CYP1B1 mutations in patients with primary congenital glaucoma from Saudi Arabia

Genetic changes and testing associated with childhood glaucoma: A systematic review

Many forms of childhood glaucoma have been associated with underlying genetic changes, and variants in many genes have been described. Currently, testing is variable as there are no widely accepted guidelines for testing. This systematic review aimed to summarize the literature describing genetic changes and testing practices in childhood glaucoma. This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic review and Meta-Analyses (PRISMA) 2020 guidelines and registered with Prospero (ID CRD42023400467). A comprehensive review of Pubmed, Embase, and Cochrane databases was performed from inception through March 2, 2023 using the search terms: (glaucoma) AND (pediatric OR childhood OR congenital OR child OR infant OR infantile) AND (gene OR genetic OR genotype OR locus OR genomic OR mutation OR variant OR test OR screen OR panel). Information was extracted regarding genetic variants including genotype-phenotype correlation. Risk of bias was assessed using the Newcastle-Ottawa Scale. Of 1,916 records screened, 196 studies met inclusion criteria and 53 genes were discussed. Among study populations, mean age±SD at glaucoma diagnosis was 8.94±9.54 years and 50.4% were male. The most common gene discussed was CYP1B1, evaluated in 109 (55.6%) studies. CYP1B1 variants were associated with region and population-specific prevalence ranging from 5% to 86% among those with primary congenital glaucoma. MYOC variants were discussed in 31 (15.8%) studies with prevalence up to 36% among patients with juvenile open angle glaucoma. FOXC1 variants were discussed in 25 (12.8%) studies, which demonstrated phenotypic severity dependent on degree of gene expression and type of mutation. Overall risk of bias was low; the most common domains of bias were selection and comparability. Numerous genes and genetic changes have been associated with childhood glaucoma. Understanding the most common genes as well as potential genotype-phenotype correlation has the potential to improve diagnostic and prognostic outcomes for children with glaucoma.

Effect of Trabeculodescemetic Window Perforation in Deep Sclerectomy on Intraocular Pressure in Primary Congenital Glaucoma

INTRODUCTION

Primary congenital glaucoma causes vision loss if intraocular pressure is uncontrolled. Nonpenetrating deep sclerectomy is effective in treating primary congenital glaucoma. However, the effects of inadvertent trabeculodescemetic window perforation remain unclear.

METHODS

This retrospective cohort study included patients with primary congenital glaucoma who underwent nonpenetrating deep sclerectomy between 2014 and 2021. The perforation group had intraoperative trabeculodescemetic window perforations; the non-perforation group did not. The primary outcome was intraocular pressure between the groups over 15 months. The secondary outcomes included surgical success and complications.

RESULTS

The study included 74 eyes of 44 patients. The cohort comprised 31 perforated and 43 non-perforated eyes. Both groups showed significant intraocular pressure reduction without significant between-group differences in complete (68 vs. 77%), qualified (19 vs. 9%), or failed (13 vs. 14%) treatments. The median intraocular pressure decreased from 39 to 14 mmHg in the perforation group and 35 to 12 mmHg in the non-perforation group. Of the 74 treated eyes, 68 (92%) showed no complications.

CONCLUSIONS

An inadvertent trabeculodescemetic window perforation during nonpenetrating deep sclerectomy for primary congenital glaucoma did not significantly affect intraocular pressure outcomes compared to non-perforated cases over 15 months. Nonpenetrating deep sclerectomy reduced intraocular pressure regardless of intraoperative perforation in patients with primary congenital glaucoma. Perforation of the trabeculodescemetic window was associated with a low incidence of postoperative complications.

Glaucoma among Saudi Arabian population: a scoping review

Despite its high risk of leading to permanent visual dysfunction, glaucoma remains underdiagnosed in primary care settings. About 11% of glaucoma patients in Saudi Arabia end up with bilateral blindness. This scoping review investigates and presents results on the glaucoma profile, including its prevalence, knowledge, attitude, and practice of Saudi Arabians towards the disease. An online search using four databases through online software (www.rayyan.ai) was performed to extract the relevant articles. Out of 76 records, 21 articles were eligible for the analysis. All included studies were published between the years 2014 and 2022. Most studies were in Riyadh city, followed by Jeddah. All participants (n=11 388) were adults >18 years old, and male participants were generally higher than females. The findings showed poor knowledge of glaucoma among the general population, while the knowledge among glaucoma patients was acceptable. The attitude was positive, while the compliance and practice were fair. More educational programs about glaucoma, its risk to the eyes, and the overall quality of life are highly recommended.

