Using recombineering methods, the CreERT2-Frt-PGK-Hygromycin-pA-Frt cassette replaced the ATG start codon in exon 1 of the Slc22a6 gene in the BAC clone RP23-457i11. The modified BAC construct was electroporated into ES cells and correctly targeted ES cells were injected into CD1 blastocysts and the resulting chimeric mice were bred to C57BL/6J mice. These mice were then bred to mice containing Flp-recombinase to remove the Frt-flanked hygromycin selection cassette. (J:243751)