Bui, T. M. | bioRxiv Science

bioRxiv2025

Targeting lysosomal damage is a new therapeutic perspective for Duchenne Muscular Dystrophy

Duchenne Muscular Dystrophy (DMD), a muscle degenerative disease affecting young boys, arises from the loss of dystrophin. Current gene therapy approaches aim to restore a shortened form of dystrophin (microdystrophin) via Adeno-Associated Vector (AAV) delivery, but clinical studies show limited efficacy, emphasizing the need for improved strategies such as combined therapies. In this study, we identified lysosomal perturbations in the myofibers of DMD patients and animal models, an overlooked mechanism of cellular damage in muscular dystrophies. These were notably marked by the upregulation and recruitment of Galectin-3, a known biomarker of lysosomal membrane permeabilization, to damaged lysosomes, alongside alterations in lysosome number, morphology, and activation of endolysosomal damage response. Importantly, microdystrophin therapy in Dmdmdx mice fails to fully correct these damages. However, combining it with trehalose, a lysosome-protective disaccharide, significantly improves outcome, enhancing muscle function, histology and transcriptome. These findings highlight lysosomal damage as a novel mechanism in DMD pathogenesis and suggest that combining trehalose with gene therapy could enhance therapeutic efficacy. TeaserLysosomal damage contributes to DMD pathology and is an interesting therapeutic target worth considering for current and future approaches.

physiology↗

bioRxiv2020

SH3KBP1 scaffolds endoplasmic reticulum and controls skeletal myofibers architecture and integrity

The building block of skeletal muscle is the multinucleated muscle fiber, formed by the fusion of hundreds of mononucleated precursor cells, myoblasts. In the normal course of muscle fiber development or regeneration, myonuclei are actively positioned throughout muscular development and adopt special localization in mature fibers: regular spacing along muscle fibers periphery, raising the notion of MyoNuclear Domains (MNDs). There is now growing support for a direct connection between myonuclear positioning and normal function of muscles, but how myonuclei affects muscle function remains poorly characterized. To identify new factors regulating forces applied on myonuclei in muscles fibers, we performed a siRNA screen and identified SH3KBP1 as a new factor controlling myonuclear positioning in early phases of myofibers formation. Depletion of SH3KBP1 induces a reset of MNDs establishment in mature fibers reflected by a dramatic reduction in pairwise distance between myonuclei. We show that SH3KBP1 scaffolds Endoplasmic Reticulum (ER) in myotubes that in turn controls myonuclei velocity and localization and thus myonuclear domains settings. Additionally, we show that in later phases of muscle maturation, SH3KBP1 contributes to the formation and maintenance of Sarcoplasmic Reticulum (SR) and Transverse-tubules (T-tubules). We also demonstrate that in muscle fibers, GTPase dynamin-2 (DNM2) binds to SH3 domains of SH3KBP1. Interestingly, we observed that Sh3kbp1 mRNA is up regulated in a mouse model harboring the most frequent mutation for Autosomal Dominant CentroNuclear Myopathy (AD-CNM): Dnm2+/R465W. SH3KBP1 thus appears as a compensation mechanism in this CNM model since its depletion contributes to an increase of CNM-like phenotypes (reduction of muscle fibers Cross-section Areas (CSA) and increase in slow fibers content). Altogether our results identify SH3KBP1 as a new regulator of myonuclear domains establishment in the early phase of muscle fibers formation through ER scaffolding and later in myofibers integrity through T-tubules scaffolding/maintenance. SummaryMyonuclei are actively positioned throughout muscular development. Guiraud, Christin, Couturier et al show that SH3KBP1 scaffolds the ER through Calnexin interaction and controls myonuclei motion during early steps of muscle fibers formation. Besides SH3KBP1 participates in cell fusion and T-tubules formation/maintenance in mature skeletal muscle fibers and contributes to slow-down CNM-like phenotypes.

cell biology↗