Cornification in reptilian epidermis occurs through the deposition of keratin-associated beta-proteins (beta-keratins) onto a scaffold of intermediate filament keratins
Article first published online: 15 OCT 2012
Copyright © 2012 Wiley Periodicals, Inc.
Journal of Morphology
Volume 274, Issue 2, pages 175–193, February 2013
How to Cite
Alibardi, L. (2013), Cornification in reptilian epidermis occurs through the deposition of keratin-associated beta-proteins (beta-keratins) onto a scaffold of intermediate filament keratins. J. Morphol., 274: 175–193. doi: 10.1002/jmor.20086
- Issue published online: 4 JAN 2013
- Article first published online: 15 OCT 2012
- Comparative Histolab
- Italian Ministry of Education and Scientific Research. Grant Number: 2008 AXS E-002
The isolation of genes for alpha-keratins and keratin-associated beta-proteins (formerly beta-keratins) has allowed the production of epitope-specific antibodies for localizing these proteins during the process of cornification epidermis of reptilian sauropsids. The antibodies are directed toward proteins in the alpha-keratin range (40–70 kDa) or beta-protein range (10–30 kDa) of most reptilian sauropsids. The ultrastructural immunogold study shows the localization of acidic alpha-proteins in suprabasal and precorneous epidermal layers in lizard, snake, tuatara, crocodile, and turtle while keratin-associated beta-proteins are localized in precorneous and corneous layers. This late activation of the synthesis of keratin-associated beta-proteins is typical for keratin-associated and corneous proteins in mammalian epidermis (involucrin, filaggrin, loricrin) or hair (tyrosine-rich or sulfur-rich proteins). In turtles and crocodilians epidermis, keratin-associated beta-proteins are synthesized in upper spinosus and precorneous layers and accumulate in the corneous layer. The complex stratification of lepidosaurian epidermis derives from the deposition of specific glycine-rich versus cysteine-glycine-rich keratin-associated beta-proteins in cells sequentially produced from the basal layer and not from the alternation of beta- with alpha-keratins. The process gives rise to Oberhäutchen, beta-, mesos-, and alpha-layers during the shedding cycle of lizards and snakes. Differently from fish, amphibian, and mammalian keratin-associated proteins (KAPs) of the epidermis, the keratin-associated beta-proteins of sauropsids are capable to form filaments of 3–4 nm which give rise to an X-ray beta-pattern as a consequence of the presence of a beta-pleated central region of high homology, which seems to be absent in KAPs of the other vertebrates. J. Morphol., 2013. © 2012 Wiley Periodicals, Inc.