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

Overview

Journal Animals (Basel)

Date 2025 Feb 13

PMID 39943227

Authors

Karin Brigit Holthaus

Julia Steinbinder

Attila Placido Sachslehner

Leopold Eckhart

Affiliations

Soon will be listed here.

Abstract

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.

References

Wu P, Ng C, Yan J, Lai Y, Chen C, Lai Y . Topographical mapping of α- and β-keratins on developing chicken skin integuments: Functional interaction and evolutionary perspectives. Proc Natl Acad Sci U S A. 2015; 112(49):E6770-9. PMC: 4679038. DOI: 10.1073/pnas.1520566112. View

Rogers M, Langbein L, Winter H, Ehmann C, Praetzel S, Schweizer J . Characterization of a first domain of human high glycine-tyrosine and high sulfur keratin-associated protein (KAP) genes on chromosome 21q22.1. J Biol Chem. 2002; 277(50):48993-9002. DOI: 10.1074/jbc.M206422200. View

Armstrong C, Cassimeris L, Da Silva Santos C, Micoogullari Y, Wagner B, Babasyan S . The expression of equine keratins K42 and K124 is restricted to the hoof epidermal lamellae of Equus caballus. PLoS One. 2019; 14(9):e0219234. PMC: 6759161. DOI: 10.1371/journal.pone.0219234. View

Presland R, Whitbread L, ROGERS G . Avian keratin genes. II. Chromosomal arrangement and close linkage of three gene families. J Mol Biol. 1989; 209(4):561-76. DOI: 10.1016/0022-2836(89)90594-9. View

Drake S, Crish S, George J, Stimmelmayr R, Thewissen J . Sensory Hairs in the Bowhead Whale, Balaena mysticetus (Cetacea, Mammalia). Anat Rec (Hoboken). 2015; 298(7):1327-35. DOI: 10.1002/ar.23163. View

Rice R . Proteomic analysis of hair shaft and nail plate. J Cosmet Sci. 2011; 62(2):229-36. PMC: 3227502. View

Alibardi L, Toni M . Immuno-cross reactivity of transglutaminase and cornification marker proteins in the epidermis of vertebrates suggests common processes of soft cornification across species. J Exp Zool B Mol Dev Evol. 2004; 302(6):526-49. DOI: 10.1002/jez.b.21016. View

Sennett R, Rendl M . Mesenchymal-epithelial interactions during hair follicle morphogenesis and cycling. Semin Cell Dev Biol. 2012; 23(8):917-27. PMC: 3496047. DOI: 10.1016/j.semcdb.2012.08.011. View

Holthaus K, Mlitz V, Strasser B, Tschachler E, Alibardi L, Eckhart L . Identification and comparative analysis of the epidermal differentiation complex in snakes. Sci Rep. 2017; 7:45338. PMC: 5366951. DOI: 10.1038/srep45338. View

10.

Strasser B, Mlitz V, Hermann M, Rice R, Eigenheer R, Alibardi L . Evolutionary origin and diversification of epidermal barrier proteins in amniotes. Mol Biol Evol. 2014; 31(12):3194-205. PMC: 4245816. DOI: 10.1093/molbev/msu251. View

11.

Langbein L, Rogers M, Praetzel S, Winter H, Schweizer J . K6irs1, K6irs2, K6irs3, and K6irs4 represent the inner-root-sheath-specific type II epithelial keratins of the human hair follicle. J Invest Dermatol. 2003; 120(4):512-22. DOI: 10.1046/j.1523-1747.2003.12087.x. View

12.

Alibardi L . Immunocytochemical observations on the cornification of soft and hard epidermis in the turtle Chrysemys picta. Zoology (Jena). 2005; 105(1):31-44. DOI: 10.1078/0944-2006-00048. View

13.

Alibardi L . Proliferation in the epidermis of chelonians and growth of the horny scutes. J Morphol. 2005; 265(1):52-69. DOI: 10.1002/jmor.10337. View

14.

Vickaryous M, Sire J . The integumentary skeleton of tetrapods: origin, evolution, and development. J Anat. 2009; 214(4):441-64. PMC: 2736118. DOI: 10.1111/j.1469-7580.2008.01043.x. View

15.

Kaung H . Development of beaks of Rana pipiens larvae. Anat Rec. 1975; 182(4):401-13. DOI: 10.1002/ar.1091820402. View

16.

Chang C, Wu P, Baker R, Maini P, Alibardi L, Chuong C . Reptile scale paradigm: Evo-Devo, pattern formation and regeneration. Int J Dev Biol. 2009; 53(5-6):813-26. PMC: 2874329. DOI: 10.1387/ijdb.072556cc. View

17.

Gomez C, Chua W, Miremadi A, Quist S, Headon D, Watt F . The interfollicular epidermis of adult mouse tail comprises two distinct cell lineages that are differentially regulated by Wnt, Edaradd, and Lrig1. Stem Cell Reports. 2013; 1(1):19-27. PMC: 3757744. DOI: 10.1016/j.stemcr.2013.04.001. View

18.

Price E, McClure P, Jacobs R, Espinoza E . Identification of rhinoceros keratin using direct analysis in real time time-of-flight mass spectrometry and multivariate statistical analysis. Rapid Commun Mass Spectrom. 2018; 32(24):2106-2112. DOI: 10.1002/rcm.8285. View

19.

Wu P, Lai Y, Widelitz R, Chuong C . Comprehensive molecular and cellular studies suggest avian scutate scales are secondarily derived from feathers, and more distant from reptilian scales. Sci Rep. 2018; 8(1):16766. PMC: 6233204. DOI: 10.1038/s41598-018-35176-y. View

20.

Eckhart L, Ehrlich F . Evolution of Trichocyte Keratins. Adv Exp Med Biol. 2018; 1054:33-45. DOI: 10.1007/978-981-10-8195-8_4. View