Autosomal recessive familial exudative vitreoretinopathy: evidence for genetic heterogeneity

Vascular features around the optic disc in familial exudative vitreoretinopathy: findings and their relationship to disease severity

BACKGROUND

Familial exudative vitreoretinopathy (FEVR) is a rare congenital disorder of retinal vascular development. We aimed to study the vascular characteristics around the optic disc in neonates with FEVR and the relationship with disease severity.

METHODS

A retrospective, case-control study including 43 (58 eyes) newborn patients with FEVR at stages 1 to 3 and 30 (53 eyes) age-matched normal full-term newborns was conducted. The peripapillary vessel tortuosity (VT), vessel width (VW) and vessel density (VD) were quantified by computer technology. The t-distributed stochastic neighbor embedding (t-SNE) algorithm was used to visualize the relationship between the severity of FEVR and the characteristics of perioptic disc vascular parameters.

RESULTS

The peripapillary VT, VW and VD were significantly increased in the FEVR group compared with the control group (P < 0.05). Subgroup analysis showed that VW and VD increased significantly with progressing FEVR stage (P < 0.05). And only VT in stage 3 FEVR was significantly increased compared with stage 1 and stage 2 (P < 0.05). After controlling the confounders, ordinal logistic regression analysis indicated that the VW (aOR: 1.75, P = 0.0002) and VD (aOR: 2.41, P = 0.0170) were significantly independent correlated with the FEVR stage, but VT (aOR: 1.07, P = 0.5454) was not correlated with FEVR staging. Visual analysis based on the t-SNE algorithm showed that peri-optic disc vascular parameters had a continuity along the direction of FEVR severity.

CONCLUSIONS

In the neonatal population, there were significant differences in peripapillary vascular parameters between patients with FEVR and normal subjects. Quantitative measurement of vascular parameters around the optic disc can be used as one of the indicators to assess the severity of FEVR.

Familial exudative vitreoretinopathy in a 4 generations family of South-East Asian Descendent with FZD4 mutation (c.1501_1502del)

BACKGROUND

Familial Exudative Vitreoretinopathy (FEVR) is a hereditary disorder characterized by peripheral avascular retina with neovascularization. Although FEVR has been thoroughly described in multiple literature publications from different countries, there are currently limited articles describing the phenotypes of FEVR among South-East Asian Descendent. This paper describes the clinical phenotype of the FZD4 gene with c.1501_1502 deletion in a 4-generation case series of a South East Asian family.

METHODS

We reviewed a 4-generation case series of a South-East Asian descendent family consisting of 27 family members with 10 members diagnosed with FEVR. We observed the clinical phenotype of these series of patients, including some of the family members who underwent whole-exome sequencing, PCR amplification and DNA sequencing techniques to identify the mutated gene.

RESULTS

Frameshift mutation (c.1501_1502del) were found in FZD4 gene in this series of patients with the age ranging from 1 month old to 69 years old. There was a 100% (4/4) of our paediatric patients being diagnosed within 21 days of life. It was also found that 75% of patients (6/8) less than 40 years old exhibited disease asymmetry of 2 stages or more and 80% (8/10) had a history of vitreoretinal surgery or diode laser photocoagulation, with a further 50% of the adult patients identified as legally blind; the mean age of blindness was 18-years-old.

CONCLUSIONS

Phenotypic manifestation of FZD4 gene with c.1501_1502del mutation can be identified within the neonatal period. They have relatively greater clinical asymmetry of 2 stages or more compared to other mutations. Without treatment, most of them will have bilateral severe visual impairment around the adolescent age group.

Identification of Two Novel Variants in the LRP5 Gene that Cause Familial Exudative Vitreoretinopathy

Background: Familial exudative vitreoretinopathy (FEVR, OMIM 133780) is a severe inherited eye disease characterized by abnormal development of the retinal vasculature. Variants in the reported genes account for ∼50% of total FEVR cases. However, the pathogenesis of other 50% of FEVR cases remains unclear. Therefore, it is crucial to identify novel variants responsible for the pathogenesis of FEVR. Aims: To find causative variants responsible for FEVR in two Han Chinses families. Materials and Methods: We recruited two families with two FEVR patients and applied exome sequencing on the genomic DNA samples from the probands. Sanger sequencing was performed for variant validation. Western blot analysis and luciferase assays were performed to test the expression levels and activity of mutant proteins. Results: We identified two novel missense variants in the LRP5 gene (NM_002335), namely c.1176 C > A (p.Asp392Glu) and c.2435 A>C (p.Asp812Ala), inherited in an autosomal dominant manner. Both variants significantly reduced Norrin/β-catenin signaling activity without affecting the expression of the LRP5 protein. Conclusion: This study expands the variant spectrum of the LRP5 gene for FEVR, providing valuable information for prenatal counseling and molecular diagnosis of FEVR.

