Faseb J

Higher cardiovascular morbidity in patients with a wide range of autoimmune diseases highlights the importance of autoimmunity in promoting atherosclerosis. Our purpose was to investigate the mechanisms of accelerated atherosclerosis and identified vascular autoantigens targeted by autoimmunity. We created a mouse model of autoimmunity-associated atherosclerosis by transplanting bone marrow (BM) from FcγRIIB knockout (FcRIIB-/-) mice into LDL receptor knockout (LDLR-/-) mice. We characterized the cellular and molecular mechanisms of atherogenesis and identified specific aortic autoantigens using serologic proteomic studies. En face lesion area analysis showed more aggressive atherosclerosis in autoimmune mice compared with control mice (0.64 ± 0.12 mm2 vs. 0.32 ± 0.05 mm2; P \textless 0.05, respectively). At the cellular level, FcRIIB-/- macrophages showed significant reduction (46-72%) in phagocytic capabilities. Proteomic analysis revealed circulating autoantibodies in autoimmune mice that targeted 25 atherosclerotic lesion proteins, including essential components of adhesion complex, cytoskeleton, and extracellular matrix (ECM), and proteins involved in critical functions and pathways. Microscopic examination of atherosclerotic plaques revealed essential colocalization of autoantibodies with endothelial cells (ECs), their adherence to basement membranes, the internal elastica lamina, and necrotic cores. The new vascular autoimmunosome may be a useful target for diagnostic and immunotherapeutic interventions in autoimmunity-associated diseases that have accelerated atherosclerosi

Association of genetic variants in complement factor H and factor H-related genes with systemic lupus erythematosus susceptibility

Systemic lupus erythematosus (SLE), a complex polygenic autoimmune disease, is associated with increased complement activation. Variants of genes encoding complement regulator factor H (CFH) and five CFH-related proteins (CFHR1-CFHR5) within the chromosome 1q32 locus linked to SLE, have been associated with multiple human diseases and may contribute to dysregulated complement activation predisposing to SLE. We assessed 60 SNPs covering the CFH-CFHRs region for association with SLE in 15,864 case-control subjects derived from four ethnic groups. Significant allelic associations with SLE were detected in European Americans (EA) and African Americans (AA), which could be attributed to an intronic CFH SNP (rs6677604, in intron 11, Pmeta = 6.6×10-8, OR = 1.18) and an intergenic SNP between CFHR1 and CFHR4 (rs16840639, Pmeta = 2.9×10-7, OR = 1.17) rather than to previously identified disease-associated CFH exonic SNPs, including I62V, Y402H, A474A, and D936E. In addition, allelic association of rs6677604 with SLE was subsequently confirmed in Asians (AS). Haplotype analysis revealed that the underlying causal variant, tagged by rs6677604 and rs16840639, was localized to a ~146 kb block extending from intron 9 of CFH to downstream of CFHR1. Within this block, the deletion of CFHR3 and CFHR1 (CFHR3-1Δ), a likely causal variant measured using multiplex ligation-dependent probe amplification, was tagged by rs6677604 in EA and AS and rs16840639 in AA, respectively. Deduced from genotypic associations of tag SNPs in EA, AA, and AS, homozygous deletion of CFHR3-1Δ (Pmeta = 3.2×10-7, OR = 1.47) conferred a higher risk of SLE than heterozygous deletion (Pmeta = 3.5×10-4, OR = 1.14). These results suggested that the CFHR3-1Δ deletion within the SLE-associated block, but not the previously described exonic SNPs of CFH, might contribute to the development of SLE in EA, AA, and AS, providing new insights into the role of complement regulators in the pathogenesis of SLE

Analysis of autosomal genes reveals gene–sex interactions and higher total genetic risk in men with systemic lupus erythematosus

ObjectivesSystemic 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.MethodsA 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 non-parametric 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.ResultsA significantly higher cumulative genetic risk for SLE was observed in men than in women. (P=4.52x10-8) 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.ConclusionsThe 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.</jats:sec

Admixture Mapping in Lupus Identifies Multiple Functional Variants within IFIH1 Associated with Apoptosis, Inflammation, and Autoantibody Production

<div><p>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 <i>IFIH1 </i>gene: an intronic variant, rs13023380 [P<i>_meta</i> = 5.20×10⁻¹⁴; odds ratio, 95% confidence interval = 0.82 (0.78–0.87)], and two missense variants, rs1990760 (Ala946Thr) [P<i>_meta</i> = 3.08×10⁻⁷; 0.88 (0.84–0.93)] and rs10930046 (Arg460His) [P<i>_dom</i> = 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 <i>in vitro</i> 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 <i>in vivo</i>. 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 <i>IFIH1</i> in apoptosis, inflammation, and autoantibody production, and explain the molecular basis of these three risk alleles for SLE pathogenesis.</p> </div

Association of genetic variants in complement factor H and factor H-related genes with systemic lupus erythematosus susceptibility.

