Calcium signaling in neuronal navigation

描述（申请人提供）：定向神经元导航，包括细胞体迁移和生长锥寻径，是建立精确连接的神经网络的先决条件，对大脑的正常功能至关重要。越来越多的证据表明，生长锥导航和早期发育中的神经元细胞导航有许多相似的特征，包括对类似的一组指导线索的反应，特定细胞内信号级联的激活以及定向运动的细胞骨架变化。例如，netrin-1，一种进化上保守的远程生长锥引导线索，对发育过程中神经回路的形成至关重要，也指导皮层神经元和嗅觉神经元的细胞迁移。Ca2+信号已经成为介导生长锥和细胞对许多指导线索的反应的中心参与者，包括netrin-1。然而，Ca2+信号在定向神经元导航下的时空调节尚不清楚。虽然神经网络的形成主要发生在产前和产后早期，但在成年哺乳动物大脑的离散区域，包括侧脑室的室下区（SVZ）和海马的亚颗粒区（SGZ），神经祖细胞不断产生新的神经元并整合到现有的神经网络中。成人大脑的神经发育概括了主要的神经发育里程碑，从神经祖细胞的增殖和命运规范，到神经元形态发生，细胞迁移，轴突和树突引导，以及神经元后代突触的形成。由于成人神经发生发生在与胚胎神经发生明显不同的环境中，神经发育的分子机制是否保守尚不清楚。我们的长期目标是了解决定神经元运动和方向性的分子和细胞机制，以响应引导信号，并制定治疗策略，促进人类中枢神经系统（CNS）损伤或疾病后的再生。在目前的项目中，我们的目标是了解Ca2+信号在早期神经发育和成人大脑中调节神经元导航中的作用，其中心假设是TRPC， STIM1和Orai蛋白合作设置生长锥和神经元定向运动的基础和诱导Ca2+水平，使用体外生长锥转动试验，免疫细胞化学，多光子共聚焦显微镜和电生理学的组合。我们的研究将为神经元导航的分子机制提供重要信息，并可能导致关于成熟大脑中神经元导航过程是否受到相似或差异调节的新见解，这对于制定促进再生的策略至关重要。

DESCRIPTION (provided by applicant): Directed neuronal navigation, including both cell body migration and growth cone path-finding, is a pre- requisite for the establishment of the precisely wired neural network and is essential for the proper function of the brain. Accumulating evidence suggests that growth cone navigation and neuronal cell navigation during early development share many similar features, including responses to a similar set of guidance cues, activation of specific intracellular signaling cascades and cytoskeletal changes for directed movements. For example, netrin-1, an evolutionally conserved long-range growth cone guidance cue essential for neural circuit formation during development, also directs cell migration of cortical neurons and olfactory neurons. Ca2+ signaling has emerged as a central player in mediating growth cone and cellular responses to many guidance cues, including netrin-1. The spatial and temporal regulation of Ca2+ signaling underlying directed neuronal navigation, however, is not well understood. While neural network formation occurs predominantly during the prenatal and early postnatal periods, new neurons are continuously generated from neural progenitors and integrated into the existing neural network in discrete regions of adult mammalian brain, including the subventricular zone (SVZ) of the lateral ventricle and the subgranular zone (SGZ) of the hippocampus. Neurodevelopment in the adult brain recapitulates the major neural developmental milestones, from proliferation and fate specification of neural progenitors, to neuronal morphogenesis, cell migration, axon and dendritic guidance, and synapse formation by neuronal progeny. Because adult neurogenesis occurs in a significantly different environment from embryonic neurogenesis, whether the molecular mechanisms underlying neural development are conserved is not clear. Our long-term goal is to understand the molecular and cellular mechanisms that determine the motility and directionality of developing neurons in response to guidance cues and to develop therapeutic strategies to promote regeneration after injury or diseases of the human central nervous system (CNS). In the current project, we aim to understand the role of Ca2+ signaling in regulating neuronal navigation during early neural development and in the adult brain with the central hypothesis that TRPC, STIM1 and Orai proteins co-operate to set the basal and induced Ca2+ levels for directed motility of growth cones and neurons, using a combination of in vitro growth cone turning assay, immunocytochemistry, multi-photon confocal microscopy and electrophysiology. Our study will provide important information on the molecular mechanisms underlying neuronal navigation and may lead to novel insights as to whether neuronal navigation processes are similarly or differentially regulated in the mature brain, which is important for developing strategies in promoting regeneration. PUBLIC HEALTH RELEVANCE: The project aims at understanding the functional roles of STIM1, TRPC and Orai proteins in regulating the calcium changes for directed growth cone guidance and neuronal cell migration during embryonic development and in the adult brain. Findings from these studies may lead to novel strategies to functionally replace damaged or lost neurons and to promote endogenous repair after injury or degenerative neurological disease.