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Poly-GR impairs translation elongation and increases ribotoxic stress response in C9ORF72-ALS/FTD

ABSTRACT: Hexanucleotide repeat expansion in the C9ORF72 gene is the most frequent inherited cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Poly-GR is one of the most toxic dipeptide repeat (DPR) proteins translated from the RNA repeats. It has been shown to affect protein synthesis, but how this contributes to neurodegeneration is not clear. Here, we found that poly-GR inhibits global translation by perturbing translation elongation. We identified that the transcripts with relatively slow elongation rate tend to be further stalled by poly-GR in iPSC-differentiated neurons. This increases ribosome collision and ZAKα-mediated ribotoxic stress response (RSR), which elevates the phosphorylation of p38 and promotes cell death. Knockdown of ZAKα or pharmacological inhibition of p38 can ameliorate the GR toxicity, and improve the survival of C9ORF72-ALS/FTD patient-derived iPSC-neurons. Our study reveals molecular mechanism of poly-GR mediated toxicity on global translatome, and identifies RSR as a potential therapeutic target for C9ORF72-ALS/FTD.

ORGANISM(S): Homo sapiens

PROVIDER: GSE230127 | GEO | 2024/08/23

REPOSITORIES: GEO

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Enhanced insulin signalling ameliorates C9orf72 hexanucleotide repeat expansion toxicity in Drosophila

Project description:G4C2 repeat expansions within the C9orf72 gene are the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). The repeats undergo repeat-associated non-ATG translation to generate toxic dipeptide repeat proteins. Here, we show that insulin/Igf signalling is reduced in fly models of C9orf72 repeat expansion using RNA-sequencing of adult brain. We further demonstrate that activation of insulin/Igf signalling can mitigate multiple neurodegenerative phenotypes in flies expressing either expanded G4C2 repeats or the toxic dipeptide repeat protein poly-GR. Levels of poly-GR are reduced when components of the insulin/Igf signalling pathway are genetically activated in the diseased flies, suggesting a mechanism of rescue. Modulating insulin signalling in mammalian cells also lowers poly-GR levels. Remarkably, systemic injection of insulin improves the survival of flies expressing G4C2 repeats. Overall, our data suggest that modulation of insulin/Igf signalling could be an effective therapeutic approach against C9orf72 ALS/FTD.

2021-03-20 | GSE151826 | GEO

N6-methyladenosine regulates RNA metabolism and neurodegeneration in C9ORF72-ALS/FTD [seq_total_RNA-MeRIP]

Project description:N6-methyladenosine (m6A) is the most prevalent internal mRNA modification and regulates RNA metabolism. Repeat expansion in C9ORF72 is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal degeneration (FTD). Here, we showed that m6A is downregulated in C9ORF72-ALS/FTD patient-derived iPSC-differentiated neurons and postmortem brain tissues. The global m6A hypomethylation leads to transcriptome-wide mRNA stabilization and upregulated gene expression, especially ones involved in synaptic activity and neuronal functions. The m6A modification in the C9ORF72 intron sequence preceding the expanded repeats enhances RNA degradation via the nuclear reader YTHDC1. The m6A reduction leads to increased accumulation of repeat RNA and poly-dipeptides. Moreover, the antisense RNA can also be regulated by m6A. Elevating m6A level significantly reduces both sense and antisense repeat RNA and poly-dipeptides, rescues global mRNA homeostasis, and improves survival of C9ORF72-ALS/FTD patient neurons.

2023-06-09 | GSE203580 | GEO

N6-methyladenosine regulates RNA metabolism and neurodegeneration in C9ORF72-ALS/FTD [seq_polyA_RNA-decay]

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N6-methyladenosine regulates RNA metabolism and neurodegeneration in C9ORF72-ALS/FTD [seq_polyA_RNA-RIP]

2023-06-09 | GSE203578 | GEO

Disruption of nuclear speckle integrity dysregulates RNA splicing in C9ORF72-FTD/ALS

Project description:Dysregulation of RNA processing contributes to neurodegenerative diseases, especially amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Expansion of an intronic (GGGGCC)n repeat within the C9ORF72 gene is the most common cause of both FTD and ALS (C9-FTD/ALS), characterized with aberrant repeat RNA foci in the nucleus and noncanonical translation-produced dipeptide repeat (DPR) protein inclusions in the cytoplasm. Here we elucidate that the (GGGGCC)n repeat RNA co-localizes with nuclear speckles and alters their phase separation properties and granule dynamics. Moreover, the essential nuclear speckle scaffold protein SRRM2 is sequestered into the poly-GR cytoplasmic inclusions in C9-FTD/ALS mouse model and patient postmortem tissues, exacerbating the nuclear speckle dysfunction. Impaired nuclear speckle integrity induces global exon-skipping and intron retention in human iPSC-derived neurons. Similar alternative splicing changes can be found in patient postmortem tissues. This work identified novel molecular mechanism of global RNA splicing defects by impaired nuclear speckle function in C9-FTD/ALS and revealed novel potential biomarkers or therapeutic targets.

