Fig. 1.

The activity of the JNK/MAPK signaling pathways is dramatically decreased, and it blocks myogenesis. a The 20-pathway assay revealed that the MAPK signaling cascade changed most during the differentiation of C2C12 myoblasts, which mimics skeletal muscle differentiation. The relative fold-change of each pathway was tested following the transfection of the pathway plasmids into C2C12 myoblasts and the maintenance of the cells in differentiation medium (DM) for 3 days and normalized to C2C12 myoblasts cultured in growth medium (D0). The data were log2-transformed. b Immunofluorescent microscopy analysis of the morphological changes and expression of p-c-Jun and myogenesis marker MHC in C2C12 cells at 48 or 72 h after the cells were treated with SP600125 or DMSO, DMSO as negative control (Ct). cMHC⁺ cells were calculated based on staining described in panel b. d The expression of myogenic markers (MHC, Mef2a, and MyoD) in b were detected by western blotting. e Relative expression in d were calculated. GAPDH was the internal control. Values are means ± SEM. The statistical significance of difference between two means was calculated with the t-test, *p < 0.05; **p < 0.01