9p21 is a Shared Susceptibility Locus Strongly for Coronary Artery Disease and Weakly for Ischemic Stroke in Chinese Han PopulationCLINICAL PERSPECTIVE
Background— Recent studies on genome-wide association have identified common variants on chromosome 9p21 associated with coronary artery disease (CAD). Given that ischemic stroke and CAD share several aspects of etiology and pathogenesis, we investigated the association of variants on chromosome 9p21 with ischemic stroke and CAD in the Chinese Han population by capturing the majority of diversity in this locus using haplotype-tagging single-nucleotide polymorphisms.
Methods and Results— We performed a shared control-cases study using 15 tagging single-nucleotide polymorphisms and 2 previously reported susceptibility single-nucleotide polymorphisms spanning 58 kb of the chromosome of 9p21 in a set of 558 patients with ischemic stroke, 510 patients with CAD, and 557 unaffected participants (controls) in the Chinese Han population. The association analyses were performed at both SNP and haplotype levels. We further verified our findings in an independent cohort of 442 ischemic stroke cases and 502 control subjects. In the first study, rs2383206, rs1004638, and rs10757278 in block 3 were significantly associated with CAD but not with ischemic stroke independent of traditional cardiovascular risk factors in additive model (P=0.002 to 0.0001, q=0.026 to 0.004). Analysis from all blocks revealed that haplotype profiles of block 3 on 9p21 were significantly different between shared control and cases of CAD (P=1.3×10−10, q=1.2×10−9) and ischemic stroke (P=1.7×10−6, q=7.7×10−6). In the expanded second case-control study, block 3 on 9p21 remained associated with ischemic stroke (P=2.6×10−4, q=6.3×10−4).
Conclusions— Our results suggest for the first time that 9p21 is a shared susceptibility locus, strongly for CAD and weakly for ischemic stroke, in a Chinese Han population.
- cerebrovascular disorders
- coronary disease
- ischemic stroke
- single-nucleotide polymorphisms
- Chinese Han population
Received July 29, 2008; accepted May 19, 2009.
Coronary artery disease (CAD) and stroke are the leading causes of morbidity and mortality worldwide.1 In China, more than 2.5 million people are affected by stroke and 1 million are affected by heart attack, leading to more than 2 million deaths each year (http://www.moh.gov.cn). It was found that the conventional cardiovascular risk factors such as abnormal lipid metabolism, smoking, diabetes, and hypertension only account for 50% to 60% of the disease susceptibility,2,3 indicating that other risk factors such as genetic predisposition are also implicated in the pathogenesis of disease development. Indeed, over the last decade, numerous genetic variations have been reported to be associated with CAD and ischemic stroke.4–6 Particularly, a genomic region on chromosome 9p21 was found to be consistently associated with CAD in several populations of European origin and East Asian origin,7–13 although genetic heterogeneity was observed in blacks.9,14
Clinical Perspective on p 338
Given the fact that ischemic stroke and CAD share several aspects of etiology and pathogenesis, the genomic interval on chromosome 9p21 could be a candidate locus for ischemic stroke as well. Consistent with this notion, Matarin et al15 reported evidence suggesting that ischemic stroke and heart disease share an association with polymorphisms on chromosome 9p21. A follow-up study further demonstrated that the chromosomal 9p21 region confers less genetic susceptibility on ischemic stroke than CAD.16 However, a genome-wide association study failed to confirm the above results.17 Therefore, additional genetic studies would be necessary to further define the genetic association between the chromosomal 9p21 region and CAD/ischemic stroke. For this purpose, we performed a case-control study in the Chinese Han population using a large cohort consisting of 558 patients with ischemic stroke, 510 patients with CAD, and 557 controls. A total of 17 SNPs flanking a 58-kb genomic interval on chromosome 9p21 were used in this study. We further replicated these tests in an independent set of populations consisting of 442 patients with ischemic stroke and 502 control subjects.
