Rupture of intracranial aneurysms (IAs) causes subarachnoid hemorrhage, a devastating condition with high morbidity and mortality. Angiographic and autopsy studies show that IA is a common disorder, with a prevalence of 3%-6%. Although IA has a substantial genetic component, little attention has been given to the genetic determinants. We report here a genomewide linkage study of IA in 104 Japanese affected sib pairs in which positive evidence of linkage on chromosomes 5q22-31 (maximum LOD score [MLS] 2.24), 7q11 (MLS 3.22), and 14q22 (MLS 2.31) were found. The best evidence of linkage is detected at D7S2472, in the vicinity of the elastin gene (ELN), a candidate gene for IA. Fourteen distinct single-nucleotide polymorphisms (SNPs) were identified in ELN, and no obvious allelic association between IA and each SNP was observed. The haplotype between the intron-20/intron-23 polymorphism of ELN is strongly associated with IA (P=3.81x10-6), and homozygous patients are at high risk (P=.002), with an odds ratio of 4.39. These findings suggest that a genetic locus for IA lies within or close to the ELN locus on chromosome 7.

Background and Purpose— The rupture of intracranial aneurysm (IA) causes subarachnoid hemorrhage associated with high morbidity and mortality. We compared gene expression profiles in aneurysmal domes between unruptured IAs and ruptured IAs (RIAs) to elucidate biological mechanisms predisposing to the rupture of IA. Methods— We determined gene expression levels of 8 RIAs, 5 unruptured IAs, and 10 superficial temporal arteries with the Agilent microarrays. To explore biological heterogeneity of IAs, we classified the samples into subgroups showing similar gene expression patterns, using clustering methods. Results— The clustering analysis identified 4 groups: superficial temporal arteries and unruptured IAs were aggregated into their own clusters, whereas RIAs segregated into 2 distinct subgroups (early and late RIAs). Comparing gene expression levels between early RIAs and unruptured IAs, we identified 430 upregulated and 617 downregulated genes in early RIAs. The upregulated genes were associated with inflammatory and immune responses and phagocytosis including S100/calgranulin genes ( S100A8 , S100A9 , and S100A12 ). The downregulated genes suggest mechanical weakness of aneurysm walls. The expressions of Krüppel-like family of transcription factors ( KLF2 , KLF12 , and KLF15 ), which were anti-inflammatory regulators, and CDKN2A , which was located on chromosome 9p21 that was the most consistently replicated locus in genome-wide association studies of IA, were also downregulated. Conclusions— We demonstrate that gene expression patterns of RIAs were different according to the age of patients. The results suggest that macrophage-mediated inflammation is a key biological pathway for IA rupture. The identified genes can be good candidates for molecular markers of rupture-prone IAs and therapeutic targets.

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Background and Purpose-The collagen ␣2(I) gene (COL1A2) on chromosome 7q22.1, a positional and functional candidate for intracranial aneurysm (IA), was extensively screened for susceptibility in Japanese IA patients. Methods-Twenty-one single nucleotide polymorphisms (SNPs) of COL1A2 were genotyped in genomic DNA from 260 IA patients (including 115 familial cases) (mean age, 59.9 years) and 293 controls (mean age, 61.6 years). Differences in allelic and genotypic frequencies between the patients and controls were evaluated with the 2 test. Circular dichroism spectrometry was monitored with collagen-related peptides that mimic triple-helical models of type I collagen with Ala-459 and Pro-459 to estimate the conformation and stability of alterations. Results-Significant genotypic association in the dominant model was observed between an exonic SNP of COL1A2 and familial IA patients ( 2 ϭ11.08; dfϭ1; Pϭ0.00087; odds ratioϭ3.19; 95% CI, 2.22 to 6.50). This SNP induces Ala to Pro substitution at amino acid 459, located on a triple-helical domain. Circular dichroism spectra showed that the Pro-459 peptide had a higher thermal stability than the Ala-459 peptide. Conclusions-The variant of COL1A2 could be a genetic risk factor for IA patients with family history.

