Studies on the role of retinoid signaling and microRNAs in adult newt spinal cord regeneration

成年哺乳动物和鸟类脊髓中的神经在受伤后不能再生，纠正这种失败是神经科学的主要目标。然而，成年蝾螈和火蜥蜴表现出惊人的再生能力，许多组织，包括脊髓和大脑的一部分。我们的主要研究目的是了解蝾螈脊髓功能再生的分子和细胞机制，作为确定哺乳动物在这一过程中失败的前奏。为此，我们研究了全反式维甲酸(RA)在这一过程中的作用，全反式维甲酸是一种由维生素A合成的脂溶小分子。我们最近发现，RA的蛋白受体--维甲酸受体β(RAR？)是再生Newt脊髓早期事件的重要调节因子。然而，我们不知道在这一过程中，RA-RAR？信号对哪些因素有影响。为了再生脊髓，必须同时激活或抑制多个信号通路，这涉及到RA反应细胞中的许多分子变化。我们推测，microRNAs(MiRNAs)是一种小的、非蛋白质编码的RNAs，能够协调调节许多基因的表达，可能是RA信号的重要靶点。我们的具体目标有三个：1.鉴定由于脊髓损伤而合成的新的miRNAs，以及那些合成的受到维甲酸治疗影响的miRNAs。2.确定再生脊髓中制造这些miRNAs的细胞，并确定其潜在的信使RNA靶点和功能。3.分析RA在再生脊髓中引导生长神经到达相应的“靶细胞”的机制。这些研究将是首次对miRNAs在再生脊髓模型中调节RA信号的作用进行全面分析。希望我们的结果将提供更深入的了解控制脊椎动物脊髓再生的分子事件，目标是将这一知识应用于包括人类在内的高等脊椎动物脊髓修复的迄今棘手的过程。

Nerves in the spinal cord of adult mammals and birds fail to regenerate after injury and correcting this failure is a major goal of neuroscience. Adult newts and salamanders, however, exhibit remarkable regenerative capacity of a number of tissues, including the spinal cord and parts of the brain. Our main research aim is to understand the molecular and cellular mechanisms that underlie functional spinal cord regeneration in the newts as a prelude to determining why mammals fail in this process. To this end, we have examined the role of all-trans retinoic acid (RA), a small, fat-soluble molecule synthesized from vitamin A, in this process. We have recently shown that a protein receptor for RA, retinoic acid receptor beta (RARß), is an important regulator of early events in the regenerating newt spinal cord. However, we do not know what factors are affected by RA-RARß signaling in this process. To regenerate the spinal cord, multiple signaling pathways must be activated or repressed simultaneously, involving numerous molecular changes in RA-responsive cells. We hypothesize that microRNAs (miRNAs), small, non-protein coding RNAs, capable of regulating the expression of many genes coordinately, may be important targets of RA signaling. Our specific objectives are threefold: 1. To identify novel miRNAs synthesized as a consequence of damage to the spinal cord as well as those whose production is affected by retinoid treatment. 2. To determine the cells in the regenerating spinal cord that make these miRNAs and identify their potential messenger RNA targets and functions. 3. Finally, to analyze the mechanism by which RA can guide growing nerves to their appropriate "target" cells in regenerating spinal cords. These studies would represent the first comprehensive analysis of the role of miRNAs in regulating RA signaling in a regenerating spinal cord model. It is hoped that our results will provide a more thorough understanding of the molecular events controlling spinal cord regeneration in newts, with the goal of applying this knowledge to the as yet intractable process of spinal cord repair in higher vertebrates, including humans.