A loxP site was inserted upstream of exon 8. An FRT-flanked neomycin resistance cassette, IRES and splice donor with a 5' loxP site was inserted downstream of exon 9. Flp-mediated recombination removed the selection cassette and left exons 8 and 9 floxed. Western blot analysis confirmed the absence of protein expression in mosue embryonic extracts. (J:204996)