Deep Resequencing of the 1q22 Locus in Non-Lobar Intracerebral Hemorrhage.

OBJECTIVE: Genome-wide association studies have identified 1q22 as a susceptibility locus for cerebral small vessel diseases, including non-lobar intracerebral hemorrhage (ICH) and lacunar stroke. In the present study, we performed targeted high-depth sequencing of 1q22 in ICH cases and controls to further characterize this locus and prioritize potential causal mechanisms, which remain unknown. METHODS: A total of 95,000 base pairs spanning 1q22, including SEMA4A, SLC25A44, and PMF1/PMF1-BGLAP were sequenced in 1,055 spontaneous ICH cases (534 lobar and 521 non-lobar) and 1,078 controls. Firth regression and Rare Variant Influential Filtering Tool analysis were used to analyze common and rare variants, respectively. Chromatin interaction analyses were performed using Hi-C, chromatin immunoprecipitation followed by sequencing, and chromatin interaction analysis with paired-end tag databases. Multivariable Mendelian randomization assessed whether alterations in gene-specific expression relative to regionally co-expressed genes at 1q22 could be causally related to ICH risk. RESULTS: Common and rare variant analyses prioritized variants in SEMA4A 5'-UTR and PMF1 intronic regions, overlapping with active promoter and enhancer regions based on ENCODE annotation. Hi-C data analysis determined that 1q22 is spatially organized in a single chromatin loop, and that the genes therein belong to the same topologically associating domain. Chromatin immunoprecipitation followed by sequencing and chromatin interaction analysis with paired-end tag data analysis highlighted the presence of long-range interactions between the SEMA4A-promoter and PMF1-enhancer regions prioritized by association testing. Multivariable Mendelian randomization analyses demonstrated that PMF1 overexpression could be causally related to non-lobar ICH risk. INTERPRETATION: Altered promoter-enhancer interactions leading to PMF1 overexpression, potentially dysregulating polyamine catabolism, could explain demonstrated associations with non-lobar ICH risk at 1q22, offering a potential new target for prevention of ICH and cerebral small vessel disease. ANN NEUROL 2024;95:325-337.

The Association of SUR1 Polymorphisms with Acute Infarct Size: The MRI-GENIE Study.

BACKGROUND: The sulfonylurea receptor 1 (SUR1) is a known mediator of cerebral edema in large ischemic strokes, however, genetically induced response variability has yet to be evaluated. SUR1, encoded by the ABCC8 gene, is an ion channel regulator in ischemia-induced cerebral edema. Previous studies in severe traumatic brain injury demonstrated four tag single nucleotide polymorphisms (SNPs) of the ABCC8 gene to be associated with cerebral edema and functional outcome. We hypothesized that these four SNPs would also be associated with acute infarct size and functional outcome in non-lacunar ischemic stroke. METHODS: Using 2,205 MRI-GENetics Interface Exploration (MRI-GENIE) study subjects with acute non-lacunar ischemic strokes, we evaluated the association between the 4 ABCC8 tag-SNPs and stroke infarct size (as measured in a standardized fashion from MRIs using diffusion-weighted imaging), adjusting for age, sex and population stratification. Modified Rankin scale (mRS) outcome was available at 3-months for a subset of 798 strokes in MRI-GENIE and was evaluated as a dichotomous variable (0-2 vs 3-6), adjusting for age, sex, stroke severity (baseline NIH Stroke Scale (NIHSS) score), and population stratification. RESULTS: The candidate SNPs, rs7105832, rs2237982, rs11024286, rs4148622, were not statistically associated with DWI (beta= -0.065, -0.057, 0.037, 0.018; p=0.053, 0.078, 0.28, 0.61) or dichotomous mRS outcome (OR=0.80, 0.86, 1.14, 0.90; p=0.117, 0.289, 0.353, 0.502). CONCLUSION: rs7105832, rs2237982, rs11024286, rs4148622 polymorphisms of the ABCC8 gene did not demonstrate a significant effect on acute ischemic infarct size or 3-month functional outcome. Nonetheless, further studies with delayed imaging and more sensitive outcome measures remain warranted.

The relevance of rich club regions for functional outcome post-stroke is enhanced in women.

