Prevalence of brain and spinal cord inclusions, including dipeptide repeat proteins, in patients with the C9ORF72 hexanucleotide repeat expansion: a systematic neuropathological review

2016 ◽  
Vol 42 (6) ◽  
pp. 547-560 ◽  
Author(s):  
L. J. Schipper ◽  
J. Raaphorst ◽  
E. Aronica ◽  
F. Baas ◽  
R. de Haan ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Repeat Expansion ◽  
Dipeptide Repeat Proteins ◽  
Hexanucleotide Repeat ◽  
Repeat Proteins ◽  
Hexanucleotide Repeat Expansion ◽  
Brain And Spinal Cord ◽  
Dipeptide Repeat

scholarly journals C9orf72 arginine-rich dipeptide repeat proteins disrupt importin β-mediated nuclear import

2019 ◽  
Author(s):  
Lindsey R. Hayes ◽  
Lauren Duan ◽  
Kelly Bowen ◽  
Petr Kalab ◽  
Jeffrey D. Rothstein
Keyword(s):  
Nuclear Import ◽  
Genetic Modifier ◽  
Nucleocytoplasmic Transport ◽  
Nuclear Pore ◽  
Dipeptide Repeat Proteins ◽  
Hexanucleotide Repeat ◽  
Repeat Proteins ◽  
Hexanucleotide Repeat Expansion ◽  
Dipeptide Repeat

AbstractDisruption of nucleocytoplasmic transport (NCT), including mislocalization of the importin β cargo, TDP-43, is a hallmark of amyotrophic lateral sclerosis (ALS), including ALS caused by a hexanucleotide repeat expansion in C9orf72. However, the mechanism(s) remain unclear. Importin β and its cargo adaptors have been shown to co-precipitate with the C9orf72-arginine-containing dipeptide repeat proteins (R-DPRs), poly-glycine arginine (GR) and poly-proline arginine (PR), and are protective in genetic modifier screens. Here, we show that R-DPRs interact with importin β, disrupt its cargo loading, and inhibit nuclear import in permeabilized mouse neurons and HeLa cells, in a manner that can be rescued by RNA. Although R-DPRs induce widespread protein aggregation in this in vitro system, transport disruption is not due to NCT protein sequestration, nor blockade of the phenylalanine-glycine (FG)-rich nuclear pore complex. Our results support a model in which R-DPRs interfere with nuclear transport receptors in the vicinity of the nuclear envelope.

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

2019 ◽  
Vol 10 (10) ◽  
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.

scholarly journals The nuclear ubiquitin ligase adaptor SPOP is a conserved regulator of C9orf72 dipeptide toxicity

2021 ◽  
Author(s):  
Carley Snoznik ◽  
Valentina Medvedeva ◽  
Jelena Mojsilovic-Petrovic ◽  
Paige Rudich ◽  
James Oosten ◽  
...  
Keyword(s):  
Amyotrophic Lateral Sclerosis ◽  
Nuclear Localization ◽  
Ubiquitin Ligase ◽  
E3 Ubiquitin Ligase ◽  
Repeat Expansion ◽  
Dipeptide Repeat Proteins ◽  
C Elegans ◽  
Repeat Proteins ◽  
Lateral Sclerosis ◽  
Dipeptide Repeat