Whole-Exome Sequencing Identified DLG1 as a Candidate Gene for Familial Exudative Vitreoretinopathy

Purpose: Familial exudative vitreoretinopathy (FEVR) is a blinding retinal vascular disease. Clinically, FEVR is characterized by incomplete vascularization of the peripheral retina and pathological neovascularization. Only about 50% of FEVR cases can be explained by known FEVR disease gene variations. This study aimed to identify novel genes associated with the FEVR phenotype and explore their pathogenic mechanisms. Materials and Methods: Exome sequencing analyses were conducted on one Chinese family with FEVR whose affected members did not exhibit pathogenic variants in the known FEVR genes (verified using Sanger sequencing analysis). Functions of the affected proteins were evaluated using reporter assays. Western blot analysis was used to detect mutant protein expression and the genes' pathogenic mechanisms. Results: A rare novel heterozygous variant in DLG1 (c.1792A>G; p.S598G) was identified. The amino acid residues surrounding the identified variant are highly conserved among vertebrates. A luciferase reporter assay revealed that the mutant DLG1 protein DLG1-S598G lost its ability to activate Wnt signaling. Moreover, a knockdown (KD) of DLG1 in human primary retinal endothelial cells impaired tube formation. Mechanistically, DLG1 KD led to a reduction in phosphorylated VEGFR2, an essential receptor for the angiogenic potency that signals the vascular endothelial growth factor molecule. Conclusions: The data reported here demonstrate that DLG1 is a novel candidate gene for FEVR.

Analysis of Predisposing Clinical Features for Worsening Traction After Treatment of Familial Exudative Vitreoretinopathy in Children

PURPOSE

To determine the incidence of worsening vitreoretinal traction after laser treatment for familial exudative vitreoretinopathy (FEVR) and to determine whether any baseline clinical features are associated with worsening.

DESIGN

Retrospective cohort comparison study in a university tertiary referral center.

METHODS

All patients 0-21 years of age treated with laser from January 1, 2001, to June 1, 2018, were studied. Worsening traction after treatment was defined as the occurrence within 6 months of worsening or development of tractional retinal detachment, folds, dragging, breaks, rhegmatogenous detachment, or worsening tractional membranes. Comparisons of baseline features between groups with and without worsening were performed to determine features associated with higher risk.

RESULTS

A total of 46 eyes from 28 patients met inclusion criteria. Of the 46 eyes, 6 (13%) had worsening after treatment. There were no significant differences in age or other baseline demographics between the cohorts with and those without worsening traction. The presence of proliferative tissue in contact with the lens was found in 2 of 6 patients with worsening compared to 1 of 40 (3%) without worsening (P = .04). Mean follow-up was 57.8 months (range, 6.6-134 months). At the 6-month follow-up, median logMAR visual acuity in the cohorts with and without worsening was 1.7 (Snellen 20/1002; n = 5) and 0.24 (Snellen 20/35; n = 16), respectively.

CONCLUSIONS

Laser treatment resulted in worsening traction in a substantial proportion of eyes with FEVR. Children with proliferative tissue in contact with the lens may be at higher risk of worsening after laser. Potential measures to reduce risk will require further study to establish efficacy.

Identification of novel variants in the FZD4 gene associated with familial exudative vitreoretinopathy in Chinese families

BACKGROUND

Familial exudative vitreoretinopathy (FEVR, OMIM 133780) is a severe hereditary retinal disease characterized by incomplete retinal vascular development and pathological neovascularization. It has been reported that variants in nine genes are associated with FEVR, but they can only explain approximately 50% of FEVR patients, suggesting that other FEVR-associated variants or genes remain to be discovered.

METHODS

Whole-exome sequencing (WES) was carried out to analyse genomic DNA samples from the probands of 68 families with FEVR. Sanger sequencing was used to verify all identified variants. Western blot analysis was utilized to detect the expression of the variant mutant proteins. A luciferase assay was conducted to test the receptor activity of the mutant FZD4 proteins in Norrin-β-catenin signaling.

RESULTS

Seven heterozygous FZD4 variants were found to cause FEVR in seven families, including six missense variants and one deletion variant: c.182C>T (p.T61I), c.205C>T (p.H69Y), c.217_234del (p.73T_78Qdel), c.264C>A (p.Y88X), c.344G>T (p.G115V), c.678G>A (p.W226X) and c.1310T>C (p.I437T). Among these variants, c.205C>T (p.H69Y) and c.678G>A (p.W226X) are known FEVR-causing variants, while the other five variants are novel pathogenic variants.

CONCLUSION

Our study revealed the cause of FEVR in seven Chinese families and identified five novel pathogenic variants in FZD4, which expanded the mutation spectrum of FEVR in the Chinese population. These findings also provided further support for using WES in the clinical diagnosis of FEVR.

Whole-Exome Sequencing Analysis Identified Novel Mutations in the TSPAN12 Gene in Chinese Families with Familial Exudative Vitreoretinopathy

Background: Familial exudative vitreoretinopathy (FEVR, OMIM 133780), characterized by incomplete retinal vascular development and pathological neovascularization, is a severe inherited retinal disorder. Mutations in 10 genes have been reported to be associated with FEVR, but this still leaves ∼50% of FEVR cases to be genetically explained. Purpose: The purpose of this study was to identify novel FEVR-causing mutations and explore the causative mutations in Chinese FEVR families. Methods: Whole-exome sequencing was performed to analyze the genomic DNA of the probands from 121 Chinese FEVR families. Sanger sequencing was carried out to verify all identified mutations. Luciferase assays were used to test the activity of a mutant protein in the Norrin-β-catenin signaling pathway. Results: Four novel heterozygous TSPAN12 (Tetraspanin 12) mutations, including two single-base substitution mutations and two small-deletion mutations, were identified in these FEVR families: c.1A>G (p.0), c.614G>A (p.G205D), c.695delT (p.V232Gfs*7), and c.833_842del (p.L278Qfs*25). Conclusion: This study revealed the causative mutations in four Chinese FEVR families and identified four novel FEVR-causing mutations, thus expanding the mutation spectrum of FEVR in the Chinese population.

