Unravelling the genetics of ischaemic stroke

Functional genomics in stroke: current and future applications of iPSCs and gene editing to dissect the function of risk variants

Stroke is an important disease with unmet clinical need. To uncover novel paths for treatment, it is of critical importance to develop relevant laboratory models that may help to shed light on the pathophysiological mechanisms of stroke. Induced pluripotent stem cells (iPSCs) technology has enormous potential to advance our knowledge into stroke by creating novel human models for research and therapeutic testing. iPSCs models generated from patients with specific stroke types and specific genetic predisposition in combination with other state of art technologies including genome editing, multi-omics, 3D system, libraries screening, offer the opportunity to investigate disease-related pathways and identify potential novel therapeutic targets that can then be tested in these models. Thus, iPSCs offer an unprecedented opportunity to make rapid progress in the field of stroke and vascular dementia research leading to clinical translation. This review paper summarizes some of the key areas in which patient-derived iPSCs technology has been applied to disease modelling and discusses the ongoing challenges and the future directions for the application of this technology in the field of stroke research.

Hybrid modelling for stroke care: Review and suggestions of new approaches for risk assessment and simulation of scenarios

Stroke is an example of a complex and multi-factorial disease involving multiple organs, timescales, and disease mechanisms. To deal with this complexity, and to realize Precision Medicine of stroke, mathematical models are needed. Such approaches include: 1) machine learning, 2) bioinformatic network models, and 3) mechanistic models. Since these three approaches have complementary strengths and weaknesses, a hybrid modelling approach combining them would be the most beneficial. However, no concrete approach ready to be implemented for a specific disease has been presented to date. In this paper, we both review the strengths and weaknesses of the three approaches, and propose a roadmap for hybrid modelling in the case of stroke care. We focus on two main tasks needed for the clinical setting: a) For stroke risk calculation, we propose a new two-step approach, where non-linear mixed effects models and bioinformatic network models yield biomarkers which are used as input to a machine learning model and b) For simulation of care scenarios, we propose a new four-step approach, which revolves around iterations between simulations of the mechanistic models and imputations of non-modelled or non-measured variables. We illustrate and discuss the different approaches in the context of Precision Medicine for stroke.

Two Novel SNPs in the PLCL2 Gene Associated with Large Artery Atherosclerotic Stroke Identified by Fine-Mapping

A genome-wide association study (GWAS) reported that the single nucleotide polymorphism (SNP) rs4618210 in the PLCL2 gene is related to myocardial infarction (MI) in the Japanese population, but no study has examined the correlation of PLCL2 with ischemic stroke (IS). The present study was designed to investigate whether the genetic variation in PLCL2 is associated with large artery atherosclerotic (LAA) stroke in a Han Chinese population. Tagging SNPs (tSNPs) of the PLCL2 gene were determined by a fine-mapping strategy and were genotyped by improved multiplex ligation detection reaction (iMLDR) technology in 669 LAA stroke patients and 668 healthy controls. A logistic regression model was used to analyze the associations between genetic variation at PLCL2 and the risk of LAA stroke. Two SNPs were significantly associated with the risk of LAA stroke after adjusting for potential confounders: for rs4685423, the AA genotype and CA genotype decreased the risk of LAA stroke compared with the CC genotype (multivariate-adjusted, P = 0.001); for rs4618210, the AA genotype and GA genotype decreased the risk of LAA stroke compared with the GG genotype (multivariate-adjusted, P = 0.007). In addition, haplotype analysis indicated that compared with haplotype TTT, haplotype TAT decreased the risk of LAA stroke in block 2 (adjusted OR, 0.706; 95% CI, 0.550-0.907; P = 0.006). The analysis of SNP-SNP interactions showed that rs4685423 was the most influential contributor to LAA stroke risk. SNPs rs4685423 and rs4618210 in the PLCL2 gene may be related to the risk of LAA stroke in Han Chinese.

Genetic testing for Mendelian stroke due to cerebrovascular anomalies and other syndromes

Stroke is defined as a focal or at times global neurological impairment of sudden onset and presumed vascular origin. 85% of strokes are due to cerebral ischemia and the other 15% to primary intracerebral hemorrhage.

