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

Genetic associations with disease in populations with Indigenous American ancestries

The genetic architecture of complex diseases affecting populations with Indigenous American ancestries is poorly understood due to their underrepresentation in genomics studies. While most of the genetic diversity associated with disease trait variation is shared among worldwide populations, a fraction of this component is expected to be unique to each continental group, including Indigenous Americans. Here, I describe the current state of knowledge from genome-wide association studies on Indigenous populations, as well as non-Indigenous populations with partial Indigenous ancestries from the American continent, focusing on disease susceptibility and anthropometric traits. While some studies identified risk alleles unique to Indigenous populations, their effects on trait variation are mostly small. I suggest that the associations rendered by many inter-population studies are probably inflated due to the absence of socio-cultural-economic covariates in the association models. I encourage the inclusion of admixed individuals in future GWAS studies to control for inter-ancestry differences in environmental factors. I suggest that some complex diseases might have arisen as trade-off costs of adaptations to past evolutionary selective pressures. Finally, I discuss how expanding panels with Indigenous ancestries in GWAS studies is key to accurately assess genetic risk in populations from the American continent, thus decreasing global health disparities.

Exploring the contribution of genetics on the clinical manifestations of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a complex autoimmune disease characterized by diverse clinical manifestations affecting multiple organs and systems. The understanding of genetic factors underlying the various manifestations of SLE has evolved considerably in recent years. This review provides an overview of the genetic implications in some of the most prevalent manifestations of SLE, including renal involvement, neuropsychiatric, cutaneous, constitutional, musculoskeletal, and cardiovascular manifestations. We discuss the current state of knowledge regarding the genetic basis of these manifestations, highlighting key genetic variants and pathways implicated in their pathogenesis. Additionally, we explore the clinical implications of genetic findings, including their potential role in risk stratification, prognosis, and personalized treatment approaches for patients with SLE. Through a comprehensive examination of the genetic landscape of SLE manifestations, this review aims to provide insights into the underlying mechanisms driving disease heterogeneity and inform future research directions in this field.

Association of the polymorphisms rs179008 (TLR7), rs2004640 (IRF5), rs1800795 (IL-6) and rs2280788 (CCL5) with systemic lupus erythematosus in women of Mayan ethnicity from Yucatan

Introduction: IFN-α is the main cytokine in SLE, and single nucleotide polymorphisms (SNP) in different genes could induce it. Aim: To determine the association of rs2004640 (IRF5), rs179008 (TLR7), rs1800795 (IL-6) and rs2280788 (CCL5) with SLE in Mexican women with Mayan ethnicity. Methods: DNA and RNA were isolated from the peripheral blood of 110 patients and 200 healthy control subjects. SNP genotyping and gene expression analysis of IRF5, TLR7, IL-6 and IFN-α were determined by real-time PCR and analyzed with SNP Stat, Stata 10.1 and Graph Pad Prism v5. Results: rs2004640, rs179008, and rs1800795 in both groups were according to Hardy-Weinberg equilibrium. Risk alleles rs179008T and rs2004640T frequencies were higher in controls (p = 0.015 and p = 0.028, respectively), whereas rs179008A frequency was higher in patients (p = 0.015). Allelic combination AGT frequency was higher in patients (p = 0.001). IL-6 rs1800795C > G and CCL5 rs2280788G > C frequencies did not show significant differences (p > 0.05), being rs2280788G (CCL5) monomorphic in controls. SLE patients showed higher TLR7, IRF5, IL6, and IFN-α mRNA levels. IRF5 expression was higher in SLE patients homozygous for rs2004640T (IRF5). Conclusion: This work showed the contribution of TLR7 and IRF5 in SLE pathogenesis in Mayan females from Yucatan.

Ancestry-dependent genetic structure of the Xq28 risk haplotype in the Mexican population and its association with childhood-onset systemic lupus erythematosus

Objective

Here we aimed to investigate the association of the Xq28 risk haplotype (H1) with susceptibility to childhood-onset systemic lupus erythematosus (SLE), and to compare its frequency and genetic structure in the Mexican population with those in other continental populations.

Methods

We genotyped 15 single-nucleotide variants (SNVs) that form the H1 haplotype, using TaqMan real-time PCR. The association analysis [case-control and transmission disequilibrium test (TDT)] included 376 cases and 400 adult controls, all of whom were mestizos (MEZ). To identify risk alleles in Mexican Indigenous individuals, SNVs were imputed from whole-exome sequencing data of 1,074 individuals. The allelic frequencies determined in MEZ and Indigenous individuals were compared with those of the continental populations from the 1,000 Genomes database phase 3. Linkage disequilibrium (LD) analysis of risk alleles was performed on all populations. Interleukin-1 receptor associated kinase 1 (IRAK1) and methyl CpG binding protein 2 (MECP2) mRNA levels were determined using real-time PCR.

Results

Case-control analysis revealed genetic association with childhood-onset SLE for all 15 SNVs (OR = 1.49-1.75; p = 0.0095 to 1.81 × 10^-4) and for the Xq28 risk haplotype (OR = 1.97, p = 4 × 10^-6). Comparing with individuals of European ancestry (0.14-0.16), the frequencies of the risk alleles were significantly higher in the MEZ individuals (0.55-0.68) and even higher in Indigenous individuals (0.57-0.83). LD analysis indicated a differential haplotype structure within the Indigenous groups, which was inherited to the MEZ population as a result of genetic admixture. Individuals homozygous for the Xq28 risk haplotype exhibited decreased levels of both MECP2A and B transcripts.

Conclusion

We found that the H1 risk haplotype differs in its conformation in the Mexican population. This difference could be attributed to positive selection within the Indigenous population, with its inheritance now having an autoimmune health impact in both the Mexican Indigenous and MEZ populations.

