Bone morphogenetic protein 10 (BMP-10) was initially cloned from embryonic heart, and expression data suggests that it plays a key role in the trabeculation of the embryonic heart. BMP-10 shares >98% amino acid sequence identity among human, mouse, and rat orthologs. BMPs are members of the transforming growth factor β (TGF β) superfamily. BMP-10 is synthetized as an inactive precursor pro-BMP10 (～60 kD) and is processed into active BMP-10 (～14 kD) by proprotein convertase(s). Furin is the main convertase responsible for the generation of BMP-10. BMPs signal through heterotetrameric complex receptors, which include four type I receptors, ALK1, ALK2, ALK3 and ALK6, and three type II receptors, BMPRII, ActRIIA, and ActRIIB. The ligands bind to the heterotetrameric complex composed of two type II receptors and two type I receptors. Under ligand binding, the type II receptors phosphorylate and activate the type I that stimulate the receptor regulated-Smads. Addditionally, a co-receptor (endoglin) binds to ALK1 increasing the signal. BMP-9 and -10 are functionally equivalent ligands of ALK1 in vascular development. Nevertheless, BMP-10 has an unique function in cardiac development and cannot be replaced by BMP-9. However, both ligands have a redundant role in postnatal vascular development. ALK1 and endoglin are specifically expressed in endothelial cells and mutations in these receptors are associated with vascular defects.