Immunochip analysis identifies multiple susceptibility loci for systemic sclerosis.

In this study, 1,833 systemic sclerosis (SSc) cases and 3,466 controls were genotyped with the Immunochip array. Classical alleles, amino acid residues, and SNPs across the human leukocyte antigen (HLA) region were imputed and tested. These analyses resulted in a model composed of six polymorphic amino acid positions and seven SNPs that explained the observed significant associations in the region. In addition, a replication step comprising 4,017 SSc cases and 5,935 controls was carried out for several selected non-HLA variants, reaching a total of 5,850 cases and 9,401 controls of European ancestry. Following this strategy, we identified and validated three SSc risk loci, including DNASE1L3 at 3p14, the SCHIP1-IL12A locus at 3q25, and ATG5 at 6q21, as well as a suggested association of the TREH-DDX6 locus at 11q23. The associations of several previously reported SSc risk loci were validated and further refined, and the observed peak of association in PXK was related to DNASE1L3. Our study has increased the number of known genetic associations with SSc, provided further insight into the pleiotropic effects of shared autoimmune risk factors, and highlighted the power of dense mapping for detecting previously overlooked susceptibility loci.

Identification of CSK as a systemic sclerosis genetic risk factor through Genome Wide Association Study follow-up.

Systemic sclerosis (SSc) is complex autoimmune disease affecting the connective tissue; influenced by genetic and environmental components. Recently, we performed the first successful genome-wide association study (GWAS) of SSc. Here, we perform a large replication study to better dissect the genetic component of SSc. We selected 768 polymorphisms from the previous GWAS and genotyped them in seven replication cohorts from Europe. Overall significance was calculated for replicated significant SNPs by meta-analysis of the replication cohorts and replication-GWAS cohorts (3237 cases and 6097 controls). Six SNPs in regions not previously associated with SSc were selected for validation in another five independent cohorts, up to a total of 5270 SSc patients and 8326 controls. We found evidence for replication and overall genome-wide significance for one novel SSc genetic risk locus: CSK [P-value = 5.04 × 10(-12), odds ratio (OR) = 1.20]. Additionally, we found suggestive association in the loci PSD3 (P-value = 3.18 × 10(-7), OR = 1.36) and NFKB1 (P-value = 1.03 × 10(-6), OR = 1.14). Additionally, we strengthened the evidence for previously confirmed associations. This study significantly increases the number of known putative genetic risk factors for SSc, including the genes CSK, PSD3 and NFKB1, and further confirms six previously described ones.

A GWAS follow-up study reveals the association of the IL12RB2 gene with systemic sclerosis in Caucasian populations.

A single-nucleotide polymorphism (SNP) at the IL12RB2 locus showed a suggestive association signal in a previously published genome-wide association study (GWAS) in systemic sclerosis (SSc). Aiming to reveal the possible implication of the IL12RB2 gene in SSc, we conducted a follow-up study of this locus in different Caucasian cohorts. We analyzed 10 GWAS-genotyped SNPs in the IL12RB2 region (2309 SSc patients and 5161 controls). We then selected three SNPs (rs3790567, rs3790566 and rs924080) based on their significance level in the GWAS, for follow-up in an independent European cohort comprising 3344 SSc and 3848 controls. The most-associated SNP (rs3790567) was further tested in an independent cohort comprising 597 SSc patients and 1139 controls from the USA. After conditional logistic regression analysis of the GWAS data, we selected rs3790567 [P(MH)= 1.92 × 10(-5) odds ratio (OR) = 1.19] as the genetic variant with the firmest independent association observed in the analyzed GWAS peak of association. After the first follow-up phase, only the association of rs3790567 was consistent (P(MH)= 4.84 × 10(-3) OR = 1.12). The second follow-up phase confirmed this finding (P(χ2) = 2.82 × 10(-4) OR = 1.34). After performing overall pooled-analysis of all the cohorts included in the present study, the association found for the rs3790567 SNP in the IL12RB2 gene region reached GWAS-level significant association (P(MH)= 2.82 × 10(-9) OR = 1.17). Our data clearly support the IL12RB2 genetic association with SSc, and suggest a relevant role of the interleukin 12 signaling pathway in SSc pathogenesis.

