Spectrum of Variants in 389 Chinese Probands With Familial Exudative Vitreoretinopathy

Familial Exudative Vitreoretinopathy With and Without Pathogenic Variants of Norrin/β-Catenin Signaling Genes

Purpose

To determine the clinical characteristics of familial exudative vitreoretinopathy (FEVR) associated with or without pathogenic variants of the Norrin/β-catenin genes.

Design

This was a multicenter, cross-sectional, observational, and genetic study.

Subjects

Two-hundred eighty-one probands with FEVR were studied.

Methods

Whole-exome sequence and/or Sanger sequence was performed for the Norrin/β-catenin genes, the FZD4, LRP5, TSPAN12, and NDP genes on blood collected from the probands. The clinical symptoms of the probands with or without the pathogenic variants were assessed as well as differences in the inter Norrin/β-catenin genes.

Main Outcome Measures

The phenotype associated with or without pathogenic variants of the Norrin/β-catenin genes.

Results

One-hundred eight probands (38.4%) had 88 different pathogenic or likely pathogenic variants in the genes: 24 with the FZD4, 42 with the LRP5, 10 with the TSPAN12, and 12 with the NDP gene. Compared with the 173 probands without pathogenic variants, the 108 variant-positive probands had characteristics of familial predisposition (63.9% vs. 37.6%, P < 0.0001), progression during infancy (75.0% vs. 53.8%, P = 0.0004), asymmetrical severity between the 2 eyes (50.0% vs. 37.6%, P = 0.0472), and nonsyndromic characteristics (10.2% vs. 17.3%, P = 0.1185). The most frequent stage at which the more severe eye conditions was present was at stage 4 in both groups (40.7% vs. 34.7%). However, the advanced stages of 3 to 5 in the more severe eye were found more frequently in probands with variants than in those without variants (83.3% vs. 58.4%, P < 0.0001). Patients with rhegmatogenous retinal detachments progressed from stage 1 or 2 were found less frequently in the variant-positive probands (8.3% vs. 17.3%, P = 0.0346). Nine probands with NDP variants had features different from probands with typical Norrin/β-catenin gene variants including the sporadic, symmetrical, and systemic characteristics consistent with Norrie disease.

Conclusions

The results showed that the clinical characteristics of FEVR of patients with variants in the Norrin/β-catenin genes are different from those with other etiologies. We recommend that clinicians who diagnose a child with FEVR perform genetic testing so that the parents can be informed on the prognosis of the vision and general health in the child.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Cyanoacrylate glue for iatrogenic retinal breaks during vitrectomy in stage 5 familial exudative vitreoretinopathy

Purpose

To describe the role of cyanoacrylate glue in sealing iatrogenic retinal breaks (IRBs) during vitrectomy in stage 5 familial exudative vitreoretinopathy (FEVR) with funneled retinal detachment (RD).

Methods

Nine eyes of nine patients diagnosed as stage 5 FEVR were treated with cyanoacrylate glue for IRBs during vitrectomy from July 2020 to January 2022. The clinical records, including patient information, surgical process, and follow-up examinations, were collected retrospectively. Anatomical outcomes and visual outcomes were summarized.

Results

The average age at surgery was 19.6 months (range: 3.8-41.1 months). The mean post-operative follow-up period was 12.5 months (range: 9.8-18.8 months). Before surgery, five eyes had an open-funnel RD and four eyes had a closed-funnel RD. All the preretinal fibroplasia membranes were removed as thoroughly as possible in the nine eyes. IRBs formed at the posterior pole in two eyes and peripheral retina in seven eyes. All the IRBs were sealed successfully by the cyanoacrylate glue when they appeared. At the final post-operative visit, eight eyes had partial retinal reattachment without progression of fibroplasia tissues, while one eye had total retinal redetachment. The rate for stable anatomical outcome was 88.9% (8/9) in this study. The visual testing available for seven eyes demonstrated light perception in five eyes and no light perception in two eyes. No severe perioperative glue-related complications were noted during the follow-ups.

Conclusion

The application of cyanoacrylate glue may be an alternative therapy for IRBs in stage 5 FEVR surgeries, while the long-term efficacy and safety still need further investigation.

Genetic Characteristics and Clinical Manifestations of Foveal Hypoplasia in Familial Exudative Vitreoretinopathy

PURPOSE

This study aimed to ascertain the occurrence of foveal hypoplasia (FH) in individuals diagnosed with familial exudative vitreoretinopathy (FEVR).

DESIGN

Retrospective cohort study.

METHODS

In this study, FEVR families and sporadic cases were diagnosed at the Eye and ENT Hospital, Fudan University, between 2017 and 2023. All patients attended routine ophthalmologic examinations and genetic screenings. The classification of FH was determined using optical coherence tomography (OCT) scans. The FH condition was classified into 2 subgroups: group A (FH being limited to the inner layers) and group B (FH affecting the outer layers). A total of 102 eyes from 58 patients were suitable for analysis.

RESULTS

Forty-nine mutations in LRP5, FZD4, NDP, TSPAN12, KIF11, CTNNB1, and ZNF408 were examined and detected, with 26 of them being novel. Forty-seven eyes (46.1%) revealed FH. The majority (53.2%) were due to the typical grade 1 FH. Patients with mutations in LRP5 and KIF11 were found to exhibit a higher prevalence of FH (P = .0088). Group B displayed the lowest visual acuity compared with group A (P = .048) and the group without FH (P < .001). The retinal arteriolar angle in group B was significantly smaller than in group A (P = .001) and those without FH (P < .001).

CONCLUSIONS

This study offers a new diagnostic approach and expands the spectrum of FEVR mutations. LRP5 and KIF11 were found to be more susceptible to causing FH in patients with FEVR. FEVR eyes with FH exhibited both greater visual impairment and reduced retinal arteriolar angles. The assessment of foveal status in patients with FEVR should be valued.

Clinician-Driven Reanalysis of Exome Sequencing Data From Patients With Inherited Retinal Diseases

Importance

Despite advances in next-generation sequencing (NGS), a significant proportion of patients with inherited retinal disease (IRD) remain undiagnosed after initial genetic testing. Exome sequencing (ES) reanalysis in the clinical setting has been suggested as one method for improving diagnosis of IRD.

Objective

To investigate the association of clinician-led reanalysis of ES data, which incorporates updated clinical information and comprehensive bioinformatic analysis, with the diagnostic yield in a cohort of patients with IRDs in Korea.

Design, Setting, and Participants

This was a multicenter prospective cohort study involving 264 unrelated patients with IRDs, conducted in Korea between March 2018 and February 2020. Comprehensive ophthalmologic examinations and ES analyses were performed, and ES data were reanalyzed by an IRD specialist for single nucleotide variants, copy number variants, mobile element insertions, and mitochondrial variants. Data were analyzed from March to July 2023.

Main Outcomes and Measures

Diagnostic rate of conventional bioinformatic analysis and clinician-driven ES reanalysis.

Results

A total of 264 participants (151 [57.2%] male; mean [SD] age at genetic testing, 33.6 [18.9] years) were enrolled, including 129 patients (48.9%) with retinitis pigmentosa and 26 patients (9.8%) with Stargardt disease or macular dystrophy. Initial bioinformatic analysis diagnosed 166 patients (62.9%). Clinician-driven reanalysis identified the molecular cause of diseases in an additional 22 patients, corresponding to an 8.3-percentage point increase in diagnostic rate. Key factors associated with new molecular diagnoses included clinical phenotype updates (4 patients) and detection of previously overlooked variation, such as structural variants (9 patients), mitochondrial variants (3 patients), filtered or not captured variants (4 patients), and noncanonical splicing variants (2 patients). Among the 22 patients, variants in 7 patients (31.8%) were observed in the initial analysis but not reported to patients, while those in the remaining 15 patients (68.2%) were newly detected by the ES reanalysis.

Conclusions and Relevance

In this cohort study, clinician-centered reanalysis of ES data was associated with improved molecular diagnostic yields in patients with IRD. This approach is important for uncovering missed genetic causes of retinal disease.

