Pseudoautosomal region 1 overdosage affects the global transcriptome in iPSCs from patients with Klinefelter syndrome and high-grade X chromosome aneuploidies
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ABSTRACT: Klinefelter syndrome (KS) is the most prevalent aneuploidy in males and is characterized by one or more supernumerary X chromosomes. Here, using a paradigmatic cohort of KS-inducible pluripotent stem cells (iPSCs) carrying 49-XXXXY, 48-XXXY, and 47-XXY karyotypes, we identified genes within the pseudoautosomal region 1 (PAR1) region as the most susceptible to dosage-dependent transcriptional dysregulation and therefore potentially responsible for the progressively worsening phenotype in higher grade X aneuploidies. By contrast, biallelically expressed non-PAR escape genes displayed high interclonal and interpatient variability in iPSCs and differentiated derivatives, suggesting that these genes could be associated with variable KS traits. By interrogating KS-iPSCs at single-cell resolution, we showed that PAR1 and non-PAR escape genes were not only resilient to X-inactive specific transcript (XIST)-mediated inactivation but also that their transcriptional regulation was disjointed from the absolute XIST expression level. Finally, we explored the transcriptional effects of X chromosome overdosage on autosomes and identified the transcription factor nuclear respiratory factor 1 as the master regulator of zinc finger protein X-linked. Our findings provided the first evidence of an X-dosage-sensitive autosomal transcription factor regulating an X-linked gene in low- and high-grade X aneuploidies.
Project description:Klinefelter syndrome (KS) is the most prevalent aneuploidy in males and is characterized by an extra copy of the X chromosome,while the non-mosaic form of KS with 47,XXY karyotype is the most frequent (80-90%), less common non-disjunction events during the early mitotic division of the zygote result in mosaic forms of KS (47,XXY/46,XY). Here, using a paradigmatic cohort of KS-inducible pluripotent stem cells (iPSCs) carrying 47,XXY karyotypes we present the first iPSC-based disease-modeling study performed on KS patients from Saudi Arabia. We profiled the transcriptome of these Saudi KS-iPSCs, virtually characterized by subduedcgenetic backgrounds. Moreover, we performed a comparative transcriptomic analysis to assess the aberrant gene expression profile due to X dosage imbalance in four Saudi and five European and North American 47,XXY patients-derived iPSCs from our previously published study on KS and high-grade sex chromosome aneuploidies (SCAs). We identified a transcriptomic signature including ten PAR1 genes and thirteen non-PAR escape genes consistently upregulated in KS compared to 46,XY controls in both groups, as well as 193 consistenty disregulated autosomal genes. Our results indicate that the global transcriptional impact of X chromosome overdosage in KS is largely attributable to X-linked genes escaping X inactivation, regardless of the geographical area of origin, ethnicity, and genetic background.
Project description:Background: In both Turner syndrome (TS) and Klinefelter syndrome (KS) copy number aberrations of the X chromosome lead to various developmental symptoms. To date there has not been a comprehensive and directly comparative analysis of TS vs. KS regarding the changes on the molecular level Methods: We analyzed gene expression patterns with RNA-Seq and DNA methylation patterns with the CpGiant assay in lymphocytes, and chromatin conformation with in situ Hi-C in lymphoblastoid cell lines, from TS and KS patients together with their same gender controls. Results: In TS, differentially expressed escape genes were downregulated but differentially expressed inactive genes were upregulated. In KS, differentially expressed escape genes were upregulated while inactive genes appeared unchanged. Interestingly, 81 differentially expressed genes (DEGs) were associated with both TS and KS, and uniformly displayed expression changes into opposite directions. DEGs on the X chromosome and the autosomes were coexpressed in both TS and KS, indicating that there are molecular ripple effects of the changes in X chromosome dosage that extend to autosomes. Four potentially candidate genes (RPS4X, SEPT6, NKRF and CX0rf57) for KS were identified on Xq. Broad hypomethylation of the X chromosome is observed in TS whereas hypermethylation of chromosome X is present in KS. Only promoters of inactive genes were differentially methylated in both TS and KS while escape genes remained unchanged. The intrachromosomal contact map of the X chromosome in TS was partitioned into two superdomains and exhibited the structure of an active X chromosome. Conclusions: Components of the molecular basis of TS and KS were identified on the levels of the transcriptome and the epigenome, with candidate central genes on Xp for TS and on Xq for KS. The discovery of shared DEGs indicates the existence of common molecular mechanisms for gene regulation in TS and KS that are transmitting the gene dosage changes to the transcriptome.
