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2.  Multiple cytokines and chemokines are associated with rheumatoid arthritis-related autoimmunity in first-degree relatives without rheumatoid arthritis: Studies of the Aetiology of Rheumatoid Arthritis (SERA) 
Annals of the rheumatic diseases  2012;72(6):901-907.
We investigated whether rheumatoid arthritis (RA)-related autoantibodies were associated with systemic inflammation in a prospective cohort of first-degree relatives (FDRs) of RA probands, a population without RA but at increased risk for its future development.
We studied 44 autoantibody positive FDRs, of whom 29 were rheumatoid factor (RF) positive, 25 were positive for the high risk autoantibody profile (HRP), that is, positive for anti-cyclic citrullinated peptide and/or for at least two RF IgM, IgG or IgA isotypes, and nine FDRs who were positive for both; and 62 FDRs who were never autoantibody positive. Twenty-five cytokines/chemokines were measured using a bead-based assay in serum. As a comprehensive measure of inflammation, we calculated a Cytokine Score by summing all cytokine/chemokine levels, weighted by their regression coefficients for RA-autoantibody association. We compared C-reactive protein, individual cytokines/chemokines and Cytokine Score to the outcomes: positivity for RF and for the HRP using logistic regression.
Adjusting for age, sex, ethnicity and ever smoking, the Cytokine Score and levels of IL-6 and IL-9 were associated with both RF and HRP. IL-2, granulocyte macrophage-colony stimulating factor (GM-CSF), and interferon (IFN)-γ were associated with HRP only. Associations between the Cytokine Score and RF and HRP positivity were replicated in an independent military personnel cohort.
In first-degree relatives of patients with RA, RA-related autoimmunity is associated with inflammation, as evidenced by associations with multiple cytokines and chemokines.
PMCID: PMC3726193  PMID: 22915618
3.  Risk for Myasthenia Gravis maps to 151Pro→ Ala change in TNIP1 and to HLA-B*08 
Annals of neurology  2012;72(6):927-935.
The objective of this study is to comprehensively define the genetic basis of Early Onset Myasthenia Gravis.
We have carried out a two-stage genome-wide association study on a total of 649 North European EOMG patients. Cases were matched 1:4 with controls of European ancestry. We performed imputation and conditional analyses across the major histocompatibility complex, as well as in the top regions of association outside the HLA region.
We observed the strongest association in the HLA class I region at rs7750641 (p = 1.2 × 10−92, OR = 6.25). By imputation and conditional analyses, HLA-B*08 proves to be the major associated allele (p = 2.87 × 10−113, OR = 6.41). In addition to the expected association with PTPN22 (rs2476601, OR =1.71, p = 8.2 ×10−10), an imputed coding variant (rs2233290) at position 151 (Pro→Ala) in the TNFAIP3-interacting protein 1, TNIP1, confers even stronger risk than PTPN22 (OR = 1.91, p = 3.2 × 10−10).
The association at TNIP1 in EOMG implies disease mechanisms involving ubiquitin-dependent dysregulation of NF-κB signaling. The localization of the major HLA signal to the HLA-B*08 allele suggests that CD8+ T-cells may play a key role in disease initiation or pathogenesis.
PMCID: PMC3535539  PMID: 23055271
4.  European Population Substructure Correlates with Systemic Lupus Erythematosus Endophenotypes in North Americans of European Descent 
Genes and immunity  2009;11(6):515-521.
Previous work has demonstrated that northern and southern European ancestries are associated with specific systemic lupus erythematosus (SLE) manifestations. Here, 1855 SLE cases of European descent were genotyped for 4965 single nucleotide polymorphisms and principal components analysis of genotype information was used to define population substructure. The first principal component (PC1) distinguished northern from southern European ancestry, PC2 differentiated eastern from western European ancestry, and PC3 delineated Ashkenazi Jewish ancestry. Compared to northern European ancestry, southern European ancestry was associated with autoantibody production (OR=1.40, 95% CI 1.07-1.83) and renal involvement (OR 1.41, 95% CI 1.06-1.87), and was protective for discoid rash (OR=0.51, 95% CI 0.32-0.82) and photosensitivity (OR=0.74, 95% CI 0.56-0.97). Both serositis (OR=1.46, 95% CI 1.12-1.89) and autoantibody production (OR=1.38, 95% CI 1.06-1.80) were associated with Western compared to Eastern European ancestry. Ashkenazi Jewish ancestry was protective against neurologic manifestations of SLE (OR=0.62, 95% CI 0.40-0.94). Homogeneous clusters of cases defined by multiple PCs demonstrated stronger phenotypic associations. Genetic ancestry may contribute to the development of SLE endophenotypes and should be accounted for in genetic studies of disease characteristics.
PMCID: PMC3951966  PMID: 19847193
Systemic lupus erythematosus; epidemiology; population substructure; genetics
5.  Integration of Sequence Data from a Consanguineous Family with Genetic Data from an Outbred Population Identifies PLB1 as a Candidate Rheumatoid Arthritis Risk Gene 
PLoS ONE  2014;9(2):e87645.
