Reduced synchroneity of intra-islet Ca.sup.2+ oscillations in vivo in Robo-deficient [beta] cells

The spatial architecture of the islets of Langerhans is hypothesized to facilitate synchronized insulin secretion among [beta] cells, yet testing this in vivo in the intact pancreas is challenging. Robo [beta]KO mice, in which the genes Robo1 and Robo2 are deleted selectively in [beta] cells, provide a unique model of altered islet spatial architecture without loss of [beta] cell differentiation or islet damage from diabetes. Combining Robo [beta]KO mice with intravital microscopy, we show here that Robo [beta]KO islets have reduced synchronized intra-islet Ca.sup.2+ oscillations among [beta] cells in vivo. We provide evidence that this loss is not due to a [beta] cell-intrinsic function of Robo, mis-expression or mis-localization of Cx36 gap junctions, or changes in islet vascularization or innervation, suggesting that the islet architecture itself is required for synchronized Ca.sup.2+ oscillations. These results have implications for understanding structure-function relationships in the islets during progression to diabetes as well as engineering islets from stem cells.