[Mechanism of the WNT family in vertebrate skeleton development]

Skeletal elements of vertebrate limb are derived from mesenchymal cells. Initially, these cells differentiate into chondrocytes which form the initial anlage element. Subsequently, chondrocytes in the middle of the cartilage element exit the cell cycle and are eventually replaced by bone through endochondral ossification. Recently, it is shown that the secreted signaling molecules encoded by members of the wnt gene family and their related elements play pivotal roles in the process of the skeleton system development. These molecules ensure the chondrocytes can differentiate continuously at proper speed in the definitive space by the negative and positive control effect on different steps of the chondrocyte differentiation and form the matural skeleton system possessing normal function and structure. However, both the members of WNT family and their related molecules in the signaling pathway expressing abnormally can disrupt the balance remained by the WNT family and result in skeleton malformation. Understanding the roles of the WNT family is helpful to explore the mechanism of vertebrate skeleton development.