraxia type 2, protects the genome by facilitating the resolution of RNA-DNA hybrids (R-loops) and other aspects of RNA processing. Disruption of this gene in mice causes failure of meiotic recombination and defective meiotic sex chromosome inactivation, leading to male infertility. Here we provide evidence that the disruption of Setx leads to reduced SUMOylation and disruption of protein localization across the XY body during meiosis. We demonstrate that senataxin and other DNA damage repair proteins, including ataxia telangiectasia and Rad3-related protein-interacting partner, are SUMOylated, and a marked downregulation of both ataxia telangiectasia and Rad3-related protein-interacting partner and TopBP1 leading to defective activation and signaling through ataxia telangiectasia and Rad3-related protein occurs in the absence of senataxin. Furthermore, chromodomain helicase DNA-binding protein 4, a component of the nucleosome remodeling and deacetylase chromatin remodeler that interacts with both ataxia telangiectasia and Rad3-related protein and senataxin was not recruited efficiently to the XY body, triggering altered histone acetylation and chromatin conformation in Setx (-/-) pachytene-staged spermatocytes. These results demonstrate that senataxin has a critical role in ataxia telangiectasia and Rad3-related protein- and chromodomain helicase DNA-binding protein 4-mediated transcriptional silencing and chromatin remodeling during meiosis providing greater insight into its critical role in gene regulation to protect against neurodegeneration. PMID:27462424

  12. Senataxin controls meiotic silencing through ATR activation and chromatin remodeling

    PubMed Central

    Yeo, Abrey J; Becherel, Olivier J; Luff, John E; Graham, Mark E; Richard, Derek; Lavin, Martin F

    2015-01-01

    Senataxin, defective in ataxia oculomotor apraxia type 2, protects the genome by facilitating the resolution of RNA–DNA hybrids (R-loops) and other aspects of RNA processing. Disruption of this gene in mice causes failure of meiotic recombination and defective meiotic sex chromosome inactivation, leading to male infertility. Here we provide evidence that the disruption of Setx leads to reduced SUMOylation and disruption of protein localization across the XY body during meiosis. We demonstrate that senataxin and other DNA damage repair proteins, including ataxia telangiectasia and Rad3-related protein-interacting partner, are SUMOylated, and a marked downregulation of both ataxia telangiectasia and Rad3-related protein-interacting partner and TopBP1 leading to defective activation and signaling through ataxia telangiectasia and Rad3-related protein occurs in the absence of senataxin. Furthermore, chromodomain helicase DNA-binding protein 4, a component of the nucleosome remodeling and deacetylase chromatin remodeler that interacts with both ataxia telangiectasia and Rad3-related protein and senataxin was not recruited efficiently to the XY body, triggering altered histone acetylation and chromatin conformation in Setx−/− pachytene-staged spermatocytes. These results demonstrate that senataxin has a critical role in ataxia telangiectasia and Rad3-related protein- and chromodomain helicase DNA-binding protein 4-mediated transcriptional silencing and chromatin remodeling during meiosis providing greater insight into its critical role in gene regulation to protect against neurodegeneration. PMID:27462424

  13. Extensive Recombination of a Yeast Diploid Hybrid through Meiotic Reversion

    PubMed Central

    Laureau, Raphaëlle; Loeillet, Sophie; Salinas, Francisco; Bergström, Anders; Legoix-Né, Patricia; Liti, Gianni; Nicolas, Alain

    2016-01-01

    In somatic cells, recombination between the homologous chromosomes followed by equational segregation leads to loss of heterozygosity events (LOH), allowing the expression of recessive alleles and the production of novel allele combinations that are potentially beneficial upon Darwinian selection. However, inter-homolog recombination in somatic cells is rare, thus reducing potential genetic variation. Here, we explored the property of S. cerevisiae to enter the meiotic developmental program, induce meiotic Spo11-dependent double-strand breaks genome-wide and return to mitotic growth, a process known as Return To Growth (RTG). Whole genome sequencing of 36 RTG strains derived from the hybrid S288c/SK1 diploid strain demonstrates that the RTGs are bona fide diploids with mosaic recombined genome, derived from either parental origin. Individual RTG genome-wide genotypes are comprised of 5 to 87 homozygous regions due to the loss of heterozygous (LOH) events of various lengths, varying between a few nucleotides up to several hundred kilobases. Furthermore, we show that reiteration of the RTG process shows incremental increases of homozygosity. Phenotype/genotype analysis of the RTG strains for the auxotrophic and arsenate resistance traits validates the potential of this procedure of genome diversification to rapidly map complex traits loci (QTLs) in diploid strains without undergoing sexual reproduction. PMID:26828862

  14. Axin-1 Regulates Meiotic Spindle Organization in Mouse Oocytes

    PubMed Central

    Liu, Rui; Liu, Yu; Zhang, Fei; Zhang, Zhen; Shen, Yu-Ting; Xu, Lin; Chen, Ming-Huang; Wang, Ya-Long; Xu, Bai-Hui; Yang, Xiang-Jun; Wang, Hai-Long

    2016-01-01

    Axin-1, a negative regulator of Wnt signaling, is a versatile scaffold protein involved in centrosome separation and spindle assembly in mitosis, but its function in mammalian oogenesis remains unknown. Here we examined the localization and function of Axin-1 during meiotic maturation in mouse oocytes. Immunofluorescence analysis showed that Axin-1 was localized around the spindle. Knockdown of the Axin1 gene by microinjection of specific short interfering (si)RNA into the oocyte cytoplasm resulted in severely defective spindles, misaligned chromosomes, failure of first polar body (PB1) extrusion, and impaired pronuclear formation. However, supplementing the culture medium with the Wnt pathway activator LiCl improved spindle morphology and pronuclear formation. Downregulation of Axin1 gene expression also impaired the spindle pole localization of γ-tubulin/Nek9 and resulted in retention of the spindle assembly checkpoint protein BubR1 at kinetochores after 8.5 h of culture. Our results suggest that Axin-1 is critical for spindle organization and cell cycle progression during meiotic maturation in mouse oocytes. PMID:27284927

  15. Mechanism and regulation of meiotic recombination initiation

    PubMed Central

    Lam, Isabel; Keeney, Scott

    2015-01-01

    Meiotic recombination involves the formation and repair of programmed DNA double-strand breaks (DSBs) catalyzed by the conserved Spo11 protein. This review summarizes recent studies pertaining to the formation of meiotic DSBs, including the mechanism of DNA cleavage by Spo11, proteins required for break formation, and mechanisms that control the location, timing, and number of DSBs. Where appropriate, findings in different organisms are discussed to highlight evolutionary conservation or divergence. PMID:25324213

  16. Whole-Genome Analysis of Individual Meiotic Events in Drosophila melanogaster Reveals That Noncrossover Gene Conversions Are Insensitive to Interference and the Centromere Effect

    PubMed Central

    Miller, Danny E.; Smith, Clarissa B.; Kazemi, Nazanin Yeganeh; Cockrell, Alexandria J.; Arvanitakis, Alexandra V.; Blumenstiel, Justin P.; Jaspersen, Sue L.; Hawley, R. Scott

    2016-01-01

    A century of genetic analysis has revealed that multiple mechanisms control the distribution of meiotic crossover events. In Drosophila melanogaster, two significant positional controls are interference and the strongly polar centromere effect. Here, we assess the factors controlling the distribution of crossovers (COs) and noncrossover gene conversions (NCOs) along all five major chromosome arms in 196 single meiotic divisions to generate a more detailed understanding of these controls on a genome-wide scale. Analyzing the outcomes of single meiotic events allows us to distinguish among different classes of meiotic recombination. In so doing, we identified 291 NCOs spread uniformly among the five major chromosome arms and 541 COs (including 52 double crossovers and one triple crossover). We find that unlike COs, NCOs are insensitive to the centromere effect and do not demonstrate interference. Although the positions of COs appear to be determined predominately by the long-range influences of interference and the centromere effect, each chromosome may display a different pattern of sensitivity to interference, suggesting that interference may not be a uniform global property. In addition, unbiased sequencing of a large number of individuals allows us to describe the formation of de novo copy number variants, the majority of which appear to be mediated by unequal crossing over between transposable elements. This work has multiple implications for our understanding of how meiotic recombination is regulated to ensure proper chromosome segregation and maintain genome stability. PMID:26944917

  17. High-density linkage mapping in a pine tree reveals a genomic region associated with inbreeding depression and provides clues to the extent and distribution of meiotic recombination

    PubMed Central

    2013-01-01

    Background The availability of a large expressed sequence tags (EST) resource and recent advances in high-throughput genotyping technology have made it possible to develop highly multiplexed SNP arrays for multi-objective genetic applications, including the construction of meiotic maps. Such approaches are particularly useful in species with a large genome size, precluding the use of whole-genome shotgun assembly with current technologies. Results In this study, a 12 k-SNP genotyping array was developed for maritime pine from an extensive EST resource assembled into a unigene set. The offspring of three-generation outbred and inbred mapping pedigrees were then genotyped. The inbred pedigree consisted of a classical F2 population resulting from the selfing of a single inter-provenance (Landes x Corsica) hybrid tree, whereas the outbred pedigree (G2) resulted from a controlled cross of two intra-provenance (Landes x Landes) hybrid trees. This resulted in the generation of three linkage maps based on SNP markers: one from the parental genotype of the F2 population (1,131 markers in 1,708 centimorgan (cM)), and one for each parent of the G2 population (1,015 and 1,110 markers in 1,447 and 1,425 cM for the female and male parents, respectively). A comparison of segregation patterns in the progeny obtained from the two types of mating (inbreeding and outbreeding) led to the identification of a chromosomal region carrying an embryo viability locus with a semi-lethal allele. Following selfing and segregation, zygote mortality resulted in a deficit of Corsican homozygous genotypes in the F2 population. This dataset was also used to study the extent and distribution of meiotic recombination along the length of the chromosomes and the effect of sex and/or genetic background on recombination. The genetic background of trees in which meiotic recombination occurred was found to have a significant effect on the frequency of recombination. Furthermore, only a small proportion of

  18. Isolation and cytogenetic characterization of male meiotic mutants of Drosophila melanogaster.

    PubMed Central

    Hirai, Kazuyuki; Toyohira, Satomi; Ohsako, Takashi; Yamamoto, Masa-Toshi

    2004-01-01

    Proper segregation of homologous chromosomes in meiosis I is ensured by pairing of homologs and maintenance of sister chromatid cohesion. In male Drosophila melanogaster, meiosis is achiasmatic and homologs pair at limited chromosome regions called pairing sites. We screened for male meiotic mutants to identify genes required for normal pairing and disjunction of homologs. Nondisjunction of the sex and the fourth chromosomes in male meiosis was scored as a mutant phenotype. We screened 2306 mutagenized and 226 natural population-derived second and third chromosomes and obtained seven mutants representing different loci on the second chromosome and one on the third. Five mutants showed relatively mild effects (<10% nondisjunction). mei(2)yh149 and mei(2)yoh7134 affected both the sex and the fourth chromosomes, mei(2)yh217 produced possible sex chromosome-specific nondisjunction, and mei(2)yh15 and mei(2)yh137 produced fourth chromosome-specific nondisjunction. mei(2)yh137 was allelic to the teflon gene required for autosomal pairing. Three mutants exhibited severe defects, producing >10% nondisjunction of the sex and/or the fourth chromosomes. mei(2)ys91 (a new allele of the orientation disruptor gene) and mei(3)M20 induced precocious separation of sister chromatids as early as prometa-phase I. mei(2)yh92 predominantly induced nondisjunction at meiosis I that appeared to be the consequence of failure of the separation of paired homologous chromosomes. PMID:15126399

  19. X-Chromosome dosage compensation.

    PubMed

    Meyer, Barbara J

    2005-01-01

    In mammals, flies, and worms, sex is determined by distinctive regulatory mechanisms that cause males (XO or XY) and females (XX) to differ in their dose of X chromosomes. In each species, an essential X chromosome-wide process called dosage compensation ensures that somatic cells of either sex express equal levels of X-linked gene products. The strategies used to achieve dosage compensation are diverse, but in all cases, specialized complexes are targeted specifically to the X chromosome(s) of only one sex to regulate transcript levels. In C. elegans, this sex-specific targeting of the dosage compensation complex (DCC) is controlled by the same developmental signal that establishes sex, the ratio of X chromosomes to sets of autosomes (X:A signal). Molecular components of this chromosome counting process have been defined. Following a common step of regulation, sex determination and dosage compensation are controlled by distinct genetic pathways. C. elegans dosage compensation is implemented by a protein complex that binds both X chromosomes of hermaphrodites to reduce transcript levels by one-half. The dosage compensation complex resembles the conserved 13S condensin complex required for both mitotic and meiotic chromosome resolution and condensation, implying the recruitment of ancient proteins to the new task of regulating gene expression. Within each C. elegans somatic cell, one of the DCC components also participates in the separate mitotic/meiotic condensin complex. Other DCC components play pivotal roles in regulating the number and distribution of crossovers during meiosis. The strategy by which C. elegans X chromosomes attract the condensin-like DCC is known. Small, well-dispersed X-recognition elements act as entry sites to recruit the dosage compensation complex and to nucleate spreading of the complex to X regions that lack recruitment sites. In this manner, a repressed chromatin state is spread in cis over short or long distances, thus establishing the

  20. ACTIN-RELATED PROTEIN6 Regulates Female Meiosis by Modulating Meiotic Gene Expression in Arabidopsis.

    PubMed

    Qin, Yuan; Zhao, Lihua; Skaggs, Megan I; Andreuzza, Sebastien; Tsukamoto, Tatsuya; Panoli, Aneesh; Wallace, Kirsten N; Smith, Steven; Siddiqi, Imran; Yang, Zhenbiao; Yadegari, Ramin; Palanivelu, Ravishankar

    2014-04-15

    In flowering plants, meiocytes develop from subepidermal cells in anthers and ovules. The mechanisms that integrate gene-regulatory processes with meiotic programs during reproductive development remain poorly characterized. Here, we show that Arabidopsis thaliana plants deficient in ACTIN-RELATED PROTEIN6 (ARP6), a subunit of the SWR1 ATP-dependent chromatin-remodeling complex, exhibit defects in prophase I of female meiosis. We found that this meiotic defect is likely due to dysregulated expression of meiotic genes, particularly those involved in meiotic recombination, including DMC1 (DISRUPTED MEIOTIC cDNA1). Analysis of DMC1 expression in arp6 mutant plants indicated that ARP6 inhibits expression of DMC1 in the megasporocyte and surrounding nonsporogeneous ovule cells before meiosis. After cells enter meiosis, however, ARP6 activates DMC1 expression specifically in the megasporocyte even as it continues to inhibit DMC1 expression in the nonsporogenous ovule cells. We further show that deposition of the histone variant H2A.Z, mediated by the SWR1 chromatin-remodeling complex at the DMC1 gene body, requires ARP6. Therefore, ARP6 regulates female meiosis by determining the spatial and temporal patterns of gene expression required for proper meiosis during ovule development. PMID:24737671

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

    SciTech Connect

    Cooper, Tim J.; Wardell, Kayleigh; Garcia, Valerie; Neale, Matthew J.

    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.

  2. [Meiotic gynogenesis in the stellate, Russian sturgeon and sterlet].

    PubMed

    Rekubratskiĭ, A V; Grunina, A S; Barmintsev, V A; Golovanova, T S; Chudinov, O S; Abramova, A B; Panchenko, N S; Kupchenko, S A

    2003-01-01

    Diploid gynogenetic progenies were obtained in the stellate sturgeon Acipenser stellatus, Russian sturgeon A. gueldenstaedtii, and sterlet A. ruthenus by means of insemination of the eggs with UV-irradiated spermatozoa and suppression of the second meiotic division by heat shock. The gynogenetic nature of experimental fish was confirmed by RAPD-PCR analysis of DNA. Effective photoreactivation of UV-induced lesions of spermatozoa was shown in the case of illumination of the fertilized eggs with visible light. This phenomenon should be taken into account when determining the doses of irradiation that allow inactivation of the male chromosomes and incubating gynogenetic embryos. Gynogenetic stellate and Russian sturgeons are viable and can be reared in order to study the mechanism of sex determination in sturgeons. PMID:12722590

  3. Region-specific meiotic recombination in Schizosaccharomyces pombe: the rec11 gene.

    PubMed

    Li, Y F; Numata, M; Wahls, W P; Smith, G R

    1997-03-01

    Mutations in the rec11 gene of Schizosaccharomyces pombe reduce meiotic recombinant frequencies by as much as a factor of 300 on chromosome III but less than a factor of 4 in the intervals tested on chromosomes I and II. To gain insight into the function of this region- (or chromosome-) specific activator of recombination, we have cloned and sequenced the rec11 gene. Meiotic crosses with rec11 disruption mutations placed the rec11 gene 6 cM from ade6 on chromosome III. Transcripts of rec11 accumulated transiently at 2-3 h after induction of melosis in a pat1-114 (Ts) mutant. Reverse transcriptase/polymerase chain reaction (RT-PCR) analysis of these transcripts revealed eight introns. The spliced RNA is predicted to encode a polypeptide of 923 amino acids with only very limited homology to reported proteins. The transient accumulation of rec11 transcripts and the phenotype of rec11 mutations suggest that the novel rec11 gene product acts early in meiosis to activate recombination preferentially on chromosome III. PMID:9076725

  4. B microchromosomes in the family Curimatidae (Characiformes): mitotic and meiotic behavior

    PubMed Central

    Sampaio, Tatiane Ramos; Gravena, Waleska; Gouveia, Juceli Gonzalez; Giuliano-Caetano, Lucia; Dias, Ana Lúcia

    2011-01-01

    Abstract In the present work, six curimatid species were analyzed: Cyphocharax voga (Hensel, 1870), Cyphocharax spilotus (Vari, 1987), Cyphocharax saladensis (Meinken, 1933), Cyphocharax modestus (Fernández-Yépez, 1948), Steindachnerina biornata (Braga & Azpelicueta, 1987) and Steindachnerina insculpta (Fernández-Yépez, 1948) collected from two hydrographic basins. All samples presented 2n=54 meta-submetacentric (m-sm) chromosomes and FN equal to 108, and 1 or 2 B microchromosomes in the mitotic and meiotic cells of the six sampled populations showing inter-and intraindividual variation. The analysis of the meiotic cells in Cyphocharax saladensis, Cyphocharax spilotus, and Cyphocharax voga showed a modal number of 54 chromosomes in the spermatogonial metaphases and 27 bivalents in the pachytene, diplotene, diakinesis and in metaphase I stages, and 27 chromosomes in metaphase II; in Cyphocharax modestus, Steindachnerina biornata, and Steindachnerina insculpta, spermatogonial metaphases with 54 chromosomes and pachytene and metaphase I with 27 bivalents were observed. The B microchromosome was observed as univalent in the spermatogonial metaphase of Cyphocharax spilotus, in the pachytene stage in the other species, with the exception of Cyphocharax saladensis, and Steindachnerina biornata in metaphase I. New occurrences of the B microchromosome in Cyphocharax voga, Cyphocharax saladensis and Steindachnerina biornata were observed, confirming that the presence of this type of chromosome is a striking characteristic of this group of fish. PMID:24260637

  5. Meiotic drive impacts expression and evolution of x-linked genes in stalk-eyed flies.

    PubMed

    Reinhardt, Josephine A; Brand, Cara L; Paczolt, Kimberly A; Johns, Philip M; Baker, Richard H; Wilkinson, Gerald S

    2014-01-01

    Although sex chromosome meiotic drive has been observed in a variety of species for over 50 years, the genes causing drive are only known in a few cases, and none of these cases cause distorted sex-ratios in nature. In stalk-eyed flies (Teleopsis dalmanni), driving X chromosomes are commonly found at frequencies approaching 30% in the wild, but the genetic basis of drive has remained elusive due to reduced recombination between driving and non-driving X chromosomes. Here, we used RNAseq to identify transcripts that are differentially expressed between males carrying either a driving X (XSR) or a standard X chromosome (XST), and found hundreds of these, the majority of which are X-linked. Drive-associated transcripts show increased levels of sequence divergence (dN/dS) compared to a control set, and are predominantly expressed either in testes or in the gonads of both sexes. Finally, we confirmed that XSR and XST are highly divergent by estimating sequence differentiation between the RNAseq pools. We found that X-linked transcripts were often strongly differentiated (whereas most autosomal transcripts were not), supporting the presence of a relatively large region of recombination suppression on XSR presumably caused by one or more inversions. We have identified a group of genes that are good candidates for further study into the causes and consequences of sex-chromosome drive, and demonstrated that meiotic drive has had a profound effect on sequence evolution and gene expression of X-linked genes in this species.

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

    PubMed Central

    Ruvalcaba-Ruiz, Domingo; Rodríguez-Garay, Benjamin

    2002-01-01

    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. PMID:12396234

  7. Meiotic double-strand breaks uncover and protect against mitotic errors in the C. elegans germline.

    PubMed

    Stevens, Deanna; Oegema, Karen; Desai, Arshad

    2013-12-01

    In sexually reproducing multicellular organisms, genetic information is propagated via the germline, the specialized tissue that generates haploid gametes. The C. elegans germline generates gametes in an assembly line-like process-mitotic divisions under the control of the stem cell niche produce nuclei that, upon leaving the niche, enter into meiosis and progress through meiotic prophase [1]. Here, we characterize the effects of perturbing cell division in the mitotic region of the C. elegans germline. We show that mitotic errors result in a spindle checkpoint-dependent cell-cycle delay, but defective nuclei are eventually formed and enter meiosis. These defective nuclei are eliminated by programmed cell death during meiotic prophase. The cell death-based removal of defective nuclei does not require the spindle checkpoint but instead depends on the DNA damage checkpoint. Removal of nuclei resulting from errors in mitosis also requires Spo11, the enzyme that creates double-strand breaks to initiate meiotic recombination. Consistent with this, double-strand breaks are increased in number and persist longer in germlines with mitotic defects. These findings reveal that the process of initiating meiotic recombination inherently selects against nuclei with abnormal chromosomal content generated by mitotic errors, thereby ensuring the genomic integrity of gametes.

  8. Intranuclear membranes and the formation of the first meiotic spindle in Xenos peckii (Acroschismus wheeleri) oocytes

    PubMed Central

    1983-01-01

    The ultrastructure of spindle formation during the first meiotic division in oocytes of the Strepsipteran insect Xenos peckii Kirby (Acroschismus wheeleri Pierce) was examined in serial thick (0.25- micron) and thin sections. During late prophase the nuclear envelope became extremely convoluted and fenestrated. At this time vesicular and tubular membrane elements permeated the nucleoplasm and formed a thin fusiform sheath, 5-7 micron in length, around each of the randomly oriented and condensing tetrads. These membrane elements appeared to arise from the nuclear envelope and/or in association with annulate lamellae in the nuclear region. All of the individual tetrads and their associated fusiform sheaths became aligned within the nucleus subsequent to the breakdown of the nuclear envelope. Microtubules (MTs) were found associated with membranes of the meiotic apparatus only after the nuclear envelope had broken down. Kinetochores, with associated MTs, were first recognizable as electron-opaque patches on the chromosomes at this time. The fully formed metaphase arrested Xenos oocyte meiotic apparatus contained an abundance of membranes and had diffuse poles that lacked distinct polar MT organizing centers. From these observations we conclude that the apparent individual chromosomal spindles--seen in the light microscope to form around each Xenos tetrad during "intranuclear prometaphase" (Hughes-Schrader, S., 1924, J. Morphol. 39:157-197)--actually form during late prophase, lack MTs, and are therefore not complete miniature bipolar spindles, as had been commonly assumed. Thus, the unique mode of spindle formation in Xenos oocytes cannot be used to support the hypothesis that chromosomes (kinetochores) induce the polymerization of their associated MTs. Our observation that MTs appeared in association with and parallel to tubular membrane components of the Xenos meiotic apparatus after these membranes became oriented with respect to the tetrads, is consistent with the

  9. H3 Thr3 phosphorylation is crucial for meiotic resumption and anaphase onset in oocyte meiosis.

    PubMed

    Wang, Qian; Wei, Haojie; Du, Juan; Cao, Yan; Zhang, Nana; Liu, Xiaoyun; Liu, Xiaoyu; Chen, Dandan; Ma, Wei

    2016-01-01

    Haspin-catalyzed histone H3 threonine 3 (Thr3) phosphorylation facilitates chromosomal passenger complex (CPC) docking at centromeres, regulating indirectly chromosome behavior during somatic mitosis. It is not fully known about the expression and function of H3 with phosphorylated Thr3 (H3T3-P) during meiosis in oocytes. In this study, we investigated the expression and sub-cellular distribution of H3T3-P, as well as its function in mouse oocytes during meiotic division. Western blot analysis revealed that H3T3-P expression was only detected after germinal vesicle breakdown (GVBD), and gradually increased to peak level at metaphase I (MI), but sharply decreased at metaphase II (MII). Immunofluorescence showed H3T3-P was only brightly labeled on chromosomes after GVBD, with relatively high concentration across the whole chromosome axis from pro-metaphase I (pro-MI) to MI. Specially, H3T3-P distribution was exclusively limited to the local space between sister centromeres at MII stage. Haspin inhibitor, 5-iodotubercidin (5-ITu), dose- and time-dependently blocked H3T3-P expression in mouse oocytes. H3T3-P inhibition delayed the resumption of meiosis (GVBD) and chromatin condensation. Moreover, the loss of H3T3-P speeded up the meiotic transition to MII of pro-MI oocytes in spite of the presence of non-aligned chromosomes, even reversed MI-arrest induced with Nocodazole. The inhibition of H3T3-P expression distinguishably damaged MAD1 recruitment on centromeres, which indicates the spindle assembly checkpoint was impaired in function, logically explaining the premature onset of anaphase I. Therefore, Haspin-catalyzed histone H3 phosphorylation is essential for chromatin condensation and the following timely transition from meiosis I to meiosis II in mouse oocytes during meiotic division. PMID:26636626

  10. Chromosome segregation in plant meiosis

    PubMed Central

    Zamariola, Linda; Tiang, Choon Lin; De Storme, Nico; Pawlowski, Wojtek; Geelen, Danny

    2014-01-01

    Faithful chromosome segregation in meiosis is essential for ploidy stability over sexual life cycles. In plants, defective chromosome segregation caused by gene mutations or other factors leads to the formation of unbalanced or unreduced gametes creating aneuploid or polyploid progeny, respectively. Accurate segregation requires the coordinated execution of conserved processes occurring throughout the two meiotic cell divisions. Synapsis and recombination ensure the establishment of chiasmata that hold homologous chromosomes together allowing their correct segregation in the first meiotic division, which is also tightly regulated by cell-cycle dependent release of cohesin and monopolar attachment of sister kinetochores to microtubules. In meiosis II, bi-orientation of sister kinetochores and proper spindle orientation correctly segregate chromosomes in four haploid cells. Checkpoint mechanisms acting at kinetochores control the accuracy of kinetochore-microtubule attachment, thus ensuring the completion of segregation. Here we review the current knowledge on the processes taking place during chromosome segregation in plant meiosis, focusing on the characterization of the molecular factors involved. PMID:24987397

  11. Spindle assembly checkpoint proteins regulate and monitor meiotic synapsis in C. elegans.

    PubMed

    Bohr, Tisha; Nelson, Christian R; Klee, Erin; Bhalla, Needhi

    2015-10-26

    Homologue synapsis is required for meiotic chromosome segregation, but how synapsis is initiated between chromosomes is poorly understood. In Caenorhabditis elegans, synapsis and a checkpoint that monitors synapsis depend on pairing centers (PCs), cis-acting loci that interact with nuclear envelope proteins, such as SUN-1, to access cytoplasmic microtubules. Here, we report that spindle assembly checkpoint (SAC) components MAD-1, MAD-2, and BUB-3 are required to negatively regulate synapsis and promote the synapsis checkpoint response. Both of these roles are independent of a conserved component of the anaphase-promoting complex, indicating a unique role for these proteins in meiotic prophase. MAD-1 and MAD-2 localize to the periphery of meiotic nuclei and interact with SUN-1, suggesting a role at PCs. Consistent with this idea, MAD-1 and BUB-3 require full PC function to inhibit synapsis. We propose that SAC proteins monitor the stability of pairing, or tension, between homologues to regulate synapsis and elicit a checkpoint response.

