The series begins with a Review of epidermal barrier formationby Julia Segre (17). In addition to serving as the body’soutermost protective covering, the skin is a barrier betweenthe body and the terrestrial environment. Barrier function iscritical in newborn animals, as shown by transgenic animal modelswith barrier defects that die shortly after birth from transepidermalwater loss.
Early studies of the skin barrier focused mainly on its remarkablephysiochemical properties and on determining the unique proteincomposition of lipids and the cornified cell envelope (1, 2,4, 5). Genetic approaches and efforts in genomic cloning haverevealed an unusually complex cluster of genes in human chromosome1q21, termed the epidermal differentiation complex, which containsmore than 30 genes involved in terminal differentiation of theskin (18).
Recent studies of the molecular mechanisms governing barrierformation, particularly transcriptional events, have begun toshed light on the molecular underpinnings of this highly regulatedprocess. In her Review (17), Segre draws some intriguing parallelsbetween the formation of the epidermal barrier and the reprisalof these processes in the setting of common skin disorders suchas psoriasis or atopic dermatitis, which display a perturbationin barrier function that may exacerbate these conditions. Takingclues from the transcriptional and molecular events involvedin forming the barrier in utero, this Review proposes that themanagement of inflammatory skin disease may benefit from therapiesthat enhance restoration of the epidermal barrier.