However, in both Eng+/- and Alk1+/- lungs, the levels of the major pro-angiogenic and vascular regulator VEGF were unchanged when compared to WT mice, suggesting that factors other than VEGF are implicated in modulation of the tissue angiogenic–angiostatic balance in these mouse models of HHT. Here, ACVRL1 is linked to hereditary hemorrhagic telangiectasia.