LoxP sites were positioned upstream of the preceding exon and downstream of the biotin binding domain exon using an Frt flanked kanamycin resistance cassette. The Frt-flanked selection cassette was removed by Flpe recombinase-mediated recombination. These two exons were deleted by Cre-mediated recombination, which introduces a frameshift and nonsense mutation after Asp865 in any translated protein. Immunoblotting showed no truncated protein expression in muscle lysates from homozygous mice.