Imaging Circuit Change in the Motor Cortex of Mouse Model of ALS

描述（由申请人提供）：肌萎缩性侧索硬化症（ALS）是一种致命的神经退行性疾病，其特征是运动皮层和脊髓中运动神经元的进行性丧失。目前还没有治愈性的治疗方法。该项目的目的是表征ALS发病机制，长期目标是确定新的治疗靶点。谷氨酸诱导的运动神经元兴奋性毒性被认为是ALS发病的主要机制。虽然大多数先前的研究都集中在缺乏谷氨酸转运体作为兴奋性毒性的主要介质，但很少注意到兴奋性毒性的潜在替代原因：功能失调抑制剂机制。“皮质高兴奋性”假说认为，皮质抑制性中间神经元（CIIN）的退化导致皮质运动神经元（CMN）的过度兴奋性和最终退化。尽管这一假说存在了几十年，但仍不清楚CIIN是否确实在ALS中发生变性，CIIN的丧失是否先于CMN的丧失，以及CIIN的丧失是否导致CMN死亡。利用一种创新的双光子显微镜系统，我们设计了一种用于小鼠神经元形态学的体内成像，我们的目的是用两种ALS小鼠模型来验证皮质高兴奋性假说。我们对ALS小鼠的初步研究表明，CIIN中树突状分支的显著缺失和运动皮质CMN中明显的树突状泡，两者都发生在疾病发病之前。这些发现表明，在ALS中，CIIN和CMN都经历了变性，这与高兴奋性假说一致。我们建议通过体内显微镜成像和体内功能测试来验证这一假设，以阐明CIIN的形态变化及其在ALS小鼠中退化的功能后果。我们将：目的1)通过ALS小鼠模型的体内成像，确定CIIN变性是否是ALS发病的起始因素；目的2)确定运动皮质中CIIN的消融是否会导致CMN死亡并加速ALS疾病进展。本课题的成功完成将为进一步了解CIIN在ALS发病机制中的作用奠定基础，为今后针对CIIN作为ALS新型治疗药物的研究铺平道路。

DESCRIPTION (provided by applicant): Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by progressive loss of motor neurons in both the motor cortex and the spinal cord. Currently, there is no curative therapy. The objective of this project is to characterize the mechanisms of ALS pathogenesis, with the long-term goal of identifying new therapeutic targets. Glutamate-induced excitotoxicity of motor neurons is considered a primary mechanism of ALS pathogenesis. While most previous studies have focused on the lack of glutamate transporter as the primary mediator of excitotoxicity, little attention has been paid to a potential alternative cause of excitotoxicity: dysfunctional inhibitor mechanisms. The "cortical hyperexcitability" hypothesis states that degeneration of cortical inhibitory interneurons (CIIN) causes excessive excitability of cortical motor neurons (CMN) and their ultimate degeneration. Despite the existence of this hypothesis for decades, it remains unclear whether CIIN indeed undergo degeneration in ALS, whether loss of CIIN precedes loss of CMN, and whether loss of CIIN results in CMN death. Using an innovative two-photon microscopy system that we designed for in vivo imaging of neuronal morphology in mice, we aim to test the cortical hyperexcitability hypothesis using two mouse models of ALS. Our preliminary studies in ALS mice demonstrated significant loss of dendritic branches in CIIN and marked dendritic blebbing in CMN in the motor cortex, both occurring prior to disease onset. These findings suggest that both CIIN and CMN undergo degeneration in ALS, consistent with the hyperexcitability hypothesis. We propose to test this hypothesis using in vivo microscopy imaging and in vivo functional tests to elucidate the morphological changes of CIIN and the functional consequences of their degeneration in ALS mice. We will: Aim 1) Determine if CIIN degeneration is an initiating factor in ALS pathogenesis, through in vivo imaging in ALS mouse models; and Aim 2) Determine if ablation of CIIN in the motor cortex causes CMN death and accelerates ALS disease progression. Successful completion of this project will establish a foundation for understanding the role of CIIN in ALS pathogenesis, paving the way for future research targeting CIIN as a novel therapeutic for ALS.