The TRAF1/C5 region is a risk factor for polyarthritis in juvenile idiopathic arthritis

TRAF1 Deficiency in Macrophages Drives Exacerbated Joint Inflammation in Rheumatoid Arthritis

The tumor necrosis factor receptor-associated factor 1 (TRAF1) plays a key role in promoting lymphocyte survival, proliferation, and cytokine production. Recent evidence showed that TRAF1 plays opposing roles in monocytes and macrophages where it controls NF-κB activation and limits pro-inflammatory cytokine production as well as inflammasome-dependent IL-1β secretion. Importantly, TRAF1 polymorphisms have been strongly linked to an increased risk of rheumatoid arthritis (RA). However, whether and how TRAF1 contributes to RA pathogenesis is not fully understood. Moreover, investigating the role of TRAF1 in driving RA pathogenesis is complicated by its multifaceted and opposing roles in various immune cells. In this study, we subjected wildtype (WT) mice to the collagen antibody-induced arthritis (CAIA) model of RA and injected them intra-articularly with WT- or TRAF1-deficient macrophages. We show that mice injected with TRAF1-deficient macrophages exhibited significantly exacerbated joint inflammation, immune cell infiltration, and tissue damage compared to mice injected with WT macrophages. This study may lay the groundwork for novel therapies for RA that target TRAF1 in macrophages.

A systematic strategy for identifying causal single nucleotide polymorphisms and their target genes on Juvenile arthritis risk haplotypes

BACKGROUND

Although genome-wide association studies (GWAS) have identified multiple regions conferring genetic risk for juvenile idiopathic arthritis (JIA), we are still faced with the task of identifying the single nucleotide polymorphisms (SNPs) on the disease haplotypes that exert the biological effects that confer risk. Until we identify the risk-driving variants, identifying the genes influenced by these variants, and therefore translating genetic information to improved clinical care, will remain an insurmountable task. We used a function-based approach for identifying causal variant candidates and the target genes on JIA risk haplotypes.

METHODS

We used a massively parallel reporter assay (MPRA) in myeloid K562 cells to query the effects of 5,226 SNPs in non-coding regions on JIA risk haplotypes for their ability to alter gene expression when compared to the common allele. The assay relies on 180 bp oligonucleotide reporters ("oligos") in which the allele of interest is flanked by its cognate genomic sequence. Barcodes were added randomly by PCR to each oligo to achieve > 20 barcodes per oligo to provide a quantitative read-out of gene expression for each allele. Assays were performed in both unstimulated K562 cells and cells stimulated overnight with interferon gamma (IFNg). As proof of concept, we then used CRISPRi to demonstrate the feasibility of identifying the genes regulated by enhancers harboring expression-altering SNPs.

RESULTS

We identified 553 expression-altering SNPs in unstimulated K562 cells and an additional 490 in cells stimulated with IFNg. We further filtered the SNPs to identify those plausibly situated within functional chromatin, using open chromatin and H3K27ac ChIPseq peaks in unstimulated cells and open chromatin plus H3K4me1 in stimulated cells. These procedures yielded 42 unique SNPs (total = 84) for each set. Using CRISPRi, we demonstrated that enhancers harboring MPRA-screened variants in the TRAF1 and LNPEP/ERAP2 loci regulated multiple genes, suggesting complex influences of disease-driving variants.

CONCLUSION

Using MPRA and CRISPRi, JIA risk haplotypes can be queried to identify plausible candidates for disease-driving variants. Once these candidate variants are identified, target genes can be identified using CRISPRi informed by the 3D chromatin structures that encompass the risk haplotypes.

Identification of a regulatory pathway governing TRAF1 via an arthritis-associated non-coding variant

TRAF1/C5 was among the first loci shown to confer risk for inflammatory arthritis in the absence of an associated coding variant, but its genetic mechanism remains undefined. Using Immunochip data from 3,939 patients with juvenile idiopathic arthritis (JIA) and 14,412 control individuals, we identified 132 plausible common non-coding variants, reduced serially by single-nucleotide polymorphism sequencing (SNP-seq), electrophoretic mobility shift, and luciferase studies to the single variant rs7034653 in the third intron of TRAF1. Genetically manipulated experimental cells and primary monocytes from genotyped donors establish that the risk G allele reduces binding of Fos-related antigen 2 (FRA2), encoded by FOSL2, resulting in reduced TRAF1 expression and enhanced tumor necrosis factor (TNF) production. Conditioning on this JIA variant eliminated attributable risk for rheumatoid arthritis, implicating a mechanism shared across the arthritis spectrum. These findings reveal that rs7034653, FRA2, and TRAF1 mediate a pathway through which a non-coding functional variant drives risk of inflammatory arthritis in children and adults.

Spondyloarthritides: Theories and beyond

Spondyloarthritides (SpA) are a family of interrelated rheumatic disorders with a typical disease onset ranging from childhood to middle age. If left untreated, they lead to a severe decrease in patients' quality of life. A succesfull treatment strategy starts with an accurate diagnosis which is achieved through careful analysis of medical symptoms. Classification criterias are used to this process and are updated on a regular basis. Although there is a lack of definite knowledge on the disease etiology of SpA, several studies have paved the way for understanding plausible risk factors and developing treatment strategies. The significant increase of HLA-B27 positivity in SpA patients makes it a strong candidate as a predisposing factor and several theories have been proposed to explain HLA-B27 driven disease progression. However, the presence of HLA-B27 negative patients underlines the presence of additional risk factors. The current treatment options for SpAs are Non-Steroidal Anti-Inflammatory Drugs (NSAIDs), TNF inhibitors (TNFis), Disease-Modifying Anti-Rheumatic Drugs (DMARDs) and physiotherapy yet there are ongoing clinical trials. Anti IL17 drugs and targeted synthetic DMARDs such as JAK inhibitors are also emerging as treatment alternatives. This review discusses the current diagnosis criteria, treatment options and gives an overview of the previous findings and theories to clarify the possible contributors to SpA pathogenesis with a focus on Ankylosing Spondylitis (AS) and enthesitis-related arthritis (ERA).

