A Māori specific RFC1 pathogenic repeat configuration in CANVAS, likely due to a founder allele

Cerebellar ataxia with neuropathy and bilateral vestibular areflexia syndrome (CANVAS) is a recently recognized neurodegenerative disease with onset in mid- to late adulthood. The genetic basis for a large proportion of Caucasian patients was recently shown to be the biallelic expansion of a pentanucleotide (AAGGG)n repeat in RFC1. Here, we describe the first instance of CANVAS genetic testing in New Zealand Māori and Cook Island Māori individuals. We show a novel, possibly population-specific CANVAS configuration (AAAGG)10-25(AAGGG)exp, which was the cause of CANVAS in all patients. There were no apparent phenotypic differences compared with European CANVAS patients. Presence of a common disease haplotype among this cohort suggests this novel repeat expansion configuration is a founder effect in this population, which may indicate that CANVAS will be especially prevalent in this group. Haplotype dating estimated the most recent common ancestor at ∼1430 ce. We also show the same core haplotype as previously described, supporting a single origin of the CANVAS mutation.

Cerebellar ataxia in the eastern and southern parts of Norway

INTRODUCTION

The relative frequencies of different ataxias vary among different ethnic and geographic groups. The aim of this study was to examine patients with cerebellar ataxia and find the occurrence of autosomal dominant and recessive cerebellar ataxias in the population of the southern and eastern parts of Norway and estimate its prevalence.

MATERIALS AND METHODS

Probands were systematically tested for spinocerebellar ataxia 1, 2, 3, 6 and Friedreich's ataxia. A total of 94 patients with ataxia were assessed.

RESULTS

We registered 60 patients from 39 unrelated families with hereditary ataxias. One family with SCA2 (two patients), one family with Friedreich's ataxia (two patients), two patients heterozygote for Friedreich's ataxia and one metabolic ataxia were identified.

CONCLUSIONS

We have few Friedreich's ataxia and SCA 1,2,3 and 6 in our population. Prevalence in Oslo County was estimated at 2.2/100,000 for autosomal recessive and 3.0/100,000 for autosomal dominant ataxia, respectively.

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.

Prevalence and ethnic differences of autosomal-dominant cerebellar ataxia in Singapore

We report the prevalence and ethnic differences of autosomal-dominant cerebellar ataxia (ADCA) in Singapore. Amongst 204 patients with ataxia who underwent genetic testing for dentatorubral-pallidoluysian atrophy (DRPLA) and for spinocerebellar ataxias (SCA) 1, 2, 3, 6, 7, 8, 10 and 12, 58 (28.4%) patients from 36 families tested positive. SCA 3 was identified in 31 (53.4%) patients from 15 families, SCA 2 in 17 (29.3%) patients from 12 families and SCA 1 in four (6.9%) patients from four families. Other SCA subtypes were rare. SCA 2 was the only subtype identified amongst ethnic Malay and ethnic Indian families. The estimated prevalence of ADCA in Singaporean families was at least 1 : 27,000. Based on the history and ancestry of Singaporeans, our study supported a founder effect for specific SCA subtypes and the association of ethnicity-specific SCA subtypes. Our findings suggest that SCA 2 is relatively common amongst the Malay race and that priority testing for SCA 3 and SCA 2 for ethnic Chinese, and SCA 2 for ethnic Malay, may be cost effective and relevant for the region.

Autosomal dominant cerebellar ataxias in ethnic Bengalees in West Bengal - an Eastern Indian state

BACKGROUND

Phenotypic and genotypic patterns of a hereditary disease in a large multiethnic country like India need to be studied in relation to geographical location and ethnicity of the population. The few reported studies from India on dominant ataxias (ADCA) have mostly been conducted on multiethnic populations and hence may not reflect the patterns observed in specific ethnic groups or geographical locations. The present study attempted to look into the patterns of ADCA amongst ethnic Bengalee patients hailing from the eastern Indian state of West Bengal.

MATERIAL AND METHODS

Between mid-1996 and mid-2000, in a clinic based study, 37 cases (from 14 families) with ADCA were studied. This included 33 affected and four asymptomatic members with abnormal physical signs. Genotypic analyses were performed on more than one affected member from each family. Clinical, neuroradiological and electrophysiological aspects were studied.

OBSERVATIONS

Genotype analysis revealed: two families with SCA-1,4 families with SCA2,5 families with SCA3 and three families with undetermined genotype. Of the latter, phenotypically 2 were of ADCA 1 and one of ADCA 2 type. No clear preponderance of one particular genotype over another was observed. We noted significant intra- and interfamily variations in phenotype within the same genotype form as well as overlapping of clinical signs between different genotypes. Slow saccadic eye movements and peripheral neuropathy were not seen consistently in our ethnic Bengalee subjects with SCA2 genotypes. Similarly, extrapyramidal features, ophthalmoplegias and distal amyotrophy were seen in some but not in all families with SCA3 mutation. A peculiar form of abduction lag during slow pursuit movement of eyes was observed in an asymptomatic girl in an SCA3 family.

