Novel membrane frizzled-related protein gene mutation as cause of posterior microphthalmia resulting in high hyperopia with macular folds

Comprehensive genetic analysis uncovers the mutational spectrum of MFRP and its genotype-phenotype correlation in a large cohort of Chinese microphthalmia patients

PURPOSE

Microphthalmia is a severe congenital ocular disease featured by abnormal ocular development. The aim of this study was to detail the genetic and clinical characteristics of a large cohort of Chinese patients with microphthalmia related to MFRP variants, focusing on uncovering genotype-phenotype correlations.

METHODS

Fifty microphthalmia patients from 44 unrelated Chinese families were recruited. Whole-exome sequencing (WES) was conducted to analyze the coding regions and adjacent intronic regions of MFRP. Axial lengths (AL) were measured for all probands and available family members. Protein structures of mutations with high frequency in our cohort were predicted. The genotype-phenotype correlations were explored by statistical analysis.

RESULTS

Sixteen MFRP variants were detected in 17 families, accounting for 38.64 % of all microphthalmia families. There were 9 novel mutations (c.427+1G>C, c.428-2A>C, c.561_575del:p.A188_E192del, c.836G>A:p.C279Y, c.1010_1021del:p.H337_E340del:p.Y479*, c.1516_1517del:p.S506Pfs*66, c.1561T>G:p.C521G, c.1616G>A:p.R539H, and c.1735C>T:p.P579S) and six previously reported variants in MFRP, with p.E496K and p.H337_E340del being highly frequent, found in eight (47.06 %) and two families (11.76 %), respectively. Seven variants (43.75 %) were located in the C-terminal cysteine-rich frizzled-related domain (CRD) (7/16, 43.75 %). Protein prediction implicated p.E496K and p.H337_E340del mutations might lead to a destabilization of the MFRP protein. The average AL of all 42 eyes was 16.02 ± 1.05 mm, and 78.36 % of eyes with AL < 16 mm harbored p.E496K variant. Twenty-six eyes with variant variant had shorter AL than that of the other 16 eyes without this variant (p = 0.006), highlighting a novel genotype-phenotype correlation.

CONCLUSIONS

In this largest cohort of Chinese patients with microphthalmia, the 9 novel variants, high frequency of p.E496W, and mutation hotspots in CRD reveals unique insights into the MFRP mutation spectrum among Chinese patients, indicating ethnic variability. A new genotype-phenotype correlation that p.E496K variant associated with a shorter AL is unveiled. Our findings enhance the current knowledge of MFRP-associated microphthalmia and provide valuable information for prenatal diagnosis as well as future therapy.

MFRP variations cause nanophthalmos in five Chinese families with distinct phenotypic diversity

Purpose

Nanophthalmos is a congenital ocular structural anomaly that can cause significant visual loss in children. The early diagnosis and then taking appropriate clinical and surgical treatment remains a challenge for many ophthalmologists because of genetic and phenotypic heterogeneity. The objective of this study is to identify the genetic cause of nanophthalmos in the affected families and analyze the clinical phenotype of nanophthalmos with MFRP gene variation (Microphthalmia, isolated; OMIM#611040 and Nanophthalmos 2; OMIM#609549, respectively).

Methods

Comprehensive ophthalmic examinations were performed on participants to confirm the phenotype. The genotype was identified using whole exome sequencing, and further verified the results among other family members by Sanger sequencing. The normal protein structure was constructed using Alphafold. Mutant proteins were visualized using pymol software. Pathogenicity of identified variant was determined by in silico analysis and the guidelines of American College of Medical Genetics and Genomics (ACMG). The relationship between genetic variants and clinical features was analyzed.