The immunological significance of tumor necrosis factor receptor-associated factors (TRAFs)

The tumor necrosis factor receptor (TNFR)-associated factor (TRAF) family of molecules are intracellular signaling adaptors and control diverse signaling pathways mediated not only by the TNFR superfamily and the Toll-like receptor/interleukin-1 receptor superfamily but also by unconventional cytokine receptors such as IL-6 and IL-17 receptors. There are seven family members, TRAF1 to TRAF7, in mammals. Exaggerated immune responses induced through TRAF signaling downstream of these receptors often lead to inflammatory and autoimmune diseases including rheumatoid arthritis, inflammatory bowel disease, psoriasis and autoinflammatory syndromes, and thus those signals are major targets for therapeutic intervention. For this reason, it has been very important to understand signaling mechanisms regulated by TRAFs that greatly impact on life/death decisions and the activation, differentiation and survival of cells of the innate and adaptive immune systems. Accumulating evidence suggests that dysregulated cellular expression and/or signaling of TRAFs causes overproduction of proinflammatory cytokines, which facilitates aberrant activation of immune cells. In this review, I will explain the structural and functional aspects that are responsible for the cellular activity and disease outcomes of TRAFs, and summarize the findings of recent studies on TRAFs in terms of how individual TRAF family molecules regulates biological and disease processes in the body in both positive and negative ways. This review also discusses how TRAF mutations contribute to human disease.

Immunome perturbation is present in patients with juvenile idiopathic arthritis who are in remission and will relapse upon anti-TNFα withdrawal

OBJECTIVES

Biologics treatment with antitumour necrosis factor alpha (TNFα) is efficacious in patients with juvenile idiopathic arthritis (JIA). Despite displaying clinical inactivity during treatment, many patients will flare on cessation of therapy. The inability to definitively discriminate patients who will relapse or continue to remain in remission after therapy withdrawal is currently a major unmet medical need. CD4 T cells have been implicated in active disease, yet how they contribute to disease persistence despite treatment is unknown.

METHODS

We interrogated the circulatory reservoir of CD4+ immune subsets at the single-cell resolution with mass cytometry (cytometry by time of flight) of patients with JIA (n=20) who displayed continuous clinical inactivity for at least 6 months with anti-TNFα and were subsequently withdrawn from therapy for 8 months, and scored as relapse or remission. These patients were examined prior to therapy withdrawal for putative subsets that could discriminate relapse from remission. We verified on a separate JIA cohort (n=16) the dysregulation of these circulatory subsets 8 months into therapy withdrawal. The immunological transcriptomic signature of CD4 memory in relapse/remission patients was examined with NanoString.

RESULTS

An inflammatory memory subset of CD3+CD4+CD45RA-TNFα+ T cells deficient in immune checkpoints (PD1-CD152-) was present in relapse patients prior to therapy withdrawal. Transcriptomic profiling reveals divergence between relapse and remission patients in disease-centric pathways involving (1) T-cell receptor activation, (2) apoptosis, (3) TNFα, (4) nuclear factor-kappa B and (5) mitogen-activated protein kinase signalling.

CONCLUSIONS

A unique discriminatory immunomic and transcriptomic signature is associated with relapse patients and may explain how relapse occurs.

Nonendocrine mechanisms of sex bias in rheumatic diseases

Rheumatic diseases affect a wide range of individuals of all ages, but the most common diseases occur more frequently in women than in men, at ratios of up to ten women to one man. Despite a growing number of studies on sex bias in rheumatic diseases, sex-specific health care is limited and sex specificity is not systematically integrated into treatment regimens. Women and men differ in three major biological points: the number of X chromosomes per cell, the type and quantities of sex hormones present and the ability to be pregnant, all of which have immunological consequences. Could a greater understanding of these differences lead to a new era of personalized sex-specific medicine? This Review focuses on the main genetic and epigenetic mechanisms that have been put forward to explain sex bias in rheumatic diseases, including X chromosome inactivation, sex chromosome aneuploidy and microchimerism. The influence of sex hormones is not discussed in detail in this Review, as it has been well described elsewhere. Understanding the sex-specific factors that contribute to the initiation and progression of rheumatic diseases will enable progress to be made in the diagnosis, treatment and management of all patients with these conditions.

TRAF1 Signaling in Human Health and Disease

Tumor necrosis factor receptor (TNFR) associated factor 1 (TRAF1) is a signaling adaptor first identified as part of the TNFR2 signaling complex. TRAF1 plays a key role in pro-survival signaling downstream of TNFR superfamily members such as TNFR2, LMP1, 4-1BB, and CD40. Recent studies have uncovered another role for TRAF1, independent of its role in TNFR superfamily signaling, in negatively regulating Toll-like receptor and Nod-like receptor signaling, through sequestering the linear ubiquitin assembly complex, LUBAC. TRAF1 has diverse roles in human disease. TRAF1 is overexpressed in many B cell related cancers and single nucleotide polymorphisms (SNPs) in TRAF1 have been linked to non-Hodgkin's lymphoma. Genome wide association studies have identified an association between SNPs in the 5' untranslated region of the TRAF1 gene with increased incidence and severity of rheumatoid arthritis and other rheumatic diseases. The loss of TRAF1 from chronically stimulated CD8 T cells results in desensitization of the 4-1BB signaling pathway, thereby contributing to T cell exhaustion during chronic infection. These apparently opposing roles of TRAF1 as both a positive and negative regulator of immune signaling have led to some confusion in the literature. Here we review the role of TRAF1 as a positive and negative regulator in different signaling pathways. Then we discuss the role of TRAF1 in human disease, attempting to reconcile seemingly contradictory roles based on current knowledge of TRAF1 signaling and biology. We also discuss avenues for future research to further clarify the impact of TRAF1 in human disease.

