The Neuropathology of Spinocerebellar Ataxia Type 3/Machado-Joseph Disease

Tract-specific spinal damage in SCA2, SCA3 and SCA6

BACKGROUND

Spinocerebellar ataxias (SCAs) are a group of neurodegenerative disorders characterized by progressive ataxia. Although previous studies have focused on cerebral and cerebellar damage, spinal cord involvement in SCAs remains underexplored.

OBJECTIVES

This study aims to characterize spinal cord abnormalities in SCA2, SCA3, and SCA6 and to identify its phenotypic correlates.

METHODS

We conducted a multimodal spinal neuroimaging study on 26 SCA3, 16 SCA2, and 14 SCA6 patients, along with matched healthy controls. MRI scanning was performed using a 3 Tesla device, and the Spinal Cord Toolbox (SCT) was employed for morphometric and diffusivity analyses of the cervical spinal cord.

RESULTS

Our findings revealed significant spinal cord atrophy and altered white matter microstructural metrics in SCA3 and SCA2 patients compared to controls, with no abnormalities in SCA6. A strong negative correlation was observed between cross-sectional cord area and disease duration in SCA2, suggesting its potential as a biomarker for disease progression.

CONCLUSIONS

This study highlights the importance of spinal cord imaging in understanding the pathophysiology of SCAs and demonstrates the utility of MRI-based metrics in identifying structural deviations and their clinical correlates. Further longitudinal studies are needed to validate these findings and explore their implications for clinical trials and therapeutic interventions.

Specific Biomarkers in Spinocerebellar Ataxia Type 3: A Systematic Review of Their Potential Uses in Disease Staging and Treatment Assessment

Spinocerebellar ataxia type 3 (SCA3) is the most common type of disease related to poly-glutamine (polyQ) repeats. Its hallmark pathology is related to the abnormal accumulation of ataxin 3 with a longer polyQ tract (polyQ-ATXN3). However, there are other mechanisms related to SCA3 progression that require identifying trait and state biomarkers for a more accurate diagnosis and prognosis. Moreover, the identification of potential pharmacodynamic targets and assessment of therapeutic efficacy necessitates valid biomarker profiles. The aim of this review was to identify potential trait and state biomarkers and their potential value in clinical trials. Our results show that, in SCA3, there are different fluid biomarkers involved in neurodegeneration, oxidative stress, metabolism, miRNA and novel genes. However, neurofilament light chain NfL and polyQ-ATXN3 stand out as the most prevalent in body fluids and SCA3 stages. A heterogeneity analysis of NfL revealed that it may be a valuable state biomarker, particularly when measured in plasma. Nonetheless, since it could be a more beneficial approach to tracking SCA3 progression and clinical trial efficacy, it is more convenient to perform a biomarker profile evaluation than to rely on only one.

Genotype-specific spinal cord damage in spinocerebellar ataxias: an ENIGMA-Ataxia study

BACKGROUND

Spinal cord damage is a feature of many spinocerebellar ataxias (SCAs), but well-powered in vivo studies are lacking and links with disease severity and progression remain unclear. Here we characterise cervical spinal cord morphometric abnormalities in SCA1, SCA2, SCA3 and SCA6 using a large multisite MRI dataset.

METHODS

Upper spinal cord (vertebrae C1-C4) cross-sectional area (CSA) and eccentricity (flattening) were assessed using MRI data from nine sites within the ENIGMA-Ataxia consortium, including 364 people with ataxic SCA, 56 individuals with preataxic SCA and 394 nonataxic controls. Correlations and subgroup analyses within the SCA cohorts were undertaken based on disease duration and ataxia severity.

RESULTS

Individuals in the ataxic stage of SCA1, SCA2 and SCA3, relative to non-ataxic controls, had significantly reduced CSA and increased eccentricity at all examined levels. CSA showed large effect sizes (d>2.0) and correlated with ataxia severity (r<-0.43) and disease duration (r<-0.21). Eccentricity correlated only with ataxia severity in SCA2 (r=0.28). No significant spinal cord differences were evident in SCA6. In preataxic individuals, CSA was significantly reduced in SCA2 (d=1.6) and SCA3 (d=1.7), and the SCA2 group also showed increased eccentricity (d=1.1) relative to nonataxic controls. Subgroup analyses confirmed that CSA and eccentricity are abnormal in early disease stages in SCA1, SCA2 and SCA3. CSA declined with disease progression in all, whereas eccentricity progressed only in SCA2.

CONCLUSIONS

Spinal cord abnormalities are an early and progressive feature of SCA1, SCA2 and SCA3, but not SCA6, which can be captured using quantitative MRI.

Fatigue Impacts Quality of Life in People with Spinocerebellar Ataxias

BACKGROUND

Fatigue is a prevalent and debilitating symptom in neurological disorders, including spinocerebellar ataxias (SCAs). However, the risk factors of fatigue in the SCAs as well as its impact have not been well investigated.

OBJECTIVES

To study the prevalence of fatigue in SCAs, the factors contributing to fatigue, and the influence of fatigue on quality of life.

METHODS

Fatigue was assessed in 418 participants with SCA1, SCA2, SCA3, and SCA6 from the Clinical Research Consortium for the Study of Cerebellar Ataxia using the Fatigue Severity Scale. We conducted multi-variable linear regression models to examine the factors contributing to fatigue as well as the association between fatigue and quality of life.

RESULTS

Fatigue was most prevalent in SCA3 (52.6%), followed by SCA1 (36.7%), SCA6 (35.7%), and SCA2 (35.6%). SCA cases with fatigue had more severe ataxia and worse depressive symptoms. In SCA3, those with fatigue had a longer disease duration and longer pathological CAG repeat numbers. In multi-variable models, depressive symptoms, but not ataxia severity, were associated with more severe fatigue. Fatigue, independent of ataxia and depression, contributed to worse quality of life in SCA3 and SCA6 at baseline, and fatigue continued affecting quality of life throughout the disease course in all types of SCA.

CONCLUSIONS

Fatigue is a common symptom in SCAs and is closely related to depression. Fatigue significantly impacts patients' quality of life. Therefore, screening for fatigue should be considered a part of standard clinical care for SCAs.

A Review of Ocular Movement Abnormalities in Hereditary Cerebellar Ataxias

Cerebellar ataxias are a wide heterogeneous group of disorders that may present with fine motor deficits as well as gait and balance disturbances that have a significant influence on everyday activities. To review the ocular movements in cerebellar ataxias in order to improve the clinical knowledge of cerebellar ataxias and related subtypes. English papers published from January 1990 to May 2022 were selected by searching PubMed services. The main search keywords were ocular motor, oculomotor, eye movement, eye motility, and ocular motility, along with each ataxia subtype. The eligible papers were analyzed for clinical presentation, involved mutations, the underlying pathology, and ocular movement alterations. Forty-three subtypes of spinocerebellar ataxias and a number of autosomal dominant and autosomal recessive ataxias were discussed in terms of pathology, clinical manifestations, involved mutations, and with a focus on the ocular abnormalities. A flowchart has been made using ocular movement manifestations to differentiate different ataxia subtypes. And underlying pathology of each subtype is reviewed in form of illustrated models to reach a better understanding of each disorder.

Satellite Glial Cells in Human Disease

Satellite glial cells (SGCs) are the main type of glial cells in sensory ganglia. Animal studies have shown that these cells play essential roles in both normal and disease states. In a large number of pain models, SGCs were activated and contributed to the pain behavior. Much less is known about SGCs in humans, but there is emerging recognition that SGCs in humans are altered in a variety of clinical states. The available data show that human SGCs share some essential features with SGCs in rodents, but many differences do exist. SGCs in DRG from patients suffering from common painful diseases, such as rheumatoid arthritis and fibromyalgia, may contribute to the pain phenotype. It was found that immunoglobulins G (IgG) from fibromyalgia patients can induce pain-like behavior in mice. Moreover, these IgGs bind preferentially to SGCs and activate them, which can sensitize the sensory neurons, causing nociception. In other human diseases, the evidence is not as direct as in fibromyalgia, but it has been found that an antibody from a patient with rheumatoid arthritis binds to mouse SGCs, which leads to the release of pronociceptive factors from them. Herpes zoster is another painful disease, and it appears that the zoster virus resides in SGCs, which acquire an abnormal morphology and may participate in the infection and pain generation. More work needs to be undertaken on SGCs in humans, and this review points to several promising avenues for better understanding disease mechanisms and developing effective pain therapies.

Cognitive-affective manifestations since premanifest phases of Spinocerebellar Ataxia Type 3/Machado-Joseph Disease

BACKGROUND

Cognitive deficits were related to Spinocerebellar Ataxia type 3/Machado-Joseph Disease (SCA3/MJD), but the Cerebellar Cognitive Affective Syndrome (CCAS) needs further investigation in this disorder. We aimed to characterize cognitive-affective deficits in manifest and premanifest SCA3/MJD carriers.

