Neural pathways in invertebrate nervous systems

无脊椎动物神经系统中的神经通路

• 批准号: RGPIN-2018-03784
• 负责人: Meinertzhagen, Ian
• 金额: $ 9.47万
• 依托单位: Dalhousie University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=764311
• 关键词: Neural; pathways; invertebrate; nervous; systems

My lab has pioneered studies on simple invertebrate nervous systems, in particular the visual system of the fruit fly Drosophila melanogaster and the central nervous system (CNS) of the tadpole larva in the ascidian Ciona intestinalis, a close sibling relative of vertebrates. Using electron microscopy, we have generated comprehensive maps, or connectomes, of synaptic networks in these tiny brains, an approach to neural function that has now become far more widely recognized than hitherto. We will continue these approaches, using advanced methods harnessed to biological diversity. The question itself is simple enough. The brain is a network, one formed by synaptic contacts between identified neurons. The complete connectome these form constitutes a formal definition of any brain, essential to know if we are ever to establish the circuit basis for animal behaviour, an ultimate objective in neuroscience. Certainly not new, this idea is now enabled by recent developments in electron imaging and especially by rapid computer 3D reconstruction methods. Functional studies that allow synaptic transmission to be disabled then reveal the role that identified neurons play in specific behaviours, the ultimate value of a connectome. We will apply these ideas to three carefully chosen nervous systems described below. 1) We will compare the visual circuits of 12 identified neuron classes in each column, or cartridge, in the optic lamina of select species of Hawaiian drosophilids, which have previously defined evolutionary relationships. This will reveal how synaptic circuits have evolved among homologous neurons to subserve different visual behaviours in related species. Our work will also address how the evolution of brains has proceeded from the evolution of their synaptic circuits, selected by the visual behaviours these support.2) Complementing our published work on the larval CNS of Ciona we will reconstruct the connectome for parts of the CNS of a related basal chordate, the larvacean, Oikopleura dioica, a species immensely important in the sea's food chains. Like Ciona, its CNS has a constant cell number, but the circuits these form are not known and may be supplemented by epithelial conduction pathways. We will work with larval stages small enough to examine from EM series, and sufficiently transparent for future imaging and other functional studies.3) In an entirely new choice of nervous system that also exploits Dalhousie's unique strength in marine resources, we will document the connectome of the brachial ganglion in the CNS of the pygmy squid, Idiosepius. This tiny cephalopod is small enough to fit in whole-mounts beneath a compound microscope immersion objective, and we will use immunolabelling to identify neurons and EM to examine their synaptic circuits in this important relay station, initially to provide the unit structure of those circuits that regulate a single arm of this tiny cephalopod.

我的实验室率先研究了简单的无脊椎动物神经系统，特别是果蝇果蝇的视觉系统和海鞘蝌蚪幼虫的中枢神经系统（CNS），海鞘是脊椎动物的近亲。使用电子显微镜，我们生成了这些微小大脑中突触网络的全面图谱或连接组，这是一种神经功能的方法，现已比迄今为止得到更广泛的认可。我们将继续使用这些方法，利用生物多样性的先进方法。这个问题本身很简单。大脑是一个网络，由已识别的神经元之间的突触接触形成。这些形式的完整连接组构成了任何大脑的正式定义，对于了解我们是否要建立动物行为的回路基础（神经科学的最终目标）至关重要。当然，这个想法并不新鲜，现在电子成像的最新发展，特别是快速计算机 3D 重建方法使这一想法成为可能。允许突触传递被禁用的功能研究揭示了所识别的神经元在特定行为中所发挥的作用，这是连接组的最终价值。我们将把这些想法应用到下面描述的三个精心选择的神经系统中。 1) 我们将比较夏威夷果蝇选定物种视神经层中每列或盒中 12 个已识别神经元类别的视觉回路，这些神经元类别之前已经定义了进化关系。这将揭示同源神经元之间的突触回路如何进化以促进相关物种的不同视觉行为。我们的工作还将解决大脑的进化是如何从其突触回路的进化开始的，突触回路是由这些支持的视觉行为选择的。2）补充我们已发表的关于 Ciona 幼虫中枢神经系统的工作，我们将重建中枢神经系统部分的连接组一种相关的基础脊索动物，即幼体动物 Oikopleura dioica，是海洋食物链中极其重要的一个物种。与海鞘一样，它的中枢神经系统具有恒定的细胞数量，但这些形成的电路尚不清楚，可能由上皮传导途径补充。我们将使用足够小的幼虫阶段，以便通过 EM 系列进行检查，并且足够透明，以便将来的成像和其他功能研究。3）在神经系统的全新选择中，也利用了达尔豪斯在海洋资源方面的独特优势，我们将记录连接组侏儒乌贼 Idiosepius 中枢神经系统的臂神经节。这种微小的头足类动物足够小，可以整体安装在复合显微镜浸没物镜下，我们将使用免疫标记来识别神经元，并使用电子显微镜来检查它们在这个重要中继站中的突触回路，最初提供这些回路的单元结构控制这种微小头足类动物的单臂。