Numerous loci have been found genetically associated with complex diseases, but only in a few cases has the functional variant and the molecular mechanism behind it been identified. Recently, the association of the BANK1 gene with systemic lupus erythematosus (SLE) was described. Here, we investigated the role of the associated polymorphisms on gene function and found that SNP rs17266594 located in the branch point consensus sequence has negligible effect on splicing or gene expression. The non-synonymous SNP rs10516487 located in exon 2 influenced splicing efficiency by creating an exonic splicing enhancer site for the SRp40 factor. Further, this same SNP generates protein isoforms with differential and measurable self-association properties. The full-length protein isoform containing the R61 variant forms larger protein scaffold complexes in the cell cytoplasm compared to the protective BANK1-61H variant. We also observed that, contrary to the full-length isoform, the short Δ2 isoform of BANK1 displays a homogeneous cytoplasmic distribution, underscoring the potential role of the exon 2-coded protein domain in the scaffolding function of BANK1.
We provide evidence that the non-synonymous SNP rs10516487 (G
SLE; BANK1; isoforms; splicing; sub-cellular localization; cytoplasmic punctae
UBE2L3 is associated with susceptibility to systemic lupus erythematosus (SLE) and rheumatoid arthritis in European ancestry populations, and this locus has not been investigated fully in non-European populations. We studied the UBE2L3 risk allele for association with SLE, interferon-α (IFN-α), and autoantibodies in a predominantly African American SLE cohort.
We studied 395 patients with SLE and 344 controls. The UBE2L3 rs5754217 polymorphism was genotyped using Taqman primer-probe sets, and IFN-α was measured using a reporter cell assay.
The UBE2L3 rs5754217 T allele was strongly enriched in African American patients with anti-La antibodies as compared to controls, and a recessive model was the best fit for this association (OR 2.55, p = 0.0061). Serum IFN-α also demonstrated a recessive association with the rs5754217 genotype in African American patients, and the TT/anti-La-positive patients formed a significantly high IFN-α subgroup (p = 0.0040). Similar nonstatistically significant patterns of association were observed in the European American patients with SLE. Case-control analysis did not show large allele frequency differences, supporting the idea that this allele is most strongly associated with anti-La-positive patients.
This pattern of recessive influence within a subgroup of patients may explain why this allele does not produce a strong signal in standard case-control studies, and subphenotypes should be included in future studies of UBE2L3. The interaction we observed between UBE2L3 genotype and autoantibodies upon serum IFN-α suggests a biological role for this locus in patients with SLE in vivo.
SYSTEMIC LUPUS ERYTHEMATOSUS; GENETICS INTERFERON-α; AUTOANTIBODIES; UBE2L3 GENOTYPE
A haplotype of the interferon regulatory factor 5 (IRF5) gene has been associated with the risk of developing systemic lupus erythematosus (SLE), and our previous studies have demonstrated that high levels of serum interferon-α (IFNα) activity are a heritable risk factor for SLE. The aim of this study was to determine whether the IRF5 SLE risk haplotype mediates the risk of SLE by predisposing patients to the development of high levels of serum IFNα activity.
IFNα levels in 199 SLE patients of European and Hispanic ancestry were measured with a sensitive functional reporter cell assay. The rs2004640, rs3807306, rs10488631, and rs2280714 single-nucleotide polymorphisms (SNPs) in IRF5 were genotyped in these patients. Haplotypes were categorized as SLE risk, neutral, or protective based on published data.
SLE patients with risk/risk and risk/neutral IRF5 genotypes had higher serum IFNα activity than did those with protective/protective and neutral/protective genotypes (P = 0.025). This differential effect of IRF5 genotype on serum IFNα levels was driven largely by SLE patients who were positive for either anti–RNA binding protein (anti-RBP) or anti–double-stranded DNA (anti-dsDNA) autoantibodies (P = 0.012 for risk/risk or risk/neutral versus protective/protective or neutral/protective). The rs3807306 genotype was independently associated with high serum IFNα in this autoantibody group. We found no difference in IFNα activity according to IRF5 genotype in patients lacking either type of autoantibody or in patients positive for both classes of autoantibody.
The IRF5 SLE risk haplotype is associated with higher serum IFNα activity in SLE patients, and this effect is most prominent in patients positive for either anti-RBP or anti-dsDNA autoantibodies. This study demonstrates the biologic relevance of the SLE risk haplotype of IRF5 at the protein level.
