HEY2 and pulmonary arterial hypertension: In our PAH transcriptomic analysis, HPV and HCV infection might be important in PAH pathogenesis, which may interact with specific membrane receptors or viral proteins (HPV-E6, HCV-NS5A, and HCV-CORE) to activate MAPK and NOTCH signaling pathways, and in turn to regulate TF expression like IRF9, BLC6, HEY2, and RXRG (Figure 5).