Identification of Novel FZD4 Mutations in Familial Exudative Vitreoretinopathy and Investigating the Pathogenic Mechanisms of FZD4 Mutations

Purpose

The purpose of this study is to report five novel FZD4 mutations identified in familial exudative vitreoretinopathy (FEVR) and to analyze and summarize the pathogenic mechanisms of 34 of 96 reported missense mutations in FZD4.

Methods

Five probands diagnosed with FEVR and their family members were enrolled in the study. Ocular examinations and targeted gene panel sequencing were conducted on all participants. Plasmids, each carrying 29 previously reported FZD4 missense mutations and five novel mutations, were constructed based on the selection of mutations from each domain of FZD4. These plasmids were used to investigate the effects of mutations on protein expression levels, Norrin/β-catenin activation capacity, membrane localization, norrin binding ability, and DVL2 recruitment ability in HEK293T, HEK293STF, and HeLa cells.

Results

All five novel mutations (S91F, V103E, C145S, E160K, C377F) responsible for FEVR were found to compromise Norrin/β-catenin activation of FZD4 protein. After reviewing a total of 34 reported missense mutations, we categorized all mutations based on their functional changes: signal peptide mutations, cysteine mutations affecting disulfide bonds, extracellular domain mutations influencing norrin binding, transmembrane domain (TM) 1 and TM7 mutations impacting membrane localization, and intracellular domain mutations affecting DVL2 recruitment.

Conclusions

We expanded the spectrum of FZD4 mutations relevant to FEVR and experimentally demonstrated that missense mutations in FZD4 can be classified into five categories based on different functional changes.

Characterization of a novel heterozygous frameshift variant in NDP gene that causes familial exudative vitreoretinopathy in female patients

Familial exudative vitreoretinopathy (FEVR) is a severe inherited disease characterized by defective retinal vascular development. With genetic and clinical heterogeneity, FEVR can be inherited in different patterns and characterized by phenotypes ranging from moderate visual defects to complete vision loss. This study was conducted to unravel the genetic and functional etiology of a 4-month-old female FEVR patient. Targeted gene panel and Sanger sequencing were utilized for genetic evaluation. Luciferase assays, western blot, quantitive real-time PCR, and immunocytochemistry were performed to verify the functional defects in the identified candidate variant. Here, we report a 4-month-old girl with bilateral retinal folds and peripheral avascularization, and identified a novel frameshift heterozygous variant c.37dup (p.Leu13ProfsTer13) in NDP. In vitro experiments revealed that the Leu13ProfsTer13 variant led to a prominent decrease in protein levels instead of mRNA levels, resulting in compromised Norrin/β-catenin signaling activity. Human androgen receptor assay further revealed that a slight skewing of X chromosome inactivation could partially cause FEVR. Thus, the pathogenic mechanism by which heterozygous frameshift or nonsense variants in female carriers cause FEVR might largely result from a loss-of-function variant in one X chromosome allele and a slightly skewed X-inactivation. Further recruitment of more FEVR-affected females carrying NDP variants and genotype-phenotype correlation analysis can ultimately offer valuable information for the prognosis prediction of FEVR.

Investigating the Impact of Dimer Interface Mutations on Norrin's Secretion and Norrin/β-Catenin Pathway Activation

Purpose

This study aimed to investigate the impact of 21 NDP mutations located at the dimer interface, focusing on their potential effects on protein assembly, secretion efficiency, and activation of the Norrin/β-catenin signaling pathway.

Methods

The expression level, secretion efficiency, and protein assembly of mutations were analyzed using Western blot. The Norrin/β-catenin signaling pathway activation ability after overexpression of mutants or supernatant incubation of mutant proteins was tested in HEK293STF cells. The mutant norrin and wild-type (WT) FZD4 were overexpressed in HeLa cells to observe their co-localization. Immunofluorescence staining was conducted in HeLa cells to analyze the subcellular localization of Norrin and the Retention Using Selective Hook (RUSH) assay was used to dynamically observe the secretion process of WT and mutant Norrin.

Results

Four mutants (A63S, E66K, H68P, and L103Q) exhibited no significant differences from WT in all evaluations. The other 17 mutants presented abnormalities, including inadequate protein assembly, reduced secretion, inability to bind to FZD4 on the cell membrane, and decreased capacity to activate Norrin/β-catenin signaling pathway. The RUSH assay revealed the delay in endoplasmic reticulum (ER) exit and impairment of Golgi transport.

Conclusions

Mutations at the Norrin dimer interface may lead to abnormal protein assembly, inability to bind to FZD4, and decreased secretion, thus contributing to compromised Norrin/β-catenin signaling. Our results shed light on the pathogenic mechanisms behind a significant proportion of NDP gene mutations in familial exudative vitreoretinopathy (FEVR) or Norrie disease.

A familial missense variant in the Alzheimer's disease gene SORL1 impairs its maturation and endosomal sorting

The SORL1 gene has recently emerged as a strong Alzheimer's Disease (AD) risk gene. Over 500 different variants have been identified in the gene and the contribution of individual variants to AD development and progression is still largely unknown. Here, we describe a family consisting of 2 parents and 5 offspring. Both parents were affected with dementia and one had confirmed AD pathology with an age of onset > 75 years. All offspring were affected with AD with ages at onset ranging from 53 years to 74 years. DNA was available from the parent with confirmed AD and 5 offspring. We identified a coding variant, p.(Arg953Cys), in SORL1 in 5 of 6 individuals affected by AD. Notably, variant carriers had severe AD pathology, and the SORL1 variant segregated with TDP-43 pathology (LATE-NC). We further characterized this variant and show that this Arginine substitution occurs at a critical position in the YWTD-domain of the SORL1 translation product, SORL1. Functional studies further show that the p.R953C variant leads to retention of the SORL1 protein in the endoplasmic reticulum which leads to decreased maturation and shedding of the receptor and prevents its normal endosomal trafficking. Together, our analysis suggests that p.R953C is a pathogenic variant of SORL1 and sheds light on mechanisms of how missense SORL1 variants may lead to AD.

Novel mutation in the NDP gene associated with Norrie disease in a Chinese pedigree

PURPOSE

Norrie disease (ND) is a rare X-linked recessive disorder characteristic of early childhood blindness. While several mutations in the NDP gene have been reported as causative for ND, the genetic etiology remains unknown for many patients. This study aims to describe a novel mutation and explore the clinical manifestations in a Chinese family with two affected males.

METHODS

Exome sequencing (ES) was employed to identify the causative gene in a four-generation pedigree. Sanger sequencing was subsequently utilized to validate the mutation detected by ES in additional family members. Ophthalmologic examination and diagnostic imaging relevant to ND were conducted.

RESULTS

The proband (IV:2), an 8-month-old male infant, presented with binocular retinal detachment. DNA sequencing revealed a novel heterozygous missense mutation (c.174G>C) within the NDP gene in the proband. This mutation affected highly conserved residues and was predicted to disrupt the normal protein structure. Furthermore, the variant co-segregated with the disease phenotypes within the family.

CONCLUSIONS

Our findings identified a novel missense mutation in the NDP gene associated with Norrie disease in China, expanding the mutation spectrum associated with ND. This discovery holds diagnostic, prognostic, and genetic counseling implications for affected individuals.

Genetic detection of two novel LRP5 pathogenic variants in patients with familial exudative vitreoretinopathy

BACKGROUND

Familial exudative vitreoretinopathy (FEVR) is a genetic eye disorder that leads to abnormal development of retinal blood vessels, resulting in vision impairment. This study aims to identify pathogenic variants by targeted exome sequencing in 9 independent pedigrees with FEVR and characterize the novel pathogenic variants by molecular dynamics simulation.

