Spinocerebellar Ataxia Type Research Articles

Autosomal Recessive Spinocerebellar Ataxia Type 9 With a Response to Phosphate Repletion: A Case Report.

Autosomal recessive spinocerebellar ataxia type 9 (SCAR9) has received attention due to its potential response to coenzyme Q10 (CoQ10) supplementation; however, the response has so far been limited and variable. We report a SCAR9 patient with severe hypophosphatemia who responded well to CoQ10 and phosphate repletion. A 70-year-old man (the offspring of a consanguineous marriage) presented with cerebellar ataxia and intense fatigue after exercise. Whole-exome sequencing identified a novel homozygous deletion mutation (NM_020247.5:c.1218_1219del) in COQ8A. We thus diagnosed him with SCAR9. Supplementation of CoQ10 alleviated his symptoms, with the Scale for the Assessment and Rating of Ataxia (SARA) dropping from 16 to 14. During the course of the disease, he demonstrated continuous hypophosphatemia caused by renal phosphate wasting. Gait dysfunction due to weakness and eye movement was partially alleviated, and SARA dropped from 17 to 13 after phosphate repletion. Phosphate repletion should be considered for patients with severe hypophosphatemia without any apparent subjective symptoms. In this case, phosphate repletion could have improved myopathy leading to partial improvement in the patient's symptoms. Further analyses regarding the association between COQ8A mutation and phosphate wasting are required to elucidate the detailed pathogenesis. This provides Class IV evidence. This is a single observational study without controls.

Differences in spontaneous speech fluency between Parkinson's disease and spinocerebellar ataxia type 3.

The basal ganglia and cerebellum both have a role in speech production although the effect of isolated involvement of these structures on speech fluency remains unclear. The study aimed to assess the differences in the articulatory pattern in patients with cerebellar vs. basal ganglia disorders. A total of 20 individuals with Parkinson's disease (PD), 20 with spinocerebellar ataxia type 3 (SCA3), and 40 controls (control group, CG) were included. Diadochokinesis (DDK) and monolog tasks were collected. The only variable that distinguished SCA3 carriers from the CG was the number of syllables in the monolog, with SCA3 patients of a significantly lower number. For patients with PD, the number of syllables, phonation time, DDK, and monolog were significantly lower than for CG. Patients with PD were significantly worse compared to patients with SCA3 in the number of syllables and phonation time in DDK, and phonation time in monolog. Additionally, there was a significant correlation between the number of syllables in the monolog and the MDS-UPDRS III for participants with PD, and the Friedreich Ataxia Rating Scale for participants with SCA3 suggesting a relationship between speech and general motor functioning. The monolog task is better at discriminating individuals with cerebellar vs. Parkinson's diseases as well as differentiating healthy control and was related to the severity of the disease.

Therapeutic Strategies for Spinocerebellar Ataxia Type 1.

Spinocerebellar ataxia type 1 (SCA1) is an autosomal dominant neurodegenerative disorder that affects one or two individuals per 100,000. The disease is caused by an extended CAG repeat in exon 8 of the ATXN1 gene and is characterized mostly by a profound loss of cerebellar Purkinje cells, leading to disturbances in coordination, balance, and gait. At present, no curative treatment is available for SCA1. However, increasing knowledge on the cellular and molecular mechanisms of SCA1 has led the way towards several therapeutic strategies that can potentially slow disease progression. SCA1 therapeutics can be classified as genetic, pharmacological, and cell replacement therapies. These different therapeutic strategies target either the (mutant) ATXN1 RNA or the ataxin-1 protein, pathways that play an important role in downstream SCA1 disease mechanisms or which help restore cells that are lost due to SCA1 pathology. In this review, we will provide a summary of the different therapeutic strategies that are currently being investigated for SCA1.

Temporal Relationship between Impairment of Cerebellar Motor Learning and Deterioration of Ataxia in Patients with Cerebellar Degeneration.