Correlating Changes in the Macular Microvasculature and Capillary Network to Peripheral Vascular Pathologic Features in Familial Exudative Vitreoretinopathy

PURPOSE

To evaluate the macular microvasculature in patients with familial exudative vitreoretinopathy (FEVR) using OCT angiography (OCTA) and to assess for peripheral vascular changes using widefield fluorescein angiography (WFA).

DESIGN

Multicenter, retrospective, comparative, observational case series.

PARTICIPANTS

We identified 411 patients with FEVR, examined between September 2014 and June 2018. Fifty-seven patients with FEVR and 60 healthy controls had OCTA images of sufficient quality for analysis.

METHODS

Custom software was used to assess for layer-specific, quantitative changes in vascular density and morphologic features on OCTA by way of vessel density (VD), skeletal density (SD), fractal dimension (FD), vessel diameter index (VDI), and foveal avascular zone (FAZ). Widefield fluorescein angiography images were reviewed for peripheral vascular changes including capillary dropout, late-phase angiographic posterior and peripheral vascular leakage (LAPPEL), vascular dragging, venous-venous shunts, and arteriovenous shunts.

MAIN OUTCOME MEASURES

Macular microvascular parameters on OCTA and peripheral angiographic findings on WFA.

RESULTS

OCT angiography analysis of 117 patients (187 eyes; 92 FEVR patients and 95 control participants) demonstrated significantly reduced VD, SD, and FD and greater VDI in patients with FEVR compared with controls in the nonsegmented retina, superficial retinal layer (SRL), and deep retinal layer (DRL). The FAZ was larger compared with that in control eyes in the DRL (P < 0.0001), but not the SRL (P = 0.52). Subanalysis by FEVR stage showed the same microvascular changes compared with controls for all parameters. Widefield fluorescein angiography analysis of 95 eyes (53 patients) with FEVR demonstrated capillary nonperfusion in all eyes: 47 eyes (49.5%) showed LAPPEL, 32 eyes (33.7%) showed vascular dragging, 30 eyes (31.6%) had venous-venous shunts, and 33 eyes (34.7%) had arteriovenous shunts. Decreasing macular VD on OCTA correlated with increasing peripheral capillary nonperfusion on WFA. Decreasing fractal dimension on OCTA correlated with increasing LAPPEL severity on WFA.

CONCLUSIONS

Patients with FEVR demonstrated abnormalities in the macular microvasculature and capillary network, in addition to the peripheral retina. The macular microvascular parameters on OCTA may serve as biomarkers of changes in the retinal periphery on WFA.

Wnt Signaling in vascular eye diseases

The Wnt signaling pathway plays a pivotal role in vascular morphogenesis in various organs including the eye. Wnt ligands and receptors are key regulators of ocular angiogenesis both during the eye development and in vascular eye diseases. Wnt signaling participates in regulating multiple vascular beds in the eye including regression of the hyaloid vessels, and development of structured layers of vasculature in the retina. Loss-of-function mutations in Wnt signaling components cause rare genetic eye diseases in humans such as Norrie disease, and familial exudative vitreoretinopathy (FEVR) with defective ocular vasculature. On the other hand, experimental studies in more prevalent vascular eye diseases, such as wet age-related macular degeneration (AMD), diabetic retinopathy (DR), retinopathy of prematurity (ROP), and corneal neovascularization, suggest that aberrantly increased Wnt signaling is one of the causations for pathological ocular neovascularization, indicating the potential of modulating Wnt signaling to ameliorate pathological angiogenesis in eye diseases. This review recapitulates the key roles of the Wnt signaling pathway during ocular vascular development and in vascular eye diseases, and pharmaceutical approaches targeting the Wnt signaling as potential treatment options.

Prenatal diagnosis of familial exudative vitreoretinopathy and Norrie disease

Background

Both familial exudative vitreoretinopathy (FEVR) and Norrie disease (ND) are hereditary retinal disorders which can cause severe visual impairment and blindness at a young age. The present study aimed to report the use of antenatal genetic testing and ultrasound in the diagnosis and counseling of FEVR and ND.

Methods

Amniocentesis and ultrasonography were performed in high‐risk mothers, with children having FEVR or ND, to predict severe ocular abnormalities.

Results

Case 1: A homozygous NDP mutation (c.376T>C, NM_000266) was detected in the proband and his mother. Molecular prenatal analysis of the fetal DNA revealed no mutations. No ocular abnormalities were detected on ultrasonography. The pregnancy progressed uneventfully to a normal outcome. Case 2: A novel heterozygous FZD4 mutation (c.1010dupA, NM_012193) was detected in the proband and his mother. The same mutation was detected in the fetus, but ultrasonography showed no ocular abnormalities. A healthy baby boy with stage 1 FEVR was born after an uneventful pregnancy. Case 3: Deletions of exons 2 and 3 in the NDP were found in the proband and his mother. The same deletion mutation was detected in the female fetus, but the ultrasound scan was normal. The pregnancy progressed uneventfully to a normal outcome.

