Epidermal differentiation and keratin gene expression.

Epidermal keratinocytes are ideal as a model system for the study of mammalian differentiation because primary cells have a high proliferative capacity and can be cultured under conditions enabling a balance of growth and differentiation. In addition, epidermal keratin genes have been cloned and characterized, and their strong promoters provide a means of high-level expression of transgenes in the epidermis of mice. For these reasons, considerable headway has been made in recent years in the quest to elucidate the biological pathways involved in the control of epidermal growth and differentiation. An understanding of these mechanisms is essential to realizing the potential of epidermal keratinocytes for drug delivery and gene therapy. This paper reviews what is presently known about epidermal growth and differentiation, with emphasis on the expression of epidermal-specific genes.