Polymorphism of the endoglin gene in patients with intracranial saccular aneurysms

Associations of Reported Genetic Risk Loci with Sporadic Brain Arteriovenous Malformations: Meta-analysis

An arteriovenous malformation (AVM) is an abnormal nidus of blood vessels that is characterized by a direct connection between arteries and veins without intervening in the capillary network. The exact underlying cause of sporadic AVMs is unknown, but many studies have reported genetic associations between genes that contribute to angiogenesis, vasculogenesis, and inflammation. Eleven studies retrieved from Medline Complete, PubMed, and Google Scholar up to February 2022 were included. Heterogeneity was assessed using I² and Q-tests. Publication bias was also assessed for the shortlisted CDKN2B-AS1 rs1333040 (T > C), ACVRL1 rs2071219 (A > G), and rs11169953 (C > T) polymorphisms. The rs1333040 polymorphism showed a lower association with sporadic brain AVM for T versus C in an allelic model (OR = 0.59, 95% confidence interval [CI] = 0.41-0.84). In the recessive model, rs2071219 for AA + AG vs. GG was OR = 0.62, 95% CI = 0.43-0.9. In the recessive model, rs11169953 CC + CT vs. TT was OR = 0.56, 95% CI = 0.33-0.95. In summary, the results of this study support the association between CDKN2B-AS1 and ACVRL1 polymorphisms and sporadic brain arteriovenous malformations. This study summarized the existing information and showed the need for more replication studies on the genetic basis of sporadic AVM. In the future, more genome-wide studies should be conducted to validate and fill existing gaps in knowledge about the mechanisms of sporadic AVM development.

Role of Endoglin Insertion and rs1800956 Polymorphisms in Intracranial Aneurysm Susceptibility: A Meta-Analysis

Endoglin is an essential molecule during angiogenesis, vascular development, and integrity. Till now, many studies have investigated the association between endoglin polymorphisms and intracranial aneurysm (IA) risk, with the results remained inconclusive. Therefore, we performed a meta-analysis to summarize the possible association.We searched PubMed and Embase until June 2015 to identify studies addressing the association between endoglin polymorphisms and IA risk. The summary odds ratios (ORs) and their corresponding 95% confidence interval (CI) were calculated to assess the strength of the association.Eleven studies with a total of 1501 cases and 2012 controls were finally included in this meta-analysis, with 10 studies investigating endoglin 6-bp insertion (6bINS) polymorphism and 4 studies investigating 1800956 polymorphism. No significant association between endoglin 6bINS polymorphism and IA risk was detected in overall estimation (I/I vs wt/I + wt/wt: OR = 1.21, 95% CI = 0.87-1.69) or in the subgroup analysis by ethnicity, control source, or ruptured status. However, we observed an association with borderline significance of 6bINS with IA occurrence (I/I vs wt/I + wt/wt: OR = 1.49, 95% CI = 0.99-2.25, P = 0.058) in studies applying matched controls. Furthermore, we detected a significant association for 6bINS polymorphism of endoglin with increased risk of familial IA (I vs wt, OR = 1.64, 95% CI = 1.10-2.42) but not sporadic IA (I vs wt, OR = 1.09, 95% CI = 0.68-1.45). With regard to rs1800956, our pooled results indicated a significantly decreased IA risk in individuals carrying C allele (C/C vs G/C + G/G: OR = 0.65; 95% CI = 0.45-0.94).This meta-analysis provided no evidence for the association between 6bINS polymorphism with overall IA risk. However, we detected a significant association of 6bINS allele with increased risk of familial IA. Also, we found that rs1800956 was significantly related to IA occurrence. Further, well-designed studies with large sample size are warranted and updated meta-analysis is needed to verify our findings.

Molecular mechanisms of the formation and progression of intracranial aneurysms

Until recently, only a little was understood about molecular mechanisms of the development of an intracranial aneurysm (IA). Recent advancements over the last decade in the field of genetics and molecular biology have provided us a wide variety of evidences supporting the notion that chronic inflammation is closely associated with the pathogenesis of IA development. In the field of genetics, large-scale Genome-wide association studies (GWAS) has identified some IA susceptible loci and genes related to cell cycle and endothelial function. Researches in molecular biology using human samples and animal models have revealed the common pathway of the initiation, progression, and rupture of IAs. IA formation begins with endothelial dysfunction followed by pathological remodeling with degenerative changes of vascular walls. Medical treatments inhibiting inflammatory cascades in IA development are likely to prevent IA progression and rupture. Statins and aspirin are expected to suppress IA progression by their anti-inflammatory effects. Decoy oligodeoxynucleotides (ODNs) inhibiting inflammatory transcription factors such as nuclear factor kappa-B (NF-κB) and Ets-1 are the other promising choice of the prevention of IA development. Further clarification of molecular mechanisms of the formation and progression of IAs will shed light to the pathogenesis of IA development and provide insight into novel diagnostic and therapeutic strategies for IAs.

Angiotensin-converting enzyme insertion/deletion gene polymorphism and risk of intracranial aneurysm in a Chinese population

Objective

The relationship between angiotensin-converting enzyme (ACE) insertion/deletion (I/D) gene polymorphisms and intracranial aneurysm (IA) has been studied in Caucasian and Japanese populations. The present study aimed to investigate this association in a Chinese population.

Methods

Patients with confirmed IA and age- and sex-matched control subjects without evidence of IA were enrolled. ACE I/D gene polymorphisms were analysed using polymerase chain reaction–restriction fragment length polymorphism.

Results

A total of 220 patients with IA and 220 matched controls were enrolled. In the IA group, 64, 106 and 50 patients were of the II, ID and DD genotypes, respectively, compared with 44, 99 and 77 subjects in the control group. The ACE DD genotype and D allele frequencies were significantly lower in the IA group compared with the control group. There were no statistically significant differences in the site, shape, size and Fisher Grade of aneurysms between genotypes in patients with IA.

