A characteristic feature in patients with type 1 diabetes is autoimmune destruction of beta-cells leading to uncontrolled hyperglycemia. Although transplantation of islets, has been used successfully to treat patients with type 1 diabetes, limitations to this approach include the availability of adequate numbers of islets/beta-cells and reduced graft survival over time. Therefore, a knowledge of the factors and processes that regulate the growth and survival of beta-cells is crucial to design experiments aimed at preserving, prolonging the survival and/or potentially stimulating the growth of beta -cells in vivo. The IGF-1 and insulin receptors mediate crucial anti-apoptotic signals in different cell types including islet beta-cells. However, an understanding of the specificity of the receptors in mediating a direct anti-apoptotic effect in the beta-cell, in vivo, is lacking. To address this question mouse models with beta-cell-specific ablation of either the IGF-1 receptor (betaIGFKO) or the insulin receptor (betaIRKO) have been created. The objective of this grant application is to use these unique mouse models to directly examine the role of the IGF-1 and insulin receptors in beta-cell survival, and susceptibility to apoptosis, during development and in the adult animal. The specific aims of the proposal are to: 1. Define the alterations in apoptosis, growth and neogenesis of islets from betaIGFKO and betaIRKO mice or beta-cell double knockouts and test the hypothesis that Akt-dependent pathways are important for beta-cell survival by rescuing the phenotype in the beta-cell double null mutants using a-cell-specific active Akt1 over-expressing mice. 2. Determine the ability of betaIGFKO and betaIRKO mice to mount an islet compensatory response, which is normally induced by a high-fat diet, and to determine the ability of the mutant beta-cells to survive after transplantation. 3. Dissect the molecular mechanisms underlying the increased apoptosis in betaIRKO cells, and define the specificity of activation of the IGF-1 and insulin signaling and their downstream partners in growth and anti-apoptotic pathways using primary islets and a-cell lines isolated from betaIGFKO and betaIRKO mice. 4. Identify IGF-1/insulin-dependent and -independent genes in islets isolated from betaIGFKO and betaIRKOs and from double mutants by using Affymetrix oligonucleotide microarrays with a focus on anti-apoptotic pathways and proteins regulating cell cycle kinetics in a-cells. We believe that the availability of knockout mice, primary islets and derived clonal cell lines provides us with powerful and unique tools to perform a combination of in vivo and in vitro experiments to analyze IGF-1/insulin signaling pathways in islet beta-cells. Genetic approaches to examine the specificity of signaling pathways in the beta-cell are extremely useful in a biological context and we expect these studies will aid in developing strategies to enhance their survival in vivo.