Neurotransmitter-mediated activity spatially controls neuronal migration in the zebrafish cerebellum

Neuronal migration during embryonic development contributes to functional brain circuitry. Many neurons migrate in morphologically distinct stages that coincide with differentiation, requiring tight spatial regulation. It had been proposed that neurotransmitter-mediated activity could exert this control. Here, we demonstrate that intracellular calcium transients occur in cerebellar neurons of zebrafish embryos during migration. We show that depolarization increases and hyperpolarization reduces the speed of tegmental hindbrain neurons using optogenetic tools and advanced track analysis optimized for in vivo migration. Finally, we introduce a compound screening assay to identify acetylcholine (ACh), glutamate, and glycine as regulators of migration, which act regionally along the neurons’ route. We summarize our findings in a model describing how different neurotransmitters spatially interact to control neuronal migration. The high evolutionary conservation of the cerebellum and hindbrain makes it likely that polarization state-driven motility constitutes an important principle in building a functional brain.胚胎发育过程中的神经元迁移（neuronal migration）对于构建功能性脑环路（functional brain circuitry）至关重要。多数神经元会在与分化进程同步的形态学独特阶段中进行迁移，这一过程需要严格的空间调控。此前已有研究提出，神经递质介导的活动可承担此类调控功能。本研究证实，斑马鱼胚胎的小脑神经元在迁移阶段会出现细胞内钙瞬变（intracellular calcium transients）。我们借助光遗传学工具（optogenetic tools）及针对活体迁移优化的先进轨迹分析技术，证明去极化（depolarization）可提升被盖后脑神经元的迁移速度，而超极化（hyperpolarization）则会降低其迁移速率。最后，我们开发了一种化合物筛选实验（compound screening assay），鉴定出乙酰胆碱（acetylcholine, ACh）、谷氨酸（glutamate）与甘氨酸（glycine）作为迁移调控因子，它们沿神经元的迁移路径发挥区域性调控作用。我们通过一个模型总结了研究发现，该模型阐释了不同神经递质如何通过空间协同作用调控神经元迁移。小脑与后脑具有高度的进化保守性（evolutionary conservation），因此由极化状态驱动的运动性很可能是构建功能性大脑的一项核心原则。