Unraveling Signatures of Local Adaptation among Indigenous Groups from Mexico

Few studies have addressed how selective pressures have shaped the genetic structure of the current Native American populations, and they have mostly limited their inferences to admixed Latin American populations. Here, we searched for local adaptation signals, based on integrated haplotype scores and population branch statistics, in 325 Mexican Indigenous individuals with at least 99% Native American ancestry from five previously defined geographical regions. Although each region exhibited its own local adaptation profile, only PPARG and AJAP1, both negative regulators of the Wnt/β catenin signaling pathway, showed significant adaptation signals in all the tested regions. Several signals were found, mainly in the genes related to the metabolic processes and immune response. A pathway enrichment analysis revealed the overrepresentation of selected genes related to several biological phenotypes/conditions, such as the immune response and metabolic pathways, in agreement with previous studies, suggesting that immunological and metabolic pressures are major drivers of human adaptation. Genes related to the gut microbiome measurements were overrepresented in all the regions, highlighting the importance of studying how humans have coevolved with the microbial communities that colonize them. Our results provide a further explanation of the human evolutionary history in response to environmental pressures in this region.

Genome Variation and Precision Medicine in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a complex autoimmune disease which is facing the difficulties in treatment. Genetics play an important role in SLE. Several studies have shown that genetic factors not only affect the development of SLE, but also affect its clinical progress. In this review article, we focus on exploring the influence of genetics on different aspects of SLE pathogenesis, clinical course, and treatment and will provide some references in further precision medicine for SLE patients. The coming era of precision medicine, SLE patients will be stratified by genetic profiling. This will enable us to make more effective and precise choices of treatment plan.

Catalytically Impaired TYK2 Variants are Protective Against Childhood- and Adult-Onset Systemic Lupus Erythematosus in Mexicans

Type I interferon (IFN-I) pathway plays a central role in the systemic lupus erythematosus (SLE) pathogenesis. Recent data suggest that SLE is associated with variants in IFN-I genes, such as tyrosine kinase 2 (TYK2), which is crucial in anti-viral immunity. Here, five TYK2 single nucleotide polymorphisms (SNPs) were genotyped in 368 childhood-onset SLE Mexican patients and 516 sex-matched healthy controls. Allele frequencies were also estimated in four indigenous groups. SLE protection was associated with TYK2 risk infection variants affecting residually its catalytic domain, rs12720356 (OR = 0.308; p = 0.041) and rs34536443 (OR = 0.370; p = 0.034), but not with rs2304256, rs12720270, and rs280500. This association was replicated in a 506 adult-onset SLE patients sample (OR = 0.250; p = 0.005, and OR = 0.277; p = 0.008, respectively). The minor alleles of both associated SNPs had a lower frequency in Mestizos than in Spaniards and were absent or rare in indigenous, suggesting that the presence of these alleles in the Mexican Mestizo population was derived from the Spaniards. For the first time, we report genetic variants with a protective effect in childhood- and adult-onset SLE Mexican population. Our results suggest that the frequency of IFN-I alleles associated with SLE, may have been shaped in populations exposed to infectious diseases for long periods, and this could be an explanation why Native American ancestry is associated with a higher SLE prevalence and an earlier onset.

Isolated postaxial polydactyly: Epidemiologic characteristics from a multicenter birth defects study

Isolated postaxial polydactyly (I-PAP), as a single defect, is a frequent malformation, characterized by an extra digit placed on the ulnar or fibular side of the limbs. Worldwide prevalence varies from as high as 225/10,000 in Nigerians to so low as 6.08/10,000 in Argentinians. Genetic-ethnic background significantly affects worldwide prevalence and type of I-PAP. Herein we describe the epidemiological characteristics of I-PAP in 697 newborns, 383 males and 314 females identified in 1,178,993 examined live births from a multicenter case-control hospital-based population study, the Mexican program of Registry and Epidemiological Surveillance of Congenital Malformations (RYVEMCE). The main characteristics analyzed included total I-PAP, stratified in Types A and B, defined as complete or incomplete extra-digit formation, respectively, sex prevalence, affected limb, laterality, parity, prematurity, delivery-type, twinning, consanguinity, and parental age. Males (6.35/10,000) are significantly more frequently affected than females (5.45/10,000), hands more than feet, left more than right limbs, and Type B (74.50%) more than A (25.50%). Prematurity and forceps use were significantly more frequent in cases than controls. An evident decreasing time-trend prevalence was present. Similar findings with other studies were males, upper and left limbs more frequently affected. Findings that were not previously reported include prematurity, forceps use, a significant decreasing time trend and an inverse ethnic prevalence for Types A (75%) and B (25%) in the Mayan population in contrast to other worldwide ethnic groups.

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

OBJECTIVE

The aim of this study is to determine whether the functional interferon regulatory factor 5 ( IRF5) polymorphism rs2004640 is associated with susceptibility to systemic lupus erythematosus (SLE) in multiple ethnic populations.

METHODS

A meta-analysis was conducted on the T allele of the IRF5 rs2004640 polymorphism in all study participants as well as each ethnic population.

RESULTS

Twenty research articles that included 28 comparative studies of 20,892 patients and 24,930 controls were included in the meta-analysis. The Asian population had a much lower prevalence of the T allele than any other study population at 28%, and the European population had the highest prevalence of the T allele at 52%. Meta-analysis showed an association between the IRF5 rs2004640 polymorphism and SLE in all participants (odds ratio = 1.472, 95% confidence interval = 1.370-1.582, p < 0.001). Analysis after stratification by ethnicity indicated that the IRF5 rs2004640 T allele is significantly associated with SLE in Europeans, Asians, Latin Americans and Arabs.

CONCLUSIONS

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.

