title: Cerebellar soluble mutant ataxin-3 level decreases during disease progression in Spinocerebellar Ataxia Type 3 mice.
abstract: Spinocerebellar Ataxia Type 3 (SCA3), also known as Machado-Joseph disease, is an autosomal dominantly inherited neurodegenerative disease caused by an expanded polyglutamine stretch in the ataxin-3 protein. A pathological hallmark of the disease is cerebellar and brainstem atrophy, which correlates with the formation of intranuclear aggregates in a specific subset of neurons. Several studies have demonstrated that the formation of aggregates depends on the generation of aggregation-prone and toxic intracellular ataxin-3 fragments after proteolytic cleavage of the full-length protein. Despite this observed increase in aggregated mutant ataxin-3, information on soluble mutant ataxin-3 levels in brain tissue is lacking. A quantitative method to analyze soluble levels will be a useful tool to characterize disease progression or to screen and identify therapeutic compounds modulating the level of toxic soluble ataxin-3. In the present study we describe the development and application of a quantitative and easily applicable immunoassay for quantification of soluble mutant ataxin-3 in human cell lines and brain samples of transgenic SCA3 mice. Consistent with observations in Huntington disease, transgenic SCA3 mice reveal a tendency for decrease of soluble mutant ataxin-3 during disease progression in fractions of the cerebellum, which is inversely correlated with aggregate formation and phenotypic aggravation. Our analyses demonstrate that the time-resolved Förster resonance energy transfer immunoassay is a highly sensitive and easy method to measure the level of soluble mutant ataxin-3 in biological samples. Of interest, we observed a tendency for decrease of soluble mutant ataxin-3 only in the cerebellum of transgenic SCA3 mice, one of the most affected brain regions in Spinocerebellar Ataxia Type 3 but not in whole brain tissue, indicative of a brain region selective change in mutant ataxin-3 protein homeostasis.
authors.affiliation: Institute of Medical Genetics and Applied Genomics, University of Tuebingen, Tuebingen, Germany.
authors.forename: Huu Phuc
authors.initials: HP
authors.lastname: Nguyen
authors.forename: Jeannette
authors.initials: J
authors.lastname: Hübener
authors.forename: Jonasz Jeremiasz
authors.initials: JJ
authors.lastname: Weber
authors.forename: Stephan
authors.initials: S
authors.lastname: Grueninger
authors.forename: Olaf
authors.initials: O
authors.lastname: Riess
authors.forename: Andreas
authors.initials: A
authors.lastname: Weiss
mesh_terms: D000367:Age Factors; D000595:Amino Acid Sequence; D000818:Animals; D000067699:Ataxin-3; D002460:Cell Line; D002531:Cerebellum / Q000378:metabolism*; D004195:Disease Models, Animal; D018450:Disease Progression; D015200:Fluoroimmunoassay / Q000379:methods; D015870:Gene Expression; D006801:Humans; D017827:Machado-Joseph Disease / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011689:Purkinje Cells / Q000378:metabolism; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019076:Transgenes
chemical_list: D009687:Nuclear Proteins; D014157:Transcription Factors; D000067699:Ataxin-3; C511594:Atxn3 protein, mouse