Circuits for spontaneous behavior and phototaxis in a simple model chordate

简单脊索动物模型中自发行为和趋光性的电路

• 批准号: 10446697
• 负责人: William Smith
• 金额: $ 66.48万
• 依托单位: UNIVERSITY OF CALIFORNIA SANTA BARBARA
• 依托单位国家: 美国
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-04-15 至 2024-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10446697
• 关键词: 3-Dimensional; Ablation; Address; Anatomy; Animals; Anterior; Automobile Driving; Behavior; Brain; Brain region; Cells; Chordata; Complement; Complex; Cues; Data; Development; Embryo; Environment; Frequencies; Human; Individual; Interneurons; Larva; Lasers; Lead; Light; Lighting; Link; Location; Modeling; Movement; Names; Nervous system structure; Neurons; Pattern; Periodicity; Pharmacology Study; Phase; Photoreceptors; Picrotoxin; Positioning Attribute; Property; Regulator Genes; Regulatory Element; Research Personnel; Role; Source; Swimming; Synapses; Tail; Testing; Trees; Urochordata; Vertebrates; Vesicle; base; behavioral outcome; cholinergic; cholinergic neuron; connectome; experimental study; falls; gamma-Aminobutyric Acid; inhibitor; insight; large datasets; mutant; neural circuit; neural model; optogenetics; time interval; tool

This proposal will investigate neural circuits driving negative phototaxis in an emerging model for neural circuit analysis: larvae of the primitive chordate Ciona. Ciona larvae have a number of features that make them ideally suited for this project. They are small and transparent, and have only 177 CNS neurons. Moreover, putative circuits for phototaxis have been identified from the Ciona connectome. Negative phototaxis in Ciona larvae consists of two phases. First, the larvae perform short orienting swims in which they attempt to discern the direction of ambient lighting by moving their bodies. Second, if the larva detects a change in light falling on their photoreceptors as they turn away from the light source, a sustained negative phototactic swim results. However, many orienting swims terminate without a sustained swim. This proposal will examine two aspects of phototaxis: 1) how neural circuits regulate the frequency of orienting swims; and 2) how orienting and sustained swims are linked at the circuit level. Ciona larvae show a wide distribution in the time intervals between short orienting swims. However, analysis of a large dataset of swim interval times points to underlying oscillations governing spontaneous swims frequency, with the dominant period being once every two seconds (O.5 Hz). In preliminary studies we have identified a VGAT-positive neuron that oscillates with a frequency of 0.5 Hz in a region of Ciona CNS called the anterior brain vesicle. We have named the oscillating neuron the anterior brain vesicle oscillator (aBVO). Moreover, mutant and pharmacological studies both point to the aBVO as a likely regulator of spontaneous swim frequency. Proposed experiments in Specific Aim 1 will target the aBVO neuron using optogenetic tools and laser ablation, and then assess the behavioral outcomes. Specific Aim 2 will address the second question: what is the circuit link between short spontaneous orienting and sustained phototactic swims? Our preliminary studies recording GCaMP activity in VACHT-positive neurons suggest a plausible and testable circuit model. We observed that short spontaneous tail movements in larvae were accompanied by Ca2+ transients in the same VACHT-positive interneurons that are the primary targets of the photoreceptors - a neuron class called photoreceptor relay neurons (prRNs). Moreover, the connectome allowed us to identify likely candidate neurons corresponding to the aBVO, based on their 3D locations and connectivities, and the major synaptic targets of these candidate neurons are also the prRNs. Thus, we hypothesize that short orienting swims are initiated in the same circuit as the sustained phototactic swims, and it is the presence or absence of input from the photoreceptors that determines if a sustained swim is initiated. Experiments in Specific Aim 2 will test this hypothesis by targeting the prRNs to determine if they are necessary for the initiation of orienting swims. We also hypothesize that in the absence of aBVO inhibition the prRNs would oscillate. We will test this hypothesis by examining a mutant line that lacks the aBV region of the CNS.

该提案将研究在新兴神经回路模型中驱动负趋光性的神经回路 分析：原始脊索动物海鞘的幼虫。海鞘幼虫具有许多特征，使它们 非常适合这个项目。它们小而透明，只有 177 个 CNS 神经元。而且， 假定的趋光性回路已从玻璃海鞘连接体中鉴定出来。 Ciona 的负趋光性 幼虫由两个阶段组成。首先，幼虫进行短暂的定向游泳，试图辨别 通过移动身体来控制环境照明的方向。其次，如果幼虫检测到照射到的光线发生变化 当它们远离光源时，它们的感光器会产生持续的负趋光性​​游泳。 然而，许多定向游泳在没有持续游泳的情况下就终止了。该提案将审查两个方面 趋光性：1）神经回路如何调节定向游泳的频率； 2）如何定向和 持续游泳与电路层面相关。海鞘幼虫在时间间隔内表现出广泛的分布 在短距离定向游泳之间。然而，对游泳间隔时间的大型数据集的分析指出了潜在的问题 控制自发游泳频率的振荡，主要周期是每两秒一次 （O.5赫兹）。在初步研究中，我们发现了一个 VGAT 阳性神经元，其振荡频率为 0.5 Hz 位于 Ciona 中枢神经系统中称为前脑泡的区域。我们将振荡神经元命名为 前脑囊泡振荡器（aBVO）。此外，突变体和药理学研究都表明 aBVO 作为自发游泳频率的可能调节器。具体目标 1 中提议的实验将针对 使用光遗传学工具和激光消融 aBVO 神经元，然后评估行为结果。具体的 目标 2 将解决第二个问题：短自发定向和自发定向之间的电路联系是什么？ 持续趋光游泳？我们的初步研究记录了 VACHT 阳性神经元中的 GCaMP 活性 建议一个合理且可测试的电路模型。我们观察到幼虫的短暂自发尾部运动 在相同 VACHT 阳性中间神经元中伴随着 Ca2+ 瞬变，这些中间神经元是 VACHT 的主要目标 光感受器 - 一种称为光感受器中继神经元 (prRN) 的神经元类别。此外，连接组 使我们能够根据 aBVO 的 3D 位置和 连接性，这些候选神经元的主要突触目标也是 prRN。因此，我们 假设短时间定向游泳与持续趋光游泳在同一回路中开始，并且 光感受器输入的存在与否决定了是否开始持续游泳。 具体目标 2 中的实验将通过针对 prRN 来测试这一假设，以确定它们是否是 开始定向游泳所必需的。我们还假设在没有 aBVO 抑制的情况下 prRNs 会振荡。我们将通过检查缺乏 aBV 区域的突变系来检验这一假设。 中枢神经系统。

项目成果

A single oscillating proto-hypothalamic neuron gates taxis behavior in the primitive chordate Ciona.

单个振荡的原下丘脑神经元控制着原始脊索动物海鞘的滑行行为。

• DOI: 10.1101/2023.04.24.538092
• 发表时间: 2023
• 期刊: bioRxiv : the preprint server for biology
• 作者: Chung,Janeva;Newman-Smith,Erin;Kourakis,MatthewJ;Miao,Yishen;Borba,Cezar;Medina,Juan;Laurent,Tao;Gallean,Benjamin;Faure,Emmanuel;Smith,WilliamC
• 通讯作者: Smith,WilliamC