The genetic landscape and phenotypic spectrum of GAA-FGF14 ataxia in China: a large cohort study.

BACKGROUND: An intronic GAA repeat expansion in FGF14 was recently identified as a cause of GAA-FGF14 ataxia. We aimed to characterise the frequency and phenotypic profile of GAA-FGF14 ataxia in a large Chinese ataxia cohort. METHODS: A total of 1216 patients that included 399 typical late-onset cerebellar ataxia (LOCA), 290 early-onset cerebellar ataxia (EOCA), and 527 multiple system atrophy with predominant cerebellar ataxia (MSA-c) were enrolled. Long-range and repeat-primed PCR were performed to screen for GAA expansions in FGF14. Targeted long-read and whole-genome sequencing were performed to determine repeat size and sequence configuration. A multi-modal study including clinical assessment, MRI, and neurofilament light chain was conducted for disease assessment. FINDINGS: 17 GAA-FGF14 positive patients with a (GAA)≥250 expansion (12 patients with a GAA-pure expansion, five patients with a (GAA)≥250-[(GAA)n (GCA)m]z expansion) and two possible patients with biallelic (GAA)202/222 alleles were identified. The clinical phenotypes of the 19 positive and possible positive cases covered LOCA phenotype, EOCA phenotype and MSA-c phenotype. Five of six patients with EOCA phenotype were found to have another genetic disorder. The NfL levels of patients with EOCA and MSA-c phenotypes were significantly higher than patients with LOCA phenotype and age-matched controls (p < 0.001). NfL levels of pre-ataxic GAA-FGF14 positive individuals were lower than pre-ataxic SCA3 (p < 0.001) and similar to controls. INTERPRETATION: The frequency of GAA-FGF14 expansion in a large Chinese LOCA cohort was low (1.3%). Biallelic (GAA)202/222 alleles and co-occurrence with other acquired or hereditary diseases may contribute to phenotypic variation and different progression. FUNDING: This study was funded by the National Key R&D Program of China (2021YFA0805200 to H.J.), the National Natural Science Foundation of China (81974176 and 82171254 to H.J.; 82371272 to Z.C.; 82301628 to L.W.; 82301438 to Z.L.; 82201411 to L.H.), the Innovation Research Group Project of Natural Science Foundation of Hunan Province (2020JJ1008 to H.J.), the Key Research and Development Program of Hunan Province (2020SK2064 to H.J.), the Innovative Research and Development Program of Development and Reform Commission of Hunan Province to H.J., the Natural Science Foundation of Hunan Province (2024JJ3050 to H.J.; 2022JJ20094 and 2021JJ40974 to Z.C.; 2022JJ40783 to L.H.; 2022JJ40703 to Z.L.), the Project Program of National Clinical Research Center for Geriatric Disorders (Xiangya Hospital, 2020LNJJ12 to H.J.), the Central South University Research Programme of Advanced Interdisciplinary Study (2023QYJC010 to H.J.) and the Science and Technology Innovation Program of Hunan Province (2022RC1027 to Z.C.). D.P. holds a Fellowship award from the Canadian Institutes of Health Research (CIHR).

Peripheral Inflammatory and Immune Landscape in Multiple System Atrophy: A Cross-Sectional Study.

BACKGROUND: Neuroinflammation might contribute to the pathogenesis of multiple systemic atrophy (MSA). However, specific alterations in the peripheral inflammatory and immune profiles of patients with MSA remain unclear. OBJECTIVES: To determine the peripheral inflammatory and immune profiles of patients with MSA and their potential value as biomarkers for facilitating clinical diagnosis and monitoring disease severity. METHODS: This cross-sectional study included 235, 240, and 235 patients with MSA, patients with Parkinson's disease (PD), and healthy controls (HCs), respectively. Inflammatory and immune parameters were measured in peripheral blood, differences between groups were assessed, and clusters were analyzed. Associations between the parameters and clinical characteristics of MSA were assessed using Spearman and partial correlation analyses. RESULTS: Significant differences were observed especially in monocytes, neutrophils-to-lymphocyte ratio (NLR) and neutrophils-to-lymphocyte ratio (MPV) between MSA patients and HCs (P < 0.01). Monocytes and uric acid (UA) levels were also significantly different between the MSA and PD patients (P < 0.05). The combination of NLR and MPV distinguished MSA-P patients from HCs (areas under the curve = 0.824). In addition, complement components C4 and C3 were significantly correlated with the Scale Outcomes in PD for Autonomic Symptoms and Wexner scale, whereas immunoglobulin G (IgG) was significantly correlated with scores of Unified Multiple System Atrophy Rating Scale (P < 0.05). CONCLUSIONS: In MSA patients, monocytes, NLR and MPV might serve as potential diagnostic biomarkers, whereas MLR, C3, C4, and IgG significantly correlate with disease severity. © 2023 International Parkinson and Movement Disorder Society.

