The R620W polymorphism of the protein tyrosine phosphatase PTPN22 is not associated with multiple sclerosis

The genetics of systemic lupus erythematosus: understanding how SNPs confer disease susceptibility

The identification of genes for autoimmune diseases is just the first step towards our understanding of disease pathogenesis. In investigating how mutations, deletions or other types of polymorphic defects occur, it is important to determine the pathways and the mechanisms through which susceptibility leads to disease. In this review I touch on three examples of studies that have attempted to understand the mechanisms of genetic susceptibility in three genes identified recently for systemic lupus erythematosus: PDCD1, PTPN22 and IRF5. We are just beginning to comprehend and much needs to be done.

Coding region polymorphisms in T cell signal transduction genes. Prevalence and association to development of multiple sclerosis

We systematically assessed 53 genes involved in T cell signaling, among which 72 SNPs in 32 genes were reported in databases as causing non-synonymous amino acid substitutions. Screening of 41 of these SNPs in DNA pools from 4000 Norwegian controls showed that only 12 SNPs (29%) were polymorphic. These were tested for association to MS in DNA pools from 364 Norwegian MS patients. To eliminate sources of variance introduced by DNA pooling, the SNPs in the best-ranked PLCG1 as well as the PTPN22 gene were thereafter genotyped in individual MS and control samples, however, without finding evidence for association to MS.

The PTPN22 1858T variant is not associated with primary biliary cirrhosis

The minor allele of a single nucleotide polymorphism (SNP) in the PTPN22 gene (1858T) encoding the Lyp-tyrosine phosphatase has been recently associated with multiple autoimmune disorders, raising the possibility that this variant may also represent a risk allele for primary biliary cirrhosis (PBC). We therefore investigated the possible association of the PTPN22(1858T) variant with PBC in a Canadian population. We studied 160 Caucasian patients with biopsy and antimitochondrial antibodies (AMA)-proven PBC who were genotyped for the PTPN22(C1858T) SNP using a single-base primer extension assay and mass spectrometry. The frequency of the PTPN22(1858T) allele was then compared between the patients and 290 healthy controls. No association was detected between the PTPN22(1858T) allele and PBC, the frequency of this variant being similar in patients with PBC (7.5%) and controls (8.4%). Restricting the analysis to patients with PBC with any second autoimmune condition or specifically with sicca syndrome or autoimmune thyroid disease also revealed no association with this variant. Thus the PTPN22(1858T) variant is not associated with PBC or with the combination of PBC and a second autoimmune disease. These data suggest that this variant does not confer risk for PBC and does not account for the frequent presence of other autoimmune diseases in patients with PBC.

Targeting the PTPome in human disease

Protein tyrosine phosphatases (PTPs) play vital roles in numerous cellular processes and are implicated in a growing number of human diseases, ranging from cancer to cardiovascular, immunological, infectious, neurological and metabolic diseases. There are at least 107 genes in the human genome, collectively referred to as the human 'PTPome'. Here the authors review the involvement of PTPs in human disease, discuss their potential as drug targets, and current efforts to develop PTP inhibitors for the treatment of human disease. Finally, the authors present their view of the future for PTPs as drug targets.

Mapping genes and pathways in autoimmune disease

Identifying novel genes and pathways controlling T-cell activation holds the promise of developing novel therapies for autoimmune disease and cancer. Recent advances in the human genome project have shown that it is timely for small groups searching for this Holy Grail to rethink their options. In this review, some alternative strategies employed in pursuing novel disease pathways in rodents and humans, including recent results, are presented. Examples include the murine Roquin and Ncf1 genes, and the PTPN22 gene identified in humans. The potential benefit of reducing the heterogeneity of clinically defined diseases by the careful phenotyping of patients, cells and lesions using advanced molecular biology and imaging techniques is highlighted.

PTPN22: setting thresholds for autoimmunity

The 620W allelic variant of the intracellular tyrosine phosphatase, PTPN22, is associated with a number of different autoimmune disorders, and this provides direct evidence for common mechanisms underlying many of these diseases. The associated allele appears to influence thresholds for T cell receptor signaling, and a variety of disease models involving both central and peripheral tolerance can be proposed. However, given the fact that PTPN22 is expressed in a variety of immunologically relevant cell types, the precise mechanisms for these associations remain unclear. In general, the PTPN22 620W allele appears to play a role in autoimmune disorders that have a prominent humoral component, suggesting that further investigation of PTPN22 activity in B cells will be useful. From a genetic perspective, the data highlights the genetic heterogeneity underlying autoimmunity in different ethnic groups.

