Pathogenic variants and associated phenotypic spectrum of TSPAN12 based on data from a large cohort

Refractive Status and Biometric Characteristics of Children With Familial Exudative Vitreoretinopathy

Purpose

To compare biometric characteristics between patients with early-stage familial exudative vitreoretinopathy (FEVR) and healthy controls.

Methods

This case-control study included 50 FEVR eyes in stage 1-2 and 50 control eyes matched by age, gender and spherical equivalent (SE). Biometric parameters including axial length (AL), white-to-white diameter (WTW), central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness (LT), pupil diameter, vitreous chamber depth, anterior and posterior corneal surface curvature radius (ACR and PCR), anterior lens surface curvature radius (ALR) and posterior lens surface curvature radius were measured using IOLMaster 700 and compared between cases and controls using paired t-test. Correlations between SE and biometric measures were assessed using Pearson correlation coefficient (r) in cases and controls.

Results

Both FEVR cases and matched controls had a mean age of 7.6 years, 48% female and mean SE of -5.3 D (80% myopia). Compared to controls, FEVR eyes had smaller AL (P = 0.009), WTW (P = 0.001), ACD (P < 0.001), and ALR (P = 0.03), but larger CCT (P = 0.02) and LT (P = 0.01). In FEVR eyes, SE was negatively correlated with AL (r = -0.79, P < 0.001), positively correlated with ACR (r = 0.29, P = 0.04) and PCR (r = 0.33, P = 0.02), whereas in controls, SE was negatively correlated with AL (r = -0.82, P < 0.001) and LT (r = -0.34, P = 0.02), positively correlated with ALR (r = 0.29, P = 0.04).

Conclusions

Patients at early stage of FEVR exhibited a unique eye morphology resembling ocular development arrest, which may help to develop screening and early detection tools for FEVR. In FEVR patients, myopia is very prevalent and significantly associated with corneal curvature increase.

Novel Exon 7 Deletions in TSPAN12 in a Three-Generation FEVR Family: A Case Report and Literature Review

Familial exudative vitreoretinopathy (FEVR) is a severe clinically and genetically heterogeneous disease that is characterized by vascular disorder. FEVR exhibits strikingly variable clinical phenotypes, ranging from asymptomatic to total blindness. In this case, we present a patient who was first treated as having high myopia and retinopathy but was finally diagnosed with FEVR caused by the heterozygous deletion of exon 7 in TSPAN12 with the aid of whole genome sequencing (WGS). Typical vascular changes, including vascular leakage and an avascular zone in the peripheral retina, were observed in the proband using fundus fluorescein angiography (FFA), and the macular dragging was shown to be progressing in the follow-up visit. Furthermore, the proband showed unreported TSPAN12-related phenotypes of FEVR: ERG (full-field electroretinogram) abnormalities and retinoschisis. Only mild vascular changes were exhibited in the FFA for the other three family members who carried the same deletion of exon 7 in TSPAN12. This case expands our understanding of the phenotype resulting from TSPAN12 mutations and signifies the importance of combining both clinical and molecular analysis approaches to establish a complete diagnosis.

Genotype-phenotype associations in familial exudative vitreoretinopathy: A systematic review and meta-analysis on more than 3200 individuals

Objective

To systematically review the relationship between genotypes and clinical phenotypes of Familial exudative vitreoretinopathy (FEVR) to support risk estimation and therapeutic decisions.

Design

Systematic review with meta-analysis.

Data sources

The data of our study were collected from PubMed, Embase, Web of Science, Cochrane, CBM, China National Knowledge Infrastructure (CNKI), WAN FANG and VIP databases since inception to August 2021.

Results

A total of 3257 patients from 32 studies were included according to the inclusion and exclusion criteria. Among all the cases, the mutation frequencies of LRP5, FZD4, NDP, TSPAN12, ZNF408 and KIF11 were 13.6%, 11.5%, 4.6%, 6.7%, 1.6%, and 5.7%, respectively. We found that the patients with NDP and FZD4 suffer more severe symptoms, among which 86.4% patients of NDP and 78.6% patients of FZD4 were in the advanced stage of FEVR. Retinal detachment is the most frequent symptom with patients of LRP5 and NDP mutations, accounting for 51.9% and 64.5%, respectively. For the patients with the mutation of TSPAN12, retinal fold is the most common clinical manifestation, and suffer the mildest clinical phenotypes compared with the other three genes.

Conclusion

The results of the meta-analysis indicate that different types of genetic mutations occur at different frequencies. In addition, the clinical manifestations of FEVR are related to the type of gene mutation. Therefore, targeted treatment strategies and follow-up recommendations should be adopted for different pathogenic genes of FEVR.