METHODS

Subjects at 50% risk, manifest carriers and unrelated controls were evaluated in-person or in virtual settings with CCAS Scale (CCAS-S), Stroop Color-Word Test (SCWT), Trail-Making Test (TMT), and Reading the Mind in the Eyes Test (RMET). Scale for Assessment and Rating of Ataxia (SARA) >2.5 or Friedreich Ataxia Rating Scale/Activities of Daily Living (FARS-adl) >4 divided carriers into manifest and premanifest. Time after onset or time left to gait ataxia onset (TimeToAfterOnset) were estimated. Differences between groups and correlations with TimeToAfterOnset, SARA and FARS-adl were checked.

RESULTS

After random selection to balance groups, 23 manifest and 35 premanifest carriers, and 58 controls were included. CCAS-S, semantic fluency, phonemic fluency, category switching, affect, SCWT, and RMET showed significant differences between manifest carriers and controls; premanifest carriers mostly displayed intermediate values between controls and manifest carriers. These variables correlated with TimeToAfterOnset and SARA scores of the carriers. Correlations with SARA were stronger in the pre-ataxic group. CCAS-S had the strongest correlations with time and SARA.

DISCUSSION

Cognitive-affective deficits in SCA3/MJD involve executive function, language, affect, and social cognition, which seem to be altered prior to the ataxia onset, and correlate with markers of motor progression. CCAS-S was the most promising biomarker and should be evaluated in longitudinal studies.

Altered binaural hearing in pre-ataxic and ataxic mutation carriers of spinocerebellar ataxia type 3

Brainstem degeneration is a prominent feature of spinocerebellar ataxia type 3 (SCA3), involving structures that execute binaural synchronization with microsecond precision. As a consequence, auditory processing may deteriorate during the course of disease. We tested whether the binaural "Huggins pitch" effect is suitable to study the temporal precision of brainstem functioning in SCA3 mutation carriers. We expected that they would have difficulties perceiving Huggins pitch at high frequencies, and that they would show attenuated neuromagnetic responses to Huggins pitch. The upper limit of Huggins pitch perception was psychoacoustically determined in 18 pre-ataxic and ataxic SCA3 mutation carriers and in 18 age-matched healthy controls. Moreover, the cortical N100 response following Huggins pitch onset was acquired by means of magnetoencephalography (MEG). MEG recordings were analyzed using dipole source modeling and comprised a monaural pitch condition and a no-pitch condition with simple binaural correlation changes. Compared with age-matched controls, ataxic but not pre-ataxic SCA3 mutation carriers had significantly lower frequency limits up to which Huggins pitch could be heard. Listeners with lower frequency limits also showed diminished MEG responses to Huggins pitch, but not in the two control conditions. Huggins pitch is a promising tool to assess brainstem functioning in ataxic SCA3 patients. Future studies should refine the psychophysiological setup to capture possible performance decrements also in pre-ataxic mutation carriers. Longitudinal observations will be needed to prove the potential of the assessment of Huggins pitch as a biomarker to track brainstem functioning during the disease course in SCA3.

Stage-Dependent Biomarker Changes in Spinocerebellar Ataxia Type 3

Spinocerebellar ataxia type 3/Machado-Joseph disease is the most common autosomal dominant ataxia. In view of the development of targeted therapies, knowledge of early biomarker changes is needed. We analyzed cross-sectional data of 292 spinocerebellar ataxia type 3/Machado-Joseph disease mutation carriers. Blood concentrations of mutant ATXN3 were high before and after ataxia onset, whereas neurofilament light deviated from normal 13.3 years before onset. Pons and cerebellar white matter volumes decreased and deviated from normal 2.2 years and 0.6 years before ataxia onset. We propose a staging model of spinocerebellar ataxia type 3/Machado-Joseph disease that includes a biomarker stage characterized by objective indicators of neurodegeneration before ataxia onset. ANN NEUROL 2024;95:400-406.

Cell-Free and In Vivo Characterization of the Inhibitory Activity of Lavado Cocoa Flavanols on the Amyloid Protein Ataxin-3: Toward New Approaches against Spinocerebellar Ataxia Type 3

Spinocerebellar ataxia type 3 (SCA3) is a neurodegenerative disorder characterized by ataxia and other neurological manifestations, with a poor prognosis and a lack of effective therapies. The amyloid aggregation of the ataxin-3 protein is a hallmark of SCA3 and one of the main biochemical events prompting its onset, making it a prominent target for the development of preventive and therapeutic interventions. Here, we tested the efficacy of an aqueous Lavado cocoa extract and its polyphenolic components against ataxin-3 aggregation and neurotoxicity. The combination of biochemical assays and atomic force microscopy morphological analysis provided clear evidence of cocoa flavanols' ability to hinder ATX3 amyloid aggregation through direct physical interaction, as assessed by NMR spectroscopy. The chemical identity of the flavanols was investigated by ultraperformance liquid chromatography-high-resolution mass spectrometry. The use of the preclinical model Caenorhabditis elegans allowed us to demonstrate cocoa flavanols' ability to ameliorate ataxic phenotypes in vivo. To the best of our knowledge, Lavado cocoa is the first natural source whose extract is able to directly interfere with ATX3 aggregation, leading to the formation of off-pathway species.

Spastic paraplegia is the main manifestation of a spinocerebellar ataxia type 8 lineage in China: a case report and review of literature

The diagnosis and treatment of cerebellar atrophy remain challenging owing to its nonspecific symptoms and laboratory indicators. Three patients with spinocerebellar ataxia type 8 caused by ATXN8OS were found among the 16 people in the studied family. The clinical manifestations of the patients included progressive spastic paraplegia of the lower extremities, mild ataxia, mild cognitive impairment, and cerebellar atrophy. After administering antispasmodic rehabilitation treatment, using oral drugs, botulinum toxin injection, baclofen pump, and other systems in our hospital, the patients' lower extremity spasticity was significantly relieved. To our knowledge, till date, this is the first domestic report of spinocerebellar ataxia type 8 affecting a family, caused by ATXN8OS with spasticity onset in early childhood. Manifestations of the disease included spastic dyskinesia (in early disease stages) and cerebellar atrophy. Through systematic rehabilitation, the daily life of patients with this movement disorder was improved. This case report adds to the literature on spinocerebellar ataxia type 8 by summarizing its features.

Therapeutic effects of engineered exosome-based miR-25 and miR-181a treatment in spinocerebellar ataxia type 3 mice by silencing ATXN3

BACKGROUND

Spinocerebellar ataxia type 3 (SCA3) is the most common autosomal dominant hereditary ataxia worldwide, which is however in a lack of effective treatment. In view of that engineered exosomes are a promising non-invasive gene therapy transporter that can overcome the traditional problem of poor drug delivery, the aim of this study was to evaluate, for the first time, the value of exosome-based microRNA therapy in SCA3 and the therapeutic effects of intravenously administrated ATXN3 targeting microRNAs in transgenic SCA3 mouse models.

METHODS

The rabies virus glycoprotein (RVG) peptide-modified exosomes loaded with miR-25 or miR-181a were peripherally injected to enable targeted delivery of miRNAs to the brain of SCA3 mice. The behaviors, ATXN3 level, purkinje cell and other neuronal loss, and neuroinflammation were evaluated 4 weeks after initial treatment.

RESULTS

The targeted and efficient delivery of miR-25 and miR-181a by modified exosomes substantially inhibited the mutant ATXN3 expression, reduced neuron apoptosis and induced motor improvements in SCA3 mouse models without increasing the neuroinflammatory response.

CONCLUSIONS

Our study confirmed the therapeutic potential of engineered exosome-based miR-25 and miR-181a treatment in substantially reducing ATXN3 aggregation and cytotoxicity by relying on its targeted and efficient drug delivery performance in SCA3 mice. This treatment method shows a promising prospect for future clinical applications in SCA3.

Cell Type Specific CAG Repeat Expansions and Toxicity of Mutant Huntingtin in Human Striatum and Cerebellum

Brain region-specific degeneration and somatic expansions of the mutant Huntingtin (mHTT) CAG tract are key features of Huntington's disease (HD). However, the relationships between CAG expansions, death of specific cell types, and molecular events associated with these processes are not established. Here we employed fluorescence-activated nuclear sorting (FANS) and deep molecular profiling to gain insight into the properties of cell types of the human striatum and cerebellum in HD and control donors. CAG expansions arise in striatal medium spiny neurons (MSNs) and cholinergic interneurons, in cerebellar Purkinje neurons, and at mATXN3 in MSNs from SCA3 donors. CAG expansions in MSNs are associated with higher levels of MSH2 and MSH3 (forming MutSβ), which can inhibit nucleolytic excision of CAG slip-outs by FAN1 in a concentration-dependent manner. Our data indicate that ongoing CAG expansions are not sufficient for cell death, and identify transcriptional changes associated with somatic CAG expansions and striatal toxicity.