  12. Spindle assembly checkpoint proteins regulate and monitor meiotic synapsis in C. elegans

    PubMed Central

    Bohr, Tisha; Nelson, Christian R.; Klee, Erin

    2015-01-01

    Homologue synapsis is required for meiotic chromosome segregation, but how synapsis is initiated between chromosomes is poorly understood. In Caenorhabditis elegans, synapsis and a checkpoint that monitors synapsis depend on pairing centers (PCs), cis-acting loci that interact with nuclear envelope proteins, such as SUN-1, to access cytoplasmic microtubules. Here, we report that spindle assembly checkpoint (SAC) components MAD-1, MAD-2, and BUB-3 are required to negatively regulate synapsis and promote the synapsis checkpoint response. Both of these roles are independent of a conserved component of the anaphase-promoting complex, indicating a unique role for these proteins in meiotic prophase. MAD-1 and MAD-2 localize to the periphery of meiotic nuclei and interact with SUN-1, suggesting a role at PCs. Consistent with this idea, MAD-1 and BUB-3 require full PC function to inhibit synapsis. We propose that SAC proteins monitor the stability of pairing, or tension, between homologues to regulate synapsis and elicit a checkpoint response. PMID:26483555

  13. Brca2-Pds5 complexes mobilize persistent meiotic recombination sites to the nuclear envelope.

    PubMed

    Kusch, Thomas

    2015-02-15

    Homologous recombination is required for reciprocal exchange between homologous chromosome arms during meiosis. Only select meiotic recombination events become chromosomal crossovers; the majority of recombination outcomes are noncrossovers. Growing evidence suggests that crossovers are repaired after noncrossovers. Here, I report that persisting recombination sites are mobilized to the nuclear envelope of Drosophila pro-oocytes during mid-pachytene. Their number correlates with the average crossover rate per meiosis. Proteomic and interaction studies reveal that the recombination mediator Brca2 associates with lamin and the cohesion factor Pds5 to secure persistent recombination sites at the nuclear envelope. In Rad51(-/-) females, all persistent DNA breaks are directed to the nuclear envelope. By contrast, a reduction of Pds5 or Brca2 levels abolishes the movement and has a negative impact on crossover rates. The data suggest that persistent meiotic DNA double-strand breaks might correspond to crossovers, which are mobilized to the nuclear envelope for their repair. The identification of Brca2-Pds5 complexes as key mediators of this process provides a first mechanistic explanation for the contribution of lamins and cohesins to meiotic recombination.

  14. Analyses of the involvement of PKA regulation mechanism in meiotic incompetence of porcine growing oocytes.

    PubMed

    Nishimura, Takanori; Fujii, Wataru; Kano, Kiyoshi; Sugiura, Koji; Naito, Kunihiko

    2012-09-01

    Mammalian growing oocytes (GOs) lack the ability to resume meiosis, although the molecular mechanism of this limitation is not fully understood. In the present study, we cloned cDNAs of cAMP-dependent protein-kinase (PKA) subunits from porcine oocytes and analyzed the involvement of the PKA regulation mechanism in the meiotic incompetence of GOs at the molecular level. We found a cAMP-independent high PKA activity in GOs throughout the in vitro culture using a porcine PKA assay system we established, and inhibition of the activity by injection of the antisense RNA of the PKA catalytic subunit (PKA-C) induced meiotic resumption in GOs. Then we examined the possibility that the amount of the PKA regulatory subunit (PKA-R), which can bind and inhibit PKA-C, was insufficient to suppress PKA activity in GOs because of the overexpression of two PKA-Rs, PRKAR1A and PRKAR2A. We found that neither of them affected PKA activity and induced meiotic resumption in GO although PRKAR2A could inhibit PKA activity and induce meiosis in cAMP-treated full-grown oocytes (FGOs). Finally, we analyzed the subcellular localization of PKA subunits and found that all the subunits were localized in the cytoplasm during meiotic arrest and that PKA-C and PRKAR2A, but not PRKAR1A, entered into the nucleus just before meiotic resumption in FGOs, whereas all of them remained in the cytoplasm in GOs throughout the culture period. Our findings suggest that the continuous high PKA activity is a primary cause of the meiotic incompetence of porcine GOs and that this PKA activity is not simply caused by an insufficient expression level of PKA-R, but can be attributed to more complex spatial-temporal regulation mechanisms. PMID:22674394

  15. Factors affecting meiotic and developmental competence of primary spermatocyte nuclei injected into mouse oocytes.

    PubMed

    Kimura, Y; Tateno, H; Handel, M A; Yanagimachi, R

    1998-10-01

    Mature mouse oocytes that have received the nuclei of pachytene primary spermatocytes (or metaphase I chromosomes of primary spermatocytes) can develop into fertile offspring. However, success rate in this study was low. No more than 3.8% of transferred 2-cell embryos arising from spermatocyte-injected oocytes developed to full term. Nevertheless, the birth of normal offspring seems to suggest that at least in some primary spermatocytes the functional genomic imprinting is complete before transfer and/or consolidated after the transfer. Although injected spermatocyte nuclei could undergo two successive meiotic divisions within oocytes, abnormalities of both divisions were commonly observed, and sister chromatids often separated prematurely during the second meiotic division. Chromosome breakage/rearrangements were also frequently seen before the first cleavage. Such abnormalities of chromosome behavior are probably the major causes of the poor preimplantation development of zygotes arising from primary spermatocyte-injected oocytes. Thus, clinical use of primary spermatocytes as substitutes for spermatozoa in assisted fertilization is not advisable until the causes of chromosomal abnormalities are better understood through extensive animal studies. PMID:9746737

  16. Preaching about the converted: how meiotic gene conversion influences genomic diversity.

    PubMed

    Cole, Francesca; Keeney, Scott; Jasin, Maria

    2012-09-01

    Meiotic crossover (CO) recombination involves a reciprocal exchange between homologous chromosomes. COs are often associated with gene conversion at the exchange site where genetic information is unidirectionally transferred from one chromosome to the other. COs and independent assortment of homologous chromosomes contribute significantly to the promotion of genomic diversity. What has not been appreciated is the contribution of another product of meiotic recombination, noncrossovers (NCOs), which result in gene conversion without exchange of flanking markers. Here, we review our comprehensive analysis of recombination at a highly polymorphic mouse hotspot. We found that NCOs make up ∼90% of recombination events. Preferential recombination initiation on one chromosome allowed us to estimate the contribution of CO and NCO gene conversion to transmission distortion, a deviation from Mendelian inheritance in the population. While NCO gene conversion tracts are shorter, and thus have a more punctate effect, their higher frequency translates into an approximately two-fold greater contribution than COs to gene conversion-based allelic shuffling and transmission distortion. We discuss the potential impact of mammalian NCO characteristics on evolution and genomic diversity. PMID:22954222

  17. Apparent Epigenetic Meiotic Double-Strand-Break Disparity in Saccharomyces cerevisiae: A Meta-Analysis

    PubMed Central

    Stahl, Franklin W.; Rehan, Maryam Binti Mohamed; Foss, Henriette M.; Borts, Rhona H.

    2016-01-01

    Previously published, and some unpublished, tetrad data from budding yeast (Saccharomyces cerevisiae) are analyzed for disparity in gene conversion, in which one allele is more often favored than the other (conversion disparity). One such disparity, characteristic of a bias in the frequencies of meiotic double-strand DNA breaks at the hotspot near the His4 locus, is found in diploids that undergo meiosis soon after their formation, but not in diploids that have been cloned and frozen. Altered meiotic DNA breakability associated with altered metabolism-related chromatin states has been previously reported. However, the above observations imply that such differing parental chromatin states can persist through at least one chromosome replication, and probably more, in a common environment. This conclusion may have implications for interpreting changes in allele frequencies in populations. PMID:27356614

  18. Meiotic checkpoints and the interchromosomal effect on crossing over in Drosophila females

    PubMed Central

    Joyce, Eric F

    2011-01-01

    During prophase of meiosis I, genetic recombination is initiated with a Spo11-dependent DNA double-strand break (DSB). Repair of these DSBs can generate crossovers, which become chiasmata and are important for the process of chromosome segregation. To ensure at least one chiasma per homologous pair of chromosomes, the number and distribution of crossovers is regulated. One system contributing to the distribution of crossovers is the pachytene checkpoint, which requires the conserved gene pch2 that encodes an AAA+ATPase family member. Pch2-dependent pachytene checkpoint function causes delays in pachytene progression when there are defects in processes required for crossover formation, such as mutations in DS B-repair genes and when there are defects in the structure of the meiotic chromosome axis. Thus, the pachytene checkpoint appears to monitor events leading up to the generation of crossovers. Interestingly, heterozygous chromosome rearrangements cause Pch2-dependent pachytene delays and as little as two breaks in the continuity of the paired chromosome axes are sufficient to evoke checkpoint activity. These chromosome rearrangements also cause an interchromosomal effect on recombination whereby crossing over is suppressed between the affected chromosomes but is increased between the normal chromosome pairs. We have shown that this phenomenon is also due to pachytene checkpoint activity. PMID:21339705

  19. Rad61/Wpl1 (Wapl), a cohesin regulator, controls chromosome compaction during meiosis

    PubMed Central

    Challa, Kiran; Lee, Min-Su; Shinohara, Miki; Kim, Keun P.; Shinohara, Akira

    2016-01-01

    Meiosis-specific cohesin, required for the linking of the sister chromatids, plays a critical role in various chromosomal events during meiotic prophase I, such as chromosome morphogenesis and dynamics, as well as recombination. Rad61/Wpl1 (Wapl in other organisms) negatively regulates cohesin functions. In this study, we show that meiotic chromosome axes are shortened in the budding yeast rad61/wpl1 mutant, suggesting that Rad61/Wpl1 negatively regulates chromosome axis compaction. Rad61/Wpl1 is required for efficient resolution of telomere clustering during meiosis I, indicating a positive effect of Rad61/Wpl1 on the cohesin function required for telomere dynamics. Additionally, we demonstrate distinct activities of Rad61/Wpl1 during the meiotic recombination, including its effects on the efficient processing of intermediates. Thus, Rad61/Wpl1 both positively and negatively regulates various cohesin-mediated chromosomal processes during meiosis. PMID:26825462

  20. Rad61/Wpl1 (Wapl), a cohesin regulator, controls chromosome compaction during meiosis.

    PubMed

    Challa, Kiran; Lee, Min-Su; Shinohara, Miki; Kim, Keun P; Shinohara, Akira

    2016-04-20

    Meiosis-specific cohesin, required for the linking of the sister chromatids, plays a critical role in various chromosomal events during meiotic prophase I, such as chromosome morphogenesis and dynamics, as well as recombination. Rad61/Wpl1 (Wapl in other organisms) negatively regulates cohesin functions. In this study, we show that meiotic chromosome axes are shortened in the budding yeast rad61/wpl1 mutant, suggesting that Rad61/Wpl1 negatively regulates chromosome axis compaction. Rad61/Wpl1 is required for efficient resolution of telomere clustering during meiosis I, indicating a positive effect of Rad61/Wpl1 on the cohesin function required for telomere dynamics. Additionally, we demonstrate distinct activities of Rad61/Wpl1 during the meiotic recombination, including its effects on the efficient processing of intermediates. Thus, Rad61/Wpl1 both positively and negatively regulates various cohesin-mediated chromosomal processes during meiosis.

  1. Analysis of chromosome segregation during mammalian meiosis using combined immunofluorescence and fluorescence in situ hubridization

    SciTech Connect

    Hunt, P.A.; Embury, P.B.; Mroz, K.M.

    1994-09-01

    Meiotic non-disjunction is thought to occur in 10-20% of all human oocytes, making this the most common genetic abnormality in our species. Aberrant recombination has been implicated in the genesis of these errors; however, direct studies of the meiotic process have been hampered by the lack of material and appropriate technology. We have developed a technique for the evaluation of meiosis in intact mammalian oocytes that combines immunofluorescence and fluorescence in situ hybridization (FISH). This allows for simultaneous, 3-dimensional visualization of the meiotic spindle, the alignment of the chromosomes on the spindle, and the placement of specific chromosomes. We have used this technology to follow meiotic progression in oocytes from XO female mice to evaluate the behavior of an unsynapsed chromosome during mammalian meiosis. Perturbations in chromosome behavior are evident early in meiosis: during the formation of the first meiotic spindle, the univalent X chromosome is properly positioned. With the onset of anaphase, the single X chromosome most commonly segregates as an intact chromosome, although equational segregation of the X chromatids is seen in a significant minority (approximately 20%) of oocytes. These observations demonstrate that failure of pairing/recombination can result in segregation of sister chromatids at meiosis I. This has obvious implications for human non-disjunction, much of which is thought to be due to recombination deficiencies; accordingly, we are now extending our studies to include analyses of human oocytes.

  2. The meiotic stage of nondisjunction in trisomy 21: Determination by using DNA polymorphisms

    PubMed Central

    Antonarakis, Stylianos E.; Petersen, Michael B.; McInnis, Melvin G.; Adelsberger, Patricia A.; Schinzel, Albert A.; Binkert, Franz; Pangalos, Constantine; Raoul, Odile; Slaugenhaupt, Susan A.; Hafez, Mohamed; Cohen, Maimon M.; Roulson, Diane; Schwartz, Stuart; Mikkelsen, Margareta; Tranebjaerg, Lisbeth; Greenberg, Frank; Hoar, David I.; Rudd, Noreen L.; Warren, Andrew C.; Metaxotou, Caterina; Bartsocas, Christos; Chakravarti, Aravinda

    1992-01-01

    We have studied DNA polymorphisms at loci in the pericentromeric region on the long arm of chromosome 21 in 200 families with trisomy 21, in order to determine the meiotic origin of nondisjunction. Maintenance of heterozygosity for parental markers in the individual with trisomy 21 was interpreted as resulting from a meiosis I error, while reduction to homozygosity was attributed to a meiosis II error. Nondisjunction was paternal in 9 cases and was maternal in 188 cases, as reported earlier. Among the 188 maternal cases, nondisjunction occurred in meiosis I in 128 cases and in meiosis II in 38 cases; in 22 cases the DNA markers used were uninformative. Therefore meiosis I was responsible for 77.1% and meiosis II for 22.9% of maternal nondisjunction. Among the 9 paternal nondisjunction cases the error occurred in meiosis I in 2 cases (22.2%) and in meiosis II in 7 (77.8%) cases. Since there was no significant difference in the distribution of maternal ages between maternal I error versus maternal II error, it is unlikely that an error at a particular meiotic stage contributes significantly to the increasing incidence of Down syndrome with advancing maternal age. Although the DNA polymorphisms used were at loci which map close to the centromere, it is likely that rare errors in meiotic-origin assignments may have occurred because of a small number of crossovers between the markers and the centromere. Analysis of these polymorphisms may provide a more accurate understanding of the meiotic stage of nondisjunction in trisomy 21 than that previously provided by chromosomal heteromorphisms. ImagesFigure 1 PMID:1347192

  3. Cytochemical study of pseudoisocyanine stained human chromosomes.

    PubMed

    Vagner-Capodano, A M; Pinna-Delgrossi, M H; Stahl, A

    1976-01-28

    Human meiotic and mitotic chromosomes were studied with N-N' diethyl pseudoisocyanine stain. Following methylation and oxydation, the staining allowed microscopic observation of slides with both monochromatic light and fluorescence. In addition, stained preparations can be permanently conserved. Preceeded by diverse methods of chromosome denaturation or 5-BUDR incorporation, PIC lends itself to a large number of banding techniques. Cytochemical study of stained chromosomes demonstrated a certain PIC affinity for DNA although tests performed do not exclude the possibility of PIC reaction with certain proteins.

  4. Protein phosphatase 4 promotes chromosome pairing and synapsis, and contributes to maintaining crossover competence with increasing age.

    PubMed

    Sato-Carlton, Aya; Li, Xuan; Crawley, Oliver; Testori, Sarah; Martinez-Perez, Enrique; Sugimoto, Asako; Carlton, Peter M

    2014-10-01

    Prior to the meiotic divisions, dynamic chromosome reorganizations including pairing, synapsis, and recombination of maternal and paternal chromosome pairs must occur in a highly regulated fashion during meiotic prophase. How chromosomes identify each other's homology and exclusively pair and synapse with their homologous partners, while rejecting illegitimate synapsis with non-homologous chromosomes, remains obscure. In addition, how the levels of recombination initiation and crossover formation are regulated so that sufficient, but not deleterious, levels of DNA breaks are made and processed into crossovers is not understood well. We show that in Caenorhabditis elegans, the highly conserved Serine/Threonine protein phosphatase PP4 homolog, PPH-4.1, is required independently to carry out four separate functions involving meiotic chromosome dynamics: (1) synapsis-independent chromosome pairing, (2) restriction of synapsis to homologous chromosomes, (3) programmed DNA double-strand break initiation, and (4) crossover formation. Using quantitative imaging of mutant strains, including super-resolution (3D-SIM) microscopy of chromosomes and the synaptonemal complex, we show that independently-arising defects in each of these processes in the absence of PPH-4.1 activity ultimately lead to meiotic nondisjunction and embryonic lethality. Interestingly, we find that defects in double-strand break initiation and crossover formation, but not pairing or synapsis, become even more severe in the germlines of older mutant animals, indicating an increased dependence on PPH-4.1 with increasing maternal age. Our results demonstrate that PPH-4.1 plays multiple, independent roles in meiotic prophase chromosome dynamics and maintaining meiotic competence in aging germlines. PP4's high degree of conservation suggests it may be a universal regulator of meiotic prophase chromosome dynamics. PMID:25340746

  5. Involvement of calcium/calmodulin-dependent protein kinase II (CaMKII) in meiotic maturation and activation of pig oocytes.

    PubMed

    Fan, Heng-Yu; Huo, Li-Jun; Meng, Xiao-Qian; Zhong, Zhi-Sheng; Hou, Yi; Chen, Da-Yuan; Sun, Qing-Yuan

    2003-11-01

    Calcium signal is important for the regulation of meiotic cell cycle in oocytes, but its downstream mechanism is not well known. The functional roles of calcium/calmodulin-dependent protein kinase II (CaMKII) in meiotic maturation and activation of pig oocytes were studied by drug treatment, Western blot analysis, kinase activity assay, indirect immunostaining, and confocal microscopy. The results indicated that meiotic resumption of both cumulus-enclosed and denuded oocytes was prevented by CaMKII inhibitor KN-93, Ant-AIP-II, or CaM antagonist W7 in a dose-dependent manner, but only germinal vesicle breakdown (GVBD) of denuded oocytes was inhibited by membrane permeable Ca2+ chelator BAPTA-AM. When the oocytes were treated with KN-93, W7, or BAPTA-AM after GVBD, the first polar body emission was inhibited. A quick elevation of CaMKII activity was detected after electrical activation of mature pig oocytes, which could be prevented by the pretreatment of CaMKII inhibitors. Treatment of oocytes with KN-93 or W7 resulted in the inhibition of pronuclear formation. The possible regulation of CaMKII on maturation promoting factor (MPF), mitogen-activated protein kinase (MAPK), and ribosome S6 protein kinase (p90rsk) during meiotic cell cycles of pig oocytes was also studied. KN-93 and W7 prevented the accumulation of cyclin B and the full phosphorylation of MAPK and p90rsk during meiotic maturation. When CaMKII activity was inhibited during parthenogenetic activation, cyclin B, the regulatory subunit of MPF, failed to be degraded, but MAPK and p90rsk were quickly dephosphorylated and degraded. Confocal microscopy revealed that CaM and CaMKII were localized to the nucleus and the periphery of the GV stage oocytes. Both proteins were concentrated to the condensed chromosomes after GVBD. In oocytes at the meiotic metaphase MI or MII stage, CaM distributed on the whole spindle, but CaMKII was localized only on the spindle poles. After transition into anaphase, both proteins

  6. Condensin-driven remodelling of X chromosome topology during dosage compensation

    NASA Astrophysics Data System (ADS)

    Crane, Emily; Bian, Qian; McCord, Rachel Patton; Lajoie, Bryan R.; Wheeler, Bayly S.; Ralston, Edward J.; Uzawa, Satoru; Dekker, Job; Meyer, Barbara J.

    2015-07-01

    The three-dimensional organization of a genome plays a critical role in regulating gene expression, yet little is known about the machinery and mechanisms that determine higher-order chromosome structure. Here we perform genome-wide chromosome conformation capture analysis, fluorescent in situ hybridization (FISH), and RNA-seq to obtain comprehensive three-dimensional (3D) maps of the Caenorhabditis elegans genome and to dissect X chromosome dosage compensation, which balances gene expression between XX hermaphrodites and XO males. The dosage compensation complex (DCC), a condensin complex, binds to both hermaphrodite X chromosomes via sequence-specific recruitment elements on X (rex sites) to reduce chromosome-wide gene expression by half. Most DCC condensin subunits also act in other condensin complexes to control the compaction and resolution of all mitotic and meiotic chromosomes. By comparing chromosome structure in wild-type and DCC-defective embryos, we show that the DCC remodels hermaphrodite X chromosomes into a sex-specific spatial conformation distinct from autosomes. Dosage-compensated X chromosomes consist of self-interacting domains (~1 Mb) resembling mammalian topologically associating domains (TADs). TADs on X chromosomes have stronger boundaries and more regular spacing than on autosomes. Many TAD boundaries on X chromosomes coincide with the highest-affinity rex sites and become diminished or lost in DCC-defective mutants, thereby converting the topology of X to a conformation resembling autosomes. rex sites engage in DCC-dependent long-range interactions, with the most frequent interactions occurring between rex sites at DCC-dependent TAD boundaries. These results imply that the DCC reshapes the topology of X chromosomes by forming new TAD boundaries and reinforcing weak boundaries through interactions between its highest-affinity binding sites. As this model predicts, deletion of an endogenous rex site at a DCC-dependent TAD boundary using

  7. Condensin-driven remodelling of X chromosome topology during dosage compensation.

    PubMed

    Crane, Emily; Bian, Qian; McCord, Rachel Patton; Lajoie, Bryan R; Wheeler, Bayly S; Ralston, Edward J; Uzawa, Satoru; Dekker, Job; Meyer, Barbara J

    2015-07-01

    The three-dimensional organization of a genome plays a critical role in regulating gene expression, yet little is known about the machinery and mechanisms that determine higher-order chromosome structure. Here we perform genome-wide chromosome conformation capture analysis, fluorescent in situ hybridization (FISH), and RNA-seq to obtain comprehensive three-dimensional (3D) maps of the Caenorhabditis elegans genome and to dissect X chromosome dosage compensation, which balances gene expression between XX hermaphrodites and XO males. The dosage compensation complex (DCC), a condensin complex, binds to both hermaphrodite X chromosomes via sequence-specific recruitment elements on X (rex sites) to reduce chromosome-wide gene expression by half. Most DCC condensin subunits also act in other condensin complexes to control the compaction and resolution of all mitotic and meiotic chromosomes. By comparing chromosome structure in wild-type and DCC-defective embryos, we show that the DCC remodels hermaphrodite X chromosomes into a sex-specific spatial conformation distinct from autosomes. Dosage-compensated X chromosomes consist of self-interacting domains (∼1 Mb) resembling mammalian topologically associating domains (TADs). TADs on X chromosomes have stronger boundaries and more regular spacing than on autosomes. Many TAD boundaries on X chromosomes coincide with the highest-affinity rex sites and become diminished or lost in DCC-defective mutants, thereby converting the topology of X to a conformation resembling autosomes. rex sites engage in DCC-dependent long-range interactions, with the most frequent interactions occurring between rex sites at DCC-dependent TAD boundaries. These results imply that the DCC reshapes the topology of X chromosomes by forming new TAD boundaries and reinforcing weak boundaries through interactions between its highest-affinity binding sites. As this model predicts, deletion of an endogenous rex site at a DCC-dependent TAD boundary using

  8. Condensin-driven remodelling of X chromosome topology during dosage compensation.

    PubMed

    Crane, Emily; Bian, Qian; McCord, Rachel Patton; Lajoie, Bryan R; Wheeler, Bayly S; Ralston, Edward J; Uzawa, Satoru; Dekker, Job; Meyer, Barbara J

    2015-07-01

    The three-dimensional organization of a genome plays a critical role in regulating gene expression, yet little is known about the machinery and mechanisms that determine higher-order chromosome structure. Here we perform genome-wide chromosome conformation capture analysis, fluorescent in situ hybridization (FISH), and RNA-seq to obtain comprehensive three-dimensional (3D) maps of the Caenorhabditis elegans genome and to dissect X chromosome dosage compensation, which balances gene expression between XX hermaphrodites and XO males. The dosage compensation complex (DCC), a condensin complex, binds to both hermaphrodite X chromosomes via sequence-specific recruitment elements on X (rex sites) to reduce chromosome-wide gene expression by half. Most DCC condensin subunits also act in other condensin complexes to control the compaction and resolution of all mitotic and meiotic chromosomes. By comparing chromosome structure in wild-type and DCC-defective embryos, we show that the DCC remodels hermaphrodite X chromosomes into a sex-specific spatial conformation distinct from autosomes. Dosage-compensated X chromosomes consist of self-interacting domains (∼1 Mb) resembling mammalian topologically associating domains (TADs). TADs on X chromosomes have stronger boundaries and more regular spacing than on autosomes. Many TAD boundaries on X chromosomes coincide with the highest-affinity rex sites and become diminished or lost in DCC-defective mutants, thereby converting the topology of X to a conformation resembling autosomes. rex sites engage in DCC-dependent long-range interactions, with the most frequent interactions occurring between rex sites at DCC-dependent TAD boundaries. These results imply that the DCC reshapes the topology of X chromosomes by forming new TAD boundaries and reinforcing weak boundaries through interactions between its highest-affinity binding sites. As this model predicts, deletion of an endogenous rex site at a DCC-dependent TAD boundary using

  9. CEP63 deficiency promotes p53-dependent microcephaly and reveals a role for the centrosome in meiotic recombination

    PubMed Central

    Marjanović, Marko; Sánchez-Huertas, Carlos; Terré, Berta; Gómez, Rocío; Scheel, Jan Frederik; Pacheco, Sarai; Knobel, Philip A.; Martínez-Marchal, Ana; Aivio, Suvi; Palenzuela, Lluís; Wolfrum, Uwe; McKinnon, Peter J.; Suja, José A.; Roig, Ignasi; Costanzo, Vincenzo; Lüders, Jens; Stracker, Travis H.

