Fig. 4.

Transmission electron micrographs of IFMs in Mhc^K1728del flies. Transmission electron micrographs of IFMs in 7-d-old control (A–C), heterozygous Mhc^K1728del/+ (D–I), and Mhc^K1728del/Mhc¹⁰ flies (J–L). (A–C) Control flies show regular sarcomere structure with well-defined Z-disk and M-bands (A and B) and dense fibers (C, transverse section). (D and F) Transverse sections of heterozygous Mhc^K1728del/+ flies reveal fibers with focal thick filament loss (D) and accumulation of Z-disk–derived material (F). (E, G, and H) Longitudinal sections reveal fibers with Z-disk streaming and extensions leading to myofibrillar disorganization. (I) Collections of mitochondria with some electron-dense inclusions. (J–L) IFMs of Mhc^K1728del/Mhc¹⁰ flies revealed severe thick filament loss, pale Z-disks and accumulation of electron dense granular material. [Scale bars: 2 µm (A, E, G, H, and J–L), 1 µm (B and C), and 0.5 µm (D, F, and I).]