Nicotinamide restricts neural precursor proliferation to enhance catecholaminergic neuronal subtype differentiation from mouse embryonic stem cells.

Emerging evidence indicates that a strong relationship exists between brain regenerative therapies and nutrition. Early life nutrition plays an important role during embryonic brain development, and there are clear consequences to an imbalance in nutritional factors on both the production and survival of mature neuronal populations and the infant's risk of diseases in later life. Our research and that of others suggest that vitamins play a fundamental role in the formation of neurons and their survival. There is a growing body of evidence that nicotinamide, the water-soluble amide form of vitamin B3, is implicated in the conversion of pluripotent stem cells to clinically relevant cells for regenerative therapies. This study investigated the ability of nicotinamide to promote the development of mature catecholaminergic neuronal populations (associated with Parkinson's disease) from mouse embryonic stem cells, as well as investigating the underlying mechanisms of nicotinamide's action. Nicotinamide selectively enhanced the production of tyrosine hydroxylase-expressing neurons and serotonergic neurons from mouse embryonic stem cell cultures (Sox1GFP knock-in 46C cell line). A 5-Ethynyl-2´-deoxyuridine (EdU) assay ascertained that nicotinamide, when added in the initial phase, reduced cell proliferation. Nicotinamide drove tyrosine hydroxylase-expressing neuron differentiation as effectively as an established cocktail of signalling factors, reducing the proliferation of neural progenitors and accelerating neuronal maturation, neurite outgrowth and neurotransmitter expression. These novel findings show that nicotinamide enhanced and enriched catecholaminergic differentiation and inhibited cell proliferation by directing cell cycle arrest in mouse embryonic stem cell cultures, thus driving a critical neural proliferation-to-differentiation switch from neural progenitors to neurons. Further research into the role of vitamin metabolites in embryogenesis will significantly advance cell-based regenerative medicine, and help realize their role as crucial developmental signalling molecules in brain development.

Th17 cells increase in RRMS as well as in SPMS, whereas various other phenotypes of Th17 increase in RRMS only.

BACKGROUND: The nature and extent of inflammation seen in multiple sclerosis (MS) varies throughout the course of the disease. Changes seen in CD4+ T-helper cells in relapsing-remitting (RR) MS and secondary progressive (SP) MS might differ qualitatively and/or quantitatively. OBJECTIVE: The objective of this paper is to study the frequencies of all major CD4+ T-helper subtypes - Th17, Th22 and Th1 lineage cells - in relapse, remission and secondary progression alongside CCR6 status, a chemokine receptor involved in migration of these cells into the central nervous system. METHODS: We compared 100 patients (50 RRMS and 50 SPMS) and 50 healthy volunteers and performed flow cytometric analysis of lymphocytes in blood samples. RESULTS: We demonstrated raised frequencies of various cell types along the Th17 axis; Th17, Th17.1 (IL-17+ interferon gamma+) and dual IL-17+ IL-22+ cells in RRMS. Th22 and CCR6+ Th1 cells (nonclassical Th1) were also increased in RRMS. All these cells were CCR6+. Only Th17 frequencies were elevated in SPMS. CONCLUSIONS: Increased frequencies of Th17 cells are implicated both in RRMS and SPMS. The CCR6 pathway includes Th17, Th22 and Th1 nonclassical cells, of which Th22 and Th1 cells represent the greatest subsets in MS.

Efficacy of three neuroprotective drugs in secondary progressive multiple sclerosis (MS-SMART): a phase 2b, multiarm, double-blind, randomised placebo-controlled trial.