Subjects for 2 Independent Case-Control Studies
This multicenter study for assessment of risk factors for stroke and CADs was sponsored by the Ministry of Science and Technology of China. Briefly, a total of 558 ischemic stroke subjects were recruited between November 2004 and June 2006 from 5 hospitals in Wuhan, China. Patients with only 1 of the 2 subtypes, cerebral thrombosis (atherothrombosis, 73.5%) and lacunar infarction (lacunar, 26.5%) of stroke were included. Confirmation of stroke was based on the results of strict neurological examination, computed tomography, or MRI according to the International Classification of Diseases (9th Revision). Other types of stroke (transient ischemic attack, intracerebral hemorrhage, subarachnoid hemorrhage, embolic brain infarction, brain tumors, and cerebrovascular malformation) and severe systemic diseases such as pulmonary fibrosis, endocrine and metabolic disease (except diabetes mellitus), severe inflammatory diseases, autoimmune disease, tumors, and serious chronic diseases (eg, hepatic cirrhosis, renal failure) were excluded from the study. Subjects with cardioembolic stroke and documented atrial fibrillation were also excluded from our study. A total of 510 subjects with CAD were recruited from the hospitalized patients in the Tongji Hospital and the Institute of Hypertension (Wuhan, China) between October 2002 and September 2006. Patients who survived an acute myocardial infarction or were documented by coronary angiography to have at least a 70% stenosis in a major epicardial artery were eligible. A detailed history of angina or myocardial infraction was obtained. Of the patients, 75% had myocardial infraction judged by typical ECG change (Minnesota Code 1.1 or 1.2 in ECG) and by changes in serum enzymes (troponin T, troponin I, creatine kinase-MB, aspartate aminotransferase, and glutamic pyruvic transaminase). Subjects with congenital heart disease, cardiomyopathy, valvular disease, and renal or hepatic disease were excluded from the study.
Five hundred fifty-seven ethnically and geographically matched controls were randomly selected either from healthy residents in the community (89.6%) or inpatients (10.4%) with minor illnesses. All control subjects were free of neurological and cardiovascular diseases following the same exclusion criteria as cases. They were also asked for a detailed medical history and received a physical examination of cardiovascular and neurological systems, including evaluation of body mass index.
To confirm credibility of results obtained from the first set of populations described earlier, we introduced the second independent case-control cohort that comprised 442 patients with ischemic stroke (65.2% cerebral thrombosis and 34.8% lacunar infarction) and 502 unaffected controls recruited simultaneously from the Xinhua Hospital, First Wuhan Hospital, and Tongji Hospital between August 2007 and October 2008 in Hubei Province, China. The diagnostic criteria for stroke and the recruited criteria for controls were identical to those used in the first study.
All the study protocols were approved by the Review Board of the Ministry of Public Health, Ministry of Science and Technology of China, and the ethics committees at all participating hospitals, and informed written consent was obtained from all participants.
Two previously reported susceptibility SNPs8 (rs10757278 and rs1333040) and 15 haplotype-tagging SNPs shown in supplementary Table I were included in the study. These SNPs flank a 58-kb genomic region on chromosome 9p21 (National Center for Biotechnology Information build 36.1 from 22 062 301 to 22 120 389). The initial set of 63 common variants (minor allele frequency >0.05) in this region can be well captured (r2>0.75) by this set of 15 haplotype-tagging SNPs, which were selected from the genotyped SNPs in the Chinese Han population of the HapMap project (the Phase II database) using the pairwise tagging method in Haploview 4.0.18
DNA Isolation and Genotyping
Genomic DNA was isolated from whole blood collected in K3-EDTA tubes using the QG-Mini80 workflow with a DB-S kit (Fujifilm Corporation, Tokyo, Japan) as instructed. DNA was quantified and diluted to a final concentration of 10 ng/μL.
