scholarly journals Development of a sensitive trial-ready poly(GP) CSF biomarker assay for C9orf72-associated frontotemporal dementia and amyotrophic lateral sclerosis

2021 ◽  
Author(s):  
Katherine M Wilson ◽  
Eszter Katona ◽  
Idoia Glaria ◽  
Imogen J Swift ◽  
Aitana Sogorb-Esteve ◽  
...  
Keyword(s):  
Clinical Trials ◽  
Amyotrophic Lateral Sclerosis ◽  
Frontotemporal Dementia ◽  
Single Molecule ◽  
Repeat Expansion ◽  
Target Engagement ◽  
Limit Of Quantification ◽  
Highly Sensitive ◽  
Lateral Sclerosis ◽  
Dipeptide Repeat

A GGGGCC repeat expansion in the C9orf72 gene is the most common cause of genetic frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS). As potential therapies targeting the repeat expansion are now entering clinical trials, sensitive biomarker assays of target engagement are urgently required. We utilised the single molecule array (Simoa) platform to develop an immunoassay for measuring poly(GP) dipeptide repeat proteins (DPRs) generated by the repeat expansion in CSF of people with C9orf72-associated FTD/ALS. We show the assay to be highly sensitive and robust, passing extensive qualification criteria including low intra- and inter-plate variability, a high precision and accuracy in measuring both calibrators and samples, dilutional parallelism, tolerance to sample and standard freeze-thaw and no haemoglobin interference. We used this assay to measure poly(GP) DPRs in the CSF of samples collected through the Genetic FTD Initiative. We found it had 100% specificity and 100% sensitivity and a large window for detecting target engagement, as the C9orf72 CSF sample with the lowest poly(GP) signal had 8-fold higher signal than controls and on average values from C9orf72 samples were 38-fold higher than controls, which all fell below the lower limit of quantification of the assay. These data indicate that a Simoa-based poly(GP) DPR assay is suitable for use in clinical trials to determine target engagement of therapeutics aimed at reducing C9orf72 repeat-containing transcripts.

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 Emerging Mechanisms Underpinning Neurophysiological Impairments in C9ORF72 Repeat Expansion-Mediated Amyotrophic Lateral Sclerosis/Frontotemporal Dementia

2021 ◽  
Vol 15 ◽  
Author(s):  
Iris-Stefania Pasniceanu ◽  
Manpreet Singh Atwal ◽  
Cleide Dos Santos Souza ◽  
Laura Ferraiuolo ◽  
Matthew R. Livesey
Keyword(s):  
Amyotrophic Lateral Sclerosis ◽  
Frontotemporal Dementia ◽  
Motor Neurons ◽  
Molecular Mechanisms ◽  
Repeat Expansion ◽  
Neuronal Function ◽  
Repeat Expansion Mutation ◽  
Expansion Mutation ◽  
The Impact ◽  
Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are characterized by degeneration of upper and lower motor neurons and neurons of the prefrontal cortex. The emergence of the C9ORF72 hexanucleotide repeat expansion mutation as the leading genetic cause of ALS and FTD has led to a progressive understanding of the multiple cellular pathways leading to neuronal degeneration. Disturbances in neuronal function represent a major subset of these mechanisms and because such functional perturbations precede degeneration, it is likely that impaired neuronal function in ALS/FTD plays an active role in pathogenesis. This is supported by the fact that ALS/FTD patients consistently present with neurophysiological impairments prior to any apparent degeneration. In this review we summarize how the discovery of the C9ORF72 repeat expansion mutation has contributed to the current understanding of neuronal dysfunction in ALS/FTD. Here, we discuss the impact of the repeat expansion on neuronal function in relation to intrinsic excitability, synaptic, network and ion channel properties, highlighting evidence of conserved and divergent pathophysiological impacts between cortical and motor neurons and the influence of non-neuronal cells. We further highlight the emerging association between these dysfunctional properties with molecular mechanisms of the C9ORF72 mutation that appear to include roles for both, haploinsufficiency of the C9ORF72 protein and aberrantly generated dipeptide repeat protein species. Finally, we suggest that relating key pathological observations in C9ORF72 repeat expansion ALS/FTD patients to the mechanistic impact of the C9ORF72 repeat expansion on neuronal function will lead to an improved understanding of how neurophysiological dysfunction impacts upon pathogenesis.

Different CSF protein profiles in amyotrophic lateral sclerosis and frontotemporal dementia with C9orf72 hexanucleotide repeat expansion

2020 ◽  
Vol 91 (5) ◽  
pp. 503-511 ◽  
Author(s):  
Peggy Barschke ◽  
Patrick Oeckl ◽  
Petra Steinacker ◽  
MHD Rami Al Shweiki ◽  
Jochen H Weishaupt ◽  
...  
Keyword(s):  
Amyotrophic Lateral Sclerosis ◽  
Frontotemporal Dementia ◽  
Multiple Reaction Monitoring ◽  
Repeat Expansion ◽  
Common Mutation ◽  
Hexanucleotide Repeat ◽  
Mutation Carriers ◽  
Csf Levels ◽  
Hexanucleotide Repeat Expansion ◽  
Lateral Sclerosis

