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1.  Peripheral blood gene expression profiling in Sjögren’s syndrome 
Genes and Immunity  2009;10(4):285-296.
Sjögren’s syndrome (SS) is a common chronic autoimmune disease characterized by lymphocytic infiltration of exocrine glands. Affected cases commonly present with oral and ocular dryness, thought to be the result of inflammatory cell-mediated gland dysfunction. To identify important molecular pathways involved in SS, we used high-density microarrays to define global gene expression profiles in peripheral blood. We first analyzed 21 SS cases and 23 controls and identified a prominent pattern of overexpressed genes that are inducible by interferons (IFNs). These results were confirmed by evaluation of a second independent dataset of 17 SS cases and 22 controls. Additional inflammatory and immune-related pathways with altered expression patterns in SS cases included B and T cell receptor, IGF-1, GM-CSF, PPARα/RXRα, and PI3/AKT signaling. Exploration of these data for relationships to clinical features of disease revealed that expression levels for most IFN-inducible genes were positively correlated with titers of anti-Ro/SSA (P<0.001) and anti-La/SSB (P<0.001) autoantibodies. Diagnostic and therapeutic approaches targeting IFN signaling pathway may prove most effective in the subset of SS cases who produce anti-Ro/SSA and anti-La/SSB autoantibodies. Our results strongly support innate and adaptive immune processes in the pathogenesis of SS and provide numerous candidate disease markers for further study.
PMCID: PMC3273959  PMID: 19404300
2.  Variation in the ATP-binding cassette transporter 2 gene is a separate risk factor for Systemic Lupus Erythematosus within the MHC 
Genes and immunity  2009;10(4):350-355.
The ATP-binding cassette transporter (TAP) proteins are functionally relevant candidates for predisposition to Systemic Lupus Erythematosus (SLE) by virtue of their role in autoantigen presentation and location in the MHC. We tested if variation in the TAP genes (TAP1 and TAP2) is associated with SLE. We genotyped tag single nucleotide polymorphisms (SNPs) and performed family-based association analysis on 390 Caucasian pedigrees. We found significant evidence of association between TAP2 and SLE (rs241453, P = 1.33 × 10-6). Conditional logistic regression analysis suggests that this TAP2 effect is separate from the HLA-DRB1 alleles. Our analyses show that both rs241453 (P = 1.6 × 10-4) and HLA-DRB1*03xx (P = 2.3 × 10-4) have significant autonomous effects not due to linkage disequilibrium. Moreover, these loci exhibit a significant statistical interaction (P < 1.0 × 10-6), demonstrated by an increase in the odds ratio for the TAP2 association from OR = 2.00 (CI=1.17-3.42) in HLA-DRB1*03xx-negative subjects to OR = 4.29 (CI=1.88-9.76) in the subjects with at least one HLA-DRB1*03xx allele group. We report the largest association study of the TAP genes with SLE to date, and the first to test for its separate effect and interaction with the HLA alleles consistently associated with SLE.
PMCID: PMC2927958  PMID: 19387463
Systemic Lupus Erythematosus; TAP2; HLA-DRB1; family-based association analysis; conditional logistic regression analysis; interaction analysis
3.  Genetic Associations of LYN with Systemic Lupus Erythematosus 
Genes and immunity  2009;10(5):397-403.
We targeted LYN, a src-tyosine kinase involved in B cell activation, in case-control association studies using populations of European American, African American and Korean subjects. Our combined European-derived population, consisting of 2463 independent cases and 3131 unrelated controls, demonstrates significant association with rs6983130 in a female-only analysis with 2254 cases and 2228 controls (p=1.1 × 10−4, OR=0.81 (95% CI: 0.73 – 0.90)). This SNP is located in the 5′ UTR within the first intron near the transcription initiation site of LYN. Additional SNPs upstream of the first exon also show weak and sporadic association in subsets of the total European American population. Multivariate logistic regression analysis implicates rs6983130 as a protective factor for SLE susceptibility when anti-dsDNA, anti-chromatin, anti-52 kDa Ro or anti-Sm autoantibody status were used as covariates. Subset analysis of the European American female cases by ACR classification criteria reveals a reduction in the risk of hematologic disorder with rs6983130 compared to cases without hematologic disorders (p=1.5 × 10−3, OR=0.75 (95% C.I.=0.62-0.89)). None of the 90 SNPs tested demonstrate significant association with SLE in the African American or Korean populations. These results support an association of LYN with European-derived individuals with SLE, especially within autoantibody or clinical subsets.
