M. Coenen

The STAT4 gene influences the genetic predisposition to systemic sclerosis phenotype

The aim of this study was to investigate the possible role of STAT4 gene in the genetic predisposition to systemic sclerosis (SSc) susceptibility or clinical phenotype. A total of 1317 SSc patients [896 with limited cutaneous SSc (lcSSc) and 421 with diffuse cutaneous SSc (dcSSc)] and 3113 healthy controls, from an initial case-control set of Spanish Caucasian ancestry and five independent cohorts of European ancestry (The Netherlands, Germany, Sweden, Italy and USA), were included in the study. The rs7574865 polymorphism was selected as STAT4 genetic marker. We observed that the rs7574865 T allele was significantly associated with susceptibility to lcSSc in the Spanish population [P = 1.9 x 10(-5) odds ratio (OR) 1.61 95% confidence intervals (CI) 1.29-1.99], but not with dcSSc (P = 0.41 OR 0.84 95% CI 0.59-1.21). Additionally, a dosage effect was observed showing individuals with rs7574865 TT genotype higher risk for lcSSc (OR 3.34, P = 1.02 x 10(-7) 95% CI 2.11-5.31). The association of the rs7574865 T allele with lcSSc was confirmed in all the replication cohorts with different effect sizes (OR ranging between 1.15 and 1.86), as well as the lack of association of STAT4 with dcSSc. A meta-analysis to test the overall effect of the rs7574865 polymorphism showed a strong risk effect of the T allele for lcSSc susceptibility (pooled OR 1.54 95% CI 1.36-1.74; P < 0.0001). Our data show a strong and reproducible association of the STAT4 gene with the genetic predisposition to lcSSc suggesting that this gene seems to be one of the genetic markers influencing SSc phenotype.

BANK1 functional variants are associated with susceptibility to diffuse systemic sclerosis in Caucasians

Objective To investigate the possible association of the BANK1 gene with genetic susceptibility to systemic sclerosis (SSc) and its subphenotypes. Methods A large multicentre case–control association study including 2380 patients with SSc and 3270 healthy controls from six independent case–control sets of Caucasian ancestry (American, Spanish, Dutch, German, Swedish and Italian) was conducted. Three putative functional BANK1 polymorphisms (rs17266594 T/C, rs10516487 G/A, rs3733197 G/A) were selected as genetic markers and genotyped by Taqman 5´ allelic discrimination assay. Results A significant association of the rs10516487 G and rs17266594 T alleles with SSc susceptibility was observed (pooled OR=1.12, 95% CI 1.03 to 1.22; p=0.01 and pooled OR=1.14, 95% CI 1.05 to 1.25; p=0.003, respectively), whereas the rs3733197 genetic variant showed no statistically significant deviation. Stratification for cutaneous SSc phenotype showed that the BANK1 rs10516487 G, rs17266594 T and rs3733197 G alleles were strongly associated with susceptibility to diffuse SSc (dcSSc) (pooled OR=1.20, 95% CI 1.05 to 1.37, p=0.005; pooled OR=1.23, 95% CI 1.08 to 1.41, p=0.001; pooled OR=1.15, 95% CI 1.02 to 1.31, p=0.02, respectively). Similarly, stratification for specific SSc autoantibodies showed that the association of BANK1 rs10516487, rs17266594 and rs3733197 polymorphisms was restricted to the subgroup of patients carrying anti-topoisomerase I antibodies (pooled OR=1.20, 95% CI 1.02 to 1.41, p=0.03; pooled OR=1.24, 95% CI 1.05 to 1.46, p=0.01; pooled OR=1.26, 95% CI 1.07 to 1.47, p=0.004, respectively). Conclusion The results suggest that the BANK1 gene confers susceptibility to SSc in general, and specifically to the dcSSc and anti-topoisomerase I antibody subsets.

Tumour necrosis factor alpha -308G->A polymorphism is not associated with response to TNFalpha blockers in Caucasian patients with rheumatoid arthritis: systematic review and meta-analysis.

