Single-nucleus transcriptomics reveals functional compartmentalization in syncytial skeletal muscle cells

AbstractSyncytial skeletal muscle cells contain hundreds of nuclei in a shared cytoplasm. We investigated nuclear heterogeneity and transcriptional dynamics in the uninjured and regenerating muscle using single-nucleus RNA-sequencing (snRNAseq) of isolated nuclei from muscle fibers. This revealed distinct nuclear subtypes unrelated to fiber type diversity, previously unknown subtypes as well as the expected ones at the neuromuscular and myotendinous junctions. In fibers of the Mdx dystrophy mouse model, distinct subtypes emerged, among them nuclei expressing a repair signature that were also abundant in the muscle of dystrophy patients, and a nuclear population associated with necrotic fibers. Finally, modifications of our approach revealed the compartmentalization in the rare and specialized muscle spindle. Our data identifies nuclear compartments of the myofiber and defines a molecular roadmap for their functional analyses; the data can be freely explored on the MyoExplorer server (https://shiny.mdc-berlin.de/MyoExplorer/).

Download Full-text

Single-nucleus transcriptomics reveals functional compartmentalization in syncytial skeletal muscle cells

10.1101/2020.04.14.041665 ◽

2020 ◽

Cited By ~ 3

Author(s):

Minchul Kim ◽

Vedran Franke ◽

Bettina Brandt ◽

Elijah D. Lowenstein ◽

Verena Schöwel ◽

...

Keyword(s):

Skeletal Muscle ◽

Mouse Model ◽

Fiber Type ◽

Muscle Cells ◽

Skeletal Muscle Cells ◽

Isolated Nuclei ◽

Nuclear Compartments ◽

Transcriptional Dynamics ◽

Single Nucleus ◽

Functional Analyses

AbstractSyncytial skeletal muscle cells contain hundreds of nuclei in a shared cytoplasm. We investigated nuclear heterogeneity and transcriptional dynamics in the uninjured and regenerating muscle using single-nucleus RNA-sequencing (snRNAseq) of isolated nuclei from muscle fibers. This revealed distinct nuclear subtypes unrelated to fiber type diversity, completely novel subtypes as well as the expected ones at the neuromuscular and myotendinous junctions. In fibers of the Mdx dystrophy mouse model, new subtypes emerged, among them nuclei expressing a repair signature that were also abundant in the muscle of dystrophy patients, and a nuclear population associated with necrotic fibers. Finally, modifications of our approach revealed the compartmentalization in the rare and specialized muscle spindle. Our data identifies new nuclear compartments of the myofiber and defines a molecular roadmap for their functional analyses; the data can be freely explored on the MyoExplorer server (https://shiny.mdc-berlin.net/MyoExplorer/).

Download Full-text

Fiber type conversion alters inactivation of voltage-dependent sodium currents in murine C2C12skeletal muscle cells

AJP Cell Physiology ◽

10.1152/ajpcell.00015.2004 ◽

2004 ◽

Vol 287 (2) ◽

pp. C270-C280 ◽

Cited By ~ 22

Author(s):

Eva Zebedin ◽

Walter Sandtner ◽

Stefan Galler ◽

Julia Szendroedi ◽

Herwig Just ◽

...

Keyword(s):

Skeletal Muscle ◽

Fiber Type ◽

Muscle Fibers ◽

Muscle Cells ◽

The Body ◽

Skeletal Muscle Cells ◽

Prolonged Treatment ◽

Type Conversion ◽

Electrophysiological Properties ◽

Slow Fiber

Each skeletal muscle of the body contains a unique composition of “fast” and “slow” muscle fibers, each of which is specialized for certain challenges. This composition is not static, and the muscle fibers are capable of adapting their molecular composition by altered gene expression (i.e., fiber type conversion). Whereas changes in the expression of contractile proteins and metabolic enzymes in the course of fiber type conversion are well described, little is known about possible adaptations in the electrophysiological properties of skeletal muscle cells. Such adaptations may involve changes in the expression and/or function of ion channels. In this study, we investigated the effects of fast-to-slow fiber type conversion on currents via voltage-gated Na+channels in the C2C12murine skeletal muscle cell line. Prolonged treatment of cells with 25 nM of the Ca2+ionophore A-23187 caused a significant shift in myosin heavy chain isoform expression from the fast toward the slow isoform, indicating fast-to-slow fiber type conversion. Moreover, Na+current inactivation was significantly altered. Slow inactivation less strongly inhibited the Na+currents of fast-to-slow fiber type-converted cells. Compared with control cells, the Na+currents of converted cells were more resistant to block by tetrodotoxin, suggesting enhanced relative expression of the cardiac Na+channel isoform Nav1.5 compared with the skeletal muscle isoform Nav1.4. These results imply that fast-to-slow fiber type conversion of skeletal muscle cells involves functional adaptation of their electrophysiological properties.

Download Full-text