This study aimed to investigate the influence of stroke lesions in predefined highly interconnected (rich-club) brain regions on functional outcome post-stroke, determine their spatial specificity and explore the effects of biological sex on their relevance. We analyzed MRI data recorded at index stroke and ~3-months modified Rankin Scale (mRS) data from patients with acute ischemic stroke enrolled in the multisite MRI-GENIE study. Spatially normalized structural stroke lesions were parcellated into 108 atlas-defined bilateral (sub)cortical brain regions. Unfavorable outcome (mRS > 2) was modeled in a Bayesian logistic regression framework. Effects of individual brain regions were captured as two compound effects for (i) six bilateral rich club and (ii) all further non-rich club regions. In spatial specificity analyses, we randomized the split into "rich club" and "non-rich club" regions and compared the effect of the actual rich club regions to the distribution of effects from 1000 combinations of six random regions. In sex-specific analyses, we introduced an additional hierarchical level in our model structure to compare male and female-specific rich club effects. A total of 822 patients (age: 64.7[15.0], 39% women) were analyzed. Rich club regions had substantial relevance in explaining unfavorable functional outcome (mean of posterior distribution: 0.08, area under the curve: 0.8). In particular, the rich club-combination had a higher relevance than 98.4% of random constellations. Rich club regions were substantially more important in explaining long-term outcome in women than in men. All in all, lesions in rich club regions were associated with increased odds of unfavorable outcome. These effects were spatially specific and more pronounced in women.

Cardiac Risk Factors for Stroke: A Comprehensive Mendelian Randomization Study.

BACKGROUND: Observational studies suggest an association of stroke with cardiac traits beyond atrial fibrillation, the leading source of cardioembolism. However, controversy remains regarding a causal role of these traits in stroke pathogenesis. Here, we leveraged genetic data to systematically assess associations between cardiac traits and stroke risk using a Mendelian Randomization framework. METHODS: We studied 66 cardiac traits including cardiovascular diseases, magnetic resonance imaging-derived cardiac imaging, echocardiographic imaging, and electrocardiographic measures, as well as blood biomarkers in a 2-sample Mendelian Randomization approach. Genetic predisposition to each trait was explored for associations with risk of stroke and stroke subtypes in data from the MEGASTROKE consortium (40 585 cases/406 111 controls). Using multivariable Mendelian Randomization, we adjusted for potential pleiotropic or mediating effects relating to atrial fibrillation, coronary artery disease, and systolic blood pressure. RESULTS: As expected, we observed strong independent associations between genetic predisposition to atrial fibrillation and cardioembolic stroke and between genetic predisposition to coronary artery disease as a proxy for atherosclerosis and large-artery stroke. Our data-driven analyses further indicated associations of genetic predisposition to both heart failure and lower resting heart rate with stroke. However, these associations were explained by atrial fibrillation, coronary artery disease, and systolic blood pressure in multivariable analyses. Genetically predicted P-wave terminal force in V1, an electrocardiographic marker for atrial cardiopathy, was inversely associated with large-artery stroke. CONCLUSIONS: Available genetic data do not support substantial effects of cardiac traits on the risk of stroke beyond known clinical risk factors. Our findings highlight the need to carefully control for confounding and other potential biases in studies examining candidate cardiac risk factors for stroke.

Black-White Differences in Ischemic Stroke Risk Factor Burden in Young Adults.

BACKGROUND AND PURPOSE: Although the US Black population has a higher incidence of stroke compared with the US White population, few studies have addressed Black-White differences in the contribution of vascular risk factors to the population burden of ischemic stroke in young adults. METHODS: A population-based case-control study of early-onset ischemic stroke, ages 15 to 49 years, was conducted in the Baltimore-Washington DC region between 1992 and 2007. Risk factor data was obtained by in-person interview in both cases and controls. The prevalence, odds ratio, and population-attributable risk percent (PAR%) of smoking, diabetes, and hypertension was determined among Black patients and White patients, stratified by sex. RESULTS: The study included 1044 cases and 1099 controls. Of the cases, 47% were Black patients, 54% were men, and the mean (±SD) age was 41.0 (±6.8) years. For smoking, the population-attributable risk percent were White men 19.7%, White women 32.5%, Black men 10.1%, and Black women 23.8%. For diabetes, the population-attributable risk percent were White men 10.5%, White women 7.4%, Black men 17.2%, and Black women 13.4%. For hypertension, the population-attributable risk percent were White men 17.2%, White women 19.3%, Black men 45.8%, and Black women 26.4%. CONCLUSIONS: Modifiable vascular risk factors account for a large proportion of ischemic stroke in young adults. Cigarette smoking was the strongest contributor to stroke among White patients while hypertension was the strongest contributor to stroke among Black patients. These results support early primary prevention efforts focused on smoking cessation and hypertension detection and treatment.

