IRF5 rs2004640-T allele, the new genetic factor for systemic lupus erythematosus, is not associated with rheumatoid arthritis

The Role of Long Non-coding RNAs in the Pathogenesis of RA, SLE, and SS

Rheumatoid diseases are a group of systemic autoimmune diseases which affect multiple organs with largely unknown etiology. In the past decade, long non-coding RNAs (lncRNAs) have emerged as important regulators of biological processes and contribute deeply to immune cell development and immune responses. Substantial evidences have been accumulated showing that LncRNAs involved in the pathogenesis of the rheumatoid diseases, including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) and Sjögren's syndrome (SS). In this review, we summarize literature combined with bioinformatics methods to analyze the unique and common lncRNAs patterns in rheumatoid diseases and try to reveal the important function of lncRNAs in RA, SLE and SS.

Association of interferon regulatory factor 5 (IRF5) gene polymorphisms with juvenile idiopathic arthritis

Interferon regulatory factor 5 (IRF5) is a member of IRF family which induce signaling pathways and are involved in modulation of cell growth, differentiation, apoptosis, and immune system activity. Juvenile idiopathic arthritis (JIA) is an auto-inflammatory syndrome where the inflammatory markers are believed to play a fundamental role in its pathogenesis. In this study, we aimed to assess the association of IRF5 gene polymorphisms with susceptibility of JIA in Iranian population. Three IRF5 single-nucleotide polymorphisms (rs10954213 A/G, rs2004640 G/T, and rs3807306 G/T) were genotyped using TaqMan assays in 55 patients with JIA and 63 matched healthy individuals. The frequency of the IRF5 rs2004640 T allele was significantly higher (69 vs 45%, P value = 0.0013) in JIA group as compared to control. The frequency of the IRF5 rs 2004640 G allele was significantly higher in the control group in comparison to JIA group (54 vs 32%, P value = 0.001). Allele and genotype frequencies of the rs10954213 and rs3807306 did not show any significant difference between JIA and control group. IRF5 rs 2004640 T allele can be considered as a risk factor for the development of JIA and presence of rs 2004640 G may be act as protective factor.

Association, characterisation and meta-analysis of SNPs linked to general reading ability in a German dyslexia case-control cohort

Dyslexia is a severe disorder in the acquisition of reading and writing. Several studies investigated the role of genetics for reading, writing and spelling ability in the general population. However, many of the identified SNPs were not analysed in case-control cohorts. Here, we investigated SNPs previously linked to reading or spelling ability in the general population in a German case-control cohort. Furthermore, we characterised these SNPs for functional relevance with in silico methods and meta-analysed them with previous studies. A total of 16 SNPs within five genes were included. The total number of risk alleles was higher in cases than in controls. Three SNPs were nominally associated with dyslexia: rs7765678 within DCDC2, and rs2038137 and rs6935076 within KIAA0319. The relevance of rs2038137 and rs6935076 was further supported by the meta-analysis. Functional profiling included analysis of tissue-specific expression, annotations for regulatory elements and effects on gene expression levels (eQTLs). Thereby, we found molecular mechanistical implications for 13 of all 16 included SNPs. SNPs associated in our cohort showed stronger gene-specific eQTL effects than non-associated SNPs. In summary, our results validate SNPs previously linked to reading and spelling in the general population in dyslexics and provide insights into their putative molecular pathomechanisms.

Interferon regulatory factor 5 in human autoimmunity and murine models of autoimmune disease

Interferon regulatory factor 5 (IRF5) has been demonstrated as a key transcription factor of the immune system, playing important roles in modulating inflammatory immune responses in numerous cell types including dendritic cells, macrophages, and B cells. As well as driving the expression of type I interferon in antiviral responses, IRF5 is also crucial for driving macrophages toward a proinflammatory phenotype by regulating cytokine and chemokine expression and modulating B-cell maturity and antibody production. This review highlights the functional importance of IRF5 in a disease setting, by discussing polymorphic mutations at the human Irf5 locus that lead to susceptibility to systemic lupus erythematosus, rheumatoid arthritis, and inflammatory bowel disease. In concordance with this, we also discuss lessons in IRF5 functionality learned from murine in vivo models of autoimmune disease and inflammation and hypothesize that modulation of IRF5 activity and expression could provide potential therapeutic benefits in the clinic.

