Per1/Per2-Igf2 axis-mediated circadian regulation of myogenic differentiation

Abstract Circadian rhythms regulate cell proliferation and differentiation but circadian control of tissue regeneration remains elusive at the molecular level. Here, we show that proper myoblast differentiation and muscle regeneration are regulated by the circadian master regulators Per1 and Per2. Depletion of Per1 or Per2 suppressed myoblast differentiation in vitro and muscle regeneration in vivo, demonstrating their non-redundant functions. Both Per1 and Per2 were required for the activation of Igf2, an autocrine promoter of myoblast differentiation, accompanied by Per-dependent recruitment of RNA polymerase II, dynamic histone modifications at the Igf2 promoter and enhancer, and the promoter-enhancer interaction. This circadian epigenetic priming created a preferred time window for initiating myoblast differentiation. Consistently, muscle regeneration was faster if initiated at night when Per1, Per2, and Igf2 were highly expressed compared with morning. This study reveals the circadian timing as a significant factor for effective muscle cell differentiation and regeneration. eTOC Summary Katoku-Kikyo et al. show that the circadian master regulators Per1 and Per2 control the efficiency of myoblast differentiation via Igf2 activation. This pathway creates a preferred circadian time window for myoblast differentiation in vitro and muscle regeneration in vivo.