Genome-Wide Association Study Identifies First Locus Associated with Susceptibility to Cerebral Venous Thrombosis.

OBJECTIVE: Cerebral venous thrombosis (CVT) is an uncommon form of stroke affecting mostly young individuals. Although genetic factors are thought to play a role in this cerebrovascular condition, its genetic etiology is not well understood. METHODS: A genome-wide association study was performed to identify genetic variants influencing susceptibility to CVT. A 2-stage genome-wide study was undertaken in 882 Europeans diagnosed with CVT and 1,205 ethnicity-matched control subjects divided into discovery and independent replication datasets. RESULTS: In the overall case-control cohort, we identified highly significant associations with 37 single nucleotide polymorphisms (SNPs) within the 9q34.2 region. The strongest association was with rs8176645 (combined p = 9.15 × 10-24 ; odds ratio [OR] = 2.01, 95% confidence interval [CI] = 1.76-2.31). The discovery set findings were validated across an independent European cohort. Genetic risk score for this 9q34.2 region increases CVT risk by a pooled estimate OR = 2.65 (95% CI = 2.21-3.20, p = 2.00 × 10-16 ). SNPs within this region were in strong linkage disequilibrium (LD) with coding regions of the ABO gene. The ABO blood group was determined using allele combination of SNPs rs8176746 and rs8176645. Blood groups A, B, or AB, were at 2.85 times (95% CI = 2.32-3.52, p = 2.00 × 10-16 ) increased risk of CVT compared with individuals with blood group O. INTERPRETATION: We present the first chromosomal region to robustly associate with a genetic susceptibility to CVT. This region more than doubles the likelihood of CVT, a risk greater than any previously identified thrombophilia genetic risk marker. That the identified variant is in strong LD with the coding region of the ABO gene with differences in blood group prevalence provides important new insights into the pathophysiology of CVT. ANN NEUROL 2021;90:777-788.

Single nucleotide variations in ZBTB46 are associated with post-thrombolytic parenchymal haematoma.

Haemorrhagic transformation is a complication of recombinant tissue-plasminogen activator treatment. The most severe form, parenchymal haematoma, can result in neurological deterioration, disability, and death. Our objective was to identify single nucleotide variations associated with a risk of parenchymal haematoma following thrombolytic therapy in patients with acute ischaemic stroke. A fixed-effect genome-wide meta-analysis was performed combining two-stage genome-wide association studies (n = 1904). The discovery stage (three cohorts) comprised 1324 ischaemic stroke individuals, 5.4% of whom had a parenchymal haematoma. Genetic variants yielding a P-value < 0.05 1 × 10-5 were analysed in the validation stage (six cohorts), formed by 580 ischaemic stroke patients with 12.1% haemorrhagic events. All participants received recombinant tissue-plasminogen activator; cases were parenchymal haematoma type 1 or 2 as defined by the European Cooperative Acute Stroke Study (ECASS) criteria. Genome-wide significant findings (P < 5 × 10-8) were characterized by in silico functional annotation, gene expression, and DNA regulatory elements. We analysed 7 989 272 single nucleotide polymorphisms and identified a genome-wide association locus on chromosome 20 in the discovery cohort; functional annotation indicated that the ZBTB46 gene was driving the association for chromosome 20. The top single nucleotide polymorphism was rs76484331 in the ZBTB46 gene [P = 2.49 × 10-8; odds ratio (OR): 11.21; 95% confidence interval (CI): 4.82-26.55]. In the replication cohort (n = 580), the rs76484331 polymorphism was associated with parenchymal haematoma (P = 0.01), and the overall association after meta-analysis increased (P = 1.61 × 10-8; OR: 5.84; 95% CI: 3.16-10.76). ZBTB46 codes the zinc finger and BTB domain-containing protein 46 that acts as a transcription factor. In silico studies indicated that ZBTB46 is expressed in brain tissue by neurons and endothelial cells. Moreover, rs76484331 interacts with the promoter sites located at 20q13. In conclusion, we identified single nucleotide variants in the ZBTB46 gene associated with a higher risk of parenchymal haematoma following recombinant tissue-plasminogen activator treatment.

