To directly test the functional requirement for FOS in SC activation and the response to muscle injury, we established a Cre recombinase (Cre)-LoxP loss-of-function system using Fosfl/fl ; ROSA26Ai9/+; Pax7CreERT2/+ (Fos-conditional knockout; FoscKO) and Fos+/+; ROSA26Ai9/+; Pax7Cr...