Expression of an activating mutation in the gene encoding the KATP channel subunit Kir6.2 in mouse pancreatic β cells recapitulates neonatal diabetes
Christophe A. Girard, … , Jens C. Brüning, Frances M. Ashcroft
Christophe A. Girard, … , Jens C. Brüning, Frances M. Ashcroft
Published December 8, 2008
Citation Information: J Clin Invest. 2009;119(1):80-90. https://doi.org/10.1172/JCI35772.
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Research Article Metabolism

Expression of an activating mutation in the gene encoding the KATP channel subunit Kir6.2 in mouse pancreatic β cells recapitulates neonatal diabetes

Abstract

Neonatal diabetes is a rare monogenic form of diabetes that usually presents within the first six months of life. It is commonly caused by gain-of-function mutations in the genes encoding the Kir6.2 and SUR1 subunits of the plasmalemmal ATP-sensitive K+ (KATP) channel. To better understand this disease, we generated a mouse expressing a Kir6.2 mutation (V59M) that causes neonatal diabetes in humans and we used Cre-lox technology to express the mutation specifically in pancreatic β cells. These β-V59M mice developed severe diabetes soon after birth, and by 5 weeks of age, blood glucose levels were markedly increased and insulin was undetectable. Islets isolated from β-V59M mice secreted substantially less insulin and showed a smaller increase in intracellular calcium in response to glucose. This was due to a reduced sensitivity of KATP channels in pancreatic β cells to inhibition by ATP or glucose. In contrast, the sulfonylurea tolbutamide, a specific blocker of KATP channels, closed KATP channels, elevated intracellular calcium levels, and stimulated insulin release in β-V59M β cells, indicating that events downstream of KATP channel closure remained intact. Expression of the V59M Kir6.2 mutation in pancreatic β cells alone is thus sufficient to recapitulate the neonatal diabetes observed in humans. β-V59M islets also displayed a reduced percentage of β cells, abnormal morphology, lower insulin content, and decreased expression of Kir6.2, SUR1, and insulin mRNA. All these changes are expected to contribute to the diabetes of β-V59M mice. Their cause requires further investigation.

Authors

Christophe A. Girard, F. Thomas Wunderlich, Kenju Shimomura, Stephan Collins, Stephan Kaizik, Peter Proks, Fernando Abdulkader, Anne Clark, Vicky Ball, Lejla Zubcevic, Liz Bentley, Rebecca Clark, Chris Church, Alison Hugill, Juris Galvanovskis, Roger Cox, Patrik Rorsman, Jens C. Brüning, Frances M. Ashcroft

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Figure 7

β-V59M islets show a decreased [Ca2+]i response to glucose.

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β-V59M islets show a decreased [Ca2+]i response to glucose. (A and B...
(A and B) Representative changes in [Ca2+]i produced by glucose and tolbutamide in WT (A) or β-V59M (B) islets. Values above the traces give mean ± SEM calcium concentrations (in nM) in 2 mM glucose (at steady state), 20 mM glucose (peak or initial and steady state), and 0.2 mM tolbutamide (peak). Data are representative of 7–9 islets (n = 2 mice). (C and D) Confocal images of WT (C) and β-V59M (D) islets stained with fluo 4–AM. Circles indicate the regions from which data in the lower panels was taken. Scale bars = 50 μm. Lower panels show representative changes in [Ca2+]i produced by increasing glucose from 2 to 20 mM in 2 different regions of the islet (indicated in upper panels) for WT (C) and β-V59M (D) islets. Insets show amplified sections to demonstrate that [Ca2+]i oscillations are synchronized in WT but not β-V59M β cells.