Autosomal Dominant Familial Exudative Vitreoretinopathy Research Articles

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

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. 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. 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. 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.

Variants in RCBTB1 are Associated with Autosomal Recessive Retinitis Pigmentosa but Not Autosomal Dominant FEVR

ABSTRACT Purpose Variants in RCBTB1 have been reported in autosomal recessive inherited retinal dystrophies and autosomal dominant familial exudative vitreoretinopathy (FEVR). This study aims to verify the correlation between RCBTB1 variations and phenotypes. Methods Variants in RCBTB1 were selected from 6303 unrelated families with different forms of eye conditions based on whole exome sequencing and targeted exome sequencing. Potential pathogenic truncation variants were filtered by multistep bioinformatics analysis and identified by Sanger sequencing. Segregation and enrichment analysis were used to evaluate the association of truncation variants in RCBTB1 with phenotypes. Results Biallelic damaging variants in RCBTB1 were found in one family while heterozygous truncation variants were detected in 28 unrelated families based on our in-house data from 6303 unrelated families. Totally, 11 variants were present in the 29 families, including seven frameshift variants, three splicing variants, and one nonsense variant. The biallelic variants, c.170delG and c.905_906insTT, were identified in an isolated case with retinitis pigmentosa (RP). Heterozygous truncation variants were distributed in different forms of eye conditions (including normal) without significant enrichment in FEVR, suggesting unrelatedness to specific eye diseases. The frequency and location of truncation variants in the 6303 samples are comparable with the East Asian data from gnomAD. Segregation analysis of available family members further demonstrated the nonpathogenic nature of heterozygous truncation variants. Conclusions Contrary to the previous report, heterozygous truncation variants in RCBTB1 are not associated with FEVR based on our data. The extreme rareness of biallelic truncation variants present in a singleton case with RP further suggests that variants in RCBTB1 are responsible for autosomal recessive RP. This result reminds us that variants of a gene with certain diseases should be thoroughly verified before the use of such information in clinical practice.

Modeling ZNF408-Associated FEVR in Zebrafish Results in Abnormal Retinal Vasculature.

PurposeFamilial exudative vitreoretinopathy (FEVR) is an inherited retinal disease in which the retinal vasculature is affected. Patients with FEVR typically lack or have abnormal vasculature in the peripheral retina, the outcome of which can range from mild visual impairment to complete blindness. A missense mutation (p.His455Tyr) in ZNF408 was identified in an autosomal dominant FEVR family. Little, however, is known about the molecular role of ZNF408 and how its defect leads to the clinical features of FEVR.MethodsUsing CRISPR/Cas9 technology, two homozygous mutant zebrafish models with truncated znf408 were generated, as well as one heterozygous and one homozygous missense znf408 model in which the human p.His455Tyr mutation is mimicked.ResultsIntriguingly, all three znf408-mutant zebrafish strains demonstrated progressive retinal vascular pathology, initially characterized by a deficient hyaloid vessel development at 5 days postfertilization (dpf) leading to vascular insufficiency in the retina. The generation of stable mutant lines allowed long-term follow up studies, which showed ectopic retinal vascular hyper-sprouting at 90 dpf and extensive vascular leakage at 180 dpf.ConclusionsTogether, our data demonstrate an important role for znf408 in the development and maintenance of the vascular system within the retina.

An FEVR-associated mutation in ZNF408 alters the expression of genes involved in the development of vasculature.

Familial exudative vitreoretinopathy (FEVR) is an inherited retinal disorder hallmarked by an abnormal development of retinal vasculature. A missense mutation in ZNF408 (p.H455Y) was reported to underlie autosomal dominant FEVR in a large Dutch family, and ZNF408 was shown to play a role in the development of vasculature. Nonetheless, little is known about the molecular mechanism of ZNF408-associated FEVR. To investigate this, an in vitro model of ZNF408-associated FEVR was generated by overexpressing wild-type and p.H455Y ZNF408 in human umbilical vein endothelial cells. Cells overexpressing mutant ZNF408 were unable to form a capillary-like network in an in vitro tube formation assay, thereby mimicking the clinical feature observed in patients with FEVR. Intriguingly, transcriptome analysis revealed that genes involved in the development of vasculature were deregulated by the p.H455Y mutation. Chromatin immunoprecipitation showed that p.H455Y ZNF408 has reduced DNA-binding ability, as compared to the wild-type protein. The fact that the p.H455Y mutation disrupts the expression of genes important for the development of vasculature sheds further light on the molecular mechanisms underlying ZNF408-associated FEVR.