Systemic lupus erythematosus (SLE), a complex polygenic autoimmune disease, is associated with increased complement activation. Variants of genes encoding complement regulator factor H (CFH) and five CFH-related proteins (CFHR1-CFHR5) within the chromosome 1q32 locus linked to SLE, have been associated with multiple human diseases and may contribute to dysregulated complement activation predisposing to SLE. We assessed 60 SNPs covering the CFH-CFHRs region for association with SLE in 15,864 case-control subjects derived from four ethnic groups. Significant allelic associations with SLE were detected in European Americans (EA) and African Americans (AA), which could be attributed to an intronic CFH SNP (rs6677604, in intron 11, P(meta) = 6.6×10(-8), OR = 1.18) and an intergenic SNP between CFHR1 and CFHR4 (rs16840639, P(meta) = 2.9×10(-7), OR = 1.17) rather than to previously identified disease-associated CFH exonic SNPs, including I62V, Y402H, A474A, and D936E. In addition, allelic association of rs6677604 with SLE was subsequently confirmed in Asians (AS). Haplotype analysis revealed that the underlying causal variant, tagged by rs6677604 and rs16840639, was localized to a ~146 kb block extending from intron 9 of CFH to downstream of CFHR1. Within this block, the deletion of CFHR3 and CFHR1 (CFHR3-1Δ), a likely causal variant measured using multiplex ligation-dependent probe amplification, was tagged by rs6677604 in EA and AS and rs16840639 in AA, respectively. Deduced from genotypic associations of tag SNPs in EA, AA, and AS, homozygous deletion of CFHR3-1Δ (P(meta) = 3.2×10(-7), OR = 1.47) conferred a higher risk of SLE than heterozygous deletion (P(meta) = 3.5×10(-4), OR = 1.14). These results suggested that the CFHR3-1Δ deletion within the SLE-associated block, but not the previously described exonic SNPs of CFH, might contribute to the development of SLE in EA, AA, and AS, providing new insights into the role of complement regulators in the pathogenesis of SLE

Identification of IRF8, TMEM39A, and IKZF3-ZPBP2 as Susceptibility Loci for Systemic Lupus Erythematosus in a Large-Scale Multiracial Replication Study

Systemic lupus erythematosus (SLE) is a chronic heterogeneous autoimmune disorder characterized by the loss of tolerance to self-antigens and dysregulated interferon responses. The etiology of SLE is complex, involving both heritable and environmental factors. Candidate-gene studies and genome-wide association (GWA) scans have been successful in identifying new loci that contribute to disease susceptibility; however, much of the heritable risk has yet to be identified. In this study, we sought to replicate 1,580 variants showing suggestive association with SLE in a previously published GWA scan of European Americans; we tested a multiethnic population consisting of 7,998 SLE cases and 7,492 controls of European, African American, Asian, Hispanic, Gullah, and Amerindian ancestry to find association with the disease. Several genes relevant to immunological pathways showed association with SLE. Three loci exceeded the genome-wide significance threshold: interferon regulatory factor 8 (IRF8; rs11644034; pmeta-Euro = 2.08 × 10−10), transmembrane protein 39A (TMEM39A; rs1132200; pmeta-all = 8.62 × 10−9), and 17q21 (rs1453560; pmeta-all = 3.48 × 10−10) between IKAROS family of zinc finger 3 (AIOLOS; IKZF3) and zona pellucida binding protein 2 (ZPBP2). Fine mapping, resequencing, imputation, and haplotype analysis of IRF8 indicated that three independent effects tagged by rs8046526, rs450443, and rs4843869, respectively, were required for risk in individuals of European ancestry. Eleven additional replicated effects (5 × 10−8 < pmeta-Euro < 9.99 × 10−5) were observed with CFHR1, CADM2, LOC730109/IL12A, LPP, LOC63920, SLU7, ADAMTSL1, C10orf64, OR8D4, FAM19A2, and STXBP6. The results of this study increase the number of confirmed SLE risk loci and identify others warranting further investigation