Physical Mechanisms of Cell State Transitions: Size Homeostasis in Budding Yeast

在所有物种中，细胞生长和分裂都紧密协调以建立稳态的细胞大小。大小控制优化了单细胞物种在可变环境条件下的适应性，对于多细胞生物体的适当器官发育和维护至关重要。在人类中，控制细胞生长、分裂或大小的网络的破坏与许多疾病有关，包括癌症、代谢综合征和心肌病。在芽殖酵母中，大小由营养物质调节。在营养丰富的情况下，细胞生长快，体积大；在营养贫乏的情况下，细胞生长缓慢，体积小。该 PI 将使用最先进的定量成像方法、遗传操作和数学模型的独特组合来构建出芽酵母细胞大小稳态的系统级框架。这些研究将回答一个长期存在的问题：细胞如何知道它们何时大到足以分裂？将此处提出的方法应用于其他重要的细胞状态转变将为私营部门开发用于组织工程和药物发现的新产品或工艺奠定基础。拟议的项目提供生物学、基因工程、物理学、计算和数学方面高度跨学科的研究生培训。作为 CBIS 本科生研究计划、针对少数族裔机构的 BCBP 暑期实习计划和 CBIS 高中学者计划的一部分，Royer 集团招收了大量本科生。参加这些项目的学生将体验到他们知识的“现实生活”应用。研究中涉及的独特广泛的技能将有助于他们为日益跨学科的科学技术做好准备。作为 RPI 生物化学和生物物理学研究生项目的主任，PI 将在每年的生物物理学周期间向东北部的四年制大学和公众组织外展活动。假设是激活 G1/S 调节子的转录因子导致分裂，差异性和动态地整合营养信号以协调生长和分裂，从而实现细胞大小的适应性营养调节。该项目有三个具体目标：i) 以超分辨率绘制 G1/S 转录激活子核组织作为大小和营养物质的函数，ii) 测量和模拟营养依赖性起始动力学，以及 iii) 定义细胞大小营养调节的上游信号通路和目标。尽管在芽殖酵母中鉴定了数百个与大小控制有关的基因，但这种复杂的遗传网络如何影响启动机制来控制大小仍然是个谜。 PI 将超越大小控制网络的定性遗传特征，进而定量了解该网络如何动态处理信息。 PI 将使用的策略将对复杂的生物状态转变、分裂承诺进行全面、定量的评估。起始因子浓度和超分辨率定位的测量将确定细胞大小营养控制的关键参数。这些数学模型将作为检验假设的概念框架，并将告知包括人类在内的高等生物体细胞分裂的物理原理。最后，结果将揭示细胞间异质性或生物噪音对细胞生长以及分裂和大小稳态动态的影响。这项工作将为严格理解进化如何塑造分子网络以应对随机环境以及如何建立稳健的细胞决策奠定基础。该项目得到了物理和细胞动力学与功能部门的生命系统物理学项目以及分子和细胞生物科学部门的系统和合成生物学项目的联合支持。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

In all species, cell growth and division are tightly coordinated to establish a homeostatic cell size. Size control optimizes fitness under variable environmental conditions in unicellular species, and is critical for proper organ development and maintenance in multi-cellular organisms. In humans, disruption of the networks that control cell growth, division or size is linked to many diseases, including cancer, metabolic syndrome, and cardiomyopathy. In budding yeast, size is modulated by nutrients. Cells grow fast and are large in rich nutrients and slowly and are small in poor nutrients. The PI will use a unique combination of state-of-the-art quantitative imaging methods, genetic manipulation, and mathematical modeling to construct a systems-level framework for cell size homeostasis in budding yeast. These studies will answer the longstanding question: How do cells know when they are big enough to divide? Application of the approach proposed here to other important cell state transitions will provide the foundation for the development in the private sector of new products or processes for in-tissue engineering and drug discovery. The proposed project provides highly interdisciplinary graduate training in biology, genetic engineering, physics, computation and mathematics. The Royer group hosts a large number of undergraduate students as part of the CBIS Undergraduate Research Program, the BCBP Summer internship program for predominantly minority institutions and the CBIS High School Scholars Program. Students participating in these programs will experience a "real life" application of their knowledge. The uniquely broad set of skills implicated in the research will help to prepare them for the increasingly interdisciplinary word of science and technology. The PI as Director of the RPI Graduate Program in Biochemistry and Biophysics will organize outreach to four-year colleges in the Northeast and to the public annually during Biophysics week.The hypothesis is that the transcription factors which activate the G1/S regulon leading to commitment to division, differentially and dynamically integrate nutrient signals to coordinate growth and division, thereby enabling adaptive nutrient modulation of cell size. This project has three specific objectives: i) Map the G1/S transcriptional activator nuclear organization at super-resolution as a function of size and nutrients, ii) Measure and model nutrient dependent Start dynamics, and iii) Define the upstream signaling pathways and targets for nutrient modulation of cell size. Despite the identification of literally hundreds of genes implicated in size control in budding yeast, it remains a mystery how this complex genetic network impacts the Start machinery to control size. The PI will move beyond the qualitative genetic characterization of the size control network to a quantitative understanding of how this network dynamically processes information. The strategy that will be used by the PI will provide a comprehensive, quantitative assessment of a complex biological state transition, commitment to division. The measurements of Start factor concentration and super-resolution localization will identify the key parameters for nutrient control of cell size. The mathematical models will serve as a conceptual framework for testing hypotheses, and will inform physical principles of cell division in higher organisms, including humans. Finally, the results will reveal the impact of cell-to-cell heterogeneity, or biological noise, on cell growth and the dynamics of commitment to division and size homeostasis. This work will provide the foundation for a rigorous understanding of how evolution has shaped molecular networks to cope with a stochastic environment and how robust cellular decision-making is established. This project is being jointly supported by the Physics of Living Systems program in the Division of Physics and the Cellular Dynamics and Function as well as the Systems and Synthetic Biology Programs in the Division of Molecular and Cellular Biosciences.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.