To confirm and define the genetic association of STAT4 and systemic lupus erythematosus, investigate the possibility of correlations with differential splicing and/or expression levels, and genetic interaction with IRF5.
30 tag SNPs were genotyped in an independent set of Spanish cases and controls. SNPs surviving correction for multiple tests were genotyped in 5 new sets of cases and controls for replication. STAT4 cDNA was analyzed by 5’-RACE PCR and sequencing. Expression levels were measured by quantitative PCR.
In the fine-mapping, four SNPs were significant after correction for multiple testing, with rs3821236 and rs3024866 as the strongest signals, followed by the previously associated rs7574865, and by rs1467199. Association was replicated in all cohorts. After conditional regression analyses, two major independent signals represented by SNPs rs3821236 and rs7574865, remained significant across the sets. These SNPs belong to separate haplotype blocks. High levels of STAT4 expression correlated with SNPs rs3821236, rs3024866 (both in the same haplotype block) and rs7574865 but not with other SNPs. We also detected transcription of alternative tissue-specific exons 1, indicating presence of tissue-specific promoters of potential importance in the expression of STAT4. No interaction with associated SNPs of IRF5 was observed using regression analysis.
These data confirm STAT4 as a susceptibility gene for SLE and suggest the presence of at least two functional variants affecting levels of STAT4. Our results also indicate that both genes STAT4 and IRF5 act additively to increase risk for SLE.
Association studies; systemic lupus erythematosus; STAT4 transcription factor; Interferon regulatory factor; genetic predisposition to disease
The tumor necrosis factor ligand superfamily member 4 gene (TNFSF4) encodes the OX40 ligand (OX40L), a co-stimulatory molecule involved in T-cell activation. A recent study demonstrated the association ofTNFSF4 haplotypes located in the upstream region with risk for- or protection from Systemic Lupus Erythematosus (SLE) (Graham et al, 2008). In order to replicate this association, five single nucleotide polymorphisms (SNPs) tagging the previously associated haplotypes and passing the proper quality control filters were tested in 1312 cases and 1801 controls from Germany, Italy, Spain, and Argentina. The association of TNFSF4 with SLE was replicated in all the sets except Spain. There was a unique risk haplotype tagged by the minor alleles of the SNPs rs1234317 (pooled OR=1.39, p=0.0009) and rs12039904 (pooled OR=1.38, p=0.0012). We did not observe association to a single protective marker (rs844644) or haplotype as the first study reported; instead, we observed different protective haplotypes, all carrying the major alleles of both SNPs rs1234317 and rs12039904. Association analysis conditioning on the haplotypic background confirmed that these two SNPs explain the entire haplotype effect. This is the first replication study that confirms the association of genetic variation in the upstream region of TNFSF4 with susceptibility to SLE.
Systemic lupus erythematosus; TNFSF4; OX40L; genetic association study
Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by autoantibody production and altered type I interferon expression. Genetic surveys and genome-wide association studies have identified more than 30 SLE susceptibility genes. One of these genes, TNIP1, encodes the ABIN1 protein. ABIN1 functions in the immune system by restricting the NF-κB signaling. In order to better understand the genetic factors that influence association with SLE in genes that regulate the NF-κB pathway, we analyzed a dense set of genetic markers spanning TNIP1 and TAX1BP1, as well as the TNIP1 homolog, TNIP2, in case-control sets of diverse ethnic origins.
We fine-mapped TNIP1, TNIP2, and TAX1BP1 in a total of 8372 SLE cases and 7492 healthy controls from European-ancestry, African-American, Hispanic, East Asian, and African-American Gullah populations. Levels of TNIP1 mRNA and ABIN1 protein were analyzed using quantitative RT-PCR and Western blotting, respectively, in EBV-transformed human B cell lines.
We found significant associations between genetic variants within TNIP1 and SLE but not in TNIP2 or TAX1BP1. After resequencing and imputation, we identified two independent risk haplotypes within TNIP1 in individuals of European-ancestry that were also present in African-American and Hispanic populations. These risk haplotypes produced lower levels of TNIP1 mRNA and ABIN1 protein suggesting they harbor hypomorphic functional variants that influence susceptibility to SLE by restricting ABIN1 expression.
Our results confirmed the association signals between SLE and TNIP1 variants in multiple populations and provide new insight into the mechanism by which TNIP1 variants may contribute to SLE pathogenesis.
Amerindian-Europeans, Asians and African-Americans have an excess morbidity from SLE and higher prevalence of lupus nephritis than Caucasians. The aim of this study was to analyze the relationship between genetic ancestry and socio-demographic characteristics and clinical features in a large cohort of Amerindian-European SLE patients.
