Background

DNA from buccal brush samples is being used for high-throughput analyses in a variety of applications, but the impact of sample type on genotyping success and downstream statistical analysis remains unclear. The objective of the current study was to determine laboratory predictors of genotyping failure among buccal DNA samples, and to evaluate the successfully genotyped results with respect to analytic quality control metrics. Sample and genotyping characteristics were compared between buccal and blood samples collected in the population-based Genetic and Environmental Risk Factors for Hemorrhagic Stroke (GERFHS) study (https://gerfhs.phs.wfubmc.edu/public/index.cfm).

Results

Seven-hundred eight (708) buccal and 142 blood DNA samples were analyzed for laboratory-based and analysis metrics. Overall genotyping failure rates were not statistically different between buccal (11.3%) and blood (7.0%, p = 0.18) samples; however, both the Contrast Quality Control (cQC) rate and the dynamic model (DM) call rates were lower among buccal DNA samples (p < 0.0001). The ratio of double-stranded to total DNA (ds/total ratio) in the buccal samples was the only laboratory characteristic predicting sample success (p < 0.0001). A threshold of at least 34% ds/total DNA provided specificity of 98.7% with a 90.5% negative predictive value for eliminating probable failures. After genotyping, median sample call rates (99.1% vs. 99.4%, p < 0.0001) and heterozygosity rates (25.6% vs. 25.7%, p = 0.006) were lower for buccal versus blood DNA samples, respectively, but absolute differences were small. Minor allele frequency differences from HapMap were smaller for buccal than blood samples, and both sample types demonstrated tight genotyping clusters, even for rare alleles.

Conclusions

We identified a buccal sample characteristic, a ratio of ds/total DNA <34%, which distinguished buccal DNA samples likely to fail high-throughput genotyping. Applying this threshold, the quality of final genotyping resulting from buccal samples is somewhat lower, but compares favorably to blood. Caution is warranted if cases and controls have different sample types, but buccal samples provide comparable results to blood samples in large-scale genotyping analyses.

Respiratory health is an important component of the ability to perform physically demanding work. We assessed the prevalence of self-reported respiratory symptoms among Latino farmworkers primarily engaged in crop production and investigated work activities as risk factors for respiratory symptoms. During June-September 2008, 122 farmworkers completed up to three interviewer-administered questionnaires. We estimated the associations between work activities and wheezing symptoms using alternating logistic regression, controlling for age and smoking. At the first data collection, 24% (n=29) of farmworkers reported ever wheezing and 8% reported wheezing within the past month. Though not statistically significant, the odds of wheezing were elevated for individuals who reported performing tobacco-related work in the last three days. The odds were decreased among individuals who reported harvesting activities (odds ratio: 0.3, 95% confidence interval: 0.1, 1.0). Among Latino farmworkers, respiratory symptoms may be associated with work activities.

Background

Two recent large meta-analyses of genome-wide association studies of lung function in general populations of European descent identified 11 candidate genes/regions. The importance of these genes in lung function in whites and African Americans with asthma is unknown.

Objectives

To determine if genes that regulate lung function in general populations are associated with lung function abnormalities in subjects with asthma from different racial groups.

Methods

SNPs were tested in five asthma populations (n = 1,441) for association with pulmonary function and meta-analysis was performed across populations. The SNPs with the highest significance were then tested for association with bronchodilator reversibility and bronchial hyperresponsiveness to methacholine (BHR). A joint analysis of consistently replicated SNPs was performed to predict lung function in asthma.

Results

Hedgehog interacting protein (HHIP) on chromosome 4q31 was associated with lung function in all five populations, rs1512288: Pmeta = 9.62E-05 and 3.23E-05 for ppFEV1 and ppFVC, respectively. The SNPs in HHIP were also associated with reversibility (P < 0.05) but not BHR. Because of differences in linkage disequilibrium in the African-American subjects, the most relevant SNPs in HHIP were identified. A subset of normal lung function genes, including HHIP, family with sequence similarity 13, member A (FAM13A), and patched homolog 1 (PTCH1), together predict lung function abnormalities, a measure of severity in whites and African Americans with asthma.

