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讯是大脑功能的基础，然而，人们对用于这种跨细胞信号传递的信号效应器知之甚少。我们工作的主要焦点是描绘控制细胞间通讯的分子通路，以了解大脑发育、功能和功能障碍的基本机制。在之前的资助期间，我们分析了血管内皮生长因子/血管内皮生长因子2轴在海马体发育中的作用。我们发现，神经元VEGFR2通过一种类似于其在血管形态发生中的作用的保守机制来指导CA3区锥体神经元的树突分支和棘突的形成。我们寻找了血管内皮生长因子的细胞来源，我们发现神经元自分泌的血管内皮生长因子对于发育中的海马区的树突形成和棘突形成是必不可少的。然而，星形胶质细胞和血管分泌的旁分泌血管内皮生长因子似乎在不同的神经元区段对VEGFR2的功能有不同的调节作用。因此，神经元VEGFR2根据血管衍生的血管内皮生长因子信号调节海马树突状突起的发育，表明内皮细胞促进神经元回路的形成，而神经元回路最终将是学习和记忆过程的基础。在下一个资金阶段，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枝状分布、颗粒细胞的迁移和Bergmann胶质细胞的组织中的作用。此外，我们将分析单个细胞和小脑神经元网络的形态变化的功能后果，特别是浦肯野细胞和颗粒细胞。我们将使用膜片钳电生理学，还将进行行为实验，以调查血管信号突变体中特定的小脑功能是否受到破坏。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(RGC)轴突的误导，使其瞄准视顶盖(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分层和树枝形成，并破译参与RGCs轴突连接过程的可能相互作用的伙伴。

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.