Differential and Overlapping Immune Programs Regulated by IRF3 and IRF5 in Plasmacytoid Dendritic Cells

We examined the signaling pathways and cell type-specific responses of IFN regulatory factor (IRF) 5, an immune-regulatory transcription factor. We show that the protein kinases IKKα, IKKβ, IKKε, and TANK-binding kinase 1 each confer IRF5 phosphorylation/dimerization, thus extending the family of IRF5 activator kinases. Among primary human immune cell subsets, we found that IRF5 is most abundant in plasmacytoid dendritic cells (pDCs). Flow cytometric cell imaging revealed that IRF5 is specifically activated by endosomal TLR signaling. Comparative analyses revealed that IRF3 is activated in pDCs uniquely through RIG-I-like receptor (RLR) signaling. Transcriptomic analyses of pDCs show that the partitioning of TLR7/IRF5 and RLR/IRF3 pathways confers differential gene expression and immune cytokine production in pDCs, linking IRF5 with immune regulatory and proinflammatory gene expression. Thus, TLR7/IRF5 and RLR-IRF3 partitioning serves to polarize pDC response outcome. Strategies to differentially engage IRF signaling pathways should be considered in the design of immunotherapeutic approaches to modulate or polarize the immune response for specific outcome.

The IRF5 rs2004640 (G/T) polymorphism is not a genetic risk factor for systemic lupus erythematosus in population from south India

Background & objectives:

Genetic aberrations disrupting toll-like receptor and interferon homeostasis enhance the risk of systemic lupus erythematosus (SLE). Raised serum interferon-alpha (IFN-α) levels in SLE patients have been ascribed to polymorphism (rs2004640 G/T) in interferon regulatory factor 5 (IRF5) gene, resulting in enhanced transcript splicing. A positive association between IRF5 polymorphism and SLE risk has been reported in many populations. This study was aimed to find out frequency of IRF5 rs2004640 G/T polymorphism in patients with SLE and healthy controls and to assess its influence on susceptibility, clinical and serological characteristics of SLE.

Methods:

IRF5 rs2004640 (G/T) polymorphism was analyzed in 300 SLE patients and 460 age and sex matched controls by real-time PCR.

Results:

The IRF5 rs2004640 (G/T) polymorphism did not confer risk of SLE or influence clinical or serological phenotype. However, the mutant allele conferred a borderline risk to develop thrombocytopenia (odds ratio: 2.05, 95% confidence interval: 0.97–4.3, P=0.06) in patients with SLE.

Interpretation & conclusions:

Our study revealed that the IRF5 rs2004640 polymorphism was not a risk factor for SLE in population from south India. It may, however, be a useful genetic marker for thrombocytopenia in SLE patients. Although we could not demonstrate susceptibility toward lupus in the presence of IRF5 rs2004640 (G/T) polymorphism, further exploration of the genetic variability of IRF5 may help uncover its pathogenic role in Indian SLE patients.

Omics studies: their use in diagnosis and reclassification of SLE and other systemic autoimmune diseases

Omics studies of systemic autoimmune diseases (SADs) in general, and SLE in particular, have delivered isolated information from transcriptome, epigenome, genome, cytokine and metabolome analyses. Such analyses have resulted in the identification of disease susceptibility genes and the description of IFN expression signatures, allowing extensive insight into the mechanisms of disease and the development of new therapies. Access to such technologies allows the recognition of patterns of disease at a pathway level, thereby, to reclassify SLE and other SADs and to develop new therapeutics from a personalized perspective. The use of omic information allows the discovery of correlative patterns involving drugs not currently suspected to be of value in SADs. In this review, we summarize the omics findings for SLE and propose ways of using the data for the identification of new biomarkers, finding new drugs and reclassifying patients not only with SLE, but also with other SADs.

Interferon regulatory factor 5 gene polymorphism in Egyptian children with systemic lupus erythematosus

Background

Increased expression of interferon-inducible genes is implicated in the pathogenesis of systemic lupus erythematosus (SLE). Interferon regulatory factor 5 (IRF5) is one of the transcription factors regulating interferon and was proved to be implicated in the pathogenesis of SLE in different populations.

Objectives

The objective of this study was to investigate the correlation between polymorphisms of the IRF5 gene and SLE susceptibility in a cohort of Egyptian children and to investigate their association with clinico-pathological features, especially lupus nephritis.

Subjects and methods

Typing of interferon regulatory factor 5 rs10954213, rs2004640 and rs2280714 polymorphisms were done using polymerase chain reaction-restriction fragment length polymorphism for 100 children with SLE and 100 matched healthy controls.

Results

Children with SLE had more frequent T allele and TT genotype of rs2004640 ( Pc = 0.003 and 0.024, respectively) compared to controls. Patients with nephritis had more frequent T allele of rs2004640 compared to controls ( Pc = 0.003). However the allele and genotype frequencies of the three studied polymorphisms did not show any difference in patients with nephritis in comparison to those without nephritis. Haplotype GTA of rs10954213, rs2004640 and rs2280714, respectively, was more frequent in lupus patients in comparison to controls ( p = 0.01) while the haplotype GGG was more frequent in controls than lupus patients ( p = 0.011).

Conclusion

The rs2004640 T allele and TT genotype and GTA haplotype of rs rs10954213, rs2004640, and rs2280714, respectively, can be considered as risk factors for the development of SLE. The presence of the rs2004640 T allele increases the risk of nephritis development in Egyptian children with SLE.