Conclusion

A subset of the genes, including HHIP, which regulate lung function in general populations are associated with abnormal lung function in asthma in non-Hispanic whites and African Americans.

Nutritional interventions are important alternatives for reducing the prevalence of many chronic diseases. Soy is a good source of protein that contains isoflavones, including genistein and daidzein, and may alter the risk of obesity, Type 2 diabetes, osteoporosis, cardiovascular disease, and reproductive cancers. We have shown previously in nonhuman primates that soy protein containing isoflavones leads to improved body weight, insulin sensitivity, lipid profiles, and atherosclerosis compared to protein without soy isoflavones (casein), and does not increase the risk of cancer. Since genistein has been shown to alter DNA methylation, we compared the methylation profiles of cynomolgus monkeys, from multiple tissues, eating two high-fat, typical American diets (TAD) with similar macronutrient contents, with or without soy protein. DNA methylation status was successfully determined for 80.6% of the probes in at least one tissue using Illumina's HumanMethylation27 BeadChip. Overall methylation increased in liver and muscle tissue when monkeys switched from the TAD-soy to the TAD-casein diets. Genes involved in epigenetic processes, specifically homeobox genes (HOXA5, HOXA11, and HOXB1), and ABCG5 were among those that changed between diets. These data support the use of the HumanMethylation27 BeadChip in cynomolgus monkeys and identify epigenetic changes associated with dietary interventions with soy protein that may potentially affect the etiology of complex diseases.

Background

Asthma is a heterogeneous disease that is caused by the interaction of genetic susceptibility with environmental influences. Genome-wide association studies (GWAS) represent a powerful approach to investigate the association of DNA variants with disease susceptibility. To date, few GWAS for asthma have been reported.

Objectives

GWAS was performed on a population of severe or difficult-to-treat asthmatics to identify genes that are involved in the pathogenesis of asthma.

Methods

292,443 SNPs were tested for association with asthma in 473 TENOR cases and 1,892 Illumina general population controls. Asthma-related quantitative traits (total serum IgE, FEV1, FVC, and FEV1/FVC) were also tested in identified candidate regions in 473 TENOR cases and 363 phenotyped controls without a history of asthma to further analyze GWAS results. Imputation was performed in identified candidate regions for analysis with denser SNP coverage.

Results

Multiple SNPs in the RAD50-IL13 region on chromosome 5q31.1 were associated with asthma: rs2244012 in intron 2 of RAD50 (P = 3.04E-07). The HLA-DR/DQ region on chromosome 6p21.3 was also associated with asthma: rs1063355 in the 3’ UTR of HLA-DQB1 (P = 9.55E-06). Imputation identified several significant SNPs in the TH2 locus control region (LCR) 3’ of RAD50. Imputation also identified a more significant SNP, rs3998159 (P = 1.45E-06), between HLA-DQB1 and HLA-DQA2.

Conclusion

This GWAS confirmed the important role of TH2 cytokine and antigen presentation genes in asthma at a genome-wide level and the importance of additional investigation of these two regions to delineate their structural complexity and biologic function in the development of asthma.

SUMMARY

Objective

A high degree of inter-individual variability in plasma lipid level response to hormone therapy (HT) has been reported. Variations in the oestrogen receptor α gene (ESR1) and in genes involved in lipid metabolism may explain some of the variability in response to HT.

Subjects

Postmenopausal Caucasian women (N=208) participating in a placebo-controlled randomized trial of 3.2 years of hormone therapy (HT).

Methods

Plasma triglycerides (TG), remnant lipoprotein cholesterol (RLP-C), and high-density lipoprotein cholesterol (HDL-C) levels and HDL subpopulations were assessed at baseline and at follow-up. Single nucleotide polymorphisms (SNPs) in ESR1 and in the ATP binding cassette A1 (ABCA1), cholesteryl ester transfer protein (CETP), hepatic lipase (LIPC), lipoprotein lipase (LPL), and scavenger receptor class B type I (SRB1) genes were assessed for their association with baseline plasma levels and HT-related changes in levels of RLP-C and HDL subpopulations.

