DUX4 and rhabdomyosarcoma: To establish a screen for genes necessary for DUX4-induced apoptosis, we transduced the RD cell line with a lentiviral vector encoding a doxycycline-inducible DUX4 coding sequence and puromycin selectable marker (see S2A Fig for schematic) and generated a clonal rhabdomyosarcoma cell line (RD-DUX4i) with robust doxycycline-inducible expression of DUX4 that showed cellular toxicity at 24 hours after DUX4 induction (S2B Fig) and more than 95% cell death by 48 hours, as determined by the ATP-based CellTiter-Glo assay (S2C Fig).