Spinocerebellar Ataxia Type 31 Is Associated with "Inserted" Penta-Nucleotide Repeats Containing (TGGAA)n
Spinocerebellar Ataxia Type 31 Is Associated with "Inserted" Penta-Nucleotide Repeats Containing (TGGAA)n
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DOI：
10.1016/j.ajhg.2009.09.019
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发表时间：
2009-11-13
影响因子：
9.8
通讯作者：
Mizusawa, Hidehiro
中科院分区：
文献类型：
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作者：
Sato, Nozomu;Amino, Takeshi;Mizusawa, Hidehiro
脊髓小脑性共济失调31型（SCA31）是一种成人发病的常染色体显性神经退行性疾病，表现为主要影响浦肯野细胞的进行性小脑性共济失调。在16q22.1染色体上的900kb区间上发现了SCA31的关键区域，该区域显示出强烈的奠基者效应。通过进行全面的Southern blot分析和基于BAC和fosmid的测序，我们分离出两个与SCA31分离的遗传变化。一个是胸苷激酶2基因（TK2）内含子的单核苷酸变化。然而，这似乎并不影响剪接或表达模式。另一个是插入，长度在2.5-3.8 kb之间，由复杂的五核苷酸重复组成，包括一个长（TGGAA）(n)延伸。在对照组中，很少发现较短（1.5-2.0 kb）的插入缺失（TGGAA）(n)。SCA31重复插入的长度与患者发病年龄呈负相关，并且在单个家庭中记录了扩展，显示出预期。重复插入位于脑组织中表达的TK2和BEAN（脑表达，与Nedd4相关）的内含子中，并在患者浦肯野细胞的细胞核中形成RNA灶。电泳迁移分析表明，必需剪接因子，富含丝氨酸/精氨酸的剪接因子SFRS1和SFRS9，在体外结合（UGGAA）(n)。由于（TGGAA）(n)是异染色质的特征序列，我们推测该插入可能来源于异染色质。SCA31很重要，因为它证明了与可通过传播扩大的“插入”微卫星重复序列相关的人类疾病。我们的发现表明，异位微卫星重复，当转录时，可能导致涉及基本剪接因子的疾病。
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 BAC- and 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 (1.5-2.0 kb) insertions lacking (TGGAA)(n) were found only rarely. The SCA31 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 (brain 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.