Antisense, but not sense, repeat expanded RNAs activate PKR/eIF2α-dependent ISR in C9ORF72 FTD/ALS
- Emory University, United States
- KU Leuven, Belgium
Abstract
GGGGCC (G4C2) hexanucleotide repeat expansion in the C9ORF72 gene is the most common genetic cause of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS). The repeat is bidirectionally transcribed and confers gain of toxicity. However, the underlying toxic species is debated, and it is not clear whether antisense CCCCGG (C4G2) repeat expanded RNAs contribute to disease pathogenesis. Our study shows that C9ORF72 antisense C4G2 repeat expanded RNAs trigger the activation of the PKR/eIF2α-dependent integrated stress response independent of dipeptide repeat proteins that are produced through repeat-associated non-AUG initiated translation, leading to global translation inhibition and stress granule formation. Reducing PKR levels with either siRNA or morpholinos mitigates integrated stress response and toxicity caused by the antisense C4G2 RNAs in cell lines, primary neurons, and zebrafish. Increased phosphorylation of PKR/eIF2α is also observed in the frontal cortex of C9ORF72 FTD/ALS patients. Finally, only antisense C4G2, but not sense G4C2, repeat expanded RNAs robustly activate the PKR/eIF2α pathway and induce aberrant stress granule formation. These results provide a mechanism by which antisense C4G2 repeat expanded RNAs elicit neuronal toxicity in FTD/ALS caused by C9ORF72 repeat expansions.
Data availability
All data generated or analysed during this study are included in the manuscript.
Article and author information
Author details
Janani Parameswaran
Funding
National Institute of Neurological Disorders and Stroke (R01NS114253)
- Anwesha Banerjee
- Gary J Bassell
National Institutes of Health (R01AG068247)
- Jie Jiang
ALS Association (21-PDF-585)
- Janani Parameswaran
Fonds Wetenschappelijk Onderzoek (G0C1620N)
- Ludo Van Den Bosch
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2023, Parameswaran et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Antisense, but not sense, repeat expanded RNAs activate PKR/eIF2α-dependent ISR in C9ORF72 FTD/ALS
eLife 12:e85902.
https://doi.org/10.7554/eLife.85902
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