DISC1 Pathway in Dendritogenesis: Implications for Dopamine Circuit and Cognition

描述（由申请人提供）：神经回路形成障碍可能是精神分裂症病理的基础。精神分裂症的许多遗传风险因素在神经发育中起作用，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起作用，在神经发育的关键表型上表现出协同作用，例如在精神分裂症中报道的异常的树突发育。此外，遗传和环境因素（如病毒感染）之间的相互作用可能在该病的病因中起作用。其中一个例子是精神分裂症基因1 (DISC1)，它通过介导与其他遗传风险因素（如核分布因子样（NDEL1））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。为了建立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该技术用于检测遗传损伤对神经元回路和脑功能影响的可行性，这些数据表明，发育中的前额叶皮层（PFC）中DISC1的敲低导致中脑皮层多巴胺能成熟和认知功能受损。然而，目前尚不清楚在特定的发育时期，disc1介导的细胞行为导致了这些表型。因此，在本研究中，为了研究DISC1通路在特定发育时期的作用，我们将利用子宫内Cre/ loxp介导的诱导基因转移系统。我们假设(1)PFC中迁移后神经元中DISC1的诱导下调（可诱导的DISC1 KD）可能分离出DISC1在树突发生中的作用，独立于由细胞增殖和/或迁移紊乱引起的DISC1在树突中的继发性作用，这可能是中皮层多巴胺成熟和适当认知功能所必需的；(2)DISC1- ndel1相互作用可能是树突发育所必需的。(3)迁移后阶段的病毒感染可能加剧诱导型DISC1 KD小鼠的表型。为了解决这些假设，首先，我们将研究DISC1在PFC迁移后阶段通过子宫诱导的RNAi转移选择性抑制DISC1的小鼠树突发育、中脑皮层多巴胺成熟和认知功能中的作用。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在迁移后阶段同时受到抑制。我们还将通过缺乏NDEL1结合域的DISC1过表达的“拯救”实验来检验DISC1-NDEL1的相互作用。最后，为了验证免疫激活和诱导性DISC1敲除的联合作用，我们将在诱导性DISC1 KD小鼠的迁移后阶段检测注射PolyI:C的影响。这项研究将有助于确定在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。

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.