A hexanucleotide repeat expansion in C9ORF72 is the cause of chromosome 9p21-linked ALS-FTD

Brain Metabolic Features of FUS-ALS: A 2-[18F]FDG-PET Study

OBJECTIVE

We aimed at evaluating the brain metabolic features of fused in sarcoma amyotrophic lateral sclerosis (FUS-ALS) compared with sporadic ALS (sALS), using 2-[fluorine-18] fluoro-2-deoxy-D-glucose positron emission tomography (2-[18F]FDG-PET).

METHODS

We employed the 2-sample t-test model of SPM12, implemented in MATLAB, to compare 12 FUS-ALS cases with 40 healthy controls (HC) and 48 sALS, randomly collected from the series of patients who underwent brain 2-[18F]FDG-PET at the ALS Center of Turin (Italy) at diagnosis from 2009 to 2019. In the comparisons between cases and HC, we included age at PET and sex as covariates. Because FUS-ALS usually shows early onset in spinal regions, in the comparison between FUS-ALS and sALS, we included singularly the following covariates in a second step, to evaluate the determinants of eventual metabolic differences: age at PET, sex, and onset (spinal/bulbar).

RESULTS

sALS patients showed significant relative hypometabolism in bilateral fronto-temporo-occipital cortex and right insula as compared with FUS-ALS. After adjusting for age, the relative hypometabolism remained in the bilateral precentral gyrus and in the right middle and inferior temporal gyrus. As compared with HC, FUS patients displayed a significant relative hypermetabolism in the pontobulbar region and right cerebellar tonsil, dentate nucleus, and uvula, while sALS showed relative hypometabolism in bilateral frontal and occipital cortices and in left temporal and parietal regions.

INTERPRETATION

Patients with FUS-ALS show relative preservation of motor cortex metabolism compared with those with sALS, possibly reflecting the prevalence of lower motor neuron impairment in their phenotype. Prospective studies are necessary to investigate the possible role of 2-[18F]FDG-PET as a biomarker to track disease spreading in clinical trials. ANN NEUROL 2025;97:1134-1143.

Frequency and Early Predictors of Cognitive Deterioration in Amyotrophic Lateral Sclerosis: A Longitudinal Population-Based Study

OBJECTIVE

The objective is to evaluate cognitive and behavioral progression and identify early predictors of these changes in a cohort of amyotrophic lateral sclerosis (ALS) patients.

METHODS

A total of 161 ALS patients were tested at diagnosis (T0), and 107 were re-tested after 1 year (T1) using cognitive/behavioral tests. All patients underwent whole-genome sequencing, and 46 patients (ALS-normal cognition [CN]) underwent [18F]Fluorodeoxyglucose positron emission tomography.

RESULTS

Of the 161 patients, 107 were re-rested at T1; non-retested patients included 10 with frontotemporal dementia and 44 who were either non-testable or deceased. At T0, 67 patients (62.6%) were classified as ALS-CN, whereas 40 (38.4%) showed some degree of cognitive/behavioral impairment. Eighteen ALS-CN patients (26.9%) experienced cognitive decline at T1. Phenoconverters had lower baseline scores in letter fluency (Letter Fluency Test [FAS]) (p < 0.001), Edinburgh Cognitive and Behavioral ALS Screen (ECAS) verbal fluency score (p = 0.017). Both tests were independently predictive of phenoconversion in binary logistic regression models, with optimal cut-off scores of 28.75 and 14.2, with good sensitivity and specificity. Other predictors included older age, lower education, and ALS-related genetic variants. Phenoconverters were hypometabolic in the left temporal lobe. Thirteen (32.5%) of the 40 patients with cognitive impairment at T0 worsened by T1, with FAS (p = 0.02) and the ECAS verbal fluency score (p = 0.023) predicting further decline.

INTERPRETATION

Approximately 30% of ALS patients experienced cognitive/behavioral decline within the first year after diagnosis. FAS and ECAS verbal fluency were predictive of cognitive phenoconversion. Our findings highlight the importance of early detection of at-risk individuals and the need for longitudinal cognitive assessments to monitor disease progression. ANN NEUROL 2025;97:1122-1133.

Heat-shock chaperone HSPB1 mitigates poly-glycine-induced neurodegeneration via restoration of autophagic flux

The CGG repeat expansions in the 5'-UTR regions of certain genes have been implicated in various neurodegenerative and muscular disorders. However, the underlying pathogenic mechanisms are not well understood. In this study, we explore the role of the small molecular chaperone HSPB1 in counteracting neurodegeneration induced by poly-glycine (poly-G) aggregates. Employing a reporter system, we demonstrate that CGG repeat expansions within the 5'-UTR of the GIPC1 gene produce poly-G proteins, by repeat-associated non-AUG (RAN) translation. Through proximity labeling and subsequent mass spectrometry analysis, we characterize the composition of poly-G insoluble aggregates and reveal that these aggregates sequester key macroautophagy/autophagy receptors, SQSTM1/p62 and TOLLIP. This sequestration disrupts MAP1LC3/LC3 recruitment and impairs autophagosome formation, thereby compromising the autophagic pathway. Importantly, we show that HSPB1 facilitates the dissociation of these receptors from poly-G aggregates and consequently restores autophagic function. Overexpressing HSPB1 alleviates poly-G-induced neurodegeneration in mouse models. Taken together, these findings highlight a mechanistic basis for the neuroprotective effects of HSPB1 and suggest its potential as a therapeutic target in treating poly-G-associated neurodegenerative diseases.Abbreviations: AD: Alzheimer disease; AIF1/Iba1: allograft inflammatory factor 1; Baf A1: bafilomycin A1; BFP: blue fluorescent protein; CQ: chloroquine; EIF2A/eIF-2α: eukaryotic translation initiation factor 2A; FRAP: fluorescence recovery after photobleaching; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GFAP: glial fibrillary acidic protein; GFP: green fluorescent protein; HSPB1: heat shock protein family B (small) member 1; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; NOTCH2NLC: notch 2 N-terminal like C; PD: Parkinson disease; PFA: paraformaldehyde; poly-A: poly-alanine; poly-G: poly-glycine; poly-R: poly-arginine; RAN translation: repeat-associated non-AUG translation; RBFOX3/NeuN: RNA binding fox-1 homolog 3; STED: stimulated emission depletion; TARDBP/TDP-43: TAR DNA binding protein; TG: thapsigargin; TOLLIP: toll interacting protein.

SOD1, A Crucial Protein for Neural Biochemistry: Dysfunction and Risk of Amyotrophic Lateral Sclerosis

Neurons are very susceptible to oxidative stress. They are the major consumers of oxygen in the brain, which is used to provide energy through oxidative phosphorylation, the major source of reactive oxygen species (ROS). In addition, compared to other tissues, neurons have lower levels of catalase and glutathione and increased susceptibility to lipid peroxidation due to the elevated levels of unsaturated fatty acids. These characteristics increasingly emphasize the antioxidant enzyme Cu/Zn superoxide dismutase 1 (SOD1) to maintain neuronal redox homeostasis. In the last decade, SOD1 gained additional roles which are also important to the metabolism of neurons. SOD1 controls the production of ROS by the electron transport chain, activates the expression of genes involved in the protection against oxidative stress, and regulates the shift from oxidative to fermentative metabolism involved in astrocyte-neuron metabolic cooperation. Furthermore, impaired interaction between the phosphatase calcineurin and SOD1 seems to result in TDP-43 hyperphosphorylation, the main proteinopathy found in amyotrophic lateral sclerosis (ALS) patients. However, this enzyme is ubiquitously expressed, mutated, and damaged forms of SOD1 cause disease in motor neurons. In this review, we discuss the pivotal functions of SOD1 in neuronal biochemistry and their implications for ALS.

Network analysis of the cerebrospinal fluid proteome reveals shared and unique differences between sporadic and familial forms of amyotrophic lateral sclerosis

BACKGROUND

Amyotrophic Lateral Sclerosis (ALS), a neurodegenerative disease involving loss of motor neurons, typically results in death within 3-5 years of disease onset. Although roughly 10% of cases can be linked to a specific inherited mutation (e.g., C9orf72 hexanucleotide repeat expansion or SOD1 mutation), the cause(s) of most cases are unknown. Consequently, there is a critical need for biomarkers that reflect disease onset and progression across ALS subgroups.

METHODS

We employed tandem mass tag mass spectrometry (TMT-MS) based proteomics on cerebrospinal fluid (CSF) to identify and quantify 2105 proteins from sporadic, C9orf72, and SOD1 ALS patients, asymptomatic C9orf72 expansion carriers, and controls (N = 101). To verify trends in our Emory University cohort we used data-independent acquisition (DIA-MS) on an expanded, four center cohort. This expanded cohort of 259 individuals included 50 sporadic ALS (sALS), 43 C9orf72 ALS, 22 SOD1 ALS, 72 asymptomatic gene carriers (59 C9orf72 and 13 SOD1) and 72 age-matched controls. We identified 2330 proteins and used differential protein abundance and network analyses to determine how protein profiles vary across disease subtypes in ALS CSF.

RESULTS

Differential abundance and co-expression network analysis identified proteomic differences between ALS and control, as well as differentially abundant proteins between sporadic, C9orf72 and SOD1 ALS. A panel of proteins differentiated forms of ALS that are indistinguishable in a clinical setting. An additional panel differentiated asymptomatic from symptomatic C9orf72 and SOD1 mutation carriers, marking a pre-symptomatic proteomic signature of genetic forms of ALS. Leveraging this large, multicenter cohort, we validated our ALS CSF network and identified ALS-specific proteins and network modules.

