A mitochondrial implication in a Tunisian patient with Friedreich's ataxia-like.

Genes encoding the DNA helicase TWINKLE (C10orf2) or the two subunits of mtDNA polymerase γ (POLγ) (POLG1 and POLG2) have a direct effect on the mitochondrial DNA replication machinery and were reported in many mitochondrial disorders. Friedreich's ataxia (FRDA) is the common cause of ataxia often associated with the expansion of a GAA repeat in intron 1 of the frataxin gene (FXN). Mitochondrial DNA could be considered as a candidate modifier factor for FRDA disease, since mitochondrial oxidative stress is thought to be involved in the pathogenesis of this disease. We screened the FXN, POLG1 and C10orf2 genes in a Tunisian patient with clinical features of Friedreich's ataxia-like. The results showed the absence of the expansion of a GAA triplet repeat in intron 1 of the FXN gene. Besides, the sequencing of all the exons and their flanking regions of the FXN, POLG1 and C10orf2 genes revealed the presence of intronic polymorphisms. In addition, screening of the mtDNA revealed the presence of several mitochondrial known variations and the absence of mitochondrial deletions in this patient. The detected m.16187C>T and the m.16189T>C change the order of the homopolymeric tract of cytosines between 16184 and 16193 in the mitochondrial D-loop and could lead to a mitochondrial dysfunction by inhibiting replication and affecting protein involved in the replication process of the mtDNA which could be responsible for the clinical features of Friedreich ataxia observed in the studied patient.

Gametic and somatic tissue-specific heterogeneity of the expanded SCA1 CAG repeat in spinocerebellar ataxia type 1.

Spinocerebellar ataxia type 1 is associated with expansion of an unstable CAG repeat within the SCA1 gene. Male gametic heterogeneity of the expanded repeat is demonstrated using single sperm and low-copy genome analysis. Low-copy genome analysis of peripheral blood also reveals somatic heterogeneity of the expanded SCA1 allele, thus establishing mitotic instability at this locus. Comparative analysis of a large normal allele and a small affected allele suggests a role of midstream CAT interspersions in stabilizing long (CAG)n stretches. Within the brain, tissue-specific mosaicism of the expanded allele is also observed. The differences in SCA1 allele heterogeneity between sperm and blood and within the brain parallels the findings in Huntington disease, suggesting that both disorders share a common mechanism for tissue-specific instability.

Identification of the spinocerebellar ataxia type 2 gene using a direct identification of repeat expansion and cloning technique, DIRECT.

Spinocerebellar ataxia type 2 (SCA2) is an autosomal dominant, neurodegenerative disorder that affects the cerebellum and other areas of the central nervous system. We have devised a novel strategy, the direct identification of repeat expansion and cloning technique (DIRECT), which allows selective detection of expanded CAG repeats and cloning of the genes involved. By applying DIRECT, we identified an expanded CAG repeat of the gene for SCA2. CAG repeats of normal alleles range in size from 15 to 24 repeat units, while those of SCA2 chromosomes are expanded to 35 to 59 repeat units. The SCA2 cDNA is predicted to code for 1,313 amino acids-with the CAG repeats coding for a polyglutamine tract. DIRECT is a robust strategy for identification of pathologically expanded trinucleotide repeats and will dramatically accelerate the search for causative genes of neuropsychiatric diseases caused by trinucleotide repeat expansions.

Spinocerebellar ataxia type 5 in a family descended from the grandparents of President Lincoln maps to chromosome 11.

Autosomal dominant ataxias are a genetically heterogeneous group of disorders for which spinocerebellar ataxia (SCA) loci on chromosomes 6p, 12q, 14q and 16q have been reported. We have examined 170 individuals (56 of whom were affected) from a previously unreported ten-generation kindred with a dominant ataxia that is clinically and genetically distinct from those previously mapped. The family has two major branches which both descend from the paternal grandparents of President Abraham Lincoln. Among those examined, 56 individuals have a generally non-life threatening cerebellar ataxia. Disease onset varies from 10-68 years and anticipation is evident. We have mapped this gene, spinocerebellar ataxia type 5 (SCA5), to the centromeric region of chromosome 11.

