Are myocardial infarction--associated single-nucleotide polymorphisms associated with ischemic stroke?

CYP2C8 and CYP2J2 gene variations increase the risk of hypertensive intracerebral hemorrhage

PURPOSE

Many studies have shown that cytochrome P450 (CYP) gene polymorphisms are usually associated with an increased risk of cardiovascular and cerebrovascular diseases. To explore the association of CYP2C8 and CYP2J2 gene polymorphisms with hypertensive intracerebral hemorrhage (HICH) in the Han Chinese population.

METHODS

Forty HICH patients and 40 control subjects were recruited for this study. Two single nucleotide polymorphisms (SNP) (rs1058932, rs2275622) in the CYP2C8 gene and two SNPs (rs2271800, rs1155002) in the CYP2J2 gene were selected for genotyping by direct sequencing. Statistical analysis was applied to examine the effect of genetic variation on HICH.

RESULTS

We found that variant alleles of CYP2C8 rs1058932 (A) and rs2275622 (C) were both significantly associated with HICH, especially in females. We also found significant associations of CYP2C8 rs1058932 (A) and rs2275622 (C) variant alleles with poor outcomes in HICH patients, especially in males.

CONCLUSIONS

CYP2C8 gene polymorphisms might increase the risk of HICH in the Han Chinese population and might lead to poor outcomes. This finding adds to the body of literature supporting novel therapeutic strategies for HICH.

Association of single-nucleotide polymorphism on chromosome 9 and ischemic stroke in Heilongjiang province in China

There is a significant correlation between ischemic stroke (IS) and chromosome 9. However, its status was uncertain in China's cold regions. 1920 IS patients, and 1920 healthy individuals were included in the study. Blood samples were collected. The association of SNPs with IS was evaluated by Sequenom, and logistic regression models adjusted for known risk factors of IS were constructed to assess the SNPs' associations in cases and controls. We found rs1333040 and rs2383207 were associated with IS, compared with primitive genotypes. The genotype CT of rs7027526 has a protective role during IS development, while the effect of the genotype TT is still not clear. These results changed after stratification by age and sex. In conclusion, rs1333040 and rs2383207 SNPs in CDKN2BAS are associated with ischemic stroke in the Chinese Han population. This study confirms the association between 9p21.3 and IS.

Association between lncRNA ANRIL genetic variants with the susceptibility to ischemic stroke: From a case-control study to meta-analysis

BACKGROUND

Recent studies have reported that lncRNA (long noncoding RNAs) antisense non-coding RNA in the INK4 locus (ANRIL) plays important roles in the development of atherosclerosis through regulating cell apoptosis, proliferation, and adhesion. GWAS (genome-wide association studies) identified common genetic variants within ANRIL could confer risk of ischemic stroke (IS) in southern Sweden.

METHODS

We performed a case-control study, including 567 IS patients and 552 healthy controls from unrelated northern Chinese Han population, aiming to explore the association between lncRNA ANRIL rs2383207, rs4977574 polymorphisms and the risk of IS. Subsequently we implemented a meta-analysis to further assess the relationship of these variants and the disease.

RESULTS

In our case-control study, no significant associations were observed in all models between above 2 polymorphisms and IS. Next in our subgroup analysis, we detected significant association between GA genotype of rs4977574 and the increased risk of LAA-IS (large-artery atherosclerotic ischemic stroke), similar elevated risk also appeared in the GG + GA genotype under the dominant model (P = .048, OR = 1.385, 95% CIs 1.002-1.914; P = .040, OR = 1.378, 95% CIs 1.015-1.872, respectively). As for rs2383207, negative results were obtained under all models and subgroups. Our meta-analysis showed a significant association between rs4977574 polymorphism and IS risk in allele model (G vs A P = .002, OR = 1.137, 95% CIs 1.048-1.234); with respect to rs2383207 polymorphism, no significant association between that and the risk of IS was detected under the dominant model (GA + AA vs GG, P = .061, OR = 0.923, 95% CIs 0.849-1.004), or recessive model (AA vs GA + GG, P = .656, OR = 0.972, 95% CIs 0.858-1.101), or allele model (A vs G, P = .326, OR = 0.952, 95% CIs 0.863-1.050). Likewise, no significant association between rs2383207 and IS was found in different stoke subtypes (P > .05).