Conclusion

The ACE DD genotype may be a protective factor for IA in a Chinese population.

Genetic screening for mutations in the chip gene in intracranial aneurysm patients of Chinese Han nationality

We performed a case-control study to investigate whether SNPs of CHIP might affect the development of IA in Chinese Han nationality. We believe we are the first to have screened IA patients for mutations in the CHIP gene to determine the association with these variants. The study group comprised 224 Chinese Han nationality patients with at least one intracranial aneurysm and 238 unrelated healthy Han nationality controls. Genomic DNA was isolated from blood leukocytes. The entire coding regions of CHIP were genotyped by PCR amplification and DNA sequencing. Differences in genotype and allele frequencies between patients and controls were tested by the chi-square method. Genotype and allele frequencies of the SNP rs116166850 was demonstrated to be in Hardy-Weinberg equilibrium. No significant difference in genotype or allele frequencies between case and control groups was detected at the SNP. Our data do not support the hypothesis of a major role for the CHIP gene in IA development in the Chinese Han population.

Interactions of interleukin-12A and interleukin-12B polymorphisms on the risk of intracranial aneurysm

Several lines of evidence indicate that inflammatory processes play pivotal role in the development of intracranial aneurysm (IA). Recently, polymorphisms in the interleukin-12 (IL-12) gene were shown to be associated with immune-mediated inflammatory disease. The aim of this study was to investigate the interactions of IL-12A and IL-12B polymorphisms on the risk of IA in a Chinese population. A total of 422 individuals (including 164 patients with IA and 258 controls) were involved in the study. The polymorphisms (i.e., rs2243115 and rs568408 in IL-12A and rs3212227 in IL-12B) were genotyped by polymerase chain reaction-restriction fragment length polymorphism assay and DNA sequencing. We found an association of the AC/CC genotypes and C allele of IL-12B rs3212227 with an increased risk of IA, compared with the AA genotype and A allele (AC/CC vs. AA: OR = 2.09, 95 % CI: 1.29-3.38; C vs. A: OR = 1.45, 95 % CI: 1.10-1.91). Moreover, a significant gene interaction of IL-12A and IL-12B was evident on the risk of IA, and subjects carrying variant genotypes of IL-12B rs3212227 had an increased risk of IA. In the stratified analysis by gender, the IL-12B rs3212227 AC/CC genotypes had an increased risk of IA compared with the AA genotype in male patients (AC/CC vs. AA: OR = 4.63, 95 % CI: 1.92-11.16). These findings suggest that the IL-12A and IL-12B independently and jointly be involved in the susceptibility to IA.

The interleukin-6-572G/C gene polymorphism and the risk of intracranial aneurysms in a Chinese population

Interleukin-6 (IL-6) is an important proinflammatory cytokine that plays an important role in the pathogenesis of intracranial aneurysms (IAs). The aim of this study was to investigate the association between the IL-6-572G/C polymorphism and the risk of IAs in a Chinese population. The IL-6-572G/C gene polymorphisms in 220 IA cases and 220 controls were analyzed using the polymerase chain reaction-restriction fragment length polymorphism method. The IL-6-572GG (odds ratio [OR]=3.35, 95% confidence intervals [CIs]=1.65, 6.82; p=0.001) and G allele frequencies (OR=1.48, 95% CIs=1.09, 2.00; p=0.01) in the IA group were higher than those in the control group. The C allele frequencies (OR=0.68, 95% CIs=0.50, 0.92; p=0.01) were significantly lower in patients than in controls. When stratified by the site, shape, size, and the Fisher Grade of IAs, no statistically significant result was observed. This study suggested that the IL-6-572GG genotype was associated with a higher risk of IA in a Chinese population.

Variation in telangiectasia predisposing genes is associated with overall radiation toxicity

PURPOSE

In patients receiving radiotherapy for breast cancer where the heart is within the radiation field, cutaneous telangiectasiae could be a marker of potential radiation-induced heart disease. We hypothesized that single nucleotide polymorphisms (SNPs) in genes known to cause heritable telangiectasia-associated disorders could predispose to such late, normal tissue vascular damage.

METHODS AND MATERIALS

The relationship between cutaneous telangiectasia as a late normal tissue radiation injury phenotype in 633 breast cancer patients treated with radiotherapy was examined. Patients were clinically assessed for the presence of cutaneous telangiectasia and genotyped at nine SNPs in three candidate genes. Candidate SNPs were within the endoglin (ENG) and activin A receptor, type II-like 1 (ACVRL1) genes, mutations in which cause hereditary hemorrhagic telangiectasia and the ataxia-telangiectasia mutated (ATM) gene associated with ataxia-telangiectasia.

RESULTS

A total of 121 (19.1%) patients exhibited a degree of cutaneous telangiectasiae on clinical examination. Regression was used to examine the associations between the presence of telangiectasiae in patients who underwent breast-conserving surgery, controlling for the effects of boost and known brassiere size (n=388), and individual geno- or haplotypes. Inheritance of ACVRL1 SNPs marginally contributed to the risk of cutaneous telangiectasiae. Haplotypic analysis revealed a stronger association between inheritance of a ATM haplotype and the presence of cutaneous telangiectasiae, fibrosis and overall toxicity. No significant association was observed between telangiectasiae and the coinheritance of the candidate ENG SNPs.

CONCLUSIONS

Genetic variation in the ATM gene influences reaction to radiotherapy through both vascular damage and increased fibrosis. The predisposing variation in the ATM gene will need to be better defined to optimize it as a predictive marker for assessing radiotherapy late effects.

The genetics of sporadic ruptured and unruptured intracranial aneurysms: a genetic meta-analysis of 8 genes and 13 polymorphisms in approximately 20,000 individuals

Object

Intracranial aneurysms (IAs) are thought to have a multifactorial origin. The authors undertook a comprehensive meta-analysis on all genes investigated using a case-control model in ruptured (subarachnoid hemorrhage) and unruptured aneurysms.

