Methods to Monitor Circadian Clock Function in Skeletal Muscle

The circadian clock exerts temporal regulation in physiology and behavior. The skeletal muscle possesses cell-autonomous clock circuits that play key roles in diverse tissue growth, remodeling, and metabolic processes. Recent advances reveal the intrinsic properties, molecular regulations, and physiological functions of the molecular clock oscillators in progenitor and mature myocytes in muscle. While various approaches have been applied to examine clock functions in tissue explants or cell culture systems, defining the tissue-intrinsic circadian clock in muscle requires sensitive real-time monitoring using a Period2 promoter-driven luciferase reporter knock-in mouse model. This chapter describes the gold standard of applying the Per2::Luc reporter line to assess clock properties in skeletal muscle. This technique is suitable for the analysis of clock function in ex vivo muscle preps using intact muscle groups, dissected muscle strips, and cell culture systems using primary myoblasts or myotubes.