Comprehensive investigation of RNF213 nonsynonymous variants associated with intracranial artery stenosis.

Intracranial artery stenosis (ICAS) is the most common cause of ischemic stroke worldwide. RNF213 single nucleotide variant c.14429G > A (p.Arg4810Lys, rs112735431) was recently reported to be associated with ICAS in East Asians. However, the disease susceptibility of other RNF213 variants has not been clarified. This study comprehensively investigated ICAS-associated RNF213 variants in a pool of 168 Japanese ICAS patients and 1,194 control subjects. We found 138 nonsynonymous germline variants by target resequencing of all coding exons in RNF213. Association study between ICAS patients and control subjects revealed that only p.Arg4810Lys had significant association with ICAS (P = 1.5 × 10-28, odds ratio = 29.3, 95% confidence interval 15.31-56.2 [dominant model]). Fourteen of 138 variants were rare variants detected in ICAS patients not harboring p.Arg4810Lys variant. Two of these rare variants (p.Cys118Arg and p.Leu2356Phe) consistent with variants previously reported in moyamoya disease patients characterized by stenosis of intracranial artery and association with RNF213, and three rare variants (p.Ser193Gly, p.Val1817Leu, and p.Asp3329Tyr) were found neither in control subjects and Single Nucleotide Polymorphism Database. The present findings may improve our understanding of the genetic background of intracranial artery stenosis.

The Clinical and Vascular Characteristics of RNF213 c.14576G>A Variant-Related Intracranial Major Artery Disease in China.

BACKGROUND AND PURPOSE: Recently, several studies indicated the c.14576G>A variant on the ring finger protein 213 (RNF213), a founder variant of moyamoya diseases (MMD), was associated with non-MMD intracranial major artery stenosis/occlusion (non-MMD ICASO). We proposed that RNF213 variant-related ICASO including MMD might be a special entity with its own characteristics based on a genetic background. The aim of the study was to learn the clinical and vascular features of RNF213 variant-related ICASO. Moreover, we tried to explore the clinical significance of a testing variant in ICASO patients in China. METHODS: Clinical material and routine image data were collected in 160 Chinese patients with ICASO, including 41 verified MMD and 119 non-MMD. DNA samples were extracted, and the c.14576G>A variant on RNF213 was genotyped. Then, the clinical and vascular features were compared between the patients with and without a relevant variant. Furthermore, the patients with RNF213 mutation were performed with high resolution magnetic resonance imaging (HR-MRI) examination to conclude features of the artery wall. RESULTS: There were 16 (10%) patients (including 9 MMD and 7 non-MMD ICASO) presenting a heterozygous c.14576G>A variant while none of homozygote was found. Compared to the patients without the c.14576G>A variant, the variant group had more female, less symptomatic patients, and more possibility of having collateral vessels in vascular imaging. In the symptomatic subgroup, there is no significant difference in clinical presentation (p > 0.05) between two groups. However, RNF213 variant-related ICASO had lower scores in NIHSS (1.0 ± 3.0 vs. 3.9 ± 5.0, p < 0.05) but not in mRS. In the symptomatic subgroup, in addition, most of the HR-MRI images of variant ICASO (77.8%, 7 of 9) were characterized by a shrunken outer diameter, concentric thickening vessel wall, and collateral vessel structures on the stenotic portion, which was prone to be diagnosed as HR-MMD (a MMD diagnosis diagnosed by HR-MRI). The rest of the two variants showed a relatively eccentric luminal narrow, normal outer diameter without collateral vessel findings, identified as HR-ICAD (intracranial atherosclerotic disease diagnosed by HR-MRI). CONCLUSIONS: Our study demonstrated that the c.14576G>A variant on RNF213 may be a biomarker to good outcome of ICASO in Chinese. The variant-related ICASO was characterized by both features of MMD and ICAD diagnosed by HR-MRI.

The Genetic Landscape of Cerebral Steno-Occlusive Arteriopathy and Stroke in Sickle Cell Anemia.

