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Clark FE, Greenberg NL, Silva DM, Trimm E, Skinner M, Walton RZ, Rosin LF, Lampson MA, Akera T. An egg sabotaging mechanism drives non-Mendelian transmission in mice. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.22.581453. [PMID: 38903120 PMCID: PMC11188085 DOI: 10.1101/2024.02.22.581453] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/22/2024]
Abstract
During meiosis, homologous chromosomes segregate so that alleles are transmitted equally to haploid gametes, following Mendel's Law of Segregation. However, some selfish genetic elements drive in meiosis to distort the transmission ratio and increase their representation in gametes. The established paradigms for drive are fundamentally different for female vs male meiosis. In male meiosis, selfish elements typically kill gametes that do not contain them. In female meiosis, killing is predetermined, and selfish elements bias their segregation to the single surviving gamete (i.e., the egg in animal meiosis). Here we show that a selfish element on mouse chromosome 2, R2d2, drives using a hybrid mechanism in female meiosis, incorporating elements of both male and female drivers. If R2d2 is destined for the polar body, it manipulates segregation to sabotage the egg by causing aneuploidy that is subsequently lethal in the embryo, so that surviving progeny preferentially contain R2d2. In heterozygous females, R2d2 orients randomly on the metaphase spindle but lags during anaphase and preferentially remains in the egg, regardless of its initial orientation. Thus, the egg genotype is either euploid with R2d2 or aneuploid with both homologs of chromosome 2, with only the former generating viable embryos. Consistent with this model, R2d2 heterozygous females produce eggs with increased aneuploidy for chromosome 2, increased embryonic lethality, and increased transmission of R2d2. In contrast to a male meiotic driver, which kills its sister gametes produced as daughter cells in the same meiosis, R2d2 eliminates "cousins" produced from meioses in which it should have been excluded from the egg.
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Affiliation(s)
- Frances E. Clark
- Cell and Developmental Biology Center, National Heart, Lung, and Blood Institute, National Institutes of Health; Bethesda, Maryland 20894, USA
| | - Naomi L. Greenberg
- Cell and Developmental Biology Center, National Heart, Lung, and Blood Institute, National Institutes of Health; Bethesda, Maryland 20894, USA
| | - Duilio M.Z.A. Silva
- Cell and Developmental Biology Center, National Heart, Lung, and Blood Institute, National Institutes of Health; Bethesda, Maryland 20894, USA
| | - Emily Trimm
- Department of Biology, School of Arts and Sciences, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Morgan Skinner
- Cell and Developmental Biology Center, National Heart, Lung, and Blood Institute, National Institutes of Health; Bethesda, Maryland 20894, USA
| | - R Zaak Walton
- Cell and Developmental Biology Center, National Heart, Lung, and Blood Institute, National Institutes of Health; Bethesda, Maryland 20894, USA
| | - Leah F. Rosin
- Unit on Chromosome Dynamics, Division of Developmental Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20894 USA
| | - Michael A. Lampson
- Department of Biology, School of Arts and Sciences, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Takashi Akera
- Cell and Developmental Biology Center, National Heart, Lung, and Blood Institute, National Institutes of Health; Bethesda, Maryland 20894, USA
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Schvarzstein M, Alam F, Toure M, Yanowitz JL. An Emerging Animal Model for Querying the Role of Whole Genome Duplication in Development, Evolution, and Disease. J Dev Biol 2023; 11:26. [PMID: 37367480 PMCID: PMC10299280 DOI: 10.3390/jdb11020026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2023] [Revised: 05/23/2023] [Accepted: 06/01/2023] [Indexed: 06/28/2023] Open
Abstract
Whole genome duplication (WGD) or polyploidization can occur at the cellular, tissue, and organismal levels. At the cellular level, tetraploidization has been proposed as a driver of aneuploidy and genome instability and correlates strongly with cancer progression, metastasis, and the development of drug resistance. WGD is also a key developmental strategy for regulating cell size, metabolism, and cellular function. In specific tissues, WGD is involved in normal development (e.g., organogenesis), tissue homeostasis, wound healing, and regeneration. At the organismal level, WGD propels evolutionary processes such as adaptation, speciation, and crop domestication. An essential strategy to further our understanding of the mechanisms promoting WGD and its effects is to compare isogenic strains that differ only in their ploidy. Caenorhabditis elegans (C. elegans) is emerging as an animal model for these comparisons, in part because relatively stable and fertile tetraploid strains can be produced rapidly from nearly any diploid strain. Here, we review the use of Caenorhabditis polyploids as tools to understand important developmental processes (e.g., sex determination, dosage compensation, and allometric relationships) and cellular processes (e.g., cell cycle regulation and chromosome dynamics during meiosis). We also discuss how the unique characteristics of the C. elegans WGD model will enable significant advances in our understanding of the mechanisms of polyploidization and its role in development and disease.
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Affiliation(s)
- Mara Schvarzstein
- Biology Department, Brooklyn College at the City University of New York, Brooklyn, NY 11210, USA
- Biology Department, The Graduate Center at the City University of New York, New York, NY 10016, USA
- Biochemistry Department, The Graduate Center at the City University of New York, New York, NY 10016, USA
| | - Fatema Alam
- Biology Department, Brooklyn College at the City University of New York, Brooklyn, NY 11210, USA
| | - Muhammad Toure
- Biology Department, Brooklyn College at the City University of New York, Brooklyn, NY 11210, USA
| | - Judith L. Yanowitz
- Magee-Womens Research Institute, Pittsburgh, PA 15213, USA;
- Department of Obstetrics, Gynecology, and Reproductive Sciences, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
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Gong T, McNally FJ. Caenorhabditis elegans spermatocytes can segregate achiasmate homologous chromosomes apart at higher than random frequency during meiosis I. Genetics 2023; 223:iyad021. [PMID: 36792551 PMCID: PMC10319977 DOI: 10.1093/genetics/iyad021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Revised: 02/05/2023] [Accepted: 02/07/2023] [Indexed: 02/17/2023] Open
Abstract
Chromosome segregation errors during meiosis are the leading cause of aneuploidy. Faithful chromosome segregation during meiosis in most eukaryotes requires a crossover which provides a physical attachment holding homologs together in a "bivalent." Crossovers are critical for homologs to be properly aligned and partitioned in the first meiotic division. Without a crossover, individual homologs (univalents) might segregate randomly, resulting in aneuploid progeny. However, Caenorhabditis elegans zim-2 mutants, which have crossover defects on chromosome V, have fewer dead embryos than that expected from random segregation. This deviation from random segregation is more pronounced in zim-2 males than that in females. We found three phenomena that can explain this apparent discrepancy. First, we detected crossovers on chromosome V in both zim-2(tm574) oocytes and spermatocytes, suggesting a redundant mechanism to make up for the ZIM-2 loss. Second, after accounting for the background crossover frequency, spermatocytes produced significantly more euploid gametes than what would be expected from random segregation. Lastly, trisomy of chromosome V is viable and fertile. Together, these three phenomena allow zim-2(tm574) mutants with reduced crossovers on chromosome V to have more viable progeny. Furthermore, live imaging of meiosis in spo-11(me44) oocytes and spermatocytes, which exhibit crossover failure on all 6 chromosomes, showed 12 univalents segregating apart in roughly equal masses in a homology-independent manner, supporting the existence of a mechanism that segregates any 2 chromosomes apart.
