In a genome comparison conducted by a working group led by molecular biologist Leopold Eckhart, Ph.D., of the University Department of Dermatology at MedUni Vienna, in Austria, it was discovered that genes for important skin proteins arose in a common ancestor shared by humans and turtles 310 million years ago. The study was published online on November 24, 2015 in an open-access article in Molecular Biology and Evolution. The article is titled “Comparative Genomics Identifies Epidermal Proteins Associated with the Evolution of the Turtle Shell.” The turtle shell is a highly successful concept of evolutionary development and its defensive function clearly distinguishes turtles and tortoises from other reptiles. In the study, Dr. Eckhart’s working group investigated the genes responsible for the skin layers of the shell of the European terrapin (photo) and a North American species of turtle, in order to compare them with the genes of human skin. The study findings suggest that a hard shell was formed as the result of mutations in a group of genes known as the epidermal differentiation complex (EDC). Comparisons of genome data from various reptiles suggest that the EDC mutations responsible occurred when turtles split off from other reptiles approximately 250 million years ago. What is remarkable is that the basic organization of the EDC genes is similar in humans and turtles. This leads to the conclusion that the prototypical EDC genes developed in a common ancestor, who lived 310 million years ago and was similar to modern reptiles. In the case of turtles, these genes developed so as to form proteins that bring about a significant hardening in the outer layer of skin, intensified cross-linking, and hence, the formation of a shell.
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