The characteristics of digenic familial exudative vitreoretinopathy

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

Purpose

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

Design

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

Subjects

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

Methods

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

Main Outcome Measures

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

Results

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

Conclusions

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

Financial Disclosures

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

Limited Added Diagnostic Value of Whole Genome Sequencing in Genetic Testing of Inherited Retinal Diseases in a Swiss Patient Cohort

The purpose of this study was to assess the added diagnostic value of whole genome sequencing (WGS) for patients with inherited retinal diseases (IRDs) who remained undiagnosed after whole exome sequencing (WES). WGS was performed for index patients in 66 families. The datasets were analyzed according to GATK's guidelines. Additionally, DeepVariant was complemented by GATK's workflow, and a novel structural variant pipeline was developed. Overall, a molecular diagnosis was established in 19/66 (28.8%) index patients. Pathogenic deletions and one deep-intronic variant contributed to the diagnostic yield in 4/19 and 1/19 index patients, respectively. The remaining diagnoses (14/19) were attributed to exonic variants that were missed during WES analysis due to bioinformatic limitations, newly described loci, or unclear pathogenicity. The added diagnostic value of WGS equals 5/66 (9.6%) for our cohort, which is comparable to previous studies. This figure would decrease further to 1/66 (1.5%) with a standardized and reliable copy number variant workflow during WES analysis. Given the higher costs and limited added value, the implementation of WGS as a first-tier assay for inherited eye disorders in a diagnostic laboratory remains untimely. Instead, progress in bioinformatic tools and communication between diagnostic and clinical teams have the potential to ameliorate diagnostic yields.

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

Importance

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

Objective

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

Design, Setting, and Participants

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

Main Outcomes and Measures

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

Results

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

Conclusions and Relevance

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

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.

Clinical characteristics and mutation spectrum in 33 Chinese families with familial exudative vitreoretinopathy

OBJECTIVE

To explore the clinical manifestations and search for the variants of six related genes (LRP5, FZD4, TSPAN12, NDP, KIF11 and ZNF408) in Chinese patients with familial exudative vitreoretinopathy (FEVR), and investigate the correlation between the genetic variants and the clinical characteristics.

PATIENTS AND METHODS

Clinical data, including the retinal artery angle, acquired from wide-field fundus imaging, structural and microvascular features of the retina obtained from optical coherence tomography (OCT) and OCT angiography (OCTA) were collected from 33 pedigrees. Furthermore, mutation screening was performed. Variants filtering, bioinformatics analysis and Sanger sequencing were conducted to verify the variants.

RESULTS

Twenty-one variants were successfully detected in 16 of 33 families, of which 10 variants were newly identified. The proportion of variants in LRP5, FZD4, TSPAN12, NDP and KIF11 was 38.1% (8/21), 33.3% (7/21), 19.1% (4/21), 4.8% (1/21) and 4.8% (1/21), respectively. Three new variants were considered to be pathogenic or likely pathogenic. The FEVR group tended to exhibit a smaller retinal artery angle, higher incidence of foveal hypoplasia and lower vascular density compared to the control group. Patients who harboured variants of FZD4 exhibited greater severity of FEVR than those with LRP5 variants. However, those who harboured LRP5 variants tended to possess lower foveal vascular density.

CONCLUSIONS

Six known pathogenic genes were screened in 33 pedigrees with FEVR in our study, which revealed 10 novel variants. These findings enrich the clinical features and mutation spectrum in Chinese patients with FEVR, revealing the genotype-phenotype relationship, and contributing to the diagnosis and treatment of the disease.Key messagesWe identified 21 variants in 5 genes (LRP5, FZD4, TSPAN12, NDP and KIF11) associated with FEVR, 10 of which are novel (three were pathogenic or likely pathogenic).The proportion of variants was the highest for the LRP5 gene.FZD4 variants may be responsible for greater FEVR severity than LRP5 variants.