A total of 2116 SLE patients of Amerindian-European origin and 4001 SLE patients of European descent with clinical data were used in the study. Genotyping of 253 continental ancestry informative markers was performed on the Illumina platform. The STRUCTURE and ADMIXTURE software were used to determine genetic ancestry of each individual. Correlation between ancestry and socio-demographic and clinical data were analyzed using logistic regression.
The average Amerindian genetic ancestry of 2116 SLE patients was 40.7%. There was an increased risk of having renal involvement (P<0.0001, OR= 3.50 95%CI 2.63-4.63) and an early age of onset with the presence of Amerindian genetic ancestry (P<0.0001). Amerindian ancestry protected against photosensitivity (P<0.0001, OR= 0.58 95%CI 0.44-0.76), oral ulcers (P<0.0001, OR= 0.55 95%CI 0.42-0.72), and serositis (P<0.0001, OR= 0.56 95%CI 0.41-0.75) after adjustment by age, gender and age of onset. However, gender and age of onset had stronger effects on malar rash, discoid rash, arthritis and neurological involvement than genetic ancestry.
In general, genetic Amerindian ancestry correlates with lower socio-demographic status and increases the risk for developing renal involvement and SLE at an earlier age of onset.
Immunoregulatory cytokine interleukin-10 (IL-10) is elevated in sera from patients with systemic lupus erythematosus (SLE) correlating with disease activity. The established association of IL10 with SLE and other autoimmune diseases led us to fine map causal variant(s) and to explore underlying mechanisms. We assessed 19 tag SNPs, covering the IL10 gene cluster including IL19, IL20 and IL24, for association with SLE in 15,533 case and control subjects from four ancestries. The previously reported IL10 variant, rs3024505 located at 1 kb downstream of IL10, exhibited the strongest association signal and was confirmed for association with SLE in European American (EA) (P = 2.7×10−8, OR = 1.30), but not in non-EA ancestries. SNP imputation conducted in EA dataset identified three additional SLE-associated SNPs tagged by rs3024505 (rs3122605, rs3024493 and rs3024495 located at 9.2 kb upstream, intron 3 and 4 of IL10, respectively), and SLE-risk alleles of these SNPs were dose-dependently associated with elevated levels of IL10 mRNA in PBMCs and circulating IL-10 protein in SLE patients and controls. Using nuclear extracts of peripheral blood cells from SLE patients for electrophoretic mobility shift assays, we identified specific binding of transcription factor Elk-1 to oligodeoxynucleotides containing the risk (G) allele of rs3122605, suggesting rs3122605 as the most likely causal variant regulating IL10 expression. Elk-1 is known to be activated by phosphorylation and nuclear localization to induce transcription. Of interest, phosphorylated Elk-1 (p-Elk-1) detected only in nuclear extracts of SLE PBMCs appeared to increase with disease activity. Co-expression levels of p-Elk-1 and IL-10 were elevated in SLE T, B cells and monocytes, associated with increased disease activity in SLE B cells, and were best downregulated by ERK inhibitor. Taken together, our data suggest that preferential binding of activated Elk-1 to the IL10 rs3122605-G allele upregulates IL10 expression and confers increased risk for SLE in European Americans.
Systemic lupus erythematosus (SLE), a debilitating autoimmune disease characterized by the production of pathogenic autoantibodies, has a strong genetic basis. Variants of the IL10 gene, which encodes cytokine interleukin-10 (IL-10) with known function of promoting B cell hyperactivity and autoantibody production, are associated with SLE and other autoimmune diseases, and serum IL-10 levels are elevated in SLE patients correlating with increased disease activity. In this study, to discover SLE-predisposing causal variant(s), we assessed variants within the genomic region containing IL10 and its gene family member IL19, IL20 and IL24 for association with SLE in case and control subjects from diverse ancestries. We identified SLE-associated SNP rs3122605 located at 9.2 kb upstream of IL10 as the most likely causal variant in subjects of European ancestry. The SLE-risk allele of rs3122605 was dose-dependently associated with elevated IL10 expression at both mRNA and protein levels in peripheral blood samples from SLE patients and controls, which could be explained, at least in part, by its preferential binding to Elk-1, a transcription factor activated in B cells during active disease of SLE patients. Elk-1-mediated IL-10 overexpression could be downregulated by inhibiting activation of mitogen-activated protein kinases, suggesting a potential therapeutic target for SLE.
