Pathogenic Mitofusin 2 variants causing myopathy drive endosomal mtDNA release and inflammation

Abstract

Pathogenic variants in Mitofusin 2 (MFN2) cause the peripheral neuropathy Charcot-Marie-Tooth Type IIA (CMT2A), with a subset of patients presenting with myopathy. Yet how MFN2 dysfunction causes these phenotypes remains mechanistically undefined. Here, we identify a conserved pathomechanism in MFN2-linked myopathy variants, where mitochondrial DNA is released into RAB5 early endosomes, robustly activating TLR9 and cGAS-STING inflammatory signaling. We further show that MFN2 dysfunction drives two mechanistically distinct pools of extra-mitochondrial mtDNA, one in endosomes and the other present mitochondrial-derived vesicles (MDVs). These two pools of released mtDNA can be distinguished based on their size, with endosomal mtDNA forming larger puncta than mtDNA present in MDVs. Finally, we show that pharmacological activation of the integrated stress response reduces both pools of extra-mitochondrial mtDNA. Together, our work defines a conserved cellular phenotype linking MFN2 dysfunction to myopathy and suggests a tractable therapeutic strategy for mtDNA release-associated pathologies.

Graphical Abstract

O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=113 SRC="FIGDIR/small/26363493v1_ufig1.gif" ALT="Figure 1"> View larger version (54K): [email protected]@45aa2corg.highwire.dtl.DTLVardef@1a734fforg.highwire.dtl.DTLVardef@886ad0_HPS_FORMAT_FIGEXP M_FIG C_FIG

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BibTeX RIS

BibTeX

@misc{zaman2026pathogenic,
  title = {{Pathogenic Mitofusin 2 variants causing myopathy drive endosomal mtDNA release and inflammation}},
  author = {M. Zaman and J. David and A. Mehrabi and C. Chute and J. Deng and T. Soule and L. Wiseman and C. N. Antonescu and P. Colarusso and G. Pfeffer and T. Shutt},
  howpublished = {medRxiv},
  year = {2026},
  month = sep,
  doi = {10.64898/2026.09.22.26363493},
  url = {https://www.medrxiv.org/content/10.64898/2026.09.22.26363493v1},
  note = {CC BY-NC-ND},
}

RIS

TY  - UNPB
TI  - Pathogenic Mitofusin 2 variants causing myopathy drive endosomal mtDNA release and inflammation
AU  - M. Zaman
AU  - J. David
AU  - A. Mehrabi
AU  - C. Chute
AU  - J. Deng
AU  - T. Soule
AU  - L. Wiseman
AU  - C. N. Antonescu
AU  - P. Colarusso
AU  - G. Pfeffer
AU  - T. Shutt
PY  - 2026
DA  - 2026/09/22
PB  - medRxiv
DO  - 10.64898/2026.09.22.26363493
UR  - https://www.medrxiv.org/content/10.64898/2026.09.22.26363493v1
AB  - Pathogenic variants in Mitofusin 2 (MFN2) cause the peripheral neuropathy Charcot-Marie-Tooth Type IIA (CMT2A), with a subset of patients presenting with myopathy. Yet how MFN2 dysfunction causes these phenotypes remains mechanistically undefined. Here, we identify a conserved pathomechanism in MFN2-linked myopathy variants, where mitochondrial DNA is released into RAB5 early endosomes, robustly activating TLR9 and cGAS-STING inflammatory signaling. We further show that MFN2 dysfunction drives two mechanistically distinct pools of extra-mitochondrial mtDNA, one in endosomes and the other present mitochondrial-derived vesicles (MDVs). These two pools of released mtDNA can be distinguished based on their size, with endosomal mtDNA forming larger puncta than mtDNA present in MDVs. Finally, we show that pharmacological activation of the integrated stress response reduces both pools of extra-mitochondrial mtDNA. Together, our work defines a conserved cellular phenotype linking MFN2 dysfunction to myopathy and suggests a tractable therapeutic strategy for mtDNA release-associated pathologies.  Graphical Abstract  O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=113 SRC="FIGDIR/small/26363493v1_ufig1.gif" ALT="Figure 1"> View larger version (54K): [email protected]@45aa2corg.highwire.dtl.DTLVardef@1a734fforg.highwire.dtl.DTLVardef@886ad0_HPS_FORMAT_FIGEXP M_FIG C_FIG
ER  -

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