Mechanisms underlying cell-fate patterns in yeast communities

描述（由申请人提供）：随着酵母菌落发育中的营养变得有限，至少可以诱导3种不同的细胞分化程序：1)假菌丝分化（觅食反应），2)产孢，3)程序性细胞死亡。有趣的是，在一个群体中，决定单个细胞命运选择的一个关键因素是地理；殖民地的不同地区有着不同的命运。事实上，我们最近发现，在菌落中有孢子和无孢子细胞层之间形成了明显的界限。酵母群落中的模式形成可能比非模式群落提供功能优势。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群落的自组织的机制。鉴于上述菌落区域之间的明显边界，这些机制的关键部分可能是细胞间的信号传导。目前这项研究的中心假设是，琼脂表面附近的一层细胞经历了凋亡程序性细胞死亡（PCD），为上一层细胞提供营养或其他信号，刺激其产生孢子。采用三种互补的方法来解决上述假设。第一种方法是确定信号通路和细胞过程在菌落发育过程中的活性。具体来说，我们将悬浮菌落并使用分子方法（如蛋白质磷酸化测定）和细胞学方法（如监测凋亡标记物）检测悬浮细胞。第二种方法是对菌落进行切片，以研究基因表达、蛋白质定位和细胞分化的空间格局。最后一种方法是监测含有不同基因型菌株混合物的群落中的细胞命运，以检验关于PCD、孢子形成和菌落模式所需的细胞自主性的假设。生物之间交流的最古老和最基本的目的之一可能是允许这些微生物自组织成功能群落。酵母菌落为研究这种类型的交流提供了机会。除了科学兴趣之外，拟议研究的健康相关性源于这样一个事实，即被称为生物膜的有组织的致病酵母菌群落可以在植入的医疗设备上形成，这些生物膜的组织对医院获得性真菌感染的致命性有重大贡献。

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.