An FRT-flanked STOP cassette with a 3' loxP site was inserted upstream of exon 3. A rox flanked hygromycin resistance (hygro) cassette with a 3' loxP site was inserted downstream of exon 3. Flp- and dre-mediated recombination removed the STOP and hygro cassettes. Cre-mediated recombination removed exon 3. Western blot analysis confirmed the absence of protein expression. (J:196401)