A loxP site was inserted 60 bp upstream of exon 2 and a floxed neo cassette was inserted approximately 1.2 kbp downstream of exon 2 via homologous recombination. Cre mediated recombination removed the neo cassette leaving exon 2 floxed. Western blot analysis revealed no detectable alteration of protein levels in the brain of homozygous mutant mice. (J:216169)