The Skeletal Muscle Molecular Clock Regulates Sarcomere Length Through Titin Splicing [2]

Circadian rhythms have been implicated in regulating skeletal muscle structure and function, but no mechanisms have connected the molecular clock to sarcomeric proteins. We identified an isoform shift in the sarcomeric ruler, titin, and showed that the skeletal muscle molecular clock regulates titin isoform and subsequently sarcomere length through RBM20, an RNA binding protein that controls titin splicing. Restoring RBM20 expression in iMSBmal1-/- TA muscle partially restored titin isoform. Tibialis anterior muscles were collected from inducible, skeletal muscle specific Bmal1 fl/fl mice 8 weeks after treatment with either tamoxifen solution and 4 weeks after AAV treatment. Muscles were pulverized under liquid nitrogen to prevent fiber type bias prior to total RNA colleciton.