C9orf72-associated Amyotrophic Lateral Sclerosis Research Articles

Safety, tolerability, and pharmacokinetics of antisense oligonucleotide BIIB078 in adults with C9orf72-associated amyotrophic lateral sclerosis: a phase 1, randomised, double blinded, placebo-controlled, multiple ascending dose study

Hexanucleotide repeat expansion of C9orf72 is a common genetic cause of amyotrophic lateral sclerosis (ALS). No C9orf72-targeted treatments are available. BIIB078 is an investigational antisense oligonucleotide targeting C9orf72 sense RNA. We aimed to assess the safety, tolerability, and pharmacokinetics of BIIB078 in participants with C9orf72-associated ALS. This phase 1, randomised controlled trial was done at 22 sites in six countries (Canada, Ireland, Netherlands, Switzerland, UK, and USA). Adults with ALS and a pathogenic repeat expansion in C9orf72 were randomly assigned within six cohorts, via Interactive Response Technology in a 3:1 ratio per cohort, to receive BIIB078 (5 mg, 10 mg, 20 mg, 35 mg, 60 mg, or 90 mg in cohorts 1-6, respectively) or placebo, via an intrathecal bolus injection. The treatment period consisted of three loading doses of study treatment, administered approximately once every 2 weeks, followed by monthly maintenance doses during a treatment period of about 3 months for cohorts 1-3 and about 6 months for cohorts 4-6. Patients and investigators were masked to treatment assignment. The primary endpoint was the incidence of adverse events and serious adverse events. This trial was registered with ClinicalTrials.gov (NCT03626012) and is completed. Between Sept 10, 2018, and Nov 17, 2021, 124 patients were screened for inclusion in the study. 18 patients were excluded and 106 participants were enrolled and randomly assigned to receive 5 mg (n=6), 10 mg (n=9), 20 mg (n=9), 35 mg (n=19), 60 mg (n=18), or 90 mg (n=18) of BIIB078, or placebo (n=27). 58 (55%) of 106 patients were female. All patients received at least one dose of study treatment and were included in all analyses. All participants had at least one adverse event; most adverse events were mild or moderate in severity and did not lead to treatment discontinuation. The most common adverse events in BIIB078-treated participants were falls, procedural pain, headache, and post lumbar puncture syndrome. 14 (18%) of 79 patients who received any dose of BIIB078 reported serious adverse events, compared with nine (33%) of 27 patients who received placebo. Five participants who received BIIB078 and three participants who received placebo had fatal adverse events: respiratory failure in a participant who received 10 mg BIIB078, ALS worsening in two participants who received 35 mg BIIB078, traumatic intracerebral haemorrhage in one participant who received 35 mg BIIB078, pulmonary embolism in one participant who received 60 mg BIIB078, and respiratory failure in three participants who received placebo. All deaths were assessed as not related to the study treatment by the reporting investigator. On the basis of these phase 1 study results, including secondary and exploratory findings showing no reduction in neurofilament levels and no benefit on clinical outcomes relative to the placebo cohort, BIIB078 clinical development has been discontinued. However, these results will be informative in furthering our understanding of the complex pathobiology of C9orf72-associated ALS. Biogen.

Understanding the relationship between cerebellum and the frontal-cortex region of C9orf72-related amyotrophic lateral sclerosis: A comparative analysis of genetic features.

Amyotrophic lateral sclerosis (ALS) is a relentlessly progressive and fatal neurodegenerative diseases for which at present no cure is available. Despite the extensive research the progress from diagnosis to prognosis in ALS and frontotemporal dementia (FTD) has been slow which represents suboptimal understanding of disease pathophysiological processes. In recent studies, several genes have been associated with the ALS and FTD diseases such as SOD1, TDP43, and TBK1, whereas the hexanucleotide GGGGCC repeat expansion (HRE) in C9orf72 gene is a most frequent cause of ALS and FTD, that has changed the understanding of these diseases. The goal of this study was to identify and spatially determine differential gene expression signature differences between cerebellum and frontal cortex in C9orf72-associated ALS (C9-ALS), to study the network properties of these differentially expressed genes, and to identify miRNAs targeting the common differentially expressed genes in both the tissues. This study thus highlights underlying differential cell susceptibilities to the disease mechanisms in C9-ALS and suggesting therapeutic target selection in C9-ALS. In this manuscript, we have identified that the genes involved in neuron development, protein localization and transcription are mostly enriched in cerebellum of C9-ALS patients, while the UPR-related genes are enriched in the frontal cortex. Of note, UPR pathway genes were mostly dysregulated both in the C9-ALS cerebellum and frontal cortex. Overall, the data presented here show that defects in normal RNA processing and the UPR pathway are the pathological hallmarks of C9-ALS. Interestingly, the cerebellum showed more strong transcriptome changes than the frontal cortex. Interestingly, the cerebellum region showed more significant transcriptomic changes as compared to the frontal cortex region suggesting its active participation in the disease process. This nuanced understanding may offer valuable insights for the development of targeted therapeutic strategies aimed at mitigating disease progression in C9-ALS.

