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.     

Autosomal dominant cerebellar ataxia: frequency analysis and clinical characterization of 45 families from Portugal

Background and purpose:  The relative frequency of the different autosomal dominant cerebellar ataxia (ADCA) varies widely amongst different geographic locations. Here we describe a series of 45 ADCA families from Portugal.
Methods:  Patients with progressive cerebellar dysfunction of autosomal dominant transmission underwent a clinical examination protocol and genetic testing for spinocerebellar ataxia (SCA)1 to Machado-Joseph disease (MJD)/SCA3, SCA6, SCA7, SCA10, SCA12, SCA17 and dentatorubral-pallidoluysian atrophy (DRPLA). We registered the clinical characteristics and frequency of each type of ataxia.
Results:  MJD/SCA3 was the most frequent ADCA (26 families, 57.8% of all families), followed by DRPLA (5 families, 11.2%), SCA7 (2 families, 4.4%), SCA2 and SCA1 (1 family each, 2.2% each); 10 families (22.2%) had no molecular diagnosis. SCA1 and SCA7 patients had African ancestry. DRPLA patients had Portuguese ancestry and were characterized by prominent anticipation and a variable combination of epilepsy, extra-pyramidal symptoms and dementia. Ophtalmoparesis, slow saccades and retinopathy were most distinctive of SCA3, SCA2 and SCA7 cases, respectively.
Conclusions:  MJD/SCA3 was the most common ADCA in this group of families. The high frequency of DRPLA and presence of SCA1 and SCA7 cases was unexpected. The presence of these rarer ADCA types probably reflects migration phenomena, posing a challenge for differential diagnosis.     

Analysis of spinocerebellar ataxias due to expanded triplet repeats in Greek patients with cerebellar ataxia

The relative frequency of different autosomal dominant cerebellar ataxias, commonly referred to as spinocerebellar ataxias (SCAs), varies considerably among populations of different ethnic origin. No data exist at present on the frequency of different SCAs in the Greek population. In the present study we investigated the presence of triplet repeat expansion SCAs (SCA1, SCA2, SCA3, SCA6, SCA7, SCA8, SCA12, SCA17 and DRPLA) in a cohort of 83 Greek patients with slowly progressive cerebellar ataxia. Twenty patients came from autosomal dominant (AD) pedigrees, seven displayed recessive or unclear inheritance and 56 were sporadic. We found four patients with pathological SCA expansions, all from AD pedigrees. Two patients had SCA1, one SCA2 and one SCA7 (10.0, 5.0 and 5.0% of the AD group, respectively). The clinical features of these patients were within the expected spectrum. In total, a pathological expansion was detected in 20% of patients from AD pedigrees. Interestingly, no cases of SCA3 or SCA6 were detected in the AD group. No expansions were found in other familial cases or in sporadic patients. Overall, no cases of SCA3, SCA6, SCA12, SCA17 or DRPLA were identified in the Greek population. In conclusion, SCA1, SCA2 and SCA7 are present in Greek patients with AD cerebellar ataxia in frequencies similar to those observed in other populations. SCA3 and SCA6 appear however to be rare in Greece. The genetic cause for the majority of AD ataxias remains to be identified.     

The complex clinical and genetic classification of inherited ataxias. II. Autosomal recessive ataxias

Autosomal recessive ataxias are a heterogeneous group of rare neurodegenerative diseases characterized by early onset cerebellar ataxia associated with various neurologic, ophthalmologic and systemic signs. In comparison with autosomal dominant ataxias, the group of recessive ataxias is less extensively characterized. In fact, only a few conditions have been genetically characterized. The pathogenesis of these forms is associated with a "loss of function" of specific cellular proteins involved in metabolic homeostasis, cell cycle, and DNA repair/protection processing. The two most common autosomal recessive ataxias, in European countries, are Friedreich's ataxia and ataxia telangiectasia. Other forms are much less frequent, and include ataxia with vitamin E deficiency, abetalipoproteinemia. Refsum's disease, spastic ataxia, infantile onset spinocerebellar ataxia, and ataxia with oculomotor apraxia. These pathological conditions, although extremely rare, have nevertheless to be carefully considered in differential diagnosis, not only for correct nosographical classification, but particularly, for specific prognostic and therapeutic implications. Some of these diseases exhibit a peculiar regional distribution. An updated review of the clinical, genetic, and pathogenic aspects of recessive ataxias is presented. Specific management problems with respect to diagnosis and genetic counseling are discussed.     

