Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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

We investigated a family manifesting progressive ataxia, with expanded SCA8 CTA/CTG repeats. Neuropathologically, degeneration of Purkinje, inferior olivary, and nigral neurons and periaqueductal gliosis were evident. The sites of Purkinje cell loss were occupied by fibrillary accumulations. The remaining Purkinje cells showed somatic sprouts, and intracytoplasmic 1C2-positive granular structures were recognizable. This characteristic distribution of neurodegeneration and Purkinje cell cytopathology were distinct from those of other hereditary spinocerebellar ataxias previously reported.
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PMID:Clinicopathologic investigation of a family with expanded SCA8 CTA/CTG repeats. 1706 May 79

Spinocerebellar ataxias (SCAs) belong to a group of autosomal dominant, late-onset neurodegenerative disorders characterized by slowly progressive ataxia that eventually leads to severe gait, speech, coordination and sensory loss. The majority of these diseases result from expanded polyglutamine tracts in the encoded protein as seen in SCA1, SCA2, SCA3, SCA6, SCA7 and Dentatorubral-Pallidoluysian Atrophy (DRPLA). However, two novel forms of SCAs, SCA8 and SCA12, are associated with trinucleotide repeat expansions in non-translated regions of the genes. In the case of SCA8, the CUG expansion occurs at the 3' end of a processed non-coding RNA. While understanding of how expanded polyglutamine tracts compromise or alter protein function has advanced rapidly in the last five years, understanding of how trinucleotide repeat expansions alter the function of the non-coding SCA8 RNA and lead to human disease remains quite limited. Encouragingly, as discussed in this review, recent studies from murine and Drosophila models have provided new insights into both the cellular context in which SCA8 normally operates and the potential role of CTG expansion in the disease. Continued exploration of these genetically tractable model systems will further illuminate the biology underlying SCA8 disease, ultimately providing the necessary foundation on which to develop effective therapeutic interventions.
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PMID:Molecular genetics of spinocerebellar ataxia type 8 (SCA8). 1713 42

The actin-binding protein Kelch-like 1 (KLHL1) is a neuronal protein that belongs to the evolutionarily-conserved Kelch protein super-family. The mammalian KLHL1 is brain-specific, cytosolic and can form multimers and bind actin filaments. KLHL1's function is likely that of an actin-organizing protein, possibly modulating neurite outgrowth, the dynamic morphology of dendritic spine heads; or anchoring proteins essential for post-synaptic function, like ion channels. Targeted deletion of the KLHL1 gene in Purkinje neurons results in dendritic deficits in these neurons, abnormal gait, and progressive loss of motor coordination in mice [He Y, Zu T, Benzow KA, Orr HT, Clark HB, Koob MD (2006) Targeted deletion of a single SCA8 ataxia locus allele in mice causes abnormal gait, progressive loss of motor coordination, and Purkinje cell dendritic deficits. J Neurosci 26:9975-9982]. Here we tested the hypothesis that KLHL1 may interact and modulate voltage-gated calcium channels by assessing the interaction of the principal subunit of P/Q-type channels, alpha(1A), with KLHL1. Experiments in human embryonic kidney line HEK 293 (HEK) cells and cerebellar primary cultures revealed co-incidence of alpha(1A) and KLHL1 immunoreactivity when testing both the endogenous or epitope-tagged versions of the proteins. Similarly, co-immunoprecipitation experiments in HEK cells and brain tissue exposed the presence of KLHL1 in protein samples immunoprecipitated with FLAG-tagged or alpha(1A) antibodies. Functional studies of KLHL1 on P/Q-type current properties probed with whole-cell patch clamp revealed a significant increase in mean current density in the presence of KLHL1 (80% increase; from -13.2+/-2.0 pA/pF to -23.7+/-4.2 pA/pF, P<0.02), as well as a shift in steady state activation V(50) of -5.5 mV (from 12.8+/-1.8 mV to 7.3+/-1.0 mV, P<0.02). Our data are consistent with a modulatory effect of KLHL1 on the P/Q-type calcium channel function and suggest a possible novel role for KLHL1 in cellular excitability.
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PMID:The Kelch-like protein 1 modulates P/Q-type calcium current density. 1728 72