Ataxia and impaired motor learning are both fundamental features in diseases affecting the cerebellum. However, it remains unclarified whether motor learning is impaired only when ataxia clearly manifests, nor it is known whether the progression of ataxia, the speed of which often varies among patients with the same disease, can be monitored by examining motor learning. We evaluated motor learning and ataxia at intervals of several months in 40 patients with degenerative conditions [i.e., multiple system atrophy (MSA), Machado-Joseph disease (MJD)/spinocerebellar ataxia type 3 (SCA3), SCA6, and SCA31]. Motor learning was quantified as the adaptability index (AI) in the prism adaptation task and ataxia was scored using the Scale for the Assessment and Rating of Ataxia (SARA). We found that AI decreased most markedly in both MSA-C and MSA-P, moderately in MJD, and mildly in SCA6 and SCA31. Overall, the AI decrease occurred more rapidly than the SARA score increase. Interestingly, AIs remained normal in purely parkinsonian MSA-P patients (n = 4), but they dropped into the ataxia range when these patients started to show ataxia. The decrease in AI during follow-up (dAI/dt) was significant in patients with SARA scores < 10.5 compared with patients with SARA scores ≥ 10.5, indicating that AI is particularly useful for diagnosing the earlier phase of cerebellar degeneration. We conclude that AI is a useful marker for progressions of cerebellar diseases, and that evaluating the motor learning of patients can be particularly valuable for detecting cerebellar impairment, which is often masked by parkinsonisms and other signs.

Effects of cerebellar transcranial alternating current stimulation in cerebellar ataxia: study protocol for a randomised controlled trial.

Cerebellar ataxia (CA) is a movement disorder that can affect balance and gait, limb movement, oculomotor control, and cognition. Multiple system atrophy-cerebellar type (MSA-C) and spinocerebellar ataxia type 3 (SCA3) are the most common forms of CA, for which no effective treatment is currently available. Transcranial alternating current stimulation (tACS) is a non-invasive method of brain stimulation supposed to alter cortical excitability and brain electrical activity, modulating functional connectivity within the brain. The cerebellar tACS can modulate the cerebellar outflow and cerebellum-linked behavior and it is a proven safe technique for humans. Therefore, the aim of this study is to 1) examine whether cerebellar tACS improves ataxia severity and various non-motor symptoms in a homogeneous cohort of CA patients consisting of MSA-C and SCA3, 2) explore the time course of these effects, and 3) assess the safety and tolerance of cerebellar tACS in all participants. This is a 2-week, triple-blind, randomised, sham-controlled study. 164 patients (MSA-C: 84, SCA3: 80) will be recruited and randomly assigned to either active cerebellar tACS or sham cerebellar tACS, in a 1:1 ratio. Patients, investigators, and outcome assessors are unaware of treatment allocation. Cerebellar tACS (40 min, 2 mA, ramp-up and down periods of 10s each) will be delivered over 10 sessions, distributed in two groups of five consecutive days with a two-day break in between. Outcomes are assessed after the tenth stimulation (T1), and after 1 month (T2) and 3 months (T3). The primary outcome measure is the difference between the active and sham groups in the proportion of patients with an improvement of 1.5 points in the Scale for the Assessment and Rating of Ataxia (SARA) score after 2 weeks of treatment. In addition, effects on a variety of non-motor symptoms, quality of life, and autonomic nerve dysfunctions are assessed via relative scales. Gait imbalance, dysarthria, and finger dexterity are objectively valued via relative tools. Finally, functional magnetic resonance imaging is performed to explore the possible mechanism of treatment effects. The results of this study will inform whether repeated sessions of active cerebellar tACS benefit CA patients and whether this form of non-invasive stimulation might be a novel therapeutic approach to consider in a neuro-rehabilitation setting.Clinical Trial Registration: ClinicalTrials.gov, identifier NCT05557786; https://www.clinicaltrials.gov/ct2/show/NCT05557786.

Spinocerebellar ataxia type 14 (SCA14) in an Argentinian family: a case report

BackgroundHereditary spinocerebellar ataxias are a group of genetic neurological disorders that result in degeneration of the cerebellum and brainstem, leading to difficulty in controlling balance and muscle coordination.Case presentationA family affected by spinocerebellar ataxia was identified in Argentina and investigated using whole exome sequencing to determine the genetic etiology. The proband, a female white Hispanic aged 48, was noted to have slowly progressive gait ataxia, dysarthria, nystagmus, and moderate cerebellar atrophy. Whole exome sequencing was performed on three affected and two unaffected family members and revealed a dominant pathogenic variant, p.Gln127Arg (19:54392986 A>G), in the protein kinase C gamma gene, and the family was diagnosed with spinocerebellar ataxia type 14.ConclusionsTo our knowledge, no previous cases of spinocerebellar ataxia type 14 have been reported in Argentina, expanding the global presence of this neurological disorder. This diagnosis supports whole exome sequencing as a high-yield method for identifying coding variants causing cerebellar ataxias and emphasizes the importance of broadening the clinical availability of whole exome sequencing for undiagnosed patients and families.

