A targeting vector was designed to replace serine 9, coded for by exon 1, with alanine (S9A) and a floxed neomycin resistance cassette was inserted at the 3' end of exon 1. The floxed neomycin selection cassette was removed by crossing to Tg(Nes-cre)1Wme, so-called Bal1 mice, which express cre recombinase ubiquitously. (J:98263)