Results

Five nanophthalmos families were autosomal recessive, of which four families carried homozygous variants and one family had compound heterozygous variants in the MFRP gene. Both family one and family three carried the homozygous missense variant c.1486G>A (p.Glu496Lys) in the MFRP gene (Clinvar:SCV005060845), which is a novel variant and evaluated as likely pathogenic according to the ACMG guidelines and in silico analysis. The proband of family one presented papilloedema in both eyes, irregular borders, thickened retinas at the posterior pole, tortuous and dilated retinal vessels, and indistinguishable arteries and veins, while the proband of family three presented uveal effusion syndrome-like changes in the right eye. In families one and 3, despite carrying the same gene variant, the probands had completely different clinical phenotypes. The homozygous nonsense variant c.271C>T (p.Gln91Ter) (Clinvar:SCV005060846) of the MFRP gene was detected in family 2, presenting shallow anterior chamber in both eyes, pigmentation of peripheral retina 360° from the equator to the serrated rim showing a clear demarcation from the normal retina in the form of strips. Family four proband carried the homozygous missense variant c.1411G>A (p.Val471Met) in the MFRP gene (Clinvar:SCV005060847), family five proband carried compound heterozygous missense variants c.1486G>A (p.Glu496Lys) and c.602G>T (p.Arg201Leu) in the MFRP gene (Clinvar:SCV005060848), which is a novel variant and evaluated as likely pathogenic according to the ACMG guidelines and in silico analysis, and they all presented clinically with binocular angle-closure glaucoma, family four also had retinal vein occlusion in the right eye during the follow-up.

Conclusion

In this study, pathogenic variants of the MFRP gene were detected in five nanophthalmos families, including two novel variants. It also revealed a distinct phenotypic diversity among five probands harboring variants in the MFRP gene. Our findings extend the phenotype associated with MFRP variants and is helpful for ophthalmologists in early diagnosis and making effective treatment and rehabilitation strategies.

Pathogenic variants of MFRP and PRSS56 genes are major causes of nanophthalmos in Japanese patients

BACKGROUND

Nanophthalmos (NNO) is a rare condition with significantly shorter axial length than normal. Several genes are known to cause NNO, among them the MFRP and PRSS56 genes have been reported to cause majority of NNOs. The purpose of this study was to determine the genetic basis of Japanese patients with NNO.

MATERIALS AND METHODS

We studied seven patients with NNO. Whole exome sequencing (WES) and Sanger sequencing were performed to determine the variants causing the NNO. We also reviewed the medical charts of the patients to determine the phenotype of these seven patients.

RESULTS

WES revealed that four patients from three families carried homozygous frameshift variants of the PRSS56 gene (c.1066dupC). Two novel variants of the MFRP gene were detected in the other two patients: one proband had a homozygous missense variant (c.1486 G>A) and the other had a compound heterozygous variant (c.1486 G>A and c.662_663insT). The axial length of the eight eyes with the PRSS56 variant was 15.69 ± 0.48 mm (mean ± SD) and that for the 4 eyes with the MFRP variant was 15.63 ± 0.69 mm. Three of the six cases with the PRSS56 or MFRP variant had the uveal effusion syndrome.

CONCLUSIONS

NNOs in Japanese patients are caused by variants of the PRSS56 and MFRP genes as in other ethnic populations. In addition, two new variants of the MFRP gene were found in our cohort. The phenotypes and anomalies in Japanese patients with NNO were similar to those reported for other ethnic populations.

The Genetic Determinants of Axial Length: From Microphthalmia to High Myopia in Childhood

The axial length of the eye is critical for normal visual function by enabling light to precisely focus on the retina. The mean axial length of the adult human eye is 23.5 mm, but the molecular mechanisms regulating ocular axial length remain poorly understood. Underdevelopment can lead to microphthalmia (defined as a small eye with an axial length of less than 19 mm at 1 year of age or less than 21 mm in adulthood) within the first trimester of pregnancy. However, continued overgrowth can lead to axial high myopia (an enlarged eye with an axial length of 26.5 mm or more) at any age. Both conditions show high genetic and phenotypic heterogeneity associated with significant visual morbidity worldwide. More than 90 genes can contribute to microphthalmia, and several hundred genes are associated with myopia, yet diagnostic yields are low. Crucially, the genetic pathways underpinning the specification of eye size are only now being discovered, with evidence suggesting that shared molecular pathways regulate under- or overgrowth of the eye. Improving our mechanistic understanding of axial length determination will help better inform us of genotype-phenotype correlations in both microphthalmia and myopia, dissect gene-environment interactions in myopia, and develop postnatal therapies that may influence overall eye growth.

