Cx37 and Cx40 expression are downregulated in pulmonary arteryendothelial cells (PAECs) from pulmonary arterial hypertension (PAH) patients.7 In addition, mice genetically deficient in Cx40 are protected against hypoxic-inducedPH and hypoxic pulmonary vasoconstriction.8 Cx43 levels are increased in pulmonary arteries from patients with PH associated withhypoxemic chronic lung disease, while Cx43 levels are decreased in pulmonary arteries frompatients with idiopathic PAH. Here, GJA4 is linked to pulmonary arterial hypertension.