The association of PTPN22 with rheumatoid arthritis and juvenile idiopathic arthritis

Role of Selected Genetic Polymorphisms in the Development of Rheumatoid Arthritis in a British White Population

BACKGROUND

Rheumatoid arthritis (RA) is a complex autoimmune disease that negatively affects synovial joints, leading to the deterioration of movement and mobility of patients. This chronic disease is considered to have a strong genetic inheritance, with genome-wide association studies (GWAS) highlighting many genetic loci associated with the disease. Moreover, numerous confounding and non-genetic factors also contribute to the risk of the disease.

AIMS

This study investigates the association of selected genetic polymorphisms with rheumatoid arthritis risk and develops a polygenic risk score (PRS) based on selected genes.

METHODS

A case-control study recruited fully consenting participants from the East Midlands region of the UK. DNA samples were genotyped for a range of polymorphisms and genetic associations were calculated under several inheritance models. PRS was calculated at crude (unweighted) and weighted levels, and its associations with clinical parameters were determined.

RESULTS

There were significant associations with the risk of RA at six genetic markers and their associated risk alleles (TNRF2*G, TRAF1*A, PTPN22*T, HLA-DRB1*G, TNFα*A, and IL4-590*T). The TTG haplotype at the VDR locus increased the risk of RA with an OR of 3.05 (CI 1.33-6.98, p = 0.009). The GA haplotype of HLADRB1-TNFα-308 was a significant contributor to the risk of RA in this population (OR = 2.77, CI 1.23-6.28, p = 0.01), although linkage disequilibrium was low. The polygenic risk score was significantly higher in cases over controls in both unweighted (mean difference = 1.48, t285 = 5.387, p < 0.001) and weighted (mean difference = 2.75, t285 = 6.437, p < 0.001) results.

CONCLUSION

Several genetic loci contribute to the increased risk of RA in the British White sample. The PRS is significantly higher in those with RA and can be used for clinical applications and personalised prevention of disease.

Advancements and progress in juvenile idiopathic arthritis: A Review of pathophysiology and treatment

Juvenile idiopathic arthritis (JIA) is a chronic clinical condition characterized by arthritic features in children under the age of 16, with at least 6 weeks of active symptoms. The etiology of JIA remains unknown, and it is associated with prolonged synovial inflammation and structural joint damage influenced by environmental and genetic factors. This review aims to enhance the understanding of JIA by comprehensively analyzing relevant literature. The focus lies on current diagnostic and therapeutic approaches and investigations into the pathoaetiologies using diverse research modalities, including in vivo animal models and large-scale genome-wide studies. We aim to elucidate the multifactorial nature of JIA with a strong focus towards genetic predilection, while proposing potential strategies to improve therapeutic outcomes and enhance diagnostic risk stratification in light of recent advancements. This review underscores the need for further research due to the idiopathic nature of JIA, its heterogeneous phenotype, and the challenges associated with biomarkers and diagnostic criteria. Ultimately, this contribution seeks to advance the knowledge and promote effective management strategies in JIA.

Genetic association between the PTPN22, IRF5 and TYK2 gene variants and susceptibility to juvenile idiopathic arthritis

Juvenile idiopathic arthritis (JIA) refers to a group of chronic childhood arthropathies of unknown etiology. In the present study, the genetic association between the variants in PTPN22, IRF5 and TYK2 genes and susceptibility to JIA was investigated. The distributions of 16 variants in PTPN22, IRF5 and TYK2 genes were analyzed by direct sequencing in 378 patients with JIA and 378 healthy controls. Odds ratios and 95% confidence intervals were used to evaluate the association between the gene variants and JIA. The gene-gene interactions were investigated using multifactor dimensionality reduction. All allelic and dominant models of PTPN22 rs1214414, rs1214418, rs1746853, rs3765598 and rs3811021 were significantly associated with JIA risk (P<0.05). IRF5 rs10954213 in both allelic and dominant models, as well as the allelic model of rs2004640, was significantly related to JIA risk (P<0.05). In addition, the allelic, recessive and dominant models of TYK2 rs280500, rs280519, rs2304256 and rs12720270 were significantly related to JIA risk (P<0.05). In addition, three haplotypes (H_{C A G T C C}, H_{C A G T T C} and H_{C G T T C T} ) in PTPN22 gene, three haplotypes (H_{D T A A}, H_{I T A C} and H_{D T G C}) in IRF5 gene and two haplotypes (H_{A G G A T} and H_{G A G G T}) in TYK2 gene were associated with the risk of JIA (P<0.05). Furthermore, a three-way interaction between IRF5 rs10954213, rs2004640 and PTPN22 rs1214414 was shown to be associated with JIA risk. In conclusion, PTPN22 rs1214418, rs1746853, rs3765598, IRF5 rs2004640, TYK2 rs280500, rs2304256 and a three-way interaction between IRF5 rs10954213, rs2004640 and PTPN22 rs1214414 may be risk factors for JIA.

The pre-clinical phase of rheumatoid arthritis: From risk factors to prevention of arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease considered as a multistep process spanning from the interaction of genetic (e.g., shared epitope or non-HLA loci), environmental and behavioral risk factors (e.g., smoking) leading to breaking immune tolerance and autoimmune processes such as the production of autoantibodies (e.g., antibodies against citrullinated proteins ACPA or rheumatoid factors, RF), development of the first symptoms without clinical arthritis, and, finally, the manifestation of arthritis. Despite the typical joint involvement in established RA, the pathogenesis of the disease likely begins far from joint structures: in the lungs or periodontium in association with citrullination, intestinal microbiome, or adipose tissue, which supports normal findings in synovial tissue in ACPA+ patients with arthralgia. The presence of ACPA is detectable even years before the first manifestation of RA. The pre-clinical phase of RA is the period preceding clinically apparent RA with ACPA contributing to the symptoms without subclinical inflammation. While the combination of ACPA and RF increases the risk of progression to RA by up to 10 times, increasing numbers of novel autoantibodies are to be investigated to contribute to the increased risk and pathogenesis of RA. With growing knowledge about the course of RA, new aspiration emerges to cure and even prevent RA, shifting the "window of opportunity" to the pre-clinical phases of RA. The clinical definition of individuals at risk of developing RA (clinically suspect arthralgia, CSA) makes it possible to unify these at-risk individuals' clinical characteristics for "preventive" treatment in ongoing clinical trials using mostly biological or conventional synthetic disease-modifying drugs. However, the combination of symptoms, laboratory, and imaging biomarkers may be the best approach to select the correct target at-risk population. The current review aims to explore different phases of RA and discuss the potential of (non)pharmacological intervention aiming to prevent RA.

