Japanese Polymorphisms Research Articles

A common polymorphism in the tissue kallikrein gene is associated with increased urinary excretions of calcium and sodium in Japanese volunteers

Tissue kallikrein is an enzyme involved in the release of kinin in peripheral tissues. It is believed to regulate hemodynamics and electrolyte transport in the kidney. The present study analyzed polymorphisms of tissue kallikrein in Japanese volunteers and examined the associations between allele H in the promoter region, which has been shown to have decreased promoter activity, and urinary kallikrein activity and physiological parameters in subjects on an ad libitum diet. Ninety and 73 volunteers were analyzed for the promoter and coding regions of the tissue kallikrein gene, respectively. The allelic frequency of allele H was found to be 24%. One synonymous and three non-synonymous polymorphisms were found in the coding regions. Urinary kallikrein activity was not significantly decreased in subjects with allele H compared to those without allele H, although they were low in two homozygotes of allele H. Urinary excretions of calcium and sodium were larger in the subjects with allele H than in those without. It is concluded that allele H is a common polymorphism in Japanese and may contribute to decreased reabsorptions of calcium and sodium in the kidney. Further interventional studies are needed to clarify the phenotype of allele H with respect to renal electrolyte handling.

Prognostic value of lemur tyrosine kinase-3 (LMTK3) polymorphism in Japanese (J) patients (PTS) with localized gastric adenocarcinoma (GAC).

4088 Background: LMTK3 is an estrogen receptor α (ERα) regulator. Recent studies show that [rs808419(r8) and rs9989661(r9)] and LMTK3 expression are prognostic in breast and colon cancers. Our group demonstrated that r9AA is associated with shorter time to recurrence in Caucasian(C) and Hispanic(H) females(F) with GAC. We investigated the significance of LMTK3 polymorphism in J PTS with GAC. Methods: Blood or tissue samples of 169 J PTS who had surgery with/without adjuvant chemotherapy (ACT) were analyzed. Genomic DNA was extracted using the QIAmp kit; all samples were analyzed using PCR-based direct DNA-sequencing. The endpoints of the study were disease-free survival (DFS) and overall survival (OS). Kaplan-Meier curves and log-rank test were used for univariate analysis. Multivariate analysis was performed to test the interaction between polymorphism and gender adjusting for other variables. Results: 60 F and 109 males were enrolled in this study, 17% stage(s) IB, 31% s II, 36% s III, 17% s IV (AJCC-6). The median age was 67(31-88). 65% of PTS received S-1 based ACT. Median follow-up was 4 years(ys). Prognosis was worse in men with r9 AA than AG/GG, at 1 year 67% (95% CI 40-83%) with AA vs 99% (95% CI 91-99%) of AG/GG were alive (p= 0.039). Median survival was not reached in the AG/GG group; in the AA group median DFS and OS was 1yr (p= 0.03) and 2ys (p= 0.039) respectively. In the multivariate analysis adjusting for s, age, and ACT, males carrying AA had increased risk of disease recurrence (HR 3.84 95%CI 1.86-7.92, p< 0.001) and dying (HR 3.47 95%CI 1.58-7.62 p=0.002) compared to those with AG/GG (HR=1, reference). Conclusions: r9 AA was associated with significantly worse DFS and OS in J male with GAC. These results confirm our previous findings that LMTK3 is an independent prognostic factor for localized GAC; interestingly the relationship between gender and prognostic significance is the opposite in J vs. C/H. The gender disparity can be due to the differences in the etiology (histological subtypes), management strategies, allele frequency, and degree of estrogen exposure in the two populations. Additional studies are warranted to identify the underlying biological mechanism.

