ECFCs represent an accessible surrogate cell type to study endothelial dysfunction in PAH and display several characteristics of the disease, including reduced BMPRII expression, disorganized angiogenesis, increased permeability, increased HIF and NF-κB activation, which also represent responses augmented by CLIC4/Arf6 signaling. Here, BMPR2 is linked to pulmonary arterial hypertension.