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The article explains the various symptoms and causes of spinocerebellar ataxia type 31 (SCA31), an adult-onset autosomal-dominant neurodegenerative disorder. The numerous insertions containing the complex penta-nucleotide repeats including a long [(TGGAA).sub.n] stretch are shown to be highly associated with the onset of the disorder.

Spinocerebellar ataxia type 31 (SCA31) is an adult-onset autosomal-dominant neurodegenerative disorder showing progressive cerebellar ataxia mainly affecting Purkinje cells. The SCA31 critical region was tracked down to a 900 kb interval in chromosome 16q22.1, where the disease shows a strong founder effect. By performing comprehensive Southern blot analysis and BACand fosmid-based sequencing, we isolated two genetic changes segregating with SCA31. One was a single-nucleotide change in an intron of the thymidine kinase 2 gene (TK2). However, this did not appear to affect splicing or expression patterns. The other was an insertion, from 2.5-3.8 kb long, consisting of complex penta-nucleotide repeats including a long (TGGAA)n stretch. In controls, shorter (1.52.0 kb) insertions lacking(TGGAA)n were found only rarely. The SCA3 1 repeat insertion's length inversely correlated with patient age of onset, and an expansion was documented in a single family showing anticipation. The repeat insertion was located in introns of TK2 and BEAN Wrain expressed, associated with Nedd4) expressed in the brain and formed RNA foci in the nuclei of patients' Purkinje cells. An electrophoretic mobility-shift assay showed that essential splicing factors, serine/arginine-rich splicing factors SFRS1 and SFRS9, bind to (UGGAA)n in vitro. Because(TGGAA)n is a characteristic sequence of paracentromeric heterochromatin, we speculate that the insertion might have originated from heterochromatin. SCA31 is important because it exemplifies human diseases associated with "inserted" microsatellite repeats that can expand through transmission. Our finding suggests that the ectopic microsatellite repeat, when transcribed, might cause a disease involving the essential splicing factors. [ABSTRACT FROM AUTHOR]

Multiple system atrophy (MSA) is a sporadic neurodegenerative disease manifested clinically by progressive ataxia, parkinsonism, and autonomic dysfunction. Its cause is unknown, and there is no curative therapy. Alpha-synuclein is an important protein forming aggregations called glial cytoplasmic inclusions (GCIs) in oligodendroglia; these aggregations are considered important in MSA pathogenesis. Overexpression of the human alpha-synuclein gene in mice induces the formation of GCI-like aggregations in oligodendrocytes, leading mice to exhibit neurological signs similar to those in MSA patients. However, previous studies have excluded mutations within the coding region of the alpha-synuclein gene in MSA patients. To determine whether alteration in the expression level of the alpha-synuclein gene is associated with MSA pathogenesis, we used TaqMan quantitative PCR assay to analyze the alpha-synuclein gene copy number in patients' genomes. We also used quantitative RT-PCR and in situ hybridization to analyze alpha-synuclein mRNA expression in MSA patients' brain tissues. We found no alteration in the alpha-synuclein gene copy number in the patients' genomes (n = 50). Quantitative analysis for alpha-synuclein mRNA by the TaqMan method showed that alpha-synuclein mRNA levels were comparable between control (n = 3) and MSA (n = 3) cerebella. On in situ hybridization, the number of neurons with alpha-synuclein mRNA expression was no greater in the cerebella of MSA patients (n = 3) than in the controls (n = 3). However, GCIs were seen in these MSA specimens on immunohistochemistry for alpha-synuclein. These results suggest that alpha-synuclein gene expression is not the fundamental cause of MSA.