Human Molecular Genetics, 2002, Vol. 11, No. 3 243-251
© 2002 Oxford University Press
The severe G480C cystic fibrosis mutation, when replicated in the mouse, demonstrates mistrafficking, normal survival and organ-specific bioelectrics
MRC Human Genetics Unit, Western General Hospital, Crewe Road, Edinburgh EH4 2XU, UK, 1Department of Gene Therapy, National Heart and Lung Institute at Imperial College, London, UK, 2CBG-Department of Clinical Genetics and 3Department of Biochemistry, Faculty of Medicine and Health Sciences, Erasmus University, PO Box 1738, 3000 DR Rotterdam, The Netherlands
The majority of cystic fibrosis patients produce a mutant form of CFTR (
F508) which has been shown to be mislocalized in both humans and mice. G480C, another clinically ‘severe’ mutation, has also been demonstrated to be defective in its intracellular processing, but when allowed to traffic in Xenopus oocytes showed similar channel characteristics to that of wild-type CFTR. We have replicated the G480C mutation in the murine Cftr gene using the ‘hit and run’ double recombination procedure. As expected, the G480C cystic fibrosis mouse model expresses the G480C mutant transcript at a level comparable to that of wild-type Cftr. The homozygous mutant mice were fertile, had normal survival, weight, tooth colour and no evidence of caecal blockage, despite mild goblet cell hypertrophy in the intestine. Analysis of the mutant protein revealed that the majority of G480C CFTR was abnormally processed and no G480C CFTR-specific immunostaining in the apical membranes of intestinal cells was detected. The bioelectric phenotype of these mice revealed organ-specific electrophysiological effects. In contrast to F508 ‘hit and run’ homozygotes, the classic defect of forskolin-induced chloride ion transport is not replicated in the caecum, but the response to low chloride in the nose is clearly defective in the G480C mutant animals. The mild phenotype of these G480C mutant animals combined with the defective chloride transport in the nose uniquely provides a valuable resource to test novel pharmacological agents aimed at improving trafficking and correcting the electrophysiological defect in the respiratory tract.
+ To whom correspondence should be addressed. Tel: +44 131 467 8410; Fax: +44 131 343 2620; Email: julia@hgu.mrc.ac.uk Present addresses: Paul Dickinson, Centre for Inflammation Research, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Summerhall, Edinburgh EH9 1QH, UK Martin S. Taylor and David J. Porteous, Medical Genetics Section, Department of Medical Sciences, University of Edinburgh, Molecular Medicine Centre, Western General Hospital, Crewe Road, Edinburgh EH4 2XU, UK The authors wish it to be known that, in their opinion, the first two authors should be regarded as joint First Authors
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