A loxP site was inserted 300 nucleotides 5' of the initiation methionine codon in exon 1 and a floxed neomycin resistance gene as well as an EGFP gene were inserted in intron2. Crossing to cre-deleter mice led to the excision of the neo resistance gene leaving the floxed partial exon 1, exons 2. The EGFP insert was non functional. (J:94941)