Evaluating the role of the 620W allele of protein tyrosine phosphatase PTPN22 in Crohn's disease and multiple sclerosis

The 620W allele of PTPN22 has been associated with susceptibility to several different forms of chronic inflammatory disease, including Type 1 diabetes (T1D), rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), and autoimmune thyroiditis (AIT). We set out to explore its possible role in two other inflammatory diseases: multiple sclerosis (MS) and Crohn's disease (CD). In our cohort of 496 MS trios from the United Kingdom, we observed reduced transmission of the PTPN22 620W allele. The CD sample consisted of 169 trios as well as 249 cases of CD with their 207 matched control subjects collected in the province of Québec, Canada; there was also no evidence of association between the PTPN22 620W allele and susceptibility for CD. Pooled analyses combining our data with published data assessed a total of 1496 cases of MS and 1019 cases of CD but demonstrated no evidence of association with either disease. Given the modest odds ratios of known risk alleles for inflammatory diseases, these analyses do not exclude a role for the PTPN22 allele in susceptibility to CD or MS, but they do suggest that such a putative role would probably be more modest than that reported so far in T1D, RA, SLE, and AIT.

Role of PTPN22 in type 1 diabetes and other autoimmune diseases

We recently discovered that a single-nucleotide polymorphism (SNP) in the lymphoid tyrosine phosphatase (LYP), encoded by the PTPN22 gene on chromosome 1p13, correlates strongly with the incidence of type 1 diabetes (T1D) in two independent populations. This findings has now been verified by numerous studies and it has been expanded to rheumatoid arthritis, juvenile rheumatoid arthritis, systemic lupus erythematosus, Graves' disease, generalized vitiligo and other autoimmune disease. Here we review the genetics of the SNP and its association with autoimmunity, discuss the function of the phosphatase in signaling, the biochemistry of the disease-predisposing allele, and the possible mechanisms by which PTPN22 contributes to the development of human disease.

Lack of association between the protein tyrosine phosphatase non-receptor 22 (PTPN22)*620W allele and systemic sclerosis in the French Caucasian population

The minor allele of the R620W missense single-nucleotide polymorphism (SNP; rs2476601) in the PTPN22 (protein tyrosine phosphatase non-receptor 22) gene has been reported to be associated with multiple autoimmune diseases, including type 1 diabetes, systemic lupus erythematosus, rheumatoid arthritis, juvenile idiopathic arthritis, autoimmune thyroiditis and vitiligo. Systemic sclerosis (SSc) is a connective tissue disease with some autoimmune abnormalities. The aim of our study was to test for association of the PTPN22*620W allele with SSc in a French Caucasian cohort with a case-control study of 121 patients with SSc and 103 controls. All patients and controls were genotyped for the PTPN22*R620W SNP. No association was found between the PTPN22*620W allele and SSc (7% v 9.2%, p = 0.39). The frequency of genotypes carrying at least one 620W allele was similar in both groups (13% v 17%, p = 0.38). The PTPN22*620W allele was also not associated with autoantibody patterns. Thus, the PTPN22*R620W polymorphism cannot be regarded as a genetic susceptibility factor for SSc in the French Caucasian population.

The functional genetic variation in the PTPN22 gene has a negligible effect on the susceptibility to develop inflammatory bowel disease

The aim of this study was to assess the possible association between the protein tyrosine phosphatase non-receptor 22 (PTPN22) gene 1858C-->T (rs2476601, encoding R620W) polymorphism and inflammatory bowel disease (IBD). Our study population consisted of 1113 IBD [544 ulcerative colitis (UC) and 569 Crohn's disease (CD)] patients and 812 healthy subjects. All the individuals were of Spanish white origin. Genotyping of the PTPN22 gene 1858C-->T polymorphism was performed by real time polymerase chain reaction technology, using TaqMan 5'-allelic discrimination assay. The frequency of the PTPN22 1858T allele in healthy subjects was 6.2% compared with 6.7% in the UC patients and 5.1% in Crohn's patients. No statistically significant differences were observed when the PTPN22 1858C-->T allele and genotype distribution among CD patients, UC patients and healthy controls were compared. These results indicate that the PTPN22 1858C-->T polymorphism does not appear to play a major role in IBD predisposition in our population.