IRF5rs2004640 single nucleotide polymorphism is associated with susceptibility to rheumatoid arthritis in South Indian Tamils

Polymorphism of interferon regulatory factor 5 (IRF5), a latent transcription factor gene has been associated with various auto-immune diseases. Our aim was to study the IRF5rs2004640 gene polymorphism and its association with disease susceptibility, disease phenotype and treatment response in South Indian Tamil patients with rheumatoid arthritis (RA).The study was conducted on 217 RA patients fulfilling the American College of Rheumatology (ACR) 2010 criteria and 482 healthy controls (HCs) without family history of autoimmune disease. The IRF5rs2004640 genotyping was performed using a TaqMan 5' allelic discrimination assay. We found that the IRF5rs2004640T allele [P < 0.0001, odds ratio (OR) 3.25, 95% confidence interval (CI) 2.55-4.12] and TT genotype (P < 0.0001, OR 4.60, 95% CI 3.23-6.57) were significantly more frequent in RA patients as compared with HCs. No association was found between IRF5rs2004640 polymorphism, clinical manifestations, autoantibody profile and treatment response. IRF5rs2004640 T (mutant) allele may be a susceptibility factor conferring risk for RA in South Indian Tamils, whereas G allele (wild type) may be protective.

Association of the IRF5 rs2004640 polymorphism with rheumatoid arthritis: a meta-analysis

Several molecular epidemiological studies have been conducted in recent years to evaluate a possible association between the interferon regulatory factor 5 (IRF5) rs2004640 polymorphism and rheumatoid arthritis risk in diverse populations. However, the results remain conflicting rather than conclusive. Our aim was to assess associations of IRF5 gene polymorphisms with rheumatoid arthritis risk. Meta-analysis was performed on six published case-control studies (from eight countries) that included 4,818 cases of rheumatoid arthritis and 4,316 controls. The rs2004640-T allele was associated with a significantly increased risk of rheumatoid arthritis when the dominant genetic model was applied (T/T + T/G versus G/G: P = 0.003, OR = 1.14, 95% CI 1.05-1.25). Upon stratified analysis by ethnicity, the rs2004640 polymorphism was associated with an increased rheumatoid arthritis risk in Caucasians when the homozygotic contrast model was employed(T/T versus G/G: P = 0.03, OR = 1.25, 95% CI 1.02-1.53) and this was also the case when the dominant genetic model was used (T/T + T/G versus G/G: P = 0.04, OR = 1.20, 95% CI 1.01-1.42), whereas, in Asian populations, only the dominant genetic model was associated with an increased rheumatoid arthritis risk (T/T + T/G versus G/G: P = 0.02, OR = 1.14, 95% CI 1.02-1.26). The results suggest that the IRF5 rs2004640 polymorphism is associated with rheumatoid arthritis especially when the dominant genetic model is applied.

Associations between interferon regulatory factor 5 polymorphisms and rheumatoid arthritis: a meta-analysis