Integrating genetic data from families with highly penetrant forms of disease together with genetic data from outbred populations represents a promising strategy to uncover the complete frequency spectrum of risk alleles for complex traits such as rheumatoid arthritis (RA). Here, we demonstrate that rare, low-frequency and common alleles at one gene locus, phospholipase B1 (PLB1), might contribute to risk of RA in a 4-generation consanguineous pedigree (Middle Eastern ancestry) and also in unrelated individuals from the general population (European ancestry). Through identity-by-descent (IBD) mapping and whole-exome sequencing, we identified a non-synonymous c.2263G>C (p.G755R) mutation at the PLB1 gene on 2q23, which significantly co-segregated with RA in family members with a dominant mode of inheritance (P = 0.009). We further evaluated PLB1 variants and risk of RA using a GWAS meta-analysis of 8,875 RA cases and 29,367 controls of European ancestry. We identified significant contributions of two independent non-coding variants near PLB1 with risk of RA (rs116018341 [MAF = 0.042] and rs116541814 [MAF = 0.021], combined P = 3.2×10−6). Finally, we performed deep exon sequencing of PLB1 in 1,088 RA cases and 1,088 controls (European ancestry), and identified suggestive dispersion of rare protein-coding variant frequencies between cases and controls (P = 0.049 for C-alpha test and P = 0.055 for SKAT). Together, these data suggest that PLB1 is a candidate risk gene for RA. Future studies to characterize the full spectrum of genetic risk in the PLB1 genetic locus are warranted.
PMCID: PMC3919745  PMID: 24520335
6.  Genome-wide association study implicates NDST3 in schizophrenia and bipolar disorder 
Nature Communications  2013;4:2739.
Schizophrenia and bipolar disorder are major psychiatric disorders with high heritability and overlapping genetic variance. Here we perform a genome-wide association study in an ethnically homogeneous cohort of 904 schizophrenia cases and 1,640 controls drawn from the Ashkenazi Jewish population. We identify a novel genome-wide significant risk locus at chromosome 4q26, demonstrating the potential advantages of this founder population for gene discovery. The top single-nucleotide polymorphism (SNP; rs11098403) demonstrates consistent effects across 11 replication and extension cohorts, totalling 23, 191 samples across multiple ethnicities, regardless of diagnosis (schizophrenia or bipolar disorder), resulting in Pmeta=9.49 × 10−12 (odds ratio (OR)=1.13, 95% confidence interval (CI): 1.08–1.17) across both disorders and Pmeta=2.67 × 10−8 (OR=1.15, 95% CI: 1.08–1.21) for schizophrenia alone. In addition, this intergenic SNP significantly predicts postmortem cerebellar gene expression of NDST3, which encodes an enzyme critical to heparan sulphate metabolism. Heparan sulphate binding is critical to neurite outgrowth, axon formation and synaptic processes thought to be aberrant in these disorders.
Schizophrenia and bipolar disorder are important psychiatric disorders with overlapping genetic components. Here, the authors identify and replicate a genome-wide significant risk locus for the two disorders, and suggest a role for NDST3 in severe psychiatric disease.
PMCID: PMC3905728  PMID: 24253340
7.  Multiple polymorphisms in the TNFAIP3 region are independently associated with systemic lupus erythematosus 
Nature genetics  2008;40(9):1062-1064.
The TNFAIP3 (tumor necrosis factor alpha–induced protein 3) gene encodes a ubiquitin editing enzyme, A20, that restricts NF-κB–dependent signaling and prevents inflammation. We show that three independent SNPs in the TNFAIP3 region (rs13192841, rs2230926 and rs6922466) are associated with systemic lupus erythematosus (SLE) among individuals of European ancestry. These findings provide critical links between A20 and the etiology of SLE.
PMCID: PMC3897246  PMID: 19165919
8.  Genome-Wide Association Study Reveals Novel Genetic Determinants of DNA Repair Capacity in Lung Cancer 
Cancer research  2012;73(1):256-264.
Suboptimal cellular DNA repair capacity (DRC) has been shown to be associated with enhanced cancer risk, but genetic variants affecting the DRC phenotype have not been comprehensively investigated. In this study, with the available DRC phenotype data, we analyzed correlations between the DRC phenotype and genotypes detected by the Illumina 317K platform in 1,774 individuals of European ancestry from a Texas lung cancer genome-wide association study. The discovery phase was followed by a replication in an independent set of 1,374 cases and controls of European ancestry. We applied a generalized linear model with SNPs as predictors and DRC (a continuous variable) as the outcome. Covariates of age, sex, pack-years of smoking, DRC assay-related variables and case-control status of the study participants were adjusted in the model. We validated that reduced DRC was associated with an increased risk of lung cancer in both independent datasets. Several suggestive loci that contributed to the DRC phenotype were defined in ERCC2/XPD, PHACTR2 and DUSP1. In summary, we determined that DRC is an independent risk factor for lung cancer and we defined several genetic loci contributing to DRC phenotype.
PMCID: PMC3537906  PMID: 23108145
DNA repair capacity; genetic susceptibility; genome-wide association; molecular epidemiology
9.  Gene expression patterns in peripheral blood cells associated with radiographic severity in African Americans with early rheumatoid arthritis 
Rheumatology international  2012;33(1):129-137.
