BANK1is a genetic risk factor for diffuse cutaneous systemic sclerosis and has additive effects withIRF5andSTAT4

Epistatic interaction between BANK1 and BLK in rheumatoid arthritis: results from a large trans-ethnic meta-analysis

BACKGROUND

BANK1 and BLK belong to the pleiotropic autoimmune genes; recently, epistasis between BANK1 and BLK was detected in systemic lupus erythematosus. Although BLK has been reproducibly identified as a risk factor in rheumatoid arthritis (RA), reports are conflicting about the contribution of BANK1 to RA susceptibility. To ascertain the real impact of BANK1 on RA genetic susceptibility, we performed a large meta-analysis including our original data and tested for an epistatic interaction between BANK1 and BLK in RA susceptibility.

PATIENTS AND METHODS

We investigated data for 1,915 RA patients and 1,915 ethnically matched healthy controls genotyped for BANK1 rs10516487 and rs3733197 and BLK rs13277113. The association of each SNP and RA was tested by logistic regression. Multivariate analysis was then used with an interaction term to test for an epistatic interaction between the SNPs in the 2 genes.

RESULTS

None of the SNPs tested individually was significantly associated with RA in the genotyped samples. However, we detected an epistatic interaction between BANK1 rs3733197 and BLK rs13277113 (P(interaction)  = 0.037). In individuals carrying the BLK rs13277113 GG genotype, presence of the BANK1 rs3733197 G allele increased the risk of RA (odds ratio 1.21 [95% confidence interval 1.04-1.41], P = 0.015. Combining our results with those of all other studies in a large trans-ethnic meta-analysis revealed an association of the BANK1 rs3733197 G allele and RA (1.11 [1.02-1.21], P = 0.012).

CONCLUSION

This study confirms BANK1 as an RA susceptibility gene and for the first time provides evidence for epistasis between BANK1 and BLK in RA. Our results illustrate the concept of pleiotropic epistatic interaction, suggesting that BANK1 and BLK might play a role in RA pathogenesis.

Inactivation of the transcription factor STAT-4 prevents inflammation-driven fibrosis in animal models of systemic sclerosis

OBJECTIVE

The transcription factor STAT-4 has recently been identified as a genetic susceptibility factor in systemic sclerosis (SSc) and other autoimmune diseases. The aim of this study was to investigate the contribution of STAT-4 in the development of a fibrotic phenotype in 2 different mouse models of experimental dermal fibrosis.

METHODS

STAT-4-deficient (stat4(-/-) ) mice and their wild-type littermates (stat4(+/+) ) were injected with bleomycin or NaCl. Infiltrating leukocytes, T cells, B cells, and monocytes were quantified in the lesional skin of stat4(-/-) and stat4(+/+) mice. Inflammatory and profibrotic cytokines were measured in sera and lesional skin samples from stat4(-/-) and stat4(+/+) mice. The outcome of mice lacking STAT-4 was also investigated in the tight skin 1 (TSK-1) mouse model.

RESULTS

Stat4(-/-) mice were protected against bleomycin-induced dermal fibrosis, with a reduction in dermal thickening (mean ± SEM 65 ± 3% decrease; P = 0.03), hydroxyproline content (68 ± 5% decrease; P = 0.02), and myofibroblast counts (71 ± 6% decrease; P = 0.005). Moreover, the number of infiltrating leukocytes, especially T cells, was significantly decreased in the lesional skin of stat4(-/-) mice (mean ± SEM 63 ± 5% reduction in T cell count; P = 0.02). Stat4(-/-) mice also displayed decreased levels of inflammatory cytokines such as tumor necrosis factor α, interleukin-6 (IL-6), IL-2, and interferon-γ in lesional skin. Consistent with a primary role of STAT-4 in inflammation, STAT-4 deficiency did not ameliorate fibrosis in TSK-1 mice.