Antigen-driven PD-1+ TOX+ BHLHE40+ and PD-1+ TOX+ EOMES+ T lymphocytes regulate juvenile idiopathic arthritis in situ

T lymphocytes accumulate in inflamed tissues of patients with chronic inflammatory diseases (CIDs) and express pro-inflammatory cytokines upon re-stimulation in vitro. Further, a significant genetic linkage to MHC genes suggests that T lymphocytes play an important role in the pathogenesis of CIDs including juvenile idiopathic arthritis (JIA). However, the functions of T lymphocytes in established disease remain elusive. Here we dissect the transcriptional and the clonal heterogeneity of synovial T lymphocytes in JIA patients by single-cell RNA sequencing combined with T cell receptor profiling on the same cells. We identify clonally expanded subpopulations of T lymphocytes expressing genes reflecting recent activation by antigen in situ. A PD-1⁺ TOX⁺ EOMES⁺ population of CD4⁺ T lymphocytes expressed immune regulatory genes and chemoattractant genes for myeloid cells. A PD-1⁺ TOX⁺ BHLHE40⁺ population of CD4⁺ , and a mirror population of CD8⁺ T lymphocytes expressed genes driving inflammation, and genes supporting B lymphocyte activation in situ. This analysis points out that multiple types of T lymphocytes have to be targeted for therapeutic regeneration of tolerance in arthritis.

Inflammation and Genes

Inflammation is a protective immune response to infection, trauma, or injury; however, only a subset of patients develops inflammation, suggesting other contributing factors involved, such as the environment and genes. Inflammationassociated genes involving those with pro- and anti-inflammatory effect should be properly balanced and regulated; the protein products of these genes ultimately determine the outcome of inflammation. Apart from gene mutations, gene polymorphisms related to some inflammatory markers also appear to correlate with the incidence and/or outcome of serious inflammatory events. Some genes recently recognized to be associated with inflammation are briefly reviewed. Modern genomic approaches, such as DNA micro-arrays and serial analysis of gene expression, allow for determining the extremely complex profile of inflammatory genes.

The Protein Tyrosine Phosphatase Nonreceptor 22 (PTPN22) R620W Functional Polymorphism in Psoriasis

Background:

Psoriasis is a complex autoimmune disease caused by the interaction of genetic and environmental factors. PTPN22 gene polymorphism has been reported to affect psoriasis susceptibility; however, no data are available for Middle Eastern populations.

Objective:

The aim of this study was to investigate the association of PTPN22 (1858C/T) R620W polymorphism with psoriasis in a Saudi cohort.

Methods:

Saudi subjects (n = 306) including patients with psoriasis (n = 106) and matched controls (n = 200) were studied for PTPN22 variants using tetra-primer amplification refractory mutation system-polymerase chain reaction method. The frequencies of alleles and genotypes of PTPN22 (1858C/T) polymorphism were compared between patients and controls.

Results:

The frequency of CT genotype of PTPN22 (1858C/T) polymorphism was significantly higher, whereas that of CC genotype was lower in patients with psoriasis than in controls (P < .001, relative risk [RR] = 7.151). The homozygous genotype TT was absent in both the patients and healthy controls. The frequency of allele T encoding tryptophan (W) was significantly increased (P < .001, RR = 5.76), whereas that of allele C encoding arginine (R) decreased in psoriasis cases as compared with controls (P < .001, RR = 0.173) indicating that individuals carrying allele T are more susceptible to psoriasis than noncarriers.

Conclusions:

PTPN22 (1858C/T) polymorphism is positively associated with susceptibility of psoriasis in Saudis and can be developed as biomarker for evaluating psoriasis risk. However, further studies on PTPN22 polymorphism in larger samples from different geographical areas and ethnicity are warranted.

Regulation of Nephrin Phosphorylation in Diabetes and Chronic Kidney Injury

Diabetes is the leading cause of microalbuminuria and end-stage renal failure in industrial countries. Disruption of the filtration barrier, seen in almost all nephrotic diseases and diabetes, is the result of the loss or effacement of the podocyte foot process, notably damage of proteins within the slit diaphragm such as nephrin. For many years, nephrin has been viewed as a structural component of the slit diaphragm. It is now well recognized that nephrin contains several tyrosine residues in its cytoplasmic domain, which influences the development of glomerular injury. In this review, we propose an overview of nephrin signaling pathways in kidney injury.

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.

Autoimmunity in primary antibody deficiency is associated with protein tyrosine phosphatase nonreceptor type 22 (PTPN22)

BACKGROUND

The 1858T allele of protein tyrosine phosphatase nonreceptor type 22 (PTPN22; R620W) exhibits one of the strongest and most consistent associations with sporadic autoimmune disease. Although autoimmunity is common in patients with primary antibody deficiency (PAD), it remains unknown whether its pathogenesis is similar when it arises in this context compared with in immunocompetent patients.

OBJECTIVE

We set out to determine whether the 1858T allele of PTPN22 was associated with PAD or with autoimmunity in the context of PAD.

METHODS

We genotyped rs2476601 (g.1858C>T), a single nucleotide polymorphism encoding substitution of arginine for tryptophan in PTPN22 (R620W), in 193 patients with PAD and 148 control subjects from an Australian cohort. We also performed a subgroup analysis according to the presence of autoimmunity and B-cell phenotypes.

