Tomoko Takahashi

Genome-wide association study to identify genetic variants present in Japanese patients harboring intracranial aneurysms

An intracranial aneurysm (IA), which results in a subarachnoid hemorrhage with a high mortality on rupture, is a major public health concern. To identify genetic susceptibility loci for IA, we carried out a multistage association study using genome-wide single nucleotide polymorphisms (SNPs) in Japanese case–control subjects. In this study, we assessed evidence for association in standard approaches, and additional tests with adjusting sex effects that act between genetic effect and disease. Consequently, five SNPs (P=1.31 × 10−5 for rs1930095 of intergenic region; P=1.32 × 10−5 for rs4628172 of TMEM195; P=2.78 × 10−5 for rs7781293 of TMEM195; P=4.93 × 10−5 for rs7550260 of ARHGEF11; and P=3.63 × 10−5 for rs9864101 of IQSEC1) with probabilities of being false positives <0.5 were associated with IA in Japanese population, and the susceptibility genes could have a role in actin remodeling in the ELN/LIMK pathway. This study indicates the presence of several susceptibility loci that deserve further investigation in the Japanese population.

Differential Effects of Chromosome 9p21 Variation on Subphenotypes of Intracranial Aneurysm Site Distribution

Background and Purpose— Recently, a genome-wide association study identified associations between single nucleotide polymorphisms on chromosome 9p21 and risk of harboring intracranial aneurysm (IA). Aneurysm characteristics or subphenotypes of IAs, such as history of subarachnoid hemorrhage, presence of multiple IAs and location of IAs, are clinically important. We investigated whether the association between 9p21 variation and risk of IA varied among these subphenotypes. Methods— We conducted a case-control study of 981 cases and 699 controls in Japanese. Four single nucleotide polymorphisms tagging the 9p21 risk locus were genotyped. The OR and 95% CI were estimated using logistic regression analyses. Results— Among the 4 single nucleotide polymorphisms, rs1333040 showed the strongest evidence of association with IA (P=1.5×10−6; per allele OR, 1.43; 95% CI, 1.24-1.66). None of the patient characteristics (gender, age, smoking, and hypertension) was a significant confounder or effect modifier of the association. Subgroup analyses of IA subphenotypes showed that among the most common sites of IAs, the association was strongest for IAs of the posterior communicating artery (OR, 1.69; 95% CI, 1.26-2.26) and not significant for IAs in the anterior communicating artery (OR, 1.22; 95% CI, 0.96-1.57). When dichotomizing IA sites, the association was stronger for IAs of the posterior circulation-posterior communicating artery group (OR, 1.73; 95% CI, 1.32-2.26) vs the anterior circulation group (OR, 1.28; 95% CI, 1.07-1.53). Heterogeneity in these ORs was significant (P=0.032). The associations did not vary when stratifying by history of subarachnoid hemorrhage (OR, 1.42; 95% CI, 1.18-1.71 for ruptured IA; OR, 1.27; 95% CI, 1.00-1.62 for unruptured IA) or by multiplicity of IA (OR, 1.57; 95% CI, 1.21-2.03 for multiple IAs; OR, 1.36; 95% CI, 1.15-1.61 for single IA). Conclusions— Our results suggest that genetic influence on formation may vary between IA subphenotypes.

Association Analysis of Genes Involved in the Maintenance of the Integrity of the Extracellular Matrix with Intracranial Aneurysms in a Japanese Cohort

Background: An association between versican (CSPG2), perlecan (HSPG2), fibrillin 2 (FBN2) and collagen 4A1 (COL4A1) gene variants and intracranial aneurysms (IA) has been reported in 2 studies analyzing Dutch IA patients. The aim of this study was to verify these associations in a Japanese IA population. In addition, a meta-analysis on the association of these genes and IA for the combined Dutch and Japanese populations was performed. Methods: The associated single nucleotide polymorphisms (SNPs) in these genes identified in the Dutch study were genotyped in 632 Japanese IA patients and 808 healthy control subjects using TaqMan SNP genotyping assays. Results: A similar association to that previously found in the Dutch population was found for the CSPG2 (rs251124) and HSPG2 (rs3767137) SNPs, although both associations were not statistically significant in the Japanese population (CSPG2 OR 1.18, 95% CI 0.98–1.41, p = 0.08; HSPG2 OR 1.09, 95% CI 0.90–1.32). Combining the Dutch and Japanese data for a meta-analysis showed an overall association between the CSPG2 SNP and IA (OR 1.29, 95% CI 1.12–1.48, p = 0.0005) and the HSPG2 SNP and IA (OR 1.22, 95% CI 1.08–1.39, p = 0.002). No differences in SNP frequency were observed for FBN2 and COL4A1 between Japanese patients and controls. Conclusions: By analyzing HSPG2, CSPG2, FBN2 and COL4A1, we were able to replicate the association of CSPG2 and show that there is a trend for HSPG2 towards association in the Japanese IA population by means of a meta-analysis combining the Dutch and Japanese results. The association of FBN2 and COL4A1 could not be replicated in the Japanese IA population.

Identification and Expression Analysis of Upregulated Genes in the Resting Egg-Producing Water Flea (Daphnia pulex)

Water fleas (Daphnia pulex) normally produce subitaneous eggs that initiate development immediately after oviposition. However, in response to habitat degradation, resting eggs are produced, which are enclosed in a sturdy outer envelope (ephippium) and can survive in harsh environments for an extended time. To understand the molecular mechanism underlying resting egg production in D. pulex, we investigated the genes whose expression patterns played a role in the production and identified the following six candidate genes: Dpfa-1, Dpfa-2, Dpep-1, Dpep-2, Dpep-3, and Dpep-4. These six genes displayed > 40-fold higher expression levels in resting egg-producing animals compared with those in subitaneous egg-producing animals at the period when the ovaries were mature. Dpfa-1 and Dpfa-2 were expressed in the fat cells, and their expression patterns were synchronized with the development of resting egg oocytes in the ovary. In contrast, Dpep-1–4 were expressed in the morphologically altered epidermal cells of the brood chamber with the formation of the ephippium, and their expression patterns were also related to ephippium formation. Our results suggest that the former two genes encode the resting egg-specific components produced by fat cells and that the latter four genes encode the components related to the ephippium formation synthesized by epidermal cells.