Multiple sclerosis genetics: leaving no stone unturned

Compelling epidemiologic and molecular data indicate that genes play a primary role in determining who is at risk for developing multiple sclerosis (MS), how the disease progresses, and how someone responds to therapy. The genetic component of MS etiology is believed to result from the action of allelic variants in several genes. Their incomplete penetrance and moderate individual effect probably reflects epistatic interactions, post-transcriptional regulatory mechanisms, and significant environmental influences. Equally significant, it is also likely that locus heterogeneity exists, whereby specific genes influence susceptibility and pathogenesis in some individuals but not in others. With the aid of novel analytical algorithms, the combined study of genomic, transcriptional, proteomic, and phenotypic information in well-controlled study groups will define a useful conceptual model of pathogenesis and a framework for understanding the mechanisms of action of existing therapies for this disorder, as well as the rationale for novel curative strategies.

Association of the truncating splice site mutation in BTNL2 with multiple sclerosis is secondary to HLA-DRB1*15

The major histocompatibility complex human leukocyte antigen (HLA)-DRB1*15 (DR2) haplotype is strongly associated with risk of multiple sclerosis (MS). The primary susceptibility has been localized to only approximately 200 kb encompassing the HLA-DR and -DQ loci. Further dissection of disease association with this region is demanding because of the high levels of linkage disequilibrium (LD). Recently, evidence was obtained for the involvement of a gene, potentially encoding an immune co-receptor, in another DR2-associated inflammatory condition, sarcoidosis. The implicated gene, BTNL2, is adjacent to DR and is in strong LD with HLA-DRB1. This fact, combined with a sequence relationship between BTNL2 and myelin oligodendrocyte glycoprotein, an autoantigen associated with MS, makes the gene an attractive candidate. To determine whether BTNL2 contributes to MS, we genotyped 1136 well-characterized MS families from the UK and the USA, as well as an African-American case-control data set, making this among the largest genetic studies in MS. Family-based and case-control association studies were performed for the BTNL2 and HLA-DRB1 loci. In all family data sets, the protein-truncating allele of BTNL2, implicated in sarcoidosis, was significantly over-transmitted to cases (combined data sets: global P=2.4x10(-11)). Given that the protein-truncating allele of BTNL2 virtually always occurred with DRB1*15, an effect could only be tested in DRB1*15-negative individuals or pedigrees. However, despite adequate power to detect an independent association, no difference in transmission of BTNL2 alleles or genotypes was observed in DRB1*15-negative individuals with MS. Conditional logistic regression modeling also strongly supported the conclusion that BTNL2 does not confer additional disease risk. The association of BTNL2 with MS observed in the African-American data set was also secondary to the primary DRB1*15 association.

Genetic susceptibility to type 1 diabetes

The recent discovery of PTPN22 as a novel susceptibility gene in human type 1 diabetes and continued progress in defining genes in animal models of the disease mark a fruitful period in the field of type 1 diabetes genetics. In addition, the similarities of the genetic and functional aspects across species have been substantiated. Future genome-wide association studies will reveal more loci, each providing a piece to the genetic puzzle of autoimmune disease.

The genetics of type 1 diabetes: lessons learned and future challenges

It has been more than 30 years since the first evidence was published suggesting the involvement of a specific chromosomal region, HLA, in modulating the risk for type 1 diabetes (T1D). In the intervening years, what have we learned regarding the identities of specific loci that modulate T1D risk, and what lessons have these studies provided that might be helpful in finding and characterizing additional susceptibility loci both for T1D and other autoimmune disorders? In the following review, we briefly address these issues.

