A loxP site was inserted upstream of exon 5 and a floxed hygro cassete was inserted downstream of exon 5. Cre mediated recombination removed exon 5 and the hygro cassette. Removal of exon 5 results in a frame shift and premature termination at amino acid 186. The absence of protein expression was confirmed by western blot analysis on brain extracts. (J:155437)