ID: 39779681
Title: A high-fidelity CRISPR-Cas13 system improves abnormalities associated with C9ORF72-linked ALS/FTD.
Abstract: An abnormal expansion of a GGGGCC (G4C2) hexanucleotide repeat in the C9ORF72 gene is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), two debilitating neurodegenerative disorders driven in part by gain-of-function mechanisms involving transcribed forms of the repeat expansion. By utilizing a Cas13 variant with reduced collateral effects, we develop here a high-fidelity RNA-targeting CRISPR-based system for C9ORF72-linked ALS/FTD. When delivered to the brain of a transgenic rodent model, this Cas13-based platform curbed the expression of the G4C2 repeat-containing RNA without affecting normal C9ORF72 levels, which in turn decreased the formation of RNA foci, reduced the production of a dipeptide repeat protein, and reversed transcriptional deficits. This high-fidelity system possessed improved transcriptome-wide specificity compared to its native form and mediated targeting in motor neuron-like cells derived from a patient with ALS. These results lay the foundation for the implementation of RNA-targeting CRISPR technologies for C9ORF72-linked ALS/FTD.

ID: 39779704
Title: Dual-targeting CRISPR-CasRx reduces C9orf72 ALS/FTD sense and antisense repeat RNAs in vitro and in vivo.
Abstract: The most common genetic cause of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) is an intronic G4C2 repeat expansion in C9orf72. The repeats undergo bidirectional transcription to produce sense and antisense repeat RNA species, which are translated into dipeptide repeat proteins (DPRs). As toxicity has been associated with both sense and antisense repeat-derived RNA and DPRs, targeting both strands may provide the most effective therapeutic strategy. CRISPR-Cas13 systems mature their own guide arrays, allowing targeting of multiple RNA species from a single construct. We show CRISPR-Cas13d variant CasRx effectively reduces overexpressed C9orf72 sense and antisense repeat transcripts and DPRs in HEK cells. In C9orf72 patient-derived iPSC-neuron lines, CRISPR-CasRx reduces endogenous sense and antisense repeat RNAs and DPRs and protects against glutamate-induced excitotoxicity. AAV delivery of CRISPR-CasRx to two distinct C9orf72 repeat mouse models significantly reduced both sense and antisense repeat-containing transcripts. This highlights the potential of RNA-targeting CRISPR systems as therapeutics for C9orf72 ALS/FTD.

ID: 41283823
Title: Amyotrophic lateral sclerosis in Saudi Arabia: a multicenter descriptive study.
Abstract: Amyotrophic lateral sclerosis (ALS) is a rare neurodegenerative disease characterized by the progressive loss of muscle control, leading to paralysis and death. While ALS has been extensively studied globally, little research has focused on ALS in the Middle East, specifically Saudi Arabia. This study aims to investigate the demographic data, clinical characteristics, disease progression, and prognosis of ALS patients in Saudi Arabia to better understand region-specific disease patterns and potential therapeutic strategies. Retrospective multicenter cohort across five tertiary Saudi centers (2003-2022). The authors identified cases from neurology/neuromuscular clinics and neurophysiology laboratories; diagnoses followed revised El Escorial criteria with EMG confirmation where indicated. ALS variants and cases lacking sufficient longitudinal evidence were excluded. Clinical genetic testing was performed at the clinician's discretion; variants were classified per ACMG and only pathogenic/likely pathogenic results were counted; C9orf72 repeat-expansion testing was not systematically available. Prespecified variables included demographics, family history, initial phenotype, MRI/EMG, genetics, treatments (riluzole, edaravone, SPT, tofersen for SOD1), times to noninvasive ventilation (NIV), gastrostomy and invasive ventilation. We included 270 patients (57% male). Mean age at first symptom was 51 years. Limb-onset occurred in 169/247 (68%) and bulbar-onset in 78/247 (32%). Among those with documented family history (97/270), 14% reported an affected relative. 37/270 underwent genetic testing; 56.7% were positive-most commonly OPTN (47.6.6% of positives) and SOD1 (38.1%). MRI brain/spine was normal in ∼53%. By 3 years from symptom onset, ∼80% of those who eventually required advanced support (NIV, invasive ventilation, and/or gastrostomy) had received it. Most patients were treated with riluzole. This study provides valuable insights into ALS in Saudi Arabia, contributing to a better understanding of the disease in this region. The younger age of onset and the high familial prevalence are notable findings that warrant further investigation. Future studies focusing on genetic and environmental influences in Saudi Arabia may help improve diagnosis and therapeutic approaches.

ID: 41341655
Title: C9orf72-related amyotrophic lateral sclerosis-frontotemporal dementia and links to the DNA damage response: a systematic review.
Abstract: The G4C2 repeat expansion in C9orf72 is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). While healthy individuals have fewer than 30 repeats, affected patients may carry hundreds to thousands. This expansion accounts for approximately 40% of familial ALS and 25% of familial FTD cases, and between 5 and 10% cases of sporadic ALS and FTD. Three overlapping pathological mechanisms have been proposed for the C9orf72 expansion: loss of function due to protein deficiency, gain of function through RNA foci, and the production of toxic dipeptide repeat proteins (DPRs) via repeat-associated non-ATG (RAN) translation. This systematic review investigates the role of DNA damage in C9orf72-related ALS-FTD. Analysis of twelve peer-reviewed studies showed that C9orf72 repeat expansions and DPRs compromise genome stability across four experimental models: human cell lines, induced pluripotent stem cell-derived neurons, rodent neurons, and postmortem tissue. We identified four mechanisms underlying DNA damage accumulation: disruption of the ATM pathway, impairment of DNA repair efficiency, formation of R-loops, and mitochondrial dysfunction with oxidative stress. In addition, several consequences of DNA damage were identified, including misrepair-mediated repeat expansion and activation of STING pathway. These findings highlight the key role of DNA damage in C9orf72-related pathology. Consistent with this, targeting DNA damage response factors extended lifespan and improved motor function in mouse models. This review highlights the contribution of DNA damage to C9orf72 pathology and suggest new therapeutic avenues, including personalized approaches based on genetic background.

ID: 41343108
Title: Distinct proteomic CSF profiles in genetic frontotemporal lobar degeneration.
Abstract: Fluid biomarkers to diagnose frontotemporal lobar degeneration (FTLD) are currently lacking. In this study, we aimed to identify proteomic changes in cerebrospinal fluid (CSF) associated with FTLD pathogenesis, focusing on signatures unique to different genetic groups. Additionally, we sought proteins distinguishing FTLD-spectrum disorders from controls. To this end, we measured a comprehensive library of over 2900 proteins in CSF using proximity extension assay technology in two well-characterized FTLD cohorts. The discovery cohort, selected from the GENFI cohort, included 47 symptomatic pathogenic variant carriers (22 C9orf72, 14 GRN, 10 MAPT and 1 TARDBP), 124 presymptomatic pathogenic variant carriers (55 C9orf72, 44 GRN, 24 MAPT and 1 TARDBP) and 57 healthy non-carriers. The validation cohort comprised individuals clinically diagnosed with an FTLD-spectrum disorder (n = 132) and cognitively intact controls (n = 32). We assessed differentially abundant proteins using linear regression, adjusting for age and sex. Overrepresentation analysis was conducted for the three genetic groups using Gene Ontology Biological Processes as ontology source. To develop diagnostic tools, we applied a LASSO regression, establishing two types of panels: one to distinguish individuals with an FTLD-spectrum disorder from controls (FTLD panel) and another to differentiate individuals with underlying TDP pathology from controls (TDP panel). We observed 23 dysregulated proteins in symptomatic carriers. Of these, four were also significantly dysregulated (NEFL, TPM3, MSLN and DNM3) in the validation cohort. When focusing on genetic subgroups, 63 upregulated proteins were observed in symptomatic MAPT carriers, with enriched biological pathways linked to immune function. In symptomatic C9orf72 carriers, four proteins - related to energy metabolism - were upregulated. When limiting symptomatic carriers to GRN, six proteins were dysregulated, with enriched pathways involved in neuronal development and projection. Notably, NEFL and TPM3 were consistently significant in all comparisons across both cohorts. We developed two diagnostic panels: one for FTLD and one for FTLD-TDP. The FTLD panel consisted of six proteins (NEFL, RBFOX3, NPTX1, TFF1, ENTPD5, and CNP). The TDP panel was made up of seven proteins (NEFL, RBFOX3, CBLN4, ENTPD5, CCL25, CNP, and MMP1). Both panels were successfully replicated in the validation cohort (AUC of 0.94 and 0.96 respectively). This study highlights distinct proteomic signatures across FTLD genetic subgroups and their associated pathologies using a targeted proteomic approach. Additionally, we present two diagnostic panels-comprising both established and novel proteins-that effectively differentiate individuals with FTLD-spectrum disorders from healthy controls, offering promising avenues for improved clinical diagnosis.

