Ectopic expression of c-Myc in the skin affects the hair growth cycle and causes an enlargement of the sebaceous gland

Background The hair follicle continually undergoes dynamic remodelling in a cyclical manner involving tightly coordinated patterns of cell proliferation, differentiation and apoptosis. The oncoprotein c‐Myc is a key regulator of these events in epidermal keratinocytes, but its importance in the hair growth cycle has not previously been determined. Objectives To determine the role of c‐Myc in the hair growth cycle. Methods We characterized the hair follicle phenotype of transgenic mice that permit expression of a switchable form of c‐Myc (c‐Myc‐ER™) in the suprabasal epithelial layers of the epidermis and hair follicle. Results c‐Myc activation increased epithelial cell proliferation in the outer root sheath and distal hair follicle, without any substantial alteration in levels of apoptosis. Moreover, chronic c‐Myc activation resulted in marked desynchronization of the murine hair growth cycle, uncoupling of hair cycle‐related skin thickness and enlargement of the sebaceous gland. Conclusions These data implicate c‐Myc in the control of hair growth cycling and hair cycle‐related epidermal and sebaceous gland homeostasis. We suggest that c‐Myc may be activating follicular stem cells either directly or indirectly and that this has important implications for control of the 'hair cycle clock', hair growth and epidermal maintenance.