Variegated expression and delayed retinal pigmentation during development in transgenic mice with a deletion in the locus control region of the tyrosinase gene

Deletion of the tyrosinase locus control region (LCR) in transgenic mice re sults in variegated expression in the skin. Here we investigate the pigment ation pattern of other tissues that express tyrosinase: iris, choroid, and retina in the same animals. A mosaic distribution of pigmentation appears i n the iris and choroid. Interestingly, a markedly different mosaic pattern is found in the retina, where central areas contain little or no melanin wh ile pigmentation rises to normal levels towards periphery. Further, there i s a temporal delay in the initiation and accumulation of pigment in retinal pigmented epithelium (RPE) cells during development, and patterns of adult retinal melanisation in these mice appear arrested at a stage found in ear ly embryogenesis in wild-type mice. These results demonstrate that the tyro sinase LCR is needed for the correct establishment and maintenance of this expression domain throughout development, but particularly during the later stages of retinal melanisation. genesis 30:21-25, 2001. (C) 2001 Wiley-Lis s, Inc.