Myelin basic protein as a novel genetic risk factor in rheumatoid arthritis--a genome-wide study combined with immunological analyses

Monitoring of the pharmacological treatment availability in patients with multiple sclerosis in the Greater Poland population

Introduction

There is no clear explanation for the availability of multiple sclerosis (MS) pharmacological treatment for patients in Greater Poland and it can be assumed that the same reason is common in most of the developed countries in the United Europe. As an autoimmune disease MS can overlap with other diseases especially rheumatic disease (RD) as well as some feature of RD may mimic MS, such as MS-like syndrome in the course of primary Sjögren's syndrome. Therefore proper diagnosis and sufficient treatment of MS is important not only for neurologists but also for other clinicians including rheumatologists.The study aims to provide insights that could help healthcare managers create more effective logistical guidelines to improve the timely initiation of pharmacological treatment for MS.

Materials and methods

The analysis of the treatment of MS patients has been conducted on a group of 500 patients who were under the management of one healthcare center in Greater Poland.

Results

The results point to the different factors influencing the delay in the undertaking the pharmacological treatment, among others the age of the patient, waiting time for clinical evaluation and the final diagnosis from first symptoms to diagnosis, and the patient's waiting time from diagnosis to referral for qualification for treatment.

Conclusions

The outcomes of this study have the potential to serve as a valuable resource for healthcare managers. The study's findings could be used as a foundation for developing logistical guidelines aimed at enhancing the pharmacological treatment of MS patients.Furthermore, the study suggests that the reasons behind treatment delays in MS patients might be prevalent in many countries across the United Europe region. However, it's important to note that confirming this conclusion requires additional comparative studies.

Integrative analysis identifies potential causal methylation-mRNA regulation chains for rheumatoid arthritis

Genome-wide association studies have identified many genetic loci for rheumatoid arthritis (RA). However, causal factors underlying these loci were largely unknown. The aim of this study was to identify potential causal methylation-mRNA regulation chains for RA. We identified differentially expressed mRNAs and methylations and conducted summary statistic data-based Mendelian randomization (SMR) analysis to detect potential causal mRNAs and methylations for RA. Then causal inference test (CIT) was performed to determine if the methylation-mRNA pairs formed causal chains. We identified 11,170 mRNAs and 24,065 methylations that were nominally associated with RA. Among them, 197 mRNAs and 104 methylations passed the SMR test. According to physical positions, we defined 16 cis methylation-mRNA pairs and inferred 5 chains containing 4 methylations and 4 genes (BACH2, MBP, MX1 and SYNGR1) to be methylation→mRNA→RA causal chains. The effect of SYNGR1 expression in peripheral blood mononuclear cells on RA risk was found to be consistent in both the in-house and public data. The identified methylations located in CpG Islands that overlap promoters in the 5' region of the genes. The promoter regions showed long-range interactions with other enhancers and promoters, suggesting a regulatory potential of these methylations. Therefore, the present study provided a new integrative analysis strategy and highlighted potential causal methylation-mRNA chains for RA. Taking the evidences together, SYNGR1 promoter methylations most probably affect mRNA expressions and then affect RA risk.

[A case of possible elderly onset rheumatoid meningitis without arthritis]

A 93-year-old man was admitted to our hospital with disturbance of consciousness. Brain magnetic resonance imaging (MRI) showed hyperintensity of the subarachnoid space in the left frontal and parietal lobes on diffusion weighted imaging (DWI) and fluid attenuated inversion recovery (FLAIR). Gadolinium-enhancement of the pia mater was also observed. We did not perform biopsy because of a high risk of perioperative complication. Although physical examination found no evidence of the rheumatoid arthritis, rheumatoid factors and anti-cyclic citrullinated peptides antibodies were elevated. He was suspected to have rheumatoid meningitis. We treated him with intravenous methylprednisolone (0.5 g/day) for 3 days. Rheumatoid meningitis often shows hyperintensity of the subarachnoid space on the DWI and FLAIR, and steroid therapy is effective.

