Melanins and Melanocytes

Abstract

Human skin colour results from the synthesis and distribution of melanins in the epidermis and hair follicles. These pigments are produced by melanocytes, specialised dendritic cells originating from the neural crest. Melanins are a heterogeneous group of compounds with different physicochemical and perhaps photochemical properties. The main physiological stimulus for human melanogenesis is ultraviolet radiation. According to conventional thinking, the most important biological role of melanin is protection against the harmful effects of sunlight. However, recent data suggest that the function of melanins is much more complex. In addition to producing melanins, melanocytes have the capacity to synthesise and secrete a wide variety of signal molecules such as growth factors, and cytokines. It is likely that melanocytes are involved in several regulatory pathways distinct from melanogenesis. Several pigmentary genes involved in the control of mouse coat colour have been characterised. These murine genes have homologues that are similarly expressed in human melanocytes. Recent advances in the molecular biology of melanin pigmentation have led to a better understanding of the mechanisms underlying normal and abnormal human skin colour.