FGFR-dependent tissue separation in Hydra: the role of actomyosin interactions and cell polarity

淡水水螅属于非两侧动物门刺胞动物，具有简单的身体构造。两个细胞单层，外胚层和内胚层，形成管状体柱，由双功能上皮-肌肉细胞组成。营养良好的珊瑚虫将组织侧向输出成芽，芽在4天后通过未知的机制与母体分离。我们先前表明，芽脱离是在FGFR信号传导的控制下，并且FGFR α靶向肌动蛋白细胞骨架。我们现在将研究最近确定的Rho依赖的候选途径下游的FGFR信号传导，这可能会改变肌动球蛋白的收缩性，流动性和刚度的肌动球蛋白复合物的细胞-细胞和细胞-基质相互作用的作用。我们的目标是：a）阐明Hydra Rho的时空激活及其与细胞形状变化的联系，B）确定特定肌动蛋白成核剂和肌球蛋白II亚型的分布（和功能），以及c）了解分离部位是否发生细胞极性变化。有趣的机制方面的问题，是否双功能上皮肌细胞使用其基础收缩肌收缩过程中除了细胞骨架肌动球蛋白复合物。我们的项目将有助于阐明组织分离的独特过程。

The freshwater polyp Hydra belongs to the nonbilaterian phylum Cnidaria and displays a simple body architecture. Two cell monolayers, the ecto- and the entoderm, form the tubular body column and consist of bifunctional epithelio-muscular cells. Well fed polyps export tissue laterally into a bud, which detaches 4 days later from the parent by an unknown mechanism. We previously showed that bud detachment is under control of FGFR signaling and that FGFRa targets the actin cytoskeleton. We will now investigate the role of a recently identified Rho-dependent candidate pathway downstream of FGFR signaling, which likely alters actomyosin contractility, fluidity and stiffness of actomyosin complexes essential for cell-cell and cell-matrix interactions. Our goals are a) to elucidate the spatiotemporal activation of Hydra Rho and its connection to cell shape changes, b) to determine the distribution (and function) of specific actin nucleators and myosin II subtypes and c) to understand, whether cell polarity changes occur at the detachment site. Interesting under mechanistic aspects is the question, whether the bi-functional epitheliomuscular cells use their basal contractile muscle processes for constriction in addition to cytoskeletal actomyosin complexes. Our project will help to elucidate a unique process of tissue separation.