Protein tyrosine phosphatase non-receptor type 22 (PTPN22) is a negative regulator of T-cell activation associated with several autoimmune diseases, including systemic lupus erythematosus (SLE). Missense rs2476601 is associated with SLE in individuals with European ancestry. Since the rs2476601 risk allele frequency differs dramatically across ethnicities, we assessed robustness of PTPN22 association with SLE and its clinical sub-phenotypes across four ethnically diverse populations. Ten SNPs were genotyped in 8220 SLE cases and 7369 controls from in European-Americans (EA), African-Americans (AA), Asians (AS), and Hispanics (HS). We performed imputation-based association followed by conditional analysis to identify independent associations. Significantly associated SNPs were tested for association with SLE clinical sub-phenotypes, including autoantibody profiles. Multiple testing was accounted for by using false discovery rate. We successfully imputed and tested allelic association for 107 SNPs within the PTPN22 region and detected evidence of ethnic-specific associations from EA and HS. In EA, the strongest association was at rs2476601 (P = 4.7×10−9, OR = 1.40 (95% CI = 1.25–1.56)). Independent association with rs1217414 was also observed in EA, and both SNPs are correlated with increased European ancestry. For HS imputed intronic SNP, rs3765598, predicted to be a cis-eQTL, was associated (P = 0.007, OR = 0.79 and 95% CI = 0.67–0.94). No significant associations were observed in AA or AS. Case-only analysis using lupus-related clinical criteria revealed differences between EA SLE patients positive for moderate to high titers of IgG anti-cardiolipin (aCL IgG >20) versus negative aCL IgG at rs2476601 (P = 0.012, OR = 1.65). Association was reinforced when these cases were compared to controls (P = 2.7×10−5, OR = 2.11). Our results validate that rs2476601 is the most significantly associated SNP in individuals with European ancestry. Additionally, rs1217414 and rs3765598 may be associated with SLE. Further studies are required to confirm the involvement of rs2476601 with aCL IgG.
Interferon-α (IFNα) is a heritable risk factor for systemic lupus erythematosus (SLE). Genetic variation near IRF7 is implicated in SLE susceptibility. SLE-associated autoantibodies can stimulate IFNα production through the Toll-like receptor/IRF7 pathway. This study was undertaken to determine whether variants of IRF7 act as risk factors for SLE by increasing IFNα production and whether autoantibodies are important to this phenomenon.
We studied 492 patients with SLE (236 African American, 162 European American, and 94 Hispanic American subjects). Serum levels of IFNα were measured using a reporter cell assay, and single-nucleotide polymorphisms (SNPs) in the IRF7/PHRF1 locus were genotyped.
In a joint analysis of European American and Hispanic American subjects, the rs702966 C allele was associated with the presence of anti–double-stranded DNA (anti-dsDNA) antibodies (odds ratio [OR] 1.83, P = 0.0069). The rs702966 CC genotype was only associated with higher serum levels of IFNα in European American and Hispanic American patients with anti-dsDNA antibodies (joint analysis P = 4.1 × 10−5 in anti-dsDNA–positive patients and P = 0.99 in anti-dsDNA–negative patients). In African American subjects, anti-Sm antibodies were associated with the rs4963128 SNP near IRF7 (OR 1.95, P = 0.0017). The rs4963128 CT and TT genotypes were associated with higher serum levels of IFNα only in African American patients with anti-Sm antibodies (P = 0.0012). In African American patients lacking anti-Sm antibodies, an effect of anti-dsDNA–rs702966 C allele interaction on serum levels of IFNα was observed, similar to the other patient groups (overall joint analysis P = 1.0 × 10−6). In European American and Hispanic American patients, the IRF5 SLE risk haplotype showed an additive effect with the rs702966 C allele on IFNα level in anti-dsDNA–positive patients.
Our findings indicate that IRF7/PHRF1 variants in combination with SLE-associated autoantibodies result in higher serum levels of IFNα, providing a biologic relevance for this locus at the protein level in human SLE in vivo.
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
High serum interferon α (IFNα) activity is a heritable risk factor for systemic lupus erythematosus (SLE). Auto-antibodies found in SLE form immune complexes which can stimulate IFNα production by activating endosomal Toll-like receptors and interferon regulatory factors (IRFs), including IRF5. Genetic variation in IRF5 is associated with SLE susceptibility; however, it is unclear how IRF5 functional genetic elements contribute to human disease.
