Background Christianson syndrome is an x-linked recessive neurodevelopmental and neurodegenerative condition caused by mutations to the SLC9A6 gene encoding NHE6, a sodium-hydrogen exchanger critical for regulating endosomal pH. Using an adeno-associated viral (AAV) vector targeting Purkinje cells (PHP.eB-L7-Slc9a6-GFP), we recently performed functional complementation studies to demonstrate that mutation to the rat Slc9a6 gene causes a Christianson syndrome-relevant cerebellar phenotype in the shaker rat.Methods We carried out a longitudinal study evaluating the impact of gene replacement targeting Purkinje cells on ataxia and tremor in the shaker rat. Further, in a smaller follow-up study, we tested administration of AAV9-CAG-hSLC9A6 to determine whether key molecular and motor findings could be replicated with a more clinically relevant viral construct. In both experimental cohorts, we performed molecular studies to evaluate expression of NHE6 and key cerebellar markers.Results Administration of either of PHP.eB-L7-Slc9a6-GFP or AAV9-CAG-hSLC9A6 AAV vectors led to significant improvement in both the molecular and motor phenotypes. The abundance of each disease-relevant cerebellar proteins was strongly correlated to motor ataxia, but less so to tremor. Further, while ataxia and tremor were initially strongly correlated early in the disease progression, this relationship weakened over time.Conclusions These findings impact future SLC9A6-targeted gene therapy efforts for Christianson syndrome and support gene replacement as a potentially viable therapeutic strategy. Common markers associated with cerebellar degeneration are much more strongly tied to ataxia than to tremor, indicating that ataxia may be more tied related to degenerative processes than tremor.

RNA-binding proteins (RBPs) play an essential role in development, normal functioning and human disease. Staufen1 (STAU1) is an RBP that regulates mRNA degradation and subcellular localization, and is part of the ATXN2 protein complex. Previously, we showed that STAU1 is overabundant in patient fibroblasts and in mouse models of Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), and spinocerebellar ataxia type 2 (SCA2), where it is associated with impaired autophagic flux due to STAU1-mediated upregulation of mTOR translation. STAU1 overabundance and impaired autophagy cause accumulation of biomolecular condensates and abnormal unfolded protein response (UPR). We generated a mouse model expressing the entire human STAU1 gene (hSTAU1) in a bacterial artificial chromosome (BAC) construct. hSTAU1 in these mice was expressed in cerebral hemispheres, cerebellum and spinal cord, as well as cultured cortical neurons and cortical and spinal cord astrocytes and microglia. Expression of hSTAU1 caused dysregulated gene expression, abnormal autophagy, glial activation, and changes in neuronal marker proteins. All of these were significantly improved by reducing STAU1 abundance by RNAi, but exacerbated in BAC-STAU1 mice crossed with Prp-TDP-43(Q331K) transgenic mice. Similar results were also obtained in eye phenotypes in ALS- and SCA2-relevant fly models upon changing staufen-1 dosage. Despite the molecular changes, we observed no overt behavioral changes in mice up to 55 weeks of age, suggesting that STAU1 may function as an epistatic modifier of neuronal degeneration. The BAC-hSTAU1 mouse will be useful for developing therapies targeting the human STAU1 gene.