Conclusions

To our knowledge, antenatal genetic analyses were used in conjunction with ultrasound for the first time, to diagnose FEVR and ND, and predict the postnatal prognoses in at‐risk babies.

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.

Familial Exudative Vitreoretinopathy With a Novel LRP5 Mutation

This report reviews the genetics of familial exudative vitreoretinopathy (FEVR) and describes the identification of a novel variant in the LRP5 gene. A 20-month-old boy presented with reduced visual acuity in the right eye from exudative retinal detachment with mild retinal traction. Fluorescein angiography in the right eye disclosed extensive peripheral retinal non-perfusion and telangiectatic vessels and the left eye showed minimal peripheral non-perfusion. These features were suggestive of FEVR. Treatment with laser photocoagulation and cryotherapy to the region of non-perfusion was performed with resolution of the exudative retinal detachment. Fundus examination of the father revealed mild signs of FEVR, such as hyperacute retinal vascular branching and slight retinal vascular traction, whereas the mother's fundus examination was unremarkable. Genetic testing revealed that the affected boy was negative for mutations in the FZD4, NDP, and TSPAN12 genes and heterozygous for a previously unreported A745V variant in the LRP5 gene. The father was also heterozygous for the A745V variant in the LRP5 gene and the unaffected mother showed no mutation. A genetic evaluation of the known genes associated with FEVR revealed a novel variant in the LRP5 gene that co-segregated with the phenotype in the family. [J Pediatr Ophthalmol Strabismus. 2016;53:e39-e42.].

Whole Exome Sequencing Analysis Identifies Mutations in LRP5 in Indian Families with Familial Exudative Vitreoretinopathy

BACKGROUND

Familial exudative vitreoretinopathy (FEVR, OMIM 133780) is a severe inherited retinal disorder characterized by incomplete retinal vascular development and neovascularization. At least five genes have been reported to be associated with FEVR, including NDP, LRP5, FZD4, TSPAN12, and ZNF408. Recently reported data showed that mutations in the KIF11 gene can also lead to FEVR conditions. Previous studies suggested that known mutations only explain approximately 40-60% of FEVR cases in different populations.

PURPOSE

To investigate the causative genetic mutations in four Indian families with FEVR.

METHODS

Whole exome sequencing was carried out to analyze the genomic DNA samples from the four FEVR proband patients and Sanger sequencing was utilized to verify all identified polymorphisms. A luciferase assay was used to test the mutant protein activity.

RESULTS

We identified four novel LRP5 missense mutations in these FEVR families: c.C1042T (p.R348W), c.G1141A (p.D381N), c.C1870T (p.R624W), and c.A4550G (p.Y1517C). The luciferase assay demonstrated that all four of these LRP5 mutations led to significant reduction of enzymatic activity with response to NORRIN, suggesting that they are pathogenic.

CONCLUSION

Our findings expand the mutational spectrum of FEVR in the Indian population and provide some guidelines in clinical diagnosis.

KIF11 mutations are a common cause of autosomal dominant familial exudative vitreoretinopathy

BACKGROUND/AIMS

To identify KIF11 mutations in patients with familial exudative vitreoretinopathy (FEVR) and to describe the associated phenotypes.

METHODS

Mutation analysis in a cohort of patients in a single institute was conducted. Bioinformatics was performed for whole exome sequencing, and the variants were confirmed by Sanger sequencing. Clinical data and DNA samples were collected from 814 unrelated Chinese probands, including 34 with FEVR, at the Pediatric and Genetic Eye Clinic, Zhongshan Ophthalmic Centre, Guangzhou, China.

RESULTS

Four novel heterozygous truncation mutations in KIF11, including c.131_132dupAT (p.P45Ifs*92), c.2230C>T (p.Q744*), c.2863C>T (p.Q955*) and c.2952_2955delGCAG (p.G985Ifs*6), were detected in four of 34 probands with FEVR. Combined with our previously identified mutations in FEVR cases (n=14), KIF11 mutations were identified in 8.3% (4/48) of all probands with FEVR. Ocular phenotypes documented in patients with KIF11 mutations showed a significant great variability of FEVR from the avascular zone in the peripheral retina to bilateral complete retinal detachment. Analysis of available family members in family QT1314 and QT937 showed segregation of KIF11 mutations with the phenotype of FEVR as expected. The family QT964 with two affected siblings and unaffected parents demonstrated a peculiar somatic mosaicism in the mother who had a low copy number variant (about 7% in her leucocyte DNA).

CONCLUSIONS

Identification of mutations in 8.3% patients suggests KIF11 mutations as a common cause of FEVR. Patients with KIF11 mutations showed typical, but variable, signs of FEVR with or without microcephaly, lymphoedema and mental retardation.

