Purity >95% as determined by SDS-PAGE. Growth differentiation factor 5 (GDF-5) is a member of the bone morphogenic protein (BMP) and transforming growth factor beta (TGF-?) families and functions to regulate cell proliferation and differentiation in embryonic and adult tissues. GDF-5 is expressed in the central nervous system and promotes the survival of dopaminergic neurons in animal models of Parkinson's disease. GDF-5 is also important during chondrogenesis and chondrocyte differentiation.