PTPN22 Variants Research Articles

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

ObjectiveTo analyse the role of the PTPN22 and CSK genes, previously associated with autoimmunity, in the predisposition and clinical phenotypes of giant cell arteritis (GCA).MethodsOur study population was composed of...

Susceptibility to childhood-onset rheumatoid arthritis: investigation of a weighted genetic risk score that integrates cumulative effects of variants at five genetic loci.

Children with childhood-onset rheumatoid arthritis (RA) include those with rheumatoid factor or anti-citrullinated protein antibody-positive juvenile idiopathic arthritis. To test the hypothesis that adult-onset RA-associated variants are also associated with childhood-onset RA, we investigated RA-associated variants at 5 loci in a cohort of patients with childhood-onset RA. We also assessed the cumulative association of these variants in susceptibility to childhood-onset RA using a weighted genetic risk score (wGRS). A total of 155 children with childhood-onset RA and 684 healthy controls were genotyped for 5 variants in the PTPN22, TRAF1/C5, STAT4, and TNFAIP3 loci. High-resolution HLA-DRB1 genotypes were available for 149 cases and 373 controls. We tested each locus for association with childhood-onset RA via logistic regression. We also computed a wGRS for each subject, with weights based on the natural log of the published odds ratios (ORs) for the alleles investigated, and used logistic regression to test the wGRS for association with childhood-onset RA. Childhood-onset RA was associated with TNFAIP3 rs10499194 (OR 0.60 [95% confidence interval 0.44-0.83]), PTPN22 rs2476601 (OR 1.61 [95% confidence interval 1.11-2.31]), and STAT4 rs7574865 (OR 1.41 [95% confidence interval 1.06-1.87]) variants. The wGRS was significantly different between cases and controls (P < 2 × 10(-16) ). Individuals in the third to fifth quintiles of wGRS had a significantly increased disease risk compared to baseline (individuals in the first quintile). Higher wGRS was associated with increased risk of childhood-onset RA, especially among males. The magnitude and direction of the association between TNFAIP3, STAT4, and PTPN22 variants and childhood-onset RA are similar to those observed in RA, suggesting that adult-onset RA and childhood-onset RA share common genetic risk factors. Using a wGRS, we have demonstrated the cumulative association of RA-associated variants with susceptibility to childhood-onset RA.

Enhanced PI3K/Akt-mediated survival of memory Th1 cells in type-1 diabetics and healthy controls carrying the autoimmunity-associated 1858T allelic variant of PTPN22 (P4097)

Abstract A C-to-T polymorphism (1858T) in the PTPN22 gene alters the function of the lymphoid phosphatase Lyp and confers increased risk for autoimmunity. The PTPN22 1858T allele is associated with altered TCR signaling and expanded memory T cell pool. To determine its impact on lineage commitment and survival, naïve CD4+ T cells from healthy subjects carrying risk or non-risk alleles were differentiated in vitro. Cultures of T cells bearing PTPN22 1858T displayed similar proliferative capacity but reduced activation-induced cell death, yielding more IFNγ+ Th1 cells than non-risk controls. In vivo, PTPN22 1858T subjects mounted enhanced IFNγ responses to the pneumococcal vaccine Prevnar, but not IL-2 production or T cell proliferation. Examination of TCR-mediated signaling revealed that elevated pAkt activity and BCL2 expression were associated with the PTPN22 1858T allele and correlated with enhanced T cell survival during in vitro stimulation. This phenotype was mirrored in T cell cultures from type-1 diabetic subjects, regardless of their PTPN22 genotype, and was reversed by a PI3Kδ-specific inhibitor. Our studies indicate that the autoimmunity-associated PTPN22 1858T allele protects T cells from apoptosis via elevated PI3K/Akt signaling, leading to the accumulation of pro-inflammatory memory Th1 cells. This T-cell intrinsic defect is a general feature of T1D and inhibition of PI3Kδ offers a potential avenue for pharmacological intervention.