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Affiliation(s)
- Ting Gong
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA 95616, USA
| | - Francis J McNally
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA 95616, USA
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Kemppainen M, Pardo A. Nucleus-directed fluorescent reporter system for promoter studies in the ectomycorrhizal fungus Laccaria bicolor. J Microbiol Methods 2021; 190:106341. [PMID: 34610385 DOI: 10.1016/j.mimet.2021.106341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Revised: 09/30/2021] [Accepted: 09/30/2021] [Indexed: 11/19/2022]
Abstract
Currently ectomycorrhizal research suffers from a lack of molecular tools specifically adapted to study gene expression in fungal symbionts. Considering that, we designed pReNuK, a cloning vector for transcriptional promoter studies in the ectomycorrhizal basidiomycete Laccaria bicolor. The pReNuK vector offers the use of a nuclear localizing and chromatin incorporating histone H2B-mCherry fluorescent reporter protein and it is specifically optimized for efficient transgene expression in Laccaria. Moreover, pReNuK is designed to work in concert with Agrobacterium-mediated transformation under hygromycin B resistance selection. The functionality of the pReNuK reporter system was tested with the constitutive Laccaria glyceraldehyde 3-phosphate dehydrogenase gene promoter and further validated with the nitrogen source regulated nitrate reductase gene promoter. The expression of the nucleus-directed H2B-mCherry reporter is highly stable in time. Moreover, the transformation of Laccaria with pReNuK and the expression of the reporter do not have negative effects on the growth of the fungus. The pReNuK offers a novel tool for studying in vivo gene expression regulation in Laccaria, the leading fungal model for ectomycorrhizal research.
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Affiliation(s)
- Minna Kemppainen
- Laboratory of Molecular Mycology, Institute of Basic and Applied Microbiology, Department of Science and Technology, National University of Quilmes and CONICET, Bernal, Province of Buenos Aires, Argentina.
| | - Alejandro Pardo
- Laboratory of Molecular Mycology, Institute of Basic and Applied Microbiology, Department of Science and Technology, National University of Quilmes and CONICET, Bernal, Province of Buenos Aires, Argentina
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Lin Z, Xie Y, Nong W, Ren X, Li R, Zhao Z, Hui JHL, Yuen KWY. Formation of artificial chromosomes in Caenorhabditis elegans and analyses of their segregation in mitosis, DNA sequence composition and holocentromere organization. Nucleic Acids Res 2021; 49:9174-9193. [PMID: 34417622 PMCID: PMC8450109 DOI: 10.1093/nar/gkab690] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Revised: 07/23/2021] [Accepted: 07/30/2021] [Indexed: 11/14/2022] Open
Abstract
To investigate how exogenous DNA concatemerizes to form episomal artificial chromosomes (ACs), acquire equal segregation ability and maintain stable holocentromeres, we injected DNA sequences with different features, including sequences that are repetitive or complex, and sequences with different AT-contents, into the gonad of Caenorhabditis elegans to form ACs in embryos, and monitored AC mitotic segregation. We demonstrated that AT-poor sequences (26% AT-content) delayed the acquisition of segregation competency of newly formed ACs. We also co-injected fragmented Saccharomyces cerevisiae genomic DNA, differentially expressed fluorescent markers and ubiquitously expressed selectable marker to construct a less repetitive, more complex AC. We sequenced the whole genome of a strain which propagates this AC through multiple generations, and de novo assembled the AC sequences. We discovered CENP-AHCP-3 domains/peaks are distributed along the AC, as in endogenous chromosomes, suggesting a holocentric architecture. We found that CENP-AHCP-3 binds to the unexpressed marker genes and many fragmented yeast sequences, but is excluded in the yeast extremely high-AT-content centromeric and mitochondrial DNA (> 83% AT-content) on the AC. We identified A-rich motifs in CENP-AHCP-3 domains/peaks on the AC and on endogenous chromosomes, which have some similarity with each other and similarity to some non-germline transcription factor binding sites.
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Affiliation(s)
- Zhongyang Lin
- School of Biological Sciences, the University of Hong Kong, Kadoorie Biological Sciences Building, Pokfulam Road, Hong Kong
| | - Yichun Xie
- School of Life Sciences, Simon F.S. Li Marine Science Laboratory, State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Hong Kong
| | - Wenyan Nong
- School of Life Sciences, Simon F.S. Li Marine Science Laboratory, State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Hong Kong
| | - Xiaoliang Ren
- Department of Biology, Baptist University of Hong Kong, Sir Run Run Shaw Building, Ho Sin Hang Campus, Kowloon Tong, Hong Kong
| | - Runsheng Li
- Department of Biology, Baptist University of Hong Kong, Sir Run Run Shaw Building, Ho Sin Hang Campus, Kowloon Tong, Hong Kong
| | - Zhongying Zhao
- Department of Biology, Baptist University of Hong Kong, Sir Run Run Shaw Building, Ho Sin Hang Campus, Kowloon Tong, Hong Kong
| | - Jerome Ho Lam Hui
- School of Life Sciences, Simon F.S. Li Marine Science Laboratory, State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Hong Kong
| | - Karen Wing Yee Yuen
- School of Biological Sciences, the University of Hong Kong, Kadoorie Biological Sciences Building, Pokfulam Road, Hong Kong
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Abstract
Female meiotic drive is the phenomenon where a selfish genetic element alters chromosome segregation during female meiosis to segregate to the egg and transmit to the next generation more frequently than Mendelian expectation. While several examples of female meiotic drive have been known for many decades, a molecular understanding of the underlying mechanisms has been elusive. Recent advances in this area in several model species prompts a comparative re-examination of these drive systems. In this review, we compare female meiotic drive of several animal and plant species, highlighting pertinent similarities.
