New insights into the genetics of primary open-angle glaucoma based on meta-analyses of intraocular pressure and optic disc characteristics

Genetic liability to higher frailty index may increase the risk of ophthalmic disease

PURPOSE

Frailty and age-related eye diseases are common in older people; however, whether there is a causal link remains unknown. We aimed to explore the causal associations between the frailty index (FI) and ophthalmic traits and identify modifiable mediators.

METHODS

Linkage disequilibrium score regression and two-sample Mendelian randomization were applied to identify genetic correlations and causal associations between FI and ophthalmic traits. Summary data for FI was obtained from a genome-wide association study that included 175,226 individuals of European ancestry. Summary-level statistics for ophthalmic traits were obtained from relative GWASs. Summary-level data for cardiovascular risk factors, inflammatory biomarkers, and the central nervous system were used to identify the possible mediators.

RESULTS

FI had a significant genetic correlation with 10 ophthalmic traits. Per SD increment of FI, the odds ratio was 1.329 (95% CI, 1.123, 1.573; P = 9.5 × 10-4) for cataracts, 1.825 (95% CI, 1.115, 2.986; P = 0.016) for keratitis, 1.798 (95% CI, 1.039, 3.11; P = 0.036) for disorders of vitreous body and 1.478 (95% CI, 1.005, 2.173; P = 0.046) for disorders of sclera, cornea, iris and ciliary body. The MR effect estimates of FI on ophthalmic traits were attenuated after adjusting for mental disorders, type 2 diabetes, triglyceride, and interleukin-8 (IL-8) levels.

CONCLUSION

This study reports a genetic correlation and causal association between FI and ophthalmic traits, in which mental disorders, type 2 diabetes, triglycerides, and IL-8 may play a mediating role. These findings highlight a possible method to reduce the risk of FI-related ophthalmic diseases.

Genetic liability to higher frailty index may increase the risk of ophthalmic disease

PURPOSE

Frailty and age-related eye diseases are common in older people; however, whether there is a causal link remains unknown. We aimed to explore the causal associations between the frailty index (FI) and ophthalmic traits and identify modifiable mediators.

METHODS

Linkage disequilibrium score regression and two-sample Mendelian randomization were applied to identify genetic correlations and causal associations between FI and ophthalmic traits. Summary data for FI was obtained from a genome-wide association study that included 175,226 individuals of European ancestry. Summary-level statistics for ophthalmic traits were obtained from relative GWASs. Summary-level data for cardiovascular risk factors, inflammatory biomarkers, and the central nervous system were used to identify the possible mediators.

RESULTS

FI had a significant genetic correlation with 10 ophthalmic traits. Per SD increment of FI, the odds ratio was 1.329 (95% CI, 1.123, 1.573; P = 9.5 × 10-4) for cataracts, 1.825 (95% CI, 1.115, 2.986; P = 0.016) for keratitis, 1.798 (95% CI, 1.039, 3.11; P = 0.036) for disorders of vitreous body and 1.478 (95% CI, 1.005, 2.173; P = 0.046) for disorders of sclera, cornea, iris and ciliary body. The MR effect estimates of FI on ophthalmic traits were attenuated after adjusting for mental disorders, type 2 diabetes, triglyceride, and interleukin-8 (IL-8) levels.

CONCLUSION

This study reports a genetic correlation and causal association between FI and ophthalmic traits, in which mental disorders, type 2 diabetes, triglycerides, and IL-8 may play a mediating role. These findings highlight a possible method to reduce the risk of FI-related ophthalmic diseases.

Highly Accurate and Precise Automated Cup-to-Disc Ratio Quantification for Glaucoma Screening

Objective

An enlarged cup-to-disc ratio (CDR) is a hallmark of glaucomatous optic neuropathy. Manual assessment of the CDR may be less accurate and more time-consuming than automated methods. Here, we sought to develop and validate a deep learning-based algorithm to automatically determine the CDR from fundus images.

Design

Algorithm development for estimating CDR using fundus data from a population-based observational study.

Participants

A total of 181 768 fundus images from the United Kingdom Biobank (UKBB), Drishti_GS, and EyePACS.

Methods

FastAI and PyTorch libraries were used to train a convolutional neural network-based model on fundus images from the UKBB. Models were constructed to determine image gradability (classification analysis) as well as to estimate CDR (regression analysis). The best-performing model was then validated for use in glaucoma screening using a multiethnic dataset from EyePACS and Drishti_GS.

Main Outcome Measures

The area under the receiver operating characteristic curve and coefficient of determination.

