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Query: UMLS:C0004134 (ataxia)
 15,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Different aspects of expanded polyglutamine tracts and of their pathogenetic role are taken into consideration here. (i) The (CAG)n length of wild-type alleles of the Huntington disease gene was analysed in instability-prone tumour tissue from colon cancer patients to test whether the process leading to the elongation of alleles towards the expansion range involves single-unit stepwise mutations or larger jumps. The analysis showed that length changes of a single unit had a relatively low frequency. (ii) The observation of an expanded spinocerebellar ataxia (SCA)1 allele with an unusual pattern of multiple CAT interruptions showed that cryptic sequence variations are critical not only for sequence length stability but also for the expression of the disease phenotype. (iii) Small expansions of the (CAG)n sequence at the CACNA1A gene have been reported as causing SCA6. The analysis of families with SCA6 and episodic ataxia type 2 showed that these phenotypes are, in fact, expressions of the same disorder caused either by point mutations or by small (CAG)n expansions. A gain of function has been hypothesized for all proteins containing an expanded polyglutamine stretch, including the alpha 1A subunit of the voltage-gated calcium channel type P/Q coded by the CACNA1A gene. Because point mutations at the same gene with similar phenotypic consequences are highly unlikely to have this effect, an alternative common pathogenetic mechanism for all these mutations, including small expansions, can be hypothesized.
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PMID:CAG repeat instability, cryptic sequence variation and pathogeneticity: evidence from different loci. 1043 11

We herein report the findings of an autopsy case of spinocerebellar ataxia type 6 (SCA6) which revealed a mild CAG-repeat expansion in the alpha1A voltage-dependent calcium channel (CACNL1A4) gene on chromosome 19p13. A 39-year-old man who showed slowly progressive mental disorders and gait ataxia was clinically diagnosed to have cortical cerebellar atrophy (CCA) and schizophrenia. None of his relatives revealed any symptoms such as spinocerebellar disease, however, his younger brother had shown some mental disorders. The patient eventually died at 52 years of age, and an autopsy was thus performed. The main histopathological findings included a severe neuronal cell loss of Purkinje cells and inferior olivary nuclei. The number of Purkinje cells in our case had decreased severely in comparison to that in either OPCA or age-matched control cases, and the Purkinje cells in the cerebellar hemisphere were more affected than those in the cerebellar vermis. The neurons of the dentate nucleus and pontine nuclei were well-preserved, and no pathological changes were seen in cerebral cortices or basal ganglia. The clinicopathological findings were similar to those of late cortical cerebellar atrophy (LCCA), Holmes' cortical cerebellar atrophy (Holmes type) or SCA6 cases reported previously. Using genomic DNA extracted from archival paraffin-embedded sections in the frontal lobe, cerebral basal ganglia and cerebellum, the identical mild CAG-repeat expansions in the CACNL1A4/SCA6 gene were revealed in all samples examined. These findings suggest that in cases with LCCA or Holmes type atrophy, we should thus examine the CAG-repeat expansions in the SCA6 gene, and the genomic DNA extracted from paraffin-embedded sections was thus found to be useful in diagnosing SCA6 retrospectively.
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PMID:An autopsy case of spinocerebellar ataxia type 6 with mental symptoms of schizophrenia and dementia. 1044 62

