A targeting vector was designed to introduce a loxP-flanked ECFP transgene to exon 2 and an FRT-flanked neomycin drug resistance cassette to intron 1 of the gene. (Enhanced cyan fluorescence protein (ECFP) has been inserted into the amino terminal of the syntaxin 1A gene.) Targeted mice were crossed with an actin promoter-driven FLP strain to remove the neomycin cassette. (J:134023)