Expression of the mouse tyrosinase gene during embryonic development: recapitulation of the temporal regulation in transgenic mice

Pigment in mammals is produced in melanocytes of the skin derived from the neural crest and in the pigmented epithelial cells of the retina derived from the optic cup. Tyrosinase (monophenol, L-dopa:oxygen oxidoreductase, EC 1.14.18.1) is regarded as the key enzyme in pigment synthesis in both these cell types. In this study, we have investigated the temporal regulation of expression of the tyrosinase gene during early eye development and in the developing hair follicle of the mouse by in situ hybridization and have asked whether transgenes would precisely mimick this pattern. We show that the mouse tyrosinase gene is expressed in the pigment epithelium of the retina as early as day 10.5 of gestation. In the hair follicle, tyrosinase gene expression in melanocytes is detected from day 16.5 onwards. This cell type-specific and temporal expression is largely reproduced in transgenic mice carrying a tyrosinase minigene. Our results suggest that sequences in the immediate vicinity of the mouse tyrosinase gene are sufficient to provide cell-type specificity and developmental regulation in melanocytes and in the pigment epithelium.