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1.  Genetic associations of leptin-related polymorphisms with systemic lupus erythematosus 
Clinical immunology (Orlando, Fla.)  2015;161(2):157-162.
Leptin is abnormally elevated in the plasma of patients with systemic lupus erythematosus (SLE), where it is thought to promote and/or sustain pro-inflammatory responses. Whether this association could reflect an increased genetic susceptibility to develop SLE is not known, and studies of genetic associations with leptin-related polymorphisms in SLE patients have been so far inconclusive. Here we genotyped DNA samples from 15,706 SLE patients and healthy matched controls from four different ancestral groups, to correlate polymorphisms of genes of the leptin pathway to risk for SLE. It was found that although several SNPs showed weak associations, those associations did not remain significant after correction for multiple testing. These data do not support associations between defined leptin-related polymorphisms and increased susceptibility to develop SLE.
PMCID: PMC4658308  PMID: 26385092
systemic lupus erythematosus; leptin pathway; gene polymorphisms
2.  Identification of a systemic lupus erythematosus risk locus spanning ATG16L2, FCHSD2, and P2RY2 in Koreans 
Systemic lupus erythematosus (SLE) is a chronic autoimmune disorder whose etiology is incompletely understood, but likely involves environmental triggers in genetically susceptible individuals. We sought to identify the genetic loci associated with SLE in a Korean population by performing an unbiased genome-wide association scan.
A total of 1,174 Korean SLE cases and 4,248 population controls were genotyped with strict quality control measures and analyzed for association. For select variants, replication was tested in an independent set of 1,412 SLE cases and 1,163 population controls of Korean and Chinese ancestries.
Eleven regions outside the HLA exceeded genome-wide significance (P<5×10−8). A novel SNP-SLE association was identified between FCHSD2 and P2RY2 peaking at rs11235667 (P = 1.0×10−8, odds ratio (OR) = 0.59) on a 33kb haplotype upstream to ATG16L2. Replication for rs11235667 resulted in Pmeta-rep=0.001 and Pmeta-overall=6.67×10−11 (OR=0.63). Within the HLA region, association peaked in the Class II region at rs116727542 with multiple independent effects. Classical HLA allele imputation identified HLA-DRB1*1501 and HLA-DQB1*0602, both highly correlated, as most strongly associated with SLE. We replicated ten previously established SLE risk loci: STAT1-STAT4, TNFSF4, TNFAIP3, IKZF1, HIP1, IRF5, BLK, WDFY4, ETS1 and IRAK1-MECP2. Of these loci, we identified previously unreported independent second effects in TNFAIP3 and TNFSF4 as well as differences in the association for a putative causal variant in the WDFY4 region.
Further studies are needed to identify true SLE risk effects in other suggestive loci and to identify the causal variant(s) in the regions of ATG16L2, FCHSD2, and P2RY2.
PMCID: PMC4981330  PMID: 26663301
3.  GWAS in an Amerindian ancestry population reveals novel systemic lupus erythematosus risk loci and the role of European admixture 
Systemic lupus erythematosus (SLE) is a chronic autoimmune disease with a strong genetic component. Our aim was to perform the first genome-wide association study on individuals from the Americas enriched for Native American heritage.
We analyzed 3,710 individuals from four countries of Latin America and the Unites States diagnosed with SLE and healthy controls. Samples were genotyped with the HumanOmni1 BeadChip. Data of out-of-study controls was obtained for the HumanOmni2.5. Statistical analyses were performed using SNPTEST and SNPGWA. Data was adjusted for genomic control and FDR. Imputation was done using IMPUTE2, and HiBAG for classical HLA alleles.
