Genetics of ischemic stroke in young adults

Recent Advances in Stroke Genetics-Unraveling the Complexity of Cerebral Infarction: A Brief Review

BACKGROUND/OBJECTIVES

Recent advances in stroke genetics have substantially enhanced our understanding of the complex genetic architecture underlying cerebral infarction and other stroke subtypes. As knowledge in this field expands, healthcare providers must remain informed about these latest developments. This review aims to provide a comprehensive overview of recent advances in stroke genetics, with a focus on cerebral infarction, and discuss their potential impact on patient care and future research directions.

METHODS

We reviewed recent literature about advances in stroke genetics, focusing on cerebral infarction, and discussed their potential impact on patient care and future research directions. Key developments include the identification of monogenic stroke syndromes, such as cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy, and cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy caused by mutations in the NOTCH3 and HTRA1 genes, respectively. In addition, the role of RNF213 in moyamoya disease and other cerebrovascular disorders, particularly in East Asian populations, has been elucidated. The development of polygenic risk scores for assessing genetic predisposition to stroke has demonstrated the potential to improve risk prediction beyond traditional factors. Genetic studies have also elucidated the distinct genetic architecture of stroke subtypes, including large artery atherosclerosis, small vessel disease, and cardioembolic stroke. Furthermore, the investigation of epigenetic modifications influencing stroke risk and its outcomes has revealed new research avenues, while advancements in pharmacogenomics highlight the potential for personalized stroke treatment based on individual genetic profiles.

CONCLUSIONS

These genetic discoveries have important clinical implications, including improved risk stratification, targeted prevention strategies, and the development of novel therapeutic approaches.

A Narrative Review of the Best Anesthesia Care for Endovascular Thrombectomy: Early Diagnosis of the Ischemic Stroke and Evaluation of Risk Factors in Female Population

Background: The increasing incidence of cerebrovascular accidents represents an emerging problem. The rise in risk factors such as lifestyle choices—smoking, poor nutrition, and metabolic diseases—poses a significant challenge for the global healthcare system. The female population, due to physiological conditions and iatrogenic risks, may be at a greater risk of developing ischemic accidents. In addition to these acquired conditions, life phases such as pregnancy or puerperium, and medical conditions like surgical treatments and hormone therapy, may elevate this risk. Methods: This narrative aims to assess the various risk factors specific to the female population and evaluate the appropriate management strategies, including anesthetic support. Anesthesia plays a crucial role in enabling pharmacological procedures, such as thrombolysis, or surgical procedures like thrombectomy, in the management of ischemic cerebrovascular events. Results: The review emphasizes the importance of early recognition of risk factors to ensure prompt diagnosis and the most appropriate treatment options for ischemic events. Anesthesia support has become essential for carrying out necessary medical interventions effectively. Choosing the right anesthesia technique for endovascular thrombectomy is particularly significant, requiring consideration of the patient’s characteristics, the timing of diagnosis, and the preferences of the interventional neuroradiologists. Conclusions: It is vital to identify risk factors in the female population early to facilitate timely diagnosis and optimize treatment outcomes. Anesthetic support plays a key role in ensuring that critical procedures, such as thrombolysis and thrombectomy, are carried out effectively. Tailoring anesthesia choices to the patient’s individual needs is critical for a successful intervention.

Current understanding of stroke and stroke mimics in adolescents and young adults: a narrative review

BACKGROUND

Stroke in adolescents and young adults are uncommon, and unlike in older adults, the etiology can be a challenging puzzle to solve. Patients often lack traditional risk factors such as hypertension or may be too young for suspected atherosclerotic disease. Additionally, among this group, various stroke mimics exist that can cloud physician judgment, leading to under- or overtreatment.

AIM

There is a significant gap in the current literature and clinical evidence regarding stroke in this population. This review of the literature aims to extract important information surrounding the etiology, risk factors, diagnosis, management, and complications of stroke in younger people and address stroke mimics and how they can appear similar and different from ischemic or hemorrhagic stroke. Additionally, we discuss the importance of furthering research in this specific population in all areas due to a concerning rise in stroke frequency and unique associated disabilities.

CONCLUSION

The acute treatment of stroke in young patients is similar to older adults. While stroke mimics may complicate suspicion and cause hesitance, delays in stroke care should be avoided. There remains a need for research in the areas of diagnosis, management, and assessment of long-term care and challenges in this population of patients.

Insights from rare variants into the genetic architecture and biology of youth-onset type 2 diabetes

Youth-onset type 2 diabetes (T2D) is a growing public health concern. Its genetic basis and relationship to other forms of diabetes are largely unknown. To gain insight into the genetic architecture and biology of youth-onset T2D, we analyzed exome sequences of 3,005 youth-onset T2D cases and 9,777 ancestry matched adult controls. We identified (a) monogenic diabetes variants in 2.1% of individuals; (b) two exome-wide significant (P < 4.3×10-7) common coding variant associations (in WFS1 and SLC30A8); (c) three exome-wide significant (P < 2.5×10-6) rare variant gene-level associations (HNF1A, MC4R, ATX2NL); and (d) rare variant association enrichments within 25 gene sets broadly related to obesity, monogenic diabetes, and β-cell function. Many association signals were shared between youth-onset and adult-onset T2D but had larger effects for youth-onset T2D risk (1.18-fold increase for common variants and 2.86-fold increase for rare variants). Both common and rare variant associations contributed more to youth-onset T2D liability variance than they did to adult-onset T2D, but the relative increase was larger for rare variant associations (5.0-fold) than for common variant associations (3.4-fold). Youth-onset T2D cases showed phenotypic differences depending on whether their genetic risk was driven by common variants (primarily related to insulin resistance) or rare variants (primarily related to β-cell dysfunction). These data paint a picture of youth-onset T2D as a disease genetically similar to both monogenic diabetes and adult-onset T2D, in which genetic heterogeneity might be used to sub-classify patients for different treatment strategies.

The future of sickle cell disease therapeutics rests in genomics

Sickle cell disease (SCD) is the most-common monogenic recessive disease in humans, annually affecting almost 300,000 newborns worldwide, 75% of whom live in Africa. Genomics research can accelerate the development of curative therapies for SCD in three ways. First, research should explore the missing heritability of foetal haemoglobin (HbF) - the strongest known modifier of SCD clinical expression - among highly genetically heterogenous and understudied African populations, to provide novel therapeutics targets for HbF induction. Second, SCD research should invest in RNA therapies, either by using microRNA to target the production of HbF proteins by binding to the transcription machinery in a cell, or by directly mediating production of HbF or adult haemoglobin through injection of messenger RNA. Third, investigators should aim to identify currently unknown genetic risk factors for SCD cardiovascular complications, which will address mortality, particularly in adults. Now is the time for global research programs to uncover genomic keys to unlock SCD therapeutics.

