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/ß-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/ß-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/ß-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.

Mutations in TSPAN12 gene causing familial exudative vitreoretinopathy.

BACKGROUND: To report newly found TSPAN12 mutations with a unique form of familial exudative vitreoretinopathy (FEVR) and find out the possible mechanism of a repeated novel intronic variant in TSPAN12 led to FEVR. RESULTS: Nine TSPAN12 mutations with a unique form of FEVR were detected by panel-based NGS. MINI-Gene assay showed two splicing modes of mRNA that process two different bands A and B, and mutant-type shows replacement with the splicing mode of Exon11 hopping. Construction of wild-type and mutant TSPAN12 vector showed the appearance of premature termination codons (PTC). In vitro expression detection showed significant down-regulated expression level of TSPAN12 mRNAs and proteins in cells transfected with mutant vectors compared with in wild-type group. On the contrary, translation inhibitor CHX and small interfering RNA of UPF1 (si-UPF1) significantly increased mRNA or protein expression of TSPAN12 in cells transfected with the mutant vectors. CONCLUSIONS: Nine mutations in TSPAN12 gene are reported in 9 FEVR patients with a unique series of ocular abnormalities. The three novel TSPAN12 mutations trigger NMD would cause the decrease of TSPAN12 proteins that participate in biosynthesis and assembly of microfibers, which might lead to FEVR, and suggest that intronic sequence analysis might be a vital tool for genetic counseling and prenatal diagnoses.

Deciphering a crucial dimeric interface governing Norrin dimerization and the pathogenesis of familial exudative vitreoretinopathy.

Familial exudative vitreoretinopathy (FEVR) is a hereditary eye disease that could cause blindness. It has been established that Norrin forms dimers to activate ß-catenin signaling, yet the core interface for Norrin dimerization and the precise mechanism by which Norrin dimerization contributes to the pathogenesis of FEVR remain elusive. Here, we report an NDP variant, c.265T>C (p.Phe89Leu), that interrupted ß-catenin signaling by disrupting Norrin dimerization. Structural and functional analysis revealed that the Phe-89 of one Norrin monomer interacts with Pro-98, Ser-101, Arg-121, and Ile-123 of another, forming two core symmetrical dimerization interfaces that are pivotal for the formation of a "hand-by-arm" dimer. Intriguingly, we proved that one of the two core symmetrical interfaces is sufficient for dimerization and activation of ß-catenin signaling, with a substantial contribution from the Phe-89/Pro-98 interaction. Further functional analysis revealed that the disruption of both dimeric interfaces eliminates potential binding sites for LRP5, which could be partially restored by over-expression of TSPAN12. In conclusion, our findings unveil a core dimerization interface that regulates Norrin/LRP5 interaction, highlighting the essential role of Norrin dimerization on ß-catenin signaling and providing potential therapeutic avenues for the treatment of FEVR.

Intra-Anterior Chamber Injection of Ranibizumab in Advanced Pediatric Vitreoretinal Diseases.

Importance: Anti-vascular endothelial growth factor (VEGF) treatment through intravitreal or subretinal administrations has been proven effective for VEGF-driven pediatric vitreoretinal diseases but are not feasible for advanced cases, such as shallow traction retinal detachments or peripheral circumferential retinal detachments which adhere to the lens. Intra-anterior chamber injection (IAcI) of anti-VEGF may be a viable alternative in such cases but needs evaluation. Objective: To investigate the effects and safety of IAcI of anti-VEGF to treat VEGF-driven pediatric vitreoretinal diseases. Design, Setting, and Participants: This was a retrospective observational case series study conducted at Xinhua Hospital, affiliated with Shanghai Jiao Tong University School of Medicine in China. The study included 14 eyes of 13 children diagnosed with vitreoretinal disease exhibiting elevated vascular activity between January and August 2023. Intervention: IAcI with ranibizumab. Main Outcomes and Measures: Retinal vascular abnormalities, vitreous hemorrhage resolution, and complications 1 month and 3 months after injection. Results: Of 13 patients included in this study, 12 were male. The mean age was 4.6 years (range, 1 month to 9 years). Six patients were diagnosed with familial exudative vitreoretinopathy, 4 with morning glory syndrome, 1 with retinopathy of prematurity, and 2 with chronic retinal detachments of unknown causes. At 1-month postoperative follow-up, vascular activity had decreased in 14 of 14 eyes. At 3-month follow-up, vascular activity had resolved in 7 of 14 eyes, persisted in 6 of 14 eyes, and reactivated in 1 of 14 eyes. On final observation, no complications were reported. Conclusions and Relevance: These findings support the possibility of treatment using IAcI with ranibizumab to decrease retinal vascular abnormalities in familial exudative vitreoretinopathy or retinopathy of prematurity or related conditions, but further studies are needed to understand more precise benefits and risks. This approach might be considered in cases where intravitreal or subretinal injection are not feasible, recognizing the limitations of these findings and that longer-term outcomes still need to be monitored.

