CD98, a novel marker of transient amplifying human keratinocytes.

Identification of plasma membrane markers of basal keratinocytes is essential for sorting basal cells and, subsequently, adult epidermal stem cells. In this study, we isolated caveolin-1-enriched microdomains from human HaCaT keratinocytes and identified proteins representing potential cell surface markers of the epidermis by a proteomic approach. The purification of this caveolae domain allowed us to characterize 53 proteins of which 26% were transmembrane and 32% associated-membrane proteins. One of them, CD98, was found to be co-localized with beta1 integrin at the plasma membrane of the basal keratinocytes of healthy human epidermis. We then isolated CD98-positive keratinocytes from fresh skin biopsies. Using clonogenic assays, we demonstrate that CD98 may be considered as a marker of transient amplifying human keratinocytes.