RESULTS

C/T and T/T PTPN22 genotypes were more common in patients with PAD than in the matched control subjects (C/T, 18.1% vs 9.5%; T/T, 1.04% vs 0.6%). The T allele was associated with an increased risk of PAD relative to control subjects (odds ratio, 2.10; 95% CI, 1.11-4.00). The distribution of genotypes in control subjects was similar to those reported previously and did not deviate significantly from Hardy-Weinberg equilibrium. We found a strong association between the 1858T allele and PAD with coexistent autoimmune diseases. In patients with PAD and autoimmunity, 16 (43.2%) of 37 had at least one T allele of PTPN22 compared with 27 (17.3%) of 156 with the C/C genotype (P=.0014; odds ratio, 3.64; 95% CI, 1.68-7.88). We found no evidence that this effect was mediated by enrichment of CD21low B cells.

CONCLUSION

The 1858T PTPN22 allele is strongly associated with autoimmunity in patients with PAD.

R620W functional polymorphism of protein tyrosine phosphatase non-receptor type 22 is not associated with pulmonary tuberculosis in Zahedan, southeast Iran

The protein tyrosine phosphatase non-receptor type 22 (PTPN22) gene, which encodes an intracellular lymphoid-specific phosphatase, is considered an important regulator of T-cell activation. We investigated a possible association between the PTPN22 C1858T (R620W) polymorphism and pulmonary tuberculosis in an Iranian population. Single nucleotide polymorphisms of PTPN22 C1858T (rs2476601) were genotyped in 172 pulmonary tuberculosis cases and 204 normal subjects from Zaheden, Iran. Frequencies of genotypes CC, CT and TT of the PTPN22 C1858T polymorphism were 98.3, 1.7 and 0% in the pulmonary tuberculosis patients, and 96.1, 3.9 and 0% in the control group, respectively (P = 0.239). The frequency of the minor (T) allele was 0.8% in pulmonary tuberculosis patients and 2.0% in controls. Significant differences were not observed in genotype or allele frequencies of PTPN22 C1858T in the comparison between pulmonary tuberculosis patients and healthy subjects in our Iranian population sample.

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.

PTPN22 R620W polymorphism in the ANCA-associated vasculitides

OBJECTIVES

PTPN22 is involved in T-cell activation and its R620W single-nucleotide polymorphism (SNP) has been shown to predispose to different autoimmune diseases. The aims of this study were to investigate the role of the PTPN22 R620W SNP in conferring susceptibility to the ANCA-associated vasculitides (AAVs), and to explore potential associations between the PTPN22 genotype and the disease manifestations.

METHODS

PTPN22 R620W SNP was genotyped in a cohort of 344 AAV patients [143 with granulomatosis with polyangiitis (Wegener's) (GPA), 102 with microscopic polyangiitis (MPA) and 99 with Churg-Strauss syndrome (CSS)] and in 945 healthy controls.

RESULTS

The frequency of the minor allele (620W) was significantly higher in GPA patients than in controls [P = 0.005, χ(2 )= 7.858, odds ratio (OR) = 1.91], while no statistically significant association was found with MPA or CSS. Among GPA patients, the 620W allele was particularly enriched in ANCA-positive patients as compared with controls (P = 0.00012, χ(2 )= 14.73, OR = 2.31); a particularly marked association was also found with ENT involvement (P = 0.0071, χ(2 )= 7.258, OR = 1.98), lung involvement (P = 0.0060, χ(2 )= 7.541, OR = 2.07) and skin manifestations of all kinds (P = 0.000047, χ(2 )= 16.567, OR = 3.73).

CONCLUSION

The PTPN22 620W allele confers susceptibility to the development of GPA (but not of MPA or CSS), and particularly of its ANCA-positive subset.

Mutated citrullinated vimentin antibodies in rheumatoid arthritis

Rheumatoid arthritis (RA) is the most common inflammatory systemic autoimmune disease, primarily affecting the peripheral joints. The past decade has been marked with revolutionary changes both in the therapeutic and diagnostic perspectives of RA. The discovery of an RA-specific citrullination-driven immune reaction gave a substantial contribution in the diagnostic approach to RA. Efforts directed towards the identification of the antigenic target specifically recognized by these autoantibodies resulted in the identification of vimentin in citrullinated form as the potential native antigen, among other proteins. Furthermore, it was found that the mutation of vimentin represents an independent trigger of antigenic properties, in addition to citrullination. As a result of this discovery, a commercial ELISA using mutated citrullinated vimentin (MCV) was developed. Increasingly, data now support the use of anti-MCV in RA diagnosis and prognosis for errosion. This review summarizes the research to date on the use of anti-MCV in RA diagnosis and prognosis and its potential use as a therapeutic marker. The pathologic role of these antibodies in RA disease is also discussed.

Genetics of rheumatoid arthritis: GWAS and beyond

The study of complex genetics in autoimmune diseases has progressed at a tremendous pace over the last 4 years, as a direct result of the enormous gains made by genome wide association studies (GWAS). Novel genetic findings are continuously being reported alongside the rapid development of genetic technologies, sophisticated statistical analysis, and larger sample collections. It is now becoming clear that multiple genes contribute to disease risk in many complex genetic disorders including rheumatoid arthritis (RA) and that there are common genetic risk factors that underlie a spectrum of autoimmune diseases. This review details the current genetic landscape of RA, and describes what GWAS has taught us in terms of missing heritability, subsets of disease, existence of genetic heterogeneity, and shared autoimmune risk loci. Finally, this review addresses the initial challenges faced in translating the wealth of genetic findings into determining the biological mechanisms that contribute to the relationship between genotype and phenotype. Unraveling the mechanism of how genes directly influence the cause of RA will lead to a better understanding of the disease and will ultimately have a direct clinical impact, informing the development of new therapies that can be utilized in the treatment of RA.

