Overexpression of Mfn2 ameliorates TNF-α-induced myotube atrophy of C2C12 cells. (A) C2C12 cells were cultured in differentiation medium for 7 days. (B) C2C12 cells were cultured in differentiation medium for 7 days in the presence of 5 ng/ml TNF-α. (C) C2C12 cells were infected with control lentivirus and then cultured with differentiation medium for 7 days in the presence of 5 ng/ml TNF-α. (D) C2C12 cells were infected with Mfn2 lentivirus and then cultured in differentiation medium in the presence of 5 ng/ml TNF-α for 7 days. (E) Determination of C2C12 myotube length. (F) Determination of myotube transverse diameter. (G) The expression levels of Mfn2, COX IV, Cyto C and β-actin in C2C12 cells that received various treatments were determined using western blotting. Data are expressed as the mean ± standard error of the mean. **P<0.01. Mfn2, mitofusin-2; TNF-α, tumor necrosis factor-α; COX-IV, cytochrome c oxidase subunit IV; Cyto C, cytochrome c.