ID: 41500252
Title: Frontotemporal dementia: Clinical aspects, genetics, and neuropathology of a family with a C9ORF72 expansion in Argentina.
Abstract: Frontotemporal dementia (FTD) is the second most common cause of early-onset dementia, typically manifesting before the age of 65, with a mean onset at 58 years. FTD may encompass a spectrum of neurodegenerative disorders resulting from frontotemporal lobar degeneration (FTLD), affecting behavior, language, and motor function. Among its clinical variants, the behavioral variant (bvFTD) is the most frequently inherited, often associated with mutations in MAPT, GRN, and C9ORF72, the latter being the most prevalent genetic cause of FTD and FTD-motor neuron disease (FTD-MND). While bvFTD is classically defined by profound behavioral changes and executive dysfunction, cases linked to C9ORF72 expansions exhibit atypical neuropsychiatric features. This study documents two cases within the same family presenting with bvFTD and atypical parkinsonism, associated with a C9ORF72 expansion. Neurocognitive assessments, genetic testing, and neuroimaging (MRI, SPECT) were performed to characterize the clinical phenotype. A detailed review of the familial aggregation of neurodegenerative and psychiatric disorders provided further insight into the genetic contributions to symptomatology. The findings highlight the phenotypic heterogeneity associated with C9ORF72 expansions, demonstrating a spectrum ranging from bvFTD to atypical parkinsonism, with variable neuropsychiatric involvement. While movement disorders in FTD have historically been underestimated, these cases reinforce the association between parkinsonism and familial bvFTD. Given the limited epidemiological data on genetic FTD in Latin America, this study underscores the importance of genetic testing in cases with prominent behavioral and psychiatric symptoms, supporting early identification and genetic counseling for affected families.

ID: 41542616
Title: Identification of molecular and clinical ALS subgroups based on TDP-43 loss of function molecular markers from population-based patient-derived iPS motor neurons.
Abstract: Amyotrophic lateral sclerosis (ALS) is a uniformly fatal neurodegenerative disease characterized by progressive cortical and spinal motor neuron loss, with most patients surviving only 2-5 years post-diagnosis. While approximately 10% of cases are familial (fALS), the remaining 90% are sporadic (sALS) with unknown genetic drivers. Importantly, clinical presentations are heterogeneous in both sporadic and familial ALS, underscoring the complexity of the disease. A pathological hallmark of ALS is the mislocalization of RNA-binding protein TDP-43 from the nucleus to the cytoplasm. This mislocalization produces both loss of function consequences, such as widespread RNA processing and splicing defects, as well as potential toxic gain of function effects associated with cytoplasmic aggregation. In this study, we used RT-PCR data from induced pluripotent stem cell-derived motor neurons derived from 180 sALS and C9orf72 fALS patients from the Answer ALS collection to identify biological subgroups based on TDP-43 loss-of-function signatures. Spectral embedding revealed four distinct molecular clusters, including one subgroup genetically similar to controls and another with the most dysregulated mRNA expression, suggesting differing disease severity. Linear mixed models were then used to assess the longitudinal trajectory of over 90 clinical measures, and the between-cluster interaction effects were evaluated. 36 clinical outcomes showed significant differences across clusters, supporting the presence of biologically and clinically distinct ALS subtypes based on the TDP-43 associated pathogenic cascade. These findings demonstrate a critical role of RNA profiling in uncovering biologically meaningful subtypes of ALS, potentially allowing for more precise prognostic tools and the development of future personalized therapeutic approaches.

ID: 41643021
Title: Blocking RAN translation without altering repeat RNAs rescues C9ORF72-related ALS and FTD phenotypes.
Abstract: GGGGCC (G4C2) repeat expansion in C9ORF72 is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Toxicity is thought to result from the accumulation of either repeat RNAs and/or dipeptide repeat proteins (DPRs) translated from repeat-containing transcripts through repeat-associated non-AUG (RAN) translation. To disentangle RNA from DPR toxicity, we mutated a CUG codon predominantly used to initiate DPR translation from all three reading frames. This mutation disrupted DPR synthesis while preserving the expression of repeat-containing RNAs. Despite the accumulation of RNA foci, behavioral deficits and pathological abnormalities, including p-TDP-43 inclusions, STING activation, motor neuron loss, neuroinflammation, and increased plasma neurofilament concentration, were alleviated in C9ORF72 mice. Base editing of the CUG codon also improved molecular phenotypes and survival in patient induced pluripotent stem cell-derived neurons, which highlights the potential of therapeutically targeting DPR production rather than repeat RNAs.

ID: 41658940
Title: MicroRNA profiling in post-mortem spinal cord of C9ORF72-related ALS patients reveals molecular pathways involved in motor neuron degeneration.
Abstract: Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder causing progressive motor neuron death in cortex, brainstem and spinal cord. The most common genetic cause is the G4C2 hexanucleotide repeat expansion in the non-coding region of exon 1 of C9ORF72, accounting for ~40% of familial and ~7% of sporadic ALS. RNA dysregulation is increasingly recognized as a key contributor to ALS pathogenesis. This study aimed to identify specific microRNAs (miRNAs) involved in motor neuron degeneration in C9ORF72-ALS. We profiled 754 miRNAs in human post-mortem spinal cord tissue from C9ORF72-ALS patients and healthy donors. Laser capture microdissection isolated ventral horn regions, and in silico target prediction identified potential genes and pathways regulated by differentially expressed miRNAs. Target genes were validated by Real time PCR. Two subsets of miRNAs were exclusively expressed in ventral horn regions: miR-200b-3p and miR-346 in C9ORF72-ALS patients, and miR-30d-5p, miR-106b-5p and miR-135a-5p in healthy donors. Target prediction and molecular analysis identified putative genes and pathways linked to cell death, inflammation, protein metabolism, DNA modification, excitotoxicity, autophagy and vesicles trafficking. This study identifies specific miRNAs and their target genes as key molecules in motor neuron degeneration in C9ORF72-ALS. Restoring their expression could represent a therapeutic approach for ALS.

ID: 41674618
Title: Transcriptomic profiling uncovers mis-splicing and gene fusions in amyotrophic lateral sclerosis.
Abstract: Advances in transcriptomics have transformed our understanding of amyotrophic lateral sclerosis (ALS), a progressive neurodegenerative disease, revealing disrupted gene expression profiles and highlighting the multi-system biology of ALS. Despite major advances, transcriptomic studies have only begun to capture the complexity and the molecular hierarchy of transcriptomic alterations in ALS. To resolve and characterize the transcriptome in ALS, we performed a comprehensive reanalysis of bulk RNA sequencing from the New York Genome Center ALS Consortium cohort across five post-mortem tissues including motor and frontal cortex, cervical and lumbar spinal cord, and cerebellum. By deploying dual analytical pipelines - one reference-based to model canonical events and one de novo to detect transcript structural novelties - we disentangled the quantitative and qualitative architectures of ALS. Our reference-based analysis revealed that ALS transcriptome is defined primarily by splicing failure rather than changes in gene expression. Aberrant splicing events, particularly intron retention, outnumbered differentially expressed genes by an order of magnitude. This widespread loss of fidelity disproportionately affected RNA-binding proteins, suggesting a collapse in their autoregulatory feedback loops. Deconvolution of these signals identified distinct cellular vulnerabilities: transcriptional disruptions were enriched in glial cells in sporadic cases but in neuronal cells in C9ORF72-positive cases. Furthermore, we observed sex-specific dysregulation, with male patients exhibiting greater disruption in guanosine triphosphatase signaling and ciliary organization pathways. In parallel, our de novo analysis uncovered a significant burden of disease-specific gene fusions that were absent in controls. Whole-genome sequencing of the same individuals, together with a larger reference population confirmed that disease-specific fusions do not arise from genomic structural variants, indicating a transcriptional rather than genomic origin. Investigation into the mechanism of these RNA-based fusions revealed a critical deviation in splice site definition: while canonical splice junctions exhibit a high density of binding motifs for polyA-binding or 3'-cleaveage proteins approximately 50 base pairs upstream of the splice donor site (left junction), ALS-specific fusion junctions displayed a dramatic depletion of these motifs in the same region. Functionally, the presence of these sparse disease-specific fusions was strongly correlated with severe splicing outliers in genes governing guanosine triphosphatase activity, converging with the tissue- and male-specific defects identified in our reference-based analysis. Altogether, our results delineated a transcriptome characterized by aberrant splicing with tissue-and sex-specific changes and identified structural-variant-independent RNA fusions as candidate disease modifiers that may amplify pathology. This integrated view provides a mechanistic scaffold for splicing-centered and RNA-structural therapeutic strategies for ALS.

