A loxP site was inserted upstream of exon 2. An FRT-flanked neo cassette with a 3' loxp site was inserted downstream of exon 2. Cre-mediated recombination removed exon 2. This allele lacks the neo cassette. Western blot analysis confirmed the absence of protein expression in the cortex, cerebellum, salivary gland, kidney, thymus and small intestine.