Jun Nakura

Positional Cloning of the Werner's Syndrome Gene

Werners syndrome (WS) is an inherited disease with clinical symptoms resembling premature aging. Early susceptibility to a number of major age-related diseases is a key feature of this disorder. The gene responsible for WS (known as WRN) was identified by positional cloning. The predicted protein is 1432 amino acids in length and shows significant similarity to DNA helicases. Four mutations in WS patients were identified. Two of the mutations are splice-junction mutations, with the predicted result being the exclusion of exons from the final messenger RNA. One of these mutations, which results in a frameshift and a predicted truncated protein, was found in the homozygous state in 60 percent of Japanese WS patients examined. The other two mutations are nonsense mutations. The identification of a mutated putative helicase as the gene product of the WS gene suggests that defective DNA metabolism is involved in the complex process of aging in WS patients.

Association of a polymorphic variant of the Werner helicase gene with myocardial infarction in a Japanese population

The Werner syndrome (WS) is a rare autosomal recessive progeroid syndrome characterized by the premature onset of multiple age-related disorders, including atherosclerosis, cancer, non-insulin-dependent diabetes mellitus (NIDDM), ocular cataracts and osteoporosis [Epstein et al., 1966]. The major cause of death (at a median age of 47) is myocardial infarction (MI) [Epstein et al., 1966]. The WS mutation involves a member (WRN) of the RecQ family of helicases and may perturb DNA replication, repair, recombination, transcription, or chromosomal segregation [Yu et al., 1996]. We now report data on 149 MI cases and age-matched controls suggesting that a polymorphic WRN variant is associated with increased risk for MI. Based on our data, homozygosity for a cysteine at amino acid 1367 (the most prevalent genotype) predicts a 2.78 times greater risk of MI (95% confidence intervals: 1.23 to 6.86). The variant was not significantly associated with NIDDM. The two alleles (cysteine vs. arginine) could influence helicase activity, turnover, macromolecular interactions or, alternatively, could be markers for haplotypes influencing WRN regulation or reflecting gene action at linked loci. However, given the caveats implicit in genetic association studies, it is imperative that the present results be replicated in independent populations.

Association of Endothelin-1 Gene Variant With Hypertension

Abstract—Endothelin-1 (ET-1) is a powerful vasoconstrictor peptide produced by endothelial and smooth muscle cells. Many lines of biological evidence suggest that the ET-1 gene is a candidate gene for hypertension. Moreover, recent association studies suggested that a G/T polymorphism with an amino acid substitution (Lys/Asn) at codon 198 in exon 5 of the ET-1 gene interacts with body mass index (BMI) in association with blood pressure. They suggested that T carriers are more sensitive to weight gain than GG homozygotes in association with blood pressure. However, association studies are often irreproducible, and the first study often suggests a stronger genetic effect than is found by subsequent studies. We therefore assessed the interaction in 2 large Japanese populations. The present study showed a nonsignificant but similar trend to the results of previous reports. Moreover, in line with previous reports, this study revealed a significant interaction between the ET-1 K198N (G/T) polymorphism and BMI in association with hypertension in our populations (P =0.027). The interaction was significant, even after adjustment for gender and age (P =0.045) and for all confounding factors (P =0.044). T carriers were more sensitive to weight gain than GG homozygotes in association with hypertension. Considering the combined impact of obesity and hypertension on the development of cardiovascular and cerebrovascular disorders, T allele carriers might represent elective targets for therapy to lower their body weight.

Common Variants in the ATP2B1 Gene Are Associated With Susceptibility to Hypertension: The Japanese Millennium Genome Project

Hypertension is one of the most common complex genetic disorders. We have described previously 38 single nucleotide polymorphisms (SNPs) with suggestive association with hypertension in Japanese individuals. In this study we extend our previous findings by analyzing a large sample of Japanese individuals (n=14 105) for the most associated SNPs. We also conducted replication analyses in Japanese of susceptibility loci for hypertension identified recently from genome-wide association studies of European ancestries. Association analysis revealed significant association of the ATP2B1 rs2070759 polymorphism with hypertension (P=5.3×10−5; allelic odds ratio: 1.17 [95% CI: 1.09 to 1.26]). Additional SNPs in ATP2B1 were subsequently genotyped, and the most significant association was with rs11105378 (odds ratio: 1.31 [95% CI: 1.21 to 1.42]; P=4.1×10−11). Association of rs11105378 with hypertension was cross-validated by replication analysis with the Global Blood Pressure Genetics consortium data set (odds ratio: 1.13 [95% CI: 1.05 to 1.21]; P=5.9×10−4). Mean adjusted systolic blood pressure was highly significantly associated with the same SNP in a meta-analysis with individuals of European descent (P=1.4×10−18). ATP2B1 mRNA expression levels in umbilical artery smooth muscle cells were found to be significantly different among rs11105378 genotypes. Seven SNPs discovered in published genome-wide association studies were also genotyped in the Japanese population. In the combined analysis with replicated 3 genes, FGF5 rs1458038, CYP17A1, rs1004467, and CSK rs1378942, odds ratio of the highest risk group was 2.27 (95% CI: 1.65 to 3.12; P=4.6×10−7) compared with the lower risk group. In summary, this study confirmed common genetic variation in ATP2B1, as well as FGF5, CYP17A1, and CSK, to be associated with blood pressure levels and risk of hypertension.

