Beta-cell Cre expression and reduced Ins1 gene dosage protect mice from type 1 diabetes

A central goal of physiological research is the understanding of cell-specific roles of disease-associated genes. Cre-mediated recombineering is the tool of choice for cell type-specific analysis of gene function in pre-clinical models. In the type 1 diabetes research field, multiple lines of NOD mice have been engineered to express Cre recombinase in pancreatic β-cells using insulin promoter fragments, but tissue promiscuity remains a concern. Constitutive Ins1 tm1.1(cre)Thor ( Ins1 Cre ) mice on the C57/bl6-J background has high β-cell specificity and with no reported off-target effects. We explored if NOD: Ins1 Cre mice could be used to investigate β-cell gene deletion in type 1 diabetes disease modeling. We studied wildtype ( Ins1 WT/WT ), Ins1 heterozygous ( Ins1 Cre/WT or Ins1 Neo/WT ), and Ins1 null ( Ins1 Cre/Neo ) littermates on a NOD background. Female Ins1 Neo/WT mice exhibited significant protection from diabetes, with further near-complete protection in Ins1 Cre/WT mice. The effects of combined neomycin and Cre knock-in in Ins1 Neo/Cre mice were not additive to the Cre knock-in alone. In Ins1 Neo/Cre mice, protection from diabetes was associated with reduced insulitis at 12 weeks of age. Collectively, these data confirm previous reports that loss of Ins1 alleles protects NOD mice from diabetes development and demonstrates, for the first time, that Cre itself may have additional protective effects. This has significant implications for the experimental design and interpretation of pre-clinical type 1 diabetes studies using β-cell-specific Cre in NOD mice.