POS0164 GENETIC ANALYSIS OF WHOLE EXOME SEQUENCING IN A COHORT OF CHILDREN WITH REFRACTORY JIA REVEALS GENETIC RISK FACTORS FOR RARE JUVENILE DISEASES

Background

Juvenile idiopathic arthritis (JIA) encompasses a group of heterogeneous rheumatic diseases of childhood onset. JIA can result in long term disability and remission is the main goal of treatment. However refractory disease can occur, which is defined as the absence of response to a standard disease therapy. A genetic basis for refractory disease has yet to be explored, where deleterious rare variants can complicate diagnosis or treatment outcome.

Objectives

To investigate, through genetic analysis, whether children with JIA that is refractory carry rare genetic risk factors in genes linked to monogenic diseases.

Methods

Whole exome sequencing of 99 children with JIA was performed with the Agilent SureSelect Human All ExonV6 kit. All quality control, variant filtering and annotation was performed in Varseq (version 2.2.1). Variants with a read depth <30 and genotype quality <80 were removed. Rarity and pathogenicity filters were then applied to remove variants with an allele frequency >1% (based on ExAC, gnomAD, gnomAD exome, NHLBI and 1KGp phase 3), classified as benign or likely benign on ClinVar, with a CADD PHRED score <15 and a REVEL score >0.7. Variants were annotated if they appeared in a gene from the primary immunodeficiency PanelApp (Martin et al., 2019), in a gene associated with an arthritis phenotype or in a gene that appeared on a paediatric monogenic gene list. The variants were then classified using ACMG guidelines (Richards et al., 2015) and benign, or likely benign, classified variants were removed.

Results

A total of 628 variants were identified and we found that 20 out of the 99 children screened were heterozygous for at least one recognised variant in a gene linked to a monogenic disease. Five of these children carried more than one recognised variant linked to monogenic genes. Here we provide a number of illustrative examples: three genes, ADAR, ATP7B and MVK, were prioritised based on prior evidence of associated disease. The variant p.Pro193Ala (gnomAD allele frequency (GAD) 2.2x10-3) of ADAR has previously been deemed pathogenic in a homozygous or compound heterozygous state for Aicardi-Goutières syndrome. Adenosine deaminases (ADARs) catalyse the hydrolytic deamination of adenosine to inosine in dsRNA and is suggested to act as a suppressor of type 1 interferon-stimulated genes. Within ATP7B, two distinct variants were detected; p.Gln1142His (GAD 1.6x10-5) and p.Ile1148Thr (GAD 4.0x10-5) have previously been reported as pathogenic, in combination with a third variant, for Wilson’s disease and were carried by one individual in this cohort. ATP7B encodes copper-transporting ATPase 2, which supplies copper to ceruloplasmin. Variant p.Val377Ile (GAD 1.6x10-3) of MVK was detected in eight individuals in this cohort, interestingly five of these individuals also carried at least one HLA-DRB1 stop-gained variant. This MVK mutation has been confirmed as pathogenic in a homozygous or compound heterozygous state for mevalonate kinase deficiency. MVK converts mevalonic acid into mevalonate-5-phosphate in the cholesterol synthesis pathway. Additionally, two stop-gained loss of function HLA-DRB1 variants, p.Tyr107Ter and p.Gln125Ter, were detected in five and 20 individuals, respectively, in this cohort. HLA-DRB1 is a recognised susceptibility locus for JIA.

Conclusion

Screening of a cohort of 99 children with JIA that have refractory disease has revealed that individuals carry deleterious variants in genes linked to monogenic forms of disease. These results highlight that the genetic basis for refractory disease needs to be further investigated. Carrying additional genetic risk factors to disease may complicate disease outcome and genetic screening of children with refractory JIA may improve treatment outcome in the future.

Acknowledgements

I would like to acknowledge the CLUSTER consortium.

Disclosure of Interests

None declared

POS0035 GENE REGULATION IN T-CELLS FROM PsA PATIENTS DIFFERS BETWEEN PERIPHERAL BLOOD AND THE INFLAMED JOINTS: IMPLICATIONS FOR THE INTERPRETATION OF GWAS SIGNALS

Background

Genome-wide association studies (GWAS) have identified variants that are associated with complex diseases such as Psoriatic Arthritis (PsA). The majority of these variants do not affect the coding sequence of proteins but rather regulatory elements which are highly cell type and state specific, and can affect distally located genes via chromatin interaction mechanisms.

We and others have previously analysed GWAS loci for multiple conditions (including PsA and Rheumatoid Arthrtitis) in cell lines using functional genomics techniques, providing putative mechanisms to many loci with previously unknown function [1].

However, multiple studies have identified large differences in gene regulatory mechanisms between cell lines and primary cells, which could significantly alter the proposed mechanisms. Differences between between samples from healthy volunteers and patients, in particular from the affected tissue, have although not been exhaustively investigated.

Objectives

To assess the impact of using primary cells derived from PsA patients compared to healthy volunteers in functional genomics studies.

Methods

CD4+ and CD8+ T cells were isolated from peripherial blood from 10 healthy controls and 48 PsA patients and from 6 PsA synovial fluid samples.

We performed RNA-seq and ATAC-seq on these two cell types to analyse the global patterns of gene expression and chromatin activity.

Results

We find subtle differences between PsA patients and healthy controls in cells isolated from blood. RNA-seq analysis identified only a handful of differentially expressed genes whilst ATAC-seq analysis identified only 28 differential loci.

On the other hand, T cells isolated from synovial fluid showed significant differences compared to T cells isolated from patient’s blood. Interestingly, we find that CD4+ T cells show substantially more differentially expressed genes compared to CD8+ T cells (1168 vs 346 Log2FoldChange > 1, FDR < 0.01). Genes overexpressed in synovial CD4+ T cells are more strongly enriched for immune pathways such as cytokine signaling and T cell proliferation compared to synovial CD8+ T cells

We also find that synovial CD4+ T cells highly overexpress MHC class II genes (Figure 1).

Figure 1.

Normalized counts of the alpha chains of MHC class 2 genes in CD4+ and CD8+ T cells purified from blood from healthy subjects and patients and synovial fluid.

Conclusion

This preliminary analysis suggests that T cells isolated from peripherial blood do not seem to differ significantly between PsA patients and healthy controls. In contrast, cells isolated from synovial fluid are highly specialized and activated. Moreover, these cells do not resemble canonically activated T cells which means that this state can not be easily emulated in vitro.

This study indicates the importance of not only studying GWAS loci in relevant primary cells from patients, but also that attention needs to be given to cells isolated from the affected site.

References

[1]Shi C, Ray-Jones H, Ding J, et al (2021) Chromatin Looping Links Target Genes with Genetic Risk Loci for Dermatological Traits. J Invest Dermatol 141:1975–1984. https://doi.org/10.1016/J.JID.2021.01.015

Acknowledgements

This work was funded by the Wellcome Trust (award references 207491/Z/17/Z and 215207/Z/19/Z), the Versus Arthritis (award reference 21754), the NIHR Manchester Biomedical Research Centre, and the Medical Research Council (award reference MR/N00017X/1).

