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G Cancel

Publications and source records attributed to G Cancel.

At least 37 records · Page 2Linked to original sources
PubMed1997

Clinical and molecular features of spinocerebellar ataxia type 6.

The mutation involved in spinocerebellar ataxia type 6 (SCA6) is a small CAG expansion in the alpha-1A subunit of the voltage-dependent calcium channel gene. We looked for this mutation in 91 families with autosomal-dominant cerebellar ataxias and found that SCA6 is a minor locus in our series (2%) and is rare in France (1%). Furthermore, we did not detect the SCA6 mutation on 146 sporadic cases with isolated cerebellar ataxia or olivopontocerebellar atrophy. The normal and expanded alleles ranged from 4 to 15 and 22 to 28 CAG repeats, respectively, and age at onset was correlated to CAG repeat length (r = -0.87). In contrast with other SCA, the expanded allele was stable during transmission. Clinically, SCA6 patients (n = 12) presented with moderate to severe cerebellar ataxia with a lower frequency of associated signs compared with other SCA and a mean age at onset of 45 +/- 14 years (range, 24 to 67). MRI showed extensive cerebellar atrophy but not of the brainstem or cerebral cortex.

Adult↗
PubMed1996

Spinocerebellar ataxia 3 and Machado-Joseph disease: clinical, molecular, and neuropathological features.

Patients with spinocerebellar ataxia 3 (SCA3) and Machado-Joseph disease (MJD) carry an expanded CAG repeat in the MJD1 gene. One hundred twenty families of different geographic origin with autosomal dominant cerebellar ataxia (ADCA) type I were tested. Thirty-four families (126 patients) carried an expanded CAG repeat. The expanded and the normal allele did not overlap and the repeat was unstable during transmission, with variation in the size of the CAG length ranging from -8 to +5 and a mean expansion of 0.86 repeats without differences according to the parental sex. There was a combined effect of the number of CAG repeats of the expanded and normal allele on the age at onset, which accounted for 70% of its variability. The length of the CAG repeat influenced the frequency of clinical signs associated with cerebellar ataxia, such as abnormal tendon reflexes or decreased vibration sense, whereas the interindividual variation of supranuclear ophthalmoplegia, sphincter and swallowing difficulties, and amyotrophy was mostly determined by different disease durations. We compared the clinical profile of 91 SCA3/MJD patients with 51 SCA1 and 32 SCA2 patients. There were striking differences between the SCA3/MJD and SCA2 but not with SCA1 groups of patients. Despite their clinical similarities, distinct neuropathological features were observed in 2 SCA3/MJD and 2 SCA1 patients.

Adult↗
PubMed1996

Autosomal dominant cerebellar ataxia type I in Martinique (French West Indies): genetic analysis of three unrelated SCA2 families.

Autosomal dominant cerebellar ataxias (ADCAs) are a group of neurodegenerative disorders that are clinically and genetically heterogeneous. We report here a genetic linkage study, with five chromosome 12q markers, of three Martinican families with ADCA type 1, for which the spinocerebellar ataxia 1 (SCA1) locus was excluded. Linkage to the SCA2 locus was demonstrated with a maximal lead score of 6.64 at theta = 0.00 with marker D12S354. Recombinational events observed by haplotype reconstruction demonstrated that the SCA2 locus is located in an approximately 7-cM interval flanked by D12S105 and D12S79. Using the z(max)-1 method, multipoint analysis further reduced the candidate interval for SCA2 to a region of 5 cM. Two families shared a common haplotype at loci spanning 7 cM, which suggests a founder effect, whereas a different haplotype segregated with the disease in the third family. Finally, a mean anticipation of 12+/-14 years was found in parent-child couples, with no parental sex effect, suggesting that the disease might be caused by an expanded and unstable triplet repeat.

Adolescent↗
PubMed1996

Cloning of the gene for spinocerebellar ataxia 2 reveals a locus with high sensitivity to expanded CAG/glutamine repeats.

Two forms of the neurodegenerative disorder spinocerebellar ataxia are known to be caused by the expansion of a CAG (polyglutamine) trinucleotide repeat. By screening cDNA expression libraries, using an antibody specific for polyglutamine repeats, we identified six novel genes containing CAG stretches. One of them is mutated in patients with spinocerebellar ataxia linked to chromosome 12q (SCA2). This gene shows ubiquitous expression and encodes a protein of unknown function. Normal SCA2 alleles (17 to 29 CAG repeats) contain one to three CAAs in the repeat. Mutated alleles (37 to 50 repeats) appear particularly unstable, upon both paternal and maternal transmissions. The sequence of three of them revealed pure CAG stretches. The steep inverse correlation between age of onset and CAG number suggests a higher sensitivity to polyglutamine length than in the other polyglutamine expansion diseases.

