E-GEOD-55490 - mTORC1 controls the systemically-induced adaptive regulation of stem cell quiescence into GAlert
Released on 10 April 2014, last updated on 11 April 2014
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.
transcription profiling by array
Joseph T Rodgers <email@example.com>, Thomas A Rando