Association between systemic lupus erythematosus and myasthenia gravis: A population-based National Study.

BACKGROUND: Systemic lupus erythematosus (SLE) and myasthenia gravis (MG) are autoimmune diseases. Previous case reports and case series suggest an association may exist between these diseases, as well as an increased risk of SLE after thymectomy for MG. We undertook this study to determine whether SLE and MG were associated in large cohorts. METHODS: We searched the IBM Watson Health Explorys platform and the Department of Veterans Affairs Million Veteran Program (MVP) database for diagnoses of SLE and MG. In addition, we examined subjects enrolled in the Lupus Family Registry and Repository (LFRR) as well as controls for a diagnosis of MG. RESULTS: Among 59,780,210 individuals captured in Explorys, there were 25,750 with MG and 65,370 with SLE. 370 subjects had both. Those with MG were >10 times more likely to have SLE than those without MG. Those with both diseases were more likely to be women, African American, and at a younger age than MG subjects without SLE. In addition, the MG patients who underwent thymectomy had an increased risk of SLE compared to MG patients who had not undergone thymectomy (OR 3.11, 95% CI: 2.12 to 4.55). Autoimmune diseases such as pernicious anemia and miscellaneous comorbidities such as chronic kidney disease were significantly more common in MG patients who developed SLE. In the MVP, SLE and MG were also significantly associated. Association of SLE and MG in a large SLE cohort with rigorous SLE classification confirmed the association of SLE with MG at a similar level. CONCLUSION: While the number of patients with both MG and SLE is small, SLE and MG are strongly associated together in very large databases and a large SLE cohort.

The Potential Utility of Salivary and Tear Proteomics to Discriminate Sjögren's Disease from Non-Sjögren's Sicca.

Sjögren's Disease (SjD) is an autoimmune disorder associated with decreased saliva and/or tear secretions, resulting in patients reporting dryness in the mouth and eyes. Serum autoantibodies directed against the Ro60/SS-A and La/SS-B autoantigens are a distinctive feature of the disease. Analysis of the saliva and tear proteomes represents one promising alternative method of both classifying and monitoring the condition, and research into salivary and tear proteomics in patients with SjD, with and without sicca, has shown its efficacy and practicality in both clinical and research settings. Studies analyzing the saliva proteomics of SjD patients have generally shown an overexpression of proteins involved in T-cell activation, the immune response, ß-2 microglobulin, and the recruitment of pro-inflammatory agents. These studies also show a decrease in or downregulation of proteins involved in salivary secretion. Studies analyzing the tear proteomics of patients with SjD have generally indicated an upregulation of proteins involved with TNF-α signaling, B-cell survival, and the recruitment of pro-inflammatory agents. Studies also note the differential expression of tear protein folding as a hallmark of ocular involvement in this condition. These findings help to elucidate the biochemical relationship between the proteomes of saliva/tear fluids and the general pathophysiology of the gland involved with the pathogenesis of this condition, giving further credence to the potential role of salivary and tear proteomics in the future of diagnosis and treatment for patients with SjD.

Loss-of-function variants in SAT1 cause X-linked childhood-onset systemic lupus erythematosus.

OBJECTIVES: Families that contain multiple siblings affected with childhood onset of systemic lupus erythematosus (SLE) likely have strong genetic predispositions. We performed whole exome sequencing (WES) to identify familial rare risk variants and to assess their effects in lupus. METHODS: Sanger sequencing validated the two ultra-rare, predicted pathogenic risk variants discovered by WES and identified additional variants in 562 additional patients with SLE. Effects of a splice site variant and a frameshift variant were assessed using a Minigene assay and CRISPR/Cas9-mediated knock-in (KI) mice, respectively. RESULTS: The two familial ultra-rare, predicted loss-of-function (LOF) SAT1 variants exhibited X-linked recessive Mendelian inheritance in two unrelated African-American families. Each LOF variant was transmitted from the heterozygous unaffected mother to her two sons with childhood-onset SLE. The p.Asp40Tyr variant affected a splice donor site causing deleterious transcripts. The young hemizygous male and homozygous female Sat1 p.Glu92Leufs*6 KI mice spontaneously developed splenomegaly, enlarged glomeruli with leucocyte infiltration, proteinuria and elevated expression of type I interferon-inducible genes. SAT1 is highly expressed in neutrophils and encodes spermidine/spermine-N1-acetyltransferase 1 (SSAT1), a rate-limiting enzyme in polyamine catabolism. Young male KI mice exhibited neutrophil defects and decreased proportions of Foxp3 +CD4+ T-cell subsets. Circulating neutrophil counts and proportions of Foxp3 +CD4+ T cells correlated with decreased plasma levels of spermine in treatment-naive, incipient SLE patients. CONCLUSIONS: We identified two novel SAT1 LOF variants, showed the ability of the frameshift variant to confer murine lupus, highlighted the pathogenic role of dysregulated polyamine catabolism and identified SAT1 LOF variants as new monogenic causes for SLE.

