The targeting cassette is composed of an FRT site followed by lacZ sequence and an initial loxP site upstream of exon 8. This first loxP site is followed by a neomycin resistance gene under the control of the human beta-actin promoter, SV40 polyA, a second FRT site and a second loxP site. A third loxP site is inserted downstream of exon 8. Flp-mediated recombination removed the lacZ and neo cassette. (J:302898)