PTPN22 genetic variation: evidence for multiple variants associated with rheumatoid arthritis

The minor allele of the R620W missense single-nucleotide polymorphism (SNP) (rs2476601) in the hematopoietic-specific protein tyrosine phosphatase gene, PTPN22, has been associated with multiple autoimmune diseases, including rheumatoid arthritis (RA). These genetic data, combined with biochemical evidence that this SNP affects PTPN22 function, suggest that this phosphatase is a key regulator of autoimmunity. To determine whether other genetic variants in PTPN22 contribute to the development of RA, we sequenced the coding regions of this gene in 48 white North American patients with RA and identified 15 previously unreported SNPs, including 2 coding SNPs in the catalytic domain. We then genotyped 37 SNPs in or near PTPN22 in 475 patients with RA and 475 individually matched controls (sample set 1) and selected a subset of markers for replication in an additional 661 patients with RA and 1,322 individually matched controls (sample set 2). Analyses of these results predict 10 common (frequency >1%) PTPN22 haplotypes in white North Americans. The sole haplotype found to carry the previously identified W620 risk allele was strongly associated with disease in both sample sets, whereas another haplotype, identical at all other SNPs but carrying the R620 allele, showed no association. R620W, however, does not fully explain the association between PTPN22 and RA, since significant differences between cases and controls persisted in both sample sets after the haplotype data were stratified by R620W. Additional analyses identified two SNPs on a single common haplotype that are associated with RA independent of R620W, suggesting that R620W and at least one additional variant in the PTPN22 gene region influence RA susceptibility.

A case-control study of tyrosine phosphatase (PTPN22) confirms the lack of association with Crohn's disease

In Crohn's disease (CD), the whole gastrointestinal tract can be affected by discontinuous and transmural inflammation. The terminal ileum and colon are especially prone to inflammation that comprises granulomata and later intestinal and perianal fistulas. Genome-wide linkage and epidemiological studies established genetic predisposition factors to CD. Recently, a variation of the intracellular protein tyrosine phosphatase nonreceptor-type 22 (PTPN22) was associated with several autoimmune diseases. Here, we analysed the functionally relevant polymorphism R620W (rs 2476601) of the PTPN22 gene in 146 patients suffering from CD using restriction fragment length polymorphism (RFLP) analyses. This study revealed evidence that PTPN22 variation may have no influence in the genetic predisposition to CD, at least not in another well-characterized Caucasian cohort.

Association analysis of the R620W polymorphism of protein tyrosine phosphatase PTPN22 in systemic lupus erythematosus families: increased T allele frequency in systemic lupus erythematosus patients with autoimmune thyroid disease

OBJECTIVE

Recent case-control studies show associations of the minor T allele (of the C1858T single-nucleotide polymorphism corresponding to the R620W amino acid substitution) of PTPN22 with multiple autoimmune diseases, including systemic lupus erythematosus (SLE). We performed family-based association studies of this polymorphism in 4 independent cohorts containing SLE patients and their parents and/or other family members.

METHODS

A total of 2,689 individuals from 902 independent Caucasian families with SLE were genotyped using polymerase chain reaction pyrosequencing (cohorts 1 and 2) and the Sequenom MassArray system (cohorts 3 and 4). The transmission disequilibrium test (TDT) and the pedigree disequilibrium test (PDT) were conducted to assess the evidence of association.

RESULTS

The 1858 C > T allele frequencies of the parents showed no deviation from Hardy-Weinberg equilibrium within each cohort. No evidence of preferential transmission of the T allele from heterozygous parents to their affected offspring was observed in each of the 4 cohorts or in the combined sample. Consistent with the TDT result, the PDT analysis revealed no significant association between the T allele and SLE. In 54 of the 661 SLE patients (cohorts 1 and 3) with documented autoimmune thyroid disease, the T allele frequency was higher than in individuals with SLE alone (16.7% versus 8.5%; P = 0.008, odds ratio 2.16 [95% confidence interval 1.25-3.72]).

CONCLUSION

The R620W polymorphism of the PTPN22 gene is not a major risk allele for SLE susceptibility in our sample of Caucasian individuals from northern America, the UK, or Finland, but it appears to be a risk factor for the concurrent autoimmune diseases of autoimmune thyroid disease and SLE.

