Modeling the Structural and Mechanical Properties of Tissue During Zebrafish Tailbud Elongation

在组织尺度上，几乎所有的生物过程中细胞都需要集体运动。理解集体细胞运动最重要的挑战之一是确定单细胞运动策略如何在组织水平上影响集体细胞行为。例如，细胞是主动感知邻近细胞的运动方向，还是主要依靠细胞间的粘附和邻近细胞间的排斥来集体运动？为了理解从单细胞特性到集体迁移的映射，PI提出了一种结合实验和计算的方法来研究斑马鱼脊柱发育过程中趋同延伸过程中的集体细胞迁移。利用共聚焦显微镜和基因变异，PI将测量细胞-细胞粘附和平面细胞极性的变化如何在三维空间上改变细胞流动。然后，他将使用可变形粒子（DP）模型在二维和三维空间中模拟发展中的斑马鱼脊柱的收敛扩展过程，这些边界条件既可变形又可收缩。DP模型还可以系统地改变细胞形状，细胞-细胞粘附和单细胞运动策略。PI将把模拟结果与野生型和突变型斑马鱼胚胎的细胞运动和形状的3D成像结果进行比较。提出的工作将为我们对集体细胞运动的理解提供两个重要的进展：(1)我们如何将单细胞属性映射到集体细胞迁移的特征，以及(2)什么是足够程度的模型复杂性来捕捉集体细胞迁移的重要特征？目前，集体细胞迁移的模型不能模拟真实的细胞变形性和现实的细胞运动策略，但它们可以定性地捕捉集体细胞迁移的几个方面。这些提出的二维和三维可变形颗粒的模拟，以及活组织的三维成像，将使研究小组确定定量描述集体细胞迁移所需的模型成分。该项目还包括一些利用pi参与物理和工程生物学综合研究生课程的教育和推广活动。计划将包括指导高中生和本科生进行研究，开发斑马鱼脊柱发育过程中细胞迁移的计算建模课程模块，以及举办旨在提高研究生向非科学观众展示科学主题的短期课程。PI提出了协调的实验和计算研究，以了解斑马鱼胚胎伸长尾芽收敛延伸过程中细胞形状变化，运动策略和粘附对细胞集体运动的作用。PI将开发新的可变形粒子（DP）模型，在二维和三维空间的动态，可变形边界中进行模拟，可以定量描述发育中的斑马鱼胚胎的细胞和组织水平的变形，并预测单细胞生物物理参数变化对集体细胞运动的影响。补充实验将在斑马鱼胚胎上进行，斑马鱼胚胎具有不同的细胞运动性和细胞-细胞粘附，通过平面细胞极性途径的突变和钙粘蛋白介导的粘附，使DP模型的预测能够通过实验进行测试。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Cells need to move collectively in nearly all biological processes at the tissue scale. One of the most significant challenges to understanding collective cell motion is determining how single-cell motility strategies affect collective cell behavior at the tissue level. For example, do cells actively sense the direction of motion of their neighbors, or do cells primarily rely on cell-cell adhesion and repulsion from their neighbors to move collectively? To understand the mapping from single-cell properties to collective migration, the PI proposes a combined experimental and computational approach to investigate collective cell migration during convergent extension processes in the developing zebrafish spinal column. Using confocal microscopy and genetic variants, the PI will measure how alterations to cell-cell adhesion and planar cell polarity alter the flow of cells in three dimensions. He will then simulate convergent extension processes in the developing zebrafish spinal column using the deformable particle (DP) model in two and three spatial dimensions in realistic boundary conditions that are both deformable and contractile. The DP model also makes it possible to systematically vary the cell shape, cell-cell adhesion, and single-cell motility strategy. The PI will compare the results of the simulations to those obtained from 3D imaging of cell motion and shape of both wildtype and mutant zebrafish embryos. The proposed work will provide two significant advances to our understanding of collective cell motion: (1) how can we map single-cell properties to features of collective cell migration, and (2) what is a sufficient degree of model complexity to capture important features of collective cell migration? Currently, models for collective cell migration do not model true cell deformability and realistic cell motility strategies, but they can qualitatively capture several aspects of collective cell migration. These proposed simulations of deformable particles in both two and three dimensions, along with three-dimensional imaging of live tissue, will allow the team to determine what model ingredients are required to quantitatively describe collective cell migration. This project also includes a number of education and outreach activities that leverage the PIs' involvement in the Integrated Graduate Program in Physical and Engineering Biology. Initiatives will include mentoring high school and undergraduate students in research, developing a course module on computational modeling of cell migration during zebrafish spinal column development, and hosting short courses aimed at improving the presentation of scientific topics to non-scientific audiences by graduate students.The PI proposes coordinated experimental and computational studies to understand the role of cell shape change, motility strategy, and adhesion on collective cell motion during the convergent extension process in the elongating tail bud of zebrafish embryos. The PI will develop novel deformable particle (DP) model simulations in dynamic, deformable boundaries in both two and three spatial dimensions, which can quantitatively describe cell- and tissue-level deformation of developing zebrafish embryos and predict the effect of changes to single-cell biophysical parameters on collective cell motion. Complementary experiments will be performed on zebrafish embryos with varied cell motility and cell-cell adhesion through mutations to the planar cell polarity pathway and cadherin-mediated adhesion that enable the predictions of the DP model to be tested experimentally.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.