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.

Polymorphisms in genes controlling inflammation and tissue repair in rheumatoid arthritis: a case control study

Background

Various cytokines and inflammatory mediators are known to be involved in the pathogenesis of rheumatoid arthritis (RA). We hypothesized that polymorphisms in selected inflammatory response and tissue repair genes contribute to the susceptibility to and severity of RA.

Methods

Polymorphisms in TNFA, IL1B, IL4, IL6, IL8, IL10, PAI1, NOS2a, C1INH, PARP, TLR2 and TLR4 were genotyped in 376 Caucasian RA patients and 463 healthy Caucasian controls using single base extension. Genotype distributions in patients were compared with those in controls. In addition, the association of polymorphisms with the need for anti-TNF-α treatment as a marker of RA severity was assessed.

Results

The IL8 781 CC genotype was associated with early onset of disease. The TNFA -238 G/A polymorphism was differentially distributed between RA patients and controls, but only when not corrected for age and gender. None of the polymorphisms was associated with disease severity.

Conclusions

We here report an association between IL8 781 C/T polymorphism and age of onset of RA. Our findings indicate that there might be a role for variations in genes involved in the immune response and in tissue repair in RA pathogenesis. Nevertheless, additional larger genomic and functional studies are required to further define their role in RA.

Abatacept in the treatment of polyarticular JIA: development, clinical utility, and place in therapy

Juvenile idiopathic arthritis (JIA) is a group of chronic arthritides affecting children. The polyarthritis category, affecting five or more joints in the first six months, tends to be more aggressive, leading to a destructive joint disease with significant morbidity, disability, and costs to society. The current treatment regimen, which primarily combines methotrexate and tumor necrosis factor alpha (TNF-α) blockade, still leaves a significant group of patients with an inadequate response. Therefore, the development of new medications that act via other mechanisms of pathogenesis is necessary. T cell lymphocytes are key components in the immune reaction in JIA. Cytotoxic lymphocyte-associated antigen-4 (CTLA-4) is a potent inhibitor of the costimulation pathway necessary to activate T cells. Abatacept is a recombinant fusion protein comprising the extracellular part of human CTLA-4 connected to a modified Fc part of IgG-1. In a randomized, multinational, blinded withdrawal study in children with polyarticular JIA, abatacept was found to be effective in about 70% of the patients, including 39% of TNF-α blockade failures, with significantly fewer flares occurring during the withdrawal phase than in patients receiving placebo. Abatacept continued to show good efficacy in a three-year open-label extension study, with a beneficial effect on health-related quality of life. The safety profile of abatacept is generally good. In 2008, the US Food and Drug Administration approved abatacept for use in children over six years of age with JIA and a polyarticular course. In 2010, the European Medicines Agency gave approval for abatacept to be used in combination with methotrexate for those who fail at least one disease-modifying medication and TNF-α blockade.

Association of the CCR5 gene with juvenile idiopathic arthritis

The CC chemokine receptor 5 (CCR5) has been shown to be important in the recruitment of T-helper cells to the synovium, where they accumulate, drive the inflammatory process and the consequent synovitis and joint destruction. A 32 base-pair insertion/deletion variant (CCR5Δ32) within the gene leads to a frame shift and a nonfunctional receptor. CCR5Δ32 has been investigated for its association with juvenile idiopathic arthritis (JIA), with conflicting results. The aim of this study was to investigate whether CCR5Δ32 is associated with JIA in an UK population. CCR5Δ32 was genotyped in JIA cases (n=1054) and healthy controls (n=3129) and genotype and allele frequencies were compared. A meta-analysis of our study combined with previously published studies was performed. CCR5Δ32 was significantly associated with protection from developing JIA, in this UK data set (P(trend)=0.006, odds ratio (OR) 0.79 95% confidence interval (95% CI): 0.66-0.94). The meta-analysis of all published case-control association studies confirmed the protective association with JIA (P=0.001 OR 0.82 95% CI: 0.73-0.93). CCR5Δ32 is a functional variant determining the number of receptors on the surface of T cells, and it is hypothesized that the level of CCR5 expression could influence the migration of proinflammatory T cells into the synovium and thus susceptibility to JIA.

PTPN2 but not PTPN22 is associated with Crohn's disease in a New Zealand population

Recent genome-wide association studies have provided evidence for the involvement of the genes PTPN2 and PTPN22 in the pathogenesis of Crohn's disease (CD). We investigated whether genetic variants in these genes were associated with CD in a New Zealand population. Single-nucleotide polymorphisms (SNPs) rs2542151 (PTPN2) and rs2476601 (PTPN22) were genotyped in 315 CD cases and 481 controls. In this sample, we were able to confirm an association between CD and PTPN2 (genotypic P = 0.019 and allelic P = 0.011), and phenotypic analysis showed an association of this SNP with late age at first diagnosis, inflammatory and penetrating CD behaviour, requirement of bowel resection and being a smoker at diagnosis. There was no evidence for an association with PTPN22.

Inclusion of a priori information in genome-wide association analysis

Genome-wide association studies (GWAS) continue to gain in popularity. To utilize the wealth of data created more effectively, a variety of methods have recently been proposed to include a priori information (e.g., biologically interpretable sets of genes, candidate gene information, or gene expression) in GWAS analysis. Six contributions to Genetic Analysis Workshop 16 Group 11 applied novel or recently proposed methods to GWAS of rheumatoid arthritis and heart disease related phenotypes. The results of these analyses were a variety of novel candidate genes and sets of genes, in addition to the validation of well-known genotype-phenotype associations. However, because many methods are relatively new, they would benefit from further methodological research to ensure that they maintain type I error rates while increasing power to find additional associations. When methods have been adapted from other study types (e.g., gene expression data analysis or linkage analysis), the lessons learned there should be used to guide implementation of techniques. Lastly, many open research questions exist concerning the logistic details of the origin of the a priori information and the way to incorporate it. Overall, our group has demonstrated a strong potential for identifying novel genotype-phenotype relationships by including a priori data in the analysis of GWAS, while also uncovering a series of questions requiring further research.

