FUS unveiled in mitochondrial DNA repair and targeted ligase-1 expression rescues repair-defects in FUS-linked motor neuron disease.

This study establishes the physiological role of Fused in Sarcoma (FUS) in mitochondrial DNA (mtDNA) repair and highlights its implications to the pathogenesis of FUS-associated neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS). Endogenous FUS interacts with and recruits mtDNA Ligase IIIα (mtLig3) to DNA damage sites within mitochondria, a relationship essential for maintaining mtDNA repair and integrity in healthy cells. Using ALS patient-derived FUS mutant cell lines, a transgenic mouse model, and human autopsy samples, we discovered that compromised FUS functionality hinders mtLig3's repair role, resulting in increased mtDNA damage and mutations. These alterations cause various manifestations of mitochondrial dysfunction, particularly under stress conditions relevant to disease pathology. Importantly, rectifying FUS mutations in patient-derived induced pluripotent cells (iPSCs) preserves mtDNA integrity. Similarly, targeted introduction of human DNA Ligase 1 restores repair mechanisms and mitochondrial activity in FUS mutant cells, suggesting a potential therapeutic approach. Our findings unveil FUS's critical role in mitochondrial health and mtDNA repair, offering valuable insights into the mechanisms underlying mitochondrial dysfunction in FUS-associated motor neuron disease.

Fluctuating salience in those living with genetic risk of motor neuron disease: A qualitative interview study.

BACKGROUND: Motor neuron disease (MND) (also known as amyotrophic lateral sclerosis) is a life-limiting neurodegenerative condition. In up to 20% of people with MND, a pathogenic variant associated with autosomal dominant inheritance can be identified. Children of people carrying a pathogenic variant have a 50% chance of inheriting this and a higher, although harder to predict, chance of developing the disease compared to the general adult population. This paper explores the experience of living with the genetic risk of MND. METHODS: We undertook a UK-based interview study with 35 individuals, including: 7 people living with genetically-mediated forms of MND; 24 asymptomatic relatives, the majority of whom had an increased risk of developing the disease; and 4 unrelated partners. RESULTS: We explore how individuals make sense of genetic risk, unpacking the interplay between genetic knowledge, personal perception, experiences of the disease in the family, age and life stage and the implications that living with risk has for different aspects of their lives. We balance an emphasis on the emotional and psychological impact described by participants, with a recognition that the salience of risk fluctuates over time. Furthermore, we highlight the diverse strategies and approaches people employ to live well in the face of uncertainty and the complex ways they engage with the possibility of developing symptoms in the future. Finally, we outline the need for open-ended, tailored support and information provision. CONCLUSIONS: Drawing on wider literature on genetic risk, we foreground how knowledge of MND risk can disrupt individuals' taken-for-granted assumptions on life and perceptions of the future, but also its contextuality, whereby its relevance becomes more prominent at critical junctures. This research has been used in the development of a public-facing resource on the healthtalk.org website. PATIENT OR PUBLIC CONTRIBUTION: People with experience of living with genetic risk were involved throughout the design and conduct of the study and advised on aspects including the topic guide, sampling and recruitment and the developing analysis. Two patient and public involvement contributors joined a formal advisory panel.

A report of resources used by clinicians in the UK to support motor neuron disease genomic testing.

Genetic testing is a key decision-making point for people with motor neuron disease (MND); to establish eligibility for clinical trials, better understand the cause of their condition, and confirm the potential risk to relatives, who may be able to access predictive testing. Given the wide-reaching implications of MND genetic and predictive testing, it is essential that families are given adequate information, and that staff are provided with appropriate training. In this report we overview the information resources available to people with MND and family members around genetic testing, and the educational and training resources available to staff, based on information obtained through a freedom of information request to UK-based NHS Trusts. MND Association resources were most commonly used in information sharing, though we highlight distinctions between neurology and genetics centers. No respondents identified comprehensive training around MND genetic testing. We conclude with practice implications and priorities for the development of resources and training.

