Autoimmune risk variants in ERAP2 are associated with gene-expression levels in thymus.

Genetic polymorphisms in the endoplasmic reticulum aminopeptidase (ERAP)1 and ERAP2 genes have been associated with several autoimmune diseases (AIDs) at a genome-wide significance level. In this study, we performed a cis expression quantitative trait locus (eQTL) screen to investigate whether seven fine-mapped AID single-nucleotide polymorphisms (SNPs) in the ERAP-region influence the gene-expression levels of ERAP1 and ERAP2 in thymus. After quality control, we identified six significant eQTLs. We further assessed the peak eQTL signals, and both genes showed highly significant and independent thymic eQTL signals (P=2.16 × 10-15 and P=8.22 × 10-23, respectively). Interestingly, the peak eQTL signal overlapped with the AID risk loci in ERAP2 (r2>0.94), but were distinct in ERAP1 (r2<0.4). Finally, among the SNPs showing the most significant eQTL associations with ERAP2 (P<3.4 × 10-20), six were located within transcription factor motifs in an enhancer region in thymus. Our study therefore reveals the fine-mapped AID risk variants that act as eQTLs with ERAP2 in thymus, and highlights the potential causal regulatory variants.

Genetic pleiotropy between multiple sclerosis and schizophrenia but not bipolar disorder: differential involvement of immune-related gene loci.

Converging evidence implicates immune abnormalities in schizophrenia (SCZ), and recent genome-wide association studies (GWAS) have identified immune-related single-nucleotide polymorphisms (SNPs) associated with SCZ. Using the conditional false discovery rate (FDR) approach, we evaluated pleiotropy in SNPs associated with SCZ (n=21,856) and multiple sclerosis (MS) (n=43,879), an inflammatory, demyelinating disease of the central nervous system. Because SCZ and bipolar disorder (BD) show substantial clinical and genetic overlap, we also investigated pleiotropy between BD (n=16,731) and MS. We found significant genetic overlap between SCZ and MS and identified 21 independent loci associated with SCZ, conditioned on association with MS. This enrichment was driven by the major histocompatibility complex (MHC). Importantly, we detected the involvement of the same human leukocyte antigen (HLA) alleles in both SCZ and MS, but with an opposite directionality of effect of associated HLA alleles (that is, MS risk alleles were associated with decreased SCZ risk). In contrast, we found no genetic overlap between BD and MS. Considered together, our findings demonstrate genetic pleiotropy between SCZ and MS and suggest that the MHC signals may differentiate SCZ from BD susceptibility.

The association of PTPN22 rs2476601 with juvenile idiopathic arthritis is specific to females.

A preponderance of females develop autoimmune disease, including juvenile idiopathic arthritis (JIA), yet the reason for this bias remains elusive. Evidence suggests that genetic risk of disease may be influenced by sex. PTPN22 rs2476601 is associated with JIA and numerous other autoimmune diseases, and has been reported to show female-specific association with type 1 diabetes. We performed main effect and sex-stratified association analyses to determine whether a sex-specific association exists in JIA. As expected, rs2476601 was associated with JIA in our discovery (413 cases and 690 controls) and replication (1008 cases and 9284 controls) samples. Discovery sample sex-stratified analyses demonstrated an association specifically in females (odds ratio (OR)=2.35, 95% confidence interval (CI)=1.52-3.63, P=0.00011) but not males (OR=0.91, 95% CI=0.52-1.60, P=0.75). This was similarly observed in the replication sample. There was evidence for genotype-by-sex interaction (Pinteraction=0.009). The association between rs2476601 and JIA appears restricted to females, partly accounting for the predominance of females with this disease.

A genome-wide association study of rheumatoid arthritis without antibodies against citrullinated peptides.

