A dual-color PAX7 and MYF5 in vivo reporter to investigate muscle stem cell heterogeneity in regeneration and aging

Stem Cell Reports. 2024 Jul 9;19(7):1024-1040. doi: 10.1016/j.stemcr.2024.05.005. Epub 2024 Jun 13.


Increasing evidence suggests that the muscle stem cell (MuSC) pool is heterogeneous. In particular, a rare subset of PAX7-positive MuSCs that has never expressed the myogenic regulatory factor MYF5 displays unique self-renewal and engraftment characteristics. However, the scarcity and limited availability of protein markers make the characterization of these cells challenging. Here, we describe the generation of StemRep reporter mice enabling the monitoring of PAX7 and MYF5 proteins based on equimolar levels of dual nuclear fluorescence. High levels of PAX7 protein and low levels of MYF5 delineate a deeply quiescent MuSC subpopulation with an increased capacity for asymmetric division and distinct dynamics of activation, proliferation, and commitment. Aging primarily reduces the MYF5Low MuSCs and skews the stem cell pool toward MYF5High cells with lower quiescence and self-renewal potential. Altogether, we establish the StemRep model as a versatile tool to study MuSC heterogeneity and broaden our understanding of mechanisms regulating MuSC quiescence and self-renewal in homeostatic, regenerating, and aged muscles.

Keywords: MYF5; PAX7; Skeletal muscle; aging; muscle stem cells; quiescence; regeneration; satellite cells; self-renewal; stemness.

MeSH terms

  • Aging* / metabolism
  • Animals
  • Cell Differentiation
  • Cell Proliferation
  • Cell Self Renewal
  • Genes, Reporter*
  • Mice
  • Mice, Transgenic
  • Muscle, Skeletal / cytology
  • Muscle, Skeletal / metabolism
  • Myogenic Regulatory Factor 5* / genetics
  • Myogenic Regulatory Factor 5* / metabolism
  • PAX7 Transcription Factor* / genetics
  • PAX7 Transcription Factor* / metabolism
  • Regeneration*
  • Stem Cells / cytology
  • Stem Cells / metabolism


  • PAX7 Transcription Factor
  • Myogenic Regulatory Factor 5
  • Myf5 protein, mouse
  • Pax7 protein, mouse