A novel frameshift variant in the TSPAN12 gene causes autosomal dominant FEVR

BACKGROUND

Familial exudative vitreoretinopathy (FEVR) is an inherited blinding eye disease with abnormal retinal vascular development. We aim to broaden the variant spectrum of FEVR and provide a basis for molecular diagnosis and genetic consultation.

METHODS

We recruited five FEVR patients from one large Chinese family. Whole-exome sequencing (WES) and Sanger sequencing were applied to sequence, analyze, and verify variants on genomic DNA samples. Immunocytochemistry, western blot, qPCR, and luciferase assay were performed to test the influence of the variant on the protein expression and activity of the Norrin/β-catenin pathway.

RESULTS

We identified a novel heterozygous frameshift variant c.533dupC (p.D179Rfs*6) in Tetraspanin 12 (TSPAN12) gene that is related to FEVR. This variant caused degradation of the entire TSPAN12 protein, which failed to activate Norrin/β-catenin signaling, possibly causing FEVR.

CONCLUSION

Our study revealed a novel frameshift variant D179Rfs*6 in TSPAN12 that is inherited in an autosomal dominant manner. We found that D179Rfs*6 caused a failure to activate Norrin/β-catenin signaling. This finding broadens the variant spectrum of TSPAN12 and provides invaluable information for the molecular diagnosis of FEVR.

Whole exome sequencing revealed 14 variants in NDP, FZD4, LRP5, and TSPAN12 genes for 20 families with familial exudative vitreoretinopathy

Background

Familial exudative vitreoretinopathy (FEVR) is a complex form of blindness-causing retinal degeneration. This study investigated the potential disease-causing variants in 20 Chinese families with FEVR.

Methods

All available family members underwent detailed ophthalmological examinations, including best-corrected visual acuity and fundus examination. All probands and most family members underwent fluorescein fundus angiography. Twenty probands underwent whole exome sequencing; 16 of them also underwent copy number variant and mitochondrial genome analysis. Bioinformatics analysis and Sanger sequencing of available family members were used to confirm the disease-causing gene variant.

Results

Twenty families were diagnosed with FEVR based on clinical symptoms, fundus manifestations, and fundus fluorescein angiography. Whole exome sequencing revealed 14 variants in NDP, FZD4, LRP5, and TSPAN12 genes among the 13 families. These variants were predicted to be damaging or deleterious according to multiple lines of prediction algorithms; they were not frequently found in multiple population databases. Seven variants had not previously been reported to cause FEVR: c.1039T>G p.(Phe347Val) in the FZD4 gene; c.1612C>T p.(Arg538Trp) and c.3237-2A>C in the LRP5 gene; and c.77T>A p.(Ile26Asn), c.170dupT p.(Leu57Phe fsTer60), c.236T>G p.(Met79Arg) and c.550dupA p.(Arg184Lys fsTer16) in the TSPAN12 gene. We did not detect any variants in the remaining seven families.

Conclusions

These results expand the spectrum of variants in the NDP, FZD4, LRP5, and TSPAN12 genes and provide insights regarding accurate diagnosis, family genetic counseling, and future gene therapy for FEVR.

Severe Exudative Vitreoretinopathy as a Common Feature for CTNNB1, KIF11 and NDP Variants Plus Sector Degeneration for KIF11

PURPOSE

To characterize ocular phenotypes in patients with CTNNB1, KIF11, or NDP variants.

DESIGN

Retrospective case series.

METHODS

Seventy-four patients from 59 unrelated families with CTNNB1, KIF11, and NDP variants were enrolled based on exome sequencing. The clinical data of ophthalmoscope, fundus photography, fluorescein angiography, and ocular ultrasound scan were evaluated.

RESULTS

A total of 55 potential pathogenic variants were identified, including 26 in KIF11 (28 families), 23 in NDP (25 families), and 6 in CTNNB1 (6 families). In total, 74 patients from the 59 families carried the variants, in whom clinical data were available from 70 patients for the current analysis. Severe familial exudative vitreoretinopathy (FEVR), stages 4 and 5, was present in 72.9% (51/70) of patients. In addition, panretinal or sector chorioretinal degeneration along with FEVR is a specific feature associated with KIF11 variants, present in 93.8% (30/32) of patients. FEVR-like change was observed in almost all patients with rare hemizygous variants in NDP, patients with heterozygous truncation variants in CTNNB1, as well as patients with heterozygous truncation or damaging missense variants in KIF11.

CONCLUSIONS

Severe FEVR-like change with or without significant chorioretinopathy is a common feature in addition to neurodevelopmental disorders for variants in CTNNB1, KIF11, and NDP. In our cohort, the frequency of families with variants in KIF11 was comparable to that in TSPAN12, so as for NDP. Recognizing the characteristics of variants in the 3 genes and associated ocular phenotypes may enrich our understanding and potential management of this disease.