Gene expression profiling may be used to stratify patients by disease severity to test the hypothesis that variable disease outcome has a genetic component. In order to define unique expression signatures in African American rheumatoid arthritis (RA) patients with severe erosive disease, we undertook a gene expression study using samples of RNA from peripheral blood mononuclear cells (PBMCs). RNA from baseline PBMC samples of 96 African American RA patients with early RA (<2 years disease duration) was hybridized to cDNA probes of the Illumina Human HT-V3 expression array. Expression analyses were performed using the ca. 25,000 cDNA probes, and then expression levels were compared to the total number of erosions in radiographs of the hands and feet at baseline and 36 months. Using a false discovery rate cutoff of Q = 0.30, 1,138 genes at baseline and 680 genes at 36 months significantly correlated with total erosions. No evidence of a signal differentiating disease progression, or change in erosion scores between baseline and 36 months, was found. Further analyses demonstrated that the differential gene expression signature was localized to the patients with the most erosive disease (>10 erosions). Ingenuity Pathway Analysis demonstrated that genes with fold change greater than 1.5 implicated immune pathways such as CTLA signaling in cytotoxic T lymphocytes. These results demonstrate that CLEAR patients with early RA having the most severe erosive disease, as compared to more mild cases (<10 erosions), may be characterized by a set of differentially expressed genes that represent biological pathways with relevance to autoimmune disease.
PMCID: PMC3769702  PMID: 22238028
Genome-wide gene expression; Sharp/van der Heijde; Pathway analysis; CLEAR; ABCoN
10.  Extended haplotype association study in Crohn’s disease identifies a novel, Ashkenazi Jewish-specific missense mutation in the NF-κB pathway gene, HEATR3 
Genes and immunity  2013;14(5):310-316.
The Ashkenazi Jewish population has a several-fold higher prevalence of Crohn’s disease compared to non-Jewish European ancestry populations and has a unique genetic history. Haplotype association is critical to Crohn’s disease etiology in this population, most notably at NOD2, in which three causal, uncommon, and conditionally independent NOD2 variants reside on a shared background haplotype. We present an analysis of extended haplotypes which showed significantly greater association to Crohn’s disease in the Ashkenazi Jewish population compared to a non-Jewish population (145 haplotypes and no haplotypes with P-value < 10−3, respectively). Two haplotype regions, one each on chromosomes 16 and 21, conferred increased disease risk within established Crohn’s disease loci. We performed exome sequencing of 55 Ashkenazi Jewish individuals and follow-up genotyping focused on variants in these two regions. We observed Ashkenazi Jewish-specific nominal association at R755C in TRPM2 on chromosome 21. Within the chromosome 16 region, R642S of HEATR3 and rs9922362 of BRD7 showed genome-wide significance. Expression studies of HEATR3 demonstrated a positive role in NOD2-mediated NF-κB signaling. The BRD7 signal showed conditional dependence with only the downstream rare Crohn’s disease-causal variants in NOD2, but not with the background haplotype; this elaborates NOD2 as a key illustration of synthetic association.
PMCID: PMC3785105  PMID: 23615072
haplotype association; Ashkenazi Jewish; Crohn’s disease; NF-κB signaling; synthetic association
11.  Quantifying Missing Heritability at Known GWAS Loci 
PLoS Genetics  2013;9(12):e1003993.
Recent work has shown that much of the missing heritability of complex traits can be resolved by estimates of heritability explained by all genotyped SNPs. However, it is currently unknown how much heritability is missing due to poor tagging or additional causal variants at known GWAS loci. Here, we use variance components to quantify the heritability explained by all SNPs at known GWAS loci in nine diseases from WTCCC1 and WTCCC2. After accounting for expectation, we observed all SNPs at known GWAS loci to explain more heritability than GWAS-associated SNPs on average (). For some diseases, this increase was individually significant: for Multiple Sclerosis (MS) () and for Crohn's Disease (CD) (); all analyses of autoimmune diseases excluded the well-studied MHC region. Additionally, we found that GWAS loci from other related traits also explained significant heritability. The union of all autoimmune disease loci explained more MS heritability than known MS SNPs () and more CD heritability than known CD SNPs (), with an analogous increase for all autoimmune diseases analyzed. We also observed significant increases in an analysis of Rheumatoid Arthritis (RA) samples typed on ImmunoChip, with more heritability from all SNPs at GWAS loci () and more heritability from all autoimmune disease loci () compared to known RA SNPs (including those identified in this cohort). Our methods adjust for LD between SNPs, which can bias standard estimates of heritability from SNPs even if all causal variants are typed. By comparing adjusted estimates, we hypothesize that the genome-wide distribution of causal variants is enriched for low-frequency alleles, but that causal variants at known GWAS loci are skewed towards common alleles. These findings have important ramifications for fine-mapping study design and our understanding of complex disease architecture.
