Polymorphisms in the prostaglandin E2 receptor subtype 2 gene confer susceptibility to aspirin-intolerant asthma: a candidate gene approach

Abstract

Aspirin-intolerant asthma (AIA) is a subtype of bronchial asthma characterized by development of bronchoconstriction evoked by non-steroidal anti-inflammatory drugs (NSAIDs). NSAIDs inhibit the cyclooxygenase pathway, leading to enhancement of the lipoxygenase pathway. We evaluated allelic association of 370 single nucleotide polymorphisms (SNPs) of 63 candidate genes, mostly from the arachidonic acid metabolic cascade, with AIA. After two rounds of screening with 198 AIA patients, multiple SNPs in the prostaglandin E(2) receptor subtype 2 (EP2) gene were associated with AIA (P<0.05). Among the 77 SNPs identified in the EP2 gene, we selected 17 SNPs on the basis of linkage disequilibrium and allelic frequencies (minor allele frequency >0.1) for further association study. SNPs in the promoter region of the EP2 gene, uS5, uS5b, and uS7, were significantly associated with AIA (permutation P=0.039-0.001). Analysis of haplotypes constructed according to the LD pattern showed a significant association with AIA (permutation P=0.001). The most significantly associated SNP, uS5, located in the regulatory region of the EP2 gene, was in a STATs-binding consensus sequence [AIA 31.1% versus control 22.1% (permutation P=0.0016) or versus aspirin-tolerant asthma 22.2% (permutation P=0.0017)]. Although STAT1 binding was not observed in gel mobility shift assay with HeLa nuclear extract, an unidentified protein was specifically bound to the allelic sequence. In in vitro reporter assay in HCT116 cells, the site containing the uS5 allele showed reduced transcription activity. Taken together, these results suggest that uS5 allele serves as a target of a transcription repressor protein. A functional SNP of the EP2 gene associated with risk of AIA should decrease the transcription level, resulting in reduction of the PGE(2) braking mechanism of inflammation and involvement in the molecular mechanism underlying AIA.

Discovery and verification of functional single nucleotide polymorphisms in regulatory genomic regions: Current and developing technologies

“…The vast majority of known SNPs were identified in comparisons of genome sequences from only a few humans (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20). Resequencing efforts such as the NHLBI Program for Genome Applications and the NIEHS Environmental Genome Project [16] have used larger groups of samples, 24 to 400 or more, with varying degrees of ethnic or racial diversity, but sampling strategies have not been employed to generate a representative population sample.…”

“…1). Indeed, there are numerous examples of rSNPs associated with disease susceptibility, including hypercholesterolemia [10], hyperbilirubinemia [11,12], myocardial infarction [13], acute lung injury [14], and asthma [15].…”

Cysteinyl leukotriene receptor 1 gene variation and risk of asthma

“…However, most reported genetic studies of asthma have examined only one or a few candidate genes in a single study. Only limited studies have systematically examined a large number of candidate genes in relation to asthma or asthma-related phenotypes [4][5][6][7][8][9][10][11].…”

Genetic Association of Low-density Lipoprotein Receptor-related Protein 2 (LRP2) with Plasma Lipid Levels

“…LD for all possible two-way combinations of variations was tested by D' and r 2 16, 17) . Haplotypes were in-ferred, and haplotype frequencies were estimated using the expectation-maximization (EM) method of haplotype inference included in the Arlequin computer program 18) .…”