TauLacZ was inserted into the locus along with a floxed neomycin resistance cassette. This caused the deletion of all of the coding sequence of the native gene. The neomycin resistance cassette was subsequently eliminated by Cre-mediated recombination. The ES line was generated in collaboration with Martyn Goulding, Salk Institute. Immunohistochemical analysis confirmed the absence of protein product. (J:123264)