Sickle cell disease (SCD) is one of the most common autosomal recessive diseases in humans, occurring at a frequency of 1 in 365 African-American and 1 in 50 sub-Saharan African births. Despite progress in managing complications of SCD, these remain a major health burden worldwide. Stroke is a common and serious complication of SCD, most often associated with steno-occlusive cerebral arteriopathy, but little is known about its pathogenesis. Transcranial Doppler ultrasonography is currently the only predictive test for future development of stroke in patients with sickle cell anemia and is used to guide preventative treatment. However, transcranial Doppler ultrasonography does not identify all patients at increased risk for stroke, and progressive arteriopathy may occur despite preventative treatment. While sibling studies have shown a strong genetic contribution to the development of steno-occlusive arteriopathy (SOA) in SCD, the only genome-wide association study compared a relatively small cohort of 177 patients with stroke to 335 patients with no history of stroke. This single study detected variants in only 2 genes, ENPP1 and GOLGB1, and only one of these was confirmed in a subsequent independent study. Thus, the underlying genes and pathogenesis of SOA in SCD remain poorly understood, greatly limiting the ability to develop more effective preventive therapies. Dissecting the molecular causes of stroke in SCD will provide valuable information that can be used to better prevent stroke, stratify risk of SOA, and optimize personalized medicine approaches.

RNF213-related susceptibility of Japanese CADASIL patients to intracranial arterial stenosis.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), caused by NOTCH3, primarily affects small cerebral arteries; however, stenosis of major intracranial arteries has occasionally been reported. Recent studies identified a close association between the c.14576G>A (p.R4859K, rs112735431) variant of the ring finger protein 213 (RNF213) gene and sporadic intracranial arterial stenosis (ICAS). To determine whether RNF213 is associated with ICAS in CADASIL, we genotyped rs112735431 for 124 patients with CADASIL. The c.14576G>A carrier rate in CADASIL patients with ICAS (4/17; 23.5%) was significantly higher compared with those without ICAS (2/107; 1.9%) (P = 0.0032). Among patients with ICAS, frequency of territorial infarction was significantly higher in c.14576G>A carriers (75.0%) than in non-carriers (20.0%) (P = 0.0410). In addition, rate of ≥50% stenosis or occlusion tended to be higher in c.14576G>A carriers (4/4; 100%) than in non-carriers (6/13; 46.2%) (P = 0.1029). We conclude that RNF213 is a gene associated with susceptibility to ICAS in CADASIL patients. MRA follow-up and close observation are necessary for CADASIL patients with the RNF213 variant, as they may be predisposed to ICAS.

Association of ABCB1 promoter methylation with aspirin exposure, platelet function, and clinical outcomes in Chinese intracranial artery stenosis patients.

PURPOSE: DNA methylation typically acts to repress gene transcription. ABCB1 is involved in the intestinal absorption of aspirin. We aimed to investigate the impact of methylation status of ABCB1 promoter on aspirin exposure, platelet function, and clinical outcomes in Chinese intracranial artery stenosis patients receiving antiplatelet treatment. METHODS: Symptomatic intracranial artery stenosis patients (without carrying CYP2C19 loss-of-function alleles) receiving antiplatelet therapy were enrolled in this study. The clinical outcome was the composite events, vascular death, recurrent ischemic stroke, myocardial infarction, or transit ischemic attack. Patients were divided into cases and controls based on the 1-year follow-up. Venous blood samples were collected for methylation level analysis, drug determination, and thromboelastographic assay. The Pearson correlation analysis was used to investigate the association of potential influencing factors and visualize them using three-dimensional plot. Receiver operator curves were applied to compare the diagnostic performance of potential factors and calculate the cut-off values. RESULTS: We assessed 438 patients, 30 (non-carrier of CYP2C19 loss-of-function alleles) experienced adverse clinical events, and 30 patients without clinical events were selected as controls. Total of 34 CpG methylation sites were investigated for ABCB1 methylation. Compared with controls, the cases had significant lower methylation levels (CpG21.22), lower salicylic acid concentration, and lower arachidonic acid inhibition (P value < 0.05). A cut-off point of CpG21.22 0.015 was identified with a specificity of 0.759. CONCLUSION: ABCB1 hypomethylation is associated with lower drug absorption, higher platelet reactivity, and an increased risk of ischemic events in our patients. This may provide important insights into the research of aspirin resistance.

RNF213 rs112735431 polymorphism in intracranial artery steno-occlusive disease and moyamoya disease in Koreans.