Ptpn22 promotes immunization responses to Influenza A (P4043)

Abstract A variant allele of PTPN22 is a potent susceptibility factor for autoimmune diseases, including Rheumatoid Arthritis and Type I Diabetes. Ptpn22 is required in myeloid cells for selective promotion of Toll-Like Receptor signaling leading to Type I IFN production. Since Type I IFN are essential for anti-viral immunity and for efficient responses to viral immunization, we investigated the role of PTPN22 in response to vaccination. We tested the ability of Ptpn22 knockout mice to mount a protective immune response to vaccination against Influenza A virus. We found that Ptpn22 is required for efficient generation of both influenza-specific cytotoxic T lymphocyte and neutralizing humoral responses after vaccination with inactivated influenza. Further, upon challenge with live influenza, vaccinated Ptpn22 KO animals exhibit increased mortality, suggesting that defects in antibody and CTL responses associated with Ptpn22 deficiency result in decreased protection engendered by inactivated influenza vaccination. These findings indicate a requirement for Ptpn22 in protective immune responses to influenza vaccine. Moreover, they suggest that further studies of vaccine responsiveness should be mounted in human carriers of the disease-associated PTPN22 variant, since such carriers exhibit diminished Toll-Like Receptor-induced Type I IFN production by myeloid cells.

Variants in PTPN22 and SMOC2 genes and the risk of thyroid disease in the Jordanian Arab population

Autoimmune thyroid diseases (AITDs) (Hashimoto thyroiditis and Graves' disease) are complex polygenic disorders with multiple genes thought to contribute to the risk of disease. The contribution of these genes differs by different populations. The PTPN22 gene is reported to be associated with multiple autoimmune diseases, but results of association are conflicting in different populations. The SMOC2 gene is reported to be associated with families with autoimmune vitiligo that had other autoimmunities including thyroid disease. The study aims to investigate the association of PTPN22 and SMOC2 single nucleotide polymorphisms with thyroid disease in a cohort of Jordanian patients. We collected blood samples from 204 thyroid patients and 216 normal controls. We used PCR-RFLP to genotype rs2476601 in PTPN22 and rs13208776 in SMOC2 genes. Both of the SNPS did not show significant association with thyroid disease, even after stratification according to subtype of disease (Hashimoto thyroiditis and Graves' disease) or gender. We reanalyzed SMOC2 SNP using a dominant and recessive models and we got marginal significance when using a dominant model with female-only patients (P = 0.052). PTPN22 SNP did not show association with autoimmune thyroid disease in our patient cohort. This may be due to the low frequency of this SNP in the Jordanian population. SMOC2 SNP, on the other hand, may play a role in AITD susceptibility as a dominant polymorphism. Additional samples might be needed to confirm or exclude association of SMOC2 with AITD.

Recipient PTPN22 −1123 C/C Genotype Predicts Acute Graft-versus-Host Disease after HLA Fully Matched Unrelated Bone Marrow Transplantation for Hematologic Malignancies

PTPN22 is a critical negative regulator of T cell responses. Its promoter gene variant (rs2488457, −1123G>C) has been reported to be associated with autoimmune diseases. This study analyzed the impact of the PTPN22 variant on transplantation outcomes in a cohort of 663 patients who underwent unrelated HLA-matched bone marrow transplantation (BMT) for hematologic malignancies through the Japan Marrow Donor Program. The recipient C/C genotype versus the recipient G/G genotype resulted in a lower incidence of grade II-IV acute graft-versus-host disease (hazard ratio [HR], 0.50; 95% confidence interval [CI], 0.29-0.85; P = .01), as well as a higher incidence of relapse (HR, 1.78; 95% CI, 1.10-2.90; P = .02), as demonstrated on multivariate analysis. In patients with high-risk disease, the recipient C/C genotype was associated with significantly worse overall survival rates than the recipient G/G genotype (HR, 1.60; 95% CI, 1.02-2.51; P = .04), whereas this effect was absent in patients with standard-risk disease. In addition, the donor G/C genotype was associated with a lower incidence of relapse (HR, 0.58; 95% CI, 0.40-0.85), which did not influence survival. Our findings suggest that PTPN22 genotyping could be useful in predicting prognoses and creating therapeutic strategies for improving the final outcomes of allogeneic BMT.

