Pharmacological Inhibition of N-terminal methyltransferase 1 promotes myogenic differentiation and muscle regeneration in a mouse model of Duchenne muscular dystrophy

BACKGROUND: Duchenne muscular dystrophy (DMD), caused by mutations of the DMD gene, is a lethal degenerative disease with no cure. Stimulating myogenesis of muscle stem cells (MuSCs) represents a promising strategy to ameliorate muscle pathology in DMD patients. Although previous work has revealed a role of N-terminal methyltransferase 1 (NTMT1) in myogenesis, its potential as a therapeutic target to ameliorate muscular dystrophy remains unexplored. METHOD: We employed GD433, a highly specific and potent pharmacological inhibitor of NTMT1, and evaluated its role in myogenesis using cell and animal models (mdx mice). C2C12 and primary myoblasts, and MuSCs were treated with GD433, and cell proliferation, differentiation, fusion, and gene expression were examined. Mdx mice were treated by intraperitoneal injection of GD433 (25 mg/kg, 5 days/week), and muscle pathology was evaluated. We finally employed co-immunoprecipitation (IP) and methylation-specific antibodies to identify NTMT1 substrates in myoblasts. RESULTS: A low dose of GD433 (300 nM) significantly enhances the differentiation and fusion of cultured C2C12 and primary myoblasts without affecting their proliferation. Similar effects are observed in myofiber-associated MuSCs. GD433 further enhances myogenic differentiation and muscle regeneration in mdx mice. Mechanistically, GD433 elevates expression of myogenic differentiation and fusion factors (Myog, Mymk, Mymx) through affecting KLHK31 methylation. Specifically, GD433 reduces the methylation level of KLHL31, promoting its interaction with MYOD and upregulating the expression of Myog, Mymk and Mymx. CONCLUSION: These results show that pharmacological inhibition of NTMT1 by GD433 promotes myogenic differentiation and enhances muscle regeneration in mdx mice. The pro-myogenic effect of GD433 is associated with reduced KLHL31 methylation, which strengthens KLHL31-MYOD interactions to upregulate genes related to myogenic differentiation. This study highlights NTMT1 inhibition as a potential therapeutic target to improve muscle repair in DMD patients.