Microphthalmia transcription factor induces both retinal pigmented epithelium and neural crest melanocytes from neuroretina cells

Mitf encodes a basic helix-loop-helix transcription factor that plays an essential role in the differentiation of the retinal pigmented epithelium (RPE) and neural crest-derived melanocytes. As cells containing melanogenic enzymes (TRP2) are found in Mitf mouse mutants, it is not clear whether Mitf is a downstream factor or a master regulator of melanocyte differentiation. To further study the role of Mitf in committing cells to the melanocyte lineage, we express Mitf in the cultured quail neuroretina cells. This leads to the induction of two types of pigmented cells: neural crest-derived melanocytes, according to their dendritic morphology, physiology, and gene expression pattern are observed together with pigmented epithelial RPE-like cells. The expression of Mitf is lower in pigmented epithelial RPE-like cells than in neural crest-derived melanocytes. Accordingly, overexpression of Mitf in cultured quail RPE causes cells to develop into neural crest-like pigmented cells. Thus, Mitf is sufficient for the proper differentiation of crest-like pigmented cells from retinal cells and its expression level may determine the type of pigment cell induced.