Topic
Skewed X-inactivation
About: Skewed X-inactivation is a research topic. Over the lifetime, 891 publications have been published within this topic receiving 58138 citations.
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TL;DR: Ohno and Hauschka1 showed that in female mice one chromosome of mammary carcinoma cells and of normal diploid cells of the ovary, mammary gland and liver was heteropyKnotic and suggested that the so-called sex chromatin was composed of one heteropyknotic X-chromosome.
Abstract: Ohno and Hauschka1 showed that in female mice one chromosome of mammary carcinoma cells and of normal diploid cells of the ovary, mammary gland and liver was heteropyknotic. They interpreted this chromosome as an X-chromosome and suggested that the so-called sex chromatin was composed of one heteropyknotic X-chromosome. They left open the question whether the heteropyknosis was shown by the paternal X-chromosome only, or the chromosome from either parent indifferently.
3,650 citations
TL;DR: A comprehensive X-inactivation profile of the human X chromosome is presented, representing an estimated 95% of assayable genes in fibroblast-based test systems, and suggests a remarkable and previously unsuspected degree of expression heterogeneity among females.
Abstract: In female mammals, most genes on one X chromosome are silenced as a result of X-chromosome inactivation. However, some genes escape X-inactivation and are expressed from both the active and inactive X chromosome. Such genes are potential contributors to sexually dimorphic traits, to phenotypic variability among females heterozygous for X-linked conditions, and to clinical abnormalities in patients with abnormal X chromosomes. Here, we present a comprehensive X-inactivation profile of the human X chromosome, representing an estimated 95% of assayable genes in fibroblast-based test systems. In total, about 15% of X-linked genes escape inactivation to some degree, and the proportion of genes escaping inactivation differs dramatically between different regions of the X chromosome, reflecting the evolutionary history of the sex chromosomes. An additional 10% of X-linked genes show variable patterns of inactivation and are expressed to different extents from some inactive X chromosomes. This suggests a remarkable and previously unsuspected degree of expression heterogeneity among females.
1,866 citations
Journal Article•
TL;DR: The human androgen-receptor gene (HUMARA) contains a highly polymorphic trinucleotide repeat in the first exon that correlates with X inactivation, and the development of a PCR assay that distinguishes between the maternal and paternal alleles and identifies their methylation status is developed.
Abstract: The human androgen-receptor gene (HUMARA; GenBank) contains a highly polymorphic trinucleotide repeat in the first exon. We have found that the methylation of HpaII and HhaI sites less than 100 bp away from this polymorphic short tandem repeat (STR) correlates with X inactivation. The close proximity of the restriction-enzyme sites to the STR allows the development of a PCR assay that distinguishes between the maternal and paternal alleles and identifies their methylation status. The accuracy of this assay was tested on (a) DNA from hamster/human hybrid cell lines containing either an active or inactive human X chromosome; (b) DNA from normal males and females; and (c) DNA from females showing nonrandom patterns of X inactivation. Data obtained using this assay correlated substantially with those obtained using the PGK, HPRT, and M27 beta probes, which detect X inactivation patterns by Southern blot analysis. In order to demonstrate one application of this assay, we examined X inactivation patterns in the B lymphocytes of potential and obligate carriers of X-linked agammaglobulinemia.
1,659 citations
TL;DR: This gene, called XIST (for Xi-specific transcripts), is a candidate for a gene either involved in or uniquely influenced by the process of X inactivation, and is described as an X-linked gene with a novel expression pattern.
Abstract: X-chromosome inactivation results in the cis-limited dosage compensation of genes on one of the pair of X chromosomes in mammalian females. Although most X-linked genes are believed to be subject to inactivation, several are known to be expressed from both active and inactive X chromosomes. Here we describe an X-linked gene with a novel expression pattern--transcripts are detected only from the inactive X chromosome (Xi) and not from the active X chromosome (Xa). This gene, called XIST (for Xi-specific transcripts), is a candidate for a gene either involved in or uniquely influenced by the process of X inactivation.
1,397 citations
TL;DR: Human XIST cDNAs containing at least eight exons and totaling 17 kb have been isolated and sequenced within the region on the X chromosome known to contain the X inactivation center, suggesting that XIST may function as a structural RNA within the nucleus.
1,244 citations