RARE DISEASE
Juvenile amyotrophic lateral sclerosis
Juvenile amyotrophic lateral sclerosis
Juvenile amyotrophic lateral sclerosis
Synonyms: JALS, Juvenile Charcot disease, Juvenile Lou Gehrig disease
Synonyms: JALS, Juvenile Charcot disease, Juvenile Lou Gehrig disease
Synonyms: JALS, Juvenile Charcot disease, Juvenile Lou Gehrig disease
Drug discovery
3
drugs
With orphan designations
Overview
Juvenile amyotrophic lateral sclerosis (JALS) is a rare, severe neurodegenerative disorder marked by progressive upper/lower motor neuron degeneration, with symptom onset before age 25 [1][6][14]. It presents with spastic dysarthria, gait disturbances, pseudobulbar affect, and muscle atrophy [1][6]. Genetic mutations (ALS2, FUS, SIGMAR1, SPG11) underlie ~40% of cases, often with autosomal recessive inheritance [1][6][19]. Diagnosis relies on clinical evaluation, electrophysiological studies, and genetic testing [1][6].
Population
Burden
Rapid progression in FUS-associated cases (median survival: 12–24 months), slower decline in ALS2-related forms [6][19][20].
High disability burden: 68% require mobility aids by adulthood; respiratory failure is the primary cause of mortality [1][16][17].
Limited epidemiological data, with underrepresentation in global ALS registries [2][4][7].
Therapies
Disease-modifying: Riluzole (glutamate inhibition), Edaravone (antioxidant), and antisense oligonucleotides (e.g., ION363 for FUS mutations) [3][8][13][19].
Symptomatic: Multidisciplinary care including physical/occupational therapy, respiratory support, and Nuedexta for pseudobulbar affect [1][3][16].
Emerging: Gene therapy trials targeting SOD1, FUS, and C9orf72 mutations [3][8][18].
Categories: rare genetic diseases, rare neurological diseases
Research Papers
59 drug discovery papers about Juvenile amyotrophic lateral sclerosis, with 1 next-in-class emerging drug candidate forecasted to outperform the average preclinical success rate. Recent publications:
59 drug discovery papers about Juvenile amyotrophic lateral sclerosis, with 1 next-in-class emerging drug candidate forecasted to outperform the average preclinical success rate. Recent publications:
categories:
Small molecules
proteins
2024-03-09 | FUS unveiled in mitochondrial DNA repair and targeted ligase-1 expression rescues repair-defects in FUS-linked motor neuron disease
Abstract 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.
2022-01-17 | SETX (senataxin), the helicase mutated in AOA2 and ALS4, functions in autophagy regulation.
SETX (senataxin) is an RNA/DNA helicase that has been implicated in transcriptional regulation and the DNA damage response through resolution of R-loop structures. Mutations in SETX result in either of two distinct neurodegenerative disorders. SETX dominant mutations result in a juvenile form of amyotrophic lateral sclerosis (ALS) called ALS4, whereas recessive mutations are responsible for ataxia called ataxia with oculomotor apraxia type 2 (AOA2). How mutations in the same protein can lead to different phenotypes is still unclear. To elucidate AOA2 disease mechanisms, we first examined gene expression changes following SETX depletion. We observed the effects on both transcription and RNA processing, but surprisingly observed decreased R-loop accumulation in SETX-depleted cells. Importantly, we discovered a strong connection between SETX and the macroautophagy/autophagy pathway, reflecting a direct effect on transcription of autophagy genes. We show that SETX depletion inhibits the progression of autophagy, leading to an accumulation of ubiquitinated proteins, decreased ability to clear protein aggregates, as well as mitochondrial defects. Analysis of AOA2 patient fibroblasts also revealed a perturbation of the autophagy pathway. Our work has thus identified a novel function for SETX in the regulation of autophagy, whose modulation may have a therapeutic impact for AOA2.Abbreviations: 3'READS: 3' region extraction and deep sequencing; ACTB: actin beta; ALS4: amyotrophic lateral sclerosis type 4; AOA2: ataxia with oculomotor apraxia type 2; APA: alternative polyadenylation; AS: alternative splicing; ATG7: autophagy-related 7; ATP6V0D2: ATPase H+ transporting V0 subunit D2; BAF: bafilomycin A1; BECN1: beclin 1; ChIP: chromatin IP; Chloro: chloroquine; CPT: camptothecin; DDR: DNA damage response; DNMT1: DNA methyltransferase 1; DRIP: DNA/RNA IP; DSBs: double strand breaks; EBs: embryoid bodies; FTD: frontotemporal dementia; GABARAP: GABA type A receptor-associated protein; GO: gene ontology; HR: homologous recombination; HTT: huntingtin; IF: immunofluorescence; IP: immunoprecipitation; iPSCs: induced pluripotent stem cells; KD: knockdown; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MN: motor neuron; MTORC1: mechanistic target of rapamycin kinase complex 1; PASS: PolyA Site Supporting; PFA: paraformaldehyde; RNAPII: RNA polymerase II; SCA: spinocerebellar ataxia; SETX: senataxin; SMA: spinal muscular atrophy; SMN1: survival of motor neuron 1, telomeric; SQSTM1/p62: sequestosome 1; TFEB: transcription factor EB; TSS: transcription start site; TTS: transcription termination site; ULK1: unc-51 like autophagy activating kinase 1; WB: western blot; WIPI2: WD repeat domain, phosphoinositide interacting 2; XRN2: 5'-3' exoribonuclease 2.
2021-08-09 | Dysregulation of IGF-1/GLP-1 signaling in the progression of ALS: potential target activators and influences on neurological dysfunctions.
The prominent causes for motor neuron diseases like ALS are demyelination, immune dysregulation, and neuroinflammation. Numerous research studies indicate that the downregulation of IGF-1 and GLP-1 signaling pathways plays a significant role in the progression of ALS pathogenesis and other neurological disorders. In the current review, we discussed the dysregulation of IGF-1/GLP-1 signaling in neurodegenerative manifestations of ALS like a genetic anomaly, oligodendrocyte degradation, demyelination, glial overactivation, immune deregulation, and neuroexcitation. In addition, the current review reveals the IGF-1 and GLP-1 activators based on the premise that the restoration of abnormal IGF-1/GLP-1 signaling could result in neuroprotection and neurotrophic effects for the clinical-pathological presentation of ALS and other brain diseases. Thus, the potential benefits of IGF-1/GLP-1 signal upregulation in the development of disease-modifying therapeutic strategies may prevent ALS and associated neurocomplications.