Identification and characterization of the gene causing type 1 spinocerebellar ataxia.

Spinocerebellar ataxia type 1 (SCA1) is a neurodegenerative disorder caused by expansion of a CAG trinucleotide repeat. In this study, we describe the identification and characterization of the gene harbouring this repeat. The SCA1 transcript is 10,660 bases and is transcribed from both the wild type and SCA1 alleles. The CAG repeat, coding for a polyglutamine tract, lies within the coding region. The gene spans 450 kb of genomic DNA and is organized in nine exons. The first seven fall in the 5' untranslated region and the last two contain the coding region, and a 7,277 basepairs 3' untranslated region. The first four non-coding exons undergo alternative splicing in several tissues. These features suggest that the transcriptional and translational regulation of ataxin-1, the SCA1 encoded protein, may be complex.

[Autosomal recessive cerebellar ataxias]. / Les ataxies cérébelleuses autosomiques récessives.

INTRODUCTION: Autosomal recessive cerebellar ataxias (ARCA) are heterogeneous and complex inherited neurodegenerative diseases that may affect the cerebellum and/or the spinocerebellar tract, the posterior column of the spinal cord and the peripheral nerves. Cerebellar ataxia is frequently proeminent and mostly associated with several neurological or extra-neurological signs, leading to a major disability before the age of 30. STATE OF ART: Friedreich's ataxia (FRDA) is clearly the most frequent ARCA and several rarer entities have been described during the past fifteen years such as ataxia with oculomotor apraxia type 1 (AOA1) and type 2 (AOA2), ataxia with vitamin E deficiency (AVED) and autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS). The ACAR are characterized by both allelic and non-allelic genetic heterogeneity. They may be divided into three groups: spino-cerebellar ataxia with pure sensory neuropathy; cerebellar ataxia with sensori-motor axonal neuropathy; pure cerebellar ataxia (i.e. ataxia of purely cerebellar origin that may be associated with other symptoms). Common physiological pathways are involved in several ARCA, such as DNA repair deficiency (AOA1, ataxia telangiectasia [AT]…), RNA termination disorder (AOA2), mitochondrial defect (FRDA, sensory ataxic neuropathy with dysarthria and ophthalmoplegia [Sando]…), lipoprotein assembly defects (AVED, abetalipoproteinemia [ABL]), chaperon protein disorders (ARSACS, Marinesco-Sjögren syndrome [MSS]) or peroxysomal diseases (Refsum disease [RD]). PERSPECTIVES: New nanotechnology methods and high throughput gene analysis as well as bioinformatics should lead to the identification of several new ARCAs in the next few years despite the rarity of these entities. However, the challenge of the next decades will be the discovery of efficient treatments for these disabling neurodegenerative disorders. CONCLUSION: Clinicians should be aware of the more frequent ARCAs, especially FRDA, in addition to ARCAs for which treatment is available (FRDA, AVED, ABL and RD for instance).

Difference in the effects of tandospirone on ataxia in various types of spinocerebellar degeneration: an open-label study.

