Regulatory haplotypes in ARG1 are associated with altered bronchodilator response.
ABSTRACT: RATIONALE:??-agonists, the most common treatment for asthma, have a wide interindividual variability in response, which is partially attributed to genetic factors. We previously identified single nucleotide polymorphisms in the arginase 1 (ARG1) gene, which are associated with ??-agonist bronchodilator response (BDR). OBJECTIVES:To identify cis-acting haplotypes in the ARG1 locus that are associated with BDR in patients with asthma and regulate gene expression in vitro. METHODS:We resequenced ARG1 in 96 individuals and identified three common, 5' haplotypes (denoted 1, 2, and 3). A haplotype-based association analysis of BDR was performed in three independent, adult asthma drug trial populations. Next, each haplotype was cloned into vectors containing a luciferase reporter gene and transfected into human airway epithelial cells (BEAS-2B) to ascertain its effect on gene expression. MEASUREMENTS AND MAIN RESULTS:BDR varied by haplotype in each of the three populations with asthma. Individuals with haplotype 1 were more likely to have higher BDR, compared to those with haplotypes 2 and 3, which is supported by odds ratios of 1.25 (95% confidence interval, 1.03-1.71) and 2.18 (95% confidence interval, 1.34-2.52), respectively. Luciferase expression was 50% greater in cells transfected with haplotype 1 compared to haplotypes 2 and 3. CONCLUSIONS:The identified ARG1 haplotypes seem to alter BDR and differentially regulate gene expression with a concordance of decreased BDR and reporter activity from haplotypes 2 and 3. These findings may facilitate pharmacogenetic tests to predict individuals who may benefit from other therapeutic agents in addition to ?(2)-agonists for optimal asthma management. Clinical trial registered with www.clinicaltrials.gov (NCT00156819, NCT00046644, and NCT00073840).
Project description:Inhaled beta-agonists are one of the most widely used classes of drugs for the treatment of asthma. However, a substantial proportion of patients with asthma do not have a favorable response to these drugs, and identifying genetic determinants of drug response may aid in tailoring treatment for individual patients.To screen variants in candidate genes in the steroid and beta-adrenergic pathways for association with response to inhaled beta-agonists.We genotyped 844 single nucleotide polymorphisms (SNPs) in 111 candidate genes in 209 children and their parents participating in the Childhood Asthma Management Program. We screened the association of these SNPs with acute response to inhaled beta-agonists (bronchodilator response [BDR]) using a novel algorithm implemented in a family-based association test that ranked SNPs in order of statistical power. Genes that had SNPs with median power in the highest quartile were then taken for replication analyses in three other asthma cohorts.We identified 17 genes from the screening algorithm and genotyped 99 SNPs from these genes in a second population of patients with asthma. We then genotyped 63 SNPs from four genes with significant associations with BDR, for replication in a third and fourth population of patients with asthma. Evidence for association from the four asthma cohorts was combined, and SNPs from ARG1 were significantly associated with BDR. SNP rs2781659 survived Bonferroni correction for multiple testing (combined P value = 0.00048, adjusted P value = 0.047).These findings identify ARG1 as a novel gene for acute BDR in both children and adults with asthma.
Project description:<h4>Background</h4>Arginases (encoded by ARG1 and ARG2 genes) might play an important role in asthma pathogenesis through effects on nitrosative stress. Arginase expression is upregulated in asthma and varies with T(H)2 cytokine levels and oxidative stress.<h4>Objective</h4>We aimed to examine whether variants in these genes are associated with asthma and whether atopy and exposures to smoking and air pollution influence the associations.<h4>Methods</h4>Among non-Hispanic and Hispanic white participants of the Children's Health Study (n = 2946), we characterized variation in each locus (including promoter region) with 6 tag single nucleotide polymorphisms for ARG1 and 10 for ARG2. Asthma was defined by parental report of physician-diagnosed asthma at study entry.<h4>Results</h4>Both ARG1 and ARG2 genetic loci were significantly associated with asthma (global locus level P = .02 and .04, respectively). Compared with the most common haplotype within each locus, 1 ARG1 haplotype was associated with reduced risk (odds ratio [OR] per haplotype copy, 0.55; 95% CI, 0.36-0.84), and 1 ARG2 haplotype was associated with increased risk (OR per haplotype copy, 1.35; 95% CI, 1.04-1.76) of asthma. The effect of the ARG1 haplotype that was significantly associated with asthma varied by the child's history of atopy and ambient ozone (P(interaction) = .04 and .02, respectively). Among atopic children living in high-ozone communities, those carrying the ARG1 haplotype had reduced asthma risk (OR per haplotype copy, 0.12; 95% CI, 0.04-0.43; P(heterogeneity) across atopy/ozone categories = .008).<h4>Conclusions</h4>ARG1 and ARG2 loci are associated with childhood asthma. The association between ARG1 variation and asthma might depend on atopy and ambient ozone levels.
