Frequency analysis of autosomal dominant cerebellar ataxias in Taiwanese patients and clinical and molecular characterization of spinocerebellar ataxia type 6

Preconditioning of exosomes derived from human olfactory ensheathing cells improved motor coordination and balance in an SCA3/MJD mouse model: A new therapeutic approach

Exosome therapy is a novel trend in regeneration medicine. However, identifying a suitable biomarker that can associate the therapeutic efficacy of exosomes with SCA3/MJD is essential. In this study, parental cells were preconditioned with butylidenephthalide (Bdph) for exosome preparation to evaluate the therapeutic effect of SCA3/MJD. The therapeutic agent hsa-miRNA-6780-5p was enriched up to 98-fold in exosomes derived from butylidenephthalide (Bdph)-preconditioned human olfactory ensheathing cells (hOECs) compared with that in naïve hOECs exosomes. The particle sizes of exosomes derived from naïve hOECs and those derived from hOECs preconditioned with Bdph were approximately 113.0 ± 3.5 nm and 128.9 ± 0.7 nm, respectively. A liposome system was used to demonstrate the role of hsa-miRNA-6780-5p, wherein hsa-miRNA-6780-5p was found to enhance autophagy and inhibit the expression of spinocerebellar ataxia type 3 (SCA3) disease proteins with the polyglutamine (polyQ) tract. Exosomes with enriched hsa-miRNA-6780-5p were further applied to HEK-293-84Q cells, leading to decreased expression of polyQ and increased autophagy. The results were reversed when 3MA, an autophagy inhibitor, was added to the cells treated with hsa-miRNA-6780-5p-enriched exosomes, indicating that the decreased polyQ expression was modulated via autophagy. SCA3 mice showed improved motor coordination behavior when they intracranially received exosomes enriched with hsa-miRNA-6780-5p. SCA3 mouse cerebellar tissues treated with hsa-miRNA-6780-5p-enriched exosomes showed decreased expression of polyQ and increased expression of LC3II/I, an autophagy marker. In conclusion, our findings can serve as a basis for developing an alternative therapeutic strategy for SCA3 disease treatment using miRNA-enriched exosomes derived from chemically preconditioned cells.

An Overview of Soft Tissue Fillers for Cosmetic Dermatology: From Filling to Regenerative Medicine

Hyaluronic acid (HA)-based injectable filling agents are at the forefront of the current demand for noninvasive dermatological procedures for the correction of age-related soft tissue defects. The present review aims to summarize currently available HA-based products and critically appraise their differences in rheological nature and clinical application. Linear HA (LHA) gels may be supplemented with amino acids, lipoic acid, vitamins, nucleosides, or minerals for synergistic antiaging and antioxidant benefits (polycomponent LHA). HA hydrogels can be generated via chemical or physical crosslinking, which increases their elasticity and decreases viscosity. The performance of crosslinked fillers depends on HA concentration, degree of crosslinking, elastic modulus, cohesivity, and type of crosslinking agent employed. PEG-crosslinked LHA displays improved elasticity and resistance to degradation, and lower swelling rates as compared to BDDE-crosslinked LHA. Physical crosslinking stabilizes HA hydrogels without employing exogenous chemical compounds or altering hyaluronans’ natural molecular structure. Thermally stabilized hybrid cooperative HA complexes (HCC) are a formulation of high- and low-molecular-weight (H-HA and L-HA) hyaluronans, achieving high HA concentration, low viscosity with optimal tissue diffusion, and a duration comparable to weakly cross-linked gel. Our critical analysis evidences the importance of understanding different fillers’ properties to assist physicians in selecting the most appropriate filler for specific uses and for predictable and sustainable results.

A PIAS1 Protective Variant S510G Delays polyQ Disease Onset by Modifying Protein Homeostasis

BACKGROUND

Polyglutamine (polyQ) diseases are dominant neurodegenerative diseases caused by an expansion of the polyQ-encoding CAG repeats in the disease-causing gene. The length of the CAG repeats is the major determiner of the age at onset (AO) of polyQ diseases, including Huntington's disease (HD) and spinocerebellar ataxia type 3 (SCA3).

OBJECTIVE

We set out to identify common genetic variant(s) that may affect the AO of polyQ diseases.

METHODS

Three hundred thirty-seven patients with HD or SCA3 were enrolled for targeted sequencing of 583 genes implicated in proteinopathies. In total, 16 genes were identified as containing variants that are associated with late AO of polyQ diseases. For validation, we further investigate the variants of PIAS1 because PIAS1 is an E3 SUMO (small ubiquitin-like modifier) ligase for huntingtin (HTT), the protein linked to HD.

RESULTS

Biochemical analyses revealed that the ability of PIAS1^S510G to interact with mutant huntingtin (mHTT) was less than that of PIAS1^WT , resulting in lower SUMOylation of mHTT and lower accumulation of insoluble mHTT. Genetic knock-in of PIAS1^S510G in a HD mouse model (R6/2) ameliorated several HD-like deficits (including shortened life spans, poor grip strength and motor coordination) and reduced neuronal accumulation of mHTT.

CONCLUSIONS

Our findings suggest that PIAS1 is a genetic modifier of polyQ diseases. The naturally occurring variant, PIAS1^S510G , is associated with late AO in polyQ disease patients and milder disease severity in HD mice. Our study highlights the possibility of targeting PIAS1 or pathways governing protein homeostasis as a disease-modifying approach for treating patients with HD.

Spinocerebellar ataxias in Asia: Prevalence, phenotypes and management

This paper reviews and summarizes three main aspects of spinocerebellar ataxias (SCA) in the Asian population. First, epidemiological studies were comprehensively reviewed. Overall, the most common subtypes include SCA1, SCA2, SCA3, and SCA6, but there are large differences in the relative prevalence of these and other SCA subtypes between Asian countries. Some subtypes such as SCA12 and SCA31 are rather specific to certain Asian populations. Second, we summarized distinctive phenotypic manifestations of SCA patients of Asian origin, for example a frequent co-occurrence of parkinsonism in some SCA subtypes. Lastly, we have conducted an exploratory survey study to map SCA-specific expertise, resources, and management in various Asian countries. This showed large differences in accessibility, genetic testing facilities, and treatment options between lower and higher income Asian countries. Currently, many Asian SCA patients remain without a final genetic diagnosis. Lack of prevalence data on SCA, lack of patient registries, and insufficient access to genetic testing facilities hamper a wider understanding of these diseases in several (particularly lower income) Asian countries.