Methods

Electronic databases were searched until and including July 2008 for any candidate gene studied in IA or subarachnoid hemorrhage using a case-control model. The ORs and 95% CIs were determined for each gene-disease association using fixed and random effect models.

Results

Thirty studies of 8 genes and 13 polymorphisms were analyzed among 19,961 individuals (6622 cases and 13,339 controls). Two genes and 3 polymorphisms were associated with IA. The eNOS gene T786C polymorphism (OR 1.24, 95% CI 1.0–1.54; p = 0.05) and IL-6 gene G572C polymorphism (OR 7.08, 95% CI 2.85–17.57; p < 0.0001) both showed a significant association with ruptured/unruptured IA. The IL-6/G174C polymorphism exerted a significant protective effect against IA (OR 0.49, 95% CI 0.25–0.95; p = 0.04). The other candidate genes investigated (ACE, endoglin, APOE, elastin, MMP-3, and SERPINA3) showed no significant associations.

Conclusions

There is a likely genetic basis to sporadic IAs. However, the evidence base is small when compared against other complex disorders.

Sequencing of TGF-beta pathway genes in familial cases of intracranial aneurysm

BACKGROUND AND PURPOSE

Familial aggregation of intracranial aneurysms (IA) strongly suggests a genetic contribution to pathogenesis. However, genetic risk factors have yet to be defined. For families affected by aortic aneurysms, specific gene variants have been identified, many affecting the receptors to transforming growth factor-beta (TGF-beta). In recent work, we found that aortic and intracranial aneurysms may share a common genetic basis in some families. We hypothesized, therefore, that mutations in TGF-beta receptors might also play a role in IA pathogenesis.

METHODS

To identify genetic variants in TGF-beta and its receptors, TGFB1, TGFBR1, TGFBR2, ACVR1, TGFBR3, and ENG were directly sequenced in 44 unrelated patients with familial IA. Novel variants were confirmed by restriction digestion analyses, and allele frequencies were analyzed in cases versus individuals without known intracranial disease. Similarly, allele frequencies of a subset of known SNPs in each gene were also analyzed for association with IA.

RESULTS

No mutations were found in TGFB1, TGFBR1, TGFBR2, or ACVR1. Novel variants identified in ENG (p.A60E) and TGFBR3 (p.W112R) were not detected in at least 892 reference chromosomes. ENG p.A60E showed significant association with familial IA in case-control studies (P=0.0080). No association with IA could be found for any of the known polymorphisms tested.

CONCLUSIONS

Mutations in TGF-beta receptor genes are not a major cause of IA. However, we identified rare variants in ENG and TGFBR3 that may be important for IA pathogenesis in a subset of families.

Molecular Genetics of Human Intracranial Aneurysms

Intracranial aneurysms (IAs) are the dilatations of blood vessels in the brain and pose potential risk of rupture leading to subarachnoid hemorrhage. Although the genetic basis of IAs is poorly understood, it is well-known that genetic factors play an important part in the pathogenesis of IAs. Therefore, the identifying susceptible genetic variants might lead to the understanding of the mechanism of formation and rupture of IAs and might also lead to the development of a pharmacological therapy. To elucidate the molecular pathogenesis of diseases has become a crucial step in the development of new treatment strategies. Although extensive genetic research and its potential implications for future prevention of this often fatal condition are urgently needed, efforts to elucidate the susceptibility loci of IAs are hindered by the issues bewildering the most common and complex genetic disorders, such as low penetrance, late onset, and uncertain modes of inheritance. These efforts are further complicated by the fact that many IA lesions remain asymptomatic or go undiagnosed. In this review, we present and discuss the current status of genetic studies of IAs and we recommend comprehensive genome-wide association studies to identify genetic loci that underlie this complex disease.

Serial analysis of the vascular endothelial transcriptome under static and shear stress conditions

We have utilized serial analysis of gene expression (SAGE) to analyze the response of human coronary artery endothelial cells (HCAECs) to laminar shear stress (LSS). Primary cultures of HCAECs were exposed to 15 dyn/cm(2) LSS for 24 h in a parallel plate flow chamber and compared with identical same passage cells cultured under static conditions. The expression levels of a number of functional categories of genes were reduced by shear stress including those encoding proteins involved in cell proliferation (CDC10, CDC20, CDC23, CCND1, CCNB1), angiogenesis (ANGPTL4, CTGF, CYR61, ENG, EPAS1, EGFR, LGALS3, PGK1, and SPARC), extracellular matrix and cell-matrix adhesion (EFEMP1, LOXL2, P4HB, FBN1, FN1, ITGA5, ITGAE, ITGAV, ILK, LAMR1) and ATP synthesis (ATP5G3, ATP5J2, ATP5L, ATP5D). We also observed an increase in the LSS-responsive expression of genes encoding stress response proteins, including HMOX1, which is significant since HMOX1 may have anti-inflammatory and vasodilatory vascular effects. The autosomal dominant polycystic kidney disease (ADPKD) genes PKD1 and PKD2 were also elevated by LSS. ADPKD is associated with vascular malfunction, including the impairment of vasoreactive processes. To our knowledge, this is the first SAGE-based analysis of the shear stress-responsive endothelial cell transcriptome. These immortal data provide a resource for further analyses of the molecular mechanisms underlying the biological response to LSS and contribute to the expanding collection of publicly available SAGE data.

A polymorphic variant of the endoglin gene is associated with increased risk for intracranial aneurysms in a Korean population

BACKGROUND

Endoglin is a component of the transforming growth factor-beta receptor complex and is predominantly expressed on the cell surface of endothelial cells. It plays an important role in vascular growth and development. There have been conflicting reports on whether a polymorphic variant, in the endoglin gene, is associated with risk for IAs. In this study, we investigated whether polymorphisms of the endoglin gene are associated with the development of cerebral aneurysms in a Korean population.

