BMP-6

Bone morphogenetic protein 6 (BMP-6) is a 57-kDa glycoprotein of the TGF-β superfamily that signals canonically through BMPR1A/ALK3 and BMPR2 to phosphorylate SMAD1/5/8, and occupies distinctive physiological niches beyond skeletal development. BMP-6 is the key hepatic iron regulator: it is produced by liver sinusoidal endothelial cells in response to iron loading and by hepatocytes, and acts on hepatocytes to induce hepcidin (HAMP) expression via SMAD1/5, thereby controlling systemic iron homeostasis; BMP-6 loss lowers hepcidin and promotes iron overload, a mechanism highly relevant to anemia of inflammation and hereditary hemochromatosis. In the nervous system, BMP-6 guides noradrenergic differentiation of neural crest and cholinergic differentiation in the basal forebrain. BMP-6 is also essential for follicular development and luteinization in the ovary, promotes osteoblast differentiation, and is silenced epigenetically in many cancers while acting pro-tumorically in gliomas and breast cancer stem-like populations.