Cannabinoid Signaling Interactions During Axon Development in situ

摘要 大麻植物大麻和印度大麻是妇女最常滥用的物质 生育年龄。但是，令人担忧的是，孕妇频繁使用大麻可能会导致持久的 在子宫内暴露的儿童的认知和神经行为问题。其机制 大麻植物中的大麻素对发育中的大脑的结构和功能影响不大 明白了。先前对动物模型的研究表明，主要的大麻素受体 CB1R 影响 通过各种分子因子（例如 Netrin 受体 DCC）发出信号来形成神经元回路， PKA 和 RhoA。然而，我们缺乏对 CB1R 的基本机制的全面了解。 影响大脑发育过程中神经元回路的形成。多年来，我们的实验室确定 Wnt 和钙粘蛋白因子、-连环蛋白在视觉投射发育中的信号传导机制 脊椎动物蛙模型非洲爪蟾的蝌蚪。这是研究神经元回路的理想系统 由于其与人类的遗传相似性，易于分子和遗传操作而形成 在单个视网膜神经节细胞中以及分子信号改变的单个视网膜神经节细胞的成像 直接在他们的原生环境中。我们现在建议确定 CB1R 是否抑制 Wnt/Cadherin/- 连环蛋白信号传导调节生长锥丝状伪足和轴突原位寻路特征。这个提议 源于其他人的工作，表明 CB1R 抑制 Wnt 并使癌细胞中的 β-连环蛋白不稳定，并且 Wnt 介导的 -连环蛋白不稳定下调钙粘蛋白细胞间粘附，我们最近 发表的论文显示 CB1R 和 -catenin 反向调节视网膜生长锥丝状伪足 神经节细胞。我们将测试两个目标：1）量化轴突寻路和生长锥缺陷 原位操纵CB1R。我们之前发表的数据表明，药理操作 CB1R 扰乱生长锥丝状伪足和轴突原位束颤。我们现在将评估细胞是否 单个视网膜神经节细胞中 CB1R 的自主（基于吗啉代）功能丧失改变了多个 生长锥和轴突寻路参数。 2）建立CB1R和CB1R之间的功能相互作用 视网膜神经节细胞中的 Wnt/钙粘蛋白信号传导。我们将确定 CB1R 丢失的表型效应是否- 生长锥丝状伪足和轴突寻路特征的功能障碍通过因子的表达来挽救 经典 Wnt 信号通路（Axin、APC）和钙粘蛋白细胞-细胞粘合剂关键参与者的突变体 复合物（-连环蛋白、-连环蛋白）。这些数据将确定一种新颖且重要的信号机制 大麻素在脊椎动物模型神经元回路发育中的作用。鉴于这些信号的保护 途径，这些结果还可能建立内源性大麻素形成的基本机制 人类胎儿的神经元回路，以及产前大麻暴露增加如何扰乱 神经元回路的建立，并导致儿童持续的认知和神经行为缺陷。

Abstract The cannabis plants marijuana and hashish are the most commonly used substances of abuse by women of reproductive age. But, concerningly, frequent use of cannabis by pregnant women may result in lasting cognitive and neuro-behavioral issues in children that were exposed in utero. The mechanisms by which cannabinoids in cannabis plants influence the structure and function of the developing brain are not well understood. Previous studies in animal models indicate that the main cannabinoid receptor, CB1R, affects formation of neuronal circuits by signaling though various molecular factors such as the Netrin receptor DCC, PKA and RhoA. However, we lack comprehensive knowledge of essential mechanisms by which CB1R influences neuronal circuit formation during brain development. For many years, our laboratory determined signaling mechanisms for Wnt and Cadherin factor, -catenin, in development of the visual projection in tadpoles of the vertebrate frog model Xenopus laevis. This is an ideal system for studying neuronal circuit formation because of its strong genetic similarity to humans, amenability to molecular and genetic manipulation in single retinal ganglion cells and imaging of individual retinal ganglion cells with altered molecular signaling directly in their native environment. We now propose to determine whether CB1R inhibits Wnt/Cadherin/- catenin signaling to regulate growth cone filopodia and axon pathfinding features in situ. This proposal stems from work from others showing that CB1R inhibits Wnt and destabilizes -catenin in cancer cells, and Wnt mediated destabilization of -catenin downregulates Cadherin cell-cell adhesion, and our recently published paper showing that CB1R and -catenin oppositely modulate growth cone filopodia in retinal ganglion cells. We will test two aims: 1) Quantify axon pathfinding and growth cone defects following manipulation of CB1R in situ. Our previously published data showed that pharmacological manipulation of CB1R perturbs growth cone filopodia and axon fasciculation in situ. We will now assess whether cell- autonomous (morpholino based) loss-of-function of CB1R in individual retinal ganglion cells alters multiple growth cone and axon pathfinding parameters. 2) Establish functional interactions between CB1R and Wnt/Cadherin signaling in retinal ganglion cells. We will determine whether phenotypic effects of CB1R loss- of-function on growth cone filopodia and axon pathfinding features are rescued by expression of factors in the canonical Wnt signaling pathway (Axin, APC) and mutants of key players in Cadherin cell-cell adhesive complex (-catenin, -catenin). This data will determine a novel and essential signaling mechanism for cannabinoids in neuronal circuit development in a vertebrate model. Given the conservation of these signaling pathways, these results may also establish a fundamental mechanism for endocannabinoids in formation of neuronal circuits in human fetuses, and for how increased prenatal cannabis exposure could disrupt establishment of neuronal circuits, and lead to persistent cognitive and neurobehavioral deficits in children.