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Transcriptomic analysis of XIST+ and XIST- hES cells

ABSTRACT: Purpose: Compare the transcriptome of homogeneous XIST+ and XIST- hES cell populations. Methods: We isolated homogeneous XIST+ and XIST- cell populations. The XIST+ cells correspond to cells with a XIST cloud and one ATRX pinpoint. The XIST- cells correspond to cells with no XIST cloud and one ATRX pinpoint. Results: We took advantage of the clonal pattern of X-chromosome inactivation in H9 cells and analyzed the data in an allelic manner. By comparing the RNA-Seq data with known H9 SNPs, we identified genomic positions which were relaxed from XCI in XIST- cells compared to XIST+ cells. Conclusions: Genic as well as unannotated transcripts are massively relaxed from XCI in H9 cells when XIST expression is lost, however, this reactivation is only partial and a large region around the centromere is protected from relaxation of silencing. Total RNA (rRNA depleted) profiles of XIST+ and XIST- human embryonic stem cells

ORGANISM(S): Homo sapiens

SUBMITTER: CÃ©line Vallot

PROVIDER: E-GEOD-39757 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Transcriptomic analysis of XIST+ and XIST- hES cells

Project description:Purpose: Compare the transcriptome of homogeneous XIST+ and XIST- hES cell populations. Methods: We isolated homogeneous XIST+ and XIST- cell populations. The XIST+ cells correspond to cells with a XIST cloud and one ATRX pinpoint. The XIST- cells correspond to cells with no XIST cloud and one ATRX pinpoint. Results: We took advantage of the clonal pattern of X-chromosome inactivation in H9 cells and analyzed the data in an allelic manner. By comparing the RNA-Seq data with known H9 SNPs, we identified genomic positions which were relaxed from XCI in XIST- cells compared to XIST+ cells. Conclusions: Genic as well as unannotated transcripts are massively relaxed from XCI in H9 cells when XIST expression is lost, however, this reactivation is only partial and a large region around the centromere is protected from relaxation of silencing.

2012-12-21 | GSE39757 | GEO

ATRX regulates binding of Polycomb repressive complex 2 to Xist RNA and Polycomb targets

Project description:In mammals, dosage compensation entails inactivation of an entire X chromosome in female cells. X-chromosome inactivation (XCI) depends on the long noncoding RNA Xist and its recruitment of Polycomb Repressive Complex 2 (PRC2). How PRC2 specifically interacts with Xist and other Polycomb targets remains unclear. Using XCI as a model, we take an unbiased proteomics approach to search for new Xist and PRC2 regulators. We identify ATRX, a chromatin remodeler associated with mental retardation, alpha thalassemia, and cancer in humans. We show that ATRX is a high-affinity RNA-binding protein. ATRX directly interacts with RepA/Xist RNA and is required for loading of PRC2 onto the RNA in vivo. The Xist gene is a hotspot of ATRX occupancy. Without ATRX, PRC2 cannot load onto Xist RNA nor spread in cis along the X-chromosome. Epigenomic profiling reveals a dependency of PRC2 on ATRX that extends beyond XCI. Depleting ATRX results in genome-wide disruptions to PRC2 localization and trimethylation of histone H3-lysine 27 (H3K27me3). PRC2 is displaced from genes and relocalized to intergenic space, causing reduced H3K27me3 and concomitant changes in expression of Polycomb targets. We conclude that ATRX is a required specificity determinant for PRC2 targeting and function.

