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Chromosoma Mar 2014Rapid chromosome movement during prophase of the first meiotic division has been observed in many organisms. It is generally concomitant with formation of the "meiotic... (Review)
Review
Rapid chromosome movement during prophase of the first meiotic division has been observed in many organisms. It is generally concomitant with formation of the "meiotic chromosome bouquet," a special chromosome configuration in which one or both chromosome ends attach to the nuclear envelope and become concentrated within a limited area. The precise function of the chromosomal bouquet is still not fully understood. Chromosome mobility is implicated in homologous chromosome pairing, synaptonemal complex formation, recombination, and resolution of chromosome entanglements. The basic mechanistic module through which forces are exerted on chromosomes is widely conserved; however, phenotypic differences have been reported among various model organisms once movement is abrogated. Movements are transmitted to the chromosome ends by the nuclear membrane-bridging SUN/KASH complex and are dependent on cytoskeletal filaments and motor proteins located in the cytoplasm. Here we review the recent findings on chromosome mobility during meiosis in an animal model system: the Caenorhabditis elegans nematode.
Topics: Animals; Caenorhabditis elegans; Chromosome Pairing; Chromosomes; Meiotic Prophase I; Movement; Pachytene Stage
PubMed: 24036686
DOI: 10.1007/s00412-013-0436-7 -
Chromosoma Jun 2006Recent progress in elucidating the function of synaptonemal complex (SC) proteins and of cohesins in meiocytes made possible, in particular, through the analysis of mice... (Review)
Review
Recent progress in elucidating the function of synaptonemal complex (SC) proteins and of cohesins in meiocytes made possible, in particular, through the analysis of mice deficient in SC or cohesin proteins has significantly enriched our understanding of how meiotic chromosome architecture is determined. Cohesins and the SC proteins act together in generating the characteristic axis-loop structure of meiotic chromosomes, their pairing into bivalents, their ability to recombine, and to be properly segregated. This minireview attempts to summarize the current knowledge with a focus on higher eukaryotic systems and to ask questions that ought to be addressed in the future.
Topics: Animals; Cell Cycle Proteins; Chromosomal Proteins, Non-Histone; Chromosomes; Gene Deletion; Meiosis; Mice; Models, Biological; Nuclear Proteins; Prophase; Synaptonemal Complex; Cohesins
PubMed: 16518630
DOI: 10.1007/s00412-006-0060-x -
Developmental Cell Apr 2002During mitosis, in most eukaryotes, cohesin is removed from chromosomes in two steps. A paper in the March issue of Molecular Cell identifies Polo-like kinase as a key... (Review)
Review
During mitosis, in most eukaryotes, cohesin is removed from chromosomes in two steps. A paper in the March issue of Molecular Cell identifies Polo-like kinase as a key regulator for the first step that releases much of cohesin during prophase.
Topics: Animals; Cell Cycle Proteins; Chromosome Segregation; Drosophila Proteins; Prophase; Protein Serine-Threonine Kinases; Xenopus Proteins
PubMed: 11970886
DOI: 10.1016/s1534-5807(02)00155-7 -
Trends in Cell Biology Dec 2005Meiosis is a specialized type of cell division leading to the production of gametes. During meiotic prophase I, homologous chromosomes interact with each other and form... (Review)
Review
Meiosis is a specialized type of cell division leading to the production of gametes. During meiotic prophase I, homologous chromosomes interact with each other and form bivalents (pairs of homologous chromosomes). Three major meiotic processes--chromosome pairing, synapsis and recombination--are involved in the formation of bivalents. Many recent reports have uncovered complex networks of interactions between these processes. Chromosome pairing is largely dependent on the initiation and progression of recombination in fungi, mammals and plants, but not in Caenorhabditis elegans or Drosophila. Synapsis and recombination are also tightly linked. Understanding the coordination between chromosome pairing, synapsis and recombination lends insight into many poorly explained aspects of meiosis, such as the nature of chromosome homology recognition.
