GDF-3 is a growth and differentiation factor which belongs to the TGF-beta superfamily. GDF-3 and GDF-9 are the only two members of the family which do not form disulfide-linked dimers. GDF-3 has been found in adult bone marrow, spleen, thymus, and adipose tissue. Although signaling in all other members of the family involve the BMP receptors ALK1,2,3, and 6, GDF-3 signals through BMP receptors ALK4 and 7.