The aim of this study was to investigate the effects of tandospirone on ataxia in various types of spinocerebellar degeneration (SCD). Fifteen milligram per day of tandospirone was administered to 39 patients with SCD (spinocerebellar atrophy (SCA) 1, five patients; SCA2, six patients; Machado-Joseph disease (MJD), 14 patient; SCA6, five patients; multiple system atrophy-cerebellar type (MSA-C), seven patients; and multiple system atrophy-Parkinson type (MSA-P), two patients). All patients were assessed before and 4 weeks after administration of the drug using the international cooperative ataxia rating scale total score (ARS), total length traveled (TLT) of body stabilometry, and a self-rating depression scale. Statistically, ARS showed a significant difference in MJD (p = 0.005) and SCA6 (p = 0.043). TLT also showed a significant difference in MJD (p = 0.002) and SCA6 (p = 0.043). Eight of 39 patients (SCA1, 1/5; SCA2, 0/6; MJD, 4/14; SCA6, 3/5; MSA-C, 0/7; and MSA-P, 0/2) showed more than a five point reduction in ARS, and 13 of 39 patients (SCA1, 0/5; SCA2, 1/6; MJD, 8/14; SCA6, 4/5; MSA-C, 0/7; and MSA-P, 0/2) showed a reduction of TLT. Our data indicate that the effects of tandospirone on ataxia are different between types of SCD. Therefore, tandospirone is useful for cerebellar ataxia in patients with MJD and SCA6.

Prevalence of spinocerebellar degenerations in the Hokuriku district in Japan.

BACKGROUND: The prevalence of disease subtypes of spinocerebellar degenerations (SCDs) varies between countries, and even between areas within a country. We report unprecedented epidemiologic data on SCDs in the Hokuriku district, which is located in the central, western part of Japan. METHODS: Clinical and genetic data on SCD patients were obtained via questionnaires distributed to all the departments of neurology, psychiatry and internal medicine in the Hokuriku district (n = 418). RESULTS: Among the SCD patients, autosomal dominant cerebellar ataxias (ADCAs) were noted in 40.4%, multiple system atrophy in 24.7%, cortical cerebellar atrophy in 13.3% and autosomal recessive cerebellar ataxia in 0.3%. Genetically confirmed ADCA patients included those with Machado-Joseph disease (MJD)/spinocerebellar ataxia type 3 (SCA3; 63.3%), SCA6 (20.0%), ADCA linked to chromosome 16q22.1 (10.0%), dentatorubral pallidoluysian atrophy (4.4%), SCA1 (1.1%) and SCA2 (1.1%). MJD/SCA3 was highly prevalent in the Toyama prefecture of the Hokuriku district, accounting for 90% of genetically confirmed ADCAs by birthplace; MJD/SCA3 patients were concentrated in the Gosei area, the western part of the Toyama prefecture, giving an estimated prevalence of 19.1 per 100,000 inhabitants. CONCLUSIONS: The Hokuriku district, especially the Gosei area of Toyama, had a surprisingly high relative frequency and prevalence of MJD/SCA3, which is comparable to that in the Azores, Portugal.

Size bias of fragile X premutation alleles in late-onset movement disorders.

BACKGROUND: Fragile X-associated tremor/ataxia syndrome (FXTAS), caused by premutation expansions (55-200 CGG repeats) of the FMR1 gene, shares clinical features with other movement disorders, particularly in the domains of gait ataxia, intention tremor and parkinsonism. However, the prevalence of FXTAS within other diagnostic categories is not well defined. METHODS: A meta-analysis was conducted of all published (n = 14) genetic screens for expanded FMR1 alleles to assess the prevalence and CGG-repeat size bias of FMR1 premutation alleles in those populations. RESULTS: In men with late-onset cerebellar ataxia, the prevalence of premutation alleles (1.5%; 16/1049) was 13 times greater than expected based on its prevalence in the general population (2%; 16/818 for age of onset >50 years; odds ratio 12.4; 95% confidence interval 1.6 to 93.5). Meta-analysis of CGG-repeat data for screened patients with premutation alleles shows a shift to larger repeat size than in the general population (p<0.001). 86% (19/22) of premutation alleles were larger than 70 repeats in the patients screened, whereas only approximately 22% of premutation alleles are larger than 70 repeats in the general population. CONCLUSIONS: Expanded FMR1 alleles contribute to cases of late-onset sporadic cerebellar ataxia, suggesting that FMR1 genetic testing should be carried out in such cases. The biased distribution of FMR1 allele sizes has substantial implications for genetic counselling of carriers with smaller alleles who are at a low risk of developing FXTAS, and suggests that the estimated prevalence of FXTAS among men >50 years of age in the general population may be two to threefold lower than the initial figure of 1 in 3000.