PTPN22 Polymorphism Presumably Plays a Role in the Genetic Background of Chronic Spontaneous Autoreactive Urticaria

Background: The association of chronic urticaria (CU) with autoimmune disorders is relatively well proved. Protein tyrosine phosphatase-22 (PTPN22) is considered to be one of the strongest genetic factors for human autoimmunity. We decided to evaluate whether additional, non 1858C>T, PTPN22 variants are independent contributors to the risk of CU occurrence in the Polish population. Methods: A total of 91 CU patients with a positive result of autologous serum skin test and 100 healthy volunteers were enrolled in the study. The Urticaria Activity Score was used in disease intensity assessment. In all subjects rs3811021, rs1310182 and rs2488457 polymorphisms were genotyped. Results: We found a higher prevalence of –1123 C allele among CU patients. No differences in the allele and genotype distribution were found in the other analyzed polymorphisms. Haplotype construction of the three SNPs revealed statistically significant CU association of rs2488457C, rs1310182T and rs3811021T. Conclusions: Contrary to previous findings, the contribution of PTPN22 to disease susceptibility is suggested. We can speculate that CU is a genetically complex disease and that its occurrence needs multiple genetic and environmental risk factors.

Modulation of T cell receptor and interleukin-2 receptor signaling in human primary CD4+ T cells (179.7)

Abstract Type 1 Diabetes (T1D) results from the aberrant autoimmune targeting and destruction of insulin-producing β-cells, and dysregulation of T cell activation is central to this break in tolerance. Regulatory T cells (Tregs) are fundamental to maintaining immune homeostasis and functional defects of this T cell subset can potentiate autoimmunity. Therefore, Tregs represent an attractive target for clinical intervention of T1D. Genetic variants of PTPN2 and PTPN22 have been linked to several autoimmune diseases, including T1D, by genome wide association studies. These genes encode for phosphates that dampen IL-2R and TCR signaling, respectively. In this study, we have utilized lentiviral vectors for dual overexpression and knockdown of these genes in primary human CD4+ T cells. We hypothesize that the suppressive function and phenotypic stability of human Tregs is enhanced by increased IL-2R and TCR signaling and deficient following downregulation of IL-2R and TCR signaling. Pathway-modified human effector T cells (Teff) will display altered lineage skewing and may be resistant to AICD and suppression when IL-2R and TCR signaling are increased. Further, simultaneous modulation of these pathways will synergistically affect T cell function. These data will provide insights into how direct modulation of these autoimmune signature pathways controls adaptive Treg and Teff activity, and further, have important implications for adoptive Treg therapy for the treatment of autoimmunity.

PTPN22.6, a Dominant Negative Isoform of PTPN22 and Potential Biomarker of Rheumatoid Arthritis

PTPN22 is a tyrosine phosphatase and functions as a damper of TCR signals. A C-to-T single nucleotide polymorphism (SNP) located at position 1858 of human PTPN22 cDNA and converting an arginine (R620) to tryptophan (W620) confers the highest risk of rheumatoid arthritis among non-HLA genetic variations that are known to be associated with this disease. The effect of the R-to-W conversion on the phosphatase activity of PTPN22 protein and the impact of the minor T allele of the C1858T SNP on the activation of T cells has remained controversial. In addition, how the overall activity of PTPN22 is regulated and how the R-to-W conversion contributes to rheumatoid arthritis is still poorly understood. Here we report the identification of an alternative splice form of human PTPN22, namely PTPN22.6. It lacks the nearly entire phosphatase domain and can function as a dominant negative isoform of the full length PTPN22. Although conversion of R620 to W620 in the context of PTPN22.1 attenuated T cell activation, expression of the tryptophan variant of PTPN22.6 reciprocally led to hyperactivation of human T cells. More importantly, the level of PTPN22.6 in peripheral blood correlates with disease activity of rheumatoid arthritis. Our data depict a model that can reconcile the conflicting observations on the functional impact of the C1858T SNP and also suggest that PTPN22.6 is a novel biomarker of rheumatoid arthritis.

