Mlc2^E38 mutant flies expressing Mlc2^Δ2-46 are able to fly or beat their wings, but they display slightly reduced flight index and decreased wing beat frequency compared with wild-type.

Mlc2^E38 mutants carrying Mlc2^Δ2-46 display sarcomeric structural abnormalities as revealed by X-ray diffraction and electron microscopy.

Flies carrying two copies of Mlc2^Δ2-46 in an Mlc2 null background (homozygous for Mlc2^E38) have a flight index and wing beat frequency that is not significantly different from that of wild-type flies. The flies often show an abnormal trajectory at the onset of flight, either hovering or dropping momentarily before flying upward (in contrast to wild-type flies which fly upwards towards a light source). The flies show a 35% reduction in peak flight performance compared to wild type in a closed-loop flight arena. Mechanical power is also reduced, due to a 7% drop in wing amplitude and a 5% drop in stroke frequency during peak force production. Muscle efficiency is not statistically different from wild type. Indirect flight muscle (IFM) ultrastructure is normal. IFMs have reduced dynamic stiffness and elastic modulus at the frequency of maximum power output.