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Sample records for meiotic chromosomal proteins

  1. The chromosome axis controls meiotic events through a hierarchical assembly of HORMA domain proteins

    Science.gov (United States)

    Kim, Yumi; Rosenberg, Scott C.; Kugel, Christine L.; Kostow, Nora; Rog, Ofer; Davydov, Vitaliy; Su, Tiffany Y.; Dernburg, Abby F.; Corbett, Kevin D.

    2014-01-01

    Summary Proteins of the HORMA domain family play central but poorly understood roles in chromosome organization and dynamics during meiosis. In C. elegans, four such proteins (HIM-3, HTP-1, HTP-2, and HTP-3) have distinct but overlapping functions. Through combined biochemical, structural, and in vivo analysis, we find that these proteins form hierarchical complexes through binding of their HORMA domains to cognate peptides within their partners’ C-terminal tails, analogous to the “safety belt” binding mechanism of Mad2. These interactions are critical for recruitment of HIM-3, HTP-1, and HTP-2 to chromosome axes. HTP-3, in addition to recruiting the other HORMA domain proteins to the axis, plays an independent role in sister chromatid cohesion and double-strand break formation. Finally, we find that mammalian HORMAD1 binds a peptide motif found both at its own C-terminus and that of HORMAD2, indicating that this mode of intermolecular association is a conserved feature of meiotic chromosome structure in eukaryotes. PMID:25446517

  2. Female meiotic sex chromosome inactivation in chicken.

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    Sam Schoenmakers

    2009-05-01

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

  3. The axial element protein HTP-3 promotes cohesin loading and meiotic axis assembly in C. elegans to implement the meiotic program of chromosome segregation.

    Science.gov (United States)

    Severson, Aaron F; Ling, Lorraine; van Zuylen, Vanessa; Meyer, Barbara J

    2009-08-01

    Faithful transmission of the genome through sexual reproduction requires reduction of genome copy number during meiosis to produce haploid sperm and eggs. Meiosis entails steps absent from mitosis to achieve this goal. When meiosis begins, sisters are held together by sister chromatid cohesion (SCC), mediated by the cohesin complex. Homologs then become linked through crossover recombination. SCC subsequently holds both sisters and homologs together. Separation of homologs and then sisters requires two successive rounds of chromosome segregation and the stepwise removal of Rec8, a meiosis-specific cohesin subunit. We show that HTP-3, a known component of the C. elegans axial element (AE), molecularly links these meiotic innovations. We identified HTP-3 in a genetic screen for factors necessary to maintain SCC until meiosis II. Our data show that interdependent loading of HTP-3 and cohesin is a principal step in assembling the meiotic chromosomal axis and in establishing SCC. HTP-3 recruits all known AE components to meiotic chromosomes and promotes cohesin loading, the first known involvement of an AE protein in this process. Furthermore, REC-8 and two paralogs, called COH-3 and COH-4, together mediate meiotic SCC, but they perform specialized functions. REC-8 alone is necessary and sufficient for the persistence of SCC after meiosis I. In htp-3 and rec-8 mutants, sister chromatids segregate away from one another in meiosis I (equational division), rather than segregating randomly, as expected if SCC were completely eliminated. AE assembly fails only when REC-8, COH-3, and COH-4 are simultaneously disrupted. Premature equational sister separation in rec8 mutants of other organisms suggests the involvement of multiple REC-8 paralogs, which may have masked a conserved requirement for cohesin in AE assembly.

  4. The Mouse Cohesin-Associated Protein PDS5B Is Expressed in Testicular Cells and Is Associated with the Meiotic Chromosome Axes

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    Christer Hoog

    2010-12-01

    Full Text Available During the first meiotic prophase, the cohesin complex is localized to the chromosome axis and contributes to chromosome organization, pairing, synapsis, and recombination. The PDS5 protein, an accessory factor of the cohesin complex, is known to be a component of meiotic chromosome cores in fungi and to be implicated in meiotic chromosome structure and function. We found by immunoblotting experiments that a mammalian PDS5 protein, PDS5B, is abundantly expressed in mouse testis compared to other tissues. Immunofluorescence labeling experiments revealed that PDS5B is highly expressed in spermatogonia and that most PDS5B is depleted from chromatin as cells enter meiosis. During the first meiotic prophase, PDS5B associates with the axial cores of chromosomes. The axial association of PDS5B was observed also in the absence of synaptonemal complex proteins, such as SYCP1 and SYCP3, suggesting that PDS5B is an integral part of the chromosome axis as defined by the cohesin complex. These results suggest that PDS5B modulates cohesin functions in spermatocytes as well as in spermatogonia, contributing to meiotic chromosome structure and function.

  5. Nuclear Envelope-Associated Chromosome Dynamics during Meiotic Prophase I

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    Xinhua Zeng

    2018-01-01

    Full Text Available Chromosome dynamics during meiotic prophase I are associated with a series of major events such as chromosomal reorganization and condensation, pairing/synapsis and recombination of the homologs, and chromosome movements at the nuclear envelope (NE. The NE is the barrier separating the nucleus from the cytoplasm and thus plays a central role in NE-associated chromosomal movements during meiosis. Previous studies have shown in various species that NE-linked chromosome dynamics are actually driven by the cytoskeleton. The linker of nucleoskeleton and cytoskeleton (LINC complexes are important constituents of the NE that facilitate in the transfer of cytoskeletal forces across the NE to individual chromosomes. The LINCs consist of the inner and outer NE proteins Sad1/UNC-84 (SUN, and Klarsicht/Anc-1/Syne (KASH domain proteins. Meiosis-specific adaptations of the LINC components and unique modifications of the NE are required during chromosomal movements. Nonetheless, the actual role of the NE in chromosomic dynamic movements in plants remains elusive. This review summarizes the findings of recent studies on meiosis-specific constituents and modifications of the NE and corresponding nucleoplasmic/cytoplasmic adaptors being involved in NE-associated movement of meiotic chromosomes, as well as describes the potential molecular network of transferring cytoplasm-derived forces into meiotic chromosomes in model organisms. It helps to gain a better understanding of the NE-associated meiotic chromosomal movements in plants.

  6. Analysis of plant meiotic chromosomes by chromosome painting.

    Science.gov (United States)

    Lysak, Martin A; Mandáková, Terezie

    2013-01-01

    Chromosome painting (CP) refers to visualization of large chromosome regions, entire chromosome arms, or entire chromosomes via fluorescence in situ hybridization (FISH). For CP in plants, contigs of chromosome-specific bacterial artificial chromosomes (BAC) from the target species or from a closely related species (comparative chromosome painting, CCP) are typically applied as painting probes. Extended pachytene chromosomes provide the highest resolution of CP in plants. CP enables identification and tracing of particular chromosome regions and/or entire chromosomes throughout all meiotic stages as well as corresponding chromosome territories in premeiotic interphase nuclei. Meiotic pairing and structural chromosome rearrangements (typically inversions and translocations) can be identified by CP. Here, we describe step-by-step protocols of CP and CCP in plant species including chromosome preparation, BAC DNA labeling, and multicolor FISH.

  7. Chromosomal rearrangement interferes with meiotic X chromosome inactivation

    Czech Academy of Sciences Publication Activity Database

    Homolka, David; Ivánek, Robert; Čapková, Jana; Jansa, Petr; Forejt, Jiří

    2007-01-01

    Roč. 17, č. 10 (2007), s. 1431-1437 ISSN 1088-9051 R&D Projects: GA MŠk(CZ) 1M0520; GA ČR GA301/06/1334; GA ČR GA301/07/1383 Grant - others:Howard Hughes Medical Institute(US) HHMI 55000306 Institutional research plan: CEZ:AV0Z50520514 Keywords : chromosomal translocations * meiotic X chromosome inactivation * spermatogenesis Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 11.224, year: 2007

  8. Meiotic transmission of Drosophila pseudoobscura chromosomal arrangements.

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    Richard P Meisel

    Full Text Available Drosophila pseudoobscura harbors a rich gene arrangement polymorphism on the third chromosome generated by a series of overlapping paracentric inversions. The arrangements suppress recombination in heterokaryotypic individuals, which allows for the selective maintenance of coadapted gene complexes. Previous mapping experiments used to determine the degree to which recombination is suppressed in gene arrangement heterozygotes produced non-recombinant progeny in non-Mendelian ratios. The deviations from Mendelian expectations could be the result of viability differences between wild and mutant chromosomes, meiotic drive because of achiasmate pairing of homologues in heterokaryotypic females during meiosis, or a combination of both mechanisms. The possibility that the frequencies of the chromosomal arrangements in natural populations are affected by mechanisms other than adaptive selection led us to consider these hypotheses. We performed reciprocal crosses involving both heterozygous males and females to determine if the frequency of the non-recombinant progeny deviates significantly from Mendelian expectations and if the frequencies deviate between reciprocal crosses. We failed to observe non-Mendelian ratios in multiple crosses, and the frequency of the non-recombinant classes differed in only one of five pairs of reciprocal crosses despite sufficient power to detect these differences in all crosses. Our results indicate that deviations from Mendelian expectations in recombination experiments involving the D. pseudoobscura inversion system are most likely due to fitness differences of gene arrangement karyotypes in different environments.

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

    African Journals Online (AJOL)

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

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

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

    2011-03-01

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

  11. Direct Visualization Reveals Kinetics of Meiotic Chromosome Synapsis.

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    Rog, Ofer; Dernburg, Abby F

    2015-03-10

    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. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

  12. Direct Visualization Reveals Kinetics of Meiotic Chromosome Synapsis

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    Ofer Rog

    2015-03-01

    Full Text Available 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.

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

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    Maria Balcova

    2016-04-01

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

  14. Chromosome number and meiotic behaviour in Brachiaria jubata ...

    Indian Academy of Sciences (India)

    c Indian Academy of Sciences. RESEARCH NOTE. Chromosome number and meiotic behaviour in. Brachiaria jubata (Gramineae). ANDREA BEATRIZ ... species, only a few of them present favourable agronomic attributes and are explored. In the genus Brachiaria, the ma- jority of species and accessions are polyploid and ...

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

    Indian Academy of Sciences (India)

    Among the diploid accessions, the rate of meiotic abnormalities was low, ranging from 0.82% to 7.93%. In the 27 tetraploid accessions, the rate of meiotic abnormalities ranged from 18.41% to 65.83%. The most common meiotic abnormalities were related to irregular chromosome segregation, but chromosome stickiness ...

  16. X-ray induction of mitotic and meiotic chromosome aberrations

    International Nuclear Information System (INIS)

    Yao, K.T.S.

    1980-01-01

    In 1964 six pairs of rat kangaroo (Potorous tridactylis) were obtained from Australia. The tissues of these animals were used to initiate cell lines. Since this species has a low chromosome number of six pairs, each pair with its own distinctive morphology, it is particularly favorable for cytogenetic research. In cell cultures derived from the corneal endothelial tissues of one animal there emerged a number of haploid cells. The number of haploid cells in the cultures reached as high as 20% of the total mitotic configurations. The in vitro diploid and haploid mixture cell cultures could be a resemblance or a coincidence to the mixture existence of the diploid primary spermatocytes and the haploid secondary spermatocytes (gametes) in the in vivo testicular tissues of the male animals. It would be interesting to compare reactions of the haploid and diploid cell mixture, either in the cultures or in the testes, to x-ray exposure. Two other studies involving x-ray effects on Chinese hamster oocyte maturation and meiotic chromosomes and the x-ray induction of Chinese hamster spermatocyte meiotic chromosome aberrations have been done in this laboratory. A review of these three studies involving diploid and haploid chromosomes may lead to further research in the x-ray induction of chromosome aberrations

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

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    Jeffrey M Cloutier

    2015-10-01

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

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

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    Tanmoy Bhattacharyya

    2014-02-01

    Full Text Available Hybrid sterility (HS belongs to reproductive isolation barriers that safeguard the integrity of species in statu nascendi. Although hybrid sterility occurs almost universally among animal and plant species, most of our current knowledge comes from the classical genetic studies on Drosophila interspecific crosses or introgressions. With the house mouse subspecies Mus m. musculus and Mus m. domesticus as a model, new research tools have become available for studies of the molecular mechanisms and genetic networks underlying HS. Here we used QTL analysis and intersubspecific chromosome substitution strains to identify a 4.7 Mb critical region on Chromosome X (Chr X harboring the Hstx2 HS locus, which causes asymmetrical spermatogenic arrest in reciprocal intersubspecific F1 hybrids. Subsequently, we mapped autosomal loci on Chrs 3, 9 and 13 that can abolish this asymmetry. Combination of immunofluorescent visualization of the proteins of synaptonemal complexes with whole-chromosome DNA FISH on pachytene spreads revealed that heterosubspecific, unlike consubspecific, homologous chromosomes are predisposed to asynapsis in F1 hybrid male and female meiosis. The asynapsis is under the trans- control of Hstx2 and Hst1/Prdm9 hybrid sterility genes in pachynemas of male but not female hybrids. The finding concurred with the fertility of intersubpecific F1 hybrid females homozygous for the Hstx2(Mmm allele and resolved the apparent conflict with the dominance theory of Haldane's rule. We propose that meiotic asynapsis in intersubspecific hybrids is a consequence of cis-acting mismatch between homologous chromosomes modulated by the trans-acting Hstx2 and Prdm9 hybrid male sterility genes.

  19. Superresolution microscopy reveals the three-dimensional organization of meiotic chromosome axes in intactCaenorhabditis eleganstissue.

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    Köhler, Simone; Wojcik, Michal; Xu, Ke; Dernburg, Abby F

    2017-06-13

    When cells enter meiosis, their chromosomes reorganize as linear arrays of chromatin loops anchored to a central axis. Meiotic chromosome axes form a platform for the assembly of the synaptonemal complex (SC) and play central roles in other meiotic processes, including homologous pairing, recombination, and chromosome segregation. However, little is known about the 3D organization of components within the axes, which include cohesin complexes and additional meiosis-specific proteins. Here, we investigate the molecular organization of meiotic chromosome axes in Caenorhabditis elegans through STORM (stochastic optical reconstruction microscopy) and PALM (photo-activated localization microscopy) superresolution imaging of intact germ-line tissue. By tagging one axis protein (HIM-3) with a photoconvertible fluorescent protein, we established a spatial reference for other components, which were localized using antibodies against epitope tags inserted by CRISPR/Cas9 genome editing. Using 3D averaging, we determined the position of all known components within synapsed chromosome axes to high spatial precision in three dimensions. We find that meiosis-specific HORMA domain proteins span a gap between cohesin complexes and the central region of the SC, consistent with their essential roles in SC assembly. Our data further suggest that the two different meiotic cohesin complexes are distinctly arranged within the axes: Although cohesin complexes containing the kleisin REC-8 protrude above and below the plane defined by the SC, complexes containing COH-3 or -4 kleisins form a central core, which may physically separate sister chromatids. This organization may help to explain the role of the chromosome axes in promoting interhomolog repair of meiotic double-strand breaks by inhibiting intersister repair.

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

    NARCIS (Netherlands)

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

    2004-01-01

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

  1. Lack of sex chromosome specific meiotic silencing in platypus reveals origin of MSCI in therian mammals.

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    Daish, Tasman J; Casey, Aaron E; Grutzner, Frank

    2015-12-10

    In therian mammals heteromorphic sex chromosomes are subject to meiotic sex chromosome inactivation (MSCI) during meiotic prophase I while the autosomes maintain transcriptional activity. The evolution of this sex chromosome silencing is thought to result in retroposition of genes required in spermatogenesis from the sex chromosomes to autosomes. In birds sex chromosome specific silencing appears to be absent and global transcriptional reductions occur through pachytene and sex chromosome-derived autosomal retrogenes are lacking. Egg laying monotremes are the most basal mammalian lineage, feature a complex and highly differentiated XY sex chromosome system with homology to the avian sex chromosomes, and also lack autosomal retrogenes. In order to delineate the point of origin of sex chromosome specific silencing in mammals we investigated whether MSCI exists in platypus. Our results show that platypus sex chromosomes display only partial or transient colocalisation with a repressive histone variant linked to therian sex chromosome silencing and surprisingly lack a hallmark MSCI epigenetic signature present in other mammals. Remarkably, platypus instead feature an avian like period of general low level transcription through prophase I with the sex chromosomes and the future mammalian X maintaining association with a nucleolus-like structure. Our work demonstrates for the first time that in mammals meiotic silencing of sex chromosomes evolved after the divergence of monotremes presumably as a result of the differentiation of the therian XY sex chromosomes. We provide a novel evolutionary scenario on how the future therian X chromosome commenced the trajectory toward MSCI.

  2. Mouse BRWD1 is critical for spermatid postmeiotic transcription and female meiotic chromosome stability.

    Science.gov (United States)

    Pattabiraman, Shrivatsav; Baumann, Claudia; Guisado, Daniela; Eppig, John J; Schimenti, John C; De La Fuente, Rabindranath

    2015-01-05

    Postmeiotic gene expression is essential for development and maturation of sperm and eggs. We report that the dual bromodomain-containing protein BRWD1, which is essential for both male and female fertility, promotes haploid spermatid-specific transcription but has distinct roles in oocyte meiotic progression. Brwd1 deficiency caused down-regulation of ∼300 mostly spermatid-specific transcripts in testis, including nearly complete elimination of those encoding the protamines and transition proteins, but was not associated with global epigenetic changes in chromatin, which suggests that BRWD1 acts selectively. In females, Brwd1 ablation caused severe chromosome condensation and structural defects associated with abnormal telomere structure but only minor changes in gene expression at the germinal vesicle stage, including more than twofold overexpression of the histone methyltransferase MLL5 and LINE-1 elements transposons. Thus, loss of BRWD1 function interferes with the completion of oogenesis and spermatogenesis through sexually dimorphic mechanisms: it is essential in females for epigenetic control of meiotic chromosome stability and in males for haploid gene transcription during postmeiotic sperm differentiation. © 2015 Pattabiraman et al.

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

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    Thomas Tischer

    2016-10-01

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

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

    Czech Academy of Sciences Publication Activity Database

    Bhattacharyya, Tanmoy; Reifová, R.; Gregorová, Soňa; Šimeček, Petr; Gergelits, Václav; Mistrik, M.; Martincová, Iva; Piálek, Jaroslav; Forejt, Jiří

    2014-01-01

    Roč. 10, č. 2 (2014), e1004088 ISSN 1553-7404 R&D Projects: GA AV ČR Premium Academiae of the Academy of Sciences of the Czech Republic; GA MŠk(CZ) LD11079; GA ČR GA206/08/0640; GA MŠk ED1.1.00/02.0109 Institutional support: RVO:68081766 ; RVO:68378050 Keywords : hybrid sterility * meiotic asynapsis * chromosome substitution strains Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 8.167, year: 2013

  5. Casein kinase 1 alpha regulates chromosome congression and separation during mouse oocyte meiotic maturation and early embryo development.

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    Lu Wang

    Full Text Available Casein kinase I alpha (CK1α is a member of serine/threonine protein kinase, generally present in all eukaryotes. In mammals, CK1α regulates the transition from interphase to metaphase in mitosis. However, little is known about its role in meiosis. Here we examined Ck1α mRNA and protein expression, as well as its subcellular localization in mouse oocytes from germinal vesicle to the late 1-cell stage. Our results showed that the expression level of CK1α was increased in metaphase. Immunostaining results showed that CK1α colocalized with condensed chromosomes during oocyte meiotic maturation and early embryo development. We used the loss-of-function approach by employing CK1α specific morpholino injection to block the function of CK1α. This functional blocking leads to failure of polar body 1 (PB1 extrusion, chromosome misalignment and MII plate incrassation. We further found that D4476, a specific and efficient CK1 inhibitor, decreased the rate of PB1 extrusion. Moreover, D4476 resulted in giant polar body extrusion, oocyte pro-MI arrest, chromosome congression failure and impairment of embryo developmental potential. In addition, we employed pyrvinium pamoate (PP, an allosteric activator of CK1α, to enhance CK1α activity in oocytes. Supplementation of PP induced oocyte meiotic maturation failure, severe congression abnormalities and misalignment of chromosomes. Taken together, our study for the first time demonstrates that CK1α is required for chromosome alignment and segregation during oocyte meiotic maturation and early embryo development.

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

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    Camila Aparecida de Oliveira dos Reis

    2008-01-01

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

  7. Meiotic chromosome behaviours in M1 generation of bread wheat irradiated by gamma-rays

    International Nuclear Information System (INIS)

    Watanabe, Y.; Takato, S.

    1982-01-01

    Growing plants of bread wheat (Triticum aestivum L. 2 n=6x=42, AABBDD) were subjected to acute or chronic irradiation by gamma-rays from 60Co and meiotic chromosome behaviours of PMCS in M 1 generation were cytologically compared. Both acute and chronic irradiations produced different types of chromosomal aberrations at the meiotic stages. Among them, translocation type was the most frequent, followed by univalent type. A mixed type, i. e. translocation accompanying one or more univalents was often detected. Even normal type which lacked translocation and univalent included laggards and briclges without exception. Other meiotic abnormalities such as deletion, iso-chromosome and micronuclei were observed frequently in both treatments. Dose dependency of translocation frequency was not recognized in this experiment. In chronic irradiation, different chromosome numbers and meiotic behaviours were found not only among florets of a spike but also among anthers of a floret. A number of plants with aneuploid-like grass types occurred at a high frequency in M 1 , especially with low exposure

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

    NARCIS (Netherlands)

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

    2017-01-01

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

  9. Sex chromosome-specific regulation in the Drosophila male germline but little evidence for chromosomal dosage compensation or meiotic inactivation.

    Directory of Open Access Journals (Sweden)

    Colin D Meiklejohn

    2011-08-01

    Full Text Available The evolution of heteromorphic sex chromosomes (e.g., XY in males or ZW in females has repeatedly elicited the evolution of two kinds of chromosome-specific regulation: dosage compensation--the equalization of X chromosome gene expression in males and females--and meiotic sex chromosome inactivation (MSCI--the transcriptional silencing and heterochromatinization of the X during meiosis in the male (or Z in the female germline. How the X chromosome is regulated in the Drosophila melanogaster male germline is unclear. Here we report three new findings concerning gene expression from the X in Drosophila testes. First, X chromosome-wide dosage compensation appears to be absent from most of the Drosophila male germline. Second, microarray analysis provides no evidence for X chromosome-specific inactivation during meiosis. Third, we confirm the previous discovery that the expression of transgene reporters driven by autosomal spermatogenesis-specific promoters is strongly reduced when inserted on the X chromosome versus the autosomes; but we show that this chromosomal difference in expression is established in premeiotic cells and persists in meiotic cells. The magnitude of the X-autosome difference in transgene expression cannot be explained by the absence of dosage compensation, suggesting that a previously unrecognized mechanism limits expression from the X during spermatogenesis in Drosophila. These findings help to resolve several previously conflicting reports and have implications for patterns of genome evolution and speciation in Drosophila.

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

    Energy Technology Data Exchange (ETDEWEB)

    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. (Queen Elizabeth Hospital for Children, London (United Kingdom))

    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.

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

    Science.gov (United States)

    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).

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

    Directory of Open Access Journals (Sweden)

    Rosane Nunes Garcia

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-09-10

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

  14. DNMT3L is a regulator of X chromosome compaction and post-meiotic gene transcription.

    Directory of Open Access Journals (Sweden)

    Natasha M Zamudio

    Full Text Available Previous studies on the epigenetic regulator DNA methyltransferase 3-Like (DNMT3L, have demonstrated it is an essential regulator of paternal imprinting and early male meiosis. Dnmt3L is also a paternal effect gene, i.e., wild type offspring of heterozygous mutant sires display abnormal phenotypes suggesting the inheritance of aberrant epigenetic marks on the paternal chromosomes. In order to reveal the mechanisms underlying these paternal effects, we have assessed X chromosome meiotic compaction, XY chromosome aneuploidy rates and global transcription in meiotic and haploid germ cells from male mice heterozygous for Dnmt3L. XY bodies from Dnmt3L heterozygous males were significantly longer than those from wild types, and were associated with a three-fold increase in XY bearing sperm. Loss of a Dnmt3L allele resulted in deregulated expression of a large number of both X-linked and autosomal genes within meiotic cells, but more prominently in haploid germ cells. Data demonstrate that similar to embryonic stem cells, DNMT3L is involved in an auto-regulatory loop in germ cells wherein the loss of a Dnmt3L allele resulted in increased transcription from the remaining wild type allele. In contrast, however, within round spermatids, this auto-regulatory loop incorporated the alternative non-coding alternative transcripts. Consistent with the mRNA data, we have localized DNMT3L within spermatids and sperm and shown that the loss of a Dnmt3L allele results in a decreased DNMT3L content within sperm. These data demonstrate previously unrecognised roles for DNMT3L in late meiosis and in the transcriptional regulation of meiotic and post-meiotic germ cells. These data provide a potential mechanism for some cases of human Klinefelter's and Turner's syndromes.

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

    African Journals Online (AJOL)

    SERVER

    2007-11-19

    ) are functional and very effective. However, chromosome pairing in the two taxa is incomplete in almost all the seven bivalents in the complement as demonstrated in Figure 2. This lowers the frequency of chiasma formation ...

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

    Directory of Open Access Journals (Sweden)

    Shaun Patrick Murphy

    2014-07-01

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

  17. The chromosomal basis of meiotic acentrosomal spindle assembly and function in oocytes.

    Science.gov (United States)

    Radford, Sarah J; Nguyen, Alexandra L; Schindler, Karen; McKim, Kim S

    2017-06-01

    Several aspects of meiosis are impacted by the absence of centrosomes in oocytes. Here, we review four aspects of meiosis I that are significantly affected by the absence of centrosomes in oocyte spindles. One, microtubules tend to assemble around the chromosomes. Two, the organization of these microtubules into a bipolar spindle is directed by the chromosomes. Three, chromosome bi-orientation and attachment to microtubules from the correct pole require modification of the mechanisms used in mitotic cells. Four, chromosome movement to the poles at anaphase cannot rely on polar anchoring of spindle microtubules by centrosomes. Overall, the chromosomes are more active participants during acentrosomal spindle assembly in oocytes, compared to mitotic and male meiotic divisions where centrosomes are present. The chromosomes are endowed with information that can direct the meiotic divisions and dictate their own behavior in oocytes. Processes beyond those known from mitosis appear to be required for their bi-orientation at meiosis I. As mitosis occurs without centrosomes in many systems other than oocytes, including all plants, the concepts discussed here may not be limited to oocytes. The study of meiosis in oocytes has revealed mechanisms that are operating in mitosis and will probably continue to do so.

  18. Genomic analysis of plant chromosomes based on meiotic pairing

    Directory of Open Access Journals (Sweden)

    Lisete Chamma Davide

    2007-12-01

    Full Text Available This review presents the principles and applications of classical genomic analysis, with emphasis on plant breeding. The main mathematical models used to estimate the preferential chromosome pairing in diploid or polyploid, interspecific or intergenera hybrids are presented and discussed, with special reference to the applications and studies for the definition of genome relationships among species of the Poaceae family.

  19. Chromosome number and meiotic behaviour in Brachiaria jubata ...

    Indian Academy of Sciences (India)

    (f) Metaphase II with precocious chromosome migration to the poles. (g) Late anaphase II with laggard. (h). Tetrad with micronuclei in one microspore. (i) Fertile (dark) and sterile pollen grains (400×). The risks associated with extensive Brachiaria monocul- ture in Brazil are obvious. The two most cultivated vari- eties in the ...

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

    Directory of Open Access Journals (Sweden)

    Olivier J Becherel

    2013-04-01

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

  1. Distinct TERB1 Domains Regulate Different Protein Interactions in Meiotic Telomere Movement

    Directory of Open Access Journals (Sweden)

    Jingjing Zhang

    2017-11-01

    Full Text Available Meiotic telomeres attach to the nuclear envelope (NE and drive the chromosome movement required for the pairing of homologous chromosomes. The meiosis-specific telomere proteins TERB1, TERB2, and MAJIN are required to regulate these events, but their assembly processes are largely unknown. Here, we developed a germ-cell-specific knockout mouse of the canonical telomere-binding protein TRF1 and revealed an essential role for TRF1 in directing the assembly of TERB1-TERB2-MAJIN. Further, we identified a TERB2 binding (T2B domain in TERB1 that is dispensable for the TRF1-TERB1 interaction but is essential for the subsequent TERB1-TERB2 interaction and therefore for telomere attachment to the NE. Meanwhile, cohesin recruitment at telomeres, which is required for efficient telomere movement, is mediated by the MYB-like domain of TERB1, but not by TERB2-MAJIN. Our results reveal distinct protein interactions through various domains of TERB1, which enable the sequential assembly of the meiotic telomere complex for their movements.

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

    Science.gov (United States)

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

    2017-10-05

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

  3. Matefin/SUN-1 phosphorylation is part of a surveillance mechanism to coordinate chromosome synapsis and recombination with meiotic progression and chromosome movement.

    Directory of Open Access Journals (Sweden)

    Alexander Woglar

    Full Text Available Faithful chromosome segregation during meiosis I depends on the establishment of a crossover between homologous chromosomes. This requires induction of DNA double-strand breaks (DSBs, alignment of homologs, homolog association by synapsis, and repair of DSBs via homologous recombination. The success of these events requires coordination between chromosomal events and meiotic progression. The conserved SUN/KASH nuclear envelope bridge establishes transient linkages between chromosome ends and cytoskeletal forces during meiosis. In Caenorhabditis elegans, this bridge is essential for bringing homologs together and preventing nonhomologous synapsis. Chromosome movement takes place during synapsis and recombination. Concomitant with the onset of chromosome movement, SUN-1 clusters at chromosome ends associated with the nuclear envelope, and it is phosphorylated in a chk-2- and plk-2-dependent manner. Identification of all SUN-1 phosphomodifications at its nuclear N terminus allowed us to address their role in prophase I. Failures in recombination and synapsis led to persistent phosphorylations, which are required to elicit a delay in progression. Unfinished meiotic tasks elicited sustained recruitment of PLK-2 to chromosome ends in a SUN-1 phosphorylation-dependent manner that is required for continued chromosome movement and characteristic of a zygotene arrest. Furthermore, SUN-1 phosphorylation supported efficient synapsis. We propose that signals emanating from a failure to successfully finish meiotic tasks are integrated at the nuclear periphery to regulate chromosome end-led movement and meiotic progression. The single unsynapsed X chromosome in male meiosis is precluded from inducing a progression delay, and we found it was devoid of a population of phosphorylated SUN-1. This suggests that SUN-1 phosphorylation is critical to delaying meiosis in response to perturbed synapsis. SUN-1 may be an integral part of a checkpoint system to monitor

  4. Meiotic HORMA domain proteins prevent untimely centriole disengagement during Caenorhabditis elegans spermatocyte meiosis.

    Science.gov (United States)

    Schvarzstein, Mara; Pattabiraman, Divya; Bembenek, Joshua N; Villeneuve, Anne M

    2013-03-05

    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.

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

    Science.gov (United States)

    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.

  6. Meiotic abnormalities

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1993-12-31

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

  7. Cohesin Removal along the Chromosome Arms during the First Meiotic Division Depends on a NEK1-PP1γ-WAPL Axis in the Mouse

    Directory of Open Access Journals (Sweden)

    Miguel A. Brieño-Enríquez

    2016-10-01

    Full Text Available Mammalian NIMA-like kinase-1 (NEK1 is a dual-specificity kinase highly expressed in mouse germ cells during prophase I of meiosis. Loss of NEK1 induces retention of cohesin on chromosomes at meiotic prophase I. Timely deposition and removal of cohesin is essential for accurate chromosome segregation. Two processes regulate cohesin removal: a non-proteolytic mechanism involving WAPL, sororin, and PDS5B and direct cleavage by separase. Here, we demonstrate a role for NEK1 in the regulation of WAPL loading during meiotic prophase I, via an interaction between NEK1 and PDS5B. This regulation of WAPL by NEK1-PDS5B is mediated by protein phosphatase 1 gamma (PP1γ, which both interacts with and is a phosphotarget of NEK1. Taken together, our results reveal that NEK1 phosphorylates PP1γ, leading to the dephosphorylation of WAPL, which, in turn, results in its retention on chromosome cores to promote loss of cohesion at the end of prophase I in mammals.

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

    Directory of Open Access Journals (Sweden)

    Ye Hong

    2016-03-01

    Full Text Available Meiotic recombination is essential for the repair of programmed double strand breaks (DSBs to generate crossovers (COs during meiosis. The efficient processing of meiotic recombination intermediates not only needs various resolvases but also requires proper meiotic chromosome structure. The Smc5/6 complex belongs to the structural maintenance of chromosome (SMC family and is closely related to cohesin and condensin. Although the Smc5/6 complex has been implicated in the processing of recombination intermediates during meiosis, it is not known how Smc5/6 controls meiotic DSB repair. Here, using Caenorhabditis elegans we show that the SMC-5/6 complex acts synergistically with HIM-6, an ortholog of the human Bloom syndrome helicase (BLM during meiotic recombination. The concerted action of the SMC-5/6 complex and HIM-6 is important for processing recombination intermediates, CO regulation and bivalent maturation. Careful examination of meiotic chromosomal morphology reveals an accumulation of inter-chromosomal bridges in smc-5; him-6 double mutants, leading to compromised chromosome segregation during meiotic cell divisions. Interestingly, we found that the lethality of smc-5; him-6 can be rescued by loss of the conserved BRCA1 ortholog BRC-1. Furthermore, the combined deletion of smc-5 and him-6 leads to an irregular distribution of condensin and to chromosome decondensation defects reminiscent of condensin depletion. Lethality conferred by condensin depletion can also be rescued by BRC-1 depletion. Our results suggest that SMC-5/6 and HIM-6 can synergistically regulate recombination intermediate metabolism and suppress ectopic recombination by controlling chromosome architecture during meiosis.

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

    Directory of Open Access Journals (Sweden)

    Jay Pyle

    2016-08-01

    Full Text Available 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.

  10. Meioc maintains an extended meiotic prophase I in mice.

    Science.gov (United States)

    Soh, Y Q Shirleen; Mikedis, Maria M; Kojima, Mina; Godfrey, Alexander K; de Rooij, Dirk G; Page, David C

    2017-04-01

    The meiosis-specific chromosomal events of homolog pairing, synapsis, and recombination occur over an extended meiotic prophase I that is many times longer than prophase of mitosis. Here we show that, in mice, maintenance of an extended meiotic prophase I requires the gene Meioc, a germ-cell specific factor conserved in most metazoans. In mice, Meioc is expressed in male and female germ cells upon initiation of and throughout meiotic prophase I. Mouse germ cells lacking Meioc initiate meiosis: they undergo pre-meiotic DNA replication, they express proteins involved in synapsis and recombination, and a subset of cells progress as far as the zygotene stage of prophase I. However, cells in early meiotic prophase-as early as the preleptotene stage-proceed to condense their chromosomes and assemble a spindle, as if having progressed to metaphase. Meioc-deficient spermatocytes that have initiated synapsis mis-express CYCLIN A2, which is normally expressed in mitotic spermatogonia, suggesting a failure to properly transition to a meiotic cell cycle program. MEIOC interacts with YTHDC2, and the two proteins pull-down an overlapping set of mitosis-associated transcripts. We conclude that when the meiotic chromosomal program is initiated, Meioc is simultaneously induced so as to extend meiotic prophase. Specifically, MEIOC, together with YTHDC2, promotes a meiotic (as opposed to mitotic) cell cycle program via post-transcriptional control of their target transcripts.

  11. MAPK-activated protein kinase 2 is required for mouse meiotic spindle assembly and kinetochore-microtubule attachment.

    Directory of Open Access Journals (Sweden)

    Ju Yuan

    Full Text Available MAPK-activated protein kinase 2 (MK2, a direct substrate of p38 MAPK, plays key roles in multiple physiological functions in mitosis. Here, we show for the first time the unique distribution pattern of MK2 in meiosis. Phospho-MK2 was localized on bipolar spindle minus ends and along the interstitial axes of homologous chromosomes extending over centromere regions and arm regions at metaphase of first meiosis (MI stage in mouse oocytes. At metaphase of second meiosis (MII stage, p-MK2 was localized on the bipolar spindle minus ends and at the inner centromere region of sister chromatids as dots. Knockdown or inhibition of MK2 resulted in spindle defects. Spindles were surrounded by irregular nondisjunction chromosomes, which were arranged in an amphitelic or syntelic/monotelic manner, or chromosomes detached from the spindles. Kinetochore-microtubule attachments were impaired in MK2-deficient oocytes because spindle microtubules became unstable in response to cold treatment. In addition, homologous chromosome segregation and meiosis progression were inhibited in these oocytes. Our data suggest that MK2 may be essential for functional meiotic bipolar spindle formation, chromosome segregation and proper kinetochore-microtubule attachments.

  12. Assignment of the human gene for pregnancy-associated plasma protein A (PAPPA) to 9q33.1 by fluorescence in situ hybridization to mitotic and meiotic chromosomes

    DEFF Research Database (Denmark)

    Silahtaroglu, A N; Tümer, Z; Kristensen, Torsten

    1993-01-01

    Low levels of pregnancy-associated plasma protein A (PAPPA) during the first trimester has been suggested as a biochemical indicator of pregnancies with aneuploid fetuses. Furthermore, the complete absence of PAPPA in pregnancies associated with Cornelia de Lange syndrome (CL) has suggested...

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

    Directory of Open Access Journals (Sweden)

    Zenzes Maria

    2004-09-01

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

  14. Error-prone ZW pairing and no evidence for meiotic sex chromosome inactivation in the chicken germ line.

    Directory of Open Access Journals (Sweden)

    Silvana Guioli

    Full Text Available In the male mouse the X and Y chromosomes pair and recombine within the small pseudoautosomal region. Genes located on the unsynapsed segments of the X and Y are transcriptionally silenced at pachytene by Meiotic Sex Chromosome Inactivation (MSCI. The degree to which MSCI is conserved in other vertebrates is currently unclear. In the female chicken the ZW bivalent is thought to undergo a transient phase of full synapsis at pachytene, starting from the homologous ends and spreading through the heterologous regions. It has been proposed that the repair of the ZW DNA double-strand breaks (DSBs is postponed until diplotene and that the ZW bivalent is subject to MSCI, which is independent of its synaptic status. Here we present a distinct model of meiotic pairing and silencing of the ZW pair during chicken oogenesis. We show that, in most oocytes, DNA DSB foci on the ZW are resolved by the end of pachytene and that the ZW desynapses in broad synchrony with the autosomes. We unexpectedly find that ZW pairing is highly error prone, with many oocytes failing to engage in ZW synapsis and crossover formation. Oocytes with unsynapsed Z and W chromosomes nevertheless progress to the diplotene stage, suggesting that a checkpoint does not operate during pachytene in the chicken germ line. Using a combination of epigenetic profiling and RNA-FISH analysis, we find no evidence for MSCI, associated with neither the asynaptic ZW, as described in mammals, nor the synaptic ZW. The lack of conservation of MSCI in the chicken reopens the debate about the evolution of MSCI and its driving forces.

  15. A Link between Meiotic Prophase Progression and CrossoverControl

    Energy Technology Data Exchange (ETDEWEB)

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

    2005-07-06

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

  16. Physical mapping of the Period gene on meiotic chromosomes of South American grasshoppers (Acridomorpha, Orthoptera).

    Science.gov (United States)

    Souza, T E; Oliveira, D L; Santos, J F; Rieger, T T

    2014-12-19

    The single-copy gene Period was located in five grasshopper species belonging to the Acridomorpha group through permanent in situ hybridization (PISH). The mapping revealed one copy of this gene in the L1 chromosome pair in Ommexecha virens, Xyleus discoideus angulatus, Tropidacris collaris, Schistocerca pallens, and Stiphra robusta. A possible second copy was mapped on the L2 chromosome pair in S. robusta, which should be confirmed by further studies. Except for the latter case, the chromosomal position of the Period gene was highly conserved among the four families studied. The S. robusta karyotype also differs from the others both in chromosome number and morphology. The position conservation of the single-copy gene Period contrasts with the location diversification of multigene families in these species. The localization of single-copy genes by PISH can provide new insights about the genomic content and chromosomal evolution of grasshoppers and others insects.

  17. A Family of Zinc Finger Proteins Is Required forChromosome-specific Pairing and Synapsis during Meiosis in C.elegans

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, Carolyn M.; Dernburg, Abby F.

    2006-06-07

    Homologous chromosome pairing and synapsis are prerequisitefor accurate chromosome segregation during meiosis. Here, we show that afamily of four related C2H2 zinc-finger proteins plays a central role inthese events in C. elegans. These proteins are encoded within a tandemgene cluster. In addition to the X-specific HIM-8 protein, threeadditional paralogs collectively mediate the behavior of the fiveautosomes. Each chromosome relies on a specific member of the family topair and synapse with its homolog. These "ZIM" proteins concentrate atspecial regions called meiotic pairing centers on the correspondingchromosomes. These sites are dispersed along the nuclear envelope duringearly meiotic prophase, suggesting a role analogous to thetelomere-mediated meiotic bouquet in other organisms. To gain insightinto the evolution of these components, wecharacterized homologs in C.briggsae and C. remanei, which revealed changes in copy number of thisgene family within the nematode lineage.

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

    Science.gov (United States)

    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.

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

    Indian Academy of Sciences (India)

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

  20. Protein tyrosine phosphorylation during meiotic divisions of starfish oocytes

    Energy Technology Data Exchange (ETDEWEB)

    Peaucellier, G.; Andersen, A.C.; Kinsey, W.H. (Univ. of Miami School of Medicine, FL (USA))

    1990-04-01

    We have used an antibody specific for phosphotyrosine to investigate protein phosphorylation on tyrosine during hormone-induced maturation of starfish oocytes. Analysis of immunoprecipitates from cortices of in vivo labeled Marthasterias glacialis oocytes revealed the presence of labeled phosphotyrosine-containing proteins only after hormone addition. Six major phosphoproteins of 195, 155, 100, 85, 45, and 35 kDa were detected. Total activity in immunoprecipitates increased until first polar body emission and was greatly reduced upon completion of meiosis but some proteins exhibited different kinetics. The labeling of the 155-kDa protein reached a maximum at germinal vesicle breakdown, while the 35-kDa appeared later and disappeared after polar body emission. Similar results were obtained with Asterias rubens oocytes. In vitro phosphorylation of cortices showed that tyrosine kinase activity is a major protein kinase activity in this fraction, the main endogenous substrate being a 68-kDa protein. The proteins phosphorylated on tyrosine in vitro were almost similar in extracts from oocytes treated or not with the hormone.

  1. The C. elegans DSB-2 protein reveals a regulatory network that controls competence for meiotic DSB formation and promotes crossover assurance.

    Directory of Open Access Journals (Sweden)

    Simona Rosu

    Full Text Available For most organisms, chromosome segregation during meiosis relies on deliberate induction of DNA double-strand breaks (DSBs and repair of a subset of these DSBs as inter-homolog crossovers (COs. However, timing and levels of DSB formation must be tightly controlled to avoid jeopardizing genome integrity. Here we identify the DSB-2 protein, which is required for efficient DSB formation during C. elegans meiosis but is dispensable for later steps of meiotic recombination. DSB-2 localizes to chromatin during the time of DSB formation, and its disappearance coincides with a decline in RAD-51 foci marking early recombination intermediates and precedes appearance of COSA-1 foci marking CO-designated sites. These and other data suggest that DSB-2 and its paralog DSB-1 promote competence for DSB formation. Further, immunofluorescence analyses of wild-type gonads and various meiotic mutants reveal that association of DSB-2 with chromatin is coordinated with multiple distinct aspects of the meiotic program, including the phosphorylation state of nuclear envelope protein SUN-1 and dependence on RAD-50 to load the RAD-51 recombinase at DSB sites. Moreover, association of DSB-2 with chromatin is prolonged in mutants impaired for either DSB formation or formation of downstream CO intermediates. These and other data suggest that association of DSB-2 with chromatin is an indicator of competence for DSB formation, and that cells respond to a deficit of CO-competent recombination intermediates by prolonging the DSB-competent state. In the context of this model, we propose that formation of sufficient CO-competent intermediates engages a negative feedback response that leads to cessation of DSB formation as part of a major coordinated transition in meiotic prophase progression. The proposed negative feedback regulation of DSB formation simultaneously (1 ensures that sufficient DSBs are made to guarantee CO formation and (2 prevents excessive DSB levels that could

  2. Multiple sex chromosomes in the light of female meiotic drive in amniote vertebrates

    Czech Academy of Sciences Publication Activity Database

    Pokorná, Martina; Altmanová, M.; Kratochvíl, L.

    2014-01-01

    Roč. 22, č. 1 (2014), s. 35-44 ISSN 0967-3849 R&D Projects: GA ČR GAP506/10/0718 Institutional support: RVO:67985904 Keywords : amniota * centromere * heterogamety * neo-sex chromosomes * reptiles Subject RIV: EG - Zoology Impact factor: 2.478, year: 2014

  3. Meiotic behaviour of individual chromosomes of Festuca pratensis in tetraploid Lolium multiflorum

    Czech Academy of Sciences Publication Activity Database

    Kopecký, David; Lukaszewski, A.J.; Doležel, Jaroslav

    2008-01-01

    Roč. 16, č. 7 (2008), s. 987-998 ISSN 0967-3849 R&D Projects: GA ČR GP521/07/P479 Institutional research plan: CEZ:AV0Z50380511 Keywords : Chromosome pairing * Festuca * Lolium Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.405, year: 2008

  4. The B chromosome in the meiotic process of the African pest ...

    African Journals Online (AJOL)

    This paper presents the first record of B chromosomes in some adult male individuals of the African pest grasshopper Taphronota thaelephora collected from Balepa – Mbouda in the Western Province of Cameroon. Of the twenty individuals examined, thirteen had the characteristic Pyrgomorphidae karyotype of 2N= ...

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

    Energy Technology Data Exchange (ETDEWEB)

    Shashi, V.; Allinson, P.S.; Golden, W.L.; Kelly, T.E. [Univ. of Virginia, Charlottesville, VA (United States)

    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. Cytological evidence of chromosomal rearrangement in the second meiotic division after exposure to X-rays

    International Nuclear Information System (INIS)

    Szemere, G.

    1982-01-01

    Metaphase II cells with unequal dyad-arms and obvious X/autosomal rearrangements were found after an exposure to X-rays (2 Gy) of male mice at different stages of meiosis (pachytene, diplotene and diakinesis) with a frequency of 0.2, 1.26 and 0.6%, respectively, giving a direct cytological evidence of structural chromosomal rearrangements in metaphase II cells, partly with autosomal and partly with X/autosomal partners. (author)

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

    Directory of Open Access Journals (Sweden)

    Valentina Kuznetsova

    2013-11-01

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

  8. Meiotic cohesin REC8 marks the axial elements of rat synaptonemal complexes before cohesins SMC1B and SMC3

    NARCIS (Netherlands)

    Eijpe, M.; Offenberg, H.H.; Jessberger, R.; Revenkova, E.; Heyting, C.

    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

  9. Solution structure and DNA-binding properties of the winged helix domain of the meiotic recombination HOP2 protein.

    Science.gov (United States)

    Moktan, Hem; Guiraldelli, Michel F; Eyster, Craig A; Zhao, Weixing; Lee, Chih-Ying; Mather, Timothy; Camerini-Otero, R Daniel; Sung, Patrick; Zhou, Donghua H; Pezza, Roberto J

    2014-05-23

    The HOP2 protein is required for efficient double-strand break repair which ensures the proper synapsis of homologous chromosomes and normal meiotic progression. We previously showed that in vitro HOP2 shows two distinctive activities: when it is incorporated into a HOP2-MND1 heterodimer, it stimulates DMC1 and RAD51 recombination activities, and the purified HOP2 alone is proficient in promoting strand invasion. The structural and biochemical basis of HOP2 action in recombination are poorly understood; therefore, they are the focus of this work. Herein, we present the solution structure of the amino-terminal portion of mouse HOP2, which contains a typical winged helix DNA-binding domain. Together with NMR spectral changes in the presence of double-stranded DNA, protein docking on DNA, and mutation analysis to identify the amino acids involved in DNA coordination, our results on the three-dimensional structure of HOP2 provide key information on the fundamental structural and biochemical requirements directing the interaction of HOP2 with DNA. These results, in combination with mutational experiments showing the role of a coiled-coil structural feature involved in HOP2 self-association, allow us to explain important aspects of the function of HOP2 in recombination. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

  10. Solution Structure and DNA-binding Properties of the Winged Helix Domain of the Meiotic Recombination HOP2 Protein*

    Science.gov (United States)

    Moktan, Hem; Guiraldelli, Michel F.; Eyster, Craig A.; Zhao, Weixing; Lee, Chih-Ying; Mather, Timothy; Camerini-Otero, R. Daniel; Sung, Patrick; Zhou, Donghua H.; Pezza, Roberto J.

    2014-01-01

    The HOP2 protein is required for efficient double-strand break repair which ensures the proper synapsis of homologous chromosomes and normal meiotic progression. We previously showed that in vitro HOP2 shows two distinctive activities: when it is incorporated into a HOP2-MND1 heterodimer, it stimulates DMC1 and RAD51 recombination activities, and the purified HOP2 alone is proficient in promoting strand invasion. The structural and biochemical basis of HOP2 action in recombination are poorly understood; therefore, they are the focus of this work. Herein, we present the solution structure of the amino-terminal portion of mouse HOP2, which contains a typical winged helix DNA-binding domain. Together with NMR spectral changes in the presence of double-stranded DNA, protein docking on DNA, and mutation analysis to identify the amino acids involved in DNA coordination, our results on the three-dimensional structure of HOP2 provide key information on the fundamental structural and biochemical requirements directing the interaction of HOP2 with DNA. These results, in combination with mutational experiments showing the role of a coiled-coil structural feature involved in HOP2 self-association, allow us to explain important aspects of the function of HOP2 in recombination. PMID:24711446

  11. The meiotic consequences of chromosomal aberrations induced by separate and simultaneous applications of gamma rays and NMU in lentil (Lens culinaris Med.)

    International Nuclear Information System (INIS)

    Dixit, Pratibha; Dubey, D.K.

    1983-01-01

    Certain meiotic abnormalities were induced by the application of 5, 10 or 15 Kr of gamma rays and/or 0.02 percent of NMU on seeds of lentil (Lens culinaris Med.) var. T36. Univalents, quadrivalents or higher multivalent associations were induced by gamma rays individually or in combination with NMU, while no such associations were recorded in plants treated with NMU alone. But nucleolar fragmentation, chromatin bridges and non-orientation of chromosome fragments were induced by both the mutagens. The percentage of cells showing meiotic abnormalities in the gamma ray treatments increased with an increase in the irradiation dose, however, the combined treatments of the two mutagens did not show a synergestic influence of the two mutagens in inducing such abnormalities. (author)

  12. Experimental population genetics of meiotic drive systems. I. Pseudo-Y chromosomal drive as a means of eliminating cage populations of Drosophila melanogaster

    International Nuclear Information System (INIS)

    Lyttle, T.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

  13. Meiotic and mitotic behaviour of a ring/deleted chromosome 22 in human embryos determined by preimplantation genetic diagnosis for a maternal carrier

    Directory of Open Access Journals (Sweden)

    Laver Sarah

    2009-01-01

    Full Text Available Abstract Background Ring chromosomes are normally associated with developmental anomalies and are rarely inherited. An exception to this rule is provided by deletion/ring cases. We were provided with a unique opportunity to investigate the meiotic segregation at oogenesis in a woman who is a carrier of a deleted/ring 22 chromosome. The couple requested preimplantation genetic diagnosis (PGD following the birth of a son with a mosaic karyotype. The couple underwent two cycles of PGD. Studies were performed on lymphocytes, single embryonic cells removed from 3 day-old embryos and un-transferred embryos. Analysis was carried out using fluorescence in situ hybridisation (FISH with specific probe sets in two rounds of hybridization. Results In total, 12 embryos were biopsied, and follow up information was obtained for 10 embryos. No embryos were completely normal or balanced for chromosome 22 by day 5. There was only one embryo diagnosed as balanced of 12 biopsied but that accumulated postzygotic errors by day 5. Three oocytes apparently had a balanced chromosome 22 complement but all had the deleted and the ring 22 and not the intact chromosome 22. After fertilisation all the embryos accumulated postzygotic errors for chromosome 22. Conclusion The study of the preimplantation embryos in this case provided a rare and significant chance to study and understand the phenomena associated with this unusual type of anomaly during meiosis and in the earliest stages of development. It is the first reported PGD attempt for a ring chromosome abnormality.

  14. Leptotene/zygotene chromosome movement via the SUN/KASH protein bridge in Caenorhabditis elegans.

    Science.gov (United States)

    Baudrimont, Antoine; Penkner, Alexandra; Woglar, Alexander; Machacek, Thomas; Wegrostek, Christina; Gloggnitzer, Jiradet; Fridkin, Alexandra; Klein, Franz; Gruenbaum, Yosef; Pasierbek, Pawel; Jantsch, Verena

    2010-11-24

    The Caenorhabditis elegans inner nuclear envelope protein matefin/SUN-1 plays a conserved, pivotal role in the process of genome haploidization. CHK-2-dependent phosphorylation of SUN-1 regulates homologous chromosome pairing and interhomolog recombination in Caenorhabditis elegans. Using time-lapse microscopy, we characterized the movement of matefin/SUN-1::GFP aggregates (the equivalent of chromosomal attachment plaques) and showed that the dynamics of matefin/SUN-1 aggregates remained unchanged throughout leptonene/zygotene, despite the progression of pairing. Movement of SUN-1 aggregates correlated with chromatin polarization. We also analyzed the requirements for the formation of movement-competent matefin/SUN-1 aggregates in the context of chromosome structure and found that chromosome axes were required to produce wild-type numbers of attachment plaques. Abrogation of synapsis led to a deceleration of SUN-1 aggregate movement. Analysis of matefin/SUN-1 in a double-strand break deficient mutant revealed that repair intermediates influenced matefin/SUN-1 aggregate dynamics. Investigation of movement in meiotic regulator mutants substantiated that proper orchestration of the meiotic program and effective repair of DNA double-strand breaks were necessary for the wild-type behavior of matefin/SUN-1 aggregates.

  15. A Gene Regulatory Program for Meiotic Prophase in the Fetal Ovary.

    Directory of Open Access Journals (Sweden)

    Y Q Shirleen Soh

    2015-09-01

    Full Text Available The chromosomal program of meiotic prophase, comprising events such as laying down of meiotic cohesins, synapsis between homologs, and homologous recombination, must be preceded and enabled by the regulated induction of meiotic prophase genes. This gene regulatory program is poorly understood, particularly in organisms with a segregated germline. We characterized the gene regulatory program of meiotic prophase as it occurs in the mouse fetal ovary. By profiling gene expression in the mouse fetal ovary in mutants with whole tissue and single-cell techniques, we identified 104 genes expressed specifically in pre-meiotic to pachytene germ cells. We characterized the regulation of these genes by 1 retinoic acid (RA, which induces meiosis, 2 Dazl, which is required for germ cell competence to respond to RA, and 3 Stra8, a downstream target of RA required for the chromosomal program of meiotic prophase. Initial induction of practically all identified meiotic prophase genes requires Dazl. In the presence of Dazl, RA induces at least two pathways: one Stra8-independent, and one Stra8-dependent. Genes vary in their induction by Stra8, spanning fully Stra8-independent, partially Stra8-independent, and fully Stra8-dependent. Thus, Stra8 regulates the entirety of the chromosomal program but plays a more nuanced role in governing the gene expression program. We propose that Stra8-independent gene expression enables the stockpiling of selected meiotic structural proteins prior to the commencement of the chromosomal program. Unexpectedly, we discovered that Stra8 is required for prompt down-regulation of itself and Rec8. Germ cells that have expressed and down-regulated Stra8 are refractory to further Stra8 expression. Negative feedback of Stra8, and subsequent resistance to further Stra8 expression, may ensure a single, restricted pulse of Stra8 expression. Collectively, our findings reveal a gene regulatory logic by which germ cells prepare for the

  16. Meiotic pairing of B chromosomes, multiple sexual system, and Robertsonian fusion in the red brocket deer Mazama americana (Mammalia, Cervidae).

    Science.gov (United States)

    Aquino, C I; Abril, V V; Duarte, J M B

    2013-09-13

    Deer species of the genus Mazama show significant inter- and intraspecific chromosomal variation due to the occurrence of rearrangements and B chromosomes. Given that carriers of aneuploidies and structural rearrangements often show anomalous chromosome pairings, we here performed a synaptonemal complex analysis to study chromosome pairing behavior in a red brocket deer (Mazama americana) individual that is heterozygous for a Robertsonian translocation, is a B chromosome carrier, and has a multiple sex chromosome system (XY₁Y₂). The synaptonemal complex in spermatocytes showed normal chromosome pairings for all chromosomes, including the autosomal and sex trivalents. The electromicrographs showed homology among B chromosomes since they formed bivalents, but they also appeared as univalents, indicating their anomalous behavior and non-Mendelian segregation. Thus, synaptonemal complex analysis is a useful tool to evaluate the role of B chromosomes and rearrangements during meiosis on the intraspecific chromosomal variation that is observed in the majority of Mazama species.

  17. Meiotic pairing of B chromosomes, multiple sexual system, and Robertsonian fusion in the red brocket deer Mazama americana (Mammalia, Cervidae)

    OpenAIRE

    Aquino, C. I. [UNESP; Abril, V. V. [UNESP; Duarte, J. M B [UNESP

    2013-01-01

    Deer species of the genus Mazama show significant inter and intraspecific chromosomal variation due to the occurrence of rearrangements and B chromosomes. Given that carriers of aneuploidies and structural rearrangements often show anomalous chromosome pairings, we here performed a synaptonemal complex analysis to study chromosome pairing behavior in a red brocket deer (Mazama americana) individual that is heterozygous for a Robertsonian translocation, is a B chromosome carrier, and has a mul...

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

    Energy Technology Data Exchange (ETDEWEB)

    Mohandas, T.K.; Passage, M.B.; Yen, P.H.; Speed, R.M.; Chandley, A.C.; Shapiro, L.J. (Univ. of California, San Francisco, CA (United States))

    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.

  19. Stage-specific expression profiling of Drosophila spermatogenesis suggests that meiotic sex chromosome inactivation drives genomic relocation of testis-expressed genes.

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    Maria D Vibranovski

    2009-11-01

    Full Text Available In Drosophila, genes expressed in males tend to accumulate on autosomes and are underrepresented on the X chromosome. In particular, genes expressed in testis have been observed to frequently relocate from the X chromosome to the autosomes. The inactivation of X-linked genes during male meiosis (i.e., meiotic sex chromosome inactivation-MSCI was first proposed to explain male sterility caused by X-autosomal translocation in Drosophila, and more recently it was suggested that MSCI might provide the conditions under which selection would favor the accumulation of testis-expressed genes on autosomes. In order to investigate the impact of MSCI on Drosophila testis-expressed genes, we performed a global gene expression analysis of the three major phases of D. melanogaster spermatogenesis: mitosis, meiosis, and post-meiosis. First, we found evidence supporting the existence of MSCI by comparing the expression levels of X- and autosome-linked genes, finding the former to be significantly reduced in meiosis. Second, we observed that the paucity of X-linked testis-expressed genes was restricted to those genes highly expressed in meiosis. Third, we found that autosomal genes relocated through retroposition from the X chromosome were more often highly expressed in meiosis in contrast to their X-linked parents. These results suggest MSCI as a general mechanism affecting the evolution of some testis-expressed genes.

  20. Chromosome movements promoted by the mitochondrial protein SPD-3 are required for homology search during Caenorhabditis elegans meiosis.

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    Leticia Labrador

    2013-05-01

    Full Text Available Pairing of homologous chromosomes during early meiosis is essential to prevent the formation of aneuploid gametes. Chromosome pairing includes a step of homology search followed by the stabilization of homolog interactions by the synaptonemal complex (SC. These events coincide with dramatic changes in nuclear organization and rapid chromosome movements that depend on cytoskeletal motors and are mediated by SUN-domain proteins on the nuclear envelope, but how chromosome mobility contributes to the pairing process remains poorly understood. We show that defects in the mitochondria-localizing protein SPD-3 cause a defect in homolog pairing without impairing nuclear reorganization or SC assembly, which results in promiscuous installation of the SC between non-homologous chromosomes. Preventing SC assembly in spd-3 mutants does not improve homolog pairing, demonstrating that SPD-3 is required for homology search at the start of meiosis. Pairing center regions localize to SUN-1 aggregates at meiosis onset in spd-3 mutants; and pairing-promoting proteins, including cytoskeletal motors and polo-like kinase 2, are normally recruited to the nuclear envelope. However, quantitative analysis of SUN-1 aggregate movement in spd-3 mutants demonstrates a clear reduction in mobility, although this defect is not as severe as that seen in sun-1(jf18 mutants, which also show a stronger pairing defect, suggesting a correlation between chromosome-end mobility and the efficiency of pairing. SUN-1 aggregate movement is also impaired following inhibition of mitochondrial respiration or dynein knockdown, suggesting that mitochondrial function is required for motor-driven SUN-1 movement. The reduced chromosome-end mobility of spd-3 mutants impairs coupling of SC assembly to homology recognition and causes a delay in meiotic progression mediated by HORMA-domain protein HTP-1. Our work reveals how chromosome mobility impacts the different early meiotic events that promote

  1. The Smc5-Smc6 complex is required to remove chromosome junctions in meiosis.

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    Sarah Farmer

    Full Text Available Meiosis, a specialized cell division with a single cycle of DNA replication round and two consecutive rounds of nuclear segregation, allows for the exchange of genetic material between parental chromosomes and the formation of haploid gametes. The structural maintenance of chromosome (SMC proteins aid manipulation of chromosome structures inside cells. Eukaryotic SMC complexes include cohesin, condensin and the Smc5-Smc6 complex. Meiotic roles have been discovered for cohesin and condensin. However, although Smc5-Smc6 is known to be required for successful meiotic divisions, the meiotic functions of the complex are not well understood. Here we show that the Smc5-Smc6 complex localizes to specific chromosome regions during meiotic prophase I. We report that meiotic cells lacking Smc5-Smc6 undergo catastrophic meiotic divisions as a consequence of unresolved linkages between chromosomes. Surprisingly, meiotic segregation defects are not rescued by abrogation of Spo11-induced meiotic recombination, indicating that at least some chromosome linkages in smc5-smc6 mutants originate from other cellular processes. These results demonstrate that, as in mitosis, Smc5-Smc6 is required to ensure proper chromosome segregation during meiosis by preventing aberrant recombination intermediates between homologous chromosomes.

  2. Theory of meiotic spindle assembly

    Science.gov (United States)

    Furthauer, Sebastian; Foster, Peter; Needleman, Daniel; Shelley, Michael

    2016-11-01

    The meiotic spindle is a biological structure that self assembles from the intracellular medium to separate chromosomes during meiosis. It consists of filamentous microtubule (MT) proteins that interact through the fluid in which they are suspended and via the associated molecules that orchestrate their behavior. We aim to understand how the interplay between fluid medium, MTs, and regulatory proteins allows this material to self-organize into the spindle's highly stereotyped shape. To this end we develop a continuum model that treats the spindle as an active liquid crystal with MT turnover. In this active material, molecular motors, such as dyneins which collect MT minus ends and kinesins which slide MTs past each other, generate active fluid and material stresses. Moreover nucleator proteins that are advected with and transported along MTs control the nucleation and depolymerization of MTs. This theory captures the growth process of meiotic spindles, their shapes, and the essential features of many perturbation experiments. It thus provides a framework to think about the physics of this complex biological suspension.