CONCLUSIONS

This study represents a comprehensive analysis of the CSF proteome across sporadic and genetic causes of ALS that resolves differences among these ALS subgroups and also identifies proteins that distinguish symptomatic from asymptomatic gene carriers. These new data point to varying pathogenic pathways that result in an otherwise clinically indistinguishable disease.

A multimodal screening platform for endogenous dipeptide repeat proteins in C9orf72 patient iPSC neurons

Repeat expansions in C9orf72 are the most common cause of amyotrophic lateral sclerosis and frontotemporal dementia. Repeat-associated non-AUG (RAN) translation generates neurotoxic dipeptide repeat proteins (DPRs). To study endogenous DPRs, we inserted the minimal HiBiT luciferase reporter downstream of sense repeat derived DPRs polyGA or polyGP in C9orf72 patient iPSCs. We show these "DPReporter" lines sensitively and rapidly report DPR levels in lysed and live cells and optimize screening in iPSC neurons. Small-molecule screening showed the ERK1/2 activator periplocin dose dependently increases DPR levels. Consistent with this, ERK1/2 inhibition reduced DPR levels and prolonged survival in C9orf72 repeat expansion flies. CRISPR knockout screening of all human helicases revealed telomere-associated helicases modulate DPR expression, suggesting common regulation of telomeric and C9orf72 repeats. These DPReporter lines allow investigation of DPRs in their endogenous context and provide a template for studying endogenous RAN-translated proteins, at scale, in other repeat expansion disorders.

Association of plasma concentration of trace metals with frontotemporal degeneration

Objective

Compare the burden of heavy metals in plasma from people with frontotemporal degeneration (FTD) and healthy controls.

Methods

A cross-sectional study of 14 FTD cases and 28 healthy controls recruited from the University of Cincinnati. Plasma samples were sent to the Trace Element Analysis Core at Dartmouth College for assessment of 24 metals or metalloids via inductively coupled plasma mass spectrometry (ICP-MS). Unconditional logistic regression models were performed with adjustments for age (centered at the median) and sex.

Results

After adjusting for age and sex, there was a significant positive association of FTD with the highest tertile of Manganese (ORadjusted = 11.1, 95% CI: 1.57-132) and Chromium (ORadjusted = 9.86, 95% CI: 1.24-218). There was significant inverse associations observed between FTD and the highest tertile of Barium (ORadjusted = 0.06, 95% CI: <0.01-0.47) and Mercury (ORadjusted = 0.13, 95% CI: 0.01-0.74), with a significant inverse trend (ptrend = 0.03).

Conclusion

Significant associations between plasma concentration of several trace metals and FTD. The significantly elevated levels of Manganese and Chromium may suggest a role of environmental exposure in the pathogenesis of FTD. However, larger, well-designed prospective studies, along with complementary experimental work, are needed to better elucidate this relationship.

RNAi-mediated silencing of SOD1 profoundly extends survival and functional outcomes in ALS mice

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative condition, with 20% of familial and 2%-3% of sporadic cases linked to mutations in the cytosolic superoxide dismutase (SOD1) gene. Mutant SOD1 protein is toxic to motor neurons, making SOD1 gene suppression a promising approach, supported by preclinical data and the 2023 Federal Drug Administration (FDA) approval of the GapmeR ASO targeting SOD1, tofersen. Despite the approval of an ASO and the optimism it brings to the field, the pharmacodynamics and pharmacokinetics of therapeutic SOD1 modulation can be improved. Here, we developed a chemically stabilized divalent siRNA scaffold (di-siRNA) that effectively suppresses SOD1 expression in vitro and in vivo. With optimized chemical modification, it achieves remarkable CNS tissue permeation and SOD1 silencing in vivo. Administered intraventricularly, di-siRNASOD1 extended survival in SOD1-G93A ALS mice, increasing survival beyond that previously seen in these mice by ASO modalities, slowed disease progression according to the standard ALS preclinical endpoints, and attenuated ALS neuropathology. These properties offer an improved therapeutic strategy for SOD1-mediated ALS and may extend to other dominantly inherited neurological disorders.

Molecular Mechanisms of Protein Aggregation in ALS-FTD: Focus on TDP-43 and Cellular Protective Responses

Amyotrophic Lateral Sclerosis (ALS) and Frontotemporal Dementia (FTD) are two neurodegenerative disorders that share common genes and pathomechanisms and are referred to as the ALS-FTD spectrum. A hallmark of ALS-FTD pathology is the abnormal aggregation of proteins, including Cu/Zn superoxide dismutase (SOD1), transactive response DNA-binding protein 43 (TDP-43), fused in sarcoma/translocated in liposarcoma (FUS/TLS), and dipeptide repeat proteins resulting from C9orf72 hexanucleotide expansions. Genetic mutations linked to ALS-FTD disrupt protein stability, phase separation, and interaction networks, promoting misfolding and insolubility. This review explores the molecular mechanisms underlying protein aggregation in ALS-FTD, with a particular focus on TDP-43, as it represents the main aggregated species inside pathological inclusions and can also aggregate in its wild-type form. Moreover, this review describes the protective mechanisms activated by the cells to prevent protein aggregation, including molecular chaperones and post-translational modifications (PTMs). Understanding these regulatory pathways could offer new insights into targeted interventions aimed at mitigating cell toxicity and restoring cellular function.

Protein kinases in neurodegenerative diseases: current understandings and implications for drug discovery

Neurodegenerative diseases (e.g., Alzheimer's, Parkinson's, Huntington's disease, and Amyotrophic Lateral Sclerosis) are major health threats for the aging population and their prevalences continue to rise with the increasing of life expectancy. Although progress has been made, there is still a lack of effective cures to date, and an in-depth understanding of the molecular and cellular mechanisms of these neurodegenerative diseases is imperative for drug development. Protein phosphorylation, regulated by protein kinases and protein phosphatases, participates in most cellular events, whereas aberrant phosphorylation manifests as a main cause of diseases. As evidenced by pharmacological and pathological studies, protein kinases are proven to be promising therapeutic targets for various diseases, such as cancers, central nervous system disorders, and cardiovascular diseases. The mechanisms of protein phosphatases in pathophysiology have been extensively reviewed, but a systematic summary of the role of protein kinases in the nervous system is lacking. Here, we focus on the involvement of protein kinases in neurodegenerative diseases, by summarizing the current knowledge on the major kinases and related regulatory signal transduction pathways implicated in diseases. We further discuss the role and complexity of kinase-kinase networks in the pathogenesis of neurodegenerative diseases, illustrate the advances of clinical applications of protein kinase inhibitors or novel kinase-targeted therapeutic strategies (such as antisense oligonucleotides and gene therapy) for effective prevention and early intervention.

Aggregates associated with amyotrophic lateral sclerosis sequester the actin-binding protein profilin 2

Amyotrophic Lateral Sclerosis (ALS) is a devastating neurodegenerative disease characterized by the degeneration of upper and lower motoneurons. The four most frequently mutated genes causing familial ALS (fALS) are C9orf72, FUS, SOD1, and TARDBP. Some of the related wild-type proteins comprise intrinsically disordered regions (IDRs) which favor their assembly in liquid droplets-the biophysical mechanism behind the formation of physiological granules such as stress granules (SGs). SGs assemble and dissolve dependent on the cellular condition. However, it has been suggested that transition from reversible SGs to irreversible aggregates contributes to the toxic properties of ALS-related mutated proteins. Sequestration of additional proteins within these aggregates may then result in downstream toxicity. While the exact downstream mechanisms remain elusive, rare ALS-causing mutations in the actin binding protein profilin 1 suggest an involvement of the actin cytoskeleton. Here, we hypothesize that profilin isoforms become sequestered in aggregates of ALS-associated proteins which induce subsequent dysregulation of the actin cytoskeleton. Interestingly, localization of neuronal profilin 2 in SGs was more pronounced compared with the ubiquitously expressed profilin 1. Accordingly, FUS and C9orf72 aggregates prominently sequestered profilin 2 but not profilin 1. Moreover, we observed a distinct sequestration of profilin 2 and G-actin to C9orf72 aggregates in different cellular models. On the functional level, we identified dysregulated actin dynamics in cells with profilin 2-sequestering aggregates. In summary, our results suggest a more common involvement of profilins in ALS pathomechanisms than indicated from the rarely occurring profilin mutations.

The cerebellum in frontotemporal dementia: From neglected bystander to potential neuromodulatory target. A narrative review

BACKGROUND

Though cortical changes in frontotemporal dementia (FTD) are well-documented, the cerebellum's role, closely linked to these areas, remains unclear.

OBJECTIVES

To provide evidence on cerebellar involvement in FTD across clinical, genetic, imaging, neuropathological, and neurophysiological perspectives. Additionally, we sought evidence supporting the application of cerebellar non-invasive brain stimulation (NIBS) in FTD for both diagnostic and therapeutic purposes.

METHODS

We performed a literature review using MEDLINE (via PubMed), Scopus, and Web of Science databases.

RESULTS

We emphasized the involvement of specific cerebellar regions which differentiate each FTD subtypes and may account for some of the characteristic symptoms. Furthermore, we highlighted peculiarities in FTD genetic alterations. Finally, we outlined neurophysiological evidence supporting a role for the cerebellum in FTD pathogenesis.