2014-11-07 | GSE56981 | GEO

SPEN is a molecular integrator that bridges Xist with transcriptional and epigenetic control of X-chromosome inactivation

Project description:Xist represents a paradigm for long non-coding RNA function in epigenetic regulation, although how it mediates X-chromosome inactivation (XCI) remains largely unexplained. Multiple Xist-RNA binding proteins have recently been identified, including SPEN/SHARP, whose knockdown has been associated with deficient XCI at multiple loci. Here we demonstrate that SPEN is a key orchestrator of XCI in vivo and unravel its mechanism of action. We show that SPEN is essential for initiating gene silencing on the X chromosome in preimplantation mouse embryos and embryonic stem cells. On the other hand, SPEN is dispensable for maintenance of XCI in neural progenitor cells, although it significantly dampens expression of genes that escape from XCI. During initiation of XCI, we show by live-cell imaging and CUT&RUN approaches that SPEN is immediately recruited to the X chromosome upon Xist up-regulation, where it is targeted to enhancers and promoters of actively transcribed genes. SPEN rapidly disengages from chromatin once silencing is accomplished, implying a need for active transcription to tether it to chromatin. We define SPEN’s SPOC (SPEN paralog and ortholog C-terminal) domain as a major effector of SPEN’s gene silencing function, and show that artificial tethering of SPOC to Xist RNA is sufficient to mediate X-linked gene silencing. We identify SPOC’s protein partners which include NCOR/SMRT, the m6A RNA methylation machinery, the NuRD complex, RNA polymerase II and factors involved in regulation of transcription initiation and elongation. We propose that SPEN acts as a molecular integrator for initiation of XCI, bridging Xist RNA with the transcription machinery as well as nucleosome remodelers and histone deacetylases, at active enhancers and promoters.

2021-04-19 | PXD015699 | Pride

Role of Chd8 in Xist regulation

Project description:In this project, we have studied the role of Chd8 in Xist regulation and XCI initiation by means of Chd8 Knock-Downs (KD) and Knock-Out (KO).

2021-09-10 | PXD024155 | Pride

Xist exploits three-dimensional chromosome architecture to spread across the X-chromosome

Project description:Many large noncoding RNAs (lncRNAs) regulate chromatin, but the mechanisms by which they localize to genomic targets remain unexplored. Here we investigate the localization mechanisms of Xist during X-chromosome inactivation (XCI), a paradigm of lncRNA-mediated chromatin regulation. During the maintenance of XCI, Xist binds broadly across the X-chromosome. During initiation of XCI, Xist initially transfers to distal regions across the X-chromosome that are not defined by specific sequences. Instead, Xist identifies these regions by exploiting the three-dimensional conformation of the X-chromosome. Xist initially accumulates on the periphery of actively transcribed regions and requires its silencing domain to spread across active regions. This suggests a model where Xist coats the entire X-chromosome by searching in three dimensions, modifying chromosome structure, and spreading to newly accessible locations. We examined the genomic localization of the Xist lncRNA using RNA Antisense Purification (RAP) in multiple cell contexts: 1) differentiated female cells (MLFs); 2) a time-course of Xist localization in male embryonic stem (ES) cells where the endogenous Xist promoter is replaced by a tet-inducible one (pSM33); 3) a time-course of Xist localization in differentiating female ES cells (F1 2-1); and 4) wild-type (delXF6) and A-repeat deletion (delSXC9) Xist transgenes incorporated into the Hprt locus under the control of a tet-inducible promoter.

2013-05-30 | E-GEOD-46918 | biostudies-arrayexpress

High-resolution chromosomal maps of Xist RNA reveal a two-step spreading mechanism during X-inactivation