Recent Advances in Research Regarding Autoantibodies in Connective Tissue Diseases and Related Disorders

Connective tissue diseases (CTDs), also known as systemic autoimmune diseases, involve a variety of autoantibodies against cellular components. An important factor regarding these autoantibodies is that each antibody is exclusively related to a certain clinical feature of the disease type, which may prove useful in clinical practice. Thus far, more than 100 types of autoantibodies have been found in CTDs, and most of their target antigens have been identified. Many of these autoantigens are enzymes or regulators involved in important cellular functions, such as gene replication, transcription, repair/recombination, RNA processing, and protein synthesis, as well as proteins that form complexes with RNA and DNA. This article reviews the autoantibodies for each CTD, along with an assessment of their clinical significance, and provides suggestions regarding their utilization for clinical practice.

How to conduct research of rare autoimmune diseases

Rare autoimmune diseases are difficult to conduct researches in spite of present era with advanced scientific progress. Research using genetic approach is a promising way since genetic findings implicate causality of diseases. Still, there are multiple obstacles preventing genetic studies of rare diseases. Here, we list up the problems and propose solutions for them with detailed examples. The biggest problem is that it is difficult to collect a substantial number of DNA samples from patients with rare diseases. We propose to collaborate not only with academic institutions and hospitals but with patients' groups. Detailed examples include studies about Takayasu arteritis (TAK), relapsing polychondritis, and systemic sclerosis. In TAK, we identified IL12B, a key gene which seems to play a central role in the disease. After getting evidence of IL12p40 encoded by IL12B as a possible therapeutic target by showing similarities of the genetic background between TAK and ulcerative colitis, we performed a pilot clinical study of ustekinumab, a monoclonal antibody against IL12p40 for patients with refractory TAK and obtained good response. This is a good example of how genetic findings in a rare disease lead to development of new therapeutic option.

Autoantibodies against myelin sheath and S100β are associated with cognitive dysfunction in patients with rheumatoid arthritis

Rheumatoid arthritis (RA) has been associated with cognitive impairment and peripheral production of autoantibodies. Autoantibodies against central nervous system (CNS) proteins and S100 calcium-binding β (S100β) were found increased in diseases characterized by cognitive impairment like Alzheimer disease and Neuropsychiatric Systemic Lupus Erythematosus (NPSLE). The aim of this study was to investigate the plasma levels of autoantibodies against myelin basic protein (anti-MBP), myelin oligodendrocyte glycoprotein (anti-MOG) and S100β, and their relationships with cognitive performance in RA patients. Twenty patients with active rheumatoid arthritis and 19 age-, sex-, and schooling-matched healthy controls were recruited. Multiple dimensions of cognitive function were evaluated by structured clinical questionnaires. Autoantibodies and S100β levels were assessed by ELISAs. Patients had significantly higher levels of anti-MBP IgG (17.51 ± 1.36 vs. 5.24 ± 0.53 ng/mL), anti-MOG IgG (5.68 ± 1.34 vs. 0.51 ± 0.49 ng/mL), and S100β protein (2.24 ± 0.50 vs. 0.47 ± 0.06) than controls (all p < 0.0001). After adjusting for potential confounders, RA group presented worse cognitive performance involving the working memory and executive functions such as inhibition, flexibility, and mental control in parallel to higher autoantibodies and S100β levels than healthy controls (all p < 0.001). Levels of anti-MBP were negatively associated with delayed verbal recall (DVR; r = -0.42, p = 0.005), Stroop Color-Word (r = -0.48, p = 0.004), and N-Back Total scores (r = -0.59, p < 0.0001) and positively with Trail Making Test B (TMB, r = 0.53, p = 0.001). Negative correlation was found between levels of anti-MOG and DVR (r = -0.64, p < 0.0001), N-Back Total scores (r = -0.35, p = 0.03), Stroop Color-Word (r = -0.51, p = 0.001), and positively with TMB (r = 0.50, p = 0.003). S100β levels were associated with DVR (r = -0.51, p = 0.002), TMB (r = 0.46, p = 0.008), Stroop Color-Word (r = -0.67, p < 0.0001), and N-Back Total (r = -0.52, p = 0.003). RA is associated with impaired cognitive performance associated with higher levels of CNS-related autoantibodies and S100β levels. Given the importance of myelin integrity to cognition, our data indicate that these autoantibodies may be harmful to proper cognitive function.