PTPN22 polymorphisms may indicate a role for this gene in atopic dermatitis in West Highland white terriers

BackgroundCanine atopic dermatitis is an allergic inflammatory skin disease common in West Highland white terriers. A genome-wide association study for atopic dermatitis in a population of West Highland white terriers identified a 1.3 Mb area of association on CFA17 containing canine protein tyrosine phosphatase non-receptor type 22 (lymphoid) PTPN22. This gene is a potential candidate gene for canine atopic dermatitis as it encodes a lymphoid-specific signalling mediator that regulates T-cell and possibly B-cell activity.FindingsSequencing of PTPN22 in three atopic and three non-atopic West Highland white terriers identified 18 polymorphisms, including five genetic variants with a bioinformatically predicted functional effect. An intronic polymorphic repeat sequence variant was excluded as the cause of the genome-wide association study peak signal, by large-scale genotyping in 72 West Highland white terriers (gene-dropping simulation method, P = 0.01).ConclusionsThis study identified 18 genetic variants in PTPN22 that might be associated with atopic dermatitis in West Highland white terriers. This preliminary data may direct further study on the role of PTPN22 in this disease. Large scale genotyping and complementary genomic and proteomic assays would be required to assess this possibility.

Overexpression of the Autoimmunity-Associated Tyrosine Phosphatase PTPN22 in CLL Cells Enhances Antiapoptotic B-Cell Receptor Signals Through Selective Activation of the AKT Pathway

Abstract 619The phosphatase PTPN22 is an important negative regulator of T cell receptor (TCR) signaling. A gain of function polymorphism in this phosphatase is strongly linked with increased risk for the development of several common autoimmune diseases, including rheumatoid arthritis, insulin-dependent diabetes mellitus and systemic lupus erythematosus. The exact mechanism how the more active PTPN22 variant contributes to the development of these autoimmune diseases is still unclear, but it is has been postulated that increased activity of this enzyme may prevent negative selection of autoreactive T cells by blocking proapoptotic TCR signals induced by autoantigen.We now report that PTPN22 is significantly overexpressed in CLL B cells. Of the 91 investigated CLL samples, in 66 (73%) the levels of PTPN22 were at least 2 fold higher and often exceeded by 10 fold the levels in normal tonsilar B cells (CLL, mean PTPN22 levels 5.7, SD +/−4.3; normal tonsilar B cells, mean PTPN22 levels 0.9, SD +/−0.1). PTPN22 levels were somewhat higher in CD38−positive than CD38−negative cases (P=0.031), whereas no association was observed with IGHV mutation status, ZAP-70 expression and time to treatment.To determine the functional consequences of PTPN22 overexpression, we performed RNA interference experiments in primary CLL B cells with high PTPN22. We evaluated the effects of PTPN22 silencing in unstimulated CLL cells as well as CLL cells stimulated