PAX7 and sarcopenia: To verify that functional MuSCs are the key factor for maintaining muscle mass and strength, and slowing the progression of sarcopenia, Liu et al. (Liu et al., 2017) compared SC-specific Spry1-overexpressing Pax7 CreER/+; CAGSpry1/+ (Spry1OX) mice with Pax7+/+; CAGSpry1/+ (control) mice.