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PubMed2026

Extracellular vesicles-mediated delivery of SpCas9 RNPs for therapeutic gene editing in Spinocerebellar Ataxia Type 3.

Spinocerebellar Ataxia Type 3 (SCA3) is a neurodegenerative dominantly-inherited disorder caused by an overexpansion of a CAG tract within the ATXN3 gene, conferring toxic properties to the ataxin-3 protein. Genome editing with CRISPR-Cas9 enzymes is a promising strategy to inactivate mutant ATXN3 alleles, however, in vivo delivery remains challenging. Extracellular vesicles (EVs) are promising delivery vehicles for Cas9 and single guide RNA (sgRNA) ribonucleoproteins that minimize genomic exposure to highly active endonucleases. In this study, we designed SpCas9 with a palmitoylation motif that enables SpCas9 and sgRNA enrichment into EVs. Introduction of a photocleavable linker - PhoCl - allowed the photo-inducible release of SpCas9 from the palmitoylation motif in EVs, increasing target engagement to ATXN3 in vitro. EVs loaded with SpCas9 ribonucleoproteins resulted in ATXN3 knockout in SCA3 patient-derived iPSCs and two SCA3 animal models. These findings highlight an innovative route for transient delivery of gene editing tools. This approach provides a promising therapeutic platform for the treatment of genetic diseases, including SCA3.

Humans↗

PubMed2026

Replication analysis of the PRKN V380L (rs1801582) variant in a Japanese cohort of spinocerebellar ataxia type 3.

BACKGROUND: Spinocerebellar ataxia type 3 (SCA3) is caused by CAG repeat expansion in ATXN3, which inversely correlates with age at onset but does not fully account for interindividual variability. A recent study in a mixed European/South and North American cohort suggested that the PRKN V380L variant (rs1801582), particularly in C/C homozygotes, was associated with earlier disease onset. We therefore performed a replication analysis to evaluate the frequency and potential clinical relevance of rs1801582 in a Japanese SCA3 cohort. METHODS: rs1801582 genotypes were determined by Sanger sequencing in 228 genetically confirmed SCA3 patients and 260 SCA6 patients as convenience disease controls. Genotype frequencies were additionally compared with East Asian reference populations from the 1000 Genomes Project Phase 3 dataset. Associations with age at onset were evaluated using multivariable linear regression adjusted for expanded ATXN3 CAG repeat length, normal ATXN3 CAG repeat length, and sex. RESULTS: Genotype frequencies in SCA3 (G/G: 86.0%, G/C: 13.2%, C/C: 0.9%) were similar to those in controls (G/G: 85.8%, G/C: 13.5%, C/C: 0.8%) and closely resembled those reported in East Asian reference populations. Because of the extremely small number of C/C carriers (n = 2), subsequent analyses focused on G/G and G/C carriers. In SCA3, median age at onset was comparable between genotypes (42 vs. 41 years), and median expanded ATXN3 CAG repeat lengths did not differ between groups (71 vs. 71 repeats). Multivariable regression analysis adjusting for expanded ATXN3 CAG repeat length, normal ATXN3 CAG repeat length, and sex demonstrated that rs1801582 was not independently associated with age at onset (β = - 0.42 years, p = 0.84), whereas expanded CAG repeat length remained a strong predictor (β = - 1.68 years per repeat, p < 0.0001). CONCLUSIONS: The rs1801582 C/C genotype is extremely rare in Japan; therefore, the present cohort had limited statistical power to directly evaluate the previously proposed recessive modifier effect. No detectable association between rs1801582 genotype and age at onset was identified among G/G and G/C carriers in this Japanese cohort. These findings highlight the importance of population-specific validation and adequately powered replication studies when evaluating candidate genetic modifiers in SCA3.

Adult↗

PubMed2026

Astragalus membranaceus therapy in patients with spinocerebellar ataxia type 3.

