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BackgroundAsthma is a common but complex disease with racial/ethnic differences in prevalence, morbidity, and response to therapies.ObjectiveWe sought to perform an analysis of genetic ancestry to identify new loci that contribute to asthma susceptibility.MethodsWe leveraged the mixed ancestry of 3902 Latinos and performed an admixture mapping meta-analysis for asthma susceptibility. We replicated associations in an independent study of 3774 Latinos, performed targeted sequencing for fine mapping, and tested for disease correlations with gene expression in the whole blood of more than 500 subjects from 3 racial/ethnic groups.ResultsWe identified a genome-wide significant admixture mapping peak at 18q21 in Latinos (P=6.8×10-6), where Native American ancestry was associated with increased risk of asthma (odds ratio [OR], 1.20; 95% CI, 1.07-1.34; P=.002) and European ancestry was associated with protection (OR, 0.86; 95% CI, 0.77-0.96; P=.008). Our findings were replicated in an independent childhood asthma study in Latinos (P=5.3×10-3, combined P=2.6×10-7). Fine mapping of 18q21 in 1978 Latinos identified a significant association with multiple variants 5' of SMAD family member 2 (SMAD2) in Mexicans, whereas a single rare variant in the same window was the top association in Puerto Ricans. Low versus high SMAD2 blood expression was correlated with case status (13.4% lower expression; OR, 3.93; 95% CI, 2.12-7.28; P&nbsp

Background IgE is a key mediator of allergic inflammation, and its levels are frequently increased in patients with allergic disorders. Objective We sought to identify genetic variants associated with IgE levels in Latinos. Methods We performed a genome-wide association study and admixture mapping of total IgE levels in 3334 Latinos from the Genes-environments & Admixture in Latino Americans (GALA II) study. Replication was evaluated in 454 Latinos, 1564 European Americans, and 3187 African Americans from independent studies. Results We confirmed associations of 6 genes identified by means of previous genome-wide association studies and identified a novel genome-wide significant association of a polymorphism in the zinc finger protein 365 gene (ZNF365) with total IgE levels (rs200076616, P = 2.3 × 10 −8 ). We next identified 4 admixture mapping peaks (6p21.32-p22.1, 13p22-31, 14q23.2, and 22q13.1) at which local African, European, and/or Native American ancestry was significantly associated with IgE levels. The most significant peak was 6p21.32-p22.1, where Native American ancestry was associated with lower IgE levels ( P = 4.95 × 10 −8 ). All but 22q13.1 were replicated in an independent sample of Latinos, and 2 of the peaks were replicated in African Americans (6p21.32-p22.1 and 14q23.2). Fine mapping of 6p21.32-p22.1 identified 6 genome-wide significant single nucleotide polymorphisms in Latinos, 2 of which replicated in European Americans. Another single nucleotide polymorphism was peak-wide significant within 14q23.2 in African Americans (rs1741099, P = 3.7 × 10 −6 ) and replicated in non–African American samples ( P = .011). Conclusion We confirmed genetic associations at 6 genes and identified novel associations within ZNF365 , HLA-DQA1 , and 14q23.2. Our results highlight the importance of studying diverse multiethnic populations to uncover novel loci associated with total IgE levels.

Background Asthma is a complex disease with both genetic and environmental causes. Genome-wide association studies of asthma have mostly involved European populations, and replication of positive associations has been inconsistent. Objective We sought to identify asthma-associated genes in a large Latino population with genome-wide association analysis and admixture mapping. Methods Latino children with asthma (n = 1893) and healthy control subjects (n = 1881) were recruited from 5 sites in the United States: Puerto Rico, New York, Chicago, Houston, and the San Francisco Bay Area. Subjects were genotyped on an Affymetrix World Array IV chip. We performed genome-wide association and admixture mapping to identify asthma-associated loci. Results We identified a significant association between ancestry and asthma at 6p21 (lowest P value: rs2523924, P −6 ). This association replicates in a meta-analysis of the EVE Asthma Consortium ( P = .01). Fine mapping of the region in this study and the EVE Asthma Consortium suggests an association between PSORS1C1 and asthma. We confirmed the strong allelic association between SNPs in the 17q21 region and asthma in Latinos ( IKZF3 , lowest P value: rs90792, odds ratio, 0.67; 95% CI, 0.61-0.75; P = 6 × 10 −13 ) and replicated associations in several genes that had previously been associated with asthma in genome-wide association studies. Conclusions Admixture mapping and genome-wide association are complementary techniques that provide evidence for multiple asthma-associated loci in Latinos. Admixture mapping identifies a novel locus on 6p21 that replicates in a meta-analysis of several Latino populations, whereas genome-wide association confirms the previously identified locus on 17q21.

