OR53-5 Surfactant protein A (SP-A) Expression is Regulated by microRNAs 199a-3p and -5p

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: OR53-Transcriptional Regulators & Epigenetic Control
Tuesday, June 18, 2013: 9:15 AM-10:45 AM
Presentation Start Time: 10:15 AM
Room 133 (Moscone Center)
Houda Benlhabib*1, Brianne Pierce2, Wei Guo1 and Carole R Mendelson3
1University of Texas Southwestern Med Ctr, Dallas, TX, 2Kansas State University, Manhattan, KS, 3University of Texas Southwestern Med Ctr, Dallas, TX
SP-A, the major surfactant protein, is developmentally regulated in fetal lung and serves as a molecular marker of type II pneumocyte differentiation and surfactant lipoprotein synthesis. Developmental induction of SP-A gene transcription in fetal lung is mediated by increased binding of Nkx2.1/TTF-1 and NF-κB to a common site in the SP-A promoter, and with permissive changes in histone modification. SP-A expression in cultured fetal lung explants and type II cells is upregulated by hormones and factors (e.g. prostaglandins) that increase cAMP and is inhibited by hypoxia. To further define mechanisms for type II cell differentiation and developmental induction of SP-A, we are investigating the roles of microRNAs (miRNAs, miRs). miRNAs are evolutionarily conserved ~22 nucleotide, single-stranded noncoding RNAs that inhibit gene expression by binding to the 3’-untranslated regions of their target mRNAs through base-pairing. This results in inhibition of mRNA translation and/or increased mRNA degradation. To identify miRNAs differentially regulated during differentiation of mid-gestation human fetal in culture, we performed miRNA microarray analysis of RNA from epithelial cells isolated from human fetal lung explants before and after 48 and 96 h of culture ± Bt2cAMP. Two miRNAs significantly downregulated during type II cell differentiation, hsa-miR-199a-5p and hsa-miR-199a-3p, are synthesized as part of a 6-kb anti-sense transcript of the Dynamin 3 gene (Dnm3os). Known targets of hsa-miR-199a-3p and -5p include COX-2, NF-κB (p50) and inhibitor of κB kinase (IKKβ), factors found to positively regulate SP-A expression in human fetal lung. Interestingly, overexpression of miR-199a-5p and -3p in cultured type II cells significantly blocked cAMP stimulation of SP-A expression. Moreover, mRNA and protein expression of the miR-199-3p target, COX-2, were undetectable in the human fetal lung epithelium before culture and were rapidly induced in association with the decline in miR-199a-3p expression. Interestingly, miR-199-5p and -3p were upregulated by hypoxia, which blocks cAMP induction of SP-A expression. Collectively, these findings suggest that the decline in miR-199a-3p and -5p during type II cell differentiation serves a permissive role in the induction of SP-A expression, possibly through de-repression of NF-κB activation and COX-2 expression.

Nothing to Disclose: HB, BP, WG, CRM

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm

Sources of Research Support: NIH R01-HL050022