Author Summary
Heritable diseases have an unknown underlying “genetic architecture” that defines the distribution of effect-sizes for disease-causing mutations. Understanding this genetic architecture is an important first step in designing disease-mapping studies, and many theories have been developed on the nature of this distribution. Here, we evaluate the hypothesis that additional heritable variation lies at previously known associated loci but is not fully explained by the single most associated marker. We develop methods based on variance-components analysis to quantify this type of “local” heritability, demonstrating that standard strategies can be falsely inflated or deflated due to correlation between neighboring markers and propose a robust adjustment. In analysis of nine common diseases we find a significant average increase of local heritability, consistent with multiple common causal variants at an average locus. Intriguingly, for autoimmune diseases we also observe significant local heritability in loci not associated with the specific disease but with other autoimmune diseases, implying a highly correlated underlying disease architecture. These findings have important implications to the design of future studies and our general understanding of common disease.
PMCID: PMC3873246  PMID: 24385918
12.  European Genetic Ancestry is Associated with a Decreased Risk of Lupus Nephritis 
Arthritis and rheumatism  2012;64(10):10.1002/art.34567.
African Americans, East Asians, and Hispanics with systemic lupus erythematosus (SLE) are more likely to develop renal disease than SLE patients of European descent. We investigated whether European genetic ancestry protects against the development of lupus nephritis and explored genetic and socioeconomic factors that might explain this effect.
This was a cross-sectional study of 1906 adults with SLE. Participants were genotyped for 126 single nucleotide polymorphisms (SNPs) informative for ancestry. A subset of participants was also genotyped for 80 SNPs in 14 candidate genes for renal disease in SLE. We used logistic regression to test the association between European ancestry and renal disease. Analyses adjusted for continental ancestries, socioeconomic status, and candidate genes.
Participants (n=1906) had on average 62.4% European, 15.8% African, 11.5% East Asian, 6.5% Amerindian, and 3.8% South Asian ancestry. Among participants, 34% (n=656) had renal disease. A 10% increase in European ancestry was associated with a 15% reduction in the odds of having renal disease after adjustment for disease duration and sex (OR 0.85, 95% CI 0.82-0.87, p=1.9 × 10−30). Adjusting for other genetic ancestries, measures of socioeconomic status, or SNPs in genes most associated with renal disease (IRF5 (rs4728142), BLK (rs2736340), STAT4 (rs3024912), ITGAM (rs9937837) and HLA-DRB1*0301 and DRB1*1501, p<0.05) did not substantively alter this relationship.
European ancestry is protective against the development of renal disease in SLE, an effect independent of other genetic ancestries, common risk alleles, and socioeconomic status.
PMCID: PMC3865923  PMID: 23023776
13.  Immunochip analyses identify a novel risk locus for primary biliary cirrhosis at 13q14, multiple independent associations at four established risk loci and epistasis between 1p31 and 7q32 risk variants 
Human Molecular Genetics  2012;21(23):5209-5221.
To further characterize the genetic basis of primary biliary cirrhosis (PBC), we genotyped 2426 PBC patients and 5731 unaffected controls from three independent cohorts using a single nucleotide polymorphism (SNP) array (Immunochip) enriched for autoimmune disease risk loci. Meta-analysis of the genotype data sets identified a novel disease-associated locus near the TNFSF11 gene at 13q14, provided evidence for association at six additional immune-related loci not previously implicated in PBC and confirmed associations at 19 of 22 established risk loci. Results of conditional analyses also provided evidence for multiple independent association signals at four risk loci, with haplotype analyses suggesting independent SNP effects at the 2q32 and 16p13 loci, but complex haplotype driven effects at the 3q25 and 6p21 loci. By imputing classical HLA alleles from this data set, four class II alleles independently contributing to the association signal from this region were identified. Imputation of genotypes at the non-HLA loci also provided additional associations, but none with stronger effects than the genotyped variants. An epistatic interaction between the IL12RB2 risk locus at 1p31and the IRF5 risk locus at 7q32 was also identified and suggests a complementary effect of these loci in predisposing to disease. These data expand the repertoire of genes with potential roles in PBC pathogenesis that need to be explored by follow-up biological studies.
PMCID: PMC3490520  PMID: 22936693
14.  Is synaesthesia more common in autism? 
Molecular Autism  2013;4:40.
Synaesthesia is a neurodevelopmental condition in which a sensation in one modality triggers a perception in a second modality. Autism (shorthand for Autism Spectrum Conditions) is a neurodevelopmental condition involving social-communication disability alongside resistance to change and unusually narrow interests or activities. Whilst on the surface they appear distinct, they have been suggested to share common atypical neural connectivity.
In the present study, we carried out the first prevalence study of synaesthesia in autism to formally test whether these conditions are independent. After exclusions, 164 adults with autism and 97 controls completed a synaesthesia questionnaire, Autism Spectrum Quotient, and Test of Genuineness-Revised (ToG-R) online.
The rate of synaesthesia in adults with autism was 18.9% (31 out of 164), almost three times greater than in controls (7.22%, 7 out of 97, P <0.05). ToG-R proved unsuitable for synaesthetes with autism.
The significant increase in synaesthesia prevalence in autism suggests that the two conditions may share some common underlying mechanisms. Future research is needed to develop more feasible validation methods of synaesthesia in autism.
PMCID: PMC3834557  PMID: 24252644
15.  Porphyromonas gingivalis and Disease-Related Autoantibodies in Individuals at Increased Risk of Rheumatoid Arthritis 
Arthritis and rheumatism  2012;64(11):10.1002/art.34595.