New insight on the Xq28 association with systemic sclerosis.

OBJECTIVE: To evaluate whether the systemic sclerosis (SSc)-associated IRAK1 non-synonymous single-nucleotide polymorphism rs1059702 is responsible for the Xq28 association with SSc or whether there are other independent signals in the nearby methyl-CpG-binding protein 2 gene (MECP2). METHODS: We analysed a total of 3065 women with SSc and 2630 unaffected controls from five independent Caucasian cohorts. Four tag single-nucleotide polymorphisms of MECP2 (rs3027935, rs17435, rs5987201 and rs5945175) and the IRAK1 variant rs1059702 were genotyped using TaqMan predesigned assays. A meta-analysis including all cohorts was performed to test the overall effect of these Xq28 polymorphisms on SSc. RESULTS: IRAK1 rs1059702 and MECP2 rs17435 were associated specifically with diffuse cutaneous SSc (PFDR=4.12×10(-3), OR=1.27, 95% CI 1.09 to 1.47, and PFDR=5.26×10(-4), OR=1.30, 95% CI 1.14 to 1.48, respectively), but conditional logistic regression analysis showed that the association of IRAK1 rs1059702 with this subtype was explained by that of MECP2 rs17435. On the other hand, IRAK1 rs1059702 was consistently associated with presence of pulmonary fibrosis (PF), because statistical significance was observed when comparing SSc patients PF+ versus controls (PFDR=0.039, OR=1.30, 95% CI 1.07 to 1.58) and SSc patients PF+ versus SSc patients PF- (p=0.025, OR=1.26, 95% CI 1.03 to 1.55). CONCLUSIONS: Our data clearly suggest the existence of two independent signals within the Xq28 region, one located in IRAK1 related to PF and another in MECP2 related to diffuse cutaneous SSc, indicating that both genes may have an impact on the clinical outcome of the disease.

Confirmation of TNIP1 but not RHOB and PSORS1C1 as systemic sclerosis risk factors in a large independent replication study.

INTRODUCTION: A recent genome-wide association study in European systemic sclerosis (SSc) patients identified three loci (PSORS1C1, TNIP1 and RHOB) as novel genetic risk factors for the disease. The aim of this study was to replicate the previously mentioned findings in a large multicentre independent SSc cohort of Caucasian ancestry. METHODS: 4389 SSc patients and 7611 healthy controls from different European countries and the USA were included in the study. Six single nucleotide polymorphisms (SNP): rs342070, rs13021401 (RHOB), rs2233287, rs4958881, rs3792783 (TNIP1) and rs3130573 (PSORS1C1) were analysed. Overall significance was calculated by pooled analysis of all the cohorts. Haplotype analyses and conditional logistic regression analyses were carried out to explore further the genetic structure of the tested loci. RESULTS: Pooled analyses of all the analysed SNPs in TNIP1 revealed significant association with the whole disease (rs2233287 p(MH)=1.94×10(-4), OR 1.19; rs4958881 p(MH)=3.26×10(-5), OR 1.19; rs3792783 p(MH)=2.16×10(-4), OR 1.19). These associations were maintained in all the subgroups considered. PSORS1C1 comparison showed association with the complete set of patients and all the subsets except for the anti-centromere-positive patients. However, the association was dependent on different HLA class II alleles. The variants in the RHOB gene were not associated with SSc or any of its subsets. CONCLUSIONS: These data confirmed the influence of TNIP1 on an increased susceptibility to SSc and reinforced this locus as a common autoimmunity risk factor.

Implication of IL-2/IL-21 region in systemic sclerosis genetic susceptibility.

