Novel truncating variants in cause familial exudative vitreoretinopathy.

BACKGROUND

Familial exudative vitreoretinopathy (FEVR) is an inheritable blinding disorder with clinical and genetic heterogeneity. Heterozygous variants in the gene have been reported to cause FEVR. However, the pathogenic basis of -associated FEVR has not been fully explored.

METHODS

Whole-exome sequencing was performed on the genomic DNA of probands. Dual-luciferase reporter assay, western blotting and co-immunoprecipitation were used to characterise the impacts of variants. Quantitative real-time PCR, EdU (5-ethynyl-2'-deoxyuridine) incorporation assay and immunocytochemistry were performed on the primary human retinal microvascular endothelial cells (HRECs) to investigate the effect of depletion on the downstream genes involved in Norrin/β-catenin signalling, cell proliferation and junctional integrity, respectively. Transendothelial electrical resistance assay was applied to measure endothelial permeability. Heterozygous endothelial-specific -knockout mouse mice were generated to verify FEVR-like phenotypes in the retina.

RESULTS

We identified two novel heterozygous variants (p.Leu103Ter and p.Val199LeufsTer11) and one previously reported heterozygous variant (p.His369ThrfsTer2) in the gene. These variants caused truncation and degradation of β-catenin that reduced Norrin/β-catenin signalling activity. Additionally, knockdown (KD) of in HRECs led to diminished mRNA levels of Norrin/β-catenin targeted genes, reduced cell proliferation and compromised junctional integrity. The Cre-mediated heterozygous deletion of in mouse endothelial cells (ECs) resulted in FEVR-like phenotypes. Moreover, LiCl treatment partially rescued the defects in -KD HRECs and EC-specific heterozygous knockout mice.

CONCLUSION

Our findings reinforced the current pathogenesis of Norrin/β-catenin for FEVR and expanded the causative variant spectrum of for the prenatal diagnosis and genetic counselling of FEVR.