1034 patients with SLE and 989 controls of European ancestry, 555 patients with SLE and 679 controls of African–American ancestry, and 73 patients with SLE of South African ancestry were genotyped at IRF5 polymorphisms, which define major haplotypes. Serum IFNα activity was measured using a functional assay.
In European ancestry subjects, anti-double-stranded DNA (dsDNA) and anti-Ro antibodies were each associated with different haplotypes characterised by a different combination of functional genetic elements (OR > 2.56, p >003C; 1.9×10−14 for both). These IRF5 haplotype-auto-antibody associations strongly predicted higher serum IFNα in patients with SLE and explained > 70% of the genetic risk of SLE due to IRF5. In African–American patients with SLE a similar relationship between serology and IFNα was observed, although the previously described European ancestry-risk haplotype was present at admixture proportions in African–American subjects and absent in African patients with SLE.
The authors define a novel risk haplotype of IRF5 that is associated with anti-dsDNA antibodies and show that risk of SLE due to IRF5 genotype is largely dependent upon particular auto-antibodies. This suggests that auto-antibodies are directly pathogenic in human SLE, resulting in increased IFNα in cooperation with particular combinations of IRF5 functional genetic elements.
SLE is a systemic autoimmune disorder affecting multiple organ systems including the skin, musculoskeletal, renal and haematopoietic systems. Humoral autoimmunity is a hallmark of SLE, and patients frequently have circulating auto-antibodies directed against dsDNA, as well as RNA binding proteins (RBP). Anti-RBP autoantibodies include antibodies which recognize Ro, La, Smith (anti-Sm), and ribonucleoprotein (anti-nRNP), collectively referred to as anti-retinol-binding protein). Anti-retinol-binding protein and anti-dsDNA auto-antibodies are rare in the healthy population.1 These auto-antibodies can be present in sera for years preceding the onset of clinical SLE illness2 and are likely pathogenic in SLE.34
Recent genome-wide association studies demonstrated association of single nucleotide polymorphisms (SNPs) in the TNFAIP3 region at 6q23 with systemic lupus erythematosus (SLE) in European-American populations. In this study, we investigated whether SNPs in the TNFAIP3 region are associated with SLE also in a Japanese population. A case-control association study was performed on the SNPs rs13192841, rs2230926, and rs6922466 in 318 Japanese SLE patients and 444 healthy controls. Association of rs2230926 G allele with SLE was replicated in Japanese (allelic association P = .033, odds ratio [OR] 1.47, recessive model P = .023, OR 8.52). The association was preferentially observed in the SLE patients with nephritis. When the TNFAIP3 mRNA levels of the HapMap samples were examined using GENEVAR database, the presence of TNFAIP3 rs2230926 G allele was associated with lower mRNA expression of TNFAIP3 (P = .013). These results indicated that TNFAIP3 is a susceptibility gene to SLE both in the Caucasian and Asian populations.
Systemic lupus erythematosus (SLE) is a predominantly female autoimmune disease that affects multiple organ systems. Herein, we report on an X-chromosome gene association with SLE. Methyl-CpG-binding protein 2 (MECP2) is located on chromosome Xq28 and encodes for a protein that plays a critical role in epigenetic transcriptional regulation of methylation-sensitive genes. Utilizing a candidate gene association approach, we genotyped 21 SNPs within and around MECP2 in SLE patients and controls. We identify and replicate association between SLE and the genomic element containing MECP2 in two independent SLE cohorts from two ethnically divergent populations. These findings are potentially related to the overexpression of methylation-sensitive genes in SLE.
Systemic lupus erythematosus (SLE) is a systemic multisystem autoimmune disorder influenced by genetic background and environmental factors. Our aim here was to replicate findings of associations between 7 of the implicated single nucleotide polymorphisms (SNPs) in IRF5, BLK, STAT4, TNFAIP3, SPP1, TNIP1 and ETS1 genes with susceptibility to childhood-onset SLE in the Japanese population. In particular, we focused on gender differences in allelic frequencies.
