DISC1 Pathway in Dendritogenesis: Implications for Dopamine Circuit and Cognition

描述(申请人提供)：神经回路形成障碍可能是精神分裂症的病理基础。精神分裂症的许多遗传风险因素在神经发育中发挥作用，这一事实支持了这一观点。其中一些可能在共同的分子途径中发挥作用，在神经发育的关键表型上显示出协同效应，例如树突发育，在精神分裂症中已有异常报道。此外，遗传和环境因素之间的相互作用，如病毒感染，可能在疾病病因中发挥作用。一个例子是精神分裂症-1中断(DISC1)，它通过调节与其他遗传风险因素的相互作用，如核分布元素样(NDEL1)，在发育中的大脑皮层的各种细胞过程中发挥作用。为了建立多个风险基因同时表达的动物模型，子宫内基因转移是一个有用的方法。我们的初步数据证实了这项技术用于检测遗传损伤对神经元回路和脑功能的影响的可行性，该数据表明，DISC1在发育中的前额叶皮质(PFC)中被敲除导致中脑皮层多巴胺能成熟和认知障碍。然而，目前还不清楚DISC1在特定发育时期介导的哪些细胞行为导致了这些表型。因此，在这项研究中，为了研究DISC1途径在特定发育阶段中的作用，我们将在子宫内利用Cre/loxP介导的诱导性基因转移系统。我们假设(1)PFC中迁移后神经元中DISC1的可诱导敲除(可诱导的DISC1KD)可能使DISC1在树突状细胞发生中的作用分离出来，而不依赖于DISC1在树突状细胞中的次要作用，这可能是中皮质多巴胺成熟和正常认知功能所必需的；(2)DISC1-NDEL1的相互作用可能是树突发育以及多巴胺回路和认知建立所必需的，以及(3)迁移后阶段的病毒感染可能会加剧可诱导DISC1KD小鼠的表型。为了解决这些假设，首先，我们将研究DISC1在小鼠树突状细胞发育、中皮质多巴胺成熟和认知功能中的作用，在小鼠中，DISC1通过宫内诱导的RNAi转移在PFC的迁移后阶段被选择性抑制。其次，我们将研究DISC1和NDEL1对这些表型的协同作用，在这些表型中，DISC1和NDEL1的同时抑制发生在迁移后阶段。我们还将通过缺乏NDEL1结合域的DISC1过表达的“救援”实验来研究DISC1与NDEL1的相互作用。最后，为了测试免疫激活和诱导性DISC1基因敲除的联合作用，我们将检测在可诱导性DISC1KD小鼠迁移后阶段注射PolyI：C的效果。这项研究将有助于确定特定发育时期可能导致疾病易感性的遗传风险介导的分子途径。 公共卫生相关性：在大脑发育过程中，遗传风险与环境因素(如病毒感染)之间的相互作用可能在精神分裂症的病因中发挥作用。在这项研究中，我们将探索精神分裂症的主要遗传危险因素DISC1在大脑发育的特定细胞过程中的作用，这可能是建立多巴胺成熟和认知功能的关键。我们还将研究DISC1基因紊乱和免疫激活的综合影响。本研究将有助于识别特定发育时期导致疾病易感性的遗传风险介导的分子途径。

DESCRIPTION (provided by applicant): Disturbances in neuronal circuit formation may underlie the pathology of schizophrenia. This notion is supported by the fact that many genetic risk factors for schizophrenia have roles in neurodevelopment. Some of them likely act in common molecular pathways, displaying synergistic effects on key phenotypes in neurodevelopment, such as dendritic development, in which abnormalities have been reported in schizophrenia. Furthermore, the interaction between genetic and environmental factors, such as viral infection, may play a role in the disease etiology. One example is the case of Disrupted-in-Schizophrenia-1 (DISC1), which plays a role in various cellular processes in the developing cerebral cortex by mediating interaction with other genetic risk factors, such as nuclear distribution element-like (NDEL1). To produce animal models in which the expression of multiple risk genes can be manipulated simultaneously, in utero gene transfer is a useful method. The feasibility of this technique for examining the effect of genetic insults on neuronal circuits and brain functions was confirmed by our preliminary data, which showed that knockdown of DISC1 in the developing prefrontal cortex (PFC) leads to the impairment of mesocortical dopaminergic maturation and cognition. Nonetheless, it is unclear which DISC1-mediated cell behaviors in the specific developmental period lead to these phenotypes. Thus, in this study, to examine the role of the DISC1 pathway in specific developmental periods, we will utilize in utero Cre/loxP-mediated inducible gene transfer system. We hypothesize that (1) inducible knockdown of DISC1 in post-migratory neurons (inducible DISC1 KD) in PFC may segregate a role for DISC1 in dendritogenesis, independent from the secondary effects of DISC1 in dendrites caused by disturbed cell proliferation and/or migration, which may be required for mesocortical dopamine maturation and proper cognitive functions, (2) DISC1-NDEL1 interaction may be necessary for dendritic development, as well as the establishment of dopamine circuit and cognition, and (3) virus infection in post-migratory stages may exacerbate the phenotypes displayed in inducible DISC1 KD mice. To address these hypotheses, first, we will examine the role of DISC1 on dendritic development, mesocortical dopamine maturation, and cognitive functions in mice in which DISC1 is selectively suppressed in post-migratory stages in PFC by in utero inducible RNAi transfer. Second, we will examine synergistic effects of DISC1 and NDEL1 on these phenotypes in which concomitant suppression of DISC1 and NDEL1 occurs in post-migratory stages. We will also examine DISC1-NDEL1 interaction by "rescue" experiments with overexpression of DISC1 lacking the NDEL1 binding domain. Finally, in order to test the combined effect of immune activation and inducible knockdown of DISC1, we will examine the effect of the injection of PolyI:C at post-migratory stages in inducible DISC1 KD mice. This study will be able to contribute to the identification of a genetic risk-mediated molecular pathway in the specific developmental periods which may lead to disease susceptibility. PUBLIC HEALTH RELEVANCE: The interaction between genetic risks and environmental factors, such as viral infection, during brain development, may play a role in the etiology of schizophrenia. In this study, we will explore a role for DISC1, a major genetic risk factor for schizophrenia, in the specific cellular process in brain development, which may be crucial for the establishment of dopamine maturation and cognitive functions. We will also examine combined effects of genetic disturbance of DISC1 and immune activation. This study will be able to contribute to the identification of genetic risk-mediated molecular pathway in the specific developmental periods which leads to disease susceptibility.