Sarcomeric length determined with SHG imaging.

(A) A cartoon illustration of a sarcomere and the architectural arrangement of its major constituent filaments. The length of a sarcomere is defined as the separation between two z-disks. (B) A high-resolution SHG image of zebrafish muscles. The image exhibits two characteristic patterns that are denoted as double (gray arrow) and single bands (white arrow), respectively. Scale bar: 5 μm. (C, D) Representative cross-sectional plots of a double band (C) and a single band (D). The length of the sarcomere was determined from the distance between the two dashed lines as shown in the two cross-sectional plots. (E) Comparison of the averaged length of the sarcomere determined from the two sarcomeric patterns. The statistics were calculated based on 12 images obtained from somites near the head (fifth to eighth somite) of three 72-hpf zebrafish.

Sarcomeric length of living and fixed zebrafish, and developing larva at different stages.

(A) Comparison of length of sarcomeres determined from zebrafish living and fixed with paraformaldehyde. The SHG images used to measure the lengths were measured on somites near the head (black, somites 5–8) and the tail (red, somites 21–24). The statistics were calculated based on 21 images obtained from three 72-hpf zebrafish. (B) Representative SHG images of zebrafish measured at three developmental stages (24, 36 and 72 hpf). The images were measured on regions near the head (somites 5~8) and the tail (somites 21–24). (C) Growth of the sarcomere from 1 to 12 dpf. The SHG images used to evaluate the length were measured on somites near the head (black, somites 5~8) and the tail (red, somites 21–24). The statistics were calculated based on 21 images obtained from three 72-hpf zebrafish.

Structural modification of zebrafish muscles induced on treatment with statin.

(A) A representative SHG image of the control (an untreated zebrafish larva, 72 hpf). (B) A representative SHG image of a zebrafish larva (72 hpf) subject to treatment with statin (50 μM) for 12 h. Image size: 140 μm (w)×100 μm (h). (C) Effect of statin treatment on zebrafish with underdeveloped sarcomeres. The zebrafish was subject to a treatment of statin (0.5 μM) at 24 hpf for 12 h, and imaged at 36 hpf (black: somites 5~8; red: somites 21–24). (D) Effect of statin treatment on zebrafish with fully developed sarcomeres. The zebrafish was subject to a treatment of the same dosage at 72 hpf for 12 h, and the image was taken at 84 hpf (head, somites 5~8).

Rescuing effect of mevalonate on the shortened sarcomere induced with statin.

Left: the control, untreated zebrafish; middle: zebrafish subject to a treatment of statin (0.5 μM) at 24 hpf for 12 h; right: zebrafish subject to a co-treatment of statin (0.5 μM) and mevalonate (100 μM) at 24 hpf for 12 h. All SHG images used to determine the sarcomere length were measured at 36 hpf on somites near the head (black, somites 5~8) and the tail (red, somites 21–24). The two images displayed as insets are representative results of co-treatment measured near the head (left) and the tail (right), respectively. Image size: 50×50 μm. The statistics were calculated based on 21 images obtained from three zebrafish.