Molecular Genetics of the Hair Follicle: The State of the Art
M. A. M. van Steensel*,1, R. Happle and P. M. Steijlen*
For those who are interested in the biology of skin and its derivatives, these are interesting times indeed. In a mere 5 years, the field has been revolutionized by the application of molecular genetics to human congenital skin disorders. Where dermatology first was limited to observation and empirics, there are now DNA-diagnostics, rational drug design, and perhaps even gene therapy available soon. In particular, the study of rare human syndromes involving abnormalities of hair growth and structure has yielded new insights into the regulation of cell growth and differentiation in the hair follicle. As this structure shows a cyclic pattern of differentiation, it may give new information concerning the regulation of cell differentiation in general. This review covers the recent developments in this fast-moving field. First, we will give a short introduction to (structural) hair biology. Next, we will try to fit these data into the framework of what is already known and attempt to present a unified model for hair follicle growth and differentiation.
"…In this model, EGF influences E-cadherin function through an Src-kinase (15). Since E-cadherin may be able to downregulate the levels of ß-catenin, it is tempting to speculate that EGF secretion by the dermal papilla modifies formation of hair follicles by the epidermis by interacting with the Wnt pathway (16). The Egf-receptor knockout mouse has, among other epithelial abnormalities, a reduced number of hair follicles. These are rudimentary and disoriented. This resembles the Lef1-knockout phenotype, supporting the notion that EGF interacts with the Wnt pathway…"