Molecular genetics of age-related cataract

Oxidative Stress in Genetic Cataract Formation

BACKGROUND

Cataracts are the leading cause of blindness worldwide, and age-related cataracts are the result of environmental insults that largely lead to oxidative stress imposed on a genetic background that determines susceptibility to these stresses.

METHODS

A comprehensive literature review was performed to identify GWAS, targeted association studies, and TWAS that identified genes associated with age-related cataract. Additional genes associated with age-related cataracts were identified through the CAT-MAP online database. Pathway analysis was performed using Qiagen Ingenuity Pathway Analysis and pathways related to oxidative stress were analyzed using the same program.

RESULTS

A large number of genes have been identified as causes of both Mendelian and complex cataracts. Of these, 10 genes related to oxidative stress were identified, and all were associated with age-related cataracts. These genes fall into seven canonical pathways primarily related to glutathione metabolism and other pathways related to detoxifying reactive oxygen species.

CONCLUSIONS

While a relatively small number of antioxidant related genes were identified as being associated with cataracts, they allow the identification of redox pathways important for lens metabolism and homeostasis. These are largely related to glutathione and its metabolism, other pathways for detoxification of reactive oxygen species, and the transcriptional systems that control their expression.

Through the Cat-Map Gateway: A Brief History of Cataract Genetics

Clouding of the transparent eye lens, or cataract(s), is a leading cause of visual impairment that requires surgical replacement with a synthetic intraocular lens to effectively restore clear vision. Most frequently, cataract is acquired with aging as a multifactorial or complex trait. Cataract may also be inherited as a classic Mendelian trait-often with an early or pediatric onset-with or without other ocular and/or systemic features. Since the early 1990s, over 85 genes and loci have been genetically associated with inherited and/or age-related forms of cataract. While many of these underlying genes-including those for lens crystallins, connexins, and transcription factors-recapitulate signature features of lens development and differentiation, an increasing cohort of unpredicted genes, including those involved in cell-signaling, membrane remodeling, and autophagy, has emerged-providing new insights regarding lens homeostasis and aging. This review provides a brief history of gene discovery for inherited and age-related forms of cataract compiled in the Cat-Map database and highlights potential gene-based therapeutic approaches to delay, reverse, or even prevent cataract formation that may help to reduce the increasing demand for cataract surgery.

Changing Trends in the Global Burden of Cataract Over the Past 30 Years: Retrospective Data Analysis of the Global Burden of Disease Study 2019

BACKGROUND

Cataracts now account for the largest proportion of the global burden of blindness and vision loss. Understanding the changing trends in the global burden of cataracts over the past 30 years and the next 15 years is of clear significance for the prevention and control of cataracts in key populations. As far as we know, research on the future burden of cataracts is lacking.

OBJECTIVE

This study aims to assess the global burden of cataracts over the past 30 years by using age-period-cohort modeling and to estimate trends in the next 15 years.

METHODS

Data were obtained from the Global Burden of Disease Study 2019, the United Nations Development Programme, and the WHO (World Health Organization) Global Health Observatory data repository. The assessment of trends and disparities in the number and rate of disability-adjusted life years (DALYs) for cataracts from 1990 to 2019 was conducted. The association between the age-standardized DALY rate (ASDR) and the socio-demographic index (SDI), human development index (HDI), national levels of particulate matter <2.5 μm in diameter (PM2.5), and ambient ultraviolet radiation (UVR) was determined using linear regression analysis. Additionally, we used the Nordpred (Harald Fekjær and Bjørn Møller) age-period-cohort model to predict the cataract burden from 2020 to 2034.

RESULTS

Globally, the number of DALYs due to cataract increased from 3,492,604 (95% uncertainty interval [UI] 2,481,846-4,719,629) in 1990 to 6,676,281 (95% UI 4,761,210-9,006,193) in 2019. The ASDRs due to cataract decreased from 93.17 (95% UI 66.14-125.32) in 1990 to 82.94 (95% UI 59.06-111.75) in 2019, with an average annual percentage change of -0.37 (95% CI -0.44 to -0.3; P<.001). Age, female sex, air pollution, smoking, high fasting plasma glucose levels, and a high body mass index were risk factors for the burden of cataracts. SDI and HDI were negatively correlated with ASDRs of cataracts, while PM2.5 and UVR were positively associated with them. Higher DALY rates were also associated with lower SDI (R2=0.1939; P<.001), lower HDI (R2=0.2828; P<.001), national PM2.5 concentration (R2=0.1874; P<.001), and ambient UVR levels (R2=0.2354; P<.001). The prediction model suggested that the number of DALYs due to cataract will continue to rise globally, while the cataract DALY rate will continue to decrease.

CONCLUSIONS

While the ASDR of cataracts has decreased, there has been a notable increase in the number of DALYs over the past 30 years. Projections suggest that the global burden of cataracts will continue to rise over the next 15 years. To address this challenge, appropriate prevention and treatment policies must be implemented.

The genetics and disease mechanisms of rhegmatogenous retinal detachment

Rhegmatogenous retinal detachment (RRD) is a sight threatening condition that warrants immediate surgical intervention. To date, 29 genes have been associated with monogenic disorders involving RRD. In addition, RRD can occur as a multifactorial disease through a combined effect of multiple genetic variants and non-genetic risk factors. In this review, we provide a comprehensive overview of the spectrum of hereditary disorders involving RRD. We discuss genotype-phenotype correlations of these monogenic disorders, and describe genetic variants associated with RRD through multifactorial inheritance. Furthermore, we evaluate our current understanding of the molecular disease mechanisms of RRD-associated genetic variants on collagen proteins, proteoglycan versican, and the TGF-β pathway. Finally, we review the role of genetics in patient management and prevention of RRD. We provide recommendations for genetic testing and prophylaxis of at-risk patients, and hypothesize on novel therapeutic approaches beyond surgical intervention.

HSP90β prevents aging-related cataract formation through regulation of the charged multivesicular body protein (CHMP4B) and p53

Cataract is a leading ocular disease causing global blindness. The mechanism of cataractogenesis has not been well defined. Here, we demonstrate that the heat shock protein 90β (HSP90β) plays a fundamental role in suppressing cataractogenesis. HSP90β is the most dominant HSP in normal lens, and its constitutive high level of expression is largely derived from regulation by Sp1 family transcription factors. More importantly, HSP90β is significantly down-regulated in human cataract patients and in aging mouse lenses, whereas HSP90β silencing in zebrafish causes cataractogenesis, which can only be rescued by itself but not other HSP90 genes. Mechanistically, HSP90β can directly interact with CHMP4B, a newly-found client protein involved in control of cytokinesis. HSP90β silencing causes upregulation of CHMP4B and another client protein, the tumor suppressor p53. CHMP4B upregulation or overexpression induces excessive division of lens epithelial cells without proper differentiation. As a result, these cells were triggered to undergo apoptosis due to activation of the p53/Bak-Bim pathway, leading to cataractogenesis and microphthalmia. Silence of both HSP90β and CHMP4B restored normal phenotype of zebrafish eye. Together, our results reveal that HSP90β is a critical inhibitor of cataractogenesis through negative regulation of CHMP4B and the p53-Bak/Bim pathway.

