Yang et al. (2013a) compared the development of bleomycin-induced lung fibrosis in wild-type and miR-145-/- mice and found that miR-145-/- mice lungs had diminished collagen deposition, reduced expression of α-SMA and increased expression of kruppel-like factor 4 (KLF4), a negative regulator of α-SMA, suggesting pro-fibrotic role of miR-145. The gene discussed is KLF4; the disease is pulmonary fibrosis.