Stage-dependent biomarker changes in spinocerebellar ataxia type 3

Spinocerebellar ataxia type 3/Machado-Joseph disease (SCA3) is the most common autosomal dominant ataxia. In view of the development of targeted therapies for SCA3, precise knowledge of stage-dependent fluid and MRI biomarker changes is needed. We analyzed cross-sectional data of 292 SCA3 mutation carriers including 57 pre-ataxic individuals, and 108 healthy controls from the European Spinocerebellar ataxia type 3/Machado-Joseph Disease Initiative (ESMI) cohort. Blood concentrations of mutant ATXN3 and neurofilament light (NfL) were determined, and volumes of pons, cerebellar white matter (CWM) and cerebellar grey matter (CGM) were measured on MRI. Mutant ATXN3 concentrations were high before and after ataxia onset, while NfL continuously increased and deviated from normal 11.9 years before onset. Pons and CWM volumes decreased, but the deviation from normal was only 2.0 years (pons) and 0.3 years (CWM) before ataxia onset. We propose a staging model of SCA3 that includes an initial asymptomatic carrier stage followed by the biomarker stage defined by absence of ataxia, but a significant rise of NfL. The biomarker stage leads into the ataxia stage, defined by manifest ataxia. The present analysis provides a robust framework for further studies aiming at elaboration and differentiation of the staging model of SCA3.

Autophagy in Spinocerebellar Ataxia Type 3: From Pathogenesis to Therapeutics

Machado-Joseph disease (MJD) or spinocerebellar ataxia 3 (SCA3) is a rare, inherited, monogenic, neurodegenerative disease, and the most common SCA worldwide. MJD/SCA3 causative mutation is an abnormal expansion of the triplet CAG at exon 10 within the ATXN3 gene. The gene encodes for ataxin-3, which is a deubiquitinating protein that is also involved in transcriptional regulation. In normal conditions, the ataxin-3 protein polyglutamine stretch has between 13 and 49 glutamines. However, in MJD/SCA3 patients, the size of the stretch increases from 55 to 87, contributing to abnormal protein conformation, insolubility, and aggregation. The formation of aggregates, which is a hallmark of MJD/SCA3, compromises different cell pathways, leading to an impairment of cell clearance mechanisms, such as autophagy. MJD/SCA3 patients display several signals and symptoms in which the most prominent is ataxia. Neuropathologically, the regions most affected are the cerebellum and the pons. Currently, there are no disease-modifying therapies, and patients rely only on supportive and symptomatic treatments. Due to these facts, there is a huge research effort to develop therapeutic strategies for this incurable disease. This review aims to bring together current state-of-the-art strategies regarding the autophagy pathway in MJD/SCA3, focusing on evidence for its impairment in the disease context and, importantly, its targeting for the development of pharmacological and gene-based therapies.

Structural alterations of spinocerebellar ataxias type 3: from pre-symptomatic to symptomatic stage

OBJECTIVES

To investigate and characterize the structural alterations of the brain in SCA3, and their correlations with the scale for the assessment and rating of ataxia (SARA) and normal brain ATXN3 expression.

METHODS

We performed multimodal analyses in 52 SCA3 (15 pre-symptomatic) and healthy controls (HCs) (n = 35) to assess the abnormalities of gray and white matter (WM) of the cerebrum, brainstem, and cerebellum via FreeSurfer, SUIT, and TBSS, and their associations with disease severity. Twenty SCA3 patients (5 pre- and 15 symptomatic) were followed for at least a year. Besides, we uncovered the normal pattern of brain ATXN3 spatial distribution.

RESULTS

Pre-symptomatic patients showed only WM damage, mainly in the cerebellar peduncles, compared to HCs. In the advanced stage, the WM damage followed a caudal-rostral pattern. Meanwhile, continuous nonlinear structure damage was characterized by brainstem volumetric reduction and relatively symmetric cerebellar and basal ganglia atrophy but spared the cerebral cortex, partially explained by the ATXN3 overexpression. The bilateral pallidum, brainstem, and cerebellar peduncles demonstrated a very large effect size. Besides, all these alterations were significantly correlated with SARA; the pons (r = -0.65) and superior cerebellar peduncle (r = -0.68) volume demonstrated a higher correlation than the cerebellum with SARA. The longitudinal study further uncovered progressive atrophy of pons in symptomatic SCA3.

CONCLUSIONS

Significant WM damage starts before the ataxia onset. The bilateral pallidum, brainstem, and cerebellar peduncles are the most vulnerable targets. The volume of pons appears to be the most promising imaging biomarker for a longitudinal study.

TRIAL REGISTRATION

ClinicalTrial ID: ChiCTR2100045857 ( http://www.chictr.org.cn/edit.aspx?pid=55652&htm=4 ) KEY POINTS: • Pre- SCA3 showed WM damage mainly in cerebellar peduncles. Continuous brain damage was characterized by brainstem, widespread, and relatively symmetric cerebellar and basal ganglia atrophy. • Volumetric abnormalities were most evident in the bilateral pallidum, brainstem, and cerebellar peduncles in SCA3. • The volume of pons might identify the disease progression longitudinally.

The Homogeneous Azorean Machado-Joseph Disease Cohort: Characterization and Contributions to Advances in Research

Machado-Joseph disease (MJD)/spinocerebellar ataxia type 3 (SCA3) is the most common autosomal dominant ataxia worldwide. MJD is characterized by late-onset progressive cerebellar ataxia associated with variable clinical findings, including pyramidal signs and a dystonic-rigid extrapyramidal syndrome. In the Portuguese archipelago of the Azores, the worldwide population cluster for this disorder (prevalence of 39 in 100,000 inhabitants), a cohort of MJD mutation carriers belonging to extensively studied pedigrees has been followed since the late 1990s. Studies of the homogeneous Azorean MJD cohort have been contributing crucial information to the natural history of this disease as well as allowing the identification of novel molecular biomarkers. Moreover, as interventional studies for this globally rare and yet untreatable disease are emerging, this cohort should be even more important for the recruitment of trial participants. In this paper, we profile the Azorean cohort of MJD carriers, constituted at baseline by 20 pre-ataxic carriers and 52 patients, which currently integrates the European spinocerebellar ataxia type 3/Machado-Joseph disease Initiative (ESMI), a large European longitudinal MJD cohort. Moreover, we summarize the main studies based on this cohort and highlight the contributions made to advances in MJD research. Knowledge of the profile of the Azorean MJD cohort is not only important in the context of emergent interventional trials but is also pertinent for the implementation of adequate interventional measures, constituting relevant information for Lay Associations and providing data to guide healthcare decision makers.

Impaired interactions of ataxin-3 with protein complexes reveals their specific structure and functions in SCA3 Ki150 model

Spinocerebellar ataxia type 3 (SCA3/MJD) is a neurodegenerative disease caused by CAG expansion in mutant ATXN3 gene. The resulting PolyQ tract in mutant ataxin-3 protein is toxic to neurons and currently no effective treatment exists. Function of both normal and mutant ataxin-3 is pleiotropic by their interactions and the influence on protein level. Our new preclinical Ki150 model with over 150 CAG/Q in ataxin-3 has robust aggregates indicating the presence of a process that enhances the interaction between proteins. Interactions in large complexes may resemble the real-life inclusion interactions and was never examined before for mutant and normal ataxin-3 and in homozygous mouse model with long polyQ tract. We fractionated ataxin-3-positive large complexes and independently we pulled-down ataxin-3 from brain lysates, and both were followed by proteomics. Among others, mutant ataxin-3 abnormally interacted with subunits of large complexes such as Cct5 and 6, Tcp1, and Camk2a and Camk2b. Surprisingly, the complexes exhibit circular molecular structure which may be linked to the process of aggregates formation where annular aggregates are intermediate stage to fibrils which may indicate novel ataxin-3 mode of interactions. The protein complexes were involved in transport of mitochondria in axons which was confirmed by altered motility of mitochondria along SCA3 Ki150 neurites.

Coenzyme Q10: Role in Less Common Age-Related Disorders

In this article we have reviewed the potential role of coenzyme Q10 (CoQ10) in the pathogenesis and treatment of a number of less common age-related disorders, for many of which effective therapies are not currently available. For most of these disorders, mitochondrial dysfunction, oxidative stress and inflammation have been implicated in the disease process, providing a rationale for the potential therapeutic use of CoQ10, because of its key roles in mitochondrial function, as an antioxidant, and as an anti-inflammatory agent. Disorders reviewed in the article include multi system atrophy, progressive supranuclear palsy, sporadic adult onset ataxia, and pulmonary fibrosis, together with late onset versions of Huntington’s disease, Alexander disease, lupus, anti-phospholipid syndrome, lysosomal storage disorders, fibromyalgia, Machado-Joseph disease, acyl-CoA dehydrogenase deficiency, and Leber’s optic neuropathy.