    2015-01-01

    CEP63 is a centrosomal protein that facilitates centriole duplication and is regulated by the DNA damage response. Mutations in CEP63 cause Seckel syndrome, a human disease characterized by microcephaly and dwarfism. Here we demonstrate that Cep63 deficient mice recapitulate Seckel syndrome pathology. The attrition of neural progenitor cells involves p53-dependent cell death and brain size is rescued by the deletion of p53. Cell death is not the result of an aberrant DNA damage response but is triggered by centrosome-based mitotic errors. In addition, Cep63 loss severely impairs meiotic recombination, leading to profound male infertility. Cep63 deficient spermatocytes display numerical and structural centrosome aberrations, chromosome entanglements and defective telomere clustering, suggesting that a reduction in centrosome-mediated chromosome movements underlies recombination failure. Our results provide novel insight into the molecular pathology of microcephaly and establish a role for the centrosome in meiotic recombination. PMID:26158450

  10. Spreading and fluorescence in situ hybridization of male and female meiocyte chromosomes from Arabidopsis thaliana for cytogenetical analysis.

    PubMed

    Armstrong, Susan

    2013-01-01

    Advances in molecular biology and in the genetics of Arabidopsis thaliana have led to it becoming an important model for the analysis of meiosis in plants. Cytogenetic investigations are pivotal to meiotic studies and a number of technological improvements for Arabidopsis cytology have provided a range of tools to investigate chromosome behavior during meiosis. This chapter contains a detailed description of cytological techniques currently used in our laboratory for the basic preparation of meiotic chromosomes for investigation of the female and male meiotic pathway and fluorescence in situ hybridization (FISH) analysis for the frequency and distribution of crossovers (chiasmata) at metaphase I.

  11. Meiotic peculiarities in hybrid buffalo.

    PubMed

    Guiraaraes, S E; Pinheiro, L E; Guimaraes, J D

    1995-02-01

    The two varieties of the Water buffalo (Bubalis bubalis var. bubalis and Bubalis bubalis var. carabao) have 2n = 50 and 2n = 48 karyotypes, respectively. The F1 hybrids are thought to exhibit a karyotype of 2n = 49 and are known to be fertile. Meiosis was studied in 10 hybrid water buffalo bulls. Karyotypes of the bulls were prepared from leukocyte cultures and testicular biopsy samples in a routine manner and examined. Phenotypically the bulls showed characteristics of the hybrid buffalo. Five of the bulls carried 2n = 50 and 5 had 2n = 49. Multivalent chromosomes were found in diakinesis (metaphase I) cells of bulls with 2n = 49 karyotypes. Synapses were found in bulls of both karyotypes.

  12. Chromosome-length polymorphism in fungi.

    PubMed Central

    Zolan, M E

    1995-01-01

    The examination of fungal chromosomes by pulsed-field gel electrophoresis has revealed that length polymorphism is widespread in both sexual and asexual species. This review summarizes characteristics of fungal chromosome-length polymorphism and possible mitotic and meiotic mechanisms of chromosome length change. Most fungal chromosome-length polymorphisms are currently uncharacterized with respect to content and origin. However, it is clear that long tandem repeats, such as tracts of rRNA genes, are frequently variable in length and that other chromosomal rearrangements are suppressed during normal mitotic growth. Dispensable chromosomes and dispensable chromosome regions, which have been well documented for some fungi, also contribute to the variability of the fungal karyotype. For sexual species, meiotic recombination increases the overall karyotypic variability in a population while suppressing genetic translocations. The range of karyotypes observed in fungi indicates that many karyotypic changes may be genetically neutral, at least under some conditions. In addition, new linkage combinations of genes may also be advantageous in allowing adaptation of fungi to new environments. PMID:8531892

  13. Meiotic and reproductive behavior of facultative apomictic BC/sub 1/ offspring derived from Pennisetum americanum-P. orientale interspecific hybrids

    SciTech Connect

    Dujardin, M.; Hanna, W.W.

    1983-01-01

    This study reports on the chromosome numbers, meiotic behavior, method of reproduction and fertility of BC/sub 1/ progenies from Pennisetum americanum L. Leeke, pearl millet X P. orientale L.C. Rich. interspecific hybrids backcrossed to P. americanum. This information would be useful for future studies on transfer of genes controlling apomixis from the tertiary gene pool to P. americanum. Two facultatively apomictic interspecific hybrids between Pennisetum americanum, (A. chromosomes) and P. orientale (O chromosomes), 2n=25, were pollinated with P. americanum. Sixteen backcross progenies were obtained which were of three cytotypes: 32-(14 A + 18 O), 23-(14 A + 9 O), and 27-(7 A + 20 O) chromosomes. They resulted from fertilization of unreduced gametes or partially reduced gametes by a 7 A chromosome gamete, or by development or unreduced aposporic embryo sacs, respectively. In 23 chromosome plants, the 14 A chromosomes paired mainly as bivalents or remained as univalents while the 9 O chromosomes appeared as univalents. Intergenomal pairing between P. americanum and P. orientale also were observed and could make segmental exchange possible. In the 27 chromosome progeny, the 20 O chromosomes paired, while the 7 A chromosomes remained as univalents. Meiotic behavior in 32-chromosome plants was regular with 7 A bivalents plus 9 O bivalents. The backcross progenies were male sterile but partially female fertile and produced a few seeds when pollinated with P. americanum pollen. The 23-chromosome, BC/sub 1/ progeny were reconstituted in BC/sub 2/ progenies of 32-chromosomes plants X pearl millet. All BC/sub 1/ had some degree of apomicitic embryo sac development and the 23-chromosome plants showed apomictic development even though the O chromosomes were in the simplex condition.

  14. Budding Yeast SLX4 Contributes to the Appropriate Distribution of Crossovers and Meiotic Double-Strand Break Formation on Bivalents During Meiosis

    PubMed Central

    Higashide, Mika; Shinohara, Miki

    2016-01-01

    The number and distribution of meiosis crossover (CO) events on each bivalent are strictly controlled by multiple mechanisms to assure proper chromosome segregation during the first meiotic division. In Saccharomyces cerevisiae, Slx4 is a multi-functional scaffold protein for structure-selective endonucleases, such as Slx1 and Rad1 (which are involved in DNA damage repair), and is also a negative regulator of the Rad9-dependent signaling pathway with Rtt107. Slx4 has been believed to play only a minor role in meiotic recombination. Here, we report that Slx4 is involved in proper intrachromosomal distribution of meiotic CO formation, especially in regions near centromeres. We observed an increase in uncontrolled CO formation only in a region near the centromere in the slx4∆ mutant. Interestingly, this phenomenon was not observed in the slx1∆, rad1∆, or rtt107∆ mutants. In addition, we observed a reduced number of DNA double-strand breaks (DSBs) and altered meiotic DSB distribution on chromosomes in the slx4∆ mutant. This suggests that the multi-functional Slx4 is required for proper CO formation and meiotic DSB formation. PMID:27172214

  15. Budding Yeast SLX4 Contributes to the Appropriate Distribution of Crossovers and Meiotic Double-Strand Break Formation on Bivalents During Meiosis.

    PubMed

    Higashide, Mika; Shinohara, Miki

    2016-07-07

    The number and distribution of meiosis crossover (CO) events on each bivalent are strictly controlled by multiple mechanisms to assure proper chromosome segregation during the first meiotic division. In Saccharomyces cerevisiae, Slx4 is a multi-functional scaffold protein for structure-selective endonucleases, such as Slx1 and Rad1 (which are involved in DNA damage repair), and is also a negative regulator of the Rad9-dependent signaling pathway with Rtt107 Slx4 has been believed to play only a minor role in meiotic recombination. Here, we report that Slx4 is involved in proper intrachromosomal distribution of meiotic CO formation, especially in regions near centromeres. We observed an increase in uncontrolled CO formation only in a region near the centromere in the slx4∆ mutant. Interestingly, this phenomenon was not observed in the slx1∆, rad1∆, or rtt107∆ mutants. In addition, we observed a reduced number of DNA double-strand breaks (DSBs) and altered meiotic DSB distribution on chromosomes in the slx4∆ mutant. This suggests that the multi-functional Slx4 is required for proper CO formation and meiotic DSB formation.

  16. Meiotic recombination protein Rec12: functional conservation, crossover homeostasis and early crossover/non-crossover decision

    PubMed Central

    Kan, Fengling; Davidson, Mari K.; Wahls, Wayne P.

    2011-01-01

    In fission yeast and other eukaryotes, Rec12 (Spo11) is thought to catalyze the formation of dsDNA breaks (DSBs) that initiate homologous recombination in meiosis. Rec12 is orthologous to the catalytic subunit of topoisomerase VI (Top6A). Guided by the crystal structure of Top6A, we engineered the rec12 locus to encode Rec12 proteins each with a single amino acid substitution in a conserved residue. Of 21 substitutions, 10 significantly reduced or abolished meiotic DSBs, gene conversion, crossover recombination and the faithful segregation of chromosomes. Critical residues map within the metal ion-binding pocket toprim (E179A, D229A, D231A), catalytic region 5Y-CAP (R94A, D95A, Y98F) and the DNA-binding interface (K201A, G202E, R209A, K242A). A subset of substitutions reduced DSBs but maintained crossovers, demonstrating crossover homeostasis. Furthermore, a strong separation of function mutation (R304A) suggests that the crossover/non-crossover decision is established early by a protein–protein interaction surface of Rec12. Fission yeast has multiple crossovers per bivalent, and chromosome segregation was robust above a threshold of about one crossover per bivalent, below which non-disjunction occurred. These results support structural and functional conservation among Rec12/Spo11/Top6A family members for the catalysis of DSBs, and they reveal how Rec12 regulates other features of meiotic chromosome dynamics. PMID:21030440

  17. A Discrete Class of Intergenic DNA Dictates Meiotic DNA Break Hotspots in Fission Yeast

    PubMed Central

    Cam, Hugh P; Farah, Joseph A; Grewal, Shiv I. S; Smith, Gerald R

    2007-01-01

    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 ∼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. PMID:17722984

  18. Meiotic recombination protein Rec12: functional conservation, crossover homeostasis and early crossover/non-crossover decision.

    PubMed

    Kan, Fengling; Davidson, Mari K; Wahls, Wayne P

    2011-03-01

    In fission yeast and other eukaryotes, Rec12 (Spo11) is thought to catalyze the formation of dsDNA breaks (DSBs) that initiate homologous recombination in meiosis. Rec12 is orthologous to the catalytic subunit of topoisomerase VI (Top6A). Guided by the crystal structure of Top6A, we engineered the rec12 locus to encode Rec12 proteins each with a single amino acid substitution in a conserved residue. Of 21 substitutions, 10 significantly reduced or abolished meiotic DSBs, gene conversion, crossover recombination and the faithful segregation of chromosomes. Critical residues map within the metal ion-binding pocket toprim (E179A, D229A, D231A), catalytic region 5Y-CAP (R94A, D95A, Y98F) and the DNA-binding interface (K201A, G202E, R209A, K242A). A subset of substitutions reduced DSBs but maintained crossovers, demonstrating crossover homeostasis. Furthermore, a strong separation of function mutation (R304A) suggests that the crossover/non-crossover decision is established early by a protein-protein interaction surface of Rec12. Fission yeast has multiple crossovers per bivalent, and chromosome segregation was robust above a threshold of about one crossover per bivalent, below which non-disjunction occurred. These results support structural and functional conservation among Rec12/Spo11/Top6A family members for the catalysis of DSBs, and they reveal how Rec12 regulates other features of meiotic chromosome dynamics. PMID:21030440

  19. The synaptonemal complex protein ZYP1 is required for imposition of meiotic crossovers in barley.

    PubMed

    Barakate, Abdellah; Higgins, James D; Vivera, Sebastian; Stephens, Jennifer; Perry, Ruth M; Ramsay, Luke; Colas, Isabelle; Oakey, Helena; Waugh, Robbie; Franklin, F Chris H; Armstrong, Susan J; Halpin, Claire

    2014-02-01

    In many cereal crops, meiotic crossovers predominantly occur toward the ends of chromosomes and 30 to 50% of genes rarely recombine. This limits the exploitation of genetic variation by plant breeding. Previous reports demonstrate that chiasma frequency can be manipulated in plants by depletion of the synaptonemal complex protein ZIPPER1 (ZYP1) but conflict as to the direction of change, with fewer chiasmata reported in Arabidopsis thaliana and more crossovers reported for rice (Oryza sativa). Here, we use RNA interference (RNAi) to reduce the amount of ZYP1 in barley (Hordeum vulgare) to only 2 to 17% of normal zygotene levels. In the ZYP1(RNAi) lines, fewer than half of the chromosome pairs formed bivalents at metaphase and many univalents were observed, leading to chromosome nondisjunction and semisterility. The number of chiasmata per cell was reduced from 14 in control plants to three to four in the ZYP1-depleted lines, although the localization of residual chiasmata was not affected. DNA double-strand break formation appeared normal, but the recombination pathway was defective at later stages. A meiotic time course revealed a 12-h delay in prophase I progression to the first labeled tetrads. Barley ZYP1 appears to function similarly to ZIP1/ZYP1 in yeast and Arabidopsis, with an opposite effect on crossover number to ZEP1 in rice, another member of the Poaceae. PMID:24563202

  20. Tel1(ATM)-mediated interference suppresses clustered meiotic double-strand-break formation.

    PubMed

    Garcia, Valerie; Gray, Stephen; Allison, Rachal M; Cooper, Tim J; Neale, Matthew J

    2015-04-01

    Meiotic recombination is a critical step in gametogenesis for many organisms, enabling the creation of genetically diverse haploid gametes. In each meiotic cell, recombination is initiated by numerous DNA double-strand breaks (DSBs) created by Spo11, the evolutionarily conserved topoisomerase-like protein, but how these DSBs are distributed relatively uniformly across the four chromatids that make up each chromosome pair is poorly understood. Here we employ Saccharomyces cerevisiae to demonstrate distance-dependent DSB interference in cis (in which the occurrence of a DSB suppresses adjacent DSB formation)--a process that is mediated by the conserved DNA damage response kinase, Tel1(ATM). The inhibitory function of Tel1 acts on a relatively local scale, while over large distances DSBs have a tendency to form independently of one another even in the presence of Tel1. Notably, over very short distances, loss of Tel1 activity causes DSBs to cluster within discrete zones of concerted DSB activity. Our observations support a hierarchical view of recombination initiation where Tel1(ATM) prevents clusters of DSBs, and further suppresses DSBs within the surrounding chromosomal region. Such collective negative regulation will help to ensure that recombination events are dispersed evenly and arranged optimally for genetic exchange and efficient chromosome segregation. PMID:25539084

  1. Sperm nuclear expansion and meiotic maturation in normal and gynogenetic eggs of the scallop, Chlamys farreri

    NASA Astrophysics Data System (ADS)

    Pan, Ying; Li, Qi; Yu, Ruihai; Wang, Rucai

    2008-02-01

    Sperm nuclear expansion, meiosis and the association of the male and female pronuclei leading to the four-cell stage in normal Chlamys farreri eggs were observed under a fluorescence microscope. The effects of ultraviolet (UV) irradiation on the fertilizing sperm were also examined. Both normal and UV-irradiated sperm nuclei enlarged at three distinct phases (phase A, metaphase I; phase B, polar body formation; and phase C, female pronuclear development and expansion) that were temporally correlated with meiotic process of the maternal chromosomes. Sperm nuclei underwent a rapid, initial enlargement during phase A, but condensed slightly during phase B, then re-enlarged during phase C. The effects of UV irradiation were not apparent during transformation of the sperm nucleus into a male pronucleus, and there was not any apparent effect on meiotic maturation and development of the female pronucleus. However, the rate of expansion of the UV-irradiated sperm nuclei and the size of male pronuclei were reduced apparently. Unlike the female pronucleus, the male pronucleus derived from sperm genome inactivated by UV irradiation did not form chromosomes, but became a dense chromatin body (DCB). At mitotic anaphase, DCB did not participate in the karyokinesis of the first cleavage as evidenced by chromosomal nondisjunction, demonstrating the effectiveness of using UV irradiation to induce gynogenetic scallop embryos.

  2. Meiotic cohesin REC8 marks the axial elements of rat synaptonemal complexes before cohesins SMC1β and SMC3

    PubMed Central

    Eijpe, Maureen; Offenberg, Hildo; Jessberger, Rolf; Revenkova, Ekaterina; Heyting, Christa

    2003-01-01

    In meiotic prophase, the sister chromatids of each chromosome develop a common axial element (AE) that is integrated into the synaptonemal complex (SC). We analyzed the incorporation of sister chromatid cohesion proteins (cohesins) and other AE components into AEs. Meiotic cohesin REC8 appeared shortly before premeiotic S phase in the nucleus and formed AE-like structures (REC8-AEs) from premeiotic S phase on. Subsequently, meiotic cohesin SMC1β, cohesin SMC3, and AE proteins SCP2 and SCP3 formed dots along REC8-AEs, which extended and fused until they lined REC8-AEs along their length. In metaphase I, SMC1β, SMC3, SCP2, and SCP3 disappeared from the chromosome arms and accumulated around the centromeres, where they stayed until anaphase II. In striking contrast, REC8 persisted along the chromosome arms until anaphase I and near the centromeres until anaphase II. We propose that REC8 provides a basis for AE formation and that the first steps in AE assembly do not require SMC1β, SMC3, SCP2, and SCP3. Furthermore, SMC1β, SMC3, SCP2, and SCP3 cannot provide arm cohesion during metaphase I. We propose that REC8 then provides cohesion. RAD51 and/or DMC1 coimmunoprecipitates with REC8, suggesting that REC8 may also provide a basis for assembly of recombination complexes. PMID:12615909

  3. Multiple meiotic errors caused by predivision of chromatids in women of advanced maternal age undergoing in vitro fertilisation

    PubMed Central

    Handyside, Alan H; Montag, Markus; Magli, M Cristina; Repping, Sjoerd; Harper, Joyce; Schmutzler, Andreas; Vesela, Katerina; Gianaroli, Luca; Geraedts, Joep

    2012-01-01

    Chromosome aneuploidy is a major cause of pregnancy loss, abnormal pregnancy and live births following both natural conception and in vitro fertilisation (IVF) and increases exponentially with maternal age in the decade preceding the menopause. Molecular genetic analysis following natural conception and spontaneous miscarriage demonstrates that trisomies arise mainly in female meiosis and particularly in the first meiotic division. Here, we studied copy number gains and losses for all chromosomes in the two by-products of female meiosis, the first and second polar bodies, and the corresponding zygotes in women of advanced maternal age undergoing IVF, using microarray comparative genomic hybridisation (array CGH). Analysis of the segregation patterns underlying the copy number changes reveals that premature predivision of chromatids rather than non-disjunction of whole chromosomes causes almost all errors in the first meiotic division and unlike natural conception, over half of aneuploidies result from errors in the second meiotic division. Furthermore, most abnormal zygotes had multiple aneuploidies. These differences in the aetiology of aneuploidy in IVF compared with natural conception may indicate a role for ovarian stimulation in perturbing meiosis in ageing oocytes. PMID:22317970

  4. The blue butterfly Polyommatus (Plebicula) atlanticus (Lepidoptera, Lycaenidae) holds the record of the highest number of chromosomes in the non-polyploid eukaryotic organisms.

    PubMed

    Lukhtanov, Vladimir A

    2015-01-01

    The blue butterfly species Polyommatus (Plebicula) atlanticus (Elwes, 1906) (Lepidoptera, Lycaenidae) is known to have a very high haploid number of chromosomes (n= circa 223). However, this approximate count made by Hugo de Lesse 45 years ago was based on analysis of a single meiotic I metaphase plate, not confirmed by study of diploid chromosome set and not documented by microphotographs. Here I demonstrate that (1) Polyommatus atlanticus is a diploid (non-polyploid) species, (2) its meiotic I chromosome complement includes at least 224-226 countable chromosome bodies, and (3) all (or nearly all) chromosome elements in meiotic I karyotype are represented by bivalents. I also provide the first data on the diploid karyotype and estimate the diploid chromosome number as 2n=ca448-452. Thus, Polyommatus atlanticus is confirmed to possess the highest chromosome number among all the non-polyploid eukaryotic organisms. PMID:26753083

  5. The blue butterfly Polyommatus (Plebicula) atlanticus (Lepidoptera, Lycaenidae) holds the record of the highest number of chromosomes in the non-polyploid eukaryotic organisms

    PubMed Central

    Lukhtanov, Vladimir A.

    2015-01-01

    Abstract The blue butterfly species Polyommatus (Plebicula) atlanticus (Elwes, 1906) (Lepidoptera, Lycaenidae) is known to have a very high haploid number of chromosomes (n= circa 223). However, this approximate count made by Hugo de Lesse 45 years ago was based on analysis of a single meiotic I metaphase plate, not confirmed by study of diploid chromosome set and not documented by microphotographs. Here I demonstrate that (1) Polyommatus atlanticus is a diploid (non-polyploid) species, (2) its meiotic I chromosome complement includes at least 224-226 countable chromosome bodies, and (3) all (or nearly all) chromosome elements in meiotic I karyotype are represented by bivalents. I also provide the first data on the diploid karyotype and estimate the diploid chromosome number as 2n=ca448-452. Thus, Polyommatus atlanticus is confirmed to possess the highest chromosome number among all the non-polyploid eukaryotic organisms. PMID:26753083

  6. High efficiency of meiotic gynogenesis in sea lamprey Petromyzon marinus.

    PubMed

    Rinchard, Jacques; Dabrowski, Konrad; Garcia-Abiado, Mary-Ann

    2006-11-15

    Induction of androgenesis and gynogenesis by applying a pressure (PS) or heat shock (HS) to double the haploid chromosomal set results in progenies possessing only chromosomes from a single parent. This has never been accomplished in representatives of Agnatha. The objective of this study was to induce gynogenesis and androgenesis in sea lamprey Petromyzon marinus. For gynogenesis experiments, ultraviolet (UV)-irradiated sperm was used to activate sea lamprey eggs and HS or PS were applied to inhibit the second meiotic division and consequently induce diploidy in the embryos. The UV irradiation of immobilized sperm was performed for 1 min at 1,719 J m(-2). HS of 35+/-1 degrees C for 2 min and PS of 9,000 psi for 4 min were applied at different times after egg activation (8, 12, 20, and 24 min or 8, 16, and 24 min for HS or PS, respectively). Regardless of the induction time of the HS, survivals at pre-hatching stage were similar. In contrast, PS applied 8 min after activation appears to increase survival rate of pre-hatched embryos in comparison to 16 and 24 min after activation. In control groups, without shock treatment (no diploidization), there were no survivors. All deformed, gynogenetic embryos were confirmed to be haploids and died prior to burying themselves in the sand. We confirmed by flow cytometry that progenies produced using both shock methods surviving to the next stage, burying in the substrate, were diploid gynogenetic. For the androgenesis experiments, UV-irradiated eggs (1,719 J m(-2) for 1 min) were fertilized with non-treated sperm and HS was applied to restore diploidy of the eggs. Several attempts have been made to optimize the parameters used. HS of 35+/-1 degrees C was applied 110, 140, 170, 200, and 230 min after activation for 2 min. Low yields of androgens were obtained and all animals died within a week after hatching. These techniques will allow to establish meiotic gynogenetic lines of sea lamprey for determining sex differentiation

  7. High efficiency of meiotic gynogenesis in sea lamprey Petromyzon marinus

    USGS Publications Warehouse

    Rinchard, J.; Dabrowski, K.; Garcia-Abiado, M. -A.