CONCLUSIONS

Our findings indicated G allele of lncRNA ANRIL rs4977574 could increase the risk of IS, and the variant may be associated with susceptibility to LAA-IS in Chinese Han population.

The association between the chromosome 9p21 CDKN2B-AS1 gene variants and the lipid metabolism: A pre-diagnostic biomarker for coronary artery disease

Objective:

Recent genome-wide association studies have established that polymorphisms within CDKN2B-AS1 of chr9p21.3 locus increased susceptibility to coronary artery disease (CAD) or myocardial infarction. Common variants of CDKN2B-AS1 (including rs4977574 A>G and rs1333040 C>T) are determined to be directly associated with CADs in many populations worldwide and suggested biomarkers for the early detection of CAD. There is a lack of investigation for the association between CDKN2B-AS1 rs4977574 A>G and rs1333040 C>T genetic modifiers and CAD in a Turkish Cypriot population. The aim of the present study was to investigate the potential effects of these variants on susceptibility to developing CAD in a Turkish Cypriot population and their contribution to lipid metabolism.

Methods:

Seventy-one patients with angiography-confirmed CAD were recruited to the CAD group, whereas 153 voluntary subjects without CAD symptoms were enrolled to the control group. Genotyping for the CDKN2B-AS1 gene polymorphisms was performed by polymerase chain reaction, followed by restriction fragment length polymorphism analysis.

Results:

There is no statistical significant association observed between rs4977574 and rs1333040 single-nucleotide polymorphisms and two studied groups [odds ratio (OR): 0.763, p=0.185, 95% confidence interval (CI): 0.511–1.139 and OR: 1.060, p=0.802, 95% CI 0.672–1.671, respectively]. However, rs2977574 G and rs1333040 T alleles–the risk alleles–were found to be associated with higher level of serum total cholesterol and lower level of high-density lipoprotein-cholesterol in the CAD group (p=0.019, p=0.006 and p=0.022, p=0.031, respectively). To our knowledge, this is the first study that establishes the effect of rs1333040 on lipid metabolism.

Conclusion:

The presence of rs4977574 G and rs1333040 T alleles and interaction may exist as environmental factors associated with lipid metabolism and might be responsible for the development of CAD in a Turkish Cypriot population.

Association between PPARG genetic polymorphisms and ischemic stroke risk in a northern Chinese Han population: a case-control study

Two common polymorphisms of the peroxisome proliferator-activated receptor gamma (PPARG) gene, rs1801282 and rs3856806, may be important candidate gene loci affecting the susceptibility to ischemic stroke. This case-control study sought to identify the relationship between these two single-nucleotide polymorphisms and ischemic stroke risk in a northern Chinese Han population. A total of 910 ischemic stroke participants were recruited from the First Hospital of China Medical University, Shenyang, China as a case group, of whom 895 completed the study. The 883 healthy controls were recruited from the Health Check Center of the First Hospital of China Medical University, Shenyang, China. All participants or family members provided informed consent. The study protocol was approved by the Ethics Committee of the First Hospital of China Medical University, China on February 20, 2012 (approval No. 2012-38-1). The protocol was registered with the Chinese Clinical Trial Registry (registration number: ChiCTR-COC-17013559). Plasma genomic DNA was extracted from all participants and analyzed for rs1801282 and rs3856806 single nucleotide polymorphisms using a SNaPshot Multiplex sequencing assay. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using unconditional logistic regression to estimate the association between ischemic stroke and a particular genotype. Results demonstrated that the G allele frequency of the PPARG gene rs1801282 locus was significantly higher in the case group than in the control group (P < 0.001). Individuals carrying the G allele had a 1.844 fold increased risk of ischemic stroke (OR = 1.844, 95% CI: 1.286-2.645, P < 0.001). Individuals carrying the rs3856806 T allele had a 1.366 fold increased risk of ischemic stroke (OR = 1.366, 95% CI: 1.077-1.733, P = 0.010). The distribution frequencies of the PPARG gene haplotypes rs1801282-rs3856806 in the control and case groups were determined. The frequency of distribution in the G-T haplotype case group was significantly higher than that in the control group. The risk of ischemic stroke increased to 2.953 times in individuals carrying the G-T haplotype (OR = 2.953, 95% CI: 2.082-4.190, P < 0.001). The rs1801282 G allele and rs3856806 T allele had a multiplicative interaction (OR = 3.404, 95% CI: 1.631-7.102, P < 0.001) and additive interaction (RERI = 41.705, 95% CI: 14.586-68.824, AP = 0.860; 95% CI: 0.779-0.940; S = 8.170, 95% CI: 3.772-17.697) on ischemic stroke risk, showing a synergistic effect. Of all ischemic stroke cases, 86% were attributed to the interaction of the G allele of rs1801282 and the T allele of rs3856806. The effect of the PPARG rs1801282 G allele on ischemic stroke risk was enhanced in the presence of the rs3856806 T allele (OR = 8.001 vs. 1.844). The effect of the rs3856806 T allele on ischemic stroke risk was also enhanced in the presence of the rs1801282 G allele (OR = 2.546 vs. 1.366). Our results confirmed that the G allele of the PPARG gene rs1801282 locus and the T allele of the rs3856806 locus may be independent risk factors for ischemic stroke in the Han population of northern China, with a synergistic effect between the two alleles.

