Rethinking Muscle: New study challenges old classifications
Our current approach to dividing muscle fibers into separate types may need to be revised following new research by an international team of scientists, including CBMR’s Deshmukh Group.
Skeletal muscle fibers are normally divided into three different types, one “slow" (type 1) and two "fast" (type 2A and type 2X) fiber types. By carrying out advanced proteomic and transcriptomic analyses on over a thousand single muscle fibers, the scientists discovered that type 2X fibers, are not significantly different from other fast fibers when evaluating the entire proteome and transcriptome. The research was published in Nature Portfolio Communications.
This study also revealed shows that the muscle fibers in people with nemaline myopathy – a genetic muscular disorder characterized by muscle weakness – become faster and less reliant on oxygen regardless of their usual "fast" or "slow" type, revealing that the disease causes more complex changes than previously thought.
"Our data suggest that muscle fibers exist on a continuum rather than in discrete categories. Features such as metabolism, contractile proteins, cell-cell adhesion, and ribosomal proteins determine their position within this spectrum. This perspective is especially crucial in understanding diseases like nemaline myopathy, where the entire fiber type spectrum shifts independently of traditional markers," said PhD Student Roger Moreno Justicia, who co-led the study with Postdoc Thibaux Van der Stede and Assistant Professor Ben Stocks commented.
Associate Professor Atul Deshmukh added: "This study highlights the complexity of human skeletal muscle fibers and underscores the importance of considering fiber type heterogeneity in both health and disease. A study like this would have been impossible to conduct five years ago, but thanks to tremendous advances in proteomics technology, we can now extract new information beyond the reach of conventional molecular biology techniques. Future research and experimental designs involving skeletal muscle should take into account the sources of heterogeneity identified in this study."
The scientists involved in the study included the teams of Professor Wim Derave from Ghent University, Associate Professor Morten Hostrup from the Department of Nutrition, Exercise and Sports by The University of Copenhagen, Associate Professor Julien Ochala from the Department of Biomedical Sciences, University of Copenhagen and the Proteomics Research Infrastructure (PRI).
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