Exon 2 was replaced with one in which a T to C transition results in the amino acid substitution of arginine for tryptophan at position 4 (W4R), mimicking a mutation found in some myocardiopathy patients. A floxed neo cassette inserted downstream of the modified exon 2 was removed by cre-mediated recombination. Reduced protein expression was confirmed by western blot analysis. (J:170878)