Expression profiles of Runx2, Osterix, and ALP mRNAs during myoblastic or osteoblastic differentiation of C2C12 cells treated with or without SB431542. C2C12 cells were treated or not with DMSO (0.01%) or SB431542 (1 μM) for 30 min in 5% FBS before stimulation. Then, cells were stimulated with or without BMP-4 (50 ng/ml) in combinations with DMSO or SB431542. Cells were harvested after stimulation at indicated time points, followed by quantitative RT–PCR. Quantitated mRNA values were normalized by the amounts of GAPDH mRNA, and results are given as fold induction. Runx2 gene (Runx2) (A), Osterix gene (Osx) (B), and liver/bone/kidney-type ALP gene (Akp2) (C) were determined. Solid lines reflect osteoblastic differentiation (treated with BMP-4), and broken lines reflect myoblastic differentiation (treated without BMP-4). N, none; D, DMSO; SB, SB431542; B4, BMP-4.