Results

Carriers of the ESR1 PvuII or IVS1-1505 variants had lower plasma TG concentrations and higher plasma HDL-C and α-1 and preα-1 HDL particle levels at baseline and showed greater increases in HDL-C, apo A-I and α-1 particle levels after HT than wild-type carriers. Carriers of the N291S and D9N variants in the LPL gene had significantly higher remnant lipoproteins and lower α-2 HDL particle levels at baseline. The CETP TaqIB SNP was a significant determinant of baseline plasma HDL-C and HDL subpopulation profile.

Conclusions

SNPs in ESR1, CETP and LPL had significant effects on baseline plasma levels of TG-rich and HDL subpopulations. With the exception of ESR1 SNPs, variation in genes involved in lipid metabolism has a very modest effect on lipoprotein response to HT.

Rationale: Asthma is a chronic inflammatory airway disease that affects more than 300 million individuals worldwide. Asthma is caused by interaction of genetic and environmental factors. Bronchial hyperresponsiveness (BHR) is a hallmark of asthma and results from increased sensitivity of the airways to physical or chemical stimulants. BHR and asthma are linked to chromosome 5q31-q33.

Objectives: To identify a gene for BHR on chromosome 5q31-q33.

Methods: In 200 Dutch families with asthma, linkage analysis and fine mapping were performed, and the Protocadherin 1 gene (PCDH1) was identified. PCDH1 was resequenced in 96 subjects from ethnically diverse populations to identify novel sequence variants. Subsequent replication studies were undertaken in seven populations from The Netherlands, the United Kingdom, and the United States, including two general population samples, two family samples, and three case-control samples. PCDH1 mRNA and protein expression was investigated using polymerase chain reaction, Western blotting, and immunohistochemistry.

Measurements and Main Results: In seven out of eight populations (n = 6,168) from The Netherlands, United Kingdom, and United States, PCHD1 gene variants were significantly associated with BHR (P values, 0.005–0.05) This association was present in both families with asthma and general populations. PCDH1 mRNA and protein were expressed in airway epithelial cells and in macrophages.

Conclusions: PCDH1 is a novel gene for BHR in adults and children. The identification of PCDH1 as a BHR susceptibility gene may suggest that a structural defect in the integrity of the airway epithelium, the first line of defense against inhaled substances, contributes to the development of BHR.

Background and Purpose

Migraine with aura is a risk factor for ischemic stroke but the mechanism by which these disorders are associated remains unclear. Both disorders exhibit familial clustering, which may imply a genetic influence on migraine and stroke risk. Genes encoding for endothelial function are promising candidate genes for migraine and stroke susceptibility because of the importance of endothelial function in regulating vascular tone and cerebral blood flow.

Methods

Using data from the Stroke Prevention in Young Women (SPYW) study, a population-based case-control study including 297 women aged 15–49 years with ischemic stroke and 422 women without stroke, we evaluated whether polymorphisms in genes regulating endothelial function, including endothelin-1 (EDN), endothelin receptor type B (EDNRB), and nitric oxide synthase-3 (NOS3), confer susceptibility to migraine and stroke.

Results

EDN SNPs rs1800542 and rs10478723 were associated with increased stroke susceptibility in Caucasians, (OR = 2.1 (95% CI, 1.1 to 4.2) and OR = 2.2 (95% CI, 1.1 to 4.4); p = 0.02 and 0.02, respectively) as were EDNRB SNPs rs4885493 and rs10507875, (OR = 1.7 (95% CI, 1.1 to 2.7) and OR = 2.4 (95% CI, 1.4 to 4.3); p = 0.01 and 0.002, respectively). Only one of the tested SNPs (NOS3 - rs3918166) was associated with both migraine and stroke.

Conclusions

In our study population, variants in EDN and EDNRB were associated with stroke susceptibility in Caucasian but not in African-American women. We found no evidence that these genes mediate the association between migraine and stroke.

Background

Organophosphate pesticides act as cholinesterase inhibitors. For those with agricultural exposure to these chemicals, risk of potential exposure-related health effects may be modified by genetic variability in cholinesterase metabolism. Cholinesterase activity is a useful, indirect measurement of pesticide exposure, especially in high-risk individuals such as farmworkers. To understand fully the links between pesticide exposure and potential human disease, analyses must be able to consider genetic variability in pesticide metabolism.

