title: Genetic and pharmacological reactivation of the mammalian inactive X chromosome.
abstract: X-chromosome inactivation (XCI), the random transcriptional silencing of one X chromosome in somatic cells of female mammals, is a mechanism that ensures equal expression of X-linked genes in both sexes. XCI is initiated in cis by the noncoding Xist RNA, which coats the inactive X chromosome (Xi) from which it is produced. However, trans-acting factors that mediate XCI remain largely unknown. Here, we perform a large-scale RNA interference screen to identify trans-acting XCI factors (XCIFs) that comprise regulators of cell signaling and transcription, including the DNA methyltransferase, DNMT1. The expression pattern of the XCIFs explains the selective onset of XCI following differentiation. The XCIFs function, at least in part, by promoting expression and/or localization of Xist to the Xi. Surprisingly, we find that DNMT1, which is generally a transcriptional repressor, is an activator of Xist transcription. Small-molecule inhibitors of two of the XCIFs can reversibly reactivate the Xi, which has implications for treatment of Rett syndrome and other dominant X-linked diseases. A homozygous mouse knockout of one of the XCIFs, stanniocalcin 1 (STC1), has an expected XCI defect but surprisingly is phenotypically normal. Remarkably, X-linked genes are not overexpressed in female Stc1(-/-) mice, revealing the existence of a mechanism(s) that can compensate for a persistent XCI deficiency to regulate X-linked gene expression.
authors.affiliation: Howard Hughes Medical Institute and Programs in Gene Function and Expression, Molecular Medicine, and.
authors.forename: Sanchita
authors.initials: S
authors.lastname: Bhatnagar
authors.affiliation: Howard Hughes Medical Institute and Programs in Gene Function and Expression, Molecular Medicine, and.
authors.forename: Xiaochun
authors.initials: X
authors.lastname: Zhu
authors.affiliation: Gene Function and Expression, Molecular Medicine, and.
authors.forename: Jianhong
authors.initials: J
authors.lastname: Ou
authors.affiliation: Howard Hughes Medical Institute and Programs in Gene Function and Expression, Molecular Medicine, and.
authors.forename: Ling
authors.initials: L
authors.lastname: Lin
authors.affiliation: Howard Hughes Medical Institute and Programs in Gene Function and Expression, Molecular Medicine, and.
authors.forename: Lynn
authors.initials: L
authors.lastname: Chamberlain
authors.affiliation: Gene Function and Expression, Molecular Medicine, and Bioinformatics and Integrative Biology, University of Massachusetts Medical School, Worcester, MA 01605; and.
authors.forename: Lihua J
authors.initials: LJ
authors.lastname: Zhu
authors.affiliation: Department of Pathology, Yale University School of Medicine, New Haven, CT 06520.
authors.forename: Narendra
authors.initials: N
authors.lastname: Wajapeyee
authors.affiliation: Howard Hughes Medical Institute and Programs in Gene Function and Expression, Molecular Medicine, and Michael.Green@umassmed.edu.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Green
mesh_terms: D000818:Animals; D002540:Cerebral Cortex / Q000166:cytology; D002867:Chromones / Q000494:pharmacology; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000235:genetics* / Q000378:metabolism; D053595:Embryonic Stem Cells / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D044127:Epigenesis, Genetic / Q000235:genetics; D005260:Female; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology; D015723:Gene Library; D015316:Genetic Therapy / Q000379:methods; D006023:Glycoproteins / Q000235:genetics*; D006801:Humans; D008322:Mammals; D051783:Methyl-CpG-Binding Protein 2 / Q000235:genetics*; D051379:Mice; D018345:Mice, Knockout; D009025:Morpholines / Q000494:pharmacology; D009474:Neurons / Q000166:cytology / Q000502:physiology; D011720:Pyrazoles / Q000494:pharmacology; D062085:RNA, Long Noncoding / Q000235:genetics*; D034741:RNA, Small Interfering / Q000235:genetics; D015518:Rett Syndrome / Q000235:genetics* / Q000628:therapy; D013449:Sulfonamides / Q000494:pharmacology; D059467:Transcriptome; D049951:X Chromosome Inactivation / Q000187:drug effects / Q000235:genetics*
chemical_list: D002867:Chromones; D004791:Enzyme Inhibitors; D006023:Glycoproteins; C497392:MECP2 protein, human; D051783:Methyl-CpG-Binding Protein 2; D009025:Morpholines; C500894:OSU 03012; D011720:Pyrazoles; D062085:RNA, Long Noncoding; D034741:RNA, Small Interfering; D013449:Sulfonamides; C077885:XIST non-coding RNA; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C051795:teleocalcin; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; C000619380:DNMT1 protein, human; C000619381:Dnmt1 protein, mouse
keywords: MECP2; RNA FISH; RNA-seq