Abstract
Purpose :
RPE65 is the key retinoid isomerase that catalyzes the synthesis of 11-cis-retinol from all-trans retinyl fatty acyl esters in RPE. Through screening of a bovine RPE cDNA library, we have previously identified ELOVL1 as a negative regulator of RPE65. In this study, we generated a mutant mouse line to define the role of ELOVL1 in regulation of the visual cycle in vivo.
Methods :
A targeting vector with LoxP sites at the up and down streams of the ELOVL1 coding region was generated by standard methods. Using this vector and ES cells, we generated Elovl1-LoxP mice. We then crossed the mutant mice with Best1-Cre mice to generate RPE-specific ELOVL1 knockout (RPE-Elovl1-/-) mice. Expression levels and cellular distribution patterns of proteins were analyzed by immunoblot analysis and immunohistochemistry. The visual cycle rates were determined by measuring synthesis of 11-cis-retinal in mice adapted to dark for different times following photobleaching of rhodopsin. Activity of retinoid isomerase was measured by monitoring synthesis of 11-cis-retinol from all-trans-retinol substrate incubated with mice RPE. Retinoid was analyzed by high performance liquid chromatography.
Results :
Immunoblot analysis showed that Cre was expressed in retina-RPE homogenates of the Best1-Cre and RPE-Elovl1-/- mice, but not wild-type and Elovl1-LoxP mice. Similar to the Best1-Cre mice, Cre was localized to nuclei of RPE cells in immunohistochemistry of retinal sections from RPE-Elovl1-/- mice. The RPE-Elovl1-/- mice are apparently normal and their structure of the neural retina was similar to that of wild-type mice. In addition, expression levels of RPE65 and LRAT in the RPE-Elovl1-/- mice RPE were similar to those in Best1-Cre and Elovl1-LoxP mice. However, synthesis activities of 11-cis-retinol from all-trans-retinol in the RPE-Elovl1-/- RPE were significantly higher than those in Best1-Cre and Elovl1-LoxP mice RPE. Consistent with this result, dark-adaptation rates measured by the synthesis rates of 11-cis-retinal were accelerated in RPE-Elovl1-/- mice, as compared to Best1-Cre mice.
Conclusions :
The RPE-Elovl1-/- mouse is a useful model for studying the role of ELOVL1 in vision and retinal health. ELOVL1 negatively regulates the visual cycle by inhibiting the synthesis of 11-cis-retinol in RPE.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.