WorldWideScience

Sample records for meiosis

  1. Marshmallow Meiosis.

    Science.gov (United States)

    Soderberg, Patti

    1992-01-01

    Presents an activity in which students model the processes of meiosis, fertilization, development, and birth using model creatures called reebops. Students breed reebops to analyze chromosome combinations. Makes recommendations for activity utilization and identifies the strengths of the activity. (MDH)

  2. Doing the Meiosis Shuffle.

    Science.gov (United States)

    Krauskopf, Sara

    1999-01-01

    Presents a game called the Meiosis Shuffle that helps students simulate the process of meiosis in which homologous cards representing chromosomes pair up, line up, and split apart. Students respond well to the simulation and are better able to conceptualize what chromosomes do and how independent assortment causes genetic variation. (CCM)

  3. Microscopic Procedures for Plant Meiosis.

    Science.gov (United States)

    Braselton, James P.

    1997-01-01

    Describes laboratory techniques designed to familiarize students with meiosis and how microscopic preparations of meiosis are made. These techniques require the use of fresh or fixed flowers. Contains 18 references. (DDR)

  4. Analysis of Schizosaccharomyces pombe Meiosis.

    Science.gov (United States)

    Yamashita, Akira; Sakuno, Takeshi; Watanabe, Yoshinori; Yamamoto, Masayuki

    2017-09-01

    Meiosis is a specialized cell cycle that generates haploid gametes from diploid cells. The fission yeast Schizosaccharomyces pombe is one of the best model organisms for studying the regulatory mechanisms of meiosis. S. pombe cells, which normally grow in the haploid state, diploidize by conjugation and initiate meiosis when starved for nutrients, especially nitrogen. Following two rounds of chromosome segregation, spore formation takes place. The switch from mitosis to meiosis is controlled by a kinase, Pat1, and an RNA-binding protein, Mei2. Mei2 is also a key factor for meiosis-specific gene expression. Studies on S. pombe have offered insights into cell cycle regulation and chromosome segregation during meiosis. Here we outline the current understanding of the molecular mechanisms regulating the initiation and progression of meiosis, and introduce methods for the study of meiosis in fission yeast. © 2017 Cold Spring Harbor Laboratory Press.

  5. Meiosis and speciation

    Indian Academy of Sciences (India)

    Meiotic analysis shows normal overall progression of meiosis in the heterozygotes, which is consistent with their normal gametogenesis. Nevertheless, both the inversion and fusion heterozygotes had undergone some alterations in the regular process of homologous synapsis, and it appeared that certain features of the ...

  6. Meiosis and SUMO

    DEFF Research Database (Denmark)

    Holm, Lærke Rebekka

    to target proteins can be catalyzed by the SUMO E3 ligase Pli1. In this study we investigate the role of Pli1 and Pmt3 during meiotic differentiation and at repetitive DNA during mitotic growth. Target proteins for Pmt3 are many; however, Pli1 has a meiosis-specic function regulating meiotic recombination...

  7. Evolutionary mysteries in meiosis.

    Science.gov (United States)

    Lenormand, Thomas; Engelstädter, Jan; Johnston, Susan E; Wijnker, Erik; Haag, Christoph R

    2016-10-19

    Meiosis is a key event of sexual life cycles in eukaryotes. Its mechanistic details have been uncovered in several model organisms, and most of its essential features have received various and often contradictory evolutionary interpretations. In this perspective, we present an overview of these often 'weird' features. We discuss the origin of meiosis (origin of ploidy reduction and recombination, two-step meiosis), its secondary modifications (in polyploids or asexuals, inverted meiosis), its importance in punctuating life cycles (meiotic arrests, epigenetic resetting, meiotic asymmetry, meiotic fairness) and features associated with recombination (disjunction constraints, heterochiasmy, crossover interference and hotspots). We present the various evolutionary scenarios and selective pressures that have been proposed to account for these features, and we highlight that their evolutionary significance often remains largely mysterious. Resolving these mysteries will likely provide decisive steps towards understanding why sex and recombination are found in the majority of eukaryotes.This article is part of the themed issue 'Weird sex: the underappreciated diversity of sexual reproduction'. © 2016 The Author(s).

  8. Evolutionary mysteries in meiosis

    NARCIS (Netherlands)

    Lenormand, Thomas; Engelstädter, Jan; Johnston, Susan E.; Wijnker, Erik; Haag, Christoph R.

    2016-01-01

    Meiosis is a key event of sexual life cycles in eukaryotes. Its mechanistic details have been uncovered in several model organisms, and most of its essential features have received various and often contradictory evolutionary interpretations. In this perspective, we present an overview of these

  9. Human female meiosis revised

    DEFF Research Database (Denmark)

    Capalbo, Antonio; Hoffmann, Eva R.; Cimadomo, Danilo

    2017-01-01

    to chromosome segregation in meiosis and mitosis. OUTCOMES Advances in genomic and imaging technologies are allowing unprecedented insight into chromosome segregation in human oocytes. This includes the identification of a novel chromosome segregation error, termed reverse segregation, as well as sister...

  10. The histone codes for meiosis.

    Science.gov (United States)

    Wang, Lina; Xu, Zhiliang; Khawar, Muhammad Babar; Liu, Chao; Li, Wei

    2017-09-01

    Meiosis is a specialized process that produces haploid gametes from diploid cells by a single round of DNA replication followed by two successive cell divisions. It contains many special events, such as programmed DNA double-strand break (DSB) formation, homologous recombination, crossover formation and resolution. These events are associated with dynamically regulated chromosomal structures, the dynamic transcriptional regulation and chromatin remodeling are mainly modulated by histone modifications, termed 'histone codes'. The purpose of this review is to summarize the histone codes that are required for meiosis during spermatogenesis and oogenesis, involving meiosis resumption, meiotic asymmetric division and other cellular processes. We not only systematically review the functional roles of histone codes in meiosis but also discuss future trends and perspectives in this field. © 2017 Society for Reproduction and Fertility.

  11. Oocyte Development, Meiosis and Aneuploidy

    OpenAIRE

    Maclennan, Marie; Crichton, James; Playfoot, Christopher J; Adams, Ian

    2015-01-01

    Meiosis is one of the defining events in gametogenesis. Male and female germ cells both undergo one round of meiotic cell division during their development in order to reduce the ploidy of the gametes, and thereby maintain the ploidy of the species after fertilisation. However, there are some aspects of meiosis in the female germline, such as the prolonged arrest in dictyate, that appear to predispose oocytes to missegregate their chromosomes and transmit aneuploidies to the next generation. ...

  12. Black hole meiosis

    Science.gov (United States)

    van Herck, Walter; Wyder, Thomas

    2010-04-01

    The enumeration of BPS bound states in string theory needs refinement. Studying partition functions of particles made from D-branes wrapped on algebraic Calabi-Yau 3-folds, and classifying states using split attractor flow trees, we extend the method for computing a refined BPS index, [1]. For certain D-particles, a finite number of microstates, namely polar states, exclusively realized as bound states, determine an entire partition function (elliptic genus). This underlines their crucial importance: one might call them the ‘chromosomes’ of a D-particle or a black hole. As polar states also can be affected by our refinement, previous predictions on elliptic genera are modified. This can be metaphorically interpreted as ‘crossing-over in the meiosis of a D-particle’. Our results improve on [2], provide non-trivial evidence for a strong split attractor flow tree conjecture, and thus suggest that we indeed exhaust the BPS spectrum. In the D-brane description of a bound state, the necessity for refinement results from the fact that tachyonic strings split up constituent states into ‘generic’ and ‘special’ states. These are enumerated separately by topological invariants, which turn out to be partitions of Donaldson-Thomas invariants. As modular predictions provide a check on many of our results, we have compelling evidence that our computations are correct.

  13. Development of a Meiosis Concept Inventory

    Science.gov (United States)

    Kalas, Pamela; O'Neill, Angie; Pollock, Carol; Birol, Gulnur

    2013-01-01

    We have designed, developed, and validated a 17-question Meiosis Concept Inventory (Meiosis CI) to diagnose student misconceptions on meiosis, which is a fundamental concept in genetics. We targeted large introductory biology and genetics courses and used published methodology for question development, which included the validation of questions by…

  14. Analysis of meiosis regulators in human gonads

    DEFF Research Database (Denmark)

    Jørgensen, Anne; Nielsen, John E; Jensen, Martin Blomberg

    2012-01-01

    The mitosis-meiosis switch is a key event in the differentiation of germ cells. In humans, meiosis is initiated in fetal ovaries, whereas in testes meiotic entry is inhibited until puberty. The purpose of this study was to examine the expression pattern of meiosis regulators in human gonads...... with their role in initiation and progression of meiosis. The putative meiosis inhibitors, CYP26B1 and NANOS2, were primarily expressed in Leydig cells and spermatocytes, respectively. In conclusion, the expression pattern of the investigated meiotic regulators is largely conserved in the human gonads compared...... with rodents, but with some minor differences, such as a stable expression of CYP26B1 in human fetal ovaries. The sexually dimorphic expression pattern of DMRT1 indicates a similar role in the mitosis-meiosis switch in human gonads as previously demonstrated in mice. The biological importance of the changes...

  15. Sister chromatid segregation in meiosis II

    Science.gov (United States)

    Wassmann, Katja

    2013-01-01

    Meiotic divisions (meiosis I and II) are specialized cell divisions to generate haploid gametes. The first meiotic division with the separation of chromosomes is named reductional division. The second division, which takes place immediately after meiosis I without intervening S-phase, is equational, with the separation of sister chromatids, similar to mitosis. This meiotic segregation pattern requires the two-step removal of the cohesin complex holding sister chromatids together: cohesin is removed from chromosome arms that have been subjected to homologous recombination in meiosis I and from the centromere region in meiosis II. Cohesin in the centromere region is protected from removal in meiosis I, but this protection has to be removed—deprotected”—for sister chromatid segregation in meiosis II. Whereas the mechanisms of cohesin protection are quite well understood, the mechanisms of deprotection have been largely unknown until recently. In this review I summarize our current knowledge on cohesin deprotection. PMID:23574717

  16. Chromosome segregation in plant meiosis

    Directory of Open Access Journals (Sweden)

    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.

  17. Meiosis.

    Science.gov (United States)

    Henderson, Paula

    This autoinstructional lesson deals with the study of cytology (or cells) with emphasis placed on cell reproduction. Knowledge of the structure of the DNA molecule and of the stages of mitotic cell division are considered prerequisites for this lesson. Approximately 15 minutes is the established time set for the activity. The behavioral objectives…

  18. Genetic Approaches to Study Meiosis and Meiosis-Specific Gene Expression in Saccharomyces cerevisiae.

    Science.gov (United States)

    Kassir, Yona; Stuart, David T

    2017-01-01

    The budding yeast Saccharomyces cerevisiae has a long history as a model organism for studies of meiosis and the cell cycle. The popularity of this yeast as a model is in large part due to the variety of genetic and cytological approaches that can be effectively performed with the cells. Cultures of the cells can be induced to synchronously progress through meiosis and sporulation allowing large-scale gene expression and biochemical studies to be performed. Additionally, the spore tetrads resulting from meiosis make it possible to characterize the haploid products of meiosis allowing investigation of meiotic recombination and chromosome segregation. Here we describe genetic methods for analysis progression of S. cerevisiae through meiosis and sporulation with an emphasis on strategies for the genetic analysis of regulators of meiosis-specific genes.

  19. Forskolin and the meiosis inducing substance synergistically initiate meiosis in fetal male germ cells

    DEFF Research Database (Denmark)

    Byskov, A G; Fenger, M; Westergaard, L

    1993-01-01

    We have shown that Meiosis Inducing Substance (MIS) and forskolin synergistically and dose dependently induce meiosis in germ cells of cultured fetal mouse testes. We used a bioassay which consists of fetal mouse testes and ovaries cultured for 6 days. In this study MIS media are spent culture...... are fixed, squashed, and DNA-stained. In these preparations germ cells and somatic cells can be distinguished, and the number of germ cells in the different stages of meiosis is counted as is the number of somatic cells in mitosis. MIS activity is defined to be present in a medium when meiosis is induced...... in male germ cells during culture. We found that MIS media as well as forskolin induced meiosis in fetal male germ cells in a dose-dependent manner. In addition, MIS media and forskolin acted synergistically by inducing meiosis. Female germ cells seem to be unaffected by the various culture media...

  20. Tradescantia: A Tool for Teaching Meiosis.

    Science.gov (United States)

    Hammersmith, Robert L.; Mertens, Thomas R.

    1997-01-01

    Describes a procedure for making slides of microsporogenesis in Tradescantia. Uses photographs to demonstrate that Tradescantia is an ideal organism for studying meiosis in the classroom. Contains 17 references. (JRH)

  1. Assessing Understanding of Biological Processes: Elucidating Students' Models of Meiosis.

    Science.gov (United States)

    Kindfield, Ann C.

    1994-01-01

    Presents a meiosis reasoning problem that provides direct access to students' current models of chromosomes and meiosis. Also included in the article are tips for classroom implementation and a summary of the solution evaluation. (ZWH)

  2. High School Students' Use of Meiosis When Solving Genetics Problems.

    Science.gov (United States)

    Wynne, Cynthia F.; Stewart, Jim; Passmore, Cindy

    2001-01-01

    Paints a different picture of students' reasoning with meiosis as they solved complex, computer-generated genetics problems, some of which required them to revise their understanding of meiosis in response to anomalous data. Students were able to develop a rich understanding of meiosis and can utilize that knowledge to solve genetics problems.…

  3. Meiosis: An Overview of Key Differences from Mitosis

    Science.gov (United States)

    Ohkura, Hiroyuki

    2015-01-01

    Meiosis is the specialized cell division that generates gametes. In contrast to mitosis, molecular mechanisms and regulation of meiosis are much less understood. Meiosis shares mechanisms and regulation with mitosis in many aspects, but also has critical differences from mitosis. This review highlights these differences between meiosis and mitosis. Recent studies using various model systems revealed differences in a surprisingly wide range of aspects, including cell-cycle regulation, recombination, postrecombination events, spindle assembly, chromosome–spindle interaction, and chromosome segregation. Although a great degree of diversity can be found among organisms, meiosis-specific processes, and regulation are generally conserved. PMID:25605710

  4. The transcriptome landscape of early maize meiosis

    Science.gov (United States)

    Meiosis, particularly meiotic recombination, is a major factor affecting yield and breeding of plants. To gain insight into the transcriptome landscape during early initiation steps of meiotic recombination, we profiled early prophase I meiocytes from maize using RNA-seq. Our analyses of genes prefe...

  5. Cuf2 Is a Novel Meiosis-Specific Regulatory Factor of Meiosis Maturation

    Science.gov (United States)

    Ioannoni, Raphael; Beaudoin, Jude; Lopez-Maury, Luis; Codlin, Sandra; Bahler, Jurg; Labbe, Simon

    2012-01-01

    Background Meiosis is the specialized form of the cell cycle by which diploid cells produce the haploid gametes required for sexual reproduction. Initiation and progression through meiosis requires that the expression of the meiotic genes is precisely controlled so as to provide the correct gene products at the correct times. During meiosis, four temporal gene clusters are either induced or repressed by a cascade of transcription factors. Principal Findings In this report a novel copper-fist-type regulator, Cuf2, is shown to be expressed exclusively during meiosis. The expression profile of the cuf2+ mRNA revealed that it was induced during middle-phase meiosis. Both cuf2+ mRNA and protein levels are unregulated by copper addition or starvation. The transcription of cuf2+ required the presence of a functional mei4+ gene encoding a key transcription factor that activates the expression of numerous middle meiotic genes. Microscopic analyses of cells expressing a functional Cuf2-GFP protein revealed that Cuf2 co-localized with both homologous chromosomes and sister chromatids during the meiotic divisions. Cells lacking Cuf2 showed an elevated and sustained expression of several of the middle meiotic genes that persisted even during late meiosis. Moreover, cells carrying disrupted cuf2Δ/cuf2Δ alleles displayed an abnormal morphology of the forespore membranes and a dramatic reduction of spore viability. Significance Collectively, the results revealed that Cuf2 functions in the timely repression of the middle-phase genes during meiotic differentiation. PMID:22558440

  6. Sister kinetochores are mechanically fused during meiosis I in yeast.

    Science.gov (United States)

    Sarangapani, Krishna K; Duro, Eris; Deng, Yi; Alves, Flavia de Lima; Ye, Qiaozhen; Opoku, Kwaku N; Ceto, Steven; Rappsilber, Juri; Corbett, Kevin D; Biggins, Sue; Marston, Adèle L; Asbury, Charles L

    2014-10-10

    Production of healthy gametes requires a reductional meiosis I division in which replicated sister chromatids comigrate, rather than separate as in mitosis or meiosis II. Fusion of sister kinetochores during meiosis I may underlie sister chromatid comigration in diverse organisms, but direct evidence for such fusion has been lacking. We used laser trapping and quantitative fluorescence microscopy to study native kinetochore particles isolated from yeast. Meiosis I kinetochores formed stronger attachments and carried more microtubule-binding elements than kinetochores isolated from cells in mitosis or meiosis II. The meiosis I-specific monopolin complex was both necessary and sufficient to drive these modifications. Thus, kinetochore fusion directs sister chromatid comigration, a conserved feature of meiosis that is fundamental to Mendelian inheritance. Copyright © 2014, American Association for the Advancement of Science.

  7. Conservation and Variability of Meiosis Across the Eukaryotes.

    Science.gov (United States)

    Loidl, Josef

    2016-11-23

    Comparisons among a variety of eukaryotes have revealed considerable variability in the structures and processes involved in their meiosis. Nevertheless, conventional forms of meiosis occur in all major groups of eukaryotes, including early-branching protists. This finding confirms that meiosis originated in the common ancestor of all eukaryotes and suggests that primordial meiosis may have had many characteristics in common with conventional extant meiosis. However, it is possible that the synaptonemal complex and the delicate crossover control related to its presence were later acquisitions. Later still, modifications to meiotic processes occurred within different groups of eukaryotes. Better knowledge on the spectrum of derived and uncommon forms of meiosis will improve our understanding of many still mysterious aspects of the meiotic process and help to explain the evolutionary basis of functional adaptations to the meiotic program.

  8. True polyploid meiosis in the human male.

    Science.gov (United States)

    Pearson, Peter L; Madan, Kamlesh

    2018-05-21

    Polyploidy does not usually occur in germinal cells of mammals and other higher vertebrates. We describe a unique example of mosaic autotetraploidy in the meiosis of a human male. Although the original observations were made in the late 1960s, we did not publish them at that time, because we expected to detect further examples that could be described together. However, this did not occur and we have now decided to make the observations available to demonstrate that polyploidy in mammalian male meiosis can arise at a higher frequency than expected by random polyploidization of individual meiotic cells, by either DNA duplication or cell fusion prior to synapsis. This is the first description of a population of primary spermatocytes exhibiting multivalent formation at leptotene /diakinesis in human spermatogenesis, with ring, chain, frying pan and other types of quadrivalents, typical of autotetraploidy. As many of the polyploid configurations showed apoptotic breakdown, it is likely that diploid and/or aneuploid spermatozoa would have rarely or never resulted from this mosaic autotetraploid meiosis.

  9. Meiosis in hematological malignancies. In situ cytogenetic morphology

    OpenAIRE

    Logothetou-Rella, H.

    1996-01-01

    This is the first study on the in situ cytogenetic morphology and analysis of malignant bone marrow cells, growing attached on a culture vessel surface. It was documented that bone marrow cells, in different types of hematological malignancies, divide by meiosis giving rise to a non-repetitive aneuploidy. Male and female gametes are formed by meiosis and fertilization occurs in a life cycle of: Fertilization Meiosis Gametes - Embryo - Gametes Immature a...

  10. Fungal Meiosis and Parasexual Reproduction – Lessons from Pathogenic Yeast

    OpenAIRE

    Sherwood, Racquel K.; Bennett, Richard J.

    2009-01-01

    Meiosis is an integral part of sexual reproduction in eukaryotic species. It performs the dual functions of halving the genetic content in the cell, as well as increasing genetic diversity by promoting recombination between chromosome homologs. Despite extensive studies of meiosis in model yeast, it is now apparent that both the regulation of meiosis and the machinery mediating recombination has significantly diverged, even between closely related species. To highlight this, we discuss new st...

  11. The Retention of Meaningful Understanding of Meiosis and Genetics.

    Science.gov (United States)

    Cavallo, Ann Liberatore

    This study investigated the retention of meaningful understanding of the biological topics of meiosis, the Punnett square method and the relations between these two topics. This study also explored the predictive influence of students' general tendency to learn meaningfully or by rote (meaningful learning orientation), prior knowledge of meiosis,…

  12. Complex regulation of sister kinetochore orientation in meiosis-I.

    Science.gov (United States)

    Bardhan, Amit

    2010-09-01

    Kinetochores mediate chromosome movement during cell division by interacting with the spindle microtubules. Sexual reproduction necessitates the daunting task of reducing ploidy (number of chromosome sets) in the gametes, which depends upon the specialized properties of meiosis. Kinetochores have a central role in the reduction process. In this review, we discuss the complexity of this role of kinetochores in meiosis-I.

  13. Comparative proteomics of mitosis and meiosis in Saccharomyces cerevisiae.

    Science.gov (United States)

    Kumar, Ravinder; Dhali, Snigdha; Srikanth, Rapole; Ghosh, Santanu Kumar; Srivastava, Sanjeeva

    2014-09-23

    Precise and timely segregation of genetic material and conservation of ploidy are the two foremost requirements for survival of a eukaryotic organism. Two highly regulated cell division processes, namely mitosis and meiosis are central to achieve this objective. The modes of chromosome segregation are distinct in these two processes that generate progeny cells of equal ploidy and half the ploidy in mitosis and meiosis, respectively. Additionally, the nutritional requirement and intracellular processing of biological cue also differ in these two processes. From this, it can be envisaged that proteome of mitotic and meiotic cells will differ significantly. Therefore, identification of proteins that differ in their level of expression between mitosis and meiosis would further reveal the mechanistic detail of these processes. In the present study, we have investigated the protein expression profile of mitosis and meiosis by comparing proteome of budding yeast cultures arrested at mitotic metaphase and metaphase-I of meiosis using proteomic approach. Approximately 1000 and 2000 protein spots were visualized on 2-DE and 2D-DIGE gels respectively, out of which 14 protein spots were significant in 2-DE and 22 in 2D-DIGE (pmitosis, an up-regulation of actin cytoskeleton and its negative regulator occurs in meiosis. Mitosis and meiosis are two different types of cell division cycles with entirely different outcomes with definite biological implication for almost all eukaryotic species. In this work, we investigated, for the first time, the differential proteomic profile of Saccharomyces cerevisiae culture arrested at mitotic metaphase (M) and metaphase-I (MI) of meiosis using 2-DE and 2D-DIGE. Our findings of up-regulation of actin and its negative regulator cofilin during meiosis suggest that the rate of actin cytoskeleton turnover is more in meiosis and actin cytoskeleton may play more crucial role during meiosis compared to mitosis. Present study also suggests that actin

  14. Control of the mitotic exit network during meiosis

    Science.gov (United States)

    Attner, Michelle A.; Amon, Angelika

    2012-01-01

    The mitotic exit network (MEN) is an essential GTPase signaling pathway that triggers exit from mitosis in budding yeast. We show here that during meiosis, the MEN is dispensable for exit from meiosis I but contributes to the timely exit from meiosis II. Consistent with a role for the MEN during meiosis II, we find that the signaling pathway is active only during meiosis II. Our analysis further shows that MEN signaling is modulated during meiosis in several key ways. Whereas binding of MEN components to spindle pole bodies (SPBs) is necessary for MEN signaling during mitosis, during meiosis MEN signaling occurs off SPBs and does not require the SPB recruitment factor Nud1. Furthermore, unlike during mitosis, MEN signaling is controlled through the regulated interaction between the MEN kinase Dbf20 and its activating subunit Mob1. Our data lead to the conclusion that a pathway essential for vegetative growth is largely dispensable for the specialized meiotic divisions and provide insights into how cell cycle regulatory pathways are modulated to accommodate different modes of cell division. PMID:22718910

  15. From equator to pole: splitting chromosomes in mitosis and meiosis

    Science.gov (United States)

    Duro, Eris

    2015-01-01

    During eukaryotic cell division, chromosomes must be precisely partitioned to daughter cells. This relies on a mechanism to move chromosomes in defined directions within the parental cell. While sister chromatids are segregated from one another in mitosis and meiosis II, specific adaptations enable the segregation of homologous chromosomes during meiosis I to reduce ploidy for gamete production. Many of the factors that drive these directed chromosome movements are known, and their molecular mechanism has started to be uncovered. Here we review the mechanisms of eukaryotic chromosome segregation, with a particular emphasis on the modifications that ensure the segregation of homologous chromosomes during meiosis I. PMID:25593304

  16. Selection on meiosis genes in diploid and tetraploid Arabidopsis arenosa

    Czech Academy of Sciences Publication Activity Database

    Wright, K. M.; Arnold, B.; Xue, K.; Šurinová, Mária; O´Connell, J.; Bomblies, K.

    2015-01-01

    Roč. 32, č. 4 (2015), s. 944-955 ISSN 0737-4038 Institutional support: RVO:67985939 Keywords : meiosis * evolution * polyploidy Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 13.649, year: 2015

  17. Atypical ploidy cycles, Spo11, and the evolution of meiosis.

    Science.gov (United States)

    Bloomfield, Gareth

    2016-06-01

    The Spo11 protein induces DNA double strand breaks before the first division of meiosis, enabling the formation of the chiasmata that physically link homologous chromosomes as they align. Spo11 is an ancient and well conserved protein, related in sequence and structure to a DNA topoisomerase subunit found in Archaea as well as a subset of eukaryotes. However the origins of its meiotic function are unclear. This review examines some apparent exceptions to the rule that Spo11 activity is specific to, and required for meiosis. Spo11 appears to function in the context of unusual forms of ploidy reduction in some protists and fungi. One lineage of amoebae, the dictyostelids, is thought to undergo meiosis during its sexual cycle despite having lost Spo11 entirely. Further experimental characterisation of these and other non-canonical ploidy cycling mechanisms may cast light of the evolution of meiosis. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. Localization of two mammalian cyclin dependent kinases during mammalian meiosis

    NARCIS (Netherlands)

    Ashley, T.; Walpita, D.; de rooij, D. G.

    2001-01-01

    Mammalian meiotic progression, like mitotic cell cycle progression, is regulated by cyclins and cyclin dependent kinases (CDKs). However, the unique requirements of meiosis (homologous synapsis, reciprocal recombination and the dual divisions that segregate first homologues, then sister chromatids)

  19. Wrestling with Chromosomes: The Roles of SUMO During Meiosis.

    Science.gov (United States)

    Nottke, Amanda C; Kim, Hyun-Min; Colaiácovo, Monica P

    2017-01-01

    Meiosis is a specialized form of cell division required for the formation of haploid gametes and therefore is essential for successful sexual reproduction. Various steps are exquisitely coordinated to ensure accurate chromosome segregation during meiosis, thereby promoting the formation of haploid gametes from diploid cells. Recent studies are demonstrating that an important form of regulation during meiosis is exerted by the post-translational protein modification known as sumoylation. Here, we review and discuss the various critical steps of meiosis in which SUMO-mediated regulation has been implicated thus far. These include the maintenance of meiotic centromeric heterochromatin , meiotic DNA double-strand break repair and homologous recombination, centromeric coupling, and the assembly of a proteinaceous scaffold between homologous chromosomes known as the synaptonemal complex.

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

    Science.gov (United States)

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

    2014-01-01

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

  1. Cytomixis impairs meiosis and influences reproductive success in ...

    Indian Academy of Sciences (India)

    MADU

    evolved but complex process to produce gametes genetically and structurally different ... All the organisms, irrespective of ... Meiosis is highly coherent and genetically programmed ..... may be genetic in nature and modified by the environment.

  2. Testing of mitosis and meiosis in female and male gametes

    Directory of Open Access Journals (Sweden)

    L. F. Kurilo

    2016-01-01

    Full Text Available Method of quantitative evaluation of the immature germ cells, their pathology in mitosis and meiosis (in semen, embryo and fetal ovaries, of gonad biopsies or fragments of sectioned material is informative method and should be introduced into the clinical practice in andrology and gynecology and fundamental research. Quantitative analysis of mitosis and female meiosis development was initiated on experimental animals and fetal gonads from spontaneous or therapeutic abortions.

  3. Meiosis and Haploid Gametes in the Pathogen Trypanosoma brucei

    OpenAIRE

    Peacock, Lori; Bailey, Mick; Carrington, Mark; Gibson, Wendy

    2014-01-01

    Summary In eukaryote pathogens, sex is an important driving force in spreading genes for drug resistance, pathogenicity, and virulence [1]. For the parasitic trypanosomes that cause African sleeping sickness, mating occurs during transmission by the tsetse vector [2, 3] and involves meiosis [4], but haploid gametes have not yet been identified. Here, we show that meiosis is a normal part of development in the insect salivary glands for all subspecies of Trypanosoma brucei, including the human...

  4. Meiosis evolves: adaptation to external and internal environments.

    Science.gov (United States)

    Bomblies, Kirsten; Higgins, James D; Yant, Levi

    2015-10-01

    306 I. 306 II. 307 III. 312 IV. 317 V. 318 319 References 319 SUMMARY: Meiosis is essential for the fertility of most eukaryotes and its structures and progression are conserved across kingdoms. Yet many of its core proteins show evidence of rapid or adaptive evolution. What drives the evolution of meiosis proteins? How can constrained meiotic processes be modified in response to challenges without compromising their essential functions? In surveying the literature, we found evidence of two especially potent challenges to meiotic chromosome segregation that probably necessitate adaptive evolutionary responses: whole-genome duplication and abiotic environment, especially temperature. Evolutionary solutions to both kinds of challenge are likely to involve modification of homologous recombination and synapsis, probably via adjustments of core structural components important in meiosis I. Synthesizing these findings with broader patterns of meiosis gene evolution suggests that the structural components of meiosis coevolve as adaptive modules that may change in primary sequence and function while maintaining three-dimensional structures and protein interactions. The often sharp divergence of these genes among species probably reflects periodic modification of entire multiprotein complexes driven by genomic or environmental changes. We suggest that the pressures that cause meiosis to evolve to maintain fertility may cause pleiotropic alterations of global crossover rates. We highlight several important areas for future research. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

  5. Polo kinase Cdc5 is a central regulator of meiosis I

    Science.gov (United States)

    Attner, Michelle A.; Miller, Matthew P.; Ee, Ly-sha; Elkin, Sheryl K.; Amon, Angelika

    2013-01-01

    During meiosis, two consecutive rounds of chromosome segregation yield four haploid gametes from one diploid cell. The Polo kinase Cdc5 is required for meiotic progression, but how Cdc5 coordinates multiple cell-cycle events during meiosis I is not understood. Here we show that CDC5-dependent phosphorylation of Rec8, a subunit of the cohesin complex that links sister chromatids, is required for efficient cohesin removal from chromosome arms, which is a prerequisite for meiosis I chromosome segregation. CDC5 also establishes conditions for centromeric cohesin removal during meiosis II by promoting the degradation of Spo13, a protein that protects centromeric cohesin during meiosis I. Despite CDC5’s central role in meiosis I, the protein kinase is dispensable during meiosis II and does not even phosphorylate its meiosis I targets during the second meiotic division. We conclude that Cdc5 has evolved into a master regulator of the unique meiosis I chromosome segregation pattern. PMID:23918381

  6. Meiosis in mice without a synaptonemal complex.

    Directory of Open Access Journals (Sweden)

    Anna Kouznetsova

    Full Text Available The synaptonemal complex (SC promotes fusion of the homologous chromosomes (synapsis and crossover recombination events during meiosis. The SC displays an extensive structural conservation between species; however, a few organisms lack SC and execute meiotic process in a SC-independent manner. To clarify the SC function in mammals, we have generated a mutant mouse strain (Sycp1(-/-Sycp3(-/-, here called SC-null in which all known SC proteins have been displaced from meiotic chromosomes. While transmission electron microscopy failed to identify any remnants of the SC in SC-null spermatocytes, neither formation of the cohesion axes nor attachment of the chromosomes to the nuclear membrane was perturbed. Furthermore, the meiotic chromosomes in SC-null meiocytes achieved pre-synaptic pairing, underwent early homologous recombination events and sustained a residual crossover formation. In contrast, in SC-null meiocytes synapsis and MLH1-MLH3-dependent crossovers maturation were abolished, whereas the structural integrity of chromosomes was drastically impaired. The variable consequences that SC inactivation has on the meiotic process in different organisms, together with the absence of SC in some unrelated species, imply that the SC could have originated independently in different taxonomic groups.

  7. Changes in gene expression during male meiosis in Petunia hybrida.

    Science.gov (United States)

    Cnudde, Filip; Hedatale, Veena; de Jong, Hans; Pierson, Elisabeth S; Rainey, Daphne Y; Zabeau, Marc; Weterings, Koen; Gerats, Tom; Peters, Janny L

    2006-01-01

    We analyzed changes in gene expression during male meiosis in Petunia by combining the meiotic staging of pollen mother cells from a single anther with cDNA-AFLP transcript profiling of mRNA from the synchronously developing sister anthers. The transcript profiling experiments focused on the identification of genes with a modulated expression profile during meiosis, while premeiotic archesporial cells and postmeiotic microspores served as a reference. About 8000 transcript tags, estimated at 30% of the total transcriptome, were generated, of which around 6% exhibited a modulated gene expression pattern at meiosis. Cluster analysis revealed a transcriptional cascade that coincides with the initiation and progression through all stages of the two meiotic divisions. Fragments that exhibited high expression specifically during meiosis I were characterized further by sequencing; 90 out of the 293 sequenced fragments showed homology with known genes, belonging to a wide range of gene classes, including previously characterized meiotic genes. In-situ hybridization experiments were performed to determine the spatial expression pattern for five selected transcript tags. Its concurrence with cDNA-AFLP transcript profiles indicates that this is an excellent approach to study genes involved in specialized processes such as meiosis. Our data set provides the potential to unravel unique meiotic genes that are as yet elusive to reverse genetics approaches.

  8. Development and Meiosis of Three Interspecific Hybrids with Cultivated Barley (Hordeum vulgare L.)

    DEFF Research Database (Denmark)

    Von Bothmer, R.; Flink, J.; Linde-Laursen, Ib

    1986-01-01

    The development and meiosis of three interspecific hybrids between cultivated barley (Hordeum vulgare L.) and H. secalinum Schreb., H. tetraploidum Covas, and H. parodii Covas, respectively, were studied. All three hybrid combinations developed very slowly vegetatively. Meiosis of the hybrids...

  9. Potential Role of Meiosis Proteins in Melanoma Chromosomal Instability

    International Nuclear Information System (INIS)

    Lindsey, S. F.; Byrnes, D. M.; Eller, M. S.; Rosa, A. M.; Dabas, N.; Escandon, J.; Grichnik, J. M.; Grichnik, J. M.; Grichnik, J. M.; Grichnik, J. M.

    2013-01-01

    Melanomas demonstrate chromosomal instability (CIN). In fact, CIN can be used to differentiate melanoma from benign nevi. The exact molecular mechanisms that drive CIN in melanoma have yet to be fully elucidated. Cancer/testis antigens are a unique group of germ cell proteins that are found to be primarily expressed in melanoma as compared to benign nevi. The abnormal expression of these germ cell proteins, normally expected only in the testis and ovaries, in somatic cells may lead to interference with normal cellular pathways. Germ cell proteins that may be particularly critical in CIN are meiosis proteins. Here, we review pathways unique to meiosis with a focus on how the aberrant expression of meiosis proteins in normal mitotic cells "meiomitosis"could impact chromosomal instability in melanoma and other cancers.

  10. Peculiarities of meiosis in radiomutants of the soft wheat

    Energy Technology Data Exchange (ETDEWEB)

    Shakaryan, Zh.O.; Avakyan, V.A. (Armyanskij Sel' skokhozyajstvennyj Inst.)

    1983-10-01

    The experiment is carried out using five constant mutant lines of soft wheat with a cylindrical ear. On the basis of the study of the dynamics and character of violations in 1 and 2 divisions of meiosis in the mutants and initial sorts a conclusion can be made that inspite of the morphological homogeneity in M/sub 8/, the mutants are characteristized by different degree of heterozygosis in translocations and micromutations. The presence of a comparatively large number of multivalents in MI of the meiosis did not cause violations in the final stage of meiosis. All the mutants have normal meiotic index and formed gametes, balanced as to genetic material, which points to the possibility of growing the economically-efficient wheat mutants with a high productivity and fertility using the method of radiation mutagenesis.

  11. The peculiarities of meiosis in radiomutants of the soft wheat

    International Nuclear Information System (INIS)

    Shakaryan, Zh.O.; Avakyan, V.A.

    1983-01-01

    The experiment is carried out using five constant mutant lines of soft wheat with a cylindrical ear. On the basis of the study of the dynamics and character of violations in 1 and 2 divisions of meiosis in the mutants and initial sorts a conclusion can be made that inspite of the morphological homogeneity in M 8 , the mutants are characteristized by different degree of heterozygosis in translocations and micromutations. The presence of a comparatively large number of multivalents in MI of the meiosis did not cause violations in the final stage of meiosis. All the mutants has a normal meiotic index and formed gametes, balanced as to genetic material, which points to the possibility of growing the economically-efficient wheat mutants with a high productivity and fertility using the method of radiation mutagenesis

  12. Understanding a Basic Biological Process: Expert and Novice Models of Meiosis.

    Science.gov (United States)

    Kindfield, Ann C. H.

    The results of a study of the meiosis models utilized by individuals at varying levels of expertise while reasoning about the process of meiosis are presented. Based on these results, the issues of sources of misconceptions/difficulties and the construction of a sound understanding of meiosis are discussed. Five individuals from each of three…

  13. Students as "Humans Chromosomes" in Role-Playing Mitosis and Meiosis

    Science.gov (United States)

    Chinnici, Joseph P.; Yue, Joyce W.; Torres, Kieron M.

    2004-01-01

    Students often find it challenging to understand mitosis and meiosis and determine their processes. To develop an easier way to understand these terms, students are asked to role-play mitosis and meiosis and students themselves act as human chromosomes, which help students to learn differences between mitosis and meiosis.

  14. Effect of guaianolides in the meiosis reinitiation of amphibian oocytes.

    Science.gov (United States)

    Zapata-Martínez, J; Sánchez-Toranzo, G; Chaín, F; Catalán, C A N; Bühler, M I

    2017-02-01

    Sesquiterpene lactones (STLs) are a large and structurally diverse group of plant metabolites generally found in the Asteraceae family. STLs exhibit a wide spectrum of biological activities and it is generally accepted that their major mechanism of action is the alkylation of the thiol groups of biological molecules. The guaianolides is one of various groups of STLs. Anti-tumour and anti-migraine effects, an allergenic agent, an inhibitor of smooth muscle cells and of meristematic cell proliferation are only a few of the most commonly reported activities of STLs. In amphibians, fully grown ovarian oocytes are arrested at the beginning of meiosis I. Under stimulus with progesterone, this meiotic arrest is released and meiosis progresses to metaphase II, a process known as oocyte maturation. There are previous records of the inhibitory effect of dehydroleucodin (DhL), a guaianolide lactone, on the progression of meiosis. It has been also shown that DhL and its 11,13-dihydroderivative (2H-DhL; a mixture of epimers at C-11) act as blockers of the resumption of meiosis in fully grown ovarian oocytes from the amphibian Rhinella arenarum (formerly classified as Bufo arenarum). The aim of this study was to analyze the effect of four closely related guaianolides, i.e., DhL, achillin, desacetoxymatricarin and estafietin as possible inhibitors of meiosis in oocytes of amphibians in vitro and discuss some structure-activity relationships. It was found that the inhibitory effect on meiosis resumption is greater when the lactone has two potentially reactive centres, either a α,β-α',β'-diunsaturated cyclopentanone moiety or an epoxide group plus an exo-methylene-γ-lactone function.

  15. Selection on meiosis genes in diploid and tetraploid Arabidopsis arenosa.

    Science.gov (United States)

    Wright, Kevin M; Arnold, Brian; Xue, Katherine; Šurinová, Maria; O'Connell, Jeremy; Bomblies, Kirsten

    2015-04-01

    Meiotic chromosome segregation is critical for fertility across eukaryotes, and core meiotic processes are well conserved even between kingdoms. Nevertheless, recent work in animals has shown that at least some meiosis genes are highly diverse or strongly differentiated among populations. What drives this remains largely unknown. We previously showed that autotetraploid Arabidopsis arenosa evolved stable meiosis, likely through reduced crossover rates, and that associated with this there is strong evidence for selection in a subset of meiosis genes known to affect axis formation, synapsis, and crossover frequency. Here, we use genome-wide data to study the molecular evolution of 70 meiosis genes in a much wider sample of A. arenosa. We sample the polyploid lineage, a diploid lineage from the Carpathian Mountains, and a more distantly related diploid lineage from the adjacent, but biogeographically distinct Pannonian Basin. We find that not only did selection act on meiosis genes in the polyploid lineage but also independently on a smaller subset of meiosis genes in Pannonian diploids. Functionally related genes are targeted by selection in these distinct contexts, and in two cases, independent sweeps occurred in the same loci. The tetraploid lineage has sustained selection on more genes, has more amino acid changes in each, and these more often affect conserved or potentially functional sites. We hypothesize that Pannonian diploid and tetraploid A. arenosa experienced selection on structural proteins that mediate sister chromatid cohesion, the formation of meiotic chromosome axes, and synapsis, likely for different underlying reasons. © The Author 2014. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  16. Elevated mutation rate during meiosis in Saccharomyces cerevisiae.

    Science.gov (United States)

    Rattray, Alison; Santoyo, Gustavo; Shafer, Brenda; Strathern, Jeffrey N

    2015-01-01

    Mutations accumulate during all stages of growth, but only germ line mutations contribute to evolution. While meiosis contributes to evolution by reassortment of parental alleles, we show here that the process itself is inherently mutagenic. We have previously shown that the DNA synthesis associated with repair of a double-strand break is about 1000-fold less accurate than S-phase synthesis. Since the process of meiosis involves many programmed DSBs, we reasoned that this repair might also be mutagenic. Indeed, in the early 1960's Magni and Von Borstel observed elevated reversion of recessive alleles during meiosis, and found that the revertants were more likely to be associated with a crossover than non-revertants, a process that they called "the meiotic effect." Here we use a forward mutation reporter (CAN1 HIS3) placed at either a meiotic recombination coldspot or hotspot near the MAT locus on Chromosome III. We find that the increased mutation rate at CAN1 (6 to 21 -fold) correlates with the underlying recombination rate at the locus. Importantly, we show that the elevated mutation rate is fully dependent upon Spo11, the protein that introduces the meiosis specific DSBs. To examine associated recombination we selected for random spores with or without a mutation in CAN1. We find that the mutations isolated this way show an increased association with recombination (crossovers, loss of crossover interference and/or increased gene conversion tracts). Polζ appears to contribute about half of the mutations induced during meiosis, but is not the only source of mutations for the meiotic effect. We see no difference in either the spectrum or distribution of mutations between mitosis and meiosis. The correlation of hotspots with elevated mutagenesis provides a mechanism for organisms to control evolution rates in a gene specific manner.

  17. The colocalization transition of homologous chromosomes at meiosis

    Science.gov (United States)

    Nicodemi, Mario; Panning, Barbara; Prisco, Antonella

    2008-06-01

    Meiosis is the specialized cell division required in sexual reproduction. During its early stages, in the mother cell nucleus, homologous chromosomes recognize each other and colocalize in a crucial step that remains one of the most mysterious of meiosis. Starting from recent discoveries on the system molecular components and interactions, we discuss a statistical mechanics model of chromosome early pairing. Binding molecules mediate long-distance interaction of special DNA recognition sequences and, if their concentration exceeds a critical threshold, they induce a spontaneous colocalization transition of chromosomes, otherwise independently diffusing.

  18. Arabidopsis SMG7 protein is required for exit from meiosis

    Czech Academy of Sciences Publication Activity Database

    Riehs, N.; Akimcheva, S.; Puizina, J.; Bulánková, P.; Idol, R.A.; Široký, Jiří; Schleiffer, A.; Schweizer, D.; Shippen, D.E.; Říha, K.

    2008-01-01

    Roč. 121, č. 13 (2008), s. 2208-2216 ISSN 0021-9533 R&D Projects: GA ČR(CZ) GA522/06/0380 Institutional research plan: CEZ:AV0Z50040507; CEZ:AV0Z50040702 Keywords : anaphase * CDK * meiosis Subject RIV: BO - Biophysics Impact factor: 6.247, year: 2008

  19. Complex regulation of sister kinetochore orientation in meiosis-I

    Indian Academy of Sciences (India)

    Kinetochores mediate chromosome movement during cell division by interacting with the spindle microtubules. Sexual reproduction necessitates the daunting task of reducing ploidy (number of chromosome sets) in the gametes, which depends upon the specialized properties of meiosis. Kinetochores have a central role in ...

  20. Meiosis and haploid gametes in the pathogen Trypanosoma brucei.

    Science.gov (United States)

    Peacock, Lori; Bailey, Mick; Carrington, Mark; Gibson, Wendy

    2014-01-20

    In eukaryote pathogens, sex is an important driving force in spreading genes for drug resistance, pathogenicity, and virulence. For the parasitic trypanosomes that cause African sleeping sickness, mating occurs during transmission by the tsetse vector and involves meiosis, but haploid gametes have not yet been identified. Here, we show that meiosis is a normal part of development in the insect salivary glands for all subspecies of Trypanosoma brucei, including the human pathogens. By observing insect-derived trypanosomes during the window of peak expression of meiosis-specific genes, we identified promastigote-like (PL) cells that interacted with each other via their flagella and underwent fusion, as visualized by the mixing of cytoplasmic red and green fluorescent proteins. PL cells had a short, wide body, a very long anterior flagellum, and either one or two kinetoplasts, but only the anterior kinetoplast was associated with the flagellum. Measurement of nuclear DNA contents showed that PL cells were haploid relative to diploid metacyclics. Trypanosomes are among the earliest diverging eukaryotes, and our results support the hypothesis that meiosis and sexual reproduction are ubiquitous in eukaryotes and likely to have been early innovations. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

  1. "Dropping Your Genes." A Genetics Simulation in Meiosis, Fertilization & Reproduction.

    Science.gov (United States)

    Atkins, Thomas; Roderick, Joyce MacFall

    1991-01-01

    An activity that introduces students to the concepts of independent assortment of alleles during meiosis and gametogenesis, the richness of the variation that occurs as a result of allele recombination, and the unique phenotypes of offspring. Reproducible handouts with the directions and model chromosomes are provided. (KR)

  2. Kif4 Is Essential for Mouse Oocyte Meiosis.

    Science.gov (United States)

    Camlin, Nicole J; McLaughlin, Eileen A; Holt, Janet E

    2017-01-01

    Progression through the meiotic cell cycle must be strictly regulated in oocytes to generate viable embryos and offspring. During mitosis, the kinesin motor protein Kif4 is indispensable for chromosome condensation and separation, midzone formation and cytokinesis. Additionally, the bioactivity of Kif4 is dependent on phosphorylation via Aurora Kinase B and Cdk1, which regulate Kif4 function throughout mitosis. Here, we examine the role of Kif4 in mammalian oocyte meiosis. Kif4 localized in the cytoplasm throughout meiosis I and II, but was also observed to have a dynamic subcellular distribution, associating with both microtubules and kinetochores at different stages of development. Co-localization and proximity ligation assays revealed that the kinetochore proteins, CENP-C and Ndc80, are potential Kif4 interacting proteins. Functional analysis of Kif4 in oocytes via antisense knock-down demonstrated that this protein was not essential for meiosis I completion. However, Kif4 depleted oocytes displayed enlarged polar bodies and abnormal metaphase II spindles, indicating an essential role for this protein for correct asymmetric cell division in meiosis I. Further investigation of the phosphoregulation of meiotic Kif4 revealed that Aurora Kinase and Cdk activity is critical for Kif4 kinetochore localization and interaction with Ndc80 and CENP-C. Finally, Kif4 protein but not gene expression was found to be upregulated with age, suggesting a role for this protein in the decline of oocyte quality with age.

  3. Sperm should evolve to make female meiosis fair.

    Science.gov (United States)

    Brandvain, Yaniv; Coop, Graham

    2015-04-01

    Genomic conflicts arise when an allele gains an evolutionary advantage at a cost to organismal fitness. Oögenesis is inherently susceptible to such conflicts because alleles compete for inclusion into the egg. Alleles that distort meiosis in their favor (i.e., meiotic drivers) often decrease organismal fitness, and therefore indirectly favor the evolution of mechanisms to suppress meiotic drive. In this light, many facets of oögenesis and gametogenesis have been interpreted as mechanisms of protection against genomic outlaws. That females of many animal species do not complete meiosis until after fertilization, appears to run counter to this interpretation, because this delay provides an opportunity for sperm-acting alleles to meddle with the outcome of female meiosis and help like alleles drive in heterozygous females. Contrary to this perceived danger, the population genetic theory presented herein suggests that, in fact, sperm nearly always evolve to increase the fairness of female meiosis in the face of genomic conflicts. These results are consistent with the apparent sperm dependence of the best characterized female meiotic driversin animals. Rather than providing an opportunity for sperm collaboration in female meiotic drive, the "fertilization requirement" indirectly protects females from meiotic drivers by providing sperm an opportunity to suppress drive. © 2015 The Author(s).

  4. Piwil1 mediates meiosis during spermatogenesis in chicken.

    Science.gov (United States)

    Xu, Lu; Chang, Guobin; Ma, Teng; Wang, Hongzhi; Chen, Jing; Li, Zhiteng; Guo, Xiaomin; Wan, Fang; Ren, Lichen; Lu, Wei; Chen, Guohong

    2016-03-01

    Piwil1 mediates spermatogenesis and ensures stable cell division rates in germline cells in mammals. However, the involvement of Piwil1 in poultry spermatogenesis and meiosis is poorly understood. In the present study, we used TaqMan RT-qPCR to characterize Piwil1 mRNA expression in different types of spermatogenic cells, including primordial germ cells (PGCs), spermatogonial stem cells (SSCs), spermatogonia cells (Sa), tetraploid cells (Tp), round sperm cells (Rs), mature sperm, and in PGCs treated with retinoic acid. Our results revealed that Piwil1 is differentially expressed during spermatogenesis in chicken. Compared to PGCs, SSCs, Tp, and Sa, Rs cells presented the highest Piwil1 mRNA expression levels. Retinoic acid significantly upregulated Piwil1 and Stra8 mRNA expression as well as Piwil1 levels in chicken PGCs. In addition, retinoic acid induced PGCs to progress through all the meiotic stages, eventually leading to haploid cell formation, which was determined using flow cytometry and western blot analysis. Taken together, our results showed that during spermatogenesis, Piwil1 was first expressed at low levels in germ stem cells, PGCs, and SSCs. Its expression levels increased during later meiosis stages. Finally, no expression was detected in mature sperm after meiosis. Treatment of PGCs with retinoic acid further demonstrated that Piwil1 plays a key role in meiosis during chicken spermatogenesis. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. The DNA Triangle and Its Application to Learning Meiosis

    Science.gov (United States)

    Wright, L. Kate; Catavero, Christina M.; Newman, Dina L.

    2017-01-01

    Although instruction on meiosis is repeated many times during the undergraduate curriculum, many students show poor comprehension even as upper-level biology majors. We propose that the difficulty lies in the complexity of understanding DNA, which we explain through a new model, the DNA triangle. The "DNA triangle" integrates three…

  6. Sperm should evolve to make female meiosis fair

    Science.gov (United States)

    Brandvain, Yaniv; Coop, Graham

    2017-01-01

    Genomic conflicts arise when an allele gains an evolutionary advantage at a cost to organismal fitness. Oögenesis is inherently susceptible to such conflicts because alleles compete for inclusion into the egg. Alleles that distort meiosis in their favor (i.e. meiotic drivers) often decrease organismal fitness, and therefore indirectly favor the evolution of mechanisms to suppress meiotic drive. In this light, many facets of oögenesis and gametogenesis have been interpreted as mechanisms of protection against genomic outlaws. That females of many animal species do not complete meiosis until after fertilization, appears to run counter to this interpretation, because this delay provides an opportunity for sperm-acting alleles to meddle with the outcome of female meiosis and help like alleles drive in heterozygous females. Contrary to this perceived danger, the population genetic theory presented herein suggests that, in fact, sperm nearly always evolve to increase the fairness of female meiosis in the face of genomic conflicts. These results are consistent with the apparent sperm dependence of the best characterized female meiotic drivers in animals. Rather than providing an opportunity for sperm collaboration in female meiotic drive, the ‘fertilization requirement’ indirectly protects females from meiotic drivers by providing sperm an opportunity to suppress drive. PMID:25662355

  7. Restructuring of Holocentric Centromeres During Meiosis in the Plant Rhynchospora pubera.

    Science.gov (United States)

    Marques, André; Schubert, Veit; Houben, Andreas; Pedrosa-Harand, Andrea

    2016-10-01

    Centromeres are responsible for the correct segregation of chromosomes during mitosis and meiosis. Holocentric chromosomes, characterized by multiple centromere units along each chromatid, have particular adaptations to ensure regular disjunction during meiosis. Here we show by detecting CENH3, CENP-C, tubulin, and centromeric repeats that holocentromeres may be organized differently in mitosis and meiosis of Rhynchospora pubera Contrasting to the mitotic linear holocentromere organization, meiotic centromeres show several clusters of centromere units (cluster-holocentromeres) during meiosis I. They accumulate along the poleward surface of bivalents where spindle fibers perpendicularly attach. During meiosis II, the cluster-holocentromeres are mostly present in the midregion of each chromatid. A linear holocentromere organization is restored after meiosis during pollen mitosis. Thus, a not yet described case of a cluster-holocentromere organization, showing a clear centromere restructuration between mitosis and meiosis, was identified in a holocentric organism. Copyright © 2016 by the Genetics Society of America.

  8. Recombination homeostasis of meiosis during spermatogenesis under nicotine treatment

    Directory of Open Access Journals (Sweden)

    Zhai Jingli

    2018-01-01

    Full Text Available Cigarette smoking can affect male fertility via the quality of semen. To explore the effects of nicotine, a major component of cigarettes, on meiotic recombination during spermatogenesis, C57BL/6J male mice were injected with nicotine at a dosage of 0.2 mg/100 g body weight daily for 35 days (nicotine-treated group; mice in the control group were injected with isopycnic normal saline. According to previous expression profiles of mouse sperm, a subset of meiosis-related genes was pooled using bioinformatic analysis. Protein expression was compared between the two groups using by Western blotting and immunohistochemistry. Recombination frequency during the meiosis phase of spermatogenesis was estimated by combined use of chromosome spread and immunofluorescence staining in mouse testes. Data mining analysis indicated that 4 genes that express meiotic topoisomerase-like protein SPO11, MutS protein homolog 4 (MSH4, strand exchange protein RAD51 and MutL protein homologue 1 (MLH1, were associated with the meiosis recombination process. The results of Western blotting and immunohistochemistry further showed that the protein expression of SPO11 (0.73-fold and MSH4 (0.73-fold was downregulated in murine testes after nicotine treatment, whereas the protein expression of both RAD51 (2.06-fold and MLH1 (1.40-fold was upregulated. Unexpectedly, we did not detect a significant difference in recombination frequency in meiosis during spermatogenesis in the nicotine-treated group as compared to the control. Taken together, these results indicate that nicotine can affect the expression profile of restructuring-related genes, but it does not significantly change the recombination frequency during male meiosis. These findings suggest there is a self-regulating mechanism during meiotic chromosome restructuring in male mice that responds to environmental stress.

  9. Cdc14 phosphatase directs centrosome re-duplication at the meiosis I to meiosis II transition in budding yeast [version 2; referees: 3 approved, 1 approved with reservations

    Directory of Open Access Journals (Sweden)

    Colette Fox

    2017-02-01

    Full Text Available Background Gametes are generated through a specialized cell division called meiosis, in which ploidy is reduced by half because two consecutive rounds of chromosome segregation, meiosis I and meiosis II, occur without intervening DNA replication. This contrasts with the mitotic cell cycle where DNA replication and chromosome segregation alternate to maintain the same ploidy. At the end of mitosis, cyclin-dependent kinases (CDKs are inactivated. This low CDK state in late mitosis/G1 allows for critical preparatory events for DNA replication and centrosome/spindle pole body (SPB duplication. However, their execution is inhibited until S phase, where further preparatory events are also prevented. This “licensing” ensures that both the chromosomes and the centrosomes/SPBs replicate exactly once per cell cycle, thereby maintaining constant ploidy. Crucially, between meiosis I and meiosis II, centrosomes/SPBs must be re-licensed, but DNA re-replication must be avoided. In budding yeast, the Cdc14 protein phosphatase triggers CDK down regulation to promote exit from mitosis. Cdc14 also regulates the meiosis I to meiosis II transition, though its mode of action has remained unclear. Methods Fluorescence and electron microscopy was combined with proteomics to probe SPB duplication in cells with inactive or hyperactive Cdc14. Results We demonstrate that Cdc14 ensures two successive nuclear divisions by re-licensing SPBs at the meiosis I to meiosis II transition. We show that Cdc14 is asymmetrically enriched on a single SPB during anaphase I and provide evidence that this enrichment promotes SPB re-duplication. Cells with impaired Cdc14 activity fail to promote extension of the SPB half-bridge, the initial step in morphogenesis of a new SPB. Conversely, cells with hyper-active Cdc14 duplicate SPBs, but fail to induce their separation. Conclusion Our findings implicate reversal of key CDK-dependent phosphorylations in the differential licensing of

  10. Mismatch repair proteins, meiosis, and mice: understanding the complexities of mammalian meiosis.

    Science.gov (United States)

    Svetlanov, Anton; Cohen, Paula E

    2004-05-15

    Mammalian meiosis differs from that seen in lower eukaryotes in several respects, not least of which is the added complexity of dealing with chromosomal interactions across a much larger genome (12 MB over 16 chromosome pairs in Saccharomyces cerevisiae compared to 2500 MB over 19 autosome pairs in Mus musculus). Thus, the recombination machinery, while being highly conserved through eukaryotes, has evolved to accommodate such issues to preserve genome integrity and to ensure propagation of the species. One group of highly conserved meiotic regulators is the DNA mismatch repair protein family that, as their name implies, were first identified as proteins that act to repair DNA mismatches that arise primarily during DNA replication. Their function in ensuring chromosomal integrity has also translated into a critical role for this family in meiotic recombination in most sexually reproducing organisms. In mice, targeted deletion of certain family members results in severe consequences for meiotic progression and infertility. This review will focus on the studies involving these mutant mouse models, with occasional comparison to the function of these proteins in other organisms.

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

    Science.gov (United States)

    Matsuhara, Hirotada; Yamamoto, Ayumu

    2016-01-01

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

  12. Multiple Duties for Spindle Assembly Checkpoint Kinases in Meiosis

    Science.gov (United States)

    Marston, Adele L.; Wassmann, Katja

    2017-01-01

    Cell division in mitosis and meiosis is governed by evolutionary highly conserved protein kinases and phosphatases, controlling the timely execution of key events such as nuclear envelope breakdown, spindle assembly, chromosome attachment to the spindle and chromosome segregation, and cell cycle exit. In mitosis, the spindle assembly checkpoint (SAC) controls the proper attachment to and alignment of chromosomes on the spindle. The SAC detects errors and induces a cell cycle arrest in metaphase, preventing chromatid separation. Once all chromosomes are properly attached, the SAC-dependent arrest is relieved and chromatids separate evenly into daughter cells. The signaling cascade leading to checkpoint arrest depends on several protein kinases that are conserved from yeast to man. In meiosis, haploid cells containing new genetic combinations are generated from a diploid cell through two specialized cell divisions. Though apparently less robust, SAC control also exists in meiosis. Recently, it has emerged that SAC kinases have additional roles in executing accurate chromosome segregation during the meiotic divisions. Here, we summarize the main differences between mitotic and meiotic cell divisions, and explain why meiotic divisions pose special challenges for correct chromosome segregation. The less-known meiotic roles of the SAC kinases are described, with a focus on two model systems: yeast and mouse oocytes. The meiotic roles of the canonical checkpoint kinases Bub1, Mps1, the pseudokinase BubR1 (Mad3), and Aurora B and C (Ipl1) will be discussed. Insights into the molecular signaling pathways that bring about the special chromosome segregation pattern during meiosis will help us understand why human oocytes are so frequently aneuploid. PMID:29322045

  13. Multiple Duties for Spindle Assembly Checkpoint Kinases in Meiosis

    Directory of Open Access Journals (Sweden)

    Adele L. Marston

    2017-12-01

    Full Text Available Cell division in mitosis and meiosis is governed by evolutionary highly conserved protein kinases and phosphatases, controlling the timely execution of key events such as nuclear envelope breakdown, spindle assembly, chromosome attachment to the spindle and chromosome segregation, and cell cycle exit. In mitosis, the spindle assembly checkpoint (SAC controls the proper attachment to and alignment of chromosomes on the spindle. The SAC detects errors and induces a cell cycle arrest in metaphase, preventing chromatid separation. Once all chromosomes are properly attached, the SAC-dependent arrest is relieved and chromatids separate evenly into daughter cells. The signaling cascade leading to checkpoint arrest depends on several protein kinases that are conserved from yeast to man. In meiosis, haploid cells containing new genetic combinations are generated from a diploid cell through two specialized cell divisions. Though apparently less robust, SAC control also exists in meiosis. Recently, it has emerged that SAC kinases have additional roles in executing accurate chromosome segregation during the meiotic divisions. Here, we summarize the main differences between mitotic and meiotic cell divisions, and explain why meiotic divisions pose special challenges for correct chromosome segregation. The less-known meiotic roles of the SAC kinases are described, with a focus on two model systems: yeast and mouse oocytes. The meiotic roles of the canonical checkpoint kinases Bub1, Mps1, the pseudokinase BubR1 (Mad3, and Aurora B and C (Ipl1 will be discussed. Insights into the molecular signaling pathways that bring about the special chromosome segregation pattern during meiosis will help us understand why human oocytes are so frequently aneuploid.

  14. 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 ...

  15. Genes Important for Schizosaccharomyces pombe Meiosis Identified Through a Functional Genomics Screen

    Science.gov (United States)

    Blyth, Julie; Makrantoni, Vasso; Barton, Rachael E.; Spanos, Christos; Rappsilber, Juri; Marston, Adele L.

    2018-01-01

    Meiosis is a specialized cell division that generates gametes, such as eggs and sperm. Errors in meiosis result in miscarriages and are the leading cause of birth defects; however, the molecular origins of these defects remain unknown. Studies in model organisms are beginning to identify the genes and pathways important for meiosis, but the parts list is still poorly defined. Here we present a comprehensive catalog of genes important for meiosis in the fission yeast, Schizosaccharomyces pombe. Our genome-wide functional screen surveyed all nonessential genes for roles in chromosome segregation and spore formation. Novel genes important at distinct stages of the meiotic chromosome segregation and differentiation program were identified. Preliminary characterization implicated three of these genes in centrosome/spindle pole body, centromere, and cohesion function. Our findings represent a near-complete parts list of genes important for meiosis in fission yeast, providing a valuable resource to advance our molecular understanding of meiosis. PMID:29259000

  16. Distinct temporal requirements for autophagy and the proteasome in yeast meiosis.

    Science.gov (United States)

    Wen, Fu-ping; Guo, Yue-shuai; Hu, Yang; Liu, Wei-xiao; Wang, Qian; Wang, Yuan-ting; Yu, Hai-Yan; Tang, Chao-ming; Yang, Jun; Zhou, Tao; Xie, Zhi-ping; Sha, Jia-hao; Guo, Xuejiang; Li, Wei

    2016-01-01

    Meiosis is a special type of cellular renovation that involves 2 successive cell divisions and a single round of DNA replication. Two major degradation systems, the autophagy-lysosome and the ubiquitin-proteasome, are involved in meiosis, but their roles have yet to be elucidated. Here we show that autophagy mainly affects the initiation of meiosis but not the nuclear division. Autophagy works not only by serving as a dynamic recycling system but also by eliminating some negative meiotic regulators such as Ego4 (Ynr034w-a). In a quantitative proteomics study, the proteasome was found to be significantly upregulated during meiotic divisions. We found that proteasomal activity is essential to the 2 successive meiotic nuclear divisions but not for the initiation of meiosis. Our study defines the roles of autophagy and the proteasome in meiosis: Autophagy mainly affects the initiation of meiosis, whereas the proteasome mainly affects the 2 successive meiotic divisions.