Black-white Differences in Left Ventricular Hypertrophy Rates Among Young Adults with Ischemic Stroke.

OBJECTIVES: Few studies have addressed Black-White differences in left ventricular hypertrophy (LVH) in young stroke patients without a history of hypertension. METHODS: A case-only cross-sectional analysis performed in 2019 of data from the Stroke Prevention in Young Adults Study, a population-based case-control study of ischemic stroke patients ages 15-49. The main outcomes were hypertension indicators at the time of stroke hospitalization: self-reported history of hypertension, LVH by echocardiography (Echo-LVH) and LVH by electrocardiogram (ECG-LVH). The prevalence of Echo-LVH was further determined in those with and without a history of hypertension. Adjusted odds ratios and 95% confidence intervals comparing blacks and whites were calculated by logistic regression. RESULTS: The study population included 1028 early-onset ischemic stroke patients, 48% Black cases, 54% men, median age 43 years (interquartile range, 38-46 years). Overall, the prevalence of hypertension history, Echo-LVH and ECG-LVH were 41.3%, 34.1% and 17.5%, respectively. Each of the hypertension indicators were more frequent in men than in women and in Black cases than in White cases. Black patients without a history of hypertension had higher rates of Echo-LVH than their white counterparts, 40.3% vs 27.7% (age and obesity adjusted OR 1.8; 95% CI 1.02-3.4) among men and 20.9% vs 7.6% (adjusted OR 2.7; 95% CI 1.2-6.2) among women. CONCLUSIONS: LVH was common in young patients with ischemic stroke, regardless of self-reported history of hypertension. These findings emphasize the need for earlier screening and more effective treatment of hypertension in young adults, particularly in the Black population.

Looking for opportunities to co-enroll: The DISCOVERY study experience.

BACKGROUND: Conducting high-quality stroke trials is complex and costly. Often these trials compete for the attention of researchers and the availability of patients. Enrolling patients in more than one study concurrently has the potential to accelerate recruitment into individual studies. DISCOVERY is a multicenter, inception cohort study of cognitive impairment and dementia following ischemic or hemorrhagic stroke. At the request of site investigators, a DISCOVERY committee reviews individual studies for approval of possible concurrent co-enrollment into DISCOVERY. The purpose of this report is to summarize the characteristics and outcomes of studies reviewed by committee for possible co-enrollment. METHODS: This analysis covers studies reviewed from 07/01/2020 to 04/26/2022 by the Site Management Committee (SMC) of the DISCOVERY Recruitment and Retention Core. Characterization of each study included study type, number and length of follow-up visits, and whether there were protocol-required blood draws, brain imaging studies, or cognitive tests. Studies were scored for patient burden and scientific overlap with Discovery. The primary outcome was SMC approval to co-enroll. RESULTS: 59 studies were reviewed, and 69.5% (n = 41, 21 clinical trials; 20 observational studies) were found by the SMC to be appropriate for co-enrollment. Higher patient burden and greater scientific overlap with DISCOVERY reduced the rates of approval for co-enrollment. CONCLUSION: A large number of diverse stroke studies are being run concurrently across the DISCOVERY study network, however, about two-thirds of the studies were considered appropriate for consideration of co-enrollment. Future studies should study how co-enrollment might improve trial network efficiency.

Marijuana Use and the Risk of Early Ischemic Stroke: The Stroke Prevention in Young Adults Study.

BACKGROUND AND PURPOSE: Few studies have examined the dose-response and temporal relationships between marijuana use and ischemic stroke while controlling for important confounders, including the amount of tobacco smoking. The purpose of our study was to address these knowledge gaps. METHODS: A population-based case-control study with 1090 cases and 1152 controls was used to investigate the relationship of marijuana use and early-onset ischemic stroke. Cases were first-ever ischemic stroke between the ages of 15 and 49 identified from 59 hospitals in the Baltimore-Washington region. Controls obtained by random digit dialing from the same geographic region were frequency-matched to cases by age, sex, region of residence and, except for the initial study phase, race. After excluding subjects with cocaine and other vasoactive substance use, the final study sample consisted of 751 cases and 813 controls. All participants underwent standardized interviews to characterize stroke risk factors and marijuana use. Unconditional logistic regression analysis was used to assess the relationships between marijuana use and risk of ischemic stroke, adjusting for age, sex, race, study phase, the amount of current tobacco smoking, current alcohol use, hypertension, and diabetes. RESULTS: After adjusting for other risk factors, including the amount of current tobacco smoking, marijuana use was not associated with ischemic stroke, regardless of the timing of use in relationship to the stroke, including ever use, use within 30 days, and use within 24 hours. There was a nonsignificant trend towards increased stroke risk among those who smoked marijuana at least once a week (odds ratio, 1.9 [95% CI, 0.8-4.9]). CONCLUSIONS: These analyses do not demonstrate an association between marijuana use and an increased risk of early-onset ischemic stroke, although statistical power was limited for assessing the association among very heavy users.

