The most definitive evidence supporting the role of bone marrow-derived cells in the development of pulmonary hypertension and pulmonary vascular remodeling comes from recent studies, in which bone marrow chimeric mice were generated from animals with canonical mutations predisposing them to human PAH, including bone morphogenetic protein receptor type II (BMPR2) [32] and calveolin–1 (Cav1) [33]. The gene discussed is BMPR2; the disease is pulmonary hypertension.