Skin Appendage Proteins of Tetrapods: Building Blocks of Claws, Feathers, Hair and Other Cornified Epithelial Structures

Reptiles, birds, mammals and amphibians, together forming the clade tetrapods, have a large diversity of cornified skin appendages, such as scales, feathers, hair and claws. The skin appendages consist of dead epithelial cells that are tightly packed with specific structural proteins. Here, we revie...

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Main Authors: Karin Brigit Holthaus, Julia Steinbinder, Attila Placido Sachslehner, Leopold Eckhart
Format: Article
Language:English
Published: MDPI AG 2025-02-01
Series:Animals
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Online Access:https://www.mdpi.com/2076-2615/15/3/457
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author Karin Brigit Holthaus
Julia Steinbinder
Attila Placido Sachslehner
Leopold Eckhart
author_facet Karin Brigit Holthaus
Julia Steinbinder
Attila Placido Sachslehner
Leopold Eckhart
author_sort Karin Brigit Holthaus
collection DOAJ
description Reptiles, birds, mammals and amphibians, together forming the clade tetrapods, have a large diversity of cornified skin appendages, such as scales, feathers, hair and claws. The skin appendages consist of dead epithelial cells that are tightly packed with specific structural proteins. Here, we review the molecular diversity and expression patterns of major types of skin appendage proteins, namely keratin intermediate filament proteins, keratin-associated proteins (KRTAPs) and proteins encoded by genes of the epidermal differentiation complex (EDC), including corneous beta-proteins, also known as beta-keratins. We summarize the current knowledge about the components of skin appendages with a focus on keratins and EDC proteins that have recently been identified in reptiles and birds. We discuss gaps of knowledge and suggest directions of future research.
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spelling doaj-art-5e14486eade349b6b69f79feb1cf89bd2025-08-20T02:48:09ZengMDPI AGAnimals2076-26152025-02-0115345710.3390/ani15030457Skin Appendage Proteins of Tetrapods: Building Blocks of Claws, Feathers, Hair and Other Cornified Epithelial StructuresKarin Brigit Holthaus0Julia Steinbinder1Attila Placido Sachslehner2Leopold Eckhart3Department of Dermatology, Medical University of Vienna, 1090 Vienna, AustriaDepartment of Dermatology, Medical University of Vienna, 1090 Vienna, AustriaDepartment of Dermatology, Medical University of Vienna, 1090 Vienna, AustriaDepartment of Dermatology, Medical University of Vienna, 1090 Vienna, AustriaReptiles, birds, mammals and amphibians, together forming the clade tetrapods, have a large diversity of cornified skin appendages, such as scales, feathers, hair and claws. The skin appendages consist of dead epithelial cells that are tightly packed with specific structural proteins. Here, we review the molecular diversity and expression patterns of major types of skin appendage proteins, namely keratin intermediate filament proteins, keratin-associated proteins (KRTAPs) and proteins encoded by genes of the epidermal differentiation complex (EDC), including corneous beta-proteins, also known as beta-keratins. We summarize the current knowledge about the components of skin appendages with a focus on keratins and EDC proteins that have recently been identified in reptiles and birds. We discuss gaps of knowledge and suggest directions of future research.https://www.mdpi.com/2076-2615/15/3/457skinkeratinocytescornificationfeatherclawnail
spellingShingle Karin Brigit Holthaus
Julia Steinbinder
Attila Placido Sachslehner
Leopold Eckhart
Skin Appendage Proteins of Tetrapods: Building Blocks of Claws, Feathers, Hair and Other Cornified Epithelial Structures
Animals
skin
keratinocytes
cornification
feather
claw
nail
title Skin Appendage Proteins of Tetrapods: Building Blocks of Claws, Feathers, Hair and Other Cornified Epithelial Structures
title_full Skin Appendage Proteins of Tetrapods: Building Blocks of Claws, Feathers, Hair and Other Cornified Epithelial Structures
title_fullStr Skin Appendage Proteins of Tetrapods: Building Blocks of Claws, Feathers, Hair and Other Cornified Epithelial Structures
title_full_unstemmed Skin Appendage Proteins of Tetrapods: Building Blocks of Claws, Feathers, Hair and Other Cornified Epithelial Structures
title_short Skin Appendage Proteins of Tetrapods: Building Blocks of Claws, Feathers, Hair and Other Cornified Epithelial Structures
title_sort skin appendage proteins of tetrapods building blocks of claws feathers hair and other cornified epithelial structures
topic skin
keratinocytes
cornification
feather
claw
nail
url https://www.mdpi.com/2076-2615/15/3/457
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AT juliasteinbinder skinappendageproteinsoftetrapodsbuildingblocksofclawsfeathershairandothercornifiedepithelialstructures
AT attilaplacidosachslehner skinappendageproteinsoftetrapodsbuildingblocksofclawsfeathershairandothercornifiedepithelialstructures
AT leopoldeckhart skinappendageproteinsoftetrapodsbuildingblocksofclawsfeathershairandothercornifiedepithelialstructures