COL1A1 and systemic sclerosis: To further delineate the roles of key mediators in the Hippo pathway in SSc fibroblasts, we knocked down YAP1, TEAD1, TEAD3, VGLL3, or TEAD1/TEAD3 simultaneously in these cells (Fig. 3p) and measured ACTA2 and COL1A1 levels.