Identification of Hypertension-Susceptibility Genes and Pathways by a Systemic Multiple Candidate Gene Approach: The Millennium Genome Project for Hypertension

A multiple candidate-gene approach was used to investigate not only candidate genes, but also candidate pathways involved in the regulation of blood pressure. We evaluated 307 single nucleotide polymorphisms (SNPs) in 307 genes and performed an association study between 758 cases and 726 controls. Genes were selected from among those encoding components of signal transduction pathways, including receptors, soluble carrier proteins, binding proteins, channels, enzymes, and G-proteins, that are potentially related to blood pressure regulation. In total, 38 SNPs were positively (p<0.05) associated with hypertension. Replication of the findings and possible polygenic interaction was evaluated in five G-protein–related positive genes (GNI2, GNA14, RGS2, RGS19, RGS20) in a large cohort population (total n=9,700, 3,305 hypertensives and 3,827 normotensive controls). In RGS20 and GNA14, dominant models for the minor allele were significantly associated with hypertension. Multiple dimension reduction (MDR) analysis revealed the presence of gene–gene interaction between GNA14 and RGS20. The MDR-proved combination of two genotypes showed a significant association with hypertension (χ2=9.93, p=0.0016) with an odds ratio of the high-risk genotype of 1.168 (95% confidence interval [CI] [1.061–1.287]). After correction for all possible confounding parameters, the MDR-proved high-risk genotype was still a risk for hypertension (p=0.0052). Furthermore, the high-risk genotype was associated with a significantly higher systolic blood pressure (133.08±19.46 vs. 132.25±19.19 mmHg, p=0.04) and diastolic blood pressure (79.65±11.49 vs. 79.01±11.32 mmHg, p=0.019) in the total population. In conclusion, a systemic multiple candidate gene approach can be used to identify not only hypertension-susceptibility genes but also hypertension-susceptibility pathways in which related genes may synergistically collaborate through gene–gene interactions to predispose to hypertension.

Risk factor-gene interaction in carotid atherosclerosis: effect of gene polymorphisms of renin-angiotensin system.

AbstractThe risk factor–gene interaction in carotid atherosclerosis was investigated in 205 community-dwelling healthy subjects aged 50 years or more in Japan. The intima–media thickness (IMT) of the common carotid artery was evaluated by ultrasonography with a 7.5-MHz probe. Gene polymorphisms were determined for each subject with angiotensin-converting enzyme (ACE) insertion/deletion (I/D), angiotensinogen (AGT) M235T, angiotensin II type 1 receptor (AT1R) A1166C, and apolipoprotein E (apoE) genotypes. There was no genotype-specific difference in carotid IMT among any genes examined. Combinations of genotypes did not increase carotid IMT compared with subjects without these genotypes. In the total population, multiple regression analysis showed that age, systolic blood pressure (SBP), sex, and body mass index (BMI) were significantly associated with carotid IMT. However, the association between risk factors and IMT was genotype-specific. Age was significantly associated with IMT in ACE D carriers, but not in subjects with the ACE II genotype. Analysis of covariance adjusted with other risk factors showed that the age-dependent change in IMT was significantly different between subjects with the ACE II genotype and the ACE D carriers (F[1.196] = 4.97; P = 0.027). Similarly, the regression of IMT on SBP was significantly different between AGT TT and AGT MT + MM (F[1.196] = 7.20; P = 0.0079). The regression of IMT on BMI was also significantly different between apo E4 carriers and noncarriers (F[1.196] = 6.78; P = 0.0099). Furthermore, general linear model analysis with risk factors, genotype, and risk factor-genotype interactions revealed that the age*ACE genotype interaction, the SBP*AGT genotype interaction, and the BMI*apoE genotype interaction were significantly associated with IMT. These findings further support the role of risk factor-gene interaction in carotid atherosclerosis.

