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.

大小是细胞的关键特性，对细胞生长有很大影响，确定蛋白质和RNA的细胞量，并且与细胞器的大小相关。因此，对细胞大小的严格控制对于单细胞和多细胞生物的存活至关重要。在整个物种之间，快速增殖的细胞群通过细胞生长和分裂的耦合来控制尺寸。自几十年以来，广泛的努力是为了理解这种耦合，但是基本的分子机制仍然很少了解。由于细胞周期调节的随机性质，一种定量方法，结合了分子生物学，生物物理概念和数学模型对于实现这一目标是必要的。非细胞模型的生物，特别是崭露头角的酵母菌，特别是有价值的，这是非常有价值的，这不仅是由于它们的简单几何学，短期的时间，而且还依靠许多方面，因此它们也是如此，因为它们的简单几何学，也是如此，因为它们是许多方面的控制，因此也是如此。最初，遗传研究揭示了与酵母细胞大小控制有关的调节网络。最近，活细胞显微镜的兴起为我们提供了大量的单细胞数据，从而促进了该领域以及新的现象学和机械洞察力。假设酵母细胞大小控制主要发生在G1/S的过渡上，这确保了在G1期间出生的细胞生长更长的细胞。在博士后工作中，我使用了活细胞显微镜来揭示潜在的尺寸感应机制。简而言之，我已经表明，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的差异合成。 CLN3合成随细胞尺寸而增加，而WHI5则以尺寸无关的速率产生。然后，较高的抑制剂与激活剂的比率可确保在进入下一个细胞周期之前较小的细胞生长更多。然而，重要的是，这项工作被限制在恒定环境的情况下，而不是考虑到细胞尺寸控制的主要目的是根据养分状况的动态变化来调整细胞大小。一个重要的步骤是揭示WHI5旁系同源物WHI7的功能，以及较知的细胞周期调节剂BCK2。然后，我们将使用以前使用的全细胞周期建模框架来解释稳态细胞尺寸分布，以解开哪些细胞周期过渡和细胞性质受到养分条件的调节。除了对萌芽酵母细胞大小控制的基本见解外，提出的工作还将提供一般概念，有助于了解更复杂的哺乳动物细胞中的细胞尺寸控制和适应。