A targeting vector was designed to insert a FRT5-flanked neo cassette (frt5-pSV40-Neo-pA-frt5) and a loxP site upstream of exon 3, and a loxP downstream of exon 3. Flp-mediated recombination removed the FRT5-flanked neo cassette. Cre-mediated recombination removed exon 3. (J:237687)