In a genome comparison conducted by a working group led by molecular biologist Leopold Eckhart of the University Department of Dermatology at MedUni Vienna, 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 has now been published in the journal Molecular Biology and Evolution.
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, the working group led by Leopold Eckhart investigated the genes responsible for the skin layers of the shell of the European terrapin 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 around 250 million years ago.
Humans and turtles share a common ancestor
What is remarkable is that the basic organisation 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. In humans, the EDC genes protect the skin from the penetration of microbes and allergens.
This new study shows that evolutionarily related genes have a protective function both in humans and also in tortoises and turtles. It is hoped that comparing the skin of humans and animals will provide a better understanding of the interaction of proteins. In future, the knowledge derived from this may lead to medical applications, for example to improved treatment for psoriasis, in which EDC gene mutations are found.
Participating in the study were: Center for Integrative Bioinformatics Vienna (CIBIV), Max F. Perutz Laboratories, University of Vienna; University of Veterinary Medicine of Vienna, Schönbrunn Zoo and the University of Bologna.
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