Type 1 diabetes and celiac disease, both of which are associated with HLA class II genes, cosegregate in populations, suggesting a common genetic origin. In this article, the authors tested whether ...any non-HLA loci are shared. They report susceptibility alleles shared by both diseases, indicating that common biologic mechanisms underlie these immune-mediated disorders.
Type 1 diabetes and celiac disease cosegregate in populations, suggesting a common genetic origin. These authors report susceptibility alleles shared by both diseases, indicating that common biologic mechanisms underlie these immune-mediated disorders.
Type 1 diabetes is caused by autoimmune destruction of the insulin-producing beta cells in the pancreatic islets. The disease affects approximately 0.4% of persons of European origin and is strongly clustered in families. The major susceptibility genes — the HLA class II loci, HLA-DQB1 and HLA-DRB1 on chromosome 6p21 — act in combination with many other non-HLA loci across the genome,
1
,
2
with unknown environmental factors playing a major role.
3
–
6
Celiac disease, which results from an immune, inflammatory reaction in the small intestine to proteins in ingested barley, wheat, and rye gluten, occurs in approximately 0.1% of persons of . . .
Association of the Vitamin D Metabolism Gene CYP27B1 With Type 1 Diabetes
Rebecca Bailey 1 ,
Jason D. Cooper 1 ,
Lauren Zeitels 1 ,
Deborah J. Smyth 1 ,
Jennie H.M. Yang 1 ,
Neil M. Walker 1 ,
Elina ...Hyppönen 2 ,
David B. Dunger 3 ,
Elizabeth Ramos-Lopez 4 ,
Klaus Badenhoop 4 ,
Sergey Nejentsev 1 and
John A. Todd 1
1 Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical
Research, University of Cambridge, U.K
2 Centre for Paediatric Epidemiology and Biostatistics, Institute of Child Health, London, U.K
3 Department of Paediatrics, University of Cambridge, Addenbrooke's Hospital, Cambridge, U.K
4 Department of Internal Medicine I, Division of Endocrinology, Diabetes, and Metabolism, University Hospital, Frankfurt, Germany
Address correspondence and reprint requests to Prof. John A. Todd, Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes
and Inflammation Laboratory, Cambridge Institute for Medical Research, University of Cambridge, WT/MRC building, Addenbrooke's
Hospital, Cambridge, CB2 0XY, U.K. E-mail: john.todd{at}cimr.cam.ac.uk
Abstract
OBJECTIVE— Epidemiological studies have linked vitamin D deficiency with the susceptibility to type 1 diabetes. Higher levels of the
active metabolite 1α,25-dihydroxyvitamin D (1α,25(OH) 2 D) could protect from immune destruction of the pancreatic β-cells. 1α,25(OH) 2 D is derived from its precursor 25-hydroxyvitamin D by the enzyme 1α-hydroxylase encoded by the CYP27B1 gene and is inactivated
by 24-hydroxylase encoded by the CYP24A1 gene. Our aim was to study the association between the CYP27B1 and CYP24A1 gene polymorphisms
and type 1 diabetes.
RESEARCH DESIGN AND METHODS— We studied 7,854 patients with type 1 diabetes, 8,758 control subjects from the U.K., and 2,774 affected families. We studied
four CYP27B1 variants, including common polymorphisms −1260C>A (rs10877012) and +2838T>C (rs4646536) and 16 tag polymorphisms in the CYP24A1
gene.
RESULTS— We found evidence of association with type 1 diabetes for CYP27B1 −1260 and +2838 polymorphisms, which are in perfect linkage disequilibrium. The common C allele of CYP27B1 −1260 was associated with an increased disease risk in the case-control analysis (odds ratio for the C/C genotype 1.22, P = 9.6 × 10 −4 ) and in the fully independent collection of families (relative risk for the C/C genotype 1.33, P = 3.9 × 10 −3 ). The combined P value for an association with type 1 diabetes was 3.8 × 10 −6 . For the CYP24A1 gene, we found no evidence of association with type 1 diabetes (multilocus test, P = 0.23).
CONCLUSIONS— The present data provide evidence that common inherited variation in the vitamin D metabolism affects susceptibility to type
1 diabetes.
1α,25(OH)2D, 1α,25-dihydroxyvitamin D
25(OH)D, 25-hydroxyvitamin D
EFSD, European Foundation for the Study of Diabetes
IL, interleukin
MAF, minor allele frequency
NCBI, National Center for Biotechnology Information
SNP, single nucleotide polymorphism
VDR, vitamin D receptor
Footnotes
Published ahead of print at http://diabetes.diabetesjournals.org on 2 July 2007. DOI: 10.2337/db07-0652.
Additional information for this article can be found in an online appendix at http://dx.doi.org/10.2337/db07-0652 .