Generation of Human-Induced Pluripotent Stem Cells from Peripheral Blood Mononuclear Cells of C9ORF72-Associated Amyotrophic Lateral Sclerosis Patients.

Disease modeling of neuromuscular disorders, such as amyotrophic lateral sclerosis (ALS), is hindered by limited accessibility of affected cells. This problem can be overcome by generation of human induced pluripotent stem cells (hiPSC), which can be then differentiated into required cells. Here, we describe the detailed protocol of hiPSC establishment from peripheral blood mononuclear cells (PBMC) of two ALS patients with detected expansion of G4C2 (GGGGCC) repeats in the first intron of C9ORF72 gene, known to be linked with the most common form of familial ALS.Successful PBMC reprogramming with non-integrating Sendai vectors was confirmed by expression of pluripotency markers: OCT4, NANOG, SSEA4, and TRA-1-60 in obtained hiPSC and their ability to differentiate into cells of three germ layers.The generated ALS-patient-specific hiPSC create a possibility for deciphering molecular basis of this devastating neuromuscular disease.

Machine Learning-Based Diagnosis and Genetic Analysis of C9ORF72-Associated Amyotrophic Lateral Sclerosis (ALS)

Abstract: Amyotrophic Lateral Sclerosis (ALS), commonly known as Lou Gehrig's disease, is a devastating neurodegenerative disorder characterized by motor neuron degeneration. This research article explores the use of machine learning algorithms to diagnose ALS by analyzing mutations and insertions/deletions (indels) in the C9orf72 gene. The study utilizes a dataset to predict three stages of ALS: normal, intermediate risk, and full mutation. Three machine learning algorithms, Random Forest, SVM, and k-NN, were employed for diagnosis. Results indicate high accuracy in identifying ALS stages, with Random Forest and SVM achieving perfect accuracy when considering mutations in the Allele2. The findings demonstrate the potential of machine learning in early ALS diagnosis, offering insights for improved patient care and genetic understanding of the disease.

Unraveling the impact of disrupted nucleocytoplasmic transport systems in C9orf72-associated ALS.

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are two adult-onset neurodegenerative diseases that are part of a common disease spectrum due to clinical, genetic, and pathological overlap. A prominent genetic factor contributing to both diseases is a hexanucleotide repeat expansion in a non-coding region of the C9orf72 gene. This mutation in C9orf72 leads to nuclear depletion and cytoplasmic aggregation of Tar DNA-RNA binding protein 43 (TDP-43). TDP-43 pathology is characteristic of the majority of ALS cases, irrespective of disease causation, and is present in ~50% of FTD cases. Defects in nucleocytoplasmic transport involving the nuclear pore complex, the Ran-GTPase cycle, and nuclear transport factors have been linked with the mislocalization of TDP-43. Here, we will explore and discuss the implications of these system abnormalities of nucleocytoplasmic transport in C9orf72-ALS/FTD, as well as in other forms of familial and sporadic ALS.

