• Barrier function of the skin
• Evolution and comparative genomics of the skin
• Mechanisms of programmed cell death
• Autophagy in tissue homeostasis and stress responses
• Evolution of innate immunity
Project: Evolution of epidermal cornification proteins
Funded by Austrian Science Fund (FWF): P 28004 (2015/07/01-2019/12/31)
The cornified layer on the surface of the skin and skin appendages such as hair, feathers, and claws are mechanically resistant protective structures at the interface of the body and the environment. Their protective properties depend on the cross-linking of proteins in epidermal keratinocytes during an evolutionarily conserved processcalled cornification. The formation of disulfide bonds between cysteine residues is an important mechanism of protein cross-linking which is most efficient if proteins contain high numbers of cysteine residues. Accordingly, cysteine-rich proteins are major constituents of human nails and hair.
The aim of this project was to characterize protein components of the cornified epidermis and skin appendages in phylogenetically diverse vertebrates (mammals, reptiles, birds, amphibians) and to investigate the evolutionary genetics of cysteine-rich epidermal cornification proteins.
We identified genes that encode cysteine-rich keratins and epidermal differentiation complex (EDC) proteins of scales, feathers, and claws. Comparative genomics, molecular phylogenetics and gene expression analyses revealed a broad variety of evolutionary trajectories including diversifying evolution from a common ancestor, convergent evolution at the molecular level, and loss of particular genes during the adaptation to a new environment. All results were published under Open Access in international peer-reviewed journals (cumulative impact factor >50).
Main findings:
Convergent evolution of cysteine-rich keratins in hard skin
appendages of terrestrial vertebrates
(https://academic.oup.com/mbe/article/37/4/982/5652086)
Differential evolution of the epidermal keratin cytoskeleton
in terrestrial and aquatic mammals
(https://academic.oup.com/mbe/article/36/2/328/5184281)
Comparative genomics suggests loss of keratin K24 in three
evolutionary lineages of mammals
(https://www.nature.com/articles/s41598-019-47422-y)
Comparative analysis of epidermal differentiation genes
of crocodilians suggests new models for the evolutionary
origin of avian feather proteins
(https://academic.oup.com/gbe/article/10/2/694/4852790)
Identification and comparative analysis of the epidermal
differentiation complex in snakes
(https://www.nature.com/articles/srep45338)
Epidermal cornification is preceded by the expression of
a keratinocyte-specific set of pyroptosis-related genes
(https://www.nature.com/articles/s41598-017-17782-4)
Filaggrin has evolved from an S100 fused-type protein (SFTP)
gene present in a common ancestor of amphibians and mammals
(https://onlinelibrary.wiley.com/doi/10.1111/exd.13317)
A stress response program at the origin of evolutionary
innovation in the skin
(https://journals.sagepub.com/doi/10.1177/1176934319862246)
Evolution of cysteine-rich type I keratins.
From: Ehrlich et al. (2020) Convergent evolution of
cysteine-rich keratins in hard skin appendages of
terrestrial vertebrates. Mol Biol Evol 37:982‐993.
Abbreviatons: Cys, cysteine; HAS, hard acidic
sauropsid-specific keratins; HK, hair keratin-like proteins.
Project: Evolution of epidermal transglutamination
Funded by Austrian Science Fund (FWF): P 32777 (start: 2020/01/01-2024/06/30)
The skin barrier to the environment depends on cross-linking of
proteins in epidermal keratinocytes. A major part of protein cross-
linking is mediated by transglutamination. Essential roles of
transglutamination have been identified in human skin but little
is known about how this important process has evolved and how it
is controlled. The aim of this project is to determine the roles
of epidermal transglutamination in the evolution of terrestrial
vertebrates. We also aim to get new insights into the molecular
regulation of transglutamination during keratinocyte cornification
which is highly relevant for a better understanding of skin barrier
defects in human patients.
Schematic depiction of protein cross-linking by transglutamination.