An Act88F promoter drives expression of the indirect flight muscle myosin isoform (IFI) of Mhc, mutated to carry a S531P amino acid substitution; this mutation is equivalent to a S532P change in the orthologous human MYH7 gene, a pathogenic variant associated with dilated cardiomyopathy. The coding sequence is composed of cDNA sequence encoding the Mhc IFI motor domain followed by a genomic fragment encompassing Mhc exons 12-19 (and associated introns and polyadenylation sites). The protein is tagged at the N-terminal end with Tag:polyHis and with the Tag:CS(TEVp) cleavage site.