A targeting vector was designed to fuse a signal peptide from rat neurexin 1 alpha followed by a GFP "emerald" cassette to the amino(N) terminus of exon 1, flank exon 2 with loxP sites, and insert an Flp-flanked neomycin resistance cassette in intron 2. Resultant mice were crossed with an FRT recombinase strain to remove the FLP-flanked neomycin cassette. Presence of the GFP fusion protein was detected by western blot analysis. (J:122459)