CONCLUSION

The results of this study demonstrate that the transcription factor STAT-4 exerts potent profibrotic effects by controlling T cell activation and proliferation and cytokine release. These findings confirm the results of genetics studies on the role of STAT-4 in the development of SSc.

The genetics of scleroderma: looking into the postgenomic era

PURPOSE OF REVIEW

The last decade has seen enormous progress in understanding genetic associations of systemic sclerosis to explain the observed heritability. This review highlights the most recent findings and places them in the context of proposed functional roles.

RECENT FINDINGS

Over 30 genes and gene regions have now been identified as scleroderma susceptibility loci. These include both human leukocyte antigen (HLA) and non-HLA genes, most of which involve immune-related pathways and modifiers of immune function. Many of these associations have also been reported in other systemic autoimmune diseases and suggest that there are multiple autoimmunity genes resulting in disease occurrence.

SUMMARY

In spite of these advances, only a small proportion of the heritability of systemic sclerosis has been explained. Ongoing studies include fine mapping and sequencing studies to identify causal variants, whereas other studies focus on functional consequences of these variants in order to identify the link between these genetic variants and disease susceptibility. Such knowledge should lead to more targeted and effective treatment in this disease.

Altered BANK1 expression is not associated with humoral autoimmunity in chronic joint inflammation

OBJECTIVE

The presence of disease-specific autoantibodies in RA but not spondyloarthritis (SpA) suggests that B-cell tolerance is preserved in the latter condition despite chronic joint inflammation. Which factors control B-cell tolerance vs autoimmunity in chronic arthritis remains incompletely understood. As single nucleotide polymorphisms in the B-cell scaffold protein with ankyrin repeats (BANK1) gene have recently been associated with various autoantibody-positive autoimmune diseases including RA, we explored whether altered expression of BANK1 was associated with humoral autoimmunity in arthritis.

METHODS

Peripheral B-cell subsets and inflamed synovial tissue were obtained from active SpA and RA. Quantitative PCR was used to assess the expression of full-length BANK1 and delta2 BANK1, a splice variant lacking exon 2 that counteracts BANK1 function. B-cell subsets, autoantibody titres and clinical disease were monitored upon CIA induction in Bank1 knockout (KO) mice.

RESULTS

Whereas full-length BANK1 was not differentially expressed, the BANK1 delta2 splicing variant was decreased in naïve peripheral B cells as well as in synovial tissue of SpA compared with RA. However, no differences were observed in seropositive vs seronegative RA. Performing functional analysis in mice, we found no differences in B-cell subsets and anti-collagen antibodies upon CIA induction between Bank1 KO mice and littermate controls. Accordingly, the incidence and severity of clinical disease were not altered in Bank1 KO mice.

CONCLUSION

This study did not reveal a major role for BANK1 in humoral autoimmunity in chronic arthritis. The decreased levels of BANK1 delta2 in SpA, however, warrant more detailed analysis of the functional consequences of an altered BANK1/BANK1 delta2 balance.

A multicenter study confirms CD226 gene association with systemic sclerosis-related pulmonary fibrosis

Introduction

CD226 genetic variants have been associated with a number of autoimmune diseases and recently with systemic sclerosis (SSc). The aim of this study was to test the influence of CD226 loci in SSc susceptibility, clinical phenotypes and autoantibody status in a large multicenter European population.

Methods

A total of seven European populations of Caucasian ancestry were included, comprising 2,131 patients with SSc and 3,966 healthy controls. Three CD226 single nucleotide polymorphisms (SNPs), rs763361, rs3479968 and rs727088, were genotyped using Taqman 5'allelic discrimination assays.

Results

Pooled analyses showed no evidence of association of the three SNPs, neither with the global disease nor with the analyzed subphenotypes. However, haplotype block analysis revealed a significant association for the TCG haplotype (SNP order: rs763361, rs34794968, rs727088) with lung fibrosis positive patients (P_Bonf = 3.18E-02 OR 1.27 (1.05 to 1.54)).