Association of TRAF1-C5 with risk of uveitis in juvenile idiopathic arthritis

OBJECTIVES

Numerous single nucleotide polymorphisms (SNPs) have been associated with JIA, but few of these studies were replicated. We conducted a candidate-gene approach study to assess if some SNPs could be related to clinical subtypes or other clinical features of the juvenile idiopathic arthritis (JIA) such as the risk of uveitis, ANA positivity and the age at onset.

METHODS

SNPs in six genes were analysed: PTPN22, STAT4, TRAF1-C5, TGFbeta, TNFAIP3, and C12orf30. We retrospectively included 104 JIA patients, fulfilling the ILAR classification criteria. Association between SNPs and JIA clinical subtypes, the presence of ANA, risk of uveitis and age at onset was evaluated using a Chi² test or a Fischer test.

RESULTS

No associations between different clinical subtypes as well as presence of ANA and the 6 SNPs were found. However, the AA genotype of TRAF1-C5 appeared associated in a subgroup of patients with uveitis in oligoarticular and polyarticular forms [OR 3.77 (95% CI: 1.1067, 12.8527); P=0.066]. Furthermore, AA TRAF1-C5 was significantly more frequent in antinuclear antibodies (ANA) positive patients presenting uveitis, compared to patients without uveitis and without ANA (P<0.05).

CONCLUSION

TRAF1-C5 genotype could identify JIA patients with a risk to develop uveitis especially in oligo and polyarticular forms and among ANA-positive children. Given the moderate size of our cohort, this association has to be confirmed in other studies.

Integration of summary data from GWAS and eQTL studies predicts complex trait gene targets

Genome-wide association studies (GWAS) have identified thousands of genetic variants associated with human complex traits. However, the genes or functional DNA elements through which these variants exert their effects on the traits are often unknown. We propose a method (called SMR) that integrates summary-level data from GWAS with data from expression quantitative trait locus (eQTL) studies to identify genes whose expression levels are associated with a complex trait because of pleiotropy. We apply the method to five human complex traits using GWAS data on up to 339,224 individuals and eQTL data on 5,311 individuals, and we prioritize 126 genes (for example, TRAF1 and ANKRD55 for rheumatoid arthritis and SNX19 and NMRAL1 for schizophrenia), of which 25 genes are new candidates; 77 genes are not the nearest annotated gene to the top associated GWAS SNP. These genes provide important leads to design future functional studies to understand the mechanism whereby DNA variation leads to complex trait variation.

Immunogenetics of juvenile idiopathic arthritis: A comprehensive review

Juvenile idiopathic arthritis (JIA) is the most common chronic inflammatory arthropathy of childhood. Juvenile idiopathic arthritis is believed to be a complex genetic trait influenced by both genetic and environmental factors. Twin and family studies suggest a substantial role for genetic factors in the predisposition to JIA. Describing the genetics is complicated by the heterogeneity of JIA; the International League of Associations for Rheumatology (ILAR) has defined seven categories of JIA based on distinct clinical and laboratory features. Utilizing a variety of techniques including candidate gene studies, the use of genotyping arrays such as Immunochip, and genome wide association studies (GWAS), both human leukocyte antigen (HLA) and non-HLA susceptibility loci associated with JIA have been described. Several of these polymorphisms (e.g. HLA class II, PTPN22, STAT4) are shared with other common autoimmune conditions; other novel polymorphisms that have been identified may be unique to JIA. Associations with oligoarticular and RF-negative polyarticular JIA are the best characterized. A strong association between HLA DRB1:11:03/04 and DRB1:08:01, and a protective effect of DRB1:15:01 have been described. HLA DPB1:02:01 has also been associated with oligoarticular and RF-negative polyarticular JIA. Besides PTPN22, STAT4 and PTPN2 variants, IL2, IL2RA, IL2RB, as well as IL6 and IL6R loci also harbor variants associated with oligoarticular and RF-negative polyarticular JIA. RF-positive polyarticular JIA is associated with many of the shared epitope encoding HLA DRB1 alleles, as well as PTPN22, STAT4 and TNFAIP3 variants. ERA is associated with HLA B27. Most other associations between JIA categories and HLA or non-HLA variants need confirmation. The formation of International Consortia to ascertain and analyze large cohorts of JIA categories, validation of reported findings in independent cohorts, and functional studies will enhance our understanding of the genetic underpinnings of JIA.

Genetic Predictors of Poor Prognosis in Portuguese Patients with Juvenile Idiopathic Arthritis: Data from Reuma.pt

Introduction. This study aimed to assess the genetic determinants of poor outcome in Portuguese patients with juvenile idiopathic arthritis (JIA). Methods. Our study was conducted in Reuma.pt, the Rheumatic Diseases Portuguese Register, which includes patients with JIA. We collected prospectively patient and disease characteristics and a blood sample for DNA analysis. Poor prognosis was defined as CHAQ/HAQ >0.75 at the last visit and/or the treatment with biological therapy. A selected panel of single nucleotide polymorphisms (SNPs) associated with susceptibility was studied to verify if there was association with poor prognosis. Results. Of the 812 patients with JIA registered in Reuma.pt, 267 had a blood sample and registered information used to define “poor prognosis.” In univariate analysis, we found significant associations with poor prognosis for allele A of TNFA1P3/20 rs6920220, allele G of TRAF1/C5 rs3761847, and allele G of PTPN2 rs7234029. In multivariate models, the associations with TRAF1/C5 (1.96 [1.17–3.3]) remained significant at the 5% level, while TNFA1P3/20 and PTPN2 were no longer significant. Nevertheless, none of associations found was significant after the Bonferroni correction was applied. Conclusion. Our study does not confirm the association between a panel of selected SNP and poor prognosis in Portuguese patients with JIA.