The aim of this study was to determine whether interferon regulatory factor 5 (IRF5) polymorphisms confers susceptibility to rheumatoid arthritis (RA) in populations with different ethnicities. We searched the literature using the Pubmed and Embase databases and conducted meta-analyses on associations between the four IRF5 polymorphisms (rs2004640, rs729302, rs752637, and rs2280714) and RA susceptibility, using fixed and random effects models. A total of 12 comparison studies were considered in this meta-analysis, which in total involved 7,916 RA patients and 6,452 controls, and eight European, three Asian, and one Argentinean population. Meta-analysis showed an association between the minor allele of rs2004640 and RA in all subjects (odds ratio [OR] = 0.928, 95 % confidence interval [CI] = 0.865-0.996, P = 0.037). After stratification by ethnicity, analysis indicated that the minor allele was significantly associated with RA in Europeans (OR = 0.889, 95 % CI = 0.839-0.941, P = 5.03 × 10(-6)), but not in Asians (OR = 1.057, 95 % CI = 0.978-1.144, P = 0.164). A direct comparison between anti-citrullinated peptide antibody-positive and -negative patients revealed no difference of the frequency of the rs2004640 minor allele (OR = 1.047, 95 % CI = 0.813-1.348, P = 0.724). Meta-analysis identified a significant association between RA and the minor allele of the rs729302 polymorphism in the overall population (OR = 0.896, 95 % CI = 0.826-0.972, P = 0.009) and in Asians (OR = 0.862, 95 % CI = 0.795-0.935, P = 3.50 × 10(-5)), but not in Europeans (OR = 0.951, 95 % CI = 0.877-1.031, P = 0.225). Meta-analysis showed an association between the minor allele of rs752637 and RA in Europeans (OR = 0.858, 95 % CI = 0.789-0.932, P = 3.03 × 10(-5)), but not in Asians (OR = 1.035, 95 % CI = 0.918-1.168, P = 0.572). No association was found between the rs2280714 polymorphism and RA susceptibility. This meta-analysis confirms that the IRF5 rs2004640, rs729302 and rs752637 polymorphisms are associated with RA susceptibility in different ethnic groups, especially in Europeans and Asians, but further study of this association is required in other ethnic groups.

Precipitating and perpetuating factors of rheumatoid arthritis immunopathology: linking the triad of genetic predisposition, environmental risk factors and autoimmunity to disease pathogenesis

Rheumatoid arthritis (RA) is considered to occur when genetic and environmental factors interact to trigger immunopathological changes and consequently an inflammatory arthritis. Over the last few decades, epidemiological and genetic studies have identified a large number of risk factors for RA development, the most prominent of which comprise cigarette smoking and the shared epitope alleles. These risks appear to differ substantially between anti-cyclic citrullinated peptide (ACPA)-positive and ACPA-negative disease. In this article, we will summarise the risk factors for RA development that have currently been identified, outlining the specific gene-environment and gene-gene interactions that may occur to precipitate and perpetuate autoimmunity and RA. We will also focus on how this knowledge of risk factors for RA may be implemented in the future to identify individuals at a high risk of disease development in whom preventative strategies may be undertaken.

Interferon regulatory factor 5 gene polymorphism confers risk to several rheumatic diseases and correlates with expression of alternative thymic transcripts

OBJECTIVES

Polymorphisms in genes related to the IFN pathway were investigated for susceptibility to rheumatic diseases and correlation with gene expression in thymus.

METHODS

Forty-five polymorphisms were genotyped in Norwegian patients with RA (n = 518), JIA (n = 440), SLE (n = 154) and healthy controls (n = 756). Forty-two thymic samples were used for gene expression analysis. Six hundred and fifty SLE patients and 737 healthy controls from Spain were available for replication.

RESULTS

We found a novel association between interferon regulatory factor 5 (IRF5), rs2004640 and JIA, in particular with the polyarthritis RF-negative patients [odds ratio (OR) = 1.60; 95% confidence interval (CI) 1.17, 2.20; P = 0.003]. Also, we confirmed the associations between rs2004640 and SLE (OR = 1.95; 95% CI 1.50, 2.53; P = 3.75 × 10(-7)), which was further strengthened in a meta-analysis (OR = 1.44; 95% CI 1.36, 1.52; P = 2.11 × 10(-37)). Suggestive evidence of association between rs2004640 and RA was found in the Norwegian discovery cohort (OR = 1.19; 95% CI 1.02, 1.40; P = 0.029) and strengthened in a meta-analysis (OR = 1.11; 95% CI 1.05, 1.18; P = 0.00028). Expression levels of exon 1B IRF5 transcripts were dependent on the presence of the rs2004640 T risk allele in thymic tissue, while exon 1A transcript levels correlated with IRF5 promoter CGGGG-indel variants.