Conclusion

Our data suggest that the tested genetic variants do not individually influence SSc susceptibility but a CD226 three-variant haplotype is related with genetic predisposition to SSc-related pulmonary fibrosis.

Genetics of systemic sclerosis: an update

Systemic sclerosis (SSc) is an autoimmune disease characterized by vasculopathy, immune cell activation, and fibrosis of the skin and internal organs. Over the past few years, a role for genetics in the susceptibility for SSc has been established. This review aims to provide an update on the progress made in the past year or so within the field of SSc genetics research. This year has been of particular interest due to the publication of a large genome-wide association study, further investigations into gene-gene interactions, and the tendency to validate genetic results in functional models.

Evidence of the contribution of the X chromosome to systemic sclerosis susceptibility: association with the functional IRAK1 196Phe/532Ser haplotype

OBJECTIVE

Several autoimmune disorders, including systemic sclerosis (SSc), are characterized by a strong sex bias. To date, it is not known whether genes on the sex chromosomes influence SSc susceptibility. Recently, an IRAK1 haplotype that contains the 196Phe functional variant (rs1059702), located on Xq28, was found to confer susceptibility to systemic lupus erythematosus (SLE). This study was undertaken to test for an association between SSc and the IRAK1 SLE risk haplotype.

METHODS

We tested for an association with the IRAK1 SLE risk haplotype in a discovery set of 849 SSc patients and 625 controls. IRAK1 rs1059702 was further genotyped in a replication set, which included Caucasian women from Italy (493 SSc patients and 509 controls) and Germany (466 SSc patients and 1,083 controls).

RESULTS

An association between the IRAK1 haplotype and SSc was detected in the discovery set. In both the discovery and replication sets, the rs1059702 TT genotype was found to be associated with specific SSc subsets, highlighting a potential contribution to disease severity. A meta-analysis provided evidence of an association of both the T allele and TT genotype with the overall disease, with an odds ratio (OR) of 1.20 and 95% confidence interval (95% CI) of 1.06-1.35 for the T allele (P = 0.003) and an OR of 1.49 and 95% CI of 1.06-2.10 for the TT genotype (P = 0.023). However, the most notable associations were observed with the diffuse cutaneous, anti-topoisomerase I antibody positive, and SSc-related fibrosing alveolitis subsets (OR 2.35 [95% CI 1.51-3.66], P = 1.56 × 10(-4), OR 2.84 [95% CI 1.87-4.32], P = 1.07 × 10(-6), and OR 2.09 [95% CI 1.35-3.24], P = 9.05 × 10(-4), respectively).

CONCLUSION

Our study provides the first evidence of an association between IRAK1 and SSc, demonstrating that a sex chromosome gene directly influences SSc susceptibility and its phenotypic heterogeneity.

An update on an immune system that goes awry in systemic sclerosis

PURPOSE OF REVIEW

This review aims to provide an overview of the recent data that emerged, further substantiating the critical role of innate immunity in systemic sclerosis (SSc).

RECENT FINDINGS

Driven by the evidence that newly identified SSc susceptibility genes are predominantly involved in immune regulation, we discuss the aberrant antigen presenting cell (APC) activation observed in the course of disease. In particular, we report the alternate activation of 'M1' and 'M2' macrophages reflecting different clinical phenotypes and the aberrant Toll-like receptor (TLR) response, whose effect on cytokine production is mostly evident in the early phases of disease; we especially highlight the increasing importance attributed to TLR3-mediated fibrosis. We next discuss the potential role for interferon (IFN) - producing plasmacytoid dendritic cells (pDCs) in triggering or perpetuating the inflammatory loop caused by TLR hyperactivation, possibly resulting in inflammasome-derived IL-1β-mediated fibrosis and IL-17 producing T helper cells (Th17) skewing.

SUMMARY

We propose to approach SSc as a multistep immune-mediated disease that is in need of a therapeutic strategy designed to interfere with one or more of these aberrant molecular pathways. Targeting of DCs could be such a target by which dampening the immune system could modify the course of SSc.

