Using homologous recombination in ES cells, the targeting construct inserted FRT-IRES-LacZ-Loxp-neo-FRT-LoxP into the intron upstream of the exon 8, and an additional LoxP was inserted into the intron downstream of the exon 8. A cre mediated deletion removed neo-cassette-FRT-LoxP and exon 8 leaving FRT-IRES-LacZ-LoxP in the intron. (J:311917)