INTRODUCTION: Rheumatoid arthritis (RA) patients can be classified based on presence or absence of anticitrullinated peptide antibodies (ACPA) in their serum. This heterogeneity among patients may reflect important biological differences underlying the disease process. To date, the majority of genetic studies have focused on the ACPA-positive group. Therefore, our goal was to analyse the genetic risk factors that contribute to ACPA-negative RA. METHODS: We performed a large-scale genome-wide association study (GWAS) in three Caucasian European cohorts comprising 1148 ACPA-negative RA patients and 6008 controls. All patients were screened using the Illumina Human Cyto-12 chip, and controls were genotyped using different genome-wide platforms. Population-independent analyses were carried out by means of logistic regression. Meta-analysis with previously published data was performed as follow-up for selected signals (reaching a total of 1922 ACPA-negative RA patients and 7087 controls). Imputation of classical HLA alleles, amino acid residues and single nucleotide polymorphisms was undertaken. RESULTS: The combined analysis of the studied cohorts resulted in identification of a peak of association in the HLA-region and several suggestive non-HLA associations. Meta-analysis with previous reports confirmed the association of the HLA region with this subset and an observed association in the CLYBL locus remained suggestive. The imputation and deep interrogation of the HLA region led to identification of a two amino acid model (HLA-B at position 9 and HLA-DRB1 at position 11) that accounted for the observed genome-wide associations in this region. CONCLUSIONS: Our study shed light on the influence of the HLA region in ACPA-negative RA and identified a suggestive risk locus for this condition.

No association between multiple sclerosis and periodontitis after adjusting for smoking habits.

BACKGROUND AND PURPOSE: Periodontitis has been reported to be associated with several systemic disorders, and recently a possible relationship with multiple sclerosis (MS) was suggested. The aim of the present study was to investigate the association between periodontitis and MS in a Norwegian cohort. METHODS: A case-control study in 756 MS patients and 1090 controls was conducted, and logistic regression analysis, adjusting for age, gender, place of residence, mononucleosis and smoking, was performed to investigate the association between MS and periodontitis. RESULTS: In the unadjusted analysis a higher prevalence of periodontitis was seen in MS patients, but this difference was not statistically significant after adjusting for the covariates. CONCLUSIONS: The previously suggested association between MS and periodontitis is not supported in this study. Our results underline the importance of adjusting for relevant covariates in epidemiological research.

Coeliac disease-associated polymorphisms influence thymic gene expression.

Significant associations between coeliac disease (CD) and single nucleotide polymorphisms (SNPs) distributed over 40 genetic regions have been established. The majority of these SNPs are non-coding and 20 SNPs were, by expression quantitative trait loci (eQTL) analysis, found to harbour cis regulatory potential in peripheral blood mononuclear cells (PBMC). Almost all regions contain genes with an immunological relevant function, of which many act in the same biological pathways. One such pathway is T-cell development in the thymus, a pathway previously not explored in CD pathogenesis. The aim of our study was to explore the regulatory potential of the CD-associated SNPs (n=50) by eQTL analysis in thymic tissue from 42 subjects. In total, 43 nominal significant (P<0.05) eQTLs were found within 24 CD-associated chromosomal regions, corresponding to 27 expression-altering SNPs (eSNPs) and 40 probes (eProbes) that represents 39 unique genes (eGenes). Nine significant probe-SNP pairs (corresponding to 8 eSNPs and 7 eGenes) overlapped with previous findings in PBMC (rs12727642-PARK7, rs296547-DDX59, rs917997-IL18RAP, rs842647-AHSA2, rs13003464-AHSA2, rs6974491-ELMO1, rs2074404-NSF (two independent probes) and rs2298428-UBE2L3). When compared across more tissues, we found that 14 eQTLs could represent potentially novel thymus-specific eQTLs. This implies that CD risk polymorphisms could affect gene regulation in thymus.

Multiple sclerosis-associated single-nucleotide polymorphisms in CLEC16A correlate with reduced SOCS1 and DEXI expression in the thymus.

