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.

ALDH1A3-related congenital microphthalmia-8 due to a novel frameshift variant.

Microphthalmia (MCOP) is a group of rare developmental malformations of eye with often reduced size of the eyeball, leading to blindness. Affecting about 1 in 7000 live births, MCOP can occur due to either environmental or genetic factors. Isolated microphthalmia-8 (MCOP8) has been proved to be caused by autosomal recessive mutations of the ALDH1A3 gene (MIM*600463) encoding aldehyde dehydrogenase 1 family, member A3. Herein, we report an 8-year-old boy with vision problems since birth from a first-cousin consanguineous parents. The main symptoms of the patient included severe bilateral microphthalmia, cyst in the left eye and blindness. The child developed behavioral disorders at the age of 7. It should be noted that there is no family history of the disease. To identify the genetic factor underlying the pathogenesis in this case Whole Exome Sequencing (WES) was performed and followed by Sanger sequencing. A novel pathogenic variant, c.1441delA (p.M482Cfs*8), in the ALDH1A3 gene was detected by WES in the proband. Further prenatal diagnosis is highly suggested to the family for the future pregnancies.

Orbital Cyst with Ependymal Differentiation Associated with Microphthalmia.

BackgroundOrbital cysts associated with microphthalmia are colobomatous lesions that typically present unilaterally and posterior to the globe. Case Report: A male infant had an orbital cyst associated with microphthalmia located anterior to the globe composed of a neuroglial wall, ependymal-like epithelial lining, with synaptophysin-positive cells resembling the retinal neuronal layer. Conclusion: This orbital cyst may represent a malformation of the eye rather than an encephalocele.

R-Ras Deficiency in Pericytes Causes Frequent Microphthalmia and Perturbs Retinal Vascular Development.

PURPOSE: The retinal vasculature is heavily invested by pericytes. Small GTPase R-Ras is highly expressed in endothelial cells and pericytes, suggesting importance of this Ras homolog for the regulation of the blood vessel wall. We investigated the specific contribution of pericyte-expressed R-Ras to the development of the retinal vasculature. METHODS: The effect of R-Ras deficiency in pericytes was analyzed in pericyte-targeted conditional Rras knockout mice at birth and during the capillary plexus formation in the neonatal retina. RESULTS: The offspring of these mice frequently exhibited unilateral microphthalmia. Analyses of the developing retinal vasculature in the eyes without microphthalmia revealed excessive endothelial cell proliferation, sprouting, and branching of the capillary plexus in these animals. These vessels were structurally defective with diminished pericyte coverage and basement membrane formation. Furthermore, these vessels showed reduced VE-cadherin staining and significantly elevated plasma leakage indicating the breakdown of the blood-retinal barrier. This defect was associated with considerable macrophage infiltration in the retina. CONCLUSIONS: The normal retinal vascular development is dependent on R-Ras expression in pericytes, and the absence of it leads to unattenuated angiogenesis and significantly weakens the blood-retinal barrier. Our findings underscore the importance of R-Ras for pericyte function during the normal eye development.

Atypical presentation of Cat Eye Syndrome in an infant with Peters anomaly and microphthalmia with cyst.

PURPOSE: To describe a unique ocular presentation of Cat Eye Syndrome and review the ocular and systemic findings associated with the syndrome. METHODS: Case report with multimodal imaging. RESULTS: A newborn female presented with a unilateral Peters anomaly with contralateral microphthalmia with cyst. The patient's other systemic findings included a hypoplastic right heart, persistent ductus arteriosus, intrauterine growth retardation, bilateral anotia, preauricular ear pits and skin tags, micrognathia, hypoplastic female genitalia, and unilateral cranial nerve VII palsy. Chromosomal microarray testing showed tetrasomy of chromosome 22 in the q11.1-q11.21 region consistent with Cat Eye Syndrome. The patient ultimately underwent a successful optical iridectomy on one side and orbitotomy with excision of the cystic mass on the other. CONCLUSIONS: The co-occurrence of unilateral Peters anomaly with contralateral microphthalmia with cyst in Cat Eye Syndrome is rare and demonstrative of the syndrome's phenotypic variability. The medical and surgical management of these patients may require a multidisciplinary approach and must be tailored to the individual findings and overall systemic health of the patient.