CONCLUSION

The cerebellum is critically involved in the FTD spectrum. Moreover, it can be speculated that cerebellar modulation, as already shown in other neurodegenerative disorders, could restore the interneuronal intracortical circuits typically impaired in FTD patients, providing clinical improvements and fundamental outcome measures in clinical trials.

Activating autophagy to eliminate toxic protein aggregates with small molecules in neurodegenerative diseases

Neurodegenerative diseases (NDs), such as Alzheimer disease, Parkinson disease, Huntington disease, amyotrophic lateral sclerosis, and frontotemporal dementia, are well known to pose formidable challenges for their treatment due to their intricate pathogenesis and substantial variability among patients, including differences in environmental exposures and genetic predispositions. One of the defining characteristics of NDs is widely reported to be the buildup of misfolded proteins. For example, Alzheimer disease is marked by amyloid beta and hyperphosphorylated Tau aggregates, whereas Parkinson disease exhibits α-synuclein aggregates. Amyotrophic lateral sclerosis and frontotemporal dementia exhibit TAR DNA-binding protein 43, superoxide dismutase 1, and fused-in sarcoma protein aggregates, and Huntington disease involves mutant huntingtin and polyglutamine aggregates. These misfolded proteins are the key biomarkers of NDs and also serve as potential therapeutic targets, as they can be addressed through autophagy, a process that removes excess cellular inclusions to maintain homeostasis. Various forms of autophagy, including macroautophagy, chaperone-mediated autophagy, and microautophagy, hold a promise in eliminating toxic proteins implicated in NDs. In this review, we focus on elucidating the regulatory connections between autophagy and toxic proteins in NDs, summarizing the cause of the aggregates, exploring their impact on autophagy mechanisms, and discussing how autophagy can regulate toxic protein aggregation. Moreover, we underscore the activation of autophagy as a potential therapeutic strategy across different NDs and small molecules capable of activating autophagy pathways, such as rapamycin targeting the mTOR pathway to clear α-synuclein and Sertraline targeting the AMPK/mTOR/RPS6KB1 pathway to clear Tau, to further illustrate their potential in NDs' therapeutic intervention. Together, these findings would provide new insights into current research trends and propose small-molecule drugs targeting autophagy as promising potential strategies for the future ND therapies. SIGNIFICANCE STATEMENT: This review provides an in-depth overview of the potential of activating autophagy to eliminate toxic protein aggregates in the treatment of neurodegenerative diseases. It also elucidates the fascinating interrelationships between toxic proteins and the process of autophagy of "chasing and escaping" phenomenon. Moreover, the review further discusses the progress utilizing small molecules to activate autophagy to improve the efficacy of therapies for neurodegenerative diseases by removing toxic protein aggregates.

Targeting Gene C9orf72 Pathogenesis for Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal adult neurodegenerative disorder. Since no cure has been found, finding effective therapeutic targets for ALS remains a major challenge. Gene C9orf72 mutations with the formation of hexanucleotide repeat (GGGGCC) expansion (HRE) have been considered the most common genetic pathogenesis of ALS. The literature review indicates that the C9orf72 HRE causes both the gain-of-function toxicity and loss of function of C9ORF72. The formation of RNA foci and dipeptide repeats (DPRs) resulting from HRE is responsible for toxic function gain. The RNA foci can interfere with RNA processing, while DPRs directly bind to and sequester associated proteins to disrupt processes of rRNA synthesis, mRNA translation, autophagy, and nucleocytoplasmic transport. The mutations of C9orf72 and HRE result in the loss of functional C9ORF72. Under physiological conditions, C9ORF72 binds to Smith-Magenis chromosome region 8 and WD repeat-containing protein and forms a protein complex. Loss of C9ORF72 leads to autophagic impairment, increased oxidative stress, nucleocytoplasmic transport impairment, and inflammatory response. The attempted treatments for ALS have been tried by targeting C9orf72 HRE; however, the outcomes are far from satisfactory yet. More studies should be performed on pharmacological and molecular modulators against C9orf72 HRE to evaluate their efficacy by targeting HRE.

Targets and Gene Therapy of ALS (Part 1)

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by the selective death of motor neurons, which causes muscle atrophy. Genetic forms of ALS are recorded only in 10% of cases. However, over the past decade, studies in genetics have substantially contributed to our understanding of the molecular mechanisms underlying ALS. The identification of key mutations such as SOD1, C9orf72, FUS, and TARDBP has led to the development of targeted therapy that is gradually being introduced into clinical trials, opening up a broad range of opportunities for correcting these mutations. In this review, we aimed to present an extensive overview of the currently known mechanisms of motor neuron degeneration associated with mutations in these genes and also the gene therapy methods for inhibiting the expression of their mutant proteins. Among these, antisense oligonucleotides, RNA interference (siRNA and miRNA), and gene-editing (CRISPR/Cas9) methods are of particular interest. Each has shown its efficacy in animal models when targeting mutant genes, whereas some of them have proven to be efficient in human clinical trials.

Deciphering distinct genetic risk factors for FTLD-TDP pathological subtypes via whole-genome sequencing

Frontotemporal lobar degeneration with neuronal inclusions of the TAR DNA-binding protein 43 (FTLD-TDP) is a fatal neurodegenerative disorder with only a limited number of risk loci identified. We report our comprehensive genome-wide association study as part of the International FTLD-TDP Whole-Genome Sequencing Consortium, including 985 patients and 3,153 controls compiled from 26 institutions/brain banks in North America, Europe and Australia, and meta-analysis with the Dementia-seq cohort. We confirm UNC13A as the strongest overall FTLD-TDP risk factor and identify TNIP1 as a novel FTLD-TDP risk factor. In subgroup analyzes, we further identify genome-wide significant loci specific to each of the three main FTLD-TDP pathological subtypes (A, B and C), as well as enrichment of risk loci in distinct tissues, brain regions, and neuronal subtypes, suggesting distinct disease aetiologies in each of the subtypes. Rare variant analysis confirmed TBK1 and identified C3AR1, SMG8, VIPR1, RBPJL, L3MBTL1 and ANO9, as novel subtype-specific FTLD-TDP risk genes, further highlighting the role of innate and adaptive immunity and notch signaling pathway in FTLD-TDP, with potential diagnostic and novel therapeutic implications.

Multi-region brain transcriptomic analysis of amyotrophic lateral sclerosis reveals widespread RNA alterations and substantial cerebellum involvement

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease that primarily affects the motor neurons, causing progressive muscle weakness and paralysis. While research has focused on understanding pathological mechanisms in the motor cortex and spinal cord, there is growing evidence that extra-motor brain regions may also play a role in the pathogenesis or progression of ALS.

METHODS

We generated 165 sample-matched post-mortem brain transcriptomes from 22 sporadic ALS patients with pTDP-43 pathological staging and 11 non-neurological controls. For each individual, five brain regions underwent mRNA sequencing: motor cortex (pTDP-43 inclusions always present), prefrontal cortex and hippocampus (pTDP-43 inclusions sometimes present), and occipital cortex and cerebellum (pTDP-43 inclusions rarely present). We examined gene expression, cell-type composition, transcript usage (% contribution of a transcript to total gene expression) and alternative splicing, comparing ALS-specific changes between brain regions. We also considered whether post-mortem pTDP-43 pathological stage classification defined ALS subgroups with distinct gene expression profiles.

RESULTS

Significant gene expression changes were observed in ALS cases for all five brain regions, with the cerebellum demonstrating the largest number of total (> 3,000) and unique (60%) differentially expressed genes. Pathway enrichment and predicted activity were largely concordant across brain regions, suggesting that ALS-linked mechanisms, including inflammation, mitochondrial dysfunction and oxidative stress, are also dysregulated in non-motor brain regions. Switches in transcript usage were identified for a small set of genes including increased usage of a POLDIP3 transcript, associated with TDP-43 loss-of-function, in the cerebellum and a XBP1 transcript, indicative of unfolded protein response activity, in the motor cortex. Extensive variation in RNA splicing was identified in the ALS brain, with 26-41% of alternatively spliced genes unique to a given brain region. This included detection of TDP-43-associated cryptic splicing events such as the STMN2 cryptic exon which was shown to have a pTDP-43 pathology-specific expression pattern. Finally, ALS patients with stage 4 pTDP-43 pathology demonstrated distinct gene and protein expression changes in the cerebellum.

CONCLUSIONS

Together our findings highlighted widespread transcriptome alterations in ALS post-mortem brain and showed that, despite the absence of pTDP-43 pathology in the cerebellum, extensive and pTDP-43 pathological stage-specific RNA changes are evident in this brain region.

