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The Position Beta57 of IAg7 Controls the Early Anti-Insulin Response and Onset of Diabetes in NOD mice to Link MHC and Disease [RT-PCR]

ABSTRACT: Abstract- The class II region of the Major Histocompatibility locus is the main contributor to the genetic susceptibility to type 1 diabetes (T1D). The loss of an aspartic acid at position 57 of diabetogenic HLA-DQ8 chains supports this association; it influences the recognition of peptides in the context of HLA-DQ8, and I-Ag7 using a mechanism termed the P9 switch. Here, we built register-specific insulin MHC tetramers, Ins12-20 and Ins13-21, to examine anti-insulin CD4 T cell responses during the early pre-diabetic phase of disease in mice. A single cell gene expression analysis and single cell T cell receptor (TCR) sequencing of anti-insulin CD4 T cells performed in 6 and 12-week-old NOD mice, revealed tissue-specific gene expression signatures. TCR signaling and clonal expansion were found only in the islets of Langerhans. and produced either classical Th1 differentiation or an unusual Treg phenotype, independent of TCR usage. The early phase of the anti-insulin response was dominated by cells specific for Ins12-20, the register that supports a P9 switch mode of recognition. The presence of the switch was demonstrated by TCR sequencing, re-expression, mutagenesis, and functional testing of alpha/beta TCR pairs in vitro. The genetic correction of the beta57 mutation resulted in the disappearance of D/E residues in the CDR3beta of anti-Ins12-20 T cells, and inability of cells normally activated by a switch to recognize the Ins9-23 peptide. These results provide the first molecular mechanistic explanation that links the unique MHC class II polymorphism of T1D with the recognition of islet antigens and disease onset.

ORGANISM(S): Mus musculus

PROVIDER: GSE134440 | GEO | 2019/07/18

REPOSITORIES: GEO

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Project description:Objective: We hypothesized that type 1 diabetes (T1D) is accompanied by changes in gene expression in peripheral blood mononuclear cells (PBMCs) due to dysregulation of adaptive and innate immunity, counterregulatory responses to immune dysregulation, insulin deficiency and hyperglycemia. Research Design and Methods: Microarray analysis was performed on PBMCs from 43 patients with newly diagnosed T1D, 12 patients with newly diagnosed type 2 diabetes (T2D) and 24 healthy controls. One and four month follow-up samples were obtained from 20 of the T1D patients. Results: Microarray analysis identified 282 genes differing in expression between newlydiagnosed T1D patients and controls at a false discovery rate of 0.05. Changes in expression of interleukin-1Î² (IL1B), early growth response gene 3 (EGR3), and prostaglandin-endoperoxide; synthase 2 (PTGS2) resolved within four months of insulin therapy and were also observed in T2D suggesting that they resulted from hyperglycemia. With use of a knowledge base, 81/282 genes could be placed within a network of interrelated genes with predicted functions including apoptosis and cell proliferation. IL1B and the MYC oncogene were the most highly-connected genes in the network. IL1B was highly overexpressed in both T1D and T2D, whereas MYC was dysregulated only in T1D. Conclusion: T1D and T2D likely share a final common pathway for beta cell dysfunction that includes secretion of interleukin-1Î² and prostaglandins by immune effector cells, exacerbating existing beta cell dysfunction, and causing further hyperglycemia. The results identify several targets for disease-modifying therapy of diabetes and potential biomarkers for monitoring treatment efficacy. Experiment Overall Design: We obtained blood samples from 24 healthy volunteers, 43 newly diagnosed T1D patients and 12 newly diagnosed T2D patients. All study participants were between the ages of 2 and 18 years. We collected samples one and four months after diagnosis from the last 20 of the T1D patients. For each time point one sample did not pass quality control and was dropped from the analysis. Patients with T2D were distinguished from T1D on the basis of age, body habitus, Experiment Overall Design: presence (11/12 patients) of acanthosis nigricans, family history of type 2 diabetes (11/12 patients), and absence of autoantibodies to insulin, IA-2, and GAD65. We allowed low titers of insulin antibodies in T2D patients (< 4 U/mL), which have been previously reported. All but two Experiment Overall Design: of the T1D patients with positive anti-insulin antibodies were also positive for at least one additional autoantibody.

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The Position Beta57 of IAg7 Controls the Early Anti-Insulin Response and Onset of Diabetes in NOD mice to Link MHC and Disease [RT-PCR]

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