Figure 8.

Ventricle chamber size reduction in actn2 morphants is rescued by cessation of contraction via blebbistatin or nifedipine treatment. A) Sarcomere integrity is disrupted in embryos treated with blebbistatin, as revealed by Tg(cmlc2:cypher-egfp). Compared to the long Z discs in DMSO-treated WT or actn2 MO fish, the Z discs in blebbistatin-treated WT or actn2 MO fish is significantly shorter, indicating disrupted Z-disc bundling. Double-ended arrow indicates the Z-disc length. B) Quantification of the Z-disc length. n, number of fish. C) Electron micrographs show that cessation of heart contraction via blebbistatin treatment cannot rescue the disrupted Z disc in actn2 MO fish heart. Bracket indicates Z-disc width. D) Quantification of the Z-disc width, which cannot be rescued by cessation of heart contraction. E) Measurement of the ventricular volume in DMSO and blebbistatin treated fish at 52 hpf. WT and actn2 morphant embryos were bathed in egg water containing 8 μM blebbistatin or 60 μM nifedipine from 37 to 52 hpf. Ventricular volume is significantly reduced in MO fish, but this defect can be rescued by either blebbistatin or nifedipine treatment. MO, actn2 MO-injected fish; Ble, blebbistatin-treated WT fish; MO Ble, blebbistatin-treated actn2 MO fish; NS, not significant. Scale bars = 10 μm (A); 200 nm (C). *P < 0.05.