Howard Hughes Medical Institute and Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA.
Howard Hughes Medical Institute and Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA; Howard Hughes Medical Institute Janelia Research Campus, Ashburn, VA 20147, USA.
Curr Biol. 2020 Oct 5;30(19):3713-3723.e3. doi: 10.1016/j.cub.2020.07.035. Epub 2020 Aug 13.
Hydra vulgaris exhibits a remarkable capacity to reassemble its body plan from a disordered aggregate of cells. Reassembly begins by sorting two epithelial cell types, endoderm and ectoderm, into inner and outer layers, respectively. The cellular features and behaviors that distinguish ectodermal and endodermal lineages to drive sorting have not been fully elucidated. To dissect this process, we use micromanipulation to position single cells of diverse lineages on the surface of defined multicellular aggregates and monitor sorting outcomes by live imaging. Although sorting has previously been attributed to intrinsic differences between the epithelial lineages, we find that single cells of all lineages sort to the interior of ectodermal aggregates, including single ectodermal cells. This reveals that cells of the same lineage can adopt opposing positions when sorting as individuals or a collective. Ectodermal cell collectives adopt their position at the aggregate exterior by rapidly reforming an epithelium that engulfs cells adhered to its surface through a collective spreading behavior. In contrast, aggregated endodermal cells persistently lose epithelial features. These non-epithelialized aggregates, like isolated cells of all lineages, are adherent passengers for engulfment by the ectodermal epithelium. We find that collective spreading of the ectoderm and persistent de-epithelialization in the endoderm also arise during local wounding in Hydra, suggesting that Hydra's wound-healing and self-organization capabilities may employ similar mechanisms. Together, our data suggest that differing propensities for epithelialization can sort cell types into distinct compartments to build and restore complex tissue architecture.
普通Hydra 具有从无序的细胞聚集体中重新组装身体形态的显著能力。重新组装首先通过将两种上皮细胞类型（内胚层和外胚层）分别分拣到内层和外层来开始。区分外胚层和内胚层谱系以驱动分拣的细胞特征和行为尚未完全阐明。为了解剖这个过程，我们使用微操作将不同谱系的单个细胞定位在定义明确的多细胞聚集体的表面上，并通过实时成像监测分拣结果。尽管以前将分拣归因于上皮谱系之间的内在差异，但我们发现所有谱系的单个细胞都可以分拣到外胚层聚集体的内部，包括单个外胚层细胞。这表明，当作为个体或集体进行分拣时，同一谱系的细胞可以采取相反的位置。外胚层细胞集体通过快速形成一个上皮细胞来采用聚集体外部的位置，该上皮细胞通过集体扩展行为吞噬附着在其表面的细胞。相比之下，聚集的内胚层细胞持续失去上皮特征。这些非上皮化的聚集体，就像所有谱系的单个细胞一样，是通过外胚层上皮吞噬的附着乘客。我们发现，外胚层的集体扩展和内胚层的持续去上皮化也在 Hydra 的局部创伤中出现，这表明 Hydra 的创伤愈合和自我组织能力可能采用类似的机制。总之，我们的数据表明，不同的上皮化倾向可以将细胞类型分拣到不同的隔室中，以构建和恢复复杂的组织架构。