Altered cerebral blood flow in patients with spinocerebellar degeneration

Objectives

Spinocerebellar degeneration (SCD) comprises a multitude of disorders with sporadic and hereditary forms, including spinocerebellar ataxia (SCA). Except for progressive cerebellar ataxia and structural atrophy, hemodynamic changes have also been observed in SCD. This study aimed to explore the whole-brain patterns of altered cerebral blood flow (CBF) and its correlations with disease severity and psychological abnormalities in SCD via arterial spin labeling (ASL).

Methods

Thirty SCD patients and 30 age- and sex-matched healthy controls (HC) were prospectively recruited and underwent ASL examination on a 3.0T MR scanner. The Scale for Assessment and Rating of Ataxia (SARA) and the International Cooperative Ataxia Rating Scale (ICARS) scores were used to evaluate the disease severity in SCD patients. Additionally, the status of anxiety, depression and sleep among all patients were, respectively, evaluated by the Self-Rating Anxiety Scale (SAS), Self-Rating Depression Scale (SDS) and Self-Rating Scale of Sleep (SRSS). We compared the whole-brain CBF value between SCD group and HC group at the voxel level. Then, the correlation analyses between CBF and disease severity, and psychological abnormalities were performed on SCD group.

Results

Compared with HC, SCD patients demonstrated decreased CBF value in two clusters (FWE corrected P < 0.05), covering bilateral dentate and fastigial nuclei, bilateral cerebellar lobules I-IV, V and IX, left lobule VI, right lobule VIIIb, lobules IX and X of the vermis in the cerebellar Cluster 1 and the dorsal part of raphe nucleus in the midbrain Cluster 2. The CBF of cerebellar Cluster 1 was negatively correlated with SARA scores (Spearman’s rho = –0.374, P = 0.042) and SDS standard scores (Spearman’s rho = –0.388, P = 0.034), respectively. And, the CBF of midbrain Cluster 2 also had negative correlations with SARA scores (Spearman’s rho = –0.370, P = 0.044) and ICARS scores (Pearson r = –0.464, P = 0.010).

Conclusion

The SCD-related whole-brain CBF changes mainly involved in the cerebellum and the midbrain of brainstem, which are partially overlapped with the related function cerebellar areas of hand, foot and tongue movement. Decreased CBF was related to disease severity and depression status in SCD. Therefore, CBF may be a promising neuroimaging biomarker to reflect the severity of SCD and suggest mental changes.

Coenzyme Q10 Supplementation Increases Removal of the ATXN3 Polyglutamine Repeat, Reducing Cerebellar Degeneration and Improving Motor Dysfunction in Murine Spinocerebellar Ataxia Type 3

Coenzyme Q10 (CoQ10), a well-known antioxidant, has been explored as a treatment in several neurodegenerative diseases, but its utility in spinocerebellar ataxia type 3 (SCA3) has not been explored. Herein, the protective effect of CoQ10 was examined using a transgenic mouse model of SCA3 onset. These results demonstrated that a diet supplemented with CoQ10 significantly improved murine locomotion, revealed by rotarod and open-field tests, compared with untreated controls. Additionally, a histological analysis showed the stratification of cerebellar layers indistinguishable from that of wild-type littermates. The increased survival of Purkinje cells was reflected by the reduced abundance of TUNEL-positive nuclei and apoptosis markers of activated p53, as well as lower levels of cleaved caspase 3 and cleaved poly-ADP-ribose polymerase. CoQ10 effects were related to the facilitation of the autophagy-mediated clearance of mutant ataxin-3 protein, as evidenced by the increased expression of heat shock protein 27 and autophagic markers p62, Beclin-1 and LC3II. The expression of antioxidant enzymes heme oxygenase 1 (HO-1), glutathione peroxidase 1 (GPx1) and superoxide dismutase 1 (SOD1) and 2 (SOD2), but not of glutathione peroxidase 2 (GPx2), were restored in 84Q SCA3 mice treated with CoQ10 to levels even higher than those measured in wild-type control mice. Furthermore, CoQ10 treatment also prevented skeletal muscle weight loss and muscle atrophy in diseased mice, revealed by significantly increased muscle fiber area and upregulated muscle protein synthesis pathways. In summary, our results demonstrated biochemical and pharmacological bases for the possible use of CoQ10 in SCA3 therapy.

Autophagic vacuolar myopathy involving the phenotype of spinocerebellar ataxia type 3

Spinocerebellar ataxia type 3 (SCA3) is a form of autosomal dominant cerebellar ataxia with a wide range of clinical manifestations, including ataxia and pyramidal and extrapyramidal signs. A few SCA3 patients have been noticed to be predisposed to the development of inclusion body myositis. It is still unknown whether muscle can be primarily involved in the pathogenesis of SCA3. This study reported an SCA3 family in which the index patient initially presented with parkinsonism, sensory ataxia, and distal myopathy but the absence of cerebellar and pyramidal symptoms. The clinical and electrophysiological studies implied a possible combination of distal myopathy and sensory-motor neuropathy or neuronopathy. MRI muscle showed selective fat infiltration and absence of denervated edema-like changes, indicating the distal muscle weakness had a myopathic origin. Muscle pathology showed the myopathic involvement, besides neurogenic involvement, characterized by chronic myopathic changes with multiple autophagic vacuoles. Genetic screening revealed expanded CAG of 61 repeats in the ATXN3 gene, which showed co-segregation in the family. Besides the neurogenic origin, the myopathic origin may be partly attributed to the limb weakness of SCA3 patients, which expands the spectrum of the clinical manifestation of SCA3.

Long-term efficacy of bilateral subthalamic deep brain stimulation in the parkinsonism of SCA 3: A rare case report

BACKGROUND AND PURPOSE

Spinocerebellar ataxia type 3 (SCA3) is an autosomal dominant inherited disorder that manifests as a mixture of cerebellar ataxia, parkinsonism, and polyneuropathy; in type IV SCA3, pure parkinsonism is the only symptom. Currently, no disease-modifying treatment is available, but variable responses to antiparkinsonism agents have been reported. However, the benefits of deep brain stimulation (DBS) for treating parkinsonism in this subtype of SCA3 remain unclear.

METHODS

A 39-year-old male patient with a rare disorder of type IV SCA3 presented with pure parkinsonism including unilateral resting tremor, rigidity, and bradykinesia at the age of 30 years. Young-onset Parkinson disease was diagnosed at the age of 32 years. His family history revealed a mild ataxia in his father since the age of 55 years. Genetic testing confirmed an expanded CAG repeated number, with 66 in this case and 63 in his father for SCA3 mutation. Excellent response to levodopa and dopamine agonists in the first 3 years was noted, but wearing-off phenomena, levodopa-induced dyskinesia, and severe impulse control disorders later developed. To alleviate drug-induced complications, he received bilateral subthalamic nucleus deep brain stimulation (STN-DBS) in the absence of cerebellar signs, depression, and cognitive impairment.

RESULTS

As of 2019, no impulsive control disorders, motor fluctuations, or DBS-related complications were observed during a 4-year follow-up, with 66% Unified Parkinson's Disease Rating Scale Part III reduction at medication OFF state noted, whereas levodopa equivalent daily dosage decreased by almost half.

CONCLUSIONS

STN-DBS may be considered as adjunct treatment for severe dopa-related motor/nonmotor complications in patients with parkinsonian phenotype of SCA 3.