C9orf72 poly(PR) aggregation in nucleus induces ALS/FTD-related neurodegeneration in cynomolgus monkeys

Poly(PR) is a dipeptide repeat protein comprising proline and arginine residues. It is one of the translational product of expanded G4C2 repeats in the C9orf72 gene, and its accumulation is contributing to the neuropathogenesis of C9orf72-associated amyotrophic lateral sclerosis and/or frontotemporal dementia (C9-ALS/FTD). In this study, we demonstrate that poly(PR) protein alone is sufficient to induce neurodegeneration related to ALS/FTD in cynomolgus monkeys. By delivering poly(PR) via AAV, we observed that the PR proteins were located within the nucleus of infected cells. The expression of (PR)50 protein, consisting of 50 PR repeats, led to increased loss of cortical neurons, cytoplasmic lipofuscin, and gliosis in the brain, as well as demyelination and loss of ChAT positive neurons in the spinal cord of monkeys. While, these pathologies were not observed in monkeys expressing (PR)5, a protein comprising only 5 PR repeats. Furthermore, the (PR)50-expressing monkeys exhibited progressive motor deficits, cognitive impairment, muscle atrophy, and abnormal electromyography (EMG) potentials, which closely resemble clinical symptoms seen in C9-ALS/FTD patients. By longitudinally tracking these monkeys, we found that changes in cystatin C and chitinase-1 (CHIT1) levels in the cerebrospinal fluid (CSF) corresponded to the phenotypic progression of (PR)50-induced disease. Proteomic analysis revealed that the major clusters of dysregulated proteins were nuclear-localized, and downregulation of the MECP2 protein was implicated in the toxic process of poly(PR). This research indicates that poly(PR) expression alone induces neurodegeneration and core phenotypes associated with C9-ALS/FTD in monkeys, which may provide insights into the mechanisms of disease pathogenesis.

C9orf72 poly-GA proteins impair neuromuscular transmission.

Amyotrophic lateral sclerosis (ALS) is a devastating motoneuron disease, in which lower motoneurons lose control of skeletal muscles. Degeneration of neuromuscular junctions (NMJs) occurs at the initial stage of ALS. Dipeptide repeat proteins (DPRs) from G4C2 repeat-associated non-ATG (RAN) translation are known to cause C9orf72-associated ALS (C9-ALS). However, DPR inclusion burdens are weakly correlated with neurodegenerative areas in C9-ALS patients, indicating that DPRs may exert cell non-autonomous effects, in addition to the known intracellular pathological mechanisms. Here, we report that poly-GA, the most abundant form of DPR in C9-ALS, is released from cells. Local administration of poly-GA proteins in peripheral synaptic regions causes muscle weakness and impaired neuromuscular transmission in vivo. The NMJ structure cannot be maintained, as evidenced by the fragmentation of postsynaptic acetylcholine receptor (AChR) clusters and distortion of presynaptic nerve terminals. Mechanistic study demonstrated that extracellular poly-GA sequesters soluble Agrin ligands and inhibits Agrin-MuSK signaling. Our findings provide a novel cell non-autonomous mechanism by which poly-GA impairs NMJs in C9-ALS. Thus, targeting NMJs could be an early therapeutic intervention for C9-ALS.

Ribosomal quality control in repeat‐associated non‐AUG translation of GC rich repeats

Nucleotide repeat expansions cause multiple neurodegenerative disorders including C9orf72‐associated amyotrophic lateral sclerosis and frontotemporal dementia (C9 ALS/FTD) and Fragile X‐associated tremor/ataxia syndrome (FXTAS). C9 ALS/FTD results from a GGGGCC (G4C2) hexanucleotide repeat expansions within an intron of C9orf72while FXTAS is caused by CGG repeat expansions in the 5’UTR of FMR1. These repeat‐containing RNAs elicit toxicity at least in part by triggering repeat‐associated non‐AUG (RAN) translation, a non‐canonical initiation process that generates toxic proteins from GC rich repeats. As repetitive RNA elements form strong RNA secondary structures might impact translational elongation, we explored the impact of ribosome‐associated quality control (RQC) pathways on RAN translation. RQC rescues stalled ribosomes and prevents translation of aberrant transcripts, with specific roles for both the mammalian nuclear export mediator factor (NEMF, homologous of Rqc2 in yeast) and the E3 ubiquitin ligase Listerin. Here we show that depletion of NEMF markedly increases the production of RAN products from both G4C2 and CGG repeats. This effect appears to be mediated post transcriptionally and does not involve the nuclear‐cytoplasmic transport functions of the protein. Ongoing studies are characterizing how loss of Listerin impacts RAN translation and repeat RNA stability while exploring whether NEMF meditated CAT‐tailing of RAN translation products impacts their turnover and toxicity.