Autosomal dominant cerebellar ataxias (ADCA) are a clinically heterogeneous group of neurodegenerative disorders caused by unstable CAG repeat expansions encoding polyglutamine tracts. Five spinocerebellar ataxia genes (SCA1, SCA2, SCA3, SCA6 and SCA7) and another related dominant ataxia gene (DRPLA) have been cloned, allowing the genetic classification of these disorders. We present here the molecular analysis of 87 unrelated familial and 60 sporadic Spanish cases of spinocerebellar ataxia. For ADCA cases 15% were SCA2, 15% SCA3, 6% SCA1, 3% SCA7, 1% SCA6 and 1% DRPLA, an extremely rare mutation in Caucasoid populations. About 58% of ADCA cases remained genetically unclassified. All the SCA1 cases belong to the same geographical area and share a common haplotype for the SCA1 mutation. The expanded alleles ranged from 41 to 59 repeats for SCA1, 35 to 46 [corrected] for SCA2, 67 to 77 for SCA3, and 38 to 113 for SCA7. One SCA6 case had 25 repeats and one DRPLA case had 63 repeats. The highest CAG repeat variation in meiotic transmission of expanded alleles was detected in SCA7, this being of +67 units in one paternal transmission and giving rise to a 113 CAG repeat allele in a patient who died at 3 years of age. Meiotic transmissions have also shown a tendency to more frequent paternal transmission of expanded alleles in SCA1 and maternal in SCA7. All SCA1 and SCA2 expanded alleles analyzed consisted of pure CAG repeats, whereas normal alleles were interrupted by 1-2 CAT trinucleotides in SCA1, except for three alleles of 6, 14 and 21 CAG repeats, and by 1-3 CAA trinucleotides in SCA2. No SCA or DRPLA mutations were detected in the 60 sporadic cases of spinocerebellar ataxia, but one late onset patient was identified as a recessive form due to GAA-repeat expansions in the Friedreich's ataxia gene.
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PMID:Spinocerebellar ataxias in Spanish patients: genetic analysis of familial and sporadic cases. The Ataxia Study Group. 1045 42

We estimated the relative contributions of known ataxia genes (SCA1, 2, 3, 6, 7 and X25) in the patient population sent to our DNA diagnostic laboratory for diagnostic testing. Approximately 28% of these patients had an abnormal triplet repeat expansion in one of these ataxia genes (3% for SCA1, 8% for SCA2, 11% for SCA3/MJD, 2% for SCA6, 3% for SCA7, and 1.5% for X25). The lack of abnormal repeat expansions in the majority of ataxis patients tested suggests that the molecular defects associated with most ataxia cases are currently undetermined and that this population includes both familial and sporadic cases. In contrast, of the patients submitted for genetic testing for Friedrich's ataxia (FRDA), 44% (69/157) showed at least one expansion in the X25 gene, indicating that FRDA accounts for a significant proportion of the recessively inherited ataxias and appears to have a high rate of accurate clinical diagnosis. On the basis of our DNA studies, we propose a comprehensive and efficient approach for molecular analysis of ataxia patients.
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PMID:Estimated contribution of known ataxia genes in ataxia patients undergoing DNA testing. 1046 57

Inherited, autosomal-dominant cerebellar ataxia (ADCA) comprises a genetically and clinically heterogenous group of neurodegenerative disorders. Clinical classification of these disorders was an important step [2] in differentiation among several types, the most common one being ADCA-I, accompanied with supranuclear ophthalmoplegia, optic nerve atrophy, symptoms of the basal ganglia lesions, dementia and amyotrophia. Molecular-genetic studies indicated genetic heterogeneity of ADCA-I with mutations of genetic loci on chromosome 6p (spinocerebellar ataxia type 1; SCA1), 12q (SCA2), 14q (SCA3), 19p (SCA6) and 16q (SCA4) [3]. Spinocerebellar ataxia type 1 (SCA1) is characterized by cerebellar ataxia, ophthalmoplegia and pyramidal signs [4], but also with other neurological findings that tend to prevent clinical differentiation among patients with SCA1, SCA2 and SCA3. The mutation inducing SCA1 is an instable expansion of trinucleotide (CAG) repeats in the coding region on chromosome 6 [5]. Herein, we report clinical features in patients from two families with SCA1: family I with 15 and family II with 8 affected members in 4 consecutive generations. The acceptable data (history, examination and/or insight into medical records) were obtained for 9 patients in family I and 7 patients in family II. The age at the onset of the disease was 37.8 +/- 11.3 years (mean value +/- SD) (range: 27-60) for all the patients, or 31.8 +/- 10.7 years (range: 7-60) for family I and 45.0 +/- 8.4 years (range: 35-55) for family II. Duration of the disease was 8.9 +/- 4.6 years (range: 3-15); 10.8 +/- 4.1 (range 5-15) and 5.7 +/- 3.8 years (range: 3-10) for families I and II, respectively. The mean number of CAG repeats in the mutated allele for SCA1 of the affected individuals was 50.5 +/- 6.2 (range 45-64). A significant inverse correlation (p < 0.05) was noted between the number of CAG repeats and the age at the onset of the disease (Figure 3). Similarity of initial symptoms in SCA1 was noted. They include simultaneous gait-related problems and dysarthria (usually slurred speech). Occurrence of other neurological signs (Table 3) was also predictable in most cases and depended on the phase of SCA1 at the time of examination. Generally, it is believed that intra- and interfamilial phenotypic heterogeneity in SCA1 is lower than in SCA2 and SCA3 [12]). In conclusion, typical clinical manifestations of SCA1, at least in early phases of the disease, according to our study, include gait ataxia, dysarthria, brisk muscle reflexes and marked hand ataxia; the age at the onset of the disease was inverse, and clinical progression was directly related to the number of CAG repeats in the mutated allele on chromosome 6. Nevertheless, significant differences in clinical properties of this inherited disease are possible among different affected families.
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PMID:[Clinico-genetic study of type I spinocerebelllar ataxia]. 1050 Apr 22

