HIF-2α is abundantly expressed in the lung in epithelial as well as endothelial cells (44) and mice with genetic inactivation of Hif-2α in pulmonary endothelial cells are protected from pulmonary hypertension induced by chronic hypoxia or genetic inactivation of Phd2 (57, 58). This evidence concerns the gene EPAS1 and pulmonary hypertension.