Cellular and Circuit Mechanisms of Upper Motor Neuron Degeneration in Amyotrophic Lateral Sclerosis (ALS)

上运动神经元（UMN）的退化是肌萎缩性侧索硬化症（ALS）的一个主要特征，这是一种破坏性疾病，其特征分别是皮质和脊髓的上、下运动神经元（LMN）的关节损伤。然而，过去的研究主要集中在对下运动神经元损伤的研究上，而对下运动神经元功能障碍的机制知之甚少。最近的研究结果表明，umn在疾病的早期就受到影响，并且它们的功能障碍先于LMN的退化。一个关键特征，不仅在ALS中突出，而且在其他神经退行性疾病中也很突出，那就是内在兴奋性的变化。据报道，在疾病的前驱阶段，由于兴奋和抑制之间的不平衡引起的高兴奋性，这明显可以影响细胞类型，而不是以迄今未知的顺序影响各自神经退行性疾病的实际主要目标。因此，了解神经回路的不同组成部分在疾病过程中是如何受损的，对于确定新的治疗靶点非常重要。该建议旨在研究ALS小鼠模型中运动皮层微回路中的关键功能单元，以揭示最终导致UMN变性的疾病皮层病理学的新方面。这些变化不仅包括UMN的结构和功能改变，还包括驱动UMN的皮质II/III层上游细胞，以及提供层内输入的脑内神经元，如皮质纹状体神经元和调节区域内活动的多类相互连接的中间神经元。此外，由小胶质细胞和星形胶质细胞传递的非细胞自主过程被认为在ALS发病中起重要作用。由于两者都强烈参与回路的调节，它们的功能障碍可能对神经元健康产生重大影响。我将在清醒的小鼠中采用最先进的体内双光子成像技术，结合分子方法，选择性地记录特定细胞群，如抑制性亚型、umn或II/III层细胞，以监测和关联整个疾病过程中神经元和神经胶质细胞的结构和功能改变。这种方法将使我能够捕捉神经元功能障碍的早期变化，例如突触不稳定，并通过描述它们对神经元反应特性的影响来解决其对神经元命运的影响。此外，我将评估结构和功能改变是否取决于分子变化，如细胞内增加。钙，形成细胞内。细胞凋亡的聚集或迹象。我相信，通过这些研究，我可以阐明M1回路中发生的一系列事件，这些事件控制着UMN的退化，并有望帮助确定新的治疗策略。

The degeneration of upper motor neurons (UMN) represents a cardinal feature of Amyotrophic Lateral Sclerosis (ALS), a devastating disease that is characterized by the joint impairment of upper and lower motor neurons (LMN) in cortex and spinal cord, respectively. However, research in the past has strongly focused on the study of lower motor neuron impairment, while little is known about the mechanisms governing UMN dysfunction. Recent findings suggest that UMNs are affected very early in the disease and that their dysfunction precedes the degeneration of LMN. One key characteristic, not only prominent in ALS, but also in other neurodegenerative diseases, are changes in intrinsic excitability. These are reported in prodromal stages of the disease as hyperexcitability, caused by a dysbalance between excitation and inhibition, which notably can affect cell types other than the actual prime target of the respective neurodegenerative disease in a hitherto unknown sequence. Understanding how different components of neural circuits are compromised in the course of the disease is, thus important in order to identify new therapeutic targets. This proposal is aimed at investigating key functional units within the motor cortex microcircuit in ALS mouse models to unravel new aspects of the cortical pathology in the disease that ultimately lead to UMN degeneration. These encompass structural and functional alterations of not only UMN, but also upstream cells in cortical layer II/III driving UMN, as well as intratelencephalic neurons, such as corticostriatal neurons, providing intralaminar input and multiple classes of interconnected interneurons regulating activity within an area. Moreover, non-cell autonomous processes, conveyed by microglia and astrocytes, were suggested to play an important role in ALS pathogenesis. As both are strongly involved in the regulation of circuits, their dysfunction likely has a major impact on neuronal health. I will employ state-of-the-art in vivo two-photon imaging in awake mice combined with molecular approaches to selectively record from defined cell populations, such as inhibitory subtypes, UMNs or layer II/III cells, to monitor and correlate structural and functional alterations of neurons and glia cells throughout the course of the disease. This approach should enable me to capture early changes of neuronal dysfunction, such as synapse instability, and to address its impact on the neuron s fate, by characterizing their consequences on neuronal response properties. Moreover, I will assess whether structural and functional alterations hinge on molecular changes, such as increased intracell. calcium, the formation of intracell. aggregates or signs of apoptosis. I believe that with these studies I can elucidate a sequence of events occurring within M1 circuits that governs the degeneration of UMN and which hopefully helps identifying new therapeutic strategies.