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

在所有物种中，细胞的生长和分裂都是紧密协调的，以建立一个稳态的细胞大小。在单细胞物种中，大小控制可以优化在可变环境条件下的适应度，在多细胞生物中，大小控制对适当的器官发育和维持至关重要。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。在出芽的酵母中，大小受营养物质的调节。在营养丰富的情况下，细胞长得快而大，在营养不足的情况下，细胞长得慢而小。PI将使用最先进的定量成像方法，遗传操作和数学建模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：细胞如何知道它们什么时候大到可以分裂？将本文提出的方法应用于其他重要的细胞状态转变，将为私营部门开发组织工程和药物发现的新产品或新工艺提供基础。该计划提供生物学、基因工程、物理学、计算和数学等跨学科的研究生培训。作为CBIS本科生研究项目、cbbp少数族裔机构暑期实习项目和CBIS高中学者项目的一部分，罗耶集团接待了大量本科生。参加这些项目的学生将体验到他们的知识在“现实生活”中的应用。研究中涉及的独特的广泛技能将帮助他们为日益跨学科的科学和技术世界做好准备。PI作为RPI生物化学和生物物理学研究生项目的主任，将在每年的生物物理周期间组织向东北四年制大学和公众的宣传活动。该假说认为，激活G1/S调控导致细胞分裂的转录因子，通过差异和动态整合营养信号来协调生长和分裂，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)测量和建模营养依赖的Start动力学，以及iii)定义营养物质调节细胞大小的上游信号通路和目标。尽管已经确定了数百个与出芽酵母大小控制有关的基因，但这个复杂的遗传网络如何影响Start机制来控制大小仍然是一个谜。PI将超越大小控制网络的定性遗传特征，对该网络如何动态处理信息进行定量理解。PI将使用的策略将提供一个复杂的生物状态转变的全面定量评估，承诺分工。起始因子浓度和超分辨率定位的测量将确定细胞大小的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，并将为包括人类在内的高等生物细胞分裂的物理原理提供信息。最后，研究结果将揭示细胞间异质性或生物噪声对细胞生长和细胞分裂和大小动态平衡的影响。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稳健的细胞决策是如何建立的提供基础。该项目由物理系的生命系统物理学项目、细胞动力学和功能以及分子和细胞生物科学系的系统和合成生物学项目共同支持。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。

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.