GSE122082
MYOD1 functions as a clock amplifier as well as a critical co-factor for downstream circadian gene expression in muscle
In the present study we show that the master myogenic regulatory factor, MYOD1, is a positive modulator of molecular clock amplitude and functions with the core clock factors for expression of clock-controlled genes in skeletal muscle. We demonstrate that MYOD1 directly regulates the expression and circadian amplitude of the positive core clock factor Bmal1. We identify a non-canonical E-box element in Bmal1 and demonstrate that is required for full MYOD1-responsiveness. Bimolecular fluorescence complementation assays demonstrate that MYOD1 colocalizes with both BMAL1 and CLOCK throughout myonuclei. We demonstrate that MYOD1 and BMAL1:CLOCK work in a synergistic fashion through a tandem Ebox to regulate the expression and amplitude of the muscle specific clock-controlled gene, Titin-cap (Tcap). In conclusion, these findings reveal mechanistic roles for the muscle specific transcription factor MYOD1 in the regulation of amplitude of the molecular clock as well as  synergistic regulation of clock-controlled genes in skeletal muscle. Overall design: Gastrocnemius muslce from male mice (C57bl6) were collected every 4hrs for 24 hrs and pooled into one sample.