Only rheumatoid factor-positive subset of anti-citrullinated peptide/protein antibody-negative rheumatoid arthritis may seroconvert to anti-citrullinated peptide/protein antibody-positive

AIM

Anti-citrullinated peptide/protein antibody (ACPA) has been reported to occur in about 60% of patients with early rheumatoid arthritis (RA), and about 80% in patients with established RA. While ACPA seroconversion is possible, previous reports have shown that it rarely occurs. We retrospectively determined the proportion of patients who underwent ACPA seroconversion and described the clinical characteristics of these cases.

METHODS

ACPA-negative RA patients who had undergone ACPA assessment more than once with an interval of 3 months or longer were investigated for ACPA seroconversion. The clinical characteristics of seroconverted patients were assessed.

RESULTS

In 149 ACPA-negative RA patients, only eight patients (5.4%) converted to ACPA-positive during follow-up. We found that all eight of the seroconverted cases were positive for rheumatoid factor (RF) and showed bone erosions by X-ray. Of 56 ACPA-negative RF-positive RA patients, 14.3% of them seroconverted to ACPA-positive. None of the ACPA-negative RF-negative RA patients seroconverted to ACPA-positive.

CONCLUSION

The proportion of total RA patients who experienced seroconversion from ACPA-negative to ACPA-positive was 5.4%. When ACPA-negative RA patients were subdivided into RF-negative and RF-positive subsets, only the RF-positive subset seroconverted to ACPA-positive. These results imply that RF-negative and RF-positive patients are distinct subsets within ACPA-negative RA patients.

Extensive Citrullination Promotes Immunogenicity of HSP90 through Protein Unfolding and Exposure of Cryptic Epitopes

Post-translational protein modifications such as citrullination have been linked to the breach of immune tolerance and clinical autoimmunity. Previous studies from our laboratory support this concept, demonstrating that autoantibodies targeting citrullinated isoforms of heat shock protein 90 (HSP90) are associated with rheumatoid arthritis complicated by interstitial lung disease. To further explore the relationship between citrullination and structural determinants of HSP90 immunogenicity, we employed a combination of ELISA-based epitope profiling, computational modeling, and mass-spectrometric sequencing of peptidylarginine deiminase (PAD)-modified protein. Remarkably, ELISAs involving selected citrullinated HSP90β/α peptides identified a key epitope corresponding to an internal Arg residue (R502 [HSP90β]/R510 [HSP90α]) that is normally buried within the crystal structure of native/unmodified HSP90. In vitro time/dose-response experiments reveal an ordered pattern of PAD-mediated deimination events culminating in citrullination of R502/R510. Conventional as well as scaled molecular dynamics simulations further demonstrate that citrullination of selected Arg residues leads to progressive disruption of HSP90 tertiary structure, promoting exposure of R502/R510 to PAD modification and subsequent autoantibody binding. Consistent with this process, ELISAs incorporating variably deiminated HSP90 as substrate Ag indicate a direct relationship between the degree of citrullination and the level of ex vivo Ab recognition. Overall, these data support a novel structural paradigm whereby citrullination-induced shifts in protein structure generate cryptic epitopes capable of bypassing B cell tolerance in the appropriate genetic context.

A Contra Capture Protein Array Platform for Studying Post-translationally Modified (PTM) Auto-antigenomes

Aberrant modifications of proteins occur during disease development and elicit disease-specific antibody responses. We have developed a protein array platform that enables the modification of many proteins in parallel and assesses their immunogenicity without the need to express, purify, and modify proteins individually. We used anticitrullinated protein antibodies (ACPAs) in rheumatoid arthritis (RA) as a model modification and profiled antibody responses to ∼190 citrullinated proteins in 20 RA patients. We observed unique antibody reactivity patterns in both clinical anticyclic citrullinated peptide assay positive (CCP+) and CCP- RA patients. At individual antigen levels, we detected antibodies against known citrullinated autoantigens and discovered and validated five novel antibodies against specific citrullinated antigens (osteopontin (SPP1), flap endonuclease (FEN1), insulin like growth factor binding protein 6 (IGFBP6), insulin like growth factor I (IGF1) and stanniocalcin-2 (STC2)) in RA patients. We also demonstrated the utility of our innovative array platform in the identification of immune-dominant epitope(s) for citrullinated antigens. We believe our platform will promote the study of post-translationally modified antigens at a breadth that has not been achieved before, by both identifying novel autoantigens and investigating their roles in disease development. The developed platforms can potentially be used to study many autoimmune disease-relevant modifications and their immunogenicity.