Project description:The Xist long noncoding RNA (lncRNA) is essential for X-chromosome inactivation (XCI), the process by which mammals compensate for unequal numbers of sex chromosomes. During XCI, Xist coats the future inactive X (Xi) and recruits Polycomb Repressive Complex 2 (PRC2) to the X-inactivation center (Xic). Currently unclear is how Xist spreads silencing on a 150 Mb scale. Here we generate high-resolution maps of Xist binding across a developmental time course using CHART-seq. In female cells undergoing XCI de novo, Xist follows a two-step mechanism in which it initially targets gene-rich islands before spreading to intervening gene-poor domains. Xist is depleted from genes that escape XCI but frequently concentrates near escapee boundaries. Xist binding was linearly proportional to PRC2 density and H3 lysine 27 trimethylation (H3K27me3), suggesting co-migration of Xist and PRC2. Interestingly, when the Xi is acutely stripped of Xist in post-XCI cells, Xist recovers quickly within both gene-rich and -poor domains on a time scale of hours instead of days, suggesting a previously primed Xi chromatin state. We conclude that Xist spreading takes on distinct stage-specific forms: During initial establishment, Xist follows a two-step mechanism, but during maintenance, Xist spreads rapidly to both gene-rich and -poor regions. Capture hybridization analysis of RNA targets (CHART) and input samples of (differentiating) mouse embryonic stem (ES) cells and immortalized mouse embryonic fibroblasts (MEF) using paired-end 75 nt reads on Illumina HiSeq2500, with 2 replicates per sample (# of samples). RNA-seq of the same cell lines with 50 nt reads on Illumina HiSeq2000, with 2 replicates per sample (2 samples, 4 datasets total). CHIP-seq: Data from GSE36905 was aligned and processed as CHART-seq samples. Resulting coverage tracks (EZH2/K27me3) are linked directly to GSE48649 (bedGraphs linked below).

2013-11-04 | E-GEOD-48649 | biostudies-arrayexpress

En bloc and segmental deletions of human XIST reveal X chromosome inactivation-involving RNA elements

Project description:RNA-seqs followed by whole and segmental deletions of XIST genes in human K562 cells. The XIST RNA is a non-coding RNA that induces X chromosome inactivation (XCI). Unlike the mouse Xist RNA, how the human XIST RNA controls XCI in female cells is less well characterized, and the XCI-involving RNA elements remain unclear. To systematically decipher the XCI-involving elements of XIST RNA, ten smaller XIST segments, including repeats A, D, and E; human-specific repeat elements; the promoter; and non-repetitive exons, as well as the entire XIST gene, were homozygously deleted using the Cas9 nuclease and paired guide RNAs at high efficiencies, followed by high-throughput RNA sequencing and fluorescence in-situ hybridization experiments on XIST RNA.

2019-01-25 | GSE65830 | GEO

The efficiency of Xist-mediated silencing of X-linked and autosomal genes is determined by the genomic environment

Project description:Xist is indispensable for X chromosome inactivation (XCI) in female mammalian cells. However, how Xist RNA directs chromosome-wide transcriptional inactivation of the X chromosome is largely unknown. Here, to study chromosome inactivation by Xist, we generated a system where ectopic Xist expression can be induced from several genomic contexts in aneuploid mouse ES cells. We found that ectopic Xist expression from any location on the X chromosome faithfully recapitulated endogenous XCI, showing the potency of Xist to initiate XCI. Genes that escape XCI remain consistently transcriptionally active upon ectopic XCI, regardless of their position relative to Xist transgenes, and the enrichment of CTCF at their promoters is implicated in directing XCI escape. Xist expression from autosomes facilitates their transcriptional silencing to different degrees, and gene density in proximity of the Xist transcription locus plays a central role in determining the efficiency of gene inactivation. We also show that the enrichment of LINE elements together with a specific chromatin environment facilitates Xist-mediated silencing of both X-linked and autosomal genes. These findings provide new insights into the epigenetic mechanisms that mediate XCI and identify genomic features that promote Xist-mediated chromosome-wide gene inactivation

2017-07-04 | GSE92894 | GEO

Genomic imprinting of Xist by maternal H3K27me3

Project description:Maternal imprinting at the Xist gene is essential to achieve paternal allele-specific imprinted X chromosome inactivation (XCI) in female mammals. However, the mechanism underlying the Xist imprinting is unclear. Here we show that the Xist gene is coated with H3K27me3 in mouse oocytes, which persists through preimplantation development. Ectopic removal of H3K27me3 induces maternal Xist expression and maternal XCI, indicating that maternal H3K27me3 is the imprinting mark of Xist.

2017-11-09 | GSE103714 | GEO