Adolescent↗
PubMed1996

Screening for proteins with polyglutamine expansions in autosomal dominant cerebellar ataxias.

Expansion of trinucleotide CAG repeats coding for polyglutamine has been implicated in five neurodegenerative disorders, including spinocerebellar ataxia (SCA) 1 and SCA3 or Machado-Joseph disease (SCA3/MJD), two forms of type I autosomal dominant cerebellar ataxias (ADCA). Using the 1C2 antibody which specifically recognizes large polyglutamine tracts, particularly those that are expanded, we recently reported the detection of proteins with pathological glutamine expansions in lymphoblasts from another form of ADCA type I, SCA2, as well as from patients presenting with the distinct phenotype of ADCA type II. We now have screened a large series of patients with ADCA or isolated cases with cerebellar ataxia, for the presence of proteins with polyglutamine expansions. A 150 kDa SCA2 protein was detected in 16 out of 40 families with ADCA type I. This corresponds to 24% of all ADCA type I families, which is much more frequent than SCA1 in this series of patients (13%). The signal intensity of the SCA2 protein was negatively correlated to age at onset, as expected for an expanded and unstable trinucleotide repeat mutation. The disease segregated with markers closely linked to the SCA2 locus in all identified SCA2 families. In addition, a specific 130 kDa protein, which segregated with the disease, was detected in lymphoblasts of patients from nine families with ADCA type II. It was also visualized in the cerebral cortex of one of the patients, demonstrating its translation in the nervous system. Finally, no new disease-related proteins containing expanded polyglutamine tracts could be detected in lymphoblasts from the remaining patients with ADCA or isolated cases with cerebellar ataxia.

Cerebellar Ataxia↗
PubMed1996

Intergenerational instability of the CAG repeat of the gene for Machado-Joseph disease (MJD1) is affected by the genotype of the normal chromosome: implications for the molecular mechanisms of the instability of the CAG repeat.

Machado-Joseph disease (MJD) is an autosomal dominant neurodegenerative disorder caused by unstable expansion of a CAG repeat in the MJD1 gene at 14q32.1. To identify elements affecting the intergenerational instability of the CAG repeat, we investigated whether the CGG/GGG polymorphism at the 3' end of the CAG repeat affects intergenerational instability of the CAG repeat. The [expanded (CAG)n-CGG]/[normal (CAG)n-GGG] haplotypes were found to result in significantly greater instability of the CAG repeat compared to the [expanded (CAG)n-CGG]/[normal (CAG)n-CGG] or [expanded (CAG)nGGG]/[normal (CAG)n-GGG] haplotypes. Multiple stepwise logistic regression analysis revealed that the relative risk for a large intergenerational change in the number of CAG repeat units (< -2 or > 2) is 7.7-fold (95% CI: 2.5-23.9) higher in the case of paternal transmission than in that of maternal transmission and 7.4-fold (95% CI: 2.4-23.3) higher in the case of transmission from a parent with the [expanded (CAG)n-CGG]/[normal (CAG)n-GGG] haplotypes than in that of transmission from a parent with the [expanded (CAG)n-CGG]/[normal (CAG)n-CGG] or [expanded (CAG)n-GGG]/[normal (CAG)n-GGG] haplotypes. The combination of paternal transmission and the [expanded (CAG)n-CGG]/[normal (CAG)n-GGG] haplotypes resulted in a 75.2-fold (95% CI: 9.0-625.0) increase in the relative risk compared with that of maternal transmission and the [expanded (CAG)n-CGG]/[normal (CAG)n-CGG] or [expanded (CAG)n-GGG]/[normal (CAG)n-GGG] haplotypes. The results suggest that an inter-allelic interaction is involved in the intergenerational instability of the expanded CAG repeat.

Chromosomes, Human, Pair 14↗
PubMed1995

Polyglutamine expansion as a pathological epitope in Huntington's disease and four dominant cerebellar ataxias.

A polyglutamine expansion (encoded by a CAG repeat) in specific proteins causes neurodegeneration in Huntington's disease (HD) and four other disorders, by an unknown mechanism thought to involve gain of function or toxicity of the mutated protein. The pathological threshold is 37-40 glutamines in three of these diseases, whereas the corresponding normal proteins contain polymorphic repeats of up to about 35 glutamines. The age of onset of clinical manifestations is inversely correlated to the length of the polyglutamine expansion. Here we report the characterization of a monoclonal antibody that selectively recognizes polyglutamine expansion in the proteins implicated in HD and in spinocerebellar ataxia (SCA) 1 and 3. The intensity of signal depends on the length of the polyglutamine expansion, and the antibody also detects specific pathological proteins expected to contain such expansion, in SCA2 and in autosomal dominant cerebellar ataxia with retinal degeneration, whose genes have not yet been identified.

