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bioRxiv · 10.1101/2025.11.25.690559

Mitochondrial Respiratory Chain Function is crucial for Muscle Toxicity in Facioscapulohumeral Muscular Dystrophy

Heher, P.·Pfeiffer-Vogl, J.·Ganassi, M.·Fulea, R.-C.·McGuire, L.·Engquist, E. N.·Tyszkiewicz, M.·Prueller, J.·Grillari, J.·Tasca, G.·Banerji, C. R.·Zammit, P. S.
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Abstract

Facioscapulohumeral muscular dystrophy (FSHD) is driven by DUX4-induced toxicity, yet the pathomechanisms remain unclear. Here, we identify persistent transcriptional suppression of the mitochondrial respiratory chain and metabolic rewiring in FSHD muscle biopsies and myotubes. Using DUX4-inducible human myogenic cells, we show that DUX4 target gene activation is accompanied by mitochondrial function impairment and Caspase 9-mediated apoptosis. Reverse electron transfer (RET) at complex I is the dominant oxidative stress generating mechanism in FSHD muscle cells. RET-driven mitochondrial reactive oxygen species (mitoROS) are the trigger for oxidative stress and apoptosis, which is a unique feature of FSHD mitochondria. Pharmacological inhibition of RET suppresses mitoROS, reduces Caspase 9 activation, and rescues abnormal myogenesis in FSHD cell lines. Importantly, DUX4 is non-toxic in oxidative phosphorylation-deficient human myogenic cells. Our findings identify the mitochondrial respiratory chain as a key mediator of DUX4 toxicity and highlight RET inhibition as a potential therapeutic approach for FSHD. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=136 SRC="FIGDIR/small/690559v1_ufig1.gif" ALT="Figure 1"> View larger version (48K): org.highwire.dtl.DTLVardef@254927org.highwire.dtl.DTLVardef@1e5c67forg.highwire.dtl.DTLVardef@4ace42org.highwire.dtl.DTLVardef@12b710e_HPS_FORMAT_FIGEXP M_FIG (Created with BioRender.com) C_FIG

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Heher, P., Pfeiffer-Vogl, J., Ganassi, M., Fulea, R.-C., McGuire, L., Engquist, E. N., Tyszkiewicz, M., Prueller, J., Grillari, J., Tasca, G., Banerji, C. R., Zammit, P. S.. 2025-11-26. Mitochondrial Respiratory Chain Function is crucial for Muscle Toxicity in Facioscapulohumeral Muscular Dystrophy. https://doi.org/10.1101/2025.11.25.690559

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