Vitreomacular interface in patients with familial exudative vitreoretinopathy

Familial exudative vitreoretinopathy (FEVR) is a rare hereditary vitreoretinal disease that occurs in young patients and results in an avascular peripheral retina, retinal neovascularization, and tractinal retinal detachment. Patients occasionally have concurrent macular diseases. However, the vitreomacular relationship in FEVR remains unclear. We report two cases, a 22-year-old woman (case 1) and a 14-year-old boy (case 2) with FEVR who have the characteristic findings of the disease in the vitreomacular interface and the macular morphology, observed using spectral-domain optical coherence tomography (SD-OCT). In case 1, the best-corrected visual acuity (BCVA) was 20/20 bilaterally. SD-OCT showed a perifoveal posterior vitreous detachment (PVD) with vitreofoveal adhesion in the left eye. In case 2, SD-OCT showed a perifoveal PVD in the right eye (BCVA, 20/30) with numerous small deposits that appeared as rod-shaped attachments perpendicular to the parafoveal face without intraretinal and subretinal materials beneath the posterior hyaloid face that corresponded to white material on the fundus examination. Fluorescein angiography showed a circumferential peripheral avascular area and peripheral neovascularization in both cases. These SD-OCT findings suggested that a perifoveal PVD and small deposits, which appeared as rod-shaped attachments perpendicular to the parafoveal face in patients with FEVR, may carry the risk of macular disease and decreased visual acuity.

Familial retinal detachment associated with COL2A1 exon 2 and FZD4 mutations

BACKGROUND

  To characterize the clinical and genetic abnormalities within two Australian pedigrees with high incidences of retinal detachment and visual disability.

DESIGN

  Prospective review of two extended Australian pedigrees with high rates of retinal detachment.

PARTICIPANTS

  Twenty-two family members from two extended Australian pedigrees with high rates of retinal detachment were examined.

METHODS

  A full ophthalmic history and examination were performed, and DNA was analysed by linkage analysis and mutation screening.

MAIN OUTCOME MEASURES

  Characterization of a causative hereditary gene mutation in each family.

RESULTS

  All affected family members of one pedigree carried a C192A COL2A1 exon 2 mutation. None of the affected family members had early-onset arthritis, hearing abnormalities, abnormal clefting or facial features characteristic of classical Stickler syndrome. All affected members of the familial exudative vitreoretinopathy pedigree carried a 957delG FZD4 mutation.

CONCLUSIONS

  Patients with retinal detachment and a positive family history should be investigated for heritable conditions associated with retinal detachment such as Stickler syndrome and familial exudative vitreoretinopathy. The absence of non-ocular features of Stickler syndrome should raise the possibility of mutations in exon 2 of COL2A1. Similarly, late-onset familial exudative vitreoretinopathy may appear more like a rhegmatogenous detachment and not be correctly diagnosed. When a causative gene mutation is identified, cascade genetic screening of the family will facilitate genetic counselling and screening of high-risk relatives, allowing targeted management of the pre-detachment changes in affected patients.

Molecular and clinical studies of X-linked deafness among Pakistani families

There are 68 sex-linked syndromes that include hearing loss as one feature and five sex-linked nonsyndromic deafness loci listed in the OMIM database. The possibility of additional such sex-linked loci was explored by ascertaining three unrelated Pakistani families (PKDF536, PKDF1132, PKDF740) segregating X-linked recessive deafness. Sequence analysis of POU3F4 (DFN3) in affected members of families PKDF536 and PKDF1132 revealed two novel nonsense mutations, p.Q136X and p.W114X, respectively. Family PKDF740 is segregating congenital blindness, mild to profound progressive hearing loss that is characteristic of Norrie disease (MIM#310600). Sequence analysis of NDP among affected members of this family revealed a novel single nucleotide deletion c.49delG causing a frameshift and premature truncation (p.V17fsX1) of the encoded protein. These mutations were not found in 150 normal DNA samples. Identification of pathogenic alleles causing X-linked recessive deafness will improve molecular diagnosis, genetic counseling, and molecular epidemiology of hearing loss among Pakistanis.

LRP5 sequence and polymorphisms in the baboon

BACKGROUND

LRP5 is known to have an important relationship with bone density and a variety of other biological processes. Mapping to human chromosome 11q13.2, LRP5 shows considerable evolutionary conservation. Orthologs of this gene exist in many species, although comparison of human LRP5 with other non-human primates has not been performed until now.

METHODS

We reported the complementary DNA (cDNA) sequence and deduced amino acid sequence for baboon LRP5, and compared the baboon and human sequences. cDNA sequences for 21 baboons were examined to identify single-nucleotide polymorphisms (SNPs).

RESULTS

Sequences of coding regions in human and baboon LRP5 showed 97- 99% homology. Twenty-five SNPs were identified in the coding region of baboon LRP5.

CONCLUSION

The observed degree of coding sequence homology in LRP5 led us to expect that the baboon may serve as a useful model for future research into the role(s) of this gene in primate metabolic diseases.

Genetic Evaluation to Establish the Diagnosis of X-Linked Familial Exudative Vitreoretinopathy

PURPOSE

To determine the usefulness of genetic analysis for confirming the diagnosis of X-linked familial exudative vitreoretinopathy (FEVR) and verifying the mode of inheritance.

