The nude gene and the skin.

The nude mutation has been known for a long time. Nevertheless, the gene responsible for the defect has been identified only recently. It encodes a transcriptional activator of the family of forkhead proteins mainly expressed in thymic epithelium and distinct keratinocyte populations in the epidermis and hair follicles. The present review focuses on the molecular and functional characterization of the nude gene and its product and gives an overview as to its role in skin biology and the first identified target genes in the skin. In addition, evolutionary aspects are highlighted stressing the importance of such investigations for a comprehensive understanding of the nude gene product and the regulation of its expression. Furthermore, these studies give a hint as to when the nude gene has occurred first and how it has developed in molecular and functional terms since then.