Anterior Segment Development Research Articles

Keratin 8/18a.1 Expression Influences Embryonic Neural Crest Cell Dynamics and Contributes to Postnatal Corneal Regeneration in Zebrafish.

A complete understanding of neural crest cell mechanodynamics during ocular development will provide insight into postnatal neural crest cell contributions to ophthalmic abnormalities in adult tissues and inform regenerative strategies toward injury repair. Herein, single-cell RNA sequencing in zebrafish during early eye development revealed keratin intermediate filament genes krt8 and krt18a.1 as additional factors expressed during anterior segment development. In situ hybridization and immunofluorescence microscopy confirmed krt8 and krt18a.1 expression in the early neural plate border and migrating cranial neural crest cells. Morpholino oligonucleotide (MO)-mediated knockdown of K8 and K18a.1 markedly disrupted the migration of neural crest cell subpopulations and decreased neural crest cell marker gene expression in the craniofacial region and eye at 48 h postfertilization (hpf), resulting in severe phenotypic defects reminiscent of neurocristopathies. Interestingly, the expression of K18a.1, but not K8, is regulated by retinoic acid (RA) during early-stage development. Further, both keratin proteins were detected during postnatal corneal regeneration in adult zebrafish. Altogether, we demonstrated that both K8 and K18a.1 contribute to the early development and postnatal repair of neural crest cell-derived ocular tissues.

Primary Cilium in Neural Crest Cells Crucial for Anterior Segment Development and Corneal Avascularity.

Intraflagellar transport 46 (IFT46) is an integral subunit of the IFT-B complex, playing a key role in the assembly and maintenance of primary cilia responsible for transducing signaling pathways. Despite its predominant expression in the basal body of cilia, the precise role of Ift46 in ocular development remains undetermined. This study aimed to elucidate the impact of neural crest (NC)-specific deletion of Ift46 on ocular development. NC-specific conditional knockout mice for Ift46 (NC-Ift46F/F) were generated by crossing Ift46F mice with Wnt1-Cre2 mice, enabling the specific deletion of Ift46 in NC-derived cells (NCCs). Sonic Hedgehog (Shh) and Notch signaling activities in NC-Ift46F/F mice were evaluated using Gli1lacZ and CBF:H2B-Venus reporter mice, respectively. Cell fate mapping was conducted using ROSAmTmG reporter mice. The deletion of Ift46 in NCCs resulted in a spectrum of ocular abnormalities, including thickened corneal stroma, hypoplasia of the anterior chamber, irregular iris morphology, and corneal neovascularization. Notably, this deletion led to reduced Shh signal activity in the periocular mesenchyme, sustained expression of key transcription factors Foxc1, Foxc2 and Pitx2, along with persistent cell proliferation. Additionally, it induced increased Notch signaling activity and the development of ectopic neovascularization within the corneal stroma. The absence of primary cilia due to Ift46 deficiency in NCCs is associated with anterior segment dysgenesis (ASD) and corneal neovascularization, suggesting a potential link to Axenfeld-Rieger syndrome, a disorder characterized by ASD. This underscores the pivotal role of primary cilia in ensuring proper anterior segment development and maintaining an avascular cornea.

Wide-field digital imaging system for assessing ocular anterior segment development in very preterm infants.

This study aims to longitudinally investigate developments of the anterior segment in very preterm infants who exhibit normal retinal development outcomes by utilizing a wide-field digital imaging system. Between June 2021 and June 2022, neonates with a birth weight of <1500 g and/or a gestational age (GA) of less than 32 weeks were included in this study. The participants underwent regular ocular examinations, including sequential evaluations of the anterior segment and the retina, at intervals of 2-5 weeks, starting from birth and continuing until they reached a corrected GA of 48 weeks. Term neonates were selected as normal controls for the study. The study recorded the weight and GA of subjects at the time of examination, as well as indicators of abnormal development in the anterior segment. A total of 48 very preterm infants with normal retinal developmental outcomes were enrolled. The control group included 59 full-term infants. Common anterior segment eye abnormalities such as persistent hyperplasia of primary vitreous, persistent pupillary membranes, iris vessels, and anterior chamber angle vessels gradually subsided with the period in very preterm infants. The vascularity of the iris was substantially higher than in term controls (P < 0.05) at term gestation. The imaging of iris vessels and anterior chamber angle vessels in very preterm infants exhibited a decline at 46 and 47 weeks, respectively, which occurred slightly later compared to term infants. In very preterm infant s with normal outcomes, although the developmental process is delayed, they may form a normal anterior segment structure similar to that of full-term infants in the late stages, which is followed up by the wide-field digital imaging system.

