Smoking Dysregulates the Human Airway Basal Cell Transcriptome at COPD-linked Risk Locus 19q13.2
Rationale: Genome-wide association studies (GWAS) and candidate gene studies have identified a number of loci linked to susceptibility of chronic obstructive pulmonary disease (COPD), a smoking-related disorder that originates in the airway epithelium. Objectives: Since airway basal cell (BC) stem/progenitor cells exhibit the earliest abnormalities associated with smoking (hyperplasia, squamous metaplasia), we hypothesized that smoker BC have a dysregulated transcriptome linked, in part, to known GWAS/candidate gene loci. Methods: Massive parallel RNA sequencing was used to compare the transcriptome of BC purified from the airway epithelium of healthy nonsmokers (n=10) and smokers (n=7). The chromosomal location of the differentially expressed genes was compared to loci identified by GWAS and candidate gene studies to confer risk for COPD. Measurements and Main Results: Smoker BC have 676 known genes differentially expressed compared to nonsmoker BC, dominated by smoking up-regulation. Strikingly, 166 (25%) of these genes are located on chromosome 19, with 13 localized to 19q13.2 (p<10-4 compared to chance), including TGFB1, LTBP4, EGLN2 and NFKBIB, genes associated with risk for COPD. Conclusions: These observations provide the first direct link of known genetic risks for smoking-related lung disease with the specific population of lung cells that undergoes the earliest changes associated with smoking. Overall design: The human airway basal cell transcriptome of 7 smokers versus 10 nonsmokers was compared using massive parallel RNA sequencing (Illumina HiSeq 2000).