Polyglutamine Ataxias: Our Current Molecular Understanding and What the Future Holds for Antisense Therapies

Polyglutamine (polyQ) ataxias are a heterogenous group of neurological disorders all caused by an expanded CAG trinucleotide repeat located in the coding region of each unique causative gene. To date, polyQ ataxias encompass six disorders: spinocerebellar ataxia types 1, 2, 3, 6, 7, and 17 and account for a larger group of disorders simply known as polyglutamine disorders, which also includes Huntington's disease. These diseases are typically characterised by progressive ataxia, speech and swallowing difficulties, lack of coordination and gait, and are unfortunately fatal in nature, with the exception of SCA6. All the polyQ spinocerebellar ataxias have a hallmark feature of neuronal aggregations and share many common pathogenic mechanisms, such as mitochondrial dysfunction, impaired proteasomal function, and autophagy impairment. Currently, therapeutic options are limited, with no available treatments that slow or halt disease progression. Here, we discuss the common molecular and clinical presentations of polyQ spinocerebellar ataxias. We will also discuss the promising antisense oligonucleotide therapeutics being developed as treatments for these devastating diseases. With recent advancements and therapeutic approvals of various antisense therapies, it is envisioned that some of the studies reviewed may progress into clinical trials and beyond.

Spinocerebellar Ataxia Type 3: A Case Report and Literature Review

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

Collaborative Efforts for Spinocerebellar Ataxia Research in the United States: CRC-SCA and READISCA

Spinocerebellar ataxias are progressive neurodegenerative disorders primarily affecting the cerebellum. Although the first disease-causing gene was identified nearly 30 years ago, there is no known cure to date, and only a few options exist for symptomatic treatment, with modest effects. The recently developed tools in molecular biology, such as CRISPR/Cas9 and antisense oligonucleotides, can directly act on the disease mechanisms at the genomic or RNA level in disease models. In a nutshell, we are finally just one step away from clinical trials with therapies targeting the underlying genetic cause. However, we still face the challenges for rare neurodegenerative diseases: difficulty in obtaining a large cohort size for sufficient statistical power and the need for biomarkers and clinical outcome assessments (COA) with adequate sensitivity to reflect progression or treatment responses. To overcome these obstacles, ataxia experts form research networks for clinical trial readiness. In this review, we retrace our steps of the collaborative efforts among ataxia researchers in the United States over the years to study and treat these relentless disorders and the future directions of such research networks.

Identifying Therapeutic Targets for Spinocerebellar Ataxia Type 3/Machado-Joseph Disease through Integration of Pathological Biomarkers and Therapeutic Strategies

Spinocerebellar ataxia type 3/Machado-Joseph disease (SCA3/MJD) is a progressive motor disease with no broadly effective treatment. However, most current therapies are based on symptoms rather than the underlying disease mechanisms. In this review, we describe potential therapeutic strategies based on known pathological biomarkers and related pathogenic processes. The three major conclusions from the current studies are summarized as follows: (i) for the drugs currently being tested in clinical trials; a weak connection was observed between drugs and SCA3/MJD biomarkers. The only two exceptions are the drugs suppressing glutamate-induced calcium influx and chemical chaperon. (ii) For most of the drugs that have been tested in animal studies, there is a direct association with pathological biomarkers. We further found that many drugs are associated with inducing autophagy, which is supported by the evidence of deficient autophagy biomarkers in SCA3/MJD, and that there may be more promising therapeutics. (iii) Some reported biomarkers lack relatively targeted drugs. Low glucose utilization, altered amino acid metabolism, and deficient insulin signaling are all implicated in SCA3/MJD, but there have been few studies on treatment strategies targeting these abnormalities. Therapeutic strategies targeting multiple pathological SCA3/MJD biomarkers may effectively block disease progression and preserve neurological function.

The Relationship Between Zebrin Expression and Cerebellar Functions: Insights From Neuroimaging Studies

The cerebellum has long been known to play an important role in motor and balance control, and accumulating evidence has revealed that it is also involved in multiple cognitive functions. However, the evidence from neuroimaging studies and clinical observations is not well-integrated at the anatomical or molecular level. The goal of this review is to summarize and link different aspects of the cerebellum, including molecular patterning, functional topography images, and clinical cerebellar disorders. More specifically, we explored the potential relationships between the cerebrocerebellar connections and the expression of particular molecules and, in particular, zebrin stripe (a Purkinje cell-specific antibody molecular marker, which is a glycolytic enzyme expressed in cerebellar Purkinje cells). We hypothesized that the zebrin patterns contribute to cerebellar functional maps—especially when cerebrocerebellar circuit changes exist in cerebellar-related diseases. The zebrin stripe receives input from climbing fibers and project to different parts of the cerebral cortex through its cerebrocerebellar connection. Since zebrin-positive cerebellar Purkinje cells are resistant to excitotoxicity and cell injury while zebrin-negative zones are more prone to damage, we suggest that motor control dysfunction symptoms such as ataxia and dysmetria present earlier and are easier to observe than non-ataxia symptoms due to zebrin-negative cell damage by cerebrocerebellar connections. In summary, we emphasize that the molecular zebrin patterns provide the basis for a new viewpoint from which to investigate cerebellar functions and clinico-neuroanatomic correlations.

Distribution of the CAG Triplet Repeat in ATXN1, ATXN3, and CACNA1A Loci in Peruvian Population

Spinocerebellar ataxia subtypes 1, 3, and 6 (SCA1, MJD/SCA3, and SCA6) are among the most prevalent autosomal dominant cerebellar ataxias worldwide, but their relative frequencies in Peru are low. Frequency of large normal (LN) alleles at spinocerebellar ataxia-causative genes has been proposed to be associated with disease prevalence. To investigate the allelic distribution of the CAG repeat in ATXN1, ATXN3, and CACNA1A genes in a Peruvian mestizo population and examine their association with the relative frequency of SCA1, MJD/SCA3, and SCA6 across populations. We genotyped 213 healthy mestizo individuals from Northern Lima, Peru, for ATXN1, ATXN3, and CACNA1A using polymerase chain reaction (PCR) and polyacrylamide gel electrophoresis (PAGE). We compared the frequency of LN alleles and relative disease frequency between populations. We also tested 40 samples for CAT repeat interruptions within the CAG tract of ATXN1. We found no association between disease frequency and population frequency of LN alleles at ATXN1 and ATXN3. All 40 ATXN1 samples tested for CAT interruptions were positive. Frequency of LN alleles at CACNA1A correlates with SCA6 frequency across several populations, but this effect was largely driven by data from a single population. Low frequency of SCA1 and MJD/SCA3 in Peru is not explained by frequency of LN alleles at ATXN1 and ATXN3, respectively. The observed correlation between CACNA1A LN alleles and SCA6 frequency requires further assessment.

