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C9orf72-derived poly-GA DPRs undergo endocytic uptake in iNPC-derived astrocytes and spread to motor neurons

Marchi, P. M.; Marrone, L.; Brasseur, L.; Bousset, L.; Webster, C. P.; Destro, M.; Walther, C. G.; Alfred, V.; Marroccella, R.; Robinson, D.; Shaw, A. C.; Wan, L. M.; Grierson, A.; Ebbens, S. J.; Hautbergue, G. M.; Ferraiuolo, L.; Melki, R.; Azzouz, M.

2021-10-12 neuroscience
10.1101/2021.10.11.463891 bioRxiv
Show abstract

Dipeptide repeat proteins (DPRs) are aggregation-prone polypeptides encoded by the pathogenic G4C2 repeat expansion in the C9orf72 gene, the most common genetic cause of amyotrophic lateral sclerosis and frontotemporal dementia (ALS/FTD). In this study, we focus on the role of poly-GA DPRs in disease spread. We demonstrate that recombinant poly-GA oligomers can directly convert into solid-like aggregates and form characteristic &[beta]-sheet fibrils in vitro. To dissect the process of cell-to-cell DPR transmission, we closely follow the fate of poly-GA DPRs in either their oligomeric or fibrillized form after administration in the cell culture medium. We observe that poly-GA DPRs are taken up via dynamin-dependent and - independent endocytosis, eventually converging at the lysosomal compartment and leading to axonal swellings in neurons. We then use a co-culture system to demonstrate astrocyte-to- motor neuron DPR propagation, showing that astrocytes may internalise and release aberrant peptides in disease pathogenesis. Overall, our results shed light on the mechanisms of poly- GA cellular uptake and cell-to-cell propagation, suggesting lysosomal impairment as a possible feature underlying the cellular pathogenicity of these DPR species.

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