Glioblastoma is the most common and deadly brain cancer in adults. Although the disease disrupts the blood-brain barrier and exposes the tumor to the systemic circulation, using circulating cell-free DNA as a non-invasive biomarker for diagnosing glioblastoma remains elusive. The main obstacles are the confounding effects from artifactual variants in cell-free DNA caused by errors during next-generation sequencing and real variants in cell-free DNA originating from white blood cells that acquired somatic mutations during normal aging. Here, we developed and validated TrueR sequencing to overcome next-generation sequencing-related false positives in cell-free DNA. Subsequently, TrueR identified molecular features unique to tumor-derived cell-free DNA (i.e., circulating tumor DNA) that are detectable in blood during a tumor-naïve search. Specifically, variants associated with glioblastoma circulating tumor DNA were exclusively present in cell-free DNA (i.e., absent in white blood cell DNA) and showed gene-specific subclones. These features were uncommon in low-grade glioma, stroke, and age-related somatic mosaicism of white blood cells. We also detail a variant-agnostic method, demonstrating that copy number gains and losses in short cell-free DNA fragments (<90 bp) support the detection of glioblastoma. Finally, we present evidence that our findings extend beyond glioblastoma, supporting the broader advancement of the liquid biopsy.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with multiple genetic causes. Given the strong evidence of mitochondrial dysfunction in ALS, this study aimed to identify genetic contributors to ALS by focusing on genes involved in mitochondrial function. Whole-genome and whole-exome sequencing data from 1,034 individuals with ALS were analyzed using two distinct computational tools, which ranked candidate genes based on functional relevance to ALS. POLG, the sole mitochondrial DNA (mtDNA) polymerase, emerged as a top candidate gene. RNA sequencing (RNA-seq) analysis revealed that among genes upregulated in samples with a POLG variant, there was an enrichment for mitochondrial pathways, including translation, localization, and mitophagy. It also revealed variants in POLG and SOD1, a well-known ALS gene, to be the most enriched in samples with expression profiles of mitochondrial-related genes that differed most from those of unaffected control subjects. POLG variant carriers also exhibited an increased burden of mitochondrial genome variants, a pattern shared by carriers of variants in other genes involved in mtDNA maintenance. Additionally, POLG variant carriers had elevated mtDNA copy number (mtDNA-CN), similar to carriers of variants in mitophagy-related genes, suggesting impaired mitophagy. Together, these findings implicate POLG as an ALS-associated gene and link mtDNA maintenance defects, altered expression of mitochondrial-related pathways, and impaired mitophagy to the ALS etiology.

Background: Spinocerebellar ataxia type 2 (SCA2) is a neurodegenerative disorder characterized not only by motor impairment but also by significant cognitive decline. While cognitive training programs have shown promising results in other neurological conditions, evidence regarding their efficacy in SCA2 remains scarce. Objective: To assess cognitive performance in patients with SCA2 and to evaluate the impact of a digital cognitive training program on cognitive functions. Methods: Twelve SCA2 patients (50