A novel CACNA1A variant causing Developmental and Epileptic Encephalopathy 42: Report of the first case in Colombia (P3-1.010)

<h3>Objective:</h3> To report a CACNA1A Novel variant causing Developmental and Epileptic Encephalopathy 42. <h3>Background:</h3> CACNA1A encodes the α1A subunit (pore-forming subunit) of a neuronal P/Q type calcium channel. Mutations within this gene lead to clinically significant neurological abnormalities with multiple phenotypic presentations, including Familial Hemiplegic Migraine (FHM), episodic ataxia type 2 (EA2), spinocerebellar ataxia type 6 (SCA6), and Developmental and Epileptic Encephalopathy 42 (DEE42). DEE42 is a disorder characterized by the developmental delay with cognitive impairment and multiple types of seizures in the neonatal period. <h3>Design/Methods:</h3> A karyotype was performed using peripheral blood lymphocytes. A Microarray-based Comparative Genomic Hybridization (aCGH) using CytoScan 750K Array (Affymetrix, Santa Clara, CA, USA) and whole exome sequencing (WES). <h3>Results:</h3> Our patient is a female born to non-consanguineous parents with a family history of speech and psychomotor developmental delay in her mother. She was born at term with uneventful antenatal and perinatal history. At 12 months, she presented to the Neurology and Genetics department with macrocephaly, frontal bossing, severe hypotonia, psychomotor delay, and repeated episodes of seizures requiring therapy with valproic acid and levetiracetam. EEG evidenced generalized spike waves. Her course was complicated by a traumatic brain injury that precipitated repeated episodes of status epilepticus. At 28 months old, she had cognitive and communication deficits with severe speech delay. The aCGH showed a 4q21.21 deletion. The final result was given as 46, XX arr[GRCh37/hg19] chr4:79766081-80327420. In this study, we describe a patient with DEE42 due to a novel mutation in CACNA1A identified using WES. WES revealed a novel heterozygous variant in the CACNA1A gene: c.4174G&gt;A (p.Val1392Met). Parent analysis was negative for the mutation. This novel variant was predicted as a disease-causing mutation. <h3>Conclusions:</h3> These findings widen the mutation and phenotypic spectrum of CACNA1A-associated disease. The potential genotype-phenotype correlation would facilitate early identification and help guide future pharmacologic treatment research. <b>Disclosure:</b> Dr. Orellana Zambrano has nothing to disclose. Dr. Candelo has nothing to disclose. Mrs. Diaz has nothing to disclose. Dr. Pacheco has nothing to disclose. Mr. Giraldo-Ocampo has nothing to disclose. Dr. Gomez-Pineda has nothing to disclose. Dr. Pachajoa has nothing to disclose.

Caspr2 Antibody-Mediated Ataxia, Parkinsonism, and Epilepsy: A Case for Escalating Immunotherapy. (P13-11.007)

<h3>Objective:</h3> To report a rare presentation of anti-Caspr2 syndrome treated successfully with rituximab. <h3>Background:</h3> Anti-Caspr2 syndrome has a variety of clinical phenotypes including encephalopathy, seizure, psychiatric disturbances, respiratory failure, dysautonomia, peripheral nerve dysfunction, as well as ataxia of a constant or episodic nature.¹ In many of the cases with ataxia, there is associated limbic encephalitis.² Anti-Caspr2 syndrome with ataxia, parkinsonism and seizure has only been reported once in the literature.³ This symptomatology can be easily mistaken for an atypical parkinsonism like cerebellar multiple systems atrophy, or spinocerebellar ataxia type 2 but this treatable cause is an important consideration. <h3>Design/Methods:</h3> To report a case of anti-Caspr2 syndrome presenting with pure ataxia, then progressing to parkinsonism, and epilepsy; its successful treatment; and accompanying video examinations. <h3>Results:</h3> A 71 year-old man was referred for 8 months of progressive, generalized ataxia and dysarthria. Immune-mediated ataxia was considered given the subacute course with rapid progression. He was found to have a Caspr2 antibody titer of 1:100. Evaluation for malignancy was unremarkable. Lumbar puncture revealed Caspr2 antibody positivity. The patient was treated with 4 days of intravenous steroids and immunoglobulins with significant improvement. He relapsed four months later with lower extremity weakness and ataxia. Despite maintenance intravenous immunoglobulin, his ataxia continued to progress. He then developed focal seizures with impaired awareness and left sided parkinsonism. He was started on rituximab immunotherapy for ongoing disease activity. His ataxia and parkinsonism significantly improved to near-baseline with continued stability 6 months later. <h3>Conclusions:</h3> This case illustrates an example of an autoimmune-mediated cerebellar ataxia of subacute onset with progression to parkinsonism and epilepsy. Special consideration for anti-Caspr2 syndrome should be taken in cases of progressive ataxia with accompanying neurologic features of parkinsonism and seizure. Escalation to rituximab can be considered for patients who continue to progress despite preliminary immunotherapy. <b>Disclosure:</b> Dr. Sugar has nothing to disclose. Dr. Witek has nothing to disclose.

