Cell Models of RNA Neurotoxicity

描述(申请人提供)：在强直性肌营养不良1型(DM1)中描述了一种新的疾病发病机制，其中细胞损伤是由带有扩展的CUG重复序列的转录本引起的。我们的小组最近描述了另一种疾病，亨廷顿病样2(HDL2)，也与CUG重复毒性有关。和DM1一样，HDL2也是一种显性疾病。与DM1不同，HDL2与亨廷顿病(HD)非常相似，中年时会开始一种毁灭性的神经退化过程，选择性地影响纹状体和大脑皮层，并不可避免地进展到死亡。我们发现HDL2是由染色体16q24.3上的JPH3(JPH3)上的CAG/CTG重复序列扩张引起的，JPH3转录后的重复序列在神经元核中聚集并形成焦点。初步的细胞实验表明，这些转录本是有毒的，可能通过重新分配类肌肉蛋白1(MBNL1)来诱导毒性，MBNL1是一种也与DM1的肌肉和大脑异常有关的蛋白质。令人惊讶的是，我们的初步实验表明，含有CAG重复扩增的未翻译亨廷顿蛋白转录本也是有毒的。这些初步的发现使我们假设，HDL2的发病机制，也许是HD，至少部分源于带有扩展重复序列的转录本。更具体地说，我们假设RNA诱导的神经毒性将由重复的类型和长度、重复两侧的序列以及表达重复的细胞类型决定。我们还假设这种神经毒性的发病机制将涉及剪接调节蛋白类肌肉毒素1(MBNL1)。在这里，我们建议开发和探索细胞模型，为慢性萎缩性胃炎和慢性萎缩性胃炎的RNA神经毒性提供线索。如果成功，我们的工作将为HDL2、HD和潜在的其他重复疾病的发病机制开辟新的研究路线，最终目标是为神经退行性疾病的治疗开发新的靶点。

DESCRIPTION (provided by applicant): A novel form of disease pathogenesis, in which cell damage is caused by transcripts with expanded CUG repeats, has been described in myotonic dystrophy type 1 (DM1). Our group recently described another disorder, Huntington's disease-like 2 (HDL2), that is also associated with CUG repeat toxicity. Like DM1, HDL2 is a dominant disorder. Unlike DM1, HDL2 is very similar to Huntington's disease (HD), with mid-life onset of a devastating neurodegenerative process selectively affecting the striatum and cerebral cortex and progressing inevitably to death. We found that HDL2 is caused by a CAG/CTG repeat expansion in junctophilin-3 (JPH3) on chromosome 16q24.3, and that JPH3 transcripts with an expanded repeat accumulate and form foci in neuronal nuclei. Preliminary cell experiments suggest that these transcripts are toxic, and may induce toxicity via redistribution of muscleblind-like protein 1 (MBNL1), a protein also implicated in the muscle and brain abnormalities of DM1. Surprisingly, our preliminary experiments indicate that untranslated huntingtin transcripts containing CAG repeat expansions are also toxic. These preliminary findings have led us to hypothesize that the pathogenesis of HDL2, and perhaps HD, may at least partly stem from transcripts with expanded repeats. More specifically, we hypothesize that RNA-induced neurotoxicity will be determined by the type and length of the repeat, the sequence flanking the repeat, and the cell types in which the repeat is expressed. We also hypothesize that the pathogenesis of this neurotoxicity will involve the splice-regulating protein muscleblind like 1 (MBNL1). Here, we propose to develop and explore cell models that will provide clues about RNA neurotoxicity in both CUG and CAG diseases. If successful, our work will open up new lines of investigation into the pathogenesis of HDL2, HD, and potentially other repeat disorders, with the ultimate goal of developing new targets for the therapeutics of neurodegenerative disease.