2019-03-28 | The discovery of shorter synthetic proteolytic peptides derived from Tob1 protein
We screened nearly 1000 synthetic peptides and found that JAL-AK22 (KYEGHWYPEKPYKGSGFRCIHI), which is derived from the BoxA domain in the Tob1 protein, activates both unfolded and folded proMMP-7. Interestingly, the smaller derivative of JAL-AK22, termed JAL-TA9 (YKGSGFRMI) possessed auto-proteolytic activity and cleaved three synthetic peptides fragment (MMP18-33, MMP18-40, and Aβ11-29) under physiological conditions. The kcat of JAL-TA9 was 4.58 × 10−4 min−1 against MMP18-33 and 6.5 × 10−4 min−1 against MMP18-40. These kinetic parameters are lower than those of general proteinases like trypsin, for which the kcat is 247.2 × 105 min−1 against benzoyl-l-arginine ethyl ester. In addition, a 5-mer peptide derived from JAL-TA9, GSGFR also cleaved Aβ11-29. These proteolytic activities were inhibited by AEBSF (4-(2-Aminoethyl) benzenesulfonyl fluoride hydrochloride), a serine protease inhibitor. Our results demonstrate that some small synthetic peptides have protease activity. Thus, we propose calling small peptides possessing with protease activity Catalytides (catalytic peptides). We expect that our findings will stimulate the development of novel Catalytides and related applications such as the development of strategic peptide drugs.
2018-02-22 | Rab5 and Alsin regulate stress-activated cytoprotective signaling on mitochondria
Mitochondrial stress response is essential for cell survival, and damaged mitochondria are a hallmark of neurodegenerative diseases. Thus, it is fundamental to understand how mitochondria relay information within the cell. Here, by investigating mitochondrial-endosomal contact sites we made the surprising observation that the small GTPase Rab5 translocates from early endosomes to mitochondria upon oxidative stress. This process is reversible and accompanied by an increase in Rab5-positive endosomes in contact with mitochondria. Interestingly, activation of Rab5 on mitochondria depends on the Rab5-GEF ALS2/Alsin, encoded by a gene mutated in amyotrophic lateral sclerosis (ALS). Alsin-deficient human-induced pluripotent stem cell-derived spinal motor neurons are defective in relocating Rab5 to mitochondria and display increased susceptibility to oxidative stress. These findings define a novel pathway whereby Alsin catalyzes the assembly of the Rab5 endocytic machinery on mitochondria. Defects in stress-sensing by endosomes could be crucial for mitochondrial quality control during the onset of ALS.
gene therapies
2026-01-27 | The genetics of autosomal recessive ALS: a review of the common forms and their phenotypes.
Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease marked by progressive degeneration of upper and lower motor neurons. Most forms of ALS associated with a suspected causal variant are inherited in an autosomal dominant manner. However, there is an important subset of autosomal recessive (AR) variants, often associated with early-onset or atypical clinical features. Advances in genetic sequencing have led to increased recognition of AR ALS. In this review, we focus on four key confirmed AR ALS-associated genes, which appear to be most common-ALS2, SPG11, OPTN, and the D90A variant of SOD1-reviewing their pathophysiology and unique clinical manifestations. We also highlight very rare AR mutations implicated in ALS, including SYNE1, ATP13A2, and FUS, and some associated with overlap syndromes or debated pathogenicity including SIGMAR1, ERLIN1, and ERLIN2. These genes are involved in an array of processes including axonal transport, endosomal trafficking, oxidative stress response, and autophagy, suggesting distinct mechanisms of motor neuron degeneration. Some forms of AR ALS more frequently present with juvenile onset and slower progression, but other genes are associated with broader phenotypic spectra. This includes overlap with hereditary spastic paraplegia (HSP) and hereditary ataxias. Understanding these AR forms of ALS may enhance diagnostic precision, improve prognostication, and may pave the way for targeted gene therapies. This review underscores the emerging significance of AR inheritance in ALS and calls for deeper investigation into its molecular and clinical dimensions.
2025-12-01 | SYNE1 Deficiency Manifesting Primarily With Motor Neuron Disease.
SYNE1 deficiency is an autosomal recessive disorder with a broad phenotypic spectrum, most commonly presenting as adult-onset cerebellar ataxia with or without motor neuron dysfunction. We aimed to expand this spectrum by describing the clinical and genetic findings in 2 unrelated families with early-onset motor neuron disease and virtually no cerebellar signs over time. We performed detailed clinical, neurophysiologic, and genetic studies of 2 unrelated families with juvenile amyotrophic lateral sclerosis (ALS) and biallelic variants in SYNE1. The phenotypes of both families showed onset of symptoms in childhood or adolescence, with signs of upper and lower motor neuron dysfunction in multiple territories suggestive of juvenile ALS. Patients developed progressive muscle weakness, eventually leading to respiratory distress and bulbar signs. Whole-exome sequencing identified SYNE1 biallelic truncating variants in both families: a homozygous nonsense variant, c.23131C>T (p.Gln7711*), in Family 1, and a novel homozygous splice-site variant, c.17851-1G>A, in Family 2. Notably, mild or no cerebellar manifestations were observed during the follow-up. This report highlights a novel phenotype of SYNE1 deficiency characterized by early-onset motor neuron disease and virtually no cerebellar manifestations, broadening the phenotypic spectrum of this complex neurodegenerative disease. These findings support investigating SYNE1 variants in juvenile ALS and including SYNE1 in motor neuron disease gene panels.
2025-08-20 | Ataxia and oculomotor apraxia caused by a large-scale deletion in the senataxin gene.
Senataxin, an RNA/DNA helicase, is a key protein providing genome stability and one of the best characterized R-loop-binding factors playing an important role in transcription and DNA repair processes. Pathogenic SETX gene variants cause autosomal recessive spinocerebellar ataxia with axonal neuropathy (AOA2, MIM #606002) and autosomal dominant juvenile amyotrophic lateral sclerosis (ALS4, MIM #602433), rare neurodegenerative disorders characterized by juvenile onset of progressive cerebellar ataxia, axonal sensorimotor peripheral neuropathy, combined upper and lower motor neuron symptoms, and increased serum alpha-fetoprotein (AFP; specific for AOA2). We report two cases of adult patients presenting with cerebellar syndrome, scanned speech, and exercise intolerance which started in the second/third decade of life and were followed by muscle weakness and impaired gait coordination. Whole exome sequencing (WES) was performed to analyze single nucleotide and copy number variants. A decreased coverage of a genomic region of around 16 kb on chromosome 9 (chr9:132,295,852-132,311,876), suggesting a deletion encompassing 5 exons of the SETX gene (exons 11-15, NM_015046.7) was observed. This homozygous SETX (9q34.13) deletion leads to a frame shift and consequently truncation of the helicase domain in the protein. Loss-of-function variants in the SETX gene are known to be pathogenic. Statistical analysis of NGS data from the Polish population identified a few heterozygous carriers, suggesting its region-specific origin.