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Affiliation(s)
- Frances E. Clark
- Cell and Developmental Biology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Takashi Akera
- Cell and Developmental Biology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
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Van Goor J, Shakes DC, Haag ES. Fisher vs. the Worms: Extraordinary Sex Ratios in Nematodes and the Mechanisms that Produce Them. Cells 2021; 10:1793. [PMID: 34359962 PMCID: PMC8303164 DOI: 10.3390/cells10071793] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Revised: 07/08/2021] [Accepted: 07/13/2021] [Indexed: 01/20/2023] Open
Abstract
Parker, Baker, and Smith provided the first robust theory explaining why anisogamy evolves in parallel in multicellular organisms. Anisogamy sets the stage for the emergence of separate sexes, and for another phenomenon with which Parker is associated: sperm competition. In outcrossing taxa with separate sexes, Fisher proposed that the sex ratio will tend towards unity in large, randomly mating populations due to a fitness advantage that accrues in individuals of the rarer sex. This creates a vast excess of sperm over that required to fertilize all available eggs, and intense competition as a result. However, small, inbred populations can experience selection for skewed sex ratios. This is widely appreciated in haplodiploid organisms, in which females can control the sex ratio behaviorally. In this review, we discuss recent research in nematodes that has characterized the mechanisms underlying highly skewed sex ratios in fully diploid systems. These include self-fertile hermaphroditism and the adaptive elimination of sperm competition factors, facultative parthenogenesis, non-Mendelian meiotic oddities involving the sex chromosomes, and environmental sex determination. By connecting sex ratio evolution and sperm biology in surprising ways, these phenomena link two "seminal" contributions of G. A. Parker.
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Affiliation(s)
- Justin Van Goor
- Department of Biology, University of Maryland, College Park, MD 20742, USA;
| | - Diane C. Shakes
- Department of Biology, William and Mary, Williamsburg, VA 23187, USA;
| | - Eric S. Haag
- Department of Biology, University of Maryland, College Park, MD 20742, USA;
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Danlasky BM, Panzica MT, McNally KP, Vargas E, Bailey C, Li W, Gong T, Fishman ES, Jiang X, McNally FJ. Evidence for anaphase pulling forces during C. elegans meiosis. J Cell Biol 2020; 219:211469. [PMID: 33064834 PMCID: PMC7577052 DOI: 10.1083/jcb.202005179] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2020] [Revised: 07/20/2020] [Accepted: 09/16/2020] [Indexed: 02/06/2023] Open
Abstract
Anaphase chromosome movement is thought to be mediated by pulling forces generated by end-on attachment of microtubules to the outer face of kinetochores. However, it has been suggested that during C. elegans female meiosis, anaphase is mediated by a kinetochore-independent pushing mechanism with microtubules only attached to the inner face of segregating chromosomes. We found that the kinetochore proteins KNL-1 and KNL-3 are required for preanaphase chromosome stretching, suggesting a role in pulling forces. In the absence of KNL-1,3, pairs of homologous chromosomes did not separate and did not move toward a spindle pole. Instead, each homolog pair moved together with the same spindle pole during anaphase B spindle elongation. Two masses of chromatin thus ended up at opposite spindle poles, giving the appearance of successful anaphase.
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9
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Lukhtanov VA, Dincă V, Friberg M, Vila R, Wiklund C. Incomplete Sterility of Chromosomal Hybrids: Implications for Karyotype Evolution and Homoploid Hybrid Speciation. Front Genet 2020; 11:583827. [PMID: 33193715 PMCID: PMC7594530 DOI: 10.3389/fgene.2020.583827] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Accepted: 09/14/2020] [Indexed: 11/17/2022] Open
Abstract
Heterozygotes for major chromosomal rearrangements such as fusions and fissions are expected to display a high level of sterility due to problems during meiosis. However, some species, especially plants and animals with holocentric chromosomes, are known to tolerate chromosomal heterozygosity even for multiple rearrangements. Here, we studied male meiotic chromosome behavior in four hybrid generations (F1–F4) between two chromosomal races of the Wood White butterfly Leptidea sinapis differentiated by at least 24 chromosomal fusions/fissions. Previous work showed that these hybrids were fertile, although their fertility was reduced as compared to crosses within chromosomal races. We demonstrate that (i) F1 hybrids are highly heterozygous with nearly all chromosomes participating in the formation of trivalents at the first meiotic division, and (ii) that from F1 to F4 the number of trivalents decreases and the number of bivalents increases. We argue that the observed process of chromosome sorting would, if continued, result in a new homozygous chromosomal race, i.e., in a new karyotype with intermediate chromosome number and, possibly, in a new incipient homoploid hybrid species. We also discuss the segregational model of karyotype evolution and the chromosomal model of homoploid hybrid speciation.
