Optogenetic dissection of hippocampal circuitry underlying Alzheimers disease

描述(申请人提供)：确定学习和记忆的基础电路是至关重要的，以便不仅要了解记忆的机制，而且要了解这些机制如何在记忆障碍中变得失调，如阿尔茨海默病(AD)。人类和啮齿动物的损伤研究表明，海马体(HPC)在长期记忆中发挥了作用，特别是在CA1亚区。当记忆必须长时间保持时，CA1优先被激活，研究表明，在重复暴露于相同环境中时，很大比例的CA1神经元被重新激活。然而，之前没有任何研究能够评估单个CA1神经元在学习和记忆中或在AD中的长期参与(&gt；1个月)，因为所有以前的转基因株都缺乏一个不可磨灭的标签。在这项应用中，将利用转基因品系ArcCreERT2小鼠来研究个体CA1神经元对经验编码和相应记忆提取的贡献。这个小鼠品系允许对表达早期直接基因Arc/Arg3.1的细胞进行不可磨灭的标记，并允许在编码经验期间激活的细胞和在提取相应记忆期间激活的细胞之间进行比较。结合光遗传报告系，这些研究将评估CA1神经元在记忆编码和提取中的长期参与。为了全面了解CA1神经元在记忆中的作用，我们将在编码过程中选择性地在CA1神经元群体中表达蓝光激活的阳离子通道视紫红质-2(ChR2)或黄光激活的外向质子泵古紫质(Arch)。然后，利用光遗传学，我们将检验这一假设，即CA1神经元的一个亚群对于检索相应的长期记忆是充分和必要的。接下来，将利用三重转基因设计在AD小鼠中描绘CA1在记忆编码和提取中的作用，在该设计中，最初在编码过程中标记的CA1神经元可以在对照组和AD小鼠中进行光遗传调节。在体内，我们将测试这一假设，即在记忆提取过程中光遗传刺激或抑制CA1锥体神经元将改善AD小鼠的记忆表达。最后，将使用光遗传操作在对照组和AD小鼠中模拟类似于脑深部刺激的方案，以改善AD小鼠的整体细胞功能、细胞存活和记忆恢复。

DESCRIPTION (provided by applicant): It is of utmost importance to identify the circuits underlying learning and memory in order to understand not only the mechanisms of memory but also the how these mechanisms become dysregulated in memory disorders, such as Alzheimer's disease (AD). Human and rodent lesion studies have suggested a role for the hippocampus (HPC) in long-term memory, specifically the subregion CA1. CA1 is preferentially activated when a memory must be retained over a long period of time, and studies have shown that a large proportion of CA1 neurons are reactivated in repeated exposures to the same environment. However, no previous studies have been able to assess the long-term (> 1 month) involvement of individual CA1 neurons in learning and memory, or in AD, since all previous transgenic lines have lacked an indelible label. In this application, the contribution of individua CA1 neurons to the encoding of an experience and to the retrieval of a corresponding memory will be investigated by utilizing a transgenic line, the ArcCreERT2 mice. This mouse line allows for the indelible labeling of cells expressing the immediate early gene Arc/Arg3.1 and allows for a comparison between the cells that are activated during the encoding of an experience and those that are activated during the retrieval of the corresponding memory. In combination with optogenetic reporter lines, these studies will assess the long- term involvement of CA1 neurons in memory encoding and retrieval. To fully characterize the role of CA1 neurons in memory, we will selectively express the blue light activated cation channel channelrhodopsin-2 (ChR2) or the yellow light activated outward proton pump archaerhodopsin (Arch) in populations of CA1 neurons during encoding. Using optogenetics, we will then test the hypothesis that a subpopulation of CA1 neurons is sufficient and necessary for the retrieval of a corresponding long-term memory. Next, the role of CA1 in memory encoding and retrieval will be delineated in AD mice by utilizing a triple transgenic design in which CA1 neurons, initially labeled during encoding, can be optogenetically modulated in control and AD mice. In vivo, we will test the hypothesis that optogenetic stimulation or inhibition of CA1 pyramidal neurons during memory retrieval will improve expression of a memory in AD mice. Finally, optogenetic manipulations will be used in order to mimic a deep brain stimulation-like protocol in control and AD mice in order to improve overall cellular function, cell survival, and memory retrieval in AD mice.