Coronary Artery Disease Genome-wide Association Studies Research Articles

Abstract 465: Deciphering the Genetic Regulation of ADAMTS7 , a Novel Locus for Coronary Artery Disease

Recent genome-wide association studies (GWAS) have identified an association between the ADAMTS7 locus and coronary artery disease (CAD) in humans. While ADAMTS7 is proposed to play a role in vascular smooth muscle cell (VSMC) migration and neointimal formation, the molecular regulation of human ADAMTS7 gene expression has not yet been explored. We assessed ADAMTS7 expression levels in primary mouse aortic smooth muscle cells (mAoSMC) as well as primary human coronary and human pulmonary artery smooth muscle cells (hCASMC, hPASMC) in response to treatment with various stimulatory agents. No differences in ADAMTS7 expression were observed upon treatment with PDGF, angiotensin II, and nicotine in any of the cell lines tested. However, TNFα upregulated ADAMTS7 by 4-fold in mAoSMC but not in human VSMCs while H 2 O 2 upregulated ADAMTS7 by 4-fold in hCASMC but not mAoSMCs. No agents modulated expression in hPASMC. Basal levels of ADAMTS7 varied among different VSMC lines; hCASMC had 2-fold greater levels of ADAMTS7 when compared to hPASMC and hAoSMC. These data demonstrate that ADAMTS7 is differentially regulated not only across different species, but also among different VSMC types, underscoring the complex genetic regulation of ADAMTS7 . In an attempt to elucidate important regulatory genomic regions controlling ADAMTS7 expression, we utilized data from the ENCODE project to identify regions surrounding ADAMTS7 that are enriched for regulatory domains, e.g. DNase hypsersensitivity (DHS) and H3K27 acetylation, in relevant cell types. We then overlayed data from CARDIoGRAM and C4D CAD GWAS to look for CAD-associated SNPs in these potential enhancers. Ultimately we selected 5 regions of interest (e.g., rs5029904 lies in region with increased H3K27 acetylation in ENCODE layered 7 cell lines, DHS peaks in serum fed and starved hAoSMCs, binding peaks for transcription factors via ENCODE ChIP-Seq experiments) for further studies in luciferase reporter assays multiple cell types to look for tissue specific expression mediated by these genomic regions. GWAS variants in these domains may affect the transcriptional regulation of ADAMTS7 , thus providing insight into the role for ADAMTS7 in human atherosclerosis.

The large non-coding RNA ANRIL, which is associated with atherosclerosis, periodontitis and several forms of cancer, regulates ADIPOR1, VAMP3 and C11ORF10

The long non-coding RNA ANRIL is the best replicated genetic risk locus of coronary artery disease (CAD) and periodontitis (PD), and is independently associated with a variety of other immune-mediated and metabolic disorders and several forms of cancer. Recent studies showed a correlation of decreased concentrations of proximal ANRIL transcripts with homozygous carriership of the CAD and PD main risk alleles. To elucidate the relation of these transcripts to disease manifestation, we constructed a short hairpin RNA in a stable inducible knock-down system of T-Rex 293 HEK cell lines, specifically targeting the proximal transcripts EU741058 and DQ485454. By genome-wide expression profiling using Affymetrix HG1.0 ST Arrays, we identified the transcription of ADIPOR1, VAMP3 and C11ORF10 to be correlated with decreased ANRIL expression in a time-dependent manner. We validated these findings on a transcriptional and translational level in different cell types. Exploration of the identified genes for the presence of disease associated variants, using Affymetrix 500K genotyping and Illumina custom genotyping arrays, highlighted a region upstream of VAMP3 within CAMTA1 to be associated with increased risk of CAD [rs10864294 P = 0.015, odds ratio (OR) = 1.30, 95% confidence interval (CI) = 1.1-1.6, 1471 cases, 2737 controls] and aggressive PD (AgP; P = 0.008, OR = 1.31, 95% CI = 1.1-1.6, 864 cases, 3664 controls). In silico replication in a meta-analysis of 14 genome-wide association studies of CAD of the CARDIoGRAM Consortium identified rs2301462, located on the same haplotype block, as associated with P = 0.001 upon adjustment for sex and age. Our results give evidence that specific isoforms of ANRIL regulate key genes of glucose and fatty acid metabolism.

