Biomechanics of Complex Microtubule Networks

人类和许多其他生物都是由细胞组成的，这些细胞拥有一个复杂的生物力学框架：细胞骨架。细胞骨架的组成和内部布局因细胞而异。有些差异纯粹是随机的，但不同类型的细胞之间也存在明显的系统性结构差异。例如，与疾病(如癌症)有关的细胞通常具有与健康生物体中的细胞明显不同的细胞骨架。目前尚不清楚不同的细胞骨架结构与整体细胞生物力学特性之间的关系。阻碍进展的问题之一是无法在受控环境中重复组装细胞骨架网络。然而，最近开发的一项纳米级组装技术正是实现了这一点：现在可以组装最长、最不灵活的细胞骨架微管，并以足够的灵活性和精度进行操作，以在模拟细胞中所见的受控环境中构建结构。根据该奖项进行的研究将使用这种新颖的方法来检查一些关键的生物相关纤维结构的生物力学特性。这项工作还将研究微管细胞骨架的生物力学如何在结构相同但细丝结构的整体大小不同时发生变化。这些测量将提供一个大的视角(微管网络结构在细胞生物力学中的作用)和小尺度的视角(应力如何在网络中传播)。这项研究将研究几个关键的微管网络拓扑。最近展示的一种全息光学捕获方法将用于在体外以3D方式组装微管网络。全息和普通陷阱将被用来在现场操纵和探测这种网络。对于给定的网络布局，本研究还将建立模型网络的生物力学特性如何随整体规模变化。因此，所选择的微管网络结构对细胞生物力学的贡献程度将被确定。不同机械性能的细丝和交联体的作用也将使用相同的实验技术进行定量研究。

Humans and many other organisms are comprised of cells which possess a complex biomechanical framework: the cytoskeleton. The composition and internal layout of the cytoskeleton is different from cell to cell. Some differences are purely random but there are also clear systematic architectural differences between various cell types. For example, cells involved in diseases (e.g. cancer) often have markedly different cytoskeleton from cells in a healthy organism. It is currently not clear how different cytoskeletal architectures relate to overall cell biomechanical properties. One of the problems hindering progress has been the inability to reproducibly assemble cytoskeletal networks in a controlled environment. However, a recently developed nano-scale assembly technique allows for exactly this: the longest and least flexible cytoskeletal filaments known as microtubules can now be assembled and manipulated with sufficient flexibility and precision to build structures in a controlled environment which mimic what is seen in cells. Research conducted under this award will use this novel approach to examine the biomechanical properties of a number of key biologically relevant filament architectures. The work will also examine how the biomechanics of microtubule cytoskeleton changes when the architecture is identical but the overall size of the filament structure is varied instead. These measurements together will provide both a big picture view (the role of microtubule network architecture in cellular biomechanics) and small scale perspective (how stress propagates across the network).This research will examine several key microtubule network topologies. A recently demonstrated holographic optical trapping approach will be used to assemble microtubule networks in vitro in 3D. Holographic and ordinary trapping will be used together to manipulate and to probe such networks in situ. For a given network layout, this study will also establish how the biomechanical properties of the model network change with overall scale. Therefore, the extent to which select microtubule network architectures contribute to cellular biomechanics will be established. The role of filaments and cross-links with different mechanical properties will also be quantitatively examined using the same experimental technique.