Roles of MED1 in Quiescence of Hair Follicle Stem Cells and Maintenance of Normal Hair Cycling
Authors
Takeshi Nakajima, Shigeki Inui, Tomohiro Fushimi, Fumihito Noguchi, Yutaka Kitagawa, Janardan K. Reddy and Satoshi Itami
Institution
Department of Regenerative Dermatology, Graduate School of Medicine, Osaka University
Country
Japan
Year
2012
Journal
Journal of Investigative Dermatology
Abstract
MED1 (mediator complex subunit 1) is expressed by human epidermal keratinocytes and functions as a coactivator of several transcription factors. To elucidate the role of MED1 in keratinocytes, we established keratinocyte-specific Med1-null (Med1epi/) mice using the K5Cre/LoxP system. Development of the epidermis and appendages of Med1epi/ mice were macroscopically and microscopically normal until the second catagen of the hair cycle. However, the hair cycle of Med1epi/ mice was spontaneously repeated after the second telogen, which does not occur in wild-type (WT) mice. Hair follicles of Med1epi/ mice could not enter anagen after 6 months of age, resulting in sparse pelage hair in older Med1epi/ mice. Interfollicular epidermis (IFE) of Med1epi/ mice was acanthotic and more proliferative than that of WT mice, whereas these findings were less evident in older Med1epi/ mice. Flow cytometric analysis revealed that the numbers of hair follicle bulge stem cells were reduced in Med1epi/ mice from a few months after birth. These results suggest that MED1 has roles in maintaining quiescence of keratinocytes and preventing depletion of the follicular stem cells.