Results

Our gradability model vgg19_batch normalization (bn) achieved an accuracy of 97.13% on a validation set of 16 045 images, with 99.26% precision and area under the receiver operating characteristic curve of 96.56%. Using regression analysis, our best-performing model (trained on the vgg19_bn architecture) attained a coefficient of determination of 0.8514 (95% confidence interval [CI]: 0.8459-0.8568), while the mean squared error was 0.0050 (95% CI: 0.0048-0.0051) and mean absolute error was 0.0551 (95% CI: 0.0543-0.0559) on a validation set of 12 183 images for determining CDR. The regression point was converted into classification metrics using a tolerance of 0.2 for 20 classes; the classification metrics achieved an accuracy of 99.20%. The EyePACS dataset (98 172 healthy, 3270 glaucoma) was then used to externally validate the model for glaucoma classification, with an accuracy, sensitivity, and specificity of 82.49%, 72.02%, and 82.83%, respectively.

Conclusions

Our models were precise in determining image gradability and estimating CDR. Although our artificial intelligence-derived CDR estimates achieve high accuracy, the CDR threshold for glaucoma screening will vary depending on other clinical parameters.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

SH-SY5Y human neuronal cells with mutations of the CDKN2B-AS1 gene are vulnerable under cultured conditions

Glaucoma is a common cause of blindness worldwide. Genetic effects are believed to contribute to the onset and progress of glaucoma, but the underlying pathological mechanisms are not fully understood. Here, we set out to introduce mutations into the CDKN2B-AS1 gene, which is known as being the closely associated with glaucoma, in a human neuronal cell line in vitro. We introduced gene mutations with CRISPR/Cas9 into exons and introns into the CDKN2B-AS1 gene. Both mutations strongly promoted neuronal cell death in normal culture conditions. RNA sequencing and pathway analysis revealed that the transcriptional factor Fos is a target molecule regulating CDKN2B-AS1 overexpression. We demonstrated that gene mutation of CDKN2B-AS1 is directly associated with neuronal cell vulnerability in vitro. Additionally, Fos, which is a downstream signaling molecule of CDKN2B-AS1, may be a potential source of new therapeutic targets for neuronal degeneration in diseases such as glaucoma.

Integrating genetic regulation and single-cell expression with GWAS prioritizes causal genes and cell types for glaucoma

Primary open-angle glaucoma (POAG), characterized by retinal ganglion cell death, is a leading cause of irreversible blindness worldwide. However, its molecular and cellular causes are not well understood. Elevated intraocular pressure (IOP) is a major risk factor, but many patients have normal IOP. Colocalization and Mendelian randomization analysis of >240 POAG and IOP genome-wide association study (GWAS) loci and overlapping expression and splicing quantitative trait loci (e/sQTLs) in 49 GTEx tissues and retina prioritizes causal genes for 60% of loci. These genes are enriched in pathways implicated in extracellular matrix organization, cell adhesion, and vascular development. Analysis of single-nucleus RNA-seq of glaucoma-relevant eye tissues reveals that the POAG and IOP colocalizing genes and genome-wide associations are enriched in specific cell types in the aqueous outflow pathways, retina, optic nerve head, peripapillary sclera, and choroid. This study nominates IOP-dependent and independent regulatory mechanisms, genes, and cell types that may contribute to POAG pathogenesis.

Single-cell multiomics of the human retina reveals hierarchical transcription factor collaboration in mediating cell type-specific effects of genetic variants on gene regulation

BACKGROUND

Systematic characterization of how  genetic variation modulates gene regulation in a cell type-specific context is essential for understanding complex traits. To address this question, we profile gene expression and chromatin accessibility in cells from healthy retinae of 20 human donors through single-cell multiomics and genomic sequencing.

RESULTS

We map eQTL, caQTL, allelic-specific expression, and allelic-specific chromatin accessibility in major retinal cell types. By integrating these results, we identify and characterize regulatory elements and genetic variants effective on gene regulation in individual cell types. The majority of identified sc-eQTLs and sc-caQTLs display cell type-specific effects, while the cis-elements containing genetic variants with cell type-specific effects are often accessible in multiple cell types. Furthermore, the transcription factors whose binding sites are perturbed by genetic variants tend to have higher expression levels in the cell types where the variants exert their effects, compared to the cell types where the variants have no impact. We further validate our findings with high-throughput reporter assays. Lastly, we identify the enriched cell types, candidate causal variants and genes, and cell type-specific regulatory mechanism underlying GWAS loci.

CONCLUSIONS

Overall, genetic effects on gene regulation are highly context dependent. Our results suggest that cell type-dependent genetic effect is driven by precise modulation of both trans-factor expression and chromatin accessibility of cis-elements. Our findings indicate hierarchical collaboration among transcription factors plays a crucial role in mediating cell type-specific effects of genetic variants on gene regulation.