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

    Science.gov (United States)

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

    2017-01-01

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

  4. Preparations of meiotic pachytene chromosomes and extended DNA fibers from cotton suitable for fluorescence in situ hybridization.

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    Renhai Peng

    Full Text Available 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

  5. Risk evaluation of carriers with chromosome reciprocal translocation t(7;13)(q34;q13) and concomitant meiotic segregation analyzed by FISH on ejaculated spermatozoa.

    Science.gov (United States)

    Midro, Alina T; Wiland, Ewa; Panasiuk, Barbara; Leśniewicz, Ryszard; Kurpisz, Maciej

    2006-02-01

    We performed the segregation analysis of a relatively large pedigree of t(7;13)(q34;q13) carriers together with the sperm karyotype analysis of the one carrier using a tri-color fluorescence in situ hybridization (FISH) method. The risk assessments for unfavorable pregnancy outcomes in a series of 36 pregnancies in eight reciprocal chromosome translocation (RCT) couples of carriers were estimated directly from a pedigree after ascertainment correction. The individual probability rate for unbalanced child was predicted according to Stengel-Rutkowski and co-workers. The unbalanced karyotypes in the form of monosomy 7q34-->qter and trisomy 13q13-->qter were detected among stillborn/early death newborns with holoprosencephaly (HPE), cyclopia and other malformations. Based on clinical description of unkaryotyped stillbirth progeny, it can be assumed that the phenotype distinctions were connected with the unbalanced karyotype from 2:2 segregation (monosomy 7q with trisomy 13q) and 3:1 segregation as interchange trisomy 13 (Patau syndrome). Probability rates for miscarriages, stillbirth/early death were 12.9 +/- 6% (4/31) and 29 +/- 8.2% (9/31), respectively. The results of the meiotic segregation pattern indicated the rate of unbalanced spermatozoa for about 60%, with the unusual high rate (29.4%) of 3:1 segregant (i.e., 13.4% of the tertiary segregation and 16% of the interchange segregation). Adjacent-1 segregation followed with 23.5% and adjacent-2 followed with 7.2% of analyzed spermatozoa. The high rate of unbalanced gametes in comparison to the number of stillborn/early death and miscarriages detected in pedigree suggests a strong selection against unbalanced chromosomal constitutions during fetal development. It corresponds to a very small probability rate (about 0.3%) of viable unbalanced progeny from 3:1 meiotic segregation predicted for maternal carriers. This knowledge can be used in genetic counseling of families with similar RCT ascertained in a different

  6. Transgenerationally precipitated meiotic chromosome instability fuels rapid karyotypic evolution and phenotypic diversity in an artificially constructed allotetraploid wheat (AADD).

    Science.gov (United States)

    Gou, Xiaowan; Bian, Yao; Zhang, Ai; Zhang, Huakun; Wang, Bin; Lv, Ruili; Li, Juzuo; Zhu, Bo; Gong, Lei; Liu, Bao

    2018-01-22

    Whereas a distinct karyotype with defined chromosome number and structure characterizes each biological species, it is intrinsically labile. Polyploidy or whole genome duplication (WGD) has played a pervasive and ongoing role in the evolution of all eukaryotes, and is the most dramatic force known to cause rapid karyotypic reconfiguration, especially at the initial stage. However, issues concerning transgenerational propagation of karyotypic heterogeneity and its translation to phenotypic diversity in nascent allopolyploidy, at the population level, have yet to be studied in detail. Here, we report a large-scale examination of transgenerationally propagated karyotypic heterogeneity and its phenotypic manifestation in an artificially constructed allotetraploid with a genome composition of AADD, i.e., involving two of the three progenitor genomes of polyploid wheat. Specifically, we show that (i) massive organismal karyotypic heterogeneity is precipitated after 12 consecutive generations of selfing from a single euploid founder individual; (ii) there exist dramatic differences in aptitudes between subgenomes and among chromosomes for whole-chromosome gain and/or loss and structural variations; (iii) majority of the numerical and structural chromosomal variations are concurrent due to mutual contingency and possible functional constraint; (iv) purposed and continuous selection and propagation for euploidy over generations did not result in enhanced karyotype stabilization; and (v) extent of karyotypic variation correlates with variability of phenotypic manifestation. Together, our results document that allopolyploidization catalyzes rampant and transgenerationally heritable organismal karyotypic heterogeneity that drives population-level phenotypic diversification, which lends fresh empirical support to the still contentious notion that WGD enhances organismal evolvability. © The Author 2018. Published by Oxford University Press on behalf of the Society for Molecular

  7. Assessing fluctuating evolutionary pressure in yeast and mammal evolutionary rate covariation using bioinformatics of meiotic protein genetic sequences

    Science.gov (United States)

    Dehipawala, Sunil; Nguyen, A.; Tremberger, G.; Cheung, E.; Holden, T.; Lieberman, D.; Cheung, T.

    2013-09-01

    The evolutionary rate co-variation in meiotic proteins has been reported for yeast and mammal using phylogenic branch lengths which assess retention, duplication and mutation. The bioinformatics of the corresponding DNA sequences could be classified as a diagram of fractal dimension and Shannon entropy. Results from biomedical gene research provide examples on the diagram methodology. The identification of adaptive selection using entropy marker and functional-structural diversity using fractal dimension would support a regression analysis where the coefficient of determination would serve as evolutionary pathway marker for DNA sequences and be an important component in the astrobiology community. Comparisons between biomedical genes such as EEF2 (elongation factor 2 human, mouse, etc), WDR85 in epigenetics, HAR1 in human specificity, clinical trial targeted cancer gene CD47, SIRT6 in spermatogenesis, and HLA-C in mosquito bite immunology demonstrate the diagram classification methodology. Comparisons to the SEPT4-XIAP pair in stem cell apoptosis, testesexpressed taste genes TAS1R3-GNAT3 pair, and amyloid beta APLP1-APLP2 pair with the yeast-mammal DNA sequences for meiotic proteins RAD50-MRE11 pair and NCAPD2-ICK pair have accounted for the observed fluctuating evolutionary pressure systematically. Regression with high R-sq values or a triangular-like cluster pattern for concordant pairs in co-variation among the studied species could serve as evidences for the possible location of common ancestors in the entropy-fractal dimension diagram, consistent with an example of the human-chimp common ancestor study using the FOXP2 regulated genes reported in human fetal brain study. The Deinococcus radiodurans R1 Rad-A could be viewed as an outlier in the RAD50 diagram and also in the free energy versus fractal dimension regression Cook's distance, consistent with a non-Earth source for this radiation resistant bacterium. Convergent and divergent fluctuating evolutionary

  8. Meiotic messenger RNA and noncoding RNA targets of the RNA-binding protein Translin (TSN) in mouse testis.

    Science.gov (United States)

    Cho, Yoon Shin; Iguchi, Naoko; Yang, Juxiang; Handel, Mary Ann; Hecht, Norman B

    2005-10-01

    In postmeiotic male germ cells, TSN, formerly known as testis brain-RNA binding protein, is found in the cytoplasm and functions as a posttranscriptional regulator of a group of genes transcribed by the transcription factor CREM-tau. In contrast, in pachytene spermatocytes, TSN is found predominantly in nuclei. Tsn-null males show a reduced sperm count and high levels of apoptosis in meiotic cells, suggesting a critical function for TSN during meiosis. To identify meiotic target RNAs that associate in vivo with TSN, we reversibly cross-linked TSN to RNA in testis extracts from 17-day-old and adult mice and immunoprecipitated the complexes with an affinity-purified TSN antibody. Extracts from Tsn-null mice were used as controls. Cloning and sequencing the immunoprecipitated RNAs, we identified four new TSN target mRNAs, encoding diazepam-binding inhibitor-like 5, arylsulfatase A, a tetratricopeptide repeat structure-containing protein, and ring finger protein 139. In contrast to the population of postmeiotic translationally delayed mRNAs that bind TSN, these four mRNAs are initially expressed in pachytene spermatocytes. In addition, anti-TSN also precipitated a nonprotein-coding RNA (ncRNA), which is abundant in nuclei of pachytene spermatocytes and has a putative polyadenylation signal, but no open reading frame. A second similar ncRNA is adjacent to a GGA repeat, a motif frequently associated with recombination hot spots. RNA gel-shift assays confirm that the four new target mRNAs and the ncRNA specifically bind to TSN in testis extracts. These studies have, for the first time, identified both mRNAs and a ncRNA as TSN targets expressed during meiosis.

  9. Bub3 is a spindle assembly checkpoint protein regulating chromosome segregation during mouse oocyte meiosis.

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    Mo Li

    Full Text Available In mitosis, the spindle assembly checkpoint (SAC prevents anaphase onset until all chromosomes have been attached to the spindle microtubules and aligned correctly at the equatorial metaphase plate. The major checkpoint proteins in mitosis consist of mitotic arrest-deficient (Mad1-3, budding uninhibited by benzimidazole (Bub1, Bub3, and monopolar spindle 1(Mps1. During meiosis, for the formation of a haploid gamete, two consecutive rounds of chromosome segregation occur with only one round of DNA replication. To pull homologous chromosomes to opposite spindle poles during meiosis I, both sister kinetochores of a homologue must face toward the same pole which is very different from mitosis and meiosis II. As a core member of checkpoint proteins, the individual role of Bub3 in mammalian oocyte meiosis is unclear. In this study, using overexpression and RNA interference (RNAi approaches, we analyzed the role of Bub3 in mouse oocyte meiosis. Our data showed that overexpressed Bub3 inhibited meiotic metaphase-anaphase transition by preventing homologous chromosome and sister chromatid segregations in meiosis I and II, respectively. Misaligned chromosomes, abnormal polar body and double polar bodies were observed in Bub3 knock-down oocytes, causing aneuploidy. Furthermore, through cold treatment combined with Bub3 overexpression, we found that overexpressed Bub3 affected the attachments of microtubules and kinetochores during metaphase-anaphase transition. We propose that as a member of SAC, Bub3 is required for regulation of both meiosis I and II, and is potentially involved in kinetochore-microtubule attachment in mammalian oocytes.

  10. Gibberellin Induces Diploid Pollen Formation by Interfering with Meiotic Cytokinesis.

    Science.gov (United States)

    Liu, Bing; De Storme, Nico; Geelen, Danny

    2017-01-01

    The plant hormone gibberellic acid (GA) controls many physiological processes, including cell differentiation, cell elongation, seed germination, and response to abiotic stress. In this study, we report that exogenous treatment of flowering Arabidopsis (Arabidopsis thaliana) plants with GA specifically affects the process of male meiotic cytokinesis leading to meiotic restitution and the production of diploid (2n) pollen grains. Similar defects in meiotic cell division and reproductive ploidy stability occur in Arabidopsis plants depleted of RGA and GAI, two members of the DELLA family that function as suppressor of GA signaling. Cytological analysis of the double rga-24 gai-t6 mutant revealed that defects in male meiotic cytokinesis are not caused by alterations in meiosis I (MI or meiosis II (MII) chromosome dynamics, but instead result from aberrations in the spatial organization of the phragmoplast-like radial microtubule arrays (RMAs) at the end of meiosis II. In line with a role for GA in the genetic regulation of the male reproductive system, we additionally show that DELLA downstream targets MYB33 and MYB65 are redundantly required for functional RMA biosynthesis and male meiotic cytokinesis. By analyzing the expression of pRGA::GFP-RGA in the wild-type Landsberg erecta background, we demonstrate that the GFP-RGA protein is specifically expressed in the anther cell layers surrounding the meiocytes and microspores, suggesting that appropriate GA signaling in the somatic anther tissue is critical for male meiotic cell wall formation and thus plays an important role in consolidating the male gametophytic ploidy consistency. © 2017 American Society of Plant Biologists. All Rights Reserved.

  11. Membrane protein expression triggers chromosomal locus repositioning in bacteria

    Science.gov (United States)

    Libby, Elizabeth A.; Roggiani, Manuela; Goulian, Mark

    2012-01-01

    It has long been hypothesized that subcellular positioning of chromosomal loci in bacteria may be influenced by gene function and expression state. Here we provide direct evidence that membrane protein expression affects the position of chromosomal loci in Escherichia coli. For two different membrane proteins, we observed a dramatic shift of their genetic loci toward the membrane upon induction. In related systems in which a cytoplasmic protein was produced, or translation was eliminated by mutating the start codon, a shift was not observed. Antibiotics that block transcription and translation similarly prevented locus repositioning toward the membrane. We also found that repositioning is relatively rapid and can be detected at positions that are a considerable distance on the chromosome from the gene encoding the membrane protein (>90 kb). Given that membrane protein-encoding genes are distributed throughout the chromosome, their expression may be an important mechanism for maintaining the bacterial chromosome in an expanded and dynamic state. PMID:22529375

  12. Regulation of Meiotic Recombination

    Energy Technology Data Exchange (ETDEWEB)

    Gregory p. Copenhaver

    2011-11-09

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

  13. Robertsonian chromosome polymorphism of Akodon molinae (Rodentia: Sigmodontinae: analysis of trivalents in meiotic prophase Polimorfismo cromosómico Robertsoniano de Akodon molinae (Rodentia: Sigmodontinae

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    RAÚL FERNÁNDEZ-DONOSO

    2001-03-01

    Full Text Available Akodon molinae (with 2n = 42-43-44 and an FN = 44 shows a remarkable polymorphism of chromosome 1 in natural and laboratory populations. Specimens 2n = 42, named single homozygotes (SH, have a chromosome pair 1 formed by two large metacentric chromosomes. Specimens 2n = 3, heterozygotes (Ht, have one chromosome 1 and two medium-sized subtelocentric chromosomes, 1a and 1b, which are homologous with the long and short arms of chromosome 1 respectively. Specimens 2n = 44 are double homozygotes (DH, with just two pairs of medium-sized subtelocentric chromosomes, 1a and 1b. Analysis of meiotic metaphases I and II showed that anomalous segregation occurs more frequently in spermatocytes carrying the 1a and 1b chromosomes. This would disturb gametogenesis and other reproductive and developmental processes, producing a marked decrease in viability of DH individuals. There is, as yet, no satisfactory explanation for these phenomena. To investigate structural elements which might explain such segregational anomalies, we have studied bivalent and trivalent synapsis in pachytene spermatocytes from SH, Ht and DH specimens. Of a total of 80 spermatocyte nuclei microspreads, the following results were obtained: of 16 microspreads from two SH individuals, 20 autosomic bivalents plus the XY bivalent were observed; of 48 microspreads from three Ht individuals, 19 autosomic bivalents, 1 trivalent and an XY bivalent were seen; and of the 16 microspreads from two DH individuals, 21 autosomic bivalents plus the XY bivalent were found. Trivalents analysed showed complete pairing between the short arms of 1a and 1b, and having an apparently normal synaptonemal complex (SC with lengths of 1 and 2.8 µm. The trivalent SC showed three telomeric ends, corresponding to arms: q1 and q1a; p1 and q1b; and p1a and p1b, with attachment plates to the nuclear envelope of normal organisation. None of the trivalents showed asynapsis or desynapsis between p1a and p1b, nor an

  14. Membrane protein expression triggers chromosomal locus repositioning in bacteria

    OpenAIRE

    Libby, Elizabeth A.; Roggiani, Manuela; Goulian, Mark

    2012-01-01

    It has long been hypothesized that subcellular positioning of chromosomal loci in bacteria may be influenced by gene function and expression state. Here we provide direct evidence that membrane protein expression affects the position of chromosomal loci in Escherichia coli. For two different membrane proteins, we observed a dramatic shift of their genetic loci toward the membrane upon induction. In related systems in which a cytoplasmic protein was produced, or translation was eliminated by m...

  15. Meiotic recombination modulates the structure and dynamics of the synaptonemal complex during C. elegans meiosis.

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    Divya Pattabiraman

    2017-03-01

    Full Text Available During meiotic prophase, a structure called the synaptonemal complex (SC assembles at the interface between aligned pairs of homologous chromosomes, and crossover recombination events occur between their DNA molecules. Here we investigate the inter-relationships between these two hallmark features of the meiotic program in the nematode C. elegans, revealing dynamic properties of the SC that are modulated by recombination. We demonstrate that the SC incorporates new subunits and switches from a more highly dynamic/labile state to a more stable state as germ cells progress through the pachytene stage of meiotic prophase. We further show that the more dynamic state of the SC is prolonged in mutants where meiotic recombination is impaired. Moreover, in meiotic mutants where recombination intermediates are present in limiting numbers, SC central region subunits become preferentially stabilized on the subset of chromosome pairs that harbor a site where pro-crossover factors COSA-1 and MutSγ are concentrated. Polo-like kinase PLK-2 becomes preferentially localized to the SCs of chromosome pairs harboring recombination sites prior to the enrichment of SC central region proteins on such chromosomes, and PLK-2 is required for this enrichment to occur. Further, late pachytene nuclei in a plk-2 mutant exhibit the more highly dynamic SC state. Together our data demonstrate that crossover recombination events elicit chromosome-autonomous stabilizing effects on the SC and implicate PLK-2 in this process. We discuss how this recombination-triggered modulation of SC state might contribute to regulatory mechanisms that operate during meiosis to ensure the formation of crossovers while at the same time limiting their numbers.

  16. Specific deletion of Cdc42 does not affect meiotic spindle organization/migration and homologous chromosome segregation but disrupts polarity establishment and cytokinesis in mouse oocytes

    DEFF Research Database (Denmark)

    Wang, Zhen-Bo; Jiang, Zong-Zhe; Zhang, Qing-Hua

    2013-01-01

    Mammalian oocyte maturation is distinguished by highly asymmetric meiotic divisions during which a haploid female gamete is produced and almost all the cytoplasm is maintained in the egg for embryo development. Actin-dependent meiosis I spindle positioning to the cortex induces the formation of a...

  17. Micromechanical study of protein-DNA interactions and chromosomes

    Science.gov (United States)

    Marko, John

    I will discuss micromechanics experiments that our group has used to analyze protein-DNA interactions and chromosome organization. In single-DNA experiments we have found that a feature of protein-DNA complexes is that their dissociation rates can depend strikingly on bulk solution concentrations of other proteins and DNA segments; I will describe experiments which demonstrate this effect, which can involve tens-fold changes in off-rates with submicromolar changes in solution concentrations. Second, I will discuss experiments aimed at analyzing large-scale human chromosome structure; we isolate metaphase chromosomes, which in their native form behave as remarkably elastic networks of chromatin. Exposure to DNA-cutting restriction enzymes completely eliminates this elasticity, indicating that there is not a mechanically contiguous protein ''scaffold'' from which the chromosome gains its stability. I will show results of siRNA experiments indicating that depletion of condensin proteins leads to destabilization of chromosome mechanics, indicating condensin's role as the major chromatin ''cross-linker'' in metaphase chromosomes. Finally I will discuss similar experiments on human G1 nuclei, where we use genetic and chemical modifications to separate the contributions of the nuclear lamina and chromatin to the mechanical stiffness of the nucleus as a whole. Supported by the NSF (DMR-1206868, MCB-1022117) and the NIH (GM105847, CA193419).

  18. A Gene Regulatory Program for Meiotic Prophase in the Fetal Ovary

    NARCIS (Netherlands)

    Soh, Y Q Shirleen; Junker, Jan Philipp; Gill, Mark E; Mueller, Jacob L; van Oudenaarden, Alexander; Page, David C

    The chromosomal program of meiotic prophase, comprising events such as laying down of meiotic cohesins, synapsis between homologs, and homologous recombination, must be preceded and enabled by the regulated induction of meiotic prophase genes. This gene regulatory program is poorly understood,

  19. RAD51AP2, a novel vertebrate- and meiotic-specific protein, sharesa conserved RAD51-interacting C-terminal domain with RAD51AP1/PIR51

    Energy Technology Data Exchange (ETDEWEB)

    Kovalenko, Oleg V.; Wiese, Claudia; Schild, David

    2006-07-25

    Many interacting proteins regulate and/or assist the activities of RAD51, a recombinase which plays a critical role in both DNA repair and meiotic recombination. Yeast two-hybrid screening of a human testis cDNA library revealed a new protein, RAD51AP2 (RAD51 Associated Protein 2), that interacts strongly with RAD51. A full-length cDNA clone predicts a novel vertebrate specific protein of 1159 residues, and the RAD51AP2 transcript was observed only in meiotic tissue (i.e. adult testis and fetal ovary), suggesting a meiotic-specific function for RAD51AP2. In HEK293 cells the interaction of RAD51 with an ectopically-expressed recombinant large fragment of RAD51AP2 requires the C-terminal 57 residues of RAD51AP2. This RAD51-binding region shows 81% homology to the C-terminus of RAD51AP1/PIR51, an otherwise totally unrelated RAD51-binding partner that is ubiquitously expressed. Analyses using truncations and point mutations in both RAD51AP1 and RAD51AP2 demonstrate that these proteins use the same structural motif for RAD51 binding. RAD54 shares some homology with this RAD51-binding motif, but this homologous region plays only an accessory role to the adjacent main RAD51-interacting region, which has been narrowed here to 40 amino acids. A novel protein, RAD51AP2, has been discovered that interacts with RAD51 through a C-terminal motif also present in RAD51AP1.

  20. Cows are not mice: the role of cyclic AMP, phosphodiesterases, and adenosine monophosphate-activated protein kinase in the maintenance of meiotic arrest in bovine oocytes.

    Science.gov (United States)

    Bilodeau-Goeseels, Sylvie

    2011-01-01

    Meiotic maturation in mammalian oocytes is initiated during fetal development, and is then arrested at the dictyate stage - possibly for several years. Oocyte meiosis resumes in preovulatory follicles in response to the lutenizing hormone (LH) surge or spontaneously when competent oocytes are removed from follicles and cultured. The mechanisms involved in meiotic arrest and resumption in bovine oocytes are not fully understood, and several studies point to important differences between oocytes from rodent and livestock species. This paper reviews earlier and contemporary studies on the effects of cAMP-elevating agents and phosphodiesterase (PDE) enzyme inhibitors on the maintenance of meiotic arrest in bovine oocytes in vitro. Contrary to results obtained with mouse oocytes, bovine oocyte meiosis is inhibited by activators of the energy sensor adenosine monophosphate-activated protein kinase (AMPK, mammalian gene PRKA), which is activated by AMP, the degradation product of cAMP. It is not clear whether or not the effects were due to AMPK activation, and they may depend on culture conditions. Evidence suggests that other signaling pathways (for example, the cGMP/nitric oxide pathway) are involved in bovine oocyte meiotic arrest, but further studies are needed to understand the interactions between the signaling pathways that lead to maturation promoting factor (MPF) being inactive or active. An improved understanding of the mechanisms involved in the control of bovine oocyte meiosis will facilitate better control of the process in vitro, resulting in increased developmental competence and increased efficiency of in vitro embryo production procedures. Copyright © 2011 Wiley Periodicals, Inc.

  1. Phosphorylation of chromosome core components may serve as axis marks for the status of chromosomal events during mammalian meiosis.

    Directory of Open Access Journals (Sweden)

    Tomoyuki Fukuda

    2012-02-01

    Full Text Available Meiotic recombination and chromosome synapsis between homologous chromosomes are essential for proper chromosome segregation at the first meiotic division. While recombination and synapsis, as well as checkpoints that monitor these two events, take place in the context of a prophase I-specific axial chromosome structure, it remains unclear how chromosome axis components contribute to these processes. We show here that many protein components of the meiotic chromosome axis, including SYCP2, SYCP3, HORMAD1, HORMAD2, SMC3, STAG3, and REC8, become post-translationally modified by phosphorylation during the prophase I stage. We found that HORMAD1 and SMC3 are phosphorylated at a consensus site for the ATM/ATR checkpoint kinase and that the phosphorylated forms of HORMAD1 and SMC3 localize preferentially to unsynapsed chromosomal regions where synapsis has not yet occurred, but not to synapsed or desynapsed regions. We investigated the genetic requirements for the phosphorylation events and revealed that the phosphorylation levels of HORMAD1, HORMAD2, and SMC3 are dramatically reduced in the absence of initiation of meiotic recombination, whereas BRCA1 and SYCP3 are required for normal levels of phosphorylation of HORMAD1 and HORMAD2, but not of SMC3. Interestingly, reduced HORMAD1 and HORMAD2 phosphorylation is associated with impaired targeting of the MSUC (meiotic silencing of unsynapsed chromatin machinery to unsynapsed chromosomes, suggesting that these post-translational events contribute to the regulation of the synapsis surveillance system. We propose that modifications of chromosome axis components serve as signals that facilitate chromosomal events including recombination, checkpoint control, transcription, and synapsis regulation.

  2. MEIOTIC BEHAVIOUR OF ERAGROSTIS TEF AND ERAGROSTIS ...

    African Journals Online (AJOL)

    Administrator

    Thesis, Addis Ababa University, Addis. Ababa, Ethiopia. Majumdar, S., Banerjee, S. and Kumar, K. 2004. Meiotic behavior of chromosomes in PMCs and karyotype of Trifolium repens L. from drajeeling Himalaya. Acta Biologica. Cracoviensia Series Botanica 46: 217-220. Mulu Ayele, Dolezel, J., Van Duren, M., Brunner,.

  3. [Identification of the meiotic events in grasshopper spermatogenesis].

    Science.gov (United States)

    Liu, Meng-Hao; Zhao, Kai-Qiang; Wang, Ya-Dong; Yang, Meng-Ping; Zhao, Ning-Ning; Yang, Da-Xiang

    2012-12-01

    The grasshoppers are ideal materials to study various meiotic stages of spermatogenesis due to their easy availability, fairly large chromosomes, and fewer numbers of chromosomes. It is easy to make temporary squash preparation of grasshopper testes; however, it is usually difficult for the beginners to differentiate between stages of meiosis. In view of this, we demonstrated the method of identification of meiotic stages by chromosome number and chromosome conformation, taking spermatogonial meiosis of Locusta migratoria manilensis as an example. We described briefly the mitosis of spermatogonia and the spermatogenesis of this species as well.

  4. CRA-1 uncovers a double-strand break-dependent pathway promoting the assembly of central region proteins on chromosome axes during C. elegans meiosis.

    Directory of Open Access Journals (Sweden)

    Sarit Smolikov

    2008-06-01

    Full Text Available The synaptonemal complex (SC, a tripartite proteinaceous structure that forms between homologous chromosomes during meiosis, is crucial for faithful chromosome segregation. Here we identify CRA-1, a novel and conserved protein that is required for the assembly of the central region of the SC during C. elegans meiosis. In the absence of CRA-1, central region components fail to extensively localize onto chromosomes at early prophase and instead mostly surround the chromatin at this stage. Later in prophase, central region proteins polymerize along chromosome axes, but for the most part fail to connect the axes of paired homologous chromosomes. This defect results in an inability to stabilize homologous pairing interactions, altered double-strand break (DSB repair progression, and a lack of chiasmata. Surprisingly, DSB formation and repair are required to promote the polymerization of the central region components along meiotic chromosome axes in cra-1 mutants. In the absence of both CRA-1 and any one of the C. elegans homologs of SPO11, MRE11, RAD51, or MSH5, the polymerization observed along chromosome axes is perturbed, resulting in the formation of aggregates of the SC central region proteins. While radiation-induced DSBs rescue this polymerization in cra-1; spo-11 mutants, they fail to do so in cra-1; mre-11, cra-1; rad-51, and cra-1; msh-5 mutants. Taken together, our studies place CRA-1 as a key component in promoting the assembly of a tripartite SC structure. Moreover, they reveal a scenario in which DSB formation and repair can drive the polymerization of SC components along chromosome axes in C. elegans.

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

    Energy Technology Data Exchange (ETDEWEB)

    Russell, L. B.

    1978-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Huei-Mei Chen

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

  7. The effect of X-irradiation on the fertility and the induction of meiotic chromosome rearrangements in mice and their first generation

    International Nuclear Information System (INIS)

    Savkovic, N.; Pecevski, J.; Maric, N.; Radivojevic, D.

    1978-01-01

    The effect of whole-body and local irradiation with a dose of 600 X-rays on the induction of chromosomal translocations in Diakinesis-Metaphase I of meiosis in treated and F 1 males and their fertility have been examined. Our results showed the high percentage of mortality in whole-body irradiated mice. The percentage of fertility was 25% in whole-body, and 93,7% in locally irradiated males. The testis weight was also reduced. The percentage of chromosomal translocations in Diakinesis-Metaphase I of meiosis was greater after whole-body than after local irradiation. In F 1 males both types of irradiation induced chromosomal translocations. (orig.) [de

  8. Meiotic analysis in induced tetraploids of Brachiaria decumbens Stapf

    Directory of Open Access Journals (Sweden)

    Carine Simioni

    2011-01-01

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

  9. Microgravity promotes differentiation and meiotic entry of postnatal mouse male germ cells.

    Directory of Open Access Journals (Sweden)

    Manuela Pellegrini

    Full Text Available A critical step of spermatogenesis is the entry of mitotic spermatogonia into meiosis. Progresses on these topics are hampered by the lack of an in vitro culture system allowing mouse spermatogonia differentiation and entry into meiosis. Previous studies have shown that mouse pachytene spermatocytes cultured in simulated microgravity (SM undergo a spontaneous meiotic progression. Here we report that mouse mitotic spermatogonia cultured under SM with a rotary cell culture system (RCCS enter into meiosis in the absence of any added exogenous factor or contact with somatic cells. We found that isolated Kit-positive spermatogonia under the RCCS condition enter into the prophase of the first meiotic division (leptotene stage, as monitored by chromosomal organization of the synaptonemal complex 3 protein (Scp3 and up-regulation of several pro-meiotic genes. SM was found to activate the phosphatidyl inositol 3 kinase (PI3K pathway and to induce in Kit-positive spermatogonia the last round of DNA replication, typical of the preleptotene stage. A PI3K inhibitor abolished Scp3 induction and meiotic entry stimulated by RCCS conditions. A positive effect of SM on germ cell differentiation was also observed in undifferentiated (Kit-negative spermatogonia, in which RCCS conditions stimulate the expression of Kit and Stra8. In conclusion, SM is an artificial environmental condition which promotes postnatal male germ cell differentiation and might provide a tool to study the molecular mechanisms underlying the switch from mitosis to meiosis in mammals.

  10. Identification of Mitosis-Specific Phosphorylation in Mitotic Chromosome-Associated Proteins.

    Science.gov (United States)

    Ohta, Shinya; Kimura, Michiko; Takagi, Shunsuke; Toramoto, Iyo; Ishihama, Yasushi

    2016-09-02

    During mitosis, phosphorylation of chromosome-associated proteins is a key regulatory mechanism. Mass spectrometry has been successfully applied to determine the complete protein composition of mitotic chromosomes, but not to identify post-translational modifications. Here, we quantitatively compared the phosphoproteome of isolated mitotic chromosomes with that of chromosomes in nonsynchronized cells. We identified 4274 total phosphorylation sites and 350 mitosis-specific phosphorylation sites in mitotic chromosome-associated proteins. Significant mitosis-specific phosphorylation in centromere/kinetochore proteins was detected, although the chromosomal association of these proteins did not change throughout the cell cycle. This mitosis-specific phosphorylation might play a key role in regulation of mitosis. Further analysis revealed strong dependency of phosphorylation dynamics on kinase consensus patterns, thus linking the identified phosphorylation sites to known key mitotic kinases. Remarkably, chromosomal axial proteins such as non-SMC subunits of condensin, TopoIIα, and Kif4A, together with the chromosomal periphery protein Ki67 involved in the establishment of the mitotic chromosomal structure, demonstrated high phosphorylation during mitosis. These findings suggest a novel mechanism for regulation of chromosome restructuring in mitosis via protein phosphorylation. Our study generated a large quantitative database on protein phosphorylation in mitotic and nonmitotic chromosomes, thus providing insights into the dynamics of chromatin protein phosphorylation at mitosis onset.

  11. Meiotic Divisions: No Place for Gender Equality.

    Science.gov (United States)

    El Yakoubi, Warif; Wassmann, Katja

    2017-01-01

    In multicellular organisms the fusion of two gametes with a haploid set of chromosomes leads to the formation of the zygote, the first cell of the embryo. Accurate execution of the meiotic cell division to generate a female and a male gamete is required for the generation of healthy offspring harboring the correct number of chromosomes. Unfortunately, meiosis is error prone. This has severe consequences for fertility and under certain circumstances, health of the offspring. In humans, female meiosis is extremely error prone. In this chapter we will compare male and female meiosis in humans to illustrate why and at which frequency errors occur, and describe how this affects pregnancy outcome and health of the individual. We will first introduce key notions of cell division in meiosis and how they differ from mitosis, followed by a detailed description of the events that are prone to errors during the meiotic divisions.

  12. Recombinant protein expression by targeting pre-selected chromosomal loci

    Directory of Open Access Journals (Sweden)

    Krömer Wolfgang

    2009-12-01

    Full Text Available Abstract Background Recombinant protein expression in mammalian cells is mostly achieved by stable integration of transgenes into the chromosomal DNA of established cell lines. The chromosomal surroundings have strong influences on the expression of transgenes. The exploitation of defined loci by targeting expression constructs with different regulatory elements is an approach to design high level expression systems. Further, this allows to evaluate the impact of chromosomal surroundings on distinct vector constructs. Results We explored antibody expression upon targeting diverse expression constructs into previously tagged loci in CHO-K1 and HEK293 cells that exhibit high reporter gene expression. These loci were selected by random transfer of reporter cassettes and subsequent screening. Both, retroviral infection and plasmid transfection with eGFP or antibody expression cassettes were employed for tagging. The tagged cell clones were screened for expression and single copy integration. Cell clones producing > 20 pg/cell in 24 hours could be identified. Selected integration sites that had been flanked with heterologous recombinase target sites (FRTs were targeted by Flp recombinase mediated cassette exchange (RMCE. The results give proof of principle for consistent protein expression upon RMCE. Upon targeting antibody expression cassettes 90-100% of all resulting cell clones showed correct integration. Antibody production was found to be highly consistent within the individual cell clones as expected from their isogenic nature. However, the nature and orientation of expression control elements revealed to be critical. The impact of different promoters was examined with the tag-and-targeting approach. For each of the chosen promoters high expression sites were identified. However, each site supported the chosen promoters to a different extent, indicating that the strength of a particular promoter is dominantly defined by its chromosomal context

  13. Studying meiosis: a review of FISH and M-FISH techniques used in the analysis of meiotic processes in humans.

    Science.gov (United States)

    Oliver-Bonet, M; Benet, J; Martin, R H

    2006-01-01

    It is well known that chromosome in situ hybridization allows the unequivocal identification of targeted human somatic chromosomes. Different fluorescent in situ hybridization (FISH) techniques have been developed throughout the years and, following the mitotic studies, meiotic analyses have been performed using these different techniques. The introduction of M-FISH techniques to the analysis of meiotic cells has allowed the study of meiotic processes for every individual human chromosome. In this paper, we review the different FISH and M-FISH techniques that have been used on human meiotic cells in both men and women. Copyright 2006 S. Karger AG, Basel.

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

    Energy Technology Data Exchange (ETDEWEB)

    Weber, B.H.F.; Vogt, G. [Institut fuer Humangenetik, Wuerzburg (Germany); Walker, D. [UBC, Vancouver (Canada)] [and others

    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.

  15. 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.

    Directory of Open Access Journals (Sweden)

    Marcia Manterola

    2009-08-01

    Full Text Available Meiosis is a complex type of cell division that involves homologous chromosome pairing, synapsis, recombination, and segregation. When any of these processes is altered, cellular checkpoints arrest meiosis progression and induce cell elimination. Meiotic impairment is particularly frequent in organisms bearing chromosomal translocations. When chromosomal translocations appear in heterozygosis, the chromosomes involved may not correctly complete synapsis, recombination, and/or segregation, thus promoting the activation of checkpoints that lead to the death of the meiocytes. In mammals and other organisms, the unsynapsed chromosomal regions are subject to a process called meiotic silencing of unsynapsed chromatin (MSUC. Different degrees of asynapsis could contribute to disturb the normal loading of MSUC proteins, interfering with autosome and sex chromosome gene expression and triggering a massive pachytene cell death. We report that in mice that are heterozygous for eight multiple simple Robertsonian translocations, most pachytene spermatocytes bear trivalents with unsynapsed regions that incorporate, in a stage-dependent manner, proteins involved in MSUC (e.g., gammaH2AX, ATR, ubiquitinated-H2A, SUMO-1, and XMR. These spermatocytes have a correct MSUC response and are not eliminated during pachytene and most of them proceed into diplotene. However, we found a high incidence of apoptotic spermatocytes at the metaphase stage. These results suggest that in Robertsonian heterozygous mice synapsis defects on most pachytene cells do not trigger a prophase-I checkpoint. Instead, meiotic impairment seems to mainly rely on the action of a checkpoint acting at the metaphase stage. We propose that a low stringency of the pachytene checkpoint could help to increase the chances that spermatocytes with synaptic defects will complete meiotic divisions and differentiate into viable gametes. This scenario, despite a reduction of fertility, allows the spreading

  16. LIN-41 and OMA Ribonucleoprotein Complexes Mediate a Translational Repression-to-Activation Switch Controlling Oocyte Meiotic Maturation and the Oocyte-to-Embryo Transition in Caenorhabditis elegans

    Science.gov (United States)

    Tsukamoto, Tatsuya; Gearhart, Micah D.; Spike, Caroline A.; Huelgas-Morales, Gabriela; Mews, Makaela; Boag, Peter R.; Beilharz, Traude H.; Greenstein, David

    2017-01-01

    An extended meiotic prophase is a hallmark of oogenesis. Hormonal signaling activates the CDK1/cyclin B kinase to promote oocyte meiotic maturation, which involves nuclear and cytoplasmic events. Nuclear maturation encompasses nuclear envelope breakdown, meiotic spindle assembly, and chromosome segregation. Cytoplasmic maturation involves major changes in oocyte protein translation and cytoplasmic organelles and is poorly understood. In the nematode Caenorhabditis elegans, sperm release the major sperm protein (MSP) hormone to promote oocyte growth and meiotic maturation. Large translational regulatory ribonucleoprotein (RNP) complexes containing the RNA-binding proteins OMA-1, OMA-2, and LIN-41 regulate meiotic maturation downstream of MSP signaling. To understand the control of translation during meiotic maturation, we purified LIN-41-containing RNPs and characterized their protein and RNA components. Protein constituents of LIN-41 RNPs include essential RNA-binding proteins, the GLD-2 cytoplasmic poly(A) polymerase, the CCR4-NOT deadenylase complex, and translation initiation factors. RNA sequencing defined messenger RNAs (mRNAs) associated with both LIN-41 and OMA-1, as well as sets of mRNAs associated with either LIN-41 or OMA-1. Genetic and genomic evidence suggests that GLD-2, which is a component of LIN-41 RNPs, stimulates the efficient translation of many LIN-41-associated transcripts. We analyzed the translational regulation of two transcripts specifically associated with LIN-41 which encode the RNA regulators SPN-4 and MEG-1. We found that LIN-41 represses translation of spn-4 and meg-1, whereas OMA-1 and OMA-2 promote their expression. Upon their synthesis, SPN-4 and MEG-1 assemble into LIN-41 RNPs prior to their functions in the embryo. This study defines a translational repression-to-activation switch as a key element of cytoplasmic maturation. PMID:28576864

  17. Genetically enhanced asynapsis of autosomal chromatin promotes transcriptional dysregulation and meiotic failure

    Czech Academy of Sciences Publication Activity Database

    Homolka, David; Jansa, Petr; Forejt, Jiří

    2012-01-01

    Roč. 121, č. 1 (2012), s. 91-104 ISSN 0009-5915 R&D Projects: GA MŠk(CZ) LD11079 Institutional research plan: CEZ:AV0Z50520514 Keywords : meiotic silencing of unsynapsed chromatin * meiotic sex chromosome inactivation * autosomal translocation Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.340, year: 2012

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

    African Journals Online (AJOL)

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

  19. Chromosome painting reveals asynaptic full alignment of homologs and HIM-8-dependent remodeling of X chromosome territories during Caenorhabditis elegans meiosis.

    Directory of Open Access Journals (Sweden)

    Kentaro Nabeshima

    2011-08-01

    Full Text Available During early meiotic prophase, a nucleus-wide reorganization leads to sorting of chromosomes into homologous pairs and to establishing associations between homologous chromosomes along their entire lengths. Here, we investigate global features of chromosome organization during this process, using a chromosome painting method in whole-mount Caenorhabditis elegans gonads that enables visualization of whole chromosomes along their entire lengths in the context of preserved 3D nuclear architecture. First, we show that neither spatial proximity of premeiotic chromosome territories nor chromosome-specific timing is a major factor driving homolog pairing. Second, we show that synaptonemal complex-independent associations can support full lengthwise juxtaposition of homologous chromosomes. Third, we reveal a prominent elongation of chromosome territories during meiotic prophase that initiates prior to homolog association and alignment. Mutant analysis indicates that chromosome movement mediated by association of chromosome pairing centers (PCs with mobile patches of the nuclear envelope (NE-spanning SUN-1/ZYG-12 protein complexes is not the primary driver of territory elongation. Moreover, we identify new roles for the X chromosome PC (X-PC and X-PC binding protein HIM-8 in promoting elongation of X chromosome territories, separable from their role(s in mediating local stabilization of pairing and association of X chromosomes with mobile SUN-1/ZYG-12 patches. Further, we present evidence that HIM-8 functions both at and outside of PCs to mediate chromosome territory elongation. These and other data support a model in which synapsis-independent elongation of chromosome territories, driven by PC binding proteins, enables lengthwise juxtaposition of chromosomes, thereby facilitating assessment of their suitability as potential pairing partners.

  20. Hormad1 mutation disrupts synaptonemal complex formation, recombination, and chromosome segregation in mammalian meiosis.

    Directory of Open Access Journals (Sweden)

    Yong-Hyun Shin

    2010-11-01

    Full Text Available 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.

  1. Initiation of Meiotic Recombination in Mammals

    Directory of Open Access Journals (Sweden)

    Rajeev Kumar

    2010-12-01

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

  2. SCP2, a major protein component of the axial elements of synaptonemal complexes

    NARCIS (Netherlands)

    Schalk, J.A.C.

    1999-01-01

    Synaptonemal complexes (SCs) are ladderlike protein structures, which are formed between homologous chromosomes during the prophase of the first meiotic division. SCs consist of two axial elements, one along each chromosome, and transverse filaments (TFs), which connect the axial elements.

  3. RNAi and heterochromatin repress centromeric meiotic recombination

    DEFF Research Database (Denmark)

    Ellermeier, Chad; Higuchi, Emily C; Phadnis, Naina

    2010-01-01

    to genetic disabilities, including birth defects. The basis by which centromeric meiotic recombination is repressed has been largely unknown. We report here that, in fission yeast, RNAi functions and Clr4-Rik1 (histone H3 lysine 9 methyltransferase) are required for repression of centromeric recombination....... Surprisingly, one mutant derepressed for recombination in the heterochromatic mating-type region during meiosis and several mutants derepressed for centromeric gene expression during mitotic growth are not derepressed for centromeric recombination during meiosis. These results reveal a complex relation between...... types of repression by heterochromatin. Our results also reveal a previously undemonstrated role for RNAi and heterochromatin in the repression of meiotic centromeric recombination and, potentially, in the prevention of birth defects by maintenance of proper chromosome segregation during meiosis....

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

    Science.gov (United States)

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

    2017-01-01

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

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

    Science.gov (United States)

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

    2017-04-01

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

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

    Directory of Open Access Journals (Sweden)

    Emanuelli Narducci da Silva

    2012-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Michelle L Churchman

    2011-07-01

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

  8. The roles of the Saccharomyces cerevisiae RecQ helicase SGS1 in meiotic genome surveillance.

    Directory of Open Access Journals (Sweden)

    Amit Dipak Amin

    2010-11-01

    Full Text Available The Saccharomyces cerevisiae RecQ helicase Sgs1 is essential for mitotic and meiotic genome stability. The stage at which Sgs1 acts during meiosis is subject to debate. Cytological experiments showed that a deletion of SGS1 leads to an increase in synapsis initiation complexes and axial associations leading to the proposal that it has an early role in unwinding surplus strand invasion events. Physical studies of recombination intermediates implicate it in the dissolution of double Holliday junctions between sister chromatids.In this work, we observed an increase in meiotic recombination between diverged sequences (homeologous recombination and an increase in unequal sister chromatid events when SGS1 is deleted. The first of these observations is most consistent with an early role of Sgs1 in unwinding inappropriate strand invasion events while the second is consistent with unwinding or dissolution of recombination intermediates in an Mlh1- and Top3-dependent manner. We also provide data that suggest that Sgs1 is involved in the rejection of 'second strand capture' when sequence divergence is present. Finally, we have identified a novel class of tetrads where non-sister spores (pairs of spores where each contains a centromere marker from a different parent are inviable. We propose a model for this unusual pattern of viability based on the inability of sgs1 mutants to untangle intertwined chromosomes. Our data suggest that this role of Sgs1 is not dependent on its interaction with Top3. We propose that in the absence of SGS1 chromosomes may sometimes remain entangled at the end of pre-meiotic replication. This, combined with reciprocal crossing over, could lead to physical destruction of the recombined and entangled chromosomes. We hypothesise that Sgs1, acting in concert with the topoisomerase Top2, resolves these structures.This work provides evidence that Sgs1 interacts with various partner proteins to maintain genome stability throughout

  9. The Mr 30,000-33,000 major protein components of the lateral elements of synaptonemal complexes of the rat

    NARCIS (Netherlands)

    Lammers, H.

    1999-01-01

    Synaptonemal complexes (SCs) are intranuclear structures which are formed during meiotic prophase between homologous chromosomes. The SC consists of two protein-rich axes, either of which is found at the basis of one of the homologous chromosomes. These axes, called lateral elements (LEs),

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

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    Yulong Liang

    2010-01-01

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

  11. Implications of cell cycle disturbances for meiotic aneuploidy: Studies on a mouse model system

    Energy Technology Data Exchange (ETDEWEB)

    Eichenlaub-Ritter, U.; Sobek-Klocke, I. [Universitaet Bielefeld (United Kingdom)

    1993-12-31

    The correlation between increased risk of aneuploid offspring with maternal age in the human and some other mammals has been documented by a number of studies in the last decades. With the advent of chromosome banding and molecular cytogenetic techniques using restriction fragment length polymorphisms to identify the origin of extra chromosomes in trisomic conditions, data have accumulated which indicate that most non-disjunction events leading to chromosomally unbalanced gametes and embryos occur during first meiotic division of maturation in the oocyte. Among others, hypotheses relating a reduction in recombination and chiasmata with increased risks for aneuploidy, or such relating hormonal imbalance, alterations in follicular pH or environmental disturbances with aberrations in chromosomal constitution and spindle components have been proposed but the cellular and physiological basis for chromosome malsegregation with increased age still remains elusive. Here we review studies in which the CBA/Ca mouse was used as a model system to analyze spindle structure and formation, chromosome behavior and progression through the cell cycle with regard to extrinsic and intrinsic factors, as well as to age and aneuploidy, respectively, to identify risk factors. The data indicate that disturbances in cell cycle progression are correlated with high risk for aneuploidy in mammalian oocytes. These disturbances may reside in altered protein phosphorylation and gene expression.

  12. Meiosis specific coiled-coil proteins in Shizosaccharomyces pombe

    Directory of Open Access Journals (Sweden)

    Okuzaki Daisuke

    2007-05-01

    Full Text Available Abstract Many meiosis-specific proteins in Schizosaccharomyces pombe contain coiled-coil motifs which play essential roles for meiotic progression. For example, the coiled-coil motifs present in Meu13 and Mcp7 are required for their function as a putative recombinase cofactor complex during meiotic recombination. Mcp6/Hrs1 and Mcp5/Num1 control horsetail chromosome movement by astral microtubule organization and anchoring dynein respectively. Dhc1 and Ssm4 are also required for horsetail chromosome movement. It is clear from these examples that the coiled-coil motif in these proteins plays an important role during the progression of cells through meiosis. However, there are still many unanswered questions on how these proteins operate. In this paper, we briefly review recent studies on the meiotic coiled-coil proteins in Sz. pombe.

  13. A chromosome-centric human proteome project (C-HPP) to characterize the sets of proteins encoded in chromosome 17.

    Science.gov (United States)

    Liu, Suli; Im, Hogune; Bairoch, Amos; Cristofanilli, Massimo; Chen, Rui; Deutsch, Eric W; Dalton, Stephen; Fenyo, David; Fanayan, Susan; Gates, Chris; Gaudet, Pascale; Hincapie, Marina; Hanash, Samir; Kim, Hoguen; Jeong, Seul-Ki; Lundberg, Emma; Mias, George; Menon, Rajasree; Mu, Zhaomei; Nice, Edouard; Paik, Young-Ki; Uhlen, Mathias; Wells, Lance; Wu, Shiaw-Lin; Yan, Fangfei; Zhang, Fan; Zhang, Yue; Snyder, Michael; Omenn, Gilbert S; Beavis, Ronald C; Hancock, William S

    2013-01-04

    We report progress assembling the parts list for chromosome 17 and illustrate the various processes that we have developed to integrate available data from diverse genomic and proteomic knowledge bases. As primary resources, we have used GPMDB, neXtProt, PeptideAtlas, Human Protein Atlas (HPA), and GeneCards. All sites share the common resource of Ensembl for the genome modeling information. We have defined the chromosome 17 parts list with the following information: 1169 protein-coding genes, the numbers of proteins confidently identified by various experimental approaches as documented in GPMDB, neXtProt, PeptideAtlas, and HPA, examples of typical data sets obtained by RNASeq and proteomic studies of epithelial derived tumor cell lines (disease proteome) and a normal proteome (peripheral mononuclear cells), reported evidence of post-translational modifications, and examples of alternative splice variants (ASVs). We have constructed a list of the 59 "missing" proteins as well as 201 proteins that have inconclusive mass spectrometric (MS) identifications. In this report we have defined a process to establish a baseline for the incorporation of new evidence on protein identification and characterization as well as related information from transcriptome analyses. This initial list of "missing" proteins that will guide the selection of appropriate samples for discovery studies as well as antibody reagents. Also we have illustrated the significant diversity of protein variants (including post-translational modifications, PTMs) using regions on chromosome 17 that contain important oncogenes. We emphasize the need for mandated deposition of proteomics data in public databases, the further development of improved PTM, ASV, and single nucleotide variant (SNV) databases, and the construction of Web sites that can integrate and regularly update such information. In addition, we describe the distribution of both clustered and scattered sets of protein families on the

  14. Identification and characterization of synaptonemal complex proteins of the rat

    NARCIS (Netherlands)

    Offenberg, H.H.

    1993-01-01

    Synaptonemal complexes (SCs) are structures that are formed between homologous chromosomes during meiotic prophase. They undergo a series of morphological alterations which closely correlate with the successive rearrangements of meiotic prophase chromatin, namely chromosome condensation,

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

    Science.gov (United States)

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

    2007-01-01

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

  16. Human synaptonemal complex protein 1 (SCP1): Isolation and characterization of the cDNA and chromosomal localization of the gene

    Energy Technology Data Exchange (ETDEWEB)

    Meuwissen, R.L.J.; Meerts, I.; Heyting, C. [Agricultural Univ., Wageningen (Netherlands)] [and others

    1997-02-01

    Synaptonemal complexes (SCs) are structures that are formed between homologous chromosomes (homologs) during meiotic prophase. They consist of two proteinaceous axes, one along each homolog, that are connected along their length by numerous transverse filaments (TFs). The cDNA encoding one major component of TFs of SCs of the rat, rnSCP1, has recently been isolated and characterized. In this paper we describe the isolation and characterization of the cDNA encoding the human protein homologous to rnSCP1, hsSCP1. hsSCP1 and rnSCP1 have 75% amino acid identity. The most prominent structural features and amino acid sequence motifs of rnSCP1 have been conserved in hsSCP1. Most probably, hsSCP1 is functionally homologous to rnSCP1. The hsSCP1 gene was assigned to human chromosome 1p12-p13 by fluorescence in situ hybridization. 44 refs., 4 figs.

  17. Expression profiling of MAP kinase-mediated meiotic progression in Caenorhabditis elegans.

    Directory of Open Access Journals (Sweden)

    Stefanie W Leacock

    2006-11-01

    Full Text Available The LET-60 (Ras/LIN-45 (Raf/MPK-1 (MAP kinase signaling pathway plays a key role in the development of multiple tissues in Caenorhabditis elegans. For the most part, the identities of the downstream genes that act as the ultimate effectors of MPK-1 signaling have remained elusive. A unique allele of mpk-1, ga111, displays a reversible, temperature-sensitive, tissue-specific defect in progression through meiotic prophase I. We performed gene expression profiling on mpk-1(ga111 animals to identify candidate downstream effectors of MPK-1 signaling in the germ line. This analysis delineated a cohort of genes whose expression requires MPK-1 signaling in germ cells in the pachytene stage of meiosis I. RNA in situ hybridization analysis shows that these genes are expressed in the germ line in an MPK-1-dependent manner and have a spatial expression pattern consistent with the location of activated MPK-1. We found that one MPK-1 signaling-responsive gene encoding a C2H2 zinc finger protein plays a role in meiotic chromosome segregation downstream of MPK-1. Additionally, discovery of genes responsive to MPK-1 signaling permitted us to order MPK-1 signaling relative to several events occurring in pachytene, including EFL-1/DPL-1 gene regulation and X chromosome reactivation. This study highlights the utility of applying global gene expression methods to investigate genes downstream of commonly used signaling pathways in vivo.

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

    Energy Technology Data Exchange (ETDEWEB)

    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. Origin of meiotic nondisjunction in Drosophila females

    International Nuclear Information System (INIS)

    Grell, R.F.

    1978-01-01

    Meiotic nondisjunction can be induced by external agents, such as heat, radiation, and chemicals, and by internal genotypic alterations, namely, point mutations and chromosomal rearrangements. In many cases nondisjunction arises from a reduction or elimination of crossing-over, leading to the production of homologous univalents which fail to co-orient on the metaphase plate and to disjoin properly. In some organisms, e.g., Drosophila and perhaps man, distributive pairing [i.e., a post-exchange, size-dependent pairing] ensures the regular segregation of such homologous univalents. When a nonhomologous univalent is present, which falls within a size range permitting nonhomologous recognition and pairing, distributive nondisjunction of the homologues may follow. Examples of nondisjunction induced by inversion heterozygosity, translocation heterozygosity, chromosome fragments, radiation, heat, and recombination-defective mutants are presented

  20. Cooperative working of bacterial chromosome replication proteins generated by a reconstituted protein expression system

    Science.gov (United States)

    Fujiwara, Kei; Katayama, Tsutomu; Nomura, Shin-ichiro M.

    2013-01-01

    Replication of all living cells relies on the multirounds flow of the central dogma. Especially, expression of DNA replication proteins is a key step to circulate the processes of the central dogma. Here we achieved the entire sequential transcription–translation–replication process by autonomous expression of chromosomal DNA replication machineries from a reconstituted transcription–translation system (PURE system). We found that low temperature is essential to express a complex protein, DNA polymerase III, in a single tube using the PURE system. Addition of the 13 genes, encoding initiator, DNA helicase, helicase loader, RNA primase and DNA polymerase III to the PURE system gave rise to a DNA replication system by a coupling manner. An artificial genetic circuit demonstrated that the DNA produced as a result of the replication is able to provide genetic information for proteins, indicating the in vitro central dogma can sequentially undergo two rounds. PMID:23737447

  1. Chromosome Formation During Fertilization in Eggs of the Teleost Oryzias latipes.

    Science.gov (United States)

    Iwamatsu, Takashi

    2017-01-01

    Upon fertilization, eggs shift their cell cycle from the meiotic to the mitotic pattern for embryogenesis. The information on chromosome formation has been accumulated by various experiments using inhibitors to affect formation and behavior of chromosomes in the cycle of cell proliferation. Based on experimental results on meiosis and early stages of development of the teleost Oryzias latipes, we discuss the roles of the activities of histone H1 kinase, microtubule-associated protein kinase, DNA polymerase, DNA topoisomerase, and other cytoplasmic factors in formation and separation of chromosomes.

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

    NARCIS (Netherlands)

    Nijhoff, J.H.

    1981-01-01

    In this thesis a start was made with meiotic observations of mouse translocation types - a Robertsonian translocation and a translocation between a metacentric and an acrocentric chromosome - which also occur in man. It is generally accepted that, when no chromosomal rearrangements are involved, man

  3. The meiotic recombination checkpoint suppresses NHK-1 kinase to prevent reorganisation of the oocyte nucleus in Drosophila.

    Directory of Open Access Journals (Sweden)

    Oscar M Lancaster

    2010-10-01

    Full Text Available The meiotic recombination checkpoint is a signalling pathway that blocks meiotic progression when the repair of DNA breaks formed during recombination is delayed. In comparison to the signalling pathway itself, however, the molecular targets of the checkpoint that control meiotic progression are not well understood in metazoans. In Drosophila, activation of the meiotic checkpoint is known to prevent formation of the karyosome, a meiosis-specific organisation of chromosomes, but the molecular pathway by which this occurs remains to be identified. Here we show that the conserved kinase NHK-1 (Drosophila Vrk-1 is a crucial meiotic regulator controlled by the meiotic checkpoint. An nhk-1 mutation, whilst resulting in karyosome defects, does so independent of meiotic checkpoint activation. Rather, we find unrepaired DNA breaks formed during recombination suppress NHK-1 activity (inferred from the phosphorylation level of one of its substrates through the meiotic checkpoint. Additionally DNA breaks induced by X-rays in cultured cells also suppress NHK-1 kinase activity. Unrepaired DNA breaks in oocytes also delay other NHK-1 dependent nuclear events, such as synaptonemal complex disassembly and condensin loading onto chromosomes. Therefore we propose that NHK-1 is a crucial regulator of meiosis and that the meiotic checkpoint suppresses NHK-1 activity to prevent oocyte nuclear reorganisation until DNA breaks are repaired.

  4. Topoisomerase 3alpha and RMI1 suppress somatic crossovers and are essential for resolution of meiotic recombination intermediates in Arabidopsis thaliana.

    Directory of Open Access Journals (Sweden)

    Frank Hartung

    2008-12-01

    Full Text Available Topoisomerases are enzymes with crucial functions in DNA metabolism. They are ubiquitously present in prokaryotes and eukaryotes and modify the steady-state level of DNA supercoiling. Biochemical analyses indicate that Topoisomerase 3alpha (TOP3alpha functions together with a RecQ DNA helicase and a third partner, RMI1/BLAP75, in the resolution step of homologous recombination in a process called Holliday Junction dissolution in eukaryotes. Apart from that, little is known about the role of TOP3alpha in higher eukaryotes, as knockout mutants show early lethality or strong developmental defects. Using a hypomorphic insertion mutant of Arabidopsis thaliana (top3alpha-2, which is viable but completely sterile, we were able to define three different functions of the protein in mitosis and meiosis. The top3alpha-2 line exhibits fragmented chromosomes during mitosis and sensitivity to camptothecin, suggesting an important role in chromosome segregation partly overlapping with that of type IB topoisomerases. Furthermore, AtTOP3alpha, together with AtRECQ4A and AtRMI1, is involved in the suppression of crossover recombination in somatic cells as well as DNA repair in both mammals and A. thaliana. Surprisingly, AtTOP3alpha is also essential for meiosis. The phenotype of chromosome fragmentation, bridges, and telophase I arrest can be suppressed by AtSPO11 and AtRAD51 mutations, indicating that the protein is required for the resolution of recombination intermediates. As Atrmi1 mutants have a similar meiotic phenotype to Attop3alpha mutants, both proteins seem to be involved in a mechanism safeguarding the entangling of homologous chromosomes during meiosis. The requirement of AtTOP3alpha and AtRMI1 in a late step of meiotic recombination strongly hints at the possibility that the dissolution of double Holliday Junctions via a hemicatenane intermediate is indeed an indispensable step of meiotic recombination.

  5. Pedigree with frontotemporal lobar degeneration – motor neuron disease and Tar DNA binding protein-43 positive neuropathology: genetic linkage to chromosome 9

    Directory of Open Access Journals (Sweden)

    Loy Clement T

    2008-08-01

    Full Text Available Abstract Background Frontotemporal lobar degeneration (FTLD represents a clinically, pathologically and genetically heterogenous neurodegenerative disorder, often complicated by neurological signs such as motor neuron-related limb weakness, spasticity and paralysis, parkinsonism and gait disturbances. Linkage to chromosome 9p had been reported for pedigrees with the neurodegenerative disorder, frontotemporal lobar degeneration (FTLD and motor neuron disease (MND. The objective in this study is to identify the genetic locus in a multi-generational Australian family with FTLD-MND. Methods Clinical review and standard neuropathological analysis of brain sections from affected pedigree members. Genome-wide scan using microsatellite markers and single nucleotide polymorphism fine mapping. Examination of candidate genes by direct DNA sequencing. Results Neuropathological examination revealed cytoplasmic deposition of the TDP-43 protein in three affected individuals. Moreover, we identify a family member with clinical Alzheimer's disease, and FTLD-Ubiquitin neuropathology. Genetic linkage and haplotype analyses, defined a critical region between markers D9S169 and D9S1845 on chromosome 9p21. Screening of all candidate genes within this region did not reveal any novel genetic alterations that co-segregate with disease haplotype, suggesting that one individual carrying a meiotic recombination may represent a phenocopy. Re-analysis of linkage data using the new affection status revealed a maximal two-point LOD score of 3.24 and a multipoint LOD score of 3.41 at marker D9S1817. This provides the highest reported LOD scores from a single FTLD-MND pedigree. Conclusion Our reported increase in the minimal disease region should inform other researchers that the chromosome 9 locus may be more telomeric than predicted by published recombination boundaries. Moreover, the existence of a family member with clinical Alzheimer's disease, and who shares the disease

  6. Heteromorphic Sex Chromosomes: Navigating Meiosis without a Homologous Partner

    OpenAIRE

    Checchi, Paula M.; Engebrecht, JoAnne

    2011-01-01

    Accurate chromosome segregation during meiosis relies on homology between the maternal and paternal chromosomes. Yet by definition, sex chromosomes of the heterogametic sex lack a homologous partner. Recent studies in a number of systems have shed light on the unique meiotic behavior of heteromorphic sex chromosomes, and highlight both the commonalities and differences in divergent species. During meiotic prophase, the homology-dependent processes of pairing, synapsis, and recombination have ...

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

    International Nuclear Information System (INIS)

    Nijhoff, J.H.

    1981-01-01

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

  8. Mammalian CNTD1 is critical for meiotic crossover maturation and deselection of excess precrossover sites.

    Science.gov (United States)

    Holloway, J Kim; Sun, Xianfei; Yokoo, Rayka; Villeneuve, Anne M; Cohen, Paula E

    2014-06-09

    Meiotic crossovers (COs) are crucial for ensuring accurate homologous chromosome segregation during meiosis I. Because the double-strand breaks (DSBs) that initiate meiotic recombination greatly outnumber eventual COs, this process requires exquisite regulation to narrow down the pool of DSB intermediates that may form COs. In this paper, we identify a cyclin-related protein, CNTD1, as a critical mediator of this process. Disruption of Cntd1 results in failure to localize CO-specific factors MutLγ and HEI10 at designated CO sites and also leads to prolonged high levels of pre-CO intermediates marked by MutSγ and RNF212. These data show that maturation of COs is intimately coupled to deselection of excess pre-CO sites to yield a limited number of COs and that CNTD1 coordinates these processes by regulating the association between the RING finger proteins HEI10 and RNF212 and components of the CO machinery. © 2014 Holloway et al.

