title: Inducible Cre-mediated control of gene expression in the murine gastrointestinal tract: effect of loss of beta-catenin.
abstract: OBJECTIVE
  A system for introducing specific gene mutations into the epithelia of the adult murine gastrointestinal tract by the transcriptional regulation of Cre recombinase is presented and applied to delete beta-catenin, a central mediator of Wnt signaling, within the small intestine (SI).
  
  
  METHODS
  In a transgenic line (Ahcre), cre expression is inducible from a cytochrome P450 promoter element that is transcriptionally up-regulated in response to lipophilic xenobiotics such as beta-napthoflavone.
  
  
  RESULTS
  Recombination at a lacZ reporter locus showed extensive expression of beta-galactosidase in liver, intestine, pancreas, gallbladder, esophagus, and stomach in response to beta-napthoflavone treatment. Expression patterns were stable in renewing epithelia for at least 6 months, implying that long-lived stem cells undergo recombination. Analysis of the intestinal epithelium showed dose responsiveness in the extent of recombination and that villus and crypt populations could be targeted differentially by varying the route of administration of beta-napthoflavone. The use of this system to delete beta-catenin in the SI caused crypt ablation, increased apoptosis, depleted numbers of goblet cells, and detachment of villus absorptive cells from the villus core as intact sheets.
  
  
  CONCLUSIONS
  The Ahcre model provides a simple route for introducing specific gene mutations into many of the epithelia of the gastrointestinal tract of the mouse. It has been used here to show that beta-catenin is required for the maintenance of intestinal cell proliferation and is implicated in goblet cell differentiation and enterocyte-matrix attachment.
authors.affiliation: Department of Oncology, Cancer Research UK, Cambridge Institute of Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Road, Cambridge CB2 2XY, UK.
authors.forename: Heather
authors.initials: H
authors.lastname: Ireland
authors.forename: Richard
authors.initials: R
authors.lastname: Kemp
authors.forename: Carol
authors.initials: C
authors.lastname: Houghton
authors.forename: Louise
authors.initials: L
authors.lastname: Howard
authors.forename: Alan R
authors.initials: AR
authors.lastname: Clarke
authors.forename: Owen J
authors.initials: OJ
authors.lastname: Sansom
authors.forename: Douglas J
authors.initials: DJ
authors.lastname: Winton
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000502:physiology; D002455:Cell Division / Q000502:physiology; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000502:physiology*; D004254:DNA Nucleotidyltransferases / Q000235:genetics*; D004064:Digestive System / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015870:Gene Expression / Q000502:physiology*; D020868:Gene Silencing; D020397:Goblet Cells / Q000166:cytology; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000166:cytology; D051379:Mice; D008817:Mice, Mutant Strains; D008822:Mice, Transgenic; D008871:Microvilli / Q000378:metabolism; D051381:Rats; D011995:Recombination, Genetic; D014018:Tissue Distribution; D015534:Trans-Activators / Q000235:genetics / Q000502:physiology*; D051176:beta Catenin; D001616:beta-Galactosidase / Q000378:metabolism; D019324:beta-Naphthoflavone / Q000494:pharmacology
chemical_list: C495267:CTNNB1 protein, mouse; C495268:Ctnnb1 protein, rat; D003598:Cytoskeletal Proteins; D004791:Enzyme Inhibitors; D015534:Trans-Activators; D051176:beta Catenin; D019324:beta-Naphthoflavone; D004254:DNA Nucleotidyltransferases; D001616:beta-Galactosidase