Intrafamilial Heterogeneity in Spinocerebellar Ataxia Type 21 (P8-11.015)

<h3>Objective:</h3> To emphasize the variability of clinical presentations of genetic movement disorders as depicted by a family with SCA21. <h3>Background:</h3> Spinocerebellar ataxia type 21 (SCA21) is a rare autosomal dominant condition that can have a variety of motor, cognitive, or behavioral manifestations. This clinical variability is seen both between and within families with the same mutation. <h3>Design/Methods:</h3> N/A <h3>Results:</h3> A 51-year-old woman presented to clinic for evaluation of lifelong worsening balance impairment and hand clumsiness. Her physical exam noted marked ataxia and dysmetria in the extremities, ataxic gait, and spastic extremities, and neuropsychiatric testing was remarkable for mild impairments. Following further workup, a family history of neurologic complaints was taken, which revealed that one of her three children had tremors. When brought to clinic, the patient’s daughter revealed a lifelong history of bilateral hand tremors with worsening over the previous two years. She further noted a slowness in her thinking that required special education courses, as well as other mild motor difficulties. Given the potential for a genetic condition, an ataxia panel was ordered, which revealed a c.509C&gt;Tp.P170L mutation in the TMEM240 gene in the patient and her daughter. <h3>Conclusions:</h3> This case emphasizes the importance of recognizing intrafamilial clinical heterogeneity in the diagnosis of genetic movement disorders. It highlights the potential benefits of an investigation into a family history notable for neurological disorders, which may provide the opportunity for appropriate testing and diagnosis. The variable presentations of spinocerebellar ataxias within families have been explored in a limited number of case reports. The identification of a possible unknown factor driving these differences in presentation could have potential therapeutic implications. While all reported cases of SCA21 have some degree of gait and limb ataxia, only one case has reported tremor onset followed by ataxia and dystonia, as seen in this case. <b>Disclosure:</b> Emma *Use 368242 Wetmore has nothing to disclose. Dr. Decker has nothing to disclose. Maysen Mesaros has nothing to disclose. An immediate family member of Dr. Rodriguez-Porcel has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Anmeal. Dr. Rodriguez-Porcel has received publishing royalties from a publication relating to health care.

Diagnosed in the Autoimmune Neurology Clinic: Two patients with different phenotypes of spinocerebellar ataxia type 27 (P10-5.014)

<h3>Objective:</h3> To describe two cases of spinocerebellar ataxia type 27 (SCA27), with a focus on the importance of differentiating episodic manifestations of neurogenetic conditions from inflammatory/autoimmune neurologic conditions. We emphasize the importance of obtaining an objective evaluation of the response to immunomodulatory treatment trials, and the significance of attaining a comprehensive family history. <h3>Background:</h3> SCA27 is an autosomal dominant condition caused by a pathogenic mutation in the fibroblast growth factor 14 (FGF14) gene located on chromosome 13. Phenotypic expression can vary in patients with the same genetic abnormality, often delaying diagnosis, especially in probands without affected relatives and/or with unremarkable or unavailable family history at the time of presentation. <h3>Design/Methods:</h3> We describe two patients referred to the Autoimmune Neurology clinic at the University of Utah for suspicion of an autoimmune/autoinflammatory disease, ultimately diagnosed with SCA27 as part of an expanded clinical evaluation. <h3>Results:</h3> A 68-year-old male patient (Case 1) presented with episodic dysarthria, dizziness, imbalance, and encephalopathy, with suspicion of a possible autoimmune etiology at the time of referral. At his first presentation, the patient reported no significant family history. Four years later, on revisiting the family history, he noted that his 49-year-old niece (Case 2) had also developed neurologic symptoms of unclear etiology. On evaluation, his niece was noted to have a tremor and ataxia. Both patients had evidence of systemic autoimmunity that likely contributed to suspicion of neurologic autoimmunity, and neither had age-advanced cerebellar or brainstem volume loss on imaging. Ultimately, genetic testing of both patients revealed a pathogenic mutation in the FGF14 gene consistent with SCA27. <h3>Conclusions:</h3> These two cases highlight the importance of a detailed interval family history at each visit, especially in undiagnosed adult patients. The presumptive autoinflammatory diagnosis in both patients reinforces the importance of comprehensive follow-up, including an objective analysis of response to any immunomodulatory diagnostic treatment trials. <b>Disclosure:</b> Dr. Hoshina has nothing to disclose. Dr. Wright has nothing to disclose. Dr. Warner has received intellectual property interests from a discovery or technology relating to health care. Dr. Richards has nothing to disclose. Karen Salzman has received publishing royalties from a publication relating to health care. Dr. Pulst has received personal compensation in the range of $500-$4,999 for serving as a Consultant for venrock. Dr. Pulst has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Arrowhead. Dr. Pulst has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Leverna. Dr. Pulst has received personal compensation in the range of $10,000-$49,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for AAN. Dr. Pulst has received personal compensation in the range of $500-$4,999 for serving as an Expert Witness for Leninthal LLC. The institution of Dr. Pulst has received research support from NINDS. Dr. Pulst has received intellectual property interests from a discovery or technology relating to health care. Ms. Spoth has stock in Applied Genetic Technologies Corporation. Ms. Spoth has stock in MeiraGTx Holdings. Ms. Spoth has stock in Ocugen. Ms. Spoth has stock in PTC Therapeutics. Dr. Clardy has received personal compensation for serving as an employee of Veterans Health Administration (VHA). Dr. Clardy has received personal compensation for serving as an employee of University of Utah Health. Dr. Clardy has received personal compensation in the range of $10,000-$49,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for Neurology/AAN Publications. The institution of Dr. Clardy has received research support from Sumaira Foundation for NMO. The institution of Dr. Clardy has received research support from Western Institute for Veteran Research. The institution of Dr. Clardy has received research support from NIH/NINDS. Dr. Clardy has received personal compensation in the range of $500-$4,999 for serving as a AAN Summer Meeting CoDirector Travel and Lodging with AAN. Dr. Clardy has received personal compensation in the range of $500-$4,999 for serving as a Grand Rounds Travel and Lodging with U of Iowa. Dr. Clardy has received personal compensation in the range of $500-$4,999 for serving as a Speaker Honoraria for Grand Rounds with Barrow Neurological Institute. Dr. Clardy has received personal compensation in the range of $500-$4,999 for serving as a Speaker Honoraria for Grand Rounds with Beaumont Health.