The essential role of docosahexaenoic acid and its derivatives for retinal integrity

The fatty acid composition of photoreceptor outer segment (POS) phospholipids diverges from other membranes, being highly enriched in polyunsaturated fatty acids (PUFAs). The most abundant PUFA is docosahexaenoic acid (DHA, C22:6n-3), an omega-3 PUFA that amounts to over 50% of the POS phospholipid fatty acid side chains. Interestingly, DHA is the precursor of other bioactive lipids such as elongated PUFAs and oxygenated derivatives. In this review, we present the current view on metabolism, trafficking and function of DHA and very long chain polyunsaturated fatty acids (VLC-PUFAs) in the retina. New insights on pathological features generated from PUFA deficient mouse models with enzyme or transporter defects and corresponding patients are discussed. Not only the neural retina, but also abnormalities in the retinal pigment epithelium are considered. Furthermore, the potential involvement of PUFAs in more common retinal degeneration diseases such as diabetic retinopathy, retinitis pigmentosa and age-related macular degeneration are evaluated. Supplementation treatment strategies and their outcome are summarized.

NOVEL MFRP MUTATION WITH NANOPHTHALMOS, OPTIC DISK DRUSEN, AND PERIPHERAL RETINOSCHISIS IMAGED WITH ULTRA-WIDEFIELD OPTICAL COHERENCE TOMOGRAPHY

PURPOSE

To describe with multimodal imaging including the use of ultra-widefield optical coherence tomography imaging a distinct phenotype of autosomal recessive nanophthalmos associated with a novel mutation of the MFRP gene (membrane-type frizzled-related protein).

METHODS

Case report of a single patient followed by the Weill Cornell Medicine Department of Ophthalmology Retina and Glaucoma Services, and review of the relevant literature.

RESULTS

A patient with a novel homozygous mutation in the MFRP gene (c.472C>T) presented with nanophthalmos, optic disk drusen, foveal hypoplasia, and extensive peripheral retinoschisis, which was revealed to be multilevel retinoschisis on ultra-widefield optical coherence tomography. Unlike other reported cases, the findings associated with this novel mutation did not include foveoschisis or clinically obvious retinitis pigmentosa. The patient underwent prophylactic peripheral laser iridotomy in both eyes.

CONCLUSION

Here, we present a patient with nanophthalmos, optic disk drusen, and foveal hypoplasia associated with extensive peripheral retinoschisis imaged by ultra-widefield optical coherence tomography, but not foveal retinoschisis or prominent retinitis pigmentosa. The findings may expand the clinical spectrum of MFRP -associated nanophthalmos.

Choroidal changes in posterior microphthalmos

PURPOSE

To describe the choroidal variations in posterior microphthalmos (PM).

METHODS

In this observational case series, four eyes of two patients diagnosed as PM based on the characteristic clinical features were included. Multimodal retinal imaging with clinical fundus documentation using ultrawide field fundus camera, optical coherence tomography (OCT) and indocyanine green angiography (ICGA) was done for these cases.

RESULTS

Multimodal imaging of these cases confirmed the variations in the choroid in PM cases. In both cases, on OCT, the retina and choroid were thick. retinal papillomacular fold (RPMF) was noted in all four eyes. On ICGA, the dye transit time from the arm to choroid and retina were within normal limits. Choroidal vasculature in the far retinal periphery was reduced and was noted as hypocyanescent areas anterior to the equator while the density of choroidal vessels was significantly more posterior to the equator. Vortex veins were not visualised in both cases.

CONCLUSION

Choroidal structure and vessels undergo alterations in PM. Further validation of these findings is required in a larger cohort of PM cases.

Genotype-phenotype spectrum in isolated and syndromic nanophthalmos

PURPOSE

To (i) describe a series of patients with isolated or syndromic nanophthalmos with the underlying genetic causes, including novel pathogenic variants and their functional characterization and (ii) to study the association of retinal dystrophy in patients with MFRP variants, based on a detailed literature review of genotype-phenotype correlations.

METHODS

Patients with nanophthalmos and available family members received a comprehensive ophthalmological examination. Genetic analysis was based on whole-exome sequencing and variant calling in core genes including MFRP, BEST1, TMEM98, PRSS56, CRB1, GJA1, C1QTNF5, MYRF and FAM111A. A minigene assay was performed for functional characterization of a splice site variant.

RESULTS

Seven patients, aged between three and 65 years, from five unrelated families were included. Novel pathogenic variants in MFRP (c.497C>T, c.899-3C>A, c.1180G>A), and PRSS56 (c.1202C>A), and a recurrent de novo variant in FAM111A (c.1706G>A) in a patient with Kenny-Caffey syndrome type 2, were identified. In addition, we report co-inheritance of MFRP-related nanophthalmos and ADAR-related Aicardi-Goutières syndrome.