through the B cell receptor (BCR), given the important role of the BCR signaling pathway in the pathophysiology of CLL. Both soluble and immobilized anti-IgM antibodies were used for BCR stimulation, as these two BCR crosslinking agents have opposing effects on leukemic cell survival.Silencing of PTPN22 had no effect on the viability of unstimulated CLL cells (n=11, viable CLL cells: siControl 49%, siPTPN22 48%, P=n.s.), but significantly inhibited the antiapoptotic effect of immobilized anti-IgM (viable CLL cells: siControl 55%, siPTPN22 48%, P=0.001) and enhanced the proapoptotic effect of soluble anti-IgM (viable CLL cells: siControl 44%, siPTPN22 31%, P<0.001). Consistent with these data, overexpression of PTPN22 in the lymphoma B cell line B104 significantly blocked apoptosis induced by soluble anti-IgM (control 22%, PTPN22 35%) without affecting the survival of unstimulated cells (control 52%, PTPN22 51%).The previous experiments suggested that PTPN22 functions as a molecular switch that enhances antiapoptotic and inhibits proapoptotic BCR signals. To establish the molecular mechanisms underlying these different activities, we studied BCR signal transduction in primary CLL cells transfected with control or PTPN22-specific siRNA. Downregulation of PTPN22 increased anti-IgM-induced activation of several BCR signaling molecules, including LYN, SYK, ERK, JNK and the proapoptotic p38MAPK, confirming that PTPN22 is primarily a negative regulator of BCR signaling. However, activation of the antiapoptotic AKT kinase was substantially reduced by silencing of PTPN22, as evidenced by decreased phosphorylation of AKT and its direct targets GSK3b and FOXO3a. Lack of PTPN22 expression was further associated with increased activity of the phosphatase SHIP, a key negative regulator of the AKT kinase. Opposite effects on the activity of these signaling molecules were observed when PTPN22 was overexpressed in B104 cells, thus validating the data obtained by PTPN22 knockdown in primary CLL cells.In summary, this study shows that the phosphatase PTPN22, which has been implicated in the pathogenesis of several common autoimmune diseases, is significantly overexpressed in CLL B-cells. Overexpression of PTPN22 inhibits activation of molecules that propagate the proapoptotic BCR signal, such as p38MAPK, but at the same time enhances the antiapoptotic signal delivered through the AKT kinase. The mechanism how PTPN22 enhances activation of AKT in response to BCR engagement is by preventing Lyn-mediated activation of the negative regulator SHIP. Collectively, these data show that PTPN22 is an important regulatory molecule in CLL and a potential therapeutic target. Inhibitors of this phosphatase, which are currently being developed for the treatment of autoimmune diseases associated with the gain of function PTPN22 variant, would be expected to convert the BCR survival signal into a death signal and may thus provide means for selective targeting of the malignant clone. Disclosures:No relevant conflicts of interest to declare.

