Structural organisations underlying auditory sensitivity

大多数细胞功能依赖于相互作用的分子的组合，以及这些复合物在细胞内的组织方式。此外，细胞本身被组织成将不同的活动划分到不同的区域，同时使这些活动能够整合，这是细胞正常运作所必需的。因此，细胞结构和细胞功能之间存在着非常密切的关系。因此，了解不同的分子如何整合到细胞中以支持其功能，以及当分子功能在疾病期间被破坏时细胞如何出错，至关重要的是了解三维细胞结构的分辨率水平，使大分子组装和它们正常运作的细胞环境可视化。电子显微镜揭示了从大分子的近似尺寸到整个细胞水平的结构细节。通过应用现在建立的“电子断层扫描”方法，可以从电子显微镜检查的组织切片中获得三维信息。在这种技术中，从许多不同的角度拍摄同一结构的图像集合。当这些图像组合在一起时，就得到了结构的三维视图。由此可以确定结构如何相互关联，例如一个分子复合物如何与另一个分子相互作用，或者在较低的分辨率下，细胞内的细胞器如何分布以及它们之间是否存在连续性。如果用保存自然状态的方法制备组织用于显微镜，这可以通过在处理前快速冷冻来实现，就有可能在接近生命的条件下获得细胞内亚细胞结构的细节。本项目将应用这些现代方法来评估内耳感觉组织的细胞结构特征。这些组织负责听觉和维持平衡，它们的结构非常立体。单个感觉“毛细胞”呈圆柱形，顶端有一束有组织的突起，这些突起的偏转会对声音振动（听觉）或运动（平衡）做出反应，从而向细胞底部的神经发出信号。每个毛细胞周围都有提供结构支撑的细胞。该项目将探索对细胞忠实地产生适当神经输出以响应机械输入的能力至关重要的结构组织。它将决定大分子复合物的结构和关系，这些大分子复合物通过头发束的偏转来控制通道的打开和关闭，从而触发神经刺激流。它将决定支撑单元内结构组件的组织，这些组件创建刚性框架，这是确保来自安静声音的小振动产生束的偏转和信号检测所必需的。它将定义毛细胞内的通路，通过这个通路，释放刺激神经的化学物质从细胞的顶端到达底部。与这些活动相关的分子异常会导致毛细胞功能障碍。毛细胞功能障碍和损失是耳聋和平衡失衡的主要原因，这是老年人特别普遍的主要致残状况。通过阐明结构与功能之间的关系，本项目将有助于了解毛细胞功能障碍的基本基础。从这些知识中，将有办法改善由此产生的生理缺陷——耳聋和/或平衡失衡。

Most cellular functions depend upon assemblies of interacting molecules, and upon the ways in which those complexes are organised within a cell. Moreover, cells themselves are organised to compartmentalise different activities into different regions while at the same time enabling the integration of those activities that is necessary for the cell to function as it should. There is, thus, a very close relationship between cellular architecture and cell function. Consequently, crucial to understanding how different molecules are integrated into a cell to support its function, and how cells go wrong when molecular function is disrupted during disease, is knowledge of the three-dimensional cellular architecture at levels of resolution that enable visualisation of macromolecular assemblies and the cellular context in which they normally function. Electron microscopy reveals such structural details across a range from the approximate dimension of macromolecules up to the level of the whole cell. Three-dimensional information can be obtained from tissue sections examined by electron microscopy by the application of now established methods for 'electron tomography'. In this technique, a collection of images of the same structure is taken from many different angles. When these images are assembled together, a three-dimensional view of the structure is obtained. From this it is possible to identify how structures are associated with one another, for example how one molecular complex interacts with another, or at a lower level of resolution, how organelles within a cell are distributed and whether there is continuity between them. If tissue is prepared for microscopy by means that preserve the natural state, which can be achieved by freezing them very rapidly before processing, it becomes possible to obtain details of sub-cellular structures in a close-to-life condition in their true context inside the cell. This project will apply these modern methods to assess features of the cellular architecture of the sensory tissues of the inner ear. These tissues are responsible for the sense of hearing and maintenance of balance and they are remarkably three-dimensional in their architecture. Individual sensory 'hair' cells are cylindrical and bear at their top ends an organised bundle of projections, deflections of which in response to sound vibrations (hearing) or motion (balance) lead to signalling to the nerves at the bottom of the cell. Each hair cell is surrounded by cells that provide structural support. The project will explore the organisation of structures crucial to the cell's ability to faithfully generate appropriate neural output in response to mechanical input. It will determine the structure and relationships of macromolecular complexes that, with deflections of the hair bundle, control the opening and closing of channels through which a current that triggers the neural stimulation flows. It will determine the organisation of the structural components within the supporting cells that create the rigid framework that is necessary to ensure that small vibrations from quiet sounds produce deflections of the bundle and signal detection. And it will define the pathway within a hair cell by which the chemical that is released to stimulate the nerve travels from where it is made at the top end of the cell to the bottom end. Abnormalities of the molecules associated with these activities cause hair cell dysfunction. Hair cell dysfunction and loss are the main causes of deafness and balance disequilibrium, major disabling conditions that are particularly prevalent in the elderly. By elucidating details of the relationships between structure and function, this project will contribute to understanding the fundamental bases underlying hair cell dysfunction. From such knowledge means to ameliorate the resultant physiological deficits -deafness and/or balance disequilibrium- will ensue.