Trinucleotide repeat expansions in neurological disease.

During the past year, new examples of human neurological disease have been discovered that have an unprecedented type of mutation as their cause: the remarkable expansion of trinucleotide repeats. These triplet repeats are normally polymorphic and exonic, though not always coding. In disease states they become markedly unstable and may expand moderately or by thousands of repeats in a single generation, influencing gene expression, message stability or protein structure.

Neurophysiologic studies in early-onset cerebellar ataxia.

The discovery of the gene for Friedreich's ataxia (FRDA) has not only broadened the FRDA phenotype, but has also identified patients with early-onset cerebellar ataxia who resemble FRDA clinically but who do not carry a mutation in the frataxin gene. In order to identify subgroups that may represent a uniform underlying disorder, we performed neurophysiologic studies, including nerve conduction studies, electromyography, and transcranial magnetic stimulation, in 15 patients with a slowly progressive, unexplained, early-onset cerebellar ataxia (EOCA). In addition, sural nerve biopsy data were available in four patients. The neurophysiologic data identified three distinctive groups of EOCA patients: three patients with normal motor and sensory conduction velocities and borderline sensory amplitudes (group 1); three patients with a mild, predominantly motor, axonal neuropathy (group 2); and nine patients with a highly uniform syndrome characterized by pyramidal features and a severe sensory and motor axonal neuropathy (group 3). We conclude that, on the basis of neurophysiologic studies, distinctive groups of patients with EOCA can be delineated, and that differentiation between patients with EOCA can be useful for differential diagnostic consideration. Whether this splitting also reflects a fundamental phenotypic difference and, therefore, may direct future DNA studies, remains to be established.

Current concepts in the treatment of hereditary ataxias.

Hereditary ataxias (HA) represents an extensive group of clinically and genetically heterogeneous neurodegenerative diseases, characterized by progressive ataxia combined with extra-cerebellar and multi-systemic involvements, including peripheral neuropathy, pyramidal signs, movement disorders, seizures, and cognitive dysfunction. There is no effective treatment for HA, and management remains supportive and symptomatic. In this review, we will focus on the symptomatic treatment of the main autosomal recessive ataxias, autosomal dominant ataxias, X-linked cerebellar ataxias and mitochondrial ataxias. We describe management for different clinical symptoms, mechanism-based approaches, rehabilitation therapy, disease modifying therapy, future clinical trials and perspectives, genetic counseling and preimplantation genetic diagnosis.

[The Nomenclature and Classification of Sporadic Spinocerebellar Degeneration].

Spinocerebellar degeneration (SCD) is a neurodegenerative disease characterized by progressive cerebellar ataxia. SCD has a wide range of clinical, pathological, and genetic features, including whether the disease is sporadic or hereditary, and whether it manifests as purely cerebellar or affects multiple systems. Therefore, the classification of SCD has been complicated and has changed over time. Recent advances in genetic testing have shed light on the classification of hereditary SCD. In contrast, the classification of sporadic SCD remains chaotic and there exist nomenclature discrepancies in sporadic SCD between Japanese and English literature. Sporadic SCD is usually divided into multiple system atrophy and cortical cerebellar atrophy in Japanese literature, but the latter nomenclature seems to be uncommon in English literature. The aim of this review is to reconsider the nomenclature and classification of sporadic SCD. At this time, sporadic adult-onset ataxia of unknown etiology is an acceptable term to describe a case of sporadic SCD that does not fit the multiple system atrophy classification.

Influence of repetitive transcranial magnetic stimulation on disease severity and oxidative stress markers in the cerebrospinal fluid of patients with spinocerebellar degeneration.

