Cell Models of RNA Neurotoxicity

描述（由申请人提供）：在1型肌强直性营养不良（DM1）中描述了一种新的疾病发病机制，其中细胞损伤是由CUG重复扩增的转录物引起的。我们的小组最近描述了另一种疾病，亨廷顿病样2 (HDL2)，它也与CUG重复毒性有关。和DM1一样，HDL2也是显性疾病。与DM1不同，HDL2与亨廷顿氏病（HD）非常相似，在中年发病时，会出现一种破坏性的神经退行性过程，选择性地影响纹状体和大脑皮层，并不可避免地发展到死亡。我们发现HDL2是由染色体16q24.3上连接蛋白3 （junctophilin-3, JPH3）的CAG/CTG重复扩增引起的，重复扩增的JPH3转录本在神经元细胞核中积累并形成病灶。初步的细胞实验表明，这些转录本是有毒的，并且可能通过肌肉盲样蛋白1 （MBNL1）的再分配诱导毒性，这种蛋白也与DM1的肌肉和大脑异常有关。令人惊讶的是，我们的初步实验表明含有CAG重复扩增的未翻译的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，或者HD，可能至少部分源于重复扩增的转录本。更具体地说，我们假设rna诱导的神经毒性将由重复序列的类型和长度、重复序列两侧的序列以及重复序列表达的细胞类型决定。我们还假设这种神经毒性的发病机制可能与剪接调节蛋白MBNL1 （muscleblind like 1）有关。在这里，我们建议开发和探索细胞模型，为CUG和CAG疾病的RNA神经毒性提供线索。如果成功，我们的工作将为研究HDL2， HD和潜在的其他重复疾病的发病机制开辟新的途径，最终目标是开发神经退行性疾病治疗的新靶点。

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.