A clinical and pathologic study of a large Japanese family with Machado-Joseph disease tightly linked to the DNA markers on chromosome 14q

Morphological changes of cerebral gray matter in spinocerebellar ataxia type 3 using fractal dimension analysis

Spinocerebellar ataxia type 3 (SCA3), or Machado-Joseph disease, presents as a cerebellar cognitive affective syndrome (CCAS) and represents the predominant SCA genotype in Taiwan. Beyond cerebellar involvement, SCA3 patients exhibit cerebral atrophy. While prior neurodegenerative disease studies relied on voxel-based morphometry (VBM) for brain atrophy assessment, its qualitative nature limits individual and region-specific evaluations. To address this, we employed fractal dimension (FD) analysis to quantify cortical complexity changes in SCA3 patients. We examined 50 SCA3 patients and 50 age- and sex-matched healthy controls (HC), dividing MRI cerebral gray matter (GM) into 68 auto-anatomical subregions. Using three-dimensional FD analysis, we identified GM atrophy manifestations in SCA3 patients. Results revealed lateral atrophy symptoms in the left frontal, parietal, and occipital lobes, and fewer symptoms in the right hemisphere's parietal and occipital lobes. Focal areas of atrophy included regions previously identified in SCA3 studies, alongside additional regions with decreased FD values. Bilateral postcentral gyrus and inferior parietal gyrus exhibited pronounced atrophy, correlating with Scale for the Assessment and Rating of Ataxia (SARA) scores and disease duration. Notably, the most notable focal areas were the bilateral postcentral gyrus and the left superior temporal gyrus, serving as imaging biomarkers for SCA3. Our study enhances understanding of regional brain atrophy in SCA3, corroborating known clinical features while offering new insights into disease progression.

A review on approach to a twitchy tongue in neurology

BACKGROUND

Several etiologies are responsible for presentation of a twitching tongue in clinical practice. Some of these etiologies cause an isolated hyperkinetic tongue muscle, and some others cause it along with other signs and symptoms.

OBJECTIVES

The present paper aims to review the causes, pathology, and presentations reported with twitchy tongue. An anatomical basis of the etiologies responsible for presentation of a twitchy tongue and hyperkinetic movement disorders of this muscle is pursued.

METHOD

The reporting of this systematic review was guided by the standards of the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) Statement. All of the research papers conducted with keywords described in the method section between 2000 and 2022 were used, and review articles and articles without any human subject and without any described hyperkinetic movement disorders of the tongue were excluded.

RESULTS

All of the etiologies responsible for hyperkinetic movement disorders of tongue were listed in the basis of their anatomical site of effect; cortical region, basal ganglia, cerebellum, brain stem, nucleus and nerve, and neuromuscular junction. One last remained part is the "not classified" section, which contains the etiologies with no particular anatomical origin.

CONCLUSION

There are a variety of responsible etiologies for presentation of a twitchy tongue, and in the matter of a complaint of hyperkinetic tongue presentation, physicians should consider anatomical, functional, and psychological etiologies and other signs and symptoms must be participated in the diagnosis process to achieve a proper medical decision.

Plasma PolyQ-ATXN3 Levels Associate With Cerebellar Degeneration and Behavioral Abnormalities in a New AAV-Based SCA3 Mouse Model

Spinocerebellar ataxia type 3 (SCA3) is a dominantly inherited cerebellar ataxia caused by the expansion of a polyglutamine (polyQ) repeat in the gene encoding ATXN3. The polyQ expansion induces protein inclusion formation in the neurons of patients and results in neuronal degeneration in the cerebellum and other brain regions. We used adeno-associated virus (AAV) technology to develop a new mouse model of SCA3 that recapitulates several features of the human disease, including locomotor defects, cerebellar-specific neuronal loss, polyQ-expanded ATXN3 inclusions, and TDP-43 pathology. We also found that neurofilament light is elevated in the cerebrospinal fluid (CSF) of the SCA3 animals, and the expanded polyQ-ATXN3 protein can be detected in the plasma. Interestingly, the levels of polyQ-ATXN3 in plasma correlated with measures of cerebellar degeneration and locomotor deficits in 6-month-old SCA3 mice, supporting the hypothesis that this factor could act as a biomarker for SCA3.

The protective role of exercise against age-related neurodegeneration

Endurance exercise is a widely accessible, low-cost intervention with a variety of benefits to multiple organ systems. Exercise improves multiple indices of physical performance and stimulates pronounced health benefits reducing a range of pathologies including metabolic, cardiovascular, and neurodegenerative disorders. Endurance exercise delays brain aging, preserves memory and cognition, and improves symptoms of neurodegenerative pathologies like Amyotrophic Lateral Sclerosis, Alzheimer's disease, Parkinson's disease, Huntington's disease, and various ataxias. Potential mechanisms underlying the beneficial effects of exercise include neuronal survival and plasticity, neurogenesis, epigenetic modifications, angiogenesis, autophagy, and the synthesis and release of neurotrophins and cytokines. In this review, we discuss shared benefits and molecular pathways driving the protective effects of endurance exercise on various neurodegenerative diseases in animal models and in humans.

Targeting the VCP-binding motif of ataxin-3 improves phenotypes in Drosophila models of Spinocerebellar Ataxia Type 3

Of the family of polyglutamine (polyQ) neurodegenerative diseases, Spinocerebellar Ataxia Type 3 (SCA3) is the most common. Like other polyQ diseases, SCA3 stems from abnormal expansions in the CAG triplet repeat of its disease gene resulting in elongated polyQ repeats within its protein, ataxin-3. Various ataxin-3 protein domains contribute to its toxicity, including the valosin-containing protein (VCP)-binding motif (VBM). We previously reported that VCP, a homo-hexameric protein, enhances pathogenic ataxin-3 aggregation and exacerbates its toxicity. These findings led us to explore the impact of targeting the SCA3 protein by utilizing a decoy protein comprising the N-terminus of VCP (N-VCP) that binds ataxin-3's VBM. The notion was that N-VCP would reduce binding of ataxin-3 to VCP, decreasing its aggregation and toxicity. We found that expression of N-VCP in Drosophila melanogaster models of SCA3 ameliorated various phenotypes, coincident with reduced ataxin-3 aggregation. This protective effect was specific to pathogenic ataxin-3 and depended on its VBM. Increasing the amount of N-VCP resulted in further phenotype improvement. Our work highlights the protective potential of targeting the VCP-ataxin-3 interaction in SCA3, a key finding in the search for therapeutic opportunities for this incurable disorder.

Emerging concepts on bradykinesia in non-parkinsonian conditions

BACKGROUND AND PURPOSE

Bradykinesia is one of the cardinal motor symptoms of Parkinson's disease. However, clinical and experimental studies indicate that bradykinesia may also be observed in various neurological diseases not primarily characterized by parkinsonism. These conditions include hyperkinetic movement disorders, such as dystonia, chorea, and essential tremor. Bradykinesia may also be observed in patients with neurological conditions that are not seen as "movement disorders," including those characterized by the involvement of the cerebellum and corticospinal system, dementia, multiple sclerosis, and psychiatric disorders.

METHODS

We reviewed clinical reports and experimental studies on bradykinesia in non-parkinsonian conditions and discussed the major findings.

RESULTS

Bradykinesia is a common motor abnormality in non-parkinsonian conditions. From a pathophysiological standpoint, bradykinesia in neurological conditions not primarily characterized by parkinsonism may be explained by brain network dysfunction.

