Project description:The maintenance of cell lineage and cell fate are essential for the function of adult stem cells. Despite this, the epigenetic mechanisms that regulate muscle stem cell (MuSC) identity are not well understood. In this study, we performed Cut&Tag of the activating histone marks H3K4me3 and H3K27ac on freshly isolated quiescent MuSCs and found that a large number of genes without transcription still maintained the permissive mark H3K4me3 but lacked the marker of active enhancers, H3K27ac. These genes included those that are essential for non-myogenic lineage determination. We found that many of the genes that were not transcribed but enriched for H3K4me3, were also enriched for the RE-1 binding motif, the motif recognized by the repressive transcription factor REST. Using a genetic mouse model where REST is conditionally knocked out of MuSCs, we further investigated the role of REST in the maintenance of quiescent MuSC cell identity. Investigation of the transcriptome and chromatin accessibility of WT and REST deficient MuSCs determined that the loss of REST results in the gain of expression of key genes of several non-myogenic tissues, particularly neuronal genes. Additionally, the loss of REST led to the dramatic reduction of the MuSC pool and the induction of muscle atrophy. The unstable cell identity caused by the genetic deletion of REST results in the MuSCs undergoing apoptosis and is the main driver of the observed loss of the MuSC pool. Together, the data presented in this study establishes a novel function of the transcription factor REST, where it safeguards the identity and myogenic lineage of MuSCs, through the repression of alternative lineages.
Project description:The maintenance of cell lineage and cell fate are essential for the function of adult stem cells. Despite this, the epigenetic mechanisms that regulate muscle stem cell (MuSC) identity are not well understood. In this study, we performed Cut&Tag of the activating histone marks H3K4me3 and H3K27ac on freshly isolated quiescent MuSCs and found that a large number of genes without transcription still maintained the permissive mark H3K4me3 but lacked the marker of active enhancers, H3K27ac. These genes included those that are essential for non-myogenic lineage determination. We found that many of the genes that were not transcribed but enriched for H3K4me3, were also enriched for the RE-1 binding motif, the motif recognized by the repressive transcription factor REST. Using a genetic mouse model where REST is conditionally knocked out of MuSCs, we further investigated the role of REST in the maintenance of quiescent MuSC cell identity. Investigation of the transcriptome and chromatin accessibility of WT and REST deficient MuSCs determined that the loss of REST results in the gain of expression of key genes of several non-myogenic tissues, particularly neuronal genes. Additionally, the loss of REST led to the dramatic reduction of the MuSC pool and the induction of muscle atrophy. The unstable cell identity caused by the genetic deletion of REST results in the MuSCs undergoing apoptosis and is the main driver of the observed loss of the MuSC pool. Together, the data presented in this study establishes a novel function of the transcription factor REST, where it safeguards the identity and myogenic lineage of MuSCs, through the repression of alternative lineages.
Project description:The maintenance of cell lineage and cell fate are essential for the function of adult stem cells. Despite this, the epigenetic mechanisms that regulate muscle stem cell (MuSC) identity are not well understood. In this study, we performed Cut&Tag of the activating histone marks H3K4me3 and H3K27ac on freshly isolated quiescent MuSCs and found that a large number of genes without transcription still maintained the permissive mark H3K4me3 but lacked the marker of active enhancers, H3K27ac. These genes included those that are essential for non-myogenic lineage determination. We found that many of the genes that were not transcribed but enriched for H3K4me3, were also enriched for the RE-1 binding motif, the motif recognized by the repressive transcription factor REST. Using a genetic mouse model where REST is conditionally knocked out of MuSCs, we further investigated the role of REST in the maintenance of quiescent MuSC cell identity. Investigation of the transcriptome and chromatin accessibility of WT and REST deficient MuSCs determined that the loss of REST results in the gain of expression of key genes of several non-myogenic tissues, particularly neuronal genes. Additionally, the loss of REST led to the dramatic reduction of the MuSC pool and the induction of muscle atrophy. The unstable cell identity caused by the genetic deletion of REST results in the MuSCs undergoing apoptosis and is the main driver of the observed loss of the MuSC pool. Together, the data presented in this study establishes a novel function of the transcription factor REST, where it safeguards the identity and myogenic lineage of MuSCs, through the repression of alternative lineages.
Project description:The data are the cut&tag data sequencing data of H3K4me3, H3K27Ac and H3K27me3 of pig muscle satellite cells at the stage of proliferation and differentiation.
Project description:Many stem cell populations exist in a quiescent state in vivo, exiting quiescence and entering the cell cycle in response to specific stimuli. In the case of skeletal muscle, the muscle stem cells (MuSCs, or “satellite cells”) are quiescent under normal homeostatic conditions and undergo activation and cell cycle entry in response to muscle fiber damage. Quiescent MuSCs are also much more potent than their proliferating progeny in assays of stem cell transplantation. In recent years, it has become increasingly apparent that the quiescent state is both actively maintained and dynamically regulated. However, most of the analyses of quiescent MuSCs have come from cells that have been removed from their niche in vivo, purified by fluorescence activated cell sorting, and then assay ex vivo. Although such cells are still in the quiescent state under these conditions, there is no doubt that significant biochemical changes will occur during the isolation and purification process. Thus, we have sought to examine the true in vivo quiescent state by analyzing the transcriptome of MuSCs. To achieve that, we have used techniques to label actively transcribing RNA in vivo using nucleoside analogs. In mice in which the enzyme uracil phosphoribosyltransferase (UPRT) is expressed specifically in MuSCs, administration of 4-thiouracil (4TU), which is converted to thiouridine (TU) by UPRT, resulted in labelling of MuSC transcripts, and the transcriptome could be analyzed following pull-down of TU-tagged RNA. Varying the timing of 4TU administration revealed the dynamic regulation of different subsets of transcripts. Notably, labeling transcripts during the isolation procedure revealed very active transcription of specific subsets of genes. Nevertheless, the ex vivo transcriptome remained largely reflective of the in vivo transcriptome. Using the transcriptional inhibitor, α-amanitin, we were also able to show that there was little difference between the steady-state transcript levels of the most highly expressed genes when comparing the ex vivo transcriptome with the in vivo transcriptome. Together, these data provide a novel view of the molecular regulation of the quiescent state at the transcriptional level, demonstrate the utility of these tools for probing transcriptional dynamics in vivo, and provide an invaluable resource for understanding stem cell state transitions.
Project description:We compared transcriptome of real quiescent MuSCs and freshly isolated MuSCs with in-situ fixation,FISC cultured for 24hrs,48hrs and 72hrs by RNA-sequencing.
Project description:Short-term fasting is beneficial for the regeneration of multiple tissue types. However, the effects of fasting on muscle regeneration are largely unknown. Here we report that fasting slows muscle repair both immediately after the conclusion of fasting as well as after multiple days of refeeding. We show that ketosis, either endogenously produced during fasting or a ketogenic diet, or exogenously administered, promotes a deep quiescent state in MuSCs. Although deep quiescent MuSCs are less poised to activate, slowing muscle regeneration, they have markedly improved survival when facing sources of cellular stress. Further, we show that ketone bodies, specifically b- hydroxybutyrate, directly promote MuSC deep quiescence via a non‐metabolic mechanism. We show that b-hydroxybutyrate functions as an HDAC inhibitor within MuSCs leading to acetylation and activation of an HDAC1 target protein p53. Finally, we demonstrate that p53 activation contributes to the deep quiescence and enhanced resilience observed during fasting.