RAB20 and pulmonary fibrosis: As revealed by H&E and Masson staining, RAB20-deficient mice exhibited many more contiguous fibrotic masses and air bubbles, and greater fibrous obliteration as compared to RAB20 knockdown mice and their WT controls (Figures 2C, D), indicating that deletion of RAB20 markedly promoted silica crystal-induced pulmonary interstitial fibrosis.