CONCLUSION

In addition to the pathophysiological implications, the present paper highlights important terminological issues and the need for a new, more accurate, and more widely used definition of bradykinesia in the context of movement disorders and other neurological conditions.

Demystifying the spontaneous phenomena of motor hyperexcitability

Possessing a discrete functional repertoire, the anterior horn cell can be in one of two electrophysiological states: on or off. Usually under tight regulatory control by the central nervous system, a hierarchical network of these specialist neurons ensures muscular strength is coordinated, gradated and adaptable. However, spontaneous activation of these cells and their axons can result in abnormal muscular twitching. The muscular twitch is the common building block of several distinct clinical patterns, namely fasciculation, myokymia and neuromyotonia. When attempting to distinguish these entities electromyographically, their unique temporal and morphological profiles must be appreciated. Detection and quantification of burst duration, firing frequency, multiplet patterns and amplitude are informative. A common feature is their persistence during sleep. In this review, we explain the accepted terminology used to describe the spontaneous phenomena of motor hyperexcitability, highlighting potential pitfalls amidst a bemusing and complex collection of overlapping terms. We outline the relevance of these findings within the context of disease, principally amyotrophic lateral sclerosis, Isaacs syndrome and Morvan syndrome. In addition, we highlight the use of high-density surface electromyography, suggesting that more widespread use of this non-invasive technique is likely to provide an enhanced understanding of these motor hyperexcitability syndromes.

Small Molecule Rescue of ATXN3 Toxicity in C. elegans via TFEB/HLH-30

Spinocerebellar ataxia type 3 (SCA3), also known as Machado-Joseph disease (MJD), is a polyglutamine expansion disease arising from a trinucleotide CAG repeat expansion in exon 10 of the gene ATXN3. There are no effective pharmacological treatments for MJD, thus the identification of new pathogenic mechanisms, and the development of novel therapeutics is urgently needed. In this study, we performed a comprehensive, blind drug screen of 3942 compounds (many FDA approved) and identified small molecules that rescued the motor-deficient phenotype in transgenic ATXN3 Caenorhabditis elegans strain. Out of this screen, five lead compounds restoring motility, protecting against neurodegeneration, and increasing the lifespan in ATXN3-CAG89 mutant worms were identified. These compounds were alfacalcidol, chenodiol, cyclophosphamide, fenbufen, and sulfaphenazole. We then investigated how these molecules might exert their neuroprotective properties. We found that three of these compounds, chenodiol, fenbufen, and sulfaphenazole, act as modulators for TFEB/HLH-30, a key transcriptional regulator of the autophagy process, and require this gene for their neuroprotective activities. These genetic-chemical approaches, using genetic C. elegans models for MJD and the screening, are promising tools to understand the mechanisms and pathways causing neurodegeneration, leading to MJD. Positively acting compounds may be promising candidates for investigation in mammalian models of MJD and preclinical applications in the treatment of this disease.

Overexpression of FKH-2/FOXG1 is neuroprotective in a C. elegans model of Machado-Joseph disease

Machado-Joseph disease (MJD), also known as spinocerebellar ataxia type 3 (SCA3), is the most common form of dominantly inherited ataxia worldwide. This disease is caused by an expanded CAG repeat in the coding region of ATXN3. Due to our incomplete understanding of mechanisms and molecular pathways related to this disease, there are no therapies that successfully treat core MJD patients. Therefore, the identification of new candidate targets related to this disease is needed. In this study, we performed a large-scale RNA interference (RNAi) screen of 387 transcription factor genes leading to the identification of several modifiers (suppressors and enhancers) of impaired motility phenotypes in a mutant ATXN3 transgenic C. elegans model. We showed that inactivation of one particular gene, fkh-2/FOXG1, enhanced the motility defect, neurodegeneration and reduced longevity in our MJD models. Opposite to genetic inactivation, the overexpression of fkh-2 rescued the impaired motility, shortened-lifespan, and neurodegeneration phenotypes of mutant ATXN3 transgenics. We found that overexpression of FKH-2/FOXG1 in ATXN3 mutant worms is neuroprotective. Using our transgenic ATXN3 C. elegans models and the screening of an RNAi library, we gained insights into the pathways contributing to neurodegeneration, and found that FKH-2/FOXG1 has neuroprotective activity. These findings may aid the development of novel therapeutic interventions for MJD.

Event-Related Desynchronization/Synchronization in Spinocerebellar Ataxia Type 3

Introduction: Spinocerebellar ataxia type 3 (SCA3) is an autosomal dominant, cerebellar degeneration predominant disease caused by excessive CAG repeats. We examined event-related dysynchronization/synchronization (ERD/ERS) in patients with SCA3.

Methods: We assessed ERD/ERS of self-paced voluntary hand movements in 15 patients with genetically proven SCA3 in comparison with healthy controls.

Results: In ERS, a significant interaction effect between group, frequency, and period (F = 1.591; p = 0.005; ρI = 0.86) was observed. The post-hoc two-tailed independent t-test showed significant differences in high beta and low beta ERS. By contrast, in ERD, no apparent differences were observed in the pattern of patients with SCA3 in comparison with healthy controls (F = 1.01; p = 0.442).

Conclusion: The study revealed a decreased ERS in patients with SCA3, especially at the frequency of 20–30 Hz. This study elucidates the significant role of cerebellum in motor control.

Identification of a potential exosomal biomarker in spinocerebellar ataxia Type 3/Machado-Joseph disease

Aim: To identify spinocerebellar ataxia Type 3 (SCA3)-related exosomal biomarkers and the underlying mechanisms. Materials & methods: Exosomal RNAs from plasma and cerebrospinal fluid (CSF) were extracted from 24 SCA3 patients and 22 controls, respectively. Small RNA sequencing and quantitative PCR verification were performed. Gene ontology annotation and Kyoto Encyclopedia of Genes and Genomes pathway analyses of the results were carried out. Results: One novel miRNA is notably downregulated in plasma-derived exosomes, while upregulated in CSF-derived exosomes of SCA3 patients. Besides, it is successively upregulated in CSF-derived exosomes from Type 1, Type 2 and Type 3 groups. The downstream target genes were enriched in protein processing in endoplasmic reticulum and axon guidance. Conclusion: One exosomal biomarker was identified in SCA3, and this is the first time to report an exosomal miRNA as a biomarker in SCA3 internationally.

The CAG-polyglutamine repeat diseases: a clinical, molecular, genetic, and pathophysiologic nosology

Throughout the genome, unstable tandem nucleotide repeats can expand to cause a variety of neurologic disorders. Expansion of a CAG triplet repeat within a coding exon gives rise to an elongated polyglutamine (polyQ) tract in the resultant protein product, and accounts for a unique category of neurodegenerative disorders, known as the CAG-polyglutamine repeat diseases. The nine members of the CAG-polyglutamine disease family include spinal and bulbar muscular atrophy (SBMA), Huntington disease, dentatorubral pallidoluysian atrophy, and six spinocerebellar ataxias (SCA 1, 2, 3, 6, 7, and 17). All CAG-polyglutamine diseases are dominantly inherited, with the exception of SBMA, which is X-linked, and many CAG-polyglutamine diseases display anticipation, which is defined as increasing disease severity in successive generations of an affected kindred. Despite widespread expression of the different polyQ-expanded disease proteins throughout the body, each CAG-polyglutamine disease strikes a particular subset of neurons, although the mechanism for this cell-type selectivity remains poorly understood. While the different genes implicated in these disorders display amino acid homology only in the repeat tract domain, certain pathologic molecular processes have been implicated in almost all of the CAG-polyglutamine repeat diseases, including protein aggregation, proteolytic cleavage, transcription dysregulation, autophagy impairment, and mitochondrial dysfunction. Here we highlight the clinical and molecular genetic features of each distinct disorder, and then discuss common themes in CAG-polyglutamine disease pathogenesis, closing with emerging advances in therapy development.