ID: 41757350
Title: C9orf72-ALS mutation drives basal mitophagy impairments in iNeurons.
Abstract: ALS is a neurodegenerative disorder characterized by progressive upper and lower motor neuron loss. A GGGGCC hexanucleotide repeat expansion (HRE) in the C9orf72 gene is the most common mutation found in populations of European descent. Mitochondrial dysfunction has been observed in C9orf72-ALS patients and models of the disease, however, reports on mitochondrial clearance via mitophagy in C9orf72-ALS are limited. iNeurons from C9orf72-ALS patients displayed reduced mitochondrial membrane potential and reduced basal mitophagy, due to reductions in autophagosome production and reduced ULK1 recruitment to mitochondria. No consistent changes to PINK1/Parkin or BNIP3 mitophagy pathways were observed. Our data show that certain aspects of mitochondrial function is impaired in C9orf72-ALS patient iNeurons. An in-depth characterization of mitophagy suggests that a deficit in autophagosome production is responsible and provides further evidence that toxic gain-of-function mechanisms in C9orf72-ALS are responsible for autophagy deficits.

ID: 41832177
Title: TYK2 mediates neuroinflammation in Alzheimer's disease brains with TDP-43 pathology.
Abstract: Neuroinflammation is a pathological feature of neurodegenerative diseases like Alzheimer's disease and ALS. Cytoplasmic dsRNA (cdsRNA) triggers a type-I interferon response in human neural cells, leading to their death, and is found in neurons of C9ORF72-ALS patients. Here, we report the spatial coincidence of cdsRNA and pTDP-43 inclusions in human postmortem tissue with Alzheimer's disease pathology, and upregulated interferon response genes in affected regions. CdsRNA also accumulates in a human TDP-43 G298S iPSC cortical neuronal model. We use cryptic exon detection as a proxy for TDP-43 mislocalization and demonstrate that FDA-approved JAK inhibitors baricitinib and ruxolitinib, which block interferon signaling, show protective effects only in brains with elevated cryptic exon expression. A CRISPR screen reveals TYK2 as a top hit, and TYK2 knockdown and the selective TYK2 inhibitor deucravacitinib rescue cdsRNA-induced toxicity. We find parallel neuroinflammatory mechanisms, dependent on TYK2 - a potential disease-modifying target - for TDP-43-associated Alzheimer's disease and C9ORF72-ALS.

ID: 41909467
Title: Exosome-like nanovesicles from acerola for CRISPR-Cas9 ribonucleoprotein delivery to the central nervous system.
Abstract: An aberrant six-base repeat in intron 1 of C9orf72 is the most frequent cause of solitary and familial amyotrophic lateral sclerosis and frontotemporal dementia. This mutation is a potential target for CRISPR/Cas9-based genome editing. However, the blood-brain barrier and limitations of current viral or nanoparticle-based delivery systems to neurons significantly restrict the clinical application of CRISPR-Cas9 in the brain. To address these challenges, we developed a drug delivery system using acerola-derived exosome-like nanoparticles (AELNs), which may overcome several limitations associated with human exosomes. AELNs stably form complexes with ribonucleoproteins (RNPs) comprised of Cas9 proteins and guide RNAs (gRNAs). We improved the delivery efficiency and selectivity of AELN/RNP complexes in GLP2-receptor-expressing neurons by incorporating GLP2 peptides into the AELN/RNP complexes. Intranasal administration of peptide-tagged AELN/RNP complexes in vivo confirmed the successful genome editing of C9orf72, demonstrating the potential of this system for treating neurodegenerative diseases. This study presents a potentially innovative approach for in vivo genome editing using a noninvasive delivery system.

ID: 41929290
Title: Pathology and genetics in a global cohort of Parkinsonian Disorders.
Abstract: Accurate diagnosis of neurodegenerative movement disorders is challenging because of a lack of in vivo biomarkers, overlapping clinical features and a delay in the emergence of pathognomonic features. To evaluate clinicopathological correlation, diagnostic accuracy, genetic association with pathology, and ancestry-related differences in a multi-ancestry brain bank cohort. Multicentre retrospective autopsy cohort study on donors enrolled between 1985 - 2024. 11 academic brain banks in the UK, US and Australia. Brain donors identified from participating brain banks with available brain tissue and a clinical diagnosis of Parkinson's disease, Parkinson's disease dementia, dementia with Lewy bodies, progressive supranuclear palsy, corticobasal syndrome, multiple system atrophy, or neurologically normal controls. Genetic variant carrier status and clinical diagnostic category. Clinical diagnostic accuracy; Lewy body and Alzheimer's disease pathology burden; survival; association with genetic variants and genetically inferred ancestry. We studied 3,353 brain donors (1281 [38.2%] female, mean [SD] age at death, 76.8 [10.6] years). Misdiagnosis rates for movement disorders ranged approximately from 10%-20%. Clinical diagnoses of dementia with parkinsonism (PDD/DLB) were more strongly associated with Lewy body pathology than Parkinson's disease without dementia (OR = 1·96, 95% CI = 1·30 - 3·04, p = 7·2e-04). Lewy pathology was identified in 4% of neurologically normal controls. Alzheimer's disease co-pathology was present in 40% of cases with Lewy body disease. GBA1 variant carriers exhibited greater Lewy body burden compared with noncarriers (OR = 1·94, 95% CI = 1·24 - 3·03, p = 0·01) or LRRK2 carriers (OR = 7·44, 95% CI = 2·16 - 25·64, p = 0·01). Pathological diagnoses differed by ancestry, with South Asian donors more likely to have progressive supranuclear palsy pathology and Ashkenazi Jewish donors more likely to have Lewy body disease (p < 0.0001), independent of GBA1 and LRRK2 mutation status. Our findings highlight the value of integrating genetic and pathological data to improve diagnostic accuracy. The high prevalence of Alzheimer's disease co-pathology and ancestry-related differences in pathology point to the need for biologically informed diagnostic tools. These results support the integration of genetically and pathologically stratified approaches, correlating pathology with in vivo biomarkers, for future therapeutic trials. Medical Research Council, Global Parkinson's Genetic Program/Aligning Science Across Parkinson's.

ID: 41961863
Title: Characterization of a C9orf72 Knockout Danio rerio model for ALS and cross-species validation of potential therapeutics screened in Caenorhabditis elegans.
Abstract: Intronic hexanucleotide repeat expansions in the C9orf72 gene represent the most common genetic cause of the neurodegenerative diseases amyotrophic lateral sclerosis (ALS) and frontotemporal dementia. This expansion decreases C9orf72 expression in affected patients, indicating that loss of C9orf72 function (LOF) acts as a pathogenic mechanism. Several models using Danio rerio (zebrafish) for C9orf72 depletion have been developed to explore disease mechanisms and the consequences of C9orf72 LOF. However, inconsistencies exist in reported phenotypes, and many have yet to be validated in stable germline ablation models. To address this, we created a zebrafish C9orf72 knockout model using CRISPR/Cas9. The C9orf72 LOF model demonstrates, in a generally dose-dependent manner, increased larval mortality, persistent growth reduction, and motor deficits. Additionally, homozygous C9orf72 LOF larvae exhibited mild overbranching of spinal motoneurons. To identify potential therapeutic compounds, we performed a screen on an established Caenorhabditis elegans (C. elegans) C9orf72 homologue (alfa-1) LOF model, identifying 12 compounds that enhanced motility, reduced neurodegeneration, and alleviated paralysis phenotypes. Motivated by the shared motor phenotype, 2 of those compounds were tested in our zebrafish C9orf72 LOF model. Pizotifen malate was found to significantly improve motor deficits in C9orf72 LOF zebrafish larvae. We introduce a novel zebrafish C9orf72 knockout model that exhibits phenotypic differences from depletion models, providing a valuable tool for in vivo C9orf72 research and ALS therapeutic validation. Furthermore, we identify pizotifen malate as a promising compound for further preclinical evaluation.