Exome sequencing in patients with microphthalmia, anophthalmia, and coloboma (MAC) from a consanguineous population.

Next-generation sequencing strategies have resulted in mutation detection rates of 21% to 61% in small cohorts of patients with microphthalmia, anophthalmia and coloboma (MAC), but despite progress in identifying novel causative genes, many patients remain without a genetic diagnosis. We studied a cohort of 19 patients with MAC who were ascertained from a population with high rates of consanguinity. Using single nucleotide polymorphism (SNP) arrays and whole exome sequencing (WES), we identified one pathogenic variant in TENM3 in a patient with cataracts in addition to MAC. We also detected novel variants of unknown significance in genes that have previously been associated with MAC, including KIF26B, MICU1 and CDON, and identified variants in candidate genes for MAC from the Wnt signaling pathway, comprising LRP6, WNT2B and IQGAP1, but our findings do not prove causality. Plausible variants were not found for many of the cases, indicating that our current understanding of the pathogenesis of MAC, a highly heterogeneous group of ocular defects, remains incomplete.

Craniosynostosis-microphthalmia syndrome belongs to the spectrum of BCOR-related disorders.

Craniosynostosis-microphthalmia linked to BCOR haploinsufficiency.

High-throughput transcriptome analysis reveals that the loss of Pten activates a novel NKX6-1/RASGRP1 regulatory module to rescue microphthalmia caused by Fgfr2-deficient lenses.

FGFR signaling is critical to development and disease pathogenesis, initiating phosphorylation-driven signaling cascades, notably the RAS-RAF-MEK-ERK and PI3 K-AKT cascades. PTEN antagonizes FGFR signaling by reducing AKT and ERK activation. Mouse lenses lacking FGFR2 exhibit microphakia and reduced ERK and AKT phosphorylation, widespread apoptosis, and defective lens fiber cell differentiation. In contrast, simultaneous deletion of both Fgfr2 and Pten restores ERK and AKT activation levels as well as lens size, cell survival and aspects of fiber cell differentiation; however, the molecular basis of this "rescue" remains undefined. We performed transcriptomic analysis by RNA sequencing of mouse lenses with conditional deletion of Fgfr2, Pten or both Fgfr2 and Pten, which reveal new molecular mechanisms that uncover how FGFR2 and PTEN signaling interact during development. The FGFR2-deficient lens transcriptome demonstrates overall loss of fiber cell identity with deregulated expression of 1448 genes. We find that ~ 60% of deregulated genes return to normal expression levels in lenses lacking both Fgfr2 and Pten. Further, application of customized filtering parameters to these RNA-seq data sets identified 68 high-priority candidate genes. Bioinformatics analyses showed that the cis-binding motif of a high-priority homeodomain transcription factor, NKX6-1, was present in the putative promoters of ~ 78% of these candidates. Finally, biochemical reporter assays demonstrate that NKX6-1 activated the expression of the high-priority candidate Rasgrp1, a RAS-activating protein. Together, these data define a novel regulatory module in which NKX6-1 directly activates Rasgrp1 expression to restore the balance of ERK and AKT activation, thus providing new insights into alternate regulation of FGFR downstream events.

Congenital Microphthalmia with Orbital Cyst: A Case Series.

