Complete congenital stationary night blindness as a tool to study myopia

Abstract

Purpose : Myopia is a multifactorial eye disorder caused by genetic and environmental factors and inhibited by light exposure. Complete congenital stationary night blindness (cCSNB) is a retinal disorder associated with high myopia in patients and caused by a signal transmission defect between photoreceptors and ON-bipolar cells. Our project aims to shed light on mechanisms implicated in myopia using cCSNB mouse models. We hypothesized that the cCSNB-related disruption of retinal signaling has the same effect as the absence of light which may lead to altered expression of myopia-related genes.

Methods : To investigate the molecular basis of myopia in cCSNB and to identify novel proteins involved in the retinal signaling cascade, we performed whole transcriptome sequencing (RNA-Seq) in three different mouse models of cCSNB (Gpr179^-/-, Lrit3^-/- and Grm6^-/-) and their wild-type littermates. To validate that cCSNB mouse models develop myopia, retinal levels of dopamine (DA) and its metabolite 3,4 dihydroxyphenylacetic acid (DOPAC) were measured using ultra performance liquid chromatography. The induction of myopia was performed using a lens-induced myopia (LIM) protocol and the myopic shift was measured using an infrared photorefractometer. Differentially expressed genes (DEGs) were investigated, according to their expression in specific retinal cell types, their association with the term “myopia” in public databases and validated on RNA and protein levels.

Results : RNA-Seq data obtained from cCSNB mouse models revealed DEGs expressed in different retinal cells and implicated in the mitogen-activated protein kinase, synaptic signaling, G protein-coupled receptor ligand binding pathways, and proteins implicated in tissue development (fold change ≥1.2, p-value ≤0.01). Half of the DEGs have been already associated with myopia. The retinal levels of both DA and DOPAC were drastically decreased in cCSNB mouse models, indicating a disruption of the dopaminergic pathway which can lead to myopia. After 3 weeks of LIM, Gpr179^−/− mice were more myopic than Gpr179^+/+ (p-value=0.0033). Preliminary data obtained in Lrit3^-/- also showed a higher myopic shift compared to Lrit3^+/+.

Conclusions : We show that cCSNB is a good model to study myopia. We identified cellular pathways involved in the onset of myopia occurring in cCSNB. This study provides the first steps to study myopia in cCSNB and for the guidance of pharmacological myopia therapies.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.