Altered glucose metabolism and its association with carbonic anhydrase 8 in Machado-Joseph Disease

Machado-Joseph disease (MJD), also known as spinocerebellar ataxia type 3 (SCA3), is an autosomal dominant neurodegenerative disease. This disorder is caused by polyglutamine (polyQ)-containing mutant ataxin-3, which tends to misfold and aggregate in neuron cells. We previously demonstrated a protective function of carbonic anhydrase 8 (CA8) in MJD disease models and a decreased glycolytic activity associated with down-regulated CA8 in a human osteosarcoma (OS) cell model. Given that a reduction in body weight accompanied by gait and balance instability was observed in MJD patients and transgenic (Tg) mice, in this study, we aimed to examine whether metabolic defects are associated with MJD and whether CA8 expression is involved in metabolic dysfunction in MJD. Our data first showed that glucose uptake ability decreases in cells harboring mutant ataxin-3, but increases in cells overexpressing CA8. In addition, the expressions of glucose transporter 3 (GLUT3) and phosphofructokinase-1 (PFK1) were significantly decreased in the presence of mutant ataxin-3. Consistently, immunohistochemistry (IHC) showed that GLUT3 was less expressed in cerebella of aged MJD Tg mice, indicating that the dysfunction of GLUT3 may be associated with late-stage disease. On the other hand, transient down-regulation of CA8 revealed decreased expressions of GLUT3 and PFK1 in HEK293 cells harboring wild-type (WT) ataxin-3, but no further reduction of GLUT3 and PFK1 expressions were observed in HEK293 cells harboring mutant ataxin-3. Moreover, immunoprecipitation (IP) and immunofluorescence (IF) demonstrated that interactions exist between ataxin-3, CA8 and GLUT3 in MJD cellular and Tg models. These lines of evidence suggest that CA8 plays an important role in glucose metabolism and has different impacts on cells with or without mutant ataxin-3. Interestingly, the decreased relative abundance of Firmicutes/Bacteroidetes (F/B) ratio in the feces of aged MJD Tg mice coincided with weight loss and metabolic dysfunction in MJD. Taken together, our results are the first to demonstrate the effects of CA8 on glucose metabolism and its involvement in the metabolic defects in MJD disease. Further investigations will be required to clarify the underlying mechanisms for the metabolic defects associated with MJD.

Glutamatergic Synapse Dysfunction in Drosophila Neuromuscular Junctions Can Be Rescued by Proteostasis Modulation

Glutamate is the major excitatory neurotransmitter in the nervous system, and the Drosophila glutamatergic neuromuscular junctions (NMJs) offer a tractable platform to understand excitatory synapse biology both in health and disease. Synaptopathies are neurodegenerative diseases that are associated with synaptic dysfunction and often display compromised proteostasis. One such rare, progressive neurodegenerative condition, Spinocerebellar Ataxia Type 3 (SCA3) or Machado-Joseph Disease (MJD), is characterized by cerebellar ataxia, Parkinsonism, and degeneration of motor neuron synapses. While the polyQ repeat mutant protein ataxin-3 is implicated in MJD, it is unclear how it leads to impaired synaptic function. In this study, we indicated that a Drosophila model of MJD recapitulates characteristics of neurodegenerative disorders marked by motor neuron dysfunction. Expression of 78 polyQ repeats of mutant ataxin-3 protein in Drosophila motor neurons resulted in behavioral defects, such as impaired locomotion in both larval and adult stages. Furthermore, defects in eclosion and lifespan were observed in adult flies. Detailed characterization of larval glutamatergic neuromuscular junctions (NMJs) revealed defects in morphological features along with compromised NMJ functioning. Autophagy, one of the key proteostasis pathways, is known to be impaired in the case of several synaptopathies. Our study reveals that overexpression of the autophagy-related protein Atg8a rescued behavioral defects. Thus, we present a model for glutamatergic synapse dysfunction that recapitulates synaptic and behavioral deficits and show that it is an amenable system for carrying out genetic and chemical biology screens to identify potential therapeutic targets for synaptopathies.

Differential Temporal Dynamics of Axial and Appendicular Ataxia in SCA3

Background

Disease severity in spinocerebellar ataxia type 3 (SCA3) is commonly defined by the Scale for the Assessment and Rating of Ataxia (SARA) sum score, but little is known about the contributions and progression patterns of individual items.

Objectives

To investigate the temporal dynamics of SARA item scores in SCA3 patients and evaluate if clinical and demographic factors are differentially associated with evolution of axial and appendicular ataxia.

Methods

In a prospective, multinational cohort study involving 11 European and 2 US sites, SARA scores were determined longitudinally in 223 SCA3 patients with a follow‐up assessment after 1 year.

Results

An increase in SARA score from 10 to 20 points was mainly driven by axial and speech items, with a markedly smaller contribution of appendicular items. Finger chase and nose‐finger test scores not only showed the lowest variability at baseline, but also the least deterioration at follow‐up. Compared with the full set of SARA items, omission of both tests would result in lower sample size requirements for therapeutic trials. Sex was associated with change in SARA sum score and appendicular, but not axial, subscore, with a significantly faster progression in men. Despite considerable interindividual variability, the average annual progression rate of SARA score was approximately three times higher in subjects with a disease duration over 10 years than in those within 10 years from onset.

Conclusion

Our findings provide evidence for a difference in temporal dynamics between axial and appendicular ataxia in SCA3 patients, which will help inform the design of clinical trials and development of new (etiology‐specific) outcome measures. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Cerebellar Transcranial Direct Current Stimulation in Spinocerebellar Ataxia Type 3: a Randomized, Double-Blind, Sham-Controlled Trial

Repeated sessions of cerebellar anodal transcranial direct current stimulation (tDCS) have been suggested to modulate cerebellar-motor cortex (M1) connectivity and decrease ataxia severity. However, therapeutic trials involving etiologically homogeneous groups of ataxia patients are lacking. The objective of this study was to investigate if a two-week regimen of daily cerebellar tDCS sessions diminishes ataxia and non-motor symptom severity and alters cerebellar-M1 connectivity in individuals with spinocerebellar ataxia type 3 (SCA3). We conducted a randomized, double-blind, sham-controlled trial in which twenty mildly to moderately affected SCA3 patients received ten sessions of real or sham cerebellar tDCS (i.e., five days per week for two consecutive weeks). Effects were evaluated after two weeks, three months, six months, and twelve months. Change in Scale for the Assessment and Rating of Ataxia (SARA) score after two weeks was defined as the primary endpoint. Static posturography, SCA Functional Index tests, various patient-reported outcome measures, the cerebellar cognitive affective syndrome scale, and paired-pulse transcranial magnetic stimulation to examine cerebellar brain inhibition (CBI) served as secondary endpoints. Absolute change in SARA score did not differ between both trial arms at any of the time points. We observed significant short-term improvements in several motor, cognitive, and patient-reported outcomes after the last stimulation session in both groups but no treatment effects in favor of real tDCS. Nonetheless, some of the patients in the intervention arm showed a sustained reduction in SARA score lasting six or even twelve months, indicating interindividual variability in treatment response. CBI, which reflects the functional integrity of the cerebellothalamocortical tract, remained unchanged after ten tDCS sessions. Albeit exploratory, there was some indication for between-group differences in SARA speech score after six and twelve months and in the number of extracerebellar signs after three and six months. Taken together, our study does not provide evidence that a two-week treatment with daily cerebellar tDCS sessions reduces ataxia severity or restores cerebellar-M1 connectivity in early-to-middle-stage SCA3 patients at the group level. In order to potentially increase therapeutic efficacy, further research is warranted to identify individual predictors of symptomatic improvement.

Cerebellar neuronal dysfunction accompanies early motor symptoms in spinocerebellar ataxia type 3

Spinocerebellar ataxia type 3 (SCA3) is an adult-onset, progressive ataxia. SCA3 presents with ataxia before any gross neuropathology. A feature of many cerebellar ataxias is aberrant cerebellar output that contributes to motor dysfunction. We examined whether abnormal cerebellar output was present in the CMVMJD135 SCA3 mouse model and, if so, whether it correlated with the disease onset and progression. In vivo recordings showed that the activity of deep cerebellar nuclei neurons, the main output of the cerebellum, was altered. The aberrant activity correlated with the onset of ataxia. However, although the severity of ataxia increased with age, the severity of the aberrant cerebellar output was not progressive. The abnormal cerebellar output, however, was accompanied by non-progressive abnormal activity of their upstream synaptic inputs, the Purkinje cells. In vitro recordings indicated that alterations in intrinsic Purkinje cell pacemaking and in their synaptic inputs contributed to abnormal Purkinje cell activity. These findings implicate abnormal cerebellar physiology as an early, consistent contributor to pathophysiology in SCA3, and suggest that the aberrant cerebellar output could be an appropriate therapeutic target in SCA3.

Summary: In a mouse model of spinocerebellar ataxia type 3 (SCA3), aberrant cerebellar physiology is apparent early in disease, prior to cerebellar neuronal pathology. Aberrant cerebellar output could be a therapeutic target in SCA3.

Cerebellar transcranial direct current stimulation modulates timing but not acquisition of conditioned eyeblink responses in SCA3 patients

BACKGROUND

Delay eyeblink conditioning is an extensively studied motor learning paradigm that critically depends on the integrity of the cerebellum. In healthy individuals, modulation of cerebellar excitability using transcranial direct current stimulation (tDCS) has been reported to alter the acquisition and/or timing of conditioned eyeblink responses (CRs). It remains unknown whether such effects can also be elicited in patients with cerebellar disorders.

