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

描述(申请人提供)：肌萎缩侧索硬化症(ALS)是一种致命的神经退行性疾病，其特征是运动皮质和脊髓中运动神经元的进行性丧失。目前，还没有根治的疗法。该项目的目标是表征ALS的发病机制，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毒性被认为是ALS发病的主要机制之一。虽然以前的研究大多集中在缺乏谷氨酸转运体作为兴奋性毒性的主要媒介，但很少有人注意到兴奋性毒性的另一个潜在原因：功能障碍的抑制机制。“皮质超兴奋性”假说认为，皮质抑制性中间神经元(Ciin)的变性导致皮质运动神经元(CMN)的过度兴奋性，并最终导致其变性。尽管这一假说已经存在了几十年，但目前尚不清楚Ciin在ALS中是否真的经历了退变，Ciin的丢失是否先于CMN的丢失，以及Ciin的丢失是否导致CMN的死亡。使用我们为在体成像小鼠神经元形态而设计的创新的双光子显微镜系统，我们的目标是使用两个ALS小鼠模型来验证皮质超兴奋性假说。我们对ALS小鼠的初步研究显示，在ALS小鼠中，Ciin的树突分支显著丢失，在运动皮质的CMN中有显著的树突气泡，这两种情况都发生在疾病发病之前。这些发现表明肌萎缩侧索硬化症中Ciin和CMN都经历了退变，这与超兴奋性假说一致。我们建议使用体内显微镜成像和体内功能测试来验证这一假说，以阐明肌钙蛋白在ALS小鼠中的形态变化及其退化的功能后果。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发病的始动因素；以及目的2)确定切除运动皮质Ciin是否导致CMN死亡并加速ALS疾病的进展。该项目的成功完成将为了解Ciin在ALS发病机制中的作用奠定基础，为未来将Ciin作为治疗ALS的新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.