Inherited disorders of the skin in human and mouse: from development to differentiation

The last ten years has revealed some of the key players in the development and differentiation of the hair follicle and the epidermis in general. In this review, we discuss how our current understanding of these processes has been made possible by the elucidation of the molecular basis of human inherited diseases and mouse mutants which display defects in the hair and epidermis. For examples, the study of ectodermal dysplasias and the basal cell carcinoma predisposition disease Gorlin syndrome have allowed the determination of signalling hierarchies critical in the formation of the hair follicle. Epidermolytic diseases and hyperkeratoses have focussed attention on the importance of the programs of keratin expression, while ichthyoses provide insight in the final stage of epidermal development, cornification. Finally, the increasing range of diseases and mouse models exhibiting alopecias are revealing the critical pathways in control of the hair follicle cycle.