A comparative search for human FcεRIα gene (FCER1A) 3′-UTR polymorphisms in Japanese and Polish populations

The high affinity immunoglobulin E (IgE) receptor (FcεRI) plays a key role in the pathogenesis of atopy and allergic disorders. Several polymorphisms located in 5'-flanking region and 5'-untranslated region (5'-UTR) of human FCER1A, the gene encoding FcεRI α-subunit, have been shown to functionally affect its transcriptional activity. All those genetic variants have been also associated with allergic diseases and/or serum IgE levels. In the present study, we sought to identify functional polymorphisms in human FCER1A 3'-untranslated region (3'-UTR), the potential candidates for future genetic association studies. Search for polymorphisms within human FCER1A 3'-UTR region, conducted in Japanese and Poles, revealed the presence of +5650A>G and +5714G>A variants. Subsequently, structure/distribution of haplotypes and LD measures were analyzed in Japanese and Poles for both 3'-UTR variants and the functional polymorphisms located in 5'-flanking region and 5'-UTR of human FCER1A. Additionally, reporter plasmids containing human FCER1A main promoter and 3'-UTR with all four possible combinations of +5650A>G and +5714G>A polymorphisms were constructed to evaluate functional potential of both 3'-UTR variants. However, no genotype-related differences in the gene expression were observed, as measured by reporter activity in cultured human basophil/mast cell-like KU812 cells, suggesting that both +5650A>G and +5714G>A have no genotype-related functional effect. In summary, we described linkage disequilibrium and the distribution of haplotypes for two identified human FCER1A 3'-UTR polymorphisms and several previously reported 5'-flanking region and 5'-UTR variants in Japanese and Poles, representative for East Asians and Caucasians, the two ethnic groups in which genetic associations between FCER1A and allergic diseases and/or serum IgE levels have been previously reported.

No associations of Toll-like receptor 2 (TLR2) -196 to -174del polymorphism with the risk of Helicobacter pylori seropositivity, gastric atrophy, and gastric cancer in Japanese

Recently, the association between gastric cancer risk and a functional polymorphism of Toll-like receptor 2 (TLR2), -196 to -174del, was reported for a Japanese population. This study aimed to confirm the associations of the polymorphism with the risk of gastric cancer, as well as Helicobacter pylori seropositivity and the risk of gastric atrophy in Japanese. The study subjects were 583 histologically diagnosed gastric cancer patients and 1636 age- and sex-frequency-matched control outpatients who visited Aichi Cancer Center Hospital from the years 2001 to 2005. Serum anti-H. pylori IgG antibody and pepsinogens were measured to evaluate H. pylori infection and gastric atrophy, respectively. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated by a logistic model. The age- and sex-adjusted ORs of gastric cancer were 1.13 (95% CI: 0.88-1.46) for ins/del, 1.17 (95% CI: 0.79-1.73) for del/del, and 1.14 (95% CI: 0.89-1.45) for ins/del + del/del, relative to the ins/ins genotype compared with gastric atrophy controls; none of these findings were statistically significant. The TLR2 -196 to 174del polymorphism was not significantly associated with either H. pylori seropositivity or gastric atrophy. Our study did not reproduce the association between gastric cancer risk and the TLR2 -196 to -174del polymorphism in Japanese. Further examinations with sufficient numbers of study subjects are required to verify our findings.

Enhanced Susceptibility of HLA-mediated Ticlopidine-induced Idiosyncratic Hepatotoxicity by CYP2B6 Polymorphism in Japanese

Hepatotoxicity is the most frequent adverse drug reaction (ADR) in Japanese treated with ticlopidine (TP). We investigated the relationship between CYP2B6 haplotype and incidence of TP-induced hepatotoxicity in 114 Japanese patients. Although 4 haplotypes (*1A, *1H, *1J and *6B) accounted for more than 80% of the inferred haplotypes in both control (n=81) and case (n=22) subjects, the prevalence was apparently different: control, *1A>*6B>*1H>*1J and case, *1J>*1H>*1A>*6B. The reporter gene assay for the two SNPs, which comprise the *1H or *1J haplotype, suggested that the *1H and *1J haplotypes may be associated with the increased expression of CYP2B6, probably due to g.-2320T>C. Combination analysis of CYP2B6 and human leukocyte antigen (HLA) haplotypes revealed that individuals possessing CYP2B6*1H or *1J with HLA-A*3303 have the highest susceptibility to TP-induced hepatotoxicity (odds ratio, 38.82; 95%CI, 8.08-196.0, P<0.001). Although this is a preliminary case-control study with some limitations, it is the first example that HLA-induced idiosyncratic ADR may be modified by individual variation in CYP activities.