BACKGROUND:Spinocerebellar ataxia 4 (SCA4) is a late-onset dominant ataxia with neuropathy caused by exonic GGC repeat expansion in the ZFHX3 gene thought to originate from a Swedish founder event. The GC-rich expansion is highly thermodynamically stable, posing challenges for standard clinical genetic testing methods. Development of a high-throughput relatively inexpensive detection method would benefit both clinical diagnostic testing and large-scale research applications. OBJECTIVE:Using a cost-effective high-throughput polymerase chain reaction (PCR) assay, we assessed the frequency of SCA4 repeat expansion in an undiagnosed US ataxia cohort. METHOD:Primers flanking the ZFHX3 repeat region were used under optimized PCR conditions to assess for expanded GGC repeats in 687 undiagnosed ataxia patients. Repeat size was determined by fragment analysis and orthogonally confirmed with long-read sequencing (Oxford Nanopore Technologies). RESULTS:We identified pathogenic SCA4 expansions in three families with cerebellar ataxia and sensory/autonomic neuropathy. The pathogenic alleles were confirmed to be of Swedish ancestry using comprehensive haplotype analysis of 14 single nucleotide polymorphisms (SNPs) previously associated with ZFHX3 expansion. Two families carried all 14 SNPs, suggesting this may represent an ancestral haplotype. Utilizing a minimal haplotype present in all reported patients, we bioinformatically assessed 852 additional subjects, for a total of 1539 screened, but did not identify additional SCA4 patients. CONCLUSION:Using a high-throughput cost-effective PCR assay, we identified three SCA4 families in a large US ataxia cohort. Haplotype analysis supports a common Swedish founder allele, consistent with previously reported SCA4 cases. SCA4 diagnostic testing is recommended for all patients of Swedish ancestry with undiagnosed ataxia. © 2026 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Background and ObjectivesAutosomal Recessive Spastic Ataxia of Charlevoix-Saguenay (ARSACS) is a neurodegenerative disease caused by pathogenic variants in SACS. ARSACS is characterized by mitochondrial abnormalities and disruptions of the neurofilament cytoskeleton. In other conditions, these features have been linked to activation of Sterile Alpha and TIR Motif Containing 1 (SARM1), an enzyme that can trigger axon degeneration and neuronal death. Inhibition of SARM1 is an attractive therapeutic strategy because SARM1 is inactive in healthy cells and knockout of SARM1 has little or no deleterious effects. We therefore asked whether SARM1 activity contributed to Purkinje cell degeneration and motor defects present in a Sacs-/- mouse model of ARSACS.MethodsWe studied 4 cohorts of mice: (1) Sacs -/-; Sarm1+/+; (2) Sacs +/+; Sarm1+/-; (3) Sacs -/-; Sarm1 +/-; and (4) Sacs -/-; Sarm1 -/-. In 9-month-old mice, we analyzed protein markers of Purkinje cells (n = 3-4 mice per genotype) and counted surviving Purkinje cells in folia III, IV, and VIII of cerebellar sections (n = 3 mice per genotype, 6 sections per mouse), and tested motor function at 3, 6, and 9 months by quantifying parameters of gait (Digigait) and coordination and balance (Rotarod) (8 male, 8 female mice of each genotype).ResultsProbing of cerebellar extracts showed that the Purkinje cell protein markers Calbindin-1, RGS8, and PCP2 were decreased in Sacs-/- mice but restored to normal levels in Sacs -/-; Sarm1-/- mice. Purkinje cell loss in Sacs-/- mice was most prominent in anterior folia, as previously noted. Sarm1 loss partially mitigated the Purkinje cell death in folium III of 9-month-old Sacs-/- mice. Similarly, longitudinal behavioral assessment of motor functions showed that disturbances in gait pattern (slower cadence, prolonged swing, and stance phases) were partially alleviated. Rotarod tests gave more ambivalent results, as the homozygous loss of Sarm1 was less effective than heterozygous loss in ameliorating the Sacs-/- phenotype.DiscussionWe conclude that SARM1 contributes to neurodegeneration in ARSACS, and its downregulation or inhibition could constitute a significant therapeutical strategy in the treatment of the disease.

The READISCA study aims to prepare for clinical trials in spinocerebellar ataxia types 1 and 3 (SCA1 and SCA3). Hence, we searched for predictive variables of ataxia onset (phenoconversion) and progression. Individuals with SCA1 or SCA3 and controls were enrolled from 2018 to 2021 in the USA and Europe. Clinical scores, MRI measures and neurofilament light chain (NfL) levels were assessed annually for 5 years. In the pre-ataxic group at baseline, we compared phenoconverters with non-converters. A Bayesian mixed model was used to model the longitudinal progression of clinical scores and NfL levels. The impact of data-driven selected baseline variables (demographic, clinical and MRI) on the expected Scale for Assessment and Rating of Ataxia progression was tested. Forty-three controls, 55 SCA1 carriers and 124 SCA3 carriers were included; a subset of the cohort (n = 109) had MRI data. Converters from pre-ataxic to ataxic stages represented 5/22 (22%) and 12/38 (32%) for SCA1 and SCA3, respectively. Converters were more depressed (Patient Health Questionnaire 9: 3.9 ± 2.9 versus 2.3 ± 2.6, P = 0.04), had higher plasma NfL levels (17.6 ± 5.7 versus 11.1 ± 5.9 pg/ml, P < 0.0001), more cerebellar white matter atrophy (1.44% ± 0.12% of total intracranial volume versus 1.54% ± 0.16%, P = 0.032) and more Inventory of Non-Ataxia Signs signs (1.8 ± 1.3 versus 0.7 ± 0.8, P = 0.002). All clinical scores except Cerebellar Cognitive Affective Syndrome significantly worsened during the study. NfL levels significantly increased in non-converters and ataxic SCA3 (1.06 ± 0.33 pg/ml/year, P = 0.002 and 0.57 ± 0.21 pg/ml/year, P = 0.01, respectively) but not in controls and ataxic SCA1 (0.31 ± 0.26 pg/ml/year, P = 0.24 and 0.26 ± 0.42 pg/ml/year, P = 0.55, respectively). In the best predictive model of Scale for Assessment and Rating of Ataxia progression after 1 year (R2 = 0.54), factors linked with faster progression were higher functional stage (P < 0.001), higher Composite Cerebellar Functional Score (P = 0.002) and higher total creatine in cerebellar white matter (P = 0.026). Factors significantly linked to conversion, namely NfL levels, depression and lower motor neuron involvement, differ from those driving disease progression. The NfL levels and lower motor neuron signs could be used as predictors of phenoconversion and MRI variables as ataxia progression predictors. Psychological care should be provided in the pre-ataxic phase of the disease.