CONCLUSION

Nanophthalmos is a genetically heterogeneous condition, and the severity of ocular manifestations appears not to correlate with variants in a specific gene. However, retinal dystrophy is only observed in patients harbouring pathogenic MFRP variants. Furthermore, heterozygous carriers of MFRP and PRSS56 should be screened for the presence of high hyperopia. Identifying nanophthalmos as an isolated condition or as part of a syndrome has implications for counselling and can accelerate the interdisciplinary care of patients.

Updates on Genes and Genetic Mechanisms Implicated in Primary Angle-Closure Glaucoma

Primary angle-closure glaucoma (PACG) is estimated to affect over 30 million people worldwide by 2040 and is highly prevalent in the Asian population. PACG is more severe and carries three times the higher risk of blindness than primary open-angle glaucoma, thus representing a significant public health concern. High heritability and ethnic-specific predisposition to PACG suggest the involvement of genetic factors in disease development. In the recent past, genetic studies have led to the successful identification of several genes and loci associated with PACG across different ethnicities. The precise cellular and molecular roles of these multiple loci in the development and progression of PACG remains to be elucidated. Nonetheless, these studies have significantly increased our understanding of the emerging cellular processes and biological pathways that might provide more significant insights into the disease’s genetic etiology and may be valuable for future clinical applications. This review aims to summarize and update the current knowledge of PACG genetics analysis research.

Novel TMEM98, MFRP, PRSS56 variants in a large United States high hyperopia and nanophthalmos cohort

Nanophthalmos is a rare condition defined by a small, structurally normal eye with resultant high hyperopia. While six genes have been implicated in this hereditary condition (MFRP, PRSS56, MYRF, TMEM98, CRB1,VMD2/BEST1), the relative contribution of these to nanophthalmos or to less severe high hyperopia (≥ + 5.50 spherical equivalent) has not been fully elucidated. We collected probands and families (n = 56) with high hyperopia or nanophthalmos (≤ 21.0 mm axial length). Of 53 families that passed quality control, plausible genetic diagnoses were identified in 10/53 (18.8%) by high-throughput panel or pooled exome sequencing. These include 1 TMEM98 family (1.9%), 5 MFRP families (9.4%), and 4 PRSS56 families (7.5%), with 4 additional families having single allelic hits in MFRP or PRSS56 (7.5%). A novel deleterious TMEM98 variant (NM_015544.3, c.602G>C, p.(Arg201Pro)) segregated with disease in 4 affected members of a family. Multiple novel missense and frameshift variants in MFRP and PRSS56 were identified. PRSS56 families were more likely to have choroidal folds than other solved families, while MFRP families were more likely to have retinal degeneration. Together, this study defines the prevalence of nanophthalmos gene variants in high hyperopia and nanophthalmos and indicates that a large fraction of cases remain outside of single gene coding sequences.

A novel MFRP gene variant in a family with posterior microphthalmos, retinitis pigmentosa, foveoschisis, and foveal hypoplasia

BACKGROUND

To characterize the phenotype and genotype of a syndrome associating posterior microphthalmos (PM), retinitis pigmentosa (RP), foveoschisis, and foveal hypoplasia (FH) in a consanguineous Portuguese family.

MATERIALS AND METHODS

Three siblings were studied and underwent comprehensive eye examinations for best-corrected visual acuity, axial length, refractive error, B-mode ultrasound, electroretinography, retinography, fluorescein angiography (FA), kinetic visual field (VF), and optical coherence tomography (OCT). Molecular analysis was performed by Sanger sequencing of the entire coding region of the MFRP gene.

RESULTS

All members presented nyctalopia, decreased visual acuity, and constriction of the VF, as well as bilateral shortening of the posterior ocular segment and normal anterior segment dimensions. The fundoscopy and ERG results were compatible with RP. Macular OCT analysis revealed schisis of the outer retinal layer, FH, as well as retinal and choroidal folds. We identified a homozygous mutation in intron 9 of the membrane frizzled-related protein (MFRP) gene (c.1124 + 1 G > A).