Hereditary spinocerebellar ataxia (SCA) is a cluster of heterogeneous disorders. At now, 29 dominant loci have been assigned. Responsible genes and mutations are determined in at least 14 of them. In recessive and X-linked SCAs, 15 loci have been mapped, and mutation in each gene is determined by 6 disorders. Molecular mechanism of those SCAs are variable. Generally, deletion, insertion, or substitution in a gene modifies the primary structure of mRNA, subsequently resulting in disturbance of transcription or in translation of mutant proteins showing loss-of-function or dominant negative effect. Large expansion of tandem repeat in promotor region or intron suppress translation of the gene, thus causing similar effect. Expansion of (CAG)n in coding exon is translated into proteins containing elongated poly-Q. Since the poly-Q fragment is cytotoxic, this kind of mutation causes protein toxic gain-of-function. In addition, RNA toxic gain-of-function mechanism recently gains attention as a new molecular mechanism of SCA8 and SCA10. Clinically, dominant SCA with dynamic mutation shows variable onset of age, severity, and variation of clinical phenotypes. Among this clinical complexity, vocal cord abductor paralysis in SCA1, familial parkinsonism in SCA2, vestibular dysfunction and axonal neuropathy in MJD, and axial myoclonus in SCA14, are reviewed for potential usefulness in clinical practice.
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PMID:[Clinical feature and molecular genetics of hereditary spinocerebellar ataxia]. 1821 Aug 1

Spinocerebellar ataxia type 8 (SCA8) is a dominantly inherited, slowly progressive neurodegenerative disorder caused by a CTG.CAG repeat expansion located on chromosome 13q21. The expansion mutation was isolated directly from the DNA of a single patient using RAPID cloning and subsequently shown to co-segregate with disease in additional ataxia families including a seven-generation kindred (the MN-A family). The size-dependent penetrance of the repeat found in the large MN-A kindred makes it appear as though some parts of the family have a dominant disorder while other parts of this same family have recessive or sporadic forms of ataxia. While the linkage and size-dependent penetrance of the SCA8 CTG.CAG expansion in the MN-A family argue that the SCA8 expansion causes ataxia, the reduced penetrance in other SCA8 families and the discovery of expansions in the general population have led to a controversy surrounding whether or not the SCA8 expansion is pathogenic. A recently reported mouse model in which SCA8 BAC-expansion but not BAC-control lines develop a progressive neurological phenotype now demonstrates the pathogenicity of the (CTG.CAG)(n) expansion. These mice show a loss of cerebellar GABAergic inhibition and, similar to human patients, have 1C2-positive intranuclear inclusions in Purkinje cells and other neurons. Additional studies demonstrate that the SCA8 expansion is expressed in both directions (CUG and CAG) and that a novel gene expressed in the CAG direction encodes a pure polyglutamine expansion protein (ataxin 8, ATXN8). Moreover, the expression of non-coding (CUG)(n) expansion transcripts (ataxin 8 opposite strand, ATXN8OS) and the discovery of intranuclear polyglutamine inclusions suggest SCA8 pathogenesis may involve toxic gain-of-function mechanisms at both the protein and RNA levels. Our data, combined with the recently reported antisense transcripts spanning the DM1 repeat expansion in the CAG direction and the growing number of reports of antisense transcripts expressed throughout the mammalian genome, raises the possibility that bidirectional expression across pathogenic microsatellite expansions may occur in other expansion disorders, and that potential pathogenic effects of mutations expressed from both strands should be considered.
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PMID:Bidirectional expression of the SCA8 expansion mutation: one mutation, two genes. 1841 92

