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

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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.