DUX4 expression activates JNK and p38 MAP kinases in myoblasts.

Facioscapulohumoral muscular dystrophy (FSHD) is caused by misexpression of the DUX4 transcription factor in skeletal muscle that results in transcriptional alterations, abnormal phenotypes, and cell death. To gain insight into the kinetics of DUX4-induced stresses, we activated DUX4 expression in myoblasts and performed longitudinal RNA sequencing paired with proteomics and phosphoproteomics. This analysis revealed changes in cellular physiology including DNA damage and altered mRNA splicing. Phosphoproteomic analysis uncovered widespread changes in protein phosphorylation rapidly following DUX4 induction indicating that alterations in kinase signaling may play a role in DUX4-mediated stress and cell death. Indeed, we demonstrate that two stress-responsive MAP kinase pathways, JNK and p38, are activated in response to DUX4 expression. Inhibition of each of these pathways ameliorated DUX4-mediated cell death in myoblasts. These findings uncover JNK as a novel pathway involved in DUX4-mediated cell death as well as provide additional insights into the role of the p38 pathway, a clinical target for the treatment of FSHD.