Ataxia severity, cerebellar hemispheric blood flow (CHBF), ascorbate free radical (AFR), superoxide dismutase protein, superoxide scavenging activity, and 8-hydroxy-2'-deoxyguanosine (8-OHdG) in cerebrospinal fluid (CSF) were compared before and after an 8-week course of repetitive transcranial magnetic stimulation (rTMS) in 20 patients with spinocerebellar degenerations (SCD). SCD patients showed higher AFR, 8-OHdG, and superoxide scavenging activity than 19 controls. In SCD patients, AFR and ataxia severity declined, and CHBF increased after rTMS. As the SCD patients showed negative correlations between ataxia severity and CHBF or superoxide scavenging activity, the therapeutic mechanism of rTMS may involve decreased oxidative stress and increased CHBF.

Hereditary ataxia and behavior.

Recognizing cognitive deficits and psychiatric disorders in patients with autosomal dominant ataxias is relatively new. At this time, the percentage of patients with these disorders who experience changes in cognition or psychiatric symptoms is unknown. Cognitive impairment, when seen, is often found on tests of executive function, probably reflecting disruption of afferent and efferent pathways of the prefrontal cortex and subcortical structures, including the cerebellum. Widespread global dysfunction does occur in some cases, especially later in the disease course. Psychiatric symptoms including depression, aggression, irritability, and psychosis have all been reported. As these behavioral changes receive further study, one hopes that guidelines for treating these symptoms will emerge. Clinicians should be mindful of the psychosocial effects that genetic testing for the hereditary ataxias may have, especially in cases of predictive testing for those who are asymptomatic but at risk because of family history. Guidelines established for genetic testing in HD may be helpful when approaching these cases.

Problems and possibilities in the differential diagnosis of Syndrome Spinocerebellar Ataxia.

Differential diagnosis in neurologic patients with spinocerebellar syndrome is complex as a result of the great degree of variability in phenotypic and genetic aspects of more than 200 nosological entities. In the past decade, genetic etiology has been discovered in part of the diseases and the term ''spinocerebellar ataxia'' has become, from a neurologic point of view, a loose definition applied to a group of autosomal dominant diseases. Topical extensive literature about differential diagnoses of ataxias usually refers to genetics classification or is produced by a group of radiologists, elektrophysiologists and biologists as well as others in the field. A further problem is that the majority of studies do not take into account other acquired illnesses and diseases which may fundamentally alter the symptomology and course of a primary disease, not to mention the possibility of concomitancy in hereditary diseases. The following article was prompted by daily contact with ataxic patients and related issues raised by colleagues; its goal is to clarify problems faced by child neurologists and neurologists in clinical practice.

Spinocerebellar degenerations in Japan: a nationwide epidemiological and clinical study.

A nationwide survey of patients in Japan with spinocerebellar degenerations (SCD), including SDS and SND, was conducted from 1988 to 1989. The survey consisted of two parts. The first revealed that the estimated total number of patients with SCD in Japan was 5,050 (range: 4,100-6,000) with an estimated prevalence of 4.53 per 100,000 in 1987. The second part investigated the neurological and functional status of patients with SCD. The percentages of those belonging to each subtype of SCD were: OPCA; 34.4%, LCCA; 15.2%, MHCA; 12.6%, HHCA; 7.5%, SDS; 7.0%, HSP; 3.9%, DRPLA; 2.5%, FA; 2.4%, MJD; 2.0% and SND; 1.5%. Compared with European epidemiological studies Japan had a higher proportion of non-hereditary types of SCD. Various clinical features of SCD subtypes were compared grouped by pathological lesion and heredity. HHCA and LCCA: cerebellar ataxia predominated in all stages, and neurological signs other than cerebellar ataxia were rare. MHCA, DRPLA and MJD: in the early phase ataxia was the most common symptom in MHCA, the AC form of DRPLA and MJD, but ataxia was less common and chorea or epilepsy were often observed in ME and PH forms of DRPLA. Other frequently observed clinical features were parkinsonian rigidity in MHCA, abnormal movements and posture in DRPLA and MJD, and disturbances of eye movements in MHCA, the AC form of DRPLA and MJD. OPCA, SDS and SND: dominant clinical features were cerebellar ataxia in OPCA, autonomic disturbance in SDS, and parkinsonian rigidity in SND. FA and HSP: both were rare in Japan. Clinical features related to supra-supinal lesions were frequently observed in FA. Functional status of SCD: the severity of illness was significantly associated with the level of independence in each item of ADL. Activities not requiring dynamic balance were performed independently for a longer period than those requiring dynamic balance. Among SCD subtypes, functional prognosis was poorest in non-hereditary, multi-systemic types (OPCA, SDS and SND) followed by hereditary multi-systemic types (MHCA, DRPLA and MJD), and better in spinal types (FA and HSP) and cerebellar types (HHCA and LCCA).

