Project description:In mammals, X-chromosomal genes are expressed from a single copy since males (XY) possess a single X chromosome, while females (XX) undergo X inactivation. To compensate for this reduction in dosage compared to two active copies of autosomes, it has been proposed that genes from the active X chromosome exhibit dosage compensation. However, the existence and mechanism of X-to-autosome dosage compensation are still under debate. Here, we show that X-chromosomal transcripts are reduced in m6A modifications and more stable compared to their autosomal counterparts. Acute depletion of m6A selectively stabilises autosomal transcripts, resulting in perturbed dosage compensation in mouse embryonic stem cells. We propose that higher stability of X-chromosomal transcripts is directed by lower levels of m6A, indicating that mammalian dosage compensation is partly regulated by epitranscriptomic RNA modifications.
Project description:In mammals, X-chromosomal genes are expressed from a single copy since males (XY) possess a single X chromosome, while females (XX) undergo X inactivation. To compensate for this reduction in dosage compared to two active copies of autosomes, it has been proposed that genes from the active X chromosome exhibit dosage compensation. However, the existence and mechanism of X-to-autosome dosage compensation are still under debate. Here, we show that X-chromosomal transcripts are reduced in m6A modifications and more stable compared to their autosomal counterparts. Acute depletion of m6A selectively stabilises autosomal transcripts, resulting in perturbed dosage compensation in mouse embryonic stem cells. We propose that higher stability of X-chromosomal transcripts is directed by lower levels of m6A, indicating that mammalian dosage compensation is partly regulated by epitranscriptomic RNA modifications.
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.
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.
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.
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.
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).
Project description:Gene dosage imbalance of heteromorphic sex chromosomes (XY or ZW) exists between the sexes, and with the autosomes. Mammalian X chromosome inactivation was long thought to imply a critical need for dosage compensation in vertebrates. However, mRNA abundance measurements that demonstrated sex chromosome transcripts are neither balanced between the sexes or with autosomes in monotreme mammals or birds brought sex chromosome dosage compensation into question. This study examines transcriptomic and proteomic levels of dosage compensation in platypus and chicken compared to mouse, a model eutherian species. We analyzed mRNA and protein levels in heart and liver tissues of chicken, mouse and platypus.
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.