They also reinforce the idea that the effect of these genes on the regulation of vascular tone is primarily due to alterations in vasodilation rather than vascular contraction, although it might be interesting to investigate the outcome in response to serotonin in endoglin-deficient mice in case it contributes to the relationship between endoglin and pulmonary hypertension. The gene discussed is ENG; the disease is pulmonary arterial hypertension.