CONCLUSIONS

Our study shows a family with PM and RP due to a mutation in the MFRP gene. The relationship has previously been proven, but this specific mutation has never been described. These gene mutations show wide phenotypic variability, being evident in the presence of foveoschisis, retinal and choroidal folds, and FH, other than PM and RP.

The majority of autosomal recessive nanophthalmos and posterior microphthalmia can be attributed to biallelic sequence and structural variants in MFRP and PRSS56

This study aimed to genetically and clinically characterize a unique cohort of 25 individuals from 21 unrelated families with autosomal recessive nanophthalmos (NNO) and posterior microphthalmia (MCOP) from different ethnicities. An ophthalmological assessment in all families was followed by targeted MFRP and PRSS56 testing in 20 families and whole-genome sequencing in one family. Three families underwent homozygosity mapping using SNP arrays. Eight distinct MFRP mutations were found in 10/21 families (47.6%), five of which are novel including a deletion spanning the 5' untranslated region and the first coding part of exon 1. Most cases harbored homozygous mutations (8/10), while a compound heterozygous and a monoallelic genotype were identified in the remaining ones (2/10). Six distinct PRSS56 mutations were found in 9/21 (42.9%) families, three of which are novel. Similarly, homozygous mutations were found in all but one, leaving 2/21 families (9.5%) without a molecular diagnosis. Clinically, all patients had reduced visual acuity, hyperopia, short axial length and crowded optic discs. Retinitis pigmentosa was observed in 5/10 (50%) of the MFRP group, papillomacular folds in 12/19 (63.2%) of MCOP and in 3/6 (50%) of NNO cases. A considerable phenotypic variability was observed, with no clear genotype-phenotype correlations. Overall, our study represents the largest NNO and MCOP cohort reported to date and provides a genetic diagnosis in 19/21 families (90.5%), including the first MFRP genomic rearrangement, offering opportunities for gene-based therapies in MFRP-associated disease. Finally, our study underscores the importance of sequence and copy number analysis of the MFRP and PRSS56 genes in MCOP and NNO.

Novel truncation mutations in MYRF cause autosomal dominant high hyperopia mapped to 11p12-q13.3

High hyperopia is a common and severe form of refractive error. Genetic factors play important roles in the development of high hyperopia but the exact gene responsible for this condition is mostly unknown. We identified a large Chinese family with autosomal dominant high hyperopia. A genome-wide linkage scan mapped the high hyperopia to chromosome 11p12-q13.3, with maximum log of the odds scores of 4.68 at theta = 0 for D11S987. Parallel whole-exome sequencing detected a novel c.3377delG (p.Gly1126Valfs*31) heterozygous mutation in the MYRF gene within the linkage interval. Whole-exome sequencing in other 121 probands with high hyperopia identified additional novel mutations in MYRF within two other families: a de novo c.3274_3275delAG (p.Leu1093Profs*22) heterozygous mutation and a c.3194+2T>C heterozygous mutation. All three mutations are located in the C-terminal region of MYRF and are predicted to result in truncation of that portion. Two patients from two of the three families developed angle-closure glaucoma. These three mutations were present in neither the ExAC database nor our in-house whole-exome sequencing data from 3280 individuals. No other truncation mutations in MYRF were detected in the 3280 individuals. Knockdown of myrf resulted in small eye size in zebrafish. These evidence all support that truncation mutations in the C-terminal region of MYRF are responsible for autosomal dominant high hyperopia in these families. Our results may provide useful clues for further understanding the functional role of the C-terminal region of this critical myelin regulatory factor, as well as the molecular pathogenesis of high hyperopia and its associated angle-closure glaucoma.

Genetics of anophthalmia and microphthalmia. Part 1: Non-syndromic anophthalmia/microphthalmia

