Genetic association of IRF5 with SLE in Mexicans: higher frequency of the risk haplotype and its homozygozity than Europeans

Association between the rs2004640 functional polymorphism of interferon regulatory factor 5 and systemic lupus erythematosus: a meta-analysis

The aim of this study is to determine whether the functional interferon regulatory factor 5 (IRF5) polymorphism, rs2004640, confers susceptibility to systemic lupus erythematosus (SLE) in multiple ethic populations. A meta-analysis was conducted on the T allele of the IRF5 rs2004640 polymorphism and 12 studies were included in the meta-analysis. Meta-analysis revealed an association between SLE and the IRF5 rs2004640 T allele in all subjects without inter-study heterogeneity (OR 1.429, 95% CI 1.359-1.503, P < 0.001). The IRF5 rs2004640 T allele was significantly associated with SLE in European and Asians. The Asian population had a much lower prevalence of the T allele (34.4%) than any other population studied. and Europeans had the highest frequency of the IRF5 rs2004640 T allele (51.8%). In conclusion, this meta-analysis confirms that the IRF5 rs2004640 polymorphism is associated with SLE susceptibility in different ethnic groups, and that its prevalence is ethnicity dependent.

Are pediatric autoimmune diseases primarily genetic diseases?

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

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.

Amerindian ancestry in Argentina is associated with increased risk for systemic lupus erythematosus

Previous studies have demonstrated that in admixed populations, West African ancestry is associated with an increased prevalence of systemic lupus erythematosus (SLE). In the current study, the effect of Amerindian ancestry in SLE was examined in an admixed population in Argentina. The Argentine population is predominantly European with approximately 20% Amerindian admixture, and a very small (<2%) contribution from West Africa. The results indicate that Amerindian admixture in this population is associated with a substantial increase in SLE susceptibility risk (Odds Ratio=7.94, P=0.00006). This difference was not due to known demographic factors, including site of collection, age and gender. In addition, there were trends towards significance for Amerindian ancestry influencing renal disease, age of onset and anti-SSA antibodies. These studies suggest that populations with Amerindian admixture, like those with West African admixture, should be considered in future studies to identify additional allelic variants that predispose to SLE.

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.

Interferon regulatory factor-5 is genetically associated with systemic lupus erythematosus in African Americans

Increased expression of interferon (IFN)-inducible genes is implicated in the pathogenesis of systemic lupus erythematosus (SLE). One transcription factor responsible for regulating IFN, interferon regulatory factor-5 (IRF5), has been associated with SLE in genetic studies of Asian, Caucasian and Hispanic populations. We genotyped up to seven polymorphic loci in or near IRF5 in a total of 4870 African-American and Caucasian subjects (1829 SLE sporadic cases and 3041 controls) from two independent studies. Population-based case-control comparisons were performed using the Pearson's chi(2)-test statistics and haplotypes were inferred using HaploView. We observed significant novel associations with the IRF5 variants rs2004640 and rs3807306 in African Americans and replicated previously reported associations in Caucasians. While we identified risk haplotypes, the majority of haplotypic effects were accounted for by one SNP (rs3807306) in conditional analyses. We conclude that genetic variants of IRF5 associate with SLE in multiple populations, providing evidence that IRF5 is likely to be a crucial component in SLE pathogenesis among multiple ethnic groups.

Comprehensive evaluation of the genetic variants of interferon regulatory factor 5 (IRF5) reveals a novel 5 bp length polymorphism as strong risk factor for systemic lupus erythematosus

We analyzed a comprehensive set of single-nucleotide polymorphisms (SNPs) and length polymorphisms in the interferon regulatory factor 5 (IRF5) gene for their association with the autoimmune disease systemic lupus erythematosus (SLE) in 485 Swedish patients and 563 controls. We found 16 SNPs and two length polymorphisms that display association with SLE (P < 0.0005, OR > 1.4). Using a Bayesian model selection and averaging approach we identified parsimonious models with exactly two variants of IRF5 that are independently associated with SLE. The variants of IRF5 with the highest posterior probabilities (1.00 and 0.71, respectively) of being causal in SLE are a SNP (rs10488631) located 3' of IRF5, and a novel CGGGG insertion-deletion (indel) polymorphism located 64 bp upstream of the first untranslated exon (exon 1A) of IRF5. The CGGGG indel explains the association signal from multiple SNPs in the IRF5 gene, including rs2004640, rs10954213 and rs729302 previously considered to be causal variants in SLE. The CGGGG indel contains three or four repeats of the sequence CGGGG with the longer allele containing an additional SP1 binding site as the risk allele for SLE. Using electrophoretic mobility shift assays we show increased binding of protein to the risk allele of the CGGGG indel and using a minigene reporter assay we show increased expression of IRF5 mRNA from a promoter containing this allele. Increased expression of IRF5 protein was observed in peripheral blood mononuclear cells from SLE patients carrying the risk allele of the CGGGG indel. We have found that the same IRF5 allele also confers risk for inflammatory bowel diseases and multiple sclerosis, suggesting a general role for IRF5 in autoimmune diseases.