METHODS

Clinical data were collected from 9 families with FEVR. The causative genes were screened by targeted next-generation sequencing (TGS) and verified by Sanger sequencing. In silico analyses (SIFT, Polyphen2, Revel, MutationTaster, and GERP + +) were carried out to evaluate the pathogenicity of the variants. Molecular dynamics was simulated to predict protein conformation and flexibility transformation alterations on pathogenesis. Furthermore, molecular docking techniques were employed to explore the interactions and binding properties between LRP5 and DKK1 proteins relevant to the disease.

RESULTS

A 44% overall detection rate was achieved with four variants including c.4289delC: p.Pro1431Argfs*8, c.2073G > T: p.Trp691Cys, c.1801G > A: p.Gly601Arg in LRP5 and c.633 T > A: p.Tyr211* in TSPAN12 in 4 unrelated probands. Based on in silico analysis and ACMG standard, two of them, c.4289delC: p.Pro1431Argfs*8 and c.2073G > T: p.Trp691Cys of LRP5 were identified as novel pathogenic variants. Based on computational predictions using molecular dynamics simulations and molecular docking, there are indications that these two variants might lead to alterations in the secondary structure and spatial conformation of the protein, potentially impacting its rigidity and flexibility. Furthermore, these pathogenic variants are speculated to potentially influence hydrogen bonding interactions and could result in an increased binding affinity with the DKK1 protein.

CONCLUSIONS

Two novel genetic variants of the LRP5 gene were identified, expanding the range of mutations associated with FEVR. Through molecular dynamics simulations and molecular docking, the potential impact of these variants on protein structure and their interactions with the DKK1 protein has been explored. These findings provide further support for the involvement of these variants in the pathogenesis of the disease.

Genetic and clinical characteristics of ZNF408-related familial exudative vitreoretinopathy

OBJECTIVE

To analyze the clinical and genetic characteristics of zinc finger protein 408 (ZNF408)-related familial exudative vitreoretinopathy (FEVR) in a Chinese cohort.

METHODS

Ninety families from Chongqing and 16 families from Xinjiang were selected according to fundus lesion characteristics. Peripheral venous blood was collected from patients and their families; genomic DNA was extracted for whole exome sequencing. Relationships between genotype and phenotype in patients with ZNF408-related FEVR were analyzed.

RESULTS

ZNF408 variants were detected in three patients (2.83%, 3/106). ZNF408 variants in these three probands were all missense mutations at novel sites. One proband had a ZNF408 and LRP5 double-gene variant, and two probands had ZNF408 single-gene variants. Patients with double-gene variants did not display more severe clinical manifestations.

CONCLUSIONS

This study expands the spectrum of known ZNF408 variants and confirms that ZNF408 variants can cause FEVR. Most variants detected in this study have not been reported in the literature and are suspected pathogenic variants of FEVR. In patients with FEVR, phenotype and genotype do not necessarily display a direct one-to-one relationship.

Loss of Tbx3 in Mouse Eye Causes Retinal Angiogenesis Defects Reminiscent of Human Disease

Purpose

Familial exudative vitreoretinopathy (FEVR) and Norrie disease are examples of genetic disorders in which the retinal vasculature fails to fully form (hypovascular), leading to congenital blindness. While studying the role of a factor expressed during retinal development, T-box factor Tbx3, we discovered that optic cup loss of Tbx3 caused the retina to become hypovascular. The purpose of this study was to characterize how loss of Tbx3 affects retinal vasculature formation.

Methods

Conditional removal of Tbx3 from both retinal progenitors and astrocytes was done using the optic cup-Cre recombinase driver BAC-Dkk3-Cre and was analyzed using standard immunohistochemical techniques.

Results

With Tbx3 loss, the retinas were hypovascular, as seen in patients with retinopathy of prematurity (ROP) and FEVR. Retinal vasculature failed to form the stereotypic tri-layered plexus in the dorsal-temporal region. Astrocyte precursors were reduced in number and failed to form a lattice at the dorsal-temporal edge. We next examined retinal ganglion cells, as they have been shown to play a critical role in retinal angiogenesis. We found that melanopsin expression and Islet1/2-positive retinal ganglion cells were reduced in the dorsal half of the retina. In previous studies, the loss of melanopsin has been linked to hyaloid vessel persistence, which we also observed in the Tbx3 conditional knockout (cKO) retinas, as well as in infants with ROP or FEVR.

Conclusions

To the best of our knowledge, these studies are the first demonstration that Tbx3 is required for normal mammalian eye formation. Together, the results provide a potential genetic model for retinal hypovascular diseases.

Unrecognized ROPER in a child with a novel pathogenic variant in ZNF408 gene

BACKGROUND

Familial exudative vitreoretinopathy (FEVR) is a rare hereditary disorder characterized by abnormal or incomplete retinal angiogenesis commonly inherited in an autosomal dominant fashion. Up to 50% of FEVR cases are linked to known genetic mutations affecting retinal vasculature development.

PURPOSE

To report a case, a novel pathogenic variant of the ZNF408 gene associated with a case of FEVR in a premature male.

MATERIALS AND METHODS

Case report.

RESULTS

A 10-month-old male who was born prematurely at 34 weeks' gestation in the Dominican Republic was referred for persistent avascular retina. The baby was treated with bilateral intravitreal ranibizumab injections for retinopathy of prematurity (ROP) with the presence of plus disease. Fundus examination several months after treatment revealed the absence of tortuosity of the vessels with avascular periphery; fluorescein angiography (FA) confirmed peripheral avascularity and demonstrated irregular sprouts of vascularization in the absence of neovascularization. We performed genetic testing under the suspicion of FEVR and results identified a heterozygous mutation in the ZNF408 gene on chromosome 11, c.1307 C > T.

CONCLUSION

FEVR is an important differential diagnosis in premature infants with retinopathy, as clinical presentation can overlap with common findings in ROP. Maintaining high suspicion for the disease is especially critical in cases with findings unusual for ROP. FEVR in the presence of prematurity has been well described, falling under the proposed term ROPER. Genetic testing is key to confirm diagnosis.

Combined X-linked familial exudative vitreoretinopathy and retinopathy of prematurity phenotype in an infant with mosaic turner syndrome with ring X chromosome

BACKGROUND

Retinopathy of prematurity (ROP) and familial exudative vitreoretinopathy (FEVR) are two distinct pathologies of retinal angiogenesis with overlapping clinical features.

METHODS

Examination, multimodal imaging, and genetic testing were used to guide diagnosis and treatment.

RESULTS

We report a combined phenotype of X-linked FEVR and ROP in a 4-month-old girl with mosaic Turner syndrome with ring X chromosome born at 26 weeks gestational age. She was initially diagnosed with atypical ROP with a vitreous band causing a localized traction retinal detachment, inferotemporal to the macula in the right eye, vessels to posterior zone 2 with no clear ridge temporally in the left eye, and fluorescein leakage in both eyes. Due to the suspicion of concurrent FEVR, genetic testing using a vitreoretinopathy panel was performed which revealed a mosaic Turner syndrome associated with 45,X/46,X,r(X), subsequently confirmed by chromosome analysis. The deleted region in the ring X chromosome included the NDP and RS1 genes. The patient was treated with laser photocoagulation of the peripheral avascular retina and sub-Tenon's triamcinolone injection in both eyes, intravitreal injection of bevacizumab in the left eye, and pars plicata vitrectomy in the right eye.

CONCLUSIONS

In premature neonates with atypical ROP, a clinical suspicion of concurrent FEVR or similar vasculopathy is important and genetic testing may elucidate a genetic etiology, which could influence management and prognosis. Turner syndrome can be connected with co-occurring Mendelian gene disorders, particularly in individuals with mosaicism. The concurrence of FEVR and ROP appears to result in atypical and possibly more severe phenotypes.

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.

A boy with amblyopia and familial exudative vitreoretinopathy harboring a new mutation of LRP5 and OPA1: A case report

Background: The study aimed to report a boy with familial exudative vitreoretinopathy and amblyopia harboring a new mutation of the LRP5 and OPA1 gene abnormality.

