Ewing’s sarcoma is a malignant bone tumour often found in children and young adults. It is commonly caused by a chromosomal translocation resulting in the fusion protein EWS-FLI1, which is unique to tumour cells and therefore a candidate for targeted therapy. Leacock et al. are the first to report EWS-FLI1 transgenic zebrafish lines, which they use to shed new light on the function of this oncogenic fusion protein. Adult zebrafish with mosaic EWS-FLI1 expression develop tumours similar to human Ewing’s sarcoma, but zebrafish embryos expressing EWS-FLI1 exhibit developmental defects suggesting that EWS-FLI1 acts in part by suppressing non-canonical Wnt signalling. Page 95

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