Ischemic stroke (IS) is characterized by complete or partial obstruction of a vessel in the brain, resulting in lack of blood supply and death of brain tissue. The most common causes of IS are atherosclerosis, cardioembolism and small-vessel disease (lacunar stroke). Genetic factors play important role. Incidence rates for IS in the 15- to 45-year age range are ≈10 per 100,000 person years.

Hemorrhagic stroke (HS) is the least treatable and the most fatal form of cerebrovascular disease. Genetic mechanisms play a role in its development. Occurrence depends on many risk factors, including hypertension, heavy alcohol intake and anticoagulant treatment. According to the World Health Organization, 15 million people suffer stroke worldwide each year. The overall incidence of spontaneous HS worldwide is 24.6 per 100,000 person years. Strokes are the third most common cause of death and the most common cause of disability in developed countries.

This Utility Gene Test was developed on the basis of an analysis of the literature and existing diagnostic protocols. It is useful for confirming diagnosis, as well as for differential diagnosis, couple risk assessment and access to clinical trials.

A genome-wide association study links small-vessel ischemic stroke to autophagy

Genome-wide association studies (GWAS) can serve as strong evidence in correlating biological pathways with human diseases. Although ischemic stroke has been found to be associated with many biological pathways, the genetic mechanism of ischemic stroke is still unclear. Here, we performed GWAS for a major subtype of stroke-small-vessel occlusion (SVO)-to identify potential genetic factors contributing to ischemic stroke. GWAS were conducted on 342 individuals with SVO stroke and 1,731 controls from a Han Chinese population residing in Taiwan. The study was replicated in an independent Han Chinese population comprising an additional 188 SVO stroke cases and 1,265 controls. Three SNPs (rs2594966, rs2594973, rs4684776) clustered at 3p25.3 in ATG7 (encoding Autophagy Related 7), with P values between 2.52 × 10-6 and 3.59 × 10-6, were identified. Imputation analysis also supported the association between ATG7 and SVO stroke. To our knowledge, this is the first GWAS to link stroke and autophagy. ATG7, which has been implicated in autophagy, could provide novel insights into the genetic basis of ischemic stroke.

Biological data sciences in genome research

The last 20 years have been a remarkable era for biology and medicine. One of the most significant achievements has been the sequencing of the first human genomes, which has laid the foundation for profound insights into human genetics, the intricacies of regulation and development, and the forces of evolution. Incredibly, as we look into the future over the next 20 years, we see the very real potential for sequencing more than 1 billion genomes, bringing even deeper insight into human genetics as well as the genetics of millions of other species on the planet. Realizing this great potential for medicine and biology, though, will only be achieved through the integration and development of highly scalable computational and quantitative approaches that can keep pace with the rapid improvements to biotechnology. In this perspective, I aim to chart out these future technologies, anticipate the major themes of research, and call out the challenges ahead. One of the largest shifts will be in the training used to prepare the class of 2035 for their highly interdisciplinary world.

Interactions Among CYP2C8, EPHX2, and CYP4A11 Variants and CYP Plasma Metabolite Levels in Ischemic Stroke

Aim: To better understand the relationship between the interactions among rs17110453, rs751141, and rs9333025 variants and plasma levels of cytochrome P450 (CYP) metabolites, i.e., 20-hydroxyeicosatetraenoic acid (20-HETE), epoxyeicosatrienoic acids (EETs), and dihydroxyeicosatrienoic acids (DiHETEs) in ischemia stroke (IS).

Methods: We measured plasma CYP metabolite levels in 218 acute IS cases and 126 controls, and a subset of samples were assessed to further understand the association between relevant variants and IS risk in our previous study. We assessed the associations between variant interactions and levels of 20-HETE, EETs, and DiHETEs as well as the associations between levels of 20-HETE, EETs, and DiHETEs and IS risk after adjusting for other potential confounders. Furthermore, the association between variant interactions and IS risk after adjusting for other covariates, including CYP metabolites levels, was evaluated.