Background There is a need for biomarkers that can predict anti-tumour necrosis factor (anti-TNF) treatment outcome in patients with rheumatoid arthritis (RA). Several studies have suggested that the rare A allele of the tumour necrosis factor α (TNFA) −308G→A polymorphism could be associated with a poorer response to anti-TNF therapy. Nevertheless, these results remain controversial. Objective To determine by a meta-analysis whether the TNFA −308G→A polymorphism is associated with response to anti-TNF treatment in patients with RA. Methods A bibliographic search identified studies in which the TNFA −308G→A gene polymorphism was investigated in Caucasian patients with RA treated with anti-TNF agents. Complementary data were requested when the 28-joint count Disease Activity Score (DAS28) was not used as the primary outcome measure. Odds ratios (ORs) for response based on DAS28 and standardised mean difference (SMD) for mean improvement of DAS28 were calculated to assess the potential association between TNFA −308 genotypes and response to anti-TNF agents. Results The bibliographic search yielded 12 studies that met the inclusion criteria, which were supplemented with the data from a large Dutch cohort (n=426). The OR based on the 12 studies including 1721 patients was 1.24 (95% CI 0.98 to 1.56) and the SMD based on 11 studies including 2579 patients was −0.18 (95% CI −0.36 to 0.1). Subgroup analysis based on the two classes of anti-TNF agents did not demonstrate any association between TNFA −308 genotypes and anti-TNF treatment outcome. Conclusion According to this meta-analysis, the TNFA −308 polymorphism is not a predictor of the clinical response to anti-TNF treatment in RA.

A rare polymorphism in the gene for Toll-like receptor 2 is associated with systemic sclerosis phenotype and increases the production of inflammatory mediators

OBJECTIVE To investigate whether polymorphisms in Toll-like receptor (TLR) genes, previously reported to be associated with immune-mediated diseases, are involved in systemic sclerosis (SSc). METHODS We genotyped 14 polymorphisms in the genes for TLRs 2, 4, 7, 8, and 9 in a discovery cohort comprising 452 SSc patients and 537 controls and a replication cohort consisting of 1,170 SSc patients and 925 controls. In addition, we analyzed 15-year followup data on 964 patients to assess the potential association of TLR variants with the development of disease complications. We analyzed the functional impact of the associated polymorphism on monocyte-derived dendritic cells. RESULTS In the discovery cohort, we observed that a rare functional polymorphism in TLR2 (Pro631His) was associated with antitopoisomerase (antitopo) positivity (odds ratio 2.24 [95% confidence interval 1.24-4.04], P=0.003). This observation was validated in the replication cohort (odds ratio 2.73 [95% confidence interval 1.85-4.04], P=0.0001). In addition, in the replication cohort the TLR2 variant was associated with the diffuse subtype of the disease (P=0.02) and with the development of pulmonary arterial hypertension (PAH) (Cox proportional hazards ratio 5.61 [95% confidence interval 1.53-20.58], P=0.003 by log rank test). Functional analysis revealed that monocyte-derived dendritic cells carrying the Pro63His variant produced increased levels of inflammatory mediators (tumor necrosis factor α and interleukin-6) upon TLR-2-mediated stimulation (both P<0.0001). CONCLUSION Among patients with SSc, the rare TLR2 Pro631His variant is robustly associated with antitopoisomerase positivity, the diffuse form of the disease, and the development of PAH. In addition, this variant influences TLR-2-mediated cell responses. Further research is needed to elucidate the precise role of TLR-2 in the pathogenesis of SSc.

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 (pFDRcorrected=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 (pFDRcorrected=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 (pFDRcorrected=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.

A genome-wide association study of rheumatoid arthritis without antibodies against citrullinated peptides

Introduction Rheumatoid arthritis (RA) patients can be classified based on presence or absence of anticitrullinated peptide antibodies (ACPA) in their serum. This heterogeneity among patients may reflect important biological differences underlying the disease process. To date, the majority of genetic studies have focused on the ACPA-positive group. Therefore, our goal was to analyse the genetic risk factors that contribute to ACPA-negative RA. Methods We performed a large-scale genome-wide association study (GWAS) in three Caucasian European cohorts comprising 1148 ACPA-negative RA patients and 6008 controls. All patients were screened using the Illumina Human Cyto-12 chip, and controls were genotyped using different genome-wide platforms. Population-independent analyses were carried out by means of logistic regression. Meta-analysis with previously published data was performed as follow-up for selected signals (reaching a total of 1922 ACPA-negative RA patients and 7087 controls). Imputation of classical HLA alleles, amino acid residues and single nucleotide polymorphisms was undertaken. Results The combined analysis of the studied cohorts resulted in identification of a peak of association in the HLA-region and several suggestive non-HLA associations. Meta-analysis with previous reports confirmed the association of the HLA region with this subset and an observed association in the CLYBL locus remained suggestive. The imputation and deep interrogation of the HLA region led to identification of a two amino acid model (HLA-B at position 9 and HLA-DRB1 at position 11) that accounted for the observed genome-wide associations in this region. Conclusions Our study shed light on the influence of the HLA region in ACPA-negative RA and identified a suggestive risk locus for this condition.