Child Neurology: Allgrove Syndrome: An Intriguing Etiology of Motor Neuron Disease in Children

Motor neuron diseases are a rare group of neurodegenerative disorders with considerable phenotypic heterogeneity and a multitude of etiologies in the pediatric population. In this study, we report 2 unrelated adolescents (a boy and a girl) who presented with 4-6 years of progressive difficulty in walking, thinning of limbs, and gradually progressive darkening of the skin. Examination revealed generalized hyperpigmentation of skin and features suggestive of motor neuron involvement such as tongue atrophy, wasting of distal extremities, and brisk deep tendon reflexes. On detailed exploration for systemic involvement, history of dysphagia, inability to produce tears, and Addisonian crises were evident. An etiologic diagnosis of Allgrove syndrome, which is characterized by a triad of achalasia, alacrimia, and adrenal insufficiency was considered. Next-generation sequencing revealed pathogenic variants in the AAAS gene, confirming the diagnosis. Steroid replacement therapy was initiated along with relevant multidisciplinary referrals. The disease stabilized in the boy and a significant improvement was noted in the girl. These cases highlight the value of non-neurologic cues in navigating the etiologic complexities of motor neuron diseases in children and adolescents. It is imperative for neurologists to develop awareness of the diverse neurologic manifestations associated with Allgrove syndrome because they are often the first to be approached. A multidisciplinary team of experts including neurologists, endocrinologists, gastroenterologists, ophthalmologists, and dermatologists is essential for planning comprehensive care for these patients.

SOD1-Related Cerebellar Ataxia and Motor Neuron Disease: Cp Variant as Functional Modifier?

We describe a novel superoxide dismutase (SOD1) mutation-associated clinical phenotype of cerebellar ataxia and motor neuron disease with a variant in the ceruloplasmin (Cp) gene, which may have possibly contributed to a multi-factorial phenotype, supported by genetic and protein structure analyses.

Familial motor neuron disease: co-occurrence of PLS and ALS (-FTD).

OBJECTIVE: To report the frequency and characteristics of patients diagnosed with primary lateral sclerosis (PLS) with a positive family history for motor neuron diseases (MND) in the Netherlands and to compare our findings to the literature. METHODS: Patients were identified through our ongoing, prospective population-based study on MND in The Netherlands, which also includes a standardized collection of patient characteristics, genetic testing, and family history. Only patients meeting the latest consensus criteria for definite PLS were included. The family history was considered positive for MND if any family members had been diagnosed with PLS, amyotrophic lateral sclerosis (ALS)(-FTD), or progressive muscular atrophy (PMA). Additionally, the literature was reviewed on PLS cases in which MND co-occurred within the same family. RESULTS: We identified 392 definite PLS cases, resulting in 9 families with a PLS patient and a positive family history for MND (2.3%). In only one of these pedigrees, a pathogenic variant (C9orf72 repeat expansion) was found. Our literature review revealed 23 families with a co-occurrence of PLS and MND, with 12 of them having a potentially pathogenic genetic variant. CONCLUSIONS: The consistent observation of PLS patients with a positive family history for MND, evident in both our study and the literature, implies the presence of shared underlying genetic factors between PLS and ALS. However, these factors are yet to be elucidated.

Amyotrophic Lateral Sclerosis and Other Motor Neuron Diseases.

OBJECTIVE: This article reviews the clinical spectrum of amyotrophic lateral sclerosis (ALS), its variant presentations, and the approach to diagnosis and management. This review includes a detailed discussion of current and emerging disease-modifying therapies and the management of respiratory and bulbar manifestations of disease. An updated review of ALS genetics and pathophysiology is also provided. This article also touches on several other important motor neuron diseases. LATEST DEVELOPMENTS: A new set of simplified diagnostic criteria may help identify patients at earlier stages of the disease. A coformulation of sodium phenylbutyrate and tauroursodeoxycholic acid has been shown to have a significant benefit on disease progression and survival, leading to approval by regulatory authorities in the United States and Canada. An oral formulation of edaravone and an antisense oligonucleotide to a SOD1 gene variation (tofersen) have also recently been approved by the US Food and Drug Administration (FDA). Phase 3 trials of intrathecal mesenchymal stem cells failed to meet primary end points for efficacy. Updated American Academy of Neurology quality measures for the care of patients with ALS were published in 2023. ESSENTIAL POINTS: There has been continued progress in ALS genetics, diagnosis, and disease-modifying therapies. However, we still lack a definitive biomarker or a treatment that can halt the progression or reverse the course of disease. The evolving understanding of the genetic and pathophysiologic underpinnings of disease offers promise for more effective and clinically meaningful treatments in the future.

[Amyotrophic lateral sclerosis-Motor neuron disease with a wide clinical and genetic spectrum]. / Amyotrophe Lateralsklerose ­ Motoneuronerkrankung mit großem klinischem und genetischem Spektrum.

