Research Article 481 Induced early expression of mrf4 but not myog rescues myogenesis in the myod/myf5 double- morphant zebrafish embryo Esther Schnapp1,*, Anna Silvia Pistocchi2,*, Evangelia Karampetsou2, Efrem Foglia2, Carla Lora Lamia2, Franco Cotelli2,‡ and Giulio Cossu1,2,‡ 1Stem Cell Research Institute, DiBiT, San Raffaele Scientific Institute, 58 via Olgettina, 20132 Milan, Italy 2Department of Biology, University of Milan, 26 via Celoria, 20133 Milan, Italy *These authors contributed equally to this work ‡Authors for correspondence (e-mails:
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[email protected]) Accepted 13 October 2008 Journal of Cell Science 122, 481-488 Published by The Company of Biologists 2009 doi:10.1242/jcs.038356 Summary Muscle regulatory factors activate myogenesis in all vertebrates, inhibition, we were able to investigate how myogenesis occurs in but their role has been studied in great detail only in the mouse the absence of a myotome. We report that in the complete absence embryo, where all but myogenin – Myod, Myf5 and Mrf4 – are of a myotome, subsequent myogenesis is abolished, whereas sufficient to activate (albeit not completely) skeletal myogenesis. myogenesis does proceed, albeit abnormally, when the In the zebrafish embryo, myod and myf5 are required for morpholino inhibition was not complete. Therefore our data also induction of myogenesis because their simultaneous ablation show that the early myotome is essential for subsequent skeletal prevents muscle development. Here we show that mrf4 but not muscle differentiation and patterning in the zebrafish. myog can fully rescue myogenesis in the myod/myf5 double morphant via a selective and robust activation of myod, in keeping Supplementary material available online at with its chromatin-remodelling function in vitro.