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WormBook : the Online Review of C.... May 2017Sexual reproduction requires the production of haploid gametes (sperm and egg) with only one copy of each chromosome; fertilization then restores the diploid chromosome... (Review)
Review
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.
Topics: Animals; Caenorhabditis elegans; Cell Division; Chromosome Segregation; Chromosomes; Meiosis; Meiotic Prophase I; Recombination, Genetic
PubMed: 26694509
DOI: 10.1895/wormbook.1.178.1 -
Reproductive Biology and Endocrinology... Jan 2019A central dogma of mammalian reproductive biology is that the size of the primordial follicle pool represents reproductive capacity in females. The assembly of the... (Review)
Review
A central dogma of mammalian reproductive biology is that the size of the primordial follicle pool represents reproductive capacity in females. The assembly of the primordial follicle starts after the primordial germ cells (PGCs)-derived oocyte releases from the synchronously dividing germline cysts. PGCs initiate meiosis during fetal development. However, after synapsis and recombination of homologous chromosomes, they arrest at the diplotene stage of the first meiotic prophase (MI). The diplotene-arrested oocyte, together with the surrounding of a single layer of flattened granulosa cells, forms a basic unit of the ovary, the primordial follicle. At the start of each estrous (animal) or menstrual cycle (human), in response to a surge of luteinizing hormone (LH) from the pituitary gland, a limited number of primordial follicles are triggered to develop into primary follicles, preantral follicles, antral follicles and reach to preovulatory follicle stage. During the transition from the preantral to antral stages, the enclosed oocyte gradually acquires the capacity to resume meiosis. Meiotic resumption from the prophase of MI is morphologically characterized by the dissolution of the oocyte nuclear envelope, which is generally termed the "germinal vesicle breakdown" (GVBD). Following GVBD and completion of MI, the oocyte enters meiosis II without an obvious S-phase and arrests at metaphase phase II (MII) until fertilization. The underlying mechanism of meiotic arrest has been widely explored in numerous studies. Many studies indicated that two cellular second messengers, cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) play an essential role in maintaining oocyte meiotic arrest. This review will discuss how these two cyclic nucleotides regulate oocyte maturation by blocking or initiating meiotic processes, and to provide an insight in future research.
Topics: Animals; Cyclic AMP; Cyclic GMP; Female; Granulosa Cells; Humans; Mammals; Meiosis; Meiotic Prophase I; Metaphase; Models, Biological; Oocytes
PubMed: 30611263
DOI: 10.1186/s12958-018-0445-8 -
Cell Reports Mar 2022The DSB machinery, which induces the programmed DNA double-strand breaks (DSBs) in the leptotene and zygotene stages during meiosis, is suppressed before the onset of...
The DSB machinery, which induces the programmed DNA double-strand breaks (DSBs) in the leptotene and zygotene stages during meiosis, is suppressed before the onset of the pachytene stage. However, the biological significance and underlying mechanisms remain largely unclear. Here, we report that ZFP541 is indispensable for the suppression of DSB formation after mid-pachytene. The deletion of Zfp541 in mice causes the aberrant recruitment of DSB machinery to chromosome axes and generation of massive DSBs in late pachytene and diplotene spermatocytes, leading to meiotic arrest at the diplotene stage. Integrated analysis of single-cell RNA sequencing (scRNA-seq) and chromatin immunoprecipitation (ChIP) sequencing data indicate that ZFP541 predominantly binds to promoters of pre-pachytene genes, including meiotic DSB formation-related genes (e.g., Prdm9 and Mei1) and their upstream activators (e.g., Meiosin and Rxra), and maintains their repression in pachytene spermatocytes. Our results reveal that ZFP541 functions as a transcriptional regulator in pachytene spermatocytes, orchestrating the transcriptome to ensure meiosis progression.
Topics: Animals; Chromosomal Proteins, Non-Histone; DNA Breaks, Double-Stranded; Histone-Lysine N-Methyltransferase; Male; Meiosis; Meiotic Prophase I; Mice; Pachytene Stage; Spermatocytes; Transcription Factors
PubMed: 35320728
DOI: 10.1016/j.celrep.2022.110540 -
Cell Research Sep 2017N-methyladenosine (mA) is the most common internal modification in eukaryotic mRNA. It is dynamically installed and removed, and acts as a new layer of mRNA metabolism,...
N-methyladenosine (mA) is the most common internal modification in eukaryotic mRNA. It is dynamically installed and removed, and acts as a new layer of mRNA metabolism, regulating biological processes including stem cell pluripotency, cell differentiation, and energy homeostasis. mA is recognized by selective binding proteins; YTHDF1 and YTHDF3 work in concert to affect the translation of mA-containing mRNAs, YTHDF2 expedites mRNA decay, and YTHDC1 affects the nuclear processing of its targets. The biological function of YTHDC2, the final member of the YTH protein family, remains unknown. We report that YTHDC2 selectively binds mA at its consensus motif. YTHDC2 enhances the translation efficiency of its targets and also decreases their mRNA abundance. Ythdc2 knockout mice are infertile; males have significantly smaller testes and females have significantly smaller ovaries compared to those of littermates. The germ cells of Ythdc2 knockout mice do not develop past the zygotene stage and accordingly, Ythdc2 is upregulated in the testes as meiosis begins. Thus, YTHDC2 is an mA-binding protein that plays critical roles during spermatogenesis.
