Enhanced insulin signalling ameliorates C9orf72 hexanucleotide repeat expansion toxicity in Drosophila

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.

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C9-ALS/FTD-linked proline–arginine dipeptide repeat protein associates with paraspeckle components and increases paraspeckle formation

Cell Death and Disease ◽

10.1038/s41419-019-1983-5 ◽

2019 ◽

Vol 10 (10) ◽

Cited By ~ 4

Author(s):

Hiroaki Suzuki ◽

Yoshio Shibagaki ◽

Seisuke Hattori ◽

Masaaki Matsuoka

Keyword(s):

Dna Binding Protein ◽

Repeat Expansion ◽

Hexanucleotide Repeat ◽

Repeat Proteins ◽

Non Coding Rna ◽

Heterogeneous Nuclear Ribonucleoproteins ◽

Hexanucleotide Repeat Expansion ◽

Lateral Sclerosis ◽

Dipeptide Repeat

Abstract A GGGGCC hexanucleotide repeat expansion in the C9ORF72 gene has been identified as the most common genetic cause of amyotrophic lateral sclerosis and frontotemporal dementia. The repeat expansion undergoes unconventional translation to produce five dipeptide repeat proteins (DPRs). Although DPRs are thought to be neurotoxic, the molecular mechanism underlying the DPR-caused neurotoxicity has not been fully elucidated. The current study shows that poly-proline-arginine (poly-PR), the most toxic DPR in vitro, binds to and up-regulates nuclear paraspeckle assembly transcript 1 (NEAT1) that plays an essential role as a scaffold non-coding RNA during the paraspeckle formation. The CRISPR-assisted up-regulation of endogenous NEAT1 causes neurotoxicity. We also show that the poly-PR modulates the function of several paraspeckle-localizing heterogeneous nuclear ribonucleoproteins. Furthermore, dysregulated expression of TAR DNA-binding protein 43 (TDP-43) up-regulates NEAT1 expression and induces neurotoxicity. These results suggest that the increase in the paraspeckle formation may be involved in the poly-PR- and TDP-43-mediated neurotoxicity.

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Effect of G4C2-Repeat Expansions on the Motion of Lysosomes Inside Neurites.

10.1101/2021.10.29.466472 ◽

2021 ◽

Author(s):

Maria Mytiliniou ◽

Joeri A.J. Wondergem ◽

Marleen Feliksik ◽

Thomas Schmidt ◽

Doris Heinrich

Keyword(s):

Neuronal Cell ◽

Repeat Expansion ◽

Time Resolved ◽

Lower Velocity ◽

Hexanucleotide Repeat ◽

Repeat Expansions ◽

Local Mean ◽

Hexanucleotide Repeat Expansion ◽

Axonal Trafficking ◽

Lateral Sclerosis

The G4C2 hexanucleotide repeat expansion in the c9orf72 locus is one among a plethora of mutations associated with amyotrophic lateral sclerosis. It accounts for the majority of disease cases. The exact processes underlying the pathology of this mutation remain elusive, yet recent evidence suggests a mechanism that disrupts axonal trafficking. Here, we used a neuronal cell line with and without the G4C2 repeats, and implemented time-resolved local mean squared displacement analysis to characterize the motion of lysosomes inside neurites. Neurites were either aligned along chemically patterned lines, or oriented randomly on the substrate. We confirmed that in the presence of the G4C2 repeats, lysosome motion was affected. Lysosomes had a smaller reach exhibited lower velocity, especially inside aligned neurites. At the same time they became more active with increasing length of the G4C2 repeats when the neurites were randomly oriented. The duration of diffusive and super-diffusive lysosome transport remained unaffected for both neurite geometries and for all lengths of the repeats, but the displacement and velocity was decreased on varying the repeat number and neurite geometry. Lastly, the ratio of anterograde/retrograde/neutral trajectories was affected disparately for the two neurite geometries. Our observations support the hypothesis that impaired axonal trafficking emerges in the presence of the G4C2 hexanucleotide repeat expansion.