Screening of candidate genes at GLC3B and GLC3C loci in Chinese primary congenital glaucoma patients with targeted next generation sequencing

BACKGROUND

Primary congenital glaucoma (PCG) is characterized by developmental abnormalities of the anterior chamber angle. Although several genes have been associated with PCG, pathogenic mutations could only be detected in about 20% of Chinese patients. GLC3B (1p36.2-36.1) and GLC3C (14q24.3) loci were previously identified in PCG pedigrees via linkage analysis. However, no causative genes were reported in these loci. This study was designed to search for novel PCG-related genes in these genetic regions.

MATERIALS AND METHODS

DNA samples from 100 PCG patients and 200 normal controls were pooled and sequenced using a customized panel of 133 positional candidate genes located around GLC3B and GLC3C loci (±1Mb). PCG-related genes were prioritized by the distribution of variants between patients and controls. Confirmation of selected variants and co-segregation analysis were performed using Sanger sequencing.

RESULTS

Patient and control group contained 116 and 147 rare variants respectively after screening. Three genes (ZC2HC1C, VPS13D, and PGF) were prioritized according to the distribution of variants between the two groups. Rare variants of PGF were only identified in PCG patients.

CONCLUSIONS

To the best of our knowledge, this is the first study aiming at exploring novel PCG-related genes at GLC3B and GLC3C loci. Our preliminary results suggest that there are potential associations between ZC2HC1C, VPS13D, PGF, and PCG. However, larger cohort studies and functional assays are required to provide further evidence for the proposed genotype-phenotype association.

Geographical Variability in CYP1B1 Mutations in Primary Congenital Glaucoma

Primary congenital glaucoma (PCG) is a rare type of glaucoma that is inherited in an autosomal recessive manner. PCG can lead to blindness if not detected early in children aged 3 or younger. PCG varies in presentation among various populations, where disease presentation and disease severity vary by mutation. The most common gene implicated in PCG is cytochrome p450 1B1 (CYP1B1). Here, we sought to review the literature for mutations in CYP1B1 and their presentation among different populations. Areas of interest include recent findings on disease presentation and potential implications on our understanding of PCG pathophysiology.

Meta-analysis of CYP1B1 gene mutations in primary congenital glaucoma patients

Primary congenital glaucoma (PCG) is a rare and severe form of glaucoma and is usually transmitted as an autosomal-recessive disease. However, PCG is more common in certain ethnic and geographic groups where consanguineous relationships are common. The importance of this review is to inspect the mutations in the cytochrome P450 1B1 gene (CYP1B1) and to highlight the interest of the genetic study of CYP1B1 mutations. An in-depth study was carried out by the following search engines: PubMed, Scopus, clinic key and direct science for articles that have been published from 2011 until 2020. One hundred and sixty-one mutations were found in 1641 tested patients and three families, including 78 novel mutations. We identified a no significant difference in the sex ratio and the bilaterality was reported in the majority of patients. We have shown through this study that inbreeding plays an important role in the pathogenesis of PCG transmission compared to the sporadic mutations that have been found in some cases. The majority of the included studies were from ASIA (64.3%), followed by Europe (17.85%), America (10.71%) and Africa (7.14%). The first and most common mutation in our study is 182 G>A (p.Gly61Glu). It was identified in Iran, Portugal and Saudi Arabia and for the first time in Brazil and Vietnam. The greatest number of mutations in common is p.Gly61Glu. Mainly within five countries: Iran, Portugal, Saudi Arabia, Brazil and Vietnam. The first step in PCG screening should be a genetic test looking for founder and common mutation coupled with a clinical examination.

Arnold-Chiari Malformation Type II and CYP1B1 Congenital Glaucoma: A Possible Association

Background

We describe a case of an infant with Arnold-Chiari Malformation Type II (ACM-II) who was born with lumbosacral myelomeningocele, hydrocephalus, and primary congenital glaucoma (PCG) together with dysmorphic features (scaphocephaly, frontal bossing, hypotelorism, entropion, and flat nasal bridge), which according to our knowledge, is a combination that has yet to be described in literature. Primary diagnosis. A 2-year-old female who is known to have ACM-II was referred due to abnormal eye examination done in a peripheral hospital that suggested infantile glaucoma in both eyes. Findings. During her last physical exam (postop), she was vitally stable, conscious with good feeding. Ophthalmic assessment revealed buphthalmia, superior paracentral scar, deep anterior chambers (AC), and round pupils with positive red reflex, clear lens, and an IOP of 16, 14 mm Hg, respectively. Neurological exam showed paraparesis and moving upper extremities and has axial hypotonia. Genetic testing showed CYP1B1 gene mutation.

