Cells have the ability to respond to various types of environmental cues, and in many cases these cues induce directed cell migration towards or away from these signals. How cells sense these cues and how they transmit that information to the cytoskeletal machinery governing cell translocation is one of the oldest and most challenging problems in biology. Chemotaxis, or migration towards diffusible chemical cues, has been studied for more than a century, but information is just now beginning to emerge about how cells respond to other cues, such as substrate-associated cues during haptotaxis (chemical cues on the surface), durotaxis (mechanical substrate compliance) and topotaxis (geometric features of substrate). Here we propose four common principles, or pillars, that underlie all forms of directed migration. First, a signal must be generated, a process that in physiological environments is much more nuanced than early studies suggested. Second, the signal must be sensed, sometimes by cell surface receptors, but also in ways that are not entirely clear, such as in the case of mechanical cues. Third, the signal has to be transmitted from the sensing modules to the machinery that executes the actual movement, a step that often requires amplification. Fourth, the signal has to be converted into the application of asymmetric force relative to the substrate, which involves mostly the cytoskeleton, but perhaps other players as well. Use of these four pillars has allowed us to compare some of the similarities between different types of directed migration, but also to highlight the remarkable diversity in the mechanisms that cells use to respond to different cues provided by their environment.

细胞具有对各种类型的环境信号做出反应的能力，并且在许多情况下，这些信号诱导细胞定向向或远离这些信号迁移。细胞如何感知这些线索以及它们如何将这些信息传递给控制细胞易位的细胞骨架机制是生物学中最古老和最具挑战性的问题之一。趋化性或向可扩散化学线索的迁移已经研究了一个多世纪，但关于细胞如何响应其他线索的信息才刚刚开始出现，例如趋触过程中与底物相关的线索（表面的化学线索）， durotaxis（基材机械顺应性）和topotaxis（基材的几何特征）。在这里，我们提出四个共同原则或支柱，作为所有形式定向移民的基础。首先，必须产生信号，这一过程在生理环境中比早期研究表明的更加微妙。其次，信号必须被感知，有时是通过细胞表面受体，但也以不完全清晰的方式感知，例如机械信号。第三，信号必须从传感模块传输到执行实际运动的机器，这一步骤通常需要放大。第四，信号必须转换为相对于基质的不对称力的应用，这主要涉及细胞骨架，但也可能涉及其他参与者。使用这四个支柱使我们能够比较不同类型定向迁移之间的一些相似性，同时也强调了细胞用于响应环境提供的不同线索的机制的显着多样性。