Hit-and-run silencing of endogenous DUX4 by targeting DNA hypomethylation on D4Z4 repeats in facioscapulohumeral muscular dystrophy [RNA-seq]

Facioscapulohumeral muscular dystrophy (FSHD), a progressive skeletal muscle disorder, is epigenetically characterized with DNA hypomethylation of D4Z4 repeats in 4q35 region, allowing aberrant DUX4 expression. Sustainable DUX4 suppression is a promising therapeutic clue to prevent disease progression, but most of the supposed methods depend on expression of their mediator biochemical entity, potentially narrowing QoL of individuals with FSHD in the clinical context. In this study, we report that by applying hit-and-run silencing with dCas9-mediated epigenetic editing targeting DNA hypomethylation on D4Z4 repeats, we could achieve suppression of endogenous DUX4 in our FSHD patients-derived iPSC model. Notably, DNA methylation was significantly upregulated in FSHD cells and suppression effect was observed at least two weeks after intervention, which was not the case by transient treatment of typical dCas9-KRAB alone. Off-target analysis showed that despite the potential genome-wide risk in DNA methylation, the impact on transcriptome was limited. We propose that hit-and-run silencing can be a promising option to prevent disease progression with minimum intervention for individuals with FSHD, motivating further study for clinical development.