Increased incidence of rheumatoid arthritis in multiple sclerosis: A nationwide cohort study

Past studies have shown inconsistent results on whether there is an association between multiple sclerosis (MS) and rheumatoid arthritis. To investigate the possible relationship between the 2 autoimmune diseases, we performed a nationwide cohort study utilizing the National Health Insurance Research Database and the Registry of Catastrophic Illness.A total of 1456 newly diagnosed patients with MS and 10,362 control patients were matched for age, sex, and initial diagnosis date. Patients with MS had a higher incidence of rheumatoid arthritis (age-adjusted standardized incidence ratio: 1.72; 95% confidence interval = 1.01-2.91). There was a positive correlation in being diagnosed with rheumatoid arthritis in patients previously diagnosed with MS when stratified by sex and age. The strength of this association remained statistically significant after adjusting for sex, age, and smoking history (hazard ratio: 1.78, 95% confidence interval = 1.24-2.56, P = 0.002).In conclusion, this study demonstrates that a diagnosis of MS increased the likelihood of a subsequent diagnosis of rheumatoid arthritis in patients, independent of sex, age, and smoking history.

Recent Advances in Defining the Genetic Basis of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is the most common inflammatory arthritis and exhibits genetic overlap with other autoimmune and inflammatory disorders. Although predominant associations with the HLA-DRB1 locus have been known for decades, recent data have revealed additional insight into the likely causative variants within HLA-DRB1 as well as within other HLA loci that contribute to disease risk. In addition, more than 100 common variants in non-HLA loci have been implicated in disease susceptibility. Genetic factors are involved not only in the development of RA, but also with various disease subphenotypes, including production and circulating levels of autoantibodies and joint destruction. The major current challenge is to integrate these new data into a precise understanding of disease pathogenesis, including the critical cell types and molecular networks involved as well as interactions with environmental factors. We predict that delineating the functional effects of genetic variants is likely to drive new diagnostic and therapeutic approaches to the disease.

Rheumatoid Factor Is Associated With the Distribution of Hand Joint Destruction in Rheumatoid Arthritis

OBJECTIVE

Rheumatoid arthritis (RA) is a chronic disease leading to joint destruction. Although many studies have addressed factors potentially correlated with the speed of joint destruction, less attention has been paid to the distribution of joint destruction in patients with RA. In this study, destruction of the hand bones in patients with RA was classified into 2 anatomic subgroups, the fingers and the non-fingers, with the aim of analyzing which factors are associated with destruction of the finger joints.

METHODS

A total of 1,215 Japanese patients with RA were recruited from 2 different populations. The degree of joint destruction was assessed using the total modified Sharp/van der Heijde score (SHS) of radiographic joint damage. The SHS score of joint damage in the finger joints was used as the dependent variable, and the SHS score in the non-finger joints was used as a covariate. Age, sex, disease duration, smoking, C-reactive protein level, treatment for RA, and positivity for and levels of anti-citrullinated protein antibodies and rheumatoid factor (RF) were evaluated as candidate correlates. Overall effect sizes were assessed in a meta-analysis. In addition, associations observed in the Japanese patients were compared to those in a cohort of 157 Dutch RA patients in the BeSt study (a randomized, controlled trial involving 4 different strictly specified treatment strategies for early RA).

RESULTS

Not surprisingly, disease duration in Japanese patients with RA was associated with the finger SHS score (P ≤ 0.00037). Both positivity for and levels of RF showed significant associations with the finger SHS score after adjustment for covariates (P = 0.0022 and P = 8.1 × 10(-7) , respectively). These associations were also true in relation to the time-averaged finger SHS score. An association between RF positivity and the finger SHS score was also observed in Dutch patients with RA in the BeSt study (P = 0.049).