2025-01-08 | Long‐Term Follow‐Up of a Patient With SPG11
ABSTRACT We present a case of a male patient with disease‐causing variants in SPG11 , a causative gene for autosomal recessive spastic paraplegia with a thin corpus callosum (ARHSP‐TCC), as well as juvenile amyotrophic lateral sclerosis (ALS5) and Charcot–Marie–Tooth disease (CMT2X). A neurological examination at age 18 revealed dysarthria, muscle weakness in bilateral lower extremities, hyperreflexia in patellar reflex, hyporeflexia in Achilles reflex with an extensor plantar reflex, and intellectual disability. Magnetic resonance imaging revealed a thin corpus callosum and ears of the lynx sign. At the age of 26, weakness and muscle atrophy progressed. While no sensory disturbances were noted, there was a mild decrease in sensory nerve action potentials of the sural nerve over the 8 years between 18 and 26. Clinicians should be aware that SPG11 belongs to the same spectrum of disorders as ALS5 and CMT2X and presents various phenotypes depending on the stage of the disease.
2024-10-19 | Phenotype and Genotype of Children with ALS2 gene-Related Disorder.
The Alsin Rho Guanine Nucleotide Exchange Factor (ALS2) gene encodes a protein alsin that functions as a guanine nucleotide exchange factor. The variations in ALS2 gene leads to degeneration of upper motor neurons of the corticospinal tract. The phenotypes resulting from variants in ALS2 gene are infantile-onset ascending hereditary spastic paralysis (IAHSP, OMIM # 607225), juvenile primary lateral sclerosis (JPLS, OMIM # 606353), and juvenile amyotrophic lateral sclerosis (JALS, OMIM # 205100). Our study objectives were to describe the clinical phenotype and genotype of children with an established diagnosis of ALS2 gene-related disorder. The clinical details, laboratory data, and genotype findings of children with an established diagnosis of ALS2 gene-related disorder were collected from the hospital electronic database after obtaining institutional review board approval. One family with three affected siblings, a second family with a proband and an affected fetus, and a third family with two affected siblings with ALS2 gene variants were identified. IAHSP was diagnosed in all of our patients with variants in ALS2 gene. The clinical findings observed in our patients were insidious onset progressive spastic paraparesis, contractures, and dysarthria. Nonsense variants were observed in four patients while frameshift variant was observed in one family. Novel variants in ALS2 gene were identified in two unrelated families. ALS2 mutation results in rare neurodegenerative disorders with the clinical spectrum encompassing IAHSP, JPLS, and JALS disorders. In view of allelic heterogeneity described in the literature, more research studies are needed for establishing genotype-phenotype correlation in patients with ALS2 gene-related disorder.
small molecules
2026-07-01 | RNA dysregulation and compromised neuronal identity drive pathogenesis in Senataxin-associated ALS
ABSTRACT RNA dysregulation is a recognized contributor to neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS), the most common motor neuron (MN) disease. However, the molecular mechanisms linking defects in RNA metabolism to selective neuronal vulnerability remain poorly understood. Alterations in the cellular levels of R-loops –structures forming by reannealing of the nascent RNA with the template DNA during transcription- have been observed in neurodegeneration, but it is unclear how perturbations in R-loop homeostasis contribute to neuronal dysfunction. Here we investigate the molecular basis of a juvenile form of ALS dubbed ALS4 that is caused by mutations in the helicase SETX, which plays important roles in the resolution of R-loops and transcription termination. Using isogenic human induced pluripotent stem cell-derived MNs, we show that ALS4-associated SETX mutations induce progressive axonal defects and widespread transcriptomic alterations, including reduced expression or altered splicing of transcripts critical for neuronal function. ALS4 MNs exhibit a transcriptional signature marked by cellular stress, aberrant cell cycle re-entry, and compromised neuronal identity that is partially shared by other forms of ALS. Mechanistically, these defects are partly driven by downstream aberrant activation of the TGF-β signaling pathway, whose pharmacological inhibition ameliorates axonal defects. Finally, our analyses support a link between mutant SETX ectopic activity at R-loops and the observed alterations in RNA expression and splicing, providing new insights into how RNA dysregulation can drive neuronal dysfunction Altogether, our work reveals how perturbations at the interface of transcription and R-loop metabolism can reshape neuronal identity and drive disease. Teaser Deregulation of TGF-β signaling drives axonal defects and compromised motor neuron identity in senataxin-mediated ALS
2026-01-13 | Compartment-specific transcriptome of motor neurons reveals impaired extracellular matrix signaling and activated cell cycle kinases in FUS-ALS.
Mutations in FUSED IN SARCOMA (FUS) cause juvenile-onset amyotrophic lateral sclerosis (ALS). Early pathogenesis of FUS-ALS involves impaired transcription and splicing, DNA damage response, and axonal degeneration. However, the molecular pathophysiology and the link between somatic and axonal phenotypes are still poorly understood. We evaluated whether compartment-specific transcriptome differences could distinguish and drive early axonal degeneration. We used iPSC-derived motor neurons (MNs) coupled with microfluidic approaches to generate RNA-sequencing profiles from axonal and somatodendritic compartments. We demonstrate that the axonal transcriptome is unique and distinct, with RNA metabolism, extracellular secretion, and matrix disassembly pathways particularly enriched in distal axonal compartments. FUS mutation leads to changes in distinct pathways that were clustered in only a few distinct protein-protein interaction (PPI) networks. Somatodendritic changes upon FUS mutation include WNT signaling, mitochondrial, extracellular matrix (ECM)-, and synapse-related functions. In contrast, analysis of the axonal transcriptome in mutant MNs centers on the PLK1 pathway, mitochondrial gene expression, and regulation of inflammation. Comparison to CLIP-seq data revealed a significant enrichment for PLK1 and DNA replication pathways in axons. PLK1 upregulation did not activate cell-cycle re-entry but contributed to mutant MNs survival, and its inhibition increased neuronal cell death. We propose that upregulation of PLK1 represents an early event in the pathogenesis of ALS and could act in response to DNA damage, mitochondrial damage, and immune response activation in the affected cells. Additionally, downregulation of ECM pathways in the somatodendritic compartment and axons could explain strongly compromised dynamics of axonal outgrowth. Overall, we provide a novel valuable resource of the potential targets and affected processes changed in the specific compartments of FUS-ALS motor neurons.
2025-08-24 | Characterization of novel and recurrent SPTLC2 variants in childhood-onset amyotrophic lateral sclerosis: Insights into sphingolipid dysregulation.
