Better explicating the strengths and shortcomings of these models will help refine projections and improve transparency in the years ahead.
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Contributed by Eric N. Olson, October 6, 2020 (sent for review September 1, 2020; reviewed by Daniel J. Garry and Thomas A. Rando)
Significance
Skeletal muscle is composed of multinucleated myofibers that are essential for movement and metabolism. Duchenne muscular dystrophy (DMD) is a devastating disease that is caused by the lack of the dystrophin protein, which maintains the integrity of muscle membranes. The absence of dystrophin results in myofiber degeneration followed by regeneration until muscle stem cells are depleted. We generated a new DMD mouse model lacking exon 51 and then used single-nucleus RNA sequencing to reveal the transcriptional diversity of individual myofiber nuclei in dystrophic muscle compared to normal muscle. Our findings uncover disease-associated pathways responsible for muscle degeneration and regeneration that might ultimately be manipulated therapeutically and reveal an unrecognized regenerative myonuclear population associated with dystrophic muscle.
Abstract
Duchenne muscular dystrophy (DMD) is a fatal muscle disorder characterized by cycles of degeneration and regeneration of multinucleated myofibers and pathological activation of a variety of other muscle-associated cell types. The extent to which different nuclei within the shared cytoplasm of a myofiber may display transcriptional diversity and whether individual nuclei within a multinucleated myofiber might respond differentially to DMD pathogenesis is unknown. Similarly, the potential transcriptional diversity among nonmuscle cell types within dystrophic muscle has not been explored. Here, we describe the creation of a mouse model of DMD caused by deletion of exon 51 of the dystrophin gene, which represents a prevalent disease-causing mutation in humans. To understand the transcriptional abnormalities and heterogeneity associated with myofiber nuclei, as well as other mononucleated cell types that contribute to the muscle pathology associated with DMD, we performed single-nucleus transcriptomics of skeletal muscle of mice with dystrophin exon 51 deletion. Our results reveal distinctive and previously unrecognized myonuclear subtypes within dystrophic myofibers and uncover degenerative and regenerative transcriptional pathways underlying DMD pathogenesis. Our findings provide insights into the molecular underpinnings of DMD, controlled by the transcriptional activity of different types of muscle and nonmuscle nuclei.
Footnotes
↵1F.C. and Z.W. contributed equally to this work.
- ↵2To whom correspondence may be addressed. Email: Eric.Olson{at}utsouthwestern.edu.
Author contributions: F.C., Z.W., N.L., R.B.-D., and E.N.O. designed research; F.C., Z.W., H.L., and J.R.M. performed research; F.C. and Z.W. analyzed data; and F.C., Z.W., N.L., R.B.-D., and E.N.O. wrote the paper.
Reviewers: D.J.G., University of Minnesota; and T.A.R., Stanford University School of Medicine.
The authors declare no competing interest.
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This article contains supporting information online at https://www.pnas.org/lookup/suppl/doi:10.1073/pnas.2018391117/-/DCSupplemental.
Statistics and Data Availability.
Statistical analyses were performed using GraphPad Prism 8 using a two-tailed unpaired t test, with P value < 0.05 considered significant. All data are displayed as mean ± SEM unless otherwise indicated. All sequencing data have been deposited in the Gene Expression Omnibus (https://www.ncbi.nlm.nih.gov/geo/) under accession number GSE156498.
Published under the PNAS license.
References
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Degenerative and regenerative pathways underlying Duchenne muscular dystrophy revealed by single-nucleus RNA sequencing
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- Cell Biology
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