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

This review examines the protein components of cornified skin appendages in tetrapods, such as claws, feathers, hair, and scales, focusing on keratins and epidermal differentiation complex (EDC) proteins. It highlights the diversity and expression patterns of these proteins, their role in the physical properties of skin appendages, and evolutionary differences among tetrapods. The study identifies gaps in knowledge, particularly regarding the three-dimensional structure and protein interactions, suggesting areas for future research. It emphasizes the importance of understanding these proteins' roles in forming diverse skin structures and calls for advancements in gene manipulation techniques and protein structure determination.