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X-chromosome hyperactivation in mammals via nonlinear relationships between chromatin states and transcription

ABSTRACT: Dosage compensation in mammals occurs at two levels. In addition to balancing X-chromosome dosage between males and females via X-inactivation, mammals also balance dosage of Xs and autosomes. It has been proposed that X-autosome equalization occurs by upregulation of Xa (active X). To investigate the mechanism, we perform allele-specific ChIP-seq for chromatin epitopes and analyze RNA-seq data (SRA010053). The hypertranscribed Xa demonstrates enrichment of active chromatin marks relative to autosomes. We derive predictive models for relationships among Pol II, active mark densities and gene expression, and we suggest that Xa upregulation involves increased transcription initiation and elongation. Enrichment of active marks on Xa does not scale proportionally with transcription output, a disparity explained by nonlinear quantitative dependencies among active histone marks, Pol II occupancy and transcription. Notably, the trend of nonlinear upregulation also occurs on autosomes. Thus, Xa upregulation involves combined increases of active histone marks and Pol II occupancy, without invoking X-specific dependencies between chromatin states and transcription.

ORGANISM(S): Mus musculus

PROVIDER: GSE33823 | GEO | 2012/01/06

SECONDARY ACCESSION(S): PRJNA148105

REPOSITORIES: GEO

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X-chromosome hyperactivation in mammals via nonlinear relationships between chromatin states and transcription

Project description:Dosage compensation in mammals occurs at two levels. In addition to balancing X-chromosome dosage between males and females via X-inactivation, mammals also balance dosage of Xs and autosomes. It has been proposed that X-autosome equalization occurs by upregulation of Xa (active X). To investigate the mechanism, we perform allele-specific ChIP-seq for chromatin epitopes and analyze RNA-seq data (SRA010053). The hypertranscribed Xa demonstrates enrichment of active chromatin marks relative to autosomes. We derive predictive models for relationships among Pol II, active mark densities and gene expression, and we suggest that Xa upregulation involves increased transcription initiation and elongation. Enrichment of active marks on Xa does not scale proportionally with transcription output, a disparity explained by nonlinear quantitative dependencies among active histone marks, Pol II occupancy and transcription. Notably, the trend of nonlinear upregulation also occurs on autosomes. Thus, Xa upregulation involves combined increases of active histone marks and Pol II occupancy, without invoking X-specific dependencies between chromatin states and transcription. Examination of 4 marks of active transcription (H3K4me3, H3K36me3, POL-II-S2P, POL-II-S5P) in a transformed female mouse embryonic fibroblast cell line (EY.T4).

2012-01-06 | E-GEOD-33823 | biostudies-arrayexpress

Expression data from human triploid and diploid fibroblast cell cultures

Project description:Dosage compensation restores a balanced network of gene expression between autosomes and sex chromosomes in males (XY) and females (XX). In mammals, this is achieved by doubling the expression of X-linked genes in both sexes, together with X inactivation in females. X up-regulation may be controlled by DNA sequence based and/or epigenetic mechanisms that double the X output potentially in response to an autosomal counting factor. Human triploids with either one or two active X chromosomes (Xa) provide a mean to test X chromosome expression in the presence of three sets of autosomes, which will help understand the underlying mechanisms of X up-regulation. We measured whole genome gene expression in human triploid cell cultures with either one or two active X. We found that overall X-linked gene expression is not tripled in the presence of three sets of autosomes. However, in triploid cells with a single active X chromosome, its expression is adjusted upward, presumably by an epigenetic mechanism that senses the active X-autosome ratio.

2009-11-06 | GSE18877 | GEO

Expression data from human triploid and diploid fibroblast cell cultures

2009-11-06 | E-GEOD-18877 | biostudies-arrayexpress

Female human induced pluripotent stem cells (hiPSCs)

Project description:Female human induced pluripotent stem cell (hiPSC) lines exhibit considerable variability in X-inactivation status. Some lines maintain one transcriptionally active X chromosome (Xa) and one inactive X (Xi) from donor cells. However, hiPSC lines that have two Xas are infrequently produced. We show here Xinactivation status in female hiPSC lines depends on derivation conditions. hiPSC lines generated using the Kyoto method, which employs leukemia inhibitory factor (LIF)-expressing SNL feeders, frequently had two Xas. Lines derived on other feeders maintained an Xi. In addition, there appears to be a window in which SNL feeders promote Xi-reactivation. Upon differentiation, Xa/Xa hiPSCs silenced one X. The efficient production of Xa/Xa hiPSC lines provides unprecedented opportunities to understand human X-reactivation and inactivation. Gene expression patterns were compared between several human embryonic stem cell (hESC) and hiPSC lines. Gene expression ratios between genes on X and those on autosomes were calculated from each cell lines.