Development of Anterior Segment Focused Biologic Therapies to Regenerate Corneal Tissue for the Treatment of Disease: Drug Development Experience.

On February 24-27, 2021, the Association for Ocular Pharmacology and Therapeutics (AOPT) held its 15th biennial scientific meeting online. The meeting was organized by Dr. Sanjoy Bhattacharya of the University of Miami in conjunction with the board of trustees of the AOPT. The 3-day conference was attended by academic scientists, clinicians, and industry and regulatory professionals. The theme of the meeting was Restoring Vision through Regeneration and it was sponsored, in part, by the National Institutes of Health, Bright Focus, Regeneron, and Santen (USA). During the 3 days of the meeting, presentations from several sessions explored different aspects of regenerative medicine in ophthalmology, including optic nerve regeneration, drugs and devices in glaucoma, retinal neuroprotection and plasticity, visual perception, and degeneration of trabecular meshwork. This article summarizes the proceedings of the session on corneal regenerative medicine research and discusses emerging concepts in drug development for corneal epithelial and endothelial regeneration. Since the meeting in 2021, several of these concepts have advanced to clinical-stage therapies, but so far as of 2023, none has been approved by regional regulatory authorities in the United States. One form of corneal endothelial cell therapy has been approved in Japan and only for bullous keratopathy. Ongoing work is proceeding in the United States and other countries. Clinical Registration No: National Clinical Trials 04894110, 04812667; Japan Registry for Clinical Trials a031210199.

First evidence of SOX2 mutations in Peters' anomaly: Lessons from molecular screening of 95 patients.

Peters' anomaly (PA) is a rare anterior segment dysgenesis characterized by central corneal opacity and irido-lenticulo-corneal adhesions. Several genes are involved in syndromic or isolated PA (B3GLCT, PAX6, PITX3, FOXE3, CYP1B1). Some copy number variations (CNVs) have also been occasionally reported. Despite this genetic heterogeneity, most of patients remain without genetic diagnosis. We retrieved a cohort of 95 individuals with PA and performed genotyping using a combination of comparative genomic hybridization, whole genome, exome and targeted sequencing of 119 genes associated with ocular development anomalies. Causative genetic defects involving 12 genes and CNVs were identified for 1/3 of patients. Unsurprisingly, B3GLCT and PAX6 were the most frequently implicated genes, respectively in syndromic and isolated PA. Unexpectedly, the third gene involved in our cohort was SOX2, the major gene of micro-anophthalmia. Four unrelated patients with PA (isolated or with microphthalmia) were carrying pathogenic variants in this gene that was never associated with PA before. Here we described the largest cohort of PA patients ever reported. The genetic bases of PA are still to be explored as genetic diagnosis was unavailable for 2/3 of patients. Nevertheless, we showed here for the first time the involvement of SOX2 in PA, offering new evidence for its role in corneal transparency and anterior segment development.

Deletion of transcription factor AP-2β from the developing murine trabecular meshwork region leads to progressive glaucomatous changes.

Glaucoma is one of the leading causes of irreversible blindness and can result from abnormalities in anterior segment structures required for aqueous humor outflow, including the trabecular meshwork (TM) and Schlemm's canal (SC). Transcription factors such as AP-2β play critical roles in anterior segment development. Here, we show that the Mgp-Cre knock-in (Mgp-Cre.KI) mouse can be used to target the embryonic periocular mesenchyme giving rise to the TM and SC. Fate mapping of male and female mice indicates that AP-2β loss causes a decrease in iridocorneal angle cells derived from Mgp-Cre.KI-expressing populations compared to controls. Moreover, histological analyses revealed peripheral iridocorneal adhesions in AP-2β mutants that were accompanied by a decrease in expression of TM and SC markers, as observed using immunohistochemistry. In addition, rebound tonometry showed significantly higher intraocular pressure (IOP) that was correlated with a progressive significant loss of retinal ganglion cells, reduced retinal thickness, and reduced retinal function, as measured using an electroretinogram, in AP-2β mutants compared with controls, reflecting pathology described in late-stage glaucoma patients. Importantly, elevated IOP in AP-2β mutants was significantly reduced by treatment with latanoprost, a prostaglandin analog that increases unconventional outflow. These findings demonstrate that AP-2β is critical for TM and SC development, and that these mutant mice can serve as a model for understanding and treating progressive human primary angle-closure glaucoma.