Familial Autoimmunity in Systemic Sclerosis — Results of a French-based Case-Control Family Study

Objective.

To assess the prevalence of autoimmune diseases in first-degree relatives of patients with systemic sclerosis (SSc), and to compare those results with control families in order to identify patterns of autoimmune diseases in relatives.

Methods.

A retrospective case-control postal questionnaire survey was performed in France to recruit patients with SSc belonging to an association of patients with SSc and unrelated age-matched and sex-matched controls. Each participant was asked to self-report on the existence of autoimmune diseases in their first-degree relatives. The prevalence of autoimmune diseases in the families of patients with SSc was compared with the corresponding prevalence in the families of controls.

Results.

A total of 121 families out of 373 (32.4%) with a member having SSc reported at least 1 autoimmune disease in 1 or more first-degree relatives. The most frequent autoimmune diseases in SSc families when adjusted for family size were autoimmune thyroid disease (AITD; 4.9%), rheumatoid arthritis (4.1%), psoriasis (3.9%), and type 1 diabetes mellitus (2.9%). Compared with control families, AITD and connective tissue diseases (SSc, systemic lupus erythematosus, or Sjögren’s syndrome) were more likely to occur in families with SSc (p = 0.01 and p = 0.01, respectively), with OR of 3.20 (95% CI 1.25–8.18) and 5.20 (95% CI 1.22–21.8). In contrast, inflammatory bowel disease was less likely to occur within families with SSc (p = 0.02, OR 0.29, 95% CI 0.11–0.80). In addition, the coexistence of more than 1 autoimmune disease in the index SSc case was associated with familial aggregation of autoimmune diseases.

Conclusion.

Our results show that autoimmune diseases cluster within families of patients with SSc. This supports the notion that these diseases might arise on a shared genetic basis underlying several autoimmune phenotypes.

Unraveling the genetic component of systemic sclerosis

Systemic sclerosis (SSc) is a severe connective tissue disorder characterized by extensive fibrosis, vascular damage, and autoimmune events. During the last years, the number of genetic markers convincingly associated with SSc has exponentially increased. In this report, we aim to offer an updated review of the classical and novel genetic associations with SSc, analyzing the firmest and replicated signals within HLA and non-HLA genes, identified by both candidate gene and genome-wide association (GWA) studies. We will also provide an insight into the future perspectives and approaches that might shed more light into the complex genetic background underlying SSc. In spite of the remarkable advance in the field of SSc genetics during the last decade, the use of the new genetic technologies such as next generation sequencing (NGS), as well as the deep phenotyping of the study cohorts, to fully characterize the genetic component of this disease is imperative.

Twin studies in autoimmune disease: genetics, gender and environment

Twin studies are powerful tools to discriminate whether a complex disease is due to genetic or environmental factors. High concordance rates among monozygotic (MZ) twins support genetic factors being predominantly involved, whilst low rates are suggestive of environmental factors. Twin studies have often been utilised in the study of systemic and organ specific autoimmune diseases. As an example, type I diabetes mellitus has been investigated to establish that that disease is largely affected by genetic factors, compared to rheumatoid arthritis or scleroderma, which have a weaker genetic association. However, large twin studies are scarce or virtually non-existent in other autoimmune diseases which have been limited to few sets of twins and individual case reports. In addition to the study of the genetic and environmental contributions to disease, it is likely that twin studies will also provide data in regards to the clinical course of disease, as well as risk for development in related individuals. More importantly, genome-wide association studies have thus far reported genomic variants that only account for a minority of autoimmunity cases, and cannot explain disease discordance in MZ twins. Future research is therefore encouraged not only in the analysis of twins with autoimmune disease, but also in regards to epigenetic factors or rare variants that may be discovered with next-generation sequencing. This review will examine the literature surrounding twin studies in autoimmune disease including discussions of genetics and gender.

