Engineering a shape-changing light-actuated living tissue

生物工程中一个长期存在的挑战是设计出能够根据需要动态改变形状的组织，例如用于再生目的或用于仿生机器的开发。为此，我们建议从胚胎形态发生中汲取灵感，当组织经历一系列戏剧性的形状变化以产生复杂的生物体时。这些是由细胞骨架产生的张力的时空梯度驱动的，并由称为RhoGTPases的分子开关控制。反过来，rhogtpase的活性源于编码其调节因子rhogef和rhogap的基因表达的空间模式。rhogef激活RhoGTPase导致肌球蛋白运动和张力增强，而rhogap下调RhoGTPase活性以降低张力。许多复杂的细胞形态发生事件，如有丝分裂形态发生，是由rhogef和rhogap在不同的亚细胞位置作用的组合控制的，从而产生陡峭的时空张力梯度，导致形状变化。在组织尺度上，类似的过程也在发挥作用，细胞群协调它们的收缩和迁移行为，从而产生组织张力的时空梯度，从而驱动胚胎形态发生。我们的目标是利用RhoGTPase信号通路来创造一种可以由光控制的可变形的活组织，灵感来自胚胎形态发生过程中观察到的设计规则。我们将重点关注两个目标。首先，我们将设计基于光遗传学控制细胞力学的分子致动器，其中一个致动器增加收缩性（基于RhoGEF），另一个致动器减少收缩性（基于RhoGAP）。然后，我们将在分钟到小时的时间尺度上描述它们对细胞和组织力学的影响。在第二个目标中，我们将把这些数据整合到一个计算框架中，该框架结合了组织弹性理论和进化算法。计算框架将提出时空驱动模式，以达到任何所需的组织形状，我们将在实验中实现这些。我们将特别关注合成复制胚胎发育过程中观察到的形态发生变化。

A long-standing challenge in bioengineering is to design tissues that can dynamically change their shapes on demand, for instance for regenerative purposes or for the development of biomimetic machines. For this, we propose to draw inspiration from embryonic morphogenesis when tissues undergo a series of dramatic shape changes to generate a complex organism. These are driven by spatiotemporal gradients of tension generated by the cytoskeleton and controlled by molecular switches called RhoGTPases.In turn, the activity of RhoGTPases arises from spatial patterns in the expression of genes encoding their regulators, RhoGEFs and RhoGAPs. RhoGEFs activate RhoGTPases leading to enhanced activity of myosin motors and tension, while RhoGAPs downregulate RhoGTPase activity to decrease tension. Many complex cellular morphogenetic events, such as mitotic morphogenesis, are controlled by combinations of RhoGEFs and RhoGAPs acting in different subcellularpatial locations to create the steep spatiotemporal tension gradients that lead to shape change. At the tissue scale, similar processes are at play with groups of cells coordinating their contractile and migratory behaviours to generate thelead to spatiotemporal gradients in tissue tension that drive embryonic morphogenesis.Our goal is to harness the RhoGTPase signalling pathway to create a shape-shifting living tissue that can be controlled by light, inspired by the design rules observed during embryonic morphogenesis. We will focus on two aims. First, we will design molecular actuators controlling cell mechanics based on optogenetics with one actuator increasing contractility (based on a RhoGEF) and the other decreasing contractility (based on a RhoGAP). We will then characterise their effects on cell and tissue mechanics at minute to hour time-scales. In the second aim, we will integrate these data into a computational framework that combines the theory of elasticity for tissues and evolutionary algorithms. The computational framework will suggest spatiotemporal actuation patterns to reach any desired tissue shape and we will implement these in experiments. We will focus in particular on synthetically replicating morphogenetic changes observed during embryonic development.