Table 9.2.

Skeletal muscle abnormalities in circadian mutants

Mutation	Circadian phenotype	Skeletal muscle pathology	Reference
Bmal1^−/−	Arrhythmic behavior and expression of clock genes in both SCN and peripheral tissues	Sarcopenia age-associated decrease in muscle fiber number and fiber diameter Reduced lifespan	Kondratov et al. (2006)
Muscle-rescued Bmal1^−/−	Arrhythmic wheel running behavior	Normal body weight Normal activity levels Improved longevity	McDearmon et al. (2006)
Bmal1^−/− Clock^Δ19	Arrhythmic wheel running behavior	Decreased maximal force production Myofilament disarrangement Mitochondrial pathology	Andrews et al. (2010)
Clock^Δ19 + Mel	Liver and skeletal muscle-specific arrhythmic expression of clock genes	Decreased GLUT4 expression Possible skeletal muscle insulin resistance	Kennaway et al. (2007)
Per2^−/−	Short circadian period (tau = 22 h) Arrhythmic in constant darkness	Reduced forced locomotor performance without alteration in skeletal muscle contractile function	Bae et al. (2006)
RORb^−/−	Slightly longer circadian period, (tau = 24.3 h)	Muscle weakness when young, gain strength with age “Duck Like” gait Locomotor difficulties	Andre et al. (1998)