BACKGROUND: Amyotrophic lateral sclerosis (ALS) is the most frequent motor neuron disease. Besides a timely diagnosis, precise knowledge of the clinical manifestations and differential diagnoses is essential. While most patients develop the disease at an older age, hereditary causes play a more frequent role in the juvenile forms. OBJECTIVE: What is the current state of ALS diagnostics, which new treatment options exist? MATERIAL AND METHOD: Literature search using Pubmed.gov. RESULTS: The main focus is on an individualized symptomatic treatment as no curative treatment approaches exist. However, new insights into the genetic and pathophysiological principles of the different forms of ALS open the way for future disease-modifying treatment options. CONCLUSION: In cases of a clinical suspicion of ALS molecular genetic diagnostics should be considered, particularly in juvenile and young adult patients, to exclude differential diagnoses and to enable patients access to new treatment approaches.

Facial onset sensory and motor neuronopathy (FOSMN syndrome): Cases series and systematic review.

OBJECTIVE: To provide new and comprehensive evidence for diagnosis and management of FOSMN syndrome. METHODS: We reviewed our database to identify patients with FOSMN syndrome. Online database including PubMed, EMBASE, and OVID were also searched for relevant cases. RESULTS: We identified a total of 71 cases, including 4 cases from our database and 67 ones from online searching. A predominance of male was observed [44 (62.0%)] with median onset age of 53 (range: 7-75) years old. The median (range) disease duration was 60 (3-552) months at the time of the visit. The initial symptoms could be sensory deficits in face (80.3%) or oral cavity (4.2%), bulbar paralysis (7.0%), dysosmia (1.4%), dysgeusia (4.2%), weakness or numbness of upper limbs (5.6%), or lower limbs (1.4%). Abnormal blink reflex was presented in 64 (90.1%) patients. CSF tests showed elevated protein level in 5 (7.0%) patients. Six (8.5%) patients had MND-related gene mutation. Five (7.0%) patients showed transient responsiveness to immunosuppressive therapy, then deteriorated relentlessly. Fourteen (19.7%) patients died, with an average survival time of around 4 years. Among them, five patients died of respiratory insufficiency. CONCLUSION: The age of onset, progress of disease course, and prognosis of FOSMN syndrome could be varied significantly. The prerequisites of diagnosis were progressive and asymmetric lower motor neuron dysfunction, with sensory dysfunction which usually showed in face at the onset. Immunosuppressive therapy could be tried in some patients with suspected inflammatory clues. In general, FOSMN syndrome tended to be motor neuron disease with sensory involvement.

Spectrum of SPTLC1-related disorders: a novel case of 'Ser331 syndrome' that expand the phenotype of hereditary sensory and autonomic neuropathy type 1A and motor neuron diseases.

We report a patient with early-onset hereditary sensory and autonomic neuropathy type 1A (HSAN-1A) who developed a distinct phenotype, with tongue fasciculation and atrophy, due to a mutation at serine 331 in the SPTLC1 gene. HSAN-1A manifestation causing tongue fasciculation and atrophy have been rarely found. Our report adds to the growing evidence of the existence of an overlap between hereditary neuropathy and motor neuron disease caused by pathogenic p.S331Y variant in SPTLC1 gene.

[Gene Therapies in Motor Neuron Diseases ALS and SMA]. / Gentherapien bei den Motoneuronerkrankungen ALS und SMA.

In the past, the diagnosis of motor neuron diseases such as amyotrophic lateral sclerosis (ALS) and 5q-associated spinal muscular atrophy (SMA) meant powerlessness in the face of seemingly untreatable diseases with severe motor-functional limitations and sometimes fatal courses. Recent advances in an understanding of the genetic causalities of these diseases, combined with success in the development of targeted gene therapy strategies, spell hope for effective, innovative therapeutic approaches, pioneering the ability to treat neurodegenerative diseases. While gene therapies have been approved for SMA since a few years, gene therapy research in ALS is still in clinical trials with encouraging results. This article provides an overview of the genetic background of ALS and SMA known to date and gene therapy approaches to them with a focus on therapy candidates that are in clinical trials or have already gained market approval.

Changing perspectives on frontotemporal dementia: A review.

