Study: Hydras regenerate heads by changing way their genes are regulated

Study: Hydras regenerate heads by changing way their genes are regulated
To regrow their own heads, hydra change the way their genes are regulated, according to new research. Photo by Frank Fox/Wikimedia

Dec. 8 (UPI) -- Researchers at the University of California, Irvine on Wednesday revealed how Hydras, a group of small aquatic animals, can regenerate their own heads.

The animals, which are known to have up to 50 heads do not appear to die due to age, or to age at all, use a process to replicate their heads called epigenetics, the researchers said in an article published Wednesday by the journal Genome Biology and Evolution.


In this process, they effectively change the way that their genes are regulated, according to the researchers.

"One exciting finding of this work is that the head regeneration and budding programs in Hydra are quite different," study co-author Aide Macias-Muñoz said in a press release.

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"Even though the result is the same, a Hydra head, gene expression is much more variable during regeneration," said Macias-Muñoz, a postdoctoral fellow in ecology and evolutionary biology at the University of California, Irvine.

Hydra belong to a group of animals that consists of about 10,000 species divided into two major groups.

The first, Anthozoa, includes sea anemones, corals and sea pens, while the second, Medusozoa, includes sea wasps and jellyfish.

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All of these species typically live in temperate and tropical regions and are commonly believed to be biologically immortal, researchers said.


Hydra stem cells have the capacity for unlimited self-renewal, research suggests, though scientists still do not understand the mechanism driving Hydra head regeneration.

Earlier studies have found evidence that multiple genes are involved in this process.

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To understand the rudiments controlling Hydra head regeneration, Macias-Muñoz and her colleagues first identified 27,137 elements that are active in one or more sections of the Hydra organism body or regenerating tissue.

The researchers then used histone modification ChIP-seq, a method designed to analyze how proteins interact with DNA, to identify 9,998 candidate proximal promoters, or regions of DNA in which proteins and other molecules combine to read that gene.

They also identified 3,018 candidate enhancer-like regions, or areas of DNA that effectively help produce genes.

Based on the analysis, a subset of these regulatory elements is remodeled during head regeneration, the researchers said.

"Accompanying dynamic gene expression is dynamic chromatin remodeling at sites where developmental transcription factors bind," Macias-Muñoz said.

"These findings suggest that complex developmental enhancers were present before the Cnidaria and Bilateria split," she said.

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