All samples were genotyped using the Taqman 7900HT Sequence Detection System, Applied Biosystems, Foster City, Calif., according to the manufacture’s instructions. Each assay was carried out using 10 ng DNA in a 5-μL reaction consisting of TaqMan universal polymerase chain reaction master mix (Applied Biosystems, Foster City, Calif), forward and reverse primers, and 6-carboxyfluorescein (FAM) and 4,7,2′-trichloro-7′-phenyl-6-carboxyfluorescein (VIC) labeled probes designed by Applied Biosystems (ABI Assays-on-Demand). Allelic discrimination was measured automatically using the Sequence Detection Systems 2.1 software (autocaller confidence level 95%). A total of 10% of all genotypes were repeated in independent polymerase chain reactions to check for consistency and to ensure intraplate and interplate genotype quality control. No genotyping discrepancies were detected between the repeated samples. In addition, all the DNA samples for cases and controls were run in the same batch.
Statistical analysis were performed with SPSS 13.0 (SPSS Inc, Chicago, Ill) for Windows (Microsoft Corp, Redmond, Wash) and SNPassoc for R statistical package.19 The level of linkage disequilibrium was indicated in our article by D′. The presence of Hardy-Weinberg equilibrium per SNP was tested using Haploview 4.0, which is based on χ2 goodness-of-fit test.
The normality of quantitative variables distribution was assessed using 1-sample Kolmogorov-Smirnov test, and the transformation was applied for those nonnormality variables when necessary. All quantitative variables were generally described as means with SD. For comparison of the baseline characteristics among different groups, 1-way ANOVA test was performed on quantitative variables, such as age, body mass index, high-density lipoprotein-cholesterol, total cholesterol, etc; χ2 test was used for qualitative variables.
For each SNP, differences of allelic and genotype frequencies between cases and controls were determined by the χ2 or Fisher exact test. Multivariable unconditional logistic regression was used to estimate odds ratio (OR) and 95% CI under different genetic models after adjusting for gender, age, body mass index, hypertension, diabetes, hyperlipidemia, and smoking status.
Haplotype frequencies for various SNP combinations were first estimated by haplo.stats19 (version 1.2.1) for the R statistical package and then verified using Haploview 4.0. Both of the aforementioned softwares use the expectation-maximization algorithm when constructing the haplotypes. The haplo.stats program could help compute global score and haplotype-specific score P values while allowing for adjusting covariates under additive model using default settings.
To minimize the false-positive results generated from multiple statistical testing in our analysis, we adopted a method proposed by Story and Tibshirani to estimate the false discovery rate-based q value using QVALUE software (setting [lambda]=0, false discovery rate level=0.05).20 In this study, we first applied the χ2 or Fisher exact test for an initial screening, and then followed by the multiple unconditional logistic regression for the verification with more rigorous evaluations. All association analyses were conducted in 3 genetic models: dominant, recessive, and additive. In our haplotype analysis, global score tests were applied to evaluate overall haplotype frequency differences between cases and controls, whereas the haplotype-specific score tests were performed to test individual haplotype difference between cases and controls and allowing for adjustment of covariates. A total of (36 allele tests, 36 genotype tests, 36 tests for different genetic models) 9 global block association analyses, 43 haplotye-specific tests, and 34 additional tests with covariates adjustments were conducted in our study. Hence, to account for multiple testing issue in above analyses, q-value correction procedure was applied from every of these tests.
The statistical power of our study was estimated by QUANTO program21 (version 1.2.3). Under the significance level of P=0.05, minor allele frequency between 0.25 and 0.40, assuming population disease prevalence between 0.5% and 1% and main genetic effect between 1.2 and 1.5, our study design can reach >84% power in additive and dominant models and up to 70% power in the recessive model. Considered about multiple comparison adjustment, the actual power in our analysis might be lower than these estimates.
