Immuno reactivity of alpha- and beta-layers in lizard epidermis

Reptilian epidermis may share some mechanisms of keratinization with those of mammalian and avian epidermis. The expression of keratins and proteins associated with the process of keratinization (filaggrin) and formation of the cell corneus envelope (loricrin) has been analysed at the light microscopic and ultrastructural level in the complex normal and regenerating lizard epidermis. The localization of alpha and beta-keratins, and of filaggrin-like and loricrin-like immunoreactivities has confirmed that the epidermis of lizards consists of two different layers, an alpha-layer localizing alpha-keratins and showing weak filaggrin- and loricrin-like immunoreactivities, as in the mammalian epidermis, and a beta-layer that localizes a beta-keratin immunoreactivity, such as in scutate scales and feathers of birds. The present study suggests that the segregation of alpha- from beta-keratin synthesis is correlated with the evolution of an intraepidermal shedding layer that allows the epidermal molt.