The 7 SNPs were genotyped using TaqMan assays in 75 patients with childhood-onset SLE and in 190 healthy controls. The relationship between the cumulative number of risk alleles and SLE manifestations was explored in childhood-onset SLE. Logistic regression was used to test the effect of each polymorphism on susceptibility to SLE, and Wilcoxon rank sum testing was used for comparison of total risk alleles. Data on rs7574865 in the STAT4 gene and rs9138 in SPP1 were replicated for associations with SLE when comparing cases and controls (corrected P values ranging from 0.0043 to 0.027). The rs2230926 allele of TNFAIP3 was associated with susceptibility to SLE in males, but after Bonferroni correction there were no significant associations with any of the other four SNPs in IRF5, BLK, TNIP1 and ETS1 genes. The cumulative number of risk alleles was significantly increased in childhood-onset SLE relative to healthy controls (P = 0.0000041). Male SLE patients had a slightly but significantly higher frequency of the TNFAIP3 (rs2230926G) risk allele than female patients (odds ratio [OR] = 4.05, 95% confidence interval [95%CI] = 1.46–11.2 P<0.05).
Associations of polymorphisms in STAT4 and SPP1 with childhood-onset SLE were confirmed in a Japanese population. Although these are preliminary results for a limited number of cases, TNFAIP3 rs2230926G may be an important predictor of disease onset in males. We also replicated findings that the cumulative number of risk alleles was significantly increased in childhood-onset SLE.
Recent genome-wide and candidate gene association studies in large numbers of systemic lupus erythematosus (SLE) patients have suggested approximately 30 susceptibility genes. These genes are involved in three types of biological processes, including immune complex processing, toll-like receptor function and type I interferon production, and immune signal transduction in lymphocytes, and they may contribute to the pathogenesis of SLE. To better understand the genetic risk factors of SLE, we investigated the associations of seven SLE susceptibility genes in a Chinese population, including FCGR3A, FCGR2A, TNFAIP3, TLR9, TREX1, ETS1 and TNIP1.
A total of 20 SNPs spanning the seven SLE susceptibility genes were genotyped in a sample of 564 unrelated SLE patients and 504 unrelated healthy controls recruited from Yunnan, southwestern China. The associations of SNPs with SLE were assessed by statistical analysis.
Five SNPs in two genes (TNFAIP3 and ETS1) were significantly associated with SLE (corrected P values ranging from 0.03 to 5.5 × 10-7). Through stratified analysis, TNFAIP3 and ETS1 showed significant associations with multiple SLE subphenotypes (such as malar rash, arthritis, hematologic disorder and antinuclear antibody) while TNIP1 just showed relatively weak association with onset age. The associations of the SNPs in the other four genes were not replicated.
The replication analysis indicates that TNFAIP3, ETS1 and TNIP1 are probably common susceptibility genes for SLE in Chinese populations, and they may contribute to the pathogenesis of multiple SLE subphenotypes.
Genetic factors influence susceptibility to systemic lupus erythematosus (SLE). A recent family-based analysis in Caucasian and Chinese populations provided evidence for association of single-nucleotide polymorphisms (SNPs) in the complement receptor 2 (CR2/CD21) gene with SLE. Here we confirmed this result in a case-control analysis of an independent European-derived population including 2084 patients with SLE and 2853 healthy controls. A haplotype formed by the minor alleles of three CR2 SNPs (rs1048971, rs17615, rs4308977) showed significant association with decreased risk of SLE (30.4% in cases vs. 32.6% in controls, P = 0.016, OR = 0.90 [0.82-0.98]). Two of these SNPs are in exon 10, directly 5′ of an alternatively spliced exon preferentially expressed in follicular dendritic cells (FDC), and the third is in the alternatively spliced exon. Effects of these SNPs as well as a fourth SNP in exon 11 (rs17616) on alternative splicing were evaluated. We found that the minor alleles of these SNPs decreased splicing efficiency of exon 11 both in vitro and ex vivo. These findings further implicate CR2 in the pathogenesis of SLE and suggest that CR2 variants alter the maintenance of tolerance and autoantibody production in the secondary lymphoid tissues where B cells and FDCs interact.
Alternative splicing; systemic lupus erythematosus; complement receptors; single-nucleotide polymorphisms; B cells; follicular dendritic cells
Vitamin D deficiency is widespread and has been associated with many chronic diseases, including autoimmune disorders. A study was undertaken to explore the impact of low vitamin D levels on autoantibody production in healthy individuals, as well as B cell hyperactivity and interferon α (IFNα) activity in patients with systemic lupus erythematosus (SLE).