OBJECTIVE: The interleukin 2 (IL-2) and interleukin 21 (IL-21) locus at chromosome 4q27 has been associated with several autoimmune diseases, and both genes are related to immune system functions. The aim of this study was to evaluate the role of the IL-2/IL-21 locus in systemic sclerosis (SSc). PATIENTS AND METHODS: The case control study included 4493 SSc Caucasian patients and 5856 healthy controls from eight Caucasian populations (Spain, Germany, The Netherlands, USA, Italy, Sweden, UK and Norway). Four single nucleotide polymorphisms (rs2069762, rs6822844, rs6835457 and rs907715) were genotyped using TaqMan allelic discrimination assays. RESULTS: We observed evidence of association of the rs6822844 and rs907715 variants with global SSc (pc=6.6E-4 and pc=7.2E-3, respectively). Similar statistically significant associations were observed for the limited cutaneous form of the disease. The conditional regression analysis suggested that the most likely genetic variation responsible for the association was the rs6822844 polymorphism. Consistently, the rs2069762A-rs6822844T-rs6835457G-rs907715T allelic combination showed evidence of association with SSc and limited cutaneous SSc subtype (pc=1.7E-03 and pc=8E-4, respectively). CONCLUSIONS: These results suggested that the IL-2/IL-21 locus influences the genetic susceptibility to SSc. Moreover, this study provided further support for the IL-2/IL-21 locus as a common genetic factor in autoimmune diseases.

Novel sequence feature variant type analysis of the HLA genetic association in systemic sclerosis.

We describe a novel approach to genetic association analyses with proteins sub-divided into biologically relevant smaller sequence features (SFs), and their variant types (VTs). SFVT analyses are particularly informative for study of highly polymorphic proteins such as the human leukocyte antigen (HLA), given the nature of its genetic variation: the high level of polymorphism, the pattern of amino acid variability, and that most HLA variation occurs at functionally important sites, as well as its known role in organ transplant rejection, autoimmune disease development and response to infection. Further, combinations of variable amino acid sites shared by several HLA alleles (shared epitopes) are most likely better descriptors of the actual causative genetic variants. In a cohort of systemic sclerosis patients/controls, SFVT analysis shows that a combination of SFs implicating specific amino acid residues in peptide binding pockets 4 and 7 of HLA-DRB1 explains much of the molecular determinant of risk.

IRF5 polymorphism predicts prognosis in patients with systemic sclerosis.

OBJECTIVE: The first genome-wide association study (GWAS) of systemic sclerosis (SSc) demonstrated three non-major histocompatibility complex (MHC) susceptibility loci. The goal of this study was to investigate the impact of these gene variants on survival and severity of interstitial lung disease (ILD) in SSc. METHODS: The authors examined 1443 Caucasian SSc patients enrolled in the Genetics versus Environment In Scleroderma Outcome Study (GENISOS) and Scleroderma Family Registry (n = 914 - discovery cohort) and The Johns Hopkins Scleroderma Cohort (n = 529 - replication cohort). Forced vital capacity (FVC)% predicted was used as a surrogate for ILD severity. Five single nucleotide polymorphisms, IRF5 (rs10488631, rs12537284, rs4728142), STAT4 (rs3821236), CD247 (rs2056626) reached genome-wide significance in the SSc-GWAS and were examined in the current study. RESULTS: Overall, 15.5% of the patients had died over the follow-up period of 5.5 years. The IRF5 rs4728142 minor allele was predictive of longer survival in the discovery cohort (p = 0.021) and in the independent replication cohort (p = 0.047) and combined group (HR: 0.75, 95% CI 0.62 to 0.90, p = 0.002). The association of this SNP with survival was independent of age at disease onset, disease type and autoantibody profile (anticentromere and antitopoisomerase antibodies). The minor allele frequency of IRF5 rs4728142 was 49.4%. Moreover, IRF5 rs4728142 minor allele correlated with higher FVC% predicted at enrolment (p = 0.019). Finally, the IRF5 rs4728142 minor allele was associated with lower IRF5 transcript expression in patients and controls (p = 0.016 and p = 0.034, respectively), suggesting that the IRF5, rs4728142 SNP, may be functionally relevant. CONCLUSION: An SNP in the IRF5 promoter region (rs4728142), associated with lower IRF5 transcript levels, was predictive of longer survival and milder ILD in patients with SSc.

