Unknown,Transcriptomics,Genomics,Proteomics

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Female-specific CTCF binding on the inactive X chromosome in mouse

ABSTRACT: In mammals, genes located on the X chromosome are present in one copy in XY males and two in XX females. To balance the dosage of X-linked gene expression between the sexes one of the two X chromosomes in females is silenced by X inactivation initiated by up-regulation of the lncRNA (long non-coding RNA) Xist and recruitment of specific chromatin modifiers for silencing. The inactivated X chromosome becomes heterochromatic and visits a specific nuclear compartment adjacent to the nucleolus. We report a novel role for the X-linked lncRNA Firre in anchoring the inactive mouse X chromosome and preserving one of its main epigenetic features, trimethylation of histone H3 at lysine 27 (H3K27me3). Similar to Dxz4, Firre is expressed from a macrosatellite repeat locus associated with a cluster of CTCF and cohesin binding specifically on the inactive X. CTCF binding initially present in both male and female mouse embryonic stem cells was found to be lost from the active X during development. The Firre and Dxz4 loci on the inactive X were preferentially located adjacent to the nucleolus. Knockdown of Firre RNA disrupted perinucleolar targeting and H3K27me3 levels in mouse fibroblasts, demonstrating an important role for this lncRNA in maintenance of one of the main epigenetic features of the X chromosome. There was no X-linked gene reactivation after Firre knockdown; however, a compensatory increase in the expression of chromatin modifier genes implicated in X silencing was observed. In female ES cells Firre RNA knockdown did not disrupt Xist expression/coating nor silencing of G6pdx during differentiation, suggesting that Firre does not play a role in the onset of X inactivation. We conclude that the X-linked lncRNA Firre helps position the inactive X chromosome near the nucleolus and preserve one of its main epigenetic features. Examination of allelic protein-binding or histone modification profiles in Patski cells.

ORGANISM(S): Mus musculus

SUBMITTER: Xinxian Deng

PROVIDER: E-GEOD-66262 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:JARID2 ChIP-seq profile mediated by Xist was investigated using two separate approaches: In the first approach, we use the TX1072 female embryonic stem cell (ESC) line; this is a genetically polymorphic ESC line derived from a mouse with one X-chromosome (X-chr) from the Mus musculus castaneus (Cast) origin and the other of Mus musculus domesticus, C57BL/6 (BL6) strain origin, containing an inducible promoter on the BL6 Xist allele; differentiation and simultaneous induction of Xist for 4 days results in the inactivation of ONLY the BL6-derived X-chr and coating by JARID2 protein. We analysed this ESC line in the undifferentiated state, in which both X-chrs are active (and not coated by JARID2), and also after 4 days of differentiation under Xist inducible conditions, in which cells display one inactive X-chr from BL6 origin and one Xa of the Cast origin; the presence of SNPs allows for the comparison of the degree and localisation of JARID2 enrichment on the inactive X-chr versus the active X-chr; our results suggests that JARID2 is enriched on the inactive X-chr chromosome-wide and not in confined peaks as elsewhere in the genome; This pattern resembles patterns of Xist enrichment published before (Engreitz et al., 2013). In the second approach, we use a male ESC line that carries an inducible Xist transgene (TG) on chromosome 11 (chr11) (Wutz et al., 2000) in the presence (36:11 WT) or the absence of Eed (36:11 Eed-/-) Induction of Xist TG results in Xist coating and enrichment of JARID2 across the chr11, regardless of the presence of Eed when assess by IF/Xist RNA FISH experiments. We compare inducible and uninducible condition in both the 36:11 WT and Eed-/- ESCs; this way, we could assess the Xist-mediated JARID2 recruitment and the effect of the absence of Eed-/-; Our results shows that Xist induction result in a chromosome-wide enrichment of JARID2 on chr11, in a manner that resembles enrichment on the inactive X-chr; this pattern seem to be independent of EED, showing that in contrast to other regions in the genome where JARID2 occupancy is abrogated in the absence of EED, Xist-mediated JARID2 recruitment is not affected. JARID2 ChIP-seq analysis in differentiating female ESCs (TX1072) and in a male ESC harbouring a Xist transgene on chromosome 11 in WT and Eed-/- genetics settings

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Female-specific CTCF binding on the inactive X chromosome in mouse

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