A genome-wide association study identifies new loci for factor VII and implicates factor VII in ischemic stroke etiology.

Factor VII (FVII) is an important component of the coagulation cascade. Few genetic loci regulating FVII activity and/or levels have been discovered to date. We conducted a meta-analysis of 9 genome-wide association studies of plasma FVII levels (7 FVII activity and 2 FVII antigen) among 27 495 participants of European and African ancestry. Each study performed ancestry-specific association analyses. Inverse variance weighted meta-analysis was performed within each ancestry group and then combined for a trans-ancestry meta-analysis. Our primary analysis included the 7 studies that measured FVII activity, and a secondary analysis included all 9 studies. We provided functional genomic validation for newly identified significant loci by silencing candidate genes in a human liver cell line (HuH7) using small-interfering RNA and then measuring F7 messenger RNA and FVII protein expression. Lastly, we used meta-analysis results to perform Mendelian randomization analysis to estimate the causal effect of FVII activity on coronary artery disease, ischemic stroke (IS), and venous thromboembolism. We identified 2 novel (REEP3 and JAZF1-AS1) and 6 known loci associated with FVII activity, explaining 19.0% of the phenotypic variance. Adding FVII antigen data to the meta-analysis did not result in the discovery of further loci. Silencing REEP3 in HuH7 cells upregulated FVII, whereas silencing JAZF1 downregulated FVII. Mendelian randomization analyses suggest that FVII activity has a positive causal effect on the risk of IS. Variants at REEP3 and JAZF1 contribute to FVII activity by regulating F7 expression levels. FVII activity appears to contribute to the etiology of IS in the general population.

Whole-Exome Sequencing in 22 Young Ischemic Stroke Patients With Familial Clustering of Stroke.

Backgrounds and Purpose- Although new methods for genetic analyses are rapidly evolving, there are currently knowledge gaps in how to detect Mendelian forms of stroke. Methods- We performed whole-exome sequencing in 22 probands, under 56 years at their first ischemic stroke episode, from multi-incident stroke families. With the use of a comprehensive stroke-gene panel, we searched for variants in stroke-related genes. The probands' clinical stroke subtype was related to clinical characteristics previously associated with pathogenic variants in these genes. Relatives were genotyped in 7 families to evaluate stroke-gene variants of unknown significance. In 2 larger families with embolic stroke of unknown source, whole-exome sequencing was performed in additional members to examine the possibility of identifying new stroke genes. Results- Six of 22 probands carried pathogenic or possibly pathogenic variants in genes reported to be associated with their stroke subtype. A known pathogenic variant in NOTCH3 and a possibly pathogenic variant in ACAD9 gene were identified. A novel JAK2:c.3188G>A (p.Arg1063His) mutation was seen in a proband with embolic stroke of undetermined source and prothrombotic status. However, penetrance in the family was incomplete. COL4A2:c.3368A>G (p.Glu1123Gly) was detected in 2 probands but did not cosegregate with the disease in their families. Whole-exome sequencing in multiple members of 2 pedigrees with embolic stroke of undetermined source revealed possibly pathogenic variants in genes not previously associated with stroke, GPR142:c.148C>G (p.Leu50Val), and PTPRN2:c.2416A>G (p.Ile806Val); LRRC1 c.808A>G (p.Ile270Val), SLC7A10c.1294dupG (p.Val432fs), IKBKB: c.1070C>T (p.Ala357Val), and OXGR1 c.392G>A (p.Arg131His), respectively. Conclusions- Screening with whole-exome sequencing using a comprehensive stroke-gene panel may identify rare monogenic forms of stroke, but careful evaluation of clinical characteristics and potential pathogenicity of novel variants remain important. In our study, the majority of individuals with familial aggregation of stroke lacked any identified genetic causes.

Sickle Cell Trait and Risk of Ischemic Stroke in Young Adults.