PMCID: PMC2750001  PMID: 19369946
systemic lupus erythematosus; association; LYN; SNP
4.  Replication of the BANK1 genetic association with systemic lupus erythematosus in a European-Derived Population 
Genes and immunity  2009;10(5):531-538.
Systemic lupus erythematosus (SLE) is an autoimmune disease with highly variable clinical presentation. Patients suffer from immunological abnormalities that target T cell, B cell and accessory cell functions. B cells are hyperactive in SLE patients. An adaptor protein expressed in B cells called BANK1 (B-cell scaffold protein with ankyrin repeats) was reported in a previous study to be associated with SLE in a European population. The objective of this study is to assess the BANK1 genotype-phenotype association in an independent replication sample. We genotyped 38 single nucleotide polymorphisms (SNPs) in BANK1 on 1892 European-derived SLE patients and 2652 European-derived controls. The strongest associations with SLE and BANK1 were at rs17266594 (corrected p-value=1.97 × 10−5, OR=1.22, 95% C.I.(1.12–1.34)) and rs10516487 (corrected p-value=2.59 × 10−5, OR=1.22, 95% C.I.(1.11–1.34)). Our findings suggest that the association is explained by these two SNPs, confirming previous reports that these polymorphisms contribute to the risk of developing lupus. Analysis of patient subsets enriched for hematological, immunological and renal ACR criteria or the levels of autoantibodies, such as anti-RNP A and anti-SmRNP, uncovers additional BANK1 associations. Our results suggest that BANK1 polymorphisms alter immune system development and function to increase the risk for developing lupus.
PMCID: PMC2736873  PMID: 19339986
systemic lupus erythematosus; replication; association; European; BANK1
5.  Meta-analysis and Imputation Identifies a 109 kb Risk Haplotype Spanning TNFAIP3 Associated with Lupus Nephritis and Hematologic Manifestations 
Genes and immunity  2009;10(5):470-477.
TNFAIP3 encodes the ubiquitin modifying enzyme, A20, a key regulator of inflammatory signaling pathways. We previously reported association between TNFAIP3 variants and systemic lupus erythematosus (SLE). In order to further localize the risk variant(s), we performed a meta-analysis using genetic data available from two Caucasian case/control datasets (1453 total cases, 3381 total controls) and 713 SLE trio families. The best result was found at rs5029939 (P = 1.67 × 10−14, OR = 2.09, 95% CI 1.68–2.60). We then imputed SNPs from the CEU Phase II HapMap using genotypes from 431 SLE cases and 2155 controls. Imputation identified eleven SNPs in addition to three observed SNPs, which together, defined a 109 kb SLE risk segment surrounding TNFAIP3. When evaluating whether the rs5029939 risk allele was associated with SLE clinical manifestations, we observed that heterozygous carriers of the TNFAIP3 risk allele at rs5029939 have a two-fold increased risk of developing renal or hematologic manifestations compared to homozygous non-risk subjects. In summary, our study strengthens the genetic evidence that variants in the region of TNFAIP3 influence risk for SLE, particularly in patients with renal and hematologic manifestations, and narrows the risk effect to a 109 kb DNA segment that spans the TNFAIP3 gene.
PMCID: PMC2714405  PMID: 19387456
systemic lupus erythematosus; TNFAIP3; imputation; meta-analysis
6.  European population substructure is associated with mucocutaneous manifestations and autoantibody production in systemic lupus erythematosus 
Arthritis and rheumatism  2009;60(8):2448-2456.
To determine whether genetic substructure in European-derived populations is associated with specific manifestations of systemic lupus erythematosus (SLE), including mucocutaneous phenotypes, autoantibody production, and renal disease.
SLE patients of European descent (n=1754) from 8 case collections were genotyped for over 1,400 ancestry informative markers that define a north/south gradient of European substructure. Based on these genetic markers, we used the STRUCTURE program to characterize each SLE patient in terms of percent northern (vs. southern) European ancestry. Non-parametric methods, including tests of trend, were used to identify associations between northern European ancestry and specific SLE manifestations.
In multivariate analyses, increasing levels of northern European ancestry were significantly associated with photosensitivity (ptrend=0.0021, OR for highest quartile of northern European ancestry compared to lowest quartile 1.64, 95% CI 1.13–2.35) and discoid rash (ptrend=0.014, ORhigh-low 1.93, 95% CI 0.98–3.83). In contrast, northern European ancestry was protective for anticardiolipin (ptrend=1.6 × 10−4, ORhigh-low 0.46, 95% CI 0.30–0.69) and anti-dsDNA (ptrend=0.017, ORhigh-low 0.67, 95% CI 0.46–0.96) autoantibody production.
