How do melanocytes get to the skin?

Melanocytes arise from the cranial and truncal neural crest cells in embryonic life. The development of melanocytes from neural crest cells, as well as their ability to migrate, is dependent upon interactions between specific receptors and extracellular ligands, including endothelin 3 and the endothelin B receptors, α;–melanocyte stimulating hormone and the melanocortin-1 receptor stem cell factor and its receptor KIT, each of which induce expression of the microphthalmiaassociated transcription factor (MITF). MITF is the most critical regulator of pigment cell development and survival. Bone morphogenic protein (BMP) is a negative regulator of this process.

Melanocytes migrate via the mesenchyme and reach their final location in the skin, uveal tract of the eye (choroid, ciliary body, and iris), leptomeninges, inner ear (cochlea), and sympathetic chain lining the colon early during embryogenesis. The melanocytes that migrate to the skin take up residence on the epidermal side of the dermal– epidermal junction, the basal layer of the hair matrix, as well as the outer root sheath of the bulge region of the hair follicle. The latter region is where melanocyte stem cells are thought to reside.