Project description:The epigenetic mechanisms coordinating the maintenance of adult cellular lineages and the inhibition of alternative cell fates are poorly understood. Here we show that targeted ablation of the histone chaperone HIRA in myogenic cells leads to extensive transcriptional modifications consistent with a major role in maintaining skeletal muscle cellular identity. Conditional ablation of HIRA in muscle stem cells of adult mice compromised their capacity to regenerate and self-renew, leading to tissue repair failure. Epigenetic analysis of Hira-deficient cells showed a drastic reduction of histone variant H3.3 deposition and H3K27ac modification at regulatory regions of muscle genes. By contrast, genes from alternative lineages were ectopically expressed in Hira-mutant cells via MLL1/MLL2-mediated increase of H3K4me3 mark at silent promoter regions. Therefore, HIRA sustains the epigenetic landscape governing muscle cell lineage identity via incorporation of H3.3 at muscle gene regulatory regions, while preventing the expression of alternative lineage genes.
Project description:The epigenetic mechanisms coordinating the maintenance of adult cellular lineages and the inhibition of alternative cell fates are poorly understood. Here we show that targeted ablation of the histone chaperone HIRA in myogenic cells leads to extensive transcriptional modifications consistent with a major role in maintaining skeletal muscle cellular identity. Conditional ablation of HIRA in muscle stem cells of adult mice compromised their capacity to regenerate and self-renew, leading to tissue repair failure. Epigenetic analysis of Hira-deficient cells showed a drastic reduction of histone variant H3.3 deposition and H3K27ac modification at regulatory regions of muscle genes. By contrast, genes from alternative lineages were ectopically expressed in Hira-mutant cells via MLL1/MLL2-mediated increase of H3K4me3 mark at silent promoter regions. Therefore, HIRA sustains the epigenetic landscape governing muscle cell lineage identity via incorporation of H3.3 at muscle gene regulatory regions, while preventing the expression of alternative lineage genes.
Project description:The epigenetic mechanisms coordinating the maintenance of adult cellular lineages and the inhibition of alternative cell fates are poorly understood. Here we show that targeted ablation of the histone chaperone HIRA in myogenic cells leads to extensive transcriptional modifications consistent with a major role in maintaining skeletal muscle cellular identity. Conditional ablation of HIRA in muscle stem cells of adult mice compromised their capacity to regenerate and self-renew, leading to tissue repair failure. Epigenetic analysis of Hira-deficient cells showed a drastic reduction of histone variant H3.3 deposition and H3K27ac modification at regulatory regions of muscle genes. By contrast, genes from alternative lineages were ectopically expressed in Hira-mutant cells via MLL1/MLL2-mediated increase of H3K4me3 mark at silent promoter regions. Therefore, HIRA sustains the epigenetic landscape governing muscle cell lineage identity via incorporation of H3.3 at muscle gene regulatory regions, while preventing the expression of alternative lineage genes.
Project description:The epigenetic mechanisms coordinating the maintenance of adult cellular lineages and the inhibition of alternative cell fates are poorly understood. Here we show that targeted ablation of the histone chaperone HIRA in myogenic cells leads to extensive transcriptional modifications consistent with a major role in maintaining skeletal muscle cellular identity. Conditional ablation of HIRA in muscle stem cells of adult mice compromised their capacity to regenerate and self-renew, leading to tissue repair failure. Epigenetic analysis of Hira-deficient cells showed a drastic reduction of histone variant H3.3 deposition and H3K27ac modification at regulatory regions of muscle genes. By contrast, genes from alternative lineages were ectopically expressed in Hira-mutant cells via MLL1/MLL2-mediated increase of H3K4me3 mark at silent promoter regions. Therefore, HIRA sustains the epigenetic landscape governing muscle cell lineage identity via incorporation of H3.3 at muscle gene regulatory regions, while preventing the expression of alternative lineage genes.
Project description:The satellite cell of skeletal muscle provides a paradigm for quiescent and activated tissue stem cell states. We have carried out transcriptome analyses by comparing satellite cells from adult skeletal muscles, where they are mainly quiescent, with cells from growing muscles, regenerating (mdx) muscles, or with cells in culture, where they are activated. Our study gives new insights into the satellite cell biology during activation and in respect with its niche. We used microarrays to study the global programme of gene expression underlying adult satellite cell quiescence compared to activation states and to identify distinct classes of up-regulated genes in these two different states Skeletal muscle satellite cells were isolated by flow cytrometry using the GFP fluorescence marker from Pax3GFP/+ mice skeletal muscle. The transcriptome of quiescent satellite cells from adult Pax3GFP/+ muscle was compared to the transcriptome of activated satellite cells obtained from three different samples: 1) regenerating Pax3GFP/+:mdx/mdx muscle (Ad.mdx) , 2) growing 1 week old Pax3GFP/+ muscle (1wk), and 3) adult Pax3GFP/+ cells after 3 days in culture (Ad.cult).