Friedreich's ataxia and other hereditary ataxias in Greece: An 18-year perspective

Limited data exist on the spectrum of heredoataxias in Greece, including the prevalence and phenotype of Friedreich's ataxia (FRDA) and the prevalence and subtypes of dominant spinocerebellar ataxias (SCAs). We analyzed clinically and investigated genetically for FRDA and triplet-repeat expansion SCAs a consecutive series of 186 patients with suspected heredoataxia referred to Athens over 18 years. For prevalence estimates we included patients with molecular diagnosis from Cyprus that were absent from the Athens cohort. The minimum prevalence of FRDA was ~ 0.9/100,000, with clusters of high prevalence in Aegean islands. FRDA was diagnosed in 73 probands. The genotypic and phenotypic spectrum of FRDA was similar to other populations, with one patient compound heterozygote for a known point mutation in FXN (Asn146Lys). Undiagnosed recessive ataxias included FRDA-like and spastic ataxias. The minimum prevalence of dominant SCAs was ~ 0.7/100,000. SCA1 (4), SCA7 (4), SCA2, SCA6, and SCA17 (1 each) probands were identified. A molecular diagnosis was reached in 31% of dominant cases. Undiagnosed dominant patients included a majority of type III autosomal dominant cerebellar ataxias. FRDA is the commonest heredoataxia in the Greek population with prevalence towards the lower end of other European populations. Dominant SCAs are almost as prevalent. SCA1, SCA2, SCA6, SCA7 and SCA17 patients complete the spectrum of cases with a specific molecular diagnosis.     

Prevalence of inherited ataxias in the province of Padua, Italy

Few population studies are available on epidemiological indexes of hereditary ataxias. An investigation on the prevalence rate of these movement disorders is in progress for the Veneto region, the main area of northeast Italy with a population of 4,490,586 inhabitants. The first results of this epidemiological survey concern the province of Padua, which numbers 845,203 residents (January 1, 2002). The prevalence rate of inherited ataxias has been estimated at 93.3 cases per million inhabitants. The most common types appeared to be the autosomal dominant forms, namely spinocerebellar ataxia type 1 and 2, with a prevalence of 24 per 1,000,000. In the same population, with a prevalence rate of 6 per 1,000,000, Friedreich's ataxia was defined as the prominent recessive autosomal form. There were very rare cases of ataxia telangiectasia, ataxia with vitamin E deficiency and cerebellar ataxia with congenital muscular dystrophy, a recently identified autosomal recessive disease.     

Cerebellar ataxia, hypogonadism and chorioretinopathy: molecular analysis of an Italian family

This study aimed to determine if cerebellar ataxia, hypogonadism and chorioretinopathy (AHCR) is associated with mutations in mitochondrial DNA or in genes responsible for spinocerebellar ataxias (SCA1, SCA2, SCA3 and Friedreich's ataxia). Two brothers with cerebellar ataxia, hypogonadism and chorioretinopathy and their unaffected parents underwent molecular analysis for duplications and deletions in mitochondrial DNA (mtDNA), point mutations in the ATP ase 6 gene, and expansions of CAG repeats (at 6p22-p23, 12q24.1, 14q32.1) and of GAA repeats (at gene X25 on chromosome 9q13). The research was negative for all mutations. Our findings confirm that AHCR is a distinct disease within the inherited cerebellar ataxias.     

Parkinsonism & related disorders. Ataxias

The ataxias are a group of progressive neurodegenerative disorders with ataxia as the leading symptom. Current classifications distinguish between hereditary and non-hereditary ataxias. The hereditary ataxias are further divided into the autosomal recessive ataxias, the most frequent of which is Friedreich's ataxia, and the autosomal dominant spinocerebellar ataxias. The non-hereditary ataxias are separated into the acquired ataxias, such as alcoholic cerebellar degeneration or paraneoplastic cerebellar degeneration, and the sporadic degenerative ataxias, such as multiple system atrophy or sporadic adult onset ataxia. The causative mutations of many hereditary ataxias have recently been identified. Therapies based on the knowledge of the underlying molecular pathogenesis are available for a number of ataxia disorders.     

