Evolution: the origin of a nervous system (Introduction)

by David Turell , Tuesday, August 13, 2024, 21:18 (101 days ago) @ David Turell

From early ion channels:

https://www.sciencedaily.com/releases/2024/08/240813131928.htm

"A new study has rewritten the conventionally understood evolutionary history of certain ion channels -- proteins critical for electrical signaling in the nervous system. The study shows that the Shaker family of ion channels were present in microscopic single cell organisms well before the common ancestor of all animals and thus before the origin of the nervous system.

"A new study has rewritten the conventionally understood evolutionary history of certain proteins critical for electrical signaling in the nervous system. The study, led by Penn State researchers, shows that the well-studied family of proteins -- potassium ion channels in the Shaker family -- were present in microscopic single cell organisms well before the common ancestor of all animals. This suggests that, rather than evolving alongside the nervous system as previously thought, these ion channels were present before the origin of the nervous system.

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"We have previously shown that the oldest living animals, those with simple nerve nets, have the highest ion channel diversity. This new finding adds to growing evidence that many of the building blocks for the nervous system were already in place in our protozoan ancestors -- before the nervous system even existed."

"Ion channels are located in the membranes of cells and regulate how charged particles called ions move in and out of the cell, a process that results in the electrical signals that are the foundation of communication in the nervous system. The Shaker family of ion channels is found in a large range of animals, from humans to mice and fruit flies, and specifically regulates how potassium ions flow out of the cell to terminate electrical signals called action potentials. These channels can open or close based on changes in the electric field, much like transistors in computer chips.

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. "We previously thought that the Shaker family of voltage-gated potassium channels were only found in animals, but now we see that the genes that code for this family of ion channels were present in several species of the closest living relatives of animals, a group of single cell organisms called choanoflagellates."

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"...this finding indicates that multiple subtypes were present at the base of the animal family tree, including Kv1, which are found in comb jellies, and the Kv2-4-like channels, which are found in choanoflagellates.

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"This work also adds to growing evidence that many elements of the nervous system were present before the nervous system as a whole evolved, Jegla noted.

"'Most of the functionally important proteins that we use in electrical signaling, which underlie neuronal communication and neuromuscular movement, are all based on proteins that existed before animals," Jegla said. "It seems that animals were able to cobble together a functioning nervous system very early in their evolution simply because most of the necessary proteins were already there.'"

Comment: nerves are an advanced form of ion channel. This story of evolution of nerves is quite reasonable.