Spinocerebellar ataxias (SCAs) are dominantly inherited diseases that lead to neurodegeneration in the cerebellum and other parts of the nervous system. This review examines the progress that has been made in SCA2 from its initial clinical description to discovery of DNA CAG-repeat expansions in the ATXN2 gene. ATXN2 repeat alleles cover the range from recessive and dominant mendelian alleles to risk alleles for amyotrophic lateral sclerosis. We review studies aimed at defining the normal function of ATXN2 and mutant ATXN2 using cellular and mouse models. Progress in testing small compounds and antisense oligonucleotides in preclinical studies is described as well including our recent focus on staufen-1 (STAU1) and mRNA metabolism and control of autophagy.

Meningiomas arise from arachnoid cells in the meninges surrounding the brain and spinal cord and are attributed to NF2 pathogenic variants in, approximately 60% of cases. Using exome sequencing, we found heterozygous germline variants in nine potential novel meningioma genes across four families and four sporadic cases. We then screened for germline and somatic variants in these genes and 11 known meningioma genes in 76 sporadic meningiomas blood/tumor pairs. We identified 18 germline and 58 somatic variants in 18 of the 20 genes, including seven of our newly proposed meningioma genes: CSMD3, EXTL3, FAT3, RAB44, RARA, RECQL4, and TNRC6A. Chromosomal abnormalities were identified in 39 of 49 tumors that also carried germline or somatic variants, with 71.8% encompassing NF2. This study provides potential novel genetic risk factors of meningiomas appropriate for further exploration from the greater scientific community and pathways to consider in the design of future therapeutic approaches.

Staufen2 (STAU2) is an RNA-binding protein that controls mRNA trafficking and expression. Previously, we showed that its paralog, Staufen1 (STAU1), was overabundant in cellular and mouse models of neurodegenerative diseases and amyotrophic lateral sclerosis (ALS) patient spinal cord. Here, we investigated features of STAU2 that might parallel STAU1. STAU2 protein, but not mRNA, was overabundant in spinocerebellar ataxia type 2 (SCA2), ALS/frontotemporal dementia patient fibroblasts, ALS patient spinal cord tissues, and in central nervous system tissues from SCA2 and ALS animal models. Exogenous expression of STAU2 in human embryonic kidney 293 cells activated mechanistic target of rapamycin (mTOR) and stress granule formation. Targeting STAU2 by RNAi normalized mTOR in SCA2 and C9ORF72 cellular models. The microRNA miR-217, previously identified as downregulated in SCA2 mice, targets the STAU2 3'-UTR. We now demonstrate that exogenous expression of miR-217 significantly reduced STAU2 and mTOR levels in cellular models of neurodegenerative disease. These results suggest a functional link between STAU2 and mTOR signaling and identify a major role for miR-217 that could be exploited in therapeutic development.