Relationship between MTHFR C677T, homocysteine, and ischemic stroke in a large sample of the Han Chinese population

Ischemic stroke, one of the prevalent causes of death and disability worldwide, is linked to environmental and genetic factors, including polymorphisms in the methylenetetrahydrofolate reductase (MTHFR) gene involved in homocysteine metabolism. The present study aimed to explore the relationship between the MTHFR C677T variant, plasma homocysteine, and risk of developing large-artery atherosclerotic ischemic stroke (LAAIS) among Han Chinese. A population-based case-control study, which included 1810 patients with LAAIS and 1765 unrelated control subjects, was conducted. Compared to the controls, LAAIS patients had a significantly higher prevalence of hypertension, diabetes mellitus, smoking, and alcohol consumption (P < .001), as well as significantly higher mean fasting blood glucose, triglyceride, total cholesterol, and plasma homocysteine levels (P < .001). The TT homozygous genotype correlated with increased risk of developing LAAIS, as indicated by a significantly higher odds ratio (OR) compared to the CT and CC genotypes, in both additive (OR = 3.215, P = .01) and recessive models (OR = 3.265, P = .01). The plasma homocysteine level was genotype-dependent according to the following trend: TT > CT > CC. In conclusion, our data demonstrate that, in spite of its low prevalence in both patients and controls (1.5% vs 0.8%), the MTHFR C677T variant could, at least in part, affect homocysteine levels and this, either alone or in combination with other factors, increases the risk of LAAIS.

Contribution and Effectiveness of Laboratory Testing in the Diagnostic Assessment of Juvenile Ischemic Stroke and Transient Ischemic Attack

Introduction

Strokes in young people require an extensive diagnostic workup to detect their possible several etiopathogenetic mechanisms. There is no consensus indicating what and when it should be tested. The clinical benefit and cost-effectiveness ratio of laboratory tests is unclear as well.

Methods

In one series of 104 consecutive juvenile ischemic stroke patients, under 45 years old, admitted between January 1, 2012, and December 31, 2017, we considered a wide panel of laboratory biomarkers exploring both the patient’s basal status and specific risk factors for thrombotic disorders. To combine conventional and unconventional risk factors, structural defects, and other stroke-related diseases, we defined four categories of etiologic probability. We then studied the contribution of laboratory testing in changing the rate of “definite or probable stroke etiology” and the “proportion of patients with at least one additional risk factor” for stroke.

Results

The mere clinical assessment clarified stroke etiopathogenesis in 31% of cases. Abnormal values of the panel of biomarkers we considered were found in 30.1% of young ischemic strokes, while 11.5% of patients had unclear or borderline values. The benefit of laboratory assessment consisted of a relevant 14% gain in patients with a “definite or probable stroke etiology.”

Conclusion

Several areas of uncertainty are still pending and herein discussed, such as the low re-testing rate during follow-up and the neglect of some relevant biomarkers. However, our results support the importance of laboratory testing in this setting. An improvement of diagnostic protocols in juvenile ischemic stroke would even increase their effectiveness, and this is still an unsolved issue in the field of cerebrovascular diseases. The same age limit, conventionally considered for juvenile stroke, could be better defined according to the effectiveness of both laboratory and clinical assessment in identifying unconventional stroke risk factors.

Vascular risk factors and staging of atherosclerosis in patients and controls: The Norwegian Stroke in the Young Study

Objectives:

We studied the prevalence of vascular risk factors (RFs) among 385 ischaemic stroke patients ⩽60 years and 260 controls, and their association with atherosclerosis in seven vascular areas.

Methods:

History of cardiovascular events (CVE), hypertension, diabetes mellitus (DM), dyslipidaemia, pack-years of smoking (PYS), alcohol, and physical inactivity were noted. Blood pressure, body mass index (BMI), waist-hip ratio (WHR), lipid profile, epicardial adipose tissue (EAT), visceral abdominal adipose tissue (VAT), and subcutaneous abdominal adipose tissue were measured. Numeric staging of atherosclerosis was done by standardized examination of seven vascular areas by right and left carotid and femoral intima-media thickness, electrocardiogram, abdominal aorta plaques, and the ankle-arm index. All results were age and sex-adjusted. Poisson regression analysis was applied.

Results:

At age ⩽49 years at least one RF was present in 95.6% patients versus 90.0% controls. Compared to controls, male patients and middle-aged female patients showed no significant differences. Young female patients compared to young female controls had a higher burden of RFs (94.3% vs 88.6%, p = 0.049). Poisson regression analysis combined for patients and controls, adjusted for age and sex, showed numeric staging of atherosclerosis associated with age, prior CVE, hypertension, DM, dyslipidaemia, PYS, alcohol, BMI, WHR, EAT, VAT, and an increased number of risk factors. Adjusted for all risk factors, numeric staging of atherosclerosis was associated with increasing age, hypertension, DM, PYS, and BMI.

Conclusion:

Vascular risk factors are highly prevalent in young- and middle-aged patients and controls, and are predictors of established atherosclerosis at study inclusion. Focus on main modifiable vascular RFs in primary prevention, and early and aggressive secondary treatment of patients are necessary to reduce further progression of atherosclerosis.