Conditional Deletion of AP-2β in the Periocular Mesenchyme of Mice Alters Corneal Epithelial Cell Fate and Stratification.

The cornea is an anterior eye structure specialized for vision. The corneal endothelium and stroma are derived from the periocular mesenchyme (POM), which originates from neural crest cells (NCCs), while the stratified corneal epithelium develops from the surface ectoderm. Activating protein-2β (AP-2β) is highly expressed in the POM and important for anterior segment development. Using a mouse model in which AP-2β is conditionally deleted in the NCCs (AP-2β NCC KO), we investigated resulting corneal epithelial abnormalities. Through PAS and IHC staining, we observed structural and phenotypic changes to the epithelium associated with AP-2β deletion. In addition to failure of the mutant epithelium to stratify, we also observed that Keratin-12, a marker of the differentiated epithelium, was absent, and Keratin-15, a limbal and conjunctival marker, was expanded across the central epithelium. Transcription factors PAX6 and P63 were not observed to be differentially expressed between WT and mutant. However, growth factor BMP4 was suppressed in the mutant epithelium. Given the non-NCC origin of the epithelium, we hypothesize that the abnormalities in the AP-2β NCC KO mouse result from changes to regulatory signaling from the POM-derived stroma. Our findings suggest that stromal pathways such as Wnt/β-Catenin signaling may regulate BMP4 expression, which influences cell fate and stratification.

Генетичні аспекти первинної відкритокутової глаукоми

Glaucoma is one of the widespread eye diseases causing visual disturbances and even blindness. Almost 15% of blindness worldwide is due to glaucoma. One of the factors of glaucoma development is heredity. Currently, identification and diagnosis of new glaucoma cases is achieved either by routine screening or examinations prompted by perceived risk. The factors associated with the pathogenesis of glaucoma include high intraocular pressure (IOP), aging, decreased blood flow and genetic factors. Traditional vision screening for disorders like primary open-angle glaucoma (POAG) is time-consuming and costly. POAG is the most common type of glaucoma which has no obvious abnormality in the eye that points to a cause. Although mutations in several genes, including myocilin, optineurin, and CYP1B1 are associated with the disease, these genes account for less than 10% of cases worldwide. The paper reviews genetic studies in POAG. The genetic basis for the development of glaucoma and a variety of its related syndromes is considered. CYP1B1 is a member of a family of cytochrome P450 genes known to encode enzymes that metabolize and detoxify both endogenous and exogenous molecules, although their activity is not limited to detoxification. The human CYP superfamily contains 57 functional genes and 58 pseudogenes. Two specific substrates of CYP1B1 (estradiols and retinoic acid) could contribute to ocular development and specifically to the development of the ocular anterior segment.

Novel Mutations in COL6A3 That Associated With Peters' Anomaly Caused Abnormal Intracellular Protein Retention and Decreased Cellular Resistance to Oxidative Stress.

Peters’ anomaly (PA) is a rare form of anterior segment dysgenesis characterized by central corneal opacity accompanied by iridocorneal or lenticulo-corneal adhesions. Although genetic mutations, particularly those affecting transcription factors that function in eye development, are known to cause PA, the etiology of this disease remains poorly understood. In this study, 23 patients with PA were recruited for panel sequencing. Four out of 23 patients were found to carry variants in known PA causal genes, PITX2 and PITX3. More importantly, two homozygous mutations (NM_057164: p.Val86Ala and p.Arg689Cys) in the COL6A3 gene (collagen type VI alpha-3 chain) that correlated with the phenotype of type I PA were identified, and then validated by following whole-exome sequencing. The expression profile of the COL6A3 gene in the cornea and the impact of the mutations on protein physiological processing and cellular function were further explored. It was shown that COL6A3 presented relatively high expression in the cornea. The mutant COL6A3 protein was relatively retained intracellularly, and its expression reduced cellular resistance to oxidative stress through an enhanced endoplasmic reticulum stress response. Taken together, our findings expanded the known genetic spectrum of PA, and provided evidence for the involvement of COL6A3 or collagen VI in ocular anterior segment development, thereby offering new insight for future investigations targeting PA.