This article examines the evolution in understanding of frontotemporal dementia (FTD) during the last four decades. A central theme is the recognition of heterogeneity. Originally construed as a disorder of behaviour and executive impairment, FTD is now known also to be associated with alterations in language, conceptual knowledge and praxis. An absence of neurological signs is the hallmark of many FTD patients, but there is also an established association with motor neurone disease (MND), progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD). FTD is commonly defined as an early onset dementia, yet about a quarter of patients present after the age of 65. The underlying pathological protein is tau, TDP-43 or more rarely fused-in-sarcoma (FUS). Distinct genetic mutations have been identified in familial FTD. There are predictable relationships between clinical phenotype, pathological substrate and genetic mutation. For example, a circumscribed semantic disorder predicts TDP-43 pathology, and speech or limb apraxia tau pathology. The co-occurrence of MND predicts TDP-43 pathology, and PSP and CBD tau pathology. FUS pathology is associated with very youthful onset, stereotyped behaviours and caudate atrophy. Non-fluent aphasia is linked to progranulin (GRN) mutations and MND and psychosis to repeat expansions in the C9orf72 gene. Despite striking worldwide consensus in findings there remain some issues of contention, largely related to the classification of FTD and its sub-variants. Understanding the diverse nature of FTD is crucial for effective diagnosis, management and the development of targeted therapies.

Loss of brainstem white matter predicts onset and motor neuron symptoms in C9orf72 expansion carriers: a GENFI study.

BACKGROUND AND OBJECTIVES: The C9orf72 expansion is the most common genetic cause of frontotemporal dementia (FTD) and/or motor neuron disease (MND). Corticospinal degeneration has been described in post-mortem neuropathological studies in these patients, especially in those with MND. We used MRI to analyze white matter (WM) volumes in presymptomatic and symptomatic C9orf72 expansion carriers and investigated whether its measure may be helpful in predicting the onset of symptoms. METHODS: We studied 102 presymptomatic C9orf72 mutation carriers, 52 symptomatic carriers: 42 suffering from FTD and 11 from MND, and 75 non-carriers from the Genetic Frontotemporal dementia Initiative (GENFI). All subjects underwent T1-MRI acquisition. We used FreeSurfer to estimate the volume proportion of WM in the brainstem regions (midbrain, pons, and medulla oblongata). We calculated group differences with ANOVA tests and performed linear and non-linear regressions to assess group-by-age interactions. RESULTS: A reduced WM ratio was found in all brainstem subregions in symptomatic carriers compared to both noncarriers and pre-symptomatic carriers. Within symptomatic carriers, MND patients presented a lower ratio in pons and medulla oblongata compared with FTD patients. No differences were found between presymptomatic carriers and non-carriers. Clinical severity was negatively associated with the WM ratio. C9orf72 carriers presented greater age-related WM loss than non-carriers, with MND patients showing significantly more atrophy in pons and medulla oblongata. DISCUSSION: We find consistent brainstem WM loss in C9orf72 symptomatic carriers with differences related to the clinical phenotype supporting the use of brainstem measures as neuroimaging biomarkers for disease tracking.

Genotype-phenotype characterisation of long survivors with motor neuron disease in Scotland.

BACKGROUND: We investigated the phenotypes and genotypes of a cohort of 'long-surviving' individuals with motor neuron disease (MND) to identify potential targets for prognostication. METHODS: Patients were recruited via the Clinical Audit Research and Evaluation for MND (CARE-MND) platform, which hosts the Scottish MND Register. Long survival was defined as > 8 years from diagnosis. 11 phenotypic variables were analysed. Whole genome sequencing (WGS) was performed and variants within 49 MND-associated genes examined. Each individual was screened for C9orf72 repeat expansions. Data from ancestry-matched Scottish populations (the Lothian Birth Cohorts) were used as controls. RESULTS: 58 long survivors were identified. Median survival from diagnosis was 15.5 years. Long survivors were significantly younger at onset and diagnosis than incident patients and had a significantly longer diagnostic delay. 42% had the MND subtype of primary lateral sclerosis (PLS). WGS was performed in 46 individuals: 14 (30.4%) had a potentially pathogenic variant. 4 carried the known SOD1 p.(Ile114Thr) variant. Significant variants in FIG4, hnRNPA2B1, SETX, SQSTM1, TAF15, and VAPB were detected. 2 individuals had a variant in the SPAST gene suggesting phenotypic overlap with hereditary spastic paraplegia (HSP). No long survivors had pathogenic C9orf72 repeat expansions. CONCLUSIONS: Long survivors are characterised by younger age at onset, increased prevalence of PLS and longer diagnostic delay. Genetic analysis in this cohort has improved our understanding of the phenotypes associated with the SOD1 variant p.(Ile114Thr). Our findings confirm that pathogenic expansion of C9orf72 is likely a poor prognostic marker. Genetic screening using targeted MND and/or HSP panels should be considered in those with long survival, or early-onset slowly progressive disease, to improve diagnostic accuracy and aid prognostication.

