Bone morphogenetic proteins (BMPs) constitute a subfamily within the TGF-beta superfamily of structurally related signaling proteins. Members of this superfamily are widely distributed throughout the body and are involved in diverse physiological processes during both pre- and postnatal life. Like BMP-7, BMP-4 is involved in the development and maintenance of bone and cartilage. Reduced expression of BMP-4 is associated with a number of bone diseases, including the heritable disorder Fibrodysplasia Ossificans Progressiva. Recombinant human BMP-4, expressed in HeLa cells, is a 31-36kD homodimeric glycoprotein.