Heterogenous Distribution of MTHFR Gene Variants among Mestizos and Diverse Amerindian Groups from Mexico

Methylenetetrahydrofolate reductase (MTHFR) is a key enzyme in folate metabolism. Folate deficiency has been related to several conditions, including neural tube defects (NTDs) and cardiovascular diseases. Hence, MTHFR genetic variants have been studied worldwide, particularly the C677T and A1298C. We genotyped the C677T and A1298C MTHFR polymorphisms in Mexican Amerindians (MAs), from the largest sample included in a genetic study (n = 2026, from 62 ethnic groups), and in a geographically-matched Mexican Mestizo population (MEZ, n = 638). The 677T allele was most frequent in Mexican individuals, particularly in MAs. The frequency of this allele in both MAs and MEZs was clearly enriched in the South region of the country, followed by the Central East and South East regions. In contrast, the frequency of the 1298C risk allele in Mexicans was one of the lowest in the world. Both in MAs and MEZs the variants 677T and 1298C displayed opposite allele frequency gradients from southern to northern Mexico. Our findings suggest that in Mestizos the 677T allele was derived from Amerindians while the 1298C allele was a European contribution. Some subgroups showed an allele frequency distribution that highlighted their genetic diversity. Notably, the distribution of the frequency of the 677T allele was consistent with that of the high incidence of NTDs reported in MEZ.

Genome-Wide Association Study in an Amerindian Ancestry Population Reveals Novel Systemic Lupus Erythematosus Risk Loci and the Role of European Admixture

OBJECTIVE

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease with a strong genetic component. We undertook the present work to perform the first genome-wide association study on individuals from the Americas who are enriched for Native American heritage.

METHODS

We analyzed 3,710 individuals from the US and 4 countries of Latin America who were diagnosed as having SLE, and healthy controls. Samples were genotyped with HumanOmni1 BeadChip. Data on out-of-study controls genotyped with HumanOmni2.5 were also included. Statistical analyses were performed using SNPtest and SNPGWA. Data were adjusted for genomic control and false discovery rate. Imputation was performed using Impute2 and, for classic HLA alleles, HiBag. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated.

RESULTS

The IRF5-TNPO3 region showed the strongest association and largest OR for SLE (rs10488631: genomic control-adjusted P [Pgcadj ] = 2.61 × 10(-29), OR 2.12 [95% CI 1.88-2.39]), followed by HLA class II on the DQA2-DQB1 loci (rs9275572: Pgcadj  = 1.11 × 10(-16), OR 1.62 [95% CI 1.46-1.80] and rs9271366: Pgcadj  = 6.46 × 10(-12), OR 2.06 [95% CI 1.71-2.50]). Other known SLE loci found to be associated in this population were ITGAM, STAT4, TNIP1, NCF2, and IRAK1. We identified a novel locus on 10q24.33 (rs4917385: Pgcadj  = 1.39 × 10(-8)) with an expression quantitative trait locus (eQTL) effect (Peqtl  = 8.0 × 10(-37) at USMG5/miR1307), and several new suggestive loci. SLE risk loci previously identified in Europeans and Asians were corroborated. Local ancestry estimation showed that the HLA allele risk contribution is of European ancestral origin. Imputation of HLA alleles suggested that autochthonous Native American haplotypes provide protection against development of SLE.

CONCLUSION

Our results demonstrate that studying admixed populations provides new insights in the delineation of the genetic architecture that underlies autoimmune and complex diseases.

The genetic basis of systemic lupus erythematosus: What are the risk factors and what have we learned

The genome-wide association study is a free-hypothesis approach based on screening of thousands or even millions of genetic variants distributed throughout the whole human genome in relation to a phenotype. The relevant role of the genome-wide association studies in the last decade is undisputed because it has permitted to elucidate multiple risk genetic factors associated with the susceptibility to several human complex diseases. Regarding systemic lupus erythematosus (SLE) this approach has allowed to identify more than 60 risk loci for SLE susceptibility across populations to date, increasing our understanding on the pathogenesis of this disease. We present the latest findings in the genetic of SLE across populations using genome-wide approaches. These studies revealed that most of the genetic risk is shared across borders and ethnicities. Finally, we focus on describing the most important risk loci for SLE attempting to cover the genetic findings in relation to functional polymorphisms, such as missense single nucleotide polymorphisms (SNPs) or regulatory variants involved in the development of the disease. The functional studies try to identify the causality of some GWAS-associated variants, many of which fall in non-coding regions of the genome, suggesting a regulatory role. Many loci show an environmental interaction, another aspect revealed by the studies of epigenetic modifications and those associated with genetic variants. Finally, new-generation sequencing technologies can open other paths in the research on SLE genetics, the role of rare variants and the detailed identification of causal regulatory variation. The clinical relevance of the genetic factors will be shown when we are able to use them or in combination with other molecular measurements to re-classify a heterogeneous disease such as SLE.

Association of the IRF5 rs2070197 polymorphism with systemic lupus erythematosus: a meta-analysis

The aim of this study was to explore whether the interferon regulatory factor 5 (IRF5) gene rs2070197 polymorphism was associated with systemic lupus erythematosus (SLE) in multiple ethic populations. A meta-analysis was conducted on the C allele of the IRF5 rs2070197 polymorphism. A total of 7 published case-control studies with 12 comparisons involving 8171 SLE patients and 8904 controls were available for this meta-analysis. This meta-analysis demonstrated the IRF5 rs2070197 polymorphism conferred susceptibility to SLE in all subjects (odds ratio (OR) = 2.128, 95 % confidence interval (CI): 1.856-2.441, P < 0.001) without inter-study heterogeneity. The IRF5 rs2070197 polymorphism was identified as risk factors for SLE in Caucasian populations (OR 1.82, 95 % CI 1.70-1.96), but it had no effects (monomorphic) in Asians. Large-scale multicenter epidemiological studies in selected populations with other risk factors were urgently required.

