Mapping of the diabetes polygene Idd3 on mouse Chromosome 3 using novel congenic strains

Development of novel congenic mouse strains has allowed us to better define the location of the diabetogenic locus, Idd3, on Chromosome (Chr) 3. Congenic strains were identified by use of published and newly developed microsatellite markers, their genomes fingerprinted by a rapid, fluorescence-based approach, and their susceptibility to type 1 diabetes evaluated. The maximum interval containing Idd3 is now approximately 4 cM

The use of Idd congenic mice to identify checkpoints of peripheral tolerance to islet antigen

Type 1 diabetes (T1D) occurs because of lack of T cell tolerance to islet antigens. We hypothesized that critical genetic susceptibility loci that control progression to T1D, designated as insulin-dependent diabetes (Idd) loci, would be responsible for preventing CD8 T cell tolerance. To test this hypothesis, we have used two different congenic non-obese diabetic (NOD) mice that are highly protected from the occurrence of T1D because they express protective alleles at Idd3 and Idd5.1, 5.2, 5.3 (Idd3/5 mice), or at Idd9.1, 9.2, and 9.3 (Idd9 mice). By examining the CD8 T response to two different islet-expressed antigens, we have determined that CD8 T tolerance is restored in both strains of mice. However, tolerance occurs at different checkpoints in each strain. In Idd3/5 mice, islet-antigen-specific CD8 T cells are eliminated in the pancreatic lymph nodes, where they are first activated by cross-presented islet antigens. In contrast, in Idd9 mice autoreactive CD8 T cells accumulate at this site and are not tolerized until after they enter the pancreas. We are currently identifying the cell types and mechanisms that are critical for tolerance induction at each checkpoint

Pancreatic islet ganglioside expression in nonobese diabetic mice: comparison with C57BL/10 mice and changes after autoimmune beta-cell destruction.

Recent observations have shown that the presumed target antigen of cytoplasmic islet cell antibodies (ICA) has properties of a monosialo-ganglioside migrating between GM2 and GM1 standards (GM2-1) and that ICA binding is higher in nonobese diabetic (NOD) than in C57BL/10SnJ mouse pancreatic frozen sections. This study aimed to characterize the ganglioside expression in NOD mouse islets in comparison with the control C57BL/10SnJ strain, taking into account possible sex differences, variations with age, and changes after autoimmune beta-cell destruction. Thus, acidic glycolipid composition was analyzed 1) in isolated islets from 11-week-old female and male NOD mice and age-matched female and male C57BL/10SnJ mice, and 2) in whole pancreas of both NOD and control mouse strains at different ages (4, 8, and 18 weeks) and of female NOD mice before and after diabetes onset. The acidic glycolipid GM2-1 is expressed in isolated female NOD islets, male NOD islets, and C57BL/10SnJ mouse islets, but quantitative analysis showed an increased amount of GM2-1 in NOD vs. C57BL/10 islets. GM3 is a ganglioside fraction expressed in female and male NOD mice and not in the C57BL/10 strain, whereas GD3 characterizes the C57BL/10 strain islets. GM2-1 is the sole ganglioside fraction in the whole pancreas to clearly decrease with age in the NOD mouse, and diabetes onset in this strain is associated with a significant decrease in the expression of this component as well as of GM3, whereas other pancreatic ganglioside (GD3, GD1a, and GT1b) levels did not significantly decrease; no age-related ganglioside change was observed in the C57BL/10SnJ mouse. Interestingly, the observed increased ICA binding in NOD islets is paralleled by the increased expression of GM2-1 islet ganglioside, and beta-cell destruction in NOD mice is associated with a significant decrease in the amount of this ganglioside in the pancreas

A type I interferon transcriptional signature precedes autoimmunity in children genetically at risk of type 1 diabetes.

Diagnosis of the autoimmune disease type 1 diabetes (T1D) is preceded by the appearance of circulating autoantibodies to pancreatic islets. However, almost nothing is known about events leading to this islet autoimmunity. Previous epidemiological and genetic data have associated viral infections and anti-viral type I interferon (IFN) immune response genes with T1D. Here, we first used DNA microarray analysis to identify IFN-β inducible genes in vitro and then used this set of genes to define an IFN-inducible transcriptional signature in peripheral blood mononuclear cells from a group of active systemic lupus erythematosus patients (N=25). Using this predefined set of 225 IFN signature genes, we investigated expression of the signature in cohorts of healthy controls (N=87), T1D patients (N=64) and a large longitudinal birth cohort of children genetically predisposed to T1D (N=109; 454 microarrayed samples). Expression of the IFN signature was increased in genetically-predisposed children prior to the development of autoantibodies (P=0.0012), but not in established T1D patients. Upregulation of IFN-inducible genes was transient, temporally associated with a recent history of upper respiratory tract infections (P=0.0064) and marked by increased expression of SIGLEC-1 (CD169), a lectin-like receptor expressed on CD14(+) monocytes. DNA variation in IFN-inducible genes altered T1D risk (P=0.007), as exemplified by IFIH1, one of the genes in our IFN signature and for which increased expression is a known disease risk factor. These findings identify transient increased expression of type I IFN genes in pre-clinical diabetes as a risk factor for autoimmunity in children with a genetic predisposition to T1D