To examine the relationship of Porphyromonas gingivalis (Pg) with the presence of autoantibodies in individuals at risk for rheumatoid arthritis (RA).
Participants included: 1) a cohort enriched with HLA-DR4 and 2) those at risk for RA by virtue of having a first-degree relative with RA. None satisfied 1987 ACR RA classification criteria. Autoantibodies measured included anti-citrullinated protein antibody (ACPA) and rheumatoid factor (RF; nephelometry, IgA, IgM, IgG). Individuals were considered autoantibody positive (n = 113) with ≥ 1 positive autoantibody with individuals further categorized as `high-risk' (n = 38; positive ACPA or ≥ 2 RF assays). Autoantibody negative individuals served as comparators (n = 171). Antibody to Pg, P. intermedia (Pi), and F. nucleatum (Fn) were measured. Associations of bacterial antibodies with group status were examined using logistic regression.
Anti-Pg concentrations were higher in high-risk (p = 0.011) and autoantibody positive group (p = 0.010) than in the autoantibody negative group. There were no group differences in anti-Pi or anti-Fn concentrations. After multivariable adjustment, anti-Pg concentrations (but not anti-Pi or anti-Fn) were significantly associated with autoantibody positive and high-risk status (p < 0.05).
Immunity to Pg, but not Pi or Fn, is significantly associated with the presence of RA-related autoantibodies in individuals at risk for RA. These results support the hypothesis that infection with Pg may play a central role in the early loss of tolerance to self-antigens in RA pathogenesis.
PMCID: PMC3467347  PMID: 22736291
rheumatoid arthritis; periodontitis; Porphyromonas gingivalis; Prevotella intermedia; Fusobacterium nucleatum; rheumatoid factor; anti-citrullinated protein antibody
16.  The autoimmunity-associated BLK haplotype exhibits cis-regulatory effects on mRNA and protein expression that are prominently observed in B cells early in development 
Human Molecular Genetics  2012;21(17):3918-3925.
The gene B lymphocyte kinase (BLK) is associated with rheumatoid arthritis, systemic lupus erythematosus and several other autoimmune disorders. The disease risk haplotype is known to be associated with reduced expression of BLK mRNA transcript in human B cell lines; however, little is known about cis-regulation of BLK message or protein levels in native cell types. Here, we show that in primary human B lymphocytes, cis-regulatory effects of disease-associated single nucleotide polymorphisms in BLK are restricted to naïve and transitional B cells. Cis-regulatory effects are not observed in adult B cells in later stages of differentiation. Allelic expression bias was also identified in primary human T cells from adult peripheral and umbilical cord blood (UCB), thymus and tonsil, although mRNA levels were reduced compared with B cells. Allelic regulation of Blk expression at the protein level was confirmed in UCB B cell subsets by intracellular staining and flow cytometry. Blk protein expression in CD4+ and CD8+ T cells was documented by western blot analysis; however, differences in protein expression levels by BLK genotype were not observed in any T cell subset. Blk allele expression differences at the protein level are thus restricted to early B cells, indicating that the involvement of Blk in the risk for autoimmune disease likely acts during the very early stages of B cell development.
PMCID: PMC3412385  PMID: 22678060
17.  A rare deletion at distal 16p11.2 is implicated in schizophrenia 
JAMA psychiatry (Chicago, Ill.)  2013;70(3):253-260.
Large genomic copy number variations (CNVs) have been implicated as strong risk factors for schizophrenia. However, the rarity of these events has created challenges for the identification of further pathogenic loci, and extremely large samples are required to provide convincing replication.
To detect novel CNVs increasing susceptibility to schizophrenia, utilizing two ethnically homogeneous discovery cohorts and replication in large samples.
Genetic association study of microarray data.
DNA samples were collected at nine sites from different countries.
Two discovery cohorts were comprised of: a) 790 cases (schizophrenia and schizoaffective disorder) and 1347 controls of Ashkenazi Jewish descent; and b) 662 trios (offspring affected with schizophrenia or schizoaffective disorder) from Bulgaria. Replication datasets consisted of 12,398 cases and 17,945 controls.
Main outcome measure
Statistically increased rate of specific CNVs in cases versus controls.
One novel locus was implicated: a deletion at distal 16p11.2, which does not overlap the proximal 16p11.2 locus previously reported in schizophrenia and autism. Deletions at this locus were found in 13 out of 13,850 cases (0.094%) and in 3 out of 19,954 controls (0.015%), Fisher Exact p = 0.0014; OR = 6.25 (95%CI = 1.78 – 21.93).
Deletions at distal 16p11.2 have been previously implicated in developmental delay and obesity. The region contains nine genes, several of which are implicated in neurological diseases, regulation of body weight, and glucose homeostasis. A telomeric extension of the deletion, observed in about half the cases but no controls, potentially implicates an additional eight genes. Our findings add a new locus to the list of CNVs that increase risk to develop schizophrenia.
PMCID: PMC3750982  PMID: 23325106
18.  CSK regulatory polymorphism is associated with systemic lupus erythematosus and influences B cell signaling and activation 
Nature genetics  2012;44(11):1227-1230.
