Topic
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 found that Nuf2 is associated with Hec1 throughout the cell cycle and that this complex is localized to the centrosomes during G1 and S phases and then moves through the nuclear membrane to the Centromere in G2 phase.
Abstract: Nuf2 and Hec1 are evolutionarily conserved centromere proteins. To clarify the functions of these proteins in vertebrate cells, we characterized them in chicken DT40 cells. We generated GFP fusion constructs of Nuf2 and Hec1 to examine in detail the localization of these proteins during the cell cycle. We found that Nuf2 is associated with Hec1 throughout the cell cycle and that this complex is localized to the centrosomes during G1 and S phases and then moves through the nuclear membrane to the centromere in G2 phase. During mitosis, this complex is localized to the centromere. We also created conditional loss-of-function mutants of Nuf2 and Hec1. In both mutants, the cell cycle arrested at prometaphase, suggesting that the Nuf2-Hec1 complex is essential for mitotic progression. The inner centromere proteins CENP-A, -C, and -H and checkpoint protein BubR1 were localized to chromosomes in the mutant cells arrested at prometaphase, but Mad2 localization was abolished. Furthermore, photobleaching experiments revealed that the Nuf2-Hec1 complex is stably associated with the centromere and that interaction of this complex with the centrosome is dynamic.
161 citations
TL;DR: It is shown that depletion of either Nuf2 or Hec1 by RNAi in HeLa cells results in reduction of both proteins at kinetochores and in the cytoplasm, which supports a model in which Nuf3 and Hec2 function to prevent microtubule-dependent stripping of Mad1 and Mad2 from kinetchores that have not yet formed stable kinet Cochore-microtubule attachments.
161 citations
TL;DR: It is demonstrated that exposure to high levels of F SH during IVM can accelerate nuclear maturation and induce chromosomal abnormalities and highlights the importance of the judicious use of FSH duringIVM.
Abstract: Follicle-Stimulating Hormone (FSH) at a wide range of doses is routinely added to culture media during in vitro maturation (IVM) of oocytes, but the effects on oocyte health are unclear. The suggestion that superovulation may cause aneuploidy and fetal abnormalities prompted us to study the potential role of FSH in the genesis of chromosomal abnormalities during meiosis I. Mouse cumulus-oocyte complexes (COCs) isolated from the antral follicles of unprimed, sexually immature B6CBF1 mice were cultured in increasing concentrations of FSH. Following culture, matured oocytes were isolated, spread, stained with DAPI, and the numbers of chromosomes counted. Significantly increased aneuploidy, arising during the first meiotic division, was observed in metaphase II oocytes matured in higher concentrations of FSH ($20 ng/ml). The effect of FSH on spindle morphology and chromosome alignment during metaphase I was then explored using immunocytochemistry and three-dimensional reconstruction of confocal sections. High FSH had no effect on gross spindle morphology but did alter chromosome congression during prometaphase and metaphase, with the spread of chromosomes across the spindle at this time being significantly greater in oocytes cultured in 2000 ng/ml compared with 2 ng/ml FSH. Analysis of three-dimensional reconstructions of spindles in oocytes matured in 2000 ng/ml FSH shows that chromosomes are more scattered and farther apart than they are following maturation in 2 ng/ml FSH. These results demonstrate that exposure to high levels of FSH during IVM can accelerate nuclear maturation and induce chromosomal abnormalities and highlights the importance of the judicious use of FSH during IVM. aneuploidy, FSH, gamete biology, IVM, meiosis, oocyte development, spindle
161 citations
TL;DR: It is claimed that secondary association is evidence of more remote affinities than can ever be expressed in primary association in a poly-ploid, proved by the occurrence of true (primary) association in triploid Pyrus between chromosomes which only show secondary association in the diploid form.
Abstract: 1. A detailed account is given of the behaviour of the chromosomes from diplotene to second anaphase in Dahlia Merckii (2n=36), D. coccinea (2n=32), D. coronata (2n=32) and D. variabilis (2n=64).2. Two kinds of chromosome association are found in these species:a) Primary Association, arising from particulate pairing at zygotene and determining segregation at metaphase.b) Secondary Association, arising at pro-metaphase and due to the general affinity of homologous chromosomes. This does not affect segregation. The chromosomes first associate at pro-metaphase when they are in close proximity to each other.3. As first described by DARLINGTON, the primary association of chromosomes at metaphase is shown to be solely due to the mainten-ance of chiasmata formed at pachytene. Only those chromosome pairs or multivalents which are materially connected by chiasmata survive the strong repulsion phase of diakinesis. This repulsion results in the radial dispersion of the bivalents to the periphery of the nucleus, coupled with an equal aversion between the pairs and the members of each pair. The repulsion is fully maintained until mid-diaknesis, and then gradually diminishes to pro-metaphase, when the close proximity and general affinity of homologous chromosome results in groups of secondarily associated chromosomes at metaphase. The frequency and size of the group is characteristic for a given species. The importance of the diakinetic Phase in differentiating primary and secondary association is emphasised.4. The theory of secondary association is discussed and evidence from the literature presented. It is claimed that secondary association is evidence of more remote affinities than can ever be expressed in primary association in a poly-ploid. This is proved by the occurrence of true (primary) association in triploid Pyrus between chromosomes which only show secondary association in the diploid form.5. The effects of fixation, the correlation between allopolyploidy and secondary association and finally the value of secondary association as a criterion of homology are discussed.
161 citations
Journal Article•
TL;DR: Trypsin G banding was performed on metaphase chromosomes from 14 cell lines derived from primary tumors or metastases of 11 patients with testicular cancer, finding consistent involvement of chromosome 1 in aberrations may be associated with the highly malignant nature of testicular cancers.
Abstract: Trypsin G banding was performed on metaphase chromosomes from 14 cell lines derived from primary tumors or metastases of 11 patients with testicular cancer Most of the cell lines, 11 of 14, have a modal number between 51 and 61 All lines have numerical and structural changes involving chromosome 1 with trisomy of the q arm being the common aberration Break points in chromosome 1 were nonrandom, being concentrated in the regions of p12, q12, p36, and p22, which resulted in morphologically identical marker chromosomes in different cases These changes probably are not artifacts of cell culture In one instance, three lines derived from the same patient, one from tissue removed at operation, and two from separate metastases removed at autopsy nearly 3 years later after unsuccessful radiotherapy and chemotherapy had identical chromosome compositions In another case, lines derived from a primary tumor and a metastasis from the same patient also had identical marker chromosomes The consistent involvement of chromosome 1 in aberrations may be associated with the highly malignant nature of testicular cancers
160 citations