ID: 41986690
Title: Somatic mosaicism in ALS and FTD identifies focal mutations associated with widespread degeneration.
Abstract: Although mutations in many genes cause familial amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), most cases are sporadic (sALS and sFTD) with unclear etiology. Here we tested whether somatic mutations contribute to sALS and sFTD by deep targeted sequencing of 88 neurodegeneration-related genes in postmortem brain and spinal cord samples from 399 sporadic cases and 144 controls. Predicted deleterious somatic variants in ALS/FTD genes were observed in 2.1% of sporadic cases lacking deleterious germline variants. These variants occurred at very low allele fractions (typically <2%) and were often focal and enriched in disease-affected regions. Analysis of bulk RNA-sequencing data from an additional cohort identified deleterious somatic variants in DYNC1H1 and LMNA, genes associated with pediatric motor neuron degeneration. Targeted long-read sequencing further identified one sFTD case with de novo somatic C9orf72 repeat expansions. Together, these findings suggest that rare, focal somatic variants can contribute to sALS and sFTD and drive widespread neurodegeneration.

ID: 41996987
Title: Decoding RNA splicing pathology: Alternative splicing in amyotrophic lateral sclerosis and its therapeutic potential.
Abstract: Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder marked by progressive motor neuron loss, leading to muscle weakness, paralysis, and respiratory failure. Dysregulation of RNA metabolism and splicing has emerged as a central mechanism in ALS pathogenesis. TARDBP (TAR DNA-binding protein), FET family proteins (FUS, EWSR1, TAF15), SOD1 (Superoxide Dismutase 1), and C9orf72 (Chromosome 9 Open Reading Frame 72) are key genes associated with ALS that regulate RNA processing, alternative splicing, and nuclear-cytoplasmic transport. Mutations or mislocalization of these proteins result in nuclear loss-of-function and cytoplasmic gain-of-function toxicity, promoting protein aggregation, sequestering spliceosomal components, and impairing spliceosome assembly. This leads to the aberrant inclusion of cryptic exons in essential neuronal genes, such as STMN2 (Stathmin 2) and UNC13A (Unc-13 Homolog A), resulting in the production of truncated proteins, defective axonal maintenance, and impaired synaptic function. TDP-43 pathology, a hallmark of ALS, disrupts splicing and RNA transport, while C9orf72 repeat expansions and FET protein mutations exacerbate cytoplasmic aggregation and stress granule dynamics. Mutant SOD1 contributes via mitochondrial dysfunction, endoplasmic reticulum stress, and disrupted axonal transport. Therapeutic strategies targeting these mechanisms are advancing rapidly. Gene replacement therapy, which restores STMN2 expression, and antisense oligonucleotides (ASOs) targeting mutant transcripts show promise in preclinical and early clinical studies. Complementary approaches, including the inhibition of stress kinases and the activation of autophagy, reduce cytoplasmic protein aggregation and support neuronal homeostasis. This review provides a comprehensive overview of RNA splicing regulation, spliceosomal dysfunction, and cryptic exon incorporation in ALS. Understanding the interplay among splicing defects, RNA-binding protein pathology, and neuronal degeneration is critical for developing next-generation multimodal therapies to restore RNA processing, reduce toxic protein accumulation, and promote motor neuron survival.

ID: 42014727
Title: A framework for the exploration of subcellular compartmentalization of RNA-binding proteins.
Abstract: The ability of RNA-binding proteins to form complexes with other biomolecules underpins a broad range of structural properties and functions. Understanding the subcellular distribution of RNA-binding proteins and their interacting partners in the steady state and upon perturbation can therefore shed light on these aspects. Here, we present the compartmentalized RNA-Binding Protein (or coRBP) map, an experimental resource and analytical pipeline to study subcellular RNA-binding proteins through multimodal dataset integration and machine learning. Using this approach, we generate a dataset of 1,768 known and putative RNA-binding proteins distributed in a broad panel of subcellular compartments and delineate their intermolecular and intercompartmental relationships. We also establish a hierarchy of RNA-binding protein-containing complexes at multiple scales across the cell, which suggests additional functions for multiple RNA-binding proteins. Furthermore, we investigate changes in RNA-binding protein complex composition and subcellular distribution in response to C9ORF72-associated amyotrophic lateral sclerosis/frontotemporal dementia dipeptide repeats and DNA damage stress. The coRBP map provides a resource to study the roles of RNA-binding proteins in homeostasis and disease.

ID: 42033225
Title: Direct targeting of C9ORF72 repeat RNA with fluorinated antisense oligonucleotides.
Abstract: Hexanucleotide repeat expansions in the C9ORF72 gene are the most common genetic cause of amyotrophic lateral sclerosis and frontotemporal dementia. These expansions give rise to pathogenic sense and antisense repeat RNAs that form nuclear foci and undergo repeat-associated non-AUG translation, producing dipeptide repeat proteins with cellular toxicity. Directly targeting the causative repeat RNAs with antisense oligonucleotides represents a promising therapeutic strategy. One barrier to further development is the propensity of this G-rich repeat-containing RNA target to form stable secondary structures, which may hinder efficient hybridization. In this study, we designed a panel of fluorine-modified ASOs that target the sense repeat expansions. We identified C-rich F-ASO gapmers that reduced translation from sense repeat RNAs in a cell-based reporter assay and lowered the RNA foci burden in patient-derived cells. Structural analyses in vitro revealed that the 2'F-RNA gapmer formed a stable hairpin structure. Our results demonstrate that structural properties of fluorine modifications can be leveraged for effective binding of repeat RNA and highlight the potential for F-ASOs to serve as therapeutic tools when targeting toxic repeat RNAs in C9ORF72-mediated FTD/ALS and other repeat expansion diseases.

ID: 42051912
Title: Amyotrophic lateral sclerosis and chronic inflammatory demyelinating polyneuropathy coexistence in a patient with a C9orf72 variant: case report.
Abstract: The C9orf72 variation has been strongly implicated in the inheritance of familial ALS, frontotemporal dementia (FTD), and combined ALS-FTD cases. Increasing evidence implicates immune changes and inflammation in some ALS patients. Several studies demonstrated that ALS coexists with CIDP or polyneuropathy. Mouse models of C9orf72 loss-of-function mutations exhibit fatal immune dysregulation. A 62-year-old Caucasian man developed right foot drop, and he underwent fibular nerve release without significant improvement. At the same time, he developed progressive weakness and numbness in his bilateral hands. MRI revealed cervical canal stenosis and neuroforaminal narrowing that prompted neurosurgical decompression without clinical improvement. Subsequently, he developed left foot drop. At the clinic presentation, he exhibited dysarthria, tongue fasciculations, weakness in all extremities, muscle atrophy, widespread fasciculations, and upper extremity hyperreflexia, meeting clinical criteria for ALS. Genetic testing identified a pathogenic variant in the C9orf72 gene, confirming a C9orf72 variant, commonly linked to familial ALS. Brain MRI demonstrated the motor band sign. Although EMG/NCS findings were consistent with lower motor neuron disease, he also had signs of demyelinating polyneuropathy based on conduction parameters. Neuromuscular ultrasound showed significant multifocal nerve enlargement typical of immune-mediated neuropathy. CSF studies revealed albuminocytologic dissociation (protein: 112 mg/dL, with normal cell count) and high albumin quotient and index. He fulfilled the 2021 EAN/PNS criteria for possible typical CIDP. He was treated with intravenous immunoglobulin in addition to riluzole with temporary improvement. This is the first case of the co-existence of CIDP and ALS in the setting of a pathogenic C9orf72 variant.

ID: 42087256
Title: Targeting the integrated stress response or Ataxin-2 alleviates neurodegeneration in PolyGR models of C9orf72 associated frontotemporal dementia and amyotrophic lateral sclerosis.
Abstract: Frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) are fatal, early-onset neurodegenerative diseases. The most common genetic cause of FTD and ALS is a G4C2 hexanucleotide repeat expansion in the C9orf72 gene. This mutation leads to the production of toxic dipeptide repeat proteins (DPRs), via repeat-associated non-AUG (RAN) translation. These DPRs disrupt stress granule (SG) dynamics, with SG regulators such as Ataxin-2 (ATXN2) implicated in disease risk. The integrated stress response (ISR), a key driver of SG formation via eIF2α phosphorylation, has been linked to C9orf72 expansions, but the role of individual DPRs in ISR activation remains unclear. Here, using Drosophila models expressing physiologically relevant repeat length DPRs, we identify poly(GR) as a novel activator of the ISR, inducing early and sustained eIF2α phosphorylation and SG accumulation prior to motor decline. Genetic inhibition of the ISR or knockdown of ATX2, the Drosophila orthologue of ATXN2, rescues motor deficits in these models. ATXN2 knockdown also reduces poly(GR) toxicity in mouse primary neurons. These findings position poly(GR) as a key driver of ISR activation and highlight ATXN2 and the ISR as promising therapeutic targets in C9orf72-associated FTD/ALS.