Hsa_circ_0010729 is Involved in Oxygen-Glucose Deprivation/Reoxygenation-Induced Human Microvascular Endothelial Cell Deprivation by Targeting miR-665/ING5

Ischemic stroke is a disease with high mortality. Circular RNA_0010729 (hsa_circ_0010729) has been reported to be involved in ischemic heart disease. However, it is not clear whether hsa_circ_0010729 is involved in the regulation of ischemic stroke. In this study, we used oxygen-glucose deprivation/reoxygenation (OGD/R) to stimulate human brain microvascular endothelial cells (HBMECs) model to investigate the potential role of hsa_circ_0010729 in stroke in vitro. The expression levels of hsa_circ_0010729, miR-665, and ING5 in ischemic stroke were detected by quantitative real-time polymerase chain reaction (qRT-PCR). HBMECs proliferation was detected by CCK-8. Cell apoptosis was detected by flow cytometry. The levels of inflammatory cytokines were detected by enzyme-linked immunosorbent assay (ELISA). Western blot was used to detect the related protein expression. Dual-luciferase reporter assay and RNA immunoprecipitation (RIP) were used to examine the target relationship between miR-665 and hsa_circ_0010729 or ING5. Compared with the control group, hsa_circ_0010729 and ING5 were highly expressed in OGD/R-induced HBMECs, while miR-665 was lowly expressed. Hsa_circ_0010729 silencing promoted OGD/R-induced cell proliferation and inhibited apoptosis. However, the effect of hsa_circ_0010729 down-regulation on OGD/R-induced cell was partially restored after co-transfection with miR-665 inhibitor. Overexpression of miR-665 can promote the proliferation and inhibit apoptosis of OGD/R-induced HBMECs by inhibiting ING5 expression. In OGD/R-induced HBMECs, hsa_circ_0010729 silencing decreased ING5 expression by upregulating miR-665. Hsa_circ_0010729 regulated miR-665/ING5 axis in OGD/R-induced HBMECs. Therefore, hsa_circ_0010729 may be a new therapeutic target for ischemic stroke.

Variant Rs556621 on Chromosome 6p21.1 and the Risk of Ischemic Stroke in Chinese Populations: A Meta-Analysis

There are inconsistencies in the published findings on the association of variant rs556621 in an intergenic region on Chromosome 6p21.1 with the risk of developing ischemic stroke (IS) and a major IS subtype (large artery atherosclerosis, LAA) in Chinese populations. We conducted a meta-analysis to evaluate the association of variant rs556621 with IS/LAA risk using ten studies involving 3644 IS cases and 3692 controls (including seven studies involving 2268 LAA cases and 2268 controls) from China. The AA genotype increased IS risk (AA versus CC: odds ratio [OR] 1.19, 95% confidence interval [CI] 1.03-1.36, P = 0.015; AA versus CA + CC: OR 1.23, 95% CI 1.09-1.39, P = 0.001). Subgroup analysis also suggested that rs556621 contributed to the risk of IS both in Chinese Han and the miscellaneous group. However, these results were stable in Chinese Han but not in the miscellaneous group. When restricting our analysis to the LAA subtype, similar results were obtained. This meta-analysis is the first meta-analysis on the correlation between rs556621 and the susceptibility of IS/LAA and demonstrates that rs556621 is associated with IS/LAA risk in Chinese populations. Further meta-analysis warrants larger well-designed investigations to assess these effects.

A Contemporary Review of Epidemiology, Risk Factors, Etiology, and Outcomes of Premature Stroke

PURPOSE OF REVIEW

Recent data identifies increases in young ischemic and hemorrhagic strokes. We provide a contemporary overview of current literature on stroke among young patients or premature stroke along with directions for future investigation.

RECENT FINDINGS

Strokes in the young are highly heterogenous and often cryptogenic. Sex distribution and risk factors shift from women among the youngest age groups (< 35) to men over the age of 45, with a coinciding rise in traditional vascular risk factors. Incidence is higher in minority and socioeconomically disadvantaged populations, and the impact of stroke among these communities may be exaggerated by disparities in symptom recognition and access to care. Special diagnostic work-up may be needed, and a lower threshold for diagnosis is warranted as potential misdiagnosis is a concern and may preclude necessary triage and management. Although "premature strokes" form a relatively small proportion of total incidence, they vary greatly across subgroups and present an outsized impact on quality of life and productivity.

ABO blood group system and occurrence of ischemic stroke

BACKGROUND

Ischemic stroke (IS) is a multifactorial disease that presents high rates of morbimortality in Brazil. Several studies proved that there is a link between the ABO blood group system and the occurrence of thrombotic events. Nonetheless, its association with IS is not well established.

OBJECTIVE

For that reason, the purpose hereof was to investigate the relation between the ABO blood groups and the occurrence of IS in a Brazilian cohort of cerebrovascular diseases.

METHODS

Five hundred and twenty-nine subjects were included over 12 months, from which 275 presented an IS episode and 254 composed the control group. Blood samples were drawn for direct and reverse serotyping. The control and IS groups were compared regarding the traditional risk factors and the distribution of the ABO blood groups.

RESULTS

The IS group presented a higher prevalence of systemic arterial hypertension (SAH), diabetes mellitus, smoking habits, family history, cardiopathy, and sedentary lifestyle in comparison with the control group. The AB blood type prevailed among the patients (5.1 vs. 1.6%; p<0.05) and this group had more SAH cases in comparison with the O type group (92.9 vs. 67.3%; p<0.05).

CONCLUSIONS

Our results suggest that the occurrence of IS is more frequent among patients of the AB blood type.

Discovering Cerebral Ischemic Stroke Associated Genes Based on Network Representation Learning

Cerebral ischemic stroke (IS) is a complex disease caused by multiple factors including vascular risk factors, genetic factors, and environment factors, which accentuates the difficulty in discovering corresponding disease-related genes. Identifying the genes associated with IS is critical for understanding the biological mechanism of IS, which would be significantly beneficial to the diagnosis and clinical treatment of cerebral IS. However, existing methods to predict IS-related genes are mainly based on the hypothesis of guilt-by-association (GBA). These methods cannot capture the global structure information of the whole protein-protein interaction (PPI) network. Inspired by the success of network representation learning (NRL) in the field of network analysis, we apply NRL to the discovery of disease-related genes and launch the framework to identify the disease-related genes of cerebral IS. The utilized framework contains three main parts: capturing the topological information of the PPI network with NRL, denoising the gene feature with the participation of a stacked autoencoder (SAE), and optimizing a support vector machine (SVM) classifier to identify IS-related genes. Superior to the existing methods on IS-related gene prediction, our framework presents more accurate results. The case study also shows that the proposed method can identify IS-related genes.

Family History of Stroke is Associated with Greater Prevalence of Certain Risk Factors and Self-Reported Stroke Symptoms

OBJECTIVES

Family history of stroke increases stroke risk, however mechanisms underlying this association remain unclear. We investigated whether family history of stroke is related to increased prevalence of stroke risk factors, unhealthy behaviors and self-reported stroke symptoms in middle-aged adults.

MATERIALS AND METHODS

In a cross-sectional study conducted from November 2018 to January 2021 in 100 primary care facilities in Poland we evaluated adults aged 40-65 years (n = 2207, women 57.4%, median age 55 years) for stroke risk factors, healthy behaviors, family history of stroke, self-reported stroke symptoms and stroke knowledge using structured questionnaires. Patients were categorized based on family history of stroke defined as ≥1 first-degree relative with documented stroke.

