Excitability in Dictyostelium Development

描述(由申请人提供)：发展背后的基本机制是什么？我们如何操纵、破坏或纠正它们？我建议研究盘基网柄菌的集体行为--一种经典的细胞-细胞信号传递的模式生物--重点研究单细胞动力学如何影响和引起聚集体的行为。在饥饿过程中，网柄苔藓细胞周期性地分泌趋化剂cAMP，诱导其他细胞产生cAMP。其结果是一个波浪形的信号中继，并最终形成细胞聚集。这种从单细胞到多细胞生命的转变提供了一个理想的系统，可以利用我在凝聚态物理方面的背景来解决生物学中的一个基本问题。在普林斯顿，我将与托马斯·格雷戈的实验室密切合作，该实验室开发了第一个细胞内cAMP浓度的FRET报告。他们的定量实验提供了一个独特的机会，将单个细胞的行为与随后的群体命运联系起来。 我的导师内德·温格伦是细菌趋化性、梯度感应和细胞间通讯方面的专家，他的指导将是一个无价的资源。通过对单细胞定量实验的分析，建立了单细胞对胞外cAMP反应的模型。我的初步研究表明，每个细胞的行为都像一个可兴奋的系统(一个最好的例子是尖峰神经元)。我将把这个模型推广到研究cAMP扩散所介导的集体空间动力学。在初步研究中，我考虑了一种“平均场”的情况，就像在良好混合的灌注室中一样，发现了一个有趣的动态群体感应转变。为了包括空间动力学，我将首先构建一个空间梯度传感模型--统一兴奋性、适应性和方向性传感的概念--由格雷戈尔实验室进行的基于微流体的实验指导。有了这个模型，我将通过模拟趋化细胞来定量复制聚集。我会将聚集保真度(通过丘状中心的大小和空间分布来衡量)与其他缺乏兴奋性动力学的趋化机制进行比较。然后，我将探索扰乱忠实聚集的方法，并预测可以在格雷戈尔实验室测试的各种网柄菌变异体的行为。回答这项建议中的问题需要在利用我在凝聚态物理理论方面的背景和参与复杂生物系统的细节之间取得适当的平衡。因此，拟议的项目是我转变为数量生物学领域的独立研究人员的理想选择-它将使我能够利用我已有的技能并开发新的技能。普林斯顿大学的环境，既得益于我的导师内德·温格伦教授和托马斯·格雷戈教授的指导，也得益于更大的定量生物学家社区，为发展成为一名有效的独立研究人员提供了理想的环境。

DESCRIPTION (provided by applicant): What basic mechanisms underlie development and how can we manipulate, disrupt, or correct them? I propose to study the collective behavior of Dictyostelium discoideum - a classic model organism for cell-cell signaling - focusing on how single-cell dynamics influence and give rise to the behavior of the aggregate. During starvation, Dictyostelium cells periodically secrete the chemoattractant cAMP, inducing production of cAMP in other cells. The result is a wavelike signal relay, and, ultimately, cellular aggregation. This transition from single-celled to multicellular life provides an ideal system to utilize my background in condensed matter physics to address a fundamental question in biology. At Princeton, I will collaborate closely with Thomas Gregor's lab, which developed the first FRET reporter of intracellular cAMP concentration. Their quantitative experiments provide a unique opportunity to connect the behavior of individual cells with the consequent fate of the population. The guidance of my mentor Ned Wingreen, an expert in bacterial chemotaxis, gradient sensing, and cell-cell communication, will be an invaluable resource. Through analysis of quantitative single-cell experiments, I have developed a model of the single-cell response to extracellular cAMP. My preliminary studies indicate that each cell behaves as an excitable system (a prime example is a spiking neuron). I will extend this model to study collective spatial dynamics mediated by diffusion of cAMP. In preliminary studies, I considered a "mean-field" situation, as in a well-mixed perfusion chamber, finding an intriguing dynamical quorum-sensing transition. To include spatial dynamics, I will first construct a model of spatial gradient sensing - unifying the concepts of excitability, adaptation, and directional sensing - guided by microfluidics-based experiments performed by the Gregor Lab. With this model, I will quantitatively reproduce aggregation through simulations of chemotactic cells. I will compare aggregation fidelity, measured by the size and spatial distribution of mound centers, against other chemotaxis mechanisms lacking excitable dynamics. I will then explore ways to disrupt faithful aggregation and make predictions for the behavior of various Dictyostelium mutants that can be tested in the Gregor Lab. Answering the questions in this proposal requires the right balance between using my background in condensed matter physics theory and engaging with the details of a complex biological system. The proposed project is therefore ideal for my transition to become an independent researcher working in the field of quantitative biology-it will allow me to use my established skills and to develop new ones. The environment at Princeton, both due to the guidance of my mentors, Professors Ned Wingreen and Thomas Gregor, and the greater community of quantitative biologists, provides an ideal setting to develop into an effective independent investigator.