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

    Science.gov (United States)

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

    2014-10-06

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

  10. Missing Protein Landscape of Human Chromosomes 2 and 14: Progress and Current Status.

    Science.gov (United States)

    Duek, Paula; Bairoch, Amos; Gateau, Alain; Vandenbrouck, Yves; Lane, Lydie

    2016-11-04

    Within the C-HPP, the Swiss and French teams are responsible for the annotation of proteins from chromosomes 2 and 14, respectively. neXtProt currently reports 1231 entries on chromosome 2 and 624 entries on chromosome 14; of these, 134 and 93 entries are still not experimentally validated and are thus considered as "missing proteins" (PE2-4), respectively. Among these entries, some may never be validated by conventional MS/MS approaches because of incompatible biochemical features. Others have already been validated but are still awaiting annotation. On the basis of information retrieved from the literature and from three of the main C-HPP resources (Human Protein Atlas, PeptideAtlas, and neXtProt), a subset of 40 theoretically detectable missing proteins (25 on chromosome 2 and 15 on chromosome 14) was defined for upcoming targeted studies in sperm samples. This list is proposed as a roadmap for the French and Swiss teams in the near future.

  11. TRF2 Protein Interacts with Core Histones to Stabilize Chromosome Ends*

    Science.gov (United States)

    Izumi, Takashi; Shimizu, Shigeomi

    2016-01-01

    Mammalian chromosome ends are protected by a specialized nucleoprotein complex called telomeres. Both shelterin, a telomere-specific multi-protein complex, and higher order telomeric chromatin structures combine to stabilize the chromosome ends. Here, we showed that TRF2, a component of shelterin, binds to core histones to protect chromosome ends from inappropriate DNA damage response and loss of telomeric DNA. The N-terminal Gly/Arg-rich domain (GAR domain) of TRF2 directly binds to the globular domain of core histones. The conserved arginine residues in the GAR domain of TRF2 are required for this interaction. A TRF2 mutant with these arginine residues substituted by alanine lost the ability to protect telomeres and induced rapid telomere shortening caused by the cleavage of a loop structure of the telomeric chromatin. These findings showed a previously unnoticed interaction between the shelterin complex and nucleosomal histones to stabilize the chromosome ends. PMID:27514743

  12. A new culture technique that allows in vitro meiotic prophase development of fetal human oocytes.

    Science.gov (United States)

    Brieño-Enríquez, M A; Robles, P; García-Cruz, R; Roig, I; Cabero, L; Martínez, F; Garcia Caldés, M

    2010-01-01

    Little is known about the mechanisms that regulate meiosis in the human female fetus as a result of the technical difficulties in obtaining samples. Currently, there is no technique for human fetal oocyte culture that permits the maintenance of fetal ovarian tissue in vitro which allows the progression of meiosis in a reproducible and standardized way. Meiotic progression was analyzed following pairing-synapsis and recombination progress. A total of 7119 oocytes were studied and analyzed. The proteins used to evaluate meiotic progression were: REC8, SYCP1, SYCP3 and MLH1, studied by immunofluorescence. Four different sample disaggregating methods were used, two enzymatic (trypsin and collagenase + hyaluronidase) and two mechanical (puncture and ovarian fragments). Two different culture media were used, control media and stem cell factor (SCF)-supplemented media. The oocytes were studied at initial time T0, and then at T7, T14 and T21 days after culture. The mechanical methods increased the total number of oocytes found at the different times of culture and decreased the number of degenerated oocytes. Independently of the disaggregation method used, oocytes cultured with SCF-supplemented media showed a higher proportion of viable oocytes and fewer degenerated cells at all culture timepoints. No evidence of abnormal homologous chromosome synapsis was observed. Meiotic recombination was only observed in oocytes mechanically disaggregated and cultured with supplemented media. The oocytes obtained by mechanical disaggregating methods and cultured with SCF-supplemented media are able to follow pairing-synapsis and recombination, comparable to oocytes in vivo. The culture conditions described herein confirm the methodology as a standardized and reproducible method.

  13. Molecular cloning and chromosome mapping of the human gene encoding protein phosphotyrosyl phosphatase 1B

    International Nuclear Information System (INIS)

    Brown-Shimer, S.; Johnson, K.A.; Bruskin, A.; Green, N.R.; Hill, D.E.; Lawrence, J.B.; Johnson, C.

    1990-01-01

    The inactivation of growth suppressor genes appears to play a major role in the malignant process. To assess whether protein phosphotyrosyl phosphatases function as growth suppressors, the authors have isolated a cDNA clone encoding human protein phosphotyrosyl phosphatase 1B for structural and functional characterization. The translation product deduced from the 1,305-nucleotide open reading frame predicts a protein containing 435 amino acids and having a molecular mass of 49,966 Da. The amino-terminal 321 amino acids deduced from the cDNA sequence are identical to the empirically determined sequence of protein phosphotyrosyl phosphatase 1B. A genomic clone has been isolated and used in an in situ hybridization to banded metaphase chromosomes to determine that the gene encoding protein phosphotyrosyl phosphatase 1B maps as a single-copy gene to the long arm of chromosome 20 in the region q13.1-q13.2

  14. The escherichia coli chromosome replication initiator protein, DnaA

    DEFF Research Database (Denmark)

    Nyborg, Malene

    The experimental work presented in this thesis involve mutational analysis of the DNA binding domain of the DnaA protein and analysis of the A184V substitution in the ATP area of domain III and other amino acid substitutions found in the DnaA5 and DnaA4G proteins....

  15. Structure and chromosomal localization of the gene encoding the human myelin protein zero (MPZ)

    Energy Technology Data Exchange (ETDEWEB)

    Hayasaka, Kiyoshi; Himoro, Masato; Takada, Goro (Akita Univ. School of Medicine, Akita (Japan)); Wang, Yimin; Takata, Mizuho; Minoshima, Shinsei; Shimizu, Nobuyoshi; Miura, Masayuki; Uyemura, Keiichi (Keio Univ. School of Medicine, Tokyo (Japan))

    1993-09-01

    The authors describe the cloning, characterization, and chromosomal mapping of the human myelin protein zero (MPZ) gene (a structural protein of myelin and an adhesive glycoprotein of the immunoglobulin superfamily). The gene is about 7 kb long and consists of six exons corresponding of the functional domains. All exon-intron junction sequences conform to the GT/AG rule. The 5[prime]-flanking region of the gene has a TA-rich element (TATA-like box), two CAAT boxes, and a single defined transcription initiation site detected by the primer extension method. The gene for human MPZ was assigned to chromosome 1q22-q23 by spot blot hybridization of flow-sorted human chromosomes and fluorescence in situ hybridization. The localization of the MPZ gene coincides with the locus for Charcot-Marie-Tooth disease type 1B, determined by linkage analysis. 20 refs., 3 figs., 1 tab.

  16. Localization of the tight junction protein gene TJP1 to human chromosome 15q13, distal to the Prader-Willi/Angelman region, and to mouse chromosome 7

    Energy Technology Data Exchange (ETDEWEB)

    Mohandas, T.K. [Darthmouth-Hitchcock Medical Center, Lebanon, NH (United States); Chen, X.N.; Korenberg, J.R. [UCLA School of Medicine, Los Angeles, CA (United States)] [and others

    1995-12-10

    The gene encoding the tight junction (zonula occludens) protein, TJP1, was mapped to human chromosome 15q13 by fluorescence in situ hybridization (FISH) using a cDNA probe. The Jackson Laboratory backcross DNA panel derived from the cross (C57BL/6JEi X SPRET/Ei) F1 females X SPRET/Ei males was used to map the mouse Tjp1 to chromosome 7 near position 30 on the Chromosome Committee Map, a region with conserved homology to human chromosome 15q13. FISH studies on metaphases from patients with the Prader-Willi (PWS) or the Angelman syndrome (AS) showed that TJP1 maps close but distal to the PWS/AS chromosome region. 13 refs., 2 figs.

  17. Chromosome stickiness during meiotic behavior analysis of Passiflora serrato-digitata L. (PassifloraCEAE Aderência cromossômica durante a análise do comportamento meiótico de Passiflora serrato-digitata L (PassifloraCEAE

    Directory of Open Access Journals (Sweden)

    Paulo Roberto Peres Kiihl

    2011-06-01

    Full Text Available Almost 90% of species of the genus Passiflora are native to the American continent, with high commercial value due to the fact that some species are used for human food while others have ornamental and medical qualities. Passiflora serrato-digitata is one of the species that integrates the Paraná Agronomic Institute germoplasm bank at its experimental base in Londrina, PR, Brazil. Collected flower buds were fixed in ethanol/acetic acid (3:1 v/v for 24h, transferred to 70% alcohol and stored under refrigeration. Slides were prepared by the squashing technique and stained with 1.0% propionic carmine; they were analyzed under an optic microscope. Irregularities in the chromosome segregation process of P. serrato-digitata have been verified by meiotic behavior analysis. These comprised precocious migration to poles in metaphase I and II, non-oriented chromosomes in metaphase plate in metaphase I and II, laggard chromosomes in anaphase I and II towards the formation of micronucleus in telophase I and II, and microspores in tetrads. Chromosome stickiness was another irregularity reported in the Passiflora genus for the first time. These irregularities which also contributed to the formation of monads, dyads and triads, resulted in normal imbalanced 2n and 4n microspores. According to the observed Meiotic Index of 71.83%, this species is not meiotically stable.Cerca de 90% das espécies do gênero Passiflora são nativas das Américas, sendo que aproximadamente 200 espécies são nativas do Brasil. Possuem grande importância comercial, pois algumas espécies são utilizadas na alimentação humana, outras apresentam propriedades medicinais e ornamentais. A espécie Passiflora serrato-digitata faz parte do banco de germoplasma do Instituto Agronômico do Paraná - IAPAR, estação experimental de Londrina, PR. Botões florais colhidos foram fixados em etanol/ácido acético (3:1 v/v por 24 horas, transferidos para álcool a 70% e acondicionado sob

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

    Directory of Open Access Journals (Sweden)

    Li Yunfei

    2010-09-01

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

  19. Condensins promote chromosome individualization and segregation during mitosis, meiosis, and amitosis inTetrahymena thermophila.

    Science.gov (United States)

    Howard-Till, Rachel; Loidl, Josef

    2018-02-15

    Condensin is a protein complex with diverse functions in chromatin packaging and chromosome condensation and segregation. We studied condensin in the evolutionarily distant protist model Tetrahymena , which features noncanonical nuclear organization and divisions. In Tetrahymena , the germline and soma are partitioned into two different nuclei within a single cell. Consistent with their functional specializations in sexual reproduction and gene expression, condensins of the germline nucleus and the polyploid somatic nucleus are composed of different subunits. Mitosis and meiosis of the germline nucleus and amitotic division of the somatic nucleus are all dependent on condensins. In condensin-depleted cells, a chromosome condensation defect was most striking at meiotic metaphase, when Tetrahymena chromosomes are normally most densely packaged. Live imaging of meiotic divisions in condensin-depleted cells showed repeated nuclear stretching and contraction as the chromosomes failed to separate. Condensin depletion also fundamentally altered chromosome arrangement in the polyploid somatic nucleus: multiple copies of homologous chromosomes tended to cluster, consistent with a previous model of condensin suppressing default somatic pairing. We propose that failure to form discrete chromosome territories is the common cause of the defects observed in the absence of condensins. © 2018 Howard-Till and Loidl. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

  20. The role of protein kinase A and mitogen-activated protein kinases 3/1 and 14 in regulation of meiotic resumption of pig cumulus-oocyte complexes

    Czech Academy of Sciences Publication Activity Database

    Procházka, Radek; Blaha, Milan; Němcová, Lucie

    2012-01-01

    Roč. 27, supplement 1 (2012), s. 1245-1246 ISSN 1355-4786. [28th Annual Meeting of the European Society of Human Reproduction and Embryology . 01.07.2012-04.07.2012, Istanbul] R&D Projects: GA ČR GAP502/11/0593 Institutional research plan: CEZ:AV0Z50450515 Keywords : protein kinase A * pig oocyte Subject RIV: ED - Physiology http://www.eshre.eu/page.aspx/11

  1. Transcription of a protein-coding gene on B chromosomes of the Siberian roe deer (Capreolus pygargus).

    Science.gov (United States)

    Trifonov, Vladimir A; Dementyeva, Polina V; Larkin, Denis M; O'Brien, Patricia C M; Perelman, Polina L; Yang, Fengtang; Ferguson-Smith, Malcolm A; Graphodatsky, Alexander S

    2013-08-06

    Most eukaryotic species represent stable karyotypes with a particular diploid number. B chromosomes are additional to standard karyotypes and may vary in size, number and morphology even between cells of the same individual. For many years it was generally believed that B chromosomes found in some plant, animal and fungi species lacked active genes. Recently, molecular cytogenetic studies showed the presence of additional copies of protein-coding genes on B chromosomes. However, the transcriptional activity of these genes remained elusive. We studied karyotypes of the Siberian roe deer (Capreolus pygargus) that possess up to 14 B chromosomes to investigate the presence and expression of genes on supernumerary chromosomes. Here, we describe a 2 Mbp region homologous to cattle chromosome 3 and containing TNNI3K (partial), FPGT, LRRIQ3 and a large gene-sparse segment on B chromosomes of the Siberian roe deer. The presence of the copy of the autosomal region was demonstrated by B-specific cDNA analysis, PCR assisted mapping, cattle bacterial artificial chromosome (BAC) clone localization and quantitative polymerase chain reaction (qPCR). By comparative analysis of B-specific and non-B chromosomal sequences we discovered some B chromosome-specific mutations in protein-coding genes, which further enabled the detection of a FPGT-TNNI3K transcript expressed from duplicated genes located on B chromosomes in roe deer fibroblasts. Discovery of a large autosomal segment in all B chromosomes of the Siberian roe deer further corroborates the view of an autosomal origin for these elements. Detection of a B-derived transcript in fibroblasts implies that the protein coding sequences located on Bs are not fully inactivated. The origin, evolution and effect on host of B chromosomal genes seem to be similar to autosomal segmental duplications, which reinforces the view that supernumerary chromosomal elements might play an important role in genome evolution.

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

    Directory of Open Access Journals (Sweden)

    Irani Sepideh Famil

    2017-06-01

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

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

    Directory of Open Access Journals (Sweden)

    Diane C Shakes

    2009-08-01

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

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

    Science.gov (United States)

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

    2014-01-01

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

  5. The cohesion stabilizer sororin favors DNA repair and chromosome segregation during mouse oocyte meiosis.

    Science.gov (United States)

    Huang, Chun-Jie; Yuan, Yi-Feng; Wu, Di; Khan, Faheem Ahmed; Jiao, Xiao-Fei; Huo, Li-Jun

    2017-03-01

    Maintenance and timely termination of cohesion on chromosomes ensures accurate chromosome segregation to guard against aneuploidy in mammalian oocytes and subsequent chromosomally abnormal pregnancies. Sororin, a cohesion stabilizer whose relevance in antagonizing the anti-cohesive property of Wings-apart like protein (Wapl), has been characterized in mitosis; however, the role of Sororin remains unclear during mammalian oocyte meiosis. Here, we show that Sororin is required for DNA damage repair and cohesion maintenance on chromosomes, and consequently, for mouse oocyte meiotic program. Sororin is constantly expressed throughout meiosis and accumulates on chromatins at germinal vesicle (GV) stage/G2 phase. It localizes onto centromeres from germinal vesicle breakdown (GVBD) to metaphase II stage. Inactivation of Sororin compromises the GVBD and first polar body extrusion (PBE). Furthermore, Sororin inactivation induces DNA damage indicated by positive γH2AX foci in GV oocytes and precocious chromatin segregation in MII oocytes. Finally, our data indicate that PlK1 and MPF dissociate Sororin from chromosome arms without affecting its centromeric localization. Our results define Sororin as a determinant during mouse oocyte meiotic maturation by favoring DNA damage repair and chromosome separation, and thereby, maintaining the genome stability and generating haploid gametes.

  6. Segregation distortion in chicken and the evolutionary consequences of female meiotic drive in birds

    DEFF Research Database (Denmark)

    Axelsson, Erik Gunnar; Albrechtsen, Anders; Van, A. P.

    2010-01-01

    As all four meiotic products give rise to sperm in males, female meiosis result in a single egg in most eukaryotes. Any genetic element with the potential to influence chromosome segregation, so that it is preferentially included in the egg, should therefore gain a transmission advantage; a proce...

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

    African Journals Online (AJOL)

    fe

    2011-11-16

    Nov 16, 2011 ... resulted from abnormal cytokinesis. Pollen fertility was correlated with meiotic abnormality. Keywords: Epimedium, meiosis, chromosomal abnormality, pollen fertility. INTRODUCTION. The genus Epimedium, with more than 60 species, is common in the Mediterranean region and the western. Asia (Stearn ...

  8. Multiple DNA Binding Proteins Contribute to Timing of Chromosome Replication in E. coli

    Science.gov (United States)

    Riber, Leise; Frimodt-Møller, Jakob; Charbon, Godefroid; Løbner-Olesen, Anders

    2016-01-01

    Chromosome replication in Escherichia coli is initiated from a single origin, oriC. Initiation involves a number of DNA binding proteins, but only DnaA is essential and specific for the initiation process. DnaA is an AAA+ protein that binds both ATP and ADP with similar high affinities. DnaA associated with either ATP or ADP binds to a set of strong DnaA binding sites in oriC, whereas only DnaAATP is capable of binding additional and weaker sites to promote initiation. Additional DNA binding proteins act to ensure that initiation occurs timely by affecting either the cellular mass at which DNA replication is initiated, or the time window in which all origins present in a single cell are initiated, i.e. initiation synchrony, or both. Overall, these DNA binding proteins modulate the initiation frequency from oriC by: (i) binding directly to oriC to affect DnaA binding, (ii) altering the DNA topology in or around oriC, (iii) altering the nucleotide bound status of DnaA by interacting with non-coding chromosomal sequences, distant from oriC, that are important for DnaA activity. Thus, although DnaA is the key protein for initiation of replication, other DNA-binding proteins act not only on oriC for modulation of its activity but also at additional regulatory sites to control the nucleotide bound status of DnaA. Here we review the contribution of key DNA binding proteins to the tight regulation of chromosome replication in E. coli cells. PMID:27446932

  9. Direct control of type IIA topoisomerase activity by a chromosomally encoded regulatory protein.

    Science.gov (United States)

    Vos, Seychelle M; Lyubimov, Artem Y; Hershey, David M; Schoeffler, Allyn J; Sengupta, Sugopa; Nagaraja, Valakunja; Berger, James M

    2014-07-01

    Precise control of supercoiling homeostasis is critical to DNA-dependent processes such as gene expression, replication, and damage response. Topoisomerases are central regulators of DNA supercoiling commonly thought to act independently in the recognition and modulation of chromosome superstructure; however, recent evidence has indicated that cells tightly regulate topoisomerase activity to support chromosome dynamics, transcriptional response, and replicative events. How topoisomerase control is executed and linked to the internal status of a cell is poorly understood. To investigate these connections, we determined the structure of Escherichia coli gyrase, a type IIA topoisomerase bound to YacG, a recently identified chromosomally encoded inhibitor protein. Phylogenetic analyses indicate that YacG is frequently associated with coenzyme A (CoA) production enzymes, linking the protein to metabolism and stress. The structure, along with supporting solution studies, shows that YacG represses gyrase by sterically occluding the principal DNA-binding site of the enzyme. Unexpectedly, YacG acts by both engaging two spatially segregated regions associated with small-molecule inhibitor interactions (fluoroquinolone antibiotics and the newly reported antagonist GSK299423) and remodeling the gyrase holoenzyme into an inactive, ATP-trapped configuration. This study establishes a new mechanism for the protein-based control of topoisomerases, an approach that may be used to alter supercoiling levels for responding to changes in cellular state. © 2014 Vos et al.; Published by Cold Spring Harbor Laboratory Press.

  10. TRF2 Protein Interacts with Core Histones to Stabilize Chromosome Ends.

    Science.gov (United States)

    Konishi, Akimitsu; Izumi, Takashi; Shimizu, Shigeomi

    2016-09-23

    Mammalian chromosome ends are protected by a specialized nucleoprotein complex called telomeres. Both shelterin, a telomere-specific multi-protein complex, and higher order telomeric chromatin structures combine to stabilize the chromosome ends. Here, we showed that TRF2, a component of shelterin, binds to core histones to protect chromosome ends from inappropriate DNA damage response and loss of telomeric DNA. The N-terminal Gly/Arg-rich domain (GAR domain) of TRF2 directly binds to the globular domain of core histones. The conserved arginine residues in the GAR domain of TRF2 are required for this interaction. A TRF2 mutant with these arginine residues substituted by alanine lost the ability to protect telomeres and induced rapid telomere shortening caused by the cleavage of a loop structure of the telomeric chromatin. These findings showed a previously unnoticed interaction between the shelterin complex and nucleosomal histones to stabilize the chromosome ends. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

  11. Comportamento mitótico e meiótico de cromossomos holocêntricos &gama; irradiados de Rhynchospora pubera (Cyperaceae Mitotic and meiotic behavior of &gama; irradiated holocentric chromosomes of Rhynchospora pubera (Cyperaceae

    Directory of Open Access Journals (Sweden)

    Waldeciro Colaço

    2002-05-01

    Full Text Available Para avaliar a ocorrência de cinetócoros difusos em Rhynchospora (Cyperaceae, cromossomos de R. pubera foram fragmentados ou fundidos por irradiação &gama;. Este material foi investigado nas gerações celulares subseqüentes, em ambas, mitose e meiose. Alterações no número e no tamanho dos cromossomos foram detectadas, mas o comportamento dos cromossomos irradiados foi normal e nenhum micronúcleo foi observado. Todos os dados apontam para a presença de cinetócoros difusos em R. pubera.In order to evaluate the occurrence of diffuse kinetochores in Rhynchospora (Cyperaceae, chromosomes of R. pubera were fragmented or fused by &gama; irradiation. This material was investigated in subsequent cell generations, in both mitosis and meiosis. Alterations in number and size of chromosomes were detected, but the anaphase behavior of irradiated chromosomes was normal and no micronucleus was observed. All these data point to the presence of diffuse kinetochores in R. pubera.

  12. A meiotic linkage map of the silver fox, aligned and compared to the canine genome.

    Science.gov (United States)

    Kukekova, Anna V; Trut, Lyudmila N; Oskina, Irina N; Johnson, Jennifer L; Temnykh, Svetlana V; Kharlamova, Anastasiya V; Shepeleva, Darya V; Gulievich, Rimma G; Shikhevich, Svetlana G; Graphodatsky, Alexander S; Aguirre, Gustavo D; Acland, Gregory M

    2007-03-01

    A meiotic linkage map is essential for mapping traits of interest and is often the first step toward understanding a cryptic genome. Specific strains of silver fox (a variant of the red fox, Vulpes vulpes), which segregate behavioral and morphological phenotypes, create a need for such a map. One such strain, selected for docility, exhibits friendly dog-like responses to humans, in contrast to another strain selected for aggression. Development of a fox map is facilitated by the known cytogenetic homologies between the dog and fox, and by the availability of high resolution canine genome maps and sequence data. Furthermore, the high genomic sequence identity between dog and fox allows adaptation of canine microsatellites for genotyping and meiotic mapping in foxes. Using 320 such markers, we have constructed the first meiotic linkage map of the fox genome. The resulting sex-averaged map covers 16 fox autosomes and the X chromosome with an average inter-marker distance of 7.5 cM. The total map length corresponds to 1480.2 cM. From comparison of sex-averaged meiotic linkage maps of the fox and dog genomes, suppression of recombination in pericentromeric regions of the metacentric fox chromosomes was apparent, relative to the corresponding segments of acrocentric dog chromosomes. Alignment of the fox meiotic map against the 7.6x canine genome sequence revealed high conservation of marker order between homologous regions of the two species. The fox meiotic map provides a critical tool for genetic studies in foxes and identification of genetic loci and genes implicated in fox domestication.

  13. GEMC1 is a TopBP1-interacting protein required for chromosomal DNA replication.

    Science.gov (United States)

    Balestrini, Alessia; Cosentino, Claudia; Errico, Alessia; Garner, Elizabeth; Costanzo, Vincenzo

    2010-05-01

    Many of the factors required for chromosomal DNA replication have been identified in unicellular eukaryotes. However, DNA replication is poorly understood in multicellular organisms. Here, we report the identification of GEMC1 (geminin coiled-coil containing protein 1), a novel vertebrate protein required for chromosomal DNA replication. GEMC1 is highly conserved in vertebrates and is preferentially expressed in proliferating cells. Using Xenopus laevis egg extract we show that Xenopus GEMC1 (xGEMC1) binds to the checkpoint and replication factor TopBP1, which promotes binding of xGEMC1 to chromatin during pre-replication complex (pre-RC) formation. We demonstrate that xGEMC1 interacts directly with replication factors such as Cdc45 and the kinase Cdk2-CyclinE, through which it is heavily phosphorylated. Phosphorylated xGEMC1 stimulates initiation of DNA replication, whereas depletion of xGEMC1 prevents the onset of DNA replication owing to the impairment of Cdc45 loading onto chromatin. Similarly, inhibition of GEMC1 expression with morpholino and siRNA oligos prevents DNA replication in embryonic and somatic vertebrate cells. These data suggest that GEMC1 promotes initiation of chromosomal DNA replication in multicellular organisms by mediating TopBP1- and Cdk2-dependent recruitment of Cdc45 onto replication origins.

  14. Angelman syndrome protein UBE3A interacts with primary microcephaly protein ASPM, localizes to centrosomes and regulates chromosome segregation.

    Directory of Open Access Journals (Sweden)

    Pooja Singhmar

    Full Text Available Many proteins associated with the phenotype microcephaly have been localized to the centrosome or linked to it functionally. All the seven autosomal recessive primary microcephaly (MCPH proteins localize at the centrosome. Microcephalic osteodysplastic primordial dwarfism type II protein PCNT and Seckel syndrome (also characterized by severe microcephaly protein ATR are also centrosomal proteins. All of the above findings show the importance of centrosomal proteins as the key players in neurogenesis and brain development. However, the exact mechanism as to how the loss-of-function of these proteins leads to microcephaly remains to be elucidated. To gain insight into the function of the most commonly mutated MCPH gene ASPM, we used the yeast two-hybrid technique to screen a human fetal brain cDNA library with an ASPM bait. The analysis identified Angelman syndrome gene product UBE3A as an ASPM interactor. Like ASPM, UBE3A also localizes to the centrosome. The identification of UBE3A as an ASPM interactor is not surprising as more than 80% of Angelman syndrome patients have microcephaly. However, unlike in MCPH, microcephaly is postnatal in Angelman syndrome patients. Our results show that UBE3A is a cell cycle regulated protein and its level peaks in mitosis. The shRNA knockdown of UBE3A in HEK293 cells led to many mitotic abnormalities including chromosome missegregation, abnormal cytokinesis and apoptosis. Thus our study links Angelman syndrome protein UBE3A to ASPM, centrosome and mitosis for the first time. We suggest that a defective chromosome segregation mechanism is responsible for the development of microcephaly in Angelman syndrome.

  15. Angelman syndrome protein UBE3A interacts with primary microcephaly protein ASPM, localizes to centrosomes and regulates chromosome segregation.

    Science.gov (United States)

    Singhmar, Pooja; Kumar, Arun

    2011-01-01

    Many proteins associated with the phenotype microcephaly have been localized to the centrosome or linked to it functionally. All the seven autosomal recessive primary microcephaly (MCPH) proteins localize at the centrosome. Microcephalic osteodysplastic primordial dwarfism type II protein PCNT and Seckel syndrome (also characterized by severe microcephaly) protein ATR are also centrosomal proteins. All of the above findings show the importance of centrosomal proteins as the key players in neurogenesis and brain development. However, the exact mechanism as to how the loss-of-function of these proteins leads to microcephaly remains to be elucidated. To gain insight into the function of the most commonly mutated MCPH gene ASPM, we used the yeast two-hybrid technique to screen a human fetal brain cDNA library with an ASPM bait. The analysis identified Angelman syndrome gene product UBE3A as an ASPM interactor. Like ASPM, UBE3A also localizes to the centrosome. The identification of UBE3A as an ASPM interactor is not surprising as more than 80% of Angelman syndrome patients have microcephaly. However, unlike in MCPH, microcephaly is postnatal in Angelman syndrome patients. Our results show that UBE3A is a cell cycle regulated protein and its level peaks in mitosis. The shRNA knockdown of UBE3A in HEK293 cells led to many mitotic abnormalities including chromosome missegregation, abnormal cytokinesis and apoptosis. Thus our study links Angelman syndrome protein UBE3A to ASPM, centrosome and mitosis for the first time. We suggest that a defective chromosome segregation mechanism is responsible for the development of microcephaly in Angelman syndrome.

  16. The gene for human erythrocyte protein 4. 2 maps to chromosome 15q15

    Energy Technology Data Exchange (ETDEWEB)

    Najfeld, V. (Mount Sinai School of Medicine, NY (United States)); Ballard, S.G.; Menninger, J.; Ward, D.C. (Yale Univ., New Haven, CT (United States)); Bouhassira, E.E.; Schwartz, R.S.; Nagel, R.L.; Rybicki, A.C. (Albert Einstein Coll. of Medicine/Montefiore Medical Center, Bronx, NY (United States))

    1992-01-01

    Protein 4.2 (P4.2), one of the major components of the red-blood-cell membrane, is located on the interior surface, where it binds with high affinity to the cytoplasmic domain of band 3. Individuals whose red blood cells are deficient in P4.2 have osmotically fragile, abnormally shaped cells and moderate hemolytic anemia. cDNA clones from both the 5{prime} and the 3{prime} coding regions of the P4.2 gene were used to map its chromosomal location by fluorescence in situ hybridization. The probes, individually or in combination, gave specific hybridization signals on chromosome 15. The hybridization locus was identified by combining fluorescence images of the probe signals with fluorescence banding patterns generated by Alu-PCR (R-like) probe and by DAPI staining (G-like). The authors results demonstrate that the locus of the P4.2 gene is located within 15q15.

  17. Polar Organizing Protein PopZ Is Required for Chromosome Segregation in Agrobacterium tumefaciens.

    Science.gov (United States)

    Ehrle, Haley M; Guidry, Jacob T; Iacovetto, Rebecca; Salisbury, Anne K; Sandidge, D J; Bowman, Grant R

    2017-09-01

    Despite being perceived as relatively simple organisms, many bacteria exhibit an impressive degree of subcellular organization. In Caulobacter crescentus , the evolutionarily conserved polar organizing protein PopZ facilitates cytoplasmic organization by recruiting chromosome centromeres and regulatory proteins to the cell poles. Here, we characterize the localization and function of PopZ in Agrobacterium tumefaciens , a genetically related species with distinct anatomy. In this species, we find that PopZ molecules are relocated from the old pole to the new pole in the minutes following cell division. PopZ is not required for the localization of the histidine kinases DivJ and PdhS1, which become localized to the old pole after PopZ relocation is complete. The histidine kinase PdhS2 is temporally and spatially related to PopZ in that it localizes to transitional poles just before they begin to shed PopZ and disappears from the old pole after PopZ relocalization. At the new pole, PopZ is required for tethering the centromere of at least one of multiple replicons (chromosome I), and the loss of popZ results in a severe chromosome segregation defect, aberrant cell division, and cell mortality. After cell division, the daughter that inherits polar PopZ is shorter in length and delayed in chromosome I segregation compared to its sibling. In this cell type, PopZ completes polar relocation well before the onset of chromosome segregation. While A. tumefaciens PopZ resembles its C. crescentus homolog in chromosome tethering activity, other aspects of its localization and function indicate distinct properties related to differences in cell organization. IMPORTANCE Members of the Alphaproteobacteria exhibit a wide range of phenotypic diversity despite sharing many conserved genes. In recent years, the extent to which this diversity is reflected at the level of subcellular organization has become increasingly apparent. However, which factors control such organization and how

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

    Science.gov (United States)

    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.

  19. Chromosome painting for plant biotechnology.

    Science.gov (United States)

    Kato, Akio; Lamb, Jonathan C; Albert, Patrice S; Danilova, Tatiana; Han, Fangpu; Gao, Zhi; Findley, Seth; Birchler, James A

    2011-01-01

    Fluorescence in situ hybridization (FISH) is an invaluable tool for chromosome analysis and engineering. The ability to visually localize endogenous genes, transposable elements, transgenes, naturally occurring organellar DNA insertions - essentially any unique sequence larger than 2 kb - greatly facilitates progress. This chapter details the labeling procedures and chromosome preparation techniques used to produce high-quality FISH signals on somatic metaphase and meiotic pachytene spreads.

  20. Fish on avian lampbrush chromosomes produces higher resolution gene mapping

    NARCIS (Netherlands)

    Galkina, S.A.; Deryusheva, S.; Fillon, V.; Vignal, A.; Crooijmans, R.P.M.A.; Groenen, M.A.M.; Rodionov, A.V.; Gaginskaya, E.

    2006-01-01

    Giant lampbrush chromosomes, which are characteristic of the diplotene stage of prophase I during avian oogenesis, represent a very promising system for precise physical gene mapping. We applied 35 chicken BAC and 4 PAC clones to both mitotic metaphase chromosomes and meiotic lampbrush chromosomes

  1. [The nuclear matrix proteins (mol. mass 38 and 50 kDa) are transported by chromosomes in mitosis].

    Science.gov (United States)

    Murasheva, M I; Chentsov, Iu S

    2010-01-01

    It was shown by immunofluorescence method that serum M68 and serum K43 from patients with autoimmune disease stain interphase nuclei and periphery of mitotic chromosomes of pig kidney cells. Western blotting reveals the polypeptide with mol. mass of 50 kDa in serum M68, and the polypeptide with mol. mass of 38 kDa in serum K43. In the nuclear protein matrix, the antibodies to protein with mol. mass of 38 kDa stained only nucleolar periphery, while the antibodies to the protein with mol. mass of 50 kDa stained both the nucleolar periphery and all the interphase nucleus. It shows that among all components of nuclear protein matrix (lamina, internuclear network, residual nucleoli) only nucleolar periphery contains the 38 kDa protein, while the 50 kDa protein is a part of residual nucleolar periphery and takes part in nuclear protein network formation. In the interphase cells, both proteins were in situ localized in the nuclei, but one of them with mol. mass of 50 kDa was in the form of small clearly outlined granules, while the other (38 kDa) was in the form of small bright granules against the background of diffusely stained nuclei. Both proteins were also revealed as continuous ring around nucleolar periphery. During all mitotic stages, the 50 kDa protein was seen on the chromosomal periphery as a cover, and the 38 kDa protein formed separate fragments and granules around them. After nuclear and chromosome decondensation induced by hypotonic treatment, both antibodies stain interphase nuclei in diffuse manner, but in mitotic cells they stained the surface of the swollen chromosomes. The polypeptide with mol. mass of 50 kDa maintained strong connection with chromosome periphery both in norm and under condition of decondensation induced by hypotonic treatment and at subsequent recondensation in isotonic medium. In contrast, the protein with mol. mass of 38 kDa partially lost the contact with a chromosome during recondensation appearing also in the form of granules in

  2. The DNA replication factor RFC1 is required for interference-sensitive meiotic crossovers in Arabidopsis thaliana.

    Directory of Open Access Journals (Sweden)

    Yingxiang Wang

    Full Text Available During meiotic recombination, induced double-strand breaks (DSBs are processed into crossovers (COs and non-COs (NCO; the former are required for proper chromosome segregation and fertility. DNA synthesis is essential in current models of meiotic recombination pathways and includes only leading strand DNA synthesis, but few genes crucial for DNA synthesis have been tested genetically for their functions in meiosis. Furthermore, lagging strand synthesis has been assumed to be unnecessary. Here we show that the Arabidopsis thaliana DNA replication factor C1 (RFC1 important for lagging strand synthesis is necessary for fertility, meiotic bivalent formation, and homolog segregation. Loss of meiotic RFC1 function caused abnormal meiotic chromosome association and other cytological defects; genetic analyses with other meiotic mutations indicate that RFC1 acts in the MSH4-dependent interference-sensitive pathway for CO formation. In a rfc1 mutant, residual pollen viability is MUS81-dependent and COs exhibit essentially no interference, indicating that these COs form via the MUS81-dependent interference-insensitive pathway. We hypothesize that lagging strand DNA synthesis is important for the formation of double Holliday junctions, but not alternative recombination intermediates. That RFC1 is found in divergent eukaryotes suggests a previously unrecognized and highly conserved role for DNA synthesis in discriminating between recombination pathways.

  3. GEMC1 is a TopBP1 interacting protein required for chromosomal DNA replication

    Science.gov (United States)

    Balestrini, Alessia; Cosentino, Claudia; Errico, Alessia; Garner, Elizabeth; Costanzo, Vincenzo

    2010-01-01

    Many factors required for chromosomal DNA replication have been identified in unicellular eukaryotes. However, DNA replication in complex multicellular organisms is poorly understood. Here, we report the identification of GEMC1, a novel vertebrate protein required for chromosomal DNA replication. GEMC1 is highly conserved in vertebrates and is preferentially expressed in proliferating cells. Using Xenopus egg extract we show that Xenopus GEMC1 (xGEMC1) binds to checkpoint and replication factor TopBP1, which promotes xGEMC1 binding to chromatin during pre-replication complex (pre-RC) formation. We demonstrate that xGEMC1 directly interacts with replication factors such as Cdc45 and Cdk2-CyclinE by which it is heavily phosphorylated. Phosphorylated xGEMC1 stimulates initiation of DNA replication whereas depletion of xGEMC1 prevents DNA replication onset due to impairment of Cdc45 loading onto chromatin. Likewise, inhibition of GEMC1 expression by morpholino and siRNA oligos prevents DNA replication in embryonic and somatic vertebrate cells. These data suggest that GEMC1 promotes initiation of chromosomal DNA replication in higher eukaryotes by mediating TopBP1 and Cdk2 dependent recruitment of Cdc45 onto replication origins. PMID:20383140

  4. Regulation of sister chromosome cohesion by the replication fork tracking protein SeqA.

    Science.gov (United States)

    Joshi, Mohan C; Magnan, David; Montminy, Timothy P; Lies, Mark; Stepankiw, Nicholas; Bates, David

    2013-01-01

    Analogously to chromosome cohesion in eukaryotes, newly replicated DNA in E. coli is held together by inter-sister linkages before partitioning into daughter nucleoids. In both cases, initial joining is apparently mediated by DNA catenation, in which replication-induced positive supercoils diffuse behind the fork, causing newly replicated duplexes to twist around each other. Type-II topoisomerase-catalyzed sister separation is delayed by the well-characterized cohesin complex in eukaryotes, but cohesion control in E. coli is not currently understood. We report that the abundant fork tracking protein SeqA is a strong positive regulator of cohesion, and is responsible for markedly prolonged cohesion observed at "snap" loci. Epistasis analysis suggests that SeqA stabilizes cohesion by antagonizing Topo IV-mediated sister resolution, and possibly also by a direct bridging mechanism. We show that variable cohesion observed along the E. coli chromosome is caused by differential SeqA binding, with oriC and snap loci binding disproportionally more SeqA. We propose that SeqA binding results in loose inter-duplex junctions that are resistant to Topo IV cleavage. Lastly, reducing cohesion by genetic manipulation of Topo IV or SeqA resulted in dramatically slowed sister locus separation and poor nucleoid partitioning, indicating that cohesion has a prominent role in chromosome segregation.

  5. Chromosomal and protein evolution in morphologically similar species of Praomys sensu lato (Rodentia, Muridae).

    Science.gov (United States)

    Qumsiyeh, M B; King, S W; Arroyo-Cabrales, J; Aggundey, I R; Schlitter, D A; Baker, R J; Morrow, K J

    1990-01-01

    Evidence of extensive chromosomal evolution in a biologically and economically important group of African murids of the Praomys/Mastomys complex was provided by examination of G- and C-band chromosomal data on P. coucha (2n = 32), P. fumatus (2n = 38), P. hildebrandti (2n = 32), P. jacksoni (2n = 28), P. misonnei (2n = 36), and P. cf. tullbergi (2n = 35). A coding system was developed for the chromosomal characters, and analyses were performed by a computer program to find the shortest tree with a minimum of 35 autosomal rearrangements (pericentric inversions, complex translocations, centric fusions, centric fissions, tandem fusions, euchromatic additions, and heterochromatic additions). The resulting phylogenetic hypothesis differs from traditionally accepted hypotheses regarding this complex group of rodents. The cytogenetic data show that 1) there is no support for the dichotomy of Mastomys/Praomys previously based on morphology, 2) the 2n = 32 species from eastern Africa (P. hildebrandti) is distinct from the 2n = 32 species from southern Africa (P. natalensis), and 3) there is a close association between P. jacksoni and P. cf. tullbergi. Polyacrylamide gel electrophoresis of liver membrane proteins demonstrated few differences in protein mobilities between species and even fewer between individuals of the same species taken from different habitats and localities in Kenya. Monoclonal antibodies produced against liver proteins of one species and tested for reactivity to other species confirmed the evolutionary similarity of species of this complex. This immunologic approach may provide a robust data set for future phylogenetic studies of muroid rodents.(ABSTRACT TRUNCATED AT 250 WORDS)

  6. Resistance to β-Lactams in Neisseria ssp Due to Chromosomally Encoded Penicillin-Binding Proteins.

    Science.gov (United States)

    Zapun, André; Morlot, Cécile; Taha, Muhamed-Kheir

    2016-09-28

    Neisseria meningitidis and Neisseria gonorrhoeae are human pathogens that cause a variety of life-threatening systemic and local infections, such as meningitis or gonorrhoea. The treatment of such infection is becoming more difficult due to antibiotic resistance. The focus of this review is on the mechanism of reduced susceptibility to penicillin and other β-lactams due to the modification of chromosomally encoded penicillin-binding proteins (PBP), in particular PBP2 encoded by the penA gene. The variety of penA alleles and resulting variant PBP2 enzymes is described and the important amino acid substitutions are presented and discussed in a structural context.

  7. Human Spermatozoa as a Model for Detecting Missing Proteins in the Context of the Chromosome-Centric Human Proteome Project.

    Science.gov (United States)

    Jumeau, Fanny; Com, Emmanuelle; Lane, Lydie; Duek, Paula; Lagarrigue, Mélanie; Lavigne, Régis; Guillot, Laëtitia; Rondel, Karine; Gateau, Alain; Melaine, Nathalie; Guével, Blandine; Sergeant, Nicolas; Mitchell, Valérie; Pineau, Charles

    2015-09-04

    The Chromosome-Centric Human Proteome Project (C-HPP) aims at cataloguing the proteins as gene products encoded by the human genome in a chromosome-centric manner. The existence of products of about 82% of the genes has been confirmed at the protein level. However, the number of so-called "missing proteins" remains significant. It was recently suggested that the expression of proteins that have been systematically missed might be restricted to particular organs or cell types, for example, the testis. Testicular function, and spermatogenesis in particular, is conditioned by the successive activation or repression of thousands of genes and proteins including numerous germ cell- and testis-specific products. Both the testis and postmeiotic germ cells are thus promising sites at which to search for missing proteins, and ejaculated spermatozoa are a potential source of proteins whose expression is restricted to the germ cell lineage. A trans-chromosome-based data analysis was performed to catalog missing proteins in total protein extracts from isolated human spermatozoa. We have identified and manually validated peptide matches to 89 missing proteins in human spermatozoa. In addition, we carefully validated three proteins that were scored as uncertain in the latest neXtProt release (09.19.2014). A focus was then given to the 12 missing proteins encoded on chromosomes 2 and 14, some of which may putatively play roles in ciliation and flagellum mechanistics. The expression pattern of C2orf57 and TEX37 was confirmed in the adult testis by immunohistochemistry. On the basis of transcript expression during human spermatogenesis, we further consider the potential for discovering additional missing proteins in the testicular postmeiotic germ cell lineage and in ejaculated spermatozoa. This project was conducted as part of the C-HPP initiatives on chromosomes 14 (France) and 2 (Switzerland). The mass spectrometry proteomics data have been deposited with the Proteome

  8. Addition of Aegilops U and M Chromosomes Affects Protein and Dietary Fiber Content of Wholemeal Wheat Flour

    Directory of Open Access Journals (Sweden)

    Marianna Rakszegi

    2017-09-01

    Full Text Available Cereal grain fiber is an important health-promoting component in the human diet. One option to improve dietary fiber content and composition in wheat is to introduce genes from its wild relatives Aegilops biuncialis and Aegilops geniculata. This study showed that the addition of chromosomes 2Ug, 4Ug, 5Ug, 7Ug, 2Mg, 5Mg, and 7Mg of Ae. geniculata and 3Ub, 2Mb, 3Mb, and 7Mb of Ae. biuncialis into bread wheat increased the seed protein content. Chromosomes 1Ug and 1Mg increased the proportion of polymeric glutenin proteins, while the addition of chromosomes 1Ub and 6Ub led to its decrease. Both Aegilops species had higher proportions of β-glucan compared to arabinoxylan (AX than wheat lines, and elevated β-glucan content was also observed in wheat chromosome addition lines 5U, 7U, and 7M. The AX content in wheat was increased by the addition of chromosomes 5Ug, 7Ug, and 1Ub while water-soluble AX was increased by the addition of chromosomes 5U, 5M, and 7M, and to a lesser extent by chromosomes 3, 4, 6Ug, and 2Mb. Chromosomes 5Ug and 7Mb also affected the structure of wheat AX, as shown by the pattern of oligosaccharides released by digestion with endoxylanase. These results will help to map genomic regions responsible for edible fiber content in Aegilops and will contribute to the efficient transfer of wild alleles in introgression breeding programs to obtain wheat varieties with improved health benefits.Key Message: Addition of Aegilops U- and M-genome chromosomes 5 and 7 improves seed protein and fiber content and composition in wheat.

  9. Chromosome locations of genes encoding human signal transduction adapter proteins, Nck (NCK), Shc (SHC1), and Grb2 (GRB2)

    DEFF Research Database (Denmark)

    Huebner, K; Kastury, K; Druck, T

    1994-01-01

    Abnormalities due to chromosomal aberration or point mutation in gene products of growth factor receptors or in ras gene products, which lie on the same signaling pathway, can cause disease in animals and humans. Thus, it can be important to determine chromosomal map positions of genes encoding...... "adapter" proteins, which are involved in transducing signals from receptor tyrosine kinases to downstream signal recipients such as ras, because adaptor protein genes could also, logically, serve as targets of mutation, rearrangement, or other aberration in disease. Therefore, DNAs from panels of rodent...... hybridization. The NCK locus is at chromosome region 3q21, a region involved in neoplasia-associated changes; the SHC cognate locus, SHC1, is at 1q21, and the GRB2 locus is at 17q22-qter telomeric to the HOXB and NGFR loci. Both SHC1 and GRB2 are in chromosome regions that may be duplicated in some tumor types....

  10. Enhanced chromatin accessibility of the dosage compensated Drosophila male X-chromosome requires the CLAMP zinc finger protein.

    Science.gov (United States)

    Urban, Jennifer; Kuzu, Guray; Bowman, Sarah; Scruggs, Benjamin; Henriques, Telmo; Kingston, Robert; Adelman, Karen; Tolstorukov, Michael; Larschan, Erica

    2017-01-01

    The essential process of dosage compensation is required to equalize gene expression of X-chromosome genes between males (XY) and females (XX). In Drosophila, the conserved Male-specific lethal (MSL) histone acetyltransferase complex mediates dosage compensation by increasing transcript levels from genes on the single male X-chromosome approximately two-fold. Consistent with its increased levels of transcription, the male X-chromosome has enhanced chromatin accessibility, distinguishing it from the autosomes. Here, we demonstrate that the non-sex-specific CLAMP (Chromatin-linked adaptor for MSL proteins) zinc finger protein that recognizes GA-rich sequences genome-wide promotes the specialized chromatin environment on the male X-chromosome and can act over long genomic distances (~14 kb). Although MSL complex is required for increasing transcript levels of X-linked genes, it is not required for enhancing global male X-chromosome chromatin accessibility, and instead works cooperatively with CLAMP to facilitate an accessible chromatin configuration at its sites of highest occupancy. Furthermore, CLAMP regulates chromatin structure at strong MSL complex binding sites through promoting recruitment of the Nucleosome Remodeling Factor (NURF) complex. In contrast to the X-chromosome, CLAMP regulates chromatin and gene expression on autosomes through a distinct mechanism that does not involve NURF recruitment. Overall, our results support a model where synergy between a non-sex-specific transcription factor (CLAMP) and a sex-specific cofactor (MSL) creates a specialized chromatin domain on the male X-chromosome.

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

    Directory of Open Access Journals (Sweden)

    Bilge Argunhan

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

  12. Clustering of double strand break-containing chromosome domains is not inhibited by inactivation of major repair proteins

    International Nuclear Information System (INIS)

    Krawczyk, P. M.; Stap, C.; Van Oven, C.; Hoebe, R.; Aten, J. A.

    2006-01-01

    For efficient repair of DNA double strand breaks (DSBs) cells rely on a process that involves the Mre11/Rad50/Nbs1 complex, which may help to protect non-repaired DNA ends from separating until they can be rejoined by DNA repair proteins. It has been observed that as a secondary effect, this process can lead to unintended clustering of multiple, initially separate, DSB-containing chromosome domains. This work demonstrates that neither inactivation of the major repair proteins XRCC3 and the DNA-dependent protein kinase (DNA-PK) nor inhibition of DNA-PK by vanillin influences the aggregation of DSB-containing chromosome domains. (authors)

  13. Mutational analysis of the terminal protein Tpg of Streptomyces chromosomes: identification of the deoxynucleotidylation site.

    Directory of Open Access Journals (Sweden)

    Chien-Chin Yang

    Full Text Available The linear chromosomes and linear plasmids of Streptomyces are capped by terminal proteins (TPs covalently bound to the 5' ends of the DNA. The TPs serve as primers for DNA synthesis that patches in the single-stranded gaps at the telomeres resulting from the bi-directional replication ('end patching'. Typical Streptomyces TPs, designated Tpgs, are conserved in sequence and size (about 185 amino acids, and contain a predicted helix-turn-helix domain and a functional nuclear localization signal. The Tpg-encoding gene (tpg is often accompanied by an upstream gene tap that encodes an essential telomere-associating protein. Five lone tpg variants (not accompanied by tap from various Streptomyces species were tested, and three were found to be pseudogenes. The lone tpg variant on the SLP2 plasmid, although functional, still requires the presence of tap on the chromosome for end patching. Using a combination of in vitro deoxynucleotidylation, physical localization, and genetic analysis, we identified the threonine at position 114 (T114 in Tpg of Streptomyces lividans chromosome as the deoxynucleotidylated site. Interestingly, T114 could be substituted by a serine without destroying the priming activity of Tpg in vitro and in vivo. Such T114S substitution is seen in and a number of pseudogenes as well as functional Tpgs. T114 lies in a predicted coil flanked by two short helixes in a highly hydrophilic region. The location and structural arrangement of the deoxynucleotidylated site in Tpg is similar to those in the TPs of phage ø 29 and adenoviruses. However, these TPs are distinct in their sequences and sizes, indicating that they have evolved independently during evolution. Using naturally occurring and artificially created tpg variants, we further identified several amino acid residues in the N-terminus and the helix-turn-helix domain that were important for functionality.

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

    Science.gov (United States)

    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.

  15. Mitochondrial ribosomal protein S18-2 evokes chromosomal instability and transforms primary rat skin fibroblasts

    KAUST Repository

    Kashuba, Elena

    2015-05-12

    We have shown earlier that overexpression of the human mitochondrial ribosomal protein MRPS18-2 (S18-2) led to immortalization of primary rat embryonic fibroblasts. The derived cells expressed the embryonic stem cell markers, and cellular pathways that control cell proliferation, oxidative phosphorylation, cellular respiration, and other redox reactions were activated in the immortalized cells. Here we report that, upon overexpression of S18-2 protein, primary rat skin fibroblasts underwent cell transformation. Cells passed more than 300 population doublings, and two out of three tested clones gave rise to tumors in experimental animals. Transformed cells showed anchorage-independent growth and loss of contact inhibition; they expressed epithelial markers, such as E-cadherin and β-catenin. Transformed cells showed increased telomerase activity, disturbance of the cell cycle, and chromosomal instability. Taken together, our data suggest that S18-2 is a newly identified oncoprotein that may be involved in cancerogenesis.

  16. ParA-like protein influences the distribution of multi-copy chromosomes in cyanobacterium Synechococcus elongatus PCC 7942.

    Science.gov (United States)

    Watanabe, Satoru; Noda, Aska; Ohbayashi, Ryudo; Uchioke, Kana; Kurihara, Ami; Nakatake, Shizuka; Morioka, Sayumi; Kanesaki, Yu; Chibazakura, Taku; Yoshikawa, Hirofumi

    2018-01-01

    While many bacteria, such as Escherichia coli and Bacillus subtilis, harbour a single-copy chromosome, freshwater cyanobacteria have multiple copies of each chromosome per cell. Although it has been reported that multi-copy chromosomes are evenly distributed along the major axis of the cell in cyanobacterium Synechococcus elongatus PCC 7942, the distribution mechanism of these chromosomes remains unclear. In S. elongatus, the carboxysome, a metabolic microcompartment for carbon fixation that is distributed in a similar manner to the multi-copy chromosomes, is regulated by ParA-like protein (hereafter ParA). To elucidate the role of ParA in the distribution of multi-copy chromosomes, we constructed and analysed ParA disruptant and overexpressing strains of S. elongatus. Our fluorescence in situ hybridization assay revealed that the parA disruptants displayed an aberrant distribution of their multi-copy chromosomes. In the parA disruptant the multiple origin and terminus foci, corresponding to the intracellular position of each chromosomal region, were aggregated, which was compensated by the expression of exogenous ParA from other genomic loci. The parA disruptant is sensitive to UV-C compared to the WT strain. Additionally, giant cells appeared under ParA overexpression at the late stage of growth indicating that excess ParA indirectly inhibits cell division. Screening of the ParA-interacting proteins by yeast two-hybrid analysis revealed four candidates that are involved in DNA repair and cell membrane biogenesis. These results suggest that ParA is involved in the pleiotropic cellular functions with these proteins, while parA is dispensable for cell viability in S. elongatus.

  17. Dynamics of response to asynapsis and meiotic silencing in spermatocytes from Robertsonian translocation carriers.

    Directory of Open Access Journals (Sweden)

    Anna K Naumova

    Full Text Available Failure of homologous synapsis during meiotic prophase triggers transcriptional repression. Asynapsis of the X and Y chromosomes and their consequent silencing is essential for spermatogenesis. However, asynapsis of portions of autosomes in heterozygous translocation carriers may be detrimental for meiotic progression. In fact, a wide range of phenotypic outcomes from meiotic arrest to normal spermatogenesis have been described and the causes of such a variation remain elusive. To better understand the consequences of asynapsis in male carriers of Robertsonian translocations, we focused on the dynamics of recruitment of markers of asynapsis and meiotic silencing at unsynapsed autosomal trivalents in the spermatocytes of Robertsonian translocation carrier mice. Here we report that the enrichment of breast cancer 1 (BRCA1 and histone γH2AX at unsynapsed trivalents declines during the pachytene stage of meiosis and differs from that observed in the sex body. Furthermore, histone variant H3.3S31, which associates with the sex chromosomes in metaphase I/anaphase I spermatocytes, localizes to autosomes in 12% and 31% of nuclei from carriers of one and three translocations, respectively. These data suggest that the proportion of spermatocytes with markers of meiotic silencing of unsynapsed chromatin (MSUC at trivalents depends on both, the stage of meiosis and the number of translocations. This may explain some of the variability in phenotypic outcomes associated with Robertsonian translocations. In addition our data suggest that the dynamics of response to asynapsis in Robertsonian translocations differs from the response to sex chromosomal asynapsis in the male germ line.

  18. ISCN rules for listing chromosomal rearrangements.

    Science.gov (United States)

    2001-05-01

    It contains the standard system for numbering human chromosomes and constitutional rearrangements and the banding pattern for normal chromosomes at 400-, 550-, and 850-band levels of resolution. ISCN 1995 also contains guidelines for cancer cytogenetics and for in situ hybridization. The complete ISCN 1995 also contains nomenclature for human meiotic chromosomes (not included here). The guidelines presented herein are recommended for use when reporting karyotypes, designating chromosome rearrangements and aberrations, and indicating regions of the genome where DNA sequences are located. It contains the standard system for numbering human chromosomes and constitutional rearrangements and the banding pattern for.

  19. A new twist in the coil: functions of the coiled-coil domain of structural maintenance of chromosome (SMC) proteins.

    Science.gov (United States)

    Matityahu, Avi; Onn, Itay

    2018-02-01

    The higher-order organization of chromosomes ensures their stability and functionality. However, the molecular mechanism by which higher order structure is established is poorly understood. Dissecting the activity of the relevant proteins provides information essential for achieving a comprehensive understanding of chromosome structure. Proteins of the structural maintenance of chromosome (SMC) family of ATPases are the core of evolutionary conserved complexes. SMC complexes are involved in regulating genome dynamics and in maintaining genome stability. The structure of all SMC proteins resembles an elongated rod that contains a central coiled-coil domain, a common protein structural motif in which two α-helices twist together. In recent years, the imperative role of the coiled-coil domain to SMC protein activity and regulation has become evident. Here, we discuss recent advances in the function of the SMC coiled coils. We describe the structure of the coiled-coil domain of SMC proteins, modifications and interactions that are mediated by it. Furthermore, we assess the role of the coiled-coil domain in conformational switches of SMC proteins, and in determining the architecture of the SMC dimer. Finally, we review the interplay between mutations in the coiled-coil domain and human disorders. We suggest that distinctive properties of coiled coils of different SMC proteins contribute to their distinct functions. The discussion clarifies the mechanisms underlying the activity of SMC proteins, and advocates future studies to elucidate the function of the SMC coiled coil domain.

  20. Chromosome-Centric Human Proteome Project Allies with Developmental Biology: A Case Study of the Role of Y Chromosome Genes in Organ Development.

    Science.gov (United States)

    Meyfour, Anna; Pooyan, Paria; Pahlavan, Sara; Rezaei-Tavirani, Mostafa; Gourabi, Hamid; Baharvand, Hossein; Salekdeh, Ghasem Hosseini

    2017-12-01

    One of the main goals of Chromosome-Centric Human Proteome Project is to identify protein evidence for missing proteins (MPs). Here, we present a case study of the role of Y chromosome genes in organ development and how to overcome the challenges facing MPs identification by employing human pluripotent stem cell differentiation into cells of different organs yielding unprecedented biological insight into adult silenced proteins. Y chromosome is a male-specific sex chromosome which escapes meiotic recombination. From an evolutionary perspective, Y chromosome has preserved 3% of ancestral genes compared to 98% preservation of the X chromosome based on Ohno's law. Male specific region of Y chromosome (MSY) contains genes that contribute to central dogma and govern the expression of various targets throughout the genome. One of the most well-known functions of MSY genes is to decide the male-specific characteristics including sex, testis formation, and spermatogenesis, which are majorly formed by ampliconic gene families. Beyond its role in sex-specific gonad development, MSY genes in coexpression with their X counterparts, as single copy and broadly expressed genes, inhibit haplolethality and play a key role in embryogenesis. The role of X-Y related gene mutations in the development of hereditary syndromes suggests an essential contribution of sex chromosome genes to development. MSY genes, solely and independent of their X counterparts and/or in association with sex hormones, have a considerable impact on organ development. In this Review, we present major recent findings on the contribution of MSY genes to gonad formation, spermatogenesis, and the brain, heart, and kidney development and discuss how Y chromosome proteome project may exploit developmental biology to find missing proteins.

  1. Thermodynamical study of interaction of histone H1 chromosomal protein and mitoxantrone anticancer drug

    Energy Technology Data Exchange (ETDEWEB)

    Jafargholizadeh, Naser [Department of Cell and Molecular Biology, School of Biology, College of Science, University of Tehran, Tehran (Iran, Islamic Republic of); Zargar, Seyed Jalal, E-mail: Zargar@khayam.ut.ac.ir [Department of Cell and Molecular Biology, School of Biology, College of Science, University of Tehran, Tehran (Iran, Islamic Republic of); Safarian, Shahrokh; Habibi-Rezaei, Mehran [Department of Cell and Molecular Biology, School of Biology, College of Science, University of Tehran, Tehran (Iran, Islamic Republic of)

    2012-06-10

    Highlights: Black-Right-Pointing-Pointer For the first time, our results show mitoxantrone anticancer drug binds to histone H1, via hydrophobic, hydrogen, van der Waals and electrostatic interactions. Black-Right-Pointing-Pointer Binding of mitoxantrone molecules to histone H1 is positive cooperative. Black-Right-Pointing-Pointer Histone H1 may be considered as a new target for mitoxantrone at the chromatin level. - Using ultraviolet spectroscopy technique, we have investigated the interaction of anticancer drug, mitoxantrone with calf thymus histone H1 chromosomal protein in 100 mM phosphate buffer, pH 7.0, at temperatures 300 and 310 K. UV spectroscopy results show interactions between mitoxantrone and histone H1 with a positive cooperative binding process which was confirmed by Scatchard plot. According to the obtained results, it is concluded that histone H1 can be considered as a target for mitoxantrone binding at the chromatin level.

  2. Thermodynamical study of interaction of histone H1 chromosomal protein and mitoxantrone anticancer drug

    International Nuclear Information System (INIS)

    Jafargholizadeh, Naser; Zargar, Seyed Jalal; Safarian, Shahrokh; Habibi-Rezaei, Mehran

    2012-01-01

    Highlights: ► For the first time, our results show mitoxantrone anticancer drug binds to histone H1, via hydrophobic, hydrogen, van der Waals and electrostatic interactions. ► Binding of mitoxantrone molecules to histone H1 is positive cooperative. ► Histone H1 may be considered as a new target for mitoxantrone at the chromatin level. - Using ultraviolet spectroscopy technique, we have investigated the interaction of anticancer drug, mitoxantrone with calf thymus histone H1 chromosomal protein in 100 mM phosphate buffer, pH 7.0, at temperatures 300 and 310 K. UV spectroscopy results show interactions between mitoxantrone and histone H1 with a positive cooperative binding process which was confirmed by Scatchard plot. According to the obtained results, it is concluded that histone H1 can be considered as a target for mitoxantrone binding at the chromatin level.

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

    Directory of Open Access Journals (Sweden)

    Divanilde Guerra

    2011-01-01

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

  4. Chip, a widely expressed chromosomal protein required for segmentation and activity of a remote wing margin enhancer in Drosophila.

