Growth differentiation factor 2 (GDF2) also known as bone morphogenetic protein (BMP)-9 is a protein that in humans is encoded by the GDF2 gene. GDF2 belongs to the transforming growth factor beta superfamily.
GDF2 has a role in inducing and maintaining the ability of embryonic basal forebrain cholinergic neurons (BFCN) to respond to a neurotransmitter called acetylcholine; BFCN are important for the processes of learning, memory and attention. GDF2 is also important for the maturation of BFCN. Another role of GDF2 has been recently suggested. GDF2 is a potent inducer of hepcidin (a cationic peptide that has a antimicrobial properties) in liver cells (hepatocytes) and can regulate iron metabolism. The physiological receptor of GDF2 is thought to be activin receptor-like kinase 1, ALK1 (also called ACVRL1), an endothelial-specific type I receptor of the TGF-beta receptor family.
GDF2 is one of the most potent BMPs to induce orthotopic bone formation in vivo. BMP3, a blocker of most BMPs seems not to affect GDF2.