BACKGROUND AND OBJECTIVES:Cerebellar cognitive-affective syndrome (CCAS) results from cerebellar degeneration, but its prevalence in spinocerebellar ataxias (SCAs) remains underexplored. This study assessed CCAS prevalence, severity, and progression across different SCAs. METHODS:We included polyglutamine (PolyQ) SCA expansion carriers (ATXN1/SCA1, ATXN2/SCA2, ATXN3/SCA3, and ATXN7/SCA7), patients with FGF14/SCA27B and SPG7, and controls. Cognitive function was assessed with the CCAS scale and ataxia severity with the Scale for the Assessment and Rating of Ataxia (SARA) and Composite Cerebellar Functional Severity (CCFS) score. We correlated CCAS score with ataxia severity, brain MRI, and plasma neurofilament light chain (NfL) levels. Subtest comparisons among genotypes were adjusted for age, education, and SARA score. In PolyQ SCA carriers, we explored CCAS progression. RESULTS:We included 371 participants: 66 with SCA1, 28 with SCA2, 158 with SCA3, 24 with SCA7, 35 with SPG7, 17 with SCA27B, and 43 controls. Those with SCA27B and SPG7 were older (69.5 ± 9.5 and 57.8 ± 10.6 years) with lower education (11.4 ± 4.2 and 12.7 ± 3.6 years) than those with PolyQ SCAs (from 40.3 ± 14.0 for SCA7 group to 45.9 ± 11.2 years in SCA3 group, p < 0.0001; education ranging from 14.4 ± 3.1 for SCA2 group to 15.4 ± 2.8 years for SCA7 group, p < 0.0001). Among ataxic patients, definite CCAS was detected in 88% of patients with SCA27B and 71% of SPG7 carriers, followed by SCA2 (67%), SCA7 (67%), SCA1 (50%), and SCA3 (41%) groups. Among preataxic PolyQ SCA carriers, CCAS was present in 11% (10/89), similar to controls (11.6%, p = 1). However, phonemic fluency showed an early impairment in preataxic SCA1 carriers (11.8 ± 4.5 vs 14.6 ± 3.8, p = 0.04). In PolyQ SCA carriers, the CCAS total raw score correlated with SARA score (r = -0.54, p < 0.0001), CCFS score (r = -0.45; p < 0.0001), and plasma NfL levels (r = -0.26, p = 0.002). CCAS scores correlated with cerebellar volume in those with SCA2 (r = 0.64, p < 0.001). Patients with SPG7 showed significantly poorer performance in executive function, short-term memory, and abstract reasoning compared with those with SCA3 and SCA7. In PolyQ SCA carriers, improvements were observed during the first 3 years after inclusion (+2.0 ± 0.7 points, p = 0.002; +2.6 ± 0.8 points, p = 0.0007; +2.7 ± 0.8, p = 0.001, respectively). By year 4, the increase was not significant (+0.73 ± 1.16 points, p = 0.52). DISCUSSION:We observed early cognitive impairment in PolyQ SCA carriers, correlating with clinical measures, NfL levels, and cerebellum volume. Improvement over 3 years likely reflects a practice effect, potentially limiting the scale's longitudinal utility.