Deep resequencing of GWAS loci identifies independent rare variants associated with inflammatory bowel disease

More than a thousand disease susceptibility loci have been identified via genome-wide association studies (GWAS) of common variants; however, the specific genes and full allelic spectrum of causal variants underlying these findings generally remain to be defined. We utilize pooled next-generation sequencing to study 56 genes in regions associated to Crohn’s Disease in 350 cases and 350 controls. Follow up genotyping of 70 rare and low-frequency protein-altering variants (MAF ~ .001-.05) in nine independent case-control series (16054 CD patients, 12153 UC patients, 17575 healthy controls) identifies four additional independent risk factors in NOD2, two additional protective variants in IL23R, a highly significant association to a novel, protective splice variant in CARD9 (p < 1e-16, OR ~ 0.29), as well as additional associations to coding variants in IL18RAP, CUL2, C1orf106, PTPN22 and MUC19. We extend the results of successful GWAS by providing novel, rare, and likely functional variants that will empower functional experiments and predictive models.

2.16 Overexpression of the Autoimmunity-Associated Tyrosine Phosphatase PTPN22 in CLL Cells Enhances Antiapoptotic B-Cell Receptor Signals Through Selective Activation of the AKT Pathway

Abstract Abstract 619 The phosphatase PTPN22 is an important negative regulator of T cell receptor (TCR) signaling. A gain of function polymorphism in this phosphatase is strongly linked with increased risk for the development of several common autoimmune diseases, including rheumatoid arthritis, insulin-dependent diabetes mellitus and systemic lupus erythematosus. The exact mechanism how the more active PTPN22 variant contributes to the development of these autoimmune diseases is still unclear, but it is has been postulated that increased activity of this enzyme may prevent negative selection of autoreactive T cells by blocking proapoptotic TCR signals induced by autoantigen. We now report that PTPN22 is significantly overexpressed in CLL B cells. Of the 91 investigated CLL samples, in 66 (73%) the levels of PTPN22 were at least 2 fold higher and often exceeded by 10 fold the levels in normal tonsilar B cells (CLL, mean PTPN22 levels 5.7, SD +/−4.3; normal tonsilar B cells, mean PTPN22 levels 0.9, SD +/−0.1). PTPN22 levels were somewhat higher in CD38−positive than CD38−negative cases (P=0.031), whereas no association was observed with IGHV mutation status, ZAP-70 expression and time to treatment. To determine the functional consequences of PTPN22 overexpression, we performed RNA interference experiments in primary CLL B cells with high PTPN22. We evaluated the effects of PTPN22 silencing in unstimulated CLL cells as well as CLL cells stimulated through the B cell receptor (BCR), given the important role of the BCR signaling pathway in the pathophysiology of CLL. Both soluble and immobilized anti-IgM antibodies were used for BCR stimulation, as these two BCR crosslinking agents have opposing effects on leukemic cell survival. Silencing of PTPN22 had no effect on the viability of unstimulated CLL cells (n=11, viable CLL cells: siControl 49%, siPTPN22 48%, P=n.s.), but significantly inhibited the antiapoptotic effect of immobilized anti-IgM (viable CLL cells: siControl 55%, siPTPN22 48%, P=0.001) and enhanced the proapoptotic effect of soluble anti-IgM (viable CLL cells: siControl 44%, siPTPN22 31%, P The previous experiments suggested that PTPN22 functions as a molecular switch that enhances antiapoptotic and inhibits proapoptotic BCR signals. To establish the molecular mechanisms underlying these different activities, we studied BCR signal transduction in primary CLL cells transfected with control or PTPN22-specific siRNA. Downregulation of PTPN22 increased anti-IgM-induced activation of several BCR signaling molecules, including LYN, SYK, ERK, JNK and the proapoptotic p38MAPK, confirming that PTPN22 is primarily a negative regulator of BCR signaling. However, activation of the antiapoptotic AKT kinase was substantially reduced by silencing of PTPN22, as evidenced by decreased phosphorylation of AKT and its direct targets GSK3b and FOXO3a. Lack of PTPN22 expression was further associated with increased activity of the phosphatase SHIP, a key negative regulator of the AKT kinase. Opposite effects on the activity of these signaling molecules were observed when PTPN22 was overexpressed in B104 cells, thus validating the data obtained by PTPN22 knockdown in primary CLL cells. In summary, this study shows that the phosphatase PTPN22, which has been implicated in the pathogenesis of several common autoimmune diseases, is significantly overexpressed in CLL B-cells. Overexpression of PTPN22 inhibits activation of molecules that propagate the proapoptotic BCR signal, such as p38MAPK, but at the same time enhances the antiapoptotic signal delivered through the AKT kinase. The mechanism how PTPN22 enhances activation of AKT in response to BCR engagement is by preventing Lyn-mediated activation of the negative regulator SHIP. Collectively, these data show that PTPN22 is an important regulatory molecule in CLL and a potential therapeutic target. Inhibitors of this phosphatase, which are currently being developed for the treatment of autoimmune diseases associated with the gain of function PTPN22 variant, would be expected to convert the BCR survival signal into a death signal and may thus provide means for selective targeting of the malignant clone. Disclosures: No relevant conflicts of interest to declare.

2.17 Activation of STAT3 Increases Mitochondrial Respiration and Protects Mitochondria from Oxidative Damage in Chronic Lymphocytic Leukemia

