Using model of excessive accumulation of HIF-1 and HIF-2 proteins by inhibiting HIF prolyl hydroxylase domain-containing protein 2 (PHD2), investigators concluded that mice with EC knockout of PHD2 developed severe pulmonary hypertension and right ventricular failure in a HIF-2 dependent manner, despite excessive accumulations of both HIF-1 and HIF-2 proteins (Kapitsinou et al., 2016). Here, HIF1A is linked to pulmonary arterial hypertension.