RationaleThe burden of asthma is highest among socioeconomically disadvantaged populations; however, its impact is differentially distributed among racial and ethnic groups.ObjectivesTo assess the collective effect of maternal educational attainment, annual household income, and insurance type on childhood asthma among minority, urban youth.MethodsWe included Mexican American (n = 485), other Latino (n = 217), and African American (n = 1,141) children (aged 8-21 yr) with and without asthma from the San Francisco Bay Area. An index was derived from maternal educational attainment, annual household income, and insurance type to assess the collective effect of socioeconomic status on predicting asthma. Logistic regression stratified by racial and ethnic group was used to estimate adjusted odds ratios (aOR) and their 95% confidence intervals (CI). We further examined whether acculturation explained the socioeconomic-asthma association in our Latino population.Measurements and main resultsIn the adjusted analyses, African American children had 23% greater odds of asthma with each decrease in the socioeconomic index (aOR, 1.23; 95% CI, 1.09-1.38). Conversely, Mexican American children have 17% reduced odds of asthma with each decrease in the socioeconomic index (aOR, 0.83; 95% CI, 0.72-0.96) and this relationship was not fully explained by acculturation. This association was not observed in the other Latino group.ConclusionsSocioeconomic status plays an important role in predicting asthma, but has different effects depending on race and ethnicity. Further steps are necessary to better understand the risk factors through which socioeconomic status could operate in these populations to prevent asthma.

Background IgE is both a marker and mediator of allergic inflammation. Despite reported differences in serum total IgE levels by race-ethnicity, African American and Latino subjects have not been well represented in genetic studies of total IgE. Objective We sought to identify the genetic predictors of serum total IgE levels. Methods We used genome-wide association data from 4292 subjects (2469 African Americans, 1564 European Americans, and 259 Latinos) in the EVE Asthma Genetics Consortium. Tests for association were performed within each cohort by race-ethnic group (ie, African American, Latino, and European American) and asthma status. The resulting P values were meta-analyzed, accounting for sample size and direction of effect. Top single nucleotide polymorphism associations from the meta-analysis were reassessed in 6 additional cohorts comprising 5767 subjects. Results We identified 10 unique regions in which the combined association statistic was associated with total serum IgE levels ( P −6 ) and the minor allele frequency was 5% or greater in 2 or more population groups. Variant rs9469220, corresponding to HLA-DQB1 , was the single nucleotide polymorphism most significantly associated with serum total IgE levels when assessed in both the replication cohorts and the discovery and replication sets combined ( P = .007 and 2.45 × 10 −7 , respectively). In addition, findings from earlier genome-wide association studies were also validated in the current meta-analysis. Conclusion This meta-analysis independently identified a variant near HLA-DQB1 as a predictor of total serum IgE levels in multiple race-ethnic groups. This study also extends and confirms the findings of earlier genome-wide association analyses in African American and Latino subjects.

Background Genome-wide association studies of asthma have implicated many genetic risk factors, with well-replicated associations at approximately 10 loci that account for only a small proportion of the genetic risk. Objectives We aimed to identify additional asthma risk loci by performing an extensive replication study of the results from the EVE Consortium meta-analysis. Methods We selected 3186 single nucleotide polymorphisms for replication based on the P values from the EVE Consortium meta-analysis. These single nucleotide polymorphisms were genotyped in ethnically diverse replication samples from 9 different studies, totaling 7202 cases, 6426 controls, and 507 case–parent trios. Association analyses were conducted within each participating study, and the resulting test statistics were combined in a meta-analysis. Results Two novel associations were replicated in European Americans: rs1061477 in the KLK3 gene on chromosome 19 (combined odds ratio = 1.18; 95% CI, 1.10-1.25) and rs9570077 (combined odds ratio =1.20; 95% CI, 1.12-1.29) on chromosome 13q21. We could not replicate any additional associations in the African Americans or Latinos. Conclusions This extended replication study identified 2 additional asthma risk loci in populations of European descent. The absence of additional loci for African Americans and Latinos highlights the difficulty in replicating associations in admixed populations.