Microphthalmos results from incomplete invagination of the optic vesicle or closure of the embryonic fissure. We present three patients with unilateral congenital microphthalmia with cyst. None of them had vision in the affected eye since birth. There was gradually increasing left eye orbital mass encroaching towards lower fornix and lower eyelid ectropion. On examination and investigations, patients had large orbital cyst with microphthalmia pushing the eyeball superiorly and posteriorly in affected orbit. Microphthalmic globe with cyst was surgically excised and histopathologically studied. Orbital cavity was big enough to occupy the conformer and the prosthetic eye after 6 weeks. Diagnosis was confirmed as large communicating orbital cyst with microphthalmia without systemic association in all the patients. None of the mothers of patients had regular antenatal check up. All the parents had consanguineous marriage. Antenatal check up with ultrasound at 14 to16 weeks of pregnancy is important for genetic counselling. Targeted abdominal ultrasound examination of pregnant women focused on the orbital region of foetus is recommended, in mothers who have children with congenital eye anomalies. Keywords: congenital anomaly; cyst; eye; microphthalmos.

Swept source-OCT and swept source-OCT angiography findings in posterior microphthalmos.

PURPOSE: To describe swept source-OCT (SS-OCT) and swept source-OCT angiography (SS-OCTA) findings in eyes with posterior microphthalmos (PM). METHODS: Twelve eyes (six patients) with PM were evaluated using SS-OCT and SS-OCTA. Structural changes, subfoveal choroidal thickness (SFCT), and perifoveal capillary changes with qualitative and quantitative assessments were analyzed. Twenty eyes served as control group. RESULTS: SS-OCT findings included elevated retinal papillo-macular fold (75%), retinal pigment epithelium folds (83%), macular cystoid spaces (42%), subretinal fluid (17%), and increased visibility of posterior vitreous cortex and hyaloid (42%). Mean SFCT in PM and in control eyes were 430.33 ± 157.48 µm and 290.05 ± 52.87 µm, respectively (p = 0.004). Perifoveal capillary changes on SS-OCTA included foveal avascular zone (FAZ) remodeling (100%), vessel tortuosity (67%), disorganization of the deep capillary network (67%), intraretinal cystoid spaces (42%), and areas of signal voids in the choriocapillaris (33%). FAZ area was significantly smaller in eyes with PM than in the control group in both the superficial (p < 0.001) and deep capillary plexuses (p = 0.001). Capillary vessel density (CVD) was significantly lower in the PM than in the control group in the deep capillary plexus (p = 0.004). Log MAR BCVA correlated negatively with axial length (r = - 0.929, p < 0.001), FAZ area in both the superficial (r = - 0.637, p < 0.001) and deep capillary plexus (r = - 0.561, p = 0002), and CVD in the deep capillary plexus (r = - 0.450, p = 0.016). CONCLUSIONS: Combined SS-OCT and SS-OCTA allow the detection of various retinal and choroidal structural and microvascular changes in eyes with PM. These findings can provide new insights onto this blinding ocular condition.

Anterior Segment Features in Nanophthalmos With Secondary Chronic Angle Closure Glaucoma: An Ultrasound Biomicroscopy Study.

Purpose: We compare anterior segment parameters and the risk of malignant glaucoma between nanophthalmos with secondary chronic angle closure glaucoma (NSCACG) and chronic primary angle-closure glaucoma (CPACG). Methods: This retrospective case-control study included 32 NSCACG (32 eyes) and 36 CPACG (36 eyes) patients. Anterior segment parameters, including anterior chamber depth (ACD) and width (ACW), pupil diameter (PD), lens vault (LV), ciliary process-ciliary process distance (CCD), angle opening distance500 (AOD500), trabecular-iris angle (TIA), trabecular-ciliary processes distance (TCPD), ciliary body max thickness (CBMT), iris convexity (IC), peripheral iris thickness (PIT), iris-zonule distance (IZD), trabecular ciliary process angle (TCPA), and anterior vault (AV), were measured by ultrasound biomicroscopy. A-scan ultrasonography measurements, including lens thickness (LT) and axial length (AL), also were reviewed. Results: ACD, ACW, CCD, TCPD, and AL were smaller, whereas the LV, LT/AL, LV/LT, LV/ACD, LT/ACD, LV/AV, and AV/AL were larger in NSCACG compared to CPACG eyes (all Bonferroni-corrected P < 0.05). Eyes with NSCACG had a higher risk of malignant glaucoma postoperatively than eyes with CPACG (P = 0.018). Conclusions: Characterized by narrower anterior segment, forward movement of larger lens, more anteriorly rotated ciliary bodies, and smaller CCD, NSCACG eyes have a higher risk of malignant glaucoma than CPACG eyes.

