A targeting vector was generated so that a dsRed-IRES-cre/ERT2-pA-Frt-neo-Frt cassette was inserted immediately after the ATG codon in exon 1 of the Lgr5 locus (deleting the remainder of exon 1 and splice donor site in intron 1 - a212 bp deletion) by homologous recombination in C2 ES cells. Correctly targeted clones were transfected with an Flpe plasmid to remove the neo cassette. (J:177145)