    Science.gov (United States)

    Morcillo, P; Rosen, C; Baylies, M K; Dorsett, D

    1997-10-15

    The mechanisms allowing remote enhancers to regulate promoters several kilobase pairs away are unknown but are blocked by the Drosophila suppressor of Hairy-wing protein (Suhw) that binds to gypsy retrovirus insertions between enhancers and promoters. Suhw bound to a gypsy insertion in the cut gene also appears to act interchromosomally to antagonize enhancer-promoter interactions on the homologous chromosome when activity of the Chip gene is reduced. This implicates Chip in enhancer-promoter communication. We cloned Chip and find that it encodes a homolog of the recently discovered mouse Nli/Ldb1/Clim-2 and Xenopus Xldb1 proteins that bind nuclear LIM domain proteins. Chip protein interacts with the LIM domains in the Apterous homeodomain protein, and Chip interacts genetically with apterous, showing that these interactions are important for Apterous function in vivo. Importantly, Chip also appears to have broad functions beyond interactions with LIM domain proteins. Chip is present in all nuclei examined and at numerous sites along the salivary gland polytene chromosomes. Embryos without Chip activity lack segments and show abnormal gap and pair-rule gene expression, although no LIM domain proteins are known to regulate segmentation. We conclude that Chip is a ubiquitous chromosomal factor required for normal expression of diverse genes at many stages of development. We suggest that Chip cooperates with different LIM domain proteins and other factors to structurally support remote enhancer-promoter interactions.

  5. The adaptor-like protein ROG-1 is required for activation of the Ras-MAP kinase pathway and meiotic cell cycle progression in Caenorhabditis elegans.

    Science.gov (United States)

    Matsubara, Yosuke; Kawasaki, Ichiro; Urushiyama, Seiichi; Yasuda, Tomoharu; Shirakata, Masaki; Iino, Yuichi; Shibuya, Hiroshi; Yamanashi, Yuji

    2007-03-01

    The Ras-MAP kinase pathway regulates varieties of fundamental cellular events. In Caenorhabditis elegans, this pathway is required for oocyte development; however, the nature of its up-stream regulators has remained elusive. Here, we identified a C. elegans gene, rog-1, which encodes the only protein having the IRS-type phosphotyrosine-binding (PTB) domain in the worms. ROG-1 has no obvious domain structure aside from the PTB domain, suggesting that it could serve as an adaptor down-stream of protein-tyrosine kinases (PTKs). RNA interference (RNAi)-mediated down-regulation of rog-1 mRNA significantly decreased brood size. rog-1(tm1031) truncation mutants showed a severe disruption in progression of developing oocytes from pachytene to diakinesis, as was seen in worms carrying a loss-of-function mutation in the let-60 Ras or mpk-1 MAP kinase gene. Furthermore, let-60 Ras-regulated activation of MPK-1 in the gonad is undetectable in rog-1(tm1031) mutants. Conversely, a gain-of-function mutation in the let-60 Ras gene rescues the brood size reduction and germ cell abnormality in rog-1(tm1031) worms. Consistently, rog-1 is preferentially expressed in the germ cells and its expression in the gonad is essential for oocyte development. Thus, ROG-1 is a key positive regulator of the Ras-MAP kinase pathway that permits germ cells to exit from pachytene.

  6. Chromosome locations of genes encoding human signal transduction adapter proteins, Nck (NCK), Shc (SHC1), and Grb2 (GRB2)

    DEFF Research Database (Denmark)

    Huebner, K; Kastury, K; Druck, T

    1994-01-01

    -human hybrids carrying defined complements of human chromosomes were assayed for the presence of the cognate genes for NCK, SHC, and GRB2, three SH2 or SH2/SH3 (Src homology 2 and 3) domain-containing adapter proteins. Additionally, NCK and SHC genes were more narrowly localized by chromosomal in situ...... hybridization. The NCK locus is at chromosome region 3q21, a region involved in neoplasia-associated changes; the SHC cognate locus, SHC1, is at 1q21, and the GRB2 locus is at 17q22-qter telomeric to the HOXB and NGFR loci. Both SHC1 and GRB2 are in chromosome regions that may be duplicated in some tumor types.......Abnormalities due to chromosomal aberration or point mutation in gene products of growth factor receptors or in ras gene products, which lie on the same signaling pathway, can cause disease in animals and humans. Thus, it can be important to determine chromosomal map positions of genes encoding...

  7. DNA damage response clamp 9-1-1 promotes assembly of ZMM proteins for formation of crossovers and synaptonemal complex

    Science.gov (United States)

    Shinohara, Miki; Hayashihara, Kayoko; Grubb, Jennifer T.; Bishop, Douglas K.; Shinohara, Akira

    2015-01-01

    Formation of crossovers between homologous chromosomes during meiosis is positively regulated by the ZMM proteins (also known as SIC proteins). DNA damage checkpoint proteins also promote efficient formation of interhomolog crossovers. Here, we examined, in budding yeast, the meiotic role of the heterotrimeric DNA damage response clamp composed of Rad17, Ddc1 and Mec3 (known as ‘9-1-1’ in other organisms) and a component of the clamp loader, Rad24 (known as Rad17 in other organisms). Cytological analysis indicated that the 9-1-1 clamp and its loader are not required for the chromosomal loading of RecA homologs Rad51 or Dmc1, but are necessary for the efficient loading of ZMM proteins. Interestingly, the loading of ZMM proteins onto meiotic chromosomes was independent of the checkpoint kinase Mec1 (the homolog of ATR) as well as Rad51. Furthermore, the ZMM member Zip3 (also known as Cst9) bound to the 9-1-1 complex in a cell-free system. These data suggest that, in addition to promoting interhomolog bias mediated by Rad51–Dmc1, the 9-1-1 clamp promotes crossover formation through a specific role in the assembly of ZMM proteins. Thus, the 9-1-1 complex functions to promote two crucial meiotic recombination processes, the regulation of interhomolog recombination and crossover formation mediated by ZMM. PMID:25736290

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

    Directory of Open Access Journals (Sweden)

    Yaniv M Elkouby

    2016-01-01

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

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

    Science.gov (United States)

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

    2016-01-01

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

  10. Level of heat shock proteins decreases in individuals carrying B-chromosomes in the grasshopper Eyprepocnemis plorans

    DEFF Research Database (Denmark)

    Teruel, M; Sørensen, Jesper Givskov; Loeschcke, Volker

    2010-01-01

    We analyzed the effect of B-chromosome presence on expression level of heat shock protein 70 (Hsp70) in cerebral ganglion and gonad in both males and females of the grasshopper Eyprepocnemis plorans. Two natural Spanish populations, Salobreña (Granada) and Torrox (Málaga) were assayed, the former...

  11. Aberrant Meiotic Modulation Partially Contributes to the Lower Germination Rate of Pollen Grains in Maize (Zea mays L.) Under Low Nitrogen Supply.

    Science.gov (United States)

    Zheng, Hongyan; Wu, Huamao; Pan, Xiaoying; Jin, Weiwei; Li, Xuexian

    2017-02-01

    Pollen germination is an essential step towards successful pollination during maize reproduction. How low niutrogen (N) affects pollen germination remains an interesting biological question to be addressed. We found that only low N resulted in a significantly lower germination rate of pollen grains after 4 weeks of low N, phosphorus or potassium treatment in maize production. Importantly, cytological analysis showed 7-fold more micronuclei in male meiocytes under the low N treatment than in the control, indicating that the lower germination rate of pollen grains was partially due to numerous chromosome loss events resulting from preceding meiosis. The appearance of 10 bivalents in the control and low N cells at diakinesis suggested that chromosome pairing and recombination in meiosis I was not affected by low N. Further gene expression analysis revealed dramatic down-regulation of Nuclear Division Cycle 80 (Ndc80) and Regulator of Chromosome Condensation 1 (Rcc1-1) expression and up-regulation of Cell Division Cycle 20 (Cdc20-1) expression, although no significant difference in the expression level of kinetochore foundation proteins Centromeric Histone H3 (Cenh3) and Centromere Protein C (Cenpc) and cohesion regulators Recombination 8 (Rec8) and Shugoshin (Sgo1) was observed. Aberrant modulation of three key meiotic regulators presumably resulted in a high likelihood of erroneous chromosome segregation, as testified by pronounced lagging chromosomes at anaphase I or cell cycle disruption at meiosis II. Thus, we proposed a cytogenetic mechanism whereby low N affects male meiosis and causes a higher chromosome loss frequency and eventually a lower germination rate of pollen grains in a staple crop plant. © The Author 2016. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

  12. Protein energy-malnutrition: does the in vitro zinc sulfate supplementation improve chromosomal damage repair?

    Science.gov (United States)

    Padula, Gisel; González, Horacio F; Varea, Ana; Seoane, Analía I

    2014-12-01

    Protein-energy malnutrition (PEM) is originated by a cellular imbalance between nutrient/energy supply and body's demand. Induction of genetic damage by PEM was reported. The purpose of this study was to determine the genetic effect of the in vitro zinc sulfate (ZnSO4) supplementation of cultured peripheral blood lymphocytes from children with PEM. Twenty-four samples from 12 children were analyzed. Anthropometric and biochemical diagnosis was made. For the anthropometric assessment, height-for-age index, weight-for-age index, and weight-for-height index were calculated (WHO, 2005). Micronutrient status was evaluated. A survey for assessed previous exposure to potentially genotoxic agents was applied. Results were statistically evaluated using paired sample t test and χ (2) test. Each sample was fractionated and cultured in two separate flasks to performed two treatments. One was added with 180 μg/dl of ZnSO4 (PEMs/ZnSO4) and the other remains non-supplemented (PEMs). Cytotoxic effects and chromosomal damage were assessed using the cytokinesis-block micronucleus assay (CBMN). All participants have at least one type of malnutrition and none have anemia, nor iron, folate, vitamin A, and zinc deficiency. All PEMs/ZnSO4 samples have a significant reduction in the micronucleus (MNi) frequency compared with PEMs (t = 6.25685; p < 0.001). Nuclear division index (NDI) increase in PEMs/ZnSO4 (t = -17.4226; p < 0.001). Nucleoplasmic bridge (NPBs) frequency was four times smaller in PEMs/ZnSO4 (χ (2) = 40.82; p < 0.001). No nuclear buds (NBuds) were observed. Cytotoxic effects and chromosomal damage observed in children suffering from PEM can be repaired in vitro with zinc sulfate supplementation.

  13. Cold-Induced Male Meiotic Restitution in Arabidopsis thaliana Is Not Mediated by GA-DELLA Signaling

    Directory of Open Access Journals (Sweden)

    Bing Liu

    2018-02-01

    Full Text Available Short periods of cold stress induce male meiotic restitution and diploid pollen formation in Arabidopsis thaliana by specifically interfering with male meiotic cytokinesis. Similar alterations in male meiotic cell division and gametophytic ploidy stability occur when gibberellic acid (GA signaling is perturbed in developing anthers. In this study, we found that exogenous application of GA primarily induces second division restitution (SDR-type pollen in Arabidopsis, similar to what cold does. Driven by the close similarity in cellular defects, we tested the hypothesis that cold-induced meiotic restitution is mediated by GA-DELLA signaling. Using a combination of chemical, genetic and cytological approaches, however, we found that both exogenously and endogenously altered GA signaling do not affect the cold sensitivity of male meiotic cytokinesis. Moreover, in vivo localization study using a GFP-tagged version of RGA protein revealed that cold does not affect the expression pattern and abundance of DELLA in Arabidopsis anthers at tetrad stage. Expression study found that transcript of RGA appears enhanced in cold-stressed young flower buds. Since our previous work demonstrated that loss of function of DELLA causes irregular male meiotic cytokinesis, we here conclude that cold-induced meiotic restitution is not mediated by DELLA-dependent GA signaling.

  14. Regulation of chromosomal replication by DnaA protein availability in Escherichia coli: effects of the datA region

    DEFF Research Database (Denmark)

    Morigen, H.; Boye, E.; Skarstad, K.

    2001-01-01

    A copy number, we introduced a minichromosome which only replicates from oriC., using a host cell which replicates its chromosome independently of oriC. Our data show that a moderate increase in datA copy number is accompanied by increased DnaA protein synthesis that allows oriC initiation to occur...... suggest that the datA locus plays a significant role in regulating oriC initiation, by its capacity to bind DnaA. They also suggest that auto regulation of the dnaA gene is of minor importance in regulation of chromosome initiation....

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-11-15

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

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

    Science.gov (United States)

    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

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

    Directory of Open Access Journals (Sweden)

    Rodríguez-Garay Benjamin

    2002-10-01

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

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

    Directory of Open Access Journals (Sweden)

    Nicole A. Najor

    2016-12-01

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

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

    Science.gov (United States)

    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.

  20. Assignment of the nuclear mitotic apparatus protein NuMA gene to human chromosome 11q13

    Energy Technology Data Exchange (ETDEWEB)

    Sparks, C.A.; Bangs, P.L.; Lawrence, J.B.; Fey, E.G.; McNeil, G.P. (Univ. of Massachusetts Medical School, Worcester, MA (United States))

    1993-07-01

    A monoclonal antibody that was specific for a nuclear matrix protein was obtained and used to screen a human [lambda]gt11 expression library. Several partial cDNA clones were isolated and sequenced. The sequence for this protein was shown to be identical to that of NuMA, a 236-kDa nuclear mitotic spindle apparatus protein. NuMA has been recently characterized by two independent studies, and is thought to be part of a family of proteins that is required for the completion of mitosis. In this report, the chromosomal localization and copy number of the NuMA gene are analyzed using cDNA clones. High-resolution in situ hybridization reveals a single pair of signals on sister chromatids of human chromosome 11 at band q13. Stringent Southern analysis of human genomic DNA resulted in simple restriction patterns. These results together indicate that the NuMA gene is present as a single copy on human chromosome 11q13. 12 refs., 1 fig.

  1. SAP-like domain in nucleolar spindle associated protein mediates mitotic chromosome loading as well as interphase chromatin interaction

    Energy Technology Data Exchange (ETDEWEB)

    Verbakel, Werner, E-mail: werner.verbakel@chem.kuleuven.be [Laboratory of Biomolecular Dynamics, Katholieke Universiteit Leuven, Celestijnenlaan 200G, Bus 2403, 3001 Heverlee (Belgium); Carmeliet, Geert, E-mail: geert.carmeliet@med.kuleuven.be [Laboratory of Experimental Medicine and Endocrinology, Katholieke Universiteit Leuven, Herestraat 49, Bus 902, 3000 Leuven (Belgium); Engelborghs, Yves, E-mail: yves.engelborghs@fys.kuleuven.be [Laboratory of Biomolecular Dynamics, Katholieke Universiteit Leuven, Celestijnenlaan 200G, Bus 2403, 3001 Heverlee (Belgium)

    2011-08-12

    Highlights: {yields} The SAP-like domain in NuSAP is a functional DNA-binding domain with preference for dsDNA. {yields} This SAP-like domain is essential for chromosome loading during early mitosis. {yields} NuSAP is highly dynamic on mitotic chromatin, as evident from photobleaching experiments. {yields} The SAP-like domain also mediates NuSAP-chromatin interaction in interphase nucleoplasm. -- Abstract: Nucleolar spindle associated protein (NuSAP) is a microtubule-stabilizing protein that localizes to chromosome arms and chromosome-proximal microtubules during mitosis and to the nucleus, with enrichment in the nucleoli, during interphase. The critical function of NuSAP is underscored by the finding that its depletion in HeLa cells results in various mitotic defects. Moreover, NuSAP is found overexpressed in multiple cancers and its expression levels often correlate with the aggressiveness of cancer. Due to its localization on chromosome arms and combination of microtubule-stabilizing and DNA-binding properties, NuSAP takes a special place within the extensive group of spindle assembly factors. In this study, we identify a SAP-like domain that shows DNA binding in vitro with a preference for dsDNA. Deletion of the SAP-like domain abolishes chromosome arm binding of NuSAP during mitosis, but is not sufficient to abrogate its chromosome-proximal localization after anaphase onset. Fluorescence recovery after photobleaching experiments revealed the highly dynamic nature of this NuSAP-chromatin interaction during mitosis. In interphase cells, NuSAP also interacts with chromatin through its SAP-like domain, as evident from its enrichment on dense chromatin regions and intranuclear mobility, measured by fluorescence correlation spectroscopy. The obtained results are in agreement with a model where NuSAP dynamically stabilizes newly formed microtubules on mitotic chromosomes to enhance chromosome positioning without immobilizing these microtubules. Interphase Nu

  2. SAP-like domain in nucleolar spindle associated protein mediates mitotic chromosome loading as well as interphase chromatin interaction

    International Nuclear Information System (INIS)

    Verbakel, Werner; Carmeliet, Geert; Engelborghs, Yves

    2011-01-01

    Highlights: → The SAP-like domain in NuSAP is a functional DNA-binding domain with preference for dsDNA. → This SAP-like domain is essential for chromosome loading during early mitosis. → NuSAP is highly dynamic on mitotic chromatin, as evident from photobleaching experiments. → The SAP-like domain also mediates NuSAP-chromatin interaction in interphase nucleoplasm. -- Abstract: Nucleolar spindle associated protein (NuSAP) is a microtubule-stabilizing protein that localizes to chromosome arms and chromosome-proximal microtubules during mitosis and to the nucleus, with enrichment in the nucleoli, during interphase. The critical function of NuSAP is underscored by the finding that its depletion in HeLa cells results in various mitotic defects. Moreover, NuSAP is found overexpressed in multiple cancers and its expression levels often correlate with the aggressiveness of cancer. Due to its localization on chromosome arms and combination of microtubule-stabilizing and DNA-binding properties, NuSAP takes a special place within the extensive group of spindle assembly factors. In this study, we identify a SAP-like domain that shows DNA binding in vitro with a preference for dsDNA. Deletion of the SAP-like domain abolishes chromosome arm binding of NuSAP during mitosis, but is not sufficient to abrogate its chromosome-proximal localization after anaphase onset. Fluorescence recovery after photobleaching experiments revealed the highly dynamic nature of this NuSAP-chromatin interaction during mitosis. In interphase cells, NuSAP also interacts with chromatin through its SAP-like domain, as evident from its enrichment on dense chromatin regions and intranuclear mobility, measured by fluorescence correlation spectroscopy. The obtained results are in agreement with a model where NuSAP dynamically stabilizes newly formed microtubules on mitotic chromosomes to enhance chromosome positioning without immobilizing these microtubules. Interphase NuSAP-chromatin interaction

  3. The chromosomal passenger protein birc5b organizes microfilaments and germ plasm in the zebrafish embryo.

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    Sreelaja Nair

    2013-04-01

    Full Text Available Microtubule-microfilament interactions are important for cytokinesis and subcellular localization of proteins and mRNAs. In the early zebrafish embryo, astral microtubule-microfilament interactions also facilitate a stereotypic segregation pattern of germ plasm ribonucleoparticles (GP RNPs, which is critical for their eventual selective inheritance by germ cells. The precise mechanisms and molecular mediators for both cytoskeletal interactions and GP RNPs segregation are the focus of intense research. Here, we report the molecular identification of a zebrafish maternal-effect mutation motley as Birc5b, a homolog of the mammalian Chromosomal Passenger Complex (CPC component Survivin. The meiosis and mitosis defects in motley/birc5b mutant embryos are consistent with failed CPC function, and additional defects in astral microtubule remodeling contribute to failures in the initiation of cytokinesis furrow ingression. Unexpectedly, the motley/birc5b mutation also disrupts cortical microfilaments and GP RNP aggregation during early cell divisions. Birc5b localizes to the tips of astral microtubules along with polymerizing cortical F-actin and the GP RNPs. Mutant Birc5b co-localizes with cortical F-actin and GP RNPs, but fails to associate with astral microtubule tips, leading to disorganized microfilaments and GP RNP aggregation defects. Thus, maternal Birc5b localizes to astral microtubule tips and associates with cortical F-actin and GP RNPs, potentially linking the two cytoskeletons to mediate microtubule-microfilament reorganization and GP RNP aggregation during early embryonic cell cycles in zebrafish. In addition to the known mitotic function of CPC components, our analyses reveal a non-canonical role for an evolutionarily conserved CPC protein in microfilament reorganization and germ plasm aggregation.

  4. Kinetochore-independent chromosome poleward movement during anaphase of meiosis II in mouse eggs.

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    Manqi Deng

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

  5. C-banding and fluorescent in situ hybridization with rDNA sequences in chromosomes of Cycloneda sanguinea Linnaeus (Coleoptera, Coccinellidae

    Directory of Open Access Journals (Sweden)

    Eliane Mariza Dortas Maffei

    2004-01-01

    Full Text Available The aim of this study was to describe mitotic and meiotic chromosomes of Cycloneda sanguinea using C-banding, fluorescent in situ hybridization (FISH rDNA probes, and sequential FISH/Ag-NOR staining. The chromosome number was 2n = 18 + XX for females and 2n = 18 + Xy for males. The X chromosome was metacentric and the Y chromosome was very small. During meiosis, the karyotypic meioformula was n = 9 + Xy p, and sex chromosomes configured a parachute at metaphase I. At the beginning of pachytene, bivalents were still individualized, and sex chromosomes were associated end-to-end through the heteropycnotic region of the X chromosome. Later in pachytene, further condensation led to the formation of a pseudo-ring by the sex bivalent. All chromosomes showed pericentromeric heterochromatin. FISH and sequential FISH/Ag-NOR staining evidenced the location of the nucleolar organizer region in one pair of autosomes (at spermatogonial metaphase. During meiosis, these genes were mapped to a region outside the sex vesicle by FISH, although Xy p was deeply stained with silver at metaphase I. These results suggest that these argyrophilic substances are of a nucleolar protein nature, and seem to be synthesized by a pair of autosomes and imported during meiosis (prophase I to the sex pair, during the association of the sex chromosomes.

  6. Chromosome segregation in plant meiosis

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    Linda eZamariola

    2014-06-01

    Full Text Available 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.

  7. Human oocytes. Error-prone chromosome-mediated spindle assembly favors chromosome segregation defects in human oocytes.

    Science.gov (United States)

    Holubcová, Zuzana; Blayney, Martyn; Elder, Kay; Schuh, Melina

    2015-06-05

    Aneuploidy in human eggs is the leading cause of pregnancy loss and several genetic disorders such as Down syndrome. Most aneuploidy results from chromosome segregation errors during the meiotic divisions of an oocyte, the egg's progenitor cell. The basis for particularly error-prone chromosome segregation in human oocytes is not known. We analyzed meiosis in more than 100 live human oocytes and identified an error-prone chromosome-mediated spindle assembly mechanism as a major contributor to chromosome segregation defects. Human oocytes assembled a meiotic spindle independently of either centrosomes or other microtubule organizing centers. Instead, spindle assembly was mediated by chromosomes and the small guanosine triphosphatase Ran in a process requiring ~16 hours. This unusually long spindle assembly period was marked by intrinsic spindle instability and abnormal kinetochore-microtubule attachments, which favor chromosome segregation errors and provide a possible explanation for high rates of aneuploidy in human eggs. Copyright © 2015, American Association for the Advancement of Science.

  8. A mutation in the centriole-associated protein centrin causes genomic instability via increased chromosome loss in Chlamydomonas reinhardtii

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    Marshall Wallace F

    2005-05-01

    Full Text Available Abstract Background The role of centrioles in mitotic spindle function remains unclear. One approach to investigate mitotic centriole function is to ask whether mutation of centriole-associated proteins can cause genomic instability. Results We addressed the role of the centriole-associated EF-hand protein centrin in genomic stability using a Chlamydomonas reinhardtii centrin mutant that forms acentriolar bipolar spindles and lacks the centrin-based rhizoplast structures that join centrioles to the nucleus. Using a genetic assay for loss of heterozygosity, we found that this centrin mutant showed increased genomic instability compared to wild-type cells, and we determined that the increase in genomic instability was due to a 100-fold increase in chromosome loss rates compared to wild type. Live cell imaging reveals an increased rate in cell death during G1 in haploid cells that is consistent with an elevated rate of chromosome loss, and analysis of cell death versus centriole copy number argues against a role for multipolar spindles in this process. Conclusion The increased chromosome loss rates observed in a centrin mutant that forms acentriolar spindles suggests a role for centrin protein, and possibly centrioles, in mitotic fidelity.

  9. Acute leukemias of different lineages have similar MLL gene fusions encoding related chimeric proteins resulting from chromosomal translocation

    NARCIS (Netherlands)

    Corral, J.; Forster, A.; Thompson, S.; Lampert, F.; Kaneko, Y.; Slater, R.; Kroes, W. G.; van der Schoot, C. E.; Ludwig, W. D.; Karpas, A.

    1993-01-01

    The MLL gene, on human chromosome 11q23, undergoes chromosomal translocation in acute leukemias, resulting in gene fusion with AF4 (chromosome 4) and ENL (chromosome 19). We report here translocation of MLL with nine different chromosomes and two paracentric chromosome 11 deletions in early B cell,

  10. Roles of CDK and DDK in Genome Duplication and Maintenance: Meiotic Singularities

    Science.gov (United States)

    Gómez-Escoda, Blanca; Wu, Pei-Yun Jenny

    2017-01-01

    Cells reproduce using two types of divisions: mitosis, which generates two daughter cells each with the same genomic content as the mother cell, and meiosis, which reduces the number of chromosomes of the parent cell by half and gives rise to four gametes. The mechanisms that promote the proper progression of the mitotic and meiotic cycles are highly conserved and controlled. They require the activities of two types of serine-threonine kinases, the cyclin-dependent kinases (CDKs) and the Dbf4-dependent kinase (DDK). CDK and DDK are essential for genome duplication and maintenance in both mitotic and meiotic divisions. In this review, we aim to highlight how these kinases cooperate to orchestrate diverse processes during cellular reproduction, focusing on meiosis-specific adaptions of their regulation and functions in DNA metabolism. PMID:28335524

  11. atz-1 Influences meiosis to maintain germline chromosomal stability in Caenorhabditis elegans.

    Science.gov (United States)

    Dawson, Joseph A; Methven-Kelley, Caitlin; Davis, Gregory M

    2017-10-01

    Exchange of genetic information during meiosis occurs in all sexually reproducing species to produce haploid gametes from diploid cells. This process involves tight coordination of a meiotic specific cohesin complex, the synaptonemal complex, and DNA damage repair mechanisms. In this study, we describe a putative myosin heavy chain protein orthologous to human myosin 1, F28D1.2, which we named Abnormal Transition Zone (atz-1). Deletion of atz-1 results in embryonic lethality and a depleted transition zone, accompanied by reduced expression of the meiotic cohesin protein, REC-8. atz-1 mutants display disorganized and aggregated chromosomal bodies in diakinetic oocytes. In addition to this, atz-1 mutants are hypersensitive to mild inhibition of DNA damage repair, suggesting that DNA replication in atz-1 mutants is impaired. Moreover, the atz-1 mutant phenotype is germline specific and resupplying somatically expressed atz-1 does not rescue the reproductive defects associated with atz-1 mutants. Overall, our data suggest that atz-1 contributes to meiosis and maintains germline chromosomal stability. © 2017 International Federation for Cell Biology.

  12. Mammalian E-type cyclins control chromosome pairing, telomere stability and CDK2 localization in male meiosis.

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    Laetitia Martinerie

    2014-02-01

    Full Text Available Loss of function of cyclin E1 or E2, important regulators of the mitotic cell cycle, yields viable mice, but E2-deficient males display reduced fertility. To elucidate the role of E-type cyclins during spermatogenesis, we characterized their expression patterns and produced additional deletions of Ccne1 and Ccne2 alleles in the germline, revealing unexpected meiotic functions. While Ccne2 mRNA and protein are abundantly expressed in spermatocytes, Ccne1 mRNA is present but its protein is detected only at low levels. However, abundant levels of cyclin E1 protein are detected in spermatocytes deficient in cyclin E2 protein. Additional depletion of E-type cyclins in the germline resulted in increasingly enhanced spermatogenic abnormalities and corresponding decreased fertility and loss of germ cells by apoptosis. Profound meiotic defects were observed in spermatocytes, including abnormal pairing and synapsis of homologous chromosomes, heterologous chromosome associations, unrepaired double-strand DNA breaks, disruptions in telomeric structure and defects in cyclin-dependent-kinase 2 localization. These results highlight a new role for E-type cyclins as important regulators of male meiosis.

  13. Synaptonemal complexes , transverse filaments and interference in mouse meiotic recombination; an immunocytological study = Synaptonemale complexen, transversale filamenten en interferentie bij de meiotsche recombinatie bij de muis; een immuuncytologische studie

    NARCIS (Netherlands)

    Boer, de E.

    2007-01-01

    During the prophase of the first meiotic division, homologous chromosomes (homologs} recognize each other and form stable pairs (bivalents). Subsequently non-sister chromatids of homologous chromosomes exchange corresponding parts (crossing over). These events are accompanied by the formation of a

  14. Bdf1 Bromodomains Are Essential for Meiosis and the Expression of Meiotic-Specific Genes.

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    Encar García-Oliver

    2017-01-01

    Full Text Available Bromodomain and Extra-terminal motif (BET proteins play a central role in transcription regulation and chromatin signalling pathways. They are present in unicellular eukaryotes and in this study, the role of the BET protein Bdf1 has been explored in Saccharomyces cerevisiae. Mutation of Bdf1 bromodomains revealed defects on both the formation of spores and the meiotic progression, blocking cells at the exit from prophase, before the first meiotic division. This phenotype is associated with a massive deregulation of the transcription of meiotic genes and Bdf1 bromodomains are required for appropriate expression of the key meiotic transcription factor NDT80 and almost all the Ndt80-inducible genes, including APC complex components. Bdf1 notably accumulates on the promoter of Ndt80 and its recruitment is dependent on Bdf1 bromodomains. In addition, the ectopic expression of NDT80 during meiosis partially bypasses this dependency. Finally, purification of Bdf1 partners identified two independent complexes with Bdf2 or the SWR complex, neither of which was required to complete sporulation. Taken together, our results unveil a new role for Bdf1 -working independently from its predominant protein partners Bdf2 and the SWR1 complex-as a regulator of meiosis-specific genes.

  15. ReCombine: a suite of programs for detection and analysis of meiotic recombination in whole-genome datasets.

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    Carol M Anderson

    Full Text Available In meiosis, the exchange of DNA between chromosomes by homologous recombination is a critical step that ensures proper chromosome segregation and increases genetic diversity. Products of recombination include reciprocal exchanges, known as crossovers, and non-reciprocal gene conversions or non-crossovers. The mechanisms underlying meiotic recombination remain elusive, largely because of the difficulty of analyzing large numbers of recombination events by traditional genetic methods. These traditional methods are increasingly being superseded by high-throughput techniques capable of surveying meiotic recombination on a genome-wide basis. Next-generation sequencing or microarray hybridization is used to genotype thousands of polymorphic markers in the progeny of hybrid yeast strains. New computational tools are needed to perform this genotyping and to find and analyze recombination events. We have developed a suite of programs, ReCombine, for using short sequence reads from next-generation sequencing experiments to genotype yeast meiotic progeny. Upon genotyping, the program CrossOver, a component of ReCombine, then detects recombination products and classifies them into categories based on the features found at each location and their distribution among the various chromatids. CrossOver is also capable of analyzing segregation data from microarray experiments or other sources. This package of programs is designed to allow even researchers without computational expertise to use high-throughput, whole-genome methods to study the molecular mechanisms of meiotic recombination.

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

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    P Rebagliati

    1998-05-01

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

  17. [Meiotic abnormalities of oocytes from patients with endometriosis submitted to ovarian stimulation].

    Science.gov (United States)

    Barcelos, Ionara Diniz Evangelista Santos; Vieira, Rodolpho Cruz; Ferreira, Elisa Melo; Araújo, Maria Cristina Picinato Medeiros de; Martins, Wellington de Paula; Ferriani, Rui Alberto; Navarro, Paula Andrea de Albuquerque Salles

    2008-08-01

    to evaluate the meiotic spindle and the chromosome distribution of in vitro mature oocytes from stimulated cycles of infertile women with endometriosis, and with male and/or tubal infertility factors (Control Group), comparing the rates of in vitro maturation (IVM) between the two groups evaluated. fourteen patients with endometriosis and eight with male and/or tubal infertility factors, submitted to ovarian stimulation for intracytoplasmatic sperm injection have been prospectively and consecutively selected, and formed a Study and Control Group, respectively. Immature oocytes (46 and 22, respectively, from the Endometriosis and Control Groups) were submitted to IVM. Oocytes presenting extrusion of the first polar corpuscle were fixed and stained for microtubules and chromatin evaluation through immunofluorescence technique. Statistical analysis has been done by the Fisher's exact test, with statistical significance at pControl Groups, respectively). The chromosome and meiotic spindle organization was observed in 18 and 11 oocytes from the Endometriosis and Control Groups, respectively. In the Endometriosis Group, eight oocytes (44.4%) presented themselves as normal metaphase II (MII), three (16.7%) as abnormal MII, five (27.8%) were in telophase stage I and two (11.1%) underwent parthenogenetic activation. In the Control Group, five oocytes (45.4%) presented themselves as normal MII, three (27.3%) as abnormal MII, one (9.1%) was in telophase stage I and two (18.2%) underwent parthenogenetic activation. There was no significant difference in meiotic anomaly rate between the oocytes in MII from both groups. the present study data did not show significant differences in the IVM or in the meiotic anomalies rate between the IVM oocytes from stimulated cycles of patients with endometriosis, as compared with controls. Nevertheless, they have suggested a delay in the outcome of oocyte meiosis I from patients with endometriosis, shown by the higher proportion of oocytes in

  18. DRH1, a p68-related RNA helicase gene, is required for chromosome breakage in Tetrahymena

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    Stephen L. McDaniel

    2016-12-01

    Full Text Available The p68 DEAD box helicases comprise a widely conserved protein family involved in a large range of biological processes including transcription, splicing and translation. The genome of the ciliate Tetrahymena thermophile encodes two p68-like helicases, Drh1p and Lia2p. We show that DRH1 is essential for growth and completion of development. In growing cells, Drh1p is excluded from the nucleus and accumulates near cortical basal bodies. In contrast, during sexual reproduction, this protein localizes to meiotic micronuclei, initially in punctate foci in regions where centromeres and telomeres are known to reside and later in post-zygotic differentiating somatic macronuclei. Differentiation of the macronuclear genome involves extensive DNA rearrangements including fragmentation of the five pairs of germline-derived chromosomes into 180 chromosomal sub-fragments that are stabilized by de novo telomere deletion. In addition, thousands of internal eliminated sequences (IESs are excised from loci dispersed throughout the genome. Strains with DRH1 deleted from the germline nuclei, which do not express the protein during post-zygotic development, fail to fragment the developing macronuclear chromosomes. IES excision still occurs in the absence of DRH1 zygotic expression; thus, Drh1p is the first protein found to be specifically required for chromosome breakage but not DNA elimination.

  19. Multiple DNA binding proteins contribute to timing of chromosome replication in E. coli

    DEFF Research Database (Denmark)

    Riber, Leise; Frimodt-Møller, Jakob; Charbon, Godefroid

    2016-01-01

    Chromosome replication in Escherichia coli is initiated from a single origin, oriC. Initiation involves a number of DNA binding proteins, but only DnaA is essential and specific for the initiation process. DnaA is an AAA+ protein that binds both ATP and ADP with similar high affinities. Dna......A associated with either ATP or ADP binds to a set of strong DnaA binding sites in oriC, whereas only DnaA(ATP) is capable of binding additional and weaker sites to promote initiation. Additional DNA binding proteins act to ensure that initiation occurs timely by affecting either the cellular mass at which DNA...... in or around oriC, (iii) altering the nucleotide bound status of DnaA by interacting with non-coding chromosomal sequences, distant from oriC, that are important for DnaA activity. Thus, although DnaA is the key protein for initiation of replication, other DNA-binding proteins act not only on ori...

  20. Non-SMC condensin I complex proteins control chromosome segregation and survival of proliferating cells in the zebrafish neural retina

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    Harris William A

    2009-07-01

    Full Text Available Abstract Background The condensation of chromosomes and correct sister chromatid segregation during cell division is an essential feature of all proliferative cells. Structural maintenance of chromosomes (SMC and non-SMC proteins form the condensin I complex and regulate chromosome condensation and segregation during mitosis. However, due to the lack of appropriate mutants, the function of the condensin I complex during vertebrate development has not been described. Results Here, we report the positional cloning and detailed characterization of retinal phenotypes of a zebrafish mutation at the cap-g locus. High resolution live imaging reveals that the progression of mitosis between prometa- to telophase is delayed and that sister chromatid segregation is impaired upon loss of CAP-G. CAP-G associates with chromosomes between prometa- and telophase of the cell cycle. Loss of the interaction partners CAP-H and CAP-D2 causes cytoplasmic mislocalization of CAP-G throughout mitosis. DNA content analysis reveals increased genomic imbalances upon loss of non-SMC condensin I subunits. Within the retina, loss of condensin I function causes increased rates of apoptosis among cells within the proliferative ciliary marginal zone (CMZ whereas postmitotic retinal cells are viable. Inhibition of p53-mediated apoptosis partially rescues cell numbers in cap-g mutant retinae and allows normal layering of retinal cell types without alleviating their aberrant nuclear sizes. Conclusion Our findings indicate that the condensin I complex is particularly important within rapidly amplifying progenitor cell populations to ensure faithful chromosome segregation. In contrast, differentiation of postmitotic retinal cells is not impaired upon polyploidization.

  1. Heavy metal accumulation, heat shock protein expression and cytogenetic changes in Tetrix tenuicornis (L.) (Tetrigidae, Orthoptera) from polluted areas

    International Nuclear Information System (INIS)

    Warchalowska-Sliwa, E.; Niklinska, M.; Goerlich, A.; Michailova, P.; Pyza, E.

    2005-01-01

    The orthopteran insect Tetrix tenuicornis, collected from polluted and unpolluted areas, was used to study heavy metal accumulation and its impact on stress protein levels and on changes in the number and morphology of chromosomes in mitotic and meiotic cells. During two consecutive years, insects were collected from polluted areas of zinc-lead mine spoils near Boleslaw (Poland) and from unpolluted areas near Busko and Staszow (Poland). T. tenuicornis from the polluted area showed 1.5, 4.03, 4.32 and 41.73 times higher concentrations of copper (Cu), zinc (Zn), lead (Pb) and cadmium (Cd), respectively, than insects of the same species collected from unpolluted areas. Insects exposed to heavy metals showed only small changes, and rather a decrease in the concentration of constitutive and inducible heat shock proteins Hsp70, the level of which increases under stress conditions. A cytogenetic study of T. tenuicornis revealed intra-population anomalies in chromosome number and morphology in mitotic and meiotic cells and the presence of an additional B chromosome in germinal cells. In 50% of females collected from polluted areas, mosaic oogonial mitotic chromosome sets and diploid, hypo- or hypertetraploid, tetraploid, and octoploid chromosome numbers were detected. In turn, 14.6% of males showed a heterozygous deficiency of chromatin in L 2 and M 3 bivalents in addition to the presence of B chromosomes. - Metals accumulation caused genotoxicity in insects

  2. Synaptonemal Complex Components Are Required for Meiotic Checkpoint Function in Caenorhabditis elegans

    Science.gov (United States)

    Bohr, Tisha; Ashley, Guinevere; Eggleston, Evan; Firestone, Kyra; Bhalla, Needhi

    2016-01-01

    Synapsis involves the assembly of a proteinaceous structure, the synaptonemal complex (SC), between paired homologous chromosomes, and is essential for proper meiotic chromosome segregation. In Caenorhabditis elegans, the synapsis checkpoint selectively removes nuclei with unsynapsed chromosomes by inducing apoptosis. This checkpoint depends on pairing centers (PCs), cis-acting sites that promote pairing and synapsis. We have hypothesized that the stability of homolog pairing at PCs is monitored by this checkpoint. Here, we report that SC components SYP-3, HTP-3, HIM-3, and HTP-1 are required for a functional synapsis checkpoint. Mutation of these components does not abolish PC function, demonstrating they are bona fide checkpoint components. Further, we identify mutant backgrounds in which the instability of homolog pairing at PCs does not correlate with the synapsis checkpoint response. Altogether, these data suggest that, in addition to homolog pairing, SC assembly may be monitored by the synapsis checkpoint. PMID:27605049

  3. The nuclear protein encoded by the Drosophila neurogenic gene mastermind is widely expressed and associates with specific chromosomal regions

    Energy Technology Data Exchange (ETDEWEB)

    Bettler, D.; Pearson, S.; Yedvobnick, B. [Emory Univ., Atlanta, GA (United States)

    1996-06-01

    The Drosophila neurogenic loci encode a diverse group of proteins that comprise an inhibitory signal transduction pathway. The pathway is used throughout development in numerous contexts. We have examined the distribution of the neurogenic locus mastermind protein (Mam). Mam is expressed through all germlayers during early embryogenesis, including ectodermal precursors to both neuroblasts and epidermoblasts. Mam is subsequently down-regulated within the nervous system and then reexpressed. It persists in the nervous system through late embryogenesis and postembryonically. Mam is ubiquitously expressed in wing and leg imaginal discs and is not down-regulated in sensory organ precursor cells of the wing margin or notum. In the eye disc, Mam shows most prominent expression posterior to the morphogenetic furrow. Expression of the protein during oogenesis appears limited to follicle cells. Immunohistochemical detection of Mam on polytene chromosomes revealed binding at >100 sites. Chromosome colocalization studies with RNA polymerase and the groucho corepressor protein implicate Mam in transcriptional regulation. 94 refs., 8 figs., 1 tab.

  4. CDE-1 affects chromosome segregation through uridylation of CSR-1-bound siRNAs.

    Science.gov (United States)

    van Wolfswinkel, Josien C; Claycomb, Julie M; Batista, Pedro J; Mello, Craig C; Berezikov, Eugene; Ketting, René F

    2009-10-02

    We have studied the function of a conserved germline-specific nucleotidyltransferase protein, CDE-1, in RNAi and chromosome segregation in C. elegans. CDE-1 localizes specifically to mitotic chromosomes in embryos. This localization requires the RdRP EGO-1, which physically interacts with CDE-1, and the Argonaute protein CSR-1. We found that CDE-1 is required for the uridylation of CSR-1 bound siRNAs, and that in the absence of CDE-1 these siRNAs accumulate to inappropriate levels, accompanied by defects in both meiotic and mitotic chromosome segregation. Elevated siRNA levels are associated with erroneous gene silencing, most likely through the inappropriate loading of CSR-1 siRNAs into other Argonaute proteins. We propose a model in which CDE-1 restricts specific EGO-1-generated siRNAs to the CSR-1 mediated, chromosome associated RNAi pathway, thus separating it from other endogenous RNAi pathways. The conserved nature of CDE-1 suggests that similar sorting mechanisms may operate in other animals, including mammals.

  5. Klinefelter syndrome comorbidities linked to increased X chromosome gene dosage and altered protein interactome activity

    DEFF Research Database (Denmark)

    Belling, Kirstine González-Izarzugaza; Russo, Francesco; Jensen, Anders Boeck

    2017-01-01

    Klinefelter syndrome (KS) (47,XXY) is the most common male sex chromosome aneuploidy. Diagnosis and clinical supervision remain a challenge due to varying phenotypic presentation and insufficient characterization of the syndrome. Here we combine health data-driven epidemiology and molecular level...

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

    Directory of Open Access Journals (Sweden)

    Chloe Girard

    2015-07-01

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

  7. Contributions of classical and molecular cytogenetic in meiotic analysis and pollen viability for plant breeding.

    Science.gov (United States)

    Lavinscky, M P; Souza, M M; Silva, G S; Melo, C A F

    2017-09-27

    The analysis of meiotic behavior has been widely used in the study of plants as they provide relevant information about the viability of a species. Meiosis boasts a host of highly conserved events and changes in genes that control these events will give rise to irregularities that can alter the normal course of meiosis and may lead to complete sterility of the plant. The recombination of genes that occur in meiosis is an important event to generate variability and has been important in studies for genetic improvement and to create viable hybrids. The use of fluorescence in situ hybridization and genomic in situ hybridization (GISH) in meiosis allows the localization of specific regions, enables to differentiate genomes in a hybrid, permits to observe the pairing of homoeologous chromosomes, and if there was a recombination between the genomes of progenitor species. Furthermore, the GISH allows us to observe the close relationship between the species involved. This article aims to report over meiosis studies on plants and hybrids, the use and importance of molecular cytogenetic in meiotic analysis and contributions of meiotic analysis in breeding programs.

  8. Discrimination of chromosome by autoradiography

    International Nuclear Information System (INIS)

    Masubuchi, Masanori

    1975-01-01

    This paper describes discrimination of chromosome by autoradiography. In this method, the difference in DNA synthetic phase between each chromosome was used as a standard, and the used chromosome was in metaphase, as morphological characteristics were markedly in this phase. Cell cycle and autoradiography with 3 H-thymidine were also examined. In order to discriminate chromosome by autoradiography, it was effective to utilize the labelled pattern in late DNA synthetic phase, where asynchronous replication of chromosome appeared most obviously. DNA synthesis in chromosome was examined in each DNA synthetic phase by culturing the chromosome after the treatment with 3 H-thymidine and altering the time to prepare chromosome specimen. Discrimination of chromosome in plants and animals by autoradiography was also mentioned. It was noticed as a structural and functional discrimination of chromosome to observe amino acid uptake into chromosome protein and to utilize the difference in labelled pattern between the sites of chromosome. (K. Serizawa)

  9. Computational modelling of meiotic entry and commitment

    OpenAIRE

    Bhola, Tanvi; Kapuy, Orsolya; Vinod, P. K.

    2018-01-01

    In response to developmental and environmental conditions, cells exit the mitotic cell cycle and enter the meiosis program to generate haploid gametes from diploid germ cells. Once cells decide to enter the meiosis program they become irreversibly committed to the completion of meiosis irrespective of the presence of cue signals. How meiotic entry and commitment occur due to the dynamics of the regulatory network is not well understood. Therefore, we constructed a mathematical model of the re...

  10. Prdm9, a major determinant of meiotic recombination hotspots, is not functional in dogs and their wild relatives, wolves and coyotes.

    Directory of Open Access Journals (Sweden)

    Violeta Muñoz-Fuentes

    Full Text Available Meiotic recombination is a fundamental process needed for the correct segregation of chromosomes during meiosis in sexually reproducing organisms. In humans, 80% of crossovers are estimated to occur at specific areas of the genome called recombination hotspots. Recently, a protein called PRDM9 was identified as a major player in determining the location of genome-wide meiotic recombination hotspots in humans and mice. The origin of this protein seems to be ancient in evolutionary time, as reflected by its fairly conserved structure in lineages that diverged over 700 million years ago. Despite its important role, there are many animal groups in which Prdm9 is absent (e.g. birds, reptiles, amphibians, diptera and it has been suggested to have disruptive mutations and thus to be a pseudogene in dogs. Because of the dog's history through domestication and artificial selection, we wanted to confirm the presence of a disrupted Prdm9 gene in dogs and determine whether this was exclusive of this species or whether it also occurred in its wild ancestor, the wolf, and in a close relative, the coyote. We sequenced the region in the dog genome that aligned to the last exon of the human Prdm9, containing the entire zinc finger domain, in 4 dogs, 17 wolves and 2 coyotes. Our results show that the three canid species possess mutations that likely make this gene non functional. Because these mutations are shared across the three species, they must have appeared prior to the split of the wolf and the coyote, millions of years ago, and are not related to domestication. In addition, our results suggest that in these three canid species recombination does not occur at hotspots or hotspot location is controlled through a mechanism yet to be determined.

  11. Prdm9, a major determinant of meiotic recombination hotspots, is not functional in dogs and their wild relatives, wolves and coyotes.

    Science.gov (United States)

    Muñoz-Fuentes, Violeta; Di Rienzo, Anna; Vilà, Carles

    2011-01-01

    Meiotic recombination is a fundamental process needed for the correct segregation of chromosomes during meiosis in sexually reproducing organisms. In humans, 80% of crossovers are estimated to occur at specific areas of the genome called recombination hotspots. Recently, a protein called PRDM9 was identified as a major player in determining the location of genome-wide meiotic recombination hotspots in humans and mice. The origin of this protein seems to be ancient in evolutionary time, as reflected by its fairly conserved structure in lineages that diverged over 700 million years ago. Despite its important role, there are many animal groups in which Prdm9 is absent (e.g. birds, reptiles, amphibians, diptera) and it has been suggested to have disruptive mutations and thus to be a pseudogene in dogs. Because of the dog's history through domestication and artificial selection, we wanted to confirm the presence of a disrupted Prdm9 gene in dogs and determine whether this was exclusive of this species or whether it also occurred in its wild ancestor, the wolf, and in a close relative, the coyote. We sequenced the region in the dog genome that aligned to the last exon of the human Prdm9, containing the entire zinc finger domain, in 4 dogs, 17 wolves and 2 coyotes. Our results show that the three canid species possess mutations that likely make this gene non functional. Because these mutations are shared across the three species, they must have appeared prior to the split of the wolf and the coyote, millions of years ago, and are not related to domestication. In addition, our results suggest that in these three canid species recombination does not occur at hotspots or hotspot location is controlled through a mechanism yet to be determined.

  12. Spontaneous and divergent hexaploid triticales derived from common wheat × rye by complete elimination of D-genome chromosomes.

    Science.gov (United States)

    Li, Hao; Guo, Xiaoxue; Wang, Changyou; Ji, Wanquan

    2015-01-01

    Hexaploid triticale could be either synthesized by crossing tetraploid wheat with rye, or developed by crossing hexaploid wheat with a hexaploid triticale or an octoploid triticale. Here two hexaploid triticales with great morphologic divergence derived from common wheat cultivar M8003 (Triticum aestivum L.) × Austrian rye (Secale cereale L.) were reported, exhibiting high resistance for powdery mildew and stripe rust and potential for wheat improvement. Sequential fluorescence in situ hybridization (FISH) and genomic in situ hybridization (GISH) karyotyping revealed that D-genome chromosomes were completely eliminated and the whole A-genome, B-genome and R-genome chromosomes were retained in both lines. Furthermore, plentiful alterations of wheat chromosomes including 5A and 7B were detected in both triticales and additionally altered 5B, 7A chromosome and restructured chromosome 2A was assayed in N9116H and N9116M, respectively, even after selfing for several decades. Besides, meiotic asynchrony was displayed and a variety of storage protein variations were assayed, especially in the HMW/LMW-GS region and secalins region in both triticales. This study confirms that whole D-genome chromosomes could be preferentially eliminated in the hybrid of common wheat × rye, "genome shock" was accompanying the allopolyploidization of nascent triticales, and great morphologic divergence might result from the genetic variations. Moreover, new hexaploid triticale lines contributing potential resistance resources for wheat improvement were produced.

  13. Spontaneous and divergent hexaploid triticales derived from common wheat × rye by complete elimination of D-genome chromosomes.

    Directory of Open Access Journals (Sweden)

    Hao Li

    Full Text Available Hexaploid triticale could be either synthesized by crossing tetraploid wheat with rye, or developed by crossing hexaploid wheat with a hexaploid triticale or an octoploid triticale.Here two hexaploid triticales with great morphologic divergence derived from common wheat cultivar M8003 (Triticum aestivum L. × Austrian rye (Secale cereale L. were reported, exhibiting high resistance for powdery mildew and stripe rust and potential for wheat improvement. Sequential fluorescence in situ hybridization (FISH and genomic in situ hybridization (GISH karyotyping revealed that D-genome chromosomes were completely eliminated and the whole A-genome, B-genome and R-genome chromosomes were retained in both lines. Furthermore, plentiful alterations of wheat chromosomes including 5A and 7B were detected in both triticales and additionally altered 5B, 7A chromosome and restructured chromosome 2A was assayed in N9116H and N9116M, respectively, even after selfing for several decades. Besides, meiotic asynchrony was displayed and a variety of storage protein variations were assayed, especially in the HMW/LMW-GS region and secalins region in both triticales.This study confirms that whole D-genome chromosomes could be preferentially eliminated in the hybrid of common wheat × rye, "genome shock" was accompanying the allopolyploidization of nascent triticales, and great morphologic divergence might result from the genetic variations. Moreover, new hexaploid triticale lines contributing potential resistance resources for wheat improvement were produced.

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

    Directory of Open Access Journals (Sweden)

    Josephine A Reinhardt

    Full Text Available 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.

  15. Chromosome complement and meiosis in three species of the Neotropical bug genus Antiteuchus (Heteroptera, Pentatomidae, Discocephalinae

    Directory of Open Access Journals (Sweden)

    Cecilia Lanzone

    2006-01-01

    Full Text Available Orcein staining of spermatocytes was used to study the meiotic behavior of holocentric chromosomes in three member of the genus Antiteuchus (commonly known as stink bugs. We describe and illustrate the karyotype of Antiteuchus mixtus, A. sepulcralis and A. macraspis which were cytogenetically characterized as having a diploid number of 2n = 14 and an XY sex chromosome system showing pre-reductional meiosis for autosomes and post-reductional meiosis for sex chromosomes. These species were also shown to have a long diffuse stage during meiotic prophase I and aberrant harlequin-type meiocytes. The chiasma frequency was also analyzed for two of the three species studied.

  16. Cooperation Between Kinesin Motors Promotes Spindle Symmetry and Chromosome Organization in Oocytes.

    Science.gov (United States)

    Radford, Sarah J; Go, Allysa Marie M; McKim, Kim S

    2017-02-01

    The oocyte spindle in most animal species is assembled in the absence of the microtubule-organizing centers called centrosomes. Without the organization provided by centrosomes, acentrosomal meiotic spindle organization may rely heavily on the bundling of microtubules by kinesin motor proteins. Indeed, the minus-end directed kinesin-14 NCD, and the plus-end directed kinesin-6 Subito are known to be required for oocyte spindle organization in Drosophila melanogaster How multiple microtubule-bundling kinesins interact to produce a functional acentrosomal spindle is not known. In addition, there have been few studies on the meiotic function of one of the most important microtubule-bundlers in mitotic cells, the kinesin-5 KLP61F. We have found that the kinesin-5 KLP61F is required for spindle and centromere symmetry in oocytes. The asymmetry observed in the absence of KLP61F depends on NCD, the kinesin-12 KLP54D, and the microcephaly protein ASP. In contrast, KLP61F and Subito work together in maintaining a bipolar spindle. We propose that the prominent central spindle, stabilized by Subito, provides the framework for the coordination of multiple microtubule-bundling activities. The activities of several proteins, including NCD, KLP54D, and ASP, generate asymmetries within the acentrosomal spindle, while KLP61F and Subito balance these forces, resulting in the capacity to accurately segregate chromosomes. Copyright © 2017 by the Genetics Society of America.

  17. Molecular characterization and chromosomal assignment of equine cartilage derived retinoic acid sensitive protein (CD-RAP)/melanoma inhibitory activity (MIA)

    DEFF Research Database (Denmark)

    Berg, Lise Charlotte; Mata, Xavier; Thomsen, Preben Dybdahl

    2008-01-01

    Cartilage-derived retinoic acid sensitive protein (CD-RAP) also known as melanoma inhibitory activity (MIA) has already been established as a marker for chondrocyte differentiation and a number of cancerous condition sin humans. Studies have also shown that CD-RAP/MIA is a potential marker of joint...... to the human gene is 90% for the translated region. The upstream sequence includes regulatory elements and putative transcription factor binding sites previously described in the human and murine promoter regions. The deduced amino acid sequence consists of 130 aa including a signal peptide of 23 aa, and has...... a 91% identity to the human protein. Using radiation hybrid mapping, the CD-RAP/MIA gene was localized to the p arm of equine chromosome 10 (ECA10p), which is in accordance with prediction based on the current human-equine comparative map. Gene expression studies showed expression of CD-RAP/MIA m...

  18. The chicken Z chromosome is enriched for genes with preferential expression in ovarian somatic cells

    Czech Academy of Sciences Publication Activity Database

    Mořkovský, L.; Storchová, R.; Plachý, Jiří; Ivánek, Robert; Divina, Petr; Hejnar, Jiří

    2010-01-01

    Roč. 70, č. 2 (2010), s. 129-136 ISSN 0022-2844 Institutional research plan: CEZ:AV0Z50520514 Keywords : Z chromosome * meiotic sex chromosome inactivation * sexual antagonisms Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 2.311, year: 2010

  19. Apoptosis in mouse fetal and neonatal oocytes during meiotic prophase one

    Directory of Open Access Journals (Sweden)

    Hartshorne Geraldine M

    2007-07-01

    Full Text Available Abstract Background The vast majority of oocytes formed in the fetal ovary do not survive beyond birth. Possible reasons for their loss include the elimination of non-viable genetic constitutions arising through meiosis, however, the precise relationship between meiotic stages and prenatal apoptosis of oocytes remains elusive. We studied oocytes in mouse fetal and neonatal ovaries, 14.5–21 days post coitum, to examine the relationship between oocyte development and programmed cell death during meiotic prophase I. Results Microspreads of fetal and neonatal ovarian cells underwent immunocytochemistry for meiosis- and apoptosis-related markers. COR-1 (meiosis-specific highlighted axial elements of the synaptonemal complex and allowed definitive identification of the stages of meiotic prophase I. Labelling for cleaved poly-(ADP-ribose polymerase (PARP-1, an inactivated DNA repair protein, indicated apoptosis. The same oocytes were then labelled for DNA double strand breaks (DSBs using TUNEL. 1960 oocytes produced analysable results. Oocytes at all stages of meiotic prophase I stained for cleaved PARP-1 and/or TUNEL, or neither. Oocytes with fragmented (19.8% or compressed (21.2% axial elements showed slight but significant differences in staining for cleaved PARP-1 and TUNEL to those with intact elements. However, fragmentation of axial elements alone was not a good indicator of cell demise. Cleaved PARP-1 and TUNEL staining were not necessarily coincident, showing that TUNEL is not a reliable marker of apoptosis in oocytes. Conclusion Our data indicate that apoptosis can occur throughout meiotic prophase I in mouse fetal and early postnatal oocytes, with greatest incidence at the diplotene stage. Careful selection of appropriate markers for oocyte apoptosis is essential.

  20. A major role for the Plasmodium falciparum ApiAP2 protein PfSIP2 in chromosome end biology.

    Directory of Open Access Journals (Sweden)

    Christian Flueck

    2010-02-01

    Full Text Available The heterochromatic environment and physical clustering of chromosome ends at the nuclear periphery provide a functional and structural framework for antigenic variation and evolution of subtelomeric virulence gene families in the malaria parasite Plasmodium falciparum. While recent studies assigned important roles for reversible histone modifications, silent information regulator 2 and heterochromatin protein 1 (PfHP1 in epigenetic control of variegated expression, factors involved in the recruitment and organization of subtelomeric heterochromatin remain unknown. Here, we describe the purification and characterization of PfSIP2, a member of the ApiAP2 family of putative transcription factors, as the unknown nuclear factor interacting specifically with cis-acting SPE2 motif arrays in subtelomeric domains. Interestingly, SPE2 is not bound by the full-length protein but rather by a 60kDa N-terminal domain, PfSIP2-N, which is released during schizogony. Our experimental re-definition of the SPE2/PfSIP2-N interaction highlights the strict requirement of both adjacent AP2 domains and a conserved bipartite SPE2 consensus motif for high-affinity binding. Genome-wide in silico mapping identified 777 putative binding sites, 94% of which cluster in heterochromatic domains upstream of subtelomeric var genes and in telomere-associated repeat elements. Immunofluorescence and chromatin immunoprecipitation (ChIP assays revealed co-localization of PfSIP2-N with PfHP1 at chromosome ends. Genome-wide ChIP demonstrated the exclusive binding of PfSIP2-N to subtelomeric SPE2 landmarks in vivo but not to single chromosome-internal sites. Consistent with this specialized distribution pattern, PfSIP2-N over-expression has no effect on global gene transcription. Hence, contrary to the previously proposed role for this factor in gene activation, our results provide strong evidence for the first time for the involvement of an ApiAP2 factor in heterochromatin formation

  1. Identification of a novel zinc finger protein gene (ZNF298) in the GAP2 of human chromosome 21q

    International Nuclear Information System (INIS)

    Shibuya, Kazunori; Kudoh, Jun; Okui, Michiyo; Shimizu, Nobuyoshi

    2005-01-01

    We have isolated a novel zinc finger protein gene, designated ZNF298, as a candidate gene for a particular phenotype of Down syndrome or bipolar affective disorder (BPAD) which maps to human chromosome 21q22.3. ZNF298 gene consists of 25 exons spanning approximately 80 kb in a direction from the telomere to centromere. There are four kinds of transcripts that harbor three types of 3' UTR. These four transcripts (ZNF298a, ZNF298b, ZNF298c, and ZNF298d) contain putative open reading frames encoding 1178, 1198, 555, and 515 amino acids, respectively. ZNF298 gene was ubiquitously expressed in various tissues at very low level. The protein motif analysis revealed that ZNF298 proteins contain a SET [Su(var)3-9, Enhancer-of-zeste, Trithorax] domain, multiple C2H2-type zinc finger (ZnF C 2H2) domains, several nuclear localization signals (NLSs), and PEST sequences. Nuclear localization of ZNF298 protein was confirmed by transfection of expression vector of GFP-tagged protein into two human cell lines. Interestingly, this gene crosses over a clone gap (GAP2) remaining in the band 21q22.3. We obtained the DNA fragments corresponding to GAP2 using ZNF298 cDNA sequence as anchor primers for PCR and determined its genomic DNA sequence

  2. Structure of the human gene encoding the associated microfibrillar protein (MFAP1) and localization to chromosome 15q15-q21

    Energy Technology Data Exchange (ETDEWEB)

    Yeh, H.; Chow, M.; Abrams, W.R. [Univ. of Pennsylvania, Philadelphia, PA (United States)] [and others

    1994-09-15

    Microfibrils with a diameter of 10-12 nm, found either in assocation with elastin or independently, are an important component of the extracellular matrix of many tissues. To extend understanding of the proteins composing these microfibrils, the cDNA and gene encoding the human associated microfibril protein (MRAP1) have been cloned and characterized. The coding portion is contained in 9 exons, and the sequence is very homologous to the previously described chick cDNA, but does not appear to share homology or domain motifs with any other known protein. Interestingly, the gene has been localized to chromosome 15q15-q21 by somatic hybrid cell and chromosome in situ analyses. This is the same chromosomal region to which the fibrillin gene, FBN1, known to be defective in the Marfan syndrome, has been mapped. MFAP1 is a candidate gene for heritable diseases affecting microfibrils. 38 refs., 6 figs.

  3. Nup132 modulates meiotic spindle attachment in fission yeast by regulating kinetochore assembly

    OpenAIRE

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

    2015-01-01

    During meiosis, the kinetochore undergoes substantial reorganization to establish monopolar spindle attachment. In the fission yeast Schizosaccharomyces pombe, the KNL1?Spc7-Mis12-Nuf2 (KMN) complex, which constitutes the outer kinetochore, is disassembled during meiotic prophase and is reassembled before meiosis I. Here, we show that the nucleoporin Nup132 is required for timely assembly of the KMN proteins: In the absence of Nup132, Mis12 and Spc7 are precociously assembled at the centromer...

  4. The cohesion protein SOLO associates with SMC1 and is required for synapsis, recombination, homolog bias and cohesion and pairing of centromeres in Drosophila Meiosis.

