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Cells Mar 2020Meiosis is a key event in the manufacturing of an oocyte. During this process, the oocyte creates a set of unique chromosomes by recombining paternal and maternal copies... (Review)
Review
Meiosis is a key event in the manufacturing of an oocyte. During this process, the oocyte creates a set of unique chromosomes by recombining paternal and maternal copies of homologous chromosomes, and by eliminating one set of chromosomes to become haploid. While meiosis is conserved among sexually reproducing eukaryotes, there is a bewildering diversity of strategies among species, and sometimes within sexes of the same species, to achieve proper segregation of chromosomes. Here, we review the very first steps of meiosis in females, when the maternal and paternal copies of each homologous chromosomes have to move, find each other and pair. We explore the similarities and differences observed in , , zebrafish and mouse females.
Topics: Animals; Caenorhabditis elegans; Chromosomes; Meiosis
PubMed: 32178277
DOI: 10.3390/cells9030696 -
Genes & Genetic Systems Jun 2022Meiosis is a crucial process for spermatogenesis and oogenesis. Initiation of meiosis coincides with spermatocyte differentiation and is followed by meiotic prophase, a... (Review)
Review
Meiosis is a crucial process for spermatogenesis and oogenesis. Initiation of meiosis coincides with spermatocyte differentiation and is followed by meiotic prophase, a prolonged G2 phase that ensures the completion of numerous meiosis-specific chromosome events. During meiotic prophase, chromosomes are organized into axis-loop structures, which underlie meiosis-specific events such as meiotic recombination and homolog synapsis. In spermatocytes, meiotic prophase is accompanied by robust alterations of gene expression programs and chromatin status for subsequent sperm production. The mechanisms regulating meiotic initiation and subsequent meiotic prophase programs are enigmatic. Recently, we discovered MEIOSIN (Meiosis initiator), a DNA-binding protein that directs the switch from mitosis to meiosis. This review mainly focuses on how MEIOSIN is involved in meiotic initiation and the meiotic prophase program during spermatogenesis. Further, we discuss the downstream genes activated by MEIOSIN, which are crucial for meiotic prophase-specific events, from the viewpoint of chromosome dynamics and the gene expression program.
Topics: Chromosome Pairing; Humans; Male; Meiosis; Mitosis; Spermatocytes; Spermatogenesis
PubMed: 34955498
DOI: 10.1266/ggs.21-00054 -
Comptes Rendus Biologies 2016Meiosis is a specialized cell division at the origin of the haploid cells that eventually develop into the gametes. It therefore lies at the heart of Mendelian heredity.... (Review)
Review
Meiosis is a specialized cell division at the origin of the haploid cells that eventually develop into the gametes. It therefore lies at the heart of Mendelian heredity. Recombination and redistribution of the homologous chromosomes arising during meiosis constitute an important source of genetic diversity, conferring to meiosis a particularly important place in the evolution and the diversification of the species. Our understanding of the molecular mechanisms governing meiotic recombination has considerably progressed these last decades, benefiting from complementary approaches led on various model species. An overview of these mechanisms will be provided as well as a discussion on the implications of these recent discoveries.
Topics: Animals; Chromosome Segregation; Chromosomes; Genetics; Humans; Meiosis; Recombination, Genetic
PubMed: 27180110
DOI: 10.1016/j.crvi.2016.04.003 -
Cells Jun 2023The synaptonemal complex (SC) is a meiosis-specific multiprotein complex that forms between homologous chromosomes during prophase of meiosis I. Upon assembly, the SC... (Review)
Review
The synaptonemal complex (SC) is a meiosis-specific multiprotein complex that forms between homologous chromosomes during prophase of meiosis I. Upon assembly, the SC mediates the synapses of the homologous chromosomes, leading to the formation of bivalents, and physically supports the formation of programmed double-strand breaks (DSBs) and their subsequent repair and maturation into crossovers (COs), which are essential for genome haploidization. Defects in the assembly of the SC or in the function of the associated meiotic recombination machinery can lead to meiotic arrest and human infertility. The majority of proteins and complexes involved in these processes are exclusively expressed during meiosis or harbor meiosis-specific subunits, although some have dual functions in somatic DNA repair and meiosis. Consistent with their functions, aberrant expression and malfunctioning of these genes have been associated with cancer development. In this review, we focus on the significance of the SC and their meiotic-associated proteins in human fertility, as well as how human genetic variants encoding for these proteins affect the meiotic process and contribute to infertility and cancer development.
