为了理解形态发生,有必要知道材料的性质或形成活组织的力。尽管有这种需要,目前可用的体内测量非常少。这里,以果蝇早期胚胎为模型,我们描述了一种新颖的基于悬臂的技术,该技术可以同时量化活胚胎中的作用力和组织位移。通过分析一系列胚胎上皮受到发育相关扰动的实验数据,我们得出的结论是,对施加力的响应是绝热的,并且受弹性力和几何约束的支配,或系统大小的影响。至关重要的是,实验数据的计算模型表明,上皮的顶端表面必须比基底表面更柔软,我们通过实验证实了这一结果。Further,我们使用实验数据和综合计算模型相结合的方法来估计根尖表面的弹性模量,并设定了基面弹性模量的下限。更一般地说,我们的调查揭示了重要的一般特征,我们认为在对任何系统中的组织力学进行定量建模时,应该更广泛地解决这些特征。具体来说,同一细胞的不同隔室可以具有非常不同的机械性能;当它们这样做时,它们可以对不同的机械刺激做出不同的贡献,并且不能仅仅被平均在一起。此外,组织几何形状可以在机械响应中发挥重要作用,不能忽视。
In order to understand morphogenesis, it is necessary to know the material properties or forces shaping the living tissue. In spite of this need, very few in vivo measurements are currently available. Here, using the early Drosophila embryo as a model, we describe a novel cantilever-based technique which allows for the simultaneous quantification of applied force and tissue displacement in a living embryo. By analyzing data from a series of experiments in which embryonic epithelium is subjected to developmentally relevant perturbations, we conclude that the response to applied force is adiabatic and is dominated by elastic forces and geometric constraints, or system size effects. Crucially, computational modeling of the experimental data indicated that the apical surface of the epithelium must be softer than the basal surface, a result which we confirmed experimentally. Further, we used the combination of experimental data and comprehensive computational model to estimate the elastic modulus of the apical surface and set a lower bound on the elastic modulus of the basal surface. More generally, our investigations revealed important general features that we believe should be more widely addressed when quantitatively modeling tissue mechanics in any system. Specifically, different compartments of the same cell can have very different mechanical properties; when they do, they can contribute differently to different mechanical stimuli and cannot be merely averaged together. Additionally, tissue geometry can play a substantial role in mechanical response, and cannot be neglected.