Asthma is a common disease with a complex risk architecture including both genetic and environmental factors. We performed a meta-analysis of North American genome-wide association studies of asthma in 5,416 individuals with asthma (cases) including individuals of European American, African American or African Caribbean, and Latino ancestry, with replication in an additional 12,649 individuals from the same ethnic groups. We identified five susceptibility loci. Four were at previously reported loci on 17q21, near IL1RL1, TSLP and IL33, but we report for the first time, to our knowledge, that these loci are associated with asthma risk in three ethnic groups. In addition, we identified a new asthma susceptibility locus at PYHIN1, with the association being specific to individuals of African descent (P = 3.9 × 10(-9)). These results suggest that some asthma susceptibility loci are robust to differences in ancestry when sufficiently large samples sizes are investigated, and that ancestry-specific associations also contribute to the complex genetic architecture of asthma.

Background Epidemiologic studies have demonstrated an association between acute exposure to ambient fine particles and both mortality and morbidity. Less is known about the relative impacts of the specific chemical constituents of particulate matter < 2.5 μm in aerodynamic diameter (PM2.5) on hospital admissions. Objective This study was designed to estimate the risks of exposure to PM2.5 and several species on hospital admissions for respiratory diseases among children. Data and Methods We obtained data on daily counts of hospitalizations for children < 19 and < 5 years of age for total respiratory diseases and several subcategories including pneumonia, acute bronchitis, and asthma for six California counties from 2000 through 2003, as well as ambient concentrations of PM2.5 and its constituents, including elemental carbon (EC), organic carbon (OC), and nitrates (NO3). We used Poisson regression to estimate risks while controlling for important covariates. Results We observed associations between several components of PM2.5 and hospitalization for all of the respiratory outcomes examined. For example, for total respiratory admissions for children < 19 years of age, the interquartile range for a 3-day lag of PM2.5, EC, OC, NO3, and sulfates was associated with an excess risk of 4.1% [95% confidence interval (CI), 1.8–6.4], 5.4% (95% CI, 0.8–10.3), 3.4% (95% CI, 1.1–5.7), 3.3% (95% CI, 1.1–5.5), and 3.0% (95% CI, 0.4–5.7), respectively. We also observed associations for several metals. Additional associations with several of the species, including potassium, were observed in the cool season. Conclusion Components of PM2.5 were associated with hospitalization for several childhood respiratory diseases including pneumonia, bronchitis, and asthma. Because exposure to components (e.g., EC, OC, NO3, and K) and their related sources, including diesel and gasoline exhaust, wood smoke, and other combustion sources, are ubiquitous in the urban environment, it likely represents an identifiable and preventable risk factor for hospitalization for children.

Background Childhood asthma prevalence and morbidity varies among Latinos in the United States, with Puerto Ricans having the highest and Mexicans the lowest. Objective To determine whether genetic ancestry is associated with the odds of asthma among Latinos, and secondarily whether genetic ancestry is associated with lung function among Latino children. Methods We analyzed 5493 Latinos with and without asthma from 3 independent studies. For each participant, we estimated the proportion of African, European, and Native American ancestry using genome-wide data. We tested whether genetic ancestry was associated with the presence of asthma and lung function among subjects with and without asthma. Odds ratios (OR) and effect sizes were assessed for every 20% increase in each ancestry. Results Native American ancestry was associated with lower odds of asthma (OR = 0.72, 95% CI: 0.66-0.78, P = 8.0 × 10 −15 ), while African ancestry was associated with higher odds of asthma (OR = 1.40, 95% CI: 1.14-1.72, P = .001). These associations were robust to adjustment for covariates related to early life exposures, air pollution, and socioeconomic status. Among children with asthma, African ancestry was associated with lower lung function, including both pre- and post-bronchodilator measures of FEV 1 (−77 ± 19 mL; P = 5.8 × 10 −5 and −83 ± 19 mL; P = 1.1 x 10 −5 , respectively) and forced vital capacity (−100 ± 21 mL; P = 2.7 × 10 −6 and −107 ± 22 mL; P = 1.0 x 10 −6 , respectively). Conclusion Differences in the proportions of genetic ancestry can partially explain disparities in asthma susceptibility and lung function among Latinos.