CPAMD8 loss-of-function underlies non-dominant congenital glaucoma with variable anterior segment dysgenesis and abnormal extracellular matrix.

Abnormal development of the ocular anterior segment may lead to a spectrum of clinical phenotypes ranging from primary congenital glaucoma (PCG) to variable anterior segment dysgenesis (ASD). The main objective of this study was to identify the genetic alterations underlying recessive congenital glaucoma with ASD (CG-ASD). Next-generation DNA sequencing identified rare biallelic CPAMD8 variants in four patients with CG-ASD and in one case with PCG. CPAMD8 is a gene of unknown function and recently associated with ASD. Bioinformatic and in vitro functional evaluation of the variants using quantitative reverse transcription PCR and minigene analysis supported a loss-of-function pathogenic mechanism. Optical and electron microscopy of the trabeculectomy specimen from one of the CG-ASD cases revealed an abnormal anterior chamber angle, with altered extracellular matrix, and apoptotic trabecular meshwork cells. The CPAMD8 protein was immunodetected in adult human ocular fluids and anterior segment tissues involved in glaucoma and ASD (i.e., aqueous humor, non-pigmented ciliary epithelium, and iris muscles), as well as in periocular mesenchyme-like cells of zebrafish embryos. CRISPR/Cas9 disruption of this gene in F0 zebrafish embryos (96 hpf) resulted in varying degrees of gross developmental abnormalities, including microphthalmia, pharyngeal maldevelopment, and pericardial and periocular edemas. Optical and electron microscopy examination of these embryos showed iridocorneal angle hypoplasia (characterized by altered iris stroma cells, reduced anterior chamber, and collagen disorganized corneal stroma extracellular matrix), recapitulating some patients' features. Our data support the notion that CPAMD8 loss-of-function underlies a spectrum of recessive CG-ASD phenotypes associated with extracellular matrix disorganization and provide new insights into the normal and disease roles of this gene.

Ciliary margin-derived BMP4 does not have a major role in ocular development.

Heterozygous Bmp4 mutations in humans and mice cause severe ocular anterior segment dysgenesis (ASD). Abnormalities include pupil displacement, corneal opacity, iridocorneal adhesions, and variable intraocular pressure, as well as some retinal and vascular defects. It is presently not known what source of BMP4 is responsible for these defects, as BMP4 is expressed in several developing ocular and surrounding tissues. In particular, BMP4 is expressed in the ciliary margins of the optic cup which give rise to anterior segment structures such as the ciliary body and iris, making it a good candidate for the required source of BMP4 for anterior segment development. Here, we test whether ciliary margin-derived BMP4 is required for ocular development using two different conditional knockout approaches. In addition, we compared the conditional deletion phenotypes with Bmp4 heterozygous null mice. Morphological, molecular, and functional assays were performed on adult mutant mice, including histology, immunohistochemistry, in vivo imaging, and intraocular pressure measurements. Surprisingly, in contrast to Bmp4 heterozygous mutants, our analyses revealed that the anterior and posterior segments of Bmp4 conditional knockouts developed normally. These results indicate that ciliary margin-derived BMP4 does not have a major role in ocular development, although subtle alterations could not be ruled out. Furthermore, we demonstrated that the anterior and posterior phenotypes observed in Bmp4 heterozygous animals showed a strong propensity to co-occur, suggesting a common, non-cell autonomous source for these defects.

Long-term effects of anti-VEGF therapy for retinopathy of prematurity

Intravitreal anti-VEGF therapy is ahighly efficacious new treatment option for retinopathy of prematurity (ROP) with significant advantages over conventional therapy using retinal laser coagulation in selected cases. With growing experience in the clinical application over the last years, data about the potential long-term effects of this therapeutic approach are increasingly becoming available, such as those related to ROP-associated myopia, neurodevelopment and late recurrences of ROP. Knowledge of these effects is of direct relevance for the clinical management of affected children. The article is based on aliterature review of the covered topics. In addition to its therapeutic effect on retinal pathology, anti-VEGF therapy in ROP can also reduce ROP-associated myopia, most likely due to anormalization of anterior segment development. As the unresolved question of potential negative effects of bevacizumab on neurodevelopment remains of concern, the use of alternative treatment options, such as ranibizumab or laser coagulation should be considered. Treatment-requiring recurrences of ROP following anti-VEGF therapy have been reported as late as 69weeks postmenstrual age, indicating that long-term frequent ophthalmological follow-up examinations are required. Long-term effects of anti-VEGF therapy in ROP differ significantly from alternative treatment options such as laser coagulation. These differences are of relevance for the choice of treatment modality and the follow-up regimen of treated children.