Amyotrophic lateral sclerosis (ALS) is a severe neurodegenerative disorder that progressively affects motor neurons. Gain-of-function mutations in serine palmitoyltransferase (SPT) genes, notably SPTLC1 and SPTLC2, have been linked to juvenile ALS. Here, we describe two childhood-onset ALS cases with distinct SPTLC2 mutations, providing new insights into sphingolipid dysregulation and its role in ALS pathogenesis. Two Chinese patients with early-onset ALS, both carrying SPTLC2 mutations, were recruited from Beijing Children's Hospital. We conducted whole-exome sequencing (WES) to identify genetic variants, followed by Sanger sequencing for validation. Sphingolipid profiles were analyzed using ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Clinical evaluations included neurological assessments, brain MRI and electromyography. Additionally, mutant cell lines were established to assess the functional effects of the specific mutations. Patient 1, a 6-year-old male, exhibited a novel heterozygous de-novo SPTLC2 variant (c.197T > G, p.T66R). Patient 2, a 7-year-old female, had a recurrent heterozygous de-novo SPTLC2 variant (c.778G > A, p.E260K). Both patients showed elevated levels of specific sphingolipids compared to controls, with distinct profiles between the SPTLC2-ALS and SPTLC1-hereditary sensory and autonomic neuropathy type 1 (HSAN1) cases. The novel p.T66R mutation was predicted to alter protein interactions within the SPT complex, potentially impairing sphingolipid homeostasis. Functional studies further revealed that the p.T66R variant reduces the inhibitory regulation of SPT by ORMDL proteins, leading to unrestrained SPT activity and excess sphingolipid production. Our findings identify a novel SPTLC2 variant linked to childhood-onset ALS and reveal altered sphingolipid profiles associated with different genetic mutations. These results underscore the importance of sphingolipid metabolism in ALS and suggest potential avenues for targeted therapeutic interventions. Further research is needed to explore treatment options aimed at modulating sphingolipid levels and correcting genetic defects, as well as investigating potential biomarkers for early diagnosis.
2025-08-20 | Cell type-specific alterations in excitability and inhibition of upper motor neurons in AlsinKO mice, a model of juvenile onset ALS.
In amyotrophic lateral sclerosis (ALS) motor cortex hyperexcitability is detected in both familial and sporadic cases, suggesting its centrality in the ALS phenotype; the underlying mechanisms, however, remain largely obscure. Here we utilize male and female UCHL1-eGFP (UeGFP) mice, in which the corticospinal neurons of the motor cortex are labeled with green fluorescent protein, to investigate the intrinsic excitability and synaptic inhibitory inputs on distinct neuron populations in WT-UeGFP and presymptomatic AlsinKO-UeGFP mice, which lack Alsin function and are a well-characterized mouse model for juvenile cases of ALS. We show that in the motor cortex of AlsinKO-UeGFP mice, eGFP-positive layer 5 pyramidal neurons, which represent upper motor neurons, show a decrease in intrinsic excitability compared with WT, whereas the electrophysiological properties of eGFP-negative cells, which identify callosal projection neurons, are unaffected. This alteration in intrinsic excitability, however, is counterbalanced by a decrease in the frequency of spontaneous inhibitory currents due to a cell-specific reduction in the number of inhibitory synaptic contacts on upper motor neurons. Thus, the overall excitability of upper motor neurons only displays negligible changes despite large alterations in intrinsic excitability and inhibitory synaptic input, which may explain why mice do not exhibit a prominent motor phenotype. The presence of this homeostatic interaction between intrinsic excitability and synaptic inhibition raises the question of which of the two changes is primary, and which is secondary, and shows that decreased function of motor cortex interneurons is an early event in ALS with Alsin mutations.Significance Statement We found that in AlsinKO mice, which recapitulate ALS disease in patients with Alsin mutations, intrinsic excitability and inhibitory synaptic input of upper motoneurons (but not callosal-projection neurons) are significantly reduced at presymptomatic disease stage. We show that in this model: 1) impaired function of cortical interneurons is an early event; 2) excitability alteration in the motor cortex is cell type-specific; 3) intrinsic excitability and synaptic inhibition are linked by a homeostatic mechanism. These results stress the importance of cortical interneurons in ALS and suggest that either homeostatic overcompensation or failure of compensation contribute to disease onset and progression. If these mechanisms are common in ALS patients, this may have important consequences for the design of novel therapeutic interventions.
2024-04-22 | Modeling sporadic juvenile ALS in iPSC-derived motor neurons explores the pathogenesis of FUSR503fs mutation
Introduction Fused in sarcoma (FUS) mutations represent the most common genetic etiology of juvenile amyotrophic lateral sclerosis (JALS), for which effective treatments are lacking. In a prior report, we identified a novel FUS mutation, c.1509dupA: p. R503fs (FUSR503fs), in a sporadic JALS patient. Methods The physicochemical properties and structure of FUSR503fs protein were analyzed by software: Multi-electrode array (MEA) assay, calcium activity imaging assay and transcriptome analysis were used to explore the pathophysiological mechanism of iPSC derived motor neurons. Results Structural analysis and predictions regarding physical and chemical properties of this mutation suggest that the reduction of phosphorylation and glycosylation sites, along with alterations in the amino acid sequence, may contribute to abnormal FUS accumulation within the cytoplasm and nucleus of induced pluripotent stem cell– derived motor neurons (MNs). Multi-electrode array and calcium activity imaging indicate diminished spontaneous electrical and calcium activity signals in MNs harboring the FUS R503fs mutation. Transcriptomic analysis reveals upregulation of genes associated with viral infection and downregulation of genes involved in neural function maintenance, such as the ATP6V1C2 gene. Treatment with ropinirole marginally mitigates the electrophysiological decline in FUS R503fs MNs, suggesting the utility of this cell model for mechanistic exploration and drug screening. Discussion iPSCs-derived motor neurons from JALS patients are promising tools for drug screening. The pathological changes in motor neurons of FUS R503fs may occur earlier than in other known mutation types that have been reported.
oligonucleotides
2025-07-15 | Pathology of three ALS patients with FUS variants, including one likely benign Q23L variant lacking FUS inclusions.