Modelling Population Genetic Screening in Rare Neurodegenerative Diseases

Importance: Genomic sequencing enables the rapid identification of a breadth of genetic variants. For clinical purposes, sequencing for small genetic variations is considered a solved problem, while challenges remain for structural variants, given the lower sensitivity and specificity. Interest has recently risen among governing bodies in developing protocols for population-wide genetic screening. However, usefulness is constrained when the probability of being affected by a rare disease remains low, despite a positive genetic test. This is a common scenario in neurodegenerative disorders. The problem is recognised among statisticians and statistical geneticists but is less well-understood by clinicians and researchers who will act on these results, and by the general public who might access screening services directly without the appropriate support for interpretation. Observations: We explore the probability of subsequent disease following genetic screening of several variants, both single nucleotide variants (SNVs) and larger repeat expansions, for two neurological conditions, Huntington's disease (HD) and amyotrophic lateral sclerosis (ALS), comparing these results with screening for phenylketonuria, which is well-established. The risk following a positive screening test was 0.5% for C9orf72 in ALS and 0.4% for HTT in HD when testing repeat expansions, for which the test had sub-optimal performance (sensitivity = 99% and specificity = 90%), and 12.7% for phenylketonuria and 10.9% for ALS SOD1 when testing pathogenic SNVs (sensitivity = 99.96% and specificity = 99.95%). Subsequent screening confirmation via PCR for C9orf72 led to a 2% risk of developing ALS as a result of the reduced penetrance (44%). Conclusions and Relevance: We show that risk following a positive screening test result can be strikingly low for rare neurological diseases, even for fully penetrant variants such as HTT, if the test has sub-optimal performance. Accordingly, to maximise the utility of screening, it is vital to prioritise protocols with very high sensitivity and specificity, and a careful selection of markers for screening, giving regard to clinical interpretability, actionability, high penetrance, and secondary testing to confirm positive findings.

Replicative DNA polymerase epsilon and delta holoenzymes show wide-ranging inhibition at G-quadruplexes in the human genome

G-quadruplexes (G4s) are functional elements of the human genome, some of which inhibit DNA replication. We investigated replication of G4s within highly abundant microsatellite (GGGA, GGGT) and transposable element (L1 and SVA) sequences. We found that genome-wide, numerous motifs are located preferentially on the replication leading strand and the transcribed strand templates. We directly tested replicative polymerase ϵ and δ holoenzyme inhibition at these G4s, compared to low abundant motifs. For all G4s, DNA synthesis inhibition was higher on the G-rich than C-rich strand or control sequence. No single G4 was an absolute block for either holoenzyme; however, the inhibitory potential varied over an order of magnitude. Biophysical analyses showed the motifs form varying topologies, but replicative polymerase inhibition did not correlate with a specific G4 structure. Addition of the G4 stabilizer pyridostatin severely inhibited forward polymerase synthesis specifically on the G-rich strand, enhancing G/C strand asynchrony. Our results reveal that replicative polymerase inhibition at every G4 examined is distinct, causing complementary strand synthesis to become asynchronous, which could contribute to slowed fork elongation. Altogether, we provide critical information regarding how replicative eukaryotic holoenzymes navigate synthesis through G4s naturally occurring thousands of times in functional regions of the human genome.

Disease-modifying effects of TMEM106B in genetic frontotemporal dementia: a longitudinal GENFI study

Common variants within TMEM106B are associated with risk for frontotemporal lobar degeneration with TDP-43 pathology (FTLD-TDP). The G allele of the top single nucleotide polymorphism, rs1990622, confers protection against FTLD-TDP, including genetic cases due to GRN mutations or C9orf72 hexanucleotide repeat expansions. However, the effects of interaction between TMEM106B-rs1990622 and frontotemporal dementia (FTD) mutations on disease endophenotypes in genetic FTD are unknown. This longitudinal cohort study was embedded within the GENetic Frontotemporal dementia Initiative (GENFI). We included 518 participants from 222 families [209 non-carriers; 222 presymptomatic carriers (C9orf72  = 79; GRN = 101, MAPT = 42); 87 symptomatic carriers (C9orf72 = 45; GRN = 29; MAPT = 13)] followed for up to 7 years. Using linear mixed-effects models, we examined the effects of a triple interaction between TMEM106B-rs1990622G allele dosage (additive model: 0, 1 or 2 alleles) and autosomal dominant FTD mutations with clinical status, and time from baseline on (i) grey matter volume using a voxel-based analysis; (ii) serum neurofilament light chain (NfL) levels; and (iii) cognitive and behavioural measures. Mean age of participants was 47.9 ± 13.8 years, 58.1% were female and 61% had at least one G allele. C9orf72: rs1990622G allele dosage was associated with less atrophy within the right occipital region in presymptomatic carriers at baseline, and reduced atrophy rate within putamen and caudate nucleus, right frontotemporal regions, left cingulate and bilateral insular cortices in symptomatic carriers over time; lower NfL levels in presymptomatic carriers at baseline; better executive functions and language abilities in presymptomatic carriers; and maintained overall cognitive functions and behaviour in symptomatic carriers over time. GRN: rs1990622G allele dosage was associated with reduced grey matter atrophy rate within the right temporal and occipital regions in presymptomatic carriers, and within the right frontal cortex and insula over time in symptomatic carriers; lower serum NfL levels over time in presymptomatic carriers and lower NfL levels at both baseline and over time in symptomatic carriers; and better global cognitive performance at baseline and higher attention/processing speed scores over time in symptomatic carriers. MAPT: rs1990622G allele dosage was associated with reduced grey matter atrophy rate within the right inferior frontal gyrus in symptomatic carriers, but no effects on serum NfL or cognitive/behavioural measures. TMEM106B-rs1990622G allele dosage showed protective effects on multiple endophenotypes predominantly in GRN and C9orf72 groups. Therefore, TMEM106B genotype should be assessed in clinical trials, particularly of GRN- and C9orf72-related genetic FTD, due to its modifying effects on biomarker, imaging, cognitive and clinical outcomes.

Changes to Average Survival of Patients With Amyotrophic Lateral Sclerosis (1995-2018): Results From the Piemonte and Valle d'Aosta Registry

BACKGROUND AND OBJECTIVES

The average survival of patients with amyotrophic lateral sclerosis (ALS) ranges from 2 to 5 years from symptom onset. However, it remains unclear whether this estimate has improved over time. The objective of this study was to analyze the survival trend of a large population-based cohort of patients with ALS over a 24-year period.

METHODS

Patients from the Piemonte and Valle d'Aosta registry for ALS (PARALS) were categorized into the first (1995-2002), second (2003-2010), or third (2011-2018) epoch based on their diagnosis date. Survival was defined as the time from diagnosis to death, tracheostomy, or censoring date. A Cox proportional hazard model was developed with diagnosis epoch as the primary variable of interest, adjusted for sex, site of onset, age at onset, diagnostic delay, forced vital capacity at diagnosis, Δbody mass index from onset to diagnosis, noninvasive mechanical ventilation use, gastrostomy use, and site of follow-up. A subset analysis comparing the 2007-2012 and 2013-2018 cohorts was conducted, incorporating riluzole prescription, genetics, and preslope category as additional covariates.

RESULTS

A total of 3,134 patients were included, evenly distributed across the 3 epochs (990, 1,023, and 1,121, respectively). The median survival remained stable during the first and second epoch (18.6 months vs 18.3 months) but improved during the third epoch (20.1 months; p = 0.0041), with a hazard ratio (HR) of 0.76 (95% CI 0.67-0.87, p = 0.00003). In the subset analysis, the most recent epoch (2013-2018) showed a continued survival advantage (HR 0.77, 95% CI 0.65-0.90). Of interest, the survival benefit was only evident among intermediate progressors (HR 0.60, 95% CI 0.45-0.80).

DISCUSSION

In the PARALS, ALS survival increased over time. In a subset analysis, the beneficial effect of the epoch was only evident among intermediate progressors. The improvement in multidisciplinary care provided by tertiary centers may be one possible explanation for this finding, although further dedicated studies are needed to confirm this hypothesis.

The G-quadruplex ligand CX-5461: an innovative candidate for disease treatment

The ribosomal DNA (rDNA) plays a vital role in regulating protein synthesis by ribosome biogenesis, essential for maintaining cellular growth, metabolism, and more. Cancer cells show a high dependence on ribosome biogenesis and exhibit elevated rDNA transcriptional activity. CX-5461, also known as Pidnarulex, is a First-in-Class anticancer drug that has received 'Fast Track Designation' approval from the FDA. Initially reported to inhibit Pol I-driven rDNA transcription, CX-5461 was recently identified as a G-quadruplex structure (G4) stabilizer and is currently completed or undergoing multiple Phase I clinical trials in patients with breast and ovarian cancers harboring BRCA1/2, PALB2, or other DNA repair deficiencies. Additionally, preclinical studies have confirmed that CX-5461 demonstrates promising therapeutic effects against multifarious non-cancer diseases, including viral infections, and autoimmune diseases. This review summarizes the mechanisms of CX-5461, including its transcriptional inhibition of rDNA, binding to G4, and toxicity towards topoisomerase, along with its research status and therapeutic effects across various diseases. Lastly, this review highlights the targeted therapy strategy of CX-5461 based on nanomedicine delivery, particularly the drug delivery utilizing the nucleic acid aptamer AS1411, which contains a G4 motif to specifically target the highly expressed nucleolin on the surface of tumor cell membranes; It also anticipates the strategy of coupling CX-5461 with peptide nucleic acids and locked nucleic acids to achieve dual targeting, thereby realizing individualized G4-targeting by CX-5461. This review aims to provide a general overview of the progress of CX-5461 in recent years and suggest potential strategies for disease treatment involving ribosomal RNA synthesis, G4, and topoisomerase.

Gene therapy breakthroughs in ALS: a beacon of hope for 20% of ALS patients

Amyotrophic lateral sclerosis (ALS) is a fatal motor neuron disease that remains incurable. Although the etiologies of ALS are diverse and the precise pathogenic mechanisms are not fully understood, approximately 20% of ALS cases are caused by genetic factors. Therefore, advancing targeted gene therapies holds significant promise, at least for the 20% of ALS patients with genetic etiologies. In this review, we summarize the main strategies and techniques of current ALS gene therapies based on ALS risk genes, and review recent findings from animal studies and clinical trials. Additionally, we highlight ALS-related genes with well-understood pathogenic mechanisms and the potential of numerous emerging gene-targeted therapeutic approaches for ALS.