A Patient with Late-Onset Cerebellar Ataxia and a Novel FAT2 Gene Variant Concerning for Spinocerebellar Ataxia Type 45: A Case Report (P9-11.009)

<h3>Objective:</h3> We describe a patient with late-onset ataxia, parkinsonism, tremor, and neuropathy with a novel <i>FAT2</i> gene frameshift variant, a gene primarily expressed in the cerebellum and recently implicated in spinocerebellar ataxia type 45 (SCA45). <h3>Background:</h3> Spinocerebellar ataxias (SCAs) are a heterogeneous group of autosomal dominant (AD), neurodegenerative disorders that manifest with cerebellar dysfunction. SCA45 is associated with <i>FAT2</i> gene variants and is characterized by late-onset, pure cerebellar ataxia with autosomal dominant inheritance pattern. So far, only two families and one sporadic case with likely pathogenic <i>FAT2</i> variants have been reported, all of which involved missense variants. <h3>Design/Methods:</h3> NA <h3>Results:</h3> A 57-year-old woman presented with 3 years of progressive ataxia, neuropathy and mild tremor in the setting of a mood disorder. Family history was notable for a mother, maternal grandfather, and maternal great grandmother with similar symptoms. Exam revealed limb and gait ataxia, normal eye movements, mild symmetric parkinsonism, subtle postural and action tremor, and length-dependent neuropathy. Medications included aripiprazole. Lab work-up for metabolic, inflammatory, and immune related etiologies was negative. MRI brain showed no significant atrophy or lesions. CT brain showed calcification in the globus pallidus internus bilaterally. Genetic testing revealed a heterozygous frameshift variant (c.3039_3040del; p.Cys1014Profs*11) in the <i>FAT2</i> gene. <h3>Conclusions:</h3> Our patient’s inheritance pattern, cerebellar dysfunction and age of onset are consistent with SCA45. However, her phenotype includes tremor and neuropathy in addition to cerebellar ataxia, which contrasts with previously reported cases of a pure cerebellar syndrome associated with <i>FAT2</i> missense variants. Our patient has a frame-shift mutation that likely resulted in a non-functional protein. This type of variant has not been reported before and can currently only be classified as a variant of unknown significance (VUS) as affected family members are deceased. This case adds to the growing body of information regarding <i>FAT2</i> gene variants and their relation to hereditary ataxia. <b>Disclosure:</b> Dr. Ameri has nothing to disclose. Dr. Rosenbaum has nothing to disclose. The institution of Dr. Kirby has received research support from Parkinson’s Foundation.