Association between single nucleotide polymorphisms in exon 3 of the alpha-A-crystallin gene and susceptibility to age-related cataract

BACKGROUND

The mutations in the αA-crystallin (CRYAA) gene may contribute to the development of age-related cataract (ARC). In this study, we searched for single nucleotide polymorphisms (SNP) in exons of CRYAA and investigated the associations between the identified SNPs and the subtypes of ARC.

MATERIALS AND METHODS

Peripheral venous blood was collected for the extraction of genomic DNA. Three exons of CRYAA were sequenced to detect SNPs. The frequency distributions of alleles and genotypes were compared between the ARC and control groups.

RESULTS

There were 618 patients with various subtypes of ARC (nuclear cataract [NC], cortical cataract [CC], posterior subcapsular cataract [PSC]). The control group comprised 236 patients. The incidence of early-onset cataract was significantly greater in PSC patients (P = .002 for NC; P = .036 for CC). One SNP was detected in exon 3 of CRYAA (rs76740365 G>A). When the distribution of rs76740365 was compared among the ARC subtypes, only the difference between the PSC group and the control group was statistically significant (allele frequency: P = .000057, OR 2.945; genotype distribution frequency: P = .000458). The heterozygote genotype (GA) carried a significantly greater risk than the homozygous wild-type genotype (GG) by 1.742 times for all types of cataracts and 2.369 times for the PSC subtype.

CONCLUSIONS

The SNP rs76740365 G>A in exon 3 of the CRYAA gene is associated with greater susceptibility of ARC, particularly the PSC subtype. Individuals carrying the SNP rs76740365 G>A may be more likely to develop PSC at a younger age than other subtypes.

Relationship between expression levels of TDRD7 and CRYBB3 and development of age-related cortico-nuclear cataracts

Background

The human lens develops age-related cataracts (ARCs) because of the complicated effects of aging and stressful conditions. Under conditions involving oxidative stress, cells form stress granules (SGs). TDRD7 has been identified as an RNA granule component and an important component of SGs. TDRD7 plays a role in the post-transcriptional expression of genes, such as the crystallin gene CRYBB3. Therefore, the present study investigated TDRD7 and CRYBB3 mRNA expressions in relation to age-related cortico-nuclear cataracts.

Methods

Quantitative real-time PCR was used to determine the expression levels of TDRD7 and CRYBB3 in 52 patients with ARC and 52 healthy controls. Anterior lens capsules and peripheral blood samples from patients with ARC were included in the patient group, and peripheral blood samples from healthy subjects and human lens epithelial cells (HLE-B3) were included in the control group. Gene expression levels in the different age groups were compared. Correlation analysis was used to assess the gene expression levels and age.

Results

The expression of TDRD7 and CRYBB3 was significantly up-regulated (P < 0.0001) in anterior lens capsules compared to that in HLE-B3 cells. Similarly, the expression of TDRD7 (P = 0.0004) and CRYBB3 (P < 0.0001) was higher in the peripheral blood samples of patients with ARC than in those of healthy subjects. Significant upregulation (P < 0.05) was observed in the 71–81-year age group of patients. No correlation was found between gene expression levels and age.

Conclusion

Significantly higher expression levels of TDRD7 and CRYBB3 in patients with ARC than in controls suggest that TDRD7 and CRYBB3 are associated with the development of age-related cortico-nuclear cataracts and the aging process under chronic stress.

The role of oxidative damage in cataract etiopathogenesis

Background

Cataract usually occurs due to age and diabetes, but the mechanisms of cataract formation have not yet been fully elucidated. In this study, the relationship between cataract and oxidative stress was evaluated by examining the aqueous humor reflecting lens metabolism.

Objective

In this study, the effect of oxidative stress on the etiopathogenesis of cataract was investigated through the total oxidant status (TOS), total antioxidant status (TAS), oxidative stress index (OSI), and arylesterase (ARE) levels in aqueous humor samples of patients with cataract.

Design

A prospective cohort study.

Methods

This study was conducted on patients who were scheduled for cataract surgery between June 2020 and March 2021. The patients were divided into four groups according to their cataract density as grades 1, 2, 3, and 4. TOS, TAS, and ARE levels of aqueous humor samples were measured spectrophotometrically, and comparisons were made between groups.

Results

A total of 100 eyes of 100 patients were included in this study. TAS levels were found significantly higher in the grade 2 group compared with the grade 4 group (p = 0.006). In addition, a significant negative correlation was present between cataract grade and TAS level (r = -0.237; p = 0.018). There was no significant difference between diabetic and nondiabetic patients in terms of TAS, TOS, OSI, and ARE levels.

Conclusion

The aqueous humor of patients with a high degree of cataract is characterized by low antioxidant capacity. Decreased antioxidant capacity has a role in cataract formation and progression.

The protective effect of pomegranate peel aqueous extract on selenite-induced cataract in rats

The present study was performed to evaluate the preventive effect of pomegranate peel extract on sodium-induced cataract in rats. Sprague-Dawley suckling male rats were divided into four groups: group C: rats received no treatment, group P: rats received pomegranate peel aqueous extract (PPE) orally, group Se: rats received an injection of sodium selenite, group Se + P: rats received PPE and sodium selenite concomitantly. After 4 weeks, rats were sacrificed, and their lenses were homogenized and evaluated for biochemical parameters and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In the Se group, developed cataract with significant lens opacity was observed. Other changes in enzymatic and non-enzymatic antioxidants, oxidative parameters, solubility of proteins, in NO and Ca levels and the electrophoresis pattern of proteins were observed in lenses of the Se group compared to control groups. After the preventive administration of PPE, most of these parameters were normalized due to antioxidant and anti-inflammatory activities of the extract. PRACTICAL APPLICATIONS: Cataract is one of the leading causes of vision impairment among the elderly, and surgery is the major therapeutic step taken to cure it. However, surgery has its limitations and complications. Therefore, prevention of cataract development, especially in high-risk individuals, can be better than cure. Pomegranate peel extract has a high potential to prevent cataract in these people.

Biochemistry of Eye Lens in the Norm and in Cataractogenesis

The absence of cellular organelles in fiber cells and very high cytoplasmic protein concentration (up to 900 mg/ml) minimize light scattering in the lens and ensure its transparency. Low oxygen concentration, powerful defense systems (antioxidants, antioxidant enzymes, chaperone-like protein alpha-crystallin, etc.) maintain lens transparency. On the other hand, the ability of crystallins to accumulate age-associated post-translational modifications, which reduce the resistance of lens proteins to oxidative stress, is an important factor contributing to the cataract formation. Here, we suggest a mechanism of cataractogenesis common for the action of different cataractogenic factors, such as age, radiation, ultraviolet light, diabetes, etc. Exposure to these factors leads to the damage and death of lens epithelium, which allows oxygen to penetrate into the lens through the gaps in the epithelial layer and cause oxidative damage to crystallins, resulting in protein denaturation, aggregation, and formation of multilamellar bodies (the main cause of lens opacification). The review discusses various approaches to the inhibition of lens opacification (cataract development), in particular, a combined use of antioxidants and compounds enhancing the chaperone-like properties of alpha-crystallin. We also discuss the paradox of high efficiency of anti-cataract drugs in laboratory settings with the lack of their clinical effect, which might be due to the late use of the drugs at the stage, when the opacification has already formed. A probable solution to this situation will be development of new diagnostic methods that will allow to predict the emergence of cataract long before the manifestation of its clinical signs and to start early preventive treatment.