Association of the AFF3 gene and IL2/IL21 gene region with juvenile idiopathic arthritis

Recent genetic studies have led to identification of numerous loci that are associated with susceptibility to autoimmune diseases. The strategy of using information from these studies has facilitated the identification of novel juvenile idiopathic arthritis (JIA) susceptibility loci, specifically, PTPN22 and IL2RA. Several novel autoimmune susceptibility loci have recently been identified, and we hypothesise that single-nucleotide polymorphisms (SNPs) within these genes may also be JIA susceptibility loci. Five SNPs within the genes AFF3, IL2/IL21, IL7R, CTLA4 and CD226, previously associated with multiple autoimmune diseases were genotyped, in a large data set of Caucasian JIA patients and controls, and tested for association with JIA. We identified two susceptibility loci for JIA, AFF3 and the IL2/IL21 region and additional weak evidence supporting an association with the CTLA4 and IL7R genes, which warrant further investigation. All results require validation in independent JIA data sets. Further characterisation of the specific causal variants will be required before functional studies can be performed.

An overview of genetics of paediatric rheumatic diseases

The evidence so far suggests that the paediatric inflammatory diseases encountered in rheumatology practice may be largely genetic in origin, where common single nucleotide polymorphisms (SNPs) in multiple genes contribute to risk, with real but variable environmental components. As far as genetic susceptibility to common paediatric rheumatic diseases is concerned, only juvenile idiopathic arthritis (JIA) has been investigated in any substantial way so far. This article discusses susceptibility for different types of JIA, the different methods used and their advantages and disadvantages. The genetic code is also modifiable by epigenetic mechanisms and examples of these in immunity and rheumatoid arthritis are given to indicate another area of research in the elucidation of the genetics of paediatric rheumatic diseases.

Comparative analysis of different approaches for dealing with candidate regions in the context of a genome-wide association study

Genome-wide association studies (GWAS) test hundreds of thousands of single-nucleotide polymorphisms (SNPs) for association to a trait, treating each marker equally and ignoring prior evidence of association to specific regions. Typically, promising regions are selected for further investigation based on p-values obtained from simple tests of association. However, loci that exert only a weak, low-penetrant role on the trait, producing modest evidence of association, are not detectable in the context of a GWAS. Implementing prior knowledge of association in GWAS could increase power, help distinguish between false and true positives, and identify better sets of SNPs for follow-up studies.

Here we performed a GWAS on rheumatoid arthritis (RA) patients and controls (Problem 1, Genetic Analysis Workshop 16). In order to include prior information in the analysis, we applied four methods that distinctively deal with markers in candidate genes in the context of GWAS. SNPs were divided into a random and a candidate subset, then we applied empirical correction by permutation, false-discovery rate, false-positive report probability, and posterior odds of association using different prior probabilities. We repeated the same analyses on two different sets of candidate markers defined on the basis of previously reported association to RA following two different approaches. The four methods showed similar relative behavior when applied to the two sets, with the proportion of candidate SNPs ranked among the top 2,000 varying from 0 to 100%. The use of different prior probabilities changed the stringency of the methods, but not their relative performance.

PTPN22 allele polymorphisms in 15 Chinese populations

Protein tyrosine phosphatase non-receptor 22 (PTPN22) is involved in the negative regulation of T-cell responsiveness. Recently, it has been reported that a single nucleotide polymorphism (SNP), C1858T, in the gene PTPN22, encoding Arg620Trp in the lymphoid protein tyrosine phosphatase (LYP), is associated with an increased risk of a number of autoimmune diseases. To study the mutant frequency and polymorphism of PTPN22 in Chinese populations, 1085 individuals from 15 Chinese populations distributing widely from north to south were collected. The genotypes of PTPN22-C1858T were determined by polymerase chain reaction-restriction fragment length polymorphism with the digestion of restriction endonuclease RsaI. Of the 1085 individuals, 31 of whom were heterozygote (PTPN22-1858C/T), the frequency of PTPN22-1858T allele in those tested individuals was 1.43%. Moreover, the frequencies of PTPN22-1858T had significant variance in 15 populations of China (chi(2) = 74.1650, P < 0.01).

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.

The R620W polymorphism of the protein tyrosine phosphatase 22 gene in autoimmune thyroid diseases and rheumatoid arthritis in the Tunisian population

BACKGROUND

Protein tyrosine phosphatase (PTPN22) is involved in the negative regulation of T-cell responsiveness. The association of a coding variant of the PTPN22 gene (R620W) with a number of autoimmune diseases has been described.

AIM

The present study investigated whether PTPN22 gene polymorphism was also involved in the genetic predisposition to autoimmune thyroid diseases (AITDs) and rheumatoid arthritis (RA) in a Tunisian case control study.

SUBJECTS AND METHODS

DNA samples from 150 patients affected with RA, 204 patients affected with AITDs and 236 healthy controls were genotyped for PTPN22 R620W polymorphism (1858C/T). Genotyping was performed by the polymerase chain reaction-restriction fragment length polymorphism method.

RESULTS

No significant differences in T allele frequency (2.3% in RA patients and 1% in AITDs patients vs 2.6% in controls; p=0.85 and p=0.08, respectively) and in genotype frequencies were detected between RA patients and controls (p=0.15) and between AITDs patients (p=0.11). Stratifying patients affected with AITDs according to their phenotype (Graves' disease and Hashimoto's thyroiditis) and RA patients according to the presence of rheumatoid factor (RF) and antibodies against cyclic citrullinated peptides (ACPA) did not show any significant association with PTPN22 R620W allele (p>0.05).

CONCLUSION

Our data suggest that the PTPN22 C1858T single nucleotide polymorphism has no or minor effect on RA and AITDs susceptibility in the Tunisian population.