  17. Functions of Aurora kinase C in meiosis and cancer

    Directory of Open Access Journals (Sweden)

    Suzanne M. Quartuccio

    2015-08-01

    Full Text Available The mammalian genome encodes three Aurora kinase protein family members: A, B, and C. While Aurora kinase A (AURKA and B (AURKB are found in cells throughout the body, significant protein levels of Aurora kinase C (AURKC are limited to cells that undergo meiosis (sperm and oocyte. Despite its discovery nearly 15 years ago, we know little about the function of AURKC compared to that of the other 2 Aurora kinases. This lack of understanding can be attributed to the high sequence homology between AURKB and AURKC preventing the use of standard approaches to understand non-overlapping and meiosis I (MI-specific functions of the two kinases. Recent evidence has revealed distinct functions of AURKC in meiosis and may aid in our understanding of why chromosome segregation during MI often goes awry in oocytes. Many cancers aberrantly express AURKC, but because we do not fully understand AURKC function in its normal cellular context, it is difficult to predict the biological significance of this expression on the disease. Here, we consolidate and update what is known about AURKC signaling in meiotic cells to better understand why it has oncogenic potential.

  18. Roles of Cohesin and Condensin in Chromosome Dynamics During Mammalian Meiosis

    OpenAIRE

    LEE, Jibak

    2013-01-01

    Meiosis is a key step for sexual reproduction in which chromosome number is halved by two successive meiotic divisions after a single round of DNA replication. In the first meiotic division (meiosis I), homologous chromosomes pair, synapse, and recombine with their partners in prophase I. As a result, homologous chromosomes are physically connected until metaphase I and then segregated from each other at the onset of anaphase I. In the subsequent second meiotic division (meiosis II), sister c...

  19. [Inverted meiosis and its place in the evolution of sexual reproduction pathways].

    Science.gov (United States)

    Bogdanov, Yu F

    2016-05-01

    Inverted meiosis is observed in plants (Cyperaceae and Juncaceae) and insects (Coccoidea, Aphididae) with holocentric chromosomes, the centromeres of which occupy from 70 to 90% of the metaphase chromosome length. In the first meiotic division (meiosis I), chiasmata are formed and rodlike bivalents orient equationally, and in anaphase I, sister chromatids segregate to the poles; the diploid chromosome number is maintained. Non-sister chromatids of homologous chromosomes remain in contact during interkinesis and prophase II and segregate in anaphase II, forming haploid chromosome sets. The segregation of sister chromatids in meiosis I was demonstrated by example of three plant species that were heterozygous for chromosomal rearrangements. In these species, sister chromatids, marked with rearrangement, segregated in anaphase I. Using fluorescent antibodies, it was demonstrated that meiotic recombination enzymes Spo11 and Rad5l, typical of canonical meiosis, functioned at the meiotic prophase I of pollen mother cells of Luzula elegance and Rhynchospora pubera. Moreover, antibodies to synaptonemal complexes proteins ASY1 and ZYP1 were visualized as filamentous structures, pointing to probable formation of synaptonemal complexes. In L. elegance, chiasmata are formed by means of chromatin threads containing satellite DNA. According to the hypothesis of the author of this review, equational division of sister chromatids at meiosis I in the organisms with inverted meiosis can be explained by the absence of specific meiotic proteins (shugoshins). These proteins are able to protect cohesins of holocentric centromeres from hydrolysis by separases at meiosis I, as occurs in the organisms with monocentric chromosomes and canonical meiosis. The basic type of inverted meiosis was described in Coccoidea and Aphididae males. In their females, the variants of parthenogenesis were also observed. Until now, the methods of molecular cytogenetics were not applied for the analysis of

  20. p53 Protein interacts specifically with the meiosis-specific mammalian RecA-like protein DMC1 in meiosis.

    Science.gov (United States)

    Habu, Toshiyuki; Wakabayashi, Nobunao; Yoshida, Kayo; Yomogida, Kenntaro; Nishimune, Yoshitake; Morita, Takashi

    2004-06-01

    The tumor suppressor protein p53 is specifically expressed during meiosis in spermatocytes. Subsets of p53 knockout mice exhibit testicular giant cell degenerative syndrome, which suggests p53 may be associated with meiotic cell cycle and/or DNA metabolism. Here, we show that p53 binds to the mouse meiosis-specific RecA-like protein Mus musculus DMC1 (MmDMC1). The C-terminal domain (amino acid 234-340) of MmDMC1 binds to DNA-binding domain of p53 protein. p53 might be involved in homologous recombination and/or checkpoint function by directly binding to DMC1 protein to repress genomic instability in meiotic germ cells.

  1. Unraveling the proteomic profile of mice testis during the initiation of meiosis.

    Science.gov (United States)

    Shao, Binbin; Guo, Yueshuai; Wang, Lei; Zhou, Quan; Gao, Tingting; Zheng, Bo; Zheng, Haoyu; Zhou, Tao; Zhou, Zuomin; Guo, Xuejiang; Huang, Xiaoyan; Sha, Jiahao

    2015-04-29

    In mice, once primordial germ cells (PGCs) are generated, they continue to proliferate and migrate to eventually reach the future gonads. They initiate sexual differentiation after their colonization of the gonads. During this process, retinoic acid (RA) induces meiosis in the female germ cells, which proceeds to the diplotene stage of meiotic prophase I, whereas the male germ cells initiate growth arrest. After birth, meiosis is initiated in mice spermatogonia by their conversion to preleptotene spermatocytes. There are evidences showing the roles of RA in the regulation of spermatogonial differentiation and meiosis initiation. However, it is still not well known on what responds to RA and how RA signaling engages meiosis. Thus, we constructed a proteomic profile of proteins associated with meiosis onset during testis development in mouse and identified 104 differentially expressed proteins (≥1.5 folds). Bioinformatic analysis showed proteins functioning in specific cell processes. The expression patterns of five selected proteins were verified via Western blot, of which we found that Tfrc gene was RA responsive, with a RA responsive element, and could be up regulated by RA in spermatogonial stem cell (SSC) line. Taken together, the results provide an important reference profile for further functional study of meiosis initiation. Spermatogenesis involves mitosis of spermatogonia, meiosis of spermatocytes and spermiogenesis, in which meiosis is a unique event to germ cells, and not in the somatic cells. Till now, the detailed molecular mechanisms of the transition from mitosis to meiosis are still not elucidated. With high-throughput proteomic technology, it is now possible to systemically identify proteins possibly involved. With TMT-6plex based quantification, we identified 104 proteins differentially between testes without meiosis (day 8.5) and those that were meiosis initiated (day 10.5). And a well-known protein essential for meiosis initiation, stra8, was

  2. Transcript profiling to analyse gene expression during male meiosis in petunia hybrida

    NARCIS (Netherlands)

    Cnudde, F.

    2004-01-01

    Meiosis is a key feature of eukaryotic sexual reproduction. So far, the molecular and functional analysis of meiosis is relatively underdeveloped in plants, but the flood of genomics data from yeast research and the availability of large mutant collections cause a growing interest in molecular

  3. An Interactive Modeling Lesson Increases Students' Understanding of Ploidy during Meiosis

    Science.gov (United States)

    Wright, L. Kate; Newman, Dina L.

    2011-01-01

    Chromosome structure is confusing to students at all levels, and chromosome behavior during meiosis is a notoriously difficult topic. Undergraduate biology majors are exposed to the process of meiosis numerous times during their presecondary and postsecondary education, yet understanding of key concepts, such as the point at which haploidy is…

  4. First-Year Biology Students' Understandings of Meiosis: An Investigation Using a Structural Theoretical Framework

    Science.gov (United States)

    Quinn, Frances; Pegg, John; Panizzon, Debra

    2009-01-01

    Meiosis is a biological concept that is both complex and important for students to learn. This study aims to explore first-year biology students' explanations of the process of meiosis, using an explicit theoretical framework provided by the Structure of the Observed Learning Outcome (SOLO) model. The research was based on responses of 334…

  5. In germ cells of mouse embryonic ovaries, the decision to enter meiosis precedes premeiotic DNA replication

    NARCIS (Netherlands)

    Baltus, Andrew E.; Menke, Douglas B.; Hu, Yueh-Chiang; Goodheart, Mary L.; Carpenter, Anne E.; de Rooij, Dirk G.; Page, David C.

    2006-01-01

    The transition from mitosis to meiosis is a defining juncture in the life cycle of sexually reproducing organisms. In yeast, the decision to enter meiosis is made before the single round of DNA replication that precedes the two meiotic divisions. We present genetic evidence of an analogous decision

  6. Meiosis I chromosome segregation is established through regulation of microtubule–kinetochore interactions

    Science.gov (United States)

    Miller, Matthew P; Ünal, Elçin; Brar, Gloria A; Amon, Angelika

    2012-01-01

    During meiosis, a single round of DNA replication is followed by two consecutive rounds of nuclear divisions called meiosis I and meiosis II. In meiosis I, homologous chromosomes segregate, while sister chromatids remain together. Determining how this unusual chromosome segregation behavior is established is central to understanding germ cell development. Here we show that preventing microtubule–kinetochore interactions during premeiotic S phase and prophase I is essential for establishing the meiosis I chromosome segregation pattern. Premature interactions of kinetochores with microtubules transform meiosis I into a mitosis-like division by disrupting two key meiosis I events: coorientation of sister kinetochores and protection of centromeric cohesin removal from chromosomes. Furthermore we find that restricting outer kinetochore assembly contributes to preventing premature engagement of microtubules with kinetochores. We propose that inhibition of microtubule–kinetochore interactions during premeiotic S phase and prophase I is central to establishing the unique meiosis I chromosome segregation pattern. DOI: http://dx.doi.org/10.7554/eLife.00117.001 PMID:23275833

  7. Meiosis in oocytes: predisposition to aneuploidy and its increased incidence with age.

    Science.gov (United States)

    Jones, Keith T

    2008-01-01

    Mammalian oocytes begin meiosis in the fetal ovary, but only complete it when fertilized in the adult reproductive tract. This review examines the cell biology of this protracted process: from entry of primordial germ cells into meiosis to conception. The defining feature of meiosis is two consecutive cell divisions (meiosis I and II) and two cell cycle arrests: at the germinal vesicle (GV), dictyate stage of prophase I and at metaphase II. These arrests are spanned by three key events, the focus of this review: (i) passage from mitosis to GV arrest during fetal life, regulated by retinoic acid; (ii) passage through meiosis I and (iii) completion of meiosis II following fertilization, both meiotic divisions being regulated by cyclin-dependent kinase (CDK1) activity. Meiosis I in human oocytes is associated with an age-related high rate of chromosomal mis-segregation, such as trisomy 21 (Down's syndrome), resulting in aneuploid conceptuses. Although aneuploidy is likely to be multifactorial, oocytes from older women may be predisposed to be becoming aneuploid as a consequence of an age-long decline in the cohesive ties holding chromosomes together. Such loss goes undetected by the oocyte during meiosis I either because its ability to respond and block division also deteriorates with age, or as a consequence of being inherently unable to respond to the types of segregation defects induced by cohesion loss.

  8. Dysregulation of the mitosis-meiosis switch in testicular carcinoma in situ

    DEFF Research Database (Denmark)

    Jørgensen, Anne; Nielsen, John E; Almstrup, Kristian

    2013-01-01

    , except in spermatocytic seminoma (not derived from CIS). In conclusion, this study indicates that meiosis signalling is dysregulated in CIS cells and that a key regulator of the mitosis-meiosis switch, DMRT1, is expressed in 'early-stage' CIS cells but is down-regulated with further invasive...

  9. TACC3 Is Important for Correct Progression of Meiosis in Bovine Oocytes

    NARCIS (Netherlands)

    Mahdipour, Mahdi; Leitoguinho, Ana Rita Canhoto; Zacarias Silva, Ricardo A; van Tol, Helena T A; Stout, Tom A E; Rodrigues, Gabriela; Roelen, Bernard A J

    2015-01-01

    Transforming acidic coiled-coil (TACC) proteins are key players during mitosis via stabilization of the spindle. The roles of TACCs during meiosis are however less clear. We used bovine oocytes to study the expression and function of TACC3 during meiosis. TACC3 mRNA was detected in bovine oocytes

  10. Mouse TRIP13/PCH2 Is Required for Recombination and Normal Higher-Order Chromosome Structure during Meiosis

    NARCIS (Netherlands)

    Roig, I.; Dowdle, J.A.; Toth, A.; de Rooij, D.G.; Jasin, M.; Keeney, S.

    2010-01-01

    Accurate chromosome segregation during meiosis requires that homologous chromosomes pair and become physically connected so that they can orient properly on the meiosis I spindle. These connections are formed by homologous recombination closely integrated with the development of meiosis-specific,

  11. Mps1 kinase-dependent Sgo2 centromere localisation mediates cohesin protection in mouse oocyte meiosis I

    NARCIS (Netherlands)

    Yakoubi, W. El; Buffin, E.; Cladiere, D.; Gryaznova, Y.; Berenguer, I.; Touati, S.A.; Gomez, R.; Suja, J.A.; Deursen, J.M.A. van; Wassmann, K.

    2017-01-01

    A key feature of meiosis is the step-wise removal of cohesin, the protein complex holding sister chromatids together, first from arms in meiosis I and then from the centromere region in meiosis II. Centromeric cohesin is protected by Sgo2 from Separase-mediated cleavage, in order to maintain sister

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

    International Nuclear Information System (INIS)

    Tang Zesheng; Yang Jun; Zhao Yan; Yuan Haiyun

    2004-01-01

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

  13. Plk1 is essential for proper chromosome segregation during meiosis I/meiosis II transition in pig oocytes.

    Science.gov (United States)

    Zhang, Zixiao; Chen, Changchao; Ma, Liying; Yu, Qiuchen; Li, Shuai; Abbasi, Benazir; Yang, Jiayi; Rui, Rong; Ju, Shiqiang

    2017-08-29

    Polo-like kinase 1 (Plk1), as a characteristic regulator in meiosis, organizes multiple biological events of cell division. Although Plk1 has been implicated in various functions in somatic cell mitotic processes, considerably less is known regarding its function during the transition from metaphase I (MI) to metaphase II (MII) stage in oocyte meiotic progression. In this study, the possible role of Plk1 during the MI-to-MII stage transition in pig oocytes was addressed. Initially, the spatiotemporal expression and subcellular localization pattern of Plk1 were revealed in pig oocytes from MI to MII stage using indirect immunofluorescence and confocal microscopy imaging techniques combined with western blot analyses. Moreover, a highly selective Plk1 inhibitor, GSK461364, was used to determine the potential role of Plk1 during this MI-to-MII transition progression. Upon expression, Plk1 exhibited a specific dynamic intracellular localization, and co-localization of Plk1 with α-tubulin was revealed in the meiotic spindle of pig oocyte during the transition from MI to MII stage. GSK461364 treatment significantly blocked the first polar body (pbI) emission in a dose-dependent manner and resulted in a failure of meiotic maturation, with a larger percentage of the GSK461364-treated oocytes arresting in the anaphase-telophase I (ATI) stage. Further subcellular structure examination results showed that inhibition of Plk1 with GSK461364 had no visible effect on spindle assembly but caused a significantly higher proportion of the treated oocytes to have obvious defects in homologous chromosome segregation at ATI stage. Thus, these results indicate that Plk1 plays an essential role during the meiosis I/meiosis II transition in porcine oocytes, and the regulation is associated with Plk1's effects on homologous chromosome segregation in the ATI stage.

  14. Observing meiosis in filamentous fungi: Sordaria and Neurospora.

    Science.gov (United States)

    Zickler, Denise

    2009-01-01

    The filamentous fungi Neurospora crassa and Sordaria macrospora are materials of choice for recombination studies because each of the DNA strands involved in meiosis can be visually analyzed using spore-color mutants. Well-advanced molecular genetic methodologies have been developed for each of these fungi, and several mutants defective in recombination and/or pairing are available. Moreover, the complete genome sequence of N. crassa has made it possible to clone virtually any gene involved in their life cycle. Both fungi provide also a particularly attractive experimental system for cytological analysis of meiosis: stages can be determined independently of chromosomal morphology and their seven chromosomes are easily identified. The techniques for light, immunofluorescence and electron microscopy presented here have been used, with success, for monitoring of chromosome behavior during both meiotic and sporulation processes. They have also proved useful for the analysis of mitochondria and peroxisomes as well as cytoskeleton and spindle pole-body components. Moreover, all techniques of this chapter can be easily applied to other filamentous ascomycetes, including other Sordaria and Neurospora species as well as Podospora, Ascobolus, Ascophanus, Fusarium, Neotiella, and Aspergillus species.

  15. Retinoic acid activates two pathways required for meiosis in mice.

    Directory of Open Access Journals (Sweden)

    Jana Koubova

    2014-08-01

    Full Text Available In all sexually reproducing organisms, cells of the germ line must transition from mitosis to meiosis. In mice, retinoic acid (RA, the extrinsic signal for meiotic initiation, activates transcription of Stra8, which is required for meiotic DNA replication and the subsequent processes of meiotic prophase. Here we report that RA also activates transcription of Rec8, which encodes a component of the cohesin complex that accumulates during meiotic S phase, and which is essential for chromosome synapsis and segregation. This RA induction of Rec8 occurs in parallel with the induction of Stra8, and independently of Stra8 function, and it is conserved between the sexes. Further, RA induction of Rec8, like that of Stra8, requires the germ-cell-intrinsic competence factor Dazl. Our findings strengthen the importance of RA and Dazl in the meiotic transition, provide important details about the Stra8 pathway, and open avenues to investigate early meiosis through analysis of Rec8 induction and function.

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

    Science.gov (United States)

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

    2015-09-01

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

  17. Dma1-dependent degradation of SIN proteins during meiosis in Schizosaccharomyces pombe.

    Science.gov (United States)

    Krapp, Andrea; Simanis, Viesturs

    2014-07-15

    The Schizosaccharomyces pombe septation initiation network (SIN) is required for cytokinesis during vegetative growth and for spore formation during meiosis. Regulation of the SIN during mitosis has been studied extensively, but less is known about its meiotic regulation. Here, we show that several aspects of SIN regulation differ between mitosis and meiosis. First, the presence of GTP-bound Spg1p is not the main determinant of the timing of Cdc7p and Sid1p association with the spindle pole body (SPB) during meiosis. Second, the localisation dependencies of SIN proteins differ from those in mitotic cells, suggesting a modified functional organisation of the SIN during meiosis. Third, there is stage-specific degradation of SIN components in meiosis; Byr4p is degraded after meiosis I, whereas the degradation of Cdc7p, Cdc11p and Sid4p occurs after the second meiotic division and depends upon the ubiquitin ligase Dma1p. Finally, Dma1p-dependent degradation is not restricted to the SIN, as we show that Dma1p is needed for the degradation of Mcp6p (also known as Hrs1p) during meiosis I. Taken together, these data suggest that stage-specific targeted proteolysis plays an important role in regulating meiotic progression. © 2014. Published by The Company of Biologists Ltd.

  18. Exposure to Brefeldin A promotes initiation of meiosis in murine female germ cells.

    Science.gov (United States)

    Zhang, Lian-Jun; Chen, Bo; Feng, Xin-Lei; Ma, Hua-Gang; Sun, Li-Lan; Feng, Yan-Min; Liang, Gui-Jin; Cheng, Shun-Feng; Li, Lan; Shen, Wei

    2015-01-01

    In mammals, ontogenesis starts from a fusion of spermatozoon and oocyte, which are produced by reductive nuclear division of a diploid germ cell in a specialised but complex biological process known as meiosis. However, little is known about the mechanism of meiotic initiation in germ cells, although many factors may be responsible for meiosis both in male and female gonads. In this study, 11.5 days post coitum (dpc) female fetal mouse genital ridges were cultured in vitro with exposure to Brefeldin A (BFA) for 6h, and the changes in meiosis were detected. Synaptonemal-complex analysis implied that BFA played a positive role in meiosis initiation and this hypothesis was confirmed by quantitative PCR of meiosis-specific genes: stimulated by retinoic acid gene 8 (Stra8) and deleted in a zoospermia-like (DAZL). At the same time, mRNA expression of retinoic acid synthetase (Raldh2) and retinoic acid (RA) receptors increased in female gonads with in vitro exposure to BFA. Transplanting genital ridges treated with BFA into the kidney capsule of immunodeficient mice demonstrated that the development capacity of female germ cells was normal, while formation of primordial follicles was seen to be a result of accelerated meiosis after exposure to BFA. In conclusion, the study indicated that BFA stimulated meiosis initiation partly by RA signalling and then promoted the development of follicles.

  19. A nutrient dependant switch explains mutually exclusive existence of meiosis and mitosis initiation in budding yeast.

    Science.gov (United States)

    Wannige, C T; Kulasiri, D; Samarasinghe, S

    2014-01-21

    Nutrients from living environment are vital for the survival and growth of any organism. Budding yeast diploid cells decide to grow by mitosis type cell division or decide to create unique, stress resistant spores by meiosis type cell division depending on the available nutrient conditions. To gain a molecular systems level understanding of the nutrient dependant switching between meiosis and mitosis initiation in diploid cells of budding yeast, we develop a theoretical model based on ordinary differential equations (ODEs) including the mitosis initiator and its relations to budding yeast meiosis initiation network. Our model accurately and qualitatively predicts the experimentally revealed temporal variations of related proteins under different nutrient conditions as well as the diverse mutant studies related to meiosis and mitosis initiation. Using this model, we show how the meiosis and mitosis initiators form an all-or-none type bistable switch in response to available nutrient level (mainly nitrogen). The transitions to and from meiosis or mitosis initiation states occur via saddle node bifurcation. This bidirectional switch helps the optimal usage of available nutrients and explains the mutually exclusive existence of meiosis and mitosis pathways. © 2013 Elsevier Ltd. All rights reserved.

  20. Meiosis in gamma-ray induced tomato mutants of line XXIV-a

    International Nuclear Information System (INIS)

    Zagorcheva, L.; Jordanov, M.

    1976-01-01

    Results are reported of investigations on meiosis in tomato mutants obtained by gamma-irradiation ( 60 Co) of seeds from line XXIV-a with doses of 20 and 30 krad. Two genome mutants (one a triploid and the other a tetraploid form) as well as a chromosome aberration of the translocation type, were selected in the course of the investigations and their meiosis is described. Meiosis in the initial form (line XXIV-a) was also studied. About 16% of the initial line XXIV-a plants proved to be trisomic forms. (author)

  1. The role of cohesin genes in the meiosis of male house mouse

    OpenAIRE

    Šebestová, Lenka

    2015-01-01

    Cohesin genes play an important role in cell division. They ensure proper chromosome segregation during mitosis and meiosis. This study is focused on the role of cohesin genes during meiosis in male house mouse (Mus musculus). At first, this study introduces key processes of mammalian meiosis. Next, the structure of cohesin complex is described; it consists of a heterodimer SMC proteins - SMC3 and SMC1α or SMC1β, which are enclosed to the ring by cleavable subunit RAD21, RAD21L or REC8. Fourt...

  2. Meiosis in untreated and irradiated cyperus eragrostis vahl

    International Nuclear Information System (INIS)

    Bokhari, F.S.

    1976-01-01

    A cytological investigation of meiosis is seed irradiated Cyperus eragrostis has shown that the diffuse centromeric type of chromosome organisation leads to the formation of inviable chromosome complements, in which complex configurations resulting from stickiness as well as pairing of homologous regions, and numerous fragments, persist to the formation of pollen grains. At the higher doses, however, there is complete sterility, and low fertility even at the lower doses. The small numbers of M 2 and M 3 plants produced at lower doses show much reduced chromosomal abnormalities, indicating severe selection among the gametes and zygotes formed. There is little advantage in terms of survival from radiation damage, resulting from the possession of the diffuse centromere. (auth.)

  3. The RNA-binding protein Spo5 promotes meiosis II by regulating cyclin Cdc13 in fission yeast.

    Science.gov (United States)

    Arata, Mayumi; Sato, Masamitsu; Yamashita, Akira; Yamamoto, Masayuki

    2014-03-01

    Meiosis comprises two consecutive nuclear divisions, meiosis I and II. Despite this unique progression through the cell cycle, little is known about the mechanisms controlling the sequential divisions. In this study, we carried out a genetic screen to identify factors that regulate the initiation of meiosis II in the fission yeast Schizosaccharomyces pombe. We identified mutants deficient in meiosis II progression and repeatedly isolated mutants defective in spo5, which encodes an RNA-binding protein. Using fluorescence microscopy to visualize YFP-tagged protein, we found that spo5 mutant cells precociously lost Cdc13, the major B-type cyclin in fission yeast, before meiosis II. Importantly, the defect in meiosis II was rescued by increasing CDK activity. In wild-type cells, cdc13 transcripts increased during meiosis II, but this increase in cdc13 expression was weaker in spo5 mutants. Thus, Spo5 is a novel regulator of meiosis II that controls the level of cdc13 expression and promotes de novo synthesis of Cdc13. We previously reported that inhibition of Cdc13 degradation is necessary to initiate meiosis II; together with the previous information, the current findings indicate that the dual control of Cdc13 by de novo synthesis and suppression of proteolysis ensures the progression of meiosis II. © 2014 The Authors Genes to Cells © 2014 by the Molecular Biology Society of Japan and Wiley Publishing Asia Pty Ltd.

  4. Induction of spontaneous and UV-induced mutations during commitment to meiosis in Saccharomyces cerevisiae

    International Nuclear Information System (INIS)

    Machida, I.; Nakai, S.

    1980-01-01

    Inductions of reversions of nonsense, missense and frameshift-type mutations were investigated in a diploid cell population of Saccharomyces cerevisiae during commitment to meiosis, by using the medium-transfer technique from sporulation medium to vegetative medium. The yields of spontaneous reverse mutations obtained from the cells that were committed to different stages during meiosis were rather constant irrespective of the alleles tested, although the yields of both intergenic and intragenic recombinations markedly increased. The susceptibilities to UV-induced reverse mutations examined during commitment to meiosis were not changed appreciably. It is concluded that induction of base-change-type mutations in meiosis is not essentially different from that in mitosis. (orig.)

  5. Regulatory Control of the Resolution of DNA Recombination Intermediates during Meiosis and Mitosis

    OpenAIRE

    Matos, Joao; Blanco, Miguel G.; Maslen, Sarah; Skehel, J. Mark; West, Stephen C.

    2011-01-01

    The efficient and timely resolution of DNA recombination intermediates is essential for bipolar chromosome segregation. Here, we show that the specialized chromosome segregation patterns of meiosis and mitosis, which require the coordination of recombination with cell-cycle progression, are achieved by regulating the timing of activation of two crossover-promoting endonucleases. In yeast meiosis, Mus81-Mms4 and Yen1 are controlled by phosphorylation events that lead to their sequential activa...

  6. Motoring through: the role of kinesin superfamily proteins in female meiosis.

    Science.gov (United States)

    Camlin, Nicole J; McLaughlin, Eileen A; Holt, Janet E

    2017-07-01

    The kinesin motor protein family consists of 14 distinct subclasses and 45 kinesin proteins in humans. A large number of these proteins, or their orthologues, have been shown to possess essential function(s) in both the mitotic and the meiotic cell cycle. Kinesins have important roles in chromosome separation, microtubule dynamics, spindle formation, cytokinesis and cell cycle progression. This article contains a review of the literature with respect to the role of kinesin motor proteins in female meiosis in model species. Throughout, we discuss the function of each class of kinesin proteins during oocyte meiosis, and where such data are not available their role in mitosis is considered. Finally, the review highlights the potential clinical importance of this family of proteins for human oocyte quality. To examine the role of kinesin motor proteins in oocyte meiosis. A search was performed on the Pubmed database for journal articles published between January 1970 and February 2017. Search terms included 'oocyte kinesin' and 'meiosis kinesin' in addition to individual kinesin names with the terms oocyte or meiosis. Within human cells 45 kinesin motor proteins have been discovered, with the role of only 13 of these proteins, or their orthologues, investigated in female meiosis. Furthermore, of these kinesins only half have been examined in mammalian oocytes, despite alterations occurring in gene transcripts or protein expression with maternal ageing, cryopreservation or behavioral conditions, such as binge drinking, for many of them. Kinesin motor proteins have distinct and important roles throughout oocyte meiosis in many non-mammalian model species. However, the functions these proteins have in mammalian meiosis, particularly in humans, are less clear owing to lack of research. This review brings to light the need for more experimental investigation of kinesin motor proteins, particularly those associated with maternal ageing, cryopreservation or exposure to

  7. Hydra meiosis reveals unexpected conservation of structural synaptonemal complex proteins across metazoans

    OpenAIRE

    Fraune, Johanna; Alsheimer, Manfred; Volff, Jean-Nicolas; Busch, Karoline; Fraune, Sebastian; Bosch, Thomas C. G.; Benavente, Ricardo

    2012-01-01

    The synaptonemal complex (SC) is a key structure of meiosis, mediating the stable pairing (synapsis) of homologous chromosomes during prophase I. Its remarkable tripartite structure is evolutionarily well conserved and can be found in almost all sexually reproducing organisms. However, comparison of the different SC protein components in the common meiosis model organisms Saccharomyces cerevisiae, Arabidopsis thaliana, Caenorhabditis elegans, Drosophila melanogaster, and Mus musculus revealed...

  8. High-Throughput Screening to Identify Regulators of Meiosis-Specific Gene Expression in Saccharomyces cerevisiae.

    Science.gov (United States)

    Kassir, Yona

    2017-01-01

    Meiosis and gamete formation are processes that are essential for sexual reproduction in all eukaryotic organisms. Multiple intracellular and extracellular signals feed into pathways that converge on transcription factors that induce the expression of meiosis-specific genes. Once triggered the meiosis-specific gene expression program proceeds in a cascade that drives progress through the events of meiosis and gamete formation. Meiosis-specific gene expression is tightly controlled by a balance of positive and negative regulatory factors that respond to a plethora of signaling pathways. The budding yeast Saccharomyces cerevisiae has proven to be an outstanding model for the dissection of gametogenesis owing to the sophisticated genetic manipulations that can be performed with the cells. It is possible to use a variety selection and screening methods to identify genes and their functions. High-throughput screening technology has been developed to allow an array of all viable yeast gene deletion mutants to be screened for phenotypes and for regulators of gene expression. This chapter describes a protocol that has been used to screen a library of homozygous diploid yeast deletion strains to identify regulators of the meiosis-specific IME1 gene.

  9. Casein Kinase 1 Coordinates Cohesin Cleavage, Gametogenesis, and Exit from M Phase in Meiosis II.

    Science.gov (United States)

    Argüello-Miranda, Orlando; Zagoriy, Ievgeniia; Mengoli, Valentina; Rojas, Julie; Jonak, Katarzyna; Oz, Tugce; Graf, Peter; Zachariae, Wolfgang

    2017-01-09

    Meiosis consists of DNA replication followed by two consecutive nuclear divisions and gametogenesis or spore formation. While meiosis I has been studied extensively, less is known about the regulation of meiosis II. Here we show that Hrr25, the conserved casein kinase 1δ of budding yeast, links three mutually independent key processes of meiosis II. First, Hrr25 induces nuclear division by priming centromeric cohesin for cleavage by separase. Hrr25 simultaneously phosphorylates Rec8, the cleavable subunit of cohesin, and removes from centromeres the cohesin protector composed of shugoshin and the phosphatase PP2A. Second, Hrr25 initiates the sporulation program by inducing the synthesis of membranes that engulf the emerging nuclei at anaphase II. Third, Hrr25 mediates exit from meiosis II by activating pathways that trigger the destruction of M-phase-promoting kinases. Thus, Hrr25 synchronizes formation of the single-copy genome with gamete differentiation and termination of meiosis. Copyright © 2017 Elsevier Inc. All rights reserved.

  10. Transcription factors SOHLH1 and SOHLH2 coordinate oocyte differentiation without affecting meiosis I.

    Science.gov (United States)

    Shin, Yong-Hyun; Ren, Yu; Suzuki, Hitomi; Golnoski, Kayla J; Ahn, Hyo Won; Mico, Vasil; Rajkovic, Aleksandar

    2017-06-01

    Following migration of primordial germ cells to the genital ridge, oogonia undergo several rounds of mitotic division and enter meiosis at approximately E13.5. Most oocytes arrest in the dictyate (diplotene) stage of meiosis circa E18.5. The genes necessary to drive oocyte differentiation in parallel with meiosis are unknown. Here, we have investigated whether expression of spermatogenesis and oogenesis bHLH transcription factor 1 (Sohlh1) and Sohlh2 coordinates oocyte differentiation within the embryonic ovary. We found that SOHLH2 protein was expressed in the mouse germline as early as E12.5 and preceded SOHLH1 protein expression, which occurred circa E15.5. SOHLH1 protein appearance at E15.5 correlated with SOHLH2 translocation from the cytoplasm into the nucleus and was dependent on SOHLH1 expression. NOBOX oogenesis homeobox (NOBOX) and LIM homeobox protein 8 (LHX8), two important regulators of postnatal oogenesis, were coexpressed with SOHLH1. Single deficiency of Sohlh1 or Sohlh2 disrupted the expression of LHX8 and NOBOX in the embryonic gonad without affecting meiosis. Sohlh1-KO infertility was rescued by conditional expression of the Sohlh1 transgene after the onset of meiosis. However, Sohlh1 or Sohlh2 transgene expression could not rescue Sohlh2-KO infertility due to a lack of Sohlh1 or Sohlh2 expression in rescued mice. Our results indicate that Sohlh1 and Sohlh2 are essential regulators of oocyte differentiation but do not affect meiosis I.

  11. Dynamics of DNA replication during premeiosis and early meiosis in wheat.

    Science.gov (United States)

    Rey, María-Dolores; Prieto, Pilar

    2014-01-01

    Meiosis is a specialised cell division that involves chromosome replication, two rounds of chromosome segregation and results in the formation of the gametes. Meiotic DNA replication generally precedes chromosome pairing, recombination and synapsis in sexually developing eukaryotes. In this work, replication has been studied during premeiosis and early meiosis in wheat using flow cytometry, which has allowed the quantification of the amount of DNA in wheat anther in each phase of the cell cycle during premeiosis and each stage of early meiosis. Flow cytometry has been revealed as a suitable and user-friendly tool to detect and quantify DNA replication during early meiosis in wheat. Chromosome replication was detected in wheat during premeiosis and early meiosis until the stage of pachytene, when chromosomes are associated in pairs to further recombine and correctly segregate in the gametes. In addition, the effect of the Ph1 locus, which controls chromosome pairing and affects replication in wheat, was also studied by flow cytometry. Here we showed that the Ph1 locus plays an important role on the length of meiotic DNA replication in wheat, particularly affecting the rate of replication during early meiosis in wheat.

  12. Sequential steps in DNA replication are inhibited to ensure reduction of ploidy in meiosis

    Science.gov (United States)

    Hua, Hui; Namdar, Mandana; Ganier, Olivier; Gregan, Juraj; Méchali, Marcel; Kearsey, Stephen E.

    2013-01-01

    Meiosis involves two successive rounds of chromosome segregation without an intervening S phase. Exit from meiosis I is distinct from mitotic exit, in that replication origins are not licensed by Mcm2-7 chromatin binding, but spindle disassembly occurs during a transient interphase-like state before meiosis II. The absence of licensing is assumed to explain the block to DNA replication, but this has not been formally tested. Here we attempt to subvert this block by expressing the licensing control factors Cdc18 and Cdt1 during the interval between meiotic nuclear divisions. Surprisingly, this leads only to a partial round of DNA replication, even when these factors are overexpressed and effect clear Mcm2-7 chromatin binding. Combining Cdc18 and Cdt1 expression with modulation of cyclin-dependent kinase activity, activation of Dbf4-dependent kinase, or deletion of the Spd1 inhibitor of ribonucleotide reductase has little additional effect on the extent of DNA replication. Single-molecule analysis indicates this partial round of replication results from inefficient progression of replication forks, and thus both initiation and elongation replication steps may be inhibited in late meiosis. In addition, DNA replication or damage during the meiosis I–II interval fails to arrest meiotic progress, suggesting absence of checkpoint regulation of meiosis II entry. PMID:23303250

  13. Coordination of cellular differentiation, polarity, mitosis and meiosis - New findings from early vertebrate oogenesis.

    Science.gov (United States)

    Elkouby, Yaniv M; Mullins, Mary C

    2017-10-15

    A mechanistic dissection of early oocyte differentiation in vertebrates is key to advancing our knowledge of germline development, reproductive biology, the regulation of meiosis, and all of their associated disorders. Recent advances in the field include breakthroughs in the identification of germline stem cells in Medaka, in the cellular architecture of the germline cyst in mice, in a mechanistic dissection of chromosomal pairing and bouquet formation in meiosis in mice, in tracing oocyte symmetry breaking to the chromosomal bouquet of meiosis in zebrafish, and in the biology of the Balbiani body, a universal oocyte granule. Many of the major events in early oogenesis are universally conserved, and some are co-opted for species-specific needs. The chromosomal events of meiosis are of tremendous consequence to gamete formation and have been extensively studied. New light is now being shed on other aspects of early oocyte differentiation, which were traditionally considered outside the scope of meiosis, and their coordination with meiotic events. The emerging theme is of meiosis as a common groundwork for coordinating multifaceted processes of oocyte differentiation. In an accompanying manuscript we describe methods that allowed for investigations in the zebrafish ovary to contribute to these breakthroughs. Here, we review these advances mostly from the zebrafish and mouse. We discuss oogenesis concepts across established model organisms, and construct an inclusive paradigm for early oocyte differentiation in vertebrates. Copyright © 2017 Elsevier Inc. All rights reserved.

  14. Separase Is Required for Homolog and Sister Disjunction during Drosophila melanogaster Male Meiosis, but Not for Biorientation of Sister Centromeres.

    Science.gov (United States)

    Blattner, Ariane C; Chaurasia, Soumya; McKee, Bruce D; Lehner, Christian F

    2016-04-01

    Spatially controlled release of sister chromatid cohesion during progression through the meiotic divisions is of paramount importance for error-free chromosome segregation during meiosis. Cohesion is mediated by the cohesin protein complex and cleavage of one of its subunits by the endoprotease separase removes cohesin first from chromosome arms during exit from meiosis I and later from the pericentromeric region during exit from meiosis II. At the onset of the meiotic divisions, cohesin has also been proposed to be present within the centromeric region for the unification of sister centromeres into a single functional entity, allowing bipolar orientation of paired homologs within the meiosis I spindle. Separase-mediated removal of centromeric cohesin during exit from meiosis I might explain sister centromere individualization which is essential for subsequent biorientation of sister centromeres during meiosis II. To characterize a potential involvement of separase in sister centromere individualization before meiosis II, we have studied meiosis in Drosophila melanogaster males where homologs are not paired in the canonical manner. Meiosis does not include meiotic recombination and synaptonemal complex formation in these males. Instead, an alternative homolog conjunction system keeps homologous chromosomes in pairs. Using independent strategies for spermatocyte-specific depletion of separase complex subunits in combination with time-lapse imaging, we demonstrate that separase is required for the inactivation of this alternative conjunction at anaphase I onset. Mutations that abolish alternative homolog conjunction therefore result in random segregation of univalents during meiosis I also after separase depletion. Interestingly, these univalents become bioriented during meiosis II, suggesting that sister centromere individualization before meiosis II does not require separase.

  15. 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.

  16. Meiosis of anther culture regenerants in asparagus (Asparagus officinalis L.

    Directory of Open Access Journals (Sweden)

    Leonardo Galli

    1998-03-01

    Full Text Available Pollen mother cells obtained from regenerated plants of asparagus (Asparagus officinalis L., in a population composed exclusively of male plants, through the process of anther culture from the hybrid G27 X 22-8, were analyzed during meiosis. It was observed that, during theprocess of anther culture by organogenesis, the pollen mother cells of the regenerants had great genomic instability, as evidenced by disturbances in all the meiotic phases of the first and second division. Furthermore, structural chromosomal abnormalities, in addition to aneuploidy and polyploidy, were observed.Foi analisada a meiose em células mãe de pólen de plantas de aspargo (Asparagus officinalis L. de uma população composta exclusivamente de plantas masculinas, obtidas através do processo de cultura de anteras do híbrido G27 X 22-8. Foi observado que, durante o processo de cultura de anteras, via calogênese, as células mãe de pólen dos regenerantes apresentaram grande instabilidade genômica, evidenciada por irregularidades nas fases de diacinese, assim como de metáfase, anáfase, telófase da primeira e segunda divisão meiótica. Além disto, o processo originou anormalidades cromossômicas estruturais em adição às aneuploidias e poliploidias.

  17. Meiosis-Specific Loading of the Centromere-Specific Histone CENH3 in Arabidopsis thaliana

    Science.gov (United States)

    Ravi, Maruthachalam; Shibata, Fukashi; Ramahi, Joseph S.; Nagaki, Kiyotaka; Chen, Changbin; Murata, Minoru; Chan, Simon W. L.

    2011-01-01

    Centromere behavior is specialized in meiosis I, so that sister chromatids of homologous chromosomes are pulled toward the same side of the spindle (through kinetochore mono-orientation) and chromosome number is reduced. Factors required for mono-orientation have been identified in yeast. However, comparatively little is known about how meiotic centromere behavior is specialized in animals and plants that typically have large tandem repeat centromeres. Kinetochores are nucleated by the centromere-specific histone CENH3. Unlike conventional histone H3s, CENH3 is rapidly evolving, particularly in its N-terminal tail domain. Here we describe chimeric variants of CENH3 with alterations in the N-terminal tail that are specifically defective in meiosis. Arabidopsis thaliana cenh3 mutants expressing a GFP-tagged chimeric protein containing the H3 N-terminal tail and the CENH3 C-terminus (termed GFP-tailswap) are sterile because of random meiotic chromosome segregation. These defects result from the specific depletion of GFP-tailswap protein from meiotic kinetochores, which contrasts with its normal localization in mitotic cells. Loss of the GFP-tailswap CENH3 variant in meiosis affects recruitment of the essential kinetochore protein MIS12. Our findings suggest that CENH3 loading dynamics might be regulated differently in mitosis and meiosis. As further support for our hypothesis, we show that GFP-tailswap protein is recruited back to centromeres in a subset of pollen grains in GFP-tailswap once they resume haploid mitosis. Meiotic recruitment of the GFP-tailswap CENH3 variant is not restored by removal of the meiosis-specific cohesin subunit REC8. Our results reveal the existence of a specialized loading pathway for CENH3 during meiosis that is likely to involve the hypervariable N-terminal tail. Meiosis-specific CENH3 dynamics may play a role in modulating meiotic centromere behavior. PMID:21695238

  18. Comparative expression profiling reveals gene functions in female meiosis and gametophyte development in Arabidopsis.

    Science.gov (United States)

    Zhao, Lihua; He, Jiangman; Cai, Hanyang; Lin, Haiyan; Li, Yanqiang; Liu, Renyi; Yang, Zhenbiao; Qin, Yuan

    2014-11-01

    Megasporogenesis is essential for female fertility, and requires the accomplishment of meiosis and the formation of functional megaspores. The inaccessibility and low abundance of female meiocytes make it particularly difficult to elucidate the molecular basis underlying megasporogenesis. We used high-throughput tag-sequencing analysis to identify genes expressed in female meiocytes (FMs) by comparing gene expression profiles from wild-type ovules undergoing megasporogenesis with those from the spl mutant ovules, which lack megasporogenesis. A total of 862 genes were identified as FMs, with levels that are consistently reduced in spl ovules in two biological replicates. Fluorescence-assisted cell sorting followed by RNA-seq analysis of DMC1:GFP-labeled female meiocytes confirmed that 90% of the FMs are indeed detected in the female meiocyte protoplast profiling. We performed reverse genetic analysis of 120 candidate genes and identified four FM genes with a function in female meiosis progression in Arabidopsis. We further revealed that KLU, a putative cytochrome P450 monooxygenase, is involved in chromosome pairing during female meiosis, most likely by affecting the normal expression pattern of DMC1 in ovules during female meiosis. Our studies provide valuable information for functional genomic analyses of plant germline development as well as insights into meiosis. © 2014 The Authors The Plant Journal © 2014 John Wiley & Sons Ltd.

  19. miR-31 Regulates Spermatogonial Stem Cells Meiosis via Targeting Stra8.

    Science.gov (United States)

    Wang, Yingjie; Zuo, Qisheng; Bi, Yulin; Zhang, Wenhui; Jin, Jing; Zhang, Liangliang; Zhang, Ya-Ni; Li, Bichun

    2017-12-01

    Stra8 (stimulated by retinoic acid gene 8) is a specific gene that is expressed in mammalian germ cells during transition from mitosis to meiosis and plays a key role in the initiation of meiosis in mammals and birds. So, the evaluation of the Stra8 pathway in cSSCs may provide a deeper insight into mammalian spermatogenesis. miRNA was also an important regulating factor for meiosis of SSCs. However, there is currently no data indicating that miRNA regulate the meiosis of SSCs via Stra8. Here, we predicted the prospective miRNA targeting to Stra8 using the online Bioinformatics database-Targetscan, and performed an analysis of the dual-luciferase recombinant vector, pGL3-CMV-LUC-MCS-Stra8-3'UTR. miR-31 mimics (miR-31m), miR-31 inhibitors (miR-31i), Control (NC, scrambled oligonucleotides transfection) were transfected into cSSCs; Stra8 and miRNA were analyzed by RT-qPCR, immunofluorescence, and Western blot. The detection of haploid was conducted by flow cytometry. The results showed that miR-31 regulates meiosis of cSSCs via targeting Stra8 in vitro and in vivo. Our study identifies a new regulatory pathway that miR-31 targets Stra8 and inhibits spermatogenesis. J. Cell. Biochem. 118: 4844-4853, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  20. Role of Securin, Separase and Cohesins in female meiosis and polar body formation in Drosophila.

    Science.gov (United States)

    Guo, Zhihao; Batiha, Osamah; Bourouh, Mohammed; Fifield, Eric; Swan, Andrew

    2016-02-01

    Chromosome segregation in meiosis is controlled by a conserved pathway that culminates in Separase-mediated cleavage of the α-kleisin Rec8, leading to dissolution of cohesin rings. Drosophila has no gene encoding Rec8, and the absence of a known Separase target raises the question of whether Separase and its regulator Securin (Pim in Drosophila) are important in Drosophila meiosis. Here, we investigate the role of Securin, Separase and the cohesin complex in female meiosis using fluorescence in situ hybridization against centromeric and arm-specific sequences to monitor cohesion. We show that Securin destruction and Separase activity are required for timely release of arm cohesion in anaphase I and centromere-proximal cohesion in anaphase II. They are also required for release of arm cohesion on polar body chromosomes. Cohesion on polar body chromosomes depends on the cohesin components SMC3 and the mitotic α-kleisin Rad21 (also called Vtd in Drosophila). We provide cytological evidence that SMC3 is required for arm cohesion in female meiosis, whereas Rad21, in agreement with recent findings, is not. We conclude that in Drosophila meiosis, cohesion is regulated by a conserved Securin-Separase pathway that targets a diverged Separase target, possibly within the cohesin complex. © 2016. Published by The Company of Biologists Ltd.

  1. Selection of G1 Phase Yeast Cells for Synchronous Meiosis and Sporulation.

    Science.gov (United States)

    Stuart, David T

    2017-01-01

    Centrifugal elutriation is a procedure that allows the fractionation of cell populations based upon their size and shape. This allows cells in distinct cell cycle stages can be captured from an asynchronous population. The technique is particularly helpful when performing an experiment to monitor the progression of cells through the cell cycle or meiosis. Yeast sporulation like gametogenesis in other eukaryotes initiates from the G1 phase of the cell cycle. Conveniently, S. cerevisiae arrest in G1 phase when starved for nutrients and so withdrawal of nitrogen and glucose allows cells to abandon vegetative growth in G1 phase before initiating the sporulation program. This simple starvation protocol yields a partial synchronization that has been used extensively in studies of progression through meiosis and sporulation. By using centrifugal elutriation it is possible to isolate a homogeneous population of G1 phase cells and induce them to sporulate synchronously, which is beneficial for investigating progression through meiosis and sporulation. An additionally benefit of this protocol is that cell populations can be isolated based upon size and both large and small cell populations can be tested for progression through meiosis and sporulation. Here we present a protocol for purification of G1 phase diploid cells for examining synchronous progression through meiosis and sporulation.

  2. Apospory appears to accelerate onset of meiosis and sexual embryo sac formation in sorghum ovules

    Directory of Open Access Journals (Sweden)

    Elliott Estella

    2011-01-01

    Full Text Available Abstract Background Genetically unreduced (2n embryo sacs (ES form in ovules of gametophytic apomicts, the 2n eggs of which develop into embryos parthenogenetically. In many apomicts, 2n ES form precociously during ovule development. Whether meiosis and sexual ES formation also occur precociously in facultative apomicts (capable of apomictic and sexual reproduction has not been studied. We determined onset timing of meiosis and sexual ES formation for 569 Sorghum bicolor genotypes, many of which produced 2n ES facultatively. Results Genotype differences for onset timing of meiosis and sexual ES formation, relative to ovule development, were highly significant. A major source of variation in timing of sexual germline development was presence or absence of apomictic ES, which formed from nucellar cells (apospory in some genotypes. Genotypes that produced these aposporous ES underwent meiosis and sexual ES formation precociously. Aposporous ES formation was most prevalent in subsp. verticilliflorum and in breeding lines of subsp. bicolor. It was uncommon in land races. Conclusions The present study adds meiosis and sexual ES formation to floral induction, apomictic ES formation, and parthenogenesis as processes observed to occur precociously in apomictic plants. The temporally diverse nature of these events suggests that an epigenetic memory of the plants' apomixis status exists throughout its life cycle, which triggers, during multiple life cycle phases, temporally distinct processes that accelerate reproduction.

  3. Two-step activation of meiosis by the mat1 locus in Schizosaccharomyces pombe

    DEFF Research Database (Denmark)

    Willer, M; Hoffmann, Ulla-Lisbeth; Styrkársdóttir, U

    1995-01-01

    in which the mat1 locus plays two roles in controlling meiosis. In the first instance, the mat1-Pc and mat1-Mc functions are required to produce the mating pheromones and receptors that allow the generation of a pheromone signal. This signal is required to induce the expression of mat1-Pm and mat1-Mm......The mat1 locus is a key regulator of both conjugation and meiosis in the fission yeast Schizosaccharomyces pombe. Two alternative DNA segments of this locus, mat1-P and mat1-M, specify the haploid cell types (Plus and Minus). Each segment includes two genes: mat1-P includes mat1-Pc and mat1-Pm....... This appears to be the major pheromone-dependent step in controlling meiosis since ectopic expression of these genes allows meiosis in the absence of mat1-Pc and mat1-Mc. The mat1-Pm and mat1-Mm products complete the initiation of meiosis by activating transcription of the mei3 gene....

  4. Phylogenomic detection and functional prediction of genes potentially important for plant meiosis.

    Science.gov (United States)

    Zhang, Luoyan; Kong, Hongzhi; Ma, Hong; Yang, Ji

    2018-02-15

    Meiosis is a specialized type of cell division necessary for sexual reproduction in eukaryotes. A better understanding of the cytological procedures of meiosis has been achieved by comprehensive cytogenetic studies in plants, while the genetic mechanisms regulating meiotic progression remain incompletely understood. The increasing accumulation of complete genome sequences and large-scale gene expression datasets has provided a powerful resource for phylogenomic inference and unsupervised identification of genes involved in plant meiosis. By integrating sequence homology and expression data, 164, 131, 124 and 162 genes potentially important for meiosis were identified in the genomes of Arabidopsis thaliana, Oryza sativa, Selaginella moellendorffii and Pogonatum aloides, respectively. The predicted genes were assigned to 45 meiotic GO terms, and their functions were related to different processes occurring during meiosis in various organisms. Most of the predicted meiotic genes underwent lineage-specific duplication events during plant evolution, with about 30% of the predicted genes retaining only a single copy in higher plant genomes. The results of this study provided clues to design experiments for better functional characterization of meiotic genes in plants, promoting the phylogenomic approach to the evolutionary dynamics of the plant meiotic machineries. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Nuclear vlimata and aneuploidy in embryonic cells is caused by meiosis. Behaviour and properties of meiotic cells

    OpenAIRE

    Logothetou-Rella, H.

    1995-01-01

    This study demonstrates that human embryonic cells divide by meiosis. The use of trophoblastic tissue cells (early embryo) and amniotic cells (late embryo) exhibited the following characteristic events of meiosis: nuclear (NVs) and nucleolar (NuVs) vlimata formation; NV invasion in host cells; extrusion of chromosomes; nuclear fusion; metaphase fusion; hybrid cell formation; nuclear, nucleolar and cytoplasmic bridges, chromosomal transfer, variablesized nuc...

  6. Meiosis peculiarities featured by first-generation spring wheat (Triticum aestivum L.) under the influence of gamma-radiation

    International Nuclear Information System (INIS)

    Sen', L.A.; Volodin, V.G.; Elef, A.V.; Mikhalenko, N.A.

    2003-01-01

    The study of meiosis of spring wheat represented by three varieties revealed intervarietal differences according to the frequency and types of disturbances. Gamma-irradiation with 10 kCi dose increased the disturbance frequency during meiosis in all varieties. However, there were substantial differences in the variety response to the irradiation. (authors)

  7. "Chromoseratops Meiosus": A Simple, Two-Phase Exercise to Represent the Connection between Meiosis & Increased Genetic Diversity

    Science.gov (United States)

    Eliyahu, Dorit

    2014-01-01

    I present an activity to help students make the connection between meiosis and genetic variation. The students model meiosis in the first phase of the activity, and by that process they produce gametes of a fictitious reptilobird species, "Chromoseratops meiosus." Later on, they will "mate" their gametes and produce a zygote…

  8. A Paper-and-Pencil Strategy for Teaching Mitosis and Meiosis, Diagnosing Learning Problems and Predicting Examination Performance.

    Science.gov (United States)

    Mertens, Thomas R.; Walker, Julie O.

    1992-01-01

    Describes the Bajema strategy for teaching meiosis and how it is used in the general genetics course at Ball State University and can be used to identify students who have misconceptions of meiosis that can interfere with their learning the basics of Mendelian inheritance. (Contains 11 references.) (MDH)

  9. Male meiosis in Crustacea: synapsis, recombination, epigenetics and fertility in Daphnia magna.

    Science.gov (United States)

    Gómez, Rocío; Van Damme, Kay; Gosálvez, Jaime; Morán, Eugenio Sánchez; Colbourne, John K

    2016-09-01

    We present the first detailed cytological study of male meiosis in Daphnia (Crustacea: Branchiopoda: Cladocera)-an aquatic microcrustacean with a cyclical parthenogenetic life cycle. Using immunostaining of the testes in Daphnia magna for baseline knowledge, we characterized the different stages of meiotic division and spermiogenesis in relation to the distribution of proteins involved in synapsis, early recombination events and sister chromatid cohesion. We also studied post-translational histone modifications in male spermatocytes, in relation to the dynamic chromatin progression of meiosis. Finally, we applied a DNA fragmentation test to measure sperm quality of D. magna, with respect to levels of inbreeding. As a proxy for fertility, this technique may be used to assess the reproductive health of a sentinel species of aquatic ecosystems. Daphnia proves to be a model species for comparative studies of meiosis that is poised to improve our understanding of the cytological basis of sexual and asexual reproduction.

  10. CENP-A regulates chromosome segregation during the first meiosis of mouse oocytes.

    Science.gov (United States)

    Li, Li; Qi, Shu-Tao; Sun, Qing-Yuan; Chen, Shi-Ling

    2017-06-01

    Proper chromosome separation in both mitosis and meiosis depends on the correct connection between kinetochores of chromosomes and spindle microtubules. Kinetochore dysfunction can lead to unequal distribution of chromosomes during cell division and result in aneuploidy, thus kinetochores are critical for faithful segregation of chromosomes. Centromere protein A (CENP-A) is an important component of the inner kinetochore plate. Multiple studies in mitosis have found that deficiencies in CENP-A could result in structural and functional changes of kinetochores, leading to abnormal chromosome segregation, aneuploidy and apoptosis in cells. Here we report the expression and function of CENP-A during mouse oocyte meiosis. Our study found that microinjection of CENP-A blocking antibody resulted in errors of homologous chromosome segregation and caused aneuploidy in eggs. Thus, our findings provide evidence that CENP-A is critical for the faithful chromosome segregation during mammalian oocyte meiosis.

  11. Cytochemical and autoradiographic studies of meiosis and microsporanogenesis in tradescantia paludosa

    International Nuclear Information System (INIS)

    Dryanovska, O.

    1981-01-01

    Labelling experiments with H 3 -thymidine, H 3 -uridine and H 3 -leucine have been carried out with Tradescantia paludosa. The results of this study showed that from pre-meiosis to the pollen grain the chromatin, the nucleoli and the cytoplasm undergo alternative structural, cytochemical and functional changes connected with the differential functioning of the genes and the differentiation of the cells. Chromatin condensation is connected with DNA synthesis only in the pre-meiosis and in the microspore. Decondensation is connected with despiralization and with slight heterochromatization of the chromatin, with development and functioning of the nucleoli, slight DNA synthesis and intense synthesis of RNAs and proteins. Probably the nucleolus in meiosis is playing a certain role. (author)

  12. Cytochemical and autoradiographic studies of meiosis and microsporanogenesis in tradescantia paludosa

    Energy Technology Data Exchange (ETDEWEB)

    Dryanovska, O. (Bylgarska Akademiya na Naukite, Sofia. Inst. po Genetika)

    1981-01-01

    Labelling experiments with H/sup 3/-thymidine, H/sup 3/-uridine and H/sup 3/-leucine have been carried out with Tradescantia paludosa. The results of this study showed that from pre-meiosis to the pollen grain the chromatin, the nucleoli and the cytoplasm undergo alternative structural, cytochemical and functional changes connected with the differential functioning of the genes and the differentiation of the cells. Chromatin condensation is connected with DNA synthesis only in the pre-meiosis and in the microspore. Decondensation is connected with despiralization and with slight heterochromatization of the chromatin, with development and functioning of the nucleoli, slight DNA synthesis and intense synthesis of RNAs and proteins. Probably the nucleolus in meiosis is playing a certain role.

  13. Mek1 Down Regulates Rad51 Activity during Yeast Meiosis by Phosphorylation of Hed1.

    Science.gov (United States)

    Callender, Tracy L; Laureau, Raphaelle; Wan, Lihong; Chen, Xiangyu; Sandhu, Rima; Laljee, Saif; Zhou, Sai; Suhandynata, Ray T; Prugar, Evelyn; Gaines, William A; Kwon, YoungHo; Börner, G Valentin; Nicolas, Alain; Neiman, Aaron M; Hollingsworth, Nancy M

    2016-08-01

    During meiosis, programmed double strand breaks (DSBs) are repaired preferentially between homologs to generate crossovers that promote proper chromosome segregation at Meiosis I. In many organisms, there are two strand exchange proteins, Rad51 and the meiosis-specific Dmc1, required for interhomolog (IH) bias. This bias requires the presence, but not the strand exchange activity of Rad51, while Dmc1 is responsible for the bulk of meiotic recombination. How these activities are regulated is less well established. In dmc1Δ mutants, Rad51 is actively inhibited, thereby resulting in prophase arrest due to unrepaired DSBs triggering the meiotic recombination checkpoint. This inhibition is dependent upon the meiosis-specific kinase Mek1 and occurs through two different mechanisms that prevent complex formation with the Rad51 accessory factor Rad54: (i) phosphorylation of Rad54 by Mek1 and (ii) binding of Rad51 by the meiosis-specific protein Hed1. An open question has been why inhibition of Mek1 affects Hed1 repression of Rad51. This work shows that Hed1 is a direct substrate of Mek1. Phosphorylation of Hed1 at threonine 40 helps suppress Rad51 activity in dmc1Δ mutants by promoting Hed1 protein stability. Rad51-mediated recombination occurring in the absence of Hed1 phosphorylation results in a significant increase in non-exchange chromosomes despite wild-type levels of crossovers, confirming previous results indicating a defect in crossover assurance. We propose that Rad51 function in meiosis is regulated in part by the coordinated phosphorylation of Rad54 and Hed1 by Mek1.

  14. Mek1 Down Regulates Rad51 Activity during Yeast Meiosis by Phosphorylation of Hed1.

    Directory of Open Access Journals (Sweden)

    Tracy L Callender

    2016-08-01

    Full Text Available During meiosis, programmed double strand breaks (DSBs are repaired preferentially between homologs to generate crossovers that promote proper chromosome segregation at Meiosis I. In many organisms, there are two strand exchange proteins, Rad51 and the meiosis-specific Dmc1, required for interhomolog (IH bias. This bias requires the presence, but not the strand exchange activity of Rad51, while Dmc1 is responsible for the bulk of meiotic recombination. How these activities are regulated is less well established. In dmc1Δ mutants, Rad51 is actively inhibited, thereby resulting in prophase arrest due to unrepaired DSBs triggering the meiotic recombination checkpoint. This inhibition is dependent upon the meiosis-specific kinase Mek1 and occurs through two different mechanisms that prevent complex formation with the Rad51 accessory factor Rad54: (i phosphorylation of Rad54 by Mek1 and (ii binding of Rad51 by the meiosis-specific protein Hed1. An open question has been why inhibition of Mek1 affects Hed1 repression of Rad51. This work shows that Hed1 is a direct substrate of Mek1. Phosphorylation of Hed1 at threonine 40 helps suppress Rad51 activity in dmc1Δ mutants by promoting Hed1 protein stability. Rad51-mediated recombination occurring in the absence of Hed1 phosphorylation results in a significant increase in non-exchange chromosomes despite wild-type levels of crossovers, confirming previous results indicating a defect in crossover assurance. We propose that Rad51 function in meiosis is regulated in part by the coordinated phosphorylation of Rad54 and Hed1 by Mek1.

  15. Cdc7-Dbf4 regulates NDT80 transcription as well as reductional segregation during budding yeast meiosis.

    Science.gov (United States)

    Lo, Hsiao-Chi; Wan, Lihong; Rosebrock, Adam; Futcher, Bruce; Hollingsworth, Nancy M

    2008-11-01

    In budding yeast, as in other eukaryotes, the Cdc7 protein kinase is important for initiation of DNA synthesis in vegetative cells. In addition, Cdc7 has crucial meiotic functions: it facilitates premeiotic DNA replication, and it is essential for the initiation of recombination. This work uses a chemical genetic approach to demonstrate that Cdc7 kinase has additional roles in meiosis. First, Cdc7 allows expression of NDT80, a meiosis-specific transcriptional activator required for the induction of genes involved in exit from pachytene, meiotic progression, and spore formation. Second, Cdc7 is necessary for recruitment of monopolin to sister kinetochores, and it is necessary for the reductional segregation occurring at meiosis I. The use of the same kinase to regulate several distinct meiosis-specific processes may be important for the coordination of these processes during meiosis.