Genome-wide association studies have revealed that the 16p13 chromosomal region, including CLEC16A, DEXI, CIITA and SOCS1, is associated with susceptibility to autoimmune diseases. As non-coding single-nucleotide polymorphisms (SNPs) may confer susceptibility to disease by affecting expression of nearby genes, we examined whether autoimmune-associated intronic CLEC16A SNPs (rs12708716, rs6498169 and rs7206912) correlate with the expression of CLEC16A itself as well as neighboring genes in whole-blood and thymic samples. Real-time quantitative PCR analyses show that SOCS1 and DEXI expression was lower in thymic samples carrying at least one of the CLEC16A risk alleles compared with non-carriers of the risk allele. Linear regression analysis revealed a significant correlation between the expression level of CLEC16A and that of SOCS1 and DEXI in thymic samples. These data indicate a possible regulatory role for multiple sclerosis-associated non-coding CLEC16A SNPs and a common control mechanism for the expression of CLEC16A, SOCS1 and DEXI.

Identification of the PTPN22 functional variant R620W as susceptibility genetic factor for giant cell arteritis.

OBJECTIVE: To analyse the role of the PTPN22 and CSK genes, previously associated with autoimmunity, in the predisposition and clinical phenotypes of giant cell arteritis (GCA). METHODS: Our study population was composed of 911 patients diagnosed with biopsy-proven GCA and 8136 unaffected controls from a Spanish discovery cohort and three additional independent replication cohorts from Germany, Norway and the UK. Two functional PTPN22 polymorphisms (rs2476601/R620W and rs33996649/R263Q) and two variants of the CSK gene (rs1378942 and rs34933034) were genotyped using predesigned TaqMan assays. RESULTS: The analysis of the discovery cohort provided evidence of association of PTPN22 rs2476601/R620W with GCA (PFDR=1.06E-04, OR=1.62, CI 95% 1.29 to 2.04). The association did not appear to follow a specific GCA subphenotype. No statistically significant differences between allele frequencies for the other PTPN22 and CSK genetic variants were evident either in the case/control or in stratified case analysis. To confirm the detected PTPN22 association, three replication cohorts were genotyped, and a consistent association between the PTPN22 rs2476601/R620W variant and GCA was evident in the overall meta-analysis (PMH=2.00E-06, OR=1.51, CI 95% 1.28 to 1.79). CONCLUSIONS: Our results suggest that the PTPN22 polymorphism rs2476601/R620W plays an important role in the genetic risk to GCA.

Association analysis of the CCL3L1 copy number locus by paralogue ratio test in Norwegian rheumatoid arthritis patients and healthy controls.

Genotyping of multiallelic copy number variants (CNVs) is technically difficult and can lead to inaccurate conclusions. This is reflected by inconsistent results published for the CNV C-C chemokine ligand 3-like 1 (CCL3L1) and its contribution to rheumatoid arthritis (RA) susceptibility. In order to draw robust conclusions about CCL3L1 involvement in RA, we have performed association analysis (CNVtools) using genotyping by the paralogue ratio test of a Norwegian RA case-control material (N=1877). We also analyzed the associations after stratification for anti-citrullinated peptide antibody (ACPA) status. Clear clusters representing specific copy number classes were evident, but significant differential bias was observed resulting in a systematic trend toward slightly higher apparent copy number for cases relative to controls. Controlling for bias revealed no significant differences in copy number distribution either between all patients and controls, or after ACPA stratification. Our results do not support involvement of the CCL3L1 CNV in RA susceptibility.

CIITA gene variants are associated with rheumatoid arthritis in Scandinavian populations.

