A Novel Variant of the FZD4 Gene in a Chinese Family Causes Autosomal Dominant Familial Exudative Vitreoretinopathy

Background/Aims: Familial exudative vitreoretinopathy (FEVR) is a complex hereditary eye disorder characterized by incomplete development of the retinal vasculature, thereby affecting retinal angiogenesis. Methods: In this study, a Chinese autosomal dominant FEVR pedigree was recruited. Ophthalmic examinations were performed, targeted next-generation sequencing was used to identify the causative gene, and Sanger sequencing was conducted to verify the candidate mutation. Co-segregation analysis was performed to evaluate pathogenicity. Semi-quantitative reverse transcription-PCR was applied to investigate the spatial and temporal expression patterns of the frizzled class receptor 4 (FZD4) gene in the mouse. Results: A novel heterozygous, deleterious variant of the FZD4 gene, c.A749G (p.Y250C), was identified in this FEVR pedigree, which co-segregated with the clinical phenotype. The amino acid tyrosine (Y) is highly conserved both orthologously and paralogously. The FZD4 gene was highly expressed in the retina, sclera of the eye, ovary, kidney, and liver; ubiquitously expressed in other tissues; and highly expressed in 6 different developmental stages/times of retinal tissue. Conclusion: Our study is the first to identify that the novel heterozygous variant c.A749G (p.Y250C) in the FZD4 gene may be the disease-causing mutation in this FEVR family, extending its mutation spectrum. These findings further our understanding of the molecular pathogenesis of FEVR and will facilitate the development of methods for the diagnosis, prevention, and genetic counseling of this disease.