Instructive roles of the vasculature during neuronal arborization and spine morphogenesis

大脑中不同细胞类型之间的适当细胞通信是大脑功能的基础，然而，人们对用于这种跨细胞信号传导的信号效应器知之甚少。我们的主要工作重点是描述控制细胞间通讯的分子途径，以了解大脑发育，功能和功能障碍的基本机制。在之前的资助期内，我们分析了VEGF/VEGFR2轴在海马发育中的作用。我们发现神经元VEGFR2通过类似于其在血管形态发生中的作用的保守机制，指导CA3锥体海马神经元的树突分支和脊柱形成。我们寻找VEGF的细胞来源，发现神经元自分泌VEGF对于发育中的海马树突发生和脊柱形成是必不可少的。然而，星形胶质细胞和血管分泌的旁分泌VEGF似乎对不同神经元室中VEGFR2的功能有不同的调节。因此，神经元VEGFR2根据血管来源的VEGF信号调节海马树突的发育，表明内皮细胞促进神经元回路的形成，最终将成为学习和记忆过程的基础。在下一个资助期，我们的目标是研究小脑的血管化以及血管在控制浦肯野细胞的树突、颗粒细胞的迁移和伯格曼胶质细胞的组织中的作用。此外，我们将分析形态学改变对小脑单细胞和神经元网络的功能后果，特别关注浦肯野细胞和颗粒细胞。我们将使用膜片钳电生理学，并将进行行为实验来研究血管信号突变是否会破坏特定的小脑功能。此外，我们发现特定的斑马鱼突变体暴露了视网膜神经节细胞（RGCs）轴突的错误引导，以瞄准视觉顶盖（OT）的上层，从而改变了视觉行为。我们将继续分析斑马鱼OT的RGCs层压和树枝化，并破译RGCs轴突布线过程中可能的相互作用伙伴。

Proper cellular communication between the different cell types in the brain is fundamental for brain function, however little is known about the signalling effectors that are used for such trans-cellular signalling. The main focus of our work is to delineate the molecular pathways that govern the inter-cellular communication to understand basic mechanisms of brain development, function and dysfunction. In the previous funding period, we analysed the role of the VEGF/VEGFR2 axis in the development of the hippocampus. We found that neuronal VEGFR2 instructs the dendritic branching and spine formation in CA3 pyramidal hippocampal neurons through a conserved mechanism similar to its role during vascular morphogenesis. We sought for the cellular source of VEGF and we found that autocrine secretion of VEGF by neurons is dispensable for dendritogenesis and spine formation in the developing hippocampus. However, paracrine VEGF secreted by astrocytes and vessels seems to differentially modulate the function of VEGFR2 in the different neuronal compartments. Thus, neuronal VEGFR2 regulates the development of the dendritic arbors of the hippocampus upon vascular derived VEGF signals, showing that the endothelial cells promote the formation of the neuronal circuits that ultimately will be fundamental for learning and memory processes. In the next funding period, we aim to study the vascularization of the cerebellum and the role of the vasculature in controlling the arborization of Purkinje cells, the migration of granular cells and the organization of the Bergmann glia. Additionally, we will analyse the functional consequences of the morphological alterations on single cells and on neuronal network in the cerebellum, with special focus on Purkinje cells and granule cells. We will use patch-clamp electrophysiology and will also perform behavioural experiments to investigate whether specific cerebellar functions are disrupted in the vascular signalling mutants. Moreover, we found that specific zebrafish mutants expose retinal ganglion cells (RGCs) axonal misguidance in targeting the upper layers of the optic tectum (OT) and consequently an altered visual behaviour. We will continue to analyse RGCs lamination and arborization of the zebrafish OT and decipher the possible interacting partners involved in the wiring process of the RGCs axons.