Efficacy of cerebellar transcranial magnetic stimulation in spinocerebellar ataxia type 3: a randomized, single-blinded, controlled trial.

BACKGROUND: Spinocerebellar ataxia type 3 (SCA3) is the most common subtype of SCA without effective treatment. This study aimed to evaluate the comparative efficacy of low-frequency repetitive transcranial magnetic stimulation (rTMS) and intermittent Theta Burst Stimulation (iTBS) in a larger cohort of SCA3 patients. METHODS: One hundred and twenty patients with SCA3 were randomly assigned to the 3 groups: 40 patients in the 1 Hz rTMS, 40 in the iTBS and 40 in the sham group. Patients underwent 10 sessions of rTMS targeting the cerebellum delivering for 5 consecutive days per week for 2 weeks (a total of 1200 pulses per session). Primary outcomes included the Scale for the Assessment and Rating of Ataxia (SARA) and the International Cooperative Ataxia Rating Scale (ICARS). Secondary outcomes included 10-m walking test (10MWT), nine-hole peg test (9-HPT), and PATA Rate Test (PRT). Outcome assessments were performed at baseline and on the last day of rTMS intervention. RESULTS: This study revealed that active rTMS outperformed sham in reducing the SARA and ICARS scores in SCA3 patients, but with no difference between the 1 Hz rTMS and iTBS protocol. Moreover, no significant differences were observed in SARA and ICARS scores between the mild and moderate to severe groups after the 1 Hz rTMS/iTBS therapy. Additionally, no severe adverse events were recorded in this study. CONCLUSIONS: The study concluded that both 1 Hz rTMS and iTBS interventions targeting the cerebellum are effective to improve the symptoms of ataxia in patients with SCA3.

No Correlation between Plasma GPNMB Levels and Multiple System Atrophy in Chinese Cohorts.

BACKGROUND: Glycoprotein nonmetastatic melanoma protein B (GPNMB) has been demonstrated to mediate pathogenicity in Parkinson's disease (PD) through interactions with α-synuclein, and plasma GPNMB tended to be a novel biomarker for PD. OBJECTIVE: The goal of this study was to investigate whether plasma GPNMB could act as a potential biomarker for the clinical diagnosis and severity monitoring of multiple system atrophy (MSA), another typical synucleinopathy. METHODS: Plasma GPNMB levels in patients with MSA, patients with PD, and healthy control subjects (HCs) were quantified using enzyme-linked immunosorbent assays. RESULTS: A total of 204 patients with MSA, 65 patients with PD, and 207 HCs were enrolled. The plasma GPNMB levels in patients with MSA were similar to those in HCs (P = 0.251) but were significantly lower than those in patients with PD (P = 0.003). Moreover, there was no significant correlation detected between the plasma GPNMB levels and disease severity scores of patients with MSA. CONCLUSIONS: No evidence was detected for the biomarker potential of plasma GPNMB in MSA. © 2023 International Parkinson and Movement Disorder Society.

Diagnostic and prognostic performance of plasma neurofilament light chain in multiple system atrophy: a cross-sectional and longitudinal study.

