A lacZ with a triple poly A signal and a floxed pgk-neo cassette replaced a 695 bp region including part of exon 5 and intron 5. Cre-mediated recombination removed the neo cassette. RT-PCR detected the presence of an alternative splice form with exon 4 fused to exon 6, skipping the targeted exon, resulting in an in frame deletion of 96 amino acids. LacZ expression is detected in the notochord, the optic vesicle, the otic placode, the eye, the apical ectodermal ridge of the fore and hindlimbs and on the surface of the branchial arches at E10.5 and E11.5. (J:229383)