The mammalian pigmentary system - a model experimental system for exploring the functional divergence of a differentiated cell type

There are two cell lineages of mammalian melanin pigment cells, one that leads to retinal pigment epithelium (RPE) cells in the eye from the optic cup and the other leading to melanocytes from vertebrate-specific neural crest cells. Melanocyte precursors have high mobility and migrate and settle into various tissues and organs, including the skin, choroid, inner ear, heart, brain, adipose tissue, lung, etc. It is well known that RPE cells are essential for visual acuity and that melanocytes in the skin provide protection against UV-damage. So, what is the function of extracutaneous melanocytes that are distributed elsewhere in the body where only very small amounts of light illuminate their existence? Here I would like to briefly introduce our research history and then discuss the important roles of melanocytes in the inner ear that are indispensable for hearing ability and those in the choroid where they seem to contribute to maintaining the structures of their habitats