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Affiliation(s)
- Vladimir A Lukhtanov
- Department of Karyosystematics, Zoological Institute of Russian Academy of Sciences, Saint Petersburg, Russia
| | - Vlad Dincă
- Ecology and Genetics Research Unit, University of Oulu, Oulu, Finland.,Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Barcelona, Spain
| | - Magne Friberg
- Biodiversity Unit, Department of Biology, Lund University, Lund, Sweden
| | - Roger Vila
- Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Barcelona, Spain
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10
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Construction and analysis of artificial chromosomes with de novo holocentromeres in Caenorhabditis elegans. Essays Biochem 2020; 64:233-249. [PMID: 32756873 DOI: 10.1042/ebc20190067] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 07/16/2020] [Accepted: 07/20/2020] [Indexed: 02/07/2023]
Abstract
Artificial chromosomes (ACs), generated in yeast (YACs) and human cells (HACs), have facilitated our understanding of the trans-acting proteins, cis-acting elements, such as the centromere, and epigenetic environments that are necessary to maintain chromosome stability. The centromere is the unique chromosomal region that assembles the kinetochore and connects to microtubules to orchestrate chromosome movement during cell division. While monocentromeres are the most commonly characterized centromere organization found in studied organisms, diffused holocentromeres along the chromosome length are observed in some plants, insects and nematodes. Based on the well-established DNA microinjection method in holocentric Caenorhabditis elegans, concatemerization of foreign DNA can efficiently generate megabase-sized extrachromosomal arrays (Exs), or worm ACs (WACs), for analyzing the mechanisms of WAC formation, de novo centromere formation, and segregation through mitosis and meiosis. This review summarizes the structural, size and stability characteristics of WACs. Incorporating LacO repeats in WACs and expressing LacI::GFP allows real-time tracking of newly formed WACs in vivo, whereas expressing LacI::GFP-chromatin modifier fusions can specifically adjust the chromatin environment of WACs. The WACs mature from passive transmission to autonomous segregation by establishing a holocentromere efficiently in a few cell cycles. Importantly, WAC formation does not require any C. elegans genomic DNA sequence. Thus, DNA substrates injected can be changed to evaluate the effects of DNA sequence and structure in WAC segregation. By injecting a complex mixture of DNA, a less repetitive WAC can be generated and propagated in successive generations for DNA sequencing and analysis of the established holocentromere on the WAC.
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Hollis JA, Glover ML, Schlientz AJ, Cahoon CK, Bowerman B, Wignall SM, Libuda DE. Excess crossovers impede faithful meiotic chromosome segregation in C. elegans. PLoS Genet 2020; 16:e1009001. [PMID: 32886661 PMCID: PMC7508374 DOI: 10.1371/journal.pgen.1009001] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 09/22/2020] [Accepted: 07/21/2020] [Indexed: 12/19/2022] Open
Abstract
During meiosis, diploid organisms reduce their chromosome number by half to generate haploid gametes. This process depends on the repair of double strand DNA breaks as crossover recombination events between homologous chromosomes, which hold homologs together to ensure their proper segregation to opposite spindle poles during the first meiotic division. Although most organisms are limited in the number of crossovers between homologs by a phenomenon called crossover interference, the consequences of excess interfering crossovers on meiotic chromosome segregation are not well known. Here we show that extra interfering crossovers lead to a range of meiotic defects and we uncover mechanisms that counteract these errors. Using chromosomes that exhibit a high frequency of supernumerary crossovers in Caenorhabditis elegans, we find that essential chromosomal structures are mispatterned in the presence of multiple crossovers, subjecting chromosomes to improper spindle forces and leading to defects in metaphase alignment. Additionally, the chromosomes with extra interfering crossovers often exhibited segregation defects in anaphase I, with a high incidence of chromatin bridges that sometimes created a tether between the chromosome and the first polar body. However, these anaphase I bridges were often able to resolve in a LEM-3 nuclease dependent manner, and chromosome tethers that persisted were frequently resolved during Meiosis II by a second mechanism that preferentially segregates the tethered sister chromatid into the polar body. Altogether these findings demonstrate that excess interfering crossovers can severely impact chromosome patterning and segregation, highlighting the importance of limiting the number of recombination events between homologous chromosomes for the proper execution of meiosis.
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Affiliation(s)
- Jeremy A. Hollis
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, United States of America
| | - Marissa L. Glover
- Institute of Molecular Biology, Department of Biology, University of Oregon, Eugene, OR, United States of America
| | - Aleesa J. Schlientz
- Institute of Molecular Biology, Department of Biology, University of Oregon, Eugene, OR, United States of America
| | - Cori K. Cahoon
- Institute of Molecular Biology, Department of Biology, University of Oregon, Eugene, OR, United States of America
| | - Bruce Bowerman
- Institute of Molecular Biology, Department of Biology, University of Oregon, Eugene, OR, United States of America
| | - Sarah M. Wignall
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, United States of America
- * E-mail: (SMW); (DEL)
| | - Diana E. Libuda
- Institute of Molecular Biology, Department of Biology, University of Oregon, Eugene, OR, United States of America
- * E-mail: (SMW); (DEL)
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12
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Cuenca L, Shin N, Lascarez-Lagunas LI, Martinez-Garcia M, Nadarajan S, Karthikraj R, Kannan K, Colaiácovo MP. Environmentally-relevant exposure to diethylhexyl phthalate (DEHP) alters regulation of double-strand break formation and crossover designation leading to germline dysfunction in Caenorhabditis elegans. PLoS Genet 2020; 16:e1008529. [PMID: 31917788 PMCID: PMC6952080 DOI: 10.1371/journal.pgen.1008529] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Accepted: 11/19/2019] [Indexed: 11/18/2022] Open
Abstract
Exposure to diethylhexyl phthalate (DEHP), the most abundant plasticizer used in the production of polyvinyl-containing plastics, has been associated to adverse reproductive health outcomes in both males and females. While the effects of DEHP on reproductive health have been widely investigated, the molecular mechanisms by which exposure to environmentally-relevant levels of DEHP and its metabolites impact the female germline in the context of a multicellular organism have remained elusive. Using the Caenorhabditis elegans germline as a model for studying reprotoxicity, we show that exposure to environmentally-relevant levels of DEHP and its metabolites results in increased meiotic double-strand breaks (DSBs), altered DSB repair progression, activation of p53/CEP-1-dependent germ cell apoptosis, defects in chromosome remodeling at late prophase I, aberrant chromosome morphology in diakinesis oocytes, increased chromosome non-disjunction and defects during early embryogenesis. Exposure to DEHP results in a subset of nuclei held in a DSB permissive state in mid to late pachytene that exhibit defects in crossover (CO) designation/formation. In addition, these nuclei show reduced Polo-like kinase-1/2 (PLK-1/2)-dependent phosphorylation of SYP-4, a synaptonemal complex (SC) protein. Moreover, DEHP exposure leads to germline-specific change in the expression of prmt-5, which encodes for an arginine methyltransferase, and both increased SC length and altered CO designation levels on the X chromosome. Taken together, our data suggest a model by which impairment of a PLK-1/2-dependent negative feedback loop set in place to shut down meiotic DSBs, together with alterations in chromosome structure, contribute to the formation of an excess number of DSBs and altered CO designation levels, leading to genomic instability. Faithful chromosome segregation during meiosis, the specialized cell division program that produces haploid gametes (i.e. eggs and sperm) from a diploid organism, is key for successful sexual reproduction. Diethylhexyl phthalate (DEHP), a commonly used plasticizer found in personal care and household products, has emerged as an endocrine disruptor that exerts reprotoxicity in mammals. In this study, we provide mechanistic insight into the modes of action by which environmentally-relevant levels of DEHP and its metabolites impair female meiosis in the C. elegans germline. Exposure to DEHP leads to defects in late prophase I chromosome remodeling, altered chromosome morphology in oocytes at diakinesis, errors in chromosome segregation, and impaired embryogenesis. Underlying these defects are higher levels of DSBs, altered DSB repair, defects in crossover (CO) designation/formation, germline-specific change in prmt-5 gene expression and altered chromosome structure. We propose that DEHP exposure induces an excess number of DSBs by interfering with mechanisms set in place to turn off DSBs once CO designation is accomplished and by altering chromosome structure resulting in increased chromatin accessibility to the DSB machinery.
