title: The severe G480C cystic fibrosis mutation, when replicated in the mouse, demonstrates mistrafficking, normal survival and organ-specific bioelectrics.
abstract: The majority of cystic fibrosis patients produce a mutant form of CFTR (DeltaF508) 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 DeltaF508 '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.
authors.affiliation: MRC Human Genetics Unit, Western General Hospital, Crewe Road, Edinburgh EH4 2XU, UK.
authors.forename: Paul
authors.initials: P
authors.lastname: Dickinson
authors.forename: Stephen N
authors.initials: SN
authors.lastname: Smith
authors.forename: Sheila
authors.initials: S
authors.lastname: Webb
authors.forename: Fiona M
authors.initials: FM
authors.lastname: Kilanowski
authors.forename: Isla J
authors.initials: IJ
authors.lastname: Campbell
authors.forename: Martin S
authors.initials: MS
authors.lastname: Taylor
authors.forename: David J
authors.initials: DJ
authors.lastname: Porteous
authors.forename: Rob
authors.initials: R
authors.lastname: Willemsen
authors.forename: Hugo R
authors.initials: HR
authors.lastname: de Jonge
authors.forename: Ray
authors.initials: R
authors.lastname: Farley
authors.forename: Eric W F W
authors.initials: EW
authors.lastname: Alton
authors.forename: Julia R
authors.initials: JR
authors.lastname: Dorin
mesh_terms: D000818:Animals; D003550:Cystic Fibrosis / Q000235:genetics*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics*; D004195:Disease Models, Animal; D004594:Electrophysiology; D005260:Female; D006720:Homozygote; D008297:Male; D051379:Mice; D009154:Mutation; D010641:Phenotype; D011499:Protein Processing, Post-Translational
chemical_list: D019005:Cystic Fibrosis Transmembrane Conductance Regulator