BACKGROUND: Neurodegeneration is the pathological substrate that causes major disability in secondary progressive multiple sclerosis. A synthesis of preclinical and clinical research identified three neuroprotective drugs acting on different axonal pathobiologies. We aimed to test the efficacy of these drugs in an efficient manner with respect to time, cost, and patient resource. METHODS: We did a phase 2b, multiarm, parallel group, double-blind, randomised placebo-controlled trial at 13 clinical neuroscience centres in the UK. We recruited patients (aged 25-65 years) with secondary progressive multiple sclerosis who were not on disease-modifying treatment and who had an Expanded Disability Status Scale (EDSS) score of 4·0-6·5. Participants were randomly assigned (1:1:1:1) at baseline, by a research nurse using a centralised web-based service, to receive twice-daily oral treatment of either amiloride 5 mg, fluoxetine 20 mg, riluzole 50 mg, or placebo for 96 weeks. The randomisation procedure included minimisation based on sex, age, EDSS score at randomisation, and trial site. Capsules were identical in appearance to achieve masking. Patients, investigators, and MRI readers were unaware of treatment allocation. The primary outcome measure was volumetric MRI percentage brain volume change (PBVC) from baseline to 96 weeks, analysed using multiple regression, adjusting for baseline normalised brain volume and minimisation criteria. The primary analysis was a complete-case analysis based on the intention-to-treat population (all patients with data at week 96). This trial is registered with ClinicalTrials.gov, NCT01910259. FINDINGS: Between Jan 29, 2015, and June 22, 2016, 445 patients were randomly allocated amiloride (n=111), fluoxetine (n=111), riluzole (n=111), or placebo (n=112). The primary analysis included 393 patients who were allocated amiloride (n=99), fluoxetine (n=96), riluzole (n=99), and placebo (n=99). No difference was noted between any active treatment and placebo in PBVC (amiloride vs placebo, 0·0% [95% CI -0·4 to 0·5; p=0·99]; fluoxetine vs placebo -0·1% [-0·5 to 0·3; p=0·86]; riluzole vs placebo -0·1% [-0·6 to 0·3; p=0·77]). No emergent safety issues were reported. The incidence of serious adverse events was low and similar across study groups (ten [9%] patients in the amiloride group, seven [6%] in the fluoxetine group, 12 [11%] in the riluzole group, and 13 [12%] in the placebo group). The most common serious adverse events were infections and infestations. Three patients died during the study, from causes judged unrelated to active treatment; one patient assigned amiloride died from metastatic lung cancer, one patient assigned riluzole died from ischaemic heart disease and coronary artery thrombosis, and one patient assigned fluoxetine had a sudden death (primary cause) with multiple sclerosis and obesity listed as secondary causes. INTERPRETATION: The absence of evidence for neuroprotection in this adequately powered trial indicates that exclusively targeting these aspects of axonal pathobiology in patients with secondary progressive multiple sclerosis is insufficient to mitigate neuroaxonal loss. These findings argue for investigation of different mechanistic targets and future consideration of combination treatment trials. This trial provides a template for future simultaneous testing of multiple disease-modifying medicines in neurological medicine. FUNDING: Efficacy and Mechanism Evaluation (EME) Programme, an MRC and NIHR partnership, UK Multiple Sclerosis Society, and US National Multiple Sclerosis Society.

Multiple Sclerosis-Secondary Progressive Multi-Arm Randomisation Trial (MS-SMART): a multiarm phase IIb randomised, double-blind, placebo-controlled clinical trial comparing the efficacy of three neuroprotective drugs in secondary progressive multiple sclerosis.

INTRODUCTION: The major unmet need in multiple sclerosis (MS) is for neuroprotective therapies that can slow (or ideally stop) the rate of disease progression. The UK MS Society Clinical Trials Network (CTN) was initiated in 2007 with the purpose of developing a national, efficient, multiarm trial of repurposed drugs. Key underpinning work was commissioned by the CTN to inform the design, outcome selection and drug choice including animal models and a systematic review. This identified seven leading oral agents for repurposing as neuroprotective therapies in secondary progressive MS (SPMS). The purpose of the Multiple Sclerosis-Secondary Progressive Multi-Arm Randomisation Trial (MS-SMART) will be to evaluate the neuroprotective efficacy of three of these drugs, selected with distinct mechanistic actions and previous evidence of likely efficacy, against a common placebo arm. The interventions chosen were: amiloride (acid-sensing ion channel antagonist); fluoxetine (selective serotonin reuptake inhibitor) and riluzole (glutamate antagonist). METHODS AND ANALYSIS: Patients with progressing SPMS will be randomised 1:1:1:1 to amiloride, fluoxetine, riluzole or matched placebo and followed for 96 weeks. The primary outcome will be the percentage brain volume change (PBVC) between baseline and 96 weeks, derived from structural MR brain imaging data using the Structural Image Evaluation, using Normalisation, of Atrophy method. With a sample size of 90 per arm, this will give 90% power to detect a 40% reduction in PBVC in any active arm compared with placebo and 80% power to detect a 35% reduction (analysing by analysis of covariance and with adjustment for multiple comparisons of three 1.67% two-sided tests), giving a 5% overall two-sided significance level. MS-SMART is not powered to detect differences between the three active treatment arms. Allowing for a 20% dropout rate, 110 patients per arm will be randomised. The study will take place at Neuroscience centres in England and Scotland. ETHICS AND DISSEMINATION: MS-SMART was approved by the Scotland A Research Ethics Committee on 13 January 2013 (REC reference: 13/SS/0007). Results of the study will be submitted for publication in a peer-reviewed journal. TRIAL REGISTRATION NUMBERS: NCT01910259; 2012-005394-31; ISRCTN28440672.