Decrease of FZD4 exon 1 methylation in probands from FZD4-associated FEVR family of phenotypic heterogeneity

Familial exudative vitreoretinopathy (FEVR) is an important cause of childhood blindness and is clinically characterized by phenotypic heterogeneity. FEVR patients harboring the same genetic mutation vary widely in disease severity. The purpose of this study was to explore non-genetic factors that regulate FEVR phenotypic heterogeneity. We detected methylation levels of 21 CpG sites located at the FZD4 exon 1 region of 11 probands, 12 asymptomatic/paucisymptomatic carriers and 11 non-carriers from 10 unrelated FZD4-associated FEVR families using bisulfite amplicon sequencing (BSAS). Our results showed reduced methylation level of FZD4 exon 1 in probands, suggesting that FZD4 exon 1 methylation level may be negatively linked with FEVR disease severity. It provided a new research direction for follow-up research, helping us better understand the complexity of the FEVR-causing mechanism.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

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

Purpose

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

Methods

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

Results

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

Conclusions

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

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

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

Bi-allelic mutation of CTNNB1 causes a severe form of syndromic microphthalmia, persistent foetal vasculature and vitreoretinal dysplasia

Background

Inherited vitreoretinopathies arise as a consequence of congenital retinal vascularisation abnormalities. They represent a phenotypically and genetically heterogeneous group of disorders that can have a major impact on vision. Several genes encoding proteins and effectors of the canonical Wnt/β-catenin pathway have been associated and precise diagnosis, although difficult, is essential for proper clinical management including syndrome specific management where appropriate. This work aimed to investigate the molecular basis of disease in a single proband born to consanguineous parents, who presented with microphthalmia, persistent foetal vasculature, posterior lens vacuoles, vitreoretinal dysplasia, microcephaly, hypotelorism and global developmental delay, and was registered severely visually impaired by 5 months of age.

Methods

Extensive genomic pre-screening, including microarray comparative genomic hybridisation and sequencing of a 114 gene panel associated with cataract and congenital ophthalmic disorders was conducted by an accredited clinical laboratory. Whole exome sequencing (WES) was undertaken on a research basis and in vitro TOPflash transcriptional reporter assay was utilised to assess the impact of the putative causal variant.

Results

In the proband, WES revealed a novel, likely pathogenic homozygous mutation in the cadherin-associated protein beta-1 gene (CTNNB1), c.884C>G; p.(Ala295Gly), which encodes a co-effector molecule of the Wnt/β-catenin pathway. The proband’s parents were shown to be heterozygous carriers but ophthalmic examination did not detect any abnormalities. Functional assessment of the missense variant demonstrated significant reduction of β-catenin activity.

Conclusions

This is the first report of a biallelic disease-causing variation in CTNNB1. We conclude that this biallelic, transcriptional inactivating mutation of CTNNB1 causes a severe, syndromic form of microphthalmia, persistent foetal vasculature and vitreoretinal dysplasia that results in serious visual loss in infancy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02239-3.

Ocular Features and Mutation Spectrum of Patients With Familial Exudative Vitreoretinopathy

Purpose

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

Methods

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

Results

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

Conclusions

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

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Genetic Causes of Oculocutaneous Albinism in Pakistani Population

Melanin pigment helps protect our body from broad wavelength solar radiation and skin cancer. Among other pigmentation disorders in humans, albinism is reported to manifest in both syndromic and nonsyndromic forms as well as with varying inheritance patterns. Oculocutaneous albinism (OCA), an autosomal recessive nonsyndromic form of albinism, presents as partial to complete loss of melanin in the skin, hair, and iris. OCA has been known to be caused by pathogenic variants in seven different genes, so far, according to all the currently published population studies. However, the detection rate of alleles causing OCA varies from 50% to 90%. One of the significant challenges of uncovering the pathological variant underlying disease etiology is inter- and intra-familial locus heterogeneity. This problem is especially pertinent in highly inbred populations. As examples of such familial locus heterogeneity, we present nine consanguineous Pakistani families with segregating OCA due to variants in one or two different known albinism-associated genes. All of the identified variants are predicted to be pathogenic, which was corroborated by several in silico algorithms and association with diverse clinical phenotypes. We report an individual affected with OCA carries heterozygous, likely pathogenic variants in TYR and OCA2, raising the question of a possible digenic inheritance. Altogether, our study highlights the significance of exome sequencing for the complete genetic diagnosis of inbred families and provides the ramifications of potential genetic interaction and digenic inheritance of variants in the TYR and OCA2 genes.

