fluorescent-situ-hybridization-5-ethynyl-2-deoxyuridine-labeling-for

Fluorescent <em>In Situ</em> Hybridization and 5-Ethynyl-2'-Deoxyuridine Labeling for Stem-Like Cells in the Hydrozoan Jellyfish <em>Cladonema pacificum</em>

Cnidarians, including sea anemones, corals, and jellyfish, exhibit diverse morphology and lifestyles that are manifested in sessile polyps and ...

Tohoku University

Jellyfish have existed on the earth for around 600 million years and have evolved in response to environmental changes. Hydrozoan jellyfish, members of phylum Cnidaria, exist in multiple life stages, including planula larvae, vegetatively-propagating polyps, and sexually-reproducing medusae. Although free-swimming medusae display complex morphology and exhibit increase in body size and regenerative ability, their underlying cellular mechanisms are poorly understood. Here, we investigate the roles of cell proliferation in body-size growth, appendage morphogenesis, and regeneration using  as a hydrozoan jellyfish model. By examining the distribution of S phase cells and mitotic cells, we revealed spatially distinct proliferating cell populations in medusae, uniform cell proliferation in the umbrella, and clustered cell proliferation in tentacles. Blocking cell proliferation by hydroxyurea caused inhibition of body size growth and defects in tentacle branching, nematocyte differentiation, and regeneration. Local cell proliferation in tentacle bulbs is observed in medusae of two other hydrozoan species,  and , indicating that it may be a conserved feature among hydrozoan jellyfish. Altogether, our results suggest that hydrozoan medusae possess actively proliferating cells and provide experimental evidence regarding the role of cell proliferation in body-size control, tentacle morphogenesis, and regeneration.

Cell proliferation controls body size growth, tentacle morphogenesis, and regeneration in hydrozoan jellyfish .

Medusozoans, the Cnidarian subphylum, have multiple life stages including sessile polyps and free-swimming medusae or jellyfish, which are typically bell-shaped gelatinous zooplanktons that exhibit diverse morphologies. Despite having a relatively complex body structure with well-developed muscles and nervous systems, the adult medusa stage maintains a high regenerative ability that enables organ regeneration as well as whole body reconstitution from the part of the body. This remarkable regeneration potential of jellyfish has long been acknowledged in different species; however, recent studies have begun dissecting the exact processes underpinning regeneration events. In this article, we introduce the current understanding of regeneration mechanisms in medusae, particularly focusing on cellular behaviors during regeneration such as wound healing, blastema formation by stem/progenitor cells or cell fate plasticity, and the organism-level patterning that restores radial symmetry. We also discuss putative molecular mechanisms involved in regeneration processes and introduce a variety of novel model jellyfish species in the effort to understand common principles and diverse mechanisms underlying the regeneration of complex organs and the entire body.

Sosuke Fujita

Graduate School of Life Sciences

Tohoku University

Fluorescent In Situ Hybridization and 5-Ethynyl-2'-Deoxyuridine Labeling for Stem-Like Cells in the Hydrozoan Jellyfish Cladonema pacificum

Sosuke Fujita

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Tohoku University

Fluorescent In Situ Hybridization and 5-Ethynyl-2'-Deoxyuridine Labeling for Stem-Like Cells in the Hydrozoan Jellyfish Cladonema pacificum

Graduate School of Life Sciences