Polyarticular juvenile idiopathic arthritis - epidemiology and management approaches

Juvenile idiopathic arthritis (JIA) is a group of disorders characterized by arthritis persisting for at least 6 weeks with onset before the age of 16 years. Within this cluster of conditions, the polyarticular form (involving more than four joints within the first 6 months) is further divided based on the presence of rheumatoid factor. Children with polyarticular JIA pose unique diagnostic and therapeutic challenges compared to children with involvement of fewer joints. Polyarticular JIA patients tend to have a more refractory course and therefore are at increased risk for joint damage, resulting in poorer functional outcomes and decreased quality of life. Although the ability to treat this disorder continues to improve, especially with the advent of biologic agents, there is still much about the epidemiology and pathogenesis of polyarticular JIA that is unknown. The epidemiology of polyarticular JIA varies worldwide with a vast difference in reported cases between different global regions as well as within individual countries. Several genetic risk loci have been identified conferring increased susceptibility to JIA, many within the human leukocyte antigen region. Beyond the genome, environmental factors also seem to contribute to the etiology of polyarticular JIA. This review article will focus on the epidemiology and current treatments of polyarticular JIA and briefly discuss genetic and environmental influences on the pathogenesis of JIA as well as new and emerging therapies.

Investigation of juvenile idiopathic arthritis susceptibility loci: results from a Greek population

The strategy of studying the putative role of RA susceptibility genetic factors in the development of juvenile idiopathic arthritis (JIA), an autoimmune disease characterized by persistent chronic arthritis, has been proven highly successful so far. Moreover, accumulated evidence indicates that an ethnic heterogeneity of genetic factors exists for rheumatic disorders. We investigated whether five single nucleotide polymorphisms (SNPs), previously found to be associated with JIA in various populations so far, are also associated with JIA in Greece. The sample set consisted of 128 Caucasian JIA patients and 221 healthy controls from Northern Greece. Five Single Nucleotide Polymorphisms (SNPs) markers, namely TRAF1/C5 rs10818488, PTPN22 rs2476601, STAT4 rs7574865, CD247 rs1773560 and PTPN2 rs7234029 SNPs were genotyped in a case-control study with Restriction Fragment Length Polymorphisms (RFLPs) or Taqman primer-probe sets. This study demonstrated for the first time in a Greek population that the PTPN22, TRAF1/C5 and CD247 polymorphisms examined are associated with an increased susceptibility to JIA, thus suggesting that the respective risk alleles may confer susceptibility to clinically distinct disorders. However, our results did not demonstrate any association of STAT4 and PTPN2 SNPs with the disease in our population, thus highlighting the importance of comparative studies in different ethnic populations.

TRAF1 gene polymorphism correlates with the titre of Gp210 antibody in patients with primary biliary cirrhosis

Background. Polymorphisms of TRAF1 (Tumor necrosis factor receptor-associated factor 1) are associated with rheumatoid arthritis (RA). Whether TRAF1 polymorphisms confer increased risk for primary biliary cirrhosis (PBC), an autoimmune liver disease which can co-exist with RA, is unknown. Aim of the Study. To assess the frequency of the RA-conferring susceptibility TRAF1 polymorphisms rs3761847 and rs2900180 in a cohort of PBC patients. The association of TRAF1 polymorphisms with clinical features and autoantibody markers was also analyzed. Methods. We studied 179 PBC patients and 300 controls. Samples were genotyped for TRAF1 gene polymorphisms by real-time PCR. Autoantibodies were tested by ELISA. Results. The frequency of rs3761847 and rs2900180 polymorphisms did not differ between patients and controls. Laboratory or clinical features were not associated with specific polymorphisms. Gp210 autoantibody titres were conspicuously higher among GG homozygotes of rs3761847 as compared with AA homozygotes (P = 0.02). In contrast, antichromatin titers were higher in AA compared to GG rs3761847 homozygotes (P = 0.04). Rheumatoid factor IgG titres were significantly higher in rs2900180 TT homozygotes than CC homozygotes (P = 0.02). Conclusions. TRAF1 polymorphisms occur with the similar frequency in PBC patients and in the general population, but their presence is probably involved in the regulation of specific PBC-related autoantibodies.

Investigation of rheumatoid arthritis susceptibility loci in juvenile idiopathic arthritis confirms high degree of overlap

OBJECTIVES

Rheumatoid arthritis (RA) shares some similar clinical and pathological features with juvenile idiopathic arthritis (JIA); indeed, the strategy of investigating whether RA susceptibility loci also confer susceptibility to JIA has already proved highly successful in identifying novel JIA loci. A plethora of newly validated RA loci has been reported in the past year. Therefore, the aim of this study was to investigate these single nucleotide polymorphisms (SNP) to determine if they were also associated with JIA.

METHODS

Thirty-four SNP that showed validated association with RA and had not been investigated previously in the UK JIA cohort were genotyped in JIA cases (n=1242), healthy controls (n=4281), and data were extracted for approximately 5380 UK Caucasian controls from the Wellcome Trust Case-Control Consortium 2. Genotype and allele frequencies were compared between cases with JIA and controls using PLINK. A replication cohort of 813 JIA cases and 3058 controls from the USA was available for validation of any significant findings.

RESULTS

Thirteen SNP showed significant association (p<0.05) with JIA and for all but one the direction of association was the same as in RA. Of the eight loci that were tested, three showed significant association in the US cohort.