BACKGROUND: The longitudinal dynamics of neurofilament light chain (NfL) in multiple system atrophy (MSA) were incompletely illuminated. This study aimed to explore whether the plasma NfL (pNfL) could serve as a potential biomarker of clinical diagnosis and disease progression for MSA. METHODS: We quantified pNfL concentrations in both a large cross-sectional cohort with 214 MSA individuals, 65 PD individuals, and 211 healthy controls (HC), and a longitudinal cohort of 84 MSA patients. Propensity score matching (PSM) was used to balance the age between the three groups. The pNfL levels between groups were compared using Kruskal-Wallis test. Linear mixed models were performed to explore the disease progression-associated factors in longitudinal MSA cohort. Random forest model as a complement to linear models was employed to quantify the importance of predictors. RESULTS: Before and after matching the age by PSM, the pNfL levels could reliably differentiate MSA from HC and PD groups, but only had mild potential to distinguish PD from HC. By combining linear and nonlinear models, we demonstrated that pNfL levels at baseline, rather than the change rate of pNfL, displayed potential prognostic value for progression of MSA. The combination of baseline pNfL levels and other modifiers, such as subtypes, Hoehn-Yahr stage at baseline, was first shown to improve the diagnosis accuracy. CONCLUSIONS: Our study contributed to a better understanding of longitudinal dynamics of pNfL in MSA, and validated the values of pNfL as a non-invasive sensitive biomarker for the diagnosis and progression. The combination of pNfL and other factors is recommended for better monitoring and prediction of MSA progression.

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

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Characterization of the central motor conduction time in a large cohort of spinocerebellar ataxia type 3 patients.

INTRODUCTION: Spinocerebellar ataxia type 3 (SCA3) is the most common subtype of hereditary ataxia. Few studies reported the CMCT features in SCA3, but with inconsistent findings. So far, CMCT in SCA3 remains largely unknown. METHODS: This study included 86 SCA3 patients and 80 healthy controls. Motor-evoked potentials were recorded bilaterally from upper and lower limbs muscles by TMS using a double-cone coil attached to CCY-IA magnetic stimulator. CMCT was determined using F wave and paravertebral magnetic stimulation (PMS). The statistical analyses were performed using R software. RESULTS: In our study, 36.5% of SCA3 patients had a slight prolongation of CMCT in lower limbs, but not upper limbs, uncorrelated with disease severity. Moreover, SCA3 patients with Babinski signs did not necessarily have abnormal CMCT, and vice versa. Our study demonstrated that PMS is a reliable method as F wave for detecting CMCT in SCA3. Additionally, CMCT to lower limbs was positively correlated with height, but not with age, sex, or weight in healthy controls. CONCLUSIONS: A small proportion of SCA3 patients had a slight prolongation of CMCT in lower limbs, but not upper limbs, uncorrelated with disease severity. Furthermore, CMCT measures were observed irrespective of pyramidal sign in SCA3; however, patients with abnormal CMCT had a higher incidence of the pyramidal sign.

Explainable artificial intelligence based on feature optimization for age at onset prediction of spinocerebellar ataxia type 3.

Existing treatments can only delay the progression of spinocerebellar ataxia type 3/Machado-Joseph disease (SCA3/MJD) after onset, so the prediction of the age at onset (AAO) can facilitate early intervention and follow-up to improve treatment efficacy. The objective of this study was to develop an explainable artificial intelligence (XAI) based on feature optimization to provide an interpretable and more accurate AAO prediction. A total of 1,008 affected SCA3/MJD subjects from mainland China were analyzed. The expanded cytosine-adenine-guanine (CAG) trinucleotide repeats of 10 polyQ-related genes were genotyped and included in related models as potential AAO modifiers. The performance of 4 feature optimization methods and 10 machine learning (ML) algorithms were compared, followed by building the XAI based on the SHapley Additive exPlanations (SHAP). The model constructed with an artificial neural network (ANN) and feature optimization of Crossing-Correlation-StepSVM performed best and achieved a coefficient of determination (R2) of 0.653 and mean absolute error (MAE), root mean square error (RMSE), and median absolute error (MedianAE) of 4.544, 6.090, and 3.236 years, respectively. The XAI explained the predicted results, which suggests that the factors affecting the AAO were complex and associated with gene interactions. An XAI based on feature optimization can improve the accuracy of AAO prediction and provide interpretable and personalized prediction.

The Natural History of Spinocerebellar Ataxia Type 3 in Mainland China: A 2-Year Cohort Study.

