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Author Notes:

Correspondence should be addressed to Ryan O. Parker, Storm Eye Institute, Medical University of South Carolina, 167 Ashley Avenue, Charleston, SC 29403-5836. E-mail: parkerry@musc.edu.

We thank Patrice Goletz for technical assistance, Dr. Baerbel Rohrer for advice on ERGs, Dr. Luanna Bartholomew for editorial assistance, and Dr. Sharon Yeatts for statistical guidance.

R.P. is the recipient of a RPB Medical Student Eye Research Fellowship.


Research Funding:

This study was supported by grants from NIH EY04939 (R.K.C.), EY14793 (MUSC vision core), EY016470 (J.N.), EY017045 (J.N.), and EY006360 (J.N.); Foundation Fighting Blindness, Inc. (Owings Mills, MD) (J.N., R.K.C.); and unrestricted awards to the Departments of Ophthalmology at MUSC and Emory University from Research to Prevent Blindness (RPB; New York); R.K.C. is an RPB Senior Scientific Investigator.

Normal Cone Function Requires the Interphotoreceptor Retinoid Binding Protein


Journal Title:

Journal of Neuroscience Nursing


Volume 29, Number 14


, Pages 4616-4621

Type of Work:

Article | Final Publisher PDF


11-cis-retinal is the light-sensitive component in rod and cone photoreceptors, and its isomerization to all-trans retinal in the presence of light initiates the visual response. For photoreceptors to function normally, all-trans retinal must be converted back into 11-cis-retinal through a series of enzymatic steps known as the visual cycle. The interphotoreceptor retinoid-binding protein (IRBP) is a proposed retinoid transporter in the visual cycle, but rods in Irbp−/− mice have a normal visual cycle. While rods are primarily responsible for dim light vision, the ability of cones to function in constant light is essential to human vision and may be facilitated by cone-specific visual cycle pathways. We analyzed the cones in Irbp−/− mice to determine whether IRBP has a cone-specific visual cycle function. Cone electroretinogram (ERG) responses were reduced in Irbp−/− mice, but similar responses from Irbp−/− mice at all ages suggest that degeneration does not underlie cone dysfunction. Furthermore, cone densities and opsin levels in Irbp−/− mice were similar to C57BL/6 (wild-type) mice, and both cone opsins were properly localized to the cone outer segments. To test for retinoid deficiency in Irbp−/− mice, ERGs were analyzed before and after intraperitoneal injections of 9-cis-retinal. Treatment with 9-cis-retinal produced a significant recovery of the cone response in Irbp−/− mice and shows that retinoid deficiency underlies cone dysfunction. These data indicate that IRBP is essential to normal cone function and demonstrate that differences exist in the visual cycle of rods and cones.

Copyright information:

©2009 Society for Neuroscience

This is an Open Access work distributed under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/).
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