PTPσ-mediated PI3P regulation modulates neurodegeneration in C9ORF72-ALS/FTD

The most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) is the repeat expansion in C9ORF72. Dipeptide repeat (DPR) proteins translated from both sense and antisense repeats, especially arginine-rich DPRs (R-DPRs), contribute to neurodegeneration. Through CRISPR interference (CRISPRi) screening in human-derived neurons, we identified receptor-type tyrosine-protein phosphatase S (PTPσ) as a strong modifier of poly-GR-mediated toxicity. We showed that reducing PTPσ promotes the survival of both poly-GR- and poly-PR-expressing neurons by elevating phosphatidylinositol 3-phosphate (PI3P), accompanied by restored early endosomes and lysosomes. Remarkably, PTPσ knockdown or inhibition substantially rescues the PI3P-endolysosomal defects and improves the survival of C9ORF72-ALS/FTD patient-derived neurons. Furthermore, the PTPσ inhibitor diminishes GR toxicity and rescues pathological and behavioral phenotypes in mice. Overall, these findings emphasize the critical role of PI3P-mediated endolysosomal deficits induced by R-DPRs in disease pathogenesis and reveal the therapeutic potential of targeting PTPσ in C9ORF72-ALS/FTD.

Pathophysiology, Clinical Heterogeneity, and Therapeutic Advances in Amyotrophic Lateral Sclerosis: A Comprehensive Review of Molecular Mechanisms, Diagnostic Challenges, and Multidisciplinary Management Strategies

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder characterized by the progressive degeneration of upper and lower motor neurons, leading to muscle atrophy, paralysis, and respiratory failure. This comprehensive review synthesizes the current knowledge on ALS pathophysiology, clinical heterogeneity, diagnostic frameworks, and evolving therapeutic strategies. Mechanistically, ALS arises from complex interactions between genetic mutations (e.g., in C9orf72, SOD1, TARDBP (TDP-43), and FUS) and dysregulated cellular pathways, including impaired RNA metabolism, protein misfolding, nucleocytoplasmic transport defects, and prion-like propagation of toxic aggregates. Phenotypic heterogeneity, manifesting as bulbar-, spinal-, or respiratory-onset variants, complicates its early diagnosis, which thus necessitates the rigorous application of the revised El Escorial criteria and emerging biomarkers such as neurofilament light chain. Clinically, ALS intersects with frontotemporal dementia (FTD) in up to 50% of the cases, driven by shared TDP-43 pathology and C9orf72 hexanucleotide expansions. Epidemiological studies have revealed a lifetime risk of 1:350, with male predominance (1.5:1) and peak onset between 50 and 70 years. Disease progression varies widely, with a median survival of 2-4 years post-diagnosis, underscoring the urgency for early intervention. Approved therapies, including riluzole (glutamate modulation), edaravone (antioxidant), and tofersen (antisense oligonucleotide), offer modest survival benefits, while dextromethorphan/quinidine alleviates the pseudobulbar affect. Non-pharmacological treatment advances, such as non-invasive ventilation (NIV), prolong survival by 13 months and improve quality of life, particularly in bulb-involved patients. Multidisciplinary care-integrating physical therapy, respiratory support, nutritional management, and cognitive assessments-is critical to addressing motor and non-motor symptoms (e.g., dysphagia, spasticity, sleep disturbances). Emerging therapies show promise in preclinical models. However, challenges persist in translating genetic insights into universally effective treatments. Ethical considerations, including euthanasia and end-of-life decision-making, further highlight the need for patient-centered communication and palliative strategies.

Behavioural effects of oral cannabidiol (CBD) treatment in the superoxide dismutase 1 G93 A (SOD1G93 A) mouse model of amyotrophic lateral sclerosis

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease affecting voluntary muscle movement as well as cognitive and other behavioural domains at later disease stages. No effective treatment for ALS is currently available. Elevated neuroinflammation, oxidative stress and alterations to the endocannabinoid system are evident in ALS. The phytocannabinoid cannabidiol (CBD) has anti-inflammatory and anti-oxidant properties. Thus, we evaluated the remedial effects of chronic oral cannabidiol (CBD) treatment on ALS-relevant behavioural domains in the copper-zinc superoxide dismutase 1 (SOD1) mouse model of ALS that carries a G93A mutation (SOD1G93A).

METHODS

Male and female SOD1G93A and wild type-like (WT) littermates were fed either a control (CHOW) or CBD-enriched chow diet (equivalent to a dose of 36 mg/kg per day) beginning from 10 weeks of age. Bodyweight and motor performance were recorded weekly from 11 to 19 weeks and open field behaviours at 12 and 18 weeks. Mice were also tested for prepulse inhibition (PPI), social behaviours, as well as fear-associated memory.

RESULTS

CBD treatment ameliorated the bodyweight loss in female SOD1G93A mice, tended to reinstate sociability in SOD1G93A males, strengthened social recognition memory in SOD1G93A females, and improved the PPI response in younger SOD1G93A females at higher prepulse intensities. CBD had no effect on motor impairments but instead reversed the anxiolytic-like phenotype of 12-week-old male SOD1G93A mice and decreased the acoustic startle response and strengthened cue freezing in male mice.

CONCLUSION

Thus, the current remedial oral dose of CBD delayed disease progression (inferred by bodyweight) in both male and female mice and improve specific cognitive deficits of SOD1G93A mice in a sex specific manner without altering the motor phenotype.

High-throughput screen of 100 000 small molecules in C9ORF72 ALS neurons identifies spliceosome modulators that mobilize G4C2 repeat RNA into nuclear export and repeat associated non-canonical translation

An intronic G4C2 repeat expansion in the C9ORF72 gene is the major known cause for Amyotrophic Lateral Sclerosis (ALS), with current evidence for both, loss of function and pathological gain of function disease mechanisms. We screened 96 200 small molecules in C9ORF72 patient iPS neurons for modulation of nuclear G4C2 RNA foci and identified 82 validated hits, including the Brd4 inhibitor JQ1 as well as novel analogs of Spliceostatin-A, a known modulator of SF3B1, the branch point binding protein of the U2-snRNP. Spliceosome modulation by these SF3B1 targeted compounds recruits SRSF1 to nuclear G4C2 RNA, mobilizing it from RNA foci into nucleocytoplasmic export. This leads to increased repeat-associated non-canonical (RAN) translation and ultimately, enhanced cell toxicity. Our data (i) provide a new pharmacological entry point with novel as well as known, publicly available tool compounds for dissection of C9ORF72 pathobiology in C9ORF72 ALS models, (ii) allowing to differentially modulate RNA foci versus RAN translation, and (iii) suggest that therapeutic RNA foci elimination strategies warrant caution due to a potential storage function, counteracting translation into toxic dipeptide repeat polyproteins. Instead, our data support modulation of nuclear export via SRSF1 or SR protein kinases as possible targets for future pharmacological drug discovery.

Amyotrophic Lateral Sclerosis: Focus on Cytoplasmic Trafficking and Proteostasis

Amyotrophic lateral sclerosis (ALS) is a progressive and fatal motor neuron disease characterized by the pathological loss of upper and lower motor neurons. Whereas most ALS cases are caused by a combination of environmental factors and genetic susceptibility, in a relatively small proportion of cases, the disorder results from mutations in genes that are inherited. Defects in several different cellular mechanisms and processes contribute to the selective loss of motor neurons (MNs) in ALS. Prominent among these is the accumulation of aggregates of misfolded proteins or peptides which are toxic to motor neurons. These accumulating aggregates stress the ability of the endoplasmic reticulum (ER) to function normally, cause defects in the transport of proteins between the ER and Golgi, and impair the transport of RNA, proteins, and organelles, such as mitochondria, within axons and dendrites, all of which contribute to the degeneration of MNs. Although dysfunction of a variety of cellular processes combines towards the pathogenesis of ALS, in this review, we focus on recent advances concerning the involvement of defective ER stress, vesicular transport between the ER and Golgi, and axonal transport.

Computational Analysis of SOD1-G93A Mouse Muscle Biomarkers for Comprehensive Assessment of ALS Progression

AIMS

To identify potential image biomarkers of neuromuscular disease by analysing morphological and network-derived features in skeletal muscle biopsies from a murine model of amyotrophic lateral sclerosis (ALS), the SOD1G93A mouse and wild-type (WT) controls at distinct stages of disease progression.

METHODS

Using the NDICIA computational framework, we quantitatively evaluated histological differences between skeletal muscle biopsies from SOD1G93A and WT mice. The process involved the selection of a subset of features revealing these differences. A subset of discriminative features was selected to characterise these differences, and their temporal dynamics were assessed across disease stages.

RESULTS

Our findings demonstrate that muscle pathology in the mutant model evolves from early alterations in muscle fibre arrangement, detectable at the presymptomatic stage through graph theory features, to the subsequent development of the typical morphological pattern of neurogenic atrophy at more advanced disease stages.

CONCLUSIONS

Our assay identifies a neurogenic signature in mutant muscle biopsies, even when the disease is phenotypically imperceptible.

Drug repurposing in amyotrophic lateral sclerosis (ALS)

INTRODUCTION

Identifying treatments that can alter the natural history of amyotrophic lateral sclerosis (ALS) is challenging. For years, drug discovery in ALS has relied upon traditional approaches with limited success. Drug repurposing, where clinically approved drugs are reevaluated for other indications, offers an alternative strategy that overcomes some of the challenges associated with de novo drug discovery.