The IRF5-TNPO3 region showed the strongest association and largest odds ratio (OR) (rs10488631, Pgcadj = 2.61×10−29, OR = 2.12, 95% CI: 1.88–2.39) followed by the HLA class II on the DQA2-DQB1 loci (rs9275572, Pgcadj = 1.11 × 10−16, OR = 1.62, 95% CI: 1.46–1.80; rs9271366, Pgcadj=6.46 × 10−12, OR = 2.06, 95% CI: 1.71–2.50). Other known SLE loci associated were ITGAM, STAT4, TNIP1, NCF2 and IRAK1. We identified a novel locus on 10q24.33 (rs4917385, Pgcadj =1.4×10−8) with a eQTL effect (Peqtl=8.0 × 10−37 at USMG5/miR1307), and describe novel loci. We corroborate SLE-risk loci previously identified in European and Asians. Local ancestry estimation showed that HLA allele risk contribution is of European ancestral origin. Imputation of HLA alleles suggested that autochthonous Native American haplotypes provide protection.
Our results show the insight gained by studying admixed populations to delineate the genetic architecture that underlies autoimmune and complex diseases.
PMCID: PMC4829354  PMID: 26606652
4.  Modulation of IL-6 induced RANKL expression in arthritic synovium by a transcription factor SOX5 
Scientific Reports  2016;6:32001.
Receptor activator of nuclear factor κB ligand (RANKL) is critically involved in bone erosion of rheumatoid arthritis (RA). We previously reported association between younger age at onset of RA and a RANKL promoter SNP that conferred an elevated promoter activity via binding to a transcription factor SOX5. Here we study the regulation of SOX5 levels in relation to RANKL expression in RA synovial fibroblasts (SF) and the development of bone erosion in the collagen-induced arthritis (CIA) mouse. Our data indicated SOX5 levels were higher in synovium and synovial fluid from RA compared to osteoarthritis patients. Pro-inflammatory cytokines upregulated SOX5 and RANKL expression in both primary RA SF and the rheumatoid synovial fibroblast cell line, MH7A. Overexpression of SOX5 resulted in significantly increased RANKL levels, while knockdown of SOX5 resulted in diminished IL-6 mediated RANKL upregulation in MH7A cells. Chromatin immunoprecipitation (ChIP) showed approximately 3-fold enrichment of RANKL-specific DNA in anti-SOX5 immunoprecipitate in IL-6 treated MH7A cells as compared to untreated cells. Locally silencing SOX5 gene significantly diminished RANKL positive cells and bone erosion in CIA mice. These findings suggest SOX5 is an important regulator of IL-6-induced RANKL expression in RA SF.
PMCID: PMC4994074  PMID: 27550416
5.  Genetic Association of CD247 (CD3ζ) with SLE in a Large-Scale Multiethnic Study 
Genes and immunity  2015;16(2):142-150.
A classic T-cell phenotype in Systemic lupus erythematosus (SLE) is the downregulation and replacement of the CD3ζ chain that alters TCR signaling. However, genetic associations with SLE in the human CD247 locus that encodes CD3ζ are not well established and require replication in independent cohorts. Our aim was therefore to examine, localize and validate CD247-SLE association in a large multi-ethnic population. We typed 44 contiguous CD247 SNPs in 8 922 SLE patients and 8 077 controls from four ethnically distinct populations. The strongest associations were found in the Asian population (11 SNPs in intron 1, 4.99×10−4
PMCID: PMC4371129  PMID: 25569266
Current opinion in rheumatology  2014;26(5):482-492.
Purpose of review
Genome-wide association studies (GWAS) have identified more than 50 robust loci associated with SLE susceptibility, and follow-up studies help reveal candidate causative genetic variants and their biological relevance contributing to the development of SLE. Epigenetic modulation is emerging as an important mechanism for understanding how the implicated genes interact with environmental factors. We review recent progress towards identifying causative variants of SLE-associated loci and epigenetic impact to lupus, especially genetic-epigenetic interactions that modulate expression levels of SLE susceptibility genes.
