BASONUCLIN AS A CELL MARKER IN THE FORMATION AND CYCLING OF THE MURINE HAIR FOLLICLE

Basonuclin, a zinc-finger protein, is found in stratified squamous epi thelia and hair follicles. In the basal keratinocytes of mouse epiderm is, basonuclin is detected mainly in the cytoplasm. During the develop ment of murine hair follicles, this protein concentrates in the nuclei of the basal cells that form the primary hair germs. As follicle morp hogenesis proceeds, the epithelial cells possessing nuclear basonuclin invade the dermis and surround the follicular papilla. In mature anag en follicles, nuclear basonuclin is principally restricted to the basa l layers of the outer root sheath and bulbar matrix; these regions are known to contain cells capable of proliferation, and to lack the feat ures of terminal differentiation. During catagen, the compartment of c ells containing nuclear basonuclin regresses, and in telogen, only a s mall number of these cells remain to form the secondary hair germ at t he follicle base. During the next anagen, this basonuclin-containing p opulation expands and regenerates the hair-producing portion of the fo llicle. It is concluded that in all hair cycles, the transient segment of the follicle originates from germinative cells possessing nuclear basonuclin.