The following elements were inserted, in order into a region 2 kb 5' of the Ubb gene by targeted recombination: CMV enhancer/beta-actin promoter, loxP site, beta-geo, 3 stop transcription sites, loxP site, 3HA-Fzd3, rabbit beta-globin 3' UTR. The 3HA tag is inserted after the signal peptide and before the cysteine-rich domain of Fzd3. (J:217610)