How immortal hydras regenerate severed heads


A little immortal hydra. Credit: Creative Commons.

Hydras, tiny aquatic animals, are among the most intriguing creatures in the animal kingdom. On the one hand, they are practically immortal. Because their stem cells have the capacity for unlimited self-renewal, unless the hydra is eaten or physically destroyed by an external force, it could theoretically live on forever. He knows the death of old age.

Even when its head is cut off, the hydra will push one away – its will to live is truly unmatched. Now California researchers have found their secret, and it’s all in their genes. Or rather, in their so-called “epigenetic” regulation.

Hydras, which are related to corals, marine wasps, and jellyfish, are asexual, meaning they can reproduce on their own without the need for a mate. Instead, they reproduce by growing buds on the surface of their bodies, miniature clones of the original individuals that simply split apart when mature. Research has shown that animals that breed later and less frequently tend to live longer. The hydra, however, begins to reproduce almost immediately after its formation.

In 2012, researchers at the Zoological Institute at the University of Kiel found that the key to hydra’s longevity was the FoxO gene, which was previously linked to aging in humans. Researchers have found that FoxO plays a fundamental role in maintaining stem cells

Hydra is basically a bag of stem cells. In fact, it is an adult who continues to produce embryonic cells, which in a way makes it a perennial embryo. Because the genes that regulate development are constantly being turned on, they are constantly rejuvenating the body.

Researchers at the University of California at Irvine thought the same mechanisms found in reproduction may also explain the death-defying act of head regeneration. But, as they reported in the newspaper Biology and evolution of the genome, the two processes are distinct.

“An interesting finding from this work is that the head regeneration and budding programs in Hydra are quite different, ”said the lead author of the article, Aide Macias-Muñoz.

“Even if the result is the same (a hydra head), gene expression is much more variable during regeneration. Dynamic gene expression is accompanied by dynamic chromatin remodeling at sites where developmental transcription factors bind, ”the scientist added.

Hydra forming a new head after being cut off. Credit: Ulrich Technau / PNAS.

Biologists have mapped more than 27,000 active elements in one or more segments of the hydra’s body or in regenerating tissue. They used a method called ChIP-seq which analyzes how proteins interact with DNA, so they can see which sections of genomes are turned on or off during a particular stage of development, such as head regeneration. They found 2,870 regions of the hydrogenome that cause head regeneration but not all are necessarily active during budding, including “activator” genes, genomic sequences that play a key role in regulating levels of dye. expression of tissue-specific genes.

According to Scientific alert, researchers have identified a family of genes called Fos who was very active in the regeneration of the head. The same genes were previously associated with regeneration processes in other species, such as fish, salamanders, and mice.

Many hydra genes involved in the regeneration of its severed head are also present in humans. It’s just that ours are activated, while theirs are activated by environmental signals – this is the essence and power of epigenetics. If humans had access to the same genetic programming, would this be a fountain of youth? It’s a rabbit hole that the researchers didn’t dare to enter. But by disentangling these mechanisms, researchers can further elucidate other key aspects of animal evolution and development, such as that of the nervous system, the authors noted in their study.


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