Naoyuki Tsuchiya

Sex-specific association of X-linked Toll-like receptor 7 (TLR7) with male systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a multisystem, autoimmune disease that predominantly affects women. Previous findings that duplicated Toll-like receptor 7 (Tlr7) promotes lupus-like disease in male BXSB mice prompted us to evaluate TLR7 in human SLE. By using a candidate gene approach, we identified and replicated association of a TLR7 3′UTR SNP, rs3853839 (G/C), with SLE in 9,274 Eastern Asians (Pcombined = 6.5 × 10−10), with a stronger effect in male than female subjects [odds ratio, male vs. female = 2.33 (95% CI = 1.64–3.30) vs. 1.24 (95% CI = 1.14–1.34); P = 4.1 × 10−4]. G-allele carriers had increased TLR7 transcripts and more pronounced IFN signature than C-allele carriers; heterozygotes had 2.7-fold higher transcripts of G-allele than C-allele. These data established a functional polymorphism in type I IFN pathway gene TLR7 predisposing to SLE, especially in Chinese and Japanese male subjects.

Association of Fcγ receptor IIIB, but not of Fcγ receptor IIA and IIIA polymorphisms with systemic lupus erythematosus in Japanese

Human Fcγ receptor (FcγR) genes form a clustered gene family on chromosome 1q21–24. Although the association of FcγR polymorphisms with systemic lupus erythematosus (SLE) has been extensively studied, the results are often contradictory. In this study, FcγRIIA-131H/R, FcγRIIIA-176F/V and FcγRIIIB-NA1/2 genotypes were determined in the Japanese patients with SLE (n = 81) or rheumatoid arthritis (RA, n = 115) as well as in healthy individuals (n = 217), and possible association with the disease was tested using case-control analysis. Unlike in other populations, significant difference was not observed in the frequencies of FcγRIIA and FcγRIIIA genotypes between patients with SLE and healthy individuals. However, significant difference was detected in the frequencies of FcγRIIIB genotypes between SLE and healthy individuals (P = 0.008). The odds ratio [OR] of the FcγRIIIB-NA2/NA2 homozygotes for the development of SLE was 2.52 (95% confidence interval [CI]: 1.33–4.79). Among the patients with SLE, individuals with NA2/2 were significantly more likely to have lupus nephritis (P = 0.007). No association was observed between any of the FcγR polymorphisms and RA. Significant linkage disequilibrium was detected between FcγRIIIA and IIIB, but neither between IIA and IIIA, nor between IIA and IIIB. These observations may underscore the relevance of defective immune complex handling in the pathogenesis of SLE, or may suggest the presence of primarily associated gene(s) in linkage disequilibrium with FcγR genes.

Analysis on the association of human BLYS (BAFF, TNFSF13B) polymorphisms with systemic lupus erythematosus and rheumatoid arthritis

Recent studies indicated a substantial role of BLyS (BAFF, TNFSF13B) in the pathogenesis of systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) in humans and in animal models. This study was conducted to screen for polymorphisms of human BLYS, and to examine whether they are involved in the genetic susceptibility to human SLE and RA. A systematic polymorphism screening was performed in the coding region, 5′ and 3′ untranslated regions, and promoter region of human BLYS. Association of the detected polymorphisms with SLE and RA was analyzed in 221 Japanese patients with RA, 156 with SLE, and 227 healthy individuals, using the case–control approach. Four single nucleotide polymorphisms (SNPs) in the promoter, one SNP in intron 1, and one rare nonsynonymous substitution (Ala105Thr) in the coding region were detected. The BLYS SNPs were found to form three common haplotypes. Significant association with the susceptibility to SLE or RA was not observed. However, a tendency for the increase of −871T/T genotype was observed in SLE patients with anti-Sm antibody (P=0.082). BLYS mRNA level was significantly elevated in the monocytes from individuals carrying −871T (P=0.010). In addition, although statistically not significant, 105Thr allele was slightly increased in patients with RA compared with controls (P=0.058). Characterizing the functional and clinical significance of these new SNPs requires further study.

