Dataset Information

The (CAG)n tract of Machado-Joseph Disease gene (ATXN3): a comparison between DNA and mRNA in patients and controls.

ABSTRACT: Machado-Joseph disease (MJD) is an autosomal dominant neurodegenerative disorder of late onset (occurring at a mean age of 40.2 years). The clinical manifestation of MJD is dependent on the presence of an expansion of the (CAG)(n) motif within exon 10 of the ATXN3 gene, located at 14q32.1. The variance in onset of MJD is only partially correlated (approximately 50-80%) with the extension of the CAG tract in genomic DNA (gDNA). The main aim of this work was to determine whether there are discrepancies in the size of the (CAG)(n) tract between gDNA and mRNA, and to establish whether there is a better association between age at onset and repeat size at the mRNA level. We typed gDNA and cDNA samples for the (CAG)(n) tract totalizing 108 wild-type and 52 expanded ATXN3 alleles. In wild-type alleles no differences were found between gDNA and cDNA. In expanded alleles, the CAG repeat size in gDNA was not always directly transcribed into the mRNA; on average there were differences of +1 repeat at the cDNA level. The slight discrepancies obtained were insufficient to cause significant differences in the distribution of the expanded alleles, and therefore no improvement in onset variance explanation was obtained with mRNA.

SUBMITTER: Bettencourt C

PROVIDER: S-EPMC2987309 | biostudies-literature | 2010 May

REPOSITORIES: biostudies-literature

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The (CAG)n tract of Machado-Joseph Disease gene (ATXN3): a comparison between DNA and mRNA in patients and controls.

Bettencourt Conceição C Santos Cristina C Montiel Rafael R Kay Teresa T Vasconcelos João J Maciel Patrícia P Lima Manuela M

European journal of human genetics : EJHG 20091125 5

Machado-Joseph disease (MJD) is an autosomal dominant neurodegenerative disorder of late onset (occurring at a mean age of 40.2 years). The clinical manifestation of MJD is dependent on the presence of an expansion of the (CAG)(n) motif within exon 10 of the ATXN3 gene, located at 14q32.1. The variance in onset of MJD is only partially correlated (approximately 50-80%) with the extension of the CAG tract in genomic DNA (gDNA). The main aim of this work was to determine whether there are discrepa ...[more]

PMID: 19935829

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Project description:Machado-Joseph Disease (MJD), also known as spinocerebellar ataxia type 3 (SCA3), represents the most common form of SCA worldwide. MJD is an autosomal dominant neurodegenerative disorder of late onset, involving predominantly the cerebellar, pyramidal, extrapyramidal, motor neuron and oculomotor systems; although sharing features with other SCAs, the identification of minor, but more specific signs, facilitates its differential diagnosis. MJD presents strong phenotypic heterogeneity, which has justified the classification of patients into three main clinical types. Main pathological lesions are observed in the spinocerebellar system, as well as in the cerebellar dentate nucleus. MJD's causative mutation consists in an expansion of an unstable CAG tract in exon 10 of the ATXN3 gene, located at 14q32.1. Haplotype-based studies have suggested that two main founder mutations may explain the present global distribution of the disease; the ancestral haplotype is of Asian origin, and has an estimated age of around 5,800 years, while the second mutational event has occurred about 1,400 years ago. The ATXN3 gene encodes for ataxin-3, which is ubiquitously expressed in neuronal and non-neuronal tissues, and, among other functions, is thought to participate in cellular protein quality control pathways. Mutated ATXN3 alleles consensually present about 61 to 87 CAG repeats, resulting in an expanded polyglutamine tract in ataxin-3. This altered protein gains a neurotoxic function, through yet unclear mechanisms. Clinical variability of MJD is only partially explained by the size of the CAG tract, which leaves a residual variance that should be explained by still unknown additional factors. Several genetic tests are available for MJD, and Genetic Counseling Programs have been created to better assist the affected families, namely on what concerns the possibility of pre-symptomatic testing. The main goal of this review was to bring together updated knowledge on MJD, covering several aspects from its initial descriptions and clinical presentation, through the discovery of the causative mutation, its origin and dispersion, as well as molecular genetics aspects considered essential for a better understanding of its neuropathology. Issues related with molecular testing and Genetic Counseling, as well as recent progresses and perspectives on genetic therapy, are also addressed.

Dataset Information

The (CAG)n tract of Machado-Joseph Disease gene (ATXN3): a comparison between DNA and mRNA in patients and controls.

Publications

The (CAG)n tract of Machado-Joseph Disease gene (ATXN3): a comparison between DNA and mRNA in patients and controls.

Similar Datasets

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