Our study establishes a key role for the TGF-β/ALK1/ENG signaling pathway in PAH and suggests that TGF-β may act upstream to pathways that are crucial in PAH in both humans and rodents, such as the Endothelin1, PDGFb, and FGF2 pathways. The gene discussed is TGFB1; the disease is pulmonary arterial hypertension.