TBX4 and pulmonary arterial hypertension: Among these, seven are known or previously reported candidate PAH risk genes: BMPR2, TBX4, GDF2, ACVRL1, SOX17, AQP1, ATP13A3, and KDR. Three are new candidate genes: COL6A5 (collagen type VI alpha 5 chain), JPT2 (Jupiter microtubule-associated homolog 2), and FBLN2 (fibulin 2).