Fused in sarcoma (FUS) is an RNA-binding protein implicated in juvenile amyotrophic lateral sclerosis (ALS). Mutations in the FUS gene, particularly those affecting the nuclear localization signal (NLS), impair nuclear import and lead to cytoplasmic accumulation of FUS inclusions in motor neurons. However, the pathological and clinical significance of FUS variants outside the NLS remains less understood. Here, we describe clinical and histopathological findings from three ALS patients carrying FUS variants: two with NLS-region variants (R495X and P525L), and one with a variant in the N-terminal region outside the NLS (Q23L). The patients carrying NLS variants presented with aggressive, juvenile-onset spinal and bulbar ALS, characterized primarily by lower motor neuron involvement and rapid disease progression. In contrast, the Q23L patient exhibited a slowly progressive disease course, with predominantly upper motor neuron signs. Neuropathological analysis revealed cytoplasmic FUS inclusions in motor neurons of patients with NLS variants, consistent with typical FUS pathology. In contrast, the Q23L patient lacked FUS inclusions and instead displayed pTDP-43 pathology in the hippocampus, neocortex (including the motor cortex), nucleus olivaris, lentiform nucleus, striatum, and some lower motor neurons. Taken together, these results suggest that Q23L is most likely a benign variant. As antisense oligonucleotides (ASOs) targeting FUS are currently being explored in clinical trials, further neuropathological investigations are needed to determine whether ASO-mediated FUS silencing would be effective for patients carrying FUS variants outside the NLS region.
proteins
2024-03-09 | FUS unveiled in mitochondrial DNA repair and targeted ligase-1 expression rescues repair-defects in FUS-linked motor neuron disease
Abstract 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.
2022-01-17 | SETX (senataxin), the helicase mutated in AOA2 and ALS4, functions in autophagy regulation.
SETX (senataxin) is an RNA/DNA helicase that has been implicated in transcriptional regulation and the DNA damage response through resolution of R-loop structures. Mutations in SETX result in either of two distinct neurodegenerative disorders. SETX dominant mutations result in a juvenile form of amyotrophic lateral sclerosis (ALS) called ALS4, whereas recessive mutations are responsible for ataxia called ataxia with oculomotor apraxia type 2 (AOA2). How mutations in the same protein can lead to different phenotypes is still unclear. To elucidate AOA2 disease mechanisms, we first examined gene expression changes following SETX depletion. We observed the effects on both transcription and RNA processing, but surprisingly observed decreased R-loop accumulation in SETX-depleted cells. Importantly, we discovered a strong connection between SETX and the macroautophagy/autophagy pathway, reflecting a direct effect on transcription of autophagy genes. We show that SETX depletion inhibits the progression of autophagy, leading to an accumulation of ubiquitinated proteins, decreased ability to clear protein aggregates, as well as mitochondrial defects. Analysis of AOA2 patient fibroblasts also revealed a perturbation of the autophagy pathway. Our work has thus identified a novel function for SETX in the regulation of autophagy, whose modulation may have a therapeutic impact for AOA2.Abbreviations: 3'READS: 3' region extraction and deep sequencing; ACTB: actin beta; ALS4: amyotrophic lateral sclerosis type 4; AOA2: ataxia with oculomotor apraxia type 2; APA: alternative polyadenylation; AS: alternative splicing; ATG7: autophagy-related 7; ATP6V0D2: ATPase H+ transporting V0 subunit D2; BAF: bafilomycin A1; BECN1: beclin 1; ChIP: chromatin IP; Chloro: chloroquine; CPT: camptothecin; DDR: DNA damage response; DNMT1: DNA methyltransferase 1; DRIP: DNA/RNA IP; DSBs: double strand breaks; EBs: embryoid bodies; FTD: frontotemporal dementia; GABARAP: GABA type A receptor-associated protein; GO: gene ontology; HR: homologous recombination; HTT: huntingtin; IF: immunofluorescence; IP: immunoprecipitation; iPSCs: induced pluripotent stem cells; KD: knockdown; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MN: motor neuron; MTORC1: mechanistic target of rapamycin kinase complex 1; PASS: PolyA Site Supporting; PFA: paraformaldehyde; RNAPII: RNA polymerase II; SCA: spinocerebellar ataxia; SETX: senataxin; SMA: spinal muscular atrophy; SMN1: survival of motor neuron 1, telomeric; SQSTM1/p62: sequestosome 1; TFEB: transcription factor EB; TSS: transcription start site; TTS: transcription termination site; ULK1: unc-51 like autophagy activating kinase 1; WB: western blot; WIPI2: WD repeat domain, phosphoinositide interacting 2; XRN2: 5'-3' exoribonuclease 2.
2021-08-09 | Dysregulation of IGF-1/GLP-1 signaling in the progression of ALS: potential target activators and influences on neurological dysfunctions.
The prominent causes for motor neuron diseases like ALS are demyelination, immune dysregulation, and neuroinflammation. Numerous research studies indicate that the downregulation of IGF-1 and GLP-1 signaling pathways plays a significant role in the progression of ALS pathogenesis and other neurological disorders. In the current review, we discussed the dysregulation of IGF-1/GLP-1 signaling in neurodegenerative manifestations of ALS like a genetic anomaly, oligodendrocyte degradation, demyelination, glial overactivation, immune deregulation, and neuroexcitation. In addition, the current review reveals the IGF-1 and GLP-1 activators based on the premise that the restoration of abnormal IGF-1/GLP-1 signaling could result in neuroprotection and neurotrophic effects for the clinical-pathological presentation of ALS and other brain diseases. Thus, the potential benefits of IGF-1/GLP-1 signal upregulation in the development of disease-modifying therapeutic strategies may prevent ALS and associated neurocomplications.
2019-03-28 | The discovery of shorter synthetic proteolytic peptides derived from Tob1 protein
We screened nearly 1000 synthetic peptides and found that JAL-AK22 (KYEGHWYPEKPYKGSGFRCIHI), which is derived from the BoxA domain in the Tob1 protein, activates both unfolded and folded proMMP-7. Interestingly, the smaller derivative of JAL-AK22, termed JAL-TA9 (YKGSGFRMI) possessed auto-proteolytic activity and cleaved three synthetic peptides fragment (MMP18-33, MMP18-40, and Aβ11-29) under physiological conditions. The kcat of JAL-TA9 was 4.58 × 10−4 min−1 against MMP18-33 and 6.5 × 10−4 min−1 against MMP18-40. These kinetic parameters are lower than those of general proteinases like trypsin, for which the kcat is 247.2 × 105 min−1 against benzoyl-l-arginine ethyl ester. In addition, a 5-mer peptide derived from JAL-TA9, GSGFR also cleaved Aβ11-29. These proteolytic activities were inhibited by AEBSF (4-(2-Aminoethyl) benzenesulfonyl fluoride hydrochloride), a serine protease inhibitor. Our results demonstrate that some small synthetic peptides have protease activity. Thus, we propose calling small peptides possessing with protease activity Catalytides (catalytic peptides). We expect that our findings will stimulate the development of novel Catalytides and related applications such as the development of strategic peptide drugs.