METHODS

Twenty-seven consecutive patients diagnosed with FEVR were enrolled for genetic analysis. All patients underwent dilated fundus examination. A complete birth, medical, and family history was obtained at the time of examination. Patients were categorized by gender and family history in an effort to identify X-linked FEVR. Participants provided a blood sample for analysis and were evaluated for a mutation in the Norrie's disease gene (NDP) by direct sequencing.

RESULTS

Of the 27 enrolled patients, four male patients had a pedigree consistent with X-linked inheritance and 12 male patients had little or no family history. Two of these 16 patients were found to have a missense mutation in the NDP gene.

CONCLUSIONS

We found genetic testing of NDP to be helpful in confirming the diagnosis of X-linked FEVR in male patients, especially when limited family history was available. As genetic diagnostics improve, we feel that confirming diagnoses and informing patients better through genetic evaluation and consultation will become more useful in the clinical practice of ophthalmology.

SNPs: impact on gene function and phenotype

Single nucleotide polymorphism (SNP) is the simplest form of DNA variation among individuals. These simple changes can be of transition or transversion type and they occur throughout the genome at a frequency of about one in 1,000 bp. They may be responsible for the diversity among individuals, genome evolution, the most common familial traits such as curly hair, interindividual differences in drug response, and complex and common diseases such as diabetes, obesity, hypertension, and psychiatric disorders. SNPs may change the encoded amino acids (nonsynonymous) or can be silent (synonymous) or simply occur in the noncoding regions. They may influence promoter activity (gene expression), messenger RNA (mRNA) conformation (stability), and subcellular localization of mRNAs and/or proteins and hence may produce disease. Therefore, identification of numerous variations in genes and analysis of their effects may lead to a better understanding of their impact on gene function and health of an individual. This improved knowledge may provide a starting point for the development of new, useful SNP markers for medical testing and a safer individualized medication to treat the most common devastating disorders. This will revolutionize the medical field in the future. To illustrate the effect of SNPs on gene function and phenotype, this minireview focuses on evidences revealing the impact of SNPs on the development and progression of three human eye disorders (Norrie disease, familial exudative vitreoretinopathy, and retinopathy of prematurity) that have overlapping clinical manifestations.

Treatment of vascularly active familial exudative vitreoretinopathy with pegaptanib sodium (Macugen)

PURPOSE

To report results of treatment of vascularly active familial exudative vitreoretinopathy (FEVR) with pegaptanib sodium (Macugen; Eyetech Pharmaceuticals, New York, NY) injection.

METHODS

In a retrospective case series, four patients with vascularly active FEVR, as demonstrated by increasing subretinal exudation despite photocoagulation, cryotherapy, and/or intravitreal steroid injection, received a single intravitreal injection of pegaptanib sodium. Preinjection and postinjection fundus photography, fluorescein angiography, and optical coherence tomography were performed to evaluate the changes in visual acuity, vascular activity, and amount of exudation.

RESULTS

The mean follow-up period was 11.2 months (range, 8.1-15.5 months) after the first intravitreal injection. All four patients had a decrease in exudation after treatment with pegaptanib sodium documented by a decrease in subretinal exudate by fundus photography and decreased leakage by fluorescein angiography. After reduction of exudation, two patients required vitrectomy to relieve vitreoretinal traction. Visual acuity improved in two patients, stabilized in one patient, and worsened in one patient secondary to tractional retinal detachment. No injection-associated systemic or ocular complications were observed in any of the treated patients.

CONCLUSIONS

Intravitreal injection of pegaptanib sodium is a potential treatment option for patients with FEVR and worsening exudation despite treatment with standard therapy. Vitreoretinal traction may develop with rapid resolution of subretinal exudates, requiring surgical intervention. However, visual acuity can improve after retinal traction is released. Further studies using anti-vascular endothelial growth factor agents are needed to better understand treatment of FEVR.

The Wnt signaling pathway in familial exudative vitreoretinopathy and Norrie disease

The Wnt signaling pathway is highly conserved among species and has an important role in many cell biological processes throughout the body. This signaling cascade is involved in regulating ocular growth and development, and recent findings indicate that this is particularly true in the retina. Mutations involving different aspects of the Wnt signaling pathway are being linked to several diseases of retinal development. The aim of this article is to first review the Wnt signaling pathway. We will then describe two conditions, familial exudative vitreoretinopathy (FEVR) and Norrie disease (ND), which have been shown to be caused in part by defects in the Wnt signaling cascade.

Familial exudative vitreoretinopathy and macular hole exhibited in same individual

This observational case report is designed to report the first known occurrence of Familial Exudative Vitreoretinopathy (FEVR) and macular hole in the same individual. Clinical exams and fluorescein angiography were used to evaluate patient. Indirect laser panretinal photocoagulation was used to treat the right eye. A nine-year old male was diagnosed with familial exudative vitreoretinopathy in both eyes, as well as a full-thickness macular hole in his right eye. Medical histories indicated that the macular hole was not caused by trauma. Indirect laser panretinal photocoagulation was performed to treat an exudative process caused by FEVR in the right eye, and the exudative retinal detachment regressed. A vitrectomy was later also performed to treat traction retinal detachment as well as macular hole in the right eye. Our conclusion is that macular hole can be associated with familial exudative vitreoretinopathy.