  16. Fission yeast APC/C activators Slp1 and Fzr1 sequentially trigger two consecutive nuclear divisions during meiosis.

    Science.gov (United States)

    Chikashige, Yuji; Yamane, Miho; Okamasa, Kasumi; Osakada, Hiroko; Tsutsumi, Chihiro; Nagahama, Yuki; Fukuta, Noriko; Haraguchi, Tokuko; Hiraoka, Yasushi

    2017-04-01

    In meiosis, two rounds of nuclear division occur consecutively without DNA replication between the divisions. We isolated a fission yeast mutant in which the nucleus divides only once to generate two spores, as opposed to four, in meiosis. In this mutant, we found that the initiation codon of the slp1 + gene is converted to ATA, producing a reduced amount of Slp1. As a member of the Fizzy family of anaphase-promoting complex/cyclosome (APC/C) activators, Slp1 is essential for vegetative growth; however, the mutant allele shows a phenotype only in meiosis. Slp1 insufficiency delays degradation of maturation-promoting factor at the first meiotic division, and another APC/C activator, Fzr1, which acts late in meiosis, terminates meiosis immediately after the delayed first division to produce two viable spores. © 2017 Federation of European Biochemical Societies.

  17. Inducing somatic meiosis-like reduction at high frequency by caffeine in root-tip cells of Vicia faba.

    Science.gov (United States)

    Chen, Y; Zhang, L; Zhou, Y; Geng, Y; Chen, Z

    2000-07-20

    Germinated seeds of Vicia faba were treated in caffeine solutions of different concentration for different durations to establish the inducing system of somatic meiosis-like reduction. The highest frequency of somatic meiosis-like reduction could reach up to 54.0% by treating the root tips in 70 mmol/l caffeine solution for 2 h and restoring for 24 h. Two types of somatic meiosis-like reduction were observed. One was reductional grouping, in which the chromosomes in a cell usually separated into two groups, and the role of spindle fibers did not show. The other type was somatic meiosis, which was analogous to meiosis presenting in gametogenesis, and chromosome pairing and chiasmata were visualized.

  18. Cdc7-Dbf4 Regulates NDT80 Transcription as Well as Reductional Segregation during Budding Yeast Meiosis

    Science.gov (United States)

    Lo, Hsiao-Chi; Wan, Lihong; Rosebrock, Adam; Futcher, Bruce

    2008-01-01

    In budding yeast, as in other eukaryotes, the Cdc7 protein kinase is important for initiation of DNA synthesis in vegetative cells. In addition, Cdc7 has crucial meiotic functions: it facilitates premeiotic DNA replication, and it is essential for the initiation of recombination. This work uses a chemical genetic approach to demonstrate that Cdc7 kinase has additional roles in meiosis. First, Cdc7 allows expression of NDT80, a meiosis-specific transcriptional activator required for the induction of genes involved in exit from pachytene, meiotic progression, and spore formation. Second, Cdc7 is necessary for recruitment of monopolin to sister kinetochores, and it is necessary for the reductional segregation occurring at meiosis I. The use of the same kinase to regulate several distinct meiosis-specific processes may be important for the coordination of these processes during meiosis. PMID:18768747

  19. Meiosis in desynaptic-chromosomal restitution mutants in Rhoeo spathacea (Commelinaceae)

    OpenAIRE

    García-Velázquez, Armando

    2008-01-01

    El estudio se llevó a cabo en recolectas de Rhoeo spathacea realizadas en Veracruz, Chiapas, Tabasco, Yucatán, Quintana Roo y Michoacán, México. Las plantas presentaron número diploide de cromosomas (2n=12) en mitosis. En meiosis los individuos formaron anillo y/o cadenas en metafase I, con excepción de varios mutantes desinápticos-RSD (separación de cromosomas apareados). En meiosis de Rhoeo no se observan bivalentes ni hay posibilidades de entrecruzamiento, y consecuentemente no habrá quias...

  20. Mouse CCDC79 (TERB1) is a meiosis-specific telomere associated protein.

    Science.gov (United States)

    Daniel, Katrin; Tränkner, Daniel; Wojtasz, Lukasz; Shibuya, Hiroki; Watanabe, Yoshinori; Alsheimer, Manfred; Tóth, Attila

    2014-05-22

    Telomeres have crucial meiosis-specific roles in the orderly reduction of chromosome numbers and in ensuring the integrity of the genome during meiosis. One such role is the attachment of telomeres to trans-nuclear envelope protein complexes that connect telomeres to motor proteins in the cytoplasm. These trans-nuclear envelope connections between telomeres and cytoplasmic motor proteins permit the active movement of telomeres and chromosomes during the first meiotic prophase. Movements of chromosomes/telomeres facilitate the meiotic recombination process, and allow high fidelity pairing of homologous chromosomes. Pairing of homologous chromosomes is a prerequisite for their correct segregation during the first meiotic division. Although inner-nuclear envelope proteins, such as SUN1 and potentially SUN2, are known to bind and recruit meiotic telomeres, these proteins are not meiosis-specific, therefore cannot solely account for telomere-nuclear envelope attachment and/or for other meiosis-specific characteristics of telomeres in mammals. We identify CCDC79, alternatively named TERB1, as a meiosis-specific protein that localizes to telomeres from leptotene to diplotene stages of the first meiotic prophase. CCDC79 and SUN1 associate with telomeres almost concurrently at the onset of prophase, indicating a possible role for CCDC79 in telomere-nuclear envelope interactions and/or telomere movements. Consistent with this scenario, CCDC79 is missing from most telomeres that fail to connect to SUN1 protein in spermatocytes lacking the meiosis-specific cohesin SMC1B. SMC1B-deficient spermatocytes display both reduced efficiency in telomere-nuclear envelope attachment and reduced stability of telomeres specifically during meiotic prophase. Importantly, CCDC79 associates with telomeres in SUN1-deficient spermatocytes, which strongly indicates that localization of CCDC79 to telomeres does not require telomere-nuclear envelope attachment. CCDC79 is a meiosis-specific telomere

  1. Evidence consistent with human L1 retrotransposition in maternal meiosis I

    NARCIS (Netherlands)

    Brouha, Brook; Meischl, Christof; Ostertag, Eric; de Boer, Martin; Zhang, Yue; Neijens, Herman; Roos, Dirk; Kazazian, Haig H.

    2002-01-01

    We have used a unique polymorphic 3' transduction to show that a human L1, or LINE-1 ((l) under bar ong (i) under bar nterspersed (n) under bar ucleotide (e) under bar lement-1), retrotransposition event most likely occurred in the maternal primary oocyte during meiosis I. We characterized a

  2. Kinetics of meiosis in azoospermic males: a joint histological and cytological approach

    NARCIS (Netherlands)

    Boer, de P.; Giele, M.; Lock, M.T.W.T.; Rooij, de D.G.; Giltay, J.; Hochstenbach, R.; Velde, ter E.R.

    2004-01-01

    We have developed a protocol for the identification of aberrant chromosome behavior during human male meiosis up to metaphase of the secondary spermatocyte. Histological evaluation by the Johnsen score of a testicular biopsy was combined with immunofluorescence of first meiotic prophase

  3. Dissecting the telomere–inner nuclear membrane interface formed in meiosis

    Energy Technology Data Exchange (ETDEWEB)

    Pendlebury, Devon F.; Fujiwara, Yasuhiro; Tesmer, Valerie M.; Smith, Eric M.; Shibuya, Hiroki; Watanabe, Yoshinori; Nandakumar, Jayakrishnan

    2017-10-30

    Tethering telomeres to the inner nuclear membrane (INM) allows homologous chromosome pairing during meiosis. The meiosis-specific protein TERB1 binds the telomeric protein TRF1 to establish telomere–INM connectivity and is essential for mouse fertility. Here we solve the structure of the human TRF1–TERB1 interface to reveal the structural basis for telomere–INM linkage. Disruption of this interface abrogates binding and compromises telomere–INM attachment in mice. An embedded CDK-phosphorylation site within the TRF1-binding region of TERB1 provides a mechanism for cap exchange, a late-pachytene phenomenon involving the dissociation of the TRF1–TERB1 complex. Indeed, further strengthening this interaction interferes with cap exchange. Finally, our biochemical analysis implicates distinct complexes for telomere–INM tethering and chromosome-end protection during meiosis. Our studies unravel the structure, stoichiometry, and physiological implications underlying telomere–INM tethering, thereby providing unprecedented insights into the unique function of telomeres in meiosis.

  4. Regulation of mitogen-activated protein kinase 3/1 activity during meiosis resumption in mammals

    Czech Academy of Sciences Publication Activity Database

    Procházka, Radek; Blaha, Milan

    2015-01-01

    Roč. 61, č. 6 (2015), s. 495-502 ISSN 0916-8818 R&D Projects: GA MZe(CZ) QJ1510138 Institutional support: RVO:67985904 Keywords : cumulus oocyte complexes * meiosis resumption * mitogen-activated protein kinase 3/1 (MAPK3/1) Subject RIV: GI - Animal Husbandry ; Breeding Impact factor: 1.453, year: 2015

  5. Inhibition of CDK7 bypasses spindle assembly checkpoint via premature cyclin B degradation during oocyte meiosis.

    Science.gov (United States)

    Wang, HaiYang; Jo, Yu-Jin; Sun, Tian-Yi; Namgoong, Suk; Cui, Xiang-Shun; Oh, Jeong Su; Kim, Nam-Hyung

    2016-12-01

    To ensure accurate chromosome segregation, the spindle assembly checkpoint (SAC) delays anaphase onset by preventing the premature activation of anaphase-promoting complex/cyclosome (APC/C) until all kinetochores are attached to the spindle. Although an escape from mitosis in the presence of unsatisfied SAC has been shown in several cancer cells, it has not been reported in oocyte meiosis. Here, we show that CDK7 activity is required to prevent a bypass of SAC during meiosis I in mouse oocytes. Inhibition of CDK7 using THZ1 accelerated the first meiosis, leading to chromosome misalignment, lag of chromosomes during chromosome segregation, and a high incidence of aneuploidy. Notably, this acceleration occurred in the presence of SAC proteins including Mad2 and Bub3 at the kinetochores. However, inhibition of APC/C-mediated cyclin B degradation blocked the THZ1-induced premature polar body extrusion. Moreover, chromosomal defects mediated by THZ1 were rescued when anaphase onset was delayed. Collectively, our results show that CDK7 activity is required to prevent premature anaphase onset by suppressing the bypass of SAC, thus ensuring chromosome alignment and proper segregation. These findings reveal new roles of CDK7 in the regulation of meiosis in mammalian oocytes. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. Dissecting the telomere-inner nuclear membrane interface formed in meiosis.

    Science.gov (United States)

    Pendlebury, Devon F; Fujiwara, Yasuhiro; Tesmer, Valerie M; Smith, Eric M; Shibuya, Hiroki; Watanabe, Yoshinori; Nandakumar, Jayakrishnan

    2017-12-01

    Tethering telomeres to the inner nuclear membrane (INM) allows homologous chromosome pairing during meiosis. The meiosis-specific protein TERB1 binds the telomeric protein TRF1 to establish telomere-INM connectivity and is essential for mouse fertility. Here we solve the structure of the human TRF1-TERB1 interface to reveal the structural basis for telomere-INM linkage. Disruption of this interface abrogates binding and compromises telomere-INM attachment in mice. An embedded CDK-phosphorylation site within the TRF1-binding region of TERB1 provides a mechanism for cap exchange, a late-pachytene phenomenon involving the dissociation of the TRF1-TERB1 complex. Indeed, further strengthening this interaction interferes with cap exchange. Finally, our biochemical analysis implicates distinct complexes for telomere-INM tethering and chromosome-end protection during meiosis. Our studies unravel the structure, stoichiometry, and physiological implications underlying telomere-INM tethering, thereby providing unprecedented insights into the unique function of telomeres in meiosis.

  7. Meiosis Drives Extraordinary Genome Plasticity in the Haploid Fungal Plant Pathogen Mycosphaerella Graminicola

    Science.gov (United States)

    Meiosis in the plant-pathogenic fungus Mycosphaerella graminicola results in eight ascospores due to a mitotic division following the two meiotic divisions. The transient diploid phase allows for recombination among homologous chromosomes. However, some chromosomes of M. graminicola lack homologs an...

  8. APC/C-Cdc20 mediates deprotection of centromeric cohesin at meiosis II in yeast.

    Science.gov (United States)

    Jonak, Katarzyna; Zagoriy, Ievgeniia; Oz, Tugce; Graf, Peter; Rojas, Julie; Mengoli, Valentina; Zachariae, Wolfgang

    2017-06-18

    Cells undergoing meiosis produce haploid gametes through one round of DNA replication followed by 2 rounds of chromosome segregation. This requires that cohesin complexes, which establish sister chromatid cohesion during S phase, are removed in a stepwise manner. At meiosis I, the separase protease triggers the segregation of homologous chromosomes by cleaving cohesin's Rec8 subunit on chromosome arms. Cohesin persists at centromeres because the PP2A phosphatase, recruited by the shugoshin protein, dephosphorylates Rec8 and thereby protects it from cleavage. While chromatids disjoin upon cleavage of centromeric Rec8 at meiosis II, it was unclear how and when centromeric Rec8 is liberated from its protector PP2A. One proposal is that bipolar spindle forces separate PP2A from Rec8 as cells enter metaphase II. We show here that sister centromere biorientation is not sufficient to "deprotect" Rec8 at meiosis II in yeast. Instead, our data suggest that the ubiquitin-ligase APC/C Cdc20 removes PP2A from centromeres by targeting for degradation the shugoshin Sgo1 and the kinase Mps1. This implies that Rec8 remains protected until entry into anaphase II when it is phosphorylated concurrently with the activation of separase. Here, we provide further support for this model and speculate on its relevance to mammalian oocytes.

  9. Cell type-specific translational repression of Cyclin B during meiosis in males.

    Science.gov (United States)

    Baker, Catherine Craig; Gim, Byung Soo; Fuller, Margaret T

    2015-10-01

    The unique cell cycle dynamics of meiosis are controlled by layers of regulation imposed on core mitotic cell cycle machinery components by the program of germ cell development. Although the mechanisms that regulate Cdk1/Cyclin B activity in meiosis in oocytes have been well studied, little is known about the trans-acting factors responsible for developmental control of these factors in male gametogenesis. During meiotic prophase in Drosophila males, transcript for the core cell cycle protein Cyclin B1 (CycB) is expressed in spermatocytes, but the protein does not accumulate in spermatocytes until just before the meiotic divisions. Here, we show that two interacting proteins, Rbp4 and Fest, expressed at the onset of spermatocyte differentiation under control of the developmental program of male gametogenesis, function to direct cell type- and stage-specific repression of translation of the core G2/M cell cycle component cycB during the specialized cell cycle of male meiosis. Binding of Fest to Rbp4 requires a 31-amino acid region within Rbp4. Rbp4 and Fest are required for translational repression of cycB in immature spermatocytes, with Rbp4 binding sequences in a cell type-specific shortened form of the cycB 3' UTR. Finally, we show that Fest is required for proper execution of meiosis I. © 2015. Published by The Company of Biologists Ltd.

  10. Students' Meaningful Learning Orientation and Their Meaningful Understandings of Meiosis and Genetics.

    Science.gov (United States)

    Cavallo, Ann Liberatore

    This 1-week study explored the extent to which high school students (n=140) acquired meaningful understanding of selected biological topics (meiosis and the Punnett square method) and the relationship between these topics. This study: (1) examined "mental modeling" as a technique for measuring students' meaningful understanding of the…

  11. Smc1β is required for activation of SAC during mouse oocyte meiosis.

    Science.gov (United States)

    Miao, Yilong; Zhou, Changyin; Cui, Zhaokang; Dai, Xiaoxin; Zhang, Mianqun; Lu, Yajuan; Xiong, Bo

    2017-03-19

    Smc1β is a meiosis-specific cohesin subunit that is essential for sister chromatid cohesion and DNA recombination. Previous studies have shown that Smc1β-deficient mice in both sexes are sterile. Ablation of Smc1β during male meiosis leads to the blockage of spermatogenesis in pachytene stage, and ablation of Smc1β during female meiosis generates a highly error-prone oocyte although it could develop to metaphase II stage. However, the underlying mechanisms regarding how Smc1β maintains the correct meiotic progression in mouse oocytes have not been clearly defined. Here, we find that GFP-fused Smc1β is expressed and localized to the chromosomes from GV to MII stages during mouse oocyte meiotic maturation. Knockdown of Smc1β by microinjection of gene-specific morpholino causes the impaired spindle apparatus and chromosome alignment which are highly correlated with the defective kinetochore-microtubule attachments, consequently resulting in a prominently higher incidence of aneuploid eggs. In addition, the premature extrusion of polar bodies and escape of metaphase I arrest induced by low dose of nocodazole treatment in Smc1β-depleted oocytes indicates that Smc1β is essential for activation of spindle assembly checkpoint (SAC) activity. Collectively, we identify a novel function of Smc1β as a SAC participant beyond its role in chromosome cohesion during mouse oocyte meiosis.

  12. Bovine ovarian cells have (pro)renin receptors and prorenin induces resumption of meiosis in vitro.

    Science.gov (United States)

    Dau, Andressa Minussi Pereira; da Silva, Eduardo Pradebon; da Rosa, Paulo Roberto Antunes; Bastiani, Felipe Tusi; Gutierrez, Karina; Ilha, Gustavo Freitas; Comim, Fabio Vasconcellos; Gonçalves, Paulo Bayard Dias

    2016-07-01

    The discovery of a receptor that binds prorenin and renin in human endothelial and mesangial cells highlights the possible effect of renin-independent prorenin in the resumption of meiosis in oocytes that was postulated in the 1980s.This study aimed to identify the (pro)renin receptor in the ovary and to assess the effect of prorenin on meiotic resumption. The (pro)renin receptor protein was detected in bovine cumulus-oocyte complexes, theca cells, granulosa cells, and in the corpus luteum. Abundant (pro)renin receptor messenger ribonucleic acid (mRNA) was detected in the oocytes and cumulus cells, while prorenin mRNA was identified in the cumulus cells only. Prorenin at concentrations of 10(-10), 10(-9), and 10(-8)M incubated with oocytes co-cultured with follicular hemisections for 15h caused the resumption of oocyte meiosis. Aliskiren, which inhibits free renin and receptor-bound renin/prorenin, at concentrations of 10(-7), 10(-5), and 10(-3)M blocked this effect (Pmeiosis resumption, cumulus-oocyte complexes and follicular hemisections were treated with prorenin and with angiotensin II or saralasin (angiotensin II antagonist). Prorenin induced the resumption of meiosis independently of angiotensin II. Furthermore, cumulus-oocyte complexes cultured with forskolin (200μM) and treated with prorenin and aliskiren did not exhibit a prorenin-induced resumption of meiosis (Pmeiosis in cattle. Copyright © 2016 Elsevier Inc. All rights reserved.

  13. Silencing of meiosis-critical genes for engineering male sterility in plants

    Science.gov (United States)

    Engineering sterile traits in plants through the tissue-specific expression of a cytotoxic gene provides an effective way for containing transgene flow; however, the microbial origin of cytotoxic genes has raised concerns. In an attempt to develop a safe alternative, we have chosen the meiosis-crit...

  14. E-type cyclins modulate telomere integrity in mammalian male meiosis.

    Science.gov (United States)

    Manterola, Marcia; Sicinski, Piotr; Wolgemuth, Debra J

    2016-06-01

    We have shown that E-type cyclins are key regulators of mammalian male meiosis. Depletion of cyclin E2 reduced fertility in male mice due to meiotic defects, involving abnormal pairing and synapsis, unrepaired DNA, and loss of telomere structure. These defects were exacerbated by additional loss of cyclin E1, and complete absence of both E-type cyclins produces a meiotic catastrophe. Here, we investigated the involvement of E-type cyclins in maintaining telomere integrity in male meiosis. Spermatocytes lacking cyclin E2 and one E1 allele (E1+/-E2-/-) displayed a high rate of telomere abnormalities but can progress to pachytene and diplotene stages. We show that their telomeres exhibited an aberrant DNA damage repair response during pachynema and that the shelterin complex proteins TRF2 and RAP2 were significantly decreased in the proximal telomeres. Moreover, the insufficient level of these proteins correlated with an increase of γ-H2AX foci in the affected telomeres and resulted in telomere associations involving TRF1 and telomere detachment in later prophase-I stages. These results suggest that E-type cyclins are key modulators of telomere integrity during meiosis by, at least in part, maintaining the balance of shelterin complex proteins, and uncover a novel role of E-type cyclins in regulating chromosome structure during male meiosis.

  15. Merotelic kinetochore attachment in oocyte meiosis II causes sister chromatids segregation errors in aged mice.

    Science.gov (United States)

    Cheng, Jin-Mei; Li, Jian; Tang, Ji-Xin; Hao, Xiao-Xia; Wang, Zhi-Peng; Sun, Tie-Cheng; Wang, Xiu-Xia; Zhang, Yan; Chen, Su-Ren; Liu, Yi-Xun

    2017-08-03

    Mammalian oocyte chromosomes undergo 2 meiotic divisions to generate haploid gametes. The frequency of chromosome segregation errors during meiosis I increase with age. However, little attention has been paid to the question of how aging affects sister chromatid segregation during oocyte meiosis II. More importantly, how aneuploid metaphase II (MII) oocytes from aged mice evade the spindle assembly checkpoint (SAC) mechanism to complete later meiosis II to form aneuploid embryos remains unknown. Here, we report that MII oocytes from naturally aged mice exhibited substantial errors in chromosome arrangement and configuration compared with young MII oocytes. Interestingly, these errors in aged oocytes had no impact on anaphase II onset and completion as well as 2-cell formation after parthenogenetic activation. Further study found that merotelic kinetochore attachment occurred more frequently and could stabilize the kinetochore-microtubule interaction to ensure SAC inactivation and anaphase II onset in aged MII oocytes. This orientation could persist largely during anaphase II in aged oocytes, leading to severe chromosome lagging and trailing as well as delay of anaphase II completion. Therefore, merotelic kinetochore attachment in oocyte meiosis II exacerbates age-related genetic instability and is a key source of age-dependent embryo aneuploidy and dysplasia.

  16. Live Imaging of Meiosis I in Late-Stage Drosophila melanogaster Oocytes.

    Science.gov (United States)

    Hughes, Stacie E; Hawley, R Scott

    2017-01-01

    Drosophila melanogaster has been studied for a century as a genetic model to understand recombination, chromosome segregation, and the basic rules of inheritance. However, it has only been about 25 years since the events that occur during nuclear envelope breakdown, spindle assembly, and chromosome orientation during D. melanogaster female meiosis I were first visualized by fixed cytological methods (Theurkauf and Hawley, J Cell Biol 116:1167-1180, 1992). Although these fixed cytological studies revealed many important details about the events that occur during meiosis I, they failed to elucidate the timing or order of these events. The development of protocols for live imaging of meiotic events within the oocyte has enabled collection of real-time information on the kinetics and dynamics of spindle assembly, as well as the behavior of chromosomes during prometaphase I. Here, we describe a method to visualize spindle assembly and chromosome movement during meiosis I by injecting fluorescent dyes to label microtubules and DNA into stage 12-14 oocytes. This method enables the events during Drosophila female meiosis I, such as spindle assembly and chromosome movement, to be observed in vivo, regardless of genetic background, with exceptional spatial and temporal resolution.

  17. Trans-Lesion DNA Polymerases May Be Involved in Yeast Meiosis

    Science.gov (United States)

    Arbel-Eden, Ayelet; Joseph-Strauss, Daphna; Masika, Hagit; Printzental, Oxana; Rachi, Eléanor; Simchen, Giora

    2013-01-01

    Trans-lesion DNA polymerases (TLSPs) enable bypass of DNA lesions during replication and are also induced under stress conditions. Being only weakly dependent on their template during replication, TLSPs introduce mutations into DNA. The low processivity of these enzymes ensures that they fall off their template after a few bases are synthesized and are then replaced by the more accurate replicative polymerase. We find that the three TLSPs of budding yeast Saccharomyces cerevisiae Rev1, PolZeta (Rev3 and Rev7), and Rad30 are induced during meiosis at a time when DNA double-strand breaks (DSBs) are formed and homologous chromosomes recombine. Strains deleted for one or any combination of the three TLSPs undergo normal meiosis. However, in the triple-deletion mutant, there is a reduction in both allelic and ectopic recombination. We suggest that trans-lesion polymerases are involved in the processing of meiotic double-strand breaks that lead to mutations. In support of this notion, we report significant yeast two-hybrid (Y2H) associations in meiosis-arrested cells between the TLSPs and DSB proteins Rev1-Spo11, Rev1-Mei4, and Rev7-Rec114, as well as between Rev1 and Rad30. We suggest that the involvement of TLSPs in processing of meiotic DSBs could be responsible for the considerably higher frequency of mutations reported during meiosis compared with that found in mitotically dividing cells, and therefore may contribute to faster evolutionary divergence than previously assumed. PMID:23550131

  18. Vesicular transport protein Arf6 modulates cytoskeleton dynamics for polar body extrusion in mouse oocyte meiosis.

    Science.gov (United States)

    Duan, Xing; Zhang, Hao-Lin; Pan, Meng-Hao; Zhang, Yu; Sun, Shao-Chen

    2018-02-01

    Arf6 (ADP-ribosylation factor 6) is known to play important roles in membrane dynamics through the regulation of actin filament reorganization for multiple cellular processes such as cytokinesis, phagocytosis, cell migration and tumor cell invasion. However, the functions of Arf6 in mammalian oocyte meiosis have not been clarified. In present study we showed that Arf6 expressed in mouse oocytes and was mainly distributed around the spindle during meiosis. Depletion of Arf6 by morpholino microinjection caused oocytes failing to extrude first polar body. Further analysis indicated that Arf6 knock down caused the aberrant actin distribution, which further induced the failure of meiotic spindle movement. And the loss of oocyte polarity also confirmed this. The regulation of Arf6 on actin filaments in mouse oocytes might be due to its effects on the phosphorylation level of cofilin and the expression of Arp2/3 complex. Moreover, we found that the decrease of Arf6 caused the disruption of spindle formation, indicating the multiple roles of Arf6 on cytoskeleton dynamics in meiosis. In summary, our results indicated that Arf6 was involved in mouse oocyte meiosis through its functional roles in actin-mediated spindle movement and spindle organization. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Is meiosis a fundamental cause of inviability among sexual and asexual plants and animals?

    Science.gov (United States)

    Levitis, Daniel A; Zimmerman, Kolea; Pringle, Anne

    2017-08-16

    Differences in viability between asexually and sexually generated offspring strongly influence the selective advantage and therefore the prevalence of sexual reproduction (sex). However, no general principle predicts when sexual offspring will be more viable than asexual offspring. We hypothesize that when any kind of reproduction is based on a more complex cellular process, it will encompass more potential failure points, and therefore lower offspring viability. Asexual reproduction (asex) can be simpler than sex, when offspring are generated using only mitosis. However, when asex includes meiosis and meiotic restitution, gamete production is more complex than in sex. We test our hypothesis by comparing the viability of asexual and closely related sexual offspring across a wide range of plants and animals, and demonstrate that meiotic asex does result in lower viability than sex; without meiosis, asex is mechanistically simple and provides higher viability than sex. This phylogenetically robust pattern is supported in 42 of 44 comparisons drawn from diverse plants and animals, and is not explained by the other variables included in our model. Other mechanisms may impact viability, such as effects of reproductive mode on heterozygosity and subsequent viability, but we propose the complexity of cellular processes of reproduction, particularly meiosis, as a fundamental cause of early developmental failure and mortality. Meiosis, the leading cause of inviability in humans, emerges as a likely explanation of offspring inviability among diverse eukaryotes. © 2017 The Author(s).

  20. Meikin-associated polo-like kinase specifies Bub1 distribution in meiosis I.

    Science.gov (United States)

    Miyazaki, Seira; Kim, Jihye; Yamagishi, Yuya; Ishiguro, Tadashi; Okada, Yuki; Tanno, Yuji; Sakuno, Takeshi; Watanabe, Yoshinori

    2017-06-01

    In meiosis I, sister chromatids are captured by microtubules emanating from the same pole (mono-orientation), and centromeric cohesion is protected throughout anaphase. Shugoshin, which is localized to centromeres depending on the phosphorylation of histone H2A by Bub1 kinase, plays a central role in protecting meiotic cohesin Rec8 from separase cleavage. Another key meiotic kinetochore factor, meikin, may regulate cohesion protection, although the underlying molecular mechanisms remain elusive. Here, we show that fission yeast Moa1 (meikin), which associates stably with CENP-C during meiosis I, recruits Plo1 (polo-like kinase) to the kinetochores and phosphorylates Spc7 (KNL1) to accumulate Bub1. Consequently, in contrast to the transient kinetochore localization of mitotic Bub1, meiotic Bub1 persists at kinetochores until anaphase I. The meiotic Bub1 pool ensures robust Sgo1 (shugoshin) localization and cohesion protection at centromeres by cooperating with heterochromatin protein Swi6, which binds and stabilizes Sgo1. Furthermore, molecular genetic analyses show a hierarchical regulation of centromeric cohesion protection by meikin and shugoshin that is important for establishing meiosis-specific chromosome segregation. We provide evidence that the meiosis-specific Bub1 regulation is conserved in mouse. © 2017 Molecular Biology Society of Japan and John Wiley & Sons Australia, Ltd.

  1. Non-homologous chromosome synapsis during mouse meiosis : consequences for male fertility and survival of progeny

    NARCIS (Netherlands)

    Peters, A.H.F.M.

    1997-01-01

    In the mouse, heterozygosity for several reciprocal and Robertsonian translocations is associated with impairment of chromosome synapsis and suppression of crossover formation in segments near the points of exchange during prophase of meiosis. This thesis describes the analysis of the consequences

  2. Dance of the Chromosomes: A Kinetic Learning Approach to Mitosis and Meiosis

    Science.gov (United States)

    Kreiser, Brian; Hairston, Rosalina

    2007-01-01

    Understanding mitosis and meiosis is fundamental to understanding the basics of Mendelian inheritance, yet many students find these concepts challenging or confusing. Here we present a visually and physically stimulating activity using minimal supplies to supplement traditional instruction in order to engage the students and facilitate…

  3. Creating a Double-Spring Model to Teach Chromosome Movement during Mitosis & Meiosis

    Science.gov (United States)

    Luo, Peigao

    2012-01-01

    The comprehension of chromosome movement during mitosis and meiosis is essential for understanding genetic transmission, but students often find this process difficult to grasp in a classroom setting. I propose a "double-spring model" that incorporates a physical demonstration and can be used as a teaching tool to help students understand this…

  4. Homologous recombination, sister chromatid cohesion, and chromosome condensation in mammalian meiosis

    NARCIS (Netherlands)

    Eijpe, M.

    2002-01-01

    In the life cycle of sexually reproducing eukaryotes, haploid and diploid generations of cells alternate. Two types of cell division occur in such a life cycle: mitosis and meiosis. They are compared in chapter 1 . Haploid and

  5. Centromeres cluster de novo at the beginning of meiosis in Brachypodium distachyon.

    Directory of Open Access Journals (Sweden)

    Ruoyu Wen

    Full Text Available In most eukaryotes that have been studied, the telomeres cluster into a bouquet early in meiosis, and in wheat and its relatives and in Arabidopsis the centromeres pair at the same time. In Arabidopsis, the telomeres do not cluster as a typical telomere bouquet on the nuclear membrane but are associated with the nucleolus both somatically and at the onset of meiosis. We therefore assessed whether Brachypodium distachyon, a monocot species related to cereals and whose genome is approximately twice the size of Arabidopsis thaliana, also exhibited an atypical telomere bouquet and centromere pairing. In order to investigate the occurrence of a bouquet and centromere pairing in B distachyon, we first had to establish protocols for studying meiosis in this species. This enabled us to visualize chromosome behaviour in meiocytes derived from young B distachyon spikelets in three-dimensions by fluorescent in situ hybridization (FISH, and accurately to stage meiosis based on chromatin morphology in relation to spikelet size and the timing of sample collection. Surprisingly, this study revealed that the centromeres clustered as a single site at the same time as the telomeres also formed a bouquet or single cluster.

  6. Transcriptome analysis of poplar rust telia reveals overwintering adaptation and tightly coordinated karyogamy and meiosis processes

    Directory of Open Access Journals (Sweden)

    Stéphane eHACQUARD

    2013-11-01

    Full Text Available Most rust fungi have a complex life cycle involving up to five different spore-producing stages. The telial stage that produces melanised overwintering teliospores is one of these and plays a fundamental role for generating genetic diversity as karyogamy and meiosis occur at that stage. Despite the importance of telia for the rust life cycle, almost nothing is known about the fungal genetic programs that are activated in this overwintering structure. In the present study, the transcriptome of telia produced by the poplar rust fungus M. larici-populina has been investigated using whole genome exon oligoarrays and RT-qPCR. Comparative expression profiling at the telial and uredinial stages identifies genes specifically expressed or up-regulated in telia including osmotins/thaumatin-like proteins and aquaporins that may reflect specific adaptation to overwintering as well numerous lytic enzymes acting on plant cell wall, reflecting extensive cell wall remodelling at that stage. The temporal dynamics of karyogamy was followed using combined RT-qPCR and DAPI-staining approaches. This reveals that fusion of nuclei and induction of karyogamy-related genes occur simultaneously between the 25-39 days post inoculation time frame. Transcript profiling of conserved meiosis genes indicate a preferential induction right after karyogamy and corroborate that meiosis begins prior to overwintering and is interrupted in Meiosis I (prophase I, diplonema stage until teliospore germination in early spring.

  7. Mps1 kinase-dependent Sgo2 centromere localisation mediates cohesin protection in mouse oocyte meiosis I.

    Science.gov (United States)

    El Yakoubi, Warif; Buffin, Eulalie; Cladière, Damien; Gryaznova, Yulia; Berenguer, Inés; Touati, Sandra A; Gómez, Rocío; Suja, José A; van Deursen, Jan M; Wassmann, Katja

    2017-09-25

    A key feature of meiosis is the step-wise removal of cohesin, the protein complex holding sister chromatids together, first from arms in meiosis I and then from the centromere region in meiosis II. Centromeric cohesin is protected by Sgo2 from Separase-mediated cleavage, in order to maintain sister chromatids together until their separation in meiosis II. Failures in step-wise cohesin removal result in aneuploid gametes, preventing the generation of healthy embryos. Here, we report that kinase activities of Bub1 and Mps1 are required for Sgo2 localisation to the centromere region. Mps1 inhibitor-treated oocytes are defective in centromeric cohesin protection, whereas oocytes devoid of Bub1 kinase activity, which cannot phosphorylate H2A at T121, are not perturbed in cohesin protection as long as Mps1 is functional. Mps1 and Bub1 kinase activities localise Sgo2 in meiosis I preferentially to the centromere and pericentromere respectively, indicating that Sgo2 at the centromere is required for protection.In meiosis I centromeric cohesin is protected by Sgo2 from Separase-mediated cleavage ensuring that sister chromatids are kept together until their separation in meiosis II. Here the authors demonstrate that Bub1 and Mps1 kinase activities are required for Sgo2 localisation to the centromere region.

  8. Nicotinamide impairs entry into and exit from meiosis I in mouse oocytes.

    Science.gov (United States)

    Riepsamen, Angelique; Wu, Lindsay; Lau, Laurin; Listijono, Dave; Ledger, William; Sinclair, David; Homer, Hayden

    2015-01-01

    Following exit from meiosis I, mammalian oocytes immediately enter meiosis II without an intervening interphase, accompanied by rapid reassembly of a bipolar spindle that maintains condensed chromosomes in a metaphase configuration (metaphase II arrest). Here we study the effect of nicotinamide (NAM), a non-competitive pan-sirtuin inhibitor, during meiotic maturation in mouse oocytes. Sirtuins are a family of seven NAD+-dependent deacetylases (Sirt1-7), which are involved in multiple cellular processes and are emerging as important regulators in oocytes and embryos. We found that NAM significantly delayed entry into meiosis I associated with delayed accumulation of the Cdk1 co-activator, cyclin B1. GVBD was also inhibited by the Sirt2-specific inhibitor, AGK2, and in a very similar pattern to NAM, supporting the notion that as in somatic cells, NAM inhibits sirtuins in oocytes. NAM did not affect subsequent spindle assembly, chromosome alignment or the timing of first polar body extrusion (PBE). Unexpectedly, however, in the majority of oocytes with a polar body, chromatin was decondensed and a nuclear structure was present. An identical phenotype was observed when flavopiridol was used to induce Cdk1 inactivation during late meiosis I prior to PBE, but not if Cdk1 was inactivated after PBE when metaphase II arrest was already established, altogether indicating that NAM impaired establishment rather than maintenance of metaphase II arrest. During meiosis I exit in NAM-treated medium, we found that cyclin B1 levels were lower and inhibitory Cdk1 phosphorylation was increased compared with controls. Although activation of the anaphase-promoting complex-Cdc20 (APC-Cdc20) occurred on-time in NAM-treated oocytes, Cdc20 levels were higher in very late meiosis I, pointing to exaggerated APC-Cdc20-mediated proteolysis as a reason for lower cyclin B1 levels. Collectively, therefore, our data indicate that by disrupting Cdk1 regulation, NAM impairs entry into meiosis I and

  9. Microarray expression analysis of meiosis and microsporogenesis in hexaploid bread wheat

    Directory of Open Access Journals (Sweden)

    Langridge Peter

    2006-10-01

    Full Text Available Abstract Background Our understanding of the mechanisms that govern the cellular process of meiosis is limited in higher plants with polyploid genomes. Bread wheat is an allohexaploid that behaves as a diploid during meiosis. Chromosome pairing is restricted to homologous chromosomes despite the presence of homoeologues in the nucleus. The importance of wheat as a crop and the extensive use of wild wheat relatives in breeding programs has prompted many years of cytogenetic and genetic research to develop an understanding of the control of chromosome pairing and recombination. The rapid advance of biochemical and molecular information on meiosis in model organisms such as yeast provides new opportunities to investigate the molecular basis of chromosome pairing control in wheat. However, building the link between the model and wheat requires points of data contact. Results We report here a large-scale transcriptomics study using the Affymetrix wheat GeneChip® aimed at providing this link between wheat and model systems and at identifying early meiotic genes. Analysis of the microarray data identified 1,350 transcripts temporally-regulated during the early stages of meiosis. Expression profiles with annotated transcript functions including chromatin condensation, synaptonemal complex formation, recombination and fertility were identified. From the 1,350 transcripts, 30 displayed at least an eight-fold expression change between and including pre-meiosis and telophase II, with more than 50% of these having no similarities to known sequences in NCBI and TIGR databases. Conclusion This resource is now available to support research into the molecular basis of pairing and recombination control in the complex polyploid, wheat.

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

    Science.gov (United States)

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

    2016-09-01

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

  11. Mouse Y-linked Zfy1 and Zfy2 are expressed during the male-specific interphase between meiosis I and meiosis II and promote the 2nd meiotic division.

    Science.gov (United States)

    Vernet, Nadège; Mahadevaiah, Shantha K; Yamauchi, Yasuhiro; Decarpentrie, Fanny; Mitchell, Michael J; Ward, Monika A; Burgoyne, Paul S

    2014-06-01

    Mouse Zfy1 and Zfy2 encode zinc finger transcription factors that map to the short arm of the Y chromosome (Yp). They have previously been shown to promote meiotic quality control during pachytene (Zfy1 and Zfy2) and at the first meiotic metaphase (Zfy2). However, from these previous studies additional roles for genes encoded on Yp during meiotic progression were inferred. In order to identify these genes and investigate their function in later stages of meiosis, we created three models with diminishing Yp and Zfy gene complements (but lacking the Y-long-arm). Since the Y-long-arm mediates pairing and exchange with the X via their pseudoautosomal regions (PARs) we added a minute PAR-bearing X chromosome derivative to enable formation of a sex bivalent, thus avoiding Zfy2-mediated meiotic metaphase I (MI) checkpoint responses to the unpaired (univalent) X chromosome. Using these models we obtained definitive evidence that genetic information on Yp promotes meiosis II, and by transgene addition identified Zfy1 and Zfy2 as the genes responsible. Zfy2 was substantially more effective and proved to have a much more potent transactivation domain than Zfy1. We previously established that only Zfy2 is required for the robust apoptotic elimination of MI spermatocytes in response to a univalent X; the finding that both genes potentiate meiosis II led us to ask whether there was de novo Zfy1 and Zfy2 transcription in the interphase between meiosis I and meiosis II, and this proved to be the case. X-encoded Zfx was also expressed at this stage and Zfx over-expression also potentiated meiosis II. An interphase between the meiotic divisions is male-specific and we previously hypothesised that this allows meiosis II critical X and Y gene reactivation following sex chromosome silencing in meiotic prophase. The interphase transcription and meiosis II function of Zfx, Zfy1 and Zfy2 validate this hypothesis.

  12. How-to-Do-It: Hands-on Activity for Mitosis, Meiosis and the Fundamentals of Heredity.

    Science.gov (United States)

    Taylor, Mark F.

    1988-01-01

    Described is an exercise which uses inexpensive and easy-to-make materials to demonstrate the basic fundamentals of heredity. Discusses two approaches using a hypothetical insert to demonstrate inheritance, mitosis, meiosis, and genotypic and phenotypic frequencies. (CW)

  13. Effect of space flight on meiosis of pollen mother cells and its derived pollens in impatiens balsamina

    International Nuclear Information System (INIS)

    Tang Zesheng; Yang Jun; Yuan Haiyun; Zhao Yan

    2005-01-01

    Effects of space flight on meiosis of pollen mother cells and meiosis of microspores in Impatiens balsamina were investigated. It was found that meiosis showed abnormal in most plants germinated from seeds after space flight, and chromosome fragment, chromosomal bridge and lagging chromosome were observed in the process of meiosis in these plants. Disproportional segregation of chromosome, multipolar division and multinucleus were also observed in most plants, which developed into paraspores with different chromosome number. Mitosis of microspores was found to be abnormal in most plants, and the number of chromosome in microspore unequal. The fertility of the pollens was tested with iodic solution; it was found that the fertility of pollens varied in different plants. (authors)

  14. Karyotype and male pre-reductional meiosis of the sharpshooter Tapajosa rubromarginata (Hemiptera: Cicadellidae

    Directory of Open Access Journals (Sweden)

    Graciela R de Bigliardo

    2011-03-01

    Full Text Available Cicadellidae in one of the best represented families in the Neotropical Region, and the tribe Proconiini comprises most of the xylem-feeding insects, including the majority of the known vectors of xylem-born phytopathogenic organisms. The cytogenetics of the Proconiini remains largely unexplored. We studied males of Tapajosa rubromarginata (Signoret collected at El Manantial (Tucumán, Argentina on native spontaneous vegetation where Sorghum halepense predominates. Conventional cytogenetic techniques were used in order to describe the karyotype and male meiosis of this sharpshooter. T. rubromarginata has a male karyological formula of 2n=21 and a sex chromosome system XO:XX (♂:♀. The chromosomes do not have a primary constriction, being holokinetic and the meiosis is pre-reductional, showing similar behavior both for autosomes and sex chromosomes during anaphase I. For this stage, chromosomes are parallel to the acromatic spindle with kinetic activities in the telomeres. They segregate reductionally in the anaphase I, and towards the equator during the second division of the meiosis. This is the first contribution to cytogenetic aspects on proconines sharpshooters, particularly on this economic relevant Auchenorrhyncha species. Rev. Biol. Trop. 59 (1: 309-314. Epub 2011 March 01.Los Cicadellidae son una de las familias mejor representadas en la región neotropical. La tribu Proconiini incluye a muchos de los insectos que se alimentan de xilema y la mayoría de los vectores de organismos fitopatógenos asociados con dicho tejido de conducción. La citogenética de los Proconiini es prácticamente inexplorada. Por lo tanto, se utilizaron técnicas citogenéticas convencionales para describir el cariotipo y la meiosis en los machos de Tapajosa rubromarginata Signoret. Este cicadélido presenta el complemento cromosómico diploide de 2n=20A+X0 en los machos. Los cromosomas no presentan constricción primaria, son holocinéticos, y la meiosis es

  15. Global gene expression analysis in fetal mouse ovaries with and without meiosis and comparison of selected genes with meiosis in the testis

    DEFF Research Database (Denmark)

    Olesen, C.; Nyeng, P.; Kalisz, M.

    2007-01-01

    IX also coincided with the first meiotic wave in the pubertal testis. This is the first time that SytIX has been reported in non-neuronal tissue. Finally, we examined the expression of one of the uncharacterized genes and found it to be gonad-specific in adulthood. We named this novel transcript "Gonad......-expressed transcript 1" (Get-1). In situ hybridization showed that Get-1 was expressed in meiotic germ cells in both fetal ovaries and mature testis. Get-1 is therefore a novel gene in both male and female meiosis....

  16. Cdc7-Dbf4 Regulates NDT80 Transcription as Well as Reductional Segregation during Budding Yeast Meiosis

    OpenAIRE

    Lo, Hsiao-Chi; Wan, Lihong; Rosebrock, Adam; Futcher, Bruce; Hollingsworth, Nancy M.

    2008-01-01

    In budding yeast, as in other eukaryotes, the Cdc7 protein kinase is important for initiation of DNA synthesis in vegetative cells. In addition, Cdc7 has crucial meiotic functions: it facilitates premeiotic DNA replication, and it is essential for the initiation of recombination. This work uses a chemical genetic approach to demonstrate that Cdc7 kinase has additional roles in meiosis. First, Cdc7 allows expression of NDT80, a meiosis-specific transcriptional activator required for the induct...

  17. Meiosis gene inventory of four ciliates reveals the prevalence of a synaptonemal complex-independent crossover pathway.

    Science.gov (United States)

    Chi, Jingyun; Mahé, Frédéric; Loidl, Josef; Logsdon, John; Dunthorn, Micah

    2014-03-01

    To establish which meiosis genes are present in ciliates, and to look for clues as to which recombination pathways may be treaded by them, four genomes were inventoried for 11 meiosis-specific and 40 meiosis-related genes. We found that the set of meiosis genes shared by Tetrahymena thermophila, Paramecium tetraurelia, Ichthyophthirius multifiliis, and Oxytricha trifallax is consistent with the prevalence of a Mus81-dependent class II crossover pathway that is considered secondary in most model eukaryotes. There is little evidence for a canonical class I crossover pathway that requires the formation of a synaptonemal complex (SC). This gene inventory suggests that meiotic processes in ciliates largely depend on mitotic repair proteins for executing meiotic recombination. We propose that class I crossovers and SCs were reduced sometime during the evolution of ciliates. Consistent with this reduction, we provide microscopic evidence for the presence only of degenerate SCs in Stylonychia mytilus. In addition, lower nonsynonymous to synonymous mutation rates of some of the meiosis genes suggest that, in contrast to most other nuclear genes analyzed so far, meiosis genes in ciliates are largely evolving at a slower rate than those genes in fungi and animals.

  18. Regulation of Centromere Localization of the Drosophila Shugoshin MEI-S332 and Sister-Chromatid Cohesion in Meiosis

    Science.gov (United States)

    Nogueira, Cristina; Kashevsky, Helena; Pinto, Belinda; Clarke, Astrid; Orr-Weaver, Terry L.

    2014-01-01

    The Shugoshin (Sgo) protein family helps to ensure proper chromosome segregation by protecting cohesion at the centromere by preventing cleavage of the cohesin complex. Some Sgo proteins also influence other aspects of kinetochore-microtubule attachments. Although many Sgo members require Aurora B kinase to localize to the centromere, factors controlling delocalization are poorly understood and diverse. Moreover, it is not clear how Sgo function is inactivated and whether this is distinct from delocalization. We investigated these questions in Drosophila melanogaster, an organism with superb chromosome cytology to monitor Sgo localization and quantitative assays to test its function in sister-chromatid segregation in meiosis. Previous research showed that in mitosis in cell culture, phosphorylation of the Drosophila Sgo, MEI-S332, by Aurora B promotes centromere localization, whereas Polo phosphorylation promotes delocalization. These studies also suggested that MEI-S332 can be inactivated independently of delocalization, a conclusion supported here by localization and function studies in meiosis. Phosphoresistant and phosphomimetic mutants for the Aurora B and Polo phosphorylation sites were examined for effects on MEI-S332 localization and chromosome segregation in meiosis. Strikingly, MEI-S332 with a phosphomimetic mutation in the Aurora B phosphorylation site prematurely dissociates from the centromeres in meiosis I. Despite the absence of MEI-S332 on meiosis II centromeres in male meiosis, sister chromatids segregate normally, demonstrating that detectable levels of this Sgo are not essential for chromosome congression, kinetochore biorientation, or spindle assembly. PMID:25081981

  19. Male and female meiosis in the mountain scorpion Zabius fuscus (Scorpiones, Buthidae): heterochromatin, rDNA and TTAGG telomeric repeats.

    Science.gov (United States)

    Adilardi, Renzo Sebastián; Ojanguren-Affilastro, Andrés Alejandro; Mattoni, Camilo Iván; Mola, Liliana María

    2015-08-01

    All cytogenetically studied scorpions present male achiasmatic meiosis and lack heteromorphic sex chromosomes. In contrast, information about female meiosis in scorpions is scarce due to the difficulty of finding meiotic cells. The genus Zabius includes three described species and no chromosome studies have been performed on it until now. We analyzed the constitutive heterochromatin distribution, NORs and telomeric sequences in mitosis and meiosis of males and females of different populations of Zabius fuscus. All specimens presented 2n = 18 holokinetic chromosomes that gradually decreased in size. Male meiosis presented nine bivalents and a polymorphism for one reciprocal translocation in one population. Telomeric signals were detected at every terminal region, confirming also the presence of a (TTAGG) n motif in Buthidae. Constitutive heterochromatin was found in three chromosome pairs at a terminal region; moreover, NORs were embedded in the heterochromatic region of the largest pair. Chromosome size and landmarks allowed us to propose the chromosomes involved in the rearrangement. In four females, cells at different prophase I stages were analyzed. We describe a diffuse stage and the presence of ring-shaped bivalents. We discuss the possible origin of these bivalents in the framework of chiasmatic or achiasmatic female meiosis. These results contribute to increase the scarce evidence of female meiosis in scorpions and raise new questions about its mechanism.

  20. The roles of cohesins in mitosis, meiosis, and human health and disease

    Science.gov (United States)

    Brooker, Amanda S.; Berkowitz, Karen M.

    2015-01-01

    Summary Mitosis and meiosis are essential processes that occur during development. Throughout these processes, cohesion is required to keep the sister chromatids together until their separation at anaphase. Cohesion is created by multi-protein subunit complexes called cohesins. Although the subunits differ slightly in mitosis and meiosis, the canonical cohesin complex is composed of four subunits that are quite diverse. The cohesin complexes are also important for DNA repair, gene expression, development, and genome integrity. Here we provide an overview of the roles of cohesins during these different events, as well as their roles in human health and disease, including the cohesinopathies. Although the exact roles and mechanisms of these proteins are still being elucidated, this review will serve as a guide for the current knowledge of cohesins. PMID:24906316

  1. Hydra meiosis reveals unexpected conservation of structural synaptonemal complex proteins across metazoans.

    Science.gov (United States)

    Fraune, Johanna; Alsheimer, Manfred; Volff, Jean-Nicolas; Busch, Karoline; Fraune, Sebastian; Bosch, Thomas C G; Benavente, Ricardo

    2012-10-09

    The synaptonemal complex (SC) is a key structure of meiosis, mediating the stable pairing (synapsis) of homologous chromosomes during prophase I. Its remarkable tripartite structure is evolutionarily well conserved and can be found in almost all sexually reproducing organisms. However, comparison of the different SC protein components in the common meiosis model organisms Saccharomyces cerevisiae, Arabidopsis thaliana, Caenorhabditis elegans, Drosophila melanogaster, and Mus musculus revealed no sequence homology. This discrepancy challenged the hypothesis that the SC arose only once in evolution. To pursue this matter we focused on the evolution of SYCP1 and SYCP3, the two major structural SC proteins of mammals. Remarkably, our comparative bioinformatic and expression studies revealed that SYCP1 and SYCP3 are also components of the SC in the basal metazoan Hydra. In contrast to previous assumptions, we therefore conclude that SYCP1 and SYCP3 form monophyletic groups of orthologous proteins across metazoans.

  2. Meiosis observation of the sterile mutant after injection of exogenous DNA into wheat

    International Nuclear Information System (INIS)

    Yang Jingcheng; Yu Yuanjie; Qi Yanfang; Shen Fafu; Liu Fengzhen

    2001-01-01

    A male sterile mutant was obtained after injection of exogenous λ DNA into wheat line 814527. Meiosis of pollen mother cells (PMC) of the mutant and its receptor (line 814527) were observed. The results showed that the frequency of chromosomal variation of the sterile line was 18%, and that of the receptor was 0.8%. The main types of variation included univalent, chromosome lagging, chromosome fragment, chromosome bridge, micronucleus, abnormal ditrad and tetrad. The fragment of DNA injected into the receptor may influence the normal genetic process of chromosomes in pollen mother cells, and this may cause variations of chromosomes. The chromosome variation in meiosis may cause a part of pollen mother cells to abort, but it is not the main cause of abortion

  3. Two-step activation of meiosis by the mat1 locus in Schizosaccharomyces pombe

    DEFF Research Database (Denmark)

    Willer, M; Hoffmann, Ulla-Lisbeth; Styrkársdóttir, U

    1995-01-01

    of meiosis is based largely on indirect observations, and a more precise investigation of these events was required to define the interaction between the mat1 genes. Here we resolve this issue using synthetic pheromones and P/M strains with mutations in either mat1-Pc or mat1-Mc. Our results suggest a model...... in which the mat1 locus plays two roles in controlling meiosis. In the first instance, the mat1-Pc and mat1-Mc functions are required to produce the mating pheromones and receptors that allow the generation of a pheromone signal. This signal is required to induce the expression of mat1-Pm and mat1-Mm...

  4. Angelman syndrome with uniparental disomy due to paternal meiosis II nondisjunction.

    Science.gov (United States)

    Gyftodimou, J; Karadima, G; Pandelia, E; Vassilopoulos, D; Petersen, M B

    1999-06-01

    We report a case of Angelman syndrome (AS) with paternal uniparental disomy (pUPD) of chromosome 15. This 6-year-old girl with overgrowth had frequent, but only provoked laughter, was mildly ataxic with limb hypertonia, and had no intelligible speech. She had deep-set eyes, protruding tongue, and prominent chin. The karyotype was normal. DNA analysis with microsatellites from chromosome 15 showed no inheritance of maternal alleles both within and outside the AS critical region. Proximal markers showed reduction to homozygosity of paternal alleles, intermediate markers showed nonreduction, and distal markers reduction, thus suggesting a meiosis II nondisjunction event in the father with two crossovers. This is, to our knowledge, the first reported case of AS due to meiosis II nondisjunction. We present detailed physical measurements in this patient, adding to the clinical description of the milder phenotype in AS due to pUPD.

  5. RNA synthesis during meiosis and spermiogenesis in Tylototriton verrucosus anderson - an annual testicular cycle

    International Nuclear Information System (INIS)

    Roy, R.R.; Ray, D.; Ghosal, S.K.

    1989-01-01

    RNA synthetic activity during various stages of meiosis and spermiogenesis in Tylotatriton verrucosus has been studied throughout the testicular cycle by autoradiographic technique. Meiocytes are 'hot' during breeding months while spermatids as well as spermatozoa has shown RNA synthetic activity during breeding and non breeding months. Continuation of RNA synthetic activity in spermatozoa suggests continued transcription necessary for sperm preservation of this seasonal breeder. (author). 8 refs., 1 tab

  6. Stage-specific effects of X-irradiation on Yeast meiosis

    International Nuclear Information System (INIS)

    Thorne, L.W.; Byers, B.

    1993-01-01

    Previous work has shown that cdc 13 causes meiotic arrest of Saccharomyces cerevisiae following DNA replication by a RAD9-dependent mechanism. In the present work, the authors have further investigated the implicit effects of chromosomal lesions on progression through meiosis by exposing yeast cells to X-irradiation at various times during sporulation. They find that exposure of RAD9 cells to X-irradiation early in meiosis prevents sporulation, arresting the cells at a stage prior to premeiotic DNA replication. rad9 meiotic cells are much less responsive to X-irradiation damage, completing sporulation after treatment with doses sufficient to cause arrest of RAD9 strains. These findings thereby reveal a RAD9-dependent checkpoint function in meiosis that is distinct from the G 2 arrest previously shown to result from cdc 13 dysfunction. Analysis of the spores that continued to be produced by either RAD9 or rad9 cultures that were X-irradiated in later stages of sporulation revealed most spores to be viable, even after exposure to radiation doses sufficient to kill most vegetative cells. This finding demonstrates that the lesions induced by X-irradiation at later times fail to trigger the checkpoint function revealed by cdc 13 arrest and suggests that the lesions may be subject to repair by serving as intermediates in the recombination process. Strains mutant for chromosomal synapsis and recombination, and therefore defective in meiotic disjunction, were tested for evidence that X-ray-induced lesions might alleviate inviability by promoting recombination. Enhancement of spore viability when spo 11 (but not hop 1) diploids were X-irradiated during meiosis indicates that induced lesions may partially substitute for SPO 11-dependent functions that are required for the initiation of recombination. 74 refs., 3 figs., 6 tabs

  7. PGRMC1 participates in late events of bovine granulosa cells mitosis and oocyte meiosis.

    Science.gov (United States)

    Terzaghi, L; Tessaro, I; Raucci, F; Merico, V; Mazzini, G; Garagna, S; Zuccotti, M; Franciosi, F; Lodde, V

    2016-08-02

    Progesterone Receptor Membrane Component 1 (PGRMC1) is expressed in both oocyte and ovarian somatic cells, where it is found in multiple cellular sub-compartments including the mitotic spindle apparatus. PGRMC1 localization in the maturing bovine oocytes mirrors its localization in mitotic cells, suggesting a possible common action in mitosis and meiosis. To test the hypothesis that altering PGRMC1 activity leads to similar defects in mitosis and meiosis, PGRMC1 function was perturbed in cultured bovine granulosa cells (bGC) and maturing oocytes and the effect on mitotic and meiotic progression assessed. RNA interference-mediated PGRMC1 silencing in bGC significantly reduced cell proliferation, with a concomitant increase in the percentage of cells arrested at G2/M phase, which is consistent with an arrested or prolonged M-phase. This observation was confirmed by time-lapse imaging that revealed defects in late karyokinesis. In agreement with a role during late mitotic events, a direct interaction between PGRMC1 and Aurora Kinase B (AURKB) was observed in the central spindle at of dividing cells. Similarly, treatment with the PGRMC1 inhibitor AG205 or PGRMC1 silencing in the oocyte impaired completion of meiosis I. Specifically the ability of the oocyte to extrude the first polar body was significantly impaired while meiotic figures aberration and chromatin scattering within the ooplasm increased. Finally, analysis of PGRMC1 and AURKB localization in AG205-treated oocytes confirmed an altered localization of both proteins when meiotic errors occur. The present findings demonstrate that PGRMC1 participates in late events of both mammalian mitosis and oocyte meiosis, consistent with PGRMC1's localization at the mid-zone and mid-body of the mitotic and meiotic spindle.

  8. Meiosis in elephant grass (Pennisetum purpureum), pearl millet (Pennisetum glaucum) (Poaceae, Poales) and their interspecific hybrids

    OpenAIRE

    Techio, Vânia Helena; Davide, Lisete Chamma; Pereira, Antônio Vander

    2006-01-01

    The cultivated and sexually compatible species Pennisetum purpureum (elephant grass, 2n = 4x = 28) and Pennisetum glaucum (pearl millet, 2n = 2x = 14) can undergo hybridization which favors the amplification of their genetic background and the introgression of favorable alleles into breeding programs. The main problem with interspecific hybrids of these species is infertility due to triploidy (2n = 3x = 21). This study describes meiosis in elephant grass x pearl millet hybrids and their proge...

  9. Large-scale functional genomic analysis of sporulation and meiosis in Saccharomyces cerevisiae.

    OpenAIRE

    Enyenihi, Akon H; Saunders, William S

    2003-01-01

    We have used a single-gene deletion mutant bank to identify the genes required for meiosis and sporulation among 4323 nonessential Saccharomyces cerevisiae annotated open reading frames (ORFs). Three hundred thirty-four sporulation-essential genes were identified, including 78 novel ORFs and 115 known genes without previously described sporulation defects in the comprehensive Saccharomyces Genome (SGD) or Yeast Proteome (YPD) phenotype databases. We have further divided the uncharacterized sp...

  10. Proteasomal degradation of ubiquitinated proteins in oocyte meiosis and fertilization in mammals

    Czech Academy of Sciences Publication Activity Database

    Karabínová, Pavla; Kubelka, Michal; Šušor, Andrej

    2011-01-01

    Roč. 346, č. 1 (2011), s. 1-9 ISSN 0302-766X R&D Projects: GA ČR GAP502/10/0944; GA ČR(CZ) GD204/09/H084 Institutional research plan: CEZ:AV0Z50450515 Keywords : Oocyte * Proteasome * Meiosis Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.114, year: 2011

  11. Evidence that masking of synapsis imperfections counterbalances quality control to promote efficient meiosis.

    Directory of Open Access Journals (Sweden)

    Susanna Mlynarczyk-Evans

    Full Text Available Reduction in ploidy to generate haploid gametes during sexual reproduction is accomplished by the specialized cell division program of meiosis. Pairing between homologous chromosomes and assembly of the synaptonemal complex at their interface (synapsis represent intermediate steps in the meiotic program that are essential to form crossover recombination-based linkages between homologs, which in turn enable segregation of the homologs to opposite poles at the meiosis I division. Here, we challenge the mechanisms of pairing and synapsis during C. elegans meiosis by disrupting the normal 1:1 correspondence between homologs through karyotype manipulation. Using a combination of cytological tools, including S-phase labeling to specifically identify X chromosome territories in highly synchronous cohorts of nuclei and 3D rendering to visualize meiotic chromosome structures and organization, our analysis of trisomic (triplo-X and polyploid meiosis provides insight into the principles governing pairing and synapsis and how the meiotic program is "wired" to maximize successful sexual reproduction. We show that chromosomes sort into homologous groups regardless of chromosome number, then preferentially achieve pairwise synapsis during a period of active chromosome mobilization. Further, comparisons of synapsis configurations in triplo-X germ cells that are proficient or defective for initiating recombination suggest a role for recombination in restricting chromosomal interactions to a pairwise state. Increased numbers of homologs prolong markers of the chromosome mobilization phase and/or boost germline apoptosis, consistent with triggering quality control mechanisms that promote resolution of synapsis problems and/or cull meiocytes containing synapsis defects. However, we also uncover evidence for the existence of mechanisms that "mask" defects, thus allowing resumption of prophase progression and survival of germ cells despite some asynapsis. We propose

  12. Chromosome complement and meiosis of Holmbergiana weyenberghii (Opiliones: Sclerosomatidae: Gagrellinae from Argentina Complemento cromosómico y meiosis de Holmbergiana weyenberghii (Opiliones: Sclerosomatidae: Gagrellinae de Argentina

    Directory of Open Access Journals (Sweden)

    Sergio G. Rodríguez Gil

    2010-12-01

    Full Text Available The cytogenetical analysis of the harvestman Holmbergiana weyenberghii (Holmberg (Eupnoi, Sclerosomatidae, Gagrellinae from Argentina is reported for the first time. The complement of males is composed of 18 chromosomes. In meiosis there are nine homomorphic bivalents: one large, five medium-sized and three small. The chromosome number of H. weyenberghii is within the range of diploid numbers of the subfamily Gagrellinae Thorell, which shows the lowest chromosome numbers among the sclerosomatids.Se analiza citogenéticamente, por primera vez, una especie de opilión proveniente de Argentina: Holmbergiana weyenberghii (Holmberg (Eupnoi, Sclerosomatidae, Gagrellinae. Los machos tienen un complemento cromosómico compuesto por 18 cromosomas. En meiosis, hay nueve bivalentes homomórficos: uno mayor, cinco medianos y tres menores. El número cromosómico de H. weyenberghii se encuentra dentro del rango de números diploides de los Gagrellinae Thorell; esta subfamilia presenta los números cromosómicos más bajos de Sclerosomatidae.