Inherited cataracts: Genetic mechanisms and pathways new and old

Cataract(s) is the clinical equivalent of lens opacity and is caused by light scattering either by high molecular weight protein aggregates in lens cells or disruption of the lens microarchitecture itself. Genetic mutations underlying inherited cataract can provide insight into the biological processes and pathways critical for lens homeostasis and transparency, classically including the lens crystallins, connexins, membrane proteins or components, and intermediate filament proteins. More recently, cataract genes have been expanded to include newly identified biological processes such as chaperone or protein degradation components, transcription or growth factors, channels active in the lens circulation, and collagen and extracellular matrix components. Cataracts can be classified by age, and in general congenital cataracts are caused by severe mutations resulting in major damage to lens proteins, while age related cataracts are associated with variants that merely destabilize proteins thereby increasing susceptibility to environmental insults over time. Thus there might be separate pathways to opacity for congenital and age-related cataracts whereby congenital cataracts induce the unfolded protein response (UPR) and apoptosis to destroy the lens microarchitecture, while in age related cataract high molecular weight (HMW) aggregates formed by denatured crystallins bound by α-crystallin result in light scattering without severe damage to the lens microarchitecture.

Pseudoexfoliation and Cataract Syndrome Associated with Genetic and Epidemiological Factors in a Mayan Cohort of Guatemala

The Mayan population of Guatemala is understudied within eye and vision research. Studying an observational homogenous, geographically isolated population of individuals seeking eye care may identify unique clinical, demographic, environmental and genetic risk factors for blinding eye disease that can inform targeted and effective screening strategies to achieve better and improved health care distribution. This study served to: (a) identify the ocular health needs within this population; and (b) identify any possible modifiable risk factors contributing to disease pathophysiology within this population. We conducted a cross-sectional study with 126 participants. Each participant completed a comprehensive eye examination, provided a blood sample for genetic analysis, and received a structured core baseline interview for a standardized epidemiological questionnaire at the Salama Lions Club Eye Hospital in Salama, Guatemala. Interpreters were available for translation to the patients’ native dialect, to assist participants during their visit. We performed a genome-wide association study for ocular disease association on the blood samples using Illumina’s HumanOmni2.5-8 chip to examine single nucleotide polymorphism SNPs in this population. After implementing quality control measures, we performed adjusted logistic regression analysis to determine which genetic and epidemiological factors were associated with eye disease. We found that the most prevalent eye conditions were cataracts (54.8%) followed by pseudoexfoliation syndrome (PXF) (24.6%). The population with both conditions was 22.2%. In our epidemiological analysis, we found that eye disease was significantly associated with advanced age. Cataracts were significantly more common among those living in the 10 districts with the least resources. Furthermore, having cataracts was associated with a greater likelihood of PXF after adjusting for both age and sex. In our genetic analysis, the SNP most nominally significantly associated with PXF lay within the gene KSR2 (p < 1 × 10⁻⁵). Several SNPs were associated with cataracts at genome-wide significance after adjusting for covariates (p < 5 × 10⁻⁸). About seventy five percent of the 33 cataract-associated SNPs lie within 13 genes, with the majority of genes having only one significant SNP (5 × 10⁻⁸). Using bioinformatic tools including PhenGenI, the Ensembl genome browser and literature review, these SNPs and genes have not previously been associated with PXF or cataracts, separately or in combination. This study can aid in understanding the prevalence of eye conditions in this population to better help inform public health planning and the delivery of quality, accessible, and relevant health and preventative care within Salama, Guatemala.

Association of Alpha-Crystallin with Fiber Cell Plasma Membrane of the Eye Lens Accompanied by Light Scattering and Cataract Formation

α-crystallin is a major protein found in the mammalian eye lens that works as a molecular chaperone by preventing the aggregation of proteins and providing tolerance to stress in the eye lens. These functions of α-crystallin are significant for maintaining lens transparency. However, with age and cataract formation, the concentration of α-crystallin in the eye lens cytoplasm decreases with a corresponding increase in the membrane-bound α-crystallin, accompanied by increased light scattering. The purpose of this review is to summarize previous and recent findings of the role of the: (1) lens membrane components, i.e., the major phospholipids (PLs) and sphingolipids, cholesterol (Chol), cholesterol bilayer domains (CBDs), and the integral membrane proteins aquaporin-0 (AQP0; formally MIP26) and connexins, and (2) α-crystallin mutations and post-translational modifications (PTMs) in the association of α-crystallin to the eye lens's fiber cell plasma membrane, providing thorough insights into a molecular basis of such an association. Furthermore, this review highlights the current knowledge and need for further studies to understand the fundamental molecular processes involved in the association of α-crystallin to the lens membrane, potentially leading to new avenues for preventing cataract formation and progression.

Polymorphisms in CRYAA Promoter with Susceptibility to Cataract: A Meta-Analysis

AIM

Polymorphisms in alpha A crystallin (CRYAA) gene have been implicated in susceptibility to cataracts, but some published studies have reported inconclusive results. Our study aimed to conduct a meta-analysis investigating the association between polymorphisms in CRYAA and susceptibility to cataracts.

METHODS

The PubMed, Excerpta Medica Database, Cochrane Library and China National Knowledge Infrastructure were searched for all articles published up to 20 March 2019 that reported cataracts and three polymorphisms (rs3761381, rs13053109, and rs7278468) of CRYAA. Afterwards, statistical analysis was performed for available articles.

RESULTS

Four articles published between 2014 and 2017 were included, involving 869 cases and 1,950 controls. There was no statistical evidence of an association between cataract risk and CRYAA gene polymorphisms rs13053109 (p > .05) and rs3761382 (p > .05). Significant decreased cataract risks were observed for different gene models of rs7278468 polymorphism: for G vs T, OR = 0.6640; 95% CI, 0.5361-0.7736, p < .001; for GG vs TT, OR = 0.3864; 95% CI, 0.2379-0.6278, p < .001; for GG vs TT+GT, OR = 0.4492; 95% CI, 0.2829-0.7134, p = .001; for GG+GT vs TT, OR = 0.6645; 95% CI, 0.5058-0.8729, p = .003; for GT vs TT, OR = 0.7508; 95% CI, 0.5639-0.9996, p = .050.

CONCLUSION

Our meta-analysis indicated that rs3761382 and rs13053109 polymorphisms of CRYAA may not be associated with susceptibility to cataracts. Individuals carrying mutant genotype of rs7278468 polymorphism are associated with a significantly decreased cataract risk.

ABBREVIATIONS

CC: Congenital cataract; ARC: Age-related cataract; SNPs: single nucleotide polymorphisms; NOS: Newcastle-Ottawa Scale; HWE: Hardy-Weinberg equilibrium; OR: odds ratio; CI: confidence interval; qPCR: quantitative polymerase chain reaction; NO: nuclear opalescence; NC: nuclear color.

RNA sequencing and bioinformatics analysis of human lens epithelial cells in age-related cataract

Background

Age-related cataract (ARC) is the main cause of blindness in older individuals but its specific pathogenic mechanism is unclear. This study aimed to identify differentially expressed genes (DEGs) associated with ARC and to improve our understanding of the disease mechanism.

Methods

Anterior capsule samples of the human lens were collected from ARC patients and healthy controls and used for RNA sequencing to detect DEGs. Identified DEGs underwent bioinformatics analyses, including Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses. Subsequently, reverse transcription quantitative RT-qPCR was used to validate the different expression levels of selected genes.

