Fig. 5

Thin filament striation was disrupted in MO-ATG morphants, but not in MO-E13 morphants. (A) Shown are images of 48 hpf embryos after immunostaining using either Tm antibody or phalloidin staining to reveal the F-actin network. Irregular actin and Tm dots were detected in MO-ATG morphants and sih mutants, while periodic dots of actin and Tm dots were detected in MO-E13 morphants. Open arrowheads, random dots of F-actin or Tm. Arrowheads, periodic F-actin or Tm dots. (B) Quantification of the length of F-actin filaments in 48 hpf embryos. Shown are mean ± s.d. *p < 0.01, if compared with WT. N, number of hearts or sarcomere units quantified. (C) Shown are images of 48 hpf embryos after two-color immunostaining to reveal Tm (green) and actin filament (red). Association of Tm and F-actin was disrupted in MO-ATG morphants, but not in MO-E13 morphants. (D) Shown are images of 48 hpf embryos after two-color immunostaining for Tm (green) and Tnni (red). Assembly of Tnni into thin filaments and sarcomeres was disrupted in both morphants. (E) Shown in the top panels are images of 48 hpf embryos after immunostaining with CH1 antibody to reveal sarcomere assembly. Shown in the lower panels are individual cardiomyocytes with EGFP signal, indicating the expression of ectopic tnnt2 transcripts. Injection of full-length tnnt2 in either MO-ATG or MO-E13 morphants completely rescued sarcomere assembly, while injection of C-terminal truncated tnnt2 in MO-ATG morphants partially rescued sarcomere assembly to achieve a striated pattern. Arrows, mature sarcomeres. Arrowheads, partially rescued sarcomeres with striated pattern. Scale bar = 5 μm.