ID: 42095061
Title: Systematic proteomics reveals plasma NEFL as a robust predictor and pathological associate in C9ORF72-related neurodegeneration.
Abstract: The C9ORF72 repeat expansion is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). While neurofilament light chain (NEFL) is an established biomarker of neuroaxonal damage, its specific dose-response relationship with the C9ORF72 expansion and its potential role beyond a passive bystander require systematic investigation. We performed a proteome-wide screen to identify plasma proteins linked to the C9ORF72 expansion and evaluated their predictive value for motor neuron disease (MND). We utilized whole-genome sequencing and plasma proteomics from the UK Biobank, analyzing 106 individuals with C9ORF72 expansions (defined as >30 repeats) and 212 age- and sex-matched controls. We screened ~3,000 proteins for associations with the continuous repeat count. The top candidate was evaluated using restricted cubic splines (RCS) to assess non-linearity and threshold effects. Its ability to independently predict MND risk was tested using regression models and a machine learning approach. Our unbiased screen identified NEFL as the sole protein significantly associated with the C9ORF72 repeat count (FDR-adjusted P = 8.39 × 10-4). NEFL levels demonstrated a step-wise increase with expansion size, which followed a stable linear trajectory across the repeat spectrum (P non - linear = 0.4435). Elevated NEFL independently predicted MND risk (OR = 2.42; HR = 2.90), even after adjusting for the C9ORF72 repeat count. Our predictive model, combining NEFL and repeat count, achieved an AUC of 0.941 with 100% sensitivity. These findings align with emerging evidence that secreted NEFL may actively modulate neuroinflammation. NEFL emerges as a robust and specific plasma biomarker for C9ORF72-related neurodegeneration. Its strong linear association with repeat burden and independent predictive power, contextualized within its potential role in immune activation, suggest that NEFL is deeply integrated into the C9ORF72 pathological landscape. These findings support NEFL-based screening and monitoring strategies for early intervention in C9ORF72 carriers.

ID: 42102258
Title: King's stages of amyotrophic lateral sclerosis: an 18F-FDG-PET study of brain connectivity.
Abstract: Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease affecting upper and lower motor neurons. TAR DNA-binding protein 43 (TDP-43) proteinopathy is the neuropathological signature of the disease, and 18F-fluorodeoxyglucose PET (18F-FDG-PET) serves as a marker of neurodegeneration in vivo. The aim of the present cross-sectional study was to disentangle 18F-FDG-PET correlates of disease severity assessed through the King's staging system, by exploring connectivity changes across motor stages. Patients with ALS classified as King's stage 1, 2 or 3, who underwent brain 18F-FDG-PET at diagnosis from 2008 to 2022 at the ALS Centre of Turin, were included. A multiple regression analysis to evaluate the relationship between brain metabolism and King's stage was performed. The clusters showing significant results were used as seed regions in an interregional correlation analysis (IRCA), performed for each stage. Of a total of 832 patients with ALS, 337 were classified as King's stage 1, 274 as stage 2 and 221 as stage 3. The three groups significantly differed in age at PET, disease duration and total ALS Functional Rating Scale Revised (ALSFRS-R) score at the time of PET, C9orf72 status and the distribution of cognitive categories. We found a decreasing metabolic gradient from King's stage 1 to King's stage 3 in a cluster encompassing motor and cognitive areas. As King's stage increases, we found a decrease of connectivity within the sensorimotor and cognitive areas. The IRCA also showed the connectivity of motor and cognitive regions with temporal and cerebellar regions. The connectivity with temporal regions found in King's stage 1 decreases in King's stage 2 and finally, disappears in King's stage 3. The connectivity with the cerebellum occurs in King's stage 2 and decreases in King's stage 3. The changes of connectivity of motor and cognitive areas with temporal and cerebellar regions among different King's stages might reflect the spread of TDP-43 proteinopathy or a compensatory mechanism, respectively. The present study suggests that 18F-FDG-PET imaging of the brain may be integrated with the King's staging system to assess the extent of the pathogenic process in the context of clinical trials.

ID: 42103041
Title: Multimodal strategies for diagnosis, stratification, and therapeutic monitoring in ALS.
Abstract: Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder of motor neurons (MN) that is currently diagnosed through a prolonged process of exclusion, often delaying intervention. This review provides an overview of fluid, imaging, electrophysiological, and genetic biomarkers, explicitly linking each modality to early detection, patient stratification, disease monitoring, therapeutic development, and clinical trial design. Fluid biomarkers (i.e., neurofilament light chain, phosphorylated neurofilament heavy chain, inflammatory cytokines, microRNAs, and proteins in blood or cerebrospinal fluid) reflect neuronal injury and/or disease activity, enabling early identification of pres-ymptomatic individuals and longitudinal tracking of neurodegeneration. Imaging biomarkers, such as structural and diffusion MRI of the motor cortex, corticospinal tracts, and spinal cord, as well as PET imaging neuroinflammation or metabolism, provide objective measures of MN degeneration and extra-motor involvement. Electrophysiological biomarkers, including high-density electromyography, motor unit number, transcranial magnetic stimulation, and electrical impedance myography, quantitatively assess upper and lower MN loss and functional reserve. Genetic biomarkers, encompassing variants in genes such as C9orf72, SOD1, FUS, and TARDBP, enable presymptomatic screening and molecular stratification. In this context, transposable elements have emerged as an additional layer linking genomic variation and RNA dysregulation. We highlight the importance of multimodal and stage-specific biomarker integration to improve diagnostic accuracy and illuminate distinct disease phases. This approach supports stratification by progression rate or molecular subtype, enrichment of clinical trial cohorts, and the development of surrogate endpoints. We conclude by discussing current challenges, including disease heterogeneity and assay standardization, and outline future directions toward biomarker-driven precision medicine in ALS.

ID: 42113599
Title: Amyotrophic Lateral Sclerosis: A Review.
Abstract: Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by progressive weakness due to degeneration of upper motor neurons in the brain and lower motor neurons in the brainstem and spinal cord. It affects approximately 25 000 individuals in the United States. Amyotrophic lateral sclerosis is characterized by progressive painless muscle weakness that typically begins in a focal region of the body, such as limb muscle weakness causing hand weakness or foot drop (65%), cranial muscle weakness causing speech or swallowing problems (20%-25%), or axial muscle weakness causing bent posture (5%-10%), and spreads to other body regions over time. The disease usually manifests with dysfunction indicative of both upper motor neurons (causing muscle stiffness and spasticity) and lower motor neurons (causing weakness, fasciculations, atrophy, and flaccidity). After onset, weakness spreads through the musculature and typically causes death due to respiratory muscle weakness. Among people with ALS, approximately 85% have sporadic ALS, which is not associated with known environmental or genetic factors, and 15% have familial ALS. Amyotrophic lateral sclerosis is diagnosed based on clinical features, which can be supported by results of electromyography. More than 60 genes have been associated with ALS, and most are autosomal dominant. Pathogenic variants in chromosome 9 open reading frame 72 (C9orf72) are found in 40% of all familial ALS cases, and pathogenic variants in superoxide dismutase 1 (SOD1) are found in 20% of patients with familial ALS. Patients with ALS survive a mean of 3 to 5 years after diagnosis, and there are currently no curative therapies. Clinical care primarily focuses on symptom management and quality of life. Three US Food and Drug Administration (FDA)-approved disease-modifying therapies are available in the United States. Riluzole and edaravone are oral medications that slow ALS progression by up to 2 to 4 months, and tofersen is an intrathecally administered gene therapy for patients with SOD1 gene variants. Specialized multidisciplinary teams, comprising neurologists, nurses, therapists, dietitians, and social workers, are associated with improved survival (4-7 months) and quality of life. Amyotrophic lateral sclerosis is a progressive and fatal neurodegenerative disorder of upper and lower motor neurons. No curative therapies exist. Two oral medications, riluzole and edaravone, are approved by the FDA and modestly decrease disease progression in sporadic ALS. Tofersen, an intrathecally administered gene-based therapy, is also FDA approved and slows disease progression in patients with SOD1 pathogenic gene variants.

