Towards an integrative model of cell adhesion and self-recognition in sponge (Porifera) tissues

从单细胞生物到多细胞生物的转变开始了动物的进化，这是生命史上最重要也是最不为人所知的事件之一。从对苍蝇和老鼠等传统研究模型的研究中，我们了解到，为了满足多细胞条件的需求，无数的机制已经进化出来，比如细胞间的附着，细胞间的交流，以及将自己的细胞与其他生物体的细胞区分开来的能力（自我识别）。该项目的目标是扩大这一研究领域，将海绵纳入其中，因为海绵与其他所有动物都有数亿年的差异。在某种程度上，海绵和任何其他动物使用相同的分子机制来介导细胞-细胞相互作用，可以从海绵的研究中推断出所有动物共同的和祖先的统一设计原则。现有证据表明，海绵细胞的附着和自我识别依赖于一种称为“聚集因子”的分子复合物，这种复合物在其他动物中没有发现。然而，聚集因子的组成尚不完全清楚；目前尚不清楚是否所有海绵都产生这种复合物；我们完全不知道它与其他动物的分子系统有什么关系。本研究的目的是了解聚集因子和其他相关蛋白在聚集、粘附和通讯中的作用。除了直接的科学目标，这项研究的影响将通过以下方式扩展：1)发展公民科学计划，记录北美淡水海绵的多样性和分布；2)开发一个开放获取的新开发的工具和技术库，用于在实验室培养和实验操作海绵；e)培训学生。长期以来的观点是，与其他动物不同，海绵组织组织松散，细胞嵌入在共同的细胞外基质中，部分由聚集因子（AF）组成。AF被认为与相邻细胞交联，并在自我/非自我识别中起作用。但是，对这一观点的一个重要警告是，聚集因子主要是在体外研究（在细胞聚集研究中），而最近对完整组织的研究揭示了钙粘蛋白和整合素为基础的细胞连接的重要作用，就像其他动物的上皮组织一样。本研究将使用1)蛋白质组学方法综合测定不同海绵谱系中AF的组成，2)免疫染色测定AF和细胞连接在组织中的相对分布，3)共免疫沉淀和拉下测试AF与细胞连接之间的内源性相互作用，以及4)小分子和肽在AF介导的细胞聚集和自我识别过程中干扰整合素信号。从概念上讲，这些结果将阐明海绵中多细胞完整性是如何维持的，并增加对动物多细胞完整性和组织组织的进化起源的理解。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The transition from unicellularity to multicellularity initiated the evolution of animals, one of the most important and least understood events in the history of life. From the study of traditional research models like flies and mice we have learned that myriad mechanisms have evolved to meet the demands of the multicellular condition, such as cell-cell attachment, cell-cell communication, and the ability to distinguish one’s own cells from those of other organisms (self-recognition). The goal of this project is to broaden this body of research to include sponges, which are hundreds of millions of years divergent from all other animals. To the extent that sponges and any other animal use the same molecular mechanisms for mediating cell-cell interactions, unifying design principles, both common and ancestral to all animals, may be inferred from the study of sponges. The available evidence indicates that sponge cell-attachment and self-recognition depend upon a molecular complex termed the ‘Aggregation Factor’ that is not found in other animals. However, the composition of the Aggregation Factor is incompletely known; it is unclear whether all sponges produce this complex; and it is entirely unknown how it relates to molecular systems in other animals. The goal of the proposed research is to understand the role of aggregation factor and other associated proteins in aggregation, adhesion, and communication. Beyond the immediate scientific goals, the impact of this research will be extended through: 1) development of a citizen science program to document the diversity and distribution of freshwater sponges in North America, 2) development of an open-access repository of newly developed tools and techniques for cultivation and experimental manipulation of sponges in the laboratory, and e) training of students.The long-held view is that, unlike any other animal, sponge tissues are loosely organized, with cells embedded in a common extracellular matrix composed, in part, of the Aggregation Factor (AF). The AF is thought to cross-link adjacent cells and to serve in self/non- self-recognition. But, an important caveat to this view is that the Aggregation Factor has predominantly been studied in vitro (in cell aggregation studies), whereas more recent studies of intact tissues have revealed an important role for cadherin- and integrin-based cell junctions, much like epithelial tissues in other animals. The proposed research will use 1) proteomic methods to comprehensively determine AF composition in diverse sponge lineages, 2) immunostaining to determine the relative distribution of the AF and cell junctions in tissues, 3) co- immunoprecipitation and pull-downs to test for endogenous interactions between the AF with cell junctions, and 4) small molecules and peptides to perturb integrin signaling in AF-mediated processes of cell aggregation and self-recognition. Conceptually, these results will clarify how multicellular integrity is maintained in sponges and increase the understanding of the evolutionary origin of multicellular integrity and tissue organization in animals.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.