How immortal jellyfish turn back time - Phys.org

How immortal jellyfish turn back time

January 12 2023, by Daniel Maeso Miguel and Maria Pascual Torner

Turritopsis dohrnii. Credit: Daniel Maeso Miguel and Maria Pascual Torner

Achieving immortality is something that has driven human beings
throughout much of their history. Many peculiar legends and fables have
been told about the search for the elixirs of life. Medieval alchemists
worked tirelessly to find the formula for the philosopher's stone, which
granted rejuvenating powers. Another well-known story is the travels of
Juan Ponce de León, who, while conquering the New World, searched
for the mysterious fountain of youth.

But to this day no one has succeeded in discovering the keys to eternal

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life. There is, however, one exception—a creature no more than four
millimeters in size Turritopsis dohrnii, also known as "the immortal
jellyfish".

Biological immortality, within reach of a jellyfish

Unlike the vast majority of living organisms, Turritopsis dohrnii is
capable of rejuvenation and biological immortality. This challenges our
perception of aging, but how does it do so?

Let's start by understanding the generic life cycle of a "mortal jellyfish".
It reproduces sexually: the male's sperm fertilizes the female's eggs and
the zygote is formed. The zygote grows as a larva and drifts until it
attaches itself to the seabed. Once settled, it grows into a polyp and,
when ready, it reproduces asexually. To do this, it releases tiny jellyfish
from its own body, which then grow to the adult stage and reproduce,
before dying.

The immortal jellyfish, Turritopsis dohrnii, also follows this cycle, but
after reproducing it does not always die: it can choose an alternative path
and reverse its life cycle. Along the path, its jellyfish body shrinks to
form something like a sphere, called a "cysto". This drifts until it sticks
to the bottom, and then generates a new polyp, which in turn gives rise to
new jellyfish, thus entering the cycle again.

This process can occur endlessly and allows the jellyfish to escape death.

Deciphering the immortal jellyfish genome

The keys to the immortality of Turritopsis dohrnii are written in its
DNA, but discovering them has been no easy task.

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Our research team led by Carlos López Otín at the University of Oviedo
has contributed to deciphering the genome of this immortal jellyfish.
The results have been published in the journal PNAS. This was done by
reading letter-by-letter and writing out gene-by-gene all its DNA as if it
were a huge instruction book.

Life cycle of Turritopsis dohrnii with the alternative rejuvenation path. Credit:
Daniel Maeso Miguel and Maria Pascual Torner

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This huge book contains all the information needed for cells to carry out
their vital functions. As a result, several genomic clues have been
defined that contribute to understanding the extraordinary longevity of
the immortal jellyfish.

Using various bioinformatics tools and comparative genomics (the
comparison of the genetic book between species), it has been discovered
that Turritopsis dohrnii possesses a number of genetic variations that
contribute to its biological plasticity and longevity.

The genes found are associated with different keys to aging such as
DNA repair and replication, renewal of the stem cell population, cell-to-
cell communication and reduction of the oxidative cellular environment
that damages cells, as well as the maintenance of telomeres
(chromosome ends).

All these processes are associated with longevity and healthy aging in
humans.

In addition, by studying each stage of their rejuvenation in detail, a
series of changes in gene expression have been identified that are
necessary for the cells to transform, through a process known as
dedifferentiation. This allows the Turritopsis dohrnii to effectively reset
its own biological clock.

All these mechanisms act synergistically as a whole, thus orchestrating
the process to ensure the successful rejuvenation of the immortal
jellyfish.

The true secret of immortality

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If Juan Ponce de León had known the secrets kept by Turritopsis dohrnii
during his search for the fountain of youth, he would have been left
parched. And the alchemists would not have found the philosopher's
stone they so longed for. That's because, unfortunately, it wouldn't be
possible for a human body to replicate what the jellyfish does. Perhaps
the only way to find such a fountain or stone is to realize that there is no
life without death. That every system, like humanity or our own body,
needs the death of some of its parts to remain in balance and survive.

From the fascinating exploits of Turritopsis dohrnii we have learned the
keys and limits of cellular plasticity, and from this knowledge we hope
to find better answers to the many aging-related diseases that trouble us
today.

Nonetheless, the dream of biological immortality for humans remains
just that: a dream. Humans have at least discovered how to be immortal
in another way—by making their contribution to history through art and
knowledge.

This article is republished from The Conversation under a Creative
Commons license. Read the original article.

Provided by The Conversation

Citation: How immortal jellyfish turn back time (2023, January 12) retrieved 9 October 2024
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