  13. FMRP Associates with Cytoplasmic Granules at the Onset of Meiosis in the Human Oocyte.

    Directory of Open Access Journals (Sweden)

    Roseanne Rosario

    Full Text Available Germ cell development and primordial follicle formation during fetal life is critical in establishing the pool of oocytes that subsequently determines the reproductive lifespan of women. Fragile X-associated primary ovarian insufficiency (FXPOI is caused by inheritance of the FMR1 premutation allele and approximately 20% of women with the premutation allele develop ovarian dysfunction and premature ovarian insufficiency. However, the underlying disease mechanism remains obscure, and a potential role of FMRP in human ovarian development has not been explored. We have characterised the expression of FMR1 and FMRP in the human fetal ovary at the time of germ cell entry into meiosis through to primordial follicle formation. FMRP expression is exclusively in germ cells in the human fetal ovary. Increased FMRP expression in germ cells coincides with the loss of pluripotency-associated protein expression, and entry into meiosis is associated with FMRP granulation. In addition, we have uncovered FMRP association with components of P-bodies and stress granules, suggesting it may have a role in mRNA metabolism at the time of onset of meiosis. Therefore, this data support the hypothesis that FMRP plays a role regulating mRNAs during pivotal maturational processes in fetal germ cells, and ovarian dysfunction resulting from FMR1 premutation may have its origins during these stages of oocyte development.

  14. Arabidopsis thaliana WAPL is essential for the prophase removal of cohesin during meiosis.

    Directory of Open Access Journals (Sweden)

    Kuntal De

    2014-07-01

    Full Text Available Sister chromatid cohesion, which is mediated by the cohesin complex, is essential for the proper segregation of chromosomes in mitosis and meiosis. The establishment of stable sister chromatid cohesion occurs during DNA replication and involves acetylation of the complex by the acetyltransferase CTF7. In higher eukaryotes, the majority of cohesin complexes are removed from chromosomes during prophase. Studies in fly and human have shown that this process involves the WAPL mediated opening of the cohesin ring at the junction between the SMC3 ATPase domain and the N-terminal domain of cohesin's α-kleisin subunit. We report here the isolation and detailed characterization of WAPL in Arabidopsis thaliana. We show that Arabidopsis contains two WAPL genes, which share overlapping functions. Plants in which both WAPL genes contain T-DNA insertions show relatively normal growth and development but exhibit a significant reduction in male and female fertility. The removal of cohesin from chromosomes during meiotic prophase is blocked in Atwapl mutants resulting in chromosome bridges, broken chromosomes and uneven chromosome segregation. In contrast, while subtle mitotic alterations are observed in some somatic cells, cohesin complexes appear to be removed normally. Finally, we show that mutations in AtWAPL suppress the lethality associated with inactivation of AtCTF7. Taken together our results demonstrate that WAPL plays a critical role in meiosis and raises the possibility that mechanisms involved in the prophase removal of cohesin may vary between mitosis and meiosis in plants.

  15. PP2A regulates kinetochore-microtubule attachment during meiosis I in oocyte.

    Science.gov (United States)

    Tang, An; Shi, Peiliang; Song, Anying; Zou, Dayuan; Zhou, Yue; Gu, Pengyu; Huang, Zan; Wang, Qinghua; Lin, Zhaoyu; Gao, Xiang

    2016-06-02

    Studies using in vitro cultured oocytes have indicated that the protein phosphatase 2A (PP2A), a major serine/threonine protein phosphatase, participates in multiple steps of meiosis. Details of oocyte maturation regulation by PP2A remain unclear and an in vivo model can provide more convincing information. Here, we inactivated PP2A by mutating genes encoding for its catalytic subunits (PP2Acs) in mouse oocytes. We found that eliminating both PP2Acs caused female infertility. Oocytes lacking PP2Acs failed to complete 1(st) meiotic division due to chromosome misalignment and abnormal spindle assembly. In mitosis, PP2A counteracts Aurora kinase B/C (AurkB/C) to facilitate correct kinetochore-microtubule (KT-MT) attachment. In meiosis I in oocyte, we found that PP2Ac deficiency destabilized KT-MT attachments. Chemical inhibition of AurkB/C in PP2Ac-null oocytes partly restored the formation of lateral/merotelic KT-MT attachments but not correct KT-MT attachments. Taken together, our findings demonstrate that PP2Acs are essential for chromosome alignments and regulate the formation of correct KT-MT attachments in meiosis I in oocytes.

  16. Resolving complex chromosome structures during meiosis: versatile deployment of Smc5/6.

    Science.gov (United States)

    Verver, Dideke E; Hwang, Grace H; Jordan, Philip W; Hamer, Geert

    2016-03-01

    The Smc5/6 complex, along with cohesin and condensin, is a member of the structural maintenance of chromosome (SMC) family, large ring-like protein complexes that are essential for chromatin structure and function. Thanks to numerous studies of the mitotic cell cycle, Smc5/6 has been implicated to have roles in homologous recombination, restart of stalled replication forks, maintenance of ribosomal DNA (rDNA) and heterochromatin, telomerase-independent telomere elongation, and regulation of chromosome topology. The nature of these functions implies that the Smc5/6 complex also contributes to the profound chromatin changes, including meiotic recombination, that characterize meiosis. Only recently, studies in diverse model organisms have focused on the potential meiotic roles of the Smc5/6 complex. Indeed, Smc5/6 appears to be essential for meiotic recombination. However, due to both the complexity of the process of meiosis and the versatility of the Smc5/6 complex, many additional meiotic functions have been described. In this review, we provide a clear overview of the multiple functions found so far for the Smc5/6 complex in meiosis. Additionally, we compare these meiotic functions with the known mitotic functions in an attempt to find a common denominator and thereby create clarity in the field of Smc5/6 research.

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

    Science.gov (United States)

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

    2016-04-01

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

  18. Widespread failure to complete meiosis does not impair fecundity in parthenogenetic whiptail lizards.

    Science.gov (United States)

    Newton, Aracely A; Schnittker, Robert R; Yu, Zulin; Munday, Sarah S; Baumann, Diana P; Neaves, William B; Baumann, Peter

    2016-12-01

    Parthenogenetic species of whiptail lizards in the genus Aspidoscelis constitute a striking example of speciation by hybridization, in which first-generation hybrids instantly attain reproductive isolation and procreate as clonal all-female lineages. Production of eggs containing a full complement of chromosomes in the absence of fertilization involves genome duplication prior to the meiotic divisions. In these pseudo-tetraploid oocytes, pairing and recombination occur exclusively between identical chromosomes instead of homologs; a deviation from the normal meiotic program that maintains heterozygosity. Whether pseudo-tetraploid cells arise early in germ cell development or just prior to meiosis has remained unclear. We now show that in the obligate parthenogenetic species A. neomexicana the vast majority of oocytes enter meiosis as diploid cells. Telomere bouquet formation is normal, but synapsis fails and oocytes accumulate in large numbers at the pairing stage. Pseudo-tetraploid cells are exceedingly rare in early meiotic prophase, but they are the only cells that progress into diplotene. Despite the widespread failure to increase ploidy prior to entering meiosis, the fecundity of parthenogenetic A. neomexicana is similar to that of A. inornata, one of its bisexual ancestors. © 2016. Published by The Company of Biologists Ltd.

  19. Cytological techniques to analyze meiosis in Arabidopsis arenosa for investigating adaptation to polyploidy.

    Science.gov (United States)

    Higgins, James D; Wright, Kevin M; Bomblies, Kirsten; Franklin, F Chris H

    2014-01-01

    Arabidopsis arenosa is a close relative of the model plant A. thaliana, and exists in nature as stable diploid and autotetraploid populations. Natural tetraploids have adapted to whole genome duplication and do not commonly show meiotic errors such as multivalent and univalent formation, which can lead to chromosome non-disjunction and reduced fertility. A genome scan for genes strongly differentiated between diploid and autotetraploid A. arenosa identified a subset of meiotic genes that may be responsible for adaptation to polyploid meiosis. To investigate the mechanisms by which A. arenosa adapted to its polyploid state, and the functionality of the identified potentially adaptive polymorphisms, a thorough cytological analysis is required. Therefore, in this chapter we describe methods and techniques to analyze male meiosis in A. arenosa, including optimum plant growth conditions, and immunocytological and cytological approaches developed with the specific purpose of understanding meiotic adaptation in an autotetraploid. In addition we present a meiotic cytological atlas to be used as a reference for particular stages and discuss observations arising from a comparison of meiosis between diploid and autotetraploid A. arenosa.

  20. Regulators of alternative polyadenylation operate at the transition from mitosis to meiosis.

    Science.gov (United States)

    Shan, Lingjuan; Wu, Chan; Chen, Di; Hou, Lei; Li, Xin; Wang, Lixia; Chu, Xiao; Hou, Yifeng; Wang, Zhaohui

    2017-02-20

    In the sexually reproductive organisms, gametes are produced by meiosis following a limited mitotic amplification. However, the intrinsic program switching cells from mitotic to meiotic cycle is unclear. Alternative polyadenylation (APA) is a highly conserved means of gene regulation and is achieved by the RNA 3'-processing machinery to generate diverse 3'UTR profiles. In Drosophila spermatogenesis, we observed distinct profiles of transcriptome-wide 3'UTR between mitotic and meiotic cells. In mutant germ cells stuck in mitosis, 3'UTRs of hundreds of genes were consistently shifted. Remarkably, altering the levels of multiple 3'-processing factors disrupted germline's progression to meiosis, indicative of APA's active role in this transition. An RNA-binding protein (RBP) Tut could directly bind 3'UTRs of 3'-processing factors whose expressions were repressed in the presence of Tut-containing complex. Further, we demonstrated that this RBP complex could execute the repression post-transcriptionally by recruiting CCR4/Twin of deadenylation complex. Thus, we propose that an RBP complex regulates the dynamic APA profile to promote the mitosis-to-meiosis transition. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

  1. Karyotype and male pre-reductional meiosis of the sharpshooter Tapajosa rubromarginata (Hemiptera: Cicadellidae

    Directory of Open Access Journals (Sweden)

    Graciela R de Bigliardo

    2011-03-01

    Full Text Available Cicadellidae in one of the best represented families in the Neotropical Region, and the tribe Proconiini comprises most of the xylem-feeding insects, including the majority of the known vectors of xylem-born phytopathogenic organisms. The cytogenetics of the Proconiini remains largely unexplored. We studied males of Tapajosa rubromarginata (Signoret collected at El Manantial (Tucumán, Argentina on native spontaneous vegetation where Sorghum halepense predominates. Conventional cytogenetic techniques were used in order to describe the karyotype and male meiosis of this sharpshooter. T. rubromarginata has a male karyological formula of 2n=21 and a sex chromosome system XO:XX (♂:♀. The chromosomes do not have a primary constriction, being holokinetic and the meiosis is pre-reductional, showing similar behavior both for autosomes and sex chromosomes during anaphase I. For this stage, chromosomes are parallel to the acromatic spindle with kinetic activities in the telomeres. They segregate reductionally in the anaphase I, and towards the equator during the second division of the meiosis. This is the first contribution to cytogenetic aspects on proconines sharpshooters, particularly on this economic relevant Auchenorrhyncha species. Rev. Biol. Trop. 59 (1: 309-314. Epub 2011 March 01.

  2. Molecular Evolution at a Meiosis Gene Mediates Species Differences in the Rate and Patterning of Recombination.

    Science.gov (United States)

    Brand, Cara L; Cattani, M Victoria; Kingan, Sarah B; Landeen, Emily L; Presgraves, Daven C

    2018-04-23

    Crossing over between homologous chromosomes during meiosis repairs programmed DNA double-strand breaks, ensures proper segregation at meiosis I [1], shapes the genomic distribution of nucleotide variability in populations, and enhances the efficacy of natural selection among genetically linked sites [2]. Between closely related Drosophila species, large differences exist in the rate and chromosomal distribution of crossing over. Little, however, is known about the molecular genetic changes or population genetic forces that mediate evolved differences in recombination between species [3, 4]. Here, we show that a meiosis gene with a history of rapid evolution acts as a trans-acting modifier of species differences in crossing over. In transgenic flies, the dicistronic gene, mei-217/mei-218, recapitulates a large part of the species differences in the rate and chromosomal distribution of crossing over. These phenotypic differences appear to result from changes in protein sequence not gene expression. Our population genetics analyses show that the protein-coding sequence of mei-218, but not mei-217, has a history of recurrent positive natural selection. By modulating the intensity of centromeric and telomeric suppression of crossing over, evolution at mei-217/-218 has incidentally shaped gross differences in the chromosomal distribution of nucleotide variability between species. We speculate that recurrent bouts of adaptive evolution at mei-217/-218 might reflect a history of coevolution with selfish genetic elements. Copyright © 2018 Elsevier Ltd. All rights reserved.

  3. RAD21L, a novel cohesin subunit implicated in linking homologous chromosomes in mammalian meiosis.

    Science.gov (United States)

    Lee, Jibak; Hirano, Tatsuya

    2011-01-24

    Cohesins are multi-subunit protein complexes that regulate sister chromatid cohesion during mitosis and meiosis. Here we identified a novel kleisin subunit of cohesins, RAD21L, which is conserved among vertebrates. In mice, RAD21L is expressed exclusively in early meiosis: it apparently replaces RAD21 in premeiotic S phase, becomes detectable on the axial elements in leptotene, and stays on the axial/lateral elements until mid pachytene. RAD21L then disappears, and is replaced with RAD21. This behavior of RAD21L is unique and distinct from that of REC8, another meiosis-specific kleisin subunit. Remarkably, the disappearance of RAD21L at mid pachytene correlates with the completion of DNA double-strand break repair and the formation of crossovers as judged by colabeling with molecular markers, γ-H2AX, MSH4, and MLH1. RAD21L associates with SMC3, STAG3, and either SMC1α or SMC1β. Our results suggest that cohesin complexes containing RAD21L may be involved in synapsis initiation and crossover recombination between homologous chromosomes.

  4. Cytological techniques to analyze meiosis in Arabidopsis arenosa for investigating adaptation to polyploidy

    Science.gov (United States)

    Higgins, James D.; Wright, Kevin M.; Bomblies, Kirsten; Franklin, F. Chris H.

    2014-01-01

    Arabidopsis arenosa is a close relative of the model plant A. thaliana, and exists in nature as stable diploid and autotetraploid populations. Natural tetraploids have adapted to whole genome duplication and do not commonly show meiotic errors such as multivalent and univalent formation, which can lead to chromosome non-disjunction and reduced fertility. A genome scan for genes strongly differentiated between diploid and autotetraploid A. arenosa identified a subset of meiotic genes that may be responsible for adaptation to polyploid meiosis. To investigate the mechanisms by which A. arenosa adapted to its polyploid state, and the functionality of the identified potentially adaptive polymorphisms, a thorough cytological analysis is required. Therefore, in this chapter we describe methods and techniques to analyze male meiosis in A. arenosa, including optimum plant growth conditions, and immunocytological and cytological approaches developed with the specific purpose of understanding meiotic adaptation in an autotetraploid. In addition we present a meiotic cytological atlas to be used as a reference for particular stages and discuss observations arising from a comparison of meiosis between diploid and autotetraploid A. arenosa. PMID:24427164

  5. Cytological techniques to analyze meiosis in Arabidopsis arenosa for investigating adaptation to polyploidy

    Directory of Open Access Journals (Sweden)

    James D Higgins

    2014-01-01

    Full Text Available Arabidopsis arenosa is a close relative of the model plant Arabidopsis thaliana, and exists in nature as stable diploid and autotetraploid populations. Natural tetraploids have adapted to whole genome duplication and do not commonly show meiotic errors such as multivalent and univalent formation, which can lead to chromosome non-disjunction and reduced fertility. A genome scan for genes strongly differentiated between diploid and autotetraploid A. arenosa identified a subset of meiotic genes that may be responsible for adaptation to polyploid meiosis. To investigate the mechanisms by which A. arenosa adapted to its polyploid state, and the functionality of the identified potentially adaptive polymorphisms, a thorough cytological analysis is required. Therefore, in this chapter we describe methods and techniques to analyze male meiosis in A. arenosa, including optimum plant growth conditions, and immunocytological and cytological approaches developed with the specific purpose of understanding meiotic adaptation in an autotetraploid. In addition we present a meiotic cytological atlas to be used as a reference for particular stages and discuss observations arising from a comparison of meiosis between diploid and autotetraploid A. arenosa.

  6. Association between presenilin-1 polymorphism and maternal meiosis II errors in Down syndrome.

    Science.gov (United States)

    Petersen, M B; Karadima, G; Samaritaki, M; Avramopoulos, D; Vassilopoulos, D; Mikkelsen, M

    2000-08-28

    Several lines of evidence suggest a shared genetic susceptibility to Down syndrome (DS) and Alzheimer disease (AD). Rare forms of autosomal-dominant AD are caused by mutations in the APP and presenilin genes (PS-1 and PS-2). The presenilin proteins have been localized to the nuclear membrane, kinetochores, and centrosomes, suggesting a function in chromosome segregation. A genetic association between a polymorphism in intron 8 of the PS-1 gene and AD has been described in some series, and an increased risk of AD has been reported in mothers of DS probands. We therefore studied 168 probands with free trisomy 21 of known parental and meiotic origin and their parents from a population-based material, by analyzing the intron 8 polymorphism in the PS-1 gene. An increased frequency of allele 1 in mothers with a meiosis II error (70.8%) was found compared with mothers with a meiosis I error (52.7%, P < 0.01), with an excess of the 11 genotype in the meiosis II mothers. The frequency of allele 1 in mothers carrying apolipoprotein E (APOE) epsilon4 allele (68.0%) was higher than in mothers without epsilon4 (52.2%, P < 0.01). We hypothesize that the PS-1 intronic polymorphism might be involved in chromosomal nondisjunction through an influence on the expression level of PS-1 or due to linkage disequilibrium with biologically relevant polymorphisms in or outside the PS-1 gene. Copyright 2000 Wiley-Liss, Inc.

  7. Zwint-1 is required for spindle assembly checkpoint function and kinetochore-microtubule attachment during oocyte meiosis.

    Science.gov (United States)

    Woo Seo, Dong; Yeop You, Seung; Chung, Woo-Jae; Cho, Dong-Hyung; Kim, Jae-Sung; Su Oh, Jeong

    2015-10-21

    The key step for faithful chromosome segregation during meiosis is kinetochore assembly. Defects in this process result in aneuploidy, leading to miscarriages, infertility and various birth defects. However, the roles of kinetochores in homologous chromosome segregation during meiosis are ill-defined. Here we found that Zwint-1 is required for homologous chromosome segregation during meiosis. Knockdown of Zwint-1 accelerated the first meiosis by abrogating the kinetochore recruitment of Mad2, leading to chromosome misalignment and a high incidence of aneuploidy. Although Zwint-1 knockdown did not affect Aurora C kinase activity, the meiotic defects following Zwint-1 knockdown were similar to those observed with ZM447439 treatment. Importantly, the chromosome misalignment following Aurora C kinase inhibition was not restored after removing the inhibitor in Zwint-1-knockdown oocytes, whereas the defect was rescued after the inhibitor washout in the control oocytes. These results suggest that Aurora C kinase-mediated correction of erroneous kinetochore-microtubule attachment is primarily regulated by Zwint-1. Our results provide the first evidence that Zwint-1 is required to correct erroneous kinetochore-microtubule attachment and regulate spindle checkpoint function during meiosis.

  8. Microparticle-Mediated Delivery of BMP4 for Generation of Meiosis-Competent Germ Cells from Embryonic Stem Cells.

    Science.gov (United States)

    Esfandiari, Fereshteh; Ashtiani, Mohammad Kazemi; Sharifi-Tabar, Mehdi; Saber, Maryam; Daemi, Hamed; Ghanian, Mohammad Hossein; Shahverdi, Abdolhossein; Baharvand, Hossein

    2017-03-01

    Producing meiosis-competent germ cells (GCs) from embryonic stem cells (ESCs) is essential for developing advanced therapies for infertility. Here, a novel approach is presented for generation of GCs from ESCs. In this regard, microparticles (MPs) have been developed from alginate sulfate loaded with bone morphogenetic protein 4 (BMP4). The results here show that BMP4 release from alginate sulfate MPs is significantly retarded by the sulfated groups compared to neat alginate. Then, BMP4-laden MPs are incorporated within the aggregates during differentiation of GCs from ESCs. It is observed that BMP4-laden MPs increase GC differentiation from ESCs at least twofold compared to the conventional soluble delivery method. Interestingly, following meiosis induction, Dazl, an intrinsic factor that enables GCs to enter meiosis, and two essential meiosis genes (Stra8 and Smc1b) are upregulated significantly in MP-induced aggregates compared to aggregates, which are formed by the conventional method. Together, these data show that controlled delivery of BMP4 during ESC differentiation into GC establish meiosis-competent GCs which can serve as an attractive GC source for reproductive medicine. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Differential effect of UV irradiation on induction of intragenic and intergenic recombination during commitment to meiosis in Saccharomyces cerevisiae

    International Nuclear Information System (INIS)

    Machida, I.; Nakai, S.

    1980-01-01

    A comparison was made between the induction of intragenic and intergenic recombinations during meiosis in a wild-type diploid of Saccharomyces cerevisiae. Under non-irradiated normal conditions, production of both intragenic and intergenic recombinants greatly increased in the cells with commitment to meiosis. The susceptibility of cells to the induction ob both the spontaneous intra- and intergenic recombinations in meiotic cells was similar. However, under condition of UV irradiation, there were striking differences between intra- and intergenic recombinations. Susceptibility to induction of intragenic recombination by UV irradiation was not enhanced at meiosis compared with mitosis, and was not altered through commitment to meiotic processes. In contrast, however, susceptibility to the induction of intergenic recombination by UV irradiation was enhanced markedly during commitment to meiosis compared with mitosis. Genetic analysis suggested that the enhanced susceptibility to recombination during meiosis is specifically concerned with reciprocal-type recombination (crossing-over) but not non-reciprocal-type recombination (gene conversion). Hence it is concluded that the meiotic that the meiotic process appears to be intimately concerned with the mechanism(s) of induction of recombination, especially reciprocal-type recombination. (orig.)

  10. How oocytes try to get it right: spindle checkpoint control in meiosis.

    Science.gov (United States)

    Touati, Sandra A; Wassmann, Katja

    2016-06-01

    The generation of a viable, diploid organism depends on the formation of haploid gametes, oocytes, and spermatocytes, with the correct number of chromosomes. Halving the genome requires the execution of two consecutive specialized cell divisions named meiosis I and II. Unfortunately, and in contrast to male meiosis, chromosome segregation in oocytes is error prone, with human oocytes being extraordinarily "meiotically challenged". Aneuploid oocytes, that are with the wrong number of chromosomes, give rise to aneuploid embryos when fertilized. In humans, most aneuploidies are lethal and result in spontaneous abortions. However, some trisomies survive to birth or even adulthood, such as the well-known trisomy 21, which gives rise to Down syndrome (Nagaoka et al. in Nat Rev Genet 13:493-504, 2012). A staggering 20-25 % of oocytes ready to be fertilized are aneuploid in humans. If this were not bad enough, there is an additional increase in meiotic missegregations as women get closer to menopause. A woman above 40 has a risk of more than 30 % of getting pregnant with a trisomic child. Worse still, in industrialized western societies, child birth is delayed, with women getting their first child later in life than ever. This trend has led to an increase of trisomic pregnancies by 70 % in the last 30 years (Nagaoka et al. in Nat Rev Genet 13:493-504, 2012; Schmidt et al. in Hum Reprod Update 18:29-43, 2012). To understand why errors occur so frequently during the meiotic divisions in oocytes, we review here the molecular mechanisms at works to control chromosome segregation during meiosis. An important mitotic control mechanism, namely the spindle assembly checkpoint or SAC, has been adapted to the special requirements of the meiotic divisions, and this review will focus on our current knowledge of SAC control in mammalian oocytes. Knowledge on how chromosome segregation is controlled in mammalian oocytes may help to identify risk factors important for questions

  11. A Proteomics Approach to Discover Drought Tolerance Proteins in Wheat Pollen Grain at Meiosis Stage.

    Science.gov (United States)

    Fotovat, Reza; Alikhani, Mehdi; Valizadeh, Mostafa; Mirzaei, Mehdi; Salekdeh, Ghasem H

    2017-01-01

    Plants reproductive phase, when grain yield and consequently farmers' investment is most in jeopardy, is considered as the most sensitive stage to drought stress. In this study, we aimed to explore the proteomic response of wheat anther at meiosis stage in a drought tolerant, Darab, and susceptible, Shiraz, wheat genotypes. Wheat plants were exposed to drought stress at meiosis stage for four days under controlled environmental conditions. Then, anthers from both genotypes were sampled, and their proteomes were examined via quantitative proteomics analysis. Our results demonstrated that short-term stress at meiosis stage reduced plant seed-setting compared to well-watered plants. This reduction was more pronounced in the susceptible genotype, Shiraz, by 51%, compared to the drought tolerant Darab by 14.3%. Proteome analysis revealed that 60 protein spots were drought responsive, out of which 44 were identified using a mass spectrometer. We observed a dramatic up-regulation of several heat shock proteins, as well as induction of Bet v I allergen family proteins, peroxiredoxin-5, and glutathione transferase with similar abundance in both genotypes. However, the abundance of proteins such as several stress response related proteins, including glutaredoxin, proteasome subunit alpha type 5, and ribosomal proteins showed a different response to drought stress in two genotypes. The differential abundance of proteins in two genotypes may suggest mechanisms by which tolerant genotype cope with drought stress. To the best of our knowledge, this is the first proteome analysis of plant reproductive tissue response to drought stress in wheat and could broaden our insight into plant adaptation to drought stress. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

  12. Intercellular signaling via cyclic GMP diffusion through gap junctions restarts meiosis in mouse ovarian follicles.

    Science.gov (United States)

    Shuhaibar, Leia C; Egbert, Jeremy R; Norris, Rachael P; Lampe, Paul D; Nikolaev, Viacheslav O; Thunemann, Martin; Wen, Lai; Feil, Robert; Jaffe, Laurinda A

    2015-04-28

    Meiosis in mammalian oocytes is paused until luteinizing hormone (LH) activates receptors in the mural granulosa cells of the ovarian follicle. Prior work has established the central role of cyclic GMP (cGMP) from the granulosa cells in maintaining meiotic arrest, but it is not clear how binding of LH to receptors that are located up to 10 cell layers away from the oocyte lowers oocyte cGMP and restarts meiosis. Here, by visualizing intercellular trafficking of cGMP in real-time in live follicles from mice expressing a FRET sensor, we show that diffusion of cGMP through gap junctions is responsible not only for maintaining meiotic arrest, but also for rapid transmission of the signal that reinitiates meiosis from the follicle surface to the oocyte. Before LH exposure, the cGMP concentration throughout the follicle is at a uniformly high level of ∼2-4 μM. Then, within 1 min of LH application, cGMP begins to decrease in the peripheral granulosa cells. As a consequence, cGMP from the oocyte diffuses into the sink provided by the large granulosa cell volume, such that by 20 min the cGMP concentration in the follicle is uniformly low, ∼100 nM. The decrease in cGMP in the oocyte relieves the inhibition of the meiotic cell cycle. This direct demonstration that a physiological signal initiated by a stimulus in one region of an intact tissue can travel across many layers of cells via cyclic nucleotide diffusion through gap junctions could provide a general mechanism for diverse cellular processes.

  13. To Break or Not To Break: Sex Chromosome Hemizygosity During Meiosis in Caenorhabditis.

    Science.gov (United States)

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

    2016-11-01

    Meiotic recombination establishes connections between homologous chromosomes to promote segregation. Hemizygous regions of sex chromosomes have no homologous chromosome to recombine with, yet must be transmitted through meiosis. An extreme case of hemizygosity exists in the genus Caenorhabditis, where males have a single X chromosome that completely lacks a homologous partner. To determine whether similar strategies have evolved to accommodate hemizygosity of the X during male meiosis in Caenorhabditis with distinct modes of sexual reproduction, we examined induction and processing of meiotic double strand breaks (DSBs) in androdioecious (hermaphrodite/male) Caenorhabditis elegans and C. briggsae, and gonochoristic (female/male) C. remanei and C. brenneri Analysis of the recombinase RAD-51 suggests more meiotic DSBs are induced in gonochoristic vs. androdioecious species. However, in late prophase in all species, chromosome pairs are restructured into bivalents around a single axis, suggesting that the holocentric nature of Caenorhabditis chromosomes dictates a single crossover per bivalent regardless of the number of DSBs induced. Interestingly, RAD-51 foci were readily observed on the X chromosome of androdioecious male germ cells, while very few were detected in gonochoristic male germ cells. As in C. elegans, the X chromosome in C. briggsae male germ cells undergoes transient pseudosynapsis and flexibility in DSB repair pathway choice. In contrast, in C. remanei and C. brenneri male germ cells, the X chromosome does not undergo pseudosynapsis and appears refractory to SPO-11-induced breaks. Together our results suggest that distinct strategies have evolved to accommodate sex chromosome hemizygosity during meiosis in closely related Caenorhabditis species. Copyright © 2016 by the Genetics Society of America.

  14. Dynamic changes in Rad51 distribution on chromatin during meiosis in male and female vertebrates.

    Science.gov (United States)

    Ashley, T; Plug, A W; Xu, J; Solari, A J; Reddy, G; Golub, E I; Ward, D C

    1995-10-01

    Antibodies against human Rad51 protein were used to examine the distribution of Rad51 on meiotic chromatin in mouse spermatocytes and oocytes as well as chicken oocytes during sequential stages of meiosis. We observed the following dynamic changes in distribution of Rad51 during meiosis: (1) in early leptotene nuclei there are multiple, apparently randomly distributed, foci that by late leptonema become organized into tracks of foci. (2) These foci persist into zygonema, but most foci are now localized on Rad51-positive axes that correspond to lateral elements of the synaptonemal complex. As homologs synapse foci from homologous axes fuse. The distribution and involvement of Rad51 foci as contact points between homologs suggest that they may be components to early recombination nodules. (3) As pachynema progresses the number of foci drops dramatically; the temporal occurrence (mice) and physical and numerical distribution of foci on axes (chickens) suggest that they may be a component of late recombination nodules. (4) In early pachynema there are numerous Rad51 foci on the single axis of the X (mouse spermatocytes) or the Z (chicken oocytes) chromosomes that neither pair, nor recombine. (5) In late pachynema in mouse spermatocytes, but not oocytes, the Rad51 signal is preferentially enhanced at both ends of all the bivalents. As bivalents in spermatocytes, but not oocytes, begin to desynapse at diplonema they are often held together at these Rad51-positive termini. These observations parallel observations that recombination rates are exceptionally high near chromosome ends in male but not female eutherian mammals. (6) From diakinesis through metaphase I, Rad51 protein is detected as low-intensity fluorescent doublets that localize with CREST-specific antigens (kinetochores), suggesting that Rad51 participates, at least as a structural component of the materials involved, in sister kinetochore cohesiveness. Finally, the changes in Rad51 distribution during meiosis

  15. C. elegans HIM-8 functions outside of meiosis to antagonize EGL-13 Sox protein function.

    Science.gov (United States)

    Nelms, Brian L; Hanna-Rose, Wendy

    2006-05-15

    egl-13 encodes a Sox domain protein that is required for proper uterine seam cell development in Caenorhabditis elegans. We demonstrate that mutations of the C2H2 zinc fingers encoded by the him-8 (high incidence of males) gene partially suppress the egg-laying and connection-of-gonad morphology defects caused by incompletely penetrant alleles of egl-13. him-8 alleles have previously characterized recessive effects on recombination and segregation of the X chromosome during meiosis due to failure of X chromosome homolog pairing and subsequent synapsis. However, we show that him-8 alleles are semi-dominant suppressors of egl-13, and the semi-dominant effect is due to haplo-insufficiency of the him-8 locus. Thus, we conclude that the wild-type him-8 gene product acts antagonistically to EGL-13. Null alleles of egl-13 cannot be suppressed, suggesting that this antagonistic interaction most likely occurs either upstream of or in parallel with EGL-13. Moreover, we conclude that suppression of egl-13 is due to a meiosis-independent function of him-8 because suppression is observed in mutants that have severely reduced meiotic germ cell populations and suppression does not depend on the function of him-8 in the maternal germ line. We also show that the chromosomal context of egl-13 seems important in the him-8 suppression mechanism. Interactions between these genes can give insight into function of Sox family members, which are important in many aspects of metazoan development, and into functions of him-8 outside of meiosis.

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

    Science.gov (United States)

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

    2016-07-17

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

  17. Ultrastructural investigations of meiosis as a tool in assessing radiation damage in man

    Energy Technology Data Exchange (ETDEWEB)

    Bojko, M.

    1985-01-01

    Part I is an introduction to the problems of assessing the short-term effects of ionizing radiation on human meiosis. Part II is an investigation of the ultrastructure of human oocytes at pachytene and diplotene stages of meiotic prophase. Processes leading to crossing over and chiasma formation in the female are compared with those in the male and in other organisms. Part III is a study of short-term effects of ..gamma.. radiation on spermatocytes in larvae of the silk moth, Bombyx mori.

  18. STAG2 and Rad21 mammalian mitotic cohesins are implicated in meiosis

    OpenAIRE

    Prieto, Ignacio; Pezzi, Nieves; Buesa, José M.; Kremer, Leonor; Barthelemy, Isabel; Carreiro, Candelas; Roncal, Fernando; Martínez, Alicia; Gómez, Lucio; Fernández, Raúl; Martínez-A, Carlos; Barbero, José L.

    2002-01-01

    STAG/SA proteins are specific cohesin complex subunits that maintain sister chromatid cohesion in mitosis and meiosis. Two members of this family, STAG1/SA1 and STAG2/SA2,‡ are classified as mitotic cohesins, as they are found in human somatic cells and in Xenopus laevis as components of the cohesinSA1 and cohesinSA2 complexes, in which the shared subunits are Rad21/SCC1, SMC1 and SMC3 proteins. A recently reported third family member, STAG3, is germinal cell-specific and is a subunit of the ...

  19. Ultrastructural investigations of meiosis as a tool in assessing radiation damage in man

    International Nuclear Information System (INIS)

    Bojko, M.

    1985-11-01

    Part I is an introduction to the problems of assesing the short-term effects of ionizing radiation on human meiosis. Part II is an investigation of the ultrastructure of human oocytes at pachytene and diplotene stages of meiotic prophase. Processes leading to crossing over and chiasma formation in the female are compared with those in the male and in other organisms. Part III is a study of short-term effects of γ radiation on spermatocytes in larvae of the silk moth, Bombyx mori. (eg)

  20. CDC25A phosphatase controls meiosis I progression in mouse oocytes

    Czech Academy of Sciences Publication Activity Database

    Šolc, Petr; Šašková, Adéla; Baran, V.; Kubelka, Michal; Schultz, R. M.; Motlík, Jan

    2008-01-01

    Roč. 317, č. 1 (2008), s. 260-269 ISSN 0012-1606 R&D Projects: GA ČR GA305/06/1413; GA ČR GD204/05/H023 Grant - others:Czech-US cooperation(CZ) ME08030; Slovenská Akademie vied(SK) VEGA 2/6176/26 Program:ME Institutional research plan: CEZ:AV0Z50450515 Keywords : resumption of meiosis * meiotic maturation * mouse oocytes Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 4.416, year: 2008

  1. The fission yeast heterochromatin protein Rik1 is required for telomere clustering during meiosis

    DEFF Research Database (Denmark)

    Tuzon, Creighton T; Borgstrøm, Britta; Weilguny, Dietmar

    2004-01-01

    Telomeres share the ability to silence nearby transcription with heterochromatin, but the requirement of heterochromatin proteins for most telomere functions is unknown. The fission yeast Rik1 protein is required for heterochromatin formation at centromeres and the mating-type locus, as it recrui...... meiosis. However, Rik1 is dispensable for the protective roles of telomeres in preventing chromosome end-fusion. Thus, a Swi6-independent heterochromatin function distinct from that at centromeres and the mating-type locus operates at telomeres during sexual differentiation....

  2. Evolutionary consequences of polyploidy in prokaryotes and the origin of mitosis and meiosis.

    Science.gov (United States)

    Markov, Alexander V; Kaznacheev, Ilya S

    2016-06-08

    The origin of eukaryote-specific traits such as mitosis and sexual reproduction remains disputable. There is growing evidence that both mitosis and eukaryotic sex (i.e., the alternation of syngamy and meiosis) may have already existed in the basal eukaryotes. The mating system of the halophilic archaeon Haloferax volcanii probably represents an intermediate stage between typical prokaryotic and eukaryotic sex. H. volcanii is highly polyploid, as well as many other Archaea. Here, we use computer simulation to explore genetic and evolutionary outcomes of polyploidy in amitotic prokaryotes and its possible role in the origin of mitosis, meiosis and eukaryotic sex. Modeling suggests that polyploidy can confer strong short-term evolutionary advantage to amitotic prokaryotes. However, it also promotes the accumulation of recessive deleterious mutations and the risk of extinction in the long term, especially in highly mutagenic environment. There are several possible strategies that amitotic polyploids can use in order to reduce the genetic costs of polyploidy while retaining its benefits. Interestingly, most of these strategies resemble different components or aspects of eukaryotic sex. They include asexual ploidy cycles, equalization of genome copies by gene conversion, high-frequency lateral gene transfer between relatives, chromosome exchange coupled with homologous recombination, and the evolution of more accurate chromosome distribution during cell division (mitosis). Acquisition of mitosis by an amitotic polyploid results in chromosome diversification and specialization. Ultimately, it transforms a polyploid cell into a functionally monoploid one with multiple unique, highly redundant chromosomes. Specialization of chromosomes makes the previously evolved modes of promiscuous chromosome shuffling deleterious. This can result in selective pressure to develop accurate mechanisms of homolog pairing, and, ultimately, meiosis. Emergence of mitosis and the first

  3. Chromosome complement and meiosis of Holmbergiana weyenberghii (Opiliones: Sclerosomatidae: Gagrellinae from Argentina

    Directory of Open Access Journals (Sweden)

    Sergio G. Rodríguez Gil

    2010-01-01

    Full Text Available Se analiza citogenéticamente, por primera vez, una especie de opilión proveniente de Argentina: Holmbergiana weyenberghii (Holmberg (Eupnoi, Sclerosomatidae, Gagrellinae. Los machos tienen un complemento cromosómico compuesto por 18 cromosomas. En meiosis, hay nueve bivalentes homomórficos: uno mayor, cinco medianos y tres menores. El número cromosómico de H. weyenberghii se encuentra dentro del rango de números diploides de los Gagrellinae Thorell; esta subfamilia presenta los números cromosómicos más bajos de Sclerosomatidae.

  4. New-age ideas about age-old sex: separating meiosis from mating could solve a century-old conundrum.

    Science.gov (United States)

    Brandeis, Michael

    2018-05-01

    Ever since Darwin first addressed it, sexual reproduction reigns as the 'queen' of evolutionary questions. Multiple theories tried to explain how this apparently costly and cumbersome method has become the universal mode of eukaryote reproduction. Most theories stress the adaptive advantages of sex by generating variation, they fail however to explain the ubiquitous persistence of sexual reproduction also where adaptation is not an issue. I argue that the obstacle for comprehending the role of sex stems from the conceptual entanglement of two distinct processes - gamete production by meiosis and gamete fusion by mating (mixis). Meiosis is an ancient, highly rigid and evolutionary conserved process identical and ubiquitous in all eukaryotes. Mating, by contrast, shows tremendous evolutionary variability even in closely related clades and exhibits wonderful ecological adaptability. To appreciate the respective roles of these two processes, which are normally linked and alternating, we require cases where one takes place without the other. Such cases are rather common. The heteromorphic sex chromosomes Y and W, that do not undergo meiotic recombination are an evolutionary test case for demonstrating the role of meiosis. Substantial recent genomic evidence highlights the accelerated rates of change and attrition these chromosomes undergo in comparison to those of recombining autosomes. I thus propose that the most basic role of meiosis is conserving integrity of the genome. A reciprocal case of meiosis without bi-parental mating, is presented by self-fertilization, which is fairly common in flowering plants, as well as most types of apomixis. I argue that deconstructing sex into these two distinct processes - meiosis and mating - will greatly facilitate their analysis and promote our understanding of sexual reproduction. © 2017 Cambridge Philosophical Society.

  5. Maternal MEMI Promotes Female Meiosis II in Response to Fertilization in Caenorhabditis elegans.

    Science.gov (United States)

    Ataeian, Maryam; Tegha-Dunghu, Justus; Curtis, Donna G; Sykes, Ellen M E; Nozohourmehrabad, Ashkan; Bajaj, Megha; Cheung, Karen; Srayko, Martin

    2016-12-01

    In most animals, female meiosis completes only after fertilization. Sperm entry has been implicated in providing a signal for the initiation of the final meiotic processes; however, a maternal component required for this process has not been previously identified. We report the characterization of a novel family of three highly similar paralogs (memi-1, memi-2, memi-3) that encode oocyte-specific proteins. A hyper-morphic mutation memi-1(sb41) results in failure to exit female meiosis II properly; however, loss of all three paralogs results in a "skipped meiosis II" phenotype. Mutations that prevent fertilization, such as fer-1(hc1), also cause a skipped meiosis II phenotype, suggesting that the MEMI proteins represent a maternal component of a postfertilization signal that specifies the meiosis II program. MEMI proteins are degraded before mitosis and sensitive to ZYG-11, a substrate-specific adapter for cullin-based ubiquitin ligase activity, and the memi-1(sb41) mutation results in inappropriate persistence of the MEMI-1 protein into mitosis. Using an RNAi screen for suppressors of memi-1(sb41), we identified a sperm-specific PP1 phosphatase, GSP-3/4, as a putative sperm component of the MEMI pathway. We also found that MEMI and GSP-3/4 proteins can physically interact via co-immunoprecipitation. These results suggest that sperm-specific PP1 and maternal MEMI proteins act in the same pathway after fertilization to facilitate proper meiosis II and the transition into embryonic mitosis. Copyright © 2016 by the Genetics Society of America.

  6. The Cell Cycle Timing of Centromeric Chromatin Assembly in Drosophila Meiosis Is Distinct from Mitosis Yet Requires CAL1 and CENP-C

    Science.gov (United States)

    Gorgescu, Walter; Tang, Jonathan; Costes, Sylvain V.; Karpen, Gary H.

    2012-01-01

    CENP-A (CID in flies) is the histone H3 variant essential for centromere specification, kinetochore formation, and chromosome segregation during cell division. Recent studies have elucidated major cell cycle mechanisms and factors critical for CENP-A incorporation in mitosis, predominantly in cultured cells. However, we do not understand the roles, regulation, and cell cycle timing of CENP-A assembly in somatic tissues in multicellular organisms and in meiosis, the specialized cell division cycle that gives rise to haploid gametes. Here we investigate the timing and requirements for CID assembly in mitotic tissues and male and female meiosis in Drosophila melanogaster, using fixed and live imaging combined with genetic approaches. We find that CID assembly initiates at late telophase and continues during G1 phase in somatic tissues in the organism, later than the metaphase assembly observed in cultured cells. Furthermore, CID assembly occurs at two distinct cell cycle phases during male meiosis: prophase of meiosis I and after exit from meiosis II, in spermatids. CID assembly in prophase I is also conserved in female meiosis. Interestingly, we observe a novel decrease in CID levels after the end of meiosis I and before meiosis II, which correlates temporally with changes in kinetochore organization and orientation. We also demonstrate that CID is retained on mature sperm despite the gross chromatin remodeling that occurs during protamine exchange. Finally, we show that the centromere proteins CAL1 and CENP-C are both required for CID assembly in meiosis and normal progression through spermatogenesis. We conclude that the cell cycle timing of CID assembly in meiosis is different from mitosis and that the efficient propagation of CID through meiotic divisions and on sperm is likely to be important for centromere specification in the developing zygote. PMID:23300382

  7. Meiosis in elephant grass (Pennisetum purpureum, pearl millet (Pennisetum glaucum (Poaceae, Poales and their interspecific hybrids

    Directory of Open Access Journals (Sweden)

    Vânia Helena Techio

    2006-01-01

    Full Text Available The cultivated and sexually compatible species Pennisetum purpureum (elephant grass, 2n = 4x = 28 and Pennisetum glaucum (pearl millet, 2n = 2x = 14 can undergo hybridization which favors the amplification of their genetic background and the introgression of favorable alleles into breeding programs. The main problem with interspecific hybrids of these species is infertility due to triploidy (2n = 3x = 21. This study describes meiosis in elephant grass x pearl millet hybrids and their progenitors. Panicles were prepared according to the conventional protocol for meiotic studies and Alexander’s stain was used for assessing pollen viability. Pearl millet accessions presented regular meiosis with seven bivalents and high pollen viability. For elephant grass, 14 bivalents in diakinesis and metaphase I were observed. The BAG 63 elephant grass accession, derived from tissue culture, presented a high frequency of meiotic abnormalities. The three hybrid accessions presented a high frequency of abnormalities characterized by irregular chromosomal segregation which resulted in the formation of sterile pollen.

  8. Significant competitive advantage conferred by meiosis and syngamy in the yeast Saccharomyces cerevisiae.

    Science.gov (United States)

    Birdsell, J; Wills, C

    1996-01-01

    The presumed advantages of genetic recombinations are difficult to demonstrate directly. To investigate the effects of recombination and background heterozygosity on competitive ability, we have performed serial-transfer competition experiments between isogenic sexual and asexual strains of the yeast Saccharomyces cerevisiae. The members of these diploid pairs of strains differed only in being heterozygous (sexual) or homozygous (asexual) at the mating type or MAT locus. Competing pairs had either a completely homozygous or a heterozygous genetic background, the latter being heterozygous at many different loci throughout the genome. A round of meiotic recombination (automixis) conferred a large and statistically significant enhancement of competitive ability on sexual strains with a heterozygous genetic background. By contrast, in homozygous background competitions, meiosis decreased the sexual strains' initial relative competitive ability. In all cases, however, the sexual strains outcompeted their isogenic asexual counterparts, whether meiotic recombination had occurred or not. In some genetic backgrounds, this was due in part to an overdominance effect on competitive advantage of heterozygosity at the MAT locus. The advantage of the sexual strains also increased significantly during the course of the homozygous background competitions, particularly when meiosis had occurred. This latter effect either did not occur or was very weak in heterozygous background competitions. Overall, sexual strains with heterozygous genetic backgrounds had a significantly higher initial relative competitive ability than those with homozygous backgrounds. The advantage of mating type heterozygosity in this organism extends far beyond the ability to recombine meiotically. PMID:8570658

  9. The methyltransferase Setdb1 is essential for meiosis and mitosis in mouse oocytes and early embryos.

    Science.gov (United States)

    Eymery, Angeline; Liu, Zichuan; Ozonov, Evgeniy A; Stadler, Michael B; Peters, Antoine H F M

    2016-08-01

    Oocytes develop the competence for meiosis and early embryogenesis during their growth. Setdb1 is a histone H3 lysine 9 (H3K9) methyltransferase required for post-implantation development and has been implicated in the transcriptional silencing of genes and endogenous retroviral elements (ERVs). To address its role in oogenesis and pre-implantation development, we conditionally deleted Setdb1 in growing oocytes. Loss of Setdb1 expression greatly impaired meiosis. It delayed meiotic resumption, altered the dynamics of chromatin condensation, and impaired kinetochore-spindle interactions, bipolar spindle organization and chromosome segregation in more mature oocytes. The observed phenotypes related to changes in abundance of specific transcripts in mutant oocytes. Setdb1 maternally deficient embryos arrested during pre-implantation development and showed comparable defects during cell cycle progression and in chromosome segregation. Finally, transcriptional profiling data indicate that Setdb1 downregulates rather than silences expression of ERVK and ERVL-MaLR retrotransposons and associated chimearic transcripts during oogenesis. Our results identify Setdb1 as a newly discovered meiotic and embryonic competence factor safeguarding genome integrity at the onset of life. © 2016. Published by The Company of Biologists Ltd.

  10. Karyotype, heterochromatin distribution and meiosis of Zabrotes subfasciatus (Bohemann) (Coleoptera: Chrysomelidae, Bruchinae)

    International Nuclear Information System (INIS)

    Correa, Ronan X.; Santos, Igor S.; Silva, Janisete G.; Costa, Marco A.; Pompolo, Silvia G.

    2008-01-01

    Zabrotes subfasciatus (Boh.) has been extensively studied in its agronomic and biochemical aspects due to its importance as a damaging insect to leguminous grains during storage. The few cytogenetic studies published on this species yielded conflicting results. In this study, the karyotype was analyzed in order to accurately describe the chromosome C-banding patterns and meiosis. The brain ganglion at the pre pupa and the adult and pupal testes were analyzed. All individuals had 26 chromosomes in both brain ganglion and spermatogonic mitotic metaphases. These chromosomes were classified as follows: the 12 th pair and the Y chromosome were telocentric; the X chromosome was acrocentric; the 4 th and 5 th pairs were sub metacentric; and the remaining pairs were all metacentric. One of the members of the 5 th pair presented a secondary constriction. All chromosomes presented pericentromeric heterochromatin. The large arms of the pairs 5, 9 and X presented heterochromatin. The X chromosome showed to be heteropyknotic throughout the prophase of the fi rst meiotic division. The sub phases of prophase I were atypical and meiosis II was rarely identified. Testes of all males showed a few cells; the bivalents were rod-like shaped in metaphase I. Karyological formulae were 2n = 24 + XX in females and 2n = 24 + XYp and either n = 12 + X or n = 12 + Y in males. (author)

  11. Daam1 regulates fascin for actin assembly in mouse oocyte meiosis.

    Science.gov (United States)

    Lu, Yujie; Zhang, Yu; Pan, Meng-Hao; Kim, Nam-Hyung; Sun, Shao-Chen; Cui, Xiang-Shun

    2017-07-18

    As a formin protein, Daam1 (Dishevelled-associated activator of morphogenesis 1) is reported to regulate series of cell processes like endocytosis, cell morphology and migration via its effects on actin assembly in mitosis. However, whether Daam1 plays roles in female meiosis remains uncertain. In this study, we investigated the expression and functions of Daam1 during mouse oocyte meiosis. Our results indicated that Daam1 localized at the cortex of oocytes, which was similar with actin filaments. After Daam1 morpholino (MO) microinjection, the expression of Daam1 significantly decreased, which resulted in the failure of oocyte polar body extrusion. These results might be due to the defects of actin assembly, since the decreased fluorescence intensity of actin filaments in oocyte cortex and cytoplasm were observed. However, Daam1 knockdown seemed not to affect the meiotic spindle movement. In addition, we found that fascin might be the down effector of Daam1, since the protein expression of fascin decreased after Daam1 knockdown. Thus, our data suggested that Daam1 affected actin assembly during oocyte meiotic division via the regulation of fascin expression.

  12. The synaptonemal complex of basal metazoan hydra: more similarities to vertebrate than invertebrate meiosis model organisms.

    Science.gov (United States)

    Fraune, Johanna; Wiesner, Miriam; Benavente, Ricardo

    2014-03-20

    The synaptonemal complex (SC) is an evolutionarily well-conserved structure that mediates chromosome synapsis during prophase of the first meiotic division. Although its structure is conserved, the characterized protein components in the current metazoan meiosis model systems (Drosophila melanogaster, Caenorhabditis elegans, and Mus musculus) show no sequence homology, challenging the question of a single evolutionary origin of the SC. However, our recent studies revealed the monophyletic origin of the mammalian SC protein components. Many of them being ancient in Metazoa and already present in the cnidarian Hydra. Remarkably, a comparison between different model systems disclosed a great similarity between the SC components of Hydra and mammals while the proteins of the ecdysozoan systems (D. melanogaster and C. elegans) differ significantly. In this review, we introduce the basal-branching metazoan species Hydra as a potential novel invertebrate model system for meiosis research and particularly for the investigation of SC evolution, function and assembly. Also, available methods for SC research in Hydra are summarized. Copyright © 2014. Published by Elsevier Ltd.

  13. Rho-GTPase effector ROCK phosphorylates cofilin in actin-meditated cytokinesis during mouse oocyte meiosis.

    Science.gov (United States)

    Duan, Xing; Liu, Jun; Dai, Xiao-Xin; Liu, Hong-Lin; Cui, Xiang-Shun; Kim, Nam-Hyung; Wang, Zhen-Bo; Wang, Qiang; Sun, Shao-Chen

    2014-02-01

    During oocyte meiosis, a spindle forms in the central cytoplasm and migrates to the cortex. Subsequently, the oocyte extrudes a small body and forms a highly polarized egg; this process is regulated primarily by actin. ROCK is a Rho-GTPase effector that is involved in various cellular functions, such as stress fiber formation, cell migration, tumor cell invasion, and cell motility. In this study, we investigated possible roles for ROCK in mouse oocyte meiosis. ROCK was localized around spindles after germinal vesicle breakdown and was colocalized with cytoplasmic actin and mitochondria. Disrupting ROCK activity by RNAi or an inhibitor resulted in cell cycle progression and polar body extrusion failure. Time-lapse microscopy showed that this may have been due to spindle migration and cytokinesis defects, as chromosomes segregated but failed to extrude a polar body and then realigned. Actin expression at oocyte membranes and in cytoplasm was significantly decreased after these treatments. Actin caps were also disrupted, which was confirmed by a failure to form cortical granule-free domains. The mitochondrial distribution was also disrupted, which indicated that mitochondria were involved in the ROCK-mediated actin assembly. In addition, the phosphorylation levels of Cofilin, a downstream molecule of ROCK, decreased after disrupting ROCK activity. Thus, our results indicated that a ROCK-Cofilin-actin pathway regulated meiotic spindle migration and cytokinesis during mouse oocyte maturation.

  14. Identification of Putative Mek1 Substrates during Meiosis in Saccharomyces cerevisiae Using Quantitative Phosphoproteomics.

    Directory of Open Access Journals (Sweden)

    Raymond T Suhandynata

    Full Text Available Meiotic recombination plays a key role in sexual reproduction as it generates crossovers that, in combination with sister chromatid cohesion, physically connect homologous chromosomes, thereby promoting their proper segregation at the first meiotic division. Meiotic recombination is initiated by programmed double strand breaks (DSBs catalyzed by the evolutionarily conserved, topoisomerase-like protein Spo11. Repair of these DSBs is highly regulated to create crossovers between homologs that are distributed throughout the genome. This repair requires the presence of the mitotic recombinase, Rad51, as well as the strand exchange activity of the meiosis-specific recombinase, Dmc1. A key regulator of meiotic DSB repair in Saccharomyces cerevisiae is the meiosis-specific kinase Mek1, which promotes interhomolog strand invasion and is required for the meiotic recombination checkpoint and the crossover/noncrossover decision. Understanding how Mek1 regulates meiotic recombination requires the identification of its substrates. Towards that end, an unbiased phosphoproteomic approach utilizing Stable Isotope Labeling by Amino Acids in Cells (SILAC was utilized to generate a list of potential Mek1 substrates, as well as proteins containing consensus phosphorylation sites for cyclin-dependent kinase, the checkpoint kinases, Mec1/Tel1, and the polo-like kinase, Cdc5. These experiments represent the first global phosphoproteomic dataset for proteins in meiotic budding yeast.

  15. Karyotype, heterochromatin distribution and meiosis of Zabrotes subfasciatus (Bohemann) (Coleoptera: Chrysomelidae, Bruchinae)

    Energy Technology Data Exchange (ETDEWEB)

    Correa, Ronan X.; Santos, Igor S.; Silva, Janisete G.; Costa, Marco A. [Universidade Estadual de Santa Cruz, Ilheus, BA (Brazil). Dept. de Ciencias Biologicas; Pompolo, Silvia G. [Universidade Federal de Vicosa, MG (Brazil). Dept. de Biologia Geral

    2008-09-15

    Zabrotes subfasciatus (Boh.) has been extensively studied in its agronomic and biochemical aspects due to its importance as a damaging insect to leguminous grains during storage. The few cytogenetic studies published on this species yielded conflicting results. In this study, the karyotype was analyzed in order to accurately describe the chromosome C-banding patterns and meiosis. The brain ganglion at the pre pupa and the adult and pupal testes were analyzed. All individuals had 26 chromosomes in both brain ganglion and spermatogonic mitotic metaphases. These chromosomes were classified as follows: the 12{sup th} pair and the Y chromosome were telocentric; the X chromosome was acrocentric; the 4{sup th} and 5{sup th} pairs were sub metacentric; and the remaining pairs were all metacentric. One of the members of the 5{sup th} pair presented a secondary constriction. All chromosomes presented pericentromeric heterochromatin. The large arms of the pairs 5, 9 and X presented heterochromatin. The X chromosome showed to be heteropyknotic throughout the prophase of the fi rst meiotic division. The sub phases of prophase I were atypical and meiosis II was rarely identified. Testes of all males showed a few cells; the bivalents were rod-like shaped in metaphase I. Karyological formulae were 2n = 24 + XX in females and 2n = 24 + XYp and either n = 12 + X or n = 12 + Y in males. (author)

  16. Role of cleavage by separase of the Rec8 kleisin subunit of cohesin during mammalian meiosis I

    Czech Academy of Sciences Publication Activity Database

    Kudo, Nobuaki R.; Anger, Martin; Peters, Antoine H. F. M.; Stemmann, O.; Theussl, H. Ch.; Helmhart, W.; Kudo, H.; Heyting, Ch.; Nasmyth, K.

    2009-01-01

    Roč. 122, - (2009), s. 2686-2698 ISSN 0021-9533 Institutional research plan: CEZ:AV0Z50450515 Keywords : Chromosome segregation * Cohesin * Meiosis * Oocyte maturation Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 6.144, year: 2009

  17. The meiosis-specific nuclear passenger protein is required for proper assembly of forespore membrane in fission yeast.

    Science.gov (United States)

    Takaine, Masak; Imada, Kazuki; Numata, Osamu; Nakamura, Taro; Nakano, Kentaro

    2014-10-15

    Sporulation, gametogenesis in yeast, consists of meiotic nuclear division and spore morphogenesis. In the fission yeast Schizosaccharomyces pombe, the four haploid nuclei produced after meiosis II are encapsulated by the forespore membrane (FSM), which is newly synthesized from spindle pole bodies (SPBs) in the cytoplasm of the mother cell as spore precursors. Although the coordination between meiosis and FSM assembly is vital for proper sporulation, the underlying mechanism remains unclear. In the present study, we identified a new meiosis-specific protein Npg1, and found that it was involved in the efficient formation of spores and spore viability. The accumulation and organization of the FSM was compromised in npg1-null cells, leading to the error-prone envelopment of nuclei. Npg1 was first seen as internuclear dots and translocated to the SPBs before the FSM assembled. Genetic analysis revealed that Npg1 worked in conjunction with the FSM proteins Spo3 and Meu14. These results suggest a possible signaling link from the nucleus to the meiotic SPBs in order to associate the onset of FSM assembly with meiosis II, which ensures the successful partitioning of gametic nuclei. © 2014. Published by The Company of Biologists Ltd.

  18. Endosulfan inhibiting the meiosis process via depressing expressions of regulatory factors and causing cell cycle arrest in spermatogenic cells.

    Science.gov (United States)

    Guo, Fang-Zi; Zhang, Lian-Shuang; Wei, Jia-Liu; Ren, Li-Hua; Zhang, Jin; Jing, Li; Yang, Man; Wang, Ji; Sun, Zhi-Wei; Zhou, Xian-Qing

    2016-10-01

    Endosulfan is a persistent organic pollutant and widely used in agriculture as a pesticide. It is present in air, water, and soil worldwide; therefore, it is a health risk affecting especially the reproductive system. The aim of this study was to evaluate the toxicity of endosulfan in the reproductive system. To investigate the effect of endosulfan on meiosis process, 32 rats were divided into four groups, treated with 0, 1, 5, and 10 mg/kg/day endosulfan, respectively, and sacrificed after the 21 days of treatments. Results show that endosulfan caused the reductions in sperm concentration and motility rate, which resulted into an increased in sperm abnormality rate; further, endosulfan induced downregulation of spermatogenesis- and oogenesis-specific basic helix-loop-helix transcription factor (Sohlh1) which controls the switch on meiosis in mammals, as well cyclin A1, cyclin-dependent kinases 1 (CDK1), and cyclin-dependent kinases 2 (CDK2). In vitro, endosulfan induced G2/M phase arrest in the spermatogenic cell cycle and caused proliferation inhibition. Moreover, endosulfan induced oxidative stress and DNA damage in vivo and vitro. The results suggested that endosulfan could inhibit the start of meiosis by downregulating the expression of Sohlh1 and induce G2/M phase arrest of cell cycle by decreasing the expression of cyclin A1, CDK1, and CDK2 via oxidative damage, which inhibits the meiosis process, and therefore decrease the amount of sperm.

  19. Ameliorative Effect of Grape Seed Proanthocyanidin Extract on Cadmium-Induced Meiosis Inhibition During Oogenesis in Chicken Embryos.

    Science.gov (United States)

    Hou, Fuyin; Xiao, Min; Li, Jian; Cook, Devin W; Zeng, Weidong; Zhang, Caiqiao; Mi, Yuling

    2016-04-01

    Cadmium (Cd) is an environmental endocrine disruptor that has toxic effects on the female reproductive system. Here the ameliorative effect of grape seed proanthocyanidin extract (GSPE) on Cd-induced meiosis inhibition during oogenesis was explored. As compared with controls, chicken embryos exposed to Cd (3 µg/egg) displayed a changed oocyte morphology, decreased number of meiotic germ cells, and decreased expression of the meiotic marker protein γH2AX. Real time RT-PCR also revealed a significant down-regulation in the mRNA expressions of various meiosis-specific markers (Stra8, Spo11, Scp3, and Dmc1) together with those of Raldh2, a retinoic acid (RA) synthetase, and of the receptors (RARα and RARβ). In addition, exposure to Cd increased the production of H2 O2 and malondialdehyde in the ovaries and caused a corresponding reduction in glutathione and superoxide dismutase. Simultaneous supplementation of GSPE (150 µg/egg) markedly alleviated the aforementioned Cd-induced embryotoxic effects by upregulating meiosis-related proteins and gene expressions and restoring the antioxidative level. Collectively, the findings provided novel insights into the underlying mechanism of Cd-induced meiosis inhibition and indicated that GSPE might potentially ameliorate related reproductive disorders. © 2016 Wiley Periodicals, Inc.

  20. Regulation of mitosis-meiosis transition by the ubiquitin ligase β-TrCP in male germ cells.

    Science.gov (United States)

    Nakagawa, Tadashi; Zhang, Teng; Kushi, Ryo; Nakano, Seiji; Endo, Takahiro; Nakagawa, Makiko; Yanagihara, Noriko; Zarkower, David; Nakayama, Keiko

    2017-11-15

    The mitosis-meiosis transition is essential for spermatogenesis. Specific and timely downregulation of the transcription factor DMRT1, and consequent induction of Stra8 expression, is required for this process in mammals, but the molecular mechanism has remained unclear. Here, we show that β-TrCP, the substrate recognition component of an E3 ubiquitin ligase complex, targets DMRT1 for degradation and thereby controls the mitosis-meiosis transition in mouse male germ cells. Conditional inactivation of β-TrCP2 in male germ cells of β-TrCP1 knockout mice resulted in sterility due to a lack of mature sperm. The β-TrCP-deficient male germ cells did not enter meiosis, but instead underwent apoptosis. The induction of Stra8 expression was also attenuated in association with the accumulation of DMRT1 at the Stra8 promoter in β-TrCP-deficient testes. DMRT1 contains a consensus β-TrCP degron sequence that was found to bind β-TrCP. Overexpression of β-TrCP induced the ubiquitylation and degradation of DMRT1. Heterozygous deletion of Dmrt1 in β-TrCP-deficient spermatogonia increased meiotic cells with a concomitant reduction of apoptosis. Collectively, our data indicate that β-TrCP regulates the transition from mitosis to meiosis in male germ cells by targeting DMRT1 for degradation. © 2017. Published by The Company of Biologists Ltd.

  1. Descripción del cromosoma profásico en la meiosis I de Bostryx conspersus

    Directory of Open Access Journals (Sweden)

    María Siles-Vallejos

    2011-08-01

    Full Text Available Bostryx es uno de los géneros de mayor diversidad dentro de los Orthalicidae (Gastropoda, siendo B. conspersus una especie endémica del ecosistema de Lomas, del desierto Costero peruano. En el presente trabajo los cromosomas de la profase I de meiosis de los espermatocitos de Bostryx conspersus son descritos.