CONCLUSION

The IFN pathway gene, IRF5, is a common susceptibility factor for several rheumatic and autoimmune diseases, and risk variants are correlated with expression of alternative IRF5 transcripts in thymus implying a regulatory role.

Genetics of rheumatoid arthritis: what have we learned?

Rheumatoid arthritis (RA) is a chronic autoimmune disease affecting 0.5–1% of the population worldwide. The disease has a heterogeneous character, including clinical subsets of anti-citrullinated protein antibody (ACPA)-positive and APCA-negative disease. Although the pathogenesis of RA is poorly understood, progress has been made in identifying genetic factors that contribute to the disease. The most important genetic risk factor for RA is found in the human leukocyte antigen (HLA) locus. In particular, the HLA molecules carrying the amino acid sequence QKRAA, QRRAA, or RRRAA at positions 70–74 of the DRβ1 chain are associated with the disease. The HLA molecules carrying these “shared epitope” sequences only predispose for ACPA-positive disease. More than two decades after the discovery of HLA-DRB1 as a genetic risk factor, the second genetic risk factor for RA was identified in 2003. The introduction of new techniques, such as methods to perform genome-wide association has led to the identification of more than 20 additional genetic risk factors within the last 4 years, with most of these factors being located near genes implicated in immunological pathways. These findings underscore the role of the immune system in RA pathogenesis and may provide valuable insight into the specific pathways that cause RA.

Recent advances in the genetics of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease characterized by the production of antinuclear autoantibodies and the inflammatory infiltration of many organ systems. SLE is a complex disorder in which multiple genetic variants, together with environmental and hormonal factors, contribute to disease risk. In this article, we summarize our current understanding of the genetic contribution to SLE in light of recent genome-wide association studies, which have brought the total number of confirmed SLE susceptibility loci to 29. In the second section, we explore the functional implications of these risk loci and, in particular, highlight the role that many of these genes play in the Toll-like receptor and type I interferon signaling pathways. Finally, we discuss the genetic overlap between SLE and other autoimmune and inflammatory conditions as several risk loci are shared among multiple disorders, suggesting common underlying pathogenic mechanisms.

Global H4 acetylation analysis by ChIP-chip in systemic lupus erythematosus monocytes

Systemic lupus erythematosus (SLE) is a polygenic disorder affecting approximately 1 in 1000 adults. Recent data have implicated interferons (IFN) in the pathogenesis, and the expressions of many genes downstream of IFNs are regulated at the level of histone modifications. We examined H4 acetylation (H4ac) and gene expression in monocytes from patients with SLE to define alterations to the epigenome. Monocytes from 14 controls and 24 SLE patients were used for analysis by chromatin immunoprecipitation for H4ac and gene expression arrays. Primary monocytes treated with alpha-IFN were used as a comparator. Data were analyzed for concordance of H4ac and gene expression. Network analyses and transcription factor analyses were conducted to identify potential pathways. H4ac was significantly altered in monocytes from patients with SLE. In all, 63% of genes with increased H4ac had the potential for regulation by IFN regulatory factor (IRF)1. IRF1 binding sites were also upstream of nearly all genes with both increased H4ac and gene expression. alpha-IFN was a significant contributor to both expression and H4ac patterns, but the greatest concordance was seen in the enrichment of certain transcription factor binding sites upstream of genes with increased H4ac in SLE and genes with increased H4ac after alpha-IFN treatment.

[Is rheumatoid arthritis without anti-citrullinated peptide antibody a genetically distinct subset?]