ID: 42123659
Title: Cumulative Incidence in Monogenic Alzheimer's Disease and Frontotemporal Dementia: Gene-Gene Interaction Effect.
Abstract: Monogenic forms of Alzheimer's Disease (AD) and Frontotemporal Dementia (FTD) represent the two principal neurodegenerative disorders leading to early-onset dementia, primarily linked to mutations in key AD- and FTD-associated genes. The marked heterogeneity in age at onset and penetrance among carriers of pathogenic mutations suggests that monogenic variants act within a broader polygenic background. The combined impact of AD- and FTD-related genetic variation on disease incidence in monogenic forms remains largely unexplored. Herein, we investigate gene-gene interaction patterns in monogenic AD and FTD, with a focus on genetic variability in key AD (APP, PSEN1, PSEN2) and FTD (MAPT, GRN, C9orf72)-associated genes and their association with cumulative disease incidence. Within the GARDENIA Consortium, we studied 426 individuals from Italian pedigrees, including patients (n = 319) and presymptomatic (n = 107) carriers of causative variants in APP (n = 39), PSEN1 (n = 71), PSEN2 (n = 13), MAPT (n = 29), GRN (n = 188), and C9orf72 (n = 86). Age at symptoms onset, age at last follow-up and sex were recorded. Whole exome sequencing was performed, focusing on non-causative variants (n = 64) in the key AD (APP, PSEN1, PSEN2) and FTD genes (MAPT, GRN, C9orf72). Weighted genetic burden scores were derived using Fine-Gray competing risk models to estimate variant-specific effects on cumulative AD and FTD incidence, accounting for mutually exclusive outcomes and family clustering. Model fit was evaluated using Akaike Information Criterion. Higher AD-risk-weighted burden scores in AD-related genes were associated with a significantly increased cumulative incidence of AD, while higher FTD-risk-weighted scores in FTD-related genes showed a trend toward association with increased cumulative incidence of FTD. A significant interaction between burden scores was observed. AD and FTD burden scores showed a negative interaction for AD (~79% attenuation) but a modest synergistic effect for FTD (~6% increase). These findings could imply context-dependent pleiotropy rather than simple additive genetic effects. Our study suggests that even in carriers oh highly penetrant AD or FTD causative variants, genetic background could substantially modulate cumulative disease incidence. Integrating polygenic information with monogenic status may improve prognostic stratification and inform precision approaches in dementia research and clinical trials.

ID: 42127907
Title: S-acylation of TDP43 regulates its condensation in amyotrophic lateral sclerosis.
Abstract: TDP43 inclusion bodies are widely present in the majority of patients with familial and sporadic amyotrophic lateral sclerosis (ALS). The mechanisms regulating TDP43 solubility remain incompletely understood. Here, we report that TDP43 undergoes S-acylation primarily at the Cys244 residue by the S-acyltransferase zDHHC23. This S-acylation maintains the liquid-like properties of TDP43 by reducing the aberrant interaction with poly(ADP-ribose) polymerase 1 (PARP1) and PARylated proteins, thereby countering the pathological condensation of TDP43. S-acylation-deficient TDP43 inclusions sequester the translational machinery and inhibit cytoplasmic protein translation, ultimately resulting in neurotoxicity. Importantly, TDP43 S-acylation is decreased in the familial ALS-associated TDP43 mutants as well as in SOD1-G93A mice and C9orf72-ALS induced pluripotent stem cell (iPSC)-derived neurons, suggesting the widespread involvement of TDP43 S-acylation in ALS pathogenesis. Our findings reveal an undescribed modification of TDP43 and provide deeper insight into the regulation of TDP43 pathological condensation in ALS.

ID: 42145633
Title: Functional Activity of TDP-43: A Direct Biomarker for ALS.
Abstract: TDP-43 dysfunction is a defining feature of amyotrophic lateral sclerosis (ALS), yet no biofluid biomarker directly measures its functional activity. We developed a serum-based homogeneous time-resolved FRET (hTR-FRET) assay that quantifies TDP-43 RNA-binding activity using synthetic UU rich RNA probes. We analyzed 1,080 serum samples from controls, sporadic ALS, and genetic subgroups (C9orf72, SOD1) across multiple biorepositories. Cross-sectionally, TDP-43 ligation activity was elevated in ALS (mean 390 a.u.) versus controls (304 a.u.), yielding AUC = 0.79. Genotype means were 392 a.u. (sporadic), 382 a.u. (C9orf72), and 323 a.u. (SOD1); with a 366 a.u threshold achieved 95% specificity against controls. Longitudinally, Target ALS showed a modest but significant inverse correlation between TDP-43 activity and ALSFRS-R, while other cohorts exhibited similar non-significant trends. Elevated signal likely reflects increased extracellular, probe-competent TDP-43 species. This assay provides direct functional measurement of disease-relevant TDP-43 biology, supporting applications in diagnostic discrimination, genotype stratification, and progression monitoring in prospective studies.

ID: 42147445
Title: Arrayed dual-gRNA CRISPR screening platform for C9orf72 repeat expansion excision in patient iPSCs.
Abstract: An intronic hexanucleotide repeat expansion in C9orf72 is the leading genetic cause of both frontotemporal dementia and amyotrophic lateral sclerosis (C9-FTD/ALS). We have previously demonstrated that CRISPR-Cas9 excision of the repeat expansion in patient iPSCs reverts pathological hallmarks of C9-FTD/ALS. Here, we aim to identify efficient and safe gRNAs for CRISPR-spCas9 dual-gRNA excision of the C9-repeat expansion. Utilizing novel ddPCR and single-molecule sequencing assays, we screened 120 gRNA pairs, comparing 64 bi-allelic, intronic excisions of the repeat region to 56 allele-specific excisions of the mutant allele in patient iPSCs, ranking them by efficiency. Bi-allelic excisions of the intronic repeat region were more efficient than excisions of the mutant allele. Single gRNA indel rates can nominate likely efficient gRNA pairs, but these pairs must be tested empirically. The length of the repeat expansion did not impact excision efficiency; rather, the activity of individual gRNAs drove excision efficiencies. Using whole genome sequencing and INDUCE-seq, we found only one detectable off-target of those nominated by Cas-OFFinder and CHANGE-seq across 4 of the most efficient gRNAs. This study advances the development of targeted therapies for C9-FTD/ALS and establishes a framework for dual-gRNA screening in patient iPSCs applicable to other repeat expansions.

ID: 42217760
Title: Fluid-based biomarkers of amyotrophic lateral sclerosis: recent advances and future prospects.
Abstract: Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disorder with no definitive cure. The absence of specific diagnostic biomarkers leads to diagnostic delays, hindering early intervention and management. This review provides a critical appraisal of fluid-based biomarkers for ALS across multiple sources-cerebrospinal fluid (CSF), blood, urine, saliva, and tears-with emphasis on their diagnostic and prognostic potential, limitations, and readiness for clinical translation. While neurofilaments (NfL, pNfH) are well-established as sensitive indicators of neuroaxonal injury and are increasingly used as prognostic and pharmacodynamic markers in clinical trials, they lack disease specificity. Biomarkers reflecting ALS-specific pathology, such as TDP-43 species and C9orf72 dipeptide repeat proteins (DPRs), show promise but remain in early validation stages with limited multicenter data. Emerging markers from non-invasive sources (urine p75ECD, salivary chromogranin A, tear metabolomics) offer potential for repeated sampling but require rigorous external validation before clinical adoption. To address current gaps, we introduce a standardized evidence grading framework (Tier 1-3) and a comprehensive reporting template for biomarker studies, including explicit performance metrics (AUC, sensitivity, specificity, confidence intervals) and validation status. We also propose minimum reporting standards for study design, pre-analytical variables, and statistical rigor, modeled on REMARK guidelines. A roadmap for biomarker validation and a cross-fluid comparison matrix are provided to guide future research. Despite considerable progress, significant challenges remain, including biological heterogeneity, pre-analytical variability, and insufficient external validation. Future efforts should prioritize multicenter prospective studies, assay harmonization, ethical frameworks for early diagnosis, and integration of emerging technologies such as artificial intelligence and digital twins. Fluid-based biomarkers, while not yet replacing clinical evaluation, are essential tools for accelerating drug development, enabling patient stratification, and moving toward personalized medicine in ALS.

