A novel splicing variant of VCAN identified in a Chinese family initially diagnosed with familial exudative vitreoretinopathy

Abstract

Background: Wagner vitreoretinopathy (WVR) is a rare autosomal dominant vitreoretinopathy caused by pathogenic variants in the VCAN gene. The aim of this study was to report a novel splicing variant in VCAN identified in a three-generation Chinese family initially diagnosed with familial exudative vitreoretinopathy and to describe the patients' clinical features.

Methods: Four affected individuals from a three-generation family underwent detailed ophthalmic examinations, including best-corrected visual acuity by Snellen E chart, slit-lamp biomicroscopy, indirect ophthalmoscopy under pupil dilatation, ocular B-ultrasonography, optical coherence tomography scans, and fundus autofluorescence. Targeted next-generation sequencing was performed to identify variants of the disease-causing gene for the proband, followed by co-segregation analysis using Sanger-DNA sequencing. Reverse transcriptase-polymerase chain reaction (RT-PCR) was carried out to verify the effects of a variant on VCAN pre-mRNA splicing in the lymphocytes from the patients.

Results: We detected a novel heterozygous variant c.4004-4_c.4004-3delinsCA of VCAN in all four affected individuals. RT-PCR revealed that the novel variant caused an abnormal splicing in exon 8 of the VCAN and imbalanced versican transcripts. All four patients presented vitreous syneresis and bilateral retinal detachment occurring at different ages. The patients also showed different extents of visual defects and diverse clinical manifestations, including cataract, iris-lens synechiae, inverted papillae, and ectopic foveas.

Conclusions: Our results expand the mutation spectrum of VCAN and further confirm that the splicing sites for exon 8 are mutation hot spots. Patients with WVR may present high phenotype variation; therefore, molecular analysis is very important for precise diagnosis of patients with inherited vitreoretinopathy.

Keywords: VCAN; Wagner vitreoretinopathy; splicing variant; versican transcripts.

FIGURE 1

Pedigree, co‐segregation for the novel variant c.4004‐4_c.4004‐3delinsCA in the family with vitreoretinopathy, and Versican (VCAN) transcript analysis. (a) Pedigree, co‐segregation for the novel variant c.4004‐4_c.4004‐3delinsCA in the family with vitreoretinopathy. (b) Schematic diagram shows the position of the novel variant and the cryptic acceptor site. (c) Agarose gel electrophoresis displays the RT‐PCR products for V0–V3 of the VCAN mRNA transcripts and the mRNA of GAPDH from lymphocytes of a normal control (NC). Agarose gel electrophoresis displays the RT‐PCR products for V0–V3 of the VCAN mRNA transcripts in the three patients and the normal controls. (d) Partial sequence chromatogram of this aberrant V0 and V1transcripts lacking the first 39 bp of VCAN exon 8.

FIGURE 2

Fundus photographs (FP), ocular B‐ultrasonography, and anterior segment photographs (ASP) of the proband and her father. (a) FP of the proband's right eye shows retinal detachment (RD). (b) Her ocular B‐ultrasonography shows bilateral RD and vitreous opacity or strands. (c) ASPs of the proband's father exhibit pupil synechiae, iris atrophy, and opacities of the lenses in both eyes, ectopic IOL in his right eye. (d) His ocular B‐ultrasonography shows dense vitreous opacity after silicon oil tamponade in the right eye and a complete RD in the left eye.

FIGURE 3

Fundus photographs (FP), fundus autofluorescence (FAF), and OCT images of the proband's sister. (a) FPs show an inverted papilla, ectopic foveas, vitreous veils, mild RPE mottling in the mid‐periphery retina, and demarcated chorioretinal atrophy in the peripheral retina (green arrowhead). (b) FAF displays relatively normal autofluorescence pattern in the right eye and abnormal hyper‐autofluorescence in the left eye. (c) OCT images show a dense posterior hyaloid forming a bridge over the foveal pit (white arrow) in both eyes and retinoschisis and outer retinal tubulations at the macula (yellow asterisk), and a vitreous veil in the left eye (blue arrow).