Results

A total of 698 up-regulated DEGs and 414 down-regulated DEGs were identified in ARC patients compared with controls by transcriptome analysis. Through GO and KEGG bioinformatics analysis, the functions of significantly DEGs and their possible molecular mechanisms were determined. Sequencing results were verified by RT-qPCR as being accurate and reliable.

Conclusions

This study identified several genes associated with ARC, which improves our knowledge of the disease mechanism.

Interaction of Alpha-Crystallin with Phospholipid Membranes

Purpose/Aim: The amount of membrane-bound α-crystallin increases significantly with age and cataract formation, accompanied by a corresponding decline in the level of α-crystallin in the lens cytoplasm. The purpose of this research is to evaluate the binding affinity of α-crystallin to the phospholipid membranes as well as the physical properties of the membranes after α-crystallin binding. Materials and Methods: The continuous wave and saturation recovery electron paramagnetic resonance (EPR) methods were used to obtain the information about the binding affinity and the physical properties of the membrane. In this approach, the cholesterol analog spin label CSL was incorporated in the membrane and the binding of α-crystallin to the membrane was monitored by this spin label. Small uni-lamellar vesicles were prepared from 1-palmitoyl-2-oleoylphosphatidylcholine (POPC) with 1% of CSL. The measured membrane properties included the mobility parameter, fluidity, and the oxygen transport parameter. Results: The binding affinity (Ka ) of α-crystallin with the POPC membrane was estimated to be 4.9 ± 2.4 µM-1. The profiles of mobility parameter showed that mobility parameter decreased with an increase in the binding of α-crystallin. The profiles of spin-lattice relaxation rate showed that the spin-lattice relaxation rate decreased with an increase in binding. These results show that the binding of α-crystallin makes the membrane more immobilized near the head group region of the phospholipids. Furthermore, the profiles of the oxygen transport parameter indicated that the oxygen transport parameter decreased with an increase of binding, indicating the binding of α-crystallin forms a barrier for the passage of non-polar molecules which supports the barrier hypothesis. Conclusions: The binding of α-crystallin to the membrane alters the physical properties of the membranes, and this plays a significant role in modulating the integrity of the membranes. EPR techniques are useful in studying α-crystallin membrane interactions.

Comprehensive Profiling of Proteome and Ubiquitome Changes in Human Lens Epithelial Cell Line after Ultraviolet-B Irradiation

Ultraviolet-B (UVB) is a recognized risk factor for age-related cataract (ARC) and can cause various changes, including ubiquitination, in lens epithelial cells (LECs). However, the relationship between ubiquitination and ARC is unclear. Herein, we used UVB-irradiated human lens epithelial cell line (SRA01/04) representing the cell model of ARC to investigate the profile changes in the proteome and ubiquitome. A total of 552 differentially expressed proteins (DEPs) and 871 differentially ubiquitinated proteins (DUPs) were identified, and 9 ubiquitination motifs were found. Bioinformatics analysis revealed diverse pathways and biological processes of differential proteins and several DNA damage repair proteins that were potentially mediated via ubiquitin-proteasome pathway. We validated the decreased protein expression of DNA-directed RNA polymerase II subunit RPB2 (POLR2B) in both human cataract capsule tissues and UVB-treated SRA01/04 cells and found that treatment with proteasome inhibitor (MG-132) could reverse the protein level of POLR2B in UVB-irradiated SRA01/04 cells. Our data provide novel information regarding protein expressions and ubiquitination modifications in UVB-induced oxidative damage model. This study might offer a cell-level reference to further investigate the pathogenesis of ARC.

Interaction of alpha-crystallin with four major phospholipids of eye lens membranes

It is well-studied that the significant factor in cataract formation is the association of α-crystallin, a major eye lens protein, with the fiber cell plasma membrane of the eye lens. The fiber cell plasma membrane of the eye lens consists of four major phospholipids (PLs), i.e., phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS), and sphingomyelin (SM). Despite several attempts to study the interaction of α-crystallin with PLs of the eye lens membrane, the role of individual PL for the binding with α-crystallin is still unclear. We recently developed the electron paramagnetic resonance (EPR) spin-labeling method to study the binding of α-crystallin to the PC membrane (Mainali et al., 2020a). Here, we use the recently developed EPR method to explicitly measure the binding affinity (K_a) of α-crystallin to the individual (PE*, PS, and SM) and two-component mixtures (SM/PE, SM/PS, and SM/PC in 70:30 and 50:50 mol%) of PL membranes as well as the physical properties (mobility parameter and maximum splitting) of these membranes upon binding with α-crystallin. One of the key findings of this study was that the K_a of α-crystallin binding to individual PL membranes followed the trends: K_a(PC) > K_a(SM) > K_a(PS) > K_a(PE*), indicating PE* inhibits binding the most whereas PC inhibits binding the least. Also, the K_a of α-crystallin binding to two-component mixtures of PL membranes followed the trends: K_a(SM/PE) > K_a(SM/PS) > K_a(SM/PC), indicating SM/PC inhibits binding the most whereas SM/PE inhibits binding the least. Except for the PE* membrane, for which there was no binding of α-crystallin, the mobility parameter for all other membranes decreased with an increase in α-crystallin concentration. It represents that the membranes become more immobilized near the headgroup regions of the PLs when more and more α-crystallin binds to them. The maximum splitting increased only for the SM and the SM/PE (70:30 mol%) membranes, with an increase in the binding of α-crystallin. It represents that the PL headgroup regions of these membranes become more ordered after binding of α-crystallin to these membranes. Our results showed that α-crystallin binds to PL membranes in a saturable manner. Also, our data suggest that the binding of α-crystallin to PL membranes likely occurs through hydrophobic interaction between α-crystallin and the hydrophobic fatty acid core of the membranes, and such interaction is modulated by the PL headgroup's size and charge, hydrogen bonding between headgroups, and PL curvature. Thus, this study provides an in-depth understanding of α-crystallin interaction with the PL membranes made of individual and two-component mixtures of the four major PLs of the eye lens membranes.

Long non‑coding RNA NONHSAT143692.2 is involved in oxidative DNA damage repair in the lens by regulating the miR‑4728‑5p/OGG1 axis

Age-related cataract (ARC) is the leading cause of blindness worldwide. Oxidative DNA damage is a biochemical feature of ARC pathogenesis. The present study investigated the role of long non-coding RNAs in the DNA repair of oxidative damage, partially the regulation of the DNA repair gene, 8-oxoguanine DNA glycosylase (OGG1), in lens affected by ARC. The ogg1 mutant zebrafish model was constructed to verify the role of ogg1 in the lens. A high-throughput lncRNA profiling was performed on human lens epithelial cells (LECs) following oxidative stress. The lncRNAs with the OGG1 target gene were analyzed for possible differentiated expression levels. The lens capsule samples of patients with ARC were collected to further verify the screening results. lncRNA was then overexpressed and knocked down in LECs to observe cell proliferation and apoptosis. The association between lncRNA, miRNA and the OGG1 mRNA 3′UTR were analyzed. The ogg1 mutant zebrafish developed more severe lens lesions following oxidative challenge. lncRNA NONHSAT143692.2 was distinctly expressed in various disease models. The knockdown of NONHSAT143692.2 downregulated the expression of OGG1 mRNA (P<0.001) and OGG1 protein (P<0.001), aggravated oxidative damage to LECs, increased apoptosis (P<0.001) and decreased cell proliferation (P<0.01). The overexpression of NONHSAT143692.2 reversed the above-mentioned outcomes. miR-4728-5p was predicted to bind to NONHSAT143692.2 and OGG1 mRNA 3′UTR. The overexpression of miR-4728-5p downregulated the expression of NONHSAT143692.2 (P<0.001), OGG1 mRNA (P<0.001) and OGG1 protein (P<0.001). The knockdown of miR-4728-5p reversed the above-mentioned outcomes. Overall, the findings of the present study demonstrate that the NONHSAT143692.2/miR-4728-5p/OGG1 axis may play an important role in the development of ARC. This novel concept may provide new insight into the molecular diagnosis and treatment of ARC.