Baseline disease activity influences subsequent achievement of patient acceptable symptom state in Sjögren's syndrome.

OBJECTIVES: To investigate longitudinal changes of the EULAR SS Patient-Reported Index (ESSPRI) and EULAR SS Disease Activity Index (ESSDAI), and identify factors associated with patient acceptable symptom state (PASS) in patients with primary SS (pSS). METHODS: We assessed ESSPRI, ESSDAI, clinical ESSDAI (ClinESSDAI), EULAR Sicca Score, EuroQoL 5-dimension (EQ-5D), Fatigue Severity Score, Beck Depression Inventory, and patient global assessment (PGA) for pSS, and visual analogue scale (VAS) scores for glandular and extra-glandular symptoms at baseline and follow-up. The responses to the currently available standards of care were evaluated by the PASS, the minimal clinically important improvement (MCII) of ESSPRI and ESSDAI, and a modified SS Responder Index-30 (mSSRI-30) response. RESULTS: Among 115 patients enrolled, 102 (88.7%) completed a median 3-year follow-up. The ESSPRI, ClinESSDAI and EQ-5D levels remained stable, although the PGA and ESSDAI significantly improved (both P <0.05). Of the 102 patients, 52 (51.0%) patients achieved the PASS at the follow-up and tended to attain the ESSPRI-MCII and mSSRI-30 (both P < 0.001) more frequently than the non-PASS group. Multivariate analysis revealed that the PASS was significantly associated with baseline ESSPRI negatively [odds ratio (OR) 0.609] and ESSDAI positively (OR 1.224). When categorized using baseline ESSPRI and ESSDAI, a subgroup of low ESSPRI and high ESSDAI reached a PASS achievement rate of 79.3%. CONCLUSION: Although longitudinal changes in ESSPRI and ClinESSDAI are stable in pSS, baseline ESSPRI and ESSDAI could provide prognostic information on the subsequent achievement of PASS, using currently available treatments. A categorization model using ESSPRI and ESSDAI may have clinical implications.

T Cell Mediated Conversion of a Non-Anti-La Reactive B Cell to an Autoreactive Anti-La B Cell by Somatic Hypermutation.

Since the first description of nuclear autoantigens in the late 1960s and early 1970s, researchers, including ourselves, have found it difficult to establish monoclonal antibodies (mabs) against nuclear antigens, including the La/SS-B (Sjögrens' syndrome associated antigen B) autoantigen. To date, only a few anti-La mabs have been derived by conventional hybridoma technology; however, those anti-La mabs were not bona fide autoantibodies as they recognize either human La specific, cryptic, or post-translationally modified epitopes which are not accessible on native mouse La protein. Herein, we present a series of novel murine anti-La mabs including truly autoreactive ones. These mabs were elicited from a human La transgenic animal through adoptive transfer of T cells from non-transgenic mice immunized with human La antigen. Detailed epitope and paratope analyses experimentally confirm the hypothesis that somatic hypermutations that occur during T cell dependent maturation can lead to autoreactivity to the nuclear La/SS-B autoantigen.

And Yet It Moves: Oxidation of the Nuclear Autoantigen La/SS-B Is the Driving Force for Nucleo-Cytoplasmic Shuttling.