SNPs Within the Chromosomal 9p21 Region Are Associated With CAD in the Chinese Han Population
The demographic details for the 2 case-control studies are shown in Table 1. To demonstrate the genetic susceptibility of chromosome 9p21 in CAD and ischemic stroke in the Chinese Han population, 17 SNPs flanking a region of 58 kb DNA sequence were genotyped with 510 subjects with CAD, 558 subjects with ischemic stroke, and 557 matched control subjects. One SNP, rs10811658, was removed from the analysis because it did not conform to Hardy-Weinberg equilibrium in the control sample, leaving 16 SNPs for association analyses.
The Pallele and Pgenotype values for each SNP by genomic position are shown in supplementary Table I. Six SNPs (rs10757269 and rs9632884 in block 1; rs1333040 in block2; rs2383206, rs1004638, and rs10757278 in block 3; Figure) were significantly associated with CAD among either allele or genotype analysis. Of important note, 3 SNPs (rs2383206, rs1004638, and rs10757278) in block 3, which were in strong LD (D′ range, 0.86 to 0.91; Figure) and only flank a 9 kb of DNA sequence, showed the strongest association with CAD. Mutiplicative-type corrections such as Bonferroni corrections for correlated genetic factors and tests are highly conservative. Therefore, we present the q value, a measure of false discovery rate expected for a given P value in the follow-up analysis. Because all q values of these 3 SNPs in block 3 were conservatively estimated to be <0.05 in both allelic and genotypic analysis (supplementary Table II), we were confident that the genomic region on 9p21 confers genetic susceptibility for CAD in the Chinese Han population. In addition, our multivariate unconditional logistic regression analyses further demonstrated that rs2383206, rs1004638, and rs10757278 remain significantly associated with CAD independent of traditional cardiovascular risk factors in additive model (P=0.002 to 0.0001, q=0.026 to 0.004), whereas rs1004638 and rs10757278 remain significantly in dominant model (P=0.002 and 0.009, q=0.028 and 0.028); and only rs1004638 remain significantly in recessive model (P=0.002, q=0.043) (Table 2 and supplementary Table II).
Haplotype Analysis for Genetic Association Between 9p21 and CAD
Table 3 shows the results of haplotype analysis for the SNPs examined. Using the genotypes of 557 controls, we defined the haploblock structure of SNPs within the region of 9p21 in the Chinese Han population. By defining a solid spine of LD as D′>0.90, we identified four haploblocks in the 9p21 region (Figure). Analysis of all blocks revealed that the associations with CAD were restricted to SNPs in blocks 1 and 3 (Table 3) as manifested by the global P values (P=2.8×10−4 and P=1.3×10−10; q=6.3×10−4 and q=1.2×10−9, respectively).
Next, we focused on the haplotyes within block 3 with the strongest association. One haplotype, GTTG, was more frequent in CAD than control subjects (39.2% versus 49.6%, P=2.54×10−6, q=5.8×10−5) and the other haplotype, ATTA, was less frequent (0.3% versus 3.9%, P=1.1×10−6, q=4.7×10−5). To determine the possible specific disease-predisposing haplotypes in patients with CAD, we performed haplotype-based hypothesis tests using the software haplo.stats to adjust the conventional risk factors. Because the most frequent haplotype may be an at-risk haplotype, we chose other common haplotypes as the baseline according to the instruction of haplo.stats. When haplotype AATA in block 3 was chosen as the baseline, haplotype GTTG in block 3 displayed a significant increased risk for CAD (GTTG versus AATA; OR, 1.08; 95% CI, 1.04 to 1.13; P=2.83×10−4; q=0.005). In contrast, individuals carrying haplotype ATTA in block 3 showed a significant protective effect for developing CAD (ATTA versus AATA; OR, 0.85; 95% CI, 0.76 to 0.95; P=0.006; q=0.047). Taken together, our results lend additional evidence supporting the existence of a genetic susceptible locus for CAD on chromosome 9p21 in the Chinese Han population.
