-
Nucleus (Austin, Tex.) Dec 2024Heterochromatin is an organizational property of eukaryotic chromosomes, characterized by extensive DNA and histone modifications, that is associated with the silencing... (Review)
Review
Heterochromatin is an organizational property of eukaryotic chromosomes, characterized by extensive DNA and histone modifications, that is associated with the silencing of transposable elements and repetitive sequences. Maintaining heterochromatin is crucial for ensuring genomic integrity and stability during the cell cycle. During meiosis, heterochromatin is important for homologous chromosome synapsis, recombination, and segregation, but our understanding of meiotic heterochromatin formation and condensation is limited. In this review, we focus on the dynamics and features of heterochromatin and how it condenses during meiosis in plants. We also discuss how meiotic heterochromatin influences the interaction and recombination of homologous chromosomes during prophase I.
Topics: Heterochromatin; Centromere; Meiosis; Chromosome Pairing
PubMed: 38488152
DOI: 10.1080/19491034.2024.2328719 -
Developmental Biology Sep 2023
Topics: Animals; Helminths; Meiosis
PubMed: 37348595
DOI: 10.1016/j.ydbio.2023.06.008 -
Journal of Experimental Botany Sep 2021Meiosis is a key feature of sexual reproduction. During meiosis homologous chromosomes replicate, recombine, and randomly segregate, followed by the segregation of... (Review)
Review
Meiosis is a key feature of sexual reproduction. During meiosis homologous chromosomes replicate, recombine, and randomly segregate, followed by the segregation of sister chromatids to produce haploid cells. The unique genotypes of recombinant gametes are an essential substrate for the selection of superior genotypes in natural populations and in plant breeding. In this review we summarize current knowledge on meiosis in diverse monocot and dicot crop species and provide a comprehensive resource of cloned meiotic mutants in six crop species (rice, maize, wheat, barley, tomato, and Brassica species). Generally, the functional roles of meiotic proteins are conserved between plant species, but we highlight notable differences in mutant phenotypes. The physical lengths of plant chromosomes vary greatly; for instance, wheat chromosomes are roughly one order of magnitude longer than those of rice. We explore how chromosomal distribution for crossover recombination can vary between species. We conclude that research on meiosis in crops will continue to complement that in Arabidopsis, and alongside possible applications in plant breeding will facilitate a better understanding of how the different stages of meiosis are controlled in plant species.
Topics: Arabidopsis; Chromosomes, Plant; Crops, Agricultural; Meiosis; Plant Breeding
PubMed: 34009331
DOI: 10.1093/jxb/erab217 -
Trends in Cell Biology Apr 2021Phase separation has emerged as a new key principle of intracellular organization. Phase-separated structures play diverse roles in various biological processes and... (Review)
Review
Phase separation has emerged as a new key principle of intracellular organization. Phase-separated structures play diverse roles in various biological processes and pathogenesis of protein aggregation diseases. Recent work has revealed crucial functions for phase separation during germline development. Phase separation controls the assembly and segregation of germ granules that determine which embryonic cells become germ cells. Phase separation promotes the formation of the Balbiani body, a structure that stores organelles and RNAs during the prolonged prophase arrest of oocytes. Phase separation also facilitates meiotic recombination that prepares homologous chromosomes for segregation, and drives the formation of a liquid-like spindle domain that promotes spindle assembly in mammalian oocytes. We review how phase separation drives these essential steps during germline development.
Topics: Animals; Germ Cell Ribonucleoprotein Granules; Germ Cells; Homologous Recombination; Meiosis; Oocytes
PubMed: 33455855
DOI: 10.1016/j.tcb.2020.12.004 -
EMBO Reports Nov 2023Chromosome segregation errors in mammalian oocyte meiosis lead to developmentally compromised aneuploid embryos and become more common with advancing maternal age. Known...
Chromosome segregation errors in mammalian oocyte meiosis lead to developmentally compromised aneuploid embryos and become more common with advancing maternal age. Known contributors include age-related chromosome cohesion loss and spindle assembly checkpoint (SAC) fallibility in meiosis-I. But how effective the SAC is in meiosis-II and how this might contribute to age-related aneuploidy is unknown. Here, we developed genetic and pharmacological approaches to directly address the function of the SAC in meiosis-II. We show that the SAC is insensitive in meiosis-II oocytes and that as a result misaligned chromosomes are randomly segregated. Whilst SAC ineffectiveness in meiosis-II is not age-related, it becomes most prejudicial in oocytes from older females because chromosomes that prematurely separate by age-related cohesion loss become misaligned in meiosis-II. We show that in the absence of a robust SAC in meiosis-II these age-related misaligned chromatids are missegregated and lead to aneuploidy. Our data demonstrate that the SAC fails to prevent cell division in the presence of misaligned chromosomes in oocyte meiosis-II, which explains how age-related cohesion loss can give rise to aneuploid embryos.
