An arginine to glutamine substitution at residue 4344 (R4344Q) was introduced in exon 60. An FRT-flanked neomycin selection cassette and loxP site were inserted in intron 59 along with a second loxP site in intron 61 so that the mutant exon 60 and exon 61 are floxed. The selection cassette was removed via Flp-mediated recombination. (J:243723)