Project description:Pseudoautosomal region 1 overdosage affects the global transcriptome in iPSCs from patients with Klinefelter syndrome and high-grade X chromosome aneuploidies
Project description:During X-inactivation (XCI), Xist RNA establishes silencing by coating the chromosome in cis and binding diverse proteins to promote formation of a heterochromatic domain. However, Xist repeat B role beyond initiation of XCI remains unclear. Here, we find that loss of Xist repeat B in female mice allows survival and leads to a small body size persisting throughout life. Epigenetic and transcriptomic analyses reveal low levels of H3K27me3 and H2AK119ub occupancy on the X chromosome, except in certain CpG island regions, and partial reactivation of X-linked genes on the inactive X across multiple tissues. Notably, overdosage of Usp9x promotes centrosome amplification and chromosome instability, increasing the propensity of tumorigenesis. We further demonstrate that Usp9x overdosage leads to abnormalities in asymmetric cell division, thereby affecting the process of cell differentiation. Thus, Xist repeat B is necessary for gene-specific silencing during XCI maintenance and impacts cell proliferation and differentiation during development. This provides insights into repeat B importance in maintaining XCI.
Project description:During X-inactivation (XCI), Xist RNA establishes silencing by coating the chromosome in cis and binding diverse proteins to promote formation of a heterochromatic domain. However, Xist repeat B role beyond initiation of XCI remains unclear. Here, we find that loss of Xist repeat B in female mice allows survival and leads to a small body size persisting throughout life. Epigenetic and transcriptomic analyses reveal low levels of H3K27me3 and H2AK119ub occupancy on the X chromosome, except in certain CpG island regions, and partial reactivation of X-linked genes on the inactive X across multiple tissues. Notably, overdosage of Usp9x promotes centrosome amplification and chromosome instability, increasing the propensity of tumorigenesis. We further demonstrate that Usp9x overdosage leads to abnormalities in asymmetric cell division, thereby affecting the process of cell differentiation. Thus, Xist repeat B is necessary for gene-specific silencing during XCI maintenance and impacts cell proliferation and differentiation during development. This provides insights into repeat B importance in maintaining XCI.
Project description:The inactive X (Xi) is formed by a process called X-Chromosome Inactivation (XCI), with Xist upregulation, retention of Xist RNA transcripts at the Xi, chromatin re-organization, and transcriptional silencing. Female lymphocytes have ‘dynamic’ XCI maintenance where Xist RNA is transcribed but absent from the Xi in naïve lymphocytes and re-localizes after in-vitro activation. How ‘dynamic’ XCI impacts Xi dosage and nuclear organization, or where Xist RNA interacts with the Xi is unknown. Here we find maintenance of Xi dosage and global structure despite the absence of Xist RNA in naïve B-cells. However, we identified 104 escape genes and observe a gain of de-novo TADs on the Xi. Stimulation-dependent Xi remodeling co-occurs with Xist RNA re-accumulation at the Xi, and loss of Xist increases TAD remodeling and decompacts the Xi in both naïve and stimulated B-cells. Altogether, these results reveal B-cell specific Xi plasticity which could underlie female-specific mechanisms in lymphocytes.
