The Rapid Growth of Jellyfish Tentacles: A Few Days’ Transformation

Japanese scientists have discovered that the cladoceran jellyfish uses stem-like proliferating cells to regenerate its tentacles, providing new insights into the process of blastogenesis and its evolutionary similarities in other organisms. . seed Like a salamander.

A type of jellyfish about the size of a little fingernail cladonema Amputated tentacles can regrow in a few days, but how do they regrow? Functional tissue regeneration across species such as salamanders and insects repairs damage and grows into missing appendages It relies on its ability to form blastocytes, which are masses of undifferentiated cells. Jellyfish, like other cnidarians such as corals and sea anemones, exhibit high regenerative abilities, but how their vital blastema cells are formed has remained a mystery until now.

Japanese research team reveals that stem-like proliferating cells (actively growing and dividing but not yet differentiated into specific cell types) appear at injury sites and help form blastomas. I made it.

The results of this study were published in the journal Science on December 21st. PLOS Biology.

The jellyfish Cladonema pacificum exhibits branched tentacles that can strongly regenerate after amputation.Credit: Sou Fujita, University of Tokyo

“Importantly, these stem-like proliferating cells in the blastema are different from the resident stem cells localized in the tentacles,” said corresponding author Yuichiro Nakajima, a lecturer at the University of Tokyo’s Graduate School of Pharmaceutical Sciences. “Repair-specific proliferating cells primarily contribute to the newly formed tentacle epithelium (thin outer layer).”

According to Nakajima, the resident stem cells present in and near the tentacles are responsible for generating all cell lineages during homeostasis and regeneration, and maintain all the cells needed throughout the jellyfish’s life. means to repair. Repair-specific proliferating cells appear only upon injury.

“The combination of resident stem cells and repair-specific proliferating cells enables the rapid regeneration of functional tentacles within a few days,” Professor Nakajima said, adding that jellyfish use their tentacles to hunt and feed. he pointed out.

Resident stem cells (green) and repair-specific proliferating cells (red) contribute to the regeneration of Cladonema tentacles.Credit: Sou Fujita, University of Tokyo

According to lead author Sosuke Fujita, a postdoctoral researcher in the same laboratory as Nakajima at the Graduate School of Pharmaceutical Sciences, the discovery will help researchers understand how blastoma formation differs between different animal groups. It shows that you understand.

“In this study, our aim was to use the tentacles of the cnidarian jellyfish to address the mechanisms of blastogenesis. cladonema “As a regeneration model for non-bilateral animals, or animals that do not form bilaterally symmetrically during embryonic development,” Professor Fujita said, explaining that this study could provide insights from an evolutionary perspective.

For example, salamanders are bilaterally symmetrical animals that can regenerate limbs. Their limbs contain stem cells that are restricted to the needs of specific cell types, and this process is thought to function similarly to the repair-specific proliferating cells observed in jellyfish.

“Given that repair-specific proliferating cells are similar to restricted stem cells in the limbs of bilateral salamanders, the formation of blastema by repair-specific proliferating cells has been linked to complex organs and appendages during animal evolution. We can infer that this is a common feature that was acquired independently for organ regeneration,” said Fujita. Said.

After 72 hours of amputation, Cladonema’s regenerating tentacles are fully functional.Credit: Sou Fujita, University of Tokyo

However, the cellular origin of the repair-specific proliferating cells observed in blastema cells remains unclear, and researchers believe that the tools currently available to investigate their origin are too limited. They say they are unable to elucidate or identify other distinct stem-like cells. cell.

“It is essential to introduce genetic tools that allow tracing and intracellular manipulation of specific cell lineages. cladonema‘ said Nakajima. “Ultimately, understanding the mechanisms of blastoma formation in regenerating animals, including jellyfish, may help us identify cellular and molecular components that improve our own regenerative abilities.”

Reference: “Distinct stem-like cell populations promote functional regeneration of Cladonema medusa tentacles” by Sosuke Fujita, Mako Takahashi, Manabu Kumano, Erina Kuranaga, Masayuki Miura, and Yuichiro Nakajima, December 21, 2023. PLOS Biology.
DOI: 10.1371/journal.pbio.3002435

This research was supported by Grants-in-Aid for Scientific Research from the Japan Society for the Promotion of Science, the Japan Science and Technology Agency, the Japan Agency for Medical Research and Development, and a grant from the National Institute for Basic Biology Joint Research Project.