Adult↗
PubMed1995

SCA2 is not a major locus for ADCA type I in French families.

Autosomal dominant cerebellar ataxias (ADCA) of type I, a group of clinically heterogeneous neurodegenerative disorders, are known to be genetically heterogeneous since a second locus for ADCA type I (SCA2) has been identified on the long arm of chromosome 12. Linkage analysis was performed in 7 French ADCA type I families in order to estimate its frequency. We analysed 121 individuals, 39 of whom were affected. In 6 families, the SCA2 candidate interval, spanning 12.8 cM, was excluded by bi- and multipoint analysis. In one family (SAL-315), however, the maximal positive lod score reached 2.03 at the D12S79 locus. A posterior probability of 94% in favor of linkage to SCA2 was calculated by homogeneity analysis. The clinical profile of this family was similar to that of previously described SCA1 and non-SCA1 families, except that dementia was observed in 2 out of 6 patients. This may be a clinical idiosyncrasy in this family and was insufficient for a genotype-phenotype correlation.

Adolescent↗
PubMed1995

Analysis of the SCA1 CAG repeat in a large number of families with dominant ataxia: clinical and molecular correlations.

Autosomal dominantly inherited ataxias are a clinically and genetically heterogeneous group of neurodegenerative disorders. The gene involved in one subtype, spinocerebellar ataxia 1 (SCA1), was first localized to chromosome 6p. An unstable CAG repeat has been identified as the responsible mutation. In this study, 88 families with various types of inherited ataxias and 16 individuals with sporadic cerebellar ataxia were investigated to determine the frequency of this mutation, the behavior of the SCA1 CAG repeat during transmission, and the clinical features specific to this form of disease. Only 12 of the families carried the SCA1 mutation; 10 of the 12 were of French origin. When transmitted paternally, the repeat was more unstable and larger in size. Age at onset was inversely correlated with the number of CAG repeats. Anticipation in age at onset of about 11 years was observed in offspring. Analysis of the clinical features did not distinguish SCA1 from other forms of dominantly inherited ataxias. In the absence of distinguishing clinical characteristics, the diagnosis of SCA1 in single affected patients or family members can only be made by direct detection of the mutation, opening the way for presymptomatic testing.

Adult↗
PubMed1995

The gene for autosomal dominant cerebellar ataxia with pigmentary macular dystrophy maps to chromosome 3p12-p21.1.

Autosomal dominant cerebellar ataxia with pigmentary macular dystrophy (ADCA type II) is a rare neurodegenerative disorder with marked anticipation. We have mapped the ADCA type II locus to chromosome 3 by linkage analysis in a genome-wide search and found no evidence for genetic heterogeneity among four families of different geographic origins. Haplotype reconstruction initially restricted the locus to the 33 cM interval flanked by D3S1300 and D3S1276 located at 3p12-p21.1. Combined multipoint analysis, using the Zmax-1 method, further reduced the candidate interval to an 8 cM region around D3S1285. Our results show that ADCA type II is a genetically homogenous disorder, independent of the heterogeneous group of type I cerebellar ataxias.

Adolescent↗
PubMed1995

Autosomal dominant cerebellar ataxia type I in Martinique (French West Indies). Clinical and neuropathological analysis of 53 patients from three unrelated SCA2 families.

Autosomal dominant cerebellar ataxia type I was diagnosed in three unrelated families from Martinique (French West Indies), and linkage to the locus for spinocerebellar ataxia 2 (SCA2) was established. Neuropathological findings in two patients were those of olivopontocerebellar atrophy without oligodendroglial cytoplasmic inclusions. Cerebellar ataxia was associated with hyporeflexia in 68% of 31 examined patients, with slowed and/or limited eye movements in 65% and with dementia in 29%. No patients had optic atrophy, pigmentary retinal degeneration, spasticity or parkinsonism. Mean age at onset was 33 +/- 16 years, and onset before the age of 20 years was correlated with a more rapid and severe course of the disease. Movement disorders, oculomotor disturbances, sphincter disturbances and cognitive impairment were significantly more frequent in early than in late onset patients. This explains why the phenotype was strikingly different in one family, in which mean age at onset was much earlier. Comparison with previously described SCA2 families indicated similarities, such as reduced saccade velocity, supranuclear ophthalmoplegia and decreased reflexes, although phenotypic heterogeneity remains the outstanding feature of this disorder.

Adolescent↗
PubMed1995

Marked phenotypic heterogeneity associated with expansion of a CAG repeat sequence at the spinocerebellar ataxia 3/Machado-Joseph disease locus.

