Genetic and Developmental Analyses of Fragile X Mental Retardation Protein

描述(由申请人提供)：脆性X智力低下蛋白(FMRP)的丢失会导致一种发育性大脑疾病，其特征是突触连接受损，并扰乱发育后期大脑的活动依赖调制。FMRP的丢失与一系列神经发育障碍(NDD)有关，症状包括智力残疾、自闭症和儿童癫痫。我们实验室建立了强大的果蝇疾病模型，并证明在该模型中人类FMRP显示出完全的功能保守性。我们一再证明，这个模型提供了对人类疾病状态的分子和细胞基础的直接见解。在这个修订的竞争性更新提案中，我请求您的迫切需要的支持，使我们能够继续利用这一奇妙的遗传系统，以及果蝇大脑中学习/记忆神经回路的相对简单及其完全表征的行为输出，以测试关于FMRP丢失的核心假设，并提出纠正由此产生的大脑发育缺陷的干预措施。实验方法将瞄准定义明确的蘑菇体(MB)回路，这是一个大脑中心，接受来自多个感觉模式的输入，以调节联想学习和记忆巩固。在第一个目标中，我们将检验FMRP调节MB回路中适当的兴奋性(E)与抑制性(I)突触平衡的发展的假设。我们提出了独立纠正E和I缺陷的遗传学和药理学手段，以测试在零突变状态下结构、功能和行为输出缺陷的恢复。我们假设这将是一条卓有成效的治疗干预新途径。在第二个目标中，我们研究了突触活性和FMRP功能在塑造MB回路成熟过程中的相互依赖关系。我们假设，突触活动通过FMRP依赖的机制调节E与I突触的消除(“修剪”)相对于稳定。我们将使用转基因活性阻滞剂(例如破伤风毒素)和光电流(例如光门离子通道)的组合，在分阶段的发育试验中对靶向E和I神经元进行研究，检查对照组与FMRP缺失和功能获得突变体的结果。同时，我们将使用转基因[Ca~(2+)]记者来绘制MB电路发育过程中依赖活动的E-I变化图。在第三个目标中，我们解决了FMRP作为翻译调节因子的角色，在MB电路成熟过程中控制发育阶段适当的蛋白质合成。我们建议在我们为FMRP功能建立的发育时间过程中描述大脑蛋白质组的特征。以前从未在任何疾病模型中进行过这种迫切需要的发育特征分析。总而言之，这些目标旨在最大限度地利用强大和经过验证的果蝇疾病模型。我的实验室是唯一准备进行这项工作的实验室，我真的相信我们可以在为认知障碍和自闭症谱系障碍这一最常见的可遗传原因提供理解和设计治疗方面提供巨大帮助。

DESCRIPTION (provided by applicant): Loss of Fragile X Mental Retardation Protein (FMRP) causes a developmental brain disorder characterized by impaired synaptic connectivity and disrupted activity-dependent modulation in the late developing brain. Loss of FMRP is associated with a range of neurodevelopmental disorders (NDDs) with symptoms including intellectual disability, autism and childhood epilepsy. Our laboratory established the powerful Drosophila disease model and showed human FMRP displays total functional conservation in this model. We have repeatedly proven this model provides direct insights into the molecular and cellular bases of the human disease state. In this revised competitive renewal proposal, I ask for your urgently needed support to allow us to continue to take advantage of this wonderful genetic system, and relative simplicity of the learning/memory neural circuit in the Drosophila brain and its thoroughly-characterized behavioral output, to test core hypotheses regarding FMRP loss and proposed interventions to correct the resultant developmental brain defects. Experimental approaches will target the well-defined Mushroom Body (MB) circuit, a brain center receiving input from multiple sensory modalities to mediate associative learning and memory consolidation. In the first aim, we will test the hypothesis that FMRP regulates the development of the appropriate excitatory (E) vs. inhibitory (I) synaptic balance within the MB circuit. We propose genetic and pharmacological means to correct E vs. I defects independently, to assay restoration of architectural, functional and behavioral output defects in the null mutant state. We hypothesize this will be a fruitful new avenue for therapeutic intervention. In the second aim, we examine the inter-dependence of synaptic activity and FMRP function in shaping MB circuit maturation. We hypothesize that synaptic activity regulates E vs. I synapse elimination ("pruning") relative to stabilization via a FMRP-dependent mechanism. We will use a combination of transgenic activity blockers (e.g. tetanus toxin) and photocurrents (e.g. light-gated ion channels) in targeted E vs. I neurons in staged developmental trials, examining outcomes in controls compared to FMRP loss and gain-of-function mutants. In parallel, we will use transgenic [Ca2+] reporters to chart activity-dependent E vs. I changes during MB circuit development. In the third aim, we tackle the role of FMRP as a translational regulator controlling development stage appropriate protein synthesis during MB circuit maturation. We propose to characterize the brain proteome over the developmental time course we have established for FMRP function. Such desperately needed developmental profiling has never before been done in any disease model. Together, these aims are designed to make maximal use of the powerful and proven Drosophila disease model. My lab is the only lab poised to pursue this work, and I truly believe we can aid enormously in providing understanding and devising treatments for this most common heritable cause of cognitive dysfunction and autism spectrum disorder.