| Abstract: | During tail regeneration in lizards, the stratified regenerating epidermis progressively gives rise to neogenic scales that form a new epidermal generation. Initially, a soft, un‐scaled, pliable, and extensible epidermis is formed that is progressively replaced by a resistant but non‐extensible scaled epidermis. This suggests that the initial corneous proteins are later replaced with harder corneous proteins. Using PCR and immunocytochemistry, the present study shows an upregulation in the synthesis of low‐cysteine type I and II alpha‐keratins and of corneous beta‐proteins with a medium cysteine content and a low content in glycine (formerly termed beta‐keratins) produced at the beginning of epidermal regeneration. Quantitative PCR indicates upregulation in the production of alpha‐keratin mRNAs, particularly of type I, between normal and the thicker regenerating epidermis. PCR‐data also indicate a higher upregulation for cysteine‐rich corneous beta‐proteins and a high but less intense upregulation of low glycine corneous protein mRNAs at the beginning of scale regeneration. Immunolabeling confirms the localization of these proteins, and in particular of beta‐proteins with a medium content in cysteine initially formed in the wound epidermis and later in the differentiating corneous layers of regenerating scales. It is concluded that the wound epidermis initially contains alpha‐keratins and corneous beta‐proteins with a lower cysteine content than more specialized beta‐proteins later formed in the mature scales. These initial corneous proteins are likely related to the pliability of the wound epidermis while more specialized alpha‐keratins and beta‐proteins richer in glycine and cysteine are synthesized later in the mature and inflexible scales. J. Morphol. 278:119–130, 2017. ©© 2016 Wiley Periodicals,Inc. |