Relation Between Angiotensin-Converting Enzyme II Genotype and Atrial Fibrillation in Japanese Patients With Hypertrophic Cardiomyopathy

AbstractAtrial fibrillation (AF) occurs in about 20% of patients with hypertrophic cardiomyopathy (HCM). HCM patients with AF have an increased risk for clinical decline and thromboembolism. In addition, AF is known to be associated with the atrial renin-angiotensin system (RAS). However, the relation between AF and the RAS in HCM has not been investigated. We genotyped the insertion/deletion (I/D) polymorphism of the angiotensin-converting enzyme (ACE) gene in 138 HCM patients (26 with AF, 112 with sinus rhythm). Distribution of the ACE genotypes (DD, ID, and II) among the total HCM patients was 15%, 46%, and 38%. AF was documented in 3 patients with the DD genotype, 7 with the ID genotype, and 16 with the II genotype (P < 0.03 vs. sinus rhythm group). The odds of AF were 3.2-fold greater in patients with the II genotype than in those with the other genotypes (P = 0.009, 95% confidence interval = 1.3–7.8). Kaplan-Meier curves examining the time to the first documented AF event showed a significant difference between genotypes during the follow-up period (mean 116 months, P < 0.05). These findings suggest that the II genotype of the ACE gene is a significant risk factor for AF in patients with HCM.

Association of ACE I/D polymorphism with cardiovascular risk factors

Abstract. Since the identification of an insertion/deletion (I/D) polymorphism in the angiotensin-converting enzyme (ACE) gene, the D allele has been recognized to be associated with cardiovascular disease. Moreover, significant associations of this polymorphism with multiple cardiovascular risk factors have been reported, although some studies failed to detect such associations. In the present study, we investigated the association of the ACE gene polymorphism with the parameters of multiple risk factors in 300 Japanese men who participated in a medical check-up. This investigation detected a significant association of the polymorphism with systolic blood pressure (P=0.007) and diastolic blood pressure (P=0.026), with their highest values in DD subjects and lowest values in II subjects. This significant association is consistent with the proposition that the polymorphism influences blood-pressure variability in men. Furthermore, we investigated the association of the polymorphism with four major disorders (obesity, hyperlipidemia, hypertension, diabetes mellitus) correlated with the risk for cardiovascular disease in the same 300 subjects. This investigation failed to detect any significant association of the polymorphism with each disorder. However, there was a trend that all four disorders were more frequent in ID and DD subjects than in II subjects. We therefore analyzed the association between the ACE gene polymorphism and having at least one of the four disorders in the same population. This analysis detected a significant difference: that ID and DD subjects had at least one of the four disorders more frequently than II subjects (P=0.008; odds ratio=1.89, 95% confidence interval=1.19–2.99). Taken together, the results of this study are compatible with the proposition that the ACE polymorphism is associated with cardiovascular disease partially mediated through the four disorders in our population.

Association of GNAS1 Gene Variant With Hypertension Depending on Smoking Status

The &bgr;-adrenoceptor (&bgr;-AR) Gs protein system has been shown to have important roles in the cardiovascular system. The gene encoding the &agr;-subunit of Gs proteins (GNAS1) is a candidate genetic determinant for hypertension. We studied the GNAS1 T393C polymorphism in >2000 Japanese individuals. &khgr;2 test showed a marginally significant difference in the frequencies of the alleles (P =0.036) and genotypes (P =0.094) between hypertensives and normotensives. Because hypertension is considered to be a complex disorder resulting from interactions between genetic and environmental factors, we further analyzed the T393C polymorphism, with consideration of interactions between the polymorphism and confounding factors in regression models. These analyses showed a significant interaction between the polymorphism and cigarette smoking in the pathogenesis of hypertension (P =0.0005). The interaction was reflected in a significant association of the polymorphism with hypertension in nonheavy smokers (P =0.0028; odds ratio, 1.52; 95% confidence interval, 1.16 to 2.00). A significant interaction between the polymorphism and aging in the pathogenesis of hypertension was also shown in nonheavy smokers. These findings may be helpful in conducting further molecular and biological studies on the relationship among cigarette smoking, the &bgr;-AR-Gs protein system, and hypertension.

Helicases and aging

Abstract. Studying monogenic hereditary disorders that manifest age-related phenotypes in cells, tissues, and the total organism would be helpful for clarifying the mechanisms of aging. In this context, seven human disorders that manifest age-related phenotypes have been found to be caused by aberrations of five proteins with seven helicase motifs conserved in most of the helicases. These disorders are xeroderma pigmentosum, Cockayne syndrome, trichothiodystrophy, Bloom syndrome, Werner syndrome, X-linked α -thalassemia/mental retardation syndrome, and Juberg-Marsidi syndrome. A decline of probably pleiotropic and fundamental function of helicases in these disorders is, therefore, implied to underlie not only the various age-related phenotypes of the disorders but also the pleiotropic and universal nature of ordinary aging. Consistent with this implication, studies of these seven disorders suggest that their various age-related phenotypes are caused by aberrations in multiple processes, especially transcription. Furthermore, a few studies imply some association between aberration of the helicases and phenotypes in ordinary aging.