Novel identification of the IRF7 region as an anticentromere autoantibody propensity locus in systemic sclerosis.

OBJECTIVE: Systemic sclerosis (SSc) and systemic lupus erythematosus (SLE) are related chronic autoimmune diseases of complex aetiology in which the interferon (IFN) pathway plays a key role. Recent studies have reported an association between IRF7 and SLE which confers a risk to autoantibody production. A study was undertaken to investigate whether the IRF7 genomic region is also involved in susceptibility to SSc and the main clinical features. METHODS: Two case-control sets of Caucasian origin from the USA and Spain, comprising a total of 2316 cases of SSc and 2347 healthy controls, were included in the study. Five single nucleotide polymorphisms (SNPs) in the PHRF1-IRF7-CDHR5 locus were genotyped using TaqMan allelic discrimination technology. A meta-analysis was performed to test the overall effect of these genetic variants on SSc. RESULTS: Four out of five analysed SNPs were significantly associated with the presence of anticentromere autoantibodies (ACA) in the patients with SSc in the combined analysis (rs1131665: p(FDR)=6.14 × 10(-4), OR=0.78; rs4963128: p(FDR)=6.14 × 10(-4), OR=0.79; rs702966: p(FDR)=3.83 × 10(-3), OR=0.82; and rs2246614: p(FDR)=3.83 × 10(-3), OR=0.83). Significant p values were also obtained when the disease was tested globally; however, the statistical significance was lost when the ACA-positive patients were excluded from the study, suggesting that these associations rely on ACA positivity. Conditional logistic regression and allelic combination analyses suggested that the functional IRF7 SNP rs1131665 is the most likely causal variant. CONCLUSIONS: The results show that variation in the IRF7 genomic region is associated with the presence of ACA in patients with SSc, supporting other evidence that this locus represents a common risk factor for autoantibody production in autoimmune diseases.

Cigarette smoking is not a risk factor for systemic sclerosis.

OBJECTIVE: To investigate the association of cigarette smoking with susceptibility to systemic sclerosis (SSc) in a large, well-defined patient population. METHODS: We conducted a review of 1,379 patients with SSc enrolled in the Scleroderma Family Registry and DNA Repository and/or the Genetics versus Environment in Scleroderma Outcome Study cohort. Smoking history was obtained from chart review or via telephone interview. Patients with SSc were subsequently categorized as never smokers or ever smokers. Patients with SSc for whom smoking data were available were matched 2:1 by age, sex, ethnicity, and state of residence to control subjects, using the Behavioral Risk Factor Surveillance System. RESULTS: The majority of patients were white (74.2%), with Hispanics and blacks representing 11.3% and 9.7%, respectively. Most patients had limited cutaneous involvement (54%). For our comparative analyses, 621 patients were matched with control subjects. There was no significant difference in age, sex, ethnicity, and SSc subtype between matched versus unmatched patients. The majority of patients had never smoked (57%), while 43% of patients were classified as ever smokers. The patients with SSc did not differ from control subjects in terms of their smoking behavior (odds ratio [OR] 1.020, 95% confidence interval [95% CI] 0.839-1.240, P=0.842). Anti-topoisomerase I antibody-positive patients were more likely to be never smokers (OR 0.648, 95% CI 0.421-0.998, P=0.049), whereas no such association was observed with anticentromere and anti-RNA polymerase III antibodies. CONCLUSION: Unlike its role in rheumatoid arthritis, smoking does not confer a risk for development of SSc, although it may impact disease severity.

HLA-DRB1*0407 and *1304 are risk factors for scleroderma renal crisis.