BACKGROUND: The rs112735431 polymorphism of the RNF213, a susceptibility variant for moyamoya disease (MMD), may be associated with non-MMD intracranial artery steno-occlusive disease of non-MMD type (non-MMD ICAD) in Asian. We investigated whether the rs112735431 polymorphism of the RNF213 affect the development of non-MMD ICAD in Koreans compared to MMD and control group. METHODS: We included 31 patients with non-MMD ICAD, 25 patients with MMD, and 100 participants as control group. The rs112735431 polymorphism of the RNF213 was evaluated by polymerase chain reaction amplification of target and detection by restriction fragment length polymorphism analysis. Clinical phenotype was compared between patients with and without the rs112735431 polymorphism in non-MMD ICAD and MMD. RESULTS: The rs112735431 polymorphism of the RNF213 was significantly associated with non-MMD ICAD (p=0.001; odds ratio, 14.3; 95% confidence interval, 2.80-73.2) and MMD (p<0.0001; odds ratio, 126.0; 95% confidence interval, 24.2-656.0). The rate of hypertension was more frequent in MMD with the rs112735431 polymorphism than MMD without polymorphism (p=0.010). CONCLUSIONS: The rs112735431 polymorphism of the RNF213 is highly associated not only with MMD but also with non-MMD ICAD in Koreans. Also, our study suggests that the rs112735431 polymorphism of the RNF213 may be linked to the hypertension in MMD. Further studies are needed to clarify the relationship between the rs112735431 polymorphism of the RNF213 and hypertension in patients with MMD.

Aldehyde dehydrogenase 2 polymorphism as a protective factor for intracranial vascular stenosis in ischemic stroke in Han Chinese.

AIM: Aldehyde dehydrogenase 2 (ALDH2) is a key enzyme that metabolizes acetaldehyde to acetic acid. ALDH2 gene polymorphism modifies its activity and the mutation of ALDH2 gene has been reported to be associated with the protection against ischemic stroke. However, the potential association of allelic variation of ALDH2 with intracranial vascular stenosis and the clinical characteristics of ischemic stroke without coronary artery disease remains unclear. METHODS: In this study, ischemic stroke patients were recruited, National Institutes of Health Stroke Scale scores were analyzed, intracranial arterial stenosis were evaluated by magnetic resonance angiography and gene typing of ALDH2 was determined by polymerase chain reaction and sequencing. RESULTS: We found that the rate of heavy drinking was significantly lower in the ALDH2 mutation group ((*)1/(*)2 and (*)2/(*)2) than in wild-type group ((*)1/(*)1) (18.6% vs. 38.0%, p = 0.01). Plasma homocysteine (Hcy) levels were significantly different in the two groups (15.45 ± 6.39 vs. 13.14 ± 4.45, p = 0.015). The ALDH2 mutation genotype was negatively correlated with severe intracranial vascular stenosis (OR, 0.34; p = 0.002), even after adjustment for high-density lipoprotein cholesterol, Hcy, and heavy drinking (adjusted OR, 0.44; p = 0.03). CONCLUSION: ALDH2(*)2 could be a protective factor and negative predictor for severe intracranial vascular stenosis in ischemic stroke in Han Chinese.

Intracranial arterial disease in CADASIL patients.

BACKGROUND: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is characterized by the involvement of cerebral small arteries. Although cerebral large artery disease has been reported in CADASIL patients, the prevalence and location of relevant cerebral arterial disease have not been elucidated. In this study, we aim to characterize infarctions associated with cerebral large artery disease in CADASIL patients. METHODS: We retrospectively reviewed 49 consecutive symptomatic patients with genetically confirmed CADASIL, who visited the Asan Medical Center between December 2002 and December 2013. Infarctions located within the territory of a relevant, large cerebral artery were identified with the use of magnetic resonance imaging and magnetic resonance angiography. Patients with or without territorial patterns associated with large artery disease were compared. RESULTS: Out of a total of 49 patients, 23 patients had cerebral infarction. Among these, seven had infarction associated with cerebral large artery disease. The corresponding vascular lesions were located in the intracranial arteries in all seven patients. There were no differences between patients with or without territorial infarction in terms of vascular risk factors, microbleeds, white matter changes, or mutations involving cysteine. A literature review illustrates that symptomatic intracranial diseases are present in CADASIL patients at least in East Asia. CONCLUSION: Infarction in association with intracranial arterial disease may be a manifestation of CADASIL. Further studies are needed to elucidate the pathologic characteristics and to see whether this occurs exclusively in East Asia.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy affecting an African American man: identification of a novel 15-base pair NOTCH3 duplication.

BACKGROUND: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is the best characterized genetic cause of vascular dementia and stroke and has been extensively reported in European and Asian populations. OBJECTIVE: To report the pathological and genetic analysis of CADASIL in an African American man with a 15-base pair NOTCH3 duplication. DESIGN: Case report. SETTING: University hospital. PATIENT: A 78-year-old man with dementia, recurrent strokes, a family history of similar neurological disease, and white matter abnormalities seen on brain magnetic resonance imaging. MAIN OUTCOME MEASURES: Brain pathology and genetic analysis of NOTCH3. RESULTS: The patient's brain showed widespread arteriopathy in large and small arteries. Using electron microscopy, granular osmiophilic material typical of CADASIL was identified abutting the plasma membrane of smooth muscle cells. Brain extracts contained elevated NOTCH3 protein levels. Sequencing of the NOTCH3 gene revealed a novel 15-base pair heterozygous duplication in exon 7, which is predicted to direct expression of a protein that contains 5 extra amino acids, including a cysteine residue. CONCLUSIONS: To our knowledge, this is the first reported pathological and genetic analysis of an African American patient with CADASIL. The mutation in NOTCH3 is the longest duplication within this gene yet reported.