Integrated multi-omics single cell atlas of the human retina

Single-cell sequencing has revolutionized the scale and resolution of molecular profiling of tissues and organs. Here, we present an integrated multimodal reference atlas of the most accessible portion of the mammalian central nervous system, the retina. We compiled around 2.4 million cells from 55 donors, including 1.4 million unpublished data points, to create a comprehensive human retina cell atlas (HRCA) of transcriptome and chromatin accessibility, unveiling over 110 types. Engaging the retina community, we annotated each cluster, refined the Cell Ontology for the retina, identified distinct marker genes, and characterized cis-regulatory elements and gene regulatory networks (GRNs) for these cell types. Our analysis uncovered intriguing differences in transcriptome, chromatin, and GRNs across cell types. In addition, we modeled changes in gene expression and chromatin openness across gender and age. This integrated atlas also enabled the fine-mapping of GWAS and eQTL variants. Accessible through interactive browsers, this multimodal cross-donor and cross-lab HRCA, can facilitate a better understanding of retinal function and pathology.

Primary open-angle glaucoma risk prediction with ABCA1 and LOC102723944 variants and their genotype-phenotype correlations in southern Chinese population

Glaucoma is a leading cause of irreversible visual impairment and blindness worldwide. Previous genome-wide association studies have identified caveolin-1 (CAV1), ATP-binding cassette A1 (ABCA1), and forkhead box C1 (FOXC1) loci associated with primary open angle glaucoma (POAG), a major subtype of glaucoma. This study aimed to fine map the association pattern of FOXC1 locus with POAG and determine the correlations of FOXC1, ABCA1, and CAV1 variants with ocular and lipidemic parameters in southern Chinese population. In total, 1291 unrelated Han Chinese subjects were recruited, including 301 high-tension glaucoma (HTG), 126 normal-tension glaucoma (NTG), and 864 control subjects. Twelve variants in FOXC1 locus, and two variants in ABCA1 and CAV1 genes, were genotyped by TaqMan assays. Genetic risk score and genotype-phenotype correlation analyses were conducted. In the FOXC1 locus, LOC102723944 rs6596830, rather than previously reported rs2745572, showed significant association with POAG (P = 8.61 × 10-4, odds ratio (OR) = 0.75) and HTG (P = 3.68 × 10-3, OR = 0.75). ABCA1 rs2487032 was also significantly associated with POAG (P = 3.00 × 10-5, OR = 0.70) and HTG (P = 2.08 × 10-4, OR = 0.70). Joint analysis showed that carriers of homozygous non-protective alleles of ABCA1 rs2487032 and LOC102723944 rs6596830 had 2.99-fold higher risk of POAG (P = 1.27 × 10-3) when compared to those carrying homozygous non-risk alleles. Patients with POAG carrying ABCA1 rs2487032 G allele had higher HDL cholesterol, and those with LOC102723944 rs6596830 A allele had lower LDL. This study revealed individual and joint association of ABCA1 and LOC102723944 variants with POAG in southern Chinese population. Subjects carrying non-protective alleles had increased risk to POAG, and corresponding genotypes would affect the lipid profiles.

Genetic Risk Assessment of Degenerative Eye Disease (GRADE): study protocol of a prospective assessment of polygenic risk scores to predict diagnosis of glaucoma and age-related macular degeneration

BACKGROUND

Glaucoma and age-related macular degeneration (AMD) account for a substantial portion of global blindness. Both conditions are highly heritable, with recognised monogenic and polygenic inheritance patterns. Current screening guidelines lack decisive recommendations. Polygenic risk scores (PRS) allow for cost-effective broad population risk stratification for these conditions. The predictive potential of PRS could facilitate earlier diagnosis and treatment, and prevent unnecessary vision loss.

METHODS

The Genetic Risk Assessment of Degenerative Eye disease (GRADE) study is a prospective study designed to generate high-quality evidence about the feasibility of PRS to stratify individuals from the general population, enabling identification of those at highest risk of developing glaucoma or AMD. The targeted recruitment is 1000 individuals aged over 50 years, from which blood or saliva samples will be used for genotyping and an individual PRS for glaucoma and AMD will be derived. Individuals with PRS values in the bottom decile (n = 100), top decile (n = 100) and middle 80% (n = 100) for both glaucoma and AMD will undergo a detailed eye examination for glaucoma and/or AMD.

DISCUSSION

The primary objective will be to compare the prevalence of glaucoma and AMD cases between low, intermediate, and high PRS risk groups. We expect to find a higher prevalence of both diseases in the high PRS risk group, as compared to the middle and low risk groups. This prospective study will assess the clinical validity of a PRS for glaucoma and AMD in the general Australian population. Positive findings will support the implementation of PRS into clinical practice.