This study demonstrates that specific SLE manifestations vary according to northern vs. southern European ancestry. Thus, genetic ancestry may contribute to the clinical heterogeneity and variation in disease outcomes among SLE patients of European descent. Moreover, these results suggest that genetic studies of SLE subphenotypes will need to carefully address issues of population substructure due to genetic ancestry.
PMCID: PMC2739103  PMID: 19644962
7.  A polymorphism within interleukin-21 receptor (IL21R) confers risk for systemic lupus erythematosus 
Arthritis and rheumatism  2009;60(8):2402-2407.
Interleukin (IL) 21 is a member of the type I cytokine superfamily that exerts a variety of effects on the immune system including B cell activation, plasma cell differentiation, and immunoglobulin production. The expression of IL21R is reduced in B cells from lupus patients, while IL21 serum levels are increased in both lupus patients and some lupus-murine models. We recently reported that polymorphisms within the IL21 gene are associated with increased susceptibility to lupus. Herein, we examined the genetic association between SNPs within IL21R and lupus.
We genotyped 17 SNPs in the IL21R gene in two large cohorts of lupus patients and ethnically-matched healthy controls. Genotyping was performed with the Illumina BeadStation 500GX instrument using Illumina Infinum II genotyping assays.
We identified and confirmed the association between rs3093301 within the IL21R gene and lupus in two independent European-derived and Hispanic cohorts (meta analysis odds ratio= 1.16, 95% CI= 1.08-1.25, meta analysis p=1.0×10-4).
We identified IL21R as a novel susceptibility gene for lupus.
PMCID: PMC2782592  PMID: 19644854
8.  High density genotyping of STAT4 gene reveals multiple haplotypic associations with Systemic Lupus Erythematosus in different racial groups 
Arthritis and rheumatism  2009;60(4):1085-1095.
Systemic lupus erythematosus (SLE) is the prototypic systemic autoimmune disorder with complex etiology and a strong genetic component. Recently, gene products involved in the interferon pathway have been under intense investigation in SLE pathogenesis. STAT1 and STAT4 are transcription factors that play key roles in the interferon and Th1 signaling pathways, making them attractive candidates for SLE susceptibility.
Fifty-six single-nucleotide polymorphisms (SNPs) across STAT1 and STAT4 genes on chromosome 2 were genotyped using Illumina platform as a part of extensive association study in a large collection of 9923 lupus cases and controls from different racial groups. DNA from patients and controls was obtained from peripheral blood. Principal component analyses and population based case-control association analyses were performed and the p values, FDR q values and Odds ratios with 95% confidence intervals (95% CIs) were calculated.
We observed strong genetic associations with SLE and multiple SNPs located within the STAT4 gene in different ethnicities (Fisher combined p= 7.02×10−25). In addition to strong confirmation of the association in the 3rd intronic region of this gene reported previously, we identified additional haplotypic association across STAT4 gene and in particular a common risk haplotype that is found in multiple racial groups. In contrast, only a relatively weak suggestive association was observed with STAT1, probably due to the proximity to STAT4.
Our findings indicate that the STAT4 gene is likely to be a crucial component in SLE pathogenesis among multiple racial groups. The functional effects of this association, when revealed, might improve our understanding of the disease and provide new therapeutic targets.
PMCID: PMC2776081  PMID: 19333953
9.  Evaluation of imputation-based association in and around the integrin-α-M (ITGAM) gene and replication of robust association between a non-synonymous functional variant within ITGAM and systemic lupus erythematosus (SLE) 
Human Molecular Genetics  2009;18(6):1171-1180.