Genetic Association Between 9p21 and Ischemic Stroke in 2 Independent Case-Control Studies
To our surprise, only SNP rs1004638 was detected to have a marginal significant association for ischemic stroke in the first study. Subjects carrying the T allele were more susceptible to ischemic stroke in the additive model (P=0.018, q=0.06) after adjusting important cardiovascular risk factors. Although the disease subjects showed a higher frequency for T allele, the difference was not significant in the univariate analysis (P=0.11).
We also performed a haplotype analysis shown in Table 4. Similar to CAD, association with ischemic stroke was restricted to SNPs in 3 as manifested by the global P values (P=1.7×10−6, q=7.7×10−6). When AATA haplotype in block 3 was chosen as the baseline for adjusting conventional risk factors, the protective effect for haplotype ATTA remained significant (ATTA versus AATA; OR, 0.78; 95% CI, 0.67 to 0.87; P=4.1×10−5; q=0.001), whereas there is no increased risk of GGTG versus AATA (Table 4).
To replicate this weak association with ischemic stroke, we genotyped 4 SNPs (rs2383206, rs1004638, rs17761442, and rs10757278) within block 3 in an additional set of 442 ischemic stroke cases and 502 control subjects. All these SNPs were found to be in Hardy-Weinberg equilibrium. Although none of the SNPs were statistically associated with ischemic stroke, rs1004638 showed trends associated with ischemic stroke in the adjusted dominant model (P=0.068, data not shown), but not with other genetic models. By contrast, block 3 on 9p21 remained associated with ischemic stroke as indicated by the global P values (P=2.6×10−4, q=6.3×10−4). In addition, when AATA haplotype in block 3 was chosen as the baseline for adjusting conventional risk factors, the protective effect for haplotype ATTA remained significant (ATTA versus AATA; OR, 0.85; 95% CI, 0.77 to 0.95; P=0.003; q=0.034; Table 4). Combining these data, our results suggest the existence of a susceptible locus for ischemic stroke on chromosome 9p21 in the Chinese Han population.
This study demonstrated a significant association between SNPs within a region on chromosome 9p21 and the risk for CAD and ischemic stroke in the Chinese Han population, which suggested that 9p21 could be a potential atherosclerotic disease-susceptibility locus. Specifically, 3 SNPs (rs2383206, rs1004638, and rs10757278) in a strong LD block 3 were associated with a significantly higher risk for developing CAD in the Chinese Han population. Haplotype profiles of block 3 on 9p21 were significantly different between shared controls and cases of CAD as well as ischemic stroke. However, the genetic variations on block 3 conferred weaker risk for ischemic stroke compared with CAD. To exclude the potential false-positive association with ischemic stroke, we conducted our analyses in 2 independent cohorts. The significant, though not very strong, associations between block 3 SNPs on chromosome 9p21 and ischemic stroke were consistent across these 2 replicates.
Recently, 4 SNPs on the susceptibility locus 9p21 previously identified in multiple cohorts of European populations had been successfully replicated in CAD in the Japanese and Korean population.12,13 In contrast, none of these SNPs was associated with CAD in blacks.9 To demonstrate these intriguing results, we made comparisons of genetic background in different ethnic groups from HapMap and identified notable ethnic differences in allelic distributions and LD structure (supplementary Table III). As a result of higher genetic diversity and lower extent of LD in the African populations,22 the YRI population (Yoruba people of Ibadan, Nigeria) have many more alleles and blocks in this region, whereas most were less common or rare compared with non-African ethnic groups. On the contrary, most CAD related variants on chromosome 9p21 seem to have acquired a high frequency (8 of 9 SNPs minor allele frequency >0.4, supplementary Table III) by positive selection in the CEU population (U.S. residents with Northern and Western European Ancestry). Because power estimates for disease association studies rely on estimates of the risk allele frequency in a population,23 the less common SNPs in blacks may not have sufficient statistic power to replicate these results. However, frequencies of SNPs on 9p21 in non-African groups is similar, and thus, non-African groups may have sufficient statistic power to replicate these results. Consequently, we successfully replicated these results in CAD in the Chinese Han population. Frequencies of these variants differ widely among different ethnic groups, and may have a different degree of influence on CAD and at least partly contribute to differences in CAD prevalence. Interestingly, 10 SNPs captured by rs17761446 in Han Chinese in Beijing (CHB) of HapMap were absent in CEU. However, we did not find an association between this tagging single-nucleotide polymorphism with CAD and ischemic stroke in our study.