Results: The interactions among variants rs17110453, rs751141, and rs9333025 were significantly associated with high 20-HETE, high DiHETEs, and low EETs after adjusting for the status of diabetes mellitus and hypertension. High 20-HETE, high DiHETEs, and low EETs were independent risk factors for IS after adjusting for hypertension, diabetes mellitus, and the interactions among rs17110453, rs751141, and rs9333025. Furthermore, the interactions among rs17110453, rs751141, and rs9333025 were significantly associated with a higher risk of IS after adjusting for CYP metabolites (OR= 2.02, 95% CI: 1.28–5.27, P = 0.007).

Conclusion: The association between the interactions among rs17110453, rs751141, and rs9333025 and IS risk in Chinese population may be partly but not exclusively mediated by plasma levels of 20-HETE, EETs, and DHETs. Further well-designed studies are warranted to replicate this finding.

Analysis of Association between MAP2K4 Gene Polymorphism rs3826392 and IL-1b Serum Level in Southern Chinese Han Ischemic Stroke Patients

BACKGROUND

Mitogen-activated protein kinase kinase 4 (MAP2K4) gene acts as the direct upstream activator of c-Jun NH2-terminal kinase pathway, which plays an important role in regulating neuron survival and apoptosis in response to cerebral ischemia. However, the association between MAP2K4 gene polymorphisms and ischemic stroke (IS) has not yet been published. Therefore, this study investigates the association between MAP2K4 gene polymorphism rs3826392 and IS susceptibility, as well as its quantitative traits in Southern Chinese Han population.

METHODS

A total of 816 Chinese patients with IS and 816 age- and sex-matched controls were recruited. Rs3826392 was genotyped using Sequenom MassARRAY iPLEX platform (Sequenom, San Diego, CA, USA). The mRNA expression of MAP2K4 gene in peripheral blood mononuclear cells was detected using reverse transcription-polymerase chain reaction. The levels of serum cytokines, including IL-1b, IL-6, IL-8, IL-12, and tumor necrosis factor-α (TNF-α), were measured by enzyme-linked immunosorbent assay.

RESULTS

Significant association was not observed between MAP2K4 gene polymorphism rs3826392 and IS susceptibility in all genetic models (P > .05). A significant difference was found in IL-1b, IL-6, IL-8, and TNF-α serum levels between patients with IS and control groups. MAP2K4 gene polymorphism rs3826392 C/A genotype carriers showed significantly higher IL-1b serum levels compared with AA genotype carriers (P = .029) in patients with IS.

CONCLUSION

MAP2K4 gene polymorphism rs3826392 did not contribute to IS susceptibility, but rs3826392 C/A genotype carriers showed significantly higher IL-1b serum levels. This result suggests that rs3826392 may play a potential role in the IS inflammatory process.

Linking genes to neurological clinical practice: the genomic basis for neurorehabilitation

Large-scale genomics projects such as the Human Genome Project and the International HapMap Project promise significant advances in the ability to diagnose and treat many conditions, including those with a neurological basis. A major focus of research has emerged in the neurological sciences to elucidate the molecular and genetic basis of various neurological diseases. Indeed, genetic factors are implicated in susceptibility for many neurological disorders, with family history studies providing strong evidence of familial risk for conditions such as stroke, Parkinson's, Alzheimer's, and Huntington's diseases. Heritability studies also suggest a strong genetic contribution to the risk for neurological diseases. Genome-wide association studies are also uncovering novel genetic variants associated with neurological disorders. Whole-genome and exome sequencing are likely to provide novel insights into the genetic basis of neurological disorders. Genetic factors are similarly associated with clinical phenotypes such as symptom severity and progression as well as response to treatment. Specifically, disease progression and functional restoration depend, in part, on the capacity for neural plasticity within residual neural tissues. Furthermore, such plasticity may be influenced in part by the presence of polymorphisms in several genes known to orchestrate neural plasticity including brain-derived neurotrophic factor (BDNF) and Apolipoprotein E. (APOE). It is important for neurorehabilitation therapist practicing in the "genomic era" to be aware of the potential influence of genetic factors during clinical encounters, as advances in molecular sciences are revealing information of critical relevance to the clinical rehabilitation management of individuals with neurological conditions. Video Abstract available (See Video, Supplemental Digital Content 1, http://links.lww.com/JNPT/A88) for more insights from the authors.

