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.
Researchers from the University of Texas Southwestern Medical Center 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, the researchers performed single-nucleus transcriptomics of skeletal muscle of mice with dystrophin exon 51 deletion. Their results reveal distinctive and previously unrecognized myonuclear subtypes within dystrophic myofibers and uncover degenerative and regenerative transcriptional pathways underlying DMD pathogenesis. These findings provide insights into the molecular underpinnings of DMD, controlled by the transcriptional activity of different types of muscle and nonmuscle nuclei.
snRNA-seq of TA muscle from WT and ΔEx51 mice
(A) Schematic of the experimental design for snRNA-seq on skeletal muscle nuclei. (B) UMAP visualization of all of the nuclei (11,222 nuclei, Left) from WT and ΔEx51 TA muscle colored by cluster identity. UMAPs depicting nuclei of WT TA muscle (7,013 nuclei, Center) and nuclei of ΔEx51 TA muscle (4,209 nuclei, Right). Percentages of nuclei in each cluster are indicated in the table. (C) Violin plots showing the expression of selected marker genes for each cluster of nuclei. (D) Heat map showing z-score–transformed average expression of the marker genes for each cluster of nuclei (Left). Selected top enriched GO terms of the marker genes for each cluster of nuclei (Right).