To minimize the impact of the multiple statistical tests conducted in our analysis, we estimated the false discovery rate q values of our findings. Three SNPs (rs2383206, rs1004638, and rs10757278) within block 3 on 9p21 have a high level of confidence in the associated with CAD. Furthermore, the results from logistic regression confirmed the importance of these SNPs. Of important note, 1 SNP rs2383207, which is well captured by rs1004638 (D′=1) in HapMap CHB, has recently been associated with increased susceptibility to CAD in another independent Chinese Han population.24 On the basis of the stringent analysis of these SNPs and replication in our research, we are confident that 9p21 region is a strong candidate locus for CAD susceptibility in the Chinese Han population.
Carotid atherosclerosis was considered as a surrogate end point of CAD and stroke25 and a population-based, prospective study recently demonstrated the association of genetic variation on chromosome 9p21 with prevalent carotid atherosclerosis and its progression.26 Our results support that variations in 9p21 region are associated with both CAD and stroke. However, it seems that the chromosomal 9p21 region confers less genetic susceptibility on ischemic stroke than CAD.
Compared with CAD, although only the rs1004638 on chromosome 9p21 showed marginal association with ischemic stroke, the association of haplotype remained and was restricted to SNPs in blocks 3. To avoid false-positive association between ischemic stroke and variations on chromosome 9p21, we replicated these tests in another independent population. Consistent with the results in our first study, association of block 3 on chromosome 9p21 with ischemic stroke was statistically significant, which provided solid evidence that the variants on 9p21 were truly associated with ischemic stroke. Thus, we can conclude that ischemic stroke and CAD share an association with variants on chromosome 9p21, but it is much weaker for the former case.
One potential pitfall of our study is the multiple comparison adjustment. Because of multiple association tests we performed for both SNP and haplotype analyses, the false-positive results are still possible even after our adjustments using the q-value correlation approach. More important, the actual statistical power in our analysis might be lower than those estimates from simulations. However, the successful replication of association signals in 2 independent cohorts improves the plausibility of our study.
In summary, this study provides the first evidence that 9p21 is a shared susceptibility locus for CAD and ischemic stroke in the Chinese Han population. More important, these variants may have different degrees of influence on CAD and ischemic stroke in Chinese. The mechanism whereby the genetic variants exert their different effects on 2 atherosclerotic phenotypes remains to be elucidated.
We thank Dr Tang-Chun Wu, the Institute of Occupational Medicine, and the Ministry of Education Key Laboratory of Environment and Health (School of Public Health, Tongji Medical College) for help in genetic statistics.
Sources of Funding
This work was supported by grants from the National Nature Science Foundation Committee of China (No. 30430320), National “863” project (No. 2006AA02A406), and “973” projects (No. 2007CB512004, 2006CB503801).
World Health Organization. World Health Statistics Annual, 1993. Geneva, Switzerland: World Health Organization; 1994.
Ecological analysis of the association between mortality and major risk factors of cardiovascular disease. The World Health Organization MONICA Project. Int J Epidemiol. 1994; 23: 505–516.
He J, Klag MJ, Wu Z, Whelton PK. Stroke in the People’s Republic of China. I. Geographic variations in incidence and risk factors. Stroke. 1995; 26: 2222–2227.
Dichgans M, Hegele RA. Update on the genetics of stroke and cerebrovascular disease 2006. Stroke. 2007; 38: 216–218.