A new rhodopsin R135W mutation induces endoplasmic reticulum stress and apoptosis in retinal pigment epithelial cells.

Rhodopsin mutations are associated with the autosomal-dominant form of retinitis pigmentosa (RP). Here we report simultaneous occurrence of RP associated with bilateral nanophthalmos and acute angle-closure glaucoma in patient with a new mutation in rhodopsin (R135W). ARPE-19 cells were transfected with myc-tagged wild-type (WT) and R135W rhodopsin constructs. The half-life of WT and R135W rhodopsin was analyzed via cycloheximide chase analysis. We found that R135W rhodopsin was accumulated in the endoplasmic reticulum (ER) and induced unfolded protein response (UPR) and apoptosis. Moreover, chaperone HSP70 alleviated ER stress and prevented apoptosis induced by R135W rhodopsin by attenuating UPR signaling. These findings reveal the novel pathogenic mechanism of RP and suggest that chaperone HSP70 has potential therapeutic significance for RP.

FSHD2- and BAMS-associated mutations confer opposing effects on SMCHD1 function.

Structural maintenance of chromosomes flexible hinge domain-containing 1 (Smchd1) plays important roles in epigenetic silencing and normal mammalian development. Recently, heterozygous mutations in SMCHD1 have been reported in two disparate disorders: facioscapulohumeral muscular dystrophy type 2 (FSHD2) and Bosma arhinia microphthalmia syndrome (BAMS). FSHD2-associated mutations lead to loss of function; however, whether BAMS is associated with loss- or gain-of-function mutations in SMCHD1 is unclear. Here, we have assessed the effect of SMCHD1 missense mutations from FSHD2 and BAMS patients on ATP hydrolysis activity and protein conformation and the effect of BAMS mutations on craniofacial development in a Xenopus model. These data demonstrated that FSHD2 mutations only result in decreased ATP hydrolysis, whereas many BAMS mutations can result in elevated ATPase activity and decreased eye size in Xenopus Interestingly, a mutation reported in both an FSHD2 patient and a BAMS patient results in increased ATPase activity and a smaller Xenopus eye size. Mutations in the extended ATPase domain increased catalytic activity, suggesting critical regulatory intramolecular interactions and the possibility of targeting this region therapeutically to boost SMCHD1's activity to counter FSHD.

A complex phenotype in a family with a pathogenic SOX3 missense variant.

Duplications and deletions of Xq26-27 including SOX3 (Xq27.1) have been associated with X-linked mental retardation and isolated growth hormone deficiency (OMIM 300123) or X-linked panhypopituitarism (OMIM 312000). Yet, pathogenic point mutations seem to be extremely rare. We report a family with three affected males with several clinical features including mild intellectual disability, microphthalmia, coloboma, hypopituitarism, facial dysmorphology and dental anomalies, including microcephaly, retrognathia and a solitary median maxillary central incisor amongst other features. Using Whole Exome Sequencing a missense variant in SOX3, NM_005634.2:c.449C>A; p.(Ser150Tyr) was identified. Segregation analysis in the family demonstrated that the variant was inherited through healthy females with its origin in the maternal grandmother showing germline mosaicism. Thus, we report one of the first cases of a pathogenic variant in SOX3 and germline mosaicism of this variant.

Both a frameshift and a missense mutation of the STRA6 gene observed in an infant with the Matthew-Wood syndrome.