Mutations in G Protein-Coupled Receptors: Mechanisms, Pathophysiology and Potential Therapeutic Approaches

There are approximately 800 annotated G protein-coupled receptor (GPCR) genes, making these membrane receptors members of the most abundant gene family in the human genome. Besides being involved in manifold physiologic functions and serving as important pharmacotherapeutic targets, mutations in 55 GPCR genes cause about 66 inherited monogenic diseases in humans. Alterations of nine GPCR genes are causatively involved in inherited digenic diseases. In addition to classic gain- and loss-of-function variants, other aspects, such as biased signaling, trans-signaling, ectopic expression, allele variants of GPCRs, pseudogenes, gene fusion, and gene dosage, contribute to the repertoire of GPCR dysfunctions. However, the spectrum of alterations and GPCR involvement is probably much larger because an additional 91 GPCR genes contain homozygous or hemizygous loss-of-function mutations in human individuals with currently unidentified phenotypes. This review highlights the complexity of genomic alteration of GPCR genes as well as their functional consequences and discusses derived therapeutic approaches. SIGNIFICANCE STATEMENT: With the advent of new transgenic and sequencing technologies, the number of monogenic diseases related to G protein-coupled receptor (GPCR) mutants has significantly increased, and our understanding of the functional impact of certain kinds of mutations has substantially improved. Besides the classical gain- and loss-of-function alterations, additional aspects, such as biased signaling, trans-signaling, ectopic expression, allele variants of GPCRs, uniparental disomy, pseudogenes, gene fusion, and gene dosage, need to be elaborated in light of GPCR dysfunctions and possible therapeutic strategies.

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

IMPORTANCE

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

BACKGROUND

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

DESIGN

Retrospective analysis.

PARTICIPANTS

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

METHODS

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

MAIN OUTCOME MEASURES

The diagnostic rate.

RESULTS

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

CONCLUSIONS AND RELEVANCE

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

Identification of Gene Mutations in Atypical Retinopathy of Prematurity Cases

Purpose

We have observed that some preterm infants whose fundus appears very similar to eyes with familial exudative vitreoretinopathy (FEVR) present with atypical retinopathy of prematurity (ROP). To establish a definitive diagnosis and explore the possible genetic mechanism of atypical ROP, we performed gene sequencing of these cases using next-generation sequencing technology.

Methods

A retrospective review of infants who presented with atypical ROP from October 2013 to February 2017 was performed. The data included gender, gestational age at birth, birth weight, family history, systemic disorders, and age-appropriate ophthalmic examinations. Fundus fluorescein angiography (FFA) of the parents was also performed. Peripheral blood was collected from the patients and their parents to sequence genes. Gene mutations were analysed.

Results

Genetic testing revealed that 9 infants had FEVR-related disease-causing gene mutations. Nine gene mutations were detected; 5 had already been reported, and the other 4 were novel. In the 18 eyes of these 9 patients, 9 eyes exhibited severe ROP. 5 cases had a positive family history.

Conclusions

Gene mutations of low-density-lipoprotein receptor-related protein 5(LRP5), frizzled-4(FZD4), Norrie disease protein (NDP), and tetraspanin-12(TSPAN12) may play a role in the pathogenesis of ROP and cause atypical ROP or preterm FEVR. The fundus lesions of ROP patients with disease-causing gene mutations were more serious. ROP cases should be carefully differentiated from preterm FEVR cases.

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

Aims

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

Methods

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

Results

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

Conclusions

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