Lineage Tracing Reveals a Subset of Reserve Muscle Stem Cells Capable of Clonal Expansion under Stress

Cell Stem Cell. 2019 Jun 6;24(6):944-957.e5. doi: 10.1016/j.stem.2019.03.020. Epub 2019 Apr 18.


Stem cell heterogeneity is recognized as functionally relevant for tissue homeostasis and repair. The identity, context dependence, and regulation of skeletal muscle satellite cell (SC) subsets remains poorly understood. We identify a minor subset of Pax7+ SCs that is indelibly marked by an inducible Mx1-Cre transgene in vivo, is enriched for Pax3 expression, and has reduced ROS (reactive oxygen species) levels. Mx1+ SCs possess potent stem cell activity upon transplantation but minimally contribute to endogenous muscle repair, due to their relative low abundance. In contrast, a dramatic clonal expansion of Mx1+ SCs allows extensive contribution to muscle repair and niche repopulation upon selective pressure of radiation stress, consistent with reserve stem cell (RSC) properties. Loss of Pax3 in RSCs increased ROS content and diminished survival and stress tolerance. These observations demonstrate that the Pax7+ SC pool contains a discrete population of radiotolerant RSCs that undergo clonal expansion under severe stress.

Keywords: Mx1; Pax3; ROS; clonal expansion; muscle stem cells; radiation; reserve stem cell; satellite cells; stress; tissue regeneration.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult Stem Cells / physiology*
  • Animals
  • Cell Differentiation
  • Cell Lineage
  • Cell Survival
  • Clone Cells
  • DNA Damage / physiology*
  • Humans
  • Mice
  • Mice, Inbred C57BL
  • Myxovirus Resistance Proteins / metabolism
  • PAX3 Transcription Factor / metabolism
  • PAX7 Transcription Factor / metabolism
  • Radiation, Ionizing
  • Reactive Oxygen Species / metabolism
  • Regeneration
  • Satellite Cells, Skeletal Muscle / physiology*
  • Up-Regulation


  • MX1 protein, human
  • Myxovirus Resistance Proteins
  • PAX3 Transcription Factor
  • PAX3 protein, human
  • PAX7 Transcription Factor
  • PAX7 protein, human
  • Reactive Oxygen Species