We previously established an 80 kb haplotype upstream of TNFSF4 as a susceptibility locus in the autoimmune disease SLE. SLE-associated alleles at this locus are associated with inflammatory disorders, including atherosclerosis and ischaemic stroke. In Europeans, the TNFSF4 causal variants have remained elusive due to strong linkage disequilibrium exhibited by alleles spanning the region. Using a trans-ancestral approach to fine-map the locus, utilising 17,900 SLE and control subjects including Amerindian/Hispanics (1348 cases, 717 controls), African-Americans (AA) (1529, 2048) and better powered cohorts of Europeans and East Asians, we find strong association of risk alleles in all ethnicities; the AA association replicates in African-American Gullah (152,122). The best evidence of association comes from two adjacent markers: rs2205960-T (P = 1.71×10−34, OR = 1.43[1.26–1.60]) and rs1234317-T (P = 1.16×10−28, OR = 1.38[1.24–1.54]). Inference of fine-scale recombination rates for all populations tested finds the 80 kb risk and non-risk haplotypes in all except African-Americans. In this population the decay of recombination equates to an 11 kb risk haplotype, anchored in the 5′ region proximal to TNFSF4 and tagged by rs2205960-T after 1000 Genomes phase 1 (v3) imputation. Conditional regression analyses delineate the 5′ risk signal to rs2205960-T and the independent non-risk signal to rs1234314-C. Our case-only and SLE-control cohorts demonstrate robust association of rs2205960-T with autoantibody production. The rs2205960-T is predicted to form part of a decameric motif which binds NF-κBp65 with increased affinity compared to rs2205960-G. ChIP-seq data also indicate NF-κB interaction with the DNA sequence at this position in LCL cells. Our research suggests association of rs2205960-T with SLE across multiple groups and an independent non-risk signal at rs1234314-C. rs2205960-T is associated with autoantibody production and lymphopenia. Our data confirm a global signal at TNFSF4 and a role for the expressed product at multiple stages of lymphocyte dysregulation during SLE pathogenesis. We confirm the validity of trans-ancestral mapping in a complex trait.
Systemic lupus erythematosus (SLE/lupus) is a complex disease in which the body's immune cells cause inflammation in one or more systems to cause the associated morbidity. Hormones, the environment and genes are all causal contributors to SLE and over the past several years the genetic component of SLE has been firmly established. Several genes which are regulators of the immune system are associated with disease risk. We have established one of these, the tumour-necrosis family superfamily member 4 (TNFSF4) gene, as a lupus susceptibility gene in Northern Europeans. A major obstacle in pinpointing the marker(s) at TNFSF4 which best explain the risk of SLE has been the strong correlation (linkage disequilibrium, LD) between adjacent markers across the TNFSF4 region in this population. To address this, we have typed polymorphisms in several populations in addition to the European groups. The mixed ancestry of these populations gives a different LD pattern than that found in Europeans, presenting a method of pinpointing the section of the TNFSF4 region which results in SLE susceptibility. The Non-European populations have allowed identification of a polymorphism likely to regulate expression of TNFSF4 to increase susceptibility to SLE.
Given the role of CD247 in the response of the T cells, its entailment in autoimmune diseases and in order to better clarify the role of this gene in RA susceptibility, we aimed to analyze CD247 gene variants previously associated with other autoimmune diseases (rs1052237, rs2056626 and rs864537) in a large independent European Caucasian population. However, no evidence of association was found for the analyzed CD247 single-nucleotide polymorphisms (SNPs) with RA and with the presence/absence of anti-cyclic citrullinated polypeptide. We performed a meta-analysis including previously published GWAS data from the rs864537 variant, revealing an overall genome-wide significant association between this CD247 SNP and RA with anti-CCP (OR = 0.90, CI 95% = 0.87–0.93, Poverall = 2.1×10−10). Our results show for first time a GWAS-level association between this CD247 polymorphism and RA risk.
The first genome-wide association study (GWAS) of systemic sclerosis (SSc) demonstrated three non-major histocompatibility complex (MHC) susceptibility loci. The goal of this study was to investigate the impact of these gene variants on survival and severity of interstitial lung disease (ILD) in SSc.
The authors examined 1443 Caucasian SSc patients enrolled in the Genetics versus Environment In Scleroderma Outcome Study (GENISOS) and Scleroderma Family Registry (n = 914 – discovery cohort) and The Johns Hopkins Scleroderma Cohort (n = 529 – replication cohort). Forced vital capacity (FVC)% predicted was used as a surrogate for ILD severity. Five single nucleotide polymorphisms, IRF5 (rs10488631, rs12537284, rs4728142), STAT4 (rs3821236), CD247 (rs2056626) reached genome-wide significance in the SSc-GWAS and were examined in the current study.
Overall, 15.5% of the patients had died over the follow-up period of 5.5 years. The IRF5 rs4728142 minor allele was predictive of longer survival in the discovery cohort (p = 0.021) and in the independent replication cohort (p = 0.047) and combined group (HR: 0.75, 95% CI 0.62 to 0.90, p = 0.002). The association of this SNP with survival was independent of age at disease onset, disease type and autoantibody profile (anticentromere and antitopoisomerase antibodies). The minor allele frequency of IRF5 rs4728142 was 49.4%.