Microsatellite expansions cause a number of dominantly-inherited neurological diseases. Expansions in coding-regions cause protein gain-of-function effects, while non-coding expansions produce toxic RNAs that alter RNA splicing activities of MBNL and CELF proteins. Bi-directional expression of the spinocerebellar ataxia type 8 (SCA8) CTG CAG expansion produces CUG expansion RNAs (CUG(exp)) from the ATXN8OS gene and a nearly pure polyglutamine expansion protein encoded by ATXN8 CAG(exp) transcripts expressed in the opposite direction. Here, we present three lines of evidence that RNA gain-of-function plays a significant role in SCA8: 1) CUG(exp) transcripts accumulate as ribonuclear inclusions that co-localize with MBNL1 in selected neurons in the brain; 2) loss of Mbnl1 enhances motor deficits in SCA8 mice; 3) SCA8 CUG(exp) transcripts trigger splicing changes and increased expression of the CUGBP1-MBNL1 regulated CNS target, GABA-A transporter 4 (GAT4/Gabt4). In vivo optical imaging studies in SCA8 mice confirm that Gabt4 upregulation is associated with the predicted loss of GABAergic inhibition within the granular cell layer. These data demonstrate that CUG(exp) transcripts dysregulate MBNL/CELF regulated pathways in the brain and provide mechanistic insight into the CNS effects of other CUG(exp) disorders. Moreover, our demonstration that relatively short CUG(exp) transcripts cause RNA gain-of-function effects and the growing number of antisense transcripts recently reported in mammalian genomes suggest unrecognized toxic RNAs contribute to the pathophysiology of polyglutamine CAG CTG disorders.
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PMID:RNA gain-of-function in spinocerebellar ataxia type 8. 1968 Apr 45

We report the case of a 29 year old woman with a complex movement disorder syndrome due to the combination of coexisting pathological triplet repeat expansions of huntingtin and ATXN8 genes. The disease course was characterized by mental disturbances including cognitive decline and changes in personality starting at the age of 12 years, followed by twisting motions, intentional tremor and gait ataxia. Later Parkinsonian symptoms of micrographia, bradykinesia, muscle rigidity and mental decline became dominant. Brain MRI showed hypoplasia of the nucleus caudatus and generalized atrophy; MR spectroscopy revealed a decrease of all typical metabolites except for an increased level of lactate and acetate. Therapeutic trials with pramipexole, ropinirole and tetrabenazine showed no benefit, while levetiracetam caused agitation and hallucinations. We discuss phenotype-genotype correlation and the rule of triplet repeat expansions of gene ATXN8.
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PMID:Coexisting huntingtin and SCA8 repeat expansion: case report of a severe complex neurodegenerative syndrome. 2040 8

We administered a large battery of neuropsychological tests to an heterogeneous cohort of genetically defined spinocerebellar ataxia (SCA) patients in order to assess their cognitive profile and to compare cognitive impairment among different SCA genotypes, particularly between SCA with the classical pattern of olivo-ponto-cerebellar atrophy (SCA1 and SCA2) and those with a relatively "pure" olivo-cerebellar atrophy (SCA6 and SCA8). Our data revealed a neuropsychological picture characterized by fronto-parietal involvement with mnestic, linguistic, visuospatial, attentional, executive, and mood changes, in agreement with the cerebellar cognitive affective syndrome definition. We found a homogeneous neuropsychological profile among SCA subgroups with a prominent role of frontal dysfunction--particularly, attention, memory, and executive functions. We analyzed the possible interactions between neuropsychological pattern and clinical, demographical, and genetic variables. We found the presence of a cognitive impairment at the early stages of the disease, without visuospatial alterations, which appeared later. Age and education represented the most important demographic factors to predict the neuropsychological performance in SCA and in controls, but their effect in patients had definitely more impact. In our sample education could represent a protective factor and a marker of an enriched environment or a better developmental cognitive differentiation. We demonstrated that in our patients there was a distinct subgroup of high functional subjects and that triplet repeats modulated the effect of aging on cognition and progression of motor disability.
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PMID:Neuropsychological picture of 33 spinocerebellar ataxia cases. 2130 72