Objective: The natural history of spinocerebellar ataxia type 3 (SCA3) has been reported in several populations and shows heterogeneity in progression rate and affecting factors. However, it remains unexplored in the population of Mainland China. This study aimed to identify the disease progression rate and its potential affecting factors in patients with SCA3 in Mainland China. Participants and Methods: We enrolled patients with genetically confirmed SCA3 in Mainland China. Patients were seen at three visits, i.e., baseline, 1 year, and 2 years. The primary outcome was the Scale for the Assessment and Rating of Ataxia (SARA), and the secondary outcomes were the Inventory of Non-Ataxia Signs (INAS) as well as the SCA Functional Index (SCAFI). Results: Between 1 October 2015, and 30 September 2016, we enrolled 263 patients with SCA3. We analyzed 247 patients with at least one follow-up visit. The annual progression rate of SARA was 1.49 points per year (SE 0.08, 95% confidence interval [CI] 1.33-1.65, p < 0.0001). The annual progression rates of INAS and SCAFI were 0.56 points per year (SE 0.05, 95% CI 0.47-0.66, p < 0.001) and -0.30 points per year (SE 0.01, 95% CI -0.33∼-0.28, p < 0.001), respectively. Faster progression in SARA was associated with longer length of the expanded allele of ATXN3 (p < 0.0001); faster progression in INAS was associated with lower INAS at baseline (p < 0.0001); faster decline in SCAFI was associated with shorter length of the normal allele of ATXN3 (p = 0.036) and higher SCAFI at baseline (p < 0.0001). Conclusion: Our results provide quantitative data on the disease progression of patients with SCA3 in Mainland China and its corresponding affecting factors, which could facilitate the sample size calculation and patient stratification in future clinical trials. Trial Registration: This study was registered with Chictr.org on 15 September 2015, number ChiCTR-OOC-15007124.

The progression rate of spinocerebellar ataxia type 3 varies with disease stage.

BACKGROUND: In polyglutamine (polyQ) diseases, the identification of modifiers and the construction of prediction model for progression facilitate genetic counseling, clinical management and therapeutic interventions. METHODS: Data were derived from the longest longitudinal study, with 642 examinations by International Cooperative Ataxia Rating Scale (ICARS) from 82 SCA3 participants. Using different time scales of disease duration, we performed multiple different linear, quadratic and piece-wise linear growth models to fit the relationship between ICARS scores and duration. Models comparison was employed to determine the best-fitting model according to goodness-of-fit tests, and the analysis of variance among nested models. RESULTS: An acceleration was detected after 13 years of duration: ICARS scores progressed 2.445 (SE: 0.185) points/year before and 3.547 (SE: 0.312) points/year after this deadline. Piece-wise growth model fitted better to studied data than other two types of models. The length of expanded CAG repeat (CAGexp) in ATXN3 gene significantly influenced progression. Age at onset of gait ataxia (AOga), a proxy for aging process, was not an independent modifier but affected the correlation between CAGexp and progression. Additionally, gender had no significant effect on progression rate of ICARS. The piece-wise growth models were determined as the predictive models, and ICARS predictions from related models were available. CONCLUSIONS: We first confirmed that ICARS progressed as a nonlinear pattern and varied according to different stages in SCA3. In addition to ATXN3 CAGexp, AOga or aging process regulated the progression by interacting with CAGexp.

Identification of the Largest SCA36 Pedigree in Asia: with Multimodel Neuroimaging Evaluation for the First Time.

Spinocerebellar ataxias (SCAs) are a large group of hereditary neurodegenerative diseases characterized by ataxia and dysarthria. Due to high clinical and genetic heterogeneity, many SCA families are undiagnosed. Herein, using linkage analysis, WES, and RP-PCR, we identified the largest SCA36 pedigree in Asia. This pedigree showed some distinct clinical characteristics. Cognitive impairment and gaze palsy are common and severe in SCA36 patients, especially long-course patients. Although no patients complained of hearing loss, most of them presented with hearing impairment in objective auxiliary examination. Voxel-based morphometry (VBM) demonstrated a reduction of volumes in cerebellum, brainstem, and thalamus (corrected P < 0.05). Reduced volumes in cerebellum were also found in presymptomatic carriers. Resting-state functional MRI (R-fMRI) found reduced ReHo values in left cerebellar posterior lobule (corrected P < 0.05). Diffusion tensor imaging (DTI) demonstrated a reduction of FA values in cerebellum, midbrain, superior and inferior cerebellar peduncle (corrected P < 0.05). MRS found reduced NAA/Cr values in cerebellar vermis and hemisphere (corrected P < 0.05). Our findings could provide new insights into management of SCA36 patients. Detailed auxiliary examination are recommended to assess hearing or peripheral nerve impairment, and we should pay more attention to eye movement and cognitive changes in patients. Furthermore, for the first time, our multimodel neuroimaging evaluation generate a full perspective of brain function and structure in SCA36 patients.