Moreover, IRF5 rs4728142 minor allele correlated with higher FVC% predicted at enrolment (p = 0.019). Finally, the IRF5 rs4728142 minor allele was associated with lower IRF5 transcript expression in patients and controls (p = 0.016 and p = 0.034, respectively), suggesting that the IRF5, rs4728142 SNP, may be functionally relevant.
An SNP in the IRF5 promoter region (rs4728142), associated with lower IRF5 transcript levels, was predictive of longer survival and milder ILD in patients with SSc.
Independent replication with large cohorts and metaanalysis of genetic associations are necessary to validate genetic susceptibility factors. The known tumor necrosis factor (ligand) superfamily, member 4 gene (TNFSF4) systemic lupus erythematosus (SLE) risk locus has been found to be associated with systemic sclerosis (SSc) in 2 studies, but with discrepancies between them for genotype-phenotype correlation. Our objective was to validate TNFSF4 association with SSc and determine the subset with the higher risk.
Known SLE and SSc TNFSF4 susceptibility variants (rs2205960, rs1234317, rs12039904, rs10912580, and rs844648) were genotyped in 1031 patients with SSc and 1014 controls of French white ancestry. Genotype-phenotype association analysis and metaanalysis of available data were performed, providing a population study of 4989 patients with SSc and 4661 controls, all of European white ancestry.
Allelic and genotypic associations were observed for the 5 single-nucleotide polymorphisms (SNP) with the subset of patients with SSc who are positive for anticentromere antibodies (ACA) and only a trend for association with SSc and limited cutaneous SSc. Rs2205960 exhibited the strongest allelic association in ACA+ patients with SSc [p = 0.0015; OR 1.37 (1.12–1.66)], with significant intracohort association when compared to patients with SSc positive for ACA. Metaanalysis confirmed overall association with SSc but also raised preferential association with the ACA+ subset and strongest effect with rs2205960 [T allele p = 0.00013; OR 1.33 (1.15–1.54) and TT genotype p = 0.00046; OR 2.02 (1.36–2.98)].
We confirm TNFSF4 as an SSc susceptibility gene and rs2205960 as a putative causal variant with preferential association in the ACA+ SSc subphenotype. (First Release March 15 2012; J Rheumatol 2012;39:997–1003; doi:10.3899/jrheum.111270)
SYSTEMIC SCLEROSIS; TNFSF4; AUTOIMMUNITY; AUTOANTIBODIES
Systemic lupus erythematosus (SLE) is a heterogeneous autoimmune disease with significant immune system aberrations resulting from complex heritable genetics as well as environmental factors. TRAF6 is a candidate gene for SLE, which has a major role in several signaling pathways that are important for immunity and organ development.
Fifteen single-nucleotide polymorphisms (SNPs), across TRAF6 were evaluated in 7,490 SLE and 6,780 control subjects from different ancestries. Population-based case-control association analyses and meta-analyses were performed. P values, false discovery rate q values, and odds ratios with 95% confidence intervals were calculated.
Evidence of associations in multiple SNPs was detected. The best overall p values were obtained for SNPs rs5030437 and rs4755453 (p=7.85×10−5 and p=4.73×10−5, respectively) without significant heterogeneity among populations (p=0.67 and p=0.50 in Q-statistic). In addition, rs540386 previously reported to be associated with RA was found to be in LD with these two SNPs (r2= 0.95) and demonstrated evidence of association with SLE in the same direction (meta-analysis p=9.15×10−4, OR=0.89, 95%CI=0.83–0.95). Thrombocytopenia improved the overall results in different populations (meta-analysis p=1.99×10−6, OR=0.57, 95%CI=0.45–0.72, for rs5030470). Finally evidence of family based association in 34 African-American pedigrees with the presence of thrombocytopenia were detected in one available SNP rs5030437 with Z score magnitude of 2.28 (p=0.02) under a dominant model.
Our data indicate the presence of association of TRAF6 with SLE in agreement with the previous report of association with RA. These data provide further support for the involvement of TRAF6 in the pathogenesis of autoimmunity.
TRAF6; polymorphism; systemic lupus erythematosus
Using the Immunochip custom single nucleotide polymorphism (SNP) array, designed for dense genotyping of 186 genome wide association study (GWAS) confirmed loci we analysed 11,475 rheumatoid arthritis cases of European ancestry and 15,870 controls for 129,464 markers. The data were combined in meta-analysis with GWAS data from additional independent cases (n=2,363) and controls (n=17,872). We identified fourteen novel loci; nine were associated with rheumatoid arthritis overall and 5 specifically in anti-citrillunated peptide antibody positive disease, bringing the number of confirmed European ancestry rheumatoid arthritis loci to 46. We refined the peak of association to a single gene for 19 loci, identified secondary independent effects at six loci and association to low frequency variants (minor allele frequency <0.05) at 4 loci. Bioinformatic analysis of the data generated strong hypotheses for the causal SNP at seven loci. This study illustrates the advantages of dense SNP mapping analysis to inform subsequent functional investigations.
