CYP1B1 and MYOC Mutations in Vietnamese Primary Congenital Glaucoma Patients

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.

Exome-based mutation screening in South African children with primary congenital glaucoma

OBJECTIVES

To identify pathogenic variants in a cohort of 23 black South African children with sporadic primary congenital glaucoma (PCG) using an exome-based approach.

METHODS

Children with PCG were recruited from two Paediatric Ophthalmology Clinics in Johannesburg, South Africa. Whole exome sequencing was performed on genomic DNA. Of the 23 children, 19 were male and 19 had bilateral PCG. A variant prioritization strategy was employed whereby variants in known PCG genes (CYP1B1, LTBP2 and TEK) were evaluated first, followed by the identification of putative disease-causing variants in other genes related to eye diseases and phenotypes.

RESULTS

Validated pathogenic variants in the CYP1B1 gene (c.1169 G>A; p.Arg390His) and TEK gene (c.922 G>A; p.Gly308Arg) were identified in one child each. No LTBP2 mutations were identified in this cohort. In silico predictions identified potentially damaging rare variants in genes previously associated with eye development phenotypes or glaucoma in a further 12 children.

CONCLUSIONS

This study demonstrates the value of whole exome sequencing in identifying disease-causing variants in African children with PCG. It is the first report of a TEK disease-causing variant in an African PCG patient. Potential causative variants detected in PCG candidate genes warrant further investigation.

Polymorphisms in CYP1B1 gene and the risk of suffering Primary Open-Angle Glaucoma: Systematic review and meta-analysis

PURPOSE

It had been reported that mutations in CYP1B1 gene probably play an important role in the pathogenesis of primary open angle glaucoma (POAG) but the existing genetic association studies show contradictory results. Thus, the objective of our study was to perform a systematic review and meta-analysis to characterize more precisely the potential association between given polymorphisms in CYP1B1 gene and the risk of suffering POAG.

METHODS

A systematic review of studies that related the risk of carrying CYP1B1 gene polymorphisms with POAG development was conducted. We selected 19 case-control studies including 3855 POAG patients and 4125 control subjects in our meta-analyses. A random effects model was used. Sensitivity analysis and assessment of bias were also included.

RESULTS

The prevalence of CYP1B1 gene polymorphisms were significantly more frequent among POAG patients compared to all controls (OR = 2.91, 95% CI = 1.37 - 6.21; P = 0.006). Moreover, their prevalence was significantly higher in juvenile-onset patients than in adult-onset ones (OR = 2.27, 95% CI = 1.20-4.28; P = 0.001).

CONCLUSION

The results of this meta-analysis uphold that being a carrier of polymorphic genetic variants in CYP1B1 gene would increase the risk of POAG, especially the juvenile onset.

Screening and Functional Analysis of TEK Mutations in Chinese Children With Primary Congenital Glaucoma

Purposes: Recent studies have suggested that loss-of-function mutations of the tunica intima endothelial receptor tyrosine kinase (TEK) are responsible for approximately 5% of primary congenital glaucoma (PCG) cases in diverse populations. However, the causative role of TEK mutations has not been studied in Chinese PCG patients. Here, we report the mutation spectrum of TEK after screening a large cohort of PCG patients of Chinese Han origin and analyze the identified variants in functional assays.

Methods: TEK-targeted next-generation sequencing (NGS) was performed in 200 PCG patients. Candidate variants were prioritized by mutation type and allele frequency in public datasets. Plasmids containing wild type and identified variants of TEK were constructed and used to assess protein expression, solubility, receptor auto-phosphorylation, and response to ligand stimulation in cell-based assays.

Results: Ten missense and one nonsense heterozygous variants were detected by NGS in 11 families. The clinical features of TEK variants carriers were comparable to that of TEK-mutated patients identified in other populations and CYP1B1-mutated individuals from in-house database. Functional analysis confirmed four variants involving evolutionarily conserved residues to be loss-of-function, while one variant (p.R1003H) located in tyrosine kinase domain seemed to be an activating mutation. However, our results did not support the pathogenicity of the other five variants (p.H52R, p.M131I, p.M228V, p.H494Y, and p.L888P).

Conclusion: We provide evidence for TEK variants to be causative in Chinese PCG patients for the first time. Attention needs to be paid to TEK mutations in future genetic testing.

