Grey in the core of each hair. Melanin is also responsible for the color of the skin and of the eyes. There are only two types of pigment: dark (eumelanin) or light (phaeomelanin). Combined in various combinations, these pigments create all natural hair colors. Melanin itself is the product of a specialized cell, the melanocyte, which is found in each hair follicle, from which the hair grows. As hair grows, the melanocyte injects melanin into the hair cells, which contain the protein keratin and which makes up our hair, skin, and nails. As long as the melanocytes continue injecting melanin into
Hair cell fish have been found to regenerate, their ability has been studied at length. In addition, lateral line hair cells, which have a mechanotransduction function, have been shown to regrow in organisms, such as the zebrafish. Researchers have identified a mammalian gene that normally acts as a molecular switch to block the regrowth of cochlear hair cells in adults. The Rb1 gene encodes the retinoblastoma protein, which is a tumor suppressor. Rb stops cells from dividing by encouraging their exit from the cell cycle. Not only do hair cells in a culture dish regenerate when the Rb1 gene is deleted, but