Abstract
Purpose :
KCNJ13 or Kir7.1 forms ion channel pores that allow the influx of potassium ions into retinal pigment epithelium (RPE) cells, thus controlling potassium ion homeostasis. Kcnj13 loss-of-function during RPE development causes early-onset photoreceptor degeneration. This study aims to investigate if Kcnj13 loss-of-function after retinal development impairs RPE and photoreceptor survival and function.
Methods :
RPE-specific Kcnj13 knockout was achieved by intraperitoneally administrating tamoxifen to 6 week-old (WO) Kcnj13f/fRpe65CreERT2/+ mice. Removal of KCNJ13 protein was assessed by immunohistostaining (IHC) of KCNJ13 and Cre-recombinase. Electroretinogram (ERG) was used to report RPE and photoreceptor electrophysiology at 1- and 2-month post injection (PI). IHC with specific markers revealed changes in RPE and photoreceptor morphology. AAV-mediated KCNJ13 augmentation was performed to rescue functional deficits in mutants.
Results :
IHC analysis confirmed the success of Kcnj13 conditional knockout in RPE cells with minimal mosaic. By 2-month PI, RPE-involved scotopic c-wave was diminished in mutants. All rod-driven and cone-driven ERG responses were greatly reduced. Correspondingly, mutants have thinner outer segment and outer nuclear layer, as well as fewer cones. By 1-month PI, c-wave was absent in the mutants, but rod- and cone-driven responses were less severely reduced than the case of 2-month PI, indicating a continuous loss of photoreceptor integrity. Hence, the deterioration in photoreceptor electrophysiology and morphology in adult mutants was attributed to the RPE dysfunction and imbalanced potassium ion homeostasis. Replacement of Kcnj13 expression at 1-month PI, using AAV-pVMD2-KCNJ13, can partially rescue c-wave as well as a- and b-wave responses.
Conclusions :
KCNJ13 is indispensable to RPE function in adult eyes. It also plays non-cell-autonomous roles in maintaining photoreceptor function. Gene therapy targeting KCNJ13 in RPE cells can ameliorate photoreceptor functional defects and degeneration, suggesting the persistent and responsive interactions between these two cell types.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.