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Fos licenses early events in stem cell activation promoting skeletal muscle regeneration [array]

ABSTRACT: Muscle stem cells, also known as satellite cells, are largely non-proliferative in uninjured skeletal muscle but transition at sites of injury into rapidly dividing progenitors that mediate muscle repair. As early events in satellite cell activation are rate-limiting for recovery from muscle damage, there is substantial interest in discovering their molecular driver(s). Using a comparative transcriptomic approach, we identified a prominent Fos signature in recently activated muscle satellite cells, which was rapidly and transiently induced by muscle damage. Functional interrogation using complementary genetic mouse models revealed that FOS is required for efficiently initiating key stem cell functions, including cell cycle entry, stem/progenitor cell expansion, and regeneration of muscle after injury. Transcriptional profiling further revealed that FOS activates critical gene circuits that stimulate cell migration, proliferation, and differentiation while simultaneously repressing quiescence-promoting gene signatures. Pharmacological and genetic disruption of one of these FOS-activated target genes, mono-ADP Ribosyl-Transferase 1 (Art1), in freshly isolated satellite cells substantially diminished cell cycle entry and expansion of the pool of regenerative stem cells. Together, these data implicate FOS as a crucial inducer of early-acting, pro-regenerative gene targets and highlight new transcriptional and post-translational modification events necessary for optimal injury-activated muscle stem cell regenerative responses.

ORGANISM(S): Mus musculus

PROVIDER: GSE119695 | GEO | 2021/01/27

REPOSITORIES: GEO

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Project description:A unique property of many adult stem cells is their ability to exist in a non-cycling, quiescent state. Although quiescence serves an essential role in preserving stem cell function until the stem cell is needed in tissue homeostasis or repair, defects in quiescence can lead to an impairment in tissue function, the extent to which stem cells can regulate quiescence is unknown. Here, we show that the stem cell quiescent state is composed of two distinct functional phases: G0 and an “alert” phase we term GAlert, and that stem cells actively and reversibly transition between these phases in response to injury-induced, systemic signals. Using genetic models specific to muscle stem cells (or satellite cells (SCs)), we show that mTORC1 activity is necessary and sufficient for the transition of SCs from G0 into GAlert and that signaling through the HGF receptor, cMet is also necessary. We also identify G0-to-GAlert transitions in several populations of quiescent stem cells. Quiescent stem cells that transition into GAlert possess enhanced tissue regenerative function. We propose that the transition of quiescent stem cells into GAlert functions as an 'alerting' mechanism, a novel adaptive response that positions stem cells to respond rapidly under conditions of injury and stress without requiring cell cycle entry or a cell fate commitment. We performed microarray analysis on muscle stem cells, harvested immediately after isolation, to investigate the transcriptional response these cells have to injury and the role of mTORC1 and cMet have in this response At least 2 weeks after tamoxifen treatment, to induce recombination and expression of the Rosa26rYFP lineage tracer in Pax7 expressing muscle stem cells using a Pax7-CreER driver, YFP+ cells were FACS purified from hindlimb muscles of animals that were noninjured (quiescent satellite cells (QSCs)) or from hindlimb muscle contralateral to muscles where we induced a BaCl2 injury (contralateral satellite cells (CSCs)). We compared the response of wild-type (WT) muscle stem cells to the response elicited by muscle stem cells with conditional ablation of TSC1, Rptor, or cMet genes. Immediately after FACS purification of cells, total RNA was extracted, processed, labeled, and hybridized to Affymetrix Mouse Gene 1.0 ST arrays. Each biological replicate is a pooled sample of muscle stem cells isolated from 3-4 mice.

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Fos licenses early events in stem cell activation promoting skeletal muscle regeneration [array]

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