OBJECTIVE: To examine the predictive role of HLA genetic markers in scleroderma renal crisis (SRC), beyond the known clinical correlates, in a large population of patients with systemic sclerosis (SSc). METHODS: SSc patients from the Scleroderma Family Registry and DNA Repository, the Genetics versus Environment in Scleroderma Outcomes Study, and the rheumatology division registry at the University of Texas Health Science Center at Houston were included in the study. Relevant clinical data were obtained by chart review, and autoantibodies were detected utilizing commercially available kits. HLA class II genotyping was performed on extracted and purified genomic DNA. RESULTS: Overall, 1,519 SSc patients were included in the study, of whom 90 (6%) had developed SRC. Among the 90 patients with SRC, the diffuse cutaneous disease subtype was found in 76%, antitopoisomerase antibodies (antitopo) in 9%, anticentromere antibodies (ACAs) in 2%, and anti-RNA polymerase III (anti-RNAP III) in 50% of patients. In multivariate analyses of clinical and demographic parameters, diffuse disease type and anti-RNAP III were strong risk factors for the presence of SRC, whereas ACAs and antitopo were protective. In the final multivariate analysis, which included HLA alleles, HLA-DRB1*0407 (odds ratio [OR] 3.21, 95% confidence interval [95% CI] 1.27-8.08; P = 0.013) and DRB1*1304 (OR 4.51, 95% CI 1.30-15.65; P = 0.018) were identified as independent risk factors for SRC. Only 3 clinical characteristics, diffuse disease type, anti-RNAP III, and ACAs, remained significantly associated with SRC in the final model. CONCLUSION: The results of this study suggest that DRB1*0407 and *1304 are independent risk factors, beyond the known clinical correlates, for the development of SRC.

Association of a functional IRF7 variant with systemic lupus erythematosus.

OBJECTIVE: A previous genome-wide association study conducted in a population of European ancestry identified rs4963128, a KIAA1542 single-nucleotide polymorphism (SNP) 23 kb telomeric to IRF7 (the gene for interferon regulatory factor 7 [IRF-7]), to be strongly associated with systemic lupus erythematosus (SLE). This study was undertaken to investigate whether genetic polymorphism within IRF7 is a risk factor for the development of SLE. METHODS: We genotyped one KIAA1542 SNP (rs4963128) and one IRF7 SNP (rs1131665 [Q412R]) in an Asian population (1,302 cases, 1,479 controls), to assess their association with SLE. Subsequently, rs1131665 was further genotyped in independent panels of Chinese subjects (528 cases, 527 controls), European American subjects (446 cases, 461 controls), and African American subjects (159 cases, 115 controls) by TaqMan genotyping assay, to seek confirmation of association in various ethnic groups. A luciferase reporter assay was used to assess the effect of Q412R polymorphism on the activation of IRF-7. RESULTS: Consistent association of rs1131665 (Q412R) with SLE was identified in Asian, European American, and African American populations (total 2,435 cases and 2,582 controls) (P(meta) = 6.18 × 10(-6) , odds ratio 1.42 [95% confidence interval 1.22-1.65]). Expression of the IRF7 412Q risk allele resulted in a 2-fold increase in interferon-stimulated response element transcriptional activity compared with expression of IRF7 412R (P = 0.0003), suggesting that IRF7 412Q confers elevated IRF-7 activity and may therefore affect a downstream interferon pathway. CONCLUSION: These findings show that the major allele of a nonsynonymous SNP, rs1131665 (412Q) in IRF7, confers elevated activation of IRF-7 and predisposes to the development of SLE in multiple ethnic groups. This result provides direct genetic evidence that IRF7 may be a risk gene for human SLE.

DRB1*15 allele is a risk factor for PR3-ANCA disease in African Americans.

