CD24 (HEAT-STABLE ANTIGEN, NECTADRIN), A NOVEL KERATINOCYTE DIFFERENTIATION MARKER, IS PREFERENTIALLY EXPRESSED IN AREAS OF THE HAIR FOLLICLE CONTAINING THE COLONY-FORMING CELLS

We have isolated, by subtractive and differential hybridization from a library constructed from keratinocyte colony-forming cells (K-CFCs), a cDNA coding for the rat CD24 (nectadrin, heat stable antigen). CD24, a glycoprotein thought to be involved in cell-cell adhesion and signa lling, is highly expressed in keratinocytes located in the bulge area of the rat vibrissa which contains the most K-CFCs. CD24 is also expre ssed in the outer epithelial sheath of human hair follicles and in gla brous epidermis, However, its expression is not restricted to K-CFCs a s demonstrated by cell sorting experiments, and it is thus not a speci fic marker of clonogenic keratinocytes. Rather, its preferential distr ibution in keratinocytes located in the most innervated area of the ra t vibrissal follicle, i.e. the bulge, suggests that its function could be related to the tactile role of the hair follicle.