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

从单细胞到多细胞的转变引发了动物的进化，这是生命史上最重要和最不为人所知的事件之一。从对苍蝇和小鼠等传统研究模型的研究中，我们了解到无数的机制已经进化到满足多细胞条件的要求，例如细胞与细胞的附着，细胞与细胞的通信，以及区分自己的细胞与其他生物体的细胞的能力（自我识别）。该项目的目标是扩大这一研究领域，将海绵包括在内，海绵与所有其他动物有数亿年的不同。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，统一的设计原则，共同的和祖先的所有动物，可以推断从海绵的研究。现有的证据表明，海绵细胞附着和自我识别依赖于一种称为“聚集因子”的分子复合物，这种分子复合物在其他动物中没有发现。然而，聚集因子的组成并不完全清楚;目前还不清楚是否所有的海绵都产生这种复合物;也完全不知道它与其他动物的分子系统有何关系。这项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大：1）发展一个公民科学计划，记录北美淡水海绵的多样性和分布，2）发展一个开放获取的知识库，其中有新开发的工具和技术，用于在实验室培养和实验操作海绵，以及e）培训学生。长期以来的观点是，与任何其他动物不同，海绵组织是松散组织的，其中细胞包埋在部分由聚集因子（AF）组成的共同细胞外基质中。AF被认为是交联相邻细胞并用于自我/非自我识别。但是，对这种观点的一个重要警告是，聚集因子主要是在体外研究的（在细胞聚集研究中），而最近对完整组织的研究揭示了基于钙粘蛋白和整合素的细胞连接的重要作用，就像其他动物的上皮组织一样。拟议的研究将使用1）蛋白质组学方法来全面确定不同海绵谱系中的AF组成，2）免疫染色来确定组织中AF和细胞连接的相对分布，3）免疫共沉淀和下拉来测试AF与细胞连接之间的内源性相互作用，和4）干扰AF介导的细胞聚集和自我识别过程中整联蛋白信号传导的小分子和肽。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进化起源的理解。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

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.