Supratentorial and Infratentorial Lesions in Spinocerebellar Ataxia Type 3

Background: Spinocerebellar ataxia type 3 (SCA) is a cerebellum-dominant degenerative disorder that is characterized primarily by infratentorial damage, although less severe supratentorial involvement may contribute to the clinical manifestation. These impairments may result from the efferent loss of the cerebellar cortex and degeneration of the cerebral cortex. Method: We used the three-dimensional fractal dimension (3D-FD) method to quantify the morphological changes in the supratentorial regions and assessed atrophy in the relatively focal regions in patients with SCA3. A total of 48 patients with SCA3 and 50 sex- and age-matched healthy individuals, as the control group, participated in this study. The 3D-FD method was proposed to distinguish 97 automatic anatomical label regions of gray matter (left cerebrum: 45, right cerebrum: 45, cerebellum: 7) between healthy individuals and patients with SCA3. Results: Patients with SCA3 exhibited reduced brain complexity within both the traditional olivopontocerebellar atrophy (OPCA) pattern and specific supratentorial regions. The study results confirmed the extensive involvement of extracerebellar regions in SCA3. The atrophied regions of SCA3 in infratentorial and supratentorial cortex showed a wide range of overlapped areas as in two functional cortexes, namely cerebellum-related cortex and basal ganglia-related cortex. Conclusions: Our results found that the atrophy of the SCA3 are not only limited in the infratentorial regions. Both cerebellar related cortex and basal ganglia related cortex were affected in the disease process of SCA3. Our findings might correlate to the common symptoms of SCA3, such as ataxia, Parkinsonism, dysarthria, and dysmetria. SCA3 should no longer be considered a disease limited to the cerebellum and its connections; rather, it should be considered a pathology affecting the whole brain.

Diffusion Tensor Magnetic Resonance Imaging for Differentiating Multiple System Atrophy Cerebellar Type and Spinocerebellar Ataxia Type 3

Multiple system atrophy cerebellar type (MSA-C) and spinocerebellar ataxia type 3 (SCA3) demonstrate similar manifestations, including ataxia, pyramidal and extrapyramidal signs, as well as atrophy and signal intensity changes in the cerebellum and brainstem. MSA-C and SCA3 cannot be clinically differentiated through T1-weighted magnetic resonance imaging (MRI) alone; therefore, clinical consensus criteria and genetic testing are also required. Here, we used diffusion tensor imaging (DTI) to measure water molecular diffusion of white matter and investigate the difference between MSA-C and SCA3. Four measurements were calculated from DTI images, including fractional anisotropy (FA), axial diffusivity (AD), radial diffusivity (RD), and mean diffusivity (MD). Fifteen patients with MSA-C, 15 patients with SCA3, and 30 healthy individuals participated in this study. Both patient groups demonstrated a significantly decreased FA but a significantly increased AD, RD, and MD in the cerebello-ponto-cerebral tracts. Moreover, patients with SCA3 demonstrated a significant decrease in FA but more significant increases in AD, RD, and MD in the cerebello-cerebral tracts than patients with MSAC. Our results may suggest that FA and MD can be effectively used for differentiating SCA3 and MSA-C, both of which are cerebellar ataxias and have many common atrophied regions in the cerebral and cerebellar cortex.

Heterogeneous nonataxic phenotypes of spinocerebellar ataxia in a Taiwanese population

BACKGROUND

Spinocerebellar ataxia (SCA) presents with variable clinical presentations in addition to ataxia. The aim of this study was to reappraise the diverse nonataxic clinical characteristics of the five most common SCA subtypes in the Asian population.

METHODS

The clinical presentations of 90 patients with genetically confirmed SCA1, SCA2, SCA3, SCA6, or SCA17 were assessed retrospectively between November 2008 and September 2018 at a tertiary referral center in Taiwan.

RESULTS

Parkinsonism was the most common nonataxic phenotype (21.1%), with a greater prevalence than Caucasian and other Asian SCA carriers. Patients with parkinsonism feature had fewer CAG repeats in SCA2 (31.0 ± 4.5 vs. 36.9 ± 6.0, p = .03) and SCA3 (65.6 ± 7.9 vs. 70.0 ± 4.2, p = .02) compared to those with pure ataxia presentation. The average age of symptom onset was significantly higher in the parkinsonism group of SCA2 (51.5 ± 8.9 vs. 35.3 ± 12.6 years, p = .007) than those with pure ataxia. Focal or segmental dystonia was identified in 4.4% of SCA patients (n = 2 each SCA2 and SCA3). Nonmotor symptoms, including impaired cognition (6.1% of SCA2 and 8.3% of SCA3 patients) and depression (9.1% of SCA2 and 8.3% of SCA3 patients), were also common nonataxic features in our SCA patients.

CONCLUSIONS

Parkinsonism, dystonia, and cognitive-psychiatric symptoms are common features in patients with SCA mutations in our population. Our study identifies a different clinical spectrum of SCA1, SCA2, SCA3, SCA6, and SCA17 compared to Caucasians.

Clinical Characteristics and Possible Drug Targets in Autosomal Dominant Spinocerebellar Ataxias

Background & Objective:

The autosomal dominant spinocerebellar ataxias (SCAs) belong to a large and expanding group of neurodegenerative disorders. SCAs comprise more than 40 subtypes characterized by progressive ataxia as a common feature. The most prevalent diseases among SCAs are caused by CAG repeat expansions in the coding-region of the causative gene resulting in polyglutamine (polyQ) tract formation in the encoded protein. Unfortunately, there is no approved therapy to treat cerebellar motor dysfunction in SCA patients. In recent years, several studies have been conducted to recognize the clinical and pathophysiological aspects of the polyQ SCAs more accurately. This scientific progress has provided new opportunities to develop promising gene therapies, including RNA interference and antisense oligonucleotides.

Conclusion:

The aim of the current work is to give a brief summary of the clinical features of SCAs and to review the cardinal points of pathomechanisms of the most common polyQ SCAs. In addition, we review the last few year’s promising gene suppression therapies of the most frequent polyQ SCAs in animal models, on the basis of which human trials may be initiated in the near future.

Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias

Autosomal dominant cerebellar ataxias (ADCAs) are a group of neurodegenerative disorders characterized by degeneration of the cerebellum and its connections. All ADCAs have progressive ataxia as their main clinical feature, frequently accompanied by dysarthria and oculomotor deficits. The most common spinocerebellar ataxias (SCAs) are 6 polyglutamine (polyQ) SCAs. These diseases are all caused by a CAG repeat expansion in the coding region of a gene. Currently, no curative treatment is available for any of the polyQ SCAs, but increasing knowledge on the genetics and the pathological mechanisms of these polyQ SCAs has provided promising therapeutic targets to potentially slow disease progression. Potential treatments can be divided into pharmacological and gene therapies that target the toxic downstream effects, gene therapies that target the polyQ SCA genes, and stem cell replacement therapies. Here, we will provide a review on the genetics, mechanisms, and therapeutic progress in polyglutamine spinocerebellar ataxias.

Unmasking adrenoleukodystrophy in a cohort of cerebellar ataxia

Adrenoleukodystrophy (ALD) is a rare and progressive neurogenetic disease that may manifest disparate symptoms. The present study aims at investigating the role of ataxic variant of ALD (AVALD) in patients with adult-onset cerebellar ataxia, as well as characterizing their clinical features that distinguish AVALD from other cerebellar ataxias. Mutations in the ATP binding cassette subfamily D member 1 gene (ABCD1) were ascertained in 516 unrelated patients with ataxia. The patients were categorized into three groups: molecularly unassigned hereditary ataxia (n = 118), sporadic ataxia with autonomic dysfunctions (n = 296), and sporadic ataxia without autonomic dysfunctions (n = 102). Brain MRIs were scrutinized for white matter hyperintensity (WMH) in the parieto-occipital lobes, frontal lobes, corticospinal tracts, pons, middle cerebellar peduncles and cerebellar hemispheres. Two ABCD1 mutations (p.S108L and p.P623fs) previously linked to cerebral ALD and adrenomyeloneuropathy but not AVALD were identified. ALD accounts for 0.85% (1/118) of the patients with molecularly unassigned hereditary ataxia and 0.34% (1/296) of the patients with sporadic ataxia with autonomic dysfunctions. WMH in the corticospinal tracts and WMH in the cerebellar hemispheres were strongly associated with AVALD rather than other ataxias. To conclude, ALD accounts for approximately 0.39% (2/516) of adult-onset cerebellar ataxias. This study expands the mutational spectrum of AVALD and underscores the importance of considering ALD as a potential etiology of cerebellar ataxia.

Treatment of Spinocerebellar Ataxia With Mesenchymal Stem Cells: A Phase I/IIa Clinical Study

Ataxia is one of the most devastating symptoms of many neurodegenerative disorders. As of today, there is not any effective treatment to retard its progression. Mesenchymal stem cells (MSCs) have shown promise in treating neurodegenerative diseases. We hereby report the results of a phase I/IIa clinical study conducted in Taiwan to primarily evaluate the safety, tolerability, and, secondarily, the possible efficacy of intravenous administration of allogeneic adipose tissue-derived MSCs from healthy donors. Six patients with spinocerebellar ataxia type 3 and one with multiple system atrophy-cerebellar type were included in this open-label study with intravenous administration of 106 cells/kg body weight. The subjects were closely monitored for 1 year for safety (vital signs, complete blood counts, serum biochemical profiles, and urinalysis) and possible efficacy (scale for assessment and rating of ataxia and sensory organization testing scores, metabolite ratios on the brain magnetic resonance spectroscopy, and brain glucose metabolism of 18-fluorodeoxyglucose using positron emission tomography). No adverse events related to the injection of MSCs during the 1-year follow-up were observed. The intravenous administration of allogeneic MSCs seemed well tolerated. Upon study completion, all patients wished to continue treatment with the allogeneic MSCs. We conclude that allogeneic MSCs given by intravenous injection seems to be safe and tolerable in patients with spinocerebellar ataxia type 3, thus supporting advancement of the clinical development of allogeneic MSCs for the treatment of spinocerebellar ataxias (SCAs) in a randomized, double-blind, placebo-controlled phase II trials.

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.

Spinocerebellar ataxia type 6 in eastern India: Some new observations

Introduction:

Spinocerebellar ataxias (SCAs) are hereditary, autosomal dominant progressive neurodegenerative disorders showing clinical and genetic heterogeneity. They are usually manifested clinically in the third to fifth decade of life although there is a wide variability in the age of onset. More than 36 different types of SCAs have been reported so far and about half of them are caused by pathological expansion of the trinucleotide, Cytosine Alanine Guanine (CAG) repeat. The global prevalence of SCA is 0.3-2 per 100,000 population, SCA3 being the commonest variety worldwide, accounting for 20-50 per cent of all cases, though SCA 2 is generally considered as the commonest one in India. However, SCA6 has not been addressed adequately from India though it is common in the eastern Asian countries like, Japan, Korea and Thailand.

Objective:

The present study was undertaken to identify the prevalence of SCA6 in the city of Kolkata and the eastern part of India.

Materials and Methods:

83 consecutive patients were recruited for the study of possible SCAs and their clinical features and genotype were investigated.

Results:

6 of the 83 subjects turned out positive for SCA6, constituting therefore, 13.33% of the patient pool.

Discussion:

SCA6 is prevalent in the eastern part of India, though not as frequent as the other common varieties.

Conclusions:

Further community based studies are required in order to understand the magnitude of SCA6 in the eastern part, as well as in other regions of India.

Clinical profile and genetic correlation of patients with spinocerebellar ataxia: A study from a tertiary care centre in Eastern India

Background:

Progressive cerebellar ataxia inherited by autosomal dominant transmission is known as Spino Cerebellar Ataxia (SCA).

Aims and Objectives:

To look for various clinical profile and molecular genetics of patients with SCAs and their phenotype-genotype correlation of patients with SCAs.

Materials and Methods:

This was a cross-sectional study conducted at Bangur Institute of Neurosciences, Kolkata from June 2010 to April 2013. We selected patients from the neurogenetic clinic of our institute and performed genetic test for SCA 1, 2, 3, 6 and 12. The diagnosis was based on suggestive clinical features and positive genetic study, done by polymerase chain reaction.

Results:

83 patients were tested for trineucleotide repeats and turned out 45 positive for the mentioned SCAs. We found 13(28.9%) SCA-1, 18(40%) SCA-2, 7(15.6%) SCA-3, 6(13.3) SCA-6 and 1(2.2%) SCA-12 patients. Half of the remaining 38 patients had positive family history. The mean age of onset were 38.46 years in SCA-1, 29.55 years in SCA-2, 38.43 years in SCA-3, 47.33 years in SCA-6. Slow saccades were observed in 7(53.8%) SCA-1, 17(94.4%) SCA-2, 4(57.1%) SCA-3, 3(50%) SCA-6 patients. Hyporeflexia was noticed in 5(27.8%) SCA-2 patients. Pyramidal tract involvement was found in 8(61.5%) SCA-1, 4(22.2%) SCA-2, 4(57.1%) SCA-3 and 1(16.7%) SCA-6 patients.

