TBX4 and pulmonary arterial hypertension: More recently, mutations in genes not directly linked to TGF-β/BMP signaling, including KCNK3 [6], TBX4 [7], as well as AQP1 [5], ATP13A3 [5], GCN2 [8], and SOX17 [5] have been linked to PAH; many of these mutations were identified by whole genome sequencing.