Next generation sequencing for systematic assessment of genetics of small-vessel disease and lacunar stroke

BACKGROUND

The pathogenesis of cerebral small-vessel disease (SVD) is still incompletely understood, although evidence from family and twin studies supports the hypothesis that genetic factors may contribute to SVD pathogenesis. Identification of genetic susceptibility factors for SVD may improve our knowledge on SVD pathogenesis. SVE-LA (Small Vessel and Lacunar) project is a multicenter prospective Lombardia region study aimed at applying innovative genetic technologies and accurate patient phenotyping to discover the genetic basis of SVD.

METHODS

A continuous series of subjects (aged 15-80 years) with a clinically and radiologically defined lacunar stroke referring to the participating Lombardia region stroke centers and an adequate number of age- and sex-matched controls are being included into the study. For each patient, clinical, demographic, instrumental, and familial data are collected applying standardized forms. After informed consent, a DNA sample for genetic analysis from patients and controls has been collected. The next generation sequencing (NGS) technology was applied to systematically screen patients for the most important genetic factors both monogenic and polygenic associated with SVD. The study includes also a centralized quantitative and qualitative analysis of neuroimaging studies.

RESULTS

Between March 2011 and October 2013, 212 lacunar stroke patients and 78 controls have been collected. Mean age of cases was 65.8 ± 11.1 years and 67% were men.

CONCLUSIONS

This is the first study applying systematically NGS technology on a wide series of lacunar stroke patients. A translational approach combining a systematic genetic screening with a detailed phenotyping may facilitate the discovery of genetic basis and improve our knowledge in the pathogenesis of SVD.

The single nucleotide polymorphism rs2208454 confers an increased risk for ischemic stroke: a case-control study

AIM

A recent genome-wide association study identified a strong association of covert magnetic resonance imaging infarcts with the single nucleotide polymorphism (SNP) rs2208454. The aim of this study was to determine whether the rs2208454 polymorphism is associated with an increased risk for ischemic stroke (IS).

METHODS

Ischemic stroke patients (n = 712) and control subjects (n = 774) from a southern Chinese Han population were included. The snapshot technique was used for genotype analysis.

RESULTS

Compared with the GT+GG or GG genotype, the frequency of the TT genotype was significantly higher in IS than in controls. After adjusting for age, gender, family history of IS, hypertension history, and history of diabetes mellitus, a significant correlation between the TT genotype and IS persisted (TT vs. GT+GG: adjusted OR = 1.79, 95% CI: 1.16-2.77; TT vs. GG: adjusted OR = 1.88, 95% CI: 1.20-2.94). In subgroup analyses, SNP rs2208454 was significantly associated with large artery atherosclerosis (LAA) (TT vs. GG: adjusted OR = 2.16, 95% CI: 1.19-3.93), but failed to show significant association with small-artery occlusion or cardioembolism IS subtypes.

CONCLUSIONS

Single nucleotide polymorphism rs2208454 confers an increased risk for IS in a southern Chinese Han population. When the IS subtype was examined, the effect of the SNP was restricted to LAA.

Variant rs1906591 on chromosome 4q25 confers increased risk of cardioembolic stroke in Chinese patients

Ischemic stroke (IS) is a heterogeneous multifactorial disorder caused by both genetic and environmental factors. A genome-wide association study on stroke in Caucasians identified a variant on chromosome 4q25 that is significantly associated with IS, with the strongest risk for cardioembolic stroke (CES). The current study aims to investigate the association of the rs1906591 variant on 4q25 with IS through a case-control study in a Chinese Han population. A total of 712 IS patients and 774 control subjects were involved in the current research. Stroke subtyping was performed according to the Trial of Org 10172 in Acute Stroke Treatment criteria. The genotypes were determined using the SNaPshot technique. The association of the genotypes with the risk of IS was estimated using logistic regression analysis. The rs1906591 single nucleotide polymorphism variant was associated with the CES subtype in both recessive and additive models (recessive model: odds ratio [OR]=2.58, 95% confidence interval [CI] 1.47-4.53, p=0.001, adjusted OR=2.71, 95% CI 1.48-4.96, p=0.001; additive model: OR=2.50, 95% CI 1.19-5.25, p=0.015, adjusted OR=2.83, 95% CI 1.24-6.50, p=0.013). This result indicates that patients with the AA genotype have a higher rate of CES than other genotypes. However, the rs1906591 variant was not significantly associated with the overall incidence of stroke or other stroke subtypes. The rs1906591 variant is significantly associated with CES in the Chinese Han population, but not with other stroke subtypes.

