Evolution of ion channels in cetaceans a natural experiment in the tree of life

Abstract

AbstractCetaceans could be seen as a natural experiment within the tree of life in which a mammalian lineage changed from terrestrial to aquatic habitats. This shift involved extensive phenotypic modifications representing an opportunity to explore the genetic bases of phenotypic diversity. Furthermore, the availability of whole genome sequences in representative species of all main cetacean groups means that we are in a golden age for this type of study. Ion channels are a crucial component of the cellular machinery for the proper physiological functioning of all living species. This study aims to explore the evolution of ion channels during the evolutionary history of cetaceans. To do so, we created a bioinformatic pipeline to annotate the repertoire of ion channels in the genome of the species included in our sampling. Our main results show that cetaceans have fewer ion channels than non-cetacean mammals and that the signal of positive selection was found in ion channels related to heart, locomotion, and hearing phenotypes. Interestingly the NaV1.5 ion channel of most toothed whales (odontocetes) seems to be sensitive to TTX, similar to NaV1.7, given the presence of tyrosine, instead of cysteine, in a specific position of the ion channel. Finally, the gene turnover rate of the cetacean crown group is more than two times faster than non-cetacean mammals.