    2006-01-01

    Induction of androgenesis and gynogenesis by applying a pressure (PS) or heat shock (HS) to double the haploid chromosomal set results in progenies possessing only chromosomes from a single parent. This has never been accomplished in representatives of Agnatha. The objective of this study was to induce gynogenesis and androgenesis in sea lamprey Petromyzon marinus. For gynogenesis experiments, ultraviolet (UV)-irradiated sperm was used to activate sea lamprey eggs and HS or PS were applied to inhibit the second meiotic division and consequently induce diploidy in the embryos. The UV irradiation of immobilized sperm was performed for 1 min at 1,719 J m-2. HS of 35 ?? 1??C for 2 min and PS of 9,000 psi for 4 min were applied at different times after egg activation (8, 12, 20, and 24 min or 8, 16, and 24 min for HS or PS, respectively). Regardless of the induction time of the HS, survivals at pre-hatching stage were similar. In contrast, PS applied 8 min after activation appears to increase survival rate of pre-hatched embryos in comparison to 16 and 24 min after activation. In control groups, without shock treatment (no diploidization), there were no survivors. All deformed, gynogenetic embryos were confirmed to be haploids and died prior to burying themselves in the sand. We confirmed by flow cytometry that progenies produced using both shock methods surviving to the next stage, burying in the substrate, were diploid gynogenetic. For the androgenesis experiments, UV-irradiated eggs (1,719 J m-2 for 1 min) were fertilized with non-treated sperm and HS was applied to restore diploidy of the eggs. Several attempts have been made to optimize the parameters used. HS of 35 ?? 1??C was applied 110, 140, 170, 200, and 230 min after activation for 2 min. Low yields of androgens were obtained and all animals died within a week after hatching. These techniques will allow to establish meiotic gynogenetic lines of sea lamprey for determining sex differentiation in this species

  8. Evidence for Sex Chromosome Turnover in Proteid Salamanders.

    PubMed

    Sessions, Stanley K; Bizjak Mali, Lilijana; Green, David M; Trifonov, Vladimir; Ferguson-Smith, Malcolm

    2016-01-01

    A major goal of genomic and reproductive biology is to understand the evolution of sex determination and sex chromosomes. Species of the 2 genera of the Salamander family Proteidae - Necturus of eastern North America, and Proteus of Southern Europe - have similar-looking karyotypes with the same chromosome number (2n = 38), which differentiates them from all other salamanders. However, Necturus possesses strongly heteromorphic X and Y sex chromosomes that Proteus lacks. Since the heteromorphic sex chromosomes of Necturus were detectable only with C-banding, we hypothesized that we could use C-banding to find sex chromosomes in Proteus. We examined mitotic material from colchicine-treated intestinal epithelium, and meiotic material from testes in specimens of Proteus, representing 3 genetically distinct populations in Slovenia. We compared these results with those from Necturus. We performed FISH to visualize telomeric sequences in meiotic bivalents. Our results provide evidence that Proteus represents an example of sex chromosome turnover in which a Necturus-like Y-chromosome has become permanently translocated to another chromosome converting heteromorphic sex chromosomes to homomorphic sex chromosomes. These results may be key to understanding some unusual aspects of demographics and reproductive biology of Proteus, and are discussed in the context of models of the evolution of sex chromosomes in amphibians. PMID:27351721

  9. Cep55 regulates spindle organization and cell cycle progression in meiotic oocyte

    PubMed Central

    Xu, Zhao-Yang; Ma, Xue-Shan; Qi, Shu-Tao; Wang, Zhen-Bo; Guo, Lei; Schatten, Heide; Sun, Qing-Yuan; Sun, Ying-Pu

    2015-01-01

    Cep55 is a relatively novel member of the centrosomal protein family. Here, we show that Cep55 is expressed in mouse oocytes from the germinal vesicle (GV) to metaphase II (MII) stages. Immuostaining and confocal microscopy as well as time lapse live imaging after injection of mRNA encoding fusion protein of Cep55 and GFP identified that Cep55 was localized to the meiotic spindle, especially to the spindle poles at metaphase, while it was concentrated at the midbody in telophase in meiotic oocytes. Knockdown of Cep55 by specific siRNA injection caused the dissociation of γ-tubulin from the spindle poles, resulting in severely defective spindles and misaligned chromosomes, leading to metaphase I arrest and failure of first polar body (PB1) extrusion. Correspondingly, cyclin B accumulation and spindle assembly checkpoint (SAC) activation were observed in Cep55 knockdown oocytes. Our results suggest that Cep55 may act as an MTOC-associated protein regulating spindle organization, and thus cell cycle progression during mouse oocyte meiotic maturation. PMID:26582107

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

    PubMed Central

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

    2015-01-01

    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. PMID:26161528

  11. The plant-specific protein FEHLSTART controls male meiotic entry, initializing meiotic synchronization in Arabidopsis.

    PubMed

    Li, Junhua; Dukowic-Schulze, Stefanie; Lindquist, Ingrid E; Farmer, Andrew D; Kelly, Bridget; Li, Tao; Smith, Alan G; Retzel, Ernest F; Mudge, Joann; Chen, Changbin

    2015-11-01

    Meiosis marks the transition from the sporophyte to the gametophyte generation in the life cycle of flowering plants, and creates genetic variations through homologous recombination. In most flowering plants, meiosis is highly synchronized within each anther, which is significant for efficient fertilization. To date, little is known about the molecular mechanisms of entry into meiosis and exit from it, and only a few genes in Arabidopsis have been characterized with a role in regulating meiotic progression. In this study, we report the functional characterization of a plant-specific basic helix-loop-helix (bHLH) protein, FEHLSTART (FST), a defect in which leads to premature meiotic entry and asynchronous meiosis, and results in decreased seed yield. Investigation of the time course of meiosis showed that the onset of leptotene, the first stage of prophase I, frequently occurred earlier in fst-1 than in the wild type. Asynchronous meiosis followed, which could manifest in the disruption of regular spindle structures and symmetric cell divisions in fst-1 mutants during the meiosis I/II transition. In accordance with frequently accelerated meiotic entry, whole-transcriptome analysis of fst-1 anthers undergoing meiosis revealed that 19 circadian rhythm genes were affected and 47 pollen-related genes were prematurely expressed at a higher level. Taken together, we propose that FST is required for normal meiotic entry and the establishment of meiotic synchrony. PMID:26382719

  12. Surface Spreading and Immunostaining of Yeast Chromosomes.

    PubMed

    Grubb, Jennifer; Brown, M Scott; Bishop, Douglas K

    2015-01-01

    The small size of nuclei of the budding yeast Saccharomyces cerevisiae limits the utility of light microscopy for analysis of the subnuclear distribution of chromatin-bound proteins. Surface spreading of yeast nuclei results in expansion of chromatin without loss of bound proteins. A method for surface spreading balances fixation of DNA bound proteins with detergent treatment. The method demonstrated is slightly modified from that described by Josef Loidl and Franz Klein. The method has been used to characterize the localization of many chromatin-bound proteins at various stages of the mitotic cell cycle, but is especially useful for the study of meiotic chromosome structures such as meiotic recombinosomes and the synaptonemal complex. We also describe a modification that does not require use of Lipsol, a proprietary detergent, which was called for in the original procedure, but no longer commercially available. An immunostaining protocol that is compatible with the chromosome spreading method is also described. PMID:26325523

  13. Surface Spreading and Immunostaining of Yeast Chromosomes

    PubMed Central

    Grubb, Jennifer; Brown, M. Scott; Bishop, Douglas K.

    2015-01-01

    The small size of nuclei of the budding yeast Saccharomyces cerevisiae limits the utility of light microscopy for analysis of the subnuclear distribution of chromatin-bound proteins. Surface spreading of yeast nuclei results in expansion of chromatin without loss of bound proteins. A method for surface spreading balances fixation of DNA bound proteins with detergent treatment. The method demonstrated is slightly modified from that described by Josef Loidl and Franz Klein1,2. The method has been used to characterize the localization of many chromatin-bound proteins at various stages of the mitotic cell cycle, but is especially useful for the study of meiotic chromosome structures such as meiotic recombinosomes and the synaptonemal complex. We also describe a modification that does not require use of Lipsol, a proprietary detergent, which was called for in the original procedure, but no longer commercially available. An immunostaining protocol that is compatible with the chromosome spreading method is also described. PMID:26325523

  14. A DNA topoisomerase VI-like complex initiates meiotic recombination.

    PubMed

    Vrielynck, Nathalie; Chambon, Aurélie; Vezon, Daniel; Pereira, Lucie; Chelysheva, Liudmila; De Muyt, Arnaud; Mézard, Christine; Mayer, Claudine; Grelon, Mathilde

    2016-02-26

    The SPO11 protein catalyzes the formation of meiotic DNA double strand breaks (DSBs) and is homologous to the A subunit of an archaeal topoisomerase (topo VI). Topo VI are heterotetrameric enzymes comprising two A and two B subunits; however, no topo VIB involved in meiotic recombination had been identified. We characterized a structural homolog of the archaeal topo VIB subunit [meiotic topoisomerase VIB-like (MTOPVIB)], which is essential for meiotic DSB formation. It forms a complex with the two Arabidopsis thaliana SPO11 orthologs required for meiotic DSB formation (SPO11-1 and SPO11-2) and is absolutely required for the formation of the SPO11-1/SPO11-2 heterodimer. These findings suggest that the catalytic core complex responsible for meiotic DSB formation in eukaryotes adopts a topo VI-like structure.

  15. Effects of simulated weightlessness on mammalian development. Part 1: Development of clinostat for mammalian tissue culture and use in studies on meiotic maturation of mouse oocytes

    NASA Technical Reports Server (NTRS)

    Wolegemuth, D. J.; Grills, G. S.

    1984-01-01

    The effects of weightlessness on three aspects of mammalian reproduction: oocyte development, fertilization, and early embryogenesis was studied. Zero-gravity conditions within the laboratory by construction of a clinostat designed to support in vitro tissue culture were simulated and the effects of simulated weightlessness on meiotic maturation in mammalian oocytes using mouse as the model system were studied. The timing and frequency of germinal vesicule breakdown and polar body extrusion, and the structural and numerical properties of meiotic chromosomes at Metaphase and Metaphase of meiosis are assessed.

  16. Sex-Linked Chromosome Heterozygosity in Males of Tityus confluens (Buthidae): A Clue about the Presence of Sex Chromosomes in Scorpions

    PubMed Central

    Adilardi, Renzo Sebastián; Ojanguren-Affilastro, Andrés Alejandro; Mola, Liliana María

    2016-01-01

    Scorpions of the genus Tityus show holokinetic chromosomes, achiasmatic male meiosis and an absence of heteromorphic sex chromosomes, like all Buthidae. In this work, we analysed the meiotic behaviour and chromosome rearrangements of a population of the scorpion Tityus confluens, characterising the cytotypes of males, females and embryos with different cytogenetic techniques. This revealed that all the females were structural homozygotes, while all the males were structural heterozygotes for different chromosome rearrangements. Four different cytotypes were described in males, which differed in chromosome number (2n = 5 and 2n = 6) and meiotic multivalent configurations (chains of four, five and six chromosomes). Based on a detailed mitotic and meiotic analysis, we propose a sequence of chromosome rearrangements that could give rise to each cytotype and in which fusions have played a major role. Based on the comparison of males, females and a brood of embryos, we also propose that the presence of multivalents in males and homologous pairs in females could be associated with the presence of cryptic sex chromosomes, with the male being the heterogametic sex. We propose that the ancestral karyotype of this species could have had homomorphic XY/XX (male/female) sex chromosomes and a fusion could have occurred between the Y chromosome and an autosome. PMID:27783630

  17. The spindle checkpoint and chromosome segregation in meiosis.

    PubMed

    Gorbsky, Gary J

    2015-07-01

    The spindle checkpoint is a key regulator of chromosome segregation in mitosis and meiosis. Its function is to prevent precocious anaphase onset before chromosomes have achieved bipolar attachment to the spindle. The spindle checkpoint comprises a complex set of signaling pathways that integrate microtubule dynamics, biomechanical forces at the kinetochores, and intricate regulation of protein interactions and post-translational modifications. Historically, many key observations that gave rise to the initial concepts of the spindle checkpoint were made in meiotic systems. In contrast with mitosis, the two distinct chromosome segregation events of meiosis present a special challenge for the regulation of checkpoint signaling. Preservation of fidelity in chromosome segregation in meiosis, controlled by the spindle checkpoint, also has a significant impact in human health. This review highlights the contributions from meiotic systems in understanding the spindle checkpoint as well as the role of checkpoint signaling in controlling the complex divisions of meiosis.

  18. The spindle checkpoint and chromosome segregation in meiosis

    PubMed Central

    Gorbsky, Gary J.

    2014-01-01

    The spindle checkpoint is a key regulator of chromosome segregation in mitosis and meiosis. Its function is to prevent precocious anaphase onset before chromosomes have achieved bipolar attachment to the spindle. The spindle checkpoint comprises a complex set of signaling pathways that integrate microtubule dynamics, biomechanical forces at the kinetochores, and intricate regulation of protein interactions and post-translational modifications. Historically, many key observations that gave rise to the initial concepts of the spindle checkpoint were carried out in meiotic systems. In contrast with mitosis, the two distinct chromosome segregation events of meiosis present a special challenge for the regulation of checkpoint signaling. Preservation of fidelity in chromosome segregation in meiosis, controlled by the spindle checkpoint, also has significant impact in human health. This review highlights the contributions from meiotic systems in understanding the spindle checkpoint as well as the role of checkpoint signaling in controlling the complex divisions of meiosis. PMID:25470754

  19. The meiotic transcriptome architecture of plants

    PubMed Central

    Dukowic-Schulze, Stefanie; Chen, Changbin

    2014-01-01

    Although a number of genes that play key roles during the meiotic process have been characterized in great detail, the whole process of meiosis is still not completely unraveled. To gain insight into the bigger picture, large-scale approaches like RNA-seq and microarray can help to elucidate the transcriptome landscape during plant meiosis, discover co-regulated genes, enriched processes, and highly expressed known and unknown genes which might be important for meiosis. These high-throughput studies are gaining more and more popularity, but their beginnings in plant systems reach back as far as the 1960's. Frequently, whole anthers or post-meiotic pollen were investigated, while less data is available on isolated cells during meiosis, and only few studies addressed the transcriptome of female meiosis. For this review, we compiled meiotic transcriptome studies covering different plant species, and summarized and compared their key findings. Besides pointing to consistent as well as unique discoveries, we finally draw conclusions what can be learned from these studies so far and what should be addressed next. PMID:24926296

  20. The Exonuclease Homolog OsRAD1 Promotes Accurate Meiotic Double-Strand Break Repair by Suppressing Nonhomologous End Joining1[OPEN

    PubMed Central

    Tang, Ding; Shen, Yi; Chen, Xiaojun; Ji, Jianhui; Du, Guijie; Li, Yafei; Cheng, Zhukuan

    2016-01-01

    During meiosis, programmed double-strand breaks (DSBs) are generated to initiate homologous recombination, which is crucial for faithful chromosome segregation. In yeast, Radiation sensitive1 (RAD1) acts together with Radiation sensitive9 (RAD9) and Hydroxyurea sensitive1 (HUS1) to facilitate meiotic recombination via cell-cycle checkpoint control. However, little is known about the meiotic functions of these proteins in higher eukaryotes. Here, we characterized a RAD1 homolog in rice (Oryza sativa) and obtained evidence that O. sativa RAD1 (OsRAD1) is important for meiotic DSB repair. Loss of OsRAD1 led to abnormal chromosome association and fragmentation upon completion of homologous pairing and synapsis. These aberrant chromosome associations were independent of OsDMC1. We found that classical nonhomologous end-joining mediated by Ku70 accounted for most of the ectopic associations in Osrad1. In addition, OsRAD1 interacts directly with OsHUS1 and OsRAD9, suggesting that these proteins act as a complex to promote DSB repair during rice meiosis. Together, these findings suggest that the 9-1-1 complex facilitates accurate meiotic recombination by suppressing nonhomologous end-joining during meiosis in rice. PMID:27512017

  1. EZH2 is required for mouse oocyte meiotic maturation by interacting with and stabilizing spindle assembly checkpoint protein BubRI

    PubMed Central

    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

  2. Meiotic Drive Impacts Expression and Evolution of X-Linked Genes in Stalk-Eyed Flies

    PubMed Central

    Reinhardt, Josephine A.; Brand, Cara L.; Paczolt, Kimberly A.; Johns, Philip M.; Baker, Richard H.; Wilkinson, Gerald S.

    2014-01-01

    Although sex chromosome meiotic drive has been observed in a variety of species for over 50 years, the genes causing drive are only known in a few cases, and none of these cases cause distorted sex-ratios in nature. In stalk-eyed flies (Teleopsis dalmanni), driving X chromosomes are commonly found at frequencies approaching 30% in the wild, but the genetic basis of drive has remained elusive due to reduced recombination between driving and non-driving X chromosomes. Here, we used RNAseq to identify transcripts that are differentially expressed between males carrying either a driving X (XSR) or a standard X chromosome (XST), and found hundreds of these, the majority of which are X-linked. Drive-associated transcripts show increased levels of sequence divergence (dN/dS) compared to a control set, and are predominantly expressed either in testes or in the gonads of both sexes. Finally, we confirmed that XSR and XST are highly divergent by estimating sequence differentiation between the RNAseq pools. We found that X-linked transcripts were often strongly differentiated (whereas most autosomal transcripts were not), supporting the presence of a relatively large region of recombination suppression on XSR presumably caused by one or more inversions. We have identified a group of genes that are good candidates for further study into the causes and consequences of sex-chromosome drive, and demonstrated that meiotic drive has had a profound effect on sequence evolution and gene expression of X-linked genes in this species. PMID:24832132

  3. ETOPOSIDE INDUCES CHROMOSOMAL ABNORMALITIES IN SPERMATOCYTES AND SPERMATOGONIAL STEM CELLS

    SciTech Connect

    Marchetti, F; Pearson, F S; Bishop, J B; Wyrobek, A J

    2005-07-15

    Etoposide (ET) is a chemotherapeutic agent widely used in the treatment of leukemia, lymphomas and many solid tumors, such as testicular and ovarian cancers, that affect patients in their reproductive years. The purpose of the study was to use sperm FISH analyses to characterize the long-term effects of ET on male germ cells. We used a mouse model to characterize the induction of chromosomal aberrations (partial duplications and deletions) and whole chromosomal aneuploidies in sperm of mice treated with a clinical dose of ET. Semen samples were collected at 25 and 49 days after dosing to investigate the effects of ET on meiotic pachytene cells and spermatogonial stem-cells, respectively. ET treatment resulted in major increases in the frequencies of sperm carrying chromosomal aberrations in both meiotic pachytene (27- to 578-fold) and spermatogonial stem-cells (8- to 16-fold), but aneuploid sperm were induced only after treatment of meiotic cells (27-fold) with no persistent effects in stem cells. These results demonstrate that male meiotic germ cells are considerably more sensitive to ET than spermatogonial stem-cell and that increased frequencies of sperm with structural aberrations persist after spermatogonial stem-cell treatment. These findings predict that patients who undergo chemotherapy with ET may have transient elevations in the frequencies of aneuploid sperm, but more importantly, may have persistent elevations in the frequencies of sperm with chromosomal aberrations, placing them at higher risk for abnormal reproductive outcomes long after the end of their chemotherapy.

  4. Heteromorphic sex chromosome system with an exceptionally large Y chromosome in a catfish Steindachneridion sp. (Pimelodidae).

    PubMed

    Swarça, A C; Fenocchio, A S; Cestari, M M; Bertollo, L A C; Dias, A L

    2006-01-01

    The chromosomes and banding patterns of Steindachneridion sp., a large catfish (Pimelodidae), endemic to the Iguaçu River, Brazil, were analyzed using conventional (C-, G-banding) and restriction enzyme banding methods. The same diploid number (2n = 56) as in other members of the genus and the family was found but the karyotype displayed an XX/XY sex chromosome system. The X chromosome was the smallest submetacentric, while the Y was the largest chromosome in the karyotype. Meiotic analysis showed 27 autosomal bivalents plus one heteromorphic XY bivalent during spermatogenesis. Sex chromosomes had no particular pattern after C-banding but G- and restriction enzyme bandings showed specific banding characteristics. The present finding represents the first report of a well-differentiated and uncommon sex chromosome system in the catfish family Pimelodidae.

  5. Chromosome interaction over a distance in meiosis.

    PubMed

    Brady, Mary; Paliulis, Leocadia V

    2015-02-01

    The challenge of cell division is to distribute partner chromosomes (pairs of homologues, pairs of sex chromosomes or pairs of sister chromatids) correctly, one into each daughter cell. In the 'standard' meiosis, this problem is solved by linking partners together via a chiasma and/or sister chromatid cohesion, and then separating the linked partners from one another in anaphase; thus, the partners are kept track of, and correctly distributed. Many organisms, however, properly separate chromosomes in the absence of any obvious physical connection, and movements of unconnected partner chromosomes are coordinated at a distance. Meiotic distance interactions happen in many different ways and in different types of organisms. In this review, we discuss several different known types of distance segregation and propose possible explanations for non-random segregation of distance-segregating chromosomes. PMID:26064610

  6. Chromosome interaction over a distance in meiosis

    PubMed Central

    Brady, Mary; Paliulis, Leocadia V.

    2015-01-01

    The challenge of cell division is to distribute partner chromosomes (pairs of homologues, pairs of sex chromosomes or pairs of sister chromatids) correctly, one into each daughter cell. In the ‘standard’ meiosis, this problem is solved by linking partners together via a chiasma and/or sister chromatid cohesion, and then separating the linked partners from one another in anaphase; thus, the partners are kept track of, and correctly distributed. Many organisms, however, properly separate chromosomes in the absence of any obvious physical connection, and movements of unconnected partner chromosomes are coordinated at a distance. Meiotic distance interactions happen in many different ways and in different types of organisms. In this review, we discuss several different known types of distance segregation and propose possible explanations for non-random segregation of distance-segregating chromosomes. PMID:26064610

  7. Normal segregation of a foreign-species chromosome during Drosophila female meiosis despite extensive heterochromatin divergence.

    PubMed

    Gilliland, William D; Colwell, Eileen M; Osiecki, David M; Park, Suna; Lin, Deanna; Rathnam, Chandramouli; Barbash, Daniel A

    2015-01-01

    The abundance and composition of heterochromatin changes rapidly between species and contributes to hybrid incompatibility and reproductive isolation. Heterochromatin differences may also destabilize chromosome segregation and cause meiotic drive, the non-Mendelian segregation of homologous chromosomes. Here we use a range of genetic and cytological assays to examine the meiotic properties of a Drosophila simulans chromosome 4 (sim-IV) introgressed into D. melanogaster. These two species differ by ∼12-13% at synonymous sites and several genes essential for chromosome segregation have experienced recurrent adaptive evolution since their divergence. Furthermore, their chromosome 4s are visibly different due to heterochromatin divergence, including in the AATAT pericentromeric satellite DNA. We find a visible imbalance in the positioning of the two chromosome 4s in sim-IV/mel-IV heterozygote and also replicate this finding with a D. melanogaster 4 containing a heterochromatic deletion. These results demonstrate that heterochromatin abundance can have a visible effect on chromosome positioning during meiosis. Despite this effect, however, we find that sim-IV segregates normally in both diplo and triplo 4 D. melanogaster females and does not experience elevated nondisjunction. We conclude that segregation abnormalities and a high level of meiotic drive are not inevitable byproducts of extensive heterochromatin divergence. Animal chromosomes typically contain large amounts of noncoding repetitive DNA that nevertheless varies widely between species. This variation may potentially induce non-Mendelian transmission of chromosomes. We have examined the meiotic properties and transmission of a highly diverged chromosome 4 from a foreign species within the fruitfly Drosophila melanogaster. This chromosome has substantially less of a simple sequence repeat than does D. melanogaster 4, and we find that this difference results in altered positioning when chromosomes align

  8. Normal segregation of a foreign-species chromosome during Drosophila female meiosis despite extensive heterochromatin divergence.

    PubMed

    Gilliland, William D; Colwell, Eileen M; Osiecki, David M; Park, Suna; Lin, Deanna; Rathnam, Chandramouli; Barbash, Daniel A

    2015-01-01

    The abundance and composition of heterochromatin changes rapidly between species and contributes to hybrid incompatibility and reproductive isolation. Heterochromatin differences may also destabilize chromosome segregation and cause meiotic drive, the non-Mendelian segregation of homologous chromosomes. Here we use a range of genetic and cytological assays to examine the meiotic properties of a Drosophila simulans chromosome 4 (sim-IV) introgressed into D. melanogaster. These two species differ by ∼12-13% at synonymous sites and several genes essential for chromosome segregation have experienced recurrent adaptive evolution since their divergence. Furthermore, their chromosome 4s are visibly different due to heterochromatin divergence, including in the AATAT pericentromeric satellite DNA. We find a visible imbalance in the positioning of the two chromosome 4s in sim-IV/mel-IV heterozygote and also replicate this finding with a D. melanogaster 4 containing a heterochromatic deletion. These results demonstrate that heterochromatin abundance can have a visible effect on chromosome positioning during meiosis. Despite this effect, however, we find that sim-IV segregates normally in both diplo and triplo 4 D. melanogaster females and does not experience elevated nondisjunction. We conclude that segregation abnormalities and a high level of meiotic drive are not inevitable byproducts of extensive heterochromatin divergence. Animal chromosomes typically contain large amounts of noncoding repetitive DNA that nevertheless varies widely between species. This variation may potentially induce non-Mendelian transmission of chromosomes. We have examined the meiotic properties and transmission of a highly diverged chromosome 4 from a foreign species within the fruitfly Drosophila melanogaster. This chromosome has substantially less of a simple sequence repeat than does D. melanogaster 4, and we find that this difference results in altered positioning when chromosomes align

  9. Normal Segregation of a Foreign-Species Chromosome During Drosophila Female Meiosis Despite Extensive Heterochromatin Divergence

    PubMed Central

    Gilliland, William D.; Colwell, Eileen M.; Osiecki, David M.; Park, Suna; Lin, Deanna; Rathnam, Chandramouli; Barbash, Daniel A.