Topics: Female; Animals; Spindle Apparatus; M Phase Cell Cycle Checkpoints; Meiosis; Oocytes; Chromatids; Aneuploidy; Chromosome Segregation; Mammals
PubMed: 37795949
DOI: 10.15252/embr.202357227 -
Current Opinion in Genetics &... Dec 2022Sterile hybrids are broadly considered evolutionary dead-ends because of their faulty sexual reproduction. While sterility in obligate sexual organisms is a clear... (Review)
Review
Sterile hybrids are broadly considered evolutionary dead-ends because of their faulty sexual reproduction. While sterility in obligate sexual organisms is a clear constraint in perpetuating the species, some facultative sexual microbes such as yeasts can propagate asexually and maintain genome plasticity. Moreover, incomplete meiotic pathways in yeasts represent alternative routes to the standard meiosis that generates genetic combinations in the population and fuel adaptation. Here, we review how aborting meiosis promotes genome-wide allele shuffling in sterile Saccharomyces hybrids and describe approaches to identify evolved clones in a cell population. We further discuss possible implications of this process in generating phenotypic novelty and report cases of abortive meiosis across yeast species.
Topics: Hybridization, Genetic; Meiosis; Saccharomyces; Genome, Fungal
PubMed: 36084497
DOI: 10.1016/j.gde.2022.101980 -
Annual Review of Genomics and Human... Aug 2023In meiosis, homologous chromosome synapsis is mediated by a supramolecular protein structure, the synaptonemal complex (SC), that assembles between homologous chromosome... (Review)
Review
In meiosis, homologous chromosome synapsis is mediated by a supramolecular protein structure, the synaptonemal complex (SC), that assembles between homologous chromosome axes. The mammalian SC comprises at least eight largely coiled-coil proteins that interact and self-assemble to generate a long, zipper-like structure that holds homologous chromosomes in close proximity and promotes the formation of genetic crossovers and accurate meiotic chromosome segregation. In recent years, numerous mutations in human SC genes have been associated with different types of male and female infertility. Here, we integrate structural information on the human SC with mouse and human genetics to describe the molecular mechanisms by which SC mutations can result in human infertility. We outline certain themes in which different SC proteins are susceptible to different types of disease mutation and how genetic variants with seemingly minor effects on SC proteins may act as dominant-negative mutations in which the heterozygous state is pathogenic.
Topics: Male; Female; Humans; Mice; Animals; Synaptonemal Complex; Chromosome Pairing; Meiosis; Infertility; Mutation; Mammals
PubMed: 37159901
DOI: 10.1146/annurev-genom-110122-090239 -
Asian Journal of Andrology 2021
Topics: Humans; Meiosis; Mitosis
PubMed: 34708720
DOI: 10.4103/aja202192 -
Genes Apr 2022has been a model system for meiosis since the discovery of nondisjunction. Subsequent studies have determined that crossing over is required for chromosome segregation,... (Review)
Review
has been a model system for meiosis since the discovery of nondisjunction. Subsequent studies have determined that crossing over is required for chromosome segregation, and identified proteins required for the pairing of chromosomes, initiating meiotic recombination, producing crossover events, and building a spindle to segregate the chromosomes. With a variety of genetic and cytological tools, remains a model organism for the study of meiosis. This review focusses on meiosis in females because in male meiosis, the use of chiasmata to link homologous chromosomes has been replaced by a recombination-independent mechanism. oocytes are also a good model for mammalian meiosis because of biological similarities such as long pauses between meiotic stages and the absence of centrosomes during the meiotic divisions.
Topics: Animals; Chromosome Segregation; Chromosomes; Drosophila; Female; Male; Mammals; Meiosis; Nondisjunction, Genetic
PubMed: 35627159
DOI: 10.3390/genes13050775 -
Journal of Molecular Cell Biology Sep 2022Meiosis is essential for evolution and genetic diversity in almost all sexual eukaryotic organisms. The mechanisms of meiotic recombination, such as synapsis, have been...
Meiosis is essential for evolution and genetic diversity in almost all sexual eukaryotic organisms. The mechanisms of meiotic recombination, such as synapsis, have been extensively investigated. However, it is still unclear whether signals from the cytoplasm or even from outside of the cell can regulate the meiosis process. Cilia are microtubule-based structures that protrude from the cell surface and function as signaling hubs to sense extracellular signals. Here, we reported an unexpected and critical role of cilia during meiotic recombination. During gametogenesis of zebrafish, cilia were specifically present in the prophase stages of both primary spermatocytes and primary oocytes. By developing a germ cell-specific CRISPR/Cas9 system, we demonstrated that germ cell-specific depletion of ciliary genes resulted in compromised double-strand break repair, reduced crossover formation, and increased germ cell apoptosis. Our study reveals a previously undiscovered role for cilia during meiosis and suggests that extracellular signals may regulate meiotic recombination via this particular organelle.
Topics: Animals; Male; Zebrafish; Cilia; Meiosis; Chromosome Pairing; DNA Repair
PubMed: 35981808
DOI: 10.1093/jmcb/mjac049