Primary biliary cirrhosis associated with systemic sclerosis: diagnostic and clinical challenges

Patients with primary biliary cirrhosis (PBC) often have concurrent limited systemic sclerosis (SSc). Conversely, up to one-fourth of SSc patients are positive for PBC-specific antimitochondrial antibodies (AMA). The mechanisms responsible for the co-occurrence of these diseases are largely unknown. Genetic, epigenetic, environmental, and infectious factors appear to be important for the pathogenesis of the disease, but the hierarchy of events are not well defined. Patients with SSc and PBC have an increased morbidity and mortality compared with the general population, but whether the presence of both diseases in an affected individual worsens the prognosis and/or outcome of either disease is not clear. Some case reports suggested that the presence of SSc in PBC patents is associated with a more favorable prognosis of the liver disease, whereas others report an increased mortality in patients with PBC and SSc compared to patients with PBC alone. This paper discusses the features of patients with PBC-associated SSc. Our aims are to clarify some of the pathogenetic, diagnostic, and clinical challenges that are currently faced in the routine management of these patients. We also intend to provide some practical hints for practitioners that will assist in the early identification of patients with PBC-associated SSc.

Novel insights on the role of the innate immune system in systemic sclerosis

Over the last several years the involvement of the innate immune system in the pathogenesis of autoimmune diseases such as systemic lupus erythematosus (SLE) has become well established. As systemic sclerosis (SSc; scleroderma) shares clinical features and autoantibodies with SLE, investigation has recently focused on the role of innate immunity in SSc. This has been supported by recent genetic studies. However, unlike SLE and other related autoimmune diseases, SSc patients suffer from pathologic fibrosis of skin and internal organs. The fibrotic component of SSc shares several features with syndromes following environmental exposures to agents such as organic solvents, silica dust and bleomycin. Recent work in SSc and these related fibrotic diseases have identified several areas in which innate immunity can stimulate inflammation as well as fibrosis. This article will focus on the recent discoveries identifying a prominent role of cells of the innate immune system, pattern recognition receptors, and activation of dendritic cells in the pathogenesis of SSc.

Deciphering the genetic background of systemic sclerosis

Systemic sclerosis (SSc) is a severe autoimmune connective tissue disease. Over the years, evidence for a genetic background of SSc susceptibility has clearly accumulated. This article aims to provide an extensive overview of genetics in SSc research. We discuss indicators for a genetic component present in SSc, family studies, chromosomal aberrances, the involvement of the HLA region and multiple candidate genes and, finally, genome-wide association studies.

Association analysis of BANK1 gene with psoriasis in Southern Han Chinese

Psoriasis is a chronic inflammatory skin disease with an immunogenetic background. This study aimed to determine the association between three functional SNPs of BANK1 (rs10516487, rs17266594 and rs3733197) with psoriasis in Southern Han Chinese population by determining their frequency in 242 patients with psoriasis and 317 healthy individuals. The genotype frequencies of the detected polymorphisms were analysed in relation to the susceptibility of psoriasis. Our data show that there is no significant difference in genotype distribution for the three BANK1 SNPs between patients and healthy controls. The AA frequency of rs3733197 is significantly higher in patients with psoriasis onset before the age of 23 than in those with late disease onset (P =  0.0069). In addition, analysis on BANK1 haplotype also suggests a protective role for TGC and CAT haplotype from psoriasis (OR 0.55, 95% CI: 0.34-0.89; P = 0.0144; OR 0.62, 95% CI: 0.42-0.92; P = 0.0175), whereas CGT haplotype is associated with increased risk of the disease (OR 1.38, 95% CI: 1.05-1.81, P = 0.0203). Overall, our result indicates that polymorphism in BANK1 is associated with susceptibility to psoriasis in Southern Han Chinese.

