Quality controls were performed as described previously.6 The Cochran-Armitage trend test was used to test for association between each SNP and disease status by using PLINK.7 AÂ linear regression ...analysis was performed to test for associations between individual genetic markers and log-adjusted total serum IgE (tIgE) concentrations and log-adjusted Eczema Area and Severity Index (EASI) scores, and a multiple logistic regression model was used to test for SNP-SNP interactions among cases only between TSLP and its receptors by using SAS version 9.1 software (SAS Institute, Inc, Cary, NC).
Background Asthma is a complex disease characterized by striking ethnic disparities not explained entirely by environmental, social, cultural, or economic factors. Of the limited genetic studies ...performed on populations of African descent, notable differences in susceptibility allele frequencies have been observed. Objectives We sought to test the hypothesis that some genes might contribute to the profound disparities in asthma. Methods We performed a genome-wide association study in 2 independent populations of African ancestry (935 African American asthmatic cases and control subjects from the Baltimore–Washington, DC, area and 929 African Caribbean asthmatic subjects and their family members from Barbados) to identify single-nucleotide polymorphisms (SNPs) associated with asthma. Results A meta-analysis combining these 2 African-ancestry populations yielded 3 SNPs with a combined P value of less than 10−5 in genes of potential biologic relevance to asthma and allergic disease: rs10515807, mapping to the α-1B-adrenergic receptor (ADRA1B) gene on chromosome 5q33 (3.57 × 10−6 ); rs6052761, mapping to the prion-related protein (PRNP) gene on chromosome 20pter-p12 (2.27 × 10−6 ); and rs1435879, mapping to the dipeptidyl peptidase 10 (DPP10) gene on chromosome 2q12.3-q14.2. The generalizability of these findings was tested in family and case-control panels of United Kingdom and German origin, respectively, but none of the associations observed in the African groups were replicated in these European studies. Evidence for association was also examined in 4 additional case-control studies of African Americans; however, none of the SNPs implicated in the discovery population were replicated. Conclusions This study illustrates the complexity of identifying true associations for a complex and heterogeneous disease, such as asthma, in admixed populations, especially populations of African descent.
Background Loss-of-function null mutations R501X and 2282del4 in the skin barrier gene, filaggrin ( FLG ), represent the most replicated genetic risk factors for atopic dermatitis (AD). Associations ...have not been reported in African ancestry populations. Atopic dermatitis eczema herpeticum (ADEH) is a rare but serious complication of AD resulting from disseminated cutaneous herpes simplex virus infections. Objective We aimed to determine whether FLG polymorphisms contribute to ADEH susceptibility. Methods Two common loss-of-function mutations plus 9 FLG single nucleotide polymorphisms were genotyped in 278 European American patients with AD, of whom 112 had ADEH, and 157 nonatopic controls. Replication was performed on 339 African American subjects. Results Significant associations were observed for both the R501X and 2282del4 mutations and AD among European American subjects ( P = 1.46 × 10−5 , 3.87 × 10−5 , respectively), but the frequency of the R501X mutation was 3 times higher (25% vs 9%) for ADEH than for AD without eczema herpeticum (EH) (odds ratio OR, 3.4; 1.7-6.8; P = .0002). Associations with ADEH were stronger with the combined null mutations (OR, 10.1; 4.7-22.1; P = 1.99 × 10−11 ). Associations with the R501X mutation were replicated in the African American population; the null mutation was absent among healthy African American subjects, but present among patients with AD (3.2%; P = .035) and common among patients with ADEH (9.4%; P = .0049). However, the 2282del4 mutation was absent among African American patients with ADEH and rare (<1%) among healthy individuals. Conclusion The R501X mutation in the gene encoding filaggrin, one of the strongest genetic predictors of AD, confers an even greater risk for ADEH in both European and African ancestry populations, suggesting a role for defective skin barrier in this devastating condition.
PDF