UNIVERSITY PARK, Pa. -- New research shows that a burst of evolutionary innovation in the genes responsible for electrical communication among nerve cells in our brains occurred over 600 million years ago in a common ancestor of humans and the sea anemone. The research, led by Timothy Jegla, assistant professor of biology at Penn State, shows that many of these genes, which when mutated in humans can lead to neurological disease, first evolved in the common ancestor of people and a group of animals called cnidarians, which includes jellyfish, coral and sea anemones.
A paper describing the research is scheduled to be posted online in the Early Edition (EE) of the journal Proceedings of the National Academy of Sciences of the United States of America sometime during the week beginning Feb. 16, 2015."Our research group has been discovering evidence for a long time that most major signaling systems in our neurons are ancient, but we never really knew when they first appeared," Jegla said. "We had always assumed that we would be able to trace most of these signaling systems to the earliest nervous systems, but in this paper we show that this is not the case. It looks like the majority of these signaling systems first appear in the common ancestor that humans share with jellyfish and sea anemones."Electrical impulses in nerve cells are generated by charged molecules known as ions moving into and out of the cell through highly specialized ion-channel proteins that form openings in the cell membrane. The new research focuses on the functional evolution of the genes that encode the proteins for potassium channels -- ion channels that allow potassium to flow out of nerve cells, stopping the cell's electrical impulses. "The channels are critical for determining how a nerve cell fires electrical signals," said Jegla. "It appears that animals such as sea anemones and jellyfish are using the same channels that shape electrical signals in our brains in essentially the same way."
"Humans and sea anemones went their separate ways evolutionarily speaking roughly 600 million years ago," said Jegla, "so we know that the mechanisms we use to generate impulses in our neurons must be at least that old." The team then tried to trace these channels back even further in evolutionary time -- to the very origins of the nervous system. "One of the exciting recent findings in evolutionary biology is that the nervous system might be much older than the ancestor of sea anemones and humans," Jegla said.