Automated detection of genetic relatedness from fundus photographs using Siamese Neural Networks

Heritability of common eye diseases and ocular traits are relatively high. Here, we develop an automated algorithm to detect genetic relatedness from color fundus photographs (FPs). We estimated the degree of shared ancestry amongst individuals in the UK Biobank using KING software. A convolutional Siamese neural network-based algorithm was trained to output a measure of genetic relatedness using 7224 pairs (3612 related and 3612 unrelated) of FPs. The model achieved high performance for prediction of genetic relatedness; when computed Euclidean distances were used to determine probability of relatedness, the area under the receiver operating characteristic curve (AUROC) for identifying related FPs reached 0.926. We performed external validation of our model using FPs from the LIFE-Adult study and achieved an AUROC of 0.69. An occlusion map indicates that the optic nerve and its surrounding area may be the most predictive of genetic relatedness. We demonstrate that genetic relatedness can be captured from FP features. This approach may be used to uncover novel biomarkers for common ocular diseases.

Large-scale multitrait genome-wide association analyses identify hundreds of glaucoma risk loci

Glaucoma, a leading cause of irreversible blindness, is a highly heritable human disease. Previous genome-wide association studies have identified over 100 loci for the most common form, primary open-angle glaucoma. Two key glaucoma-associated traits also show high heritability: intraocular pressure and optic nerve head excavation damage quantified as the vertical cup-to-disc ratio. Here, since much of glaucoma heritability remains unexplained, we conducted a large-scale multitrait genome-wide association study in participants of European ancestry combining primary open-angle glaucoma and its two associated traits (total sample size over 600,000) to substantially improve genetic discovery power (263 loci). We further increased our power by then employing a multiancestry approach, which increased the number of independent risk loci to 312, with the vast majority replicating in a large independent cohort from 23andMe, Inc. (total sample size over 2.8 million; 296 loci replicated at P < 0.05, 240 after Bonferroni correction). Leveraging multiomics datasets, we identified many potential druggable genes, including neuro-protection targets likely to act via the optic nerve, a key advance for glaucoma because all existing drugs only target intraocular pressure. We further used Mendelian randomization and genetic correlation-based approaches to identify novel links to other complex traits, including immune-related diseases such as multiple sclerosis and systemic lupus erythematosus.

10 Years of GWAS in intraocular pressure

Intraocular pressure (IOP) is the only modifiable risk factor for glaucoma, the leading cause of irreversible blindness worldwide. In this review, we summarize the findings of genome-wide association studies (GWASs) of IOP published in the past 10 years and prior to December 2022. Over 190 genetic loci and candidate genes associated with IOP have been uncovered through GWASs, although most of these studies were conducted in subjects of European and Asian ancestries. We also discuss how these common variants have been used to derive polygenic risk scores for predicting IOP and glaucoma, and to infer causal relationship with other traits and conditions through Mendelian randomization. Additionally, we summarize the findings from a recent large-scale exome-wide association study (ExWAS) that identified rare variants associated with IOP in 40 novel genes, six of which are drug targets for clinical treatment or are being evaluated in clinical trials. Finally, we discuss the need for future genetic studies of IOP to include individuals from understudied populations, including Latinos and Africans, in order to fully characterize the genetic architecture of IOP.

Mendelian Randomization Implicates Bidirectional Association between Myopia and Primary Open-Angle Glaucoma or Intraocular Pressure

PURPOSE

Observational studies suggest that myopic eyes carry a greater risk of primary open-angle glaucoma (POAG); however, the evidence for this association is inconsistent. This may be the result of confounding factors that arise from myopia that complicate clinical tests for glaucoma. This study used Mendelian randomization (MR) analysis to determine genetic causal associations among myopia, glaucoma, and glaucoma-related traits that overcome the effects of external confounders.

DESIGN

Bidirectional genetic associations between myopia and refractive spherical equivalent (RSE), POAG, and POAG endophenotypes were investigated.

PARTICIPANTS

Data from the largest publicly available genetic banks (n = 216,257-542,934) were analyzed.

METHODS

Multiple MR models and multivariate genomic structural modeling to identify significant mediators for the relationship between myopia and POAG.

MAIN OUTCOME MEASURES

Genetic causal associations between myopia and POAG and POAG endophenotypes.

RESULTS

We found consistent bidirectional genetic associations between myopia and POAG and between myopia and intraocular pressure (IOP) using multiple MR models at Bonferroni-corrected levels of significance. Intraocular pressure showed the most significant mediation effect on RSE and POAG (Sobel test, 0.13; 95% confidence interval, 0.09-0.17; P = 1.37 × 10^-8).

CONCLUSIONS

A strong bidirectional genetic causal link exists between myopia and POAG that is mediated mainly by IOP. Our findings suggest that IOP-lowering treatment for glaucoma may be beneficial in myopic eyes, despite the challenges of establishing a clear clinical diagnosis.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

The causal relationship between COVID-19 and increased intraocular pressure: A bidirectional two-sample Mendelian randomization study

Background

Coronavirus disease 2019 (COVID-19) has brought great challenges to the global public health system and huge economic burdens to society, the causal effect of COVID-19 and intraocular pressure was blank.