Systemic lupus erythematosus (SLE) is a sexually dimorphic autoimmune disease which is more common in women, but affected men often experience a more severe disease. The genetic basis of sexual dimorphism in SLE is not clearly defined. A study was undertaken to examine sex-specific genetic effects among SLE susceptibility loci.
A total of 18 autosomal genetic susceptibility loci for SLE were genotyped in a large set of patients with SLE and controls of European descent, consisting of 5932 female and 1495 male samples. Sex-specific genetic association analyses were performed. The sex–gene interaction was further validated using parametric and nonparametric methods. Aggregate differences in sex-specific genetic risk were examined by calculating a cumulative genetic risk score for SLE in each individual and comparing the average genetic risk between male and female patients.
A significantly higher cumulative genetic risk for SLE was observed in men than in women. (P = 4.52×10−8) A significant sex–gene interaction was seen primarily in the human leucocyte antigen (HLA) region but also in IRF5, whereby men with SLE possess a significantly higher frequency of risk alleles than women. The genetic effect observed in KIAA1542 is specific to women with SLE and does not seem to have a role in men.
The data indicate that men require a higher cumulative genetic load than women to develop SLE. These observations suggest that sex bias in autoimmunity could be influenced by autosomal genetic susceptibility loci.
The ubiquitin associated and Src-homology 3 (SH3) domain containing A (UBASH3a) is a suppressor of T-cell receptor signaling, underscoring antigen presentation to T-cells as a critical shared mechanism of diseases pathogenesis. The aim of the present study was to determine whether the UBASH3a gene influence the susceptibility to systemic lupus erythematosus (SLE) in Caucasian populations. We evaluated five UBASH3a polymorphisms (rs2277798, rs2277800, rs9976767, rs13048049 and rs17114930), using TaqMan® allelic discrimination assays, in a discovery cohort that included 906 SLE patients and 1165 healthy controls from Spain. The SNPs that exhibit statistical significance difference were evaluated in a German replication cohort of 360 SLE patients and 379 healthy controls. The case-control analysis in the Spanish population showed a significant association between the rs9976767 and SLE (Pc = 9.9E-03 OR = 1.21 95%CI = 1.07–1.37) and a trend of association for the rs2277798 analysis (P = 0.09 OR = 0.9 95%CI = 0.79–1.02). The replication in a German cohort and the meta-analysis confirmed that the rs9976767 (Pc = 0.02; Pc = 2.4E-04, for German cohort and meta-analysis, respectively) and rs2277798 (Pc = 0.013; Pc = 4.7E-03, for German cohort and meta-analysis, respectively) UBASH3a variants are susceptibility factors for SLE. Finally, a conditional regression analysis suggested that the most likely genetic variation responsible for the association was the rs9976767 polymorphism. Our results suggest that UBASH3a gene plays a role in the susceptibility to SLE. Moreover, our study indicates that UBASH3a can be considered as a common genetic factor in autoimmune diseases.
Several confirmed genetic susceptibility loci for lupus have been described. To date, no clear evidence for genetic epistasis is established in lupus. We test for gene-gene interactions in a number of known lupus susceptibility loci.
Eighteen SNPs tagging independent and confirmed lupus susceptibility loci were genotyped in a set of 4,248 lupus patients and 3,818 normal healthy controls of European descent. Epistasis was tested using a 2-step approach utilizing both parametric and non-parametric methods. The false discovery rate (FDR) method was used to correct for multiple testing.
We detected and confirmed gene-gene interactions between the HLA region and CTLA4, IRF5, and ITGAM, and between PDCD1 and IL21 in lupus patients. The most significant interaction detected by parametric analysis was between rs3131379 in the HLA region and rs231775 in CTLA4 (Interaction odds ratio=1.19, z-score= 3.95, P= 7.8×10−5 (FDR≤0.05), PMDR= 5.9×10−45). Importantly, our data suggest that in lupus patients the presence of the HLA lupus-risk alleles in rs1270942 and rs3131379 increases the odds of also carrying the lupus-risk allele in IRF5 (rs2070197) by 17% and 16%, respectively (P= 0.0028 and 0.0047).
We provide evidence for gene-gene epistasis in systemic lupus erythematosus. These findings support a role for genetic interaction contributing to the complexity of lupus heritability.
Replacement of dental restorations has been the traditional treatment for defective restorations. This five-year prospective clinical trial evaluated amalgam restorations with localized defects that were treated by means of repair or refurbishing. Fifty-two patients (50% female and 50% male, mean age 28.3 ± 18.1
years, range 18–80) with 160 class I and class II defective restorations were included. The study focused on the application of two minimally invasive treatments for localized restoration defects and compared these with no treatment and total replacement as negative and positive controls, respectively. Restorations were assessed by two calibrated examiners according to modified U.S. Public Health Service criteria, including marginal adaptation, anatomic form, secondary caries, and roughness. At five years, recall was examined in 45 patients with 108 restorations (67.5%). The results suggest that repair treatment is as effective as total replacement of restorations with localized defects, reducing biological costs to the patient and providing new tools to the clinician. Refinishing restoration is a useful treatment for localized anatomic form defects.
