GDAP1 orchestrates redox signaling at membrane contact sites to preserve axonal integrity in Charcot-Marie-Tooth disease.

Pathogenic variants in GDAP1 cause Charcot-Marie-Tooth disease (CMT), an inherited peripheral neuropathy characterized by progressive axonal degeneration. Although GDAP1 is an atypical glutathione S-transferase localized to the outer mitochondrial membrane, it has been proposed to function as a redox sensor that likely maintains inter-organelle communication in neurons. However, the mechanisms by which GDAP1 performs these functions remain unclear. To address this question, we here used a robust multi-tier approach that combines high-resolution and live-cell imaging with pH-sensitive probes, membrane contact sites (MCSs) analysis, lipid studies, transcriptomics, and nerve ultrastructural studies in both patient-derived fibroblasts and Gdap1-/- mice. We find that deletion of the GDAP1 gene induces localized pH and redox imbalances at mitochondria-lysosomes contact sites, which propagate to defective mitochondria-peroxisome interactions, impaired peroxisome biogenesis and morphology, leading to altered lipid homeostasis. These defects are accompanied by axonal organelle mislocalization, disruption of nodes of Ranvier, and structural abnormalities in peripheral nerves. Investigations on the potential reversibility of these processes, reveal that restoration of redox balance rescues MCS organization, identifying a therapeutically tractable MCS-peroxisome axis downstream of GDAP1. Together, our findings position GDAP1 as a redox-sensing organizer of mitochondrial membrane contact sites whose dysfunction triggers a cascade of organelle and axonal defects underlying CMT pathogenesis. Thus, this new knowledge should be taken into consideration in the future design of therapeutic interventions that can ameliorate the symptoms of this dismal disease.