Towards systemic sclerosis and away from primary biliary cirrhosis: the case of PTPN22

Primary biliary cirrhosis (PBC) is a chronic cholestatic liver disease characterized by immune-mediated destruction of the small and medium size intrahepatic bile ducts. PBC patients often have concomitant autoimmune diseases, which are most often autoimmune thyroid disease, as well as Sicca syndrome. Occasionally, some PBC patients will also have systemic sclerosis of the limited cutaneous type (lcSSc). Conversely, up to one-fourth of SSc patients are positive for antimitochondrial antibody, the serologic hallmark of PBC. It is also common for SSc patients to have concomitant autoimmune disease, which may include PBC in rare cases. This has led to speculation of shared environmental and/or genetic factors, which lead to the development of PBC in SSc patients and vice versa. Recent genetic studies have revealed associations with several genes in both SSc and PBC. PTPN22 is one gene that has been associated with SSc, but not with PBC. It may be argued that some SSc patients with a particular genotype, which shares genes found in both conditions may develop PBC. Likewise, particular genes such as PTPN22 may infer susceptibility to SSc alone. The presence of PTPN22 may also contribute to the development of SSc in PBC patients. The lack of a large number of overlapping genes may, in part, explain the relative rarity of PBC with SSc and vice versa. This review will examine the literature surrounding the genetic associations of PBC and SSc, and the role of PTPN22 in particular.

Identification of novel genetic markers associated with clinical phenotypes of systemic sclerosis through a genome-wide association strategy

The aim of this study was to determine, through a genome-wide association study (GWAS), the genetic components contributing to different clinical sub-phenotypes of systemic sclerosis (SSc). We considered limited (lcSSc) and diffuse (dcSSc) cutaneous involvement, and the relationships with presence of the SSc-specific auto-antibodies, anti-centromere (ACA), and anti-topoisomerase I (ATA). Four GWAS cohorts, comprising 2,296 SSc patients and 5,171 healthy controls, were meta-analyzed looking for associations in the selected subgroups. Eighteen polymorphisms were further tested in nine independent cohorts comprising an additional 3,175 SSc patients and 4,971 controls. Conditional analysis for associated SNPs in the HLA region was performed to explore their independent association in antibody subgroups. Overall analysis showed that non-HLA polymorphism rs11642873 in IRF8 gene to be associated at GWAS level with lcSSc (P = 2.32×10⁻¹², OR = 0.75). Also, rs12540874 in GRB10 gene (P = 1.27 × 10⁻⁶, OR = 1.15) and rs11047102 in SOX5 gene (P = 1.39×10⁻⁷, OR = 1.36) showed a suggestive association with lcSSc and ACA subgroups respectively. In the HLA region, we observed highly associated allelic combinations in the HLA-DQB1 locus with ACA (P = 1.79×10⁻⁶¹, OR = 2.48), in the HLA-DPA1/B1 loci with ATA (P = 4.57×10⁻⁷⁶, OR = 8.84), and in NOTCH4 with ACA P = 8.84×10⁻²¹, OR = 0.55) and ATA (P = 1.14×10⁻⁸, OR = 0.54). We have identified three new non-HLA genes (IRF8, GRB10, and SOX5) associated with SSc clinical and auto-antibody subgroups. Within the HLA region, HLA-DQB1, HLA-DPA1/B1, and NOTCH4 associations with SSc are likely confined to specific auto-antibodies. These data emphasize the differential genetic components of subphenotypes of SSc.

Scleroderma or systemic sclerosis is a complex autoimmune disease affecting one individual of every 100,000 in Caucasian populations. Even though current genetic studies have led to better understanding of the pathogenesis of the disease, much remains unknown. Scleroderma is a heterogeneous disease, which can be subdivided according to different criteria, such as the involvement of organs and the presence of specific autoantibodies. Such subgroups present more homogeneous genetic groups, and some genetic associations with these manifestations have already been described. Through reanalysis of a genome-wide association study data, we identify three novel genes containing genetic variations which predispose to subphenotypes of the disease (IRF8, GRB10, and SOX5). Also, we better characterize the patterns of associated loci found in the HLA region. Together, our findings lead to a better understanding of the genetic component of scleroderma.

