How do neurons recognize self from non-self?

项目总结 本文旨在了解神经元的一个基本属性：它们自我识别和自我识别的能力。 避免。自我回避是神经元功能的一个基本方面，因为它确保从相同的 细胞最大限度地减少它们的重叠，同时最大化它们与其他细胞分支的交互。在哺乳动物中， 这一过程的核心是产生足够的原钙粘蛋白(Pcdh)蛋白质亚型多样性，从而 基本上，大脑中的每个神经元在其表面都有不同的条码，因此看起来不同于 其他神经元。Pcdh蛋白异构体多样性的产生需要复杂的Pcdh机制 转录和前信使核糖核酸剪接使得不同的Pcdh信使核糖核酸分子带有不同的5‘端 (可变外显子)，但相同的3‘端(恒定外显子)-在单个细胞中表达。了解如何 不同的Pcdh mRNA分子的产生代表了神经科学领域的一个长期谜团。 回答这个根本的谜团是阐明神经元自我回避和 代表了解剖这种Pcdh的失调如何介导自我回避的第一个基本步骤 会导致严重的神经疾病，例如自闭症谱系障碍和精神分裂症。 然而，尽管它们在大脑中起着关键的作用，但在了解它们是如何 与基因表达调控的一般模型一样，Pcdh mRNAs被转录并正确拼接 未能概括这一复杂的机制，因为直接在体内研究它所需的工具已经滞后 在后面。在这个建议中，我们的目标是(I)测试Pcdh RNA转录和 基于在其上串联编码的可变和恒定外显子的交替反式剪接的剪接 DNA链--我们认为这是一种受Pcdh基因座3D基因组拓扑调控的机制-- 以及(Ii)设计能够在体内精确操纵Pcdh基因簇的技术创新 直接在神经元中测试我们的假设。这些研究有可能解释这种复合体。 PcdH异构体多样性的产生机制及其在神经元自我回避和连接中的作用 健康和疾病的大脑。这些研究的发现也有望开辟一类新的 RNA加工反应的调节机制，以前没有被观察到，也没有被描述 但我们推测，哺乳动物被细胞利用来克服前mRNA剪接的挑战性问题 与复杂的基因结构有关。

PROJECT SUMMARY This essay aims to understand a fundamental property of neurons: their ability to self-recognize and self- avoid. Self-avoidance is an essential aspect of a neuron's function as it ensures that branches from the same cell minimize their overlap while maximizing their interactions with branches from other cells. In mammals, at the core of this process is the generation of sufficient Protocadherin (Pcdh) protein isoform diversity such that essentially every neuron in the brain is differentially barcoded at its surface and therefore appears different to other neurons. The generation of Pcdh protein isoform diversity requires complex mechanisms of Pcdh transcriptional and pre-mRNA splicing such that distinct Pcdh mRNA molecules - bearing a different 5' end (variable exon) but an identical 3' end (constant exons) - are expressed in individual cells. Understanding how different Pcdh mRNA molecules are produced represents a long-term mystery in the field of neuroscience. Answering this fundamental mystery is key in illuminating the process of neuronal self-avoidance and represents the first essential step toward dissecting how dysregulation of this Pcdh mediated self-avoidance can lead to severe neurological disorders, such as for instance autism spectrum disorder and schizophrenia. Despite their critical function in the brain, however, limited progress has been made in understanding how Pcdh mRNAs are transcribed and properly spliced as general models of gene expression regulation have failed to recapitulate this complex mechanism and as the tools required to study it directly in vivo have lagged behind. In this proposal, we aim to (i) test a paradigm-shifting hypothesis of Pcdh RNA transcription and splicing based on alternative trans-splicing of variable and constant exons encoded in tandem on the same DNA strand - a mechanism that we propose to be regulated by the 3D genome topology of the Pcdh locus - and (ii) design technological innovations that will allow precise manipulation of the Pcdh gene cluster in vivo to test our hypothesis directly in neurons. These studies have the potential to illuminate the complex mechanism of the generation of Pcdh isoform diversity and its role in neuronal self-avoidance and wiring of healthy and disease brains. The findings from these studies are also poised to open up a new class of regulatory mechanisms of RNA processing reactions, previously unobserved and uncharacterized in mammals but that we speculate are utilized by cells to overcome challenging problems of pre-mRNA splicing associated with complex gene architectures.