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Affiliation(s)
- Luciann Cuenca
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Nara Shin
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Laura I. Lascarez-Lagunas
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Marina Martinez-Garcia
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Saravanapriah Nadarajan
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Rajendiran Karthikraj
- Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, New York, United States of America
| | - Kurunthachalam Kannan
- Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, New York, United States of America
- Department of Pediatrics, New York University School of Medicine, New York City, New York, United States of America
| | - Mónica P. Colaiácovo
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, Massachusetts, United States of America
- * E-mail:
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13
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Versatility of multivalent orientation, inverted meiosis, and rescued fitness in holocentric chromosomal hybrids. Proc Natl Acad Sci U S A 2018; 115:E9610-E9619. [PMID: 30266792 DOI: 10.1073/pnas.1802610115] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Chromosomal rearrangements (e.g., fusions/fissions) have the potential to drive speciation. However, their accumulation in a population is generally viewed as unlikely, because chromosomal heterozygosity should lead to meiotic problems and aneuploid gametes. Canonical meiosis involves segregation of homologous chromosomes in meiosis I and sister chromatid segregation during meiosis II. In organisms with holocentric chromosomes, which are characterized by kinetic activity distributed along almost the entire chromosome length, this order may be inverted depending on their metaphase I orientation. Here we analyzed the evolutionary role of this intrinsic versatility of holocentric chromosomes, which is not available to monocentric ones, by studying F1 to F4 hybrids between two chromosomal races of the Wood White butterfly (Leptidea sinapis), separated by at least 24 chromosomal fusions/fissions. We found that these chromosomal rearrangements resulted in multiple meiotic multivalents, and, contrary to the theoretical prediction, the hybrids displayed relatively high reproductive fitness (42% of that of the control lines) and regular behavior of meiotic chromosomes. In the hybrids, we also discovered inverted meiosis, in which the first and critical stage of chromosome number reduction was replaced by the less risky stage of sister chromatid separation. We hypothesize that the ability to invert the order of the main meiotic events facilitates proper chromosome segregation and hence rescues fertility and viability in chromosomal hybrids, potentially promoting dynamic karyotype evolution and chromosomal speciation.
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14
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Ulicna L, Rohozkova J, Hozak P. Multiple Aspects of PIP2 Involvement in C. elegans Gametogenesis. Int J Mol Sci 2018; 19:ijms19092679. [PMID: 30201859 PMCID: PMC6163852 DOI: 10.3390/ijms19092679] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 08/28/2018] [Accepted: 09/05/2018] [Indexed: 12/20/2022] Open
Abstract
One of the most studied phosphoinositides is phosphatidylinositol 4,5-bisphosphate (PIP2), which localizes to the plasma membrane, nuclear speckles, small foci in the nucleoplasm, and to the nucleolus in mammalian cells. Here, we show that PIP2 also localizes to the nucleus in prophase I, during the gametogenesis of C. elegans hermaphrodite. The depletion of PIP2 by type I PIP kinase (PPK-1) kinase RNA interference results in an altered chromosome structure and leads to various defects during meiotic progression. We observed a decreased brood size and aneuploidy in progeny, defects in synapsis, and crossover formation. The altered chromosome structure is reflected in the increased transcription activity of a tightly regulated process in prophase I. To elucidate the involvement of PIP2 in the processes during the C. elegans development, we identified the PIP2-binding partners, leucine-rich repeat (LRR-1) protein and proteasome subunit beta 4 (PBS-4), pointing to its involvement in the ubiquitin–proteasome pathway.
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Affiliation(s)
- Livia Ulicna
- Department of Biology of the Cell Nucleus, Institute of Molecular Genetics of the Czech Academy of Sciences, v.v.i., Prague 142 20, Czech Republic.
| | - Jana Rohozkova
- Department of Epigenetics of the Cell Nucleus, Institute of Molecular Genetics of the Czech Academy of Sciences, v.v.i., Division BIOCEV, Vestec 252 50, Czech Republic.
| | - Pavel Hozak
- Department of Biology of the Cell Nucleus, Institute of Molecular Genetics of the Czech Academy of Sciences, v.v.i., Prague 142 20, Czech Republic.
- Department of Epigenetics of the Cell Nucleus, Institute of Molecular Genetics of the Czech Academy of Sciences, v.v.i., Division BIOCEV, Vestec 252 50, Czech Republic.
- Microscopy Centre, Institute of Molecular Genetics of the Czech Academy of Sciences, v.v.i., Prague 142 20, Czech Republic.