BACKGROUND AND PURPOSE: Approximately 8% of Blacks have sickle cell trait (SCT), and there are conflicting reports from recent cohort studies on the association of SCT with ischemic stroke (IS). Most prior studies focused on older populations, with few data available in young adults. METHODS: A population-based case-control study of early-onset IS was conducted in the Baltimore-Washington region between 1992 and 2007. From this study, 342 Black IS cases, ages 15 to 49, and 333 controls without IS were used to examine the association between SCT and IS. Each participant's SCT status was established by genotyping and imputation. For analysis, χ2 tests and logistic regression models were performed with adjustment for potential confounding variables. RESULTS: Participants with SCT (n=55) did not differ from those without SCT (n=620) in prevalence of hypertension, previous myocardial infarction, diabetes mellitus, and current smoking status. Stroke cases had increased prevalence in these risk factors compared with controls. We did not find an association between SCT and early-onset IS in our overall population (odds ratio=0.9 [95% CI, 0.5-1.7]) or stratified by sex in males (odds ratio=1.26 [95% CI, 0.56-2.80]) and females (odds ratio=0.67 [95% CI, 0.28-1.69]). CONCLUSIONS: Our data did not find evidence of increased risk of early-onset stroke with SCT.

Exome Array Analysis of Early-Onset Ischemic Stroke.

BACKGROUND AND PURPOSE: The genetic contribution to ischemic stroke may include rare- or low-frequency variants of high-penetrance and large-effect sizes. Analyses focusing on early-onset disease, an extreme-phenotype, and on the exome, the protein-coding portion of genes, may increase the likelihood of identifying such rare functional variants. To evaluate this hypothesis, we implemented a 2-stage discovery and replication design, and then addressed whether the identified variants also associated with older-onset disease. METHODS: Discovery was performed in UMD-GEOS Study (University of Maryland-Genetics of Early-Onset Stroke), a biracial population-based study of first-ever ischemic stroke cases 15 to 49 years of age (n=723) and nonstroke controls (n=726). All participants had prior GWAS (Genome Wide Association Study) and underwent Illumina exome-chip genotyping. Logistic-regression was performed to test single-variant associations with all-ischemic stroke and TOAST (Trial of ORG 10172 in Acute Stroke Treatment) subtypes in Whites and Blacks. Population level results were combined using meta-analysis. Gene-based aggregation testing and meta-analysis were performed using seqMeta. Covariates included age and gender, and principal-components for population structure. Pathway analyses were performed across all nominally associated genes for each stroke outcome. Replication was attempted through lookups in a previously reported meta-analysis of early-onset stroke and a large-scale stroke genetics study consisting of primarily older-onset cases. RESULTS: Gene burden tests identified a significant association with NAT10 in small-vessel stroke (P=3.79×10-6). Pathway analysis of the top 517 genes (P<0.05) from the gene-based analysis of small-vessel stroke identified several signaling and metabolism-related pathways related to neurotransmitter, neurodevelopmental notch-signaling, and lipid/glucose metabolism. While no individual SNPs reached chip-wide significance (P<2.05×10-7), several were near, including an intronic variant in LEXM (rs7549251; P=4.08×10-7) and an exonic variant in TRAPPC11 (rs67383011; P=5.19×10-6). CONCLUSIONS: Exome-based analysis in the setting of early-onset stroke is a promising strategy for identifying novel genetic risk variants, loci, and pathways.

Genome-Wide Association Study Meta-Analysis of Stroke in 22 000 Individuals of African Descent Identifies Novel Associations With Stroke.

