A loxP site was inserted 40 nucleotides 5' of the initiation methionine codon in exon 3 and a floxed neomycin resistance gene as well as an EGFP gene were inserted in the intron between exons 5 and 6. Crossing to cre-deleter mice led to the excision of the coding portion of exon 3, exon 4 and exon 5 as well as the neo resistance gene. RT-PCR and western blot analysis confirmed the absence of transcription and translation. The EGFP insert was non functional. (J:94941)