African Americans are disproportionately burdened by asthma. We assessed the individual and joint contribution of socioeconomic status (SES) on asthma morbidity among African American youth.We examined 686 African Americans (8-21 years) with asthma. To account for the joint effects of SES, a composite index was derived from maternal educational attainment, household income, and insurance status. Ordinal logistic regression was used to estimate the individual and joint effect of SES on asthma control. Models were adjusted for age, sex, controller medication use, in utero smoke exposure, family history of asthma, family history of rhinitis, breastfeeding, daycare attendance, and mold exposure.Participants were classified as Poorly Controlled Asthma (40.8%), Partially Controlled Asthma (29.7%), or Controlled Asthma (30.2%). Of the individual SES indicators, low income was the strongest predictor of poor asthma control. Children with low income had worse asthma control than those with higher income (OR 1.39; 95% CI 0.92-2.12). The SES index ranged from 4-9. SES was associated with 17% increased odds of poor asthma control with each decrease in the index (95% CI 1.05-1.32). The SES index was associated with asthma-related symptoms, nocturnal awakenings, limited activity, and missed school days.The negative effects of SES were observed along the entire socioeconomic gradient, and the adverse asthma outcomes observed in African American youth were not limited to the very poor. We also found that the SES index may be a more consistent and useful predictor of poor asthma outcomes than each indicator alone.

Asthma is a complex genetic disease caused by a combination of genetic and environmental risk factors. We sought to test classes of genetic variants largely missed by genome-wide association studies (GWAS), including copy number variants (CNVs) and low-frequency variants, by performing whole-genome sequencing (WGS) on 16 individuals from asthma-enriched and asthma-depleted families. The samples were obtained from an extended 13-generation Hutterite pedigree with reduced genetic heterogeneity due to a small founding gene pool and reduced environmental heterogeneity as a result of a communal lifestyle. We sequenced each individual to an average depth of 13-fold, generated a comprehensive catalog of genetic variants, and tested the most severe mutations for association with asthma. We identified and validated 1960 CNVs, 19 nonsense or splice-site single nucleotide variants (SNVs), and 18 insertions or deletions that were out of frame. As follow-up, we performed targeted sequencing of 16 genes in 837 cases and 540 controls of Puerto Rican ancestry and found that controls carry a significantly higher burden of mutations in IL27RA (2.0% of controls; 0.23% of cases; nominal p = 0.004; Bonferroni p = 0.21). We also genotyped 593 CNVs in 1199 Hutterite individuals. We identified a nominally significant association (p = 0.03; Odds ratio (OR) = 3.13) between a 6 kbp deletion in an intron of NEDD4L and increased risk of asthma. We genotyped this deletion in an additional 4787 non-Hutterite individuals (nominal p = 0.056; OR = 1.69). NEDD4L is expressed in bronchial epithelial cells, and conditional knockout of this gene in the lung in mice leads to severe inflammation and mucus accumulation. Our study represents one of the early instances of applying WGS to complex disease with a large environmental component and demonstrates how WGS can identify risk variants, including CNVs and low-frequency variants, largely untested in GWAS.

Background Atopy varies by ethnicity, even within Latino groups. This variation might be due to environmental, sociocultural, or genetic factors. Objective We sought to examine risk factors for atopy within a nationwide study of US Latino children with and without asthma. Methods Aeroallergen skin test responses were analyzed in 1830 US Latino subjects. Key determinants of atopy included country/region of origin, generation in the United States, acculturation, genetic ancestry, and site to which subjects migrated. Serial multivariate zero-inflated negative binomial regressions stratified by asthma status examined the association of each key determinant variable with the number of positive skin test responses. In addition, the independent effect of each key variable was determined by including all key variables in the final models. Results In baseline analyses African ancestry was associated with 3 times (95% CI, 1.62-5.57) as many positive skin test responses in asthmatic participants and 3.26 times (95% CI, 1.02-10.39) as many positive skin test responses in control participants. Generation and recruitment site were also associated with atopy in crude models. In final models adjusted for key variables, asthmatic patients of Puerto Rican (exp[β] [95% CI], 1.31 [1.02-1.69]) and mixed (exp[β] [95% CI], 1.27 [1.03-1.56]) ethnicity had a greater probability of positive skin test responses compared with Mexican asthmatic patients. Ancestry associations were abrogated by recruitment site but not region of origin. Conclusions Puerto Rican ethnicity and mixed origin were associated with degree of atopy within US Latino children with asthma. African ancestry was not associated with degree of atopy after adjusting for recruitment site. Local environment variation, represented by site, was associated with degree of sensitization.