Rescue of ATXN3 neuronal toxicity in Caenorhabditiselegans by chemical modification of endoplasmic reticulum stress

Polyglutamine expansion diseases are a group of hereditary neurodegenerative disorders that develop when a CAG repeat in the causative genes is unstably expanded above a certain threshold. The expansion of trinucleotide CAG repeats causes hereditary adult-onset neurodegenerative disorders, such as Huntington's disease, dentatorubral–pallidoluysian atrophy, spinobulbar muscular atrophy and multiple forms of spinocerebellar ataxia (SCA). The most common dominantly inherited SCA is the type 3 (SCA3), also known as Machado–Joseph disease (MJD), which is an autosomal dominant, progressive neurological disorder. The gene causatively associated with MJD is ATXN3. Recent studies have shown that this gene modulates endoplasmic reticulum (ER) stress. We generated transgenic Caenorhabditiselegans strains expressing human ATXN3 genes in motoneurons, and animals expressing mutant ATXN3-CAG89 alleles showed decreased lifespan, impaired movement, and rates of neurodegeneration greater than wild-type ATXN3-CAG10 controls. We tested three neuroprotective compounds (Methylene Blue, guanabenz and salubrinal) believed to modulate ER stress and observed that these molecules rescued ATXN3-CAG89 phenotypes. Furthermore, these compounds required specific branches of the ER unfolded protein response (UPR^ER), reduced global ER and oxidative stress, and polyglutamine aggregation. We introduce new C. elegans models for MJD based on the expression of full-length ATXN3 in a limited number of neurons. Using these models, we discovered that chemical modulation of the UPR^ER reduced neurodegeneration and warrants investigation in mammalian models of MJD.

Summary: We introduce a novel C. elegans model for Machado–Joseph disease for use in preclinical drug discovery and identified guanabenz as a potent neuroprotective molecule.

Deregulation of autophagy in postmortem brains of Machado-Joseph disease patients

Autophagy, the major pathway for protein turnover, is critical to maintain cellular homeostasis and has been implicated in neurodegenerative diseases. The aim of this research was to analyze the expression of autophagy markers in postmortem brains from Machado-Joseph disease (MJD) patients. The expression of autophagy markers in the cerebellum and the oculomotor nucleus from MJD patients and age-matched controls with no signs of neuropathology was inspected postmortem by immunohistochemistry (IHC) and Western blot. Furthermore, autophagy was examined by means of transmission electron microscopy (TEM). Western blot and IHC revealed nuclear accumulation of misfolded ataxin-3 (ATXN3) and the presence of ubiquitin- and p62-positive aggregates in MJD patients as compared to controls. Moreover, the autophagic proteins, autophagy-related gene (Atg) protein (ATG)-7, ATG-12, ATG16L2 and autophagosomal microtubule-associated protein light chain 3 (LC3) were significantly increased in MJD brains relative to controls, while beclin-1 levels were reduced in MJD patients. Increase in the levels of lysosomal-associated membrane protein 2 (LAMP-2) and of the endosomal markers (Rab7 and Rab1A) were observed in MJD patients relatively to controls. In addition, these findings were further confirmed by TEM in brain tissue where large vesicles accumulating electron-dense materials were highly enriched in MJD patients. Postmortem brains with MJD exhibit increased markers of autophagy relative to age-matched control brains, therefore suggesting strong dysregulation of autophagy that may have an important role in the course of MJD pathogenesis.

n-Butylidenephthalide exhibits protection against neurotoxicity through regulation of tryptophan 2, 3 dioxygenase in spinocerebellar ataxia type 3

Spinocerebellar ataxia type 3 or Machado-Joseph disease (SCA3/MJD) is characterized by the repetition of a CAG codon in the ataxin-3 gene (ATXN3), which leads to the formation of an elongated mutant ATXN3 protein that can neither be denatured nor undergo proteolysis in the normal manner. This abnormal proteolysis leads to the accumulation of cleaved fragments, which have been identified as toxic and further they act as a seed for more aggregate formation, thereby increasing toxicity in neuronal cells. To date, there have been few studies or treatment strategies that have focused on controlling toxic fragment formation. The aim of this study is to develop a potential treatment strategy for addressing the complications of toxic fragment formation and to provide an alternative treatment strategy for SCA3. Our preliminary data on anti-aggregation and toxic fragment formation using an HEK (human embryonic kidney cells) 293T-84Q-eGFP (green fluorescent protein) cell model identified n-butylidenephthalide (n-BP) as a potential drug treatment for SCA3. n-BP decreased toxic fragment formation in both SCA3 cell and animal models. Moreover, results showed that n-BP can improve gait, motor coordination, and activity in SCA3 mice. To comprehend the molecular basis behind the control of toxic fragment formation, we used microarray analysis to identify tryptophan metabolism as a major player in controlling the fate of mutant ATXN3 aggregates. We also demonstrated that n-BP functions by regulating the early part of the kynurenine pathway through the downregulation of tryptophan 2, 3-dioxygenase (TDO2), which decreases the downstream neurotoxic product, quinolinic acid (QA). In addition, through the control of TDO2, n-BP also decreases active calpain levels, an important enzyme involved in the proteolysis of mutant ATXN3, thereby decreasing toxic fragment formation and associated neurotoxicity. Collectively, these findings indicate a correlation between n-BP, TDO2, QA, calpain, and toxic fragment formation. Thus, this study contributes to a better understanding of the molecular interactions involved in SCA3, and provides a novel potential treatment strategy for this neurodegenerative disease.

Using the shared genetics of dystonia and ataxia to unravel their pathogenesis

In this review we explore the similarities between spinocerebellar ataxias and dystonias, and suggest potentially shared molecular pathways using a gene co-expression network approach. The spinocerebellar ataxias are a group of neurodegenerative disorders characterized by coordination problems caused mainly by atrophy of the cerebellum. The dystonias are another group of neurological movement disorders linked to basal ganglia dysfunction, although evidence is now pointing to cerebellar involvement as well. Our gene co-expression network approach identified 99 shared genes and showed the involvement of two major pathways: synaptic transmission and neurodevelopment. These pathways overlapped in the two disorders, with a large role for GABAergic signaling in both. The overlapping pathways may provide novel targets for disease therapies. We need to prioritize variants obtained by whole exome sequencing in the genes associated with these pathways in the search for new pathogenic variants, which can than be used to help in the genetic counseling of patients and their families.

CAG repeat length does not associate with the rate of cerebellar degeneration in spinocerebellar ataxia type 3

This cross-sectional study investigated the correlation between the CAG repeat length and the degeneration of cerebellum in spinocerebellar ataxia type 3 (SCA3) patients based on neuroimaging approaches. Forty SCA3 patients were recruited and classified into two subgroups according to their CAG repeat lengths (≥ 74 and < 74). We measured each patient's Scale for the Assessment and Rating of Ataxia (SARA) score, N-acetylaspartate (NAA)/creatine (Cr) ratios based on magnetic resonance spectroscopy (MRS), and 3-dimensional fractal dimension (3D-FD) values derived from magnetic resonance imaging (MRI) results. Furthermore, the 3D-FD values were used to construct structural covariance networks based on graph theoretical analysis. The results revealed that SCA3 patients with a longer CAG repeat length demonstrated earlier disease onset. However, the CAG repeat length did not significantly correlate with their SARA scores, cerebellar NAA/Cr ratios or cerebellar 3D-FD values. Network dissociation between cerebellar regions and parietal-occipital regions was found in SCA3 patients with CAG ≥ 74, but not in those with CAG < 74. In conclusion, the CAG repeat length is uncorrelated with the change of SARA score, cerebellar function and cerebellar structure in SCA3. Nevertheless, a longer CAG repeat length may indicate early structural covariance network dissociation.