Decades ago, we and many other groups showed a nucleo-cytoplasmic translocation of La protein in cultured cells. This shuttling of La protein was seen after UV irradiation, virus infections, hydrogen peroxide exposure and the Fenton reaction based on iron or copper ions. All of these conditions are somehow related to oxidative stress. Unfortunately, these harsh conditions could also cause an artificial release of La protein. Even until today, the shuttling and the cytoplasmic function of La/SS-B is controversially discussed. Moreover, the driving mechanism for the shuttling of La protein remains unclear. Recently, we showed that La protein undergoes redox-dependent conformational changes. Moreover, we developed anti-La monoclonal antibodies (anti-La mAbs), which are specific for either the reduced form of La protein or the oxidized form. Using these tools, here we show that redox-dependent conformational changes are the driving force for the shuttling of La protein. Moreover, we show that translocation of La protein to the cytoplasm can be triggered in a ligand/receptor-dependent manner under physiological conditions. We show that ligands of toll-like receptors lead to a redox-dependent shuttling of La protein. The shuttling of La protein depends on the redox status of the respective cell type. Endothelial cells are usually resistant to the shuttling of La protein, while dendritic cells are highly sensitive. However, the deprivation of intracellular reducing agents in endothelial cells makes endothelial cells sensitive to a redox-dependent shuttling of La protein.

Two Be or Not Two Be: The Nuclear Autoantigen La/SS-B Is Able to Form Dimers and Oligomers in a Redox Dependent Manner.

According to the literature, the autoantigen La is involved in Cap-independent translation. It was proposed that one prerequisite for this function is the formation of a protein dimer. However, structural analyses argue against La protein dimers. Noteworthy to mention, these structural analyses were performed under reducing conditions. Here we describe that La protein can undergo redox-dependent structural changes. The oxidized form of La protein can form dimers, oligomers and even polymers stabilized by disulfide bridges. The primary sequence of La protein contains three cysteine residues. Only after mutation of all three cysteine residues to alanine La protein becomes insensitive to oxidation, indicating that all three cysteines are involved in redox-dependent structural changes. Biophysical analyses of the secondary structure of La protein support the redox-dependent conformational changes. Moreover, we identified monoclonal anti-La antibodies (anti-La mAbs) that react with either the reduced or oxidized form of La protein. Differential reactivities to the reduced and oxidized form of La protein were also found in anti-La sera of autoimmune patients.

A plausibly causal functional lupus-associated risk variant in the STAT1-STAT4 locus.

Systemic lupus erythematosus (SLE or lupus) (OMIM: 152700) is a chronic autoimmune disease with debilitating inflammation that affects multiple organ systems. The STAT1-STAT4 locus is one of the first and most highly replicated genetic loci associated with lupus risk. We performed a fine-mapping study to identify plausible causal variants within the STAT1-STAT4 locus associated with increased lupus disease risk. Using complementary frequentist and Bayesian approaches in trans-ancestral Discovery and Replication cohorts, we found one variant whose association with lupus risk is supported across ancestries in both the Discovery and Replication cohorts: rs11889341. In B cell lines from patients with lupus and healthy controls, the lupus risk allele of rs11889341 was associated with increased STAT1 expression. We demonstrated that the transcription factor HMGA1, a member of the HMG transcription factor family with an AT-hook DNA-binding domain, has enriched binding to the risk allele compared with the non-risk allele of rs11889341. We identified a genotype-dependent repressive element in the DNA within the intron of STAT4 surrounding rs11889341. Consistent with expression quantitative trait locus (eQTL) analysis, the lupus risk allele of rs11889341 decreased the activity of this putative repressor. Altogether, we present a plausible molecular mechanism for increased lupus risk at the STAT1-STAT4 locus in which the risk allele of rs11889341, the most probable causal variant, leads to elevated STAT1 expression in B cells due to decreased repressor activity mediated by increased binding of HMGA1.

Genetics in Sjögren's syndrome: where we are and where we go.

