Exon 3 was replaced with a floxed neo cassette and a modified exon 3 in which an A to C and T to A transversion results in the amino acid substitutions of alanine for aspartic acid at position 2880 (D2880A) and lysine for asparagine at position 2885 (N2885K). These mutations result in a kinase dead protein. Cre-mediated recombination removed the neo cassette. (J:191288)