The R620W C/T polymorphism of the gene PTPN22 is associated with SLE independently of the association of PDCD1

The gene PTPN22 is located on chromosome 1p13 and encodes a protein tyrosine phosphatase called the lymphoid-specific phosphatase (Lyp). Lyp is expressed in lymphocytes, where it physically associates through its proline-rich motif (called P1) with the SH3 domain of the protein tyrosine kinase Csk, an important suppressor of the Src family of kinases Lck and Fyn, which mediate TCR signaling. Therefore, it is said that interaction between Lyp and Csk enables these effectors to inhibit T-cell activation synergistically. It was reported that a missense single nucleotide polymorphism , R620W (rs2476601), 1858C->T encodes an amino-acid change in the P1 proline-rich motif of the gene PTPN22 and is associated with SLE in North American white individuals. PTPN22 gene polymorphisms were genotyped in 571 Swedish SLE patients and 1042 healthy controls using TaqMan SNP Genotyping Assay. Differences were observed between cases and control subjects at both the allele (chi(2)=11.2895;P=0.0007,1df) and genotype (chi(2)=10.2243;P=0.0013, 1df) levels. We also found evidence of a genetic association between PTPN22 and renal disorder (chi(2)=9.5660;P=0.0019). We then analyzed if in patients with renal disorder associations with PDCD1 and PTPN22 were independent. Our data suggest that this appears to be the case although we observed some degree of interaction.

Pathways to gene identification in rheumatoid arthritis: PTPN22 and beyond

Rheumatoid arthritis (RA), like other autoimmune diseases, has a complex genetic basis. Rapid technical advances in high-throughput genotyping and analysis have now reached a point where genes of low-to-moderate risk can be identified using a variety of study designs, including whole genome association studies. The availability of large, well-characterized populations of cases and controls are critical to the success of these efforts. A functional variant (R620W) of the intracellular protein tyrosine phosphatase N22 (PTPN22) has now been conclusively shown to confer approximately two-fold risk for seropositive RA as well as several other autoimmune disorders. PTPN22 appears to act primarily by setting thresholds for T-cell receptor signaling, and the current data suggest that the PTPN22 620W allele is likely to be a general risk factor for the development of humoral autoimmunity. PTPN22 is expressed widely in hematopoietic cells, but other than in T cells, its role is unknown. These results provide strong evidence for the longstanding hypothesis that common genes underlie different autoimmune phenotypes and emphasize that finding genes of only moderate risk can provide important insights into disease pathogenesis.

C1858T Functional Variant of PTPN22 Gene Is Not Associated With Celiac Disease Genetic Predisposition

Recent findings have demonstrated that the single nucleotide polymorphism 1858C-->T located at the P1 motif of the PTPN22 (protein tyrosine phosphatase nonreceptor 22) gene has functional relevance and is associated with a variety of autoimmune diseases. The aim of this study was to assess the role of the PTPN22 1858C-->T polymorphism in the genetic predisposition to celiac disease (CD). We analyzed a case-control cohort composed by 534 patients with CD and 653 healthy controls and additionally a panel of 271 celiac families. The PTPN22 1858C-->T genotyping was performed by TaqMan 5' allelic discrimination assay. We did not observed any statistically significant deviation after comparing allele and genotypic frequencies of PTPN22 1858C-->T between patients with CD and controls. Accordingly, the familial analysis did not reach statistically significant deviation in the transmission of PTPN22 1858C-->T alleles to the affected offspring. Therefore, our data suggest that the PTPN22 1858 single nucleotide polymorphism has no, or only a negligible, effect on CD susceptibility in this Spanish population.

No evidence for association between 1858 C/T single-nucleotide polymorphism of PTPN22 gene and primary Sjögren's syndrome

One-third of first-degree relatives of patients with primary Sjögren's syndrome (pSS) suffer from other autoimmune diseases, including type I diabetes, systemic lupus erythematosus and autoimmune thyroiditis. Recently, 1858 C/T polymorphism of PTPN22 gene was reported to predispose to these autoimmune diseases. We decided to investigate whether PTPN22 gene polymorphism was also involved in the genetic predisposition to pSS in a case-control study, including 183 patients with pSS and 172 healthy controls. No significant differences in allele (T allele frequency: 7.7% in patients with pSS vs 7.8% in controls, P=0.9) and genotype frequencies of PTPN22 polymorphism were detected between patients with pSS and controls. PTPN 22 gene polymorphism was not associated with a specific pattern of autoantibody secretion either. Thus, 1858 C/T polymorphism of PTPN22 gene is not involved in genetic predisposition to pSS.