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.

Impact of the 1425G/A polymorphism of PRKCH on the recurrence of ischemic stroke: Fukuoka Stroke Registry

BACKGROUND

Epidemiologic studies have elucidated that the 1425G/A single-nucleotide polymorphism (rs2230500 single-nucleotide polymorphism) in exon 9 of the protein kinase C eta (PRKCH) gene is an independent risk factor for ischemic stroke: stroke incidence is significantly higher in the subjects with AA than those with AG or GG genotype. However, its impact on stroke recurrence remains unknown. The aim of the present study was to clarify whether the polymorphism is also a risk factor for recurrent stroke in patients with acute ischemic stroke.

METHODS

We enrolled 2418 consecutive patients with acute and first-ever ischemic stroke and investigated the 1425G/A polymorphism of PRKCH. Patients were followed up for a median of 733 days. The association between the polymorphism and stroke recurrence was investigated using the Cox proportional hazard model.

RESULTS

In the enrolled patients, the GG genotype was the most prevalent (63%), followed by AG (32%) and AA genotypes (5%). Recurrent stroke occurred in 302 patients during the follow-up period. Kaplan-Meier analyses revealed no difference in the rate of recurrent stroke after first-ever stroke among the 3 genotypes. The incidence of recurrent stroke was not significantly different in patients with AA (hazard ratio [HR] 1.02, 95% confidence interval .59-1.64, P=.94) or AG (HR .89, 95% confidence interval .69-1.14, P=.36) genotypes compared with those with the GG genotype after adjusting for multiple confounders.

CONCLUSIONS

The 1425G/A polymorphism in PRKCH is not a significant predictor of stroke recurrence in patients with acute ischemic stroke during a 2-year follow-up period.

Genetic profiles in ischaemic stroke

Stroke represents a clinical syndrome rather than a single disease. A number of stroke subtypes can be distinguished based on careful phenotyping, with each of these having distinct and overlapping risk factor profiles. Recent evidence has suggested that genetics plays an important part in stroke risk, with at least 2 genes specific to stroke risk directly now having been identified. This review will explore our current understanding of the genetics underlying stroke risk and whether this information is currently useful in a clinical setting for patient benefit.

TGF-beta1 is associated with the progression of intracranial deep white matter lesions: a pilot study with 5 years of magnetic resonance imaging follow-up

OBJECTIVES

Elevated expression of transforming growth factor (TGF)-beta1 has been reported in hereditary cerebral small-vessel (HCSV) disease. The aim of this study was to clarify whether TGF-beta1 is a risk factor for intracranial deep white matter lesions (DWLs) and their progression in a general elderly population.

METHODS

The subjects included 81 participants (Groups DWL, DWLP, and C) who had voluntarily undergone a health examination and brain magnetic resonance imaging (MRI) in 2003 and 2008 and 43 age-matched patients with previous symptomatic brain infarctions. Deep white matter lesions were graded from Grade 0 to 3 according to the Fazekas classification. Group DWL (23 subjects) was defined as DWLs with no progression in the grade level, and Group DWLP (progression of DWL) (12 subjects) was defined as DWLs with an increase in one or more grade number and an apparent worsening of Grade 3. Forty-six age-matched control subjects with consistent normal brain MRI were included in Group C. The associations between DWLs and various vascular risk factors, including peripheral blood TGF-beta1 levels, were examined.

RESULTS

In addition to the classical risk factors, the highest TGF-beta1 levels were found in Group DWLP. The TGF-beta1 levels were significantly higher in Group DWLP than in Group DWL, and DWLP was significantly correlated with elevated TGF-beta1 levels (odds ratio [OR]  =  1·72).