Conclusion

The aim of reporting this case is to share the findings in this infant as it may be a new association. The main learning message here is that ACM-II patients may present with certain ocular symptoms, including glaucoma-related ones that may mimic neurological disorders. This report brings information that could alert general practitioners, neurologists, and neurosurgeons. A deeper understanding of this rare disorder may aid the diagnosis of cases with similar characteristic physical findings by referring them to an ophthalmology clinic for further evaluation. Case presentation. A 2-year-old female who is known to have Arnold Chiari Malformation Type II (ACM- II) was referred due to abnormal eye examination done in a peripheral hospital that suggested infantile glaucoma in both eyes. MRI at 3 months of age showed lumbosacral myelomeningocele and hydrocephalus. Genetic testing confirmed a CYP1B1 mutation. These combinations of symptoms were never described in the literature before.

Risk Factors for Blindness in Children With Primary Congenital Glaucoma-Follow-up of a Registry Cohort

PURPOSE

To evaluate the baseline features associated with blindness in a cohort of children with primary congenital glaucoma (PCG) from a hospital registry.

DESIGN

Retrospective clinical cohort study.

METHODS

Setting: Observational cohort study. StudyPopulation: The registry included all children who presented to our tertiary care institute between 1995 and 2014 with a diagnosis of childhood glaucoma. ObservationProcedure: Baseline characteristics at initial presentation of children with PCG in the registry who were blind at the last follow-up were compared with those who were not blind, using bivariate and then multivariate regressions to account for potential confounders. MainOutcomeMeasures: Blindness was defined as a best-corrected visual acuity of 3/60 (20/400) or worse in the better eye at the final follow-up.

RESULTS

The eligible sample consisted of 196 children with a mean age of 9.54 ± 22.44 months at presentation. After a mean ± standard deviation follow-up of 8.49 ± 3.85 years, 20 (10.2%) children were blind. The baseline demographic factors, intraocular pressure, horizontal corneal diameter, spherical equivalent, axial length, and corneal thickness, were similar for the "blind" and "not blind" groups (P > .05). In the multivariate regression, only the severity of corneal opacification remained significantly (P < .001) associated with the risk of blindness (odds ratio = 4.05; 95% confidence interval: 1.89-8.85).

CONCLUSION

Corneal clouding is a predictor of future blindness in children with PCG. Children with severe corneal clouding may need more aggressive intraocular pressure control, closer follow-up, and earlier counseling.

The loss of microglia activities facilitates glaucoma progression in association with CYP1B1 gene mutation (p.Gly61Glu)

Background

Glaucoma represents the second main cause of irreversible loss of eyesight worldwide. Progression of the disease is due to changes around the optic nerve, eye structure and optic nerve environment. Focusing on primary congenital glaucoma, which is not completely understood, we report an evaluation of an untested mutation (c.182G>A, p.Gly61Glu) within the CYP1B1 gene in the context of microglia, astrocytes and mesenchymal stem cells. We investigated the behaviours of these cells, which are needed to maintain eye homeostasis, in response to the CYP1B1 mutation.

Methods and results

CRISPR technology was used to edit normal CYP1B1 genes within normal astrocytes, microglia and stem cells in vitro. Increased metabolic activities were found in microglia and astrocytes 24 hours after CYP1B1 manipulation. However, these activities dropped by 40% after 72 hrs. In addition, the nicotinamide adenine dinucleotide phosphate (NADP)/NADPH reducing equivalent process decreased by 50% on average after 72 hrs of manipulation. The cytokines measured in mutated microglia showed progressive activation leading to apoptosis, which was confirmed with annexin-V. The cytokines evaluated in mutant astrocytes were abnormal in comparison to those in the control.

Conclusions

The results suggest a progressive inflammation that was induced by mutations (p.Gly61Glu) on CYP1B1. Furthermore, the mutations enhanced the microglia’s loss of activity. We are the first to show the direct impact of the mutation on microglia. This progressive inflammation might be responsible for primary congenital glaucoma complications, which could be avoided via an anti-inflammatory regimen. This finding also reveals that progressive inflammation affects recovery failure after surgeries to relieve glaucoma. Moreover, microglia are important for the survival of ganglion cells, along with the clearing of pathogens and inflammation. The reduction of their activities may jeopardise homeostasis within the optic nerve environment and complicate the protection of optic nerve components (such as retinal ganglion and glial cells).

