Deletion of miR-146a enhances therapeutic protein restoration in model of dystrophin exon skipping

Duchenne muscular dystrophy (DMD) is a progressive muscle disease caused by the absence of dystrophin protein. One current DMD therapeutic strategy, exon skipping, produces a truncated dystrophin isoform using phosphorodiamidate morpholino oligomers (PMOs). However, the potential of exon skipping th...

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Bibliographic Details
Published in:	Molecular therapy. Nucleic acids Vol. 35; no. 3; p. 102228
Main Authors:	McCormack, Nikki M., Calabrese, Kelsey A., Sun, Christina M., Tully, Christopher B., Heier, Christopher R., Fiorillo, Alyson A.
Format:	Journal Article
Language:	English
Published:	United States Elsevier Inc 10-09-2024 American Society of Gene & Cell Therapy
Subjects:	antisense oligonucleotides Becker muscular dystrophy Duchenne muscular dystrophy dystrophin exon skipping microRNA miR-146a-5p MT: Non-coding RNAs Original RNA therapeutics miR-146a-5p Becker muscular dystrophy exon skipping Duchenne muscular dystrophy antisense oligonucleotides microRNA RNA therapeutics dystrophin MT: Non-coding RNAs
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Summary:	Duchenne muscular dystrophy (DMD) is a progressive muscle disease caused by the absence of dystrophin protein. One current DMD therapeutic strategy, exon skipping, produces a truncated dystrophin isoform using phosphorodiamidate morpholino oligomers (PMOs). However, the potential of exon skipping therapeutics has not been fully realized as increases in dystrophin protein have been minimal in clinical trials. Here, we investigate how miR-146a-5p, which is highly elevated in dystrophic muscle, impacts dystrophin protein levels. We find inflammation strongly induces miR-146a in dystrophic, but not wild-type myotubes. Bioinformatics analysis reveals that the dystrophin 3′ UTR harbors a miR-146a binding site, and subsequent luciferase assays demonstrate miR-146a binding inhibits dystrophin translation. In dystrophin-null mdx52 mice, co-injection of miR-146a reduces dystrophin restoration by an exon 51 skipping PMO. To directly investigate how miR-146a impacts therapeutic dystrophin rescue, we generated mdx52 with body-wide miR-146a deletion (146aX). Administration of an exon skipping PMO via intramuscular or intravenous injection markedly increases dystrophin protein levels in 146aX vs. mdx52 muscles while skipped dystrophin transcript levels are unchanged supporting a post-transcriptional mechanism of action. Together, these data show that miR-146a expression opposes therapeutic dystrophin restoration, suggesting miR-146a inhibition warrants further research as a potential DMD exon skipping co-therapy. [Display omitted] Fiorillo and colleagues found elevated miR-146a-5p in DMD and BMD muscles. They show miR-146a-5p is induced by inflammation and inhibits dystrophin translation. Using mdx52 mice with genetic deletion of miR-146a, the authors demonstrate proof of principal for miR-146a as a target to improve dystrophin restoration via exon skipping.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 Present address: Center for Inherited Muscle Research, Virginia Commonwealth University, Richmond, VA, USA
ISSN:	2162-2531 2162-2531
DOI:	10.1016/j.omtn.2024.102228