To investigate the clinical range of spinocerebellar ataxia type 6 (SCA6), we screened CAG repeat expansion in the voltage-dependent alpha 1A calcium channel gene (CACNL1A4) in 71 ataxic patients in 60 families; 54 patients in 43 families with hereditary ataxia and 17 sporadic patients. Thirteen patients with SCA6 were detected to have elongated CAG in CACNL1A4. Of these, 7 patients had been diagnosed as having hereditary cerebellar cortical atrophy, and 6 patients had been found to have sporadic occurrence. One patient showed distinct pontine atrophy with prominent horizontal or oblique gaze nystagmus which is an unusual feature in sporadic olivopontocerebellar atrophy. For the efficient screening of SCA6, we would propose testing CAG repeat expansion in CACNL1A4, in patients with one of two markers: (1) horizontal or oblique gaze nystagmus without other eye movement disorders, (2) pure cerebellar atrophy, even if occurrence is sporadic. We should note that the pontine atrophy could also be caused by CAG repeat expansion in CACNL1A4.
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PMID:Pontine atrophy in spinocerebellar ataxia type 6. 1060 3

The autosomal dominant spinocerebellar ataxias (SCA) are a heterogeneous group of degenerative diseases presenting with ataxic gait, limbs ataxia, dysarthria and cerebellar oculomotor disturbances. Usually, cerebellar signs are associated with pyramidal signs, extra-pyramidal signs, spinal signs and signs of peripheral neuropathy. Neuropathological studies have disclosed an involvement of the cerebellum and its afferent/efferent pathways, of the brainstem and of the spinal cord. Distinct entities are now recognized: SCA1, SCA2, SCA3/Machado-Joseph disease, SCA4, SCA5,SCA6, SCA7 and dentatorubropillidoluysian atrophy (DRPLA). In most cases, a CAG trinucleotide repeat expansion has been demonstrated by genetic investigations. Moreover, recent studies have shown that autosomal dominant spinocerebellar ataxias are characterized by intra-nuclear inclusions containing polyglutamine in affected cells. These complexes might pl ay a determinant role in the neurodegenerative process. Cell death could be due to accumulation of a polyglutamine as a result of trinucleotide repeats.
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PMID:[Autosomal dominant spinocerebellar ataxia]. 1067 73