Objectives

We studied participants in the Community Participatory Approach to Measuring Farmworker Pesticide Exposure (PACE3) study to determine whether cholinesterase levels are associated with single-nucleotide polymorphisms (SNPs) involved in pesticide metabolism.

Methods

Cholinesterase levels were measured from blood samples taken from 287 PACE3 participants at up to four time points during the 2007 growing season. We performed association tests of cholinesterase levels and 256 SNPs in 30 candidate genes potentially involved in pesticide metabolism. A false discovery rate (FDR) p-value was used to account for multiple testing.

Results

Thirty-five SNPs were associated (unadjusted p < 0.05) based on at least one of the genetic models tested (general, additive, dominant, and recessive). The strongest evidence of association with cholinesterase levels was observed with two SNPs, rs2668207 and rs2048493, in the butyrylcholinesterase (BCHE) gene (FDR adjusted p = 0.15 for both; unadjusted p = 0.00098 and 0.00068, respectively). In participants with at least one minor allele, cholinesterase levels were lower by 4.3–9.5% at all time points, consistent with an effect that is independent of pesticide exposure.

Conclusions

Common genetic variation in the BCHE gene may contribute to subtle changes in cholinesterase levels.

Background

Population-based association studies are used to identify common susceptibility variants for complex genetic traits. These studies are susceptible to confounding from unknown population substructure. Here we apply a model-based clustering approach to our case-control study of stroke among young women to examine if self-reported ethnicity can serve as a proxy for genetic ancestry.

Findings

A population-based case-control study of stroke among women aged 15-49 identified 361 cases of first ischemic stroke and 401 age-comparable control subjects. Thirty single nucleotide polymorphisms (SNPs) throughout the genome unrelated to stroke risk and with established ancestry-based allele frequency differences were genotyped in all participants. The Structure program was used to iteratively evaluate for K = 1 to 5 potential genetic-based subpopulations. Evaluating the population as a whole, the Structure output plateaued at K = 2 clusters. 98% of self-reported Caucasians had an estimated probability ≥50% of belonging to Cluster 1, while 94% of self-reported African-Americans had an estimated probability ≥50% of belonging to Cluster 2. Stratifying the participants by self-reported ethnicity and repeating the analyses revealed the presence of two clusters among Caucasians, suggesting that potential substructure may exist.

Conclusions

Among our combined sample of African-American and Caucasian participants there is no large unknown subpopulation and self-reported ethnicity can serve as a proxy for genetic ancestry. Ethnicity-specific analyses indicate that population substructure may exist among the Caucasian participants indicating that further studies are warranted.

Background

Previous studies suggest β adrenergic receptor (βAR) single nucleotide polymorphisms (SNPs) are associated with out-of-hospital sudden cardiac death (SCD) and overall mortality, but did not specifically examine risk of ventricular arrhythmias (VA).

Objective

We examined the effects of functional SNPs of β1AR and β2AR on the risk of VA and SCD in patients with coronary artery disease (CAD).

Methods

β1AR (Ser49Gly, Arg389Gly) and β2AR (Gly16Arg, Gln27Glu) SNPs were genotyped in a case-control study comparing 107 patients with CAD and aborted SCD due to VA to 287 CAD controls and 101 healthy controls. These variants were also examined in the Heart and Estrogen Replacement Study (HERS) cohort of women with CAD followed for SCD (n = 66) and non-fatal VA (NFVA) (n = 33) over 6.8 years.

Results

In the case-control study, no statistically significant association was observed for odds of SCD with any of the SNPs or haplotypes tested. Similarly, HERS revealed null effects for these SNPs and haplotypes in relation to risk of SCD, SCD + NFVA, and all-cause mortality. Point estimates and confidence intervals for risk of SCD associated with β2AR27 were similar in both populations (Glu27 carriers vs. Gln27 homozygotes: adjusted OR 1.23 [95% CI 0.75–2.03, p=0.41] in the case-control study, and adjusted RR 1.18 [95% CI 0.69–2.00, p=0.55] in HERS). These null findings trend in the opposite direction and differ from previous published estimates (p=0.01 and 0.07, respectively).

Conclusion

We did not find an increase in risk of SCD associated with any of these common βAR polymorphisms.