RESULTS

Family history of stroke was reported by 571 (25.9%) individuals who were older (median age 56 vs. 54 years, p = 0.00001) and after adjustment for age more frequently suffered from hypertension (61.5% vs. 53.7%, p = 0.024) and prior transient ischemic attack (2.1% vs. 0.9%, p = 0.019), but not other risk factors. However, they were less obese (34.5% vs. 39.1%, p = 0.03). Women, but not men, with family history of stroke (n = 339, 26.8%) had greater prevalence of atrial fibrillation (7.4% vs. 3.9%, p = 0.037). Family history of stroke was associated with higher prevalence of any self-reported stroke symptom (32.9% vs. 23.2%, p < 0.00001), but not with unhealthy dietary behaviors or low level of knowledge about stroke.

CONCLUSIONS

Family history of stroke is associated with greater prevalence of certain risk factors and self-reported stroke symptoms, which indicates the need for closer surveillance of middle-aged individuals at risk.

A Functional Polymorphism in HIF-3α Is Related to an Increased Risk of Ischemic Stroke

Hypoxia-inducible factor-3α (HIF-3α), a member of HIF family, can mediate adaptive responses to low oxygen and ischemia. It is believed that HIF plays crucial roles in stroke-related diseases. However, there are no reports on the association between HIF-3α genetic variants and ischemic stroke (IS) susceptibility. Therefore, we examined the association between HIF-3α gene polymorphisms (rs3826795, rs2235095, and rs3764609) and IS risk. The study population included 302 controls and 310 patients with ischemic stroke. Three polymorphisms in HIF-3α (rs3826795, rs2235095, and rs3764609) were genotyped using SNPscan technique. Our study showed a strong association of rs3826795 in HIF-3α with the risk of IS. The genotype and allele frequencies were shown to differ between the two groups. The rs3826795 in an intron of HIF-3α was related to a prominent increased IS risk (AA vs GG adjusted odd ratio [OR], 2.21; 95% confidence intervals [95% CI], 1.10-4.44; P = 0.03; AA vs AG/GG OR = 1.74, 95% CI, 1.02-2.97, P = 0.04; A vs G OR = 1.48, 95% CI, 1.05-2.07, P = 0.02). Logistic regression analysis suggested that rs3826795 posed a risk factor for IS in addition to common factors. Furthermore, when compared to controls, increased levels of homocysteic acid and level of non-esterified fatty acid were found in the cases (P < 0.01). However, no significant association was found between rs2235095 or rs3264609 and IS risk. These findings indicated that the rs3826795 polymorphism may be a potential target for predicting the risk of IS.

The copy number variation and stroke (CaNVAS) risk and outcome study

BACKGROUND AND PURPOSE

The role of copy number variation (CNV) variation in stroke susceptibility and outcome has yet to be explored. The Copy Number Variation and Stroke (CaNVAS) Risk and Outcome study addresses this knowledge gap.

METHODS

Over 24,500 well-phenotyped IS cases, including IS subtypes, and over 43,500 controls have been identified, all with readily available genotyping on GWAS and exome arrays, with case measures of stroke outcome. To evaluate CNV-associated stroke risk and stroke outcome it is planned to: 1) perform Risk Discovery using several analytic approaches to identify CNVs that are associated with the risk of IS and its subtypes, across the age-, sex- and ethnicity-spectrums; 2) perform Risk Replication and Extension to determine whether the identified stroke-associated CNVs replicate in other ethnically diverse datasets and use biomarker data (e.g. methylation, proteomic, RNA, miRNA, etc.) to evaluate how the identified CNVs exert their effects on stroke risk, and lastly; 3) perform outcome-based Replication and Extension analyses of recent findings demonstrating an inverse relationship between CNV burden and stroke outcome at 3 months (mRS), and then determine the key CNV drivers responsible for these associations using existing biomarker data.

RESULTS

The results of an initial CNV evaluation of 50 samples from each participating dataset are presented demonstrating that the existing GWAS and exome chip data are excellent for the planned CNV analyses. Further, some samples will require additional considerations for analysis, however such samples can readily be identified, as demonstrated by a sample demonstrating clonal mosaicism.

CONCLUSION

The CaNVAS study will cost-effectively leverage the numerous advantages of using existing case-control data sets, exploring the relationships between CNV and IS and its subtypes, and outcome at 3 months, in both men and women, in those of African and European-Caucasian descent, this, across the entire adult-age spectrum.

Protein C Promotor Haplotypes Associated with Large-Artery Atherosclerosis Stroke in Iranian Population

Ischemic stroke (IS) is a complex disease regarding its risk factors; among those factors, genetics has an important role. Protein C (PC) is an important antithrombotic enzyme which its genetic variations disrupt the normal cascade of blood coagulation, resulting in thrombosis and increases the chance of stroke. Therefore, we aimed to investigate three single-nucleotide polymorphisms (SNPs) located in the core promoter of PC in order to find their role in this condition in the Iranian population. Blood samples from IS patients (n = 249) and healthy volunteers (n = 203) were collected. Biochemical analysis was performed. Genotyping was conducted on the extracted DNA from blood samples via the HRM technique. Bioinformatic investigations were used to assess how these SNPs may be involved in the IS. Smoking, hypertension, low-density lipoprotein cholesterol, and fasting blood glucose were significantly different between healthy and IS groups. rs1799809 and rs1799810 SNPs were significantly more frequent among IS patients. Also, among four identified haplotypes, CGT was found associated with IS (p = 0.001). It was also found that these SNPs may interfere with the binding of transcription factors to alter the expression of PC. Our data predict that SNPs at the core promoter of PC can affect the binding affinity of transcription factors which in turn reduces the expression of PC and increases the risk of IS.

Circular RNA circPHC3 Promotes Cell Death and Apoptosis in Human BMECs After Oxygen Glucose Deprivation via miR-455-5p/TRAF3 Axis in vitro

OBJECTIVE

Brain microvascular endothelial cells (BMECs) are involved in brain vascular dysfunction in ischemic stroke. Abnormal expression of circular RNAs regulate physiological and pathophysiological processes in the central nervous system. The aim of the present study was to investigate profile circRNAs in human BMECs after oxygen glucose deprivation (OGD), which was an in vitro model of ischemic stroke, and find promising biomarkers in ischemic stroke.