Interferon regulatory factor 3 as key element of the interferon signature in plasmacytoid dendritic cells from systemic lupus erythematosus patients: novel genetic associations in the Mexican mestizo population

Many genetic studies have found an association between interferon regulatory factors (IRF) single nucleotide polymorphisms (SNPs) and systemic lupus erythematosus (SLE); however, specific dendritic cell (DC) alterations have not been assessed. The aim of the present study was to address the expression of IRF3 and IRF5 on different DC subsets from SLE patients, as well as their association with interferon (IFN)-α production and novel SNPs. For the genetic association analyses, 156 SLE patients and 272 healthy controls from the Mexican mestizo population were included. From these, 36 patients and 36 controls were included for functional analysis. Two IRF3 SNPs - rs2304206 and rs2304204 - were determined. We found an increased percentage of circulating pDC in SLE patients in comparison to controls (8.04 ± 1.48 versus 3.35 ± 0.8, P = 0.032). We also observed enhanced expression of IRF3 (64 ± 6.36 versus 36.1 ± 5.57, P = 0.004) and IRF5 (40 ± 5.25 versus 22.5 ± 2.6%, P = 0.010) restricted to this circulating pDC subset from SLE patients versus healthy controls. This finding was associated with higher IFN-α serum levels in SLE (160.2 ± 21 versus 106.1 ± 14 pg/ml, P = 0.036). Moreover, the IRF3 rs2304206 polymorphism was associated with increased susceptibility to SLE [odds ratio (OR), 95% confidence interval (CI) = 2.401 (1.187-4.858), P = 0.021] as well as enhanced levels of serum type I IFN in SLE patients who were positive for dsDNA autoantibodies. The IRF3 rs2304204 GG and AG genotypes conferred decreased risk for SLE. Our findings suggest that the predominant IRF3 expression on circulating pDC is a key element for the increased IFN-α activation based on the interplay between the rs2304206 gene variant and the presence of dsDNA autoantibodies in Mexican mestizo SLE patients.

The IRF5-TNPO3 association with systemic lupus erythematosus has two components that other autoimmune disorders variably share

Exploiting genotyping, DNA sequencing, imputation and trans-ancestral mapping, we used Bayesian and frequentist approaches to model the IRF5-TNPO3 locus association, now implicated in two immunotherapies and seven autoimmune diseases. Specifically, in systemic lupus erythematosus (SLE), we resolved separate associations in the IRF5 promoter (all ancestries) and with an extended European haplotype. We captured 3230 IRF5-TNPO3 high-quality, common variants across 5 ethnicities in 8395 SLE cases and 7367 controls. The genetic effect from the IRF5 promoter can be explained by any one of four variants in 5.7 kb (P-valuemeta = 6 × 10(-49); OR = 1.38-1.97). The second genetic effect spanned an 85.5-kb, 24-variant haplotype that included the genes IRF5 and TNPO3 (P-valuesEU = 10(-27)-10(-32), OR = 1.7-1.81). Many variants at the IRF5 locus with previously assigned biological function are not members of either final credible set of potential causal variants identified herein. In addition to the known biologically functional variants, we demonstrated that the risk allele of rs4728142, a variant in the promoter among the lowest frequentist probability and highest Bayesian posterior probability, was correlated with IRF5 expression and differentially binds the transcription factor ZBTB3. Our analytical strategy provides a novel framework for future studies aimed at dissecting etiological genetic effects. Finally, both SLE elements of the statistical model appear to operate in Sjögren's syndrome and systemic sclerosis whereas only the IRF5-TNPO3 gene-spanning haplotype is associated with primary biliary cirrhosis, demonstrating the nuance of similarity and difference in autoimmune disease risk mechanisms at IRF5-TNPO3.

Association of STAT4 polymorphism with severe renal insufficiency in lupus nephritis

Lupus nephritis is a cause of significant morbidity in systemic lupus erythematosus (SLE) and its genetic background has not been completely clarified. The aim of this investigation was to analyze single nucleotide polymorphisms (SNPs) for association with lupus nephritis, its severe form proliferative nephritis and renal outcome, in two Swedish cohorts. Cohort I (n = 567 SLE cases, n = 512 controls) was previously genotyped for 5676 SNPs and cohort II (n = 145 SLE cases, n = 619 controls) was genotyped for SNPs in STAT4, IRF5, TNIP1 and BLK. Case-control and case-only association analyses for patients with lupus nephritis, proliferative nephritis and severe renal insufficiency were performed. In the case-control analysis of cohort I, four highly linked SNPs in STAT4 were associated with lupus nephritis with genome wide significance with p = 3.7 × 10(-9), OR 2.20 for the best SNP rs11889341. Strong signals of association between IRF5 and an HLA-DR3 SNP marker were also detected in the lupus nephritis case versus healthy control analysis (p <0.0001). An additional six genes showed an association with lupus nephritis with p <0.001 (PMS2, TNIP1, CARD11, ITGAM, BLK and IRAK1). In the case-only meta-analysis of the two cohorts, the STAT4 SNP rs7582694 was associated with severe renal insufficiency with p = 1.6 × 10(-3) and OR 2.22. We conclude that genetic variations in STAT4 predispose to lupus nephritis and a worse outcome with severe renal insufficiency.

Genetics of the type I interferon pathway in systemic lupus erythematosus

Genetic studies of systemic lupus erythematosus (SLE) have been successful, identifying numerous risk factors for human disease. While the list is not yet complete, it is clear that important immune system pathways are represented, one of which being type I interferon (IFN). Circulating type I IFN levels are high in SLE patients and this IFN pathway activation is heritable in families with SLE. We summarize our current understanding of the genetics of the type I IFN pathway in SLE, with an emphasis on studies that demonstrate an impact of the SLE-risk alleles upon type I IFN pathway activation in SLE patients. These studies illustrate that variations in type I IFN pathway genes represent a common genetic feature of SLE. By understanding the genetic regulation of type I IFN, we may be able to intervene in a more personalized fashion, based upon the molecular dysregulation present in a given individual.