Biology of Inherited Cataracts and Opportunities for Treatment

Cataract, the clinical correlate of opacity or light scattering in the eye lens, is usually caused by the presence of high-molecular-weight (HMW) protein aggregates or disruption of the lens microarchitecture. In general, genes involved in inherited cataracts reflect important processes and pathways in the lens including lens crystallins, connexins, growth factors, membrane proteins, intermediate filament proteins, and chaperones. Usually, mutations causing severe damage to proteins cause congenital cataracts, while milder variants increasing susceptibility to environmental insults are associated with age-related cataracts. These may have different pathogenic mechanisms: Congenital cataracts induce the unfolded protein response and apoptosis. By contrast, denatured crystallins in age-related cataracts are bound by α-crystallin and form light-scattering HMW aggregates. New therapeutic approaches to age-related cataracts use chemical chaperones to solubilize HMW aggregates, while attempts are being made to regenerate lenses using endogenous stem cells to treat congenital cataracts.

lncRNA H19 contributes to oxidative damage repair in the early age-related cataract by regulating miR-29a/TDG axis

Age‐related cataract (ARC) is caused by the exposure of the lens to UVB which promotes oxidative damage and cell death. This study aimed to explore the role of lncRNA H19 in oxidative damage repair in early ARC. lncRNAs sequencing technique was used to identify different lncRNAs in the lens of early ARC patients. Human lens epithelial cells (HLECs) were exposed to ultraviolet irradiation; and 8‐OHdG ELISA, Cell counting kit 8 (CCK8), EDU, flow cytometry and TUNEL assays were used to detect DNA damage, cell viability, proliferation and apoptosis. Luciferase assay was used to examine the interaction among H19, miR‐29a and thymine DNA glycosylase (TDG) 3'UTR. We found that lncRNA H19 and TDG were highly expressed while miR‐29a was down‐regulated in the three types of early ARC and HLECs exposed to ultraviolet irradiation, compared to respective controls. lncRNA H19 knockdown aggravated oxidative damage, reduced cell viability and proliferation, and promoted apoptosis in HLECs, while lncRNA H19 overexpression led to opposite effects in HLECs. Mechanistically, miR‐29a bound TDG 3'UTR to repress TDG expression. lncRNA H19 up‐regulated the expression of TDG by repressing miR‐29a because it acted as ceRNA through sponging miR‐29a. In conclusion, the interaction among lncRNA H19, miR‐29a and TDG is involved in early ARC. lncRNA H19 could be a useful marker of early ARC and oxidative damage repair pathway of lncRNA H19/miR‐29a/TDG may be a promising target for the treatment of ARC.

Medicinal Plants and Natural Products Used in Cataract Management

Cataract is the leading reason of blindness worldwide and is defined by the presence of any lens opacities or loss of transparency. The most common symptoms of cataract are impaired vision, decreased contrast sensitivity, color disturbance, and glare. Oxidative stress is among the main mechanisms involved in the development of age-related cataract. Surgery through phacoemulsification and intraocular lens implantation is the most effective method for cataract treatment, however, there are chances of serious complications and irreversible loss of vision associated with the surgery. Natural compounds consisting of antioxidant or anti-inflammatory secondary metabolites can serve as potential leads for anticataract agents. In this review, we tried to document medicinal plants and plant-based natural products used for cataract treatment worldwide, which are gathered from available ethnopharmacological/ethnobotanical data. We have extensively explored a number of recognized databases like Scifinder, PubMed, Science Direct, Google Scholar, and Scopus by using keywords and phrases such as “cataract”, “blindness”, “traditional medicine”, “ethnopharmacology”, “ethnobotany”, “herbs”, “medicinal plants”, or other relevant terms, and summarized the plants/phytoconstituents that are evaluated in different models of cataract and also tabulated 44 plants that are traditionally used in cataract in various folklore medical practices. Moreover, we also categorized the plants according to scientific studies carried out in different cataract models with their mechanisms of action.

A Rat Eye Lens Model of Cataract Formation

This chapter describes the use of lenses obtained from rats as a model of cataractogenesis. At the molecular level, this is visualized as reduced activity of oxidative reductive enzymes such as aldose reductase and increased proteolysis of lens structural proteins including vimentin. In this chapter, protocols for assessment of these two pathways are presented. Specifically, this analysis shows a comparison of aldose reductase activity and vimentin cleavage in male and female rat lenses. This is because female rats are more susceptible to cataract formation compared to males.

2D-DIGE Analysis of Eye Lens Proteins as a Measure of Cataract Formation

This chapter describes the basics of two-dimensional difference gel electrophoresis (2D-DIGE) for multiplex analysis of two distinct proteomes. The example given describes the analysis of male and female rat lens soluble proteins labeled with fluorescent Cy3 and Cy5 dyes in comparison to a pooled standard labeled with Cy2. After labeling the proteomes are mixed together and electrophoresed on the same 2D gels. Scanning the gels at wavelengths specific for each dye allows direct overlay the two different proteomes. Differences in abundance of specific protein spots can be determined through comparison to the pooled standard.

A review on ocular findings in mouse lemurs: potential links to age and genetic background

Mouse lemurs, the world's smallest primates, inhabit forests in Madagascar. They are nocturnal, arboreal and dependent on vision for their everyday lives. In the last decades, the grey mouse lemur became increasingly important for biomedical research, in particular aging research. Experiments which require the combination of visual fitness and old age consequently depend on a solid knowledge of ocular pathologies. Although ocular diseases in mouse lemurs have been described as being common, they have not received much attention so far. Yet it is important to know when and why ocular diseases in captive mouse lemurs may occur. This review aims to provide a comprehensive overview of known ocular findings in mouse lemurs. It summarizes the frequency of ocular findings in captive mouse lemur colonies and points to their likely causes and treatment options based on the evidence available from other animals and humans. In addition, it shall be discussed whether age or genetic background may affect their development. This review may be used as a reference for future studies which require an assessment of visual performance in mouse lemurs and help to evaluate observed clinical signs and ocular diseases. Furthermore, the high incidence of specific diseases may provide new perspectives and set the groundwork for a new animal model for ocular research.

