Mélanogenèse

Melanin is synthesized by the melanocytes which are specialized dentritic cells originating from the neural crest. The melanocytes are located in the basal layer of the epidermis and in the hair bulb and the follicular wall. The melanin is produced within specialized organelles that share characteristics with lysosomes, and called melanosomes. Two kinds of melanin are produced, the black – brown eumelanins, and the yellow – red phaeomelanins which are the less photoprotective ones. Three key enzymes for melanogenesis are identified: tyrosinase and tyrosinase related proteins 1 and 2. A significant number of genes control the embryogenesis of melanocytes, the biogenesis of melanosomes, their transport within melanocytes and their final transfer to keratinocytes. Many factors of melanogenesis regulation have been identified (ultraviolet, melanotropic hormones, cytokines…). The mechanisms of cell signalling involved in the melanogenesis are progressively analysed. These recent data will allow bettering understanding the genetic mechanisms of the melanin photoprotection of the skin. They have allowed identifying new targets for the treatment of hyper- and hypo-melanosis.