A Mouse Model of RNA-induced Neurotoxcity

描述（由申请人提供）：含有长CUG重复序列的RNA转录物的毒性是疾病发病的一种新机制，最近在肌强直性营养不良1型（DM1）中被描述，DM1是最常见的成人发病肌营养不良。CUG扩增导致细胞毒性的确切机制尚不清楚，但可能涉及剪接的错误调节。我们的研究小组最近发现了一种常染色体显性疾病，亨廷顿病样2 (HDL2)，其临床和病理特征几乎与亨廷顿病（HD）相同，亨廷顿病是一种持续进行性的成人神经退行性疾病。像HD一样，HDL2是由CAG/CTG扩增突变引起的。令我们惊讶的是，HDL2的发病机制与DM1一样，与HD不同，似乎至少部分源于含有长CUG重复序列的RNA转录本的毒性作用。为了验证未翻译的CUG扩增可导致哺乳动物大脑神经毒性的假设，我们提出在大脑中产生特异性表达扩增CUG重复序列的转基因小鼠。在Specific Aim 1中，我们将使用包含JPH3短片段的不可翻译构建体，在脑特异性PrP启动子的控制下，具有正常或扩增的CTG重复序列，从而产生CUG转基因小鼠。在特异性目标2中，将检查这些小鼠的行为，运动和病理表型。在Specific Aim 3中，将在小鼠中检查CUG重复扩增疾病的特异性特征，重点是RNA病灶和蛋白质聚集。我们预测，扩大的CUG重复将导致神经毒性，在运动行为和神经病理学中很明显。如果这一预测是正确的，那么这里产生的小鼠将成为解剖DM1、HD和HDL2致病途径的宝贵工具。发现这些疾病的致病趋同点可能为开发合理的治疗方法提供新的线索。

DESCRIPTION (provided by applicant): Toxicity of RNA transcripts containing long CUG repeats, a novel mechanism of disease pathogenesis, was recently described in myotonic dystrophy type 1 (DM1), the most common form of adult onset muscular dystrophy. The precise mechanism by which CUG expansions lead to cell toxicity is unclear, though misregulation of splicing may be involved. Our group recently identified an autosomal dominant disorder, Huntington's disease-like 2 (HDL2), with clinical and pathological features almost identical to Huntington's disease (HD), a relentlessly progressive adult onset neurodegenerative disorder. Like HD, HDL2 is caused by a CAG/CTG expansion mutation. To our surprise, the pathogenesis of HDL2, like DM1 and unlike HD, appears to arise at least in part from the toxic effect of RNA transcripts containing long CUG repeats. To test the hypothesis that untranslated CUG expansions can lead to neurotoxicity in the mammalian brain, we propose to generate a transgenic mouse specifically expressing an expanded CUG repeat in the brain. In Specific Aim 1, we will generate CUG transgenic mice, using an untranslatable construct that contains a short fragment of JPH3 with either a normal or an expanded CTG repeat under the control of the brain-specific PrP promoter. In Specific Aim 2, the behavioral, motoric, and pathological phenotype of these mice will be examined. In Specific Aim 3, specific characteristics of CUG repeat expansion diseases will be examined in the mice, with an emphasis on RNA foci and protein aggregation. We predict that the expanded CUG repeat will lead to neurotoxicity, evident in motor behavior and neuropathology. If this prediction is correct, the mice generated here will become invaluable tools for dissecting the pathogenic pathways of DM1, HD, and HDL2. Finding the points of pathogenic convergence in these diseases may provide novel leads for the development of rational therapeutics.