Eye formation is the result of coordinated induction and differentiation processes during embryogenesis. Disruption of any one of these events has the potential to cause ocular growth and structural defects, such as anophthalmia and microphthalmia (A/M). A/M can be isolated or occur with systemic anomalies, when they may form part of a recognizable syndrome. Their etiology includes genetic and environmental factors; several hundred genes involved in ocular development have been identified in humans or animal models. In humans, around 30 genes have been repeatedly implicated in A/M families, although many other genes have been described in single cases or families, and some genetic syndromes include eye anomalies occasionally as part of a wider phenotype. As a result of this broad genetic heterogeneity, with one or two notable exceptions, each gene explains only a small percentage of cases. Given the overlapping phenotypes, these genes can be most efficiently tested on panels or by whole exome/genome sequencing for the purposes of molecular diagnosis. However, despite whole exome/genome testing more than half of patients currently remain without a molecular diagnosis. The proportion of undiagnosed cases is even higher in those individuals with unilateral or milder phenotypes. Furthermore, even when a strong gene candidate is available for a patient, issues of incomplete penetrance and germinal mosaicism make diagnosis and genetic counseling challenging. In this review, we present the main genes implicated in non-syndromic human A/M phenotypes and, for practical purposes, classify them according to the most frequent or predominant phenotype each is associated with. Our intention is that this will allow clinicians to rank and prioritize their molecular analyses and interpretations according to the phenotypes of their patients.

Clinical features of posterior microphthalmic and nanophthalmic eyes

AIM

To clinically differentiate nanophthalmos (NO) and posterior microphthalmos (PM) and to explore the mechanisms related to papillomacular folds (PMF).

METHODS

Medical records of 34 unrelated patients with microphthalmos (54 eyes) from April 2009 to October 2017 were retrospectively reviewed.

RESULTS

Fourteen eyes of 7 unrelated patients with NO and PM were included in the study. The presenting age of the NO cohort was significantly higher compared with the PM cohort (NO: 27±16y; PM: 3.7±0.6y). PMF was more likely to occur in cases with PM than in NO (25% in NO, 100% in PM). The anatomic features of PMF from optical coherence tomography (OCT) included: ganglion cell layer, inner plexiform layer, inner nuclear layer, outer plexiform layer and outer nuclear layer. In eyes without an apparent PMF (these were all NO eyes), rudimentary fovea without a foveal pit was noted. Four eyes that were NO developed angle closure glaucoma. Three NO eyes developed exudative retinal detachment and were successfully treated with lamellar sclerectomy.

CONCLUSION

Posterior segment changes are pervasive both in PM and NO. Complications like angle closure glaucoma and exudative retinal detachment are likely to occur in eyes with NO but not with PM. Detailed OCT analysis found that PMF was partially a neural retinal issue, suggesting that redundancy of retinal issues involved only inner retinal layers.

Nanophthalmos: A Review of the Clinical Spectrum and Genetics

Nanophthalmos is a clinical spectrum of disorders with a phenotypically small but structurally normal eye. These disorders present significant clinical challenges to ophthalmologists due to a high rate of secondary angle-closure glaucoma, spontaneous choroidal effusions, and perioperative complications with cataract and retinal surgeries. Nanophthalmos may present as a sporadic or familial disorder, with autosomal-dominant or recessive inheritance. To date, five genes (i.e., MFRP, TMEM98, PRSS56, BEST1, and CRB1) and two loci have been implicated in familial forms of nanophthalmos. Here, we review the definition of nanophthalmos, the clinical and pathogenic features of the condition, and the genetics of this disorder.

Loss of Zebrafish Mfrp Causes Nanophthalmia, Hyperopia, and Accumulation of Subretinal Macrophages

Purpose

Mutations in membrane frizzled-related protein (MFRP) are associated with nanophthalmia, hyperopia, foveoschisis, irregular patches of RPE atrophy, and optic disc drusen in humans. Mouse mfrp mutants show retinal degeneration but no change in eye size or refractive state. The goal of this work was to generate zebrafish mutants to investigate the loss of Mfrp on eye size and refractive state, and to characterize other phenotypes observed.

Methods

Clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 methods were used to generate multiple frameshift mutations in zebrafish mfrp causing premature translational stops in Mfrp. Spectral-domain optical coherence tomography (SD-OCT) was used to measure eye metrics and refractive state, and immunohistochemistry was used to study adult eyes. Gene expression levels were measured using quantitative PCR.

Results

Zebrafish Mfrp was shown to localize to apical and basal regions of RPE cells, as well as the ciliary marginal zone. Loss of Mfrp in mutant zebrafish was verified histologically. Zebrafish eyes that were mfrp mutant showed reduced axial length causing hyperopia, RPE folding, and macrophages were observed subretinally. Visual acuity was reduced in mfrp mutant animals.