Significant advances have been made in understanding the genetic basis of systemic sclerosis (scleroderma) in recent years. Can these discoveries lead to individualized monitoring and treatment? Besides robustly replicated genetic susceptibility loci, several genes have been recently linked to various systemic sclerosis disease manifestations. Furthermore, inclusion of genetic studies in design and analysis of drug trials could lead to development of genetic biomarkers that predict treatment response. Future genetic studies in well-characterized systemic sclerosis cohorts paired with advanced analytic approaches can lead to development of genetic biomarkers for targeted diagnostic and therapeutic interventions in systemic sclerosis.
systemic sclerosis; scleroderma; genetic; biomarker; severity
Altered signaling in B-cells is a predominant feature of systemic lupus erythematosus (SLE). The genes BANK1 and BLK were recently described as associated with SLE. BANK1 codes for a B-cell-specific cytoplasmic protein involved in B-cell receptor signaling and BLK codes for an Src tyrosine kinase with important roles in B-cell development. To characterize the role of BANK1 and BLK in SLE, we performed a genetic interaction analysis hypothesizing that genetic interactions could reveal functional pathways relevant to disease pathogenesis.
We Used the method GPAT16 to analyze the gene-gene interactions of BANK1 and BLK. Confocal microscopy was used to investigate co-localization, and immunoprecipitation was used to verify the physical interaction of BANK1 and BLK.
Epistatic interactions between BANK1 and BLK polymorphisms associated with SLE were observed in a discovery set of 279 patients and 515 controls from Northern Europe. A meta-analysis with 4399 European individuals confirmed the genetic interactions between BANK1 and BLK.
As BANK1 was identified as a binding partner of the Src tyrosine kinase LYN, we tested the possibility that BANK1 and BLK could also show a protein-protein interaction. We demonstrated co-immunoprecipitation and co-localization of BLK and BANK1. In a Daudi cell line and primary naïve B-cells the endogenous binding was enhanced upon B-cell receptor stimulation using anti-IgM antibodies.
Here, we show a genetic interaction between BANK1 and BLK, and demonstrate that these molecules interact physically. Our results have important consequences for the understanding of SLE and other autoimmune diseases and identify a potential new signaling pathway.
systemic lupus erythematosus; genetics; polymorphism; B-cells; autoantibodies
Objective. To determine the role of Class II HLAs in SSc patients from Italy and Spain and in SSc patients of Caucasian ancestry.
Methods. Nine hundred and forty-four SSc patients (Italy 392 patients; Spain 452 patients) and 1320 ethnically matched healthy controls (Italy 398 patients; Spain 922 patients) were genotyped up to the fourth digit by PCR with sequence-specific oligonucleotides for HLA-DRB1, DQA1 and DQB1 loci. Patients included 390 ACA-positive and 254 anti-topo I-positive subjects. Associations between SSc or SSc-specific antibodies and HLA alleles or HLA haplotypes were sought via the chi-square test after 10 000-fold permutation testing. A meta-analysis including this study cohort and other Caucasoids samples was also conducted.
Results. In both the cohorts, the strongest association was observed between the HLA-DRB1*1104 allele and SSc or anti-topo I antibodies. The HLA-DRB1*1104 -DQA1*0501 -DQB1*0301 haplotype was overrepresented in Italian [odds ratio (OR) = 2.069, 95% asymptotic CIs (CI95) 1.486, 2.881; P < 0.001] and in Spanish patients (OR = 6.707, CI95 3.974, 11.319; P < 0.001) as well as in anti-topo-positive patients: Italy (OR = 2.642, CI95 1.78, 3.924; P < 0.001) and Spain (OR = 20.625, CI95 11.536, 36.876; P < 0.001). In both the populations we also identified an additional risk allele (HLA-DQB1*03) and a protective allele (HLA-DQB1*0501) in anti-topo-positive patients. The meta-analysis showed different statistically significant associations, the most interesting being the differential association between HLA-DRB1*01 alleles and ACAs (OR = 1.724, CI95 1.482, 2.005; P < 0.001) or topo I antibodies (OR = 0.5, CI95 0.384, 0.651; P < 0.001).
