The targeting vector inserted uptream of the endogenous exon 10 a floxed neomycin resistance cassette. The targeting vector also inserted downstream of the endogenous exon 10 a loxP site, 48 nucleotide spacer sequence and a modified exon 10 with nucleotide substitutions (AAC to CAG). The substitutions results in the amino acid substitution of glutamine for asparagine at position 595 (N595Q). Cre-mediated recombination removed the selection cassette and left the endogenous exon 10 floxed. (J:232063)