BackgroundThe primary rescue medication to treat acute asthma exacerbation is the short-acting β₂-adrenergic receptor agonist; however, there is variation in how well a patient responds to treatment. Although these differences might be due to environmental factors, there is mounting evidence for a genetic contribution to variability in bronchodilator response (BDR).ObjectiveTo identify genetic variation associated with bronchodilator drug response in Latino children with asthma.MethodsWe performed a genome-wide association study (GWAS) for BDR in 1782 Latino children with asthma using standard linear regression, adjusting for genetic ancestry and ethnicity, and performed replication studies in an additional 531 Latinos. We also performed admixture mapping across the genome by testing for an association between local European, African, and Native American ancestry and BDR, adjusting for genomic ancestry and ethnicity.ResultsWe identified 7 genetic variants associated with BDR at a genome-wide significant threshold (P < 5 × 10(-8)), all of which had frequencies of less than 5%. Furthermore, we observed an excess of small P values driven by rare variants (frequency

Background Bronchial airway expression profiling has identified inflammatory subphenotypes of asthma, but the invasiveness of this technique has limited its application to childhood asthma. Objectives We sought to determine whether the nasal transcriptome can proxy expression changes in the lung airway transcriptome in asthmatic patients. We also sought to determine whether the nasal transcriptome can distinguish subphenotypes of asthma. Methods Whole-transcriptome RNA sequencing was performed on nasal airway brushings from 10 control subjects and 10 asthmatic subjects, which were compared with established bronchial and small-airway transcriptomes. Targeted RNA sequencing nasal expression analysis was used to profile 105 genes in 50 asthmatic subjects and 50 control subjects for differential expression and clustering analyses. Results We found 90.2% overlap in expressed genes and strong correlation in gene expression (ρ = .87) between the nasal and bronchial transcriptomes. Previously observed asthmatic bronchial differential expression was strongly correlated with asthmatic nasal differential expression (ρ = 0.77, P = 5.6 × 10 −9 ). Clustering analysis identified T H 2-high and T H 2-low subjects differentiated by expression of 70 genes, including IL13 , IL5 , periostin (POSTN) , calcium-activated chloride channel regulator 1 (CLCA1) , and serpin peptidase inhibitor, clade B (SERPINB2) . T H 2-high subjects were more likely to have atopy (odds ratio, 10.3; P = 3.5 × 10 −6 ), atopic asthma (odds ratio, 32.6; P = 6.9 × 10 −7 ), high blood eosinophil counts (odds ratio, 9.1; P = 2.6 × 10 −6 ), and rhinitis (odds ratio, 8.3; P = 4.1 × 10 −6 ) compared with T H 2-low subjects. Nasal IL13 expression levels were 3.9-fold higher in asthmatic participants who experienced an asthma exacerbation in the past year ( P = .01). Several differentially expressed nasal genes were specific to asthma and independent of atopic status. Conclusion Nasal airway gene expression profiles largely recapitulate expression profiles in the lung airways. Nasal expression profiling can be used to identify subjects with IL13 -driven asthma and a T H 2-skewed systemic immune response.

Rationale: Air pollution is a known asthma trigger and has been associated with short-term asthma symptoms, airway inflammation, decreased lung function, and reduced response to asthma rescue medications. Objectives: To assess a causal relationship between air pollution and childhood asthma using data that address temporality by estimating air pollution exposures before the development of asthma and to establish the generalizability of the association by studying diverse racial/ethnic populations in different geographic regions. Methods: This study included Latino (n = 3,343) and African American (n = 977) participants with and without asthma from five urban regions in the mainland United States and Puerto Rico. Residential history and data from local ambient air monitoring stations were used to estimate average annual exposure to five air pollutants: ozone, nitrogen dioxide (NO2), sulfur dioxide, particulate matter not greater than 10 μm in diameter, and particulate matter not greater than 2.5 μm in diameter. Within each region, we performed logistic regression to determine the relationship between early-life exposure to air pollutants and subsequent asthma diagnosis. A random-effects model was used to combine the region-specific effects and generate summary odds ratios for each pollutant. Measurements and Main Results: After adjustment for confounders, a 5-ppb increase in average NO2 during the first year of life was associated with an odds ratio of 1.17 for physician-diagnosed asthma (95% confidence interval, 1.04–1.31). Conclusions: Early-life NO2 exposure is associated with childhood asthma in Latinos and African Americans. These results add to a growing body of evidence that traffic-related pollutants may be causally related to childhood asthma.