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.

Genetic association of the major histocompatibility complex with rheumatoid arthritis implicates two non-DRB1 loci

OBJECTIVE

The HLA-DRB1 locus within the major histocompatibility complex (MHC) at 6p21.3 has been identified as a susceptibility gene for rheumatoid arthritis (RA); however, there is increasing evidence of additional susceptibility genes in the MHC region. The aim of this study was to estimate their number and location.

METHODS

A case-control study was performed involving 977 control subjects and 855 RA patients. The HLA-DRB1 locus was genotyped together with 2,360 single-nucleotide polymorphisms in the MHC region. Logistic regression was used to detect DRB1-independent effects.

RESULTS

After adjusting for the effect of HLA-DRB1, 18 markers in 14 genes were strongly associated with RA (P<10(-4)). Multivariate logistic regression analysis of these markers and DRB1 led to a model containing DRB1 plus the following 3 markers: rs4678, a nonsynonymous change in the VARS2L locus, approximately 1.7 Mb telomeric of DRB1; rs2442728, upstream of HLA-B, approximately 1.2 Mb telomeric of DRB1; and rs17499655, located in the 5'-untranslated region of DQA2, only 0.1 Mb centromeric of DRB1. In-depth investigation of the DQA2 association, however, suggested that it arose through cryptic linkage disequilibrium with an allele of DRB1. Two non-shared epitope alleles were also strongly associated with RA (P<10(-4)): *0301 with anti- cyclic citrullinated peptide-negative RA and *0701 independently of autoantibody status.

CONCLUSION

These results confirm the polygenic contribution of the MHC to RA and implicate 2 additional non-DRB1 susceptibility loci. The role of the HLA-DQ locus in RA has been a subject of controversy, but in our data, it appears to be spurious.

Are pediatric autoimmune diseases primarily genetic diseases?

PURPOSE OF REVIEW

Powerful new methods are allowing identification of genetic risk factors in large populations of adults with autoimmune diseases. In this review, we describe the advantages and limitations of genetic methodologies, and how these methods have been used to discover candidate genes in smaller populations of pediatric patients. We also introduce novel concepts for nontraditional modes of genetic inheritance that may be important in the pathogenesis of autoimmunity.

RECENT FINDINGS

Candidate genes identified by linkage analyses and genome-wide association scans in adult populations have led to focused genetic studies in pediatric populations. Some genes are associated with subsets of both adult and pediatric patients; others appear to be age specific. Novel concepts in genetics have uncovered potential contributions of maternal compared with paternal transmission, noninherited maternal alleles that may work through maternal microchimerism, and sex-specific epigenetic mechanisms of immunoregulation.

SUMMARY

Advancing methods are leading to the discovery of genes associated with childhood autoimmune diseases. However, the genetic contribution to disease risk for any one gene remains less than 30% for most diseases, suggesting that pediatric autoimmunity is not primarily genetic in a classical sense. A combinatorial approach considering the contributions of multiple genes, mode of inheritance, and environmental influences will be required to fully understand the mechanisms of pathogenesis in pediatric autoimmune disease.

The protein tyrosine phosphatase N22 gene is associated with juvenile and adult idiopathic inflammatory myopathy independent of the HLA 8.1 haplotype in British Caucasian patients

OBJECTIVE

To examine single-nucleotide polymorphisms (SNPs) of the protein tyrosine phosphatase N22 gene (PTPN22) and to study the relationship between PTPN22 and the HLA region in patients with idiopathic inflammatory myopathies (IIMs).

METHODS

PTPN22 SNPs were assessed in a large, cross-sectional, case-control study from the UK involving patients with adult or juvenile IIM, comprising patients with polymyositis (PM) (n=114), dermatomyositis (DM) (n=102), myositis associated with another connective tissue disease (myositis-CTD overlap syndrome) (n=64), or juvenile DM (n=101), in comparison with 748 control subjects. Seventeen PTPN22 SNPs were genotyped using the Sequenom MassArray iPLEX platform. Serotyping for myositis-specific/myositis-associated autoantibodies (MSAs/MAAs) was performed by radioimmunoprecipitation.

RESULTS

A significant association was noted between the R620W variant (rs2476601) and IIM (corrected P [Pcorr]=0.0009 versus controls), and specifically with the clinical subgroup of PM (Pcorr=0.003 versus controls). A weaker association was noted with juvenile DM (Pcorr=0.009 versus controls). No significant associations were noted after stratification by serologic subgroups. The association with the R620W variant was independent of alleles forming the HLA 8.1 haplotype. No other PTPN22 SNPs were associated with IIM. The PTPN22 haplotype containing the R620W T allele was the only haplotype significantly associated with IIM.

CONCLUSION

The R620W variant is a significant risk factor for IIM, independent of the HLA 8.1 haplotype. Unlike that in the HLA region, risk is not increased in individuals possessing MSAs/MAAs. These results are further evidence that the PTPN22 gene confers autoimmune susceptibility.

Re-evaluation of putative rheumatoid arthritis susceptibility genes in the post-genome wide association study era and hypothesis of a key pathway underlying susceptibility

Rheumatoid arthritis (RA) is an archetypal, common, complex autoimmune disease with both genetic and environmental contributions to disease aetiology. Two novel RA susceptibility loci have been reported from recent genome-wide and candidate gene association studies. We, therefore, investigated the evidence for association of the STAT4 and TRAF1/C5 loci with RA using imputed data from the Wellcome Trust Case Control Consortium (WTCCC). No evidence for association of variants mapping to the TRAF1/C5 gene was detected in the 1860 RA cases and 2930 control samples tested in that study. Variants mapping to the STAT4 gene did show evidence for association (rs7574865, P = 0.04). Given the association of the TRAF1/C5 locus in two previous large case–control series from populations of European descent and the evidence for association of the STAT4 locus in the WTCCC study, single nucleotide polymorphisms mapping to these loci were tested for association with RA in an independent UK series comprising DNA from >3000 cases with disease and >3000 controls and a combined analysis including the WTCCC data was undertaken. We confirm association of the STAT4 and the TRAF1/C5 loci with RA bringing to 5 the number of confirmed susceptibility loci. The effect sizes are less than those reported previously but are likely to be a more accurate reflection of the true effect size given the larger size of the cohort investigated in the current study.