Case presentation: A 9-year-old boy presented with a 2-year history of deteriorating visual acuity in the right eye. His best-corrected visual acuity was −7.00/−1.75 × 100 = 0.3 in the right eye and −2.50/−1.50 × 170 = 0.8 in the left eye. Two autosomal dominant gene mutation sites were identified in the patient: LRP5 (c.2551C > T, p.His851Tyr) from his father and OPA1 (c.565G > A, p.Glu189Lys) from his mother. Interestingly, his fraternal twin brother harbored no abnormal gene mutations, and his eye tests were normal.

Conclusion: This case expands the spectrum of LRP5 gene mutations among Chinese patients with familial exudative vitreoretinopathy, and it is the first time to report a patient harboring both LRP5 and OPA1 gene mutations having anisometropic amblyopia and strabismus as the primary manifestations. These four family members exhibited individual heterogeneity of phenotypes and genotypes associated with hereditary ophthalmopathy. A comprehensive analysis of clinical phenotypes and genotypes provides clinical clues for improving the level of clinical and genetic diagnoses and a deeper understanding of the disease.

Mutation spectrum in a cohort with familial exudative vitreoretinopathy

Purpose

To expand the mutation spectrum of patients with familial exudative vitreoretinopathy (FEVR) disease.

Participants

74 probands (53 families and 21 sporadic probands) with familial exudative vitreoretinopathy (FEVR) disease and their available family members (n = 188) were recruited for sequencing.

Methods

Panel‐based targeted screening was performed on all subjects. Before sanger sequencing, variants of LRP5, NDP, FZD4, TSPAN12, ZNF408, KIF11, RCBTB1, JAG1, and CTNNA1 genes were verified by a series of bioinformatics tools and genotype–phenotype co‐segregation analysis.

Results

40.54% (30/74) of the probands were sighted to possess at least one etiological mutation of the nine FEVR‐causative genes. The etiological mutation detection rate was 37.74% (20/53) in family‐attainable probands while 47.62% (10/21) in sporadic cases. The diagnosis rate of patients in the early‐onset subgroup (≤5 years old, 45.4%) is higher than that of the children or adolescence‐onset subgroup (6–16 years old, 42.1%) and the late‐onset subgroup (≥17 years old, 39.4%). A total of 36 etiological mutations were identified in this study, comprising 26 novel mutations and 10 reported mutations. LRP5 was the most prevalent mutant gene among the 36 mutation types with a percentage of 41.67% (15/36). Followed by FZD4 (10/36, 27.78%), TSPAN12 (5/36, 13.89%), NDP (4/36, 11.11%), KIF11 (1/36, 2.78%), and RCBTB1 (1/36, 2.78%). Among these mutations, 63.89% (23/36) were missense mutations, 25.00% (9/36) were frameshift mutations, 5.56% (2/36) were splicing mutations, 5.56% (2/36) were nonsense mutations. Moreover, the clinical pathogenicity of these variants was defined according to American College of Medical Genetics (ACMG) and genomics guidelines: 41.67% (15/36) were likely pathogenic variants, 27.78% (10/36) pathogenic variants, 30.55% (11/36) variants of uncertain significance. No etiological mutations discovered in the ZNF408, JAG1, and CTNNA1 genes in this FEVR cohort.

Conclusions

We systematically screened nine FEVR disease‐associated genes in a cohort of 74 Chinese probands with FEVR disease. With a detection rate of 40.54%, 36 etiological mutations of six genes were authenticated in 30 probands, including 26 novel mutations and 10 reported mutations. The most prevalent mutated gene is LRP5, followed by FZD4, TSPAN12, NDP, KIF11, and RCBTB1. In total, a de novo mutation was confirmed. Our study significantly clarified the mutation spectrum of variants bounded up to FEVR disease.

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.

Spectrum of Mutations in NDP Resulting in Ocular Disease; a Systematic Review

Aims and Rationale: The inner retina is supplied by three intraretinal capillary plexi whereas the outer retina is supplied by the choroidal circulation: NDP is essential for normal intraretinal vascularisation. Pathogenic variants in NDP (Xp11.3) may result in either a severe retinal phenotype associated with hearing loss (Norrie Disease) or a moderate retinal phenotype (Familial Exudative Vitreoretinopathy, FEVR). However, little is known about whether the nature or location of the NDP variant is predictive of severity. In this systematic review we summarise all reported NDP variants and draw conclusions about whether the nature of the NDP variant is predictive of the severity of the resulting ocular pathology and associated hearing loss and intellectual disability.

Findings: 201 different variants in the NDP gene have been reported as disease-causing. The pathological phenotype that may result from a disease-causing NDP variant is quite diverse but generally comprises a consistent cluster of features (retinal hypovascularisation, exudation, persistent foetal vasculature, tractional/exudative retinal detachment, intellectual disability and hearing loss) that vary predictably with severity. Previous reviews have found no clear pattern in the nature of NDP mutations that cause either FEVR or Norrie disease, with the exception that mutations affecting cysteine residues have been associated with Norrie Disease and that visual loss amongst patients with Norrie disease tends to be more severe if the NDP mutation results in an early termination of translation as opposed to a missense related amino acid change. A key limitation of previous reviews has been variability in the case definition of Norrie disease and FEVR amongst authors. We thus reclassified patients into two groups based only on the severity of their retinal disease. Of the reported pathogenic variants that have been described in more than one patient, we found that any given variant caused an equivalent severity of retinopathy each time it was reported with very few exceptions. We therefore conclude that specific NDP mutations generally result in a consistent retinal phenotype each time they arise. Reports by different authors of the same variant causing either FEVR or Norrie disease conflict primarily due to variability in the authors’ respective case definitions rather than true differences in disease severity.

Heterozygote loss-of-function variants in the LRP5 gene cause familial exudative vitreoretinopathy

BACKGROUND

Familial exudative vitreoretinopathy (FEVR) is an inherited ocular disease with clinical manifestations of aberrant retinal vasculature. We aimed to identify novel causative variants responsible for FEVR and provided evidence for the genetic counselling of FEVR.

METHODS

We applied whole-exome sequencing (WES) on the genomic DNA samples from the probands and performed Sanger sequencing for variant validation. Western blot analysis and luciferase assays were performed to test the expression levels and the activity of mutant proteins.

RESULTS

We identified one novel heterozygous nonsense variant, and three novel heterozygous frameshift variants including c.1801G>T (p.G601*), c.1965delC (p.H656Tfs*41), c.4445delC (p.S1482Cfs*17), and c.4482delC (p.P1495Rfs*4), which disabled the function of LRP5 on the Norrin/β-catenin signalling. Overexpression of variant-carrying LRP5 proteins resulted in down regulation of the protein levels of β-catenin and the Norrin/β-catenin signalling target genes c-Myc and Glut1.

CONCLUSION

Our study showed that four inherited LRP5 variants can cause autosomal dominant FEVR via down regulation of Norrin/β-catenin signalling and expanded the spectrum of FEVR-associated LRP5 variants.

Dry-Lensectomy Assisted Lensectomy in the Management for End-Stage Familial Exudative Vitreoretinopathy Complicated With Anterior Segment Abnormalities

Purpose

To report a modified technique of dry-lensectomy assisted lensectomy in the management of end-stage familial exudative vitreoretinopathy (FEVR) complicated with capsule-endothelial, iris-endothelial adhesion and secondary glaucoma.

Methods

24 eyes of 16 patients with severe complications of advanced pediatric total retinal detachment caused by FEVR who received limbus-based dry-lensectomy were studied retrospectively. Preoperative and postoperative clinical information was collected and reviewed.

Results

Among the 24 eyes, three eyes (12.50%) underwent lensectomy combined with vitrectomy and membrane peeling simultaneously. 21 (87.50%) eyes underwent lensectomy without membrane peeling due to severe corneal opacity or retinal vascular activity, of which eight underwent another vitrectomy combined with membrane peeling. At the last visit (mean:13.86 ± 5.24 months of follow-up), all eyes had a reconstructed anterior chamber with normal depth. Among 21 eyes having preoperative corneal opacity, 15 (71.43%) had a clearer cornea with reduced opacity, 5 (23.81%) showed similar corneal opacification without deterioration. Among 11 eyes undergone retrolental fibroplasia peeling, seven (63.64%) eyes showed partial retinal reattachment in open-funnel type.

