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，如多巴胺（DA）缺乏和异常突触活动，这些事件发生在运动、学习和情绪异常之前并导致异常。利用BAC转基因方法，我们在小鼠模型中研究了富亮氨酸重复激酶2 （LRRK2）的正常和病理生理功能，LRRK2是一种新发现的家族性帕金森病的致病基因。我们最近报道了LRRK2参与调节纹状体DA传递和随之而来的运动功能控制。LRRK2突变G2019S是帕金森病最常见的单一遗传原因，它通过破坏LRRK2的这些功能来发挥致病作用。因此，新出现的证据表明，这种LRRK2与PD相关的突变可以在PD的黑质纹状体变性之前的早期阶段启动一系列病理事件（包括纹状体DA传递的损伤）。我们的初步研究表明，LRRK2- g2019s导致我们的LRRK2 BAC转基因的纹状体和海马突触可塑性异常。因此，这些结果表明，LRRK2-G2019S触发了多种神经致病途径的失调，这些通路与PD的运动和认知缺陷异常一致。此外，我们发现脑LRRK2- g2019s具有增强的激酶活性，并且在小鼠脑LRRK2激酶负责Erzin/Radixin/Moesin （ERM）的磷酸化，这一事件与脊柱形态发生有关。我们假设LRRK2的致病作用在突触前和突触后两个位点：(1)LRRK2调节DA稳态/传递，而G2019S突变损害DA传递并导致DA缺乏；(2) LRRK2-G2019S触发PD运动、认知和精神症状临床表现相关的多个神经回路的失调；(3) PD的一些病理后果是由DA传递缺陷和突触后异常共同引起的。因此，我们计划在表达LRRK2变体的BAC转基因小鼠中验证这些假设：目的1：确定LRRK2调节pd相关突变G2019S的多巴胺传递的细胞和分子机制；目的2：分析LRRK2在纹状体和海马电生理中的致病作用；目的3：分析LRRK2对树突形态及其可塑性的致病作用；目的4：确定LRRK2转基因小鼠是否出现认知缺陷和多巴胺相关的运动异常。本研究的结果有望揭示帕金森病运动和非运动症状的致病机制，揭示帕金森病初期的致病分子事件，这对生物标志物鉴定、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. PUBLIC HEALTH RELEVANCE: The proposed research plan is expected to elucidate the pathogenic mechanism underlying the motor and cognitive symptoms of Parkinson's disease, and reveal causative molecular events at an initial stage of Parkinson's disease that are critical for biomarker identification, early diagnostics and therapeutic intervention.