These days, rheumatoid arthritis (RA) is reported to be subclassified into two subsets by anti-citrullinated peptide antibody (ACPA) positivity. Clinically, ACPA positive RA tends to develop more severe arthritis than ACPA negative RA. In addition, a lot of reported susceptibility genes to RA (ie. HLA-DRB1(*)04, PTPN22, TRAF1/C5, CTLA4) are found to be associated only with ACPA positive RA but not with ACPA negative RA. It is getting clear that HLA-DRB1(*)04, which was believed to be primarily associated with RA, is not a primary risk factor but ACPA is. Then, a hypothesis for the disease mechanism of ACPA positive RA is set as follows; citrullination possibly due to smoking, etc, provokes ACPA production in individuals who have susceptibility alleles of genes including HLA, followed by joint inflammation in autoantibody-dependent manner. The search for susceptibility genes for ACPA negative RA is slowly progressing, but only a few genes are so far reported: HLA-DRB1(*)03 for Caucasian, HLA-DRB1(*)09 for Japanese, IRF5 and STAT4. When we investigate the disease mechanisms of RA, we should manage independently the two disease subsets : ACPA positive and ACPA negative RA.

Predicting the development of RA in patients with early undifferentiated arthritis

The rapidity with which bone and cartilage damage occurs in patients with rheumatoid arthritis (RA), and the increasing body of evidence for the effectiveness of early intervention in RA, mean that there is a great need for approaches to accurately predict the development of RA in patients with early undifferentiated arthritis. We will review developments in the prediction of outcome on the basis of clinical and laboratory features, including measures of anti-citrullinated protein/peptide antibody status. Although accurate predictions are possible in the majority of patients using recently developed predictive algorithms which utilize clinical and serological variables, there remains a group of patients for whom it is very difficult to predict the development of RA. The utility of new strategies for prediction will be discussed, including recently discovered genetic associations of RA, an assessment of material from the primary site of pathology (the joint), and assessment using the highly sensitive imaging modalities of ultrasound and magnetic resonance imaging.

Testing for the association of the KIAA1109/Tenr/IL2/IL21 gene region with rheumatoid arthritis in a European family-based study

Introduction

A candidate gene approach, in a large case–control association study in the Dutch population, has shown that a 480 kb block on chromosome 4q27 encompassing KIAA1109/Tenr/IL2/IL21 genes is associated with rheumatoid arthritis. Compared with case–control association studies, family-based studies have the added advantage of controlling potential differences in population structure. Therefore, our aim was to test this association in populations of European origin by using a family-based approach.

Methods

A total of 1,302 West European white individuals from 434 trio families were genotyped for the rs4505848, rs11732095, rs6822844, rs4492018 and rs1398553 polymorphisms using the TaqMan Allelic discrimination assay (Applied Biosystems). The genetic association analyses for each SNP and haplotype were performed using the Transmission Disequilibrium Test and the genotype relative risk.

Results

We observed evidence for association of the heterozygous rs4505848-AG genotype with rheumatoid arthritis (P = 0.04); however, no significance was found after Bonferroni correction. In concordance with previous findings in the Dutch population, we observed a trend of undertransmission for the rs6822844-T allele and rs6822844-GT genotype to rheumatoid arthritis patients. We further investigated the five SNP haplotypes of the KIAA1109/Tenr/IL2/IL21 gene region. We observed, as described in the Dutch population, a nonsignificant undertransmission of the AATGG haplotype to rheumatoid arthritis patients.

Conclusions

Using a family-based study, we have provided a trend for the association of the KIAA1109/Tenr/IL2/IL21 gene region with rheumatoid arthritis in populations of European descent. Nevertheless, we failed to replicate a significant association of this region in our rheumatoid arthritis family sample. Further investigation of this region, including detection and testing of all variants, is required to confirm rheumatoid arthritis association.

Association of Polymorphisms in Interferon Regulatory Factor 5 Gene with Rheumatoid Arthritis: A Metaanalysis

Objective.