Conclusion:

Our study showed SCA-2 is the most common variety of SCA and genotypic-phenotypic correlation was observed in SCA-1,2,6 and 12 patients.

Autosomal Dominant Spinocerebellar Ataxias: An Asian Perspective

Autosomal dominant cerebellar ataxias, frequently referred to as spinocerebellar ataxias (SCAs) have been under intense scientific research limelight since expansions of coded CAG trinucleotide repeats were demonstrated to cause several dominantly inherited SCAs. The number of new SCA loci has expanded dramatically in recent years. At least ten genes have been identified for SCAs 1, 2, 3, 6, 7, 8, 10, 12, 17, dentatorubral-pallidoluysian atrophy (DRPLA), and six loci responsible for SCAs 4, 5, 11,13, 14, and 16 have been mapped. Genetic testing is essential for diagnosis due to the overlapping and varied phenotypic features of the different SCAs. While there is no effective treatment available, genetic counseling is important for addressing the many ethical, social, legal, and psychological issues facing SCA patients. Researchers have recently provided valuable information on the pathogenesis of the disease and hopefully a cure will be available in the near future.

The potential of indole and a synthetic derivative for polyQ aggregation reduction by enhancement of the chaperone and autophagy systems

In polyglutamine (polyQ)-mediated disorders, the expansion of translated CAG repeats in the disease genes result in long polyQ tracts in their respective proteins, leading to intracellular accumulation of aggregated polyQ proteins, production of reactive oxygen species, and cell death. The molecular chaperones act in preventing protein misfolding and aggregation, thus inhibiting a wide range of harmful downstream events. In the circumstance of accumulation of aggregated polyQ proteins, the autophagic pathway is induced to degrade the misfolded or aggregated proteins. In this study, we used Flp-In 293/SH-SY5Y cells with inducible SCA3 ATXN3/Q75-GFP expression to test the effect of indole and synthetic derivatives for neuroprotection. We found that ATXN3/Q75 aggregation can be significantly prohibited in Flp-In 293 cells by indole and derivative NC001-8. Meanwhile, indole and NC001-8 up-regulated chaperones and autophagy in the same cell models. Both of them further promote neurite outgrowth in neuronal differentiated SH-SY5Y ATXN3/Q75-GFP cells. Our results demonstrate how indole and derivative NC001-8 are likely to work in reduction of polyQ-aggregation and provide insight into the possible effectual mechanism of indole compounds in polyQ spinocerebellar ataxia (SCA) patients. These findings may have therapeutic applications in a broad range of clinical situations.

Clinical analysis of adult-onset spinocerebellar ataxias in Thailand

Background

Non-ataxic symptoms of spinocerebellar ataxias (SCAs) vary widely and often overlap with various types of SCAs. Duration and severity of the disease and genetic background may play a role in such phenotypic diversity. We conducted the study in order to study clinical characteristics of common SCAs in Thailand and the factors that may influence their phenotypes.

Methods

131 (49.43%) out of 265 Thai ataxia families with cerebellar degeneration had positive tests for SCA1, SCA2, Machado-Joseph disease (MJD) or SCA6. The study evaluated 83 available families including SCA1 (21 patients), SCA2 (15), MJD (39) and SCA6 (8). Comparisons of frequency of each non-ataxic sign among different SCA subtypes were analysed. Multivariate logistic regression analyses were undertaken to analyze parameters in association with disease severity and size of CAG repeat.

Results

Mean ages at onset were not different among patients with different SCAs (40.31 ± 11.33 years, mean ± SD). Surprisingly, SCA6 patients often had age at onset and phenotypes indistinguishable from SCA1, SCA2 and MJD. Frequencies of ophthalmoparesis, nystagmus, hyperreflexia and areflexia were significantly different among the common SCAs, whilst frequency of slow saccade was not. In contrast to Caucasian patients, parkinsonism, dystonia, dementia, and facial fasciculation were uncommon in Thai patients. Multivariate logistic regression analysis demonstrated that ophthalmoparesis (p < 0.001) and sensory impairment (p = 0.025) were associated with the severity of the disease.

Conclusions

We described clinical characteristics of the 4 most common SCAs in Thailand accounting for almost 90% of familial spinocerebellar ataxias. There were some different observations compared to Caucasian patients including earlier age at onset of SCA6 and the paucity of extrapyramidal features, cognitive impairment and facial fasciculation. Severity of the disease, size of the pathological CAG repeat allele, genetic background and somatic heterogeneity of pathological alleles may influence clinical expressions of these common SCAs.

Clinical characteristics of patients with spinocerebellar ataxias 1, 2, 3 and 6 in the US; a prospective observational study

Background

All spinocerebellar ataxias (SCAs) are rare diseases. SCA1, 2, 3 and 6 are the four most common SCAs, all caused by expanded polyglutamine-coding CAG repeats. Their pathomechanisms are becoming increasingly clear and well-designed clinical trials will be needed.

Methods

To characterize the clinical manifestations of spinocerebellar ataxia (SCA) 1, 2, 3 and 6 and their natural histories in the United States (US), we conducted a prospective multicenter study utilized a protocol identical to the European consortium study, using the Scale for the Assessment and Rating of Ataxia (SARA) score as the primary outcome, with follow-ups every 6 months up to 2 years.

Results

We enrolled 345 patients (60 SCA1, 75 SCA2, 138 SCA3 and 72 SCA6) at 12 US centers. SCA6 patients had a significantly later onset, and SCA2 patients showed greater upper-body ataxia than patients with the remaining SCAs. The annual increase of SARA score was greater in SCA1 patients (mean ± SE: 1.61 ± 0.41) than in SCA2 (0.71 ± 0.31), SCA3 (0.65 ± 0.24) and SCA6 (0.87 ± 0.28) patients (p = 0.049). The functional stage also worsened faster in SCA1 than in SCA2, 3 and 6 (p = 0.002).

Conclusions

The proportions of different SCA patients in US differ from those in the European consortium study, but as in the European patients, SCA1 progress faster than those with SCA2, 3 and 6. Later onset in SCA6 and greater upper body ataxia in SCA2 were noted. We conclude that progression rates of these SCAs were comparable between US and Europe cohorts, suggesting the feasibility of international collaborative clinical studies.

Mutations in KCND3 cause spinocerebellar ataxia type 22

OBJECTIVE

To identify the causative gene in spinocerebellar ataxia (SCA) 22, an autosomal dominant cerebellar ataxia mapped to chromosome 1p21-q23.