C-src tyrosine kinase, Csk, physically interacts with the intracellular phosphatase Lyp (PTPN22) and can modify the activation state of downstream Src kinases, such as Lyn, in lymphocytes. We identified an association of Csk with systemic lupus erythematosus (SLE) and refined its location to an intronic polymorphism rs34933034 (OR 1.32, p = 1.04 × 10−9). The risk allele is associated with increased CSK expression and augments inhibitory phosphorylation of Lyn. In carriers of the risk allele, B cell receptor (BCR)-mediated activation of mature B cells, as well as plasma IgM, are increased. Moreover, the fraction of transitional B cells is doubled in the cord blood of carriers of the risk allele compared to non-risk haplotypes due to an expansion of the late transitional cells, a stage targeted by selection mechanisms. This suggests that the Lyp-Csk complex increases susceptibility to lupus at multiple maturation and activation points of B cells.
PMCID: PMC3715052  PMID: 23042117
19.  Genome-wide association scan in women with systemic lupus erythematosus identifies susceptibility variants in ITGAM, PXK, KIAA1542 and other loci 
Nature genetics  2008;40(2):204-210.
Systemic lupus erythematosus (SLE) is a common systemic autoimmune disease with complex etiology but strong clustering in families (λS = ~30). We performed a genome-wide association scan using 317,501 SNPs in 720 women of European ancestry with SLE and in 2,337 controls, and we genotyped consistently associated SNPs in two additional independent sample sets totaling 1,846 affected women and 1,825 controls. Aside from the expected strong association between SLE and the HLA region on chromosome 6p21 and the previously confirmed non-HLA locus IRF5 on chromosome 7q32, we found evidence of association with replication (1.1 × 10−7 < Poverall < 1.6 × 10−23; odds ratio 0.82–1.62)in four regions: 16p11.2 (ITGAM), 11p15.5 (KIAA1542), 3p14.3 (PXK) and 1q25.1 (rs10798269). We also found evidence for association (P < 1 × 10−5) at FCGR2A, PTPN22 and STAT4, regions previously associated with SLE and other autoimmune diseases, as well as at ≥9 other loci (P < 2 × 10−7). Our results show that numerous genes, some with known immune-related functions, predispose to SLE.
PMCID: PMC3712260  PMID: 18204446
20.  Genome-wide Association Study of N370S Homozygous Gaucher Disease Reveals the Candidacy of CLN8 gene as a Genetic Modifier Contributing to Extreme Phenotypic Variation 
American journal of hematology  2012;87(4):377-383.
Mutations in GBA1 gene result in defective acid β-glucosidase and the complex phenotype of Gaucher disease (GD) related to the accumulation of glucosylceramide-laden macrophages. The phenotype is highly variable even among patients harboring identical GBA1 mutations. We hypothesized that modifier gene(s) underlie phenotypic diversity in GD and performed a GWAS study in Ashkenazi Jewish patients with type 1 GD (GD1), homozygous for N370S mutation. Patients were assigned to mild, moderate or severe disease category using composite disease severity scoring systems. Whole-genome genotyping for >500,000 SNPs was performed to search for associations using OQLS algorithm in 139 eligible patients. Several SNPs in linkage disequilibrium within the CLN8 gene locus were associated with the GD1 severity: SNP rs11986414 was associated with GD1 severity at p value 1.26 × 10−6. Compared to mild disease, risk allele A at rs11986414 conferred an odds ratio of 3.72 for moderate/severe disease. Loss of function mutations in CLN8 causes neuronal ceroid-lipofuscinosis but our results indicate that its increased expression may protect against severe GD1. In cultured skin fibroblasts, the relative expression of CLN8 was higher in mild GD compared to severely affected patients in whom CLN8 risk alleles were over-represented. In an in vitro cell model of GD, CLN8 expression was increased which was further enhanced in the presence of bioactive substrate, glucosylsphingosine. Taken together, CLN8 is a candidate modifier gene for GD1 that may function as a protective sphingolipid sensor and/or in glycosphingolipid trafficking. Future studies should explore the role of CLN8 in pathophysiology of GD.
PMCID: PMC3684025  PMID: 22388998
Gaucher disease; GWAS; genotype/phenotype correlations; phenotypic diversity; modifier genes; CLN8; N370S; GBA mutations
21.  High density genetic mapping identifies new susceptibility loci for rheumatoid arthritis 
Nature genetics  2012;44(12):1336-1340.
Using the Immunochip custom single nucleotide polymorphism (SNP) array, designed for dense genotyping of 186 genome wide association study (GWAS) confirmed loci we analysed 11,475 rheumatoid arthritis cases of European ancestry and 15,870 controls for 129,464 markers. The data were combined in meta-analysis with GWAS data from additional independent cases (n=2,363) and controls (n=17,872). We identified fourteen novel loci; nine were associated with rheumatoid arthritis overall and 5 specifically in anti-citrillunated peptide antibody positive disease, bringing the number of confirmed European ancestry rheumatoid arthritis loci to 46. We refined the peak of association to a single gene for 19 loci, identified secondary independent effects at six loci and association to low frequency variants (minor allele frequency <0.05) at 4 loci. Bioinformatic analysis of the data generated strong hypotheses for the causal SNP at seven loci. This study illustrates the advantages of dense SNP mapping analysis to inform subsequent functional investigations.