CONCLUSIONS

A novel JIA susceptibility locus was identified, CD247, which represents another JIA susceptibility gene whose protein product is important in T-cell activation and signalling. The authors have also confirmed association of the PTPN2 and IL2RA genes with JIA, both reaching genome-wide significance in the combined analysis.

Single nucleotide polymorphisms at the TRAF1/C5 locus are associated with rheumatoid arthritis in a Han Chinese population

BACKGROUND

Genetic variants in TRAF1C5 and PTPN22 genes have been shown to be significantly associated with arthritis rheumatoid in Caucasian populations. This study investigated the association between single nucleotide polymorphisms (SNPs) in TRAF1/C5 and PTPN22 genes and rheumatoid arthritis (RA) in a Han Chinese population. We genotyped SNPs rs3761847 and rs7021206 at the TRAF1/C5 locus and rs2476601 SNP in the PTPN22 gene in a Han Chinese cohort composed of 576 patients with RA and 689 controls. The concentrations of anti-cyclic citrullinated peptide antibodies (CCP) and rheumatoid factor (RF) were determined for all affected patients. The difference between the cases and the controls was compared using χ2 analysis.

RESULTS

Significant differences in SNPs rs3761847 and rs7021206 at TRAF1/C5 were observed between the case and control groups in this cohort; the allelic p-value was 0.0018 with an odds ratio of 1.28 for rs3761847 and 0.005 with an odds ratio of 1.27 for rs7021206. This significant association between rs3761847 and RA was independent of the concentrations of anti-CCP and RF. No polymorphism of rs2476601 was observed in this cohort.

CONCLUSIONS

We first demonstrated that genetic variants at the TRAF1/C5 locus are significantly associated with RA in Han Chinese, suggesting that TRAF1/C5 may play a role in the development of RA in this population, which expands the pathogenesis role of TRAF1/C5 in a different ethnicity.

[Genetics of rheumatoid arthritis]

Genetic influences on susceptibility to and clinical course of rheumatoid arthritis have been known for a long time, but have so far eluded systematic, genome-wide analysis. In recent years, the availability of new typing techniques and international consortia with large patient cohorts has generated a wealth of new information on the genetic basis of this autoimmune disease. Newly described associations between immunologically relevant gene polymorphisms and RA susceptibility have already been replicated with great statistical power, and are currently incorporated into new, pathogenetically relevant functional pathways. The resulting new concepts identify cell populations of great potential relevance for the pathogenesis of the disease, and ultimately might lead to new diagnostic and therapeutic approaches in RA.

The susceptibility loci juvenile idiopathic arthritis shares with other autoimmune diseases extend to PTPN2, COG6, and ANGPT1

OBJECTIVE

To test for associations between non-major histocompatibility complex susceptibility loci previously reported in autoimmune diseases and juvenile idiopathic arthritis (JIA).

METHODS

Published autoimmune disease genome-wide association studies were reviewed, and 519 single-nucleotide polymorphisms (SNPs) were selected for association testing. The initial cohort included 809 JIA cases and 3,535 controls of non-Hispanic, European ancestry. Of the SNPs, 257 were successfully genotyped, while 168 were imputed with quality. Based on findings in the initial cohort, replication was sought for 21 SNPs in a second cohort of 1,015 JIA cases and 1,569 controls collected in the US and Germany. For the initial cohort, tests for association were adjusted for potential confounding effects of population structure by including principal components derived from a genome-wide association study as covariates in logistic regression models. Odds ratios (ORs) and 95% confidence intervals were calculated.

RESULTS

Testing for association of previously reported autoimmune disease genetic associations in the initial cohort suggested associations with JIA in 13 distinct loci. Of these, 7 were validated in the replication cohort. Meta-analysis results for the replicating loci included PTPN22 (rs6679677 [OR 1.58, P = 1.98 × 10(-12) ], rs2476601 [OR 1.64, P = 1.90 × 10(-13) ], and rs2488457 [OR 1.32, P = 6.74 × 10(-8) ]), PTPN2 (rs1893217 [OR = 1.33, P = 1.60 × 10(-9) ] and rs7234029 [OR 1.35, P = 1.86 × 10(-10) ]), ADAD1-IL2-IL21 (rs17388568 [OR 1.24, P = 1.13 × 10(-6) ] and rs13143866 [OR 0.83, P = 1.95 × 10(-4) ]), STAT4 (rs3821236 [OR = 1.27, P = 2.36 × 10(-6) ] and rs7574865 [OR = 1.31, P = 2.21 × 10(-6) ]), C12orf30 (rs17696736 [OR = 1.19, P = 2.59 × 10(-5) ]), COG6 (rs7993214 [OR = 0.76, P = 1.10 × 10(-5) ]), and ANGPT1 (rs1010824 [OR = 0.79, P = 2.91 × 10(-4) ]). These polymorphisms have been reported in diseases such as rheumatoid arthritis, type 1 diabetes mellitus, Crohn's disease, and multiple sclerosis.

CONCLUSION

General susceptibility loci for autoimmunity are shared across diseases, including JIA, suggesting the potential for common therapeutic targets and mechanisms.

Overlapping genetic susceptibility variants between three autoimmune disorders: rheumatoid arthritis, type 1 diabetes and coeliac disease

INTRODUCTION

Genome wide association studies, replicated by numerous well powered validation studies, have revealed a large number of loci likely to play a role in susceptibility to many multifactorial diseases. It is now well established that some of these loci are shared between diseases with similar aetiology. For example, a number of autoimmune diseases have been associated with variants in the PTPN22, TNFAIP3 and CTLA4 genes. Here we have attempted to define overlapping genetic variants between rheumatoid arthritis (RA), type 1 diabetes (T1D) and coeliac disease (CeD).

