RelA Inhibits Embryonic Myogenesis by Coordinately Regulating a Novel Distal Enhancer of Myogenin.

Skeletal muscle is crucial for lifelong metabolic health, with its development initiating during embryogenesis and guiding later growth. Single-cell RNA sequencing of E13.5 mouse embryos suggests that maternal obesity impairs embryonic myogenesis, primarily during myotube formation, and is correlated with the downregulation of myogenin (Myog) expression. Spatial transcriptomic sequencing further confirms these findings. Conversely, maternal obesity induces the upregulation of RelA, a transcription factor and inflammatory signaling effector, in the myogenic cells of obese embryos. Additionally, single-cell ATAC sequencing suggests that a cis-regulatory region, located 4 kb proximal to the Myog promoter, exhibits coordinated expression with Myog and acts as an enhancer of Myog. In obese embryonic myogenic cells, RelA is recruited to this region, inhibiting Myog expression and myotube formation. Notably, in vitro RelA knockdown or inhibition rescues Myog expression and promotes myogenic differentiation. Similarly, metformin treatment of obese mothers restores embryonic Myog expression and myogenesis by suppressing RelA. Together, the multi-omics analyses demonstrate that RelA targets a distal Myog enhancer to coordinately inhibit Myog expression and embryonic myogenesis.