Abstract
Purpose :
Deletion of mouse AdipoR1 gene leads to selective reduction of docosahexaenoic acid (DHA) uptake and incorporation by RPE and photoreceptors (PRCs), a flecked retina, accumulation of subretinal macrophages/microglia, decreased electroretinograms (ERGs), followed by progressive loss of PRCs. The purpose of the present study is to understand the mechanism/s by which AdipoR1 influences the health of the retina, by selectively deleting AdipoR1 in the PRCs, the RPE, and the Muller glia (MG) cells.
Methods :
Mice with LoxP sites flanking exons 2-4 of the AdipoR1 gene (AdipoR1flox/flox) were mated with transgenic mice expressing Cre recombinase driven by Cone rod homeobox promoter (PRC cKO), Bestrophin 1 promoter (RPE cKO), or Solute Carrier Family 1 Member 3 promoter (MG cKO). AdipoR1 global KO and wild-type (WT) mice were used as controls. Optical coherence tomography (OCT), electroretinography (ERG), and MALDI imaging mass spectrometry were conducted, and retina and eyecup RNA extracted for RT-qPCR.
Results :
PRC thickness for PRC and RPE cKOs were comparable to WT. There were PRC and RPE morphological abnormalities without overt degeneration, particularly in the MG cKO. ERGs demonstrated progressive attenuation of retinal function for the three cKOs, PRC cKO being the most affected. Gene profiling (1 month) revealed expression levels of phototransduction-related genes(Rhodopsin, Pde6b, Gnat2, Opn1sw, Grk1, and Rcvrn) to be unchanged in cKOs; however, Rdh12 revealed a 3-fold decrease in the RPE of the PRC cKO. MALDI imaging of WT and all KOs revealed no specific retinal PRC differences; however, DHA-phosphatidylcholines, mainly the molecular species containing very long chain polyunsaturated fatty acids were decreased in RPE of the conditional KOs.
Conclusions :
RDH12 mutations result in decreased 11-cis retinal and retinal degeneration. Reduced RDH12 in PRC cKO links the abundance of PRC DHA with a functioning visual cycle. Moreover, lipidomics showed reduction of DHA-containing phosphatidylcholines in PRC and MG cKOs, but increases in RPE cKO, suggesting that lack of DHA within retina proper is compensated for by accumulation of DHA-containing PCs when RPE supply DHA is impaired. Moreover clearly the conditional KOs evidence early PRC dysfunction.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.