Thiopurine S-methyltransferase and inosine triphosphate pyrophosphohydrolase genes in Japanese patients with inflammatory bowel disease in whom adverse drug reactions were induced by azathioprine/6-mercaptopurine treatment

The main cause of azathioprine (AZA)/6-mercaptopurine (6MP)-induced adverse reactions is a reduction in the activities of the metabolizing enzymes thiopurine S-methyltransferase (TPMT) and inosine triphosphate pyrophosphohydrolase (ITPA). Adverse reactions develop at a high frequency in Japanese patients at half the dose required for European and American patients; however, the association with TPMT and ITPA gene polymorphisms in Japanese has not been fully investigated. Gene mutations of TPMT and ITPA, the major AZA/6-MP -metabolizing enzymes, were investigated retrospectively in 16 Japanese patients with inflammatory bowel disease (IBD) in whom AZA/6MP treatment induced adverse reactions. The TPMT gene was found to have a wild-type sequence in all patients, but in the ITPA gene a mutation, 94C>A, was detected at a rate of 50% (8/16), with 83.3% (5/6) occurring in patients with acute bone marrow suppression and 75% (3/4) in those with agranulocytosis. The 94C>A allele frequency was 10 of 32 (0.313; 95% CI, 0.180-0.486). Adverse reactions developed earlier in patients with the 94C>A mutation. However, in half the patients, no gene polymorphism was noted. It is suggested that the ITPA gene mutation is closely related to the adverse reactions of AZA/6-MP in Japanese patients, and screening for the mutant allele is useful for predicting the most serious adverse reactions, agranulocytosis and acute bone marrow suppression.

Cytochrome P450 2J2*7 polymorphisms in Japanese, Mongolians and Ovambos.

Human cytochrome P450 2J2 (CYP2J2) is abundant in cardiovascular tissue and active in the metabolism of arachidonic acid to eicosanoids that have potent vasodilatory properties. Variability of the CYP2J2 gene is highly constrained except for its proximal promoter: there is a relatively common and functionally relevant single nucleotide polymorphism, indicated by -50G > T polymorphism (CYP2J2*7). Although genetic variation is known among ethnic groups, data for allele frequency are limited to a few Caucasian, Asian, and one African populations. In the present study, genotype distribution of CYP2J2*7 polymorphisms was investigated using polymerase chain reaction and restriction fragment length polymorphism assay in Japanese (n = 338), Mongolian (n = 118), and Ovambo (n = 186) populations and the findings compared with other populations. The mutant (CYP2J2*7) frequencies in the Japanese, Mongolians, and Ovambos were 0.0621, 0.0339, and 0.0672, respectively. Except for the Taiwanese, a general uniformity in the polymorphism in the Asian populations was observed. The mutation frequency of Ovambos was relatively lower than that of the African-American population. This study is the first to investigate the distribution of the CYP2J2*7 gene polymorphisms in Japanese, Mongolians, and Ovambos. These data will be informative and facilitate genetic association studies, in Asian and African populations for CYP2J2-related diseases such as cardiovascular disorders.