Genetics in primary congenital glaucoma: Implications in disease management and counseling

Primary congenital glaucoma is an important cause of visual impairment in children. It can develop both pre- and postnatally. Angle surgery is the first line treatment modality. If the disease remains untreated or if the diagnosis is delayed, it can lead to irreversible visual loss and blindness. The genetics of primary congenital glaucoma are complex and not yet entirely understood. At present multiple disease-causing genes have been identified. CYP1B1 is the most well known gene causing autosomal recessive congenital glaucoma. Other genes have been found to play a role through recessive, dominant or polygenic mechanisms. Here we provide an overview of the known genes and mechanisms described in patients with PCG. Furthermore, we provide a practical counseling and follow-up guideline for relatives of a proband.

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.

Genetic analysis of patients with primary congenital glaucoma

PURPOSE

To determine the common gene mutation in patients with primary congenital glaucoma (PCG) in the Southeast region of Turkey via genetic analysis and to evaluate whether there were other gene mutations in these patients.

METHODS

A total of 25 patients with PCG were included in this study. We performed sequence analysis including all exons of cytochrome p450 1B1 (CYP1B1), myocilin (MYOC), forkhead box C1 (FOXC1), and paired-like homeodomain 2 (PITX2) genes of the obtained samples. Further, we analyzed the results using the Nextgen analysis program.

RESULTS

The CYP1B1 gene mutation was detected in 20 (80%) of 25 patients, and FOXC1 gene mutation was detected in one (4%) patient. The mutation site of nine (45%) of the 20 CYP1B1 genes was found in the second exon. The pathogenic variant (p.Gly61Glu) was observed in 12 (60%) patients (in the first and second exons); the mutation type of six (50%) of these patients was homozygous. The mutation site of one patient with FOXC1 gene mutation was found to be in the first exon; its pathogenic variant was p.Met400lle. The mutation type in this gene was observed to be heterozygous. Lastly, there were no mutations in the MYOC, FOXC1, and PITX2 genes in combination with the CYP1B1 gene mutation.

CONCLUSION

The most common cause of PCG in our region is the CYP1B1 gene mutation, and the most frequent pathogenic variant is c.182G > A (p.Gly61Glu). We also determined that the CYP1B1 gene mutation was alone and did not occur with other gene mutations (MYOC, FOXC1, and PITX2).

Biological roles of cytochrome P450 1A1, 1A2, and 1B1 enzymes

Human cytochrome P450 enzymes (CYPs) play a critical role in various biological processes and human diseases. CYP1 family members, including CYP1A1, CYP1A2, and CYP1B1, are induced by aryl hydrocarbon receptors (AhRs). The binding of ligands such as polycyclic aromatic hydrocarbons activates the AhRs, which are involved in the metabolism (including oxidation) of various endogenous or exogenous substrates. The ligands that induce CYP1 expression are reported to be carcinogenic xenobiotics. Hence, CYP1 enzymes are correlated with the pathogenesis of cancers. Various endogenous substrates are involved in the metabolism of steroid hormones, eicosanoids, and other biological molecules that mediate the pathogenesis of several human diseases. Additionally, CYP1s metabolize and activate/inactivate therapeutic drugs, especially, anti-cancer agents. As the metabolism of drugs determines their therapeutic efficacy, CYP1s can determine the susceptibility of patients to some drugs. Thus, understanding the role of CYP1s in diseases and establishing novel and efficient therapeutic strategies based on CYP1s have piqued the interest of the scientific community.

CYP1B1 gene: Implications in glaucoma and cancer

Glaucoma is a serious disease that can lead to irreversible loss of vision. Patients with primary congenital glaucoma may have elevated intraocular pressure. Hypertension causes damages to intraocular structures and affects the Schlemm's canal, collector channels, trabecular meshwork, and optic nerve's molecular structures. An important gene that is defective in patients with glaucoma is CYP1B1, a gene associated with optic nerve deterioration. CYP1B1is a key enzyme involved in the metabolism of exogenous and endogenous compounds. Also, it is critical in the detoxification of pre-carcinogens, such as polycyclic aromatic hydrocarbons and estrogen. It catalyzes their conversion into metabolites subsequently eliminated from the body. In malignant tumors, the CYP1B1 promoter is hypomethylated. CYP1B1 overexpression results in the conversion of estrogens to quinone forms, which bind with DNA and create a predisposition for cancer in several organs, such as the brain, breast, and ovary. Increased cytokine interleukin-6 and leptin lead to elevated CYP1B1 activity, which possibly causes cancer. In addition, the expression of aromatic hydrocarbon receptors is increased in tumor tissues, and it elevates oxidative stress and cell growth. TCGA database analysis showed increased survival at bladder and renal carcinoma when CYP1B1 expression is low. Therefore, alteration of CYP1B1 expression may suggest a therapeutic benefit for multiple diseases such as glaucoma and cancer.