Mitochondrial NADH Dehydrogenase Subunit 3 Polymorphism Associated with an Earlier Age at Onset in Male Machado-Joseph disease Patients

AIMS

To investigate the potential effect of six previously reported candidate single nucleotide polymorphisms on age at onset (AAO) among Chinese patients with Machado-Joseph disease (MJD).

METHODS

Three hundred and twenty-four unrelated molecular-confirmed MJD patients were recruited between January 2006 and December 2014. The screening of candidate polymorphisms was first performed in 173 subjects using the SNaPshot(®) Multiplex System. The mitochondrial NADH dehydrogenase subunit 3 (MT-ND3) polymorphism 10398A>G (rs2853826) was further verified with Sanger sequencing in additional 151 patients.

RESULTS

An inverse correlation was found between expanded CAG repeat length and AAO. The expanded CAG repeat length can explain 63% of AAO variance. The 10398A polymorphism was significantly associated with a 3-year earlier AAO in male patients with MJD (P = 0.001). Stepwise multiple regressions revealed that the 10398A polymorphism could account for nearly 2% of AAO variance in male patients.

CONCLUSION

Six candidate SNPs have been screened in Chinese patients with MJD. A remarkable earlier AAO was noted in male Chinese MJD patients with MT-ND3 gene 10398A polymorphism.

Population genetics and new insight into range of CAG repeats of spinocerebellar ataxia type 3 in the Han Chinese population

Spinocerebellar ataxia type 3 (SCA3), also called Machado-Joseph disease (MJD), is one of the most common SCAs worldwide and caused by a CAG repeat expansion located in ATXN3 gene. Based on the CAG repeat numbers, alleles of ATXN3 can be divided into normal alleles (ANs), intermediate alleles (AIs) and expanded alleles (AEs). It was controversial whether the frequency of large normal alleles (large ANs) is related to the prevalence of SCA3 or not. And there were huge chaos in the comprehension of the specific numbers of the range of CAG repeats which is fundamental for genetic analysis of SCA3. To illustrate these issues, we made a novel CAG repeat ladder to detect CAG repeats of ATXN3 in 1003 unrelated Chinese normal individuals and studied haplotypes defined by three single nucleotide polymorphisms (SNPs) closed to ATXN3. We found that the number of CAG repeats ranged from 13 to 49, among them, 14 was the most common number. Positive skew, the highest frequency of large ANs and 4 AIs which had never been reported before were found. Also, AEs and large ANs shared the same haplotypes defined by the SNPs. Based on these data and other related studies, we presumed that de novo mutations of ATXN3 emerging from large ANs are at least one survival mechanisms of mutational ATXN3 and we can redefine the range of CAG repeats as: ANs≤44, 45 ≤AIs ≤49 and AEs≥50.

Toward therapeutic targets for SCA3: Insight into the role of Machado-Joseph disease protein ataxin-3 in misfolded proteins clearance

Machado-Joseph disease (MJD, also known as spinocerebellar ataxia type 3, SCA3), an autosomal dominant neurological disorder, is caused by an abnormal expanded polyglutamine (polyQ) repeat in the ataxin-3 protein. The length of the expanded polyQ stretch correlates positively with the severity of the disease and inversely with the age at onset. To date, we cannot fully explain the mechanism underlying neurobiological abnormalities of this disease. Yet, accumulating reports have demonstrated the functions of ataxin-3 protein in the chaperone system, ubiquitin-proteasome system, and aggregation-autophagy, all of which suggest a role of ataxin-3 in the clearance of misfolded proteins. Notably, the SCA3 pathogenic form of ataxin-3 (ataxin-3(exp)) impairs the misfolded protein clearance via mechanisms that are either dependent or independent of its deubiquitinase (DUB) activity, resulting in the accumulation of misfolded proteins and the progressive loss of neurons in SCA3. Some drugs, which have been used as activators/inducers in the chaperone system, ubiquitin-proteasome system, and aggregation-autophagy, have been demonstrated to be efficacious in the relief of neurodegeneration diseases like Huntington's disease (HD), Parkinson's (PD), Alzheimer's (AD) as well as SCA3 in animal models and clinical trials, putting misfolded protein clearance on the list of potential therapeutic targets. Here, we undertake a comprehensive review of the progress in understanding the physiological functions of ataxin-3 in misfolded protein clearance and how the polyQ expansion impairs misfolded protein clearance. We then detail the preclinical studies targeting the elimination of misfolded proteins for SCA3 treatment. We close with future considerations for translating these pre-clinical results into therapies for SCA3 patients.

Change in the cortical complexity of spinocerebellar ataxia type 3 appears earlier than clinical symptoms

Patients with spinocerebellar ataxia type 3 (SCA3) have exhibited cerebral cortical involvement and various mental deficits in previous studies. Clinically, conventional measurements, such as the Mini-Mental State Examination (MMSE) and electroencephalography (EEG), are insensitive to cerebral cortical involvement and mental deficits associated with SCA3, particularly at the early stage of the disease. We applied a three-dimensional fractal dimension (3D-FD) method, which can be used to quantify the shape complexity of cortical folding, in assessing cortical degeneration. We evaluated 48 genetically confirmed SCA3 patients by employing clinical scales and magnetic resonance imaging and using 50 healthy participants as a control group. According to the Scale for the Assessment and Rating of Ataxia (SARA), the SCA3 patients were diagnosed with cortical dysfunction in the cerebellar cortex; however, no significant difference in the cerebral cortex was observed according to the patients’ MMSE ratings. Using the 3D-FD method, we determined that cortical involvement was more extensive than involvement of traditional olivopontocerebellar regions and the corticocerebellar system. Moreover, the significant correlation between decreased 3D-FD values and disease duration may indicate atrophy of the cerebellar cortex and cerebral cortex in SCA3 patients. The change of the cerebral complexity in the SCA3 patients can be detected throughout the disease duration, especially it becomes substantial at the late stage of the disease. Furthermore, we determined that atrophy of the cerebral cortex may occur earlier than changes in MMSE scores and EEG signals.

Inactivation of PNKP by mutant ATXN3 triggers apoptosis by activating the DNA damage-response pathway in SCA3

Spinocerebellar ataxia type 3 (SCA3), also known as Machado-Joseph disease (MJD), is an untreatable autosomal dominant neurodegenerative disease, and the most common such inherited ataxia worldwide. The mutation in SCA3 is the expansion of a polymorphic CAG tri-nucleotide repeat sequence in the C-terminal coding region of the ATXN3 gene at chromosomal locus 14q32.1. The mutant ATXN3 protein encoding expanded glutamine (polyQ) sequences interacts with multiple proteins in vivo, and is deposited as aggregates in the SCA3 brain. A large body of literature suggests that the loss of function of the native ATNX3-interacting proteins that are deposited in the polyQ aggregates contributes to cellular toxicity, systemic neurodegeneration and the pathogenic mechanism in SCA3. Nonetheless, a significant understanding of the disease etiology of SCA3, the molecular mechanism by which the polyQ expansions in the mutant ATXN3 induce neurodegeneration in SCA3 has remained elusive. In the present study, we show that the essential DNA strand break repair enzyme PNKP (polynucleotide kinase 3'-phosphatase) interacts with, and is inactivated by, the mutant ATXN3, resulting in inefficient DNA repair, persistent accumulation of DNA damage/strand breaks, and subsequent chronic activation of the DNA damage-response ataxia telangiectasia-mutated (ATM) signaling pathway in SCA3. We report that persistent accumulation of DNA damage/strand breaks and chronic activation of the serine/threonine kinase ATM and the downstream p53 and protein kinase C-δ pro-apoptotic pathways trigger neuronal dysfunction and eventually neuronal death in SCA3. Either PNKP overexpression or pharmacological inhibition of ATM dramatically blocked mutant ATXN3-mediated cell death. Discovery of the mechanism by which mutant ATXN3 induces DNA damage and amplifies the pro-death signaling pathways provides a molecular basis for neurodegeneration due to PNKP inactivation in SCA3, and for the first time offers a possible approach to treatment.