2012-07-06 | E-GEOD-34527 | biostudies-arrayexpress

Xi-reactivation in female human induced pluripotent stem cells (hiPSCs)

2013-02-06 | E-GEOD-44044 | biostudies-arrayexpress

Upregulation of the mammalian X chromosome is associated with enhanced transcription initiation, MOF-mediated H4K16 acetylation, and longer RNA half-life

Project description:Many animal species employ a chromosome-based mechanism of sex determination, which has led to coordinate evolution of dosage compensation systems. Dosage compensation not only corrects the imbalance in the number of X-chromosomes between the sexes, but is also hypothesized to correct dosage imbalance within cells due to mono-allelic X expression and bi-allelic autosomal expression, by upregulating X-linked genes (termed M-bM-^@M-^XOhnoM-bM-^@M-^Ys hypothesisM-bM-^@M-^Y). To identify molecular mechanisms of X upregulation in mammals we established genome-wide profiles for the initiation and elongation forms of RNA polymerase II (PolII), PolII-S5p (phosphorylated at serine 5) and PolII-S2p (phosphorylated at serine 2), and for histone modifications in mouse cell lines and tissues. We found that in addition to being enriched in PolII-S5p but not in PolII-S2p, X-linked promoters were also enriched in two epigenetic marks, H4K16ac and H2AZ, dependent on expression levels. To address the function of the H4K16 acetyltransferase MOF occupancy profiles were established and knockdowns of MOF and MSL1 were done in mouse ES cells. Our results support a conserved role for the MSL complex to enhance transcription initiation of X-linked genes. Comparison of the profiles of RNA PolII, the H4K16ac acetyltransferase MOF and histone active marks on the X versus autosomes in mouse

2013-03-05 | E-GEOD-44835 | biostudies-arrayexpress

Enrichment profiles of Ser-5 phosphorylated RNA polymerase II (PolII S5p) in mouse female ES cells

Project description:Many animal species employ a chromosome-based mechanism of sex determination, which has led to coordinate evolution of dosage compensation systems. Dosage compensation not only corrects the imbalance in the number of X-chromosomes between the sexes, but is also hypothesized to correct dosage imbalance within cells due to mono-allelic X expression and bi-allelic autosomal expression, by upregulating X-linked genes (termed ‘Ohno’s hypothesis’). It is unknown whether any epigenetic mark or protein is involved in X upregulation in mammals. Ser-5 phosphorylated RNA polymerase II (PolII S5p) is required for transcription initiation. Chromatin immunoprecipitation combined with DNA tiling array analysis (ChIP-chip) of PolII S5p in mouse female ES cells with two active X chromosomes demonstrated a greater enrichment of RNA polymerase II on X-linked genes relative to autosomal genes, suggesting that enhanced transcription initiation may play a role in X upregulation. Comparison of RNA PolII S5p enrichment on the X versus autosomes in mouse

2011-07-18 | E-GEOD-30689 | biostudies-arrayexpress

Allele-specific maps of RNA polymerase II phosphorylated at serine 5 in mouse cultured hybrid cells and mouse hybrid brain

Project description:We report the application of single-molecule-based sequencing technology for high-throughput profiling of RNA polymerase II phosphorylated at serine 5 (PolII-S5p; the transcription initiation form) in female mouse cultured hybrid cells and female hybrid brain derived from mouse systems with skewed X inactivation based on crosses between C57BL/6J (BL6) and M. spretus. In these systems, alleles can be differentiated by frequent SNPs between mouse species, and the active X (Xa) compared to the haploid set of autosomes from the same species. To examine PolII-S5p occupancy in vivo, ChIP-seq was done in brain from an adult female F1 mouse in which the BL6 X is always active and the spretus X inactive. Uniquely mapped reads containing informative SNPs were assigned to each haploid chromosome set (BL6 or spretus) and were counted to establish allele-specific PolII-S5p occupancy profiles. We found that PolII-S5p allele-specific occupancy with or without normalization by input genomic DNA sequencing data showed that expressed genes on the Xa (>1RPKM) had 30% higher PolII-S5p peak levels at their promoters compared to autosomal genes from the same species (BL6). This result was confirmed by performing an independent allele-specific ChIP-seq analysis on fibroblasts derived from embryonic kidney (Patski cell line) that have the opposite X inactivation pattern from the brain sample, i.e. an Xa from M. spretus and an Xi from BL6. These findings suggest that transcription initiation of X-linked genes is enhanced to contribute to X upregulation in cell lines and in vivo. Examination of allele-specific PolII-S5p occupancy in mouse hybrid cells and brain.

2013-02-15 | E-GEOD-44255 | biostudies-arrayexpress

RNA stability controlled by m6A methylation provides X to autosome compensation in mammals [miCLIP2]

Project description:In therian mammals, X-chromosomal genes are expressed only from a single active X chromosome, both in males (XY) as well as females (XX). To compensate for this reduction in dosage compared to the evolutionary ancestral state on two autosomes, it has been proposed that genes from the active X chromosome exhibit dosage compensation (“Ohno’s hypothesis”). However, the existence and mechanism of X-to-autosome dosage compensation are still under debate. Here, we show that dosage compensation is achieved via differential N6-methyladenosine (m6A) RNA modification. X-chromosomal transcripts are reduced in m6A modifications and more stable compared to the autosomal counterparts. Acute depletion of m6A using a small molecule inhibitor differentially affects autosomal and X-chromosomal transcripts across sexes, cell types, tissues and species, resulting in perturbed dosage compensation. We propose that higher stability of X-chromosomal transcripts is directed by lower levels of m6A, indicating that mammalian dosage compensation occurs via epitranscriptomic RNA regulation.

2023-02-14 | GSE203652 | GEO

RNA stability controlled by m6A methylation provides X to autosome compensation in mammals [RNA-seq]

2023-02-14 | GSE203642 | GEO

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