Contrary to these findings, a recent investigation by Tu et al. associated the loss of BMP9, either by deletion or inhibition, with protection against hypoxia and monocrotaline induced PAH; additionally, they described lower mRNA levels of ET-1, and higher levels of ADM, translating a de-regulation of endogenous vasoactive agents (215). The gene discussed is EDN1; the disease is pulmonary arterial hypertension.