METHODS

RNA sequencing (RNA-seq) technology was conducted to analyze the differential expression of circRNAs between BMECs after OGD and non-OGD treated BMECs. RT-qPCR, cell proliferation, cell apoptosis and dual-luciferase assay, and so on, were used to investigate the functions and molecular mechanisms of hsa_circ_0001360 (named circPHC3 in this study) in ischemic stroke.

RESULTS

CircPHC3 was highly expressed in human BMECs after OGD. Knockdown of circPHC3 inhibited cell death and apoptosis in human BMECs treated with OGD. Mechanistically, circPHC3 acted as miR-455-5p sponge to activate TRAF3 to promote cell death and apoptosis in human BMECs after OGD.

CONCLUSION

In short, circPHC3 promotes cell death and apoptosis in ischemic stroke in vitro model, which might be a novel molecular target for acute cerebrovascular protection.

Genetic modifiers of long-term survival in sickle cell anemia

BACKGROUND

Sickle cell anemia (SCA) is a clinically heterogeneous, monogenic disorder. Medical care has less-than-optimal impact on clinical outcomes in SCA in Africa due to several factors, including patient accessibility, poor access to resources, and non-availability of specific effective interventions for SCA.

METHODS

Against this background, we investigated 192 African participants who underwent whole exome sequencing. Participants included 105 SCA patients spanning variable clinical expression: a "long survivor" group (age over 40 years), a "stroke" group (at least one episode of overt stroke), and a "random" group (patients younger than 40 years without overt cerebrovascular disease). Fifty-eight ethnically matched homozygous hemoglobin A controls were also studied. Findings were validated in an independently recruited sample of 29 SCA patients. Statistical significance of the mutational burden of deleterious and loss-of-function variants per gene against a null model was estimated for each group, and gene-set association tests were conducted to test differences between groups.

RESULTS

In the "long survivor" group, deleterious/loss-of-function variants were enriched in genes including CLCN6 (a voltage-dependent chloride channel for which rare deleterious variants have been associated with lower blood pressure) and OGHDL (important in arginine metabolism, which is a therapeutic target in SCA). In the "stroke" group, significant genes implicated were associated with increased activity of the blood coagulation cascade and increased complement activation, for example, SERPINC1, which encodes antithrombin. Oxidative stress and glutamate biosynthesis pathways were enriched in "long survivors" group. Published transcriptomic evidence provides functional support for the role of the identified pathways.

CONCLUSIONS

This study provides new gene sets that contribute to variability in clinical expression of SCA. Identified genes and pathways suggest new avenues for other interventions.

Bosnian Study on Markers of Ischaemic Stroke in Adults 20-50 Years Old (SMISAO): Preliminary Report

Previous research suggested that several genetic polymorphisms are associated with increased risk of ischaemic stroke (IS) in young adults. However, the predictive biomarkers of IS in young adults are still unclear. Our aim was to assess the contribution of modifiable and genetic factors in IS in young adults. In total, 40 stroke patients and 40 healthy controls aged 20 to 50 years were recruited. Data on modifiable factors were collected, then participants were genotyped for seven SNPs linked to thrombophilia: ACE rs1799752, PAI-1 rs1799889, APOE rs1412 and rs429358, FV rs6025 and rs1800595, and FII rs62623459. Significantly increased risk factors: hypertension and dyslipidaemia in stroke patients compared with the controls: 50.0 % vs 27.5 % and 75.0 % vs 40.0% (P = 0.039 and P = 0.002, respectively) were observed. Stroke patients compared with controls did not differ in distribution of ACE, APOE, FV, and FII variants. The 4G4G homozygotes of the PAI-1 gene were significantly more prevalent in stroke patients compared to the controls: 42.5 % vs 17.5 %, (P = 0.033). In the group with the small vessel occlusion subtype of stroke, statistically significant overrepresentation of 4G4G homozygotes and frequency of the 4G allele compared with controls: 57.1 % vs 17.5 % and 0.7 vs 0.45 (P = 0.026 and P = 0.03, respectively) were observed. Independent predictors of stroke incident were: dyslipidaemia (OR (95% CI) = 4.2 (1.4-12.4)) and 4G4G genotype (OR (95% CI) = 3.9 (1.1-13.7)). These results confirm the contribution of dyslipidaemia and 4G4G genotype in the increased risk of IS in young Bosnian adults.

Human genetics and genomics research in Ecuador: historical survey, current state, and future directions

BACKGROUND

In South America, the history of human genetics is extensive and its beginnings go back to the onset of the twentieth century. In Ecuador, the historical record of human genetics and genomics research is limited. In this context, our work analyzes the current status and historical panorama of these fields, based on bibliographic searches in Scopus, Google Scholar, PubMed, and Web of Science.

RESULTS

Our results determined that the oldest paper in human genetics coauthored by an Ecuadorian institution originates from the Central University of Ecuador in 1978. From a historical standpoint, the number of articles has increased since the 1990s. This growth has intensified and it is reflected in 137 manuscripts recorded from 2010 to 2019. Areas such as human population genetics, phylogeography, and forensic sciences are the core of genetics and genomics-associated research in Ecuador. Important advances have been made in the understanding of the bases of cancer, some genetic diseases, and congenital disorders. Fields such as pharmacogenetics and pharmacogenomics have begun to be explored during the last years.

CONCLUSIONS

This work paints a comprehensive picture and provides additional insights into the future panorama of human genetic and genomic research in Ecuador as an example of an emerging, resource-limited country with interesting phylogeographic characteristics and public health implications.

Increased burden of rare deleterious variants of the KCNQ1 gene in patients with large‑vessel ischemic stroke

The impact of rare and damaging variants in genes associated with platelet function in large‑vessel ischemic stroke (LVIS) remains unknown. The aim of this study was to investigate the contribution of some of these variants to the genetic susceptibility to LVIS in Polish patients using a deep re‑sequencing of 54 selected genes, coding for proteins associated with altered platelet function. Targeted pooled re‑sequencing (Illumina HiSeq 2500) was performed on genomic DNA of 500 cases (patients with history of clinically proven diagnosis of LVIS) and 500 age‑, smoking status‑, and sex‑matched controls (no history of any type of stroke), and from the same population as patients with LVIS. After quality control and prioritization based on allele frequency and damaging probability, individual genotyping of all deleterious rare variants was performed in patients from the original cohort, and stratified to concomitant cardiac conditions differing between the study and stroke groups. We demonstrated a statistically significant increase in the number of rare and potentially damaging variants in some of the investigated genes in the LVIS pool (an increase in the genomic variants burden). Furthermore, we identified an association between LVIS and 6 rare functional and damaging variants in the Kv7.1 potassium channel gene (KCNQ1). The predicted functional properties (partial loss‑of function) for the three most damaging variants in KCNQ1 coding locus were further confirmed in vitro by analyzing the membrane potential changes in cell lines co‑transfected heterogeneously with human muscarinic type 1 receptor and wild‑type or mutated KCNQ1 cDNA constructs using fluorescence imaging plate reader. The study demonstrated an increased rare variants burden for 54 genes associated with platelet function, and identified a putative role for rare damaging variants in the KCNQ1 gene on LVIS susceptibility in the Polish population.