The merit of proton magnetic resonance spectroscopy in the longitudinal assessment of spinocerebellar ataxias and multiple system atrophy-cerebellar type

BACKGROUND

Spinocerebellar ataxia (SCA) and multiple system atrophy-cerebellar type (MSA-C) often present with similar clinical manifestations in the beginning. Magnetic resonance spectroscopy (MRS) has been proved to be a useful tool to help differentiate different types of SCA and MSA-C on cross-sectional studies. However, longitudinal changes of the MRS metabolites in these subjects have never been reported. The purpose of this study was to track the longitudinal evolution of the MRS metabolites in these patients and to ascertain the correlation between clinical severity measured by Scale of the Assessment and Rating of Ataxia (SARA) and MRS metabolites.

RESULTS

Significant reductions of NAA/Cr and NAA/Cho in the cerebellar hemispheres in all patients and lower Cho/Cr in the cerebellar hemispheres in patients with SCA2 or MSA-C were found at all times. At initial assessments, patients with MSA-C or SCA2 tended to have lower NAA/Cr and Cho/Cr in the cerebellar hemispheres than those with SCA3 or SCA6. At follow-ups, patients with SCA2 or MSA-C had a lower NAA/Cr in cerebellar hemispheres than those with SCA3 or SCA6. Patients with MSA-C had a lower NAA/Cr in the vermis and Cho/Cr in the cerebellar hemispheres than those with SCA2 at the start, and had a lower NAA/Cr in cerebellar hemispheres than those with SCA2 at follow-ups.

CONCLUSION

Characteristic patterns of neurodegenerative evolution were observed in patients with disparate SCAs and MSA-C using MRS and SARA. A continual impairment of neuronal integrity was observed in all groups of patients. The longitudinal changes of MRS metabolites and SARA scores were most striking in patients with SCA2 and MSA-C. Although the changes in the metabolites on MRS may still be used to help understand the pathophysiology of ataxia disorders, they are short of being a good biomarker.

The role of apolipoprotein E as a risk factor for an earlier age at onset for Machado-Joseph disease is doubtful

Machado-Joseph disease (MJD) is an inherited neurodegenerative disease caused by an expanded CAG repeat in the ATXN3 gene. Although the principal genetic determinant of the age at onset (AAO) is the length of the expanded CAG repeat, the additional genetic contribution of MJD toward the AAO has mostly not yet been clarified. It was recently suggested in two independent studies that apolipoprotein E (APOE) might be associated with AAO variability in MJD patients. To identify the potential modifier effect of APOE polymorphisms on the AAO of MJD patients, 403 patients with MJD (confirmed by molecular tests) from eastern and southeastern China were enrolled in the present study. CAG repeats in the ATXN3 and APOE polymorphisms were genotyped. Data were analyzed using a statistical package. No contribution of APOE polymorphisms to the variance in disease onset was observed using ANCOVA (F = 0.183, P = 0.947). However, significant effects on the AAO of MJD were found for the normal ATXN3 allele and for the interaction of mutant and normal ATXN3 alleles in a multiple linear regression model (P = 0.043 and P = 0.035, respectively). Our study does not support a role for APOE as a genetic modifier of the AAO of MJD. Additionally, our study presents evidence that the normal ATXN3 allele and its interaction with mutant alleles contribute toward AAO variance in MJD patients.

RNA interference mitigates motor and neuropathological deficits in a cerebellar mouse model of Machado-Joseph disease

Machado-Joseph disease or Spinocerebellar ataxia type 3 is a progressive fatal neurodegenerative disorder caused by the polyglutamine-expanded protein ataxin-3. Recent studies demonstrate that RNA interference is a promising approach for the treatment of Machado-Joseph disease. However, whether gene silencing at an early time-point is able to prevent the appearance of motor behavior deficits typical of the disease when initiated before onset of the disease had not been explored. Here, using a lentiviral-mediated allele-specific silencing of mutant ataxin-3 in an early pre-symptomatic cerebellar mouse model of Machado-Joseph disease we show that this strategy hampers the development of the motor and neuropathological phenotypic characteristics of the disease. At the histological level, the RNA-specific silencing of mutant ataxin-3 decreased formation of mutant ataxin-3 aggregates, preserved Purkinje cell morphology and expression of neuronal markers while reducing cell death. Importantly, gene silencing prevented the development of impairments in balance, motor coordination, gait and hyperactivity observed in control mice. These data support the therapeutic potential of RNA interference for Machado-Joseph disease and constitute a proof of principle of the beneficial effects of early allele-specific silencing for therapy of this disease.

Ocular motor characteristics of different subtypes of spinocerebellar ataxia: distinguishing features

Because of frequent involvement of the cerebellum and brainstem, ocular motor abnormalities are key features of spinocerebellar ataxias and may aid in differential diagnosis. Our objective for this study was to distinguish the subtypes by ophthalmologic features after head-shaking and positional maneuvers, which are not yet recognized as differential diagnostic tools in most common forms of spinocerebellar ataxias. Of the 302 patients with a diagnosis of cerebellar ataxia in 3 Korean University Hospitals from June 2011 to June 2012, 48 patients with spinocerebellar ataxia types 1, 2, 3, 6, 7, or 8 or with undetermined spinocerebellar ataxias were enrolled. All patients underwent a video-oculographic recording of fixation abnormalities, gaze-evoked nystagmus, positional and head-shaking nystagmus, and dysmetric saccades. Logistic regression analysis controlling for disease duration revealed that spontaneous and positional downbeat nystagmus and perverted head-shaking nystagmus were strong predictors for spinocerebellar ataxia 6, whereas saccadic intrusions and oscillations were identified as positive indicators of spinocerebellar ataxia 3. In contrast, the presence of gaze-evoked nystagmus and dysmetric saccades was a negative predictor of spinocerebellar ataxia 2. Positional maneuvers and horizontal head shaking occasionally induced or augmented saccadic intrusions/oscillations in patients with spinocerebellar ataxia types 1, 2, and 3 and undetermined spinocerebellar ataxia. The results indicated that perverted head-shaking nystagmus may be the most sensitive parameter for SCA6, whereas saccadic intrusions/oscillations are the most sensitive for spinocerebellar ataxia 3. In contrast, a paucity of gaze-evoked nystagmus and dysmetric saccades is more indicative of spinocerebellar ataxia 2. Head-shaking and positional maneuvers aid in defining ocular motor characteristics in spinocerebellar ataxias. © 2013 Movement Disorder Society.

