Towards a quantitative and molecular understanding of budding yeast cell size control

对芽殖酵母细胞大小控制的定量和分子理解

• 批准号: 431480687
• 负责人: Dr. Kurt Michael Schmoller
• 金额: --
• 依托单位: Institut für Funktionale Epigenetik (IFE)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/431480687?language=en
• 关键词: Towards; quantitative; molecular; understanding; budding

Size is a key property of cells that has a strong impact on cell growth, determines the cellular amount of proteins and RNA, and is intricately linked to the size of organelles. Accordingly, tight control of cell size is crucial for survival of uni- and multicellular organisms. Across species, rapidly proliferating cell populations achieve size control by a coupling of cell growth and division. Since several decades, extensive efforts were directed towards understanding this coupling, but the underlying molecular mechanisms are still poorly understood. Due to the stochastic nature of cell cycle regulation, a quantitative approach, combining molecular biology, biophysical concepts and mathematical modeling will be necessary to achieve this goal.Unicellular model organisms, in particular budding and fission yeasts, have proven extremely valuable, not only due to their simple geometry, short generation time, and powerful tools available, but also because many aspects of cell cycle control are conserved from yeast to humans. Initially, genetic studies have revealed the regulatory networks involved in yeast cell size control. More recently, the rise of live-cell microscopy provided us with a wealth of single-cell data that resulted in a boost for the field and new phenomenological and mechanistic insights.Budding yeast cell size control occurs mainly at the G1/S transition, which ensures that cells that are born small grow longer during G1. During my postdoctoral work, I have used live-cell microscopy to reveal the underlying size-sensing mechanism. Briefly, I have shown that cell size control is based on the differential synthesis of a cell cycle activator, Cln3, and a cell cycle inhibitor, Whi5, with cell size. Cln3 synthesis increases with cell size, while Whi5 is produced with a size-independent rate. The higher inhibitor-to-activator ratio then ensures that smaller cells grow more before entering the next cell cycle. Importantly, however, this work was constrained to the situation of a constant environment, not accounting for the fact that a major purpose of cell size control is to adjust cell size according to dynamic changes in nutrient conditions.Here, I propose to use a combination of quantitative live-cell microscopy, molecular cell biology, and mathematical modeling, to obtain a quantitative understanding of nutrient-dependent cell size-adaptation. An important step will be to reveal the function of the Whi5 paralog Whi7, and the poorly understood cell cycle regulator Bck2. We will then use a full-cell-cycle modeling framework that we have previously used to explain the steady-state cell size distribution to unravel which cell cycle transitions and cell properties are regulated with changing nutrient conditions. In addition to fundamental insights into budding yeast cell size control, the proposed work will provide general concepts that will be helpful to understand cell size control and adaptation in more complex mammalian cells.

大小是细胞的一个关键属性，对细胞生长有很大影响，决定细胞中蛋白质和 RNA 的量，并且与细胞器的大小密切相关。因此，严格控制细胞大小对于单细胞和多细胞生物的生存至关重要。在物种之间，快速增殖的细胞群通过细胞生长和分裂的耦合来实现大小控制。几十年来，人们为理解这种耦合做出了广泛的努力，但其潜在的分子机制仍然知之甚少。由于细胞周期调节的随机性，需要结合分子生物学、生物物理概念和数学模型的定量方法来实现这一目标。单细胞模型生物，特别是芽殖酵母和裂殖酵母，已被证明极具价值，这不仅是因为其简单的几何结构、短的生成时间和强大的可用工具，还因为细胞周期控制的许多方面从酵母到人类都是保守的。最初，遗传学研究揭示了参与酵母细胞大小控制的调控网络。最近，活细胞显微镜的兴起为我们提供了丰富的单细胞数据，从而推动了该领域的发展，并带来了新的现象学和机制见解。出芽酵母细胞大小控制主要发生在 G1/S 转变时，确保出生时较小的细胞在 G1 期间生长得更长。在我的博士后工作期间，我使用活细胞显微镜来揭示潜在的尺寸传感机制。简而言之，我已经证明细胞大小控制是基于细胞周期激活剂 Cln3 和细胞周期抑制剂 Whi5 与细胞大小的差异合成。 Cln3 的合成随着细胞大小的增加而增加，而 Whi5 的生成速度与大小无关。较高的抑制剂与激活剂比率可确保较小的细胞在进入下一个细胞周期之前生长得更多。然而重要的是，这项工作仅限于恒定环境的情况，没有考虑到细胞大小控制的一个主要目的是根据营养条件的动态变化来调整细胞大小。在这里，我建议使用组合定量活细胞显微镜、分子细胞生物学和数学建模，以获得对营养依赖性细胞大小适应的定量理解。重要的一步是揭示 Whi5 旁系同源物 Whi7 的功能，以及人们知之甚少的细胞周期调节因子 Bck2。然后，我们将使用之前用于解释稳态细胞大小分布的全细胞周期建模框架，以阐明哪些细胞周期转变和细胞特性是随着营养条件变化而调节的。除了对芽殖酵母细胞大小控制的基本见解外，拟议的工作还将提供有助于理解更复杂的哺乳动物细胞中的细胞大小控制和适应的一般概念。