CONCLUSION

Positivity for and levels of RF are associated with finger joint destruction independent of non-finger joint destruction and other covariates. Our findings suggest that there are different mechanisms of joint destruction operating in the finger joints of patients with RA.

An association between amino acid position 74 of HLA-DRB1 and anti-citrullinated protein antibody levels in Japanese patients with anti-citrullinated protein antibody-positive rheumatoid arthritis

OBJECTIVE

Anti-citrullinated protein antibodies (ACPAs) are highly specific to rheumatoid arthritis (RA), and strong associations between HLA-DRB1 alleles and ACPA levels have been detected in RA patients. We undertook this study to elucidate the associations between particular amino acid positions in HLA-DRB1 and ACPA levels in patients with RA.

METHODS

We analyzed ACPA data on a total of 4,371 Japanese ACPA-positive RA patients in whom HLA-DRB1 allele genotyping had been performed. Generalized linear regression analysis and omnibus testing were carried out to determine associations of HLA-DRB1 alleles, amino acid residues, or amino acid positions with levels of ACPA.

RESULTS

HLA-DRB1*09:01 and HLA-DR15 were confirmed to be associated with ACPA levels. HLA-DRB1*08:03 and DRB1*14:06 were associated with reduced and increased ACPA levels, respectively. We detected a strong association between ACPA levels and amino acid position 74 (P = 1.9 × 10(-51) ). The association was mainly conferred by alanine residue (P = 4.5 × 10(-51) ). After adjustment for position 74, amino acid positions 60 and 57 were found to be associated with ACPA levels. Amino acid positions 74 and 57 had previously been reported to be associated with susceptibility to ACPA-positive RA in Asians. Combinations of the amino acid residues at position 74 and position 60 or 57 could induce improvement in Akaike's information criterion comparable to that induced by the 5 significant HLA-DRB1 alleles (HLA-DRB1*08:03, DRB1*09:01, DRB1*14:06, DRB1*15:01, and DRB1*15:02).

CONCLUSION

Amino acid position 74 in HLA-DRB1 is strongly associated with ACPA levels in ACPA-positive RA, as well as with RA susceptibility. The mechanisms of ACPA production and susceptibility to ACPA-positive RA seem to partly overlap.

Revisited HLA and non-HLA genetics of Takayasu arteritis--where are we?

Takayasu arteritis (TAK) is an immune-mediated vasculitis affecting large arteries first reported in 1908 from Japan. Case reports of familial onset of TAK from Japan and other countries indicated genetic contribution to TAK onset beyond ethnicity. Genetic studies of TAK have been performed mainly addressing the human leukocyte antigen (HLA) locus. HLA genetic studies of TAK that have previously been reported are reviewed in this manuscript. HLA-B*52:01 is associated with TAK beyond population. Many of the associations other than HLA-B*52:01 can be explained by a haplotype with HLA-B*52:01. HLA-B*67:01 is a novel susceptibility HLA-B allele to TAK confirmed in the Japanese population. Further independent associations are suggested in the HLA locus. Involvement of the 171st and 67th amino acid residues with TAK onset has been indicated. The 67th amino acid may explain the difference in susceptibility effects to TAK and Behçet's disease between HLA-B*52:01 and *51:01. HLA-B*52:01 is associated not only with TAK susceptibility but also with clinical phenotypes. Recent genome-wide association studies of TAK revealed multiple non-HLA susceptibility genes. In particular, the IL12B region seems to have a central role in TAK onset and its progression. Whether TAK and giant cell arteritis (GCA), the other vasculitis affecting large arteries, are the same disease is an interesting question to address in spite of different clinical manifestations between the two diseases. GCA is associated with HLA-DR4, which is not associated with TAK. GCA is not associated with HLA-Bw52. These two diseases seem not to share non-HLA susceptibility loci based on the recent genetic studies.