The spinocerebellar ataxia 3 locus (SCA3) for type I autosomal dominant cerebellar ataxia (ADCA type I), a clinically and genetically heterogeneous group of neurodegenerative disorders, has been mapped to chromosome 14q32.1. ADCA type I patients from families segregating SCA3 share clinical features in common with those with Machado-Joseph disease (MJD), the gene of which maps to the same region. We show here that the disease gene segregating in each of three French ADCA type I kindreds and in a French family with neuropathological findings suggesting the ataxochoreic form of dentatorubropallidoluysian atrophy carries an expanded CAG repeat sequence located at the same locus as that for MJD. Analysis of the mutation in these families shows a strong negative correlation between size of the expanded CAG repeat and age at onset of clinical disease. Instability of the expanded triplet repeat was not found to be affected by sex of the parent transmitting the mutation. Evidence was found for somatic and gonadal mosaicism for alleles carrying expanded trinucleotide repeats.

Adolescent↗
PubMed1995

Autosomal dominant cerebellar ataxia type I linked to chromosome 12q (SCA2: spinocerebellar ataxia type 2).

Spinocerebellar ataxia 2 (SCA2) is one of the loci for the clinically and genetically heterogeneous group of autosomal dominant type I cerebellar ataxias. After initial linkage to chromosome 12q in Cuban families, SCA2 was shown to be the gene responsible for the disease in Italian, Tunisian, French-Canadian, Austrian-Canadian and Martinican kindreds with dominant ataxia, and the candidate interval was reduced to 6.4 cM between markers D12S84 and D12S79. Comparison of patients from families of different geographical origins clearly demonstrates the clinical interfamilial variability of the clinical signs which reaches statistical significance for the frequency of extrapyramidal rigidity, postural tremor and dementia. The most striking difference between the 29 Martinican SCA2 patients and those with SCA1 on chromosome 6p or SCA3/MJD on chromosome 14q is the greater frequency of hyporeflexia in the former. A mean 12.5 year anticipation is observed, with a more rapid clinical course of the disease in successive generations, indicating that an expanded trinucleotide repeat probably constitutes the underlying molecular mechanism.

Adolescent↗
PubMed1995

The gene for spinal cerebellar ataxia 3 (SCA3) is located in a region of approximately 3 cM on chromosome 14q24.3-q32.2.

SCA3, the gene for spinal cerebellar ataxia 3, was recently mapped to a 15-cM interval between D14S67 and D14S81 on chromosome 14q, by linkage analysis in two families of French ancestry. The SCA3 candidate region has now been refined by linkage analysis with four new microsatellite markers (D14S256, D14S291, D14S280, and AFM343vf1) in the same two families, in which 19 additional individuals were genotyped, and in a third French family. Combined two-point linkage analyses show that the new markers, D14S280 and AFM343vf1, are tightly linked to the SCA3 locus, with maximal lod scores, at recombination fraction, (theta) = .00, of 7.05 and 13.70, respectively. Combined multipoint and recombinant haplotype analyses localize the SCA3 locus to a 3-cM interval flanked by D14S291 and D14S81. The same allele for D14S280 segregates with the disease locus in the three kindreds. This allele is frequent in the French population, however, and linkage disequilibrium is not clearly established. The SCA3 locus remains within the 29-cM region on 14q24.3-q32.2 containing the gene for the Machado-Joseph disease, which is clinically related to the phenotype determined by SCA3, but it cannot yet be concluded that both diseases result from alterations of the same gene.

Adult↗
PubMed1995

[Does the ataxo-choreic form of DRPLA exist in Europe? Search of mutation in 120 families].

Dentatorubral-pallidoluysian atrophy (DRPLA) is an autosomal dominant neurodegenerative disorder characterized by a degeneration of cerebellar and pallidal efferents, more frequent in Japan. Isolated cases are also encountered. Patients present with variable combination of signs including myoclonus, ataxia, epilepsy, choreoathetosis and dementia, with onset from childhood to the seventh decade. Clinically, DRPLA may be undistinguishable from other genetic disorders, in particular Huntington's disease or the spinocerebellar ataxias. The genetic basis of the inherited form of DRPLA is an expansion to more than 49 repeats of an unstable trinucleotide (CAG) in the DRPLA gene on the short arm of chromosome 12. We determined the frequency of this mutation in patients with the DRPLA phenotype. One hundred and seventeen patients with cerebellar ataxia, from 94 families and 23 isolated cases, as well as 3 patients from families with undiagnosed autosomal dominant neurodegenerative disorders were investigated for the presence of the expanded sequence. None of the patients carried this mutation. This finding suggests that DRPLA is rare in the French population. The search for the DRPLA mutation is justified in patients with the DRPLA phenotype, however, since genetic counselling is often requested and neither clinical, nor neuropathological examinations permit a definite diagnosis of the underlying disease.

Atrophy↗