A novel chemical-combination screen in zebrafish identifies epigenetic small molecule candidates for the treatment of Duchenne muscular dystrophy

Gist H Farr,Melanie Morris,Shery Said,Lisa Maves,Elisabeth Kilroy,Elizabeth U Parker,Arianna Gomez,Clarissa Henry,Thao Pham

doi:10.1186/s13395-020-00251-4

Abstract

BackgroundDuchenne muscular dystrophy (DMD) is a severe neuromuscular disorder and is one of the most common muscular dystrophies. There are currently few effective therapies to treat the disease, although many small-molecule approaches are being pursued. Certain histone deacetylase inhibitors (HDACi) have been shown to ameliorate DMD phenotypes in mouse and zebrafish animal models. The HDACi givinostat has shown promise for DMD in clinical trials. However, beyond a small group of HDACi, other classes of epigenetic small molecules have not been broadly and systematically studied for their benefits for DMD.MethodsWe used an established animal model for DMD, the zebrafish dmd mutant strain sapje. A commercially available library of epigenetic small molecules was used to treat embryonic-larval stages of dmd mutant zebrafish. We used a quantitative muscle birefringence assay in order to assess and compare the effects of small-molecule treatments on dmd mutant zebrafish skeletal muscle structure.ResultsWe performed a novel chemical-combination screen of a library of epigenetic compounds using the zebrafish dmd model. We identified candidate pools of epigenetic compounds that improve skeletal muscle structure in dmd mutant zebrafish. We then identified a specific combination of two HDACi compounds, oxamflatin and salermide, that ameliorated dmd mutant zebrafish skeletal muscle degeneration. We validated the effects of oxamflatin and salermide on dmd mutant zebrafish in an independent laboratory. Furthermore, we showed that the combination of oxamflatin and salermide caused increased levels of histone H4 acetylation in zebrafish larvae.ConclusionsOur results provide novel, effective methods for performing a combination of small-molecule screen in zebrafish. Our results also add to the growing evidence that epigenetic small molecules may be promising candidates for treating DMD.

Highlights

Duchenne muscular dystrophy (DMD) is a severe neuromuscular disorder and is one of the most common muscular dystrophies
We identified a specific combination of two histone deacetylase inhibitors (HDACi) compounds, oxamflatin and salermide, that ameliorated dmd mutant zebrafish skeletal muscle degeneration
Epigenetic small-molecule library pooling approach In a previous study, we showed that the pan-HDACi Trichostatin A (TSA) could improve the zebrafish dmd muscle lesion phenotype [27]

Summary

Introduction

Duchenne muscular dystrophy (DMD) is a severe neuromuscular disorder and is one of the most common muscular dystrophies. Duchenne muscular dystrophy (DMD) is a severe neuromuscular disorder caused by mutations in the X-linked DMD gene, which encodes the protein dystrophin [1, 2]. DMD is the most common type of muscular dystrophy, affecting approximately 1 in 3500-5000 male births [14, 15]. It first presents as motor difficulties in early childhood and progresses rapidly, leaving most affected boys in need of a wheelchair in their early teens and in need of respiratory aid in their 20s [16]. The disease is usually fatal in the third or fourth decade due to respiratory or cardiovascular failure

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