AREAS COVERED

In this review, the authors discuss the challenge of drug discovery in ALS and examine the potential of drug repurposing for the identification of new effective treatments. The authors consider a range of approaches, from screening in experimental models to computational approaches, and outline some general principles for preclinical and clinical research to help bridge the translational gap. Literature was reviewed from original publications, press releases and clinical trials.

EXPERT OPINION

Despite remaining challenges, drug repurposing offers the opportunity to improve therapeutic options for ALS patients. Nevertheless, stringent preclinical research will be necessary to identify the most promising compounds together with innovative experimental medicine studies to bridge the translational gap. The authors further highlight the importance of combining expertise across academia, industry and wider stakeholders, which will be key in the successful delivery of repurposed therapies to the clinic.

Genetic risk for neurodegenerative conditions is linked to disease-specific microglial pathways

Genome-wide association studies have identified thousands of common variants associated with an increased risk of neurodegenerative disorders. However, the noncoding localization of these variants has made the assignment of target genes for brain cell types challenging. Genomic approaches that infer chromosomal 3D architecture can link noncoding risk variants and distal gene regulatory elements such as enhancers to gene promoters. By using enhancer-to-promoter interactome maps for human microglia, neurons, and oligodendrocytes, we identified cell-type-specific enrichment of genetic heritability for brain disorders through stratified linkage disequilibrium score regression. Our analysis suggests that genetic heritability for multiple neurodegenerative disorders is enriched at microglial chromatin contact sites, while schizophrenia heritability is predominantly enriched at chromatin contact sites in neurons followed by oligodendrocytes. Through Hi-C coupled multimarker analysis of genomic annotation (H-MAGMA), we identified disease risk genes for Alzheimer's disease, Parkinson's disease, multiple sclerosis, amyotrophic lateral sclerosis and schizophrenia. We found that disease-risk genes were overrepresented in microglia compared to other brain cell types across neurodegenerative conditions and within neurons for schizophrenia. Notably, the microglial risk genes and pathways identified were largely specific to each disease. Our findings reinforce microglia as an important, genetically informed cell type for therapeutic interventions in neurodegenerative conditions and highlight potentially targetable disease-relevant pathways.

Neuronal polyunsaturated fatty acids are protective in ALS/FTD

Here we report a conserved transcriptomic signature of reduced fatty acid and lipid metabolism gene expression in a Drosophila model of C9orf72 repeat expansion, the most common genetic cause of amyotrophic lateral sclerosis and frontotemporal dementia (ALS/FTD), and in human postmortem ALS spinal cord. We performed lipidomics on C9 ALS/FTD Drosophila, induced pluripotent stem (iPS) cell neurons and postmortem FTD brain tissue. This revealed a common and specific reduction in phospholipid species containing polyunsaturated fatty acids (PUFAs). Feeding C9 ALS/FTD flies PUFAs yielded a modest increase in survival. However, increasing PUFA levels specifically in neurons of C9 ALS/FTD flies, by overexpressing fatty acid desaturase enzymes, led to a substantial extension of lifespan. Neuronal overexpression of fatty acid desaturases also suppressed stressor-induced neuronal death in iPS cell neurons of patients with both C9 and TDP-43 ALS/FTD. These data implicate neuronal fatty acid saturation in the pathogenesis of ALS/FTD and suggest that interventions to increase neuronal PUFA levels may be beneficial.

Aberrant Short Tandem Repeats: Pathogenicity, Mechanisms, Detection, and Roles in Neuropsychiatric Disorders

Short tandem repeat (STR) sequences are highly variable DNA segments that significantly contribute to human neurodegenerative disorders, highlighting their crucial role in neuropsychiatric conditions. This article examines the pathogenicity of abnormal STRs and classifies tandem repeat expansion disorders(TREDs), emphasizing their genetic characteristics, mechanisms of action, detection methods, and associated animal models. STR expansions exhibit complex genetic patterns that affect the age of onset and symptom severity. These expansions disrupt gene function through mechanisms such as gene silencing, toxic gain-of-function mutations leading to RNA and protein toxicity, and the generation of toxic peptides via repeat-associated non-AUG (RAN) translation. Advances in sequencing technologies-from traditional PCR and Southern blotting to next-generation and long-read sequencing-have enhanced the accuracy of STR variation detection. Research utilizing these technologies has linked STR expansions to a range of neuropsychiatric disorders, including autism spectrum disorders and schizophrenia, highlighting their contribution to disease risk and phenotypic expression through effects on genes involved in neurodevelopment, synaptic function, and neuronal signaling. Therefore, further investigation is essential to elucidate the intricate interplay between STRs and neuropsychiatric diseases, paving the way for improved diagnostic and therapeutic strategies.

Unraveling Molecular Targets for Neurodegenerative Diseases Through Caenorhabditis elegans Models

Neurodegenerative diseases (NDDs), including Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), Huntington's disease (HD), and prion disease, represent a group of age-related disorders that pose a growing and formidable challenge to global health. Despite decades of extensive research that has uncovered key genetic factors and biochemical pathways, the precise molecular mechanisms underlying these diseases and effective therapeutic strategies remain elusive. Caenorhabditis elegans (C. elegans) has emerged as a powerful model organism for studying NDDs due to its unique biological features such as genetic tractability, conserved molecular pathways, and ease of high-throughput screening. This model provides an exceptional platform for identifying molecular targets associated with NDDs and developing novel therapeutic interventions. This review highlights the critical role of C. elegans in elucidating the complex molecular mechanisms of human NDDs, with a particular focus on recent advancements and its indispensable contributions to the discovery of molecular targets and therapeutic strategies for these NDDs.

Analysis of C9orf72 repeat length in progressive supranuclear palsy, corticobasal syndrome, corticobasal degeneration, and atypical parkinsonism

BACKGROUND

Pathogenic hexanucleotide repeat expansions in C9orf72 are the commonest genetic cause of frontotemporal dementia and/or amyotrophic lateral sclerosis. There is growing interest in intermediate repeat expansions in C9orf72 and their relationship to a wide range of neurological presentations, including Alzheimer's disease, Parkinson's disease, progressive supranuclear palsy, corticobasal degeneration, and corticobasal syndromes.

AIMS

To assess the prevalence of intermediate C9orf72 repeat expansions in a large cohort of prospectively-recruited patients clinically diagnosed with progressive supranuclear palsy (PSP), corticobasal syndrome (CBS), and atypical parkinsonism (APS), compared with healthy controls. We also sought to replicate the association between C9orf72 repeat length and CBD in neuropathologically confirmed cases.

METHODS

626 cases, including PSP (n = 366), CBS (n = 130), and APS (n = 53) from the PROSPECT study, and 77 cases with pathologically confirmed CBD were screened for intermediate repeat expansions in C9orf72 using repeat-primed PCR. These were compared to controls from the PROSPECT-M-UK study and from the 1958 Birth Cohort.

RESULTS

There was no difference in the mean or largest allele size in any affected patient group compared with controls. A higher proportion of our affected cohort had large C9orf72 repeat expansions compared to controls, but there was no difference when comparing the frequency of intermediate expansions between affected patients and controls. There was no relationship between repeat length and age at onset, level of disability, or survival.

CONCLUSIONS

Intermediate expansions in C9orf72 do not appear to be a genetic risk factor for PSP, CBS, CBD, or atypical parkinsonism. They are not associated with age at onset, disability, or survival in our study.

C9ORF72 poly-PR disrupts expression of ALS/FTD-implicated STMN2 through SRSF7

A hexanucleotide repeat expansion in C9ORF72 is the most common genetic cause of amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), and combined ALS/FTD. The repeat is transcribed in the sense and the antisense directions to produce several dipeptide repeat proteins (DPRs) that have toxic gain-of-function effects; however, the mechanisms by which DPRs lead to neural dysfunction remain unresolved. Here, we observed that poly-proline-arginine (poly-PR) was sufficient to inhibit axonal regeneration of human induced pluripotent stem cell (iPSC)-derived neurons. Global phospho-proteomics revealed that poly-PR selectively perturbs nuclear RNA binding proteins (RBPs). In neurons, we found that depletion of one of these RBPs, SRSF7 (serine/arginine-rich splicing factor 7), resulted in decreased abundance of STMN2 (stathmin-2), though not TDP-43. STMN2 supports axon maintenance and repair and has been recently implicated in the pathogenesis of ALS/FTD. We observed that depletion of SRSF7 impaired axonal regeneration, a phenotype that could be rescued by exogenous STMN2. We propose that antisense repeat-encoded poly-PR perturbs RBPs, particularly SRSF7, resulting in reduced STMN2 and axonal repair defects in neurons. Hence, we provide a potential link between DPRs gain-of-function effects and STMN2 loss-of-function phenotypes in neurodegeneration.