CONCLUSIONS

The present data suggest that TGF-beta1 may be important in the pathogenesis and progression of DWLs, and it is expected to be useful as a clinical indicator reflecting the presence of intracranial white matter lesions.

Genetic heritability of ischemic stroke and the contribution of previously reported candidate gene and genomewide associations

BACKGROUND AND PURPOSE

The contribution of genetics to stroke risk, and whether this differs for different stroke subtypes, remainsuncertain. Genomewide complex trait analysis allows heritability to be assessed from genomewide association study (GWAS) data. Previous candidate gene studies have identified many associations with stoke but whether these are important requires replication in large independent data sets. GWAS data sets provide a powerful resource to perform replication studies.

METHODS

We applied genomewide complex trait analysis to a GWAS data set of 3752 ischemic strokes and 5972 controls and determined heritability for all ischemic stroke and the most common subtypes: large-vessel disease, small-vessel disease, and cardioembolic stroke. By systematic review we identified previous candidate gene and GWAS associations with stroke and previous GWAS associations with related cardiovascular phenotypes (myocardial infarction, atrial fibrillation, and carotid intima-media thickness). Fifty associations were identified.

RESULTS

For all ischemic stroke, heritability was 37.9%. Heritability varied markedly by stroke subtype being 40.3% for large-vessel disease and 32.6% for cardioembolic but lower for small-vessel disease (16.1%). No previously reported candidate gene was significant after rigorous correction for multiple testing. In contrast, 3 loci from related cardiovascular GWAS studies were significant: PHACTR1 in large-vessel disease (P=2.63e(-6)), PITX2 in cardioembolic stroke (P=4.78e(-8)), and ZFHX3 in cardioembolic stroke (P=5.50e(-7)).

CONCLUSIONS

There is substantial heritability for ischemic stroke, but this varies for different stroke subtypes. Previous candidate gene associations contribute little to this heritability, but GWAS studies in related cardiovascular phenotypes are identifying robust associations. The heritability data, and data from GWAS, suggest detecting additional associations will depend on careful stroke subtyping.

Stroke genetics: prospects for personalized medicine

Epidemiologic evidence supports a genetic predisposition to stroke. Recent advances, primarily using the genome-wide association study approach, are transforming what we know about the genetics of multifactorial stroke, and are identifying novel stroke genes. The current findings are consistent with different stroke subtypes having different genetic architecture. These discoveries may identify novel pathways involved in stroke pathogenesis, and suggest new treatment approaches. However, the already identified genetic variants explain only a small proportion of overall stroke risk, and therefore are not currently useful in predicting risk for the individual patient. Such risk prediction may become a reality as identification of a greater number of stroke risk variants that explain the majority of genetic risk proceeds, and perhaps when information on rare variants, identified by whole-genome sequencing, is also incorporated into risk algorithms. Pharmacogenomics may offer the potential for earlier implementation of 'personalized genetic' medicine. Genetic variants affecting clopidogrel and warfarin metabolism may identify non-responders and reduce side-effects, but these approaches have not yet been widely adopted in clinical practice.

Associations between incident ischemic stroke events and stroke and cardiovascular disease-related genome-wide association studies single nucleotide polymorphisms in the Population Architecture Using Genomics and Epidemiology study

BACKGROUND

Genome-wide association studies (GWAS) have identified loci associated with ischemic stroke (IS) and cardiovascular disease (CVD) in European-descent individuals, but their replication in different populations has been largely unexplored.

METHODS AND RESULTS

Nine single nucleotide polymorphisms (SNPs) selected from GWAS and meta-analyses of stroke, and 86 SNPs previously associated with myocardial infarction and CVD risk factors, including blood lipids (high density lipoprotein [HDL], low density lipoprotein [LDL], and triglycerides), type 2 diabetes, and body mass index (BMI), were investigated for associations with incident IS in European Americans (EA) N=26 276, African-Americans (AA) N=8970, and American Indians (AI) N=3570 from the Population Architecture using Genomics and Epidemiology Study. Ancestry-specific fixed effects meta-analysis with inverse variance weighting was used to combine study-specific log hazard ratios from Cox proportional hazards models. Two of 9 stroke SNPs (rs783396 and rs1804689) were significantly associated with [corrected] IS hazard in AA; none were significant in this large EA cohort. Of 73 CVD risk factor SNPs tested in EA, 2 (HDL and triglycerides SNPs) were associated with IS. In AA, SNPs associated with LDL, HDL, and BMI were significantly associated with IS (3 of 86 SNPs tested). Out of 58 SNPs tested in AI, 1 LDL SNP was significantly associated with IS.