Helgadottir A, Manolescu A, Thorleifsson G, Gretarsdottir S, Jonsdottir H, Thorsteinsdottir U, Samani NJ, Gudmundsson G, Grant SF, Thorgeirsson G, Sveinbjornsdottir S, Valdimarsson EM, Matthiasson SE, Johannsson H, Gudmundsdottir O, Gurney ME, Sainz J, Thorhallsdottir M, Andresdottir M, Frigge ML, Topol EJ, Kong A, Gudnason V, Hakonarson H, Gulcher JR, Stefansson K. The gene encoding 5-lipoxygenase activating protein confers risk of myocardial infarction and stroke. Nat Genet. 2004; 36: 233–239.
Helgadottir A, Thorleifsson G, Manolescu A, Gretarsdottir S, Blondal T, Jonasdottir A, Sigurdsson A, Baker A, Palsson A, Masson G, Gudbjartsson DF, Magnusson KP, Andersen K, Levey AI, Backman VM, Matthiasdottir S, Jonsdottir T, Palsson S, Einarsdottir H, Gunnarsdottir S, Gylfason A, Vaccarino V, Hooper WC, Reilly MP, Granger CB, Austin H, Rader DJ, Shah SH, Quyyumi AA, Gulcher JR, Thorgeirsson G, Thorsteinsdottir U, Kong A, Stefansson K. A common variant on chromosome 9p21 affects the risk of myocardial infarction. Science. 2007; 316: 1491–1493.
McPherson R, Pertsemlidis A, Kavaslar N, Stewart A, Roberts R, Cox DR, Hinds DA, Pennacchio LA, Tybjaerg-Hansen A, Folsom AR, Boerwinkle E, Hobbs HH, Cohen JC. A common allele on chromosome 9 associated with coronary heart disease. Science. 2007; 316: 1488–1491.
Samani NJ, Erdmann J, Hall AS, Hengstenberg C, Mangino M, Mayer B, Dixon RJ, Meitinger T, Braund P, Wichmann HE, Barrett JH, Konig IR, Stevens SE, Szymczak S, Tregouet DA, Iles MM, Pahlke F, Pollard H, Lieb W, Cambien F, Fischer M, Ouwehand W, Blankenberg S, Balmforth AJ, Baessler A, Ball SG, Strom TM, Braenne I, Gieger C, Deloukas P, Tobin MD, Ziegler A, Thompson JR, Schunkert H. Genomewide association analysis of coronary artery disease. N Engl J Med. 2007; 357: 443–453.
Schunkert H, Gotz A, Braund P, McGinnis R, Tregouet DA, Mangino M, Linsel-Nitschke P, Cambien F, Hengstenberg C, Stark K, Blankenberg S, Tiret L, Ducimetiere P, Keniry A, Ghori MJ, Schreiber S, El Mokhtari NE, Hall AS, Dixon RJ, Goodall AH, Liptau H, Pollard H, Schwarz DF, Hothorn LA, Wichmann HE, Konig IR, Fischer M, Meisinger C, Ouwehand W, Deloukas P, Thompson JR, Erdmann J, Ziegler A, Samani NJ. Repeated replication and a prospective meta-analysis of the association between chromosome 9p21.3 and coronary artery disease. Circulation. 2008; 117: 1675–1684.
Shen GQ, Li L, Rao S, Abdullah KG, Ban JM, Lee BS, Park JE, Wang QK. Four SNPs on chromosome 9p21 in a South Korean population implicate a genetic locus that confers high cross-race risk for development of coronary artery disease. Arterioscler Thromb Vasc Biol. 2008; 28: 360–365.
Hinohara K, Nakajima T, Takahashi M, Hohda S, Sasaoka T, Nakahara K, Chida K, Sawabe M, Arimura T, Sato A, Lee BS, Ban JM, Yasunami M, Park JE, Izumi T, Kimura A. Replication of the association between a chromosome 9p21 polymorphism and coronary artery disease in Japanese and Korean populations. J Hum Genet. 2008; 53: 357–359.
