HDAC6 Interacts With Poly (GA) and Modulates its Accumulation in c9FTD/ALS

The aberrant translation of a repeat expansion in chromosome 9 open reading frame 72 (C9orf72), the most common cause of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS), results in the accumulation of toxic dipeptide repeat (DPR) proteins in the central nervous system We have found that, among the sense DPR proteins, HDAC6 specifically interacts with the poly (GA) and co-localizes with inclusions in both patient tissue and a mouse model of this disease (c9FTD/ALS). Overexpression of HDAC6 increased poly (GA) levels in cultured cells independently of HDAC6 deacetylase activity, suggesting that HDAC6 can modulate poly (GA) pathology through a mechanism that depends upon their physical interaction. Moreover, decreasing HDAC6 expression by stereotaxic injection of antisense oligonucleotides significantly reduced the number of poly (GA) inclusions in c9FTD/ALS mice. These findings suggest that pharmacologically reducing HDAC6 levels could be of therapeutic value in c9FTD/ALS.

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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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The Emerging Role of DNA Damage in the Pathogenesis of the C9orf72 Repeat Expansion in Amyotrophic Lateral Sclerosis

International Journal of Molecular Sciences ◽

10.3390/ijms19103137 ◽

2018 ◽

Vol 19 (10) ◽

pp. 3137 ◽

Cited By ~ 12

Author(s):

Anna Konopka ◽

Julie Atkin

Keyword(s):

Dna Damage ◽

Amyotrophic Lateral Sclerosis ◽

Motor Neurons ◽

Repeat Expansion ◽

Chromosome 9 ◽

Gene Encoding ◽

C9orf72 Repeat Expansion ◽

Reading Frame ◽

Early Onset Dementia ◽

Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal, rapidly progressing neurodegenerative disease affecting motor neurons, and frontotemporal dementia (FTD) is a behavioural disorder resulting in early-onset dementia. Hexanucleotide (G4C2) repeat expansions in the gene encoding chromosome 9 open reading frame 72 (C9orf72) are the major cause of familial forms of both ALS (~40%) and FTD (~20%) worldwide. The C9orf72 repeat expansion is known to form abnormal nuclei acid structures, such as hairpins, G-quadruplexes, and R-loops, which are increasingly associated with human diseases involving microsatellite repeats. These configurations form during normal cellular processes, but if they persist they also damage DNA, and hence are a serious threat to genome integrity. It is unclear how the repeat expansion in C9orf72 causes ALS, but recent evidence implicates DNA damage in neurodegeneration. This may arise from abnormal nucleic acid structures, the greatly expanded C9orf72 RNA, or by repeat-associated non-ATG (RAN) translation, which generates toxic dipeptide repeat proteins. In this review, we detail recent advances implicating DNA damage in C9orf72-ALS. Furthermore, we also discuss increasing evidence that targeting these aberrant C9orf72 confirmations may have therapeutic value for ALS, thus revealing new avenues for drug discovery for this disorder.

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

10.1101/2021.03.09.434618 ◽

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.

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Novel Optineurin Frameshift Insertion in a Family With Frontotemporal Dementia and Parkinsonism Without Amyotrophic Lateral Sclerosis

Frontiers in Neurology ◽

10.3389/fneur.2021.645913 ◽

2021 ◽

Vol 12 ◽

Author(s):

Jacqueline Dominguez ◽

Jeryl Tan Yu ◽

Yi Jayne Tan ◽

Arlene Ng ◽

Ma Fe De Guzman ◽

...

Keyword(s):

Amyotrophic Lateral Sclerosis ◽

Frontotemporal Dementia ◽

Positive Family History ◽

Clinical Manifestations ◽

The Philippines ◽

Chromosome 9 ◽

Genetic Modifiers ◽

Reading Frame ◽

Hexanucleotide Repeat ◽

Lateral Sclerosis

Frontotemporal Dementia (FTD) is a common cause of Young Onset Dementia and has diverse clinical manifestations involving behavior, executive function, language and motor function, including parkinsonism. Up to 50% of FTD patients report a positive family history, supporting a strong genetic basis, particularly in cases with both FTD and amyotrophic lateral sclerosis (FTD-ALS). Mutations in three genes are associated with the majority of familial FTD (fFTD) cases - microtubule associated protein tau gene (MAPT), granulin precursor (GRN), and hexanucleotide repeat expansions in chromosome 9 open reading frame 72- SMCR8complex subunit (C9orf72) while mutations in other genes such as optineurin (OPTN) have rarely been reported. Mutations in OPTN have been reported mostly in familial and sporadic cases of ALS, or in rare cases of FTD-ALS, but not in association with pure or predominant FTD and/or parkinsonian phenotype. Here, we report for the first time, a family from the Philippines with four members harboring a novel frameshift insertion at OPTN (Chr 10:13166090 G>GA) p.Lys328GluTer11, three of whom presented with FTD-related phenotypes. Additionally, one sibling heterozygous for the frameshift insertion had a predominantly parkinsonian phenotype resembling corticobasal syndrome, but it remains to be determined if this phenotype is related to the frameshift insertion. Notably, none of the affected members showed any evidence of motor neuron disease or ALS at the time of writing, both clinically and on electrophysiological testing, expanding the phenotypic spectrum of OPTN mutations. Close follow-up of mutation carriers for the development of new clinical features and wider investigation of additional family members with further genetic analyses will be conducted to investigate the possibility of other genetic modifiers in this family which could explain phenotypic heterogeneity.

