Exons 3-8 and an adjacent frt-flanked neomycin selection cassette were deleted via Cre-mediated recombination of flanking loxP sites. RT-PCR analysis revealed the absence of mRNA expression in several tissues (including testes) and mouse embryonic fibroblasts (MEFs) obtained from homozygous mutant mice. Immunoblot analysis using a mouse specific antibody confirmed the absence of protein expression in mutant testes and MEFs. (J:251603)