Conclusion

Dry-lensectomy offered a simple way to lower the intraocular pressure and simplified the surgery, which helped to solve the severe anterior segment complications and offer a chance for following retrolental fibroplasia peeling and potential visual gain for selected end-stage FEVR patients.

Update on the Phenotypic and Genotypic Spectrum of KIF11-Related Retinopathy

Background: This study aimed to report the frequency of KIF11-mutations in a large familial exudative vitreoretinopathy (FEVR) population, extend the clinical spectrum of KIF11-associated retinopathy and compare KIF11-associated retinopathy to FEVR with mutations in other genes. Methods: Genetic data collected from 696 FEVR families were reviewed. The ocular phenotypes in patients with KIF11 mutations were analyzed and compared with those of FEVR patients with mutations in other genes (FZD4, TSPAN12, LRP5, NDP and JAG1). Results: In a cohort of 696 FEVR families, disease-causing KIF11 mutations were identified in 3.6% of families (25/696). Among 25 KIF11 mutations, 80% (20/25) carried variants of loss of function and 48% (12/25) of variants were de novo. The phenotypes were variable. Compared with FEVR with disease-causing mutations in other genes, chorioretinal dysplasia was observed in 44.2% (31/70) of eyes with KIF11-associated retinopathy and in only 1.3% (1/70) of eyes with FEVR with mutations in other genes (p < 0.01). Increase and straightening of peripheral vessels (ISPV) was observed in 17.1% (12/70) of eyes with KIF11-associated retinopathy, and in 50% (39/78) of eyes with FEVR with mutations in other genes (p < 0.01). Conclusions: The frequency of the KIF11 mutation in FEVR was 3.6% in our database. The manifestation of KIF11-associated retinopathy was variable and different from the phenotype in FEVR caused by other genes. Chorioretinal dysplasia, instead of retinal folds, was the dominant phenotype in KIF11-associated retinopathy. ISPV was rare in KIF11-associated retinopathy. Moreover, our study revealed that most pathogenic KIF11 mutations were de novo.

FZD4 in a Large Chinese Population With Familial Exudative Vitreoretinopathy: Molecular Characteristics and Clinical Manifestations

Purpose

The purpose of this study was to establish a genotype-phenotype correlation of familial exudative vitreoretinopathy (FEVR) caused by FZD4 gene mutations.

Methods

Six hundred fifty-one probands and their family members were recruited based on a clinical diagnosis of FEVR between 2015 and 2021 at Zhongshan Ophthalmic Center. Ocular examinations were performed in all participants. Targeted gene panel sequencing and whole-exome sequencing were performed in the probands, and Sanger sequencing was used to verify the mutations and segregation analysis was performed in the family members.

Results

Fifty-one FZD4 mutations (24 novels and 27 known) were detected in 84 families. Of these 168 eyes with FEVR, the eyes at stages 1, 2, 3, 4, and 5 were 29 (17.3%), 15 (8.9%), 19 (11.3%), 55 (32.7%), and 12 (7.1%), respectively. Exact stage of 38 (22.6%) eyes could not be determined. The FEVR phenotypes were more severe in the probands than the phenotypes in the family members (P < 0.001). The families were divided into two groups, probands that inherited the variant from the mother, and probands that inherited the variant from the father. In addition, the FEVR stage differences between these two groups were different (P < 0.05). Despite the mutations being located in different domains of FZD4, no significant differences were identified among the domains in terms of FEVR staging, retinal folds, retinal detachment, temporal midperipheral vitreoretinal interface abnormality, and foveal hypoplasia.

Conclusions

The FZD4 probands had severer phenotype than the family members, and the FEVR stage difference was greater between the probands and mothers than that between the probands and fathers.

A Survey of Multigenic Protein-Altering Variant Frequency in Familial Exudative Vitreo-Retinopathy (FEVR) Patients by Targeted Sequencing of Seven FEVR-Linked Genes

While Inherited Retinal Diseases (IRDs) are typically considered rare diseases, Familial Exudative Vitreo-Retinopathy (FEVR) and Norrie Disease (ND) are more rare than retinitis pigmentosa. We wanted to determine if multigenic protein-altering variants are common in FEVR subjects within a set of FEVR-related genes. The potential occurrence of protein-altering variants in two different genes has been documented in a very small percentage of patients, but potential multigenic contributions to FEVR remain unclear. Genes involved in these orphan pediatric retinal diseases are not universally included in available IRD targeted-sequencing panels, and cost is also a factor limiting multigenic-sequence-based testing for these rare conditions. To provide an accurate solution at lower cost, we developed a targeted-sequencing protocol that includes seven genes involved in Familial Exudative Vitreo-Retinopathy (FEVR) and Norrie disease. Seventy-six DNA samples from persons refered to clinic with possible FEVR and some close relatives were sequenced using a novel Oakland-ERI orphan pediatric retinal disease panel (version 2) providing 900 times average read coverage. The seven genes involved in FEVR/ND were: NDP (ChrX), CTNNB1 (Chr3); TSPAN12 (Chr7); KIF11 (Chr10), FZD4 (Chr11), LRP5 (Chr11), ZNF408 (Chr11). A total of 33 variants were found that alter protein sequence, with the following relative distribution: LRP5 13/33 (40%), FZD4 9/33 (27%), ZNF408 6/33 (18%), (KIF11 3/33 (9%), NDP 1/33 (3%), CTNNB1 1/33 (3%). Most protein-altering variants, 85%, were found in three genes: FZD4, LRP5, and ZNF408. Four previously known pathogenic variants were detected in five families and two unrelated individuals. Two novel, likely pathogenic variants were detected in one family (FZD4: Cys450ter), and a likely pathogenic frame shift termination variant was detected in one unrelated individual (LRP5: Ala919CysfsTer67). The average number of genes with protein-altering variants was greater in subjects with confirmed FEVR (1.46, n = 30) compared to subjects confirmed unaffected by FEVR (0.95, n = 20), (p = 0.009). Thirty-four percent of persons sequenced had digenic and trigenic protein-altering variants within this set of FEVR genes, which was much greater than expected in the general population (3.6%), as derived from GnomAD data. While the potential contributions to FEVR are not known for most of the variants in a multigenic context, the high multigenic frequency suggests that potential multigenic contributions to FEVR severity warrant future investigation. The targeted-sequencing format developed will support such exploration by reducing the testing cost to $250 (US) for seven genes and facilitating greater access to genetic testing for families with this very rare inherited retinal disease.

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.

Ocular phenotype and genetical analysis in patients with retinopathy of prematurity

Background

Retinopathy of prematurity (ROP) is a multifactorial retinal disease, involving both environmental and genetic factors; The purpose of this study is to evaluate the clinical presentations and genetic variants in Chinese patients with ROP.

Methods

A total of 36 patients diagnosed with ROP were enrolled in this study, their medical and ophthalmic histories were obtained, and comprehensive clinical examinations were performed. Genomic DNA was isolated from peripheral blood of ROP patients, polymerase chain reaction and direct sequencing of the associated pathogenic genes (FZD4, TSPAN12, and NDP) were performed.

Results

All patients exhibited the clinical manifestations of ROP. No mutations were detected in the TSPAN12 and NDP genes in all patients; Interestingly, three novel missense mutations were identified in the FZD4 gene (p.A2P, p.L79M, and p.Y378C) in four patients, for a detection rate of 11.1% (4/36).

Conclusions

This study expands the genotypic spectrum of FZD4 gene in ROP patients, and our findings underscore the importance of obtaining molecular analyses and comprehensive health screening for this retinal disease.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-022-02252-x.