Expression of the major autoimmune risk loci DRB1 and DQB1 is regulated by the class II MHC (major histocompatibility complex) transactivator (CIITA), making the CIITA gene a strong autoimmune risk locus candidate. A CIITA promoter single-nucleotide polymorphism (SNP), rs3087456 (-168 A/G), has indeed been associated with several autoimmune diseases, including rheumatoid arthritis (RA). Recently, an intronic SNP rs8048002 has been suggested as a better susceptibility marker in Addison's disease. Therefore, we tested both SNPs in a panel of autoimmune diseases, consisting of Norwegian patients with RA (n=819), juvenile idiopathic arthritis (JIA; n=524), or type 1 diabetes (T1D; n=1211), and 2149 controls. We also included an independent Swedish RA cohort (n=2503) and controls (n=1416). Both rs3087456 and rs8048002 were significantly associated with RA (combined Norwegian and Swedish patients P(corrected)=0.012 and P(corrected)=0.0016, respectively), but not with JIA or T1D. Meta-analysis of 16 RA cohorts confirmed rs3087456 with only marginal significance (P=0.016). However, results were stronger in the Scandinavian subgroup (4 cohorts, P=3.8 × 10(-4)), indicating a population-dependent effect. A similar pattern was observed in a meta-analysis of rs8048002. Our results support involvement of CIITA in RA, but imply that this is population dependent and that the aetiological variant is yet to be discovered.

HLA-DRB1, -DQA1 and -DQB1 alleles and haplotypes in first-generation Pakistani immigrants in Norway.

Human leucocyte antigen (HLA) polymorphisms among immigrants from Pakistan have not been well investigated. Immigration to Norway started in the late 1960s for working purposes. From 1975, immigration was mainly for marriages and family reunion. When recruiting couples for a birth cohort study, we ended up with 65.5% of the 374 parents genotyped being closely related. This was also reflected in that 21% of newborns were homozygotes for their DRB1-DQA1-DQB1 genotype. For being able to study HLA class II genes frequencies among unrelated individuals, we had to exclude 195 of the parents from data analysis. High-resolution typing for the DRB1 locus, low/intermediate for the DQA1 locus and resolution genotyping for the DQB1 locus were performed in all the 179 parents and their newborns from the Punjab province of Pakistan. We identified 25 DRB1, nine DQA1 and 14 DRB1 alleles in the 179 unrelated parents included in our analysis. The most frequent alleles were DRB1*03:01:01 (15.9%) and DRB1*07:01:01 (15.9%), DQA1*01:03 (22.1%) and DQB1*02:01:01 (26.0%). Forty-one haplotypes were identified, including DRB1*13:02:01-DQA1*01:02-DQB1*06:03:01, not earlier reported. Supported by the few earlier reports on Pakistani groups living in Pakistan, it appears that alleles found among those living in Norway are of Indo-European or mixed ethnic origin. This study provides the first comprehensive report of HLA class II alleles and haplotypes in Norwegian Pakistani immigrants. When the unrelated parents were compared with all parents genotyped, there were, however, no significant differences in allele frequencies, confirming that consanguineous marriages are usual in Pakistan.

Exploring the CLEC16A gene reveals a MS-associated variant with correlation to the relative expression of CLEC16A isoforms in thymus.

Genomewide association studies have implicated the CLEC16A gene in several autoimmune diseases, including multiple sclerosis (MS) and type 1 diabetes. However, the most associated single-nucleotide polymorphism (SNP) varies, and causal variants are still to be defined. In MS, two SNPs in partial linkage disequilibrium with each other, rs6498169 and rs12708716, have been validated at genomewide significance level. To explore the CLEC16A association in MS in more detail, we genotyped 57 SNPs in 807 Norwegian MS patients and 1027 Norwegian controls. Six highly associated SNPs emerged and were then replicated in two large independent sample sets (Norwegian and British), together including 1153 MS trios, 2308 MS patients and 4044 healthy controls. In combined analyses, SNP rs12708716 gave the strongest association signal in MS (P=5.3 x 10⁻8, odds ratio 1.18, 95% confidence interval=1.11-1.25), and was found to be superior to the other SNP associations in conditional logistic regression analyses. Expression analysis revealed that rs12708716 genotype was significantly associated with the relative expression levels of two different CLEC16A transcripts in thymus (P=0.004), but not in blood, possibly implying a thymus- or cell-specific splice regulation.

No extreme genetic risk for type 1 diabetes among DR3/4-DQ8 siblings sharing both extended HLA haplotypes with their diabetic proband.