AbstractA hexanucleotide repeat expansion in the C9orf72 gene is the most common cause of inherited amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Unconventional translation of the C9orf72 repeat produces dipeptide repeat proteins (DPRs). Previously, we showed that the DPRs (PR)50 and (GR)50 are highly toxic when expressed in C. elegans and this toxicity depends on nuclear localization of the DPR. In an unbiased genome-wide RNAi screen for suppressors of (PR)50 toxicity, we identified 12 genes that consistently suppressed either the developmental arrest and/or paralysis phenotype evoked by (PR)50 expression. All of these genes have vertebrate homologs and 7/12 contain predicted nuclear localization signals. One of these genes was spop-1, the C. elegans homolog of SPOP, a nuclear localized E3 ubiquitin ligase adaptor only found in metazoans. SPOP is also required for (GR)50 toxicity and functions in a genetic pathway that includes cul-3, which is the canonical E3 ligase partner for SPOP. Genetic or pharmacological inhibition of SPOP in mammalian primary spinal cord motor neurons suppressed DPR toxicity without affecting DPR expression levels. Finally, we find that genetic inhibition of bet-1, the C. elegans homolog of the known SPOP ubiquitination targets BRD2/3/4, suppresses the protective effect of SPOP mutations. Together, these data suggest a model in which SPOP promotes the DPR-dependent ubiquitination and degradation of BRD proteins. We speculate the pharmacological manipulation of this pathway, which is currently underway for multiple cancer subtypes, could also represent a novel entry point for therapeutic intervention to treat C9 FTD/ALS.Significance statementThe G4C2 repeat expansion in the C9orf72 gene is a major cause of Fronto-Temporal Dementia (FTD) and Amyotrophic Lateral Sclerosis (ALS). Unusual translation of the repeat sequence produces two highly toxic dipeptide repeat proteins, PRX and GRX, which accumulate in the brain tissue of individuals with these diseases. Here, we show that PR and GR toxicity in both C. elegans and mammalian neurons depends on the E3 ubiquitin ligase adaptor SPOP. SPOP acts through the bromodomain protein BET-1 to mediate dipeptide toxicity. SPOP inhibitors, which are currently being developed to treat SPOP-dependent renal cancer, also protect neurons against DPR toxicity. Our findings identify a highly conserved and ‘druggable’ pathway that may represent a new strategy for treating these currently incurable diseases.

scholarly journals C9orf72 arginine-rich dipeptide repeat proteins disrupt karyopherin-mediated nuclear import

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Lindsey R Hayes ◽  
Lauren Duan ◽  
Kelly Bowen ◽  
Petr Kalab ◽  
Jeffrey D Rothstein
Keyword(s):  
Nuclear Import ◽  
Genetic Modifier ◽  
Nucleocytoplasmic Transport ◽  
Nuclear Pore ◽  
Dipeptide Repeat Proteins ◽  
Hexanucleotide Repeat ◽  
Repeat Proteins ◽  
Importin Α ◽  
Dipeptide Repeat

Disruption of nucleocytoplasmic transport is increasingly implicated in the pathogenesis of neurodegenerative diseases, including ALS caused by a C9orf72 hexanucleotide repeat expansion. However, the mechanism(s) remain unclear. Karyopherins, including importin β and its cargo adaptors, have been shown to co-precipitate with the C9orf72 arginine-containing dipeptide repeat proteins (R-DPRs), poly-glycine arginine (GR) and poly-proline arginine (PR), and are protective in genetic modifier screens. Here, we show that R-DPRs interact with importin β, disrupt its cargo loading, and inhibit nuclear import of importin β, importin α/β, and transportin cargoes in permeabilized mouse neurons and HeLa cells, in a manner that can be rescued by RNA. Although R-DPRs induce widespread protein aggregation in this in vitro system, transport disruption is not due to nucleocytoplasmic transport protein sequestration, nor blockade of the phenylalanine-glycine (FG)-rich nuclear pore complex. Our results support a model in which R-DPRs interfere with cargo loading on karyopherins.

scholarly journals Enhanced insulin signalling ameliorates C9orf72 hexanucleotide repeat expansion toxicity in Drosophila

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Magda L Atilano ◽  
Sebastian Grönke ◽  
Teresa Niccoli ◽  
Liam Kempthorne ◽  
Oliver Hahn ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Insulin Signalling ◽  
Repeat Expansion ◽  
Adult Brain ◽  
Systemic Injection ◽  
Hexanucleotide Repeat ◽  
Repeat Expansions ◽  
Hexanucleotide Repeat Expansion ◽  
Lateral Sclerosis ◽  
Dipeptide Repeat