Interferon regulatory factor 5 is critical for the development of lupus in MRL/lpr mice

OBJECTIVE

Interferon regulatory factor 5 (IRF-5) is a transcription factor that mediates intracellular signals activated by engagement of Toll-like receptors (TLRs). IRF5 polymorphisms are associated with an increased or decreased risk of systemic lupus erythematosus (SLE) in various human populations, but the precise role of IRF5 in SLE development is not fully understood. This study was undertaken to examine the role of IRF5 in the development of murine lupus.

METHODS

We crossed gene-targeted IRF5-deficient (IRF5(-/-) ) mice with MRL/MpJ-lpr/lpr (MRL/lpr) mice and examined the progeny for survival, glomerulonephritis, autoantibody levels, immune system cell populations, and dendritic cell function.

RESULTS

IRF5(-/-) MRL/lpr mice survived longer than control IRF5(+/+) MRL/lpr mice and displayed only very mild glomerulonephritis. Autoantibodies to SLE-related nuclear antigens were lower in IRF5(-/-) MRL/lpr mouse serum, and numbers of activated CD4+ T cells were reduced in the spleen. Splenic DCs from IRF5(-/-) MRL/lpr mice produced lower levels of inflammatory cytokines when treated in vitro with TLR-7 or TLR-9 ligands or immune complexes. Interferon-α production in response to CpG was also decreased.

CONCLUSION

Our results show that IRF5 is a crucial driver of lupus development in mice, and indicate that IRF5 may be an attractive new target for therapeutic intervention to control disease in SLE patients.

Interferon regulatory factor 5 in the pathogenesis of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by multiple genetic risk factors, high levels of interferon alpha (IFN-α), and the production of autoantibodies against components of the cell nucleus. Interferon regulatory factor 5 (IRF5) is a transcription factor which induces the transcription of IFN-α and other cytokines, and genetic variants of IRF5 have been strongly linked to SLE pathogenesis. IRF5 functions downstream of Toll-like receptors and other microbial pattern-recognition receptors, and immune complexes made up of SLE-associated autoantibodies seem to function as a chronic endogenous stimulus to this pathway. In this paper, we discuss the physiologic role of IRF5 in immune defense and the ways in which IRF5 variants may contribute to the pathogenesis of human SLE. Recent data regarding the role of IRF5 in both serologic autoimmunity and the overproduction of IFN-α in human SLE are summarized. These data support a model in which SLE-risk variants of IRF5 participate in a “feed-forward” mechanism, predisposing to SLE-associated autoantibody formation, and subsequently facilitating IFN-α production downstream of Toll-like receptors stimulated by immune complexes composed of these autoantibodies.

Emerging therapies for systemic lupus erythematosus--focus on targeting interferon-alpha

Current therapies for systemic lupus erythematosus (SLE), a debilitating, potentially lethal, multifactorial systemic autoimmune disease, are limited to suppressing disease activity and are associated with multiple adverse effects. Recent advances in basic and translational sciences have elucidated a crucial role for the interferon-alpha (IFNα) pathway in the pathogenesis of this enigmatic disease. The so-called "type I interferon signature" has emerged as a major risk factor for disease activity of SLE. Multiple genes encoding for molecules within the type I interferon pathway have been associated with SLE in genome wide association studies. In addition, innate immune receptors are thought to be triggered by either endogenous and/or exogenous stimuli that lead to hypersecretion of IFNα. We review the multiple emerging treatment strategies targeting IFNα-related pathways. These include monoclonal antibodies against IFNα, anti-IFNα antibody-inducing vaccines, and inhibitors of Toll-like receptors. We also summarize the current status of these pharmaceutical agents in early clinical trials.

Effects of IRF5 lupus risk haplotype on pathways predicted to influence B cell functions

Both genetic and environmental interactions affect systemic lupus erythematosus (SLE) development and pathogenesis. One known genetic factor associated with lupus is a haplotype of the interferon regulatory factor 5 (IRF5) gene. Analysis of global gene expression microarray data using gene set enrichment analysis identified multiple interferon- and inflammation-related gene sets significantly overrepresented in cells with the risk haplotype. Pathway analysis using expressed genes from the significant gene sets impacted by the IRF5 risk haplotype confirmed significant correlation with the interferon pathway, Toll-like receptor pathway, and the B-cell receptor pathway. SLE patients with the IRF5 risk haplotype have a heightened interferon signature, even in an unstimulated state (P = 0.011), while patients with the IRF5 protective haplotype have a B cell interferon signature similar to that of controls. These results identify multiple genes in functionally significant pathways which are affected by IRF5 genotype. They also establish the IRF5 risk haplotype as a key determinant of not only the interferon response, but also other B-cell pathways involved in SLE.

Interferon regulatory factors: beyond the antiviral response and their link to the development of autoimmune pathology

Abnormal production of interferon type I has been widely related to multiple autoimmune diseases, particularly systemic lupus erythematosus (SLE). It has been considered the molecular signature characterized by the overexpression of type I Interferon related genes in SLE patients. Among these, are the interferon regulatory factors (IRF). These transcription factors have been involved in the innate immune response, mainly the one related to the defense against viral infections; the development of immune cells and carcinogenesis. The role of IRF in autoimmune pathology has been addressed in diverse murine models. However, evidence in humans is quite scant. This review will focus on the evidence that supports the role of IRF in the development or susceptibility to autoimmune diseases. Specific emphasis will be made over the role of IRF-5 and IRF-7, since evidence of its association to the development of pathology, particularly systemic lupus erythematosus is the strongest.