Topics: Adenosine; Animals; Base Sequence; Female; Male; Meiotic Prophase I; Mice, Inbred C57BL; Protein Binding; Protein Biosynthesis; RNA Helicases; RNA, Messenger; Spermatogenesis; Testis
PubMed: 28809393
DOI: 10.1038/cr.2017.99 -
Biology of Reproduction Jun 2020
Topics: Animals; Cell Cycle Checkpoints; Cell Cycle Proteins; Humans; Male; Meiosis; Meiotic Prophase I; Metaphase; SKP Cullin F-Box Protein Ligases; Spermatozoa; Ubiquitin
PubMed: 32338765
DOI: 10.1093/biolre/ioaa063 -
Development (Cambridge, England) Jun 2013There is currently particular interest in the field of nuclear reprogramming, a process by which the identity of specialised cells may be changed, typically to an... (Review)
Review
There is currently particular interest in the field of nuclear reprogramming, a process by which the identity of specialised cells may be changed, typically to an embryonic-like state. Reprogramming procedures provide insight into many mechanisms of fundamental cell biology and have several promising applications, most notably in healthcare through the development of human disease models and patient-specific tissue-replacement therapies. Here, we introduce the field of nuclear reprogramming and briefly discuss six of the procedures by which reprogramming may be experimentally performed: nuclear transfer to eggs or oocytes, cell fusion, extract treatment, direct reprogramming to pluripotency and transdifferentiation.
Topics: Animals; Cell Membrane; Cell Transdifferentiation; Cellular Reprogramming; Embryo, Mammalian; Epigenesis, Genetic; Humans; Induced Pluripotent Stem Cells; Meiotic Prophase I; Metaphase; Nuclear Transfer Techniques; Ovum; Transcription, Genetic
PubMed: 23715540
DOI: 10.1242/dev.092049 -
Current Genetics Apr 2018The meiotic cell cycle provides a unique model to study the relationship between recombinational DNA repair and the cell cycle, since homologous recombination, induced... (Review)
Review
The meiotic cell cycle provides a unique model to study the relationship between recombinational DNA repair and the cell cycle, since homologous recombination, induced by programmed DNA double-strand breaks (DSBs), is integrated as an essential step during meiosis. The pachytene checkpoint, which is situated towards the end of meiotic prophase I, coordinates homologous recombination and cell cycle progression, similar to the DNA damage checkpoint mechanisms operating in vegetative cells. However, there are a number of features unique to meiosis, making the system optimized for the purpose of meiosis. Our recent work highlights the involvement of three major cell cycle kinases, Dbf4-dependent Cdc7 kinase, Polo kinase and CDK, in coordinating homologous recombination and the meiotic cell cycle. In this review, we will discuss the unique interplay between meiotic cell cycle control and homologous recombination during meiosis I.
Topics: Cell Cycle Proteins; DNA Breaks, Double-Stranded; DNA Damage; DNA-Binding Proteins; Meiosis; Meiotic Prophase I; Phosphorylation; Protein Serine-Threonine Kinases; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins
PubMed: 29071381
DOI: 10.1007/s00294-017-0771-y -
Hereditas 1974
Topics: Aged; Chromosomes; Crossing Over, Genetic; Humans; Karyotyping; Kinetics; Male; Meiosis; Spermatozoa; Staining and Labeling; Testis
PubMed: 4136005
DOI: 10.1111/j.1601-5223.1974.tb01177.x -
Molecular Biology of the Cell Apr 2013During meiosis, evolutionarily conserved mechanisms regulate chromosome remodeling, leading to the formation of a tight bivalent structure. This bivalent, a linked pair...
During meiosis, evolutionarily conserved mechanisms regulate chromosome remodeling, leading to the formation of a tight bivalent structure. This bivalent, a linked pair of homologous chromosomes, is essential for proper chromosome segregation in meiosis. The formation of a tight bivalent involves chromosome condensation and restructuring around the crossover. The synaptonemal complex (SC), which mediates homologous chromosome association before crossover formation, disassembles concurrently with increased condensation during bivalent remodeling. Both chromosome condensation and SC disassembly are likely critical steps in acquiring functional bivalent structure. The mechanisms controlling SC disassembly, however, remain unclear. Here we identify akir-1 as a gene involved in key events of meiotic prophase I in Caenorhabditis elegans. AKIR-1 is a protein conserved among metazoans that lacks any previously known function in meiosis. We show that akir-1 mutants exhibit severe meiotic defects in late prophase I, including improper disassembly of the SC and aberrant chromosome condensation, independently of the condensin complexes. These late-prophase defects then lead to aberrant reconfiguring of the bivalent. The meiotic divisions are delayed in akir-1 mutants and are accompanied by lagging chromosomes. Our analysis therefore provides evidence for an important role of proper SC disassembly in configuring a functional bivalent structure.
Topics: Alleles; Animals; Caenorhabditis elegans; Caenorhabditis elegans Proteins; Cell Cycle Proteins; Chromosomal Proteins, Non-Histone; Chromosome Pairing; Chromosomes; Crossing Over, Genetic; Female; In Situ Hybridization, Fluorescence; Luminescent Proteins; Male; Meiotic Prophase I; Microscopy, Fluorescence; Mutation; Nuclear Proteins; Oocytes; RNA Interference; Rad51 Recombinase; Synaptonemal Complex; Time-Lapse Imaging
PubMed: 23363597
DOI: 10.1091/mbc.E12-11-0841 -
Reproduction (Cambridge, England) Dec 2005
Topics: Animals; Female; Gene Expression Regulation, Developmental; Humans; Luteinizing Hormone; Mammals; Meiosis; Meiotic Prophase I; Oocytes
PubMed: 16322536
DOI: 10.1530/rep.1.01008