  2. RSPO1/β-catenin signaling pathway regulates oogonia differentiation and entry into meiosis in the mouse fetal ovary.

    Directory of Open Access Journals (Sweden)

    Anne-Amandine Chassot

    Full Text Available Differentiation of germ cells into male gonocytes or female oocytes is a central event in sexual reproduction. Proliferation and differentiation of fetal germ cells depend on the sex of the embryo. In male mouse embryos, germ cell proliferation is regulated by the RNA helicase Mouse Vasa homolog gene and factors synthesized by the somatic Sertoli cells promote gonocyte differentiation. In the female, ovarian differentiation requires activation of the WNT/β-catenin signaling pathway in the somatic cells by the secreted protein RSPO1. Using mouse models, we now show that Rspo1 also activates the WNT/β-catenin signaling pathway in germ cells. In XX Rspo1(-/- gonads, germ cell proliferation, expression of the early meiotic marker Stra8, and entry into meiosis are all impaired. In these gonads, impaired entry into meiosis and germ cell sex reversal occur prior to detectable Sertoli cell differentiation, suggesting that β-catenin signaling acts within the germ cells to promote oogonial differentiation and entry into meiosis. Our results demonstrate that RSPO1/β-catenin signaling is involved in meiosis in fetal germ cells and contributes to the cellular decision of germ cells to differentiate into oocyte or sperm.

  3. 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

  4. Oocyte-specific deletion of N-WASP does not affect oocyte polarity, but causes failure of meiosis II completion.

    Science.gov (United States)

    Wang, Zhen-Bo; Ma, Xue-Shan; Hu, Meng-Wen; Jiang, Zong-Zhe; Meng, Tie-Gang; Dong, Ming-Zhe; Fan, Li-Hua; Ouyang, Ying-Chun; Snapper, Scott B; Schatten, Heide; Sun, Qing-Yuan

    2016-09-01

    There is an unexplored physiological role of N-WASP (neural Wiskott-Aldrich syndrome protein) in oocyte maturation that prevents completion of second meiosis. In mice, N-WASP deletion did not affect oocyte polarity and asymmetric meiotic division in first meiosis, but did impair midbody formation and second meiosis completion. N-WASP regulates actin dynamics and participates in various cell activities through the RHO-GTPase-Arp2/3 (actin-related protein 2/3 complex) pathway, and specifically the Cdc42 (cell division cycle 42)-N-WASP-Arp2/3 pathway. Differences in the functions of Cdc42 have been obtained from in vitro compared to in vivo studies. By conditional knockout of N-WASP in mouse oocytes, we analyzed its in vivo functions by employing a variety of different methods including oocyte culture, immunofluorescent staining and live oocyte imaging. Each experiment was repeated at least three times, and data were analyzed by paired-samples t-test. Oocyte-specific deletion of N-WASP did not affect the process of oocyte maturation including spindle formation, spindle migration, polarity establishment and maintenance, and homologous chromosome or sister chromatid segregation, but caused failure of cytokinesis completion during second meiosis (P meiosis completion and failures in this process that affect oocyte quality. None. This work was supported by the National Basic Research Program of China (No. 2012CB944404) and the National Natural Science Foundation of China (Nos 30930065, 31371451, 31272260 and 31530049). There are no potential conflicts of interests. © The Author 2016. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  5. Polyploidy Enhances F1 Pollen Sterility Loci Interactions That Increase Meiosis Abnormalities and Pollen Sterility in Autotetraploid Rice.

    Science.gov (United States)

    Wu, Jinwen; Shahid, Muhammad Qasim; Chen, Lin; Chen, Zhixiong; Wang, Lan; Liu, Xiangdong; Lu, Yonggen

    2015-12-01

    Intersubspecific autotetraploid rice (Oryza sativa ssp. indica × japonica) hybrids have greater biological and yield potentials than diploid rice. However, the low fertility of intersubspecific autotetraploid hybrids, which is largely caused by high pollen abortion rates, limits their commercial utility. To decipher the cytological and molecular mechanisms underlying allelic interactions in autotetraploid rice, we developed an autotetraploid rice hybrid that was heterozygous (S(i)S(j)) at F1 pollen sterility loci (Sa, Sb, and Sc) using near-isogenic lines. Cytological studies showed that the autotetraploid had higher percentages (>30%) of abnormal chromosome behavior and aberrant meiocytes (>50%) during meiosis than did the diploid rice hybrid control. Analysis of gene expression profiles revealed 1,888 genes that were differentially expressed between the autotetraploid and diploid hybrid lines at the meiotic stage, among which 889 and 999 were up- and down-regulated, respectively. Of the 999 down-regulated genes, 940 were associated with the combined effect of polyploidy and pollen sterility loci interactions (IPE). Gene Ontology enrichment analysis identified a prominent functional gene class consisting of seven genes related to photosystem I (Gene Ontology 0009522). Moreover, 55 meiosis-related or meiosis stage-specific genes were associated with IPE in autotetraploid rice, including Os02g0497500, which encodes a DNA repair-recombination protein, and Os02g0490000, which encodes a component of the ubiquitin-proteasome pathway. These results suggest that polyploidy enhances epistatic interactions between alleles of pollen sterility loci, thereby altering the expression profiles of important meiosis-related or meiosis stage-specific genes and resulting in high pollen sterility. © 2015 American Society of Plant Biologists. All Rights Reserved.

  6. Polyploidy Enhances F1 Pollen Sterility Loci Interactions That Increase Meiosis Abnormalities and Pollen Sterility in Autotetraploid Rice1[OPEN

    Science.gov (United States)

    Wu, Jinwen; Chen, Lin; Chen, Zhixiong; Wang, Lan; Lu, Yonggen

    2015-01-01

    Intersubspecific autotetraploid rice (Oryza sativa ssp. indica × japonica) hybrids have greater biological and yield potentials than diploid rice. However, the low fertility of intersubspecific autotetraploid hybrids, which is largely caused by high pollen abortion rates, limits their commercial utility. To decipher the cytological and molecular mechanisms underlying allelic interactions in autotetraploid rice, we developed an autotetraploid rice hybrid that was heterozygous (SiSj) at F1 pollen sterility loci (Sa, Sb, and Sc) using near-isogenic lines. Cytological studies showed that the autotetraploid had higher percentages (>30%) of abnormal chromosome behavior and aberrant meiocytes (>50%) during meiosis than did the diploid rice hybrid control. Analysis of gene expression profiles revealed 1,888 genes that were differentially expressed between the autotetraploid and diploid hybrid lines at the meiotic stage, among which 889 and 999 were up- and down-regulated, respectively. Of the 999 down-regulated genes, 940 were associated with the combined effect of polyploidy and pollen sterility loci interactions (IPE). Gene Ontology enrichment analysis identified a prominent functional gene class consisting of seven genes related to photosystem I (Gene Ontology 0009522). Moreover, 55 meiosis-related or meiosis stage-specific genes were associated with IPE in autotetraploid rice, including Os02g0497500, which encodes a DNA repair-recombination protein, and Os02g0490000, which encodes a component of the ubiquitin-proteasome pathway. These results suggest that polyploidy enhances epistatic interactions between alleles of pollen sterility loci, thereby altering the expression profiles of important meiosis-related or meiosis stage-specific genes and resulting in high pollen sterility. PMID:26511913

  7. A Comparative Proteome Profile of Female Mouse Gonads Suggests a Tight Link between the Electron Transport Chain and Meiosis Initiation.

    Science.gov (United States)

    Shen, Cong; Li, Mingrui; Zhang, Pan; Guo, Yueshuai; Zhang, Hao; Zheng, Bo; Teng, Hui; Zhou, Tao; Guo, Xuejiang; Huo, Ran

    2018-01-01

    Generation of haploid gametes by meiosis is a unique property of germ cells and is critical for sexual reproduction. Leaving mitosis and entering meiosis is a key step in germ cell development. Several inducers or intrinsic genes are known to be important for meiotic initiation, but the regulation of meiotic initiation, especially at the protein level, is still not well understood. We constructed a comparative proteome profile of female mouse fetal gonads at specific time points (11.5, 12.5, and 13.5 days post coitum), spanning a critical window for initiation of meiosis in female germ cells. We identified 3666 proteins, of which 473 were differentially expressed. Further bioinformatics analysis showed that these differentially expressed proteins were enriched in the mitochondria, especially in the electron transport chain and, notably, 9 proteins in electron transport chain Complex I were differentially expressed. We disrupted the mitochondrial electron transport chain function by adding the complex I inhibitor, rotenone to 11.5 days post coitum female gonads cultured in vitro. This treatment resulted in a decreased proportion of meiotic germ cells, as assessed by staining for histone γH2AX. Rotenone treatment also caused decreased ATP levels, increased reactive oxygen species levels and failure of the germ cells to undergo premeiotic DNA replication. These effects were partially rescued by adding Coenzyme Q10. Taken together, our results suggested that a functional electron transport chain is important for meiosis initiation. Our characterization of the quantitative proteome of female gonads provides an inventory of proteins, useful for understanding the mechanisms of meiosis initiation and female fertility. © 2018 by The American Society for Biochemistry and Molecular Biology, Inc.

  8. Duplications created by transformation in Sordaria macrospora are not inactivated during meiosis.

    Science.gov (United States)

    Le Chevanton, L; Leblon, G; Lebilcot, S

    1989-09-01

    We present here the first report of a transformation system developed for the filamentous fungus Sordaria macrospora. Protoplasts from a ura-5 strain were transformed using the cloned Sordaria gene at a frequency of 2 x 10(-5) transformants per viable protoplast (10 per microgram of DNA). Transformation occurred by integration of the donor sequences in the chromosomes of the recipient strain. In 71 cases out of 74, integration occurred outside the ura5 locus; frequently several (two to four) copies were found at a unique integration site. Using the advantage of the spore colour phenotype of the ura5-1 marker, we have shown that the transformed phenotype is stable through mitosis and meiosis in all transformants analysed. No methylation of the duplicated sequences could be observed during meiotic divisions in the transformants.

  9. Role of animal pole protuberance and microtubules during meiosis in sea cucumber Apostichopus japonicus oocytes

    Science.gov (United States)

    Pang, Zhenguo; Chang, Yaqing; Sun, Huiling; Yu, Jiaping

    2010-05-01

    Fully grown oocytes of Apostichopus japonicus have a cytoplasmic protuberance where the oocyte attaches to the follicle. The protuberance and the oolamina located on the opposite side of the oocyte indicate the animal-vegetal axis. Two pre-meiotic centrosomes are anchored to the protuberance by microtubules between centrosomes and protuberance. After meiosis reinitiation induced by DTT solution, the germinal vesicle (GV) migrates towards the protuberance. The GV breaks down after it migrates to the oocyte membrane on the protuberance side. The protuberance then contracts back into the oocyte and the first polar body extrudes from the site of the former protuberance. The second polar body forms beneath the first. Thus the oocyte protuberance indicates the presumptive animal pole well before maturation of the oocyte.

  10. Induction of mutation and recombination following UV irradiation during meiosis in Saccharomyces cerevisiae

    Energy Technology Data Exchange (ETDEWEB)

    Kelly, S.L.; Parry, J.M. (University Coll. of Swansea (UK). Dept. of Genetics)

    1983-03-01

    Irradiation of yeast cultures with ultraviolet light at discrete stages during meiosis produces cyclic variations in sensitivity, i.e. cells are more sensitive to the lethal effects of UV light prior to entry into the meiotic DNA synthesis, and this corresponds to a peak of induction of point mutation. Cells become more resistant to both induced point mutation and lethality as they enter meiotic DNA synthesis, but become more sensitive again during spore formation. The induced level of intragenic recombination rises during the period of commitment ot recombination to a level indistinguishable from the full meiotic level of spontaneous intragenic recombination. Induced reciprocal recombination remains above the spontaneous level up to the point of commitment to sporulation.

  11. Cytogenetics of Mimosa bimucronata (DC. O. Kuntze (Mimosoideae, Leguminosae: chromosome number, polysomaty and meiosis.

    Directory of Open Access Journals (Sweden)

    Denise Olkoski

    2011-06-01

    Full Text Available Chromosome numbers (somatic and/or gametic were determined in 50 populations of M. bimucronata (DC. O.Kuntze collected in the species area of distribution in Rio Grande do Sul, south Brazil. All populations were diploid (2n = 2x = 26,n = 13. Polysomatic (mostly tetraploid cells were detected in the seedlings root-tip cells in 39 out of the 41 populations examined,ranging from 3.0 to 28.2 % among populations, but were absent in the root-tips of grown plants. Polysomaty was as well absent inpollen-mother cells. In M. bimucronata pollen-mother cells are joined two-by-two before the onset of meiosis, remaining attachedduring all the meiotic division until the formation of pollen grain polyads, composed of two sets of four pollen grains each, that aredispersed in this way, which, according to previous suggestions would be an adaptation to ensure high seed set after a singlepollination event.

  12. Ret Finger Protein: An E3 Ubiquitin Ligase Juxtaposed to the XY Body in Meiosis

    Directory of Open Access Journals (Sweden)

    Isabelle Gillot

    2009-01-01

    Full Text Available During prophase I of male meiosis, the sex chromosomes form a compact structure called XY body that associates with the nuclear membrane of pachytene spermatocytes. Ret Finger Protein is a transcriptional repressor, able to interact with both nuclear matrix-associated proteins and double-stranded DNA. We report the precise and unique localization of Ret Finger Protein in pachytene spermatocytes, in which Ret Finger Protein takes place of lamin B1, between the XY body and the inner nuclear membrane. This localization of Ret Finger Protein does not seem to be associated with O-glycosylation or sumoylation. In addition, we demonstrate that Ret Finger Protein contains an E3 ubiquitin ligase activity. These observations lead to an attractive hypothesis in which Ret Finger Protein would be involved in the positioning and the attachment of XY body to the nuclear lamina of pachytene spermatocytes.

  13. The induction of mutation and recombination following UV irradiation during meiosis in Saccharomyces cerevisiae

    International Nuclear Information System (INIS)

    Kelly, S.L.; Parry, J.M.

    1983-01-01

    Irradiation of yeast cultures with ultraviolet light at discrete stages during meiosis produces cyclic variations in sensitivity, i.e. cells are more sensitive to the lethal effects of UV light prior to entry into the meiotic DNA synthesis, and this corresponds to a peak of induction of point mutation. Cells become more resistant to both induced point mutation and lethality as they enter meiotic DNA synthesis, but become more sensitive again during spore formation. The induced level of intragenic recombination rises during the period of commitment ot recombination to a level indistinguishable from the full meiotic level of spontaneous intragenic recombination. Induced reciprocal recombination remains above the spontaneous level up to the point of commitment to sporulation. (orig.)

  14. The induction of mutation and recombination following UV irradiation during meiosis in Saccharomyces cerevisiae.

    Science.gov (United States)

    Kelly, S L; Parry, J M

    1983-03-01

    Irradiation of yeast cultures with ultraviolet light at discrete stages during meiosis produces cyclic variations in sensitivity, i.e. cells are more sensitive to the lethal effects of UV light prior to entry into the meiotic DNA synthesis, and this corresponds to a peak of induction of point mutation. Cells become more resistant to both induced point mutation and lethality as they enter meiotic DNA synthesis, but become more sensitive again during spore formation. The induced level of intragenic recombination rises during the period of commitment to recombination to a level indistinguishable from the full meiotic level of spontaneous intragenic recombination. Induced reciprocal recombination remains above the spontaneous level up to the point of commitment to sporulation.

  15. The multiple roles of Bub1 in chromosome segregation during mitosis and meiosis

    Energy Technology Data Exchange (ETDEWEB)

    Marchetti, Francesco; Venkatachalam, Sundaresan

    2009-06-19

    Aneuploidy, any deviation from an exact multiple of the haploid number of chromosomes, is a common occurrence in cancer and represents the most frequent chromosomal disorder in newborns. Eukaryotes have evolved mechanisms to assure the fidelity of chromosome segregation during cell division that include a multiplicity of checks and controls. One of the main cell division control mechanisms is the spindle assembly checkpoint (SAC) that monitors the proper attachment of chromosomes to spindle fibers and prevents anaphase until all kinetochores are properly attached. The mammalian SAC is composed by at least 14 evolutionary-conserved proteins that work in a coordinated fashion to monitor the establishment of amphitelic attachment of all chromosomes before allowing cell division to occur. Among the SAC proteins, the budding uninhibited by benzimidazole protein 1 (Bub1), is a highly conserved protein of prominent importance for the proper functioning of the SAC. Studies have revealed many roles for Bub1 in both mitosis and meiosis, including the localization of other SAC proteins to the kinetochore, SAC signaling, metaphase congression and the protection of the sister chromatid cohesion. Recent data show striking sex specific differences in the response to alterations in Bub1 activity. Proper Bub1 functioning is particularly important during oogenesis in preventing the generation of aneuploid gametes that can have detrimental effects on the health status of the fetus and the newborn. These data suggest that Bub1 is a master regulator of SAC and chromosomal segregation in both mitosis and meiosis. Elucidating its many essential functions in regulating proper chromosome segregation can have important consequences for preventing tumorigenesis and developmental abnormalities.

  16. Identification of transcripts involved in meiosis and follicle formation during ovine ovary development

    Directory of Open Access Journals (Sweden)

    Poumerol Elodie

    2008-09-01

    Full Text Available Abstract Background The key steps in germ cell survival during ovarian development are the entry into meiosis of oogonies and the formation of primordial follicles, which then determine the reproductive lifespan of the ovary. In sheep, these steps occur during fetal life, between 55 and 80 days of gestation, respectively. The aim of this study was to identify differentially expressed ovarian genes during prophase I meiosis and early folliculogenesis in sheep. Results In order to elucidate the molecular events associated with early ovarian differentiation, we generated two ovary stage-specific subtracted cDNA libraries using SSH. Large-scale sequencing of these SSH libraries identified 6,080 ESTs representing 2,535 contigs. Clustering and assembly of these ESTs resulted in a total of 2,101 unique sequences depicted in 1,305 singleton (62.11% and 796 contigs (37.9% ESTs (clusters. BLASTX evaluation indicated that 99% of the ESTs were homologous to various known genes/proteins in a broad range of organisms, especially ovine, bovine and human species. The remaining 1% which exhibited any homology to known gene sequences was considered as novel. Detailed study of the expression patterns of some of these genes using RT-PCR revealed new promising candidates for ovary differentiation genes in sheep. Conclusion We showed that the SSH approach was relevant to determining new mammalian genes which might be involved in oogenesis and early follicle development, and enabled the discovery of new potential oocyte and granulosa cell markers for future studies. These genes may have significant implications regarding our understanding of ovarian function in molecular terms, and for the development of innovative strategies to both promote and control fertility.

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

    Directory of Open Access Journals (Sweden)

    Fang Jin

    2010-09-01

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

  18. Identification of transcripts involved in meiosis and follicle formation during ovine ovary development.

    Science.gov (United States)

    Baillet, Adrienne; Mandon-Pépin, Béatrice; Cabau, Cédric; Poumerol, Elodie; Pailhoux, Eric; Cotinot, Corinne

    2008-09-23

    The key steps in germ cell survival during ovarian development are the entry into meiosis of oogonies and the formation of primordial follicles, which then determine the reproductive lifespan of the ovary. In sheep, these steps occur during fetal life, between 55 and 80 days of gestation, respectively. The aim of this study was to identify differentially expressed ovarian genes during prophase I meiosis and early folliculogenesis in sheep. In order to elucidate the molecular events associated with early ovarian differentiation, we generated two ovary stage-specific subtracted cDNA libraries using SSH. Large-scale sequencing of these SSH libraries identified 6,080 ESTs representing 2,535 contigs. Clustering and assembly of these ESTs resulted in a total of 2,101 unique sequences depicted in 1,305 singleton (62.11%) and 796 contigs (37.9%) ESTs (clusters). BLASTX evaluation indicated that 99% of the ESTs were homologous to various known genes/proteins in a broad range of organisms, especially ovine, bovine and human species. The remaining 1% which exhibited any homology to known gene sequences was considered as novel. Detailed study of the expression patterns of some of these genes using RT-PCR revealed new promising candidates for ovary differentiation genes in sheep. We showed that the SSH approach was relevant to determining new mammalian genes which might be involved in oogenesis and early follicle development, and enabled the discovery of new potential oocyte and granulosa cell markers for future studies. These genes may have significant implications regarding our understanding of ovarian function in molecular terms, and for the development of innovative strategies to both promote and control fertility.

  19. Connexin 43 reboots meiosis and reseals blood-testis barrier following toxicant-mediated aspermatogenesis and barrier disruption.

    Science.gov (United States)

    Li, Nan; Mruk, Dolores D; Mok, Ka-Wai; Li, Michelle W M; Wong, Chris K C; Lee, Will M; Han, Daishu; Silvestrini, Bruno; Cheng, C Yan

    2016-04-01

    Earlier studies have shown that rats treated with an acute dose of 1-(2,4-dichlorobenzyl)-1H-indazole-3-carbohydrazide (adjudin, a male contraceptive under development) causes permanent infertility due to irreversible blood-testis barrier (BTB) disruption even though the population of undifferentiated spermatogonia remains similar to normal rat testes, because spermatogonia fail to differentiate into spermatocytes to enter meiosis. Since other studies have illustrated the significance of connexin 43 (Cx43)-based gap junction in maintaining the homeostasis of BTB in the rat testis and the phenotypes of Sertoli cell-conditional Cx43 knockout mice share many of the similarities of the adjudin-treated rats, we sought to examine if overexpression of Cx43 in these adjudin-treated rats would reseal the disrupted BTB and reinitiate spermatogenesis. A full-length Cx43 cloned into mammalian expression vector pCI-neo was used to transfect testes of adjudin-treated ratsversusempty vector. It was found that overexpression of Cx43 indeed resealed the Sertoli cell tight junction-permeability barrier based on a functionalin vivoassay in tubules displaying signs of meiosis as noted by the presence of round spermatids. Thus, these findings suggest that overexpression of Cx43 reinitiated spermatogenesis at least through the steps of meiosis to generate round spermatids in testes of rats treated with an acute dose of adjudin that led to aspermatogenesis. It was also noted that the round spermatids underwent eventual degeneration with the formation of multinucleated cells following Cx43 overexpression due to the failure of spermiogenesis because no elongating/elongated spermatids were detected in any of the tubules examined. The mechanism by which overexpression of Cx43 reboots meiosis and rescues BTB function was also examined. In summary, overexpression of Cx43 in the testis with aspermatogenesis reboots meiosis and reseals toxicant-induced BTB disruption, even though it fails to

  20. Frequent and efficient use of the sister chromatid for DNA double-strand break repair during budding yeast meiosis.

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    Tamara Goldfarb

    2010-10-01

    Full Text Available Recombination between homologous chromosomes of different parental origin (homologs is necessary for their accurate segregation during meiosis. It has been suggested that meiotic inter-homolog recombination is promoted by a barrier to inter-sister-chromatid recombination, imposed by meiosis-specific components of the chromosome axis. Consistent with this, measures of Holliday junction-containing recombination intermediates (joint molecules [JMs] show a strong bias towards inter-homolog and against inter-sister JMs. However, recombination between sister chromatids also has an important role in meiosis. The genomes of diploid organisms in natural populations are highly polymorphic for insertions and deletions, and meiotic double-strand breaks (DSBs that form within such polymorphic regions must be repaired by inter-sister recombination. Efforts to study inter-sister recombination during meiosis, in particular to determine recombination frequencies and mechanisms, have been constrained by the inability to monitor the products of inter-sister recombination. We present here molecular-level studies of inter-sister recombination during budding yeast meiosis. We examined events initiated by DSBs in regions that lack corresponding sequences on the homolog, and show that these DSBs are efficiently repaired by inter-sister recombination. This occurs with the same timing as inter-homolog recombination, but with reduced (2- to 3-fold yields of JMs. Loss of the meiotic-chromosome-axis-associated kinase Mek1 accelerates inter-sister DSB repair and markedly increases inter-sister JM frequencies. Furthermore, inter-sister JMs formed in mek1Δ mutants are preferentially lost, while inter-homolog JMs are maintained. These findings indicate that inter-sister recombination occurs frequently during budding yeast meiosis, with the possibility that up to one-third of all recombination events occur between sister chromatids. We suggest that a Mek1-dependent reduction in

  1. A wide reprogramming of histone H3 modifications during male meiosis I in rice is dependent on the Argonaute protein MEL1.

    Science.gov (United States)

    Liu, Hua; Nonomura, Ken-Ichi

    2016-10-01

    The roles of epigenetic mechanisms, including small-RNA-mediated silencing, in plant meiosis largely remain unclear, despite their importance in plant reproduction. This study unveiled that rice chromosomes are reprogrammed during the premeiosis-to-meiosis transition in pollen mother cells (PMCs). This large-scale meiotic chromosome reprogramming (LMR) continued throughout meiosis I, during which time H3K9 dimethylation (H3K9me2) was increased, and H3K9 acetylation and H3S10 phosphorylation were broadly decreased, with an accompanying immunostaining pattern shift of RNA polymerase II. LMR was dependent on the rice Argonaute protein, MEIOSIS ARRESTED AT LEPTOTENE1 (MEL1), which is specifically expressed in germ cells prior to meiosis, because LMR was severely diminished in mel1 mutant anthers. Pivotal meiotic events, such as pre-synaptic centromere association, DNA double-strand break initiation and synapsis of homologous chromosomes, were also disrupted in this mutant. Interestingly, and as opposed to the LMR loss in most chromosomal regions, aberrant meiotic protein loading and hypermethylation of H3K9 emerged on the nucleolar organizing region in the mel1 PMCs. These results suggest that MEL1 plays important roles in epigenetic LMR to promote faithful homologous recombination and synapsis during rice meiosis. © 2016. Published by The Company of Biologists Ltd.

  2. Ex vivo culture of human fetal gonads: manipulation of meiosis signalling by retinoic acid treatment disrupts testis development.

    Science.gov (United States)

    Jørgensen, A; Nielsen, J E; Perlman, S; Lundvall, L; Mitchell, R T; Juul, A; Rajpert-De Meyts, E

    2015-10-01

    What are the effects of experimentally manipulating meiosis signalling by addition of retinoic acid (RA) in cultured human fetal gonads? RA-treatment accelerated meiotic entry in cultured fetal ovary samples, while addition of RA resulted in a dysgenetic gonadal phenotype in fetal testis cultures. One of the first manifestations of sex differentiation is the initiation of meiosis in fetal ovaries. In contrast, meiotic entry is actively prevented in the fetal testis at this developmental time-point. It has previously been shown that RA-treatment mediates initiation of meiosis in human fetal ovary ex vivo. This was a controlled ex vivo study of human fetal gonads treated with RA in 'hanging-drop' tissue cultures. The applied experimental set-up preserves germ cell-somatic niche interactions and the investigated outcomes included tissue integrity and morphology, cell proliferation and survival and the expression of markers of meiosis and sex differentiation. Tissue from 24 first trimester human fetuses was included in this study, all from elective terminations at gestational week (GW) 7-12. Gonads were cultured for 2 weeks with and without addition of 1 µM RA. Samples were subsequently formalin-fixed and investigated by immunohistochemistry and cell counting. Proteins investigated and quantified included; octamer-binding transcription factor 4 (OCT4), transcription factor AP-2 gamma (AP2γ) (embryonic germ cell markers), SRY (sex determining region Y)-box 9 (SOX9), anti-Müllerian hormone (AMH) (immature Sertoli cell markers), COUP transcription factor 2 (COUP-TFII) (marker of interstitial cells), forkhead box L2 (FOXL2) (granulosa cell marker), H2A histone family, member X (γH2AX) (meiosis marker), doublesex and mab-3 related transcription factor 1 (DMRT1) (meiosis regulator), cleaved poly ADP ribose polymerase (PARP), cleaved Caspase 3 (apoptosis markers) and Ki-67 antigen (Ki-67) (proliferation marker). Also, proliferation was determined using a 5'-bromo-2

  3. H2B ubiquitination: Conserved molecular mechanism, diverse physiologic functions of the E3 ligase during meiosis.

    Science.gov (United States)

    Wang, Liying; Cao, Chunwei; Wang, Fang; Zhao, Jianguo; Li, Wei

    2017-09-03

    RNF20/Bre1 mediated H2B ubiquitination (H2Bub) has various physiologic functions. Recently, we found that H2Bub participates in meiotic recombination by promoting chromatin relaxation during meiosis. We then analyzed the phylogenetic relationships among the E3 ligase for H2Bub, its E2 Rad6 and their partner WW domain-containing adaptor with a coiled-coil (WAC) or Lge1, and found that the molecular mechanism underlying H2Bub is evolutionarily conserved from yeast to mammals. However, RNF20 has diverse physiologic functions in different organisms, which might be caused by the evolutionary divergency of their domain/motif architectures. In the current extra view, we not only elucidate the evolutionarily conserved molecular mechanism underlying H2Bub, but also discuss the diverse physiologic functions of RNF20 during meiosis.

  4. Cis-Acting Determinants Affecting Centromere Function, Sister-Chromatid Cohesion and Reciprocal Recombination during Meiosis in Saccharomyces Cerevisiae

    OpenAIRE

    Sears, D. D.; Hegemann, J. H.; Shero, J. H.; Hieter, P.

    1995-01-01

    We have employed a system that utilizes homologous pairs of human DNA-derived yeast artificial chromosomes (YACs) as marker chromosomes to assess the specific role (s) of conserved centromere DNA elements (CDEI, CDEII and CDEIII) in meiotic chromosome disjunction fidelity. Thirteen different centromere (CEN) mutations were tested for their effects on meiotic centromere function. YACs containing a wild-type CEN DNA sequence segregate with high fidelity in meiosis I (99% normal segregation) and...

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

    Directory of Open Access Journals (Sweden)

    Yukinobu Hirose

    2011-03-01

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

  6. Phosphorylation of the Synaptonemal Complex Protein Zip1 Regulates the Crossover/Noncrossover Decision during Yeast Meiosis.

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    Xiangyu Chen

    2015-12-01

    Full Text Available Interhomolog crossovers promote proper chromosome segregation during meiosis and are formed by the regulated repair of programmed double-strand breaks. This regulation requires components of the synaptonemal complex (SC, a proteinaceous structure formed between homologous chromosomes. In yeast, SC formation requires the "ZMM" genes, which encode a functionally diverse set of proteins, including the transverse filament protein, Zip1. In wild-type meiosis, Zmm proteins promote the biased resolution of recombination intermediates into crossovers that are distributed throughout the genome by interference. In contrast, noncrossovers are formed primarily through synthesis-dependent strand annealing mediated by the Sgs1 helicase. This work identifies a conserved region on the C terminus of Zip1 (called Zip1 4S, whose phosphorylation is required for the ZMM pathway of crossover formation. Zip1 4S phosphorylation is promoted both by double-strand breaks (DSBs and the meiosis-specific kinase, MEK1/MRE4, demonstrating a role for MEK1 in the regulation of interhomolog crossover formation, as well as interhomolog bias. Failure to phosphorylate Zip1 4S results in meiotic prophase arrest, specifically in the absence of SGS1. This gain of function meiotic arrest phenotype is suppressed by spo11Δ, suggesting that it is due to unrepaired breaks triggering the meiotic recombination checkpoint. Epistasis experiments combining deletions of individual ZMM genes with sgs1-md zip1-4A indicate that Zip1 4S phosphorylation functions prior to the other ZMMs. These results suggest that phosphorylation of Zip1 at DSBs commits those breaks to repair via the ZMM pathway and provides a mechanism by which the crossover/noncrossover decision can be dynamically regulated during yeast meiosis.

  7. Dual roles of TRF1 in tethering telomeres to the nuclear envelope and protecting them from fusion during meiosis.

    Science.gov (United States)

    Wang, Lina; Tu, Zhaowei; Liu, Chao; Liu, Hongbin; Kaldis, Philipp; Chen, Zijiang; Li, Wei

    2018-01-08

    Telomeres integrity is indispensable for chromosomal stability by preventing chromosome erosion and end-to-end fusions. During meiosis, telomeres attach to the inner nuclear envelope and cluster into a highly crowded microenvironment at the bouquet stage, which requires specific mechanisms to protect the telomeres from fusion. Here, we demonstrate that germ cell-specific knockout of a shelterin complex subunit, Trf1, results in arrest of spermatocytes at two different stages. The obliterated telomere-nuclear envelope attachment in Trf1-deficient spermatocytes impairs homologue synapsis and recombination, resulting in a pachytene-like arrest, while the meiotic division arrest might stem from chromosome end-to-end fusion due to the failure of recruiting meiosis specific telomere associated proteins. Further investigations uncovered that TRF1 could directly interact with Speedy A, and Speedy A might work as a scaffold protein to further recruit Cdk2, thus protecting telomeres from fusion at this stage. Together, our results reveal a novel mechanism of TRF1, Speedy A, and Cdk2 in protecting telomere from fusion in a highly crowded microenvironment during meiosis.

  8. Meiosis-specific cohesin component, Stag3 is essential for maintaining centromere chromatid cohesion, and required for DNA repair and synapsis between homologous chromosomes.

    Science.gov (United States)

    Hopkins, Jessica; Hwang, Grace; Jacob, Justin; Sapp, Nicklas; Bedigian, Rick; Oka, Kazuhiro; Overbeek, Paul; Murray, Steve; Jordan, Philip W

    2014-07-01

    Cohesins are important for chromosome structure and chromosome segregation during mitosis and meiosis. Cohesins are composed of two structural maintenance of chromosomes (SMC1-SMC3) proteins that form a V-shaped heterodimer structure, which is bridged by a α-kleisin protein and a stromal antigen (STAG) protein. Previous studies in mouse have shown that there is one SMC1 protein (SMC1β), two α-kleisins (RAD21L and REC8) and one STAG protein (STAG3) that are meiosis-specific. During meiosis, homologous chromosomes must recombine with one another in the context of a tripartite structure known as the synaptonemal complex (SC). From interaction studies, it has been shown that there are at least four meiosis-specific forms of cohesin, which together with the mitotic cohesin complex, are lateral components of the SC. STAG3 is the only meiosis-specific subunit that is represented within all four meiosis-specific cohesin complexes. In Stag3 mutant germ cells, the protein level of other meiosis-specific cohesin subunits (SMC1β, RAD21L and REC8) is reduced, and their localization to chromosome axes is disrupted. In contrast, the mitotic cohesin complex remains intact and localizes robustly to the meiotic chromosome axes. The instability of meiosis-specific cohesins observed in Stag3 mutants results in aberrant DNA repair processes, and disruption of synapsis between homologous chromosomes. Furthermore, mutation of Stag3 results in perturbation of pericentromeric heterochromatin clustering, and disruption of centromere cohesion between sister chromatids during meiotic prophase. These defects result in early prophase I arrest and apoptosis in both male and female germ cells. The meiotic defects observed in Stag3 mutants are more severe when compared to single mutants for Smc1β, Rec8 and Rad21l, however they are not as severe as the Rec8, Rad21l double mutants. Taken together, our study demonstrates that STAG3 is required for the stability of all meiosis-specific cohesin

  9. Meiosis-specific cohesin component, Stag3 is essential for maintaining centromere chromatid cohesion, and required for DNA repair and synapsis between homologous chromosomes.

    Directory of Open Access Journals (Sweden)

    Jessica Hopkins

    2014-07-01

    Full Text Available Cohesins are important for chromosome structure and chromosome segregation during mitosis and meiosis. Cohesins are composed of two structural maintenance of chromosomes (SMC1-SMC3 proteins that form a V-shaped heterodimer structure, which is bridged by a α-kleisin protein and a stromal antigen (STAG protein. Previous studies in mouse have shown that there is one SMC1 protein (SMC1β, two α-kleisins (RAD21L and REC8 and one STAG protein (STAG3 that are meiosis-specific. During meiosis, homologous chromosomes must recombine with one another in the context of a tripartite structure known as the synaptonemal complex (SC. From interaction studies, it has been shown that there are at least four meiosis-specific forms of cohesin, which together with the mitotic cohesin complex, are lateral components of the SC. STAG3 is the only meiosis-specific subunit that is represented within all four meiosis-specific cohesin complexes. In Stag3 mutant germ cells, the protein level of other meiosis-specific cohesin subunits (SMC1β, RAD21L and REC8 is reduced, and their localization to chromosome axes is disrupted. In contrast, the mitotic cohesin complex remains intact and localizes robustly to the meiotic chromosome axes. The instability of meiosis-specific cohesins observed in Stag3 mutants results in aberrant DNA repair processes, and disruption of synapsis between homologous chromosomes. Furthermore, mutation of Stag3 results in perturbation of pericentromeric heterochromatin clustering, and disruption of centromere cohesion between sister chromatids during meiotic prophase. These defects result in early prophase I arrest and apoptosis in both male and female germ cells. The meiotic defects observed in Stag3 mutants are more severe when compared to single mutants for Smc1β, Rec8 and Rad21l, however they are not as severe as the Rec8, Rad21l double mutants. Taken together, our study demonstrates that STAG3 is required for the stability of all meiosis

  10. Genetic Interactions Between the Meiosis-Specific Cohesin Components, STAG3, REC8, and RAD21L.

    Science.gov (United States)

    Ward, Ayobami; Hopkins, Jessica; Mckay, Matthew; Murray, Steve; Jordan, Philip W

    2016-06-01

    Cohesin is an essential structural component of chromosomes that ensures accurate chromosome segregation during mitosis and meiosis. Previous studies have shown that there are cohesin complexes specific to meiosis, required to mediate homologous chromosome pairing, synapsis, recombination, and segregation. Meiosis-specific cohesin complexes consist of two structural maintenance of chromosomes proteins (SMC1α/SMC1β and SMC3), an α-kleisin protein (RAD21, RAD21L, or REC8), and a stromal antigen protein (STAG1, 2, or 3). STAG3 is exclusively expressed during meiosis, and is the predominant STAG protein component of cohesin complexes in primary spermatocytes from mouse, interacting directly with each α-kleisin subunit. REC8 and RAD21L are also meiosis-specific cohesin components. Stag3 mutant spermatocytes arrest in early prophase ("zygotene-like" stage), displaying failed homolog synapsis and persistent DNA damage, as a result of unstable loading of cohesin onto the chromosome axes. Interestingly, Rec8, Rad21L double mutants resulted in an earlier "leptotene-like" arrest, accompanied by complete absence of STAG3 loading. To assess genetic interactions between STAG3 and α-kleisin subunits RAD21L and REC8, our lab generated Stag3, Rad21L, and Stag3, Rec8 double knockout mice, and compared them to the Rec8, Rad21L double mutant. These double mutants are phenotypically distinct from one another, and more severe than each single knockout mutant with regards to chromosome axis formation, cohesin loading, and sister chromatid cohesion. The Stag3, Rad21L, and Stag3, Rec8 double mutants both progress further into prophase I than the Rec8, Rad21L double mutant. Our genetic analysis demonstrates that cohesins containing STAG3 and REC8 are the main complex required for centromeric cohesion, and RAD21L cohesins are required for normal clustering of pericentromeric heterochromatin. Furthermore, the STAG3/REC8 and STAG3/RAD21L cohesins are the primary cohesins required for

  11. The temporal and spatial distribution of the proliferation associated Ki-67 protein during female and male meiosis.

    Science.gov (United States)

    Traut, Walther; Endl, Elmar; Scholzen, Thomas; Gerdes, Johannes; Winking, Heinz

    2002-09-01

    We used immunolocalization in tissue sections and cytogenetic preparations of female and male gonads to study the distribution of the proliferation marker pKi-67 during meiotic cell cycles of the house mouse, Mus musculus. During male meiosis, pKi-67 was continuously present in nuclei of all stages from the spermatogonium through spermatocytes I and II up to the earliest spermatid stage (early round spermatids) when it appeared to fade out. It was not detected in later spermatid stages or sperm. During female meiosis, pKi-67 was present in prophase I oocytes of fetal ovaries. It was absent in oocytes from newborn mice and most oocytes of primordial follicles from adults. The Ki-67 protein reappeared in oocytes of growing follicles and was continuously present up to metaphase II. Thus, pKi-67 was present in all stages of cell growth and cell division while it was absent from resting oocytes and during the main stages of spermiocytogenesis. Progression through the meiotic cell cycle was associated with extensive intranuclear relocation of pKi-67. In the zygotene and pachytene stages, most of the pKi-67 colocalized with centromeric (centric and pericentric) heterochromatin and adjacent nucleoli; the heterochromatic XY body in male pachytene, however, was free of pKi-67. At early diplotene, pKi-67 was mainly associated with nucleoli. At late diplotene, diakinesis, metaphase I and metaphase II of meiosis, pKi-67 preferentially bound to the perichromosomal layer and was almost absent from the heterochromatic centromeric regions of the chromosomes. After the second division of male meiosis, the protein reappeared at the centromeric heterochromatin and an adjacent region in the earliest spermatid stage and then faded out. The general patterns of pKi-67 distribution were comparable to those in mitotic cell cycles. With respect to the timing, it is interesting to note that relocation from the nucleolus to the perichromosomal layer takes place at the G2/M-phase transition in

  12. Interplay between microtubule bundling and sorting factors ensures acentriolar spindle stability during C. elegans oocyte meiosis.

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    Timothy J Mullen

    2017-09-01

    Full Text Available In many species, oocyte meiosis is carried out in the absence of centrioles. As a result, microtubule organization, spindle assembly, and chromosome segregation proceed by unique mechanisms. Here, we report insights into the principles underlying this specialized form of cell division, through studies of C. elegans KLP-15 and KLP-16, two highly homologous members of the kinesin-14 family of minus-end-directed kinesins. These proteins localize to the acentriolar oocyte spindle and promote microtubule bundling during spindle assembly; following KLP-15/16 depletion, microtubule bundles form but then collapse into a disorganized array. Surprisingly, despite this defect we found that during anaphase, microtubules are able to reorganize into a bundled array that facilitates chromosome segregation. This phenotype therefore enabled us to identify factors promoting microtubule organization during anaphase, whose contributions are normally undetectable in wild-type worms; we found that SPD-1 (PRC1 bundles microtubules and KLP-18 (kinesin-12 likely sorts those bundles into a functional orientation capable of mediating chromosome segregation. Therefore, our studies have revealed an interplay between distinct mechanisms that together promote spindle formation and chromosome segregation in the absence of structural cues such as centrioles.

  13. Distinct mechanisms eliminate mother and daughter centrioles in meiosis of starfish oocytes.

    Science.gov (United States)

    Borrego-Pinto, Joana; Somogyi, Kálmán; Karreman, Matthia A; König, Julia; Müller-Reichert, Thomas; Bettencourt-Dias, Mónica; Gönczy, Pierre; Schwab, Yannick; Lénárt, Péter

    2016-03-28

    Centriole elimination is an essential process that occurs in female meiosis of metazoa to reset centriole number in the zygote at fertilization. How centrioles are eliminated remains poorly understood. Here we visualize the entire elimination process live in starfish oocytes. Using specific fluorescent markers, we demonstrate that the two older, mother centrioles are selectively removed from the oocyte by extrusion into polar bodies. We show that this requires specific positioning of the second meiotic spindle, achieved by dynein-driven transport, and anchorage of the mother centriole to the plasma membrane via mother-specific appendages. In contrast, the single daughter centriole remaining in the egg is eliminated before the first embryonic cleavage. We demonstrate that these distinct elimination mechanisms are necessary because if mother centrioles are artificially retained, they cannot be inactivated, resulting in multipolar zygotic spindles. Thus, our findings reveal a dual mechanism to eliminate centrioles: mothers are physically removed, whereas daughters are eliminated in the cytoplasm, preparing the egg for fertilization. © 2016 Borrego-Pinto et al.

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

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    Fabiana Fabbretti

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

  15. Maternal SENP7 programs meiosis architecture and embryo survival in mouse.

    Science.gov (United States)

    Huang, Chun-Jie; Wu, Di; Jiao, Xiao-Fei; Khan, Faheem Ahmed; Xiong, Cheng-Liang; Liu, Xiao-Ming; Yang, Jing; Yin, Tai-Lang; Huo, Li-Jun

    2017-07-01

    Understanding the mechanisms underlying abnormal egg production and pregnancy loss is significant for human fertility. SENP7, a SUMO poly-chain editing enzyme, has been regarded as a mitotic regulator of heterochromatin integrity and DNA repair. Herein, we report the roles of SENP7 in mammalian reproductive scenario. Mouse oocytes deficient in SENP7 experienced meiotic arrest at prophase I and metaphase I stages, causing a substantial decrease of mature eggs. Hyperaceylation and hypomethylation of histone H3 and up-regulation of Cdc14B/C accompanied by down-regulation of CyclinB1 and CyclinB2 were further recognized as contributors to defective M-phase entry and spindle assembly in oocytes. The spindle assembly checkpoint activated by defective spindle morphogenesis, which was also caused by mislocalization and ubiquitylation-mediated proteasomal degradation of γ-tubulin, blocked oocytes at meiosis I stage. SENP7-depleted embryos exhibited severely defective maternal-zygotic transition and progressive degeneration, resulting in nearly no blastocyst production. The disrupted epigenetic landscape on histone H3 restricted Rad51C loading onto DNA lesions due to elevated HP1α euchromatic deposition, and reduced DNA 5hmC challenged the permissive status for zygotic DNA repair, which induce embryo death. Our study pinpoints SENP7 as a novel determinant in epigenetic programming and major pathways that govern oocyte and embryo development programs in mammals. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Ndj1, a telomere-associated protein, regulates centrosome separation in budding yeast meiosis

    Science.gov (United States)

    Li, Ping; Shao, Yize; Jin, Hui

    2015-01-01

    Yeast centrosomes (called spindle pole bodies [SPBs]) remain cohesive for hours during meiotic G2 when recombination takes place. In contrast, SPBs separate within minutes after duplication in vegetative cells. We report here that Ndj1, a previously known meiosis-specific telomere-associated protein, is required for protecting SPB cohesion. Ndj1 localizes to the SPB but dissociates from it ∼16 min before SPB separation. Without Ndj1, meiotic SPBs lost cohesion prematurely, whereas overproduction of Ndj1 delayed SPB separation. When produced ectopically in vegetative cells, Ndj1 caused SPB separation defects and cell lethality. Localization of Ndj1 to the SPB depended on the SUN domain protein Mps3, and removal of the N terminus of Mps3 allowed SPB separation and suppressed the lethality of NDJ1-expressing vegetative cells. Finally, we show that Ndj1 forms oligomeric complexes with Mps3, and that the Polo-like kinase Cdc5 regulates Ndj1 protein stability and SPB separation. These findings reveal the underlying mechanism that coordinates yeast centrosome dynamics with meiotic telomere movement and cell cycle progression. PMID:25897084

  17. Effects of 2450 MHz microwave radiation on meiosis and reproduction in male mice

    International Nuclear Information System (INIS)

    Manikowska-Czerska, E.; Czerski, P.; Leach, W.M.

    1988-01-01

    A series of studies to examine effects od continuous wave 2450 MHz radiation on meiosis and on chromosomes of germ cells in male CBA/CAY or ICR mice, by means of the spermatocyte (SCT), heritable translocation (HTT) and dominant lethal (DLT) tests is presented. Animals were exposed in an environmentally controlled waveguide system during two consecutive weeks, 30 minutes daily, six days a week. Specific absorption rates (SAR) were used in the range from 0.05 to 20 W/kg. With the SCT, it was demonstrated that chromosomal translocations can be induced by exposure during the first meiotic prophase, particularly during initial and early pachytene stages. The HTT results demonstrated that balanced translocations may be recovered among offspring of exposed males. The DLT provided confirmatory data on effects during prophase and indicated that chromosomal damage may be also induced by exposure of spermatids, during the maturation stage, and of spermatozoa. No changes were observed in spermatogonia. Thus, the effects of exposure were limited to one spermatogenic cycle. Genetically significant effects were induced at an SAR of 2 W/kg in the testes. For comparison, an SAR of 0.4 W/kg is used commonly as a basis for occupational exposure limits

  18. Noninvasive three-dimensional live imaging methodology for the spindles at meiosis and mitosis

    Science.gov (United States)

    Zheng, Jing-gao; Huo, Tiancheng; Tian, Ning; Chen, Tianyuan; Wang, Chengming; Zhang, Ning; Zhao, Fengying; Lu, Danyu; Chen, Dieyan; Ma, Wanyun; Sun, Jia-lin; Xue, Ping

    2013-05-01

    The spindle plays a crucial role in normal chromosome alignment and segregation during meiosis and mitosis. Studying spindles in living cells noninvasively is of great value in assisted reproduction technology (ART). Here, we present a novel spindle imaging methodology, full-field optical coherence tomography (FF-OCT). Without any dye labeling and fixation, we demonstrate the first successful application of FF-OCT to noninvasive three-dimensional (3-D) live imaging of the meiotic spindles within the mouse living oocytes at metaphase II as well as the mitotic spindles in the living zygotes at metaphase and telophase. By post-processing of the 3-D dataset obtained with FF-OCT, the important morphological and spatial parameters of the spindles, such as short and long axes, spatial localization, and the angle of meiotic spindle deviation from the first polar body in the oocyte were precisely measured with the spatial resolution of 0.7 μm. Our results reveal the potential of FF-OCT as an imaging tool capable of noninvasive 3-D live morphological analysis for spindles, which might be useful to ART related procedures and many other spindle related studies.

  19. Bloom syndrome helicase in meiosis: Pro-crossover functions of an anti-crossover protein.

    Science.gov (United States)

    Hatkevich, Talia; Sekelsky, Jeff

    2017-09-01

    The functions of the Bloom syndrome helicase (BLM) and its orthologs are well characterized in mitotic DNA damage repair, but their roles within the context of meiotic recombination are less clear. In meiotic recombination, multiple repair pathways are used to repair meiotic DSBs, and current studies suggest that BLM may regulate the use of these pathways. Based on literature from Saccharomyces cerevisiae, Arabidopsis thaliana, Mus musculus, Drosophila melanogaster, and Caenorhabditis elegans, we present a unified model for a critical meiotic role of BLM and its orthologs. In this model, BLM and its orthologs utilize helicase activity to regulate the use of various pathways in meiotic recombination by continuously disassembling recombination intermediates. This unwinding activity provides the meiotic program with a steady pool of early recombination substrates, increasing the probability for a DSB to be processed by the appropriate pathway. As a result of BLM activity, crossovers are properly placed throughout the genome, promoting proper chromosomal disjunction at the end of meiosis. This unified model can be used to further refine the complex role of BLM and its orthologs in meiotic recombination. © 2017 WILEY Periodicals, Inc.

  20. Recombinational hotspot specific to female meiosis in the mouse major histocompatibility complex.

    Science.gov (United States)

    Shiroishi, T; Hanzawa, N; Sagai, T; Ishiura, M; Gojobori, T; Steinmetz, M; Moriwaki, K

    1990-01-01

    The wm7 haplotype of the major histocompatibility complex (MHC), derived from the Japanese wild mouse Mus musculus molossinus, enhances recombination specific to female meiosis in the K/A beta interval of the MHC. We have mapped crossover points of fifteen independent recombinants from genetic crosses of the wm7 and laboratory haplotypes. Most of them were confined to a short segment of approximately 1 kilobase (kb) of DNA between the A beta 3 and A beta 2 genes, indicating the presence of a female-specific recombinational hotspot. Its location overlaps with a sex-independent hotspot previously identified in the Mus musculus castaneus CAS3 haplotype. We have cloned and sequenced DNA fragments surrounding the hotspot from the wm7 haplotype and the corresponding regions from the hotspot-negative B10.A and C57BL/10 strains. There is no significant difference between the sequences of these three strains, or between these and the published sequences of the CAS3 and C57BL/6 strains. However, a comparison of this A beta 3/A beta 2 hotspot with a previously characterized hotspot in the E beta gene revealed that they have a very similar molecular organization. Each hotspot consists of two elements, the consensus sequence of the mouse middle repetitive MT family and the tetrameric repeated sequences, which are separated by 1 kb of DNA.

  1. LIM kinase activity is required for microtubule organising centre positioning in mouse oocyte meiosis.

    Science.gov (United States)

    Li, Xin; Zhu, Yubo; Cao, Yan; Wang, Qian; Du, Juan; Tian, Jianhui; Liang, Yuanjing; Ma, Wei

    2017-04-01

    LIM kinase 1 (LIMK1) activity is essential for cell migration and cell cycle progression. Little is known about LIMK1 expression and function in mammalian oocytes. In the present study we assessed LIMK1 protein expression, subcellular distribution and function during mouse oocyte meiosis. Western blot analysis revealed high and stable expression of LIMK1 from the germinal vesicle (GV) to MII stage. In contrast, activated LIMK1 (i.e. LIMK1 phosphorylated at threonine 508 (pLIMK1 Thr508 )) was only detected after GV breakdown, with levels increasing gradually to peak at MI and MII. Immunofluorescence showed pLIMK1 Thr508 was colocalised with the microtubule organising centre (MTOC) components pericentrin and γ-tubulin at the spindle poles. A direct interaction between γ-tubulin and pLIMK1 Thr508 was confirmed by co-immunoprecipitation. LIMK inhibition with 1μM BMS3 damaged MTOC protein localisation to spindle poles, undermined the formation and positioning of functional MTOC and thus disrupted spindle formation and chromosome alignment. These effects were phenocopied by microinjection of LIMK1 antibody into mouse oocytes. In summary, the data demonstrate that LIMK activity is essential for MTOC organisation and distribution and so bipolar spindle formation and maintenance in mouse oocytes.

  2. Sequential actin-based pushing forces drive meiosis I chromosome migration and symmetry breaking in oocytes

    Science.gov (United States)

    Yi, Kexi; Rubinstein, Boris; Unruh, Jay R.; Guo, Fengli; Slaughter, Brian D.

    2013-01-01

    Polar body extrusion during oocyte maturation is critically dependent on asymmetric positioning of the meiotic spindle, which is established through migration of the meiosis I (MI) spindle/chromosomes from the oocyte interior to a subcortical location. In this study, we show that MI chromosome migration is biphasic and driven by consecutive actin-based pushing forces regulated by two actin nucleators, Fmn2, a formin family protein, and the Arp2/3 complex. Fmn2 was recruited to endoplasmic reticulum structures surrounding the MI spindle, where it nucleated actin filaments to initiate an initially slow and poorly directed motion of the spindle away from the cell center. A fast and highly directed second migration phase was driven by actin-mediated cytoplasmic streaming and occurred as the chromosomes reach a sufficient proximity to the cortex to activate the Arp2/3 complex. We propose that decisive symmetry breaking in mouse oocytes results from Fmn2-mediated perturbation of spindle position and the positive feedback loop between chromosome signal-induced Arp2/3 activation and Arp2/3-orchestrated cytoplasmic streaming that transports the chromosomes. PMID:23439682

  3. Expression and functional analysis of TaASY1 during meiosis of bread wheat (Triticum aestivum

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    Langridge Peter

    2007-08-01

    Full Text Available Abstract Background Pairing and synapsis of homologous chromosomes is required for normal chromosome segregation and the exchange of genetic material via recombination during meiosis. Synapsis is complete at pachytene following the formation of a tri-partite proteinaceous structure known as the synaptonemal complex (SC. In yeast, HOP1 is essential for formation of the SC, and localises along chromosome axes during prophase I. Homologues in Arabidopsis (AtASY1, Brassica (BoASY1 and rice (OsPAIR2 have been isolated through analysis of mutants that display decreased fertility due to severely reduced synapsis of homologous chromosomes. Analysis of these genes has indicated that they play a similar role to HOP1 in pairing and formation of the SC through localisation to axial/lateral elements of the SC. Results The full length wheat cDNA and genomic clone, TaASY1, has been isolated, sequenced and characterised. TaASY1 is located on chromosome Group 5 and the open reading frame displays significant nucleotide sequence identity to OsPAIR2 (84% and AtASY1 (63%. Transcript and protein analysis showed that expression is largely restricted to meiotic tissue, with elevated levels during the stages of prophase I when pairing and synapsis of homologous chromosomes occur. Immunolocalisation using transmission electron microscopy showed TaASY1 interacts with chromatin that is associated with both axial elements before SC formation as well as lateral elements of formed SCs. Conclusion TaASY1 is a homologue of ScHOP1, AtASY1 and OsPAIR2 and is the first gene to be isolated from bread wheat that is involved in pairing and synapsis of homologous chromosomes.

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

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    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.

  5. Revisiting Meiosis in Sugarcane: Chromosomal Irregularities and the Prevalence of Bivalent Configurations

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    Maria Lucia C. Vieira

    2018-06-01

    Full Text Available Traditional sugarcane cultivars (Saccharum officinarum proved highly susceptible to diseases, and this led breeders to progress to interspecific crosses resulting in disease resistance. A backcrossing program to S. officinarum was then required to boost sucrose content. Clonal selection across generations and incorporation of other germplasm into cultivated backgrounds established the (narrow genetic base of modern cultivars (Saccharum spp., which have a man-made genome. The genome complexity has inspired several molecular studies that have elucidated aspects of sugarcane genome constitution, architecture, and cytogenetics. However, there is a critical shortage of information on chromosome behavior throughout meiosis in modern cultivars. In this study, we examined the microsporogenesis of a contemporary variety, providing a detailed analysis of the meiotic process and chromosome association at diakinesis, using FISH with centromeric probes. Chromosomal abnormalities were documented by examining high quality preparations of pollen mother cells (700 in total. Approximately 70% of the cells showed abnormalities, such as metaphase chromosomes not lined up at the plate, lagging chromosomes and chromosomal bridges, and tetrad cells with micronuclei. Some dyads with asynchronous behavior were also observed. Due to the hybrid composition of the sugarcane genome, we suggest that bivalent incomplete pairing may occur in the first prophase leading to univalency. The presence of rod bivalents showing the lagging tendency is consistent with a reduction in chiasma frequency. Finally, the presence of chromatin bridges indicates the indirect occurrence of chromosomal inversions, although chromosome fragments were not clearly recognized. Possible reasons for such meiotic abnormalities and the large prevalence of bivalent formation are discussed.

  6. Joint molecule resolution requires the redundant activities of MUS-81 and XPF-1 during Caenorhabditis elegans meiosis.

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    Nigel J O'Neil

    Full Text Available The generation and resolution of joint molecule recombination intermediates is required to ensure bipolar chromosome segregation during meiosis. During wild type meiosis in Caenorhabditis elegans, SPO-11-generated double stranded breaks are resolved to generate a single crossover per bivalent and the remaining recombination intermediates are resolved as noncrossovers. We discovered that early recombination intermediates are limited by the C. elegans BLM ortholog, HIM-6, and in the absence of HIM-6 by the structure specific endonuclease MUS-81. In the absence of both MUS-81 and HIM-6, recombination intermediates persist, leading to chromosome breakage at diakinesis and inviable embryos. MUS-81 has an additional role in resolving late recombination intermediates in C. elegans. mus-81 mutants exhibited reduced crossover recombination frequencies suggesting that MUS-81 is required to generate a subset of meiotic crossovers. Similarly, the Mus81-related endonuclease XPF-1 is also required for a subset of meiotic crossovers. Although C. elegans gen-1 mutants have no detectable meiotic defect either alone or in combination with him-6, mus-81 or xpf-1 mutations, mus-81;xpf-1 double mutants are synthetic lethal. While mus-81;xpf-1 double mutants are proficient for the processing of early recombination intermediates, they exhibit defects in the post-pachytene chromosome reorganization and the asymmetric disassembly of the synaptonemal complex, presumably triggered by crossovers or crossover precursors. Consistent with a defect in resolving late recombination intermediates, mus-81; xpf-1 diakinetic bivalents are aberrant with fine DNA bridges visible between two distinct DAPI staining bodies. We were able to suppress the aberrant bivalent phenotype by microinjection of activated human GEN1 protein, which can cleave Holliday junctions, suggesting that the DNA bridges in mus-81; xpf-1 diakinetic oocytes are unresolved Holliday junctions. We propose that the

  7. DNA double strand breaks but not interstrand crosslinks prevent progress through meiosis in fully grown mouse oocytes.

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    Wai Shan Yuen

    Full Text Available There is some interest in how mammalian oocytes respond to different types of DNA damage because of the increasing expectation of fertility preservation in women undergoing chemotherapy. Double strand breaks (DSBs induced by ionizing radiation and agents such as neocarzinostatin (NCS, and interstrand crosslinks (ICLs induced by alkylating agents such as mitomycin C (MMC, are toxic DNA lesions that need to be repaired for cell survival. Here we examined the effects of NCS and MMC treatment on oocytes collected from antral follicles in mice, because potentially such oocytes are readily collected from ovaries and do not need to be in vitro grown to achieve meiotic competency. We found that oocytes were sensitive to NCS, such that this ionizing radiation mimetic blocked meiosis I and caused fragmented DNA. In contrast, MMC had no impact on the completion of either meiosis I or II, even at extremely high doses. However, oocytes treated with MMC did show γ-H2AX foci and following their in vitro maturation and parthenogenetic activation the development of the subsequent embryos was severely compromised. Addition of MMC to 1-cell embryos caused a similarly poor level of development, demonstrating oocytes have eventual sensitivity to this ICL-inducing agent but this does not occur during their meiotic division. In oocytes, the association of Fanconi Anemia protein, FANCD2, with sites of ICL lesions was not apparent until entry into the embryonic cell cycle. In conclusion, meiotic maturation of oocytes is sensitive to DSBs but not ICLs. The ability of oocytes to tolerate severe ICL damage and yet complete meiosis, means that this type of DNA lesion goes unrepaired in oocytes but impacts on subsequent embryo quality.

  8. Upregulation of meiosis-specific genes in lymphoma cell lines following genotoxic insult and induction of mitotic catastrophe

    International Nuclear Information System (INIS)

    Kalejs, Martins; Ivanov, Andrey; Plakhins, Gregory; Cragg, Mark S; Emzinsh, Dzintars; Illidge, Timothy M; Erenpreisa, Jekaterina

    2006-01-01

    We have previously reported that p53 mutated radioresistant lymphoma cell lines undergo mitotic catastrophe after irradiation, resulting in metaphase arrest and the generation of endopolyploid cells. A proportion of these endopolyploid cells then undergo a process of de-polyploidisation, stages of which are partially reminiscent of meiotic prophase. Furthermore, expression of meiosis-specific proteins of the cancer/testis antigens group of genes has previously been reported in tumours. We therefore investigated whether expression of meiosis-specific genes was associated with the polyploidy response in our tumour model. Three lymphoma cell lines, Namalwa, WI-L2-NS and TK6, of varying p53 status were exposed to a single 10 Gy dose of gamma radiation and their responses assessed over an extended time course. DNA flow cytometry and mitotic counts were used to assess the kinetics and extent of polyploidisation and mitotic progression. Expression of meiotic genes was analysed using RT-PCR and western blotting. In addition, localisation of the meiotic cohesin REC8 and its relation to centromeres was analysed by immunofluorescence. The principal meiotic regulator MOS was found to be significantly post-transcriptionally up-regulated after irradiation in p53 mutated but not p53 wild-type lymphoma cells. The maximum expression of MOS coincided with the maximal fraction of metaphase arrested cells and was directly proportional to both the extent of the arrest and the number of endopolyploid cells that subsequently emerged. The meiotic cohesin REC8 was also found to be up-regulated after irradiation, linking sister chromatid centromeres in the metaphase-arrested and subsequent giant cells. Finally, RT-PCR revealed expression of the meiosis-prophase genes, DMC1, STAG3, SYCP3 and SYCP1. We conclude that multiple meiotic genes are aberrantly activated during mitotic catastrophe in p53 mutated lymphoma cells after irradiation. Furthermore, we suggest that the coordinated expression

  9. Constitutive Activation of the Fission Yeast Pheromone-Responsive Pathway Induces Ectopic Meiosis and Reveals Ste11 as a Mitogen-Activated Protein Kinase Target

    DEFF Research Database (Denmark)

    Kjærulff, Søren; Lautrup-Larsen, I.; Truelsen, S.