Spinocerebellar ataxia type 2 (SCA2) is a neurodegenerative disorder characterized by cerebellar motor symptoms. The extent and timing of cognitive involvement, particularly in pre-ataxic carriers, remain unclear. To assess cognitive performance across clinical stages of SCA2 and investigate early neurocognitive changes in pre-ataxic individuals. We evaluated 52 genetically confirmed participants from a rural Brazilian cohort: 16 pre-ataxic carriers, 12 symptomatic patients, and 24 intrafamilial controls. A standardized neuropsychological battery assessed global cognition, executive function, memory, visuospatial abilities, attention/working memory, mood, and language. Group comparisons and correlations were adjusted using False Discovery Rate (FDR) correction. Pre-ataxic carriers performed comparably to their intrafamilial controls across all cognitive domains, with no significant group differences except for the FAB total score, and showed no associations with estimated time to disease onset. Executive dysfunction emerged as the most prominent cognitive feature of manifest SCA2 and was more strongly associated with CAG repeat length than with clinical disease markers. In this genetically and environmentally homogeneous cohort, only limited measurable cognitive impairment was observed in pre-ataxic carriers. These findings underscore the importance of longitudinal and multimodal studies to elucidate the timing and underlying mechanisms of cognitive decline in SCA2.

Hereditary ataxias are progressive neurodegenerative disorders primarily affecting the cerebellum. Since 2009, the Clinical Research Consortium for the Study of Cerebellar Ataxias (CRC-SCA) has studied the natural history of common types of spinocerebellar ataxias (SCAs). The CRC-SCA is a 17-site academic collaboration supported by the National Ataxia Foundation. In 2024, the CRC-SCA expanded its scope by incorporating newly identified late-onset ataxias, including repeat expansion mutations in RFC1 and FGF14 causing Cerebellar Ataxia with Neuropathy and Vestibular Areflexia Syndrome (CANVAS) and SCA27B, respectively. These ongoing efforts have enriched the understanding of disease progression and facilitated access to biofluid and neuroimaging data for biomarker discovery, setting the stage for therapeutic development in hereditary ataxias. The CRC-SCA's natural history study and biomarker collection have validated several clinical outcome assessments (COAs) to capture important aspects of hereditary ataxias. We have also developed new COAs for cognitive and patient-reported outcome measures. A key component of the study includes biofluid collection-cerebrospinal fluid, plasma, and serum-to identify molecular biomarkers for disease progression and therapeutic response. Additionally, an incorporated magnetic resonance imaging (MRI) substudy provides critical imaging biomarkers, enhancing our ability to track macro- and microstructural, chemical and functional changes in the cerebellum and relate these to clinical presentations. The comprehensive, longitudinal dataset comprising COAs, biofluid biomarkers, and neuroimaging enhances clinical trial readiness in the field and accelerates therapeutic advancements for hereditary ataxias. This review highlights the collective efforts of CRC-SCA, details the study protocol, and emphasizes the integrity and specificity of the collected data elements.

OBJECTIVE:Suicidal ideation has not been extensively studied in spinocerebellar ataxias (SCAs). The authors examined whether individuals with SCAs have increased suicidal ideation and related factors. METHODS:The authors studied patients with genetically confirmed SCAs enrolled in the Clinical Research Consortium for the Study of Cerebellar Ataxia cohort, examining the percentages of patients with SCA subtypes 1, 2, 3, and 6 who reported suicidal ideation and comparing findings with nationally representative data from the National Survey on Drug Use and Health (NSDUH). Clinical characteristics that may contribute to suicidal ideation in SCAs, including age, disease duration, sex, ataxia severity, depression, and SCA subtype, were also studied. RESULTS:Suicidal ideation was present among 12% of 769 patients with SCAs and 4.3% of individuals in the general population recorded in the NSDUH. Compared with individuals in the general population, SCA patients had higher odds of suicidal ideation (OR=2.72). Compared with patients with SCA without suicidal ideation, patients with SCA and suicidal ideation had a longer disease duration (mean±SD=13.1±8.2 years vs. 11.2±9.4 years), more severe ataxia (Scale for the Assessment and Rating of Ataxia mean score=15.9±8.6 vs. 12.9±7.6), and more severe depression. Having suicidal ideation at baseline significantly increased the odds of suicidality later in the disease course (OR=58.73, 95% CI=36.00-98.40). CONCLUSIONS:Suicidal ideation was more prevalent among patients with SCAs than in the general population. The findings of this study underscore the importance of continuous suicidal risk screening among individuals with SCAs and the need for effective depression management.