Reduced bone mineral density and hyaloid vasculature remnants in a consanguineous recessive FEVR family with a mutation in LRP5

BACKGROUND/AIMS

Familial exudative vitreoretinopathy (FEVR) is an inherited blinding condition characterised by abnormal development of the retinal vasculature. FEVR has multiple modes of inheritance, and homozygous mutations in LRP5 have recently been reported as underlying the recessive form of this disease. The aim of this study was to examine LRP5 in a consanguineous recessive FEVR family and to clarify the eye and bone phenotype associated with recessive FEVR.

METHODS

All family members were examined by slit lamp biomicroscopy and indirect ophthalmoscopy. Linkage to LRP5 was determined by genotyping microsatellite markers, constructing haplotypes and calculating lod scores. Mutation screening of LRP5 was performed by polymerase chain reaction amplification of genomic DNA followed by direct sequencing. Bone mineral density (BMD) was evaluated in all family members using dual energy x ray absorptiometry (DEXA).

RESULTS

The clinical features observed in this family were consistent with a diagnosis of recessive FEVR. A homozygous LRP5 missense mutation, G550R, was identified in all affected individuals and all unaffected family members screened were heterozygous carriers of this mutation. Reduced BMD, hyaloid vasculature remnants, and nystagmus were features of the phenotype.

CONCLUSION

Recessive mutations in LRP5 can cause FEVR with reduced BMD and hyaloid vasculature remnants. Assessment of a patient with a provisional diagnosis of FEVR should therefore include investigation of BMD, with reduced levels suggestive of an underlying LRP5 mutation.

Complexity of the genotype-phenotype correlation in familial exudative vitreoretinopathy with mutations in theLRP5and/orFZD4genes

Familial exudative vitreoretinopathy (FEVR) is a hereditary blinding disorder that features defects in retinal vascular development. The mutations in the genes encoding the Wnt receptor pair, frizzled 4 (FZD4) and low-density-lipoprotein receptor-related protein 5 (LRP5), have been shown to cause FEVR. In this study we screened 56 unrelated patients with FEVR (31 familial and 25 simplex cases) for possible mutations in LRP5 and FZD4. Six novel mutations in either LRP5 or FZD4 were identified in six familial cases. Four novel mutations in LRP5 and one known mutation in FZD4 were detected in three simplex cases, and two of these patients carried compound heterozygous mutations in LRP5. Remarkably, c.1330C>T [p.R444C] in LRP5 was found in the family in which c.1250G>A [p.R417Q] in FZD4 had previously been identified. The phenotype of these patients suggested a synergistic effect of the two mutations in the independent FEVR-causing genes. We also demonstrated that reduced bone density is a common feature in patients with FEVR who harbor LRP5 mutations. The profile of the mutations obtained in the current study further illustrates the complexity of the disease and provides a better understanding of the spectrum, frequencies, and genotype-phenotype correlation.

Further evidence of genetic heterogeneity in familial exudative vitreoretinopathy; exclusion of EVR1, EVR3, and EVR4 in a large autosomal dominant pedigree

BACKGROUND/AIMS

Familial exudative vitreoretinopathy (FEVR) is an inherited blinding condition characterised by abnormal development of the retinal vasculature. The aim of this study was to perform linkage analysis in a large family affected with FEVR to determine whether the mutation involved was in one of the three known autosomal dominant FEVR loci or in another as yet unidentified gene.

METHODS

Genomic DNA samples from family members were polymerase chain reaction (PCR) amplified with fluorescently tagged microsatellite markers spanning the EVR1/EVR4 locus (11q13-14) and the EVR3 locus (11p12-13). The resulting PCR products were resolved using an automated DNA sequencer and the alleles sized. These data were used to construct haplotypes across each locus and linkage analysis was performed to prove or exclude linkage.

RESULTS

The clinical evaluation in this family suggested features typical of FEVR, with deficient peripheral retinal vascularisation being the common phenotype in all affected individuals. However, linkage analysis proved that this family has a form of FEVR genetically distinct from the EVR1, EVR3 and EVR4 loci.

CONCLUSION

The exclusion of linkage in this family to any of the known FEVR loci proves the existence of a fourth locus for autosomal dominant FEVR and shows that this rare disorder is far more heterogeneous than previously thought.

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.

Frizzled 4 gene (FZD4) mutations in patients with familial exudative vitreoretinopathy with variable expressivity

AIMS

To search for mutations in the frizzled 4 (FZD4) gene in patients with familial exudative vitreoretinopathy (FEVR) and to delineate the defective gene associated clinical features.

METHODS

Direct sequencing following polymerase chain reaction of exons of FZD4 was performed for 24 probands with FEVR (18 familial and six sporadic), and some of their families. Clinical symptoms among individuals with mutations were assessed.

RESULTS

Four novel mutations were identified in four patients with familial and one with sporadic FEVR. Three of these mutations were missense (M105V, R417Q, and G488D) and one was a nonsense change (W319X). M105V, R417Q, and G488D co-segregated with the disease. None of these sequence changes was found among 300 chromosomes from 150 healthy volunteers. The severity of vitreoretinopathy in the individuals involved in this study varied, but no patient with mutations in FZD4 exhibited rhegmatogenous retinal detachment although this pathology is thought to be the most common type of retinal detachment in FEVR.