Lymphoid tyrosine phosphatase (PTPN22/LYP) variant and Graves' disease in a Polish population: association and gene dose-dependent correlation with age of onset

OBJECTIVE

Susceptibility to Graves' disease (GD) is to a significant extent determined by genetic factors of which the best known are those associated with the HLA and the CTLA4 locus. Recently, two studies on British Caucasians reported that a single nucleotide polymorphism, 1858 C > T in PTPN22, encoding Arg620Trp in the lymphoid protein tyrosine phosphatase (LYP), which is a negative regulator of T-cell activation, increases the risk of GD. The purpose of our study was to investigate whether the PTPN22 'T' allele is associated with GD and/or its subsets, defined by clinical or genetic parameters, in a Polish population.

SUBJECTS AND DESIGN

A cohort of 290 patients and 310 controls was genotyped using a PCR-RFLP method. The distribution of PTPN22 alleles and genotypes among patients and controls was compared, and correlation was sought between PTPN22 'T' and sex, tobacco smoking status, family history of GD, age of disease onset, presence (and severity) of ophthalmopathy, and presence of the CTLA4 A49G or DRB1*03 alleles.

RESULTS

Association between GD and the PTPN22 'T' allele was confirmed (OR 1.7, P < 0.0008). Furthermore, a significant correlation between the PTPN22 genotype and the age of GD onset was demonstrated (r = -0.18, P = 0.0019). The PTPN22 'TT' and 'CC' genotypes defined groups characterized by more than twofold difference in median age of disease onset (20.8 years vs. 42 years, P < 0.003) whereas the 'CT' genotype was associated with an intermediate value (35 years). There were no statistically significant correlations with other analysed clinical or genetic parameters.

CONCLUSIONS

We replicated the association between Graves' disease and PTPN22 'T' reported in British Caucasians. We also found a gene dose-dependent effect of PTPN22 'T' on the age of onset of Graves' disease.

Complex interactions among MHC haplotypes in multiple sclerosis: susceptibility and resistance

Mechanisms for observed associations within the major histocompatibility complex (MHC) and autoimmune diseases including multiple sclerosis (MS) remain uncertain. Genotyping of the HLA Class II DRB1 locus in 4347 individuals from 873 multiplex families with MS highlights the genetic complexity of this locus. Excess allele sharing in sibling pair families lacking DRB1*15 and DRB1*17 (58.5% sharing; P=0.012) was comparable to that seen where parents were DRB1*15 positive (62%, P=0.0006). DRB1*17 (P=0.00027) was clearly established as an MS susceptibility allele in addition to DRB1*15 (P<10(-14)). DRB1*14 showed striking under-transmission (P=0.000032) to affected offspring newly establishing this allele as a broadly acting resistance factor. Trans interactions were seen in both DRB1*15 and non-DRB1*15 bearing genotype combinations. DRB1*08 was transmitted preferentially with DRB1*15 (P=0.0114) and, in the presence of DRB1*08, the transmission of DRB1*15 was almost invariable (37 transmissions to one non-transmission). DRB1*01 was under-transmitted to offspring in the presence of DRB1*15 (P=0.019). Both DRB1*01 and DRB1*14 haplotypes carry DQA1*01-DQB1*05 alleles, suggesting a common DQ-related mechanism for the protection mediated by these haplotypes. These studies demonstrate that it is the Class II genotype that determines susceptibility and resistance to MS. By analogy with celiac disease and type I diabetes, the pattern of susceptibility strongly supports an autoimmune aetiology.

Differential association of the PTPN22 coding variant with autoimmune diseases in a Dutch population

Protein tyrosine phosphatase PTPN22 is involved in the negative regulation of T-cell responsiveness. Recently, the association of a coding variant of the PTPN22 gene-R620W(1858C>T) with a number of autoimmune diseases has been described. Therefore, we tested the association of PTPN22 1858*T allele in Dutch early onset type 1 diabetes (T1D) and rheumatoid arthritis (RA) patients, as well as celiac disease (CD) patients, for which no previous study of PTPN22 has been reported. The PTPN22 variant was strongly associated with T1D in cases vs controls (P=2 x 10(-7), OR=2.3, 95% CI=1.7-3.1) as well as in a transmission disequilibrium test in nuclear trio's (P=9 x 10(-9), OR=3.3, CI=2.1-5.0), RA (case/control: P=0.003, OR=1.8 CI =1.2-2.6), but not CD, in spite of a trend of increased homozygosity (P=0.05) and early age at onset (P=0.01). PTPN22 is not generally associated with T-cell mediated autoimmune diseases, although it might play a role in the CD patients with early clinical manifestation.