    2005-01-01

    In the fission yeast Schizosaccharomyces pombe, meiosis normally takes place in diploid zygotes resulting from conjugation of haploid cells. In the present study, we report that the expression of a constitutively activated version of the pheromone-responsive mitogen-activated protein kinase kinase...... found that haploid meiosis was dramatically reduced when Ste11 was mutated to mimic phosphorylation by Pat1. The mutation of two putative MAPK sites in Ste11 also dramatically reduced the level of haploid meiosis, suggesting that Ste11 is a direct target of Spk1. Supporting this, we show that Spk1 can...... interact physically with Ste11 and also phosphorylate the transcription factor in vitro. Finally, we demonstrate that ste11 is required for pheromone-induced G1 arrest. Interestingly, when we mutated Ste11 in the sites for Pat1 and Spk1 phosphorylation simultaneously, the cells could still arrest in G1...

  10. Csm4, in collaboration with Ndj1, mediates telomere-led chromosome dynamics and recombination during yeast meiosis.

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    Jennifer J Wanat

    2008-09-01

    Full Text Available Chromosome movements are a general feature of mid-prophase of meiosis. In budding yeast, meiotic chromosomes exhibit dynamic movements, led by nuclear envelope (NE-associated telomeres, throughout the zygotene and pachytene stages. Zygotene motion underlies the global tendency for colocalization of NE-associated chromosome ends in a "bouquet." In this study, we identify Csm4 as a new molecular participant in these processes and show that, unlike the two previously identified components, Ndj1 and Mps3, Csm4 is not required for meiosis-specific telomere/NE association. Instead, it acts to couple telomere/NE ensembles to a force generation mechanism. Mutants lacking Csm4 and/or Ndj1 display the following closely related phenotypes: (i elevated crossover (CO frequencies and decreased CO interference without abrogation of normal pathways; (ii delayed progression of recombination, and recombination-coupled chromosome morphogenesis, with resulting delays in the MI division; and (iii nondisjunction of homologs at the MI division for some reason other than absence of (the obligatory CO(s. The recombination effects are discussed in the context of a model where the underlying defect is chromosome movement, the absence of which results in persistence of inappropriate chromosome relationships that, in turn, results in the observed mutant phenotypes.

  11. Unique properties of multiple tandem copies of the M26 recombination hotspot in mitosis and meiosis in Schizosaccharomyces pombe.

    Science.gov (United States)

    Steiner, Walter W; Recor, Chelsea L; Zakrzewski, Bethany M

    2016-11-15

    The M26 hotspot of the fission yeast Schizosaccharomyces pombe is one of the best-characterized eukaryotic hotspots of recombination. The hotspot requires a seven bp sequence, ATGACGT, that serves as a binding site for the Atf1-Pcr1 transcription factor, which is also required for activity. The M26 hotspot is active in meiosis but not mitosis and is active in some but not all chromosomal contexts and not on a plasmid. A longer palindromic version of M26, ATGACGTCAT, shows significantly greater activity than the seven bp sequence. Here, we tested whether the properties of the seven bp sequence were also true of the longer sequence by placing one, two, or three copies of the sequence into the ade6 gene, where M26 was originally discovered. These constructs were tested for activity when located on a plasmid or on a chromosome in mitosis and meiosis. We found that two copies of the 10bp M26 motif on a chromosome were significantly more active for meiotic recombination than one, but no further increase was observed with three copies. However, three copies of M26 on a chromosome created an Atf1-dependent mitotic recombination hotspot. When located on a plasmid, M26 also appears to behave as a mitotic recombination hotspot; however, this behavior most likely results from Atf1-dependent inter-allelic complementation between the plasmid and chromosomal ade6 alleles. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Non-introgressive genome chimerisation by malsegregation in autodiploidised allotetraploids during meiosis of Saccharomyces kudriavzevii x Saccharomyces uvarum hybrids.

    Science.gov (United States)

    Karanyicz, Edina; Antunovics, Zsuzsa; Kallai, Z; Sipiczki, M

    2017-06-01

    Saccharomyces strains with chimerical genomes consisting of mosaics of the genomes of different species ("natural hybrids") occur quite frequently among industrial and wine strains. The most widely endorsed hypothesis is that the mosaics are introgressions acquired via hybridisation and repeated backcrosses of the hybrids with one of the parental species. However, the interspecies hybrids are sterile, unable to mate with their parents. Here, we show by analysing synthetic Saccharomyces kudriavzevii x Saccharomyces uvarum hybrids that mosaic (chimeric) genomes can arise without introgressive backcrosses. These species are biologically separated by a double sterility barrier (sterility of allodiploids and F1 sterility of allotetraploids). F1 sterility is due to the diploidisation of the tetraploid meiosis resulting in MAT a /MAT α heterozygosity which suppresses mating in the spores. This barrier can occasionally be broken down by malsegregation of autosyndetically paired chromosomes carrying the MAT loci (loss of MAT heterozygosity). Subsequent malsegregation of additional autosyndetically paired chromosomes and occasional allosyndetic interactions chimerise the hybrid genome. Chromosomes are preferentially lost from the S. kudriavzevii subgenome. The uniparental transmission of the mitochondrial DNA to the hybrids indicates that nucleo-mitochondrial interactions might affect the direction of the genomic changes. We propose the name GARMe (Genome AutoReduction in Meiosis) for this process of genome reduction and chimerisation which involves no introgressive backcrossings. It opens a way to transfer genetic information between species and thus to get one step ahead after hybridisation in the production of yeast strains with beneficial combinations of properties of different species.

  13. The protein expression landscape of mitosis and meiosis in diploid budding yeast.

    Science.gov (United States)

    Becker, Emmanuelle; Com, Emmanuelle; Lavigne, Régis; Guilleux, Marie-Hélène; Evrard, Bertrand; Pineau, Charles; Primig, Michael

    2017-03-06

    Saccharomyces cerevisiae is an established model organism for the molecular analysis of fundamental biological processes. The genomes of numerous strains have been sequenced, and the transcriptome and proteome ofmajor phases during the haploid and diploid yeast life cycle have been determined. However, much less is known about dynamic changes of the proteome when cells switch from mitotic growth to meiotic development. We report a quantitative protein profiling analysis of yeast cell division and differentiation based on mass spectrometry. Information about protein levels was integrated with strand-specific tiling array expression data. We identified a total of 2366 proteins in at least one condition, including 175 proteins showing a statistically significant>5-fold change across the sample set, and 136 proteins detectable in sporulating but not respiring cells. We correlate protein expression patterns with biological processes and molecular function by Gene Ontology term enrichment, chemoprofiling, transcription interference and the formation of double stranded RNAs by overlapping sense/antisense transcripts. Our work provides initial quantitative insight into protein expression in diploid respiring and differentiating yeast cells. Critically, it associates developmentally regulated induction of antisense long noncoding RNAs and double stranded RNAs with fluctuating protein concentrations during growth and development. This integrated genomics analysis helps better understand how the transcriptome and the proteome correlate in diploid yeast cells undergoing mitotic growth in the presence of acetate (respiration) versus meiotic differentiation (Meiosis I and II). The study (i) provides quantitative expression data for 2366 proteins and their cognate mRNAs in at least one sample, (ii) shows strongly fluctuating protein levels during growth and differentiation for 175 cases, and (iii) identifies 136 proteins absent in mitotic but present in meiotic yeast cells. We

  14. Polycomb protein SCML2 associates with USP7 and counteracts histone H2A ubiquitination in the XY chromatin during male meiosis

    NARCIS (Netherlands)

    Luo, Mengcheng; Zhou, Jian; Leu, N. Adrian; Abreu, Carla M.; Wang, Jianle; Anguera, Montserrat C.; de Rooij, Dirk G.; Jasin, Maria; Wang, P. Jeremy

    2015-01-01

    Polycomb group proteins mediate transcriptional silencing in diverse developmental processes. Sex chromosomes undergo chromosome-wide transcription silencing during male meiosis. Here we report that mouse SCML2 (Sex comb on midleg-like 2), an X chromosome-encoded polycomb protein, is specifically

  15. Rice MEL2, the RNA recognition motif (RRM) protein, binds in vitro to meiosis-expressed genes containing U-rich RNA consensus sequences in the 3'-UTR.

    Science.gov (United States)

    Miyazaki, Saori; Sato, Yutaka; Asano, Tomoya; Nagamura, Yoshiaki; Nonomura, Ken-Ichi

    2015-10-01

    Post-transcriptional gene regulation by RNA recognition motif (RRM) proteins through binding to cis-elements in the 3'-untranslated region (3'-UTR) is widely used in eukaryotes to complete various biological processes. Rice MEIOSIS ARRESTED AT LEPTOTENE2 (MEL2) is the RRM protein that functions in the transition to meiosis in proper timing. The MEL2 RRM preferentially associated with the U-rich RNA consensus, UUAGUU[U/A][U/G][A/U/G]U, dependently on sequences and proportionally to MEL2 protein amounts in vitro. The consensus sequences were located in the putative looped structures of the RNA ligand. A genome-wide survey revealed a tendency of MEL2-binding consensus appearing in 3'-UTR of rice genes. Of 249 genes that conserved the consensus in their 3'-UTR, 13 genes spatiotemporally co-expressed with MEL2 in meiotic flowers, and included several genes whose function was supposed in meiosis; such as Replication protein A and OsMADS3. The proteome analysis revealed that the amounts of small ubiquitin-related modifier-like protein and eukaryotic translation initiation factor3-like protein were dramatically altered in mel2 mutant anthers. Taken together with transcriptome and gene ontology results, we propose that the rice MEL2 is involved in the translational regulation of key meiotic genes on 3'-UTRs to achieve the faithful transition of germ cells to meiosis.

  16. SMC5/6 is required for the formation of segregation-competent bivalent chromosomes during meiosis I in mouse oocytes.

    Science.gov (United States)

    Hwang, Grace; Sun, Fengyun; O'Brien, Marilyn; Eppig, John J; Handel, Mary Ann; Jordan, Philip W

    2017-05-01

    SMC complexes include three major classes: cohesin, condensin and SMC5/6. However, the localization pattern and genetic requirements for the SMC5/6 complex during mammalian oogenesis have not previously been examined. In mouse oocytes, the SMC5/6 complex is enriched at the pericentromeric heterochromatin, and also localizes along chromosome arms during meiosis. The infertility phenotypes of females with a Zp3-Cre -driven conditional knockout (cKO) of Smc5 demonstrated that maternally expressed SMC5 protein is essential for early embryogenesis. Interestingly, protein levels of SMC5/6 complex components in oocytes decline as wild-type females age. When SMC5/6 complexes were completely absent in oocytes during meiotic resumption, homologous chromosomes failed to segregate accurately during meiosis I. Despite what appears to be an inability to resolve concatenation between chromosomes during meiosis, localization of topoisomerase IIα to bivalents was not affected; however, localization of condensin along the chromosome axes was perturbed. Taken together, these data demonstrate that the SMC5/6 complex is essential for the formation of segregation-competent bivalents during meiosis I, and findings suggest that age-dependent depletion of the SMC5/6 complex in oocytes could contribute to increased incidence of oocyte aneuploidy and spontaneous abortion in aging females. © 2017. Published by The Company of Biologists Ltd.

  17. Identification of the meiotic toolkit in diatoms and exploration of meiosis-specific SPO11 and RAD51 homologs in the sexual species Pseudo-nitzschia multistriata and Seminavis robusta.

    Science.gov (United States)

    Patil, Shrikant; Moeys, Sara; von Dassow, Peter; Huysman, Marie J J; Mapleson, Daniel; De Veylder, Lieven; Sanges, Remo; Vyverman, Wim; Montresor, Marina; Ferrante, Maria Immacolata

    2015-11-14

    Sexual reproduction is an obligate phase in the life cycle of most eukaryotes. Meiosis varies among organisms, which is reflected by the variability of the gene set associated to the process. Diatoms are unicellular organisms that belong to the stramenopile clade and have unique life cycles that can include a sexual phase. The exploration of five diatom genomes and one diatom transcriptome led to the identification of 42 genes potentially involved in meiosis. While these include the majority of known meiosis-related genes, several meiosis-specific genes, including DMC1, could not be identified. Furthermore, phylogenetic analyses supported gene identification and revealed ancestral loss and recent expansion in the RAD51 family in diatoms. The two sexual species Pseudo-nitzschia multistriata and Seminavis robusta were used to explore the expression of meiosis-related genes: RAD21, SPO11-2, RAD51-A, RAD51-B and RAD51-C were upregulated during meiosis, whereas other paralogs in these families showed no differential expression patterns, suggesting that they may play a role during vegetative divisions. An almost identical toolkit is shared among Pseudo-nitzschia multiseries and Fragilariopsis cylindrus, as well as two species for which sex has not been observed, Phaeodactylum tricornutum and Thalassiosira pseudonana, suggesting that these two may retain a facultative sexual phase. Our results reveal the conserved meiotic toolkit in six diatom species and indicate that Stramenopiles share major modifications of canonical meiosis processes ancestral to eukaryotes, with important divergences in each Kingdom.

  18. Meiosis en mutantes desinápticos con restitución cromosómica en Rhoeo spathacea (Commelinaceae Meiosis in desynaptic-chromosomal restitution mutants in Rhoeo spathacea (Commelinaceae

    Directory of Open Access Journals (Sweden)

    Armando García-Velázquez

    2008-10-01

    Full Text Available El estudio se llevó a cabo en recolectas de Rhoeo spathacea realizadas en Veracruz, Chiapas, Tabasco, Yucatán, Quintana Roo y Michoacán, México. Las plantas presentaron número diploide de cromosomas (2n=12 en mitosis. En meiosis los individuos formaron anillo y/o cadenas en metafase I, con excepción de varios mutantes desinápticos-RSD (separación de cromosomas apareados. En meiosis de Rhoeo no se observan bivalentes ni hay posibilidades de entrecruzamiento, y consecuentemente no habrá quiasmas ya que no hay cuatro cromátidas de las cuales dos deberían ser no-hermanas. Sin embargo, en anafase I hay disyunción altamente regular 6:6 que se presentan como "anillos o donas" con los brazos cortos hacia el interior de esas figuras. De la autofecundación de un mutante desináptico-RSD (GAVA 1.1 se obtuvo una progenie F2 de 123 individuos: 90 diploides-formadores de anillos y 1 acrotrisómico (2n=13. Esto es, 91 individuos "revirtieron" el comportamiento y 29 fueron diploandróginos tetraploides desinápticos (2n=24 y 3 hipertetraploides (2n=25 desinápticos. Este comportamiento diferente entre hermanos confirma que Rhoeo es dicarión: los diploides- con anillo tendrán el subgenoma A, y los tetraploides el B, que incluyen cromatidas hermanas en la restitución en segunda división (2n.This study was carried out with collected material of Rhoeo spathacea in the states of Veracruz, Chiapas, Tabasco, Yucatan, Quintana Roo and Michoacan, Mexico. All material exhibited a diploid chromosome number (2n =12 in mitosis. In meiosis, all individuals showedring and /or chains at metaphase I. Exceptionally several desynaptic mutants resulted desynaptic - SDR (dissociation of paired chromosomes. Therefore, in meiosis Rhoeo did not exhibit synapsis in parallel-fashion instead the chromosomes are united in end-to-end (no chiasmata- fashion. Then, there are not bivalents, no chiasmata-achiasmata- as there are not four chromatids two of which resulted sister

  19. Short periods of high temperature during meiosis prevent normal meiotic progression and reduce grain number in hexaploid wheat (Triticum aestivum L.).

    Science.gov (United States)

    Draeger, Tracie; Moore, Graham

    2017-09-01

    Exposure of wheat to high temperatures during male meiosis prevents normal meiotic progression and reduces grain number. We define a temperature-sensitive period and link heat tolerance to chromosome 5D. This study assesses the effects of heat on meiotic progression and grain number in hexaploid wheat (Triticum aestivum L. var. Chinese Spring), defines a heat-sensitive stage and evaluates the role of chromosome 5D in heat tolerance. Plants were exposed to high temperatures (30 or 35 °C) in a controlled environment room for 20-h periods during meiosis and the premeiotic interphase just prior to meiosis. Examination of pollen mother cells (PMCs) from immature anthers immediately before and after heat treatment enabled precise identification of the developmental phases being exposed to heat. A temperature-sensitive period was defined, lasting from premeiotic interphase to late leptotene, during which heat can prevent PMCs from progressing through meiosis. PMCs exposed to 35 °C were less likely to progress than those exposed to 30 °C. Grain number per spike was reduced at 30 °C, and reduced even further at 35 °C. Chinese Spring nullisomic 5D-tetrasomic 5B (N5DT5B) plants, which lack chromosome 5D, were more susceptible to heat during premeiosis-leptotene than Chinese Spring plants with the normal (euploid) chromosome complement. The proportion of plants with PMCs progressing through meiosis after heat treatment was lower for N5DT5B plants than for euploids, but the difference was not significant. However, following exposure to 30 °C, in euploid plants grain number was reduced (though not significantly), whereas in N5DT5B plants the reduction was highly significant. After exposure to 35 °C, the reduction in grain number was highly significant for both genotypes. Implications of these findings for the breeding of thermotolerant wheat are discussed.

  20. A switch from a gradient to a threshold mode in the regulation of a transcriptional cascade promotes robust execution of meiosis in budding yeast.

    Directory of Open Access Journals (Sweden)

    Vyacheslav Gurevich

    Full Text Available Tight regulation of developmental pathways is of critical importance to all organisms, and is achieved by a transcriptional cascade ensuring the coordinated expression of sets of genes. We aimed to explore whether a strong signal is required to enter and complete a developmental pathway, by using meiosis in budding yeast as a model. We demonstrate that meiosis in budding yeast is insensitive to drastic changes in the levels of its consecutive positive regulators (Ime1, Ime2, and Ndt80. Entry into DNA replication is not correlated with the time of transcription of the early genes that regulate this event. Entry into nuclear division is directly regulated by the time of transcription of the middle genes, as premature transcription of their activator NDT80, leads to a premature entry into the first meiotic division, and loss of coordination between DNA replication and nuclear division. We demonstrate that Cdk1/Cln3 functions as a negative regulator of Ime2, and that ectopic expression of Cln3 delays entry into nuclear division as well as NDT80 transcription. Because Ime2 functions as a positive regulator for premeiotic DNA replication and NDT80 transcription, as well as a negative regulator of Cdk/Cln, we suggest that a double negative feedback loop between Ime2 and Cdk1/Cln3 promotes a bistable switch from the cell cycle to meiosis. Moreover, our results suggest a regulatory mode switch that ensures robust meiosis as the transcription of the early meiosis-specific genes responds in a graded mode to Ime1 levels, whereas that of the middle and late genes as well as initiation of DNA replication, are regulated in a threshold mode.

  1. Meiosis en mutantes desinápticos con restitución cromosómica en Rhoeo spathacea (Commelinaceae

    Directory of Open Access Journals (Sweden)

    Armando García-Velázquez

    2008-10-01

    Full Text Available El estudio se llevó a cabo en recolectas de Rhoeo spathacea realizadas en Veracruz, Chiapas, Tabasco, Yucatán, Quintana Roo y Michoacán, México. Las plantas presentaron número diploide de cromosomas (2n=12 en mitosis. En meiosis los individuos formaron anillo y/o cadenas en metafase I, con excepción de varios mutantes desinápticos-RSD (separación de cromosomas apareados. En meiosis de Rhoeo no se observan bivalentes ni hay posibilidades de entrecruzamiento, y consecuentemente no habrá quiasmas ya que no hay cuatro cromátidas de las cuales dos deberían ser no-hermanas. Sin embargo, en anafase I hay disyunción altamente regular 6:6 que se presentan como "anillos o donas" con los brazos cortos hacia el interior de esas figuras. De la autofecundación de un mutante desináptico-RSD (GAVA 1.1 se obtuvo una progenie F2 de 123 individuos: 90 diploides-formadores de anillos y 1 acrotrisómico (2n=13. Esto es, 91 individuos "revirtieron" el comportamiento y 29 fueron diploandróginos tetraploides desinápticos (2n=24 y 3 hipertetraploides (2n=25 desinápticos. Este comportamiento diferente entre hermanos confirma que Rhoeo es dicarión: los diploides- con anillo tendrán el subgenoma A, y los tetraploides el B, que incluyen cromatidas hermanas en la restitución en segunda división (2n.

  2. Pch2 acts through Xrs2 and Tel1/ATM to modulate interhomolog bias and checkpoint function during meiosis.

    Directory of Open Access Journals (Sweden)

    Hsuan-Chung Ho

    2011-11-01

    Full Text Available Proper segregation of chromosomes during meiosis requires the formation and repair of double-strand breaks (DSBs to form crossovers. Repair is biased toward using the homolog as a substrate rather than the sister chromatid. Pch2 is a conserved member of the AAA(+-ATPase family of proteins and is implicated in a wide range of meiosis-specific processes including the recombination checkpoint, maturation of the chromosome axis, crossover control, and synapsis. We demonstrate a role for Pch2 in promoting and regulating interhomolog bias and the meiotic recombination checkpoint in response to unprocessed DSBs through the activation of axial proteins Hop1 and Mek1 in budding yeast. We show that Pch2 physically interacts with the putative BRCT repeats in the N-terminal region of Xrs2, a member of the MRX complex that acts at sites of unprocessed DSBs. Pch2, Xrs2, and the ATM ortholog Tel1 function in the same pathway leading to the phosphorylation of Hop1, independent of Rad17 and the ATR ortholog Mec1, which respond to the presence of single-stranded DNA. An N-terminal deletion of Xrs2 recapitulates the pch2Δ phenotypes for signaling unresected breaks. We propose that interaction with Xrs2 may enable Pch2 to remodel chromosome structure adjacent to the site of a DSB and thereby promote accessibility of Hop1 to the Tel1 kinase. In addition, Xrs2, like Pch2, is required for checkpoint-mediated delay conferred by the failure to synapse chromosomes.

  3. Mutations that affect meiosis in male mice influence the dynamics of the mid-preleptotene and bouquet stages

    International Nuclear Information System (INIS)

    Liebe, B.; Petukhova, G.; Barchi, M.; Bellani, M.; Braselmann, H.; Nakano, T.; Pandita, T.K.; Jasin, M.; Fornace, A.; Meistrich, M.L.; Baarends, W.M.; Schimenti, J.; Lange, T. de; Keeney, S.; Camerini-Otero, R.D.; Scherthan, H.

    2006-01-01

    Meiosis pairs and segregates homologous chromosomes and thereby forms haploid germ cells to compensate the genome doubling at fertilization. Homologue pairing in many eukaryotic species depends on formation of DNA double strand breaks (DSBs) during early prophase I when telomeres begin to cluster at the nuclear periphery (bouquet stage). By fluorescence in situ hybridization criteria, we observe that mid-preleptotene and bouquet stage frequencies are altered in male mice deficient for proteins required for recombination, ubiquitin conjugation and telomere length control. The generally low frequencies of mid-preleptotene spermatocytes were significantly increased in male mice lacking recombination proteins SPO11, MEI1, MLH1, KU80, ubiquitin conjugating enzyme HR6B, and in mice with only one copy of the telomere length regulator Terf1. The bouquet stage was significantly enriched in Atm -/- , Spo11 -/- , Mei1 m1Jcs/m1Jcs , Mlh1 -/- , Terf1 +/- and Hr6b -/- spermatogenesis, but not in mice lacking recombination proteins DMC1 and HOP2, the non-homologous end-joining DNA repair factor KU80 and the ATM downstream effector GADD45a. Mice defective in spermiogenesis (Tnp1 -/- , Gmcl1 -/- , Asm -/- ) showed wild-type mid-preleptotene and bouquet frequencies. A low frequency of bouquet spermatocytes in Spo11 -/- Atm -/- spermatogenesis suggests that DSBs contribute to the Atm -/- -correlated bouquet stage exit defect. Insignificant changes of bouquet frequencies in mice with defects in early stages of DSB repair (Dmc1 -/- , Hop2 -/- ) suggest that there is an ATM-specific influence on bouquet stage duration. Altogether, it appears that several pathways influence telomere dynamics in mammalian meiosis

  4. Synapsis-defective mutants reveal a correlation between chromosome conformation and the mode of double-strand break repair during Caenorhabditis elegans meiosis.

    Science.gov (United States)

    Smolikov, Sarit; Eizinger, Andreas; Hurlburt, Allison; Rogers, Eric; Villeneuve, Anne M; Colaiácovo, Mónica P

    2007-08-01

    SYP-3 is a new structural component of the synaptonemal complex (SC) required for the regulation of chromosome synapsis. Both chromosome morphogenesis and nuclear organization are altered throughout the germlines of syp-3 mutants. Here, our analysis of syp-3 mutants provides insights into the relationship between chromosome conformation and the repair of meiotic double-strand breaks (DSBs). Although crossover recombination is severely reduced in syp-3 mutants, the production of viable offspring accompanied by the disappearance of RAD-51 foci suggests that DSBs are being repaired in these synapsis-defective mutants. Our studies indicate that once interhomolog recombination is impaired, both intersister recombination and nonhomologous end-joining pathways may contribute to repair during germline meiosis. Moreover, our studies suggest that the conformation of chromosomes may influence the mode of DSB repair employed during meiosis.

  5. The asymmetric meiosis in pentaploid dogroses (Rosa sect. Caninae) is associated with a skewed distribution of rRNA gene families in the gametes

    Czech Academy of Sciences Publication Activity Database

    Kovařík, Aleš; Werlemark, G.; Leitch, A.R.; Skalická, Kamila; Lim, Y.K.; Crhák Khaitová, Lucie; Koukalová, Blažena; Nybom, H.

    2008-01-01

    Roč. 101, - (2008), s. 359-367 ISSN 0018-067X R&D Projects: GA ČR(CZ) GA521/07/0116; GA MŠk(CZ) LC06004 Institutional research plan: CEZ:AV0Z50040507; CEZ:AV0Z50040702 Keywords : polyploids * meiosis * rDNA Subject RIV: BO - Biophysics Impact factor: 3.823, year: 2008

  6. Down-regulation of Rad51 activity during meiosis in yeast prevents competition with Dmc1 for repair of double-strand breaks.

    Directory of Open Access Journals (Sweden)

    Yan Liu

    2014-01-01

    Full Text Available Interhomolog recombination plays a critical role in promoting proper meiotic chromosome segregation but a mechanistic understanding of this process is far from complete. In vegetative cells, Rad51 is a highly conserved recombinase that exhibits a preference for repairing double strand breaks (DSBs using sister chromatids, in contrast to the conserved, meiosis-specific recombinase, Dmc1, which preferentially repairs programmed DSBs using homologs. Despite the different preferences for repair templates, both Rad51 and Dmc1 are required for interhomolog recombination during meiosis. This paradox has recently been explained by the finding that Rad51 protein, but not its strand exchange activity, promotes Dmc1 function in budding yeast. Rad51 activity is inhibited in dmc1Δ mutants, where the failure to repair meiotic DSBs triggers the meiotic recombination checkpoint, resulting in prophase arrest. The question remains whether inhibition of Rad51 activity is important during wild-type meiosis, or whether inactivation of Rad51 occurs only as a result of the absence of DMC1 or checkpoint activation. This work shows that strains in which mechanisms that down-regulate Rad51 activity are removed exhibit reduced numbers of interhomolog crossovers and noncrossovers. A hypomorphic mutant, dmc1-T159A, makes less stable presynaptic filaments but is still able to mediate strand exchange and interact with accessory factors. Combining dmc1-T159A with up-regulated Rad51 activity reduces interhomolog recombination and spore viability, while increasing intersister joint molecule formation. These results support the idea that down-regulation of Rad51 activity is important during meiosis to prevent Rad51 from competing with Dmc1 for repair of meiotic DSBs.

  7. Prophase I arrest and progression to metaphase I in mouse oocytes: comparison of resumption of meiosis and recovery from G2-arrest in somatic cells

    Czech Academy of Sciences Publication Activity Database

    Šolc, Petr; Schultz, R. M.; Motlík, Jan

    2010-01-01

    Roč. 16, č. 9 (2010), s. 654-664 ISSN 1360-9947 R&D Projects: GA ČR(CZ) GC301/09/J036; GA MŠk ME08030 Grant - others:NIH(US) HD22681 Institutional research plan: CEZ:AV0Z50450515 Keywords : resumption of meiosis * prophase I arrest * oocyte Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.506, year: 2010

  8. Temporal and SUMO-specific SUMOylation contribute to the dynamics of Polo-like kinase 1 (PLK1) and spindle integrity during mouse oocyte meiosis.

    Science.gov (United States)

    Feitosa, Weber Beringui; Hwang, KeumSil; Morris, Patricia L

    2018-02-15

    During mammalian meiosis, Polo-like kinase 1 (PLK1) is essential during cell cycle progression. In oocyte maturation, PLK1 expression is well characterized but timing of posttranslational modifications regulating its activity and subcellular localization are less clear. Small ubiquitin-related modifier (SUMO) posttranslational modifier proteins have been detected in mammalian gametes but their precise function during gametogenesis is largely unknown. In the present paper we report for mouse oocytes that both PLK1 and phosphorylated PLK1 undergo SUMOylation in meiosis II (MII) oocytes using immunocytochemistry, immunoprecipitation and in vitro SUMOylation assays. At MII, PLK1 is phosphorylated at threonine-210 and serine-137. MII oocyte PLK1 and phosphorylated PLK1 undergo SUMOylation by SUMO-1, -2 and -3 as shown by individual in vitro assays. Using these assays, forms of phosphorylated PLK1 normalized to PLK1 increased significantly and correlated with SUMOylated PLK1 levels. During meiotic progression and maturation, SUMO-1-SUMOylation of PLK1 is involved in spindle formation whereas SUMO-2/3-SUMOylation may regulate PLK1 activity at kinetochore-spindle attachment sites. Microtubule integrity is required for PLK1 localization with SUMO-1 but not with SUMO-2/3. Inhibition of SUMOylation disrupts proper meiotic bipolar spindle organization and spindle-kinetochore attachment. The data show that both temporal and SUMO-specific-SUMOylation play important roles in orchestrating functional dynamics of PLK1 during mouse oocyte meiosis, including subcellular compartmentalization. Copyright © 2018 Elsevier Inc. All rights reserved.

  9. Erratic Male Meiosis Resulting in 2n Pollen Grain Formation in a 4x Cytotype (2n=28 of Ranunculus laetus Wall. ex Royle

    Directory of Open Access Journals (Sweden)

    Puneet Kumar

    2012-01-01

    Full Text Available Two accessions were studied for male meiosis in Ranunculus laetus from the cold regions of Northwest Himalayas. One accession showed the presence of 14 bivalents at diakinesis and regular segregation of bivalents at anaphase I which lead to normal tetrad formation with four n microspores and consequently n pollen grains and 100% pollen fertility. Second accession from the same locality revealed the erratic meiosis characterized by the presence of all the 28 chromosomes as univalents in meiocytes at metaphase I. Univalent chromosomes failed to segregate during anaphases and produced restitution nuclei at meiosis I and II. These restitution nuclei resulted into dyads and triads which subsequently produced two types of apparently fertile pollen grains. On the basis of size, the two types of pollen grains were categorized as n (normal reduced and 2n (unreduced, 1.5-times larger than the n pollen grains. The estimated frequency of 2n pollen grains from dyads and triads (61.59% was almost the same as that of the observed one (59.90%, which indicated that 2n pollen grains in R. laetus were the result of dyads and triads. The present paper herein may provide an insight into the mechanisms of the formation of various intraspecific polyploids through sexual polyploidization in R. laetus.

  10. Levels of the ubiquitin ligase substrate adaptor MEL-26 are inversely correlated with MEI-1/katanin microtubule-severing activity during both meiosis and mitosis.

    Science.gov (United States)

    Johnson, Jacque-Lynne F A; Lu, Chenggang; Raharjo, Eko; McNally, Karen; McNally, Francis J; Mains, Paul E

    2009-06-15

    The MEI-1/MEI-2 microtubule-severing complex, katanin, is required for oocyte meiotic spindle formation and function in C. elegans, but the microtubule-severing activity must be quickly downregulated so that it does not interfere with formation of the first mitotic spindle. Post-meiotic MEI-1 inactivation is accomplished by two parallel protein degradation pathways, one of which requires MEL-26, the substrate-specific adaptor that recruits MEI-1 to a CUL-3 based ubiquitin ligase. Here we address the question of how MEL-26 mediated MEI-1 degradation is triggered only after the completion of MEI-1's meiotic function. We find that MEL-26 is present only at low levels until the completion of meiosis, after which protein levels increase substantially, likely increasing the post-meiotic degradation of MEI-1. During meiosis, MEL-26 levels are kept low by the action of another type of ubiquitin ligase, which contains CUL-2. However, we find that the low levels of meiotic MEL-26 have a subtle function, acting to moderate MEI-1 activity during meiosis. We also show that MEI-1 is the only essential target for MEL-26, and possibly for the E3 ubiquitin ligase CUL-3, but the upstream ubiquitin ligase activating enzyme RFL-1 has additional essential targets.

  11. Meiosis en mutantes desinápticos con restitución cromosómica en Rhoeo spathacea (Commelinaceae

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    García-Velasquez Armando

    2008-09-01

    Full Text Available El estudio se llevó a cabo en recolectas de Rhoeo spathacea realizadas en Veracruz, Chiapas, Tabasco, Yucatán, Quintana Roo y Michoacán, México. Las plantas presentaron número diploide de cromosomas (2n=12 en mitosis. En meiosis los individuos formaron anillo y/o cadenas en metafase I, con excepción de varios mutantes desinápticos-RSD (separación de cromosomas apareados. En meiosis de Rhoeo no se observan bivalentes ni hay posibilidades de entrecruzamiento, y consecuentemente no habrá quiasmas ya que no hay cuatro cromátidas de las cuales dos deberían ser no-hermanas. Sin embargo, en anafase I hay disyunción altamente regular 6:6 que se presentan como "anillos o donas" con los brazos cortos hacia el interior de esas figuras. De la autofecundación de un mutante desináptico-RSD (GAVA 1.1 se obtuvo una progenie F2 de 123 individuos: 90 diploides-formadores de anillos y 1 acrotrisómico (2n=13. Esto es, 91 individuos "revirtieron" el comportamiento y 29 fueron diploandróginos tetraploides desinápticos (2n=24 y 3 hipertetraploides (2n=25 desinápticos. Este comportamiento diferente entre hermanos confirma que Rhoeo es dicarión: los diploides- con anillo tendrán el subgenoma A, y los tetraploides el B, que incluyen cromatidas hermanas en la restitución en segunda división (2n.

  12. TGMS in Rapeseed (Brassica napus Resulted in Aberrant Transcriptional Regulation, Asynchronous Microsporocyte Meiosis, Defective Tapetum, and Fused Sexine

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    Xi-Qiong Liu

    2017-07-01

    Full Text Available The thermo-sensitive genic male sterility (TGMS line SP2S is a spontaneous rapeseed mutation with several traits that are favorable for the production of two-line hybrids. To uncover the key cellular events and genetic regulation associated with TGMS expression, a combined study using cytological observation, transcriptome profiling, and gene expression analysis was conducted for SP2S and its near-isogenic line SP2F grown under warm conditions. Asynchronous microsporocyte meiosis and abnormal tapetal plastids and elaioplasts were demonstrated in the anther of SP2S. The tetrad microspore did not undergo mitosis before the cytoplasm degenerated. Delayed degradation of the tetrad wall, which led to tetrad microspore aggregation, resulted in postponement of sexine (outer layer of pollen exine formation and sexine fusion in the tetrad. The nexine (foot layer of exine was also absent. The delay of tetrad wall degradation and abnormality of the exine structure suggested that the defective tapetum lost important functions. Based on transcriptomic comparisons between young flower buds of SP2S and SP2F plants, a total of 465 differentially expressed transcripts (DETs were identified, including 303 up-regulated DETs and 162 down-regulated DETs in SP2S. Several genes encoding small RNA degrading nuclease 2, small RNA 2′-O-methyltransferase, thioredoxin reductase 2, regulatory subunit A alpha isoform of serine/threonine-protein phosphatase 2A, glycine rich protein 1A, transcription factor bHLH25, leucine-rich repeat receptor kinase At3g14840 like, and fasciclin-like arabinogalactan proteins FLA19 and FLA20 were greatly depressed in SP2S. Interestingly, a POLLENLESS3-LIKE 2 gene encoding the Arabidopsis MS5 homologous protein, which is necessary for microsporocyte meiosis, was down-regulated in SP2S. Other genes that were up-regulated in SP2S encoded glucanase A6, ethylene-responsive transcription factor 1A-like, pollen-specific SF3, stress

  13. HAL-2 promotes homologous pairing during Caenorhabditis elegans meiosis by antagonizing inhibitory effects of synaptonemal complex precursors.

    Science.gov (United States)

    Zhang, Weibin; Miley, Natasha; Zastrow, Michael S; MacQueen, Amy J; Sato, Aya; Nabeshima, Kentaro; Martinez-Perez, Enrique; Mlynarczyk-Evans, Susanna; Carlton, Peter M; Villeneuve, Anne M

    2012-01-01

    During meiosis, chromosomes align with their homologous pairing partners and stabilize this alignment through assembly of the synaptonemal complex (SC). Since the SC assembles cooperatively yet is indifferent to homology, pairing and SC assembly must be tightly coordinated. We identify HAL-2 as a key mediator in this coordination, showing that HAL-2 promotes pairing largely by preventing detrimental effects of SC precursors (SYP proteins). hal-2 mutants fail to establish pairing and lack multiple markers of chromosome movement mediated by pairing centers (PCs), chromosome sites that link chromosomes to cytoplasmic microtubules through nuclear envelope-spanning complexes. Moreover, SYP proteins load inappropriately along individual unpaired chromosomes in hal-2 mutants, and markers of PC-dependent movement and function are restored in hal-2; syp double mutants. These and other data indicate that SYP proteins can impede pairing and that HAL-2 promotes pairing predominantly but not exclusively by counteracting this inhibition, thereby enabling activation and regulation of PC function. HAL-2 concentrates in the germ cell nucleoplasm and colocalizes with SYP proteins in nuclear aggregates when SC assembly is prevented. We propose that HAL-2 functions to shepherd SYP proteins prior to licensing of SC assembly, preventing untimely interactions between SC precursors and chromosomes and allowing sufficient accumulation of precursors for rapid cooperative assembly upon homology verification.

  14. Cytomictic Anomalous Male Meiosis and 2n Pollen Grain Formation in Mertensia echioides Benth. (Boraginaceae from Kashmir Himalaya

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    Reyaz Ahmad Malik

    2014-01-01

    Full Text Available Presently Mertensia echioides Benth. (Boraginaceae collected from Kashmir Himalaya, India, is cytologically analyzed for the first time revealing 2n=2x=24 (diploid. Interestingly we found 4.3–6.2% syncytic meiocytes/PMCs with 2n=4x=48 (tetraploid in addition to normal meiocytes (2n=24 during male meiosis. These comparatively larger PMCs (pollen mother cells lead to the formation of fertile giant 2n pollen grains. A frequency of 6.4–13.3% PMCs shows transfer of chromatin material at prophase-I and, therefore, results in aneuploid meiocytes. Whole chromatin transfer by the process of cytomixis could also have led to the formation of tetraploid cells. Translocation heterozygosity is also evident in the form of multivalents in 12–17% diploid (2x meiocytes at diakinesis and metaphase-I and is reported for the first time in this species. The syncytes formed depict open chain hexavalent and quadrivalent formation in the three populations with different frequencies. Moreover chromatin stickiness at metaphase-I is observed in 45% of PMCs in population-1 (P-1. Syncyte or unreduced PMC formation leading to unreduced fertile gametes is here speculated to act as a possible way out for infraspecific polyploidization in the species.

  15. A Motor-Gradient and Clustering Model of the Centripetal Motility of MTOCs in Meiosis I of Mouse Oocytes

    Science.gov (United States)

    2016-01-01

    Asters nucleated by Microtubule (MT) organizing centers (MTOCs) converge on chromosomes during spindle assembly in mouse oocytes undergoing meiosis I. Time-lapse imaging suggests that this centripetal motion is driven by a biased ‘search-and-capture’ mechanism. Here, we develop a model of a random walk in a drift field to test the nature of the bias and the spatio-temporal dynamics of the search process. The model is used to optimize the spatial field of drift in simulations, by comparison to experimental motility statistics. In a second step, this optimized gradient is used to determine the location of immobilized dynein motors and MT polymerization parameters, since these are hypothesized to generate the gradient of forces needed to move MTOCs. We compare these scenarios to self-organized mechanisms by which asters have been hypothesized to find the cell-center- MT pushing at the cell-boundary and clustering motor complexes. By minimizing the error between simulation outputs and experiments, we find a model of “pulling” by a gradient of dynein motors alone can drive the centripetal motility. Interestingly, models of passive MT based “pushing” at the cortex, clustering by cross-linking motors and MT-dynamic instability gradients alone, by themselves do not result in the observed motility. The model predicts the sensitivity of the results to motor density and stall force, but not MTs per aster. A hybrid model combining a chromatin-centered immobilized dynein gradient, diffusible minus-end directed clustering motors and pushing at the cell cortex, is required to comprehensively explain the available data. The model makes experimentally testable predictions of a spatial bias and self-organized mechanisms by which MT asters can find the center of a large cell. PMID:27706163

  16. Male meiosis, heterochromatin characterization and chromosomal location of rDNA in Microtomus lunifer (Berg, 1900 (Hemiptera: Reduviidae: Hammacerinae

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    María Poggio

    2011-05-01

    Full Text Available In the present work, we analysed the male meiosis, the content and distribution of heterochromatin and the number and location of nucleolus organizing regions in Microtomus lunifer (Berg, 1900 by means of standard technique, C- and fluorescent bandings, and fluorescent in situ hybridization with an 18S rDNA probe. This species is the second one cytogenetically analysed within the Hammacerinae. Its male diploid chromosome number is 31 (2n=28+X1X2Y, including a minute pair of m-chromosomes. The diploid autosomal number and the presence of m-chromosomes are similar to those reported in M. conspicillaris (Drury, 1782 (2n=28+XY. However, M. lunifer has a multiple sex chromosome system X1X2Y (male that could have originated by fragmentation of the ancestral X chromosome. Taking into account that M. conspicillaris and M. lunifer are the only two species within Reduviidae that possess m-chromosomes, the presence of this pair could be a synapomorphy for the species of this genus. C- and fluorescent bandings showed that the amount of heterochromatin in M. lunifer was small, and only a small CMA3 bright band was observed in the largest autosomal pair at one terminal region. FISH with the 18S rDNA probe demonstrated that ribosomal genes were terminally placed on the largest autosomal pair. Our present results led us to propose that the location of rDNA genes could be associated with variants  of the sex chromosome systems in relation with a kind of the sex chromosome systems within this family. Furthermore, the terminal location of NOR in the largest autosomal pair allowed us to use it as a chromosome marker and, thus, to infer that the kinetic activity of both ends is not a random process, and there is an inversion of this activity.

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

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    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.

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

    Science.gov (United States)

    Yan, Rihui; McKee, Bruce D

    2013-01-01

    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 (LE)s 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(3)G, 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 chromosome

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

    Science.gov (United States)

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

    2016-03-01

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

  20. Fidgetin-like1 is a strong candidate for a dynamic impairment of male meiosis leading to reduced testis weight in mice.

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    David L'Hôte

    Full Text Available BACKGROUND: In a previous work, using an interspecific recombinant congenic mouse model, we reported a genomic region of 23 Mb on mouse chromosome 11 implicated in testis weight decrease and moderate teratozoospermia (∼20-30%, a Quantitative Trait Locus (QTL called Ltw1. The objective of the present study is to identify the gene underlying this phenotype. RESULTS: In the present study, we refined the QTL position to a 5 Mb fragment encompassing only 11 genes. We showed that the low testis weight phenotype was due to kinetic alterations occurring during the first wave of the spermatogenesis where we could point out to an abnormal lengthening of spermatocyte prophase. We identify Fidgetin-like 1 (Fignl1 as the gene underlying the phenotype, since if fulfilled both the physiological and molecular characteristics required. Indeed, amongst the 11 positional candidates it is the only gene that is expressed during meiosis at the spermatocyte stage, and that presents with non-synonymous coding variations differentiating the two mouse strains at the origin of the cross. CONCLUSIONS: This work prompted us to propose Fignl1 as a novel actor in mammal's male meiosis dynamics which has fundamental interest. Besides, this gene is a new potential candidate for human infertilities caused by teratozoospermia and blockades of spermatogenesis. In addition this study demonstrates that interspecific models may be useful for understanding complex quantitative traits.

  1. Condensin suppresses recombination and regulates double-strand break processing at the repetitive ribosomal DNA array to ensure proper chromosome segregation during meiosis in budding yeast

    Science.gov (United States)

    Li, Ping; Jin, Hui; Yu, Hong-Guo

    2014-01-01

    During meiosis, homologues are linked by crossover, which is required for bipolar chromosome orientation before chromosome segregation at anaphase I. The repetitive ribosomal DNA (rDNA) array, however, undergoes little or no meiotic recombination. Hyperrecombination can cause chromosome missegregation and rDNA copy number instability. We report here that condensin, a conserved protein complex required for chromosome organization, regulates double-strand break (DSB) formation and repair at the rDNA gene cluster during meiosis in budding yeast. Condensin is highly enriched at the rDNA region during prophase I, released at the prophase I/metaphase I transition, and reassociates with rDNA before anaphase I onset. We show that condensin plays a dual role in maintaining rDNA stability: it suppresses the formation of Spo11-mediated rDNA breaks, and it promotes DSB processing to ensure proper chromosome segregation. Condensin is unnecessary for the export of rDNA breaks outside the nucleolus but required for timely repair of meiotic DSBs. Our work reveals that condensin coordinates meiotic recombination with chromosome segregation at the repetitive rDNA sequence, thereby maintaining genome integrity. PMID:25103240

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

    Science.gov (United States)

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

    1992-01-01

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

  3. Cleavage of the SUN-domain protein Mps3 at its N-terminus regulates centrosome disjunction in budding yeast meiosis.

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    Ping Li

    2017-06-01

    Full Text Available Centrosomes organize microtubules and are essential for spindle formation and chromosome segregation during cell division. Duplicated centrosomes are physically linked, but how this linkage is dissolved remains unclear. Yeast centrosomes are tethered by a nuclear-envelope-attached structure called the half-bridge, whose components have mammalian homologues. We report here that cleavage of the half-bridge protein Mps3 promotes accurate centrosome disjunction in budding yeast. Mps3 is a single-pass SUN-domain protein anchored at the inner nuclear membrane and concentrated at the nuclear side of the half-bridge. Using the unique feature in yeast meiosis that centrosomes are linked for hours before their separation, we have revealed that Mps3 is cleaved at its nucleus-localized N-terminal domain, the process of which is regulated by its phosphorylation at serine 70. Cleavage of Mps3 takes place at the yeast centrosome and requires proteasome activity. We show that noncleavable Mps3 (Mps3-nc inhibits centrosome separation during yeast meiosis. In addition, overexpression of mps3-nc in vegetative yeast cells also inhibits centrosome separation and is lethal. Our findings provide a genetic mechanism for the regulation of SUN-domain protein-mediated activities, including centrosome separation, by irreversible protein cleavage at the nuclear periphery.

  4. Cleavage of the SUN-domain protein Mps3 at its N-terminus regulates centrosome disjunction in budding yeast meiosis

    Science.gov (United States)

    Koch, Bailey A.; Han, Xuemei

    2017-01-01

    Centrosomes organize microtubules and are essential for spindle formation and chromosome segregation during cell division. Duplicated centrosomes are physically linked, but how this linkage is dissolved remains unclear. Yeast centrosomes are tethered by a nuclear-envelope-attached structure called the half-bridge, whose components have mammalian homologues. We report here that cleavage of the half-bridge protein Mps3 promotes accurate centrosome disjunction in budding yeast. Mps3 is a single-pass SUN-domain protein anchored at the inner nuclear membrane and concentrated at the nuclear side of the half-bridge. Using the unique feature in yeast meiosis that centrosomes are linked for hours before their separation, we have revealed that Mps3 is cleaved at its nucleus-localized N-terminal domain, the process of which is regulated by its phosphorylation at serine 70. Cleavage of Mps3 takes place at the yeast centrosome and requires proteasome activity. We show that noncleavable Mps3 (Mps3-nc) inhibits centrosome separation during yeast meiosis. In addition, overexpression of mps3-nc in vegetative yeast cells also inhibits centrosome separation and is lethal. Our findings provide a genetic mechanism for the regulation of SUN-domain protein-mediated activities, including centrosome separation, by irreversible protein cleavage at the nuclear periphery. PMID:28609436

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

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    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.

  6. Unique geometry of sister kinetochores in human oocytes during meiosis I may explain maternal age-associated increases in chromosomal abnormalities

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    Jessica Patel

    2016-02-01

    Full Text Available The first meiotic division in human oocytes is highly error-prone and contributes to the uniquely high incidence of aneuploidy observed in human pregnancies. A successful meiosis I (MI division entails separation of homologous chromosome pairs and co-segregation of sister chromatids. For this to happen, sister kinetochores must form attachments to spindle kinetochore-fibres emanating from the same pole. In mouse and budding yeast, sister kinetochores remain closely associated with each other during MI, enabling them to act as a single unified structure. However, whether this arrangement also applies in human meiosis I oocytes was unclear. In this study, we perform high-resolution imaging of over 1900 kinetochores in human oocytes, to examine the geometry and architecture of the human meiotic kinetochore. We reveal that sister kinetochores in MI are not physically fused, and instead individual kinetochores within a pair are capable of forming independent attachments to spindle k-fibres. Notably, with increasing female age, the separation between kinetochores increases, suggesting a degradation of centromeric cohesion and/or changes in kinetochore architecture. Our data suggest that the differential arrangement of sister kinetochores and dual k-fibre attachments may explain the high proportion of unstable attachments that form in MI and thus indicate why human oocytes are prone to aneuploidy, particularly with increasing maternal age.

  7. Separable Crossover-Promoting and Crossover-Constraining Aspects of Zip1 Activity during Budding Yeast Meiosis.

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    Karen Voelkel-Meiman

    2015-06-01

    Full Text Available Accurate chromosome segregation during meiosis relies on the presence of crossover events distributed among all chromosomes. MutSγ and MutLγ homologs (Msh4/5 and Mlh1/3 facilitate the formation of a prominent group of meiotic crossovers that mature within the context of an elaborate chromosomal structure called the synaptonemal complex (SC. SC proteins are required for intermediate steps in the formation of MutSγ-MutLγ crossovers, but whether the assembled SC structure per se is required for MutSγ-MutLγ-dependent crossover recombination events is unknown. Here we describe an interspecies complementation experiment that reveals that the mature SC is dispensable for the formation of Mlh3-dependent crossovers in budding yeast. Zip1 forms a major structural component of the budding yeast SC, and is also required for MutSγ and MutLγ-dependent crossover formation. Kluyveromyces lactis ZIP1 expressed in place of Saccharomyces cerevisiae ZIP1 in S. cerevisiae cells fails to support SC assembly (synapsis but promotes wild-type crossover levels in those nuclei that progress to form spores. While stable, full-length SC does not assemble in S. cerevisiae cells expressing K. lactis ZIP1, aggregates of K. lactis Zip1 displayed by S. cerevisiae meiotic nuclei are decorated with SC-associated proteins, and K. lactis Zip1 promotes the SUMOylation of the SC central element protein Ecm11, suggesting that K. lactis Zip1 functionally interfaces with components of the S. cerevisiae synapsis machinery. Moreover, K. lactis Zip1-mediated crossovers rely on S. cerevisiae synapsis initiation proteins Zip3, Zip4, Spo16, as well as the Mlh3 protein, as do the crossovers mediated by S. cerevisiae Zip1. Surprisingly, however, K. lactis Zip1-mediated crossovers are largely Msh4/Msh5 (MutSγ-independent. This separation-of-function version of Zip1 thus reveals that neither assembled SC nor MutSγ is required for Mlh3-dependent crossover formation per se in budding yeast

  8. 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.

  9. Studies on meiosis and sterility in the first and second generations derived from x-ray treated seeds of linum usitatissimum L

    International Nuclear Information System (INIS)

    Dutta, T.K.; Bhattacharyya, N.K.; Sen, S.

    1985-01-01

    Turn over of meiotic irregularities, pollen, capsule and seed sterility in M 1 and M 2 generations, derived from x-ray treated dry seeds of Linum usitatissimum L.(CV. B-67, Mukta and Neelum) were compared. Total percentage of meiotic abnormalities was highest in B-67 amongst the control population. But in comparison with respective controls, the turn over of meiotic irregularities was high in the M 1 populations of Mukta and Neelum. The extent of irregularities in meiosis of M 2 was less than that of M 1 generation. The pollen sterility percentage in the two generations remained almost unchanged, while capsule and seed sterility were reduced in M 2 generation. (author)

  10. Proliferating cell nuclear antigen (PCNA) interacts with a meiosis-specific RecA homologues, Lim15/Dmc1, but does not stimulate its strand transfer activity

    International Nuclear Information System (INIS)

    Hamada, Fumika N.; Koshiyama, Akiyo; Namekawa, Satoshi H.; Ishii, Satomi; Iwabata, Kazuki; Sugawara, Hiroko; Nara, Takayuki Y.; Sakaguchi, Kengo; Sawado, Tomoyuki

    2007-01-01

    PCNA is a multi-functional protein that is involved in various nuclear events. Here we show that PCNA participates in events occurring during early meiotic prophase. Analysis of protein-protein interactions using surface plasmon resonance indicates that Coprinus cinereus PCNA (CoPCNA) specifically interacts with a meiotic specific RecA-like factor, C. cinereus Lim15/Dmc1 (CoLim15) in vitro. The binding efficiency increases with addition of Mg 2+ ions, while ATP inhibits the interaction. Co-immunoprecipitation experiments indicate that the CoLim15 protein interacts with the CoPCNA protein in vitro and in the cell extracts. Despite the interaction between these two factors, no enhancement of CoLim15-dependent strand transfer activity by CoPCNA was found in vitro. We propose that the interaction between Lim15/Dmc1 and PCNA mediates the recombination-associated DNA synthesis during meiosis

  11. Dgp71WD is required for the assembly of the acentrosomal Meiosis I spindle, and is not a general targeting factor for the γ-TuRC

    Directory of Open Access Journals (Sweden)

    Richard F. Reschen

    2012-03-01

    Dgp71WD/Nedd1 proteins are essential for mitotic spindle formation. In human cells, Nedd1 targets γ-tubulin to both centrosomes and spindles, but in other organisms the function of Dgp71WD/Nedd1 is less clear. In Drosophila cells, Dgp71WD plays a major part in targeting γ-tubulin to spindles, but not centrosomes, while in Xenopus egg extracts, Nedd1 acts as a more general microtubule (MT organiser that can function independently of γ-tubulin. The interpretation of these studies, however, is complicated by the fact that some residual Dgp71WD/Nedd1 is likely present in the cells/extracts analysed. Here we generate a Dgp71WD null mutant lacking all but the last 12 nucleotides of coding sequence. The complete loss of Dgp71WD has no quantifiable effect on γ-tubulin or Centrosomin recruitment to the centrosome in larval brain cells. The recruitment of γ-tubulin to spindle MTs, however, is severely impaired, and spindle MT density is reduced in a manner that is indistinguishable from cells lacking Augmin or γ-TuRC function. In contrast, the absence of Dgp71WD leads to defects in the assembly of the acentrosomal female Meiosis I spindle that are more severe than those seen in Augmin or γ-TuRC mutants, indicating that Dgp71WD has additional functions that are independent of these complexes in oocytes. Moreover, the localisation of bicoid RNA during oogenesis, which requires γ-TuRC function, is unperturbed in Dgp71WD120 mutants. Thus, Dgp71WD is not simply a general cofactor required for γ-TuRC and/or Augmin targeting, and it appears to have a crucial role independent of these complexes in the acentrosomal Meiosis I spindle.

  12. Human female meiosis revised: new insights into the mechanisms of chromosome segregation and aneuploidies from advanced genomics and time-lapse imaging.

    Science.gov (United States)

    Capalbo, Antonio; Hoffmann, Eva R; Cimadomo, Danilo; Ubaldi, Filippo Maria; Rienzi, Laura

    2017-11-01

    The unbalanced transmission of chromosomes in human gametes and early preimplantation embryos causes aneuploidy, which is a major cause of infertility and pregnancy failure. A baseline of 20% of human oocytes are estimated to be aneuploid and this increases exponentially from 30 to 35 years, reaching on average 80% by 42 years. As a result, reproductive senescence in human females is predominantly determined by the accelerated decline in genetic quality of oocytes from 30 years of age. Understanding mechanisms of chromosome segregation and aneuploidies in the female germline is a crucial step towards the development of new diagnostic approaches and, possibly, for the development of therapeutic targets and molecules. Here, we have reviewed emerging mechanisms that may drive human aneuploidy, in particular the maternal age effect. We conducted a systematic search in PubMed Central of the primary literature from 1990 through 2016 following the PRISMA guidelines, using MeSH terms related to human aneuploidy. For model organism research, we conducted a literature review based on references in human oocytes manuscripts and general reviews related to chromosome segregation in meiosis and mitosis. Advances in genomic and imaging technologies are allowing unprecedented insight into chromosome segregation in human oocytes. This includes the identification of a novel chromosome segregation error, termed reverse segregation, as well as sister kinetochore configurations that were not predicted based on murine models. Elucidation of mechanisms that result in errors in chromosome segregation in meiosis may lead to therapeutic developments that could improve reproductive outcomes by reducing aneuploidy. © The Author 2017. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved. For Permissions, please email: journals.permissions@oup.com

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

    Science.gov (United States)

    Smolikov, Sarit; Schild-Prüfert, Kristina; Colaiácovo, Mónica P

    2008-06-06

    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.

  14. Male meiosis, morphometric analysis and distribution pattern of 2× and 4× cytotypes of Ranunculus hirtellus Royle, 1834 (Ranunculaceae from the cold regions of northwest Himalayas (India

    Directory of Open Access Journals (Sweden)

    Puneet Kumar

    2011-08-01

    Full Text Available In this study, we examined the chromosome number, detailed male meiosis, microsporogenesis, pollen fertility and morphological features and distribution of 2× and 4× cytotypes of Ranunculus hirtellus Royle, 1834. The majority of the populations scored now from cold regions of the northwest Himalayas showed tetraploid (n=16 meiotic chromosome count and one of the populations studied from the Manimahesh hills existed at diploid level (n=8. The individuals of diploid cytotype exhibited perfectly normal meiotic course resulting in 100% pollen fertility and pollen grains of uniform sizes. On the other hand, the plants of the tetraploid cytotype from all the populations in spite of showing normal bivalent formation and equal distribution to the opposite poles at anaphases showed various meiotic abnormalities. The most prominent among these meiotic abnormalities was the cytomixis which involved inter PMC (pollen mother cell chromatin material transfer at different stages of meiosis-I. The phenomenon of cytomixis induced various meiotic abnormalities which include chromatin stickiness, pycnotic chromatin, laggards and chromatin bridges, out of plate bivalents at metaphase-I, disoriented chromatin material at anaphase/telophase and micronuclei. Consequently, these populations exhibited varying percentages of pollen sterility (24 - 77 % and pollen grains of heterogeneous sizes. Analysis of various morphometric features including the stomata in 2× and 4× cytotypes showed that increase in ploidy level in the species is correlated with gigantism of vegetative and floral characters and the two cytotypes can be distinguished from each other on the basis of morphological characters. The distribution patterns of the 2× and 4× cytotypes now detected and 2×, 3×, 4× cytotypes detected earlier by workers from other regions of the Indian Himalayas have also been discussed.

  15. Luteinizing hormone signaling phosphorylates and activates the cyclic GMP phosphodiesterase PDE5 in mouse ovarian follicles, contributing an additional component to the hormonally induced decrease in cyclic GMP that reinitiates meiosis.

    Science.gov (United States)

    Egbert, Jeremy R; Yee, Siu-Pok; Jaffe, Laurinda A

    2018-03-01

    Prior to birth, oocytes within mammalian ovarian follicles initiate meiosis, but then arrest in prophase until puberty, when with each reproductive cycle, one or more follicles are stimulated by luteinizing hormone (LH) to resume meiosis in preparation for fertilization. Within preovulatory follicles, granulosa cells produce high levels of cGMP, which diffuses into the oocyte to maintain meiotic arrest. LH signaling restarts meiosis by rapidly lowering the levels of cGMP in the follicle and oocyte. Part of this decrease is mediated by the dephosphorylation and inactivation the NPR2 guanylyl cyclase in response to LH, but the mechanism for the remainder of the cGMP decrease is unknown. At least one cGMP phosphodiesterase, PDE5, is activated by LH signaling, which would contribute to lowering cGMP. PDE5 exhibits increased cGMP-hydrolytic activity when phosphorylated on serine 92, and we recently demonstrated that LH signaling phosphorylates PDE5 on this serine and increases its activity in rat follicles. To test the extent to which this mechanism contributes to the cGMP decrease that restarts meiosis, we generated a mouse line in which serine 92 was mutated to alanine (Pde5-S92A), such that it cannot be phosphorylated. Here we show that PDE5 phosphorylation is required for the LH-induced increase in cGMP-hydrolytic activity, but that this increase has only a modest effect on the LH-induced cGMP decrease in mouse follicles, and does not affect the timing of meiotic resumption. Though we show that the activation of PDE5 is among the mechanisms contributing to the cGMP decrease, these results suggest that another cGMP phosphodiesterase is also activated by LH signaling. Copyright © 2018 Elsevier Inc. All rights reserved.

  16. NatB domain-containing CRA-1 antagonizes hydrolase ACER-1 linking acetyl-CoA metabolism to the initiation of recombination during C. elegans meiosis.

    Directory of Open Access Journals (Sweden)

    Jinmin Gao

    2015-03-01

    Full Text Available The formation of DNA double-strand breaks (DSBs must take place during meiosis to ensure the formation of crossovers, which are required for accurate chromosome segregation, therefore avoiding aneuploidy. However, DSB formation must be tightly regulated to maintain genomic integrity. How this regulation operates in the context of different chromatin architectures and accessibility, and how it is linked to metabolic pathways, is not understood. We show here that global histone acetylation levels undergo changes throughout meiotic progression. Moreover, perturbations to global histone acetylation levels are accompanied by changes in the frequency of DSB formation in C. elegans. We provide evidence that the regulation of histone acetylation requires CRA-1, a NatB domain-containing protein homologous to human NAA25, which controls the levels of acetyl-Coenzyme A (acetyl-CoA by antagonizing ACER-1, a previously unknown and conserved acetyl-CoA hydrolase. CRA-1 is in turn negatively regulated by XND-1, an AT-hook containing protein. We propose that this newly defined protein network links acetyl-CoA metabolism to meiotic DSB formation via modulation of global histone acetylation.

  17. Male meiosis and gametogenesis in wild house mice (Mus musculus domesticus) from a chromosomal hybrid zone; a comparison between "simple" Robertsonian heterozygotes and homozygotes.

    Science.gov (United States)

    Wallace, B M; Searle, J B; Everett, C A

    1992-01-01

    Wild male house mice Mus musculus domesticus were collected from the hybrid zone between the John o'Groats race (2n = 32) and the standard race (2n = 40) in northern Scotland. Meiosis in both homozygotes (2n = 32, 36, and 40) and single Robertsonian heterozygotes (2n = 33, 35, and 37) was found to be orderly. At prophase/metaphase I in heterozygotes, a trivalent was formed from the metacentric and two homologous acrocentrics. At pachytene, this trivalent usually had a single side arm at the position of the centromeres, as a result of nonhomologous pairing of the acrocentrics. This side arm persisted into diplotene. Generally only a single chiasma was formed between each acrocentric and the metacentric. Anaphase I nondisjunction frequencies were estimated as 1.5% for the homozygotes and 2.7% for the heterozygotes. The extent of germ cell death between the pachytene and round spermatid stages was 18% greater in heterozygotes than in homozygotes. Our results concur with previous studies which indicate that single Robertsonian heterozygotes in wild house mice have near-normal fertility.