Blood Neurofilament Light Chain in Genetic Ataxia: A Meta-Analysis.

BACKGROUND: No comprehensive meta-analysis has ever been performed to assess the value of neurofilament light chain (NfL) as a biomarker in genetic ataxia. OBJECTIVE: We conducted a meta-analysis to summarize NfL concentration and evaluate its utility as a biomarker in genetic ataxia. METHODS: Studies were included if they reported NfL concentration of genetic ataxia. We used log (mean ± SD) NfL to describe mean raw value of NfL. The effect size of NfL between genetic ataxia and healthy controls (HC) was expressed by mean difference. Correlation between NfL and disease severity was calculated. RESULTS: We identified 11 studies of 624 HC and 1006 patients, here referred to as spinocerebellar ataxia (SCA1, 2, 3, 6, and 7), Friedreich ataxia (FRDA), and ataxia telangiectasia (A-T). The concentration of blood NfL (bNfL) elevated with proximity to expected onset, and progressively increased from asymptomatic to preclinical to clinical stage in SCA3. Compared with HC, bNfL levels were significantly higher in SCA1, 2, 3, and 7, FRDA, as well as A-T, and the difference increased with the advancing disease in SCA3. bNfL levels correlated with disease severity in SCA3. There was a significant correlation between bNfL and longitudinal progression in SCA3. Additionally, bNfL increased with age in HC, yet this is probably masked by higher disease-related effects on bNfL in genetic ataxia. CONCLUSIONS: bNfL can be used as a potential biomarker to predict disease onset, severity, and progression of genetic ataxia. Reference-value setting of bNfL should be divided according to age. © 2021 International Parkinson and Movement Disorder Society.

CRISPR/Cas9 mediated gene correction ameliorates abnormal phenotypes in spinocerebellar ataxia type 3 patient-derived induced pluripotent stem cells.

Spinocerebellar ataxia type 3/Machado-Joseph disease (SCA3/MJD) is a progressive autosomal dominant neurodegenerative disease caused by abnormal CAG repeats in the exon 10 of ATXN3. The accumulation of the mutant ataxin-3 proteins carrying expanded polyglutamine (polyQ) leads to selective degeneration of neurons. Since the pathogenesis of SCA3 has not been fully elucidated, and no effective therapies have been identified, it is crucial to investigate the pathogenesis and seek new therapeutic strategies of SCA3. Induced pluripotent stem cells (iPSCs) can be used as the ideal cell model for the molecular pathogenesis of polyQ diseases. Abnormal CAG expansions mediated by CRISPR/Cas9 genome engineering technologies have shown promising potential for the treatment of polyQ diseases, including SCA3. In this study, SCA3-iPSCs can be corrected by the replacement of the abnormal CAG expansions (74 CAG) with normal repeats (17 CAG) using CRISPR/Cas9-mediated homologous recombination (HR) strategy. Besides, corrected SCA3-iPSCs retained pluripotent and normal karyotype, which can be differentiated into a neural stem cell (NSCs) and neuronal cells, and maintained electrophysiological characteristics. The expression of differentiation markers and electrophysiological characteristics were similar among the neuronal differentiation from normal control iPSCs (Ctrl-iPSCs), SCA3-iPSCs, and isogenic control SCA3-iPSCs. Furthermore, this study proved that the phenotypic abnormalities in SCA3 neurons, including aggregated IC2-polyQ protein, decreased mitochondrial membrane potential (MMP) and glutathione expressions, increased reactive oxygen species (ROS), intracellular Ca2+ concentrations, and lipid peroxidase malondialdehyde (MDA) levels, all were rescued in the corrected SCA3-NCs. For the first time, this study demonstrated the feasibility of CRISPR/Cas9-mediated HR strategy to precisely repair SCA3-iPSCs, and reverse the corresponding abnormal disease phenotypes. In addition, the importance of genetic control using CRISPR/Cas9-mediated iPSCs for disease modeling. Our work may contribute to providing a potential ideal model for molecular mechanism research and autologous stem cell therapy of SCA3 or other polyQ diseases, and offer a good gene therapy strategy for future treatment.

Genetic etiology of a Chinese ataxia cohort: Expanding the mutational spectrum of hereditary ataxias.

