In the field of TGF-β–related biology, ALK1 has only recently abandoned the role of a pure mediator of endothelial identity and function in favor of a more multifaceted player in different homeostatic processes and diseases, including normal hair maintenance, pulmonary hypertension, and atherosclerosis (62–65). The gene discussed is TGFB1; the disease is pulmonary arterial hypertension.