OBJECTIVE

To investigate if repeated sessions of cerebellar tDCS modify acquisition and/or timing of CRs in patients with spinocerebellar ataxia type 3 (SCA3) and to evaluate possible associations between disease severity measures and eyeblink conditioning parameters.

METHODS

Delay eyeblink conditioning was examined in 20 mildly to moderately affected individuals with SCA3 and 31 healthy controls. After the baseline session, patients were randomly assigned to receive ten sessions of cerebellar anodal tDCS or sham tDCS (i.e., five days per week for two consecutive weeks). Patients and investigators were blinded to treatment allocation. The same eyeblink conditioning protocol was administered directly after the last tDCS session. The Scale for the Assessment and Rating of Ataxia (SARA), cerebellar cognitive affective syndrome scale (CCAS-S), and disease duration were used as clinical measures of disease severity.

RESULTS

At baseline, SCA3 patients exhibited significantly fewer CRs than healthy controls. Acquisition was inversely associated with the number of failed CCAS-S test items but not with SARA score. Onset and peak latencies of CRs were longer in SCA3 patients and correlated with disease duration. Repeated sessions of cerebellar anodal tDCS did not affect CR acquisition, but had a significant treatment effect on both timing parameters. While a shift of CRs toward the conditioned stimulus was observed in the sham group (i.e., timing became more similar to that of healthy controls, presumably reflecting the effect of a second eyeblink conditioning session), anodal tDCS induced a shift of CRs in the opposite direction (i.e., toward the unconditioned stimulus).

CONCLUSION

Our findings provide the first evidence that cerebellar tDCS is capable of modifying cerebellar function in SCA3 patients. Future studies should assess whether this intervention similarly modulates temporal processing in other degenerative ataxias.

Sleep disorders among Aboriginal Australians with Machado-Joseph Disease: Quantitative results from a multiple methods study to assess the experience of people living with the disease and their caregivers

Background

Machado-Joseph Disease (MJD), or Spinocerebellar Ataxia Type 3 (SCA3), is a genetic disorder that causes progressive muscle weakness, loss of motor control, ataxia and permanent physical disability. Sleep disturbances are associated with MJD but remain poorly understood.

Objective

To investigate frequency and characteristics of sleep disorders and their association with health-related quality of life and psychosocial wellbeing for Aboriginal Australians living with MJD.

Methods

A convenience sample of MJD participants n = 24 participated in a semi-attended, ambulatory diagnostic sleep study to capture polysomnography, actigraphy and sleep diary data. Self-report measures collected were the Pittsburgh Sleep Quality Index (PSQI), STOP-BANG Questionnaire for Obstructive Sleep Apnoea (OSA), International Restless Legs Syndrome Study Group rating scale (IRLS), Kessler-5 (K5) and EuroQoL-5 Dimension (EQ5D). Caregivers (n = 22) reported EQ-5D, K5 and bed partners’ sleep behaviour (Mayo Sleep Questionnaire-Informant). Environmental factors were measured.

Results

We observed Nocturia, Sleep Related Leg Cramps, OSA, REM Behaviour Disorder, and RLS, respectively in 100%, 71%, 47%, 43%, and 33% of participants with a significant positive correlation between Body mass index (BMI) and Apnoea hypopnea index (AHI). The majority of sleep was spent in non-rapid eye movement sleep (NREM)-N2 stage (77.8% (67.7, 81.6)). Overcrowding (92%) and overnight care needs (42%) interrupted sleep. MJD participants and caregivers reported high psychological distress (K5 median 12.5 IQR 7, 16.5 & 8 IQR 6, 12 respectively).

Conclusion

Poor sleep quality and sleep disturbances are prevalent among this cohort. Disease manifestations and environmental factors are driving factors. Larger sample sizes are required to predict risk factors and confirm observed associations.

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Aboriginal People living with MJD in Australia experience numerous sleep disorders.

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Majority of sleep was spent in non-rapid eye movement sleep.

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Overcrowding and overnight care needs interrupt sleep.

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MJD participants and caregivers reported high psychological distress.

Mesenchymal stem cells for lysosomal storage and polyglutamine disorders: Possible shared mechanisms

BACKGROUND

Mesenchymal stem cells' (MSC) therapeutic potential has been investigated for the treatment of several neurodegenerative diseases. The fact these cells can mediate a beneficial effect in different neurodegenerative contexts strengthens their competence to target diverse mechanisms. On the other hand, distinct disorders may share similar mechanisms despite having singular neuropathological characteristics.

METHODS

We have previously shown that MSC can be beneficial for two disorders, one belonging to the groups of Lysosomal Storage Disorders (LSDs) - the Krabbe Disease or Globoid Cell Leukodystrophy, and the other to the family of Polyglutamine diseases (PolyQs) - the Machado-Joseph Disease or Spinocerebellar ataxia type 3. We gave also input into disease characterization since neuropathology and MSC's effects are intrinsically associated. This review aims at describing MSC's multimode of action in these disorders while emphasizing to possible mechanistic alterations they must share due to the accumulation of cellular toxic products.

RESULTS

Lysosomal storage disorders and PolyQs have different aetiology and associated symptoms, but both result from the accumulation of undegradable products inside neuronal cells due to inefficient clearance by the endosomal/lysosomal pathway. Moreover, numerous cellular mechanisms that become compromised latter are also shared by these two disease groups.

CONCLUSIONS

Here, we emphasize MSC's effect in improving proteostasis and autophagy cycling turnover, neuronal survival, synaptic activity and axonal transport. LSDs and PolyQs, though rare in their predominance, collectively affect many people and require our utmost dedication and efforts to get successful therapies due to their tremendous impact on patient s' lives and society.

Cerebellar morphometric and spectroscopic biomarkers for Machado-Joseph Disease

Machado-Joseph disease (MJD) or Spinocerebellar ataxia type 3 (SCA3) is the most common form of dominant SCA worldwide. Magnetic Resonance Imaging (MRI) and Proton Magnetic Resonance Spectroscopy (¹H-MRS) provide promising non-invasive diagnostic and follow-up tools, also serving to evaluate therapies efficacy. However, pre-clinical studies showing relationship between MRI-MRS based biomarkers and functional performance are missing, which hampers an efficient clinical translation of therapeutics. This study assessed motor behaviour, neurochemical profiles, and morphometry of the cerebellum of MJD transgenic mice and patients aiming at establishing magnetic-resonance-based biomarkers. ¹H-MRS and structural MRI measurements of MJD transgenic mice were performed with a 9.4 Tesla scanner, correlated with motor performance on rotarod and compared with data collected from human patients. We found decreased cerebellar white and grey matter and enlargement of the fourth ventricle in both MJD mice and human patients as compared to controls. N-acetylaspartate (NAA), NAA + N-acetylaspartylglutamate (NAA + NAAG), Glutamate, and Taurine, were significantly decreased in MJD mouse cerebellum regardless of age, whereas myo-Inositol (Ins) was increased at early time-points. Lower neurochemical ratios levels (NAA/Ins and NAA/total Choline), previously correlated with worse clinical status in SCAs, were also observed in MJD mice cerebella. NAA, NAA + NAAG, Glutamate, and Taurine were also positively correlated with MJD mice motor performance. Importantly, these ¹H-MRS results were largely analogous to those found for MJD in human studies and in our pilot data in human patients. We have established a magnetic resonance-based biomarker approach to monitor novel therapies in preclinical studies and human clinical trials.

Brain structural abnormalities in the preclinical stage of Machado-Joseph disease/spinocerebellar ataxia type 3 (MJD/SCA3): evaluation by MRI morphometry, diffusion tensor imaging and neurite orientation dispersion and density imaging

OBJECTIVE

To investigate whether neurite orientation dispersion and density imaging (NODDI) could provide the added value for detecting brain microstructural alterations in the preclinical stage of Machado-Joseph disease/spinocerebellar ataxia type 3 (MJD/SCA3) compared with MRI morphometry and diffusion tensor imaging (DTI).

METHODS

Twenty preclinical MJD/SCA3 patients and 21 healthy controls were enrolled. Three b values DWI and 3D T1-weighted images were acquired at 3.0 T. Tract-based spatial statistics (TBSS) approach was used to investigate the white matter (WM) alterations in the DTI metrics and NODDI metrics. Gray matter-based spatial statistics (GBSS) approach was used to investigate the grey matter (GM) alterations in the NODDI metrics. Voxel-based morphometry (VBM) approach was performed on the 3D T1-weighted images. The relationship between the cytosine-adenine-guanine (CAG) repeat length and brain microstructural alterations of preclinical MJD/SCA3 was identified.

RESULTS

Compared with healthy controls, the preclinical MJD/SCA3 patients showed decreased FA and NDI as well as increased MD, AD, and RD in the WM of cerebellum and brainstem (corrected P < 0.05), and decreased NDI in the GM of cerebellar vermis (corrected P < 0.05). The CAG repeat length in preclinical MJD/SCA3 patients was negatively correlated with the reduced FA and NDI of the infratentorial WM and the reduced NDI of the cerebellum, and positively with the increased MD and RD of the infratentorial WM.