FCER1A gene exon 1A polymorphisms in Japanese and Polish subjects – a comparative analysis of haplotypes

FCER1A gene exon 1A polymorphisms in Japanese and Polish subjects – a comparative analysis of haplotypes

Differential Effects of Aging, Drinking and Exercise on Serum Cholesterol Levels Dependent on the PPARA‐V227A Polymorphism

Peroxisome proliferator-activated receptor alpha (PPARA alpha) plays a pivotal role in lipid metabolism. Our previous study reported that PPARA-V227A was a major polymorphism in Japanese, which was associated with markedly lower serum total cholesterol (TC) levels, which were significantly affected by alcohol drinking compared to subjects with the wild-type (PPARA-WT) allele. However, serum lipids are also associated with aging and exercise frequency. The objective of the present study was to evaluate the relationship between PPARA-V227A and these factors. Genetic analysis of the polymorphism was performed in 1058 Japanese men and 281 women, and the relationship with aging, drinking and exercise on serum lipids was analyzed in 989 men and 245 women after exclusion criteria had been applied. In men, drinking increased high-density lipoprotein cholesterol (HDL-C) levels in both PPARA-WT and A227 carriers, but to a significantly higher degree in the latter. In women, TC and low-density lipoprotein cholesterol (LDL-C) levels in the A227 carriers drinking at least once a week were significantly higher than in PPARA-WT carriers. TC and LDL-C levels in males with PPARA-WT increased with aging regardless of drinking habit, while LDL-C levels in the A227 drinking carriers were significantly lower in 45-yr-old or older subjects than in 35- to 45-yr-olds. In addition, no effect of exercising was observed in the A227 carriers, while increase in the HDL-C of the PPARA-WT carriers was exercise frequency dependent. These results suggest that the influence of drinking, aging or exercise on TC, LDL-C and HDL-C levels in the A227 carriers may be different from those in the PPARA-WT subjects.

Characterization of CCR5 chemokine receptor gene polymorphisms in Japanese and Thai populations (45.11)

Abstract Variations in the human CCR5 gene may alter the expression and/or function of the protein product, thereby altering chemokine binding/signaling or HIV infection of the cells that normally express CCR5 protein. We performed a systematic survey of genetic variations in the entire CCR5 gene as well as CCR2V64I in 50 Japanese subjects and evaluated the effects of those variations on CCR5 promoter activity. We also analyzed CCR5 promoter and CCR2V64I genotypes in 80 more Japanese and 186 Thais. Two types of non-synonymous substitutions in Japanese CCR5 gene were found. Our results showed several novel characteristics of the CCR2-CCR5 haplotype structure that were not reported from studies on Caucasians and African-Americans. Specifically, we were able to show that the G allele at position -2852 from the CCR5 translational start codon in Japanese and Thais is the representative of the CCR5 promoter haplotype that was reported to be associated with rapid progression to AIDS in HIV-infected individuals. Furthermore, nearly all non-synonymous polymorphisms in Japanese CCR5 gene occurred in haplotypes with elevated promoter activity. We thus hypothesized that there was certain selective pressure favoring low levels of CCR5 expression during human evolution.

CYP2A6 Polymorphism Reveals Differences in Japan and the Existence of a Specific Variant in Ovambo and Turk Populations

CYP2A6 is a polymorphic enzyme, and CYP2A6 genotype has been shown to be associated with smoking habits and lung cancer. We investigated CYP2A6 polymorphism in Japanese from four different geographic areas of Japan and in the Ovambo and Turk populations. Using two polymerase chain reaction restriction fragment length polymorphisms (PCR-RFLPs), we identified the functionally important variants of CYP2A6: *1A, *1B, *1F, *1G, *4A, and *4D. In the Japanese population the highest frequencies of the CYP2A6*1A allele were observed in subjects from the Fukuoka (Kyushu Island) and Ehime (Shikoku Island) prefectures, whereas subjects in Shimane and Tottori (both located on the Japan Sea side of Honshu Island) showed the highest frequencies of the CYP2A6*1B allele. In the Tottori and Shimane groups no subject was homozygous for the CYP2A6*4A allele, a whole gene deletion type that is prevalent among Asians. In the Ovambo and Turk populations the CYP2A6*1A allele was predominant. Furthermore, two alleles undetected in the Japanese were observed in these latter two ethnic groups: CYP2A6*1G was found solely in the Ovambos, and CYP2A6*1F was found solely in the Turks. The present study is the first to show interprefecture differences in CYP2A6 polymorphism in Japanese who live in relatively close but distinct geographic areas; this is also the first study to evaluate CYP2A6 variations among these Japanese and the Ovambo and Turk populations. The distribution results of these alleles could help to define the true significance of CYP2A6 polymorphism as a genetic susceptibility marker in worldwide populations.