Characterisation of tissue-type metabolic content in secondary progressive multiple sclerosis: a magnetic resonance spectroscopic imaging study.

Proton magnetic resonance spectroscopy yields metabolic information and has proved to be a useful addition to structural imaging in neurological diseases. We applied short-echo time Spectroscopic Imaging in a cohort of 42 patients with secondary progressive multiple sclerosis (SPMS). Linear modelling with respect to brain tissue type yielded metabolite levels that were significantly different in white matter lesions compared with normal-appearing white matter, suggestive of higher myelin turnover (higher choline), higher metabolic rate (higher creatine) and increased glial activity (higher myo-inositol) within the lesions. These findings suggest that the lesions have ongoing cellular activity that is not consistent with the usual assumption of 'chronic' lesions in SPMS, and may represent a target for repair therapies.

Urinary Excretion of Aluminium and Silicon in Secondary Progressive Multiple Sclerosis.

BACKGROUND: Progressive multiple sclerosis is a chronic autoimmune condition of unknown aetiology and few therapeutic options. Human exposure to aluminium has been linked with multiple sclerosis and affected individuals are known to excrete unusually high amounts of aluminium in their urine. Silicon-rich mineral waters facilitate the removal of aluminium from the body in urine and herein we have tested their efficacy in affecting urinary excretion of aluminium in individuals diagnosed with secondary progressive multiple sclerosis (SPMS). METHODS: Urinary excretion of aluminium and silicon, measured using transversely-heated graphite furnace atomic absorption spectrometry, was determined in 15 individuals diagnosed with SPMS over 24weeks, a 12week baseline period (control) followed by a 12week treatment period, during which individuals consumed up to 1.5L of a silicon-rich mineral water every day. FINDINGS: Individuals with SPMS excreted high amounts of aluminium during the baseline period (135.2nmol/mmol Crt (70.3-222.2, n=180) and females excreted significantly more aluminium than males. Regular drinking of a silicon-rich mineral water increased the urinary excretion of aluminium significantly (349.0nmol/mmol Crt (231.7-524.7, n=180; three-way ANOVA, F1,13=59.17, p-value=0.000003) relative to the baseline period. The majority of individuals, 14 out of 15, excreted more aluminium (µmol/24h) following drinking of a silicon-rich mineral water (independent-test, p<0.05). Silicon-rich mineral waters may be an effective and non-invasive therapy for the removal of aluminium from the body of individuals with SPMS.

Nicotinamide alone accelerates the conversion of mouse embryonic stem cells into mature neuronal populations.

