Abstract: Skeletal myogenesis is dynamic, involving cell shape changes in concert with cell fusion and rearrangements. Yet, the final muscle arrangement is highly robust with stereotypic pattern of striated fibres. Here, we combined spatiotemporal live imaging with quantitative analyses to dissect in toto fast-twitch myocyte fusion in zebrafish embryos. We found a strong mediolateral bias in fusion timing within each somite. However, at a cellular scale there was significant heterogeneity in cell shape at fusion and the relationship between initial position within the somite and fusion partner. We observed a close coordination between slow muscle rearrangements and fast myocyte fusion. In mutants lacking slow fibres, fusion is substantially noisier, with reduced spatiotemporal coordination. We propose a model where slow muscles “guide” fast myocytes by funnelling them closer together and thus enhancing fusion rate. Finally, we show that expression of myomaker , which encodes a key fusogen, is permissive but not instructive in determining where and when fusion will occur. Our study establishes that cell fusion and robust myotome formation depends on coordination between cell-specific factors and interactions between different cell populations.

Biography: Though originally trained as a theoretical physicist, Dr Timothy Saunders, Associate Professor, now runs a developmental biology laboratory that focuses on deciphering the mechanisms by which organ shape emerges during embryogenesis. His lab uses quantitative live imaging of Drosophila and zebrafish combined with theoretical modelling to unravel how biochemical and mechanical inputs drive organ morphogenesis.

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