An analysis of anterior segment development in the chicken eye

Precise anterior segment (AS) development in the vertebrate eye is essential for maintaining ocular health throughout life. Disruptions to genetic programs can lead to severe structural AS disorders at birth, while more subtle AS defects may disrupt the drainage of ocular fluids and cause dysregulation of intraocular pressure homeostasis, leading to progressive vision loss. To date, the mouse has served as the major model to study AS development and pathogenesis. Here we present an accurate histological atlas of chick AS formation throughout eye development, with a focus on the formation of drainage structures. We performed expression analyses for a panel of known AS disorder genes, and showed that chick PAX6 was localized to cells of neural retina and surface ectoderm derived structures, displaying remarkable similarity to the mouse. We provide a comparison to mouse and humans for chick AS developmental sequences and structures and confirm that AS development shares common features in all three species, although the main AS structures in the chick are developed prior to hatching. These features enable the unique experimental advantages inherent to chick embryos, and we therefore propose the chick as an appropriate additional model for AS development and disease.

Retinal pathology in the PPCD1 mouse.

Retinal phenotypes of the PPCD1 mouse, a mouse model of posterior polymorphous corneal dystrophy, have been characterized. PPCD1 mice on the DBA/2J background (D2.Ppcd1) have previously been reported to develop an enlarged anterior chamber due to epithelialization and proliferation of the corneal endothelium and subsequent blockage of the iridocorneal angle. Results presented here show that D2.Ppcd1 mice develop increased intraocular pressure (IOP), with measurements at three months of age revealing significant increases in IOP. Significant retinal ganglion cell layer cell loss is observed at five months of age. D2.Ppcd1 animals also exhibit marked degeneration of the outer nuclear layer in association with hyperplasia of the retinal pigment epithelium. Evidence of retinal detachment is present as early as three weeks of age. By 3.5 months of age, focal areas of outer nuclear layer loss are observed. Although the GpnmbR150X mutation leads to increased IOP and glaucoma in DBA/2J mice, development of anterior segment and retinal defects in D2.Ppcd1 animals does not depend upon presence of the GpnmbR150X mutation.

Generation of a new mouse model of glaucoma characterized by reduced expression of the AP-2\u03b2 and AP-2\u03b4 proteins

We generated 6 transgenic lines with insertion of an expression plasmid for the R883/M xanthine dehydrogenase (XDH) mutant protein. Approximately 20% of the animals deriving from one of the transgenic lines show ocular abnormalities and an increase in intra-ocular pressure which are consistent with glaucoma. The observed pathologic phenotype is not due to expression of the transgene, but rather the consequence of the transgene insertion site, which has been defined by genome sequencing. The insertion site maps to chromosome 1qA3 in close proximity to the loci encoding AP-2β and AP-2δ, two proteins expressed in the eye. The insertion leads to a reduction in AP-2β and AP-2δ levels. Down-regulation of AP-2β expression is likely to be responsible for the pathologic phenotype, as conditional deletion of the Tfap2b gene in the neural crest has recently been shown to cause defective development of the eye anterior segment and early-onset glaucoma. In these conditional knock-out and our transgenic mice, the morphological/histological features of the glaucomatous pathology are surprisingly similar. Our transgenic mouse represents a model of angle-closure glaucoma and a useful tool for the study of the pathogenesis and the development of innovative therapeutic strategies.

Differences in neural crest sensitivity to ethanol account for the infrequency of anterior segment defects in the eye compared with craniofacial anomalies in a zebrafish model of fetal alcohol syndrome.