Recent findings
A few SLE-risk loci have been refined to localize likely causative variants responsible for the observed GWAS signals. Few of such variants disrupt coding sequences resulting in gain or loss of function for the encoded protein, while most fall in noncoding regions with potential to regulate gene expression through alterations in transcriptional activity, splicing, mRNA stability and epigenetic modifications. Multiple key pathways related to the SLE pathogenesis have been indicated by the identified genetic risk factors, including type I interferon signaling pathway that can also be regulated by epigenetic changes occurred in SLE.
These findings provide novel insights of the disease pathogenesis, and promise better diagnostic accuracy and new therapeutic targets for patient management.
PMCID: PMC4222581  PMID: 25010439
genetics; epigenetics; causative variant; molecular pathways; systemic lupus erythematous
Systemic lupus erythematosus (SLE) is a prototypic systemic autoimmune disorder. Considerable progress has been made to delineate the genetic control of this complex disorder. In this review, selected aspects of human and mouse genetics related to SLE are reviewed with emphasis on genes that contribute to both innate and adaptive immunity and to genes that contribute directly to susceptibility to end organ damage. It is concluded that the interactions among these two major pathways will provide further insight into the pathogenesis of SLE. An interactive model of the two major pathways is proposed without emphasis on the importance of breaking tolerance to autoantigens.
PMCID: PMC4274270  PMID: 25458999
eLife  null;5:e12089.
Targeted sequencing of sixteen SLE risk loci among 1349 Caucasian cases and controls produced a comprehensive dataset of the variations causing susceptibility to systemic lupus erythematosus (SLE). Two independent disease association signals in the HLA-D region identified two regulatory regions containing 3562 polymorphisms that modified thirty-seven transcription factor binding sites. These extensive functional variations are a new and potent facet of HLA polymorphism. Variations modifying the consensus binding motifs of IRF4 and CTCF in the XL9 regulatory complex modified the transcription of HLA-DRB1, HLA-DQA1 and HLA-DQB1 in a chromosome-specific manner, resulting in a 2.5-fold increase in the surface expression of HLA-DR and DQ molecules on dendritic cells with SLE risk genotypes, which increases to over 4-fold after stimulation. Similar analyses of fifteen other SLE risk loci identified 1206 functional variants tightly linked with disease-associated SNPs and demonstrated that common disease alleles contain multiple causal variants modulating multiple immune system genes.
eLife digest
The human immune system defends the body against microbes and other threats. However, if this process goes wrong the immune system can attack the body’s own healthy cells, which can lead to serious autoimmune diseases.
Systemic lupus erythematosus (SLE) is an autoimmune disease in which immune cells often attack internal organs – including the kidneys, nervous system and heart. Over the past decade, multiple genes have been linked with an increased risk of SLE. However, it is largely unknown how the sequences of these genes differ between individuals with SLE and healthy individuals, and the precise changes that lead to an increased risk of SLE are also not clear.
Now, Raj, Rai et al. have determined the genetic sequences of over 700 people with SLE and over 500 healthy individuals and looked for differences that influence susceptibility to the disease. The vast majority of differences were discovered in stretches of DNA that regulate the expression of nearby genes, rather than in DNA that encodes the structures of proteins. Notably, extensive differences were found in a region of the human genome that regulates the production of proteins called Human Leukocyte Antigen class II molecules; which are known to play a critical role in activating the immune system. Raj, Rai et al. found that slight changes to the regulatory DNA sequences resulted in an overabundance of these proteins, which led to a hyperactive immune system that is strongly associated with SLE.
Future studies could now ask if the changes to the regulatory DNA sequences highlighted by Raj, Rai et al. increase susceptibility to other autoimmune disorders as well. It may also be possible to use the increased understanding of how the immune system is regulated to develop new ways to minimize the rejection of organ transplants.
PMCID: PMC4811771  PMID: 26880555
targeted sequencing; HLA; SLE risk; haplotype; risk allele; LD; Human
Annals of the Rheumatic Diseases  2014;75(1):242-252.
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.
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.
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.
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.
