In 2009, Li et al. reported that human pulmonary hypertension could be characterized by the overexpression of NOTCH3 (OMIM 600276) in small pulmonary artery smooth muscle cells (SMCs), and that the severity of the disease in humans and rodents is correlated with the amount of NOTCH3 protein in the lungs (Li et al. 2009). Here, NOTCH3 is linked to pulmonary arterial hypertension.