Anti-neutrophil cytoplasmic autoantibody (ANCA) disease rarely occurs in African Americans and risk factors for the disease in this population are unknown. Here, we genotyped MHC class II alleles and found that, among African Americans, those with proteinase 3-ANCA (PR3-ANCA) had 73.3-fold higher odds of having HLA-DRB1*15 alleles than community-based controls (OR 73.3; 95% CI 9.1 to 591). In addition, a disproportionate number of African American patients carried the DRB1*1501 allelic variant of Caucasian descent rather than the DRB1*1503 allelic variant of African descent. Among Caucasians, those with PR3-ANCA had 2.2-fold higher odds of carrying DRB1*1501 than controls (OR 2.2; 95% CI 1.2 to 4.0). A validation study supported by the Vasculitis Clinical Research Consortium confirmed the strong association between the DRB1*15 allele and PR3-ANCA disease, among African Americans. Furthermore, we found that DRB1*1501 protein binds with high affinity to amino acid sequences of sense-PR3, purportedly an antigenic epitope, and to the amino acid sequence complementary to this epitope in vitro. Peptides of sense-PR3 and complementary-PR3 also bound to TNF-α-induced surface expression of DRB1*1501 on peripheral neutrophils. Taken together, these data suggest HLA-DRB1*15 alleles contribute to the pathogenesis of PR3-ANCA disease.

A loss-of-function variant of PTPN22 is associated with reduced risk of systemic lupus erythematosus.

A gain-of-function R620W polymorphism in the PTPN22 gene, encoding the lymphoid tyrosine phosphatase LYP, has recently emerged as an important risk factor for human autoimmunity. Here we report that another missense substitution (R263Q) within the catalytic domain of LYP leads to reduced phosphatase activity. High-resolution structural analysis revealed the molecular basis for this loss of function. Furthermore, the Q263 variant conferred protection against human systemic lupus erythematosus, reinforcing the proposal that inhibition of LYP activity could be beneficial in human autoimmunity.

Major histocompatibility complex (MHC) class II alleles, haplotypes and epitopes which confer susceptibility or protection in systemic sclerosis: analyses in 1300 Caucasian, African-American and Hispanic cases and 1000 controls.

OBJECTIVE: To determine human leucocyte antigen-class II (HLA-class II) (DRB1, DQB1, DQA1 and DPB1) alleles, haplotypes and shared epitopes associated with scleroderma (systemic sclerosis (SSc)) and its subphenotypes in a large multi-ethnic US cohort by a case-control association study. PATIENTS AND METHODS: 1300 SSc cases (961 white, 178 black and 161 Hispanic subjects) characterised for clinical skin forms (limited vs diffuse), SSc-specific autoantibodies (anticentromere (ACA), anti-topoisomerase I (ATA), anti-RNA polymerase III (ARA), anti-U3 ribonucleoprotein (fibrillarin)) and others were studied using molecular genotyping. Statistical analyses in SSc itself by ethnicity, gender, skin type and autoantibodies were performed using exact logistic regression modelling for dominant, additive and recessive effects from HLA. RESULTS: The strongest positive class II associations with SSc in white and Hispanic subjects were the DRB1*1104, DQA1*0501, DQB1*0301 haplotype and DQB1 alleles encoding a non-leucine residue at position 26 (DQB1 26 epi), while the DRB1*0701, DQA1*0201, DQB1*0202 haplotype and DRB1*1501 haplotype were negatively correlated and possibly protective in dominant and recessive models, respectively. These associations did not discriminate between limited and diffuse SSc. SSc in black subjects was associated with DRB1*0804, DQA1*0501, DQB1*0301 alleles. DPB1*1301 showed the highest odds ratio for ATA (OR = 14). Moreover, it showed no linkage disequilibrium or gene interaction with DR/DQ. ACA was best explained by DQB1*0501 and DQB1*26 epi alleles and ARA by DRB1*0404, DRB1*11 and DQB1*03 alleles in white and Hispanic subjects but DRB1*08 in black subjects. CONCLUSION: These data indicate unique and multiple HLA-class II effects in SSc, especially on autoantibody markers of different subphenotypes.

Association of TNFSF4 (OX40L) polymorphisms with susceptibility to systemic sclerosis.