    2015-01-01

    The abundance and composition of heterochromatin changes rapidly between species and contributes to hybrid incompatibility and reproductive isolation. Heterochromatin differences may also destabilize chromosome segregation and cause meiotic drive, the non-Mendelian segregation of homologous chromosomes. Here we use a range of genetic and cytological assays to examine the meiotic properties of a Drosophila simulans chromosome 4 (sim-IV) introgressed into D. melanogaster. These two species differ by ∼12–13% at synonymous sites and several genes essential for chromosome segregation have experienced recurrent adaptive evolution since their divergence. Furthermore, their chromosome 4s are visibly different due to heterochromatin divergence, including in the AATAT pericentromeric satellite DNA. We find a visible imbalance in the positioning of the two chromosome 4s in sim-IV/mel-IV heterozygote and also replicate this finding with a D. melanogaster 4 containing a heterochromatic deletion. These results demonstrate that heterochromatin abundance can have a visible effect on chromosome positioning during meiosis. Despite this effect, however, we find that sim-IV segregates normally in both diplo and triplo 4 D. melanogaster females and does not experience elevated nondisjunction. We conclude that segregation abnormalities and a high level of meiotic drive are not inevitable byproducts of extensive heterochromatin divergence. Animal chromosomes typically contain large amounts of noncoding repetitive DNA that nevertheless varies widely between species. This variation may potentially induce non-Mendelian transmission of chromosomes. We have examined the meiotic properties and transmission of a highly diverged chromosome 4 from a foreign species within the fruitfly Drosophila melanogaster. This chromosome has substantially less of a simple sequence repeat than does D. melanogaster 4, and we find that this difference results in altered positioning when chromosomes align

  10. Variation in Meiotic Recombination Frequencies Between Allelic Transgenes Inserted at Different Sites in the Drosophila melanogaster Genome

    PubMed Central

    McMahan, Susan; Kohl, Kathryn P.; Sekelsky, Jeff

    2013-01-01

    Meiotic crossovers are distributed nonrandomly across the genome. Classic studies in Drosophila suggest that the position of a gene along a chromosome arm can affect the outcome of the recombination process, with proximity to the centromere being associated with lower crossing over. To examine this phenomenon molecularly, we developed an assay that measures meiotic crossovers and noncrossover gene conversions between allelic transgenes inserted into different genomic positions. To facilitate collecting a large number of virgin females, we developed a useful genetic system that kills males and undesired classes of females. We found that the recombination frequency at a site in the middle of the X chromosome, where crossovers are normally frequent, was similar to the frequency at the centromere-proximal end of the euchromatin, where crossovers are normally infrequent. In contrast, we recovered no recombinants—crossovers or noncrossovers—at a site on chromosome 4 and at a site toward the distal end of the X chromosome. These results suggest that local sequence or chromatin features have a stronger impact on recombination rates in this transgene assay than position along the chromosome arm. PMID:23797104

  11. A positive but complex association between meiotic double-strand break hotspots and open chromatin in Saccharomyces cerevisiae

    PubMed Central

    Berchowitz, Luke E.; Hanlon, Sean E.; Lieb, Jason D.; Copenhaver, Gregory P.

    2009-01-01

    During meiosis, chromatin undergoes extensive changes to facilitate recombination, homolog pairing, and chromosome segregation. To investigate the relationship between chromatin organization and meiotic processes, we used formaldehyde-assisted isolation of regulatory elements (FAIRE) to map open chromatin during the transition from mitosis to meiosis in the budding yeast Saccharomyces cerevisiae. We found that meiosis-induced opening of chromatin is associated with meiotic DSB hotpots. The positive association between open chromatin and DSB hotspots is most prominent 3 h into meiosis, when the early meiotic genes DMC1 and HOP1 exhibit maximum transcription and the early recombination genes SPO11 and RAD51 are strongly up-regulated. While the degree of chromatin openness is positively associated with the occurrence of recombination hotspots, many hotspots occur outside of open chromatin. Of particular interest, many DSB hotspots that fell outside of meiotic open chromatin nonetheless occurred in chromatin that had recently been open during mitotic growth. Finally, we find evidence for meiosis-specific opening of chromatin at the regions adjacent to boundaries of subtelomeric sequences, which exhibit specific crossover control patterns hypothesized to be regulated by chromatin. PMID:19801530

  12. Capturing Chromosome Conformation

    NASA Astrophysics Data System (ADS)

    Dekker, Job; Rippe, Karsten; Dekker, Martijn; Kleckner, Nancy

    2002-02-01

    We describe an approach to detect the frequency of interaction between any two genomic loci. Generation of a matrix of interaction frequencies between sites on the same or different chromosomes reveals their relative spatial disposition and provides information about the physical properties of the chromatin fiber. This methodology can be applied to the spatial organization of entire genomes in organisms from bacteria to human. Using the yeast Saccharomyces cerevisiae, we could confirm known qualitative features of chromosome organization within the nucleus and dynamic changes in that organization during meiosis. We also analyzed yeast chromosome III at the G1 stage of the cell cycle. We found that chromatin is highly flexible throughout. Furthermore, functionally distinct AT- and GC-rich domains were found to exhibit different conformations, and a population-average 3D model of chromosome III could be determined. Chromosome III emerges as a contorted ring.

  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

    PubMed Central

    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. Differential Association of the Conserved SUMO Ligase Zip3 with Meiotic Double-Strand Break Sites Reveals Regional Variations in the Outcome of Meiotic Recombination

    PubMed Central

    Serrentino, Maria-Elisabetta; Chaplais, Emmanuel; Sommermeyer, Vérane; Borde, Valérie

    2013-01-01

    During the first meiotic prophase, programmed DNA double-strand breaks (DSBs) are distributed non randomly at hotspots along chromosomes, to initiate recombination. In all organisms, more DSBs are formed than crossovers (CO), the repair product that creates a physical link between homologs and allows their correct segregation. It is not known whether all DSB hotspots are also CO hotspots or if the CO/DSB ratio varies with the chromosomal location. Here, we investigated the variations in the CO/DSB ratio by mapping genome-wide the binding sites of the Zip3 protein during budding yeast meiosis. We show that Zip3 associates with DSB sites that are engaged in repair by CO, and Zip3 enrichment at DSBs reflects the DSB tendency to be repaired by CO. Moreover, the relative amount of Zip3 per DSB varies with the chromosomal location, and specific chromosomal features are associated with high or low Zip3 per DSB. This work shows that DSB hotspots are not necessarily CO hotspots and suggests that different categories of DSB sites may fulfill different functions. PMID:23593021

  15. Ancient Male Recombination Shaped Genetic Diversity of Neo-Y Chromosome in Drosophila albomicans.

    PubMed

    Satomura, Kazuhiro; Tamura, Koichiro

    2016-02-01

    Researchers studying Y chromosome evolution have drawn attention to neo-Y chromosomes in Drosophila species due to their resembling the initial stage of Y chromosome evolution. In the studies of neo-Y chromosome of Drosophila miranda, the extremely low genetic diversity observed suggested various modes of natural selection acting on the nonrecombining genome. However, alternative possibility may come from its peculiar origin from a single chromosomal fusion event with male achiasmy, which potentially caused and maintained the low genetic diversity of the neo-Y chromosome. Here, we report a real case where a neo-Y chromosome is in transition from an autosome to a typical Y chromosome. The neo-Y chromosome of Drosophila albomicans harbored a rich genetic diversity comparable to its gametologous neo-X chromosome and an autosome in the same genome. Analyzing sequence variations in 53 genes and measuring recombination rates between pairs of loci by cross experiments, we elucidated the evolutionary scenario of the neo-Y chromosome of D. albomicans having high genetic diversity without assuming selective force, i.e., it originated from a single chromosomal fusion event, experienced meiotic recombination during the initial stage of evolution and diverged from neo-X chromosome by the suppression of recombination tens or a few hundreds of thousand years ago. Consequently, the observed high genetic diversity on the neo-Y chromosome suggested a strong effect of meiotic recombination to introduce genetic variations into the newly arisen sex chromosome. PMID:26494844

  16. Ancient Male Recombination Shaped Genetic Diversity of Neo-Y Chromosome in Drosophila albomicans.

    PubMed

    Satomura, Kazuhiro; Tamura, Koichiro

    2016-02-01

    Researchers studying Y chromosome evolution have drawn attention to neo-Y chromosomes in Drosophila species due to their resembling the initial stage of Y chromosome evolution. In the studies of neo-Y chromosome of Drosophila miranda, the extremely low genetic diversity observed suggested various modes of natural selection acting on the nonrecombining genome. However, alternative possibility may come from its peculiar origin from a single chromosomal fusion event with male achiasmy, which potentially caused and maintained the low genetic diversity of the neo-Y chromosome. Here, we report a real case where a neo-Y chromosome is in transition from an autosome to a typical Y chromosome. The neo-Y chromosome of Drosophila albomicans harbored a rich genetic diversity comparable to its gametologous neo-X chromosome and an autosome in the same genome. Analyzing sequence variations in 53 genes and measuring recombination rates between pairs of loci by cross experiments, we elucidated the evolutionary scenario of the neo-Y chromosome of D. albomicans having high genetic diversity without assuming selective force, i.e., it originated from a single chromosomal fusion event, experienced meiotic recombination during the initial stage of evolution and diverged from neo-X chromosome by the suppression of recombination tens or a few hundreds of thousand years ago. Consequently, the observed high genetic diversity on the neo-Y chromosome suggested a strong effect of meiotic recombination to introduce genetic variations into the newly arisen sex chromosome.

  17. Meiotic Recombination Hotspots of Fission Yeast Are Directed to Loci that Express Non-Coding RNA

    PubMed Central

    Wahls, Wayne P.; Siegel, Eric R.; Davidson, Mari K.

    2008-01-01

    Background Polyadenylated, mRNA-like transcripts with no coding potential are abundant in eukaryotes, but the functions of these long non-coding RNAs (ncRNAs) are enigmatic. In meiosis, Rec12 (Spo11) catalyzes the formation of dsDNA breaks (DSBs) that initiate homologous recombination. Most meiotic recombination is positioned at hotspots, but knowledge of the mechanisms is nebulous. In the fission yeast genome DSBs are located within 194 prominent peaks separated on average by 65-kbp intervals of DNA that are largely free of DSBs. Methodology/Principal Findings We compared the genome-wide distribution of DSB peaks to that of polyadenylated ncRNA molecules of the prl class. DSB peaks map to ncRNA loci that may be situated within ORFs, near the boundaries of ORFs and intergenic regions, or most often within intergenic regions. Unconditional statistical tests revealed that this colocalization is non-random and robust (P≤5.5×10−8). Furthermore, we tested and rejected the hypothesis that the ncRNA loci and DSB peaks localize preferentially, but independently, to a third entity on the chromosomes. Conclusions/Significance Meiotic DSB hotspots are directed to loci that express polyadenylated ncRNAs. This reveals an unexpected, possibly unitary mechanism for what directs meiotic recombination to hotspots. It also reveals a likely biological function for enigmatic ncRNAs. We propose specific mechanisms by which ncRNA molecules, or some aspect of RNA metabolism associated with ncRNA loci, help to position recombination protein complexes at DSB hotspots within chromosomes. PMID:18682829

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

    SciTech Connect

    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.

  19. Triploid planarian reproduces truly bisexually with euploid gametes produced through a different meiotic system between sex.

    PubMed

    Chinone, Ayako; Nodono, Hanae; Matsumoto, Midori

    2014-06-01

    Although polyploids are common among plants and some animals, polyploidization often causes reproductive failure. Triploids, in particular, are characterized by the problems of chromosomal pairing and segregation during meiosis, which may cause aneuploid gametes and results in sterility. Thus, they are generally considered to reproduce only asexually. In the case of the Platyhelminthes Dugesia ryukyuensis, populations with triploid karyotypes are normally found in nature as both fissiparous and oviparous triploids. Fissiparous triploids can also be experimentally sexualized if they are fed sexual planarians, developing both gonads and other reproductive organs. Fully sexualized worms begin reproducing by copulation rather than fission. In this study, we examined the genotypes of the offspring obtained by breeding sexualized triploids and found that the offspring inherited genes from both parents, i.e., they reproduced truly bisexually. Furthermore, meiotic chromosome behavior in triploid sexualized planarians differed significantly between male and female germ lines, in that female germ line cells remained triploid until prophase I, whereas male germ line cells appeared to become diploid before entry into meiosis. Oocytes at the late diplotene stage contained not only paired bivalents but also unpaired univalents that were suggested to produce diploid eggs if they remained in subsequent processes. Triploid planarians may therefore form euploid gametes by different meiotic systems in female and male germ lines and thus are be able to reproduce sexually in contrast to many other triploid organisms. PMID:24402417

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

    PubMed

    Ellefson, Marina L; McNally, Francis J

    2011-06-27

    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.

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

    PubMed Central

    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

  2. Separate effects of sex hormones and sex chromosomes on brain structure and function revealed by high-resolution magnetic resonance imaging and spatial navigation assessment of the Four Core Genotype mouse model.

    PubMed

    Corre, Christina; Friedel, Miriam; Vousden, Dulcie A; Metcalf, Ariane; Spring, Shoshana; Qiu, Lily R; Lerch, Jason P; Palmert, Mark R

    2016-03-01

    Males and females exhibit several differences in brain structure and function. To examine the basis for these sex differences, we investigated the influences of sex hormones and sex chromosomes on brain structure and function in mice. We used the Four Core Genotype (4CG) mice, which can generate both male and female mice with XX or XY sex chromosome complement, allowing the decoupling of sex chromosomes from hormonal milieu. To examine whole brain structure, high-resolution ex vivo MRI was performed, and to assess differences in cognitive function, mice were trained on a radial arm maze. Voxel-wise and volumetric analyses of MRI data uncovered a striking independence of hormonal versus chromosomal influences in 30 sexually dimorphic brain regions. For example, the bed nucleus of the stria terminalis and the parieto-temporal lobe of the cerebral cortex displayed steroid-dependence while the cerebellar cortex, corpus callosum, and olfactory bulbs were influenced by sex chromosomes. Spatial learning and memory demonstrated strict hormone-dependency with no apparent influence of sex chromosomes. Understanding the influences of chromosomes and hormones on brain structure and function is important for understanding sex differences in brain structure and function, an endeavor that has eventual implications for understanding sex biases observed in the prevalence of psychiatric disorders.

  3. Chromosomal Conditions

    MedlinePlus

    ... 150 babies is born with a chromosomal condition. Down syndrome is an example of a chromosomal condition. Because ... all pregnant women be offered prenatal tests for Down syndrome and other chromosomal conditions. A screening test is ...

  4. Drosophila PCH2 Is Required for a Pachytene Checkpoint That Monitors Double-Strand-Break-Independent Events Leading to Meiotic Crossover Formation

    PubMed Central

    Joyce, Eric F.; McKim, Kim S.

    2009-01-01

    During meiosis, programmed DNA double-strand breaks (DSBs) are repaired to create at least one crossover per chromosome arm. Crossovers mature into chiasmata, which hold and orient the homologous chromosomes on the meiotic spindle to ensure proper segregation at meiosis I. This process is usually monitored by one or more checkpoints that ensure that DSBs are repaired prior to the meiotic divisions. We show here that mutations in Drosophila genes required to process DSBs into crossovers delay two important steps in meiotic progression: a chromatin-remodeling process associated with DSB formation and the final steps of oocyte selection. Consistent with the hypothesis that a checkpoint has been activated, the delays in meiotic progression are suppressed by a mutation in the Drosophila homolog of pch2. The PCH2-dependent delays also require proteins thought to regulate the number and distribution of crossovers, suggesting that this checkpoint monitors events leading to crossover formation. Surprisingly, two lines of evidence suggest that the PCH2-dependent checkpoint does not reflect the accumulation of unprocessed recombination intermediates: the delays in meiotic progression do not depend on DSB formation or on mei-41, the Drosophila ATR homolog, which is required for the checkpoint response to unrepaired DSBs. We propose that the sites and/or conditions required to promote crossovers are established independently of DSB formation early in meiotic prophase. Furthermore, the PCH2-dependent checkpoint is activated by these events and pachytene progression is delayed until the DSB repair complexes required to generate crossovers are assembled. Interestingly, PCH2-dependent delays in prophase may allow additional crossovers to form. PMID:18957704

  5. Meiotic transmission of an in vitro-assembled autonomous maize minichromosome.

    PubMed

    Carlson, Shawn R; Rudgers, Gary W; Zieler, Helge; Mach, Jennifer M; Luo, Song; Grunden, Eric; Krol, Cheryl; Copenhaver, Gregory P; Preuss, Daphne

    2007-10-01

    Autonomous chromosomes are generated in yeast (yeast artificial chromosomes) and human fibrosarcoma cells (human artificial chromosomes) by introducing purified DNA fragments that nucleate a kinetochore, replicate, and segregate to daughter cells. These autonomous minichromosomes are convenient for manipulating and delivering DNA segments containing multiple genes. In contrast, commercial production of transgenic crops relies on methods that integrate one or a few genes into host chromosomes; extensive screening to identify insertions with the desired expression level, copy number, structure, and genomic location; and long breeding programs to produce varieties that carry multiple transgenes. As a step toward improving transgenic crop production, we report the development of autonomous maize minichromosomes (MMCs). We constructed circular MMCs by combining DsRed and nptII marker genes with 7-190 kb of genomic maize DNA fragments containing satellites, retroelements, and/or other repeats commonly found in centromeres and using particle bombardment to deliver these constructs into embryogenic maize tissue. We selected transformed cells, regenerated plants, and propagated their progeny for multiple generations in the absence of selection. Fluorescent in situ hybridization and segregation analysis demonstrated that autonomous MMCs can be mitotically and meiotically maintained. The MMC described here showed meiotic segregation ratios approaching Mendelian inheritance: 93% transmission as a disome (100% expected), 39% transmission as a monosome crossed to wild type (50% expected), and 59% transmission in self crosses (75% expected). The fluorescent DsRed reporter gene on the MMC was expressed through four generations, and Southern blot analysis indicated the encoded genes were intact. This novel approach for plant transformation can facilitate crop biotechnology by (i) combining several trait genes on a single DNA fragment, (ii) arranging genes in a defined sequence

  6. A novel chromosome segregation mechanism during female meiosis.

    PubMed

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

    2016-08-15

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

  7. A novel chromosome segregation mechanism during female meiosis

    PubMed Central

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

    2016-01-01

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

  8. The pam1 gene is required for meiotic bouquet formation and efficient homologous synapsis in maize (Zea mays L.).

    PubMed Central

    Golubovskaya, Inna N; Harper, Lisa C; Pawlowski, Wojciech P; Schichnes, Denise; Cande, W Zacheus

    2002-01-01

    The clustering of telomeres on the nuclear envelope (NE) during meiotic prophase to form the bouquet arrangement of chromosomes may facilitate homologous chromosome synapsis. The pam1 (plural abnormalities of meiosis 1) gene is the first maize gene that appears to be required for telomere clustering, and homologous synapsis is impaired in pam1. Telomere clustering on the NE is arrested or delayed at an intermediate stage in pam1. Telomeres associate with the NE during the leptotene-zygotene transition but cluster slowly if at all as meiosis proceeds. Intermediate stages in telomere clustering including miniclusters are observed in pam1 but not in wild-type meiocytes. The tight bouquet normally seen at zygotene is a rare event. In contrast, the polarization of centromeres vs. telomeres in the nucleus at the leptotene-zygotene transition is the same in mutant and wild-type cells. Defects in homologous chromosome synapsis include incomplete synapsis, nonhomologous synapsis, and unresolved interlocks. However, the number of RAD51 foci on chromosomes in pam1 is similar to that of wild type. We suggest that the defects in homologous synapsis and the retardation of prophase I arise from the irregularity of telomere clustering and propose that pam1 is involved in the control of bouquet formation and downstream meiotic prophase I events. PMID:12524364

  9. Cytoplasmic and genomic effects on meiotic pairing in Brassica hybrids and allotetraploids from pair crosses of three cultivated diploids.

    PubMed

    Cui, Cheng; Ge, Xianhong; Gautam, Mayank; Kang, Lei; Li, Zaiyun

    2012-07-01

    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.

  10. Cytoplasmic and Genomic Effects on Meiotic Pairing in Brassica Hybrids and Allotetraploids from Pair Crosses of Three Cultivated Diploids

    PubMed Central

    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

  11. Cytoplasmic and genomic effects on meiotic pairing in Brassica hybrids and allotetraploids from pair crosses of three cultivated diploids.

    PubMed

    Cui, Cheng; Ge, Xianhong; Gautam, Mayank; Kang, Lei; Li, Zaiyun

    2012-07-01

    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

  12. [Induction of meiotic disturbances in spermatocytes I by pheromones as an inhibiting mechanism of male reproductive function in house mice].

    PubMed

    Daev, E V; Dukel'skaia, A V

    2005-01-01

    The influence of pheromons on reproduction and other important physiological characteristics has been reported for many mammalian species. However, mechanisms of this action at the level of target cells still remain unclear. A study was made of the influence of non-identified pheromones from adult males and a female pheromone 2,5-dimethylpyrazine on germ cells of CBA inbred strain mice. Cytogenetic analysis shows a significant increase in such meiotic disturbances as multivalent associations and autsomal univalents 24 h after exposure to pheromonal cues. Results of in situ hybridization show that the level of c-fos and c-jun expression is significantly higher 3.5 h after exposure to pheromones of adult males. It is likely that destabilization of chromosomal apparatus in dividing meiotic cells forms the basis of some reproductive effects of murine pheromones. Possible mechanisms of pheromone influence on reproduction are discussed.

  13. Two rare aneutriploids in the unisexual Ambystoma (Amphibia, Caudata) identified by GISH indicating two different types of meiotic errors.

    PubMed

    Bi, K; Bogart, J P; Fu, J

    2007-01-01

    We report two types of aneutriploids in unisexual salamanders Ambystomalaterale-2jeffersonianum (LJJ) and Ambystoma 2 laterale-jeffersonianum (LLJ). One karyotype has 3n = 42: L27 (L8-); J15 (J8p+), and we suggest that it was induced by homoeologous pairing after premeiotic endomitosis followed by an unequal L8;J8 segregation. The second karyotype has 3n = 43: L14 (L10q); J29 (J12+), which can be explained by meiotic nondisjunction followed by unbalanced segregation. These two rare aneutriploids demonstrate two different types of meiotic errors that might help to explain the high mortality observed in this complex. Case one also indicates that contemporary intergenomic exchanges and homoeologous recombinations may occur after a premeiotic chromosome doubling event. Our study provides additional evidence for the extremely flexible reproduction of unisexual Ambystoma. PMID:18160791

  14. A rare Robertsonian translocation rob(14;22) carrier with azoospermia, meiotic defects, and testicular sperm aneuploidy.

    PubMed

    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.

  15. A rare Robertsonian translocation rob(14;22) carrier with azoospermia, meiotic defects, and testicular sperm aneuploidy.

    PubMed

    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. PMID:26043179

  16. A Taz1- and Microtubule-Dependent Regulatory Relationship between Telomere and Centromere Positions in Bouquet Formation Secures Proper Meiotic Divisions.

    PubMed

    Katsumata, Kazuhiro; Hirayasu, Ami; Miyoshi, Junpei; Nishi, Eriko; Ichikawa, Kento; Tateho, Kazuki; Wakuda, Airi; Matsuhara, Hirotada; Yamamoto, Ayumu

    2016-09-01

    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. PMID:27611693

  17. A Taz1- and Microtubule-Dependent Regulatory Relationship between Telomere and Centromere Positions in Bouquet Formation Secures Proper Meiotic Divisions

    PubMed Central

    Katsumata, Kazuhiro; Hirayasu, Ami; Miyoshi, Junpei; Nishi, Eriko; Ichikawa, Kento; Tateho, Kazuki; Wakuda, Airi; Matsuhara, Hirotada; Yamamoto, Ayumu

    2016-01-01

    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. PMID:27611693

  18. Meiotic drive and evolution of female choice.

    PubMed

    Reinhold, K; Engqvist, L; Misof, B; Kurtz, J

    1999-07-01

    As a special version of the good-genes hypothesis, it was recently proposed that females could benefit from choosing drive-resistant males in a meiotic drive system. Here, we examine with a three-locus, six-allele population genetic model whether female choice for drive resistance can evolve. An allele leading to female preference for drive-resistant males was introduced at low frequency into a population polymorphic for meiotic drive and drive resistance. Our simulations show that female choice of drive-resistant males is disadvantageous when resistance is Y-linked. This disadvantage occurs because, at equilibrium, drive-resistant males have lower reproductive success than drive-susceptible males. Thus, female choice of drive-susceptible males can evolve when resistance is Y-linked. When resistance is autosomal, selection on female choice for drive resistance is less strong and depends on the frequency of choice: female preference of resistant males is favoured when choice is rare and disadvantageous when choice is frequent, leading to a stable equilibrium at a low frequency of the choice allele. Independent of the location of drive resistance alleles, males with the non-driving allele always have above average reproductive success. Female choice is therefore beneficial when choosy females prefer males with the non-driving allele.

  19. Meiotic drive and evolution of female choice.

    PubMed Central

    Reinhold, K; Engqvist, L; Misof, B; Kurtz, J

    1999-01-01

    As a special version of the good-genes hypothesis, it was recently proposed that females could benefit from choosing drive-resistant males in a meiotic drive system. Here, we examine with a three-locus, six-allele population genetic model whether female choice for drive resistance can evolve. An allele leading to female preference for drive-resistant males was introduced at low frequency into a population polymorphic for meiotic drive and drive resistance. Our simulations show that female choice of drive-resistant males is disadvantageous when resistance is Y-linked. This disadvantage occurs because, at equilibrium, drive-resistant males have lower reproductive success than drive-susceptible males. Thus, female choice of drive-susceptible males can evolve when resistance is Y-linked. When resistance is autosomal, selection on female choice for drive resistance is less strong and depends on the frequency of choice: female preference of resistant males is favoured when choice is rare and disadvantageous when choice is frequent, leading to a stable equilibrium at a low frequency of the choice allele. Independent of the location of drive resistance alleles, males with the non-driving allele always have above average reproductive success. Female choice is therefore beneficial when choosy females prefer males with the non-driving allele. PMID:10445289

  20. Spindle Assembly and Chromosome Segregation Requires Central Spindle Proteins in Drosophila Oocytes.

    PubMed

    Das, Arunika; Shah, Shital J; Fan, Bensen; Paik, Daniel; DiSanto, Daniel J; Hinman, Anna Maria; Cesario, Jeffry M; Battaglia, Rachel A; Demos, Nicole; McKim, Kim S

    2016-01-01

    Oocytes segregate chromosomes in the absence of centrosomes. In this situation, the chromosomes direct spindle assembly. It is still unclear in this system which factors are required for homologous chromosome bi-orientation and spindle assembly. The Drosophila kinesin-6 protein Subito, although nonessential for mitotic spindle assembly, is required to organize a bipolar meiotic spindle and chromosome bi-orientation in oocytes. Along with the chromosomal passenger complex (CPC), Subito is an important part of the metaphase I central spindle. In this study we have conducted genetic screens to identify genes that interact with subito or the CPC component Incenp. In addition, the meiotic mutant phenotype for some of the genes identified in these screens were characterized. We show, in part through the use of a heat-shock-inducible system, that the Centralspindlin component RacGAP50C and downstream regulators of cytokinesis Rho1, Sticky, and RhoGEF2 are required for homologous chromosome bi-orientation in metaphase I oocytes. This suggests a novel function for proteins normally involved in mitotic cell division in the regulation of microtubule-chromosome interactions. We also show that the kinetochore protein, Polo kinase, is required for maintaining chromosome alignment and spindle organization in metaphase I oocytes. In combination our results support a model where the meiotic central spindle and associated proteins are essential for acentrosomal chromosome segregation.

