Development of the primary assay. (A) Cell death of iC2C12-DUX4 cells 36 h after addition of 500 ng/mL doxycycline. (B) Optimization of cell number and dox concentration. The clearest difference between viability of control and DUX4-induced cells was seen at 1,000 cells per well with 500 ng/mL dox. n = 6. Error bars represent SEM.