PMCID: PMC4717392  PMID: 25180293
Systemic Lupus Erythematosus; Autoantibodies; Gene Polymorphism; B cells
Kottyan, Leah C. | Zoller, Erin E. | Bene, Jessica | Lu, Xiaoming | Kelly, Jennifer A. | Rupert, Andrew M. | Lessard, Christopher J. | Vaughn, Samuel E. | Marion, Miranda | Weirauch, Matthew T. | Namjou, Bahram | Adler, Adam | Rasmussen, Astrid | Glenn, Stuart | Montgomery, Courtney G. | Hirschfield, Gideon M. | Xie, Gang | Coltescu, Catalina | Amos, Chris | Li, He | Ice, John A. | Nath, Swapan K. | Mariette, Xavier | Bowman, Simon | Rischmueller, Maureen | Lester, Sue | Brun, Johan G. | Gøransson, Lasse G. | Harboe, Erna | Omdal, Roald | Cunninghame-Graham, Deborah S. | Vyse, Tim | Miceli-Richard, Corinne | Brennan, Michael T. | Lessard, James A. | Wahren-Herlenius, Marie | Kvarnström, Marika | Illei, Gabor G. | Witte, Torsten | Jonsson, Roland | Eriksson, Per | Nordmark, Gunnel | Ng, Wan-Fai | Anaya, Juan-Manuel | Rhodus, Nelson L. | Segal, Barbara M. | Merrill, Joan T. | James, Judith A. | Guthridge, Joel M. | Hal Scofield, R. | Alarcon-Riquelme, Marta | Bae, Sang-Cheol | Boackle, Susan A. | Criswell, Lindsey A. | Gilkeson, Gary | Kamen, Diane L. | Jacob, Chaim O. | Kimberly, Robert | Brown, Elizabeth | Edberg, Jeffrey | Alarcón, Graciela S. | Reveille, John D. | Vilá, Luis M. | Petri, Michelle | Ramsey-Goldman, Rosalind | Freedman, Barry I. | Niewold, Timothy | Stevens, Anne M. | Tsao, Betty P. | Ying, Jun | Mayes, Maureen D. | Gorlova, Olga Y. | Wakeland, Ward | Radstake, Timothy | Martin, Ezequiel | Martin, Javier | Siminovitch, Katherine | Moser Sivils, Kathy L. | Gaffney, Patrick M. | Langefeld, Carl D. | Harley, John B. | Kaufman, Kenneth M.
Human Molecular Genetics  2014;24(2):582-596.
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.
PMCID: PMC4275071  PMID: 25205108
Cellular and Molecular Immunology  2015;13(1):119-131.
Complement receptor 2 (CR2/CD21) is predominantly expressed on the surface of mature B cells where it forms part of a coreceptor complex that functions, in part, to modulate B-cell receptor signal strength. CR2/CD21 expression is tightly regulated throughout B-cell development such that CR2/CD21 cannot be detected on pre-B or terminally differentiated plasma cells. CR2/CD21 expression is upregulated at B-cell maturation and can be induced by IL-4 and CD40 signaling pathways. We have previously characterized elements in the proximal promoter and first intron of CR2/CD21 that are involved in regulating basal and tissue-specific expression. We now extend these analyses to the CR2/CD21 core promoter. We show that in mature B cells, CR2/CD21 transcription proceeds from a focused TSS regulated by a non-consensus TATA box, an initiator element and a downstream promoter element. Furthermore, occupancy of the general transcriptional machinery in pre-B versus mature B-cell lines correlate with CR2/CD21 expression level and indicate that promoter accessibility must switch from inactive to active during the transitional B-cell window.
PMCID: PMC4711682  PMID: 25640655
B cells; core promoter; CR2/CD21; molecular biology; transcription factor
Arthritis and rheumatism  2011;63(9):2755-2763.
T cells from patients with SLE express increased amounts of PP2Ac which contribute to decreased production of IL-2. Because IL-2 is important in the regulation of several aspects of the immune response, it has been proposed that PP2Ac contributes to the expression of SLE. This study was designed to determine whether genetic variants of PPP2AC are linked to the expression of SLE and specific clinical manifestations and account for the increased expression of PP2Ac.
