BMP4 is a polypeptide belonging to the TGF-βsuperfamily of proteins, which binds to 2 different types of serine-threonine kinase receptors known as BMPR1 and BMPR2. Signal transduction via these receptors occurs via Smad and map kinase pathways to effect transcription of its target genes. Like other bone morphogenetic proteins, it is involved in bone and cartilage development, specifically tooth and limb development and fracture repair, playing an important role in the onset of endochondral bone formation in humans. It has been shown to be involved in muscle development, bone mineralization, and ureteric bud development.