Serum samples from 32 European American female patients with SLE and 32 matched controls were tested for 25-hydroxyvitamin D (25(OH)D) levels, lupus-associated autoantibodies and serum IFNα activity. Isolated peripheral blood mononuclear cells were tested for intracellular phospho-ERK 1/2 as a measure of B cell activation status.
Vitamin D deficiency (25(OH)D <20 ng/ml) was significantly more frequent among patients with SLE (n=32, 69%) and antinuclear antibody (ANA)-positive controls (n=14, 71%) compared with ANA-negative controls (n=18, 22%) (OR 7.7, 95% CI 2.0 to 29.4, p=0.003 and OR 8.8, 95% CI 1.8 to 43.6, p=0.011, respectively). Patients with high B cell activation had lower mean (SD) 25(OH)D levels than patients with low B cell activation (17.2 (5.1) vs 24.2 (3.9) ng/ml; p=0.009). Patients with vitamin D deficiency also had higher mean (SD) serum IFNα activity than patients without vitamin D deficiency (3.5 (6.6) vs 0.3 (0.3); p=0.02).
The observation that ANA-positive healthy controls are significantly more likely to be deficient in vitamin D than ANA-negative healthy controls, together with the finding that vitamin D deficiency is associated with certain immune abnormalities in SLE, suggests that vitamin D plays an important role in autoantibody production and SLE pathogenesis.
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.
Serologic association, cross-reactivity of select EBV-specific antibodies with SLE autoantigens, SLE-like autoimmunity after immunization with EBV peptides, increased EB viral load in SLE patients, and SLE-specific alterations in EBV humoral and cellular immunity implicate Epstein–Barr virus (EBV) in the development of systemic lupus erythematosus (SLE). To investigate SLE-specific differences in EBV gene expression, levels of eight EBV genes were compared between SLE patients and controls by using both ex vivo-infected and un-manipulated peripheral blood mononuclear cells (PBMCs). Expression levels of mRNA were significantly greater by Wilcoxen signed rank test in the ex vivo-infected SLE patient-derived cells for 4 of 8 EBV genes, including BLLF1, 3.2-fold (p<0.004); LMP-2, 1.7-fold (p<0.008); EBNA-1, 1.7-fold (p<0.01); and BcRF1, a proposed DNA binding protein, 1.7-fold (p<0.02). The frequency of LMP-1 gene expression was significantly greater by Chi square analysis in the peripheral blood from SLE patients than controls (44% of patients, 10% of controls p<0.05). PBMCs from SLE patients had greater expression of latent genes as well as increased expression of both latent and lytic genes after infection, suggesting that EBV may participate in SLE etiology through several mechanisms. Such altered infection patterns may contribute to the increased levels of EBV and the molecular mimicry seen in sera from SLE patients.
Systemic lupus erythematosus; Epstein–Barr virus; Gene expression; Latency
Background: In systemic lupus erythematosus (SLE), antibodies directed at RNA-binding proteins (anti-RBP) are associated with high serum type I interferon (IFN), which plays an important role in SLE pathogenesis. African-Americans (AA) are more likely to develop SLE, and SLE is also more severe in this population. We hypothesized that peripheral blood gene expression patterns would differ between AA and European-American (EA) SLE patients, and between those with anti-RBP antibodies and those who lack these antibodies.
Methods: Whole blood RNA from 33 female SLE patients and 16 matched female controls from AA and EA ancestral backgrounds was analyzed on Affymetrix Gene 1.0 ST gene expression arrays. Ingenuity Pathway Analysis was used to compare the top differentially expressed canonical pathways amongst the sample groups. An independent cohort of 116 SLE patients was used to replicate findings using quantitative real-time PCR (qPCR).
Results: Both AA and EA patients with positive anti-RBP antibodies showed over-expression of similar IFN-related canonical pathways, such as IFN Signaling (P = 1.3 × 10−7 and 6.3 × 10−11 in AA vs. EA respectively), Antigen Presenting Pathway (P = 1.8 × 10−5 and 2.5 × 10−6), and a number of pattern recognition receptor pathways. In anti-RBP negative (RBP−) patients, EA subjects demonstrated similar IFN-related pathway activation, whereas no IFN-related pathways were detected in RBP−AA patients. qPCR validation confirmed similar results.