We conducted a trans-ethnic study consisting of 8,695 SLE cases and 7,308 controls from four different ancestries. Eighteen single-nucleotide polymorphisms (SNPs) across the PPP2CA were genotyped using an Illumina custom array. PPP2CA expression in SLE and control T cells was analyzed by real-time PCR.
A 32-kb haplotype comprised of multiple SNPs of PPP2CA showed significant association with SLE in Hispanic Americans (HA), European Americans (EA) and Asians but not in African-Americans (AA). Conditional analyses revealed that SNP rs7704116 in intron 1 showed consistently strong association with SLE across Asian, EA and HA populations (pmeta=3.8×10−7, OR=1.3[1.14–1.31]). In EA, the largest ethnic dataset, the risk A allele of rs7704116 was associated with the presence of renal disease, anti-dsDNA and anti-RNP antibodies. PPP2CA expression was approximately 2-fold higher in SLE patients carrying the rs7704116 AG genotype than those carrying GG genotype (p = 0.008).
Our data provide the first evidence for an association between PPP2CA polymorphisms and elevated PP2Ac transcript levels in T cells, which implicates a new molecular pathway for SLE susceptibility in EA, HA and Asians.
PMCID: PMC3163110  PMID: 21590681
Arthritis and Rheumatism  2011;63(3):749-754.
Previous genome wide association study conducted in a population of European ancestry identified rs4963128, a KIAA1542 SNP 23kb telomeric to IRF7, in strong association with SLE. This study was undertaken to investigate whether genetic polymorphism within IRF7 is a risk factor for the development of SLE.
We genotyped one KIAA1542 SNP rs4963128 and one IRF7 SNP rs1131665 (Q412R) in an Asian population (cases vs. controls: 1302 vs.1479) to assess their association with SLE using custom-designed Beadstation Infinium II platform (Illumina). Subsequently, rs1131665 was further genotyped in independent panels of Chinese (528 vs.527), European American (EA) (446 vs.461) and African American (AA) (159 vs.115) by Taqman genotyping assay to seek confirmation of association in various ethnic groups. Luciferase reporter assay was used to assess the effect of Q412R polymorphism on the activation of IRF7.
Consistent association of rs1131665 (Q412R) with SLE was identified in Asian, EA and AA populations (case vs. control: 2435 vs. 2582; Pmeta = 6.18×10−6, OR = 1.42[1.22–1.65]). Expression of IRF7 412Q risk allele resulted in a 2-fold increase in ISRE transcriptional activity compared with expression of IRF7 412R (P = 0.0003), suggesting IRF7 412Q confers elevated IRF7 activity and may therefore affect downstream IFN pathway.
We showed that the major allele of a nonsynonymous SNP rs1131665 (412Q) in IRF7 confers elevated IRF7 activation and predisposes to the development of SLE in multiple ethnic groups. This result provides direct genetic evidence supporting IRF7 may be a risk gene for human SLE.
PMCID: PMC3063317  PMID: 21360504
Arthritis and rheumatism  2010;62(10):2864-2875.
We previously reported association of co-occurrence of HLA-DRB1 shared epitope (SE) and RANKL SNPs with younger age of RA onset in 182 rheumatoid factor positive (RF) European American (EA) early RA patients. Here, we fine-mapped the 48 kb RANKL region in the extended 210 EA RF-positive early RA cohort, sought replication of RA-associated SNPs in additional 501 EA and 298 African-Americans (AA) RA cohorts, and explored functional consequences of RA-associated SNPs.
SNP genotyping was conducted using pyrosequencing or TaqMan PCR assays. Associations of rs7984870 with RANKL expression in plasma, PBMC and isolated T cells were quantified using ELISA and RT-PCR. Site-directed mutagenesis of rs7984870 within the 2kb RANKL promoter was performed to drive the luciferase reporter gene in osteoblast and stromal cell lines. Interaction of DNA and protein was determined by electrophoretic mobility shift assay.
