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Exp Dermatol. 2017 Nov;26(11):1039-1045. doi: 10.1111/exd.13364. Epub 2017 Jul 3.

Ectopic expression of the transcription factor MafB in basal keratinocytes induces hyperproliferation and perturbs epidermal homeostasis.

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Laboratory of Molecular and Developmental Biology, Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Japan.
Laboratory of Molecular Medical Bioscience, Graduate School of Medical Life Science, Yokohama City University, Yokohama, Japan.
Laboratory of Molecular and Cell Genetics, Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Japan.
Department of Dermatology, Graduate School of Medicine, University of the Ryukyus, Okinawa, Japan.


Mammalian epidermis is composed of four morphologically and functionally distinct layers of keratinocytes. The innermost basal layer consists of proliferating self-renewing keratinocytes, which also undergo asymmetric cell division to differentiate into postmitotic suprabasal cells throughout life. Control of the balance between growth and differentiation of basal cells is important for epidermal homeostasis to prevent skin disorders including malignancies; however, the underlying mechanism remains to be elucidated. Recently, MafB was identified as one of the transcription factors that regulate epidermal keratinocyte differentiation. MafB is expressed in postmitotic differentiating keratinocytes, and epidermal differentiation is partially impaired in MafB-deficient mice. To further establish the roles of MafB in the epidermis in vivo, we generated mice transgenic for MafB under the control of the basal cell-specific keratin (Krt) 14 promoter. In the epidermis of transgenic mice at embryonic day 18.5, the number of proliferating Krt14-positive basal-like cells was increased, and the granular and cornified layers were thickened. Furthermore, these MafB transgenic mice developed papillomas spontaneously with age. Therefore, MafB promotes differentiation in postmitotic keratinocytes and simultaneously has potential to promote growth when ectopically expressed in undifferentiated basal keratinocytes.


MafB; cell proliferation; epidermal homeostasis; keratinocyte differentiation; transcription factor

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