viable CLL cells treated with siControl 55% vs treated with siPTPN22 48%, P 0.001) and enhanced the proapoptotic effect of soluble anti-IgM (mean viable CLL cells treated with siControl 44% vs treated with siPTPN22 31%; P 0.001). Consistent with these data, overexpression of PTPN22 in the lymphoma B-cell line B104 significantly blocked apoptosis induced by soluble anti-IgM (mean viable cells transfected with control messenger RNA [mRNA] 22% vs transfected with PTPN22 mRNA 35%) without affecting the survival of unstimulated cells (mean viable cells transfected with control mRNA 52% vs. transfected with PTPN22 mRNA 51%). The previous experiments suggested that PTPN22 functions as a molecular switch that enhances antiapoptotic and inhibits proapoptotic B-cell receptor (BCR) signals. To establish the molecular mechanisms underlying these different activities, we studied BCR signal transduction in primary CLL cells transfected with control or PTPN22-specific siRNA. Downregulation of PTPN22 increased anti-IgM-induced activation of several BCR signaling molecules, including LYN, SYK, ERK, JNK and the proapoptotic p38MAPK, confirming that PTPN22 is primarily a negative regulator of BCR signaling. However, anti-IgM–induced activation of the antiapoptotic AKT kinase was substantially reduced by silencing of PTPN22, as evidenced by decreased phosphorylation of AKT and its direct targets GSK3b and FOXO3a. Lack of PTPN22 expression was further associated with increased activity of the phosphatase SHIP, a key negative regulator of the AKT kinase. Opposite effects on the activity of these signaling molecules were observed when PTPN22 was overexpressed in B104 cells, thus validating the data obtained by PTPN22 knockdown in primary CLL cells. In summary, this study shows that the phosphatase PTPN22, which has been implicated in the pathogenesis of several common autoimmune diseases, is significantly overexpressed in CLL B-cells. Overexpression of PTPN22 inhibits activation of molecules that propagate the proapoptotic BCR signal, such as p38MAPK, but at the same time amplifies the antiapoptotic signal delivered through the AKT kinase. The mechanism by which PTPN22 enhances activation of AKT in response to BCR engagement is prevention of Lyn-mediated activation of the negative regulator SHIP. Collectively, these data show that PTPN22 is an important regulatory molecule in CLL and a potential therapeutic target. Inhibitors of this phosphatase, which are currently being developed for the treatment of autoimmune diseases associated with the gain-of-function PTPN22 variant, would be expected to convert the BCR survival signal into a death signal and may thus provide means for selective targeting of the malignant clone.

The autoimmune disease–associated PTPN22 variant promotes calpain-mediated Lyp/Pep degradation associated with lymphocyte and dendritic cell hyperresponsiveness

A variant of the PTPN22-encoded Lyp phosphatase (Lyp620W) confers risk for autoimmune disease, but the mechanisms underlying this association remain unclear. We show here that mice expressing the Lyp variant homolog Pep619W manifest thymic and splenic enlargement accompanied by increases in T-cell number, activation and positive selection and in dendritic- and B-cell activation. Although Ptpn22 (Pep) transcript levels were comparable in Pep619W and wild-type Pep619R mice, Pep protein levels were dramatically reduced in the mutant mice, with Pep619W protein being more rapidly degraded and showing greater association with and in vitro cleavage by calpain 1 than Pep619R. Similarly, levels of the Lyp620W variant were decreased in human T and B cells, and its calpain binding and cleavage were increased relative to wild-type Lyp620R. Thus, calpain-mediated degradation with consequently reduced Lyp/Pep expression and lymphocyte and dendritic cell hyperresponsiveness represents a mechanism whereby Lyp620W may increase risk for autoimmune disease.

Association of variants in MMEL1 and CTLA4 with rheumatoid arthritis in the Han Chinese population

BackgroundThe genome-wide association study era has made great progress in identifying susceptibility genes and genetic loci for rheumatoid arthritis (RA) in populations of White European ancestry. However, few studies have...

The PTPN22 R263Q polymorphism is a risk factor for rheumatoid arthritis in Caucasian case–control samples