We investigated potential associations between rheumatoid arthritis (RA) and interferon regulatory factor 5 (IRF5) polymorphisms in a metaanalysis.

Methods.

This metaanalysis included 5 case-control studies, which provided a total of 6582 RA cases and 5375 controls. Odds ratios (OR) were employed to evaluate the risk of RA according to the 4 single-nucleotide polymorphisms (SNP) inIRF5(rs729302, rs2004640, rs752637, and rs2280714) and data were analyzed in respect to association between alleles.

Results.

Among 4 candidate SNP, rs729302, rs2004640, and rs2280714 were statistically significant; both allele C of rs729302 and allele G of rs2004640 within the promoter region ofIRF5were associated with a protective effect [random-effects (RE) OR 0.889, 95% confidence interval (CI) 0.803–0.977, p = 0.015 for rs729302; and RE OR 0.905, 95% CI 0.848–0.965, p = 0.002 for rs2004640]. Similar results were also obtained in T allele of rs2280714 in the 3’-untranslated region (RE OR 0.927, 95% CI 0.866–0.992, p = 0.029). There was no evidence of publication bias from funnel-plot asymmetry and Egger’s regression test.

Conclusion.

Our metaanalysis supported the evidence of the significant role ofIRF5polymorphisms in RA.

Association of interferon regulatory factor 5 haplotypes, similar to that found in systemic lupus erythematosus, in a large subgroup of patients with rheumatoid arthritis

OBJECTIVE

Previous studies have shown either a lack of effect of IRF5 polymorphisms or an association of the IRF5 gene in only a minor subset of rheumatoid arthritis (RA) patients in whom anti-citrullinated protein antibodies (ACPAs) are absent. The present study was undertaken to investigate the role of genetic variation in IRF5 in susceptibility to RA.

METHODS

Nine IRF5 single-nucleotide polymorphisms (SNPs) were studied in 1,338 patients with RA and 1,342 control subjects in analyses of exploratory and replication sample collections, with stratification according to sex and by the presence or absence of ACPAs, rheumatoid factor, the shared epitope, the 620W PTPN22 allele, and erosions. A meta-analysis that included results from previous studies was also carried out.

RESULTS

Our findings together with those from previous studies, in a total of 4,620 RA patients and 3,741 controls, showed a significant association of the rs2004640 IRF5 SNP in RA patients as a whole (odds ratio [OR] 0.88, 95% confidence interval [95% CI] 0.83-0.94; P = 6.5 x 10(-5) versus controls). This association was stronger in ACPA- patients, but was also present in ACPA+ patients (from 3 sample collections). Further analysis of our exploratory sample collection showed that only patients in the ACPA+ and SE- group lacked an association with IRF5 SNPs. All of the remaining RA patients (ACPA- or SE+) showed a strong association with IRF5 SNPs, which followed a complex pattern of opposing effects mediated by independent haplotypes. The susceptibility haplotype showed an OR of 1.8 (95% CI 1.4-2.3; P = 1.2 x 10(-6) versus controls), whereas the protective haplotype showed an OR of 0.76 (95% CI 0.6-0.98; P = 0.046 versus controls).

CONCLUSION

IRF5 polymorphisms seem to influence RA susceptibility in a large subgroup of patients, following a pattern of association very similar to that described in patients with systemic lupus erythematosus.

The ITGAV rs3738919-C allele is associated with rheumatoid arthritis in the European Caucasian population: a family-based study

The integrin αvβ3, whose αv subunit is encoded by the ITGAV gene, plays a key role in angiogenesis. Hyperangiogenesis is involved in rheumatoid arthritis (RA) and the ITGAV gene is located in 2q31, one of the suggested RA susceptibility loci. Our aim was to test the ITGAV gene for association and linkage to RA in a family-based study from the European Caucasian population.