ObjectivesThe hexanucleotide repeat expansion in the C9orf72 gene is the most common mutation associated with amyotrophic lateral sclerosis (C9-ALS) and frontotemporal dementia (C9-FTD). Until now, it is unknown which factors define whether C9orf72 mutation carriers develop ALS or FTD. Our aim was to identify protein biomarker candidates in the cerebrospinal fluid (CSF) which differentiate between C9-ALS and C9-FTD and might be indicative for the outcome of the mutation.MethodsWe compared the CSF proteome of 16 C9-ALS and 8 C9-FTD patients and 11 asymptomatic C9orf72 mutation carriers (CAR) by isobaric tags for relative and absolute quantitation. Eleven biomarker candidates were selected from the pool of differentially regulated proteins for further validation by multiple reaction monitoring and single-molecule array in a larger cohort (n=156).ResultsIn total, 2095 CSF proteins were identified and 236 proteins were significantly different in C9-ALS versus C9-FTD including neurofilament medium polypeptide (NEFM) and chitotriosidase-1 (CHIT1). Eight candidates were successfully validated including significantly increased ubiquitin carboxyl-terminal hydrolase isozyme L1 (UCHL1) levels in C9-ALS compared with C9-FTD and controls and decreased neuronal pentraxin receptor (NPTXR) levels in C9-FTD versus CAR.ConclusionsThis study presents a deep proteomic CSF analysis of C9-ALS versus C9-FTD patients. As a proof of concept, we observed higher NEFM and CHIT1 CSF levels in C9-ALS. In addition, we also show clear upregulation of UCHL1 in C9-ALS and downregulation of NPTXR in C9-FTD. Significant differences in UCHL1 CSF levels may explain diverging ubiquitination and autophagy processes and NPTXR levels might reflect different synapses organisation processes.

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

2017 ◽  
Vol 89 (2) ◽  
pp. 162-168 ◽  
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.

scholarly journals Cognition and behaviour in frontotemporal dementia with and without amyotrophic lateral sclerosis

2020 ◽  
Vol 91 (12) ◽  
pp. 1304-1311 ◽  
Author(s):  
Jennifer A Saxon ◽  
Jennifer C Thompson ◽  
Jennifer M Harris ◽  
Anna M Richardson ◽  
Tobias Langheinrich ◽  
...  
Keyword(s):  
Amyotrophic Lateral Sclerosis ◽  
Frontotemporal Dementia ◽  
Neuropsychological Testing ◽  
Behavioural Change ◽  
Repeat Expansion ◽  
Phenotypic Differences ◽  
Prospective Comparative Study ◽  
Precise Relationship ◽  
The Relationship ◽  
Lateral Sclerosis

ObjectiveThe precise relationship between frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) is incompletely understood. The association has been described as a continuum, yet data suggest that this may be an oversimplification. Direct comparisons between patients who have behavioural variant FTD (bvFTD) with and without ALS are rare. This prospective comparative study aimed to determine whether there are phenotypic differences in cognition and behaviour between patients with FTD-ALS and bvFTD alone.MethodsPatients with bvFTD or FTD-ALS and healthy controls underwent neuropsychological testing, focusing on language, executive functions and social cognition. Behavioural change was measured through caregiver interview. Blood samples were screened for known FTD genes.Results23 bvFTD, 20 FTD-ALS and 30 controls participated. On cognitive tests, highly significant differences were elicited between patients and controls, confirming the tests’ sensitivities to FTD. bvFTD and FTD-ALS groups performed similarly, although with slightly greater difficulty in patients with ALS-FTD on category fluency and a sentence-ordering task that assesses grammar production. Patients with bvFTD demonstrated more widespread behavioural change, with more frequent disinhibition, impulsivity, loss of empathy and repetitive behaviours. Behaviour in FTD-ALS was dominated by apathy. The C9ORF72 repeat expansion was associated with poorer performance on language-related tasks.ConclusionsDifferences were elicited in cognition and behaviour between bvFTD and FTD-ALS, and patients carrying the C9ORF72 repeat expansion. The findings, which raise the possibility of phenotypic variation between bvFTD and FTD-ALS, have clinical implications for early detection of FTD-ALS and theoretical implications for the nature of the relationship between FTD and ALS.

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

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.

Ribosome Profiling Reveals Novel Regulation of C9ORF72 GGGGCC Repeat-Containing RNA Translation

RNA ◽  
2021 ◽  
pp. rna.078963.121
Author(s):  
Heleen M van 't Spijker ◽  
Emily E Stackpole ◽  
Sandra Almeida ◽  
Olga Katsara ◽  
Botao Liu ◽  
...  
Keyword(s):  
Amyotrophic Lateral Sclerosis ◽  
Translation Initiation ◽  
Repeat Expansion ◽  
Ribosome Profiling ◽  
Initiation Factor ◽  
Rna Translation ◽  
First Intron ◽  
Translational Mechanisms ◽  
Lateral Sclerosis ◽  
Dipeptide Repeat

GGGGCC (G4C2) repeat expansion in the first intron of C9ORF72 causes amyotrophic lateral sclerosis and frontotemporal dementia. Repeat-containing RNA is translated into dipeptide repeat (DPR) proteins, some of which are neurotoxic. Using dynamic ribosome profiling, we identified three translation initiation sites in the intron upstream of (G4C2) repeats; these sites are detected irrespective of the presence or absence of the repeats. During translocation, ribosomes appear to be stalled on the repeats. An AUG in the preceding C9ORF72 exon initiates a uORF that inhibits downstream translation. Polysome isolation indicates that unspliced (G4C2) repeat-containing RNA is a substrate for DPR protein synthesis. (G4C2) repeat-containing RNA translation is 5’ cap-independent but inhibited by the initiation factor DAP5, suggesting an interplay with uORF function. These results define novel translational mechanisms of expanded (G4C2) repeat-containing RNA in disease.

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