Prevalence of hereditary ataxias and spastic paraplegias in Molise,a region of Italy

Summary An epidemiological survey of hereditary ataxias and paraplegias was conducted in Molise, a region of Italy (335, 211 inhabitants on 1 January 1989). Total prevalence was 7.5 x 10^–5 inhabitants (95% confidence limits 4.8–11.1). There were 7 patients with Friedreich's disease, 5 with early onset cerebellar ataxia with retained tendon reflexes, 4 with ataxia-telangiectasia, 9 with hereditary spastic paraplegias (2 autosomal dominant and 7 autosomal recessive cases). There was no patient with autosomal dominant cerebellar ataxia.     

Spinocerebellar ataxia type 6: CAG trinucleotide expansion, clinical characteristics and sperm analysis

Spinocerebellar ataxia type 6 (SCA6) is an autosomal dominant spinocerebellar degeneration caused by CAG repeat expansions in the human α1A voltage-dependent calcium channel subunit gene. We analyzed 16 SCA6 patients in 14 unrelated Japanese families, and documented the clinical and molecular properties correlating with the CAG repeat expansion. Three of them were sporadic. The CAG repeat number of the expanded and normal alleles was 22.7 ± 2.0 (mean ± SD, n = 15) and 13.8 ± 2.0 (n = 15), respectively, and the repeat size of the expanded alleles correlated inversely with age at onset. The patients presented here were clinically characterized by a slowly progressive cerebellar ataxia and nystagmus. In leukocytes, the strict pattern of the peak in the expanded allele on polyacrylamide gel electrophoresis did not show the presence of cell mosaicism in SCA6, in contrast to other trinucleotide disorders. Moreover, in each patient, the number of CAG repeats in sperm was the same as in leukocytes, and the expanded alleles in sperm indicated uniform peaks as well. In our geographic area, the frequency of SCA6 was as high as MJD, in contrast to the low frequency of other autosomal dominant cerebellar ataxias. Thus, a geographic difference in the frequency of autosomal dominant spinocerebellar ataxias may be present in Japan.     

Primary degenerative cerebellar ataxias in ethnic Bengalees in West Bengal: some observations

Seventy cases of primary degenerative cerebellar ataxias in ethnic Bengalees from southern West Bengal, India, were studied by the authors. Of these, 50 cases were of the familial type (hereditary ataxias) encountered in 23 families and the remaining 20 were of sporadic onset. 18 cases (from 11 families) were of "probable" autosomal recessive (AR) inheritance, 12 cases (8 families) had Friedreich's type ataxia (FA), 4 cases (2 families) had FA type ataxia with retained reflexes and in 2 cases (1 family) the exact phenotypic characterization could not be made. AR inheritance in these cases seemed most likely in view of the occurrence in a single generation with unaffected parents and history of consanguinity in many of the families studied. Genotypic confirmation of FA type ataxia and its variants could not be done in any case due to the non-availability of technology for studying the FA locus but some common dominant ataxia genotypes could be excluded. Thirty-two cases (from 12 families) with autosomal dominant ataxias (ADCA) were studied. Genotype analysis revealed 4 families with SCA2 genotype, 5 families with SCA3 and 3 families where genotypic characterization could not be made (phenotypically 2 were of ADCA I and 1 of ADCA II). No clear preponderance of one particular genotype of SCA over another could be demonstrated in our ethnic Bengalee patients. We also noted significant intra and inter-family variations in phenotypes within the same genotypic form as well as overlapping of clinical signs between different genotypes. Slow saccades and peripheral neuropathy were not seen consistently in our ethnic Bengalee subjects with SCA2 genotype. Similarly, extrapyramidal features, ophthalmoplegias and distal amyotrophy were seen in some but not all families with the SCA3 genotype. Phenotypic expression appeared to be an inconsistent marker of the SCA genotype in our patients. Of the 20 sporadic cases with cerebellar ataxia, genotype analysis revealed 2 cases with SCA1 and 1 with SCA2. Some of the sporadic ataxia cases had extracerebellar involvement and may warrant classification as Multiple System Atrophy. In all the 3 subjects with genotype characterization, phenotype correlation was lacking. The clinical pattern of hereditary ataxias in ethnic Bengalees seems to be somewhat different from that seen in Western India. The need for clinical and genetic studies of ataxias in different specific ethnic populations of India has been stressed.     

