Talk:Molecular Development - X Inactivation: Difference between revisions

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==2010==


===Active Chromatin Marks Are Retained on X Chromosomes Lacking Gene or Repeat Silencing Despite XIST/Xist Expression in Somatic Cell Hybrids===
===Active Chromatin Marks Are Retained on X Chromosomes Lacking Gene or Repeat Silencing Despite XIST/Xist Expression in Somatic Cell Hybrids===

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Cite this page: Hill, M.A. (2024, March 28) Embryology Molecular Development - X Inactivation. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Talk:Molecular_Development_-_X_Inactivation

2010

Active Chromatin Marks Are Retained on X Chromosomes Lacking Gene or Repeat Silencing Despite XIST/Xist Expression in Somatic Cell Hybrids

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0010787

2007

Meiotic sex chromosome inactivation

Development. 2007 May;134(10):1823-31. Epub 2007 Feb 28.

Turner JM.

Division of Stem Cell Biology and Developmental Genetics, MRC NIMR, The Ridgeway, Mill Hill, London NW7 1AA, UK. jturner@nimr.mrc.ac.uk Abstract X chromosome inactivation is most commonly studied in the context of female mammalian development, where it performs an essential role in dosage compensation. However, another form of X-inactivation takes place in the male, during spermatogenesis, as germ cells enter meiosis. This second form of X-inactivation, called meiotic sex chromosome inactivation (MSCI) has emerged as a novel paradigm for studying the epigenetic regulation of gene expression. New studies have revealed that MSCI is a special example of a more general mechanism called meiotic silencing of unsynapsed chromatin (MSUC), which silences chromosomes that fail to pair with their homologous partners and, in doing so, may protect against aneuploidy in subsequent generations. Furthermore, failure in MSCI is emerging as an important etiological factor in meiotic sterility.

PMID: 17329371 http://www.ncbi.nlm.nih.gov/pubmed/17329371

2006

The X chromosome is organized into a gene-rich outer rim and an internal core containing silenced nongenic sequences

Proc Natl Acad Sci U S A. 2006 May 16;103(20):7688-93. Epub 2006 May 8.

Clemson CM, Hall LL, Byron M, McNeil J, Lawrence JB. Department of Cell Biology, University of Massachusetts Medical Center, 55 Lake Avenue North, Worcester, MA 01655, USA.

Abstract

We investigated whether genes escape X chromosome inactivation by positioning outside of the territory defined by XIST RNA. Results reveal an unanticipated higher order organization of genes and noncoding sequences. All 15 X-linked genes, regardless of activity, position on the border of the XIST RNA territory, which resides outside of the DAPI-dense Barr body. Although more strictly delineated on the inactive X chromosome (Xi), all genes localized predominantly to the outer rim of the Xi and active X chromosome. This outer rim is decorated only by X chromosome DNA paints and is excluded from both the XIST RNA and dense DAPI staining. The only DNA found well within the Barr body and XIST RNA territory was centromeric and Cot-1 DNA; hence, the core of the X chromosome essentially excludes genes and is composed primarily of noncoding repeat-rich DNA. Moreover, we show that this core of repetitive sequences is expressed throughout the nucleus yet is silenced throughout Xi, providing direct evidence for chromosome-wide regulation of "junk" DNA transcription. Collective results suggest that the Barr body, long presumed to be the physical manifestation of silenced genes, is in fact composed of a core of silenced noncoding DNA. Instead of acting at a local gene level, XIST RNA appears to interact with and silence core architectural elements to effectively condense and shut down the Xi.

PMID: 16682630 http://www.ncbi.nlm.nih.gov/pubmed/16682630

http://www.pnas.org/content/103/20/7688.full

http://www.pnas.org/content/103/20/7688/F4.expansion.html

http://www.pnas.org/content/103/20/7688/F4.large.jpg