Growth Differentiation Factor-7 (GDF-7; also called BMP-12 and CDMP-3) is a member of the BMP family of TGF-beta superfamily proteins. GDF­7 is synthesized as a large precursor protein that consists of an N-­terminal 19 amino acid (aa) signal sequence, a 302 aa pro region and a 129 aa C-terminal mature peptide. At the amino acid level, mature human GDF-7 shares 85% and 88% aa sequence identity with mature GDF-7 in mouse and rat, respectively. Mature human GDF-7 lacks a glycine repeat that is found in both mouse and rat GDF-7. Based on sequence similarity, GDF-7 is categorized with GDF-5 and -6, as a subgroup within the BMP family. GDF-7 functions as a homodimer and elicits its bioactivity by mediating the formation of a heterodimeric receptor complex consisting of a type 1 (BMPR-IB) and a type II (BMPR-II or Activin RII) serine/threonine kinase receptor. GDF-7 signaling results in the phosphorylation and activation of cytosolic Smad proteins (Smad1, 5, and 8).