PMCID: PMC3605761  PMID: 23143596
22.  Human Genetics in Rheumatoid Arthritis Guides a High-Throughput Drug Screen of the CD40 Signaling Pathway 
PLoS Genetics  2013;9(5):e1003487.
Although genetic and non-genetic studies in mouse and human implicate the CD40 pathway in rheumatoid arthritis (RA), there are no approved drugs that inhibit CD40 signaling for clinical care in RA or any other disease. Here, we sought to understand the biological consequences of a CD40 risk variant in RA discovered by a previous genome-wide association study (GWAS) and to perform a high-throughput drug screen for modulators of CD40 signaling based on human genetic findings. First, we fine-map the CD40 risk locus in 7,222 seropositive RA patients and 15,870 controls, together with deep sequencing of CD40 coding exons in 500 RA cases and 650 controls, to identify a single SNP that explains the entire signal of association (rs4810485, P = 1.4×10−9). Second, we demonstrate that subjects homozygous for the RA risk allele have ∼33% more CD40 on the surface of primary human CD19+ B lymphocytes than subjects homozygous for the non-risk allele (P = 10−9), a finding corroborated by expression quantitative trait loci (eQTL) analysis in peripheral blood mononuclear cells from 1,469 healthy control individuals. Third, we use retroviral shRNA infection to perturb the amount of CD40 on the surface of a human B lymphocyte cell line (BL2) and observe a direct correlation between amount of CD40 protein and phosphorylation of RelA (p65), a subunit of the NF-κB transcription factor. Finally, we develop a high-throughput NF-κB luciferase reporter assay in BL2 cells activated with trimerized CD40 ligand (tCD40L) and conduct an HTS of 1,982 chemical compounds and FDA–approved drugs. After a series of counter-screens and testing in primary human CD19+ B cells, we identify 2 novel chemical inhibitors not previously implicated in inflammation or CD40-mediated NF-κB signaling. Our study demonstrates proof-of-concept that human genetics can be used to guide the development of phenotype-based, high-throughput small-molecule screens to identify potential novel therapies in complex traits such as RA.
Author Summary
A current challenge in human genetics is to follow-up “hits” from genome-wide association studies (GWAS) to guide drug discovery for complex traits. Previously, we identified a common variant in the CD40 locus as associated with risk of rheumatoid arthritis (RA). Here, we fine-map the CD40 signal of association through a combination of dense genotyping and exonic sequencing in large patient collections. Further, we demonstrate that the RA risk allele is a gain-of-function allele that increases the amount of CD40 on the surface of primary human B lymphocyte cells from healthy control individuals. Based on these observations, we develop a high-throughput assay to recapitulate the biology of the RA risk allele in a system suitable for a small molecule drug screen. After a series of primary screens and counter screens, we identify small molecules that inhibit CD40-mediated NF-kB signaling in human B cells. While this is only the first step towards a more comprehensive effort to identify CD40-specific inhibitors that may be used to treat RA, our study demonstrates a successful strategy to progress from a GWAS to a drug screen for complex traits such as RA.
PMCID: PMC3656093  PMID: 23696745
23.  Rheumatoid Arthritis Risk Allele PTPRC Is Also Associated With Response to Anti–Tumor Necrosis Factor α Therapy 
Arthritis and rheumatism  2010;62(7):1849-1861.
Anti–tumor necrosis factor α (anti-TNF) therapy is a mainstay of treatment in rheumatoid arthritis (RA). The aim of the present study was to test established RA genetic risk factors to determine whether the same alleles also influence the response to anti-TNF therapy.
A total of 1,283 RA patients receiving etanercept, infliximab, or adalimumab therapy were studied from among an international collaborative consortium of 9 different RA cohorts. The primary end point compared RA patients with a good treatment response according to the European League Against Rheumatism (EULAR) response criteria (n = 505) with RA patients considered to be nonresponders (n = 316). The secondary end point was the change from baseline in the level of disease activity according to the Disease Activity Score in 28 joints (ΔDAS28). Clinical factors such as age, sex, and concomitant medications were tested as possible correlates of treatment response. Thirty-one single-nucleotide polymorphisms (SNPs) associated with the risk of RA were genotyped and tested for any association with treatment response, using univariate and multivariate logistic regression models.
Of the 31 RA-associated risk alleles, a SNP at the PTPRC (also known as CD45) gene locus (rs10919563) was associated with the primary end point, a EULAR good response versus no response (odds ratio [OR] 0.55, P = 0.0001 in the multivariate model). Similar results were obtained using the secondary end point, the ΔDAS28 (P = 0.0002). There was suggestive evidence of a stronger association in autoantibody-positive patients with RA (OR 0.55, 95% confidence interval [95% CI] 0.39–0.76) as compared with autoantibody-negative patients (OR 0.90, 95% CI 0.41–1.99).
Statistically significant associations were observed between the response to anti-TNF therapy and an RA risk allele at the PTPRC gene locus. Additional studies will be required to replicate this finding in additional patient collections.