Recently, a functional PTPN22 variant (R263Q; rs33996649) was found to be associated with systemic lupus erythematosus (SLE). This study was undertaken to analyze the influence of this polymorphism on the risk of rheumatoid arthritis (RA). RA patients (n = 5,579) were recruited from outpatient clinics from 6 different countries (Spain, New Zealand, the UK, Norway, The Netherlands, and Germany). Healthy controls (n = 5,392) were recruited from the same areas. There was 100% power to detect an effect equivalent to that observed in SLE. Samples were genotyped for the PTPN22 R263Q (rs33996649) and PTPN22 R620W (rs2476601) polymorphisms using a TaqMan 5'-allele discrimination assay. The effect of the R263Q variant was analyzed in isolation and in combination with the effect of R620W, using Unphased and Stata 10 software. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were determined. The minor allele A of PTPN22 R263Q was significantly associated with a lower risk of RA in the pooled analysis of the 6 populations (P = 0.016, Mantel-Haenszel pooled OR 0.80 [95% CI 0.67-0.96]), independent of the effect of the R620W polymorphism. Both polymorphisms had an additive effect. The more RA risk alleles carried (R263Q G allele, R620W T allele), the higher the RA risk (for 2 versus 1 risk allele P = 0.014, OR 1.28 [95% CI 1.05-1.55], for 3 versus 1 risk allele P = 6.67 × 10(-11) , OR 2.01 [1.63-2.48], and for 4 versus 1 risk allele P = 6.50 × 10(-11) , OR 3.55 [2.42-5.20]). Our findings indicate that the minor allele of the PTPN22 R263Q polymorphism is associated with a lower risk of RA. This association is independent of the well-established association between PTPN22 R620W and RA. Both polymorphisms have an additive effect on the risk of RA.

The PTPN22 Locus and Rheumatoid Arthritis: No Evidence for an Effect on Risk Independent of Arg620Trp

ObjectivesThe Trp620 allotype of PTPN22 confers susceptibility to rheumatoid arthritis (RA) and certain other classical autoimmune diseases. There has been a report of other variants within the PTPN22 locus that alter risk of RA; protective haplotype ‘5’, haplotype group ‘6–10’ and susceptibility haplotype ‘4’, suggesting the possibility of other PTPN22 variants involved in the pathogenesis of RA independent of R620W (rs2476601). Our aim was to further investigate this possibility.MethodsA total of 4,460 RA cases and 4,481 controls, all European, were analysed. Single nucleotide polymorphisms rs3789607, rs12144309, rs3811021 and rs12566340 were genotyped over New Zealand (NZ) and UK samples. Publically-available Wellcome Trust Case Control Consortium (WTCCC) genotype data were used.ResultsThe protective effect of haplotype 5 was confirmed (rs3789607; (OR = 0.91, P = 0.016), and a second protective effect (possibly of haplotype 6) was observed (rs12144309; OR = 0.90, P = 0.021). The previously reported susceptibility effect of haplotype 4 was not replicated; instead a protective effect was observed (rs3811021; OR = 0.85, P = 1.4×10−5). Haplotypes defined by rs3789607, rs12144309 and rs3811021 coalesced with the major allele of rs12566340 within the adjacent BFK (B-cell lymphoma 2 (BCL2) family kin) gene. We, therefore, tested rs12566340 for association with RA conditional on rs2476601; there was no evidence for an independent effect at rs12566340 (P = 0.76). Similarly, there was no evidence for an independent effect at rs12566340 in type 1 diabetes (P = 0.85).ConclusionsWe have no evidence for a common variant additional to rs2476601 within the PTPN22 locus that influences the risk of RA. Arg620Trp is almost certainly the single common causal variant.

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.

Mutation screening of PTPN22: association of the 1858T-allele with Addison's disease

The tyrosine-protein phosphatase non-receptor type 22 (PTPN22) gene was recently identified as an important genetic susceptibility factor in several autoimmune diseases. The increased risk has been broadly explained by the 1858T-allele (rs2476601). As two smaller studies on Addison's disease (AD) have shown diverging results, we aimed to elucidate the predisposing effect of the single-nucleotide polymorphism (SNP) 1858CT in a larger population of AD patients, especially focusing on the AD patients with known autoimmune etiology. We also screened for unknown rare or common variants in the PTPN22 gene that could predispose for AD. The case-control study of Norwegian AD patients (n=332) and controls (n=990) showed a significant association between autoimmune AD (n=302) and the PTPN22 1858T risk allele (P=0.016). The association of AD with 1858T was supported by a meta-analysis combining our genotype data with that of others published previously (P=0.003). The mutation screening of PTPN22 in AD patients (n=332) and controls (n=112) revealed eight missense variants, five of which have not been reported previously. In conclusion, the 1858T-allele is a PTPN22 genetic susceptibility factor for autoimmune AD. Other rare variants in PTPN22 do occur, and may also be involved in the pathogenesis.