YAP1 and pulmonary arterial hypertension: Extracellular matrix stiffness, which is an early pathologic event in PAH, stimulates the proliferation of pulmonary ECs and SMCs due to the induction of GLS1 by the two transcriptional co-activators Yes Associate Protein 1 (YAP) and Transcriptional Coactivator with PDZ-Binding Motif (TAZ) [12].