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 aspartic acid for alanine at position 2870 (A2870D) and lysine for asparagine at position 2875 (N2875K). These mutations result in a kinase dead protein. (J:191288)