OBJECTIVE: It is increasingly being appreciated that multiple autoimmune diseases share common susceptibility genes. The tumour necrosis factor ligand superfamily member 4 gene (TNFSF4, OX40L), which encodes for the T cell costimulatory molecule OX40 ligand, has been identified as a susceptibility gene for the development of systemic lupus erythematosus (SLE). Accordingly, the aim of the current study was to investigate the possible association of the TNFSF4 gene region with systemic sclerosis (SSc), an autoimmune disease that leads to the development of cutaneous and visceral fibrosis. METHODS: A total of 9 single nucleotide polymorphisms (SNPs) in the TNFSF4 gene region, previously associated with susceptibility to SLE, were tested for association with SSc in a collection of 1059 patients with SSc and 698 controls. RESULTS: Case-control comparisons revealed a significant association between susceptibility to SSc and the minor alleles at SNPs rs1234314 (OR 1.20, 95% CI 1.04 to 1.4, p(FDR)=0.019), rs2205960 (OR 1.24, 95% CI 1.10 to 1.50, p(FDR)=0.019) and rs844648 (OR 1.16, 95% CI 1.01 to 1.30, p(FDR)=0.032). The minor allele at rs844644 was protective (OR 0.84, 95% CI 0.70 to 0.97, p(FDR)=0.038). Analysis of subsets of patients with SSc demonstrated significant associations of the TNFSF4 SNPs with limited and diffuse SSc as well as specific SNPs that were associated with SSc-associated autoantibodies. Finally, the analyses suggest a potential interaction between two TNFSF4 SNPs, rs2205960 and rs844648, with regards to SSc susceptibility. CONCLUSIONS: Polymorphisms in the TNFSF4 gene region are associated with susceptibility to SSc and its clinical and autoantibody subsets. TNFSF4 may be another gene that confers risk to multiple autoimmune diseases.

Autoimmune diseases and autoantibodies in the first degree relatives of patients with systemic sclerosis.

OBJECTIVE: To determine aggregation of autoimmune diseases in the first degree relatives (FDR) of patients with systemic sclerosis (SSc) and to investigate frequencies of antinuclear antibodies (ANA) and other autoantibodies in the FDRs and spouses of patients with SSc. METHODS: Information on FDRs including history of autoimmune disease was obtained from unrelated SSc probands in the Scleroderma Family Registry and DNA Repository. FDRs were contacted to verify any reported autoimmune diseases. The prevalence of autoimmune disease in probands' families was compared with the corresponding prevalence in controls' families as reported in the literature. Furthermore, sera from probands' FDRs and spouses in addition to unrelated controls were investigated for the presence of autoantibodies (ANA). RESULTS: We investigated 4612 FDRs of 1071 SSc probands. SSc probands with anti-centromere antibodies (ACA) and limited disease type were more likely to report familial autoimmunity (p=0.022 and p=0.041, respectively). The four most prevalent autoimmune diseases among SSc probands' FDRs were hypothyroidism (4%), Rheumatoid arthritis (1.5%), hyperthyroidism (1.3%) and systemic lupus erythematosus-SLE (0.4%). Compared to control families, SLE, hypothyroidism and hyperthyroidism were more common in SSc probands' families. The most striking increase for familial prevalence was observed in SLE (OR=16.98, 95% CI=1.02-227.82, p=0.004). ANA was present in 14.2% of probands' FDR's and 8.6% of spouses and did not differ from the prevalence of ANA among controls (p=0.124 and p=0.477, respectively). Only two FDRs of probands had ACA while none had anti-topoisomerase antibodies. CONCLUSION: Our study implies varying degrees of risk for familial autoimmunity among subtypes of SSc and provides further support for common genetic and potentially environmental factors leading to SSc and SLE.

Association of the C8orf13-BLK region with systemic sclerosis in North-American and European populations.