Disclosure of Interests

None declared

POS1418 SEPARATING THE EFFECTS OF CHILDHOOD AND ADULT BODY SIZE ON INFLAMMATORY ARTHRITIS: A MENDELIAN RANDOMISATION STUDY

Background

Obesity is strongly associated with inflammation and inflammatory arthritis, but most studies to date have only examined adulthood body mass index (BMI). Whether childhood obesity has a direct and long-term influence on risk of inflammatory arthritis is unclear. This question is important as childhood obesity becomes a growing and global public health crisis [1], but traditional epidemiologic approaches may be limited by reverse causation (obesity can be cause and consequence of disease) and confounding. Mendelian randomisation (MR) uses genetic variants as instrumental variables to estimate the effect of an exposure on an outcome. Since variants are randomly allocated at conception, MR is less susceptible to reverse causation and confounding.

Objectives

To examine whether childhood body size affects risk of inflammatory arthritides – rheumatoid arthritis (RA), ankylosing spondylitis (AS), psoriatic arthritis (PsA), gout and systemic lupus erythematosus (SLE) – after accounting for the effect of adult body size using two-sample univariable and multivariable MR.

Methods

Genetic instruments for childhood (age 10 years) and adult body size were derived using data from 453,169 individuals from the UK biobank study (313 and 580 variants respectively; r2<0.001, p<5x10-8), which have been previously validated using BMI data from three independent populations [2]. Participants recalled their body size at age 10 as “thinner”, “about average” or “plumper”. Adult body size was determined using BMI at a mean age of 57 years and, to facilitate comparison, split into three groups to match the proportions for childhood body size. Genome-wide association data comprised of 22,350 RA, 9,069 AS, 3,609 PsA, 13,179 gout and 5,201 SLE cases. We conducted univariable MR to estimate the total effects of childhood and adult body size on outcomes and multivariable MR to examine the independent effect of childhood body size after accounting for adult body size. F statistics were calculated for each exposure with a value >10 considered suggestive of adequate instrument strength.

Results

The F statistic for childhood and adult body size instruments were 30 and 23 respectively. Genetically predicted childhood body size had a total effect on risk of PsA (OR 2.18 per change in body size category; 95%CI 1.43, 3.31), gout (OR 2.18; 1.43, 3.31) and SLE (OR 2.44; 1.14, 5.22), but not RA (OR 0.95; 0.70, 1.29) or AS (OR 0.96; 0.61, 1.52). After accounting for adult body size, the direct effect of childhood body size was little changed for PsA (OR 1.92; 1.14, 3.25) and SLE (OR 2.69; 1.24, 5.87), but was attenuated for gout (OR 1.40; 0.94, 2.09).

Figure 1.

Mendelian randomisation estimates of the effect of childhood and adult body size on inflammatory arthritis.

Conclusion

Results of this study suggest that the risk conferred from having a larger body size during childhood may not be fully reversable even when a healthy size is achieved in adulthood. How the immune system is altered by early life adiposity to increase risk of PsA and SLE is unclear. Differential effect estimates of body size on each inflammatory arthritis (PsA vs AS, RA vs SLE) may help shed light on their unique pathophysiology in future studies.

References

[1]Han et al. Childhood obesity. Lancet 2010;375:1737–48.

[2]Richardson et al. Use of genetic variation to separate the effects of early and later life adiposity on disease risk: mendelian randomisation study. BMJ 2020;369:m1203.

Acknowledgements

We thank the participants of the UK Biobank study and the genome-wide association study consortia who made their summary statistics publicly available for this study.

Disclosure of Interests

None declared

POS0395 EXPLORING THE POTENTIAL OF GENOMIC RISK PREDICTION FOR CORONARY ARTERY DISEASE IN PATIENTS WITH RHEUMATOID ARTHRITIS

Background

Patients with rheumatoid arthritis (RA) have a higher prevalence of coronary artery disease (CAD) than the general population which contributes to early mortality. However, CAD screeing tools developed in the general population are less effective for estimating CAD risk in RA patients. This is mainly due to the differing contribution from traditional risk factors and the contribution from disease-specific factors. Understanding of the genetic basis of CAD has improved over recent years and shows promise for improving risk prediction in the form of genetic risk scores (GRs), in particular with the development of the metaGRS approach, which combines multiple polygenic risk scores.

Objectives

This study hypothesise that the metaGRS approach can help us improve CAD risk prediction in patients with RA.

Methods

Patients were recruited from the Norfolk Arthritis Register (NOAR), a longitudinal observational study focused on the cause and outcome of inflammatory polyarthritis. Analysis was restricted to patients who satisfied the 2010 ACR criteria cumulatively over five years and had detailed clinical history at baseline and follow-up for ten years. We developed a prediction model based on traditional risk factors[1], and explored the inclusion of a metaGRS. We used a meta-analytic approach to calculate a new metaGRS for CAD, using the effect-sizes from three large-scale, genome-wide, and targeted GRs derived from 1,745,179 [2], 6,630,150 [3], and 40,079 SNPs [4]. We tested the metaGRS in combination with available data on traditional risk factors in a subset of patients with available genetic data. Cox proportional hazards models were used to derive risk equations for evaluation of 10-year risk of CAD. We applied multiple imputations with chained equations to replace missing values. Calibration and discrimination were determined in a separate cohort of 423 individuals.

Results

A total of 2123 patients were included in the analysis with 136 incident cases of self-reported CAD (defined as a composite outcome of myocardial infarction, angina, heart attack, arrhythmia, angioplasty, and coronary artery bypass grafting).The model using only traditional risk factors achieved an AUC of 0.81 (95% CI 0.80, 0.82), with a calibration slope of 1.10, and explained approximately 71% (95% CI 69, 72%) of the variance of the outcome. The hazard ratio for age was found to be 1.00 (95% CI 0.99, 1.01) indicating risk remains the same across all age groups. Inclusion of a CAD metaGRS improves the AUC to 0.82 (95% CI 0.80, 0.83), explains more of the variance at 81% (95% CI 79, 82%) but worsens calibration slope to 0.93. A likelihood ratio test indicates that the integrated model is a better fit (p = 0.04).

Conclusion

An integrated risk score, that combines traditional risk factors with a metaGRS, improves CAD prediction in patients with RA. Further research is required to better understand the role of heritable components contributing to CAD risk in RA patients. By refining the underlying GRS, we hope to further improve risk prediction, through this integrated approach.

References

[1]Hippisley-Cox, Julia, Carol Coupland, and Peter Brindle. “Development and validation of QRISK3 risk prediction algorithms to estimate future risk of cardiovascular disease: prospective cohort study.” bmj 357 (2017).

[2]Inouye M, Abraham G, Nelson CP, Wood AM, Sweeting MJ, Dudbridge F, et al. Genomic Risk Prediction of Coronary Artery Disease in 480,000 Adults: Implications for Primary Prevention. J Am Coll Cardiol. 2018;72(16):1883–93.

[3]Khera A V., Chaffin M, Aragam KG, Haas ME, Roselli C, Choi SH, et al. Genome-wide polygenic scores for common diseases identify individuals with risk equivalent to monogenic mutations. Nat Genet [Internet]. 2018;50(9):1219–24. Available from: http://dx.doi.org/10.1038/s41588-018-0183-z

[4]Elliott J, Bodinier B, Bond TA, Chadeau-Hyam M, Evangelou E, Moons KGM, et al. Predictive Accuracy of a Polygenic Risk Score-Enhanced Prediction Model vs a Clinical Risk Score for Coronary Artery Disease. JAMA - J Am Med Assoc. 2020;323(7):636–45.

Disclosure of Interests

None declared.