Evidence suggests that interleukin-1 receptor associated kinase-1 (IRAK1), fundamental in the toll-like receptor pathway (TLR), may play a more specific role in atherosclerosis.

Methods

Caucasian women (N=529) and men (N=467) from the Diabetes Heart Study (DHS) were genotyped at four loci within the IRAK1 gene located on the X chromosome. Generalized estimating equations (GEE1) were used to evaluate association with C-reactive protein (CRP) for both single SNP and haplotype analyses.

Results

For each SNP genotyped, Caucasian women carrying one or two copies of the variant allele had greater CRP concentrations than those carrying the common genotype in both crude and adjusted models. There were 2 major haplotypes, CTTT (82%) and its complement, TCCG (13%). The presence of the TCCG haplotype was associated with greater CRP concentrations in Caucasian women (p=0.0004) and this relationship was maintained after adjustment for age, BMI, smoking, diabetes, and cholesterol-lowering therapy (p=0.003). There was no association between CRP and IRAK1 SNPs in Caucasian men.

Conclusion

Variation in the IRAK1 gene is associated with CRP concentration in Caucasian women in DHS. Further studies are needed to reproduce the current finding and to understand the biological relationship between IRAK1 and inflammation related to atherosclerosis.

Background and Purpose

Endothelial nitric oxide exerts a variety of protective effects on endothelial cells and blood vessels, and therefore the nitric oxide synthase 3 gene (NOS3) is a logical candidate gene for stroke susceptibility.

Methods

We used the population-based Stroke Prevention in Young Women case-control study to assess the association of five NOS3 polymorphisms in 110 cases (46% black) with ischemic stroke and 206 controls (38% black), 15 to 44 years of age. Polymorphisms included 3 single nucleotide polymorphisms (SNPs) in the promoter region (−1468 T>A, −922 G>A, −786 T>C), 1 SNP in exon 7 (G894T), and 1 insertion/deletion polymorphism within intron 4.

Results

Significant associations with both the −922 G>A and −786 T>C SNPs with ischemic stroke were observed in the black, but not the white, population. This association was attributable to an increased prevalence of the −922 A allele (OR=3.0, 95% CI=1.3 to 6.8; P=0.005) and the −786 T allele (OR=2.9, 95% CI=1.3 to 6.4; P=0.005) in cases versus controls. These 2 SNPs were in strong linkage disequilibrium (D′=1.0), making it impossible to determine, within the confines of this genetic study, whether 1 or both of these polymorphisms are functionally related to NOS3 expression. Two sets of haplotypes were also identified, 1 of which may confer an increased susceptibility to stroke in blacks, whereas the other appears to be protective.

Conclusion

Promoter variants in NOS3 may be associated with ischemic stroke susceptibility among young black women.

Changes in pulmonary function are important in determining asthma outcome. Genetic factors may influence airway obstruction in asthma. We performed a genomewide screen in 200 families of probands objectively diagnosed with asthma in the 1960s to identify chromosomal regions related to changes in pre- and postbronchodilator lung function (FEV1, VC, and FEV1%VC) and assess influences of early-life smoke exposure. Smoking (pack-years), age, sex, and height were covariates in variance component analyses. Significant evidence for linkage of pre- and postbronchodilator FEV1%VC was obtained for chromosome 2q32 (LOD,4.9, increasing to 6.03 with additional fine-mapping markers, and 3.2, respectively). Linkage existed for chromosome 5q for pre- and postbronchodilator VC (likelihood of disease [LOD], 1.8 and 2.6, respectively). Results for pre- and postbronchodilator FEV1 were less significant (LOD, 1.5 and 1.6, chromosomes 11p and 10q, respectively). Results were not affected by passive smoke exposure. There is significant evidence for linkage of FEV1%VC to chromosome 2q32 in families of probands with asthma, 35 cM proximal from linkage previously observed in families of probands with early-onset chronic obstructive pulmonary disease. Thus, there may be multiple genes on chromosome 2q that are important in determining presence and degree of airflow limitation in families ascertained for obstructive airway disease.