Accurate DNA Methylation Predictor for C9orf72 Repeat Expansion Alleles in the Pathogenic Range

The hexanucleotide (G 4 C 2 ) repeat expansion in the promoter region of C9orf72 is the most frequent genetic cause of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS). In this study, we conducted a genome-wide DNA methylation (DNAm) analysis using EPIC version 2 (EPICv2) arrays on an FTD cohort comprising 27 carriers and 250 non-carriers of the pathogenic C9orf72 repeat expansion from the Amsterdam Dementia Cohort. We identified differentially methylated CpGs probes associated with the pathogenic C9orf72 expansion and used these findings to create a DNAm Least Absolute Shrinkage and Selection Operator (LASSO) predictor to identify repeat expansion carriers. Eight CpG sites at the C9orf72 locus were significantly differentially hypermethylated in repeat expansion carriers compared to non-carriers. The LASSO model predicted repeat expansion status with an average accuracy of 98.6%. The LASSO predictor was further validated in an independent cohort of 2,548 subjects with available EPICv2 data, identifying four C9orf72 repeat expansion carriers, subsequently confirmed by repeat-primed PCR. This result not only illustrates the accuracy of the DNAm predictor of C9orf72 repeat expansion carriers but also suggests that repeat expansion carriers may be more prevalent than expected. The identification of a highly accurate DNAm biomarker for a repeat expansion locus associated with neurodegenerative disorders may provide great value for studying this locus. The approach holds significant promise for investigating this and other repeat expansion loci, particularly given the growing interest in epigenetic epidemiological studies involving large cohorts with available DNAm data.

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Unveiling amyotrophic lateral sclerosis complexity: insights from proteomics, metabolomics and microbiomics

Amyotrophic lateral sclerosis is the most common motor neuron disease and manifests as a clinically and genetically heterogeneous neurodegenerative disorder mainly affecting the motor systems. To date, despite promising results and accumulating knowledge on the pathomechanisms of amyotrophic lateral sclerosis, a specific disease-modifying treatment is still not available. In vitro and in vivo disease models coupled with multiomics techniques have helped elucidate the pathomechanisms underlying this disease. In particular, omics approaches are powerful tools for identifying new potential disease biomarkers that may be particularly useful for diagnosis, prognosis and assessment of treatment response. In turn, these findings could support physicians in stratifying patients into clinically relevant subgroups for the identification of the best therapeutic targets. Here, we provide a comprehensive review of the most relevant literature highlighting the importance of proteomics approaches in determining the role of pathogenic misfolded/aggregated proteins and the molecular mechanisms involved in the pathogenesis and progression of amyotrophic lateral sclerosis. In addition, we explored new findings arising from metabolomic and lipidomic studies, which can aid to elucidate the intricate metabolic alterations underlying amyotrophic lateral sclerosis pathology. Moreover, we integrated these insights with microbiomics data, providing a thorough understanding of the interplay between metabolic dysregulation and microbial dynamics in disease progression. Indeed, a greater integration of these multiomics data could lead to a deeper understanding of disease mechanisms, supporting the development of specific therapies for amyotrophic lateral sclerosis.

Combined impact of CHCHD10 p.Gly66Val and three other variants suggests oligogenic contributions to ALS

Introduction

Amyotrophic lateral sclerosis (ALS) is a severe neurodegenerative disease characterized by a progressive loss of motor neurons and muscle atrophy. Genetic factors are known to play important roles in ALS and concomitant presence of rare variants in ALS patients have been increasingly reported.

Methods

In order to explore the genetic variants in ALS patients within the context of oligogenic inheritance and to elucidate the clinical heterogeneity observed in these patients, we conducted whole-genome sequencing on 34 familial ALS (FALS) probands.

Results

In one proband, we identified a CHCHD10 p.Gly66Val variant, along with three additional variants: UNC13A p.Leu1034Val, SUSD1 p.Trp704Ser, and SQSTM1 p.His359del. This patient exhibited a slow disease progression and a prolonged survival duration, consistent with the clinical features of ALS patients with CHCHD10 variants. This suggests that the CHCHD10 p.Gly66Val variant may play a predominant role in shaping the patient's phenotype, while the other variants may primarily contribute to ALS occurrence.

Discussion

Variants in CHCHD10 have been found in ALS and other neurodegenerative diseases, exhibiting significant clinical variability. However, the combinatorial effect of CHCHD10 and other ALS-related gene variants has not been fully studied. Our findings suggest that the combined impact of these four variants contributes to this patient's ALS phenotype, distinguishing it from other, less severe neuromuscular disorders associated with CHCHD10 mutations. Overall, this study further supports the oligogenic pathogenic basis of ALS and offers new insights into understanding the intricate clinical presentations associated with CHCHD10 variants.

Emerging Ferroptosis Involvement in Amyotrophic Lateral Sclerosis Pathogenesis: Neuroprotective Activity of Polyphenols

Neurodegenerative diseases are a group of diseases that share common features, such as the generation of misfolded protein deposits and increased oxidative stress. Among them, amyotrophic lateral sclerosis (ALS), whose pathogenesis is still not entirely clear, is a complex neurodegenerative disease linked both to gene mutations affecting different proteins, such as superoxide dismutase 1, Tar DNA binding protein 43, Chromosome 9 open frame 72, and Fused in Sarcoma, and to altered iron homeostasis, mitochondrial dysfunction, oxidative stress, and impaired glutamate metabolism. The purpose of this review is to highlight the molecular targets common to ALS and ferroptosis. Indeed, many pathways implicated in the disease are hallmarks of ferroptosis, a recently discovered type of iron-dependent programmed cell death characterized by increased reactive oxygen species (ROS) and lipid peroxidation. Iron accumulation results in mitochondrial dysfunction and increased levels of ROS, lipid peroxidation, and ferroptosis triggers; in addition, the inhibition of the Xc- system results in reduced cystine levels and glutamate accumulation, leading to excitotoxicity and the inhibition of GPx4 synthesis. These results highlight the potential involvement of ferroptosis in ALS, providing new molecular and biochemical targets that could be exploited in the treatment of the disease using polyphenols.

Recurrent patterns of widespread neuronal genomic damage shared by major neurodegenerative disorders

Amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), and Alzheimer's disease (AD) are common neurodegenerative disorders for which the mechanisms driving neuronal death remain unclear. Single-cell whole-genome sequencing of 429 neurons from three C9ORF72 ALS, six C9ORF72 FTD, seven AD, and twenty-three neurotypical control brains revealed significantly increased burdens in somatic single nucleotide variant (sSNV) and insertion/deletion (sIndel) in all three disease conditions. Mutational signature analysis identified a disease-associated sSNV signature suggestive of oxidative damage and an sIndel process, affecting 28% of ALS, 79% of FTD, and 65% of AD neurons but only 5% of control neurons (diseased vs. control: OR=31.20, p = 2.35×10-10). Disease-associated sIndels were primarily two-basepair deletions resembling signature ID4, which was previously linked to topoisomerase 1 (TOP1)-mediated mutagenesis. Duplex sequencing confirmed the presence of sIndels and identified similar single-strand events as potential precursor lesions. TOP1-associated sIndel mutagenesis and resulting genome instability may thus represent a common mechanism of neurodegeneration.

The Relationship Between Ribosome-Associated Quality Control and Neurological Disorders

Ribosome-associated quality control (RQC), a ubiquitous process essential for maintaining protein homeostasis in eukaryotes, acts as a critical surveillance system for protein translation. By identifying and eliminating stalled ribosomes, RQC prevents aberrant translation and the production of potentially toxic misfolded proteins. The review focuses on the role of RQC in mammals, where its complete functionality remains to be elucidated. This study delves into the mechanisms through which dysfunction in RQC plays a role in the development of neurological disorders, focusing on neurodegenerative and neurodevelopmental diseases. We explore the underlying mechanisms by which RQC dysfunction contributes to the pathogenesis of neurological disorders, particularly neurodegenerative and neurodevelopmental diseases. Further research is crucial to unravel the intricate mechanisms governing RQC's influence on neurological function. This knowledge will pave the way for exploring therapeutic avenues targeting RQC factors as potential interventions for these debilitating diseases. By shedding light on RQC's contribution to neurological disorders, this review opens doors for developing targeted therapies and interventions.

Integrated transcriptomic profiling reveals a STING-mediated Type II Interferon signature in SOD1-mutant amyotrophic lateral sclerosis models

Inflammation is a hallmark of amyotrophic lateral sclerosis (ALS), particularly in cases with SOD1 mutations. Using integrative transcriptomics, we analyzed gene expression changes in mouse models throughout progression, human induced-pluripotent stem cells (hiPSCs), and post-mortem spinal cord tissue from ALS patients. We identified a conserved upregulation of interferon (IFN) genes and IFN-stimulating genes (ISGs) in both mouse models and human ALS, with a predominance Type I IFNs (IFN-α/β) in mice and Type II IFNs (IFN-γ) in humans. In mouse models, we observed robust and sustained upregulation of Type I and II ISGs, including ATF3, beginning at disease onset stage and persisting throughout disease progression. Single-cell transcriptomics further pinpointed vascular endothelial cells as a major source of ISGs. Furthermore, we found that the STING-TBK1 axis is essential for the induction of Type II ISGs in ALS, as its deletion impaired their expression. Our study uncovers a conserved ISGs signature across ALS models and patients, highlighting the potential role of innate immune activation in ALS pathogenesis. These findings suggest that ISGs may serve as potential biomarkers and therapeutic targets for ALS.

Functional Landscape of hnRNPA3 in Disease Pathogenesis

The heterogeneous nuclear ribonucleic acid protein family participates in various intracellular reactions, such as RNA splicing, transport, DNA repair, cellular signal transduction, and gene expression regulation, and is involved in various disease processes. As a late-discovered member, heterogeneous nuclear ribonucleoprotein A3 has received increasing attention, but its main physiological functions and exact mechanisms involved in disease processes have not yet reached a consensus. In this review, we summarize the function of heterogeneous nuclear ribonucleoprotein A3 and the literature on its role in neurodegenerative and metabolic diseases, as well as in various tumors, to explore the applicability of heterogeneous nuclear ribonucleoprotein A3 as a therapeutic target and prognostic indicator.