Genetics of the thrombomodulin-endothelial cell protein C receptor system and the risk of early-onset ischemic stroke

BACKGROUND AND PURPOSE

Polymorphisms in coagulation genes have been associated with early-onset ischemic stroke. Here we pursue an a priori hypothesis that genetic variation in the endothelial-based receptors of the thrombomodulin-protein C system (THBD and PROCR) may similarly be associated with early-onset ischemic stroke. We explored this hypothesis utilizing a multi-stage design of discovery and replication.

METHODS

Discovery was performed in the Genetics-of-Early-Onset Stroke (GEOS) Study, a biracial population-based case-control study of ischemic stroke among men and women aged 15-49 including 829 cases of first ischemic stroke (42.2% African-American) and 850 age-comparable stroke-free controls (38.1% African-American). Twenty-four single-nucleotide-polymorphisms (SNPs) in THBD and 22 SNPs in PROCR were evaluated. Following LD pruning (r2≥0.8), we advanced uncorrelated SNPs forward for association analyses. Associated SNPs were evaluated for replication in an early-onset ischemic stroke population (onset-age<60 years) consisting of 3676 cases and 21118 non-stroke controls from 6 case-control studies. Lastly, we determined if the replicated SNPs also associated with older-onset ischemic stroke in the METASTROKE data-base.

RESULTS

Among GEOS Caucasians, PROCR rs9574, which was in strong LD with 8 other SNPs, and one additional independent SNP rs2069951, were significantly associated with ischemic stroke (rs9574, OR = 1.33, p = 0.003; rs2069951, OR = 1.80, p = 0.006) using an additive-model adjusting for age, gender and population-structure. Adjusting for risk factors did not change the associations; however, associations were strengthened among those without risk factors. PROCR rs9574 also associated with early-onset ischemic stroke in the replication sample (OR = 1.08, p = 0.015), but not older-onset stroke. There were no PROCR associations in African-Americans, nor were there any THBD associations in either ethnicity.

CONCLUSION

PROCR polymorphisms are associated with early-onset ischemic stroke in Caucasians.

Identification of nine genes as novel susceptibility loci for early-onset ischemic stroke, intracerebral hemorrhage, or subarachnoid hemorrhage

Given that substantial genetic components have been shown in ischemic stroke, intracerebral hemorrhage (ICH), and subarachnoid hemorrhage (SAH), heritability may be higher in early-onset than late-onset individuals with these conditions. Although genome-wide association studies (GWASs) have identified various genes and loci significantly associated with ischemic stroke, ICH, or intracranial aneurysm mainly in European ancestry populations, genetic variants that contribute to susceptibility to these disorders remain to be identified definitively. We performed exome-wide association studies (EWASs) to identify genetic variants that confer susceptibility to ischemic stroke, ICH, or SAH in early-onset subjects with these conditions. A total of 6,649 individuals aged ≤65 years were examined. For the EWAS of ischemic or hemorrhagic stroke, 6,224 individuals (450 subjects with ischemic stroke, 5,774 controls) or 6,179 individuals (261 subjects with ICH, 176 subjects with SAH, 5,742 controls), respectively, were examined. EWASs were performed with the use of Illumina Human Exome-12 v1.2 DNA Analysis BeadChip or Infinium Exome-24 v1.0 BeadChip. To compensate for multiple comparisons of allele frequencies with ischemic stroke, ICH, or SAH, we applied a false discovery rate (FDR) of <0.05 for statistical significance of association. The association of allele frequencies of 31,245 single nucleotide polymorphisms (SNPs) that passed quality control to ischemic stroke was examined with Fisher's exact test, and 31 SNPs were significantly (FDR <0.05) associated with ischemic stroke. The association of allele frequencies of 31,253 or 30,970 SNPs to ICH or SAH, respectively, was examined with Fisher's exact test, and six or two SNPs were significantly associated with ICH or SAH, respectively. Multivariable logistic regression analysis with adjustment for age, sex, and the prevalence of hypertension and diabetes mellitus revealed that 12 SNPs were significantly [P<0.0004 (0.05/124)] related to ischemic stroke. Similar analysis with adjustment for age, sex, and the prevalence of hypertension revealed that six or two SNPs were significantly [P<0.0016 (0.05/32)] related to ICH or SAH, respectively. After examination of linkage disequilibrium of identified SNPs and results of previous GWASs, we identified HHIPL2, CTNNA3, LOC643770, UTP20, and TRIB3 as susceptibility loci for ischemic stroke, DNTTIP2 and FAM205A as susceptibility loci for ICH, and FAM160A1 and OR52E4 as such loci for SAH. Therefore, to the best of our knowledge, we have newly identified nine genes that confer susceptibility to early-onset ischemic stroke, ICH, or SAH. Determination of genotypes for the SNPs in these genes may prove informative for assessment of the genetic risk for ischemic stroke, ICH, or SAH in Japanese.

Population-Specific Associations of Deleterious Rare Variants in Coding Region of P2RY1-P2RY12 Purinergic Receptor Genes in Large-Vessel Ischemic Stroke Patients

The contribution of low-frequency and damaging genetic variants associated with platelet function to ischemic stroke (IS) susceptibility remains unknown. We employed a deep re-sequencing approach in Polish patients in order to investigate the contribution of rare variants (minor allele frequency, MAF < 1%) to the IS genetic susceptibility in this population. The genes selected for re-sequencing consisted of 26 genes coding for proteins associated with the surface membrane of platelets. Targeted pooled re-sequencing (Illumina HiSeq 2500) was performed on genomic DNA of 500 cases (patients with history of clinically proven diagnosis of large-vessel IS) and 500 controls. After quality control and prioritization based on allele frequency and damaging probability, follow-up individual genotyping of deleterious rare variants was performed in patients from the original cohort. Gene-based analyses identified an association between IS and 6 rare functional and damaging variants in the purinergic genes (P2RY1 and P2RY12 locus). The predicted properties of the most damaging rare variants in P2RY1 and P2RY12 were confirmed by using mouse fibroblast cell cultures transfected with plasmid constructs containing cDNA of mutated variants (FLIPR on FlexStation3). This study identified a putative role for rare variants in P2RY1 and P2RY12 genes involved in platelet reactivity on large-vessel IS susceptibility in a Polish population.