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

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

Genotype-Phenotype Characterization of Novel Variants in Six Italian Patients with Familial Exudative Vitreoretinopathy.

Familial exudative vitreoretinopathy (FEVR) is a complex disorder characterized by incomplete development of the retinal vasculature. Here, we report the results obtained on the spectrum of genetic variations and correlated phenotypes found in a cohort of Italian FEVR patients. Eight probands (age range 7–19 years) were assessed by genetic analysis and comprehensive age-appropriate ophthalmic examination. Genetic testing investigated the genes most widely associated in literature with FEVR: FZD4, LRP5, TSPAN12, and NDP. Clinical and genetic evaluations were extended to relatives of probands positive to genetic testing. Six out of eight probands (75%) showed a genetic variation probably related to the phenotype. We identified four novel genetic variants, one variant already described in association with Norrie disease and one previously described linked to autosomal dominant FEVR. Pedigree analysis of patients led to the classification of four autosomal dominant cases of FEVR (caused by FZD4 and TSPAN12 variants) and two X-linked FEVR probands (NDP variants). None of the patients showed variants in the LRP5 gene. This study represents the largest cohort study in Italian FEVR patients. Our findings are in agreement with the previous literature confirming that FEVR is a clinically and genetically heterogeneous retinal disorder, even when it manifests in the same family.

Simultaneous fzd4 and lrp5 mutation in autosomal dominant familial exudative vitreoretinopathy.

The purpose of this study was to report simultaneous mutations of FZD4 and LRP5 genes associated with autosomal dominant familial exudative vitreoretinopathy in members of one family. Case report. A 16-month-old white boy with a 6-month history of leukocoria was referred for possible retinoblastoma. On examination, the left eye displayed extensive white vitreoretinal fibrosis filling the entire vitreous cavity up to the lens and with additional dystrophic calcification and iris neovascularization. The right eye showed temporal peripheral fibrovascular ridge. Fluorescein angiography showed 360° of peripheral nonperfusion with leakage from the fibrovascular ridge of the right eye and diffuse leakage from the massive vitreoretinal fibrosis and iris neovascularization of the left eye, consistent with familial exudative vitreoretinopathy. Laser photocoagulation of the avascular areas of the right eye was performed with disease stabilization. Clinical examination and genetic testing of the family members demonstrated that the proband and a male sibling had similar clinical findings and simultaneous mutations in the FZD4 and LRP5 genes. Both affected patients had normal bone mineral dual-energy X-ray absorptiometry. Familial exudative vitreoretinopathy is a retinal vascular disorder usually caused by a single mutation. Rarely, multiple simultaneous mutations can occur and, in this case, result in classic ophthalmic phenotypic and known risk for bone disorders.

Mutations in TSPAN12 Cause Autosomal-Dominant Familial Exudative Vitreoretinopathy

Familial exudative vitreoretinopathy (FEVR) is an inherited blinding disorder of the retinal vascular system. Although mutations in three genes (LRP5, FZD4, and NDP) are known to cause FEVR, these account for only a fraction of FEVR cases. The proteins encoded by these FEVR genes form part of a signaling complex that activates the Norrin-beta-catenin signaling pathway. Recently, through a large-scale reverse genetic screen in mice, Junge and colleagues identified an additional member of this signaling complex, Tspan12. Here, we report that mutations in TSPAN12 also cause autosomal-dominant FEVR. We describe seven mutations identified in a cohort of 70 FEVR patients in whom we had already excluded the known FEVR genes. This study provides further evidence for the importance of the Norrin-beta-catenin signaling pathway in the development of the retinal vasculature and also indicates that more FEVR genes remain to be identified.

