Fig. 5

Cdkn1c rescue of slow myogenesis is Myod-dependent. Slow MyHC (A,B confocal sections) or pan MyHC (C, dorsal flatmount) in embryos lacking Hh signalling. (A). Cdkn1c MO injection reduces residual slow muscle fibres in 24 hpf smo^b641 mutants. (B). Mosaic over-expression of zebrafish cdkn1c induced by heat-shock of hs70/4:cdkn1cIRESeGFP at 12 ss rescues slow MyHC at 18 ss. Inset shows co-expression of myc-Cdkn1c and eGFP. eGFP mosaicism was ≤ 5%, which corresponds to ~ 36 somitic adaxial cells at 18 ss. Bar: 10 μm; inset 50 μm. (C). Mosaic Xenopus cdkn1 expression rescues adaxial muscle in smo^b641 mutant or cyA-treated embryos at 10–12 ss. Cdkn1-driven rescue is prevented by myod knockdown. Charts show rescue of slow fibres (left, mean ± sem; Wilcoxon significance test) and fraction of embryos showing rescue (right; n = total embryos). Note that mosaic expression in ~ 10% of adaxial cells would mark ~ 33 somitic slow fibres per embryo at this stage. Bar: 50 μm.