OP0088 STRATIFIED MEDICINE: GENETIC PREDICTORS OF RADIOGRAPHIC OUTCOME IN RHEUMATOID ARTHRITIS

Background

Rheumatoid arthritis (RA) displays great heterogeneity between patients for susceptibility to developing erosions. Genetic variations within the HLA-DRB1 gene (the shared epitope (SE) and polymorphisms coding for Valine at position 11) have been consistently associated with both susceptibility and radiographic outcome in RA.(1) However, associations of non-HLA markers are much less conclusive. Most studies looking outside the HLA have been candidate gene studies and very few have been replicated in independent cohorts.

Objectives:

1. Identify all single nucleotide polymorphisms (SNPs) outside the HLA that have ever been associated with radiographic outcome in RA

2. To perform a replication study to determine which of these are associated with radiographic outcome in the Norfolk Arthritis Register (NOAR), the worldwide largest prospective cohort with genetic and radiographic outcome data.

Methods

A systematic literature search was conducted as shown in the Figure 1.

Figure 1.

Flow chart for systematic review.

The Norfolk Arthritis register (NOAR) is a large primary care-based inception cohort of patients diagnosed with inflammatory polyarthritis. Patients were recruited at baseline from 1989 and followed up prospectively for up to 20 years with serial X-rays. Genome-wide genotyping was performed on the Illumina Human/Infinium Core Exome array and imputed with Minimac4 to the Haplotype Reference Consortium panel. Quality control resulted in 7.5 million SNPs available in each patient. SNPs identified from the literature were extracted and tested for an association with the presence of erosions (as a longitudinal binary variable) using a generalized estimating equation (GEE) model in STATA/IC 14.0.in NOAR.

Results

A total of 2119 participants (2440 radiographs) were identified with both genetic and radiographic data available. 66.2% of these patients were female and 33.3% were anti-CCP positive. Median age of onset was 54.5 and 74.9% satisfied the American College of Rheumatology (ACR) 1987 criteria for rheumatoid arthritis.

A total of 113 different non-HLA SNPs associated with radiographic outcome in RA were identified from the literature. Of these, 102 were successfully identified within NOAR and 91 were deemed to be independent SNPs based on R2 of 0.6. 14 SNPs were found to be significantly associated with the presence of erosions within NOAR (Table 1).

Table 1.

SNPs found to be associated with radiographic severity within NOAR. *Significant results only; Dominant models used (Odds ratios displayed in relation to minor alleles)

GeneChromosomeSNP (single nucleotide polymorphismOdds ratio (95% CI)P valueIL2RB2rs7437771.23 (1.01, 1.05)0.0398IL154rs68211710.82 (0.67, 1.00)0.0451IL45rs22432501.36 (1.08, 1.70)0.0094FOX036rs122120670.75 (0.58, 0.97)0.0278OPG8rs20736180.79 (0.64, 0.98)0.0295TRAF19rs107601301.33 (1.06, 1.65)0.0118TRAF19rs108184881.32 (1.06, 1.64)0.0141TRAF19rs29001801.32 (1.07, 1.61)0.0079IL4r16rs18050101.25 (1.01, 1.56)0.0393IL4r16rs18050111.31 (1.03, 1.66)0.0260LGALS917rs37639591.28 (1.03, 1.59)0.0260SOST17rs47929091.34 (1.09, 1.65)0.0052LILRA319rs1032940.80 (0.65, 0.98)0.0334MMP920rs119083520.70 (0.57, 0.85)0.0005

Conclusion

113 non-HLA SNPs have been previously reported to be associated with radiographic outcome in RA. Of these, only ~15% also showed an association in NOAR, the largest cohort with genetic and radiographic outcome data worldwide. Interestingly, rs2243250, a SNP located on chromosome 5 (IL4), previously found to be associated in a small Egyptian cohort, has been replicated in NOAR.(2) Current work consists of assessing the added clinical value of a genetic risk score based on HLA and non-HLA markers in predicting radiographic outcome when combined with clinical/serological/demographic markers.

References

[1]S. Viatte et al., JAMA313, 1645-1656 (2015).

[2]Y. M. Hussein, A. S. El-Shal, N. A. Rezk, S. M. Abdel Galil, S. S. Alzahrani, Cytokine61, 849-855 (2013).

Disclosure of Interests

None declared.

POS0307 IMPAIRED GLYCAEMIC CONTROL IS ASSOCIATED WITH INCREASED RISK OF PSORIATIC ARTHRITIS: MENDELIAN RANDOMISATION STUDY

Background

Psoriatic arthritis (PsA) and psoriasis are both strongly associated with impaired glycaemic control and type 2 diabetes. The risk of developing type 2 diabetes is estimated to be ~40% higher in PsA compared to controls [1]. However, these observational findings are susceptible to bias from reverse causation: Insulin resistance and impaired glycaemic control are evident well over a decade before clinical onset of type 2 diabetes [2]. Therefore, whether impaired glycaemic control is a cause or consequence of PsA is unclear. Testing this hypothesis using traditional observational designs is challenging since longitudinal assessments of glycaemic control before PsA onset are often not available. Mendelian randomisation (MR) is an epidemiologic method that provides evidence about putative causal relationships between modifiable exposures and disease outcomes using genetic variants as instrumental variables. MR is less likely to be affected by confounding or reverse causation than conventional observational designs because genetic variants are randomly allocated at conception.

Objectives

To estimate the effect of genetically predicted glycaemic traits - glycated haemoglobin (HbA1c), 2-hour glucose after oral glucose challenge (2hG), fasting glucose (FG), and fasting insulin (FI) - on risk of PsA and psoriasis compared to controls using two-sample MR.

Methods

We selected 320 independent (r2<0.001) genome-wide significant (p<5x10-8) variants as instruments for HbA1c from a UK biobank genome-wide association study (GWAS) of 344,182 individuals, and 14 variants for 2hG, 67 for FG and 38 for FI from up to 200,622 individuals from a MAGIC consortium meta-analysis that adjusted for body mass index. Genetic associations for PsA were obtained from a GWAS comprising 3,609 cases (majority fulfilling CASPAR criteria) and 9,192 controls. Psoriasis data were obtained from 5,278 cases (96% European, defined using ICD and phecodes) and 650,391 controls from the UK biobank, FinnGen and BioBank Japan [3]. We used the inverse-variance weighted method to combine effect estimates from each variant using fixed-effect meta-analysis.

Results

Genetically predicted HbA1c increased risk of PsA (OR 1.18 per standard deviation (6.7 mmol/mol) increase in HbA1c; 95%CI 1.02, 1.36). 2hG (OR 1.55 per SD (0.6 mmol/L) increase; 95%CI 1.26, 1.89) and FG (OR 1.73 per SD (1.6 mmol/L) increase; 95%CI 1.35, 2.21) similarly increased PsA risk (Figure 1). FI was not associated with PsA risk. 2hG was the only glycaemic trait significantly associated with psoriasis (OR 1.21; 95%CI 1.04, 1.40).

Figure 1.

Mendelian randomisation estimates of the effect of glycaemic traits on risk of psoriatic arthritis and psoriasis.

Conclusion

This study provides supportive genetic evidence that impaired glycaemic control increases risk of PsA. By contrast, estimates were smaller when comparing psoriasis against controls with confidence intervals including the null. Improving glycaemic control may reduce PsA risk, although further studies are required to confirm these findings and to compare PsA directly against cutaneous only psoriasis.

References

[1]Solomon et al. The Risk of Diabetes Among Patients with Rheumatoid Arthritis, Psoriatic Arthritis, and Psoriasis. Ann Rheum Dis 2010;69:21147-7.

[2]Tabák et al. Prediabetes: A high-risk state for developing diabetes. Lancet 2012;379:2279-90.

