Dual roles of smad proteins in the conversion from myoblasts to osteoblastic cells by bone morphogenetic proteins.

Bone morphogenetic proteins (BMPs) induce ectopic bone formation in muscle tissue in vivo and convert myoblasts such that they differentiate into osteoblastic cells in vitro. We report here that constitutively active Smad1 induced osteoblastic differentiation of C2C12 myoblasts in cooperation with Smad4 or Runx2. In floxed Smad4 mice-derived cells, Smad4 ablation partially suppressed BMP-4-induced osteoblast differentiation.