BMP receptors in limb and tooth formation

Members of the TGF-beta superfamily signal through receptor complexes compr ised of type I and type II receptors. These receptors, which are serine/thr eonine kinases, form two new classes of transmembrane receptor kinases. The activity of both of the kinases is necessary for signal transduction in re sponse to ligand binding. Bone morphogenetic proteins (BMPs), which are mem bers of the TGF-beta superfamily, bind to multiple type I and type Il recep tors. There is growing evidence to support the hypothesis that the BMP rece ptors are differentially regulated during development and that they have bo th unique and overlapping functions. Thus, the nature and distribution of t he BMP receptors, which are reviewed here in the context of the development of limbs and teeth, appear to be critical in the control of the diverse ac tivities of BMPs.