Mendelian randomization evaluation of causal effects of fibrinogen on incident coronary heart disease

BACKGROUND

Fibrinogen is an essential hemostatic factor and cardiovascular disease risk factor. Early attempts at evaluating the causal effect of fibrinogen on coronary heart disease (CHD) and myocardial infraction (MI) using Mendelian randomization (MR) used single variant approaches, and did not take advantage of recent genome-wide association studies (GWAS) or multi-variant, pleiotropy robust MR methodologies.

METHODS AND FINDINGS

We evaluated evidence for a causal effect of fibrinogen on both CHD and MI using MR. We used both an allele score approach and pleiotropy robust MR models. The allele score was composed of 38 fibrinogen-associated variants from recent GWAS. Initial analyses using the allele score used a meta-analysis of 11 European-ancestry prospective cohorts, free of CHD and MI at baseline, to examine incidence CHD and MI. We also applied 2 sample MR methods with data from a prevalent CHD and MI GWAS. Results are given in terms of the hazard ratio (HR) or odds ratio (OR), depending on the study design, and associated 95% confidence interval (CI). In single variant analyses no causal effect of fibrinogen on CHD or MI was observed. In multi-variant analyses using incidence CHD cases and the allele score approach, the estimated causal effect (HR) of a 1 g/L higher fibrinogen concentration was 1.62 (CI = 1.12, 2.36) when using incident cases and the allele score approach. In 2 sample MR analyses that accounted for pleiotropy, the causal estimate (OR) was reduced to 1.18 (CI = 0.98, 1.42) and 1.09 (CI = 0.89, 1.33) in the 2 most precise (smallest CI) models, out of 4 models evaluated. In the 2 sample MR analyses for MI, there was only very weak evidence of a causal effect in only 1 out of 4 models.

CONCLUSIONS

A small causal effect of fibrinogen on CHD is observed using multi-variant MR approaches which account for pleiotropy, but not single variant MR approaches. Taken together, results indicate that even with large sample sizes and multi-variant approaches MR analyses still cannot exclude the null when estimating the causal effect of fibrinogen on CHD, but that any potential causal effect is likely to be much smaller than observed in epidemiological studies.

Associations between thromboxane A synthase 1 gene polymorphisms and the risk of ischemic stroke in a Chinese Han population

Thromboxane A synthase 1 (TBXAS1) catalyses the synthesis of thromboxane A2 (TXA2), which plays an important role in the pathogenesis of ischemic stroke. Thus, the TBXAS1 gene was investigated as a candidate gene involved in the formation of atherosclerosis. This case-control study collected peripheral blood specimens and clinical data of 370 ischemic stroke patients and 340 healthy controls in the Northern Chinese Han population from October 2010 to May 2011. Two TBXAS1 single-nucleotide polymorphisms, rs2267682 and rs10487667, were analyzed using a SNaPshot Multiplex sequencing assay to explore the relationships between the single-nucleotide polymorphisms in TBXAS1 and ischemic stroke. The TT genotype frequency and T allele frequency of rs2267682 in the patients with ischemic stroke were significantly higher than those in the controls (P < 0.01 and P = 0.02). Furthermore, compared with the GG + GT genotype, the TT rs2267682 genotype was associated with increased risk of ischemic stroke (odds ratio (OR) = 1.80, 95% confidence interval (CI): 1.16–2.79, P < 0.01). Multivariate logistic analysis with adjustments for confounding factors revealed that rs2267682 was still associated with ischemic stroke (OR = 1.94, 95% CI : 1.13–3.33, P = 0.02). The frequency of the T-G haplotype in the patients was significantly higher than that in the controls according haplotype analysis (OR = 1.49, 95% CI: 1.10–2.00, P < 0.01). These data reveal that the rs2267682 TBXAS1 polymorphism is associated with ischemic stroke. The TT genotype of TBXAS1 and T allele of rs2267682 increase susceptibility to ischemic stroke in this Northern Chinese Han population. The protocol has been registered with the Chinese Clinical Trial Registry (registration number: ChiCTR-COC-17013559).