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.

scholarly journals The carboxyl-termini of RAN translated GGGGCC nucleotide repeat expansions modulate toxicity in models of ALS/FTD

2020 ◽  
Author(s):  
Fang He ◽  
Brittany N. Flores ◽  
Amy Krans ◽  
Michelle Frazer ◽  
Sam Natla ◽  
...  
Keyword(s):  
Nuclear Accumulation ◽  
Carboxyl Terminus ◽  
Sporadic Amyotrophic Lateral Sclerosis ◽  
Reading Frame ◽  
Dipeptide Repeat Proteins ◽  
Hexanucleotide Repeat ◽  
Repeat Proteins ◽  
Differential Toxicity ◽  
Reading Frames ◽  
Dipeptide Repeat

AbstractAn intronic hexanucleotide repeat expansion in C9ORF72 causes familial and sporadic amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). This repeat is thought to elicit toxicity through RNA mediated protein sequestration and repeat-associated non-AUG (RAN) translation of dipeptide repeat proteins (DPRs). We generated a series of transgenic Drosophila models expressing GGGGCC (G4C2) repeats either inside of an artificial intron within a GFP reporter or within the 5’ UTR of GFP placed in different downstream reading frames. Expression of 484 intronic repeats elicited minimal alterations in eye morphology, viability, longevity, or larval crawling but did trigger RNA foci formation, consistent with prior reports. In contrast, insertion of repeats into the 5’ UTR elicited differential toxicity that was dependent on the reading frame of GFP relative to the repeat. Greater toxicity correlated with a short and unstructured carboxyl terminus in the glycine-arginine (GR) RAN protein reading frame. This change in C-terminal sequence triggered nuclear accumulation of all three RAN DPRs. A similar differential toxicity and dependence on the GR carboxyl terminus was observed when repeats were expressed in rodent neurons. The presence of the native carboxyl-termini across all three reading frames was partly protective. Taken together, these findings suggest that carboxyl terminal sequences outside of the repeat region may alter the behavior and toxicity of dipeptide repeat proteins derived from GGGGCC repeats.

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

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.

scholarly journals Hypothesis and Theory: Roles of Arginine Methylation in C9orf72-Mediated ALS and FTD

2021 ◽  
Vol 15 ◽  
Author(s):  
Anna L. Gill ◽  
Alan S. Premasiri ◽  
Fernando G. Vieira
Keyword(s):  
Rna Binding ◽  
Protein Localization ◽  
Arginine Methylation ◽  
Dipeptide Repeat Proteins ◽  
Cellular Processes ◽  
Experimental Systems ◽  
Hexanucleotide Repeat ◽  
Repeat Proteins ◽  
Arginine Residues ◽  
Dipeptide Repeat

Hexanucleotide repeat expansion (G4C2n) mutations in the gene C9ORF72 account for approximately 30% of familial cases of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), as well as approximately 7% of sporadic cases of ALS. G4C2n mutations are known to result in the production of five species of dipeptide repeat proteins (DRPs) through non-canonical translation processes. Arginine-enriched dipeptide repeat proteins, glycine-arginine (polyGR), and proline-arginine (polyPR) have been demonstrated to be cytotoxic and deleterious in multiple experimental systems. Recently, we and others have implicated methylation of polyGR/polyPR arginine residues in disease processes related to G4C2n mutation-mediated neurodegeneration. We previously reported that inhibition of asymmetric dimethylation (ADMe) of arginine residues is protective in cell-based models of polyGR/polyPR cytotoxicity. These results are consistent with the idea that PRMT-mediated arginine methylation in the context of polyGR/polyPR exposure is harmful. However, it remains unclear why. Here we discuss the influence of arginine methylation on diverse cellular processes including liquid-liquid phase separation, chromatin remodeling, transcription, RNA processing, and RNA-binding protein localization, and we consider how methylation of polyGR/polyPR may disrupt processes essential for normal cellular function and survival.

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