Convergent Evolution Has Led to the Loss of Claw Proteins in Snakes and Worm Lizards

The study investigates the evolutionary loss of claw proteins in the Florida worm lizard (Rhineura floridana) and snakes, focusing on the degeneration of genes associated with claw functions. Researchers examined three gene families related to epithelial cell architecture: type I keratins, type II keratins, and the epidermal differentiation complex (EDC). They found that genes homologous to mammalian hair and nail keratins have become pseudogenes in R. floridana, and EDC genes like EDYM1 and EDCCs are absent. These genes are present in clawed lizards but not in snakes. Proteomic analysis of the bearded dragon's claws confirmed the presence of these proteins in squamates. The findings suggest that the evolution of a limbless body in these species is linked to the convergent loss of claw keratins and differentiation genes.