HDAC9 Variant Rs2107595 Modifies Susceptibility to Coronary Artery Disease and the Severity of Coronary Atherosclerosis in a Chinese Han Population

A previous genome-wide association study showed that a single nucleotide polymorphism (SNP) rs2107595 in histone deacetylase 9 (HDAC9) gene was associated with large artery stroke (LAS) in Caucasians. Based on the similar atherosclerotic pathogenesis between LAS and coronary artery disease (CAD), we aimed to evaluate the associations of SNP rs2107595 with CAD risk and the severity of coronary atherosclerosis in a Chinese Han population, and explore the potential gene-environment interactions among SNP rs2107595 and conventional CAD risk factors. In a two-stage case-control study with a total of 2317 CAD patients and 2404 controls, the AG + AA genotypes of SNP rs2107595 were significantly associated with increased CAD risk (Adjusted odds ratio (OR) = 1.23, P_adj = 0.001) and higher modified Gensini scores (Adjusted OR = 1.38, P_adj < 0.001). These associations remained significant in subtype analyses for unstable angina pectoris (UAP), non-ST-segment elevation myocardial infarction (NSTEMI) and ST-segment elevation myocardial infarction (STEMI). Subgroup and multifactor dimensionality reduction analyses (MDR) further found the gene-environment interactions among SNP rs2107595, body mass index, type 2 diabetes and hyperlipidemia in CAD risk and the severity of coronary atherosclerosis. Moreover, patients with CAD had higher levels of HDAC9 mRNA expression and plasma HDAC9 than controls. Subsequent genotype-phenotype analyses observed the significant correlations of SNP rs2107595 with HDAC9 mRNA expression and plasma HDAC9 levels in controls and patients with NSTEMI and STEMI. Taken together, our data suggest that SNP rs2107595 may contribute to coronary atherosclerosis and CAD risk through a possible mechanism of regulating HDAC9 expression and gene-environment interactions.

Chromosome 9p21 and ABCA1 Genetic Variants and Their Interactions on Coronary Heart Disease and Ischemic Stroke in a Chinese Han Population

The single nucleotide polymorphisms (SNPs) related to both coronary heart disease (CHD) and ischemic stroke (IS) in Chinese individuals have not been identified definitely. This study was developed to evaluate the genetic susceptibility to CHD and IS on the chromosome 9p21 and the adenosine triphosphate (ATP)-binding cassette transporter A1 genes (ABCA1) in a Chinese Han population. Genotypes of the rs1333040, rs1333042, rs4977574, rs2066715 and rs2740483 SNPs were determined in 1134 unrelated patients (CHD, 565 and IS, 569) and 541 controls. The frequencies of the rs4977574 genotypes and alleles between CHD and control groups, and the rs2740483 genotypes and alleles between IS and control groups were different (p = 0.006–0.001). The subjects with rs1333042GG genotype and the carriers of the rs4977574G allele were associated with increased risk of CHD. The carriers of the rs4977574G allele were associated with increased risk of IS. However, the carriers of the rs2740483C allele had lower risk of IS than the non-carriers of the rs2740483C allele after controlling for potential confounders. The rs4977574GG-age (>60 year) interaction increased the risk of CHD (p = 0.022), whereas the rs2740483CG/CC-body mass index (>24 kg/m²) interaction decreased the risk of IS (p = 0.035). The interactions of rs1333040-rs1333042 on the risk of CHD and IS were relatively strong, whereas the interactions of rs1333040-rs1333042-rs2066715 and rs1333040-rs1333042-rs2066715-rs2740483 on the risk of CHD, and rs1333040-rs1333042-rs4977574 and rs1333040-rs1333042-rs4977574-rs2740483 on the risk of IS were relatively weak. These findings suggest that some common variants on the chromosome 9p21 and ABCA1 and their interactions may significantly modify the risk of CHD and IS independent of effects on serum lipid levels.