Phenotype-genotype analysis of CYP1A2 in Japanese patients receiving oral theophylline therapy

To clarify the association between the cytochrome P450 (CYP) 1A2 genotype with the CYP1A2 phenotype and to search for the CYP1A2*1K haplotype, which has been shown to decrease CYP1A2 inducibility and/or other functional polymorphisms in Japanese. Two polymorphisms, CYP1A2*1C and CYP1A2*1F, were genotyped in 126 patients receiving oral slow-release theophylline (TP) therapy and in 224 healthy volunteers. The CYP1A2 phenotype was assessed by the plasma [1-methyluric acid (1U)+3-methylxanthine (3X)]/TP ratio in the patients. The volunteers were given 150 mg caffeine, and the urine [1X+1U+5-acetylamino-6-amino-3-methyluracil (AAMU)]/17U ratio was used for CYP1A2 phenotyping. CYP1A2 intron 1 and six exons (exon 2-exon 7) were sequenced in the patients whose (1U+3X)/TP ratios were below the mean-2SD of those of all patients, and intron 1 was also sequenced in an additional 20 healthy volunteers exhibiting putative low CYP1A2 activities. The individual (1U+3X)/TP ratios ranged from 0.007 to 0.21 (a 30-fold difference) in the patients, and the (1X+1U+AAMU)/17U ratios ranged from 1.6 to 112 (a 70-fold difference) in the healthy volunteers. The CYP1A2 activities were not significantly influenced by CYP1A2*1C or CYP1A2*1F. We found no functional polymorphisms by a sequencing analysis. These results suggest that the CYP1A2*1C and CYP1A2*1F genotypes are not crucial factors for the variability of CYP1A2 activity and that the CYP1A2*1K haplotype is either nil or only shows a very low frequency in Japanese.

Genetic variations in the WFS1 gene in Japanese with type 2 diabetes and bipolar disorder

Diabetic and psychiatric symptoms often appear in patients with Wolfram syndrome, and obligate carriers of WFS1 have increased prevalence of type 2 diabetes and are more likely to require hospitalization for psychiatric illness including bipolar disorder. To identify the polymorphisms in Japanese, we examined a region of ∼50 kb covering the entire WFS1 gene, and evaluated the patterns of linkage disequilibrium. We found a total of 42 variations including 8 novel coding single nucleotide polymorphisms (A6T, A134A, N159N, T170T, E237K, R383C, V412L, and V503G), 14 novel non-coding polymorphisms, and 2 linkage disequilibrium blocks. We also performed association studies in patients with type 2 diabetes mellitus and patients with bipolar disorder. The haplotype comprising R456 and H611 was most associated with type 2 diabetes ( p=0.013) and the haplotype comprising g. −15503C/T and g. 16226G/A was most associated with bipolar disorder ( p=0.006), but neither reached significant difference after multiple adjustment. These genetic variations and linkage disequilibrium patterns in WFS1 in Japanese should be useful in further investigation of genetic diversities of WFS1 and various related disorders.

No associations of p73 G4C14-to-A4T14 at exon 2 and p53 Arg72Pro polymorphisms with the risk of digestive tract cancers in Japanese

A case-control study was conducted to examine the possible association between digestive tract cancers and p73 G4C14-to-A4T14 at exon 2 and p53 Arg72Pro polymorphisms in Japanese. Cases were 102 esophageal cancer patients, 144 stomach cancer patients, and 147 colorectal cancer patients, and controls were 241 non-cancer outpatients. The genotype frequencies among controls were 55.3% for p73 GG at position 4, 40.4% for GA, and 4.3% for AA, and 37.7% for p53 ArgArg, 44.4% for ArgPro, and 18.0% for ProPro. No significant differences in the genotype frequencies were observed between the controls and each case group or cases as a whole.