Neuropathological and molecular studies of spinocerebellar ataxia type 6 (SCA6)

SCA6 is an autosomal dominant spinocerebellar ataxia (SCA) caused by a small CAG repeat expansion of the gene encoding an α-1a-voltage-dependent Ca channel gene subunit on chromosome 19p13. A Japanese woman with SCA6, with a 7-year history of progressive pure cerebellar ataxia, died of malignant lymphoma. Systematic neuropathological examination showed that neuronal degeneration was confined to the cerebellar Purkinje cells and, to a lesser degree, the granular cells, without any involvement of other central nervous system structures. Such pathological selectivity correlates with the localized expression of the responsible gene, and coincides with the neurological manifestation. These findings might contribute to establishing the phenotype of the SCA6 via comparison with other dominant ataxias. Received: 7 July 1997 / Revised, accepted: 14 August 1997     

Frequency analysis and clinical characterization of different types of spinocerebellar ataxia in Serbian patients.

The relative frequencies of different spinocerebellar ataxias (SCAs) vary widely among different ethnic groups, presumably due to a founder effect. We investigated the relative prevalence of SCA1-3, 6-8, 12, 17; dentate-rubro-pallidoluysian atrophy; and Friedreich's ataxia (FRDA) in Serbian patients with adult-onset (>20 years of age) hereditary and sporadic SCAs, and compared clinical features of patients with genetically confirmed SCAs. A total of 108 patients from 54 families (38 apparently dominant [ADCA] and 16 apparently recessive) with adult-onset hereditary ataxia and 75 apparently sporadic patients were assessed. Of 38 families with ADCA, 13 (34%) were positive for an expansion in an SCA1 and 5 families (13%) for an expansion in an SCA2 allele. In 20 families (53%), no expansions have been identified in any of the analyzed genes. Gaze palsy, spasticity, and hyperreflexia were significantly more common in SCA1, whereas slow saccades, hypotonia, hyporeflexia, and dystonia prevailed in SCA2 patients. Among the 16 families with an apparently recessive mode of ataxia inheritance, 4 (25%) were identified as having the FRDA mutation. Ataxia-causing mutations were identified in 8 (10.6%) of patients with apparently sporadic adult-onset ataxia.     

Electroretinographic findings in inherited ataxias

Electroretinogram was performed in 18 patients with inherited ataxias. Eight had Friedreich's disease, 9 autosomal dominant cerebellar ataxia and one early onset cerebellar ataxia with retained tendon reflexes. Abnormalities were found in one patient for each group. The most frequent were decreased b-wave amplitude in photopic and scotopic conditions and prolonged implicit time.     

Rare forms of autosomal recessive neurodegenerative ataxia

There has been a recent explosion in knowledge regarding the genetic basis of several autosomal recessive ataxias. This article summarizes current information regarding rare forms of recessive ataxias. Friedreich's ataxia and ataxia telangiectasia are dealt with in other articles in this issue. The rarer recessive ataxias can be clinically classified as sensory and spinocerbellar ataxias, cerebellar ataxia with sensory-motor polyneuropathy, and purely cerebellar ataxias. Examples of the first category include ataxia with isolated vitamin E deficiency, abetalipoproteinemia, Refsum's disease, infantile-onset spinocerebellar ataxia, and ataxia with blindness and deafness. Examples of ataxia with sensory-motor polyneuropathy include ataxia with oculomotor apraxia 1 and 2 and spinocerebellar ataxia with neuropathy 1. Examples of purely cerebellar ataxia include autosomal recessive spastic ataxia of Charlevoix-Saguenay and ataxia with hypogonadotropic hypogonadism. This review summarizes the clinical and genetic features of these entities and concludes that the pathogenic basis of such ataxias at this time appear to involve two broad types of processes: free-radical injury and defects of DNA single- or double-strand break repair.     

A review of the inherited ataxias: recent advances in genetic, clinical and neuropathologic aspects

Inherited ataxias are a heterogeneous group of disorders characterized by autosomal dominant and recessive inheritance. Recent advances in genetic research have resulted in an improved comprehension of their clinical presentation. Autosomal dominant cerebellar ataxias (ADCAs) include spinocerebellar ataxias (SCAs) and dentatorubral-pallidoluysian atrophy (DRPLA); six of these have been found to be trinucleotide repeat disorders. Episodic ataxia, types 1 and 2, are at present recognized to be channelopathies, caused by point mutations. Friedreich’s ataxia (FA) which is an autosomal recessive disorder, resulting from a a unique trinucleotide repeat, is now recognized to have a wide age of onset and clinical spectrum. Ataxia-telangiectasia (AT), also an autosomal recessive cerebellar ataxia, is characterized by immunodeficiency. In this article, the genetic and clinical characteristics of these diseases are reviewed in detail.     

