A genome-wide CRISPR/Cas phenotypic screen formodulators of DUX4 cytotoxicity reveals screen complications

Abstract

Facioscapulohumeral muscular dystrophy (FHSD), a fundamentally complex muscle disorder that thus far remains untreatable. As the name implies, FSHD starts in the muscles of the face and shoulder gridle. The main perturbator of the disease is the pioneer transcription factor DUX4, which is misexpressed in affected tissues due to a failure in epigenetic repressive mechanisms. In pursuit of unraveling the underlying mechanism of FSHD and finding potential therapeutic targets or treatment options, we performed an exhaustive genome-wide CRISPR/Cas9 phenotypic rescue screen to identify modulators of DUX4 cytotoxicity. We found no key effectors other than DUX4 itself, suggesting treatment efforts in FSHD should be directed towards its direct modulation. The screen did however reveal some rare and unexpected Cas9-induced genomic events, that may provide important considerations for planning future CRISPR/Cas9 knock-out screens.