Epidemiology of intracranial stenosis.

Intracranial stenosis is a common etiology for ischemic stroke. Due to limitations of imaging studies, there are limited data on the prevalence of symptomatic and asymptomatic intracranial stenosis. Intracranial stenosis is more prevalent in Asian, Hispanic, and African-American populations. The reported proportion of patients with symptomatic intracranial stenosis among those hospitalized for ischemic cerebral events varies from 1% in non-Hispanic whites to as high as 50% in Asian populations. In population-based studies, the estimated prevalence of symptomatic intracranial disease varies from 1 in 100,000 for whites to 15 in 100,000 in African Americans. A Chinese population-based study reported intracranial stenosis in 7% of the population aged more than 40 years. Autopsy studies have noted intracranial atherosclerotic disease in about 23% of population in the 6th decade and 80% of population in the 9th decade of life. Angiotensin-converting enzyme polymorphisms, plasma endostatin/vascular endothelial growth factor ratio, glutathione S-transferase omega-1 gene polymorphism, and plasma homocysteine levels are non-modifiable risk factors noted to be associated with intracranial stenosis. Hypertension and serum lipid profile are major modifiable risk factors, whereas sickle cell disease is an uncommon risk factor that can be managed to reduce risk. Associations of intracranial atherosclerosis with diabetes mellitus, metabolic syndrome, Alzheimer's disease, aortic plaques, radiotherapy, and meningitis are less well documented.

Methylenetetrahydrofolate reductase gene polymorphism and childhood stroke.

Genotyping for the methylenetetrahydrofolate reductase gene (MTHFR) has been recommended for part of the evaluation for underlying prothrombotic state in childhood stroke; however, studies are inconclusive regarding the role of this gene and also the role of hyperhomocysteinemia, which is the putative mechanism by which MTHFR polymorphism is related to stroke. The prevalence of MTHFR polymorphism in childhood arterial ischemic stroke and cerebral sinovenous thrombosis was compared with that of a reference population, and prevalence of hyperhomocysteinemia was reviewed. In arterial ischemic stroke, the prevalence of at-risk methylenetetrahydrofolate reductase genotypes was 27%, and in cerebral sinovenous thrombosis it was 13%; the population prevalence was 26%. The odds ratio for at-risk genotype in childhood arterial ischemic stroke was 1.06 (95% confidence interval, 0.22-4.0); in cerebral sinovenous thrombosis, it was 0.42 (95% confidence interval, 0.01-3.6). No tested cases had hyperhomocysteinemia. MTHFR polymorphism and hyperhomocysteinemia were not risk factors in childhood arterial ischemic stroke or cerebral sinovenous thrombosis in the Intermountain West region.

Genetic risk factors for arterial ischemic stroke in children: a possible MTHFR and eNOS gene-gene interplay?

In order to investigate the influence of genetic factors in childhood stroke, we compared the distributions of mutations/ polymorphisms affecting hemostasis and/or endothelial function (factor V [FV] Leiden, factor II [FII] G20210A, methylenetetrahydrofolate reductase [MTHFR] C677T, angiotensin-converting enzyme [ACE] insertion/deletion [ID], and endothelial nitric oxide synthase [eNOS] G894T) among children with stroke and controls. A total number of 26 children with arterial ischemic stroke and a control group of 50 healthy children were included in the study. No statistically significant differences in allelic and genotypic distribution were detected in comparisons between groups. However, when combined genotypes were analyzed, statistical significance was observed for the association of MTHFR CT and eNOS TT gene variants. The results of our study suggest that this genotype combination represents a risk factor of 7.2 (P = .017) for arterial ischemic stroke in children.

The archetypal R90C CADASIL-NOTCH3 mutation retains NOTCH3 function in vivo.