INTRODUCTION: Vitamin B3 has been shown to play an important role during embryogenesis. Specifically, there is growing evidence that nicotinamide, the biologically active form of vitamin B3, plays a critical role as a morphogen in the differentiation of stem cells to mature cell phenotypes, including those of the central nervous system (CNS). Detailed knowledge of the action of small molecules during neuronal differentiation is not only critical for uncovering mechanisms underlying lineage-specification, but also to establish more effective differentiation protocols to obtain clinically relevant cells for regenerative therapies for neurodegenerative conditions such as Huntington's disease (HD). Thus, this study aimed to investigate the potential of nicotinamide to promote the conversion of stem cells to mature CNS neurons. METHODS: Nicotinamide was applied to differentiating mouse embryonic stem cells (mESC; Sox1GFP knock-in 46C cell line) during their conversion towards a neural fate. Cells were assessed for changes in their proliferation, differentiation and maturation; using immunocytochemistry and morphometric analysis methods. RESULTS: Results presented indicate that 10 mM nicotinamide, when added at the initial stages of differentiation, promoted accelerated progression of ESCs to a neural lineage in adherent monolayer cultures. By 14 days in vitro (DIV), early exposure to nicotinamide was shown to increase the numbers of differentiated ßIII-tubulin-positive neurons. Nicotinamide decreased the proportion of pluripotent stem cells, concomitantly increasing numbers of neural progenitors at 4 DIV. These progenitors then underwent rapid conversion to neurons, observed by a reduction in Sox 1 expression and decreased numbers of neural progenitors in the cultures at 14 DIV. Furthermore, GABAergic neurons generated in the presence of nicotinamide showed increased maturity and complexity of neurites at 14 DIV. Therefore, addition of nicotinamide alone caused an accelerated passage of pluripotent cells through lineage specification and further to non-dividing mature neurons. CONCLUSIONS: Our results show that, within an optimal dose range, nicotinamide is able to singly and selectively direct the conversion of embryonic stem cells to mature neurons, and therefore may be a critical factor for normal brain development, thus supporting previous evidence of the fundamental role of vitamins and their metabolites during early CNS development. In addition, nicotinamide may offer a simple effective supplement to enhance the conversion of stem cells to clinically relevant neurons.

Associations between onset age and disability in multiple sclerosis patients studied using MSSS and a progression model.

BACKGROUND: While many factors have been examined, male gender and older age at multiple sclerosis onset are among few variables consistently associated with increased disability. Interestingly, the association between onset age and disability may not be linear with some data suggesting a faster rate of accumulation of disability in patients aged more than 30 years at onset. OBJECTIVE: Explore the relationship between onset age and disability. METHODS: We studied 500 MS patients grouped by cut-offs in onset age. Disability was assessed using Multiple Sclerosis Severity Scale (MSSS) and, a model based on time to reach an Extended Disability Severity Score (EDSS) (progression model). Data were analyzed using linear and logistic regression. RESULTS: The association between disability (assessed by both MSSS and the progression model) and onset age was different in patients whose MS onset occurred after an age band of 30-35 years. Before this age range, changing age was not associated with changes in disability while during and after this age range, disability was increased. CONCLUSION: We found a significant change in the relationship between disability and onset age after about 31 years supporting the idea that while onset age does not define a sharp cut-off, it can help define subgroups of patients with differing rates of accumulation of disability.

Nicotinamide promotes neuronal differentiation of mouse embryonic stem cells in vitro.

Factors controlling proliferation and differentiation are crucial in advancement of neural cell-based experimental neurodegenerative therapies. In this regard, nicotinamide has been shown to determine the fate of neural cells, enhance neuralization, and influence DNA repair and apoptosis. This study investigated whether the biologically active vitamin B3 metabolite, nicotinamide, could direct the differentiation of mouse embryonic stem cells, cultured as monolayers, into neurons at either early or late stages of development. Interestingly, we observed a dose-responsive increase in the percentage of neurons when nicotinamide was added at early stages to the cells undergoing differentiation (days 0-7). Nicotinamide (10 mM) had a significant effect on neuronal differentiation, increasing the ßIII-tubulin-positive neuronal population and concomitantly decreasing the total number of cells in culture, measured by quantification of 4',6-diamidino-2-phenylindole (DAPI)-positive cells. Nicotinamide added between days 7 and 14 had no effect on neuronal induction. High levels of nicotinamide (20 mM) induced cytotoxicity and cell death. Current work is focusing on elucidating the mechanism(s) mediating neural specification by nicotinamide--that is, induction of cell-cycle exit and/or selective apoptosis in non-neural populations. Preliminary data suggest a reduction in the proportion of proliferating cells in nicotinamide-treated cultures--that is, nicotinamide enhances cell-cycle exit, thereby promoting neuronal differentiation. Future work will focus on evaluating the effect of nicotinamide on the differentiation of midbrain dopamine neurons, towards a therapy for Parkinson's disease.

Progression of disability in multiple sclerosis: A study of factors influencing median time to reach an EDSS value.