Frameshift variants in the C-terminal of CTNNB1 cause familial exudative vitreoretinopathy by AXIN1-mediated ubiquitin-proteasome degradation condensation.

The ß-catenin has two intrinsically disordered regions in both C- and N-terminal domains that trigger the formation of phase-separated condensates. Variants in its C-terminus are associated with familial exudative vitreoretinopathy (FEVR), yet the pathogenesis and the role of these variants in inducing abnormal condensates, are unclear. In this study, we identified a novel heterozygous frameshift variant, c.2104-2105insCC (p.Gln703ProfsTer33), in CTNNB1 from a FEVR-affected family. This variant encodes an unstable truncated protein that was unable to activate Wnt signal transduction, which could be rescued by the inhibition of proteasome or phosphorylation. Further functional experiments revealed the propensity of the Gln703ProfsTer33 variant to form cytoplasmic condensates, exhibiting a lower turnover rate after fluorescent bleaching due to enhanced interaction with AXIN1. LiCl, which specifically blocks GSK3ß-mediated phosphorylation, restored signal transduction, cell proliferation, and junctional integrity in primary human retinal microvascular endothelial cells over-expressed with Gln703ProfsTer33. Finally, experiments on two reported FEVR-associated mutations in the C-terminal domain of ß-catenin exhibited several functional defects similar to the Gln703ProfsTer33. Together, our findings unravel that the C-terminal region of ß-catenin is pivotal for the regulation of AXIN1/ß-catenin interaction, acting as a switch to mediate nucleic and cytosolic condensates formation that is implicated in the pathogenesis of FEVR.

A Literary Pediatric Retina Fellowship With Michael T. Trese, MD.

Michael T. Trese, MD (1946-2022), a vitreoretinal surgeon, made significant contributions to the field of retina. Although most known for his work in pediatric retina surgery, he was a pioneer in areas such as medical retina, translational research, and telemedicine. This article reviews his major contributions to spread his knowledge more widely to vitreoretinal trainees and specialists. We discuss six areas where Trese made a lasting impact: lens-sparing vitrectomy, familial exudative vitreoretinopathy, congenital X-linked retinoschisis, autologous plasmin enzyme, regenerative medicine, and telemedicine. [Ophthalmic Surg Lasers Imaging Retina 2023;54:701-712.].

[The role of endothelin-1 in the pathogenesis of familial exudative vitreoretinopathy]. / Rol' endotelina-1 v patogeneze semeinoi ekssudativnoi vitreoretinopatii.

Familial exudative vitreoretinopathy (FEVR) is a rare hereditary disease characterized by pathological retinal vascularization with a progressive and variable course. The mechanisms of disease progression remain unclear. One substance that plays an important role in the pathogenesis of retinal vascular diseases is endothelin (ET). It was found that tissue hypoxia enhances the expression of the gene encoding ET-1, and ET-1 can be locally produced in the eye. PURPOSE: The study evaluates the possible role of endothelin-1 in the pathogenesis of FEVR. MATERIAL AND METHODS: The study included 85 patients with FEVR aged from 1 months to 17 years who were examined in Helmholtz National Medical Research Center of Eye Diseases. The concentration of ET-1 was evaluated in 19 patients with FEVR in the blood serum (n=17), lacrimal fluid (n=18) and 16 patients from the control group. RESULTS: The median of ET-1 in the lacrimal fluid in patients with FEVR was 13.74 pg/mL, respectively, which exceeded the same indicator of the control group 4.66 pg/mL by 2.5 times (p<0.001). The median of ET-1 in the blood serum exceeded the control group by 2.4 times (21.61 pg/mL and 9.21 pg/mL, respectively, p<0.001). CONCLUSIONS: An increase in the concentration of ET-1 in the lacrimal fluid and blood serum of patients with FEVR in comparison with the control group indicates its involvement in the pathogenesis of the disease.