Project description:Asthma is a multifactorial pathology influenced by environmental and genetic factors. Glucocorticoid treatment decreases symptoms by regulating genes involved in the inflammatory process through binding to specific DNA sequences. Polymorphisms located in the promoter region of the Prostaglandin D Receptor (PTGDR) gene have been related to asthma. We aimed to analyze the effect of PTGDR promoter haplotypes on gene expression and response to corticosteroid therapy. A549 lung epithelial cells were transfected with vectors carrying four different PTGDR haplotypes (CTCT, CCCC, CCCT and TCCT), and treated with dexamethasone. Different approaches to study the promoter activity (Dual Luciferase Reporter System), gene expression levels (qPCR) and cytokine secretion (Multiplexed Bead-based Flow Cytometric) were used. In addition, in silico analysis was also performed. Cells carrying the TCCT haplotype showed the lowest promoter activity (p-value<0.05) and mRNA expression levels in basal conditions. After dexamethasone treatment, cells carrying the wild-type variant CTCT showed the highest response, and those carrying the TCCT variant the lowest (p-value<0.05) in luciferase assays. Different transcription factor binding patterns were identified in silico. Moreover, differences in cytokine secretion were also found among different promoter haplotypes. Polymorphisms of PTGDR gene influence basal promoter activity and gene expression, as well as the cytokine secretory pattern. Furthermore, an association between these positions and response to corticoid treatment was observed.
Project description:The current study aimed at investigate the potential association of ARG1 polymorphisms in subjects affected by idiopathic dilated cardiomyopathy (IDCM).We have investigated 352 subjects affected by IDCM and 352 population-matched healthy controls by exploiting case-control study. The serum lipids were quantified using spectrophotometric assay, serum arginase activity was done by enzyme colorimetric assay and 2 polymorphisms (rs2781666 and rs2781667) in ARG1 were typed by polymerase chain reaction (PCR) followed by restriction fragment length polymorphism (RFLP) to find out disease associate allele/haplotype segregating in subjects affected by IDCM.Significantly high arginase activity was found to be associated with IDCM subjects when compared with population-matched healthy controls (P?<?.0001). The higher arginase level in IDCM subjects is negatively correlated with nitrite and nitrate (r?=?-0.4687, and r?=?-0.6435, respectively) in our study. There was a significant difference in the distribution of rs2781666 and rs2781667 genotypes of ARG1 polymorphism in patients and controls (P?<?.0001). Similarly, variant allele T at both loci showed a significant association with the disease phenotypes (P?<?.0001). Haplotype TT at rs2781666G/T and rs2781667C/T also showed a significantly association (P?<?.0001).To our knowledge, this is the first report to show a significant involvement of ARG1 polymorphisms to produce IDCM symptoms in subjects originating in Pakistan.
Project description:?2-Agonists are the most common form of treatment of asthma, but there is significant variability in response to these medications. A significant proportion of this responsiveness may be heritable.To investigate whether a genome-wide association study (GWAS) could identify novel pharmacogenetic loci in asthma.We performed a GWAS of acute bronchodilator response (BDR) to inhaled ?2-agonists. A total of 444,088 single-nucleotide polymorphisms (SNPs) were examined in 724 individuals from the SNP Health Association Resource (SHARe) Asthma Resource Project (SHARP). The top 50 SNPs were carried forward to replication in a population of 444 individuals.The combined P value for four SNPs reached statistical genome-wide significance aftercorrecting for multiple comparisons. Combined P values for rs350729, rs1840321, rs1384918, and rs1319797 were 2.21?×?10(-10), 5.75?×?10(-8), 9.3?×?10(-8), and 3.95?×?10(-8), respectively. The significant variants all map to a novel genetic region on chromosome 2 near the ASB3 gene, a region associated with smooth muscle proliferation. As compared with the wild type, the presence of the minor alleles reduced the degree of BDR by 20% in the original population and by a similar percentage in the confirmatory population.These GWAS findings for BDR in subjects with asthma suggest that a gene associated with smooth muscle proliferation may influence a proportion of the smooth muscle relaxation that occurs in asthma.