Sjögren's syndrome is a complex autoimmune disease that involves dysregulation of immune responses that preferentially target exocrine glands. Systemic manifestations vary and may involve nearly every organ system. Genetic studies to date are in their infancy relative to other autoimmune diseases such as systemic lupus erythematosus and rheumatoid arthritis, each with more than 100 genetic associations now established. However, recent work in SS has successfully established associations that shed light on pathophysiology and implicate aberrant innate and adaptive immune responses. In this review, we provide an overview of genetic approaches used to identify risk variants in SS, discuss major findings and their relevance to SS, and describe the future directions that are likely to lead to understanding fundamental causes of this disease and new opportunities for improving clinical care.

Lupus Risk Variant Increases pSTAT1 Binding and Decreases ETS1 Expression.

Genetic variants at chromosomal region 11q23.3, near the gene ETS1, have been associated with systemic lupus erythematosus (SLE), or lupus, in independent cohorts of Asian ancestry. Several recent studies have implicated ETS1 as a critical driver of immune cell function and differentiation, and mice deficient in ETS1 develop an SLE-like autoimmunity. We performed a fine-mapping study of 14,551 subjects from multi-ancestral cohorts by starting with genotyped variants and imputing to all common variants spanning ETS1. By constructing genetic models via frequentist and Bayesian association methods, we identified 16 variants that are statistically likely to be causal. We functionally assessed each of these variants on the basis of their likelihood of affecting transcription factor binding, miRNA binding, or chromatin state. Of the four variants that we experimentally examined, only rs6590330 differentially binds lysate from B cells. Using mass spectrometry, we found more binding of the transcription factor signal transducer and activator of transcription 1 (STAT1) to DNA near the risk allele of rs6590330 than near the non-risk allele. Immunoblot analysis and chromatin immunoprecipitation of pSTAT1 in B cells heterozygous for rs6590330 confirmed that the risk allele increased binding to the active form of STAT1. Analysis with expression quantitative trait loci indicated that the risk allele of rs6590330 is associated with decreased ETS1 expression in Han Chinese, but not other ancestral cohorts. We propose a model in which the risk allele of rs6590330 is associated with decreased ETS1 expression and increases SLE risk by enhancing the binding of pSTAT1.

Minor salivary gland fibrosis in Sjögren's syndrome is elevated, associated with focus score and not solely a consequence of aging.

OBJECTIVES: Evaluate the presence of minor salivary gland (SG) fibrosis in primary Sjögren's syndrome (pSS) as a function of disease pathology or a consequence of ageing. METHODS: Subjects with sicca symptoms attending a Sjögren's research clinic were classified by American European Consensus Group (AECG) criteria as either pSS or non-SS (nSS). Discovery (n=34 pSS, n=28 nSS) and replication (n=35 pSS, n=31 nSS) datasets were evaluated. Minor SG cross-sections from haematoxylin and eosin stained slides were imaged, digitally reconstructed and analysed for percent area fibrosis. Relationships between SG fibrosis, age, and clinical measures were evaluated using Spearman correlations. Association with SS was assessed by: ROC curve, Variable Selection Using Random Forests (VSURF) and uni- and bi-variate regression analyses. RESULTS: SS subjects had significantly more fibrotic tissue in their minor labial salivary glands (median 24.39%, range 5.12-51.67%) than nSS participants (median 16.7%, range 5.97-38.65%, p<0.0001); age did not differ between groups (average ± SD pSS 50.2 ±13.9 years, nSS 53.8±12.4 years). In both the discovery and replication data sets, multiple regression models showed that the area of minor salivary gland fibrosis predicted pSS significantly better than age alone. Age-corrected linear regression revealed that the area of minor salivary gland fibrosis positively associated with vanBijsterveld score (p=0.042) and biopsy focus score (p=0.002). ROC curve and VSURF analyses ranked fibrosis as a significantly more important variable for subject discrimination than age. CONCLUSIONS: SG fibrosis is an element of pSS pathology that is related to focus score and is not solely attributable to age.

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.

Two functional lupus-associated BLK promoter variants control cell-type- and developmental-stage-specific transcription.