Mechanisms Underlying Rare Inherited Pediatric Retinal Vascular Diseases: FEVR, Norrie Disease, Persistent Fetal Vascular Syndrome.

Familial Exudative Vitreoretinopathy (FEVR), Norrie disease, and persistent fetal vascular syndrome (PFVS) are extremely rare retinopathies that are clinically distinct but are unified by abnormal retinal endothelial cell function, and subsequent irregular retinal vascular development and/or aberrant inner blood-retinal-barrier (iBRB) function. The early angiogenesis of the retina and its iBRB is a delicate process that is mediated by the canonical Norrin Wnt-signaling pathway in retinal endothelial cells. Pathogenic variants in genes that play key roles within this pathway, such as NDP, FZD4, TSPAN12, and LRP5, have been associated with the incidence of these retinal diseases. Recent efforts to further elucidate the etiology of these conditions have not only highlighted their multigenic nature but have also resulted in the discovery of pathological variants in additional genes such as CTNNB1, KIF11, and ZNF408, some of which operate outside of the Norrin Wnt-signaling pathway. Recent discoveries of FEVR-linked variants in two other Catenin genes (CTNND1, CTNNA1) and the Endoplasmic Reticulum Membrane Complex Subunit-1 gene (EMC1) suggest that we will continue to find additional genes that impact the neural retinal vasculature, especially in multi-syndromic conditions. The goal of this review is to briefly highlight the current understanding of the roles of their encoded proteins in retinal endothelial cells to understand the essential functional mechanisms that can be altered to cause these very rare pediatric retinal vascular diseases.

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.

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.

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.

Peripheral and central retinal vascular changes in asymptomatic family members of patients with familial exudative vitreoretinopathy.

PURPOSE: To evaluate the peripheral vascular changes and effects of these on macular microvasculature in asymptomatic family members of familial exudative vitreoretinopathy (FEVR) patients. METHODS: This is a retrospective study including 61 eyes of asymptomatic family members of FEVR patients. Retinal abnormalities were assessed via ultra-widefield fluorescein angiography (UWF-FA) and optical coherence tomography angiography (OCTA). The eyes were grouped into 3: the first group comprised of eyes with normal findings on UWF-FA; the second group comprised of eyes with abnormal findings on UWF-FA but without any retinal ischemia; and the third group involved eyes with retinal ischemia or neovascularization. RESULTS: Best corrected visual acuity (BCVA) was 20/20 in all eyes. Forty eyes (65.6%) had abnormalities on UWF-FA. The most common feature was peripheral vascular looping, increased tortuosity, and anastomosis (63.9%). ODM/ODD ratio was higher in group 3 compared to groups 1 and 2. Deep foveal VD was lower in group 1 compared to groups 2 and 3. The mean FAZ area and perimeter were smaller in groups 2 and 3 compared to group 1. CONCLUSION: Even asymptomatic family members of FEVR patients may have significant peripheral retinal vascular abnormalities which may be associated with smaller optic disc, macular ectopia, and macular microvascular changes.

Five novel dysfunctional variants in the TSPAN12 gene in familial exudative vitreoretinopathy.

