A loxP site and an FRT site flanked neomycin resistance gene cassette were inserted into intron 3 and a second loxP site into intron 6. The neo cassette was removed through subsequent flp-mediated recombination and exons 4-6 were deleted through cre-mediated recombination. Immunohistochemistry showed no peptide is expressed from this allele. (J:281205)