Evolution tunes the excitability of individual neurons.

TitleEvolution tunes the excitability of individual neurons.
Publication TypeJournal Article
Year of Publication2001
AuthorsSalkoff, L, Butler, A, Fawcett, G, Kunkel, M, McArdle, C, Paz-y-Mino, G, Nonet, M, Walton, N, Wang, ZW, Yuan, A, Wei, A
JournalNeuroscience
Volume103
Issue4
Pagination853-9
Date Published2001
ISSN0306-4522
KeywordsAdaptation, Physiological, Animals, Base Sequence, Biological Evolution, Caenorhabditis, Caenorhabditis elegans, DNA, Enhancer Elements, Genetic, Gene Expression, Molecular Sequence Data, Multigene Family, Neurons, Potassium Channels, Protein Isoforms
Abstract

The relationship between the genome and the evolution of the nervous system may differ between an animal like C. elegans with 302 neurons, and mammals with tens of billions of neurons. Here we report that a class of nonconserved potassium channels highly expanded in C. elegans may play a special role in the evolution of its nervous system. The C. elegans genome contains an extended gene family of potassium channels whose members fall into two evolutionary divergent classes. One class constitutes an ancient conserved "set" of K+ channels with orthologues in both humans and Drosophila and a second larger class made up of rapidly evolving genes unique to C. elegans. Chief among this second class are novel potassium channels having four transmembrane domains per subunit that function as regulated leak conductances to modulate cell electrical excitability. This inventory of novel potassium channels is far larger in C. elegans than in humans or Drosophila. We found that, unlike conserved channel genes, the majority of these genes are expressed in very few cells. We also identified DNA enhancer elements associated with these genes that direct gene expression to individual neurons. We conclude that C. elegans may maintain an exceptionally large inventory of these channels (as well as ligand-gated channels) as an adaptive mechanism to "fine tune" individual neurons, making the most of its limited circuitry.

Alternate JournalNeuroscience
PubMed ID11301195