2018-02-22 | Rab5 and Alsin regulate stress-activated cytoprotective signaling on mitochondria
Mitochondrial stress response is essential for cell survival, and damaged mitochondria are a hallmark of neurodegenerative diseases. Thus, it is fundamental to understand how mitochondria relay information within the cell. Here, by investigating mitochondrial-endosomal contact sites we made the surprising observation that the small GTPase Rab5 translocates from early endosomes to mitochondria upon oxidative stress. This process is reversible and accompanied by an increase in Rab5-positive endosomes in contact with mitochondria. Interestingly, activation of Rab5 on mitochondria depends on the Rab5-GEF ALS2/Alsin, encoded by a gene mutated in amyotrophic lateral sclerosis (ALS). Alsin-deficient human-induced pluripotent stem cell-derived spinal motor neurons are defective in relocating Rab5 to mitochondria and display increased susceptibility to oxidative stress. These findings define a novel pathway whereby Alsin catalyzes the assembly of the Rab5 endocytic machinery on mitochondria. Defects in stress-sensing by endosomes could be crucial for mitochondrial quality control during the onset of ALS.
gene therapies
2026-01-27 | The genetics of autosomal recessive ALS: a review of the common forms and their phenotypes.
Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease marked by progressive degeneration of upper and lower motor neurons. Most forms of ALS associated with a suspected causal variant are inherited in an autosomal dominant manner. However, there is an important subset of autosomal recessive (AR) variants, often associated with early-onset or atypical clinical features. Advances in genetic sequencing have led to increased recognition of AR ALS. In this review, we focus on four key confirmed AR ALS-associated genes, which appear to be most common-ALS2, SPG11, OPTN, and the D90A variant of SOD1-reviewing their pathophysiology and unique clinical manifestations. We also highlight very rare AR mutations implicated in ALS, including SYNE1, ATP13A2, and FUS, and some associated with overlap syndromes or debated pathogenicity including SIGMAR1, ERLIN1, and ERLIN2. These genes are involved in an array of processes including axonal transport, endosomal trafficking, oxidative stress response, and autophagy, suggesting distinct mechanisms of motor neuron degeneration. Some forms of AR ALS more frequently present with juvenile onset and slower progression, but other genes are associated with broader phenotypic spectra. This includes overlap with hereditary spastic paraplegia (HSP) and hereditary ataxias. Understanding these AR forms of ALS may enhance diagnostic precision, improve prognostication, and may pave the way for targeted gene therapies. This review underscores the emerging significance of AR inheritance in ALS and calls for deeper investigation into its molecular and clinical dimensions.
2025-12-01 | SYNE1 Deficiency Manifesting Primarily With Motor Neuron Disease.
SYNE1 deficiency is an autosomal recessive disorder with a broad phenotypic spectrum, most commonly presenting as adult-onset cerebellar ataxia with or without motor neuron dysfunction. We aimed to expand this spectrum by describing the clinical and genetic findings in 2 unrelated families with early-onset motor neuron disease and virtually no cerebellar signs over time. We performed detailed clinical, neurophysiologic, and genetic studies of 2 unrelated families with juvenile amyotrophic lateral sclerosis (ALS) and biallelic variants in SYNE1. The phenotypes of both families showed onset of symptoms in childhood or adolescence, with signs of upper and lower motor neuron dysfunction in multiple territories suggestive of juvenile ALS. Patients developed progressive muscle weakness, eventually leading to respiratory distress and bulbar signs. Whole-exome sequencing identified SYNE1 biallelic truncating variants in both families: a homozygous nonsense variant, c.23131C>T (p.Gln7711*), in Family 1, and a novel homozygous splice-site variant, c.17851-1G>A, in Family 2. Notably, mild or no cerebellar manifestations were observed during the follow-up. This report highlights a novel phenotype of SYNE1 deficiency characterized by early-onset motor neuron disease and virtually no cerebellar manifestations, broadening the phenotypic spectrum of this complex neurodegenerative disease. These findings support investigating SYNE1 variants in juvenile ALS and including SYNE1 in motor neuron disease gene panels.
2025-08-20 | Ataxia and oculomotor apraxia caused by a large-scale deletion in the senataxin gene.
Senataxin, an RNA/DNA helicase, is a key protein providing genome stability and one of the best characterized R-loop-binding factors playing an important role in transcription and DNA repair processes. Pathogenic SETX gene variants cause autosomal recessive spinocerebellar ataxia with axonal neuropathy (AOA2, MIM #606002) and autosomal dominant juvenile amyotrophic lateral sclerosis (ALS4, MIM #602433), rare neurodegenerative disorders characterized by juvenile onset of progressive cerebellar ataxia, axonal sensorimotor peripheral neuropathy, combined upper and lower motor neuron symptoms, and increased serum alpha-fetoprotein (AFP; specific for AOA2). We report two cases of adult patients presenting with cerebellar syndrome, scanned speech, and exercise intolerance which started in the second/third decade of life and were followed by muscle weakness and impaired gait coordination. Whole exome sequencing (WES) was performed to analyze single nucleotide and copy number variants. A decreased coverage of a genomic region of around 16 kb on chromosome 9 (chr9:132,295,852-132,311,876), suggesting a deletion encompassing 5 exons of the SETX gene (exons 11-15, NM_015046.7) was observed. This homozygous SETX (9q34.13) deletion leads to a frame shift and consequently truncation of the helicase domain in the protein. Loss-of-function variants in the SETX gene are known to be pathogenic. Statistical analysis of NGS data from the Polish population identified a few heterozygous carriers, suggesting its region-specific origin.
2025-01-08 | Long‐Term Follow‐Up of a Patient With SPG11
ABSTRACT We present a case of a male patient with disease‐causing variants in SPG11 , a causative gene for autosomal recessive spastic paraplegia with a thin corpus callosum (ARHSP‐TCC), as well as juvenile amyotrophic lateral sclerosis (ALS5) and Charcot–Marie–Tooth disease (CMT2X). A neurological examination at age 18 revealed dysarthria, muscle weakness in bilateral lower extremities, hyperreflexia in patellar reflex, hyporeflexia in Achilles reflex with an extensor plantar reflex, and intellectual disability. Magnetic resonance imaging revealed a thin corpus callosum and ears of the lynx sign. At the age of 26, weakness and muscle atrophy progressed. While no sensory disturbances were noted, there was a mild decrease in sensory nerve action potentials of the sural nerve over the 8 years between 18 and 26. Clinicians should be aware that SPG11 belongs to the same spectrum of disorders as ALS5 and CMT2X and presents various phenotypes depending on the stage of the disease.
2024-10-19 | Phenotype and Genotype of Children with ALS2 gene-Related Disorder.