DNAH11 rs12670798 variant and G × E interactions on serum lipid levels, coronary heart disease, ischemic stroke and the lipid-lowering efficacy of atorvastatin

Previous genome-wide association studies have showed that the rs12670798 variant in the dynein axonemal heavy chain 11 gene (DNAH11) is associated with some serum lipid phenotypes. The present study was undertaken to detect the DNAH11 rs12670798 variant and G × E interactions on serum lipid levels, coronary heart disease (CHD), ischemic stroke (IS), and the lipid-lowering efficacy of atorvastatin in the Chinese Han population. This study included 1,108 unrelated patients (CHD, 568 and IS, 540) and 541 healthy controls. Genotypes of the DNAH11 rs12670798 were determined by the Snapshot technology. A total of 724 hyperlipidemic patients were treated with atorvastatin calcium tablet 20 mg per day for 8 weeks after genotyping. Serum total cholesterol (TC) levels in controls were different among the three genotypes of the rs12670798 (P = 0.019), the C allele carriers had higher TC levels than the C allele non-carriers. The C allele carriers were associated with an increased risk of CHD (CT genotype: OR = 1.345, 95% CI = 0.975-1.855, P = 0.071; CC genotype: OR = 1.590, 95% CI = 1.109-2.278, P = 0.012). The C allele carriers were also associated with an increased risk of IS (CT genotype: OR = 1.597, 95% CI = 1.153-2.213, P = 0.005; CC genotype: OR = 1.722, 95% CI = 1.192-2.488, P = 0.004). The C allele carriers had lower TC, low-density lipoprotein cholesterol, apolipoprotein (Apo) A1 and ApoB levels than the C allele non-carriers after atorvastatin treatment. Stratified analysis showed that the DNAH11 rs12670798 may interact with the gender, age, body mass index, cigarette smoking, and alcohol consumption to affect the risk of CHD and IS. The DNAH11 rs12670798 variant was associated with elevated serum TC levels, and increased risk of CHD and IS in the Chinese Han population. The C allele carriers had higher serum TC levels and the risk of CHD and IS than the C allele non-carriers, but they had lower TC, LDL-C, ApoA1 and ApoB levels than the C allele non-carriers after atorvastatin treatment.

Genetic Risk Factors for Ischemic and Hemorrhagic Stroke

Understanding the genetic risk factors for stroke is an essential step to decipher the underlying mechanisms, facilitate the identification of novel therapeutic targets, and optimize the design of prevention strategies. A very small proportion of strokes are attributable to monogenic conditions, the vast majority being multifactorial, with multiple genetic and environmental risk factors of small effect size. Genome-wide association studies and large international consortia have been instrumental in finding genetic risk factors for stroke. While initial studies identified risk loci for specific stroke subtypes, more recent studies also revealed loci associated with all stroke and all ischemic stroke. Risk loci for ischemic stroke and its subtypes have been implicated in atrial fibrillation (PITX2 and ZFHX3), coronary artery disease (ABO, chr9p21, HDAC9, and ALDH2), blood pressure (ALDH2 and HDAC9), pericyte and smooth muscle cell development (FOXF2), coagulation (HABP2), carotid plaque formation (MMP12), and neuro-inflammation (TSPAN2). For hemorrhagic stroke, two loci (APOE and PMF1) have been identified.

Searching for Explanations for Cryptogenic Stroke in the Young: Revealing the Triggers, Causes, and Outcome (SECRETO): Rationale and design

BACKGROUND

Worldwide, about 1.3 million annual ischaemic strokes (IS) occur in adults aged <50 years. Of these early-onset strokes, up to 50% can be regarded as cryptogenic or associated with conditions with poorly documented causality like patent foramen ovale and coagulopathies.

KEY HYPOTHESES/AIMS

(1) Investigate transient triggers and clinical/sub-clinical chronic risk factors associated with cryptogenic IS in the young; (2) use cardiac imaging methods exceeding state-of-the-art to reveal novel sources for embolism; (3) search for covert thrombosis and haemostasis abnormalities; (4) discover new disease pathways using next-generation sequencing and RNA gene expression studies; (5) determine patient prognosis by use of phenotypic and genetic data; and (6) adapt systems medicine approach to investigate complex risk-factor interactions.

DESIGN

Searching for Explanations for Cryptogenic Stroke in the Young: Revealing the Etiology, Triggers, and Outcome (SECRETO; NCT01934725) is a prospective multi-centre case-control study enrolling patients aged 18-49 years hospitalised due to first-ever imaging-proven IS of undetermined etiology. Patients are examined according to a standardised protocol and followed up for 10 years. Patients are 1:1 age- and sex-matched to stroke-free controls. Key study elements include centralised reading of echocardiography, electrocardiography, and neurovascular imaging, as well as blood samples for genetic, gene-expression, thrombosis and haemostasis and biomarker analysis. We aim to have 600 patient-control pairs enrolled by the end of 2018.

SUMMARY

SECRETO is aiming to establish novel mechanisms and prognosis of cryptogenic IS in the young and will provide new directions for therapy development for these patients. First results are anticipated in 2019.

The very long-term risk and predictors of recurrent ischaemic events after a stroke at a young age: The FUTURE study

Introduction

Patients who suffer a stroke at a young age, remain at a substantial risk of developing recurrent vascular events and information on very long-term prognosis and its risk factors is indispensable. Our aim is to investigate this very long-term risk and associated risk factors up to 35 years after stroke.

Patients and methods

Prospective cohort study among 656 patients with a first-ever ischaemic stroke or transient ischaemic stroke (TIA), aged 18-50, who visited our hospital (1980-2010). Outcomes assessed at follow-up (2014-2015) included TIA or ischaemic stroke and other arterial events, whichever occurred first. Kaplan-Meier analysis quantified cumulative risks. A prediction model was constructed to assess risk factors independently associated with any ischaemic event using Cox proportional hazard analyses followed by bootstrap validation procedure to avoid overestimation.

