HIF2α expression is significantly increased in cultured primary endothelial cells of Irp1-/- mice, and endothelin-1 expression is also significantly increased in lung tissues of Irp1-/- mice, supporting a pathogenic role of these molecules in the pulmonary hypertension (Ghosh et al., 2013). The gene discussed is EPAS1; the disease is pulmonary arterial hypertension.