METHODS

This was a hospital-based, case-control study conducted at the Chonnam University Hospital, Gwangju, Korea. The study population consisted of 342 patients who had been treated for intracranial aneurysm and 253 healthy, hospital-based controls. Two polymorphic loci were amplified by polymerase chain reaction. The well-known in/del in intron 7 of the endoglin gene and the rs1800956 coding nonsynonymous SNP were amplified by PCR and analyzed by MADGE or the pyrosequencing system.

RESULTS

The endoglin insertion polymorphism was not associated with IAs in comparisons between cases and controls (OR, 0.11 [95% CI, 0.79-1.57] vs OR, 0.88 [95% CI, 0.50-1.56]). An association was found with rs1800956 in the heterozygous type (OR, 1.71); however, the association was not evident for the homozygous type. These differences were statistically significant. In addition, the C allele was significantly associated with an increased risk for IAs (OR, 1.73).

CONCLUSION

The rs1800956 (G/C transversion with D366H substitution, National Center for Biotechnology Information SNP database) of endoglin may play an important role in the pathogenesis of IAs in the Korean population. However, the in/del of intron 7 was not associated with an increased risk for IAs, which is consistent with the findings of previous reports.

The interleukin-6 gene -572G>C promoter polymorphism is related to intracranial aneurysms in Chinese Han nationality

There is evidence suggesting that inflammation plays an important role in the pathogenesis of intracranial aneurysms (IAs). Interleukin-6 (IL-6) is an important pro-inflammatory cytokine, and some authors have demonstrated that IL-6 promoter polymorphism -572G>C is associated with IAs in Caucasian population. We performed a case-control study to investigate whether this single nucleotide polymorphism (SNP) might affect the development of IAs in Chinese Han population. The study groups comprised 240 Chinese Han nationality aneurysmal patients and 240 controls. Differences in genotype and allele frequencies between patients and controls were tested by the chi-square method. The results showed that among the Chinese Han subjects, there were significant differences in genotypic distribution and allele frequencies between aneurysmal patients and controls. The GG genotype was significantly more common in patients than in controls (24.5% vs. 3.7%, p<0.001, odds ratio 8.366, 95% CI: 4.040-17.324), and the G allele was much more frequent in patients than in controls (51.7% vs. 20.8%, p<0.001, odds ratio 4.062, 95% CI: 3.058-5.395).

The influence of genetics on intracranial aneurysm formation and rupture: current knowledge and its possible impact on future treatment

The etiology of intracranial aneurysm formation and rupture remains mostly unknown, but lately several studies have increasingly supported the role of genetic factors. In reports so far, genome-wide linkage studies suggest several susceptibility loci that may contain one or more predisposing genes. Depending on the examined ethnic population, several different non-matching chromosomal regions have been found. Studies of several candidate genes report association with intracranial aneurysms. To date, no single gene has been identified as responsible for intracranial aneurysm formation or rupture. In addition to the well-published environmental factors, such as alcohol intake, hypertension and smoking, only the recent progress in molecular genetics enables us to investigate the possible genetic determinants of this disease. Although a familial predisposition is the strongest risk factor for the development of intracranial aneurysms, the mode of Mendelian inheritance is uncertain in most families. Therefore, multiple genetic susceptibilities in conjunction with the environmental factors are considered to act together in the disease's etiology. Accordingly, researchers performed linkage studies and case-control association studies for the genetic analysis and have identified several genes to be susceptible to intracranial aneurysms. The identification of susceptible genes may lead to the understanding of the mechanism of formation and rupture and possibly lead to the development of a pharmacological therapy. Furthermore, should it be possible to identify a genetic marker associated with an increased risk of formation and rupture of an intracranial aneurysm, the necessity for screening and urgency of treatment could be determined more easily. In this review we summarize the current knowledge of intracranial aneurysm genetics and also discuss the method to detect the causalities. In view of the recent advances made in this field, we also give an outlook on possible future genetically engineered therapies, whose development are well underway.

TUMOR NECROSIS FACTOR-α GENE AND CEREBRAL ANEURYSMS

OBJECTIVE

The pathogenesis of intracranial aneurysms is still uncertain. In addition to atherosclerosis, immunological factors may play a role in the disease. Recent studies have suggested that tumor necrosis factor-alpha (TNF-alpha), one of the main proinflammatory cytokines, may play a key role in the formation and rupture of cerebral aneurysms. The purpose of this study is to evaluate the association of a functionally active polymorphism (-308 G<A) in the TNF-alpha gene with the risk and the clinical features of aneurysmal subarachnoid hemorrhage.

METHODS

A total of 171 consecutive aneurysmal subarachnoid hemorrhage patients and 144 healthy controls were involved in the study. Computed tomographic scan findings were assessed by Fisher grade; clinical neurological assessment was performed using the Hunt and Hess grading system. Patients and controls were genotyped for the-308 biallelic (G<A) polymorphism of the TNF-alpha gene.

RESULTS

The TNF-alpha G allele was significantly more frequent in patients than in controls (chi2 = 5.59; P = 0.0181) and homozygosity for the G allele, compared with remaining genotypes, was associated with a significantly increased risk of aneurysmal subarachnoid hemorrhage (odds ratio = 2.20; 95% confidence interval = 1.29<odds ratio<3.75). Allelic and genotypic frequencies of the examined polymorphism were not significantly different in disease subgroups. The different TNF-alpha genotypes do not seem to significantly modify the main clinical features of the disease.

CONCLUSION

Our data suggests that the TNF-alpha gene or a linked locus significantly modulates the risk for aneurysmal subarachnoid hemorrhage. Additional studies in different populations are warranted to confirm our findings.

