Axonal FMRP in Synaptic Development

项目摘要 这个项目将解决的问题，如何异常突触的发展出现在神经发育 紊乱我们的总体假设是，紊乱的突触粘附和延迟的功能组装， 突触囊泡（SV）损害突触前终末的形成和生理成熟， 突触连接和功能的后续发育缺陷。我们将在脆性X中检验这一假设 综合征（FXS），一种主要的遗传性自闭症和智力残疾，由功能丧失引起， 脆性X智力低下蛋白（FMRP）。实验观察将利用进化上保守的 endbulb终端，很容易在体内细胞自主表征鸡胚胎。 我们将追求两个具体的目标，以测试从我们的初步研究中得出的几个重要假设。 ·在具体目标1中，我们将确定FMRP调节的突触粘附在突触前神经元中的作用。 终端形成我们假设轴突FMRP促进终末的形成、稳定， 通过发育轮廓的突触粘附选择性回缩。为了验证这个假设，我们将 使用细胞群特异性和时间控制的遗传操作与体内活的 成像，以确定FMRP介导的轴突运输与蛋白质翻译在动态 终端周转率我们还将在发育过程中鉴定FMRP调节的突触粘附元件。 终末，并评估纠正这些元素对FMRP丢失诱导的突触前和突触后的影响。 轴突改变 ·在具体目标2中，我们将确定FMRP调节的突触结合蛋白（Syt）在功能性突触结合蛋白中的作用。 突触前末梢的成熟。Syt 1/2是SV上触发囊泡融合的主要钙传感器 和神经递质的释放我们假设FMRP通过以下方式调节突触前功能成熟： 控制新生末梢中Syt 2的及时上调。为了验证这一假设，我们将确定 表达Syt 2对FMRP缺失诱导的SV活性、突触前蛋白 机械和谷氨酸释放。我们还将确定突触粘附与 调节和SV组装在FMRP控制下使用救援研究。 总之，这些结果将确定有缺陷的突触表型的起源，这是神经发育障碍的标志。 紊乱这方面的知识至关重要，因为它将有助于建立一个敏感的时间窗口， 用于预防或至少减少FXS中突触缺陷的进展的新的治疗候选物， 其他神经发育障碍。

Project Summary This project will address the question of how abnormal synaptic development emerges in neurodevelopmental disorders. Our overall hypothesis is that disorganized synaptic adhesion and delayed functional assembly of synaptic vesicles (SVs) impair the formation and physiological maturation of presynaptic terminals, which triggers subsequent developmental deficits in synaptic connectivity and function. We will test this hypothesis in Fragile X syndrome (FXS), a leading inheritable form of autism and intellectual disability caused by functional loss of Fragile X mental retardation protein (FMRP). Experimental observations will utilize the evolutionally conserved endbulb terminals that are readily accessible for in vivo cell-autonomous characterizations in chicken embryos. We will pursue two specific aims to test several important hypotheses derived from our preliminary studies. · In Specific Aim 1, we will determine the role of FMRP-regulated synaptic adhesion in presynaptic terminal formation. We hypothesize that axonal FMRP promotes terminal formation, stabilization, and selective retraction through developmentally profiled synaptic adhesion. To test this hypothesis, we will use cell-group specific and temporally-controlled genetic manipulations combined with in vivo live imaging to identify the exact actions of FMRP-mediated axon transport vs. protein translation in dynamic terminal turnover. We will also identify FMRP-regulated synaptic adhesion elements in developing terminals and assess the effects of correcting these elements on FMRP loss-induced presynaptic and axon alterations. · In Specific Aim 2, we will determine the role of FMRP-regulated synaptotagmin (Syt) in functional maturation of presynaptic terminals. Syt1/2 are primary calcium sensors on SVs that trigger vesicle fusion and neurotransmitter release. We hypothesize that FMRP regulates presynaptic functional maturation by controlling the timely upregulation of Syt2 in nascent terminals. To test this hypothesis, we will determine the effects of expressing Syt2 on FMRP loss-induced deficits in SV activity, presynaptic protein machinery, and glutamate release. We will also determine the interplay between synaptic adhesion regulation and SV assembly under FMRP control using rescue studies. Together, these results will identify an origin of defective synaptic phenotypes, a hallmark of neurodevelopmental disorders. This knowledge is of vital importance because it will help establish a sensitive time window and identify novel therapeutic candidates for preventing, or at least reducing, the progress of synaptic deficits in FXS and other neurodevelopmental disorders.