[3]Sakaue et al. A cross-population atlas of genetic associations for 220 human phenotypes. Nature Genetics 2021;53:1415-24.

Acknowledgements

This work was supported by Versus Arthritis (grant number 21173, grant number 21754 and grant number 21755).

Disclosure of Interests

None declared

POS0509 DEVELOPMENT OF A MULITNOMIAL PREDICTION MODEL OF TREATMENT RESPONSE TO ETANERCEPT IN A MULTI-CENTRE COHORT OF PATIENTS WITH ESTABLISHED RA

Background

Treatment response in rheumatoid arthritis (RA) is assessed through EULAR response groups of good, moderate, and poor response. Clinical prediction models from the literature typically frame this as a binary model, to differentiate poor from good and moderate responders. Here, we develop a multinomial model, to predict each group separately, after 3 months on the anti-TNF drug Etanercept (ETN).

Objectives

Develop and validate a multinomial prediction model of treatment response to ETN in RA, based on baseline clinical covariates.

Methods

We identified patients treated with ETN or biosimilars (N = 778) from the Biologics in RA Genetics and Genomics Study Syndicate (BRAGGSS). Response groups were derived from the CRP based 4C-DAS28 at baseline and 3 month follow up, yielding 310 good, 320 moderate, and 148 poor responders. A multinomial logistic regression model was fitted, using good responders as reference category. Multiple imputation by chained equations was used to impute missing data, and models were internally validated via bootstrapping. We report model accuracy, as well as calibration, and compare effect sizes across response groups. Table 1shows the baseline statistics, and odds ratios for the included covariates.

Table 1.

Baseline covariate statistics and odds ratios (in bold: significant at p < 0.05); HADS: Hospital Anxiety and Depression Scale

VariableMean (± SD)ORModerate [95% CI]pORPoor [95% CI]por % YesSwollen Joint8.84450.980.350.948e-3Count (SJC)(± 5.20)[0.95 1.02][0.89 0.98]Tender Joint14.68771.076e-61.050.01Count (TJC)(± 6.74)[1.04 1.10][1.01 1.08]General Health74.74291.000.60.981e-3Visual Analog Scale (GHVAS)(±17.79)[0.99 1.01][0.97 0.99]CRP19.07391.000.220.990.26(±25.07)[1.00 1.01][0.98 1.00]BMI30.30351.000.481.000.41(±23.28)[0.99 1.01][0.99 1.01]Age of47.33301.010.121.020.06onset(±13.86)[1.00 1.03][1.00 1.04]Disease9.94011.000.840.990.45duration(±10.35)[0.98 1.02][0.96 1.02]HAQ1.60851.480.022.951e-6(± 0.65)[1.06 2.08][1.91 4.54]HADS-Anxiety8.08681.040.191.060.12(± 4.54)[0.98 1.10][0.99 1.13]HADS-Depression7.38411.060.120.970.55(± 4.02)[0.99 1.13][0.89 1.06]Concurrent81.49%0.412e-40.520.03DMARD[0.26 0.66][0.28 0.94]Female78.66%1.390.121.110.71[0.92 2.10][0.65 1.87]Seropositive77.89%0.540.020.470.01[0.33 0.89][0.26 0.86]1st Biologic90.62%1.060.860.480.03[0.55 2.06][0.24 0.94]

Results

Adjusted for optimism, the multinomial model achieves an accuracy of 50.7% (IQR: 50 – 51.3%), with calibration slopes of 0.574 (IQR: 0.569 - 0.579) and 0.534 (IQR: 0.525 - 0.544) for moderate and poor response, respectively. Figure 1 shows a comparison of odds ratios (OR) for the different outcome groups. The Health Assessment Questionnaire (HAQ) score is the biggest driver of both moderate and poor response. Previous biologic treatment also predicts poor but not moderate response. Compared to the multinomial model, a binary model, that discriminates poor from moderate and good responders, underestimates the effect size of HAQ.

Figure 1.

Odds ratios of FIRSTBIO and HAQ for moderate and poor response. Size of crosses indicate 95% confidence intervals.

Conclusion

The model predicts EULAR response groups moderately well but is poorly calibrated, which can partly be explained by the generally higher sample size requirement of multinomial modelling. In the multinomial model, moderate and poor response is largely driven by the same covariates, which leads to blurred boundaries between good and poor responders, when response groups are merged to create a binary problem. Future research should consider the most appropriate model choice to describe data, including the use of multinomial instead of binomial models. More research and bigger sample sizes are required to improve on this multinomial model.

Disclosure of Interests

Michael Stadler: None declared, Stephanie Ling: None declared, Nisha Nair: None declared, John Isaacs Speakers bureau: Abbvie, Gilead, Roche, UCB, Grant/research support from: GSK, Janssen, Pfizer, Kimme Hyrich Speakers bureau: Abbvie, Grant/research support from: Pfizer and BMS, Ann Morgan Speakers bureau: Roche/ Chuga, Consultant of: GSK, Roche, Chugai, AstraZeneka, Regeneron, Sanofi, Vifor, Grant/research support from: Roche, Kiniksa Pharmaceuticals, Anthony G Wilson: None declared, Darren Plant: None declared, John Bowes: None declared, Anne Barton Grant/research support from: Pfizer, Galapagos, Scipher Medicine, and Bristol Myers Squibb.

OP0222 IDENTIFICATION OF CAUSAL GENES AND MECHANISMS BY WHICH GENETIC VARIATION MEDIATES JUVENILE IDIOPATHIC ARTHRITIS SUSCEPTIBILITY USING FUNCTIONAL GENOMICS AND CRISPR-CAS9

Background

We recently performed the largest juvenile idiopathic arthritis (JIA) genome-wide association study (GWAS) to date 1. Disease-associated loci contain multiple single nucleotide polymorphism (SNPs), and the majority map to non-coding enhancers, making it challenging to define causal variants and genes.

Functional genomics datasets in disease-relevant tissues have shown to be essential for the functional interpretation of GWAS loci. In particular, capture Hi-C (CHi-C) has been successful in detecting chromosomal interactions linking GWAS loci to their target genes. However, such datasets are lacking in JIA.

Objectives

The aim of this study is to bridge this gap and advance the knowledge of the biological mechanisms that underpin susceptibility to JIA, by integrating GWAS with public epigenomics datasets and in-house generated CHi-C from JIA patients. We focus on CD4+ T-cells, which have been shown to be one of the most relevant cell types in JIA. In addition, we use CRISPR-Cas9 to validate the regulatory effect of prioritised variants on their predicted target genes.

Methods

Credible SNP sets for the top JIA risk loci (P < 5x10-6) were annotated using EpiMap data 2. Low input whole genome promoter CHi-C (PCHi-C) was performed on CD4+ T-cells isolated from blood from 3 JIA oligoarthritis patients, and data was analysed using CHiCAGO 3. GWAS and PCHi-C data were combined to prioritise causal genes using the Capture Hi-C Omnibus Gene Score (COGS) pipeline 4. We subsequently employed CRISPR activation (CRISPRa) and CRISPR interference (CRISPRi) in Jurkats to assess whether prioritized JIA variants were capable of regulating the expression of the interacting genes.

Results

614 credible SNPs (out of 735) were found to overlap active enhancers in CD4+ T-cells, and were prioritized for further analysis.

We identified numerous significant chromatin interactions in 19 out of 44 non-MHC JIA associated loci, linking JIA SNPs mapping to T-cell enhancers to a total of 61 target genes and revealing potential novel disease pathways. Moreover, COGS prioritised a total of 7 genes (RGS14, ERAP2, HIPK1, CCR4, CCRL2, CCR2, CCR3).

