Increased transgene expression by the mouse tyrosinase enhancer is restricted to neural crest-derived pigment cells

In this study, we have addressed the impact of the mouse tyrosinase enhance r on regulated expression from the mouse tyrosinase promoter during embryon ic development. Stable and transient transgenic experiments using the repor ter gene lacZ reveal that (1) expression is detected in neural crest-derive d melanoblasts from E11.5 onward, (2) the enhancer does not increase transg enic expression in optic cup-derived pigment cells of the retinal pigment e pithelium (RPE), and (3) expression in the telencephalon is not any longer detected. The importance of the enhancer for expression in pigment cells of the eye was further investigated in adult mice using an attenuated diphthe ria toxin A gene. This demonstrated that in presence of the enhancer the tr ansgene expression is specifically targeted to neural crest-derived melanoc ytes of the choroid and not, or slightly, to the RPE, This suggests that ty rosinase is differentially regulated in the two pigment cell lineages, and that this promoter can be used to target expression preferentially to the n eural crest-derived melanocyte lineage. (C) 2001 Wiley-Liss, Inc.