Functional non-coding polymorphism in an EPHA2 promoter PAX2 binding site modifies expression and alters the MAPK and AKT pathways

To identify possible genetic variants influencing expression of EPHA2 (Ephrin-receptor Type-A2), a tyrosine kinase receptor that has been shown to be important for lens development and to contribute to both congenital and age related cataract when mutated, the extended promoter region of EPHA2 was screened for variants. SNP rs6603883 lies in a PAX2 binding site in the EPHA2 promoter region. The C (minor) allele decreased EPHA2 transcriptional activity relative to the T allele by reducing the binding affinity of PAX2. Knockdown of PAX2 in human lens epithelial (HLE) cells decreased endogenous expression of EPHA2. Whole RNA sequencing showed that extracellular matrix (ECM), MAPK-AKT signaling pathways and cytoskeleton related genes were dysregulated in EPHA2 knockdown HLE cells. Taken together, these results indicate a functional non-coding SNP in EPHA2 promoter affects PAX2 binding and reduces EPHA2 expression. They further suggest that decreasing EPHA2 levels alters MAPK, AKT signaling pathways and ECM and cytoskeletal genes in lens cells that could contribute to cataract. These results demonstrate a direct role for PAX2 in EPHA2 expression and help delineate the role of EPHA2 in development and homeostasis required for lens transparency.

New cataract markers: Mechanisms of disease

Cataract is caused by nutritional, metabolic, environmental, and genetic factors, and is a significant cause of blindness and visual impairment. In recent years, extensive research into the human genome has revealed that numerous genetic mutations are associated with cataract. These mutations affect a variety of genes, including those encoding crystallin, membrane proteins, cytoskeletal proteins, transcription factors, and metabolism-related proteins. Elucidation of these mutations and the genetic and molecular mechanisms has helped clarify the etiology of cataract and may facilitate its early diagnosis and treatment. This review summarizes recent advances in our knowledge and potential clinical of genetic markers of cataract.

Novel Mutations in the Crystallin Gene in Age-Related Cataract Patients from a North Indian Population

Cataract is the most prevalent leading cause of visual impairment and blindness worldwide. In comparison to congenital cataract, which affects relatively few individuals, age-related cataract is responsible for slightly half of all cases of blindness worldwide. Although significant work has been done, the genetic aspect of age-related cataract is still in its infancy. The current study was performed to analyze the mutations and polymorphisms in the CRYAA, CRYAB, CRYBB1, and GJA8 genes in 40 unrelated age-related cataract patients. Mutational analysis of the above-mentioned genes in 40 cataract cases revealed 14 different substitutions of which 8 variants were novel and 6 were reported SNPs. Two disease-causing mutations, g.44590631G>A (p.R65Q) and g.44592224G>A (p.R119H), were also observed in the CRYAA gene. The disease-causing variants mildly affect the stability, functionality, and localization of crystallin, and, with progressing age, a small change in the microenvironment of the crystallin lens occurs. This change in combination with a mutation may significantly alter the functionality of the crystallin protein, leading to age-related cataract.

Mutations and mechanisms in congenital and age-related cataracts

The crystalline lens plays an important role in the refractive vision of vertebrates by facilitating variable fine focusing of light onto the retina. Loss of lens transparency, or cataract, is a frequently acquired cause of visual impairment in adults and may also present during childhood. Genetic studies have identified mutations in over 30 causative genes for congenital or other early-onset forms of cataract as well as several gene variants associated with age-related cataract. However, the pathogenic mechanisms resulting from genetic determinants of cataract are only just beginning to be understood. Here, we briefly summarize current concepts pointing to differences in the molecular mechanisms underlying congenital and age-related forms of cataract.

Effect of lanosterol on human cataract nucleus

Aim:

To study the effect of lanosterol on age-related cataractous human lens nuclei.

Materials and Methods:

Forty age-related cataractous nuclei removed during manual small incision cataract surgery were obtained and randomly immersed in 25 mM lanosterol solution or in control solution and stored at room temperature for 6 days. Pre- and post-immersion photographs were graded by two masked observers and collated for the regression or progression of lens opacity.

Results:

Both lanosterol and control groups showed progression or no change in the lens opacity at the end of 6 days.

Conclusion:

Lanosterol 25 mM solution did not reverse opacification of human age-related cataractous nuclei.

Functional SNP in 3'-UTR MicroRNA-Binding Site of ZNF350 Confers Risk for Age-Related Cataract

Many studies have suggested that individual susceptibility to age-related cataract (ARC) may be associated with DNA sequence polymorphisms affecting gene regulation. As DNA repair is implicated in ARC pathogenesis and single-nucleotide polymorphisms (SNPs) in the 3'-terminal untranslated region (3'-UTR) targeted by microRNAs (miRNAs) can alter the gene function, we hypothesize that the miRNA-binding SNPs (miRSNPs) in DNA double-strand break repair (DSBR) and nucleotide excision repair (NER) pathways might associate with ARC risk. We genotyped nine miRSNPs of eight genes in DSBR and NER pathways in Chinese population and found that ZNF350- rs2278414:G>A was significantly associated with ARC risk. Even though the Comet assay of cellular DNA damage indicated that all the subtypes of ARC patients had more DNA breaks in peripheral lymphocytes than the controls independent of rs2278414 genotypes, individuals carrying the variant A allele (AA and AG) had lower ZNF350 mRNA levels compared with individuals with GG genotype. Moreover, the in vitro experiment indicated that miR-21-3p and miR-150-5p specifically downregulated luciferase reporter expression in the cell lines transfected with rs2278414 A allele compared with rs2278414 G. These results suggested that the association of SNP rs2278414 with ARC might involve an altered miRNA regulation of ZNF350.

Role of long non-coding RNA MIAT in proliferation, apoptosis and migration of lens epithelial cells: a clinical and in vitro study

Age‐related cataract is among the most common chronic disorders of ageing and is the world's leading blinding disorder. Long non‐coding RNAs play important roles in several biological processes and complicated diseases. However, the role of lncRNAs in the setting of cataract is still unknown. Here, we extracted total RNAs from the transparent and age‐matched cataractous human lenses, and determined lncRNA expression profiles using microarray analysis. We found that 38 lncRNAs were differentially expressed between transparent and cataractous lenses. 17 of 20 differentially expressed lncRNAs were further verified by quantitative RT‐PCRs. One top abundant lncRNA, MIAT, was specifically up‐regulated both in the plasma fraction of whole blood and aqueous humor of cataract patients. MIAT knockdown could affect the proliferation, apoptosis and migration of Human lens epithelial cells (HLECs) upon oxidative stress. Posterior capsule opacification (PCO) is a common complication of cataract surgery, which is associated with abnormal production of inflammatory factors. MIAT knockdown could repress tumour necrosis factor‐α‐induced abnormal proliferation and migration of HLECs, suggesting a potential role of MIAT in PCO‐related pathological process. Moreover, we found that MIAT acted as a ceRNA, and formed a feedback loop with Akt and miR‐150‐5p to regulate HLEC function. Collectively, this study provides a novel insight into the pathogenesis of age‐related cataract.

The Polymorphisms with Cataract Susceptibility Impair the EPHA2 Receptor Stability and Its Cytoprotective Function

Despite accumulating evidence revealing susceptibility genes for age-related cataract, its pathophysiology leading to visual impairment at the cellular and molecular level remains poorly understood. Recent bioinformatic studies uncovered the association of two single nucleotide polymorphisms in human EPHA2, rs2291806 and rs1058371, with age-related cataract. Here we investigated the role of EPHA2 in counteracting oxidative stress-induced apoptosis of lens epithelial cells. The cataract-associated missense mutations resulted in the destabilization of EPHA2 receptor without altering the mRNA transcription. The cytoprotective and antiapoptotic function of EPHA2 in lens epithelial cells was abolished by the functional polymorphisms. Furthermore, our results suggest that the downstream signaling of activated EPHA2 promotes the antioxidative capacity of lens epithelial cells to eradicate the overproduction of reactive oxygen species. In contrast, the overexpression of EPHA2 with nonsynonymous mutations in the lens epithelial cells offered limited antioxidative protection against oxidative stress. Thus, our study not only sheds the light on the potential cytoprotective function of EPHA2 signaling in lens but also provides the cellular mechanisms underlying the pathogenesis of age-related cataract.