Updating the genetics of systemic sclerosis

PURPOSE OF REVIEW

Systemic sclerosis (SSc) is a connective tissue disease characterized by early generalized microangiopathy, immune system disturbances and massive deposits of collagen and other matrix substances in the connective tissue. Although rare, SSc presents a major medical challenge, being recognized as the most severe connective tissue disorder in terms of its prognosis. Molecular biology has provided unparalleled insight into the susceptibility genes conferring a predisposition to this disease and has improved our understanding of its complex immune pathogenesis. In this review, we focus on recent large candidate gene studies that have included replication and very recent genome-wide approaches.

RECENT FINDINGS

Attention has recently focused on both known and new susceptibility genes. Large studies have revealed various striking associations within the immune system, but associations with vascular or fibrotic factors were found to be weaker or were not replicated. The major histocompatibility complex genes are the predominant genetic region of importance for many autoimmune disorders, including SSc. Candidate gene studies and genome-wide studies have also provided evidence that various autoimmune genes implicated in innate immunity, T-cell differentiation and immune signaling play a critical role in this disease.

SUMMARY

The use of powerful molecular tools has shed light on the nature of the susceptibility genes for SSc and the pathophysiology of this disease. Postgenomic studies are now required to clarify the role of these genes. Improvements in diagnostic and prognostic tools are anticipated in the near future, together with the development of more specific immune therapy.

Pulmonary manifestations of scleroderma and mixed connective tissue disease

Pulmonary manifestations are common in connective tissue diseases, and are associated with significant morbidity and mortality in this patient population. Systemic sclerosis (SSc) and mixed connective tissue disease (MCTD) are clinical entities for which the detection of lung involvement is essential to improve patient care and outcomes. This article discusses the pathogenesis, clinical presentation, and evaluation of the patient with pulmonary disease related to SSc and MCTD, with an emphasis on interstitial lung disease and pulmonary hypertension.

Analysis of the influence of PTPN22 gene polymorphisms in systemic sclerosis

OBJECTIVE

Two functional single nucleotide polymorphisms (SNP) in the PTPN22 gene (rs24746601 and rs33996649) have been associated with autoimmunity. The aim of this study was to investigate the role of the R263Q SNP for the first time and to re-evaluate the role of the R620W SNP in the genetic predisposition to systemic sclerosis (SSc) susceptibility and clinical phenotypes.

METHODS

3422 SSc patients (2020 with limited cutaneous SSc and 1208 with diffuse cutaneous SSc) and 3638 healthy controls of Caucasian ancestry from an initial case--control set of Spain and seven additional independent replication cohorts were included in our study. Both rs33996649 and rs2476601 PTPN22 polymorphisms were genotyped by TaqMan allelic discrimination assay. A meta-analysis was performed to test the overall effect of these PTPN22 polymorphisms in SSc.

RESULTS

The meta-analysis revealed evidence of association of the rs2476601 T allele with SSc susceptibility (p(FDRcorrected)=0.03 pooled, OR 1.15, 95% CI 1.03 to 1.28). In addition, the rs2476601 T allele was significantly associated with anticentromere-positive status (p(FDRcorrected)=0.02 pooled, OR 1.22, 95% CI 1.05 to 1.42). Although the rs33996649 A allele was significantly associated with SSc in the Spanish population (p(FDRcorrected)=0.04, OR 0.58, 95% CI 0.36 to 0.92), this association was not confirmed in the meta-analysis (p=0.36 pooled, OR 0.89, 95% CI 0.72 to 1.1).

CONCLUSION

The study suggests that the PTPN22 R620W polymorphism influences SSc genetic susceptibility but the novel R263Q genetic variant does not. These data strengthen evidence that the R620W mutation is a common risk factor in autoimmune diseases.