METHODS

We selected eight SNPs previously identified as being associated with CeD and six T1D-associated SNPs for validation in a sample of 3,962 RA patients and 3,531 controls. Genotyping was performed using the Sequenom MassArray platform and comparison of genotype and allele frequencies between cases and controls was undertaken. A trend test P-value < 0.004 was regarded as significant.

RESULTS

We found statistically significant evidence for association of the TAGAP locus with RA (P = 5.0 × 10-4). A marker at one other locus, C1QTNF6, previously associated with T1D, showed nominal association with RA in the current study but did not remain statistically significant at the corrected threshold.

CONCLUSIONS

In exploring the overlap between T1D, CeD and RA, there is strong evidence that variation within the TAGAP gene is associated with all three autoimmune diseases. Interestingly a number of loci appear to be specific to one of the three diseases currently studied suggesting that they may play a role in determining the particular autoimmune phenotype at presentation.

Overlap of disease susceptibility loci for rheumatoid arthritis and juvenile idiopathic arthritis

BACKGROUND

Genome-wide association studies (GWAS) have been extremely successful in the search for susceptibility risk factors for complex genetic autoimmune diseases. As more studies are published, evidence is emerging of considerable overlap of loci between these diseases. In juvenile idiopathic arthritis (JIA), another complex genetic autoimmune disease, the strategy of using information from autoimmune disease GWAS or candidate gene studies to help in the search for novel JIA susceptibility loci has been successful, with confirmed association with two genes, PTPN22 and IL2RA. Rheumatoid arthritis (RA) is an autoimmune disease that shares similar clinical and pathological features with JIA and, therefore, recently identified confirmed RA susceptibility loci are also excellent JIA candidate loci.

OBJECTIVE

To determine the overlap of disease susceptibility loci for RA and JIA.

METHODS

/st> Fifteen single nucleotide polymorphisms (SNPs) at nine RA-associated loci were genotyped in Caucasian patients with JIA (n=1054) and controls (n=3531) and tested for association with JIA. Allele and genotype frequencies were compared between cases and controls using the genetic analysis software, PLINK.

RESULTS

Two JIA susceptibility loci were identified, one of which was a novel JIA association (STAT4) and the second confirmed previously published associations of the TRAF1/C5 locus with JIA. Weak evidence of association of JIA with three additional loci (Chr6q23, KIF5A and PRKCQ) was also obtained, which warrants further investigation.

CONCLUSION

All these loci are good candidates in view of the known pathogenesis of JIA, as genes within these regions (TRAF1, STAT4, TNFAIP3, PRKCQ) are known to be involved in T-cell receptor signalling or activation pathways.

Update on the genetic risk factors for rheumatoid arthritis

Rheumatoid arthritis (RA) is a complex disease, meaning that multiple genetic variants, environmental factors and random events interact to trigger pathological pathways. Although many of these etiological factors have not yet been identified, recent groundbreaking advances have expanded our knowledge about the genetic factors that contribute to RA. Here, we review the most recent findings on the genetic risk factors for RA. First, we give an overview of the genetics of RA and briefly describe the susceptibility loci discovered prior to the availability of genome-wide association studies (GWAS). Second, we focus on the newly discovered RA loci that have arisen from GWAS in populations of European ancestry. Through these studies, the number of established RA susceptibility loci has now grown to 13. Third, we discuss several important issues emerging from GWAS, such as ethnic heterogeneity and shared autoimmunity risk loci. Finally, we discuss what still needs to be accomplished before a more complete picture of the genetic risk to RA can be attained.

The TRAF1-C5 region on chromosome 9q33 is associated with multiple autoimmune diseases

OBJECTIVES

The TRAF1-C5 locus has recently been identified as a genetic risk factor for rheumatoid arthritis (RA). Since genetic risk factors tend to overlap with several autoimmune diseases, a study was undertaken to investigate whether this region is associated with type 1 diabetes (TID), celiac disease (CD), systemic sclerosis (SSc) and systemic lupus erythematosus (SLE).

METHODS

The most consistently associated SNP, rs10818488, was genotyped in a total of 735 patients with T1D, 1049 with CD, 367 with SSc, 746 with SLE and 3494 ethnically- and geographically-matched healthy individuals. The replication sample set consisted of 99 patients with T1D, 272 with SLE and 482 healthy individuals from Crete.

RESULTS

A significant association was detected between the rs10818488 A allele and T1D (OR 1.14, p=0.027) and SLE (OR 1.16, p=0.016), which was replicated in 99 patients with T1D, 272 with SLE and 482 controls from Crete (OR 1.64, p=0.002; OR 1.43, p=0.002, respectively). Joint analysis of all patients with T1D (N=961) and all patients with SLE (N=1018) compared with 3976 healthy individuals yielded an allelic common OR of 1.19 (p=0.002) and 1.22 (p=2.6 x 10(-4)), respectively. However, combining our dataset with the T1D sample set from the WTCCC resulted in a non-significant association (OR 1.06, p=0.087). In contrast, previously unpublished results from the SLEGEN study showed a significant association of the same allele (OR 1.19, p=0.0038) with an overall effect of 1.22 (p=1.02 x 10(-6)) in a total of 1577 patients with SLE and 4215 healthy individuals.

CONCLUSION

A significant association was found for the TRAF1-C5 locus in SLE, implying that this region lies in a pathway relevant to multiple autoimmune diseases.