BACKGROUND: The Matthew-Wood syndrome is associated with mutations of the STRA6 gene. It combines a pulmonary agenesis/hypoplasia; microphthalmia/anophthalmia; congenital cardiac, digestive, and urogenital malformations; and diaphragmatic defects. CASE: A 23-year-old nulliparous woman was referred to our center after a fetal ultrasound examination at 26 weeks of pregnancy revealed an abnormal head shape, a heart malformation, multiple cysts in both kidneys, and dilated ureters. A male baby (46, XY; 3600g; Apgar score 1) was delivered at 38 weeks of gestation and died 1 hr later due to respiratory failure. The diagnosis of Matthew-Wood syndrome was suspected given the association of bilateral anophthalmia, agenesis of the left lung, and heart and kidney defects. It was confirmed by the identification of two deleterious mutations of the STRA6 gene. RESULTS: The child was a compound heterozygote for two previously reported mutations, a paternally inherited missense mutation (c.878C>T [p.Pro293Leu] and a maternally inherited frameshift mutation (c.50_52delACTinsCC [p. Asp17Alafs*55]), producing a premature stop codon. CONCLUSION: The diagnosis of Matthew-Wood syndrome should be considered in all fetuses with microphthalmia/anophthalmia. It requires an extensive ultrasound/MRI examination of the lung, heart, and diaphragm. Birth Defects Research 109:251-253, 2017. © 2017 Wiley Periodicals, Inc.

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.

Requirement of Smad4 from Ocular Surface Ectoderm for Retinal Development.

Microphthalmia is characterized by abnormally small eyes and usually retinal dysplasia, accounting for up to 11% of the blindness in children. Right now there is no effective treatment for the disease, and the underlying mechanisms, especially how retinal dysplasia develops from microphthalmia and whether it depends on the signals from lens ectoderm are still unclear. Mutations in genes of the TGF-ß superfamily have been noted in patients with microphthalmia. Using conditional knockout mice, here we address the question that whether ocular surface ectoderm-derived Smad4 modulates retinal development. We found that loss of Smad4 specifically on surface lens ectoderm leads to microphthalmia and dysplasia of retina. Retinal dysplasia in the knockout mice is caused by the delayed or failed differentiation and apoptosis of retinal cells. Microarray analyses revealed that members of Hedgehog and Wnt signaling pathways are affected in the knockout retinas, suggesting that ocular surface ectoderm-derived Smad4 can regulate Hedgehog and Wnt signaling in the retina. Our studies suggest that defective of ocular surface ectoderm may affect retinal development.

A Novel Mutation in OTX2 Causes Combined Pituitary Hormone Deficiency, Bilateral Microphthalmia, and Agenesis of the Left Internal Carotid Artery.

BACKGROUND: Mutations in OTX2 cause hypopituitarism, ranging from isolated growth hormone deficiency to combined pituitary hormone deficiency (CPHD), which are commonly detected in association with severe eye abnormalities, including anophthalmia or microphthalmia. Pituitary phenotypes of OTX2 mutation carriers are highly variable; however, ACTH deficiency during the neonatal period is not common in previous reports. OBJECTIVE: We report a novel missense OTX2 (R89P) mutation in a CPHD patient with severe hypoglycemia in the neonatal period due to ACTH deficiency, bilateral microphthalmia, and agenesis of the left internal carotid artery (ICA). RESULTS: We identified a novel heterozygous mutation in OTX2 (c.266G>C, p.R89P). R89P OTX2 showed markedly reduced transcriptional activity of HESX1 and POU1F1 reporters compared with wild-type OTX2. A dominant negative effect was noted only in the transcription analysis with POU1F1 promoter. Electrophoretic mobility shift assay experiments showed that R89P OTX2 abrogated DNA-binding ability. CONCLUSION: OTX2 mutations can cause ACTH deficiency in the neonatal period. Our study also shows that OTX2 mutations are associated with agenesis of the ICA. To the best of our knowledge, this is the first report of a transcription factor gene mutation, which was identified due to agenesis of the ICA of a patient with CPHD. This study extends our understanding of the phenotypic features, molecular mechanism, and developmental course associated with mutations in OTX2.