Sea Anemones Reveal Ancient Blueprint for Body Symmetry

Study Uncovers Evolutionary Secrets of Back-to-Belly Axis Formation

Scientists at the University of Vienna have made a groundbreaking discovery about the evolutionary origins of body symmetry. Their research shows that sea anemones utilize a developmental mechanism previously only known in bilaterian animals, providing new insight into how complex body plans emerged over millions of years.

Unveiling the Mechanism

The study focuses on “BMP shuttling,” a molecular process that enables cells to organize themselves during development. This process involves Bone Morphogenetic Proteins (BMPs) and their inhibitor Chordin. In bilaterian animals like humans, BMPs determine cell fate by creating signaling gradients, with Chordin either blocking or transporting them. The researchers investigated if sea anemones, which are cnidarians traditionally seen as radially symmetric, also use this system.

“Not all Bilateria use Chordin-mediated BMP shuttling, for example, frogs do, but fish don’t, however, shuttling seems to pop up over and over again in very distantly related animals making it a good candidate for an ancestral patterning mechanism.”

—David Mörsdorf, Postdoctoral Researcher

This research provides significant implications for understanding evolution. According to the National Institutes of Health, understanding developmental processes is crucial for comprehending the origins of human disease and developing new treatments (NIH 2024).

Ancient Origins

To test this, the researchers blocked Chordin production in the sea anemone Nematostella vectensis. The team then reintroduced Chordin to a part of the embryo. The team then used both a membrane-bound and a diffusible form of Chordin, determining that only the diffusible form was capable of restoring BMP signaling at a distance, and demonstrating that Chordin acts as a BMP shuttle in sea anemones.

The findings suggest that the mechanism for establishing the back-to-belly axis evolved much earlier than previously believed. The presence of BMP shuttling in both cnidarians and bilaterians indicates it predates their divergence some 600-700 million years ago. This means a common ancestor likely used the Chordin-mediated BMP shuttling process.

Grigory Genikhovich, senior author of the study, stated: “We might never be able to exclude the possibility that bilaterians and bilaterally symmetric cnidarians evolved their bilateral body plans independently. However, if the last common ancestor of Cnidaria and Bilateria was a bilaterally symmetric animal, chances are that it used Chordin to shuttle BMPs to make its back-to-belly axis. Our new study showed that.”