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BackgroundA founder variant of RNF213, p.R4810K (c.14429G>A, rs112735431), was recently identified as a major genetic risk factor for moyamoya disease (MMD) in Japan. Although the association of p.R4810K was reported to be highly significant and reproducible, the disease susceptibility of other RNF213 variants remains largely unknown. In the present study, we systematically evaluated the coding variants detected in Japanese patients and controls for associations with MMD.Methods and ResultsTo detect variants of RNF213, all coding exons were sequenced in 27 Japanese MMD patients without p.R4810K. We also validated all previously reported variants in our case–control samples and tested for associations in combination with previous Japanese study cohorts, including the 1000 Genomes Project data set, as population-based controls. Forty-six missense variants other than p.R4810K were identified among 370 combined patients and 279 combined controls in Japan. Sixteen of 46 variants were polymorphisms with minor allele frequency >1%, and, after conditioning on the p.R4810K genotype, were not associated with MMD. We conducted a variable threshold test using Combined Annotation-Dependent Depletion on the remaining 30 rare variants (minor allele frequency <1%), and the results showed that the frequency of potentially functional variants was significantly higher in patients than in controls (permutation, minimum P=0.045).ConclusionsNot only p.4810K but also other functional missense variants of RNF213 conferred susceptibility to MMD. Our analysis also revealed that ≈20% of Japanese MMD patients did not harbor susceptibility variants of RNF213, indicating the presence of other susceptibility genes for MMD.

The rupture of an intracranial aneurysm (IA) results in subarachnoid hemorrhage, a catastrophic neurological condition with high morbidity and mortality. Following-up on our previous genome-wide linkage study in Japanese population, we extensively analyzed a 4.6 Mb linkage region around D7S2472 on 7q11 by genotyping 168 single nucleotide polymorphisms (SNPs). SNP association and window scan haplotype-based association studies revealed a susceptibility locus for IA on a single LD block covering the 3'-untranslated region (3'-UTR) of ELN and the entire region of LIMK1. An association study with 404 IA patients and 458 non-IA controls revealed that the ELN 3'-UTR G(+659)C SNP has the strongest association to IA (P=0.000002) and constitutes a tag-SNP for an at-risk haplotype, which contains two functional SNPs, the ELN 3'-UTR (+502) A insertion and the LIMK1 promoter C(-187)T SNP. These allelic and haplotype-based associations were confirmed in a Korean population. Ex vivo and in vitro analyses demonstrate that the functional impact of both SNPs is the decrease of transcript levels, either through accelerated ELN mRNA degradation or through decreased LIMK1 promoter activity. Elastin and LIMK1 protein are involved in the same actin depolymerization signaling pathway; therefore, these lines of evidence suggest a combined effect of the SNPs in the at-risk haplotype possibly by weakening the vascular wall and promoting the development of IA.

Background and Purpose-Maintenance of an adequate intravascular volume is important in the management of patients with subarachnoid hemorrhage (SAH). The purpose of this study was to investigate the circulating blood volume (CBV) after SAH with the use of indocyanine green pulse spectrophotometry. Methods-CBV and plasma hormones related to stress and fluid regulation were measured 4 times: day 2 to 3, day 4 to 5, day 7 to 8, and day 14 in 50 consecutive patients with SAH surgically treated within 48 hours. Results-The mean value of CBV was 64 mL/kg on day 2 to 3, which gradually increased to 69 mL/kg on day 4 to 5, 71 mL/kg on day 7 to 8, and 70 mL/kg on day 14 (Pϭ0.005) (control, 72 mL/kg). The clinical grades and plasma corticotropin levels were higher in patients with Ͻ60 mL/kg of CBV on day 2 to 3 (PϽ0.05 for both). There were no significant differences in other physiological and laboratory parameters such as time for surgery, estimated blood loss, levels of plasma noradrenaline, brain natriuretic peptide, serum sodium, and hematocrit. When CBV was decreased Ͼ10% of the former level, there were decreases in hematocrit (PϽ0.05), serum sodium (PϽ0.01), and serum albumin (PϽ0.05) and an increase in urinary sodium (PϽ0.05). Conclusions-A significant reduction of CBV, especially in patients with poor clinical grades, was noted after SAH and early surgery, which could not be detected by routine examinations. Anemia, central salt wasting, and hypoalbuminemia may be related to a decrease in CBV from the former level. Indocyanine green pulse spectrophotometry may be a powerful tool for the management of patients with SAH.