The potential value of disease-modifying therapy in patients with spinocerebellar ataxia type 1: an early health economic modeling study

ObjectiveThere currently is no disease-modifying therapy for spinocerebellar ataxia type 1 (SCA1). Genetic interventions, such as RNA-based therapies, are being developed but those currently available are very expensive. Early evaluation of costs and benefits is, therefore, crucial. By developing a health economic model, we aimed to provide first insights into the potential cost-effectiveness of RNA-based therapies for SCA1 in the Netherlands.MethodsWe simulated disease progression of individuals with SCA1 using a patient-level state-transition model. Five hypothetical treatment strategies with different start and endpoints and level of effectiveness (5–50% reduction in disease progression) were evaluated. Consequences of each strategy were measured in terms of quality-adjusted life years (QALYs), survival, healthcare costs, and maximum costs to be cost effective.ResultsMost QALYs (6.68) are gained when therapy starts during the pre-ataxic stage and continues during the entire disease course. Incremental costs are lowest (− €14,048) if therapy is stopped when the severe ataxia stage is reached. The maximum costs per year to be cost-effective are €19,630 in the “stop after moderate ataxia stage” strategy at 50% effectiveness.DiscussionOur model indicates that the maximum price for a hypothetical therapy to be cost-effective is considerably lower than currently available RNA-based therapies. Most value for money can be gained by slowing progression in the early and moderate stages of SCA1 and by stopping therapy upon entering the severe ataxia stage. To allow for such a strategy, it is crucial to identify individuals in early stages of disease, preferably just before symptom onset.

Blood transcriptome sequencing identifies biomarkers able to track disease stages in spinocerebellar ataxia type 3.

Transcriptional dysregulation has been described in spinocerebellar ataxia type 3/Machado-Joseph disease (SCA3/MJD), an autosomal dominant ataxia caused by a polyglutamine expansion in the ataxin-3 protein. As ataxin-3 is ubiquitously expressed, transcriptional alterations in blood may reflect early changes that start before clinical onset and might serve as peripheral biomarkers in clinical and research settings. Our goal was to describe enriched pathways and report dysregulated genes, which can track disease onset, severity or progression in carriers of the ATXN3 mutation (pre-ataxic subjects and patients). Global dysregulation patterns were identified by RNA sequencing of blood samples from 40 carriers of ATXN3 mutation and 20 controls and further compared with transcriptomic data from post-mortem cerebellum samples of MJD patients and controls. Ten genes-ABCA1, CEP72, PTGDS, SAFB2, SFSWAP, CCDC88C, SH2B1, LTBP4, MEG3 and TSPOAP1-whose expression in blood was altered in the pre-ataxic stage and simultaneously, correlated with ataxia severity in the overt disease stage, were analysed by quantitative real-time PCR in blood samples from an independent set of 170 SCA3/MJD subjects and 57 controls. Pathway enrichment analysis indicated the Gαi signalling and the oestrogen receptor signalling to be similarly affected in blood and cerebellum. SAFB2, SFSWAP and LTBP4 were consistently dysregulated in pre-ataxic subjects compared to controls, displaying a combined discriminatory ability of 79%. In patients, ataxia severity was associated with higher levels of MEG3 and TSPOAP1. We propose expression levels of SAFB2, SFSWAP and LTBP4 as well as MEG3 and TSPOAP1 as stratification markers of SCA3/MJD progression, deserving further validation in longitudinal studies and in independent cohorts.

Regional and age-dependent changes in ubiquitination in cellular and mouse models of spinocerebellar ataxia type 3.

Spinocerebellar ataxia type 3 (SCA3), also known as Machado-Joseph disease, is the most common dominantly inherited ataxia. SCA3 is caused by a CAG repeat expansion in the ATXN3 gene that encodes an expanded tract of polyglutamine in the disease protein ataxin-3 (ATXN3). As a deubiquitinating enzyme, ATXN3 regulates numerous cellular processes including proteasome- and autophagy-mediated protein degradation. In SCA3 disease brain, polyQ-expanded ATXN3 accumulates with other cellular constituents, including ubiquitin (Ub)-modified proteins, in select areas like the cerebellum and the brainstem, but whether pathogenic ATXN3 affects the abundance of ubiquitinated species is unknown. Here, in mouse and cellular models of SCA3, we investigated whether elimination of murine Atxn3 or expression of wild-type or polyQ-expanded human ATXN3 alters soluble levels of overall ubiquitination, as well as K48-linked (K48-Ub) and K63-linked (K63-Ub) chains. Levels of ubiquitination were assessed in the cerebellum and brainstem of 7- and 47-week-old Atxn3 knockout and SCA3 transgenic mice, and also in relevant mouse and human cell lines. In older mice, we observed that wild-type ATXN3 impacts the cerebellar levels of K48-Ub proteins. In contrast, pathogenic ATXN3 leads to decreased brainstem abundance of K48-Ub species in younger mice and changes in both cerebellar and brainstem K63-Ub levels in an age-dependent manner: younger SCA3 mice have higher levels of K63-Ub while older mice have lower levels of K63-Ub compared to controls. Human SCA3 neuronal progenitor cells also show a relative increase in K63-Ub proteins upon autophagy inhibition. We conclude that wild-type and mutant ATXN3 differentially impact K48-Ub- and K63-Ub-modified proteins in the brain in a region- and age-dependent manner.