Clinical Presentation and Genetic Correlation of Patients With Mutations Affecting the FZD4 Gene

To correlate the ophthalmic findings of patients with pediatric vitreoretinopathies with mutations occurring in the FZD4 gene. A total of 123 patients diagnosed with autosomal-dominant familial exudative vitreoretinopathy (AdFEVR) or retinopathy of prematurity (ROP) and 42 control patients were enrolled in the study. Diagnoses were based on retinal findings at each patient's first examination or during ROP screening. Genomic DNA was isolated and polymerase chain reaction and direct sequencing of the FZD4 gene performed. FZD4 gene mutations were discovered in 13 of the 123 (10.6%) patients. Nine of the 63 patients with AdFEVR (14.3%) has mutations in the FZD4 gene. Four heterozygous mutations were identified: C117R, C181Y, Q505X, and P33S/P168S. Four of the 60 patients with ROP (6.7%) have a double missense mutation P33S/P168S that was also found in the patients with FEVR. No other FZD4 mutations were found in the patients with ROP. Additionally, patients expressing the double mutation had clinical presentations that overlapped, making it difficult to assign a definitive diagnosis. None of the mutations found in the patients with FEVR or ROP were seen in the control chromosomes. Mutations occurring in the FZD4 gene affect patients diagnosed with both FEVR and ROP. The clinical picture often overlaps and may require a detailed birth and family history for diagnosis. Genetic testing confirms inherited vitreoretinopathy and helps direct clinical management. Clinical Relevance Patients diagnosed with ROP may have a mutation in the FZD4 gene and display characteristics consistent with FEVR. Analysis of the FZD4 gene should be considered.

Macular neovascularization in familial exudative vitreoretinopathy.

To describe an unusual patient with autosomal dominant familial exudative vitreoretinopathy (FEVR) who also presented with preretinal fibrosis overlying the macula, extensive macular telangiectasis, and multiple foci of macular neovascularization. A clinical case is presented including fundus images and fluorescein angiography studies of the patient's left eye containing the unusual manifestations. To our knowledge, this is the first report of the formation of multifocal, preretinal macular neovascularization in FEVR. The sites of neovascularization corresponded to the attachment points of the vitreous stalk overlying the macula. Two small areas of intraretinal neovascularization were also noted. The concordance of the vitreoretinal adhesions with the sites of neovascularization suggests that the focal scaffolding may have played a direct mechanical role in encouraging the growth of the macular neovascular tissue in this patient.

Autosomal Recessive Familial Exudative Vitreoretinopathy Is Associated with Mutations in LRP5

Familial exudative vitreoretinopathy (FEVR) is a hereditary eye disorder that affects both the retina and vitreous body. Autosomal recessive FEVR was diagnosed in multiple individuals from three consanguineous families of European descent. A candidate-locus-directed genome scan shows linkage to the region on chromosome 11q flanked by markers D11S905 and D11S1314. The maximum LOD score of 3.6 at theta =0 is obtained with marker D11S987. Haplotype analysis confirms that the critical region is the 22-cM (311-Mb) interval flanked by markers D11S905 and D11S1314. This region contains LRP5 but not FZD4; mutations in both of these genes cause autosomal dominant FEVR. Sequencing of LRP5 shows, in all three families, homozygous mutations R570Q, R752G, and E1367K. This suggests that mutations in this gene can cause autosomal recessive as well as autosomal dominant FEVR.

Mutations in LRP5 or FZD4 Underlie the Common Familial Exudative Vitreoretinopathy Locus on Chromosome 11q

Familial exudative vitreoretinopathy (FEVR) is an inherited blinding disorder of the retinal vascular system. Autosomal dominant FEVR is genetically heterogeneous, but its principal locus, EVR1, is on chromosome 11q13-q23. The gene encoding the Wnt receptor frizzled-4 (FZD4) was recently reported to be the EVR1 gene, but our mutation screen revealed fewer patients harboring mutations than expected. Here, we describe mutations in a second gene at the EVR1 locus, low-density-lipoprotein receptor-related protein 5 (LRP5), a Wnt coreceptor. This finding further underlines the significance of Wnt signaling in the vascularization of the eye and highlights the potential dangers of using multiple families to refine genetic intervals in gene-identification studies.

