Fig. 7

Myf5 or Myod is required for myogenesis. Wholemounts (A), flatmounts (B) and confocal stacks (C,D) in lateral (A–C) or ventral (D) view of zebrafish embryos from myf5^hu2022/+;myod^fh261/+ in-cross analysed at the indicated stage by in situ mRNA hybridization for mylz2 (B) or immunohistochemistry for all-MyHC (green), smooth muscle myosin heavy chain 11 (red) and Hoechst (blue) in C,D, anterior to left. A. By 24 hpf, double mutant embryos are curved and have misshapen somites with signs of cell death. B. mRNA encoding fast myosin is reduced in putativemyod^fh261 mutants and absent in doubles. C. Confocal stacks of somite-16 region at 4 dpf embryos show that no skeletal muscle MyHC is detected in genotyped double mutants, in which embryos are severely reduced in size. Smooth muscle myosin in the gut (red arrowheads) are unaffected. D. Confocal stacks of the head region of 4 dpf embryos show that all skeletal muscle is missing in myf5^hu2022;myod^fh261 double mutant, while heart (yellow arrows) and smooth muscle are intact. myod^fh261 mutant is missing all muscle except for the sternohyoideus (white arrows), adductor operculi and levator operculi (orange arrows). E. Alcian blue and alizarin red double staining for cartilage and bone in 6.5 dpf myf5^hu2022;myod^fh261 shows a more severe phenotype than in myod^fh261 mutants and siblings. Flatmounts of the dissected pharyngeal skeleton (ventral view, left panels) or neurocranium (dorsal view, right panels). Cartilage components in double mutants stain poorly. Bone is only detected in the double mutant in cleithrum (cl) and teeth (left panel) and faintly in the notochord (nc) and parasphenoid (ps) (right panel). oc, occipitals; op, opercle; en, enteropterygoid; cb5, ceratobranchial 5. Bars = 100 μm.