Conclusions. We describe multiple robust associations between SSc and HLA Class II antigens in Caucasoids that may help to understand the genetic architecture of SSc.
systemic sclerosis; HLA; genetics; epidemiology
Systemic lupus erythematosus (SLE) is an autoimmune disease with diverse clinical manifestations characterized by the development of pathogenic autoantibodies manifesting in inflammation of target organs such as the kidneys, skin and joints. Genome-wide association studies have identified genetic variants in the UBE2L3 region that are associated with SLE in subjects of European and Asian ancestry. UBE2L3 encodes an ubiquitin-conjugating enzyme, UBCH7, involved in cell proliferation and immune function. In this study, we sought to further characterize the genetic association in the region of UBE2L3 and use molecular methods to determine the functional effect of the risk haplotype. We identified significant associations between variants in the region of UBE2L3 and SLE in individuals of European and Asian ancestry that exceeded a Bonferroni corrected threshold (P < 1 × 10−4). A single risk haplotype was observed in all associated populations. Individuals harboring the risk haplotype display a significant increase in both UBE2L3 mRNA expression (P = 0.0004) and UBCH7 protein expression (P = 0.0068). The results suggest that variants carried on the SLE associated UBE2L3 risk haplotype influence autoimmunity by modulating UBCH7 expression.
Systemic Lupus Erythematosus; UBE2L3; Multi Ethnic Association Study; UBCH7 Expression
Potassium voltage-gated channel shaker-related subfamily member 5 (KCNA5) is implicated in vascular tone regulation, and its inhibition during hypoxia produces pulmonary vasoconstriction. Recently, a protective association of the KCNA5 locus with systemic sclerosis (SSc) patients with pulmonary arterial hypertension (PAH) was reported. Hence, the aim of this study was to replicate these findings in an independent multicenter Caucasian SSc cohort.
The 2,343 SSc cases (179 PAH positive, confirmed by right-heart catheterization) and 2,690 matched healthy controls from five European countries were included in this study. Rs10744676 single-nucleotide polymorphism (SNP) was genotyped by using a TaqMan SNP genotyping assay.
Individual population analyses of the selected KCNA5 genetic variant did not show significant association with SSc or any of the defined subsets (for example, limited cutaneous SSc, diffuse cutaneous SSc, anti-centromere autoantibody positive and anti-topoisomerase autoantibody positive). Furthermore, pooled analyses revealed no significant evidence of association with the disease or any of the subsets, not even the PAH-positive group. The comparison of PAH-positive patients with PAH-negative patients showed no significant differences among patients.
Our data do not support an important role of KCNA5 as an SSc-susceptibility factor or as a PAH-development genetic marker for SSc patients.
Systemic lupus erythematosus (SLE; OMIM 152700) is a chronic autoimmune disease for which the aetiology includes genetic and environmental factors. ITGAM, integrin αΜ (complement component 3 receptor 3 subunit) encoding a ligand for intracellular adhesion molecule (ICAM) proteins, is an established SLE susceptibility locus. This study aimed to evaluate the independent and joint effects of genetic variations in the genes that encode ITGAM and ICAM.
The authors examined several markers in the ICAM1–ICAM4–ICAM5 locus on chromosome 19p13 and the single ITGAM polymorphism (rs1143679) using a large-scale case–control study of 17 481 unrelated participants from four ancestry populations. The single marker association and gene–gene interaction were analysed for each ancestry, and a meta-analysis across the four ancestries was performed.
The A-allele of ICAM1–ICAM4–ICAM5 rs3093030, associated with elevated plasma levels of soluble ICAM1, and the A-allele of ITGAM rs1143679 showed the strongest association with increased SLE susceptibility in each of the ancestry populations and the trans-ancestry meta-analysis (ORmeta=1.16, 95% CI 1.11 to 1.22; p=4.88×10−10 and ORmeta=1.67, 95% CI 1.55 to 1.79; p=3.32×10−46, respectively). The effect of the ICAM single-nucleotide polymorphisms (SNPs) was independent of the effect of the ITGAM SNP rs1143679, and carriers of both ICAM rs3093030-AA and ITGAM rs1143679-AA had an OR of 4.08 compared with those with no risk allele in either SNP (95% CI 2.09 to 7.98; p=3.91×10−5).
These findings are the first to suggest that an ICAM–integrin-mediated pathway contributes to susceptibility to SLE.
Systemic lupus erythematosus is a clinically heterogeneous autoimmune disease. A number of genetic loci that increase lupus susceptibility have been established. This study examines if these genetic loci also contribute to the clinical heterogeneity in lupus.
Materials and methods
4001 European-derived, 1547 Hispanic, 1590 African-American and 1191 Asian lupus patients were genotyped for 16 confirmed lupus susceptibility loci. Ancestry informative markers were genotyped to calculate and adjust for admixture. The association between the risk allele in each locus was determined and compared in patients with and without the various clinical manifestations included in the ACR criteria.
