Systemic delivery of a DUX4-targeting antisense oligonucleotide to treat facioscapulohumeral muscular dystrophy

Linde F Bouwman,Bianca Den Hamer,Anita Van Den Heuvel,Marnix Franken,Michaela Jackson,Chrissa A Dwyer,Stephen J Tapscott,Frank Rigo,Silvère M Van Der Maarel,Jessica C De Greef

doi:10.1016/j.omtn.2021.09.010

Abstract

Facioscapulohumeral muscular dystrophy (FSHD) is one of the most prevalent skeletal muscle dystrophies. Skeletal muscle pathology in individuals with FSHD is caused by inappropriate expression of the transcription factor DUX4, which activates different myotoxic pathways. At the moment there is no molecular therapy that can delay or prevent skeletal muscle wasting in FSHD. In this study, a systemically delivered antisense oligonucleotide (ASO) targeting the DUX4 transcript was tested in vivo in ACTA1-MCM;FLExDUX4 mice that express DUX4 in skeletal muscles. We show that the DUX4 ASO was well tolerated and repressed the DUX4 transcript, DUX4 protein, and mouse DUX4 target gene expression in skeletal muscles. In addition, the DUX4 ASO alleviated the severity of skeletal muscle pathology and partially prevented the dysregulation of inflammatory and extracellular matrix genes. DUX4 ASO-treated ACTA1-MCM;FLExDUX4 mice performed better on a treadmill; however, the hanging grid and four-limb grip strength tests were not improved compared to control ASO-treated ACTA1-MCM;FLExDUX4 mice. This study shows that systemic delivery of ASOs targeting DUX4 is a promising therapeutic strategy for FSHD and strategies that further improve the ASO efficacy in skeletal muscle are warranted.

Highlights

Facioscapulohumeral muscular dystrophy (FSHD) is a progressive skeletal muscle disorder mainly affecting the facial, scapular, and humeral muscles
To assess whether the double homeobox 4 (DUX4) antisense oligonucleotide (ASO) (DUX4aso) causes severe organ toxicity, wild-type mice were treated for 3 weeks with the DUX4aso or injected with phosphate-buffered saline (PBS) as a control (n = 4 per group)
As skeletal muscle pathology is caused by derepression of the transcription factor DUX4, inhibiting the DUX4 transcript could halt the activation of all downstream toxic cascades.[2]

Summary

Introduction

Facioscapulohumeral muscular dystrophy (FSHD) is a progressive skeletal muscle disorder mainly affecting the facial, scapular, and humeral muscles. Individuals with FSHD show clinical heterogeneity, and the disease severity, the age of onset, and which skeletal muscles are affected are highly variable between patients.[1] Skeletal muscle pathology is caused by epigenetic derepression of the transcription factor double homeobox 4 (DUX4).[2] DUX4 is expressed during the 4-cell stage in human embryos, where it activates the transcription of zygotic genome activation (ZGA) genes.[3,4] After early development, the DUX4 gene is epigenetically repressed in most tissues. An overlap between D4Z4 repeat unit sizes from 8–10 between FSHD and non-affected individuals suggests that more factors are involved in disease penetrance.[2,10] In $5% of patients (FSHD2), DUX4 derepression is caused by digenic inheritance of a relatively short permissive 4qA allele and mutations in one of the epigenetic D4Z4 repressors SMCHD1, DNMT3B, and LRIF1.11–13

Methods

Results

Conclusion