Spinocerebellar ataxia type 2. Genotype and phenotype in German kindreds.

BACKGROUND: Spinocerebellar ataxia type 2 (SCA2) is an autosomal dominant cerebellar ataxia (ADCA) for which the disease-causing mutation has recently been characterized as an expanded CAG trinucleotide repeat. We investigated 64 families of German ancestry with ADCA and 55 patients with sporadic ataxia for the SCA2 mutation. RESULTS: Expanded alleles were found in 6 of the 64 families and in 1 patient with sporadic ataxia. This patient had a de novo mutation from an intermediate paternal allele. Length of repeats in 21 patients with SCA2 ranged from 36 to 52 CAG motifs and was inversely correlated with age at onset and progression of the disease. Expanded alleles were unstable during meiosis; paternal transmission especially caused significant anticipation of onset up to 26 years earlier. The SCA2 phenotype differed from those of SCA1 and SCA3 with higher frequencies of slowed ocular movements, postural and action tremor, myoclonus, and hyporeflexia. However, no single feature was sufficient to permit a specific clinical diagnosis. CONCLUSIONS: Spinocerebellar ataxia type 2 accounts for about 10% of German families with ADCA but may also be present in sporadic ataxia due to de novo mutations. Clinical features are highly variable among and even within families. However, the size of the expanded repeat influences the phenotype and is relevant for course and prognosis of the disease.

Clinical and molecular analysis of a pedigree of southern Italian ancestry with spinocerebellar ataxia type 2.

We describe patients from five generations of a pedigree with mutations in the spinocerebellar ataxia type 2 gene (SCA2). The predominant clinical features observed included both appendicular and truncal ataxia, dysarthria, slowness of saccades, and impaired optokinetic responses. Successive generations demonstrated both earlier ages of onset as well as increasing numbers of trinucleotide repeat sequences. The signs found in this family are compared with the description of other families with SCA2 as well as with other types of dominantly inherited spinocerebellar ataxias.

The expansion of the CAG repeat in ataxin-2 is a frequent cause of autosomal dominant spinocerebellar ataxia.

The autosomal dominant spinocerebellar ataxias (ADSCAs) are a heterogeneous group of late-onset neurodegenerative disorders with overlapping clinical features. Genetic linkage studies have identified at least seven distinct loci for the ADSCAs, allowing the genetic classification of these disorders. The spinocerebellar ataxia type 2 (SCA2) locus was mapped to chromosome 12, and a gene responsible for this disorder was recently isolated. The mutation causing SCA2 is an expansion of a trinucleotide CAG repeat contained within the coding region of a novel gene. We describe the results of genotypic analysis for the SCA2 repeat in individuals with ADSCA who were previously found negative for CAG repeat expansions in the SCA1, SCA3, or SCA6 genes. The expanded CAG repeat has been identified in 15 independent families. Repeat instability and anticipation were observed in two large kindreds. The SCA2 mutation was found in 18% of our ADSCA kindreds, confirming the high proportion of SCA2 among this group of disorders.