CONCLUSIONS

Although SCA2 has been claimed to be the commonest form of ADCA in India, this does not appear to be so in our ethnic Bengalee subjects. Phenotypic expression of the genotype also appears to be variable amongst families and individuals. Hence, phenotypic expression appears to be an inconsistent marker of the SCA genotype in our patients.

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

BACKGROUND

Spinocerebellar ataxia (SCA) is a heterogeneous group of neurodegenerative disorders. The mutational basis for most of these disorders is an expanded CAG repeat sequence within the coding regions of the genes involved. The prevalence of SCA in the ethnic Chinese on Taiwan remains unclear. Moreover, there has been no report of SCA type 6 (SCA6) among Chinese people.

OBJECTIVES

To characterize the prevalence of SCA in the ethnic Chinese on Taiwan, and to specifically characterize Chinese patients with SCA6 in terms of clinical and molecular features.

PATIENTS AND METHODS

Using a molecular approach, we investigated SCA in 74 Taiwanese families with dominantly inherited ataxias and in 49 Taiwanese patients with sporadic ataxias. Clinical and molecular features of SCA6 were further characterized in 12 patients from 8 families and in 2 sporadic cases. Furthermore, the intragenic polymorphic marker D19S1150 was amplified by polymerase chain reaction to analyze for linkage disequilibrium.

RESULTS

Machado-Joseph disease-SCA3 was the most common type of autosomal dominant SCA in the Taiwanese cohort, accounting for 35 cases (47.3%), followed by SCA6 (8 [10.8%]), SCA2 (8 [10.8%]), SCA1 (4 [5.4%]), SCA7 (2 [2.7%]), dentatorubropallidoluysian atrophy (1 [1.4%]), and SCA8 (0%). The genes responsible for 16 (21.6%) of Taiwanese dominantly inherited SCA cases remain to be determined. Among the 49 patients with sporadic ataxias in the present series, 2 (4.1%) were found to harbor SCA6 mutations. In the families with SCA6, we found significant anticipation in the absence of genetic instability on transmission, indicating that some other mechanism might account for the anticipation. The same frequent allele of the intragenic DNA marker (D19S1150) was shared by 7 of 10 Taiwanese families with SCA6.

CONCLUSIONS

Although SCA6 has, so far, not been reported in mainland Chinese, we found a geographic cluster of families with SCA6 on Taiwan. Genotyping studies suggest a founder effect in the Taiwanese patients with SCA6.

Genetic analysis of early onset cerebellar ataxia with retained tendon reflexes in four Tunisian families

Spinocerebellar ataxias comprise a poorly understood group of inherited degenerative neurological diseases. Attempts to classify hereditary ataxias on the basis of the neurological features or specific clinical signs such as tendon reflex changes have proven to be unsatisfactory. Early onset cerebellar ataxia (EOCA) is generally inherited as an autosomal-recessive trait. Thus far, we do not have accurate answers to several questions about its classification. However, significant clinical heterogeneity observed in four Tunisian families with typical EOCA clinical features reinforces the hypothesis of genetic heterogeneity underlying this phenotype. We have demonstrated that three of the four families studied were not linked to Friedreich's ataxia (FA), vitamin E deficiency ataxia (AVED), and autosomal dominant cerebellar ataxia (ADCA) loci. The fourth family showed homozygosity for a large pathological expansion of GAA repeat in all patients, the parents being heterozygous for this mutation. We have also noted, in the case of the family studied, that there was instability in the transmission of the mutation, along with a phenomenon of anticipation comparable to that observed in dominant triplet repeat diseases. EOCA is thus clinically indistinguishable from FA, yet genetically independent of all known candidate genes. Genetic mapping is required for research into the causal gene and an understanding of the disease's physiopathologic mechanisms.

