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Diabetes 54:1798-1807, 2005
© 2005 by the American Diabetes Association, Inc.

Loss of Connexin36 Channels Alters ß-Cell Coupling, Islet Synchronization of Glucose-Induced Ca2+ and Insulin Oscillations, and Basal Insulin Release

Magalie A. Ravier1, Martin Güldenagel2, Anne Charollais3, Asllan Gjinovci3, Dorothée Caille3, Goran Söhl2, Claes B. Wollheim3, Klaus Willecke2, Jean-Claude Henquin1, and Paolo Meda3

1 Unit of Endocrinology and Metabolism, University of Louvain Faculty of Medicine, Brussels, Belgium
2 Institute of Genetics, University of Bonn, Bonn, Germany
3 Department of Cell Physiology and Metabolism, Geneva University Medical Center, Geneva, Switzerland

Normal insulin secretion requires the coordinated functioning of ß-cells within pancreatic islets. This coordination depends on a communications network that involves the interaction of ß-cells with extracellular signals and neighboring cells. In particular, adjacent ß-cells are coupled via channels made of connexin36 (Cx36). To assess the function of this protein, we investigated islets of transgenic mice in which the Cx36 gene was disrupted by homologous recombination. We observed that compared with wild-type and heterozygous littermates that expressed Cx36 and behaved as nontransgenic controls, mice homozygous for the Cx36 deletion (Cx36–/–) featured ß-cells devoid of gap junctions and failing to exchange microinjected Lucifer yellow. During glucose stimulation, islets of Cx36–/– mice did not display the regular oscillations of intracellular calcium concentrations ([Ca2+]i) seen in controls due to the loss of cell-to-cell synchronization of [Ca2+]i changes. The same islets did not release insulin in a pulsatile fashion, even though the overall output of the hormone in response to glucose stimulation was normal. However, under nonstimulatory conditions, islets lacking Cx36 showed increased basal release of insulin. These data show that Cx36-dependent signaling is essential for the proper functioning of ß-cells, particularly for the pulsatility of [Ca2+]i and insulin secretion during glucose stimulation.

Address correspondence and reprint requests to Paolo Meda, MD, Department of Cell Physiology and Metabolism, University of Geneva, C.M.U., 1 rue Michel Servet, 1211 Geneva 4, Switzerland. E-mail: paolo.meda{at}medecine.unige.ch. Jean-Claude Henquin, Unit of Endocrinology and Metabolism, University of Louvain Faculty of Medicine, UCL 55.30, Avenue Hippocrate 55, B-1200 Brussels, Belgium. E-mail: henquin{at}endo.ucl.ac.be

Abbreviations: [Ca2+]i, intracellular calcium concentration; Cx36, connexin36; LY, Lucifer yellow


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