A floxed neo cassette was inserted upstream of exon 13 and a T to G mutation was introduced in exon 13 resulting in a Ser to Ala substitution at position 522 (S522A). Cre mediated recombination removed the neo cassette. In brain lysates from homozygous mice phosphorylation of Ser522 and Thr509 is completely suppressed. (J:180581)