Michael Layden: Human Brain Shares its Blueprint with Sea Anemones

The human brain is an evolutionary marvel, but don’t get too big a head about it. After all, it shares its blueprint with sea anemones.

How can it be that perhaps the world’s greatest evolutionary wonder has such commonality with a simple, hollow sea creature?

New research from the Layden Lab at Lehigh has demonstrated that the gene mechanisms at work during neurogenesis in the brain actually predate the evolutionary development of the central nervous system. In other words, to build our brains, nature is borrowing the blueprints from much simpler creatures that predate us and other animals on the evolutionary timeline.

“Sea anemones are cnidarians, the sister taxon to bilaterians, which includes humans and most other animals,” said Michael Layden,associate professor of biological sciences and director of the Layden Lab. “Our research demonstrates that these gene programs may have been inherited from the common ancestor of cnidarians and bilaterians, and may not have been specifically adapted for brain development.”

Researchers first injected Nematostella embryos with mRNA at the single-cell stage to control the expression of genes of interest. They then assessed the changes in neuronal development using marker genes for different neuron types.

They found that the gene program involved in patterning the brain along the anterior-posterior axis was also responsible for patterning Nematostella’s much simpler neural net. They also found that the genes in neural nets that are involved in regionalization—allocating cells to different regions of the nervous system—also function to regionalize all other kinds of cells as well. Thus, their roles are not restricted to patterning the brain.

This finding also supports the hypothesis that the central nervous system patterning evolved via the co-option of broadly acting regionalization programs that were present in an ancestor and can still be observed in many species today.

“At a minimum our findings reject the argument that conserved regionalization programs are sufficient to support the homology of bilaterian brains,” Layden said. “Our findings support the co-option hypothesis because no novel function would need to evolve for axial programs to be independently co-opted.”

The research is an example of how scientists look to other creatures to unlock understanding of ourselves. Layden’s lab also studies the mechanisms at work in Nematostella during the separate but similar process of neural regeneration, or the regrowing or repairing of dead or damaged nerve cells.

He believes that establishing an understanding of these processes could help lay the groundwork for potential human applications, such as regenerative therapies.

Of course, evolution has led to extraordinary advancements in animals’ fully developed central nervous systems over the primitive neural nets of cnidarians. The respective nervous systems of humans and cnidarians have evolved in very different ways to meet the very different needs of their respective species. But the basic blueprint remains the same.

“By investigating how these animals build their nervous systems, we can gain an understanding of the building blocks,” Layden said. “If you don’t know where you started, it’s hard to know how you got where you are.”

By Dan Armstrong

Inside the Layden Lab

The Layden Lab includes a lab manager, a postdoctoral researcher, three graduate students, and three undergraduate students who help carry out research using Nematostella vectensis.

Their day-to-day work includes preparing artificial seawater and running a controlled schedule of reproduction of Nematostella vectensis. The sea anemones’ spawning is triggered by light and heat. By controlling these conditions, the lab can net an abundance of embryos daily, which allows them to continuously perform experiments to investigate gene function in this exciting model system.

According to “Nematostella vectensis as a Model System,” a book chapter Layden and his team contributed to the 2021 Handbook of Marine Model Organisms in Experimental Biology, the starlet sea anemone has many characteristics that make it a great subject for research.

Among those are the ability to compare multiple developmental trajectories of embryogenesis, regeneration and asexual reproduction within a single organism. It is also highly amenable to the study of evolution and development, neurophysiology and behavioral ecology.

In 2007, the creature’s genome was published, resulting in a rapid expansion of studies using Nematostella vectensis. Layden estimates that two decades ago, perhaps two or three labs nationwide were dedicated to research using the creatures. That number is now about 70-80 labs, many of which use the injection and observation protocol that the Layden Lab developed and published a decade ago.

The team takes pride in not only the importance of its research findings, but also the efficiency of its processes. Using their protocol, experienced researchers can inject an embryo every three seconds, or thousands within an hour.