Surgical Outcomes in Children With Primary Congenital Glaucoma: An Eight-Year Experience

Background

Primary congenital glaucoma (PCG) is a congenital anomaly arising from an unusual development of the filtration angle, causing a remarkable rise in intraocular pressure (IOP) that is irrelevant to other ocular or systemic deformities.

Purpose

The aim of the current study was to evaluate the surgical outcome in PCG patients between 2011 and February 2019.

Methods

This was a retrospective study of PCG patients who underwent trabeculotomy, trabeculectomy, deep sclerectomy, Ahmed valve, and/or cyclophotocoagulation (CPC) at a tertiary hospital. The IOP must be equal or less than 21 mmHg with or without medication to be designated a successful surgery.

Results

A total of 80 eyes (41 patients) were included in the study, with a slight male predominance of 65.9%. At presentation, the most reported age group was under 30 days (46.3%). Moreover, deep sclerotomy was the most common procedure, followed by CPC, which were performed in 48 (58.5%) and 18 (21.9%) eyes, respectively. In the overall group, the mean initial IOP was 23.65±8.52 mmHg, while the mean IOP was 16.73±8.56 mmHg at final follow-ups (p < 0.001), with a 46% reduction. The mean axial length showed a slight progression from 21.11±2.58 at the initial visit to 22.92±3.57 mm at the last follow-up (p<0.001). However, the mean horizontal diameter increased from 12.63±1.83 mm at the initial visit to 13.31±1.13 mm at the final visit (p=0.004).

Conclusion 

An excellent IOP reduction could be accomplished in the majority of eyes. Deep sclerectomy can effectively reduce IOP in PCG without the occurrences of serious complications that are commonly seen after other procedures like trabeculectomy or trabeculotomy.

Analysis of variants in Chinese individuals with primary open-angle glaucoma using molecular inversion probe (MIP)-based panel sequencing

Purpose

Family-based genetic linkage analysis and genome-wide association studies (GWASs) have identified many genomic loci associated with primary open-angle glaucoma (POAG). Several causative genes of POAG have been intensively analyzed by sequencing in different populations. However, few investigations have been conducted on the identification of variants of coding region in the genes identified in GWASs. Therefore, further research is needed to investigate whether they harbor pathogenically relevant rare coding variants and account for the observed association.

Methods

To identify the potentially disease-relevant variants (PDVs) in POAG-associated genes in Chinese patients, we applied molecular inversion probe (MIP)-based panel sequencing to analyze 26 candidate genes in 235 patients with POAG and 241 control subjects.

Results

The analysis identified 82 PDVs in 66 individuals across 235 patients with POAG. By comparison, only 18 PDVs in 19 control subjects were found, indicating an enrichment of PDVs in the POAG cohort (28.1% versus 7.9%, p = 8.629e-09). Among 26 candidate genes, the prevalence rate of PDVs in five genes showed a statistically significant difference between patients and controls (33 out of 235 versus 1 out of 241, p = 4.533e-10), including ATXN2 (p = 0.0033), TXNRD2 (p = 0.0190), MYOC (p = 0.0140), FOXC1 (p = 0.0140), and CDKN2B (p = 0.0287). Furthermore, two sisters harboring a stop-loss mutation EFEMP1 p.Ter494Glu were found in the POAG cohort, and further analysis of the family strongly suggested that EFEMP1 p.Ter494Glu was a potentially disease-causing mutation for POAG. A statistically significant difference in age at diagnosis between patients with PDVs and those without PDVs was found, implying that some of the identified PDVs may have a role in promoting the early onset of POAG disease.

Conclusions

The results suggest that some of the associations identified in POAG risk loci can be ascribed to rare coding variants with likely functional effects that modify POAG risk.

