YAP1 and pulmonary fibrosis: One of the important genes upregulated in IPAH and downregulated upon HDAC2 knockdown was transcriptional regulator yes-associated protein 1 (YAP1) (Fig. 4F, Supplementary Fig. 3I), which is typically linked to the development of stiffness-dependent remodeling and fibrotic phenotypes in both idiopathic pulmonary fibrosis and pulmonary vascular disease15.