Asthma is a common chronic respiratory disease characterized by airway hyperresponsiveness (AHR). The genetics of asthma have been widely studied in mouse and human, and homologous genomic regions have been associated with mouse AHR and human asthma-related phenotypes. Our goal was to identify asthma-related genes by integrating AHR associations in mouse with human genome-wide association study (GWAS) data. We used Efficient Mixed Model Association (EMMA) analysis to conduct a GWAS of baseline AHR measures from males and females of 31 mouse strains. Genes near or containing SNPs with EMMA p-values

RationaleObesity is associated with increased asthma morbidity, lower drug responsiveness to inhaled corticosteroids, and worse asthma control. However, most prior investigations on obesity and asthma control have not focused on pediatric populations, considered environmental exposures, or included minority children.ObjectivesTo examine the association between body mass index categories and asthma control among boys and girls; and whether these associations are modified by age and race/ethnicity.MethodsChildren and adolescents ages 8-19 years (n = 2,174) with asthma were recruited from the Genes-environments and Admixture in Latino Americans (GALA II) Study and the Study of African Americans, Asthma, Genes, and Environments (SAGE II). Ordinal logistic regression was used to estimate odds ratios (OR) and their confidence intervals (95% CI) for worse asthma control.Measurements and main resultsIn adjusted analyses, boys who were obese had a 33% greater chance of having worse asthma control than their normal-weight counterparts (OR, 1.33; 95% CI, 1.04-1.71). However, for girls this association varied with race and ethnicity (P interaction = 0.008). When compared with their normal-weight counterparts, obese African American girls (OR, 0.65; 95% CI, 0.41-1.05) were more likely to have better controlled asthma, whereas Mexican American girls had a 1.91 (95% CI, 1.12-3.28) greater odds of worse asthma control.ConclusionsWorse asthma control is uniformly associated with increased body mass index in boys. Among girls, the direction of this association varied with race/ethnicity.

Background Lung function is a long-term predictor of mortality and morbidity. Objective We sought to identify single nucleotide polymorphisms (SNPs) associated with lung function. Methods We performed a genome-wide association study (GWAS) of FEV 1 , forced vital capacity (FVC), and FEV 1 /FVC in 1144 Hutterites aged 6 to 89 years, who are members of a founder population of European descent. We performed least absolute shrinkage and selection operation regression to select the minimum set of SNPs that best predict FEV 1 /FVC in the Hutterites and used the GRAIL algorithm to mine the Gene Ontology database for evidence of functional connections between genes near the predictive SNPs. Results Our GWAS identified significant associations between FEV 1 /FVC and SNPs at the THSD4-UACA-TLE3 locus on chromosome 15q23 ( P = 5.7 × 10 −8 to 3.4 × 10 −9 ). Nine SNPs at or near 4 additional loci had P −5 with FEV 1 /FVC. Only 2 SNPs were found with P −5 for FEV 1 or FVC. We found nominal levels of significance with SNPs at 9 of the 27 previously reported loci associated with lung function measures. Among a predictive set of 80 SNPs, 6 loci were identified that had a significant degree of functional connectivity (GRAIL P CCL18 and CXCL12 ), and TNFRSF13B . Conclusion This study identifies genome-wide significant associations and replicates results of previous GWASs. Multimarker modeling implicated for the first time common variation in genes involved in antimicrobial immunity in airway mucosa that influences lung function.