An extreme genetic risk for type 1 diabetes (T1D) was reported for DR3/4-DQ8 siblings sharing both extended human leukocyte antigen (HLA) haplotypes identical-by-descent (IBD) with their diabetic proband. We attempted to replicate this finding in our prospective Dutch T1D cohort and in families from the Type 1 Diabetes Genetics Consortium (T1DGC). Only 2 of the 14 Dutch siblings, sharing both DR3-DQ2/DR4-DQ8 haplotypes IBD with their diabetic proband, developed T1D in a 12-year follow-up period. No differential sharing of HLA haplotypes or significant transmission distortion in parents homozygous for HLA risk alleles was found in T1DGC material. Therefore, we could not confirm the reported extreme risk for T1D, suggesting that the risk conferred by other HLA complex loci is moderate.

Four novel coeliac disease regions replicated in an association study of a Swedish-Norwegian family cohort.

Recent genome-wide association studies have identified 1q31 (RGS1), 2q11-12 (IL18RAP), 3p21 (CCR1/CCR3/CCR2), 3q25-26 (IL12A/SCHIP1), 3q28 (LPP), 4q27 (IL2/IL21), 6q25 (TAGAP) and 12q24 (SH2B3) as susceptibility regions for coeliac disease (CD). We have earlier replicated association with the IL2/IL21 region. This study aimed at replicating the remaining regions in a family cohort using the transmission disequilibrium test, which is not prone to population stratification as a source of false-positive results. Nine single nucleotide polymorphisms (SNPs) within these regions were genotyped in 325 Swedish-Norwegian CD families. We found significant associations with the same alleles in the regions 1q31 (rs2816316; P(nc)=0.0060), 3p21 (rs6441961; P(nc)=0.0006), 3q25-26 (rs17810564; P(nc)=0.0316 and rs9811792; P(nc)=0.0434) and 3q28 (rs1464510; P(nc)=0.0037). Borderline, but non-significant, associations were found for rs917997 (IL18RAP), whereas no evidence for association could be obtained for rs13015714 (IL18RAP) or rs1738074 (TAGAP). The lack of replication of the latter SNPs could be because of limited power. rs3184504 (SH2B3) was not analysed because of assay failure. The most significantly associated region, 3p21 (CCR1/CCR3/CCR2), was further analysed by typing of 30 SNPs, with the aim of identifying the causal variant responsible for the initial association. Several SNPs showed association with CD, but none displayed associations stronger than rs6441961, nor did any of them add to the effect initially marked by rs6441961 in a conditional analysis. However, differential effects of rs6441961(*)C carrying haplotypes were indicated, and we thus cannot exclude the possibility that our inability to obtain evidence for multiple independent effects in the CCR1/CCR3/CCR2 gene region was related to a power issue.

Norwegian Sami differs significantly from other Norwegians according to their HLA profile.

This study reports extensive genomic data for both human leukocyte antigen (HLA) class I and II loci in Norwegian Sami, a native population living in the northwest of Europe. The Sami have a distinct culture and their own languages, which belong to the Uralic linguistic family. Norwegian Sami (n = 200) were typed at the DNA level for the HLA-A, -C, -B, -DRB1 and -DQB1 loci, and compared with a non-Sami Norwegian population (n = 576). The two populations exhibited some common genetic features but also differed significantly at all HLA loci. The most significantly deviating allele frequencies were an increase of HLA-A*03, -B*27, -DRB1*08 and -DQB1*04 and a decrease of HLA-A*01, C*01, -DRB1*04 and -DQB1*02 among Sami compared with non-Sami Norwegians. The Sami showed no deviation from Hardy-Weinberg equilibrium. The hypothesis of selective neutrality was rejected at all loci except for the A- and C- loci for the Sami. HLA haplotype frequencies also differed between the two populations. The most common extended HLA haplotypes were A*02-B*27-C*01-DR*08-DQB1*04 in the Sami and A*01-B*08-C*07-DR*03-DQB1*02 in the other Norwegians. Genetic distance analyses indicated that the Norwegian Sami were highly differentiated from other Europeans and were most closely related to Finns whose language also belongs to the Uralic linguistic family. In conclusion, the Norwegian Sami and the non-Sami Norwegians were significantly different at all HLA loci. Our results can be explained by the fact that the two populations have different origins and that the Sami population has remained smaller and more isolated than its neighbors.

