The single exon and the 3 untranslated region containing the polyadenylation signal were flanked by loxP sites. A modified yellow fluorescent protein, YPet, cDNA was inserted downstream of the 3 loxP site such that when the floxed region is removed, YPet is expressed under the endogenous Htr1a promoter. An inserted FRT-flanked PGK-EM7-Neomycin minigene was removed via flp-mediated recombination. (J:254164)