Immortal jellyfish genes identified that may explain their long lives

By performing a DNA comparison of two similar jellyfish species, researchers have found the genes that could stop and reverse ageing in immortal jellyfish

By Jason P. Dinh

An immortal species of jellyfish has double copies of genes that protect and repair DNA. The finding could provide clues to human ageing and age-related conditions.

Jellyfish start their lives as drifting larvae. They eventually attach to the seafloor and develop into sprout-like polyps. The bottom-dwellers clone themselves, forming stacked, sedentary colonies that bud off into free-swimming umbrella-shaped medusas.

That stage is a dead end for most jellyfish – but the immortal jellyfish (Turritopsis dohrnii) can reverse the cycle. When times get tough, like in harsh environments or after injury, they melt their bodies into amorphous cysts, reattach to the seafloor and regress into polyps. They can restart the cycle indefinitely to skirt death by old age.

To find out how the immortal jellyfish staves off aging, Maria Pascual-Torner at the University of Oviedo in Spain and her colleagues sequenced its genome – its full set of genetic instructions – and compared it to that of the related but mortal crimson jellyfish (Turritopsis rubra).

They found the immortal jellyfish had twice as many copies of genes associated with DNA repair and protection. These duplicates could produce greater amounts of protective and restorative proteins. The jellyfish also had unique mutations that stunted cell division and prevented telomeres – chromosomes’ protective caps – from deteriorating.

Then, to pinpoint how T. dohrnii reverts into polyp form, the scientists looked at which genes were active during this reverse metamorphosis. They found the jellies silenced developmental genes to return cells to a primordial state and activated other genes that allow the nascent cells to re-specialise once a new medusa buds off. Together, Pascual-Torner says, these genetic alterations shield the animal from the weathering of time.

But Maria Pia Miglietta at Texas A&M University at Galveston points out that the crimson jellyfish can also rejuvenate, just not as commonly as T. dohrnii. Using them for comparison might reveal differences in the degree of immortality rather than the key to immortality itself, she says.

Still, Pascual-Torner says the genes they identified could be relevant to human ageing. They could inspire regenerative medicine or provide insights into age-related diseases like cancer and neurodegeneration. “The next step is to explore these gene variants in mice or in humans,” she says.

Journal reference: Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.2118763119