Chromosome 1q Terminal Deletion and Congenital Glaucoma: A Case Report

BACKGROUND This paper aims to highlight the presence of primary congenital glaucoma (PCG) in a patient with chromosome 1 q31 and q42.1 deletion of the distal long arm. The characteristic combination of phenotypic features in this deletion include dysmorphic features, psychomotor retardation and neurological signs; however, PCG has never been recognized as part of these features before. CASE REPORT This is a case of an 8-year-old female with chromosome 1 q31 and q42.1 deletion with congenital glaucoma since birth. She was found to have bilateral buphthalmos and large cloudy corneas and was also unable to follow or fixate in any directional gaze with either eye. Family history was negative for congenital glaucoma and both parents are healthy and non-consanguineous. Karyotyping showed chromosome 1 microdeletion, 46, XX, del (1) (q31q42.1) on high resolution G-banding. Further genetic testing showed no mutations in the CYP1B1 gene. CONCLUSIONS In summary, we describe a rare presentation of congenital bilateral glaucoma in the context of chromosome 1 q31 and q42.1 deletion. This clinical manifestation is uncommon when compared with that of other subsets of chromosome 1 deletions. Thus, we emphasize the need to explore factors contributing to the development of PCG in patients with chromosomal 1 deletion.

Primary congenital glaucoma: An updated review

Primary congenital glaucoma (PCG) is a rare disease affecting children early in life. PCG was considered untreatable with inevitable blindness. However, recent advances in biochemical and genetic studies, the introduction of new diagnostic tools, intraocular pressure (IOP) lowering medications and improvement of surgical techniques have led to a better understanding of this devastating disease and preserving the vision of affected children. This paper presents an updated and broad overview of PCG in terms of the epidemiology and genetic aspects, particularly in Saudi Arabia, the clinical presentation and diagnostic approach to PCG with major emphasis on the treatment options.

Mutational analysis of the CYP1B1 gene in Pakistani primary congenital glaucoma patients: Identification of four known and a novel causative variant at the 3' splice acceptor site of intron 2

Primary congenital glaucoma (PCG) causes blindness in early age. It has an autosomal recessive pattern of inheritance, hence is more prevalent in populations with frequent consanguineous marriages that occur in the Pakistani population. Mutations in the CYP1B1 gene are commonly associated with PCG. The aim of the present study was to identify genetic mutations in the CYP1B1 gene in PCG cases belonging to 38 Pakistani families. DNA was extracted using blood samples collected from all enrolled patients, their available unaffected family members and controls. Direct sequencing of the CYP1B1 gene revealed a novel 3' splice acceptor site causative variant segregating in an autosomal recessive manner in a large consanguineous family with four PCG-affected individuals. The novel variant was not detected in 93 ethnically matched controls. Furthermore, four already reported mutations, including p.G61E, p.R355X, p.R368H, and p.R390H were also detected in patients belonging to nine different families. All identified causative variants were evaluated by computational programs, that is, SIFT, PolyPhen-2, and MutationTaster. Pathogenicity of the novel splice site variant identified in this study was analyzed by Human Splicing Finder and MaxEntScan. Ten out of 38 families with PCG had the disease due to CYP1B1 mutations, suggesting CYP1B1 was contributing to PCG in these Pakistani patients. Identification of this novel 3' splice acceptor site variant in intron 2 is the first report for the CYP1B1 gene contributing to genetic heterogeneity of disease.

Cyp1B1 expression patterns in the developing chick inner ear

BACKGROUND

Retinoic acid (RA) plays an important role in organogenesis as a paracrine signal through transcriptional regulation of an increasing number of known downstream target genes, regulating cell proliferation, and differentiation. During the development of the inner ear, RA directly governs the morphogenesis and specification processes mainly by means of RA-synthesizing retinaldehyde dehydrogenase (RALDH) enzymes. Interestingly, CYP1B1, a cytochrome P450 enzyme, is able to mediate the oxidative metabolisms also leading to RA generation, its expression patterns being associated with many known sites of RA activity.

RESULTS

This study describes for the first time the presence of CYP1B1 in the developing chick inner ear as a RALDH-independent RA-signaling mechanism. In our in situ hybridization analysis, Cyp1B1 expression was first observed in a domain located in the ventromedial wall of the otic anlagen, being included within the rostralmost aspect of an Fgf10-positive pan-sensory domain. As development proceeds, all identified Fgf10-positive areas were Cyp1B1 stained, with all sensory patches being Cyp1B1 positive at stage HH34, except the macula neglecta.

CONCLUSIONS

Cyp1B1 expression suggested a possible contribution of CYP1B1 action in the specification of the lateral-to-medial and dorsal-to-ventral axes of the developing chick inner ear.

