Mechanisms underlying the effects of retinoic acid on neurite outgrowth and network plasticity

视黄酸对神经突生长和网络可塑性影响的机制

• 批准号: RGPIN-2015-03780
• 负责人: Spencer, Gaynor
• 金额: $ 3.28万
• 依托单位: Brock University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=689021
• 关键词: Mechanisms; underlying; effects; retinoic; acid

The main aim of my research program is to study the effects of the essential Vitamin A metabolite, retinoic acid, on nervous system function. Retinoic acid is important for nervous system development and regeneration, as well as for learning and memory in the adult brain. We study these aspects of retinoid signaling using the central nervous system (CNS) of the mollusc, Lymnaea stagnalis. Unlike most vertebrate species, molluscan adult CNS neurons can regenerate. Growth cones, which are located at the tips of growing nerve fibres (neurites) play an important role in axon guidance during development and regeneration. In Lymnaea, growth cones of cultured regenerating CNS neurons are large and robust and we have shown that they respond to and turn toward a focal source of retinoic acid, which we hypothesize is acting as an important guidance molecule during development and regeneration. It is known that many guidance molecules are well conserved across vertebrate and invertebrate species, so Lymnaea neurons are ideal for investigating the cellular and molecular mechanisms underlying retinoic acid-induced growth cone turning, which are currently largely unknown. Over the next grant cycle, we will  investigate the role of retinoid receptors and potential downstream second messengers in the growth cone turning response to retinoic acid. ***Recently, we have also discovered an extremely novel "floating growth cone" phenomenon, where regenerating neurites from the cut nerves of a dissected Lymnaea CNS, grow along the air-water interface. As substrate-adhesion is normally required for neurite outgrowth and regeneration, this is a novel regenerating event which will be used to provide novel insights into growth cone behaviour that can not easily be addressed in cell culture or in the intact animal.****Another advantage of using Lymnaea is that many neurons located on the surface of its CNS are individually identifiable, with known transmitters, synaptic partners and functions. We can culture and/or electrically record from single identifiable neurons involved in a specific behavior, such as feeding or respiration. Furthermore, these behaviours can be modified by training, and animals demonstrate both learning and memory.  We have shown that inhibiting retinoic acid signaling in Lymnaea prevents long-term memory formation, and we are now studying the cellular and network properties affected by this essential signaling molecule. To this end, we can study single identified neurons or synapses in cell culture, but also study these same identified neurons embedded in their neuronal networks in the intact isolated CNS, or a behaving "semi-intact" preparation, in which we can simultaneously monitor behavior and neuronal activity. These studies provide us with a unique opportunity to investigate retinoid functioning in memory formation and the underlying network changes, using a relatively simple nervous system.********

我的研究计划的主要目的是研究必需的维生素A代谢物维甲酸对神经系统功能的影响。维甲酸对神经系统的发育和再生以及成人大脑的学习和记忆都很重要。我们利用软体动物Lymneea stagnalis的中枢神经系统(CNS)来研究维甲酸信号的这些方面。与大多数脊椎动物不同，软体动物的成年中枢神经系统神经元可以再生。生长锥体位于生长神经纤维(神经突起)的顶端，在轴突发育和再生过程中起着重要的指导作用。在Lymneea中，培养的再生CNS神经元的生长锥体大而健壮，我们已经证明它们对维甲酸的焦点来源做出反应并转向维甲酸，我们假设维甲酸在发育和再生过程中扮演着重要的指导分子的角色。众所周知，许多导向分子在脊椎动物和无脊椎动物物种中非常保守，因此Lymneea神经元是研究维甲酸诱导生长锥转向的细胞和分子机制的理想选择，目前大部分机制尚不清楚。在下一个赠款周期中，我们将进一步研究维甲酸受体和潜在的下游第二信使在视黄酸的生长锥翻转反应中的作用。*最近，我们还发现了一种非常新颖的“浮动生长锥”现象，即从解剖的淋巴神经切断的神经中再生出的神经突起，沿着空气-水界面生长。由于神经突起的生长和再生通常需要基质黏附，这是一种新的再生事件，将用于提供对生长锥行为的新见解，这些行为在细胞培养或完整的动物中不容易解决。*使用Lymneea的另一个优势是，位于其CNS表面的许多神经元是可单独识别的，具有已知的递质、突触伙伴和功能。我们可以培养和/或电记录参与特定行为的单个可识别神经元，如进食或呼吸。此外，这些行为可以通过训练来改变，动物表现出学习和记忆。我们已经证明，抑制淋巴管中的维甲酸信号可以防止长期记忆的形成，我们现在正在研究这种关键信号分子影响的细胞和网络特性。为此，我们可以在细胞培养中研究单个识别的神经元或突触，也可以研究在完整的分离中枢神经系统中嵌入其神经元网络中的这些相同识别的神经元，或者是行为“半完整”的准备，在这种准备中，我们可以同时监测行为和神经元活动。这些研究为我们提供了一个独特的机会，利用相对简单的神经系统来研究维甲酸在记忆形成中的功能和潜在的网络变化。