Matarin M, Brown WM, Singleton A, Hardy JA, Meschia JF. Whole genome analyses suggest ischemic stroke and heart disease share an association with polymorphisms on chromosome 9p21. Stroke. 2008; 39: 1586–1589.
Helgadottir A, Thorleifsson G, Magnusson KP, Gretarsdottir S, Steinthorsdottir V, Manolescu A, Jones GT, Rinkel GJ, Blankensteijn JD, Ronkainen A, Jaaskelainen JE, Kyo Y, Lenk GM, Sakalihasan N, Kostulas K, Gottsater A, Flex A, Stefansson H, Hansen T, Andersen G, Weinsheimer S, Borch-Johnsen K, Jorgensen T, Shah SH, Quyyumi AA, Granger CB, Reilly MP, Austin H, Levey AI, Vaccarino V, Palsdottir E, Walters GB, Jonsdottir T, Snorradottir S, Magnusdottir D, Gudmundsson G, Ferrell RE, Sveinbjornsdottir S, Hernesniemi J, Niemela M, Limet R, Andersen K, Sigurdsson G, Benediktsson R, Verhoeven EL, Teijink JA, Grobbee DE, Rader DJ, Collier DA, Pedersen O, Pola R, Hillert J, Lindblad B, Valdimarsson EM, Magnadottir HB, Wijmenga C, Tromp G, Baas AF, Ruigrok YM, van Rij AM, Kuivaniemi H, Powell JT, Matthiasson SE, Gulcher JR, Thorgeirsson G, Kong A, Thorsteinsdottir U, Stefansson K. The same sequence variant on 9p21 associates with myocardial infarction, abdominal aortic aneurysm and intracranial aneurysm. Nat Genet. 2008; 40: 217–224.
Matarin M, Brown WM, Scholz S, Simon-Sanchez J, Fung HC, Hernandez D, Gibbs JR, De Vrieze FW, Crews C, Britton A, Langefeld CD, Brott TG, Brown RD Jr, Worrall BB, Frankel M, Silliman S, Case LD, Singleton A, Hardy JA, Rich SS, Meschia JF. A genome-wide genotyping study in patients with ischaemic stroke: initial analysis and data release. Lancet Neurol. 2007; 6: 414–420.
Barrett JC, Fry B, Maller J, Daly MJ. Haploview: analysis and visualization of LD and haplotype maps. Bioinformatics. 2005; 21: 263–265.
Storey JD, Tibshirani R. Statistical significance for genomewide studies. Proc Natl Acad Sci USA. 2003; 100: 9440–9445.
Gauderman W, Morrison J. QUANTO 1.1: A computer program for power and sample size calculations for genetic-epidemiology studies, http://hydra.usc.edu/gxe (2006).
Purcell S, Cherny SS, Sham PC. Genetic power calculator: design of linkage and association genetic mapping studies of complex traits. Bioinformatics. 2003; 19: 149–150.
Zhou L, Zhang X, He M, Cheng L, Chen Y, Hu FB, Wu T. Associations between single nucleotide polymorphisms on chromosome 9p21 and risk of coronary heart disease in chinese Han population. Arterioscler Thromb Vasc Biol. 2008; 28: 2085–2089.
The results of this study extend the findings from recent genome-wide association studies that common genetic variants on chromosome 9p21 were strongly associated with increased susceptibility to coronary artery disease. Our data suggest that this locus is also associated with the risk of ischemic stroke in the Chinese Han population. Genetic variants may contribute to the estimation of the absolute risk of developing cardiovascular disease events when combined with traditional cardiovascular risk factors. However, it remains to be determined whether genetic variants on chromosome 9p21 would improve discrimination or classification of cardiovascular risk when combined with traditional risk factors in different populations. Therefore, the practical utility of our data needs further investigation.
Drs Ding and Xu equally contributed to this work.
The online-only Data Supplement is available at http://circgenetics.ahajournals.org/cgi/content/full/CIRCGENETICS.108.810226/DC1.