Conclusion: Our data show that IFN-induced gene expression is completely dependent on the presence of autoantibodies in AA SLE patients but not in EA patients. This molecular heterogeneity suggests differences in IFN-pathway activation between ancestral backgrounds in SLE. This heterogeneity may be clinically important, as therapeutics targeting this pathway are being developed.
systemic lupus erythematosus; interferon alpha; autoantibodies; ancestral background; interferon gamma
We aimed to investigate whether the effect size of the systemic lupus erythematosus (SLE) risk alleles varies across European subpopulations.
European SLE patients (n = 1,742) and ethnically matched healthy controls (n = 2,101) were recruited at 17 centres from 10 different countries. Only individuals with self-reported ancestry from the country of origin were included. In addition, participants were genotyped for top ancestry informative markers and for 25 SLE associated SNPs. The results were used to compare effect sizes between the Central Eureopan and Southern European subgroups.
Twenty of the 25 SNPs showed independent association with SLE, These SNPs showed a significant bias to larger effect sizes in the Southern subgroup, with 15/20 showing this trend (P = 0.019) and a larger mean odds ratio of the 20 SNPs (1.46 vs. 1.34, P = 0.02) as well as a larger difference in the number of risk alleles (2.06 vs. 1.63, P = 0.027) between SLE patients and controls than for Central Europeans. This bias was reflected in a very significant difference in the cumulative genetic risk score (4.31 vs. 3.48, P = 1.8 × 10-32). Effect size bias was accompanied by a lower number of SLE risk alleles in the Southern subjects, both patients and controls, the difference being more marked between the controls (P = 1.1 × 10-8) than between the Southern and Central European patients (P = 0.016). Seven of these SNPs showed significant allele frequency clines.
Our findings showed a bias to larger effect sizes of SLE loci in the Southern Europeans relative to the Central Europeans together with clines of SLE risk allele frequencies. These results indicate the need to study risk allele clines and the implications of the polygenic model of inheritance in SLE.
Genetic variants of interferon regulatory factor 5 (IRF5) are associated with susceptibility to systemic lupus erythematosus (SLE). IRF5 regulates the expression of proinflammatory cytokines and type I interferons (IFN) believed to be involved in SLE pathogenesis. The aim of this study was to determine the activation status of IRF5 by assessing its nuclear localization in immune cells of SLE patients and healthy donors, and to identify SLE triggers of IRF5 activation.
IRF5 nuclear localization in subpopulations of peripheral blood mononuclear cells (PBMC) from 14 genotyped SLE patients and 11 healthy controls was assessed using imaging flow cytometry. IRF5 activation and function were examined after ex vivo stimulation of healthy donor monocytes with SLE serum or components of SLE serum. Cellular localization was determined by ImageStream and cytokine expression by Q-PCR and ELISA.
IRF5 was activated in a cell type-specific manner; monocytes of SLE patients had constitutively elevated levels of nuclear IRF5 compared to NK and T cells. SLE serum was identified as a trigger for IRF5 nuclear accumulation; however, neither IFNα nor SLE immune complexes could induce nuclear localization. Instead, autoantigens comprised of apoptotic/necrotic material triggered IRF5 nuclear accumulation in monocytes. Production of cytokines IFNα, TNFα and IL6 in monocytes stimulated with SLE serum or autoantigens was distinct yet correlated with the kinetics of IRF5 nuclear localization.
This study provides the first formal proof that IRF5 activation is altered in monocytes of SLE patients that is in part contributed by the SLE blood environment.
Systemic lupus erythematosus (SLE) is a systemic autoimmune disease that predominantly affects women. Despite Klinefelter's syndrome (47,XXY) and SLE coexisting in isolated cases, no association has been established with SLE or any other autoimmune disease. Methods: Sex chromosome genotyping was performed in 981 SLE patients (213 were men). A first group of 843 SLE patients from 378 multiplex families and a second group of 138 men with non-familial SLE were evaluated. Fluorescent in situ hybridization (FISH) and karyotyping in transformed B cell lines enumerated chromosomes for selected cases.
Of 213 men with SLE, five had Klinefelter's syndrome (or 1 in 43). Four of them were heterozygous at X markers. FISH and karyotyping confirmed Klinefelter’s syndrome in the fifth. An overall rate of 235 47,XXY per 10,000 male SLE patients (95%CI: 77 to 539) was found, a dramatic increase over the known prevalence of Klinefelter's syndrome in an unselected population (17 per 10,000 live male births). Asking men with SLE about fertility was highly sensitive (100%) for Klinefelter’s syndrome. All 768 SLE women were heterozygous at X.