Two single nucleotide polymorphisms were genotyped by PCR-restriction fragment length polymorphism in 100 French Caucasian RA trio families (one RA patient and both parents), 100 other French families and 265 European families available for replication. The genetic analyses for association and linkage were performed using the comparison of allelic frequencies (affected family-based controls), the transmission disequilibrium test, and the genotype relative risk.

We observed a significant RA association for the C allele of rs3738919 in the first sample (affected family-based controls, RA index cases 66.5% versus controls 56.7%; P = 0.04). The second sample showed the same trend, and the third sample again showed a significant RA association. When all sets were combined, the association was confirmed (affected family-based controls, RA index cases 64.6% versus controls 58.1%; P = 0.005). The rs3738919-C allele was also linked to RA (transmission disequilibrium test, 56.5% versus50% of transmission; P = 0.009) and the C-allele-containing genotype was more frequent in RA index cases than in controls (RA index cases 372 versus controls 339; P = 0.002, odds ratio = 1.94, 95% confidence interval = 1.3–2.9).

The rs3738919-C allele of the ITGAV gene is associated with RA in the European Caucasian population, suggesting ITGAV as a new minor RA susceptibility gene.

Advances in the genetics of rheumatoid arthritis point to subclassification into distinct disease subsets

In the past few years considerable advances have been made in the genetics of susceptibility to rheumatoid arthritis (RA). For decades the HLA-DRB1 alleles were the only extensively replicated genetic factor, but more genetic risk factors have now been identified that predispose to RA. Interestingly, several of the observed genetic variants conferred risk to anticitrulline-peptide antibody (ACPA)-positive RA and two variants may be restricted to ACPA-negative RA, pointing to the need for subclassification of RA. The current manuscript reviews recently identified genetic factors predisposing to ACPA-positive RA and ACPA-negative RA. Additionally, although being scarcely explored, genetic variants affecting the severity of disease course are discussed.

The genetics and biology of Irf5-mediated signaling in lupus

Recently much attention was attracted to the importance of the type I interferon pathway in the initiation and development of the autoimmune disease systemic lupus erythematosus (SLE). Many SLE patients have increased serum levels of IFN-alpha and display an IFN gene expression "signature" characterized by strong overexpression of IFN-responsive genes in leukocytes and target tissues. Moreover, about 20% of cancer patients treated with IFN-alpha therapy manifest symptoms resembling SLE and some later develop the disease. One of the key genes of the IFN-alpha pathway, IRF5, was found to be strongly associated with SLE. Two functional SNPs lead to alternative splicing and altered steady-state level of IRF5 gene expression. Besides, the gene has a polymorphic inserion/deletion in exon 6, which contributes to the diversity in the isoform pattern of IRF5. Interestingly, recent studies have not found association of IRF5 with the other autoimmune diseases, such as rheumatoid arthritis or psoriasis, suggesting the unique role for IRF5 in the development of lupus. Here, we present the current knowledge on IRF5 genetics and its biological function and discuss the possible ways in which IRF5 contributes to susceptibility to SLE.

HSPD1 is not a major susceptibility gene for rheumatoid arthritis in the French Caucasian population

The heat shock 60-kDa protein 1 (HSP60) is involved in immune and inflammatory reactions, which are hallmarks of rheumatoid arthritis (RA). HSP60 is encoded by the HSPD1 gene located on 2q33, one of the suggested RA susceptibility loci in the French Caucasian population. Our aim was to test whether HSPD1 is a major susceptibility gene by studing families from the French Caucasian population. Three single nucleotide polymorphisms (SNPs) were studied in 100 RA trio families, and 100 other families were used for replication. Genetic analyses were performed by comparing allelic frequencies, by applying the transmission disequilibrium test, and by assessing the genotype relative risk. We observed a significant RA association for the C/C genotype of rs2340690 in the first sample. However, this association was not confirmed when the second sample was added. The two other SNPs and the haplotype analysis did not give any significant results. We conclude that HSPD1 is not a major RA susceptibility gene in the French Caucasian population.