ROLE OF HUMAN CYTOCHROME P450 (CYP) IN THE METABOLIC ACTIVATION OF NITROSAMINE DERIVATIVES: APPLICATION OF GENETICALLY ENGINEERED SALMONELLA EXPRESSING HUMAN CYP

The role of human cytochrome P450 (CYP) in the metabolic activation of tobacco-related N-nitrosamines was examined by Salmonella mutation test using a series of genetically engineered Salmonella typhimurium YG7108 strains each co-expressing a form of CYP (CYP1A1, CYP1A2, CYP1B1, CYP2A6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, CYP3A4, and CYP3A5) together with human NADPH–cytochrome P450 reductase. Seven tobacco-related N-nitrosamines such as 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, N-nitrosodiethylamine, N-nitrosopyrrolidine, N-nitrosopiperidine, N-nitrosonornicotine, N-nitrosoanabasine, and N-nitrosoanatabine were used. The CYP2A6 was found to be responsible for the mutagenic activation of essentially all tobacco-related N-nitrosamines examined.On the basis of the evidence, genetic polymorphism of the CYP2A6 gene appeared to be one of the factors determining cancer susceptibility caused by smoking. Previously, we found the whole deletion of the CYP2A6 gene (CYP2A6*4C) as a type of genetic polymorphism in Japanese. We hypothesized that individuals possessing the gene homozygous for CYP2A6*4C were incapable of activating tobacco-related N-nitrosamines and showed lower susceptibility to lung cancer induced by tobacco smoke. Thus, the relationship between the CYP2A6*4C and the susceptibility to the lung cancer was evaluated. The frequency of the CYP2A6*4C was significantly lower in the lung cancer patients than healthy volunteers, suggesting that the subjects carrying the CYP2A6*4C alleles are resistant to carcinogenesis caused by N-nitrosamines because of the poor metabolic activation capacity.Taking these results into account, CYP2A6 is an enzyme enhancing lung cancer risk.

Association of BMI with the beta3-adrenergic receptor gene polymorphism in Japanese: meta-analysis.

To assess the effect of the Trp64Arg polymorphism in the beta3-adrenergic receptor gene (ADRB3) on body mass index (BMI) in the Japanese population. We selected studies that evaluated the association between BMI and ADRB3 polymorphism among Japanese, using MEDLINE and PubMed. After data collection, an extension of ANOVA was performed to assess the differences according to the genotype. In a total of 35 subgroups including 2316 subjects with the Trp64Arg variant and 4266 subjects without this variant, the weighted mean difference in BMI was 0.26 kg/m(2) (95% confidence interval: 0.18 to 0.42; p < 0.01), indicating that variant carriers exhibited higher BMI than did normal homozygous subjects. Although it is known that the allele frequency of the ADRB3 polymorphism differs among races, this study focuses on the Japanese population, which has a high allele frequency of ADRB3 polymorphism. We assumed that statistical errors would be prevented due to the sufficient number of subjects. In conclusion, the results support the hypothesis that ADRB3 gene polymorphism is associated with BMI.

Platelet glycoprotein (GP) V polymorphisms in Japanese.

The glycoprotein (GP) V is a subunit of a platelet receptor for von Willebrand factor, the GPIb/IX/V complex. Recently, polymorphisms in the GPV gene, four involving amino acid changes and five silent, were identified. We developed an allele-specific restriction method to determine the gene frequencies of the non-synonymous substitutions in Japanese and Caucasians. The gene frequencies for 341Gly/Arg polymorphism were 0.94 for 341Gly and 0.06 for 341Arg, and 0.95 for 341Gly and 0.05 for 341Arg, in Japanese and Caucasians, respectively. We could not find rare variants for 114Asp/Tyr, 273Met/Ile or 397Leu/Arg. Flow cytometric analysis showed that the 341Arg variant is expressed normally on the platelet membranes, suggesting the possibility of the involvement of the 341Gly/Arg polymorphism as a platelet alloantigen.