Systematic screening of lysyl oxidase-like (LOXL) family genes demonstrates that LOXL2 is a susceptibility gene to intracranial aneurysms

Four lysyl oxidase family genes (LOXL1, LOXL2, LOXL3, and LOXL4), which catalyze cross-linking of collagen and elastin, were considered to be functional candidates for intracranial aneurysms (IA) and were extensively screened for genetic susceptibility in Japanese IA patients. Total RNA was isolated from four paired ruptured IA and superficial temporal artery (STA) tissue and examined by real-time RT-PCR. The expression of LOXL2 in the paired IA and STA tissues was elevated in the IA tissue. A total of 55 single nucleotide polymorphisms (SNPs) of LOXL1-4 were genotyped for an allelic association study in 402 Japanese IA patients and 462 Japanese non-IA controls. Allelic associations were evaluated with the chi-square test and the permutation test especially designed for adjustment of multiple testing. SNPs of LOXL1 and LOXL4 were not significantly associated with IA, while several SNPs of LOXL2 and LOXL3 showed nominally significant associations in IA patients. We detected an empirically significant association with one SNP of LOXL2 in familial IA patients after adjustment for multiple testing [chi(2) = 10.23, empirical P = 0.023, OR (95% CI) = 1.49 (1.17, 1.90)]. Furthermore, multilocus interaction was evaluated by multifactor dimensionality reduction analysis. We found that the SNPs of LOXL2 have an interactive effect with elastin (ELN) and LIM kinase 1 (LIMK1) that have been previously found to be associated with IA. In conclusion, one SNP of LOXL2 showed a significant association with IA individually, and we also detected a gene-gene interaction of LOXL2 with ELN/LIMK1, which may play an important role in susceptibility to IA.

Genetics Of Intracranial Aneurysms

Despite advances in the treatment of intracranial aneurysms (IA) in recent years, the overall outcome of patients with aneurysmal subarachnoid hemorrhage has shown only modest improvement. Given this poor prognosis, diagnosis of IA before rupture is of paramount importance. Currently, there are no reliable methods other than screening imaging studies of high-risk individuals to diagnose asymptomatic patients. Multiple levels of evidence suggest that environmental factors acting in concert with genetic susceptibilities lead to the formation, growth, and rupture of aneurysms in these patients. Epidemiological studies have already identified aneurysm-specific risk factors such as size and location, as well as patient-specific risk factors, such as age, sex, and presence of medical comorbidities, such as hypertension. In addition, exposure to certain environmental factors such as smoking have been shown to be important in the formation of IA. Furthermore, substantial evidence proves that certain loci contribute genetically to IA pathogenesis. Genome-wide linkage studies using relative pairs or rare families that are affected with the Mendelian forms of IA have already shown genetic heterogeneity of IA, suggesting that multiple genes, alone or in combination, are important in the disease pathophysiology. The linkage results, along with association studies, will ultimately lead to the identification of IA susceptibility genes. Identification of the genes important in IA pathogenesis will not only provide novel insights into the primary determinants of IA, but will also result in new opportunities for early diagnosis in the preclinical setting. Ultimately, novel therapeutic strategies based on biology will be developed, which will target these newly elucidated genetic susceptibilities.

A study on the relationship between HLA-DR, DQ antigen, and intracranial aneurysm in the Han nationality

BACKGROUND

To investigate the relationship between HLA-DR, DQ antigen, and intracranial aneurysm in the Han nationality.

METHODS

We compared the occurrence of HLA-DR and HLA-DQ antigens in patients with intracranial saccular aneurysm and in the control group by PCR and agarose gel electrophoresis.

RESULTS

No statistically significant correlation between HLA-DR, HLA-DQ antigen frequency, and the pathogenesis and clinical characteristics of intracranial aneurysm has been found.

CONCLUSIONS

We have not found any relationship between HLA-DR and HLA-DQ antigen frequency, haplotype frequency, and pathogenesis and clinical characteristics of intracranial aneurysm, but the patients who presented with HLA-DR53, DR52, DQ7(3), and DQ5(1) seem to be more likely to bear multiple intracranial aneurysms.

Association of a polymorphism of the ACVRL1 gene with sporadic arteriovenous malformations of the central nervous system

OBJECT

Important central nervous system (CNS) manifestations in patients with hereditary hemorrhagic telangiectasia (HHT) include arteriovenous malformations (AVMs) and dural arteriovenous fistulas (DAVFs). Hereditary hemorrhagic telangiectasia is caused by germline mutations of two genes: ENG (HHT Type 1) and ACVRL1 (HHT Type 2). The ENG gene variations have been associated with the formation of intracranial aneurysms. The authors studied whether sequence variations in ACVRL1 or ENG are associated with the development of clinically sporadic arteriovenous dysplasias and aneurysms of the CNS.

METHODS

The coding sequence (in 44 patients with AVMs and 27 with aneurysms) and the 5' end and the polyA site (in 53 patients with AVMs) of the ACVRL1 gene were analyzed for sequence variations using direct sequencing and single-strand conformational polymorphism analysis. One ENG and three ACVRL1 gene polymorphisms were genotyped using restriction enzyme-based analysis in 101 patients with sporadic AVMs and DAVFs of the CNS, 79 patients treated for intracranial aneurysms, and 202 control volunteers. The authors identified a statistically significant association between the IVS3 -35A/T polymorphism in intron 3 of the ACVRL1 gene and the development of AVMs and DAVFs (p = 0.004; odds ratio [OR] 1.73; 95% confidence interval [CI] 1.19-2.51; after adjustments for age and sex), but not aneurysms (crude OR 0.82; 95% CI 0.55-1.18).

CONCLUSIONS

The results of this study link ACVRL1 (HHT Type 2 gene) to the formation of the clinically sporadic variants of vascular malformations of the CNS most commonly seen in patients with HHT, that is, AVMs and DAVFs.

