Polyglutamine Expansion Length Dependent Pathology

 描述（由申请人提供）：至少有9种遗传性神经变性疾病是由相应疾病蛋白中的多聚谷氨酰胺（polyQ）结构域的扩增引起的，包括亨廷顿病（HD）和几种脊髓小脑共济失调（SCA）疾病。虽然所有polyQ疾病蛋白在整个大脑和身体中表达，但它们以年龄依赖性方式选择性地影响神经元和一些其他类型的细胞。此外，不同的polyQ长度在青少年和成人患者中引起不同的症状，表明polyQ重复序列可以诱导细胞类型特异性和年龄依赖性病理学。如果我们要开发治疗这些polyQ疾病的有效治疗策略，了解扩展的含polyQ的蛋白质如何介导选择性病理是至关重要的。 虽然我们知道蛋白质环境调节polyQ疾病中所见的polyQ扩增的毒性，但重复长度依赖性选择性病理学背后的机制仍然未知。蛋白质环境赋予polyQ毒性的选择性，因为它决定蛋白质-蛋白质相互作用、半衰期和稳定性以及亚细胞定位。然而， polyQ还可以调节polyQ蛋白毒性的选择性。强有力的证据是，在HD中，大于60个谷氨酰胺的polyQ重复序列导致青少年病例显示出与成人HD患者不同的症状。类似地，TBP中polyQ束（> 42个谷氨酰胺）的扩张在SCA17患者中诱导临床症状。然而，当polyQ重复序列超过63 Q时，突变型TBP导致青少年发作的SCA-17病例生长迟缓，进行性临床症状，早期死亡以及明显的肌无力，这与成人发作的SCA-17患者不同。 我们假设polyQ重复序列长度通过其对细胞或组织依赖性方式的蛋白质相互作用的影响来确定差异病理学。为了检验这一假设，我们将使用SCA17小鼠，其表达在神经元或肌肉细胞中含有不同polyQ重复序列的突变TBP。SCA-17是我们研究polyQ疾病中差异病理学背后的机制的极好模型，因为TBP的功能得到了很好的表征。具体而言，在目标1中，我们将表征SCA17敲入小鼠中的细胞类型依赖性病理学。在目标2中，我们将使用SCA17敲入小鼠和表达含有不同polyQ重复序列的TBP的AAV载体来研究神经元和肌肉细胞中的polyQ重复序列长度依赖性病理学。在目标3中，我们将通过研究不同polyQ重复长度对突变TBP与神经元和肌肉细胞中转录因子相互作用的影响来探索polyQ长度的特定效应的潜在机制。这些研究将为青少年和成人polyQ疾病中不同polyQ重复长度引起的差异病理学和表型提供新的见解。

 DESCRIPTION (provided by applicant): There are at least nine inherited neurodegenerative disorders caused by the expansion of a polyglutamine (polyQ) domain in the respective disease proteins, including Huntington's disease (HD) and several spinocerebellar ataxia (SCA) disorders. Although all polyQ disease proteins are expressed throughout the brain and body, they selectively affect neurons and a few other types of cells in an age-dependent manner. In addition, different polyQ lengths cause different symptoms in juvenile and adult patients, indicating that polyQ repeats can induce cell-type specific and age-dependent pathology. Understanding how the expanded polyQ-containing proteins mediate the selective pathology is critical if we are to develop effective therapeutic strategies for treating these polyQ diseases. Although we know that protein context modulates the toxicity of polyQ expansion seen in polyQ diseases, the mechanism behind the repeat length dependent selective pathology remains unknown Protein context confers the selectivity of polyQ toxicity because it determines protein-protein interactions, half-life and stability, and subcellular localization. However, the length of polyQ also can modulate the selectivity of polyQ protein toxicity. The strong evidence is that in HD, polyQ repeats larger than 60 glutamines cause juvenile cases that show symptoms different from those in adult HD patients. Similarly, expansion of the polyQ tract (>42 glutamines) in TBP induces clinical symptoms in SCA17 patients. However, when polyQ repeats are more than 63Q, mutant TBP causes juvenile-onset SCA-17 cases with retarded growth, progressive clinical symptoms, and early death as well as marked muscle weakness, which are different from those in adult-onset SCA17 patients. We hypothesize that polyQ repeat length determines differential pathology via its effect on protein interactions in cell- or tissue-dependet manner. To test this hypothesis, we will use SCA17 mice that express mutant TBP containing different polyQ repeats in neuronal or muscles cells. SCA-17 is an excellent model for us to investigate the mechanism behind the differential pathology in polyQ disease as the function of TBP is well characterized. Specifically, in Aim 1 we will characterize the cell type-dependent pathology in SCA17 knock-in mice. In Aim 2 we will use SCA17 knock-in mice and AAV vectors expressing TBP containing different polyQ repeats to investigate polyQ repeat length-dependent pathology in neuronal and muscle cells. In Aim 3 we will explore the mechanisms underlying specific effects of polyQ lengths by examining the effects of different polyQ repeat lengths on the interactions of mutant TBP with transcription factors in neuronal and muscle cells. These studies will provide new insight into the differential pathology and phenotypes caused by different polyQ repeat lengths in juvenile and adult polyQ diseases.