GDF2 and pulmonary arterial hypertension: The roles of BMP-9 and -10 in the cardiovascular system have largely focused on their important roles in arteriovenous differentiation during development and the pulmonary vasculature largely due to human genetic evidence showing that loss of function mutations in ALK-1, or its coreceptors, lead to hereditary hemorrhagic telangiectasia and/or pulmonary hy-pertension.