Project description:Here, we show that the Kdm5c/Smcx member of the Jarid1 family of H3K4 demethylases is recruited to both enhancer and core promoter elements in ES and neuronal progenitor cells (NPC). Knockdown of Kdm5c deregulates transcription via a local increase in H3K4me3. While at core promoters the function of Kdm5c is to restrict transcription, loss of Kdm5c impairs enhancer function. Remarkably, an impaired enhancer function activates promoter activity from Kdm5c-bound intergenic regions. Our results demonstrate that the Kdm5c demethylase plays a crucial role in the functional identity and discrimination of enhancers and core promoters. We speculate that this is related to recruitment of H3K4me3 binders like the TFIID and NURF complexes6-8. Providing functional identity to genomic regions through balancing enzymes that deposit and remove histone modifications may prove to be a general epigenetic mechanism for the functional indexing of eukaryotic genomes. Examination of the KDM5C binding sites in mouse embryonic stem cells and in neuronal progenitor cells. Effect of KDM5C knock down on H3K4me3 and H3K4me1 levels and gene expression.
Project description:Introgressed variants from other species can be an important source of genetic variation because they may arise rapidly, can include multiple mutations on a single haplotype, and have often been pretested by selection in the species of origin. Although introgressed alleles are generally deleterious, several studies have reported introgression as the source of adaptive alleles-including the rodenticide-resistant variant of Vkorc1 that introgressed from Mus spretus into European populations of Mus musculus domesticus. Here, we conducted bidirectional genome scans to characterize introgressed regions into one wild population of M. spretus from Spain and three wild populations of M. m. domesticus from France, Germany, and Iran. Despite the fact that these species show considerable intrinsic postzygotic reproductive isolation, introgression was observed in all individuals, including in the M. musculus reference genome (GRCm38). Mus spretus individuals had a greater proportion of introgression compared with M. m. domesticus, and within M. m. domesticus, the proportion of introgression decreased with geographic distance from the area of sympatry. Introgression was observed on all autosomes for both species, but not on the X-chromosome in M. m. domesticus, consistent with known X-linked hybrid sterility and inviability genes that have been mapped to the M. spretus X-chromosome. Tract lengths were generally short with a few outliers of up to 2.7 Mb. Interestingly, the longest introgressed tracts were in olfactory receptor regions, and introgressed tracts were significantly enriched for olfactory receptor genes in both species, suggesting that introgression may be a source of functional novelty even between species with high barriers to gene flow.
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. 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. Dispersed Xist configuration and autosomal localization also occur transiently during XCI initiation in mouse PSCs. Together, our results identify XIST as the regulator of X-chromosome dampening, uncover an evolutionarily conserved trans-acting role of XIST/Xist, and reveal 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. 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. Dispersed Xist configuration and autosomal localization also occur transiently during XCI initiation in mouse PSCs. Together, our results identify XIST as the regulator of X-chromosome dampening, uncover an evolutionarily conserved trans-acting role of XIST/Xist, and reveal a correlation between XIST/Xist dispersal and autosomal targeting.
Project description:To uncover novel epigenetic regulators in AML, we performed an in vivo short hairpin RNA (shRNA) screen in the context of Cebpa mutant AML. This led to the identification of the Histone 3 Lysine 4 (H3K4) demethylase, KDM5C, as a novel tumor suppressor in AML. KDM5C potentially functions as a transcriptional repressor via its demethylase activity at promoters, and dysregulation could therefore have widespread consequences. Here, we found that reduced Kdm5c/KDM5C expression is associated with accelerated growth in both human and murine AML cell lines. In vivo, Kdm5c knockdown in a Cebpa mutant AML mouse model resulted in a more aggressive, immature and short-latency phenotype. Mechanistically, we show that knockdown of Kdm5c increased H3K4me3 globally. This translated into the up-regulation of a group of bivalently marked immature genes, resulting in a de-differentiation phenotype which could be reversed by modulating levels of pro-differentiation factors. Finally, we demonstrated that low levels of KDM5C were associated with a decrease in long-term disease-free survival, specifically in female patients. This emphasizes the clinical relevance of our findings and identifies KDM5C as a novel female-biased tumor suppressor in AML.
Project description:The long non-coding RNA (lncRNA) Xist is a master regulator of X-chromosome inactivation in mammalian cells. Models for how Xist and other lncRNAs function depend on thermodynamically stable secondary and higher-order structures that RNAs can form in the context of a cell. Probing accessible RNA bases can provide data to build models of RNA conformation that provide insight into RNA function, molecular evolution, and modularity. To study the structure of Xist in cells, we built upon recent advances in RNA secondary structure mapping and modeling to develop Targeted Structure-Seq, which combines chemical probing of RNA structure in cells with target-specific massively parallel sequencing. By enriching for signals from the RNA of interest, Targeted Structure-Seq achieves high coverage of the target RNA with relatively few sequencing reads, thus providing a targeted and scalable approach to analyze RNA conformation in cells. We use this approach to probe the full-length Xist lncRNA to develop new models for functional elements within Xist, including the repeat A element in the 5'-end of Xist. This analysis also identified new structural elements in Xist that are evolutionarily conserved, including a new element proximal to the C repeats that is important for Xist function. Examination of dimethylsufate reactivity of Xist lncRNA and 18S rRNA in cells using targeted reverse transcription to determine reactivity, and comparisons with untreated control samples.
Project description:Translational research is commonly performed in the C57B6/J mouse strain, chosen for its genetic homogeneity and phenotypic uniformity. Here, we evaluate the suitability of the white-footed deer mouse (Peromyscus leucopus) as a model organism for aging research, offering a comparative analysis against C57B6/J and diversity outbred (DO) Mus musculus strains. Our study includes comparisons of body composition, skeletal muscle function, and cardiovascular parameters, shedding light on potential applications and limitations of P. leucopus in aging studies. Notably, P. leucopus exhibits distinct body composition characteristics, emphasizing reduced muscle force exertion and a unique metabolism, particularly in fat mass. Cardiovascular assessments showed changes in arterial stiffness, challenging conventional assumptions and highlighting the need for a nuanced interpretation of aging-related phenotypes. Our study also highlights inherent challenges associated with maintaining and phenotyping P. leucopus cohorts. Behavioral considerations, including anxiety-induced responses during handling and phenotyping assessment, pose obstacles in acquiring meaningful data. Moreover, the unique anatomy of P. leucopus necessitates careful adaptation of protocols designed for Mus musculus. While showcasing potential benefits, further extensive analyses across broader age ranges and larger cohorts are necessary to establish the reliability of P. leucopus as a robust and translatable model for aging studies.