Objective

This study aimed to explore the causal association between coronavirus disease (COVID-19) susceptibility, severity and criticality and intraocular pressure (IOP) by bidirectional Mendelian randomization (MR) analysis.

Materials and methods

Genetic associations with COVID-19 susceptibility, severity and criticality were obtained from the COVID-19 Host Genetics Initiative. Genetic associations with IOP were obtained from GWAS summary data. The standard inverse variance weighted (IVW) method was used in the primary assessment of this causality. Other methods were also implemented in supplementary analyses. Finally, sensitivity analysis was performed to evaluate the reliability and stability of the results.

Results

The results showed that COVID-19 susceptibility had null effect on IOP (β = 0.131; Se = 0.211; P = 0.533) as assessed by the IVW method. Moreover, the results revealed that COVID-19 severity, specifically, hospitalization due to COVID-19, had a positive effect on IOP with nominal significance (β = 0.228; Se = 0.116; P = 0.049). However, there were null effect of COVID-19 criticality on IOP (β = 0.078; Se = 0.065; P = 0.227). Sensitivity analysis showed that all the results were reliable and stable. The reverse MR analysis revealed that there was null effect of IOP on COVID-19.

Conclusions

We demonstrated that hospitalization due to COVID-19 might increase IOP; therefore, greater attention should be given to monitoring IOP in inpatients with COVID-19.

Diversity is key for cross-ancestry transferability of glaucoma genetic risk scores in Hispanic Veterans in the Million Veteran Program

A major goal of precision medicine is to stratify patients based on their genetic risk for a disease to inform future screening and intervention strategies. For conditions like primary open-angle glaucoma (POAG), the genetic risk architecture is complicated with multiple variants contributing small effects on risk. Following the tepid success of genome-wide association studies for high-effect disease risk variant discovery, genetic risk scores (GRS), which collate effects from multiple genetic variants into a single measure, have shown promise for disease risk stratification. We assessed the application of GRS for POAG risk stratification in Hispanic-descent (HIS) and European-descent (EUR) Veterans in the Million Veteran Program. Unweighted and cross-ancestry meta-weighted GRS were calculated based on 127 genomic variants identified in the most recent report of cross-ancestry POAG meta-analyses. We found that both GRS types were associated with POAG case-control status and performed similarly in HIS and EUR Veterans. This trend was also seen in our subset analysis of HIS Veterans with less than 50% EUR global genetic ancestry. Our findings highlight the importance of evaluating GRS based on known POAG risk variants in different ancestry groups and emphasize the need for more multi-ancestry POAG genetic studies.

Genetic variants associated with glaucomatous visual field loss in primary open-angle glaucoma

Primary open-angle glaucoma (POAG) is characterized by a progressive optic neuropathy with visual field loss. To investigate the genetic variants associated with visual field loss in POAG, Japanese POAG patients (n = 426) and control subjects (n = 246) were genotyped for 22 genetic variants predisposing to POAG that can be classified into those associated with intraocular pressure (IOP) elevation (IOP-related genetic variants) and optic nerve vulnerability independent of IOP (optic nerve-related genetic variants). The genetic risk score (GRS) of the 17 IOP-related and five optic nerve-related genetic variants was calculated, and the associations between the GRS and the mean deviation (MD) of automated static perimetry as an indicator of the severity of visual field loss and pattern standard deviation (PSD) as an indicator of the focal disturbance were evaluated. There was a significant association (Beta = - 0.51, P = 0.0012) between the IOP-related GRS and MD. The severity of visual field loss may depend on the magnitude of IOP elevation induced by additive effects of IOP-related genetic variants. A significant association (n = 135, Beta = 0.65, P = 0.0097) was found between the optic nerve-related, but not IOP-related, GRS and PSD. The optic nerve-related (optic nerve vulnerability) and IOP-related (IOP elevation) genetic variants may play an important role in the focal and diffuse visual field loss respectively. To our knowledge, this is the first report to show an association between additive effects of genetic variants predisposing to POAG and glaucomatous visual field loss, including severity and focal/diffuse disturbance of visual field loss, in POAG.

Assessing the contribution of genetic nurture to refractive error

Parents pass on both their genes and environment to offspring, prompting debate about the relative importance of nature versus nurture in the inheritance of complex traits. Advances in molecular genetics now make it possible to quantify an individual's genetic predisposition to a trait via his or her 'polygenic score'. However, part of the risk captured by an individual's polygenic score may actually be attributed to the genotype of their parents. In the most well-studied example of this indirect 'genetic nurture' effect, about half the genetic contribution to educational attainment was found to be attributed to parental alleles, even if those alleles were not inherited by the child. Refractive errors, such as myopia, are a common cause of visual impairment and pose high economic and quality-of-life costs. Despite strong evidence that refractive errors are highly heritable, the extent to which genetic risk is conferred directly via transmitted risk alleles or indirectly via the environment that parents create for their children is entirely unknown. Here, an instrumental variable analysis in 1944 pairs of adult siblings from the United Kingdom was used to quantify the proportion of the genetic risk ('single nucleotide polymorphism (SNP) heritability') of refractive error contributed by genetic nurture. We found no evidence of a contribution from genetic nurture: non-within-family SNP-heritability estimate = 0.213 (95% confidence interval 0.134-0.310) and within-family SNP-heritability estimate = 0.250 (0.152-0.372). Our findings imply the genetic contribution to refractive error is principally an intrinsic effect from alleles transmitted from parents to offspring.