Serum total TDP-43 levels are decreased in frontotemporal dementia patients with C9orf72 repeat expansion or concomitant motoneuron disease phenotype.

BACKGROUND: Frontotemporal dementia (FTD) covers a spectrum of neurodegenerative disorders with various clinical and neuropathological subtypes. The two major pathological proteins accumulating in the brains of FTD patients, depending on their genetic background, are TDP-43 and tau. We aimed to evaluate whether total TDP-43 levels measured from the serum associate with the genotype or clinical phenotype of the FTD patients and whether serum TDP-43 provides prognostic or diagnostic value in the FTD spectrum disorders. METHODS: The study cohort included 254 participants with a clinical diagnosis of FTD (including all major genotypes and clinical phenotypes) and 105 cognitively healthy controls. Serum total TDP-43 levels measured with a single-molecule array (Simoa) were compared within the FTD group according to the genotype, clinical phenotype, and predicted neuropathological subtype of the patients. We also evaluated the associations between the TDP-43 levels and disease severity or survival in FTD. RESULTS: Total TDP-43 levels in the serum were significantly lower in the FTD group as compared to the healthy control group (275.3 pg/mL vs. 361.8 pg/mL, B = 0.181, 95%CI = 0.014-0.348, p = 0.034). The lowest TDP-43 levels were observed in the subgroup of FTD patients harboring predicted TDP-43 brain pathology (FTD-TDP, 241.4 pg/mL). The low levels in the FTD-TDP group were especially driven by C9orf72 repeat expansion carriers (169.2 pg/mL) and FTD patients with concomitant motoneuron disease (FTD-MND, 113.3 pg/mL), whereas GRN mutation carriers did not show decreased TDP-43 levels (328.6 pg/mL). Serum TDP-43 levels showed no correlation with disease severity nor progression in FTD. CONCLUSIONS: Our results indicate that the total levels of TDP-43 in the serum are decreased especially in FTD patients with the C9orf72 repeat expansion or FTD-MND phenotype, both subtypes strongly associated with TDP-43 type B brain pathology. Serum-based measurement of TDP-43 could represent a useful tool in indicating C9orf72 repeat expansion and FTD-MND-related TDP-43 neuropathology for future diagnostics and intervention studies.

BiP inactivation due to loss of the deAMPylation function of FICD causes a motor neuron disease.

PURPOSE: The chaperone protein BiP is the master regulator of the unfolded protein response in the endoplasmic reticulum. BiP chaperone activity is regulated by the post-translational modification AMPylation, exclusively provided by FICD. We investigated whether FICD variants identified in patients with motor neuron disease could interfere with BiP activity regulation. METHODS: Exome sequencing was performed to identify causative pathogenic variants associated with motor neuron diseases. Functional studies were conducted on fibroblasts from patients to explore the molecular mechanism of the disease. RESULTS: We identified biallelic variants in FICD causing a neurodegenerative disease of upper and lower motor neurons. Affected individuals harbor a specific missense variant, Arg374His, positioned in the catalytic motif of the enzyme and important for adenosine triphosphate binding. The mutated residue abolishes intramolecular interaction with the regulatory residue Glu234, essential to inhibit AMPylation and to promote de-AMPylation by FICD. Consequently, fibroblasts from patients with FICD variants have abnormally increased levels of AMPylated and thus inactivated BiP. CONCLUSION: Loss of BiP chaperone activity in patients likely results in a chronic impairment of the protein quality control system in the endoplasmic reticulum. These findings will guide the development of therapeutic strategies for motoneuron and related diseases linked to proteotoxic stress.

The role of autophagy-lysosomal pathway in motor neuron diseases.