CONCLUSION

FZD4 gene mutations were found in some cases of autosomal dominant and sporadic FEVR. FZD4 mutations were responsible for FEVR with variable clinical manifestations.

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.

Mutant frizzled-4 disrupts retinal angiogenesis in familial exudative vitreoretinopathy

Familial exudative vitreoretinopathy (FEVR) is a hereditary ocular disorder characterized by a failure of peripheral retinal vascularization. Loci associated with FEVR map to 11q13-q23 (EVR1; OMIM 133780, ref. 1), Xp11.4 (EVR2; OMIM 305390, ref. 2) and 11p13-12 (EVR3; OMIM 605750, ref. 3). Here we have confirmed linkage to the 11q13-23 locus for autosomal dominant FEVR in one large multigenerational family and refined the disease locus to a genomic region spanning 1.55 Mb. Mutations in FZD4, encoding the putative Wnt receptor frizzled-4, segregated completely with affected individuals in the family and were detected in affected individuals from an additional unrelated family, but not in normal controls. FZD genes encode Wnt receptors, which are implicated in development and carcinogenesis. Injection of wildtype and mutated FZD4 into Xenopus laevis embryos revealed that wildtype, but not mutant, frizzled-4 activated calcium/calmodulin-dependent protein kinase II (CAMKII) and protein kinase C (PKC), components of the Wnt/Ca(2+) signaling pathway. In one of the mutants, altered subcellular trafficking led to defective signaling. These findings support a function for frizzled-4 in retinal angiogenesis and establish the first association between a Wnt receptor and human disease.

Retinopathy of prematurity: recent advances in our understanding

Retinopathy of prematurity (ROP) has been recognised as an important cause of childhood visual impairment and blindness since the 1940s when improved facilities and treatment increased the survival rate of premature infants. Although its incidence and severity have been decreasing in developed countries over the past two decades, both are increasing in developing nations. ROP is consequently targeted as an important but avoidable disease. This review provides an updated summary and discussion of much of the work that has been produced through population, animal, cell culture, and genetic research. The authors examine the prevalence, risk factors, and possible causes of the disease with a particular focus on genetic studies. They conclude that while significant reductions in the disease have occurred in developed countries, further research is required to fully understand and prevent the disease. In the meantime, development and implementation of appropriate screening and treatment strategies will be critical in reducing blindness in developing countries.

Retinopathy of prematurity: recent advances in our understanding

Retinopathy of prematurity (ROP) has been recognised as an important cause of childhood visual impairment and blindness since the 1940s when improved facilities and treatment increased the survival rate of premature infants. Although its incidence and severity have been decreasing in developed countries over the past two decades, both are increasing in developing nations. ROP is consequently targeted as an important but avoidable disease. This review provides an updated summary and discussion of much of the work that has been produced through population, animal, cell culture, and genetic research. The authors examine the prevalence, risk factors, and possible causes of the disease with a particular focus on genetic studies. They conclude that while significant reductions in the disease have occurred in developed countries, further research is required to fully understand and prevent the disease. In the meantime, development and implementation of appropriate screening and treatment strategies will be critical in reducing blindness in developing countries.

A new locus for autosomal dominant familial exudative vitreoretinopathy maps to chromosome 11p12-13

We report a new locus for familial exudative vitreoretinopathy (FEVR), on chromosome 11p12-13 in a large autosomal dominant pedigree. Statistically significant linkage was achieved across a 14-cM interval flanked by markers GATA34E08 and D11S4102, with a maximum multipoint LOD score of 6.6 at D11S2010. FEVR is a disease characterized by the failure of development of peripheral retinal blood vessels, and it is difficult to diagnose clinically because of the wide spectrum of fundus abnormalities associated with it. The identification of a new locus is important for genetic counseling and potentiates further studies aimed toward the identification of a gene with an important role in angiogenesis within neuroepithelial tissues. Such a gene may also have a role in the genetic predisposition to retinopathy of prematurity, a sporadic disorder with many clinical similarities to FEVR.

Genetic heterogeneity in familial exudative vitreoretinopathy; exclusion of the EVR1 locus on chromosome 11q in a large autosomal dominant pedigree

BACKGROUND/AIMS

Familial exudative vitreoretinopathy (FEVR) is associated with mutations in the Norrie disease gene in X linked pedigrees and with linkage to the EVR1 locus at 11q13 in autosomal dominant cases. A large autosomal dominant FEVR family was studied, both clinically and by linkage analysis, to determine whether it differed from the known forms of FEVR.

METHODS

Affected members and obligate gene carriers from this family were examined by slit lamp biomicroscopy, indirect ophthalmoscopy, and in some cases fluorescein angiography. Patient DNAs were genotyped for markers at the EVR1 locus on chromosome 11q13.

RESULTS

The clinical evaluation in this family is consistent with previous descriptions of FEVR pedigrees, but linkage analysis proves that it has a form of FEVR genetically distinct from the EVR1 locus on 11q.

CONCLUSION

This proves that there are at least three different loci associated with comparable FEVR phenotypes, a situation similar to that existing for many forms of retinal degeneration.