Autosomal dominant familial exudative vitreoretinopathy in two Japanese families with FZD4mutations (H69Y and C181R)

Background:Familial exudative vitreoretinopathy (FEVR) is a hereditary disorder characterized by impaired vascularization of parts of the peripheral retina. Autosomal dominant FEVR (adFEVR), a major form of FEVR and assigned to chromosome 11q13–23 (EVR1) locus, is caused by deletion mutations in the C-terminal region of the frizzled-4 (FZD4) gene. This paper describes the clinical phenotype of adFEVR in two Japanese families with two different mutations in the FZD4gene. Methods:We encountered three Japanese patients with adFEVR and studied them using mutation analysis of the FZD4gene with PCR, sequencing, and a restriction enzyme digestion. Results:Two previously unreported missense mutations, p.H69Y and p.C181R, were identified in the N-terminal extracellular region of two of the patients. This region was highly conserved among other vertebrate species and FZD family members, unlike the C-terminal region. Co-segregation analysis revealed that all affected individuals carried one of these mutations, while unaffected individuals did not. The mutations were not detected in normal individuals (n = 120). The affected individuals had mild to severe retinal abnormalities. Conclusions: FZD4mutations in either the N- or C-terminal region underlie adFEVR, which indicates that FZD4plays an important role in retinal angiogenesis. Analysis of FZD4mutations in families with adFEVR is useful for genetic counseling and for early diagnosis.

Cosegregation of two unlinked mutant alleles in some cases of autosomal dominant familial exudative vitreoretinopathy.

Familial exudative vitreoretinopathy (FEVR) is a bilateral, clinically and genetically heterogeneous hereditary eye disorder that affects both the retina and the vitreous body. The condition has a high degree of penetrance and variable expressivity. In some cases of autosomal dominant FEVR (AD FEVR), mutations in the frizzled-4 gene (FZD-4) have been shown to be involved in FEVR pathology. In this study, we report that a second unlinked gene (Factor V) is also mutated (Leiden mutation) in the same family, which harbors the FZD-4 gene mutation. These results show for the first time that some families with FEVR could be digenic. While this is unlikely to be a widespread problem, the occurrence of digenic disorders with apparently simple Mendelian inheritance patterns renders the current method of analysis of monogenic disorders by linkage and mutation screening incomplete.

Evectins: vesicular proteins that carry a pleckstrin homology domain and localize to post-Golgi membranes.

We have identified two vesicular proteins, designated evectin (evt)-1 and -2. These proteins are approximately 25 kDa in molecular mass, lack a cleaved N-terminal signal sequence, and appear to be inserted into membranes through a C-terminal hydrophobic anchor. They also carry a pleckstrin homology domain at their N termini, which potentially couples them to signal transduction pathways that result in the production of lipid second messengers. evt-1 is specific to the nervous system, where it is expressed in photoreceptors and myelinating glia, polarized cell types in which plasma membrane biosynthesis is prodigious and regulated; in contrast, evt-2 is widely expressed in both neural and nonneural tissues. In photoreceptors, evt-1 localizes to rhodopsin-bearing membranes of the post-Golgi, an important transport compartment for which specific molecular markers have heretofore been lacking. The structure and subcellular distribution of evt-1 strongly implicate this protein as a mediator of post-Golgi trafficking in cells that produce large membrane-rich organelles. Its restricted cellular distribution and genetic locus make it a candidate gene for the inherited human retinopathy autosomal dominant familial exudative vitreoretinopathy and suggest that it also may be a susceptibility gene for multiple sclerosis.

Familial exudative vitreoretinopathy linked to D11S533 in a large Asian family with consanguinity.

Familial exudative vitreoretinopathy (FEVR) is a disorder characterised by peripheral retinal vascularisation with subsequent traction of retinal vessels and detachment. Recently, autosomal dominant FEVR (ad FEVR) has been mapped to 11q13 by linkage in four northern European families. We describe a large consanguineous Asian family in which the severity of the proband's eye disease suggested homozygosity for a disease allele. Thirty family members were assessed by ophthalmological examination and fluorescein angiography. Thirteen had unequivocal features of FEVR. A further two were classified as unknown. Two point linkage analysis for DIIS533 and FEVR generated a lod score of 5.55 at a recombination fraction of 0.00. This supports autosomal dominant inheritance and demonstrates genetic homogeneity for the ad FEVR disease locus. The severely affected proband was heterozygous for alleles at this closely linked locus. Other causes, including non-genetic factors, should be considered to explain the extreme variability characteristic of ad FEVR.