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Arginine-rich dipeptide-repeat proteins as phase disruptors in C9-ALS/FTD

Emerging Topics in Life Sciences ◽

10.1042/etls20190167 ◽

2020 ◽

Vol 4 (3) ◽

pp. 293-305

Author(s):

Hana M. Odeh ◽

James Shorter

Keyword(s):

Rna Binding ◽

Rna Binding Proteins ◽

Low Complexity ◽

Repeat Expansion ◽

Chromosome 9 ◽

Reading Frame ◽

Hexanucleotide Repeat ◽

Hexanucleotide Repeat Expansion ◽

Lateral Sclerosis ◽

Dipeptide Repeat

A hexanucleotide repeat expansion GGGGCC (G4C2) within chromosome 9 open reading frame 72 (C9orf72) is the most common genetic cause of amyotrophic lateral sclerosis and frontotemporal dementia (C9-ALS/FTD). This seminal realization has rapidly focused our attention to the non-canonical translation (RAN translation) of the repeat expansion, which yields dipeptide-repeat protein products (DPRs). The mechanisms by which DPRs might contribute to C9-ALS/FTD are widely studied. Arginine-rich DPRs (R-DPRs) are the most toxic of the five different DPRs produced in neurons, but how do R-DPRs promote C9-ALS/FTD pathogenesis? Proteomic analyses have uncovered potential pathways to explore. For example, the vast majority of the R-DPR interactome is comprised of disease-linked RNA-binding proteins (RBPs) with low-complexity domains (LCDs), strongly suggesting a link between R-DPRs and aberrations in liquid–liquid phase separation (LLPS). In this review, we showcase several potential mechanisms by which R-DPRs disrupt various phase-separated compartments to elicit deleterious neurodegeneration. We also discuss potential therapeutic strategies to counter R-DPR toxicity in C9-ALS/FTD.

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Circadian sleep/wake-associated cells show dipeptide repeat protein aggregates in C9orf72-related ALS and FTLD cases

Acta Neuropathologica Communications ◽

10.1186/s40478-019-0845-9 ◽

2019 ◽

Vol 7 (1) ◽

Cited By ~ 4

Author(s):

Lieselot Dedeene ◽

Evelien Van Schoor ◽

Rik Vandenberghe ◽

Philip Van Damme ◽

Koen Poesen ◽

...

Keyword(s):

Frontotemporal Lobar Degeneration ◽

Sleep Disturbances ◽

Motor Behavior ◽

Repeat Expansion ◽

Repeat Protein ◽

Hexanucleotide Repeat ◽

Gland Tissue ◽

Hexanucleotide Repeat Expansion ◽

Lateral Sclerosis ◽

Dipeptide Repeat

AbstractMotor-, behavior- and/or cognition-related symptoms are key hallmarks in patients with amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) with TDP-43 pathology (FTLD-TDP), respectively. It has been reported that these patients also experience sleep disturbances, which might implicate a disturbed circadian rhythm of the sleep/wake cycle. It remains unknown, however, whether cells involved in the circadian sleep/wake cycle are affected by ALS- and FTLD-related neuropathological changes including phosphorylated TDP-43 (pTDP-43) aggregates and dipeptide repeat protein (DPR) inclusions resulting from the C9orf72 hexanucleotide repeat expansion. Immunohistochemistry for DPR and pTDP-43 pathology was performed in post-mortem hypothalamus and pineal gland tissue of patients with ALS and/or FTLD-TDP with and without the C9orf72 repeat expansion and healthy controls. Circadian sleep/wake-associated cells, including pinealocytes and hypothalamic neurons related to the suprachiasmatic nucleus (SCN), were microscopically assessed. We observed numerous DPR inclusions (poly(GA), poly(GP), poly(GR) and poly(PR)) in the pinealocytes and few poly(GA) inclusions in the SCN-related neurons in C9orf72-related ALS and/or FTLD-TDP cases. These circadian sleep/wake-associated cells, however, were devoid of pTDP-43 pathology both in C9orf72- and nonC9orf72-related ALS and/or FTLD-TDP cases. Our neuropathological findings show that pinealocytes and, to a lesser extent, SCN-related neurons are affected by DPR pathology. This may reflect an involvement of these cells in sleep/wake disturbances observed in ALS and/or FTLD-TDP patients.

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