The Alsin Rho Guanine Nucleotide Exchange Factor (ALS2) gene encodes a protein alsin that functions as a guanine nucleotide exchange factor. The variations in ALS2 gene leads to degeneration of upper motor neurons of the corticospinal tract. The phenotypes resulting from variants in ALS2 gene are infantile-onset ascending hereditary spastic paralysis (IAHSP, OMIM # 607225), juvenile primary lateral sclerosis (JPLS, OMIM # 606353), and juvenile amyotrophic lateral sclerosis (JALS, OMIM # 205100). Our study objectives were to describe the clinical phenotype and genotype of children with an established diagnosis of ALS2 gene-related disorder. The clinical details, laboratory data, and genotype findings of children with an established diagnosis of ALS2 gene-related disorder were collected from the hospital electronic database after obtaining institutional review board approval. One family with three affected siblings, a second family with a proband and an affected fetus, and a third family with two affected siblings with ALS2 gene variants were identified. IAHSP was diagnosed in all of our patients with variants in ALS2 gene. The clinical findings observed in our patients were insidious onset progressive spastic paraparesis, contractures, and dysarthria. Nonsense variants were observed in four patients while frameshift variant was observed in one family. Novel variants in ALS2 gene were identified in two unrelated families. ALS2 mutation results in rare neurodegenerative disorders with the clinical spectrum encompassing IAHSP, JPLS, and JALS disorders. In view of allelic heterogeneity described in the literature, more research studies are needed for establishing genotype-phenotype correlation in patients with ALS2 gene-related disorder.
small molecules
2026-07-01 | RNA dysregulation and compromised neuronal identity drive pathogenesis in Senataxin-associated ALS
ABSTRACT RNA dysregulation is a recognized contributor to neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS), the most common motor neuron (MN) disease. However, the molecular mechanisms linking defects in RNA metabolism to selective neuronal vulnerability remain poorly understood. Alterations in the cellular levels of R-loops –structures forming by reannealing of the nascent RNA with the template DNA during transcription- have been observed in neurodegeneration, but it is unclear how perturbations in R-loop homeostasis contribute to neuronal dysfunction. Here we investigate the molecular basis of a juvenile form of ALS dubbed ALS4 that is caused by mutations in the helicase SETX, which plays important roles in the resolution of R-loops and transcription termination. Using isogenic human induced pluripotent stem cell-derived MNs, we show that ALS4-associated SETX mutations induce progressive axonal defects and widespread transcriptomic alterations, including reduced expression or altered splicing of transcripts critical for neuronal function. ALS4 MNs exhibit a transcriptional signature marked by cellular stress, aberrant cell cycle re-entry, and compromised neuronal identity that is partially shared by other forms of ALS. Mechanistically, these defects are partly driven by downstream aberrant activation of the TGF-β signaling pathway, whose pharmacological inhibition ameliorates axonal defects. Finally, our analyses support a link between mutant SETX ectopic activity at R-loops and the observed alterations in RNA expression and splicing, providing new insights into how RNA dysregulation can drive neuronal dysfunction Altogether, our work reveals how perturbations at the interface of transcription and R-loop metabolism can reshape neuronal identity and drive disease. Teaser Deregulation of TGF-β signaling drives axonal defects and compromised motor neuron identity in senataxin-mediated ALS
2026-01-13 | Compartment-specific transcriptome of motor neurons reveals impaired extracellular matrix signaling and activated cell cycle kinases in FUS-ALS.
Mutations in FUSED IN SARCOMA (FUS) cause juvenile-onset amyotrophic lateral sclerosis (ALS). Early pathogenesis of FUS-ALS involves impaired transcription and splicing, DNA damage response, and axonal degeneration. However, the molecular pathophysiology and the link between somatic and axonal phenotypes are still poorly understood. We evaluated whether compartment-specific transcriptome differences could distinguish and drive early axonal degeneration. We used iPSC-derived motor neurons (MNs) coupled with microfluidic approaches to generate RNA-sequencing profiles from axonal and somatodendritic compartments. We demonstrate that the axonal transcriptome is unique and distinct, with RNA metabolism, extracellular secretion, and matrix disassembly pathways particularly enriched in distal axonal compartments. FUS mutation leads to changes in distinct pathways that were clustered in only a few distinct protein-protein interaction (PPI) networks. Somatodendritic changes upon FUS mutation include WNT signaling, mitochondrial, extracellular matrix (ECM)-, and synapse-related functions. In contrast, analysis of the axonal transcriptome in mutant MNs centers on the PLK1 pathway, mitochondrial gene expression, and regulation of inflammation. Comparison to CLIP-seq data revealed a significant enrichment for PLK1 and DNA replication pathways in axons. PLK1 upregulation did not activate cell-cycle re-entry but contributed to mutant MNs survival, and its inhibition increased neuronal cell death. We propose that upregulation of PLK1 represents an early event in the pathogenesis of ALS and could act in response to DNA damage, mitochondrial damage, and immune response activation in the affected cells. Additionally, downregulation of ECM pathways in the somatodendritic compartment and axons could explain strongly compromised dynamics of axonal outgrowth. Overall, we provide a novel valuable resource of the potential targets and affected processes changed in the specific compartments of FUS-ALS motor neurons.
2025-08-24 | Characterization of novel and recurrent SPTLC2 variants in childhood-onset amyotrophic lateral sclerosis: Insights into sphingolipid dysregulation.
Amyotrophic lateral sclerosis (ALS) is a severe neurodegenerative disorder that progressively affects motor neurons. Gain-of-function mutations in serine palmitoyltransferase (SPT) genes, notably SPTLC1 and SPTLC2, have been linked to juvenile ALS. Here, we describe two childhood-onset ALS cases with distinct SPTLC2 mutations, providing new insights into sphingolipid dysregulation and its role in ALS pathogenesis. Two Chinese patients with early-onset ALS, both carrying SPTLC2 mutations, were recruited from Beijing Children's Hospital. We conducted whole-exome sequencing (WES) to identify genetic variants, followed by Sanger sequencing for validation. Sphingolipid profiles were analyzed using ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Clinical evaluations included neurological assessments, brain MRI and electromyography. Additionally, mutant cell lines were established to assess the functional effects of the specific mutations. Patient 1, a 6-year-old male, exhibited a novel heterozygous de-novo SPTLC2 variant (c.197T > G, p.T66R). Patient 2, a 7-year-old female, had a recurrent heterozygous de-novo SPTLC2 variant (c.778G > A, p.E260K). Both patients showed elevated levels of specific sphingolipids compared to controls, with distinct profiles between the SPTLC2-ALS and SPTLC1-hereditary sensory and autonomic neuropathy type 1 (HSAN1) cases. The novel p.T66R mutation was predicted to alter protein interactions within the SPT complex, potentially impairing sphingolipid homeostasis. Functional studies further revealed that the p.T66R variant reduces the inhibitory regulation of SPT by ORMDL proteins, leading to unrestrained SPT activity and excess sphingolipid production. Our findings identify a novel SPTLC2 variant linked to childhood-onset ALS and reveal altered sphingolipid profiles associated with different genetic mutations. These results underscore the importance of sphingolipid metabolism in ALS and suggest potential avenues for targeted therapeutic interventions. Further research is needed to explore treatment options aimed at modulating sphingolipid levels and correcting genetic defects, as well as investigating potential biomarkers for early diagnosis.
