A Drosophila Study Model for EWS::FLI1-Induced Molecular Pathways.

Ewing sarcoma (EwS) is an aggressive, human-exclusive tumor typically driven by the EWS::FLI1 fusion protein. The paucity of genetically modified animal models hinders in vivo functional studies of this oncogene. Here, we describe the generation of transgenic Drosophila lines expressing different levels of human EWS::FLI1 and fluorescent reporters of conversion of quiescent GGAA-repeat microsatellites (GGAAμSats) into neoenhancers. We also describe experimental setups to test EWS::FLI1 activity, and to carry out genetic and chemical screens. Altogether, the collection of transgenic Drosophila lines described here permits quantifiable, spatial, and temporal control of EWS::FLI1 expression in vivo, thus offering new experimental tools to investigate the molecular pathways affected by varying levels of EWS::FLI1 in different cell lineages within a living organism. This platform is a versatile resource for hypothesis-driven research, as well as high-content genetic and chemical screening that may facilitate the identification of potential therapeutic targets and lead compounds.