Generation of hES/iPS cell-derived sensory neurons: a new approach to study mechanosensation

感知和辨别机械刺激的能力对我们的健康至关重要。在一天的过程中，我们会遇到各种各样的触觉刺激。这些刺激大体上可以分为令人愉悦的两类，比如让我们区分不同纹理和表面的机械刺激，或者是令人痛苦的，比如针刺，这可以作为改变我们行为的警告信号，以避免组织损伤。虽然在过去的几十年里，我们已经了解了负责检测不同形式的机械刺激的感觉神经元的不同亚型（机械感受器响应无害的机械刺激，而伤害感受器专门检测有害的机械输入），但负责转导不同类型机械刺激的分子机制才刚刚开始被发现。Piezo2是一种由多种不同感觉神经元亚型表达的大型跨膜蛋白，被确定为哺乳动物机械感受器中无害机械刺激的主要换能器。但目前尚不清楚，这种蛋白质是否也参与了传导有害的机械刺激以引起疼痛的感觉。同样，Piezo2传导机械刺激的机制，以及它是如何被调节和微调以作为分子机械感受器的，目前还不得而知。与其他已知的感觉受体类似，我们提出需要一些辅助蛋白来帮助Piezo2实现其高度专业化的功能。因此，我们建议使用人类胚胎干细胞（hESC）衍生的伤害感受器和机械感受器作为模型系统，更详细地研究Piezo2在感觉神经生物学中的作用。我们的目标是首先了解Piezo2在介导疼痛感知的伤害感受器中传导有害机械刺激的作用。接下来，我们要分析Piezo2蛋白组，以确定Piezo2功能所需的调节蛋白。我们相信，我们基于人类细胞的模型系统是找到这些问题答案的绝佳工具，这不仅有助于我们更好地理解这种高度专业化的感觉转导机制的基本机制，而且也是在疼痛感知变得不适应时开发干预措施的必要先决条件。

The ability to perceive and discriminate mechanical stimuli is of fundamental importance to our wellbeing. We encounter a large variety of tactile stimuli during the course of a day. These stimuli can broadly be categorized as pleasant -such as mechanical stimuli that allow us to discriminate different textures and surfaces - or painful such as a pinprick, which can serve as warning signal to change our behavior in order to avoid tissue damage.Although over the last decades we have learned a great deal about the different subtypes of sensory neurons responsible for the detection of different forms of mechanical stimulation (mechanoreceptors respond to innocuous mechanical stimuli while nociceptors are specialized to detect noxious mechanical input), the molecular mechanisms responsible for transducing the different types of mechanical stimuli are just beginning to be uncovered.Piezo2, a large transmembrane protein expressed by a variety of different sensory neuron subtypes, was identified as one main transducer of innocuous mechanical stimuli in mammalian mechanoreceptors. But it is still unclear, if this protein is also involved in transducing noxious mechanical stimuli to elicit painful sensations. Likewise, nothing is known yet about the mechanism by which Piezo2 is transducing mechanical stimuli and how it is modulated and fine-tuned to serve as a molecular mechanoreceptor. Similarto other known sensory receptors, we propose that a number of accessory proteins are required to assist Piezo2 in fulfilling its highly specialized function.We therefore propose to investigate the role of Piezo2 in sensory neurobiology in more detail, using human embryonic stem cell (hESC)-derived nociceptors and mechanoreceptors as a model system. Our aim is first to understand the role of Piezo2 in transducing noxious mechanical stimuli in nociceptors that mediate the perception of pain. We next want to analyze the Piezo2 proteom in order to identify regulatory proteins required for Piezo2 function. We are confident that our human cell-based modelsystem is an excellent tool to find answers to these questions, which will not only help us to better understand the basic mechanisms underlying this highly specialized sensory transduction machinery, but are also essential prerequisites to develop interventions when pain perception becomes maladaptive.