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Analysis of known amyotrophic lateral sclerosis and frontotemporal dementia genes reveals a substantial genetic burden in patients manifesting both diseases not carrying the C9orf72 expansion mutation

Journal of Neurology Neurosurgery & Psychiatry ◽

10.1136/jnnp-2017-316820 ◽

2017 ◽

Vol 89 (2) ◽

pp. 162-168 ◽

Cited By ~ 23

Author(s):

Oriol Dols-Icardo ◽

Alberto García-Redondo ◽

Ricardo Rojas-García ◽

Daniel Borrego-Hernández ◽

Ignacio Illán-Gala ◽

...

Keyword(s):

Amyotrophic Lateral Sclerosis ◽

Frontotemporal Dementia ◽

Pathogenic Mutation ◽

Genetic Alterations ◽

Repeat Expansion ◽

Chromosome 9 ◽

Systematic Screening ◽

Expansion Mutation ◽

Genetic Burden ◽

Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are part of a clinical, pathological and genetic continuum.ObjectivesThe purpose of the present study was to assess the mutation burden that is present in patients with concurrent ALS and FTD (ALS/FTD) not carrying the chromosome 9 open reading frame 72 (C9orf72) hexanucleotide repeat expansion, the most important genetic cause in both diseases.MethodsFrom an initial group of 973 patients with ALS, we retrospectively selected those patients fulfilling diagnostic criteria of concomitant ALS and FTD lacking the repeat expansion mutation in C9orf72. Our final study group consisted of 54 patients clinically diagnosed with ALS/FTD (16 with available postmortem neuropathological diagnosis). Data from whole exome sequencing were used to screen for mutations in known ALS and/or FTD genes.ResultsWe identified 11 patients carrying a probable pathogenic mutation, representing an overall mutation frequency of 20.4%. TBK1 was the most important genetic cause of ALS/FTD (n=5; 9.3%). The second most common mutated gene was SQSTM1, with three mutation carriers (one of them also harboured a TBK1 mutation). We also detected probable pathogenic genetic alterations in TAF15, VCP and TARDBP and possible pathogenic mutations in FIG4 and ERBB4.ConclusionOur results indicate a high genetic burden underlying the co-occurrence of ALS and FTD and expand the phenotype associated with TAF15, FIG4 and ERBB4 to FTD. A systematic screening of ALS and FTD genes could be indicated in patients manifesting both diseases without the C9orf72 expansion mutation, regardless of family history of disease.

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Genetics and Sex in the Pathogenesis of Amyotrophic Lateral Sclerosis (ALS): Is There a Link?

International Journal of Molecular Sciences ◽

10.3390/ijms21103647 ◽

2020 ◽

Vol 21 (10) ◽

pp. 3647 ◽

Cited By ~ 1

Author(s):

Francesca Trojsi ◽

Giulia D’Alvano ◽

Simona Bonavita ◽

Gioacchino Tedeschi

Keyword(s):

Amyotrophic Lateral Sclerosis ◽

Disease Risk ◽

Genetic Mutation ◽

Chromosome 9 ◽

Patient Specific ◽

Reading Frame ◽

Hexanucleotide Repeat ◽

Sporadic Als ◽

Als Patients ◽

Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with no known cure. Approximately 90% of ALS cases are sporadic, although multiple genetic risk factors have been recently revealed also in sporadic ALS (SALS). The pathological expansion of a hexanucleotide repeat in chromosome 9 open reading frame 72 (C9orf72) is the most common genetic mutation identified in familial ALS, detected also in 5–10% of SALS patients. C9orf72-related ALS phenotype appears to be dependent on several modifiers, including demographic factors. Sex has been reported as an independent factor influencing ALS development, with men found to be more susceptible than women. Exposure to both female and male sex hormones have been shown to influence disease risk or progression. Moreover, interplay between genetics and sex has been widely investigated in ALS preclinical models and in large populations of ALS patients carrying C9orf72 repeat expansion. In light of the current need for reclassifying ALS patients into pathologically homogenous subgroups potentially responsive to targeted personalized therapies, we aimed to review the recent literature on the role of genetics and sex as both independent and synergic factors, in the pathophysiology, clinical presentation, and prognosis of ALS. Sex-dependent outcomes may lead to optimizing clinical trials for developing patient-specific therapies for ALS.