Project description:The inactive X (Xi) is formed by a process called X-Chromosome Inactivation (XCI), with Xist upregulation, retention of Xist RNA transcripts at the Xi, chromatin re-organization, and transcriptional silencing. Female lymphocytes have ‘dynamic’ XCI maintenance where Xist RNA is transcribed but absent from the Xi in naïve lymphocytes and re-localizes after in-vitro activation. How ‘dynamic’ XCI impacts Xi dosage and nuclear organization, or where Xist RNA interacts with the Xi is unknown. Here we find maintenance of Xi dosage and global structure despite the absence of Xist RNA in naïve B-cells. However, we identified 104 escape genes and observe a gain of de-novo TADs on the Xi. Stimulation-dependent Xi remodeling co-occurs with Xist RNA re-accumulation at the Xi, and loss of Xist increases TAD remodeling and decompacts the Xi in both naïve and stimulated B-cells. Altogether, these results reveal B-cell specific Xi plasticity which could underlie female-specific mechanisms in lymphocytes.
Project description:X chromosome inactivation (XCI) is a dosage compensation phenomenon that occurs in females. Initiation of XCI depends on Xist RNA, which triggers silencing of one of the two X chromosomes, except for XCI escape genes that continue to be biallelically expressed. In the soma XCI is stably maintained with continuous Xist expression. How Xist impacts XCI maintenance remains an open question. Here we conditionally deleted Xist in hematopoietic system of mice and report differentiation and cell cycle defects in female hematopoietic stem and progenitor cells (HPSCs). By utilizing female HSPCs and mouse embryonic fibroblasts, we find that X-linked genes show variable tolerance to Xist loss. Specifically, XCI escape genes exhibit preferential transcriptional upregulation, which associates with low H3K27me3 occupancy, and high chromatin accessibility that accommodates preexisting binding of transcription factors such as Yin Yang 1 (YY1) at the basal state. We conclude that Xist is necessary for gene-specific silencing during XCI maintenance and impacts lineage-specific cell differentiation and proliferation during hematopoiesis.
Project description:X chromosome inactivation (XCI) is a dosage compensation phenomenon that occurs in females. Initiation of XCI depends on Xist RNA, which triggers silencing of one of the two X chromosomes, except for XCI escape genes that continue to be biallelically expressed. In the soma XCI is stably maintained with continuous Xist expression. How Xist impacts XCI maintenance remains an open question. Here we conditionally deleted Xist in hematopoietic system of mice and report differentiation and cell cycle defects in female hematopoietic stem and progenitor cells (HPSCs). By utilizing female HSPCs and mouse embryonic fibroblasts, we find that X-linked genes show variable tolerance to Xist loss. Specifically, XCI escape genes exhibit preferential transcriptional upregulation, which associates with low H3K27me3 occupancy, and high chromatin accessibility that accommodates preexisting binding of transcription factors such as Yin Yang 1 (YY1) at the basal state. We conclude that Xist is necessary for gene-specific silencing during XCI maintenance and impacts lineage-specific cell differentiation and proliferation during hematopoiesis.
Project description:X chromosome inactivation (XCI) is a dosage compensation phenomenon that occurs in females. Initiation of XCI depends on Xist RNA, which triggers silencing of one of the two X chromosomes, except for XCI escape genes that continue to be biallelically expressed. In the soma XCI is stably maintained with continuous Xist expression. How Xist impacts XCI maintenance remains an open question. Here we conditionally deleted Xist in hematopoietic system of mice and report differentiation and cell cycle defects in female hematopoietic stem and progenitor cells (HPSCs). By utilizing female HSPCs and mouse embryonic fibroblasts, we find that X-linked genes show variable tolerance to Xist loss. Specifically, XCI escape genes exhibit preferential transcriptional upregulation, which associates with low H3K27me3 occupancy, and high chromatin accessibility that accommodates preexisting binding of transcription factors such as Yin Yang 1 (YY1) at the basal state. We conclude that Xist is necessary for gene-specific silencing during XCI maintenance and impacts lineage-specific cell differentiation and proliferation during hematopoiesis.