Shedding light on myopia by studying complete congenital stationary night blindness

Abstract

Purpose: Myopia is the most common eye disorder, caused by heterogeneous genetic and environmental factors. Rare inherited retinal disorders are often associated with high myopia. Genes implicated in myopia encode proteins involved in eye morphogenesis, extracellular matrix organization, visual perception, circadian rhythms, and retinal signalling. Differentially expressed genes (DEGs) identified in animal models mimicking myopia are helpful in suggesting candidate genes implicated in human myopia. Complete congenital stationary night blindness (cCSNB) in humans and animal models represents an ON‐bipolar cell signal transmission defect and is also associated with high myopia. The purpose of this work was to identify the molecular cause of myopia present in cCSNB. Methods: A whole transcriptome sequencing (RNA‐seq) approach was performed using retina from three mouse lines with cCSNB, Gpr179−/−, Lrit3−/− and Grm6−/− and the expression data compared to data of age‐matched wild‐type littermates (n = 5). DEGs with fold changes of at least 1.2, p‐values of ≤0.01, an expression value of at least 5 transcripts per million reads and appearing in at least two cCSNB mouse lines were investigated in detail. A meta‐analysis was performed by (a) comparing our data with published transcriptome data from purified retinal cells and single cell RNA‐Seq data, (b) pathway analyses, (c) myopia databases and publications concerning their role in normal vision. Several of the DEGs were validated by RT‐qPCR experiments and analysed by western blot and immunolocalization studies. Results: More than 50 DEGs were found in at least two cCSNB mouse lines. Expression of those was found in different retinal cell types. The difference in expression was independent of the number of nuclei present in wild‐type and mutant inner retina. Pathway analysis revealed that mitogen‐activated protein kinase pathways, synaptic signalling, G protein‐coupled receptor ligand binding pathways, and proteins implicated in eye, endoderm and connective tissue development were affected in cCSNB. More than half of the genes were already associated with myopia. Conclusions: Our study reveals DEGs in all retinal cell types of cCSNB models, previously associated with myopia and novel candidates. These studies combined with pathway analyses provide the basis for the development of pharmacological and optical myopia therapies.