Chinese patients with spinocerebellar ataxia type 3 presenting with rare clinical symptoms

Clinical heterogeneity is the prominent feature of spinocerebellar ataxia type 3 (SCA3) which is sometimes neglected and often impedes the timely diagnosis of patients. In this study, the clinical data of 201 unrelated Chinese SCA3 patients were retrospectively studied. The rare clinical features were summarized and the underlying genetic mutations were screened by direct DNA sequencing. Three patients were found primarily presenting with the rare clinical features, including dystonic phenotype without response to levodopa, chorea and memory decline, and hearing impairment, respectively. We firstly reported three diverse heterogeneities of SCA3 patients, which are quite uncommon in the Chinese SCA3 patients. Our results expanded the variable phenotypes of SCA3 and provided the explicit information for the rare and special SCA3 manifestations. Based on this new knowledge, we suggested that when the presentation was consistent with HD or DRD while negative in the corresponding genetic testing, SCA3 should be considered, and clinicians should divert partial attention to the examinations on the auditory system of SCA3 patients.

Differences between spinocerebellar ataxias and multiple system atrophy-cerebellar type on proton magnetic resonance spectroscopy

Purpose

A broad spectrum of diseases can manifest cerebellar ataxia. In this study, we investigated whether proton magnetic resonance spectroscopy (MRS) may help differentiate spinocerebellar ataxias (SCA) from multiple systemic atrophy- cerebellar type (MSA-C).

Material and Methods

This prospective study recruited 156 patients with ataxia, including spinocerebellar ataxia (SCA) types 1, 2, 3, 6 and 17 (N = 94) and MSA-C (N = 62), and 44 healthy controls. Single voxel proton MRS in the cerebellar hemispheres and vermis were measured. The differences were evaluated using nonparametric statistic tests.

Results

When compared with healthy controls, the cerebellar and vermis NAA/Cr and NAA/Cho were lower in all patients(p<0.002). The Cho/Cr was lower in SCA2 and MSA-C (p<0.0005). The NAA/Cr and Cho/Cr were lower in MSA-C or SCA2 comparing with SCA3 or SCA6. The MRS features of SCA1 were in between (p<0.018). The cerebellar NAA/Cho was lower in SCA2 than SCA1, SCA3 or SCA6 (p<0.04). The cerebellar NAA/Cho in MSA-C was lower than SCA3 (p<0.0005). In the early stages of diseases (SARA score<10), significant lower NAA/Cr and NAA/Cho in SCA2, SCA3, SCA6 or MSA-C were observed comparing with healthy controls (p<0.017). The Cho/Cr was lower in MSA-C or SCA2 (p<0.0005). Patients with MSA-C and SCA2 had lower NAA/Cr and Cho/Cr than SCA3 or SCA6 (p<0.016).

Conclusion

By using MRS, significantly lower NAA/Cr, Cho/Cr and NAA/Cho in the cerebellar hemispheres and vermis were found in patients with ataxia (SCAs and MSA-C). Rapid neuronal degeneration and impairment of membrane activities were observed more often in patients with MSA-C than those with SCA, even in early stages. MRS could also help distinguish between SCA2 and other subtypes of SCAs. MRS ratios may be of use as biomarkers in early stages of disease and should be further assessed in a longitudinal study.

Association between proton magnetic resonance spectroscopy measurements and CAG repeat number in patients with spinocerebellar ataxias 2, 3, or 6

The aim of this study was to correlate magnetic resonance spectroscopy (MRS) measurements, including that for the N-acetyl aspartate (NAA)/creatine (Cr) ratio in the vermis (denoted V-NAA), right cerebellar hemisphere (R-NAA), and left (L-NAA) cerebellar hemisphere, with the clinical scale for the assessment and rating of ataxia (SARA) score for patients with spinocerebellar ataxia (SCA) types 2, 3, and 6. A total of 24 patients with SCA2, 48 with SCA3, and 16 with SCA6 were recruited; 12 patients with SCA2, 43 with SCA3, and 8 with SCA6 underwent detailed magnetic resonance neuroimaging. Forty-four healthy, age-matched individuals without history of neurologic disease served as control subjects. V-NAA and patient age were used to calculate the predicted age at which a patient with SCA2 or SCA3 would reach an onset V-NAA value. Results showed the following: the NAA/Cr ratio decreased with increasing age in patients with SCA but not in control subjects; the SARA score increased progressively with age and duration of illness; V-NAA showed a better correlation with SARA score than R-NAA in patients with SCA2 or SCA3; the ratio of age to V-NAA correlated well with CAG repeat number; the retrospectively predicted age of onset for SCA2 and SCA3 was consistent with patient-reported age of onset; R-NAA showed a better correlation with SARA score than V-NAA in patients with SCA6; V-NAA and R-NAA correlated with clinical severity (SARA score) in patients with SCA. The correlation between CAG repeat number and age could be expressed as a simple linear function, which might explain previous observations claiming that the greater the CAG repeat number, the earlier the onset of illness and the faster the disease progression. These findings support the use of MRS values to predict age of disease onset and to retrospectively evaluate the actual age of disease onset in SCA.

Machado-Joseph disease/spinocerebellar ataxia type 3

Machado-Joseph disease (MJD), also known as spinocerebellar ataxia type 3 (SCA3), may be the most common dominantly inherited ataxia in the world. Here I will review historical, clinical, neuropathological, genetic, and pathogenic features of MJD, and finish with a brief discussion of present, and possible future, treatment for this currently incurable disorder. Like many other dominantly inherited ataxias, MJD/SCA3 shows remarkable clinical heterogeneity, reflecting the underlying genetic defect: an unstable CAG trinucleotide repeat that varies in size among affected persons. This pathogenic repeat in MJD/SCA3 encodes an expanded tract of the amino acid glutamine in the disease protein, which is known as ataxin-3. MJD/SCA3 is one of nine identified polyglutamine neurodegenerative diseases which share features of pathogenesis centered on protein misfolding and accumulation. The specific properties of MJD/SCA3 and its disease protein are discussed in light of what is known about the entire class of polyglutamine diseases.

A new sulcus-corrected approach for assessing cerebellar volume in spinocerebellar ataxia

Precise volumetry of the cerebellum still remains challenging, due to thin sulci and gyri. We present a new fast and reliable sulcus-corrected approach for quantitative assessment of cerebellar atrophy, evaluated on patients with spinocerebellar ataxia (SCA). Thin-sliced T1-weighted magnetic resonance images (MPRAGE) were acquired in 11 genetically confirmed SCA6 patients and in a group of age-matched control subjects (n=14). Post-processing involves a morphological image segmentation pipeline as a basis for a sulcus-corrected cerebellar volume measurement. Cerebellar volumes and intra-rater, inter-rater and scan-rescan reproducibility were quantified. Reliability of the measurements was validated using an anatomical preparation of the cerebellum. Repeatability coefficients (RC: intra-rater/inter-rater/scan-rescan) of the method were 1.07%/1.11%/1.35%. Absolute cerebellar volumes showed good agreement with the actual volume of the anatomical preparation. The cerebellar volume of the SCA 6 was 96.3±12.1ml (mean±S.D.), which was significantly lower than the results of the corresponding control groups. The cerebellar volume correlated significantly to clinical dysfunction in SCA6. This is the first study to demonstrate the feasibility of a new sulcus-corrected approach to assess cerebellar volume. In contrast to currently used methods, this new approach may be more sensitive even to small atrophic changes affecting sulcal widening.

Multimodal neurophysiological study of SCA2 and SCA3 autosomal dominant hereditary spinocerebellar ataxias

BACKGROUND

The spinocerebellar ataxias (SCA) are a group of genetic neurodegenerative diseases, clinically and pathologically heterogeneous, characterized by slowly progressive cerebellar ataxia.

