Enhanced transforming growth factor (TGF) - signaling contributes to idiopathic pulmonary fibrosis (IPF), a progressive and fatal disease characterized by alveolar epithelial type II (ATII) cell hyperplasia, (myo)fibroblast accumulation, and excessive extracellular matrix deposition. TGF- is a potent inducer of lung fibrosis, and it regulates the ATII cell phenotype; however, direct TGF- target genes controlling the ATII cell phenotype remain elusive. Here, we identified the transgelin (tagln) gene as a novel immediate target of TGF-/Smad3-dependent gene expression in ATII cells using a Smad3 chromatin immunoprecipitation (ChIP) screen. Direct ChIP confirmed the rapid and specific binding of Smad3 to the tagln promoter. Luciferase assays demonstrated transactivation of the tagln promoter by activin-like kinase (Alk) 5-mediated TGF- signaling. TGF- treatment resulted in rapid up-regulation of tagln, but not tagln2, mRNA and protein expression, assessed by reverse transcription-polymerase chain reaction (RT-PCR), Western blotting, and immunofluorescence. In vivo, tagln expression was significantly increased in ATII cells of mice during bleomycin-induced lung fibrosis, as well as in lung specimen obtained from IPF patients, as assessed by RT-PCR and immunohistochemistry. Knockdown of tagln using siRNA inhibited TGF--induced migration of lung epithelial A549 cells, as well as primary ATII cells. We thus identified tagln as a novel target of TGF-/Smad3-dependent gene expression in ATII cells. Increased ATII cell expression of tagln in experimental and idiopathic pulmonary fibrosis may contribute to TGF--dependent ATII cell injury, repair, and migration in lung fibrosis.—Yu, H., Königshoff, M., Jayachandran, A., Handley, D., Seeger, W., Kaminski, N., Eickelberg, O. Transgelin is a direct target of TGF-/Smad3-dependent epithelial cell migration in lung fibrosis.