2025-08-20 | Cell type-specific alterations in excitability and inhibition of upper motor neurons in AlsinKO mice, a model of juvenile onset ALS.
In amyotrophic lateral sclerosis (ALS) motor cortex hyperexcitability is detected in both familial and sporadic cases, suggesting its centrality in the ALS phenotype; the underlying mechanisms, however, remain largely obscure. Here we utilize male and female UCHL1-eGFP (UeGFP) mice, in which the corticospinal neurons of the motor cortex are labeled with green fluorescent protein, to investigate the intrinsic excitability and synaptic inhibitory inputs on distinct neuron populations in WT-UeGFP and presymptomatic AlsinKO-UeGFP mice, which lack Alsin function and are a well-characterized mouse model for juvenile cases of ALS. We show that in the motor cortex of AlsinKO-UeGFP mice, eGFP-positive layer 5 pyramidal neurons, which represent upper motor neurons, show a decrease in intrinsic excitability compared with WT, whereas the electrophysiological properties of eGFP-negative cells, which identify callosal projection neurons, are unaffected. This alteration in intrinsic excitability, however, is counterbalanced by a decrease in the frequency of spontaneous inhibitory currents due to a cell-specific reduction in the number of inhibitory synaptic contacts on upper motor neurons. Thus, the overall excitability of upper motor neurons only displays negligible changes despite large alterations in intrinsic excitability and inhibitory synaptic input, which may explain why mice do not exhibit a prominent motor phenotype. The presence of this homeostatic interaction between intrinsic excitability and synaptic inhibition raises the question of which of the two changes is primary, and which is secondary, and shows that decreased function of motor cortex interneurons is an early event in ALS with Alsin mutations.Significance Statement We found that in AlsinKO mice, which recapitulate ALS disease in patients with Alsin mutations, intrinsic excitability and inhibitory synaptic input of upper motoneurons (but not callosal-projection neurons) are significantly reduced at presymptomatic disease stage. We show that in this model: 1) impaired function of cortical interneurons is an early event; 2) excitability alteration in the motor cortex is cell type-specific; 3) intrinsic excitability and synaptic inhibition are linked by a homeostatic mechanism. These results stress the importance of cortical interneurons in ALS and suggest that either homeostatic overcompensation or failure of compensation contribute to disease onset and progression. If these mechanisms are common in ALS patients, this may have important consequences for the design of novel therapeutic interventions.
2024-04-22 | Modeling sporadic juvenile ALS in iPSC-derived motor neurons explores the pathogenesis of FUSR503fs mutation
Introduction Fused in sarcoma (FUS) mutations represent the most common genetic etiology of juvenile amyotrophic lateral sclerosis (JALS), for which effective treatments are lacking. In a prior report, we identified a novel FUS mutation, c.1509dupA: p. R503fs (FUSR503fs), in a sporadic JALS patient. Methods The physicochemical properties and structure of FUSR503fs protein were analyzed by software: Multi-electrode array (MEA) assay, calcium activity imaging assay and transcriptome analysis were used to explore the pathophysiological mechanism of iPSC derived motor neurons. Results Structural analysis and predictions regarding physical and chemical properties of this mutation suggest that the reduction of phosphorylation and glycosylation sites, along with alterations in the amino acid sequence, may contribute to abnormal FUS accumulation within the cytoplasm and nucleus of induced pluripotent stem cell– derived motor neurons (MNs). Multi-electrode array and calcium activity imaging indicate diminished spontaneous electrical and calcium activity signals in MNs harboring the FUS R503fs mutation. Transcriptomic analysis reveals upregulation of genes associated with viral infection and downregulation of genes involved in neural function maintenance, such as the ATP6V1C2 gene. Treatment with ropinirole marginally mitigates the electrophysiological decline in FUS R503fs MNs, suggesting the utility of this cell model for mechanistic exploration and drug screening. Discussion iPSCs-derived motor neurons from JALS patients are promising tools for drug screening. The pathological changes in motor neurons of FUS R503fs may occur earlier than in other known mutation types that have been reported.
oligonucleotides
2025-07-15 | Pathology of three ALS patients with FUS variants, including one likely benign Q23L variant lacking FUS inclusions.
Fused in sarcoma (FUS) is an RNA-binding protein implicated in juvenile amyotrophic lateral sclerosis (ALS). Mutations in the FUS gene, particularly those affecting the nuclear localization signal (NLS), impair nuclear import and lead to cytoplasmic accumulation of FUS inclusions in motor neurons. However, the pathological and clinical significance of FUS variants outside the NLS remains less understood. Here, we describe clinical and histopathological findings from three ALS patients carrying FUS variants: two with NLS-region variants (R495X and P525L), and one with a variant in the N-terminal region outside the NLS (Q23L). The patients carrying NLS variants presented with aggressive, juvenile-onset spinal and bulbar ALS, characterized primarily by lower motor neuron involvement and rapid disease progression. In contrast, the Q23L patient exhibited a slowly progressive disease course, with predominantly upper motor neuron signs. Neuropathological analysis revealed cytoplasmic FUS inclusions in motor neurons of patients with NLS variants, consistent with typical FUS pathology. In contrast, the Q23L patient lacked FUS inclusions and instead displayed pTDP-43 pathology in the hippocampus, neocortex (including the motor cortex), nucleus olivaris, lentiform nucleus, striatum, and some lower motor neurons. Taken together, these results suggest that Q23L is most likely a benign variant. As antisense oligonucleotides (ASOs) targeting FUS are currently being explored in clinical trials, further neuropathological investigations are needed to determine whether ASO-mediated FUS silencing would be effective for patients carrying FUS variants outside the NLS region.
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Drug Discovery Landscape
3 orphan drug designations for Juvenile amyotrophic lateral sclerosis.
3 orphan drug designations for Juvenile amyotrophic lateral sclerosis.
Drug | Therapy type | Orphan designation | Clinical trial status | Sponsor |
|---|---|---|---|---|
2-(3-Chlorophenyl)-N-[6-(trifluoromethyl)-1,3-benzothiazol-2-yl]acetamide | small molecules | EMA | — | Molefy Pharma S.L. |
Adeno-associated virus encoding small hairpin RNA against ATXN2 mRNA | gene therapies | EMA | — | Scendea (NL) B.V. |
2-(2-(2-[2-(4-Benzothiazol-2-yl-phenoxy)-ethoxy]-ethoxy)-ethoxy)-ethanol | small molecules | EMA | Somerville Development Partners B.V. |
“Terminated” – programs with discontinued clinical trials, or with no updates reported for 5 years after completion or 12 years after the last trial started.
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