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Novel truncating variants in CTNNB1 cause familial exudative vitreoretinopathy

Yunqi He ^{#  1   2   3   4} , Mu Yang ^{#  2   3} , Rulian Zhao  ^{2   3} , Li Peng  ^{2   3} , Erkuan Dai  ⁵ , Lulin Huang  ^{2   3} , Peiquan Zhao  ⁶ , Shujin Li  ^{7   3} , Zhenglin Yang  ^{8   2   3   4}

Affiliations

Affiliations

• ¹ Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, Sichuan, China.
• ² Sichuan Provincial Key Laboratory for Human Disease Gene Study, the Department of Medical Genetics, Sichuan Provincial People’s Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan, China.
• ³ Research Unit for Blindness Prevention of Chinese Academy of Medical Sciences (2019RU026), Sichuan Academy of Medical Sciences & Sichuan Provincial People’s Hospital, Chengdu, Sichuan, China.
• ⁴ University of Chinese Academy of Sciences, Beijing, China.
• ⁵ Department of Ophthalmology, Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China.
• ⁶ Department of Ophthalmology, Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China zliny@yahoo.com lishujin91@126.com zhaopeiquan@126.com.
• ⁷ Sichuan Provincial Key Laboratory for Human Disease Gene Study, the Department of Medical Genetics, Sichuan Provincial People’s Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan, China zliny@yahoo.com lishujin91@126.com zhaopeiquan@126.com.
• ⁸ Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, Sichuan, China zliny@yahoo.com lishujin91@126.com zhaopeiquan@126.com.

^# Contributed equally.

• PMID: 35361685
• DOI: 10.1136/jmedgenet-2021-108259

Abstract

Background: Familial exudative vitreoretinopathy (FEVR) is an inheritable blinding disorder with clinical and genetic heterogeneity. Heterozygous variants in the CTNNB1 gene have been reported to cause FEVR. However, the pathogenic basis of CTNNB1-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 CTNNB1 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 Ctnnb1-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 CTNNB1 gene. These variants caused truncation and degradation of β-catenin that reduced Norrin/β-catenin signalling activity. Additionally, knockdown (KD) of CTNNB1 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 Ctnnb1 in mouse endothelial cells (ECs) resulted in FEVR-like phenotypes. Moreover, LiCl treatment partially rescued the defects in CTNNB1-KD HRECs and EC-specific Ctnnb1 heterozygous knockout mice.

Conclusion: Our findings reinforced the current pathogenesis of Norrin/β-catenin for FEVR and expanded the causative variant spectrum of CTNNB1 for the prenatal diagnosis and genetic counselling of FEVR.

Keywords: frameshift mutation; ophthalmology.