Stress responses and neuronal death mediated by the p53 pathway play a central role in the progression of neurodegenerative disease, constituting a common target to extend neuronal function and survival. Interaction of p53 and its signaling network with RNA-binding proteins (RBPs) helps fine-tune its activation and the resulting cell fates. Preclinical therapeutics based on depletion of the RBP STAUFEN-1 (STAU1) protein successfully prevent neurodegeneration, however, the specific mechanisms are not fully understood. STAU1 is pathologically overabundant in multiple neurological disorders and contributes to neurodegeneration by exacerbating autophagy dysfunction, endoplasmic reticulum stress, and RNA-protein condensate accumulation. We previously showed that lowering STAU1 levels mitigates these disease-related features and prevents neuronal death in animal models of amyotrophic lateral sclerosis/frontotemporal dementia (ALS/FTD) and spinocerebellar ataxia type 2 (SCA2). Here, we show by combined transcriptomic and functional analyses that STAU1 reduction results in the inhibition of apoptosis through the p53 pathway. In both proliferating and post-mitotic cell types—human iPSC-derived neurons, mouse cortical neurons, SH-SY5Y cells, and fibroblasts—STAU1 reduction effectively prevented p53-mediated apoptosis and DNA damage induced by Nutlin-3 and etoposide. Further examination in C9orf72-expanded patient-derived fibroblasts and a C9orf72 mouse model of ALS/FTD, which exhibit baseline overabundance of STAU1 and activation of the p53 pathway, confirmed that STAU1 reduction also prevented p53-driven pro-apoptotic signaling. These findings establish STAU1 as a novel modulator of DNA damage and p53-dependent apoptosis, suggesting that targeting STAU1 could be a promising approach to prevent neurodegeneration in ALS/FTD.

Spinocerebellar ataxia type 2 (SCA2) is an autosomal dominant neurodegenerative disorder marked by cerebellar dysfunction, ataxic gait, and progressive motor impairments. SCA2 is caused by the pathologic expansion of CAG repeats in the ataxin-2 (ATXN2) gene, leading to a toxic gain-of-function mutation of the ataxin-2 protein. Currently, SCA2 therapeutic efforts are expanding beyond symptomatic relief to include disease-modifying approaches such as antisense oligonucleotides (ASOs), high-throughput screening (HTS) for small molecule inhibitors, and gene therapy aimed at reducing ATXN2 expression. In the present study, data mining and machine learning techniques were employed to analyze HTS data and identify robust molecular properties of potential inhibitors of ATXN2. Three HTS datasets were selected for analysis: ATXN2 gene expression, CMV promoter expression, and biochemical control (luciferase) gene expression. Compounds displaying significant ATXN2 inhibition with minimal impact on control assays were deciphered based on effectiveness (E) values (n = 1321). Molecular descriptors associated with these compounds were calculated using MarvinSketch (n = 82). The molecular descriptor data (MD model) was analyzed separately from the experimentally determined screening data (S model) as well as together (MD-S model). Compounds were clustered based on structural similarity independently for the three models using the SimpleKMeans algorithm into the optimal number of clusters (n = 26). For each model, the maximum response assay values were analyzed, and E values and total rank values were applied. The S clusters were further subclustered, and the molecular properties of compounds in the top candidate subcluster were compared to those from the bottom candidate subcluster. Six compounds with high ATXN2 inhibiting potential and 16 molecular descriptors were identified as significantly unique to those compounds (p < 0.05). These results are consistent with a quantitative HTS study that identified and validated similar small-molecule compounds, like cardiac glycosides, that reduce endogenous ATXN2 in a dose-dependent manner. Overall, these findings demonstrate that the integration of HTS analysis with data mining and machine learning is a promising approach for discovering chemical properties of candidate drugs for SCA2.