INTRODUCTION: Hereditary ataxias demonstrate a high degree of clinical and genetic heterogeneity. Understanding the genetic etiology of hereditary ataxias is crucial for genetic counseling and clinical management. METHODS: The clinical and genetic data of patients with familial or sporadic ataxias who referred to our tertiary medical center were retrospectively analyzed. Probands in this study underwent SCA repeat expansion panel firstly to screen for repeat expansion SCAs; those with negative results had NGS-targeted panels or WES testing to detect conventional mutations. RESULTS: A total of 223 patients were enrolled from 206 families. 5 kinds of coexisting SCA repeat expansions were observed (SCA3/SCA17, SCA3/SCA8, SCA2/SCA8, SCA3/SCA12 and SCA8/SCA12) in 12 patients from 8 families, among which SCA2/SCA8, SCA8/SCA12 and SCA3/SCA12 were reported for the first time. The coexistence of expanded SCA3 with SCA17 alleles was the most common in our study. NGS identified pathogenic/likely pathogenic variants in 12 ataxia causative genes in 13 probands. Spastic paraplegia ataxia was the most common diagnosis. Six novel mutations were detected in five ataxia-related genes. CONCLUSION: Coexistence may not specific to a certain SCA subtype and the frequency might have been underestimated before. SCA repeat expansion panel should be considered in patients with overlapping SCA features. In addition, our study broadened the conventional mutation spectrum in ataxia-related genes. These results facilitate a better understanding of the genetic basis for hereditary ataxias.

New Model for Estimation of the Age at Onset in Spinocerebellar Ataxia Type 3.

OBJECTIVES: The aim of this study was to develop an appropriate parametric survival model to predict patient's age at onset (AAO) for spinocerebellar ataxia type 3/Machado-Joseph disease (SCA3/MJD) populations from mainland China. METHODS: We compared the efficiency and performance of 6 parametric survival analysis methods (exponential, weibull, log-gaussian, gaussian, log-logistic, and logistic) based on cytosine-adenine-guanine (CAG) repeat length at ATXN3 to predict the probability of AAO in the largest cohort of patients with SCA3/MJD. A set of evaluation criteria, including -2 log-likelihood statistic, Akaike information criterion (AIC), bayesian information criterion (BIC), Nagelkerke R-squared (Nagelkerke R^2), and Cox-Snell residual plot, were used to identify the best model. RESULTS: Among these 6 parametric survival models, the logistic model had the lowest -2 log-likelihood (6,560.12), AIC (6,566.12), and BIC (6,566.14) and the highest value of Nagelkerke R^2 (0.54), with the closest graph to the bisector Cox-Snell residual graph. Therefore, the logistic survival model was the best fit to the studied data. Using the optimal logistic survival model, we indicated the age-specific probability distribution of AAO according to the CAG repeat size and current age. CONCLUSIONS: We first demonstrated that the logistic survival model provided the best fit for AAO prediction in patients with SCA3/MJD from mainland China. This optimal model can be valuable in clinical and research. However, the rigorous clinical testing and practice of other independent cohorts are needed for its clinical application. A unified model across multiethnic cohorts is worth further exploration by identifying regional differences and significant modifiers in AAO determination.

Generation of spinocerebellar ataxia type 3 patient-derived induced pluripotent stem cell line (CSUXHi005-A) from human urine epithelial cells.

Urine epithelial cells were harvested from a 32-year old female patient with spinocerebellar ataxia type 3 (SCA3) and reprogrammed into induced pluripotent stem cells (iPSCs) by non-integration system. The SCA3 derived iPSCs line, CSUXHi005-A, maintained 76 CAG expansions in the ATXN3 gene, was characterized by the expression of pluripotency markers and normal karyotype. The newly generated iPSCs retain the ability to differentiate into three germ layers by teratoma test, which provide an ideal tool for disease modeling, drug screening, and cellular therapy.

Prediction of the Age at Onset of Spinocerebellar Ataxia Type 3 with Machine Learning.

