CCDC80 and pulmonary arterial hypertension: SMAD6 is connected to endothelin 1 (EDN1) and GZMA. COL1A1, IGF1, and EDN1 have all been associated with the pathophysiology of PAH (Ooi et al., 2010; Pullamsetti et al., 2014; Madonna et al., 2015; McLaughlin et al., 2015), supporting our hypothesis that CCDC80, SMAD6, and GZMA may be involved in the disease pathophysiology.