Bone morphogenetic protein inhibits differentiation and affects expression of helix-loop-helix regulatory molecules in myoblastic cells.

Bone morphogenetic protein (BMP) reproducibly induces chondrogenesis and osteogenesis when implanted into skeletal muscle. The exact identity of the cell that responds to BMP is not known. Furthermore, controversy exists regarding the possibility that myoblastic cells may transdifferentiate to chondrocytes and osteoblasts under the influence of BMP. We have therefore, undertaken studies on the effects of BMP on differentiation in L6 and C2C12 cells, two rodent myoblastic cell lines. To gain insights into the mechanisms of action of BMP, we have studied the effects of BMP on the levels of expression of the four known myogenic determination genes: myogenin, Myo D, herculin, and myf-5. BMP inhibited myogenesis in myoblastic cells. Convincing evidence of transdifferentiation of myoblasts to chondrocytes or osteoblasts was not seen. BMP inhibited the expression of all four myogenic determination genes.