Cytochrome P450: Polymorphisms and Roles in Cancer, Diabetes and Atherosclerosis

Cytochromes P450s (CYPs) constitute a superfamily of enzymes that catalyze the metabolism of drugs and other substances. Endogenous substrates of CYPs include eicosanoids, estradiol, arachidonic acids, cholesterol, vitamin D and neurotransmitters. Exogenous substrates of CYPs include the polycyclic aromatic hydrocarbons and about 80% of currently used drugs. Some isoforms can activate procarcinogens to ultimate carcinogens. Genetic polymorphisms of CYPs may affect the enzyme catalytic activity and have been reported among different populations to be associated with various diseases and adverse drug reactions. With regard of drug metabolism, phenotypes for CYP polymorphism range from ultrarapid to poor metabolizers. In this review, we discuss some of the most clinically important CYPs isoforms (CYP2D6, CYP2A6, CYP2C19, CYP2C9, CYP1B1 and CYP1A2) with respect to gene polymorphisms and drug metabolism. Moreover, we review the role of CYPs in renal, lung, breast and prostate cancers and also discuss their significance for atherosclerosis and type 2 diabetes mellitus.

Evaluation of preoperative speed of progression and its association with surgical outcomes in primary congenital glaucoma patients: a retrospective study

Background

Surgeries are inevitable for treating primary congenital glaucoma (PCG) and risk factors of surgical failure play a key role in surgical decision making. The aim of this study was to investigate the influence of delay of surgery and preoperative speed of progression (SP) on the surgical outcomes in these patients.

Methods

Medical records of 83 eyes of 51 PCG patients with trabeculotomy within 3 years were retrospectively observed. Surgical outcomes, demographic and clinical data were compared after separating the eyes into two groups based on the interval (between onset of PCG and trabeculotomy) and SP index (SPI) respectively. Student’s t-test, Wilcoxon rank-sum test, Pearson’s chi-square test and Kaplan-Meier survival analysis were used in the statistical analysis.

Results

Comparative analysis showed better outcomes in the group with longer interval and lower SPIs. Better intraocular pressure (IOP) control was found in patients with lower SPI at 1, 3, 6, 12 and 24 months postoperatively (19.54 ± 4.84 mmHg vs. 24.75 ± 8.87 mmHg, p = 0.004; 19.88 ± 7.78 mmHg vs. 23.19 ± 6.74 mmHg, p = 0.089; 17.45 ± 6.23 mmHg vs. 21.31 ± 7.28 mmHg, p = 0.031; 15.09 ± 6.21 mmHg vs. 19.18 ± 6.66 mmHg, p = 0.008; 14.95 ± 2.95 mmHg vs. 18.10 ± 3.96 mmHg, p = 0.004). The correlation between SPI and IOP at 1, 3, 6, 12 and 24 months postoperatively was 0.328 (CI = 0.105 to 0.529, p = 0.005), 0.192 (CI = −0.070 to 0.429, p = 0.149), 0.261 (CI = 0.010 to 0.481, p = 0.042), 0.046 (CI = −0.183 to 0.270, p = 0.70), and 0.230 (CI = −0.072 to 0.493, p = 0.134), respectively. Patients with lower SPI were less likely to fail (χ2 = 22.71, p = 0.000, OR: 0.174; 95%CI: 0.059–0.510). Kaplan-Meier analysis showed a much slower decline of success rate in patients with lower SPI (χ2 = 25.52, p = 0.000).

Conclusions

In PCG patients, lower preoperative SPI was associated with better short-term IOP control and success rate. Evaluation of preoperative SPI may help with surgical decision. However, early detection and treatment are important given the same SPI.

Cyp1b1 Regulates Ocular Fissure Closure Through a Retinoic Acid-Independent Pathway

Purpose

Mutations in the CYP1B1 gene are the most commonly identified genetic causes of primary infantile-onset glaucoma. Despite this disease association, the role of CYP1B1 in eye development and its in vivo substrate remain unknown. In the present study, we used zebrafish to elucidate the mechanism by which cyp1b1 regulates eye development.

Methods

Zebrafish eye and neural crest development were analyzed using live imaging of transgenic zebrafish embryos, in situ hybridization, immunostaining, TUNEL assay, and methylacrylate sections. Cyp1b1 and retinoic acid (RA) levels were genetically (morpholino oligonucleotide antisense and mRNA) and pharmacologically manipulated to examine gene function.

Results

Using zebrafish, we observed that cyp1b1 was expressed in a specific spatiotemporal pattern in the ocular fissures of the developing zebrafish retina and regulated fissure patency. Decreased Cyp1b1 resulted in the premature breakdown of laminin in the ventral fissure and altered subsequent neural crest migration into the anterior segment. In contrast, cyp1b1 overexpression inhibited cell survival in the ventral ocular fissure and prevented fissure closure via an RA-independent pathway. Cyp1b1 overexpression also inhibited the ocular expression of vsx2, pax6a, and pax6b and increased the extraocular expression of shha. Importantly, embryos injected with human wild-type but not mutant CYP1B1 mRNA also showed colobomas, demonstrating the evolutionary and functional conservation of gene function between species.