Topics: Animals; Chromosome Pairing; Chromosome Segregation; Humans; Meiosis; Meiotic Prophase I; Recombination, Genetic
PubMed: 16257210
DOI: 10.1016/j.tcb.2005.10.005 -
Trends in Cell Biology Jul 2011The coordinated execution of cell cycle processes during meiosis is essential for the production of viable gametes and fertility. Coordination is particularly important... (Review)
Review
The coordinated execution of cell cycle processes during meiosis is essential for the production of viable gametes and fertility. Coordination is particularly important during meiotic prophase, when nuclei undergo a dramatic reorganization that requires the precise choreography of chromosome movements, pairing interactions and DNA double-strand break (DSB) repair. Analysis of the underlying regulatory mechanisms has revealed crucial and widespread roles for DNA-damage checkpoint proteins, not only in cell cycle surveillance, but also in controlling many processes uniquely characteristic of meiosis. The resulting regulatory network uses checkpoint machinery to provide an integral coordinating mechanism during every meiotic division and enables cells to safely maintain an error-prone event such as DSB formation as an essential part of the meiotic program.
Topics: Animals; Cell Cycle Proteins; Chromosome Pairing; DNA Breaks, Double-Stranded; DNA Repair; Humans; Meiotic Prophase I
PubMed: 21531561
DOI: 10.1016/j.tcb.2011.03.004 -
Cell Cycle (Georgetown, Tex.) 2015During meiotic prophase, DNA double-strand break (DSB) repair-mediated homologous recombination (HR) occurs for exchange of genetic information between homologous... (Review)
Review
During meiotic prophase, DNA double-strand break (DSB) repair-mediated homologous recombination (HR) occurs for exchange of genetic information between homologous chromosomes. Unlike autosomes or female sex chromosomes, human male sex chromosomes X and Y share little homology. Although DSBs are generated throughout male sex chromosomes, homologous recombination does not occur for most regions and DSB repair process is significantly prolonged. As a result, male sex chromosomes are coated with many DNA damage response proteins and form a unique chromatin structure known as the XY body. Interestingly, associated with the prolonged DSB repair, transcription is repressed in the XY body but not in autosomes, a phenomenon known as meiotic sex chromosome inactivation (MSCI), which is critical for male meiosis. Here using mice as model organisms, we briefly summarize recent progress on DSB repair in meiotic prophase and focus on the mechanism and function of DNA damage response in the XY body.
Topics: Animals; Carrier Proteins; Crossing Over, Genetic; DNA Breaks, Double-Stranded; DNA Repair; Male; Mice; Models, Biological; Prophase; Sex Chromosomes; Ubiquitin-Protein Ligases
PubMed: 25565522
DOI: 10.1080/15384101.2014.998070 -
Journal of Genetics and Genomics = Yi... Mar 2014Meiosis is a key event in gametogenesis that generates new combinations of genetic information and is required to reduce the chromosome content of the gametes. Meiotic... (Review)
Review
Meiosis is a key event in gametogenesis that generates new combinations of genetic information and is required to reduce the chromosome content of the gametes. Meiotic chromosomes undergo a number of specialised events during prophase to allow meiotic recombination, homologous chromosome synapsis and reductional chromosome segregation to occur. In mammalian cells, DNA physically associates with histones to form chromatin, which can be modified by methylation, phosphorylation, ubiquitination and acetylation to help regulate higher order chromatin structure, gene expression, and chromosome organisation. Recent studies have identified some of the enzymes responsible for generating chromatin modifications in meiotic mammalian cells, and shown that these chromatin modifying enzymes are required for key meiosis-specific events that occur during meiotic prophase. This review will discuss the role of chromatin modifications in meiotic recombination, homologous chromosome synapsis and regulation of meiotic gene expression in mammals.