Signatures of genetic variation in human microRNAs point to processes of positive selection and population-specific disease risks

The occurrence of natural variation in human microRNAs has been the focus of numerous studies during the last 20 years. Most of them have been focused on the role of specific mutations in disease, while a minor proportion seek to analyse microRNA diversity in the genomes of human populations. We analyse the latest human microRNA annotations in the light of the most updated catalogue of genetic variation provided by the 1000 Genomes Project. By means of the in silico analysis of microRNA genetic variation we show that the level of evolutionary constraint of these sequences is governed by the interplay of different factors, like their evolutionary age or genomic location. The role of mutations in the shaping of microRNA-driven regulatory interactions is emphasized with the acknowledgement that, while the whole microRNA sequence is highly conserved, the seed region shows a pattern of higher genetic diversity that appears to be caused by the dramatic frequency shifts of a fraction of human microRNAs. We highlight the participation of these microRNAs in population-specific processes by identifying that not only the seed, but also the loop, are particularly differentiated regions among human populations. The quantitative computational comparison of signatures of population differentiation showed that candidate microRNAs with the largest differences are enriched in variants implicated in gene expression levels (eQTLs), selective sweeps and pathological processes. We explore the implication of these evolutionary-driven microRNAs and their SNPs in human diseases, such as different types of cancer, and discuss their role in population-specific disease risk.

Adamts10 controls transforming growth factor β family signaling that contributes to retinal ganglion cell development

Although mutations in ADAMTS10 have long been known to cause autosomal recessive Weill-Marchesani Syndrome which is characterized by short stature and ocular abnormalities, more recent work has shown that certain mutations in ADAMTS10 cause glaucoma in dogs. In humans, glaucoma is the leading cause of irreversible vision loss that affects tens of millions of people world-wide. Vision loss in glaucoma is a result of neurodegeneration of retinal ganglion cells that form the inner-most layer of the retina and whose axons form the optic nerve which relays visual information to the brain. ADAMTS10 contributes to the formation of microfibrils which sequester latent transforming growth factor β (TGFβ). Among its many biological functions, TGFβ promotes the development of retinal ganglion cells and is also known to play other roles in glaucoma pathogenesis. The aim of this study was to test the hypothesis that ADAMTS10 plays a role in retinal ganglion cell development through regulation of TGFβ signaling. To this end, Adamts10 expression was targeted for reduction in zebrafish embryos carrying either a fluorescent reporter that labels retinal ganglion cells, or a fluorescent reporter of pSmad3-mediated TGFβ family signaling. Loss of adamts10 function in zebrafish embryos reduced retinal ganglion cell reporter fluorescence and prevented formation of an ordered retinal ganglion cell layer. Targeting adamts10 expression also drastically reduced constitutive TGFβ signaling in the eye. Direct inhibition of the TGFβ receptor reduced retinal ganglion cell reporter fluorescence similar to the effect of targeting adamts10 expression. These findings unveil a previously unknown role for Adamts10 in retinal ganglion cell development and suggest that the developmental role of Adamts10 is mediated by active TGFβ family signaling. In addition, our results show for the first time that Adamts10 is necessary for pSmad3-mediated constitutive TGFβ family signaling.

Association Between Myopic Refractive Error and Primary Open-Angle Glaucoma: A 2-Sample Mendelian Randomization Study

Importance

Refractive error (RE) is the most common form of visual impairment, and myopic RE is associated with an increased risk of primary open-angle glaucoma (POAG). Whether this association represents a causal role of RE in the etiology of POAG remains unknown.

Objective

To evaluate shared genetic influences and investigate the association of myopic RE with the risk for POAG.

Design, Setting, and Participants

Observational analyses were used to evaluate the association between mean spherical equivalent (MSE) RE (continuous trait) or myopia (binary trait) and POAG risk in individuals from the Genetic Epidemiology Research on Adult Health and Aging (GERA) cohort. To quantify genetic overlap, genome-wide genetic correlation analyses were performed using genome-wide association studies (GWAS) of MSE RE or myopia and POAG from GERA. Potential causal effects were assessed between MSE RE and POAG using 2-sample Mendelian randomization. Genetic variants associated with MSE RE were derived using GWAS summary statistics from a GWAS of RE conducted in 102 117 UK Biobank participants. For POAG, we used GWAS summary statistics from our previous GWAS (3836 POAG cases and 48 065 controls from GERA). Data analyses occurred between July 2020 and October 2021.

