transcript regulates C2C12 differentiation. (A,B) Effect of knockdown of FL-Irs-1 mRNA on differentiation of C2C12 myoblast. Fusion index (A) and a mean diameter of myotubes (B) are shown. Mean ± SD, n = 50, *p < 0.01 versus no treatment (none). (C) Effect of knockdown of FL- Irs-1 mRNA on expression levels of myosin heavy chain in differentiating C2C12 cells (DM2, 4 and 6).