Shared genetic susceptibility of vascular-related biomarkers with ischemic and recurrent stroke

OBJECTIVE

To investigate the genetic contributors to cerebrovascular disease and variation in biomarkers of ischemic stroke.

METHODS

The Vitamin Intervention for Stroke Prevention Trial (VISP) was a randomized, controlled clinical trial of B vitamin supplementation to prevent recurrent stroke, myocardial infarction, or death. VISP collected baseline measures of C-reactive protein (CRP), fibrinogen, creatinine, prothrombin fragments F1+2, thrombin-antithrombin complex, and thrombomodulin prior to treatment initiation. Genome-wide association scans were conducted for these traits and follow-up replication analyses were performed.

RESULTS

We detected an association between CRP single nucleotide polymorphisms (SNPs) and circulating CRP levels (most associated SNP, rs2592902, p = 1.14 × 10(-9)) in 2,100 VISP participants. We discovered a novel association for CRP level in the AKR1D1 locus (rs2589998, p = 7.3 × 10(-8), approaching genome-wide significance) that also is an expression quantitative trait locus for CRP gene expression. We replicated previously identified associations of fibrinogen with SNPs in the FGB and LEPR loci. CRP-associated SNPs and CRP levels were significantly associated with risk of ischemic stroke and recurrent stroke in VISP as well as specific stroke subtypes in METASTROKE. Fibrinogen levels but not fibrinogen-associated SNPs were also found to be associated with recurrent stroke in VISP.

CONCLUSIONS

Our data identify a genetic contribution to inflammatory and hemostatic biomarkers in a stroke population. Additionally, our results suggest shared genetic contributions to circulating CRP levels measured poststroke and risk for incident and recurrent ischemic stroke. These data broaden our understanding of genetic contributors to biomarker variation and ischemic stroke risk, which should be useful in clinical risk evaluation.

The PlA1/A2 polymorphism of glycoprotein IIIa as a risk factor for stroke: a systematic review and meta-analysis

BACKGROUND

The PlA1/A2 polymorphism of glycoprotein IIIa (GPIIIa) has been reported to be associated with risk of stroke in some studies, although other studies suggest no such association. This meta-analysis and systematic review was conducted to investigate the hypothesis that carriage of the PlA2 allele is a risk factor for stroke.

METHODS

Electronic databases (MEDLINE and EMBASE) were searched for all articles evaluating carriage of the PlA2 allele and the incidence of stroke. Pooled odds ratios (ORs) were calculated using fixed-effect and random-effect models.

FINDINGS

A total of 35 articles were eligible for inclusion, of which 25 studies were suitable for statistical analysis. For carriage of the PlA2 allele, OR 1.12 (n = 11,873; 95% CI = 1.03-1.22; p = 0.011) was observed for the incidence of stroke in adults, with subgroup analyses identifying the association driven by stroke of an ischaemic (n = 10,494; OR = 1.15, 95% CI = 1.05-1.27; p = 0.003) but not haemorrhagic aetiology (n = 2,470; OR = 0.90, 95% CI = 0.71-1.14; p = 0.398). This association with ischaemic stroke was strongest in individuals homozygous for the PlA2 allele compared to those homozygous for wild-type PlA1 (n = 5,906; OR = 1.74, 95% CI = 1.34-2.26; p<0.001). Subgroup analysis of ischaemic stroke subtypes revealed an increased association with stroke of cardioembolic (n = 1,271; OR 1.56, 95% CI 1.14-2.12; p = 0.005) and large vessel (n = 1,394; OR = 1.76, 95% CI 1.34-2.31; p<0.001) aetiology, but not those of small vessel origin (n = 1,356; OR = 0.99, 95% CI 0.74-1.33; p = 0.950). Egger's regression test suggested a low probability of publication bias for all analyses (p>0.05).

CONCLUSIONS

The totality of published data supports the hypothesis that carriage of the PlA2 polymorphism of GPIIIa is a risk factor for ischaemic strokes, and specifically those of cardioembolic and large vessel origin.