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15
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Hernandez MR, Davis MB, Jiang J, Brouhard EA, Severson AF, Csankovszki G. Condensin I protects meiotic cohesin from WAPL-1 mediated removal. PLoS Genet 2018; 14:e1007382. [PMID: 29768402 PMCID: PMC5973623 DOI: 10.1371/journal.pgen.1007382] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Revised: 05/29/2018] [Accepted: 04/27/2018] [Indexed: 11/22/2022] Open
Abstract
Condensin complexes are key determinants of higher-order chromatin structure and are required for mitotic and meiotic chromosome compaction and segregation. We identified a new role for condensin in the maintenance of sister chromatid cohesion during C. elegans meiosis. Using conventional and stimulated emission depletion (STED) microscopy we show that levels of chromosomally-bound cohesin were significantly reduced in dpy-28 mutants, which lack a subunit of condensin I. SYP-1, a component of the synaptonemal complex central region, was also diminished, but no decrease in the axial element protein HTP-3 was observed. Surprisingly, the two key meiotic cohesin complexes of C. elegans were both depleted from meiotic chromosomes following the loss of condensin I, and disrupting condensin I in cohesin mutants increased the frequency of detached sister chromatids. During mitosis and meiosis in many organisms, establishment of cohesion is antagonized by cohesin removal by Wapl, and we found that condensin I binds to C. elegans WAPL-1 and counteracts WAPL-1-dependent cohesin removal. Our data suggest that condensin I opposes WAPL-1 to promote stable binding of cohesin to meiotic chromosomes, thereby ensuring linkages between sister chromatids in early meiosis.
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Affiliation(s)
- Margarita R. Hernandez
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, United States of America
| | - Michael B. Davis
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, United States of America
| | - Jianhao Jiang
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, United States of America
| | - Elizabeth A. Brouhard
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, United States of America
| | - Aaron F. Severson
- Center for Gene Regulation in Health and Disease and Department of Biological, Geological and Environmental Sciences, Cleveland State University, Cleveland, OH, United States of America
| | - Györgyi Csankovszki
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, United States of America
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16
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Clarke EK, Rivera Gomez KA, Mustachi Z, Murph MC, Schvarzstein M. Manipulation of Ploidy in Caenorhabditis elegans. J Vis Exp 2018. [PMID: 29608173 PMCID: PMC5931776 DOI: 10.3791/57296] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Mechanisms that involve whole genome polyploidy play important roles in development and evolution; also, an abnormal generation of tetraploid cells has been associated with both the progression of cancer and the development of drug resistance. Until now, it has not been feasible to easily manipulate the ploidy of a multicellular animal without generating mostly sterile progeny. Presented here is a simple and rapid protocol for generating tetraploid Caenorhabditis elegans animals from any diploid strain. This method allows the user to create a bias in chromosome segregation during meiosis, ultimately increasing ploidy in C. elegans. This strategy relies on the transient reduction of expression of the rec-8 gene to generate diploid gametes. A rec-8 mutant produces diploid gametes that can potentially produce tetraploids upon fertilization. This tractable scheme has been used to generate tetraploid strains carrying mutations and chromosome rearrangements to gain insight into chromosomal dynamics and interactions during pairing and synapsis in meiosis. This method is efficient for generating stable tetraploid strains without genetic markers, can be applied to any diploid strain, and can be used to derive triploid C. elegans. This straightforward method is useful for investigating other fundamental biological questions relevant to genome instability, gene dosage, biological scaling, extracellular signaling, adaptation to stress, development of resistance to drugs, and mechanisms of speciation.
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Affiliation(s)
- Erlyana K Clarke
- Brooklyn College, Biology Department, City University of New York
| | - Katherine A Rivera Gomez
- Brooklyn College, Biology Department, City University of New York; The Graduate Center, Biology Department, City University of New York
| | - Zaki Mustachi
- Brooklyn College, Biology Department, City University of New York
| | - Mikaela C Murph
- Brooklyn College, Biology Department, City University of New York; Advanced Science Research Center, City University of New York
| | - Mara Schvarzstein
- Brooklyn College, Biology Department, City University of New York; The Graduate Center, Biology Department, City University of New York; Advanced Science Research Center, City University of New York;
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17
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Sex- and Gamete-Specific Patterns of X Chromosome Segregation in a Trioecious Nematode. Curr Biol 2017; 28:93-99.e3. [PMID: 29276124 PMCID: PMC5772170 DOI: 10.1016/j.cub.2017.11.037] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Revised: 11/13/2017] [Accepted: 11/16/2017] [Indexed: 01/09/2023]
Abstract
Three key steps in meiosis allow diploid organisms to produce haploid gametes: (1) homologous chromosomes (homologs) pair and undergo crossovers; (2) homologs segregate to opposite poles; and (3) sister chromatids segregate to opposite poles. The XX/XO sex determination system found in many nematodes [1] facilitates the study of meiosis because variation is easily recognized [2-4]. Here we show that meiotic segregation of X chromosomes in the trioecious nematode Auanema rhodensis [5] varies according to sex (hermaphrodite, female, or male) and type of gametogenesis (oogenesis or spermatogenesis). In this species, XO males exclusively produce X-bearing sperm [6, 7]. The unpaired X precociously separates into sister chromatids, which co-segregate with the autosome set to generate a functional haplo-X sperm. The other set of autosomes is discarded into a residual body. Here we explore the X chromosome behavior in female and hermaphrodite meioses. Whereas X chromosomes segregate following the canonical pattern during XX female oogenesis to yield haplo-X oocytes, during XX hermaphrodite oogenesis they segregate to the first polar body to yield nullo-X oocytes. Thus, crosses between XX hermaphrodites and males yield exclusively male progeny. During hermaphrodite spermatogenesis, the sister chromatids of the X chromosomes separate during meiosis I, and homologous X chromatids segregate to the functional sperm to create diplo-X sperm. Given these intra-species, intra-individual, and intra-gametogenesis variations in the meiotic program, A. rhodensis is an ideal model for studying the plasticity of meiosis and how it can be modulated.
