Exon 17 was flanked with a loxP site and a floxed neo cassette via homologous recombination. The neo cassette and exon 17 were subsequently removed via in vivo Cre-mediated recombination. This results in a frameshift, premature termination codon and truncated protein. PCR analysis confirmed the presence of a 0.4 kb truncated transcript in mice carrying this allele. (J:131043)