Pax7 is back

Two recent studies have reinvigorated the conversation regarding the role of Pax7 in adult satellite. Studies by Gunther et al (Cell Stem Cell 13:590–601, 2013) and Von Maltzhen et al (Proc Natl Acad Sci U S A 110:16474–16479) show that Pax7 is critical for adult satellite cell function and their contribution to muscle repair. Previously, Lepper et al (Nature 460:627–631, 2009) demonstrated that Pax7 was dispensable for adult muscle repair. In this commentary I have summarized the results from these studies, focusing on the differences in experimental paradigms that led the authors to different conclusions. I also take this opportunity to discuss the potential limitations and hurdles of Cre-lox technology that are responsible for the discrepant results.