Dataset Information

A genome-wide association study on African-ancestry populations for asthma.

ABSTRACT:

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 alpha-1B-adrenergic receptor (ADRA1B) gene on chromosome 5q33 (3.57 x 10(-6)); rs6052761, mapping to the prion-related protein (PRNP) gene on chromosome 20pter-p12 (2.27 x 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.

SUBMITTER: Mathias RA

PROVIDER: S-EPMC3606015 | biostudies-literature | 2010 Feb

REPOSITORIES: biostudies-literature

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Publications

A genome-wide association study on African-ancestry populations for asthma.

Mathias Rasika A RA Grant Audrey V AV Rafaels Nicholas N Hand Tracey T Gao Li L Vergara Candelaria C Tsai Yuhjung J YJ Yang Mao M Campbell Monica M Foster Cassandra C Gao Peisong P Togias A A Hansel Nadia N NN Diette Gregory G Adkinson N Franklin NF Liu Mark C MC Faruque Mezbah M Dunston Georgia M GM Watson Harold R HR Bracken Michael B MB Hoh Josephine J Maul Pissamai P Maul Trevor T Jedlicka Anne E AE Murray Tanda T Hetmanski Jacqueline B JB Ashworth Roxann R Ongaco Chrissie M CM Hetrick Kurt N KN Doheny Kimberly F KF Pugh Elizabeth W EW Rotimi Charles N CN Ford Jean J Eng Celeste C Burchard Esteban G EG Sleiman Patrick M A PM Hakonarson Hakon H Forno Erick E Raby Benjamin A BA Weiss Scott T ST Scott Alan F AF Kabesch Michael M Liang Liming L Abecasis Gonçalo G Moffatt Miriam F MF Cookson William O C WO Ruczinski Ingo I Beaty Terri H TH Barnes Kathleen C KC

The Journal of allergy and clinical immunology 20091111 2

<h4>Background</h4>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.<h4>Objectives</h4>We sought to test the hypothesis that some genes might contribute to the profound disparities in asthma.<h4>Methods</h4>We performed a genome-wide associatio ...[more]

PMID: 19910028

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Project description:Central obesity, measured by waist circumference (WC) or waist-hip ratio (WHR), is a marker of body fat distribution. Although obesity disproportionately affects minority populations, few studies have conducted genome-wide association study (GWAS) of fat distribution among those of predominantly African ancestry (AA). We performed GWAS of WC and WHR, adjusted and unadjusted for BMI, in up to 33,591 and 27,350 AA individuals, respectively. We identified loci associated with fat distribution in AA individuals using meta-analyses of GWA results for WC and WHR (stage 1). Overall, 25 SNPs with single genomic control (GC)-corrected p-values<5.0 × 10(-6) were followed-up (stage 2) in AA with WC and with WHR. Additionally, we interrogated genomic regions of previously identified European ancestry (EA) WHR loci among AA. In joint analysis of association results including both Stage 1 and 2 cohorts, 2 SNPs demonstrated association, rs2075064 at LHX2, p = 2.24×10(-8) for WC-adjusted-for-BMI, and rs6931262 at RREB1, p = 2.48×10(-8) for WHR-adjusted-for-BMI. However, neither signal was genome-wide significant after double GC-correction (LHX2: p = 6.5 × 10(-8); RREB1: p = 5.7 × 10(-8)). Six of fourteen previously reported loci for waist in EA populations were significant (p<0.05 divided by the number of independent SNPs within the region) in AA studied here (TBX15-WARS2, GRB14, ADAMTS9, LY86, RSPO3, ITPR2-SSPN). Further, we observed associations with metabolic traits: rs13389219 at GRB14 associated with HDL-cholesterol, triglycerides, and fasting insulin, and rs13060013 at ADAMTS9 with HDL-cholesterol and fasting insulin. Finally, we observed nominal evidence for sexual dimorphism, with stronger results in AA women at the GRB14 locus (p for interaction = 0.02). In conclusion, we identified two suggestive loci associated with fat distribution in AA populations in addition to confirming 6 loci previously identified in populations of EA. These findings reinforce the concept that there are fat distribution loci that are independent of generalized adiposity.

Project description:BackgroundFew genetic studies that focus on moderate-to-severe asthma exist. We aimed to identity novel genetic variants associated with moderate-to-severe asthma, see whether previously identified genetic variants for all types of asthma contribute to moderate-to-severe asthma, and provide novel mechanistic insights using expression analyses in patients with asthma.MethodsIn this genome-wide association study, we used a two-stage case-control design. In stage 1, we genotyped patient-level data from two UK cohorts (the Genetics of Asthma Severity and Phenotypes [GASP] initiative and the Unbiased BIOmarkers in PREDiction of respiratory disease outcomes [U-BIOPRED] project) and used data from the UK Biobank to collect patient-level genomic data for cases and controls of European ancestry in a 1:5 ratio. Cases were defined as having moderate-to-severe asthma if they were taking appropriate medication or had been diagnosed by a doctor. Controls were defined as not having asthma, rhinitis, eczema, allergy, emphysema, or chronic bronchitis as diagnosed by a doctor. For stage 2, an independent cohort of cases and controls (1:5) was selected from the UK Biobank only, with no overlap with stage 1 samples. In stage 1 we undertook a genome-wide association study of moderate-to-severe asthma, and in stage 2 we followed up independent variants that reached the significance threshold of p less than 1 × 10-6 in stage 1. We set genome-wide significance at p less than 5 × 10-8. For novel signals, we investigated their effect on all types of asthma (mild, moderate, and severe). For all signals meeting genome-wide significance, we investigated their effect on gene expression in patients with asthma and controls.FindingsWe included 5135 cases and 25 675 controls for stage 1, and 5414 cases and 21 471 controls for stage 2. We identified 24 genome-wide significant signals of association with moderate-to-severe asthma, including several signals in innate or adaptive immune-response genes. Three novel signals were identified: rs10905284 in GATA3 (coded allele A, odds ratio [OR] 0·90, 95% CI 0·88-0·93; p=1·76 × 10-10), rs11603634 in the MUC5AC region (coded allele G, OR 1·09, 1·06-1·12; p=2·32 × 10-8), and rs560026225 near KIAA1109 (coded allele GATT, OR 1·12, 1·08-1·16; p=3·06 × 10-9). The MUC5AC signal was not associated with asthma when analyses included mild asthma. The rs11603634 G allele was associated with increased expression of MUC5AC mRNA in bronchial epithelial brush samples via proxy SNP rs11602802; (p=2·50 × 10-5) and MUC5AC mRNA was increased in bronchial epithelial samples from patients with severe asthma (in two independent analyses, p=0·039 and p=0·022).InterpretationWe found substantial shared genetic architecture between mild and moderate-to-severe asthma. We also report for the first time genetic variants associated with the risk of developing moderate-to-severe asthma that regulate mucin production. Finally, we identify candidate causal genes in these loci and provide increased insight into this difficult to treat population.FundingAsthma UK, AirPROM, U-BIOPRED, UK Medical Research Council, and Rosetrees Trust.

Dataset Information

A genome-wide association study on African-ancestry populations for asthma.

Background

Objectives

Methods

Results

Conclusions

Publications

A genome-wide association study on African-ancestry populations for asthma.

Similar Datasets

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