Expression of ΔN89β-catenin following doxycycline treatment in vivo. (A) Schematic representation of the system used to express ΔN89β-catenin in ES cells and mice. A cassette containing ΔN89-βcatenin under control of the doxycycline-responsive promoter was flipped downstream of the collagen locus. Tet-o, tetracycline/doxycycline responsive operator; attB, gateway recombination site; M, myc protein tag; FRT, flippase recognition target site; pgkp, hygro, hygromycin resistance gene; ATG, transcriptional initiation codon; M2-rtTA, M2 reverse tetracycline transactivator. (B) ΔN89β-catenin mRNA level in the intestine of control and Tet-OΔN89β-catenin mice after 10 days doxycycline treatment (*, p<0.05, Mann Whitney, n=4). (C) Western blot analysis of myc tagged ΔN89β-catenin protein in the intestine after 10 days doxycycline treatment. (D) Detection of myc tagged ΔN89β-catenin by immunohistochemistry (left) and total β-catenin by immunofluorescence (right) following 10 days doxycycline treatment. Dox: doxycycline.