NR2F2 and hereditary hemorrhagic telangiectasia: Endoglin is a TGF-β co-receptor necessary for angiogenesis [130] and its haplo-insufficiency is associated with hereditary hemorrhagic Telangiectasia, a hereditary form of vessel malformation; null mice for the TGF-β co-receptor are defective in vessel differentiation and show ectopic COUP-TFII expression in the arterial compartment [130], a piece of evidence that strengthen the notion of COUP-TFII as a causative agent of AVM.