Clin Genet.2009;76:332
Hereditary hair loss and the ancient signaling pathways that regulate ectodermal appendage formation.

Van Raamsdonk CD.

Epidermal appendages such as hair, teeth, and nails, begin with ectodermal thickening. This placode arises from a primary induction signal sent from the underlying mesenchyme to the overlying epidermis. In mammals, the precise arrangement of hair follicles is due to the amount and distribution of signals that promote and inhibit hair placode formation. Continued development of a hair follicle after placode formation requires a complex cross-talk between the mesenchyme and epidermis. Here, I will review recent studies in humans and mice that have increased our understanding of the role of these signaling pathways in normal development and in hereditary hair loss syndromes. The study of normal hair development and regrowth may suggest ways to restore or eliminate hair and might identify possible targets for the treatment of basal cell carcinoma, a cancer which strongly resembles embryonic hair follicles.