RNA-Seq Quantification of the Transcriptome of Genes Expressed in the Small Airway Epithelium of Nonsmokers and Smokers

The small airway epithelium (SAE) the pseudostratified epithelium that covers the majority of the human airway surface from the 6th generation to the alveoli, is the major site of lung disease caused by smoking, and the cell population that exhibits the earliest manifestations of smoking-induced disease. The focus of this study is to use RNA-Seq (massive parallel sequencing technology) to sequence all polyA+ mRNAs expressed by the SAE of healthy nonsmokers to gain new insights into the biology of the SAE, and how these cells respond to cigarette smoke. Taking advantage of RNA-Seq providing quantitative mRNA levels, that data demonstrates that while the SAE shares its transcriptome with many cell types, it has unique characteristics that are enriched in this cell population, with the mostly highly expressed genes (SCGB1A1) characteristics of Clara cells, an airway epithelial cell unique to the human small airways. Among other genes expressed by the SAE are those characteristic of ciliated and mucin-producing cells, basal cells and neuroendocrine cells. The RNA-Seq data includes identification of the highly expressed SAE transcription factors, transmembrane receptors, signaling ligands and growth factors. RNA-Seq permitted quantification of expression of highly homologous gene families, the absolute smoking-induced changes in SAE gene expression, including genes expressed at low levels, and assessment of the effect of smoking on SAE gene splicing. Together, these observations can serve as the baseline for assessment of the dysregulation of SAE gene expression in human airway disease.

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Hackett NR, Butler MW, Shaykhiev R, Salit J, Omberg L, Rodriguez-Flores JL, Mezey JG, Strulovici-Barel Y, Wang G, Didon L, Crystal RG