Efforts to identify lupus-associated causal variants in the FAM167A/BLK locus on 8p21 are hampered by highly associated noncausal variants. In this report, we used a trans-population mapping and sequencing strategy to identify a common variant (rs922483) in the proximal BLK promoter and a tri-allelic variant (rs1382568) in the upstream alternative BLK promoter as putative causal variants for association with systemic lupus erythematosus. The risk allele (T) at rs922483 reduced proximal promoter activity and modulated alternative promoter usage. Allelic differences at rs1382568 resulted in altered promoter activity in B progenitor cell lines. Thus, our results demonstrated that both lupus-associated functional variants contribute to the autoimmune disease association by modulating transcription of BLK in B cells and thus potentially altering immune responses.

Familial Pallister-Hall in adulthood.

Pallister Hall syndrome is autosomal dominant disorder usually diagnosed in infants and children. Current diagnostic criteria include presence of hypothalamic hamartoma, post axial polydactyly and positive family history, but the disease has variable manifestations. Herein we report Pallister Hall syndrome diagnosed in a family where both patients were adults. A 59 year old man developed seizures 4 years prior to our evaluation of him, at which time imaging showed a hypothalamic hamartoma. The seizures were controlled medically. He did well until he had visual changes after a traumatic head injury. Repeat MRI showed slight expansion of the mass with formal visual field testing demonstrating bitemporal hemianopsia. There was no evidence of pituitary dysfunction except for large urine volume. He underwent surgery to debulk the hamartoma and the visual field defects improved. There was no hypopituitarism post-operatively, and the polydyspia resolved. His 29 year old daughter also had seizures and hypothalamic hamartoma. Both patients had had polydactyly with prior surgical correction in childhood. The daughter underwent genetic testing, which revealed a previously undescribed heterozygous single base pair deletion in exon 13 of the GLI3 gene causing a frameshift mutation. Further investigation into family history revealed multiple members in previous generations with polydactyly and/or seizures. Pallister-Hall syndrome is caused by an inherited autosomal dominant or de novo mutation in GLI3 gene. This rare syndrome has not had prevalence defined, however. Generally, diagnoses are made in the pediatric population. Our report adds to the few cases detected in adulthood.

Klinefelter's syndrome (47,XXY) is in excess among men with Sjögren's syndrome.

Primary Sjögren's syndrome (pSS) has a strong female bias. We evaluated an X chromosome dose effect by analyzing 47,XXY (Klinefelter's syndrome, 1 in 500 live male births) among subjects with pSS. 47,XXY was determined by examination of fluorescence intensity of single nucleotide polymorphisms from the X and Y chromosomes. Among 136 pSS men there were 4 with 47,XXY. This was significantly different from healthy controls (1 of 1254 had 47,XXY, p=0.0012 by Fisher's exact test) as well men with rheumatoid arthritis (0 of 363 with 47,XXY), but not different compared to men with systemic lupus erythematosus (SLE) (4 of 136 versus 8 of 306, Fisher's exact test p=NS). These results are consistent with the hypothesis that the number of X chromosomes is critical for the female bias of pSS, a property that may be shared with SLE but not RA.

Interaction between innate immunity and Ro52-induced antibody causes Sjögren's syndrome-like disorder in mice.

OBJECTIVES: Autoantibodies reactive with Ro52 are often found in sera of patients with Sjögren's syndrome (SS). This study was undertaken to investigate the role of Ro52-induced immune responses in pathogenesis of SS. METHODS: New Zealand Mixed (NZM) 2758 mice were immunised with Ro52 in alum adjuvant. Control mice were immunised either with maltose-binding protein or injected with alum alone. Mice were monitored for anti-Ro52 antibody, sialoadenitis and pilocarpine-induced salivation. Antibody binding to salivary gland (SG) cells was analysed in vivo and in vitro by immunofluorescence. Sera from immunised mice were passively transferred into untreated or alum injected NZM2758 mice. RESULTS: By day 30 post-immunisation, Ro52 immunised mice generated immunoprecipitating anti-Ro52 antibodies and they had the maximum drop in saliva production. Both Ro52 immunised and control mice showed evidence of mild sialoadenitis. However, only Ro52 immunised mice had antibody deposition in their SG. Passive transfer of Ro52-immune sera induced SG dysfunction in recipient mice, only if the recipients were primed with alum. In vitro, antibodies from Ro52-immune sera were internalised by a SG cell line and this uptake was inhibited by cytochalasin D treatment. CONCLUSIONS: Our data show for the first time that antibodies induced by Ro52 are capable of inducing SG dysfunction, and that this phenomenon is dependent on the activation of innate immunity. The mouse model described in this study implies that autoantibody deposition in the SG might be an important step in the induction of xerostomia and pathogenesis of SS.

