An FRT-flanked neo cassette with a 5' loxP site was inserted upstream of exon 7. An additional loxP site was inserted downstream of exon 7. Cre-mediated recombination remvoed exon 7. RT-PCR confirmed the expression of a truncated transcript. Immunohistochemistry confirmed the absence of protein expression in the stratum spinosum and stratum granulosum. (J:179754)