Type I autosomal dominant cerebellar ataxia (ADCA) is a type of spinocerebellar ataxia (SCA) characterized by ataxia with other neurological signs, including oculomotor disturbances, cognitive deficits, pyramidal and extrapyramidal dysfunction, bulbar, spinal and peripheral nervous system involvement. The global prevalence of this disease is not known. The most common type I ADCA is SCA3 followed by SCA2, SCA1, and SCA8, in descending order. Founder effects no doubt contribute to the variable prevalence between populations. Onset is usually in adulthood but cases of presentation in childhood have been reported. Clinical features vary depending on the SCA subtype but by definition include ataxia associated with other neurological manifestations. The clinical spectrum ranges from pure cerebellar signs to constellations including spinal cord and peripheral nerve disease, cognitive impairment, cerebellar or supranuclear ophthalmologic signs, psychiatric problems, and seizures. Cerebellar ataxia can affect virtually any body part causing movement abnormalities. Gait, truncal, and limb ataxia are often the most obvious cerebellar findings though nystagmus, saccadic abnormalities, and dysarthria are usually associated. To date, 21 subtypes have been identified: SCA1-SCA4, SCA8, SCA10, SCA12-SCA14, SCA15/16, SCA17-SCA23, SCA25, SCA27, SCA28 and dentatorubral pallidoluysian atrophy (DRPLA). Type I ADCA can be further divided based on the proposed pathogenetic mechanism into 3 subclasses: subclass 1 includes type I ADCA caused by CAG repeat expansions such as SCA1-SCA3, SCA17, and DRPLA, subclass 2 includes trinucleotide repeat expansions that fall outside of the protein-coding regions of the disease gene including SCA8, SCA10 and SCA12. Subclass 3 contains disorders caused by specific gene deletions, missense mutation, and nonsense mutation and includes SCA13, SCA14, SCA15/16, SCA27 and SCA28. Diagnosis is based on clinical history, physical examination, genetic molecular testing, and exclusion of other diseases. Differential diagnosis is broad and includes secondary ataxias caused by drug or toxic effects, nutritional deficiencies, endocrinopathies, infections and post-infection states, structural abnormalities, paraneoplastic conditions and certain neurodegenerative disorders. Given the autosomal dominant pattern of inheritance, genetic counseling is essential and best performed in specialized genetic clinics. There are currently no known effective treatments to modify disease progression. Care is therefore supportive. Occupational and physical therapy for gait dysfunction and speech therapy for dysarthria is essential. Prognosis is variable depending on the type of ADCA and even among kindreds.
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PMID:Autosomal dominant cerebellar ataxia type I: a review of the phenotypic and genotypic characteristics. 2161 91

Autosomal dominant cerebellar ataxias (ADCAs) encompass a heterogeneous group of rare diseases that affect the cerebellum and its connections. The most common forms have been associated with dynamic mutations while some rarer forms with conventional mutations. Studies in different populations revealed differences in their relative frequencies both within and between the studied populations, showing that the frequencies are depended on ethnic and geographical factors. Previous investigation of triplet repeat expansion SCAs (SCA1, SCA2, SCA3, SCA6, SCA7, SCA8, SCA12, SCA17 and DRPLA) in the Cypriot population, revealed no pathogenic expansion in the Cypriot SCA patients. We hereby present our recent investigation of the SCA10 pentanucleotide repeat expansion. Forty-two ascertained Cypriot sporadic ataxia patients, the index case from 1 ADCA and 14 ARCA families and a cohort of normal population individuals were included in the study. All our patients have normal range ATXN10 gene ATTCT repeat numbers (10-19). In the normal population group, repeat lengths ranged from 11 to 20 with the 14 repeats allele being the most frequent. Therefore, all currently established dynamic repeat SCA mutations are absent from the Cypriot population, indicating distinct genetic causes.
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PMID:Investigation of SCA10 in the Cypriot population: further exclusion of SCA dynamic repeat mutations. 2302 38


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