FOXK2 in skeletal muscle development: a new pathogenic gene for congenital myopathy with ptosis

Congenital ptosis, a genetic disorder involving levator palpebrae muscle dysfunction, is often associated with congenital myopathy. The genetic causes of this condition remain poorly understood. In this study, we identified FOXK2 mutations in five pedigrees with congenital myopathy and ptosis through whole exome sequencing and Sanger sequencing. Zebrafish with foxk2 deficiency exhibited underdeveloped skeletal muscles and reduced mobility, while mice with Foxk2 deletion in skeletal muscle stem cells (MuSCs) showed generalized skeletal muscle abnormalities. Further analysis revealed that FOXK2 deficiency impaired myogenic differentiation in C2C12 cells and disrupted mitochondrial homeostasis in both mouse MuSCs and C2C12 cells. Rescue experiments confirmed the loss-of-function effects of FOXK2 mutation. Coenzyme Q10 treatment improved mitochondrial function and alleviated skeletal muscle development defects in Foxk2-deficient mice. Preliminary omics analysis suggested FOXK2 directly regulates the expression of mitochondrial function-related genes by modulating chromatin accessibility at its binding sites. Our study identifies FOXK2 as a novel pathogenic gene for congenital myopathy with ptosis and highlights its essential role in skeletal muscle development and mitochondrial homeostasis, offering insights for potential diagnostics and therapies.