Preclinical evaluation of WVE-004, an investigational stereopure oligonucleotide for the treatment of C9orf72-associated ALS or FTD

A large hexanucleotide (G4C2) repeat expansion in the first intronic region of C9orf72 is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Several mechanisms have been proposed to explain how the repeat expansion drives disease, and we hypothesize that a variant-selective approach, in which transcripts affected by the repeat expansion are preferentially decreased, has the potential to address most of them. We report a stereopure antisense oligonucleotide, WVE-004, that executes this variant-selective mechanism of action. WVE-004 dose-dependently and selectively reduces repeat-containing transcripts in patient-derived motor neurons carrying a C9orf72-repeat expansion, as well as in the spinal cord and cortex of C9 BAC transgenic mice. In mice, selective transcript knockdown was accompanied by substantial decreases in dipeptide-repeat proteins, which are pathological biomarkers associated with the repeat expansion, and by preservation of healthy C9orf72 protein expression. These in vivo effects were durable, persisting for at least 6 months. These data support the advancement of WVE-004 as an investigational stereopure antisense oligonucleotide targeting C9orf72 for the treatment of C9orf72-associated ALS or FTD.

ALS in Finland: Major Genetic Variants and Clinical Characteristics of Patients With and Without the C9orf72 Hexanucleotide Repeat Expansion.

Background and ObjectivesTo analyze the frequencies of major genetic variants and the clinical features in Finnish patients with amyotrophic lateral sclerosis (ALS) with or without the C9orf72 hexanucleotide repeat expansion.MethodsA cohort of patients with motor neuron disease was recruited between 1993 and 2020 at the Helsinki University Hospital and 2 second-degree outpatient clinics in Helsinki. Finnish ancestry patients with ALS fulfilled the diagnosis according to the revised El Escorial criteria and the Awaji-criteria. Two categories of familial ALS (FALS) were used. A patient was defined FALS-A if at least 1 first- or second-degree family member had ALS, and FALS-NP, if family members had additional neurologic or psychiatric endophenotypes.ResultsOf the 815 patients, 25% had FALS-A and 45% FALS-NP. C9orf72 expansion (C9pos) was found in 256 (31%) of all patients, in 58% of FALS-A category, in 48% of FALS-NP category, and in 23 or 17% of sporadic cases using the FALS-A or FALS-NP definition. C9pos or SOD1 p.D91A homozygosity was found in 328 (40%) of the 815 patients. We compared demographic and clinical characteristics between C9pos and patients with unknown cause of ALS (Unk). We found that the age at onset was significantly earlier and survival markedly shorter in the C9pos vs Unk patients with ALS. The shortest survival was found in bulbar-onset male C9pos patients, whereas the longest survival was found in Unk limb-onset males. Older age at onset associated consistently with shorter survival in C9pos and Unk patients in both limb-onset and bulbar-onset groups. There were no significant differences in the frequencies of bulbar-onset and limb-onset patients in C9pos and Unk groups. ALS-frontotemporal dementia (FTD) was more common in C9pos (17%) than in Unk (4%) patients, and of all patients with ALS-FTD, 70% were C9pos.DiscussionThese results provide further evidence for the short survival of C9orf72-associated ALS. A prominent role of the C9orf72 and SOD1 variants was found in the Finnish population. An unusually high frequency of C9pos was also found among patients with sporadic ALS. The enrichment of these 2 variants likely contributes to the high incidence of ALS in Finland.

Segmental involvement of the corpus callosum inC9orf72-associated ALS: a tract of interest-based DTI study

