Protein involved in osteogenesis, the mechanism of bone formation wether intramembranous or endochondral. In intramembranous ossification, bone is formed by differentiation of mesenchymal cells into osteoblasts with absence of a cartilaginous model. The flat bones of the skull, the sternum, and the scapula are examples of bones that develop by intramembranous ossification. The term endochondral refers to the close association of the developing bone with the pre-existing hyaline cartilage model of that bone. The long bones of the limbs (including the phalanges) and the ribs develop by endochondral ossification.