Fig. 3

Suppression of mysterin-α leads to impaired muscle fiber formation in fast muscle.

(a) Muscular composition of zebrafish embryos at 2 dpf. Slow muscle cells (red) form a monolayer structure beneath the skin. By contrast, fast muscle cells (blue) occupy the deeper region. MPCs (green) are located lateral to the notochord. (b) Fast and slow muscle structures. Fast and slow muscles in the trunk are stained with phalloidin, which recognizes actin fibers of both muscle types, and an anti-myosin heavy chain antibody (F59), which labels slow myosin fibers. F59 labeling revealed normal slow muscle fibers in control and mysterin morphants (left panels). Phalloidin labeling revealed an impaired fast muscle structure in morphants (right panels). (c) Cross-section of the trunk region. Slow and fast muscle structures are stained with phalloidin at 2 dpf. The density of F-actin fibers in the fast muscle region is severely decreased in morphants treated with a low dose of MO. White arrows indicate the slow muscle monolayer, which appears to be normal in morphants treated with a low dose of MO. (d–o) EM of the muscle structures of control animals and morphants treated with a low dose of MO at 2 dpf. Cross-sections (d–i) and vertical sections (j–o) of a control animal and morphant. The orientation of actin and myosin is shown in (h–i). The sarcomeric structure is shown in (n–o). The M-line and Z-disk are indicated by red and black arrows, respectively.