To understand the role of MSX1 in PAH lung, we first created an MSX1OE mouse model by pronuclear injection with the construct described in Figure 1A. These Rosa26-rtTA2 × TetO7-Msx1 mice (referred to hereafter as MSX1OE mice) had a roughly 3.7× increase in MSX1 expression when induced (not shown), which resulted in a roughly 2.6× increase in protein levels (Figure 1C,D) in whole lung. This evidence concerns the gene MSX1 and pulmonary arterial hypertension.