Control of Excitatory Synapse Formation by Huntingtin

标题：亨廷顿对兴奋性突触形成的控制 摘要： 亨廷顿病(HD)是一种遗传性、致命性神经退行性疾病，由 多聚谷氨酰胺(PolyQ)位于亨廷顿蛋白(Htt)的N端。而致病突变 由于HD可以在疾病发作之前很久就被检测到，目前还没有预防或延迟的治疗方法 HD的神经退行性变。Htt突变的显性本质导致了HD是由 突变的Htt蛋白的毒性功能增强。因此，大多数HD治疗策略是 专注于减少或消除突变的Htt。我们实验室和其他实验室最近的研究表明 另一种假说认为，Htt功能的丧失也是疾病发病的主要驱动因素。在鼠标中 通过遗传学研究，我们的实验室发现，皮质Htt是正确建立皮质和皮质的必需的。 纹状体兴奋性突触连接，当突变的Htt存在时，Htt的这一功能就会丧失。什么 野生型Htt在建立和维持突触连接中的作用吗？何以 野生型Htt功能障碍与HD发病机制有关？这些都是我将回答的问题 我在杜克大学卡格拉·埃罗格鲁博士的实验室做博士后研究时回答道。 在我的初步实验中，我发现神经元Htt作为星形胶质细胞的调节器扮演了一个意想不到的角色- 诱导突触发生。星形胶质细胞分泌凝血酶敏感蛋白家族蛋白，诱导突触 通过它们的神经元受体，加巴喷丁受体α2δ-1形成。在生化实验中，我发现 α2δ-1直接与野生型Htt相互作用，但当致病的PolyQ-Q Htt出现了重复扩张。此外，Htt是神经元抑制突触发生所必需的。 缺乏TSP信号，提示Htt和α2δ-1具有相反的功能，平衡细胞的生长 兴奋性突触连接。基于这些发现，我提出了一个假设，即Htt是一种 兴奋性突触形成。我将使用原代神经元培养，分子生物学， 生物化学、共聚焦显微镜和小鼠遗传学，以验证Htt控制突触的假设 通过与α2δ-1的相互作用，Htt的这一功能受到损害 扩张是存在的。此外，我将确定对α2δ-1表达的遗传操作是否可以 挽救HD模型小鼠的突触缺陷，延缓或阻止疾病进展。总而言之，我希望这些 研究将通过确定特定的分子机制来显著推动HD研究领域的发展 其中野生型Htt功能丧失参与了疾病的发病机制。此外，这些发现是 准备提供新的治疗策略来治疗早期突触功能障碍并延迟或预防 HD的神经退行性变。

Title: Control of Excitatory Synapse Formation by Huntingtin Abstract: Huntington’s Disease (HD) is an inherited, fatal neurodegenerative disease caused by an expansion of poly-glutamine (poly-Q) repeats in the N-terminus of the Huntingtin (Htt) protein. While the causative mutation for HD can be detected long before disease onset, there are currently no treatments to prevent or delay neurodegeneration in HD. The dominant nature of the Htt mutation led to the hypothesis that HD is caused by a toxic gain-of-function of the mutant Htt protein. Therefore, the majority of HD therapeutic strategies are focused on reducing or eliminating mutant Htt. Recent work from our laboratory and others suggests an alternative hypothesis, that loss of Htt function is also a major driver of disease pathogenesis. In mouse genetic studies, our lab found that cortical Htt is required for the correct establishment of cortical and cortico- striatal excitatory synaptic connections, and that this function of Htt is lost when mutant Htt is present. What are the functions of wild-type Htt in establishing and maintaining synaptic connections? How does disruption of wild-type Htt function contribute to HD pathogenesis? These are the questions that I will answer during my postdoctoral research in Dr. Cagla Eroglu’s laboratory at Duke University. In my preliminary experiments I found an unexpected role for neuronal Htt as a regulator of astrocyte- induced synaptogenesis. Astrocytes secrete thrombospondin (TSP) family proteins, which induce synapse formation via their neuronal receptor, the gabapentin receptor α2δ-1. In biochemical experiments, I found that α2δ-1 directly interacts with wildtype Htt, but this interaction is impaired when the disease-causing poly-Q repeat expansion is present in Htt. Furthermore, Htt is required in neurons to suppress synaptogenesis in the absence of TSP signaling, suggesting that Htt and α2δ-1 have opposing functions that balance the growth of excitatory synaptic connectivity. Based on these findings, I developed the hypothesis that Htt is an inhibitor of excitatory synapse formation. I will use a combination of primary neuronal culture, molecular biology, biochemistry, confocal microscopy, and mouse genetics, to test the hypothesis that Htt controls synaptic connectivity through its interaction with α2δ-1, and that this function of Htt is impaired when the poly-Q expansion is present. Additionally, I will determine whether the genetic manipulation of α2δ-1 expression can rescue synaptic deficits and delay or stop disease progression in HD model mice. Collectively, I expect these studies will significantly advance the field of HD research by identifying specific molecular mechanisms through which loss of wild-type Htt function contributes to disease pathogenesis. Furthermore, these findings are poised to provide novel therapeutic strategies to treat early synaptic dysfunction and delay or prevent onset of neurodegeneration in HD.