CONCLUSIONS

NOODI can provide novel quantitative microstructural changes in MJD/SCA3 carriers, expanding our understanding of the gray and white matter (axons and dendrites) degeneration in this frequent ataxia syndrome.

The cerebellar cognitive affective syndrome scale reveals early neuropsychological deficits in SCA3 patients

BACKGROUND

The cerebellar cognitive affective syndrome scale (CCAS-S) was recently developed to detect specific neuropsychological deficits in patients with cerebellar diseases in an expedited manner.

OBJECTIVES

To evaluate the discriminative ability of the CCAS-S in an etiologically homogeneous cohort of spinocerebellar ataxia type 3 (SCA3) patients and to examine relationships between cognitive deficits and motor symptom severity.

METHODS

The CCAS-S was administered to twenty mildly to moderately affected SCA3 patients and eighteen healthy controls matched for age, sex, and educational level. Disease severity was measured by the Scale for the Assessment and Rating of Ataxia (SARA), Inventory of Non-Ataxia Signs (INAS), 8 m walk test, nine-hole peg test (9HPT), and Patient Health Questionnaire-9 (PHQ-9).

RESULTS

SCA3 patients had a lower total CCAS-S score (p < 0.001) and higher number of failed tests (p = 0.006) than healthy controls. Patients displayed impairments in semantic fluency, phonemic fluency, category switching, cube drawing, and affect regulation. Total CCAS-S score showed high discriminative ability (area under the curve [AUC]: 0.96) and was associated with disease duration, SARA score, walking speed, and dominant hand 9HPT performance. No correlations were observed with INAS count, repeat length, and PHQ-9 score. Discriminative capacity of the number of failed tests was moderate (AUC: 0.76).

CONCLUSION

Essentially all SCA3 patients exhibited some form of cognitive impairment. The CCAS-S differentiates SCA3 patients from healthy controls, detects neuropsychological deficits early in the disease course, and correlates with relevant ataxia severity measures.

Regional Brain and Spinal Cord Volume Loss in Spinocerebellar Ataxia Type 3

Background:

Given that new therapeutic options for spinocerebellar ataxias are on the horizon, there is a need for markers that reflect disease-related alterations, in particular, in the preataxic stage, in which clinical scales are lacking sensitivity.

Objective:

The objective of this study was to quantify regional brain volumes and upper cervical spinal cord areas in spinocerebellar ataxia type 3 in vivo across the entire time course of the disease.

Methods:

We applied a brain segmentation approach that included a lobular subsegmentation of the cerebellum to magnetic resonance images of 210 ataxic and 48 preataxic spinocerebellar ataxia type 3 mutation carriers and 63 healthy controls. In addition, cervical cord cross-sectional areas were determined at 2 levels.

Results:

The metrics of cervical spinal cord segments C3 and C2, medulla oblongata, pons, and pallidum, and the cerebellar anterior lobe were reduced in preataxic mutation carriers compared with controls. Those of cervical spinal cord segments C2 and C3, medulla oblongata, pons, midbrain, cerebellar lobules crus II and X, cerebellar white matter, and pallidum were reduced in ataxic compared with nonataxic carriers. Of all metrics studied, pontine volume showed the steepest decline across the disease course. It covaried with ataxia severity, CAG repeat length, and age. The multivariate model derived from this analysis explained 46.33% of the variance of pontine volume.

Conclusion:

Regional brain and spinal cord tissue loss in spinocerebellar ataxia type 3 starts before ataxia onset. Pontine volume appears to be the most promising imaging biomarker candidate for interventional trials that aim at slowing the progression of spinocerebellar ataxia type 3.

The cerebellar cognitive affective syndrome scale reveals early neuropsychological deficits in SCA3 patients

Background

The cerebellar cognitive affective syndrome scale (CCAS-S) was recently developed to detect specific neuropsychological deficits in patients with cerebellar diseases in an expedited manner.

Objectives

To evaluate the discriminative ability of the CCAS-S in an etiologically homogeneous cohort of spinocerebellar ataxia type 3 (SCA3) patients and to examine relationships between cognitive deficits and motor symptom severity.

Methods

The CCAS-S was administered to twenty mildly to moderately affected SCA3 patients and eighteen healthy controls matched for age, sex, and educational level. Disease severity was measured by the Scale for the Assessment and Rating of Ataxia (SARA), Inventory of Non-Ataxia Signs (INAS), 8 m walk test, nine-hole peg test (9HPT), and Patient Health Questionnaire-9 (PHQ-9).

Results

SCA3 patients had a lower total CCAS-S score (p < 0.001) and higher number of failed tests (p = 0.006) than healthy controls. Patients displayed impairments in semantic fluency, phonemic fluency, category switching, cube drawing, and affect regulation. Total CCAS-S score showed high discriminative ability (area under the curve [AUC]: 0.96) and was associated with disease duration, SARA score, walking speed, and dominant hand 9HPT performance. No correlations were observed with INAS count, repeat length, and PHQ-9 score. Discriminative capacity of the number of failed tests was moderate (AUC: 0.76).

Conclusion

Essentially all SCA3 patients exhibited some form of cognitive impairment. The CCAS-S differentiates SCA3 patients from healthy controls, detects neuropsychological deficits early in the disease course, and correlates with relevant ataxia severity measures.

Inverse associations between cerebellar inhibition and motor impairment in spinocerebellar ataxia type 3

BACKGROUND

Cerebellar ataxia generally results from a lesion disrupting the corticopontocerebellar or cerebellothalamocortical tract. The cerebellar inhibition (CBI) paradigm represents a dual-coil transcranial magnetic stimulation protocol that interrogates the integrity of the latter pathway. Whether CBI has clinical relevance in ataxia patients remains largely unknown because associations with pertinent disease severity measures in etiologically homogeneous cohorts have not been previously examined.

OBJECTIVE

To investigate if CBI correlates with clinical and functional indices of disease severity in individuals with spinocerebellar ataxia type 3 (SCA3).

METHODS

CBI was assessed in fourteen SCA3 patients by paired-pulse cerebellar-motor cortex (M1) stimulation using interstimulus intervals of 3, 5, and 10 ms. Correlation coefficients were determined between CBI and ataxia severity, manual dexterity, and walking speed.

RESULTS

Suppression of M1 excitability occurred 5 ms following a contralateral cerebellar conditioning stimulus in SCA3 patients, but, on average, CBI was significantly reduced as compared to a healthy control group from the literature (p < 0.001). A significant association was found between decreased CBI levels and higher Scale for the Assessment and Rating of Ataxia (SARA) scores (r = -0.62, p = 0.019). CBI was negatively correlated with axial, appendicular, and speech subscores, as well as with nine-hole peg test performance (r = -0.69, p = 0.006). No association was observed between CBI and walking speed. As expected, there were no significant clinical-neurophysiological correlations at 3 and 10 ms interstimulus intervals.

CONCLUSION

Our results provide the first neurophysiological evidence for an inverse association between cerebellothalamocortical tract integrity, as reflected by reduced levels of CBI, and ataxia severity in SCA3 patients. Longitudinal studies are required to evaluate if CBI could serve as a marker of disease progression.

Human stem cell models of polyglutamine diseases: Sources for disease models and cell therapy

Polyglutamine (polyQ) diseases are a group of neurodegenerative disorders involving expanded CAG repeats in pathogenic genes that are translated into extended polyQ tracts and lead to progressive neuronal degeneration in the affected brain. To date, there is no effective therapy for these diseases. Due to the complex pathologic mechanisms of these diseases, intensive research on the pathogenesis of their progression and potential treatment strategies is being conducted. However, animal models cannot recapitulate all aspects of neuronal degeneration. Pluripotent stem cells (PSCs), such as induced pluripotent stem cells (iPSCs) and embryonic stem cells (ESCs), can be used to study the pathological mechanisms of polyQ diseases, and the ability of autologous stem cell transplantation to treat these diseases. Differentiated PSCs, neuronal precursor cells/neural progenitor cells (NPCs) and mesenchymal stem cells (MSCs) are valuable resources for preclinical and clinical cell transplantation therapies. Here, we discuss diverse stem cell models and their ability to generate neurons involved in polyQ diseases, such as medium spiny neurons (MSNs), cortical neurons, cerebellar Purkinje cells (PCs) and motor neurons. In addition, we discuss potential therapeutic approaches, including stem cell replacement therapy and gene therapy.

