Abstract
Purpose :
An ocular phenotypic screen of chemically mutagenized mice in the Translational Vision Research Models program identified tvrm283, which displayed a mottled phenotype in the superior fundus. Mottled phenotypes in other mouse models (for example, Ctnna1tvrm5, Adamtsl4tvrm267 mice) are associated with retinal pigment epithelium (RPE) dysmorphology and dysfunction, which are relevant to human ocular diseases. Thus, we aimed to characterize RPE defects and their molecular basis in tvrm283 mice.
Methods :
High-throughput exome sequencing was used to identify the gene disrupted in tvrm283. A mapping cross of homozygous tvrm283 intercross progeny was tested to confirm the map position of the disease allele. Pathological changes in the retina and RPE were assessed longitudinally by histology, electroretinography (ERG), electron microscopy, and immunostaining of RPE flatmounts and cryosections.
Results :
The tvrm283 locus mapped to mouse chromosome 15. Sequence analysis of DNA from affected tvrm283 mutants identified a homozygous 5-bp insertion in the Lratd2 gene which encodes a protein of unknown function containing a domain related to lecithin: retinol acyltransferase. The mutation is predicted to cause a frameshift and premature termination. Complete loss of LRATD2 protein in tvrm283 posterior eyecups was demonstrated by western analysis. Longitudinal ERG tests of tvrm283 mice showed a progressive loss of visual function. Ultrastructural imaging of tvrm283 mutants revealed extracellular debris in the subretinal and RPE basolateral space. Examination of phalloidin- and antibody-stained RPE flatmounts and cryosections showed RPE cell duplication and derangement of the RPE actin cytoskeleton. The loss of visual function, abnormal RPE cellular phenotypes, and the predominant distribution of mottled lesions in the superior RPE near the optic nerve head mimic the Ctnna1tvrm5 model.
Conclusions :
We identified a new mouse model exhibiting retinal degeneration and RPE structural defects similar to those reported previously for the Ctnna1tvrm5 model of human maculopathy. The shared pathological features of tvrm283 and tvrm5 mice raise the possibility that LRATD2 and CTNNA1 may influence RPE integrity through shared pathways, discovery of which may lead to new therapeutic targets to ameliorate or prevent RPE dysfunction in retinal disease.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.