Background:C9orf72 hexanucleotide repeat expansions are associated with widespread cerebral alterations, including white matter alterations. However, there is lack of information on changes in commissure fibres. Diffusion tensor imaging (DTI) can identify amyotrophic lateral sclerosis (ALS)-associated patterns of regional brain alterations at the group level. The objective of this study was to investigate the structural connectivity of the corpus callosum (CC) in ALS patients with C9orf72 expansions.Methods:DTI-based white matter mapping was performed by a hypothesis-guided tractwise analysis of fractional anisotropy (FA) maps for 25 ALS patients with C9orf72 expansion versus 25 matched healthy controls. Furthermore, a comparison with a patient control group of 25 sporadic ALS patients was performed. DTI-based tracts that originate from callosal sub-areas I to V were identified and correlated with clinical data.Results:The analysis of white matter integrity demonstrated regional FA reductions for tracts of the callosal areas II and III for ALS patients with C9orf72 expansions while FA reductions in sporadic ALS patients were observed only for tracts of the callosal area III; these reductions were correlated with clinical parameters.Conclusion:The tract-of-interest-based analysis showed a microstructural callosal involvement pattern in C9orf72-associated ALS that included the motor segment III together with frontal callosal connections, as an imaging signature of the C9orf72-associated overlap of motor neuron disease and frontotemporal pathology.

LSM12-EPAC1 defines a neuroprotective pathway that sustains the nucleocytoplasmic RAN gradient.

Nucleocytoplasmic transport (NCT) defects have been implicated in neurodegenerative diseases such as C9ORF72-associated amyotrophic lateral sclerosis and frontotemporal dementia (C9-ALS/FTD). Here, we identify a neuroprotective pathway of like-Sm protein 12 (LSM12) and exchange protein directly activated by cyclic AMP 1 (EPAC1) that sustains the nucleocytoplasmic RAN gradient and thereby suppresses NCT dysfunction by the C9ORF72-derived poly(glycine-arginine) protein. LSM12 depletion in human neuroblastoma cells aggravated poly(GR)-induced impairment of NCT and nuclear integrity while promoting the nuclear accumulation of poly(GR) granules. In fact, LSM12 posttranscriptionally up-regulated EPAC1 expression, whereas EPAC1 overexpression rescued the RAN gradient and NCT defects in LSM12-deleted cells. C9-ALS patient-derived neurons differentiated from induced pluripotent stem cells (C9-ALS iPSNs) displayed low expression of LSM12 and EPAC1. Lentiviral overexpression of LSM12 or EPAC1 indeed restored the RAN gradient, mitigated the pathogenic mislocalization of TDP-43, and suppressed caspase-3 activation for apoptosis in C9-ALS iPSNs. EPAC1 depletion biochemically dissociated RAN-importin β1 from the cytoplasmic nuclear pore complex, thereby dissipating the nucleocytoplasmic RAN gradient essential for NCT. These findings define the LSM12-EPAC1 pathway as an important suppressor of the NCT-related pathologies in C9-ALS/FTD.

Study to Assess the Safety, Tolerability, Pharmacokinetics, and Effect on Disease Progression of BIIB078 Administered to Previously Treated Adults C9ORF72-Associated Amyotrophic Lateral Sclerosis (ALS)

Study to Assess the Safety, Tolerability, Pharmacokinetics, and Effect on Disease Progression of BIIB078 Administered to Previously Treated Adults C9ORF72-Associated Amyotrophic Lateral Sclerosis (ALS)

Nucleocytoplasmic Proteomic Analysis Uncovers eRF1 and Nonsense-Mediated Decay as Modifiers of ALS/FTD C9orf72 Toxicity

The most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) is a hexanucleotide repeat expansion in C9orf72 (C9-HRE). While RNA and dipeptide repeats produced by C9-HRE disrupt nucleocytoplasmic transport, the proteins that become redistributed remain unknown. Here, we utilized subcellular fractionation coupled with tandem mass spectrometry and identified 126 proteins, enriched for protein translation and RNA metabolism pathways, which collectively drive a shift toward a more cytosolic proteome in C9-HRE cells. Among these was eRF1, which regulates translation termination and nonsense-mediated decay (NMD). eRF1 accumulates within elaborate nuclear envelope invaginations in patient induced pluripotent stem cell (iPSC) neurons and postmortem tissue and mediates a protective shift from protein translation to NMD-dependent mRNA degradation. Overexpression of eRF1 and the NMD driver UPF1 ameliorate C9-HRE toxicity invivo. Our findings provide a resource for proteome-wide nucleocytoplasmic alterations across neurodegeneration-associated repeat expansion mutations and highlight eRF1 and NMD as therapeutic targets in C9orf72-associated ALS and/or FTD.