The effect of GSTT1, GSTM1 and GSTP1 gene polymorphisms on the susceptibility of age-related cataract in Chinese Han population

OBJECTIVE

Age-related cataract (ARC) is one of the most common eye diseases in the elderly worldwide, especially in China. The genetic polymorphisms of many glutathione S-transferases coding genes are likely to be closely related to the development of ARC, especially the GSTT1, the GSTM1 and the GSTP1. This investigation is aimed to determine the possible associations of GSTT1, GSTM1 and GSTP1 polymorphisms with the susceptibility of ARC in Chinese Han Population.

METHODS

A case-control study including ARC cases (n = 312) and controls (n = 256) in Chinese Han Population was performed. GSTT1 and GSTM1 polymorphisms were detected by duplex polymerase chain reaction (PCR), and two SNPs (rs1695, A/G and rs1138272, C/T) in GSTP1 gene were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method, all the results were verified by sequencing method.

RESULTS

The GSTT1 null genotype carriers had a much higher risk of ARC compared with non-null genotype (χ(2) = 14.091, P<0.001), and the allele G carriers also had a increased risk over the allele A carriers in the SNP (rs1695, A/G) in GSTP1 gene (χ(2) = 7.696, P = 0.006), while the GSTM1 polymorphism and the SNP (rs1138272, C/T) in GSTP1 gene seem had no association with the susceptibility of ARC in Chinese Han Population.

CONCLUSIONS

These preliminary results indicated carriage of null GSTT1 and GSTP1 Val/Val genotypes may contribute to genetic susceptibility to ARC in Chinese Han Population, and these genetic polymorphisms might be used as molecular markers for detecting ARC susceptibility.

Biology-Driven Gene-Gene Interaction Analysis of Age-Related Cataract in the eMERGE Network

Bioinformatics approaches to examine gene-gene models provide a means to discover interactions between multiple genes that underlie complex disease. Extensive computational demands and adjusting for multiple testing make uncovering genetic interactions a challenge. Here, we address these issues using our knowledge-driven filtering method, Biofilter, to identify putative single nucleotide polymorphism (SNP) interaction models for cataract susceptibility, thereby reducing the number of models for analysis. Models were evaluated in 3,377 European Americans (1,185 controls, 2,192 cases) from the Marshfield Clinic, a study site of the Electronic Medical Records and Genomics (eMERGE) Network, using logistic regression. All statistically significant models from the Marshfield Clinic were then evaluated in an independent dataset of 4,311 individuals (742 controls, 3,569 cases), using independent samples from additional study sites in the eMERGE Network: Mayo Clinic, Group Health/University of Washington, Vanderbilt University Medical Center, and Geisinger Health System. Eighty-three SNP-SNP models replicated in the independent dataset at likelihood ratio test P < 0.05. Among the most significant replicating models was rs12597188 (intron of CDH1)-rs11564445 (intron of CTNNB1). These genes are known to be involved in processes that include: cell-to-cell adhesion signaling, cell-cell junction organization, and cell-cell communication. Further Biofilter analysis of all replicating models revealed a number of common functions among the genes harboring the 83 replicating SNP-SNP models, which included signal transduction and PI3K-Akt signaling pathway. These findings demonstrate the utility of Biofilter as a biology-driven method, applicable for any genome-wide association study dataset.

Aging and regeneration in vertebrates

Aging is marked by changes that affect organs and resident stem cell function. Shorting of telomeres, DNA damage, oxidative stress, deregulation of genes and proteins, impaired cell-cell communication, and an altered systemic environment cause the eventual demise of cells. At the same time, reparative activities also decline. It is intriguing to correlate aging with the decline of regenerative abilities. Animal models with strong regenerative capabilities imply that aging processes might not be affecting regeneration. In this review, we selectively present age-dependent changes in stem/progenitor cells that are vital for tissue homeostasis and repair. In addition, the aging effect on regeneration following injury in organs such as lung, skeletal muscle, heart, nervous system, cochlear hair, lens, and liver are discussed. These tissues are also known for diseases such as heart attack, stroke, cognitive impairment, cataract, and hearing loss that occur mostly during aging in humans. Conclusively, vertebrate regeneration declines with age with the loss of stem/progenitor cell function. Future studies on improving the function of stem cells, along with studies in fish and amphibians where regeneration does not decline with age, will undoubtedly provide insights into both processes.

Mutational screening of EFNA5 in Chinese age-related cataract patients

BACKGROUND/AIM

In the past few years, Ephrin-A5 (EFNA5) had been identified to be associated with lens development, but so far no sequence variation in EFNA5 has been reported in humans. Therefore, we conduct this study to investigate the EFNA5 genetic variations in Chinese age-related cataract (ARC) patients.

METHODS

Sequencing of EFNA5 was performed in 140 sporadic ARC patients and 142 random unrelated healthy subjects. Genomic DNA was extracted from peripheral blood leukocytes. All exons of EFNA5 were sequenced after being amplified by polymerase chain reaction. The functional consequences of the variations were analyzed using PolyPhen2.

RESULTS

Three single nucleotide polymorphisms in EFNA5, c.668C>T (rs201008479), c.102C>T (rs199980747) and c.-27C>G (rs200187971), were found in the patients, and none of them presented in the normal controls. Using PolyPhen2, c.668C>T in EFNA5 is predicted to be possibly damaging.

CONCLUSIONS

The genetic variations c.668C>T (rs201008479), c.102C>T (rs199980747) and c.-27C>G (rs200187971) may present an additional genetic risk factor for ARC in the Chinese population. This study shows the first cases of these genetic variations in EFNA5 in human beings.

Electronic medical records and genomics (eMERGE) network exploration in cataract: several new potential susceptibility loci

PURPOSE

Cataract is the leading cause of blindness in the world, and in the United States accounts for approximately 60% of Medicare costs related to vision. The purpose of this study was to identify genetic markers for age-related cataract through a genome-wide association study (GWAS).

METHODS

In the electronic medical records and genomics (eMERGE) network, we ran an electronic phenotyping algorithm on individuals in each of five sites with electronic medical records linked to DNA biobanks. We performed a GWAS using 530,101 SNPs from the Illumina 660W-Quad in a total of 7,397 individuals (5,503 cases and 1,894 controls). We also performed an age-at-diagnosis case-only analysis.

RESULTS

We identified several statistically significant associations with age-related cataract (45 SNPs) as well as age at diagnosis (44 SNPs). The 45 SNPs associated with cataract at p<1×10(-5) are in several interesting genes, including ALDOB, MAP3K1, and MEF2C. All have potential biologic relationships with cataracts.

CONCLUSIONS

This is the first genome-wide association study of age-related cataract, and several regions of interest have been identified. The eMERGE network has pioneered the exploration of genomic associations in biobanks linked to electronic health records, and this study is another example of the utility of such resources. Explorations of age-related cataract including validation and replication of the association results identified herein are needed in future studies.