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18
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Saito TT, Colaiácovo MP. Regulation of Crossover Frequency and Distribution during Meiotic Recombination. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2017; 82:223-234. [PMID: 29222342 DOI: 10.1101/sqb.2017.82.034132] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Crossover recombination is essential for generating genetic diversity and promoting accurate chromosome segregation during meiosis. The process of crossover recombination is tightly regulated and is initiated by the formation of programmed meiotic DNA double-strand breaks (DSBs). The number of DSBs is around 10-fold higher than the number of crossovers in most species, because only a limited number of DSBs are repaired as crossovers during meiosis. Moreover, crossovers are not randomly distributed. Most crossovers are located on chromosomal arm regions and both centromeres and telomeres are usually devoid of crossovers. Either loss or mislocalization of crossovers frequently results in chromosome nondisjunction and subsequent aneuploidy, leading to infertility, miscarriages, and birth defects such as Down syndrome. Here, we will review aspects of crossover regulation observed in most species and then focus on crossover regulation in the nematode Caenorhabditis elegans in which both the frequency and distribution of crossovers are tightly controlled. In this system, only a single crossover is formed, usually at an off-centered position, between each pair of homologous chromosomes. We have identified C. elegans mutants with deregulated crossover distribution, and we are analyzing crossover control by using an inducible single DSB system with which a single crossover can be produced at specific genomic positions. These combined studies are revealing novel insights into how crossover position is linked to accurate chromosome segregation.
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Affiliation(s)
- Takamune T Saito
- Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115
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19
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Vargas E, McNally K, Friedman JA, Cortes DB, Wang DY, Korf IF, McNally FJ. Autosomal Trisomy and Triploidy Are Corrected During Female Meiosis in Caenorhabditis elegans. Genetics 2017; 207:911-922. [PMID: 28882988 PMCID: PMC5676225 DOI: 10.1534/genetics.117.300259] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2017] [Accepted: 09/05/2017] [Indexed: 11/18/2022] Open
Abstract
Trisomy and triploidy, defined as the presence of a third copy of one or all chromosomes, respectively, are deleterious in many species including humans. Previous studies have demonstrated that Caenorhabditis elegans with a third copy of the X chromosome are viable and fertile. However, the extra X chromosome was shown to preferentially segregate into the first polar body during oocyte meiosis to produce a higher frequency of euploid offspring than would be generated by random segregation. Here, we demonstrate that extra autosomes are preferentially eliminated by triploid C. elegans and trisomy IV C. elegans Live imaging of anaphase-lagging chromosomes and analysis of REC-8 staining of metaphase II spindles revealed that, in triploids, some univalent chromosomes do not lose cohesion and preferentially segregate intact into the first polar body during anaphase I, whereas other autosomes segregate chromatids equationally at anaphase I and eliminate some of the resulting single chromatids during anaphase II. We also demonstrate asymmetry in the anaphase spindle, which may contribute to the asymmetric segregation. This study reveals a pathway that allows aneuploid parents to produce euploid offspring at higher than random frequency.
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Affiliation(s)
- Elizabeth Vargas
- Department of Molecular and Cellular Biology, University of California, Davis, California 95616
| | - Karen McNally
- Department of Molecular and Cellular Biology, University of California, Davis, California 95616
| | - Jacob A Friedman
- Department of Molecular and Cellular Biology, University of California, Davis, California 95616
| | - Daniel B Cortes
- Department of Molecular and Cellular Biology, University of California, Davis, California 95616
| | - David Y Wang
- Department of Molecular and Cellular Biology, University of California, Davis, California 95616
| | - Ian F Korf
- Department of Molecular and Cellular Biology, University of California, Davis, California 95616
| | - Francis J McNally
- Department of Molecular and Cellular Biology, University of California, Davis, California 95616
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20
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Flynn JR, McNally FJ. A casein kinase 1 prevents expulsion of the oocyte meiotic spindle into a polar body by regulating cortical contractility. Mol Biol Cell 2017; 28:2410-2419. [PMID: 28701347 PMCID: PMC5576904 DOI: 10.1091/mbc.e17-01-0056] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Revised: 05/25/2017] [Accepted: 07/05/2017] [Indexed: 01/20/2023] Open
Abstract
During female meiosis, haploid eggs are generated from diploid oocytes. This reduction in chromosome number occurs through two highly asymmetric cell divisions, resulting in one large egg and two small polar bodies. Unlike mitosis, where an actomyosin contractile ring forms between the sets of segregating chromosomes, the meiotic contractile ring forms on the cortex adjacent to one spindle pole, then ingresses down the length of the spindle to position itself at the exact midpoint between the two sets of segregating chromosomes. Depletion of casein kinase 1 gamma (CSNK-1) in Caenorhabditis elegans led to the formation of large polar bodies that contain all maternal DNA, because the contractile ring ingressed past the spindle midpoint. Depletion of CSNK-1 also resulted in the formation of deep membrane invaginations during meiosis, suggesting an effect on cortical myosin. Both myosin and anillin assemble into dynamic rho-dependent cortical patches that rapidly disassemble in wild-type embryos. CSNK-1 was required for disassembly of both myosin patches and anillin patches. Disassembly of anillin patches was myosin independent, suggesting that CSNK-1 prevents expulsion of the entire meiotic spindle into a polar body by negatively regulating the rho pathway rather than through direct inhibition of myosin.
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Affiliation(s)
- Jonathan R Flynn
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA 95616
| | - Francis J McNally
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA 95616
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21
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Abstract
Sexual reproduction requires the production of haploid gametes (sperm and egg) with only one copy of each chromosome; fertilization then restores the diploid chromosome content in the next generation. This reduction in genetic content is accomplished during a specialized cell division called meiosis, in which two rounds of chromosome segregation follow a single round of DNA replication. In preparation for the first meiotic division, homologous chromosomes pair and synapse, creating a context that promotes formation of crossover recombination events. These crossovers, in conjunction with sister chromatid cohesion, serve to connect the two homologs and facilitate their segregation to opposite poles during the first meiotic division. During the second meiotic division, which is similar to mitosis, sister chromatids separate; the resultant products are haploid cells that become gametes. In Caenorhabditis elegans (and most other eukaryotes) homologous pairing and recombination are required for proper chromosome inheritance during meiosis; accordingly, the events of meiosis are tightly coordinated to ensure the proper execution of these events. In this chapter, we review the seminal events of meiosis: pairing of homologous chromosomes, the changes in chromosome structure that chromosomes undergo during meiosis, the events of meiotic recombination, the differentiation of homologous chromosome pairs into structures optimized for proper chromosome segregation at Meiosis I, and the ultimate segregation of chromosomes during the meiotic divisions. We also review the regulatory processes that ensure the coordinated execution of these meiotic events during prophase I.
