HOXC13

The development of hair was of central importance for the evolution of mammals and thus also of humans. However, the evolutionary origin of the genetic program of hair was previously unknown. Researchers have now been able to show that important hair components and their genetic control have already evolved in amphibians. Human hair therefore shows unexpected similarities to the claws of clawed frogs. The development of hair was of central importance for the evolution of mammals and thus also of humans. However, the evolutionary origin of the genetic programme of hair was previously unknown. An international research team led by Leopold Eckhart from MedUni Vienna has now been able to show that important hair components and their genetic control have already evolved in amphibians. Human hair therefore shows unexpected similarities to the claws of clawed frogs. The results were recently published in the scientific journal Nature Communications. In order to investigate the evolution of skin appendages, which include human hair and nails, the MedUni Vienna research team, in collaboration with the University of Ghent (Belgium), used the tropical clawed frog (Xenopus tropicalis) as an experimental model. The study revealed that the cornified claws of Xenopus frogs consist of special proteins (keratins) that are very similar to the main components of mammalian hair and nails. The formation of these keratins was found to be controlled by a specific gene, Hoxc13, in both humans and frogs. "It is known that patients with mutations in the Hoxc13 gene have defects in the growth of hair and nails. In our study, we were able to block the formation of claws in the clawed frog by switching off this gene," reports Leopold Eckhart from MedUni Vienna's Department of Dermatology. These results indicate that the genetic programme for the development of keratinized claws originated in a common ancestor of humans and frogs. "During the evolution of mammals, the programme of claw formation was modified for the development of hair," says Eckhart. Important research question clarified The evolution of terrestrial vertebrates is characterized by the appearance of an effective skin barrier against water loss in a dry environment and by the development of hard, keratinized skin appendages such as claws, scales, feathers and hair, which are crucial for catching prey, protection, supporting special types of locomotion and thermal insulation. The evolution of skin appendages is therefore an important research question. The findings from the project, which is funded by the Austrian Science Fund (FWF), contribute to clarifying the evolutionary origin of keratinized skin appendages and also help to better understand the regulation of hair in humans. "Our publication will stimulate further exciting studies in basic and preclinical research," concludes Leopold Eckhart.