Spinocerebellar Ataxia Type 3: A Case Report and Literature Review

Spinocerebellar ataxia type 3 (SCA3), also known by the eponym Machado-Joseph disease, is an autosomal dominant CAG trinucleotide (polyglutamine) repeat disease that presents in young- to middle-aged adults. SCA3 was first described in Azorean individuals and has interesting epidemiological patterns. It is characterized clinically by progressive ataxia and neuropathologically by progressive degenerative changes in the spinal cord and cerebellum, along with degeneration of the cortex and basal ganglia. Here, we describe the clinical and neuropathologic features in a case of SCA3 with unique findings, including involvement of the inferior olivary nucleus and cerebellar Purkinje cell layer, which are classically spared in the disease. We also discuss research into the disease mechanisms of SCA3 and the potential for therapeutic intervention.

Molecular and Cellular Substrates for the Friedreich Ataxia. Significance of Contactin Expression and of Antioxidant Administration

In this study, the neural phenotype is explored in rodent models of the spinocerebellar disorder known as the Friedreich Ataxia (FA), which results from mutations within the gene encoding the Frataxin mitochondrial protein. For this, the M12 line, bearing a targeted mutation, which disrupts the Frataxin gene exon 4 was used, together with the M02 line, which, in addition, is hemizygous for the human Frataxin gene mutation (Pook transgene), implying the occurrence of 82-190 GAA repeats within its first intron. The mutant mice phenotype was compared to the one of wild type littermates in regions undergoing differential profiles of neurogenesis, including the cerebellar cortex and the spinal cord by using neuronal (β-tubulin) and glial (Glial Fibrillary Acidic Protein) markers as well as the Contactin 1 axonal glycoprotein, involved in neurite growth control. Morphological/morphometric analyses revealed that while in Frataxin mutant mice the neuronal phenotype was significantly counteracted, a glial upregulation occurred at the same time. Furthermore, Contactin 1 downregulation suggested that changes in the underlying gene contributed to the disorder pathogenesis. Therefore, the FA phenotype implies an alteration of the developmental profile of neuronal and glial precursors. Finally, epigallocatechin gallate polyphenol administration counteracted the disorder, indicating protective effects of antioxidant administration.

Therapeutic antisense oligonucleotides for movement disorders

Movement disorders are a group of neurological conditions characterized by abnormalities of movement and posture. They are broadly divided into akinetic and hyperkinetic syndromes. Until now, no effective symptomatic or disease-modifying therapies have been available. However, since many of these disorders are monogenic or have some well-defined genetic component, they represent strong candidates for antisense oligonucleotide (ASO) therapies. ASO therapies are based on the use of short synthetic single-stranded ASOs that bind to disease-related target RNAs via Watson-Crick base-pairing and pleiotropically modulate their function. With information arising from the RNA sequence alone, it is possible to design ASOs that not only alter the expression levels but also the splicing defects of any protein, far exceeding the intervention repertoire of traditional small molecule approaches. Following the regulatory approval of ASO therapies for spinal muscular atrophy and Duchenne muscular dystrophy in 2016, there has been tremendous momentum in testing such therapies for other neurological disorders. This review article initially focuses on the chemical modifications aimed at improving ASO effectiveness, the mechanisms by which ASOs can interfere with RNA function, delivery systems and pharmacokinetics, and the common set of toxicities associated with their application. It, then, describes the pathophysiology and the latest information on preclinical and clinical trials utilizing ASOs for the treatment of Parkinson's disease, Huntington's disease, and ataxias 1, 2, 3, and 7. It concludes with issues that require special attention to realize the full potential of ASO-based therapies.

Neurofilaments in spinocerebellar ataxia type 3: blood biomarkers at the preataxic and ataxic stage in humans and mice

With molecular treatments coming into reach for spinocerebellar ataxia type 3 (SCA3), easily accessible, cross-species validated biomarkers for human and preclinical trials are warranted, particularly for the preataxic disease stage. We assessed serum levels of neurofilament light (NfL) and phosphorylated neurofilament heavy (pNfH) in ataxic and preataxic subjects of two independent multicentric SCA3 cohorts and in a SCA3 knock-in mouse model. Ataxic SCA3 subjects showed increased levels of both NfL and pNfH. In preataxic subjects, NfL levels increased with proximity to the individual expected onset of ataxia, with significant NfL elevations already 7.5 years before onset. Cross-sectional NfL levels correlated with both disease severity and longitudinal disease progression. Blood NfL and pNfH increases in human SCA3 were each paralleled by similar changes in SCA3 knock-in mice, here also starting already at the presymptomatic stage, closely following ataxin-3 aggregation and preceding Purkinje cell loss in the brain. Blood neurofilaments, particularly NfL, might thus provide easily accessible, cross-species validated biomarkers in both ataxic and preataxic SCA3, associated with earliest neuropathological changes, and serve as progression, proximity-to-onset and, potentially, treatment-response markers in both human and preclinical SCA3 trials.

Losing the Beat: Contribution of Purkinje Cell Firing Dysfunction to Disease, and Its Reversal

The cerebellum is a brain structure that is highly interconnected with other brain regions. There are many contributing factors to cerebellar-related brain disease, such as altered afferent input, local connectivity, and/or cerebellar output. Purkinje cells (PC) are the principle cells of the cerebellar cortex, and fire intrinsically; that is, they fire spontaneous action potentials at high frequencies. This review paper focuses on PC intrinsic firing activity, which is altered in multiple neurological diseases, including ataxia, Huntington Disease (HD) and autism spectrum disorder (ASD). Notably, there are several cases where interventions that restore or rescue PC intrinsic activity also improve impaired behavior in these mouse models of disease. These findings suggest that rescuing PC firing deficits themselves may be sufficient to improve impairment in cerebellar-related behavior in disease. We propose that restoring PC intrinsic firing represents a good target for drug development that might be of therapeutic use for several disorders.

Disrupted Calcium Signaling in Animal Models of Human Spinocerebellar Ataxia (SCA)

Spinocerebellar ataxias (SCAs) constitute a heterogeneous group of more than 40 autosomal-dominant genetic and neurodegenerative diseases characterized by loss of balance and motor coordination due to dysfunction of the cerebellum and its efferent connections. Despite a well-described clinical and pathological phenotype, the molecular and cellular events that underlie neurodegeneration are still poorly undaerstood. Emerging research suggests that mutations in SCA genes cause disruptions in multiple cellular pathways but the characteristic SCA pathogenesis does not begin until calcium signaling pathways are disrupted in cerebellar Purkinje cells. Ca²⁺ signaling in Purkinje cells is important for normal cellular function as these neurons express a variety of Ca²⁺ channels, Ca²⁺-dependent kinases and phosphatases, and Ca²⁺-binding proteins to tightly maintain Ca²⁺ homeostasis and regulate physiological Ca²⁺-dependent processes. Abnormal Ca²⁺ levels can activate toxic cascades leading to characteristic death of Purkinje cells, cerebellar atrophy, and ataxia that occur in many SCAs. The output of the cerebellar cortex is conveyed to the deep cerebellar nuclei (DCN) by Purkinje cells via inhibitory signals; thus, Purkinje cell dysfunction or degeneration would partially or completely impair the cerebellar output in SCAs. In the absence of the inhibitory signal emanating from Purkinje cells, DCN will become more excitable, thereby affecting the motor areas receiving DCN input and resulting in uncoordinated movements. An outstanding advantage in studying the pathogenesis of SCAs is represented by the availability of a large number of animal models which mimic the phenotype observed in humans. By mainly focusing on mouse models displaying mutations or deletions in genes which encode for Ca²⁺ signaling-related proteins, in this review we will discuss the several pathogenic mechanisms related to deranged Ca²⁺ homeostasis that leads to significant Purkinje cell degeneration and dysfunction.

Modeling Polyglutamine Expansion Diseases with Induced Pluripotent Stem Cells

Polyglutamine expansion disorders, which include Huntington's disease, have expanded CAG repeats that result in polyglutamine expansions in affected proteins. How this specific feature leads to distinct neuropathies in 11 different diseases is a fascinating area of investigation. Most proteins affected by polyglutamine expansions are ubiquitously expressed, yet their mechanisms of selective neurotoxicity are unknown. Induced pluripotent stem cells have emerged as a valuable tool to model diseases, understand molecular mechanisms, and generate relevant human neural and glia subtypes, cocultures, and organoids. Ideally, this tool will generate specific neuronal populations that faithfully recapitulate specific polyglutamine expansion disorder phenotypes and mimic the selective vulnerability of a given disease. Here, we review how induced pluripotent technology is used to understand the effects of the disease-causing polyglutamine protein on cell function, identify new therapeutic targets, and determine how polyglutamine expansion affects human neurodevelopment and disease. We will discuss ongoing challenges and limitations in our use of induced pluripotent stem cells to model polyglutamine expansion diseases.