The autosomal dominant Arg141Trp (R141W) mutation found in a family with dilated cardiomyopathy was introduced into exon 9 followed by a floxed neo/zeo cassette via homologous recombination. The neo/zeo cassette was removed via cre-mediated recombination. Reverse transcription-PCR and sequencing of total cardiac RNA confirmed expression of mutant mRNA. (J:243725)