胆碱能环路在瑞特综合症样行为中的作用及机制

发布时间：2018-04-04 01:27

本文选题：MeCP2　切入点：胆碱能神经元　出处：《浙江大学》2017年博士论文

【摘要】：瑞特综合症是一种严重影响人类精神健康的疾病,主要表现为运动能力的异常,社交障碍,认知紊乱以及癫痫的高发性。研究发现位于X染色体上的MECP2基因是瑞特综合症的致病基因,MECP2基因敲除的小鼠可以表现出瑞特综合症样的表型。由于发病症状的广泛性及特异的神经紊乱,瑞特综合症至今缺乏有效的治疗手段。因此,对瑞特综合症发病机制的研究从而找到相应的治疗靶点显得尤为重要。临床结果显示,瑞特综合症的严重程度与胆碱能标志物的表达量相一致。胆碱能系统是大脑中的弥散性调节系统。主要分布在基底前脑,纹状体和脑干等脑区,调控运动,学习记忆以及睡眠觉醒等功能。但是,关于胆碱能系统特别是不同脑区的胆碱能环路在瑞特综合症致病中的作用却鲜有报道。因此,本研究结合电生理,生化以及光遗传学等手段,试图回答三个问题:第一,胆碱能系统是否参与到瑞特综合症的致病过程中?第二,瑞特综合症是一种多症状的神经疾病,不同脑区的胆碱能环路在各个症状中的作用是否相同?我们主要关注基底前脑和纹状体这两个胆碱能相关脑区。第三,基底前脑和纹状体胆碱能神经元分别通过怎样的机制调节瑞特综合症的症状?即能否找到相应的分子靶点从而达到治疗的效果?我们发现,在胆碱能系统中敲除MeCP2可以造成部分瑞特综合症样表型,包括焦虑/抑郁相关行为的改变,社会交往能力的异常,癫痫的易感性以及恐惧记忆的缺失。为了研究不同脑区的胆碱能神经元对瑞特综合症的作用,我们分别在基底前脑以及纹状体胆碱能神经元上恢复MeCP2的表达,结果发现,在基底前脑胆碱能神经元上重新表达MeCP2可以特异性逆转Chat-Mecp2~(-/y)小鼠焦虑/抑郁相关行为,社会交往能力的改变。在纹状体胆碱能神经元上重新表达MeCP2可以特异性改善Chat-Mecp2~(-/y)小鼠的恐惧编码能力。接下来,我们分成两个部分分别探讨不同脑区的胆碱能神经元在瑞特综合症相关症状发生中的分子机制。第一部分:基底前脑:在胆碱能系统中敲除MeCP2影响了基底前脑到海马的胆碱能神经环路,使得海马PV神经元上α7乙酰胆碱受体的表达降低。海马定点给药PNU282987或尼古丁都可以逆转Chat-Mecp2~(-/y)小鼠的行为学表型。第二部分:纹状体:在胆碱能系统中敲除MeCP2使得纹状体胆碱能神经元上α2GABAA受体的表达上调,增加的抑制性输入造成纹状体神经元兴奋性降低。用RNA干扰的方法敲减α2 GABAA受体或者直接兴奋胆碱能神经元都可以逆转Chat-Mecp2~(-/y)小鼠的恐惧记忆行为。纹状体胆碱能神经元是一种中间神经元,可以调控整个纹状体环路,用光遗传的方法兴奋纹状体神经元也可以改善恐惧记忆的编码。
[Abstract]:Ritter syndrome is a disease that severely affects human mental health. It is characterized by abnormal motor ability, social disorder, cognitive disorder and high incidence of epilepsy.It was found that the MECP2 gene located on the X chromosome was the pathogenic gene of Ruit syndrome, and that the mice knockout the MECP2 gene could exhibit the Ruit syndrome like phenotype.Due to the prevalence of symptoms and specific neurological disorders, Rhett syndrome has not been effective treatment.Therefore, it is very important to study the pathogenesis of Rhett syndrome and find the corresponding therapeutic target.The clinical results showed that the severity of Rhett syndrome was consistent with the expression of cholinergic markers.The cholinergic system is a diffuse regulatory system in the brain.It is mainly distributed in the basal forebrain, striatum and brain stem, regulating motor, learning and memory, and sleep arousal.However, the role of cholinergic system, especially the cholinergic loop in different brain regions, in the pathogenesis of Rhett syndrome is rarely reported.Therefore, this study combines electrophysiology, biochemistry and photogenetics to answer three questions: first, is the cholinergic system involved in the pathogenesis of Rhett syndrome?Second, Ritter syndrome is a multi-symptomatic neurological disease. Does the cholinergic loop in different brain regions play the same role in each symptom?We focus on the basal forebrain and striatum, the two cholinergic related brain regions.Third, how do basal forebrain and striatal cholinergic neurons regulate the symptoms of Rhett syndrome?That is, can we find the corresponding molecular target to achieve the therapeutic effect?We found that knockout of MeCP2 in the cholinergic system resulted in a portion of the Rhett syndrome phenotype, including changes in anxiety / depression-related behavior, abnormal social interaction, susceptibility to epilepsy, and loss of fear and memory.In order to study the effect of cholinergic neurons in different brain regions on the expression of MeCP2 in basal forebrain and striatal cholinergic neurons, we found that,The reexpression of MeCP2 in basal forebrain cholinergic neurons can specifically reverse the anxiety / depression-related behavior and the change of social communication ability in Chat-Mecp2- / -rymice.Reexpression of MeCP2 on striatal cholinergic neurons can specifically improve the fear coding ability of Chat-Mecp2- / -rymice.Next, we divided into two parts to explore the molecular mechanism of cholinergic neurons in different brain regions in the pathogenesis of Ruit syndrome related symptoms.Part I: basal forebrain: knockout of MeCP2 in cholinergic system affects cholinergic nerve loop from basal forebrain to hippocampus and reduces the expression of 伪 7 acetylcholine receptor in hippocampal PV neurons.Hippocampal targeted administration of either PNU282987 or nicotine could reverse the behavioral phenotype of Chat-Mecp2-/ -rymice.The second part: striatum: knockout of MeCP2 in the cholinergic system up-regulates the expression of 伪 2GABAA receptor in striatal cholinergic neurons, resulting in decreased excitability of striatal neurons due to increased inhibitory input.Knockout of 伪 2 GABAA receptor or direct stimulation of cholinergic neurons by RNA interference can reverse the fear memory behavior in Chat-Mecp2- / -rymice.Striatal cholinergic neurons are intermediate neurons which can regulate the entire striatal loop. The stimulation of striatal neurons by photogenetic method can also improve the coding of fear memory.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：R741

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