Tuesday, December 4, 2012

The secret of immortality unlocked? No, anyone can do it

The cover story in the Sunday New York Times Magazine by Nathaniel Rich, "Can a Jellyfish Unlock the Secret of Immortality?," tells a fascinating tale.  But an incomplete one, and as usual is over-stated, because interesting as the story genuinely is, the 'secret' has been known for a long time.

German marine-biology student Christian Sommer was studying hydrozoans -- hydra, coral, jellyfish, and so on, most of which live in saltwater -- in the 1980's, when among the hundreds of organisms he collected off the coast of Portofino, Italy was a very small jellyfish called Turritopsis dohrnii, or what has since become known as the immortal jellyfish.  It is tiny, about the size, Rich writes, of a trimmed pinkie fingernail.  Sommer was interested in the reproductive behavior of the animals he collected, and this one interested him particularly because he found it very hard to explain. 
Plainly speaking, it refused to die. It appeared to age in reverse, growing younger and younger until it reached its earliest stage of development, at which point it began its life cycle anew.
Further work on this organism by other biologists resulted in a paper in which:
The scientists described how the species — at any stage of its development — could transform itself back to a polyp, the organism’s earliest stage of life, “thus escaping death and achieving potential immortality.” This finding appeared to debunk the most fundamental law of the natural world — you are born, and then you die. 
Source: A silent invasion, Miglietta and Lessios, 2008
It is now known that during rejuvenation, some cell types transform into others, so that, say, a skin cell can become a nerve cell, though the process by which this happens is not understood. Rich says, it's still unclear how the jellyfish grows young again.  And, of course the idea is that if we understand that, if we could unlock that secret, we could harness it for medicine and change the world.  Indeed, Rich quotes the only scientist currently able to culture Turritopsis in the lab, a Japanese marine biologist named Shin Kubota who Rich visited for the story:
“Turritopsis application for human beings is the most wonderful dream of mankind,” he told me the first time I called him. “Once we determine how the jellyfish rejuvenates itself, we should achieve very great things. My opinion is that we will evolve and become immortal ourselves.”
Some marine biologists believe that this jellyfish isn't the only immortal organism the ocean hosts, but that some sea urchins and sponges and hydra might also be in on the secret.  And, since humans share genetic ancestry with all these forms of life, the excitement for using them to learn more about cancer and aging grows. Though some people are less romantic about this than is Kubota, saying that the idea that we'll learn to be immortal is nonsense, but that the more we understand about the processes, the more likely this might help improve the quality of end-of-life.

Rich watched Kubota mutilate one of the jellyfish specimens he maintains in Petri dishes in his lab, stabbing it numerous times and admonishing it to rejuvenate.  When he's not punching them into rejuvenating, he treats these organisms almost like his children, laboriously feeding the hundreds of specimens he keeps everyday, even taking them with him in a cooler whenever he travels because they are so fragile. 
We checked on the stab victim every day that week to watch its transformation. On the second day, the depleted, gelatinous mess had attached itself to the floor of the petri dish; its tentacles were bent in on themselves. “It’s transdifferentiating,” Kubota said. “Dynamic changes are occurring.” By the fourth day the tentacles were gone, and the organism ceased to resemble a medusa entirely; it looked instead like an amoeba. Kubota called this a “meatball.” By the end of the week, stolons had begun to shoot out of the meatball.
But, they are fragile, fragile enough to be mortal, so their ability to rejuvenate isn't mythic.  What happens is that most of the cells die, but some are able to de-differentiate and begin the formation of a new organism, that is, form a polyp which is the juvenile stage of the jellyfish's life cycle.

This does suggest a sort of 'immortality', though at some point enough mutations will have accumulated that this may not be possible and that individual will die out.  Why the property is there in the first place is something to think about.

However, the excess claims have to do with the fact that essentially all organisms can do the same thing in their own way.  Trees and humans shed single gamete (sperm or egg) cells, dedifferentiated so they can form a whole new individual.  But during your (and a tree's) lifetime, the lineage of cells that will form gametes are differentiated from the original fertilized egg, so they can form the reproductive organs.  Then, specific cells are prepared and enabled to undergo meiosis, to produce sperm or egg.  That is, they dedifferentiate.

In that sense, of course all of us here today are proof that 'immmortality' is nothing unusual at all.  Each of us, each bug, bird, tree, etc. is the descendant of 3.5 billion years of successful reproduction.  We don't dedifferentiate the same way a jellyfish does, but the idea seems to be essentially the same.  Unless we misunderstand that story (always possible, of course!), there is nothing new at all about this--just a different particular mechanism.

Nonetheless, the story is interesting.  It could stand on its own legs without the excess claims.


David Evans said...

"Rich watched Kubota mutilate one of the jellyfish specimens he maintains in Petri dishes in his lab, stabbing it numerous times and admonishing it to rejuvenate. He treats these organisms almost like his children.."

Best laugh of the day.

Anne Buchanan said...

Oh, oops. Could have been better said!

Anonymous said...

Thanks for the thoughtful observations!