The major genetic cause of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) is a C9orf72 G4C2 repeat expansion1,2. Proposed mechanisms by which the expansion causes c9FTD/ALS include toxicity from repeat-containing RNA and from dipeptide repeat proteins translated from these transcripts. To investigate the contribution of poly(GR) dipeptide repeat proteins to c9FTD/ALS pathogenesis in a mammalian in vivo model, we generated mice that expressed GFP–(GR)100 in the brain. GFP–(GR)100 mice developed age-dependent neurodegeneration, brain atrophy, and motor and memory deficits through the accumulation of diffuse, cytoplasmic poly(GR). Poly(GR) co-localized with ribosomal subunits and the translation initiation factor eIF3η in GFP–(GR)100 mice and, of importance, in c9FTD/ALS patients. Combined with the differential expression of ribosome-associated genes in GFP–(GR)100 mice, these findings demonstrate poly(GR)-mediated ribosomal distress. Indeed, poly(GR) inhibited canonical and non-canonical protein translation in HEK293T cells, and also induced the formation of stress granules and delayed their disassembly. These data suggest that poly(GR) contributes to c9FTD/ALS by impairing protein translation and stress granule dynamics, consequently causing chronic cellular stress and preventing cells from mounting an effective stress response. Decreasing poly(GR) and/or interrupting interactions between poly(GR) and ribosomal and stress granule-associated proteins may thus represent potential therapeutic strategies to restore homeostasis.
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We are grateful to all patients who agreed to donate post-mortem tissue. This work was supported by the National Institutes of Health/National Institute of Neurological Disorders and Stroke (R35NS097273 (L.P.); P01NS084974 (L.P., D.W.D., R.R. and B.O.); P01NS099114 (T.F.G. and L.P.); R01NS088689 (L.P.); R35NS097263(10) (A.D.G.)); the Mayo Clinic Foundation (L.P.); the Amyotrophic Lateral Sclerosis Association (T.F.G., L.P., Y.-J.Z. and M.P.), the Robert Packard Center for ALS Research at Johns Hopkins (A.D.G. and L.P.) and the Target ALS Foundation (T.F.G., A.D.G., L.P. and Y.-J.Z.). We would like to thank J. N. Stankowski, E. A. Perkerson, L. Rousseau and V. Phillips for technical support. This manuscript is dedicated to Dr Antimo D’Aniello.
The authors declare no competing interests.
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Zhang, YJ., Gendron, T.F., Ebbert, M.T.W. et al. Poly(GR) impairs protein translation and stress granule dynamics in C9orf72-associated frontotemporal dementia and amyotrophic lateral sclerosis. Nat Med 24, 1136–1142 (2018). https://doi.org/10.1038/s41591-018-0071-1
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