Background Polymorphisms in more than 100 genes have been associated with asthma susceptibility, yet much of the heritability remains to be explained. Asthma disproportionately affects different racial and ethnic groups in the United States, suggesting that admixture mapping is a useful strategy to identify novel asthma-associated loci. Objective We sought to identify novel asthma-associated loci in Latino populations using case-control admixture mapping. Methods We performed genome-wide admixture mapping by comparing levels of local Native American, European, and African ancestry between children with asthma and nonasthmatic control subjects in Puerto Rican and Mexican populations. Within candidate peaks, we performed allelic tests of association, controlling for differences in local ancestry. Results Between the 2 populations, we identified a total of 62 admixture mapping peaks at a P value of less than 10 −3 that were significantly enriched for previously identified asthma-associated genes ( P = .0051). One of the peaks was statistically significant based on 100 permutations in the Mexican sample (6q15); however, it was not significant in Puerto Rican subjects. Another peak was identified at nominal significance in both populations (8q12); however, the association was observed with different ancestries. Conclusion Case-control admixture mapping is a promising strategy for identifying novel asthma-associated loci in Latino populations and implicates genetic variation at 6q15 and 8q12 regions with asthma susceptibility. This approach might be useful for identifying regions that contribute to both shared and population-specific differences in asthma susceptibility.

Author(s): Kovacic, Melinda Butsch; Myers, Jocelyn M Biagini; Wang, Ning; Martin, Lisa J; Lindsey, Mark; Ericksen, Mark B; He, Hua; Patterson, Tia L; Baye, Tesfaye M; Torgerson, Dara; Roth, Lindsey A; Gupta, Jayanta; Sivaprasad, Umasundari; Gibson, Aaron M; Tsoras, Anna M; Hu, Donglei; Eng, Celeste; Chapela, Rocio; Rodriguez-Santana, Jose R; Rodriguez-Cintron, William; Avila, Pedro C; Beckman, Kenneth; Seibold, Max A; Gignoux, Chris; Musaad, Salma M; Chen, Weiguo; Burchard, Esteban Gonzalez; Hershey, Gurjit K Khurana | Abstract: BackgroundAsthma is a chronic inflammatory disease with a strong genetic predisposition. A major challenge for candidate gene association studies in asthma is the selection of biologically relevant genes.Methodology/principal findingsUsing epithelial RNA expression arrays, HapMap allele frequency variation, and the literature, we identified six possible candidate susceptibility genes for childhood asthma including ADCY2, DNAH5, KIF3A, PDE4B, PLAU, SPRR2B. To evaluate these genes, we compared the genotypes of 194 predominantly tagging SNPs in 790 asthmatic, allergic and non-allergic children. We found that SNPs in all six genes were nominally associated with asthma (pl0.05) in our discovery cohort and in three independent cohorts at either the SNP or gene level (pl0.05). Further, we determined that our selection approach was superior to random selection of genes either differentially expressed in asthmatics compared to controls (p = 0.0049) or selected based on the literature alone (p = 0.0049), substantiating the validity of our gene selection approach. Importantly, we observed that 7 of 9 SNPs in the KIF3A gene more than doubled the odds of asthma (OR = 2.3, pl0.0001) and increased the odds of allergic disease (OR = 1.8, pl0.008). Our data indicate that KIF3A rs7737031 (T-allele) has an asthma population attributable risk of 18.5%. The association between KIF3A rs7737031 and asthma was validated in 3 independent populations, further substantiating the validity of our gene selection approach.Conclusions/significanceOur study demonstrates that KIF3A, a member of the kinesin superfamily of microtubule associated motors that are important in the transport of protein complexes within cilia, is a novel candidate gene for childhood asthma. Polymorphisms in KIF3A may in part be responsible for poor mucus and/or allergen clearance from the airways. Furthermore, our study provides a promising framework for the identification and evaluation of novel candidate susceptibility genes.

Contemporary genetic variation among Latin Americans human groups reflects population migrations shaped by complex historical, social and economic factors. Consequently, admixture patterns may vary by geographic regions ranging from countries to neighborhoods. We examined the geographic variation of admixture across the island of Puerto Rico and the degree to which it could be explained by historic and social events. We analyzed a census-based sample of 642 Puerto Rican individuals that were genotyped for 93 ancestry informative markers (AIMs) to estimate African, European and Native American ancestry. Socioeconomic status (SES) data and geographic location were obtained for each individual. There was significant geographic variation of ancestry across the island. In particular, African ancestry demonstrated a decreasing East to West gradient that was partially explained by historical factors linked to the colonial sugar plantation system. SES also demonstrated a parallel decreasing cline from East to West. However, at a local level, SES and African ancestry were negatively correlated. European ancestry was strongly negatively correlated with African ancestry and therefore showed patterns complementary to African ancestry. By contrast, Native American ancestry showed little variation across the island and across individuals and appears to have played little social role historically. The observed geographic distributions of SES and genetic variation relate to historical social events and mating patterns, and have substantial implications for the design of studies in the recently admixed Puerto Rican population. More generally, our results demonstrate the importance of incorporating social and geographic data with genetics when studying contemporary admixed populations.