Project description:BACKGROUND:A recent microarray study implicated arginase I (ARG1) and arginase II (ARG2) in mouse allergic asthma models and human asthma. OBJECTIVES:To examine the association between genetic variation in ARG1 and ARG2 and childhood asthma and atopy risk. METHODS:We enrolled 433 case-parent triads, consisting of patients with asthma 4 to 17 years old and their biologic parents, from the allergy clinic of a public hospital in Mexico City between 1998 and 2003. Atopy to 24 aeroallergens was determined by skin prick tests. We genotyped 4 single nucleotide polymorphisms (SNPs) of ARG1 and 4 SNPs of ARG2 with minor allele frequencies higher than 10% by using the TaqMan assay (Roche Molecular Systems, Pleasanton, Calif). RESULTS:ARG1 SNPs and haplotypes were not associated with asthma, but all 4 ARG1 SNPs were associated with the number of positive skin tests (P = .007-.018). Carrying 2 copies of minor alleles for either of 2 highly associated ARG2 SNPs was associated with a statistically significant increased relative risk (RR) of asthma (1.5, 95% CI = 1.1-2.1 for arg2s1; RR = 1.6, 95% CI = 1.1-2.3 for arg2s2). The association was slightly stronger among children with a smoking parent (arg2s1 RR = 2.1, 95% CI = 1.2 - 3.9 with a smoking parent; RR = 1.2, 95% CI = 0.8-1.9 without; interaction P = .025). Haplotype analyses reduced the sample size but supported the single SNP results. One ARG2 SNP was related to the number of positive skin tests (P = .027). CONCLUSION:Variation in arginase genes may contribute to asthma and atopy in children.
Project description:Short-acting ?2-adrenergic receptor agonists (SABAs) are the most commonly prescribed asthma medications worldwide. Response to SABAs is measured as bronchodilator drug response (BDR), which varies among racial/ethnic groups in the United States. However, the genetic variation that contributes to BDR is largely undefined in African Americans with asthma. To identify genetic variants that may contribute to differences in BDR in African Americans with asthma, we performed a genome-wide association study (GWAS) of BDR in 949 African-American children with asthma, genotyped with the Axiom World Array 4 (Affymetrix, Santa Clara, CA) followed by imputation using 1000 Genomes phase III genotypes. We used linear regression models adjusting for age, sex, body mass index (BMI) and genetic ancestry to test for an association between BDR and genotype at single-nucleotide polymorphisms (SNPs). To increase power and distinguish between shared vs. population-specific associations with BDR in children with asthma, we performed a meta-analysis across 949 African Americans and 1830 Latinos (total?=?2779). Finally, we performed genome-wide admixture mapping to identify regions whereby local African or European ancestry is associated with BDR in African Americans. We identified a population-specific association with an intergenic SNP on chromosome 9q21 that was significantly associated with BDR (rs73650726, p?=?7.69?×?10-9). A trans-ethnic meta-analysis across African Americans and Latinos identified three additional SNPs within the intron of PRKG1 that were significantly associated with BDR (rs7903366, rs7070958 and rs7081864, p???5?×?10-8). Our results failed to replicate in three additional populations of 416 Latinos and 1615 African Americans. Our findings indicate that both population-specific and shared genetic variation contributes to differences in BDR in minority children with asthma, and that the genetic underpinnings of BDR may differ between racial/ethnic groups.
