Convergent Evolution of Cysteine-Rich Keratins in Hard Skin Appendages of Terrestrial Vertebrates

November 2019 in “ Molecular biology and evolution ”

Florian Ehrlich, Julia Lachner, Marcela Hermann, Erwin Tschachler, Leopold Eckhart

cysteine-rich keratins hard skin appendages hair claws hard acidic keratins hard basic keratins HBS1 keratin chicken feathers molecular phylogenetics convergent evolution structural proteins keratins feathers evolution

Studysummary This study suggests that the keratins found in reptile and bird skin appendages evolved independently from mammalian hair keratins, highlighting convergent evolution in these species. Our plain-language summary of this paper — not a Tressless recommendation.

The study demonstrated that cysteine-rich keratins, crucial for the structural integrity of hard skin appendages like hair and claws in mammals, also evolved independently in reptiles and birds. These keratins, termed hard acidic (HAS) and hard basic (HBS) sauropsid-specific keratins, were found in various reptiles and birds, with HBS1 keratin specifically expressed in chicken feathers. Molecular phylogenetics indicated that these keratins evolved through convergent evolution, suggesting that similar biomechanical functions in different clades' hard skin appendages arose independently. The findings proposed an evolutionary model where HAS and HBS keratins became structural proteins in reptiles, with at least one HBS keratin being co-opted into feathers post-divergence of birds from reptiles.

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Research cited in this study

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