title: The MicroRNA 29 Family Promotes Type II Cell Differentiation in Developing Lung.
abstract: Lung alveolar type II cells uniquely synthesize surfactant, a developmentally regulated lipoprotein that is essential for breathing. Expression of the gene (SFTPA) encoding the major surfactant protein, SP-A, in midgestation human fetal lung (HFL) is dramatically induced by cyclic AMP (cAMP). cAMP induction of SP-A expression is repressed by transforming growth factor β (TGF-β) and by hypoxia. In this study, we found that expression of the microRNA 29 (miR-29) family was significantly upregulated in epithelial cells isolated from mouse fetal lung during late gestation and in epithelial cells isolated from HFL explants during type II cell differentiation in culture. miR-29 expression in cultured HFL epithelial cells was increased by cAMP and inhibited by hypoxia, whereas the miR-29 target, TGF-β2, was coordinately decreased. Knockdown of the miR-29 family in cultured HFL type II cells blocked cAMP-induced SP-A expression and accumulation of surfactant-containing lamellar bodies, suggesting their physiological relevance. This occurred through derepression of TGF-β signaling. Notably, cAMP increased binding of endogenous thyroid transcription factor 1 (TTF-1/Nkx2.1) to the miR-29ab1 promoter in HFL type II cells, and TTF-1 increased miR-29ab1 promoter-driven luciferase activity in cotransfection assays. Together, these findings identify miR-29 family members as TTF-1-driven mediators of SP-A expression and type II cell differentiation through repression of TGF-β signaling.
authors.affiliation: Departments of Biochemistry and Obstetrics and Gynecology, North Texas March of Dimes Birth Defects Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Guo
authors.affiliation: Departments of Biochemistry and Obstetrics and Gynecology, North Texas March of Dimes Birth Defects Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
authors.forename: Houda
authors.initials: H
authors.lastname: Benlhabib
authors.affiliation: Departments of Biochemistry and Obstetrics and Gynecology, North Texas March of Dimes Birth Defects Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA carole.mendelson@utsouthwestern.edu.
authors.forename: Carole R
authors.initials: CR
authors.lastname: Mendelson
mesh_terms: D000072283:A549 Cells; D056809:Alveolar Epithelial Cells / Q000166:cytology*; D000818:Animals; D002454:Cell Differentiation; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D008168:Lung / Q000166:cytology / Q000196:embryology*; D051379:Mice; D035683:MicroRNAs / Q000235:genetics*; D009687:Nuclear Proteins / Q000235:genetics*; D011401:Promoter Regions, Genetic; D015398:Signal Transduction; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors / Q000235:genetics*; D016212:Transforming Growth Factor beta / Q000378:metabolism; D015854:Up-Regulation
chemical_list: C547014:MIRN29 microRNA, mouse; C532045:MIRN29a microRNA, human; D035683:MicroRNAs; C000614412:NKX2-1 protein, human; C000614414:Nkx2-1 protein, mouse; D009687:Nuclear Proteins; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D000242:Cyclic AMP