A genome-wide association study on frequent exacerbation of asthma depending on smoking status.

PURPOSE:Exacerbation of asthma is affected by genetic and environmental factors, but little is known about genetic differences according to smoking status. We evaluated genetic factors associated with asthma exacerbations in smokers and non-smokers, and identified the underlying mechanisms via a genome-wide association study (GWAS) and gene-level analyses according to smoking status. METHODS:A GWAS on the annual frequency of asthma exacerbations was performed in 420 non-smoking and 188 smoking patients with asthma. Gene-wise associations were analyzed by Multi-marker Analysis of GenoMic Annotation (MAGMA); Gene Ontology analysis was also performed. RESULTS:In the non-smoker group, 189 genes showed significant associations with the annual frequency of exacerbations (permutated P < 0.001). The top 10 genes were F5, KLRC1, TAFA2, AIRE, IER3IP1, CHMP2A, IL31RA, ZNF497, DNMT3L, and MYT1L (permutated P = 1.0 × 10-4 - 1.7 × 10-4). In smoking asthmatics, 140 genes-including KANK1, ZMYND12, ZNF34, ANXA11, VAV2, CCDC150, CCDC30, CATSPER3, ARMH2, and MPRIP (permutated P = 9.23 × 10-5 - 5.50 × 10-4)-were associated with asthma exacerbations. Genes participating in the innate immune response in non-smokers and the regulation of cell fate (including apoptosis) in smokers were the major causal genes of asthma exacerbation (FDR q < 0.05). CONCLUSIONS:Our findings not only suggest novel genetic candidates for predicting asthma exacerbations, but also that asthma treatment strategies should take into account smoking behavior.