Ethanol (ETOH) exposure during pregnancy is associated with craniofacial and neurologic abnormalities, but infrequently disrupts the anterior segment of the eye. In these studies, we used zebrafish to investigate differences in the teratogenic effect of ETOH on craniofacial, periocular, and ocular neural crest. Zebrafish eye and neural crest development was analyzed by means of live imaging, TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) assay, immunostaining, detection of reactive oxygen species, and in situ hybridization. Our studies demonstrated that foxd3-positive neural crest cells in the periocular mesenchyme and developing eye were less sensitive to ETOH than sox10-positive craniofacial neural crest cells that form the pharyngeal arches and jaw. ETOH increased apoptosis in the retina, but did not affect survival of periocular and ocular neural crest cells. ETOH also did not increase reactive oxygen species within the eye. In contrast, ETOH increased ventral neural crest apoptosis and reactive oxygen species production in the facial mesenchyme. In the eye and craniofacial region, sod2 showed high levels of expression in the anterior segment and in the setting of Sod2 knockdown, low levels of ETOH decreased migration of foxd3-positive neural crest cells into the developing eye. However, ETOH had minimal effect on the periocular and ocular expression of transcription factors (pitx2 and foxc1) that regulate anterior segment development. Neural crest cells contributing to the anterior segment of the eye exhibit increased ability to withstand ETOH-induced oxidative stress and apoptosis. These studies explain the rarity of anterior segment dysgenesis despite the frequent craniofacial abnormalities in fetal alcohol syndrome. Birth Defects Research 109:1212-1227, 2017. © 2017 Wiley Periodicals, Inc.

Foxc1 and Foxc2 in the Neural Crest Are Required for Ocular Anterior Segment Development.

PurposeThe large Forkhead (Fox) transcription factor family has essential roles in development, and mutations cause a wide range of ocular and nonocular disease. One member, Foxc2 is expressed in neural crest (NC)-derived periocular mesenchymal cells of the developing murine eye; however, its precise role in the development, establishment, and maintenance of the ocular surface has yet to be investigated.MethodsTo specifically delete Foxc2 from NC-derived cells, conditional knockout mice for Foxc2 (NC-Foxc2−/−) were generated by crossing Foxc2F mice with Wnt1-Cre mice. Similarly, we also generated compound NC-specific mutations of Foxc2 and a closely related gene, Foxc1 (NC-Foxc1−/−;NC-Foxc2−/−) in mice.ResultsNeural crest-Foxc2−/− mice show abnormal thickness in the peripheral-to-central corneal stroma and limbus and displaced pupils with irregular iris. The neural crest-specific mutation in Foxc2 also leads to ectopic neovascularization in the cornea, as well as impaired ocular epithelial cell identity and corneal conjunctivalization. Compound, NC-specific Foxc1; Foxc2 homozygous mutant mice have more severe defects in structures of the ocular surface, such as the cornea and eyelids, accompanied by significant declines in the expression of another key developmental factor, Pitx2, and its downstream effector Dkk2, which antagonizes canonical Wnt signaling.ConclusionsThe neural crest-Foxc2 mutation is associated with corneal conjunctivalization, ectopic corneal neovascularization, and disrupted ocular epithelial cell identity. Furthermore, Foxc2 and Foxc1 cooperatively function in NC-derived mesenchymal cells to ensure proper morphogenesis of the ocular surface via the regulation of Wnt signaling. Together, Foxc2 is required in the NC lineage for mesenchymal-epithelial interactions in corneal and ocular surface development.

Update on Anterior Segment Development with Emphasis on Genetics and Correlation with Pathogenesis of Developmental &amp; Primary Open Angle Glaucoma

The ocular anterior segment structures are derived from periocular mesenchyme which consists of neural crest cells and cranial paraxial mesoderm Many embryological facts have been developed based on the fates of neural crest and mesoderm in mice and in chick The interactions between the ocular mesenchyme and the surface ectoderm derived cells are also essential for the coordination of anterior segment development These interactions are mediated by several transcription factors expressed in both the epithelial and mesenchymal cells and are being extensively studied Anterior Segment dysgenesis ASD is a spectrum of disorders of variable phenotypic expressions caused by abnormal migration and differentiation of neural crest cells Patients with ASD are susceptible to develop infantile glaucoma congenital endothelial dystrophy sclerocornea and aniridia There has been an evident overlapping observation in the genetic mutations between the ASD phenotypic spectrum and glaucoma especially the primary congenital glaucoma PCG since it involves abnormal development of Schlemm rsquo s canal and the drainage structures In this review we are highlighting the steps in the embryological development of the anterior segment chamber structures We also present the role of various transcription factors and link the above information to some of the genetic abnormalities which are known in association with the pathogenesis of glaucoma