Background

Cystic fibrosis (CF) lung disease manifest by impaired chloride secretion leads to eventual respiratory failure. Candidate genes that may modify CF lung disease severity include alternative chloride channels. The objectives of this study are to identify single nucleotide polymorphisms (SNPs) in the airway epithelial chloride channel, CLC-2, and correlate these polymorphisms with CF lung disease.

Methods

The CLC-2 promoter, intron 1 and exon 20 were examined for SNPs in adult CF dF508/dF508 homozygotes with mild and severe lung disease (forced expiratory volume at one second (FEV1) > 70% and < 40%).

Results

PCR amplification of genomic CLC-2 and sequence analysis revealed 1 polymorphism in the hClC -2 promoter, 4 in intron 1, and none in exon 20. Fisher's analysis within this data set, did not demonstrate a significant relationship between the severity of lung disease and SNPs in the CLC-2 gene.

Conclusions

CLC-2 is not a key modifier gene of CF lung phenotype. Further studies evaluating other phenotypes associated with CF may be useful in the future to assess the ability of CLC-2 to modify CF disease severity.

Background

Carotid-femoral pulse wave velocity (CFPWV) is a heritable measure of aortic stiffness that is strongly associated with increased risk for major cardiovascular disease events.

Methods and Results

We conducted a meta-analysis of genome-wide association data in 9 community-based European ancestry cohorts consisting of 20,634 participants. Results were replicated in 2 additional European ancestry cohorts involving 5,306 participants. Based on a preliminary analysis of 6 cohorts, we identified a locus on chromosome 14 in the 3′-BCL11B gene desert that is associated with CFPWV (rs7152623, minor allele frequency = 0.42, beta=−0.075±0.012 SD/allele, P = 2.8 x 10−10; replication beta=−0.086±0.020 SD/allele, P = 1.4 x 10−6). Combined results for rs7152623 from 11 cohorts gave beta=−0.076±0.010 SD/allele, P=3.1x10−15. The association persisted when adjusted for mean arterial pressure (beta=−0.060±0.009 SD/allele, P = 1.0 x 10−11). Results were consistent in younger (<55 years, 6 cohorts, N=13,914, beta=−0.081±0.014 SD/allele, P = 2.3 x 10−9) and older (9 cohorts, N=12,026, beta=−0.061±0.014 SD/allele, P=9.4x10−6) participants. In separate meta-analyses, the locus was associated with increased risk for coronary artery disease (hazard ratio [HR]=1.05, confidence interval [CI]=1.02 to 1.08, P=0.0013) and heart failure (HR=1.10, CI=1.03 to 1.16, P=0.004).

Conclusions

Common genetic variation in a locus in the BCL11B gene desert that is thought to harbor one or more gene enhancers is associated with higher CFPWV and increased risk for cardiovascular disease. Elucidation of the role this novel locus plays in aortic stiffness may facilitate development of therapeutic interventions that limit aortic stiffening and related cardiovascular disease events.

Background

Coronary artery calcification (CAC) detected by computed tomography is a non-invasive measure of coronary atherosclerosis, that underlies most cases of myocardial infarction (MI). We aimed to identify common genetic variants associated with CAC and further investigate their associations with MI.

Methods and Results

Computed tomography was used to assess quantity of CAC. A meta-analysis of genome-wide association studies for CAC was carried out in 9,961 men and women from five independent community-based cohorts, with replication in three additional independent cohorts (n=6,032). We examined the top single nucleotide polymorphisms (SNPs) associated with CAC quantity for association with MI in multiple large genome-wide association studies of MI. Genome-wide significant associations with CAC for SNPs on chromosome 9p21 near CDKN2A and CDKN2B (top SNP: rs1333049, P=7.58×10−19) and 6p24 (top SNP: rs9349379, within the PHACTR1 gene, P=2.65×10−11) replicated for CAC and for MI. Additionally, there is evidence for concordance of SNP associations with both CAC and with MI at a number of other loci, including 3q22 (MRAS gene), 13q34 (COL4A1/COL4A2 genes), and 1p13 (SORT1 gene).

Conclusions

SNPs in the 9p21 and PHACTR1 gene loci were strongly associated with CAC and MI, and there are suggestive associations with both CAC and MI of SNPs in additional loci. Multiple genetic loci are associated with development of both underlying coronary atherosclerosis and clinical events.