Design, synthesis and biological evaluation of pyrrolopyrimidine derivatives as novel and selective positive modulator of the small conductance Ca2+-activated K+ channels

The type 2 small conductance Ca2+-activated K+ channels (SK2) have been considered as one of the most promising therapeutic targets for spinocerebellar ataxias type 2 (SCA2) by playing a critical role in the control of normal purkinje cells (PCs) pacemaking. Herein, a novel series of pyrrolopyrimidine derivatives were designed and synthesized from the lead compound NS13001 as subtype-selective modulators of SK channels. Among them, the halogen-substituted compound 12b (EC50 = 0.34 ± 0.044 μM) was identified with a ∼5.4-fold higher potency on potentiating SK2-a channels at submicromolar concentrations as compared to NS13001 (EC50 = 1.83 ± 0.50 μM). Furthermore, compound 12b exhibited selectivity on SK2-a/SK3 subtype by displaying 93.33 ± 3.26% efficacies on SK2-a channels, and 84.54% ± 7.49% on SK3 channels. In addition, compound 12b demonstrated the potential to cross the blood-brain barrier (BBB) with suitable pharmacokinetic properties and low cytotoxicity. Molecular docking study also unveiled the binding interactions of compound 12b with SK2-CaM protein complex. Overall, the novel pyrrolopyrimidines provide an insightful guidance for future structural optimization of SK channel agonists.

Synaptic Loss in Spinocerebellar Ataxia Type 3 Revealed by SV2A Positron Emission Tomography.

Severe reduced synaptic density was observed in spinocerebellar ataxia (SCA) in postmortem neuropathology, but in vivo assessment of synaptic loss remains challenging. OBJECTIVE SPINOCEREBELLAR ATAXIA TYPE 3: The objective of this study was to assess in vivo synaptic loss and its clinical correlates in spinocerebellar ataxia type 3 (SCA3) patients by synaptic vesicle glycoprotein 2A (SV2A)-positron emission tomography (PET) imaging. We recruited 74 SCA3 individuals including preataxic and ataxic stages and divided into two cohorts. All participants received SV2A-PET imaging using 18 F-SynVesT-1 for synaptic density assessment. Specifically, cohort 1 received standard PET procedure and quantified neurofilament light chain (NfL), and cohort 2 received simplified PET procedure for exploratory purpose. Bivariate correlation was performed between synaptic loss and clinical as well as genetic assessments. In cohort 1, significant reductions of synaptic density were observed in cerebellum and brainstem in SCA3 ataxia stage compared to preataxic stage and controls. Vermis was found significantly involved in preataxic stage compared to controls. Receiver operating characteristic (ROC) curves highlighted SV2A of vermis, pons, and medulla differentiating preataxic stage from ataxic stage, and SV2A combined with NfL improved the performance. Synaptic density was significantly negatively correlated with disease severity in cerebellum and brainstem (International Co-operative Ataxia Rating Scale: ρ ranging from -0.467 to -0.667, P ≤ 0.002; Scale of Assessment and Rating of Ataxia: ρ ranging from -0.465 to -0.586, P ≤ 0.002). SV2A reduction tendency of cerebellum and brainstem identified in cohort 1 was observed in cohort 2 with simplified PET procedure. We first identified in vivo synaptic loss was related to disease severity of SCA3, suggesting SV2A PET could be a promising clinical biomarker for disease progression of SCA3. © 2023 International Parkinson and Movement Disorder Society.