Interferon regulatory factors in human lupus pathogenesis

Systemic lupus erythematosus (SLE) is a severe multisystem autoimmune disease that results from both genetic predisposition and environmental factors. Many lines of investigation support interferon alpha (IFN-α) as a causal agent in human lupus, and high levels of serum IFN-α are a heritable risk factor for SLE. Interferon regulatory factors (IRFs) are a family of transcription factors involved in host defense, which can induce transcription of IFN-α and other immune response genes after activation. In SLE, circulating immune complexes that contain nucleic acid are prevalent. These complexes are recognized by endosomal Toll-like receptors, resulting in activation of downstream IRF proteins. Genetic variants in the IRF5 and IRF7 genes have been associated with SLE susceptibility, and these same variants are associated with increased serum IFN-α in SLE patients. The increase in serum IFN-α related to IRF5 and 7 genotypes is observed only in patients with particular antibody specificities. This suggests that chronic stimulation of the endosomal Toll-like receptors by autoantibody immune complexes is required for IRF SLE-risk variants to cause elevation of circulating IFN-α and subsequent risk of SLE. Recently, genetic variation in the IRF8 gene has been associated with SLE and multiple sclerosis, and studies support an impact of IRF8 genotype on the IFN-α pathway. In summary, the SLE-associated polymorphisms in the IRF family of proteins seem to be gain-of-function variants, and understanding the impact of these variants on the IFN-α pathway in vivo may guide therapeutic strategies directed at the Toll-like receptor/IRF/IFN-α pathway in SLE.

Genetically determined Amerindian ancestry correlates with increased frequency of risk alleles for systemic lupus erythematosus

OBJECTIVE

To assess whether genetically determined Amerindian ancestry predicts increased presence of risk alleles of known susceptibility genes for systemic lupus erythematosus (SLE).

METHODS

Single-nucleotide polymorphisms (SNPs) within 16 confirmed genetic susceptibility loci for SLE were genotyped in a set of 804 Mestizo lupus patients and 667 Mestizo healthy controls. In addition, 347 admixture informative markers were genotyped. Individual ancestry proportions were determined using STRUCTURE. Association analysis was performed using PLINK, and correlation between ancestry and the presence of risk alleles was analyzed using linear regression.

RESULTS

A meta-analysis of the genetic association of the 16 SNPs across populations showed that TNFSF4, STAT4, ITGAM, and IRF5 were associated with lupus in a Hispanic Mestizo cohort enriched for European and Amerindian ancestry. In addition, 2 SNPs within the major histocompatibility complex region, previously shown to be associated in a genome-wide association study in Europeans, were also associated in Mestizos. Using linear regression, we predicted an average increase of 2.34 risk alleles when comparing an SLE patient with 100% Amerindian ancestry versus an SLE patient with 0% Amerindian ancestry (P < 0.0001). SLE patients with 43% more Amerindian ancestry were predicted to carry 1 additional risk allele.

CONCLUSION

Our results demonstrate that Amerindian ancestry is associated with an increased number of risk alleles for SLE.

Interferon alpha in systemic lupus erythematosus

The pleiotropic cytokine interferon alpha is involved in multiple aspects of lupus etiology and pathogenesis. Interferon alpha is important under normal circumstances for antiviral responses and immune activation. However, heightened levels of serum interferon alpha and expression of interferon response genes are common in lupus patients. Lupus-associated autoantibodies can drive the production of interferon alpha and heightened levels of interferon interfere with immune regulation. Several genes in the pathways leading to interferon production or signaling are associated with risk for lupus. Clinical and cellular manifestations of excess interferon alpha in lupus combined with the genetic risk factors associated with interferon make this cytokine a rare bridge between genetic risk and phenotypic effects. Interferon alpha influences the clinical picture of lupus and may represent a therapeutic target. This paper provides an overview of the cellular, genetic, and clinical aspects of interferon alpha in lupus.

Genetic associations in type I interferon related pathways with autoimmunity

Type I interferons play an outstanding role in innate and adaptive immunity by enhancing functions of dendritic cells, inducing differentiation of monocytes, promoting immunoglobulin class switching in B cells and stimulating effector functions of T cells. The increased production of IFNα/β by plasmacytoid dendritic cells could be responsible for not only efficient antiviral defence, but it also may be a pathological factor in the development of various autoimmune disorders. The first evidence of a genetic link between type I interferons and autoimmune diseases was the observation that elevated IFNα activity is frequently detected in the sera of patients with systemic lupus erythematosus, and that this trait shows high heritability and familial aggregation in their first-degree healthy relatives. To date, a number of genes involved in interferon signalling have been associated with various autoimmune diseases. Patients with systemic lupus erythematosus, Sjögren's syndrome, dermatomyositis, psoriasis, and a fraction of patients with rheumatoid arthritis display a specific expression pattern of interferon-dependent genes in their leukocytes, termed the interferon signature. Here, in an attempt to understand the role of type I interferons in the pathogenesis of autoimmunity, we review the recent advances in the genetics of autoimmune diseases focusing on the association of genes involved in type I interferon pathways.

Promoter insertion/deletion in the IRF5 gene is highly associated with susceptibility to systemic lupus erythematosus in distinct populations, but exerts a modest effect on gene expression in peripheral blood mononuclear cells

OBJECTIVE

We examined the genetic association of the promoter insertion/deletion (indel) in IRF5 gene with systemic lupus erythematosus (SLE) in distinct populations and assessed its role in gene expression.

METHODS

Four IRF5 polymorphisms were genotyped in 1488 SLE patients and 1466 controls. Gene expression was analyzed by quantitative real-time PCR using RNA from peripheral blood mononuclear cells (PBMC).

RESULTS

The promoter indel and rs2070197 had independent genetic effects, which accounted for the association of rs2004640 and rs10954213. Gene expression analysis revealed that rs10954213 exerted the greatest influence on IRF5 transcript levels.