METHODS

We previously characterized a large Chinese family with progressive ataxia designated SCA22, which overlaps with the locus of SCA19. The disease locus in a French family and an Ashkenazi Jewish American family was also mapped to this region. Members from all 3 families were enrolled. Whole exome sequencing was performed to identify candidate mutations, which were narrowed by linkage analysis and confirmed by Sanger sequencing and cosegregation analyses. Mutational analyses were also performed in 105 Chinese and 55 Japanese families with cerebellar ataxia. Mutant gene products were examined in a heterologous expression system to address the changes in protein localization and electrophysiological functions.

RESULTS

We identified heterozygous mutations in the voltage-gated potassium channel Kv4.3-encoding gene KCND3: an in-frame 3-nucleotide deletion c.679_681delTTC p.F227del in both the Chinese and French pedigrees, and a missense mutation c.1034G>T p.G345V in the Ashkenazi Jewish family. Direct sequencing of KCND3 further identified 3 mutations, c.1034G>T p.G345V, c.1013T>C p.V338E, and c.1130C>T p.T377M, in 3 Japanese kindreds. Immunofluorescence analyses revealed that the mutant p.F227del Kv4.3 subunits were retained in the cytoplasm, consistent with the lack of A-type K(+) channel conductance in whole cell patch-clamp recordings.

INTERPRETATION

Our data identify the cause of SCA19/22 in patients of diverse ethnic origins as mutations in KCND3. These findings further emphasize the important role of ion channels as key regulators of neuronal excitability in the pathogenesis of cerebellar degeneration.

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.

Spinocerebellar ataxia type 7

Spinocerebellar ataxia type 7 (SCA7) is associated with progressive blindness, dominant transmission, and marked anticipation. SCA7 represents one of the polyglutamine expansion diseases with increase of CAG repeats. The gene maps to chromosome 3p12-p21.1. Normal values of CAG repeats range from 4 to 18. The SCA7 gene encodes a protein of largely unknown function, called ataxin-7. SCA7 is reported in many countries and ethnic groups. Its phenotypic expression depends on the number of expanded repeats. The infantile phenotype is very severe, with more than 100 repeats. The classic type has 50 to 55 repeats and is characterized by a combination of visual and ataxic disturbances lasting for 20-40 years.When the number of CAG repeats is between 36 and 43, the evolution is much slower, with few or no retinal abnormalities. A CAG repeat number from 18 to 35 is asymptomatic but predisposes to the development of the disorder when expanding to the pathological range through transmission. The diagnosis is made by molecular genetics. The neuropathology of the disorder includes atrophy of the spinocerebellar pathways, pyramidal tracts, and motor nuclei in the brainstem and spinal cord, a cone-rod sytrophy of the retina, and ataxin-7 immunoreactive neuronal intranuclear inclusions. The neuropathological features vary as a function of the number of CAG repeats. Present research deals mainly with the study of ataxin-7 in transfected neural cells and transgenic mouse models.

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.

Brain stem and cerebellum volumetric analysis of Machado Joseph disease patients

Machado-Joseph disease, or spinocerebellar ataxia type 3(MJD/SCA3), is the most frequent late onset spinocerebellar ataxia and results from a CAG repeat expansion in the ataxin-3 gene. Previous studies have found correlation between atrophy of cerebellum and brainstem with age and CAG repeats, although no such correlation has been found with disease duration and clinical manifestations. In this study we test the hypothesis that atrophy of cerebellum and brainstem in MJD/SCA3 is related to clinical severity, disease duration and CAG repeat length as well as to other variables such as age and ICARS (International Cooperative Ataxia Rating Scale). Whole brain high resolution MRI and volumetric measurement with cranial volume normalization were obtained from 15 MJD/SCA3 patients and 15 normal, age and sex-matchedcontrols. We applied ICARS and compared the score with volumes and CAG number, disease duration and age. We found significant correlation of both brain stem and cerebellar atrophy with CAG repeat length, age, disease duration and degree of disability. The Spearman rank correlation was stronger with volumetric reduction of the cerebellum than with brain stem. Our data allow us to conclude that volumetric analysis might reveal progressive degeneration after disease onset, which in turn is linked to both age and number of CAG repeat expansions in SCA 3.

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.

The 'hot cross bun' sign in the patients with spinocerebellar ataxia

BACKGROUND AND PURPOSE

The 'hot cross bun' sign (HCBS), typically seen in the patients with multiple system atrophy, refers to a cruciform hyperintensity in the pons on T2-weighted MRI. Little is known about its pathological basis and prevalence in other degenerative cerebellar diseases and healthy population. We investigate the frequency of HCBS in the patients with spinocerebellar ataxia (SCA) and healthy controls.

METHODS

The presence of HCBS on T2-weighted axial MRIs from 138 SCA patients (three SCA1, 35 SCA2, 76 SCA3, 18 SCA6, one SCA7, three SCA8, and two SCA17) and 102 healthy controls was evaluated retrospectively.

RESULTS

The overall prevalence of HCBS in the SCA patients is 8.7%, but the frequency varies in different subtypes: 25.7% in SCA2, 1.3% in SCA3, and none in SCA6 or healthy controls. Notably, one patient with SCA7 and one with SCA8 were also found to have HCBS.

CONCLUSIONS

The differential list of HCBS should be expanded to include SCA7 and SCA8. The elucidation of frequency of HCBS in various SCA subtypes may help prioritize the genetic testing in late-onset dominant ataxia.

Frequencies of spinocerebellar ataxia subtypes in Thailand: window to the population history?

Spinocerebellar ataxias (SCAs) are a heterogeneous group of disorders with almost 30 subtypes. The prevalence and relative frequency of each subtype vary among different populations. In this article, we report the relative frequency of six SCA subtypes in the Thai population and attempt to explain the observed pattern when compared with other populations in this region. We searched for SCA type 1, SCA2, SCA3, SCA6, SCA7 and dentatorubral-pallidoluysian atrophy mutations using GeneScan analysis in 340 patients from 182 families, in which at least one person had a clinical diagnosis of SCA. We analyzed the relative frequencies of SCA subtypes on a family basis, and compared these with the data in the Chinese and Indian populations. SCA3 was found in 19.2% of the patients (Agresti-Coull 95% confidence interval: 14.1-25.6%), SCA1 in 11.5% (7.6-17.1%) and SCA2 in 10.4% (6.7-15.8%). SCA6 was found in three families, with a relative frequency of 1.6% (0.3-5.0%). Compared with the related populations, the Thai SCA3 frequency was less than that of the Chinese, whereas it was higher than that in most of the Indian studies. The reverse is true for the SCA1/SCA2 frequency. A similar study in Singapore, where there was a clear history of population admixture, also showed the frequencies between those of the Chinese and the Indian populations. Although SCA3 was the most common identifiable SCA subtype in Thailand, SCA1 and SCA2 were also relatively common. Our results also supported some degree of admixture with the Indians in the Thai population and justify further study in the area.