Genetic architectures of seropositive and seronegative rheumatic diseases

Rheumatoid arthritis, systemic lupus erythematosus, ankylosing spondylitis and some other rheumatic diseases are genetically complex, with evidence of familial clustering, but not of Mendelian inheritance. These diseases are thought to result from contributions and interactions of multiple genetic and nongenetic risk factors, which have small effects individually. Genome-wide association studies (GWAS) of large collections of data from cases and controls have revealed many genetic factors that contribute to non-Mendelian rheumatic diseases, thus providing insights into associated molecular mechanisms. This Review summarizes methods for the identification of gene variants that influence genetically complex diseases and focuses on what we have learned about the rheumatic diseases for which GWAS have been reported. Our review of the disease-associated loci identified to date reveals greater sharing of risk loci among the groups of seropositive (diseases in which specific autoantibodies are often present) or seronegative diseases than between these two groups. The nature of the shared and discordant loci suggests important similarities and differences among these diseases.

Anti-citrullinated peptide/protein antibody (ACPA)-negative RA shares a large proportion of susceptibility loci with ACPA-positive RA: a meta-analysis of genome-wide association study in a Japanese population

Introduction

Although susceptibility genes for anti-citrullinated peptide/protein antibodies (ACPA)-positive rheumatoid arthritis (RA) have been successfully discovered by genome-wide association studies (GWAS), little is known about the genetic background of ACPA-negative RA. We intended to elucidate genetic background of ACPA-negative RA.

Method

We performed a meta-analysis of GWAS comprising 670 ACPA-negative RA and 16,891 controls for 1,948,138 markers, followed by a replication study of the top 35 single nucleotide polymorphisms (SNPs) using 916 cases and 3,764 controls. Inverse-variance method was applied to assess overall effects. To assess overlap of susceptibility loci between ACPA-positive and -negative RA, odds ratios (ORs) of the 21 susceptibility markers to RA in Japanese were compared between the two subsets. In addition, SNPs were stratified by the p-values in GWAS meta-analysis for either ACPA-positive RA or ACPA-negative RA to address the question whether weakly-associated genes were also shared. The correlations between ACPA-positive RA and the subpopulations of ACPA-negative RA (rheumatoid factor (RF)-positive and RF-negative subsets) were also addressed.

Results

Rs6904716 in LEMD2 of the human leukocyte antigen (HLA) locus showed a borderline association with ACPA-negative RA (overall p = 5.7 × 10⁻⁸), followed by rs6986423 in CSMD1 (p = 2.4 × 10⁻⁶) and rs17727339 in FCRL3 (p = 1.4 × 10⁻⁵). ACPA-negative RA showed significant correlations of ORs with ACPA-positive RA for the 21 susceptibility SNPs and non-HLA SNPs with p-values far from significance. These significant correlations with ACPA-positive RA were true for ACPA-negative RF-positive and ACPA-negative RF-negative RA. On the contrary, positive correlations were not observed between the ACPA-negative two subpopulations.

Conclusion

Many of the susceptibility loci were shared between ACPA-positive and -negative RA.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0623-4) contains supplementary material, which is available to authorized users.

Significant association of periodontal disease with anti-citrullinated peptide antibody in a Japanese healthy population - The Nagahama study

Anti-citrullinated peptide antibody (ACPA) is a highly specific autoantibody to rheumatoid arthritis (RA). Recent studies have revealed that periodontal disease (PD) is closely associated with RA and production of ACPA in RA. Analyses of associations between PD and ACPA production in a healthy population may deepen our understandings. Here, we analyzed a total of 9554 adult healthy subjects. ACPA and IgM-rheumatoid factor (RF) was quantified and PD status was evaluated using the number of missing teeth (MT), the Community Periodontal Index (CPI) and Loss of Attachment (LA) for these subjects. PD status was analyzed for its association with the positivity and categorical levels of ACPA and RF conditioned for covariates which were shown to be associated with PD, ACPA or RF. As a result, all of MT, CPI and LA showed suggestive or significant associations with positivity (p = 0.024, 0.0042 and 0.037, respectively) and levels of ACPA (p ≤ 0.00031), but none of the PD parameters were associated with those of RF. These association patterns were also observed when we analyzed 6206 non-smokers of the participants. The significant associations between PD parameters and positivity and levels of ACPA in healthy population support the fundamental involvement of PD with ACPA production.