Renal disorder was significantly correlated with the lupus risk allele in ITGAM (p=5.0×10−6, OR 1.25, 95% CI 1.12 to 1.35) and in TNFSF4 (p=0.0013, OR 1.14, 95% CI 1.07 to 1.25). Other significant findings include the association between risk alleles in FCGR2A and malar rash (p=0.0031, OR 1.11, 95% CI 1.17 to 1.33), ITGAM and discoid rash (p=0.0020, OR 1.20, 95% CI 1.06 to 1.33), STAT4 and protection from oral ulcers (p=0.0027, OR 0.89, 95% CI 0.83 to 0.96) and IL21 and haematological disorder (p=0.0027, OR 1.13, 95% CI 1.04 to 1.22). All these associations are significant with a false discovery rate of <0.05 and pass the significance threshold using Bonferroni correction for multiple testing.
Significant associations were found between lupus clinical manifestations and the FCGR2A, ITGAM, STAT4, TNSF4 and IL21 genes. The findings suggest that genetic profiling might be a useful tool to predict disease manifestations in lupus patients in the future.
The number of copies of the HLA-DRB1 shared epitope, and the minor alleles of the STAT4 rs7574865 and the PTPN22 rs2476601 polymorphisms have all been linked with an increased risk of developing rheumatoid arthritis. In the present study, we investigated the effects of these genetic variants on disease activity and disability in patients with early arthritis.
Methodology and Results
We studied 640 patients with early arthritis (76% women; median age, 52 years), recording disease-related variables every 6 months during a 2-year follow-up. HLA-DRB1 alleles were determined by PCR-SSO, while rs7574865 and rs2476601 were genotyped with the Taqman 5′ allelic discrimination assay. Multivariate analysis was performed using generalized estimating equations for repeated measures. After adjusting for confounding variables such as gender, age and ACPA, the TT genotype of rs7574865 in STAT4 was associated with increased disease activity (DAS28) as compared with the GG genotype (β coefficient [95% confidence interval] = 0.42 [0.01–0.83], p = 0.044). Conversely, the presence of the T allele of rs2476601 in PTPN22 was associated with diminished disease activity during follow-up in a dose-dependent manner (CT genotype = −0.27 [−0.56– −0.01], p = 0.042; TT genotype = −0.68 [−1.64– −0.27], p = 0.162). After adjustment for gender, age and disease activity, homozygosity for the T allele of rs7574865 in STAT4 was associated with greater disability as compared with the GG genotype.
Our data suggest that patients with early arthritis who are homozygous for the T allele of rs7574865 in STAT4 may develop a more severe form of the disease with increased disease activity and disability.
To perform fine mapping of the autoimmunity susceptibility gene BLK and identify functional variants involved in SLE.
Genotyping of 1163 European SLE patients and 1482 controls and imputation were performed covering the BLK gene with 158 SNPs. Logistic regression analysis was done using PLINK and conditional analyses using GENABEL’s test score. Transfections of BLK constructs on HEK293 cells containing the novel mutation or the wild-type form were made to analyse their effect on protein half-life using a protein stability assay, cycloheximide and Western blot. CHiP-qPCR for NFkB binding.
Fine mapping of BLK identified two independent genetic effects with functional consequences: one represented by two tightly linked associated haplotype blocks significantly enriched for NFκB-binding sites and numerous putative regulatory variants whose risk alleles correlated with low BLK mRNA levels. Binding of NFkBp50 and p65 to an associated 1.2Kb haplotype segment was confirmed. A second independent genetic effect was represented by an Ala71Thr, low-frequency missense substitution with an OR = 2.31 (95% c.i. 1.38–3.86). The 71Thr decreased BLK protein half-life.
Our results show that rare and common regulatory variants in BLK are involved in disease susceptibility and both, albeit independently lead to reduced levels of BLK protein.
systemic lupus erythematosus; autoimmunity; genetics; polymorphism; B-cells; autoantibodies; B-lymphocyte tyrosine kinase
The aim of the present study was to investigate the possible role of CD40 and CD40 ligand (CD40LG) genes in the susceptibility and phenotype expression of systemic sclerosis (SSc).
In total, 2,670 SSc patients and 3,245 healthy individuals from four European populations (Spain, Germany, The Netherlands, and Italy) were included in the study. Five single-nucleotide polymorphisms (SNPs) of CD40 (rs1883832, rs4810485, rs1535045) and CD40LG (rs3092952, rs3092920) were genotyped by using a predesigned TaqMan allele-discrimination assay technology. Meta-analysis was assessed to determine whether an association exists between the genetic variants and SSc or its main clinical subtypes.
No evidence of association between CD40 and CD40LG genes variants and susceptibility to SSc was observed. Similarly, no significant statistical differences were observed when SSc patients were stratified by the clinical subtypes, the serologic features, and pulmonary fibrosis.
Our results do not suggest an important role of CD40 and CD40LG gene polymorphisms in the susceptibility to or clinical expression of SSc.