Objective As a result of the California heat wave in July 2006, county coroners reported that the high temperatures during that period caused approximately 147 deaths. However, heat wave-related deaths are likely to be underreported due to a lack of a clear case definition and the multi-factorial nature of heat-related mortality. Public health policy suggests a need for a careful assessment of mortality following a heat wave. In addition, it is useful to provide a comparison of the mortality impact per degree change during heat waves versus high temperatures observed during non-heat wave periods. Design Daily data were collected for mortality, weather and ozone in seven California counties impacted by the July 2006 heat wave. The association between apparent temperature and daily mortality was assessed using a Poisson regression model and combined across counties in a meta-analysis. These results were then used to estimate the increases in the number of deaths during the heat wave. Results Our analysis indicated that during the July heat wave, there was a 9% (95% CI=1.6, 16.3) increase in daily mortality per 10° Fahrenheit (F) change in apparent temperature for all counties combined. This estimate is almost 3 times larger than the effect estimated for the full warm season of May–September, during the non-heat wave years. Our estimates also determined that actual mortality during the July 2006 heat wave was 2–3 times greater than the coroner estimates. Conclusion This multi-county analysis provides additional evidence that the attributable risk of mortality following a heat wave may be underestimated by examining only direct heat-related deaths. In addition, we have found that the mortality effect per °F is several times higher than that reported during non-heat wave periods.

Background Among patients with asthma, the clinical effect and relative contribution of maternal smoking during pregnancy ( in utero smoking) and current secondhand smoke (SHS) exposure on asthma control is poorly documented, and there is a paucity of research involving minority populations. Objectives We sought to examine the association between poor asthma control and in utero smoking and current SHS exposure among Latino and black children with asthma. Methods We performed a case-only analysis of 2 multicenter case-control studies conducted from 2008-2010 with similar protocols. We recruited 2481 Latino and black subjects with asthma (ages 8-17 years) from the mainland United States and Puerto Rico. Ordinal logistic regression was used to estimate the effect of in utero smoking and current SHS exposures on National Heart, Lung, and Blood Institute–defined asthma control. Results Poor asthma control among children 8 to 17 years of age was independently associated with in utero smoking (odds ratio [OR], 1.5; 95% CI, 1.1-2.0). In utero smoking through the mother was also associated with secondary asthma outcomes, including early-onset asthma (OR, 1.7; 95% CI, 1.1-2.4), daytime symptoms (OR, 1.6; 95% CI, 1.1-2.1), and asthma-related limitation of activities (OR, 1.6; 95% CI, 1.2-2.2). Conclusions Maternal smoking while in utero is associated with poor asthma control in black and Latino subjects assessed at 8-17 years of age.

Background Although Mexicans and Puerto Ricans are jointly classified as "Hispanic/Latino," there are significant differences in asthma prevalence, severity, and mortality between the 2 groups. We sought to examine the possibility that population-specific genetic risks contribute to this disparity. Objectives More than 100 candidate genes have been associated with asthma and replicated in an independent population, and 7 genome-wide association studies in asthma have been performed. We compared the pattern of replication of these associations in Puerto Ricans and Mexicans. Methods We genotyped Mexican and Puerto Rican trios using an Affymetrix 6.0 GeneChip and used a family-based analysis to test for genetic associations in 124 genes previously associated with asthma. Results We identified 32 single nucleotide polymorphisms (SNPs) in 17 genes associated with asthma in at least 1 of the 2 populations. Twenty-two of these SNPs in 11 genes were significantly associated with asthma in the combined population and showed no significant heterogeneity of association, whereas 5 SNPs were associated in only 1 population and showed statistically significant heterogeneity. In a gene-based approach 2 additional genes were associated with asthma in the combined population, and 3 additional genes displayed ethnic-specific associations with heterogeneity. Conclusions Our results show that only a minority of genetic association studies replicate in our population of Mexican and Puerto Rican asthmatic subjects. Among SNPs that were successfully replicated, most showed no significant heterogeneity across populations. However, we identified several population-specific genetic associations.