Celedón, Juan C.

Abstract Background Asthma exacerbations are a serious public health concern due to high healthcare resource utilization, work/school productivity loss, impact on quality of life, and risk of mortality. The genetic basis of asthma exacerbations has been studied in several populations, but no prior study has performed a multi‐ancestry meta‐analysis of genome‐wide association studies (meta‐GWAS) for this trait. We aimed to identify common genetic loci associated with asthma exacerbations across diverse populations and to assess their functional role in regulating DNA methylation and gene expression. Methods A meta‐GWAS of asthma exacerbations in 4989 Europeans, 2181 Hispanics/Latinos, 1250 Singaporean Chinese, and 972 African Americans analyzed 9.6 million genetic variants. Suggestively associated variants ( p ≤ 5 × 10 −5 ) were assessed for replication in 36,477 European and 1078 non‐European asthma patients. Functional effects on DNA methylation were assessed in 595 Hispanic/Latino and African American asthma patients and in publicly available databases. The effect on gene expression was evaluated in silico. Results One hundred and twenty‐six independent variants were suggestively associated with asthma exacerbations in the discovery phase. Two variants independently replicated: rs12091010 located at vascular cell adhesion molecule‐1/exostosin like glycosyltransferase‐2 ( VCAM1 / EXTL2 ) (discovery: odds ratio (OR T allele ) = 0.82, p = 9.05 × 10 −6 and replication: OR T allele = 0.89, p = 5.35 × 10 −3 ) and rs943126 from pantothenate kinase 1 ( PANK1 ) (discovery: OR C allele = 0.85, p = 3.10 × 10 −5 and replication: OR C allele = 0.89, p = 1.30 × 10 −2 ). Both variants regulate gene expression of genes where they locate and DNA methylation levels of nearby genes in whole blood. Conclusions This multi‐ancestry study revealed novel suggestive regulatory loci for asthma exacerbations located in genomic regions participating in inflammation and host defense.

Abstract Rationale Patients with severe chronic obstructive pulmonary disease (COPD) may have varying levels of disability despite similar levels of lung function. This variation may reflect different COPD subtypes, which may have different genetic predispositions. Objectives To identify genetic associations for COPD-related phenotypes, including measures of exercise capacity, pulmonary function, and respiratory symptoms. Methods In 304 subjects from the National Emphysema Treatment Trial, we genotyped 80 markers in 22 positional and/or biologically plausible candidate genes. Regression models were used to test for association, using a test–replication approach to guard against false-positive results. For significant associations, effect estimates were recalculated using the entire cohort. Positive associations with dyspnea were confirmed in families from the Boston Early-Onset COPD Study. Results The test–replication approach identified four genes—microsomal epoxide hydrolase (EPHX1), latent transforming growth factor-β binding protein-4 (LTBP4), surfactant protein B (SFTPB), and transforming growth factor-β1 (TGFB1)—that were associated with COPD-related phenotypes. In all subjects, single-nucleotide polymorphisms (SNPs) in EPHX1 (p ⩽ 0.03) and in LTBP4 (p ⩽ 0.03) were associated with maximal output on cardiopulmonary exercise testing. Markers in LTBP4 (p ⩽ 0.05) and SFTPB (p = 0.005) were associated with 6-min walk test distance. SNPs in EPHX1 were associated with carbon monoxide diffusing capacity (p ⩽ 0.04). Three SNPs in TGFB1 were associated with dyspnea (p ⩽ 0.002), one of which replicated in the family study (p = 0.02). Conclusions Polymorphisms in several genes seem to be associated with COPD-related traits other than FEV1. These associations may identify genes in pathways important for COPD pathogenesis.