The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore
be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
Accepted June 27, 2007.
Received May 15, 2007.
DIABETES
Many disease-associated variants identified by genome-wide association (GWA) studies are expected to regulate gene expression. Allele-specific expression (ASE) quantifies transcription from both ...haplotypes using individuals heterozygous at tested SNPs. We performed deep human transcriptome-wide resequencing (RNA-seq) for ASE analysis and expression quantitative trait locus discovery. We resequenced double poly(A)-selected RNA from primary CD4+ T cells (n = 4 individuals, both activated and untreated conditions) and developed tools for paired-end RNA-seq alignment and ASE analysis. We generated an average of 20 million uniquely mapping 45 base reads per sample. We obtained sufficient read depth to test 1371 unique transcripts for ASE. Multiple biases inflate the false discovery rate which we estimate to be ∼50% for random SNPs. However, after controlling for these biases and considering the subset of SNPs that pass HapMap QC, 4.6% of heterozygous SNP-sample pairs show evidence of imbalance (P < 0.001). We validated four findings by both bacterial cloning and Sanger sequencing assays. We also found convincing evidence for allelic imbalance at multiple reporter exonic SNPs in CD6 for two samples heterozygous at the multiple sclerosis-associated variant rs17824933, linking GWA findings with variation in gene expression. Finally, we show in CD4+ T cells from a further individual that high-throughput sequencing of genomic DNA and RNA-seq following enrichment for targeted gene sequences by sequence capture methods offers an unbiased means to increase the read depth for transcripts of interest, and therefore a method to investigate the regulatory role of many disease-associated genetic variants.
Despite early clinical successes, the mechanisms of action of low-dose interleukin-2 (LD-IL-2) immunotherapy remain only partly understood. Here we examine the effects of interval administration of ...low-dose recombinant IL-2 (iLD-IL-2) in type 1 diabetes using high-resolution single-cell multiomics and flow cytometry on longitudinally-collected peripheral blood samples. Our results confirm that iLD-IL-2 selectively expands thymic-derived FOXP3
HELIOS
regulatory T cells and CD56
NK cells, and show that the treatment reduces the frequency of IL-21-producing CD4
T cells and of two innate-like mucosal-associated invariant T and V
V
CD8
T cell subsets. The cellular changes induced by iLD-IL-2 associate with an anti-inflammatory gene expression signature, which remains detectable in all T and NK cell subsets analysed one month after treatment. These findings warrant investigations into the potential longer-term clinical benefits of iLD-IL-2 in immunotherapy.
One mechanism by which disease-associated DNA variation can alter disease risk is altering gene expression. However, linkage disequilibrium (LD) between variants, mostly single-nucleotide ...polymorphisms (SNPs), means it is not sufficient to show that a particular variant associates with both disease and expression, as there could be two distinct causal variants in LD. Here, we describe a formal statistical test of colocalization and apply it to type 1 diabetes (T1D)-associated regions identified mostly through genome-wide association studies and expression quantitative trait loci (eQTLs) discovered in a recently determined large monocyte expression data set from the Gutenberg Health Study (1370 individuals), with confirmation sought in an additional data set from the Cardiogenics Transcriptome Study (558 individuals). We excluded 39 out of 60 overlapping eQTLs in 49 T1D regions from possible colocalization and identified 21 coincident eQTLs, representing 21 genes in 14 distinct T1D regions. Our results reflect the importance of monocyte (and their derivatives, macrophage and dendritic cell) gene expression in human T1D and support the candidacy of several genes as causal factors in autoimmune pancreatic beta-cell destruction, including AFF3, CD226, CLECL1, DEXI, FKRP, PRKD2, RNLS, SMARCE1 and SUOX, in addition to the recently described GPR183 (EBI2) gene.
Genome-wide association studies (GWAS) have identified over 300 regions associated with more than 70 common diseases. However, identifying causal genes within an associated region remains a major ...challenge. One approach to resolving causal genes is through the dissection of gene-phenotype correlations. Here we use polychromatic flow cytometry to show that differences in surface expression of the human interleukin-2 (IL-2) receptor alpha (IL2RA, or CD25) protein are restricted to particular immune cell types and correlate with several haplotypes in the IL2RA region that have previously been associated with two autoimmune diseases, type 1 diabetes (T1D) and multiple sclerosis. We confirm our strongest gene-phenotype correlation at the RNA level by allele-specific expression (ASE). We also define key parameters for the design and implementation of post-GWAS gene-phenotype investigations and demonstrate the usefulness of a large bioresource of genotype-selectable normal donors from whom fresh, primary cells can be analyzed.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Type 1 diabetes is characterized by a loss of tolerance to pancreatic β-cell autoantigens and defects in regulatory T-cell (Treg) function. In preclinical models, immunotherapy with MHC-selective, ...autoantigenic peptides restores immune tolerance, prevents diabetes, and shows greater potency when multiple peptides are used. To translate this strategy into the clinical setting, we administered a mixture of six HLA-DRB1*0401-selective, β-cell peptides intradermally to patients with recent-onset type 1 diabetes possessing this genotype in a randomized placebo-controlled study at monthly doses of 10, 100, and 500 μg for 24 weeks. Stimulated C-peptide (measuring insulin functional reserve) had declined in all placebo subjects at 24 weeks but was maintained at ≥100% baseline levels in one-half of the treated group. Treatment was accompanied by significant changes in islet-specific immune responses and a dose-dependent increase in Treg expression of the canonical transcription factor FOXP3 and changes in Treg gene expression. In this first-in-human study, multiple-peptide immunotherapy shows promise as a strategy to correct immune regulatory defects fundamental to the pathobiology of autoimmune diabetes.
