Several EGR1 downstream genes, such as periostin (POSTN), tenascin C (TNC), fibronectin (FN1), and transforming growth factor beta 2 (TGFB2), were highly expressed in the diseased hearts of iPAH and CTEPH patients (Figure 4E). This evidence concerns the gene FN1 and chronic thromboembolic pulmonary hypertension.