A JIA associated locus on chromosome 3 contains 39 SNPs. It maps to an intergenic region and the causal gene/s are unclear. Our PCHi-C data revealed that this JIA locus presents chromatin interactions with the promoters of several genes, such as CCRL2, CCR2, CCR3 and CCR5, three of which were prioritised by COGS. Two variants were selected for further analysis: rs79815064, which had the highest posterior probability, and rs8005404,the only variant within a CD4+ T-cell enhancer linked to surrounding gene activity.

When both SNPs were targeted with CRISPRa and CRISPRi, we observed an increased and decreased expression, respectively, of CCRL2, CCR2, CCR3 and CCR5, confirming their role in disease. These genes belong to the chemokine receptor family and are important regulators of the inflammatory response.

Conclusion

Our work shows how functional genomics can help identify biological mechanisms by which GWAS variants increase risk of JIA, which in turn will benefit patients through personalised medicine and the identification of therapeutic targets.

References

[1]López-Isac, E. et al. Combined genetic analysis of juvenile idiopathic arthritis clinical subtypes identifies novel risk loci, target genes and key regulatory mechanisms. Ann. Rheum. Dis.80, 321–328 (2021).

[2]Boix, C. A., James, B. T., Park, Y. P., Meuleman, W. & Kellis, M. Regulatory genomic circuitry of human disease loci by integrative epigenomics. Nat. 2021 5907845590, 300–307 (2021).

[3]Cairns, J. et al. CHiCAGO: Robust detection of DNA looping interactions in Capture Hi-C data. Genome Biol.17, 1–17 (2016).

[4]Javierre, B. M. et al. Lineage-Specific Genome Architecture Links Enhancers and Non-coding Disease Variants to Target Gene Promoters. Cell167, 1369 (2016).

Disclosure of Interests

Antonio Frantzesko: None declared, Valeriya Malysheva: None declared, Chenfu Shi: None declared, James Ding: None declared, John Bowes: None declared, Wendy Thomson: None declared, Stephen Eyre: None declared, Mikhail Spivakov Shareholder of: co-founder and shareholder of Enhanc3D Genomics Ltd, Gisela Orozco: None declared

OP0014 HLA ASSOCIATIONS IN PATIENTS WITH JUVENILE IDIOPATHIC ARTHRITIS ASSOCIATED UVEITIS AND CLINICAL SUBTYPES

Background:

Juvenile idiopathic arthritis (JIA) is a childhood onset rheumatic disease which is classified into seven different clinical subtypes based upon the ILAR classification criteria. The most common extra articular manifestation of JIA is its associated uveitis (JIAU); particularly chronic anterior uveitis (CAU). Uveitis is a serious complication with the potential to lead to visual impairment and blindness. The rheumatoid factor negative polyarthritis and oligoarthritis ILAR subtypes, often referred to as the “polygo” subgroup, are at a higher risk for developing JIAU, with up to 30% of polygos afflicted by CAU. The HLA region has long been reported as a genetic risk factor for JIA susceptibility, with evidence suggesting that different amino acids of HLA genes infer risk to different JIA subtypes.

Objectives:

Investigate the association of amino acids and genetic variants in the HLA region with susceptibility to JIAU and the ILAR clinical subtypes.

Methods:

Samples were genotyped using the Illumina Infinium CoreExome and Infinium Onmiexpress arrays. Samples were excluded based on <98% call rate, discrepancy between genetically inferred sex and database records, inferred relatedness (identify-by-descent) and ancestral outliers based on principal component analysis (PCA). SNPs were excluded based on <0.01 minor allele frequency (MAF), and call rate <98%. SNP2HLA was used to impute HLA amino acids, SNPs and alleles. Analysis was then executed on markers with an information score >0.9 and MAF >.01 using logistic regression or an omnibus test for multiallelic markers, including 3 PCs as covariates. Independent associations were identified using forward stepwise logistic regression including previously identified variants as covariates. Comparison of regression models was performed using a likelihood ratio test (LRT).

Results:

We analysed 7425 markers within the HLA region in 450 JIAU and 2024 JIA cases without uveitis. The most significant association was to amino acid positions 13 of HLA-DRB1 (p=2.9×10-30). Conditional analysis on DRB1 position 13 revealed an independent signal at DRB1 position 67 (p=2.4×10-6). Conditioning on all DRB1 alleles revealed an independent signal at HLA-DPB1 position 69 (p=5.3×10-7). As expected, ILAR subtype was found to be associated with JIAU (p=1.58×10-6). We used LRT to test if genetics provided further information above ILAR subtype alone and found that including residues at DRB1 position 13 significantly improved the fit of a model based on ILAR subtype alone (LRT p = 3.6×10-27). The reciprocal analysis, adding ILAR subtype to a model based on DRB1 position 13 alone, did not significantly improve the fit of a model (LRT p=0.83). Exploring associations in the polygo subgroup (n=1646) we found significant associations to the three previously described amino acids and JIAU (DRB1 position 13 p=3.4×10-20, DRB1 position 67 p=3.3×10-4, DPB1 position 69 p=2.2×10-6).

Conclusion:

This is largest analysis of HLA markers in JIAU patients to date and we identify two independent associations to amino acids in HLA-DRB1 and a further independent association to HLA-DPB1. This analysis demonstrates that including data on genetic risk factors adds further information to that captured by ILAR subtype alone. It also reveals that the previously validated associations at position 13 of HLA-DRB1 are also correlated with JIAU in the polygo subtype suggesting that genetic risk factors will help refine risk within clinical subtypes. Conditioning on DRB1 alleles reveals that the secondary independent DRB1 position 69 association is also strongly associated in the polygo subset of this cohort. Together these results highlight the potential future use of genetics risk factors for risk classification for uveitis in patients with JIA

Disclosure of Interests:

None declared

POS0471 ASSOCIATION OF HLA-DRB1 HAPLOTYPES WITH CARDIOVASCULAR MORTALITY IN INFLAMMATORY POLYARTHRITIS: RESULTS FROM THE NORFOLK ARTHRITIS REGISTER

Background:

Haplotypes defined by amino acids at HLA-DRB1 positions 11, 71 and 74 associated with susceptibility to rheumatoid arthritis (RA), are associated with radiological outcome, anti-TNF response and all cause-mortality in RA.(1, 2) RA is associated with cardiovascular (CV) morbidity and mortality, but the increased prevalence of risk factors of CV disease in RA only partially explains this association.

Objectives:

The aim was to investigate whether haplotypes associated with RA disease susceptibility and disease severity are also associated with CV mortality.

Methods:

The Norfolk Arthritis register (NOAR) is a primary care-based inception cohort of patients with inflammatory polyarthritis (IP).(1, 2) NOAR patients with at least 2 years of follow-up and available mortality and genetic data were included in this study. Mortality data was provided by the Office for National Statistics.

Univariate Cox proportional hazard models were applied using STATA/IC 14.0. Models for CV mortality were adjusted for CV risk factors selected using stepwise regression: namely obesity, gender and hypertension. Hazard models were applied to the entire cohort of patients with inflammatory polyarthritis (IP). When calculating differences between highest and lowest risk genetic factors, bivariate analysis was used.

