The pigmentation of the skin protects the body against ultraviolet radiation and determines
how it is visually perceived by members of the own and other species. The pigment of the
skin, melanin, is produced by cells known as melanocytes and subsequently transferred to
epithelial cells. This mechanism of skin pigmentation is conserved in humans and other
vertebrates. Another, so far uncharacterized mode of epithelial pigmentation is active in
specialized skin structures of amphibians, such as the claws of clawed frogs. This type of
pigmentation does not depend on melanocytes, but occurs autonomously in epithelial cells.
The aim of the project is to determine the mechanism, function and evolution of non-
canonical pigmentation in amphibians. The study uses recombinant enzymes and gene
editing in Xenopus frogs to investigate the molecular control of pigment formation. The
specific suppression of non-canonical pigmentation allows to determine its role in the
establishment of the material properties of skin appendages. This project defines a unique
mode of epithelial pigmentation and helps to understand the evolutionary adaptations of
amphibians.