Divergent sequential variation of TRPA1 in cetaceans and its potential adaptive role in aquatic adaptation

Gene loss represents a key mechanism of adaptive evolution. Owing to their evolutionary transition from land to water, cetaceans serve as an excellent model for studying this process. In this study, we examined the sequences of the cold-sensitive ion channel transient receptor potential ankyrin 1 (TRPA1) in cetaceans and identified distinct evolutionary changes in toothed and baleen whales. The ancestor of toothed whales exhibited substantial exon loss in the TRPA1 gene, whereas baleen whales likely experienced reduced or absent TRPA1 expression. These sequence changes resulted in impaired or lost TRPA1 protein function in cetaceans. Drawing on previous experimental studies of TRPA1 in humans and mice, we propose several adaptive hypotheses for TRPA1 gene loss, including adaptation to rapid cooling events, diminished pain sensitivity in marine environments, skin specialization, and the evolution of echolocation in toothed whales. Our study adds a new entry to the gene loss repertoire of cetaceans, offering novel insights into the secondary aquatic adaptation of mammals.