An FRT-flaneked neomycin resistance cassette with a 5' loxP site was inserted upstream of exon 5. A second loxP site was inserted downstream, of exon 6. Cre-mediated mutation removed the selection cassette and exons 5 and 6. Western blot analysis confirmed the absence of protein expression in skeletal muscle, brain, heart, lung, spleen and white adipose tissue. (J:235640)