Mutually Exclusive Expression of Human Red and Green Visual Pigment-Reporter Transgenes Occurs at High Frequency in Murine Cone Photoreceptors

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 96; no. 9; pp. 5251 - 5256
• Main Authors: Wang, Yanshu, Smallwood, Philip M., Cowan, Mitra, Blesh, Diane, Lawler, Ann, Nathans, Jeremy
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences of the United States of America 27.04.1999; National Acad Sciences; National Academy of Sciences; The National Academy of Sciences
• Subjects: Animals; Biological Sciences; Biology; Color Perception - genetics; Color vision; Eye Proteins - genetics; Eyes & eyesight; Gene Expression; Gene Transfer Techniques; Genes; Humans; Mammals; Mice; Pigments; Primates; Retina; Retinal Cone Photoreceptor Cells - physiology; Retinal pigments; Retinal Pigments - genetics; Stem cells; Stochastic models; Transgenes; X Chromosome
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.96.9.5251

This study examines the mechanism of mutually exclusive expression of the human X-linked red and green visual pigment genes in their respective cone photoreceptors by asking whether this expression pattern can be produced in a mammal that normally carries only a single X-linked visual pigment gene. To address this question, we generated transgenic mice that carry a single copy of a minimal human X chromosome visual pigment gene array in which the red and green pigment gene transcription units were replaced, respectively, by alkaline phosphatase and β -galactosidase reporters. As determined by histochemical staining, the reporters are expressed exclusively in cone photoreceptor cells. In 20 transgenic mice carrying any one of three independent transgene insertion events, an average of 63% of expressing cones have alkaline phosphatase activity, 10% have β -galactosidase activity, and 27% have activity for both reporters. Thus, mutually exclusive expression of red and green pigment transgenes can be achieved in a large fraction of cones in a dichromat mammal, suggesting a facile evolutionary path for the development of trichromacy after visual pigment gene duplication. These observations are consistent with a model of visual pigment expression in which stochastic pairing occurs between a locus control region and either the red or the green pigment gene promotor.