Cell-biological mechanisms directing primary cilium mediated control of neuron polarisation

神经元的一个关键特征是它们能够对周围组织的提示做出反应，这使它们能够区分它们的前部和后部，从而实现极化。发育中的胚胎脊髓中的新生神经元脱落其尖端以移动到其最终位置。由于这种脱落事件，这些新生神经元失去了定义其极性的关键蛋白质以及它们的细胞天线，称为初级纤毛，这使得这些细胞能够感知来自周围组织的外部线索。因此，新生神经元停止响应Shh信号并退出细胞周期，这是神经元分化的关键步骤。在此之后，神经元必须迅速重新建立其极性。这一步是至关重要的，因为它允许神经元延伸一个长的细胞过程，称为轴突，它与其目标，如肌肉或其他神经元连接。在发育中的胚胎中，神经元对来自周围组织的外部线索做出极化反应。这些外部线索决定了这种极化的方向，从而决定了轴突的行进方向，或者决定了轴突是否形成。因此，这是一个关键的事件，是必不可少的功能性神经元回路的形成。我们最近发现，新生神经元在准备延伸轴突时，会迅速重组新的初级纤毛。这个新的初级纤毛现在允许新生神经元将其响应转换为Shh信号，Shh信号现在起作用以确定轴突投射的方向。这项建议的目的是调查的细胞生物学机制，指导这个开关的Shh信号的重新组装的初级纤毛的解释。此外，我们还旨在研究如何通过重新组装的初级纤毛信号引导神经元细胞骨架的重塑，以产生特征性的神经元形态。为了实现这一目标，我们将使用尖端的显微镜技术来制作发育中胚胎中极化神经元的电影，并将这些与固定胚胎组织的超分辨率荧光成像联合收割机结合起来。这将使我们能够识别和调节介导Shh信号传导的细胞反应开关的机制，以及这如何影响分化神经元的细胞骨架重塑。这项工作可能会导致新的临床干预措施的发展，以促进这一进程的情况下，神经发育障碍或以下损伤在成年期。

A key feature of neurons is their ability to respond to cues from the surrounding tissues which allow them to distinguish their front from their back and thus achieve polarisation. Newborn neurons in the spinal cord of the developing embryo shed their tips to move to their final location. As a result of this shedding event, these newborn neurons lose the key proteins that define their polarity as well as their cellular antenna, called the primary cilium, which allows these cells to sense external cues from the surrounding tissues. Consequently, newborn neurons stop responding to Shh signalling and exit the cell cycle, which is a key step of neuronal differentiation. Following this, the neuron must now rapidly re-establish its polarity. This step is crucial, as it allows the neuron to extend a long cell-process, called an axon, which makes connections with its targets, such as muscles or other neurons. In the developing embryo, the neuron polarises in response to external cues from the surrounding tissue. These external cues determine the orientation of this polarisation and therefore determine the direction in which the axon will travel, or if it forms at all. This is thus a critical event that is essential for the formation of functional neuronal circuitry. We have recently discovered that newborn neurons quickly reassemble a new primary cilium as they prepare to extend an axon. This new primary cilium now allows the newborn neuron to switch its response to Shh signalling, which now acts to determine the direction in which the axon projects. This proposal aims to investigate the cell biological mechanisms that direct this switch in the interpretation of Shh signalling by the reassembled primary cilium. Furthermore, we also aim to investigate how signalling through the reassembled primary cilium directs remodelling of the neuronal cytoskeleton to generate the characteristic neuronal morphology. To achieve this, we will use cutting-edge microscopy techniques to make movies of polarising neurons in developing embryos and combine these with super-resolution fluorescence imaging of fixed embryonic tissue. This will allow us to identify and modulate the mechanisms that mediate the switch in the cellular response to Shh signalling and how this influences cytoskeletal remodelling in differentiating neurons. This work may lead to the development of novel clinical interventions to promote this process in the case of neurodevelopmental disorders or following injury during adulthood.