A loxP site was inserted upstream of exon 2. An FRT-flanked neomycin resistance cassette and a second loxP site were inserted downstream of exon 3. Flp-mediated recombination removed the selection cassette and left exons 2 and 3 floxed. Cre-mediated recombination removed exons 2 and 3, generating a truncated protein lacking the N-terminal. (J:233694)