  1. The Program of Sex Chromosome Pairing in Meiosis Is Highly Conserved Across Marsupial Species

    PubMed Central

    Page, Jesús; Berríos, Soledad; Parra, María Teresa; Viera, Alberto; Suja, José Ángel; Prieto, Ignacio; Barbero, José Luis; Rufas, Julio S.; Fernández-Donoso, Raúl

    2005-01-01

    Marsupials present a series of genetic and chromosomal features that are highly conserved in very distant species. One of these features is the absence of a homologous region between X and Y chromosomes. According to this genetic differentiation, sex chromosomes do not synapse during the first meiotic prophase in males, and a special structure, the dense plate, maintains sex chromosome association. In this report we present results on the process of meiotic sex chromosome pairing obtained from three different species, Thylamys elegans, Dromiciops gliroides, and Rhyncholestes raphanurus, representing the three orders of American marsupials. We have investigated the relationships between the axial structures organized along sex chromosomes and the formation of the dense plate. We found that in the three species the dense plate arises as a modification of sex chromosomal axial elements, but without the involvement of other meiotic axial structures, such as the cohesin axes. Considering the phylogenetic relationships among the marsupials studied here, our data reinforce the idea that the dense plate emerged early in marsupial evolution as an efficient mechanism to ensure the association of the nonhomologous sex chromosomes. This situation could have influenced the further evolution of sex chromosomes in marsupials. PMID:15802509

  2. Cytogenetic mapping with centromeric bacterial artificial chromosomes contigs shows that this recombination-poor region comprises more than half of barley chromosome 3H.

    PubMed

    Aliyeva-Schnorr, Lala; Beier, Sebastian; Karafiátová, Miroslava; Schmutzer, Thomas; Scholz, Uwe; Doležel, Jaroslav; Stein, Nils; Houben, Andreas

    2015-10-01

    Genetic maps are based on the frequency of recombination and often show different positions of molecular markers in comparison to physical maps, particularly in the centromere that is generally poor in meiotic recombinations. To decipher the position and order of DNA sequences genetically mapped to the centromere of barley (Hordeum vulgare) chromosome 3H, fluorescence in situ hybridization with mitotic metaphase and meiotic pachytene chromosomes was performed with 70 genomic single-copy probes derived from 65 fingerprinted bacterial artificial chromosomes (BAC) contigs genetically assigned to this recombination cold spot. The total physical distribution of the centromeric 5.5 cM bin of 3H comprises 58% of the mitotic metaphase chromosome length. Mitotic and meiotic chromatin of this recombination-poor region is preferentially marked by a heterochromatin-typical histone mark (H3K9me2), while recombination enriched subterminal chromosome regions are enriched in euchromatin-typical histone marks (H3K4me2, H3K4me3, H3K27me3) suggesting that the meiotic recombination rate could be influenced by the chromatin landscape.

  3. 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.

    PubMed

    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. PMID:24967676

  4. 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

    PubMed Central

    Vernet, Nadège; Mahadevaiah, Shantha K.; Yamauchi, Yasuhiro; Decarpentrie, Fanny; Mitchell, Michael J.; Ward, Monika A.; Burgoyne, Paul S.

    2014-01-01

    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. PMID:24967676

  5. 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.

    PubMed

    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.

  6. A new light on the meiotic DSB catalytic complex.

    PubMed

    Robert, Thomas; Vrielynck, Nathalie; Mézard, Christine; de Massy, Bernard; Grelon, Mathilde

    2016-06-01

    Meiotic recombination is initiated by the formation of programmed DNA double-strand breaks (DSBs). More than 15 years ago, Spo11 was identified as the protein responsible for meiotic DSB formation, notably because of its striking similarities with the A subunit of topoisomerase VI (TopoVI). TopoVI are enzymes that modify DNA topology by generating transient DSBs and are active as heterotetramers, composed of two A and two B subunits. A2 dimers catalyse the DNA cleavage reaction, whereas the B subunits regulate A2 conformation, DNA capture, cleavage and re-ligation. The recent identification in plants and mammals of a B-like TopoVI subunit that interacts with SPO11 and is required for meiotic DSB formation makes us to reconsider our understanding of the meiotic DSB catalytic complex. We provide here an overview of the knowledge on TopoVI structure and mode of action and we compare them with their meiotic counterparts. This allows us to discuss the nature, structure and functions of the meiotic TopoVI-like complex during meiotic DSB formation.

  7. Organization of the sex-ratio Meiotic Drive Region in Drosophila simulans

    PubMed Central

    Montchamp-Moreau, Catherine; Ogereau, David; Chaminade, Nicole; Colard, Alexandre; Aulard, Sylvie

    2006-01-01

    Sex-ratio meiotic drive is the preferential transmission of the X chromosome by XY males, which occurs in several Drosophila species and results in female-biased progeny. Although the trait has long been known to exist, its molecular basis remains completely unknown. Here we report a fine-mapping experiment designed to characterize the major drive locus on a sex-ratio X chromosome of Drosophila simulans originating from the Seychelles (XSR6). This primary locus was found to contain two interacting elements at least, both of which are required for drive expression. One of them was genetically tracked to a tandem duplication containing six annotated genes (Trf2, CG32712, CG12125, CG1440, CG12123, org-1), and the other to a candidate region located ∼110 kb away and spanning seven annotated genes. RT–PCR showed that all but two of these genes were expressed in the testis of both sex-ratio and standard males. In situ hybridization to polytene chromosomes revealed a complete association of the duplication with the sex-ratio trait in random samples of X chromosomes from Madagascar and Reunion. PMID:16387875

  8. Meiotic Instability of Pythium Sylvaticum as Demonstrated by Inheritance of Nuclear Markers and Karyotype Analysis

    PubMed Central

    Martin, F.

    1995-01-01

    Progeny from a sexual outcross between opposite mating types of Pythium sylvaticum were analyzed for inheritance of RFLP and random amplified polymorphic DNA (RAPD) markers. Although most were inherited in expected Mendelian frequencies, several were not. Pulsed field gel electrophoresis was employed to examine these unexpected patterns of marker inheritance at a karyotypic level. Parental oogonial and antheridial isolates had different electrophoretic karyotypes and minimum number of chromosome-sized DNAs (13 and 12, respectively), however, summation of the sizes of all chromosomal bands for each isolate was similar at ~37 Mb. Progeny karyotypes differed significantly from each other and the parental isolates, ranging in estimated minimum number of chromosome-sized DNAs from 9 to 13 and the summation of band sizes within each isolate from 28.1 to 39.0 Mb. For the eight isolates most extensively analyzed, 80% of the progeny chromosome-sized DNAs were nonparental in size or hybridization grouping of cDNA clones and isolated RAPD markers. Based on the results of Southern analysis it appears that length mutations and perhaps aneuploidy and translocations have contributed to generation of karyotypic polymorphisms. Nineteen field isolates of P. sylvaticum collected from the same location also exhibited significantly different karyotypes, suggesting that the meiotic instability observed in the laboratory also is occurring in field populations. PMID:7768436

  9. ms17: a meiotic mutation causing partial male sterility in a corn silage hybrid.

    PubMed

    Pagliarini, M S; Souza, V F; Silva, N; Scapim, C A; Rodovalho, M; Faria, M V

    2011-09-09

    Cytological analysis under light microscopy of the single hybrid P30R50 of silage corn revealed an abnormal pattern of microsporogenesis that affected the meiotic products. Meiosis progressed normally until diakinesis, but before migration to the metaphase plate, bivalents underwent total desynapsis and 20 univalent chromosomes were scattered in the cytoplasm. At this stage, meiocytes also exhibited a number of chromatin-like fragments scattered throughout the cell. Metaphase I was completely abnormal in the affected cells, and univalent chromosomes and fragments were distributed among several curved spindles. Anaphase I did not occur, and each chromosome or group of chromosomes originated a micronucleus. After this phase, an irregular cytokinesis occurred, and secondary meiocytes with several micronuclei were observed. Metaphase II and anaphase II also did not occur, and after the second cytokinesis, the genomes were fractionated into polyads, generating several unbalanced microspores, with various-sized nuclei. About 35% of the tetrads were abnormal in the hybrid. This spontaneous mutation had been previously reported in a USA maize line called ms17 and was found to cause male sterility.

  10. Combined fluorescent and electron microscopic imaging unveils the specific properties of two classes of meiotic crossovers.

    PubMed

    Anderson, Lorinda K; Lohmiller, Leslie D; Tang, Xiaomin; Hammond, D Boyd; Javernick, Lauren; Shearer, Lindsay; Basu-Roy, Sayantani; Martin, Olivier C; Falque, Matthieu

    2014-09-16

    Crossovers (COs) shuffle genetic information and allow balanced segregation of homologous chromosomes during the first division of meiosis. In several organisms, mutants demonstrate that two molecularly distinct pathways produce COs. One pathway produces class I COs that exhibit interference (lowered probability of nearby COs), and the other pathway produces class II COs with little or no interference. However, the relative contributions, genomic distributions, and interactions of these two pathways are essentially unknown in nonmutant organisms because marker segregation only indicates that a CO has occurred, not its class type. Here, we combine the efficiency of light microscopy for revealing cellular functions using fluorescent probes with the high resolution of electron microscopy to localize and characterize COs in the same sample of meiotic pachytene chromosomes from wild-type tomato. To our knowledge, for the first time, every CO along each chromosome can be identified by class to unveil specific characteristics of each pathway. We find that class I and II COs have different recombination profiles along chromosomes. In particular, class II COs, which represent about 18% of all COs, exhibit no interference and are disproportionately represented in pericentric heterochromatin, a feature potentially exploitable in plant breeding. Finally, our results demonstrate that the two pathways are not independent because there is interference between class I and II COs. PMID:25197066

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

    PubMed

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

    2014-10-01

    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.

  12. Accuracy of preimplantation genetic diagnosis (PGD) of single gene and chromosomal disorders

    SciTech Connect

    Verlinsky, Y.; Strom, C.; Rechitsky, S.

    1994-09-01

    We have developed a polar body inferred approach for preconception diagnosis of single gene and chromosomal disorders. Preconception PCR or FISH analysis was performed in a total of 310 first polar bodies for the following genetic conditions: cystic fibrosis, hemophilia A, alpha-1-antitrypsin deficiency, Tay Sachs disease, retinitis pigmentosa and common chromosomal trisomies. An important advantage of this approach is the avoidance of sperm (DNA) contamination, which is the major problem of PGD. We are currently applying FISH analysis of biopsied blastomeres, in combination with PCR or separately, and have demonstrated a significant improvement of the accuracy of PGD of X-linked disorders at this stage. Our data have also demonstrated feasibility of the application of FISH technique for PGD of chromosomal disorders. It was possible to detect chromosomal non-disjunctions and chromatid malsegregations in the first meiotic division, as well as to evaluate chromosomal mutations originating from the second meiotic nondisjunction.

  13. Nondisjunction of chromosome 15: Origin and recombination

    SciTech Connect

    Robinson, W.P.; Bernasconi, F.; Schinzel, A.A.; Mutirangura, A.; Ledbetter, D.H. ); Langlois, S. ); Morris, M.A.; Malcolm, S.

    1993-09-01

    Thirty-two cases of uniparental disomy (UPD), ascertained from Prader-Willi syndrome patients (N=27) and Angelman syndrome patients (N-5), are used to investigate the pattern of recombination associated with nondisjunction of chromosome 15. In addition, the meiotic stage of nondisjunction is inferred by using markers mapping near the centromere. Two basic approaches to the analysis of recombination in specific pairwise intervals along the chromosome. This method shows a significant reduction in recombination for two of five intervals examined. Second, the observed frequency of each recombinant class (i.e., zero, one, two, three, or more observable crossovers) is compared with expected values. This is useful for testing whether the reduction in recombination can be attributed solely to a proportion of cases with no recombination at all (because of asynapsis), with the remaining groups showing normal recombination (or even excess recombination), or whether recombination is uniformly reduced. Analysis of maternal UPD(15) data shows a slight reduction in the multiple-recombinant classes, with a corresponding increase in both the zero- and one-recombinant classes over expected values. The majority, more than 82%, of the extra chromosomes in maternal UPD(15) cases are due to meiotic I nondisjunction events. In contrast, more paternal UPD(15) cases so far examined appear to have a postzygotic origin of the extra paternal chromosome. 33 refs., 1 fig., 7 tabs.

  14. Nondisjunction of chromosome 15: origin and recombination.

    PubMed Central

    Robinson, W P; Bernasconi, F; Mutirangura, A; Ledbetter, D H; Langlois, S; Malcolm, S; Morris, M A; Schinzel, A A

    1993-01-01

    Thirty-two cases of uniparental disomy (UPD), ascertained from Prader-Willi syndrome patients (N = 27) and Angelman syndrome patients (N = 5), are used to investigate the pattern of recombination associated with nondisjunction of chromosome 15. In addition, the meiotic stage of nondisjunction is inferred by using markers mapping near the centromere. Two basic approaches to the analysis of recombination are utilized. Standard methods of centromere mapping are employed to determine the level of recombination in specific pairwise intervals along the chromosome. This method shows a significant reduction in recombination for two of five intervals examined. Second, the observed frequency of each recombinant class (i.e., zero, one, two, three, or more observable crossovers) is compared with expected values. This is useful for testing whether the reduction in recombination can be attributed solely to a proportion of cases with no recombination at all (because of asynapsis), with the remaining groups showing normal recombination (or even excess recombination), or whether recombination is uniformly reduced. Analysis of maternal UPD(15) data shows a slight reduction in the multiple-recombinant classes, with a corresponding increase in both the zero- and one-recombinant classes over expected values. The majority, more than 82%, of the extra chromosomes in maternal UPD(15) cases are due to meiotic I nondisjunction events. In contrast, most paternal UPD(15) cases so far examined appear to have a postzygotic origin of the extra paternal chromosome. PMID:8352279

  15. Insertion DNA Accelerates Meiotic Interchromosomal Recombination in Arabidopsis thaliana.

    PubMed

    Sun, Xiao-Qin; Li, Ding-Hong; Xue, Jia-Yu; Yang, Si-Hai; Zhang, Yan-Mei; Li, Mi-Mi; Hang, Yue-Yu

    2016-08-01

    Nucleotide insertions/deletions are ubiquitous in eukaryotic genomes, and the resulting hemizygous (unpaired) DNA has significant, heritable effects on adjacent DNA. However, little is known about the genetic behavior of insertion DNA. Here, we describe a binary transgenic system to study the behavior of insertion DNA during meiosis. Transgenic Arabidopsis lines were generated to carry two different defective reporter genes on nonhomologous chromosomes, designated as "recipient" and "donor" lines. Double hemizygous plants (harboring unpaired DNA) were produced by crossing between the recipient and the donor, and double homozygous lines (harboring paired DNA) via self-pollination. The transfer of the donor's unmutated sequence to the recipient generated a functional β-glucuronidase gene, which could be visualized by histochemical staining and corroborated by polymerase chain reaction amplification and sequencing. More than 673 million seedlings were screened, and the results showed that meiotic ectopic recombination in the hemizygous lines occurred at a frequency  >6.49-fold higher than that in the homozygous lines. Gene conversion might have been exclusively or predominantly responsible for the gene correction events. The direct measurement of ectopic recombination events provided evidence that an insertion, in the absence of an allelic counterpart, could scan the entire genome for homologous counterparts with which to pair. Furthermore, the unpaired (hemizygous) architectures could accelerate ectopic recombination between itself and interchromosomal counterparts. We suggest that the ectopic recombination accelerated by hemizygous architectures may be a general mechanism for interchromosomal recombination through ubiquitously dispersed repeat sequences in plants, ultimately contributing to genetic renovation and eukaryotic evolution. PMID:27189569

  16. Depletion of H2A-H2B dimers in Saccharomyces cerevisiae triggers meiotic arrest by reducing IME1 expression and activating the BUB2-dependent branch of the spindle checkpoint.

    PubMed Central

    Hanlon, Sean E; Norris, David N; Vershon, Andrew K

    2003-01-01

    In the yeast Saccharomyces cerevisiae, diploid strains carrying homozygous hta1-htb1Delta mutations express histone H2A-H2B dimers at a lower level than do wild-type cells. Although this mutation has only minor effects on mitotic growth, it causes an arrest in sporulation prior to the first meiotic division. In this report, we show that the hta1-htb1Delta mutant exhibits reduced expression of early and middle-sporulation-specific genes and that the meiotic arrest of the hta1-htb1Delta mutant can be partially bypassed by overexpression of IME1. Additionally, deletions of BUB2 or BFA1, components of one branch of the spindle checkpoint pathway, bypass the meiotic arrest. Mutations in the other branch of the pathway or in the pachytene checkpoint are unable to suppress the meiotic block. These observations indicate that depletion of the H2A-H2B dimer blocks sporulation by at least two mechanisms: disruption of the expression of meiotic regulatory genes and activation of the spindle checkpoint. Our results show that the failure to progress through the meiotic pathway is not the result of global chromosomal alterations but that specific aspects of meiosis are sensitive to depletion of the H2A-H2B dimer. PMID:12930743

  17. Meiotic HORMA domain proteins prevent untimely centriole disengagement during Caenorhabditis elegans spermatocyte meiosis.

    PubMed

    Schvarzstein, Mara; Pattabiraman, Divya; Bembenek, Joshua N; Villeneuve, Anne M

    2013-03-01

    In many species where oocytes lack centrosomes, sperm contribute both genetic material and centriole(s) to the zygote. Correct centriole organization during male meiosis is critical to guarantee a normal bipolar mitotic spindle in the zygote. During Caenorhabditis elegans male meiosis, centrioles normally undergo two rounds of duplication, resulting in haploid sperm each containing a single tightly engaged centriole pair. Here we identify an unanticipated role for C. elegans HORMA (Hop1/Rev7/Mad2) domain proteins HTP-1/2 and HIM-3 in regulating centriole disengagement during spermatocyte meiosis. In him-3 and htp-1 htp-2 mutants, centrioles separate inappropriately during meiosis II, resulting in spermatids with disengaged centrioles. Moreover, extra centrosomes are detected in a subset of zygotes. Together, these data implicate HIM-3 and HTP-1/2 in preventing centriole disengagement during meiosis II. We showed previously that HTP-1/2 prevents premature loss of sister chromatid cohesion during the meiotic divisions by inhibiting removal of meiotic cohesin complexes containing the REC-8 subunit. Worms lacking REC-8, or expressing a mutant separase protein with elevated local concentration at centrosomes and in sperm, likewise exhibit inappropriate centriole separation during spermatocyte meiosis. These observations are consistent with HIM-3 and HTP-1/2 preventing centriole disengagement by inhibiting separase-dependent cohesin removal. Our data suggest that the same specialized meiotic mechanisms that function to prevent premature release of sister chromatid cohesion during meiosis I in C. elegans also function to inhibit centriole separation at meiosis II, thereby ensuring that the zygote inherits the appropriate complement of chromosomes and centrioles.

  18. Evidence for meiotic sex in bdelloid rotifers.

    PubMed

    Signorovitch, Ana; Hur, Jae; Gladyshev, Eugene; Meselson, Matthew

    2016-08-22

    In their study of genetic exchange in the bdelloid rotifer Adineta vaga, Debortoli et al. [1] conclude that the patchwork pattern of allele sharing among three individuals in the genomic regions they examined is "…unlikely to arise in cases of PTH (Oenothera-like) meiosis since haplotypes are transferred as entire blocks…" and therefore that "Genetic exchange among bdelloid rotifers is more likely due to horizontal gene transfer than to meiotic sex." This assumes without justification that horizontal gene transfer (HGT) in bdelloids precludes the sexual transmission of entire haplotypes, for which we have reported evidence in the bdelloid Macrotrachela quadricornifera[2]. And it does not consider the contribution to such a patchwork pattern that would result from conversion and subsequent outcrossing, even in Oenothera-like systems. PMID:27554650

  19. Meiotic behavior of Brachiaria decumbens hybrids.

    PubMed

    Souza, V F; Pagliarini, M S; Valle, C B; Bione, N C P; Menon, M U; Mendes-Bonato, A B

    2015-01-01

    Brachiaria decumbens is a forage grass of inestimable value for livestock in Brazil due to its production of good quality forage even when planted on acid and poor soils, although it is susceptible to pasture spittlebugs. Only one cultivar, cv. Basilisk, has been used as the pollen donor in crosses with Brachiaria ruziziensis since 1988 at Embrapa Gado de Corte Research Center. Breeding within the species only became possible from 2009 when sexual accessions were successfully tetraploidized using colchicine. Three sexual genotypes were obtained and hybridization within B. decumbens was finally achieved. Here, we evaluated microspore tetrads using conventional cytology and found meiotic indexes above 78% for all three female genitors (cD24-2, cD24-27, cD24-45), but a low meiotic index (<22%) in the natural apomictic genitor D62 (cv. Basilisk) and in 49 hybrids. Analysis of the relationship between abnormal tetrad frequency and non-viable pollen grains yielded a highly significant Pearson correlation coefficient. The t-test proved significant for the progeny of cD24-45 x D62, with lower abnormalities and pollen sterility when compared to the other two progenies resulting from cD24-2 and cD24-27 crossed to D62, but these two did not differ. Apomictic hybrids such as S036 and X030 with low pollen sterility have the potential for use in cultivar development, whereas the sexual hybrids T012, X072, and X078 might be of use as female genitors in polycross blocks if they display good agronomic traits. PMID:26505437

  20. Local and sex-specific biases in crossover vs. noncrossover outcomes at meiotic recombination hot spots in mice.

    PubMed

    de Boer, Esther; Jasin, Maria; Keeney, Scott

    2015-08-15

    Meiotic recombination initiated by programmed double-strand breaks (DSBs) yields two types of interhomolog recombination products, crossovers and noncrossovers, but what determines whether a DSB will yield a crossover or noncrossover is not understood. In this study, we analyzed the influence of sex and chromosomal location on mammalian recombination outcomes by constructing fine-scale recombination maps in both males and females at two mouse hot spots located in different regions of the same chromosome. These include the most comprehensive maps of recombination hot spots in oocytes to date. One hot spot, located centrally on chromosome 1, behaved similarly in male and female meiosis: Crossovers and noncrossovers formed at comparable levels and ratios in both sexes. In contrast, at a distal hot spot, crossovers were recovered only in males even though noncrossovers were obtained at similar frequencies in both sexes. These findings reveal an example of extreme sex-specific bias in recombination outcome. We further found that estimates of relative DSB levels are surprisingly poor predictors of relative crossover frequencies between hot spots in males. Our results demonstrate that the outcome of mammalian meiotic recombination can be biased, that this bias can vary depending on location and cellular context, and that DSB frequency is not the only determinant of crossover frequency.

  1. Microtubule-Depolymerizing Kinesin KLP10A Restricts the Length of the Acentrosomal Meiotic Spindle in Drosophila Females

    PubMed Central

    Radford, Sarah J.; Harrison, Andrew M.; McKim, Kim S.

