Cellular and Molecular Basis for Initial PD Pathogenic Events in LRRK2 BAC Models

描述（由申请人提供）：我们的长期目标是了解帕金森病（PD）初始致病事件的细胞和分子基础，例如多巴胺（DA）缺乏和异常突触活动，这些活动先于并导致运动、学习和情绪异常。使用BAC转基因的方法，我们以前研究了正常和病理生理功能的亮氨酸丰富的重复序列激酶2（LRRK 2），一个新发现的致病基因家族性PD，在小鼠模型。我们最近报道，LRRK 2参与调节纹状体DA的传输和随之而来的运动功能的控制。LRRK 2突变G2019 S是PD最常见的遗传原因，通过损害LRRK 2的这些功能发挥致病作用。因此，新出现的证据表明，这种LRRK 2 PD连锁突变可以在黑质纹状体变性之前的PD早期阶段启动一系列病理事件（包括纹状体DA传递受损）。我们的初步研究表明，LRRK 2-G2019 S在我们的LRRK 2 BAC转基因的纹状体和海马中引起异常的突触可塑性。因此，这些结果表明，LRRK 2-G2019 S触发了多种神经致病途径的失调，这些途径与PD中运动和认知缺陷的异常一致。此外，我们发现脑LRRK 2-G2019 S具有增强的激酶活性，并且在小鼠脑中，LRRK 2激酶负责Erzin/Radixin/Moesin（ERM）的磷酸化，这是与脊柱形态发生相关的事件。我们假设LRRK 2的致病作用在突触前和突触后位点：（1）LRRK 2调节DA稳态/传递，而G2019 S突变损害DA传递并导致DA缺乏;（2）LRRK 2-G2019 S触发涉及PD的运动、认知和精神症状的临床表现的多个神经回路的失调;（3）PD的某些病理后果是由DA传递障碍和突触后异常共同作用引起的。因此，我们计划在我们建立的表达LRRK 2变体的BAC转基因小鼠中测试这些假设：目的1：确定LRRK 2调节受损PD连锁突变G2019 S的多巴胺传递的细胞和分子机制;目的2：分析LRRK 2在纹状体和海马电生理学中的致病作用;目的3：分析LRRK 2在树突形态学及其可塑性方面的致病作用;目的4：确定LRRK 2转基因小鼠是否出现认知功能障碍和多巴胺相关的运动异常。这项研究的结果有望阐明PD运动和非运动症状的致病机制，并揭示PD初始阶段的致病分子事件，这些事件对于生物标志物识别，早期诊断和治疗干预至关重要。

DESCRIPTION (provided by applicant): Our long-term goal is to understand the cellular and molecular basis for the initial pathogenic events of Parkinson's disease (PD), such as dopamine (DA) deficiency and aberrant synaptic activity that precedes and contributes to abnormalities in movement, learning and emotion. Using a BAC transgenic approach, we have previously investigated normal and pathophysiological functions of Leucine-rich-repeat-kinase 2 (LRRK2), a newly identified causative gene for familial PD, in mouse models. We have recently reported that LRRK2 is involved in regulating striatal DA transmission and consequent control of motor function. The LRRK2 mutation G2019S, which is the single most common genetic cause of PD, exerts pathogenic effects by impairing these functions of LRRK2. The emerging evidence thus suggests that this LRRK2 PD-linked mutation can initiate a series of pathological events (including the impairment of striatal DA transmission) at an early phase of PD preceding nigrostriatal degeneration. Our preliminary study has shown that LRRK2-G2019S causes aberrant synaptic plasticity in the striatum and hippocampus of our LRRK2 BAC transgenics. Therefore, these results suggest that LRRK2-G2019S triggers the deregulation of multiple neural pathogenic pathways that are consistent with abnormalities in both motor and cognitive deficits in PD. Furthermore, we found that brain LRRK2-G2019S has enhanced kinase activity, and in mouse brain LRRK2 kinase is responsible for the phosphorylation of Erzin/Radixin/Moesin (ERM), an event that is associated with spine morphogenesis. We hypothesize that the pathogenic role of LRRK2 is at both presynaptic and postsynaptic sites: (1) LRRK2 regulates DA homeostasis/transmission, whereas the G2019S mutation impairs DA transmission and causes DA deficiency; (2) LRRK2-G2019S triggers deregulation of multiple neural circuits implicated in clinical manifestations of motor, cognitive and psychiatric symptoms of PD; (3) Some pathological consequences of PD are caused by a combination of DA transmission deficits and postsynaptic abnormalities. Hence, we plan to test these hypotheses in our established BAC transgenic mice expressing LRRK2 variants: Aim 1: Determine cellular and molecular mechanisms through which LRRK2 regulates dopamine transmission that is impaired the PD-linked mutation G2019S; Aim 2: Analyze the pathogenic effects of LRRK2 in the electrophysiology of striatum and hippocampus; Aim 3: Analyze the pathogenic effects of LRRK2 in dendritic morphology and its plasticity; Aim 4: Determine whether LRRK2 transgenic mice develop cognitive deficits and dopamine-related motor abnormalities. The outcome of this study is expected to shed light on the pathogenic mechanism underlying the motor and non-motor symptoms of PD, and reveal causative molecular events at an initial stage of PD that are critical for biomarker identification, early diagnostics and therapeutic intervention.