The ectopic expression of neuronal P/Q-type voltage-gated calcium channels in small cell lung carcinoma (SCLC) is thought to induce antisynaptic autoimmunity in the paraneoplastic Lambert-Eaton myasthenic syndrome. The gene CACNL1A4, encoding the principal (alpha1A) subunit of this calcium channel, is mutated in several inherited neurological disorders. One of these disorders (spinocerebellar ataxia, type 6, or SCA-6) involves the expansion of a trinucleotide (CAG) repeat unit. We hypothesized that a somatic CAG repeat instability of this gene in neoplastic cells might generate a non-self epitope capable of initiating autoimmunity to P/Q-type calcium channels. We therefore analyzed the CACNL1A4 gene in SCLC lines established from metastases derived from seven individual patients (four associated with Lambert-Eaton myasthenic syndrome, one associated with myasthenia gravis, and two not associated with neurological autoimmunity). We compared their CAG repeat numbers (determined by polymerase chain reaction (PCR) amplification followed by separation of products on a 6% polyacrylamide/8M urea gel) to published norms and to DNA from a patient with SCA-6. The number of CAG repeats in SCLC DNA fell within a normal range whether or not the neoplasm was complicated by neurological autoimmunity. Therefore, it is unlikely that somatically unstable CAG repeat units in the gene encoding the P/Q-type voltage-gated calcium channel account for this tumor protein's immunogenicity in the Lambert-Eaton myasthenic syndrome.
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PMID:Immunogenicity of P/Q-type calcium channel in small cell lung cancer: investigation of alpha1 subunit polyglutamine expansion. 1067 74

The autosomal dominant spinocerebellar ataxias (SCAs) are a group of late-onset, neurodegenerative disorders for which 10 loci have been mapped (SCA1, SCA2, SCA4-SCA8, SCA10, MJD, and DRPLA). The mutant proteins have shown an expanded polyglutamine tract in SCA1, SCA2, MJD/SCA3, SCA6, SCA7, and DRPLA; a glycine-to-arginine substitution was found in SCA6 as well. Recently, an untranslated (CTG)n expansion on chromosome 13q was described as being the cause of SCA8. We have now (1) assessed the repeat size in a group of patients with ataxia and a large number of controls, (2) examined the intergenerational transmission of the repeat, and (3) estimated the instability of repeat size in the sperm of one patient and two healthy controls. Normal SCA8 chromosomes showed an apparently trimodal distribution, with classes of small (15-21 CTGs), intermediate (22-37 CTGs), and large (40-91 CTGs) alleles; large alleles accounted for only0.7% of all normal-size alleles. No expanded alleles (>/=100 CTGs) were found in controls. Expansion of the CTG tract was found in five families with ataxia; expanded alleles (all paternally transmitted) were characterized mostly by repeat-size contraction. There was a high germinal instability of both expanded and normal alleles: in one patient, the expanded allele (152 CTGs) had mostly contraction in size (often into the normal range); in the sperm of two normal controls, contractions were also more frequent, but occasional expansions into the upper limit of the normal size range were also seen. In conclusion, our results show (1) no overlapping between control (15-91) and pathogenic (100-152) alleles and (2) a high instability in spermatogenesis (both for expanded and normal alleles), suggesting a high mutational rate at the SCA8 locus.
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PMID:High germinal instability of the (CTG)n at the SCA8 locus of both expanded and normal alleles. 1071 99

Approximately 44% of cases of spinocerebellar ataxia (SCA) in Hokkaido, the northernmost island of Japan, were estimated to be inherited. To determine the prevalence of triplet repeat expansion in hereditary SCA patients, we genotyped seven genetically defined dominant SCAs in 349 patients, including 266 patients from 77 families, 78 probands from unrelated families with hereditary late-onset SCA, and five patients in whom a family history of SCA was not demonstrated. The frequency of each disorder in a total of 155 unrelated families was 23.9% for Machado-Joseph disease (MJD), 29.0% for SCA6, 9.7% for SCA1, 7.7% for SCA2, and 2.6% for dentatorubral-pallidoluysian atrophy. Abnormal expansion of triplet repeats for SCA7 and SCA8 was not detected. A total of 27.1% of the patients had still unknown SCA mutations. In addition, the GAA repeat in the frataxin gene was not abnormally expanded in 13 early-onset SCA patients with clinical features similar to those of Friedreich ataxia. Comparison of our results with those from other centers handling SCA showed that MJD is prevalent throughout Japan, but the frequencies of other dominant SCAs differ considerably even within Japan.
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PMID:Prevalence of triplet repeat expansion in ataxia patients from Hokkaido, the northernmost island of Japan. 1078 56


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