A floxed neo cassette was inserted within intron 3, and specific nucleotide mutations in exon 3 were introduced by homologous recombination. Mutation resulted in the JNK protein kinase phosphorylation site (Ser-74) in exon 3 to be substituted with an Asp (S74D). The neo cassette was then excised with Cre mediated recombination leaving a single loxP site in intron 3. (J:153652)