CONCLUSIONS

Our analyses showing lack of replication in spite of reasonable power for many stroke SNPs and differing results by ancestry highlight the need to follow up on GWAS findings and conduct genetic association studies in diverse populations. We found modest IS associations with BMI and lipids SNPs, though these findings require confirmation.

No Time to ‘Weight’: The Link between Obesity and Stroke in Women

The obesity epidemic in the USA threatens the gains that have been made in the prevention and treatment of stroke. Both obesity and stroke disproportionately affect women more than men. Understanding the effect of obesity on stroke risk in women may be a useful stepping stone to reducing the burden of stroke in this vulnerable population. This article reviews the association between stroke and general obesity, abdominal obesity and metabolic syndrome in women. All three factors have been shown to independently increase stroke risk in women.

Estimating the magnitude of genetic factors by calculating the genetic relative risk of stroke in first-ever lacunar stroke patients

BACKGROUND

Positive family history of stroke is an independent risk factor for lacunar stroke. However, the magnitude of familial aggregation of a certain disease is better evaluated by the genetic relative risk. This is calculated by dividing the prevalence of specific disease in family members of patients by the prevalence of this disease in the general population. In a cohort of lacunar stroke patients, who were subtyped clinically and radiologically, we determined the genetic relative risk of stroke.

METHODS

By questionnaire and additional interview, we obtained a complete first-degree family history of stroke. The prevalence of stroke in first-degree relatives of these lacunar stroke patients was compared to the self-reported prevalence of stroke in a Dutch community based cohort of elderly volunteers. Secondly, the influence of proband characteristics and family composition on parental and sibling history of stroke were evaluated.

PRINCIPAL FINDINGS

We collected data of 1066 first-degree relatives of 195 lacunar stroke patients. Strokes occurred in 13.5% of first-degree relatives. The genetic relative risk was 2.94 (95%CI 2.45-3.53) for overall first-degree relatives, 4.52 (95%CI 3.61-5.65) for patients' parents and 2.10 (95%CI 1.63-2.69) for patients' siblings. Age of proband and proband status for hypertension influenced the chance of having a parent with a history of stroke whereas the likelihood of having a concordant sibling increased with sibship size.

CONCLUSIONS

We found an increased genetic relative risk of stroke in first-degree relatives of patients with lacunar stroke. Our data warrant further genomic research in this well-defined high risk population for stroke.

[Molecular mechanism and therapeutic strategy for cerebral small vessel disease]

Hypertension is a well known risk factor for cerebral small vessel disease (SVD) characterized by MRI white matter hyperintensities called "leukoaraiosis". However, the molecular basis of SVD remains to be elucidated. Both twin and family studies have shown that leukoaraiosis is the most heritable cerebrovascular phenotype with a heritability estimated to be between 55% and 71%, suggesting genetic factors for SVD. Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL) is hereditary SVD lacking hypertension. We have recently identified the causative gene, FHtrA1, for CARASIL by genome-wide linkage study and a candidate gene approach. HtrA1 is a serine protease that represses signaling by TGF-β family members. We found that mutated HtrA1 did not repress signaling by the TGF-β family members (BMP2, BMP4, and TGF-β1), resulting in vascular fibrosis with synthesis of extracellular matrix proteins. Our results indicate that disinhibition of TGF-β signaling underlies the molecular basis of CARASIL. Marfan's syndrome is an autosomal dominant connective tissue disorder caused by disinhibition of TGF-β signaling associated with FBN1 mutations. In a small cohort study, angiotensin II-receptor blockers (ARBs) therapy in patients with Marfan's syndrome significantly slowed the rate of progressive aortic-root dilatation. This study provides a potential for developing a therapy targeting TGF-β signaling for SVD.