Sea anemones can regrow their entire body to its original shape

The human body excels at maintaining internal balance in a process known as homeostasis. This vital mechanism keeps our core temperature constant at 37°C regardless of external conditions.

But now groundbreaking research from the Ikmi group at EMBL Heidelberg shows that homeostasis goes beyond internal regulation – it can actively redefine the shape of an organism.

The Star Sea Anemone (Nematostella vectensis) is an impressive example of this phenomenon. Known for its extraordinary regenerative abilities, this creature can regrow a lost head or foot and even rebuild a complete, functional body from a dismembered fragment.

But unlike many regenerating animals, which rebuild parts in proportion to what’s left, the sea anemone reshapes its entire body to maintain its overall shape, even adjusting undamaged areas.

Regeneration in sea anemones

“Regeneration is about restoring function after tissue loss or damage,” explained Aissam Ikmi, group leader at EMBL Heidelberg and lead author of a new study published in the journal Developmental cell.

“Most research studies mainly consider patterns and sizes in regeneration, but our results show that maintaining shape is also crucial – and this is something the organism actively controls.”

The discovery began when Stephanie Cheung, a graduate student in Ikmi’s group, noticed an unexpected phenomenon: When a sea anemone’s foot was injured, cell division occurred not only at the wound site, but also at the opposite end of the body near the mouth. This suggested that signals are sent throughout the organism in response to injury.

Molecular changes triggered by injury

Using spatial transcriptomics and advanced imaging techniques, the research team mapped gene activity throughout the anemone’s body during regeneration.

They found that injuries triggered molecular changes both near and far from the wound. Cells moved, tissues reorganized, and the entire body reshaped itself to maintain its original proportions.

The extent of this remodeling depended on the severity of the injury. Losing a foot resulted in minor adjustments, while the halving resulted in significant remodeling.

A key player in this process was a family of enzymes called metalloproteases, which became more active the more tissue was lost. These enzymes helped realign tissue, not just at the wound site but throughout the body.

“Metalloprotease activity has never been detected in animals like this before,” said Petrus Steenbergen, one of the study’s lead authors and senior research technician at Ikmi Group.

“I had to design and optimize experimental conditions Nematostella based on the scant literature available on other species. It took some time, but the end results were very rewarding.”

Sea anemones regain their shape

The team found that restoring the sea anemone’s shape, even after a serious injury, is a top priority.

By measuring aspect ratio – the ratio of length to width – they found that the anemone kept returning to its pre-injury proportions. This proportional response allowed the organism to maintain its shape even as it became smaller.

“We witnessed the company-wide coordination driving this transformation,” explained Ikmi. “This proportional response allows the anemone to restore its shape, showing how organisms like it Nematostella Interpret tissue loss and respond appropriately to the resulting damage.”

Collaborative efforts and advanced techniques

The study was a collaborative project. Rik Korswagen’s team at the Hubrecht Institute in the Netherlands helped implement spatial transcriptomics in the sea anemone.

In addition, Oliver Stegle’s team at EMBL Heidelberg and the German Cancer Research Center (DKFZ) provided bioinformatics expertise and statistical methods for analyzing spatial gene expression data.

“It was a pleasure to develop the results of the study together by combining the team’s expertise in data analysis and cell biology,” said Tobias Gerber, another lead author of the study. “This work has been a truly collaborative journey and I’m glad I was a part of it.”

Questions remain about sea anemone regeneration

While research offers fascinating insights into how Nematostella While regeneration maintains its shape, it raises new questions.

“The next big question is why is it so important to maintain form,” Ikmi said. “And how does the organism perceive its own form? How does it know what it looks like now?”

Using the star sea anemone as a model, the team aims to explore the mechanisms underlying these abilities. Their work promises to understand how organisms heal, maintain balance and adapt to injury, potentially opening new avenues in regenerative medicine and biology.

Matthew Be

Photo credit: Matthew Benton/EMBLtMatthew Bentonhew Benton/EMBL: M: Matthew Benton/EMBLatthew Matthew BentonBenton/EM

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