Exons 6-10 were replaced with a construct containing exons 6 and 7, a loxP site, a minigene containing exons 8-11, a polyadenylation STOP sequence, a FRT-flanked neomycin resistance gene, a second loxP site, a mutated exon 8, and exons 9-10. The mutated exon 8 contains a C to T mutation at position 1402 and a G to T mutation at position 1404, resulting in an arginine to cysteine change at amino acid 468. The R468C mutation corresponds to the human R465C mutation, frequently detected in primary tumors. Cre-mediated recombination removed the floxed minigene and selection cassette, leaving a mutated exon 8. (J:258194)