A genome-wide association study of serum levels of prostate-specific antigen in the Japanese population

BACKGROUND

Prostate-specific antigen (PSA) is a useful marker for prostate cancer (PCa) and is widely used for screening of PCa. Previous studies have shown that genetic components influence the levels of PSA, and some of these genetic components would lead to better diagnostic sensitivity and specificity to PCa. However, genetic studies for PSA from Asian countries are limited. Our aim was to identify genetic components influencing PSA levels in the Japanese population using genome-wide association study (GWAS) and to analyse whether genetic components would lead to better screening abilities of PCa.

METHODS

We performed a GWAS comprising 1086 male subjects using 303 283 single nucleotide proteins, followed by a replication study of 1302 subjects. PSA levels were quantified by chemiluminescence immunoassay method. Quantitative linear regression analysis was performed to assess genetic components of PSA levels. A total of 413 subjects with prostate biopsies were analysed to examine whether genetic determinants would improve diagnostic ability.

RESULTS

Rs16856139 in SLC45A3, the same region as the previous Chinese study, showed an overall significant association with PSA levels (p=2.4×10(-11)) along with rs1058205 in KLK3. In silico analysis revealed significant association between rs16856139 and expression of SLC45A3. Genetic scores of PSA showed a dose-dependent decrease of area under curve (AUC) of PCa and successfully subgrouped the individuals with significantly different AUC (p≤0.0097).

CONCLUSIONS

Rs16856139, associated with the expression of SLC45A3, is significantly associated with the levels of PSA in the Japanese population. Classification of subjects based on PSA genetic determinants would improve screening ability of PSA to detect PCa.

RAvariome: a genetic risk variants database for rheumatoid arthritis based on assessment of reproducibility between or within human populations

Rheumatoid arthritis (RA) is a common autoimmune inflammatory disease of the joints and is caused by both genetic and environmental factors. In the past six years, genome-wide association studies (GWASs) have identified many risk variants associated with RA. However, not all associations reported from GWASs are reproduced when tested in follow-up studies. To establish a reliable set of RA risk variants, we systematically classified common variants identified in GWASs by the degree of reproducibility among independent studies. We collected comprehensive genetic associations from 90 papers of GWASs and meta-analysis. The genetic variants were assessed according to the statistical significance and reproducibility between or within nine geographical populations. As a result, 82 and 19 single nucleotide polymorphisms (SNPs) were confirmed as intra- and inter-population-reproduced variants, respectively. Interestingly, majority of the intra-population-reproduced variants from European and East Asian populations were not common in two populations, but their nearby genes appeared to be the components of common pathways. Furthermore, a tool to predict the individual’s genetic risk of RA was developed to facilitate personalized medicine and preventive health care. For further clinical researches, the list of reliable genetic variants of RA and the genetic risk prediction tool are provided by open access database RAvariome.

Database URL: http://hinv.jp/hinv/rav/

Genetics in rheumatoid arthritis beyond HLA genes: what meta-analyses have shown?

OBJECTIVE

Rheumatoid arthritis (RA) is a complex disorder with many genetic and environmental factors to account for disease susceptibility. Individual genetic association studies usually suffer from small sample size leading to biased results of polymorphisms association with RA liability. Therefore, meta-analyses seem to resolve this limitation, up to a point, increasing the power of statistical analyses. In this review, we summarize the current knowledge of non-HLA genetic factors contributing to RA predisposition based on meta-analyses.

METHODS

Using the key words: rheumatoid arthritis, meta-analysis, and polymorphism, we searched the PubMed database for the associated articles. Up to the middle of November 2012, seventy-nine articles fulfilled the criteria and highlighted the current findings on the genetic factors contributing to RA susceptibility.

RESULTS

The association with RA was confirmed for 32 gene polymorphisms, being population specific in some cases. However, meta-analyses did not confirm an association in case of 16 gene variants, previously studied in individual studies for their association with RA.

CONCLUSIONS

The use of bioinformatics tools and functional studies of the summarized implicated genes in RA pathogenesis could shed light on the molecular pathways related to the disorder, helping to the development of new drug targets for a better treatment of RA.

PLD4 as a novel susceptibility gene for systemic sclerosis in a Japanese population

OBJECTIVE

Systemic sclerosis (SSc) is an autoimmune disease for which multiple susceptibility genes have been reported. Genome-wide association studies have shown that large numbers of susceptibility genes are shared among autoimmune diseases. Recently, our group identified 9 novel susceptibility genes associated with rheumatoid arthritis (RA) in a Japanese population. The aim of this study was to elucidate whether the 18 genes that displayed associations or suggestive associations for RA in our previous study are associated with SSc in Japanese.