The tumour necrosis factor receptor superfamily member 1b 676T>G polymorphism in relation to response to infliximab and adalimumab treatment and disease severity in rheumatoid arthritis

Objective: To assess the effect of a functional polymorphism (676T>G, M196R) in the tumour necrosis factor receptor super family 1b (TNFSF1b) gene on disease activity, radiological joint damage and response to infliximab and adalimumab treatment in patients with rheumatoid arthritis (RA). Methods: Two cohorts of patients with RA were genotyped for the 676T>G polymorphism (rs1061622) in exon 6 of the TNFSF1b gene by restriction fragment length polymorphism analysis. One cohort (n = 234) included patients from the Dutch Rheumatoid Arthritis Monitoring register with detailed information on their response to anti-TNF therapy (infliximab and adalimumab), the other cohort comprised patients from a long-term observational early inception cohort at our centre (n = 248). Results: The 676T>G polymorphism was not associated with anti-TNF response after 3 or 6 months of treatment. Linear regression analysis showed no significant difference in the progression of radiological joint damage during the first 3 and 6 years of disease between the three genotype groups (TT, TG and GG). Additionally, no difference in mean disease activity between genotypes was seen after 3 and 6 years of disease. Conclusion: Despite its demonstrated functionality, the 676T>G polymorphism in the TNFSF1b gene does not have a major role in either the response to anti-TNF therapy or in the disease severity or radiological progression in RA.

Gene expression profiling in rheumatoid arthritis: current concepts and future directions

Over the last years microarray technologies have generated new perspectives for the high-throughput analysis of biological systems. Nowadays, it is possible to monitor thousands of genes in a single experiment. This molecular profiling technology combined with standardised and validated clinical measurements can allow a more precise characterisation of a patient’s phenotype, and may lead to the design of therapeutic protocols and procedures better tailored to an individual patient’s needs. In this report we provide an overview of expression profiling studies in rheumatoid arthritis (RA). RA is a chronic inflammatory disease in which both genetic and environmental factors are involved. The precise molecular mechanisms underlying RA are not fully understood. A systematic literature search revealed nine array-based expression profiling studies in patients with RA. Findings from these studies were compared with those of linkage and genome-wide association (GWA) studies. Although we observed many differences in study design, analysis and interpretation of results between the different studies, we extracted two sets of genes: (1) those differentially expressed in more than one study, and (2) genes differentially expressed in at least one of the reviewed studies and present in RA linkage or GWA loci. We suggest that both sets of genes include interesting candidate genes for further study in RA.

The interleukin 23 receptor gene does not confer risk to systemic sclerosis and is not associated with systemic sclerosis disease phenotype

OBJECTIVES Multiple studies indicate the role of the interleukin (IL)-17/IL-23 axis in autoimmune diseases, including systemic sclerosis (SSc). The aim of the current study was to investigate the possible implication of the IL23R gene in SSc susceptibility and/or clinical phenotype. METHODS An initial case-control study in 143 Dutch patients with SSc and geographically matched healthy individuals (n = 246) was carried out and followed by a replication study in a cohort of 365 Spanish patients with SSc and 515 healthy individuals. Seven single nucleotide polymorphisms (SNPs) spanning the IL23R gene were selected and genotyped using a Taqman assay. RESULTS Using a Dutch cohort of patients with SSc and controls we observed an association between two (rs11209032, rs1495965) of the seven tested SNPs and disease susceptibility (allelic p values: p = 0.02 and p = 0.01 respectively). However, a replication study in an independent Spanish cohort did not confirm these findings and reveal no association of any of the IL23R-tested SNP with disease susceptibility or clinical phenotype. Similarly, a meta-analysis considering both populations did not reveal any significant association. In addition, no association was observed between IL23R genetic variants and SSc clinical phenotypes. CONCLUSIONS Our results suggest that the IL23R gene is not associated with SSc susceptibility or clinical phenotype.

A large multicentre analysis of CTGF −945 promoter polymorphism does not confirm association with systemic sclerosis susceptibility or phenotype

Objective: To conduct a replication study to investigate whether the −945 CTGF genetic variant is associated with systemic sclerosis (SSc) susceptibility or specific SSc phenotype. Methods: The study population comprised 1180 patients with SSc and 1784 healthy controls from seven independent case–control sets of European ancestry (Spanish, French, Dutch, German, British, Swedish and North American). The −945 CTGF genetic variant was genotyped using a Taqman 5′ allelic discrimination assay. Results: An independent association study showed in all the case–control cohorts no association of the CTGF −945 polymorphism with SSc susceptibility. These findings were confirmed by a meta-analysis giving a pooled OR = 1.12 (95% CI 0.99 to 1.25), p = 0.06. Investigation of the possible contribution of the −945 CTGF genetic variant to SSc phenotype showed that stratification according to SSc subtypes (limited or diffuse), selective autoantibodies (anti-topoisomerase I or anticentromere) or pulmonary involvement reached no statistically significant skewing. Conclusion: The results do not confirm previous findings and suggest that the CTGF −945 promoter polymorphism does not play a major role in SSc susceptibility or clinical phenotype.