Although no mutations were identified in HES1 or HES5, we identified two NOTCH3 missense mutations in two independent probands with IPAH: a c.2519 G>A p.G840E mutation in proband A, and a c.2698 A>C p.T900P mutation in proband B (Fig. 2A). The gene discussed is NOTCH3; the disease is idiopathic pulmonary arterial hypertension.