METHODS

We performed an association study that included 415 patients with SSc and 16,891 control subjects, followed by a replication study that included 315 patients and 21,054 control subjects. The 18 markers reported to display association with RA were analyzed for their associations with SSc in the first study, and 5 markers were further analyzed in the replication study. The inverse variance method was used to evaluate the associations of these markers with SSc in a combined study.

RESULTS

In the phospholipase D4 gene (PLD4), rs2841277 displayed a significant association with SSc in Japanese patients (P = 0.00017). We observed that rs2841280 in exon 2 of PLD4 was in strong linkage disequilibrium with rs2841277 and introduced an amino acid alteration. We also observed associations between SSc and rs6932056 in TNFAIP3 and rs2280381 in IRF8 (P = 0.0000095 and P = 0.0030, respectively), both of which displayed associations with SSc in a European population.

CONCLUSION

We determined that PLD4 is a novel susceptibility gene for SSc in Japanese, thus confirming the involvement of PLD4 in autoimmunity. Associations between SSc and TNFAIP3 or IRF8 were also detected in our Japanese population. SSc and RA appear to share relatively large proportions of their genetic backgrounds.

Cutting-edge issues in autoimmunity and allergy of the digestive system

Autoimmunity and allergy involving the digestive system may be considered as paradigmatic for numerous common themes of complex diseases secondary to tolerance breakdown. Among gastrointestinal autoimmune diseases, for example, we encounter diseases in which a clear environmental trigger is identified (i.e., celiac disease), serum autoantibodies are most specific (i.e., primary biliary cirrhosis), or in which the disease pathophysiology is clearly understood (i.e., autoimmune gastritis). Similarly, it is intriguing that the gastrointestinal tract and the liver circulation represent the crucial environment for the development of immune tolerance. This issue is dedicated to the discussion of recent concepts while identifying two major common issues, i.e., the need for serum biomarkers and the role of vitamin D. Other common themes characterize the etiology and effector mechanisms of these and other autoimmune diseases and are discussed in each cutting-edge overview.

ACPA-negative RA consists of two genetically distinct subsets based on RF positivity in Japanese

HLA-DRB1, especially the shared epitope (SE), is strongly associated with rheumatoid arthritis (RA). However, recent studies have shown that SE is at most weakly associated with RA without anti-citrullinated peptide/protein antibody (ACPA). We have recently reported that ACPA-negative RA is associated with specific HLA-DRB1 alleles and diplotypes. Here, we attempted to detect genetically different subsets of ACPA-negative RA by classifying ACPA-negative RA patients into two groups based on their positivity for rheumatoid factor (RF). HLA-DRB1 genotyping data for totally 954 ACPA-negative RA patients and 2,008 healthy individuals in two independent sets were used. HLA-DRB1 allele and diplotype frequencies were compared among the ACPA-negative RF-positive RA patients, ACPA-negative RF-negative RA patients, and controls in each set. Combined results were also analyzed. A similar analysis was performed in 685 ACPA-positive RA patients classified according to their RF positivity. As a result, HLA-DRB1*04:05 and *09:01 showed strong associations with ACPA-negative RF-positive RA in the combined analysis (p = 8.8×10⁻⁶ and 0.0011, OR: 1.57 (1.28–1.91) and 1.37 (1.13–1.65), respectively). We also found that HLA-DR14 and the HLA-DR8 homozygote were associated with ACPA-negative RF-negative RA (p = 0.00022 and 0.00013, OR: 1.52 (1.21–1.89) and 3.08 (1.68–5.64), respectively). These association tendencies were found in each set. On the contrary, we could not detect any significant differences between ACPA-positive RA subsets. As a conclusion, ACPA-negative RA includes two genetically distinct subsets according to RF positivity in Japan, which display different associations with HLA-DRB1. ACPA-negative RF-positive RA is strongly associated with HLA-DRB1*04:05 and *09:01. ACPA-negative RF-negative RA is associated with DR14 and the HLA-DR8 homozygote.