The PTPN22 promoter polymorphism -1123G>C association cannot be distinguished from the 1858C>T association in a Norwegian rheumatoid arthritis material

The protein tyrosine phosphatase nonreceptor 22 (PTPN22) gene has, during the last 2 years, been recognized as a susceptibility gene for numerous autoimmune diseases, including rheumatoid arthritis (RA) and type 1 diabetes. An association between the exonic 1858C>T single nucleotide polymorphism (SNP) and RA has repeatedly been replicated in several Caucasian populations. The SNP is not associated with autoimmune diseases in Asian populations, as the 1858T allele is almost absent. Recently, a promoter polymorphism -1123G>C was proposed to be associated with acute-onset type 1 diabetes in Japanese and Korean populations. Furthermore, in Caucasian populations, the presence of additional PTPN22 risk variants has been suggested, indicating that the 1858C>T risk variant cannot explain the entire disease association observed in the region. In this study, we wanted to jointly address and integrate these separate findings to further elucidate the association between the PTPN22 gene and RA in a Norwegian material of 861 RA patients and 559 healthy controls. Our results revealed that the strength of the association with the PTPN22 promoter polymorphism, -1123G>C, is analogous to that observed for 1858C>T. As the -1123G>C variant is also polymorphic in Asian populations, our data underpin the need to further explore the association between this variant and autoimmune diseases in different populations.

Genetic polymorphisms in susceptibility to Type 1 Diabetes

Type 1 Diabetes is a serious complex disease caused by several environmental and genetic factors. It is one of most common childhood diseases, requires life-long treatment, and is associated with increased mortality, mainly due to complications that occur later in life. More than three decades of genetic studies have identified several genetic disease variants and a longer list of putative associated genetic loci. These findings have greatly increased our understanding of the genetic background of T1D and have encouraged the development of genetic tools for mapping complex diseases. Here we review the wealth of data on T1D and discuss the major genetic polymorphisms involved in the disease. We place some putative genetic risk factors in perspective and look at those still to be detected.

Association of interleukin-6 and interleukin-10 genotypes with radiographic damage in rheumatoid arthritis is dependent on autoantibody status

Objective

Recent evidence has highlighted a major genetic contribution to radiographic damage in rheumatoid arthritis (RA). The objective of this study was to determine whether genetic variants in the loci for interleukin-1 (IL-1), IL-6, IL-10, protein tyrosine phosphatase N22 (PTPN22), and selenoprotein S are associated with radiographic damage.

Methods

Modified Larsen scores of radiographic damage were determined in a cross-sectional population of patients with RA (n = 964). Rheumatoid factor (RF) and anti–cyclic citrullinated peptide (anti-CCP) were also assayed. The Kruskal-Wallis nonparametric test was used to compare median radiographic damage scores across genotype groups, followed by the Cuzick nonparametric test for trend to assess gene-dose effects.

Results

An allele-dose association of IL-6 −174G with increasing radiographic damage was present (P = 0.005), but only in patients who were RF positive (P = 0.004) or anti-CCP positive (P = 0.01). Patients with the IL-10 −592CC genotype had more extensive radiographic damage than did those with the AC or AA genotype (P = 0.006), but this was observed only among patients who were RF negative (P = 0.002) or anti-CCP negative (P = 0.002). However, RF status and anti-CCP status were not associated with the IL-6 or IL-10 genotype. No other genetic associations were detected, apart from a marginal association of PTPN22 +1858T with increased radiographic damage.

Conclusion

The reported associations of IL-6 −174G with high IL-6 production and IL-10 −592 with low IL-10 production and our own results support a role of genetically determined dysregulated cytokine production in disease severity. The lack of association of these genotypes with RF and anti-CCP antibody status suggests that they act downstream of autoantibody production. We conclude that IL-6 and IL-10 genotypes may be useful in predicting disease severity in autoantibody-positive and autoantibody-negative patients, respectively.

The PTPN22*C1858T functional polymorphism is associated with susceptibility to inflammatory polyarthritis but neither this nor other variants spanning the gene is associated with disease outcome

BACKGROUND

The PTPN22 gene has been widely confirmed as a susceptibility gene for rheumatoid arthritis (RA) in populations of Northern European descent. The aim of the current study was to explore the role of variants spanning the PTPN22 gene in determining susceptibility to and outcome of inflammatory polyarthritis (IP).

PATIENTS AND METHODS

Single nucleotide polymorphism (SNP) variants spanning the gene were genotyped using the Sequenom MassArray platform and tested, firstly for their association with susceptibility to IP. Genotype frequencies were compared between new onset IP cases (n = 843) and population controls (n = 471). Secondly, a within-cohort analysis was performed testing each variant for association with a number of clinical outcome measures reflecting disease severity including radiological erosions, physical function, measured using the Health Assessment Questionnaire (HAQ) score, and disease activity at defined time-points following disease presentation.

RESULTS

A significant association between carriage of the PTPN22*1858T allele and IP (odds ratio (OR) = 1.4 (95% CI 1.1-1.9), p = 0.02) was observed. The strength of the effect was similar in the RA subgroup (OR = 1.4 (95% CI 1.0-1.9), p = 0.05). No association between IP susceptibility and any of the other SNPs was detected. No association was detected for any of the SNPs tested, including the PTPN22*C1858T polymorphism, for either erosive status, Larsen score by 5 years or other markers of clinical outcome.

CONCLUSION

The PTPN22*C1858T polymorphism is associated with susceptibility to IP, but we have found no evidence for association of this or other variants spanning the gene with clinical outcome measures.

