Introduction
Peter J. Koch, Anna L. Bruckner and Maranke I. Koster Biology of Keratinocytes 56
Key features
The epidermis functions as a barrier that provides protection against harmful substances, ultraviolet radiation, and water loss
Through a complex terminal differentiation program, the progeny of epidermal stem cells undergo molecular and biochemical changes that generate the morphologically and functionally distinct layers of the epidermis
Keratinocyte terminal differentiation culminates in the replacement of the plasma membrane with the cornified cell envelope
Keratin intermediate filaments, which are expressed by keratino- cytes in a differentiation-specific manner, are required to maintain epidermal integrity and have additional roles in the regulation of basic cell functions
Desmosomes, which integrate the keratin cytoskeleton into the cell membrane and establish adhesive points between adjacent cells, are necessary for epidermal stability and stress resistance; these cell–cell junctions also function as signaling centers in epidermal morphogenesis and homeostasis
Other cell–cell junctions that are found in keratinocytes include adherens junctions, tight junctions, and gap junctions
A variety of inherited skin diseases are caused by a failure of normal epidermal differentiation and function