ID: 42222887
Title: Multimodal analysis of cell-free DNA identifies epigenetic biomarkers for amyotrophic lateral sclerosis diagnosis and progression.
Abstract: The role of the epigenome in age-related neurodegenerative disorders remains understudied. Here, we analyzed circulating cell-free DNA (cfDNA) from blood to detect methylation changes as a liquid biopsy for Amyotrophic Lateral Sclerosis (ALS). Our study included 20 patients with sporadic ALS, 10 patients with C9orf72-associated ALS, 10 asymptomatic carriers of the C9orf72 repeat expansion mutation, and 21 nondisease control individuals. Following targeted enzymatic methyl-sequencing (EM-seq) of approximately 4 million CpG sites, we detected numerous differentially methylated genes, including several implicated in ALS disease risk and pathogenesis. By integrating multiple epigenetic features, we delineated a distinct epigenetic signature, which achieved an average area under the curve (AUC) of 0.91 ± 0.10 upon receiver operator characteristic (ROC) analysis, which enabled detection of approximately 70% of patients with ALS with close to 100% specificity. Furthermore, we also identified a set of genes whose methylation status significantly correlated with clinical disease progression and cerebrospinal fluid (CSF) neurofilament levels. Our results reveal the potential of cfDNA-based biomarkers to accurately diagnose ALS and potentially predict disease progression.

ID: 42296226
Title: Innate immune signaling as a potential pathomechanistic biomarker for distinct subtypes in amyotrophic lateral sclerosis.
Abstract: Stimulation of the innate immune system has been implicated in ALS and particularly in distinct monogenic forms of ALS. To address whether this is of diagnostic value, we performed a proof-of concept study using qPCR to assess the Interferon score in blood samples of genetic ALS. 56.5% of genetic ALS patients showed significant IFN activation, highest in C9orf72HRE patients (77.3%). About half of FUS-ALS (52.2%), but none of SOD1-ALS patients demonstrated pathological IFN scores. The IFN score significantly correlated with the ALSFRS-R slope and inversely with the time to severe event as a survival surrogate in this genetic ALS cohort. IFN + patients were more likely to be male, showed more rapid disease progression and higher neurofilament levels. The IFN score might have the potential as a stratification and readout tool for biomarker-guided individualized therapy in ALS.

ID: 42315356
Title: Strategic Amyotrophic Lateral Sclerosis Australia-Systems Genomics Consortium (SALSA-SGC): cohort profile.
Abstract: Amyotrophic lateral sclerosis (ALS) is a rapidly progressive neurodegenerative motor neuron disease (MND) with heterogeneity in disease onset, progression and treatment response. The Strategic ALS Australia-Systems Genomics Consortium (SALSA-SGC) was established in recognition of the need for large data sets of clinical data matched with biological samples to enable and foster ALS research and better understanding of aetiology and biological mechanisms. SALSA-SGC brought together the major Australian MND clinics to set up sustainable infrastructure that could facilitate long-term human ALS research and clinical trials nationally and internationally. Between April 2016 and December 2024, SALSA-SGC recruited 1813 participants, including 1386 ALS/MND cases, 388 controls and 39 others (asymptomatic relatives and ALS mimics). Clinical data and biospecimens are available for 1333 and 1189 ALS cases, respectively, with longitudinal data spanning 4442 total clinic visits and 3201 samples. An open-access online data explorer showcases collected datasets. Detailed clinical and questionnaire data allow an in-depth description of the cohort, informing clinical and health policy research. Screening for known ALS large-effect risk variants identified 125 mutation carriers (11.5% from N=1059), including 70 with C9orf72 expansions. Single Nucleotide Polymorphism (SNP)-array data (N=1088 cases; N=244 controls) have supported multiple published studies. SALSA-SGC resources are actively used by national and international researchers. Ongoing efforts aim to expand recruitment into regional Australia and enhance sample processing for cell-based studies. The SALSA-SGC resource is accessible by researchers under agreements governed by participant consent, human ethics committee guidelines and agreed use of data and samples.

ID: 42316301
Title: Intrathecal (G4C2)149 delivery in C9orf72-deficient mice yields mild motor dysfunction and ALS/FTD pathological hallmarks.
Abstract: A repeat expansion in C9ORF72 is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), yet existing mouse models incompletely engage spinal regions implicated in disease. Here, an adeno-associated virus encoding (G4C2)149 repeats was delivered via neonatal intrathecal injection, achieving widespread CNS expression with robust spinal cord targeting. This approach was applied to mice with graded loss of endogenous C9orf72 to interrogate both gain- and loss-of-function mechanisms. Longitudinal motor, behavioral, and pathological analyses revealed that repeat expression primarily drives mild, progressive muscle weakness, whereas coordination deficits were largely genotype dependent. Subtle gait abnormalities and hyperactivity were also observed. Within spinal motor regions, repeat-expressing mice exhibited dipeptide repeat protein accumulation, reduced NeuN-positive area, fewer motor neurons, glial activation, sparse phosphorylated TDP-43 pathology, and increased cryptic TDP-43 splicing. Cross-domain correlations further linked repeat expression, spinal pathology, and motor dysfunction. Collectively, these findings establish that CNS-wide repeat expression combined with reduced C9orf72 produces a coherent, mild ALS/FTD model.

ID: 42331066
Title: Fibroblasts carrying intermediate C9orf72 hexanucleotide repeat expansions from iNPH patients show changes in energy metabolism but no cell pathologies.
Abstract: Long C9orf72 hexanucleotide repeat expansions (C9-HRE) are the most common genetic cause of frontotemporal dementia (FTD), a group of neurodegenerative syndromes leading to cognitive dysfunction and frontal and temporal atrophy. FTD is a potential comorbidity of idiopathic normal pressure hydrocephalus (iNPH) and carrying the C9-HRE can modify the age-of-onset in iNPH patients. While intermediate-length C9-HRE (<30 repeats) are often considered non-pathogenic, the exact pathological cutoff is unclear. In this study, we assessed whether skin fibroblasts from iNPH patients carrying intermediate C9-HRE display C9-HRE-associated pathological hallmarks and changes in cellular function. C9-HRE-associated RNA foci, present in the long (>60 repeats) C9-HRE carrier fibroblasts, were not detected in those of the intermediate carriers. The number of p62-positive puncta was significantly increased in long but not intermediate C9-HRE carrier fibroblasts, in line with p62-positive intracellular inclusions observed in a brain biopsy from the patient. Induction of autophagy did not suggest any defects in the intermediate carrier fibroblasts. Fibroblasts from the intermediate C9-HRE carriers showed upregulated glycolytic activity, possibly to counteract the slightly reduced mitochondrial respiration. This could not be observed in the long C9-HRE carrier fibroblasts. In conclusion, these data suggest that while the long C9-HRE leads to more severe cellular pathologies than intermediate C9-HRE, the latter might predispose cells to deficits in specific cellular functions, such as energy metabolism.

ID: 42334646
Title: Behavioral variant frontotemporal dementia associated with a NEK1 missense variant: exploring a possible phenotypic association.
Abstract: NEK1 variants are recognized genetic contributors to amyotrophic lateral sclerosis (ALS) and have occasionally been reported within the ALS-frontotemporal dementia (FTD) spectrum. However, their association with isolated behavioral variant frontotemporal dementia (bvFTD) remains unclear. Here, we describe a 69-year-old man who developed progressive behavioral symptoms beginning in his early 60s. Cognitive evaluation demonstrated reduced verbal fluency with relative preservation of memory functions. Structural and functional neuroimaging demonstrated right-predominant frontotemporal atrophy and hypometabolism. Genetic testing for common FTD-associated genes (MAPT, GRN, and C9orf72) was negative. Whole-exome sequencing identified a heterozygous NEK1 c.899T > C (p.Ile300Thr) missense variant, currently classified as a variant of uncertain significance. This observation raises the possibility that NEK1-associated disease may extend beyond ALS or ALS-FTD phenotypes and may include isolated bvFTD presentations. However, further genetic and functional studies are required to clarify the clinical significance of this variant.

