DUX4 expression activates JNK and p38 MAP kinases in myoblasts

Facioscapulohumoral muscular dystrophy (FSHD) is a progressive muscle wasting disease caused by misexpression of the DUX4 transcription factor. DUX4 expression in skeletal muscle cells results in a dramatic alteration in their transcriptional profile and cellular phenotype and subsequently, 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 such as DNA damage and altered mRNA splicing before detectable changes in protein levels. Implementation of phosphoproteomics uncovered that widespread changes in protein phosphorylation preceded changes in protein levels indicating that alterations in kinase signaling may play a role in DUX4-mediated stress and cell death. Here we demonstrate that two stress-responsive MAP kinase pathways, JNK and p38, are activated in response to DUX4 expression. Pharmacological inhibition of either 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. Differential gene expression and splicing analysis of inducible DUX4 myoblasts treated with DMSO or at 2 hr, 6 hr, or 14 hr after doxycycline induction of DUX4 and WT myoblasts after 14 hr of doxycycline treatment or DMSO. N=4 culture wells per condition.