BACKGROUND AND PURPOSE: Stroke is a complex disease with multiple genetic and environmental risk factors. Blacks endure a nearly 2-fold greater risk of stroke and are 2× to 3× more likely to die from stroke than European Americans. METHODS: The COMPASS (Consortium of Minority Population Genome-Wide Association Studies of Stroke) has conducted a genome-wide association meta-analysis of stroke in >22 000 individuals of African ancestry (3734 cases, 18 317 controls) from 13 cohorts. RESULTS: In meta-analyses, we identified one single nucleotide polymorphism (rs55931441) near the HNF1A gene that reached genome-wide significance (P=4.62×10-8) and an additional 29 variants with suggestive evidence of association (P<1×10-6), representing 24 unique loci. For validation, a look-up analysis for a 100 kb region flanking the COMPASS single nucleotide polymorphism was performed in SiGN (Stroke Genetics Network) Europeans, SiGN Hispanics, and METASTROKE (Europeans). Using a stringent Bonferroni correction P value of 2.08×10-3 (0.05/24 unique loci), we were able to validate associations at the HNF1A locus in both SiGN (P=8.18×10-4) and METASTROKE (P=1.72×10-3) European populations. Overall, 16 of 24 loci showed evidence for validation across multiple populations. Previous studies have reported associations between variants in the HNF1A gene and lipids, C-reactive protein, and risk of coronary artery disease and stroke. Suggestive associations with variants in the SFXN4 and TMEM108 genes represent potential novel ischemic stroke loci. CONCLUSIONS: These findings represent the most thorough investigation of genetic determinants of stroke in individuals of African descent, to date.

Ischaemic stroke in young adults: a global perspective.

Ischaemic stroke at young age is an increasing problem in both developing and developed countries due to rising incidence, high morbidity and mortality and long-term psychological, physical and social consequences. Compared with stroke in older adults, stroke in young adults is more heterogeneous due to the wide variety of possible underlying risk factors and aetiologies. In this review, we will provide an overview of the global variation in the epidemiology of stroke in young adults, with special attention to differences in geography, ethnicity/race and sex, as well as traditional and novel risk factors for early-onset ischaemic stroke, such as air pollution. Understanding global differences is an important prerequisite for better region-specific prevention and treatment of this devastating condition.

Impact of Cerebral Small Vessel Disease on Functional Recovery After Intracerebral Hemorrhage.

Background and Purpose- In this study, we aim to investigate the association of computed tomography-based markers of cerebral small vessel disease with functional outcome and recovery after intracerebral hemorrhage. Methods- Computed tomographic scans of patients in the ERICH study (Ethnic and Racial Variations of Intracerebral Hemorrhage) were evaluated for the extent of leukoaraiosis and cerebral atrophy using visual rating scales. Poor functional outcome was defined as a modified Rankin Scale (mRS) of ≥3. Multivariable logistic and linear regression models were used to explore the associations of cerebral small vessel disease imaging markers with poor functional outcome at discharge and, as a measure of recovery, change in mRS from discharge to 90 days poststroke. Results- After excluding in-hospital deaths, data from 2344 patients, 583 (24.9%) with good functional outcome (mRS of 0-2) at discharge and 1761 (75.1%) with poor functional outcome (mRS of 3-5) at discharge, were included. Increasing extent of leukoaraiosis (P for trend, 0.01) and only severe (grade 4) global atrophy (odds ratio, 2.02; 95% CI, 1.22-3.39, P=0.007) were independently associated with poor functional outcome at discharge. Mean (SD) mRS change from discharge to 90-day follow-up was 0.57 (1.18). Increasing extent of leukoaraiosis (P for trend, 0.002) and severe global atrophy (ß [SE], -0.23 [0.115]; P=0.045) were independently associated with less improvement in mRS from discharge to 90 days poststroke. Conclusions- In intracerebral hemorrhage survivors, the extent of cerebral small vessel disease at the time of intracerebral hemorrhage is associated with poor functional outcome at hospital discharge and impaired functional recovery from discharge to 90 days poststroke.

Genetic Imbalance Is Associated With Functional Outcome After Ischemic Stroke.

Background and Purpose- We sought to explore the effect of genetic imbalance on functional outcome after ischemic stroke (IS). Methods- Copy number variation was identified in high-density single-nucleotide polymorphism microarray data of IS patients from the CADISP (Cervical Artery Dissection and Ischemic Stroke Patients) and SiGN (Stroke Genetics Network)/GISCOME (Genetics of Ischaemic Stroke Functional Outcome) networks. Genetic imbalance, defined as total number of protein-coding genes affected by copy number variations in an individual, was compared between patients with favorable (modified Rankin Scale score of 0-2) and unfavorable (modified Rankin Scale score of ≥3) outcome after 3 months. Subgroup analyses were confined to patients with imbalance affecting ohnologs-a class of dose-sensitive genes, or to those with imbalance not affecting ohnologs. The association of imbalance with outcome was analyzed by logistic regression analysis, adjusted for age, sex, stroke subtype, stroke severity, and ancestry. Results- The study sample comprised 816 CADISP patients (age 44.2±10.3 years) and 2498 SiGN/GISCOME patients (age 67.7±14.2 years). Outcome was unfavorable in 122 CADISP and 889 SiGN/GISCOME patients. Multivariate logistic regression analysis revealed that increased genetic imbalance was associated with less favorable outcome in both samples (CADISP: P=0.0007; odds ratio=0.89; 95% CI, 0.82-0.95 and SiGN/GISCOME: P=0.0036; odds ratio=0.94; 95% CI, 0.91-0.98). The association was independent of age, sex, stroke severity on admission, stroke subtype, and ancestry. On subgroup analysis, imbalance affecting ohnologs was associated with outcome (CADISP: odds ratio=0.88; 95% CI, 0.80-0.95 and SiGN/GISCOME: odds ratio=0.93; 95% CI, 0.89-0.98) whereas imbalance without ohnologs lacked such an association. Conclusions- Increased genetic imbalance was associated with poorer functional outcome after IS in both study populations. Subgroup analysis revealed that this association was driven by presence of ohnologs in the respective copy number variations, suggesting a causal role of the deleterious effects of genetic imbalance.