Motor neuron diseases (MNDs) include a broad group of diseases in which neurodegeneration mainly affects upper and/or lower motor neurons (MNs). Although the involvement of specific MNs, symptoms, age of onset, and progression differ in MNDs, the main pathogenic mechanism common to most MNDs is represented by proteostasis alteration and proteotoxicity. This pathomechanism may be directly related to mutations in genes encoding proteins involved in the protein quality control system, particularly the autophagy-lysosomal pathway (ALP). Alternatively, proteostasis alteration can be caused by aberrant proteins that tend to misfold and to aggregate, two related processes that, over time, cannot be properly handled by the ALP. Here, we summarize the main ALP features, focusing on different routes utilized to deliver substrates to the lysosome and how the various ALP pathways intersect with the intracellular trafficking of membranes and vesicles. Next, we provide an overview of the mutated genes that have been found associated with MNDs, how these gene products are involved in different steps of ALP and related processes. Finally, we discuss how autophagy can be considered a valid therapeutic target for MNDs treatment focusing on traditional autophagy modulators and on emerging approaches to overcome their limitations.

Identification of quantitative trait loci for survival in the mutant dynactin p150Glued mouse model of motor neuron disease.

Amyotrophic lateral sclerosis (ALS) is the most common degenerative motor neuron disorder. Although most cases of ALS are sporadic, 5-10% of cases are familial, with mutations associated with over 40 genes. There is variation of ALS symptoms within families carrying the same mutation; the disease may develop in one sibling and not in another despite the presence of the mutation in both. Although the cause of this phenotypic variation is unknown, it is likely related to genetic modifiers of disease expression. The identification of ALS causing genes has led to the development of transgenic mouse models of motor neuron disease. Similar to families with familial ALS, there are background-dependent differences in disease phenotype in transgenic mouse models of ALS suggesting that, as in human ALS, differences in phenotype may be ascribed to genetic modifiers. These genetic modifiers may not cause ALS rather their expression either exacerbates or ameliorates the effect of the mutant ALS causing genes. We have reported that in both the G93A-hSOD1 and G59S-hDCTN1 mouse models, SJL mice demonstrated a more severe phenotype than C57BL6 mice. From reciprocal intercrosses between G93A-hSOD1 transgenic mice on SJL and C57BL6 strains, we identified a major quantitative trait locus (QTL) on mouse chromosome 17 that results in a significant shift in lifespan. In this study we generated reciprocal intercrosses between transgenic G59S-hDCTN1 mice on SJL and C57BL6 strains and identified survival QTLs on mouse chromosomes 17 and 18. The chromosome 17 survival QTL on G93A-hSOD1 and G59S-hDCTN1 mice partly overlap, suggesting that the genetic modifiers located in this region may be shared by these two ALS models despite the fact that motor neuron degeneration is caused by mutations in different proteins. The overlapping region contains eighty-seven genes with non-synonymous variations predicted to be deleterious and/or damaging. Two genes in this segment, NOTCH3 and Safb/SAFB1, have been associated with motor neuron disease. The identification of genetic modifiers of motor neuron disease, especially those modifiers that are shared by SOD1 and dynactin-1 transgenic mice, may result in the identification of novel targets for therapies that can alter the course of this devastating illness.

Increased surface P2X4 receptors by mutant SOD1 proteins contribute to ALS pathogenesis in SOD1-G93A mice.

Amyotrophic lateral sclerosis (ALS) is a fatal motoneuron (MN) disease characterized by protein misfolding and aggregation leading to cellular degeneration. So far neither biomarker, nor effective treatment has been found. ATP signaling and P2X4 receptors (P2X4) are upregulated in various neurodegenerative diseases. Here we show that several ALS-related misfolded proteins including mutants of SOD1 or TDP-43 lead to a significant increase in surface P2X4 receptor density and function in vitro. In addition, we demonstrate in the spinal the cord of SOD1-G93A (SOD1) mice that misfolded SOD1-G93A proteins directly interact with endocytic adaptor protein-2 (AP2); thus, acting as negative competitors for the interaction between AP2 and P2X4, impairing constitutive P2X4 endocytosis. The higher P2X4 surface density was particularly observed in peripheral macrophages of SOD1 mice before the onset and during the progression of ALS symptoms positioning P2X4 as a potential early biomarker for ALS. P2X4 expression was also upregulated in spinal microglia of SOD1 mice during ALS and affect microglial inflammatory responses. Importantly, we report using double transgenic SOD1 mice expressing internalization-defective P2X4mCherryIN knock-in gene or invalidated for the P2X4 gene that P2X4 is instrumental for motor symptoms, ALS progression and survival. This study highlights the role of P2X4 in the pathophysiology of ALS and thus its potential for the development of biomarkers and treatments. We also decipher the molecular mechanism by which misfolded proteins related to ALS impact P2X4 trafficking at early pathological stage in cells expressing-P2X4.