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Affiliation(s)
- Kenneth J Hillers
- Biological Sciences Department, California Polytechnic State University, San Luis Obispo, CA 93407, United States
| | - Verena Jantsch
- Department of Chromosome Biology, Max F. Perutz Laboratories, University of Vienna, Vienna Biocenter,1030 Vienna, Austria
| | | | - Judith L Yanowitz
- Magee-Womens Research Institute, Department of Obstetrics, Gynecology, and Reproductive Sciences, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, United States
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22
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Cell Biology of Cheating—Transmission of Centromeres and Other Selfish Elements Through Asymmetric Meiosis. CENTROMERES AND KINETOCHORES 2017; 56:377-396. [DOI: 10.1007/978-3-319-58592-5_16] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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23
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Abstract
In sexually reproducing organisms, the formation of healthy gametes (sperm and eggs) requires the proper establishment and release of meiotic sister chromatid cohesion (SCC). SCC tethers replicated sisters from their formation in premeiotic S phase until the stepwise removal of cohesion in anaphase of meiosis I and II allows the separation of homologs and then sisters. Defects in the establishment or release of meiotic cohesion cause chromosome segregation errors that lead to the formation of aneuploid gametes and inviable embryos. The nematode Caenorhabditis elegans is an attractive model for studies of meiotic sister chromatid cohesion due to its genetic tractability and the excellent cytological properties of the hermaphrodite gonad. Moreover, mutants defective in the establishment or maintenance of meiotic SCC nevertheless produce abundant gametes, allowing analysis of the pattern of chromosome segregation. Here I describe two approaches for analysis of meiotic cohesion in C. elegans. The first approach relies on cytology to detect and quantify defects in SCC. The second approach relies on PCR and restriction digests to identify embryos that inherited an incorrect complement of chromosomes due to aberrant meiotic chromosome segregation. Both approaches are sensitive enough to identify rare errors and precise enough to reveal distinctive phenotypes resulting from mutations that perturb meiotic SCC in different ways. The robust, quantitative nature of these assays should strengthen phenotypic comparisons of different meiotic mutants and enhance the reproducibility of data generated by different investigators.
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Affiliation(s)
- Aaron F Severson
- Department of Biological, Geological, and Environmental Sciences, Center for Gene Regulation in Health and Disease, Cleveland State University, 2121 Euclid Avenue SI 219, Cleveland, OH, 44115-2214, USA.
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24
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Radford SJ, Nguyen AL, Schindler K, McKim KS. The chromosomal basis of meiotic acentrosomal spindle assembly and function in oocytes. Chromosoma 2016; 126:351-364. [PMID: 27837282 DOI: 10.1007/s00412-016-0618-1] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Revised: 10/25/2016] [Accepted: 10/26/2016] [Indexed: 12/20/2022]
Abstract
Several aspects of meiosis are impacted by the absence of centrosomes in oocytes. Here, we review four aspects of meiosis I that are significantly affected by the absence of centrosomes in oocyte spindles. One, microtubules tend to assemble around the chromosomes. Two, the organization of these microtubules into a bipolar spindle is directed by the chromosomes. Three, chromosome bi-orientation and attachment to microtubules from the correct pole require modification of the mechanisms used in mitotic cells. Four, chromosome movement to the poles at anaphase cannot rely on polar anchoring of spindle microtubules by centrosomes. Overall, the chromosomes are more active participants during acentrosomal spindle assembly in oocytes, compared to mitotic and male meiotic divisions where centrosomes are present. The chromosomes are endowed with information that can direct the meiotic divisions and dictate their own behavior in oocytes. Processes beyond those known from mitosis appear to be required for their bi-orientation at meiosis I. As mitosis occurs without centrosomes in many systems other than oocytes, including all plants, the concepts discussed here may not be limited to oocytes. The study of meiosis in oocytes has revealed mechanisms that are operating in mitosis and will probably continue to do so.
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Affiliation(s)
- Sarah J Radford
- Waksman Institute, 190 Frelinghuysen Rd, Piscataway, NJ, 08854, USA
| | | | - Karen Schindler
- Department of Genetics, Rutgers University, Piscataway, NJ, 08854, USA
| | - Kim S McKim
- Waksman Institute, 190 Frelinghuysen Rd, Piscataway, NJ, 08854, USA.
- Department of Genetics, Rutgers University, Piscataway, NJ, 08854, USA.
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25
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Abstract
Gametogenesis in animal oocytes reduces the diploid genome content of germline precursors to a haploid state in gametes by discarding ¾ of the duplicated chromosomes through a sequence of two meiotic cell divisions called meiosis I and II. The assembly of the microtubule-based spindle structure that mediates this reduction in genome content remains poorly understood compared to our knowledge of mitotic spindle assembly and function. In this review, we consider the diversity of oocyte meiotic spindle assembly and structure across animal phylogeny, review recent advances in our understanding of how animal oocytes assemble spindles in the absence of the centriole-based microtubule-organizing centers that dominate mitotic spindle assembly, and discuss different models for how chromosomes are captured and moved to achieve chromosome segregation during oocyte meiotic cell division.
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Affiliation(s)
- Aaron F Severson
- Department of Biological, Geological, and Environmental Sciences, Center for Gene Regulation in Health and Disease, Cleveland State University, Cleveland, Ohio, USA
| | - George von Dassow
- Oregon Institute of Marine Biology, University of Oregon, Charleston, Oregon, USA
| | - Bruce Bowerman
- Institute of Molecular Biology, University of Oregon, Eugene, Oregon, USA.
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26
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The Rho guanine exchange factor RHGF-2 acts through the Rho-binding kinase LET-502 to mediate embryonic elongation in C. elegans. Dev Biol 2015; 405:250-9. [DOI: 10.1016/j.ydbio.2015.07.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Revised: 07/08/2015] [Accepted: 07/11/2015] [Indexed: 12/31/2022]
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