PMCID: PMC3652476  PMID: 20309874
24.  Association of Single Nucleotide Polymorphisms (SNPs) in CCR6, TAGAP and TNFAIP3 with Rheumatoid Arthritis in African Americans 
Arthritis and Rheumatism  2012;64(5):1355-1358.
We previously reported an analysis of single nucleotide polymorphisms (SNPs) in three validated European rheumatoid arthritis (RA) susceptibility loci, TAGAP, TNFAIP3, and CCR6 in African-Americans with RA. Unexpectedly, the disease-associated alleles were different in African-Americans than in Europeans. In an effort to better define their contribution, we performed additional SNP genotyping in these genes.
Seven SNPs were genotyped in 446 African Americans with RA and 733 African American controls. Differences in minor allele frequency between cases and controls were analyzed after controlling for global proportion of European admixture, and pairwise linkage disequilibrium (LD) was estimated among the SNPs.
Three SNPs were significantly associated with RA: TNFAIP3 rs719149 A allele (OR (95% CI) 1.22 (1.03–1.44) (p =0.02); TAGAP rs1738074 G allele OR 0.75 (0.63–0.89), (p =0.0012); and TAGAP rs4709267 G allele 0.74 (0.60–0.91), (p =0.004). Pairwise LD between the TAGAP SNPs was low (R2=0.034). The haplotype containing minor alleles for both TAGAP SNPs was uncommon (4.5%). After conditional analysis on each TAGAP SNP, its counterpart remained significantly associated with RA (rs1738074 for rs4709267 p=0.00001; rs4709267 for rs1738074 p=0.00005), suggesting independent effects.
SNPs in regulatory regions of TAGAP and an intronic SNP (TNFAIP3) are potential susceptibility loci in African Americans. Pairwise LD, haplotype analysis, and SNP conditioning analysis suggest that these two SNPs in TAGAP are independent susceptibility alleles. Additional fine mapping of this gene and functional genomic studies of these SNPs should provide additional insight into the role of these genes in RA.
PMCID: PMC3299842  PMID: 22127930
25.  Genome-Wide Association Study and Gene Expression Analysis Identifies CD84 as a Predictor of Response to Etanercept Therapy in Rheumatoid Arthritis 
PLoS Genetics  2013;9(3):e1003394.
Anti-tumor necrosis factor alpha (anti-TNF) biologic therapy is a widely used treatment for rheumatoid arthritis (RA). It is unknown why some RA patients fail to respond adequately to anti-TNF therapy, which limits the development of clinical biomarkers to predict response or new drugs to target refractory cases. To understand the biological basis of response to anti-TNF therapy, we conducted a genome-wide association study (GWAS) meta-analysis of more than 2 million common variants in 2,706 RA patients from 13 different collections. Patients were treated with one of three anti-TNF medications: etanercept (n = 733), infliximab (n = 894), or adalimumab (n = 1,071). We identified a SNP (rs6427528) at the 1q23 locus that was associated with change in disease activity score (ΔDAS) in the etanercept subset of patients (P = 8×10−8), but not in the infliximab or adalimumab subsets (P>0.05). The SNP is predicted to disrupt transcription factor binding site motifs in the 3′ UTR of an immune-related gene, CD84, and the allele associated with better response to etanercept was associated with higher CD84 gene expression in peripheral blood mononuclear cells (P = 1×10−11 in 228 non-RA patients and P = 0.004 in 132 RA patients). Consistent with the genetic findings, higher CD84 gene expression correlated with lower cross-sectional DAS (P = 0.02, n = 210) and showed a non-significant trend for better ΔDAS in a subset of RA patients with gene expression data (n = 31, etanercept-treated). A small, multi-ethnic replication showed a non-significant trend towards an association among etanercept-treated RA patients of Portuguese ancestry (n = 139, P = 0.4), but no association among patients of Japanese ancestry (n = 151, P = 0.8). Our study demonstrates that an allele associated with response to etanercept therapy is also associated with CD84 gene expression, and further that CD84 expression correlates with disease activity. These findings support a model in which CD84 genotypes and/or expression may serve as a useful biomarker for response to etanercept treatment in RA patients of European ancestry.
Author Summary
There are no genetic predictors of response to one of the most widely used classes of drugs in the treatment of rheumatoid arthritis—biological modifiers of the inflammatory cytokine tumor necrosis factor-alpha (or anti-TNF therapy). To identify genetic predictors, we performed the largest genome-wide association study (GWAS) to date as part of an international collaboration. In our study, which included 2,706 RA patients treated with one of three anti-TNF drugs, the most significant finding was restricted to RA patients treated with etanercept (P = 8×10−8), a drug that acts as a soluble receptor to bind circulating cytokine and prevents TNF from binding to its cell surface receptor. The associated variant influences expression of a nearby immune-related gene, CD84, whose expression is correlated with disease activity in RA patients. Together, our data support a model in which genomic factors related to CD84 expression serve as a predictor of disease activity and response to etanercept therapy among RA patients of European ancestry, but not anti-TNF therapies that act through different biological mechanisms or potentially in RA patients of other genetic ancestries.
PMCID: PMC3610685  PMID: 23555300

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