Systems Biology of Molecular Noise in Yeast

描述(申请人提供)：细胞对细胞外信号的正确评估对于所有生物体的正常功能是必不可少的。然而，细胞对环境做出适当反应的能力受到单个细胞反应中的生物变异性或“噪音”的限制。在同质环境中，即使是基因相同的细胞也是如此。我们的全球假设是，存在类似于人类工程系统中使用的遗传编码的细胞控制系统，它调节噪音并塑造表型结果，特别是在涉及细胞分化的复杂细胞电路中。我们试图通过i)理论指导的实验和ii)利用单个细胞表型的精确测量的高通量正向遗传学的组合来检验这一假设。作为一个模型系统，我们选择了发芽酵母信息素反应分化途径，这提供了许多实验优势。我们寻求继续进行已经卓有成效的合作，将工程控制系统的理论专业知识和随机理论与高通量模型生物遗传学和分子生物学的专业知识结合在一起。为了实现我们的目标，我们将在大量前期工作的基础上，1)了解信息素途径MAP激酶反应转录激活剂抑制噪声的机制，2)确定信息素信号过程中噪声调制的遗传决定因素，以及3)测试多个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。这些系统水平的研究将共同揭示细胞控制分子噪声以实现可定量重现的反应的遗传机制。公共卫生相关性：鉴于MAPK信号在人类癌症中的核心作用，了解MAPK信号级联中噪音抑制的机制可能会影响我们对肿瘤进展和异质性的理解，同时暴露出系统中用于治疗干预的薄弱环节。

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.