Growth/differentiation factors (GDF-1 to GDF-15) are members of the BMP family of TGF-beta superfamily proteins. At the amino acid level, mature human GDF-7 shares 85% and 88% aa sequence identity with mature GDF-7 in mouse and rat. They are produced as inactive preproproteins which are then cleaved and assembled into active secreted homodimers. GDF dimers are disulfide-linked with the exception of GDF-3 and -9. GDF proteins are important during embryonic development, particularly in the skeletal, nervous, and muscular systems. GDF-7 is involved in tendon and ligament formation and repair. GDF-7 also regulates bone formation, mesenchymal stem cell differentiation, neuronal differentiation, and axon guidance in the central nervous system.