Familial exudative vitreoretinopathy (FEVR) is an inheritable vitreoretinal disease characterized by incomplete retinal vascular development, which often leads to multiple retinal complications and causes severe vision loss in children. We reported the TSPAN12 variants' frequency in a cohort of FEVR and five novel TSPAN12 variants and related clinical features in six Chinese families. Seven hundred thirty-four families' genetic in-house data were reviewed. Whole-exome sequencing (WES) was performed in all probands; Sanger sequencing was conducted in the family members. Five novel variants from six families were noted, and clinical data were collected. Luciferase assays were applied to test the activity of the Norrin/ß-catenin signal caused by the mutant TSPAN12 genes. The frequency of TSPAN12 variants in FEVR is 8.79% (50/569). Five novel variants in TSPAN12 were identified in six families, including two missense variants, c.476G > A(p.Cys159Tyr) and c.81T > G(p.Ser27Arg), two frameshift variants, c.628_629insA(p.Met210Asnfs*42) and c.251delG(p.Gly84Glufs*3) and one nonsense, c.352G > T(p.Glu118*). Low vision, high myopia, nystagmus, and leukocoria are the common symptom at the first presentation. All variants were also predicted as pathogenic in silico. Moreover, the luciferase assay demonstrated that all variants caused severely compromised Norrin/ß-catenin signaling activity. In conclusion, the frequency of TSPAN12 variants in FEVR was 8.79% in our cohort. Five novel variants of TSPAN12 were identified. Moreover, we demonstrated the dysfunction of mutant variants via the downregulation of Norrin/ß-catenin signaling. These findings expanded the genetic and clinical spectrum of FEVR with TSPAN12 variants.

Rapid Improvement in Lipid Maculopathy Following Faricimab Therapy in Recalcitrant Familial Exudative Vitreoretinopathy.

A monocular 22-year-old man with recalcitrant familial exudative vitreoretinopathy presented with progressive subretinal lipid exudation and lipid maculopathy that responded poorly to repeated aflibercept injections. The subretinal exudation started temporally and gradually progressed, involving the macula and the retinal periphery in all 4 quadrants. At the 22-month follow-up visit, macular and peripheral subretinal exudation persisted despite a total of 29 injections. Faricimab was then injected once every 2 weeks for a total of 3 injections, which resulted in rapid dramatic resolution of the macular and most of the peripheral subretinal exudation. No ocular or systemic adverse events were noted. [Ophthalmic Surg Lasers Imaging Retina 2023;54:426-428.].

Two types of childhood glaucoma secondary to familial exudative vitreoretinopathy.

BACKGROUND: Glaucoma secondary to familial exudative vitreoretinopathy presents as angle closure by either neovascular or non-neovascular mechanisms. We analyze the presentation and outcomes of two types of childhood glaucoma secondary to familial exudative vitreoretinopathy (FEVR). METHODS: This retrospective cross-sectional study included all patients <18 years of age diagnosed with glaucoma after or concurrently with a diagnosis of FEVR between 2010 and 2020 from Queen Sirikit National Institute of Child Health in Bangkok, Thailand. Two groups were analyzed: neovascular or non-neovascular angle-closure status. Primary outcome measures were final visual acuity and intraocular pressure (IOP) in both groups. RESULTS: Of 144 FEVR patients, 8 children (5.5%; 11 eyes, 3 bilateral cases) developed childhood glaucoma. Mean time between FEVR presentation and glaucoma was 42.2 ± 40.0 months. In the neovascular group, 3 of 9 eyes presented with glaucoma at FEVR diagnosis; 3 of 9 eyes (33%) required glaucoma surgery. In the non-neovascular group, 2 eyes presented with acute angle closure secondary to a phacomorphic lens. Both were treated with trabeculectomy, with resolution of pupillary block. All eyes had stage 4B FEVR or greater. Six of 8 eyes had stable or better visual acuity, and 10 eyes (91%) had IOP <21 mm Hg at final follow-up. CONCLUSIONS: Childhood glaucoma secondary to FEVR is a rare complication caused by later stages of the disease. It may present as neovascular or non-neovascular angle closure, often requiring complex care. Therefore, awareness and adequate management of FEVR can help prevent additional morbidity from childhood glaucoma.

The Characteristic of Optical Coherence Tomography Angiography and Retinal Arteries Angle in Familial Exudative Vitreoretinopathy with Inner Retinal Layer Persistence.