    2012-01-01

    During cell division, a bipolar array of microtubules forms the spindle through which the forces required for chromosome segregation are transmitted. Interestingly, the spindle as a whole is stable enough to support these forces even though it is composed of dynamic microtubules, which are constantly undergoing periods of growth and shrinkage. Indeed, the regulation of microtubule dynamics is essential to the integrity and function of the spindle. We show here that a member of an important class of microtubule-depolymerizing kinesins, KLP10A, is required for the proper organization of the acentrosomal meiotic spindle in Drosophila melanogaster oocytes. In the absence of KLP10A, microtubule length is not controlled, resulting in extraordinarily long and disorganized spindles. In addition, the interactions between chromosomes and spindle microtubules are disturbed and can result in the loss of contact. These results indicate that the regulation of microtubule dynamics through KLP10A plays a critical role in restricting the length and maintaining bipolarity of the acentrosomal meiotic spindle and in promoting the contacts that the chromosomes make with microtubules required for meiosis I segregation. PMID:22865737

  2. Local and sex-specific biases in crossover vs. noncrossover outcomes at meiotic recombination hot spots in mice

    PubMed Central

    de Boer, Esther; Jasin, Maria; Keeney, Scott

    2015-01-01

    Meiotic recombination initiated by programmed double-strand breaks (DSBs) yields two types of interhomolog recombination products, crossovers and noncrossovers, but what determines whether a DSB will yield a crossover or noncrossover is not understood. In this study, we analyzed the influence of sex and chromosomal location on mammalian recombination outcomes by constructing fine-scale recombination maps in both males and females at two mouse hot spots located in different regions of the same chromosome. These include the most comprehensive maps of recombination hot spots in oocytes to date. One hot spot, located centrally on chromosome 1, behaved similarly in male and female meiosis: Crossovers and noncrossovers formed at comparable levels and ratios in both sexes. In contrast, at a distal hot spot, crossovers were recovered only in males even though noncrossovers were obtained at similar frequencies in both sexes. These findings reveal an example of extreme sex-specific bias in recombination outcome. We further found that estimates of relative DSB levels are surprisingly poor predictors of relative crossover frequencies between hot spots in males. Our results demonstrate that the outcome of mammalian meiotic recombination can be biased, that this bias can vary depending on location and cellular context, and that DSB frequency is not the only determinant of crossover frequency. PMID:26251527

  3. Multiple mechanisms limit meiotic crossovers: TOP3α and two BLM homologs antagonize crossovers in parallel to FANCM

    PubMed Central

    Séguéla-Arnaud, Mathilde; Crismani, Wayne; Larchevêque, Cécile; Mazel, Julien; Froger, Nicole; Choinard, Sandrine; Lemhemdi, Afef; Macaisne, Nicolas; Van Leene, Jelle; Gevaert, Kris; De Jaeger, Geert; Chelysheva, Liudmilla; Mercier, Raphael

    2015-01-01

    Meiotic crossovers (COs) have two important roles, shuffling genetic information and ensuring proper chromosome segregation. Despite their importance and a large excess of precursors (i.e., DNA double-strand breaks, DSBs), the number of COs is tightly regulated, typically one to three per chromosome pair. The mechanisms ensuring that most DSBs are repaired as non-COs and the evolutionary forces imposing this constraint are poorly understood. Here we identified Topoisomerase3α (TOP3α) and the RECQ4 helicases—the Arabidopsis slow growth suppressor 1 (Sgs1)/Bloom syndrome protein (BLM) homologs—as major barriers to meiotic CO formation. First, the characterization of a specific TOP3α mutant allele revealed that, in addition to its role in DNA repair, this topoisomerase antagonizes CO formation. Further, we found that RECQ4A and RECQ4B constitute the strongest meiotic anti-CO activity identified to date, their concomitant depletion leading to a sixfold increase in CO frequency. In both top3α and recq4ab mutants, DSB number is unaffected, and extra COs arise from a normally minor pathway. Finally, both TOP3α and RECQ4A/B act independently of the previously identified anti-CO Fanconi anemia of complementation group M (FANCM) helicase. This finding shows that several parallel pathways actively limit CO formation and suggests that the RECQA/B and FANCM helicases prevent COs by processing different substrates. Despite a ninefold increase in CO frequency, chromosome segregation was unaffected. This finding supports the idea that CO number is restricted not because of mechanical constraints but likely because of the long-term costs of recombination. Furthermore, this work demonstrates how manipulating a few genes holds great promise for increasing recombination frequency in plant-breeding programs. PMID:25825745

  4. Chromosome assortment in Saccharum.

    PubMed

    Al-Janabi, S M; Honeycutt, R J; Sobral, B W

    1994-12-01

    Recent work has revealed random chromosome pairing and assortment in Saccharum spontaneum L., the most widely distributed, and morphologically and cytologically variable of the species of Saccharum. This conclusion was based on the analysis of a segregating population from across between S. spontaneum 'SES 208' and a spontaneously-doubled haploid of itself, derived from anther culture. To determine whether polysomic inheritance is common in Saccharum and whether it is observed in a typical biparental cross, we studied chromosome pairing and assortment in 44 progeny of a cross between euploid, meiotically regular, 2n=80 forms of Saccharum officinarum 'LA Purple' and Saccharum robustum ' Mol 5829'. Papuan 2n=80 forms of S. robustum have been suggested as the immediate progenitor species for cultivated sugarcane (S. officinarum). A total of 738 loci in LA Purple and 720 loci in Mol 5829 were amplified and typed in the progeny by arbitrarily primed PCR using 45 primers. Fifty and 33 single-dose polymorphisms were identified in the S. officinarum and S. robustum genomes, respectively (χ 2 at 98%). Linkage analysis of single-dose polymorphisms in both genomes revealed linkages in repulsion and coupling phases. In the S. officinarum genome, a map hypothesis gave 7 linkage groups with 17 linked and 33 unlinked markers. Four of 13 pairwise linkages were in repulsion phase and 9 were in coupling phase. In the S. robustum genome, a map hypothesis gave 5 linkage groups, defined by 12 markers, with 21 markers unlinked, and 2 of 9 pairwise linkages were in repulsion phase. Therefore, complete polysomic inheritance was not observed in either species, suggesting that chromosomal behavior is different from that observed by linkage analysis of over 500 markers in the S. spontaneum map. Implications of this finding for evolution and breeding are discussed.

  5. Hormad1 mutation disrupts synaptonemal complex formation, recombination, and chromosome segregation in mammalian meiosis.

    PubMed

    Shin, Yong-Hyun; Choi, Youngsok; Erdin, Serpil Uckac; Yatsenko, Svetlana A; Kloc, Malgorzata; Yang, Fang; Wang, P Jeremy; Meistrich, Marvin L; Rajkovic, Aleksandar

    2010-11-01

    Meiosis is unique to germ cells and essential for reproduction. During the first meiotic division, homologous chromosomes pair, recombine, and form chiasmata. The homologues connect via axial elements and numerous transverse filaments to form the synaptonemal complex. The synaptonemal complex is a critical component for chromosome pairing, segregation, and recombination. We previously identified a novel germ cell-specific HORMA domain encoding gene, Hormad1, a member of the synaptonemal complex and a mammalian counterpart to the yeast meiotic HORMA domain protein Hop1. Hormad1 is essential for mammalian gametogenesis as knockout male and female mice are infertile. Hormad1 deficient (Hormad1(-/) (-)) testes exhibit meiotic arrest in the early pachytene stage, and synaptonemal complexes cannot be visualized by electron microscopy. Hormad1 deficiency does not affect localization of other synaptonemal complex proteins, SYCP2 and SYCP3, but disrupts homologous chromosome pairing. Double stranded break formation and early recombination events are disrupted in Hormad1(-/) (-) testes and ovaries as shown by the drastic decrease in the γH2AX, DMC1, RAD51, and RPA foci. HORMAD1 co-localizes with γH2AX to the sex body during pachytene. BRCA1, ATR, and γH2AX co-localize to the sex body and participate in meiotic sex chromosome inactivation and transcriptional silencing. Hormad1 deficiency abolishes γH2AX, ATR, and BRCA1 localization to the sex chromosomes and causes transcriptional de-repression on the X chromosome. Unlike testes, Hormad1(-/) (-) ovaries have seemingly normal ovarian folliculogenesis after puberty. However, embryos generated from Hormad1(-/) (-) oocytes are hyper- and hypodiploid at the 2 cell and 8 cell stage, and they arrest at the blastocyst stage. HORMAD1 is therefore a critical component of the synaptonemal complex that affects synapsis, recombination, and meiotic sex chromosome inactivation and transcriptional silencing. PMID:21079677

  6. Unique subcellular distribution of phosphorylated Plk1 (Ser137 and Thr210) in mouse oocytes during meiotic division and pPlk1(Ser137) involvement in spindle formation and REC8 cleavage.

    PubMed

    Du, Juan; Cao, Yan; Wang, Qian; Zhang, Nana; Liu, Xiaoyu; Chen, Dandan; Liu, Xiaoyun; Xu, Qunyuan; Ma, Wei

    2015-01-01

    Polo-like kinase 1 (Plk1) is pivotal for proper mitotic progression, its targeting activity is regulated by precise subcellular positioning and phosphorylation. Here we assessed the protein expression, subcellular localization and possible functions of phosphorylated Plk1 (pPlk1(Ser137) and pPlk1(Thr210)) in mouse oocytes during meiotic division. Western blot analysis revealed a peptide of pPlk1(Ser137) with high and stable expression from germinal vesicle (GV) until metaphase II (MII), while pPlk1(Thr210) was detected as one large single band at GV stage and 2 small bands after germinal vesicle breakdown (GVBD), which maintained stable up to MII. Immunofluorescence analysis showed pPlk1(Ser137) was colocalized with microtubule organizing center (MTOC) proteins, γ-tubulin and pericentrin, on spindle poles, concomitantly with persistent concentration at centromeres and dynamic aggregation between chromosome arms. Differently, pPlk1(Thr210) was persistently distributed across the whole body of chromosomes after meiotic resumption. The specific Plk1 inhibitor, BI2536, repressed pPlk1(Ser137) accumulation at MTOCs and between chromosome arms, consequently disturbed γ-tubulin and pericentrin recruiting to MTOCs, destroyed meiotic spindle formation, and delayed REC8 cleavage, therefore arresting oocytes at metaphase I (MI) with chromosome misalignment. BI2536 completely reversed the premature degradation of REC8 and precocious segregation of chromosomes induced with okadaic acid (OA), an inhibitor to protein phosphatase 2A. Additionally, the protein levels of pPlk1(Ser137) and pPlk1(Thr210), as well as the subcellular distribution of pPlk1(Thr210), were not affected by BI2536. Taken together, our results demonstrate that Plk1 activity is required for meiotic spindle assembly and REC8 cleavage, with pPlk1(Ser137) is the action executor, in mouse oocytes during meiotic division. PMID:26654596

  7. Molecular mechanisms of homologous chromosome pairing and segregation in plants.

    PubMed

    Zhang, Jing; Zhang, Bing; Su, Handong; Birchler, James A; Han, Fangpu

    2014-03-20

    In most eukaryotic species, three basic steps of pairing, recombination and synapsis occur during prophase of meiosis I. Homologous chromosomal pairing and recombination are essential for accurate segregation of chromosomes. In contrast to the well-studied processes such as recombination and synapsis, many aspects of chromosome pairing are still obscure. Recent progress in several species indicates that the telomere bouquet formation can facilitate homologous chromosome pairing by bringing chromosome ends into close proximity, but the sole presence of telomere clustering is not sufficient for recognizing homologous pairs. On the other hand, accurate segregation of the genetic material from parent to offspring during meiosis is dependent on the segregation of homologs in the reductional meiotic division (MI) with sister kinetochores exhibiting mono-orientation from the same pole, and the segregation of sister chromatids during the equational meiotic division (MII) with kinetochores showing bi-orientation from the two poles. The underlying mechanism of orientation and segregation is still unclear. Here we focus on recent studies in plants and other species that provide insight into how chromosomes find their partners and mechanisms mediating chromosomal segregation. PMID:24656232

  8. Microgravitational effects on chromosome behavior (7-IML-1)

    NASA Technical Reports Server (NTRS)

    Bruschi, Carlo

    1992-01-01

    The effects of the two major space-related conditions, microgravity and radiation, on the maintenance and transmission of genetic information have been partially documented in many organisms. Specifically, microgravity acts at the chromosomal level, primarily on the structure and segregation of chromosomes, in producing major abberations such as deletions, breaks, nondisjunction, and chromosome loss, and to a lesser degree, cosmic radiation appears to affect the genic level, producing point mutations and DNA damage. To distinguish between the effects from microgravity and from radiation, it is necessary to monitor both mitotic and meiotic genetic damage in the same organism. The yeast Saccharomyces cerevisiae is used to monitor at high resolution the frequency of chromosome loss, nondisjunction, intergenic recombination, and gene mutation in mitotic and meiotic cells, to a degree impossible in other organisms. Because the yeast chromosomes are small, sensitive measurements can be made that can be extrapolated to higher organisms and man. The objectives of the research are: (1) to quantitate the effects of microgravity and its synergism with cosmic radiation on chromosomal integrity and transmission during mitosis and meiosis; (2) to discriminate between chromosomal processes sensitive to microgravity and/or radiation during mitosis and meiosis; and (3) to relate these findings to anomalous mitotic mating type switching and ascosporogenesis following meiosis.

  9. Meiotic Recombination in Schizosaccharomyces pombe: A Paradigm for Genetic and Molecular Analysis

    PubMed Central

    Cromie, Gareth; Smith, Gerald R.

    2009-01-01

    The fission yeast Schizosaccharomyces pombe is especially well-suited for both genetic and biochemical analysis of meiotic recombination. Recent studies have revealed ~50 gene products and two DNA intermediates central to recombination, which we place into a pathway from parental to recombinant DNA. We divide recombination into three stages – chromosome alignment accompanying nuclear “horsetail” movement, formation of DNA breaks, and repair of those breaks – and we discuss the roles of the identified gene products and DNA intermediates in these stages. Although some aspects of recombination are similar to those in the distantly related budding yeast Saccharomyces cerevisiae, other aspects are distinctly different. In particular, many proteins required for recombination in one species have no clear ortholog in the other, and the roles of identified orthologs in regulating recombination often differ. Furthermore, in S. pombe the dominant joint DNA molecule intermediates contain single Holliday junctions, and intersister joint molecules are more frequent than interhomolog types, whereas in S. cerevisiae interhomolog double Holliday junctions predominate. We speculate that meiotic recombination in other organisms shares features of each of these yeasts. PMID:20157622

  10. Arabidopsis meiotic crossover hotspots overlap with H2A.Z nucleosomes at gene promoters

    PubMed Central

    Choi, Kyuha; Zhao, Xiaohui; Kelly, Krystyna A.; Venn, Oliver; Higgins, James D.; Yelina, Nataliya E.; Hardcastle, Thomas J.; Ziolkowski, Piotr A.; Copenhaver, Gregory P.; Franklin, F. Chris H.; McVean, Gil; Henderson, Ian R.

    2013-01-01

    PRDM9 directs human meiotic crossover hotspots to intergenic sequence motifs, whereas budding yeast hotspots overlap low nucleosome density regions in gene promoters. To investigate hotspots in plants, which lack PRDM9, we used coalescent analysis of Arabidopsis genetic variation. Crossovers increase towards gene promoters and terminators, and hotspots are associated with active chromatin modifications, including H2A.Z, histone H3K4me3, low nucleosome density and low DNA methylation. Hotspot-enriched A-rich and CTT-repeat DNA motifs occur upstream and downstream of transcriptional start respectively. Crossovers are asymmetric around promoters and highest over CTT-motifs and H2A.Z-nucleosomes. Pollen-typing, segregation and cytogenetic analysis show decreased crossovers in the arp6 H2A.Z deposition mutant, at multiple scales. During meiosis H2A.Z and DMC1/RAD51 recombinases form overlapping chromosomal foci. As arp6 reduces DMC1/RAD51 foci, H2A.Z may promote formation or processing of meiotic DNA double-strand breaks. We propose that gene chromatin ancestrally designates hotspots within eukaryotes and PRDM9 is a derived state within vertebrates. PMID:24056716

  11. APCFZR1 prevents nondisjunction in mouse oocytes by controlling meiotic spindle assembly timing

    PubMed Central

    Holt, Janet E.; Lane, Simon I. R.; Jennings, Phoebe; García-Higuera, Irene; Moreno, Sergio; Jones, Keith T.

    2012-01-01

    FZR1 is an anaphase-promoting complex (APC) activator best known for its role in the mitotic cell cycle at M-phase exit, in G1, and in maintaining genome integrity. Previous studies also established that it prevents meiotic resumption, equivalent to the G2/M transition. Here we report that mouse oocytes lacking FZR1 undergo passage through meiosis I that is accelerated by ∼1 h, and this is due to an earlier onset of spindle assembly checkpoint (SAC) satisfaction and APCCDC20 activity. However, loss of FZR1 did not compromise SAC functionality; instead, earlier SAC satisfaction was achieved because the bipolar meiotic spindle was assembled more quickly in the absence of FZR1. This novel regulation of spindle assembly by FZR1 led to premature bivalent attachment to microtubules and loss of kinetochore-bound MAD2. Bivalents, however, were observed to congress poorly, leading to nondisjunction rates of 25%. We conclude that in mouse oocytes FZR1 controls the timing of assembly of the bipolar spindle and in so doing the timing of SAC satisfaction and APCCDC20 activity. This study implicates FZR1 as a major regulator of prometaphase whose activity helps to prevent chromosome nondisjunction. PMID:22918942

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

    PubMed Central

    Li, Xuan; Wang, Yan-Kui; Song, Zhi-Qiang; Du, Zhi-Qiang; Yang, Cai-Xia

    2016-01-01

    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. PMID:27348312

  13. Giant meiotic spindles in males from Drosophila species with giant sperm tails.

    PubMed

    Lattao, Ramona; Bonaccorsi, Silvia; Gatti, Maurizio

    2012-02-01

    The spindle is a highly dynamic molecular machine that mediates precise chromosome segregation during cell division. Spindle size can vary dramatically, not only between species but also between different cells of the same organism. However, the reasons for spindle size variability are largely unknown. Here we show that variations in spindle size can be linked to a precise developmental requirement. Drosophila species have dramatically different sperm flagella that range in length from 0.3 mm in D. persimilis to 58.3 mm in D. bifurca. We found that males of different species exhibit striking variations in meiotic spindle size, which positively correlate with sperm length, with D. bifurca showing 30-fold larger spindles than D. persimilis. This suggests that primary spermatocytes of Drosophila species manufacture and store amounts of tubulin that are proportional to the axoneme length and use these tubulin pools for spindle assembly. These findings highlight an unsuspected plasticity of the meiotic spindle in response to the selective forces controlling sperm length.

  14. Detection of mitotic and meiotic aneuploidy in the yeast Saccharomyces cerevisiae.

    PubMed Central

    Parry, J M; Sharp, D; Parry, E M

    1979-01-01

    A number of genetic systems are described which involve the use of the yeast Saccharomyces cerevisiae. The systems may be used to detect the production of aneuploid cells produced during both mitotic and meiotic cell division in the presence of genetically active chemicals. During mitotic cell division, monosomic colonies (2n - 1) may be detected by plating upon selective medium. Increases in such monosomic colonies are produced by exposure of cells to a number of chemical mutagens such as ethyl methane-sulfonate and mitomycin C. More importantly, monosomic colonies are also induced by nonmutagens such as sulfacetamide and saccharin, which suggests that such chemicals are capable of inducing aneuploidy (aneugenic) in the absence of mutagenic activity. Genetic analysis of aneuploid colonies produced on nonselective medium indicate that at least a proportion of the monosomic colonies were the result of mitotic nondisjunction. During meiotic cell division, disomic cells (n + 1) produced by chromosome nondisjunction may be detected by plating on selective media. The frequency of disomic cells has been shown to increase after exposure to p-fluorophenylalanine. PMID:387403

  15. Transmission distortion affecting human noncrossover but not crossover recombination: a hidden source of meiotic drive.

    PubMed

    Odenthal-Hesse, Linda; Berg, Ingrid L; Veselis, Amelia; Jeffreys, Alec J; May, Celia A

    2014-02-01

    Meiotic recombination ensures the correct segregation of homologous chromosomes during gamete formation and contributes to DNA diversity through both large-scale reciprocal crossovers and very localised gene conversion events, also known as noncrossovers. Considerable progress has been made in understanding factors such as PRDM9 and SNP variants that influence the initiation of recombination at human hotspots but very little is known about factors acting downstream. To address this, we simultaneously analysed both types of recombinant molecule in sperm DNA at six highly active hotspots, and looked for disparity in the transmission of allelic variants indicative of any cis-acting influences. At two of the hotspots we identified a novel form of biased transmission that was exclusive to the noncrossover class of recombinant, and which presumably arises through differences between crossovers and noncrossovers in heteroduplex formation and biased mismatch repair. This form of biased gene conversion is not predicted to influence hotspot activity as previously noted for SNPs that affect recombination initiation, but does constitute a powerful and previously undetected source of recombination-driven meiotic drive that by extrapolation may affect thousands of recombination hotspots throughout the human genome. Intriguingly, at both of the hotspots described here, this drive favours strong (G/C) over weak (A/T) base pairs as might be predicted from the well-established correlations between high GC content and recombination activity in mammalian genomes. PMID:24516398

  16. Telomere dynamics unique to meiotic prophase: formation and significance of the bouquet.

    PubMed

    Bass, H W

    2003-11-01

    Telomeres carry out conserved and possibly ancient functions in meiosis. During the specialized prophase of meiosis I, meiotic prophase, telomeres cluster on the nuclear envelope and move the diploid genetic material around within the nucleus so that homologous chromosomes can align two by two and efficiently recombine with precision. This recombination is in turn required for proper segregation of the homologs into viable haploid daughter cells. The meiosis-specific telomere clustering on the nuclear envelope defines the bouquet stage, so named for its resemblance to the stems from a bouquet of cut flowers. Here, a comparative analysis of the literature on meiotic telomeres from a variety of different species illustrates that the bouquet is nearly universal among life cycles with sexual reproduction. The bouquet has been well documented for over 100 years, but our understanding of how it forms and how it functions has only recently begun to increase. Early and recent observations document the timing and provide clues about the functional significance of these striking telomere movements.

  17. Whole chromosome gain does not in itself confer cancer-like chromosomal instability

    PubMed Central

    Valind, Anders; Jin, Yuesheng; Baldetorp, Bo; Gisselsson, David

    2013-01-01

    Constitutional aneuploidy is typically caused by a single-event meiotic or early mitotic error. In contrast, somatic aneuploidy, found mainly in neoplastic tissue, is attributed to continuous chromosomal instability. More debated as a cause of aneuploidy is aneuploidy itself; that is, whether aneuploidy per se causes chromosomal instability, for example, in patients with inborn aneuploidy. We have addressed this issue by quantifying the level of somatic mosaicism, a proxy marker of chromosomal instability, in patients with constitutional aneuploidy by precise background-filtered dual-color FISH. In contrast to previous studies that used less precise methods, we find that constitutional trisomy, even for large chromosomes that are often trisomic in cancer, does not confer a significantly elevated rate of somatic chromosomal mosaicism in individual cases. Constitutional triploidy was associated with an increased level of somatic mosaicism, but this consisted mostly of reversion from trisomy to disomy and did not correspond to a proportionally elevated level of chromosome mis-segregation in triploids, indicating that the observed mosaicism resulted from a specific accumulation of cells with a hypotriploid chromosome number. In no case did the rate of somatic mosaicism in constitutional aneuploidy exceed that of “chromosomally stable” cancer cells. Our findings show that even though constitutional aneuploidy was in some cases associated with low-level somatic mosaicism, it was insufficient to generate the cancer-like levels expected if aneuploidy single-handedly triggered cancer-like chromosomal instability. PMID:24324169

  18. Contrasting behavior of heterochromatic and euchromatic chromosome portions and pericentric genome separation in pre-bouquet spermatocytes of hybrid mice.

    PubMed

    Scherthan, Harry; Schöfisch, Karina; Dell, Thomas; Illner, Doris

    2014-12-01

    The spatial distribution of parental genomes has attracted much interest because intranuclear chromosome distribution can modulate the transcriptome of cells and influence the efficacy of meiotic homologue pairing. Pairing of parental chromosomes is imperative to sexual reproduction as it translates into homologue segregation and genome haploidization to counteract the genome doubling at fertilization. Differential FISH tagging of parental pericentromeric genome portions and specific painting of euchromatic chromosome arms in Mus musculus (MMU) × Mus spretus (MSP) hybrid spermatogenesis disclosed a phase of homotypic non-homologous pericentromere clustering that led to parental pericentric genome separation from the pre-leptoteneup to zygotene stages. Preferential clustering of MMU pericentromeres correlated with particular enrichment of epigenetic marks (H3K9me3), HP1-γ and structural maintenance of chromosomes SMC6 complex proteins at the MMU major satellite DNA repeats. In contrast to the separation of heterochromatic pericentric genome portions, the euchromatic arms of homeologous chromosomes showed considerable presynaptic pairing already during leptotene stage of all mice investigated. Pericentric genome separation was eventually disbanded by telomere clustering that concentrated both parental pericentric genome portions in a limited nuclear sector of the bouquet nucleus. Our data disclose the differential behavior of pericentromeric heterochromatin and the euchromatic portions of the parental genomes during homologue search. Homotypic pericentromere clustering early in prophase I may contribute to the exclusion of large repetitive DNA domains from homology search, while the telomere bouquet congregates and registers spatially separated portions of the genome to fuel synapsis initiation and high levels of homologue pairing, thus contributing to the fidelity of meiosis and reproduction.

  19. Genetic control of mammalian meiotic recombination. I. Variation in exchange frequencies among males from inbred mouse strains.

    PubMed

    Koehler, Kara E; Cherry, Jonathan P; Lynn, Audrey; Hunt, Patricia A; Hassold, Terry J

    2002-09-01

    Genetic background effects on the frequency of meiotic recombination have long been suspected in mice but never demonstrated in a systematic manner, especially in inbred strains. We used a recently described immunostaining technique to assess meiotic exchange patterns in male mice. We found that among four different inbred strains--CAST/Ei, A/J, C57BL/6, and SPRET/Ei--the mean number of meiotic exchanges per cell and, thus, the recombination rates in these genetic backgrounds were significantly different. These frequencies ranged from a low of 21.5 exchanges in CAST/Ei to a high of 24.9 in SPRET/Ei. We also found that, as expected, these crossover events were nonrandomly distributed and displayed positive interference. However, we found no evidence for significant differences in the patterns of crossover positioning between strains with different exchange frequencies. From our observations of >10,000 autosomal synaptonemal complexes, we conclude that achiasmate bivalents arise in the male mouse at a frequency of 0.1%. Thus, special mechanisms that segregate achiasmate chromosomes are unlikely to be an important component of mammalian male meiosis.

  20. Correlation of meiotic events in testis sections and microspreads of mouse spermatocytes relative to the mid-pachytene checkpoint.

    PubMed

    Ashley, Terry; Gaeth, Ann P; Creemers, Laura B; Hack, Adelle M; de Rooij, Dirk G

    2004-09-01

    In mouse, asynaptic meiotic mutants arrest at Testis Epithelial Stage IV. This arrest is 4.5 days after homologous chromosomes begin to synapse and approximately 2.5 days after synapsis is usually completed. To correlate cytological events with meiotic progression in testis and to determine which meiotic events are normally completed by Stage IV, we induced spermatogenic arrest by placing mice on a vitamin A deficient diet. Subsequent injection of retinoic acid and a return to a normal diet resulted in resumption of spermatogenesis with all spermatocytes proceeding through meiosis in a highly synchronous cohort. Between Days 11 and 16 post-injection we prepared one testis for immunocytological and the other for histological evaluation, then used antibodies to SCP3 and either RPA, or MLH1 to follow quantitative changes in synapsis and recombination. RPA was found at sites along the synaptonemal complex as soon as homologs synapsed, and most, but not all, RPA disappeared by Stage IV. MLH1 foci appeared between Stage II and IV and remained through Stage VII, the end point of the study. The data suggest that the earliest the mid-pachytene checkpoint can be activated is Epithelial Stage IV, but that activities monitored by the checkpoint may not be completed by this time.

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

    PubMed

    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.

  2. Alteration of chromosome behavior and synchronization of parental chromosomes after successive generations in Brassica napus x Orychophragmus violaceus hybrids.