Ocular Features and Mutation Spectrum of Patients With Familial Exudative Vitreoretinopathy

Purpose

To investigate the clinical findings in Chinese patients diagnosed with familial exudative vitreoretinopathy (FEVR) and carrying pathogenic mutations.

Methods

One hundred twenty unrelated patients with FEVR were enrolled in this study. Genomic DNA and ophthalmic examinations were collected from all the patients and their available relatives. Targeted next-generation sequencing was performed to detect mutations. In silico programs were used to evaluate the pathogenicity of all the mutations.

Results

Eighty identified mutations were found in 81 unrelated patients (31/81 in LRP5, 25/81 in FZD4, 12/81 in TSPAN12, 8/81 in NDP, 4/81 in KIF11, and 1/81 in ZNF408). Among those mutations, 53 were novel (23/35 in LRP5, 15/21 in FZD4, 8/11 in TSPAN12, 3/8 in NDP, 3/4 in KIF11, 1/1 in ZNF408). Patients with LRP5, FZD4, TSPAN12, or NDP mutations were mainly classified into stage 4 and stage 5 and one-half of patients with KIF11 mutations were in stage 4. In addition, all the patients in NDP group were found to have bilateral symmetry in FEVR stage.

Conclusions

Our results present profound phenotypic variability and a wide mutation spectrum of FEVR in the Chinese population, which could be useful for a precise and comprehensive genetic diagnosis for patients with FEVR in the future.

A novel stop codon mutation of TSPAN12 gene in Chinese patients with familial exudative vitreoretinopathy

BACKGROUND

Familial exudative vitreoretinopathy (FEVR) is a group of inherited eye diseases characterized by premature arrest of retinal vessel development. The purpose of our study was to characterize the genetic causes and clinical features in eight Chinese families with FEVR using next-generation sequencing (NGS) technology.

MATERIALS AND METHODS

Eight families with FEVR were included in genetic and clinical analyses. We screened the proband and the parents in eight pedigrees with FEVR using targeted NGS approach and in silico analysis to determine the causative mutation for their family's phenotype.

RESULTS

Four cases (4/8, 50.0%) were confirmed to harbor mutations in known genes, including 3 novel mutations and one previously reported mutation. Among the detected mutations, TSPAN12 accounted for 75% (3/4). We identified a novel stop codon of TSPAN12, a heterozygous missense mutation NM_012338.4:c.633T>A, NP_036470.1:p.Tyr211Ter involved in highly conserved residues in the proband. Retrospective analysis of its clinical manifestation showed that the mutant carrier presented mild clinical features.

CONCLUSIONS

We found the novel stop codon mutation p.Tyr211Ter in the TSPAN12, which creates a milder phenotype. Discovery of this novel mutation expands the mutation spectrum of TSPAN12, and would be valuable for future genetic disease diagnosis.

Macular Retinal Pigment Epithelial Clumping Leading to a Diagnosis of FEVR

Familial exudative vitreoretinopathy (FEVR) is a rare hereditary disorder characterized by abnormal or incomplete retinal angiogenesis. The peripheral avascularity, irregular neovascularization, and vascular leakage seen in FEVR are similar to changes that may be seen in retinopathy of prematurity (ROP). The authors report a case of atypical macular pigment clumping leading to the diagnosis of ROPER (ie, ROP vs FEVR) in a premature infant born at 23 weeks of gestation with a birth weight of 451 grams, who presented with atypical aggressive posterior ROP and a heterozygous variant in the LRP5 gene. [Ophthalmic Surg Lasers Imaging Retina. 2021;52:505-508.].

INTRAVITREAL RANIBIZUMAB TREATMENT FOR ADVANCED FAMILIAL EXUDATIVE VITREORETINOPATHY WITH HIGH VASCULAR ACTIVITY

PURPOSE

To determine the efficacy of intravitreal ranibizumab (IVR) treatment for advanced familial exudative vitreoretinopathy with high vascular activity.

METHODS

The retrospective interventional case series included 28 eyes (20 patients) that had IVR in combination or not with other treatment, for Stage 3 to 5 familial exudative vitreoretinopathy with active fibrovascular proliferation and prominent subretinal exudation. Outcome measures were fundus features after treatment, associated clinical variables, and genetic mutations.

RESULTS

The age of patients at the first IVR ranged from 0.2 to 36 months. An average of 1.3 IVR injections per eye were given. Familial exudative vitreoretinopathy regressed in 16 (57%) eyes and progressed in 12 eyes (43%) after IVR. Laser and/or vitrectomy was performed on 13 eyes. The retina was reattached in 22 eyes (78%) after 24 to 58 months follow-up. Clinical variables associated with progression after IVR were preexisting fibrovascular proliferation over one quadrant and persistent vascular activity after the initial injection (P < 0.05). Familial exudative vitreoretinopathy-causative genetic mutations in 11 patients were related to variable response to IVR treatment.

CONCLUSION

Intravitreal ranibizumab treatment may effectively regress advanced familial exudative vitreoretinopathy with high vascular activity in selected cases. Different treatment outcomes may be relevant to variable presentation and genetic heterogeneity of familial exudative vitreoretinopathy.

Novel mutation in TSPAN12 associated with familial exudative vitreoretinopathy in a Chinese pedigree

BACKGROUND

Familial exudative vitreoretinopathy (FEVR) is a rare retinal disorder characterised by incomplete retinal vascular development. Symptoms vary widely from none to blindness even within the same family. Multiple genes related to the Wnt pathway have been found to be associated with FEVR. Recent studies identified tetraspanin 12 (TSPAN12) as a cause of the autosomal dominant inheritance form of FEVR. Here, we describe a novel TSPAN12 mutation in a Chinese family with FEVR.

METHODS

Targeted next-generation sequencing was performed on the proband to define the TSPAN12 mutation. Sanger sequencing was used to confirm the mutation in five family members (I-1, II-2, II-3, II-4, and III-3) in a three-generation FEVR pedigree. Ophthalmologic examinations and diagnostic imaging related to FEVR were performed.

RESULTS

The proband (II-3) was a 32-year-old man with early-stage peripheral retinal vascular anomalies, but no visual acuity problems. DNA sequencing identified a heterozygous missense mutation (c.241 G > A: p.Gly81Arg) in TSPAN12 in the proband. The mutation was in a highly conserved region and was predicted to affect the normal protein structure. The patient's father and daughter were also diagnosed with FEVR and carried the same mutation, with varying degrees of manifestations. Other family members had good vision and normal eye examinations with negative genetic testing.

CONCLUSIONS

We identified a novel missense mutation in TSPAN12 associated with autosomal dominant FEVR. These results will facilitate the diagnosis, prognosis, and genetic counselling for this disease. Further studies are needed to identify the mechanisms underlying clinical variations among individuals in the family.

A mouse model for kinesin family member 11 (Kif11)-associated familial exudative vitreoretinopathy

During mitosis, Kif11, a kinesin motor protein, promotes bipolar spindle formation and chromosome movement, and during interphase, Kif11 mediates diverse trafficking processes in the cytoplasm. In humans, inactivating mutations in KIF11 are associated with (1) retinal hypovascularization with or without microcephaly and (2) multi-organ syndromes characterized by variable combinations of lymphedema, chorioretinal dysplasia, microcephaly and/or mental retardation. To explore the pathogenic basis of KIF11-associated retinal vascular disease, we generated a Kif11 conditional knockout (CKO) mouse and investigated the consequences of early postnatal inactivation of Kif11 in vascular endothelial cells (ECs). The principal finding is that postnatal EC-specific loss of Kif11 leads to severely stunted growth of the retinal vasculature, mildly stunted growth of the cerebellar vasculature and little or no effect on the vasculature elsewhere in the central nervous system (CNS). Thus, in mice, Kif11 function in early postnatal CNS ECs is most significant in the two CNS regions-the retina and cerebellum-that exhibit the most rapid rate of postnatal growth, which may sensitize ECs to impaired mitotic spindle function. Several lines of evidence indicate that these phenotypes are not caused by reduced beta-catenin signaling in ECs, despite the close resemblance of the Kif11 CKO phenotype to that caused by EC-specific reductions in beta-catenin signaling. Based on prior work, defective beta-catenin signaling had been the only known mechanism responsible for monogenic human disorders of retinal hypovascularization. The present study implies that retinal hypovascularization can arise from a second and mechanistically distinct cause.

