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

描述（由申请人提供）：肌阵挛-肌张力障碍（M-D）是一种遗传性运动障碍，其主要特征为上身不自主抽搐（肌阵挛）和激动肌和拮抗肌持续收缩，导致疼痛、扭曲姿势（肌张力障碍）。运动症状在儿童或青春期发作，并引起不同程度的疼痛，残疾和心理社会困扰。M-D是由SGCE基因的功能缺失突变引起的，该基因编码蛋白质β-肌聚糖（？SG），但该病症的病理生理学仍然知之甚少。目前还没有治愈或有效治疗M-D的方法。这种疾病的一个显著特征是运动症状随着饮酒而改善。虽然酒精可能不适合治疗，但了解它如何缓解症状将有助于深入了解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，最近被认为与某些肌张力障碍的病理生理有关。本实验室获得的初步数据也表明小脑与M-D有关。这项研究的目的是检验小脑异常活动导致M-D肌阵挛和肌张力障碍的假设，以及通过作用于小脑中的靶点，酒精使小脑活动正常化以缓解运动症状。初步数据表明，在小脑中的小鼠sgce的短发夹RNA（shRNA）的急性敲低导致酒精反应性肌阵挛和肌张力障碍，这是与异常小脑活动。第一个目标是扩展这些数据，并确定sgce敲低对小脑特定细胞类型的影响。体内sgce敲低对浦肯野细胞和DCN神经元的影响将通过清醒、头部受限小鼠中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，并确定有助于M-D中肌阵挛和肌张力障碍发展的特定细胞类型。第二个目的是阐明酒精在sgce shRNA敲低模型中改善症状的机制。这将是第一个研究酒精对M-D运动症状治疗作用的机制。将使用体内电生理学来检验以下假设：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注射小鼠中的张力障碍症状。对乙醇的拟议靶点进行药理学操作将能够鉴定与乙醇相互作用以缓解M-D症状的潜在受体或蛋白质。这一目标的实现将为M-D的治疗提供潜在的靶点，并揭示酒精在大脑中作用的一些机制。

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.