Analysis of families in the multiple autoimmune disease genetics consortium (MADGC) collection: the PTPN22 620W allele associates with multiple autoimmune phenotypes

Autoimmune disorders constitute a diverse group of phenotypes with overlapping features and a tendency toward familial aggregation. It is likely that common underlying genes are involved in these disorders. Until very recently, no specific alleles--aside from a few common human leukocyte antigen class II genes--had been identified that clearly associate with multiple different autoimmune diseases. In this study, we describe a unique collection of 265 multiplex families assembled by the Multiple Autoimmune Disease Genetics Consortium (MADGC). At least two of nine "core" autoimmune diseases are present in each of these families. These core diseases include rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), type 1 diabetes (T1D), multiple sclerosis (MS), autoimmune thyroid disease (Hashimoto thyroiditis or Graves disease), juvenile RA, inflammatory bowel disease (Crohn disease or ulcerative colitis), psoriasis, and primary Sjogren syndrome. We report that a recently described functional single-nucleotide polymorphism (rs2476601, encoding R620W) in the intracellular tyrosine phosphatase (PTPN22) confers risk of four separate autoimmune phenotypes in these families: T1D, RA, SLE, and Hashimoto thyroiditis. MS did not show association with the PTPN22 risk allele. These findings suggest a common underlying etiologic pathway for some, but not all, autoimmune disorders, and they suggest that MS may have a pathogenesis that is distinct from RA, SLE, and T1D. DNA and clinical data for the MADGC families are available to the scientific community; these data will provide a valuable resource for the dissection of the complex genetic factors that underlie the various autoimmune phenotypes.

Association analysis of the 1858C>T polymorphism in the PTPN22 gene in juvenile idiopathic arthritis and other autoimmune diseases

A functional single nucleotide polymorphism, 1858C>T, in the PTPN22 gene, encoding a tyrosine phosphatase, has been reported to be associated with type I diabetes and some other autoimmune diseases. To further investigate whether this polymorphism may be a general susceptibility factor for autoimmunity, we performed an association study in five different autoimmune diseases, three previously not tested. We found an association with juvenile idiopathic arthritis (OR=1.41; P=0.04), not previously reported, and a tendency for an association with coeliac disease (OR=1.35; P=0.08). In primary sclerosing cholangitis, no association was observed (OR=0.95; P=0.8). Furthermore, we confirmed the increased risk in rheumatoid arthritis (OR=1.58; P=0.001), but could not find support for an association with systemic lupus erythematosus (OR=0.94; P=0.8). Altogether, we have provided further evidence of an association between autoimmune diseases and the 1858C>T polymorphism in PTPN22.

Association between thePTPN22 gene and rheumatoid arthritis and juvenile idiopathic arthritis in a UK population: Further support thatPTPN22 is an autoimmunity gene

OBJECTIVE

The protein tyrosine phosphatase N22 (PTPN22) gene exhibits regulatory activities for both T cells and B cells. A missense single-nucleotide polymorphism (SNP) within this gene (rs2476601) has recently been associated with 4 autoimmune diseases: rheumatoid arthritis (RA), systemic lupus erythematosus, autoimmune thyroid disease, and type 1 diabetes mellitus, all of which are T cell-mediated and associated with the elaboration of autoantibody. The aim of this study was to investigate associations of the missense SNP of PTPN22 in a number of autoimmune diseases in the UK population, including RA, juvenile idiopathic arthritis (JIA), psoriasis, psoriatic arthritis (PsA), and multiple sclerosis (MS), some of which have not been examined previously.

METHODS

The PTPN22 missense SNP was genotyped in 886 RA, 661 JIA, 279 psoriasis, 455 PsA, and 379 MS patients and in 595 healthy controls. Association with the PTPN22 SNP was analyzed by chi-square test as implemented in Stata software.

RESULTS

There was a significant association between the PTPN22 SNP and RA (P = 1.8 x 10(-8)) and JIA (P = 0.0005). In contrast, no association with psoriasis, PsA, or MS was detected.

CONCLUSION

We replicated the findings of a previous association with RA and identified a novel association with JIA. Together with previous data showing associations with other autoimmune diseases, our findings provide further evidence that the PTPN22 gene plays a role in the pathogenesis of a subgroup of autoimmune diseases.