BACKGROUND AND AIM: Spinocerebellar ataxia type 3 (SCA3) is the most common form of hereditary cerebellar ataxia. The insulin/insulin-like growth factor 1 (IGF1) system (IIS) has been proposed as a potential target for disease-modifying therapy. Astragalus membranaceus (AM) may modulate the IIS pathway and reduce neurodegeneration, as indicated by plasma neurofilament light chain (NfL), a biomarker of disease progression. EXPERIMENTAL PROCEDURE: A randomized, triple-blind, placebo-controlled crossover trial was conducted in 32 patients with SCA3. Participants received AM or placebo for three months, followed by a one-month washout, then crossed over to the alternate treatment. Plasma NfL and IIS-related markers were measured. Twenty-three participants completed the trial. RESULTS AND CONCLUSION: Intention-to-treat analysis revealed a modest within-treatment reduction in NfL levels (27.6 ± 10.7 vs. 25.6 ± 9.8 pg/mL, P = 0.040) and increased insulin (12.5 ± 15.2 vs. 21.1 ± 15.5 μIU/mL, P = 0.004) after AM. However, the adjusted regression model showed no significant between-treatment difference in NfL (P = 0.127), and changes in NfL were not correlated with insulin. No significant changes were observed in IGF1 or IGF-binding proteins. Exploratory subgroup analyses suggested larger biomarker changes in later-stage patients. No carryover effects or demographic differences were noted. Overall, AM administration was associated with modest within-treatment biomarker changes in NfL and insulin, although the adjusted between-treatment difference in NfL was not statistically significant. These findings should be interpreted cautiously as preliminary and hypothesis-generating observations rather than confirmatory evidence of therapeutic efficacy.

Astragalus membranaceus↗

PubMed2026

Characterising the motif composition and allele length distribution of ZFHX3 GGC repeat expansions in amyotrophic lateral sclerosis.

A pathogenic GGC repeat expansion in zinc finger homeobox 3 (ZFHX3), encoding a pure polyglycine (polyG) tract, causes spinocerebellar ataxia type 4 (SCA4). Intermediate expansions of other SCA loci have been implicated in amyotrophic lateral sclerosis (ALS), while repeat motif composition is recognised to influence pathogenicity in neurodegenerative diseases. Given the genetic pleiotropy between ALS and SCA, we evaluated whether ZFHX3 GGC expansions are associated with ALS and characterised repeat motif composition. ZFHX3 GGC repeat sizes were genotyped using ExpansionHunter in short-read whole-genome sequencing data from ALS cases and healthy controls of European ancestry. Repeat sizes were visually inspected using REViewer, and motif configurations were manually derived from a subset. Receiver operating characteristic analysis and Youden's J statistic identified a candidate repeat size threshold. Logistic regression tested associations of repeat length and motif composition with ALS, while regression models assessed clinical phenotypes. Across 5785 ALS cases and 7982 controls, no association was observed between ZFHX3 expansions and ALS risk. Longer alleles showed a nominal association with later disease onset, however this did not remain significant after Bonferroni correction. Among 802 ALS cases and 800 controls, 50 distinct motif compositions were identified, including 11 encoding pure polyG tracts characteristic of pathogenic SCA4 expansions; none were associated with ALS. Although no association with ALS was observed, this study established the dynamic nature of ZFHX3 repeat motif composition and configuration. Variation within and between repeat sizes, including pure polyG repeats, supports consideration of motif composition alongside allele length when evaluating neurodegenerative disease risk.

Journal Article↗

PubMed2026

A mouse model of autosomal dominant spastic ataxia and myopathy caused by a mutation in Tuba4a.

Hereditary ataxias are a heterogeneous group of neurodegenerative disorders characterized by impaired balance and coordination, often due to cerebellar dysfunction. Despite advances in identifying genetic causes, animal models remain essential for dissecting underlying mechanisms and testing therapeutic strategies. Here we describe a mouse model of spastic ataxia and myopathy caused by a missense mutation in Tuba4a (n.A626C, p.Gln176Pro). In an ENU mutagenesis screen, a male C57BL/6 J mouse exhibiting muscle wasting and an intention tremor starting at approximately 4 weeks-of-age was identified. The male was bred by in vitro fertilization to BALB/cByJ oocyte donors. Genetic mapping determined dominant inheritance and localized the mutation to Chromosome 1. Genome sequencing revealed single nucleotide polymorphisms (SNPs) in serine threonine kinase 36 (Stk36Y1003N) and alpha-tubulin 4A (Tuba4aQ176P) in the mapping interval. These SNPs were CRISPR-engineered into C57BL/6 J mice, which confirmed the Tuba4aQ176P variant as the causative mutation. Mutant mice are normal at 3 weeks, except for decrement in muscle response following repetitive nerve stimulation. However, by 30 days these mice have overt ataxia, Purkinje neuron degeneration, and extensive skeletal muscle defects, which contribute to a decreased lifespan. Dominant TUBA4A mutations in humans are associated with spastic ataxia type 11 (SPAX11), congenital myopathy type 26 (CMYO26), and frontotemporal dementia/amyotrophic lateral sclerosis type 9 (FTDALS9). Our mice exhibit hallmark features of SPAX11 and CMYO26, but do not show motor neuron degeneration. This specificity makes this model a valuable tool for studying cell-type selective effects of TUBA4A mutations in neurodegeneration and myopathy.

