Human Molecular Genetics Advance Access originally published online on March 28, 2006
Human Molecular Genetics 2006 15(10):1600-1609; doi:10.1093/hmg/ddl081
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WFS1-deficiency increases endoplasmic reticulum stress, impairs cell cycle progression and triggers the apoptotic pathway specifically in pancreatic ß-cells
1Division of Molecular Metabolism and Diabetes and 2Division of Advanced Therapeutics for Metabolic Diseases, Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8575, Japan, 3Division of Stem Cell Regulation Research, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan and 4Genome Science Division, Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo 153-8904, Japan
* To whom correspondence should be addressed. Tel: +81 227177611; Fax: +81 227177612; Email: hisamitsu-ishihara{at}mail.tains.tohoku.ac.jp
Received January 28, 2006; Accepted March 24, 2006
Wolfram syndrome, an autosomal recessive disorder associated with diabetes mellitus and optic atrophy, is caused by mutations in the WFS1 gene encoding an endoplasmic reticulum (ER) membrane protein. Herein, we report that pancreatic islets of wfs1-deficient mice exhibit increases in phosphorylation of RNA-dependent protein kinase-like ER kinase, chaperone gene expressions and active XBP1 protein levels, indicating an enhanced ER stress response. We established wfs1-deficient MIN6 clonal ß-cells by crossing wfs1-deficient mice with mice expressing simian virus 40 large T antigen in ß-cells. These cells show essentially the same alterations in ER stress responses as wfs1-deficient islets, which were reversed by re-expression of WFS1 protein or overexpression of GRP78, a master regulator of the ER stress response. In contrast, these changes are not observed in heart, skeletal muscle or brown adipose tissues with WFS1-deficiency. The increased ER stress response was accompanied by reduced BrdU incorporation and increased caspase-3 cleavage, indicating impaired cell cycle progression and accelerated apoptotic processes in the mutant islets. These changes are associated with increased expression of the cell cycle regulator p21CIP1 in wfs1-deficient islets and clonal ß-cells. Treatment of islets with thapsigargin, an ER stress inducer, caused upregulation of p21CIP1. In addition, forced expression of p21CIP1 resulted in reduced MIN6 ß-cell numbers, suggesting the ER stress-induced increase in p21CIP1 expression to be involved in ß-cell loss in the mutant islets. These data indicate that WFS1-deficiency activates the ER stress response specifically in ß-cells, causing ß-cell loss through impaired cell cycle progression and increased apoptosis.
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