The genetics of intracranial aneurysms

The rupture of an intracranial aneurysm (IA) leads to a subarachnoid hemorrhage, a sudden onset disease that can lead to severe disability and death. Several risk factors such as smoking, hypertension and excessive alcohol intake are associated with subarachnoid hemorrhage. IAs, ruptured or unruptured, can be treated either surgically via a craniotomy (through an opening in the skull) or endovascularly by placing coils through a catheter in the femoral artery. Even though the etiology of IA formation is mostly unknown, several studies support a certain role of genetic factors. In reports so far, genome-wide linkage studies suggest several susceptibility loci that may contain one or more predisposing genes. Studies of several candidate genes report association with IAs. To date, no single gene has been identified as responsible for IA formation or rupture. The identification of susceptible genes may lead to the understanding of the mechanism of formation and rupture and possibly lead to the development of a pharmacological therapy.

A haplotype spanning two genes, ELN and LIMK1, decreases their transcripts and confers susceptibility to intracranial aneurysms

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.

A DNA Sequence Polymorphism in the Endoglin Gene Is Not Associated with Intracranial Aneurysm or Aneurysmal Subarachnoid Hemorrhage

BACKGROUND AND PURPOSE

Endoglin is a member of the transforming growth factor beta family of proteins and plays a central role in vascular growth and development. There have been conflicting reports that polymorphic variation in the endoglin gene is a risk factor for intracranial aneurysms (IAs). We sought to further investigate the intron 7 5'-TCCCCC-3' endoglin polymorphism as a risk factor for IA and subarachnoid hemorrhage (SAH) in a population of patients from western Pennsylvania.

METHODS

We genotyped 98 IA patients and 191 unaffected controls for a length polymorphism in intron 7 using PCR-based methods.

RESULTS

The endoglin polymorphism was not associated with IA or the incidence of aneurysm rupture and SAH. No association was found when data were stratified by smoking and hypertension.

CONCLUSION

These data, from a population recruited in western Pennsylvania, support recent findings in Japanese and German populations that, despite earlier observation to the contrary, endoglin is not associated with IA. Furthermore, our study extends previous observations by demonstrating no association between endoglin and either IA or SAH regardless of whether data were stratified for modifiable risk factors such as smoking and hypertension.

Endoglin gene insertion polymorphism not associated with aneurysmal subarachnoid hemorrhage

Object. Data concerning an association between the ENG gene intronic insertion polymorphism and intracranial aneurysms (IAs) remain inconsistent. In this study the authors investigated whether this polymorphism is associated with a subarachnoid hemorrhage (SAH) caused by a ruptured IA in a Polish population.

Methods. One hundred nineteen patients with aneurysmal SAH and 119 sex-matched healthy volunteers were studied. The insertion ENG gene polymorphism in intron 7 was identified using polymerase chain reaction—single-strand chain polymorphism method.

The distribution of the insertion allele did not differ between the SAH (13%) and control (16%) cases (p = 0.36). The homozygous insertion/insertion genotype frequencies in these cases were 3.4 and 0.8%, respectively (p = 0.18).

Conclusions. The authors failed to find an association between the intronic insertion polymorphism of the ENG gene and aneurysmal SAH in a Polish population.

Syndrome d'Angelman et anévrisme intracrânien : association fortuite ou prédisposition génétique commune ?

Although the pathogenesis of cerebral aneurysms has been studied intensively, it is yet poorly understood. However, a genetic predisposition to this pathology has been often suspected. We describe a patient with both intracranial aneurysm and Angelman syndrome. Angelman syndrome is characterized by severe mental retardation, inappropriate laughter, absent speech, dysmorphic facial features and seizures. It is due to genetic abnormalities of chromosome 15. Cerebral aneurysms are sometimes associated with inherited diseases like autosomal dominant polycystic kidney disease. Moreover several candidate genes have been analysed, to search for genetic variants which might be associated with the occurrence of intracranial aneurysms. Our question is: is the association described in our observation fortuitous or do these diseases share a same genetic predisposition? Our observation also supports the hypothesis of a genetic participation in the genesis of cerebral aneurysms.

Mapping a Mendelian form of intracranial aneurysm to 1p34.3-p36.13

The identification of pathways that underlie common disease has been greatly impacted by the study of rare families that segregate single genes with large effect. Intracranial aneurysm is a common neurological problem; the rupture of these aneurysms constitutes a frequently catastrophic neurologic event. The pathogenesis of these aneurysms is largely unknown, although genetic and environmental factors are believed to play a role. Previous genomewide studies in affected relative pairs have suggested linkage to several loci, but underlying genes have not been identified. We have identified a large kindred that segregates nonsyndromic intracranial aneurysm as a dominant trait with high penetrance. Genomewide analysis of linkage was performed using a two-stage approach: an analysis of ~10,000 single-nucleotide polymorphisms in the 6 living affected subjects, followed by the genotyping of simple tandem repeats across resulting candidate intervals in all 23 kindred members. Analysis revealed significant linkage to a single locus, with a LOD score of 4.2 at 1p34.3-p36.13 under a dominant model with high penetrance. These findings identify a Mendelian form of intracranial aneurysm and map the location of the underlying disease locus.

Are There Genetic Influences on Sporadic Brain Arteriovenous Malformations?

The genesis of brain arteriovenous malformations remains enigmatic. We reviewed some pathways involving inflammatory and angiogenic signals that are amenable to the study of genetic single-nucleotide polymorphisms associated with the sporadic disease. Such study can yield insights into arteriovenous malformation pathogenesis and suggest possible fruitful approaches to developing medical therapy. Moreover, single-nucleotide polymorphisms identification would provide targets for risk stratification for planning clinical trials and eventually guiding management.

Gene Therapy and Endovascular Treatment of Intracranial Aneurysms

Background— Endovascular treatment of intracranial aneurysms is safe and effective but too often is followed by recurrences. Gene therapy may improve healing after embolization, and endovascular approaches may offer future in situ delivery systems designed to prevent aneurysm rupture.