Results:

HLA-DRB1 amino acids, haplotypes or haplotype groups associated with RA susceptibility are also associated with CV mortality as shown in the table 1. HLA-DRB1 polymorphisms encoding amino-acid haplotypes associated with an increased or decreased susceptibility to RA consistently show the same magnitude and direction of association for overall and CV mortality in IP. For example, the SEA-haplotype, associated with the lowest susceptibility to RA, and the best radiographic outcome, was found to be associated with decreased CV mortality (HR 0.67, 95% CI 0.47, 0.91, p=0.023). The relative difference in CV mortality between carriers of the high susceptibility VKA haplotype and carriers of the SEA haplotype was significant (HR 1.67, 95% CI 1.13, 2.48, p=0.01).

Table 1.

Hazard ratios for CV mortality by genetic factors among patients with IP. Total number (n) of deaths are also displayed alongside the total number (n) of patients included in each analysis.

Amino acid / Haplotype /GroupHazard Ratio (95% CI)Nvaline 111.10 (0.93, 1.30)343 (2514)serine 110.82 (0.70, 0.96)*343 (2514)Difference1.23 (1.01, 1.49)*VKA haplotype1.16 (0.94, 1.43)310 (2328)SEA haplotype0.67 (0.47, 0.94) *310 (2328)Difference1.67 (1.13, 2.48)*Group 1 †1.10 (0.93, 1.31)319 (2328)Group 4 †0.73 (0.60, 0.89)*319 (2328)Difference1.37 (1.09, 1.72)*

* p<0.05

†Haplotype groups as defined previously (2)

HLA-DRB1 haplotypes can be ranked according to the magnitude of their association with RA susceptibility and this hierarchy is conserved for various measures of disease outcome and overall mortality.(2, 3) The figure 1 shows that this risk hierarchy is also conserved for CV mortality: HLA-DRB1 haplotypes that predispose to RA also predispose to increased CV mortality, independent of known CV risk factors.

Figure 1.

Haplotypes with frequency >12% in NOAR are shown. X axis: susceptibility to ACPA-positive RA as ORs.(2) Y axis: CV mortality risk in IP as HRs, derived from multi-variate cox-proportional hazard models adjusted for CV risk factors. Values are on a logarithmic scale. A one-tailed p value was calculated using linear regression to determine the association between β coefficients of susceptibility and CV mortality.

Conclusion:

The originally reported genetic associations between HLA-DRB1 polymorphisms and overall mortality were likely driven by associations with CV mortality.

References:

[1]S. Viatte et al., JAMA313, 1645-1656 (2015).

[2]S. Raychaudhuri et al., Nat Genet44, 291-296 (2012).

[3]D. P. Symmons, A. J. Silman, Clin Exp Rheumatol21, S94-99 (2003).

Disclosure of Interests:

None declared

Fine-mapping the MHC locus in juvenile idiopathic arthritis (JIA) reveals genetic heterogeneity corresponding to distinct adult inflammatory arthritic diseases

Objectives

Juvenile idiopathic arthritis (JIA) is a heterogeneous group of diseases, comprising seven categories. Genetic data could potentially be used to help redefine JIA categories and improve the current classification system. The human leucocyte antigen (HLA) region is strongly associated with JIA. Fine-mapping of the region was performed to look for similarities and differences in HLA associations between the JIA categories and define correspondences with adult inflammatory arthritides.

Methods

Dense genotype data from the HLA region, from the Immunochip array for 5043 JIA cases and 14 390 controls, were used to impute single-nucleotide polymorphisms, HLA classical alleles and amino acids. Bivariate analysis was performed to investigate genetic correlation between the JIA categories. Conditional analysis was used to identify additional effects within the region. Comparison of the findings with those in adult inflammatory arthritic diseases was performed.

Results

We identified category-specific associations and have demonstrated for the first time that rheumatoid factor (RF)-negative polyarticular JIA and oligoarticular JIA are genetically similar in their HLA associations. We also observe that each JIA category potentially has an adult counterpart. The RF-positive polyarthritis association at HLA-DRB1 amino acid at position 13 mirrors the association in adult seropositive rheumatoid arthritis (RA). Interestingly, the combined oligoarthritis and RF-negative polyarthritis dataset shares the same association with adult seronegative RA.

Conclusions

The findings suggest the value of using genetic data in helping to classify the categories of this heterogeneous disease. Mapping JIA categories to adult counterparts could enable shared knowledge of disease pathogenesis and aetiology and facilitate transition from paediatric to adult services.

Identification of loci associated with late-onset psoriasis using dense genotyping of immune-related regions

BACKGROUND

Chronic plaque psoriasis can be subdivided into two groups according to the age of onset: type 1 (early onset, before 40 years) and type 2 (late onset, at or beyond 40 years). So far, 36 genetic loci have been associated with early-onset psoriasis in genome-wide association studies of white populations, while few studies have investigated genetic susceptibility to late-onset psoriasis.

OBJECTIVES

To characterize the genetics underpinning late-onset psoriasis.

METHODS

We genotyped 543 cases of late-onset psoriasis and 4373 healthy controls using the Immunochip array, a dense genotyping chip containing single-nucleotide polymorphisms previously associated with autoimmune diseases. Imputation using SNP2HLA and stepwise logistic regression analysis was performed for markers spanning the human leucocyte antigen gene region.

RESULTS

Two loci (HLA-C and IL12B) previously associated with early-onset psoriasis showed significant association at a genome-wide threshold in the current study (P < 5 × 10(-8)). Six more loci (TRAF3IP2, IL23R, RNF114, IFIH1, IL23A and HLA-A) showed study-wide significant association (P < 2·3 × 10(-5); calculated using Genetic type 1 error calculator). Additionally, we identified an association at IL1R1 on chromosome 2q13, which is not associated with early-onset disease.

CONCLUSIONS

This is the largest study to date of genetic loci in late-onset psoriasis, and demonstrates the overlap that exists with early-onset psoriasis. It also suggests that some loci are associated exclusively with late-onset psoriasis.

Investigation of connexin 43 uncoupling and prolongation of the cardiac QRS complex in preclinical and marketed drugs

BACKGROUND AND PURPOSE

Prolongation of the cardiac QRS complex is linked to increased mortality and may result from drug-induced inhibition of cardiac sodium channels (hNaV 1.5). There has been no systematic evaluation of preclinical and marketed drugs for their additional potential to cause QRS prolongation via gap junction uncoupling.

EXPERIMENTAL APPROACH

Using the human cardiac gap junction connexin 43 (hCx43), a dye transfer 'parachute' assay to determine IC50 values for compound ranking was validated with compounds known to uncouple gap junctions. Uncoupling activity (and hNaV 1.5 inhibition by automated patch clamp) was determined in a set of marketed drugs and preclinical candidate drugs, each with information regarding propensity to prolong QRS.

KEY RESULTS

The potency of known gap junction uncouplers to uncouple hCx43 was ranked (according to IC50 ) as phorbol ester>digoxin>meclofenamic acid>carbenoxolone>heptanol. Among the drugs associated with QRS prolongation, 29% were found to uncouple hCx43 (IC50 < 50 μM), whereas no uncoupling activity was observed in drugs not associated with QRS prolongation. In preclinical candidate drugs, hCx43 and hNaV 1.5 IC50 values were similar (within threefold). No consistent margin over preclinical Cmax (free) was apparent for QRS prolongation associated with Cx43 inhibition. However, instances were found of QRS prolonging compounds that uncoupled hCx43 with significantly less activity at hNaV 1.5.

CONCLUSION AND IMPLICATIONS

These results demonstrate that off-target uncoupling activity is apparent in drug and drug-like molecules. Although the full ramifications of Cx inhibition remain to be established, screening for hCx43 off-target activity could reduce the likelihood of developing candidate drugs with a risk of causing QRS prolongation.

