EXPRESSION OF THE BCL-2 PROTOONCOGENE IN THE CYCLING ADULT-MOUSE HAIRFOLLICLE

The hair follicle undergoes a cycle of growing, regressing, and restin g phases (anagen, catagen, telogen, respectively). As the follicle ent ers catagen, the cells of the lower, cycling portion undergo a process of controlled cell death (apoptosis). Understanding the mechanism of apoptosis in the follicle should give insight into one of the control steps of hair cycling. In this study we sought the expression of bcl-2 , a protooncogene associated with apoptosis control, in the cycling fo llicle of the adult mouse. Using a monoclonal antibody to the mouse pr otein we immunolocalized bcl-2 gene product in the cycling pelage foll icle of the C57/B6 adult mouse. The protein was expressed in the folli cular papilla (a non-cycling portion of the follicle) throughout the c ycle-including telogen. The cycling follicular epithelium, however, sh owed positive antibody staining in anagen, which decreased in catagen and disappeared in telogen. In anagen the cells of the bulb, bulge, an d basal layer of the outer root sheath expressed the bcl-2 protein. Un derstanding the action of this apoptosis-inhibiting molecule should se rve to elucidate the dynamics of follicular cycling.