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.

Ataxias

Gait disorders in elderly individuals are a major cause of falls and their attendant morbidities. Ataxia is one of the neurologic components of fall risk, as are inattention or confusion, visual impairment, vestibular impairment, subcortical white matter disease, parkinsonism, weakness, sensory loss, orthostasis or arrhythmia with alterations in blood pressure, pain, medication use, and environmental hazards. Ataxia in the geriatric population has many causes. Correctly identifying them can improve clinicians' ability to offer treatment and management strategies to patients and their families. The goals should be safe mobility and preserved activities of daily living.

Cambodian founder effect for spinocerebellar ataxia type 3 (Machado–Joseph disease)

Four families from the same region of Cambodia immigrated to the Pacific Northwest of the United States. All four families have been discovered to have spinocerebellar ataxia type 3 (SCA 3; Machado-Joseph disease) with a similar clinical phenotype. CAG repeat expansions in the ATXN3 gene range from 72 to 77. Mean age of onset has varied from 19 to 44 years and mean age at death of 4 individuals has been 60 years. The prevalence of the various subtypes of SCA varies worldwide from country to country. Neurologists should be alert to the possibility of SCA 3 in Cambodian patients with unexplained cerebellar ataxia.

Adult onset spinocerebellar ataxia in a Canadian movement disorders clinic

BACKGROUND

The spinocerebellar ataxias (SCAs) are a genetically and clinically heterogeneous group of neurodegenerative disorders. Relative frequencies vary within different ethnic groups and geographical locations.

OBJECTIVES

1) To determine the frequencies of hereditary and sporadic adult onset SCAs in the Movement Disorders population; 2) to assess if the fragile X mental retardation gene 1 (FMR1) premutation is found in this population.

METHODS

A retrospective chart review of individuals with a diagnosis of adult onset SCA was carried out. Testing for SCA types 1, 2, 3, 6, 7, and 8, Dentatorubral-pallidoluysian atrophy (DRPLA), Friedreich ataxia and the FMR1 expansion was performed.

RESULTS

A total of 69 patients in 60 families were identified. Twenty-one (35%) of the families displayed autosomal dominant and two (3.3%) showed autosomal recessive (AR) pattern of inheritance. A positive but undefined family history was noted in nine (15%). The disorder appeared sporadic in 26 patients (43.3%). In the AD families, the most common mutation was SCA3 (23.8%) followed by SCA2 (14.3%) and SCA6 (14.3%). The SCA1 and SCA8 were each identified in 4.8%. FA was found in a pseudodominant pedigree, and one autosomal recessive pedigree. One sporadic patient had a positive test (SCA3).Dentatorubral-pallidoluysian atrophy and FMR1 testing was negative.

CONCLUSION

A positive family history was present in 53.3% of our adult onset SCA patients. A specific genetic diagnosis could be given in 61.9% of dominant pedigrees with SCA3 being the most common mutation, followed by SCA2 and SCA6. The yield in sporadic cases was low. The fragile X premutation was not found to be responsible for SCA.

Spinocerebellar ataxia type 6 in Mainland China: Molecular and clinical features in four families

The hereditary spinocerebellar ataxias (SCAs) are a clinically and genetically heterogeneous group of neurodegenerative disorders. The genes causing 11 of these diseases have been identified. To date, there is no report of SCA type 6 (SCA6) in Mainland Chinese. Using a molecular approach, we investigated SCA6 as well as other SCA subtype in 120 Mainland Chinese families with dominantly inherited ataxias and in 60 Mainland Chinese patients with sporadic ataxias. Clinical and molecular features of SCA6 were further characterized in 13 patients from 4 families. We found that SCA3/MJD was the most common type of autosomal dominant SCA in Mainland Chinese, accounting for 83 patients from 59 families (49.2%), followed by SCA2 (8 [6.7%]), SCA1 (7 [5.8%]), SCA6 (4 [3.3%]), SCA7 (1 [0.8%]), SCA8 (0%), SCA10 (0%), SCA12 (1 [0.8%]), SCA14 (0%), SCA17 (0%) and DRPLA (0%). The genes responsible for 40 (33.3%) of dominantly inherited SCA families remain to be determined. Among the 60 patients with sporadic ataxias in the present series, 3 (5.0%) were found to harbor SCA3 mutations, whereas none were found to harbor SCA6 mutations. In the 4 families with SCA6, we found significant anticipation in the absence of genetic instability on transmission. This is the first report of geographic cluster of families with SCA6 subtype in Mainland China.

The occurrence of dominant spinocerebellar ataxias among 251 Finnish ataxia patients and the role of predisposing large normal alleles in a genetically isolated population

OBJECTIVES

Frequency and distribution of dominant ataxias caused by dynamic mutations may vary in different populations, which has been explained on the basis of relative frequency of predisposing normal alleles. The aim of the study was to evaluate the occurrence of spinocerebellar ataxias (SCAs) and dentatorubral-pallidoluysian atrophy (DRPLA) in Finland, and to investigate the role of predisposing normal alleles in a genetically homogenous population.

MATERIAL AND METHODS

Mutation analyses for SCA1, 2, 3, 6, 7, 8, 10, 12, 17, and DRPLA and frataxin genes were performed for 251 unrelated Finnish patients who presented with progressive ataxia disorder.

RESULTS

Expansions of SCA1, SCA2, SCA6, SCA7, SCA8, and SCA17 genes were detected in 2, 1, 1, 7, 22, and 1 patients, respectively. Altogether, 39 and 7% of dominant and sporadic SCA patients, respectively, harboured expansions at some of the investigated loci. Normal variation, collected from 477 to 502 chromosomes at each disease loci, revealed that Finns were different from the Japanese but largely similar to other Caucasians.

CONCLUSIONS

Lack of SCA3 and excess of SCA8 are characteristic to the Finnish population. Homozygosity for the SCA8 expansion increases penetrance. Frequencies of large normal alleles at the SCA loci predict poorly prevalence of the respective diseases in Finland. Prioritization in DNA testing, based on ethnic origin and geographical location, is recommendable in Finland, and analogous approach may be applied to other countries as well.

