Mechanisms underlying cell-fate patterns in yeast communities

描述（由申请人提供）：由于营养物质在发育中的酵母菌落中变得有限，可以诱导至少3种不同的细胞分化程序：1）假菌丝分化（觅食反应），2）孢子形成和3）程序性细胞死亡。有趣的是，决定单个细胞在群体中命运选择的一个关键因素是地理因素;殖民地的不同区域会有不同的命运。事实上，我们最近发现菌落中形成孢子的细胞层和未形成孢子的细胞层之间形成明显的边界。酵母菌群内的模式形成可能提供了比非模式社区的功能优势。Honigberg实验室的长期目标是确定调节酵母菌落从同质到高度模式化社区的自组织机制。鉴于上述菌落区域之间的清晰边界，这些机制的关键部分可能是细胞间信号传导。当前建议的中心假设是，琼脂表面附近的菌落中的细胞层经历凋亡程序性细胞死亡（PCD），提供营养物或其他信号，刺激上覆细胞层中的孢子形成。三个互补的方法来解决上述假设。第一种方法是确定集落发育时信号传导途径和细胞过程的活性。具体来说，我们将悬浮集落和分析悬浮细胞使用分子方法，如蛋白磷酸化测定或细胞学方法，如监测凋亡标志物。第二种方法是将集落切片以研究基因表达、蛋白定位和细胞分化的空间模式。最后一种方法是监测细胞命运的社区含有不同基因型的菌株的混合物，以测试假设所需的PCD，孢子形成和图案的殖民地的细胞自主性。生物体之间交流的最古老和最基本的目的之一可能是让这些微生物自我组织成功能性社区。酵母菌群提供了一个机会，调查这种类型的通信。除了科学兴趣之外，拟议研究的健康相关性还来自以下事实：被称为生物膜的病原性酵母菌的有组织群落可以在植入的医疗器械上形成，并且这些生物膜的组织对医院获得性真菌感染的致命性有显著贡献。

DESCRIPTION (provided by applicant): As nutrients become limiting in developing yeast colonies, at least 3 different cell differentiation programs can be induced: 1) pseudohyphal differentiation (a foraging response), 2) sporulation, and 3) programmed cell death. Intriguingly, a key aspect determining an individual cell's choice of fate within a colony is geographical; different regions of the colony adopt different fates. Indeed, we recently discovered that sharp boundaries form between layers of sporulated and unsporulated cells in colonies. Pattern formation within yeast communities likely provides functional advantages over unpatterns communities. The long-range goal of the Honigberg lab is to identify the mechanisms that regulate the self- organization of yeast colonies from homogeneous to highly patterned communities. Given the sharp boundaries between the colonies regions mentioned above, a key part of these mechanisms is likely cell-to- cell signaling. The central hypothesis of the current proposal is that a layer of cells in colonies near the agar surface undergoes apoptotic programmed cell death (PCD), providing nutrients or other signals the stimulate sporulation in an overlying layer of cells. Three complementary approaches are taken to address the above hypothesis. The first approach is to determine the activity of signaling pathways and cellular processes as colonies develop. Specifically, we will suspend colonies and assay the suspended cells using molecular approaches such as protein phosphorylation assays or and cytological approaches such as monitoring apoptotic markers. The second approach is to section colonies to investigate spatial patterns of gene expression, protein localization and cell differentiation. The last approach is to monitor cell fates in communities containing mixtures of strains of different genotypes to test hypotheses regarding the cell autonomy required for PCD, sporulation and patterning in colonies. One of the most ancient and fundamental purposes for communication between organisms may have been to allow these microbes to self-organize into functional communities. Yeast colonies provide an opportunity to investigate this type of communication. In addition to the scientific interest, the health relevance of the proposed research derives from the fact that organized communities of pathogenic yeast termed biofilms can form on implanted medical devices, and that the organization of these biofilms contributes significantly to the lethality of hospital-acquired fungal infections.