Micro-Doses of DNP Preserve Motor and Muscle Function with a Period of Functional Recovery in Amyotrophic Lateral Sclerosis Mice

OBJECTIVE

Mitochondrial dysfunction is one of the earliest pathological events observed in amyotrophic lateral sclerosis (ALS). The aim of this study is to evaluate the therapeutic efficacy of 2,4-dinitrophenol (DNP), a mild mitochondrial uncoupler, in an ALS mouse model to provide preclinical proof-of-concept evidence of using DNP as a potential therapeutic drug for ALS.

METHODS

hSOD1G93A mice were treated with 0.5-1.0 mg/kg DNP through daily oral gavage from presymptomatic stage or disease onset until 18 weeks old. Longitudinal behavioral studies were performed weekly or biweekly from 6 to 18 weeks old. In situ muscle contraction measurements in extensor digitorum longus muscles were conducted to evaluate the preservation of contractile force and motor unit numbers in hSOD1G93A mice following DNP treatment. Muscle innervation and inflammatory markers were assessed using immunostaining. Extent of protein oxidation and activation of Akt pathway were also examined.

RESULTS

DNP delayed disease onset; improved motor coordination and muscle performance in vivo; preserved muscle contractile function, neuromuscular junction morphology, and muscle innervation; and reduced inflammation and protein oxidation at 18 weeks old in hSOD1G93A mice. Strikingly, symptomatic hSOD1G93A mice exhibited a period of recovery in running ability at 20 cm/s several weeks after 2,4-dinitrophenol treatment started at disease onset, offering the first observation in disease phenotype reversal using a small molecule.

INTERPRETATION

Our results strongly support that micro-dose DNP may be used as a potential novel treatment for ALS patients, with a possibility for recovery, when used at optimal doses and time of intervention. ANN NEUROL 2025;97:542-557.

Amyotrophic lateral sclerosis caused by hexanucleotide repeat expansions in C9orf72: from genetics to therapeutics

GGGGCC repeat expansions in C9orf72 are a common genetic cause of amyotrophic lateral sclerosis in people of European ancestry; however, substantial variability in the penetrance of the mutation, age at disease onset, and clinical presentation can complicate diagnosis and prognosis. The repeat expansion is bidirectionally transcribed in the sense and antisense directions into repetitive RNAs and translated into dipeptide repeat proteins, and both accumulate in the cortex, cerebellum, and the spinal cord. Furthermore, neuropathological aggregates of phosphorylated TDP-43 are observed in motor cortex and other cortical regions, and in the spinal cord of patients at autopsy. C9orf72 repeat expansions can also cause frontotemporal dementia. The GGGGCC repeat induces a complex interplay of loss-of-function and gain-of-function pathological mechanisms. Clinical trials using antisense oligonucleotides to target the GGGGCC repeat RNA have not been successful, potentially because they only target a single gain-of-function mechanism. Novel therapeutic approaches targeting the DNA repeat expansion, multiple repeat-derived RNA species, or downstream targets of TDP-43 dysfunction are, however, on the horizon, together with the development of diagnostic and prognostic biomarkers.

Driving Forces of RNA Condensation Revealed through Coarse-Grained Modeling with Explicit Mg2

RNAs are major drivers of phase separation in the formation of biomolecular condensates, and can undergo protein-free phase separation in the presence of divalent ions or crowding agents. Much remains to be understood regarding how the complex interplay of base stacking, base pairing, electrostatics, ion interactions, and particularly structural propensities governs RNA phase behavior. Here we develop an intermediate resolution model for condensates of RNAs (iConRNA) that can capture key local and long-range structure features of dynamic RNAs and simulate their spontaneous phase transitions with Mg2+. Representing each nucleotide using 6-7 beads, iConRNA accurately captures base stacking and pairing and includes explicit Mg2+. The model does not only reproduce major conformational properties of poly(rA) and poly(rU), but also correctly folds small structured RNAs and predicts their melting temperatures. With an effective model of explicit Mg2+, iConRNA successfully recapitulates experimentally observed lower critical solution temperature phase separation of poly(rA) and triplet repeats, and critically, the nontrivial dependence of phase transitions on RNA sequence, length, concentration, and Mg2+ level. Further mechanistic analysis reveals a key role of RNA folding in modulating phase separation as well as its temperature and ion dependence, besides other driving forces such as Mg2+-phosphate interactions, base stacking, and base pairing. These studies also support iConRNA as a powerful tool for direct simulation of RNA-driven phase transitions, enabling molecular studies of how RNA conformational dynamics and its response to complex condensate environment control the phase behavior and condensate material properties.

SIGNIFICANCE STATEMENT

Dynamic RNAs and proteins are major drivers of biomolecular phase separation that has been recently discovered to underlie numerous biological processes and be involved in many human diseases. Molecular simulation has an indispensable role to play in dissecting the driving forces and regulation of biomolecular phase separation. The current work describes a high-resolution coarse-grained RNA model that is capable of describing the structure dynamics and complex sequence, concentration, temperature and ion dependent phase transitions of flexible RNAs. The study further reveals a central role of RNA folding in coordinating Mg2+-phosphate interactions, base stacking, and base pairing to drive phase separation, paving the road for studies of RNA-mediated phase separation in relevant biological contexts.

Investigation of the role of miRNA variants in neurodegenerative brain diseases

Introduction

miRNAs are small noncoding elements known to regulate different molecular processes, including developmental and executive functions in the brain. Dysregulation of miRNAs could contribute to brain neurodegeneration, as suggested by miRNA profiling studies of individuals suffering from neurodegenerative brain diseases (NBDs). Here, we report rare miRNA variants in patients with Alzheimer's dementia (AD) and frontotemporal dementia (FTD).

Methods

We initially used whole exome sequencing data in a subset of FTD patients (n = 209) from Flanders-Belgium. We then performed targeted resequencing of variant-harboring miRNAs in an additional subset of FTD patients (n = 126) and control individuals (n = 426). Lastly, we sequenced the MIR885 locus in a Flanders-Belgian AD cohort (n = 947) and a total number of n = 755 controls.

Results

WES identified rare seed variants in MIR656, MIR423, MIR122 and MIR885 in FTD patients. Most of these miRNAs bind to FTD-associated genes, implicated in different biological pathways. Additionally, some miRNA variants create novel binding sites for genes associated with FTD. Sequencing of the MIR885 locus in the AD cohort initially showed a significant enrichment of MIR885 variants in AD patients compared to controls (SKAT-O, p-value = 0.026). Genetic association was not maintained when we included sex and APOE status as covariates. Using the miRVaS prediction tool, variants rs897551430 and rs993255773 appeared to evoke significant structural changes in the primary miRNA. These variants are also predicted to strongly downregulate mature miR885 levels, in line with what is reported for MIR885 in the context of AD.

Discussion

Functional investigation of miRNAs/variants described in this study could propose novel miRNA-mediated molecular cascades in FTD and AD pathogenicity. Furthermore, we believe that the genetic evidence presented here suggests a role for MIR885 in molecular mechanisms involved in AD and warrants genetic follow-up in larger cohorts to explore this hypothesis.

Prevalence of Pathogenic Variants and Eligibility Criteria for Genetic Testing in Patients Who Visit a Memory Clinic

BACKGROUND AND OBJECTIVES

Identifying genetic causes of dementia in patients visiting memory clinics is important for patient care and family planning. Traditional clinical selection criteria for genetic testing may miss carriers of pathogenic variants in dementia-related genes. This study aimed identify how many carriers we are missing and to optimize criteria for selecting patients for genetic counseling in memory clinics.

METHODS

In this clinical cohort study, we retrospectively genetically tested patients during 2.5 years (2010-2012) visiting the Alzheimer Center Amsterdam, a specialized memory clinic. Genetic tests consisted of a 54-gene dementia panel, focusing on Class IV/V variants per American College of Medical Genetics and Genomics guidelines, including APP duplications and the C9ORF72 repeat expansion. We determined the prevalence of pathogenic variants and propose new eligibility criteria for genetic testing in memory clinics. The eligibility criteria were prospectively applied for 1 year (2021-2022), and results were compared with the retrospective cohort.

RESULTS

Genetic tests were retrospectively performed in in 1,022 of 1,138 patients (90%) who consecutively visited the memory clinic. Among these, 1,022 patients analyzed (mean age 62.1 ± 8.9 years; 40.4% were female), 34 pathogenic variant carriers were identified (3.3%), with 24 being symptomatic. Previous clinical criteria would have identified only 15 carriers (44% of all carriers, 65% of symptomatic carriers). The proposed criteria increased identification to 22 carriers (62.5% of all carriers, 91% of symptomatic carriers). In the prospective cohort, 148 (28.7%) of 515 patients were eligible for testing under the new criteria. Of the 90 eligible patients who consented to testing, 13 pathogenic carriers were identified, representing a 73% increase compared with the previous criteria.

DISCUSSION

We found that patients who visit a memory clinic and carry a pathogenic genetic variant are often not eligible for genetic testing. The proposed new criteria improve the identification of patients with a genetic cause for their cognitive complaints. In systems without practical or financial barriers to genetic testing, the new criteria can enhance personalized care. In other countries where the health care systems differs and in other genetic ancestry groups, the performance of the criteria may be different.