Cbfa1 is a member of runt-domain gene family. Cbfa1-deficient mice lack of bone formation and introduction of Cbfa1 into non-osteoblastic cells induced the expression of osteoblast specific genes. Cbfa1-deficient calvarial cells were composed of immature mesenchymal cells and can differentiated into adipocytes and chondrocytes. Based on these findings, Cbfa1 has been identified as a master regulatory gene of the osteoblast differentiation and it has been suggested that Cbfa1 plays an essential role in determining the lineage of multipotential mesenchymal precursor cells.