Association between 9p21 genomic markers and ischemic stroke risk: evidence based on 21 studies

Epidemiological studies indicate a genetic contribution to ischemic stroke risk, but specific genetic variants remain unknown. Recently independent studies reported an association between coronary heart disease and single-nucleotide polymorphisms (SNPs) located at chromosome 9p21 (rs10757278 and proxy SNPs). Given that stroke is a common complication after myocardial infarction, several validation studies have been conducted among various ethnic populations to investigate if the same loci was associated with ischemic stroke (IS), but the results have been inconsistent. To investigate this inconsistency and derive a more precise estimation of the relationship, a meta-analysis of 34,128 cases and 153,428 controls from 21 studies was performed. Potential sources of heterogeneity including ethnicity, sample size, control source and ischemic stroke subtypes were also assessed. Overall, the summary odds ratio of IS was 1.11 (95% CI: 1.07–1.15, P<10⁻⁵) for rs10757278. In the subgroup analysis by ethnicity, significantly increased risks were found in East Asians (3188 cases and 4503 controls; OR = 1.14, 95% CI: 1.07–1.21, P<10⁻⁵) and Caucasians (30505 cases and 145153controls; OR = 1.08, 95% CI: 1.04–1.12, P<10⁻⁵) for the polymorphism; while no significant associations were found among African Americans (435 cases and 3772 controls; OR = 0.97, 95% CI: 0.63–1.51, P = 0.90) in all genetic models. In the subgroup analyses by IS subtypes, significant association was detected only in large vessel stroke group, while no significant associations among small vessel or cardioembolic stroke. When stratified by sample size, and control source, significantly increased risks were found for the polymorphism in all genetic models. This meta-analysis provides accurate and comprehensive estimates of the association of genetic variant at chromosome 9p21 and IS, but these associations vary in different ethnic populations.

LDL-c-linked SNPs are associated with LDL-c and myocardial infarction despite lipid-lowering therapy in patients with established vascular disease

BACKGROUND

Several single-nucleotide polymorphisms (SNPs) are associated with both plasma low-density lipoprotein cholesterol (LDL-c) level and coronary artery disease in the general population. It is unclear whether these associations also apply to patients with vascular disease and whether the associations are independent of lipid-lowering therapy.

DESIGN

Single-nucleotide polymorphisms associated with plasma LDL-c and vascular risk in the general population (rs11206510 (PCSK9), rs1122608 (LDLR), rs579459 (ABO) and rs599839 (SORT1)) were genotyped in a prospective cohort study of 5482 patients with vascular disease. We determined the association between LDL-c-associated alleles and plasma LDL-c levels and the risk of new vascular events.

RESULTS

All tested SNPs were associated with LDL-c plasma levels with a magnitude between +0·06 (95% CI 0·02-0·10) mM and +0·14 (95% CI 0·09-0·18) mM per LDL-c-increasing allele. The associations were independent of the use of lipid-lowering medication, except for rs579459, for which the association was not present in patients using lipid-lowering medication. In patients with 7-8 risk alleles for these SNPs, 59% of the patients treated with lipid-lowering medication did not reach the LDL-c target of <2·5 mM compared with 45% in patients with 3 or fewer risk alleles. LDL-c-increasing alleles were not associated with increased risk of vascular events in patients not using lipid-lowering medication (HRs: 1·01; 95% CI: 0·93-1·09). In patients using lipid-lowering medication, the risk of myocardial infarction increased with 14% (HRs: 1·14; 95% CI: 1·01-1·28) per allele.

CONCLUSIONS

In patients with established vascular disease, the studied SNPs increase LDL-c plasma levels. LDL-c-increasing alleles may be associated with increased risk of myocardial infarction in patients treated with lipid-lowering medication, but not in patients not treated with lipid-lowering medication.

Genetics of ischaemic stroke

Recent advances in genomics and statistical computation have allowed us to begin addressing the genetic basis of stroke at a molecular level. These advances are at the cusp of making important changes to clinical practice of some monogenic forms of stroke and, in the future, are likely to revolutionise the care provided to these patients. In this review we summarise the state of knowledge in ischaemic stroke genetics particularly in the context of how a practicing clinician can best use this knowledge.