OBJECTIVE

To identify the neural pathways affected neurophysiologically, correlate the findings with the size of CAG expansion and determine the contribution of neurophysiological studies in the differential diagnosis of the two most prevalent genotypes in Spain, SCA2 and SCA3.

METHOD

We examined 10 SCA2 and 12 SCA3 patients by electromyography, electroneurography motor and sensory, multimodal evoked potentials, transcranial magnetic stimulation, blink reflex and masseter reflex. In the statistical analysis linear regression studies were performed, and the, Spearman correlation coefficient and nonparametric test U of Mann-Whitney calculated.

RESULTS

We detected the presence of a predominantly sensory neuropathy in most SCA2 patients and in a minority of SCA3 patients; the central somatosensory pathway showed significant defects in both populations. We recorded a high incidence of brain-stem electrophysiological abnormalities in SCA2 patients; in particular, the masseter reflex was abnormal in all SCA2 patients, remaining intact in all SCA3 patients. The study of cortico-spinal pathway showed a greater percentage of abnormalities in both populations than in previous studies.

CONCLUSION

SCA2 is a model of sensory neuronopathy with central and peripheral axonopathy. Studies of brain-stem pathways show a higher incidence of abnormalities in SCA2 patients. SCA3 patients show major changes in the central somatosensory pathway with relative normality of the electroneurography. The masseter reflex was the most useful test in the differential diagnosis between both genotypes.

Spinocerebellar ataxias: microsatellite and allele frequency in unaffected and affected individuals

The diagnosis and incidence of spinocerebelar ataxias (SCA) is sometimes difficult to analyze due the overlap of phenotypes subtypes and are disorders of mutations caused by CAG trinucleotide repeat expansion. To investigate the incidence of the SCA in Southern Brazil, we analyzed the trinucleotide repeats (CAG)n at the SCA1, SCA2, SCA3, SCA6 and SCA7 loci to identify allele size ranges and frequencies. We examined blood sample from 154 asymptomatic blood donors and 115 individuals with progressive ataxias. PCR products were submitted to capillary electrophoresis. In the blood donors, the ranges of the five loci were: SCA1, 19 to 36 (CAG)n; SCA2, 6 to 28 (CAG)n; SCA3, 12 to 34 (CAG)n; SCA6, 2 to 13 (CAG)n; and SCA7, 2 to 10 (CAG)n. No deviations from Hardy-Weinberg equilibrium were detected. In the ataxia group, we found (CAG)n above the range of the asymptomatic blood donors in SCA3 (21.74%) followed by SCA2 (5.22%), SCA7 (2.61%), SCA6 (0.87%), and no cases of SCA1. The remaining 80 cases (69.56%) have different diagnoses from the type here studied. These data defined the alleles and their frequencies, as well as demonstrated their stability in the population not affected. The molecular diagnosis test confirmed the clinical diagnosis in 28/45 cases and classified another 7/70 from the clinical unclassified ataxias group.

High frequency of Machado-Joseph disease identified in southeastern Chinese kindreds with spinocerebellar ataxia

Background

Machado-Joseph disease (MJD), caused by a CAG repeat expansion located in exon10 of the ATXN3 gene, is now regarded as one of the most common spinocerebellar ataxia (SCA) in the world. The relative frequency of MJD among SCA has previously been estimated at about 50% in the Chinese population and has been reported to be related to the frequency of large normal alleles in some populations. Taq polymerase has been used for PCR in nearly all studies reported previously.

Methods

Normal and expanded alleles of ATXN3 were detected via PCR using LA Taq DNA polymerase (better for GC-rich sequences) and denaturing polyacrylamide gel electrophoresis in 150 normal individuals and 138 unrelated probands from autosomal dominant SCA families. To compare reaction efficiency, 12 MJD patients' expanded alleles were amplified with La Taq and Taq polymerase respectively in the same amplifying systems and reaction conditions.

Results

Normal alleles ranged from 12 to 42 CAG repeats. The most common allele contained 14 repeats with a frequency of 23.3%, which corroborates previous reports. The frequency of large normal alleles (>27 repeats) was 0.28, which was very high relative to previous reports. The frequency of MJD in SCA patients was 72.5%, which was significantly higher than those in previous reports about the Chinese and other Asian populations. This frequency was one of the highest reported worldwide, with only Portuguese and Brazilian populations exhibiting higher proportions. All 12 expanded alleles were amplified in PCR with La Taq polymerase, whereas only 2 expanded alleles were amplified with Taq polymerase.

Conclusion

We have first reported the highest relative frequency of MJD in Asia, and we attribute this high frequency to a more efficient PCR using LA Taq polymerase and hypothesized that large ANs may act as a reservoir for expanded alleles in the Southeastern Chinese population.

Silencing ataxin-3 mitigates degeneration in a rat model of Machado-Joseph disease: no role for wild-type ataxin-3?

Machado-Joseph disease or spinocerebellar ataxia type 3 (MJD/SCA3) is a fatal, autosomal dominant disorder caused by a cytosine-adenine-guanine expansion in the coding region of the MJD1 gene. RNA interference has potential as a therapeutic approach but raises the issue of the role of wild-type ataxin-3 (WT ATX3) in MJD and of whether the expression of the wild-type protein must be maintained. To address this issue, we both overexpressed and silenced WT ATX3 in a rat model of MJD. We showed that (i) overexpression of WT ATX3 did not protect against MJD pathology, (ii) knockdown of WT ATX3 did not aggravate MJD pathology and that (iii) non-allele-specific silencing of ataxin-3 strongly reduced neuropathology in a rat model of MJD. Our findings indicate that therapeutic strategies involving non-allele-specific silencing to treat MJD patients may be safe and effective.

Reversibility of symptoms in a conditional mouse model of spinocerebellar ataxia type 3

Spinocerebellar ataxia type 3 (SCA3) is caused by the expansion of a CAG repeat tract that affects the MJD1 gene which encodes the ataxin-3 protein. In order to analyze whether symptoms caused by ataxin-3 with an expanded repeat are reversible in vivo, we generated a conditional mouse model of SCA3 using the Tet-Off system. We used a full-length human ataxin-3 cDNA with 77 repeats in order to generate the responder mouse line. After crossbreeding with a PrP promoter mouse line, double transgenic mice developed a progressive neurological phenotype characterized by neuronal dysfunction in the cerebellum, reduced anxiety, hyperactivity, impaired Rotarod performance and lower body weight gain. When ataxin-3 expression was turned off in symptomatic mice in an early disease state, the transgenic mice were indistinguishable from negative controls after 5 months of treatment. These results show that reducing the production of pathogenic ataxin-3 indeed may be a promising approach to treat SCA3, provided that such treatment is applied before irreversible damage has taken place and that it is continued for a sufficiently long time.