Decreased SMG7 expression associates with lupus-risk variants and elevated antinuclear antibody production.

OBJECTIVES: Following up the systemic lupus erythematosus (SLE) genome-wide association studies (GWAS) identification of NMNAT2 at rs2022013, we fine-mapped its 150 kb flanking regions containing NMNAT2 and SMG7 in a 15 292 case-control multi-ancestry population and tested functions of identified variants. METHODS: We performed genotyping using custom array, imputation by IMPUTE 2.1.2 and allele specific functions using quantitative real-time PCR and luciferase reporter transfections. SLE peripheral blood mononuclear cells (PBMCs) were cultured with small interfering RNAs to measure antinuclear antibody (ANA) and cyto/chemokine levels in supernatants using ELISA. RESULTS: We confirmed association at NMNAT2 in European American (EA) and Amerindian/Hispanic ancestries, and identified independent signal at SMG7 tagged by rs2702178 in EA only (p=2.4×10-8, OR=1.23 (95% CI 1.14 to 1.32)). In complete linkage disequilibrium with rs2702178, rs2275675 in the promoter region robustly associated with SMG7 mRNA levels in multiple expression quantitative trait locus (eQTL) datasets. Its risk allele was dose-dependently associated with decreased SMG7 mRNA levels in PBMCs of 86 patients with SLE and 119 controls (p=1.1×10-3 and 6.8×10-8, respectively) and conferred reduced transcription activity in transfected HEK-293 (human embryonic kidney cell line) and Raji cells (p=0.0035 and 0.0037, respectively). As a critical component in the nonsense-mediated mRNA decay pathway, SMG7 could regulate autoantigens including ribonucleoprotein (RNP) and Smith (Sm). We showed SMG7 mRNA levels in PBMCs correlated inversely with ANA titres of patients with SLE (r=-0.31, p=0.01), and SMG7 knockdown increased levels of ANA IgG and chemokine (C-C motif) ligand 19 in SLE PBMCs (p=2.0×10-5 and 2.0×10-4, respectively). CONCLUSION: We confirmed NMNAT2 and identified independent SMG7 association with SLE. The inverse relationship between levels of the risk allele-associated SMG7 mRNAs and ANA suggested the novel contribution of mRNA surveillance pathway to SLE pathogenesis.

Preferential association of a functional variant in complement receptor 2 with antibodies to double-stranded DNA.

OBJECTIVES: Systemic lupus erythematosus (SLE; OMIM 152700) is characterised by the production of antibodies to nuclear antigens. We previously identified variants in complement receptor 2 (CR2/CD21) that were associated with decreased risk of SLE. This study aimed to identify the causal variant for this association. METHODS: Genotyped and imputed genetic variants spanning CR2 were assessed for association with SLE in 15 750 case-control subjects from four ancestral groups. Allele-specific functional effects of associated variants were determined using quantitative real-time PCR, quantitative flow cytometry, electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP)-PCR. RESULTS: The strongest association signal was detected at rs1876453 in intron 1 of CR2 (pmeta=4.2×10(-4), OR 0.85), specifically when subjects were stratified based on the presence of dsDNA autoantibodies (case-control pmeta=7.6×10(-7), OR 0.71; case-only pmeta=1.9×10(-4), OR 0.75). Although allele-specific effects on B cell CR2 mRNA or protein levels were not identified, levels of complement receptor 1 (CR1/CD35) mRNA and protein were significantly higher on B cells of subjects harbouring the minor allele (p=0.0248 and p=0.0006, respectively). The minor allele altered the formation of several DNA protein complexes by EMSA, including one containing CCCTC-binding factor (CTCF), an effect that was confirmed by ChIP-PCR. CONCLUSIONS: These data suggest that rs1876453 in CR2 has long-range effects on gene regulation that decrease susceptibility to lupus. Since the minor allele at rs1876453 is preferentially associated with reduced risk of the highly specific dsDNA autoantibodies that are present in preclinical, active and severe lupus, understanding its mechanisms will have important therapeutic implications.

