Immunocytochemical localization of cysteine-rich beta-proteins in the extensible epidermis of the dewlap in the lizard Anolis carolinensis

The dewlap in the lizard Anolis carolinensis is made of scales separated by large interscale regions capable of broad stretching during fan extension. This indicates that the skin contains proteins that allow extension of interscale regions. The immunocytochemical analysis of the epidermis indicates that HgG5, a glycine-rich hydrophobic beta-protein poor in cysteine is localized only in the stiff beta-layer of the outer scale surface, but is completely absent in mesos and alpha-layers and in hinge regions. HgGC10, a cysteine-medium-rich beta-protein is present in beta-layers but especially in alpha-layers of interscale epidermis that presents folds and lacks a beta-layer. HgGC3 is weakly localized in the alpha-layer, but is mainly found in hinge regions. HgGC8 and HgG13 are low to absent in the alpha-and beta-layer. The immunolocalization of cysteine-rich beta-proteins such as HgGC10/3 in alpha-layers and interscale epidermis suggests that these small proteins are involved in the formation of a corneous material compatible with dewlap extension. The basement membrane underneath scales is joined to bundles of collagen fibrils in the dermis through anchoring fibrils that likely determine flattening of the epidermis during the extension of the throat fan.