BMP-9/GDF-2

BMP-9 is also known as growth differentiation factor-2 (GDF-2). BMP-9 belongs to TGFβ superfamily and signals through ALK1. BMP-9 is a vascular quiescence factor maintaining endothelial homeostasis^[1]. BMP-9 binds to ALK1 with a very high affinity (K_d: 29 nM). BMP-9 is mainly produced by the liver, specifically by hepatocytes, and at a lower level by the lungs and the brain^[2]. BMP-9 also induces bone formation. Specifically, the activation of ALK1 will eventually lead to phosphorylation and heterodimeric formation of Smad proteins. These Smads proteins can then interact with Smad4 for proper nuclear localization, which is necessary for proper BMP9-induced osteogenic differentiation^[3]. Human BMP-9 shares about 80% aa sequence identity with mouse.

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