The genetic evolution of European eels has revealed a fascinating mechanism for restoring ancestral functions. Researchers from the Institute of Science Tokyo have discovered that a series of gene duplication and mutation events has enabled European eels to regain broad solute permeability, a trait that was lost in their common ancestor. This process, known as 'birth-and-death evolution', involves the loss of function, duplication, mutation, and functional diversification of genes. The key genes involved are aqp10.2b2 and aqp10.2b3, which have evolved to mimic the function of the lost aqp10.1 gene, transporting water and uncharged solutes like glycerol across cell membranes. The common ancestor of ray-finned fishes possessed two Aqp10 genes, aqp10.1 and aqp10.2, but the aqp10.1 gene was lost during the evolution of eels. Most Anguilliformes species, such as congers and morays, retain only one aqp10.2b gene variant, but European eels have evolved to possess three aqp10.2b genes. The study, conducted in collaboration with researchers from The University of Tokyo and Shinshu University, Japan, found that the Aqp10.2b2 and Aqp10.2b3 genes have a unique amino acid composition in their selectivity filter, which allows them to transport urea and boric acid, similar to the original aqp10.1 gene. This discovery highlights the potential of aquaporin gene analysis for understanding physiological adaptation in aquatic vertebrates and offers new insights into the birth-and-death evolution of the aquaporin gene family.