ID: 42348055
Title: Clinical and literature insights into the frontotemporal dementia and motor neuron disease spectrum.
Abstract: Frontotemporal dementia represents a heterogeneous group of neurodegenerative disorders primarily affecting the frontal and temporal lobes. The overlap between FTD and motor neuron disease is increasingly recognized, presenting a complex clinical syndrome characterized by progressive cognitive, behavioral, and motor decline. We describe a 69-year-old patient with a 4-year history of excessive ambulation. Over the last year, behavioral changes including disorganized conduct, irritability, spitting, and cold water foot immersion developed. The patient experienced compelling auditory hallucinations driving her to walk continuously for up to 10 h per day. Four months prior to admission, gait impairment with frequent falls, along with hyperorality developed. Neurological examination revealed asymmetric mild weakness, marked muscle atrophy of facial and limb muscles, hyperreflexia, and impaired postural control. Brain MRI showed diffuse cerebral atrophy; electrophysiological studies indicated probable motor neuron disease; and TRODAT SPECT demonstrated impaired presynaptic dopaminergic function bilaterally, consistent with parkinsonism. Final diagnosis was frontotemporal dementia with probable motor neuron disease. A review of the literature highlights the clinical, radiological, and molecular features of FTD-MND overlap, emphasizing the role of TDP-43 pathology, C9orf72 mutations, and the need for multidisciplinary management. Current strategies are symptomatic, though novel therapies such as antisense oligonucleotides and biomarkers like neurofilament light chain (NfL) show promise. This case highlights the diagnostic complexity of FTD with MND overlap syndrome, emphasizing the need for comprehensive clinical, neuroimaging, and electrophysiological evaluation. Multimodal treatment approaches focusing on behavioral symptoms and functional support are essential for optimizing patient outcomes.

ID: 42353250
Title: Microglial Dysfunction Induced by C9ORF72 Dipeptide Repeat Proteins: Biomarker and Therapeutic Perspectives.
Abstract: The GGGGCC hexanucleotide repeat expansion (HRE) in C9ORF72 was recognized as the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Repeat-associated non-AUG (RAN) translation of the expanded repeat generated dipeptide repeat proteins (DPRs), which disrupted multiple cellular processes and contributed to neurodegeneration. Emerging evidence indicated that disease pathogenesis involved both gain-of-function (GOF) and loss-of-function (LOF) mechanisms. DPR-mediated GOF toxicity induced ribosomal dysfunction, nucleolar stress, proteostatic impairment, and neuronal injury, whereas C9ORF72 LOF disrupted lysosomal and autophagic pathways in microglia, impairing the immune homeostasis. Neuronal injury further promoted the release of damage-associated signals that triggered secondary microglial activations and chronic neuroinflammations. This review summarized current knowledge of DPR biology, microglial dysfunction, and their contributions to disease progression in C9ORF72-associated ALS/FTD. Therapeutic strategies targeting repeated RNA, DPR productions, proteostasis, autophagy, and neuroinflammatory pathways were also discussed. In addition, the potentials of fluid biomarkers, including cerebrospinal fluid poly (GP) and blood neurofilament light chain (NfL), for diagnosis, disease monitoring, and therapeutic assessment were shown. Together, these findings provided important insights into disease mechanisms and potential avenues for improved clinical management.

ID: 42359357
Title: Innate immune crosstalk in ALS/FTD pathogenesis.
Abstract: Marked by protein aggregation, impaired proteostasis, organelle stress, and chronic neuroinflammation, amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) form a clinically, genetically, and pathologically overlapping disease spectrum. Increasing evidence indicates that innate immune activation is not merely a secondary response to neuronal injury, but an active driver of disease progression. In this review, we elaborate on how ALS/FTD-associated genetic lesions and pathogenic protein aggregates, including TDP-43, SOD1, FUS, and C9orf72-derived dipeptide repeat proteins, engage three interconnected innate immune pathways: cGAS-STING, NLRP3 inflammasomes, and TREM2-DAP12 signaling. We further highlight emerging crosstalk among these pathways, in which cGAS-STING and NLRP3 reinforce inflammatory signaling, while NLRP3-driven TREM2 shedding may impair microglial clearance and perpetuate proteostatic failure. Understanding this immune network may help define disease subtypes, identify biomarkers, and guide combinatorial therapeutic strategies that suppress harmful inflammation while preserving protective microglial functions.

ID: 42367691
Title: Chronic Inflammatory Demyelinating Polyradiculoneuropathy-Like Neuropathy in Heterozygous C9orf72 Mutation: A Case Report.
Abstract: C9orf72 repeat expansion is usually associated with amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), and ALS/FTD overlap. We report an atypical neuromuscular presentation of C9orf72 repeat expansion. A 68-year-old patient developed a sensorimotor polyneuropathy with slow continuous worsening over 3 years. Symptoms started in the left foot and slowly extended to all four limbs. Nerve conduction studies were consistent with a non-length-dependent predominantly axonal sensorimotor polyneuropathy, with some additional demyelinating features (proximal temporal dispersion and F-wave latency prolongation). Electro-clinical presentation fulfilled EAN/PNS 2021 criteria for CIDP, but the patient was not responsive to IVIg. RT-PCR revealed a heterozygous pathogenic expansion of the C9orf72 gene. The patient's father and brother died from ALS. At onset, his brother also had sensorimotor involvement and was misdiagnosed with CIDP. This case may expand the phenotypic spectrum associated with C9orf72 repeat expansion. The initial phenotype could be a non-length-dependent sensorimotor polyneuropathy with demyelinating features that potentially mimics CIDP.

ID: 42385702
Title: Recurrent patterns of TOP1-mediated neuronal genomic damage shared by major neurodegenerative disorders.
Abstract: Amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), and Alzheimer's disease (AD) represent two major categories of neurodegenerative disorders-TAR DNA-binding protein 43 (TDP-43) and tau proteinopathies-for which the mechanisms driving neuronal death remain unclear. Single-cell whole-genome sequencing of 469 neurons from C9ORF72 ALS, C9ORF72 FTD, AD, and control brains revealed increased somatic single-nucleotide variants (sSNVs) and insertions/deletions (sIndels) in all three diseases. Mutational signature analysis identified a disease-associated sSNV signature consistent with oxidative damage and an sIndel process affecting 22% of ALS, 76% of FTD, and 61% of AD neurons-but only 2% of control neurons-resembling signature ID4, previously linked to topoisomerase 1 (TOP1)-mediated mutagenesis. Rapid approach to DNA adduct recovery (RADAR) assays confirmed increased TOP1-DNA covalent complexes, and duplex sequencing confirmed the increased sIndels and identified single-strand events as likely precursor lesions. TOP1-associated sIndel mutagenesis and genome instability thus represent a mechanism shared by both TDP-43 and tau neurodegeneration.

ID: 42412610
Title: Striatal neuron dysfunction in C9ORF72-FTD/ALS is driven by AIS and potassium channel dysregulation.
Abstract: Frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) form a neurodegenerative spectrum characterized by progressive cognitive, behavioral, and motor decline, yet the contribution of the striatum to disease pathophysiology remains poorly understood. Here, we generate inhibitory striatal medium spiny neurons (MSNs) from human induced pluripotent stem cells carrying the C9ORF72 repeat expansion, the most common genetic cause of FTD/ALS, and compare them with isogenic-corrected, control, and patient-derived motor neurons. Using whole-cell electrophysiology, pharmacological manipulation, and high-resolution imaging, we identify a vulnerability of C9ORF72 MSNs to develop intrinsic hypoexcitability with linked synaptic dysfunction. These abnormalities are associated with axon initial segment shortening and altered voltage-gated potassium channel function relative to control and isogenic-corrected neurons. Pharmacological modulation partially restores action potential waveform properties, indicating that key electrophysiological abnormalities are reversible. These findings identify the striatum as a critical site of dysfunction in FTD/ALS and highlight striatal excitability as a potential therapeutic target.

ID: 42418533
Title: Multi-regional transcriptomic profiling reveals divergent molecular mechanisms in ALS-related neurodegeneration.
Abstract: Neurodegenerative disorders including amyotrophic lateral sclerosis (ALS) remain largely unsolved, with complex etiology yet to be fully elucidated. The most common genetic cause of ALS in both familial and sporadic cases is the expansion of a hexanucleotide repeat in the C9orf72 gene. To systemically dissect the molecular landscape of ALS, we performed integrative transcriptomic analyses across multiple central nervous system regions from ALS patients carrying pathological C9orf72 repeat expansions (ALS-C9) and those without the mutation (ALS-non-C9). In parallel, we performed transcriptome-wide cell-type deconvolution to assess the cellular composition of neuronal and non-neuronal populations. We identified a set of dysregulated molecular pathways that were consistently altered in both ALS-C9 and ALS-non-C9 patients, suggesting shared pathogenic mechanisms. Distinct gene-specific alterations also pointed to divergent subtype-dependent molecular trajectories. Gene-specific alterations were also associated with short clinical duration in ALS-non-C9, highlighting a sex-dependent immunological contribution to disease outcome. Our cross-regional integrative transcriptomic analyses reveal both convergent and divergent molecular and cellular features between ALS-C9 and ALS-non-C9 subgroups, underscoring the clinical heterogeneity of ALS and providing a framework for subtype- and sex-specific therapeutic stratifications.