A loxP site was inserted upstream of exon 2 and a loxP-flanked PGKneo cassette site was inserted downstream of exon 3. Cre-mediated recombination removed the neo cassette. Exons 2 and 3 were subsequently removed from properly targeted mice by crossing to transgenic mice carrying Tg(EIIa-cre)C5379Lmgd. (J:94077)