Anatomy

Keratin 6A

Cytoskeleton

Cell

Evolutionary biology

Biology

Zoology

Gene

Feather

Cell biology

Morphogenesis

Appendage

Keratin 8

Genetics

Intermediate filament

Keratin

Proceedings of the National Academy of Sciences

Significance Avian skin appendages include feathers, scales, claws, and beaks. They are mainly composed of α-keratins, found in all vertebrates, and β-keratins, found only in birds and reptiles. Scientists have wondered how keratins are interwoven to form different skin appendages. By studying keratin gene expression patterns in different chicken skin appendages, we found α- and β-keratin interactions crucial for appendage morphogenesis. Mutations in either α- or β-keratins can disrupt keratin expression and cause structural defects. Thus, different combinations of α- and β-keratins contribute to the structural diversity of feathers. The expansion of β-keratin genes during bird evolution might have greatly increased skin appendage diversity because it increased the possible interactions between α- and β-keratins.

Topographical mapping of α- and β-keratins on developing chicken skin integuments: Functional interaction and evolutionary perspectives