A single promoter SNP rs7984870 was consistently significantly associated with earlier age of RA onset in 3 independent seropositive (RF or anti-cyclic citrullinated peptide antibody positive) RA cohorts but not in seronegative RA patients. The risk C allele of rs7984870 conferred 2-fold higher plasma RANKL levels in RF-positive RA patients, significantly elevated RANKL mRNA expression in activated normal T cells, and increased promoter activity after stimulation in vitro via differential binding to transcription factor SOX5.
The RANKL promoter allele that increased transcriptional levels upon stimulation might promote interaction between activated T cells and dendritic cells, predisposing to younger RA onset in seropositive EA and/or AA individuals.
PMCID: PMC2944013  PMID: 20533289
Genes and immunity  2014;16(1):15-23.
Systemic Lupus Erythematosus (SLE) is a chronic autoimmune disorder characterized by inflammation of multiple organ systems and dysregulated interferon responses. SLE is both genetically and phenotypically heterogeneous, greatly reducing the power of case-control studies in SLE. Elevated circulating interferon alpha (IFN-α) is a stable, heritable trait in SLE, which has been implicated in primary disease pathogenesis. 40–50% of patients have high IFN-α, and high levels correspond with clinical differences. To study genetic heterogeneity in SLE, we performed a case-case study comparing patients with high vs. low IFN-α in over 1550 SLE cases, including GWAS and replication cohorts. In meta-analysis, the top associations in European ancestry were PRKG1 rs7897633 (PMeta=2.75 × 10−8) and PNP rs1049564 (PMeta=1.24 × 10−7). We also found evidence for cross-ancestral background associations with the ANKRD44 and PLEKHF2 loci. These loci have not been previously identified in case-control SLE genetic studies. Bioinformatic analyses implicated these loci functionally in dendritic cells and natural killer cells, both of which are involved in IFN-α production in SLE. As case-control studies of heterogeneous diseases reach a limit of feasibility with respect to subject number and detectable effect size, the study of informative pathogenic subphenotypes becomes an attractive strategy for genetic discovery in complex disease.
PMCID: PMC4305028  PMID: 25338677
Arthritis and rheumatism  2003;48(3):737-745.
To test the feasibility of applying a mimetic (specific for a patient-derived prothrombotic anticardiolipin antibody [aCL]) to study the homologous, disease-associated aCL in patients with antiphospholipid syndrome (APS).
We used the CL15 monoclonal aCL to screen 17 phage-display peptide libraries. Peptides (corresponding to recurrent peptide sequences) and their derivatives were synthesized and analyzed for binding to CL15 and for their abilities to inhibit CL15 from binding to cardiolipin. A peptide was chosen and used to study CL15-like IgG aCL in plasma samples from patients with APS, patients with systemic lupus erythematosus (SLE) but without APS, and normal healthy donors.
Library screening with CL15 yielded 4 recurrent peptide sequences. Analyses of peptides showed that peptide CL154C reacted with antibody CL15 and inhibited binding of CL15 to cardiolipin, indicating that peptide CL154C may be a peptide mimetic for the CL15 aCL. Initial studies with plasma samples revealed that CL154C-reactive IgG was present (positivity defined as the mean + 3 SD optical density of the 25 normal controls) in 15 of 21 APS patients and 1 of 12 SLE patients.
These findings suggest that it is feasible to develop a specific enzyme-linked immunosorbent assay for each immunologically and functionally distinct disease-associated aCL. Additional testing of CL154C with a larger number of APS patients and SLE patients, as well as identification of peptide mimetics for each distinct aCL, will reveal the diagnostic potential of CL154C and other mimetics in identifying patients with aCL who are at risk of developing life-threatening thrombosis.
PMCID: PMC2206208  PMID: 12632428
Genes and immunity  2014;15(6):347-354.
