Characterizing Wnt Signaling Pathways in Axon Guidance

摘要/摘要 阿尔茨海默病(AD)的特征是Aβ斑块和Tau缠结，这对 突触的稳定性和突触的可塑性，并导致神经元死亡和记忆丧失。载脂蛋白E4 载脂蛋白E4(ApoE4)是晚发性AD的主要遗传危险因素。最近的研究表明，apoE4具有深远的影响 关于突出的AD病理，包括淀粉样蛋白-β、tau病理、神经炎症和神经网络 功能障碍，提示AD的发病机制是一个共同的靶点。我们实验室的工作表明，平面细胞 在发育过程中，极性(PCP)在突触的形成中起着至关重要的作用。我们还证明了低聚物 β结合Celsr3，减弱Celsr3和Frizzled3之间的相互作用，并辅助Vangl2在 分解突触。β诱导的突触丢失也需要一种PCP信号调节因子Ryk 与Vangl2一起工作。在阿尔茨海默病5XFAD小鼠模型中，Ryk条件基因敲除 在神经元或脑室内注入功能阻断的Ryk抗体保护的突触 并保留了认知功能。我们的新的初步结果表明，PCP在突触中具有新的功能。我们 研究发现，PCP成分Dvl2和Vangl2对突触的调节不是突触维持所必需的 可塑性。此外，Dvl2在5XFAD小鼠的突触体中下调。问五氯苯酚是否 途径也可能是载脂蛋白E的病理靶点，我们检测了载脂蛋白E3和载脂蛋白E4中PCP蛋白的水平 Knockin小鼠与加州大学旧金山分校格莱斯通研究所的黄亚东合作。我们发现 在年龄较大的动物(19-19.9个月大)中，载脂蛋白E4动物的突触数量显著减少 与ApoE3相比，突触中的一些PCP蛋白有减少的趋势。在更年轻的动物身上 (5.8-5.9月龄)，没有明显的突触丢失，而电生理变化已经 可检测到的。我们的初步结果表明，具有特定成分的突触存在选择性丢失 PCP蛋白。在本补充材料中，我们提出了一组试验性实验，以询问Dvl2的丢失是否 对突触可塑性的丧失和最终的稳定性负责。我们将测试不同的成分 突触中的PCP蛋白在ApoE模型中显示出不同的脆弱性。建议的结果 实验将使我们不仅能够为未来对突触变性的研究制定假说 阿尔茨海默病，也获得了PCP蛋白如何正常调节 突触及其如何调节脊髓损伤后功能恢复的突触再生， 这也是我们父母资助的目的之一。

Summary/Abstract Alzheimer's disease (AD) is characterized by Aβ plaques and Tau tangles, which negatively impact synaptic stability and synaptic plasticity and cause neuronal death and loss of memory. Apolipoprotein E4 (apoE4) is the major genetic risk factor for late-onset AD. Recent work suggests that apoE4 has profound effects on prominent AD pathologies, including amyloid-β, tau pathology, neuroinflammation, and neural network dysfunction, suggesting a common target for pathogenesis of AD. Work from our lab showed that planar cell polarity (PCP) plays an essential role in synapses formation in development. We also showed that oligomeric Aβ binds to Celsr3 and weakens the interaction between Celsr3 and Frizzled3 and assists Vangl2 in disassembling synapses. A regulator of PCP signaling, Ryk, is also required for Aβ-induced synapse loss functioning together with Vangl2. In the 5XFAD mouse model of Alzheimer’s disease, Ryk conditional knockout in neurons or intracerebroventricular infusion of a function-blocking monoclonal Ryk antibody protected synapses and preserved cognitive function. Our new preliminary results suggest a novel function of PCP in synapses. We found that PCP components, Dvl2 and Vangl2, which are not require for synapse maintenance, regulate synaptic plasticity. In addition, Dvl2 is down regulated in the synaptosome of the 5XFAD mice. To ask whether PCP pathway may also be the pathological target of ApoE, we tested the levels of PCP proteins in ApoE3 and ApoE4 knockin mice in collaboration with Yadong Huang of the Gladstone Institute at UC San Francisco. We found that in older animals (19-19.9 months old), there is a dramatic reduction of synapse numbers in ApoE4 animals compared to ApoE3 and a trend of reduction of some of the PCP proteins in the synapses. In younger animals (5.8-5.9 months old), there was no significant loss of synapses, while electrophysiological changes are already detectable. Our preliminary results show that there is a selective loss of synapses with specific compositions of PCP proteins. In this supplement, we propose a set of pilot experiments to ask whether the loss of Dvl2 is responsible for the loss of synaptic plasticity and eventually stability. We will test whether different compositions of PCP proteins in the synapses show different vulnerability in the ApoE model. The results from the proposed experiments will allow us to not only formulate hypothesis for future studies of synapse degeneration in Alzheimer’s disease but also obtain clues of how PCP proteins normally regulate the formation and function of synapses and how they regulate the regeneration of synapses for functional recovery after spinal cord injury, which is one of the aims of our parent grant.