BACKGROUND: The extended disability severity scale (EDSS) is clinically useful in assessing disability in multiple sclerosis (MS) patients. It is also being used in studies to determine how genes and environment influence disability. However, since it has a complex relationship with functional scores and mobility and is strongly determined by disease duration its use can be limiting. OBJECTIVE: Study associations of variables with progression described by time from disease onset until EDSS. METHODS: We used a variable based on below/above median time from MS onset to reach a single EDSS value to define slow or fast progression. We compared patient categorization using this variable and MSSS, and in 533 patients (EDSS 1-8) and 242 of these patients with EDSS1-4, studied associations with skin type, gender, ultraviolet radiation and MC1R Asp294His. RESULTS: Classifying patients into quartiles of slow/fast progression showed mean MSSS increased with faster progression (p<0.001). For EDSS 1-8: MSSS, late onset age and childhood sunburning were associated with fast and MC1R CG/GG(294) with slow progression. Combinations of skin type (1/2 or 3/4) with childhood weekend exposure (< or ≥median) or sunburning (yes/no) were not associated with progression. However, in patients with EDSS1-4, relative to other combinations, those with no sunburning history and types 1/2 demonstrated slow progression (odds ratio=0.15, 95% CI=0.04, 0.57). CONCLUSION: This method, though a pilot, allows study of associations of variables with EDSS. It is based on local patients and could substitute for MSSS. In patients with EDSS1-4 but not 1-8, skin type 1/2 with no history of childhood sunburning was associated with slow progression. This is compatible with the view that disability develops through a first stage dependent on inflammation.

Genetic risk and a primary role for cell-mediated immune mechanisms in multiple sclerosis.

Multiple sclerosis is a common disease of the central nervous system in which the interplay between inflammatory and neurodegenerative processes typically results in intermittent neurological disturbance followed by progressive accumulation of disability. Epidemiological studies have shown that genetic factors are primarily responsible for the substantially increased frequency of the disease seen in the relatives of affected individuals, and systematic attempts to identify linkage in multiplex families have confirmed that variation within the major histocompatibility complex (MHC) exerts the greatest individual effect on risk. Modestly powered genome-wide association studies (GWAS) have enabled more than 20 additional risk loci to be identified and have shown that multiple variants exerting modest individual effects have a key role in disease susceptibility. Most of the genetic architecture underlying susceptibility to the disease remains to be defined and is anticipated to require the analysis of sample sizes that are beyond the numbers currently available to individual research groups. In a collaborative GWAS involving 9,772 cases of European descent collected by 23 research groups working in 15 different countries, we have replicated almost all of the previously suggested associations and identified at least a further 29 novel susceptibility loci. Within the MHC we have refined the identity of the HLA-DRB1 risk alleles and confirmed that variation in the HLA-A gene underlies the independent protective effect attributable to the class I region. Immunologically relevant genes are significantly overrepresented among those mapping close to the identified loci and particularly implicate T-helper-cell differentiation in the pathogenesis of multiple sclerosis.

The Multiple Sclerosis Severity Score: associations with MC1R single nucleotide polymorphisms and host response to ultraviolet radiation.

BACKGROUND: Multiple sclerosis outcome may be influenced by ultraviolet radiation and vitamin D synthesis, suggesting skin type and genes determining this phenotype are candidates for disability. However, though associations between melanocortin 1 receptor (MC1R) single nucleotide polymorphisms and disability are reported, some data are incompatible with their expected influence on skin type. OBJECTIVE: Determine which MC1R single nucleotide polymorphisms affect disability and establish if ultraviolet radiation modifies such associations. METHODS: We studied using linear regression in 525 cases, associations of the Multiple Sclerosis Severity Score (MSSS) with skin type, gender, ultraviolet radiation exposure and six MC1R single nucleotide polymorphisms (rs1805005, rs1805006, rs2228479, rs1805007, rs1805008, rs1805009). RESULTS: CG(294) with GG(294) genotypes (rs1805009) (coefficient = -1.44, 95% CI -2.30, -0.59, mean MSSS +/- SD = 4.33 +/- 2.87) and AC(84) (rs1805006) (coefficient = 1.62, 95% CI 0.17, 3.06, mean MSSS = 7.62 +/- 2.43) were associated with MSSS. Associations with Asp294His were found in those with skin types 1/2 and 3/4, and cases stratified by ultraviolet radiation exposure. However, they were seen only in cases with a history of childhood sunburn and not in those without sunburn. We found no significant associations between exposure parameters and MSSS. CONCLUSIONS: Multiple sclerosis outcome is influenced by interactions between host response to ultraviolet radiation and MC1R single nucleotide polymorphisms. The influence of the single nucleotide polymorphisms appears distinct from their association with skin type.