    Directory of Open Access Journals (Sweden)

    Rihui Yan

    Full Text Available Cohesion between sister chromatids is mediated by cohesin and is essential for proper meiotic segregation of both sister chromatids and homologs. solo encodes a Drosophila meiosis-specific cohesion protein with no apparent sequence homology to cohesins that is required in male meiosis for centromere cohesion, proper orientation of sister centromeres and centromere enrichment of the cohesin subunit SMC1. In this study, we show that solo is involved in multiple aspects of meiosis in female Drosophila. Null mutations in solo caused the following phenotypes: 1 high frequencies of homolog and sister chromatid nondisjunction (NDJ and sharply reduced frequencies of homolog exchange; 2 reduced transmission of a ring-X chromosome, an indicator of elevated frequencies of sister chromatid exchange (SCE; 3 premature loss of centromere pairing and cohesion during prophase I, as indicated by elevated foci counts of the centromere protein CID; 4 instability of the lateral elements (LEs and central regions of synaptonemal complexes (SCs, as indicated by fragmented and spotty staining of the chromosome core/LE component SMC1 and the transverse filament protein C(3G, respectively, at all stages of pachytene. SOLO and SMC1 are both enriched on centromeres throughout prophase I, co-align along the lateral elements of SCs and reciprocally co-immunoprecipitate from ovarian protein extracts. Our studies demonstrate that SOLO is closely associated with meiotic cohesin and required both for enrichment of cohesin on centromeres and stable assembly of cohesin into chromosome cores. These events underlie and are required for stable cohesion of centromeres, synapsis of homologous chromosomes, and a recombination mechanism that suppresses SCE to preferentially generate homolog crossovers (homolog bias. We propose that SOLO is a subunit of a specialized meiotic cohesin complex that mediates both centromeric and axial arm cohesion and promotes homolog bias as a component of

  5. Chromosome pairing and synapsis during Caenorhabditis elegans meiosis.

    Science.gov (United States)

    Rog, Ofer; Dernburg, Abby F

    2013-06-01

    Meiosis is the specialized cell division cycle that produces haploid gametes to enable sexual reproduction. Reduction of chromosome number by half requires elaborate chromosome dynamics that occur in meiotic prophase to establish physical linkages between each pair of homologous chromosomes. Caenorhabditis elegans has emerged as an excellent model organism for molecular studies of meiosis, enabling investigators to combine the power of molecular genetics, cytology, and live analysis. Here we focus on recent studies that have shed light on how chromosomes find and identify their homologous partners, and the structural changes that accompany and mediate these interactions. Copyright © 2013 Elsevier Ltd. All rights reserved.

  6. Chromosome pairing and synapsis during C. elegans meiosis

    Science.gov (United States)

    Rog, Ofer; Dernburg, Abby F.

    2013-01-01

    Meiosis is the specialized cell division cycle that produces haploid gametes to enable sexual reproduction. Reduction of chromosome number by half requires elaborate chromosome dynamics that occur in meiotic prophase to establish physical linkages between each pair of homologous chromosomes. C. elegans has emerged as an excellent model organism for molecular studies of meiosis, enabling investigators to combine the power of molecular genetics, cytology, and live analysis. Here we focus on recent studies that have shed light on how chromosomes find and identify their homologous partners, and the structural changes that accompany and mediate these interactions. PMID:23578368

  7. Chromosome number reports in Astragalus sect. Onobrychoidei (Fabaceae from Iran

    Directory of Open Access Journals (Sweden)

    Massoud Ranjbar

    2015-01-01

    Full Text Available In this study, original mitotic chromosome counts have been presented for 10 populations belonging to 6 species of Astragalus sect. Onobrychoidei: A. aduncus, A. arguricus, A. cancellatus, A. lilacinus and A. vegetus. All taxa were diploid and possessed 2n = 2x = 16 chromosome number, consistent with the proposed base number of x = 8. In addition, meiotic studies revealed chromosome number of 2n = 2x = 16 for A. aduncus21 and A. brevidens and also 2n = 4x = 32 for A. vegetus99. Although this taxon displayed regular bivalent pairing and chromosome segregation at meiosis, some abnormalities were observed.

  8. Model of chromosome associations in Mus domesticus spermatocytes

    Directory of Open Access Journals (Sweden)

    Soledad Berríos

    2010-01-01

    Full Text Available Understanding the spatial organization of the chromosomes in meiotic nuclei is crucial to our knowledge of the genome's functional regulation, stability and evolution. This study examined the nuclear architecture of Mus domesticus 2n=40 pachytene spermatocytes, analyzing the associations among autosomal bivalents via their Centromere Telomere Complexes (CTC. The study developed a nuclear model in which each CTC was represented as a 3D computer object. The probability of a given combination of associations among CTC was estimated by simulating a random distribution of 19 indistinguishable CTC over n indistinguishable "cells" on the nuclear envelope. The estimated association frequencies resulting from this numerical approach were similar to those obtained by quantifying actual associations in pachytene spermatocyte spreads. The nuclear localization and associations of CTC through the meiotic prophase in well-preserved nuclei were also analyzed. We concluded that throughout the meiotic prophase: 1 the CTC of autosomal bivalents are not randomly distributed in the nuclear space; 2 the CTC associate amongst themselves, probably at random, over a small surface of the nuclear envelope, at the beginning of the meiotic prophase; 3 the initial aggregation of centromere regions occurring in lepto-zygotene likely resolves into several smaller aggregates according to patterns of preferential partitioning; 4 these smaller aggregates spread over the inner face of the nuclear envelope, remaining stable until advanced stages of the meiotic prophase or even until the first meiotic division.

  9. Cryo-EM visualization of the protein machine that replicates the chromosome

    Science.gov (United States)

    Li, Huilin

    Structural knowledge is key to understanding biological functions. Cryo-EM is a physical method that uses transmission electron microscopy to visualize biological molecules that are frozen in vitreous ice. Due to recent advances in direct electron detector and image processing algorithm, cryo-EM has become a high-resolution technique. Cryo-EM field is undergoing a rapid expansion and vast majority research institutions and research universities around the world are setting up cryo-EM research. Indeed, the method is revolutionizing structural and molecular biology. We have been using cryo-EM to study the structure and mechanism of eukaryotic chromosome replication. Despite an abundance of cartoon drawings found in review articles and biology textbooks, the structure of the eukaryotic helicase that unwinds the double stranded DNA has been unknown. It has also been unknown how the helicase works with DNA polymerases to accomplish the feat of duplicating the genome. In my presentation, I will show how we have used cryo-EM to derive at structures of the eukaryotic chromosome replication machinery and describe mechanistic insights we have gleaned from the structures.

  10. Meiotic Parthenogenesis in a Root-Knot Nematode Results in Rapid Genomic Homozygosity

    Science.gov (United States)

    Liu, Qingli L.; Thomas, Varghese P.; Williamson, Valerie M.

    2007-01-01

    Many isolates of the plant-parasitic nematode Meloidogyne hapla reproduce by facultative meiotic parthenogenesis. Sexual crosses can occur, but, in the absence of males, the diploid state appears to be restored by reuniting sister chromosomes of a single meiosis. We have crossed inbred strains of M. hapla that differ in DNA markers and produced hybrids and F2 lines. Here we show that heterozygous M. hapla females, upon parthenogenetic reproduction, produce progeny that segregate 1:1 for the presence or absence of dominant DNA markers, as would be expected if sister chromosomes are rejoined, rather than the 3:1 ratio typical of a Mendelian cross. Codominant markers also segregate 1:1 and heterozygotes are present at low frequency (parthenogenesis would be expected to result in rapid genomic homozygosity. This type of high negative crossover interference coupled with positive chromatid interference has not been observed in fungal or other animal systems in which it is possible to examine the sister products of a single meiosis and may indicate that meiotic recombination in this nematode has novel features. PMID:17483427

  11. Non-Mendelian Single-Nucleotide Polymorphism Inheritance and Atypical Meiotic Configurations are Prevalent in Hop.

    Science.gov (United States)

    Zhang, Dong; Easterling, Katherine A; Pitra, Nicholi J; Coles, Mark C; Buckler, Edward S; Bass, Hank W; Matthews, Paul D

    2017-11-01

    Hop ( L.) breeding programs seek to exploit genetic resources for bitter flavor, aroma, and disease resistance. However, these efforts have been thwarted by segregation distortion including female-biased sex ratios. To better understand the transmission genetics of hop, we genotyped 4512 worldwide accessions of hop, including cultivars, landraces, and over 100 wild accessions using a genotyping-by-sequencing (GBS) approach. From the resulting ∼1.2 million single-nucleotide polymorphisms (SNPs), prequalified GBS markers were validated by inferences in population structures and phylogeny. Analysis of pseudo-testcross (Pt) mapping data from F families revealed mixed patterns of Mendelian and non-Mendelian segregation. Three-dimensional (3D) cytogenetic analysis of late meiotic prophase nuclei from two wild and two cultivated hop revealed conspicuous and prevalent occurrences of multiple, atypical, nondisomic chromosome complexes including autosomes. We used genome-wide association studies (GWAS) and fixation index (F) analysis to demonstrate selection mapping of genetic loci for key traits including sex, bitter acids, and drought tolerance. Among the possible mechanisms underlying the observed segregation distortion from the genomic data analysis, the cytogenetic analysis points to meiotic chromosome behavior as one of the contributing factors. The findings shed light on long-standing questions on the unusual transmission genetics and phenotypic variation in hop, with major implications for breeding, cultivation, and the natural history of . Copyright © 2017 Crop Science Society of America.

  12. A Mutation in Mtap2 Is Associated with Arrest of Mammalian Spermatocytes before the First Meiotic Division

    Directory of Open Access Journals (Sweden)

    Fengyun Sun

    2011-01-01

    Full Text Available In spite of evolutionary conservation of meiosis, many of the genes that control mammalian meiosis are still unknown. We report here that the ENU-induced repro4 mutation, identified in a screen to uncover genes that control mouse meiosis, causes failure of spermatocytes to exit meiotic prophase I via the G2/MI transition. Major events of meiotic prophase I occurred normally in affected spermatocytes and known regulators of the meiotic G2/MI transition were present and functional. Deep sequencing of mutant DNA revealed a mutation located in an intron of the Mtap2 gene, encoding microtubule-associated protein 2, and levels of Mtap2 transcript were reduced in mutant testes. This evidence implicates MTAP2 as required directly or indirectly for completion of meiosis and normal spermatogenesis in mammals.

  13. Evolution and tinkering: what do a protein kinase, a transcriptional regulator and chromosome segregation/cell division proteins have in common?

    Science.gov (United States)

    Derouiche, Abderahmane; Shi, Lei; Kalantari, Aida; Mijakovic, Ivan

    2016-02-01

    In this study, we focus on functional interactions among multi-domain proteins which share a common evolutionary origin. The examples we develop are four Bacillus subtilis proteins, which all possess an ATP-binding Walker motif: the bacterial tyrosine kinase (BY-kinase) PtkA, the chromosome segregation protein Soj (ParA), the cell division protein MinD and a transcription regulator SalA. These proteins have arisen via duplication of the ancestral ATP-binding domain, which has undergone fusions with other functional domains in the process of divergent evolution. We point out that these four proteins, despite having very different physiological roles, engage in an unusually high number of binary functional interactions. Namely, MinD attracts Soj and PtkA to the cell pole, and in addition, activates the kinase function of PtkA. SalA also activates the kinase function of PtkA, and it gets phosphorylated by PtkA as well. The consequence of this phosphorylation is the activation of SalA as a transcriptional repressor. We hypothesize that these functional interactions remain preserved during divergent evolution and represent a constraint on the process of evolutionary "tinkering", brought about by fusions of different functional domains.

  14. New vectors for chromosomal integration enable high-level constitutive or inducible magnetosome expression of fusion proteins in Magnetospirillum gryphiswaldense.

    Science.gov (United States)

    Borg, Sarah; Hofmann, Julia; Pollithy, Anna; Lang, Claus; Schüler, Dirk

    2014-04-01

    The alphaproteobacterium Magnetospirillum gryphiswaldense biomineralizes magnetosomes, which consist of monocrystalline magnetite cores enveloped by a phospholipid bilayer containing specific proteins. Magnetosomes represent magnetic nanoparticles with unprecedented magnetic and physicochemical characteristics. These make them potentially useful in a number of biotechnological and biomedical applications. Further functionalization can be achieved by expression of foreign proteins via genetic fusion to magnetosome anchor peptides. However, the available genetic tool set for strong and controlled protein expression in magnetotactic bacteria is very limited. Here, we describe versatile vectors for either inducible or high-level constitutive expression of proteins in M. gryphiswaldense. The combination of an engineered native PmamDC promoter with a codon-optimized egfp gene (Mag-egfp) resulted in an 8-fold increase in constitutive expression and in brighter fluorescence. We further demonstrate that the widely used Ptet promoter is functional and tunable in M. gryphiswaldense. Stable and uniform expression of the EGFP and β-glucuronidase (GusA) reporters was achieved by single-copy chromosomal insertion via Tn5-mediated transposition. In addition, gene duplication by Mag-EGFP-EGFP fusions to MamC resulted in further increased magnetosome expression and fluorescence. Between 80 and 210 (for single MamC-Mag-EGFP) and 200 and 520 (for MamC-Mag-EGFP-EGFP) GFP copies were estimated to be expressed per individual magnetosome particle.

  15. Genome-Wide Analysis of Heteroduplex DNA in Mismatch Repair–Deficient Yeast Cells Reveals Novel Properties of Meiotic Recombination Pathways

    Science.gov (United States)

    Martini, Emmanuelle; Borde, Valérie; Legendre, Matthieu; Audic, Stéphane; Regnault, Béatrice; Soubigou, Guillaume; Dujon, Bernard; Llorente, Bertrand

    2011-01-01

    Meiotic DNA double-strand breaks (DSBs) initiate crossover (CO) recombination, which is necessary for accurate chromosome segregation, but DSBs may also repair as non-crossovers (NCOs). Multiple recombination pathways with specific intermediates are expected to lead to COs and NCOs. We revisited the mechanisms of meiotic DSB repair and the regulation of CO formation, by conducting a genome-wide analysis of strand-transfer intermediates associated with recombination events. We performed this analysis in a SK1 × S288C Saccharomyces cerevisiae hybrid lacking the mismatch repair (MMR) protein Msh2, to allow efficient detection of heteroduplex DNAs (hDNAs). First, we observed that the anti-recombinogenic activity of MMR is responsible for a 20% drop in CO number, suggesting that in MMR–proficient cells some DSBs are repaired using the sister chromatid as a template when polymorphisms are present. Second, we observed that a large fraction of NCOs were associated with trans–hDNA tracts constrained to a single chromatid. This unexpected finding is compatible with dissolution of double Holliday junctions (dHJs) during repair, and it suggests the existence of a novel control point for CO formation at the level of the dHJ intermediate, in addition to the previously described control point before the dHJ formation step. Finally, we observed that COs are associated with complex hDNA patterns, confirming that the canonical double-strand break repair model is not sufficient to explain the formation of most COs. We propose that multiple factors contribute to the complexity of recombination intermediates. These factors include repair of nicks and double-stranded gaps, template switches between non-sister and sister chromatids, and HJ branch migration. Finally, the good correlation between the strand transfer properties observed in the absence of and in the presence of Msh2 suggests that the intermediates detected in the absence of Msh2 reflect normal intermediates. PMID

  16. Genome-wide analysis of heteroduplex DNA in mismatch repair-deficient yeast cells reveals novel properties of meiotic recombination pathways.

    Directory of Open Access Journals (Sweden)

    Emmanuelle Martini

    2011-09-01

    Full Text Available Meiotic DNA double-strand breaks (DSBs initiate crossover (CO recombination, which is necessary for accurate chromosome segregation, but DSBs may also repair as non-crossovers (NCOs. Multiple recombination pathways with specific intermediates are expected to lead to COs and NCOs. We revisited the mechanisms of meiotic DSB repair and the regulation of CO formation, by conducting a genome-wide analysis of strand-transfer intermediates associated with recombination events. We performed this analysis in a SK1 × S288C Saccharomyces cerevisiae hybrid lacking the mismatch repair (MMR protein Msh2, to allow efficient detection of heteroduplex DNAs (hDNAs. First, we observed that the anti-recombinogenic activity of MMR is responsible for a 20% drop in CO number, suggesting that in MMR-proficient cells some DSBs are repaired using the sister chromatid as a template when polymorphisms are present. Second, we observed that a large fraction of NCOs were associated with trans-hDNA tracts constrained to a single chromatid. This unexpected finding is compatible with dissolution of double Holliday junctions (dHJs during repair, and it suggests the existence of a novel control point for CO formation at the level of the dHJ intermediate, in addition to the previously described control point before the dHJ formation step. Finally, we observed that COs are associated with complex hDNA patterns, confirming that the canonical double-strand break repair model is not sufficient to explain the formation of most COs. We propose that multiple factors contribute to the complexity of recombination intermediates. These factors include repair of nicks and double-stranded gaps, template switches between non-sister and sister chromatids, and HJ branch migration. Finally, the good correlation between the strand transfer properties observed in the absence of and in the presence of Msh2 suggests that the intermediates detected in the absence of Msh2 reflect normal intermediates.

  17. Meiotic behaviour in three interspecific three-way hybrids between ...

    Indian Academy of Sciences (India)

    development and which can be successfully used in the breeding. Hybrids with high frequency of meiotic abnormalities can seriously compromise seed production, a key trait in assuring adoption of a new apomictic cultivar of Brachiaria for pasture formation. [Adamowski E. V., Pagliarini M. S. and Valle C. B. 2008 Meiotic ...

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

    Directory of Open Access Journals (Sweden)

    Judith Mary Lamo

    2017-10-01

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

  19. Rye B chromosomes encode a functional Argonaute-like protein with in vitro slicer activities similar to its A chromosome paralog

    Czech Academy of Sciences Publication Activity Database

    Ma, W.; Gabriel, T.S.; Martis, M.M.; Gursinsky, T.; Schubert, V.; Vrána, Jan; Doležel, Jaroslav; Grundlach, H.; Altschmied, L.; Scholz, U.; Himmelbach, A.; Behrens, S.E.; Banaei-Moghaddam, A.M.; Houben, A.

    2017-01-01

    Roč. 213, č. 2 (2017), s. 916-928 ISSN 0028-646X R&D Projects: GA MŠk(CZ) LO1204; GA ČR GBP501/12/G090 Institutional support: RVO:61389030 Keywords : rna-polymerase-ii * ribosomal-rna * accessory chromosomes * plant argonautes * gene-expression * evolution * transcription * pseudogenes * sequences * identification * Argonaute * B chromosomes * B-located genes * gene erosion. gene expression * pseudogenization * Secale cereale Subject RIV: EB - Genetics ; Molecular Biology OBOR OECD: Plant sciences, botany Impact factor: 7.330, year: 2016

  20. Meiotic Progression in Arabidopsis Is Governed by Complex Regulatory Interactions between SMG7, TDM1, and the Meiosis I–Specific Cyclin TAM[W][OA

    Science.gov (United States)

    Bulankova, Petra; Riehs-Kearnan, Nina; Nowack, Moritz K.; Schnittger, Arp; Riha, Karel

    2010-01-01

    Meiosis is a modified cell division that produces four haploid nuclei from a single diploid cell in two rounds of chromosome segregation. Here, we analyze the role of Arabidopsis thaliana SUPPRESSOR WITH MORPHOGENETIC EFFECTS ON GENITALIA7 (SMG7), THREE DIVISION MUTANT1 (TDM1), and TARDY ASYNCHRONOUS MEIOSIS (TAM) in meiotic progression. SMG7 is a conserved nonsense-mediated mRNA decay factor that is also, in Arabidopsis, essential for completion of meiosis. Examination of activating CYCLIN DEPENDENT KINASE A;1 phosophorylation at Thr-161 suggests that the meiotic arrest observed in smg7 mutants is likely caused by a failure to downregulate cyclin-dependent kinase (CDK) activity at the end of the second meiotic division. Genetic analysis indicates that SMG7 and TDM1 act in the same pathway to facilitate exit from meiosis. We further demonstrate that the cyclin TAM is specifically expressed in meiosis I and has both stimulatory and inhibitory effects on progression to meiosis II. TAM knockouts skip the second meiotic division producing unreduced gametes, but inactivation of SMG7 or TDM1 alleviates TAM’s requirement for entry into meiosis II. We propose a model that meiotic progression in Arabidopsis pollen mother cells is driven by a yet to be identified cyclin-CDK activity that is modulated by regulatory interactions between TDM1, SMG7, and TAM. PMID:21119056

  1. Multiple chromosomal gene integration for production of pharmaceutical proteins in S. cerevisiae

    DEFF Research Database (Denmark)

    Jensen, Malene; Mortensen, Uffe Hasbro; Gunnarsson, Nina

    2014-01-01

    When studying protein folding and secretion the general conception is that all cells in a population express an equal amount of protein. Recent work has shown that expression levels vary greatly in cell populations which express proteins on plasmids. Hence a yeast expression platform has been dev....... An amplification method has been developed for the platform which enables fast integration of genes. Future perspectives involve exploring the capabilities of the platform for recombinant protein production including performance and stability studies.......When studying protein folding and secretion the general conception is that all cells in a population express an equal amount of protein. Recent work has shown that expression levels vary greatly in cell populations which express proteins on plasmids. Hence a yeast expression platform has been......, expressing CFP and RFP on the separate plasmids or expressing CFP and RFP using the yeast expression platform shows expression varies greatly in a cell population based on plasmid expression compared to the yeast expression platform. When expressed on plasmids a few cells are high performers on both proteins...

  2. Cytoplasmic and Genomic Effects on Meiotic Pairing in Brassica Hybrids and Allotetraploids from Pair Crosses of Three Cultivated Diploids

    Science.gov (United States)

    Cui, Cheng; Ge, Xianhong; Gautam, Mayank; Kang, Lei; Li, Zaiyun

    2012-01-01

    Interspecific hybridization and allopolyploidization contribute to the origin of many important crops. Synthetic Brassica is a widely used model for the study of genetic recombination and “fixed heterosis” in allopolyploids. To investigate the effects of the cytoplasm and genome combinations on meiotic recombination, we produced digenomic diploid and triploid hybrids and trigenomic triploid hybrids from the reciprocal crosses of three Brassica diploids (B. rapa, AA; B. nigra, BB; B. oleracea, CC). The chromosomes in the resultant hybrids were doubled to obtain three allotetraploids (B. juncea, AA.BB; B. napus, AA.CC; B. carinata, BB.CC). Intra- and intergenomic chromosome pairings in these hybrids were quantified using genomic in situ hybridization and BAC-FISH. The level of intra- and intergenomic pairings varied significantly, depending on the genome combinations and the cytoplasmic background and/or their interaction. The extent of intragenomic pairing was less than that of intergenomic pairing within each genome. The extent of pairing variations within the B genome was less than that within the A and C genomes, each of which had a similar extent of pairing. Synthetic allotetraploids exhibited nondiploidized meiotic behavior, and their chromosomal instabilities were correlated with the relationship of the genomes and cytoplasmic background. Our results highlight the specific roles of the cytoplasm and genome to the chromosomal behaviors of hybrids and allopolyploids. PMID:22505621

  3. Efficient repair of DNA damage induced by heavy ion particles in meiotic prophase I nuclei of Caenorhabditis elegans

    International Nuclear Information System (INIS)

    Takanami, Takako; Zhang, Yongzhao; Aoki, Hidetoshi; Takahashi, Hideyuki; Higashitani, Atsushi; Abe, Tomoko; Yoshida, Shigeo; Horiuchi, Saburo

    2003-01-01

    The effects of heavy ion particle irradiation on meiosis and reproductive development in the nematode Caenorhabditis elegans were studied. Meiotic pachytene nuclei are significantly resistant to particle irradiation by the heavy ions carbon and argon, as well as to X-rays, but not ultraviolet (UV), whereas diplotene to diakinesis stage oocytes and early embryonic cells are not. Chromosomal abnormalities appear in mitotic cells and in maturing oocytes irradiated with heavy ion particles during the diplotene to the early diakinesis stages, but not in oocytes irradiated during the pachytene stage. The pachytene nuclei of ced-3 mutants, which are defective in apoptosis, are similarly resistant to ionizing radiation, but pachytene nuclei depleted for Ce-atl-1 (ataxia-telangiectasia like 1) or Ce-rdh-1/rad-51 are more sensitive. Pachytene nuclei thus appear to effectively repair heavy ion-induced DNA damage by the meiotic homologous recombination system. (author)

  4. Mouse microsomal triglyceride transfer protein large subunit: cDNA cloning, tissue-specific expression, and chromosomal localization

    Energy Technology Data Exchange (ETDEWEB)

    Nakamuta, Makoto; Chang, Benny Hung-Junn; Hoogeveen, R. [Baylor College of Medicine, Houston, TX (United States)] [and others

    1996-04-15

    Microsomal triglyceride transfer protein (MTP) catalyzes the transfer of triglyceride, cholesteryl ester, and phospholipid between membranes. It is essential for the secretion of apolipoprotein B from the cell. Mutations in MTP are a major cause of abetalipoproteinemia. The mouse is a popular animal model for lipoprotein metabolism. We have cloned and sequenced mouse MTP cDNA. The DNA-deduced amino acid sequence indicates that mouse protein shows 93, 86, and 83% sequence indicates that mouse MTP contains 894 amino acids; the mouse protein shows 93, 86, and 83% sequence identity to the hamster, human, and bovine sequences, respectively. Northern blot analysis indicates that mouse MTP mRNA is expressed at high levels in the small intestine and at substantially lower levels in the liver and that it is not detectable in six other tissues examined. The mouse MTP gene has been localized to the distal region of chromosome 3 by Southern blots of interspecific backcross panels using progeny derived from matings of (C57BL/6J x SPRET/Ei)F1 x SPRET/Ei. Comparison of MTP sequences from human, bovine, hamster, and mouse indicates that the C-terminal region of MTP is better conserved than its N-terminal region. 21 refs., 2 figs.

  5. Assignment of adenosine deaminase complexing protein (ADCP) gene(s) to human chromosome 2 in rodent-human somatic cell hybrids.

    Science.gov (United States)

    Herbschleb-Voogt, E; Grzeschik, K H; Pearson, P L; Meera Khan, P

    1981-01-01

    The experiments reported in this paper indicate that the expression of human adenosine deaminase complexing protein (ADCP) in the human-rodent somatic cell hybrids is influenced by the state of confluency of the cells and the background rodent genome. Thus, the complement of the L-cell derived A9 or B82 mouse parent apparently prevents the expression of human ADCP in the interspecific somatic cell hybrids. In the a3, E36, or RAG hybrids the human ADCP expression was not prevented by the rodent genome and was found to be proportional to the degree of confluency of the cell in the culture as in the case of primary human fibroblasts. An analysis of human chromosomes, chromosome specific enzyme markers, and ADCP in a panel of rodent-human somatic cell hybrids optimally maintained and harvested at full confluency has shown that the expression of human ADCP in the mouse (RAG)-human as well as in the hamster (E36 or a3)-human hybrids is determined by a gene(s) in human chromosome 2 and that neither chromosome 6 nor any other of the chromosomes of man carry any gene(s) involved in the formation of human ADCP at least in the Chinese hamster-human hybrids. A series of rodent-human hybrid clones exhibiting a mitotic separation of IDH1 and MDH1 indicated that ADCP is most probably situated between corresponding loci in human chromosome 2.

  6. Know Your Chromosomes

    Indian Academy of Sciences (India)

    In each of our cells there is about 6 feet long DNA packed. Into 46 units called chromosomes. Chromosome: is a long thread of DNA wrapped around proteins. ... application of. Mendel's 'gene' concept to a human trait was' by the physician A. Garrod. He described the genetic disease alkaptonuria as an alteration In specific.

  7. Characterization of bacterial artificial chromosome transgenic mice expressing mCherry fluorescent protein substituted for the murine smooth muscle-alpha-actin gene

    Science.gov (United States)

    Smooth muscle a actin (SMA) is a cytoskeletal protein expressed by mesenchymal and smooth muscle cell types, including mural cells(vascular smooth muscle cells and pericytes). Using Bacterial Artificial Chromosome (BAC) recombineering technology, we generated transgenic reporter mice that express a ...

  8. OsSPL regulates meiotic fate acquisition in rice.

    Science.gov (United States)

    Ren, Lijun; Tang, Ding; Zhao, Tingting; Zhang, Fanfan; Liu, Changzhen; Xue, Zhihui; Shi, Wenqing; Du, Guijie; Shen, Yi; Li, Yafei; Cheng, Zhukuan

    2018-04-01

    In angiosperms, the key step in sexual reproduction is successful acquisition of meiotic fate. However, the molecular mechanism determining meiotic fate remains largely unknown. Here, we report that OsSPOROCYTELESS (OsSPL) is critical for meiotic entry in rice (Oryza sativa). We performed a large-scale genetic screen of rice sterile mutants aimed to identify genes regulating meiotic entry and identified OsSPL using map-based cloning. We showed that meiosis-specific callose deposition, chromatin organization, and centromere-specific histone H3 loading were altered in the cells corresponding to pollen mother cells in Osspl anthers. Global transcriptome analysis showed that the enriched differentially expressed genes in Osspl were mainly related to redox status, meiotic process, and parietal cell development. OsSPL might form homodimers and interact with TEOSINTE BRANCHED1/CYCLOIDEA/PCF (TCP) transcription factor OsTCP5 via the SPL dimerization and TCP interaction domain. OsSPL also interacts with TPL (TOPLESS) corepressors, OsTPL2 and OsTPL3, via the EAR motif. Our results suggest that the OsSPL-mediated signaling pathway plays a crucial role in rice meiotic entry, which appears to be a conserved regulatory mechanism for meiotic fate acquisition in angiosperms. © 2018 The Authors. New Phytologist © 2018 New Phytologist Trust.

  9. Chromosomal rearrangements and protein globularity changes in Mycobacterium tuberculosis isolates from cerebrospinal fluid

    Directory of Open Access Journals (Sweden)

    Seow Hoon Saw

    2016-09-01

    Full Text Available Background Meningitis is a major cause of mortality in tuberculosis (TB. It is not clear what factors promote central nervous system invasion and pathology but it has been reported that certain strains of Mycobacterium tuberculosis (Mtb might have genetic traits associated with neurotropism. Methods In this study, we generated whole genome sequences of eight clinical strains of Mtb that were isolated from the cerebrospinal fluid (CSF of patients presenting with tuberculous meningitis (TBM in Malaysia, and compared them to the genomes of H37Rv and other respiratory Mtb genomes either downloaded from public databases or extracted from local sputum isolates. We aimed to find genomic features that might be distinctly different between CSF-derived and respiratory Mtb. Results Genome-wide comparisons revealed rearrangements (translocations, inversions, insertions and deletions and non-synonymous SNPs in our CSF-derived strains that were not observed in the respiratory Mtb genomes used for comparison. These rearranged segments were rich in genes for PE (proline-glutamate/PPE (proline-proline-glutamate, transcriptional and membrane proteins. Similarly, most of the ns SNPs common in CSF strains were noted in genes encoding PE/PPE proteins. Protein globularity differences were observed among mycobacteria from CSF and respiratory sources and in proteins previously reported to be associated with TB meningitis. Transcription factors and other transcription regulators featured prominently in these proteins. Homologs of proteins associated with Streptococcus pneumoniae meningitis and Neisseria meningitidis virulence were identified in neuropathogenic as well as respiratory mycobacterial spp. examined in this study. Discussion The occurrence of in silico genetic differences in CSF-derived but not respiratory Mtb suggests their possible involvement in the pathogenesis of TBM. However, overall findings in this comparative analysis support the postulation that TB

  10. SMC1B is present in mammalian somatic cells and interacts with mitotic cohesin proteins.

    Science.gov (United States)

    Mannini, Linda; Cucco, Francesco; Quarantotti, Valentina; Amato, Clelia; Tinti, Mara; Tana, Luigi; Frattini, Annalisa; Delia, Domenico; Krantz, Ian D; Jessberger, Rolf; Musio, Antonio

    2015-12-17

    Cohesin is an evolutionarily conserved protein complex that plays a role in many biological processes: it ensures faithful chromosome segregation, regulates gene expression and preserves genome stability. In mammalian cells, the mitotic cohesin complex consists of two structural maintenance of chromosome proteins, SMC1A and SMC3, the kleisin protein RAD21 and a fourth subunit either STAG1 or STAG2. Meiotic paralogs in mammals were reported for SMC1A, RAD21 and STAG1/STAG2 and are called SMC1B, REC8 and STAG3 respectively. It is believed that SMC1B is only a meiotic-specific cohesin member, required for sister chromatid pairing and for preventing telomere shortening. Here we show that SMC1B is also expressed in somatic mammalian cells and is a member of a mitotic cohesin complex. In addition, SMC1B safeguards genome stability following irradiation whereas its ablation has no effect on chromosome segregation. Finally, unexpectedly SMC1B depletion impairs gene transcription, particularly at genes mapping to clusters such as HOX and PCDHB. Genome-wide analyses show that cluster genes changing in expression are enriched for cohesin-SMC1B binding.

  11. [Study on prohibition of high mobility group chromosomal protein N2 against human oral squamous cell carcinoma in vitro].

    Science.gov (United States)

    Dong, Xiaoqian; Liu, Xiqian; Zhang, Yonghong; Zhang, Ping; Lu, Libing; Li, Xiaoyu; Huang, Ping; Feng, Yun

    2013-02-01

    Take human oral squamous cell carcinoma Tca8113 as experimental model, and study the anti oral squamous cell carcinoma activity of high mobility group chromosomal protein N2 (HMGN2) molecule. Train a large number of recombinant human HMGN2 expression vector Escherichia coli BL21. HMGN2 was expressed under isopropyl-1-thio-beta-galactopyranoside (IPTG) induction and purified by B-PER GST Fusion Protein Purification Kit. A variety of concentrations HMGN2 were added to cell culture medium, cells were tested by MTT, Hoechst 33342 fluorescence staining, flow cytometry assay and Western-blot. MTT results proved that HMGN2 could significantly inhibit human oral squamous cell carcinoma Tca8113 growth. Hoechst 33342 fluorescence staining, flow cytometry assay test and Western-blot proved HMGN2 could make Tca8113 cells morphological change, make Tca8113 cells block in S period of cell cycle and strongly promote Tca8113 cells to apoptosis. HMGN2 can promote apoptosis of oral squamous cell carcinoma cells.

  12. RABL6A, a Novel RAB-Like Protein, Controls Centrosome Amplification and Chromosome Instability in Primary Fibroblasts

    Science.gov (United States)

    Zhang, Xuefeng; Hagen, Jussara; Muniz, Viviane P.; Smith, Tarik; Coombs, Gary S.; Eischen, Christine M.; Mackie, Duncan I.; Roman, David L.; Van Rheeden, Richard; Darbro, Benjamin; Tompkins, Van S.; Quelle, Dawn E.

    2013-01-01

    RABL6A (RAB-like 6 isoform A) is a novel protein that was originally identified based on its association with the Alternative Reading Frame (ARF) tumor suppressor. ARF acts through multiple p53-dependent and p53-independent pathways to prevent cancer. How RABL6A functions, to what extent it depends on ARF and p53 activity, and its importance in normal cell biology are entirely unknown. We examined the biological consequences of RABL6A silencing in primary mouse embryo fibroblasts (MEFs) that express or lack ARF, p53 or both proteins. We found that RABL6A depletion caused centrosome amplification, aneuploidy and multinucleation in MEFs regardless of ARF and p53 status. The centrosome amplification in RABL6A depleted p53−/− MEFs resulted from centrosome reduplication via Cdk2-mediated hyperphosphorylation of nucleophosmin (NPM) at threonine-199. Thus, RABL6A prevents centrosome amplification through an ARF/p53-independent mechanism that restricts NPM-T199 phosphorylation. These findings demonstrate an essential role for RABL6A in centrosome regulation and maintenance of chromosome stability in non-transformed cells, key processes that ensure genomic integrity and prevent tumorigenesis. PMID:24282525

  13. Thermus thermophilis dnaX homolog encoding gamma- and tau-like proteins of the chromosomal replicase.

    Science.gov (United States)

    Yurieva, O; Skangalis, M; Kuriyan, J; O'Donnell, M

    1997-10-24

    This report identifies the dnaX homolog from Thermus thermophilis. Replicases from bacteria to humans contain subunits that are homologous to one another. These homologs are subunits of a clamp loading apparatus that loads sliding clamps onto DNA, which in turn act as mobile tethers for the replication machinery. In Escherichia coli, two of these subunits (gamma and tau) are encoded by one gene (dnaX) in nearly equal amounts by way of an efficient translational frameshift. The gamma and tau subunits form the central touchpoint that holds together two DNA polymerases with one clamp loading apparatus to form the E. coli chromosomal replicase, DNA polymerase III holoenzyme. The E. coli holoenzyme is an efficient replication machine that simultaneously replicates both strands of duplex DNA. The T. thermophilis dnaX homolog also contains a frameshift signature and produces both tau- and gamma-like proteins. Recombinant T. thermophilis tau- and gamma-like proteins, expressed in E. coli, have an oligomeric state similar to that of their E. coli counterparts and display ATPase activity that is stimulated by DNA. These results imply that T. thermophilis utilizes a DNA polymerase III holoenzyme replication machinery similar to that of E. coli.

  14. Looping in on Ndc80 - how does a protein loop at the kinetochore control chromosome segregation?

    DEFF Research Database (Denmark)

    Nilsson, Jakob

    2012-01-01

    through a calponin homology domain and an unstructured tail in the N terminus of the Ndc80 protein. A recent flurry of papers has highlighted the importance of an internal loop region in Ndc80 in establishing end-on attachment to microtubules. Here I discuss these recent findings that suggest that the Ndc...

  15. Borealin/Dasra B is a cell cycle-regulated chromosomal passenger protein and its nuclear accumulation is linked to poor prognosis for human gastric cancer

    International Nuclear Information System (INIS)

    Chang, J.-L.; Chen, T.-H.; Wang, C.-F.; Chiang, Y.-H.; Huang, Y.-L.; Wong, F.-H.; Chou, C.-K.; Chen, C.-M.

    2006-01-01

    Chromosomal passenger proteins including Aurora B, Survivin, and Borealin/Dasra B, also called CDCA8/FLJ10468, are known to play crucial roles during mitosis and cell division. Inappropriate chromosomal segregation and cell division may cause auneuploidy leading to cancer. However, it is still unclear how the expression of chromosomal passenger proteins may be linked to cancer. In this study, we demonstrated that Borealin is a cell cycle-regulated gene and is upregulated at G2-M phases of the cell cycle. We showed that Borealin interacts with Survivin but not with Aurora B. The interaction domain of Survivin in Borealin was mapped to the N-terminal 92 amino-acid residues of Borealin. To examine the linkage between expression of Borealin and cancer, we performed immunohistochemistry analysis using anti-Borealin specific antibody on the paraffin-embedded gastric cancer tissues. Our results showed that Borealin expression is significantly correlated with Survivin (P = 0.003) and Ki67 (P = 0.007) in gastric cancer. Interestingly, an increased nuclear Borealin level reveals borderline association with a poor survival rate (P = 0.047). Taken together, our results demonstrated that Borealin is a cell cycle-regulated chromosomal passenger protein and its aberrant expression is linked to a poor prognosis for gastric cancer

  16. Txndc9 Is Required for Meiotic Maturation of Mouse Oocytes

    Directory of Open Access Journals (Sweden)

    Fanhua Ma

    2017-01-01

    Full Text Available Txndc9 (thioredoxin domain containing protein 9 has been shown to be involved in mammalian mitosis; however, its function in mammalian oocyte meiosis remains unclear. In this study, we initially found that Txndc9 is expressed during meiotic maturation of mouse oocytes and higher expression of Txndc9 mRNA and protein occurred in germinal vesicle (GV stage. By using confocal scanning, we observed that Txndc9 localized at both nucleus and cytoplasm, especially at spindle microtubules. Specific depletion of Txndc9 by siRNA in mouse oocyte resulted in decreasing the rate of first polar body extrusion and increasing abnormal spindle assemble. Moreover, knockdown of Txndc9 in germinal vesicle (GV stage oocytes led to higher level of reactive oxygen species (ROS and lower level of antioxidant glutathione (GSH as compared with control oocytes, which indicated that Txndc9 may be involved in mediating the redox balance. In summary, our results demonstrated that Txndc9 is crucial for mouse oocyte maturation by regulating spindle assembly, polar body extrusion, and redox status.

  17. The Use of Living Cancer Cells Expressing Green Fluorescent Protein in the Nucleus and Red Fluorescence Protein in the Cytoplasm for Real-time Confocal Imaging of Chromosome and Cytoplasmic Dynamics During Mitosis.

    Science.gov (United States)

    Suetsugu, Atsushi; Jiang, Ping; Yang, Meng; Yamamoto, Norio; Moriwaki, Hisataka; Saji, Shigetoyo; Hoffman, Robert M

    2015-05-01

    A library of dual-color fluorescent cancer cells with green fluorescent protein (GFP), linked to histone H2B, expressed in the nucleus and red fluorescent protein (RFP) expressed in the cytoplasm was previously genetically engineered. The aim of the current study was to use the dual-color cancer cells to visualize chromosome and cytoplasmic dynamics during mitosis. Using an Olympus FV1000 confocal microscope, a library of dual-color cells from the major cancer types was cultured on plastic. The cells were imaged by confocal microscopy to demonstrate chromosome and cytoplasmic dynamics during mitosis. Nuclear GFP expression enabled visualization of chromosomes behavior, whereas simultaneous cytoplasmic RFP expression enabled visualization of cytoplasmic behavior during mitosis. Thus, total cellular dynamics can be visualized at high resolution, including individual chromosomes in some cases, in living dual-color cells in real time. Dual-color cancer cells expressing H2B-GFP in the nucleus and RFP in the cytoplasm provide unique tools for visualizing subcellular nuclear and cytoplasm dynamics, including the behavior of individual chromosomes during mitosis. The dual-color cells can be used to evaluate chromosomal loss or gain in real time during treatment with a variety of agents or as the cells are selected for increased or decreased malignancy in culture or in vivo. The dual color cells will be a useful tool to discover and evaluate novel strategies for killing cancer cells. Copyright© 2015 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.

  18. Human SGT interacts with Bag-6/Bat-3/Scythe and cells with reduced levels of either protein display persistence of few misaligned chromosomes and mitotic arrest

    International Nuclear Information System (INIS)

    Winnefeld, Marc; Grewenig, Annabel; Schnoelzer, Martina; Spring, Herbert; Knoch, Tobias A.; Gan, Eugene C.; Rommelaere, Jean; Cziepluch, Celina

    2006-01-01

    The human small glutamine-rich TPR-containing protein (hSGT) is essential for cell division since RNA-interference-mediated strong reduction of hSGT protein levels causes mitotic arrest (M. Winnefeld, J. Rommelaere, and C. Cziepluch, The human small glutamine-rich TPR-containing protein is required for progress through cell division, Exp. Cell Res. 293 (2004), 43-57). Analysis of HeLa cells expressing a histone 2A-YFP fusion protein revealed the continuous presence of few mislocalized chromosomes close to the spindle poles as possible cause for hSGT depletion-dependent prometaphase arrest. Cells unable to rescue these mislocalized chromosomes into the metaphase plate died at this stage through apoptosis. In order to address hSGT function at the molecular level, mass spectrometry analysis of proteins which co-immunoprecipitated with Flag-tagged hSGT was performed. Thereby, Hsp70 and Bag-6/Bat-3/Scythe were identified as novel hSGT interaction partners while interaction with Hsc70 was confirmed. Results obtained with truncated versions of the hSGT protein revealed that Bag-6/Bat-3/Scythe and Hsp70 or Hsc70 were independently able to form complexes with hSGT. Interaction of hSGT with Hsc70, Hsp70 or Bag-6/Bat-3/Scythe was demonstrated in prometaphase, thereby suggesting a possible role for complexes containing hSGT and distinct (co)-chaperones during mitosis. Finally, cells from populations with reduced levels of Bag-6/Bat-3/Scythe also displayed persistence of mislocalized chromosomes and mitotic arrest, which strongly indicated that hSGT-Bag-6/Bat-3/Scythe complexes could be directly or indirectly required for complete chromosome congression

  19. Magic with moulds: Meiotic and mitotic crossing over in Neurospora ...

    Indian Academy of Sciences (India)

    2006-02-16

    Feb 16, 2006 ... Home; Journals; Journal of Biosciences; Volume 31; Issue 1. Commentary: Magic with moulds: Meiotic and mitotic crossing over in Neurospora inversions and duplications. Durgadas P Kasbekar. Volume 31 Issue 1 March 2006 pp 3-4 ...

  20. Commentary: Magic with moulds: Meiotic and mitotic crossing over ...

    Indian Academy of Sciences (India)

    2006-02-16

    Feb 16, 2006 ... Home; Journals; Journal of Biosciences; Volume 31; Issue 1. Commentary: Magic with moulds: Meiotic and mitotic crossing over in Neurospora inversions and duplications. Durgadas P Kasbekar. Volume 31 Issue 1 March 2006 pp 3-4 ...

  1. A casein kinase 1 prevents expulsion of the oocyte meiotic spindle into a polar body by regulating cortical contractility

    Science.gov (United States)

    Flynn, Jonathan R.; McNally, Francis J.

    2017-01-01

    During female meiosis, haploid eggs are generated from diploid oocytes. This reduction in chromosome number occurs through two highly asymmetric cell divisions, resulting in one large egg and two small polar bodies. Unlike mitosis, where an actomyosin contractile ring forms between the sets of segregating chromosomes, the meiotic contractile ring forms on the cortex adjacent to one spindle pole, then ingresses down the length of the spindle to position itself at the exact midpoint between the two sets of segregating chromosomes. Depletion of casein kinase 1 gamma (CSNK-1) in Caenorhabditis elegans led to the formation of large polar bodies that contain all maternal DNA, because the contractile ring ingressed past the spindle midpoint. Depletion of CSNK-1 also resulted in the formation of deep membrane invaginations during meiosis, suggesting an effect on cortical myosin. Both myosin and anillin assemble into dynamic rho-dependent cortical patches that rapidly disassemble in wild-type embryos. CSNK-1 was required for disassembly of both myosin patches and anillin patches. Disassembly of anillin patches was myosin independent, suggesting that CSNK-1 prevents expulsion of the entire meiotic spindle into a polar body by negatively regulating the rho pathway rather than through direct inhibition of myosin. PMID:28701347

  2. Accuracy of preimplantation genetic diagnosis (PGD) of single gene and chromosomal disorders

    Energy Technology Data Exchange (ETDEWEB)

    Verlinsky, Y.; Strom, C.; Rechitsky, S. [Reproductive Genetics Institute, Chicage, IL (United States)] [and others

    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.

  3. Cytological techniques to study human female meiotic prophase.

    Science.gov (United States)

    Roig, Ignasi; Garcia-Caldés, Montserrat

    2009-01-01

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

  4. Nondisjunction of chromosome 15: Origin and recombination

    Energy Technology Data Exchange (ETDEWEB)

    Robinson, W.P.; Bernasconi, F.; Schinzel, A.A.; Mutirangura, A.; Ledbetter, D.H. (Baylor College of Medicine, Houston, TX (United States)); Langlois, S. (Univ. of Britisch Columbia, Vancouver (Canada)); 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.

  5. Dynamics of tobacco DNA topoisomerases II in cell cycle regulation: to manage topological constrains during replication, transcription and mitotic chromosome condensation and segregation.

    Science.gov (United States)

    Singh, Badri Nath; Achary, V Mohan Murali; Panditi, Varakumar; Sopory, Sudhir K; Reddy, Malireddy K

    2017-08-01

    The topoisomerase II expression varies as a function of cell proliferation. Maximal topoisomerase II expression was tightly coupled to S phase and G2/M phase via both transcriptional and post-transcriptional regulation. Investigation in meiosis using pollen mother cells also revealed that it is not the major component of meiotic chromosomes, it seems to diffuse out once meiotic chromosomal condensation is completed. Synchronized tobacco BY-2 cell cultures were used to study the role of topoisomerase II in various stages of the cell cycle. Topoisomerase II transcript accumulation was observed during the S- and G2/M- phase of cell cycle. This biphasic expression pattern indicates the active requirement of topoisomerase II during these stages of the cell cycle. Through immuno-localization of topoisomerase II was observed diffusely throughout the nucleoplasm in interphase nuclei, whereas, the nucleolus region exhibited a more prominent immuno-positive staining that correlated with rRNA transcription, as shown by propidium iodide staining and BrUTP incorporation. The immuno-staining analysis also showed that topoisomerase II is the major component of mitotic chromosomes and remain attached to the chromosomes during cell division. The inhibition of topoisomerase II activity using specific inhibitors revealed quite dramatic effect on condensation of chromatin and chromosome individualization from prophase to metaphase transition. Partially condensed chromosomes were not arranged on metaphase plate and chromosomal perturbations were observed when advance to anaphase, suggesting the importance of topoisomerase II activity for proper chromosome condensation and segregation during mitosis. Contrary, topoisomerase II is not the major component of meiotic chromosomes, even though mitosis and meiosis share many processes, including the DNA replication, chromosome condensation and precisely regulated partitioning of chromosomes into daughter cells. Even if topoisomerase II is

  6. Non-disjunction of chromosome 13

    DEFF Research Database (Denmark)

    Bugge, Merete; Collins, Andrew; Hertz, Jens Michael

    2007-01-01

    We performed a molecular study with 21 microsatellites on a sample of 82 trisomy 13 conceptuses, the largest number of cases studied to date. The parental origin was determined in every case and in 89% the extra chromosome 13 was of maternal origin with an almost equal number of maternal MI and MII...... errors. The latter finding is unique among human autosomal trisomies, where maternal MI (trisomies 15, 16, 21, 22) or MII (trisomy 18) errors dominate. Of the nine paternally derived cases five were of MII origin but none arose from MI errors. There was some evidence for elevated maternal age in cases...... with maternal meiotic origin for liveborn infants. Maternal and paternal ages were elevated in cases with paternal meiotic origin. This is in contrast to results from a similar study of non-disjunction of trisomy 21 where paternal but not maternal age was elevated. We find clear evidence for reduced...

  7. Arabidopsis SMG7 protein is required for exit from meiosis.

    Science.gov (United States)

    Riehs, Nina; Akimcheva, Svetlana; Puizina, Jasna; Bulankova, Petra; Idol, Rachel A; Siroky, Jiri; Schleiffer, Alexander; Schweizer, Dieter; Shippen, Dorothy E; Riha, Karel

    2008-07-01

    Meiosis consists of two nuclear divisions that are separated by a short interkinesis. Here we show that the SMG7 protein, which plays an evolutionarily conserved role in nonsense-mediated RNA decay (NMD) in animals and yeast, is essential for the progression from anaphase to telophase in the second meiotic division in Arabidopsis. Arabidopsis SMG7 is an essential gene, the disruption of which causes embryonic lethality. Plants carrying a hypomorphic smg7 mutation exhibit an elevated level of transcripts containing premature stop codons. This suggests that the role of SMG7 in NMD is conserved in plants. Furthermore, hypomorphic smg7 alleles render mutant plants sterile by causing an unusual cell-cycle arrest in anaphase II that is characterized by delayed chromosome decondensation and aberrant rearrangement of the meiotic spindle. The smg7 phenotype was mimicked by exposing meiocytes to the proteasome inhibitor MG115. Together, these data indicate that SMG7 counteracts cyclin-dependent kinase (CDK) activity at the end of meiosis, and reveal a novel link between SMG7 and regulation of the meiotic cell cycle.

  8. CBFβ and the leukemogenic fusion protein CBFβ-SMMHC associate with mitotic chromosomes to epigenetically regulate ribosomal genes.

    Science.gov (United States)

    Lopez-Camacho, Cesar; van Wijnen, Andre J; Lian, Jane B; Stein, Janet L; Stein, Gary S

    2014-12-01

    Mitotic bookmarking is an epigenetic control mechanism that sustains gene expression in progeny cells; it is often found in genes related to the maintenance of cellular phenotype and growth control. RUNX transcription factors regulate a broad spectrum of RNA Polymerase (Pol II) transcribed genes important for lineage commitment but also regulate RNA Polymerase I (Pol I) driven ribosomal gene expression, thus coordinating control of cellular identity and proliferation. In this study, using fluorescence microscopy and biochemical approaches we show that the principal RUNX co-factor, CBFβ, associates with nucleolar organizing regions (NORs) during mitosis to negatively regulate RUNX-dependent ribosomal gene expression. Of clinical relevance, we establish for the first time that the leukemogenic fusion protein CBFβ-SMMHC (smooth muscle myosin heavy chain) also associates with ribosomal genes in interphase chromatin and mitotic chromosomes to promote and epigenetically sustain regulation of ribosomal genes through RUNX factor interactions. Our results demonstrate that CBFβ contributes to the transcriptional regulation of ribosomal gene expression and provide further understanding of the epigenetic role of CBFβ-SMMHC in proliferation and maintenance of the leukemic phenotype. © 2014 Wiley Periodicals, Inc.

  9. NuMA in rat testis--evidence for roles in proliferative activity and meiotic cell division.

    Science.gov (United States)

    Taimen, Pekka; Parvinen, Martti; Osborn, Mary; Kallajoki, Markku

    2004-08-15

    NuMA is a well-characterized organizer of the mitotic spindle, which is believed to play a structural role in interphase nucleus. We studied the expression of NuMA in rat seminiferous epithelium in detail. Different stages of the cycle of the seminiferous epithelium were identified using transillumination. Corresponding areas were microdissected and analysed using immunofluorescence, immunohistochemistry, or immunoblotting. NuMA was expressed in Sertoli cells, proliferating type A and B spermatogonia, and early spermatids but it was absent in late spermatids and mature spermatozoa. Interestingly, NuMA-positive primary spermatocytes lost their nuclear NuMA at the beginning of long-lasting prophase of the first meiotic division. A strong expression was again observed at the end of the prophase and finally, a redistribution of NuMA into pole regions of the meiotic spindle was observed in first and second meiotic divisions. In immunoblotting, a single 250-kDa protein present in all stages of the rat seminiferous epithelial cycle was detected. Our results show that NuMA is not essential for the organization of nuclear structure in all cell types and suggest that its presence is more likely connected to the proliferation phase of the cells. They also suggest that NuMA may play an important role in meiotic cell division.

  10. Telomere dysfunction and chromosome instability

    Energy Technology Data Exchange (ETDEWEB)

    Murnane, John P., E-mail: jmurnane@radonc.ucsf.edu [Department of Radiation Oncology, University of California San Francisco, 2340 Sutter Street, San Francisco, CA 94143-1331 (United States)

    2012-02-01

    The ends of chromosomes are composed of a short repeat sequence and associated proteins that together form a cap, called a telomere, that keeps the ends from appearing as double-strand breaks (DSBs) and prevents chromosome fusion. The loss of telomeric repeat sequences or deficiencies in telomeric proteins can result in chromosome fusion and lead to chromosome instability. The similarity between chromosome rearrangements resulting from telomere loss and those found in cancer cells implicates telomere loss as an important mechanism for the chromosome instability contributing to human cancer. Telomere loss in cancer cells can occur through gradual shortening due to insufficient telomerase, the protein that maintains telomeres. However, cancer cells often have a high rate of spontaneous telomere loss despite the expression of telomerase, which has been proposed to result from a combination of oncogene-mediated replication stress and a deficiency in DSB repair in telomeric regions. Chromosome fusion in mammalian cells primarily involves nonhomologous end joining (NHEJ), which is the major form of DSB repair. Chromosome fusion initiates chromosome instability involving breakage-fusion-bridge (B/F/B) cycles, in which dicentric chromosomes form bridges and break as the cell attempts to divide, repeating the process in subsequent cell cycles. Fusion between sister chromatids results in large inverted repeats on the end of the chromosome, which amplify further following additional B/F/B cycles. B/F/B cycles continue until the chromosome acquires a new telomere, most often by translocation of the end of another chromosome. The instability is not confined to a chromosome that loses its telomere, because the instability is transferred to the chromosome donating a translocation. Moreover, the amplified regions are unstable and form extrachromosomal DNA that can reintegrate at new locations. Knowledge concerning the factors promoting telomere loss and its consequences is

  11. Sexual dimorphism in prophase I of meiosis in the Northern mole vole (Ellobius talpinus Pallas, 1770 with isomorphic (XX chromosomes in males and females

    Directory of Open Access Journals (Sweden)

    O Kolomiets

    2010-07-01

    Full Text Available The synaptonemal complex (SC surface-spreading technique was used to visualize the process of chromosome synapsis in spermatocytes and oocytes of E. talpinus Pallas, 1770, a species with the XX sex chromosome system in both males and females. We used electron microscopy and immunofluorescent localization of synaptonemal complex protein (SCP3 and centromeric proteins to analyze the structure and behaviour of synaptonemal complexes in prophase I of meiosis, aiming to reveal signs of meiotic sexual dimorphism in this species. We present evidence of considerable differences in the structure and behaviour of the axial structures of sex bivalents in male and female meiosis, despite the isomorphic G- and C-banding patterns of mitotic sex chromosomes. During meiotic prophase I, the sex bivalent in females behaved as autosomal bivalents, but it was not involved in the formation of the bouquet configuration or it was the first to leave it. The XX chromosomes of males formed closed sex bivalents. Only short tracts of SC were formed at both ends of the sex bivalent, while large middle segments of the lateral elements remained unpaired. The male sex chromosomes also formed characteristic “sex bodies”. In fact, electron microscopy revealed dense nucleolus-like bodies associated with unpaired parts of the axial elements. These regions of the sex chromosomes were poorly immunostained, because the distribution of SCP3 had a peculiar powder-like pattern, but SCP3 was not associated with the nucleolus-like bodies. We also revealed signs of sexual dimorphism in the dynamics of formation and destruction of autosomal SCs. In males, the total SC length was shorter than in females. The chromosome bouquet configuration was preserved up to the stage of early pachytene in females. The bouquet configuration in males was not expressed. At late pachytene, gaps were revealed in the structure of autosomal SCs in spermatocytes immunostained with antibodies to SCP3. The

  12. Sister chromosome pairing maintains heterozygosity in parthenogenetic lizards.

    Science.gov (United States)

    Lutes, Aracely A; Neaves, William B; Baumann, Diana P; Wiegraebe, Winfried; Baumann, Peter

    2010-03-11

    Although bisexual reproduction has proven to be highly successful, parthenogenetic all-female populations occur frequently in certain taxa, including the whiptail lizards of the genus Aspidoscelis. Allozyme analysis revealed a high degree of fixed heterozygosity in these parthenogenetic species, supporting the view that they originated from hybridization events between related sexual species. It has remained unclear how the meiotic program is altered to produce diploid eggs while maintaining heterozygosity. Here we show that meiosis commences with twice the number of chromosomes in parthenogenetic versus sexual species, a mechanism that provides the basis for generating gametes with unreduced chromosome content without fundamental deviation from the classic meiotic program. Our observation of synaptonemal complexes and chiasmata demonstrate that a typical meiotic program occurs and that heterozygosity is not maintained by bypassing recombination. Instead, fluorescent in situ hybridization probes that distinguish between homologues reveal that bivalents form between sister chromosomes, the genetically identical products of the first of two premeiotic replication cycles. Sister chromosome pairing provides a mechanism for the maintenance of heterozygosity, which is critical for offsetting the reduced fitness associated with the lack of genetic diversity in parthenogenetic species.

  13. Expression and human chromosomal localization to 17q25 of the growth-regulated gene encoding the mitochondrial ribosomal protein MRPL12

    Energy Technology Data Exchange (ETDEWEB)

    Marty, L.; Fort, P. [Institut de Genetique Moleculaire, Montpellier (France); Taviaux, S. [INSERM, Montpellier (France)

    1997-05-01

    Mitochondrial activity requires the expression of nuclear genes, whose products are part of multiproteic complexes leading to ATP production and delivery. We recently characterized a growth-activated mRNA encoding the human mitochondrial ribosomal MRPL12 protein, which is thought to act as a translational regulator of mitochondrial mRNAs. We show here that MRPL12 mRNA expression is enhanced in growth-stimulated cells as a result of transcriptional activation, a feature lost in transformed cell lines. MRPL12 mRNA is highly expressed in the colon, in which a reduction in mitochondrial activity was shown to be associated with tumor formation. The human MRPL12 protein is encoded by a unique gene located on chromosome 17 (q25-qter). As no predisposition to colon cancer linked to this chromosomal region was hitherto reported, the MRPL12 gene might be involved in the process of differentiation of colonic epithelial cells. 16 refs., 2 figs.

  14. Whole chromosome gain does not in itself confer cancer-like chromosomal instability.

    Science.gov (United States)

    Valind, Anders; Jin, Yuesheng; Baldetorp, Bo; Gisselsson, David

    2013-12-24

    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.

  15. Molecular cloning and chromosomal localization of a pseudogene related to the human Acyl-CoA binding protein/diazepam binding inhibitor

    Energy Technology Data Exchange (ETDEWEB)

    Gersuk, V.H. [Virginia Mason Research Center, Seattle, WA (United States); Rose, T.M.; Todaro, G.J. [Univ. of Washington, Seattle, WA (United States)

    1995-01-20

    The acyl-CoA binding protein (ACBP) and the diazepam binding inhibitor (DBI) or endozepine are independent isolates of a single 86-amino-acid, 10-kDa protein. ACBP/DBI is highly conserved between species and has been identified in several diverse organisms, including human, cow, rat, frog, duck, insects, plants, and yeast. Although the genomic locus has not yet been cloned in humans, complementary DNA clones with different 5{prime} ends have been isolated and characterized. These cDNA clones appear to be encoded by a single gene. However, Southern blot analyses, in situ hybridizations, and somatic cell hybrid chromosomal mapping all suggest that there are multiple ACBP/DBI-related sequences in the genome. To identify potential members of this gene family, degenerate oligonucleotides corresponding to highly conserved regions of ACBP/DBI were used to screen a human genomic DNA library using the polymerase chain reaction. A novel gene, DBIP1, that is closely related to ACBP/DBI but is clearly distinct was identified. DBIP1 bears extensive sequence homology to ACBP/DBI but lacks the introns predicted by rat and duck genomic sequence studies. A 1-base deletion in the coding region results in a frameshift and, along with the absence of introns and the lack of a detectable transcript, suggests that DBIP1 is a pseudogene. ACBP/DBI has previously been mapped to chromosome 2, although this was recently disputed, and a chromosome 6 location was suggested. We show that ACBP/DBI is correctly placed on chromosome 2 and that the gene identified on chromosome 6 is DBIP1. 33 refs., 3 figs., 1 tab.

  16. A specific family of interspersed repeats (SINEs facilitates meiotic synapsis in mammals

    Directory of Open Access Journals (Sweden)

    Johnson Matthew E

    2013-01-01

    Full Text Available Abstract Background Errors during meiosis that affect synapsis and recombination between homologous chromosomes contribute to aneuploidy and infertility in humans. Despite the clinical relevance of these defects, we know very little about the mechanisms by which homologous chromosomes interact with one another during mammalian meiotic prophase. Further, we remain ignorant of the way in which chromosomal DNA complexes with the meiosis-specific structure that tethers homologs, the synaptonemal complex (SC, and whether specific DNA elements are necessary for this interaction. Results In the present study we utilized chromatin immunoprecipitation (ChIP and DNA sequencing to demonstrate that the axial elements of the mammalian SC are markedly enriched for a specific family of interspersed repeats, short interspersed elements (SINEs. Further, we refine the role of the repeats to specific sub-families of SINEs, B1 in mouse and AluY in old world monkey (Macaca mulatta. Conclusions Because B1 and AluY elements are the most actively retrotransposing SINEs in mice and rhesus monkeys, respectively, our observations imply that they may serve a dual function in axial element binding; i.e., as the anchoring point for the SC but possibly also as a suppressor/regulator of retrotransposition.