Regional features of autosomal-dominant cerebellar ataxia in Nagano: clinical and molecular genetic analysis of 86 families

The frequency of autosomal-dominant cerebellar ataxia (ADCA) subtypes was examined in 86 unrelated families originating from Nagano prefecture. In Nagano, the prevalence of spinocerebellar degeneration (SCD) was approximately 22 per 100,000 population. Among ADCA families, SCA6 was the most prevalent subtype (16 families, 19%), followed by DRPLA (nine families, 10%), SCA3/MJD (three families, 3%), SCA1 (two families, 2%), and SCA2 (one family, 1%). No families with SCA7, SCA12, or SCA17 were detected. Compared with other districts in Japan, the prevalence of SCA3/MJD was very low in Nagano. More interestingly, the ratio of genetically undetermined ADCA families was much higher in Nagano (55 families, 65%) than in other districts in Japan. These families tended to accumulate in geographically restricted areas such as Kiso, Saku, and Ina, indicating that the founder effect might be responsible for the high frequency of ADCA in these areas. Most patients clinically showed slowly progressive pure cerebellar ataxia of late-onset (ADCA III). In the case of 36 patients from 36 genetically undetermined ADCA III families, however, no one was completely consistent with the founder allele proposed for 16q-ADCA. These results indicate that there might be genetically distinct ADCA subtypes in Nagano.

Analysis of trinucleotide repeats in different SCA loci in spinocerebellar ataxia patients and in normal population of Taiwan

OBJECTIVE

To identify various subtypes of spinocerebellar ataxias (SCAs) among autosomal dominant cerebellar ataxia (ADCA) patients referred to our research center, SCA1, SCA2, SCA3/MJD (Machado-Joseph disease), SCA6, SCA7, SCA8 and SCA12 loci were assessed for expansion of trinucleotide repeats.

PATIENTS AND METHODS

A total of 211 ADCA patients, including 202 patients with dominantly inherited ataxia from 81 Taiwanese families and nine patients with sporadic ataxia, were included in this study and subjected to polymerase chain reaction (PCR) analysis. The amplified products of all loci were analyzed on both 3% agarose gels and 6% denaturing urea-polyacrylamide gels. PCR-based Southern blots were also applied for the detection of SCA7 locus.

RESULTS

The SCA1 mutation was detected in six affected individuals from one family (1.2%) with expanded alleles of 50-53 CAG repeats. Fourteen individuals from nine families (11%) had a CAG trinucleotide repeat expansion at the SCA2 locus, while affected SCA2 alleles have 34-49 CAG repeats. The SCA3/MJD CAG trinucleotide repeat expansion in 60 affected individuals from 26 families (32%) was expanded to 71-85 CAG repeats. As for the SCA7 locus, there were two affected individuals from one family (1.2%) possessed 41 and 100 CAG repeats, respectively. However, we did not detect expansion in the SCA6, SCA8 and SCA12 loci in any patient.

CONCLUSIONS

The SCA3/MJD CAG expansion was the most frequent mutation among the SCA patients. The relative prevalence of SCA3/MJD in Taiwan was higher than that of SCA2, SCA1 and SCA7.

Genetic testing in spinocerebellar ataxia in Taiwan: expansions of trinucleotide repeats in SCA8 and SCA17 are associated with typical Parkinson's disease

DNA tests in normal subjects and patients with ataxia and Parkinson's disease (PD) were carried out to assess the frequency of spinocerebellar ataxia (SCA) and to document the distribution of SCA mutations underlying ethnic Chinese in Taiwan. MJD/SCA3 (46%) was the most common autosomal dominant SCA in the Taiwanese cohort, followed by SCA6 (18%) and SCA1 (3%). No expansions of SCA types 2, 10, 12, or dentatorubropallidoluysian atrophy (DRPLA) were detected. The clinical phenotypes of these affected SCA patients were very heterogeneous. All of them showed clinical symptoms of cerebellar ataxia, with or without other associated features. The frequencies of large normal alleles are closely associated with the prevalence of SCA1, SCA2, MJD/SCA3, SCA6, and DRPLA among Taiwanese, Japanese, and Caucasians. Interestingly, abnormal expansions of SCA8 and SCA17 genes were detected in patients with PD. The clinical presentation for these patients is typical of idiopathic PD with the following characteristics: late onset of disease, resting tremor in the limbs, rigidity, bradykinesia, and a good response to levodopa. This study appears to be the first report describing the PD phenotype in association with an expanded allele in the TATA-binding protein gene and suggests that SCA8 may also be a cause of typical PD.

Spinocerebellar ataxia type 7 associated with pigmentary retinal dystrophy

Spinocerebellar ataxia type 7 (SCA7) is an autosomal-dominant, late-onset, slowly progressive disorder, primarily characterized by gradual loss of motor coordination, resulting from dysfunction and degeneration of the cerebellum and its connecting pathways. The disease is caused by expansion of a CAG trinucleotide repeat within the SCA7 gene, which encodes a polyglutamine tract within a novel protein, termed ataxin-7. The expansion of polyglutamine-encoding CAG repeats in dissimilar genes underlies eight neurodegenerative conditions besides SCA7, including a number of dominant ataxias related to SCA7. Although elongated polyglutamine itself can initiate neuronal dysfunction and death, its toxicity is modulated by the context of the disease proteins, as evidenced by the differing clinical and pathological presentation of the various disorders. In this respect, it is exciting that SCA7 constitutes the only polyglutamine disorder, in which the photoreceptors of the retina are also severely affected, leading to retinal degeneration and blindness. Since the discovery of the SCA7 mutation, numerous studies attempted to pinpoint the molecular mechanisms underlying the unique features of SCA7, particularly the retinal involvement. Here we summarize the clinical, pathological, and genetic aspects of SCA7, and review the current understanding of the pathogenesis of this disorder.

The hereditary spinocerebellar ataxias in Japan

In Japan, multiple system atrophy (MSA) accounts for 40% of all spinocerebellar ataxias (SCAs) and hereditary disorders account for 30%. Among the latter, autosomal dominant disorders are common and recessive ataxias are rare. Although the frequency of SCA genotypes differs between geographic regions throughout Japan, SCA6, SCA3/MJD, and DRPLA are the three major disorders, while SCA7, SCA8, SCA10, SCA12, and SCA17 are infrequent or almost undetected. SCA1 predominantly occurs in the northern part of Japan. Overall, 20-40% of dominant SCAs are due to unknown mutations. From this cluster, pure cerebellar ataxias linked with the SCA4, SCA14, and SCA16 locus have been isolated. Among the recessive SCAs, patients with AVED and EAOH have been detected. However, FRDA associated with GAA repeat expansion in the frataxin gene has not been reported so far.