A Genome-Wide Association Study in Europeans and South Asians Identifies 5 New Loci for Coronary Artery Disease

### Study Hypothesis Recently, genome-wide association studies (GWAS) have identified several common variants associated with increased risk of coronary artery disease (CAD) and myocardial infarction (MI) by 10% to 30%. The authors state that these loci explain only a small proportion of the predicted genetic risk and that all of the current loci for CAD and MI by GWAS have been discovered in European populations. The authors hypothesized that discovery of new susceptibility loci of smaller effect sizes would be aided by conducting much larger studies in addition to an emphasis on early-onset CAD and clearly defined clinical end points. Therefore, they assembled the Coronary Artery Disease (C4D) Genetics Consortium.1 ### How Was the Hypothesis Tested? The authors performed a meta-analysis of 4 large GWAS of CAD, 2 of European ancestry (PROCARDIS and HPS) and 2 of South Asian ancestry (PROMIS and LOLLIPOP), with ≈575 000 genotyped single-nucleotide polymorphisms (SNPs) in a discovery data set comprising 15 420 individuals with CAD (cases) (8424 Europeans and 6996 South Asians) and 15 062 control subjects. They observed little evidence for ancestry-specific associations, supporting the use of combined analyses. Furthermore, the authors state that because all individuals were genotyped on the same platform (whole-genome Illumina BeadChips), a meta-analysis of actual genotypes rather than imputed data enabled analysis of low-frequency variants (1% to 5%), which have been excluded from GWAS either because of sample size or because imputation has been required to combine data from different genotyping platforms. After the meta-analysis, they selected 59 SNPs from 50 loci that showed potential new associations from the meta-analysis of the European and South Asian studies (41 SNPs; P <1.0×10−4), the European-only meta-analysis (8 SNPs; P <3.0×10−5), the South …

Large-Scale Association Analysis Identifies 13 New Susceptibility Loci for Coronary Artery Disease

1. The CARDIoGRAM Consortium. Large-scale association analysis identifies 13 new susceptibility loci for coronary artery disease. Nature Genetics. 2011;43:333–338. ### Study Hypothesis Recently, genome-wide association studies (GWAS) have identified several common variants that are associated with risk of coronary artery disease (CAD) and myocardial infarction (MI). The authors state that the current loci discovered in CAD and MI GWAS explain only a small fraction of the heritability of this complex disease. The authors hypothesized that a larger study would provide more power to discover common variants with modest effect sizes. Therefore, they formed the Coronary ARtery DIsease Genome-wide Replication And Meta-analysis (CARDIoGRAM) consortium, which consisted of data from 14 GWAS of CAD and MI.1 ### How Was the Hypothesis Tested? The authors performed a meta-analysis of 14 GWAS of CAD comprising 22 233 cases and 64 762 control subjects, all of European ancestry. CAD was defined angiographically in a subset (n=7364) and by history in the entire sample. Presence of MI ranged from 48.1% to 100% of each cohort. After the meta-analysis, they genotyped the lead single-nucleotide polymorphisms (SNPs) within the most promising (defined a priori as P 90% power to detect effect sizes observed in the GWAS meta-analysis. Finally, to understand potential mechanisms and intermediate pathways by which novel loci may mediate risk, the authors interrogated 3 genome-wide studies that also assessed gene expression in multiple tissues, using human cell lines, a genome-wide map of allelic expression imbalance, and other human disease traits. ### Principal Findings The analysis of approximately 135 000 individuals more than doubled the number of loci with CAD association, yielding 13 previously unidentified loci and confirming at …

Genome-wide association identifies a susceptibility locus for coronary artery disease in the Chinese Han population