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

    Science.gov (United States)

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

    2015-05-01

    Arthropod sex ratios can be manipulated by a diverse range of selfish genetic elements, including maternally inherited Wolbachia bacteria. Feminization by Wolbachia is rare but has been described for Eurema mandarina butterflies. In this species, some phenotypic and functional females, thought to be ZZ genetic males, are infected with a feminizing Wolbachia strain, wFem. Meanwhile, heterogametic WZ females are not infected with wFem. Here, we establish a quantitative PCR assay allowing reliable sexing in three Eurema species. Against expectation, all E. mandarina females, including wFem females, had only one Z chromosome that was paternally inherited. Observation of somatic interphase nuclei confirmed that W chromatin was absent in wFem females, but present in females without wFem. We conclude that the sex bias in wFem lines is due to meiotic drive (MD) that excludes the maternal Z and thus prevents formation of ZZ males. Furthermore, wFem lines may have lost the W chromosome or harbour a dysfunctional version, yet rely on wFem for female development; removal of wFem results in all-male offspring. This is the first study that demonstrates an interaction between MD and Wolbachia feminization, and it highlights endosymbionts as potentially confounding factors in MD of sex chromosomes. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  18. Karyotypic Determinants of Chromosome Instability in Aneuploid Budding Yeast

    Science.gov (United States)

    Bradford, William D.; Li, Rong

    2012-01-01

    Recent studies in cancer cells and budding yeast demonstrated that aneuploidy, the state of having abnormal chromosome numbers, correlates with elevated chromosome instability (CIN), i.e. the propensity of gaining and losing chromosomes at a high frequency. Here we have investigated ploidy- and chromosome-specific determinants underlying aneuploidy-induced CIN by observing karyotype dynamics in fully isogenic aneuploid yeast strains with ploidies between 1N and 2N obtained through a random meiotic process. The aneuploid strains exhibited various levels of whole-chromosome instability (i.e. chromosome gains and losses). CIN correlates with cellular ploidy in an unexpected way: cells with a chromosomal content close to the haploid state are significantly more stable than cells displaying an apparent ploidy between 1.5 and 2N. We propose that the capacity for accurate chromosome segregation by the mitotic system does not scale continuously with an increasing number of chromosomes, but may occur via discrete steps each time a full set of chromosomes is added to the genome. On top of such general ploidy-related effect, CIN is also associated with the presence of specific aneuploid chromosomes as well as dosage imbalance between specific chromosome pairs. Our findings potentially help reconcile the divide between gene-centric versus genome-centric theories in cancer evolution. PMID:22615582

  19. Origin of extra chromosome in Patau syndrome.

    Science.gov (United States)

    Ishikiriyama, S; Niikawa, N

    1984-01-01

    Five live-born infants with Patau syndrome were studied for the nondisjunctional origin of the extra chromosome. Transmission modes of chromosomes 13 from parents to a child were determined using both QFQ- and RFA-heteromorphisms as markers, and the origin was ascertained in all of the patients. The extra chromosome had originated in nondisjunction at the maternal first meiotic division in two patients, at the maternal second meiosis in other two, and at the paternal first meiosis in the remaining one. Summarizing the results of the present study, together with those of the previous studies on a liveborn and abortuses with trisomy 13, nondisjunction at the maternal and the paternal meiosis occurred in this trisomy in the ratio of 14:3. This ratio is not statistically different from that inferred from the previous studies for Down syndrome. These findings suggest that there may be a fundamental mechanism common to the occurrence of nondisjunction in the acrocentric trisomies.

  20. [Tripartite motif-containing protein 34 (TRIM34) colocalized with micronuclei chromosome and hampers its movement to equatorial plate during the metaphase stage of mitosis].

    Science.gov (United States)

    Sun, Dakang; An, Xinye; Ji, Bing; Cheng, Yanli; Gao, Honglian; Tian, Mingming

    2016-06-01

    Objective To examine whether tripartite motif-containing protein 34 (TRIM34) is colocalized with micronuclei and investigate the influence on the movement of micronuclei chromosome in mitosis. Methods The eukaryotic expression vector TRIM34-pEGFP-N3 was constructed, identified and then transfected into HEK293T cells. With 4', 6-diamidino-2-phenylindole 2HCI (DAPI) staining, the colocalization between TRIM34 and micronuclei was observed under a fluorescence microscope. Moreover, MitoTracker(R)Deep Red was used to identify the colocalization between the complex of TRIM34-micronulei and mitochondria under a confocal microscope. Finally, the effect of TRIM34 on the movement of micronuclei chromosome in mitosis was examined. Results DNA sequencing confirmed that the vector TRIM34-pEGFP-N3 was constructed successfully. A fluorescence microscope revealed that TRIM34 could be colocalized with micronuclei in HEK293T cells transfected with TRIM34-pEGFP-N3. In the same manner, a confocal microscope distinctly showed that TRIM34 was colocalized with micronuclei similarly in appearance. However, there was no distinguished colocalization relationship between the complex of TRIM34-micronulei and mitochondria. Interestingly, the micronuclei chromosome conjugated with TRIM34 was hardly transferred to equatorial plate during the metaphase stage of mitosis. Conclusion TRIM34 is colocalized with micronuclei chromosome and hampers its movement to equatorial plate in mitosis.

  1. Occurrence of differential meiotic associations and additional ...

    Indian Academy of Sciences (India)

    Abstract. A small population of complex translocation heterozygote plants of Allium roylei from the Bani region of Jammu Province was studied for meiosis in the female track. This study resulted in identification of two variants, having embryo-sac mother cells (EMCs) with more than 16 chromosomes. EMCs of the remaining ...

  2. Chromosome 21-derived microRNAs provide an etiological basis for aberrant protein expression in human Down syndrome brains.

    Science.gov (United States)

    Kuhn, Donald E; Nuovo, Gerard J; Terry, Alvin V; Martin, Mickey M; Malana, Geraldine E; Sansom, Sarah E; Pleister, Adam P; Beck, Wayne D; Head, Elizabeth; Feldman, David S; Elton, Terry S

    2010-01-08

    Down syndrome (DS), or Trisomy 21, is the most common genetic cause of cognitive impairment and congenital heart defects in the human population. Bioinformatic annotation has established that human chromosome 21 (Hsa21) harbors five microRNA (miRNAs) genes: miR-99a, let-7c, miR-125b-2, miR-155, and miR-802. Our laboratory recently demonstrated that Hsa21-derived miRNAs are overexpressed in DS brain and heart specimens. The aim of this study was to identify important Hsa21-derived miRNA/mRNA target pairs that may play a role, in part, in mediating the DS phenotype. We demonstrate by luciferase/target mRNA 3'-untranslated region reporter assays, and gain- and loss-of-function experiments that miR-155 and -802 can regulate the expression of the predicted mRNA target, the methyl-CpG-binding protein (MeCP2). We also demonstrate that MeCP2 is underexpressed in DS brain specimens isolated from either humans or mice. We further demonstrate that, as a consequence of attenuated MeCP2 expression, transcriptionally activated and silenced MeCP2 target genes, CREB1/Creb1 and MEF2C/Mef2c, are also aberrantly expressed in these DS brain specimens. Finally, in vivo silencing of endogenous miR-155 or -802, by antagomir intra-ventricular injection, resulted in the normalization of MeCP2 and MeCP2 target gene expression. Taken together, these results suggest that improper repression of MeCP2, secondary to trisomic overexpression of Hsa21-derived miRNAs, may contribute, in part, to the abnormalities in the neurochemistry observed in the brains of DS individuals. Finally these results suggest that selective inactivation of Hsa21-derived miRNAs may provide a novel therapeutic tool in the treatment of DS.

  3. SLX-1 is required for maintaining genomic integrity and promoting meiotic noncrossovers in the Caenorhabditis elegans germline.

    Directory of Open Access Journals (Sweden)

    Takamune T Saito

    2012-08-01

    Full Text Available Although the SLX4 complex, which includes structure-specific nucleases such as XPF, MUS81, and SLX1, plays important roles in the repair of several kinds of DNA damage, the function of SLX1 in the germline remains unknown. Here we characterized the endonuclease activities of the Caenorhabditis elegans SLX-1-HIM-18/SLX-4 complex co-purified from human 293T cells and determined SLX-1 germline function via analysis of slx-1(tm2644 mutants. SLX-1 shows a HIM-18/SLX-4-dependent endonuclease activity toward replication forks, 5'-flaps, and Holliday junctions. slx-1 mutants exhibit hypersensitivity to UV, nitrogen mustard, and camptothecin, but not gamma irradiation. Consistent with a role in DNA repair, recombination intermediates accumulate in both mitotic and meiotic germ cells in slx-1 mutants. Importantly, meiotic crossover distribution, but not crossover frequency, is altered on chromosomes in slx-1 mutants compared to wild type. This alteration is not due to changes in either the levels or distribution of double-strand breaks (DSBs along chromosomes. We propose that SLX-1 is required for repair at stalled or collapsed replication forks, interstrand crosslink repair, and nucleotide excision repair during mitosis. Moreover, we hypothesize that SLX-1 regulates the crossover landscape during meiosis by acting as a noncrossover-promoting factor in a subset of DSBs.

  4. Observation of Extensive Chromosome Axis Remodeling during the “Diffuse-Phase” of Meiosis in Large Genome Cereals

    Science.gov (United States)

    Colas, Isabelle; Darrier, Benoit; Arrieta, Mikel; Mittmann, Sybille U.; Ramsay, Luke; Sourdille, Pierre; Waugh, Robbie

    2017-01-01

    The production of balanced fertile haploid gametes requires the faithful separation of paired (synapsed) chromosomes toward the end of meiotic prophase I (desynapsis). This involves the timely dissolution of the synaptonemal complex during the pachytene-diplotene transition, a stage traditionally referred to as the “diffuse stage.” In species with large genomes such as, barley (Hordeum vulgare L.) and wheat (Triticum aestivum L.) we know most about the early stages of meiotic prophase I. There, synapsis initiates at the telomeric ends of chromosomes and progresses toward the centromeric regions through the ordered assembly of the synaptonemal complex (SC). Synapsis is impacted by recombination (crossing over, CO) which locally modifies the extent of chromatin compaction and extension. CO is uneven along the chromosomes, occurring mainly toward the telomeric regions resulting in a highly skewed distribution of recombination events. However, we know very little about the process of desynapsis which occurs during the “diffuse stage,” where the synapsed and recombined chromosomes faithfully desynapse and separate into daughter cells. Here, using 3D-SIM super-resolution immuno-cytology combined with the use of antibodies directed against two crucial SC proteins, ASY1 and ZYP1, we followed the whole of meiosis I (i.e., both synapsis and desynapsis) in both barley and wheat. We showed that synapsis forms a characteristic tri-partite SC structure in zygotene (more clearly seen in barley). Toward the end of meiosis I, as the SC starts to disassemble, we show that extensive chromosome axis remodeling results in the formation of characteristic “tinsel-like” structures in both wheat and barley. By using a mutant (des10) that is severely compromised in polymerization of ZYP1during synapsis, we show that tinsel structure formation during SC dissolution is not dependant on full synapsis and may relate instead to changes in expansion stress. Our observations highlight

  5. Mapping of the human gene for a melanocyte protein Pmel 17 (D12S53E) to chromosome 12q13-q14

    Energy Technology Data Exchange (ETDEWEB)

    Kubota, Ryo; Wang, Yimin; Minoshima, Shinsei [Keio Univ. School of Medicine, Tokyo (Japan)] [and others

    1995-03-20

    We have isolated several new cDNA clones that are differentially expressed in retina from a human retina cDNA library using a new combined method of subtractive hybridization and differential hybridization. Among these cDNAs, we found that cDNA clone BA7 was identical to the previously reported Pmel 17 cDNA in its nucleotide sequence. Pmel 17 mRNA is preferentially expressed in melanocytes, and the protein expressed in Escherichia coli cross-reacts with anti-tyrosinase antibodies. The mouse Pmel 17 gene was mapped to the pter-q21 region of human chromosome 12. In this paper, we present evidence precisely locating the human Pmel 17 gene to chromosome 12q13-q14. 7 refs., 1 fig.

  6. A YAC contig spanning a cluster of human type III receptor protein tyrosine kinase genes (PDGFRA-KIT-KDR) in chromosome segment 4q12

    Energy Technology Data Exchange (ETDEWEB)

    Spritz, R.A.; Strunk, K.M.; Lee, S.T. [Univ. of Wisconsin, Madison, WI (United States)] [and others

    1994-07-15

    The authors have mapped five genes encoding protein tyrosine kinases (PTKs) to the pericentromeric region of human chromosome 4. PTK4 and TYRO4, which encode nonreceptor intracellular PTKs, are located at 4p12 and 4q13, respectively. The other three genes, PDGFRA, KIT, and KDR, encode type III transmembrane receptor PTKs for known ligands. The authors have developed a contig of 29 yeast artificial chromosomes (YACs) spanning approximately 2 Mb of DNA at 4q12 that includes PDGFRA, KIT, and KDR, and have used this YAC contig to map 12 different sequence-tagged sites in this region. PDGFRA, KIT, and KDR thus constitute a cluster of genes at 4q12 encoding closely related type III receptor PTKs. Mutations of the human KIT gene result in piebaldism, an autosomal dominant disorder of melanocyte development. 42 refs., 3 figs., 2 tabs.

  7. B-Chromosome Ribosomal DNA Is Functional in the Grasshopper Eyprepocnemis plorans

    OpenAIRE

    Ruiz-Est??vez, Mercedes; L??pez-Le??n, Mar??a Dolores; Cabrero, Josefa; Mart??nez Camacho, Juan Pedro

    2012-01-01

    B-chromosomes are frequently argued to be genetically inert elements, but activity for some particular genes has been reported, especially for ribosomal RNA (rRNA) genes whose expression can easily be detected at the cytological level by the visualization of their phenotypic expression, i.e., the nucleolus. The B(24) chromosome in the grasshopper Eyprepocnemis plorans frequently shows a nucleolus attached to it during meiotic prophase I. Here we show the presence of rRNA transcripts that uneq...

  8. A novel genetic tool for clonal analysis of fourth chromosome mutations

    OpenAIRE

    Sousa-Neves, Rui; Schinaman, Joseph M.

    2012-01-01

    The fourth chromosome of Drosophila remains one of the most intractable regions of the fly genome to genetic analysis. The main difficulty posed to the genetic analyses of mutations on this chromosome arises from the fact that it does not undergo meiotic recombination, which makes recombination mapping impossible, and also prevents clonal analysis of mutations, a technique which relies on recombination to introduce the prerequisite recessive markers and FLP-recombinase recognition targets (FR...

  9. Production and meiotic pairing behaviour of new hybrids of winter wheat (Triticum aestivum) x winter barley (Hordeum vulgare).

    Science.gov (United States)

    Molnár-Láng, M; Linc, G; Logojan, A; Sutka, J

    2000-12-01

    New winter wheat (Triticum aestivum L.) x winter barley (Hordeum vulgare L.) hybrids produced using cultivated varieties (wheat 'Martonvásári 9 krl'(Mv9 krl) x barley 'Igri', Mv9 krl x 'Osnova', 'Asakazekomugi' x 'Manas') were multiplied in tissue culture because of the high degree of sterility and then pollinated with wheat to obtain backcross progenies. Meiotic analysis of the hybrids Mv9 krl x 'Igri' and 'Asakazekomugi' x 'Manas' and their in vitro regenerated progenies with the Feulgen method revealed 1.59 chromosome arm associations per cell in both initial hybrids. The number of chromosome arm associations increased after in vitro culture to 4.72 and 2.67, respectively, in the two combinations. According to the genomic in situ hybridization (GISH) analysis, wheat-barley chromosome arm associations made up 3.6% of the total in the initial Mv9 krl x 'Igri' hybrid and 6.6% and 16.5% of the total in in vitro regenerated progenies of the 'Asakazekomugi' x 'Manas' and Mv9 krl x 'Igri' hybrids, respectively. The demonstration by GISH of wheat-barley chromosome pairing in the hybrids and especially in their in vitro regenerated progenies proves the possibility of producing recombinants between these two genera, and thus of transferring useful characters from barley into wheat. In vitro conditions caused an increase in chromosome arm association frequency in both combinations and in fertility in some regenerants.

  10. New chromosome reports in Lamiaceae of Kashmir (Northwest Himalaya), India.

    Science.gov (United States)

    Malik, Reyaz Ahmad; Gupta, Raghbir Chand; Singh, Vijay; Bala, Santosh; Kumari, Santosh

    2017-03-01

    Meiotic studies and chromosome data are imperative in order to have an overall germplasm evaluation of a taxon. In the present effort, the meiotic study is carried out in 48 populations belonging to 26 species of Lamiaceae collected from their natural habitats in Kashmir Himalaya, which forms an important part of Northwest Himalaya. Chromosome counts in the five species viz. Dracocephalum nutans (2n = 10), Lycopus europaeus (2n = 22), Marrubium vulgare (2n = 54), Nepeta nervosa (2n = 18) and Salvia sclarea (2n = 22) are first time reported from India. Besides, 17 species are cytologically evaluated for the first time from the study area-Kashmir Himalaya. In Marrubium vulgare, hexaploid cytotype (2n = 6 × =54) is reported for the first time. Also, diploid and tetraploid cytomorphovariants are observed in Calamintha vulgaris (2n = 20, 40), Elsholtzia ciliata (2n = 16, 32) and Mentha longifolia (2n = 20, 40). Various meiotic abnormalities like chromatin stickiness, cytomixis, nonsynchronous disjunction, laggards, chromatin bridges, etc. leading to pollen abnormalities have been documented for the first time in some species. The worldwide status of chromosome number data in each genus is presented.

  11. Chromosomal characteristics of a Brazilian whip spider (Amblypygi) and evolutionary relationships with other arachnid orders.

    Science.gov (United States)

    Paula-Neto, E; Araujo, D; Carvalho, L S; Cella, D M; Schneider, M C

    2013-09-19

    We analyzed mitotic and meiotic cells of a Brazilian amblypygid, Heterophrynus longicornis, using conventional and molecular cytogenetic techniques (Giemsa staining, C-banding, Ag-NOR, and FISH with rDNA probe). This is the first study that focuses solely on amblypygid chromosomes; it was undertaken to add data on cytogenetic knowledge of this group and contribute to the understanding of chromosome evolution in the Arachnida. We found 2n = 66 for male and female individuals, monocentric chromosomes, and absence of morphologically differentiated sex chromosomes. C-banding showed heterochromatin in the pericentromeric region of most chromosomes. Mitotic and meiotic nuclei submitted to silver impregnation and FISH revealed, respectively, Ag-NORs and ribosomal genes in the terminal region of two chromosome pairs. Most chromosome features that we observed in H. longicornis are shared with species of other arachnid orders; however, the absence of morphologically differentiated sex chromosomes in amblypygid contrasts with the remarkable variety of sex chromosome systems recorded for the Araneae. Consequently, we conclude that analysis of species of the Tetrapulmonata clade is useful for understanding the trends of sex chromosome evolution in this arachnid group.

  12. TRIP13 is a protein-remodeling AAA+ ATPase that catalyzes MAD2 conformation switching.

    Science.gov (United States)

    Ye, Qiaozhen; Rosenberg, Scott C; Moeller, Arne; Speir, Jeffrey A; Su, Tiffany Y; Corbett, Kevin D

    2015-04-28

    The AAA+ family ATPase TRIP13 is a key regulator of meiotic recombination and the spindle assembly checkpoint, acting on signaling proteins of the conserved HORMA domain family. Here we present the structure of the Caenorhabditis elegans TRIP13 ortholog PCH-2, revealing a new family of AAA+ ATPase protein remodelers. PCH-2 possesses a substrate-recognition domain related to those of the protein remodelers NSF and p97, while its overall hexameric architecture and likely structural mechanism bear close similarities to the bacterial protein unfoldase ClpX. We find that TRIP13, aided by the adapter protein p31(comet), converts the HORMA-family spindle checkpoint protein MAD2 from a signaling-active 'closed' conformer to an inactive 'open' conformer. We propose that TRIP13 and p31(comet) collaborate to inactivate the spindle assembly checkpoint through MAD2 conformational conversion and disassembly of mitotic checkpoint complexes. A parallel HORMA protein disassembly activity likely underlies TRIP13's critical regulatory functions in meiotic chromosome structure and recombination.

  13. TRIP13 is a protein-remodeling AAA+ ATPase that catalyzes MAD2 conformation switching

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Qiaozhen [Ludwig Institute for Cancer Research, San Diego Branch, La Jolla, United States; Rosenberg, Scott C. [Ludwig Institute for Cancer Research, San Diego Branch, La Jolla, United States; Moeller, Arne [National Resource for Automated Molecular Microscopy, Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, United States; Speir, Jeffrey A. [National Resource for Automated Molecular Microscopy, Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, United States; Su, Tiffany Y. [Ludwig Institute for Cancer Research, San Diego Branch, La Jolla, United States; Corbett, Kevin D. [Ludwig Institute for Cancer Research, San Diego Branch, La Jolla, United States; Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, United States

    2015-04-28

    The AAA+ family ATPase TRIP13 is a key regulator of meiotic recombination and the spindle assembly checkpoint, acting on signaling proteins of the conserved HORMA domain family. Here we present the structure of the Caenorhabditis elegans TRIP13 ortholog PCH-2, revealing a new family of AAA+ ATPase protein remodelers. PCH-2 possesses a substrate-recognition domain related to those of the protein remodelers NSF and p97, while its overall hexameric architecture and likely structural mechanism bear close similarities to the bacterial protein unfoldase ClpX. We find that TRIP13, aided by the adapter protein p31(comet), converts the HORMA-family spindle checkpoint protein MAD2 from a signaling-active ‘closed’ conformer to an inactive ‘open’ conformer. We propose that TRIP13 and p31(comet) collaborate to inactivate the spindle assembly checkpoint through MAD2 conformational conversion and disassembly of mitotic checkpoint complexes. A parallel HORMA protein disassembly activity likely underlies TRIP13's critical regulatory functions in meiotic chromosome structure and recombination.

  14. SGO1 maintains bovine meiotic and mitotic centromeric cohesions of sister chromatids and directly affects embryo development.

    Directory of Open Access Journals (Sweden)

    Feng-Xia Yin

    Full Text Available Shugoshin (SGO is a critical factor that enforces cohesion from segregation of paired sister chromatids during mitosis and meiosis. It has been studied mainly in invertebrates. Knowledge of SGO(s in a mammalian system has only been reported in the mouse and Hela cells. In this study, the functions of SGO1 in bovine oocytes during meiotic maturation, early embryonic development and somatic cell mitosis were investigated. The results showed that SGO1 was expressed from germinal vesicle (GV to the metaphase II stage. SGO1 accumulated on condensed and scattered chromosomes from pre-metaphase I to metaphase II. The over-expression of SGO1 did not interfere with the process of homologous chromosome separation, although once separated they were unable to move to the opposing spindle poles. This often resulted in the formation of oocytes with 60 replicated chromosomes. Depletion of SGO1 in GV oocytes affected chromosomal separation resulting in abnormal chromosome alignment at a significantly higher proportion than in control oocytes. Knockdown of SGO1 expression significantly decreased the embryonic developmental rate and quality. To further confirm the function(s of SGO1 during mitosis, bovine embryonic fibroblast cells were transfected with SGO1 siRNAs. SGO1 depletion induced the premature dissociation of chromosomal cohesion at the centromere and along the chromosome arm giving rise to abnormal appearing mitotic patterns. The results of this study infer that SGO1 is involved in the centromeric cohesion of sister chromatids and chromosomal movement towards the spindle poles. Depletion of SGO1 causes arrestment of cell division in meiosis and mitosis.

  15. First description of multivalent ring structures in eutherian mammalian meiosis: new chromosomal characterization of Cormura brevirostris (Emballonuridae, Chiroptera).

    Science.gov (United States)

    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.

  16. Ex-vivo assessment of chronic toxicity of low levels of cadmium on testicular meiotic cells

    Energy Technology Data Exchange (ETDEWEB)

    Geoffroy-Siraudin, Cendrine [Aix-Marseille Univ, UMR CNRS IMBE 7263, FR 3098 ECCOREV, 13005, Marseille (France); Laboratoire de Biologie de la Reproduction, AP-HM, Hôpital de la Conception, 147, Boulevard Baille, 13385 Marseille cedex 5 (France); Perrard, Marie-Hélène [Institut de Génomique Fonctionnelle de Lyon, UMR 5242 CNRS INRA Ecole Normale Supérieure de Lyon 1, 46 allée d' Italie, F-69364 Lyon Cedex 07 (France); Ghalamoun-Slaimi, Rahma [Aix-Marseille Univ, UMR CNRS IMBE 7263, FR 3098 ECCOREV, 13005, Marseille (France); Laboratoire de Biologie de la Reproduction, AP-HM, Hôpital de la Conception, 147, Boulevard Baille, 13385 Marseille cedex 5 (France); Ali, Sazan [Aix-Marseille Univ, UMR CNRS IMBE 7263, FR 3098 ECCOREV, 13005, Marseille (France); Chaspoul, Florence [Aix-Marseille Univ, UMR CNRS IMBE 7263, FR 3098 ECCOREV, 13005, Marseille (France); Unité de Chimie-Physique, Faculté de Pharmacie 13005, Marseille (France); Lanteaume, André [Aix-Marseille Univ, UMR CNRS IMBE 7263, FR 3098 ECCOREV, 13005, Marseille (France); Achard, Vincent [Laboratoire de Biologie de la Reproduction, AP-HM, Hôpital de la Conception, 147, Boulevard Baille, 13385 Marseille cedex 5 (France); Gallice, Philippe [Aix-Marseille Univ, UMR CNRS IMBE 7263, FR 3098 ECCOREV, 13005, Marseille (France); Unité de Chimie-Physique, Faculté de Pharmacie 13005, Marseille (France); Durand, Philippe [Institut de Génomique Fonctionnelle de Lyon, UMR 5242 CNRS INRA Ecole Normale Supérieure de Lyon 1, 46 allée d' Italie, F-69364 Lyon Cedex 07 (France); and others

    2012-08-01

    Using a validated model of culture of rat seminiferous tubules, we assessed the effects of 0.1, 1 and 10 μg/L cadmium (Cd) on spermatogenic cells over a 2‐week culture period. With concentrations of 1 and 10 μg/L in the culture medium, the Cd concentration in the cells, determined by ICP-MS, increased with concentration in the medium and the day of culture. Flow cytometric analysis enabled us to evaluate changes in the number of Sertoli cells and germ cells during the culture period. The number of Sertoli cells did not appear to be affected by Cd. By contrast, spermatogonia and meiotic cells were decreased by 1 and 10 μg/L Cd in a time and dose dependent manner. Stage distribution of the meiotic prophase I and qualitative study of the synaptonemal complexes (SC) at the pachytene stage were performed by immunocytochemistry with an anti SCP3 antibody. Cd caused a time-and-dose-dependent increase of total abnormalities, of fragmented SC and of asynapsis from concentration of 0.1 μg/L. Additionally, we observed a new SC abnormality, the “motheaten” SC. This abnormality is frequently associated with asynapsis and SC widening which increased with both the Cd concentration and the duration of exposure. This abnormality suggests that Cd disrupts the structure and function of proteins involved in pairing and/or meiotic recombination. These results show that Cd induces dose-and-time-dependent alterations of the meiotic process of spermatogenesis ex-vivo, and that the lowest metal concentration, which induces an adverse effect, may vary with the cell parameter studied. -- Highlights: ► Cadmium induces ex-vivo severe time- and dose-dependent germ cell abnormalities. ► Cadmium at very low concentration (0.1 µg/l) induces synaptonemal complex abnormalities. ► The lowest concentration inducing adverse effect varied with the cell parameter studied. ► Cadmium alters proteins involved in pairing and recombination. ► Cadmium leads to achiasmate univalents and

  17. Chromosome 21-derived MicroRNAs Provide an Etiological Basis for Aberrant Protein Expression in Human Down Syndrome Brains*

    Science.gov (United States)

    Kuhn, Donald E.; Nuovo, Gerard J.; Terry, Alvin V.; Martin, Mickey M.; Malana, Geraldine E.; Sansom, Sarah E.; Pleister, Adam P.; Beck, Wayne D.; Head, Elizabeth; Feldman, David S.; Elton, Terry S.

    2010-01-01

    Down syndrome (DS), or Trisomy 21, is the most common genetic cause of cognitive impairment and congenital heart defects in the human population. Bioinformatic annotation has established that human chromosome 21 (Hsa21) harbors five microRNA (miRNAs) genes: miR-99a, let-7c, miR-125b-2, miR-155, and miR-802. Our laboratory recently demonstrated that Hsa21-derived miRNAs are overexpressed in DS brain and heart specimens. The aim of this study was to identify important Hsa21-derived miRNA/mRNA target pairs that may play a role, in part, in mediating the DS phenotype. We demonstrate by luciferase/target mRNA 3′-untranslated region reporter assays, and gain- and loss-of-function experiments that miR-155 and -802 can regulate the expression of the predicted mRNA target, the methyl-CpG-binding protein (MeCP2). We also demonstrate that MeCP2 is underexpressed in DS brain specimens isolated from either humans or mice. We further demonstrate that, as a consequence of attenuated MeCP2 expression, transcriptionally activated and silenced MeCP2 target genes, CREB1/Creb1 and MEF2C/Mef2c, are also aberrantly expressed in these DS brain specimens. Finally, in vivo silencing of endogenous miR-155 or -802, by antagomir intra-ventricular injection, resulted in the normalization of MeCP2 and MeCP2 target gene expression. Taken together, these results suggest that improper repression of MeCP2, secondary to trisomic overexpression of Hsa21-derived miRNAs, may contribute, in part, to the abnormalities in the neurochemistry observed in the brains of DS individuals. Finally these results suggest that selective inactivation of Hsa21-derived miRNAs may provide a novel therapeutic tool in the treatment of DS. PMID:19897480

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

    Directory of Open Access Journals (Sweden)

    Martin M. Möckel

    2017-04-01

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

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

    Directory of Open Access Journals (Sweden)

    Logan M. Decker

    2017-04-01

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

  20. Loss-of-function mutants and overexpression lines of the Arabidopsis cyclin CYCA1;2/Tardy Asynchronous Meiosis exhibit different defects in prophase-i meiocytes but produce the same meiotic products.

    Directory of Open Access Journals (Sweden)

    Yixing Wang

    Full Text Available In Arabidopsis, loss-of-function mutations in the A-type cyclin CYCA1;2/Tardy Asynchronous Meiosis (TAM gene lead to the production of abnormal meiotic products including triads and dyads. Here we report that overexpression of TAM by the ASK1:TAM transgene also led to the production of triads and dyads in meiosis, as well as shriveled seeds, in a dominant fashion. However, the partial loss-of-function mutant tam-1, an ASK1:TAM line, and the wild type differed in dynamic changes in chromosome thread thickness from zygotene to diplotene. We also found that the pericentromeric heterochromatin regions in male meiocytes in tam-1 and tam-2 (a null allele frequently formed a tight cluster at the pachytene and diplotene stages, in contrast to the infrequent occurrences of such clusters in the wild type and the ASK1:TAM line. Immunolocalization studies of the chromosome axial component ASY1 revealed that ASY1 was highly expressed at the appropriate male meiotic stages but not localized to the chromosomes in tam-2. The level of ASY1, however, was greatly reduced in another ASK1:TAM line with much overexpressed TAM. Our results indicate that the reduction and increase in the activity of TAM differentially affect chromosomal morphology and the action of ASY1 in prophase I. Based on these results, we propose that either the different meiotic defects or a common defect such as missing ASY1 on the chromosomal axes triggers a hitherto uncharacterized cell cycle checkpoint in the male meiocytes in the tam mutants and ASK1:TAM lines, leading to the production of the same abnormal meiotic products.

  1. Congenital diaphragmatic hernia interval on chromosome 8p23.1 characterized by genetics and protein interaction networks

    DEFF Research Database (Denmark)

    Longoni, Mauro; Hansen, Kasper Lage; Russell, Meaghan K.

    2012-01-01

    expressed in the E11.5–12.5 primordial mouse diaphragm, the developmental stage at which CDH is thought to occur. This combination of bioinformatics and expression studies can be applied to other chromosomal hotspots, as well as private microdeletions or microduplications, to identify causative genes...

  2. Destabilized SMC5/6 complex leads to chromosome breakage syndrome with severe lung disease

    NARCIS (Netherlands)

    van der Crabben, Saskia N; Hennus, Marije P; McGregor, Grant A; Ritter, Deborah I; Nagamani, Sandesh C S; Wells, Owen S; Harakalova, Magdalena; Chinn, Ivan K; Alt, Aaron; Vondrova, Lucie; Hochstenbach, Ron; van Montfrans, Joris M; Terheggen-Lagro, Suzanne W; van Lieshout, Stef; van Roosmalen, Markus J; Renkens, Ivo; Duran, Karen; Nijman, Isaäc J.; Kloosterman, Wigard P; Hennekam, Eric; Orange, Jordan S; van Hasselt, Peter M; Wheeler, David A; Palecek, Jan J; Lehmann, Alan R; Oliver, Antony W; Pearl, Laurence H; Plon, Sharon E; Murray, Johanne M; van Haaften, Gijs

    The structural maintenance of chromosomes (SMC) family of proteins supports mitotic proliferation, meiosis, and DNA repair to control genomic stability. Impairments in chromosome maintenance are linked to rare chromosome breakage disorders. Here, we have identified a chromosome breakage syndrome

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

    Directory of Open Access Journals (Sweden)

    Shaheen Husain

    2013-01-01

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

  4. Global transcriptome analysis of two ameiotic1 alleles in maize anthers: defining steps in meiotic entry and progression through prophase I

    Directory of Open Access Journals (Sweden)

    Fernandes John F

    2011-08-01

    Full Text Available Abstract Background Developmental cues to start meiosis occur late in plants. Ameiotic1 (Am1 encodes a plant-specific nuclear protein (AM1 required for meiotic entry and progression through early prophase I. Pollen mother cells (PMCs remain mitotic in most am1 mutants including am1-489, while am1-praI permits meiotic entry but PMCs arrest at the leptotene/zygotene (L/Z transition, defining the roles of AM1 protein in two distinct steps of meiosis. To gain more insights into the roles of AM1 in the transcriptional pre-meiotic and meiotic programs, we report here an in depth analysis of gene expression alterations in carefully staged anthers at 1 mm (meiotic entry and 1.5 mm (L/Z caused by each of these am1 alleles. Results 1.0 mm and 1.5 mm anthers of am1-489 and am1-praI were profiled in comparison to fertile siblings on Agilent® 4 × 44 K microarrays. Both am1-489 and am1-praI anthers are cytologically normal at 1.0 mm and show moderate transcriptome alterations. At the 1.5-mm stage both mutants are aberrant cytologically, and show more drastic transcriptome changes. There are substantially more absolute On/Off and twice as many differentially expressed genes (sterile versus fertile in am1-489 than in am1-praI. At 1.5 mm a total of 4,418 genes are up- or down-regulated in either am1-489 or am1-praI anthers. These are predominantly stage-specific transcripts. Many putative meiosis-related genes were found among them including a small subset of allele-specific, mis-regulated genes specific to the PMCs. Nearly 60% of transcriptome changes in the set of transcripts mis-regulated in both mutants (N = 530 are enriched in PMCs, and only 1% are enriched in the tapetal cell transcriptome. All array data reported herein will be deposited and accessible at MaizeGDB http://www.maizegdb.org/. Conclusions Our analysis of anther transcriptome modulations by two distinct am1 alleles, am1-489 and am1-praI, redefines the role of AM1 as a modulator of expression

  5. Genetic Analysis of Meiotic Recombination in Schizosaccharomyces pombe

    OpenAIRE

    Smith, Gerald R.

    2009-01-01

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

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

    African Journals Online (AJOL)

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

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

    Indian Academy of Sciences (India)

    RESEARCH ARTICLE. Meiotic behaviour of tetraploid wheats (Triticum turgidum L.) .... a Nikon Eclipse E600(Tokyo, Japan) light microscope using. Photo grab 300Z software Fujix TM 300 z sh-3z version 2.1 ..... SAS Institute 2003 SAS/STAT User's Guide, version 9. 1. SAS In- stitute, Cary, USA. Sato S., Peet M. M. and ...

  8. Meiotic faults as a major cause of offspring inviability

    DEFF Research Database (Denmark)

    Levitis, Daniel; Zimmerman, Kolea; Pringle, Anne

    2014-01-01

    The extensive literature on the costs and benefits of sexual reproduction often concludes that increased offspring viability is a benefit of sexual reproduction as compared to parthenogenesis. We show that all comparisons contributing to this conclusion involve cases of meiotic parthenogenesis, t...

  9. Cloning of a conserved receptor-like protein kinase gene and its use as a functional marker for homoeologous group-2 chromosomes of the triticeae species.

    Directory of Open Access Journals (Sweden)

    Bi Qin

    Full Text Available Receptor-like kinases (RLKs play broad biological roles in plants. We report on a conserved receptor-like protein kinase (RPK gene from wheat and other Triticeae species. The TaRPK1 was isolated from the Triticum aestivum cv. Prins - Triticum timopheevii introgression line IGVI-465 carrying the powdery mildew resistance gene Pm6. The TaRPK1 was mapped to homoeologous chromosomes 2A (TaRPK1-2A, 2D (TaRPK1-2D and the Pm6-carrier chromosome 2G (TaRPK1-2G of IGVI-465. Under the tested conditions, only the TaRPK1-2G allele was actively transcribed, producing two distinct transcripts via alternative splicing. The predicted 424-amino acid protein of TaRPK1-2G contained a signal peptide, a transmembrane domain and an intracellular serine/threonine kinase domain, but lacked a typical extracellular domain. The expression of TaRPK1-2G gene was up-regulated upon the infection by Blumeria graminis f.sp. tritici (Bgt and treatment with methyl jasmonate (MeJA, but down-regulated in response to treatments of SA and ABA. Over-expression of TaRPK1-2G in the powdery mildew susceptible wheat variety Prins by a transient expression assay showed that it slightly reduced the haustorium index of the infected Bgt. These data indicated that TaRPK1-2G participated in the defense response to Bgt infection and in the JA signaling pathway. Phylogenetic analysis indicated that TaRPK1-2G was highly conserved among plant species, and the amino acid sequence similarity of TaRPK1-2G among grass species was more than 86%. Based on its conservation, the RPK gene-based STS primers were designed, and used to amplify the RPK orthologs from the homoeologous group-2 chromosomes of all the tested Triticeae species, such as chromosome 2G of T. timopheevii, 2R of Secale cereale, 2H of Hordeum vulgare, 2S of Aegilops speltoides, 2S(l of Ae. longissima, 2M(g of Ae. geniculata, 2S(p and 2U(p of Ae. peregrina. The developed STS markers serve as conserved functional markers for the

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

    Directory of Open Access Journals (Sweden)

    Frédéric Baudat

    2007-06-01

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

  11. Interaction of NuMA protein with the kinesin Eg5: its possible role in bipolar spindle assembly and chromosome alignment.

    Science.gov (United States)

    Iwakiri, Yuko; Kamakura, Sachiko; Hayase, Junya; Sumimoto, Hideki

    2013-04-15

    Bipolar spindle assembly in mitotic cells is a prerequisite to ensure correct alignment of chromosomes for their segregation to each daughter cell; spindle microtubules are tethered at plus ends to chromosomes and focused at minus ends to either of the two spindle poles. NuMA (nuclear mitotic apparatus protein) is present solely in the nucleus in interphase cells, but relocalizes during mitosis to the spindle poles to play a crucial role in spindle assembly via focusing spindle microtubules to each pole. In the present study we show that the kinesin-5 family motor Eg5 is a protein that directly interacts with NuMA, using a proteomics approach and various binding assays both in vivo and in vitro. During mitosis Eg5 appears to interact with NuMA in the vicinity of the spindle poles, whereas the interaction does not occur in interphase cells, where Eg5 is distributed throughout the cytoplasm but NuMA exclusively localizes to the nucleus. Slight, but significant, depletion of Eg5 in HeLa cells by RNA interference results in formation of less-focused spindle poles with misaligned chromosomes in metaphase; these phenotypes are similar to those induced by depletion of NuMA. Since NuMA is less accumulated at the spindle poles in Eg5-depleted cells, Eg5 probably contributes to spindle assembly via regulating NuMA localization. Furthermore, depletion of cytoplasmic dynein induces mislocalization of NuMA and phenotypes similar to those observed in NuMA-depleted cells, without affecting Eg5 localization to the spindles. Thus dynein appears to control NuMA function in conjunction with Eg5.

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

    Directory of Open Access Journals (Sweden)

    Jana Link

    2014-02-01

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

  13. Contrasted patterns of crossover and non-crossover at Arabidopsis thaliana meiotic recombination hotspots.

    Directory of Open Access Journals (Sweden)

    Jan Drouaud

    2013-11-01

    Full Text Available The vast majority of meiotic recombination events (crossovers (COs and non-crossovers (NCOs cluster in narrow hotspots surrounded by large regions devoid of recombinational activity. Here, using a new molecular approach in plants, called "pollen-typing", we detected and characterized hundreds of CO and NCO molecules in two different hotspot regions in Arabidopsis thaliana. This analysis revealed that COs are concentrated in regions of a few kilobases where their rates reach up to 50 times the genome average. The hotspots themselves tend to cluster in regions less than 8 kilobases in size with overlapping CO distribution. Non-crossover (NCO events also occurred in the two hotspots but at very different levels (local CO/NCO ratios of 1/1 and 30/1 and their track lengths were quite small (a few hundred base pairs. We also showed that the ZMM protein MSH4 plays a role in CO formation and somewhat unexpectedly we also found that it is involved in the generation of NCOs but with a different level of effect. Finally, factors acting in cis and in trans appear to shape the rate and distribution of COs at meiotic recombination hotspots.

  14. Molecular analysis of recombination in a family with Duchenne muscular dystrophy and a large pericentric X chromosome inversion

    Energy Technology Data Exchange (ETDEWEB)

    Shashi, V.; Golden, W.L.; Allinson, P.S. [Univ. of Virginia Health Sciences Center, Charlottesville, VA (United States)] [and others

    1996-06-01

    It has been demonstrated in animal studies that, in animals heterozygous for pericentric chromosomal inversions, loop formation is greatly reduced during meiosis. This results in absence of recombination within the inverted segment, with recombination seen only outside the inversion. A recent study in yeast has shown that telomeres, rather than centromeres, lead in chromosome movement just prior to meiosis and may be involved in promoting recombination. We studied by cytogenetic analysis and DNA polymorphisms the nature of meiotic recombination in a three-generation family with a large pericentric X chromosome inversion, inv(X)(p21.1q26), in which Duchenne muscular dystrophy (DMD) was cosegregating with the inversion. On DNA analysis there was no evidence of meiotic recombination between the inverted and normal X chromosomes in the inverted segment. Recombination was seen at the telomeric regions, Xp22 and Xq27-28. No deletion or point mutation was found on analysis of the DMD gene. On the basis of the FISH results, we believe that the X inversion is the mutation responsible for DMD in this family. Our results indicate that (1) pericentric X chromosome inversions result in reduction of recombination between the normal and inverted X chromosomes; (2) meiotic X chromosome pairing in these individuals is likely initiated at the telomeres; and (3) in this family DMD is caused by the pericentric inversion. 50 refs., 7 figs., 1 tab.

  15. Rab5 GTPase controls chromosome alignment through Lamin disassembly and relocation of the NuMA-like protein Mud to the poles during mitosis.

    Science.gov (United States)

    Capalbo, Luisa; D'Avino, Pier Paolo; Archambault, Vincent; Glover, David M

    2011-10-18

    The small GTPase Rab5 is a conserved regulator of membrane trafficking; it regulates the formation of early endosomes, their transport along microtubules, and the fusion to the target organelles. Although several members of the endocytic pathway were recently implicated in spindle organization, it is unclear whether Rab5 has any role during mitosis. Here, we describe that Rab5 is required for proper chromosome alignment during Drosophila mitoses. We also found that Rab5 associated in vivo with nuclear Lamin and mushroom body defect (Mud), the Drosophila counterpart of nuclear mitotic apparatus protein (NuMA). Consistent with this finding, Rab5 was required for the disassembly of the nuclear envelope at mitotic entry and the accumulation of Mud at the spindle poles. Furthermore, Mud depletion caused chromosome misalignment defects that resembled the defects of Rab5 RNAi cells, and double-knockdown experiments indicated that the two proteins function in a linear pathway. Our results indicate a role for Rab5 in mitosis and reinforce the emerging view of the contributions made by cell membrane dynamics to spindle function.

  16. Histone H3 lysine 9 acetylation pattern suggests that X and B chromosomes are silenced during entire male meiosis in a grasshopper.

    Science.gov (United States)

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

    2007-01-01

    The facultative heterochromatic X chromosome in leptotene spermatocytes of the grasshopper Eyprepocnemis plorans showed marked hypoacetylation for lysine 9 in the H3 histone (H3-K9) with no sign of histone H2AX phosphorylation. Since H3-K9 hypoacetylation precedes the meiotic appearance of phosphorylated H2AX (gamma-H2AX), which marks the beginning of recombinational DNA double-strand breaks (DSBs), it seems that meiotic sex-chromosome inactivation (MSCI) in this grasshopper occurs prior to the beginning of recombination and hence synapsis (which in this species begins later than recombination). In addition, all constitutively heterochromatic chromosome regions harbouring a 180-bp tandem-repeat DNA and rDNA (B chromosomes and pericentromeric regions of A chromosomes) were H3-K9 hypoacetylated at early leptotene even though they will synapse at subsequent stages. This also suggests that meiotic silencing in this grasshopper might be independent of synapsis. The H3-K9 hypoacetylated state of facultative and constitutive heterochromatin persisted during subsequent meiotic stages and was even apparent in round spermatids. Finally, the fact that B chromosomes are differentially hypoacetylated in testis and embryo interphase cells suggests that they might be silenced early in development and remain this way for most (or all) life-cycle stages. Copyright (c) 2007 S. Karger AG, Basel.

  17. The Consequences of Chromosome Segregation Errors in Mitosis and Meiosis

    Directory of Open Access Journals (Sweden)

    Tamara Potapova

    2017-02-01

    Full Text Available Mistakes during cell division frequently generate changes in chromosome content, producing aneuploid or polyploid progeny cells. Polyploid cells may then undergo abnormal division to generate aneuploid cells. Chromosome segregation errors may also involve fragments of whole chromosomes. A major consequence of segregation defects is change in the relative dosage of products from genes located on the missegregated chromosomes. Abnormal expression of transcriptional regulators can also impact genes on the properly segregated chromosomes. The consequences of these perturbations in gene expression depend on the specific chromosomes affected and on the interplay of the aneuploid phenotype with the environment. Most often, these novel chromosome distributions are detrimental to the health and survival of the organism. However, in a changed environment, alterations in gene copy number may generate a more highly adapted phenotype. Chromosome segregation errors also have important implications in human health. They may promote drug resistance in pathogenic microorganisms. In cancer cells, they are a source for genetic and phenotypic variability that may select for populations with increased malignance and resistance to therapy. Lastly, chromosome segregation errors during gamete formation in meiosis are a primary cause of human birth defects and infertility. This review describes the consequences of mitotic and meiotic errors focusing on novel concepts and human health.

  18. The Consequences of Chromosome Segregation Errors in Mitosis and Meiosis.

    Science.gov (United States)

    Potapova, Tamara; Gorbsky, Gary J

    2017-02-08

    Mistakes during cell division frequently generate changes in chromosome content, producing aneuploid or polyploid progeny cells. Polyploid cells may then undergo abnormal division to generate aneuploid cells. Chromosome segregation errors may also involve fragments of whole chromosomes. A major consequence of segregation defects is change in the relative dosage of products from genes located on the missegregated chromosomes. Abnormal expression of transcriptional regulators can also impact genes on the properly segregated chromosomes. The consequences of these perturbations in gene expression depend on the specific chromosomes affected and on the interplay of the aneuploid phenotype with the environment. Most often, these novel chromosome distributions are detrimental to the health and survival of the organism. However, in a changed environment, alterations in gene copy number may generate a more highly adapted phenotype. Chromosome segregation errors also have important implications in human health. They may promote drug resistance in pathogenic microorganisms. In cancer cells, they are a source for genetic and phenotypic variability that may select for populations with increased malignance and resistance to therapy. Lastly, chromosome segregation errors during gamete formation in meiosis are a primary cause of human birth defects and infertility. This review describes the consequences of mitotic and meiotic errors focusing on novel concepts and human health.

  19. Molecular studies of translocations and trisomy involving chromosome 13

    Energy Technology Data Exchange (ETDEWEB)

    Robinson, W.P.; Bernasconi, F.; Dutly, F.; Schinzel, A.A. [Univ. of British Columbia, Vancouver (Canada)] [and others

    1996-01-11

    Twenty-four cases of trisomy 13 and one case with disomy 13, but a de novo dic(13,13)(p12p12) chromosome, were examined with molecular markers to determine the origin of the extra (or rearranged) chromosome. Twenty-one of 23 informative patients were consistent with a maternal origin of the extra chromosome. Lack of a third allele at any locus in both paternal origin cases indicate a somatic duplication of the paternal chromosome occurred. Five cases had translocation trisomy. The patient with a paternal rob(13q14q) had a maternal meiotic origin of the trisomy; thus, the paternal inheritance of the translocation chromosome was purely coincidental. Since there is not a significantly increased risk for unbalanced offspring of a t(13q14q) carrier and most trisomies are maternal in origin, this result should not be surprising; however, it illustrates that one cannot infer the origin of translocation trisomy based on parental origin of the translocation. Lack of a third allele at any locus in one of the three t(13q13q) cases indicates that it was most likely an isochromosome of postmeiotic origin, whereas the other two cases showed evidence of recombination. One balanced (nontrisomic) case with a nonmosaic 45, -13, -13, +t(13;13) karyotype was also investigated and was determined to be a somatic Robertsonian translocation between the maternal and paternal homologues, as has been found for all balanced homologous Robertsonian translocations so far investigated. Thus, it is also incorrect to assume in de novo translocation cases that the two involved chromosomes are even from the same parent. Despite a maternal origin of the trisomy, we cannot therefore infer anything about the parental origin of the chromosomes 13 and 14 involved in the translocation in the de novo t(13q14q) case nor for the two t(13;13) chromosomes showing a meiotic origin of the trisomy. 30 refs., 1 fig., 2 tabs.

  20. A Rare De novo Complex Chromosomal Rearrangement (CCR) Involving Four Chromosomes in An Oligo-asthenosperm Infertile Man.

    Science.gov (United States)

    Asia, Saba; Vaziri Nasab, Hamed; Sabbaghian, Marjan; Kalantari, Hamid; Zari Moradi, Shabnam; Gourabi, Hamid; Mohseni Meybodi, Anahita

    2014-01-01

    Complex chromosomal rearrangements (CCRs) are rare events involving more than two chromosomes and over two breakpoints. They are usually associated with infertility or sub fertility in male carriers. Here we report a novel case of a CCR in a 30-year-old oligoasthenosperm man with a history of varicocelectomy, normal testes size and normal endocrinology profile referred for chromosome analysis to the Genetics unit of Royan Reproductive Biomedicine Research Center. Chromosomal analysis was performed using peripheral blood lymphocyte cultures and analyzed by GTG banding. Additional tests such as C-banding and multicolor fluorescence in situ hybridization (FISH) procedure for each of the involved chromosomes were performed to determine the patterns of the segregations. Y chromosome microdeletions in the azoospermia factor (AZF) region were analyzed with multiplex polymerase chain reaction. To identify the history and origin of this CCR, all the family members were analyzed. No micro deletion in Y chromosome was detected. The same de novo reciprocal exchange was also found in his monozygous twin brother. The other siblings and parents were normal. CCRs are associated with male infertility as a result of spermatogenic disruption due to complex meiotic configurations and the production of chromosomally abnormal sperms. These chromosomal rearrangements might have an influence on decreasing the number of sperms.

  1. Inhibition of the Binding between RGS2 and β-Tubulin Interferes with Spindle Formation and Chromosome Segregation during Mouse Oocyte Maturation In Vitro.

    Directory of Open Access Journals (Sweden)

    Man-Xi Jiang

    Full Text Available RGS2 is a negative regulator of G protein signaling that contains a GTPase-activating domain and a β-tubulin binding region. This study aimed to determine the localization and function of RGS2 during mouse oocyte maturation in vitro. Immunofluorescent staining revealed that RGS2 was widely expressed in the cytoplasm with a greater abundance on both meiotic spindles and first/second polar bodies from the fully-grown germinal vesicle (GV stage to the MII stages. Co-expression of RGS2 and β-tubulin could also be detected in the spindle and polar body of mouse oocytes at the MI, AI, and MII stages. Inhibition of the binding site between RGS2 and β-tubulin was accomplished by injecting anti-RGS2 antibody into GV-stage oocytes, which could result in oocytes arrest at the MI or AI stage during in vitro maturation, but it did not affect germinal vesicle breakdown. Moreover, injecting anti-RGS2 antibody into oocytes resulted in a significant reduction in the rate of first polar body extrusion and abnormal spindle formation. Additionally, levels of phosphorylated MEK1/2 were significantly reduced in anti-RGS2 antibody injected oocytes compared with control oocytes. These findings suggest that RGS2 might play a critical role in mouse oocyte meiotic maturation by affecting β-tubulin polymerization and chromosome segregation.

  2. Chromosomal aberration

    International Nuclear Information System (INIS)

    Ishii, Yutaka

    1988-01-01

    Chromosomal aberrations are classified into two types, chromosome-type and chromatid-type. Chromosom-type aberrations include terminal deletion, dicentric, ring and interstitial deletion, and chromatid-type aberrations include achromatic lesion, chromatid deletion, isochromatid deletion and chromatid exchange. Clastogens which induce chromosomal aberration are divided into ''S-dependent'' agents and ''S-independent''. It might mean whether they can induce double strand breaks independent of the S phase or not. Double strand breaks may be the ultimate lesions to induce chromosomal aberrations. Caffeine added even in the G 2 phase appeared to modify the frequency of chromatid aberrations induced by X-rays and mitomycin C. Those might suggest that the G 2 phase involves in the chromatid aberration formation. The double strand breaks might be repaired by ''G 2 repair system'', the error of which might yield breakage types of chromatid aberrations and the by-pass of which might yield chromatid exchanges. Chromosome-type aberrations might be formed in the G 1 phase. (author)

  3. A noncoding RNA containing a SINE-B1 motif associates with meiotic metaphase chromatin and has an indispensable function during spermatogenesis.

    Directory of Open Access Journals (Sweden)

    Ryusuke Nakajima

    Full Text Available A search for early response genes that are activated following germ cell induction from mouse embryonic stem cells in vitro led us to the isolation of a long noncoding RNA that contains a SINE (short interspersed element-B1F motif that was named R53. In situ hybridization and northern blot analyses revealed that the R53 subfragment RNA bears a B1F motif, is processed from the primary transcript, is expressed in adult testis and is predominantly localized in meiotic metaphase chromatin during spermatogenesis. Recent studies of chromosome-associated RNAs have explored novel functions of noncoding RNAs. Specifically, chromosome-bound noncoding RNAs function not only as structural components of chromosome but also as scaffolds that recruit epigenetic modulators for transcriptional regulation, and they are dynamically rearranged during the cell cycle. However, few studies have explored meiotic chromatin; thus, R53 RNA appears to be the first long noncoding RNA to be tightly associated with the metaphase chromatin during spermatogenesis. Furthermore, R53 knockdown using a lentivirus-mediated RNAi injected into mouse testis and organ culture of the fragments revealed a remarkable reduction in postmeiotic cells and irregular up-regulation of several postmeiotic genes, which suggests the possibility that the SINE-B1-derived noncoding RNA R53 plays an indispensable role in the transcriptional regulation of key spermatogenesis genes.

  4. Inversions of chromosome arms 4AL and 2BS in wheat invert the patterns of chiasma distribution

    Czech Academy of Sciences Publication Activity Database

    Lukaszewski, A.J.; Kopecký, David; Linc, G.

    2012-01-01

    Roč. 121, č. 2 (2012), s. 201-208 ISSN 0009-5915 Grant - others:GA MŠk(CZ) ED0007/01/01 Program:ED Institutional research plan: CEZ:AV0Z50380511 Keywords : PHYSICAL DISTRIBUTION * MEIOTIC PROPHASE * RYE CHROMOSOME Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.340, year: 2012

  5. Methods for Cytogenetic Chromosome Barcoding and Chromosome Painting in Brachypodium distachyon and Its Relative Species.

    Science.gov (United States)

    Idziak-Helmcke, Dominika; Betekhtin, Alexander

    2018-01-01

    Brachypodium distachyon provides a particularly appealing object for molecular cytogenetic analysis due to its compact genome and low repetitive DNA content, as well as low (x = 5) basic number of chromosomes easily identifiable on the basis of their morphometric features. Some of these features, such as genome compactness, are shared by the other members of the genus, thus making them amenable for comparative cytogenetic mapping. Cytogenetic infrastructure established for B. distachyon was initially based on fluorescence in situ hybridization with various tandemly repeated sequences as probes. The molecular cytogenetic studies advanced greatly with the development of B. distachyon large DNA insert genomic libraries. These resources coupled with the access to the fully sequenced genome of B. distachyon enabled chromosome painting in monocots for the first time. This pioneering work was subsequently extended to other Brachypodium species, allowing insight into grass karyotype evolution. In this protocol we describe the methods of making somatic and meiotic chromosome preparations, probe labeling, FISH with BAC clones, a strategy for chromosome barcoding and chromosome painting in B. distachyon, and comparative chromosome painting in the other Brachypodium species.

  6. Somatic pairing, endomitosis and chromosome aberrations in snakes (Viperidae and Colubridae

    Directory of Open Access Journals (Sweden)

    Beçak Maria Luiza

    2003-01-01

    Full Text Available The positioning of macrochromosomes of Bothrops jararaca and Bothrops insularis (Viperidae was studied in undistorted radial metaphases of uncultured cells (spermatogonia and oogonia not subjected to spindle inhibitors. Colchicinized metaphases from uncultured (spleen and intestine and cultured tissues (blood were also analyzed. We report two antagonic non-random chromosome arrangements in untreated premeiotic cells: the parallel configuration with homologue chromosomes associated side by side in the metaphase plate and the antiparallel configuration having homologue chromosomes with antipolar distribution in the metaphase ring. The antiparallel aspect also appeared in colchicinized cells. The spatial chromosome arrangement in both configurations is groupal size-dependent and maintained through meiosis. We also describe, in untreated gonia cells, endomitosis followed by reductional mitosis which restores the diploid number. In B. jararaca males we observed that some gonad regions present changes in the meiotic mechanism. In this case, endoreduplicated cells segregate the diplochromosomes to opposite poles forming directly endoreduplicated second metaphases of meiosis with the suppression of first meiosis. By a successive division, these cells form nuclei with one set of chromosomes. Chromosome doubling in oogonia is known in hybrid species and in parthenogenetic salamanders and lizards. This species also presented chromosome rearrangements leading to aneuploidies in mitosis and meiosis. It is suggested that somatic pairing, endomitosis, meiotic alterations, and chromosomal aberrations can be correlated processes. Similar aspects of nuclei configurations, endomitosis and reductional mitosis were found in other Viperidae and Colubridae species.

  7. Chromosome 21-derived MicroRNAs Provide an Etiological Basis for Aberrant Protein Expression in Human Down Syndrome Brains*

    OpenAIRE

    Kuhn, Donald E.; Nuovo, Gerard J.; Terry, Alvin V.; Martin, Mickey M.; Malana, Geraldine E.; Sansom, Sarah E.; Pleister, Adam P.; Beck, Wayne D.; Head, Elizabeth; Feldman, David S.; Elton, Terry S.

    2009-01-01

    Down syndrome (DS), or Trisomy 21, is the most common genetic cause of cognitive impairment and congenital heart defects in the human population. Bioinformatic annotation has established that human chromosome 21 (Hsa21) harbors five microRNA (miRNAs) genes: miR-99a, let-7c, miR-125b-2, miR-155, and miR-802. Our laboratory recently demonstrated that Hsa21-derived miRNAs are overexpressed in DS brain and heart specimens. The aim of this study was to identify important Hsa21-derived miRNA/mRNA t...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1978-01-01

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

  9. Meiotic origin of trisomy in confined placental mosaicism is correlated with presence of fetal uniparental disomy, high levels of trisomy in trophoblast, and increased risk of fetal intrauterine growth restriction.

    Science.gov (United States)

    Robinson, W P; Barrett, I J; Bernard, L; Telenius, A; Bernasconi, F; Wilson, R D; Best, R G; Howard-Peebles, P N; Langlois, S; Kalousek, D K

    1997-04-01

    Molecular studies were performed on 101 cases of confined placental mosaicism (CPM) involving autosomal trisomy. The origin of the trisomic cell line was determined in 54 cases (from 51 pregnancies), 47 of which were also analyzed for the presence of uniparental disomy (UPD) in the disomic cell line. An additional 47 cases were analyzed for parental origin in the disomic cell line only. A somatic (postmeiotic) origin of the trisomy was observed in 22 cases and included the majority of cases with CPM for trisomy 2, 7, 8, 10, and 12. Most cases of CPM involving trisomy 9, 16, and 22 were determined to be meiotic. Fetal maternal UPD was found in 17 of 94 informative CPM cases, involving trisomy 2 (1 case), 7 (1 case), 16 (13 cases), and 22 (2 cases). The placental trisomy was of meiotic origin in all 17 cases associated with fetal UPD (P = .00005). A meiotic origin also correlated with the levels of trisomy in cultured chorionic villi samples (CVS) (P = .0002) and trophoblast (P = .00005). Abnormal pregnancy outcome (usually IUGR) correlated with meiotic origin (P = .0003), the presence of fetal UPD (P = 4 x 10(-7)), and the level of trisomy in trophoblast (P = 3 x 10(-7)) but not with the level of trisomy in CVS or term chorion. The good fit of somatic errors with the expected results could have been observed only if few true meiotic errors were misclassified by these methods as a somatic error. These data indicate that molecular determination of origin is a useful predictor of pregnancy outcome, whereas the level of trisomy observed in cultured CVS is not. In addition, UPD for some chromosomes may affect prenatal, but not postnatal, development, possibly indicating that imprinting effects for these chromosomes are confined to placental tissues.

  10. Insights into evolution of multicellular fungi from the assembled chromosomes of the mushroom Coprinopsis cinerea (Coprinus cinereus)

    OpenAIRE

    Stajich, Jason E.; Wilke, Sarah K.; Ahrén, Dag; Au, Chun Hang; Birren, Bruce W.; Borodovsky, Mark; Burns, Claire; Canbäck, Björn; Casselton, Lorna A.; Cheng, C.K.; Deng, Jixin; Dietrich, Fred S.; Fargo, David C.; Farman, Mark L.; Gathman, Allen C.

    2010-01-01

    The mushroom Coprinopsis cinerea is a classic experimental model for multicellular development in fungi because it grows on defined media, completes its life cycle in 2 weeks, produces some 108 synchronized meiocytes, and can be manipulated at all stages in development by mutation and transformation. The 37-megabase genome of C. cinerea was sequenced and assembled into 13 chromosomes. Meiotic recombination rates vary greatly along the chromosomes, and retrotransposons are absent in large regi...