  18. An essential role for trimethylguanosine RNA caps in Saccharomyces cerevisiae meiosis and their requirement for splicing of SAE3 and PCH2 meiotic pre-mRNAs.

    Science.gov (United States)

    Qiu, Zhicheng R; Shuman, Stewart; Schwer, Beate

    2011-07-01

    Tgs1 is the enzyme that converts m(7)G RNA caps to the 2,2,7-trimethylguanosine (TMG) caps characteristic of spliceosomal snRNAs. Fungi grow vegetatively without TMG caps, thereby raising the question of what cellular transactions, if any, are TMG cap-dependent. Here, we report that Saccharomyces cerevisiae Tgs1 methyltransferase activity is essential for meiosis. tgs1Δ cells are specifically defective in splicing PCH2 and SAE3 meiotic pre-mRNAs. The TMG requirement for SAE3 splicing is alleviated by two intron mutations: a UAUUAAC to UACUAAC change that restores a consensus branchpoint and disruption of a stem-loop encompassing the branchpoint. The TMG requirement for PCH2 splicing is alleviated by a CACUAAC to UACUAAC change restoring a consensus branchpoint and by shortening the PCH2 5' exon. Placing the SAE3 and PCH2 introns within a HIS3 reporter confers Tgs1-dependent histidine prototrophy, signifying that the respective introns are portable determinants of TMG-dependent gene expression. Analysis of in vitro splicing in extracts of TGS1 versus tgs1Δ cells showed that SAE3 intron removal was enfeebled without TMG caps, whereas splicing of ACT1 was unaffected. Our findings illuminate a new mode of tunable splicing, a reliance on TMG caps for an essential developmental RNA transaction, and three genetically distinct meiotic splicing regulons in budding yeast.

  19. Centromere separation and association in the nuclei of an interspecific hybrid between Torenia fournieri and T. baillonii (Scrophulariaceae) during mitosis and meiosis.

    Science.gov (United States)

    Kikuchi, Shinji; Tanaka, Hiroyuki; Wako, Toshiyuki; Tsujimoto, Hisashi

    2007-10-01

    In the nuclei of some interspecific hybrid and allopolyploid plant species, each genome occupies a separate spatial domain. To analyze this phenomenon, we studied localization of the centromeres in the nuclei of a hybrid between Torenia fournieri and T. baillonii during mitosis and meiosis using three-dimensional fluorescence in situ hybridization (3D-FISH) probed with species-specific centromere repeats. Centromeres of each genome were located separately in undifferentiated cells but not differentiated cells, suggesting that cell division might be the possible force causing centromere separation. However, no remarkable difference of dividing distance was detected between chromatids with different centromeres in anaphase and telophase, indicating that tension of the spindle fiber attached to each chromatid is not the cause of centromere separation in Torenia. In differentiated cells, centromeres in both genomes were not often observed for the expected chromosome number, indicating centromere association. In addition, association of centromeres from the same genome was observed at a higher frequency than between different genomes. This finding suggests that centromeres within one genome are spatially separated from those within the other. This close position may increase possibility of association between centromeres of the same genome. In meiotic prophase, all centromeres irrespective of the genome were associated in a certain portion of the nucleus. Since centromere association in the interspecific hybrid and amphiploid was tighter than that in the diploid parents, it is possible that this phenomenon may be involved in sorting and pairing of homologous chromosomes.

  20. NatB domain-containing CRA-1 antagonizes hydrolase ACER-1 linking acetyl-CoA metabolism to the initiation of recombination during C. elegans meiosis.

    Science.gov (United States)

    Gao, Jinmin; Kim, Hyun-Min; Elia, Andrew E; Elledge, Stephen J; Colaiácovo, Monica P

    2015-03-01

    The formation of DNA double-strand breaks (DSBs) must take place during meiosis to ensure the formation of crossovers, which are required for accurate chromosome segregation, therefore avoiding aneuploidy. However, DSB formation must be tightly regulated to maintain genomic integrity. How this regulation operates in the context of different chromatin architectures and accessibility, and how it is linked to metabolic pathways, is not understood. We show here that global histone acetylation levels undergo changes throughout meiotic progression. Moreover, perturbations to global histone acetylation levels are accompanied by changes in the frequency of DSB formation in C. elegans. We provide evidence that the regulation of histone acetylation requires CRA-1, a NatB domain-containing protein homologous to human NAA25, which controls the levels of acetyl-Coenzyme A (acetyl-CoA) by antagonizing ACER-1, a previously unknown and conserved acetyl-CoA hydrolase. CRA-1 is in turn negatively regulated by XND-1, an AT-hook containing protein. We propose that this newly defined protein network links acetyl-CoA metabolism to meiotic DSB formation via modulation of global histone acetylation.

  1. Tradescantia cytogenetic tests (root-tip mitosis, pollen mitosis, pollen mother-cell meiosis). A report of the US Environmental Protection Agency gene-tox program

    Energy Technology Data Exchange (ETDEWEB)

    Ma, T H

    1982-01-01

    3 kinds of cytogenetic tests for screening of environmental mutagens were established for Tradescantia, namely, root-tip mitosis, pollen mitosis, and pollen mother-cell meiosis (commonly referred to as the Tradescantia-micronucleus (Trad-MCN) test). All these tests are technically simple, inexpensive, and can yield reliable results in a relatively short time (36 to 72 h). The root-tip mitosis test is suitable only for liquid agents, while pollen mitosis is suitable for both liquid and gaseous agents. Pollen tube mitotic chromosomes are extremely sensitive to mutagens; therefore, they are good materials for detecting very low concentrations of mutagens. Both root-tip mitosis and pollen mitosis tests use chromosome and/or chromatid aberrations as end points for scoring. The Trad-MCN test is suitable for both liquid and gaseous agents. In addition, it is especially suitable for in situ monitoring of water and air pollutants. Of the 12 chemicals tested, 5-fluorouracil and 1,2-dibromoethane indicate that they are very potent mutagens based on the effective dosages used to produce a positive response. Sulfur dioxide, ethyl methanesulfonate, sodium azide, Phosdrin, and Bladex rank next in potency.

  2. Nuclear Progestin Receptor (Pgr Knockouts in Zebrafish Demonstrate Role for Pgr in Ovulation But Not in Rapid Nongenomic Steroid Mediated Meiosis Resumption

    Directory of Open Access Journals (Sweden)

    Yong eZhu

    2015-03-01

    Full Text Available Progestins, progesterone derivatives, are the most critical signaling steroid for initiating final oocyte maturation (FOM and ovulation, in order to advance fully-grown immature oocytes to become fertilizable eggs in basal vertebrates. It is well-established that progestin induces FOM via an elusive membrane receptor and a nongenomic steroid signaling process, which precedes progestin triggered ovulation that is mediated through a nuclear progestin receptor (Pgr and genomic signaling pathway. To determine whether Pgr plays a role in a nongenomic signaling mechanism during FOM, we knocked out Pgr in zebrafish using transcription activator-like effector nucleases (TALENs and studied the oocyte maturation phenotypes of Pgr knockouts (Pgr-KOs. Three TALENs-induced mutant lines with different frame shift mutations were generated. Homozygous Pgr-KO female fish were all infertile while no fertility effects were evident in homozygous Pgr-KO males. Oocytes developed and underwent FOM normally in vivo in homozygous Pgr-KO female compared to the wildtype controls, but these mature oocytes were trapped within the follicular cells and failed to ovulate from the ovaries. These oocytes also underwent normal germinal vesicle breakdown (GVBD and FOM in vitro, but failed to ovulate even after treatment with human chronic gonadotropin (HCG or progestin (17alpha,20beta-dihydroxyprogesterone or DHP, which typically induce FOM and ovulation in wildtype oocytes. The results indicate that anovulation and infertility in homozygous Pgr-KO female fish was, at least in part, due to a lack of functional Pgr-mediated genomic progestin signaling in the follicular cells adjacent to the oocytes. Our study of Pgr-KO supports previous results that demonstrate a role for Pgr in steroid-dependent genomic signaling pathways leading to ovulation, and the first convincing evidence that Pgr is not essential for initiating nongenomic progestin signaling and triggering meiosis resumption.

  3. DNA helicase HIM-6/BLM both promotes MutSγ-dependent crossovers and antagonizes MutSγ-independent interhomolog associations during caenorhabditis elegans meiosis.

    Science.gov (United States)

    Schvarzstein, Mara; Pattabiraman, Divya; Libuda, Diana E; Ramadugu, Ajit; Tam, Angela; Martinez-Perez, Enrique; Roelens, Baptiste; Zawadzki, Karl A; Yokoo, Rayka; Rosu, Simona; Severson, Aaron F; Meyer, Barbara J; Nabeshima, Kentaro; Villeneuve, Anne M

    2014-09-01

    Meiotic recombination is initiated by the programmed induction of double-strand DNA breaks (DSBs), lesions that pose a potential threat to the genome. A subset of the DSBs induced during meiotic prophase become designated to be repaired by a pathway that specifically yields interhomolog crossovers (COs), which mature into chiasmata that temporarily connect the homologs to ensure their proper segregation at meiosis I. The remaining DSBs must be repaired by other mechanisms to restore genomic integrity prior to the meiotic divisions. Here we show that HIM-6, the Caenorhabditis elegans ortholog of the RecQ family DNA helicase BLM, functions in both of these processes. We show that him-6 mutants are competent to load the MutSγ complex at multiple potential CO sites, to generate intermediates that fulfill the requirements of monitoring mechanisms that enable meiotic progression, and to accomplish and robustly regulate CO designation. However, recombination events at a subset of CO-designated sites fail to mature into COs and chiasmata, indicating a pro-CO role for HIM-6/BLM that manifests itself late in the CO pathway. Moreover, we find that in addition to promoting COs, HIM-6 plays a role in eliminating and/or preventing the formation of persistent MutSγ-independent associations between homologous chromosomes. We propose that HIM-6/BLM enforces biased outcomes of recombination events to ensure that both (a) CO-designated recombination intermediates are reliably resolved as COs and (b) other recombination intermediates reliably mature into noncrossovers in a timely manner. Copyright © 2014 by the Genetics Society of America.

  4. Recruitment of RecA homologs Dmc1p and Rad51p to the double-strand break repair site initiated by meiosis-specific endonuclease VDE (PI-SceI).

    Science.gov (United States)

    Fukuda, Tomoyuki; Ohya, Yoshikazu

    2006-02-01

    During meiosis, VDE (PI-SceI), a homing endonuclease in Saccharomyces cerevisiae, introduces a double-strand break (DSB) at its recognition sequence and induces homologous recombinational repair, called homing. Meiosis-specific RecA homolog Dmc1p, as well as mitotic RecA homolog Rad51p, acts in the process of meiotic recombination, being required for strand invasion and exchange. In this study, recruitment of Dmc1p and Rad51p to the VDE-induced DSB repair site is investigated by chromatin immunoprecipitation assay. It is revealed that Dmc1p and Rad51p are loaded to the repair site in an independent manner. Association of Rad51p requires other DSB repair proteins of Rad52p, Rad55p, and Rad57p, while loading of Dmc1p is facilitated by the different protein, Sae3p. Absence of Tid1p, which can bind both RecA homologs, appears specifically to cause an abnormal distribution of Dmc1p. Lack of Hop2, Mnd1p, and Sae1p does not impair recruitment of both RecA homologs. These findings reveal the discrete functions of each strand invasion protein in VDE-initiated homing, confirm the similarity between VDE-initiated homing and Spo11p-initiated meiotic recombination, and demonstrate the availability of VDE-initiated homing for the study of meiotic recombination.

  5. Inter-homolog crossing-over and synapsis in Arabidopsis meiosis are dependent on the chromosome axis protein AtASY3.

    Directory of Open Access Journals (Sweden)

    Maheen Ferdous

    2012-02-01

    Full Text Available In this study we have analysed AtASY3, a coiled-coil domain protein that is required for normal meiosis in Arabidopsis. Analysis of an Atasy3-1 mutant reveals that loss of the protein compromises chromosome axis formation and results in reduced numbers of meiotic crossovers (COs. Although the frequency of DNA double-strand breaks (DSBs appears moderately reduced in Atasy3-1, the main recombination defect is a reduction in the formation of COs. Immunolocalization studies in wild-type meiocytes indicate that the HORMA protein AtASY1, which is related to Hop1 in budding yeast, forms hyper-abundant domains along the chromosomes that are spatially associated with DSBs and early recombination pathway proteins. Loss of AtASY3 disrupts the axial organization of AtASY1. Furthermore we show that the AtASY3 and AtASY1 homologs BoASY3 and BoASY1, from the closely related species Brassica oleracea, are co-immunoprecipitated from meiocyte extracts and that AtASY3 interacts with AtASY1 via residues in its predicted coiled-coil domain. Together our results suggest that AtASY3 is a functional homolog of Red1. Since studies in budding yeast indicate that Red1 and Hop1 play a key role in establishing a bias to favor inter-homolog recombination (IHR, we propose that AtASY3 and AtASY1 may have a similar role in Arabidopsis. Loss of AtASY3 also disrupts synaptonemal complex (SC formation. In Atasy3-1 the transverse filament protein AtZYP1 forms small patches rather than a continuous SC. The few AtMLH1 foci that remain in Atasy3-1 are found in association with the AtZYP1 patches. This is sufficient to prevent the ectopic recombination observed in the absence of AtZYP1, thus emphasizing that in addition to its structural role the protein is important for CO formation.

  6. The C. elegans anaphase promoting complex and MBK-2/DYRK kinase act redundantly with CUL-3/MEL-26 ubiquitin ligase to degrade MEI-1 microtubule-severing activity after meiosis.

    Science.gov (United States)

    Lu, Chenggang; Mains, Paul E

    2007-02-15

    The C. elegans embryo supports both meiotic and mitotic spindles, requiring careful regulation of components specific to each spindle type. The MEI-1/katanin microtubule-severing complex is required for meiosis but must be inactivated prior to mitosis. Downregulation of MEI-1 depends on MEL-26, which binds MEI-1, targeting it for degradation by the CUL-3 E3 ubiquitin ligase complex. Here we report that other protein degradation pathways, involving the anaphase promoting complex (APC) and the MBK-2/DYRK kinase, act in parallel to MEL-26 to inactivate MEI-1. At 25 degrees all mel-26(null) embryos die due to persistence of MEI-1 into mitosis, but at 15 degrees a significant portion of embryos hatch due to lower levels of ectopic MEI-1, suggesting that a redundant pathway also regulates MEI-1 degradation at 15 degrees. Previously the MBK-2/DYRK kinase was suggested to trigger MEL-26 mediated MEI-1 degradation. However, mbk-2 enhances the incomplete lethality of mel-26(null) at 15 degrees, arguing that MEL-26 acts in parallel to MBK-2. APC mutants behave similarly. In mel-26 embryos, ectopic MEI-1 remains until the onset of gastrulation, but in mbk-2; apc embryos, MEI-1 only persists through the first mitosis. We propose that mbk-2 and apc couple the initial phase of MEI-1 degradation to meiotic exit, after which MEL-26 completes MEI-1 degradation.

  7. Meiosis in a triploid hybrid of Gossypium

    Indian Academy of Sciences (India)

    During meiotic metaphase I, 13 AA bivalents and 13 D univalents are expected in the hybrid. However, only 28% of the PMCs had this expected configuration. The rest of the PMCs had between 8 and 12 bivalents and between 12 and 17 univalents. Univalents lagged at anaphase I, and at metaphase II one or a group of ...

  8. Mining meiosis and gametogenesis with DNA microarrays.

    Science.gov (United States)

    Schlecht, Ulrich; Primig, Michael

    2003-04-01

    Gametogenesis is a key developmental process that involves complex transcriptional regulation of numerous genes including many that are conserved between unicellular eukaryotes and mammals. Recent expression-profiling experiments using microarrays have provided insight into the co-ordinated transcription of several hundred genes during mitotic growth and meiotic development in budding and fission yeast. Furthermore, microarray-based studies have identified numerous loci that are regulated during the cell cycle or expressed in a germ-cell specific manner in eukaryotic model systems like Caenorhabditis elegans, Mus musculus as well as Homo sapiens. The unprecedented amount of information produced by post-genome biology has spawned novel approaches to organizing biological knowledge using currently available information technology. This review outlines experiments that contribute to an emerging comprehensive picture of the molecular machinery governing sexual reproduction in eukaryotes.

  9. Female Meiosis: Synapsis, Recombination, and Segregation in Drosophila melanogaster

    Science.gov (United States)

    Hughes, Stacie E.; Miller, Danny E.; Miller, Angela L.; Hawley, R. Scott

    2018-01-01

    A century of genetic studies of the meiotic process in Drosophila melanogaster females has been greatly augmented by both modern molecular biology and major advances in cytology. These approaches, and the findings they have allowed, are the subject of this review. Specifically, these efforts have revealed that meiotic pairing in Drosophila females is not an extension of somatic pairing, but rather occurs by a poorly understood process during premeiotic mitoses. This process of meiotic pairing requires the function of several components of the synaptonemal complex (SC). When fully assembled, the SC also plays a critical role in maintaining homolog synapsis and in facilitating the maturation of double-strand breaks (DSBs) into mature crossover (CO) events. Considerable progress has been made in elucidating not only the structure, function, and assembly of the SC, but also the proteins that facilitate the formation and repair of DSBs into both COs and noncrossovers (NCOs). The events that control the decision to mature a DSB as either a CO or an NCO, as well as determining which of the two CO pathways (class I or class II) might be employed, are also being characterized by genetic and genomic approaches. These advances allow a reconsideration of meiotic phenomena such as interference and the centromere effect, which were previously described only by genetic studies. In delineating the mechanisms by which the oocyte controls the number and position of COs, it becomes possible to understand the role of CO position in ensuring the proper orientation of homologs on the first meiotic spindle. Studies of bivalent orientation have occurred in the context of numerous investigations into the assembly, structure, and function of the first meiotic spindle. Additionally, studies have examined the mechanisms ensuring the segregation of chromosomes that have failed to undergo crossing over. PMID:29487146

  10. Cytomixis impairs meiosis and influences reproductive success in ...

    Indian Academy of Sciences (India)

    MADU

    Un cas de cytomixie dans un hybride interspecifique; Cytologia 29 191–195. Falistocco E, Lorenzetti S and Falcinelli M 1994 Microsporo- genesis in desynaptic mutant of Dactylis; Cytologia 59. 309–316. Falistocco E, Tosti N and Falcinelli M 1995 Cytomixis in pollen mother cells of diploid Dactylis, one of the origins of 2n.

  11. Aurora kinase A controls meiosis I progression in mouse oocytes

    Czech Academy of Sciences Publication Activity Database

    Šašková, Adéla; Šolc, Petr; Baran, V.; Kubelka, Michal; Schultz, R. M.; Motlík, Jan

    2008-01-01

    Roč. 7, č. 15 (2008), s. 2368-2376 ISSN 1538-4101 R&D Projects: GA ČR GA305/06/1413; GA ČR GD204/05/H023 Institutional research plan: CEZ:AV0Z50450515 Keywords : aurora-A * MTOC * CDK1 Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 4.120, year: 2008 www.landesbioscience.com/journals/cc/article/6361

  12. Univalents and fragments in the meiosis of mammals

    International Nuclear Information System (INIS)

    Vyglenov, A.

    1987-01-01

    The manifestation of univalents and fragments in spermatocytes in diakinese-metaphase was studied on mice, rats, Syrian hamsters and rabbits irradiated with various dose rates. It was established that the incidence of the univalents resulting from the separation of the XY and autosomic bivalents and of the fragments did not depend on the dose rate and there were no differences between the control and the irradiated animals. A species specificity was found in the manifestation of the gonosomic and to some extent of the autosomic univalents. To a certain extent the differences in the incidence of the autosomic univalents and particularly of the fragments most probably were a consequence of the various measuring methods. In comparative aspect, the investigated mammals rank as follows: with the lowest incidence of univalents and fragments was the macaque-rhesus, with higher was the rat, followed by the Syrian hamster and with very high - the mouse and rabbit

  13. Signal transduction during mating and meiosis in S. pombe

    DEFF Research Database (Denmark)

    Nielsen, O; Nielsen, Olaf

    1993-01-01

    When starved, the fission yeast Schizosaccharomyces pombe responds by producing mating factors or pheromones that signal to cells of the opposite sex to initiate mating. Like its distant relative Saccharomyces cerevisiae, cells of the two mating types of S. pombe each produce a distinct pheromone...

  14. CENTROSOMES AND MICROTUBULES DURING MEIOSIS IN THE MUSHROOM BOLETUS RUBINELLUS

    Science.gov (United States)

    McLaughlin, David J.

    1971-01-01

    The double centrosome in the basidium of Boletus rubinellus has been observed in three planes with the electron microscope at interphase preceding nuclear fusion, at prophase I, and at interphase I. It is composed of two components connected by a band-shaped middle part. At anaphase I a single, enlarged centrosome is found at the spindle pole, which is attached to the cell membrane. Microtubules mainly oriented parallel to the longitudinal axis of the basidium are present at prefusion, prophase I and interphase I. Cytoplasmic microtubules are absent when the spindle is present. The relationship of the centrosome in B. rubinellus to that in other organisms and the role of the cytoplasmic microtubules are discussed. PMID:4329156

  15. Using "Chromosomal Socks" to Demonstrate Ploidy in Mitosis and Meiosis

    Science.gov (United States)

    Chinnici, Joseph P.; Neth, Somalin Zaroh; Sherman, Leah R.

    2006-01-01

    Today, many biology instructors use visual models to help students understand abstract concepts like cell division. For all biology instructors, dealing with student misconceptions of cell division may seem hopeless at times--even after using visual models. Although student errors in cell division are built around the three key events of cell…

  16. Ddb1 controls genome stability and meiosis in fission yeast

    DEFF Research Database (Denmark)

    Holmberg, Christian Henrik; Fleck, Oliver; Hansen, H. A.

    2005-01-01

    The human UV-damaged DNA-binding protein Ddb1 associates with cullin 4 ubiquitin ligases implicated in nucleotide excision repair (NER). These complexes also contain the signalosome (CSN), but NER-relevant ubiquitination targets have not yet been identified. We report that fission yeast Ddb1......, Cullin 4 (Pcu4), and CSN subunits Csn1 and Csn2 are required for degradation of the ribonucleotide reductase (RNR) inhibitor protein Spd1. Ddb1-deficient cells have >20-fold increased spontaneous mutation rate. This is partly dependent on the error-prone translesion DNA polymerases. Spd1 deletion...... substantially reduced the mutation rate, suggesting that insufficient RNR activity accounts for ~50% of observed mutations. Epistasis analysis indicated that Ddb1 contributed to mutation avoidance and tolerance to DNA damage in a pathway distinct from NER. Finally, we show that Ddb1/Csn1/Cullin 4-mediated Spd1...

  17. Functions and Dynamics of DNA Repair Proteins in Mitosis and Meiosis

    NARCIS (Netherlands)

    E.J. Uringa

    2005-01-01

    textabstractMy PhD project encompassed studies on the functions of several different proteins, all involved in DNA repair, in somatic and germ-line cells. Hr6b and Rad18Sc are involved in a DNA repair mechanism called ‘Replicative Damage Bypass’ (RDB), and function as ubiquitin conjugating

  18. OsRAD51C Is Essential for Double Strand Break Repair in Rice Meiosis

    Directory of Open Access Journals (Sweden)

    Ding eTang

    2014-05-01

    Full Text Available RAD51C is one of the RAD51 paralogs that plays an important role in DNA double-strand break repair by homologous recombination. Here, we identified and characterized OsRAD51C, the rice homolog of human RAD51C. The Osrad51c mutant plant is normal in vegetative growth but exhibits complete male and female sterility. Cytological investigation revealed that homologous pairing and synapsis were severely disrupted. Massive chromosome fragmentation occurred during metaphase I in Osrad51c meiocytes, and was fully suppressed by the CRC1 mutation. Immunofluorescence analysis showed that OsRAD51C localized onto the chromosomes from leptotene to early pachytene during prophase I, and that normal loading of OsRAD51C was dependent on OsREC8, PAIR2, and PAIR3. Additionally, ZEP1 did not localize properly in Osrad51c, indicating that OsRAD51C is required for synaptonemal complex assembly. Our study also provided evidence in support of a functional divergence in RAD51C among organisms.

  19. Abnormal spindles in second meiosis in canola (Brassica napus and Brassica campestris

    Directory of Open Access Journals (Sweden)

    Alice Maria de Souza

    1999-01-01

    Full Text Available Studies were carried out on the occurrence of abnormal spindles in the second meiotic division in some canola cultivars recently introduced in Brazil. Fusion of spindles was observed in metaphase II rejoining the two sets of chromosomes segregated in anaphase I and also sequential and tripolar spindles were discovered rejoining two sets of chromatids segregated in anaphase II. The frequency of cells with abnormal spindles ranged from 3.18 to 8.10%. The results suggested that this abnormality was caused by environmental stress that affected the plants during the blooming period.O presente estudo descreve a ocorrência de fusos anormais na segunda divisão meiótica em algumas cultivares da canola recentemente introduzidas no Brasil. Fusão de fusos foi observada em metáfase II reunindo os dois conjuntos cromossômicos segregados na anáfase I; fusos sequenciais e tripolares reunindo cromátides segregadas na anáfase II também foram observados. A frequência de células com fusos anormais variou de 3,18 a 8,10% entre as variedades. Os resultados sugerem que estas anormalidades foram causadas por condições climáticas adversas que afetaram as plantas no período de florescimento. As implicações genéticas destas anormalidades são descritas.

  20. Transgenic reporter mice with promoter region of murine LRAT specifically marks lens and meiosis spermatocytes

    Czech Academy of Sciences Publication Activity Database

    Průková, Dana; Ileninová, Zuzana; Antošová, Barbora; Kašpárek, Petr; Gregor, Martin; Sedláček, Radislav

    2015-01-01

    Roč. 64, č. 2 (2015), s. 247-254 ISSN 0862-8408 R&D Projects: GA ČR GAP305/10/2143; GA MŠk(CZ) ED1.1.00/02.0109 Institutional support: RVO:68378050 Keywords : retinoid metabolism * retinyl esters * spermatogenesis * EGFP Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 1.643, year: 2015

  1. Evolution of karyotype, sex chromosomes, and meiosis in mygalomorph spiders (Araneae: Mygalomorphae)

    Czech Academy of Sciences Publication Activity Database

    Král, J.; Kořínková, T.; Krkavcová, L.; Musilová, J.; Forman, M.; Ávila Herrera, I. M.; Haddad, C. R.; Vítková, Magda; Henriques, S.; Palacios Vargas, J. G.; Hedin, M.

    2013-01-01

    Roč. 109, č. 2 (2013), s. 377-408 ISSN 0024-4066 Grant - others:AV ČR(CZ) IAA601110808; GA ČR(CZ) GA206/08/0813; Univerzita Karlova v Praze(CZ) SVV-2013-267205; Univerzita Karlova v Praze(CZ) SVV-2012-265202 Institutional support: RVO:60077344 Keywords : achiasmatic * chromosome pairing * deactivation Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 2.535, year: 2013 http://onlinelibrary.wiley.com/doi/10.1111/bij.12056/pdf

  2. Polo-like kinase I controls nuclear envelope break down and chromosome dynamics in meiosis I

    Czech Academy of Sciences Publication Activity Database

    Šolc, Petr; Kitajima, T.; Baran, V.; Brzáková, Adéla; Mayer, Alexandra; Šámalová, P.; Motlík, Jan; Ellenberg, J.

    2012-01-01

    Roč. 58, Suppl (2012), 66-66 ISSN 0916-8818. [Japan-Czech Joint Symposium/2./. 10.09.2012-10.09.2012, Tokyo] R&D Projects: GA ČR(CZ) GC301/09/J036; GA ČR(CZ) GPP301/11/P081 Institutional support: RVO:67985904 Keywords : PLK1 Subject RIV: EB - Genetics ; Molecular Biology

  3. The simulation of meiosis in diploid and tetraploid organisms using various genetic models

    NARCIS (Netherlands)

    Voorrips, R.E.; Maliepaard, C.A.

    2012-01-01

    Background: While the genetics of diploid inheritance are well studied and software for linkage mapping, haplotyping and QTL analysis are available, for tetraploids the available tools are limited. In order to develop such tools it would be helpful if simulated populations based on a variety of

  4. Meiosis in radiation induced triploid and tetraploid plants of pearl millet

    International Nuclear Information System (INIS)

    Singh, R.B.; Singh, B.D.; Singh, R.M.; Laxmi, V.

    1977-01-01

    A triploid and a tetraploid plant were isolated from mutagen treated populations of HB3 (Tif23AxJ104) and HBI (Tif23AxBi13B) hybrid pearl millet, respectively. The triploid plant regularly showed univalents (1 to 9 per cell) and trivalents (1 to 6 per cell) at MI. In the case of the tetraploid, only bivalents were observed which showed loose or tight secondary associations at MI; at AI bivalents separated as units (instead of chromosomes) while at AII chromosomes (instead of chromatids) moved to the opposite poles. Although the chromosome behaviour was quite regular, the plant was highly sterile (98%). It is suggested that gamma-rays had induced mutations in a number of genes, including those affecting pairing, concomitant to the induction of tetraploidy. (auth.)

  5. Resolving complex chromosome structures during meiosis: versatile deployment of Smc5/6

    NARCIS (Netherlands)

    Verver, Dideke E.; Hwang, Grace H.; Jordan, Philip W.; Hamer, Geert

    2016-01-01

    The Smc5/6 complex, along with cohesin and condensin, is a member of the structural maintenance of chromosome (SMC) family, large ring-like protein complexes that are essential for chromatin structure and function. Thanks to numerous studies of the mitotic cell cycle, Smc5/6 has been implicated to

  6. Efficacy of a Meiosis Learning Module Developed for the Virtual Cell Animation Collection

    Science.gov (United States)

    Goff, Eric E.; Reindl, Katie M.; Johnson, Christina; McClean, Phillip; Offerdahl, Erika G.; Schroeder, Noah L.; White, Alan R.

    2017-01-01

    Recent reports calling for change in undergraduate biology education have resulted in the redesign of many introductory biology courses. Reports on one common change to course structure, the active-learning environment, have placed an emphasis on student preparation, noting that the positive outcomes of active learning in the classroom depend…

  7. Zili is required for germ cell differentiation and meiosis in zebrafish.

    NARCIS (Netherlands)

    Houwing, S.; Berezikov, E.; Ketting, R.F.

    2008-01-01

    Small RNAs exert an effect through diverse RNA interference pathways to transcriptionally or post-transcriptionally silence their targets. The Piwi-interacting RNAs (piRNAs) represent a germline-specific small RNA pathway where Piwi proteins themselves are thought to mediate piRNA biosynthesis.

  8. DNA degradation and reduced recombination following UV irradiation during meiosis in yeast (Saccharomyces cerevisiae)

    International Nuclear Information System (INIS)

    Salts, Y.; Pinon, R.; Simchen, G.

    1976-01-01

    Irradiation of meiotic yeast cells with moderate doses of ultraviolet irradiation (1,600 erg/mm 2 ) leads to the arrest of premeiotic DNA synthesis, massive (5-40%) DNA degradation, and a 40-50% loss of cell viability. In contrast, such doses of UV irradiation had a minor effect on viability (15-20% loss) of logarithmically growing cells, and no comparable DNA degradation was observed in irradiated synchronized vegetative cells. Meiotic recombination is also affected by UV irradiation. When administered at a stage comparable to meiotic prophase, low doses of irradiation result in a reduction in recombination frequency without significantly affecting cell viability. (orig.) [de

  9. Role for rodent Smc6 in pericentromeric heterochromatin domains during spermatogonial differentiation and meiosis

    NARCIS (Netherlands)

    Verver, D. E.; van Pelt, A. M. M.; Repping, S.; Hamer, G.

    2013-01-01

    Chromatin structure and function are for a large part determined by the six members of the structural maintenance of chromosomes (SMC) protein family, which form three heterodimeric complexes: Smc1/3 (cohesin), Smc2/4 (condensin) and Smc5/6. Each complex has distinct and important roles in chromatin

  10. UV and gamma-ray sensitivity of meiosis-deficient mutants in Podospora anserina

    International Nuclear Information System (INIS)

    Simonet, J.M.

    1976-01-01

    Two mutants, mei1 and mei2, were isolated by screening for deficiencies occurring in the meiotic process. The sensitivity of mei1 and mei2 mutant strains to UV irradiation showed a significant increase as compared with that of the wild-type stock, hwhereas the sensitivity to γ-rays remained unchanged. The double-mutant strains were no more sensitive than each single mutant. The data indicate that both mei1 and mei2 loci are probably involved in the same pathway of excision-repair of UV-induced lesions

  11. Effects of gravity on meiosis, fertilization and early embryogenesis in Caenorhabditis elegans

    Science.gov (United States)

    Sasagawa, Y.; Saito, Y.; Shimizu, M.; Ishioka, N.; Yamashita, M.; Takahashi, H.; Higashitani, A.

    The embryonic development of the nematode Caenorhabditis elegans was examined under different gravitational conditions. The first cleavage plane in the 1-cell embryo was slid to some extent by re-orientation of liquid culture vessel, but the pattern and timing of cleavages were not affected. Under 100G of hypergravity condition with swing-centrifuge, the number of eggs laid from an adult hermaphrodite decreased and their hatching rate was drastically reduced. On the other hand, the embryonic development after fertilization normally occurred and grew to adulthood at more than 100G of hypergravity. When the adult hermaphrodites cultured under 100G of hypergravity transferred to a ground condition (1G), the newly fertilized embryos normally developed and their hatching rate was fully recovered. These results indicated that the reproductive process except spermatogenesis, oogenesis and embryogenesis after fertilization is impaired under 100G of hypergravity condition, and the effect is transient. Namely, the fertilization process including meiotic divisions I and II is sensitive to hypergravity in the nematode C. elegans.

  12. High School Students' Understanding of Chromosome/Gene Behavior during Meiosis.

    Science.gov (United States)

    Stewart, Jim; Dale, Michael

    1989-01-01

    Investigates high school students' understanding of the physical relationship of chromosomes and genes as expressed in their conceptual models and in their ability to manipulate the models to explain solutions to dihybrid cross problems. Describes three typical models and three students' reasoning processes. Discusses four implications. (YP)

  13. Mouse Tafazzin Is Required for Male Germ Cell Meiosis and Spermatogenesis

    NARCIS (Netherlands)

    Cadalbert, Laurence C.; Ghaffar, Farah Naz; Stevenson, David; Bryson, Sheila; Vaz, Frédéric M.; Gottlieb, Eyal; Strathdee, Douglas

    2015-01-01

    Barth syndrome is an X-linked mitochondrial disease, symptoms of which include neutropenia and cardiac myopathy. These symptoms are the most significant clinical consequences of a disease, which is increasingly recognised to have a variable presentation. Mutation in the Taz gene in Xq28 is thought

  14. Effects of simulated weightlessness on meiosis. Fertilization, and early development in mice

    Science.gov (United States)

    Wolgemuth, D. J.

    1986-01-01

    The initial goal was to construct a clinostat which could support mammalian cell culture. The clinostat was selected as a means by which to simulate microgravity conditions within the laboratory, by constant re-orientation of cells with respect to the gravity vector. The effects of this simulated microgravity on in-vitro meiotic maturation of oocytes, using mouse as the model system, was investigated. The effects of clinostat rotation on fertilization in-vitro was then examined. Specific endpoints included examining the timely appearance of male and female pronuclei (indicating fertilization) and the efficiency of extrusion of the second polar body. Particular attention was paid to detecting anomalies of fertilization, including parthenogenetic activation and multiple pronuclei. Finally, for the preliminary studies on mouse embryogenesis, a key feature of the clinostat was modified, that of the position of the cells during rotation. A means was found to immobilize the cells during the clinostat reotation, permitting the cells to remain at the axis of rotation yet not interfering with cellular development.

  15. Asynchronous meiosis in Cucumis hystrix-cucumber synthetic tetraploids resulting in low male fertility

    Science.gov (United States)

    Wide hybridization is an important tool for crop improvement. Recently, we successfully developed a synthetic allotetraploid from interspecific cross between cucumber and its relative Cucumis hystrix-(2n = 2x =24) followed by chemical induction of chromosome doubling. The resulting allotetraploid wa...

  16. Structure and DNA-binding of meiosis-specific protein Hop2

    Science.gov (United States)

    Zhou, Donghua; Moktan, Hem; Pezza, Roberto

    2014-03-01

    Here we report structure elucidation of the DNA binding domain of homologous pairing protein 2 (Hop2), which is important to gene diversity when sperms and eggs are produced. Together with another protein Mnd1, Hop2 enhances the strand invasion activity of recombinase Dmc1 by over 30 times, facilitating proper synapsis of homologous chromosomes. However, the structural and biochemical bases for the function of Hop2 and Mnd1 have not been well understood. As a first step toward such understanding, we recently solved the structure for the N-terminus of Hop2 (1-84) using solution NMR. This fragment shows a typical winged-head conformation with recognized DNA binding activity. DNA interacting sites were then investigated by chemical shift perturbations in a titration experiment. Information of these sites was used to guide protein-DNA docking with MD simulation, revealing that helix 3 is stably lodged in the DNA major groove and that wing 1 (connecting strands 2 and 3) transiently comes in contact with the minor groove in nanosecond time scale. Mutagenesis analysis further confirmed the DNA binding sites in this fragment of the protein.

  17. Novel meiotic miRNAs and indications for a role of phasiRNAs in meiosis

    Science.gov (United States)

    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 isolate...

  18. Pairing and recombination features during meiosis in Cebus paraguayanus (Primates: Platyrrhini

    Directory of Open Access Journals (Sweden)

    Garcia-Cruz Raquel

    2009-06-01

    Full Text Available Abstract Background Among neotropical Primates, the Cai monkey Cebus paraguayanus (CPA presents long, conserved chromosome syntenies with the human karyotype (HSA as well as numerous C+ blocks in different chromosome pairs. In this study, immunofluorescence (IF against two proteins of the Synaptonemal Complex (SC, namely REC8 and SYCP1, two recombination protein markers (RPA and MLH1, and one protein involved in the pachytene checkpoint machinery (BRCA1 was performed in CPA spermatocytes in order to analyze chromosome meiotic behavior in detail. Results Although in the vast majority of pachytene cells all autosomes were paired and synapsed, in a small number of nuclei the heterochromatic C-positive terminal region of bivalent 11 remained unpaired. The analysis of 75 CPA cells at pachytene revealed a mean of 43.22 MLH1 foci per nucleus and 1.07 MLH1 foci in each CPA bivalent 11, always positioned in the region homologous to HSA chromosome 21. Conclusion Our results suggest that C blocks undergo delayed pairing and synapsis, although they do not interfere with the general progress of pairing and synapsis.

  19. Cytogenetics of Mimosa bimucronata (DC.) O. Kuntze (Mimosoideae, Leguminosae): chromosome number, polysomaty and meiosis

    OpenAIRE

    Olkoski, Denise; Wittmann, Maria Teresa Schifino

    2011-01-01

    Chromosome numbers (somatic and/or gametic) were determined in 50 populations of M. bimucronata (DC.) O. Kuntze collected in the species area of distribution in Rio Grande do Sul, south Brazil. All populations were diploid (2n = 2x = 26, n = 13). Polysomatic (mostly tetraploid) cells were detected in the seedlings root-tip cells in 39 out of the 41 populations examined, ranging from 3.0 to 28.2 % among populations, but were absent in the root-tips of grown plants. Polysomaty was as well absen...

  20. The master Greatwall kinase, a critical regulator of mitosis and meiosis.

    Science.gov (United States)

    Vigneron, Suzanne; Robert, Perle; Hached, Khaled; Sundermann, Lena; Charrasse, Sophie; Labbé, Jean-Claude; Castro, Anna; Lorca, Thierry

    2016-01-01

    Entry into mitosis requires the coordinated activation of various protein kinases and phosphatases that together activate sequential signaling pathways allowing entry, progression and exit of mitosis. The limiting step is thought to be the activation of the mitotic Cdk1-cyclin B kinase. However, this model has recently evolved with new data showing that in addition to the Cdk1-cyclin B complex, Greatwall (Gwl) kinase is also required to enter into and maintain mitosis. This new concept proposes that entry into mitosis is now based on the combined activation of both kinases Cdk1-cyclin B and Gwl, the former promoting massive phosphorylation of mitotic substrates and the latter inhibiting PP2A-B55 phosphatase responsible for dephosphorylation of these substrates. Activated Gwl phosphorylates both Arpp19 and ENSA, which associate and inhibit PP2A-B55. This pathway seems relatively well conserved from yeast to humans, although some differences appear based on models or techniques used. While Gwl is activated by phosphorylation, its inactivation requires dephosphorylation of critical residues. Several phosphatases such as PP1, PP2A-B55 and FCP1 are required to control the dephosphorylation and inactivation of Gwl and a properly regulated mitotic exit. Gwl has also been reported to be involved in cancer processes and DNA damage recovery. These new findings support the idea that the Gwl-Arpp19/ENSA-PP2A-B55 pathway is essential to achieve an efficient division of cells and to maintain genomic stability.

  1. The Robertsonian phenomenon in the house mouse: mutation, meiosis and speciation.

    Science.gov (United States)

    Garagna, Silvia; Page, Jesus; Fernandez-Donoso, Raul; Zuccotti, Maurizio; Searle, Jeremy B

    2014-12-01

    Many different chromosomal races with reduced chromosome number due to the presence of Robertsonian fusion metacentrics have been described in western Europe and northern Africa, within the distribution area of the western house mouse Mus musculus domesticus. This subspecies of house mouse has become the ideal model for studies to elucidate the processes of chromosome mutation and fixation that lead to the formation of chromosomal races and for studies on the impact of chromosome heterozygosities on reproductive isolation and speciation. In this review, we briefly describe the history of the discovery of the first and subsequent metacentric races in house mice; then, we focus on the molecular composition of the centromeric regions involved in chromosome fusion to examine the molecular characteristics that may explain the great variability of the karyotype that house mice show. The influence that metacentrics exert on the nuclear architecture of the male meiocytes and the consequences on meiotic progression are described to illustrate the impact that chromosomal heterozygosities exert on fertility of house mice-of relevance to reproductive isolation and speciation. The evolutionary significance of the Robertsonian phenomenon in the house mouse is discussed in the final section of this review.

  2. 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.

  3. Impact of cytomixis on meiosis, pollen viability and pollen size in ...

    Indian Academy of Sciences (India)

    Srinivas

    prefers light woodlands, moist soils, rock crevices and grows among ... Well-filled pollen grains with stained nuclei were regarded as apparently .... individuals of the Bhairon Ghati population, as they did not depict any .... Ajay and Sarbhoy 1987; Haroun 1995), pollution ( Haroun ... effect of some chlorinated pesticides II.

  4. Impact of cytomixis on meiosis, pollen viability and pollen size in ...

    Indian Academy of Sciences (India)

    Srinivas

    mother cells of Medicago sativa L.; J. Heredity 94 512–516. Bhat T A, Parveen S and Khan A H 2006 MMS-induced cytomixis in pollen mother cells of broad bean (Vicia faba L.); Turk. J. Bot. 30 273–279. Bione N C P, Pagliarini M S and de Toledo J F F 2000 Meiotic behavior of several Brazilian soybean varieties; Genet.

  5. Meiosis and speciation: a study in a speciating Mus terricolor complex

    Indian Academy of Sciences (India)

    Unknown

    2000-12-27

    Dec 27, 2000 ... (see reviews by White 1978; King 1981) or would lead to reduced viability of ... Indian pygmy field mice Mus terricolor, vis-à-vis the fixa- tion of autosomal ... plexes (SCs) were prepared and stained with silver nitrate. (Fletcher ...

  6. Live Imaging of Centriole Dynamics by Fluorescently Tagged Proteins in Starfish Oocyte Meiosis.

    Science.gov (United States)

    Borrego-Pinto, Joana; Somogyi, Kálmán; Lénárt, Péter

    2016-01-01

    High throughput DNA sequencing, the decreasing costs of DNA synthesis, and universal techniques for genetic manipulation have made it much easier and quicker to establish molecular tools for any organism than it has been 5 years ago. This opens a great opportunity for reviving "nonconventional" model organisms, which are particularly suited to study a specific biological process and many of which have already been established before the era of molecular biology. By taking advantage of transcriptomics, in particular, these systems can now be easily turned into full fetched models for molecular cell biology.As an example, here we describe how we established molecular tools in the starfish Patiria miniata, which has been a popular model for cell and developmental biology due to the synchronous and rapid development, transparency, and easy handling of oocytes, eggs, and embryos. Here, we detail how we used a de novo assembled transcriptome to produce molecular markers and established conditions for live imaging to investigate the molecular mechanisms underlying centriole elimination-a poorly understood process essential for sexual reproduction of animal species.

  7. Meiosis en mutantes desinápticos con restitución cromosómica en rhoeo spathacea (commelinaceae)

    OpenAIRE

    García-Velasquez, Armando

    2009-01-01

    El estudio se llevó a cabo en recolectas de Rhoeo spathacea realizadas en Veracruz, Chiapas, Tabasco, Yucatán, Quintana Roo y Michoacán, México. Las plantas presentaron número diploide de cromosomas (2n=12) en mit...

  8. Differentiation of human lymphocytes into nuclear vlimata by meiosis. The cytotoxic effect of calcium-activated neutral proteinase inhibitor

    OpenAIRE

    Logothetou-Rella, H.

    1994-01-01

    Phytohaemagglutinin (PHA)-activated lymphocytes differentiated into nuclear vlimata (NVs) in vitro. Lymphocyte attachment was followed by formation and extrusion of cytoplasmic vesicles. nuclear elongation and fragmentation into NVs. NVs and cytoplasmic vesicles were detached and organized into large cell nodules in suspension. Immunocytochemistry showed that T-lymphocytes differentiated mainly to NVs while B-lymphocytes to buds. During differentiation ther...

  9. Control of PNG kinase, a key regulator of mRNA translation, is coupled to meiosis completion at egg activation.

    Science.gov (United States)

    Hara, Masatoshi; Petrova, Boryana; Orr-Weaver, Terry L

    2017-05-30

    The oocyte-to-embryo transition involves extensive changes in mRNA translation, regulated in Drosophila by the PNG kinase complex whose activity we show here to be under precise developmental control. Despite presence of the catalytic PNG subunit and the PLU and GNU activating subunits in the mature oocyte, GNU is phosphorylated at Cyclin B/CDK1sites and unable to bind PNG and PLU. In vitro phosphorylation of GNU by CyclinB/CDK1 blocks activation of PNG. Meiotic completion promotes GNU dephosphorylation and PNG kinase activation to regulate translation. The critical regulatory effect of phosphorylation is shown by replacement in the oocyte with a phosphorylation-resistant form of GNU, which promotes PNG-GNU complex formation, elevation of Cyclin B, and meiotic defects consistent with premature PNG activation. After PNG activation GNU is destabilized, thus inactivating PNG. This short-lived burst in kinase activity links development with maternal mRNA translation and ensures irreversibility of the oocyte-to-embryo transition.

  10. E3 ligase Hei10: a multifaceted structure-based signaling molecule with roles within and beyond meiosis

    Science.gov (United States)

    De Muyt, Arnaud; Zhang, Liangran; Piolot, Tristan; Kleckner, Nancy; Espagne, Eric; Zickler, Denise

    2014-01-01

    Human enhancer of invasion-10 (Hei10) mediates meiotic recombination and also plays roles in cell proliferation. Here we explore Hei10’s roles throughout the sexual cycle of the fungus Sordaria with respect to localization and effects of null, RING-binding, and putative cyclin-binding (RXL) domain mutations. Hei10 makes three successive types of foci. Early foci form along synaptonemal complex (SC) central regions. At some of these positions, depending on its RING and RXL domains, Hei10 mediates development and turnover of two sequential types of recombination complexes, each demarked by characteristic amplified Hei10 foci. Integration with ultrastructural data for recombination nodules further reveals that recombination complexes differentiate into three types, one of which corresponds to crossover recombination events during or prior to SC formation. Finally, Hei10 positively and negatively modulates SUMO localization along SCs by its RING and RXL domains, respectively. The presented findings suggest that Hei10 integrates signals from the SC, associated recombination complexes, and the cell cycle to mediate both the development and programmed turnover/evolution of recombination complexes via SUMOylation/ubiquitination. Analogous cell cycle-linked assembly/disassembly switching could underlie localization and roles for Hei10 in centrosome/spindle pole body dynamics and associated nuclear trafficking. We suggest that Hei10 is a unique type of structure-based signal transduction protein. PMID:24831702

  11. Aurora kinase a drives mtoc biogenesis but does not trigger resumption of meiosis in mouse oocytes matured in vivo

    Czech Academy of Sciences Publication Activity Database

    Šolc, Petr; Baran, Vladimír; Mayer, Alexandra; Böhmová, Tereza; Panenková, Gabriela; Šašková, Adéla; Schultz, R. M.; Motlík, Jan

    2012-01-01

    Roč. 87, č. 4 (2012), s. 1-12 ISSN 0006-3363 R&D Projects: GA MŠk ME08030; GA MŠk LH12057; GA ČR(CZ) GPP301/11/P081 Institutional research plan: CEZ:AV0Z50450515 Keywords : γ-tubulin * AURKA * CDC25B Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 4.027, year: 2012

  12. Some Misconceptions in Meiosis Shown by Students Responding to an Advanced Level Practical Examination Question in Biology.

    Science.gov (United States)

    Brown, C. R.

    1990-01-01

    Discussed are problems revealed in student responses to a practical task which formed part of an advanced level examination. The frequencies with which some misconceptions about cell reproduction and genetics occurred are presented. The nature of these misconceptions is analyzed and their implications discussed. (CW)

  13. Completion of meiosis in male zebrafish (Danio rerio) despite lack of DNA mismatch repair gene mlh1.

    NARCIS (Netherlands)

    Leal, M.C.; Feitsma, H.; Cuppen, E.; Franca, L.R.; Schulz, R.W.

    2008-01-01

    Mlh1 is a member of DNA mismatch repair (MMR) machinery and is also essential for the stabilization of crossovers during the first meiotic division. Recently, we have shown that zebrafish mlh1 mutant males are completely infertile because of a block in metaphase I, whereas females are fertile but

  14. The Effects of Meiosis/Genetics Integration and Instructional Sequence on College Biology Student Achievement in Genetics.

    Science.gov (United States)

    Browning, Mark

    The purpose of the research was to manipulate two aspects of genetics instruction in order to measure their effects on college, introductory biology students' achievement in genetics. One instructional sequence that was used dealt first with monohybrid autosomal inheritance patterns, then sex-linkage. The alternate sequence was the reverse.…

  15. The kinesin AtPSS1 promotes synapsis and is required for proper crossover distribution in meiosis.

    Directory of Open Access Journals (Sweden)

    Yann Duroc

    2014-10-01

    Full Text Available Meiotic crossovers (COs shape genetic diversity by mixing homologous chromosomes at each generation. CO distribution is a highly regulated process. CO assurance forces the occurrence of at least one obligatory CO per chromosome pair, CO homeostasis smoothes out the number of COs when faced with variation in precursor number and CO interference keeps multiple COs away from each other along a chromosome. In several organisms, it has been shown that cytoskeleton forces are transduced to the meiotic nucleus via KASH- and SUN-domain proteins, to promote chromosome synapsis and recombination. Here we show that the Arabidopsis kinesin AtPSS1 plays a major role in chromosome synapsis and regulation of CO distribution. In Atpss1 meiotic cells, chromosome axes and DNA double strand breaks (DSBs appear to form normally but only a variable portion of the genome synapses and is competent for CO formation. Some chromosomes fail to form the obligatory CO, while there is an increased CO density in competent regions. However, the total number of COs per cell is unaffected. We further show that the kinesin motor domain of AtPSS1 is required for its meiotic function, and that AtPSS1 interacts directly with WIP1 and WIP2, two KASH-domain proteins. Finally, meiocytes missing AtPSS1 and/or SUN proteins show similar meiotic defects suggesting that AtPSS1 and SUNs act in the same pathway. This suggests that forces produced by the AtPSS1 kinesin and transduced by WIPs/SUNs, are required to authorize complete synapsis and regulate maturation of recombination intermediates into COs. We suggest that a form of homeostasis applies, which maintains the total number of COs per cell even if only a part of the genome is competent for CO formation.

  16. Completion of meiosis in male zebrafish (Danio rerio) despite lack of DNA mismatch repair gene mlh1

    NARCIS (Netherlands)

    Leal, M.C.; Feitsma, H.; Cuppen, E.; França, L.R.; Schulz, R.W.

    2008-01-01

    Mlh1 is a member of DNA mismatch repair (MMR) machinery and is also essential for the stabilization of crossovers during the first meiotic division. Recently, we have shown that zebrafish mlh1 mutant males are completely infertile because of a block in metaphase I, whereas females are fertile

  17. Distinct effects of the recurrent Mlh1G67R mutation on MMR functions, cancer, and meiosis

    OpenAIRE

    Avdievich, Elena; Reiss, Cora; Scherer, Stefan J.; Zhang, Yongwei; Maier, Sandra M.; Jin, Bo; Hou, Harry; Rosenwald, Andreas; Riedmiller, Hubertus; Kucherlapati, Raju; Cohen, Paula E.; Edelmann, Winfried; Kneitz, Burkhard

    2008-01-01

    Mutations in the human DNA mismatch repair (MMR) gene MLH1 are associated with hereditary nonpolyposis colorectal cancer (Lynch syndrome, HNPCC) and a significant proportion of sporadic colorectal cancer. The inactivation of MLH1 results in the accumulation of somatic mutations in the genome of tumor cells and resistance to the genotoxic effects of a variety of DNA damaging agents. To study the effect of MLH1 missense mutations on cancer susceptibility, we generated a mouse line carrying the ...

  18. Lack of evidence that the XqYq pairing tips at meiosis in the mouse show hypersensitivity to DNAse I.

    Science.gov (United States)

    Separovic, E R; Chandley, A C

    1987-01-01

    In situ nick translation procedures have been applied to meiotic metaphase I divisions of the normal and XY, Sxr mouse. Unlike in man, where the pairing tips of the XY bivalent show a special sensitivity to DNAse I nicking, no such sensitivity can be detected for either of these types of mouse. Hypersensitivity in the D-band equivalent region of the X chromosome does, however, exist, this site being early replicating in somatic cells and housing the X inactivation centre (Xce).

  19. Can epigenetic control explain pronounced within plant heterogeneity of meiosis in a translocation trisome of Secale L.?

    NARCIS (Netherlands)

    Sybenga, J.

    2012-01-01

    Meiotic metaphase I configuration frequencies were determined in different tillers of genetically related plants of rye (Secale cereale L.) heterozygous for reciprocal translocation T248W (between chromosome arms 1RS and 6RS) and with an additional (telocentric) arm 1RS. Seventeen different

  20. An Ancient Transcription Factor Initiates the Burst of piRNA Production During Early Meiosis in Mouse Testes

    Science.gov (United States)

    Li, Xin Zhiguo; Roy, Christian K.; Dong, Xianjun; Bolcun-Filas, Ewelina; Wang, Jie; Han, Bo W.; Xu, Jia; Moore, Melissa J.; Schimenti, John C.; Weng, Zhiping; Zamore, Phillip D.

    2013-01-01

    SUMMARY Animal germ cells produce PIWI-interacting RNAs (piRNAs), small silencing RNAs that suppress transposons and enable gamete maturation. Mammalian transposon-silencing piRNAs accumulate early in spermatogenesis, whereas pachytene piRNAs are produced later during post-natal spermatogenesis and account for >95% of all piRNAs in the adult mouse testis. Mutants defective for pachytene piRNA pathway proteins fail to produce mature sperm, but neither the piRNA precursor transcripts nor the trigger for pachytene piRNA production is known. Here, we show that the transcription factor A-MYB initiates pachytene piRNA production. A-MYB drives transcription of both pachytene piRNA precursor RNAs and the mRNAs for core piRNA biogenesis factors, including MIWI, the protein through which pachytene piRNAs function. A-MYB regulation of piRNA pathway proteins and piRNA genes creates a coherent feed-forward loop that ensures the robust accumulation of pachytene piRNAs. This regulatory circuit, which can be detected in rooster testes, likely predates the divergence of birds and mammals. PMID:23523368

  1. Meiosis and ISSR analysis on genetic variation of {sup 60}Co {gamma}-rays irradiated variants of cut chrysanthemum

    Energy Technology Data Exchange (ETDEWEB)

    Lili, Xing; Fadi, Chen; Hengbin, Miao [College of Horticulture, Nanjing Agricultural University, Nanjing, Jiangsu (China)

    2009-08-15

    Cytology and ISSR technology were used to analyze genetic variations of {sup 60}Co {gamma}-rays induced variants of cut chrysanthemum 'Changzi', for further exploring the mechanism of irradiation and providing theoretical basis for breeding of chrysanthemum. The results showed that, meiotic abnormality ratio of lagging chromosome and chromosome bridge in variants were significantly higher than those in the control at anaphase I and II. The abnormality ratio was also raised with irradiation doses increasing. The highest ratio of two abnormal phenomena at anaphase I was 9.0%, 11.3%, and at anaphase II 15.5%, 8.6%, respectively. Polymorphic bands of 112 were amplified by 21 ISSR primers and the polymorphism rate was 71.3%, which proved that DNA changed in different degrees. These variants were divided into 5 groups by UPGMA based on Jaccard coefficient. It was observed that the clustering result related to their characters of flower shape and color variations. (authors)

  2. Meiosis and ISSR analysis on genetic variation of 60Co γ-rays irradiated variants of cut chrysanthemum

    International Nuclear Information System (INIS)

    Xing Lili; Chen Fadi; Miao Hengbin

    2009-01-01

    Cytology and ISSR technology were used to analyze genetic variations of 60 Co γ-rays induced variants of cut chrysanthemum 'Changzi', for further exploring the mechanism of irradiation and providing theoretical basis for breeding of chrysanthemum. The results showed that, meiotic abnormality ratio of lagging chromosome and chromosome bridge in variants were significantly higher than those in the control at anaphase I and II. The abnormality ratio was also raised with irradiation doses increasing. The highest ratio of two abnormal phenomena at anaphase I was 9.0%, 11.3%, and at anaphase II 15.5%, 8.6%, respectively. Polymorphic bands of 112 were amplified by 21 ISSR primers and the polymorphism rate was 71.3%, which proved that DNA changed in different degrees. These variants were divided into 5 groups by UPGMA based on Jaccard coefficient. It was observed that the clustering result related to their characters of flower shape and color variations. (authors)

  3. RSPO1/β-catenin signaling pathway regulates oogonia differentiation and entry into meiosis in the mouse fetal ovary

    NARCIS (Netherlands)

    Chassot, Anne-Amandine; Gregoire, Elodie P.; Lavery, Rowena; Taketo, Makoto M.; de Rooij, Dirk G.; Adams, Ian R.; Chaboissier, Marie-Christine

    2011-01-01

    Differentiation of germ cells into male gonocytes or female oocytes is a central event in sexual reproduction. Proliferation and differentiation of fetal germ cells depend on the sex of the embryo. In male mouse embryos, germ cell proliferation is regulated by the RNA helicase Mouse Vasa homolog

  4. RSPO1/beta-Catenin Signaling Pathway Regulates Oogonia Differentiation and Entry into Meiosis in the Mouse Fetal Ovary

    NARCIS (Netherlands)

    Chassot, A.A.; Gregoire, E.P.; Lavery, R.; Taketo, M.M.; de Rooij, D.G.; Adams, I.R.; Chaboissier, M.C.

    2011-01-01

    Differentiation of germ cells into male gonocytes or female oocytes is a central event in sexual reproduction. Proliferation and differentiation of fetal germ cells depend on the sex of the embryo. In male mouse embryos, germ cell proliferation is regulated by the RNA helicase Mouse Vasa homolog

  5. 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.

  6. Depletion of a Drosophila homolog of yeast Sup35p disrupts spindle assembly, chromosome segregation, and cytokinesis during male meiosis.

    Science.gov (United States)

    Basu, J; Williams, B C; Li, Z; Williams, E V; Goldberg, M L

    1998-01-01

    In the course of a genetic screen for male-sterile mutations in Drosophila affecting chromosome segregation during the meiotic divisions in spermatocytes, we identified the mutation dsup35(63D). Examination of mutant testes showed that chromosome misbehavior was a consequence of major disruptions in meiotic spindle assembly. These perturbations included problems in aster formation, separation, and migration around the nuclear envelope; aberrations in spindle organization and integrity; and disappearance of the ana/telophase central spindle, which in turn disrupts cytokinesis. The dsup35(63D) mutation is caused by a P element insertion that affects, specifically in the testis, the expression of a gene (dsup35) encoding the Drosophila homolog of the yeast Sup35p and Xenopus eRF3 proteins. These proteins are involved in the termination of polypeptide synthesis on ribosomes, but previous studies have suggested that Sup35p and closely related proteins of the same family also interact directly with microtubules. An affinity-purified antibody directed against the product of the dsup35 gene was prepared; interestingly, this antibody specifically labels primary spermatocytes in one or two discrete foci of unknown structure within the nucleoplasm. We discuss how depletion of the dsup35 gene product in spermatocytes might lead to the global disruptions in meiotic spindle assembly seen in mutant spermatocytes.

  7. Meiose e viabilidade polínica em acessos de Capsicum annuum e Capsicum baccatum Meiosis and pollen viability in accessions of Capsicum annuum and Capsicum baccatum

    Directory of Open Access Journals (Sweden)

    Kellen Coutinho Martins

    2010-08-01

    Full Text Available O objetivo deste trabalho foi estudar o comportamento meiótico e a viabilidade polínica em quatro acessos das espécies Capsicum annuum e Capsicum baccatum. Em todos os acessos, foram observados 12 bivalentes, confirmando o número e nível de ploidia relatados na literatura para essas espécies. Os resultados mostraram uma divisão celular normal, porém algumas anormalidades foram detectadas, tais como migração precoce dos cromossomos em metáfases I e II, cromossomos retardatários em anáfase I e divisão assincrônica. Os acessos estudados apresentaram um índice meiótico variando de 75,6 a 93,6%, e a viabilidade polínica em todos os acessos foi superior a 90%, demonstrando que as irregularidades meióticas observadas não comprometeram a viabilidade destes.The objective of this research was to study the meiotic behavior and pollen viability in four accessions of species Capsicum annuum and Capsicum baccatum. In all accessions, twelve bivalents were observed, confirming the number and ploidy level reported in the literature for these species. The results showed a normal cell division although some abnormalities had been detected, as early chromosome migration at metaphases I and II, later chromosomes at anaphase I and asynchronous division. The studied accessions presented a meiotic index (MI that varied from 75.6 to 93.6% and the pollen viability in all accessions was higher than 90%, demonstrating that the meiotic irregularities observed didn't affect their viability.

  8. Evolution in an autopolyploid group displaying predominantly bivalent pairing at meiosis: genomic similarity of diploid Vaccinium darrowi and autotetraploid V. corymbosum (Ericaceae).

    Science.gov (United States)

    Qu, L; Hancock, J; Whallon, J

    1998-05-01

    The genomic relationship between V. darrowi Camp (2n = 2x = 24) and V. corymbosum L. (2n = 4x = 48) was examined using an interspecific tetraploid hybrid, US 75, and representatives of the parental species. Two features in the background of US 75 led to the prediction that it was an allopolyploid: (1) the parental species are quite distinct morphologically and geographically, and (2) the diploid genome was incorporated into US 75 via an unreduced gamete. However, US 75 recently was shown to display tetrasomic inheritance using molecular markers. In the present cytological study, US 75 was found to have a lower than expected number of multivalents for an autopolyploid, although it had a significantly higher number of quadrivalents than its autotetraploid parent, V. corymbosum. Normal chromosome distributions were observed at anaphase I and II, and pollen viability was high. Our findings suggest that little genomic divergence has developed between the Vaccinium species and that the polyploids may freely exchange genes with sympatric diploid species via unreduced gametes. This pattern of hybridization could be an important component of evolution in all autopolyploid groups, making them much more dynamic than traditionally assumed.