BACKGROUND: In polyglutamine (polyQ) disease, the investigation of the prediction of a patient's age at onset (AAO) facilitates the development of disease-modifying intervention and underpins the delay of disease onset and progression. Few polyQ disease studies have evaluated AAO predicted by machine-learning algorithms and linear regression methods. OBJECTIVE: The objective of this study was to develop a machine-learning model for AAO prediction in the largest spinocerebellar ataxia type 3/Machado-Joseph disease (SCA3/MJD) population from mainland China. METHODS: In this observational study, we introduced an innovative approach by systematically comparing the performance of 7 machine-learning algorithms with linear regression to explore AAO prediction in SCA3/MJD using CAG expansions of 10 polyQ-related genes, sex, and parental origin. RESULTS: Similar prediction performance of testing set and training set in each models were identified and few overfitting of training data was observed. Overall, the machine-learning-based XGBoost model exhibited the most favorable performance in AAO prediction over the traditional linear regression method and other 6 machine-learning algorithms for the training set and testing set. The optimal XGBoost model achieved mean absolute error, root mean square error, and median absolute error of 5.56, 7.13, 4.15 years, respectively, in testing set 1, with mean absolute error (4.78 years), root mean square error (6.31 years), and median absolute error (3.59 years) in testing set 2. CONCLUSION: Machine-learning algorithms can be used to predict AAO in patients with SCA3/MJD. The optimal XGBoost algorithm can provide a good reference for the establishment and optimization of prediction models for SCA3/MJD or other polyQ diseases. © 2020 International Parkinson and Movement Disorder Society.

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.

Central motor conduction time in spinocerebellar ataxia: a meta-analysis.

The dominantly inherited spinocerebellar ataxias (SCAs) are a large class of neurodegenerative diseases. Transcranial magnetic stimulation has been used to evaluate the function of the pyramidal tract, and central motor conduction time (CMCT) is one index used to detect pyramidal tract dysfunction. We conducted a comprehensive search of PubMed, Embase and Web of Science. Eight eligible studies were included in the meta-analysis. For upper limb CMCT, the mean difference (95% confidence interval (CI)) between the combined SCA group and the control group was 2.24 [1.76-2.72], while the mean differences (95% CIs) between the subtypes and the control group were as follows: 4.43 [3.58-5.28] for SCA1, 0.25 [-0.15,0.65] for SCA2, 1.04 [-0.37,2.46] for SCA3 and 0.49 [-0.29,1.28] for SCA6. Additionally, SCA1 significantly differed from SCA2 and SCA3 in terms of CMCT (P=0.0006 and P=0.010, respectively). We also compared lower limb CMCT between the SCA2 and control groups. The mean difference (95% CI) was 6.58 [4.49-8.67], which was clearly statistically significant. The differences in CMCT values among different subtypes suggests diverse pathological mechanisms. In general, CMCT is a promising objective index to judge the severity of disease deserving further investigation.

Biallelic Intronic AAGGG Expansion of RFC1 is Related to Multiple System Atrophy.

OBJECTIVE: A recessive biallelic repeat expansion, (AAGGG)exp , in the RFC1 gene has been reported to be a frequent cause of late-onset ataxia. For cerebellar ataxia, neuropathy, and vestibular areflexia syndrome (CANVAS), the recessive biallelic (AAGGG)exp genotype was present in ~92% of cases. This study aimed to examine whether the pentanucleotide repeat (PNR) was related to multiple system atrophy (MSA), which shares a spectrum of symptoms with CANVAS. METHODS: In this study, we screened the pathogenic (AAGGG)exp repeat and 5 other PNRs in 104 Chinese sporadic adult-onset ataxia of unknown aetiology (SAOA) patients, 282 MSA patients, and 203 unaffected individuals. Multiple molecular genetic tests were used, including long-range polymerase chain reaction (PCR), repeat-primed PCR (RP-PCR), Sanger sequencing, and Southern blot. Comprehensive clinical assessments were conducted, including neurological examination, neuroimaging, nerve electrophysiology, and examination of vestibular function. RESULTS: We identified biallelic (AAGGG)exp in 1 SAOA patient and 3 MSA patients. Additionally, 1 MSA patient had the (AAGGG)exp /(AAAGG)exp genotype with uncertain pathogenicity. We also described the carrier frequency for different PNRs in our cohorts. Furthermore, we summarized the distinct phenotypes of affected patients, suggesting that biallelic (AAGGG)exp in RFC1 could be associated with MSA and should be screened routinely in the MSA diagnostic workflow. INTERPRETATION: Our results expanded the clinical phenotypic spectrum of RFC1-related disorders and raised the possibility that MSA might share the same genetic background as CANVAS, which is crucial for re-evaluating the current CANVAS and MSA diagnostic criteria. ANN NEUROL 2020;88:1132-1143.