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Cell-Clearing Systems Bridging Repeat Expansion Proteotoxicity and Neuromuscular Junction Alterations in ALS and SBMA

International Journal of Molecular Sciences ◽

10.3390/ijms21114021 ◽

2020 ◽

Vol 21 (11) ◽

pp. 4021 ◽

Cited By ~ 3

Author(s):

Fiona Limanaqi ◽

Carla Letizia Busceti ◽

Francesca Biagioni ◽

Federica Cantini ◽

Paola Lenzi ◽

...

Keyword(s):

Neuromuscular Junction ◽

Motor Neurons ◽

Acetylcholine Receptors ◽

Molecular Mechanisms ◽

Muscular Atrophy ◽

Ubiquitin Proteasome System ◽

Repeat Expansion ◽

Chromosome 9 ◽

Reading Frame ◽

Spinal Bulbar Muscular Atrophy

The coordinated activities of autophagy and the ubiquitin proteasome system (UPS) are key to preventing the aggregation and toxicity of misfold-prone proteins which manifest in a number of neurodegenerative disorders. These include proteins which are encoded by genes containing nucleotide repeat expansions. In the present review we focus on the overlapping role of autophagy and the UPS in repeat expansion proteotoxicity associated with chromosome 9 open reading frame 72 (C9ORF72) and androgen receptor (AR) genes, which are implicated in two motor neuron disorders, amyotrophic lateral sclerosis (ALS) and spinal-bulbar muscular atrophy (SBMA), respectively. At baseline, both C9ORF72 and AR regulate autophagy, while their aberrantly-expanded isoforms may lead to a failure in both autophagy and the UPS, further promoting protein aggregation and toxicity within motor neurons and skeletal muscles. Besides proteotoxicity, autophagy and UPS alterations are also implicated in neuromuscular junction (NMJ) alterations, which occur early in both ALS and SBMA. In fact, autophagy and the UPS intermingle with endocytic/secretory pathways to regulate axonal homeostasis and neurotransmission by interacting with key proteins which operate at the NMJ, such as agrin, acetylcholine receptors (AChRs), and adrenergic beta2 receptors (B2-ARs). Thus, alterations of autophagy and the UPS configure as a common hallmark in both ALS and SBMA disease progression. The findings here discussed may contribute to disclosing overlapping molecular mechanisms which are associated with a failure in cell-clearing systems in ALS and SBMA.

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Nuclear export and translation of circular repeat-containing intronic RNA in C9ORF72-ALS/FTD

Nature Communications ◽

10.1038/s41467-021-25082-9 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Shaopeng Wang ◽

Malgorzata J. Latallo ◽

Zhe Zhang ◽

Bo Huang ◽

Dmitriy G. Bobrovnikov ◽

...

Keyword(s):

Single Molecule ◽

Nuclear Export ◽

Repeat Expansion ◽

Disease Etiology ◽

Molecular Identity ◽

Translation Template ◽

Imaging Approach ◽

Intronic Rna ◽

Lateral Sclerosis ◽

Dipeptide Repeat

AbstractC9ORF72 hexanucleotide GGGGCC repeat expansion is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Repeat-containing RNA mediates toxicity through nuclear granules and dipeptide repeat (DPR) proteins produced by repeat-associated non-AUG translation. However, it remains unclear how the intron-localized repeats are exported and translated in the cytoplasm. We use single molecule imaging approach to examine the molecular identity and spatiotemporal dynamics of the repeat RNA. We demonstrate that the spliced intron with G-rich repeats is stabilized in a circular form due to defective lariat debranching. The spliced circular intron, instead of pre-mRNA, serves as the translation template. The NXF1-NXT1 pathway plays an important role in the nuclear export of the circular intron and modulates toxic DPR production. This study reveals an uncharacterized disease-causing RNA species mediated by repeat expansion and demonstrates the importance of RNA spatial localization to understand disease etiology.

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Type I PRMT inhibition protects against C9ORF72 arginine-rich dipeptide repeat toxicity

10.1101/2020.05.20.106260 ◽

2020 ◽

Cited By ~ 2

Author(s):

Alan S. Premasiri ◽

Anna L. Gill ◽

Fernando G. Vieira

Keyword(s):

Repeat Expansion ◽

Type I ◽

Arginine Methyltransferase ◽

Repeat Proteins ◽

C9orf72 Gene ◽

Expansion Mutation ◽

Determining Factor ◽

Lateral Sclerosis ◽

Ran Translation ◽

Dipeptide Repeat

ABSTRACTThe most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) is a repeat expansion mutation in the C9orf72 gene. Repeat-associated non-AUG (RAN) translation of this expansion produces five species of dipeptide repeat proteins (DRPs). The arginine containing DRPs, polyGR and polyPR, are consistently reported to be the most toxic. Here, we uncover Type I protein arginine methyltransferase (PRMT) inhibitors as possible therapeutics for polyGR- and polyPR- related toxicity. Furthermore, we reveal data that suggest that asymmetric dimethylation (ADMe) of polyGR is a determining factor in its pathogenesis.

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Enhanced insulin signalling ameliorates C9orf72 hexanucleotide repeat expansion toxicity in Drosophila

eLife ◽

10.7554/elife.58565 ◽

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.

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