We recently identified a novel non-synonymous variant, rs1143679, at exon 3 of the ITGAM gene associated with systemic lupus erythematosus (SLE) susceptibility in European-Americans (EAs) and African-Americans. Using genome-wide association approach, three other studies also independently reported an association between SLE susceptibility and ITGAM or ITGAM-ITGAX region. The primary objectives of this study are to assess whether single or multiple causal variants from the same gene or any nearby gene(s) are involved in SLE susceptibility and to confirm a robust ITGAM association across nine independent data sets (n = 8211). First, we confirmed our previously reported association of rs1143679 (risk allele ‘A’) with SLE in EAs (P = 1.0 × 10−8) and Hispanic-Americans (P = 2.9 × 10−5). Secondly, using a comprehensive imputation-based association test, we found that ITGAM is one of the major non-human leukocyte antigen susceptibility genes for SLE, and the strongest association for EA is the same coding variant rs1143679 (log10Bayes factor=20, P = 6.17 × 10−24). Thirdly, we determined the robustness of rs1143679 association with SLE across three additional case–control samples, including UK (P = 6.2 × 10−8), Colombian (P = 3.6 × 10−7), Mexican (P = 0.002), as well as two independent sets of trios from UK (PTDT = 1.4 × 10−5) and Mexico (PTDT = 0.015). A meta-analysis combing all independent data sets greatly reinforces the association (Pmeta = 7.1 × 10−50, odds ratio = 1.83, 95% confidence interval = 1.69–1.98, n = 10 046). However, this ITGAM association was not observed in the Korean or Japanese samples, in which rs1143679 is monomorphic for the non-risk allele (G). Taken together along with our earlier findings, these results demonstrate that the coding variant, rs1143679, best explains the ITGAM-SLE association, especially in European- and African-derived populations, but not in Asian populations.
PMCID: PMC2649018  PMID: 19129174
10.  Complement receptor 2 polymorphisms associated with systemic lupus erythematosus modulate alternative splicing 
Genes and immunity  2009;10(5):457-469.
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.
PMCID: PMC2714407  PMID: 19387458
Alternative splicing; systemic lupus erythematosus; complement receptors; single-nucleotide polymorphisms; B cells; follicular dendritic cells
11.  High-Density SNP Screening of the Major Histocompatibility Complex in Systemic Lupus Erythematosus Demonstrates Strong Evidence for Independent Susceptibility Regions 
PLoS Genetics  2009;5(10):e1000696.
A substantial genetic contribution to systemic lupus erythematosus (SLE) risk is conferred by major histocompatibility complex (MHC) gene(s) on chromosome 6p21. Previous studies in SLE have lacked statistical power and genetic resolution to fully define MHC influences. We characterized 1,610 Caucasian SLE cases and 1,470 parents for 1,974 MHC SNPs, the highly polymorphic HLA-DRB1 locus, and a panel of ancestry informative markers. Single-marker analyses revealed strong signals for SNPs within several MHC regions, as well as with HLA-DRB1 (global p = 9.99×10−16). The most strongly associated DRB1 alleles were: *0301 (odds ratio, OR = 2.21, p = 2.53×10−12), *1401 (OR = 0.50, p = 0.0002), and *1501 (OR = 1.39, p = 0.0032). The MHC region SNP demonstrating the strongest evidence of association with SLE was rs3117103, with OR = 2.44 and p = 2.80×10−13. Conditional haplotype and stepwise logistic regression analyses identified strong evidence for association between SLE and the extended class I, class I, class III, class II, and the extended class II MHC regions. Sequential removal of SLE–associated DRB1 haplotypes revealed independent effects due to variation within OR2H2 (extended class I, rs362521, p = 0.006), CREBL1 (class III, rs8283, p = 0.01), and DQB2 (class II, rs7769979, p = 0.003, and rs10947345, p = 0.0004). Further, conditional haplotype analyses demonstrated that variation within MICB (class I, rs3828903, p = 0.006) also contributes to SLE risk independent of HLA-DRB1*0301. Our results for the first time delineate with high resolution several MHC regions with independent contributions to SLE risk. We provide a list of candidate variants based on biologic and functional considerations that may be causally related to SLE risk and warrant further investigation.
Author Summary
Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by autoantibody production and involvement of multiple organ systems. Although the cause of SLE remains unknown, several lines of evidence underscore the importance of genetic factors. As is true for most autoimmune diseases, a substantial genetic contribution to disease risk is conferred by major histocompatibility complex (MHC) gene(s) on chromosome 6. This region of the genome contains a large number of genes that participate in the immune response. However, the full contribution of this genomic region to SLE risk has not yet been defined. In the current study we characterize a large number of SLE patients and family members for approximately 2,000 MHC region variants to identify the specific genes that influence disease risk. Our results, for the first time, implicate four different MHC regions in SLE risk. We provide a list of candidate variants based on biologic and functional considerations that may be causally related to SLE risk and warrant further investigation.
PMCID: PMC2758598  PMID: 19851445

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