47,XXY Klinefelter's syndrome, often subclinical, is increased in men with SLE by ~14-fold, compared to its prevalence in men without SLE. Diagnostic vigilance for 47,XXY males in SLE is warranted. These data are the first to associate Klinefelter's syndrome with an autoimmune disease found predominantly in women. The risk of SLE in Klinefelter's syndrome is predicted to be similar to the risk in normal 46,XX women and ~14-fold higher than in 46,XY men, consistent with SLE susceptibility being partly explained by a X chromosome gene dose effect.
Objective. Healthcare utilization and costs associated with systemic lupus erythematosus (SLE) in a US Medicaid population were examined. Methods. Patients ≥ 18 years old with SLE diagnosis (ICD-9-CM 710.0x) were extracted from a large Medicaid database 2002–2009. Index date was date of the first SLE diagnosis. Patients with and without SLE were matched. All patients had a variable length of followup with a minimum of 12 months. Annualized healthcare utilization and costs associated with SLE and costs of SLE flares were assessed during the followup period. Multivariate regressions were conducted to estimate incremental healthcare utilization and costs associated with SLE. Results. A total of 14,777 SLE patients met the study criteria, and 14,262 were matched to non-SLE patients. SLE patients had significantly higher healthcare utilization per year than their matched controls. The estimated incremental annual cost associated with SLE was $10,984, with the highest increase in inpatient costs (P < 0.001). Cost per flare was $11,716 for severe flares, $562 for moderate flares, and $129 for mild flares. Annual total costs for patients with severe flares were $49,754. Conclusions. SLE patients had significantly higher healthcare resource utilization and costs than non-SLE patients. Patients with severe flares had the highest costs.
There are several studies on the association of TLR9 polymorphisms with systemic lupus erythematosus (SLE) in different ethnicities; however, the results are inconsistent. Therefore, we studied the distribution of the TLR9 C > T (rs352140) polymorphism in patients with SLE (n = 254) and controls (n = 521) in a Polish population. We did not observe significant differences in the prevalence of the TLR9 C > T genotype and alleles between patients with SLE and controls. However, we found a contribution of the T/T and T/C genotypes to renal [OR = 2.949 (95 % CI = 1.523–5.711, p = 0.001), (pcorr = 0.017)] and immunologic disorders [OR = 2.938 (95 % CI 1.500–5.755, p = 0.0012), (pcorr = 0.0204)] in SLE patients. Moreover, we observed a significant association between the TLR9 T/T and T/C genotypes and the presence of anti-dsDNA Ab [OR = 3.682 (1.647–8.230, p = 0.001), (pcorr = 0.017)]. Our studies suggest that the TLR9 C > T (rs352140) polymorphism might contribute to renal and immunologic disorders and to the presence of anti-dsDNA Ab.
TLR9; Polymorphisms; SLE
Recent genome-wide association studies (GWASs) conducted in Asian populations have identified novel risk loci for systemic lupus erythematosus (SLE). Here, we genotyped 10 single-nucleotide polymorphisms (SNPs) in eight such loci and investigated their disease associations in three independent Caucasian SLE case–control cohorts recruited from Sweden, Finland and the United States. The disease associations of the SNPs in ETS1, IKZF1, LRRC18-WDFY4, RASGRP3, SLC15A4, TNIP1 and 16p11.2 were replicated, whereas no solid evidence of association was observed for the 7q11.23 locus in the Caucasian cohorts. SLC15A4 was significantly associated with renal involvement in SLE. The association of TNIP1 was more pronounced in SLE patients with renal and immunological disorder, which is corroborated by two previous studies in Asian cohorts. The effects of all the associated SNPs, either conferring risk for or being protective against SLE, were in the same direction in Caucasians and Asians. The magnitudes of the allelic effects for most of the SNPs were also comparable across different ethnic groups. On the contrary, remarkable differences in allele frequencies between Caucasian and Asian populations were observed for all associated SNPs. In conclusion, most of the novel SLE risk loci identified by GWASs in Asian populations were also associated with SLE in Caucasian populations. We observed both similarities and differences with respect to the effect sizes and risk allele frequencies across ethnicities.
systemic lupus erythematosus; genetic-association study; Asian; Caucasian