Background:Christianson syndrome (CS) is an x-linked recessive neurodevelopmental and neurodegenerative condition characterized by severe intellectual disability, cerebellar degeneration, ataxia, and epilepsy. Mutations to the SLC9A6 gene encoding NHE6 are responsible for CS, and we recently demonstrated that a mutation to the rat Slc9a6 gene causes a similar phenotype in the spontaneous shaker rat model, which exhibits cerebellar degeneration with motor dysfunction. In previous work, we used the PhP.eB-L7-Slc9a6-GFP adeno-associated viral (AAV) vector to demonstrate that gene replacement in Purkinje cells reduced the shaker motor and molecular phenotype. Methods:We carried out a 20-week longitudinal study evaluating the impact of Purkinje cell-specific gene replacement on ataxia and tremor. Taking advantage of the high homology between human SLC9A6 and rat Slc9a6, we tested a more clinically relevant construct, AAV9-CAG-hSLC9A6 AAV vector in the shaker rat. In both experimental cohorts, we performed molecular studies to evaluate expression of NHE6 and key cerebellar markers. We then characterized the relationship between molecular markers and motor function, as well between tremor and ataxia. Results:Administration of either of PhP.eB-L7-Slc9a6-GFP or AAV9-CAG-hSLC9A6 AAV vectors led to significant improvement in the molecular and motor phenotypes. The abundance of each disease-relevant cerebellar proteins was significantly correlated to motor ataxia. Further, we found that the relationship between cerebellar ataxia and tremor devolved over time, with disease modifying therapy disrupting their temporal relationship. Conclusions:These findings impact future SLC9A6-targeted gene therapy efforts for CS and strongly support gene replacement as a viable therapeutic strategy. Furthermore, tremor and ataxia phenotypes may arise from dissociable cerebellar mechanisms.

Background and Objectives:Micro-RNAs (miRNAs) are critical for regulating the expression of genes in multiple neurodegenerative diseases, but miRNAs have not been investigated in spinocerebellar ataxia type 2 (SCA2). SCA2, a dominantly inherited progressive neurodegenerative polyglutamine (polyQ) disease, is caused by a CAG repeat expansion in the ataxin-2 (ATXN2) gene. In this study, we determined miRNA transcriptomes in SCA2-BAC-ATXN2[Q72] transgenic mice.Methods:We assessed the expression of miRNAs in SCA2 transgenic mouse cerebella using the HiSeq Illumina sequencer. We used the miRNA target filter tool in Qiagen Ingenuity Pathway Analysis (IPA) to identify target genes of differentially expressed miRNAs (DEmiRs) within in the SCA2 mouse transcriptomes and then performed pathway analyses.Results:Our analysis revealed significant changes in the expression levels of multiple miRNAs in mice with SCA2. We identified 81 DEmiRs in mice with SCA2, with 52 miRNAs upregulated and 29 miRNAs downregulated after onset of rotarod deficit. Subsequent IPA processing enabled us to establish connections between these DEmiRs and specific biological regulatory functions. Furthermore, by using the IPA miRNA target filter, we identified target genes of DEmiRs in the SCA2-BAC-ATXN2[Q72] transcriptome data set and demonstrated their significant impact on several biological functional and disease pathways.Discussion:Our study establishes the role of both DEmiRs and their targets in SCA2 pathogenesis. By expressing mutant ATXN2 under the control of its endogenous regulatory elements in the SCA2-BAC-ATXN2[Q72] mouse model, we identified a set of DEmiRs that are shared across multiple neurodegenerative diseases including other SCAs, Alzheimer disease (AD), Parkinson disease (PD), and amyotrophic lateral sclerosis (ALS). There was a significant overlap of both DEmiRs and their targets of BAC-ATXN2[Q72] transcriptomes in dysregulated pathways that characterize SCA2. This observation also extended to dysregulated pathways in ALS, AD, and PD. DEmiRs identified in this study may represent therapeutic targets for neurodegeneration or lead to biomarkers for characterizing various neurodegenerative diseases.