Mechanism of autophagy-controlled axon branching

自噬控制轴突分支的机制

• 批准号: BB/T013753/1
• 负责人: Uwe Drescher
• 金额: $ 62.51万
• 依托单位: King's College London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2020
• 资助国家: 英国
• 起止时间: 2020 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FT013753%2F1
• 关键词: Mechanism; autophagy; controlled; axon; branching

One of the most important unsolved questions for scientists is how the nervous system is formed. During embryonic development nerve cells send out long thread-like structures, or axons, which grow over long distance to reach their destinations, where they will wire up with other nerve cells. In order to form connections with multiple other nerve cells, axons must branch in the target area which follows an intricate and specific pattern. This process is crucial for the development of neuronal circuits. Our research seeks to understand axon branching in the visual system, which connects the retina of the eye with the brain. The large body of knowledge accrued about the visual system makes it ideal for uncovering fundamental principles of development. Our previous work has shown that when retinal neurons are cultured, they form branched patterns which are closely similar to those found in the intact organism. We have recently found that the neuron's waste disposal processes, termed autophagy, is involved in this process. Neurons deploy autophagy as a means of degrading unwanted molecules. We have shown that an increase in autophagy leads to an increase in the number of branches, while a reduction autophagy leads to a decrease in the number of branches. We believe that neurons control the number and location of branches by locally destroying (via autophagy) molecules which normally suppress the formation of axon branches. Thus during development, axon branching is normally suppressed, and only in regions where autophagy is activated, branching can occur. We have shown that a small molecule called Arl8B, which transports lysosomes in axons, might control where autophagy is activated. Changes in the expression level of Arl8B correlate with changes in the distribution and density of vesicles having a key role in executing autophagy, named autophagosomes. This exciting project will test the hypothesis that autophagy shapes axonal branching and neural circuit development. Our data so far show a good correlation, and we aim to show now a causal relationship. For this we will use time lapse experiments to unravel the spatio-temporal correlation between the movement of autophagosomes/lysosomes and the formation of branches. Then we would like to identify the extracellular molecules which control where along an axon autophagy is activated, and we would like to identify the suppressor molecules which normally block branching. This work on neuronal cell culture will be extended into intact animals. We would like to show for individual axons that genetically eliminating autophagy in the retina disturbs their connectivity in the visual system of mice. This will suggest that the mechanisms we have discovered in culture play a role during the development of the visual system. We think that an integration of these interwoven approaches will lead to a deeper understanding of the role of autophagy and one of its key components, Arl8B, in circuit development within the nervous system. Up to now, very little is known about the role of autophagy during nervous system development, and our research will provide substantial new information on these issues. Recent publications have uncovered a close link between deregulation of autophagy and the aetiology of autism spectrum disorders. We predict that our investigation of the small G protein Arl8B will integrate these different aspects into one concept, and represents a novel approach to investigate the connection between autophagy and neural circuit formation. We predict that this investigation will contribute to a better understanding of the aetiology of autism spectrum disorders.

对科学家来说，最重要的未解决的问题之一是神经系统是如何形成的。在胚胎发育过程中，神经细胞发出长长的线状结构或轴突，这些轴突长距离生长，到达目的地，在那里它们将与其他神经细胞连接起来。为了与多个其他神经细胞形成连接，轴突必须在目标区域中分支，其遵循复杂和特定的模式。这个过程对于神经元回路的发育至关重要。我们的研究旨在了解视觉系统中的轴突分支，它连接眼睛的视网膜和大脑。关于视觉系统积累的大量知识使其成为揭示发展基本原则的理想工具。我们以前的工作已经表明，当视网膜神经元被培养时，它们形成分支模式，这与在完整生物体中发现的分支模式非常相似。我们最近发现，神经元的废物处理过程，称为自噬，参与了这一过程。神经元利用自噬作用降解不需要的分子。我们已经表明，自噬的增加导致分支数量的增加，而自噬的减少导致分支数量的减少。我们认为神经元通过局部破坏（通过自噬）通常抑制轴突分支形成的分子来控制分支的数量和位置。因此，在发育过程中，轴突分支通常受到抑制，只有在自噬被激活的区域，才能发生分支。我们已经表明，一种名为Arl8B的小分子，它在轴突中运输溶酶体，可能控制自噬被激活的位置。Arl8B表达水平的变化与在执行自噬中具有关键作用的囊泡（称为自噬体）的分布和密度的变化相关。 这个令人兴奋的项目将测试自噬塑造轴突分支和神经回路发育的假设。到目前为止，我们的数据显示了良好的相关性，我们现在的目标是显示因果关系。为此，我们将使用延时实验来解开自噬体/溶酶体的运动和分支的形成之间的时空相关性。然后，我们想确定控制沿着轴突自噬被激活的细胞外分子，我们想确定通常阻止分支的抑制分子。这项神经元细胞培养的工作将扩展到完整的动物。我们想展示的是，通过基因消除视网膜中的自噬会干扰小鼠视觉系统中的单个轴突的连接。这将表明，我们在文化中发现的机制在视觉系统的发展过程中发挥了作用。我们认为，这些交织的方法的整合将导致更深入地了解自噬及其关键成分之一Arl8B在神经系统回路发育中的作用。到目前为止，对自噬在神经系统发育中的作用知之甚少，我们的研究将为这些问题提供大量新信息。最近的出版物揭示了自噬失调与自闭症谱系障碍病因之间的密切联系。我们预测，我们对小G蛋白Arl8B的研究将把这些不同的方面整合到一个概念中，并代表了一种新的方法来研究自噬和神经回路形成之间的联系。我们预测，这项调查将有助于更好地了解自闭症谱系障碍的病因。