Relatives of the Jellyfish, researchers at the University of Geneva (Switzerland) have now proven the regenerative abilities of Hydra involved reprogramming cells. Does this have any implications for Neurodegenerative disease?

hydra_geneva_regenerationRemember the Greek myth of Hydra? Amongst other twelve labours, Hercules had to slay the nine-headed monster Hydra which, in case nine jaws weren’t enough, had the capacity of regenerating two heads everytime one was cut off…Well, it turns out that the myth wasn’t that far from reality.

Researchers at University of Geneva (UNIGE) have discovered the polyps of freshwater Hydra are indeed capable of reforming a complete individual from any fragment of its body. The ancient Greeks just miscalculated the proportions – i.e. the tubular polyp is not very monstrous at all, being just a couple of centimeters long (even if they are still voracious predators, nonetheless).

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(Source: Stefan Gründer, Marc Assmann Journal of Experimental Biology 2015 218: 551-561; doi: 10.1242/jeb.111666 )

Hydra are Cnidarians (same group as Jelly Fish), many types of which are fresh water based predators (Source: Stefan Gründer, Marc Assmann
Journal of Experimental Biology 2015 218: 551-561; doi: 10.1242/jeb.111666 )

The regenerative abilities of this animal were on biologists’ target, as Hydra don’t seem to senesce or die of old age, in part due to its well known semi-regenerative capabilities termed Morphallaxis – but the cellular and biochemical pathways for this survival mechanism were never properly understood…

In a new study published in Philosophical Transactions of the Royal Society, the researchers at UNIGE led by Brigitte Galliot compared gene expression at various positions along the body axis in polyps lacking or conserving their nervous stem cells.

The results were  shocking…

Hydra were found to completely modify their epithelial cells to function as neurons – i.e. reverse differentiation! Twenty-five over-expressed genes were identified in epithelial cells in animals depleted of these cells, some of these genes were involved neurogenesis or neurotransmission. Wanda Buzgariu, co-first author of the paper, explained:

Hydra’s loss of neurogenesis induces epithelial cells to modify their genetic program accordingly, indicating that they are ready to assume some of these functions. These ‘naturally’ genetically modified epithelial cells are thus likely to enhance their sensitivity and response to environmental signals, to partially compensate for the lack of nervous system

Left: The nervous system of about 1 cm-long Hydra revealed here with a fluorescent green marker. (Source: Brigitte Galliot). Right: The Yorck Project (Source: Gustave Moreau)

Left: The nervous system of about 1 cm-long Hydra revealed here with a fluorescent green marker. (Source: Brigitte Galliot). Right: The Yorck Project (Source: Gustave Moreau)

The animal’s cellular plasticity may have a deep impact in the study of Neurodegenerative diseases (read our 2015 review of the field here). In fact, some of the genes present in Hydra are known for playing an important role in reprogramming or in neurogenesis in mammals…..

Would it be possible in a near future to reprogram other cells to function as neurons once they stopped operating the way Hydra does? There is still so much to learn.

Once again, no matter how advanced our technology is, we are once again humbled by Nature.

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