Immunolocalization of keratin‐associated beta‐proteins in developing epidermis of lizard suggests that adhesive setae contain glycine–cysteine‐rich proteins

Abstract

The localization of specific keratin-associated beta-proteins (formerly referred to as beta-keratins) in the embryonic epidermis of lizards is not known. Two specific keratin-associated beta-proteins of the epidermis, one representing the glycine-rich subfamily (HgG5) and the other the glycine-cysteine medium-rich subfamily (HgGC10), have been immunolocalized at the ultrastructural level in the lizard Anolis lineatopus. The periderm and granulated subperiderm are most immunonegative for these proteins. HgG5 is low to absent in theOberhäutchen layer while is present in the forming beta-layer, and disappears in mesos- and alpha-layers. Instead, HgGC10 is present in the Oberhäutchen, beta-, and also in the following alpha-layers, and specifically accumulates in the developing adhesive setae but not in the surrounding cells of the clear layer. Therefore, setae and their terminal spatulae that adhere to surfaces allowing these lizards to walk vertically contain cysteine-glycine rich proteins. The study suggests that, like in adult and regenerating epidermis, the HgGC10 protein is not only accumulated in cells of the beta-layer but also in those forming the alpha-layer. This small protein therefore is implicated in resistance, flexibility, and stretching of the epidermal layers. It is also hypothesized that the charges of these proteins may influence adhesion of the setae of pad lamellae. Conversely, glycine-rich beta-proteins like HgG5 give rise to the dense, hydrophobic, and chromophobic corneous material of the resistant beta-layer. This result suggests that the differential accumulation of keratin-associated beta-proteins over the alpha-keratin network determines differences in properties of the stratified layers of the epidermis of lizards.