PURPOSE: To compare the angle of retinal arteries and macular vessel density and foveal avascular zone (FAZ) in early stage familial exudative vitreoretinopathy (FEVR) patients with inner retinal layer (IRL) persistence with FEVR patients without IRL persistence and normal people. METHODS: This study enrolled 113 early stage FEVR patients and 55 age-matched normal subjects. FEVR patients were divided into IRL group and non-IRL group based on the presence or absence of IRL in fovea. The angle of superior temporal and inferior temporal branch retinal arteries on ultra-wide-field fundus images were measured. Superficial and deep vessel density of whole image, fovea and parafovea, the area and perimeter of FAZ, A-circularity index (AI, perimeter/standard circle perimeter with equal area) and vessel density around the 300-µm width of the FAZ (FD), central macular thickness (CMT) on 3 mm × 3mm OCTA were measured. RESULTS: 30 FEVR patients in IRL group, 83 FEVR patients in non-IRL group, 55 normal people in control group were evaluated. BCVA were worst in IRL group (p < .001). The angle of retinal arteries was smaller in FEVR groups (p < .001) and were smallest in IRL group (p < .001). Superficial and deep vessel density of whole and parafovea area in FEVR patients were significantly lower than that in normal people (p < .05), AI were biggest (p = .01) and FD were smallest in IRL group (p < .001). CMT in IRL group were thicker than non-IRL group and control group (p < .05). CONCLUSION: Worse BCVA, smaller angle of retinal arteries (more vessels traction), lower macular vessel density, smaller and more irregular FAZ and thicker CMT were observed in FEVR patients with IRL persistence even in early stage.

LONG-TERM CLINICAL OUTCOMES AND GENOTYPE-PHENOTYPE CORRELATION IN FAMILIAL EXUDATIVE VITREORETINOPATHY IN A TERTIARY REFERRAL CENTER.

BACKGROUND/PURPOSE: To evaluate clinical outcomes and assess genotype-phenotype correlations in patients with familial exudative vitreoretinopathy (FEVR). METHODS: Clinical charts of 40 patients with FEVR were reviewed. FEVR was staged per Pendergast and Trese, and retinal dragging and folds further classified per Yaguchi et al. We performed whole-exome sequencing and compared clinical characteristics between genetic-positive and genetic-negative groups. RESULTS: The mean duration of follow-up was 5.4 years (range: 0.33, 15) for genetic-positive and 6.9 (range: 1, 20) for genetic-negative patients. The mean age at diagnosis was 5.6 years (0.25, 27) for genetic-positive and 6.0 (0, 32) for genetic-negative patients. Genetic-positive patients reported 100% full-term births and genetic-negative patients reported 45% full-term births ( P = 0.0012). There were more patients with retinal folds with all major vessels affected (Yaguchi's Group 4) in genetic-positive compared with genetic-negative patients (21.4% vs. 2.6%, P = 0.045). TSPAN12 was the most common (57.1%) genetic mutation in our population of which 50% exhibited asymmetric presentation. CONCLUSION: Patients who test positive for a typical FEVR gene mutation reported more term births and had more severe disease by Yaguchi's classification. TSPAN12 was the most common genetic mutation in our population and had highly asymmetrical disease.

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.

Identification of Five Novel Variants in the TSPAN12 Gene in Chinese Families With Familial Exudative Vitreoretinopathy.

Purpose: To report the novel causative variants in five Chinese families with familial exudative vitreoretinopathy (FEVR). Methods: Five unrelated Chinese families diagnosed with FEVR were enrolled in this study. Ocular examinations and genetic analysis were performed on the probands and family members. Luciferase assay was performed to evaluate the variants' impacts on Norrin/ß-catenin signaling activity. Results: Five novel variants, including two frameshifts, c.518delA (p.Glu173Glyfs*42) and c.719delT (p.Leu240Profs*21), two missenses, c.482G>T (p.Gly161Val) and c. 614G>C (p. Gly205Ala), and one nonsense, c.375G>A (p.Trp125*), were identified in the TSPAN12 gene in this study. All the variants were co-segregated within each family and were predicted as pathogenic in silico. The luciferase assay showed all variants lead to various degrees of compromised Norrin/ß-catenin signaling activity. Conclusions: Our study expanded the variant spectrum and provided information for the genetic testing of FEVR by showing five novel FEVR-associated pathogenic variants in TSPAN12. Translational Relevance: Our study expanded the spectrum of FEVR-associated TSPAN12 variants and further supported the inclusion of TSPAN12 gene in the evaluation of cases concerning for FEVR.