  11. Meiotic behavior of economically important plant species: the relationship between fertility and male sterility

    Directory of Open Access Journals (Sweden)

    Maria Suely Pagliarini

    2000-12-01

    Full Text Available Meiosis is an event of high evolutionary stability which culminates in a reduction of chromosome number. The normal and harmonious course of meiosis ensures gamete viability. The cytologic events of gametogenesis are controlled by a large number of genes that act from premeiotic to postmeiotic mitosis. Mutations in these genes cause anomalies that may impair fertility, and many abnormalities affecting plant fertility or causing total male sterility have been detected during the evaluation of meiotic behavior in some species. Some of these abnormalities have been frequently described in the literature, while others have not been previously reported. The most frequent abnormalities found in the species analyzed were irregular chromosome segregation, cytomixis, chromosome stickiness, mixoploidy, chromosome fragmentation, syncyte formation, abnormal spindles, and failure of cytokinesis. Uncommon abnormalities, such as chromosome elimination during microsporogenesis, were found in one species. Original meiotic mutations affecting different steps of meiosis were also observed in these species, especially in maize, Paspalum and soybean. Some mutants present characteristics that may be exploited successfully in breeding programs because they cause total male sterility.A meiose é um evento de alta estabilidade evolucionária que culmina na redução do número de cromossomos. O curso normal e harmonioso da meiose garante a viabilidade gamética. Os eventos citológicos da gametogênese são controlados por um grande número de genes que atuam desde as mitoses pré-meióticas até as pós-meióticas. Mutações nestes genes causam anomalias que podem afetar a fertilidade. Durante a avaliação do comportamento meiótico em algumas espécies de plantas, muitas anormalidades que afetaram a fertilidade ou causaram total macho-esterilidade foram detectadas. Algumas das anormalidades encontradas já eram descritas na literatura, enquanto outras eram

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

    Science.gov (United States)

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

    2014-01-01

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

  13. Origin of triploid Arachis pintoi (Leguminosae) by autopolyploidy evidenced by FISH and meiotic behaviour.

    Science.gov (United States)

    Lavia, Graciela Inés; Ortiz, Alejandra Marcela; Robledo, Germán; Fernández, Aveliano; Seijo, Guillermo

    2011-07-01

    Polyploidy is a dominant feature of flowering-plant genomes, including those of many important crop species. Arachis is a largely diploid genus with just four polyploid species. Two of them are economically important: the cultivated peanut and A. glabrata, a tropical forage crop. Even though it is usually accepted that polyploids within papilionoid legumes have arisen via hybridization and further chromosome doubling, it has been recently suggested that peanut arose through bilateral sexual polyploidization. In this paper, the polyploid nature of the recent, spontaneously originated triploid cytotype of the tropical lucerne, A. pintoi, was analysed, and thereby the mechanism by which polyploids may arise in the genus. Chromosome morphology of 2x and 3x A. pintoi was determined by the Feulgeńs technique and the rDNA sites were mapped by FISH. To investigate whether polyploidization occurred by means of unreduced gametes, a detailed analysis of the microsporogenesis and pollen grains was made. The 2x and 3x plants presented 9m + 1sm and a satellited chromosome type 2 in each haploid genome. Physical mapping revealed a cluster of 18S-26S rDNA, proximally located on chromosome 6, and two 5S rDNA loci on chromosomes 3 and 5. Diploid plants presented 10II in meiosis while trivalents were observed in all triploids, with a maximum of 10III by cell. Diploid A. pintoi produced normal tetrads, but also triads, dyads and monads. Two types of pollen grains were detected: (1) normal-sized with a prolate shape and (2) large ones with a tetrahedral morphology. Karyotype and meiotic analysis demonstrate that the 3x clone of A. pintoi arose by autopolyploidy. The occurrence of unreduced gametes strongly supports unilateral sexual polyploidization as the most probable mechanism that could have led to the origin of the triploid cytotype. This mechanism of polyploidization would probably be one of the most important mechanisms involved in the origin of economically important species

  14. Alteration/Deficiency in Activation 3 (ADA3) Protein, a Cell Cycle Regulator, Associates with the Centromere through CENP-B and Regulates Chromosome Segregation*

    Science.gov (United States)

    Mohibi, Shakur; Srivastava, Shashank; Wang-France, Jun; Mirza, Sameer; Zhao, Xiangshan; Band, Hamid; Band, Vimla

    2015-01-01

    ADA3 (alteration/deficiency in activation 3) is a conserved component of several transcriptional co-activator and histone acetyltransferase (HAT) complexes. Recently, we generated Ada3 knock-out mice and demonstrated that deletion of Ada3 leads to early embryonic lethality. The use of Ada3FL/FL mouse embryonic fibroblasts with deletion of Ada3 using adenovirus Cre showed a critical role of ADA3 in cell cycle progression through mitosis. Here, we demonstrate an association of ADA3 with the higher order repeat region of the α-satellite region on human X chromosome centromeres that is consistent with its role in mitosis. Given the role of centromere proteins (CENPs) in mitosis, we next analyzed whether ADA3 associates with the centromere through CENPs. Both an in vivo proximity ligation assay and immunofluorescence studies confirmed the association of ADA3 with CENP-B protein, a highly conserved centromeric protein that binds to the 17-bp DNA sequences on α-satellite DNA. Deletional analysis showed that ADA3 directly associates with CENP-B through its N terminus, and a CENP-B binding-deficient mutant of ADA3 was incompetent in cell proliferation rescue. Notably, knockdown of ADA3 decreased binding of CENP-B onto the centromeres, suggesting that ADA3 is required for the loading of CENP-B onto the centromeres. Finally, we show that deletion of Ada3 from Ada3FL/FL mouse embryonic fibroblasts exhibited various chromosome segregation defects. Taken together, we demonstrate a novel ADA3 interaction with CENP-B-centromere that may account for its previously known function in mitosis. This study, together with its known function in maintaining genomic stability and its mislocalization in cancers, suggests an important role of ADA3 in mitosis. PMID:26429915

  15. Alteration/Deficiency in Activation 3 (ADA3) Protein, a Cell Cycle Regulator, Associates with the Centromere through CENP-B and Regulates Chromosome Segregation.

    Science.gov (United States)

    Mohibi, Shakur; Srivastava, Shashank; Wang-France, Jun; Mirza, Sameer; Zhao, Xiangshan; Band, Hamid; Band, Vimla

    2015-11-20

    ADA3 (alteration/deficiency in activation 3) is a conserved component of several transcriptional co-activator and histone acetyltransferase (HAT) complexes. Recently, we generated Ada3 knock-out mice and demonstrated that deletion of Ada3 leads to early embryonic lethality. The use of Ada3(FL/FL) mouse embryonic fibroblasts with deletion of Ada3 using adenovirus Cre showed a critical role of ADA3 in cell cycle progression through mitosis. Here, we demonstrate an association of ADA3 with the higher order repeat region of the α-satellite region on human X chromosome centromeres that is consistent with its role in mitosis. Given the role of centromere proteins (CENPs) in mitosis, we next analyzed whether ADA3 associates with the centromere through CENPs. Both an in vivo proximity ligation assay and immunofluorescence studies confirmed the association of ADA3 with CENP-B protein, a highly conserved centromeric protein that binds to the 17-bp DNA sequences on α-satellite DNA. Deletional analysis showed that ADA3 directly associates with CENP-B through its N terminus, and a CENP-B binding-deficient mutant of ADA3 was incompetent in cell proliferation rescue. Notably, knockdown of ADA3 decreased binding of CENP-B onto the centromeres, suggesting that ADA3 is required for the loading of CENP-B onto the centromeres. Finally, we show that deletion of Ada3 from Ada3(FL/FL) mouse embryonic fibroblasts exhibited various chromosome segregation defects. Taken together, we demonstrate a novel ADA3 interaction with CENP-B-centromere that may account for its previously known function in mitosis. This study, together with its known function in maintaining genomic stability and its mislocalization in cancers, suggests an important role of ADA3 in mitosis. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

  16. The C-terminal domain of the bacterial SSB protein acts as a DNA maintenance hub at active chromosome replication forks.

    Directory of Open Access Journals (Sweden)

    Audrey Costes

    2010-12-01

    Full Text Available We have investigated in vivo the role of the carboxy-terminal domain of the Bacillus subtilis Single-Stranded DNA Binding protein (SSB(Cter as a recruitment platform at active chromosomal forks for many proteins of the genome maintenance machineries. We probed this SSB(Cter interactome using GFP fusions and by Tap-tag and biochemical analysis. It includes at least 12 proteins. The interactome was previously shown to include PriA, RecG, and RecQ and extended in this study by addition of DnaE, SbcC, RarA, RecJ, RecO, XseA, Ung, YpbB, and YrrC. Targeting of YpbB to active forks appears to depend on RecS, a RecQ paralogue, with which it forms a stable complex. Most of these SSB partners are conserved in bacteria, while others, such as the essential DNA polymerase DnaE, YrrC, and the YpbB/RecS complex, appear to be specific to B. subtilis. SSB(Cter deletion has a moderate impact on B. subtilis cell growth. However, it markedly affects the efficiency of repair of damaged genomic DNA and arrested replication forks. ssbΔCter mutant cells appear deficient in RecA loading on ssDNA, explaining their inefficiency in triggering the SOS response upon exposure to genotoxic agents. Together, our findings show that the bacterial SSB(Cter acts as a DNA maintenance hub at active chromosomal forks that secures their propagation along the genome.

  17. Meiotic gene conversion mutants in Saccharomyces cerevisiae. I. Isolation and characterization of PMS1-1 and PMS1-2

    International Nuclear Information System (INIS)

    Williamson, M.S.; Game, J.C.; Fogel, S.

    1985-01-01

    The PMS1 mutants, isolated on the basis of sharply elevated meiotic prototroph frequencies for two closely linked HIS4 alleles, display pleiotropic phenotypes in meiotic and mitotic cells. Two isolates carrying recessive mutations in PMS1 were characterized. They identify a function required to maintain low postmeiotic segregation (PMS) frequencies at many heterozygous sites. In addition, they are mitotic mutators. In mutant diploids, spore viability is reduced, and among survivors, gene conversion and postmeiotic segregation frequencies are increased, but reciprocal exchange frequencies are not affected. The conversion event pattern is also dramatically changed in multiply marked regions in PMS1 homozygotes. The PMS1 locus maps near MET4 on chromosome XIV. The PMS1 gene may identify an excision-resynthesis long patch mismatch correction function or a function that facilitates correction tract elongation. The PMS1 gene product may also play an important role in spontaneous mitotic mutation avoidance and correction of mismatches in heteroduplex DNA formed during spontaneous and UV-induced mitotic recombination. Based on meiotic recombination models emphasizing mismatch correction in heteroduplex DNA intermediates, this interpretation is favored, but alternative interpretations involving longer recombination intermediates in the mutants are also considered

  18. Expression of Six Proteins Causes Reprogramming of Porcine Fibroblasts Into Induced Pluripotent Stem Cells With Both Active X Chromosomes.

    Science.gov (United States)

    Fukuda, Tomokazu; Tani, Tetsuya; Haraguchi, Seiki; Donai, Kenichiro; Nakajima, Nobuyoshi; Uenishi, Hirohide; Eitsuka, Takahiro; Miyagawa, Makoto; Song, Sanghoun; Onuma, Manabu; Hoshino, Yumi; Sato, Eimei; Honda, Arata

    2017-03-01

    In this study, we created porcine-induced pluripotent stem (iPS) cells with the expression of six reprogramming factors (Oct3/4, Klf4, Sox2, c-Myc, Lin28, and Nanog). The resulting cells showed growth dependent on LIF (leukemia inhibitory factor) and expression of multiple stem cell markers. Furthermore, the iPS cells caused teratoma formation with three layers of differentiation and had both active X chromosomes (XaXa). Our iPS cells satisfied the both of important characteristics of stem cells: teratoma formation and activation of both X chromosomes. Injection of these iPS cells into morula stage embryos showed that these cells participate in the early stage of porcine embryogenesis. Furthermore, the RNA-Seq analysis detected that expression levels of endogenous pluripotent related genes, NANOG, SOX2, ZFP42, OCT3/4, ESRRB, and ERAS were much higher in iPS with six factors than that with four reprogramming factors. We can conclude that the expression of six reprogramming factors enables the creation of porcine iPS cells, which is partially close to naive iPS state. J. Cell. Biochem. 118: 537-553, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  19. A system for the detection of chromosomal rearrangements using Sordaria macrospora

    International Nuclear Information System (INIS)

    Arnaise, S.; Leblon, G.; Lares, L.

    1984-01-01

    A system is described for the detection and diagnosis of induced chromosomal rearrangement using Sordaria macrospora. The system uses the property of the rearrangement to produce defective white ascospores as meiotic progeny from heterozygous crosses. Two reconstruction experiments have shown that this system is able to give reliable quantitative measures of rearrangement frequencies. Evidence for a photoreactivation process was obtained, suggesting that pyrimidine dimers may well be an important lesion in UV-induced chromosomal rearrangement. No evidence of induction of chromosomal rearrangement was obtained in experiments with the powerful chemical mutagen N-methyl-N'-nitro-N-nitrosoguanidine. (orig.)

  20. Meiotic development initiation in the fungus Podospora anserina requires the peroxisome receptor export machinery.

    Science.gov (United States)

    Suaste-Olmos, Fernando; Zirión-Martínez, Claudia; Takano-Rojas, Harumi; Peraza-Reyes, Leonardo

    2018-04-01

    Peroxisomes are versatile organelles essential for diverse developmental processes. One such process is the meiotic development of Podospora anserina. In this fungus, absence of the docking peroxin PEX13, the RING-finger complex peroxins, or the PTS2 co-receptor PEX20 blocks sexual development before meiocyte formation. However, this defect is not seen in the absence of the receptors PEX5 and PEX7, or of the docking peroxins PEX14 and PEX14/17. Here we describe the function of the remaining uncharacterized P. anserina peroxins predictably involved in peroxisome matrix protein import. We show that PEX8, as well as the peroxins potentially mediating receptor monoubiquitination (PEX4 and PEX22) and membrane dislocation (PEX1, PEX6 and PEX26) are indeed implicated in peroxisome matrix protein import in this fungus. However, we observed that elimination of PEX4 and PEX22 affects to different extent the import of distinct PEX5 cargoes, suggesting differential ubiquitination-complex requirements for the import of distinct proteins. In addition, we found that elimination of PEX1, PEX6 or PEX26 results in loss of peroxisomes, suggesting that these peroxins restrain peroxisome removal in specific physiological conditions. Finally, we demonstrate that all analyzed peroxins are required for meiocyte formation, and that PEX20 function in this process depends on its potential monoubiquitination target cysteine. Our results suggest that meiotic induction relies on a peroxisome import pathway, which is not dependent on PEX5 or PEX7 but that is driven by an additional cycling receptor. These findings uncover a collection of peroxins implicated in modulating peroxisome activity to facilitate a critical developmental cell fate decision. Copyright © 2018 Elsevier B.V. All rights reserved.

  1. Release from Xenopus oocyte prophase I meiotic arrest is independent of a decrease in cAMP levels or PKA activity.

    Science.gov (United States)

    Nader, Nancy; Courjaret, Raphael; Dib, Maya; Kulkarni, Rashmi P; Machaca, Khaled

    2016-06-01

    Vertebrate oocytes arrest at prophase of meiosis I as a result of high levels of cyclic adenosine monophosphate (cAMP) and protein kinase A (PKA) activity. In Xenopus, progesterone is believed to release meiotic arrest by inhibiting adenylate cyclase, lowering cAMP levels and repressing PKA. However, the exact timing and extent of the cAMP decrease is unclear, with conflicting reports in the literature. Using various in vivo reporters for cAMP and PKA at the single-cell level in real time, we fail to detect any significant changes in cAMP or PKA in response to progesterone. More interestingly, there was no correlation between the levels of PKA inhibition and the release of meiotic arrest. Furthermore, we devised conditions whereby meiotic arrest could be released in the presence of sustained high levels of cAMP. Consistently, lowering endogenous cAMP levels by >65% for prolonged time periods failed to induce spontaneous maturation. These results argue that the release of oocyte meiotic arrest in Xenopus is independent of a reduction in either cAMP levels or PKA activity, but rather proceeds through a parallel cAMP/PKA-independent pathway. © 2016. Published by The Company of Biologists Ltd.

  2. Pir51, a Rad51-interacting protein with high expression in aggressive lymphoma, controls mitomycin C sensitivity and prevents chromosomal breaks

    Energy Technology Data Exchange (ETDEWEB)

    Henson, Sarah E. [Department of Microbiology, Immunology, and Molecular Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095 (United States); Tsai, Shih-Chang [Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095 (United States); Malone, Cindy Sue [Department of Biology, California State University Northridge, Northridge, CA 91330 (United States); Soghomonian, Shahe V. [Department of Microbiology, Immunology, and Molecular Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095 (United States); Ouyang, Yan [Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095 (United States); Wall, Randolph [Department of Microbiology, Immunology, and Molecular Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095 (United States); Molecular Biology Institute and Jonsson Comprehensive Cancer Center, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095 (United States); Marahrens, York [Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095 (United States) and Molecular Biology Institute and Jonsson Comprehensive Cancer Center, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095 (United States)]. E-mail: YMarahrens@mednet.ucla.edu; Teitell, Michael A. [Molecular Biology Institute and Jonsson Comprehensive Cancer Center, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095 (United States) and Department of Pathology and Laboratory Medicine, California NanoSystems Institute, and Institute for Stem Cell Biology and Medicine, University of California Los Angeles, Los Angeles, CA 90095 (United States)]. E-mail: mteitell@ucla.edu

    2006-10-10

    Pir51, a protein of unknown function that interacts with Rad51, was identified in a screen for genes that were highly expressed in aggressive mantle cell lymphoma (MCL) versus indolent small lymphocytic lymphoma (SLL) patient samples. We show that Pir51 is a nuclear protein expressed in a variety of cell types and that its expression is regulated during the cell cycle in a pattern nearly identical to Rad51. Also similar to Rad51, Pir51 levels did not change in response to a variety of DNA damaging agents. siRNA depletion of Pir51 did not reduce homologous recombination repair (HRR), but sensitized cells to mitomycin C (MMC)-induced DNA crosslinking and resulted in elevated levels of double-strand breaks (DSBs) in metaphase chromosome spreads and reduced colony formation. Therefore, Pir51 maintains genomic integrity and potentially connects the early response to DNA crosslinks, orchestrated by the ATR kinase and Fanconi Anemia (FA) proteins, to later stages of Rad51-dependent repair. Our results provide the first example of a Rad51-binding protein that influences DNA crosslink repair without affecting homologous recombination repair.

  3. Comportamiento meiótico de diferentes especies de lulo, Solanum sp Meiotic behavior of lulo species, Solanum sp

    Directory of Open Access Journals (Sweden)

    Nancy Maricela Pareja Ordóñez

    2010-10-01

    good parental for use in crossbreeding programs. The three species have the same number of chromosomes (2n = 2x = 24. The frequency of abnormalities during the meiotic process was lower for S. hirtum, and high for S. quitoense, however, the pollen viability was of great magnitude (91.2-97.3%.

  4. Stage-specific damage to synaptonemal complexes and metaphase chromosomes induced by X rays in male mouse germ cells

    International Nuclear Information System (INIS)

    Backer, L.C.; Sontag, M.R.; Allen, J.W.

    1991-01-01

    Synaptonemal complexes (SCs) reveal mutagen-induced effects in germ cell meiotic chromosomes. The study was aimed at characterizing relationships between SC and metaphase I chromosome damage following radiation exposure at various stages of spermatogenesis. Male mice were irradiated with doses of 0, 2, or 4 Gy, and spermatocytes were harvested at times consistent with earlier exposures as spermatogonial stem cells, preleptotene cells (premeiotic DNA synthesis), or meiotic prophase cells. After stem-cell exposure, twice as many rearrangements were observed in SCs as in metaphase I chromosomes. Irradiation during premeiotic DNA synthesis resulted in dose-related increases in SC breakage and rearrangements (including novel forms) and in metaphase chromosomal aberrations. Following prophase exposure, various types and levels of SC and metaphase damage were observed. Irradiation of zygotene cells led to high frequencies of chromosome multivalents in metaphase I without a correspondingly high level of damage in preceding prophase SCs. Thus, irradiation of premeiotic and meiotic cells results in variable relationships between SC and metaphase chromosome damage

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-11-13

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

  6. Core Binding Factor β (CBFβ) and the Leukemogenic Fusion Protein CBFβ-Smooth Muscle Myosin Heavy Chain (SMMHC) Associate with Mitotic Chromosomes to Epigenetically Regulate Ribosomal Gene Expression*

    Science.gov (United States)

    Lopez-Camacho, Cesar; van Wijnen, Andre J.; Lian, Jane B.; Stein, Janet L.; Stein, Gary S.

    2014-01-01

    Mitotic bookmarking is an epigenetic control mechanism that sustains gene expression in progeny cells; it is often found in genes related to the maintenance of cellular phenotype and growth control. RUNX transcription factors regulate a broad spectrum of RNA Polymerase (Pol II) transcribed genes important for lineage commitment but also regulate RNA Polymerase I (Pol I) driven ribosomal gene expression, thus coordinating control of cellular identity and proliferation. In this study, using fluorescence microscopy and biochemical approaches we show that the principal RUNX co-factor, CBFβ, associates with nucleolar organizing regions (NORs) during mitosis to negatively regulate RUNX-dependent ribosomal gene expression. Of clinical relevance, we establish for the first time that the leukemogenic fusion protein CBFβ-SMMHC (smooth muscle myosin heavy chain) also associates with ribosomal genes in interphase chromatin and mitotic chromosomes to promote and epigenetically sustain regulation of ribosomal genes through RUNX factor interactions. Our results demonstrate that CBFβ contributes to the transcriptional regulation of ribosomal gene expression and provide further understanding of the epigenetic role of CBFβ-SMMHC in proliferation and maintenance of the leukemic phenotype. Background Runt-related transcription factors (RUNX) bookmark genes important for phenotype, but the mitotic behavior of RUNX cofactor, Core Binding Factor β (CBFβ) is unknown. Results CBFβ and leukemogenic fusion protein CBFβ-SMMHC associate with chromosomes during mitosis and regulate ribosomal genes. Conclusion CBFβ and CBFβ-SMMHC contribute to epigenetic control of ribosomal genes. Significance CBFβ-SMMHC alters regulation linking phenotypic control with cell growth, thereby promoting cancer. PMID:25079347

  7. Effects of a chromosome-3 mutator gene on radiation-induced mutability in Drosophila melanogaster females

    International Nuclear Information System (INIS)

    Sankaranarayanan, K.

    1982-01-01

    A series of X-irradiation experiments was carried out using Drosophila melanogaster females homozygous for a third chromosome mutator gene and females which had a similar genetic background except that the mutator-bearing third chromosomes were substituted by normal wild-type chromosomes. In the present work, the sensitivity of the pre-meiotic germ cells of mutator and normal females to the X-ray induction (2000 R) of sex-linked recessive lethals was studied. In addition, experiments were conducted to examine the sensitivity of the immature (stage 7; prophase I of meiosis) oocytes of both kinds of females to the induction of dominant lethals, X-linked recessive lethals and X-chromosome losses. The results show that in pre-meiotic germ cells, the frequencies of radiation-induced recessive lethals are similar in both kinds of females. However, the proportion of these mutations that occur in clusters of size 3 and higher, is higher in mutator than in normal females. In stage-7 oocytes, the frequencies of radiation-induced dominant lethals and sex-linked recessive lethals were similar in both kinds of females. The X-loss frequencies however, were consistently higher in mutator females although statistical significance was obtained only at higher exposures (3000 and 3750 R) and not at lower ones (750-2250 R). Possible reasons for the discrepancy between the present results and those of Gold and Green with respect to pre-meiotic germ cells are discussed. (orig./MG)

  8. Micromechanical study of mitotic chromosome structure

    Science.gov (United States)

    Marko, John

    2011-03-01

    Our group has developed micromanipulation techniques for study of the highly compacted mitotic form of chromosome found in eukaryote cells during cell division. Each metaphase chromosome contains two duplicate centimeter-long DNA molecules, folded up by proteins into cylindrical structures several microns in length. Native chromosomes display linear and reversible stretching behavior over a wide range of extensions (up to 5x native length for amphibian chromosomes), described by a Young modulus of about 300 Pa. Studies using DNA-cutting and protein-cutting enzymes have revealed that metaphase chromosomes behave as a network of chromatin fibers held together by protein-based isolated crosslinks. Our results are not consistent with the more classical model of loops of chromatin attached to a protein-based structural organizer or ``scaffold". In short, our experiments indicate that metaphase chromosomes can be considered to be ``gels" of chromatin; the stretching modulus of a whole chromosome is consistent with stretching of the chromatin fibers contained within it. Experiments using topoisomerases suggest that topological constraints may play an appreciable role in confining chromatin in the metaphase chromosome. Finally, recent experiments on human chromosomes will be reviewed, including results of experiments where chromosome-folding proteins are specifically depleted using siRNA methods. Supported by NSF-MCB-1022117, DMR-0715099, PHY-0852130, DMR-0520513, NCI 1U54CA143869-01 (NU-PS-OC), and the American Heart Association.

  9. Autosomal mutations affecting Y chromosome loops in Drosophila melanogaster

    Directory of Open Access Journals (Sweden)

    Petrucci Romano

    2008-04-01

    Full Text Available Abstract Background The Y chromosome of Drosophila melanogaster harbors several genes required for male fertility. The genes for these fertility factors are very large in size and contain conspicuous amounts of repetitive DNA and transposons. Three of these loci (ks-1, kl-3 and kl-5 have the ability to develop giant lampbrush-like loops in primary spermatocytes, a cytological manifestation of their active state in these cells. Y-loops bind a number of non-Y encoded proteins, but the mechanisms regulating their development and their specific functions are still to be elucidated. Results Here we report the results of a screen of 726 male sterile lines to identify novel autosomal genes controlling Y-loop function. We analyzed mutant testis preparations both in vivo and by immunofluorescence using antibodies directed against Y-loop-associated proteins. This screen enabled us to isolate 17 mutations at 15 loci whose wild-type function is required for proper Y-loop morphogenesis. Six of these loci are likely to specifically control loop development, while the others display pleiotropic effects on both loops and meiotic processes such as spermiogenesis, sperm development and maturation. We also determined the map position of the mutations affecting exclusively Y-loop morphology. Conclusion Our cytological screening permitted us to identify novel genetic functions required for male spermatogenesis, some of which show pleiotropic effects. Analysis of these mutations also shows that loop development can be uncoupled from meiosis progression. These data represent a useful framework for the characterization of Y-loop development at a molecular level and for the study of the genetic control of heterochromatin.

  10. The unfolded protein response is not necessary for the G1/S transition, but it is required for chromosome maintenance in Saccharomyces cerevisiae.

    Directory of Open Access Journals (Sweden)

    Kelsey A Henry

    Full Text Available BACKGROUND: The unfolded protein response (UPR is a eukaryotic signaling pathway, from the endoplasmic reticulum (ER to the nucleus. Protein misfolding in the ER triggers the UPR. Accumulating evidence links the UPR in diverse aspects of cellular homeostasis. The UPR responds to the overall protein synthesis capacity and metabolic fluxes of the cell. Because the coupling of metabolism with cell division governs when cells start dividing, here we examined the role of UPR signaling in the timing of initiation of cell division and cell cycle progression, in the yeast Saccharomyces cerevisiae. METHODOLOGY/PRINCIPAL FINDINGS: We report that cells lacking the ER-resident stress sensor Ire1p, which cannot trigger the UPR, nonetheless completed the G1/S transition on time. Furthermore, loss of UPR signaling neither affected the nutrient and growth rate dependence of the G1/S transition, nor the metabolic oscillations that yeast cells display in defined steady-state conditions. Remarkably, however, loss of UPR signaling led to hypersensitivity to genotoxic stress and a ten-fold increase in chromosome loss. CONCLUSIONS/SIGNIFICANCE: Taken together, our results strongly suggest that UPR signaling is not necessary for the normal coupling of metabolism with cell division, but it has a role in genome maintenance. These results add to previous work that linked the UPR with cytokinesis in yeast. UPR signaling is conserved in all eukaryotes, and it malfunctions in a variety of diseases, including cancer. Therefore, our findings may be relevant to other systems, including humans.

  11. Silica nanoparticles induce multinucleation through activation of PI3K/Akt/GSK-3β pathway and downregulation of chromosomal passenger proteins in L-02 cells

    Energy Technology Data Exchange (ETDEWEB)

    Geng, Weijia; Li, Yang; Yu, Yongbo; Yu, Yang; Duan, Junchao; Jiang, Lizhen; Li, Qiuling; Sun, Zhiwei, E-mail: zwsun@ccmu.edu.cn, E-mail: zwsun@hotmail.com [Capital Medical University, School of Public Health (China)

    2016-04-15

    Silica nanoparticles (SNPs) are applicable in various fields due to their unique physicochemical characteristics. However, concerns over their potential adverse effects have been raised. In our previous studies, we reported that SNPs could induce abnormal high incidence of multinucleation. The aim of this study is to further investigate the mechanisms of multinucleation induced by SNPs (68 nm) in human normal liver L-02 cells (L-02 cells). In order to determine the cytotoxicity of SNPs, MTT assay was performed, and the cell viability was decreased in a dose-dependent manner. The intracellular reactive oxygen species (ROS) detected by flow cytometry and multinucleation observed by Giemsa stain showed that ROS generation and rate of multinucleated cells increased after SNPs exposure. N-acetyl-cysteine (NAC), a glutathione precursor against SNP-induced toxicity, was used as a ROS inhibitor to elucidate the relationship between ROS and multinucleation. The presence of NAC resulted in inhibition of both ROS generation and rate of multinucleation. Moreover, Western blot analysis showed that the protein levels of Cdc20, Aurora B, and Survivin were down-regulated, and the PI3K/Akt/GSK-3β pathway was activated by SNPs. In conclusion, our findings strongly suggested that multinucleation induced by SNPs was related to PI3K/Akt/GSK-3β signal pathway activation and downregulation of G2/M phase-related protein and chromosomal passenger proteins.

  12. Somatic segregation errors predominantly contribute to the gain or loss of a paternal chromosome leading to uniparental disomy for chromosome 15.

    Science.gov (United States)

    Robinson, W P; Christian, S L; Kuchinka, B D; Peñaherrera, M S; Das, S; Schuffenhauer, S; Malcolm, S; Schinzel, A A; Hassold, T J; Ledbetter, D H

    2000-05-01

    Paternal uniparental disomy (UPD) for chromosome 15 (UPD15), which is found in approximately 2% of Angelman syndrome (AS) patients, is much less frequent than maternal UPD15, which is found in 25% of Prader-Willi syndrome patients. Such a difference cannot be easily accounted for if 'gamete complementation' is the main mechanism leading to UPD. If we assume that non-disjunction of chromosome 15 in male meiosis is relatively rare, then the gain or loss of the paternal chromosome involved in paternal and maternal UPD15, respectively, may be more likely to result from a post-zygotic rather than a meiotic event. To test this hypothesis, the origin of the extra chromosome 15 was determined in 21 AS patients with paternal UPD15 with a paternal origin of the trisomy. Only 4 of 21 paternal UPD15 cases could be clearly attributed to a meiotic error. Furthermore, significant non-random X-chromosome inactivation (XCI) observed in maternal UPD15 patients (p UPD15 cases are increased as compared with normal controls. This may be simply the consequence of an age association with maternal non-disjunction leading to nullisomy for chromosome 15 in the oocyte, although the higher paternal age in paternal UPD15 as compared with maternal UPD15 cases is suggestive that paternal age may also play a role in the origin of paternal UPD15.

  13. MvaT Family Proteins Encoded on IncP-7 Plasmid pCAR1 and the Host Chromosome Regulate the Host Transcriptome Cooperatively but Differently.

    Science.gov (United States)

    Yun, Choong-Soo; Takahashi, Yurika; Shintani, Masaki; Takeda, Toshiharu; Suzuki-Minakuchi, Chiho; Okada, Kazunori; Yamane, Hisakazu; Nojiri, Hideaki

    2016-02-01

    MvaT proteins are members of the H-NS family of proteins in pseudomonads. The IncP-7 conjugative plasmid pCAR1 carries an mvaT-homologous gene, pmr. In Pseudomonas putida KT2440 bearing pCAR1, pmr and the chromosomally carried homologous genes, turA and turB, are transcribed at high levels, and Pmr interacts with TurA and TurB in vitro. In the present study, we clarified how the three MvaT proteins regulate the transcriptome of P. putida KT2440(pCAR1). Analyses performed by a modified chromatin immunoprecipitation assay with microarray technology (ChIP-chip) suggested that the binding regions of Pmr, TurA, and TurB in the P. putida KT2440(pCAR1) genome are almost identical; nevertheless, transcriptomic analyses using mutants with deletions of the genes encoding the MvaT proteins during the log and early stationary growth phases clearly suggested that their regulons were different. Indeed, significant regulon dissimilarity was found between Pmr and the other two proteins. Transcription of a larger number of genes was affected by Pmr deletion during early stationary phase than during log phase, suggesting that Pmr ameliorates the effects of pCAR1 on host fitness more effectively during the early stationary phase. Alternatively, the similarity of the TurA and TurB regulons implied that they might play complementary roles as global transcriptional regulators in response to plasmid carriage. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

  14. The Ste locus, a component of the parasitic cry-Ste system of Drosophila melanogaster, encodes a protein that forms crystals in primary spermatocytes and mimics properties of the beta subunit of casein kinase 2

    DEFF Research Database (Denmark)

    Bozzetti, M P; Massari, S; Finelli, P

    1995-01-01

    Males of Drosophila melanogaster lacking the Y chromosome-linked crystal locus show multiple meiotic alterations including chromosome disorganization and prominent crystal formation in primary spermatocytes. These alterations are due to the derepression of the X chromosome-linked Stellate sequenc...

  15. The Ph1 Locus from Wheat Controls Meiotic Chromosome Pairing in Autotetraploid Rye (Secale cereale L.)

    Czech Academy of Sciences Publication Activity Database

    Lukaszewski, A.J.; Kopecký, David

    2010-01-01

    Roč. 129, 1-3 (2010), s. 117-123 ISSN 1424-8581 Institutional research plan: CEZ:AV0Z50380511 Keywords : Diploid-like pairing * Introgression * Meiosis Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 1.783, year: 2010

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

    Indian Academy of Sciences (India)

    2011-08-19

    Aug 19, 2011 ... Seixas M. A. C. and Esteves A. 2000 Determinação de poli- ploidia e avaliação da quantidade de DNA total em diferentes espécies de gênero Brachiaria. Boletim de Pesquisa 11, Embrapa. Gado de Corte, Campo Grande, MS, Brazil. Pritchard A. J. 1967 Apomixis in Brachiaria decumbens Stapf. J. Aust.

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

    Indian Academy of Sciences (India)

    2011-08-19

    Aug 19, 2011 ... GLÉIA CRISTINA LAVERDE RICCI1, ALICE MARIA DE SOUZA-KANESHIMA1,. MARIANA FERRARI FELISMINO1, ANDREA BEATRIZ MENDES-BONATO1,. MARIA SUELY PAGLIARINI1∗ and CACILDA BORGES DO VALLE2. 1Department of Cell Biology and Genetics, State University of Maringá, ...

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

    Czech Academy of Sciences Publication Activity Database

    Balcová, Mária; Faltusová, Barbora; Gergelits, Václav; Bhattacharyya, Tanmoy; Mihola, Ondřej; Trachtulec, Zdeněk; Knopf, Corinna; Fotopulosová, Vladana; Chvátalová, Irena; Gregorová, Soňa; Forejt, Jiří

    2016-01-01

    Roč. 12, č. 4 (2016), e1005906-e1005906 ISSN 1553-7404 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0109; GA ČR GA13-08078S; GA ČR(CZ) GA14-20728S Institutional support: RVO:68378050 Keywords : Histochine H3 methyltransferase * Crossing-Over * Complex Traits Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 6.100, year: 2016

  19. Human rab11a: transcription, chromosome mapping and effect on the expression levels of host GTP-binding proteins

    DEFF Research Database (Denmark)

    Gromov, P S; Celis, J E; Hansen, Claus

    1998-01-01

    ) that are believed to control gene expression by regulating the rate of mRNA degradation. Southern blots of human DNA digested with several rare restriction enzymes, and separated by pulse-field gel electrophoresis, yielded the same macro-restriction fragment pattern when hybridised with probes that discriminate......-1 cells, and surprisingly, upregulated the proteome expression profile (de novo synthesis or posttranslational modification of preexisting proteins) of a few other, yet unknown GTP-binding proteins....

  20. Mitotic chromosome condensation in vertebrates

    Energy Technology Data Exchange (ETDEWEB)

    Vagnarelli, Paola, E-mail: P.Vagnarelli@ed.ac.uk

    2012-07-15

    Work from several laboratories over the past 10-15 years has revealed that, within the interphase nucleus, chromosomes are organized into spatially distinct territories [T. Cremer, C. Cremer, Chromosome territories, nuclear architecture and gene regulation in mammalian cells, Nat. Rev. Genet. 2 (2001) 292-301 and T. Cremer, M. Cremer, S. Dietzel, S. Muller, I. Solovei, S. Fakan, Chromosome territories-a functional nuclear landscape, Curr. Opin. Cell Biol. 18 (2006) 307-316]. The overall compaction level and intranuclear location varies as a function of gene density for both entire chromosomes [J.A. Croft, J.M. Bridger, S. Boyle, P. Perry, P. Teague,W.A. Bickmore, Differences in the localization and morphology of chromosomes in the human nucleus, J. Cell Biol. 145 (1999) 1119-1131] and specific chromosomal regions [N.L. Mahy, P.E. Perry, S. Gilchrist, R.A. Baldock, W.A. Bickmore, Spatial organization of active and inactive genes and noncoding DNA within chromosome territories, J. Cell Biol. 157 (2002) 579-589] (Fig. 1A, A'). In prophase, when cyclin B activity reaches a high threshold, chromosome condensation occurs followed by Nuclear Envelope Breakdown (NEB) [1]. At this point vertebrate chromosomes appear as compact structures harboring an attachment point for the spindle microtubules physically recognizable as a primary constriction where the two sister chromatids are held together. The transition from an unshaped interphase chromosome to the highly structured mitotic chromosome (compare Figs. 1A and B) has fascinated researchers for several decades now; however a definite picture of how this process is achieved and regulated is not yet in our hands and it will require more investigation to comprehend the complete process. From a biochemical point of view a vertebrate mitotic chromosomes is composed of DNA, histone proteins (60%) and non-histone proteins (40%) [6]. I will discuss below what is known to date on the contribution of these two different classes

  1. Mitotic chromosome condensation in vertebrates

    International Nuclear Information System (INIS)

    Vagnarelli, Paola

    2012-01-01

    Work from several laboratories over the past 10–15 years has revealed that, within the interphase nucleus, chromosomes are organized into spatially distinct territories [T. Cremer, C. Cremer, Chromosome territories, nuclear architecture and gene regulation in mammalian cells, Nat. Rev. Genet. 2 (2001) 292–301 and T. Cremer, M. Cremer, S. Dietzel, S. Muller, I. Solovei, S. Fakan, Chromosome territories—a functional nuclear landscape, Curr. Opin. Cell Biol. 18 (2006) 307–316]. The overall compaction level and intranuclear location varies as a function of gene density for both entire chromosomes [J.A. Croft, J.M. Bridger, S. Boyle, P. Perry, P. Teague,W.A. Bickmore, Differences in the localization and morphology of chromosomes in the human nucleus, J. Cell Biol. 145 (1999) 1119–1131] and specific chromosomal regions [N.L. Mahy, P.E. Perry, S. Gilchrist, R.A. Baldock, W.A. Bickmore, Spatial organization of active and inactive genes and noncoding DNA within chromosome territories, J. Cell Biol. 157 (2002) 579–589] (Fig. 1A, A'). In prophase, when cyclin B activity reaches a high threshold, chromosome condensation occurs followed by Nuclear Envelope Breakdown (NEB) [1]. At this point vertebrate chromosomes appear as compact structures harboring an attachment point for the spindle microtubules physically recognizable as a primary constriction where the two sister chromatids are held together. The transition from an unshaped interphase chromosome to the highly structured mitotic chromosome (compare Figs. 1A and B) has fascinated researchers for several decades now; however a definite picture of how this process is achieved and regulated is not yet in our hands and it will require more investigation to comprehend the complete process. From a biochemical point of view a vertebrate mitotic chromosomes is composed of DNA, histone proteins (60%) and non-histone proteins (40%) [6]. I will discuss below what is known to date on the contribution of these two different

  2. Ipl1/Aurora kinase suppresses S-CDK-driven spindle formation during prophase I to ensure chromosome integrity during meiosis.

    Directory of Open Access Journals (Sweden)

    Louise Newnham

    Full Text Available Cells coordinate spindle formation with DNA repair and morphological modifications to chromosomes prior to their segregation to prevent cell division with damaged chromosomes. Here we uncover a novel and unexpected role for Aurora kinase in preventing the formation of spindles by Clb5-CDK (S-CDK during meiotic prophase I and when the DDR is active in budding yeast. This is critical since S-CDK is essential for replication during premeiotic S-phase as well as double-strand break induction that facilitates meiotic recombination and, ultimately, chromosome segregation. Furthermore, we find that depletion of Cdc5 polo kinase activity delays spindle formation in DDR-arrested cells and that ectopic expression of Cdc5 in prophase I enhances spindle formation, when Ipl1 is depleted. Our findings establish a new paradigm for Aurora kinase function in both negative and positive regulation of spindle dynamics.

  3. Krtap16, characterization of a new hair keratin-associated protein (KAP) gene complex on mouse chromosome 16 and evidence for regulation by Hoxc13.

    Science.gov (United States)

    Pruett, Nathanael D; Tkatchenko, Tatiana V; Jave-Suarez, Luis; Jacobs, Donna F; Potter, Christopher S; Tkatchenko, Andrei V; Schweizer, Jürgen; Awgulewitsch, Alexander

    2004-12-03

    Intermediate filament (IF) keratins and keratin-associated proteins (KAPs) are principal structural components of hair and encoded by members of multiple gene families. The severe hair growth defects observed upon aberrant expression of certain keratin and KAP genes in both mouse and man suggest that proper hair growth requires their spatio-temporally coordinated activation. An essential prerequisite for studying these cis-regulatory mechanisms is to define corresponding gene families, their genomic organization, and expression patterns. This work characterizes eight recently identified high glycine/tyrosine (HGT)-type KAP genes collectively designated Krtap16-n. These genes are shown to be integrated into a larger KAP gene domain on mouse chromosome 16 (MMU16) that is orthologous to a recently described HGT- and high sulfur (HS)-type KAP gene complex on human chromosome 21q22.11. All Krtap16 genes exhibit strong expression in a narrowly defined pattern restricted to the lower and middle cortical region of the hair shaft in both developing and cycling hair. During hair follicle regression (catagen), expression levels decrease until expression is no longer detectable in follicles at resting stage (telogen). Since isolation of the Krtap16 genes was based on their differential expression in transgenic mice overexpressing the Hoxc13 transcriptional regulator in hair, we examined whether bona fide Hoxc13 binding sites associated with these genes might be functionally relevant by performing electrophoretic mobility shift assays (EMSAs). The data provide evidence for sequence-specific interaction between Hoxc13 and Krtap16 genes, thus supporting the concept of a regulatory relationship between Hoxc13 and these KAP genes.

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

    African Journals Online (AJOL)

    fe

    2011-11-16

    Nov 16, 2011 ... genus Epimedium are few and only available in hybrid populations (Sheng et al., ... in hybrids (>76.10%) and meiotic abnormalities occurred .... 619-625. Pagliarini MS (2000). Meiotic behavior of economically important plant species: the relationship between fertility and male sterility. Genet. Mol. Biol.

  5. Spore-killing meiotic drive factors in a natural population of the fungus Podospora anserina

    NARCIS (Netherlands)

    Gaag, van der M.; Debets, A.J.M.; Oosterhof, J.; Slakhorst, S.M.; Thijssen, J.A.G.M.; Hoekstra, R.F.

    2000-01-01

    In fungi, meiotic drive is observed as spore killing. In the secondarily homothallic ascomycete Podospora anserina it is characterized by the abortion of two of the four spores in the ascus. We have identified seven different types of meiotic drive elements (Spore killers). Among 99 isolates from

  6. PLD2 regulates microtubule stability and spindle migration in mouse oocytes during meiotic division

    Directory of Open Access Journals (Sweden)

    Xiaoyu Liu

    2017-05-01

    Full Text Available Phospholipase D2 (PLD2 is involved in cytoskeletal reorganization, cell migration, cell cycle progression, transcriptional control and vesicle trafficking. There is no evidence about PLD2 function in oocytes during meiosis. Herein, we analyzed PLD2 expression and its relationship with spindle formation and positioning in mouse oocyte meiosis. High protein level of PLD2 was revealed in oocytes by Western blot, which remained consistently stable from prophase I with intact germinal vesicle (GV up to metaphase II (MII stage. Immunofluorescence showed that PLD2 appeared and gathered around the condensed chromosomesafter germinal vesicle breakdown (GVBD, and co-localized with spindle from pro-metaphase I (pro-MI to metaphase I (MI and at MII stage. During anaphase I (Ana I to telophase I (Tel I transition, PLD2 was concentrated in the spindle polar area but absent from the midbody. In oocytes incubated with NFOT, an allosteric and catalytic inhibitor to PLD2, the spindle was enlarged and center-positioned, microtubules were resistant to cold-induced depolymerization and, additionally, the meiotic progression was arrested at MI stage. However, spindle migration could not be totally prevented by PLD2 catalytic specific inhibitors, FIPI and 1-butanol, implying at least partially, that PLD2 effect on spindle migration needs non-catalytic domain participation. NFOT-induced defects also resulted in actin-related molecules’ distribution alteration, such as RhoA, phosphatidylinosital 4, 5- biphosphate (PIP2, phosphorylated Colifin and, consequently, unordered F-actin dynamics. Taken together, these data indicate PLD2 is required for the regulation of microtubule dynamics and spindle migration toward the cortex in mammalian oocytes during meiotic progression.

  7. Cloning of human basic A1, a distinct 59-kDa dystrophin-associated protein encoded on chromosome 8q23-24

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, A.H. [Harvard Medical School, Boston, MA (United States); Yoshida, Mikiharu; Hagiwara, Yasuko; Ozawa, Eijiro [National Institute of Neuroscience, Ogawa Higashi, Kodaira (Japan); Anderson, M.S.; Feener, C.A.; Selig, S. [Howard Hughes Medical Institute at Children`s Hospital, Boston, MA (United States); Kunkel, L.M. [Harvard Medical School, Boston, MA (United States)]|[Howard Hughes Medical Institute at Children`s Hosptial, Boston, MA (United States)

    1994-05-10

    Duchenne and Becker muscular dystrophies are caused by defects of dystrophin, which forms a part of the membrane cytoskeleton of specialized cells such as muscle. It has been previously shown that the dystrophin-associated protein A1 (59-kDa DAP) is actually a heterogeneous group of phosphorylated proteins consisting of an acidic ({alpha}-A1) and a distinct basic ({beta}-A1) component. Partial peptide sequence of the A1 complex purified from rabbit muscle permitted the design of oligonucleotide probes that were used to isolate a cDNA for one human isoform of A1. This cDNA encodes a basic A1 isoform that is distinct from the recently described syntrophins in Torpedo and mouse and is expressed in many tissues with at least five distinct mRNA species of 5.9, 4.8, 4.3, 3.1, and 1.5 kb. A comparison of the human cDNA sequence with the GenBank expressed sequence tag (EST) data base has identified a relative from human skeletal muscle, EST25263, which is probably a human homologue of the published mouse syntrophin 2. The authors have mapped the human basic component of A1 and EST25263 genes to chromosomes 8q23-24 and 16, respectively.

  8. The Additional sex combs gene of Drosophila encodes a chromatin protein that binds to shared and unique Polycomb group sites on polytene chromosomes.

    Science.gov (United States)

    Sinclair, D A; Milne, T A; Hodgson, J W; Shellard, J; Salinas, C A; Kyba, M; Randazzo, F; Brock, H W

    1998-04-01

    The Additional sex combs (Asx) gene of Drosophila is a member of the Polycomb group of genes, which are required for maintenance of stable repression of homeotic and other loci. Asx is unusual among the Polycomb group because: (1) one Asx allele exhibits both anterior and posterior transformations; (2) Asx mutations enhance anterior transformations of trx mutations; (3) Asx mutations exhibit segmentation phenotypes in addition to homeotic phenotypes; (4) Asx is an Enhancer of position-effect variegation and (5) Asx displays tissue-specific derepression of target genes. Asx was cloned by transposon tagging and encodes a protein of 1668 amino acids containing an unusual cysteine cluster at the carboxy terminus. The protein is ubiquitously expressed during development. We show that Asx is required in the central nervous system to regulate Ultrabithorax. ASX binds to multiple sites on polytene chromosomes, 70% of which overlap those of Polycomb, polyhomeotic and Polycomblike, and 30% of which are unique. The differences in target site recognition may account for some of the differences in Asx phenotypes relative to other members of the Polycomb group.

  9. Dynein-dependent processive chromosome motions promote homologous pairing in C. elegans meiosis

    Science.gov (United States)

    Wynne, David J.; Rog, Ofer; Carlton, Peter M.

    2012-01-01

    Meiotic chromosome segregation requires homologue pairing, synapsis, and crossover recombination, which occur during meiotic prophase. Telomere-led chromosome motion has been observed or inferred to occur during this stage in diverse species, but its mechanism and function remain enigmatic. In Caenorhabditis elegans, special chromosome regions known as pairing centers (PCs), rather than telomeres, associate with the nuclear envelope (NE) and the microtubule cytoskeleton. In this paper, we investigate chromosome dynamics in living animals through high-resolution four-dimensional fluorescence imaging and quantitative motion analysis. We find that chromosome movement is constrained before meiosis. Upon prophase onset, constraints are relaxed, and PCs initiate saltatory, processive, dynein-dependent motions along the NE. These dramatic motions are dispensable for homologous pairing and continue until synapsis is completed. These observations are consistent with the idea that motions facilitate pairing by enhancing the search rate but that their primary function is to trigger synapsis. This quantitative analysis of chromosome dynamics in a living animal extends our understanding of the mechanisms governing faithful genome inheritance. PMID:22232701

  10. New chromosome characteristics of the monozoic tapeworm Caryophyllaeus laticeps (Cestoda, Caryophyllidea

    Directory of Open Access Journals (Sweden)

    Bombarová M.

    2015-12-01

    Full Text Available The karyotype of a caryophyllidean tapeworm Caryophyllaeus laticeps (Pallas, 1781 from the freshwater bream Abramis brama (L. caught in the Slovak part of the River Tisa, was described and originally inspected for amount of heterochromatin and its chromosome localization. The chromosome set comprised nine metacentric and one submetacentric (No. 3 pairs (2n = 20. The chromosomes were up to 12.0 ± 2.5 μm long and the mean total length of haploid genome (TLC reached 80.6 μm that represents one of the highest yet recorded values among tapeworms. C-banding and staining with fl uorescent dyes DAPI and YOYO1 revealed a distinct banding pattern explicitly on chromosomes with centromeric bright heterochromatin bands present on all 10 chromosome pairs; no pair showed any interstitial heterochromatin. A complete course of spermatocyte meiosis and dynamics of nucleolus formation and degradation during meiotic division was described.

  11. Analysis of the meiotic segregation in intergeneric hybrids of tilapias.

    Science.gov (United States)

    Bezault, Etienne; Rognon, Xavier; Clota, Frederic; Gharbi, Karim; Baroiller, Jean-Francois; Chevassus, Bernard

    2012-01-01

    Tilapia species exhibit a large ecological diversity and an important propensity to interspecific hybridisation. This has been shown in the wild and used in aquaculture. However, despite its important evolutionary implications, few studies have focused on the analysis of hybrid genomes and their meiotic segregation. Intergeneric hybrids between Oreochromis niloticus and Sarotherodon melanotheron, two species highly differentiated genetically, ecologically, and behaviourally, were produced experimentally. The meiotic segregation of these hybrids was analysed in reciprocal second generation hybrid (F2) and backcross families and compared to the meiosis of both parental species, using a panel of 30 microsatellite markers. Hybrid meioses showed segregation in accordance to Mendelian expectations, independent from sex and the direction of crosses. In addition, we observed a conservation of linkage associations between markers, which suggests a relatively similar genome structure between the two parental species and the apparent lack of postzygotic incompatibility, despite their important divergence. These results provide genomics insights into the relative ease of hybridisation within cichlid species when prezygotic barriers are disrupted. Overall our results support the hypothesis that hybridisation may have played an important role in the evolution and diversification of cichlids.

  12. Centromere-associated protein-E is essential for the mammalian mitotic checkpoint to prevent aneuploidy due to single chromosome loss

    OpenAIRE

    Weaver, Beth A.A.; Bonday, Zahid Q.; Putkey, Frances R.; Kops, Geert J.P.L.; Silk, Alain D.; Cleveland, Don W.

    2003-01-01

    Centromere-associated protein-E (CENP-E) is an essential mitotic kinesin that is required for efficient, stable microtubule capture at kinetochores. It also directly binds to BubR1, a kinetochore-associated kinase implicated in the mitotic checkpoint, the major cell cycle control pathway in which unattached kinetochores prevent anaphase onset. Here, we show that single unattached kinetochores depleted of CENP-E cannot block entry into anaphase, resulting in aneuploidy in 25% of divisions in p...

  13. Mapping meiotic single-strand DNA reveals a new landscape of DNA double-strand breaks in Saccharomyces cerevisiae.

    Directory of Open Access Journals (Sweden)

    Cyril Buhler

    2007-12-01

    Full Text Available DNA double-strand breaks (DSBs, which are formed by the Spo11 protein, initiate meiotic recombination. Previous DSB-mapping studies have used rad50S or sae2Delta mutants, which are defective in break processing, to accumulate Spo11-linked DSBs, and report large (> or = 50 kb "DSB-hot" regions that are separated by "DSB-cold" domains of similar size. Substantial recombination occurs in some DSB-cold regions, suggesting that DSB patterns are not normal in rad50S or sae2Delta mutants. We therefore developed a novel method to map genome-wide, single-strand DNA (ssDNA-associated DSBs that accumulate in processing-capable, repair-defective dmc1Delta and dmc1Delta rad51Delta mutants. DSBs were observed at known hot spots, but also in most previously identified "DSB-cold" regions, including near centromeres and telomeres. Although approximately 40% of the genome is DSB-cold in rad50S mutants, analysis of meiotic ssDNA from dmc1Delta shows that most of these regions have substantial DSB activity. Southern blot assays of DSBs in selected regions in dmc1Delta, rad50S, and wild-type cells confirm these findings. Thus, DSBs are distributed much more uniformly than was previously believed. Comparisons of DSB signals in dmc1, dmc1 rad51, and dmc1 spo11 mutant strains identify Dmc1 as a critical strand-exchange activity genome-wide, and confirm previous conclusions that Spo11-induced lesions initiate all meiotic recombination.

  14. Tethering of the conserved piggyBac transposase fusion protein CSB-PGBD3 to chromosomal AP-1 proteins regulates expression of nearby genes in humans.

    Science.gov (United States)

    Gray, Lucas T; Fong, Kimberly K; Pavelitz, Thomas; Weiner, Alan M

    2012-09-01

    The CSB-PGBD3 fusion protein arose more than 43 million years ago when a 2.5-kb piggyBac 3 (PGBD3) transposon inserted into intron 5 of the Cockayne syndrome Group B (CSB) gene in the common ancestor of all higher primates. As a result, full-length CSB is now coexpressed with an abundant CSB-PGBD3 fusion protein by alternative splicing of CSB exons 1-5 to the PGBD3 transposase. An internal deletion of the piggyBac transposase ORF also gave rise to 889 dispersed, 140-bp MER85 elements that were mobilized in trans by PGBD3 transposase. The CSB-PGBD3 fusion protein binds MER85s in vitro and induces a strong interferon-like innate antiviral immune response when expressed in CSB-null UVSS1KO cells. To explore the connection between DNA binding and gene expression changes induced by CSB-PGBD3, we investigated the genome-wide DNA binding profile of the fusion protein. CSB-PGBD3 binds to 363 MER85 elements in vivo, but these sites do not correlate with gene expression changes induced by the fusion protein. Instead, CSB-PGBD3 is enriched at AP-1, TEAD1, and CTCF motifs, presumably through protein-protein interactions with the cognate transcription factors; moreover, recruitment of CSB-PGBD3 to AP-1 and TEAD1 motifs correlates with nearby genes regulated by CSB-PGBD3 expression in UVSS1KO cells and downregulated by CSB rescue of mutant CS1AN cells. Consistent with these data, the N-terminal CSB domain of the CSB-PGBD3 fusion protein interacts with the AP-1 transcription factor c-Jun and with RNA polymerase II, and a chimeric CSB-LacI construct containing only the N-terminus of CSB upregulates many of the genes induced by CSB-PGBD3. We conclude that the CSB-PGBD3 fusion protein substantially reshapes the transcriptome in CS patient CS1AN and that continued expression of the CSB-PGBD3 fusion protein in the absence of functional CSB may affect the clinical presentation of CS patients by directly altering the transcriptional program.

  15. Tethering of the conserved piggyBac transposase fusion protein CSB-PGBD3 to chromosomal AP-1 proteins regulates expression of nearby genes in humans.

    Directory of Open Access Journals (Sweden)

    Lucas T Gray

    2012-09-01

    Full Text Available The CSB-PGBD3 fusion protein arose more than 43 million years ago when a 2.5-kb piggyBac 3 (PGBD3 transposon inserted into intron 5 of the Cockayne syndrome Group B (CSB gene in the common ancestor of all higher primates. As a result, full-length CSB is now coexpressed with an abundant CSB-PGBD3 fusion protein by alternative splicing of CSB exons 1-5 to the PGBD3 transposase. An internal deletion of the piggyBac transposase ORF also gave rise to 889 dispersed, 140-bp MER85 elements that were mobilized in trans by PGBD3 transposase. The CSB-PGBD3 fusion protein binds MER85s in vitro and induces a strong interferon-like innate antiviral immune response when expressed in CSB-null UVSS1KO cells. To explore the connection between DNA binding and gene expression changes induced by CSB-PGBD3, we investigated the genome-wide DNA binding profile of the fusion protein. CSB-PGBD3 binds to 363 MER85 elements in vivo, but these sites do not correlate with gene expression changes induced by the fusion protein. Instead, CSB-PGBD3 is enriched at AP-1, TEAD1, and CTCF motifs, presumably through protein-protein interactions with the cognate transcription factors; moreover, recruitment of CSB-PGBD3 to AP-1 and TEAD1 motifs correlates with nearby genes regulated by CSB-PGBD3 expression in UVSS1KO cells and downregulated by CSB rescue of mutant CS1AN cells. Consistent with these data, the N-terminal CSB domain of the CSB-PGBD3 fusion protein interacts with the AP-1 transcription factor c-Jun and with RNA polymerase II, and a chimeric CSB-LacI construct containing only the N-terminus of CSB upregulates many of the genes induced by CSB-PGBD3. We conclude that the CSB-PGBD3 fusion protein substantially reshapes the transcriptome in CS patient CS1AN and that continued expression of the CSB-PGBD3 fusion protein in the absence of functional CSB may affect the clinical presentation of CS patients by directly altering the transcriptional program.

  16. The conserved histone deacetylase Rpd3 and the DNA binding regulator Ume6 repress BOI1's meiotic transcript isoform during vegetative growth in Saccharomyces cerevisiae.

    Science.gov (United States)

    Liu, Yuchen; Stuparevic, Igor; Xie, Bingning; Becker, Emmanuelle; Law, Michael J; Primig, Michael

    2015-05-01

    BOI1 and BOI2 are paralogs important for the actin cytoskeleton and polar growth. BOI1 encodes a meiotic transcript isoform with an extended 5'-untranslated region predicted to impair protein translation. It is, however, unknown how the isoform is repressed during mitosis, and if Boi1 is present during sporulation. By interpreting microarray data from MATa cells, MATa/α cells, a starving MATα/α control, and a meiosis-impaired rrp6 mutant, we classified BOI1's extended isoform as early meiosis-specific. These results were confirmed by RNA-Sequencing, and extended by a 5'-RACE assay and Northern blotting, showing that meiotic cells induce the long isoform while the mitotic isoform remains detectable during meiosis. We provide evidence via motif predictions, an in vivo binding assay and genetic experiments that the Rpd3/Sin3/Ume6 histone deacetylase complex, which represses meiotic genes during mitosis, also prevents the induction of BOI1's 5'-extended isoform in mitosis by direct binding of Ume6 to its URS1 target. Finally, we find that Boi1 protein levels decline when cells switch from fermentation to respiration and sporulation. The histone deacetylase Rpd3 is conserved, and eukaryotic genes frequently encode transcripts with variable 5'-UTRs. Our findings are therefore relevant for regulatory mechanisms involved in the control of transcript isoforms in multi-cellular organisms. © 2015 John Wiley & Sons Ltd.

  17. Abnormal meiotic behavior in three species of Crotalaria Comportamento meiótico anormal em três espécies de Crotalaria

    Directory of Open Access Journals (Sweden)

    Kátia Ferreira

    2009-12-01

    Full Text Available The objective of this work was to compare the meiotic behavior and pollen grain viability of three species of Crotalaria. Slides for meiotic analysis were prepared by the air-drying technique. Pollen grain viability was measured by three staining procedures (Alexander's solution, tetrazolium chloride and fluorescein diacetate and in vitro germination in a sucrose solution. Eight bivalents were observed, confirming previous reports on populations from other regions of Brazil, as well as from other countries. All species showed abnormal meiotic behavior as follows: in Crotalaria micans, cytomixis and abnormal chromosome pairing in diakinesis; in C. spectabilis, abnormal chromosome pairing in diplotene; in C. zanzibarica, shrunk nuclei in leptotene and zygotene. Pollen grains of all three species show low viability, which may be associated with the irregularities of the meiotic behavior.O objetivo deste trabalho foi comparar o comportamento meiótico e a viabilidade dos grãos de pólen de três espécies de Crotalaria. A análise meiótica foi realizada por meio da técnica de secagem ao ar. A viabilidade dos grãos de pólen foi avaliada por testes de coloração (corante de Alexander, cloreto de tetrazólio e diacetato de fluoresceína e por teste de germinação em solução de sacarose. Foram observados oito bivalentes, confirmando relatos prévios em populações de outras regiões do Brasil e de outros países. As três espécies apresentaram comportamento meiótico irregular: em Crotalaria micans, citomixia e pareamento irregular na diacinese; em C. spectabilis, pareamento irregular no diplóteno; e em C. zanzibarica, núcleo fortemente condensado nas fases de leptóteno e zigóteno. A viabilidade dos grãos de pólen das três espécies é baixa, o que pode estar associado às irregularidades do comportamento meiótico.

  18. Genesis by meiotic unequal crossover of a de novo deletion that contributes to steroid 21-hydroxylase deficiency

    International Nuclear Information System (INIS)

    Sinnott, P.; Collier, S.; Dyer, P.A.; Harris, R.; Strachan, T.; Costigan, C.