Electrophysiological Characterization of C9ORF72-Associated Amyotrophic Lateral Sclerosis: A Retrospective Study

Objective: C9ORF72 is the most common genetic cause of amyotrophic lateral sclerosis (ALS). The aim of the present study was to determine whether C9ORF72-associated ALS (C9-ALS) patients present distinctive electrophysiological characteristics that could differentiate them from non C9ORF72-associated ALS (nonC9-ALS) patients. Methods: Clinical and electrodiagnostic data from C9-ALS patients and nonC9-ALS patients were collected retrospectively. For electroneuromyography, the mean values of motor conduction, myography, and the mean values of sensory conduction were considered. Furthermore, the proportion of ALS patients with electrophysiological sensory neuropathy was determined. Results: No significant difference was observed between 31 C9-ALS patients and 22 nonC9-ALS patients for mean motor conduction and myography. For sensory conduction analyses, mean sensory conduction was not significantly different between both groups. In total, 38% of ­C9-ALS patient and 21% of nonC9-ALS patients presented electrophysiological sensory neuropathy (p = 0.33). In ­C9-ALS patients with electrophysiological sensory neuropathy, 80% (8/10) were male and 67% (6/9) presented spinal onset compare to 25% (4/16, p = 0.014) male and 25% (4/16, p = 0.087) with spinal onset in those without electrophysiological sensory neuropathy. Conclusion: Although not different from nonC9-ALS, these results suggest that sensory involvement is a frequent feature of C9-ALS patients, expanding the phenotype of the disease beyond the motor and cognitive domains.

In vivo histopathological staging in C9orf72-associated ALS: A tract of interest DTI study

BackgroundDiffusion tensor imaging (DTI) can identify amyotrophic lateral sclerosis (ALS)-associated patterns of brain alterations at the group level according to a neuropathological staging system. ObjectiveThe study was designed to investigate the in vivo staging in ALS patients with the C9orf72 expansion and potential differences to ALS patients with the SOD1 mutation. MethodsDTI-based white matter mapping was performed both by an unbiased voxel-wise statistical comparison and by a hypothesis-guided tract-wise analysis of fractional anisotropy (FA) maps according to the ALS-staging pattern for 27 ALS patients with C9orf72 expansion vs 15 ALS patients with SOD1 mutation vs 32 matched healthy controls. Clinical and neuropsychological data were acquired and correlated to DTI data. ResultsThe analysis of white matter integrity demonstrated regional FA reductions along the CST and also in frontal and prefrontal brain areas according to the proposed propagation pattern for the ALS patients with C9orf72 expansion and sporadic patients. This pattern could not be identified for the SOD1 mutation at the group level. In contrast, in the tract-specific analysis according to the neuropathological ALS-staging pattern, C9orf72 expansion ALS patients showed significant alterations of ALS-related tract systems similar to sporadic patients. ConclusionsThe DTI study including the tract-of-interest-based analysis showed a microstructural corticoefferent involvement pattern according to the staging scheme in C9orf72-associated ALS patients but not in the SOD1 mutation.

A Peptidylic Inhibitor for Neutralizing r(GGGGCC)exp-Associated Neurodegeneration in C9ALS-FTD

One drug, two diseases is a rare and economical therapeutic strategy that is highly desirable in the pharmaceutical industry. We previously reported a 21-amino acid peptide named beta-structured inhibitor for neurodegenerative diseases (BIND) that can effectively inhibit expanded CAG trinucleotide toxicity in polyglutamine (polyQ) diseases. Here we report that BIND also effectively inhibits GGGGCC repeat-mediated neurodegeneration in vitro and in vivo. When fused with a cell-penetrating peptide derived from the transactivator of transcription (TAT) protein of the HIV, TAT-BIND reduces cell death, formation of GGGGCC RNA foci, and levels of poly-GR, poly-GA, and poly-GP dipeptide proteins in cell models of C9ORF72-associated amyotrophic lateral sclerosis and frontotemporal dementia (C9ALS-FTD). We showed that TAT-BIND disrupts the interaction between GGGGCC RNA and nucleolin protein, restores rRNA maturation, and inhibits mislocalization of nucleolin and B23, which eventually suppresses nucleolar stress in C9ALS-FTD. In a Drosophila model of C9ALS-FTD, TAT-BIND suppresses retinal degeneration, rescues climbing ability, and extends the lifespan of flies. In contrast, TAT-BIND has no effect on UAS-poly-glycine-arginine (poly-GR)100-expressing flies, which generate only poly-GR protein toxicity, indicating BIND ameliorates toxicity in C9ALS-FTD models via a r(GGGGCC)exp-dependent inhibitory mechanism. Our findings demonstrated that, apart from being a potential therapeutic for polyQ diseases, BIND is also a potent peptidylic inhibitor that suppresses expanded GGGGCC RNA-mediated neurodegeneration, highlighting its potential application in C9ALS-FTD treatment.

