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

在组织规模的几乎所有生物过程中，细胞都需要集体运动。理解集体细胞运动的最大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，细胞是否主动感知邻居的运动方向，或者细胞主要依靠细胞与细胞之间的黏附和邻居的排斥来集体移动？为了理解从单细胞属性到集体迁移的映射，PI提出了一种实验和计算相结合的方法来研究斑马鱼脊柱发育过程中收敛延伸过程中的集体细胞迁移。利用共聚焦显微镜和遗传变异，PI将测量细胞间黏附和平面细胞极性的变化如何改变细胞在三维中的流动。然后，他将在现实边界条件下使用可变形粒子(DP)模型在二维和三维空间模拟斑马鱼脊柱发育中的收敛伸展过程，这些边界条件既可变形又可收缩。DP模型还使得系统地改变细胞形状、细胞-细胞黏附和单细胞运动策略成为可能。PI将把模拟的结果与野生型和突变斑马鱼胚胎的细胞运动和形状的3D成像获得的结果进行比较。拟议的工作将为我们理解集体细胞运动提供两个重要的进步：(1)我们如何将单个细胞的属性映射到集体细胞迁移的特征，以及(2)什么是足够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。这些拟议的对二维和三维可变形粒子的模拟，以及对活组织的三维成像，将使该团队能够确定需要哪些模型成分来定量描述集体细胞迁移。该项目还包括一些教育和外展活动，这些活动利用了PIS对物理和工程生物学综合研究生课程的参与。计划将包括指导高中生和本科生的研究，开发一个课程模块，在斑马鱼脊柱发育过程中建立细胞迁移的计算模型，并举办旨在改善研究生向非科学受众展示科学主题的短期课程。PI建议进行协调的实验和计算研究，以了解细胞形状变化、运动策略和黏附在斑马鱼胚胎细长尾芽的会聚延伸过程中对集体细胞运动的作用。PI将在二维和三维动态可变形边界上开发新的可变形粒子(DP)模型模拟，该模型可以定量描述斑马鱼胚胎发育中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。将在斑马鱼胚胎上进行补充实验，通过突变平面细胞极性途径和钙粘附素介导的黏附，使DP模型的预测能够得到实验验证。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.