OBJECTIVE: Genetic studies in the systemic sclerosis (SSc), an autoimmune disease that clinically manifests with dermal and internal organ fibrosis and small vessel vasculopathy, have identified multiple susceptibility genes including HLA-class II, PTPN22, IRF5, and STAT4 which have also been associated with other autoimmune diseases, such as systemic lupus erythematosus (SLE). These data suggest that there are common autoimmune disease susceptibility genes. The current report sought to determine if polymorphisms in the C8orf13-BLK region (chromosome 8p23.1-B lymphoid tyrosine kinase), which is associated with SLE, are associated also with SSc. METHODS: Two variants in the C8orf13-BLK region (rs13277113 & rs2736340) were tested for association with 1050 SSc cases and 694 controls of North Americans of European descent and replicated in a second series 589 SSc cases and 722 controls from Spain. RESULTS: The "T" allele at rs2736340 variant was associated with SSc in both the U.S. and Spanish case-control series (P = 6.8 x 10(-5), OR 1.27, 95% CI 1.1-1.4). The "A" allele at rs13277113 variant was associated with SSc in the U.S. series only (P = 3.6 x 10(-4), OR 1.32, 95% CI 1.1-1.6) and was significant in the combined analyses of the two series (P = 2.0 x 10(-3); OR 1.20, 95% CI 1.1-1.3). Both variants demonstrated an association with the anti-centromere antibody (P = 2.2 x 10(-6) and P = 5.5 x 10(-4), respectively) and limited SSc (P = 3.3 x 10(-5) and P = 2.9 x 10(-3), respectively) in the combined analysis. Peripheral blood gene expression profiles suggest that B-cell receptor and NFkappaB signaling are dysregulated based on the risk haplotype of these variants. CONCLUSION: We identify and replicate the association of the C8orf13-BLK region as a novel susceptibility factor for SSc, placing it in the category of common autoimmune disease susceptibility genes.

Genetics and genomic studies in scleroderma (systemic sclerosis).

It currently is believed that scleroderma is a complex polygenic disease that occurs in genetically predisposed individuals who have encountered specific environment exposures and/or other stochastic factors. The nature of these genetic determinants and how they interact with environmental factors are areas of active investigation. This article discusses the evidence that supports a strong genetic link to scleroderma. These studies implicate potential pathogenetic mechanisms involved in scleroderma, which, it is hoped, may translate into clinical utility, including determination of disease risk, diagnosis, prognosis, and novel therapeutics.

Gene-level association analysis of systemic sclerosis: A comparison of African-Americans and White populations.

Gene-level analysis of ImmunoChip or genome-wide association studies (GWAS) data has not been previously reported for systemic sclerosis (SSc, scleroderma). The objective of this study was to analyze genetic susceptibility loci in SSc at the gene level and to determine if the detected associations were shared in African-American and White populations, using data from ImmunoChip and GWAS genotyping studies. The White sample included 1833 cases and 3466 controls (956 cases and 2741 controls from the US and 877 cases and 725 controls from Spain) and the African American sample, 291 cases and 260 controls. In both Whites and African Americans, we performed a gene-level analysis that integrates association statistics in a gene possibly harboring multiple SNPs with weak effect on disease risk, using Versatile Gene-based Association Study (VEGAS) software. The SNP-level analysis was performed using PLINK v.1.07. We identified 4 novel candidate genes (STAT1, FCGR2C, NIPSNAP3B, and SCT) significantly associated and 4 genes (SERBP1, PINX1, TMEM175 and EXOC2) suggestively associated with SSc in the gene level analysis in White patients. As an exploratory analysis we compared the results on Whites with those from African Americans. Of previously established susceptibility genes identified in Whites, only TNFAIP3 was significant at the nominal level (p = 6.13x10-3) in African Americans in the gene-level analysis of the ImmunoChip data. Among the top suggestive novel genes identified in Whites based on the ImmunoChip data, FCGR2C and PINX1 were only nominally significant in African Americans (p = 0.016 and p = 0.028, respectively), while among the top novel genes identified in the gene-level analysis in African Americans, UNC5C (p = 5.57x10-4) and CLEC16A (p = 0.0463) were also nominally significant in Whites. We also present the gene-level analysis of SSc clinical and autoantibody phenotypes among Whites. Our findings need to be validated by independent studies, particularly due to the limited sample size of African Americans.