Conclusions

Cyp1b1 regulation of ocular fissure closure indirectly affects neural crest migration and development through an RA-independent pathway. These studies provide insight into the role of Cyp1b1 in eye development and further elucidate the pathogenesis of primary infantile-onset glaucoma.

Analysis of CYP1B1 Gene Mutations in Patients with Primary Congenital Glaucoma

Primary congenital glaucoma (PCG) is the most common type of infantile glaucoma, yet it remains a relatively rare disease, because the disease is often transmitted in an autosomal recessive pattern. However, PCG occurs up to 10 times more frequently in certain ethnic and geographical groups where consanguineous relationships are common. The aim of this study was to investigate the distribution of mutations in the cytochrome P450 1B1 gene ( CYP1B1 ) in patients with PCG among different populations around the world from 2011 until May 2016. We referred to the electronic databases, such as Medline, Clinicalkey, Scopus, and ScienceDirect, to search for articles that were published in this area. Nineteen records were included in this qualitative synthesis. CYP1B1 mutations were assessed in 1,220 patients with PCG and identified in 41.6% of them. According to these studies, 99 mutations including 60 novel mutations were found. Nonsignificant difference in the sex ratio has been reported. This current review shows that consanguinity plays an important role in the PCG pathogenesis and transmission; however, sporadic mutations have been found in some cases. A difference in penetrance was highlighted by some mutations. The CYP1B1 mutations were mostly found in the Middle East and the Maghreb with a rate of 64.8 and 54.4%, respectively, followed by Europe (34.7%), Asia (21.3%), and finally the United States (14.9%). Founder mutations in different geographical areas have been discovered. For instance, the p.Gly61Glu, p.Arg390His, p.Gly61Glu, c.4,339delG, p.E387Lys, and p.Val320Leu were considered founder mutations for Iran/Saudi Arabia, Pakistan, Lebanon, Morocco, Europe, and Vietnam/South Korea, respectively. Many common mutations in different countries were found, such as in Morocco, where its mutations were similar to seven other countries. These findings suggest that the ethnic differences and the geographical distribution of PCG give us a large CYP1B1 mutation pattern. Genetic tests looking for founder and common mutations should be the first step in genetic screening for patients with PCG.

Candidate Gene Analysis Identifies Mutations in CYP1B1 and LTBP2 in Indian Families with Primary Congenital Glaucoma

BACKGROUND

Primary congenital glaucoma (PCG) is a severe ocular disorder that presents early in life. Cytochrome P4501B1 (CYP1B1) and latent transforming growth factor-beta-binding protein 2 (LTBP2) are the most commonly mutated genes in PCG.

AIM

To investigate the causative genetic mutations in eight Indian families with PCG.

MATERIALS AND METHODS

Whole-exome sequencing was applied to analyze the genomic DNA samples from PCG probands. Sanger sequencing was utilized to confirm the identified mutations.

RESULTS

We identified four homozygous missense mutations (c.1405C>T, p.R469W; c.1397G>T, p.G466V; c.1198C>T, p.P400S; and c.1103G>A, p.R368H) in CYP1B1 and one nonsense mutation (c.2421G>A, p.W807X) in LTBP2 in eight Indian families. Among the five mutations identified, G466V in CYP1B1 and W807X in LTBP2 represent novel mutations.

CONCLUSIONS

Our study expands the mutational spectrum of PCG in the Indian population.

Definition of transcriptome-based indices for quantitative characterization of chemically disturbed stem cell development: introduction of the STOP-Toxukn and STOP-Toxukk tests

