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Transgenic Mice: Fade to grey
TRANSGENIC MICE
BIOLOGY IN PICTURES
Fade to grey Expression of different amounts of tyrosinase from varying numbers of transgenes rescues the coat colour and eye pigmentation of albino mice in an approximately dose-dependent manner.
Tyrosinase, the key enzyme in the production of melanin, is the product of the albino (c) locus in mice. Tyrosinase expression is tightly regulated during development and is high specifically in two cell types of different origin: neural crest-derived melanocytes, found in the skin, iris and choroid of the eye; and cells from the pigmented epithelium of the retina, derived from the optic cup. Albino mutant mice carry a point-mutation in the first exon of the tyrosinase gene, leading to the production of a non-functional protein. The albino phenotype of a recipient mouse strain was rescued by making the mice transgenic for a functional tyrosinase minigene driven by the tyrosinase promoter and a melanocyte-specific enhancer located 12 kilobases upstream of the gene. The coat colour of several different transgenic mouse lines derived in this way can be seen on the left of the photograph. On the right is a series of bright-field photomicrographs of sections through the retinae of these mice (scale bar = 20Lm). The expression of tyrosinase, as detected either by the colour intensity of the coat (left) or by pigment accumulation in the choroid (CH) and retinal pigmented epithelium (RPE; indicated by arrows, right), correlates with the copy number of the transgene, as a result of the proportional increase in enhancer activity with each copy of the transgene. Albino and wild-type pigmented mice are included at the top and bottom of the figure, respectively, for comparison. For further information see R. Ganss, L. Montoliu, A.P Monaghan and G. Schutz, EMBOJournal 1994, 13:3083-3093, from which part of the figure is reproduced by permission of Oxford University Press. Photographs and text kindly provided by Lluis Montoliu, Division of Molecular Biology of the Cell, German Cancer Research Centre, Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany.
© Current Biology 1994, Vol 4 No 11
1025
BIOLOGY IN PICTURES
Fade to grey Expression of different amounts of tyrosinase from varying numbers of transgenes rescues the coat colour and eye pigmentation of albino mice in an approximately dose-dependent manner.
Tyrosinase, the key enzyme in the production of melanin, is the product of the albino (c) locus in mice. Tyrosinase expression is tightly regulated during development and is high specifically in two cell types of different origin: neural crest-derived melanocytes, found in the skin, iris and choroid of the eye; and cells from the pigmented epithelium of the retina, derived from the optic cup. Albino mutant mice carry a point-mutation in the first exon of the tyrosinase gene, leading to the production of a non-functional protein. The albino phenotype of a recipient mouse strain was rescued by making the mice transgenic for a functional tyrosinase minigene driven by the tyrosinase promoter and a melanocyte-specific enhancer located 12 kilobases upstream of the gene. The coat colour of several different transgenic mouse lines derived in this way can be seen on the left of the photograph. On the right is a series of bright-field photomicrographs of sections through the retinae of these mice (scale bar = 20Lm). The expression of tyrosinase, as detected either by the colour intensity of the coat (left) or by pigment accumulation in the choroid (CH) and retinal pigmented epithelium (RPE; indicated by arrows, right), correlates with the copy number of the transgene, as a result of the proportional increase in enhancer activity with each copy of the transgene. Albino and wild-type pigmented mice are included at the top and bottom of the figure, respectively, for comparison. For further information see R. Ganss, L. Montoliu, A.P Monaghan and G. Schutz, EMBOJournal 1994, 13:3083-3093, from which part of the figure is reproduced by permission of Oxford University Press. Photographs and text kindly provided by Lluis Montoliu, Division of Molecular Biology of the Cell, German Cancer Research Centre, Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany.
© Current Biology 1994, Vol 4 No 11
1025