Prediction of radiographic progression in rheumatoid arthritis and the role of antibodies against mutated citrullinated vimentin: results from a 10-year prospective study.

OBJECTIVES: Anti-citrullinated peptide antibodies (ACPAs) are established as useful predictors of radiographic progression in rheumatoid arthritis (RA). The main objective of this study was to test the prognostic capacity of the recently developed test for anti-mutated citrullinated vimentin (anti-MCV). METHODS: A cohort of 238 patients with RA was followed longitudinally for 10 years; 125 patients with complete x ray sets were included in the main analyses. Radiographs were scored according to the van der Heijde modified Sharp score (SHS). Patients were analysed for anti-MCV and anti-cyclic citrullinated peptide (CCP), and were genotyped for human leukocyte antigen (HLA)-DRB1 "shared epitope" (SE) and protein tyrosine phosphatase, non-receptor type 22 (PTPN22) 1858T. RESULTS: Anti-MCV and anti-CCP were strongly associated with regard to status and level. Both antibodies were associated with SE, but only anti-MCV was significantly associated with PTPN22 1858T. A positive anti-MCV test increased the odds of radiographic progression by 7.3 (95% confidence interval (CI) 3.2 to 16.5) compared to 5.7 (95% CI 2.6 to 12.5) for a positive anti-CCP. Presence of MCV antibodies gave an average increase in the total SHS of 30 U compared to an average increase of 25 U for the presence of CCP antibodies. Anti-MCVs were more strongly associated to progression in erosions than joint space narrowing. Associations remained after adjustment for other predictors of radiographic progression. The odds of progression increased with increasing anti-MCV level. CONCLUSIONS: Presence of anti-MCV predicted joint damage, and the strength of this prediction was at least as strong as for anti-CCP. Antibody status showed a stronger association to bone than to cartilage destruction. This study also indicates that higher anti-MCV levels add prognostic information compared to their mere presence or absence.

Conditional analyses on the T1DGC MHC dataset: novel associations with type 1 diabetes around HLA-G and confirmation of HLA-B.

The major histocompatibility complex (MHC) is known to harbour genetic risk factors for type 1 diabetes (T1D) additional to the class II determinants HLA-DRB1, -DQA1 and -DQB1, but strong linkage disequilibrium (LD) has made efforts to establish their location difficult. This study utilizes a dataset generated by the T1D genetics consortium (T1DGC), with genotypes for 2965 markers across the MHC in 2321 T1D families of multiple (mostly Caucasian) ethnicities. Using a comprehensive approach consisting of complementary conditional methods and LD analyses, we identified three regions with T1D association, independent both of the known class II determinants and of each other. A subset of polymorphisms that could explain most of the association in each region included single nucleotide polymorphisms (SNPs) in the vicinity of HLA-G, particular HLA-B and HLA-DPB1 alleles, and SNPs close to the COL11A2 and RING1 genes. Apart from HLA-B and HLA-DPB1, all of these represent novel associations, and subpopulation analyses did not indicate large population-specific differences among Caucasians for our findings. On account of the unusual genetic complexity of the MHC, further fine mapping is demanded, with the possible exception of HLA-B. However, our results mean that these efforts can be focused on narrow, defined regions of the MHC.

Genetic variants of the HLA-A, HLA-B and AIF1 loci show independent associations with type 1 diabetes in Norwegian families.

