DISC1 Pathway in Dendritogenesis: Implications for Dopamine Circuit and Cognition

描述（由申请人提供）：神经元回路形成障碍可能是精神分裂症病理的基础。这一观点得到了以下事实的支持：精神分裂症的许多遗传风险因素在神经发育中发挥作用。它们中的一些可能在共同的分子途径中起作用，对神经发育中的关键表型表现出协同作用，例如树突发育，其中已报告精神分裂症中的异常。此外，遗传和环境因素（如病毒感染）之间的相互作用可能在疾病病因学中发挥作用。其中一个例子是分裂症1型（DISC 1），它通过介导与其他遗传风险因子（如核分布元件样（NDEL 1））的相互作用，在发育中的大脑皮层的各种细胞过程中发挥作用。为了产生可以同时操纵多个风险基因表达的动物模型，子宫内基因转移是一种有用的方法。我们的初步数据证实了这种技术用于检查遗传损伤对神经元回路和脑功能的影响的可行性，这些数据表明，在发育中的前额叶皮层（PFC）中，DISC 1的敲低导致中皮层多巴胺能成熟和认知的损害。尽管如此，目前还不清楚DISC 1介导的细胞行为在特定的发育时期导致这些表型。因此，在本研究中，我们将利用子宫内Cre/loxP介导的诱导型基因转移系统来研究DISC 1通路在特定发育时期的作用。我们假设：（1）迁移后神经元中DISC 1的诱导性敲低PFC中的诱导型DISC 1 KD可能分离DISC 1在树突发生中的作用，独立于DISC 1在树突中由受干扰的细胞增殖和/或迁移引起的继发作用，这可能是中皮层多巴胺成熟和适当的认知功能所需的，（2）DISC 1-NDEL 1相互作用可能是树突发育以及多巴胺回路和认知的建立所必需的;（3）迁移后阶段的病毒感染可能加剧诱导型DISC 1 KD小鼠中显示的表型。为了解决这些假设，首先，我们将研究DISC 1对树突发育，中皮层多巴胺成熟和小鼠的认知功能的作用，其中DISC 1在PFC的迁移后阶段通过子宫内诱导的RNAi转移被选择性抑制。其次，我们将研究DISC 1和NDEL 1对这些表型的协同作用，其中DISC 1和NDEL 1的伴随抑制发生在迁移后阶段。我们还将通过用缺乏NDEL 1结合结构域的DISC 1过表达的“拯救”实验来检查DISC 1-NDEL 1相互作用。最后，为了测试免疫激活和DISC 1的诱导性敲低的组合效应，我们将检查在诱导性DISC 1 KD小鼠中在迁移后阶段注射PolyI：C的效应。本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，遗传风险和环境因素（如病毒感染）之间的相互作用可能在精神分裂症的病因学中发挥作用。在这项研究中，我们将探索DISC 1（精神分裂症的主要遗传风险因素）在大脑发育的特定细胞过程中的作用，这可能对多巴胺成熟和认知功能的建立至关重要。我们还将研究DISC 1遗传紊乱和免疫激活的综合效应。本研究将有助于确定特定发育时期导致疾病易感性的遗传风险介导的分子通路。

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.