Validation of a Long-Read PCR Assay for Sensitive Detection and Sizing of C9orf72 Hexanucleotide Repeat Expansions

A hexanucleotide GGGGCC repeat expansion in C9orf72 is the most common genetic cause of amyotrophic lateral sclerosis and frontotemporal degeneration. Accurate determination and quantitation of the repeat length is critical in both clinical and research settings. However, because of the complexity of the C9orf72 expansion with high GC content, large size of repeats, and high rate of insertions/deletions (indels) and sequence variations in the flanking regions, molecular genetic analysis of the locus is challenging. To improve the performance characteristics for clinical testing, we evaluated a commercially available long-read C9orf72 PCR assay for research use only, AmplideX PCR/CE C9orf72 assay (AmplideX-C9), and compared its performance with our existing laboratory-developed C9orf72 expansion procedure. Overall, in comparison to the laboratory-developed C9orf72 expansion procedure, AmplideX-C9 demonstrated a more efficient workflow, greater PCR efficiency for sizing of repeat expansions, and improved peak amplitude with lower DNA input and higher analytic sensitivity. This, in turn, permitted detection of indels in the 3' downstream of the repeat expansion region in expanded alleles, showed a higher success rate with formalin-fixed, paraffin-embedded tissue specimens, and facilitated the assessment of repeat mosaicism. In summary, AmplideX-C9 will not only help to improve clinical testing for C9orf72-associated amyotrophic lateral sclerosis and frontotemporal degeneration but will also be a valuable research tool to better characterize the complexity of expansions and study the effects of indels/sequence variations in the flanking region.

RAN translation at C9orf72-associated repeat expansions is selectively enhanced by the integrated stress response

Repeat-associated non-AUG (RAN) translation allows for unconventional initiation at disease-causing repeat expansions. As RAN translation contributes to pathogenesis in multiple neurodegenerative disorders, determining its mechanistic underpinnings may inform therapeutic development. Here we analyze RAN translation at G4C2 repeat expansions that cause C9orf72-associated amyotrophic lateral sclerosis and frontotemporal dementia (C9RAN) and at CGG repeats that cause fragile X-associated tremor/ataxia syndrome. We find that C9RAN translation initiates through a cap- and eIF4A-dependent mechanism that utilizes a CUG start codon. C9RAN and CGG RAN are both selectively enhanced by integrated stress response (ISR) activation. ISR-enhanced RAN translation requires an eIF2α phosphorylation-dependent alteration in start codon fidelity. In parallel, both CGG and G4C2 repeats trigger phosphorylated-eIF2α-dependent stress granule formation and global translational suppression. These findings support a model whereby repeat expansions elicit cellular stress conditions that favor RAN translation of toxic proteins, creating a potential feed-forward loop that contributes to neurodegeneration.

Phosphorylated neurofilament heavy chain: A biomarker of survival for C9ORF72-associated amyotrophic lateral sclerosis.

As potential treatments for C9ORF72-associated amyotrophic lateral sclerosis (c9ALS) approach clinical trials, the identification of prognostic biomarkers for c9ALS becomes a priority. We show that levels of phosphorylated neurofilament heavy chain (pNFH) in cerebrospinal fluid (CSF) predict disease status and survival in c9ALS patients, and are largely stable over time. Moreover, c9ALS patients exhibit higher pNFH levels, more rapid disease progression, and shorter survival after disease onset than ALS patients without C9ORF72 expansions. These data support the use of CSF pNFH as a prognostic biomarker for clinical trials, which will increase the likelihood of successfully developing a treatment for c9ALS. Ann Neurol 2017;82:139-146.