In a Genome Wide Association Study (GWAS) of individuals of European ancestry afflicted with Systemic Lupus Erythematosus (SLE) the extensive utilization of imputation, stepwise multiple regression, lasso regularization, and increasing study power by utilizing False Discovery Rate (FDR) instead of a Bonferroni multiple test correction enabled us to identify 13 novel non-human leukocyte antigen (HLA) genes and confirmed the association of 4 genes previously reported to be associated. Novel genes associated with SLE susceptibility included two transcription factors (EHF, and MED1), two components of the NFκB pathway (RASSF2 and RNF114), one gene involved in adhesion and endothelial migration (CNTN6), and two genes involved in antigen presentation (BIN1 and SEC61G). In addition, the strongly significant association of multiple single nucleotide polymorphisms (SNPs) in the HLA region was assigned to HLA alleles and serotypes and deconvoluted into four primary signals. The novel SLE-associated genes point to new directions for both the diagnosis and treatment of this debilitating autoimmune disease.
PMCID: PMC4156543  PMID: 24871463
Journal of Clinical Investigation  1999;103(8):1135-1140.
Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by various autoantibodies that recognize autoantigens displayed on the surface of cells undergoing apoptosis. The genetic contribution to SLE susceptibility has been widely recognized. We previously reported evidence for linkage to SLE of the human chromosome 1q41–q42 region and have now narrowed it from 15 to 5 cM in an extended sample using multipoint linkage analysis. Candidate genes within this region include (a) PARP, poly(ADP-ribose) polymerase, encoding a zinc-finger DNA-binding protein that is involved in DNA repair and apoptosis; (b) TGFB2, encoding a transforming growth factor that regulates cellular interactions and responses; and (c) HLX1, encoding a homeobox protein that may regulate T-cell development. Using a multiallelic, transmission-disequilibrium test (TDT), we found overall skewing of transmission of PARP alleles to affected offspring in 124 families (P = 0.00008), preferential transmission of a PARP allele to affected offspring (P = 0.0003), and lack of transmission to unaffected offspring (P = 0.004). Similar TDT analyses of TGFB2 and HLX1 polymorphisms yielded no evidence for association with SLE. These results suggest that PARP may be (or is close to) the susceptibility gene within the chromosome 1q41–q42 region linked to SLE.
PMCID: PMC408279  PMID: 10207165
Frontiers in Genetics  2015;5:450.
Genome wide association studies have identified variants in PXK that confer risk for humoral autoimmune diseases, including systemic lupus erythematosus (SLE or lupus), rheumatoid arthritis and more recently systemic sclerosis. While PXK is involved in trafficking of epidermal growth factor Receptor (EGFR) in COS-7 cells, mechanisms linking PXK to lupus pathophysiology have remained undefined. In an effort to uncover the mechanism at this locus that increases lupus-risk, we undertook a fine-mapping analysis in a large multi-ancestral study of lupus patients and controls. We define a large (257kb) common haplotype marking a single causal variant that confers lupus risk detected only in European ancestral populations and spans the promoter through the 3′ UTR of PXK. The strongest association was found at rs6445972 with P < 4.62 × 10−10, OR 0.81 (0.75–0.86). Using stepwise logistic regression analysis, we demonstrate that one signal drives the genetic association in the region. Bayesian analysis confirms our results, identifying a 95% credible set consisting of 172 variants spanning 202 kb. Functionally, we found that PXK operates on the B-cell antigen receptor (BCR); we confirmed that PXK influenced the rate of BCR internalization. Furthermore, we demonstrate that individuals carrying the risk haplotype exhibited a decreased rate of BCR internalization, a process known to impact B cell survival and cell fate. Taken together, these data define a new candidate mechanism for the genetic association of variants around PXK with lupus risk and highlight the regulation of intracellular trafficking as a genetically regulated pathway mediating human autoimmunity.
