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Background: Previous haplotype‐based association studies identified chromosome 4q21 as an allergic rhinitis (AR) susceptibility locus; however, the functional role of 4q21 single nucleotide polymorphisms (SNPs) on AR risk remains unclear. Objective: To investigate the functional effect of 4q21 SNPs on AR risk by conducting cohort‐based functional genomics and genetic association analyses. Methods: The associations between 4q21 SNPs and mRNA expression levels of three 4q21‐associated genes (SDAD1, NAAA and CXCL9) in peripheral blood mononuclear cells (PBMCs) were assessed in a Singapore/Malaysia Chinese cohort (n = 291). Exon expression levels of these genes in PBMCs were tested against the tag‐SNP genotypes in a Singapore Chinese cohort (n = 30). Serum protein levels of these genes were assessed with tag‐SNP genotypes in a Singapore Chinese cohort (n = 193). SNP functions were characterized through luciferase assay. In a Singapore Chinese cohort (n = 1794), we confirmed the associations between functional SNPs and AR. Results: Forty SNPs in 4q21 showed significant associations with NAAA (but not SDAD1 or CXCL9) mRNA expression in PBMCs, of which were tagged by two tag‐SNPs, rs17001237 and rs2242470. Both tag‐SNPs rs2242470 and rs12648687 (a proxy for rs17001237) were also significantly associated with the expression level of NAAA exon 1. Tag‐SNP rs12648687 was correlated with serum NAAA level. A four promoter SNPs‐haplotype tagged by rs17001237 influenced the NAAA promoter activity in HEK293T cells. Lastly, individuals carrying the risk allele A of rs12648687 exhibited significantly higher AR risk in the Singapore Chinese population. Conclusions & Clinical Relevance: The rs17001237 linkage set SNPs in the 4q21 locus are associated with NAAA expression at both gene and protein levels ex vivo, have functional consequences in vitro and contribute to AR susceptibility in our study population. Our findings provided a better understanding of the genetic mechanism that contributes to AR pathogenesis. [ABSTRACT FROM AUTHOR]

Background: The polymorphism Arg16 in β2‐adrenergic receptor (ADRB2) gene has been associated with an increased risk of exacerbations in asthmatic children treated with long‐acting β2‐agonists (LABA). However, it remains unclear whether this increased risk is mainly attributed to this single variant or the combined effect of the haplotypes of polymorphisms at codons 16 and 27. Objective: We assessed whether the haplotype analysis could explain the association between the polymorphisms at codons 16 (Arg16Gly) and 27 (Gln27Glu) in ADRB2 and risk of asthma exacerbations in patients treated with inhaled corticosteroids (ICS) plus LABA. Methods: The study was undertaken using data from 10 independent studies (n = 5903) participating in the multi‐ethnic Pharmacogenomics in Childhood Asthma (PiCA) consortium. Asthma exacerbations were defined as asthma‐related use of oral corticosteroids or hospitalizations/emergency department visits in the past 6 or 12 months prior to the study visit/enrolment. The association between the haplotypes and the risk of asthma exacerbations was performed per study using haplo.stats package adjusted for age and sex. Results were meta‐analysed using the inverse variance weighting method assuming random‐effects. Results: In subjects treated with ICS and LABA (n = 832, age: 3–21 years), Arg16/Gln27 versus Gly16/Glu27 (OR: 1.40, 95% CI: 1.05–1.87, I2 = 0.0%) and Arg16/Gln27 versus Gly16/Gln27 (OR: 1.43, 95% CI: 1.05–1.94, I2 = 0.0%), but not Gly16/Gln27 versus Gly16/Glu27 (OR: 0.99, 95% CI: 0.71–1.39, I2 = 0.0%), were significantly associated with an increased risk of asthma exacerbations. The sensitivity analyses indicated no significant association between the ADRB2 haplotypes and asthma exacerbations in the other treatment categories, namely as‐required short‐acting β2‐agonists (n = 973), ICS monotherapy (n = 2623), ICS plus leukotriene receptor antagonists (LTRA; n = 338), or ICS plus LABA plus LTRA (n = 686). Conclusion and clinical relevance: The ADRB2 Arg16 haplotype, presumably mainly driven by the Arg16, increased the risk of asthma exacerbations in patients treated with ICS plus LABA. This finding could be beneficial in ADRB2 genotype‐guided treatment which might improve clinical outcomes in asthmatic patients. [ABSTRACT FROM AUTHOR]