Expression of ataxin-7 in CNS and non-CNS tissue of normal and SCA7 individuals

Spinocerebellar ataxia type 7 (SCA7) is a neurodegenerative disorder primarily affecting the cerebellum, brain stem and retina. The disease is caused by an expanded polyglutamine tract in the protein ataxin-7. In this study we analyzed the expression pattern of ataxin-7 in CNS and non-CNS tissue from three SCA7 patients and age-matched controls. SCA7 is a rare autosomal dominant disorder, limiting the number of patients available for analysis. We therefore compiled data on ataxin-7 expression from all SCA7 patients (n=5) and controls (n=7) published to date, and compared with the results obtained in this study. Expression of ataxin-7 was found in neurons throughout the CNS and was highly abundant in Purkinje cells of the cerebellum, in regions of the hippocampus and in cerebral cortex. Ataxin-7 expression was not restricted to regions of pathology, and there were no apparent regional differences in ataxin-7 expression patterns between patients and controls. The subcellular distribution of ataxin-7 was primarily nuclear in all brain regions studied. In cerebellar Purkinje cells, however, differences in subcellular distribution of ataxin-7 were observed between patients and controls of different ages. Here we provide an increased understanding of the distribution of ataxin-7, and the possible implication of subcellular localization of this protein on disease pathology is discussed.