Distinct roles of somatically and dendritically synthesized BDNF in spine morphog

描述(申请人提供)：绝大多数兴奋性突触发生在棘突上，这是一种动态结构，在发育过程中会经历大小、形状和数量的变化，并对神经活动和学习等生理刺激做出反应。本研究的总体目标是阐明调控树突棘形态发生的分子机制。脊椎发育包括形成、成熟和修剪。尽管已发现许多蛋白质对脊柱形成具有重要作用，但控制脊柱形成的分子途径尚不完全清楚。对于调节脊椎发育后期的分子机制，特别是脊椎修剪，更是知之甚少，这是一个依赖活动的过程，可能在突触连接的精细化中发挥重要作用。脑源性神经营养因子(BDNF)基因产生两个信使核糖核酸(MRNA)池，有一个或短或长的3‘非翻译区(3’UTR)。我们最近的发现表明，短的3‘UTRBDNF mRNA仅限于胞体，而长的3’UTRBDNF mRNA也被转运到树突进行局部翻译。这一应用旨在验证一种假说，即在胞体和树突中合成的BDNF通过不同的信号级联调节脊柱的形成、成熟和修剪，以及人类BDNF3‘非编码区的单核苷酸多态(SNP)可能会损害BDNF mRNA在树突中的定位和翻译，导致脊柱畸形发育和认知障碍。这些假设将在三个具体目标上得到检验。特定目的1旨在研究在培养的大鼠海马神经元中，躯体合成和树突合成的BDNF在脊髓形态发生中的不同作用。特定目的2建议阐明BDNF对脊柱的形成、成熟和修剪的影响的信号级联。具体目的3旨在确定长BDNF3‘非编码区中人类SNP对脊髓形态发生和突触可塑性的影响。这些研究的发现可能揭示了控制基因功能和脊柱形态发生的新机制，并为深入了解SNPs在非编码序列中的功能后果提供了见解。

DESCRIPTION (provided by applicant): The vast majority of excitatory synapses occur on spines, which are dynamic structures that undergo changes in size, shape, and number during development and in response to physiological stimuli such as neuronal activity and learning. The overall goal of this research project is to elucidate the molecular mechanisms that regulate dendritic spine morphogenesis. Spine development includes formation, maturation, and pruning. Although many proteins have been found to be important for spine formation, the molecular pathway controlling spine formation is not fully understood. Even less is known about the molecular mechanism regulating the later phases of spine development, especially spine pruning, which is an activity-dependent process and likely plays an important role in the refinement of synaptic connections. The gene for brain-derived neurotrophic factor (BDNF) produces two pools of mRNA, with either a short or long 3' untranslated region (3'UTR). Our recent findings show that short 3'UTR Bdnf mRNA is restricted to the soma, whereas long 3'UTR Bdnf mRNA is also transported to dendrites for local translation. This application is aimed at testing the hypothesis that BDNF synthesized in the soma and dendrites regulates formation, maturation, and pruning of spines via distinct signaling cascades and that single nucleotide polymorphisms (SNP) in the human Bdnf 3'UTR may impair localization and translation of Bdnf mRNA in dendrites, leading to spine dysmorphogenesis and cognitive impairments. These hypotheses will be tested in three specific aims. Specific aim 1 proposes to examine the distinct roles of somatically and dendritically synthesized BDNF in spine morphogenesis in cultured rat hippocampal neurons. Specific aim 2 proposes to elucidate the signaling cascades mediating the effects of BDNF on the formation, maturation, and pruning of spines. Specific aim 3 proposes to determine the effects of a human SNP in the long Bdnf 3'UTR on spine morphogenesis and synaptic plasticity. Findings from these studies likely reveal novel mechanisms governing gene function and spine morphogenesis, and provide insights into the functional consequence of SNPs in non-coding sequences.