B-Myb
(Mybl2) is a member of the Myb gene family of transcription factors involved in
the control of cell growth, differentiation, and apoptosis. The effects of
B-Myb on keratinocyte proliferation and differentiation have not yet been
clarified. The present study was performed to examine the role of B-Myb in
proliferation and differentiation of the spontaneously immortalized human skin
keratinocyte cell line HaCaT and normal human keratinocytes (NHK) with
formation of a stratified epidermoid structure in air–liquid interface
3-dimensional culture. B-Myb was expressed specifically in undifferentiated
normal keratinocytes and downregulated during differentiation. The constitutive
overexpression of B-Myb in HaCaT cells during air exposure-induced
differentiation resulted in an undifferentiated phenotype, i.e., thickening of
the stratified layers, suppression of differentiation marker expression, and
retention of proliferative activity with activation of cell cycle regulatory
proteins in the S and G2/M phases. In contrast, suppression of B-Myb caused
their downregulation and constrained proliferation with retention of
differentiation capacity. These findings suggested that B-Myb may play an
important role in maintenance of the undifferentiated phenotype of
keratinocytes in the basal epidermal layer.