Topics: Synaptonemal Complex; Humans; Meiosis; Neoplasms; Infertility; Male; Female; Recombination, Genetic
PubMed: 37443752
DOI: 10.3390/cells12131718 -
Journal of Experimental Botany Jan 2013Meiosis is at the heart of Mendelian heredity. Recently, much progress has been made in the understanding of this process, in various organisms. In the last 15 years,... (Review)
Review
Meiosis is at the heart of Mendelian heredity. Recently, much progress has been made in the understanding of this process, in various organisms. In the last 15 years, the functional characterization of numerous genes involved in meiosis has dramatically deepened our knowledge of key events, including recombination, the cell cycle, and chromosome distribution. Through a constantly advancing tool set and knowledge base, a number of advances have been made that will allow manipulation of meiosis from a plant breeding perspective. This review focuses on the aspects of meiosis that can be tinkered with to create and propagate new varieties. We would like to dedicate this review to the memory of Simon W. Chan (1974-2012) (http://www.plb.ucdavis.edu/labs/srchan/).
Topics: Breeding; Crossing Over, Genetic; Germ Cells, Plant; Meiosis; Plant Cells; Recombination, Genetic
PubMed: 23136169
DOI: 10.1093/jxb/ers314 -
Biology of Reproduction Nov 2019Oocyte meiotic maturation is a vital and final process in oogenesis. Unlike somatic cells, the oocyte needs to undergo two continuous meiotic divisions (meiosis I and... (Review)
Review
Oocyte meiotic maturation is a vital and final process in oogenesis. Unlike somatic cells, the oocyte needs to undergo two continuous meiotic divisions (meiosis I and meiosis II) to become a haploid gamete. Notably, oocyte meiotic progression includes two rounds of unique meiotic arrest and resumption. The first arrest occurs at the G2 (germinal vesicle) stage and meiosis resumption is stimulated by a gonadotropin surge; the second arrest takes place at the metaphase II stage, the stage from which it is released when fertilization takes place. The maturation-promoting factor, which consists of cyclin B1 (CCNB1) and cyclin-dependent kinase 1 (CDK1), is responsible for regulating meiotic resumption and progression, while CDK1 is the unique CDK that acts as the catalytic subunit of maturation-promoting factor. Recent studies showed that except for cyclin B1, multiple cyclins interact with CDK1 to form complexes, which are involved in the regulation of meiotic progression at different stages. Here, we review and discuss the control of oocyte meiotic progression by cyclins A1, A2, B1, B2, B3, and O.
Topics: Animals; Cell Cycle; Cyclins; Female; Meiosis; Oocytes
PubMed: 31347666
DOI: 10.1093/biolre/ioz143 -
Philosophical Transactions of the Royal... Oct 2016Meiosis 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... (Review)
Review
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'.
Topics: Biological Evolution; Eukaryota; Meiosis; Recombination, Genetic; Sex
PubMed: 27619705
DOI: 10.1098/rstb.2016.0001 -
Genes Jan 2022Meiosis is critically different from mitosis in that during meiosis, pairing and segregation of homologous chromosomes occur. During meiosis, the morphology of sister... (Review)
Review
Meiosis is critically different from mitosis in that during meiosis, pairing and segregation of homologous chromosomes occur. During meiosis, the morphology of sister chromatids changes drastically, forming a prominent axial structure in the synaptonemal complex. The meiosis-specific cohesin complex plays a central role in the regulation of the processes required for recombination. In particular, the Rec8 subunit of the meiotic cohesin complex, which is conserved in a wide range of eukaryotes, has been analyzed for its function in modulating chromosomal architecture during the pairing and recombination of homologous chromosomes in meiosis. Here, we review the current understanding of Rec8 cohesin as a structural platform for meiotic chromosomes.
Topics: Cell Cycle Proteins; Chromatids; Chromosomal Proteins, Non-Histone; Meiosis; Cohesins
PubMed: 35205245
DOI: 10.3390/genes13020200 -
Acta Biochimica Et Biophysica Sinica Jul 2020Canonical meiosis is characterized by two sequential rounds of nuclear divisions following one round of DNA replication-reductional segregation of homologous chromosomes... (Review)
Review
Canonical meiosis is characterized by two sequential rounds of nuclear divisions following one round of DNA replication-reductional segregation of homologous chromosomes during the first division and equational segregation of sister chromatids during the second division. Meiosis in an inverted order of two nuclear divisions-inverted meiosis has been observed in several species with holocentromeres as an adaptive strategy to overcome the obstacle in executing a canonical meiosis due to the holocentric chromosome structure. Recent findings of co-existence of inverted and canonical meiosis in two monocentric organisms, human and fission yeast, suggested that inverted meiosis could be common and also lead to the puzzle regarding the mechanistic feasibility for executing two meiosis programs simultaneously. Here, we discuss apparent conflicts for concurrent canonical meiosis and inverted meiosis. Furthermore, we attempt to provide a working model that may be compatible for both forms of meiosis.
Topics: Animals; Chromatids; Chromosome Segregation; Humans; Meiosis; Reproduction
PubMed: 32548620
DOI: 10.1093/abbs/gmaa054 -
Asian Journal of Andrology 2021
Topics: Humans; Meiosis; Mitosis
PubMed: 34708720
DOI: 10.4103/aja202192