Overexpression of miniparamyosin causes muscle dysfunction and age-dependant myofibril degeneration in the indirect flight muscles of Drosophila melanogaster

Miniparamyosin (mPM) is a protein of invertebrate muscle thick filaments. I ts similarity to paramyosin (PM) suggests that it regulates thick filament and myofibril assembly. To determine its role in muscle structure and funct ion we overexpressed mPM in muscles of Drosophila melanogaster. Surprisingl y, myofibrils accumulating excess mPM assemble nearly normally, with thick filament electron density and sarcomere length unaffected. Myofibrils in so me indirect flight muscle groups are misaligned and young flies exhibit a m oderate level of flight impairment. This phenotype is exacerbated with age. Transgenic flies undergo progressive myofibril deterioration that increase s flight muscle dysfunction. Our observations indicate that the correct sto ichiometry of mPM is important for maintenance of myofibril integrity and f or the proper function of the flight musculature.