2024-08-23 | GSE248404 | GEO

PolyGR and polyPR knock-in mice reveal a conserved neuroprotective extracellular matrix signature in C9orf72 ALS/FTD neurons

Project description:A GGGGCC repeat expansion in C9orf72 is the most common genetic cause of ALS and FTD (C9ALS/FTD). Dipeptide repeat (DPR) proteins, generated by translation of the expanded repeat, are a major pathogenic feature of C9ALS/FTD pathology, but their physiological impact has yet to be fully determined. Here, we generated C9orf72 DPR knock-in mouse models characterised by expression of 400 codon-optimised polyGR or polyPR repeats, and heterozygous C9orf72 reduction. (GR)400 and (PR)400 knock-in mice recapitulate key features of C9ALS/FTD, including cortical neuronal hyperexcitability, age-dependent spinal motor neuron loss and progressive motor dysfunction. Quantitative proteomics revealed an increase in extracellular matrix (ECM) proteins in (GR)400 and (PR)400 spinal cord, with the collagen COL6A1 the most increased protein. This increase in ECM protein levels looked to be a conserved feature of C9ALS/FTD, with a similar signature also present in C9ALS patient iPSC-motor neurons. TGF-β1 was one of the top predicted regulators of this ECM signature and polyGR expression in human iPSC-neurons was sufficient to induce TGF-β1 followed by COL6A1. Knockdown of TGF-β1 or COL6A1 orthologues in polyGR model Drosophila exacerbated neurodegeneration, while expression of TGF-β1 or COL6A1 in C9ALS/FTD patient iPSC motor neurons protected against glutamate-induced cell death. Altogether, our C9orf72 DPR knock-in mice have revealed a neuroprotective and conserved ECM signature in C9ALS/FTD.

2024-03-04 | PXD047502 | Pride

Translation deficits drive C9orf72 associated poly-GR/PR toxicity

Project description:Frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) patients with the C9orf72 mutation show predominantly cytoplasmic aggregates of poly-GR and poly-PR proteins that are acutely toxic in various model systems. To identify the molecular mediators of neurotoxicity of poly-GR/PR, we analyzed their interactomes in primary neurons. GFP-(GR)149 and (PR)175-GFP preferentially interacted with RNA-binding proteins, including stress granule-associated and nucleolar proteins, as well as ribosomes. Overexpression of the poly-GR/PR interactors Staufen 1/2 (STAU1/2) and YBX1 led to cytoplasmic aggregation of poly-GR/PR into large stress granule-like inclusions, while the poly-GR/PR interactor nucleophosmin (NPM1) recruited poly-GR into the nucleolus. In addition, poly-PR expression reduced ribosome levels and translation, which is consistent with the widespread reduction of synaptic proteins detected by proteomics. Surprisingly, only GFP-(GR)53, but not GFP-(GR)149, localized to the nucleolus and reduced ribosome levels and translation in neurons, suggesting impaired ribosome biogenesis is driving the acute toxicity commonly observed in vitro. In C9orf72 patient brains, we detected co-aggregation of poly-GR/PR inclusions with ribosomes, but not stress granules. Partial sequestration of ribosomes may chronically impair protein synthesis and contribute to C9orf72 ALS/FTD pathogenesis.

2018-06-27 | PXD008691 | Pride

The C9ORF72 Repeat Epansion Impairs Neurodevelopment

Project description:RNA sequencing analysis of human iPSC-derived neural stem cells generated from Control, C9ORF72 FTD/ALS, an isogenic control, and a C9ORF72 knockout line. The goal of this study is to determine the effects of the C9ORF72 repeat expansion on neural stem cell proliferation and differentiation.

2023-08-12 | GSE238005 | GEO

Moderate intrinsic phenotypic alterations in C9orf72 ALS/FTD iPSC-microglia despite the presence of C9orf72 pathological features

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2023-05-23 | GSE233262 | GEO

Single cell RNA-sequencing of long-term human control and C9ORF72 ALS/FTD patient-specific iPSC-derived cortical organoid slice cultures

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2021-10-21 | GSE180122 | GEO

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