Replication of the tumor necrosis factor receptor-associated factor 1/complement component 5 region as a susceptibility locus for rheumatoid arthritis in a European family-based study

OBJECTIVE

We recently showed, using a candidate gene approach in a case-control association study, that a 65-kb block encompassing tumor necrosis factor receptor-associated factor 1 (TRAF1) and C5 is strongly associated with rheumatoid arthritis (RA). Compared with case-control association studies, family-based studies have the added advantage of controlling potential differences in population structure and are not likely to be hampered by variation in population allele frequencies, as is seen for many genetic polymorphisms, including the TRAF1/C5 locus. The aim of this study was to confirm this association in populations of European origin by using a family-based approach.

METHODS

A total of 1,356 western European white individuals from 452 "trio" families were genotyped for the rs10818488 polymorphism, using the TaqMan allelic discrimination assay.

RESULTS

We observed evidence for association, demonstrating departure from Mendel's law, with an overtransmission of the rs10818488 A allele (A = 55%; P = 0.036). By taking into consideration parental phenotypes, we also observed an increased A allele frequency in affected versus unaffected parents (A = 64%; combined P = 0.015). Individuals carrying the A allele had a 1.2-fold increased risk of developing RA (allelic odds ratio 1.24, 95% confidence interval 1.04-1.50).

CONCLUSION

Using a family-based study that is robust against population stratification, we provide evidence for the association of the TRAF1/C5 rs10818488 A allele and RA in populations of European descent, further substantiating our previous findings. Future functional studies should yield insight into the biologic relevance of this locus to the pathways involved in RA.

TRAF1/C5 polymorphism is not associated with increased mortality in rheumatoid arthritis: two large longitudinal studies

Introduction

Recently an association between a genetic variation in TRAF1/C5 and mortality from sepsis or cancer was found in rheumatoid arthritis (RA). The most prevalent cause of death, cardiovascular disease, may have been missed in that study, since patients were enrolled at an advanced disease stage. Therefore, we used an inception cohort of RA patients to investigate the association between TRAF1/C5 and cardiovascular mortality, and replicate the findings on all-cause mortality. As TRAF1/C5 associated mortality may not be restricted to RA, we also studied a large cohort of non-RA patients.

Methods

615 RA patients from the Leiden Early Arthritis Clinic (EAC) (mean follow-up 7.6 years) were genotyped for rs10818488. In addition 5634 persons enrolled in the PROspective Study of Pravastatin in the Elderly at Risk (mean follow-up 3.2 years) were genotyped for rs2416808 (R² >0.99 with rs10818488). The life/death status was determined and for the deceased persons the cause of death was ascertained. Cox proportional hazards and regression models were used to assess hazard ratios (HR) and 95% confidence intervals (CI).

Results

Seventy-seven RA patients died. The main death causes in RA patients were cardiovascular diseases (37.7%), cancer (28.6%) and death due to infections (9.1%). No association was observed between the rs10818488 susceptible genotype AA and cardiovascular mortality (HR 1.08 95%CI 0.54 to 2.15) and all-cause mortality (HR 0.81 95%CI 0.27 to 2.43). Similar findings were observed for rs2416808 susceptible genotype GG in the non-RA cohort (HR 0.99; 95%CI 0.79 to 1.25 and HR 0.89; 95%CI 0.64 to 1.25, respectively).

Conclusions

The TRAF1/C5 region is not associated with an increased mortality risk.

Susceptibility variants for rheumatoid arthritis in the TRAF1-C5 and 6q23 loci: a meta-analysis

BACKGROUND

Genome-wide association studies have proposed susceptibility variants for rheumatoid arthritis in the TRAF1-C5 locus and 6q23 region. Furthermore, additional independent studies have investigated the same or highly linked polymorphisms in the same regions.

OBJECTIVE

To carry out a meta-analysis of the available evidence for the association of polymorphisms in the TRAF1-C5 locus and 6q23 region with rheumatoid arthritis.

METHODS

Data were synthesised for four polymorphisms: rs3761847 (n=13 datasets) and rs2900180 (n=9 datasets) in the TRAF1-C5 locus, and rs10499194 (n=5 datasets) and rs6920220 (n=7 datasets) in the 6q23 region. Meta-analyses for subgroups defined by anti-cyclic citrullinated peptide (anti-CCP) and rheumatoid factor (RF) status were also performed.

RESULTS

The polymorphism rs6920220 reached genome-wide statistical significance with p=7.9 x 10(-17) and an allelic odds ratio of 1.24 (95% CI 1.18 to 1.30) and no between-study heterogeneity (I(2)=0%). The risk was significantly stronger in patients with anti-CCP antibodies and in patients with RF. The other three variants showed large between-study heterogeneity across datasets (I(2) range 74-82%); rs10499194 was nominally statistically significant after exclusion of the discovery data. Two variants had genome-wide statistical significance in subgroups defined by the presence of RF (rs3761847 and rs6920220) or anti-CCP (rs6920220).

CONCLUSIONS

Genetic markers in the 6q23 region and TRAF1-C5 are associated with rheumatoid arthritis, in particular with positive anti-CCP and RF profile. With the exception of rs6920220, which shows highly consistent results, other proposed markers have high between-study heterogeneity that may reflect unrecognised phenotypic or genetic variability (eg, gene environment interactions) within rheumatoid arthritis. Furthermore, these markers may not be the true causative loci but rather be in linkage disequilibrium with the true ones.

Association study of TRAF1-C5 polymorphisms with susceptibility to rheumatoid arthritis and systemic lupus erythematosus in Japanese

OBJECTIVE

The primary aim of this study was to investigate the association of polymorphisms of TRAF1-C5, a newly identified rheumatoid arthritis (RA) risk locus in Caucasians, with susceptibility to RA and systemic lupus erythematosus (SLE) in Japanese populations. Gene expression levels of TRAF1 and C5 to assess the functional significance of genotypes were also analysed.

