Transcription factor MAFA regulates muscle growth via calcium ion channels and receptor tyrosine kinase activation

MAFA, a member of the large Maf transcription factor family, is known primarily for its role in regulating insulin gene expression. However, its function in non-pancreatic tissues remains largely unexplored. This study aims to investigate the role of MAFA in skeletal muscle and to elucidate the underlying molecular mechanisms. Quantitative PCR analysis showed that MAFA is highly expressed in sheep skeletal muscle, and its expression level is positively correlated with muscle mass. By integrating ChIP-Seq and RNA-Seq data from longissimus dorsi muscle, we identified that MAFA preferentially binds and regulates genes enriched in calcium signaling and receptor tyrosine kinase (RTK)-related pathways. Functional studies were conducted in primary sheep myoblasts using MAFA overexpression and siRNA-mediated knockdown. These gain- and loss-of-function assays demonstrated that MAFA promotes myoblast proliferation and inhibits differentiation. Mechanistically, MAFA upregulates STIM1 and PPP3CA, promoting intracellular Ca²⁺ influx. In parallel, MAFA transcriptionally activates INSR and EGFR, thereby enhancing PI3K/Akt signaling and inducing phosphorylation-dependent nuclear exclusion of FOXO3, a key catabolic transcription factor. These findings suggest that MAFA may play an important regulatory role in skeletal muscle development through calcium- and RTK-mediated signaling pathways, offering new insights into muscle biology and potential targets for improving livestock production and muscle-related disorders.