Humans have been interested in the notion of immortality since the beginning. While modern technology is making an effort to slow down the aging process, senescence is inevitable in any living organism. Our organs and cells gradually deteriorate until everything ceases to function. However, the discovery of immortal jellyfish shifted our perception of eternal life.

In the 1980s, students Christian Sommer and Giorgio Bavestrello accidentally discovered the regenerative abilities of immortal jellyfish (Turritopsis dohrnii). Their experiment was initially focused on monitoring polyps until they matured into medusae. When planula larvae, free-swimming, immature jellyfish, land on the seafloor, small stalked animals or polyps are generated. Eventually, polyps bud out or create small segments on top of each other that can mature into medusae, which are the adult forms of jellyfish.

Sommer and Bavestrello were expecting the jellyfish to mature before producing larvae, but to their surprise, many newly-generated polyps latched onto the jar. Through extensive observations, they realized that medusae could fall to the bottom of the jar when they are threatened and transform into polyps without fertilization. In other words, they have the ability to transform back into their juvenile form.

The cellular mechanism behind the rejuvenation of immortal jellyfish is called transdifferentiation. In the transdifferentiation process, a mature somatic cell can be transformed into another mature somatic cell with different functions. To investigate the exact genes that control this process, scientists take a detailed look at the genomes of the immortal jellyfish.

In a 2022 paper published in The Proceedings of the National Academy of Science, scientists Maria Pascual-Torner and Dido Carrero (among others) identified the genes of immortal jellyfish that are associated with telomere maintenance, stem cell reproduction, and DNA repair. To stimulate rejuvenation, researchers put the jellyfish under stress and recorded images of their genes during different stages of their development. The scientists observed opposite tendencies of two different types of genes during the transformation process.

First, the genes related to DNA silencing are expressed at a high level in their adult stage, but these genes become less active in making proteins when they become polyps again. However, genes associated with a cell’s ability to grow into many forms did the opposite. According to Dr. Pascual-Torner, this experiment suggests that DNA that is normally in storage is brought out during the transformation, and genes that coax cells to reset go into overdrive.

This research aroused many possibilities regarding the applications of regenerative genes. Is it possible that the same mechanism can benefit human beings? Science Teacher James Booth shared his thoughts on a process of making “induced pluripotent stem cells (iPSCs),” which reminds him of transdifferentiation. This technology tricks adult human cells into becoming embryonic cells (like rewinding the clock) and then differentiating those cells to become new adult cells. Since its discovery in 2006, people have been using this technology for clinical uses. Booth concluded that the process does not make us immortal, but rather takes some of our cells and lets them start over. Maybe that's a plausible path to increased human longevity (if not immortality): fixing broken parts, using similar "cellular rejuvenation" approaches, even if doing so at the level of an entire human organism the way the jellyfish does is a lot harder to imagine.”