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

ABSTRACT: 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.

ORGANISM(S): Homo sapiens

PROVIDER: GSE203580 | GEO | 2023/06/09

REPOSITORIES: GEO

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

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 | GSE203579 | GEO

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

2023-06-09 | GSE203578 | GEO

Dual-targeting CRISPR-CasRx reduces C9orf72 ALS/FTD sense and antisense repeat RNAs in vitro and in vivo

Project description:The most common genetic cause of both frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) is a G4C2 repeat expansion in intron 1 of the C9orf72 gene. This repeat expansion undergoes bidirectional transcription to produce sense and antisense repeat RNA species. Both sense and antisense-derived repeat RNAs undergo repeat-associated non-AUG translation in all reading frames to generate five distinct dipeptide repeat proteins (DPRs). Importantly, toxicity has been associated with both sense and antisense repeat-derived RNA and DPRs. This suggests targeting both sense and antisense repeat RNA may provide the most effective therapeutic strategy. The RNA-targeting CRISPR-Cas13 systems offer a promising avenue for simultaneous targeting of multiple RNA transcripts, as they mature their own guide arrays, thus allowing targeting of more than one RNA species from a single construct. We show that CRISPR-Cas13d originating from Ruminococcus flavefaciens (CasRx) can successfully reduce C9orf72 sense and antisense repeat transcripts and DPRs to background levels in HEK cells overexpressing C9orf72 repeats. CRISPR-CasRx also markedly reduced the endogenous sense and antisense repeat RNAs and DPRs in three independent C9orf72 patient-derived iPSC-neuron lines, without detectable off-target effects. To determine whether CRISPR-CasRx is effective in vivo, we treated two distinct C9orf72 repeat mouse models using AAV delivery and observed a significant reduction in both sense and antisense repeat-containing transcripts. Taken together this work highlights the potential for RNA-targeting CRISPR systems as therapeutics for C9orf72 ALS/FTD.

2024-11-15 | GSE255022 | GEO

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

Project description: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.

2024-08-23 | GSE230127 | GEO

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

C9orf72 BAC Transgenic Mice Display Typical Pathologic Features of ALS/FTD

Project description:Noncoding expansions of a hexanucleotide repeat (GGGGCC) in the C9orf72 gene are the most common cause of familial amyotrophic lateral sclerosis and frontotemporal dementia. Here we report transgenic mice carrying a bacterial artificial chromosome (BAC) containing the full human C9orf72 gene with either a normal allele (15 repeats) or disease-associated expansion (~100â??1,000 repeats; C9-BACexp). C9-BACexp mice displayed pathologic features seen in C9orf72 expansion patients, including widespread RNA foci and repeat-associated non-ATG (RAN) translated dipeptides, which were suppressed by antisense oligonucleotides targeting human C9orf72. Nucleolin distribution was altered, supporting that either C9orf72 transcripts or RAN dipeptides promote nucleolar dysfunction. Despite early and widespread production of RNA foci and RAN dipeptides in C9-BACexp mice, behavioral abnormalities and neurodegeneration were not observed even at advanced ages, supporting the hypothesis that RNA foci and RAN dipeptides occur presymptomatically and are not sufficient to drive neurodegeneration in mice at levels seen in patients. To compare the RNA Seq profiles from the cortex and spinal cord of transgenic mice expressing unexpanded human C9orf72 (F08, n=4), expanded human C9orf72 (F112, n=3/4), and nontransgenic controls (n=4).

2016-02-10 | E-GEOD-77720 | biostudies-arrayexpress

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.

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C9orf72 BAC Transgenic Mice Display Typical Pathologic Features of ALS/FTD

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2016-02-10 | GSE77720 | GEO

The C9ORF72 Repeat Epansion Impairs Neurodevelopment

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2023-08-12 | GSE238005 | GEO

C9orf72 deficiency promotes microglial mediated synaptic loss in aging and amyloid accumulation [bulk RNA-seq]

Project description:C9orf72 repeat expansions cause inherited amyotrophic lateral sclerosis/frontotemporal dementia (ALS/FTD) and result in both loss of C9orf72 protein expression and production of potentially toxic RNA and dipeptide repeat proteins. In addition to ALS/FTD, C9orf72 repeat expansions have been reported in a broad array of neurodegenerative syndromes including Alzheimer’s disease. Here we show that C9orf72 deficiency promotes loss of homeostatic signatures in microglia and transition to an inflammatory state characterized by an enhanced type I IFN signature. Furthermore, C9orf72-depleted microglia trigger age-dependent neuronal defects, in particular enhanced cortical synaptic pruning, leading to altered learning and memory behaviors in mice. Interestingly, C9orf72 deficient microglia also promote enhanced synapse loss and neuronal deficits in a mouse model of amyloid accumulation, while paradoxically improving plaque clearance. These findings suggest that altered microglial function due to decreased C9orf72 expression directly contributes to neurodegeneration in repeat expansion carriers independent of gain of function toxicities.

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