Postnatal Expression of Kitl Affects Pigmentation of the Epidermis

KITL signaling is important for melanocyte development in mammals; however, its function in the melanocyte stem cells in adult skin is not well-understood. In this study, we have generated genetically modified mice that express a Kitl transgene under the control of a doxycycline-inducible promoter to investigate the impact of its overexpression in embryo, young postnatal, and adult skin with intact hair follicles. We report that overexpression of KITL influences the proliferation and differentiation of melanocytes as well as the self-renewal capacity of resident melanocyte stem cells within the follicular niche. Notably, activation of Kit–KITL signaling induced the migration of melanocytes from hair follicles to the epidermis. In addition, we demonstrate that a single pulse of Kitl transgene expression in postnatal mice results in long-lasting effects on melanocyte stem cells and their differentiated progeny as pigmented skin cells that persist through adulthood. Our findings indicate that regulation of KITL signaling in melanocyte lineage is crucial for melanocyte stem cell homeostasis and melanocyte cell differentiation in postnatal and adult mice.