Stem cell-based in vitro test systems can recapitulate specific phases of human development. In the UKK test system, human pluripotent stem cells (hPSCs) randomly differentiate into cells of the three germ layers and their derivatives. In the UKN1 test system, hPSCs differentiate into early neural precursor cells. During the normal differentiation period (14 days) of the UKK system, 570 genes [849 probe sets (PSs)] were regulated >fivefold; in the UKN1 system (6 days), 879 genes (1238 PSs) were regulated. We refer to these genes as 'developmental genes'. In the present study, we used genome-wide expression data of 12 test substances in the UKK and UKN1 test systems to understand the basic principles of how chemicals interfere with the spontaneous transcriptional development in both test systems. The set of test compounds included six histone deacetylase inhibitors (HDACis), six mercury-containing compounds ('mercurials') and thalidomide. All compounds were tested at the maximum non-cytotoxic concentration, while valproic acid and thalidomide were additionally tested over a wide range of concentrations. In total, 242 genes (252 PSs) in the UKK test system and 793 genes (1092 PSs) in the UKN1 test system were deregulated by the 12 test compounds. We identified sets of 'diagnostic genes' appropriate for the identification of the influence of HDACis or mercurials. Test compounds that interfered with the expression of developmental genes usually antagonized their spontaneous development, meaning that up-regulated developmental genes were suppressed and developmental genes whose expression normally decreases were induced. The fraction of compromised developmental genes varied widely between the test compounds, and it reached up to 60 %. To quantitatively describe disturbed development on a genome-wide basis, we recommend a concept of two indices, 'developmental potency' (D _p) and 'developmental index' (D _i), whereby D _p is the fraction of all developmental genes that are up- or down-regulated by a test compound, and D _i is the ratio of overrepresentation of developmental genes among all genes deregulated by a test compound. The use of D _i makes hazard identification more sensitive because some compounds compromise the expression of only a relatively small number of genes but have a high propensity to deregulate developmental genes specifically, resulting in a low D _p but a high D _i. In conclusion, the concept based on the indices D _p and D _i offers the possibility to quantitatively express the propensity of test compounds to interfere with normal development.

Surgical outcomes in children with primary congenital glaucoma: a 20-year experience

PURPOSE

To describe demographic criteria of primary congenital glaucoma (PCG) subjects and to evaluate the surgical outcomes of children who underwent angle surgery over a 20-year period.

METHODS

This is a retrospective study of patients diagnosed with PCG who underwent trabeculotomy, trabeculectomy, or combined trabeculotomy-trabeculectomy (CTT). The surgery was considered to be successful if intraocular pressure (IOP) was 21 mm Hg or less with or without treatment.

RESULTS

A total of 148 eyes (85 patients) were included in the study. The majority of the patients were younger than 6 months of age (78.9%), with a median age of 2 months. Sex distribution was relatively even between girls and boys (45:40) (53%/47%). Bilateral disease was seen in 63 patients (74%). The overall success rate was achieved in 80.4%. The majority of the eyes needed only one surgery (105 [70.9%]), 34 eyes (23.0%) needed 2 surgeries, and 7 eyes (4.7%) had 3 surgeries. There was no statistically significant difference in success rate between types of surgery and number of performed procedures. A progressive decline in success rate over time was evident, as success rate dropped from 96.6% at 5 months to less than 50% after 11 years of follow-up.

CONCLUSIONS

Excellent IOP control can be achieved in a majority of patients with equally effective results from all 3 surgical procedures. The surgical outcome of PCG was more favorable in infants presenting before the age of 6 months. Adjuvant topical antiglaucoma medications can augment the surgical success rate.

Neural crest derivatives in ocular development: discerning the eye of the storm

Neural crest cells (NCCs) are vertebrate-specific transient, multipotent, migratory stem cells that play a crucial role in many aspects of embryonic development. These cells emerge from the dorsal neural tube and subsequently migrate to different regions of the body, contributing to the formation of diverse cell lineages and structures, including much of the peripheral nervous system, craniofacial skeleton, smooth muscle, skin pigmentation, and multiple ocular and periocular structures. Indeed, abnormalities in neural crest development cause craniofacial defects and ocular anomalies, such as Axenfeld-Rieger syndrome and primary congenital glaucoma. Thus, understanding the molecular regulation of neural crest development is important to enhance our knowledge of the basis for congenital eye diseases, reflecting the contributions of these progenitors to multiple cell lineages. Particularly, understanding the underpinnings of neural crest formation will help to discern the complexities of eye development, as these NCCs are involved in every aspect of this process. In this review, we summarize the role of ocular NCCs in eye development, particularly focusing on congenital eye diseases associated with anterior segment defects and the interplay between three prominent molecules, PITX2, CYP1B1, and retinoic acid, which act in concert to specify a population of neural crest-derived mesenchymal progenitors for migration and differentiation, to give rise to distinct anterior segment tissues. We also describe recent findings implicating this stem cell population in ocular coloboma formation, and introduce recent evidence suggesting the involvement of NCCs in optic fissure closure and vascular development.