Replication analysis identifies TYK2 as a multiple sclerosis susceptibility factor.

In a recent genome-wide association study (GWAS) based on 12,374 non-synonymous single nucleotide polymorphisms we identified a number of candidate multiple sclerosis susceptibility genes. Here, we describe the extended analysis of 17 of these loci undertaken using an additional 4234 patients, 2983 controls and 2053 trio families. In the final analysis combining all available data, we found that evidence for association was substantially increased for one of the 17 loci, rs34536443 from the tyrosine kinase 2 (TYK2) gene (P=2.7 x 10(-6), odds ratio=1.32 (1.17-1.47)). This single nucleotide polymorphism results in an amino acid substitution (proline to alanine) in the kinase domain of TYK2, which is predicted to influence the levels of phosphorylation and therefore activity of the protein and so is likely to have a functional role in multiple sclerosis.

Short-term combination of glatiramer acetate with i.v. steroid treatment preceding treatment with GA alone assessed by MRI-disease activity in patients with relapsing-remitting multiple sclerosis.

OBJECTIVES: To assess if short-term combination of glatiramer acetate (GA) and i.v. steroid in patients with relapsing-remitting multiple sclerosis (RRMS) is safe and sustains the effect of GA treatment on MRI-disease activity. METHODS: RRMS patients with >or=2 gadolinium (Gd)-enhancing lesions on screening MRI and EDSS score

A medical overview of encephalitis.

Encephalitis is uncommon but is a neurological emergency which must be considered in a patient presenting with altered consciousness. Encephalitis is a diffuse inflammatory process of the brain parenchyma associated with evidence of brain dysfunction. The presentation of encephalitis can be acute or chronic. The aetiology of encephalitis can be broadly divided into two major subtypes. (1) Infection-related encephalitis which is a direct consequence of pathogenic viral, bacterial or parasitic agents. Herpes simplex virus (HSV) and varicella-zoster virus (VZV) are the most common cause of acute infectious encephalitis. (2) Autoimmune-mediated encephalitis which is mediated by an aberrant immune response. This can be triggered by a recent viral infection or vaccination. An example of this would be acute disseminated encephalitis (ADEM). This article will focus on the medical management of acute encephalitis. This will involve an extensive overview of the literature reviewing the diagnosis, investigation and treatment of acute viral encephalitis, ADEM and acute haemorrhagic leukoencephalopathy (AHLE). Encephalitis can also present chronically, and some of the different types of chronic encephalitis will be discussed.

Elevated urinary excretion of aluminium and iron in multiple sclerosis.

Multiple sclerosis (MS) is a chronic, immune-mediated, demyelinating disease of the central nervous system of as yet unknown aetiology. A consensus of opinion has suggested that the disorder is the result of an interplay between environmental factors and susceptibility genes. We have used a battery of analytical techniques to determine if the urinary excretion of i) markers of oxidative damage; ii) iron and iii) the environmental toxin aluminium and its antagonist, silicon, are altered in relapsing-remitting (RRMS) and secondary progressive MS (SPMS). Urinary concentrations of oxidative biomarkers, MDA and TBARS, were not found to be useful indicators of inflammatory disease in MS. However, urinary concentrations of another potential marker for inflammation and oxidative stress, iron, were significantly increased in SPMS (P<0.01) and insignificantly increased in RRMS (P>0.05). Urinary concentrations of aluminium were also significantly increased in RRMS (P<0.001) and SPMS (P <0.05) such that the levels of aluminium excretion in the former were similar to those observed in individuals undergoing metal chelation therapy. The excretion of silicon was lower in MS and significantly so in SPMS (P<0.05). Increased excretion of iron in urine supported a role for iron dysmetabolism in MS. Levels of urinary aluminium excretion similar to those seen in aluminium intoxication suggested that aluminium may be a hitherto unrecognized environmental factor associated with the aetiology of MS. If aluminium is involved in MS then an increased dietary intake of its natural antagonist, silicon, might be a therapeutic option.

Association between the PTPN22 gene and rheumatoid arthritis and juvenile idiopathic arthritis in a UK population: further support that PTPN22 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.