Circadian rhythms regulate cell proliferation and differentiation; however, little is known about their roles in myogenic differentiation. Our synchronized differentiation studies demonstrate that myoblast proliferation and subsequent myotube formation by cell fusion occur in circadian manners. We found that one of the core regulators of circadian rhythms, Cry2, but not Cry1, is critical for the circadian patterns of these two critical steps in myogenic differentiation. This is achieved through the specific interaction between Cry2 and Bclaf1, which stabilizes mRNAs encoding cyclin D1, a G1/S phase transition regulator, and Tmem176b, a transmembrane regulator for myogenic cell fusion. Myoblasts lacking Cry2 display premature cell cycle exit and form short myotubes because of inefficient cell fusion. Consistently, muscle regeneration is impaired in Cry2 −/− mice. Bclaf1 knockdown recapitulated the phenotypes of Cry2 knockdown: early cell cycle exit and inefficient cell fusion. This study uncovers a post-transcriptional regulation of myogenic differentiation by circadian rhythms. Lowe et al. demonstrates that the core circadian regulator Cry2 interacts with Bclaf1, controlling circadian expression of cyclin D1 and Tmem176b mRNAs. This promotes myoblast proliferation and subsequent myocyte fusion to form myotubes in a circadian manner. This study highlights circadian regulation of myogenic differentiation and regeneration.
Bibliographical noteFunding Information:
We acknowledge Minnesota Supercomputing Institute, University of Minnesota Informatics Institute, and University of Minnesota Genomics Center for providing high-performance computing resources and the gopher pipelines. We recognize the Center for Mass Spectrometry and Proteomics at the University of Minnesota and various supporting agencies, including the National Science Foundation for Major Research Instrumentation (grants 9871237 and NSF-DBI-0215759 ). Supporting agencies are listed at http://www.cbs.umn.edu/msp/about . A.Y. was supported by the Minnesota Stem Cell Institute . A.A. was supported by the NIH ( R01 AR062142 and R21 AR070319 ). N.K was supported by the NIH ( R01 GM098294 , R21 AR066158 , R21 HD083648 , and R21 CA187232 ), the Engdahl Foundation , an Adjacent Possible Grant , and the University of Minnesota Foundation ( 4160-9227-13 ).
- cell cycle
- cell fusion
- circadian rhythm
- cyclin D1
- muscle differentiation
- muscle regeneration