Results

Mean follow-up was 12.4 (SD 8.2) years (8105 person-years). Twenty-five years cumulative risk was 45.4% (95%CI: 39.4-51.5) for any ischaemic event, 30.1% (95%CI: 24.8-35.4) for cerebral ischaemia and 27.0% (95%CI: 21.1-33.0) for other arterial events. Risk factors retained in the prediction model were smoking (HR 1.35, 95%CI: 1.04-1.74), poor kidney function (HR 2.10, 95%CI: 1.32-3.35), history of peripheral arterial disease (HR 2.10, 95%CI: 1.08-3.76) and cardiac disease (HR 1.84, 95%CI: 1.06-3.18) (C-statistic 0.59 (95%CI: 0.55-0.64)).

Discussion and conclusion

Young stroke patients remain at a substantial risk for recurrent events; almost 1 of 2 develops a recurrent ischaemic event and 1 of 3 develops a recurrent stroke or TIA during 25 years of follow-up. Risk factors independently associated with recurrent events were poor kidney function, smoking, history of peripheral arterial disease and cardiac disease.

Towards the genetic basis of cerebral venous thrombosis-the BEAST Consortium: a study protocol

INTRODUCTION

Cerebral venous thrombosis (CVT) is a rare cerebrovascular condition accounting for <1% of all stroke cases and mainly affects young adults. Its genetic aetiology is not clearly elucidated.

METHODS AND ANALYSIS

To better understand the genetic basis of CVT, we have established an international biobank of CVT cases, Biorepository to Establish the Aetiology of Sinovenous Thrombosis (BEAST) which aims to recruit highly phenotyped cases initially of European descent and later from other populations. To date we have recruited 745 CVT cases from 12 research centres. As an initial step, the consortium plans to undertake a genome-wide association analysis of CVT using the Illumina Infinium HumanCoreExome BeadChip to assess the association and impact of common and low-frequency genetic variants on CVT risk by using a case-control study design. Replication will be performed to confirm putative findings. Furthermore, we aim to identify interactions of genetic variants with several environmental and comorbidity factors which will likely contribute to improve the understanding of the biological mechanisms underlying this complex disease.

ETHICS AND DISSEMINATION

BEAST meets all ethical standards set by local institutional review boards for each of the participating sites. The research outcomes will be published in international peer-reviewed open-access journals with high impact and visibility. The results will be presented at national and international meetings to highlight the contributions into improving the understanding of the mechanisms underlying this uncommon but important disease. This international DNA repository will become an important resource for investigators in the field of haematological and vascular disorders.

Ischemic stroke in the young: Current perspectives on incidence, risk factors, and cardiovascular prognosis

About one-fourth of ischemic strokes occur in working-aged individuals in the high-income countries, with worldwide increasing incidence in this age group from 1980s to present. Recent evidence suggests that traditional vascular risk factors are more prevalent than previously suggested in young adult stroke patients and they accumulate with age particularly in men. Accordingly, relatively high rates of atherosclerotic changes have been detected in these patients. The strength of association of vascular risk factors has gone poorly studied, however. Many young patients with ischemic stroke have, in turn, no traditional risk factors, while they may harbor other conditions with weak or uncertain association with the stroke alone. These individual conditions often represent a risk factor that may be strictly young-age specific, more prevalent in younger than older stroke patients (e.g. patent foramen ovale), or more prevalent among the young in the population. Despite high rates of vascular risk factors and atherosclerotic changes, these findings do not translate to higher frequencies of identified classical stroke mechanisms. In fact, cryptogenic causes are markedly common and even more frequent among the very young patients. Limited randomized trial evidence exists to support secondary prevention decision-making in patients, yet they face an increased risk of death and future vascular events for years to come-dependent on risk factor profile and cause of the stroke. This review provides an overview of recent data on epidemiology, risk factors, and their strength of association in ischemic stroke in the young. Furthermore, the relationship between with the risk factors and cardiovascular outcomes and key features on the evidence related to secondary prevention will be discussed.

Genome-Wide Association Analysis of Young-Onset Stroke Identifies a Locus on Chromosome 10q25 Near HABP2

BACKGROUND AND PURPOSE

Although a genetic contribution to ischemic stroke is well recognized, only a handful of stroke loci have been identified by large-scale genetic association studies to date. Hypothesizing that genetic effects might be stronger for early- versus late-onset stroke, we conducted a 2-stage meta-analysis of genome-wide association studies, focusing on stroke cases with an age of onset <60 years.

METHODS

The discovery stage of our genome-wide association studies included 4505 cases and 21 968 controls of European, South-Asian, and African ancestry, drawn from 6 studies. In Stage 2, we selected the lead genetic variants at loci with association P<5×10(-6) and performed in silico association analyses in an independent sample of ≤1003 cases and 7745 controls.

RESULTS

One stroke susceptibility locus at 10q25 reached genome-wide significance in the combined analysis of all samples from the discovery and follow-up stages (rs11196288; odds ratio =1.41; P=9.5×10(-9)). The associated locus is in an intergenic region between TCF7L2 and HABP2. In a further analysis in an independent sample, we found that 2 single nucleotide polymorphisms in high linkage disequilibrium with rs11196288 were significantly associated with total plasma factor VII-activating protease levels, a product of HABP2.

CONCLUSIONS

HABP2, which encodes an extracellular serine protease involved in coagulation, fibrinolysis, and inflammatory pathways, may be a genetic susceptibility locus for early-onset stroke.

Heritability of young- and old-onset ischaemic stroke

BACKGROUND AND PURPOSE

Although the genetic contribution to stroke risk is well known, it remains unclear if young-onset stroke has a stronger genetic contribution than old-onset stroke. This study aims to compare the heritability of ischaemic stroke risk between young and old, using common genetic variants from whole-genome array data in population-based samples.

METHODS

This analysis included 4050 ischaemic stroke cases and 5765 controls from six study populations of European ancestry; 47% of cases were young-onset stroke (age < 55 years). To quantify the heritability for stroke risk in these unrelated individuals, the pairwise genetic relatedness was estimated between individuals based on their whole-genome array data using a mixed linear model. Heritability was estimated separately for young-onset stroke and old-onset stroke (age ≥ 55 years).

RESULTS

Heritabilities for young-onset stroke and old-onset stroke were estimated at 42% (±8%, P < 0.001) and 34% (±10%, P < 0.001), respectively.

CONCLUSIONS

Our data suggest that the genetic contribution to the risk of stroke may be higher in young-onset ischaemic stroke, although the difference was not statistically significant.