METHODS

A multicentre association study consisting of 4 RA case-control series (4397 cases and 2857 controls) and 3 SLE case-control series (591 cases and 2199 shared controls) was conducted. Genotyping was performed using TaqMan genotyping assay for two single nucleotide polymorphisms (SNPs) that showed the best evidence of association in the previous Caucasian studies. Quantifications of TRAF1 and C5 expression were performed with TaqMan expression assay.

RESULTS

Significant differences in allele frequency for both SNPs were observed between RA and control subjects (combined odds ratio = 1.09), while no significant difference was detected between patients with SLE and controls. Interestingly, alleles rs3761847 A and rs10818488 G had increased the risk for RA in the present study, while they decreased the risk in the original studies. A significant difference was found between risk allele carriers and non-carriers of rs10818488 for the expression level of TRAF1 in phorbol myristate acetate-stimulated lymphoblastoid cell lines (p = 0.04).

CONCLUSION

Association of TRAF1-C5 locus with RA susceptibility was detected in the Japanese populations with modest magnitude, while no significant association was observed for SLE. Significant positive effect of genotype on the expression of TRAF1 might support the genetic association between TRAF1 and RA.

Variants in TNFAIP3, STAT4, and C12orf30 loci associated with multiple autoimmune diseases are also associated with juvenile idiopathic arthritis

OBJECTIVE

Subtypes of juvenile idiopathic arthritis (JIA) share phenotypic features with other autoimmune disorders. We investigated several genetic variants associated with rheumatoid arthritis (RA) and other autoimmune disorders for association with JIA to test the hypothesis that clinically distinct phenotypes share common genetic susceptibility factors.

METHODS

Cases were 445 children with JIA, and controls were 643 healthy adults. Using the TaqMan assay, subjects were genotyped for 8 single-nucleotide polymorphisms in 7 loci including rs10499194 and rs6920220 in the TNFAIP3 locus, rs6679677 in the RSBN1 locus, rs17696736 in the C12orf30 locus, rs3761847 in the TRAF1/C5 locus, rs2104286 in the IL2RA locus, rs7574865 in the STAT4 locus, and rs2542151 in the PTPN2 locus. Alleles and genotypes were analyzed for association with JIA and JIA subtypes. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated.

RESULTS

The strongest associations with JIA risk or protection were observed for TNFAIP3 variants rs10499194 (OR 0.74 [95% CI 0.61-0.91], P < 0.004) and rs6920220 (OR 1.30 [95% CI 1.05-1.61], P = 0.015). We also observed associations between JIA and both STAT4 (OR 1.24 [95% CI 1.02-1.51], P = 0.029) and C12orf30 (OR 1.20 [95% CI 1.01-1.43], P = 0.041) variants. The PTPN2 variant rs2542151 deviated from Hardy-Weinberg equilibrium and was excluded from analyses. Variants in IL2RA, TRAF1/C5, and RSBN1 were not associated with JIA. After stratification by JIA subtype, the TNFAIP3 and C12orf30 variants were associated with oligoarticular JIA, while the STAT4 variant was associated primarily with polyarticular JIA.

CONCLUSION

We have demonstrated associations between JIA and variants in the TNFAIP3, STAT4, and C12orf30 regions that have previously shown associations with other autoimmune diseases, including RA and systemic lupus erythematosus. Our results suggest that clinically distinct autoimmune phenotypes share common genetic susceptibility factors.

Immune regulation by 4-1BB and 4-1BBL: complexities and challenges

SUMMARY

The tumor necrosis factor receptor family member 4-1BB plays a key role in the survival of activated and memory CD8(+) T cells. Depending on the disease model, 4-1BB can participate at different stages and influence different aspects of the immune response, likely due to the differential expression of receptor and ligand relative to other costimulatory molecules. Studies comparing mild versus severe influenza infection of mice suggest that the immune system uses inducible receptors such as 4-1BB to prolong the immune response when pathogens take longer to clear. The expression of 4-1BB on diverse cell types, evidence for bidirectional as well as receptor-independent signaling by 4-1BBL, the unexpected hyperproliferation of 4-1BB-deficient T cells, and complex effects of agonistic anti-4-1BB therapy have revealed additional roles for the 4-1BB/4-1BBL receptor/ligand pair in the immune system. In this review, we discuss these diverse roles of 4-1BB and its ligand in the immune response, exploring possible mechanisms for the observed complexities and implications for therapeutic applications of 4-1BB/4-1BBL.

Association of the autoimmunity locus 4q27 with juvenile idiopathic arthritis

OBJECTIVE

Juvenile idiopathic arthritis (JIA) is characterized by chronic arthritis and an autoimmune etiology. In several autoimmune diseases, including rheumatoid arthritis (RA), an association with the 4q27 locus has been reported. We undertook this study to investigate the possible role of the 4q27 locus in JIA.

METHODS

A case-control association study was conducted, with a total of 655 Caucasian JIA patients and 791 healthy controls divided into 2 independent sample sets. The rs6822844 marker in the 4q27 locus was genotyped.

RESULTS

In the first and larger sample set, a 5% decrease in T allele frequency was observed in patients compared with controls (allelic odds ratio [OR] 0.72 [95% confidence interval 0.55-0.95], P = 0.019), and in the second set, a 3% decrease was observed (allelic OR 0.81 [95% confidence interval 0.61-1.09], P = 0.169). The combined data set generated an OR of 0.76 (95% confidence interval 0.62-0.93, P = 7.08 x 10(-3)). When the different JIA subtypes were analyzed individually, significant decreases were seen in the subtypes with a polyarticular course of disease (extended oligoarthritis [P = 0.019] and rheumatoid factor-negative polyarthritis [P = 0.038]).

CONCLUSION

Our findings suggest that the 4q27 locus, previously reported to be associated with RA, type 1 diabetes mellitus, celiac disease, and psoriatic arthritis, is also associated with susceptibility to JIA.