The neuropathology of cerebellum in spinal muscular atrophy

这是申请1R15 NS120154-01的重新提交(A1)，“脊髓中小脑的神经病理学” 肌肉萎缩“，于2020年6月在ZRG1 MdCN-R(86)部分进行了审查。 脊髓性肌萎缩症(SMA)是导致婴儿死亡的主要遗传原因。它产生于基因突变 存活运动神经元1(SMN1)基因。尽管经过了几十年的研究，但其神经病理机制仍远未明朗。 最近美国FDA批准的SMN修复疗法(Nusinesen、Zolgensma和Risplam)在抢救中有效 运动功能障碍但不能治愈的SMA。目前还不清楚这种影响会持续多久，也不清楚患者是否会受到影响 由于神经系统其他部分的SMN缺陷神经元功能障碍引起的问题。积累证据 提示低水平的SMN不仅改变了脊髓运动神经元的功能，也改变了神经元和神经回路的功能 在汽车网络的其他部分。然而，目前对SMA的神经元病理学了解甚少。 脊髓运动神经元(MN)电路。随着新的治疗方法让患者活得更长，对中枢神经系统作用的了解 SMA神经病理中的运动网络将是制定SMA长期预后和治疗策略的关键 病人。 本应用的目的是研究SMA小鼠的小脑病理和神经回路功能障碍 使用磁共振成像(MRI)和电生理技术的模型。此项目的Rational基于 关于小脑在运动控制中的重要作用，人类SMA患者的小脑病理报告，以及 我们的初步数据显示，在SMA小鼠模型中，小脑神经网络的结构和功能发生了变化。 我们的中心假设是，在SMA中，小脑神经元和神经回路的变化减少 小脑输出和改变从运动皮质和脑干到脊髓的下行运动指令， 导致神经病理和运动系统功能障碍。这一核心假设将通过三个具体目标进行检验： 1)磁学检测SMNΔ7和MN救治小鼠小脑形态和纤维连接的变化 磁共振成像技术；2)阐明小脑神经元的功能改变和与之相关的神经回路 使用电生理技术的SMA病理生理学；3)小脑结构和神经回路的变化 对MN救治小鼠模型SMA疾病进展的影响。确定结构和功能的贡献 病理在小脑中表现为SMA的表型，我们将利用MRI和电生理来研究 SMA症状前期(出生后3-4天，P3-P4)、早期(P7-P8)和症状末期(P12-P13)小脑的神经病理发展。 SMNΔ7和运动神经元MN小鼠模型的比较研究将证实和阐明 SMA小鼠小脑神经病理与脊髓运动神经元功能障碍的关系。确定起点和 小脑神经病理学的进展将表明小脑结构或功能病理或两者如何起作用 SMA表型。这项拟议的研究具有创新性，因为它将是对功能障碍的第一次彻底研究。 结合电生理学、磁共振成像对SMA小鼠小脑神经网络及其机制的研究 和免疫组织化学技术。这类研究需要发展一个完整的系统的理解 SMA的病理生理学，到目前为止，几乎没有研究探讨大脑网络功能障碍的关键问题 以及它对运动功能障碍的贡献。这项拟议的研究具有重要意义，因为了解特定的异常 小脑网络可以为旨在保护SMA患者运动功能的潜在治疗方法带来新的靶点。

This is a resubmission (A1) of application 1R15 NS120154-01, “The neuropathology of cerebellum in spinal muscular atrophy”, which was reviewed in June 2020 at the ZRG1 MDCN-R (86) section. Spinal muscular atrophy (SMA) is the leading genetic cause of infant mortality. It arises from the mutation of the survival motor neuron one (SMN1) gene. Despite decades of research, its mechanisms of neuropathology are far from clear. The recent US FDA approved SMN restoration therapies (Nusinersen, Zolgensma, and Risdiplam) are effective in rescuing the motor dysfunction but not cure for SMA. It is not clear how long the effect will last, nor whether patients will suffer problems due to dysfunction of SMN deficient neurons in other parts of the nervous system. Accumulating evidence suggests that low levels of SMN not only alter the function of spinal motor neurons, but also of neurons and neural circuits in other parts of the motor network. However, currently there is little understanding of neuronal pathology in SMA beyond the spinal cord motor neuron (MN) circuit. As new treatments allow patients to live longer, knowledge of the role of central motor network in the neuropathology of SMA will be key for developing long-term prognoses and treatment strategies for patients. The objective of this application is to investigate cerebellar pathology and neural circuit dysfunction in SMA mouse models using magnetic resonance imaging (MRI) and electrophysiological techniques. The rational for this project is based on the important role of cerebellum in motor control, the reports of cerebellar pathology in human SMA patients, as well as our preliminary data showing alterations in the structure and function of cerebellar neural network in mouse models of SMA. Our central hypothesis is that in SMA, alterations in the neurons and neural circuits of the cerebellum decrease cerebellar output and alter descending motor commands from the motor cortex and brainstem to the spinal cord, contributing to neuropathology and motor system dysfunction. This central hypothesis will be tested by three specific aims: 1) Identify changes in the morphology and fiber connections of the cerebellum in SMNΔ7 and MN rescue mice by magnetic resonance imaging techniques; 2) Elucidate the functional alteration of cerebellar neurons and neural circuits related to SMA pathophysiology using electrophysiological techniques; 3) Relate changes in cerebellar structure and neural circuit function to SMA disease progression in MN rescue mouse model. To determine the contribution of structural and functional pathology in the cerebellum to the phenotype of SMA, we will use MRI and electrophysiology to investigate the development of neuropathology in the cerebellum at pre-symptomatic (postnatal day 3–4, P3–P4), early- (P7–P8), and end-symptomatic (P12–P13) stage of SMA. The comparison studies between SMNΔ7 and motor neuron MN mouse models will confirm and elucidate the correlation of cerebellar neuropathology with spinal motor neuron dysfunction in SMA mice. Identifying the start and progression of cerebellar neuropathology will indicate how cerebellar structural or functional pathology or both contribute to the SMA phenotype. The proposed research is innovative because it will be the first thorough study of the dysfunction and its mechanisms of the cerebellar neural network in SMA mice with a unique combination of electrophysiological, MRI and immunohistochemical techniques. This kind of study is required to develop a complete systematic understanding of the pathophysiology of SMA, and almost no studies so far have investigated the critical issue of dysfunction in the brain network and its contribution to motor dysfunction. The proposed research is significant because understanding specific abnormalities cerebellar network can lead to new targets for potential therapeutics aimed at preserving motor function in SMA patients.