Compound Heterozygous Mutations in ZNF408 in a Patient with a Late Onset Pigmentary Retinopathy and Relatively Preserved Central Retina

PURPOSE

To describe in detail the phenotype of a patient with compound heterozygous mutations in ZNF408 and an adult-onset pigmentary retinopathy rather than familial exudative vitreoretinopathy as expected with heterozygous mutations in this gene.

METHODS

A 70-year-old male presented with a pigmentary retinopathy, which prompted a genetic evaluation that revealed two variants in trans in the ZNF408 gene. He underwent an ophthalmic examination, kinetic fields, electroretinography (ERG), spectral-domain optical coherence tomography (SD-OCT), fundus autofluorescence, wide-angle fluorescein angiography and near-infrared imaging.

RESULTS

Visual acuity was 20/20 for both eyes. Fundus examination showed epiretinal membrane, vascular attenuation and peripheral bone spicule pigmentation in both eyes. Fluorescein angiography showed no vascular anomalies in both eyes. Fundus autofluorescence showed a preserved island of fundus autofluorescence centrally. Visual field by kinetic perimetry (V-4e stimulus) showed generalized constriction to 40 degrees of eccentricity and by an I-4e target showed generalized constriction to 10 degrees of eccentricity. ERG showed detectable but reduced cone-mediated responses. SD-OCT demonstrated preserved outer nuclear layer thickness centrally, which decreased with eccentricity. Static perimetry showed substantial rod and cone sensitivities centrally that declined with eccentricity. A next-generation sequencing panel revealed bi-allelic variants (p.Arg567Ter; c.1699C > T and p.Leu566His; c.1697 T > A) in the ZNF408 gene.

CONCLUSIONS

ZNF408-associated retinal dystrophies can present with predominantly retinal findings and should be considered in the differential diagnosis of retinitis pigmentosa. Our study revealed a novel variant p.L566H, which to our knowledge has not previously been reported.

Whole-Gene Deletions of FZD4 Cause Familial Exudative Vitreoretinopathy

Familial exudative vitreoretinopathy (FEVR) is an inherited disorder characterized by abnormalities in the retinal vasculature. The FZD4 gene is associated with FEVR, but the prevalence and impact of FZD4 copy number variation (CNV) on FEVR patients are unknown. The aim of this study was to better understand the genetic features and clinical manifestations of patients with FZD4 CNVs. A total of 651 FEVR families were recruited. Families negative for mutations in FEVR-associated genes were selected for CNV analysis using SeqCNV. Semiquantitative multiplex polymerase chain reaction and multiplex ligation-dependent probe amplification were conducted to verify the CNVs. Four probands were found to carry whole-gene deletions of FZD4, accounting for 5% (4/80) of probands with FZD4 mutations and 0.6% (4/651) of all FEVR probands. The four probands exhibited similar phenotypes of unilateral retinal folds. FEVR in probands with CNVs was not more severe than in probands with FZD4 missense mutations (p = 1.000). Although this is the first report of FZD4 CNVs and the associated phenotypes, the interpretation of FZD4 CNVs should be emphasized when analyzing the next-generation sequencing data of FEVR patients because of their high prevalence.

Retinal Features of Family Members With Familial Exudative Vitreoretinopathy Caused By Mutations in KIF11 Gene

Purpose

To determine the clinical characteristics of patients and family members with familial exudative vitreoretinopathy (FEVR) caused by mutations in the KIF11 gene.

Methods

Twenty-one patients from 10 FEVR families with mutations in the KIF11 gene were studied. The retinal and systemic features were examined. The genetic analyses performed included Sanger sequencing of the KIF11 gene, whole exome sequencing, as well as array comparative genomic hybridization (CGH) analysis and multiple ligation probe assay (MLPA).

Results

Sequence analysis revealed seven different KIF11 mutations. Array CGH with MLPA revealed two different exon deletions. All probands had advanced FEVR with retinal detachments (RDs) and microcephaly with or without developmental disabilities. Patients with bilateral RDs were more frequently associated with developmental disabilities (P = 0.023). Multimodal imaging of the family members revealed that six of nine patients without RDs (66%) had varying degrees of chorioretinopathy. The retinal folds in FEVR patients were associated with severe retinal avascularization. However, funduscopic changes in the peripheral retina were unremarkable in family members without RDs. A score representing the peripheral vascular anomalies determined from the fluorescein angiograms was lower than that of control eyes of patients with mutations of the Wnt signaling genes (P = 0.0029).

Conclusions

The probands with KIF11 mutations were associated with severe ocular and systemic pathologies, whereas affected family members showed highly variable clinical manifestations. Peripheral vascular anomalies can often be unremarkable in eyes without RDs.

Translational Relevance

These findings highlight more diverse mechanisms that underlie the pathological changes in patients with FEVR.

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

PURPOSE

The pathogenic variants in TSPAN12 could lead to familial exudative vitreoretinopathy (FEVR), which has high clinical variability. This study aims to assess the pathogenicity of TSPAN12 variants and their phenotypic spectrum based on exome sequencing from 7092 probands with different eye conditions.

METHODS

The variants in TSPAN12 were selected from exome sequencing data of samples from 7092 probands with different forms of eye conditions. Potentially pathogenic variants were evaluated through the annotation of types, locations, population frequencies, and in silico predictions of variants from in-house data, gnomAD, and published literature. The clinical features of patients with potentially pathogenic variants in TSPAN12 were assessed.

RESULTS

A total of 45 variants in TSPAN12 with coding effects were detected based on the exome data from 7092 probands, among which 31 were classified as pathogenic variants including 15 novels. The 31 variants were identified in 34 probands with various initial diagnoses, including FEVR in 21 probands and diseases other than FEVR in the remaining 13 probands. Biallelic pathogenic variants were identified in one proband with initial diagnosis of high myopia.

CONCLUSION

Truncating variants and the missense variants that are predicted as deleterious are likely pathogenic variants of TSPAN12. Approximately 61.8% of patients with pathogenic variants in this gene had an initial diagnosis of FEVR, and the remaining 38.2% of patients had various initial diagnoses. These findings expand the understanding about variant evaluation of TSPAN12 and phenotypic spectrum of TSPAN12-associated FEVR.

eys +/- ; lrp5 +/- Zebrafish Reveals Lrp5 Can Be the Receptor of Retinol in the Visual Cycle

Vision is essential for vertebrates including humans. Sustained vision is accomplished by retinoid metabolism, the “visual cycle,” where all-trans retinol (atROL) is incorporated into the retinal pigment epithelium (RPE) from photoreceptors presumably through decade-long missing receptor(s). Here, we show that the LDL-related receptor-5 (Lrp5) protein is linked to the retinol binding protein 1a (Rbp1a), the transporter of atROL in the visual cycle, by generating and analyzing the digenic eyes shut homolog^+/-; lrp5^+/− zebrafish, the same form of gene defect detected in a human case of inherited retinal degeneration. Global gene expression analysis followed by genetic study clarified that rbp1a played a role downstream of lrp5. Rbp1a protein was colocalized with Lrp5 protein at microvilli of RPE cells. Furthermore, Rbp1a directly bound to the C-terminal intracellular region of Lrp5 in vitro. Collectively, these results strongly suggest that Lrp5 is a potent candidate of the receptor of atROL in the visual cycle.

