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.