A loxP site was inserted into intron 5 and an FRT site flanked neomycin resistance gene cassette and a second loxP site into intron 7. Subsequent flp-mediated recombination removed the neo cassette. Exons 6 and 7 were deleted through subsequent cre-mediated recombination. These two exons code for part of the coiled-coil domains. RT-PCR and western blots on testes samples showed the absence of expression from this allele. (J:254117)