The functional significance of the skeletal muscle clock: lessons from Bmal1 knockout models

Skeletal Muscle

Table 1 Global phenotypes of different Bmal1 knockout models

	Whole body Bmal1 KO			Muscle-specific Bmal1 KO
	Standard	Standard + rescue with mBmal1 ^a	Inducible	Standard	Inducible
Circadian locomotor rhythm	No	No	No	Yes	Yes	Yes
Total activity level	↓	=	=	↑	=	=
Life span	↓	=	=	=	=	ND
Body weight	↓	=	=	=	=	ND
Muscle weight	↓	ND	ND^b	↑	=	ND
Muscle fiber CSA	↓	ND	ND	↑	=	=
Muscle force (normalized)	↓	ND	ND	↓	=	↓
Muscle fiber-type profile (fast muscles)	ND	ND	ND	↓ 2X	=	↓ 2B
References	[18, 19, 26]	[32]	[30]	[27]	[27]	[31, 55]

ND not determined, = unchanged, ↓ decreased, ↑ increased, CSA cross-sectional area
^aMice with muscle-specific rescue of Bmal1 null mice, obtained by crossing Bmal1 global KO mice with Bmal1 transgenic mice bearing a Bmal1 DNA construct driven by the muscle-specific α-actin promoter
^bMuscle weight was not determined but was likely unchanged because body weight and the weight of most organs, including fat deposits, were unchanged

ISSN: 2044-5040