  9. A sequential analysis of meiosis in the male mouse using a restricted spermatocyte population obtained by a hydroxyurea/triaziquone treatment

    NARCIS (Netherlands)

    Oud, J. L.; de Jong, J. H.; de rooij, D. G.

    1979-01-01

    A method is described to restrict the spermatocyte population in mice and other rodents using hydroxyurea (HU) and triaziquone (T). HU affects cells in S-phase, whereas T is an agent especially active on spermatogonia and not on spermatocytes. An application of three i.p. HU injections with 12 h

  10. Abnormal meiosis in an intersectional allotriploid of Populus L. and segregation of ploidy levels in 2x × 3x progeny.

    Directory of Open Access Journals (Sweden)

    Jun Wang

    Full Text Available Triploid plants are usually highly aborted owing to unbalanced meiotic chromosome segregation, but limited viable gametes can participate in the transition to different ploidy levels. In this study, numerous meiotic abnormalities were found with high frequency in an intersectional allotriploid poplar (Populus alba × P. berolinensis 'Yinzhong', including univalents, precocious chromosome migration, lagging chromosomes, chromosome bridges, micronuclei, and precocious cytokinesis, indicating high genetic imbalance in this allotriploid. Some micronuclei trigger mini-spindle formation in metaphase II and participate in cytokinesis to form polyads with microcytes. Unbalanced chromosome segregation and chromosome elimination resulted in the formation of microspores with aneuploid chromosome sets. Fusion of sister nuclei occurs in microsporocytes with precocious cytokinesis, which could form second meiotic division restitution (SDR-type gametes. However, SDR-type gametes likely contain incomplete chromosome sets due to unbalanced segregation of homologous chromosomes during the first meiotic division in triploids. Misorientation of spindles during the second meiotic division, such as fused and tripolar spindles with low frequency, could result in the formation of first meiotic division restitution (FDR-type unreduced gametes, which most likely contain three complete chromosome sets. Although 'Yinzhong' yields 88.7% stainable pollen grains with wide diameter variation from 23.9 to 61.3 μm, the pollen viability is poor (2.78% ± 0.38. A cross of 'Yinzhong' pollen with a diploid female clone produced progeny with extensive segregation of ploidy levels, including 29 diploids, 18 triploids, 4 tetraploids, and 48 aneuploids, suggesting the formation of viable aneuploidy and unreduced pollen in 'Yinzhong'. Individuals with different chromosome compositions are potential to analyze chromosomal function and to integrate the chromosomal dosage variation into breeding programs of Populus.

  11. Localization and roles of Ski8p protein in Sordaria meiosis and delineation of three mechanistically distinct steps of meiotic homolog juxtaposition.

    Science.gov (United States)

    Tessé, Sophie; Storlazzi, Aurora; Kleckner, Nancy; Gargano, Silvana; Zickler, Denise

    2003-10-28

    Ski8p is implicated in degradation of non-poly(A) and double-stranded RNA, and in meiotic DNA recombination. We have identified the Sordaria macrospora SKI8 gene. Ski8p is cytoplasmically localized in all vegetative and sexual cycle cells, and is nuclear localized, specifically in early-mid-meiotic prophase, in temporal correlation with Spo11p, the meiotic double-strand break (DSB) transesterase. Localizations of Ski8p and Spo11p are mutually interdependent. ski8 mutants exhibit defects in vegetative growth, entry into the sexual program, and sporulation. Diverse meiotic defects, also seen in spo11 mutants, are diagnostic of DSB absence, and they are restored by exogenous DSBs. These results suggest that Ski8p promotes meiotic DSB formation by acting directly within meiotic prophase chromosomes. Mutant phenotypes also divide meiotic homolog juxtaposition into three successive, mechanistically distinct steps; recognition, presynaptic alignment, and synapsis, which are distinguished by their differential dependence on DSBs.

  12. Cytological studies of human meiosis: sex-specific differences in recombination originate at, or prior to, establishment of double-strand breaks.

    Directory of Open Access Journals (Sweden)

    Jennifer R Gruhn

    Full Text Available Meiotic recombination is sexually dimorphic in most mammalian species, including humans, but the basis for the male:female differences remains unclear. In the present study, we used cytological methodology to directly compare recombination levels between human males and females, and to examine possible sex-specific differences in upstream events of double-strand break (DSB formation and synaptic initiation. Specifically, we utilized the DNA mismatch repair protein MLH1 as a marker of recombination events, the RecA homologue RAD51 as a surrogate for DSBs, and the synaptonemal complex proteins SYCP3 and/or SYCP1 to examine synapsis between homologs. Consistent with linkage studies, genome-wide recombination levels were higher in females than in males, and the placement of exchanges varied between the sexes. Subsequent analyses of DSBs and synaptic initiation sites indicated similar male:female differences, providing strong evidence that sex-specific differences in recombination rates are established at or before the formation of meiotic DSBs. We then asked whether these differences might be linked to variation in the organization of the meiotic axis and/or axis-associated DNA and, indeed, we observed striking male:female differences in synaptonemal complex (SC length and DNA loop size. Taken together, our observations suggest that sex specific differences in recombination in humans may derive from chromatin differences established prior to the onset of the recombination pathway.

  13. Proteasomal activity has multiple functions in oocyte meiosis, in cumulus expansion, in synthesis and processing of cumulus extracellular matrix and steroidogenesis

    Czech Academy of Sciences Publication Activity Database

    Nagyová, Eva

    2014-01-01

    Roč. 3, č. 2 (2014), s. 163-163 ISSN 2161-1017. [International Conference on Endocrinology /2./. 20.10.2014-22.10.2014, Chicago] Institutional support: RVO:67985904 Keywords : oocyte-cumulus complexes Subject RIV: EB - Genetics ; Molecular Biology

  14. Karyotypes, male meiosis and comparative FISH mapping of 18S ribosomal DNA and telomeric (TTAGGn repeat in eight species of true bugs (Hemiptera, Heteroptera

    Directory of Open Access Journals (Sweden)

    Snejana Grozeva

    2011-11-01

    Full Text Available Eight species belonging to five true bug families were analyzed using DAPI/CMA3-staining and fluorescence in situ hybridization (FISH with telomeric (TTAGGn and 18S rDNA probes. Standard chromosomal complements are reported for the first time for Deraeocoris rutilus (Herrich-Schäffer, 1838 (2n=30+2m+XY and D. ruber (Linnaeus, 1758 (2n=30+2m+XY from the family Miridae. Using FISH, the location of a 18S rDNA cluster was detected in these species and in five more species: Megaloceroea recticornis (Geoffroy, 1785 (2n=30+XY from the Miridae; Oxycarenus lavaterae (Fabricius, 1787 (2n=14+2m+XY from the Lygaeidae s.l.; Pyrrhocoris apterus (Linnaeus, 1758 (2n=22+X from the Pyrrhocoridae; Eurydema oleracea (Linnaeus, 1758 (2n=12+XY and Graphosoma lineatum (Linnaeus, 1758 (2n=12+XY from the Pentatomidae. The species were found to differ with respect to location of a 18S rRNA gene cluster which resides on autosomes in O. lavaterae and P. apterus, whereas it locates on sex chromosomes in other five species. The 18S rDNA location provides the first physical landmark of the genomes of the species studied. The insect consensus telomeric pentanucleotide (TTAGGn was demonstrated to be absent in all the species studied in this respect, D. rutilus, M. recticornis, Cimex lectularius Linnaeus, 1758 (Cimicidae, E. oleracea, and G. lineatum, supporting the hypothesis that this motif was lost in early evolution of the Heteroptera and secondarily replaced with another motif (yet unknown or the alternative telomerase-independent mechanisms of telomere maintenance. Dot-blot hybridization analysis of the genomic DNA from C. lectularius, Nabis sp. and O. lavaterae with (TTAGGn and six other telomeric probes likewise provided a negative result.

  15. Meiose e viabilidade polínica em linhagens avançadas de pimenta Meiosis and pollen viability in advanced lines of pepper

    Directory of Open Access Journals (Sweden)

    Marisa T Pozzobon

    2011-06-01

    Full Text Available Doze linhagens de pimenta, incluindo exemplares do tipo Jalapeño (CNPH 2862, CNPH 2864, Dedo-de-Moça (CNPH 1397, CNPH 0039, CNPH 0053, Cambuci (CNPH 0283, Peixe-Boi (CNPH 0434, Falsa Cumari (CNPH 3761, Bode Vermelha (CNPH 3773, Biquinho Doce (CNPH 3870, Tabasco (CNPH 3000 e Malagueta (CNPH 2869 tiveram o comportamento meiótico e a estimativa da viabilidade do pólen analisados, com o objetivo de indicar materiais potencialmente férteis para o programa de melhoramento de Capsicum da Embrapa. A análise convencional, por coloração, revelou um comportamento relativamente normal, durante a microsporogênese, para a maioria das linhagens, com índice meiótico (IM e percentual médio de viabilidade polínica acima de 90%. As principais anormalidades observadas foram aderências cromossômicas, cromossomos não orientados, retardatários, pontes, micronúcleos, micrócitos e citomixia. Três linhagens, CNPH 0283, CNPH 3000 e CNPH 3773 mostraram menor percentual de pólens viáveis, respectivamente 77, 66 e 58%. Somente para CNPH 0283 a baixa fertilidade do pólen esteve associada à maior frequência de irregularidades e, consequentemente, ao baixo IM (77%. Os resultados do presente trabalho confirmam a importância da análise citológica como ferramenta auxiliar na seleção de linhagens meioticamente estáveis e potencialmente férteis o que possibilita o planejamento de programas de produção de sementes das cultivares em vias de lançamento.Twelve lines of pepper, from different groups {Jalapeño (CNPH 2862, CNPH 2864, Dedo-de-Moça (CNPH 1397, CNPH 0039, CNPH 0053, Cambuci (CNPH 0283, Peixe-Boi (CNPH 0434, Falsa Cumari (CNPH 3761, Bode Vermelha (CNPH 3773, Biquinho Doce (CNPH 3870, Tabasco (CNPH 3000 and Malagueta (CNPH 2869 had their meiotic behavior and the estimation of pollen viability analyzed with the aim of indicating potentially fertile material for the Capsicum breeding program. Conventional analysis by staining revealed a slightly irregular behavior during microsporogenesis for the majority of lines: the meiotic index (MI and pollen viability were over 90%, therefore considered meiotically stable. The main abnormalities observed were chromosome stickiness, unoriented chromosomes, laggards, bridges, micronuclei, microcytes and cytomixis. Three lines (CNPH 0283, CNPH 3000 and CNPH 3773 showed lower pollen viability, 77, 66 and 58% respectively. The lower pollen viability in CNPH 0283 was associated with higher frequency of irregularities and consequently the low MI (77%. The findings of the present manuscript confirm the importance of the cytological analyzes as a useful tool in selecting of lines meiotically stable and potentially fertile enabling a better planning of seed production of promising cultivars.

  16. Synapsis-Defective Mutants Reveal a Correlation Between Chromosome Conformation and the Mode of Double-Strand Break Repair During Caenorhabditis elegans Meiosis

    OpenAIRE

    Smolikov, Sarit; Eizinger, Andreas; Hurlburt, Allison; Rogers, Eric; Villeneuve, Anne M.; Colaiácovo, Mónica P.

    2007-01-01

    SYP-3 is a new structural component of the synaptonemal complex (SC) required for the regulation of chromosome synapsis. Both chromosome morphogenesis and nuclear organization are altered throughout the germlines of syp-3 mutants. Here, our analysis of syp-3 mutants provides insights into the relationship between chromosome conformation and the repair of meiotic double-strand breaks (DSBs). Although crossover recombination is severely reduced in syp-3 mutants, the production of viable offspri...

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

    Science.gov (United States)

    Nabeshima, Kentaro; Mlynarczyk-Evans, Susanna; Villeneuve, Anne M

    2011-08-01

    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.

  18. Chromosome Painting Reveals Asynaptic Full Alignment of Homologs and HIM-8–Dependent Remodeling of X Chromosome Territories during Caenorhabditis elegans Meiosis

    Science.gov (United States)

    Nabeshima, Kentaro; Mlynarczyk-Evans, Susanna; Villeneuve, Anne M.

    2011-01-01

    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. PMID:21876678

  19. Gclust Server: 16514 [Gclust Server

    Lifescience Database Archive (English)

    Full Text Available ced by exposure to mutagens, also induced during meiosis at a time nearly coincident with commitment to reco...posure to mutagens, also induced during meiosis at a time nearly coincident with commitment to recombination

  20. Fulltext PDF

    Indian Academy of Sciences (India)

    Srinivas

    Functional embryo sac formation in Arabidopsis without meiosis – one ... centromere organization during meiosis. In swi1 ... megaspore undergoes three rounds of mitosis to produce a seven-celled gamete structure also called an embryo sac.

  1. Yeast Interacting Proteins Database: YDR439W, YCR086W [Yeast Interacting Proteins Database

    Lifescience Database Archive (English)

    Full Text Available inetochores during meiosis I to mediate accurate homolog segregation; required for condensin recruitment to ...and then Mam1p at kinetochores during meiosis I to mediate accurate homolog segregation; required for condensin recruitment...p, and then Mam1p at kinetochores during meiosis I to mediate accurate homolog segregation; required for condensin recruitment...with Lrs4p and then Mam1p at kinetochores during meiosis I to mediate accurate homolog segregation; required for condensin recruitmen

  2. New Insights into the Regulation of Serine Palmitoyltransferase

    Science.gov (United States)

    2014-02-07

    34 Tetrad dissection and analysis of products of meiosis ...ORF - Open reading frame PHS - Phytosphingosine P.0.M-Products of meiosis SIP - S phingosine-1-phosphate SC - Sodium citrate SD - Synthetic...analysis of products of meiosis : Yeast mating and sporulation was done according to the standard protocols (79). Yeast transformation: All yeast

  3. Sequence Classification: 890748 [

    Lifescience Database Archive (English)

    Full Text Available in, involved in maintaining sister chromatid cohesion during meiosis I as well as promoting proper attachmen...t of kinetochores to the spindle during meiosis I and meiosis II; Spo13p || http://www.ncbi.nlm.nih.gov/protein/6321802 ...

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

    Science.gov (United States)

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

  5. Short-term high temperature growth conditions during vegetative-to-reproductive phase transition irreversibly compromise cell wall invertase-mediated sucrose catalysis and microspore meiosis in grain sorghum

    Science.gov (United States)

    Grain sorghum (Sorghum bicolor L. Moench) crop yield is significantly compromised by high temperature stress-induced male sterility, and is attributed to reduced cell wall invertase (CWI)-mediated sucrose hydrolysis in microspores and anthers leading to altered carbohydrate metabolism and starch def...

  6. Identification of Checkpoint Genes Involved in the kar3 Cell Cycle Arrest

    National Research Council Canada - National Science Library

    Shanks, Robert

    2001-01-01

    ...) including Cik1p and Vik1p. We have explored the roles of these KAPs in mejosis. Cik1p is essential for meiosis, while Vik1p has a very minor role. These data are consistent with Cik1p and Kar3p acting together to perform the essential role of Kar3p in meiosis. We have also localized Kar3p, Cik1p,and Vik1p during meiosis.

  7. Meiotic faults as a major cause of offspring inviability

    DEFF Research Database (Denmark)

    Levitis, Daniel; Zimmerman, Kolea; Pringle, Anne

    2014-01-01

    , this result demonstrates that failures associated with meiosis are a major cause of offspring inviability not only for meiotic parthenogenesis, but for sexual reproducers such as humans. Meiosis is necessary for genetic recombination in eukaryotes, but is vestigial, and costly, in parthenogens. The question...... range of organisms....

  8. Effect of jasplakinolide on the in vitro maturation of bovine oocytes ...

    African Journals Online (AJOL)

    Jasplakinolide (JAS), a cytotoxic natural product, induces actin polymerization and increases microfilament assembly. The knowledge about the effect of JAS on oocyte meiosis in mammals is limited. The present study was to investigate the effect of JAS on the events of oocyte meiosis such as spindle configuration, ...

  9. Early gonad development in zebrafish ( Danio rerio ) | Okuthe ...

    African Journals Online (AJOL)

    Gonadogenesis in zebrafish goes through an initial ovarian phase then subsequently into either ovarian or testicular phases. How germ cells choose to commit to an oogenic fate and enter meiosis or alternatively not enter meiosis and commit to a spermatogenetic fate remains a key question. This study investigated events ...

  10. Distribution pattern of histone H3 phosphorylation at serine 10

    Indian Academy of Sciences (India)

    We evaluated the pattern of H3 phosphorylation using immunodetection during mitosis and meiosis in both diploid and tetraploid genotypes of Brachiaria species. Results revealed differences in chromosome distribution of H3S10ph when mitosis and meiosis were compared. Whole chromosomes were phosphorylated ...

  11. RNAi and heterochromatin repress centromeric meiotic recombination

    DEFF Research Database (Denmark)

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

    2010-01-01

    During meiosis, the formation of viable haploid gametes from diploid precursors requires that each homologous chromosome pair be properly segregated to produce an exact haploid set of chromosomes. Genetic recombination, which provides a physical connection between homologous chromosomes, is essen......During meiosis, the formation of viable haploid gametes from diploid precursors requires that each homologous chromosome pair be properly segregated to produce an exact haploid set of chromosomes. Genetic recombination, which provides a physical connection between homologous chromosomes....... 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....

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

    Directory of Open Access Journals (Sweden)

    Thomas Tischer

    2016-10-01

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

  13. Analysis of the meiotic transcriptome reveals the genes related to the regulation of pollen abortion in cytoplasmic male-sterile pepper (Capsicum annuum L.).

    Science.gov (United States)

    Qiu, Yilan; Liao, Lijuan; Jin, Xiaorui; Mao, Dandan; Liu, Rushi

    2018-01-30

    CMS, which refers to the inability to generate functional pollen grains while still producing a normal gynoecium, has been widely used for pepper hybrid seed production. Pepper line 8214A is an excellent CMS line exhibiting 100% male sterility and superior economic characteristics. A TUNEL assay revealed the nuclear DNA is damaged in 8214A PMCs during meiosis. TEM images indicated that the 8214A PMCs exhibited asynchronous meiosis after prophase I, and some PMCs degraded prematurely with morphological features typical of PCD. Additionally, at the end of meiosis, the 8214A PMCs formed abnormal non-tetrahedral tetrads that degraded in situ. To identify the genes involved in the pollen abortion of line 8214A, the transcriptional profiles of the 8214A and the 8214B anthers (i.e., from the fertile maintainer line) during meiosis were analyzed using an RNA-seq approach. A total of 1355 genes were determined to be differentially expressed, including 424 and 931 up- and down- regulated genes, respectively, in the 8214A anthers during meiosis relative to the expression levels in the 8214B. The expression levels of ubiquitin ligase and cell cycle-related genes were apparently down-regulated, while the expression of methyltransferase genes was up-regulated in the 8214A anthers during meiosis, which likely contributed to the PCD of these PMCs during meiosis. Thus, our results may be useful for revealing the molecular mechanism regulating the pollen abortion of CMS pepper. Copyright © 2017. Published by Elsevier B.V.

  14. Effect of concentration and exposure period to butyrolactone I on meiosis progression in bovine oocytes Efeito de concentração e tempo de exposição à butirolactona I na progressão da meiose de oócitos bovinos

    Directory of Open Access Journals (Sweden)

    P.R. Adona

    2006-06-01

    Full Text Available The effect of concentration and exposure period of bovine oocytes to butyrolactone I (BLI on meiotic block and in vitro maturation (IVM kinetics was studied. In experiment 1, all oocytes were at germinal vesicle stage (GV, after 6h in culture with 0, 50 and 100µM BLI. After 12h, all oocytes cultured with 50 and 100µM BLI remained in GV. After 24h, less oocytes were in GV with 50µM (82% than with 100µM BLI (99%, P0.05. After 18h IVM, metaphase II (MII rates were similar for all groups (76-81%. In experiment 3, after 6h IVM, 74% of treated oocytes (50 or 100µM BLI for 12h were in GV. This rate was lower than for control oocytes (97.3%, P0.05 were in MII with BLI than for control (73%, PEstudou-se o efeito da concentração e do tempo de exposição à butirolactona I (BLI no bloqueio meiótico e na cinética da maturação in vitro (MIV de oócitos bovinos. No experimento 1, todos os oócitos encontravam-se em vesícula germinativa (VG após 6h de cultivo nas concentrações de 0,50 e 100µM BLI. Após 12h, somente oócitos cultivados com BLI (50 e 100µM estavam em VG. Após 24h, menos oócitos tratados com 50µM (82% estavam em VG em relação a 100µM (99%, P0,05. A taxa de metáfase II (MII, 76-81% foi similar para todos os tempos de exposição, após 18h de MIV. No experimento 3, após 6h de MIV, menos oócitos tratados (74% para 50 ou 100µM BLI por 12h estavam em VG comparados aos controles (97%, P0,05 do que os controles (73%, P<0.05. Conclui-se que para cultivos mais curtos, a concentração mais baixa de BLI bloqueia a meiose a cinética da maturação nuclear é acelerada em oócitos expostos à BLI e isso é afetado pelo tempo de cultivo, mas não pela concentração da droga.

  15. Positive Feedback of NDT80 Expression Ensures Irreversible Meiotic Commitment in Budding Yeast

    Science.gov (United States)

    Tsuchiya, Dai; Yang, Yang; Lacefield, Soni

    2014-01-01

    In budding yeast, meiotic commitment is the irreversible continuation of the developmental path of meiosis. After reaching meiotic commitment, cells finish meiosis and gametogenesis, even in the absence of the meiosis-inducing signal. In contrast, if the meiosis-inducing signal is removed and the mitosis-inducing signal is provided prior to reaching meiotic commitment, cells exit meiosis and return to mitosis. Previous work has shown that cells commit to meiosis after prophase I but before entering the meiotic divisions. Since the Ndt80 transcription factor induces expression of middle meiosis genes necessary for the meiotic divisions, we examined the role of the NDT80 transcriptional network in meiotic commitment. Using a microfluidic approach to analyze single cells, we found that cells commit to meiosis in prometaphase I, after the induction of the Ndt80-dependent genes. Our results showed that high-level expression of NDT80 is important for the timing and irreversibility of meiotic commitment. A modest reduction in NDT80 levels delayed meiotic commitment based on meiotic stages, although the timing of each meiotic stage was similar to that of wildtype cells. A further reduction of NDT80 resulted in the surprising finding of inappropriately uncommitted cells: withdrawal of the meiosis-inducing signal and addition of the mitosis-inducing signal to cells at stages beyond metaphase I caused return to mitosis, leading to multi-nucleate cells. Since Ndt80 enhances its own transcription through positive feedback, we tested whether positive feedback ensured the irreversibility of meiotic commitment. Ablating positive feedback in NDT80 expression resulted in a complete loss of meiotic commitment. These findings suggest that irreversibility of meiotic commitment is a consequence of the NDT80 transcriptional positive feedback loop, which provides the high-level of Ndt80 required for the developmental switch of meiotic commitment. These results also illustrate the

  16. Computer Center: Software Review.

    Science.gov (United States)

    Duhrkopf, Richard, Ed.; Belshe, John F., Ed.

    1988-01-01

    Reviews a software package, "Mitosis-Meiosis," available for Apple II or IBM computers with colorgraphics capabilities. Describes the documentation, presentation and flexibility of the program. Rates the program based on graphics and usability in a biology classroom. (CW)

  17. Molecular control of rodent spermatogenesis

    NARCIS (Netherlands)

    Jan, Sabrina Z.; Hamer, Geert; Repping, Sjoerd; de Rooij, Dirk G.; van Pelt, Ans M. M.; Vormer, Tinke L.

    2012-01-01

    Spermatogenesis is a complex developmental process that ultimately generates mature spermatozoa. This process involves a phase of proliferative expansion, meiosis, and cytodifferentiation. Mouse models have been widely used to study spermatogenesis and have revealed many genes and molecular

  18. Fluorescent in situ hybridization shows DIPLOSPOROUS located on one of the NOR chromosomes in apomictic dandelions (Taraxacum) in the absence of a large hemizygous chromosomal region

    NARCIS (Netherlands)

    Vasut, R.J.; Vijverberg, K.; Dijk, van P.J.; Jong, de J.H.S.G.M.

    2014-01-01

    Apomixis in dandelions (Taraxacum: Asteraceae) is encoded by two unlinked dominant loci and a third yet undefined genetic factor: diplosporous omission of meiosis (DIPLOSPOROUS, DIP), parthenogenetic embryo development (PARTHENOGENESIS, PAR), and autonomous endosperm formation, respectively. In this

  19. Karyomorphotypic variation in Eriospermum abyssinicum

    African Journals Online (AJOL)

    Tosin Adeigbe

    2013-03-06

    Mar 6, 2013 ... Male meiotic products, mostly tetrads were also recorded at x400 magnification. Micrographs of meiosis .... unstable hybrid with 2n = 12 and the hybrid undergoes .... Microsporogenesis and sexual sterility in. Drimiopsis barteri ...

  20. The Role of Drosophila Merlin in the Control of Mitosis Exit and Development

    National Research Council Canada - National Science Library

    Chang, Long-Sheng

    2008-01-01

    ... determination of dorsal/ventral compartment border during wing imaginal disc development. We show that the Merlin protein is dynamically redistributed during meiosis and demonstrate, for the first time, Merlin immunoreactivity in mitochondria...

  1. Neurospora tetrasperma crosses heterozygous for hybrid ...

    Indian Academy of Sciences (India)

    2017-02-10

    nucleus stage that follows meiosis and a post-meiotic mitosis, and the ascospores that form in eight-spored asci are usually homokaryotic. We had previously created novel TNt strains by introgressing four Neurospora crassa ...

  2. Neurospora tetrasperma crosses heterozygous for hybrid

    Indian Academy of Sciences (India)

    nucleus stage that follows meiosis and apost-meiotic mitosis, and the ascospores that form in eight-spored asci are usually homokaryotic. We had previouslycreated novel TNt strains by introgressing four Neurospora crassa insertional ...

  3. Crossbreeding Holstein-Friesian with Ethiopian Boran cattle in a ...

    African Journals Online (AJOL)

    Unknown

    Friesian with Boran (unselected for milk), the epistatic interaction genes might have been lost due to the free recombination process during meiosis. Similar negative recombination effects on milk yield were reported even for crossing between two B.

  4. DNA damage in the oocytes SACs

    Czech Academy of Sciences Publication Activity Database

    Macůrek, Libor

    2016-01-01

    Roč. 15, č. 4 (2016), s. 491-492 ISSN 1538-4101 Institutional support: RVO:68378050 Keywords : DNA damage response * oocyte * meiosis * checkpoint Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.530, year: 2016

  5. Journal of Genetics | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    /jgen/088/01/0001-0007. Keywords. Down syndrome; trisomy 21; meiosis; Penrose; parental age; nondisjunction; human genetics. Author Affiliations. Santhosh Girirajan1. Department of Genome Sciences, University of Washington, Seattle, ...

  6. Deletion of the pluripotency-associated Tex19.1 gene causes activation of endogenous retroviruses and defective spermatogenesis in mice

    DEFF Research Database (Denmark)

    Ollinger, Rupert; Childs, Andrew J; Burgess, Hannah M

    2008-01-01

    . During male spermatogenesis, Tex19.1 expression is highest in mitotic spermatogonia and diminishes as these cells differentiate and progress through meiosis. In pluripotent stem cells, Tex19.1 expression is also downregulated upon differentiation. However, it is not clear whether Tex19.1 has an essential...... spermatogenesis. Immunostaining and histological analysis revealed defects in meiotic chromosome synapsis, the persistence of DNA double-strand breaks during meiosis, and a loss of post-meiotic germ cells in the testis. Furthermore, expression of a class of endogenous retroviruses is upregulated during meiosis...... in the Tex19.1(-/-) testes. Increased transposition of endogenous retroviruses in the germline of Tex19.1(-/-) mutant mice, and the concomitant increase in DNA damage, may be sufficient to disrupt the normal processes of recombination and chromosome synapsis during meiosis and cause defects...

  7. Whole-genome sequencing of spermatocytic tumors provides insights into the mutational processes operating in the male germline

    DEFF Research Database (Denmark)

    Giannoulatou, Eleni; Maher, Geoffrey J; Ding, Zhihao

    2017-01-01

    Adult male germline stem cells (spermatogonia) proliferate by mitosis and, after puberty, generate spermatocytes that undertake meiosis to produce haploid spermatozoa. Germ cells are under evolutionary constraint to curtail mutations and maintain genome integrity. Despite constant turnover...

  8. Meiotic interference among MLH1 foci requires neither an intact axial element structure nor full synapsis

    NARCIS (Netherlands)

    Boer, den E.; Dietrich, A.J.J.; Höög, C.; Stam, P.; Heyting, C.

    2007-01-01

    During meiosis, homologous chromosomes (homologs) perform reciprocal exchanges (crossovers) at a high frequency. Crossovers display interference, i.e. their spacing is more even than would be expected if they were placed randomly along the chromosomes. Concomitantly with crossover formation,

  9. Cellular and molecular biology of filamentous fungi

    National Research Council Canada - National Science Library

    Borkovich, Katherine A; Ebbole, Daniel J

    2010-01-01

    ... AND EXPRESSION OF THE GENETIC CODE / 61 6 Mitotic Cell Cycle Control / 63 COLIN P. C. DE SOUZA AND STEPHEN A. OSMANI 7 Meiosis / 81 CLAIRE BURNS, PATRICIA J. PUKKILA, AND MIRIAM E. ZOLAN 8 DNA Repa...

  10. Understanding Recombination.

    Science.gov (United States)

    Zimmerman, Ira

    2003-01-01

    Describes a science activity on the importance of meiosis for variability. Uses a coin flip to demonstrate the random arrangement of genetic materials and explains how this results in zygotes with a new DNA combination. (YDS)

  11. Biotechnical Microbiology, yeast and bacteria

    DEFF Research Database (Denmark)

    Villadsen, Ingrid Stampe

    1999-01-01

    This section contains the following single lecture notes: Eukaryotic Cell Biology. Kingdom Fungi. Cell Division. Meiosis and Recombination. Genetics of Yeast. Organisation of the Chromosome. Organization and genetics of the mitochondrial Geneme. Regulatio of Gene Expression. Intracellular Compart...

  12. 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

  13. Sequence Classification: 890096 [

    Lifescience Database Archive (English)

    Full Text Available ome, induced by exposure to mutagens, also induced during meiosis at a time nearly coincident with commitment to recombination; Din7p || http://www.ncbi.nlm.nih.gov/protein/6320469 ...

  14. A mother with variant Turner syndrome and two daughters with ...

    Indian Academy of Sciences (India)

    ... and two daughters with trisomy X: a case report ... has been reported, spontaneous pregnancy is rare with risk ... phenotype and includes learning disabilities, speech delays, .... X arise in maternal meiosis make this explanation less likely.

  15. Regulation of meiotic entry and gonadal sex differentiation in the human

    DEFF Research Database (Denmark)

    Jørgensen, Anne; Rajpert-De Meyts, Ewa

    2014-01-01

    Meiosis is a unique type of cell division that is performed only by germ cells to form haploid gametes. The switch from mitosis to meiosis exhibits a distinct sex-specific difference in timing, with female germ cells entering meiosis during fetal development and male germ cells at puberty when...... spermatogenesis is initiated. During early fetal development, bipotential primordial germ cells migrate to the forming gonad where they remain sexually indifferent until the sex-specific differentiation of germ cells is initiated by cues from the somatic cells. This irreversible step in gonadal sex...... in the context of fetal gonad development and germ cell differentiation, with emphasis on results obtained in humans. Furthermore, the consequences of dysregulated meiosis signaling in humans are briefly discussed in the context of selected pathologies, including testicular germ cell cancer and some forms...

  16. Genomic Instability and Breast Cancer

    Science.gov (United States)

    2011-06-01

    distinguish these possibilities. The possible function of human SWI5-MEI5 in meiosis also needs to be investigated. It remains to be determined whether the... human SWI5-MEI5 complex acts in meiosis and, if it does, whether it acts with DMC1, RAD51, or both. Considering that SWI5-MEI5 is the only human ...tumorigenesis. This has been clearly illustrated in familial breast cancer, since human genetic studies reveal that many genes involved in DNA damage response

  17. The inhibitor of calcium activated neutral proteinase is an anti-meiotic agent. The spermicidal and anti-viral action

    OpenAIRE

    Logothetou-Rella, H.

    1995-01-01

    In situ cytogenetic morphology and analysis showed that Epstein-Barr Virus (EBV)-infected Raji and EBV-producing P3HR-1 cells divide by meiosis and follow the life cycle of malignant cells in vitro. Meiosis was documented by the presence of condensed chromosomes, «o» chromosome, nuclear vlimata (NVs), NV invasion, extrusion of chromosomes, chromosomal transfer, metaphase fusion and aneuploidy. EBV-Raji, EBV-producing P3HR, HIV1-infected MOLT-4 cells (dividi...

  18. Kinetics of recombination yield in the storing of irradiated seeds

    International Nuclear Information System (INIS)

    Zhuchenko, A.A.; Korol', A.B.; Tyarina, V.S.; Grati, V.G.; Andryushchenko, V.K.; Bocharnikova, N.I.; Grati, M.I.

    1979-01-01

    Studied was the dependence of recombination frequency between marker locuses in meiosis on the storing durability of gamma irradiated seeds of tomatoes. It is shown that while gamma-irradiated seed storing observed is the definite kinetics in changes of the level of chromosome aberrations in mitosis and meiosis, frequencies of crossing-over, frequencies of noncoupled marker recombinations, besides all these indices, with the exception of the latter, correlate one with another

  19. Many functions of the meiotic cohesin.

    Science.gov (United States)

    Bardhan, Amit

    2010-12-01

    Sister chromatids are held together from the time of their formation in S phase until they segregate in anaphase by the cohesin complex. In meiosis of most organisms, the mitotic Mcd1/Scc1/Rad21 subunit of the cohesin complex is largely replaced by its paralog named Rec8. This article reviews the specialized functions of Rec8 that are crucial for diverse aspects of chromosome dynamics in meiosis, and presents some speculations relating to meiotic chromosome organization.

  20. Meiotic Consequences of Genetic Divergence Across the Murine Pseudoautosomal Region

    OpenAIRE

    Dumont, Beth L.

    2017-01-01

    The production of haploid gametes during meiosis is dependent on the homology-driven processes of pairing, synapsis, and recombination. On the mammalian heterogametic sex chromosomes, these key meiotic activities are confined to the pseudoautosomal region (PAR), a short region of near-perfect sequence homology between the X and Y chromosomes. Despite its established importance for meiosis, the PAR is rapidly evolving, raising the question of how proper X/Y segregation is buffered against the ...

  1. A Critical Review of Concepts and Methods Used in Classical Genome Analysis

    DEFF Research Database (Denmark)

    Seberg, Ole; Petersen, Gitte

    1998-01-01

    A short account of the development of classical genome analysis, the analysis of chromosome behaviour in metaphase I of meiosis, primarily in interspecific hybrids, is given. The application of the concept of homology to describe chromosome pairing between the respective chromosomes of a pair...... breeding but it has no place in systematics. With an increased knowledge and understanding of the mechanism behind meiosis, data useful in a systematic context may eventually be produced....

  2. Development of the pollen in the antarctic flowering plant Colobanthus quitensis (Kunth) Bartl.

    OpenAIRE

    Irena Giełwanowska; Anna Bochenek; Ewa Szczuka

    2012-01-01

    Colobanthus quitensis (Kunth) Bartl. produced two types very small bisexual fl owers. In the Antarctic natural conditions chasmogamic and cleistogamic fl owers most often form fi ve stamina with short fi laments. Two microsporangia with a three-layer wall form in the anther. Microspore mother cells, which develop into microspores after meiosis, form inside the microsporangium. Microsporocytes of Colobanthus quitensis are surrounded with a thick callose layer, the special wall. After meiosis, ...

  3. Repression of Meiotic Genes by Antisense Transcription and by Fkh2 Transcription Factor in Schizosaccharomyces pombe

    OpenAIRE

    Chen, Huei-Mei; Rosebrock, Adam P.; Khan, Sohail R.; Futcher, Bruce; Leatherwood, Janet K.

    2012-01-01

    In S. pombe, about 5% of genes are meiosis-specific and accumulate little or no mRNA during vegetative growth. Here we use Affymetrix tiling arrays to characterize transcripts in vegetative and meiotic cells. In vegetative cells, many meiotic genes, especially those induced in mid-meiosis, have abundant antisense transcripts. Disruption of the antisense transcription of three of these mid-meiotic genes allowed vegetative sense transcription. These results suggest that antisense transcription ...

  4. New insights into human nondisjunction of chromosome 21 in oocytes.

    Directory of Open Access Journals (Sweden)

    Tiffany Renee Oliver

    2008-03-01

    Full Text Available Nondisjunction of chromosome 21 is the leading cause of Down syndrome. Two risk factors for maternal nondisjunction of chromosome 21 are increased maternal age and altered recombination. In order to provide further insight on mechanisms underlying nondisjunction, we examined the association between these two well established risk factors for chromosome 21 nondisjunction. In our approach, short tandem repeat markers along chromosome 21 were genotyped in DNA collected from individuals with free trisomy 21 and their parents. This information was used to determine the origin of the nondisjunction error and the maternal recombination profile. We analyzed 615 maternal meiosis I and 253 maternal meiosis II cases stratified by maternal age. The examination of meiosis II errors, the first of its type, suggests that the presence of a single exchange within the pericentromeric region of 21q interacts with maternal age-related risk factors. This observation could be explained in two general ways: 1 a pericentromeric exchange initiates or exacerbates the susceptibility to maternal age risk factors or 2 a pericentromeric exchange protects the bivalent against age-related risk factors allowing proper segregation of homologues at meiosis I, but not segregation of sisters at meiosis II. In contrast, analysis of maternal meiosis I errors indicates that a single telomeric exchange imposes the same risk for nondisjunction, irrespective of the age of the oocyte. Our results emphasize the fact that human nondisjunction is a multifactorial trait that must be dissected into its component parts to identify specific associated risk factors.

  5. A novel RNA-recognition-motif protein is required for premeiotic G1/S-phase transition in rice (Oryza sativa L..

    Directory of Open Access Journals (Sweden)

    Ken-Ichi Nonomura

    2011-01-01

    Full Text Available The molecular mechanism for meiotic entry remains largely elusive in flowering plants. Only Arabidopsis SWI1/DYAD and maize AM1, both of which are the coiled-coil protein, are known to be required for the initiation of plant meiosis. The mechanism underlying the synchrony of male meiosis, characteristic to flowering plants, has also been unclear in the plant kingdom. In other eukaryotes, RNA-recognition-motif (RRM proteins are known to play essential roles in germ-cell development and meiosis progression. Rice MEL2 protein discovered in this study shows partial similarity with human proline-rich RRM protein, deleted in Azoospermia-Associated Protein1 (DAZAP1, though MEL2 also possesses ankyrin repeats and a RING finger motif. Expression analyses of several cell-cycle markers revealed that, in mel2 mutant anthers, most germ cells failed to enter premeiotic S-phase and meiosis, and a part escaped from the defect and underwent meiosis with a significant delay or continued mitotic cycles. Immunofluorescent detection revealed that T7 peptide-tagged MEL2 localized at cytoplasmic perinuclear region of germ cells during premeiotic interphase in transgenic rice plants. This study is the first report of the plant RRM protein, which is required for regulating the premeiotic G1/S-phase transition of male and female germ cells and also establishing synchrony of male meiosis. This study will contribute to elucidation of similarities and diversities in reproduction system between plants and other species.

  6. Nonequivalence of maternal centrosomes/centrioles in starfish oocytes: selective casting-off of reproductive centrioles into polar bodies.

    Science.gov (United States)

    Uetake, Yumi; Kato, Koichi H; Washitani-Nemoto, Setsuko; Nemoto Si, Shin-ichi

    2002-07-01

    It is believed that in most animals only the paternal centrosome provides the division poles for mitosis in zygotes. This paternal inheritance of the centrosomes depends on the selective loss of the maternal centrosome. In order to understand the mechanism of centrosome inheritance, the behavior of all maternal centrosomes/centrioles was investigated throughout the meiotic and mitotic cycles by using starfish eggs that had polar body (PB) formation suppressed. In starfish oocytes, the centrioles do not duplicate during meiosis II. Hence, each centrosome of the meiosis II spindle has only one centriole, whereas in meiosis I, each has a pair of centrioles. When two pairs of meiosis I centrioles were retained in the cytoplasm of oocytes by complete suppression of PB extrusion, they separated into four single centrioles in meiosis II. However, after completion of the meiotic process, only two of the four single centrioles were found in addition to the pronucleus. When the two single centrioles of a meiosis II spindle were retained in the oocyte cytoplasm by suppressing the extrusion of the second PB, only one centriole was found with the pronucleus after the completion of the meiotic process. When these PB-suppressed eggs were artificially activated to drive the mitotic cycles, all the surviving single centrioles duplicated repeatedly to form pairs of centrioles, which could organize mitotic spindles. These results indicate that the maternal centrioles are not equivalent in their intrinsic stability and reproductive capacity. The centrosomes with the reproductive centrioles are selectively cast off into the PBs, resulting in the mature egg inheriting a nonreproductive centriole, which would degrade shortly after the completion of meiosis. (c) 2002 Elsevier Science (USA).

  7. RPA homologs and ssDNA processing during meiotic recombination.

    Science.gov (United States)

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

    2016-06-01

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

  8. 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.

  9. Replication and meiotic transmission of yeast ribosomal RNA genes.

    Science.gov (United States)

    Brewer, B J; Zakian, V A; Fangman, W L

    1980-11-01

    The yeast Saccharomyces cerevisiae has approximately 120 genes for the ribosomal RNAs (rDNA) which are organized in tandem within chromosomal DNA. These multiple-copy genes are homogeneous in sequence but can undergo changes in copy number and topology. To determine if these changes reflect unusual features of rDNA metabolism, we have examined both the replication of rDNA in the mitotic cell cycle and the inheritance of rDNA during meiosis. The results indicate that rDNA behaves identically to chromosomal DNA: each rDNA unit is replicated once during the S phase of each cell cycle and each unit is conserved through meiosis. Therefore, the flexibility in copy number and topology of rDNA does not arise from the selective replication of units in each S phase nor by the selective inheritance of units in meiosis.

  10. Shaping meiotic chromosomes with SUMO: a feedback loop controls the assembly of the synaptonemal complex in budding yeast

    Directory of Open Access Journals (Sweden)

    Hideo Tsubouchi

    2016-02-01

    Full Text Available The synaptonemal complex (SC is a meiosis-specific chromosomal structure in which homologous chromosomes are intimately linked through arrays of specialized proteins called transverse filaments (TF. Widely conserved in eukaryote meiosis, the SC forms during prophase I and is essential for accurate segregation of homologous chromosomes at meiosis I. However, the basic mechanism overlooking formation and regulation of the SC has been poorly understood. By using the budding yeast Saccharomyces cerevisiae, we recently showed that SC formation is controlled through the attachment of multiple molecules of small ubiquitin-like modifier (SUMO to a regulator of TF assembly. Intriguingly, this SUMOylation is activated by TF, implicating the involvement of a positive feedback loop in the control of SC assembly. We discuss the implication of this finding and possible involvement of a similar mechanism in regulating other processes.

  11. The parental origin of the extra X chromosome in 47,XXX females.

    Science.gov (United States)

    May, K M; Jacobs, P A; Lee, M; Ratcliffe, S; Robinson, A; Nielsen, J; Hassold, T J

    1990-01-01

    We used X-linked DNA polymorphisms to study the parental origin of X chromosome nondisjunction in 28 47,XXX live-born females. Errors in oogenesis accounted for 26 of the cases, with the majority of these being attributable to an error at meiosis I. We observed an association between advanced parental age and meiosis I nondisjunction--but not meiosis II nondisjunction--in the maternally derived cases. In studies of recombination we found little evidence for an association between pairing failure and X chromosome nondisjunction, but our results suggest that increased recombination near the centromere may play a role in the etiology of the 47,XXX condition. Images Figure 1 Figure 2 PMID:2316522

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

    DEFF Research Database (Denmark)

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

    2003-01-01

    continentalis var. continentalis, and M. continentalis var. borealis. Asci were dissected and the segregation patterns for various phenotypes analyzed. In all cases (n = 47) both mating types (h(+) and h(-)) were recovered in pairs of sister spores, casting further uncertainty as to whether normal meiosis takes...... place. However, the segregation patterns for cycloheximide resistance and several auxotrophic markers were random, suggesting that normal meiosis indeed occurs. To explain the lack of second-division segregation of mating types, we concluded that crossing-over does not occur between the mating......-type locus and the centromere, and that meiosis I is tied to spore formation, which explains why the number of spores is limited to two. The latter assumption was also supported by fluorescence microscopy. The second meiotic division takes place inside the spores and is followed by the resorption of two...

  13. Morphogenetic chromatin reorganization aspects at the preleptoten stage of human spermatogenesis

    Directory of Open Access Journals (Sweden)

    M. I. Shtaut

    2016-01-01

    Full Text Available Male germ cells pool forms due to proliferation of germ cells during migration into the embryonic gonads and apoptosis. At the different stages of antenatal development a part of germ сells population in the seminiferous cords is represented by cells at the preleptotene stage of meiosis I. In newborns and infants a number of gametes at this stage of meiosis varies. Male germ cells enter meiotic development mainly in the puberty period. One of the theories of the unique chromatin condensation at the preleptotene stage (prochromosome is a lack of special signal molecules responsible for the male gametes development. Another theory is that it is a modification that marks the germ сells capable of meiosis activation.

  14. Regulation of meiotic gene expression in plants

    Directory of Open Access Journals (Sweden)

    Adele eZhou

    2014-08-01

    Full Text Available With the recent advances in genomics and sequencing technologies, databases of transcriptomes representing many cellular processes have been built. Meiotic transcriptomes in plants have been studied in Arabidopsis thaliana, rice (Oryza sativa, wheat (Triticum aestivum, petunia (Petunia hybrida, sunflower (Helianthus annuus, and maize (Zea mays. Studies in all organisms, but particularly in plants, indicate that a very large number of genes are expressed during meiosis, though relatively few of them seem to be required for the completion of meiosis. In this review, we focus on gene expression at the RNA level and analyze the meiotic transcriptome datasets and explore expression patterns of known meiotic genes to elucidate how gene expression could be regulated during meiosis. We also discuss mechanisms, such as chromatin organization and non-coding RNAs, that might be involved in the regulation of meiotic transcription patterns.

  15. OSD1 promotes meiotic progression via APC/C inhibition and forms a regulatory network with TDM and CYCA1;2/TAM.

    Science.gov (United States)

    Cromer, Laurence; Heyman, Jefri; Touati, Sandra; Harashima, Hirofumi; Araou, Emilie; Girard, Chloe; Horlow, Christine; Wassmann, Katja; Schnittger, Arp; De Veylder, Lieven; Mercier, Raphael

    2012-01-01

    Cell cycle control is modified at meiosis compared to mitosis, because two divisions follow a single DNA replication event. Cyclin-dependent kinases (CDKs) promote progression through both meiosis and mitosis, and a central regulator of their activity is the APC/C (Anaphase Promoting Complex/Cyclosome) that is especially required for exit from mitosis. We have shown previously that OSD1 is involved in entry into both meiosis I and meiosis II in Arabidopsis thaliana; however, the molecular mechanism by which OSD1 controls these transitions has remained unclear. Here we show that OSD1 promotes meiotic progression through APC/C inhibition. Next, we explored the functional relationships between OSD1 and the genes known to control meiotic cell cycle transitions in Arabidopsis. Like osd1, cyca1;2/tam mutation leads to a premature exit from meiosis after the first division, while tdm mutants perform an aberrant third meiotic division after normal meiosis I and II. Remarkably, while tdm is epistatic to tam, osd1 is epistatic to tdm. We further show that the expression of a non-destructible CYCA1;2/TAM provokes, like tdm, the entry into a third meiotic division. Finally, we show that CYCA1;2/TAM forms an active complex with CDKA;1 that can phosphorylate OSD1 in vitro. We thus propose that a functional network composed of OSD1, CYCA1;2/TAM, and TDM controls three key steps of meiotic progression, in which OSD1 is a meiotic APC/C inhibitor.

  16. Coordination of BRCA1/BARD1- and MRE11/RAD50/NBS1-Dependent DNA Transactions in Breast Tumor Suppression

    Science.gov (United States)

    2011-07-01

    human DNA repair proteins at a unique double-strand break in vivo, EMBO J 25, 222-231. 19. Berkovich, E., Monnat, R. J., Jr., and Kastan, M. B...structures around DNA as SMC complexes do. Rad50 exhibits ATPase activity in vitro, which is required for DNA repair and meiosis (3, 57). The rad50S...151). Exo1 expression is induced dur- ing meiosis , suggesting a role in meiotic DSB resection (149). Studies in the dmc1 mutant, which exhibits hyper

  17. Generation of meiomaps of genome-wide recombination and chromosome segregation in human oocytes

    DEFF Research Database (Denmark)

    Ottolini, Christian S; Capalbo, Antonio; Newnham, Louise

    2016-01-01

    We have developed a protocol for the generation of genome-wide maps (meiomaps) of recombination and chromosome segregation for the three products of human female meiosis: the first and second polar bodies (PB1 and PB2) and the corresponding oocyte. PB1 is biopsied and the oocyte is artificially......-nucleotide polymorphisms (SNPs) genome-wide by microarray. Informative maternal heterozygous SNPs are phased using a haploid PB2 or oocyte as a reference. A simple algorithm is then used to identify the maternal haplotypes for each chromosome, in all of the products of meiosis for each oocyte. This allows mapping...

  18. Functional Analysis of Chk2-Kiaa0170 Interaction

    Science.gov (United States)

    2006-09-01

    Biology ( Human Press) : Use of siRNA to study the function of MDC1 in DNA damage responses. Methods in Molecular Biology, 281(2): 179-187. Humana...male infertility phenotype has also been reported in ATM2/2 and H2AX2/2 animals, albeit due to distinctive defects during meiosis (Barlow et al., 1996...suggest that MDC1 functions in DSB repair. Failure to repair DNA damage is linked to genomic in - stability. The observed defects in meiosis , class switch

  19. Circumstantial evidence of life history events in loricate choanoflagellates

    DEFF Research Database (Denmark)

    Thomsen, Helge Abildhauge; Østergaard, Jette Buch

    2017-01-01

    Sex is found in all major eukaryotic groups of organisms. It has been known for some time that the choanoflagellates also possess the genes involved in meiosis and a full sexual cycle was also recently accounted for in Salpingoeca rosetta. With reference to the loricate choanoflagellates the curr......Sex is found in all major eukaryotic groups of organisms. It has been known for some time that the choanoflagellates also possess the genes involved in meiosis and a full sexual cycle was also recently accounted for in Salpingoeca rosetta. With reference to the loricate choanoflagellates...

  20. [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.

  1. The Schizosaccharomyces pombe map1 gene encodes an SRF/MCM1-related protein required for P-cell specific gene expression

    DEFF Research Database (Denmark)

    Nielsen, O; Friis, T; Kjaerulff, S

    1996-01-01

    Cells of Schizosaccharomyces pombe undergo mating and meiosis when starved for a nitrogen source. In this process a P and and M cell first mate to generate a diploid zygote, which subsequently enters meiosis and sporulates. The P mating type is controlled by the mat1-Pc gene at the mating type lo...... cerevisiae MCM1. The Mat1-Pc protein contains a motif characteristic for proteins that interact with MADS-box factors, suggesting that Mat-Pc and Map1 may form a heterodimer that activates the P-specific map3 gene....

  2. Assessment of pheromone production and response in fission yeast by a halo test of induced sporulation

    DEFF Research Database (Denmark)

    Egel, R; Willer, M; Kjaerulff, S

    1994-01-01

    We describe a rapid, sensitive and semi-quantitative plate assay for monitoring pheromone activity in the fission yeast Schizosaccharomyces pombe. It is based on the observation that meiosis requires stimulation by pheromone and exploits diploid strains that will only sporulate after addition...... of exogenous pheromone. The tester strains are heterozygous for mating type, are non-switching, and are mutated in one of the early subfunctions (either mat1-Mc or mat1-Pc), so that meiosis is only induced after exposure to exogenous pheromone (M-factor or P-factor, respectively). Pheromone activity...

  3. Yeast Interacting Proteins Database: YDL239C, YDR273W [Yeast Interacting Proteins Database

    Lifescience Database Archive (English)

    Full Text Available of a Don1p-containing structure at the leading edge of the prospore membrane via interaction with spindle p...it as prey (1) YDR273W DON1 Meiosis-specific component of the spindle pole body, part of the leading... edge protein (LEP) coat, forms a ring-like structure at the leading edge of the prospore...ption Protein required for spore wall formation, thought to mediate assembly of a Don1p-containing structure at the leading...description Meiosis-specific component of the spindle pole body, part of the leading edge protein (LEP) coat

  4. Plasma HDL cholesterol and risk of myocardial infarction

    DEFF Research Database (Denmark)

    Voight, Benjamin F; Peloso, Gina M; Orho-Melander, Marju

    2012-01-01

    High plasma HDL cholesterol is associated with reduced risk of myocardial infarction, but whether this association is causal is unclear. Exploiting the fact that genotypes are randomly assigned at meiosis, are independent of non-genetic confounding, and are unmodified by disease processes...

  5. Repression of meiotic genes by antisense transcription and by Fkh2 transcription factor in Schizosaccharomyces pombe.

    Science.gov (United States)

    Chen, Huei-Mei; Rosebrock, Adam P; Khan, Sohail R; Futcher, Bruce; Leatherwood, Janet K

    2012-01-01

    In S. pombe, about 5% of genes are meiosis-specific and accumulate little or no mRNA during vegetative growth. Here we use Affymetrix tiling arrays to characterize transcripts in vegetative and meiotic cells. In vegetative cells, many meiotic genes, especially those induced in mid-meiosis, have abundant antisense transcripts. Disruption of the antisense transcription of three of these mid-meiotic genes allowed vegetative sense transcription. These results suggest that antisense transcription represses sense transcription of meiotic genes in vegetative cells. Although the mechanism(s) of antisense mediated transcription repression need to be further explored, our data indicates that RNAi machinery is not required for repression. Previously, we and others used non-strand specific methods to study splicing regulation of meiotic genes and concluded that 28 mid-meiotic genes are spliced only in meiosis. We now demonstrate that the "unspliced" signal in vegetative cells comes from the antisense RNA, not from unspliced sense RNA, and we argue against the idea that splicing regulates these mid-meiotic genes. Most of these mid-meiotic genes are induced in mid-meiosis by the forkhead transcription factor Mei4. Interestingly, deletion of a different forkhead transcription factor, Fkh2, allows low levels of sense expression of some mid-meiotic genes in vegetative cells. We propose that vegetative expression of mid-meiotic genes is repressed at least two independent ways: antisense transcription and Fkh2 repression.

  6. 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.

  7. Laboratory Exercises to Examine Recombination & Aneuploidy in "Drosophila"

    Science.gov (United States)

    Venema, Dennis R.

    2009-01-01

    Chromosomal aneuploidy, a deviation from an exact multiple of an organism's haploid chromosome number, is a difficult concept for students to master. Aneuploidy arising from chromosomal non-disjunction (NDJ) is particularly problematic for students, since it arises in the context of meiosis, itself a challenging subject. Students learning NDJ are…

  8. Rad52 SUMOylation affects the efficiency of the DNA repair

    DEFF Research Database (Denmark)

    Altmannova, Veronika; Eckert-Boulet, Nadine; Arneric, Milica

    2010-01-01

    Homologous recombination (HR) plays a vital role in DNA metabolic processes including meiosis, DNA repair, DNA replication and rDNA homeostasis. HR defects can lead to pathological outcomes, including genetic diseases and cancer. Recent studies suggest that the post-translational modification by ...

  9. Chromosomal changes in pathology and during evolution: analysis of pericentric inversions

    International Nuclear Information System (INIS)

    Dutrillaux, B.; Aurias, A.; Viegas-Pequignot, E.

    1980-01-01

    The great similarities between pericentric inversions observed in human pathology, having occurred during evolution, or radio-induced in human cells, indicate that they do not occur at random. About 1/3rd to 1/4th of these chromosomal rearrangements are capable to induce abnormal progeny after aneusomy of recombination, during meiosis [fr

  10. Rec8p, a meiotic recombination and sister chromatid cohesion phosphoprotein of the Rad21p family conserved from fision yeast to humans.

    NARCIS (Netherlands)

    S. Parisi; M.J. McKay (Michael); M. Molnar; M.A. Thompson (Anne); P.J. van der Spek (Peter); E. van Drunen-Schoenmaker; R. Kanaar (Roland); E. Lehmann; J.H.J. Hoeijmakers (Jan); J. Kohli

    1999-01-01

    textabstractOur work and that of others defined mitosis-specific (Rad21 subfamily) and meiosis-specific (Rec8 subfamily) proteins involved in sister chromatid cohesion in several eukaryotes, including humans. Mutation of the fission yeast Schizosaccharomyces pombe rec8 gene was previously shown to

  11. 76 FR 29770 - Center for Scientific Review; Notice of Closed Meetings

    Science.gov (United States)

    2011-05-23

    ... DEPARTMENT OF HEALTH AND HUMAN SERVICES National Institutes of Health Center for Scientific Review... public in accordance with the provisions set forth in sections 552b(c)(4) and 552b(c)(6), Title 5 U.S.C...: Center for Scientific Review Special Emphasis Panel; Program Project: Regulation of Mammalian Meiosis...

  12. Difficulties in Genetics Problem Solving.

    Science.gov (United States)

    Tolman, Richard R.

    1982-01-01

    Examined problem-solving strategies of 30 high school students as they solved genetics problems. Proposes a new sequence of teaching genetics based on results: meiosis, sex chromosomes, sex determination, sex-linked traits, monohybrid and dihybrid crosses (humans), codominance (humans), and Mendel's pea experiments. (JN)

  13. In vivo binding of PRDM9 reveals interactions with noncanonical genomic sites

    DEFF Research Database (Denmark)

    Grey, Corinne; Clément, Julie A.J.; Buard, Jérôme

    2017-01-01

    In mouse and human meiosis, DNA double-strand breaks (DSBs) initiate homologous recombination and occur at specific sites called hotspots. The localization of these sites is determined by the sequence-specific DNA binding domain of the PRDM9 histone methyl transferase. Here, we performed...

  14. The role of DNA double-strand breaks in spontaneous homologous recombination in S. cerevisiae

    DEFF Research Database (Denmark)

    Lettier, Gaëlle; Feng, Q.; Mayolo, A.A. de

    2006-01-01

    of meiosis and result from the induction of a large number of DNA double-strand breaks (DSBs). By analogy, it is generally believed that the rare spontaneous mitotic HR events are due to repair of DNA DSBs that accidentally occur during mitotic growth. Here we provide the first direct evidence that most...

  15. Functional substitution for TAF(II)250 by a retroposed homolog that is expressed in human spermatogenesis.

    Science.gov (United States)

    Wang, P Jeremy; Page, David C

    2002-09-15

    TAF(II)250, the largest subunit of the general transcription factor TFIID, is expressed from the human X chromosome, at least in somatic cells. In male meiosis, however, the sex chromosomes are transcriptionally silenced, while the autosomes remain active. How then are protein-encoding genes transcribed during human male meiosis? Here we present a novel autosomal human gene, TAF1L, which is homologous to TAF(II)250 and is expressed specifically in the testis, apparently in germ cells. We hypothesize that during male meiosis, transcription of protein-encoding genes relies upon TAF1L as a functional substitute for TAF(II)250. Like TAF(II)250, the human TAF1L protein can bind directly to TATA-binding protein, an essential component of TFIID. Most importantly, transfection with human TAF1L rescued the temperature-sensitive lethality of a hamster cell line mutant in TAF(II)250. TAF1L lacks introns and evidently arose by retroposition of a processed TAF(II)250 mRNA during primate evolution. The observation that TAF1L can functionally replace TAF(II)250 provides experimental support for the hypothesis that during male meiosis, autosomes provide cellular functions usually supplied by the X chromosome in somatic cells.

  16. Preferential inclusion of extrachromosomal genetic elements in yeast meiotic spores.

    Science.gov (United States)

    Brewer, B J; Fangman, W L

    1980-09-01

    During meiosis and sporulation in the yeast Saccharomyces cerevisiae, extrachromosomal traits are efficiently transmitted to haploid spores. Although the pattern of inheritance of chromosomal traits reflects the mechanism of regular chromosomal segregation in meiosis, it is not known what processes are reflected by the efficient inheritance of extrachromosomal traits. Because extrachromosomal genetic elements in yeast are present in multiple copies, perpetuation of an extrachromosomal trait could occur by the passive envelopment of a subset of copies or by an active sequestering of all or a subset of copies within the four spores. We show that only subsets of the four extrachromosomal nucleic acids commonly found in yeast are transmitted through meiosis--55% of mitochondrial DNA copies, 82% of the 2-micron DNA plasmids, and about 70% of the L and M double-stranded RNAs. However, electron micrographs of serial sections through yeast asci indicate that the four spore enclose only 30% of the total ascus material. Thus these extrachromosomal elements are preferentially included within the spores, indicating that their inheritance is not a random process. Transmission of mitochondrial DNA can be accounted for by the observed enclosure of 52% of the mitochondrial volume within the spores. The high transmission frequencies of the double-stranded RNAs (which exist as virus-like particles in the cytoplasm) and 2-micron DNA must indicate that either these nucleic acids are actively recruited from the cytoplasm by some mechanism or they are associated in some way with the nucleus during meiosis.

  17. High temperatures influence sexual development differentially in ...

    Indian Academy of Sciences (India)

    Samadhan Krushna Phuge

    2017-06-20

    Jun 20, 2017 ... E) on the night of. 17 June 2011. Each pair .... days. At metamorphosis, the proportion of males and females in the control group (24°C) was ... cells (figure 2A); B, seminiferous tubule formation (figure 2D); and C, meiosis in ...

  18. Triploidy--Observations in 154 Diandric Cases.

    Directory of Open Access Journals (Sweden)

    Nanna Brink Scholz

    Full Text Available Hydatidiform moles (HMs are abnormal human pregnancies with vesicular chorionic villi, imposing two clinical challenges; miscarriage and a risk of gestational trophoblastic neoplasia (GTN. The parental type of most HMs are either diandric diploid (PP or diandric triploid (PPM. We consecutively collected 154 triploid or near-triploid samples from conceptuses with vesicular chorionic villi. We used analysis of DNA markers and/or methylation sensitive-MLPA and collected data from registries and patients records. We performed whole genome SNP analysis of one case of twinning (PP+PM.In all 154 triploids or near-triploids we found two different paternal contributions to the genome (P1P2M. The ratios between the sex chromosomal constitutions XXX, XXY, and XYY were 5.7: 6.9: 1.0. No cases of GTN were observed. Our results corroborate that all triploid human conceptuses with vesicular chorionic villi have the parental type P1P2M. The sex chromosomal ratios suggest approximately equal frequencies of meiosis I and meiosis II errors with selection against the XYY conceptuses or a combination of dispermy, non-disjunction in meiosis I and meiosis II and selection against XYY conceptuses. Although single cases of GTN after a triploid HM have been reported, the results of this study combined with data from previous prospective studies estimate the risk of GTN after a triploid mole to 0% (95% CI: 0-1,4%.

  19. insights from a linkage map of the damselfly Ischnura elegans

    Indian Academy of Sciences (India)

    tion of achiasmiatic meiosis. Biochem. Genet. 19, 1237–. 1245. Cooper G., Miller P. L. and Holland P. W. H. 1994 Molecular genetic analysis of sperm competition in the damselfly Ischnura elegans (Vander Linden). Proc. R. Soc. London, Ser. B 263,. 1343–1349. Huxley J. S. 1928 Sexual differences in linkage in Gammar-.

  20. 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