A loxP site was inserted upstream of exon 1 and an FRT flanked neo cassette and loxP site were inserted downstream of exon 2 via homologous recombination. Recombinase mediated recombination removed the neo cassette and exons 1 and 2. RT-PCR and western blot analysis confirmed the absence of expression in homozygous MEFs and testicular cells. (J:185584)