Conclusions

Mutation of zebrafish mfrp results in hyperopia with subretinal macrophage infiltration, phenocopying aspects of human and mouse Mfrp deficiency. These mutant zebrafish will be useful in studying the onset and progression of Mfrp-related nanophthalmia, the cues that initiate the recruitment of macrophages, and the mechanisms of Mfrp function.

Choroidal thickness findings in two siblings with nanophthalmos by swept source-OCT: a case report

Background

We investigated choroidal thicknesses at five sites in two siblings (four eyes) with nanophthalmos using swept-source optical coherence tomography.

Case presentation

Case 1, a 51-year-old Japanese female with high hyperopia (Right: +20.5 Dioptors, Left: +19.5 Dioptors), had axial lengths of 15.6 mm in both eyes. Case 2, a 55-year-old Japanese male with high hyperopia (Right: +22.5 Dioptors, Left: +22.8 Dioptors), had axial lengths of 14.8 and 14.7 mm in the right and left eyes, respectively. Choroidal thickness was measured at five sites in each eye using swept-source optical coherence tomography; subfoveal, nasal, temporal, superior and inferior (the 4 non-subfoveal sites were measured 3000 µm from the fovea).

Conclusion

The mean choroidal thickness was 355.8 ± 63.6 μm at the subfoveal, 466.3 ± 85.1 μm at the nasal, 274.8 ± 77.2 μm at the temporal, 396.8 ± 54.6 μm at the superior, and 480.8 ± 66.8 μm at the inferior (mean ± standard deviation) site. Choroidal thickness was maximal at the inferior site. The choroid was thinnest, in diminishing order, at the nasal, superior, subfoveal and temporal sites.

Optic disk drusen in children

Optic disk drusen occur in 0.4% of children and consist of acellular intracellular and extracellular deposits that often become calcified over time. They are typically buried early in life and generally become superficial, and therefore visible, later in childhood, at the average age of 12 years. Their main clinical significance lies in the ability of optic disk drusen, particularly when buried, to simulate true optic disk edema. Misdiagnosing drusen as true disk edema may lead to an invasive and unnecessary workup for elevated intracranial pressure. Ancillary testing, including ultrasonography, fluorescein angiography, fundus autofluorescence, and optical coherence tomography, may aid in the correct diagnosis of optic disk drusen. Complications of optic disk drusen in children include visual field defects, hemorrhages, choroidal neovascular membrane, nonarteritic anterior ischemic optic neuropathy, and retinal vascular occlusions. Treatment options for these complications include ocular hypotensive agents for visual field defects and intravitreal anti-vascular endothelial growth factor agents for choroidal neovascular membranes. In most cases, however, children with optic disk drusen can be managed by observation with serial examinations and visual field testing once true optic disk edema has been excluded.

Identification of MFRP Mutations in Chinese Families with High Hyperopia

PURPOSE

Mutations in MFRP have been reported to cause autosomal recessive posterior microphthalmia, nanophthalmos, and an ophthalmic syndrome characterized by posterior microphthalmia, high hyperopia, retinitis pigmentosa, foveoschisis, and optic disc drusen. High hyperopia is a consistent sign of this syndrome. The purpose of this study was to detect MFRP mutations in 46 unrelated Chinese probands with high hyperopia.

METHODS

Clinical data and genomic DNA were collected from 46 Chinese probands diagnosed as having high hyperopia. Genomic DNA from 42 probands was initially analyzed by whole exome sequencing. MFRP variants were confirmed by Sanger sequencing. The coding sequence of MFRP for four additional probands was also analyzed by Sanger sequencing. Candidate MFRP variants were further validated in available family members and 192 normal individuals.

RESULTS

Potential pathogenic compound heterozygous mutations, including c.287_291del (p.P96Lfs*6), c.1615C>T (p.R539C), c.664C>A (p.P222T), c.1150dup (p.H384Pfs*8), and c.1549C>T (p.R517W), were detected in three of the 46 probands included in this study. The clinical data revealed that all patients in this study had high hyperopia of +13.50D or higher and an eye axial length of 16.78 mm or less. Electroretinography showed normal responses in a patient with missense mutations and reduced rod responses in another patient with missense and truncation mutations in whom optical coherence tomography showed developmental cystoid macular degeneration in both eyes.

CONCLUSIONS

The current study expands our knowledge of the mutation spectrum of MFRP and its associated phenotypes. To our knowledge, this is the first report of MFRP mutations in a Chinese cohort.