Association between DNA repair genes (XPD and XRCC1) polymorphisms and susceptibility to age-related cataract (ARC): a meta-analysis

BACKGROUND

DNA repair gene (XPD and XRCC1) polymorphisms have been considered as risk factors for the development of age-related cataract (ARC). To confirm the association between DNA repair gene (XPD and XRCC1) polymorphisms and the risk of ARC, a meta-analysis was conducted.

METHODS

A search was made of published literature from Institute for Scientific Information (ISI) Web of Knowledge, PubMed, Google Scholar, China National Knowledge Infrastructure (CNKI), and Wanfang Data. In addition, all studies evaluating the association between DNA repair genes (XPD and XRCC1) polymorphisms and the risk for ARC were included in our analysis. Pooled odds ratio (OR) and 95 % confidence interval (CI) were calculated by using fixed- or random-effects model. The Egger's test was used to check the publication bias.

RESULTS

Six studies on XRCC1 Arg399Gln (1,300 cases, 1,222 controls) and five studies on XPD Lys751Gln (1,092 cases, 1,061 controls) were included. For the XPD Lys751Gln (A/C) SNP, the overall analysis demonstrated that the CC genotype showed a significant association with a decreased risk for ARC compared with the AA genotype (OR = 0.59, 95 % CI, 0.38-0.92, P = 0.019). Similarly, the CC genotype showed a significant association with a decreased risk for ARC compared with the (AA + AC) genotype (OR = 0.65, 95 % CI, 0.43-0.98, P = 0.040). Subgroup analysis showed that the association between the CC genotype and decreased risk for ARC is statistically significant in Caucasians (OR = 0.41, 95 % CI, 0.24-0.73, P = 0.002) but not in Asians (OR = 1.06, 95 % CI, 0.51-2.19, P = 0.877). For the XRCC1 Arg399Gln (G/A) SNP, the overall analysis demonstrated that the A allele showed a significant association with an increased risk for ARC compared with the G allele (OR = 1.16, 95 % CI, 1.03-1.31, P = 0.015). Subgroup analyses exhibited that the association between the A allele and the risk for ARC was statistically significant in Asians (OR = 1.23, 95 % CI, 1.07-1.41, P = 0.003) but not in Caucasians (OR = 0.94, 95 % CI, 0.73-1.22, P = 0.660). Compared with the GG genotype, the GA genotype showed a significant association with an increased risk for ARC in Asians (OR = 1.32, 95 % CI, 1.08-1.61, P = 0.006) but not in Caucasians (OR = 0.58, 95 % CI, 0.27-1.26, P = 0.171). The Egger's test did not reveal an obvious publication bias among the included studies.

CONCLUSIONS

Our meta-analysis suggested that the CC genotype of XPD Lys751Gln (A/C) SNP seemed to portend a decreased risk for ARC in Caucasian populations but not in Asian populations. The A allele and GA genotype of XRCC1 Arg399Gln (G/A) SNP might increase risk for ARC in Asian populations but not in Caucasian populations. More researches with larger and more different ethnic populations on this issue are therefore necessary.

Polymorphism of GST and FTO Genes in Risk Prediction of Cataract among a North Indian Population

BACKGROUND

The present study was carried out to investigate the association of GST and FTO gene polymorphisms with cataract cases and controls.

MATERIALS AND METHODS

The study included 131 cases and 126 controls. GST and FTO gene polymorphisms were evaluated by PCR-RFLP.

RESULTS

The frequency of the GSTM1-positive and GSTT1-positive in cataract cases were 62.13% and 86.40% while in the controls it was 46.39% and 95.87% with odds ratios of 1.9 (95% CI, 1.08-3.32; p value 0.025) and 0.27 (95% CI, 0.09-0.86; p value, 0.019) respectively. There was a statistically significant association between the GSTM1 null genotype and the risk of cataract development with an odds ratio of 0.43 (95% CI, 0.24-0.76; p value, 0.003). Significant differences were obtained in the frequencies of FTO AA and TT genotype (p = 0.023 and 0.023) between cases and controls.

CONCLUSION

The present study suggested that GSTM1, GSTT1 and FTO gene polymorphisms are associated with increased risk for cataract in North Indian populations. Due to the limited sample size, the finding on GST and FTO gene polymorphisms need further investigation.

Polymorphism of FABP2 and PPARG2 genes in risk prediction of cataract among North Indian population

BACKGROUND

Cataract is the leading cause of bilateral blindness in India. It has been reported that cataract is responsible for 50-80% of the bilaterally blind in the country. Cataract formation is a natural part of the ageing process. At present, adequate data are not available regarding the FABP2 and PPARG2 gene polymorphisms and their susceptibility with cataract cases in the North Indian population. Thus, the present study was carried out to investigate the association of FABP2 and PPARG2 gene polymorphisms with cataract cases and controls.

MATERIALS AND METHODS

This study includes 130 cataract cases and 118 controls. FABP2 and PPARG2 gene polymorphisms in cases and controls were evaluated by PCR-RFLP.

RESULTS

Frequencies of Ala54Ala, Ala54Thr and Thr54Thr genotypes in FABP2 gene in cataract cases and controls were 50.76%, 39.23%, 10% and 25.42%, 61.86%, 12.71% respectively. The PPARG2 gene CC, CG, GG genotype frequencies were 11.53%, 87.69% and 0.76% in cases and 21.18%, 39.83% and 38.98% in healthy controls respectively. Significant differences were observed in the frequencies of FABP2 Ala54Ala, Ala54Thr genotype (p < 0.05) and PPARG2 CC, CG, GG genotype (p < 0.05) between cases and controls.

CONCLUSION

The findings of this study suggest that FABP2 and PPARG2 gene polymorphisms can be an informative marker for early identification of population at risk of cataract. The potential role of FABP2 and PPARG2 gene polymorphisms as a marker of susceptibility to cataract needs further studies in a larger number of patients.

Polymorphisms of the WRN gene and DNA damage of peripheral lymphocytes in age-related cataract in a Han Chinese population

Werner syndrome is caused by mutations in the DNA repair Werner helicase (WRN) gene and characterized by accelerated aging including cataracts. Age-related cataract (ARC) cases (N = 504) and controls (N = 244) were recruited from a population-based study to evaluate the association of single-nucleotide polymorphisms (SNPs) of WRN and another DNA repair gene (human 8-oxoguanine DNA N-glycosylase 1) with ARC. Among the five SNPs tested, only WRN rs1346044 was found to be significantly associated between cases and controls before multiple-testing adjustment. The minor C allele of rs1346044 was associated with ARC with an odds ratio (OR) of 0.66, suggesting a protective role of the C allele for developing ARC. The stratification analysis on the subtypes of ARC showed that rs1346044 was significantly associated with cortical cataract, but not with nuclear, posterior subcapsular, and mixed types after multiple-testing adjustment (OR = 0.51, p< 0.01). The genetic model analysis showed that the results fit the dominant model (OR = 0.44, p < 0.001). The comet assay used to assess the extent of DNA damage in peripheral lymphocytes of ARC cases found that the DNA damage in lymphocytes from patients with CC genotype was significantly less than that in patients with TT genotype. We concluded that the C allele of rs1346044, a non-synonymous SNP resulting in the conversion of Cys to Arg at amino acid position 1367 of WRN, alters susceptibility to ARC, especially the cortical type of the disease, in the Han Chinese. The underlying mechanism of its protective role might be related to the improved DNA repair function.