Project description:Naïve human embryonic stem cells (hESCs) can be derived from primed hESCs or directly from blastocysts, but their X-chromosome state has remained unresolved. We found that the inactive X-chromosome (Xi) of primed hESCs was reactivated in naïve culture conditions. Similar to cells of the blastocyst, resulting naive cells exhibited two active X-chromosomes with XIST expression and chromosome-wide transcriptional dampening, and initiated XIST-mediated X-inactivation upon differentiation. Both establishment and exit from the naïve state (differentiation) happened via an XIST-negative XaXa intermediate. Together, these findings identify a cell culture system for functionally exploring the two X-chromosome dosage compensation processes in early human development: X-dampening and X-inactivation. Furthermore, the naïve state reset Xi abnormalities of primed hESCs, providing cells better suited for downstream applications. However, naïve hESCs displayed differences to the embryo because XIST expression was predominantly mono-allelic instead of bi-allelic, and X-inactivation was non-random, indicating the need for further culture improvement.
Project description:Naïve human embryonic stem cells (hESCs) can be derived from primed hESCs or directly from blastocysts, but their X-chromosome state has remained unresolved. We found that the inactive X-chromosome (Xi) of primed hESCs was reactivated in naïve culture conditions. Similar to cells of the blastocyst, resulting naive cells exhibited two active X-chromosomes with XIST expression and chromosome-wide transcriptional dampening, and initiated XIST-mediated X-inactivation upon differentiation. Both establishment and exit from the naïve state (differentiation) happened via an XIST-negative XaXa intermediate. Together, these findings identify a cell culture system for functionally exploring the two X-chromosome dosage compensation processes in early human development: X-dampening and X-inactivation. Furthermore, the naïve state reset Xi abnormalities of primed hESCs, providing cells better suited for downstream applications. However, naïve hESCs displayed differences to the embryo because XIST expression was predominantly mono-allelic instead of bi-allelic, and X-inactivation was non-random, indicating the need for further culture improvement.
Project description:Naïve human embryonic stem cells (hESCs) can be derived from primed hESCs or directly from blastocysts, but their X-chromosome state has remained unresolved. We found that the inactive X-chromosome (Xi) of primed hESCs was reactivated in naïve culture conditions. Similar to cells of the blastocyst, resulting naive cells exhibited two active X-chromosomes with XIST expression and chromosome-wide transcriptional dampening, and initiated XIST-mediated X-inactivation upon differentiation. Both establishment and exit from the naïve state (differentiation) happened via an XIST-negative XaXa intermediate. Together, these findings identify a cell culture system for functionally exploring the two X-chromosome dosage compensation processes in early human development: X-dampening and X-inactivation. Furthermore, the naïve state reset Xi abnormalities of primed hESCs, providing cells better suited for downstream applications. However, naïve hESCs displayed differences to the embryo because XIST expression was predominantly mono-allelic instead of bi-allelic, and X-inactivation was non-random, indicating the need for further culture improvement.
Project description:X-chromosome inactivation (XCI) serves as a paradigm for RNA-mediated regulation of gene expression, wherein the long non-coding RNA XIST spreads across the X-chromosome in cis to mediate chromosome-wide gene silencing. In female naïve human pluripotent stem cells (hPSCs), XIST is in a dispersed configuration and XCI does not occur, raising questions about XIST’s function. We found that XIST spreads across the X-chromosome and induces dampening of X-linked gene expression in naïve hPSCs. Surprisingly, XIST also targets specific autosomal regions, where it induces repressive chromatin changes and gene expression dampening. Thereby, XIST equalizes X-linked gene dosage between male and female cells while inducing differences on autosomes. The dispersed Xist configuration and autosomal localization also occur transiently during XCI initiation in mouse PSCs. Together, our study identifies XIST as the regulator of X-chromosome dampening, uncovers an evolutionarily conserved trans-acting role of XIST/Xist, and reveals a correlation between XIST/Xist dispersal and autosomal targeting.
Project description:X-chromosome inactivation (XCI) serves as a paradigm for RNA-mediated regulation of gene expression, wherein the long non-coding RNA XIST spreads across the X-chromosome in cis to mediate chromosome-wide gene silencing. In female naïve human pluripotent stem cells (hPSCs), XIST is in a dispersed configuration and XCI does not occur, raising questions about XIST’s function. We found that XIST spreads across the X-chromosome and induces dampening of X-linked gene expression in naïve hPSCs. Surprisingly, XIST also targets specific autosomal regions, where it induces repressive chromatin changes and gene expression dampening. Thereby, XIST equalizes X-linked gene dosage between male and female cells while inducing differences on autosomes. The dispersed Xist configuration and autosomal localization also occur transiently during XCI initiation in mouse PSCs. Together, our study identifies XIST as the regulator of X-chromosome dampening, uncovers an evolutionarily conserved trans-acting role of XIST/Xist, and reveals a correlation between XIST/Xist dispersal and autosomal targeting.
Project description:X-chromosome inactivation (XCI) serves as a paradigm for RNA-mediated regulation of gene expression, wherein the long non-coding RNA XIST spreads across the X-chromosome in cis to mediate chromosome-wide gene silencing. In female naïve human pluripotent stem cells (hPSCs), XIST is in a dispersed configuration and XCI does not occur, raising questions about XIST’s function. We found that XIST spreads across the X-chromosome and induces dampening of X-linked gene expression in naïve hPSCs. Surprisingly, XIST also targets specific autosomal regions, where it induces repressive chromatin changes and gene expression dampening. Thereby, XIST equalizes X-linked gene dosage between male and female cells while inducing differences on autosomes. The dispersed Xist configuration and autosomal localization also occur transiently during XCI initiation in mouse PSCs. Together, our study identifies XIST as the regulator of X-chromosome dampening, uncovers an evolutionarily conserved trans-acting role of XIST/Xist, and reveals a correlation between XIST/Xist dispersal and autosomal targeting.