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eys^+/-; lrp5^+/− zebrafish showed mild photoreceptor degeneration

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Microarray analysis identified dramatical decrease of rbp1a expression

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Rbp1a protein was colocalized with Lrp5 protein at the microvilli of the RPE

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Rbp1a directly bound to the C-terminal intracellular region of Lrp5 in vitro

Novel FZD4 and LRP5 mutations in a small cohort of patients with familial exudative vitreoretinopathy (FEVR)

Purpose: To report novel mutations in the FZD4 and LRP5 genes, associated with familial exudative vitreoretinopathy (FEVR), and to correlate with clinical features of 7 FEVR patients.Methods: In this retrospective case series, 7 patients who had undergone genetic panel testing and carried a diagnosis of FEVR were identified. Comprehensive ophthalmic examination and direct DNA sequencing of FEVR-associated genes were performed in all patients. Identified sequence variants were analyzed in silico.Results: Eight mutations were identified amongst the 7 patients, that included 4 FZD4 mutations and 4 LRP5 mutations. Four novel mutations were identified, two in FZD4 (c.615delC, p.Y206MfsX34) and (c.964A>T, p.I322F), and two in LRP5 (c.2585A>T, p.D862V) and (c.1412 + 1 G > A, splice donor). A broad phenotypic spectrum was noted and no clear genotypic-phenotypic correlation was observed.Conclusion: These findings expand the mutation spectrum of FZD4 and LRP5.

Molecular diagnosis based on comprehensive genetic testing in 800 Chinese families with non-syndromic inherited retinal dystrophies

IMPORTANCE

Inherited retinal dystrophies (IRDs) are a group of monogenic diseases, one of the leading causes of blindness.

BACKGROUND

Introducing a comprehensive genetic testing strategy by combining single gene Sanger sequencing, next-generation sequencing (NGS) including whole exome sequencing (WES), and a specific hereditary eye disease enrichment panel (HEDEP) sequencing, to identify the disease-causing variants of 800 Chinese probands affected with non-syndromic IRDs.

DESIGN

Retrospective analysis.

PARTICIPANTS

Eight hundred Chinese non-syndromic IRDs probands and their families.

METHODS

A total of 149 patients were subjected to Sanger sequencing. Of the 651 patients subjected to NGS, 86 patients underwent WES and 565 underwent HEDEP. Patients that likely carried copy number variations (CNVs) detected by HEDEP were further validated by multiplex ligation-dependent probe amplification (MLPA) or quantitative fluorescence PCR (QF-PCR).

MAIN OUTCOME MEASURES

The diagnostic rate.

RESULTS

(Likely) pathogenic variants were determined in 481 cases (60.13% detection rate). The detection rates of single gene Sanger sequencing, WES and HEDEP were 86.58%, 31.40% and 56.99%, respectively. Approximately 11.64% of 481 cases carried autosomal dominant variants, 72.97% carried AR variants and 15.39% were found to be X-linked. CNVs were confirmed by MLPA or QF-PCR in 17 families. Fourteen genes that each caused disease in 1% or more of the cohort were detected, and these genes were collectively responsible for disease in almost one half (46.38%) of the families.

CONCLUSIONS AND RELEVANCE

Sanger sequencing is ideal to detect pathogenic variants of clinical homogeneous diseases, whereas NGS is more appropriate for patients without an explicit clinical diagnosis.

Toward the Clinical Application of Therapeutic Angiogenesis Against Pediatric Ischemic Retinopathy

Therapeutic angiogenesis refers to strategies of inducing angiogenesis to treat diseases involving ischemic conditions. Historically, most attempts and achievements have been related to coronary and peripheral artery diseases. In this review, we propose the clinical application of therapeutic angiogenesis for the treatment of pediatric ischemic retinopathy, including retinopathy of prematurity, familial exudative retinopathy, and NDP-related retinopathy. These diseases are all characterized by the reduction of physiological angiogenesis and the following induction of pathological angiogenesis. Therapeutic angiogenesis, which supplements insufficient physiological angiogenesis, may be a therapeutic approach for ischemic conditions. Various molecules and modalities can be utilized to apply therapeutic angiogenesis for the treatment of ischemic retinopathy, as in coronary and peripheral artery diseases. Experiences with cardiovascular diseases provide a useful reference for the further clinical application of therapeutic angiogenesis in pediatric ischemic retinopathy. Recombinant proteins and gene therapy are powerful tools to deliver angiogenic factors to retinal tissues directly. Furthermore, endothelial progenitor or bone marrow-derived cells can be injected into the vitreous cavity of the eye for therapeutic angiogenesis. Intraocular injections are highly promising for the delivery of therapeutics for therapeutic angiogenesis. We expect that therapeutic angiogenesis will be a breakthrough in the treatment of pediatric ischemic retinopathy.

Clinical and genetical features of probands and affected family members with familial exudative vitreoretinopathy in a large Chinese cohort

Aims

To explore the clinical and genetical features of families with strictly confirmed familial exudative vitreoretinopathy (FEVR) in a large Chinese cohort.

Methods

A retrospective chart review study was conducted on the FEVR families diagnosed by both angiography and targeted next-generation sequencing in six FEVR known genes (FZD4, LRP5, TSPAN12, NDP, KIF11, ZNF408) in the probands and at least one first-degree family member. Variation in expressivity and severity was evaluated in different gene groups.

Results

105 FEVR families (223 FEVR affected subjects with 434 eyes) met the inclusion criteria. There were 105 probands with mean age of 3.8 years old and 118 affected family members of 32.7 years old averagely. Mutations in FZD4 were most prevalent (33.33%), followed by LRP5 (29.52%), TSPAN12 (22.86%), NDP (5.71%), KIF11 (1.9%) and ZNF408 (0.95%). 81% of the probands were classified as stage 4 or worse which most prevalently contributed to FZD4 mutations. All of the three affected family members with stage 4 or worse carried FZD4 variants. More than half (51.43%) of the probands in FZD4 group showed asymmetry. Unilateral FEVR was detected in 11 (10.5%) families consisting of six probands and six affected relatives, and FZD4 mutations accounted for 63.64% of all the cases with variant (c.1282_1285del, p. D428fs) identified in three families.

Conclusions

Genotype-phenotype correlation in FEVR was complex with family dependent. Mutations in FZD4 might initiate the most diverse and asymmetric phenotypes.

The spectrum of genetic mutations in patients with asymptomatic mild familial exudative vitreoretinopathy

Familial exudative vitreoretinopathy (FEVR) is a disease exhibits a wide range of clinical signs, ranging mild peripheral retinal vascular anomalies to severe retinal detachments. Individuals with mild FEVR are frequently asymptomatic with good visual function and are often undiagnosed. However, little is known about the genetic characters of the cohort. The purpose of this study was to investigate the clinical characteristics and genetic spectrum of in patients with asymptomatic mild FEVR. Herein, sixty-two patients (124 eyes) with asymptomatic mild FEVR were studied in a case series. Comprehensive ophthalmic examinations and genetic testing were performed in all patients. Clinical examinations showed that the avascular zone was seen in all 124 eyes and was the most common abnormality observed. Increased vessel branching and straightened peripheral vessel branches were found in 122 (98.4%) eyes. Late-phase angiographic posterior and peripheral leakage (LAPPEL) was observed in 80 (64.5%) eyes and V-shape degeneration was noted in 36 (29.0%) eyes. Other manifestations including extensive anastomoses, retinal ridges, and extraretinal neovascularization, which were detected in 30 (24.2%), 10 (8.1%) and 2 (1.6%) eyes respectively. Overall, pathogenic mutations were identified in 48.4% (30/62) of individuals with asymptomatic mild FEVR. Mutations in FZD4, LRP5, TSPAN12, and KIF11 were detected in 21.0% (13/62), 12.9% (8/62), 12.9% (8/62), and 1.6% (1/62) of our patients respectively. Ten novel mutations were found. In conclusion: Pathogenic mutations in the known FEVR-associated genes were detected in nearly half (48.4%) of the asymptomatic mild FEVR cohort. Among these mutations, FZD4 was predominant, appearing in 21.0% of all individuals. Patients with asymptomatic mild FEVR should receive timely examinations, lifelong monitoring, and some of them need preventive therapy and treatment. Additionally, we discovered 10 novel variants, which may enable a deeper understanding of this disease.