Linkage to chromosome 13q11-12 of an autosomal recessive cerebellar ataxia in a Tunisian family

OBJECTIVE: To report the clinical findings and the genetic linkage mapping of an autosomal recessive cerebellar ataxia associated to peripheral neuropathy, showing an early onset cerebellar ataxia with retained tendon reflexes (EOCA) phenotype. BACKGROUND: EOCA is a clinical syndrome delimited by Harding distinguished from Friedreich's ataxia (FA) mainly by the preservation of tendon reflexes. Molecular genetic study of patients with EOCA has demonstrated genetic heterogeneity. A form of autosomal recessive spastic ataxia has been described in Charlevoix Saguenay area in Quebec (ARSACS); the gene responsible has been mapped to chromosome 13q. METHODS: Genetic linkage analysis was performed on 18 members of a large family including 8 of 9 members with EOCA. After exclusion of FA and ataxia with vitamin E deficiency loci as well as loci of autosomal dominant cerebellar ataxias, we performed a linkage analysis to markers of 13q11-12 region. RESULTS: The 9 affected members of this family showed stereotyped clinical features with cerebellar ataxia, pyramidal syndrome, and a variable degree of axonal peripheral neuropathy. Linkage was detected between the disease locus and the microsatellite marker D13S232. Surrounding markers to D13S232 confirmed the linkage and showed the homozygosity of the affected members. CONCLUSION: The family reported here showed the same locus as autosomal recessive spastic ataxia Charlevoix Saguenay disease.     

LINKAGE TO CHROMOSOME 13Q11-12 OF AN AUTOSOMAL RECESSIVE CEREBELLAR ATAXIA IN A TUNISIAN FAMILY

OBJECTIVE: To report the clinical findings and the genetic linkage mapping of an autosomal recessive cerebellar ataxia associated to peripheral neuropathy, showing an early onset cerebellar ataxia with retained tendon reflexes (EOCA) phenotype. BACKGROUND: EOCA is a clinical syndrome delimited by Harding distinguished from Friedreich's ataxia (FA) mainly by the preservation of tendon reflexes. Molecular genetic study of patients with EOCA has demonstrated genetic heterogeneity. A form of autosomal recessive spastic ataxia has been described in Charlevoix Saguenay area in Quebec (ARSACS); the gene responsible has been mapped to chromosome 13q. METHODS: Genetic linkage analysis was performed on 18 members of a large family including 8 of 9 members with EOCA. After exclusion of FA and ataxia with vitamin E deficiency loci as well as loci of autosomal dominant cerebellar ataxias, we performed a linkage analysis to markers of 13q11-12 region. RESULTS: The 9 affected members of this family showed stereotyped clinical features with cerebellar ataxia, pyramidal syndrome, and a variable degree of axonal peripheral neuropathy. Linkage was detected between the disease locus and the microsatellite marker D13S232. Surrounding markers to D13S232 confirmed the linkage and showed the homozygosity of the affected members. CONCLUSION: The family reported here showed the same locus as autosomal recessive spastic ataxia Charlevoix Saguenay disease.     

Autosomal dominant cerebellar ataxia type I in Morocco: presence of the SCA1 and SCA3/MJD mutations

We searched for CAG repeat expansions at the SCA1 and SCA3/MJD loci in nine families, including 15 examined patients, with autosomal dominant cerebellar ataxia type I from Morocco. Expansion of the CAG repeat was found in one family at the SCA1 and two at the SCA3/MJD locus, demonstrating the existence of genetic heterogeneity among ADCA type I families in Morocco. Instability during transmission was observed at both loci as in other unstable mutations. The phenotypes of the SCA1 and SCA3/MJD patients were similar.     

Clinical and MRI findings in spinocerebellar ataxia type 5.

Spinocerebellar ataxia type 5 (SCA5), one of the genetically heterogeneous autosomal dominant cerebellar ataxias, was assigned to chromosome 11 in a single family descending from the grandparents of President Abraham Lincoln. We report a second, apparently unrelated, SCA5 family of French origin. The overall clinical picture was a slowly progressive cerebellar syndrome beginning mostly in the third decade (27+/-10 years, range 14 to 40). MRI showed a marked global cerebellar atrophy similar to SCA6.