CONCLUSION

We corroborated the association of the promoter indel with SLE in 5 different populations and revealed that rs10954213 is the main single-nucleotide polymorphism responsible for altered IRF5 expression in PBMC.

The geoepidemiology of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease with manifold clinical manifestations and immunological abnormalities, affecting primarily women. Although accurate current data on its incidence and prevalence are largely lacking, there are numerous indications that SLE is far less common in Europeans and their descendants compared to all other ethnicities. The clinical manifestations of the disease show geographic or ethnic variation, generally being less severe in patients of European ancestry than in African, Asian, certain "Hispanic" or mestizo, and various indigenous populations. In particular, renal involvement is far more common in non-European patients. Genetic as well as environmental, sociodemographic and sociocultural factors are likely to contribute to the differences in the incidence and clinical expression of SLE.

Kallikrein genes are associated with lupus and glomerular basement membrane-specific antibody-induced nephritis in mice and humans

Immune-mediated nephritis contributes to disease in systemic lupus erythematosus, Goodpasture syndrome (caused by antibodies specific for glomerular basement membrane [anti-GBM antibodies]), and spontaneous lupus nephritis. Inbred mouse strains differ in susceptibility to anti-GBM antibody-induced and spontaneous lupus nephritis. This study sought to clarify the genetic and molecular factors that maybe responsible for enhanced immune-mediated renal disease in these models. When the kidneys of 3 mouse strains sensitive to anti-GBM antibody-induced nephritis were compared with those of 2 control strains using microarray analysis, one-fifth of the underexpressed genes belonged to the kallikrein gene family,which encodes serine esterases. Mouse strains that upregulated renal and urinary kallikreins exhibited less evidence of disease. Antagonizing the kallikrein pathway augmented disease, while agonists dampened the severity of anti-GBM antibody-induced nephritis. In addition, nephritis-sensitive mouse strains had kallikrein haplotypes that were distinct from those of control strains, including several regulatory polymorphisms,some of which were associated with functional consequences. Indeed, increased susceptibility to anti-GBM antibody-induced nephritis and spontaneous lupus nephritis was achieved by breeding mice with a genetic interval harboring the kallikrein genes onto a disease-resistant background. Finally, both human SLE and spontaneous lupus nephritis were found to be associated with kallikrein genes, particularly KLK1 and the KLK3 promoter, when DNA SNPs from independent cohorts of SLE patients and controls were compared. Collectively, these studies suggest that kallikreins are protective disease-associated genes in anti-GBM antibody-induced nephritis and lupus.

Tumor necrosis factor-alpha is a common genetic risk factor for asthma, juvenile rheumatoid arthritis, and systemic lupus erythematosus in a Mexican pediatric population

There is a great deal of evidence that points to the association of the tumor necrosis factor-alpha (TNF-alpha) gene as a common genetic factor in the pathogenesis of diseases that are caused by inflammatory and/or autoimmune etiologies. Two single nucleotide polymorphisms (SNPs) identified in the TNF-alpha promoter region have been associated with disease susceptibility and severity. We investigated whether -308G/A and -238G/A TNF-alpha polymorphisms were associated with asthma, systemic lupus erythematosus (SLE), and juvenile rheumatoid arthritis (JRA) in a pediatric Mexican population. In a case-control study of 725 patients (asthma: 226, JRA: 171, and SLE: 328) and 400 control subjects, the participants were analyzed using the allelic discrimination technique. The genotype distribution of both TNF-alpha polymorphisms was in Hardy-Weinberg equilibrium in each group. However, there were significant differences in the allele frequency of TNF-alpha-308A between the patients and the healthy controls. This allele was detected in 2.9% of the controls, 6.0% of asthmatic and JRA patients (p = 0.002 and p = 0.0086), and 6.7% of SLE patients (p = 0.00049); statistical significance was maintained after ancestry stratification (asthma: p = 0.0143, JRA: p = 0.0083, and SLE: p = 0.0026). Stratification by gender showed that the risk for the -308A allele in asthma and JRA was greater in females (OR = 4.16, p = 0.0008 and OR = 4.4, p = 0.0002, respectively). The TNF-alpha -238A allele showed an association only with JRA in males (OR = 2.89, p = 0.004). These results support the concept that the TNF-alpha gene is a genetic risk factor for asthma, SLE, and JRA in the pediatric Mexican population.

Genes and Sjögren's syndrome

The evidence for a strong genetic component conferring susceptibility to primary Sjögren's syndrome (SS) is mounting. Several associations with SS have been reported and provide evidence that the HLA region harbors important susceptibility loci and that multiple genes outside the HLA region play a role. Genetic discovery lags behind success observed in related autoimmune diseases. Identifying genetic factors that cause SS will allow more precise definition of pathogenic mechanisms leading to the overall SS phenotype and clinically heterogeneous subsets of patients. Critical opportunities are certain to follow for translation into improved diagnosis and therapies for SS and its spectrum diseases.

Recent advances in the genetics of autoimmune disease

Extraordinary technical advances in the field of human genetics over the past few years have catalyzed an explosion of new information about the genetics of human autoimmunity. In particular, the ability to scan the entire genome for common polymorphisms that associate with disease has led to the identification of numerous new risk genes involved in autoimmune phenotypes. Several themes are emerging. Autoimmune disorders have a complex genetic basis; multiple genes contribute to disease risk, each with generally modest effects independently. In addition, it is now clear that common genes underlie multiple autoimmune disorders. There is also heterogeneity among subphenotypes within a disease and across major racial groups. The current crop of genetic associations are only the start of a complete catalog of genetic factors for autoimmunity, and it remains unclear to what extent common variation versus multiple rare variants contribute to disease susceptibility. The current review focuses on recent discoveries within functionally related groups of genes that provide clues to novel pathways of pathogenesis for human autoimmunity.