Fig. S3

Lack of fusion in myog^kg125 and myog^kg128 persists until 6 dpf and is phenocopied by Myogenin knockdown.

a. Individual quantification of fusion within somite 17 (summarized as pie charts in Fig. 4e-f) showing fraction of fibres with given number of nuclei and fraction of nuclei in fibres with given number of nuclei. Dots represent individual embryos. Mean ± SEM. b. Lack of fusion persists in myog mutants. GFP staining of β-actin:EGFP; myogkg125/+ incross at 6 dpf. Nuclei were stained with Hoechst (red). Transverse sections (YZ) report position of parasaggital sections (pink and yellow lines). c. Schematic of myog mRNA showing the position and nucleotide sequence of morpholino (red bold line), which anneals close upstream of ATG start codon. d. To knock down Myog, morpholino (MO) was injected at 1-cell stage into β-actin:EGFP embryos. Myog immunodetection and Hoechst stained nuclei (blue) at 16.5 hpf showed loss of nuclear Myog immunoreactivity in MO embryos. White lines indicate somite borders. e. At 2 dpf, MO and control injected embryos were fixed and incubated with Hoechst to highlight nuclei (red) prior to confocal imaging. As in myog mutants, knockdown of Myog led to overabundance of smaller mononucleated muscle fibres and reduced the size of the myotome. Multinucleated fibres remained in deep regions (‘deep’, right panel) of the myotome. White dashed lines outline somite cross-section, white plain lines outline multinucleated fibres, arrows indicate nuclei within a fibre and blue line indicates the position of the cross sections. nt; neural tube, nc; notochord. Replicate numbers are given in Supplementary Table 2. Bars = 50 μm.