Previous diagnosis of Sjögren's Syndrome as rheumatoid arthritis or systemic lupus erythematosus.

OBJECTIVE: The diagnosis of SS is often difficult and many patients are symptomatic for years with other diagnoses before confirmation of SS. Our aim was to determine whether overlapping clinical and serologic features with RA and SLE may in part drive the misdiagnoses. METHODS: A total of 1175 sicca patients were evaluated in a multidisciplinary clinic and classified as having SS based on the American-European Consensus Group Criteria. They were interrogated for a past history of suspicion or diagnosis of RA, SLE or SSc. These diseases were confirmed or ruled out by applying the corresponding classification criteria if the patients responded affirmatively. RESULTS: Of these, 524 (44.6%) subjects reported previous diagnosis or suspicion of RA, SLE or SSc, which was confirmed in 130 (24.8%) but excluded in 394 (75.2%) subjects. Of those previously diagnosed with another illness, 183 (34.9%) met the criteria for primary SS. RF was present in 70/191 patients with previous diagnosis of RA compared with 445/845 without a prior RA diagnosis (P = 3.38E-05), while 128/146 with a diagnosis of SLE had positive ANA compared with 622/881 without the diagnosis (P = 8.77E-06). Age also influenced former diagnoses: people with suspected RA were older than those without the diagnosis (P = 5.89E-06), while patients with SLE suspicion were younger (P = 0.0003). Interestingly, the previous diagnoses did not significantly delay a final classification of SS. CONCLUSION: Among subjects classified as SS, the presence of a positive ANA or RF was associated with a previous, apparently erroneous diagnosis of SLE or RA, respectively.

Admixture mapping in lupus identifies multiple functional variants within IFIH1 associated with apoptosis, inflammation, and autoantibody production.

Systemic lupus erythematosus (SLE) is an inflammatory autoimmune disease with a strong genetic component. African-Americans (AA) are at increased risk of SLE, but the genetic basis of this risk is largely unknown. To identify causal variants in SLE loci in AA, we performed admixture mapping followed by fine mapping in AA and European-Americans (EA). Through genome-wide admixture mapping in AA, we identified a strong SLE susceptibility locus at 2q22-24 (LOD=6.28), and the admixture signal is associated with the European ancestry (ancestry risk ratio ~1.5). Large-scale genotypic analysis on 19,726 individuals of African and European ancestry revealed three independently associated variants in the IFIH1 gene: an intronic variant, rs13023380 [P(meta) = 5.20×10(-14); odds ratio, 95% confidence interval = 0.82 (0.78-0.87)], and two missense variants, rs1990760 (Ala946Thr) [P(meta) = 3.08×10(-7); 0.88 (0.84-0.93)] and rs10930046 (Arg460His) [P(dom) = 1.16×10(-8); 0.70 (0.62-0.79)]. Both missense variants produced dramatic phenotypic changes in apoptosis and inflammation-related gene expression. We experimentally validated function of the intronic SNP by DNA electrophoresis, protein identification, and in vitro protein binding assays. DNA carrying the intronic risk allele rs13023380 showed reduced binding efficiency to a cellular protein complex including nucleolin and lupus autoantigen Ku70/80, and showed reduced transcriptional activity in vivo. Thus, in SLE patients, genetic susceptibility could create a biochemical imbalance that dysregulates nucleolin, Ku70/80, or other nucleic acid regulatory proteins. This could promote antibody hypermutation and auto-antibody generation, further destabilizing the cellular network. Together with molecular modeling, our results establish a distinct role for IFIH1 in apoptosis, inflammation, and autoantibody production, and explain the molecular basis of these three risk alleles for SLE pathogenesis.