PMCID: PMC4288052  PMID: 25620976
lupus; PXK; fine-mapping; B cells; BCR
Lupus nephritis (LN) is a severe manifestation of systemic lupus erythematosus (SLE) that exhibits familial aggregation and may progress to end-stage renal disease (ESRD). LN is more prevalent among African Americans than among European Americans. This study was undertaken to investigate the hypothesis that the apolipoprotein L1 gene (APOL1) nephropathy risk alleles G1/G2, common in African Americans and rare in European Americans, contribute to the ethnic disparity in risk.
APOL1 G1 and G2 nephropathy alleles were genotyped in 855 African American SLE patients with LN-ESRD (cases) and 534 African American SLE patients without nephropathy (controls) and tested for association under a recessive genetic model, by logistic regression.
Ninety percent of the SLE patients were female. The mean ± SD age at SLE diagnosis was significantly lower in LN-ESRD cases than in SLE non-nephropathy controls (27.3 ± 10.9 years versus 39.5 ± 12.2 years). The mean ± SD time from SLE diagnosis to development of LN-ESRD in cases was 7.3 ± 7.2 years. The G1/G2 risk alleles were strongly associated with SLE-ESRD, with 25% of cases and 12% of controls having 2 nephropathy alleles (odds ratio [OR] 2.57, recessive model P = 1.49 × 10−9), and after adjustment for age, sex, and ancestry admixture (OR 2.72, P = 6.23 × 10−6). The age-, sex-, and admixture-adjusted population attributable risk for ESRD among patients with G1/G2 polymorphisms was 0.26, compared to 0.003 among European American patients. The mean time from SLE diagnosis to ESRD development was ~2 years earlier among individuals with APOL1 risk genotypes (P = 0.01).
APOL1 G1/G2 alleles strongly impact the risk of LN-ESRD in African Americans, as well as the time to progression to ESRD. The high frequency of these alleles in African Americans with near absence in European Americans explains an important proportion of the increased risk of LN-ESRD in African Americans.
PMCID: PMC4002759  PMID: 24504811
Arthritis and rheumatism  2013;65(1):211-215.
The increased risk of thrombosis in systemic lupus erythematosus (SLE) may be partially explained by interrelated genetic pathways for thrombosis and SLE. In a case-control analysis, we investigated whether 33 established and novel single nucleotide polymorphisms (SNP) in 20 genes involved in hemostasis pathways that have been associated with deep venous thrombosis in the general population were risk factors for SLE development among Asians.
Patients in the discovery cohort were enrolled in one of two North American SLE cohorts. Patients in the replication cohort were enrolled in one of four Asian or two North American cohorts. SLE cases met American College of Rheumatology classification criteria. We first genotyped 263 Asian SLE and 357 healthy Asian control individuals for 33 SNPs using Luminex multiplex technology in the discovery phase, and then used Taqman and Immunochip assays to examine 5 SNPs in up to an additional 1496 cases and 993 controls in the Replication phase. SLE patients were compared to healthy controls for association with minor alleles in allelic models. Principal components analysis was used to control for intra-Asian ancestry in an analysis of the replication cohort.
Two genetic variants in the gene VKORC1, rs9934438 and rs9923231, were highly significant in both the discovery and replication cohorts: OR(disc) = 2.45 (p=2×10−9), OR(rep) = 1.53 (p=5×10−6) and OR(disc) = 2.40 (p=6×10−9), OR(rep) = 1.53 (p=5×10−6), respectively. These associations were significant in the replication cohort after adjustment for intra-Asian ancestry: rs9934438 OR(adj) = 1.34 (p=0.0029) and rs9923231 OR(adj) = 1.34 (p=0.0032).
Genetic variants in VKORC1, involved in vitamin K reduction and associated with DVT, are associated with SLE development in Asians. These results suggest intersecting genetic pathways for the development of SLE and thrombosis.
PMCID: PMC3670944  PMID: 23124848
systemic lupus erythematosus; single nucleotide polymorphisms; genetic risk factors
Arthritis and rheumatism  2012;64(11):3695-3705.
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.
PMCID: PMC3485412  PMID: 22833143

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