BRG1 variant rs1122608 on chromosome 19p13.2 confers protection against stroke and regulates expression of pre-mRNA-splicing factor SFRS3

A single nucleotide polymorphism (SNP) rs1122608 on chromosome 19p13.2 and in the BRG1/SMARCA4 gene was previously associated with coronary artery disease (CAD). CAD and ischemic stroke are both associated with atherosclerosis. Thus, we tested the hypothesis that rs1122608 is associated with ischemic stroke. Further studies were used to identify the most likely mechanism by which rs1122608 regulates atherosclerosis. For case-control association studies, two independent Chinese Han GeneID cohorts were used, including a Central cohort with 1,075 cases and 2,685 controls and the Northern cohort with 1,208 cases and 824 controls. eQTL and real-time RT-PCR analyses were used to identify the potential candidate gene(s) affected by rs1122608. The minor allele T of SNP rs1122608 showed significant association with a decreased risk of ischemic stroke in the Central GeneID cohort (adjusted P adj = 2.1 × 10(-4), OR 0.61). The association was replicated in an independent Northern GeneID cohort (P adj = 6.00 × 10(-3), OR 0.69). The association became more significant in the combined population (P adj = 7.86 × 10(-5), OR 0.73). Allele T of SNP rs1122608 also showed significant association with a decreased total cholesterol level (P adj = 0.013). Allele T of rs1122608 was associated with an increased expression level of SFRS3 encoding an mRNA splicing regulator, but not with the expression of BRG1/SMARCA4 or LDLR (located 36 kb from rs1122608). Increased expression of SFSR3 may decrease IL-1β expression and secretion, resulting in reduced risk of atherosclerosis and stroke. This is the first study that demonstrates that rs1122608 confers protection against ischemic stroke and implicates splicing factor SFSR3 in the disease process.

Genome-wide analysis of blood pressure variability and ischemic stroke

BACKGROUND AND PURPOSE

Visit-to-visit variability in blood pressure (vBP) is associated with ischemic stroke. We sought to determine whether such variability has genetic causes and whether genetic variants associated with BP variability are also associated with ischemic stroke.

METHODS

A Genome Wide Association Study (GWAS) for loci influencing BP variability was undertaken in 3802 individuals from the Anglo-Scandinavian Cardiac Outcome Trial (ASCOT) study, in which long-term visit-to-visit and within-visit BP measures were available. Because BP variability is strongly associated with ischemic stroke, we genotyped the sentinel single nucleotide polymorphism in an independent ischemic stroke population comprising 8624 cases and 12 722 controls and in 3900 additional (Scandinavian) participants from the ASCOT study to replicate our findings.

RESULTS

The ASCOT discovery GWAS identified a cluster of 17 correlated single nucleotide polymorphisms within the NLGN1 gene (3q26.31) associated with BP variability. The strongest association was with rs976683 (P=1.4×10(-8)). Conditional analysis of rs976683 provided no evidence of additional independent associations at the locus. Analysis of rs976683 in patients with ischemic stroke found no association for overall stroke (odds ratio, 1.02; 95% CI, 0.97-1.07; P=0.52) or its subtypes: cardioembolic (odds ratio, 1.07; 95% CI, 0.97-1.16; P=0.17), large vessel disease (odds ratio, 0.98; 95% CI, 0.89-1.07; P=0.60), and small vessel disease (odds ratio, 1.07; 95% CI, 0.97-1.17; P=0.19). No evidence for association was found between rs976683 and BP variability in the additional (Scandinavian) ASCOT participants (P=0.18).

CONCLUSIONS

We identified a cluster of single nucleotide polymorphisms at the NLGN1 locus showing significant association with BP variability. Follow-up analyses did not support an association with risk of ischemic stroke and its subtypes.

Are 25 SNPs from the CARDIoGRAM study associated with ischaemic stroke?

BACKGROUND AND PURPOSE

The Coronary Artery Disease Genome-Wide Replication and Meta-Analysis Study (CARDIoGRAM) reported 25 single-nucleotide polymorphisms (SNPs) on 15 chromosomes to be associated with coronary artery disease (CAD) risk. Because common vascular risk factors are shared between CAD and ischaemic stroke (IS), these SNPs may also be related to IS overall or one or more of its pathogenetic subtypes.

METHODS

We performed a candidate gene study comprising 3986 patients with IS and 2459 control subjects. The 25 CAD-associated SNPs reported by CARDIoGRAM were examined by allelic association analysis including logistic regression. Weighted and unweighted genetic risk scores (GRSs) were also compiled and likewise analysed against IS. We furthermore considered the IS main subtypes large-vessel disease (LVD), small-vessel disease and cardioembolic stroke [according to Trial of Org 10172 in Acute Stroke Treatment (TOAST)] separately.

