Cerebellar Involvement and Alcohol Effects in a Mouse Model of Myoclonus Dystonia

描述(申请人提供)：肌阵挛-肌张力障碍(M-D)是一种遗传性运动障碍，其主要特征是上半身不自主的痉挛(肌阵挛)和激动肌和拮抗肌的持续收缩，导致疼痛、扭曲的姿势(肌张力障碍)。运动症状起病于儿童或青春期，并引起不同程度的疼痛、残疾和心理社会痛苦。M-D是由编码肌聚糖(？-sg)蛋白的SGCE基因功能丧失突变引起的，但其病理生理机制仍知之甚少。目前还没有治愈或有效治疗多发性硬化症的方法。这种疾病的一个显著特征是，随着饮酒的增加，运动症状会有所改善。虽然酒精可能不适合治疗，但了解它是如何缓解症状的将有助于深入了解M-D的病理生理学，并提供潜在的治疗靶点。小脑对酒精非常敏感，最近被认为与一些肌张力障碍的病理生理学有关。该实验室获得的初步数据也表明小脑与多发性硬化症有关。这项拟议的研究的目的是检验这样一种假设，即小脑的异常活动会导致M-D中的肌阵挛和肌张力障碍，而酒精通过作用于小脑中的靶点，使小脑活动正常化，从而缓解运动症状。初步数据表明，小鼠小脑SGCE被短发夹状RNA(ShRNA)急性敲除导致酒精反应性肌阵挛和肌张力障碍，这与小脑活动异常有关。第一个目标是扩大这些数据，并确定SGCE基因敲除对小脑特定细胞类型的影响。SGCE基因敲除对体内浦肯野细胞和DCN神经元的影响将通过清醒的头枕小鼠的单单位记录来表征，而切片电生理学将用于剖析这些影响的机制。这一目标的完成将进一步阐明小脑功能障碍在运动障碍中的作用，并确定导致M-D肌阵挛和肌张力障碍发生的特定细胞类型。第二个目的是阐明酒精改善SGCE shRNA基因敲除模型中症状的机制。这将是第一个研究酒精对多发性硬化症运动症状的治疗机制的研究。在体内，电生理学将被用来检验这样的假设，即乙醇通过恢复浦肯野细胞和DCN神经元的正常放电模式来改善SGCE shRNA注射小鼠的肌张力障碍症状。对所提出的乙醇靶标进行药理学操作，将能够识别乙醇与其相互作用以缓解多发性硬化症症状的潜在受体或蛋白质。这一目标的完成将为多发性硬化症的治疗提供潜在的靶点，并阐明酒精在大脑中发挥作用的一些机制。

DESCRIPTION (provided by applicant): Myoclonus-dystonia (M-D) is an inherited movement disorder characterized predominantly by involuntary jerking of the upper body (myoclonus) and sustained contraction of agonist and antagonist muscles that result in painful, twisted postures (dystonia). Motor symptoms onset in childhood or adolescence and cause varying degrees of pain, disability, and psychosocial distress. M-D is caused by loss-of-function mutations in the gene SGCE, which encodes the protein epsilon sarcoglycan (?-sg), but the pathophysiology of the disorder remains poorly understood. There is currently is no cure or effective treatment for M-D. A striking characteristic of this disorder is that motor symptoms improve with alcohol consumption. While alcohol may be inappropriate for therapy, understanding how it acts to relieve symptoms would offer insights into the pathophysiology of M-D and provide potential therapeutic targets. The cerebellum is exquisitely sensitive to alcohol and has recently been implicated in the pathophysiology of some dystonias. Preliminary data obtained in this lab also implicate cerebellum in M-D. The purpose of the proposed study is to test the hypothesis that aberrant activity of the cerebellum causes myoclonus and dystonia in M-D and that by acting on targets in the cerebellum, alcohol normalizes cerebellar activity to relieve motor symptoms. Preliminary data suggests that acute knockdown of mouse sgce in the cerebellum by short hairpin RNA (shRNA) leads to alcohol-responsive myoclonus and dystonia that is correlated with aberrant cerebellar activity. The first aim is to expand on these data and identify the effect of sgce knockdown on particular cell types in the cerebellum. The effects of sgce knockdown on Purkinje cells and DCN neurons in vivo will be characterized by single-unit recordings in awake, head-restrained mice, while slice electrophysiology will be used to dissect the mechanism underlying these effects. Completion of this aim will further illustrate the role of cerebellar dysfunction in movement disorders and identify particular cell types that contribute to the development of myoclonus and dystonia in M-D. The second aim is to elucidate the mechanism by which alcohol improves symptoms in the sgce shRNA knockdown model. This will be the first study to examine the mechanism underlying the therapeutic effect of alcohol on motor symptoms in M-D. In vivo electrophysiology will be used to test the hypothesis that ethanol improves dystonic symptoms in sgce shRNA-injected mice by restoring the normal firing pattern of Purkinje cells and DCN neurons. Pharmacological manipulation of proposed targets of ethanol will then enable identification of potential receptors or proteins with which ethanol interacts to relieve symptoms in M-D. Completion of this aim would provide potential targets for the treatment of M-D and shed light on some of the mechanisms by which alcohol acts in the brain.