Temporal Regulation of Myopia and Inflammation-Associated Pathways in the Interphotoreceptor Retinoid-Binding Protein Knockout Mouse Model

Abstract

Purpose Myopia is a complex disorder with etiology involving an interplay between several genetic and environmental factors. Interphotoreceptor retinoid-binding protein (IRBP) is found in the subretinal space and is crucial in the visual cycle. The interphotoreceptor retinoid-binding protein knockout mouse (IRBP KO) was established as a model system to understand myopia and retinal degeneration. The current study investigated genes associated with myopia, retinal homeostasis, and inflammation in IRBP KO. Methods RNA from retinas of congenic IRBP KO and wild-type C57BL/6J (WT) mice at postnatal day 5 (P5), P40, and P213 were subjected to digital droplet PCR (ddPCR) using a Bio-Rad automated droplet generator and QX200 reader. Target genes were selected based on genome-wide association studies, animal models, myopia studies, and other genes associated with retinal homeostasis and inflammation. HPRT, a housekeeping gene, was used for normalization. An average expression ratio (target/HPRT) and standard deviation (SD) were calculated. ANOVA assessed statistical significance, and a p < 0.05 was considered significant. Results The ddPCR data analysis indicated that numerous myopia and inflammation-associated genes were differentially regulated in IRBP KO retinas with distinct temporal variation (upregulated at P5, decreased at P40, and no change at P213 relative to WT). C1qa, Gjd2, Sntb1, and Vsx2 emerged as top genetic candidate pathways. Compared with WT, immunoblotting analysis of C1qa showed no significant differences at P5 but significantly increased protein levels at P7 in IRBP KOs. Vsx2 remained unaltered at P5 and P7 in KO when compared with WT. Conclusions Data analysis indicated significant contributions from C1q, Gjd2, Sntb1, and Vsx2 genes in IRBP deficiency.