C9orf72-ALS mutation drives mitophagy impairments in iNeurons

Introduction: ALS 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. Results: iNeurons 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. Conclusions: Our 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.