Neurodevelopmental Role of an RNA Binding Protein Required for Cognitive Function

 描述（由申请人提供）：定义确保细胞正确模式的分子机制：发育中的神经系统中的细胞连接部分依赖于脊椎动物和无脊椎动物模型中的遗传研究，部分依赖于绘制人类脑功能障碍遗传形式的基因座。这些努力已经鉴定了几种RNA结合蛋白，其个体损失改变神经元形态和连接，表明转录后机制在神经发育中起重要作用。 我们共同发现了一种遗传性智力残疾，这种智力残疾是由编码聚腺苷RNA结合蛋白（称为ZC 3 H14）的基因突变引起的。我们对一个D.通过缺失唯一的无脊椎动物ZC 3 H14同源物dNab 2产生的这种疾病的黑腹动物模型已经揭示了蘑菇体（MB）中神经元投射的细胞自主缺陷，所述蘑菇体是大脑中涉及学习和记忆的孪生神经元结构。来自野生型MB神经元的轴突向成人脑的中线投射，而来自dNab 2缺陷型MB神经元的轴突通过中线错误投射到对侧脑半球。鉴于dNab 2/ZC 3 H14作为RNA结合蛋白的共同分子作用，我们假设由功能性dNab 2/ZC 3 H14丧失引起的轴突错误投射和认知缺陷是靶RNA转录后控制缺陷的结果。我们发表的发现，人类ZC 3 H14在果蝇神经元中表达时部分补偿了dNab 2的损失，这表明至少有一些RNA靶标是共享的。 该建议的重点是识别dNab 2结合RNA从苍蝇脑神经元编码的因素参与轴突发生。在目标1中，我们建议使用一种经过验证的方法，RNA标记，特异性地恢复dNab 2结合的RNA从果蝇神经元在其自然的情况下在原位。该技术的试点应用已经产生了两种RNA编码蛋白，其在神经元发育中具有确定的作用。目的2将追求的假设，dNab 2损失改变这些dNab 2结合的mRNA的转录后调控的一个关键方面，最终影响其同源蛋白的表达。目的3通过应用遗传工具来评估这些因子中的每一个对野生型脑发育的体内作用以及它们在发育中的蘑菇体中的dNab 2无效表型中的作用来完成循环。 这些目标利用我们的果蝇dNab 2模型的优势来支持我们的长期目标，即定义脊椎动物中ZC 3 H14相关神经元缺陷的机制基础。我们的方法并没有折扣dNab 2在其他神经元过程或细胞类型中的作用，而是让我们专注于一个新的功能dNab 2（轴突发生）在实验上可访问的一组神经元（MB细胞）。深入了解MB神经元中dNab 2的分子作用可能与缺乏ZC 3 H14的人类患者神经元中的分子缺陷有关。

 DESCRIPTION (provided by applicant): Defining molecular mechanisms that ensure proper patterns of cell: cell connectivity in the developing nervous system has relied in part on genetic studies in vertebrate and invertebrate models, and in part on mapping loci responsible for heritable forms of brain dysfunction in humans. These efforts have identified several RNA binding proteins, whose individual loss alters neuronal morphology and connectivity, suggesting that post- transcriptional mechanisms play an important role in neurodevelopment. We co-discovered a form of heritable intellectual disability caused by mutations in the gene encoding a polyadenosine RNA binding protein termed ZC3H14. Our analysis of a D. melanogaster model of this disease created by deletion of the sole invertebrate ZC3H14 homolog, dNab2, has revealed cell-autonomous defects in neuronal projection in the mushroom bodies (MBs), twin neuropil structures in the brain involved in learning and memory. Axons from wildtype MB neurons project towards the midline of the adult brain, while those from dNab2-deficient MB neurons misproject through the midline and into the contralateral brain hemisphere. Given the shared molecular role of dNab2/ZC3H14 as RNA binding proteins, we hypothesize that the axon misprojection and cognitive defects resulting from loss of functional dNab2/ZC3H14 are the result of defects in post-transcriptional control of target RNAs. Our published finding that human ZC3H14 partially compensates for dNab2 loss when expressed in fly neurons indicates that at least some of these RNA targets are shared. This proposal focuses on identification of dNab2-bound RNAs from fly brain neurons that encode factors involved in axononogenesis. In Aim 1 we propose to use a validated approach, RNA Tagging, to specifically recover dNab2-bound RNAs from Drosophila neurons in their natural context in situ. A pilot application of this technique has already yielded two RNAs encoding protein with established roles in neuronal development. Aim 2 will pursue the hypothesis that dNab2 loss alters a key aspect of the post-transcriptional regulation of these dNab2-bound mRNAs, with ultimate effects on expression of their cognate proteins. Aim 3 completes the cycle by applying genetic tools to assess the in vivo role of each of these factors to wt brain development and their roles in dNab2 null phenotypes in the developing mushroom bodies. These Aims leverage the strength of our Drosophila dNab2 model to support our long-term goal of defining the mechanistic basis of ZC3H14-associated neuronal defects in vertebrates. Our approach does not discount roles for dNab2 in other neuronal processes or cell types, but rather allows us to focus on one novel function of dNab2 (axonogenesis) in an experimentally accessible group of neurons (MB cells). Insights into molecular roles for dNab2 in MB neurons could be relevant to molecular defects in the neurons of human patients lacking ZC3H14.