Main Outcomes and Measure

Our main outcome was POAG risk as odds ratio (OR) caused by per-unit difference in MSE RE (in diopters).

Results

Our observational analyses included data for 54 755 non-Hispanic White individuals (31 926 [58%] females and 22 829 [42%] males). Among 4047 individuals with POAG, mean (SD) age was 73.64 (9.20) years; mean (SD) age of the 50 708 controls was 65.38 (12.24) years. Individuals with POAG had a lower refractive MSE and were more likely to have myopia or high myopia compared with the control participants (40.2% vs 34.1%, P = 1.31 × 10-11 for myopia; 8.5% vs 6.8%, P = .004 for high myopia). Our genetic correlation analyses demonstrated that POAG was genetically correlated with MSE RE (rg, -0.24; SE, 0.06; P = 3.90 × 10-5), myopia (rg, 0.21; SE, 0.07; P = .004), and high myopia (rg, 0.23; SE, 0.09; P = .01). Genetically assessed refractive MSE was negatively associated with POAG risk (inverse-variance weighted model: OR per diopter more hyperopic MSE = 0.94; 95% CI, 0.89-0.99; P = .01).

Conclusions and Relevance

These findings demonstrate a shared genetic basis and an association between myopic RE and POAG risk. This may support population POAG risk stratification and screening strategies, based on RE information.

Association of EFEMP1 with juvenile-onset open angle glaucoma in a patient with concomitant COL11A1-related Stickler syndrome

BACKGROUND

Juvenile onset open-angle glaucoma is described as a primary open-angle glaucoma, with an age of onset before 40 years. These patients have a higher prevalence of myopia.

PURPOSE

We describe the phenotype of juvenile onset open-angle glaucoma in a patient with a rare variant in EFEMP1 gene, who was also detected to have Stickler syndrome(STL).

METHODS

Whole exome sequencing (WES) was undertaken in 40 unrelated families where the proband had juvenile onset open-angle glaucoma (JOAG).

RESULTS

Out of these, eight were autosomal dominant, while the rest did not have any other affected first-degree relative. Out of the 8 autosomal dominant JOAG families, MYOC mutations were detected in 3(37.5%) and LTBP2 in 1(12.5%). One family (12.5%) had a rare EFEMP1 sequence variant in both affected father and daughter. The daughter also had high myopia and a pathogenic COL11A1 sequence variant that led to a coincidental diagnosis of STL in her.

CONCLUSIONS

This is a rare association of EFEMP1 and COL11A1 sequence variants in a JOAG patient with STL. The study also reiterates the association of JOAG with EFEMP1, which should be looked for, especially in families with autosomal dominant JOAG.

Genome-Wide Association Study Identifies Two Common Loci Associated with Pigment Dispersion Syndrome/Pigmentary Glaucoma and Implicates Myopia in its Development

PURPOSE

To identify genetic variants associated with pigment dispersion syndrome (PDS) and pigmentary glaucoma (PG) in unrelated patients and to further understand the genetic and potentially causal relationships between PDS and associated risk factors.

DESIGN

A 2-stage genome-wide association meta-analysis with replication and subsequent in silico analyses including Mendelian randomization.

PARTICIPANTS

A total of 574 cases with PG or PDS and 52 627 controls of European descent.

METHODS

Genome-wide association analyses were performed in 4 cohorts and meta-analyzed in 3 stages: (1) a discovery meta-analysis was performed in 3 cohorts, (2) replication was performed in the fourth cohort, and (3) all 4 cohorts were meta-analyzed to increase statistical power. Two-sample Mendelian randomization was used to determine whether refractive error and intraocular pressure exert causal effects over PDS.

MAIN OUTCOME MEASURES

The association of genetic variants with PDS and whether myopia exerts causal effects over PDS.

RESULTS

Significant association was present at 2 novel loci for PDS/PG. These loci and follow-up analyses implicate the genes gamma secretase activator protein (GSAP) (lead single nucleotide polymorphism [SNP]: rs9641220, P = 6.0×10-10) and glutamate metabotropic receptor 5 (GRM5)/TYR (lead SNP: rs661177, P = 3.9×10-9) as important factors in disease risk. Mendelian randomization showed significant evidence that negative refractive error (myopia) exerts a direct causal effect over PDS (P = 8.86×10-7).

CONCLUSIONS

Common SNPs relating to the GSAP and GRM5/TYR genes are associated risk factors for the development of PDS and PG. Although myopia is a known risk factor, this study uses genetic data to demonstrate that myopia is, in part, a cause of PDS and PG.

