Mechanisms of pathology and neuronal hyperactivity in a memory circuit in Alzheimer's disease

Tsai实验室之前的工作(Canter等人，2019年)确定乳头体(MB)是 5XFAD模型小鼠中淀粉样蛋白沉积的第一个部位，该区域也与 人类患者的痴呆症严重程度。小鼠MB鉴定为2的单细胞RNA测序 MB内不同的神经元群体，具有分离的分布、靶点投影和 独特的电生理学。在5XFAD小鼠中对这些群体的分析发现，其中一个 这些人群，那些在外侧MB(Lm)发现的人群，特别容易患上多动症 和神经退行性变，而第二人群(中间MB，MM)基本上不受影响。 Lm群体的活动也直接影响小鼠的记忆能力 任务。此外，使用博伊登实验室的迭代直接膨胀显微镜(IdExM)，我们 已经发现了与穹隆特定投射相关的有趣的淀粉样蛋白模式， 白质从小脑向下丘走，轴突传入延髓。这笔赠款建议 研究淀粉样蛋白与MB和穹隆兴奋性变化之间的联系，包括 开发实现这一目标所需的工具。这里要检验的假设是 应用是淀粉样蛋白优先与下丘脑-LM投射相联系，并且 这些轴突表现出高度兴奋性。AIM 1将绘制出这一新的 使用一种新的方法，研究来自海马区的Lm神经元及其上游输入的数量 开发了原位测序技术，以及探索白质的病理学 在5XFAD小鼠和人脑样本中的该回路的投射区域，最近使用 发展了膨胀显微镜。目标2将描述来源和位置 通过高级电压成像在LM神经元中发现多动，以及扩展这一 适用于AD的其他小鼠模型。目标3将使用光遗传学和药理学 确定特定异常回路活动是否驱动病理和行为的方法 阿尔茨海默病模型小鼠的变化。

Previous work from the Tsai lab (Canter et al 2019) identified the mamillary body (MB) as one of the first sites of amyloid deposition in 5XFAD model mice, a region that also correlates with dementia severity in human patients. Single cell RNA sequencing of the mouse MB identified 2 distinct neuronal populations within the MB, with segregated distribution, target projection, and unique electrophysiology. Analysis of these populations in the 5XFAD mice found that one of these populations, those found in the lateral MB (LM), are uniquely susceptible to hyperactivity and neurodegeneration, while the second population (medial MB, MM) is largely unaffected. The activity of the LM population also directly contributes to mouse performance in memory tasks. Additionally, using iterative direct-expansion microscopy (idExM) from the Boyden lab, we have identified intriguing patterns of amyloid associated with specific projections in the fornix, the white matter tract from the subiculum with axonal inputs to the MB. This grant proposes to investigate the links between amyloid and excitability changes in the MB and fornix, including development of the tools necessary to achieve this goal. The hypothesis to be tested in this application is that amyloid preferentially associates with the subiculum-LM projection and that these axons exhibit hyperexcitability. Aim 1 will map the connections between this new population of LM neurons and its upstream inputs from the hippocampus, using a newly developed in situ sequencing techniques, as well as exploring pathology in the white matter projection regions of this circuit in 5XFAD mice and human brain samples, using recently developed expansion microscopy. Aim 2 will characterize the source and location of hyperactivity found in the LM neurons through advanced voltage imaging, as well as expand this work to other mouse models of AD. Aim 3 will use optogenetics and pharmacological approaches to determine if specific aberrant circuit activity drives the pathology and behavioral changes seen in the AD model mice.