Fig. 5.

Sources of differentiated melanocytes. During embryonic development, melanoblast originate from a bipotent melanoblast/glial precursor cell. Melanoblasts that reach developing hair follicles will be segregated into two distinct and physically separated populations during hair follicle morphogenesis. One population will localize in the hair follicle bulb, where they differentiate into mature melanocytes and immediately contribute to hair pigmentation during the first hair cycle. The other population consists of melanocyte stem cells that reside within a specialized stem cell niche, referred to as the hair follicle bulge, and serve as reservoir to replenish the cycling hair follicles with new melanocytes. Schwann cell precursor cells (SCP) may also differentiate into mature melanocytes in vitro or after wounding in vivo. While the relative contribution of SCPs to embryonic and physiological melanocytes in mice remains to be elucidated, in chick embryos SCPs contribute to melanocytes from early embryonic development