What this means
Researchers turned off three related genes in adult mouse muscles. The fast muscle fibers then changed into slower types and became less strong. This is a preprint, not yet checked by other scientists, so it does not show the same effect in people.
Plain-English summary written by an AI model from the abstract. The original is below.
- Who it was tested in
- Mice
- Kind of research
- Early results, not yet checked by other scientists
The science
- Original title
- Continuous Large Maf Activity Maintains Fast Myofiber Identity and Multicellular Homeostasis in Adult Skeletal Muscle
- Authors
- Sadaki, S., Tsuji, R., Matsumoto, T. et al.
- Journal
- bioRxiv (preprint, not yet peer reviewed)
- Published
- Oct 13, 2026
- Study type
- Preprint
Abstract
Fast myofibers are preferentially affected during aging, exhibiting atrophy and shifts toward slower myofiber programs, yet the mechanisms preserving established fast-fiber identity remain unclear. Here, we show that the large Maf transcription factors Mafa, Mafb, and Maf are continuously required to maintain type IIb myofiber identity in adult skeletal muscle. Inducible deletion of large Mafs caused near-complete loss of type IIb fibers, a transition toward type IIx/IIa states, reduced strength, and increased fatigue resistance. RNA-seq and ATAC-seq revealed transcriptional and chromatin accessibility remodeling across the fast myosin locus, characterized by persistent loss of Myh4 expression and increased accessibility around Myh1. Single-nucleus RNA-seq identified transient myonuclei co-expressing multiple myosin isoforms before emergence of a Myh1-dominant state, accompanied by remodeling of non-myonuclear cell populations. These changes shared features with aging- and denervation-associated muscle remodeling. Thus, continuous large Maf activity maintains adult fast myofiber identity and coordinates skeletal muscle tissue homeostasis.
Sadaki, S., Tsuji, R., Matsumoto, T. et al. Continuous Large Maf Activity Maintains Fast Myofiber Identity and Multicellular Homeostasis in Adult Skeletal Muscle. bioRxiv. 2026. doi:10.64898/2026.10.09.758120. https://doi.org/10.64898/2026.10.09.758120