Polyglutamine-expanded ataxin-3 causes cerebellar dysfunction of SCA3 transgenic mice by inducing transcriptional dysregulation

In the present study, we prepared a SCA3 animal model by generating transgenic mice expressing polyglutamine-expanded ataxin-3-Q79. Ataxin-3-Q79 was expressed in brain areas implicated in SCA3 neurodegeneration, including cerebellum, pontine nucleus and substantia nigra. Ataxin-3-Q79 transgenic mice displayed motor dysfunction with an onset age of 5-6 months, and neurological symptoms deteriorated in the following months. A prominent neuronal loss was not found in the cerebellum of 10 to 11-month-old ataxin-3-Q79 mice displaying pronounced ataxic symptoms, suggesting that instead of neuronal demise, ataxin-3-Q79 causes neuronal dysfunction of the cerebellum and resulting ataxia. To test the involvement of transcriptional dysregulation in ataxin-3-Q79-induced cerebellar malfunction, microarray analysis and real-time RT-PCR assays were performed to identify altered cerebellar mRNA expressions of ataxin-3-Q79 mice. Compared to non-transgenic mice or mice expressing wild-type ataxin-3-Q22, 10 to 11-month-old ataxin-3-Q79 mice exhibited downregulated mRNA expressions of proteins involved in glutamatergic neurotransmission, intracellular calcium signaling/mobilization or MAP kinase pathways, GABA(A/B) receptor subunits, heat shock proteins and transcription factor regulating neuronal survival and differentiation. Upregulated expressions of Bax, cyclin D1 and CDK5-p39, which may mediate neuronal death, were also observed in ataxin-3-Q79 transgenic mice. The involvement of transcriptional abnormality in initiating the pathological process of SCA3 was indicated by the finding that 4 to 5-month-old ataxin-3-Q79 mice, which did not display neurological phenotype, exhibited downregulated mRNA levels of genes involved in glutamatergic signaling and signal transduction. Our study suggests that polyglutamine-expanded ataxin-3 causes cerebellar dysfunction and ataxia by disrupting the normal pattern of gene transcriptions.

Cognition in hereditary ataxia

Apart from motor control the cerebellum has been implicated in higher cortical functions such as memory, fronto-executive functions, visuoconstructive skills and emotion. Clinical descriptions of hereditary ataxias mention cognitive impairment to a variable extent. Systematic neuropsychological studies are limited. Regarding the neuropathological pattern in different SCA types, cognitive deficits in hereditary ataxias are not likely to be contingent upon cerebellar degeneration but to result from disruption of cerebrocerebellar circuitries at various levels in the CNS.

Linear T2 hyperintensity along the medial margin of the globus pallidus in patients with Machado-Joseph disease and Parkinson disease, and in healthy subjects

BACKGROUND AND PURPOSE

Linear hyperintensity along the medial margin of the internal segment of the globus pallidus (GPi) on T2-weighted images from patients with Machado-Joseph disease (MJD) was recently reported. In this study, we aimed to compare the prevalence of this linear hyperintensity between patients with MJD and patients with Parkinson disease, and in control subjects.

MATERIALS AND METHODS

We report the prevalence of linear hyperintensity along the GPi in 10 consecutive patients with MJD, 38 with Parkinson disease (PD), and 25 control subjects. We evaluated the prevalence of linear hyperintensities on T2-weighted axial images in these groups, and in nearly age-matched subjects younger than 60 years. We performed statistical analysis using the chi(2) test and Fisher exact test to compare the prevalence of the hyperintensity in each group.

RESULTS

The prevalence of the linear hyperintensity in patients with MJD was significantly higher than that in patients with PD and in control subjects (P = .014 and .006, respectively). In subjects younger than 60 years, the prevalence of the hyperintensity in patients with MJD was significantly higher than that in patients with PD and control subjects (P = .011 and P < .001, respectively). In the control subjects, the linear hyperintensity tended to be greater in subjects older than 60 years (8/14 [57%] patients) than in subjects younger than 60 years (2/11 [18%] patients; P = .058). In patients with PD, the prevalence did not differ between patients older than 60 years and patients younger than 60 years.

CONCLUSION

Linear hyperintensity along the globus pallidus is frequently found in patients with MJD, but it can be also found in patients with PD and in control subjects, probably because of the normal aging process.

Nuclear localization of ataxin-3 is required for the manifestation of symptoms in SCA3: in vivo evidence

Spinocerebellar ataxia type 3 (SCA3) is an autosomal dominantly inherited neurodegenerative disorder caused by the expansion of a CAG repeat in the MJD1 gene resulting in an expanded polyglutamine repeat in the ataxin-3 protein. To study the course of the disease, we generated transgenic mice for SCA3 using full-length ataxin-3 constructs containing 15, 70, or 148 CAG repeats, respectively. Control mice (15 CAGs) were phenotypically normal and had no neuropathological findings. However, mice transgenic for ataxin-3 with expanded polyglutamine repeats were severely affected by a strong neurological phenotype with tremor, behavioral deficits, strongly reduced motor and exploratory activity, a hunchback, and premature death at 3 to 6 months of age. Neuropathological examination by immunohistochemical staining revealed ubiquitin- and ataxin-3-positive intranuclear inclusion bodies in a multitude of neurons. Directing ataxin-3 with 148 CAGs to the nucleus revealed an even more pronounced phenotype with more inclusions and earlier death, whereas mice transgenic with the same construct but attached to a nuclear export signal developed a milder phenotype with less inclusions. These studies indicate that nuclear localization of ataxin-3 is required for the manifestation of symptoms in SCA3 in vivo.

Regional patterns of cerebral glucose metabolism in spinocerebellar ataxia type 2, 3 and 6 : a voxel-based FDG-positron emission tomography analysis

The purpose of this study was to investigate the regional patterns of cerebral metabolic deficits by voxel-based FDGPET analysis in patients with distinct spinocerebellar ataxia (SCA) genotypes, including SCA type 2 (SCA2), SCA3, and SCA6. Nine patients with SCA2, 12 with SCA3, seven with SCA6, and 23 healthy control subjects were recruited. The clinical severity of the patients' cerebellar ataxia was evaluated according to the International Cooperative Ataxia Rating Scale. The brain glucose metabolism was evaluated with 2- [fluorine 18]-fluoro-2-deoxy-D: -glucose (FDG) positron emission tomography. Group data were analyzed and compared by voxelbased analysis. In SCA2, FDG utilization was significantly reduced in the cerebellum, pons, parahippocampal gyrus and frontal cortex. In SCA3, FDG metabolism in the cerebellum, parahippocampal gyrus of the limbic system, and lentiform nucleus was decreased. In SCA6, FDG metabolism was diminished in the cerebellum and the frontal and prefrontal cortices. On group comparisons, while all SCAs have impaired cerebellar functions, the cerebellar FDG metabolism was most severely compromised in SCA2. Instead, the FDG metabolism in the lentiform nucleus and medulla was characteristically worst in SCA3. There was no brainstem involvement in SCA6.

Dissociation of grey and white matter reduction in spinocerebellar ataxia type 3 and 6: A voxel-based morphometry study

The aim of this study was to examine the different patterns of cerebellar and/or brainstem atrophy in spinocerebellar ataxia (SCA) type 3 and 6. Eighteen patients (SCA3 n=9, SCA6 n=9) and 15 healthy volunteers were studied. Voxel-based morphometry (VBM) was applied to segmented grey matter (GM) and white matter (WM) of high-resolution T1-weighted brain volumes of each group. We found reduction of grey matter in the pons as well as in the vermis in SCA3 as compared to control subjects. In SCA6 significant grey matter loss was found in hemispheric lobules bilaterally as well as in the vermis. White matter analysis revealed significant changes in SCA3, especially in the pons, in the white matter surrounding the dentate nucleus (DN) and in the cerebellar peduncles, whereas no significant white matter reduction was found in SCA6 patients. Our results demonstrate different patterns of grey and white matter affection detected by magnetic resonance imaging (MRI) in SCA3 and SCA6 patients, confirming the pathological concept of cortical cerebellar atrophy in SCA6. In contrast, SCA3 represents a form of ponto-cerebellar atrophy with predominant affection of pontine nuclei and fibre tracts.