The targeting vector used for homologous recombination contained a cre/GFP fusion sequence (cre fused in frame with EGFP at the C-terminus), N-terminal nuclear localization signal and myc tag, and frt-flanked PGK-neo marker. Cre was inserted at the initiation ATG codon in exon 2 of the gene. Chimeric animals were bred with Flper mice to remove the PGK-neo selection marker. (J:206070)