The main genetic predisposition to type 1 diabetes (T1D) is known to be conferred by the HLA-DRB1, -DQA1 and -DQB1 genes in the major histocompatibility complex (MHC). Other genetic factors within this complex are known to contribute, but their identity has often been controversial. This picture is shared with several other autoimmune diseases (AIDs). Moreover, as common genetic factors are known to exist between AIDs, associations reported with other AIDs may also be involved in T1D. In this study, we have used these observations in a candidate gene approach to look for additional MHC risk factors in T1D. Using complementary conditional methods (involving conditional logistic regression and family-based haplotype tests) and analyses of linkage disequilibrium (LD) patterns, we confirmed association for alleles of the HLA-A and HLA-B genes and found preliminary evidence for a novel association of a single-nucleotide polymorphism (rs2259571) in the AIF1 gene, independent of the DRB1-DQA1-DQB1 genes and of each other. However, no evidence of independent associations for a number of previously suggested candidate polymorphisms was detected. Our results illustrate the importance of a comprehensive adjustment for LD effects when performing association studies in this complex.

Reproducible association with type 1 diabetes in the extended class I region of the major histocompatibility complex.

The high-risk human leukocyte antigen (HLA)-DRB1, DQA1 and DQB1 alleles cannot explain the entire type 1 diabetes (T1D) association observed within the extended major histocompatibility complex. We have earlier identified an association with D6S2223, located 2.3 Mb telomeric of HLA-A, on the DRB1(*)03-DQA1(*)0501-DQB1(*)0201 haplotype, and this study aimed to fine-map the associated region also on the DRB1(*)0401-DQA1(*)03-DQB1(*)0302 haplotype, characterized by less extensive linkage disequilibrium. To exclude associations secondary to DRB1-DQA1-DQB1 haplotypes, 205 families with at least one parent homozygous for these loci, were genotyped for 137 polymorphisms. We found novel associations on the DRB1(*)0401-DQA1(*)03-DQB1(*)0302 haplotypic background with eight single nucleotide polymorphisms (SNPs) located within or near the PRSS16 gene. In addition, association at the butyrophilin (BTN)-gene cluster, particularly the BTN3A2 gene, was observed by multilocus analyses. We replicated the associations with SNPs in the PRSS16 region and, albeit weaker, to the BTN3A2 region, in an independent material of 725 families obtained from the Type 1 Diabetes Genetics Consortium. It is important to note that these associations were independent of the HLA-DRB1-DQA1-DQB1 genes, as well as of associations observed at HLA-A, -B and -C. Taken together, our results identify PRSS16 and BTN3A2, two genes thought to play important roles in regulating the immune response, as potentially novel susceptibility genes for T1D.

A coding polymorphism in NALP1 confers risk for autoimmune Addison's disease and type 1 diabetes.

Variants in the gene encoding NACHT leucine-rich-repeat protein 1 (NALP1), an important molecule in innate immunity, have recently been shown to confer risk for vitiligo and associated autoimmunity. We hypothesized that sequence variants in this gene may be involved in susceptibility to a wider spectrum of autoimmune diseases. Investigating large patient cohorts from six different autoimmune diseases, that is autoimmune Addison's disease (n=333), type 1 diabetes (n=1086), multiple sclerosis (n=502), rheumatoid arthritis (n=945), systemic lupus erythematosus (n=156) and juvenile idiopathic arthritis (n=505), against 3273 healthy controls, we analyzed four single nucleotide polymorphisms (SNPs) in NALP1. The major allele of the coding SNP rs12150220 revealed significant association with autoimmune Addison's disease compared with controls (OR=1.25, 95% CI: 1.06-1.49, P=0.007), and with type 1 diabetes (OR=1.15, 95% CI: 1.04-1.27, P=0.005). Trends toward the same associations were seen in rheumatoid arthritis, systemic lupus erythematosus and, although less obvious, multiple sclerosis. Patients with juvenile idiopathic arthritis did not show association with NALP1 gene variants. The results indicate that NALP1 and the innate immune system may be implicated in the pathogenesis of many autoimmune disorders, particularly organ-specific autoimmune diseases.