    PubMed

    Zhao, Zhigang; Ma, Ni; Li, Zaiyun

    2007-02-01

    In an earlier study, the progenies of intergeneric hybrids Brassica napus (2n = 38) x Orychophragmus violaceus (2n = 24) were investigated in successive generations (F1-F4) for the cytological phenomenon of parental genome separation during mitotic and meiotic division. In the present study, inbred lines (F5-F8) derived from 1 such hybrid were characterized for morphology, chromosome pairing behaviour, and genome composition. One F5 plant (2n = 31) with slightly yellow petals and 12:19 and 15:16 segregation ratios in its pollen mother cells (PMCs) produced F6 plants with distinct morphological characteristics and wide variations in fertility and chromosome numbers (2n = 25-38). F7 and F8 lines with distinctive morphology and wide ranges in chromsome numbers were established. In PMCs of F7 plants from 4 F6 plants, 0-12 labelled chromosomes from O. violaceus, which predominantly appeared as bivalents, were identified by genomic in situ hybridization. They behaved synchronously with B. napus chromosomes during meiotic division. The results provide molecular cytogenetic evidence of the inclusion of O. violaceus chromosomes in the original hybrids and the cytology in the hybrids documented earlier. They also show that chromosome behaviour was altered and the parental chromosomes became synchronized after successive generations.

  3. A surge of late-occurring meiotic double-strand breaks rescues synapsis abnormalities in spermatocytes of mice with hypomorphic expression of SPO11.

    PubMed

    Faieta, Monica; Di Cecca, Stefano; de Rooij, Dirk G; Luchetti, Andrea; Murdocca, Michela; Di Giacomo, Monica; Di Siena, Sara; Pellegrini, Manuela; Rossi, Pellegrino; Barchi, Marco

    2016-06-01

    Meiosis is the biological process that, after a cycle of DNA replication, halves the cellular chromosome complement, leading to the formation of haploid gametes. Haploidization is achieved via two successive rounds of chromosome segregation, meiosis I and II. In mammals, during prophase of meiosis I, homologous chromosomes align and synapse through a recombination-mediated mechanism initiated by the introduction of DNA double-strand breaks (DSBs) by the SPO11 protein. In male mice, if SPO11 expression and DSB number are reduced below heterozygosity levels, chromosome synapsis is delayed, chromosome tangles form at pachynema, and defective cells are eliminated by apoptosis at epithelial stage IV at a spermatogenesis-specific endpoint. Whether DSB levels produced in Spo11 (+/-) spermatocytes represent, or approximate, the threshold level required to guarantee successful homologous chromosome pairing is unknown. Using a mouse model that expresses Spo11 from a bacterial artificial chromosome, within a Spo11 (-/-) background, we demonstrate that when SPO11 expression is reduced and DSBs at zygonema are decreased (approximately 40 % below wild-type level), meiotic chromosome pairing is normal. Conversely, DMC1 foci number is increased at pachynema, suggesting that under these experimental conditions, DSBs are likely made with delayed kinetics at zygonema. In addition, we provide evidences that when zygotene-like cells receive enough DSBs before chromosome tangles develop, chromosome synapsis can be completed in most cells, preventing their apoptotic elimination.

  4. Mapping pachytene chromosomes of coffee using a modified protocol for fluorescence in situ hybridization

    PubMed Central

    Iacia, Ana Amélia Sanchez; Pinto-Maglio, Cecília A. F.

    2013-01-01

    Fluorescence in situ hybridization (FISH) is the most direct method for physically mapping DNA sequences on chromosomes. Fluorescence in situ hybridization mapping of meiotic chromosomes during the pachytene stage is an important tool in plant cytogenetics, because it provides high-resolution measurements of physical distances. Fluorescence in situ hybridization mapping of coffee pachytene chromosomes offers significant advantages compared with FISH mapping of somatic chromosomes, because pachytene chromosomes are 30 times longer and provide additional cytological markers. However, the application of this technique to pachytene chromosomes has been complicated by problems in making preparations of meiotic chromosomes and by difficulties in the application of standard FISH protocols. We have been able to overcome most of these obstacles in applying the FISH technique to the pachytene chromosomes of coffee plants. Digesting the external callose layer surrounding the pollen mother cells (PMCs) in conjunction with other procedures permitted suitable pachytene chromosomes to be obtained by increasing cell permeability, which allowed the probe sequences to enter the cells. For the first time, hybridization signals were registered on coffee pachytene chromosomes using the FISH technique with a repetitive sequence as a probe. We obtained slides on which 80 % of the PMCs had hybridization signals, resulting in FISH labelling with high efficiency. The procedure does not seem to be dependent on the genotype, because hybridization signals were detected in genetically different coffee plants. These findings enhance the possibilities for high-resolution physical mapping of coffee chromosomes. PMID:24244840

  5. Drosophila brca2 Is Required for Mitotic and Meiotic DNA Repair and Efficient Activation of the Meiotic Recombination Checkpoint

    PubMed Central

    Klovstad, Martha; Abdu, Uri; Schüpbach, Trudi

    2008-01-01

    Heterozygous mutations in the tumor suppressor BRCA2 confer a high risk of breast and other cancers in humans. BRCA2 maintains genome stability in part through the regulation of Rad51-dependent homologous recombination. Much about its precise function in the DNA damage responses is, however, not yet known. We have made null mutations in the Drosophila homolog of BRCA2 and measured the levels of homologous recombination, non-homologous end-joining, and single-strand annealing in the pre-meiotic germline of Drosophila males. We show that repair by homologous recombination is dramatically decreased in Drosophila brca2 mutants. Instead, large flanking deletions are formed, and repair by the non-conservative single-strand annealing pathway predominates. We further show that during meiosis, Drosophila Brca2 has a dual role in the repair of meiotic double-stranded breaks and the efficient activation of the meiotic recombination checkpoint. The eggshell patterning defects that result from activation of the meiotic recombination checkpoint in other meiotic DNA repair mutants can be strongly suppressed by mutations in brca2. In addition, Brca2 co-immunoprecipitates with the checkpoint protein Rad9, suggesting a direct role for Brca2 in the transduction of the meiotic recombination checkpoint signal. PMID:18266476

  6. Oocyte-specific differences in cell-cycle control create an innate susceptibility to meiotic errors.

    PubMed

    Nagaoka, So Iha; Hodges, Craig A; Albertini, David F; Hunt, Patricia Ann

    2011-04-26

    Segregation of homologs at the first meiotic division (MI) is facilitated by crossovers and by a physical constraint imposed on sister kinetochores that facilitates monopolar attachment to the MI spindle. Recombination failure or premature separation of homologs results in univalent chromosomes at MI, and univalents constrained to form monopolar attachments should be inherently unstable and trigger the spindle assembly checkpoint (SAC). Although univalents trigger cell-cycle arrest in the male, this is not the case in mammalian oocytes. Because the spindle assembly portion of the SAC appears to function normally, two hypotheses have been proposed to explain the lack of response to univalents: (1) reduced stringency of the oocyte SAC to aberrant chromosome behavior, and (2) the ability of univalents to satisfy the SAC by forming bipolar attachments. The present study of Mlh1 mutant mice demonstrates that metaphase alignment is not a prerequisite for anaphase onset and provides strong evidence that MI spindle stabilization and anaphase onset require stable bipolar attachment of a critical mass--but not all--of chromosomes. We postulate that subtle differences in SAC-mediated control make the human oocyte inherently error prone and contribute to the age-related increase in aneuploidy.

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

    PubMed Central

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

    2015-01-01

    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. PMID:25948567

  8. Disruption of Chtf18 Causes Defective Meiotic Recombination in Male Mice

    PubMed Central

    Berkowitz, Karen M.; Sowash, Aislinn R.; Koenig, Lydia R.; Urcuyo, Dawnette; Khan, Fahmida; Yang, Fang; Wang, P. Jeremy; Jongens, Thomas A.; Kaestner, Klaus H.

    2012-01-01

    CHTF18 (chromosome transmission fidelity factor 18) is an evolutionarily conserved subunit of the Replication Factor C-like complex, CTF18-RLC. CHTF18 is necessary for the faithful passage of chromosomes from one daughter cell to the next during mitosis in yeast, and it is crucial for germline development in the fruitfly. Previously, we showed that mouse Chtf18 is expressed throughout the germline, suggesting a role for CHTF18 in mammalian gametogenesis. To determine the role of CHTF18 in mammalian germ cell development, we derived mice carrying null and conditional mutations in the Chtf18 gene. Chtf18-null males exhibit 5-fold decreased sperm concentrations compared to wild-type controls, resulting in subfertility. Loss of Chtf18 results in impaired spermatogenesis; spermatogenic cells display abnormal morphology, and the stereotypical arrangement of cells within seminiferous tubules is perturbed. Meiotic recombination is defective and homologous chromosomes separate prematurely during prophase I. Repair of DNA double-strand breaks is delayed and incomplete; both RAD51 and γH2AX persist in prophase I. In addition, MLH1 foci are decreased in pachynema. These findings demonstrate essential roles for CHTF18 in mammalian spermatogenesis and meiosis, and suggest that CHTF18 may function during the double-strand break repair pathway to promote the formation of crossovers. PMID:23133398

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

    PubMed

    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.

  10. Elevated testosterone during meiotic segregation stimulates laying hens to produce more sons than daughters.

    PubMed

    Pinson, Sara E; Wilson, Jeanna L; Navara, Kristen J

    2011-11-01

    Biases in avian sex ratios have been documented in relation to a variety of social and environmental conditions. Previous studies suggest that treatment with hormones can stimulate females to manipulate offspring sex, and that this effect occurs before ovulation. For example, acute and chronic treatments with testosterone stimulated significant skews towards male offspring. Hormones may act by influencing which sex chromosome is donated by the heterogametic female bird into the oocyte. However, it is difficult to pinpoint when effects of testosterone on offspring sex occurred in previous experiments because testosterone treatments were given either chronically over the entire period of follicular development or many hours before the critical period of chromosome segregation. We injected laying hens with testosterone injections 5 h prior to ovulation to target this critical period and quantified the sexes of the subsequently ovulated eggs. We hypothesized that an injection of testosterone coincident with segregation of sex chromosomes would stimulate hens to produce more male than female offspring. As hypothesized, hens injected with testosterone produced a significant bias towards male offspring compared to controls, nearly 70%. These results suggest that acute testosterone elevation during meiotic segregation may mediate skews in avian primary sex ratios.

  11. Analysis of Recombination and Chromosome Structure during Yeast Meiosis.

    PubMed

    Börner, G Valentin; Cha, Rita S

    2015-11-02

    Meiosis is a diploid-specific differentiation program that consists of a single round of genome duplication followed by two rounds of chromosome segregation. These events result in halving of the genetic complement, which is a requirement for formation of haploid reproductive cells (i.e., spores in yeast and gametes in animals and plants). During meiosis I, homologous maternal and paternal chromosomes (homologs) pair and separate, whereas sister chromatids remain connected at the centromeres and separate during the second meiotic division. In most organisms, accurate homolog disjunction requires crossovers, which are formed as products of meiotic recombination. For the past two decades, studies of yeast meiosis have provided invaluable insights into evolutionarily conserved mechanisms of meiosis.

  12. Mcp7, a meiosis-specific coiled-coil protein of fission yeast, associates with Meu13 and is required for meiotic recombination.

    PubMed

    Saito, Takamune T; Tougan, Takahiro; Kasama, Takashi; Okuzaki, Daisuke; Nojima, Hiroshi

    2004-01-01

    We previously showed that Meu13 of Schizosaccharomyces pombe functions in homologous pairing and recombination at meiosis I. Here we show that a meiosis-specific gene encodes a coiled-coil protein that complexes with Meu13 during meiosis in vivo. This gene denoted as mcp7+ (after meiotic coiled-coil protein) is an ortholog of Mnd1 of Saccharomyces cerevisiae. Mcp7 proteins are detected on meiotic chromatin. The phenotypes of mcp7Delta cells are similar to those of meu13Delta cells as they show reduced recombination rates and spore viability and produce spores with abnormal morphology. However, a delay in initiation of meiosis I chromosome segregation of mcp7Delta cells is not so conspicuous as meu13Delta cells, and no meiotic delay is observed in mcp7Deltameu13Delta cells. Mcp7 and Meu13 proteins depend on each other differently; Mcp7 becomes more stable in meu13Delta cells, whereas Meu13 becomes less stable in mcp7Delta cells. Genetic analysis shows that Mcp7 acts in the downstream of Dmc1, homologs of Escherichia coli RecA protein, for both recombination and subsequent sporulation. Taken together, we conclude that Mcp7 associates with Meu13 and together they play a key role in meiotic recombination. PMID:15210864

  13. Mcp7, a meiosis-specific coiled-coil protein of fission yeast, associates with Meu13 and is required for meiotic recombination

    PubMed Central

    Saito, Takamune T.; Tougan, Takahiro; Kasama, Takashi; Okuzaki, Daisuke; Nojima, Hiroshi

    2004-01-01

    We previously showed that Meu13 of Schizosaccharomyces pombe functions in homologous pairing and recombination at meiosis I. Here we show that a meiosis-specific gene encodes a coiled-coil protein that complexes with Meu13 during meiosis in vivo. This gene denoted as mcp7+ (after meiotic coiled-coil protein) is an ortholog of Mnd1 of Saccharomyces cerevisiae. Mcp7 proteins are detected on meiotic chromatin. The phenotypes of mcp7Δ cells are similar to those of meu13Δ cells as they show reduced recombination rates and spore viability and produce spores with abnormal morphology. However, a delay in initiation of meiosis I chromosome segregation of mcp7Δ cells is not so conspicuous as meu13Δ cells, and no meiotic delay is observed in mcp7Δmeu13Δ cells. Mcp7 and Meu13 proteins depend on each other differently; Mcp7 becomes more stable in meu13Δ cells, whereas Meu13 becomes less stable in mcp7Δ cells. Genetic analysis shows that Mcp7 acts in the downstream of Dmc1, homologs of Escherichia coli RecA protein, for both recombination and subsequent sporulation. Taken together, we conclude that Mcp7 associates with Meu13 and together they play a key role in meiotic recombination. PMID:15210864

  14. The nucleotide mapping of DNA double-strand breaks at the CYS3 initiation site of meiotic recombination in Saccharomyces cerevisiae.

    PubMed Central

    de Massy, B; Rocco, V; Nicolas, A

    1995-01-01

    Initiation of meiotic recombination in the yeast Saccharomyces cerevisiae occurs by localized DNA double-strand breaks (DSBs) at several locations in the genome, corresponding to hot spots for meiotic gene conversion and crossing over. The meiotic DSBs occur in regions of chromatin that are hypersensitive to nucleases. To gain insight into the molecular mechanism involved in the formation of these DSBs, we have determined their positions at the nucleotide level at the CYS3 hot spot of gene conversion on chromosome I. We found four major new features of these DSBs: (i) sites of DSBs are multiple with varying intensities and spacing within the promoter region of the CYS3 gene; (ii) no consensus sequence can be found at these sites, indicating that the activity involved in DSB formation has little or no sequence specificity; (iii) the breaks are generated by blunt cleavages; and (iv) the 5' ends are modified in rad50S mutant strains, where the processing of these ends is known to be prevented. We present a model for the initiation of meiotic recombination taking into account the implications of these results. Images PMID:7556102

  15. Localisation of the SMC loading complex Nipbl/Mau2 during mammalian meiotic prophase I.

    PubMed

    Visnes, T; Giordano, F; Kuznetsova, A; Suja, J A; Lander, A D; Calof, A L; Ström, L

    2014-06-01

    Evidence from lower eukaryotes suggests that the chromosomal associations of all the structural maintenance of chromosome (SMC) complexes, cohesin, condensin and Smc5/6, are influenced by the Nipbl/Mau2 heterodimer. Whether this function is conserved in mammals is currently not known. During mammalian meiosis, very different localisation patterns have been reported for the SMC complexes, and the localisation of Nipbl/Mau2 has just recently started to be investigated. Here, we show that Nipbl/Mau2 binds on chromosomal axes from zygotene to mid-pachytene in germ cells of both sexes. In spermatocytes, Nipbl/Mau2 then relocalises to chromocenters, whereas in oocytes it remains bound to chromosomal axes throughout prophase to dictyate arrest. The localisation pattern of Nipbl/Mau2, together with those seen for cohesin, condensin and Smc5/6 subunits, is consistent with a role as a loading factor for cohesin and condensin I, but not for Smc5/6. We also demonstrate that Nipbl/Mau2 localises next to Rad51 and γH2AX foci. NIPBL gene deficiencies are associated with the Cornelia de Lange syndrome in humans, and we find that haploinsufficiency of the orthologous mouse gene results in an altered distribution of double-strand breaks marked by γH2AX during prophase I. However, this is insufficient to result in major meiotic malfunctions, and the chromosomal associations of the synaptonemal complex proteins and the three SMC complexes appear cytologically indistinguishable in wild-type and Nipbl (+/-) spermatocytes. PMID:24287868

  16. Recombination-independent mechanisms and pairing of homologous chromosomes during meiosis in plants.

    PubMed

    Da Ines, Olivier; Gallego, Maria E; White, Charles I

    2014-03-01

    Meiosis is the specialized eukaryotic cell division that permits the halving of ploidy necessary for gametogenesis in sexually reproducing organisms. This involves a single round of DNA replication followed by two successive divisions. To ensure balanced segregation, homologous chromosome pairs must migrate to opposite poles at the first meiotic division and this means that they must recognize and pair with each other beforehand. Although understanding of the mechanisms by which meiotic chromosomes find and pair with their homologs has greatly advanced, it remains far from being fully understood. With some notable exceptions such as male Drosophila, the recognition and physical linkage of homologs at the first meiotic division involves homologous recombination. However, in addition to this, it is clear that many organisms, including plants, have also evolved a series of recombination-independent mechanisms to facilitate homolog recognition and pairing. These implicate chromosome structure and dynamics, telomeres, centromeres, and, most recently, small RNAs. With a particular focus on plants, we present here an overview of understanding of these early, recombination-independent events that act in the pairing of homologous chromosomes during the first meiotic division. PMID:24375719

  17. Possible origin of B chromosome in Dichotomius sericeus (Coleoptera).

    PubMed

    Amorim, Igor Costa; Milani, Diogo; Cabral-de-Mello, Diogo Cavalcanti; Rocha, Marília França; Moura, Rita Cássia

    2016-08-01

    B chromosomes have so far been described in about 80 species of Coleoptera, mainly using conventional staining analysis. In this study, 152 individuals of the dung beetle Dichotomius sericeus (Coleoptera), collected from three isolated geographical areas in the State of Pernambuco, Brazil, were analyzed to determine the frequency, prevalence, distribution, meiotic behavior, and possible B chromosome origin. The cytogenetic analysis consisted of conventional staining, C-banding, triple fluorochrome staining (CMA3/DA/DAPI), and fluorescent in situ hybridization using ribosomal DNAs (rDNAs) and H3 histone gene as probes, as well as microdissection and chromosome painting of the B chromosome. The B chromosomes were detected in all populations analyzed. Analysis revealed the heterochromatic nature and the presence of G+C-rich blocks and 18S rDNA on the B chromosome. FISH with DNA from microdissected B chromosome painted the entire extension of the B chromosome for all populations, besides the pericentromeric regions of all the autosomes, as well as the X chromosome. Finally, cross-hybridization in nine related species of Dichotomius using the microdissected B chromosome as probe did not reveal any hybridization signal. The results suggest an intraspecific and monophyletic origin for B chromosomes in D. sericeus, probably from the second or third autosomal pair.

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

    PubMed

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

    2016-06-01

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

  19. The tricky path to recombining X and Y chromosomes in meiosis.

    PubMed

    Kauppi, Liisa; Jasin, Maria; Keeney, Scott

    2012-09-01

    Sex chromosomes are the Achilles' heel of male meiosis in mammals. Mis-segregation of the X and Y chromosomes leads to sex chromosome aneuploidies, with clinical outcomes such as infertility and Klinefelter syndrome. Successful meiotic divisions require that all chromosomes find their homologous partner and achieve recombination and pairing. Sex chromosomes in males of many species have only a small region of homology (the pseudoautosomal region, PAR) that enables pairing. Until recently, little was known about the dynamics of recombination and pairing within mammalian X and Y PARs. Here, we review our recent findings on PAR behavior in mouse meiosis. We uncovered unexpected differences between autosomal chromosomes and the X-Y chromosome pair, namely that PAR recombination and pairing occurs later, and is under different genetic control. These findings imply that spermatocytes have evolved distinct strategies that ensure successful X-Y recombination and chromosome segregation.

  20. Spatial regulation of kinetochore microtubule attachments by destabilization at spindle poles in meiosis I

    PubMed Central

    Chmátal, Lukáš; Yang, Karren; Schultz, Richard M.; Lampson, Michael A.

    2015-01-01

    Summary To ensure accurate chromosome segregation in cell division, erroneous kinetochore-microtubule (MT) attachments are recognized and destabilized [1]. Improper attachments typically lack tension between kinetochores and are positioned off-center on the spindle. Low tension is a widely accepted mechanism for recognizing errors [2], but whether chromosome position regulates MT attachments has been difficult to test. We exploited a meiotic system in which kinetochores attached to opposite spindle poles differ in their interactions with microtubules, and therefore position and tension can be uncoupled. In this system homologous chromosomes are positioned off-center on the spindle in oocytes in meiosis I, while under normal tension, as a result of crossing mouse strains with different centromere strengths, manifested by unequal kinetochore protein levels [3]. We show that proximity to spindle poles destabilizes kinetochore-MTs, and that stable attachments are restored by inhibiting Aurora A kinase at spindle poles. During the correction of attachment errors, kinetochore MTs detach near spindle poles to allow formation of correct attachments. We propose that chromosome position on the spindle provides spatial cues for the fidelity of cell division. PMID:26166779

  1. A Nucleoporin at the Meiotic Kinetochore.

    PubMed

    Bonner, Amanda M; Hawley, R Scott

    2016-09-12

    In this issue of Developmental Cell, Hattersley et al. (2016) use the unique biology of meiosis I, in which the cell can exit the division without reforming the nuclear envelope, to uncover an intriguing role of the nucleoporin MEL-28 in mediating chromosome segregation via its interaction with PP1 at the kinetochore. PMID:27623378

  2. Analysis of Meiotic Recombination Pathways in the Yeast Saccharomyces Cerevisiae

    PubMed Central

    Mao-Draayer, Y.; Galbraith, A. M.; Pittman, D. L.; Cool, M.; Malone, R. E.

    1996-01-01

    In the yeast, Saccharomyces cerevisiae, several genes appear to act early in meiotic recombination. HOP1 and RED1 have been classified as such early genes. The data in this paper demonstrate that neither a red1 nor a hop1 mutation can rescue the inviable spores produced by a rad52 spo13 strain; this phenotype helps to distinguish these two genes from other early meiotic recombination genes such as SPO11, REC104, or MEI4. In contrast, either a red1 or a hop1 mutation can rescue a rad50S spo13 strain; this phenotype is similar to that conferred by mutations in the other early recombination genes (e.g., REC104). These two different results can be explained because the data presented here indicate that a rad50S mutation does not diminish meiotic intrachromosomal recombination, similar to the mutant phenotypes conferred by red1 or hop1. Of course, RED1 and HOP1 do act in the normal meiotic interchromosomal recombination pathway; they reduce interchromosomal recombination to ~10% of normal levels. We demonstrate that a mutation in a gene (REC104) required for initiation of exchange is completely epistatic to a mutation in RED1. Finally, mutations in either HOP1 or RED1 reduce the number of double-strand breaks observed at the HIS2 meiotic recombination hotspot. PMID:8878674

  3. Kinesin 5B (KIF5B) is required for progression through female meiosis and proper chromosomal segregation in mitotic cells.

    PubMed

    Kidane, Dawit; Sakkas, Denny; Nottoli, Timothy; McGrath, James; Sweasy, Joann B

    2013-01-01

    The fidelity of chromosomal segregation during cell division is important to maintain chromosomal stability in order to prevent cancer and birth defects. Although several spindle-associated molecular motors have been shown to be essential for cell division, only a few chromosome arm-associated motors have been described. Here, we investigated the role of Kinesin 5b (Kif5b) during female mouse meiotic cell development and mitotic cell division. RNA interference (RNAi)-mediated silencing of Kif5b in mouse oocytes induced significant delay in germinal vesicle breakdown (GVBD) and failure in extrusion of the first polar body (PBE). In mitotic cells, knockdown of Kif5b leads to centrosome amplification and a chromosomal segregation defect. These data suggest that KIF5B is critical in suppressing chromosomal instability at the early stages of female meiotic cell development and mitotic cell division.

  4. First description of multivalent ring structures in eutherian mammalian meiosis: new chromosomal characterization of Cormura brevirostris (Emballonuridae, Chiroptera).

    PubMed

    de Araújo, Ramon Everton Ferreira; Nagamachi, Cleusa Yoshiko; da Costa, Marlyson Jeremias Rodrigues; Noronha, Renata Coelho Rodrigues; Rodrigues, Luís Reginaldo Ribeiro; Pieczarka, Julio César

    2016-08-01

    Twelve specimens of the bat Cormura brevirostris (Emballonuridae: Chiroptera) were collected from four localities in the Brazilian Amazon region and analyzed by classical and molecular cytogenetics. The diploid number and autosomal fundamental number were as previously reported (2n = 22 and FNa = 40, respectively). Fluorescence in situ hybridization using rDNA probes and silver nitrate technique demonstrated the presence of two NOR sites and the presence of internal telomeric sequences at pericentromeric regions of all chromosomes with exception of Y. Based on meiotic studies and chromosome banding we suggest that the sex chromosome pair of C. brevirostris was equivocally identified as it appears in the literature. Meiotic analysis demonstrated that at diplotene-diakinesis the cells had a ring conformation involving four chromosome pairs. This suggests the occurrence of multiple reciprocal translocations among these chromosomes, which is a very rare phenomenon in vertebrates, and has never been described in Eutheria.

  5. PRDM9 Drives Evolutionary Erosion of Hotspots in Mus musculus through Haplotype-Specific Initiation of Meiotic Recombination

    PubMed Central

    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 Prdm9 Cst 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