Extracellular vesicle-based delivery of silencing sequences for the treatment of Machado-Joseph disease/spinocerebellar ataxia type 3

Machado-Joseph disease (MJD)/spinocerebellar ataxia type 3 (SCA3) is the most common autosomal dominantly inherited ataxia worldwide. It is caused by an over-repetition of the trinucleotide CAG within the ATXN3 gene, which confers toxic properties to ataxin-3 (ATXN3) species. RNA interference technology has shown promising therapeutic outcomes but still lacks a non-invasive delivery method to the brain. Extracellular vesicles (EVs) emerged as promising delivery vehicles due to their capacity to deliver small nucleic acids, such as microRNAs (miRNAs). miRNAs were found to be enriched into EVs due to specific signal motifs designated as ExoMotifs. In this study, we aimed at investigating whether ExoMotifs would promote the packaging of artificial miRNAs into EVs to be used as non-invasive therapeutic delivery vehicles to treat MJD/SCA3. We found that miRNA-based silencing sequences, associated with ExoMotif GGAG and ribonucleoprotein A2B1 (hnRNPA2B1), retained the capacity to silence mutant ATXN3 (mutATXN3) and were 3-fold enriched into EVs. Bioengineered EVs containing the neuronal targeting peptide RVG on the surface significantly decreased mutATXN3 mRNA in primary cerebellar neurons from MJD YAC 84.2 and in a novel dual-luciferase MJD mouse model upon daily intranasal administration. Altogether, these findings indicate that bioengineered EVs carrying miRNA-based silencing sequences are a promising delivery vehicle for brain therapy.

SCAview: an Intuitive Visual Approach to the Integrative Analysis of Clinical Data in Spinocerebellar Ataxias

With SCAview, we present a prompt and comprehensive tool that enables scientists to browse large datasets of the most common spinocerebellar ataxias intuitively and without technical effort. Basic concept is a visualization of data, with a graphical handling and filtering to select and define subgroups and their comparison. Several plot types to visualize all data points resulting from the selected attributes are provided. The underlying synthetic cohort is based on clinical data from five different European and US longitudinal multicenter cohorts in spinocerebellar ataxia type 1, 2, 3, and 6 (SCA1, 2, 3, and 6) comprising > 1400 patients with overall > 5500 visits. First, we developed a common data model to integrate the clinical, demographic, and characterizing data of each source cohort. Second, the available datasets from each cohort were mapped onto the data model. Third, we created a synthetic cohort based on the cleaned dataset. With SCAview, we demonstrate the feasibility of mapping cohort data from different sources onto a common data model. The resulting browser-based visualization tool with a thoroughly graphical handling of the data offers researchers the unique possibility to visualize relationships and distributions of clinical data, to define subgroups and to further investigate them without any technical effort. Access to SCAview can be requested via the Ataxia Global Initiative and is free of charge.

A standardised protocol for blood and cerebrospinal fluid collection and processing for biomarker research in ataxia.

The European Spinocerebellar Ataxia Type 3/Machado-Joseph Disease Initiative (ESMI) is a consortium established with the ambition to set up the largest European longitudinal trial-ready cohort of Spinocerebellar Ataxia Type 3/Machado-Joseph Disease (SCA3/MJD), the most common autosomal dominantly inherited ataxia worldwide. A major focus of ESMI has been the identification of SCA3/MJD biomarkers to enable future interventional studies. As biosample collection and processing variables significantly impact the outcomes of biomarkers studies, biosampling procedures standardisation was done previously to study visit initiation. Here, we describe the ESMI consensus biosampling protocol, developed within the scope of ESMI, that ultimately might be translated to other neurodegenerative disorders, particularly ataxias, being the first step to protocol harmonisation in the field.

ATXN3 controls DNA replication and transcription by regulating chromatin structure.

The deubiquitinating enzyme Ataxin-3 (ATXN3) contains a polyglutamine (PolyQ) region, the expansion of which causes spinocerebellar ataxia type-3 (SCA3). ATXN3 has multiple functions, such as regulating transcription or controlling genomic stability after DNA damage. Here we report the role of ATXN3 in chromatin organization during unperturbed conditions, in a catalytic-independent manner. The lack of ATXN3 leads to abnormalities in nuclear and nucleolar morphology, alters DNA replication timing and increases transcription. Additionally, indicators of more open chromatin, such as increased mobility of histone H1, changes in epigenetic marks and higher sensitivity to micrococcal nuclease digestion were detected in the absence of ATXN3. Interestingly, the effects observed in cells lacking ATXN3 are epistatic to the inhibition or lack of the histone deacetylase 3 (HDAC3), an interaction partner of ATXN3. The absence of ATXN3 decreases the recruitment of endogenous HDAC3 to the chromatin, as well as the HDAC3 nuclear/cytoplasm ratio after HDAC3 overexpression, suggesting that ATXN3 controls the subcellular localization of HDAC3. Importantly, the overexpression of a PolyQ-expanded version of ATXN3 behaves as a null mutant, altering DNA replication parameters, epigenetic marks and the subcellular distribution of HDAC3, giving new insights into the molecular basis of the disease.