Fig. S1

Early myogenesis occurs properly in Myogenin mutant.

a. Immunoreactivity of Myog in nuclei is lost in myogkg128 mutants at 20 ss. Insets show magnification of boxed areas; dashed lines denote how nuclei (white) or nucleus-free background area (green) was selected for analysis (see Methods). Graph shows quantification of relative myotomal nuclear Myog immunofluorescence; Myog is significantly reduced in mutants but unchanged in heterozygotes compared to wt sibs (summarized data is shown in Fig. 1d). b. Dorsal view of ISH for smyhc1 and mylpfa mRNAs at 15 ss embryos from a myogkg125/+ incross showing that initial differentiation occurs normally despite absence of Myog. c. ISH for smyhc1 and mylpfa (brackets highlighting difference in expression) at 20 hpf (22 ss) confirming that myogkg125 mutant and sib are indistinguishable. d. Dual immunodetection using S58 (sMyHC) and EB165 (fMyHC) in 20 hpf embryos from a myogkg125/+ incross showing that accumulation of slow and fast myosins occurs normally in mutants. e. Immunodetection using A4.1025 antibody showing no difference in slow fibre number in mutant compared to sib at 1 dpf (24 hpf). Mean ± SEM, t-test. f. Fish from β-actin:EGFP;myogkg125/+ incross were moved from fish water (FW) to 0.6% methyl-cellulose (MC) solution at 5 dpf and left to grow for 72 hours, then confocallyimaged to assess muscle fibre detachment. Sibling and mutant larvae retain attached muscle throughout the myotome. The locations of three different medio-lateral images per larva within somites 16-18 are shown in transverse sections. Remaining images in a, c-f are lateral views anterior to left, dorsal to top. Replicate numbers are given in Supplementary Table 2. Bars = 50 μm, except for a insets (10 μm).