BMPR1B is a member of the bone morphogenetic protein (BMP) receptor family of transmembrane serine/threonine kinases. The ligands of this receptor are BMPs, which are members of the TGF-beta superfamily. BMPs are involved in endochondral bone formation and embryogenesis. These proteins transduce their signals through the formation of heteromeric complexes of 2 different types of serine (threonine) kinase receptors: type I receptors of about 50-55 kD and type II receptors of about 70-80 kD. The BMPR1B receptor plays a role in the formation of middle and proximal phalanges. Mutations in this gene have been associated with primary pulmonary hypertension. In the chick embryo, it has been shown that BMPR1B is found in precartilaginous condensations.