Topic
X chromosome
About: X chromosome is a research topic. Over the lifetime, 9862 publications have been published within this topic receiving 407354 citations. The topic is also known as: GO:0000805 & chrX.
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TL;DR: The results indicate that the presence of a univalent chromosome causes severe meiotic disruption during mammalian meiosis, affecting the alignment and segregation of other chromosomes in the complement, and suggests that cell cycle control differs between male and female meiosis and that monitoring of meiotic chromosome behavior is less efficient in the female.
Abstract: To monitor the behavior of specific chromosomes at various stages of mammalian female meiosis, we have combined immunofluorescence staining and fluorescence in situ hybridization (FISH) on intact oocytes. We have utilized this technique to evaluate the behavior of the single X chromosome in oocytes from XO female mice, providing the first observations on segregation of an achiasmate chromosome during mammalian female meiosis and its effect on the meiotic process. As has been described in other species, we found that the univalent chromosome could either segregate as an intact chromosome to one pole or divide equationally at the first meiotic division. Our results also indicate that the presence of a univalent chromosome causes severe meiotic disruption during mammalian meiosis, affecting the alignment and segregation of other chromosomes in the complement. Despite these meiotic abnormalities, the vast majority of oocytes from XO females were able to resume and successfully complete the first meiotic division. This is in contrast to previous studies of male mice with sex chromosome abnormalities where the presence of a univalent acts to arrest meiosis at metaphase of the first meiotic division. This sex-specific difference in the ability of a cell with a univalent chromosome to initiate anaphase suggests that cell cycle control differs between male and female meiosis and that monitoring of meiotic chromosome behavior is less efficient in the female. The combined use of immunofluorescence staining and FISH on intact oocytes has obvious application to the study of meiotic chromosome non-disjunction in the human female. Simultaneous study of the meiotic cell cycle, protein components of the meiotic apparatus, and chromosome-specific behaviors during mammalian female meiosis provides a new approach to defining age-related changes in the meiotic process that result in increased chromosome malsegregation.
150 citations
TL;DR: It is found that only a quarter of the Drosophila melanogaster Y-linked genes (3 out of 12) are Y- linked in all sequenced species, and that most of them were acquired less than 63 Myr ago, whereas the organization of other Drosphila chromosomes traces back to the common ancestor with mosquitoes, the gene content of the Y chromosome is much younger.
Abstract: Chromosomal organization is sufficiently evolutionarily stable that large syntenic blocks of genes can be recognized even between species as distantly related as mammals and puffer fish (450 million years (Myr) of divergence). In Diptera, the gene content of the X chromosome and the autosomes is well conserved: in Drosophila more than 95% of the genes have remained on the same chromosome arm in the 12 sequenced species (63 Myr of divergence, traversing 400 Myr of evolution), and the same linkage groups are clearly recognizable in mosquito genomes (260 Myr of divergence). Here we investigate the conservation of Y-linked gene content among the 12 sequenced Drosophila species. We found that only a quarter of the Drosophila melanogaster Y-linked genes (3 out of 12) are Y-linked in all sequenced species, and that most of them (7 out of 12) were acquired less than 63 Myr ago. Hence, whereas the organization of other Drosophila chromosomes traces back to the common ancestor with mosquitoes, the gene content of the D. melanogaster Y chromosome is much younger. Gene losses are known to have an important role in the evolution of Y chromosomes, and we indeed found two such cases. However, the rate of gene gain in the Drosophila Y chromosomes investigated is 10.9 times higher than the rate of gene loss (95% confidence interval: 2.3-52.5), indicating a clear tendency of the Y chromosomes to increase in gene content. In contrast with the mammalian Y chromosome, gene gains have a prominent role in the evolution of the Drosophila Y chromosome.
150 citations
TL;DR: A mechanism involving antagonistic activity of XIST and XACT in controlling X chromosome activity in early human embryos is suggested, and the contribution of rapidly evolving lncRNAs to species-specific developmental mechanisms is highlighted.
150 citations
TL;DR: In this article, the authors used recombinant-DNA probes to detect restriction-fragment-length polymorphisms and patterns of methylation of X-chromosome genes.
Abstract: We used a recently developed strategy to analyze patterns of X-chromosome inactivation in human cell populations in order to study female members of families with X-linked agammaglobulinemia--i.e., to detect the carrier state and to test the hypothesis that the disorder results from a defect intrinsic in the development of B cells. According to this strategy, recombinant-DNA probes simultaneously detect restriction-fragment-length polymorphisms and patterns of methylation of X-chromosome genes. Random X-inactivation patterns were observed in isolated peripheral-blood granulocytes, T lymphocytes, and B lymphocytes of women who were not carriers. In contrast, one of the two X chromosomes was preferentially active in the peripheral B cells, but not the T cells or granulocytes, of three carriers of the disorder. This observation strongly supports the hypothesis that X-linked agammaglobulinemia results from an intrinsic defect in B-cell development. Moreover, the analysis described here can be used for direct identification of carriers in families with this disease.
149 citations
TL;DR: It is concluded that massively parallel sequencing is useful to characterize large candidate linkage intervals and that it can be used successfully to allow identification of disease-causing gene mutations.
Abstract: Micrognathia, glossoptosis, and cleft palate comprise one of the most common malformation sequences, Robin sequence. It is a component of the TARP syndrome, talipes equinovarus, atrial septal defect, Robin sequence, and persistent left superior vena cava. This disorder is X-linked and severe, with apparently 100% pre- or postnatal lethality in affected males. Here we characterize a second family with TARP syndrome, confirm linkage to Xp11.23-q13.3, perform massively parallel sequencing of X chromosome exons, filter the results via a number of criteria including the linkage region, use a unique algorithm to characterize sequence changes, and show that TARP syndrome is caused by mutations in the RBM10 gene, which encodes RNA binding motif 10. We further show that this previously uncharacterized gene is expressed in midgestation mouse embryos in the branchial arches and limbs, consistent with the human phenotype. We conclude that massively parallel sequencing is useful to characterize large candidate linkage intervals and that it can be used successfully to allow identification of disease-causing gene mutations.
149 citations