Coronary artery disease (CAD) causes more than 700,000 deaths each year in China. Previous genome-wide association studies (GWAS) in populations of European ancestry identified several genetic loci for CAD, but no such study has yet been reported in the Chinese population. Here we report a three-stage GWAS in the Chinese Han population. We identified a new association between rs6903956 in a putative gene denoted as C6orf105 on chromosome 6p24.1 and CAD (P = 5.00 × 10⁻³, stage 2 validation; P = 3.00 × 10⁻³, P = 1.19 × 10⁻⁸ and P = 4.00 × 10⁻³ in three independent stage 3 replication populations; P = 4.87 × 10⁻¹², odds ratio = 1.51 in the combined population). The minor risk allele A of rs6903956 is associated with decreased C6orf105 mRNA expression. We report the first GWAS for CAD in the Chinese Han population and identify a SNP, rs6903956, in C6orf105 associated with susceptibility to CAD in this population.

A genome-wide association study in Europeans and South Asians identifies five new loci for coronary artery disease

Genome-wide association studies have identified 11 common variants convincingly associated with coronary artery disease (CAD)¹⁻⁷, a modest number considering the apparent heritability of CAD⁸. All of these variants have been discovered in European populations. We report a meta-analysis of four large genome-wide association studies of CAD, with ∼575,000 genotyped SNPs in a discovery dataset comprising 15,420 individuals with CAD (cases) (8,424 Europeans and 6,996 South Asians) and 15,062 controls. There was little evidence for ancestry-specific associations, supporting the use of combined analyses. Replication in an independent sample of 21,408 cases and 19,185 controls identified five loci newly associated with CAD (P < 5 × 10⁻⁸ in the combined discovery and replication analysis): LIPA on 10q23, PDGFD on 11q22, ADAMTS7-MORF4L1 on 15q25, a gene rich locus on 7q22 and KIAA1462 on 10p11. The CAD-associated SNP in the PDGFD locus showed tissue-specific cis expression quantitative trait locus effects. These findings implicate new pathways for CAD susceptibility.

Improved Prediction of Cardiovascular Disease Based on a Panel of Single Nucleotide Polymorphisms Identified Through Genome-Wide Association Studies

Genome-wide association studies (GWAS) have identified single-nucleotide polymorphisms (SNPs) at multiple loci that are significantly associated with coronary artery disease (CAD) risk. In this study, we sought to determine and compare the predictive capabilities of 9p21.3 alone and a panel of SNPs identified and replicated through GWAS for CAD. We used the Ottawa Heart Genomics Study (OHGS) (3323 cases, 2319 control subjects) and the Wellcome Trust Case Control Consortium (WTCCC) (1926 cases, 2938 control subjects) data sets. We compared the ability of allele counting, logistic regression, and support vector machines. Two sets of SNPs, 9p21.3 alone and a set of 12 SNPs identified by GWAS and through a model-fitting procedure, were considered. Performance was assessed by measuring area under the curve (AUC) for OHGS using 10-fold cross-validation and WTCCC as a replication set. AUC for logistic regression using OHGS increased significantly from 0.555 to 0.608 (P=3.59×10⁻¹⁴) for 9p21.3 versus the 12 SNPs, respectively. This difference remained when traditional risk factors were considered in a subgroup of OHGS (1388 cases, 2038 control subjects), with AUC increasing from 0.804 to 0.809 (P=0.037). The added predictive value over and above the traditional risk factors was not significant for 9p21.3 (AUC 0.801 versus 0.804, P=0.097) but was for the 12 SNPs (AUC 0.801 versus 0.809, P=0.0073). Performance was similar between OHGS and WTCCC. Logistic regression outperformed both support vector machines and allele counting. Using the collective of 12 SNPs confers significantly greater predictive capabilities for CAD than 9p21.3, whether traditional risks are or are not considered. More accurate models probably will evolve as additional CAD-associated SNPs are identified.