Summary of Review— Advances in coil technology have focused on coating strategies designed to modify the biological reaction to the embolic agent. Gene therapy in cardiovascular applications is limited by low efficiency and transient gene expression. Current advances include the potential use of circulating progenitor cells for ex vivo genetic manipulations followed by in vivo delivery. Direct gene transfer may also be enhanced in situ by coils carrying antibody-tethered adenovirus or through the use of cell-specific or radiation-inducible promoters. Candidate genes that may be of value in promoting healing after endovascular treatment include growth factors and metalloproteinase inhibitors. A better understanding of the biology of aneurysm is necessary to conceive strategies designed to control the development of these lesions before their rupture.

Conclusions— Many technical difficulties remain to be solved, but the combination of gene therapy and endovascular techniques offers multiple therapeutic possibilities in the future control of intracranial aneurysms.

Association of positional and functional candidate genes FGF1, FBN2, and LOX on 5q31 with intracranial aneurysm

We previously performed a genome-wide linkage study of intracranial aneurysm (IA) and found positive evidence of linkage at chromosomes 5q22-31, 7q11, and 14q22. In the present study, we focus on 5q31, where three candidate genes, fibroblast growth factor 1 (FGF1), fibrillin 2 (FBN2), and lysyl oxidase gene ( LOX) lie, and evaluate associations with IA. Genomic DNAs were obtained from 172 IA patients and 192 controls. Association analysis was performed with ten, five, and four single-nucleotide polymorphisms (SNPs) identified in FGF1, FBN2, and LOX, respectively. A difference in allelic frequency was observed for only the SNP at intron 4 in FGF1 (chi(2)=4.44, df=1, P=0.035). Although a haplotype association was observed with the combination of ten SNPs in FGF1 (chi(2)=16.04, df=1, P=0.00006), significant haplotype associations were not observed when haplotypes were constructed with the three, two, and four SNPs in FGF1 according to the linkage disequilibrium structure. No associations of FBN2 and LOX with IA were detected in the present study.

Tissue inhibitor of metalloproteinases-1, -2, and -3 polymorphisms in a white population with intracranial aneurysms

BACKGROUND AND PURPOSE

Remodeling of the extracellular matrix seems to be a crucial event in the pathogenesis of cerebral aneurysms. Matrix metalloproteinases are the most important degrading enzymes in the extracellular matrix. Their activity is controlled predominantly by tissue inhibitors of metalloproteinases (TIMPs). To investigate the possible impact of genetic variants within the genes encoding TIMP-1, -2, and -3, we conducted this case-control study.

METHODS

A study sample was analyzed that comprised 44 patients with intracranial aneurysms and 44, 41, and 40 controls for the analysis of TIMP-1, -2, and -3, respectively. Differences in genotype and allele frequencies of identified polymorphisms were determined. The entire coding regions and parts of the promoter sequences of the TIMP-1, -2, and -3 genes were with using the automated laser fluorescence technique.

RESULTS

Nine polymorphisms were identified, 3 located in TIMP-1 (-19C>T, 261C>T, 372T>C), 4 in TIMP-2 (-621C>T, -596A>C, -261G>A, 303G>A), and 2 in TIMP-3 (249T>C, 261C>T), whereas -621C>T, -596A>C, and -261G>A of the TIMP-2 gene are newly identified polymorphisms. We detected no deviation from Hardy-Weinberg equilibrium in any of the groups. The C allele of the 372T>C polymorphism was more frequently found in female than in male controls (exact nominal P=0.0012). However, this finding could not be validated by analysis of a second sample of 113 controls (exact nominal P=1.0000). There were no differences in genotype and allele frequencies between any of the other groups.

CONCLUSIONS

Our analysis of the entire coding region of 3 TIMPs, which are the main inhibitors of metalloproteinase activity in the extracellular matrix, failed to show an association between genetic polymorphisms and an intracranial aneurysm. These data do not support the hypothesis that genetic variants within these genes have an impact on aneurysm development in the white population.

Endoglin is not a major susceptibility gene for intracranial aneurysm among Japanese

BACKGROUND AND PURPOSE

A 6-base insertion (6bINS) polymorphism in intron 7 of the endoglin gene (ENG), which codes for a component of the transforming growth factor-beta receptor complex, was reported to be associated with intracranial aneurysm (IA) in a Japanese population. A recent report using a white population could not replicate the association. We tested for this association with high statistical power in our independent Japanese subjects and evaluated the linkage between markers on chromosome 9, which contains ENG, and IA.

METHODS

The sample for the linkage study comprised 179 individuals with IA in 85 nuclear families, with 104 possible affected sibpairs. For the association study of the 6bINS polymorphism and 4 single nucleotide polymorphisms (SNPs) in ENG, 172 Japanese patients with IA and 192 control subjects were examined.

RESULTS

There was no evidence of linkage in the vicinity of ENG by analysis of affected sibpairs. The allele frequency of the 6bINS polymorphism was 104 of 344 (30.2%) in the total IA group and 122 of 382 (31.9%) in the control group. The statistical difference in allele frequency between the 2 groups was not significant (chi2=0.245, df=1, P=0.620). The power of the present association study was 98.3% at a significance level of 0.05 on the basis of the allele frequencies in the previous study. In addition, no associations between the 4 SNPs in ENG and IA were detected.

CONCLUSIONS

We provide evidence that there is no association between the 6bINS polymorphism or 4 SNPs in ENG and IA and that there is no linkage between the ENG locus and IA, indicating that ENG is not a major susceptibility gene for IA in Japanese.

Absence of linkage of familial intracranial aneurysms to 7q11 in highly aggregated Japanese families

BACKGROUND AND PURPOSE

We sought to test the linkage of familial intracranial aneurysms (FIAs) to the ELN (elastin) locus in chromosome 7q11 reported previously.

