title: Sex-specific silencing of X-linked genes by Xist RNA.
abstract: X-inactive specific transcript (Xist) long noncoding RNA (lncRNA) is thought to catalyze silencing of X-linked genes in cis during X-chromosome inactivation, which equalizes X-linked gene dosage between male and female mammals. To test the impact of Xist RNA on X-linked gene silencing, we ectopically induced endogenous Xist by ablating the antisense repressor Tsix in mice. We find that ectopic Xist RNA induction and subsequent X-linked gene silencing is sex specific in embryos and in differentiating embryonic stem cells (ESCs) and epiblast stem cells (EpiSCs). A higher frequency of X(ΔTsix)Y male cells displayed ectopic Xist RNA coating compared with X(ΔTsix)X female cells. This increase reflected the inability of X(ΔTsix)Y cells to efficiently silence X-linked genes compared with X(ΔTsix)X cells, despite equivalent Xist RNA induction and coating. Silencing of genes on both Xs resulted in significantly reduced proliferation and increased cell death in X(ΔTsix)X female cells relative to X(ΔTsix)Y male cells. Thus, whereas Xist RNA can inactivate the X chromosome in females it may not do so in males. We further found comparable silencing in differentiating X(ΔTsix)Y and 39,X(ΔTsix) (X(ΔTsix)O) ESCs, excluding the Y chromosome and instead implicating the X-chromosome dose as the source of the sex-specific differences. Because X(ΔTsix)X female embryonic epiblast cells and EpiSCs harbor an inactivated X chromosome prior to ectopic inactivation of the active X(ΔTsix) X chromosome, we propose that the increased expression of one or more X-inactivation escapees activates Xist and, separately, helps trigger X-linked gene silencing.
authors.affiliation: Department of Human Genetics, University of Michigan Medical School, Ann Arbor, MI 48109.
authors.forename: Srimonta
authors.initials: S
authors.lastname: Gayen
authors.affiliation: Department of Human Genetics, University of Michigan Medical School, Ann Arbor, MI 48109.
authors.forename: Emily
authors.initials: E
authors.lastname: Maclary
authors.affiliation: Department of Human Genetics, University of Michigan Medical School, Ann Arbor, MI 48109.
authors.forename: Michael
authors.initials: M
authors.lastname: Hinten
authors.affiliation: Department of Human Genetics, University of Michigan Medical School, Ann Arbor, MI 48109 kalantry@umich.edu.
authors.forename: Sundeep
authors.initials: S
authors.lastname: Kalantry
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000235:genetics; D010064:Embryo Implantation; D004622:Embryo, Mammalian / Q000378:metabolism; D005260:Female; D020868:Gene Silencing; D050172:Genes, X-Linked; D005855:Germ Layers / Q000166:cytology; D008297:Male; D051379:Mice; D008954:Models, Biological; D000066450:Mouse Embryonic Stem Cells / Q000378:metabolism; D062085:RNA, Long Noncoding / Q000235:genetics* / Q000378:metabolism; D012727:Sex Characteristics; D049951:X Chromosome Inactivation / Q000235:genetics; D014998:Y Chromosome / Q000235:genetics
chemical_list: D062085:RNA, Long Noncoding; C077885:XIST non-coding RNA
keywords: Tsix; X inactivation; Xist; embryonic stem cells; epiblast stem cells