Exon 2 was replaced with an exon 2 that contained a nucleotide substitution that resulted in an amino acid substitution of arginine for glycine at position 67 (G67R). This substitition occurs within the ATPase domain. A floxed neo cassette was also inserted into intron 1 but was subsequently removed by germ-line, cre-mediated recombination. (J:133352)