The clock regulator Bmal1 protects against muscular dystrophy.

The muscle-intrinsic clock machinery is required for the maintenance of muscle growth, remodeling and function. Our previous studies demonstrated that the essential transcription activator of the molecular clock feed-back loop, Brain and Muscle Arnt-Like 1(Bmal1), plays a critical role in myogenic progenitor behavior to promote and regenerative myogenesis. Using genetic approaches targeting Bmal1 in the DMD(mdx) (mdx) dystrophic mouse model, here we report that the loss of Bmal1 function significantly accelerated dystrophic disease progression. In contrast to the mild dystrophic changes in mdx mice, the genetic loss-of-function of Bmal1 aggravated muscle damage in this dystrophic disease background, as indicated by persistently elevated creatine kinase levels, increased injury area and reduced muscle grip strength. Mechanistic studies revealed that markedly impaired myogenic progenitor proliferation and myogenic response underlie the defective new myofiber formation in the chronic dystrophic milieu. Taken together, our study identified the function of pro-myogenic clock gene Bmal1 in protecting against dystrophic damage, suggesting the potential for augmenting Bmal1 function to ameliorate dystrophic or degenerative muscle diseases.