    1990-01-01

    The HLA-linked human steroid 21-hydroxylase gene CYP21B and its closely homologous pseudogene CYP21A are each normally located centromeric to a fourth component of complement (C4) gene, C4B and C4A, respectively, in an organization suggesting tandem duplication of a ca. 30-kilobase DNA unit containing a CYP21 gene and a C4 gene. Such an organization has been considered to facilitate gene deletion and addition events by unequal crossover between the tandem repeats. The authors have identified a steroid 21-hydroxylase deficiency patient who has a maternally inherited disease haplotype that carries a de novo deletion of a ca. 30-kilobase repeat unit including the CYP21B gene and associated C4B gene. This disease haplotype appears to have been generated as a result of meiotic unequal crossover between maternal homologous chromosomes. One of the maternal haplotypes is the frequently occurring HLA-DR3,B8,A1 haplotype that normally carries a deletion of a ca. 30-kilobase unit including the CYP21A gene and C4A gene. Haplotypes of this type may possible act as premutations, increasing the susceptibility of developing a 21-hydroxylase deficiency mutation by facilitating unequal chromosome pairing

  19. Green fluorescent protein fused to the C terminus of RAD51 specifically interferes with secondary DNA binding by the RAD51-ssDNA complex.

    Science.gov (United States)

    Kobayashi, Wataru; Sekine, Satoshi; Machida, Shinichi; Kurumizaka, Hitoshi

    2014-01-01

    Green fluorescent protein (GFP), fused to the N or C terminus of a protein of interest, is widely used to monitor the localization and mobility of proteins in cells. RAD51 is an essential protein that functions in mitotic DNA repair and meiotic chromosome segregation by promoting the homologous recombination reaction. A previous genetic study with Arabidopsis thaliana revealed that GFP fused to the C terminus of RAD51 (RAD51-GFP) inhibits mitotic DNA repair, but meiotic homologous recombination remained unaffected. To determine how the C-terminal GFP specifically inhibits mitotic DNA repair by RAD51, we purified rice RAD51A1-GFP and RAD51A2-GFP, and performed biochemical analyses. Interestingly, purified RAD51A1-GFP and RAD51A2-GFP are proficient in DNA binding and ATP hydrolysis. However, nucleoprotein complexes containing single-stranded DNA and RAD51A1-GFP or RAD51A2-GFP are significantly defective in binding to the second DNA molecule (secondary DNA binding), and consequently fail to catalyze homologous pairing. In contrast, RAD51A1-GFP and RAD51A2-GFP efficiently stimulated homologous pairing promoted by the meiosis-specific RAD51 isoform DMC1. These biochemical characteristics are well conserved in human RAD51-GFP. Therefore, GFP fused to the C terminus of RAD51 abolishes the homologous pairing activity of RAD51 by disrupting secondary DNA binding, but does not affect its DMC1-stimulating activity.

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

    Indian Academy of Sciences (India)

    Unknown

    Mus terricolor I, II and III are the three chromosomal species which differ in stable autosomal short-arm heterochromatin variations established in ... About one month old first generation pups born in the laboratory were used for .... The X and Y chromosomes showed different degrees of dissociation in all the F1 hybrids ...

  1. Sex chromosome repeats tip the balance towards speciation.

    Science.gov (United States)

    O'Neill, Michael J; O'Neill, Rachel J

    2018-04-06

    Because sex chromosomes, by definition, carry genes that determine sex, mutations that alter their structural and functional stability can have immediate consequences for the individual by reducing fertility, but also for a species by altering the sex ratio. Moreover, the sex-specific segregation patterns of heteromorphic sex chromosomes make them havens for selfish genetic elements that not only create sub-optimal sex ratios, but can also foster sexual antagonism. Compensatory mutations to mitigate antagonism or return sex ratios to a Fisherian optimum can create hybrid incompatibility and establish reproductive barriers leading to species divergence. The destabilizing influence of these selfish elements is often manifest within populations as copy number variants (CNVs) in satellite repeats and transposable elements (TE) or as CNVs involving sex determining genes, or genes essential to fertility and sex chromosome dosage compensation. This review catalogs several examples of well-studied sex chromosome CNVs in Drosophilids and mammals that underlie instances of meiotic drive, hybrid incompatibility and disruptions to sex differentiation and sex chromosome dosage compensation. While it is difficult to pinpoint a direct cause/effect relationship between these sex chromosome CNVs and speciation, it is easy to see how their effects in creating imbalances between the sexes, and the compensatory mutations to restore balance, can lead to lineage splitting and species formation. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  2. Analysis of DNA polymerase ν function in meiotic recombination, immunoglobulin class-switching, and DNA damage tolerance.

    Directory of Open Access Journals (Sweden)

    Kei-Ichi Takata

    2017-06-01

    Full Text Available DNA polymerase ν (pol ν, encoded by the POLN gene, is an A-family DNA polymerase in vertebrates and some other animal lineages. Here we report an in-depth analysis of pol ν-defective mice and human cells. POLN is very weakly expressed in most tissues, with the highest relative expression in testis. We constructed multiple mouse models for Poln disruption and detected no anatomic abnormalities, alterations in lifespan, or changed causes of mortality. Mice with inactive Poln are fertile and have normal testis morphology. However, pol ν-disrupted mice have a modestly reduced crossover frequency at a meiotic recombination hot spot harboring insertion/deletion polymorphisms. These polymorphisms are suggested to generate a looped-out primer and a hairpin structure during recombination, substrates on which pol ν can operate. Pol ν-defective mice had no alteration in DNA end-joining during immunoglobulin class-switching, in contrast to animals defective in the related DNA polymerase θ (pol θ. We examined the response to DNA crosslinking agents, as purified pol ν has some ability to bypass major groove peptide adducts and residues of DNA crosslink repair. Inactivation of Poln in mouse embryonic fibroblasts did not alter cellular sensitivity to mitomycin C, cisplatin, or aldehydes. Depletion of POLN from human cells with shRNA or siRNA did not change cellular sensitivity to mitomycin C or alter the frequency of mitomycin C-induced radial chromosomes. Our results suggest a function of pol ν in meiotic homologous recombination in processing specific substrates. The restricted and more recent evolutionary appearance of pol ν (in comparison to pol θ supports such a specialized role.

  3. Generation of a Stable Transgenic Swine Model Expressing a Porcine Histone 2B-eGFP Fusion Protein for Cell Tracking and Chromosome Dynamics Studies.

    Science.gov (United States)

    Sper, Renan B; Koh, Sehwon; Zhang, Xia; Simpson, Sean; Collins, Bruce; Sommer, Jeff; Petters, Robert M; Caballero, Ignacio; Platt, Jeff L; Piedrahita, Jorge A

    2017-01-01

    Transgenic pigs have become an attractive research model in the field of translational research, regenerative medicine, and stem cell therapy due to their anatomic, genetic and physiological similarities with humans. The development of fluorescent proteins as molecular tags has allowed investigators to track cell migration and engraftment levels after transplantation. Here we describe the development of two transgenic pig models via SCNT expressing a fusion protein composed of eGFP and porcine Histone 2B (pH2B). This fusion protein is targeted to the nucleosomes resulting a nuclear/chromatin eGFP signal. The first model (I) was generated via random insertion of pH2B-eGFP driven by the CAG promoter (chicken beta actin promoter and rabbit Globin poly A; pCAG-pH2B-eGFP) and protected by human interferon-β matrix attachment regions (MARs). Despite the consistent, high, and ubiquitous expression of the fusion protein pH2B-eGFP in all tissues analyzed, two independently generated Model I transgenic lines developed neurodegenerative symptoms including Wallerian degeneration between 3-5 months of age, requiring euthanasia. A second transgenic model (II) was developed via CRISPR-Cas9 mediated homology-directed repair (HDR) of IRES-pH2B-eGFP into the endogenous β-actin (ACTB) locus. Model II transgenic animals showed ubiquitous expression of pH2B-eGFP on all tissues analyzed. Unlike the pCAG-pH2B-eGFP/MAR line, all Model II animals were healthy and multiple pregnancies have been established with progeny showing the expected Mendelian ratio for the transmission of the pH2B-eGFP. Expression of pH2B-eGFP was used to examine the timing of the maternal to zygotic transition after IVF, and to examine chromosome segregation of SCNT embryos. To our knowledge this is the first viable transgenic pig model with chromatin-associated eGFP allowing both cell tracking and the study of chromatin dynamics in a large animal model.

  4. Structural rearrangements of chromosome 15 satellites resulting in Prader-Willi syndrome suggest a complex mechanism for uniparental disomy

    Energy Technology Data Exchange (ETDEWEB)

    Toth-Fijel, S.; Gunter, K.; Olson, S. [Oregon Health Sciences Univ., Portland, OR (United States)] [and others

    1994-09-01

    We report two cases of PWS in which there was abnormal meiosis I segregation of chromosome 15 following a rare translocation event between the heteromorphic satellite regions of chromosomes 14 and 15 and an apparent meiotic recombination in the unstable region of 15q11.2. PWS and normal appearing chromosomes in case one prompted a chromosome 15 origin analysis. PCR analysis indicated maternal isodisomy for the long arm of chromosome. However, only one chromosome 15 had short arm heteromorphisms consistent with either paternal or maternal inheritance. VNTR DNA analysis and heteromorphism data suggest that a maternal de novo translocation between chromosome 14 and 15 occurred prior to meiosis I. This was followed by recombination between D15Z1 and D15S11 and subsequent meiosis I nondisjunction. Proband and maternal karyotype display a distamycin A-DAPI positive region on the chromosome 14 homolog involved in the translocation. Fluorescent in situ hybridization (FISH) analyses of ONCOR probes D15S11, SNRPN, D15S11 and GABRB 3 were normal, consistent with the molecular data. Case two received a Robertsonian translocation t(14;15)(p13;p13) of maternal origin. Chromosome analysis revealed a meiosis I error producing UPD. FISH analysis of the proband and parents showed normal hybridization of ONCOR probes D15Z1, D15S11, SNRPN, D15S10 and GABRB3. In both cases the PWS probands received a structurally altered chromosome 15 that had rearranged with chromosome 14 prior to meiosis. If proper meiotic segregation is dependent on the resolution of chiasmata and/or the binding to chromosome-specific spindle fibers, then it may be possible that rearrangements of pericentric or unstable regions of the genome disrupt normal disjunction and lead to uniparental disomy.

  5. Deciphering evolutionary strata on plant sex chromosomes and fungal mating-type chromosomes through compositional segmentation.

    Science.gov (United States)

    Pandey, Ravi S; Azad, Rajeev K

    2016-03-01

    Sex chromosomes have evolved from a pair of homologous autosomes which differentiated into sex determination systems, such as XY or ZW system, as a consequence of successive recombination suppression between the gametologous chromosomes. Identifying the regions of recombination suppression, namely, the "evolutionary strata", is central to understanding the history and dynamics of sex chromosome evolution. Evolution of sex chromosomes as a consequence of serial recombination suppressions is well-studied for mammals and birds, but not for plants, although 48 dioecious plants have already been reported. Only two plants Silene latifolia and papaya have been studied until now for the presence of evolutionary strata on their X chromosomes, made possible by the sequencing of sex-linked genes on both the X and Y chromosomes, which is a requirement of all current methods that determine stratum structure based on the comparison of gametologous sex chromosomes. To circumvent this limitation and detect strata even if only the sequence of sex chromosome in the homogametic sex (i.e. X or Z chromosome) is available, we have developed an integrated segmentation and clustering method. In application to gene sequences on the papaya X chromosome and protein-coding sequences on the S. latifolia X chromosome, our method could decipher all known evolutionary strata, as reported by previous studies. Our method, after validating on known strata on the papaya and S. latifolia X chromosome, was applied to the chromosome 19 of Populus trichocarpa, an incipient sex chromosome, deciphering two, yet unknown, evolutionary strata. In addition, we applied this approach to the recently sequenced sex chromosome V of the brown alga Ectocarpus sp. that has a haploid sex determination system (UV system) recovering the sex determining and pseudoautosomal regions, and then to the mating-type chromosomes of an anther-smut fungus Microbotryum lychnidis-dioicae predicting five strata in the non

  6. Rapid chromosome evolution in recently formed polyploids in Tragopogon (Asteraceae.

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    K Yoong Lim

    Full Text Available Polyploidy, frequently termed "whole genome duplication", is a major force in the evolution of many eukaryotes. Indeed, most angiosperm species have undergone at least one round of polyploidy in their evolutionary history. Despite enormous progress in our understanding of many aspects of polyploidy, we essentially have no information about the role of chromosome divergence in the establishment of young polyploid populations. Here we investigate synthetic lines and natural populations of two recently and recurrently formed allotetraploids Tragopogon mirus and T. miscellus (formed within the past 80 years to assess the role of aberrant meiosis in generating chromosomal/genomic diversity. That diversity is likely important in the formation, establishment and survival of polyploid populations and species.Applications of fluorescence in situ hybridisation (FISH to natural populations of T. mirus and T. miscellus suggest that chromosomal rearrangements and other chromosomal changes are common in both allotetraploids. We detected extensive chromosomal polymorphism between individuals and populations, including (i plants monosomic and trisomic for particular chromosomes (perhaps indicating compensatory trisomy, (ii intergenomic translocations and (iii variable sizes and expression patterns of individual ribosomal DNA (rDNA loci. We even observed karyotypic variation among sibling plants. Significantly, translocations, chromosome loss, and meiotic irregularities, including quadrivalent formation, were observed in synthetic (S(0 and S(1 generations polyploid lines. Our results not only provide a mechanism for chromosomal variation in natural populations, but also indicate that chromosomal changes occur rapidly following polyploidisation.These data shed new light on previous analyses of genome and transcriptome structures in de novo and establishing polyploid species. Crucially our results highlight the necessity of studying karyotypes in young (<150 years

  7. Novel meiotic miRNAs and indications for a role of phasiRNAs in meiosis

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    Stefanie eDukowic-Schulze

    2016-06-01

    Full Text Available Small RNAs (sRNA add additional layers to the regulation of gene expression, with siRNAs directing gene silencing at the DNA level by RdDM (RNA-directed DNA methylation, and miRNAs directing post-transcriptional regulation of specific target genes, mostly by mRNA cleavage. We used manually isolated male meiocytes from maize (Zea mays to investigate sRNA and DNA methylation landscapes during zygotene, an early stage of meiosis during which steps of meiotic recombination and synapsis of paired homologous chromosomes take place. We discovered two novel miRNAs from meiocytes, and identified putative target genes. Furthermore, we detected abundant phasiRNAs of 21 nt and 24 nt length. PhasiRNAs are phased small RNAs which occur in 21 nt or 24 nt intervals, at a few hundred loci, specifically in male reproductive tissues in grasses. So far, the function of phasiRNAs remained elusive. Data from isolated meiocytes now revealed elevated DNA methylation at phasiRNA loci, especially in the CHH context, suggesting a role for phasiRNAs in cis DNA methylation. In addition, we consider a role of these phasiRNAs in chromatin remodeling/ dynamics during meiosis. However, this is not well supported yet and will need more additional data. Here, we only lay out the idea due to other relevant literature and our additional observation of a peculiar GC content pattern at phasiRNA loci. Chromatin remodeling is also indicated by the discovery that histone genes were enriched for sRNA of 22 nt length. Taken together, we gained clues that lead us to hypothesize sRNA-driven DNA methylation and possibly chromatin remodeling during male meiosis in the monocot maize which is in line with and extends previous knowledge.

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

    Science.gov (United States)

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

    2015-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Hongzhou An

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

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

    Directory of Open Access Journals (Sweden)

    Jun Takagi

    2013-10-01

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

  11. Does MAX open up a new avenue for meiotic research?

    Science.gov (United States)

    Suzuki, Ayumu; Hirasaki, Masataka; Okuda, Akihiko

    2017-02-01

    Meiosis is a central event of sexual reproduction. Like somatic cells, germ cells conduct mitosis to increase their cell number, but unlike somatic cells, germ cells switch their cell division mode from mitosis to meiosis at a certain point in gametogenesis. However, the molecular basis of this switch remains elusive. In this review article, we give an overview of the onset of mammalian meiosis, including our recent finding that MYC Associated Factor X (MAX) prevents ectopic and precocious meiosis in embryonic stem cells (ESCs) and germ cells, respectively. We present a hypothetical model of a MAX-centered molecular network that regulates meiotic entry in mammals and propose that inducible Max knockout ESCs provide an excellent platform for exploring the molecular mechanisms of meiosis initiation, while excluding other aspects of gametogenesis. © 2017 Japanese Society of Developmental Biologists.

  12. Phosphorylation of the Ndc80 complex protein, HEC1, by Nek2 kinase modulates chromosome alignment and signaling of the spindle assembly checkpoint.

    Science.gov (United States)

    Wei, Randy; Ngo, Bryan; Wu, Guikai; Lee, Wen-Hwa

    2011-10-01

    The spindle assemble checkpoint (SAC) is critical for accurate chromosome segregation. Hec1 contributes to chromosome segregation in part by mediating SAC signaling and chromosome alignment. However, the molecular mechanism by which Hec1 modulates checkpoint signaling and alignment remains poorly understood. We found that Hec1 serine 165 (S165) is preferentially phosphorylated at kinetochores. Phosphorylated Hec1 serine 165 (pS165) specifically localized to kinetochores of misaligned chromosomes, showing a spatiotemporal distribution characteristic of SAC molecules. Expressing an RNA interference (RNAi)-resistant S165A mutant in Hec1-depleted cells permitted normal progression to metaphase, but accelerated the metaphase-to-anaphase transition. The S165A cells were defective in Mad1 and Mad2 localization to kinetochores, regardless of attachment status. These cells often entered anaphase with lagging chromosomes and elicited increased segregation errors and cell death. In contrast, expressing S165E mutant in Hec1-depleted cells triggered defective chromosome alignment and severe mitotic arrest associated with increased Mad1/Mad2 signals at prometaphase kinetochores. A small portion of S165E cells eventually bypassed the SAC but showed severe segregation errors. Nek2 is the primary kinase responsible for kinetochore pS165, while PP1 phosphatase may dephosphorylate pS165 during SAC silencing. Taken together, these results suggest that modifications of Hec1 S165 serve as an important mechanism in modulating SAC signaling and chromosome alignment.

  13. Sequential Immunofluorescent Light Microscopy and Electron Microscopy of Recombination Nodules During Meiotic Prophase I.

    Science.gov (United States)

    Anderson, Lorinda K

    2017-01-01

    Immunolocalization using either fluorescence for light microscopy (LM) or gold particles for electron microscopy (EM) has become a common tool to pinpoint proteins involved in recombination during meiotic prophase. Each method has its advantages and disadvantages. For example, LM immunofluorescence is comparatively easier and higher throughput compared to immunogold EM localization. In addition, immunofluorescence has the advantages that a faint signal can often be enhanced by longer exposure times and colocalization using two (or more) probes with different absorbance and emission spectra is straightforward. However, immunofluorescence is not useful if the object of interest does not label with an antibody probe and is below the resolution of the LM. In comparison, immunogold EM localization is higher resolution than immunofluorescent LM localization, and individual nuclear structures, such as recombination nodules, can be identified by EM regardless of whether they are labeled or not. However, immunogold localization has other disadvantages including comparatively low signal-to-noise ratios, more difficult colocalization using gold particles of different sizes, and the inability to evaluate labeling efficiency before examining the sample using EM (a more expensive and time-consuming technique than LM). Here we describe a method that takes advantage of the good points of both immunofluorescent LM and EM to analyze two classes of late recombination nodules (RNs), only one of which labels with antibodies to MLH1 protein, a marker of crossovers. The method can be used readily with other antibodies to analyze early recombination nodules or other prophase I structures.

  14. X chromosome and suicide.

    Science.gov (United States)

    Fiori, L M; Zouk, H; Himmelman, C; Turecki, G

    2011-02-01

    Suicide completion rates are significantly higher in males than females in most societies. Although gender differences in suicide rates have been partially explained by environmental and behavioral factors, it is possible that genetic factors, through differential expression between genders, may also help explain gender moderation of suicide risk. This study investigated X-linked genes in suicide completers using a two-step strategy. We first took advantage of the genetic structure of the French-Canadian population and genotyped 722 unrelated French-Canadian male subjects, of whom 333 were suicide completers and 389 were non-suicide controls, using a panel of 37 microsatellite markers spanning the entire X chromosome. Nine haplotype windows and several individual markers were associated with suicide. Significant results aggregated primarily in two regions, one in the long arm and another in the short arm of chromosome X, limited by markers DXS8051 and DXS8102, and DXS1001 and DXS8106, respectively. The second stage of the study investigated differential brain expression of genes mapping to associated regions in Brodmann areas 8/9, 11, 44 and 46, in an independent sample of suicide completers and controls. Six genes within these regions, Rho GTPase-activating protein 6, adaptor-related protein complex 1 sigma 2 subunit, glycoprotein M6B, ribosomal protein S6 kinase 90  kDa polypeptide 3, spermidine/spermine N(1)-acetyltransferase 1 and THO complex 2, were found to be differentially expressed in suicide completers.

  15. Functional conservation of the pre-sensor one beta-finger hairpin (PS1-hp) structures in mini-chromosome maintenance proteins of Saccharomyces cerevisiae and archaea.

    Science.gov (United States)

    Ramey, Christopher J; Sclafani, Robert A

    2014-05-28

    Mini-chromosome maintenance (MCM) proteins form complexes that are required for DNA replication and are highly conserved throughout evolution. The replicative helicase of eukaryotic organisms is composed of the six paralogs MCM2-7, which form a heterohexameric ring structure. In contrast, the structure of the archaean replicative MCM helicase is a single Mcm protein that forms a homohexameric complex. Atomic structures of archaeal MCMs have identified multiple beta-finger structures in Mcm proteins whose in vivo function is unknown. In the present study, we have investigated the physiological role of the pre-sensor 1 beta-hairpin (PS1-hp) beta-fingers of Saccharomyces cerevisiae Mcm4p and Mcm5p in DNA replication initiation and elongation in vivo. The PS1-hp beta-finger mutant of Mcm5p (mcm5-HAT K506A::URA3) has a growth defect at both 18° and 37°. Mutation of the Mcm4p PS1-hp beta-finger (mcm4-HA K658A::TRP1) does not have a growth defect, indicating different functional contributions of the PS1-hp beta-finger structures of different MCM helicase subunits. Both Mcm4p and Mcm5p PS1-hp beta-finger mutants can coimmunoprecipitate Mcm2p, indicating the formation of the hexameric MCM helicase complex. Both PS1-hp beta-finger mutants have a plasmid loss phenotype that is suppressible by origin dosage, indicating a defective replication initiation. Surprisingly, a defect in the binding of PS1-hp MCM mutants to origins of DNA replication was not found by chromatin immunoprecipitation, suggesting a novel interpretation in which the defect is in a subsequent step of DNA strand separation by the MCM helicase. The double mutant mcm4-HA K658A::TRP1 mcm5-HAT K506A::URA3 is lethal, displaying a terminal MCM mutant phenotype of large budded cells. Copyright © 2014 Ramey and Sclafani.

  16. GSK-3 inhibitors induce chromosome instability

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    Staples Oliver D

    2007-08-01

    Full Text Available Abstract Background Several mechanisms operate during mitosis to ensure accurate chromosome segregation. However, during tumour evolution these mechanisms go awry resulting in chromosome instability. While several lines of evidence suggest that mutations in adenomatous polyposis coli (APC may promote chromosome instability, at least in colon cancer, the underlying mechanisms remain unclear. Here, we turn our attention to GSK-3 – a protein kinase, which in concert with APC, targets β-catenin for proteolysis – and ask whether GSK-3 is required for accurate chromosome segregation. Results To probe the role of GSK-3 in mitosis, we inhibited GSK-3 kinase activity in cells using a panel of small molecule inhibitors, including SB-415286, AR-A014418, 1-Azakenpaullone and CHIR99021. Analysis of synchronised HeLa cells shows that GSK-3 inhibitors do not prevent G1/S progression or cell division. They do, however, significantly delay mitotic exit, largely because inhibitor-treated cells have difficulty aligning all their chromosomes. Although bipolar spindles form and the majority of chromosomes biorient, one or more chromosomes often remain mono-oriented near the spindle poles. Despite a prolonged mitotic delay, anaphase frequently initiates without the last chromosome aligning, resulting in chromosome non-disjunction. To rule out the possibility of "off-target" effects, we also used RNA interference to selectively repress GSK-3β. Cells deficient for GSK-3β exhibit a similar chromosome alignment defect, with chromosomes clustered near the spindle poles. GSK-3β repression also results in cells accumulating micronuclei, a hallmark of chromosome missegregation. Conclusion Thus, not only do our observations indicate a role for GSK-3 in accurate chromosome segregation, but they also raise the possibility that, if used as therapeutic agents, GSK-3 inhibitors may induce unwanted side effects by inducing chromosome instability.

  17. Differential expression and sex chromosome association of CHD3/4 and CHD5 during spermatogenesis.

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    Judith W Bergs

    Full Text Available ATP-dependent nucleosome remodelers of the CHD family play important roles in chromatin regulation during development and differentiation. The ubiquitously expressed CHD3 and CHD4 proteins are essential for stem cell function and serve to orchestrate gene expression in different developmental settings. By contrast, the closely related CHD5 is predominantly expressed in neural tissue and its role is believed to be restricted to neural differentiation. Indeed, loss of CHD5 contributes to neuroblastoma. In this study, we first demonstrate that CHD5 is a nucleosome-stimulated ATPase. We then compare CHD3/4 and CHD5 expression in mouse brain and show that CHD5 expression is restricted to a subset of cortical and hippocampal neurons whereas CHD3/4 expression is more widespread. We also uncover high levels of CHD5 expression in testis. CHD5 is transiently expressed in differentiating germ cells. Expression is first detected in nuclei of post-meiotic round spermatids, reaches a maximum in stage VIII spermatids and then falls to undetectable levels in stage IX spermatids. Surprisingly, CHD3/4 and CHD5 show complementary expression patterns during spermatogenesis with CHD3/4 levels progressively decreasing as CHD5 expression increases. In spermatocytes, CHD3/4 localizes to the pseudoautosomal region, the X centromeric region and then spreads into the XY body chromatin. In postmeiotic cells, CHD5 colocalises with macroH2A1.2 in association with centromeres and part of the Y chromosome. The subnuclear localisations of CHD4 and CHD5 suggest specific roles in regulation of sex chromosome chromatin and pericentromeric chromatin structure prior to the histone-protamine switch.

  18. Meiotic behavior of Adesmia DC. (Leguminosae-Faboideae species native to Rio Grande do Sul, Brazil

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    Coelho Liliana Gressler May

    1998-01-01

    Full Text Available Meiotic behavior in Adesmia DC. is described for the first time. The study encompassed twelve populations of seven Adesmia DC. species native to Rio Grande do Sul, Brazil. Populations with 2n = 2x = 20 are A. securigerifolia 9615, A. riograndensis 9590 (subnudae, A. latifolia 1568, 1775, 15025, A. bicolor JB-UFSM, A. incana var. incana 9636, 10288, A. punctata var. hilariana 6885, 10812, and A. tristis 10757. A. incana var. incana 9637 is a tetraploid with 2n = 4x = 40. The material was stained with 1% acetic orcein. The meiotic behavior of the populations studied was considered normal. The meiotic index (MI and the estimates of pollen grain viability were above 95%, except for A. latifolia 1568 (MI = 89%. The present data indicate that these plants are meiotically stable and potentially fertile, apparently with no problems for use in programs of selection, crossing and viable seed production.

  19. Inherited variants in the inner centromere protein (INCENP) gene of the chromosomal passenger complex contribute to the susceptibility of ER-negative breast cancer

    DEFF Research Database (Denmark)

    Kabisch, Maria; Lorenzo Bermejo, Justo; Dünnebier, Thomas

    2015-01-01

    The chromosomal passenger complex (CPC) plays a pivotal role in the regulation of cell division. Therefore, inherited CPC variability could influence tumor development. The present candidate gene approach investigates the relationship between single nucleotide polymorphisms (SNPs) in genes encodi...

  20. Chromosome sites play dual roles to establish homologous synapsisduring meiosis in C. elegans

    Energy Technology Data Exchange (ETDEWEB)

    MacQueen, Amy J.; Phillips, Carolyn M.; Bhalla, Needhi; Weiser,Pinky; Villeneuve, Anne M.; Dernburg, Abby F.

    2005-06-05

    required for accurate segregation of homologous chromosomesduring meiosisin C. elegans. We find that these sites play two distinctroles that contribute to proper segregation. Chromosomes lacking PCsusually fail to synapse and also lack a synapsis-independentstabilization activity. The presence of a PC on justone copy of achromosome pair promotes synapsis but does not supportsynapsis-independent pairing stabilization, indicating that thesefunctions are separable. Once initiated, synapsis is highly processive,even between non homologous chromosomes of disparate lengths, elucidatinghow translocations suppress meiotic recombination in C. elegans. Thesefindings suggest a multistep pathway for chromosome synapsis in which PCsimpart selectivity and efficiency through a kinetic proofreadingmechanism. We speculate that concentration of these activities at oneregion per chromosome may have co-evolved with the loss of a pointcentromere to safeguard karyotype stability.

  1. Effects of antitopoisomerase drugs on chromosome recombinations and segregation in grasshopper

    Energy Technology Data Exchange (ETDEWEB)

    Palitti, F. [Universita degli Studi della Tuscia, Via San Camillo de Lellius (Italy); Motta, S.; Grazioso, C.; Pisano, M.C. [Universita di Catania (Italy)

    1993-12-31

    The role of different cellular functions which are required for the production of euploid cells can be studied through the use of mutants that are defective in the control of both the meiotic and mitotic cell cycle or through the use of compounds which interface with the various cellular targets which have a role in the segregation of chromosomes. The role of the achromatic part of the mitotic apparatus in the production of aneuploidy is well recognized. Substantial progress has been made in understanding the role of the chromatic part, for example, there are observations that disturbances in the normal {open_quotes}metabolism{close_quotes} of the chromosomes (i.e. chromosome condensation, defective DNA repair or recombination) can affect chromosome segregation. Between the processes of both meiosis and mitosis that lead to nuclear division there are, however, important differences.

  2. Chromosome homogeneity in populations of Triatoma brasiliensis Neiva 1911 (Hemiptera - Reduviidae - Triatominae

    Directory of Open Access Journals (Sweden)

    Panzera Francisco

    2000-01-01

    Full Text Available Triatoma brasiliensis is the most important vector of Chagas disease in the semiarid zone of the Northeast of Brazil. Several authors have reported the occurrence of four chromatic patterns with morphological, ecological, and genetic differences. In order to determine the existence of cytogenetic differentiation between these chromatic forms, we analyzed their karyotypes and the chromosome behavior during the male meiotic process. Triatoma brasiliensis shows distinct and specific chromosome characteristics, which differ from those observed in all other triatomine species. However, no cytogenetic differences were observed between the four chromatic forms of T. brasiliensis. The lack of chromosome differentiation among them could indicate that the populations of this species are in a process of differentiation that does not involve their chromosomal organization.

  3. Sex Chromosome-wide Transcriptional Suppression and Compensatory Cis-Regulatory Evolution Mediate Gene Expression in the Drosophila Male Germline.

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    Emily L Landeen

    2016-07-01

    Full Text Available The evolution of heteromorphic sex chromosomes has repeatedly resulted in the evolution of sex chromosome-specific forms of regulation, including sex chromosome dosage compensation in the soma and meiotic sex chromosome inactivation in the germline. In the male germline of Drosophila melanogaster, a novel but poorly understood form of sex chromosome-specific transcriptional regulation occurs that is distinct from canonical sex chromosome dosage compensation or meiotic inactivation. Previous work shows that expression of reporter genes driven by testis-specific promoters is considerably lower-approximately 3-fold or more-for transgenes inserted into X chromosome versus autosome locations. Here we characterize this transcriptional suppression of X-linked genes in the male germline and its evolutionary consequences. Using transgenes and transpositions, we show that most endogenous X-linked genes, not just testis-specific ones, are transcriptionally suppressed several-fold specifically in the Drosophila male germline. In wild-type testes, this sex chromosome-wide transcriptional suppression is generally undetectable, being effectively compensated by the gene-by-gene evolutionary recruitment of strong promoters on the X chromosome. We identify and experimentally validate a promoter element sequence motif that is enriched upstream of the transcription start sites of hundreds of testis-expressed genes; evolutionarily conserved across species; associated with strong gene expression levels in testes; and overrepresented on the X chromosome. These findings show that the expression of X-linked genes in the Drosophila testes reflects a balance between chromosome-wide epigenetic transcriptional suppression and long-term compensatory adaptation by sex-linked genes. Our results have broad implications for the evolution of gene expression in the Drosophila male germline and for genome evolution.

  4. Chromosome engineering: power tools for plant genetics.

    Science.gov (United States)

    Chan, Simon W L

    2010-12-01

    The term "chromosome engineering" describes technologies in which chromosomes are manipulated to change their mode of genetic inheritance. This review examines recent innovations in chromosome engineering that promise to greatly increase the efficiency of plant breeding. Haploid Arabidopsis thaliana have been produced by altering the kinetochore protein CENH3, yielding instant homozygous lines. Haploid production will facilitate reverse breeding, a method that downregulates recombination to ensure progeny contain intact parental chromosomes. Another chromosome engineering success is the conversion of meiosis into mitosis, which produces diploid gametes that are clones of the parent plant. This is a key step in apomixis (asexual reproduction through seeds) and could help to preserve hybrid vigor in the future. New homologous recombination methods in plants will potentiate many chromosome engineering applications. Copyright © 2010 Elsevier Ltd. All rights reserved.

  5. Chromosomal contact permits transcription between coregulated genes

    CSIR Research Space (South Africa)

    Fanucchi, Stephanie

    2013-10-01

    Full Text Available Transcription of coregulated genes occurs in the context of long-range chromosomal contacts that form multigene complexes. Such contacts and transcription are lost in knockout studies of transcription factors and structural chromatin proteins...

  6. Sexual dimorphism in white campion: complex control of carpel number is revealed by Y chromosome deletions

    International Nuclear Information System (INIS)

    Lardon, A.; Georgiev, S.; Aghmir, A.; Le Merrer, G.; Negrutiu, I.

    1999-01-01

    Sexual dimorphism in the dioecious plant white campion (Silene latifolia = Melandrium album) is under the control of two main regions on the Y chromosome. One such region, encoding the gynoecium-suppressing function (GSF), is responsible for the arrest of carpel initiation in male flowers. To generate chromosomal deletions, we used pollen irradiation in male plants to produce hermaphroditic mutants (bsx mutants) in which carpel development was restored. The mutants resulted from alterations in at least two GSF chromosomal regions, one autosomal and one located on the distal half of the (p)-arm of the Y chromosome. The two mutations affected carpel development independently, each mutation showing incomplete penetrance and variegation, albeit at significantly different levels. During successive meiotic generations, a progressive increase in penetrance and a reduction in variegation levels were observed and quantified at the level of the Y-linked GSF (GSF-Y). Possible mechanisms are proposed to explain the behavior of the bsx mutations: epigenetic regulation or/and second-site mutation of modifier genes. In addition, studies on the inheritance of the hermaphroditic trait showed that, unlike wild-type Y chromosomes, deleted Y chromosomes can be transmitted through both the male and the female lines. Altogether, these findings bring experimental support, on the one hand, to the existence on the Y chromosome of genic meiotic drive function(s) and, on the other hand, to models that consider that dioecy evolved through multiple mutation events. As such, the GSF is actually a system containing more than one locus and whose primary component is located on the Y chromosome

  7. The CYCLIN-A CYCA1;2/TAM Is Required for the Meiosis I to Meiosis II Transition and Cooperates with OSD1 for the Prophase to First Meiotic Division Transition

    OpenAIRE

    d'Erfurth, Isabelle; Cromer, Laurence; Jolivet, Sylvie; Girard, Chlo?; Horlow, Christine; Sun, Yujin; To, Jennifer P. C.; Berchowitz, Luke E.; Copenhaver, Gregory P.; Mercier, Raphael

    2010-01-01

    Meiosis halves the chromosome number because its two divisions follow a single round of DNA replication. This process involves two cell transitions, the transition from prophase to the first meiotic division (meiosis I) and the unique meiosis I to meiosis II transition. We show here that the A-type cyclin CYCA1;2/TAM plays a major role in both transitions in Arabidopsis. A series of tam mutants failed to enter meiosis II and thus produced diploid spores and functional diploid gametes. These d...

  8. Homologous chromosome pairing and recombination during meiosis in wild type and synaptic mutants of tomato = Homologe chomosoomparing en recombinatie tijdens de meiose van wild type en synaptische mutanten van de tomaat

    NARCIS (Netherlands)

    Havekes, F.W.J.

    1999-01-01

    This thesis presents the results of a cytogenetic investigation of meiotic prophase I stages in tomato (Lycopersicon esculentum). The aim of this study was to analyse the relationships between chromosome pairing, and formation of recombination nudules and chiasmata. Tomato was chosen as

  9. Guanine nucleotides in the meiotic maturation of starfish oocytes: regulation of the actin cytoskeleton and of Ca(2+ signaling.

    Directory of Open Access Journals (Sweden)

    Keiichiro Kyozuka

    Full Text Available BACKGROUND: Starfish oocytes are arrested at the first prophase of meiosis until they are stimulated by 1-methyladenine (1-MA. The two most immediate responses to the maturation-inducing hormone are the quick release of intracellular Ca(2+ and the accelerated changes of the actin cytoskeleton in the cortex. Compared with the later events of oocyte maturation such as germinal vesicle breakdown, the molecular mechanisms underlying the early events involving Ca(2+ signaling and actin changes are poorly understood. Herein, we have studied the roles of G-proteins in the early stage of meiotic maturation. METHODOLOGY/PRINCIPAL FINDINGS: By microinjecting starfish oocytes with nonhydrolyzable nucleotides that stabilize either active (GTPgammaS or inactive (GDPbetaS forms of G-proteins, we have demonstrated that: i GTPgammaS induces Ca(2+ release that mimics the effect of 1-MA; ii GDPbetaS completely blocks 1-MA-induced Ca(2+; iii GDPbetaS has little effect on the amplitude of the Ca(2+ peak, but significantly expedites the initial Ca(2+ waves induced by InsP(3 photoactivation, iv GDPbetaS induces unexpectedly striking modification of the cortical actin networks, suggesting a link between the cytoskeletal change and the modulation of the Ca(2+ release kinetics; v alteration of cortical actin networks with jasplakinolide, GDPbetaS, or actinase E, all led to significant changes of 1-MA-induced Ca(2+ signaling. CONCLUSIONS/SIGNIFICANCE: Taken together, these results indicate that G-proteins are implicated in the early events of meiotic maturation and support our previous proposal that the dynamic change of the actin cytoskeleton may play a regulatory role in modulating intracellular Ca(2+ release.

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

    International Nuclear Information System (INIS)

    Schmalzing, G.; Eckard, P.; Kroener, S.P.; Passow, H.

    1990-01-01

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

  11. Mre11 Deficiency in Arabidopsis Is Associated with Chromosomal Instability in Somatic Cells and Spo11-Dependent Genome Fragmentation during Meiosis

    Science.gov (United States)

    Puizina, Jasna; Siroky, Jiri; Mokros, Petr; Schweizer, Dieter; Riha, Karel

    2004-01-01

    The Mre11/Rad50/Nbs1 complex is involved in many aspects of chromosome metabolism. Aberrant function of the complex is associated with defects in the DNA checkpoint, double-strand break repair, meiosis, and telomere maintenance. In this article, we report the consequences of Mre11 dysfunction for the stability of mitotic and meiotic chromosomes in Arabidopsis thaliana. Although plants homozygous for a T-DNA insertion in a conserved region of the MRE11 gene are viable, they exhibit growth defects and are infertile. Analysis of mitotic chromosomes prepared from the mutant plants revealed abundant dicentric chromosomes and chromosomal fragments. Fluorescence in situ hybridization showed that anaphase bridges are often formed by homologous chromosome arms. The frequency of chromosome fusions was not reduced in mre11 ku70 double mutants, suggesting that plants possess DNA end-joining activities independent of the Ku70/80 and Mre11 complexes. Cytogenetic examination of pollen mother cells revealed massive chromosome fragmentation and the absence of synapsis in the initial stages of meiosis. The fragmentation was substantially suppressed in mre11 spo11-1 double mutants, indicating that Mre11 is required for repair but not for the induction of Spo11-dependent meiotic DNA breaks in Arabidopsis. PMID:15258261

  12. NEUROD2 and NEUROD3 genes map to human chromosomes 17q12 and 5q23-q31 and mouse chromosomes 11 and 13, respectively

    Energy Technology Data Exchange (ETDEWEB)

    Tamimi, R.M.; Montgomery-Dyer, K.; Tapscott, S.J. [Fred Hutchinson Cancer Research Center, Seattle, WA (United States)] [and others

    1997-03-01

    NEUROD2 and NEUROD3 are transcription factors involved in neurogenesis that are related to the basic helix-loop-helix protein NEUROD. NEUROD2 maps to human chromosome 17q12 and mouse chromosome 11. NEUROD3 maps to human chromosome 5q23-q31 and mouse chromosome 13. 16 refs., 2 figs.

  13. Microtus oeconomus (Rodentia), a useful mammal for studying the induction of sex-chromosome nondisjunction and diploid gametes in male germ cells

    Energy Technology Data Exchange (ETDEWEB)

    Tates, A.D.

    1979-08-01

    A method is described for the detection of sex-chromosome nondisjunction and diploid spermatids in male germ cells of the field vole Microtus oeconomus. The method is based on the unique distribution pattern of heterochromatin in Microtus cells, which makes it possible to identify X and Y chromosomes in early spermatids with a simple C-banding procedure. With the Microtus system it has now been demonstrated that radiation of spermatocyte stages with doses of 50, 100 and 200 R results in a higher frequency of sex chromosome nondisjunction and of diploid gametes. Both types of aberrant gametes can be produced during the first and second meiotic division.

  14. Recombinant chromosome 7 in a mosaic 45,X/47,XXX patient.

    Science.gov (United States)

    Tirado, Carlos A; Gotway, Garrett; Torgbe, Emmanuel; Iyer, Santha; Dallaire, Stephanie; Appleberry, Taylor; Suterwala, Mohamed; Garcia, Rolando; Valdez, Federico; Patel, Sangeeta; Koduru, Prasad

    2012-01-01

    Individuals with pericentric inversions are at risk for producing offspring with chromosomal gains and losses, while those carrying paracentric inversions usually produce unviable gametes [Madan, 1995]. In this current study, we present a newborn with dysmorphic features and malformations, whose karyotype showed an abnormal copy of chromomosome 7 described at first as add(7)(q32) as well as mos 45,X/47,XXX. Array comparative genomic hybridization (CGH) revealed an interstitial deletion in the long arm of chromosome 7 involving bands q35 to q36.3 but retaining the 7q subtelomere. The patient's deletion is believed to be due to meiotic recombination in the inversion loop in the phenotypically normal father who seems to carry two paracentric inversions in the long arm of chromosome 7, which was described as rec(7)(7pter- > q35::q36.3- > 7qter)pat. The abnormal copy of chromosome 7 in the father has been described as: der(7)(7pter- > q22.1::q36.3- > q35::q22.1- > q35::q36.3- > 7qter). This is a unique karyotype that to our knowledge has not been previously reported in the literature and predisposes to meiotic recombination that can result in deletions or duplications of 7q35-36. Copyright © 2011 Wiley Periodicals, Inc.

  15. Induction of congenital malformations in the offspring of male mice treated with X-rays at pre-meiotic and post-meiotic stages

    International Nuclear Information System (INIS)

    Kirk, K.M.; Lyon, M.F.

    1984-01-01

    The induction of congenital malformations among the offspring of male mice treated with X-rays at pre-meiotic and post-meiotic stages has been studied in two experiments. Firstly, animals were exposed to varying doses of X-rays and mated at various time intervals, so as to sample spermatozoa, spermatids and spermatogonial stem cells. In the second experiment, only treated spermatogonial stem cells were sampled. One group of males was given a single dose, a second group a fractionated dose and a third group was left unexposed. In the first experiment, induced post-implantation dominant lethality increased with dose, and was highest in week 3, in line with the known greater radiosensitivity of the early spermatid stage. Preimplantation loss also increased with dose and was highest in week 3. There was no clear induction of either pre-implantation or post-implantation loss at spermatogonial stem cell stages. There was a clear induction of congenital malformations at post-meiotic stages. At the two highest doses the early spermatids (15-21 days) appeared more sensitive than spermatozoa, and at this stage the incidence of malformations increased with dose. Expt. 2 showed a statistically significant induction of malformations at both dose levels. The relative sensitivities of male stem cells, post-meiotic stages and mature oocytes to the induction of congenital malformations were reasonably similar to their sensitivities for specific-locus mutations, except that the expected enhancing effect of the fractionation regime used was not seen. (Auth.)

  16. The Precarious Prokaryotic Chromosome

    Science.gov (United States)

    2014-01-01

    Evolutionary selection for optimal genome preservation, replication, and expression should yield similar chromosome organizations in any type of cells. And yet, the chromosome organization is surprisingly different between eukaryotes and prokaryotes. The nuclear versus cytoplasmic accommodation of genetic material accounts for the distinct eukaryotic and prokaryotic modes of genome evolution, but it falls short of explaining the differences in the chromosome organization. I propose that the two distinct ways to organize chromosomes are driven by the differences between the global-consecutive chromosome cycle of eukaryotes and the local-concurrent chromosome cycle of prokaryotes. Specifically, progressive chromosome segregation in prokaryotes demands a single duplicon per chromosome, while other “precarious” features of the prokaryotic chromosomes can be viewed as compensations for this severe restriction. PMID:24633873

  17. B chromosome prevalence and physical mapping of 18S rDNA and H4 histone sites in the grasshopper Xyleus discoideus angulatus (Romaleidae).

    Science.gov (United States)

    Machado, C B; Silva Neto, L C; Loreto, V; Souza, M J

    2014-03-26

    We sampled 11 natural populations of the grasshopper Xyleus discoideus angulatus in Northeastern Brazil to analyze B chromosome frequency and meiotic behavior. We observed a single large B chromosome, resembling the X chromosome, in 29 of the 402 specimens. Eight of the 11 populations had B chromosomes, with a rather broad geographical distribution, suggesting that this is an ancient polymorphism; significant differences were observed in B chromosome prevalence among the populations. Presence of the B chromosome was associated with increased frequency of macrospermatids. Fluorescent in situ hybridization revealed 18S rDNA sites in the pericentromeric regions of the X and L3 chromosomes, although some populations had an additional locus on the M4 chromosome. No variation was found for chromosome location of H4 histone genes, which were always observed in paracentromeric regions of the L2, M4 and X chromosomes, a rather unusual location compared to locations known from the families Acrididae and Proscopiidae. These B chromosomes lacked these two kinds of repetitive DNA, at least in amounts that can be visualized by fluorescent in situ hybridization, suggesting that these B chromosomes did not originate from any of the four chromosomes carrying rDNA or H4 histone genes.

  18. Genomic structures of the kW1 loci on the Z and W chromosomes in ratite birds: structural changes at an early stage of W chromosome differentiation.

    Science.gov (United States)

    Ishijima, Junko; Uno, Yoshinobu; Nishida, Chizuko; Matsuda, Yoichi

    2014-01-01

    The W chromosome of ratite birds shows minimal morphological differentiation and retains homology of genetic linkage and gene order with a substantial stretch of the Z chromosome; however, the molecular structure in the differentiated region is still not well known. The kW1 sequence was isolated from the kiwi as a W-specific DNA marker for PCR-based molecular sexing of ratite birds. In ratite W chromosomes, this sequence commonly contains a ∼200-bp deletion. To characterize the very early event of avian sex chromosome differentiation, we performed molecular cytogenetic analyses of kW1 and its flanking sequences in paleognathous and neognathous birds and reptiles. Female-specific repeats were found in the kW1-flanking sequence of the cassowary (Casuarius casuarius), and the repeats have been amplified in the pericentromeric region of the W chromosomes of ratites, which may have resulted from the cessation of meiotic recombination between the Z and W chromosomes at an early stage of sex chromosome differentiation. The presence of the kW1 sequence in neognathous birds and a crocodilian species suggests that the kW1 sequence was present in the ancestral genome of Archosauria; however, it disappeared in other reptilian taxa and several lineages of neognathous birds. © 2014 S. Karger AG, Basel.

  19. Human embryonic stem cells as models for aneuploid chromosomal syndromes.

    Science.gov (United States)

    Biancotti, Juan-Carlos; Narwani, Kavita; Buehler, Nicole; Mandefro, Berhan; Golan-Lev, Tamar; Yanuka, Ofra; Clark, Amander; Hill, David; Benvenisty, Nissim; Lavon, Neta

    2010-09-01

    Syndromes caused by chromosomal aneuploidies are widely recognized genetic disorders in humans and often lead to spontaneous miscarriage. Preimplantation genetic screening is used to detect chromosomal aneuploidies in early embryos. Our aim was to derive aneuploid human embryonic stem cell (hESC) lines that may serve as models for human syndromes caused by aneuploidies. We have established 25 hESC lines from blastocysts diagnosed as aneuploid on day 3 of their in vitro development. The hESC lines exhibited morphology and expressed markers typical of hESCs. They demonstrated long-term proliferation capacity and pluripotent differentiation. Karyotype analysis revealed that two-third of the cell lines carry a normal euploid karyotype, while one-third remained aneuploid throughout the derivation, resulting in eight hESC lines carrying either trisomy 13 (Patau syndrome), 16, 17, 21 (Down syndrome), X (Triple X syndrome), or monosomy X (Turner syndrome). On the basis of the level of single nucleotide polymorphism heterozygosity in the aneuploid chromosomes, we determined whether the aneuploidy originated from meiotic or mitotic chromosomal nondisjunction. Gene expression profiles of the trisomic cell lines suggested that all three chromosomes are actively transcribed. Our analysis allowed us to determine which tissues are most affected by the presence of a third copy of either chromosome 13, 16, 17 or 21 and highlighted the effects of trisomies on embryonic development. The results presented here suggest that aneuploid embryos can serve as an alternative source for either normal euploid or aneuploid hESC lines, which represent an invaluable tool to study developmental aspects of chromosomal abnormalities in humans.

  20. Sequencing of Single Pollen Nuclei Reveals Meiotic Recombination Events at Megabase Resolution and Circumvents Segregation Distortion Caused by Postmeiotic Processes

    Directory of Open Access Journals (Sweden)

    Steven Dreissig

    2017-09-01

    Full Text Available Meiotic recombination is a fundamental mechanism to generate novel allelic combinations which can be harnessed by breeders to achieve crop improvement. The recombination landscape of many crop species, including the major crop barley, is characterized by a dearth of recombination in 65% of the genome. In addition, segregation distortion caused by selection on genetically linked loci is a frequent and undesirable phenomenon in double haploid populations which hampers genetic mapping and breeding. Here, we present an approach to directly investigate recombination at the DNA sequence level by combining flow-sorting of haploid pollen nuclei of barley with single-cell genome sequencing. We confirm the skewed distribution of recombination events toward distal chromosomal regions at megabase resolution and show that segregation distortion is almost absent if directly measured in pollen. Furthermore, we show a bimodal distribution of inter-crossover distances, which supports the existence of two classes of crossovers which are sensitive or less sensitive to physical interference. We conclude that single pollen nuclei sequencing is an approach capable of revealing recombination patterns in the absence of segregation distortion.

  1. THE LRP GENE ENCODING A MAJOR VAULT PROTEIN ASSOCIATED WITH DRUG-RESISTANCE MAPS PROXIMAL TO MRP ON CHROMOSOME-16 - EVIDENCE THAT CHROMOSOME BREAKAGE PLAYS A KEY ROLE IN MRP OR LRP GENE AMPLIFICATION

    NARCIS (Netherlands)

    SLOVAK, ML; HO, JP; COLE, SPC; DEELEY, RG; GREENBERGER, L; DEVRIES, EGE; BROXTERMAN, HJ; SCHEFFER, GL; SCHEPER, RJ

    1995-01-01

    A cDNA encoding the novel drug resistance gene, LRP (originally termed lung resistance-related protein), was isolated from HT1080/DR4, a 220-fold doxorubicin-resistant human fibrosarcoma cell line which displays a multidrug resistance phenotype and overexpresses the multidrug resistance protein

  2. Meiotic behaviour in three interspecific three-way hybrids between ...

    Indian Academy of Sciences (India)

    Chromosome paired predominantly as multivalents suggesting that genetic recombination and introgression of specific target genes from B. brizantha into B. ruziziensis can be expected. Arrangement of parental genomes in distinct metaphase plates was observed in H27 and H34, which have different male genitors.

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

    Indian Academy of Sciences (India)

    Unknown

    field mice of India. In contrast to the highly conservative. Mus musculus–like karyotype in M. booduga (2n = 40) with all acrocentric chromosomes in the complement, in. M. terricolor species-specific centric heterochromatin has evolved, and its repatterning has resulted in acrocen- tric and submetacentric autosomes in the ...

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

    Indian Academy of Sciences (India)

    Mus terricolor I, II and III are the three chromosomal species which differ in stable autosomal short-arm heterochromatin variations established in homozygous condition. Analysis of meiosis in the laboratorygenerated F1 male hybrids from crosses (both ways) between M. terricolor I and II and between M. terricolor I and III ...

  5. Meiotic sister chromatid cohesion and recombination in two filamentous fungi

    NARCIS (Netherlands)

    Heemst, van D.

    2000-01-01

    Homologous recombination and sister chromatid cohesion play important roles in the maintenance of genome integrity and the fidelity of chromosome segregation in mitosis and meiosis. Within the living cell, the integrity of the DNA is threatened by various factors that cause DNA-lesions, of

  6. A small (sSMC) chromosome 22 due to a maternal translocation between chromosomes 8 and 22: a case report.

    Science.gov (United States)

    Mundhofir, F E P; Kooper, A J A; Winarni, T I; Smits, A P T; Faradz, S M H; Hamel, B C J

    2010-01-01

    We report on a boy with partial trisomies for chromosomes 8 and 22 caused by the presence of a small supernumerary marker chromosome (sSMC), a der(22)t(8;22)(p22;q11.21), inherited from a t(8;22)(p22;q11.21) translocation carrier mother. He has mild mental retardation, unability to speak distinct words and several minor anomalies i.e. high forehead and hairline, telecanthus, upslanting palpebral fissures, depressed nasal bridge, nail hypoplasia, toe position anomaly and 5th finger clinodactyly. He has two maternal uncles and one maternal aunt with mental retardation. G-banding technique showed 47,XY,+mar whilst his mother's karyotype showed a balanced reciprocal translocation between the chromosomes 8 and 22. Fluorescence In Situ Hybridization (FISH) technique with probes for centromere 22 and 8pter were used to detect the origin of marker chromosome and confirmed the marker chromosome in the proband showing to be extra chromosomal material originated from chromosome 8 and 22. Additional genome wide microarray analysis, using the Affymetrix Nspl 250K SNP array platform was performed to further characterize the marker chromosome and resulted in a der(22)t(8;22)(p22;q11.21). Furthermore, cytogenetic analysis of three affected family members showed the same unbalanced translocation, due to 3:1 meiotic segregation. This indicated the viability of this unbalanced pattern and combined with the recurrent miscarriages by the proband's mother, the mechanism of transmitting extrachromosomal material is probably not a random process. Since, there is no similar translocation (8p;22q) reported and the chromosomal translocation largely exists of additional 8p22-8pter we compare the clinical outcomes with reported cases of 8p22-8pter triplication, although there is a part of genetic material derived from chromosome 22 present. This unique familial chromosome translocation case from Indonesia will give insight in the underlying mechanism of this recurrent chromosomal abnormality

  7. Ipl1/Aurora Kinase Suppresses S-CDK-Driven Spindle Formation during Prophase I to Ensure Chromosome Integrity during Meiosis

    OpenAIRE

    Newnham, Louise; Jordan, Philip W.; Carballo, Jesus A.; Newcombe, Sonya; Hoffmann, Eva

    2013-01-01

    Cells coordinate spindle formation with DNA repair and morphological modifications to chromosomes prior to their segregation to prevent cell division with damaged chromosomes. Here we uncover a novel and unexpected role for Aurora kinase in preventing the formation of spindles by Clb5-CDK (S-CDK) during meiotic prophase I and when the DDR is active in budding yeast. This is critical since S-CDK is essential for replication during premeiotic S-phase as well as double-strand break induction tha...

  8. GMI1, a structural-maintenance-of-chromosomes-hinge domain-containing protein, is involved in somatic homologous recombination in Arabidopsis

    Czech Academy of Sciences Publication Activity Database

    Bohmdorfer, G.; Schleiffer, A.; Brunmeir, R.; Ferscha, S.; Nizhynska, V.; Kozák, Jaroslav; Angelis, Karel; Kreil, D. P.; Schweizer, D.

    2011-01-01

    Roč. 67, č. 3 (2011), s. 420-433 ISSN 0960-7412 R&D Projects: GA MŠk 1M0505; GA MŠk(CZ) LC06004 Institutional research plan: CEZ:AV0Z50380511 Keywords : structural maintenance of chromosomes * DNA repair * somatic homologous recombination Subject RIV: EI - Biotechnology ; Bionics Impact factor: 6.160, year: 2011

  9. BCL2L1 has a functional role in colorectal cancer and its protein expression is associated with chromosome 20q gain

    NARCIS (Netherlands)

    Sillars-Hardebol, A.H.; Carvalho, B.; Belien, J.A.M.; de Wit, M.; Delis-van Diemen, P.M.; Tijssen, M.; van de Wiel, M.A.; Ponten, F.; Fijneman, R.J.A.; Meijer, G.A.

    2012-01-01

    Colorectal cancer (CRC) is the second leading cause of cancer death in the western world. The majority of CRCs, which develop from adenoma precursor lesions, show gain of chromosome arm 20q, where BCL2L1 is located. BCL2L1 is an important apoptosis regulating gene that codes for both an

  10. Sexually antagonistic "zygotic drive" of the sex chromosomes.

    Directory of Open Access Journals (Sweden)

    William R Rice

    2008-12-01

    Full Text Available Genomic conflict is perplexing because it causes the fitness of a species to decline rather than improve. Many diverse forms of genomic conflict have been identified, but this extant tally may be incomplete. Here, we show that the unusual characteristics of the sex chromosomes can, in principle, lead to a previously unappreciated form of sexual genomic conflict. The phenomenon occurs because there is selection in the heterogametic sex for sex-linked mutations that harm the sex of offspring that does not carry them, whenever there is competition among siblings. This harmful phenotype can be expressed as an antagonistic green-beard effect that is mediated by epigenetic parental effects, parental investment, and/or interactions among siblings. We call this form of genomic conflict sexually antagonistic "zygotic drive", because it is functionally equivalent to meiotic drive, except that it operates during the zygotic and postzygotic stages of the life cycle rather than the meiotic and gametic stages. A combination of mathematical modeling and a survey of empirical studies is used to show that sexually antagonistic zygotic drive is feasible, likely to be widespread in nature, and that it can promote a genetic "arms race" between the homo- and heteromorphic sex chromosomes. This new category of genomic conflict has the potential to strongly influence other fundamental evolutionary processes, such as speciation and the degeneration of the Y and W sex chromosomes. It also fosters a new genetic hypothesis for the evolution of enigmatic fitness-reducing traits like the high frequency of spontaneous abortion, sterility, and homosexuality observed in humans.

  11. Silencing expression of the catalytic subunit of DNA-dependent protein kinase by small interfering RNA sensitizes human cells for radiation-induced chromosome damage, cell killing, and mutation

    Science.gov (United States)

    Peng, Yuanlin; Zhang, Qinming; Nagasawa, Hatsumi; Okayasu, Ryuichi; Liber, Howard L.; Bedford, Joel S.

    2002-01-01

    Targeted gene silencing in mammalian cells by RNA interference (RNAi) using small interfering RNAs (siRNAs) was recently described by Elbashir et al. (S. M. Elbashir et al., Nature (Lond.), 411: 494-498, 2001). We have used this methodology in several human cell strains to reduce expression of the Prkdc (DNA-PKcs) gene coding for the catalytic subunit of the DNA-dependent protein kinase (DNA-PKcs) that is involved in the nonhomologous end joining of DNA double-strand breaks. We have also demonstrated a radiosensitization for several phenotypic endpoints of radiation damage. In low-passage normal human fibroblasts, siRNA knock-down of DNA-PKcs resulted in a reduced capacity for restitution of radiation-induced interphase chromosome breaks as measured by premature chromosome condensation, an increased yield of acentric chromosome fragments at the first postirradiation mitosis, and an increased radiosensitivity for cell killing. For three strains of related human lymphoblasts, DNA-PKcs-targeted siRNA transfection resulted in little or no increase in radiosensitivity with respect to cell killing, a 1.5-fold decrease in induced mutant yield in TK6- and p53-null NH32 cells, but about a 2-fold increase in induced mutant yield in p53-mutant WTK1 cells at both the hypoxanthine quanine phosphoribosyl transferase (hprt) and the thymidine kinase loci.

  12. B-chromosome ribosomal DNA is functional in the grasshopper Eyprepocnemis plorans.

    Science.gov (United States)

    Ruiz-Estévez, Mercedes; López-León, Ma Dolores; Cabrero, Josefa; Camacho, Juan Pedro M

    2012-01-01

    B-chromosomes are frequently argued to be genetically inert elements, but activity for some particular genes has been reported, especially for ribosomal RNA (rRNA) genes whose expression can easily be detected at the cytological level by the visualization of their phenotypic expression, i.e., the nucleolus. The B(24) chromosome in the grasshopper Eyprepocnemis plorans frequently shows a nucleolus attached to it during meiotic prophase I. Here we show the presence of rRNA transcripts that unequivocally came from the B(24) chromosome. To detect these transcripts, we designed primers specifically anchoring at the ITS-2 region, so that the reverse primer was complementary to the B chromosome DNA sequence including a differential adenine insertion being absent in the ITS2 of A chromosomes. PCR analysis carried out on genomic DNA showed amplification in B-carrying males but not in B-lacking ones. PCR analyses performed on complementary DNA showed amplification in about half of B-carrying males. Joint cytological and molecular analysis performed on 34 B-carrying males showed a close correspondence between the presence of B-specific transcripts and of nucleoli attached to the B chromosome. In addition, the molecular analysis revealed activity of the B chromosome rDNA in 10 out of the 13 B-carrying females analysed. Our results suggest that the nucleoli attached to B chromosomes are actively formed by expression of the rDNA carried by them, and not by recruitment of nucleolar materials formed in A chromosome nucleolar organizing regions. Therefore, B-chromosome rDNA in E. plorans is functional since it is actively transcribed to form the nucleolus attached to the B chromosome. This demonstrates that some heterochromatic B chromosomes can harbour functional genes.

  13. B-chromosome ribosomal DNA is functional in the grasshopper Eyprepocnemis plorans.

    Directory of Open Access Journals (Sweden)

    Mercedes Ruiz-Estévez

    Full Text Available B-chromosomes are frequently argued to be genetically inert elements, but activity for some particular genes has been reported, especially for ribosomal RNA (rRNA genes whose expression can easily be detected at the cytological level by the visualization of their phenotypic expression, i.e., the nucleolus. The B(24 chromosome in the grasshopper Eyprepocnemis plorans frequently shows a nucleolus attached to it during meiotic prophase I. Here we show the presence of rRNA transcripts that unequivocally came from the B(24 chromosome. To detect these transcripts, we designed primers specificall