Associations between the PTPN22 1858C->T polymorphism and radiographic joint destruction in patients with rheumatoid arthritis: results from a 10-year longitudinal study

OBJECTIVE

To investigate whether the PTPN22 1858T risk variant is associated with the rate of radiographic progression in rheumatoid arthritis (RA).

METHODS

A longitudinally followed cohort of 238 Norwegian patients with RA (the EURIDISS cohort) was genotyped for the PTPN22 1858C-->T polymorphism. Radiographic damage was assessed by hand radiographs at baseline and after 1, 2, 5 and 10 years, and the radiographs were scored with the Sharp method modified by van der Heijde (Sharp-van der Heijde score) by a single experienced reader. Baseline serum levels of rheumatoid factor and anti-cyclic citrullinated peptide autoantibodies were also examined.

RESULTS

The reported association between RA susceptibility and carriage of the T allele (34.4% in patients vs 21.4% in controls; odds ratio 1.92, 95% confidence interval 1.36 to 2.71, p = 0.0002) was confirmed. An association between annual progression rate of Sharp-van der Heijde score and T-allele carriers (p = 0.01),was also found, which was also present when only patients positive for the shared epitope were analysed (p = 0.03). This association was also maintained in multivariate analyses adjusting for shared epitope and demographic variables.

CONCLUSIONS

An association between the PTPN22 risk variant and increased progression rate for structural damage was found. The results indicate that the PTPN22 gene may not only be associated with disease susceptibility, but also with disease progression.

Linkage proof for PTPN22, a rheumatoid arthritis susceptibility gene and a human autoimmunity gene

The tyrosine phosphatase PTPN22 allele 1858T has been associated with rheumatoid arthritis (RA) and other autoimmune diseases. RA is the most frequent of those multifactorial diseases. The RA association was usually restricted to serum rheumatoid factor positive disease (RF+). No interaction was shown with HLA-DRB1, the first RA gene. Many case-control studies replicated the RA association, showing an allele frequency increase of approximately 5% on average and large variations of population allele frequencies (2.1-15.5%). In multifactorial diseases, the final proof for a new susceptibility allele is provided by departure from Mendel's law (50% transmission from heterozygous parents). For PTPN22-1858T allele, convincing linkage proof was available only for type 1 diabetes. We aimed at providing this proof for RA. We analyzed 1,395 West European Caucasian individuals from 465 "trio" families. We replicated evidence for linkage, demonstrating departure from Mendel's law in this subset of early RA onset patients. We estimated the overtransmission of the 1858T allele in RF+ families: T = 63%, P < 0.0007. The 1858T allele frequency increased from 11.0% in controls to 17.4% in RF+ RA for the French Caucasian population and the susceptibility genotype (1858T/T or T/C) from 20.2% to 31.6% [odds ratio (OR) = 1.8 (1.2-2.8)]. In conclusion, we provided the linkage proof for the PTPN22-1858T allele and RF+ RA. With diabetes and RA, PTPN22 is therefore a "linkage-proven" autoimmunity gene. PTPN22 accounting for approximately 1% of the RA familial aggregation, many new genes could be expected that are as many leads to definitive therapy for autoimmune diseases.

Aspects of early arthritis. Biological therapy in early arthritis--overtreatment or the way to go?

The availability of newer, and more expensive, therapies for patients with rheumatoid arthritis has changed treatment beyond recognition. Disease remission is the goal for all new patients. Studies have shown that a combination of tumour necrosis factor (TNF)-blocking drugs and methotrexate produces superior outcomes over monotherapy alone; however, use is limited by cost and potential side-effects. Currently, anti-TNF therapy is normally reserved for patients who have failed traditional disease-modifying anti-rheumatic drugs. The question that remains is whether TNF-blocking drugs are better used if given early; the high direct costs are countered by both direct and indirect savings in healthcare costs from optimal control of disease, and the benefits of early control outweigh the increased risk of infection and malignancy.

Recent advances in the genetics of rheumatoid arthritis

Recent progress in defining the role of genetic factors in rheumatoid arthritis (RA) has been remarkable. Anticyclic citrullinated peptide (anti-CCP) antibody-positive disease appears to be immunogenetically distinct from anti-CCP-negative disease, with the former subgroup primarily responsible for association and linkage with the HLA-DRB1 shared epitope (SE). There is preliminary evidence that non-HLA genes contribute differentially to anti-CCP-positive and negative disease. The phenotypic differences evident in anti-CCP-positive and negative disease suggest a need to reclassify RA based on the presence or absence of this autoantibody. Some recent work also suggests marked interactions between cigarette smoking, anti-CCP antibodies, and the SE, though these relationships may vary across populations. Lastly, a recent single nucleotide polymorphism-based genome-wide linkage analysis of multicase RA families revealed novel genomic regions that likely contain genes that predispose to RA or more specific phenotypes.

Investigation of genetic variation across the protein tyrosine phosphatase gene in patients with rheumatoid arthritis in the UK

OBJECTIVE

To investigate single-nucleotide polymorphisms (SNPs) across the PTPN22 gene region in a UK cohort of patients with rheumatoid arthritis (RA), to look for evidence of disease associations independent of the well-characterised R620W variant (rs2476601).

METHODS

951 RA cases in the UK satisfying American Rheumatism Association (ARA) criteria and 448 population controls were genotyped for 11 SNPs across the PTPN22 gene region using the Sequenom MassArray MassEXTEND technology. Allele, genotype and estimated haplotype frequencies of cases and controls were compared.

RESULTS

In addition to the R620W (rs2476601) SNP, three SNPs were associated with RA in this study. The sole haplotype on which the associated T allele of R620W occurred was associated with RA; no other haplotypes showed a significant difference in frequencies between RA cases and controls.

CONCLUSION

In contrast with a study of American patients with RA no evidence of association with PTPN22 independent of the well-characterised R620W variant was found, suggesting that in these patients this variant alone explains the association with the PTPN22 gene.