The targeting construct includes a loxP site upstream of exon 14, 3 point mutations inserted into exon 14 to create amino acid substitutions (amino acids 5 (G->R), 10 (F->Y) and 13 (R->H)) (ENSMUSE00000131684), a loxP site downstream of exon 14 and a FRT-flanked neo selection cassette, which is removed by FLP-mediated recombination. (J:304519)