Roome, K. | Search bioRxiv

bioRxiv2025

C9orf72-ALS mutation drives mitophagy impairments in iNeurons

IntroductionALS is a neurodegenerative disorder characterised by progressive upper and lower motor neuron loss. A GGGGCC hexanucleotide repeat expansion (HRE) in the C9orf72 gene is the most common mutation found in populations of European descent. Mitochondrial dysfunction has been observed in C9orf72-ALS patients and models of the disease, however reports on mitochondrial clearance via mitophagy in C9orf72-ALS are limited. ResultsiNeurons from C9orf72-ALS patients displayed reduced mitochondrial membrane potential and reduced mitophagy, due to reductions in autophagosome production and reduced ULK1 recruitment to mitochondria. No consistent changes to PINK1/Parkin or BNIP3 mitophagy pathways were observed. ConclusionsOur data show that mitochondrial function is impaired in C9orf72-ALS patient iNeurons. An in-depth characterisation of mitophagy suggests that a deficit in autophagosome production is responsible and provides further evidence that toxic gain-of-function mechanisms in C9orf72-ALS are responsible for autophagy deficits.

neuroscience↗

bioRxiv2023

Activation of the Keap1/Nrf2 pathway suppresses mitochondrial dysfunction in C9orf72 ALS/FTD in vivo models and patient iNeurons

Mitochondrial dysfunction such as excess production of reactive oxygen species (ROS) and defective mitochondrial dynamics are common features of C9orf72 Amyotrophic Lateral Sclerosis/Frontotemporal Dementia (ALS/FTD), but it remains unclear whether these are causative or a consequence of the pathogenic process. To address this, we have performed a comprehensive characterisation of mitochondrial dysfunction in vivo model, analysing multiple transgenic Drosophila models of C9orf72-related pathology, which can be correlated to disease-relevant locomotor deficits. Genetic manipulations to reverse different aspects of mitochondrial disruption revealed that only genetic upregulation of antioxidants such as mitochondrial Sod2 and catalase were able to rescue C9orf72 locomotor deficits, suggesting a causative link between mitochondrial dysfunction, ROS and behavioural phenotypes. By analysing the Keap1/Nuclear factor erythroid 2-related factor 2 (Nrf2) pathway, a central antioxidant response pathway, we observed a blunted response in the C9orf72 models. However, both genetic reduction of Keap1 and its pharmacological targeting by dimethyl fumarate (DMF), was able to rescue C9orf72-related motor deficits. In addition, analysis of C9orf72 patient-derived iNeurons showed increased ROS that was suppressed by DMF treatment. These results indicate that mitochondrial oxidative stress is an upstream pathogenic mechanism leading to downstream mitochondrial dysfunction such as alterations in mitochondrial function and turnover. Consequently, our data support targeting the Keap1/Nrf2 signalling pathway as a viable therapeutic strategy for C9orf72-related ALS/FTD.

neuroscience↗