Topics: Acetylation; Animals; Centromere; Chromatin; DNA; Gene Expression; Histones; Methylation; Methyltransferases; Mice; Phosphorylation; Polycomb-Group Proteins; Prophase; Ubiquitination
PubMed: 24656230
DOI: 10.1016/j.jgg.2014.01.003 -
Current Topics in Developmental Biology 1998We review the synaptonemal complex, SC, of the synapsed homologous chromosomes at meiotic prophase in insects and mammals in terms of its formation, and the association... (Review)
Review
We review the synaptonemal complex, SC, of the synapsed homologous chromosomes at meiotic prophase in insects and mammals in terms of its formation, and the association of specific chromatin elements with the synaptonemal complexes. The focus is: (1) The SC as visualized with a variety of techniques; (2) The nature of the chromatin loops where they are associated with the SCs--the bases of the loops may be instrumental in recombinant events judging from the presence of Rad51 protein and late recombination nodules at the SCs; (3) Differences in DNA content of similarly sized loops; (4) Requirements for chromatin attachment to the chromosome cores, requirements that are apparently lacking in foreign DNA inserts; (5) Regulation of loop size by the position along the chromosome; (6) The structural correlates of recombination at the SCs--these comments are based on studies of SC structure, DNA-core protein associations, fluorescent in situ hybridization to visualize specific DNA segments, and fluorescent immunocytology to visualize the chromosome core proteins.
Topics: Animals; Chromatin; Chromosomes; DNA; Meiosis; Microscopy, Electron; Prophase; Synaptonemal Complex; Transcription, Genetic
PubMed: 9352188
DOI: 10.1016/s0070-2153(08)60176-3 -
Seminars in Cell & Developmental Biology Aug 1998This review focuses on recent developments in our understanding of meiotic chromosome behavior in mammalian spermatogenesis, with a special emphasis on prophase I events... (Review)
Review
This review focuses on recent developments in our understanding of meiotic chromosome behavior in mammalian spermatogenesis, with a special emphasis on prophase I events in the best characterized organism, the laboratory mouse. The dynamics of chromosome movement prior to pairing and synapsis of chromosomes are complex and implicate function for both centromeres and telomeres in getting homologous chromosomes together in intimate synapsis. Likely candidates for mediating pairing and recombination include a host of proteins implicated in DNA repair and recombination, which have been shown to localize to the synaptonemal complex during meiotic prophase I. Precocious induction of meiotic metaphase in cultured pachytene spermatocytes has led to new information about requirements for MPF and topoisomerase II activity during the transition from meiotic prophase to metaphase. Together, the studies reviewed here increase our understanding of how chromosomes get together with their homologous partners and how these partners subsequently come apart.
Topics: Animals; Cell Division; Humans; Male; Meiosis; Mesothelin; Prophase; Spermatogenesis
PubMed: 9813191
DOI: 10.1006/scdb.1998.0202 -
Cell Reports May 2020Centrosome separation in late G2/ early prophase requires precise spatial coordination that is determined by a balance of forces promoting and antagonizing separation....
Centrosome separation in late G2/ early prophase requires precise spatial coordination that is determined by a balance of forces promoting and antagonizing separation. The major effector of centrosome separation is the kinesin Eg5. However, the identity and regulation of Eg5-antagonizing forces is less well characterized. By manipulating candidate components, we find that centrosome separation is reversible and that separated centrosomes congress toward a central position underneath the flat nucleus. This positioning mechanism requires microtubule polymerization, as well as actin polymerization. We identify perinuclear actin structures that form in late G2/early prophase and interact with microtubules emanating from the centrosomes. Disrupting these structures by breaking the interactions of the linker of nucleoskeleton and cytoskeleton (LINC) complex with perinuclear actin filaments abrogates this centrosome positioning mechanism and causes an increase in subsequent chromosome segregation errors. Our results demonstrate how geometrical cues from the cell nucleus coordinate the orientation of the emanating spindle poles before nuclear envelope breakdown.
Topics: Actins; Centrosome; Chromosome Segregation; Humans; Prophase
PubMed: 32460023
DOI: 10.1016/j.celrep.2020.107681