Comparison of statistical power between 2^*2 allele frequency and allele positivity tables in case-control studies of complex disease genes

In case-control studies of complex disease genes, allele frequencies or allele positivities at candidate loci or markers are compared between cases and controls. Although 2 x 2 contingency tables based on allele frequency and allele positivity are generally used to perform simple statistical tests (e.g. a comparison of two proportions and a chi2 test), little is known about the difference in power between the two tables. In this study, we investigated the number of subjects required to obtain a power of 1-beta with a significance level of alpha for the allele frequency and allele positivity tables. A large difference in the required number of subjects was found between the two tables. Allele positivity tables were suitable for the detection of susceptibility alleles showing a dominant mode of inheritance (MOI). On the other hand, allele frequency tables were suitable for the identification of susceptibility alleles showing a recessive MOI or a multiplicative MOI. In the case of an additive MOI, a suitable table was determined by combining the frequency of the susceptibility allele and the penetrance. These results imply that there are cases in which true association is detected based on one contingency table and is not detected based on another. A simulation analysis revealed that the type I error rate was not much inflated under the null hypothesis of no association, even when a statistical test was performed twice using both allele frequency and allele positivity tables. In contrast, under the alternative hypothesis, the loss of power was marked when a test was performed once using an unsuitable table. In conclusion, statistical tests should be performed using both tables, without adjustment of multiplicity, in case-control studies of complex disease genes when the study objective is exploratory.

Association of a functional polymorphism in the IRF5 region with systemic sclerosis in a Japanese population

OBJECTIVE Interferon regulatory factor 5, an established susceptibility factor for systemic lupus erythematosus (SLE), plays a role in type I interferon and proinflammatory cytokine induction. A recent study showed association of a functional single-nucleotide polymorphism (SNP) in intron 1 of IRF5, rs2004640, with systemic sclerosis (SSc) in a European French population. We undertook the present study to determine whether IRF5 polymorphisms are also associated with a predisposition to SSc in Japanese. METHODS A case-control association study was performed for rs2004640 as well as for rs10954213 and rs2280714, all of which were previously reported to be associated with SLE, in 281 SSc patients and 477 healthy controls. Patients with SSc complicated by SLE or Sjögrens syndrome were excluded. Association of the rs2280714 genotype with messenger RNA (mRNA) levels of IRF5 and adjacently located transportin 3 (TNPO3) was examined using the GENEVAR database. RESULTS All 3 SNPs were significantly associated with SSc, with the rs2280714 A allele having the strongest association (allele frequency P=0.0012, odds ratio 1.42 [95% confidence interval 1.15-1.75]). Association was preferentially observed in subsets of patients with diffuse cutaneous SSc (dcSSc) and anti-topoisomerase I antibody positivity. Conditional analysis revealed that rs2280714 could account for most of the association of these SNPs, while an additional contribution of rs2004640 was also suggested for dcSSc. The genotype of rs2280714 was strongly associated with IRF5 mRNA expression, while only marginal association was detected with TNPO3 mRNA expression. CONCLUSION Association of IRF5 with SSc was replicated in a Japanese population. Whether the causal SNP is different among populations requires further investigation.

A compass that points to lupus: genetic studies on type I interferon pathway.

It was more than 20 years ago that patients with systemic lupus erythematosus (SLE) were first reported to display elevated serum levels of type I interferon (IFN). Since then, extensive studies revealed a crucial role for type I IFN in SLE pathogenesis. The current model proposes that small increase of type I IFN production by plasmacytoid dendritic cells (pDCs) is sufficient to induce unabated activation of immature peripheral DCs. IFN-matured DCs select and activate autoreactive T cells and B cells, rather than deleting them, resulting in peripheral tolerance breakdown, a characteristic feature of SLE. Furthermore, immune complexes provide an amplification loop to pDCs for further IFN production. In the past 5 years, high-throughput technologies such as expression profiling and single-nucleotide polymorphism (SNP) typing established the role of altered type I IFN system in SLE, and a detailed picture of its molecular mechanisms is beginning to emerge. In this review, we discuss two major lines of genetics studies on type I IFN pathway related to human SLE: (1) expression profiling of IFN-responsive genes and (2) disease-associated SNPs of IFN-related genes, especially IRF5 (IFN-regulatory factor 5). Lastly, we discuss how such genetic alterations in type I IFN pathway fit in the current model of SLE pathogenesis.

Crucial Role of Inhibitor of DNA Binding/Differentiation in the Vascular Endothelial Growth Factor-Induced Activation and Angiogenic Processes of Human Endothelial Cells

Angiogenesis plays a pivotal role in the aggressive proliferation of synovial cells in rheumatoid arthritis. We have previously reported the overexpression of inhibitor of DNA binding/differentiation (Id) in the endothelial cells within the synovial tissues of rheumatoid arthritis. In this study, we investigated the role of Id in inflammation and angiogenesis in an in vitro model using HUVECs. Vascular endothelial growth factor (VEGF) and TGFβ induced the expression of Id1 and Id3 in HUVECs. Forced expression of Id induced proliferative activity in HUVECs accompanied by down-regulation of p16INK4a. Overexpression of Id enhanced expression of ICAM-1 and E-selectin, and induced angiogenic processes such as transmigration, matrix metalloproteinase-2 and -9 expression, and tube formation. In contrast, knockdown of Id1 and Id3 with RNA interference abolished proliferation, activation, and angiogenic processes of HUVECs induced by VEGF. These results indicated that Id plays a crucial role in VEGF-induced signals of endothelial cells by causing activation and potentiation of angiogenic processes. Based on these findings, it was proposed that inhibition of expression and/or function of Id1 and Id3 may potentially be of therapeutic value for conditions associated with pathological angiogenesis.

