YOU CAN BUY an authentic mermaid corpse at a current auction on eBay. Scientific readers will know that integrins are a family of heterodimeric receptors essential to cell adhesion in all metazoans. Scientific papers have presented phylogenetic reconstructions for the α and β integrin subunits based on sequences from 24 invertebrate and vertebrate species, including the fully sequenced genomes of the ascidian Ciona intestinalis (a urochordate) and the pufferfish Takifugu rubripes (a teleost). Both genomes contain integrin α subunits that have the inserted αI domain. Although the Ciona αI domains are missing the distinctive characteristics of mammalian collagen receptors, they form a new subgroup of α subunits with αI domains. Each of the pufferfish αI domain sequences does have characteristics of the collagen receptor αI domains, but no leukocyte-specific αI domains were found in pufferfish. Comparative protein modeling suggests that several of these fish αI domains are structurally compatible with binding to a GFOGER sequence in a collagen triple helix. So it is possible that humans trace their evolution to fish.
Science Direct -- "Integrin Evolution: Insights from ascidian and teleost fish genomes"
