Scientists from the Stowers Institute have discovered that the brain development of sea lampreys shows striking similarities with the development of the human brain. The sea lamprey, an ancient creature with a suction cup-like mouth and sharp teeth that existed 500 million years ago, looks like it was lifted from a horror story. Recent research from the Stower Institute for Medical Research has shown that the hindbrain, which controls basic functions such as blood pressure and heart rate in both sea lampreys and humans, is built using a remarkably similar set of molecular and genetic tools.

A recently published study from the laboratory of researcher Robb Krumlauf, Ph.D. Nature Communication, It gives an insight into how the brains of ancient animals developed. The team unexpectedly discovered that an important molecular signal is required during the development of the vertebrate hindbrain.

Co-author Ph.D. “This study of the hindbrain is essentially a window into the distant past and serves as a model for understanding the evolution of complexity,” said Hugo Parker.

Unique features of sea lampreys

Like other vertebrates, sea lampreys have a spine and skeleton, but they are conspicuously missing the head element, the jaws. Since most vertebrates, including humans, have jaws, this striking difference in sea lampreys makes them valuable models for understanding the evolution of vertebrate traits.

D., Ph.D., a former researcher in Krumlauf’s lab and the study’s lead author. “About 500 million years ago, at the origin of vertebrates, there was a distinction between jawless and jawed,” said Alice Bedois. “We wanted to understand how the vertebrate brain evolved and whether there was something unique in jawed vertebrates that their jawless relatives lacked.”

A team of scientists at the Stowers Institute found that in both sea lampreys and humans, the hindbrain (the part of the brain that controls vital functions such as blood pressure and heart rate) is built with remarkably similar molecular genetic tools. Credit: Stower Institute for Medical Research

Krumlauf’s lab and Caltech’s Ph.D. Previous work by Marianna Bronner’s lab found that the genes that structure and segment the sea lamprey’s hindbrain are identical to those of jawed vertebrates, including humans.

But these genes are part of an interconnected network, or circuit, that must be initiated and directed to properly form the hindbrain. A new study has identified a common molecular feature as part of the gene circuit that controls patterning of the lamprey hindbrain, although it is known to control head-to-tail patterning in many animals.

“We found that sea lamprey hindbrain development involved not only the same genes but also the same signaling, suggesting that this process is ancestral to all vertebrates,” Bedevi said.

Discovery of the role of retinoic acid

This property is called retinoic acid and is commonly known as vitamin A. Although researchers knew that retinoic acid controlled the gene circuit that forms the hindbrain of complex species, it was thought to be absent in more primitive animals such as sea lampreys. Surprisingly, they found that the sea lamprey’s hindbrain core circuit was also triggered by retinoic acid; This provided evidence that these sea monsters and humans were much more closely related than expected.

“People thought that because sea lampreys did not have jaws, their hindbrains were not developed like other vertebrates,” Krumlauf said. said. “We showed that this fundamental part of the brain is built in exactly the same way in mice and even in humans.”

There are well-known signaling molecules that communicate the fate of cells during development. Now researchers have discovered that retinoic acid is another important player that determines vital developmental stages such as the formation of the brainstem. Moreover, if hindbrain formation is a conserved feature across all vertebrates, other mechanisms must be responsible for explaining their incredible diversity.

“We all come from a common ancestor,” Bedouin said. “Sea lamps provided an additional clue. We now need to look further back in evolutionary time to find when the gene pattern controlling hindbrain formation first emerged.”