Enrichment of vitamin D response elements in RA-associated loci supports a role for vitamin D in the pathogenesis of RA

The aim of this study was to explore the role of vitamin D in rheumatoid arthritis (RA) pathogenesis by investigating the enrichment of vitamin D response elements (VDREs) in confirmed RA susceptibility loci and testing variants associated with vitamin D levels for association with RA. Bioinformatically, VDRE genomic positions were overlaid with non-HLA (human leukocyte antigen)-confirmed RA susceptibility regions. The number of VDREs at RA loci was compared to a randomly selected set of genomic loci to calculate an average relative risk (RR). Single-nucleotide polymorphisms (SNPs) in the DHCR7/NADSYN1 (nicotinamide adenine dinucleotide synthase 1) and CYP2R1 loci, previously associated with circulating vitamin D levels, were tested in UK RA cases (n=3870) and controls (n=8430). Significant enrichment of VDREs was seen at RA loci (P=9.23 × 10(-8)) when regions were defined either by gene (RR 5.50) or position (RR 5.86). SNPs in the DHCR7/NADSYN1 locus showed evidence of positive association with RA, rs4944076 (P=0.008, odds ratio (OR) 1.14, 95% confidence interval (CI) 1.03-1.24). The significant enrichment of VDREs at RA-associated loci and the modest association of variants in loci-controlling levels of circulating vitamin D supports the hypothesis that vitamin D has a role in the development of RA.

An investigation of rheumatoid arthritis loci in patients with early-onset psoriasis validates association of the REL gene

BACKGROUND

Phenotypically diverse autoimmune conditions share common genetic susceptibility loci and underlying molecular pathways.

OBJECTIVES

By systematically searching for single nucleotide polymorphisms (SNPs) associated with another autoimmune disease, rheumatoid arthritis (RA), we aimed to elucidate novel genetic markers of psoriasis.

METHODS

We investigated 18 SNPs, previously confirmed as being associated with RA, in a U.K. cohort of 623 patients with early-onset psoriasis (presenting before age 40 years), comparing them with 2662 control subjects.

RESULTS

Our findings confirm the association of early-onset psoriasis with REL (rs13031237, P=0·0027). The minor allele of REL had opposing effects upon susceptibility to disease in patients with psoriasis and RA.

CONCLUSION

Similar exploration of additional autoimmune loci and fine mapping of such regions may provide further insight into the genetics and molecular pathophysiology of psoriasis.

Information and professional support: key factors in the provision of family-centred early childhood intervention services

BACKGROUND

Much has been written on the principles of family-centred practice and on the service delivery methods and skills required of its practitioners. Far less has been written from the perspective of families whose children have a disability. The aims of this study were twofold: firstly to understand families' experiences of family-centred early childhood intervention services and secondly to explore other factors that might impact on these experiences.

METHODS

One hundred and thirty families attending two established early childhood intervention services in New South Wales, Australia completed a survey incorporating the Measure of Processes of Care-56, the Family Empowerment Scale, the Family Support Scale and the Parenting Daily Hassles Scale.

RESULTS

Consistent with previous research using the Measure of Processes of Care-56, 'respectful and supportive care' was the domain of care families rated to occur most and 'provision of general information' was the domain they rated to occur least. Significant positive relationships existed between families' ratings of family-centred care and feelings of empowerment. Being provided with general information was strongly correlated with family empowerment. Families' social support networks played an important role but support from professionals was most strongly correlated with families' experiences of family-centred care. Finally, families whose children's early intervention services were co-ordinated by a professional experienced significantly better care.

CONCLUSIONS

The provision of general information and professional support are key components of family-centred early childhood intervention services.

Bowel cancer screening is safe, detects earlier stage cancer and adenomas in 50% of cases: experience of the prevalent round of screening from two first wave centres in the North East of England

OBJECTIVE

The NHS Bowel Cancer Screening Programme (BCSP) began roll-out in 2006 aiming to reduce cancer mortality through detection at an earlier stage. We report results from the prevalent round of screening at two first wave centres and compare with the UK pilot study.

DESIGN

This is a service evaluation study. Data were collected prospectively for all individuals undergoing faecal occult blood testing (FOBt) and colonoscopy including: uptake and outcomes of FOBt, colonoscopic performance, findings, histological data and complications. Continuous data were compared using a two-tailed test of two proportions.

SETTING

The South of Tyne and Tees Bowel Cancer Screening centres.

PATIENTS

Participants of the BCSP.

MAIN OUTCOME MEASURES

1) Colonoscopy Quality Assurance and 2) Cancer stage shift.

RESULTS

195,772 individuals were invited to participate. Uptake was 54% and FOBt positivity 1.7%. 1524 underwent colonoscopy with caecal intubation in 1485 (97%). 180 (12%) cancers were detected. Dukes stages were: 76 (42%) A; 47 (26%) B; 47 (26%) C; 8 (4%) D and 2 (1%) unknown. This demonstrates a significantly earlier stage at diagnosis compared with data from 2867 non-screening detected cancers (p<0.001). Adenomas were detected in 758 (50%). One perforation occurred (0.07%) and two intermediate bleeds requiring transfusion only (0.12%). Both caecal intubation and adenoma detection were significantly higher than in the UK pilot study (p<0.001).

CONCLUSIONS

The prevalent round of screening demonstrates a high adenoma and cancer detection rate and significantly earlier stage at diagnosis. Complications were few providing reassurance regarding safety. Efforts are required to improve uptake.

MTHFR gene polymorphisms and outcome of methotrexate treatment in patients with rheumatoid arthritis: analysis of key polymorphisms and meta-analysis of C677T and A1298C polymorphisms

Association of two key variants mapping to the MTHFR gene (C677T (rs1801133) and A1298C (rs1801131)) with response to methotrexate (MTX) remains controversial. We investigated these and other markers spanning the gene as predictors of MTX efficacy and adverse events in a UK rheumatoid arthritis (RA) patient cohort and performed a meta-analysis of the two key variants using all published data. The tagging single nucleotide polymorphisms (SNPs) were genotyped in 309 patients with well-defined outcomes to MTX treatment and 17 studies were included in the meta-analysis. No association of the SNPs tested was detected with MTX efficacy or toxicity in our UK cohort. After combining our data with previous studies by meta-analysis, the random effects pooled odds ratios (OR) for both C677T and A1298C showed no association with efficacy or toxicity for either of the SNPs (efficacy: OR=1.05 (95% confidence interval (CI) 0.83-1.32) and OR=0.81 (95% CI 0.53-1.24), respectively; toxicity: OR=1.38 (95% CI 0.90-2.12) and OR=1.19 (95% CI 0.80-1.78), respectively). The available evidence suggests that the MTHFR C677T and A1298C gene polymorphisms are not reliable predictors of response to MTX treatment in RA patients.

Examining the overlap between genome-wide rare variant association signals and linkage peaks in rheumatoid arthritis

OBJECTIVE

With the exception of the major histocompatibility complex (MHC) and STAT4, no other rheumatoid arthritis (RA) linkage peak has been successfully fine-mapped to date. This apparent failure to identify association under peaks of linkage could be ascribed to the examination of common variation, when linkage is likely to be driven by rare variants. The purpose of this study was to investigate the overlap between genome-wide rare variant RA association signals observed in the Wellcome Trust Case Control Consortium (WTCCC) study and 11 replicating RA linkage peaks, defined as regions with evidence for linkage in >1 study.