METHODS

Intracranial aneurysm (IA) probands were searched from patient records or neurosurgeons' recalls in collaborating hospitals. Members of the participating probands' families who had unknown affection status were screened by MR angiography and diagnosed by digital subtraction angiography. Inclusion criteria of families for genetic analyses were as follows: at least 3 alive affected members or 2 alive affected members with at least 1 unaffected member (>or=60 years). Linkage to the ELN locus was tested with the use of GENEHUNTER by parametric and nonparametric methods. To exclude false-negatives in the linkage analysis, the lowest 5% limits of logarithms of the odds (LOD) and nonparametric LOD (NPL) scores for individual families and for the total set of families were simulated on assumption that the ELN locus is linked to FIAs.

RESULTS

Questionnaires were sent to 885 patients, and 563 responded. Seventy-nine probands were positive for family history. One hundred thirty-four family members of unknown affection status were screened. A total of 14 families with 64 members met the criteria. Linkage to the ELN locus was discarded in 11 families and was inconclusive for 3 families. The total LOD and total NPL scores for 14 families were -8.04 and -0.643, respectively. Our conclusion did not change even when the values of penetrance were changed or only affected members were analyzed.

CONCLUSIONS

The majority of aggregated IA Japanese families may not have a genetic linkage to chromosome 7q11.

The phenotype of normal tension glaucoma patients with and without OPA1 polymorphisms

AIM

Polymorphisms in OPA1, the gene responsible for autosomal dominant optic atrophy, were recently found to be strongly associated with normal tension glaucoma (NTG). The aim of this study was to determine whether OPA1 polymorphisms affect the phenotype of NTG patients.

METHODS

A retrospective analysis was performed of 108 well characterised NTG patients who had been genotyped for OPA1 variations, and who had previously undergone automated perimetry and Heidelberg retina tomography (HRT). 25 NTG patients had the at-risk OPA1 genotype (IVS 8 +4 C/T; +32 T/C) and 83 NTG patients did not. Differences between groups were sought in a wide range of structural, psychophysical, and demographic factors. These included sex, age at diagnosis, family history of glaucoma, history of ischaemic risk factors and vasospasm, laterality of glaucoma, presenting and highest diurnal intraocular pressure (IOP), initial cup-disc (CD) ratio, baseline visual field global indices, and optic disc parameters as measured by HRT. For a subgroup of patients with at least 5 years of follow up and 10 visual field tests, pointwise linear regression analysis (PROGRESSOR for Windows software) was applied to the visual field series.

RESULTS

There was no significant difference in the two groups with respect to sex, age at diagnosis, family history of glaucoma, history of ischaemic risk factors and vasospasm, or laterality of glaucoma. The comparison of IOP, CD ratio and visual field global indices, MD and CPSD in the two groups showed no significant difference. There were no differences in the mean values for any of the HRT parameters analysed. For the subgroup of patients with at least 5 years of follow up, there was also no significant difference in the number of patients with progressing locations, the mean number of progressing locations per subject, the mean slope of the progressing locations or the mean slope for whole visual field.

CONCLUSIONS

The absence of phenotypic differences in normal tension glaucoma patients with and without the OPA1 polymorphisms IVS 8 +4 C/T; +32 T/C suggest that these OPA1 polymorphisms do not underlie any major phenotypic diversity in these patients.

Ultrastructural connective tissue aberrations in patients with intracranial aneurysms

BACKGROUND AND PURPOSE

An unknown connective tissue defect might predispose for the development and rupture of intracranial aneurysms in some patients. This study of connective tissue samples of a series of patients with intracranial aneurysms investigates the morphology of the extracellular matrix with methods that are currently used in the routine diagnosis of inherited connective tissue disorders.

METHODS

Skin biopsies from 21 patients with intracranial aneurysms, many with multiple aneurysms, were studied by electron microscopy. None of the patients included in this study showed clinical signs of a known connective tissue disorder.

RESULTS

In 7 patients (33%), we observed repetitive aberrations in the morphology of collagen fibrils and elastic fibers of the reticular dermis. The observed ultrastructural findings were somewhat similar to those typically observed in patients with Ehlers-Danlos syndrome (EDS) and in a subgroup of patients with spontaneous cervical artery dissections. The patterns of abnormalities fell into 2 classes: 4 patients displayed abnormalities that resembled those found in patients with EDS type III, and the electron microscopic findings in the skin biopsies from 3 patients resembled those of EDS type IV patients. The sequence of the COL3A1 gene from the patients with EDS type IV-like alterations of the connective tissue morphology was analyzed. No mutation was detected.

CONCLUSIONS

Connective tissue alterations were found in skin biopsies from a minority of patients with intracranial aneurysms. Electron microscopic investigation of skin biopsies from patients and their relatives might become valuable for clinical diagnostics, identification of persons at risk, and basic studies of the pathogenesis of this vascular disease.

Genetics of primary intracerebral hemorrhage

Genetic studies of primary intracerebral hemorrhage (PICH) have begun to yield important biologic insights into the pathogenesis of this disorder. This review of candidate genes for PICH emphasizes the value of focusing on individual pathogenic phenotypes. One type of PICH in particular, cerebral amyloid angiopathy, is known to have specific genetic factors regulating both its familial and sporadic forms. Another promising research method is to focus on pathways involved in hemostasis that may be etiologically relevant to all types of PICH. Genetic studies will improve our understanding of the biology of PICH, and may eventually be incorporated into clinical decision making regarding anticoagulation.

Genetics of intracranial aneurysm

Subarachnoid hemorrhage (SAH) secondary to ruptured saccular intracranial aneurysm (IA) is a complex trait, with both genetic and environmental risk factors playing an important part. The 30-day mortality rate of patients with SAH is 40% to 44%, with many survivors suffering from major disability. Because most of the mortality after SAH is caused by rapid and massive brain injury from the initial bleeding, primary prevention of aneurysm formation and rupture is of paramount importance. This article reviews the evidence supporting a genetic predisposition to SAH from saccular IA, the conditions commonly associated with saccular IA, and the search for genetic risk factors.