Genetic polymorphism of CYP2A6 in relation to cancer

To clarify the roles of human cytochrome P450 (P450 or CYP) 2A6 and 2E1 on the metabolic activation of N-nitrosamines, we established genetically engineered Salmonella typhimurium strains harboring human CYP2A6 or CYP2E1 together with NADPH-P450 reductase (OR). The 5′-terminus of CYP cDNA was modified to achieve a high-level expression in S. typhimurium. Modified CYP2A6 or CYP2E1 cDNA and native OR cDNA were introduced into a pCW vector. S. typhimurium YG7108 cells were transformed with this vector. The mutagen producing ability of these enzymes for some N-nitrosamines were evaluated using the established S. typhimurium cells. We found that the substrate specificity of CYP2A6 and CYP2E1 was different among mutagens. CYP2A6 was responsible for the metabolic activation of N-nitrosamines possessing relatively long alkyl chains, whereas CYP2E1 was responsible for the metabolic activation of N-nitrosamines with relatively short alkyl chains. It is likely that CYP2A6 gene polymorphism is responsible for the interindividual variability on the cancer susceptibility. We found the whole deletion of CYP2A6 gene as a type of genetic polymorphism in Japanese. Thus, we developed a gene diagnosis method to detect the variant. We evaluated the relationship between the CYP2A6 gene whole deletion and the susceptibility to the lung cancer. The frequency of CYP2A6 gene whole deletion was significantly lower in the lung cancer patients than that of healthy volunteers.

MIC-A polymorphism in Japanese and a MIC-A-MIC-B null haplotype.

A polymorphic gene, MIC-A, is one of the MIC family of genes which is composed of a group of homologous genes interspersed in the class III and class I regions of the major histocompatibility complex. MIC-A is located 46 kilobases (kb) centromeric of HLA-B, and is preferentially expressed in the epithelial cells and intestinal mucosa. Recently, MIC-A and the closely related MIC-B were reported as the molecules that conferred specificity in the recognition by the Vdelta1gammadeltaT cells. In the present study, polymorphic exons 2, 3, and 4 of the MIC-A gene were analyzed using the polymerase chain reaction-single-strand conformation polymorphism method. The number of patterns found in exons 2, 3, and 4 were 5, 6, and 4, respectively, in 114 healthy Japanese subjects. Eight MIC-A alleles were observed in Japanese individuals, among which one, tentatively named MIC-AMW, has not previously been reported. There was a strong linkage disequilibrium between MIC-A and HLA-B loci: each MIC-A allele showed strong association with a particular HLA-B group. In contrast, B*3901 showed association with multiple MIC-A alleles. Furthermore, the existence of a MIC-A-MIC-B null haplotype, which is associated with HLA-B*4801, was identified. In this haplotype, a large-scale deletion (of approximately 100 kb) including the entire MIC-A gene was indicated and the MIC-B gene possessed a stop codon.

MtDNA Polymorphisms in Japanese Sporadic Alzheimer’s Disease

We screened 92 Japanese patients with sporadic AD (clinically diagnosed: 72 cases; autopsy-confirmed: 20 cases) and 59 age-matched controls for mitochondrial polymorphisms previously reported to be associated with increased risk in Caucasian AD. The polymorphisms in tRNA Gln (nt. 4336), 16S rRNA (nt. 3196), and ND1 (nt. 3397) were not found in either in Japanese AD or age-matched controls. The frequencies of these polymorphisms in Japanese seems to be very rare if not absent, indicating that these three mutations are not likely to be genetic risk factors of Japanese AD. In the analysis of polymorphisms of 12S rRNA, however, we identified two novel mutations, an insertion of three cytosines and an A to G transition at nt. 856, which have not been described before. The insertion of three cytosines was observed in one of the 90 AD cases, but not in 59 normal controls. The A to G transition at nt. 856 was found in 2 of the 90 AD cases, but not in 59 normal controls. These results raise the possibility that the mutations in the 12S rRNA are genetic risk factors for AD in Japanese population.