Refractive errors in premature infants with retinopathy of prematurity after anti-vascular endothelial growth factor (anti-VEGF) therapy

Background/Aim. Retinopathy of prematurity (ROP) is a vasoproliferative retinopathy which affects the blood vessels of the retina during its development. The aim of this study was to evaluate the incidence and the degree of refractive errors in premature infants with severe ROP treated with antivascular endothelial growth factor (anti-VEGF) (bevacizumab). Methods. This prospective study included 21 patients (42 eyes) nine months old who received intravitreal injection of anti-VEGF therapy. The control group consisted of 45 patients (90 eyes) who were subjected to laser treatment. In cycloplegia each patient underwent retinoscopy, keratorefractometry, and A-scan ultrasonography. Results. Myopia was present in 47.62% of the eyes in the study group and in 33.33% of the eyes in the control group, but there were no statistically significant differences between these groups. Seven (16.67%) eyes in the study group and 17 (18.89%) eyes in the control group were discovered to have high myopia (SE? spherical equivalents &lt; -3.0 D ? dioptre). Clinically significant hypermetropia was higher in the study group (47.62%) than in the control group (34.44%), but with no statistically significant difference. In addition, high hypermetropia was significantly greater in the control group (15.56%) than in the study group (11.90%) (p &lt; 0.001). Astigmatism was more common in the control group than in the study group (81.11% vs 71.43%, respectively), especially high astigmatism (56% vs 43%, respectively). Also the more common form of astigmatism was with the rule (WTR) both in the study and the control group (42.86% vs 55.56%, respectively). Anisometropia was significantly greater in the control group (24.44%) than in the study group (9.52%) (p &lt; 0.05). The children from the study group had significantly greater lens thickness, and a shorter anterior chamber depth than children from the control group (p &lt; 0.01). There was no significant difference in the axial length of the eye between the groups. Conclusion. At the 9-month follow-up myopia was present in the patients with severe ROP treated with anti-VEGF, but high myopia was present to a lesser degree than in the laser treated patients. This difference is possibly related to anterior segment development. Research into the longer-term refractive outcomes is necessary with observation of the biometric components, visual acuity, and the visual field in order to monitor the real effects of this therapy.

Mutations in CPAMD8 Cause a Unique Form of Autosomal-Recessive Anterior Segment Dysgenesis

Anterior segment dysgeneses (ASDs) comprise a spectrum of developmental disorders affecting the anterior segment of the eye. Here, we describe three unrelated families affected by a previously unclassified form of ASD. Shared ocular manifestations include bilateral iris hypoplasia, ectopia lentis, corectopia, ectropion uveae, and cataracts. Whole-exome sequencing and targeted Sanger sequencing identified mutations in CPAMD8 (C3 and PZP-like alpha-2-macroglobulin domain-containing protein 8) as the cause of recessive ASD in all three families. A homozygous missense mutation in the evolutionarily conserved alpha-2-macroglobulin (A2M) domain of CPAMD8, c.4351T>C (p. Ser1451Pro), was identified in family 1. In family 2, compound heterozygous frameshift, c.2352_2353insC (p.Arg785Glnfs∗23), and splice-site, c.4549-1G>A, mutations were identified. Two affected siblings in the third family were compound heterozygous for splice-site mutations c.700+1G>T and c.4002+1G>A. CPAMD8 splice-site mutations caused aberrant pre-mRNA splicing in vivo or in vitro. Intriguingly, our phylogenetic analysis revealed rodent lineage-specific CPAMD8 deletion, precluding a developmental expression study in mice. We therefore investigated the spatiotemporal expression of CPAMD8 in the developing human eye. RT-PCR and in situ hybridization revealed CPAMD8 expression in the lens, iris, cornea, and retina early in development, including strong expression in the distal tips of the retinal neuroepithelium that form the iris and ciliary body, thus correlating CPAMD8 expression with the affected tissues. Our study delineates a unique form of recessive ASD and defines a role for CPAMD8, a protein of unknown function, in anterior segment development, implying another pathway for the pathogenicity of ASD.