Cerebral Autosomal Dominant Arteriopathy with Subcortical infarcts and Leukoencephalopathy (CADASIL) is the most prominent known cause of inherited stroke and vascular dementia in human adult. The disease gene, NOTCH3, encodes a transmembrane receptor primarily expressed in arterial smooth muscle cells (SMC). Pathogenic mutations lead to an odd number of cysteine residues within the NOTCH3 extracellular domain (NOTCH3(ECD)), and are associated with progressive accumulation of NOTCH3(ECD) at the SMC plasma membrane. The murine homolog, Notch3, is dispensable for viability but required post-natally for the elaboration and maintenance of arteries. How CADASIL-associated mutations impact NOTCH3 function remains a fundamental, yet unresolved issue. Particularly, whether NOTCH3(ECD) accumulation may titrate the ligand and inhibit the normal pathway is unknown. Herein, using genetic analyses in the mouse, we assessed the functional significance of an archetypal CADASIL-associated mutation (R90C), in vivo, in brain arteries. We show that transgenic mouse lines expressing either the wild-type human NOTCH3 or the mutant R90C human NOTCH3, at comparable and physiological levels, can rescue the arterial defects of Notch3-/- mice to similar degrees. In vivo assessment of NOTCH3/RBP-Jk activity provides evidence that the mutant NOTCH3 protein exhibits normal level of activity in brain arteries. Remarkably, the mutant NOTCH3 protein remains functional and does not exhibit dominant negative interfering activity, even when NOTCH3(ECD) accumulates. Collectively, these data suggest a model that invokes novel pathogenic roles for the mutant NOTCH3 protein rather than compromised NOTCH3 function as the primary determinant of the CADASIL arteriopathy.

Recurrent thromboembolism in infants and children suffering from symptomatic neonatal arterial stroke: a prospective follow-up study.

BACKGROUND AND PURPOSE: The present study was performed to evaluate the rate of recurrent symptomatic thromboembolism with respect to prothrombotic risk factors and underlying clinical conditions. METHODS: In a series of 215 consecutively enrolled neonates with arterial ischemic stroke (AIS), the factor V G1691A mutation, factor II G20210A variant, methylenetetrahydrofolate reductase (MTHFR) T677T genotype, lipoprotein (Lp) (a), antithrombin, protein C, protein S, and anticardiolipin antibodies (ACA) were investigated. Patient median follow-up was 3.5 years (range, 1 to 8 years). RESULTS: During follow-up, 7 infants and children (3.3%) showed recurrent symptomatic thromboembolism (AIS, n=4; venous sinus thrombosis, n=2; deep vein thrombosis of the leg, n=1). The factor V mutation, factor II variant, elevated Lp(a) >30 mg/dL, protein C deficiency, and protein S or antithrombin deficiency were associated with first stroke onset. In 5 of 7 cases (71.4%), prothrombotic risk factors [MTHFR T677T, elevated Lp(a), hyperhomocysteinemia, protein C deficiency] were involved at the time of recurrence. Furthermore, a second thromboembolic event was triggered additionally by underlying diseases (71%), eg, cardiac malformation and immobilization, diarrhea, mastoiditis, and moyamoya syndrome. CONCLUSIONS: Data shown here give evidence that symptomatic recurrent thromboembolism is not common in children with neonatal AIS. The risk of a second event, however, is increased when underlying diseases occur and prothrombotic risk factors are involved.

Vertebral artery hypoplasia--sex-specific frequencies in 36 parent-offspring pairs.

The major interest in vertebral artery (VA) hypoplasia comes from its possible connection to migraines with aura as well as from the fact that it is one of the risk factors for a stroke. Therefore, the aim of this preliminary study was to investigate the mode of inheritance of VA hypoplasia. Initially, color Doppler of VA was performed in 64 first- and second-degree relatives of 33 probands, and the presence of VA hypoplasia was confirmed according to the already established criteria. Since a higher prevalence of VA hypoplasia (15.6%) in probands'relatives in comparison with 2.34% in the general population of Croatia was indicative of a strong familial predisposition for this condition, an analysis of family data by means of Pearson's chi-square statistics has been performed. In this analysis, the observed sex-specific frequencies of 36 parent-offspring pairs composed only of affected parent and his/her (affected or non-affected) offspring are compared to the frequencies as expected under eight proposed models. For both--autosomal and X-linked monogenetic inheritance--four hypotheses have been chosen, assuming that the individuals having the affected allele (in combination with a healthy one) have 100%, 50%, 40% and 0% chances of developing VA hypoplasia. Out of eight tested models only two--completely dominant and completely recessive X-linked models--were rejected. But, from the six non-rejected models, goodness-of-fit statistics showed that the hypothesis of X-linked inheritance of VA hypoplasia with the "healthy" allele being stronger (60% effect on phenotype)--almost perfectly fit the data (chi2 = 2.0023; df = 7; p = 0.9597). Further research encompassing a more enlarged family sample is needed to confirm the present findings.