AQP1 and pulmonary arterial hypertension: Genes not directly impacting on the TGF-β/BMP pathway, including aquaporin 1 (AQP1), which encodes the plasma membrane water channel aquaporin 1, and ATPase family homolog up-regulated in senescence cells 1 (ATP13A3), an ATPases involved in ion channel transport, were reported to be associated with PAH (2, 6, 8).