A Conserved RNA Binding Protein Regulates RNAs Critical for Neurodevelopment

项目摘要 智力残疾是一种常见的神经发育障碍，其特征是智力功能受限 和受损的适应行为。智力残疾的临床异质性反映在极端的遗传 复杂性，超过60%的确诊患者的病因尚未解决。强调这种复杂性，病变 超过700个基因与智力残疾有关。重要的是，新出现的证据表明， 这些不同的基因集中在一组有限的分子途径上，主要是那些对 大脑的发育和功能。这种趋同性表明，单基因的研究，实验上容易处理， 智力残疾的形式可以提供对所有形式疾病共同机制的分子见解。 有趣的是，许多与智力残疾有关的基因编码RNA结合蛋白（RBP）， 在基因表达的转录后调节中起关键作用。我导师的实验室共同发现了一个 由广泛表达的RBP中的功能缺失突变引起的单基因形式的智力残疾 ZC3H14为了发现ZC 3 H14基因突变损害脑功能的原因，我们开发了一种 果蝇中删除直系同源基因Nab 2导致ZC 3 H14丢失的实验易处理模型 黑腹菌这项工作揭示了Nab 2在所有细胞中表达，但在神经元中特异性需要 在发育中的神经系统中支持轴突引导、运动和嗅觉记忆。然而，在这方面， ZC 3 H14/Nab 2调节的RNA的身份以及提高ZC 3 H14/Nab 2功能的机制， 神经元仍然难以捉摸。最近，我的实验室发现了证据，证明Nab 2作为一种调节剂， 选择性剪接通过抑制N6-甲基腺苷（m6 A）沉积在一个子集的神经富集 mRNA，代表了神经元生长过程中基因表达的表转录调控的关键层， 发展因此，我将检验Nab 2调控关键神经元m6 A依赖性表达的假设。 通过结合它们的前mRNA转录物和抑制m6 A超甲基化来控制适当的大脑 形态学和功能，这里集中在一个Nab 2调节的转录本，三，它显示异常内含子 失去Nab 2后的保留。Trio蛋白在脊椎动物中是保守的，TRIO基因以显性突变， Trio是人类智力残疾的一种形式，Trio在轴突引导和神经元形态学中起着关键作用。的 本项目的具体目的是：1）确定Nab 2作为m6 A依赖性表达的调节剂的作用， 神经元富集的转录本;和2）检查Nab 2依赖性调节Trio表达如何控制 果蝇蘑菇体中轴突束的发育，海马体的类似物， 嗅觉和味觉记忆。成功完成拟议的目标将提供深入了解 通过在m6 A调节的神经元特异性作用将Nab 2与Trio表达连接的明显保守的途径 剪接，揭示了m6 A，剪接和人类神经发育缺陷之间的更普遍的联系。的 建议的合作研究项目将为我提供最佳的培训经验。

PROJECT SUMMARY Intellectual disability is a common neurodevelopmental disorder characterized by limited intellectual functioning and impaired adaptive behavior. The clinical heterogeneity of intellectual disability is reflected by extreme genetic complexity, leaving etiology unresolved in over 60% of diagnosed patients. Underscoring this complexity, lesions in more than 700 genes have been linked to intellectual disability. Critically, emerging evidence suggests that this diverse group of these genes converge on a limited set of molecular pathways, principally those critical for brain development and function. This convergence suggests that studies of monogenic, experimentally tractable forms of intellectual disability can provide molecular insight into mechanisms common to all forms of the disease. Interestingly, many of the genes linked to intellectual disability encode RNA binding proteins (RBPs) that play critical roles in post-transcriptional regulation of gene expression. My mentors’ labs co-discovered one such monogenic form of intellectual disability caused by loss of function mutations in the ubiquitously expressed RBP ZC3H14. To discover why mutations in the ZC3H14 gene impair brain function, we have developed an experimentally tractable model of ZC3H14 loss by deleting the ortholog, Nab2, in the fruit fly Drosophila melanogaster. This work has revealed that Nab2 is expressed in all cells but required specifically in neurons within the developing nervous system to support axon guidance, locomotion, and olfactory memory. However, the identity of ZC3H14/Nab2-regulated RNAs as well as mechanisms that elevate ZC3H14/Nab2 function in neurons remain elusive. Recently, my labs have uncovered evidence for a novel role of Nab2 as a regulator of alternative splicing through inhibition of N6-methyladenosine (m6A) deposition on a subset of neuronally enriched mRNAs, representing a critical layer of epitranscriptomic regulation of gene expression during neuronal development. Thus, I will test the hypothesis that Nab2 governs m6A-dependent expression of key neuronal targets by binding their pre-mRNA transcripts and inhibiting m6A hypermethylation to govern proper brain morphology and function here by focusing on one Nab2-regulated transcript, trio, which displays aberrant intron retention upon loss of Nab2. The Trio protein is conserved in vertebrates, the TRIO gene is mutated in a dominant form of human intellectual disability, and Trio plays a key role in axon guidance and neuronal morphology. The Specific Aims of this project are to: 1) define the role of Nab2 as a regulator of m6A-dependent expression of neuronally-enriched transcripts; and 2) examine how Nab2-dependent regulation of Trio expression governs development of axon tracts in the Drosophila mushroom body, an analog of the hippocampus that supports olfactory and gustatory memory. Successful completion of the proposed Aims will provide insights into an apparently conserved pathway linking Nab2 to Trio expression through a neuron-specific role in m6A-regulated splicing, uncovering more general links between m6A, splicing, and neurodevelopmental defects in humans. The proposed collaborative research project will provide me with an optimal training experience.