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Metaphase

About: Metaphase is a research topic. Over the lifetime, 6925 publications have been published within this topic receiving 291590 citations. The topic is also known as: GO:0007091 & mitotic metaphase/anaphase transition.


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TL;DR: It is demonstrated that chromosome resolution is not simply a consequence of compacting chromosome arms and that overall rDNA compaction is necessary to mediate the segregation of the long arm of chromosome XII.
Abstract: Mitotic cell division involves the equal segregation of all chromosomes during anaphase The presence of ribosomal DNA (rDNA) repeats on the right arm of chromosome XII makes it the longest in the budding yeast genome Previously, we identified a stage during yeast anaphase when rDNA is stretched across the mother and daughter cells Here, we show that resolution of sister rDNAs is achieved by unzipping of the locus from its centromere-proximal to centromere-distal regions We then demonstrate that during this stretched stage sister rDNA arrays are neither compacted nor segregated despite being largely resolved from each other Surprisingly, we find that rDNA segregation after this period no longer requires spindles but instead involves Cdc14-dependent rDNA axial compaction These results demonstrate that chromosome resolution is not simply a consequence of compacting chromosome arms and that overall rDNA compaction is necessary to mediate the segregation of the long arm of chromosome XII

84 citations

Journal ArticleDOI
TL;DR: Myocyte cellular hyperplasia is present in the adult and aging myocardium as a compensatory mechanism to regenerate tissue mass and recover function, which are lost with the progression of life and senescence.
Abstract: To determine whether myocyte mitotic division occurs in the adult mammalian heart and whether this cellular process is affected by aging, we measured the percentage of myocyte nuclei showing metaphase chromosomes in myocytes isolated from the left and right ventricles of rats at 8-12, 19-24, and 28-32 months after birth. Metaphase chromosomes were found at all ages in both ventricles. However, from 8-12 to 28-32 months, the fraction of nuclei exhibiting metaphase chromosomes increased 6.3-fold and 2.3-fold in the left and right ventricles, respectively. Thus, myocyte cellular hyperplasia is present in the adult and aging myocardium as a compensatory mechanism to regenerate tissue mass and recover function, which are lost with the progression of life and senescence.

84 citations

Journal ArticleDOI
TL;DR: The reliability of 1PB analysis by CGH is demonstrated, to detect almost any chromosome abnormality in oocytes as well as unbalanced segregations of maternal translocations in a time frame compatible with regular in vitro fertilization (IVF).
Abstract: BACKGROUND: Preimplantation Genetic Diagnosis (PGD) using FISH to analyze up to nine chromosomes to discard chromosomally abnormal embryos has resulted in an increase of pregnancy rates in certain groups of patients. However, the number of chromosomes that can be analyzed is a clear limitation. We evaluate the reliability of using comparative genomic hybridization (CGH) to detect the whole set of chromosomes, as an alternative to PGD using FISH. METHODS and RESULTS: We have analysed by CGH both, first polar bodies (lPBs) and metaphase II (MII) oocytes from 30 oocytes donated by 24 women. The aneuploidy rate was 48%. Considering two maternal age groups, a higher number of chromosome abnormalities were detected in the older group of oocytes (23% versus 75%, P < 0.02). About 33% of the 1PB-MII oocyte doublets diagnosed as aneuploid by CGH would have been misdiagnosed as normal if FISH with nine chromosome probes had been used. CONCLUSION: We demonstrate the reliability of 1PB analysis by CGH, to detect almost any chromosome abnormality in oocytes as well as unbalanced segregations of maternal translocations in a time frame compatible with regular in vitro fertilization (IVF). The selection of euploid oocytes could help to increase implantation and pregnancy rates of patients undergoing IVF treatment.

84 citations

Journal ArticleDOI
TL;DR: The results suggest that HCP-1 is a centromere-associated protein that is involved in the fidelity of chromosome segregation.
Abstract: To learn more about holocentric chromosome structure and function, we generated a monoclonal antibody (mAb), 6C4, that recognizes the poleward face of mitotic chromosomes in Caenorhabditis elegans . Early in mitosis, mAb 6C4 stains dots throughout the nucleoplasm. Later in prophase, mAb 6C4 stains structures on opposing faces of chromosomes which orient towards the centrosomes at metaphase. Colocalization with an antibody against a centromeric histone H3–like protein and the MPM-2 antibody, which identifies a kinetochore-associated phosphoepitope present in a variety of organisms, shows that the mAb 6C4 staining is present adjacent to the centromere. Expression screening using mAb 6C4 identified a protein in C . elegans that we named HCP-1 (for holocentric protein 1). We also identified a second protein from the C . elegans genome sequence database, HCP-2, that is 54% similar to HCP-1. When expression of HCP-1 is reduced by RNA interference (RNAi), staining with mAb 6C4 is eliminated, indicating that hcp-1 encodes the major mAb 6C4 antigen. RNAi with hcp-1 and hcp-2 together results in aberrant anaphases and embryonic arrest at ∼100 cells with different amounts of DNA in individual nuclei. These results suggest that HCP-1 is a centromere-associated protein that is involved in the fidelity of chromosome segregation.

84 citations

Journal ArticleDOI
TL;DR: It is concluded that the fenestrated nuclear envelope may significantly contribute to the normal process of spindle assembly in Drosophila spermatocytes and that these anastral microtubule arrays could be a constitutive component of wild-type spindles, normally masked by the abundance of centrosome-derived microtubules and revealed when asters are kept away.
Abstract: Previous data suggested that anastral spindles, morphologically similar to those found in oocytes, can assemble in a centrosome-independent manner in cells that contain centrosomes. It is assumed that the microtubules that build these acentrosomal spindles originate over the chromatin. However, the actual processes of centrosome-independent microtubule nucleation, polymerisation, and sorting have not been documented in centrosome-containing cells. We have identified two experimental conditions in which centrosomes are kept close to the plasma membrane, away from the nuclear region, throughout meiosis I in Drosophila spermatocytes. Time-lapse confocal microscopy of these cells labelled with fluorescent chimeras reveals centrosome-independent microtubule nucleation, growth, and sorting into a bipolar spindle array over the nuclear region, away from the asters. The onset of noncentrosomal microtubule nucleation is significantly delayed with respect to nuclear envelope breakdown and coincides with the end of chromosome condensation. It takes place in foci that are close to the membranes that ensheath the nuclear region, not over the condensed chromosomes. Metaphase plates are formed in these spindles, and, in a fraction of them, some degree of polewards chromosome segregation takes place. In these cells that contain both membrane-bound asters and an anastral spindle, the orientation of the cytokinesis furrow correlates with the position of the asters and is independent of the orientation of the spindle. We conclude that the fenestrated nuclear envelope may significantly contribute to the normal process of spindle assembly in Drosophila spermatocytes. We also conclude that the anastral spindles that we have observed are not likely to provide a robust back-up able to ensure successful cell division. We propose that these anastral microtubule arrays could be a constitutive component of wild-type spindles, normally masked by the abundance of centrosome-derived microtubules and revealed when asters are kept away. These observations are consistent with a model in which centrosomal and noncentrosomal microtubules contribute to the assembly and are required for the robustness of the cell division spindle in cells that contain centrosomes.

84 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202373
2022116
202182
202087
2019113
201888