Project description:An unaddressed and important issue is the role age plays in modulating response to short acting ?2-agonists in individuals with asthma. The objective of this study was to identify whether age modifies genetic associations of single nucleotide polymorphisms (SNPs) with bronchodilator response (BDR) to ?2-agonists. Using three cohorts with a total of 892 subjects, we ran a genome wide interaction study (GWIS) for each cohort to examine SNP by age interactions with BDR. A fixed effect meta-analysis was used to combine the results. In order to determine if previously identified BDR SNPs had an age interaction, we also examined 16 polymorphisms in candidate genes from two published genome wide association studies (GWAS) of BDR. There were no significant SNP by age interactions on BDR using the genome wide significance level of 5 × 10<sup>-8</sup>. Using a suggestive significance level of 5 × 10<sup>-6</sup>, three interactions, including one for a SNP within <i>PRAG1</i> (rs4840337), were significant and replicated at the significance level of 0.05. Considering candidate genes from two previous GWAS of BDR, three SNPs (rs10476900 (near <i>ADRB2</i>) [<i>p</i>-value = 0.009], rs10827492 (<i>CREM</i>) [<i>p</i>-value = 0.02], and rs72646209 (<i>NCOA3</i>) [<i>p</i>-value = 0.02]) had a marginally significant interaction with age on BDR (<i>p</i> < 0.05). Our results suggest age may be an important modifier of genetic associations for BDR in asthma.
Project description:Bronchodilator response (BDR) is an important asthma phenotype that measures reversibility of airway obstruction by comparing lung function (i.e. FEV(1)) before and after the administration of a short-acting ?(2)-agonist, the most common rescue medications used for the treatment of asthma. BDR also serves as a test of ?(2)-agonist efficacy. BDR is a complex trait that is partly under genetic control. A genome-wide association study (GWAS) of BDR, quantified as percent change in baseline FEV(1) after administration of a ?(2)-agonist, was performed with 1,644 non-Hispanic white asthmatic subjects from six drug clinical trials: CAMP, LOCCS, LODO, a medication trial conducted by Sepracor, CARE, and ACRN. Data for 469,884 single-nucleotide polymorphisms (SNPs) were used to measure the association of SNPs with BDR using a linear regression model, while adjusting for age, sex, and height. Replication of primary P-values was attempted in 501 white subjects from SARP and 550 white subjects from DAG. Experimental evidence supporting the top gene was obtained via siRNA knockdown and Western blotting analyses. The lowest overall combined P-value was 9.7E-07 for SNP rs295137, near the SPATS2L gene. Among subjects in the primary analysis, those with rs295137 TT genotype had a median BDR of 16.0 (IQR = [6.2, 32.4]), while those with CC or TC genotypes had a median BDR of 10.9 (IQR = [5.0, 22.2]). SPATS2L mRNA knockdown resulted in increased ?(2)-adrenergic receptor levels. Our results suggest that SPATS2L may be an important regulator of ?(2)-adrenergic receptor down-regulation and that there is promise in gaining a better understanding of the biological mechanisms of differential response to ?(2)-agonists through GWAS.
Project description:Among asthmatic subjects, bronchodilator response (BDR) to inhaled beta(2)-adrenergic agonists is variable, and the significance of a consistent response over time is unknown.We assessed baseline clinical variables and determined the clinical outcomes associated with a consistently positive BDR over 4 years in children with mild-to-moderate persistent asthma.In the 1041 participants in the Childhood Asthma Management Program, subjects with a change in FEV(1) of 12% or greater (and 200 mL) after inhaled beta(2)-agonist administration at each of their yearly follow-up visits (consistent BDR) were compared with those who did not have a consistent BDR.We identified 52 children with consistent BDRs over the 4-year trial. Multivariable logistic regression modeling demonstrated that lower baseline prebronchodilator FEV(1) values (odds ratio, 0.71; P < .0001), higher log10 IgE levels (odds ratio, 1.97; P = .002), and lack of treatment with inhaled corticosteroids (odds ratio, 0.31; P = .009) were associated with a consistent BDR. Individuals who had a consistent BDR had more hospital visits (P = .007), required more prednisone bursts (P = .0007), had increased nocturnal awakenings caused by asthma (P < .0001), and missed more days of school (P = .03) than nonresponders during the 4-year follow-up.We have identified predictors of consistent BDR and determined that this phenotype is associated with poor clinical outcomes.