Japanese families with autosomal dominant pure cerebellar ataxia map to chromosome 19p13.1-p13.2 and are strongly associated with mild CAG expansions in the spinocerebellar ataxia type 6 gene in chromosome 19p13.1

Autosomal dominant cerebellar ataxia is a group of clinically and genetically heterogeneous disorders. We carried out genomewide linkage analysis in 15 families with autosomal dominant pure cerebellar ataxia (ADPCA). Evidence for linkage to chromosome 19p markers was found in nine families, and combined multipoint analysis refined the candidate region to a 13.3-cM interval in 19p13.1-p13.2. The remaining six families were excluded for this region. Analysis of CAG-repeat expansion in the alpha1A-voltage-dependent calcium channel (CACNL1A4) gene lying in 19p13.1, recently identified among 8 small American kindreds with ADPCA (spinocerebellar ataxia type 6 [SCA6]), revealed that 8 of the 15 families studied had similar, very small expansion in this gene: all affected individuals had larger alleles (range of CAG repeats 21-25), compared with alleles observed in neurologically normal Japanese (range 5-20 repeats). Inverse correlation between the CAG-repeat number and the age at onset was found in affected individuals with expansion. The number of CAG repeats in expanded chromosomes was completely stable within each family, which was consistent with the fact that anticipation was not statistically proved in the SCA6 families that we studied. We conclude that more than half of Japanese cases of ADPCA map to 19p13.1-p13.2 and are strongly associated with the mild CAG expansion in the SCA6/CACNL1A4 gene.

[Neuromyelopathy in the population of Noir-marron of Saint-Laurent du Maroni in French Guiana]

The neurological observations have been reported at André Bouron Hospital of Saint-Laurent du Maroni and at General Hospital of Cayenne during a period of 5 years. All patients belonged to the "Noir Marron" ethnic group and lived in the area of Saint-Laurent. There were six women and four men, aged 15-35 years. Neurological symptoms were isolated or associated to other organ failure. Neurological manifestations included retrobulbar optic neuropathy, spastic paraparesis, sensitive ataxia and cerebellar ataxia, psychiatric symptoms were observed. Other organs affected were cardiovascular, digestive, cutaneous or endocrinologic (thyroid). Diet consist mainly in cassava. Thiamin deficiency has been observed several times. Improvement of neurological deficits following thiamin administration points towards Thiamin as an etiological factor. Ethnological specificity of Saint-Laurent area may explain that such neurological manifestation have not been observed in the rest of the department.

Autosomal dominant cerebellar ataxias in the Kinki area of Japan

The autosomal dominant cerebellar ataxias are a heterogeneous group of neurodegenerative disorders characterized by slowly progressive cerebellar ataxia. Recently, among the ataxias, spinocerebellar ataxia type 1 (SCA1), Machado-Joseph disease (MJD) and dentatorubral-pallidoluysian atrophy have been found to be caused by expansion of a CAG trinucleotide repeat in the coding region of the disease genes. We have analyzed the CAG repeats of 67 patients from 47 families with dominantly inherited ataxia who lived in the Kinki area of Japan. The following results were obtained. First, 31 patients from 22 families were found to be positive for the MJD repeat expansion, indicating that MJD is the most common dominantly inherited ataxia in the Kinki area of Japan. Second, no SCA1 repeat expansion was found among the families studied. This presents a striking contrast to the fact that there are many families with SCA1 in Hokkaido and the Tohoku area of Japan. These findings suggest geographic variation in autosomal dominant cerebellar ataxias in Japan.

Genetic heterogeneity of autosomal dominant cerebellar ataxia type 1: clinical and genetic analysis of 10 French families

We performed linkage analysis between the gene responsible for spinal cerebellar ataxia 1 (SCA1) and the highly polymorphic chromosome 6 locus, D6S89, in 10 French families with autosomal dominant cerebellar ataxia (ADCA) type 1. These families were clinically indistinguishable except for one family with loss of hearing and vision. Very close linkage was observed in four families, with no evidence of recombination between SCA1 and D6S89. Linkage with D6S89 was excluded in the six others, thus demonstrating genetic heterogeneity for ADCA type 1. The D6S89 marker, which is very closely linked to the disease locus, can be used to identify SCA1 families and will lead to predictive testing.

Molecular heterogeneity of autosomal dominant cerebellar ataxia: analysis of flanking microsatellites of the spinocerebellar ataxia 1 locus in a northern European family unequivocally demonstrates non-linkage

This study addresses the question whether the different forms of autosomal dominant cerebellar ataxia (ADCA) are related to different ethnic/geographical regions in Europe. One mutation in families originating from Holland, Prussia and Italy has previously been localized to chromosome 6p (SCA1 locus), whereas the mutation in families of Iberic origin has been excluded from chromosome 6p. In a Danish five-generation pedigree with ADCA and in which previous HLA-serotyping had shown inconclusive linkage results, the present study shows unequivocal exclusion from the SCA1 locus, firstly through the use of the new, highly informative microsatellites D6S89 and D6S109, which closely flank the SCA1 locus, and secondly through the manifestation of disease in four pedigree members previously scored as unaffected. Additional molecular genetic analysis of the HLA DRbeta and F13A polymorphisms also argue against a cluster of ADCA genes on chromosome 6p. Since this study demonstrates the existence of non-SCA1 families and therefore heterogeneity in the North-European population, molecular family counselling remains restricted to the few known SCA1 families.