METHODS

The WTCCC data set contained 40,482 variants with minor allele frequency of ≤0.05 in 1,860 RA patients and 2,938 controls. Genotypes of all rare variants within a given gene region were collapsed into a single locus and a global P value was calculated per gene.

RESULTS

The distribution of rare variant signals (association P≤10(-5)) was found to differ significantly between regions with and without linkage evidence (P=2×10(-17) by Fisher's exact test). No significant difference was observed after data from the MHC region were removed or when the effect of the HLA-DRB1 locus was accounted for.

CONCLUSION

The results suggest that rare variant association signals are significantly overrepresented under linkage peaks in RA, but the effect is driven by the MHC. This is the first study to examine the overlap between linkage peaks and rare variant association signals genome-wide in a complex disease.

A systematic investigation of confirmed autoimmune loci in early-onset psoriasis reveals an association with IL2/IL21

BACKGROUND

Many autoimmune diseases share common susceptibility loci suggesting similar underlying cellular mechanisms involved in disease expression.

OBJECTIVES

The purpose of this investigation was to study 21 genetic variants in 14 genes that are confirmed autoimmune loci in a cohort of patients with early-onset psoriasis.

METHODS

Patients with early-onset psoriasis (n = 750) and controls (n = 3531) were genotyped using the Sequenom(®) MassArray™ iPLEX Gold platform.

RESULTS

We found strong evidence of association with two variants in the IL2/IL21 (rs6822844, genotypic P = 3·3 × 10(-4) ; rs2069778, genotypic P = 7·86 × 10(-4)) region.

CONCLUSIONS

The findings, although requiring replication, suggest that IL2/IL21 may play a key role in the pathogenesis of psoriasis as well as in other diverse autoimmune diseases.

Recent advances in the genetics of RA susceptibility

RA is a common autoimmune disease with a complex aetiology in which genetic and environmental factors contribute to disease. The genetic component of RA is largely undefined and, up until very recently, there were only two reproducible associations. The strongest of these associations is of genes within the HLA region, particularly the HLA-DRB1 gene. A second, more modest, association identified has been of the protein tyrosine phosphatase non-receptor 22 (PTPN22) gene. Advances in genotyping technology have facilitated the application of whole genome association approaches to identify disease causal variants. This, coupled with the availability of large case and control collections has enabled the identification of low-to-moderate risk loci. These newer study designs combined with traditional linkage and association studies have accelerated the identification of novel risk loci. The past few months alone have witnessed the identification of three new RA risk loci. In this review, we aim to give an update on recent progress in RA genetics, focusing mainly on the identification of novel loci.

Investigation of polymorphisms in the PADI4 gene in determining severity of inflammatory polyarthritis

BACKGROUND

A functional haplotype of the peptidylarginine deiminase 4 (PADI4) gene has recently been identified as a rheumatoid arthritis susceptibility gene in a Japanese but not in a UK population. One possible explanation for this disparity is that the gene determines severity of rather than susceptibility to inflammatory polyarthritis (IP) and that the UK and Japanese cohorts differed in terms of outcome.

AIM

To examine the association between individual PADI4 single nucleotide polymorphisms (SNPs) and haplotypes, with the development and severity of erosions by five years in patients with IP.

METHODS

438 patients from the NOAR inception cohort of patients with IP were x rayed five years after presentation with early IP. Association with four exonic SNPs (padi4_89*G/A, padi4_90*T/C, padi4_92*G/C, and padi4_104*T/C), mapping to the PADI4 gene and defining a haplotype previously reported to be associated with rheumatoid arthritis, was investigated. Patients were compared for the presence, extent, and progression of erosions by five years and the presence of antibodies to citrullinated peptide (anti-CCP antibodies).

RESULTS

There was no association between individual PADI4 SNPs or haplotypes and the development or extent of erosions by five years. Restricting analysis to patients who satisfied ACR criteria for rheumatoid arthritis by five years did not alter the conclusions. No association with presence of anti-CCP antibodies was detected.

CONCLUSIONS

No evidence was found for association of the PADI4 gene with severity as assessed by erosive outcome at five years or with presence of anti-CCP antibodies in patients with IP.

Tempol reduces infarct size in rodent models of regional myocardial ischemia and reperfusion

Reactive oxygen species (ROS) contribute to ischemia-reperfusion injury of the heart. This study investigates the effects of tempol, a membrane-permeable radical scavenger on (i) the infarct size caused by regional myocardial ischemia and reperfusion of the heart in vivo (rat, rabbit) and in vitro (rat), and (ii) the cell injury caused by hydrogen peroxide (H2O2) in rat cardiac myoblasts (H9c2 cells). In the anesthetized rat, tempol reduced the infarct size caused by regional myocardial ischemia (25 min) and reperfusion (2 h) from 60 +/- 3% (control, n = 8) to 24 +/- 5% (n = 6, p < .05). In the anesthetized rabbit, tempol also attenuated the infarct size caused by myocardial ischemia (45 min) and reperfusion (2 h) from 59 +/- 3% (control, n = 6) to 39 +/- 5% (n = 5, p < .05). Regional ischemia (35 min) and reperfusion (2 h) of the isolated, buffer-perfused heart of the rat resulted in an infarct size of 54 +/- 4% (control n = 7). Reperfusion of hearts with buffer containing tempol (n = 6) caused a 37% reduction in infarct size (n = 6, p < .05). Pretreatment of rat cardiac myoblasts with tempol attenuated the impairment in mitochondrial respiration caused by H2O2 (1 mM for 4 h). Thus, the membrane-permeable radical scavenger tempol reduces myocardial infarct size in rodents.

Inhibitors of poly (ADP-ribose) synthetase protect rat cardiomyocytes against oxidant stress

OBJECTIVE

Inhibitors of poly (ADP-ribose) synthetase (PARS) activity reduce the infarct size caused by regional myocardial ischaemia and reperfusion in the rabbit and rat in vivo. The mechanism of action of these inhibitors is unclear. Here we investigate the effects of the PARS inhibitor 3-aminobenzamide (3-AB) on infarct size caused by ischaemia and reperfusion of the isolated, perfused heart of the rat. We also investigate the role of PARS in the hydrogen peroxide-mediated cell injury/necrosis in rat cardiac myoblasts.

METHODS

Rat isolated hearts perfused at constant pressure (80 mmHg) were subjected to 35 min of regional ischaemia and 2 h of reperfusion. Infarct size was determined at the end of the experiment using nitro-blue tetrazolium. 3-AB (300 microM) or 3-aminobenzoic acid (3-ABA, 300 microM) were infused during the reperfusion period. Rat cardiac myoblasts (H9c2 cells) were preincubated with the PARS inhibitors, 3-AB. nicotinamide (Nic) or 1,5-dihydroxyisoquinoline (ISO) or the inactive analogues 3-ABA or nicotinic acid (NicA) prior to exposure with hydrogen peroxide (1 mM). Cell injury was assessed by measuring mitochondrial respiration and cell necrosis by measuring the release of LDH. PARS activity was determined by measuring the incorporation of NAD into nuclear proteins.

RESULTS

Regional ischaemia and reperfusion of the isolated rat heart resulted in an infarct size of 54% which was reduced by 3-AB, but not by 3-ABA. Exposure of rat cardiac myoblasts to hydrogen peroxide caused an increase in PARS activity and cell injury/necrosis which was attenuated by pretreatment with the PARS inhibitors.

CONCLUSION

Inhibition of the activity of PARS attenuates the cell death associated with oxidant stress in rat cardiac myoblasts and heart.