Animals↗

PubMed2025

Genetic analysis of three patients from two unrelated Chinese families with autosomal recessive spastic ataxia of Charlevoix-Saguenay.

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is a rare early-onset neurodegenerative disorder characterized by progressive cerebellar ataxia, spasticity, and sensorimotor peripheral neuropathy. This disorder is caused by homozygous or compound heterozygous variants in the sacsin (SACS) gene on chromosome 13q12.12. Three patients with ARSACS from two unrelated Chinese families were recruited for this study. Patient #1 was an 18-year-old male who had been walking unstably for 12 years. Patient #2, the younger sister of Patient #1, was a 5-year-old girl who had been walking unstably for 2 years. Patient #3 was a 19-year-old female who had been walking unstably and a tendency to fall for 17 years. For Patient #1, whole-exome sequencing (WES) identified a hemizygous variant c.8310_8313delAGAT (p.Asp2771fs4*) in SACS (NM_014363.6), with the father being heterozygous, the mother wild-type, and Patient #2 hemizygous, as verified by Sanger sequencing. Additional copy number variant analysis of the WES data indicated that Patient #1 had a heterozygous gross deletion of chr13q12.12 (chr13:23,808,732 - 24,890,322). Low-coverage whole-genome sequencing results revealed that Patient #2 carried a chr13q12.12 deletion (chr13:23,520,000-24,940,000). Together with Sanger sequencing results, this gross deletion was speculated to have been inherited from the mother, further explaining the hemizygous state of c.8310_8313delAGAT (p.Asp2771fs4*) in Patients #1 and #2. Through WES, Patient #3 was identified as having suspected compound heterozygous variants of c.2881 C > T (p.Arg961*) and c.6409 C > T (p.Gln2137*), inherited from the father and mother, respectively, as confirmed by Sanger sequencing. This study identified three variants in SACS. The c.8310_8313delAGAT (p.Asp2771fs4*) is novel, whereas c.2881 C > T (p.Arg961*) and c.6409 C > T (p.Gln2137*) have been reported previously. Moreover, this study highlights the growing trend that ARSACS has become increasingly prevalent worldwide rather than being localized to a specific region or race. As an increasing number of patients with ARSACS are diagnosed, the genetic spectrum of ARSACS will gradually broaden, providing an accurate genetic basis for prenatal diagnosis of mothers in the years ahead, if possible.

Adolescent↗

PubMed2026

Dissecting the relationship between haplotypes around ATXN2 CAG repeats and the number of CAA interruptions by long-read sequencing.

BACKGROUND: CAG repeat expansions in ATXN2 are implicated as risk factors for several neurological diseases, including spinocerebellar ataxia type 2 (SCA2) when >=33 CAG repeats are present, and amyotrophic lateral sclerosis (ALS) when 27-33 CAG repeats are present. However, how haplotypes around the repeats and CAA interruptions within the repeats are associated with disease phenotypes remains poorly understood. Previous studies on haplotypes around ATXN2 were limited to SNPs very close to the repeats (<5kb) or were based on statistical inference only. METHODS: Here, we used long-read sequencing on the Oxford Nanopore Technologies (ONT) platform to simultaneously infer haplotypes around ATXN2, the number of CAG repeats, and the number of CAA interruptions, along with NYGC ALS Consortium NGS dataset. We further sequenced 41 individuals (EUR = 39) with neurological diseases with intermediate repeats by ONT. RESULTS: We found that haplotypes around ATXN2 and the number of interruptions show ethnicity-specific and ALS-specific distribution. Three CAA interruptions are present at low prevalence (~1%) in control populations in multiple ancestry groups, but high prevalence (~55%) in ALS individuals with intermediate repeats. Furthermore, we examined 159 individuals with ALS (~90% European ancestry) with intermediate ATXN2 repeats and found a unique haplotype in ALS individuals with three CAA interruptions, which can be tagged by an SNV, rs148019457. We also validated that the rs148019457-G allele is only present in haplotypes with three CAA interruptions. CONCLUSIONS: In summary, our study shows that 3 CAA interruptions are rarely seen in healthy controls but are common in those with expanded ATXN2 CAG repeats who have neurological disorders, and that rs148019457 tags a specific haplotype with 3 CAA interruptions within expanded ATXN2 CAG repeats in individuals of European ancestry. These results have implications for the development of precision genomic medicine for neurological disorders, and the tag SNP may help identify those with interruptions from existing population genotyping data.

ATXN2↗