Mechanisms of noise regulation in cell fate transitions

 描述(申请人提供)：细胞行为受环境信号控制，包括营养物质、渗透压力、激素和神经递质。直到最近，研究人员才开始研究不同细胞对这些刺激的反应是如何变化的。本项目主要研究细胞信号转导中的噪声调节机制及其在决定细胞命运中的作用。我们的研究利用了酵母中的一个原型G蛋白信号通路。在这个系统中，多肽交配信息素激活细胞表面受体、G蛋白和MAP激酶信号级联。我们最近的工作揭示了几个通路组件以动态的方式调节通路的依赖于时间的噪声特性。这一观察结果激发了我们的初步假设，即负责细胞间可变性的噪声源受到调控，以促进细胞在不断变化的环境条件下存活。在某些情况下，波动可以作为“更好的对冲”机制，使一群同基因细胞的反应多样化，而在其他情况下，当细胞面临多种竞争刺激时，可能需要噪声抑制来适当协调反应途径。我们的研究计划使用微流控设备和荧光成像在受控良好的环境中跟踪单个细胞，使用定量图像分析来表征信号和基因表达的波动，并使用随机建模来建议和测试噪声调节机制。以下目的将用于确定噪音在塑造细胞行为中的作用，并确定调节IS特性的生物回路：目的1分析噪音对细胞分化或增殖决策的影响。目的2分析两个MAPK通路之间协调所需的噪声抑制机制，一个促进分化，另一个是适应渗透胁迫所必需的。目的3分析噪音在向年龄相关不孕症转变过程中的影响。我们的发现将揭示调节噪声的信号电路的组织和逻辑，以及噪声在多大程度上影响细胞的命运、决定和生存。这样的系统水平原则可能被从酵母到人类的各种有机体中的许多信号通路所共享。酵母是这些分析的理想平台；种群中的所有细胞在基因上都是相同的，并且可以在统一和容易调节的生长条件下保持。基因的可操纵性是无与伦比的，任何变化的后果都很容易量化。因此，通过遗传或环境变化来调制噪声，测量其功能后果，开发计算模型并进行实验测试是可行的。这种综合方法既适用于假设生成，也适用于假设检验。最后，酵母中的信号通路使用了与人类同源的细胞表面受体、G蛋白、MAP蛋白和细胞周期蛋白依赖蛋白(CDK)。因此，酵母中发现的信号机制将为人类的生理学和药理学提供信息。

 DESCRIPTION (provided by applicant): Cellular behavior is controlled by environmental signals including nutrients, osmotic stress, hormones and neurotransmitters. Only recently have investigators begun to address how the response to any of these stimuli varies from cell to cell. This project focuses on mechanisms of noise regulation in cellular signal transduction and their role in determining cell fate. Our investigation exploits a prototype G protein signaling pathway in yeast. In this system, a peptide mating pheromone activates a cell surface receptor, a G protein, and a MAP kinase signaling cascade. Our recent work revealed that several pathway components act in a dynamic manner to regulate the time-dependent noise characteristics of the pathway. This observation motivated our primary hypothesis that the sources of noise responsible for cell-to-cell variability are regulated to promote cellular survival under changing environmental conditions. In certain contexts, fluctuations may serve as "bet-hedging" mechanisms to diversify the response of a population of isogenic cells, whereas in other contexts noise suppression may be required to properly coordinate response pathways when cells are faced with multiple competition stimuli. Our research plan uses microfluidic devices and fluorescent imaging to follow single cells in well controlled environments, quantitative image analysis to characterize fluctuations in signaling and gene expression, and stochastic modeling to suggest and test noise regulation mechanisms. The following aims will be used to determine the role of noise in shaping cellular behavior and identify the biological circuits that regulate is properties: Aim 1 analyzes effects of noise on the cellular decision to differentiate or proliferat. Aim 2 analyzes mechanisms of noise suppression required for coordination between two MAP kinase pathways, one that promotes differentiation and one that is required for adaptation to osmotic stress. Aim 3 analyzes effects of noise in the transition to age-dependent sterility. Our findings will reveal the organization and logic of signaling circuits that regulate noise and to wht extent noise influences cell fate decisions and survival. Such systems level principles are likely to be shared by many signal pathways in organisms ranging from yeast to humans. Yeast is an ideal platform for these analyses; all of the cells in the population are genetically identical, an can be maintained under uniform and easily modulated growth conditions. Genetic manipulability is unparalleled and the consequences of any changes are easily quantified. Thus it is practical to modulate noise by genetic or environmental changes, measure the functional consequences, develop computational models and test them experimentally. This integrated approach is ideal for both hypothesis-generating and hypothesis- testing. Finally, the signaling pathway in yeast employs cell-surface receptors, G proteins, MAP kinases, and cyclin dependent kinases (CDKs) homologous to those found in humans. Thus signaling mechanisms identified in yeast will inform human physiology and pharmacology.