Role of STAT4 polymorphisms in systemic lupus erythematosus in a Japanese population: a case-control association study of the STAT1-STAT4 region

IntroductionRecent studies identified STAT4 (signal transducers and activators of transcription-4) as a susceptibility gene for systemic lupus erythematosus (SLE). STAT1 is encoded adjacently to STAT4 on 2q32.2-q32.3, upregulated in peripheral blood mononuclear cells from SLE patients, and functionally relevant to SLE. This study was conducted to test whether STAT4 is associated with SLE in a Japanese population also, to identify the risk haplotype, and to examine the potential genetic contribution of STAT1. To accomplish these aims, we carried out a comprehensive association analysis of 52 tag single nucleotide polymorphisms (SNPs) encompassing the STAT1-STAT4 region.MethodsIn the first screening, 52 tag SNPs were selected based on HapMap Phase II JPT (Japanese in Tokyo, Japan) data, and case-control association analysis was carried out on 105 Japanese female patients with SLE and 102 female controls. For associated SNPs, additional cases and controls were genotyped and association was analyzed using 308 SLE patients and 306 controls. Estimation of haplotype frequencies and an association study using the permutation test were performed with Haploview version 4.0 software. Population attributable risk percentage was estimated to compare the epidemiological significance of the risk genotype among populations.ResultsIn the first screening, rs7574865, rs11889341, and rs10168266 in STAT4 were most significantly associated (P < 0.01). Significant association was not observed for STAT1. Subsequent association studies of the three SNPs using 308 SLE patients and 306 controls confirmed a strong association of the rs7574865T allele (SLE patients: 46.3%, controls: 33.5%, P = 4.9 × 10-6, odds ratio 1.71) as well as TTT haplotype (rs10168266/rs11889341/rs7574865) (P = 1.5 × 10-6). The association was stronger in subgroups of SLE with nephritis and anti-double-stranded DNA antibodies. Population attributable risk percentage was estimated to be higher in the Japanese population (40.2%) than in Americans of European descent (19.5%).ConclusionsThe same STAT4 risk allele is associated with SLE in Caucasian and Japanese populations. Evidence for a role of STAT1 in genetic susceptibility to SLE was not detected. The contribution of STAT4 for the genetic background of SLE may be greater in the Japanese population than in Americans of European descent.

Association of the FAM167A-BLK region with systemic sclerosis.

OBJECTIVE An association of single-nucleotide polymorphisms (SNPs) in the FAM167A (previously referred to as C8orf13)-BLK region with systemic lupus erythematosus (SLE) has been demonstrated in Caucasians and in Asians. Recent studies have shown that many genes, including IRF5, STAT4, and PTPN22, are shared susceptibility genes in multiple autoimmune diseases. We undertook the current study to examine whether the FAM167A-BLK region is also associated with susceptibility to systemic sclerosis (SSc). METHODS Japanese patients with SSc (n = 309) and healthy controls (n = 769) were enrolled in a 2-tiered case-control association study. In tier 1, 124 patients and 412 controls were tested to determine association of 16 tag SNPs encompassing the FAM167A-BLK region with SSc. In tier 2, an additional 185 patients and 357 controls were analyzed for SNP rs13277113. RESULTS Two haplotype blocks that correspond approximately to FAM167A and BLK were observed. In tier 1 of the study, the rs13277113A allele in the BLK block exhibited the most significant association with SSc after correction for multiple testing (permutated P = 0.024). Two SNP haplotypes formed by rs13277113 and the most significant SNP in the FAM167A block did not exhibit stronger association. When samples from tier 1 and tier 2 were combined, the rs13277113A allele was significantly associated with SSc (odds ratio 1.45 [95% confidence interval 1.17-1.79], P = 6.1 x 10(-4)). Association or a tendency toward association of rs13277113A with SSc was observed regardless of a patients autoantibody profile or whether a patient had diffuse cutaneous or limited cutaneous SSc. CONCLUSION Our findings indicate that the rs13277113A allele is associated not only with SLE but also with SSc and that the FAM167A-BLK region is a common genetic risk factor for both SLE and SSc.

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

Abstract 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 Vδ1γδT 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.