Big Data Approaches to Phenotyping Acute Ischemic Stroke Using Automated Lesion Segmentation of Multi-Center Magnetic Resonance Imaging Data.

Background and Purpose- We evaluated deep learning algorithms' segmentation of acute ischemic lesions on heterogeneous multi-center clinical diffusion-weighted magnetic resonance imaging (MRI) data sets and explored the potential role of this tool for phenotyping acute ischemic stroke. Methods- Ischemic stroke data sets from the MRI-GENIE (MRI-Genetics Interface Exploration) repository consisting of 12 international genetic research centers were retrospectively analyzed using an automated deep learning segmentation algorithm consisting of an ensemble of 3-dimensional convolutional neural networks. Three ensembles were trained using data from the following: (1) 267 patients from an independent single-center cohort, (2) 267 patients from MRI-GENIE, and (3) mixture of (1) and (2). The algorithms' performances were compared against manual outlines from a separate 383 patient subset from MRI-GENIE. Univariable and multivariable logistic regression with respect to demographics, stroke subtypes, and vascular risk factors were performed to identify phenotypes associated with large acute diffusion-weighted MRI volumes and greater stroke severity in 2770 MRI-GENIE patients. Stroke topography was investigated. Results- The ensemble consisting of a mixture of MRI-GENIE and single-center convolutional neural networks performed best. Subset analysis comparing automated and manual lesion volumes in 383 patients found excellent correlation (ρ=0.92; P<0.0001). Median (interquartile range) diffusion-weighted MRI lesion volumes from 2770 patients were 3.7 cm3 (0.9-16.6 cm3). Patients with small artery occlusion stroke subtype had smaller lesion volumes ( P<0.0001) and different topography compared with other stroke subtypes. Conclusions- Automated accurate clinical diffusion-weighted MRI lesion segmentation using deep learning algorithms trained with multi-center and diverse data is feasible. Both lesion volume and topography can provide insight into stroke subtypes with sufficient sample size from big heterogeneous multi-center clinical imaging phenotype data sets.

Post-stroke fatigue as an indicator of underlying bioenergetics alterations.

Approximately half of stroke survivors suffer from clinically significant fatigue, contributing to poor quality of life, depression, dependency, and increased mortality. The etiology of post-stroke fatigue is not well understood and treatment is limited. This study tested the hypothesis that systemic aerobic energy metabolism, as reflected by platelet oxygen consumption, is negatively associated with fatigue and systemic inflammation is positively associated with fatigue in chronic ischemic stroke survivors. Data on self-reported level of fatigue, platelet oxygen consumption rates (OCR) and plasma inflammatory markers were analyzed from 20 ischemic stroke survivors. DNA copy number for two mitochondrial genes was measured as a marker of platelet mitochondrial content. Basal and protonophore-stimulated maximal platelet OCR showed a biphasic relationship to fatigue. Platelet OCR was negatively associated with low to moderate fatigue but was positively associated with moderate to high fatigue. DNA copy number was not associated with either fatigue or platelet OCR. Fatigue was negatively associated with C-reactive protein but not with other inflammatory markers. Post-stroke fatigue may be indicative of a systemic cellular energy dysfunction that is reflected in platelet energy metabolism. The biphasic relationship of fatigue to platelet OCR may indicate an ineffective bioenergetic compensatory response that has been observed in other pathological states.