Systems Biology of Molecular Noise in Yeast

描述（由申请人提供）：细胞对细胞外信号的适当评估对所有生物体的正常功能至关重要。然而，细胞对环境作出适当反应的能力受到个体细胞反应中的生物变异或“噪声”的限制。即使基因相同的细胞在同质环境中也是如此。我们的总体假设是存在遗传编码的细胞控制系统，类似于人类工程系统中使用的那些调节噪声和塑造表型结果的系统，特别是在涉及细胞分化的复杂细胞回路中。我们试图通过i)理论指导的定向实验和ii)利用精确测量单个细胞表型的高通量正向遗传学的组合来验证这一假设。作为一个模型系统，我们选择了出芽酵母酿酒酵母的信息素反应分化途径，该途径具有许多实验优势。我们寻求继续一项已经富有成效的合作，将工程控制系统和随机理论的理论专业知识与高通量模式生物遗传学和分子生物学的专业知识结合起来。为了实现我们的目标，我们将建立在大量的初步工作基础上，以1)了解信息素途径MAP激酶反应性转录激活因子抑制剂抑制噪声的机制，2)确定信息素信号传导过程中噪声调节的遗传决定因素，以及3)验证多重反馈控制作为一个系统来防止灾难性信号转导事件的假设。总之，这些系统级的研究将揭示细胞控制分子噪声的遗传机制，以实现定量可复制的反应。公共卫生相关性：鉴于MAPK激酶信号在人类癌症中的核心作用，了解MAPK信号级联中的噪声抑制机制可能会影响我们对肿瘤进展和异质性的理解，同时暴露出治疗干预系统中的薄弱环节。

DESCRIPTION (provided by applicant): Proper assessment by cells of extracellular cues is essential for the normal functioning of all organisms. However, the ability of cells to respond properly to their environment is limited by biological variability or "noise" in the responses of individual cells. This is true of even genetically identical cells in a homogenous environment. Our global hypothesis is that there exist genetically-encoded cellular control systems akin to those used in human-engineered systems that modulate noise and shape phenotypic outcomes, particularly in complex cellular circuits involved in cell differentiation. We seek to test this hypothesis through a combination of i) theory- guided directed experiments, and ii) high-throughput forward genetics that exploit precise measurements of individual cell phenotypes. As a model system, we have chosen the pheromone response differentiation pathway of the budding yeast Saccharomyces cerevisiae, which offers numerous experimental advantages. We seek to continue an already-productive collaboration that brings together theoretical expertise in engineering control systems and stochastic theories with expertise in high-throughput model organism genetics and molecular biology. To achieve our goals, we will build on substantial preliminary work to 1) understand the mechanism of noise suppression by an inhibitor of the pheromone pathway MAP kinase- responsive transcriptional activator, 2) identify the genetic determinants of noise modulation during pheromone signaling, and 3) test the hypothesis that multiple feedback controls act as a system to prevent catastrophic signal transduction events. Together these systems-level studies will reveal the genetic mechanisms by which cells control molecular noise to achieve responses that are quantitatively reproducible. PUBLIC HEALTH RELEVANCE: Given the central role of MAP kinase signaling in human cancers, understanding the mechanisms of noise suppression within a MAPK signaling cascade may impact our understanding of tumor progression and heterogeneity while exposing weak links in the system for therapeutic intervention.