Mhc genomic DNA in which exons 15a and 15b and their flanking introns are replaced with cDNA containing exons 14, 15b and 16 resulting in the expression of an isovariant containing slow muscle hinge B in place of the fast muscle isovariant hinge A in the Mhc isoforms of indirect flight and jump muscles.
Compared with wild-type, the flight ability of Mhc10 mutants expressing Mhc15b is impaired. The flight ability of these flies declines more rapidly with age than that of controls.
Compared with controls, Mhc10 mutant flies expressing Mhc15b display a reduced ability to jump.
Electrophysiological responses of flight muscles in Mhc10 mutants expressing Mhc15b appear normal.
Expression of Mhc15b in Mhc10 mutants results in myofibrils with generally wild-type structure. However, there are a variety of minor defects not observed in the control line including myofibrils with disrupted M lines and rough edges. The frequency and severity of defects vary among different insertion lines. Myofibril dimensions of Mhc10 mutants expressing Mhc15b differ from that of wild-type. The myofibril defects appear use-dependent as they are less frequent and less severe in newly eclosed flies than in older adults.