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Y Fu, VJ Kefalov, J Lai, KW Yau; Study of Cone Pigment Function With a Transgenic Mouse Model . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1962.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: We have produced transgenic mice expressing human red-cone opsin in their rods. These mice may allow us to address the role of visual pigment in the functional differences between rods and cones. They may also allow us to examine the relationship between opsin activity and photoreceptor degeneration in rods. Methods: A 4.4-kb mouse rhodopsin promoter was fused to a human red-cone opsin cDNA to direct specific transgene expression. After positive lines were established, transgene expression was evaluated by immunohistochemistry. These mice were further bred into heterozygous (R+/-) and homozygous (R-/-) rhodopsin knock-out backgrounds by mating with rhodopsin -/- mice. Results: The cone opsin was expressed specifically in mouse rod outer segments (ROSs), as indicated by immunostaining with an antibody against human red-cone opsin. The ROS labeling was intense and uniform in retinal cross-sections. Double-immunostaining with this antibody and one against rhodopsin (1D4) showed complete co-localization. Transgenic mice expressing the cone opsin on WT background (R+/+) showed a very mild degeneration at 7 weeks. This mild degeneration could be due to overexpression of the transgene or to a high rate of thermal isomerization of the exogenous red-cone opsin. To distinguish between these possibilities, the transgenic mice are currently bred into a transducin -/- background. Suction-pipette recordings from single rods of these various animals are in progress. Conclusion: We have successfully produced transgenic mice that express human red-cone opsin in the outer segments of their rods. Electrophysiological studies may provide insights into the role of visual pigment in the low sensitivity of cones to light and their faster response kinetics.
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