The targeting vector contains a loxP-flanked neomycin inserted into intron 3 and a lysine to asparagine amino acid substitution at position 132 (K132N; AAG to AAC) inserted into exon 4. The mutation corresponds to the human tumor-associated mutation, K140N and found in two patients with colorectal carcinoma or uterine corpus endometrial carcinoma. Cre-mediated recombination removed the neo cassette. (J:94077)