Fig. S4

Myog overexpression rescues fast myogenesis in myog mutants but does not promote fusion by slow fibres.

a. Quantitative analysis of fusion rescue in a myogkg128/+ incross injected at 1-cell stage with DNA encoding myog:MyogCDS-IRES-GFP (Myog O/E) or myog:GFP (Control) plasmids. Myog and GFP immunodetection and Hoechst stained nuclei (blue) at 2 dpf showed accumulation of Myog in Myog O/E GFP+ fibres but not in control GFP+ fibres in sibling embryos. b,c. Individual quantification of fraction of GFP+ fast fibres with the indicated number of nuclei in mutant (b) or sibling (c) embryos from same incross (mutant data also summarized as pie charts in Fig. 4i). Mosaic Myog expression rescues mutant phenotype but does not increase fusion frequency in sibs. Symbol shape represents individual embryos. Mean ± SEM, χ2 test. d. Schematic of analysis (e,f) of myog:MyogCDS-IRES-GFP (Myog O/E) or myog:GFP (Control) mosaic expression in slow fibres in a myogkg128/+ incross. e. Slow MyHC (sMyHC, F59), GFP and Myog immunodetection at 2 dpf in a sibling showing accumulation of Myog in a Myog O/E GFP+ slow fibre but not in a control GFP+ slow fibre. Myog O/E in slow fibres fails to induce fusion but leads to thin fibres with mis-positioned myofibrils (arrowhead). f. Quantification of fibre width in mutant (myogkg128) or sibling (sibs) embryos mosaically expressing myog:MyogCDS-IRES-GFP (Myog O/E, magenta) or myog:GFP (Control, green). Symbols represent fibre width of GFP+ (magenta or green symbols) or neighbouring GFP- (black symbols) slow fibres within individual embryos, compared by paired t-test statistic. Replicate numbers are given in Supplementary Table 2.