Numerous reports have demonstrated that CD4(+)CD25(+) regulatory T cells (Tregs) from individuals with a range of human autoimmune diseases, including type 1 diabetes, are deficient in their ability ...to control autologous proinflammatory responses when compared with nondiseased, control individuals. Treg dysfunction could be a primary, causal event or may result from perturbations in the immune system during disease development. Polymorphisms in genes associated with Treg function, such as IL2RA, confer a higher risk of autoimmune disease. Although this suggests a primary role for defective Tregs in autoimmunity, a link between IL2RA gene polymorphisms and Treg function has not been examined. We addressed this by examining the impact of an IL2RA haplotype associated with type 1 diabetes on Treg fitness and suppressive function. Studies were conducted using healthy human subjects to avoid any confounding effects of disease. We demonstrated that the presence of an autoimmune disease-associated IL2RA haplotype correlates with diminished IL-2 responsiveness in Ag-experienced CD4(+) T cells, as measured by phosphorylation of STAT5a, and is associated with lower levels of FOXP3 expression by Tregs and a reduction in their ability to suppress proliferation of autologous effector T cells. These data offer a rationale that contributes to the molecular and cellular mechanisms through which polymorphisms in the IL-2RA gene affect immune regulation, and consequently upon susceptibility to autoimmune and inflammatory diseases.
Defective immune homeostasis in the balance between FOXP3+ regulatory T cells (Tregs) and effector T cells is a likely contributing factor in the loss of self-tolerance observed in type 1 diabetes ...(T1D). Given the importance of interleukin-2 (IL-2) signaling in the generation and function of Tregs, observations that polymorphisms in genes in the IL-2 pathway associate with T1D and that some individuals with T1D exhibit reduced IL-2 signaling indicate that impairment of this pathway may play a role in Treg dysfunction and the pathogenesis of T1D. Here, we have examined IL-2 sensitivity in CD4+ T-cell subsets in 70 individuals with long-standing T1D, allowing us to investigate the effect of low IL-2 sensitivity on Treg frequency and function. IL-2 responsiveness, measured by STAT5a phosphorylation, was a very stable phenotype within individuals but exhibited considerable interindividual variation and was influenced by T1D-associated PTPN2 gene polymorphisms. Tregs from individuals with lower IL-2 signaling were reduced in frequency, were less able to maintain expression of FOXP3 under limiting concentrations of IL-2, and displayed reduced suppressor function. These results suggest that reduced IL-2 signaling may be used to identify patients with the highest Treg dysfunction and who may benefit most from IL-2 immunotherapy.
CD4⁺CD25⁺FOXP3⁺ Tregs constitute a heterogeneous lymphocyte subpopulation essential for curtailing effector T cells and establishing peripheral tolerance. Calcineurin inhibitors (CNIs) are among the ...most effective agents in controlling effector T-cell responses in humans. However, CNIs also reduce the size of the Treg pool. The functional consequences of this negative effect and the mechanisms responsible remain to be elucidated. We report here that CNIs compromise the overall Treg immunoregulatory capacity to a greater extent than would be predicted by the reduction in the size of the Treg compartment, given that they selectively promote the apoptosis of the resting and activated Treg subsets that are known to display the most powerful suppressive function. These effects are caused by reduced access to IL-2, because Tregs remain capable of translocating NFAT even in the presence of high CNI levels. Exogenous IL-2 restores the phenotypic changes and overall gene-expression effects exerted by CNIs and can even promote Treg expansion by enhancing antiapoptotic Bcl-2 expression. In a skin transplant model, the addition of IL-2 synergizes with CNIs treatment, promoting intragraft accumulation of Tregs and prolonged allograft survival. Hence, the combination of IL-2 and CNIs constitutes an optimal immunomodulatory regimen that enhances the pool of suppressive Treg subsets while effectively controlling cytopathic T cells.
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