RESULTS

SNP rs4977574 on chromosome 9p21.3 was associated with overall IS [odds ratio (OR) = 1.12; 95% confidence interval (CI): 1.04-1.20; P = 0.002] as well as LVD (OR = 1.36; 95% CI: 1.13-1.64; P = 0.001). No other SNP was significantly associated with IS or any of its main subtypes. Analogously, the GRSs did not show any noticeable effect.

CONCLUSIONS

Besides the previously reported association with SNPs on chromosome 9p21, this study did not detect any significant association between IS and CAD-susceptible genetic variants. Also, GRSs compiled from these variants did not predict IS or any pathogenetic IS subtype, despite a total sample size of 6445 participants.

Lack of association between a functional variant of the BRCA-1 related associated protein (BRAP) gene and ischemic stroke

Background

Atherosclerosis shares common pathogenic features with myocardial infarction (MI) and ischemic stroke. BRCA-1 associated protein (BRAP), a newly identified risk gene for MI, aggravates the inflammatory response in atherosclerosis. The aim of this study was to test the association between the BRAP gene and stroke in a Taiwanese population.

Methods

A total of 1,074 stroke patients and 1,936 controls were genotyped for the functional SNP rs11066001. In our previous studies, the rare allele of this SNP has been repeatedly shown to exert a recessive effect. Therefore, in the current study, we tested for the same recessive model. First, the genotype distributions between all the controls and all the stroke cases were compared. Then to reduce heterogeneity, we explored several population subsets by selecting young stroke subjects (using 45 years of age as the cutoff point), age- and sex-comparable controls, plaque-free controls, and stroke subtypes.

Results

We did not find any significant association for the entire data set (OR = 0.94, p = 0.74) or for the subset analyses using age- and sex-comparable controls (p = 0.70) and plaque-free controls (p = 0.91). Analyses of the four stroke subtypes also failed to show any significant associations (p = 0.42 – 0.98). For both young and old subjects, the GG genotype of rs11066001 was similar in the stroke cases and unmatched controls (8.1% vs. 9.4% in young subjects and 8.0% vs. 7.8% in old subjects). Comparing stroke cases with plaque-free controls also failed to find any significant association.

Conclusions

The BRAP polymorphism may not play an important role in ischemic stroke in the studied population.

Genetic variants associated with myocardial infarction in the PSMA6 gene and Chr9p21 are also associated with ischaemic stroke

BACKGROUND

Ischaemic stroke shares common traditional risk factors with coronary artery disease (CAD) and myocardial infarction (MI). This study evaluated whether genetic risk factors for CAD and MI also affect susceptibility to ischaemic stroke in Caucasians and African Americans.

METHODS

Included in the study were a Caucasian series (713 ischaemic stroke patients, 708 controls) and a small African American series (166 ischaemic stroke patients, 117 controls). Twenty single-nucleotide polymorphisms (SNPs) previously shown to be associated with CAD or MI were genotyped and assessed for association with ischaemic stroke and ischaemic stroke subtypes using odds ratios (ORs) from multivariable logistic regression models.

RESULTS

In Caucasians, four SNPs on chromosome 9p21 were significantly associated with risk of cardioembolic stroke, the strongest of which was rs1333040 (OR 1.55, P = 0.0007); similar but weaker trends were observed for small vessel stroke, with no associations observed regarding large vessel stroke. Chromosome 9p21 SNPs were also associated with risk of ischaemic stroke in African Americans (rs1333040, OR 0.65, P = 0.023; rs1333042, OR 0.55, P = 0.070; rs2383207, OR 0.55, P = 0.070). The PSMA6 SNP rs1048990 on chromosome 14q13 was associated with overall ischaemic stroke in both Caucasians (OR 0.80, P = 0.036) and African Americans (OR 0.31, P = 0.020).

CONCLUSIONS

Our results provide evidence that chromosome 9p21 variants are associated with cardioembolic ischaemic stroke in Caucasians and with overall ischaemic stroke in African Americans. The PSMA6 variant rs1048990 also appears to affect susceptibility to ischaemic stroke in both populations. These findings require validation, particularly the preliminary findings regarding African Americans given the small size of that series.