Update in Genetics and Surgical Management of Primary Congenital Glaucoma

Primary congenital glaucoma (PCG) continues to be an important cause of visual impairment in children despite advances in medical and surgical treatment options. The progressive and blinding nature of the disease, together with the long lifespan of the affected population, necessitates a thorough understanding of the pathophysiology of PCG and the development of long-lasting treatment options. The first part of this review discusses the genetic features and makeup of this disorder, including all currently identified genetic loci (GLC3A, GLC3B, GLC3C and GLC3D) and relevant protein targets important for trabecular and Schlemm canal dysgenesis. These target molecules primarily include CYP1B1, LTBP2, and TEK/Tie2 proteins. Their potential roles in PCG pathogenesis are discussed with the purpose of bringing the readers up to date on the molecular genetics aspect of this disorder. Special emphasis is placed on functional implications of reported genetic mutations in the setting of PCG. The second part of the review focuses on various modifications and refinements to the traditional surgical approaches performed to treat PCG, including advances in goniotomy and trabeculotomy ab externo techniques, glaucoma drainage implant surgery and cyclodiode photocoagulation techniques that ultimately provide safer surgical approaches and more effective intraocular pressure control in the 21st century.

Long non-coding RNAs in ocular diseases: new and potential therapeutic targets

Long non-coding RNAs (lncRNAs) are non-protein coding transcripts containing more than 200 nucleotides. In the past, lncRNAs were considered as 'transcript noise' or 'pseudogenes' and were thus ignored. However, in recent years, lncRNAs have been proven to regulate gene expression at the epigenetic, transcriptional and translational level, and thereby influence cell proliferation, apoptosis, viability, immune response and oxidative stress. Furthermore, increasing evidence points to their involvement in different diseases, including cancer and heart diseases. Recently, lncRNAs were shown to be differentially expressed in ocular tissues and play a significant role in the pathogenesis of ophthalmological disorders such as glaucoma, corneal diseases, cataract, diabetic retinopathy, proliferative vitreoretinopathy and ocular tumors. In this review, we summarize the classification and mechanisms of known lncRNAs, while detailing their biological functions and roles in ocular diseases. Moreover, we provide a concise review of the clinical relevance of lncRNAs as novel, potential therapeutic targets in the treatment of eye diseases.

Research progress on human genes involved in the pathogenesis of glaucoma (Review)

Glaucoma is the leading cause of irreversible blindness globally. It is known that the incidence of glaucoma is closely associated with inheritance. A large number of studies have suggested that genetic factors are involved in the occurrence and development of glaucoma, and even affect the drug sensitivity and prognosis of glaucoma. In the present review, 22 loci of glaucoma are presented, including the relevant genes (myocilin, interleukin 20 receptor subunit B, optineurin, ankyrin repeat- and SOCS box-containing protein 10, WD repeat-containing protein 36, EGF-containing fibulin-like extracellular matrix protein 1, neurotrophin 4, TANK-binding kinase 1, cytochrome P450 subfamily I polypeptide 1, latent transforming growth factor β binding protein 2 and TEK tyrosine kinase endothelial) and 74 other genes (including toll-like receptor 4, sine oculis homeobox Drosophila homolog of 1, doublecortin-like kinase 1, RE repeats-encoding gene, retinitis pigmentosa GTPase regulator-interacting protein, lysyl oxidase-like protein 1, heat-shock 70-kDa protein 1A, baculoviral IAP repeat-containing protein 6, 5,10-methylenetetrahydrofolate reductase and nitric oxide synthase 3 and nanophthalmos 1) that are more closely associated with glaucoma. The pathogenesis of these glaucoma-associated genes, glaucomatous genetics and genetic approaches, as well as glaucomatous risk factors, including increasing age, glaucoma family history, high myopia, diabetes, ocular trauma, smoking, intraocular pressure increase and/or fluctuation were also discussed.

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.