N-cadherin整合导向信号调节皮层神经元辐射迁移的研究

The neuronal radial migration is one of the most important processes during the cortical development. Postmitotic projection neurons undergo orientational selection, morphological transition, locomotion and somal translocation to migrate radially upwards from the ventricular zone through the intermediate zone to the final position in the cortical plate. Latest research suggested that N-cadherin has important roles in regulating radial migration in mammal cortex. On one hand, N-cadherin may control the interaction between neurons as an adhesion molecule,and on the other hand, it may induce migration-related signaling pathway as a membrane protein. Several evidences implied that the neural guidance cues Netrin-1 and its receptor DCC are involved in the Reelin signaling pathway, which is proved to be significant in cortical migration. With our recent results, we hypothesized that N-cadherin is a key factor in integrating the crosstalk between Reelin and Netrin-1/DCC. This research is based on the functional research about N-cadherin in the cerebral cortex. In vitro neuronal migration and time-lapse will be implemented to investigate the roles that N-cadherin influences radial migration. In plus, with both in vitro and in vivo techniques in the experimental systems of intermolecular interaction, cell-cell interaction and in utero electroporation, we will analyze the mechanisms how N-cadherin influences the Reelin and N-cadherin signaling pathways.

发育中皮层神经元的辐射迁移是构成功能性神经环路的基础。新生神经元经过方向确立、形态转变、动态迁移和胞体异位几个过程，从室管膜区向外穿过中间层到达皮层板的最终目的地。跨膜信号转导和细胞黏附在皮层辐射迁移过程中起重要作用，然而，导向性因子及受体潜在的调控机制缺乏深入的研究。结合近几年研究进展和我们的工作基础，推测钙粘蛋白(N-cadherin)整合了DCC与reelin信号通路交叉的关键因子。本研究以N-cadherin在皮层神经元辐射迁移中的功能研究为核心环节，借助一系列体内、体外研究手段，通过分子间相互作用、细胞间相互作用、体内电场转基因等不同层面的研究体系，分析其参与reelin和netrin-1-DCC信号通路的分子机制。

皮层神经元辐射迁移是构成功能性神经环路的基础，其中跨膜信号传导和细胞黏附对其至关重要。课题组根据已有工作基础，提出粘附分子N-cadherin与迁移信号传导有关，导向因子DCC可能介导不同信号通路交叉传递。基于以上推测，分别通过分子间相互作用、细胞间相互作用及体内电穿孔等研究手段，深入探究了：N-cadherin与DCC的相互关系；N-cadherin介导皮层神经元迁移情况；神经元与胶质相互作用调节辐射迁移；导向因子DCC调节皮层神经元迁移情况；Reelin信号通路因子Dab1参与DCC对神经元的迁移及定位等。发现N-cadherin与DCC共定位，干扰DCC表达或外源表达DCC胞内段导致N-cadherin的表达降低。N-cadherin通过全长Myo10介导细胞与胶质间的粘附，调节神经元的辐射迁移。DCC是Netrin-1信号通路的重要蛋白，在发育的大脑皮层中呈现动态表达，缺失DCC胞内P3结构域或降低DCC表达，均会引起胼胝体投射神经元的辐射迁移异常以及投射神经元多极向双极形态转换障碍，但并不影响神经元前体细胞的增殖、分化、凋亡和放射胶质细胞骨架投射。Dab1为Reelin信号通路下游的接头分子，研究发现Dab1与DCC在发育的大脑皮层中共表达，二者存在直接的相互作用。在Netrin-1刺激下，活化的DCC可介导Dab1磷酸化；且激活的Dab1能够补救沉默DCC所造成的迁移阻滞，揭示了神经元迁移过程中两条关键信号通路，即Netrin-1信号和Reelin信号通路存在信号交叉传递的分子机制。.课题组已完成任务书中的研究内容及目标，发表SCI论文6篇，尚有1篇关于Dab1与DCC介导两条信号通路交叉传递的研究结果待发表。本项目的研究有助于深刻认识神经环路的形成，对发育性神经系统疾病的认知和防治具有重要的意义。

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