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Genotype-Smoking Environment Interactions affecting eQTL in the Human Lung

ABSTRACT: Background: Cases where genotype-phenotype relationships depend on environmental factors have been quantified for many complex diseases. Such genotype-environment interactions (GEI or GxE) may also affect expression Quantitative Trait Loci (eQTL) present in tissues critical for the manifestation of disease. To assess this hypothesis, we performed an analysis of eQTL-GEI resulting from an individual's smoking environment in the lung small airway epithelium (SAE). While the SAE is challenging to sample, this is the cell population that shows the first signs of smoking related stress and gene expression in the SAE appears to play a role in mediating smoking effects on lung disease. Results: We used expression microarrays to assay the SAE transcriptome for a small sample of African-American individuals and we analyzed SNPs genotyped genome-wide to identify GEI affecting eQTL. While a genome-wide trans- analysis identified few instances of GEI after a multiple test correction, an analysis of cis-genotypes identified a small but significant number of GEI affecting lung SAE gene expression. We determined that significant cases of eQTL-GEI were not driven by outliers and we were also able to find corroborative evidence for a few of these eQTL-GEI in a small, independent sample of individuals of European ancestry. Conclusion: Given that the power of GEI tests is low compared to tests of genotype association and that the total sample size of our study was small, including only 61 African American individuals in our focal population, the identification of significant GEI in our study implies that there may be considerable genotype-specific effects on eQTL due to smoking environment. We discuss individual cases of GEI of interest for lung disease, such as SDC1 and ZAK, as well as the broader implications of our results for the analysis of eQTL and for genome-wide association analysis of complex diseases.

ORGANISM(S): Homo sapiens

PROVIDER: GSE23087 | GEO | 2024/06/05

REPOSITORIES: GEO

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Project description: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. The small airway epithelium (SAE) is the major site of lung disease caused by smoking, and the cell population that exhibits the earliest manifestations of smoking-induced disease. This study used RNA-Seq to sequence all polyA+ mRNAs expressed by the SAE of 5 healthy nonsmokers to gain new insights into the biology of the SAE, and evaluate how these cells respond to cigarette smoke using 6 healthy smoker samples (SRA029282.1). 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. Coverage of RNA-Seq expression was also compared to the HG-U133 Plus 2.0 microarray expression of 27 previously published healthy nonsmoker samples presented here.

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Genotype-Smoking Environment Interactions affecting eQTL in the Human Lung

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