Restoring the oxidative balance in age-related diseases - An approach in glaucoma

As human life expectancy increases, age-related health issues including neurodegenerative diseases continue to rise. Regardless of genetic or environmental factors, many neurodegenerative conditions share common pathological mechanisms, such as oxidative stress, a hallmark of many age-related health burdens. In this review, we describe oxidative damage and mitochondrial dysfunction in glaucoma, an age-related neurodegenerative eye disease affecting 80 million people worldwide. We consider therapeutic approaches used to counteract oxidative stress in glaucoma, including untapped treatment options such as novel plant-derived antioxidant compounds that can reduce oxidative stress and prevent neuronal loss. We summarize the current pre-clinical models and clinical work exploring the therapeutic potential of a range of candidate plant-derived antioxidant compounds. Finally, we explore advances in drug delivery systems, particular those employing nanotechnology-based carriers which hold significant promise as a carrier for antioxidants to treat age-related disease, thus reviewing the key current state of all of the aspects required towards translation.

Identification of Estrogen Signaling in a Prioritization Study of Intraocular Pressure-Associated Genes

Elevated intraocular pressure (IOP) is the only modifiable risk factor for primary open-angle glaucoma (POAG). Herein we sought to prioritize a set of previously identified IOP-associated genes using novel and previously published datasets. We identified several genes for future study, including several involved in cytoskeletal/extracellular matrix reorganization, cell adhesion, angiogenesis, and TGF-β signaling. Our differential correlation analysis of IOP-associated genes identified 295 pairs of 201 genes with differential correlation. Pathway analysis identified β-estradiol as the top upstream regulator of these genes with ESR1 mediating 25 interactions. Several genes (i.e., EFEMP1, FOXC1, and SPTBN1) regulated by β-estradiol/ESR1 were highly expressed in non-glaucomatous human trabecular meshwork (TM) or Schlemm’s canal (SC) cells and specifically expressed in TM/SC cell clusters defined by single-cell RNA-sequencing. We confirmed ESR1 gene and protein expression in human TM cells and TM/SC tissue with quantitative real-time PCR and immunofluorescence, respectively. 17β-estradiol was identified in bovine, porcine, and human aqueous humor (AH) using ELISA. In conclusion, we have identified estrogen receptor signaling as a key modulator of several IOP-associated genes. The expression of ESR1 and these IOP-associated genes in TM/SC tissue and the presence of 17β-estradiol in AH supports a role for estrogen signaling in IOP regulation.

[Analysis of the functional role of polymorphism in the CDKN2B-AS1 gene GWAS-significant for primary open-angle glaucoma (an in-silico study)]

Primary open-angle glaucoma (POAG) is the most common form of glaucoma in which genetic factors play a significant role. According to genome-wide studies (GWAS), the CDKN2B-AS1 gene is associated with POAG.

PURPOSE

To study in silico the functional significance of the CDKN2B-AS1 gene polymorphism GWAS-significant for primary open-angle glaucoma.

MATERIAL AND METHODS

The in-silico analysis was based on data from the GWAS catalog, five polymorphic loci of the CDKN2B-AS1 gene (rs1063192, rs7865618, rs2157719, rs944800, rs4977756) associated with POAG were selected. The study evaluated the regulatory potential, the relationship with the expression and alternative splicing of genes of the CDKN2B-AS1 gene polymorphism using modern databases for functional genomics - HaploReg and GTExportal.

RESULTS

An important functional significance of the polymorphic loci rs1063192, rs7865618, rs2157719, rs944800, rs4977756 of the CDKN2B-AS1 gene was revealed. These loci are located in the region of histones marking enhancers and in the region of hypersensitivity to DNAse-1, can be found in more than ten different organs and tissues, in the regions of regulatory DNA motifs to five transcription factors (AIRE, GATA, Tgif1, Pou2f2, and Zfp187), and are associated with expression of three genes (CDKN2B-AS1, CDKN2B, CDKN2A) and alternative splicing of transcripts of two genes (CDKN2B-AS1 and RP11-149I2.4) in cell cultures, organs and tissues with pathogenic significance for glaucoma development.

CONCLUSION

Polymorphism of the CDKN2B-AS1 gene (rs1063192, rs7865618, rs2157719, rs944800, rs4977756) has significant regulatory potential and is associated with the expression and alternative splicing of genes, which possibly underlies its association with primary open-angle glaucoma.

Altered Ocular Fibrillin Microfibril Composition in Mice With a Glaucoma-Causing Mutation of Adamts10

Purpose

Previously, we identified a G661R mutation of ADAMTS10 (a disintegrin-like and metalloprotease with thrombospondin type 1 motif 10) as being disease causative in a colony of Beagles with inherited primary open-angle glaucoma (POAG). Mutations in ADAMTS10 are known to cause Weill-Marchesani syndrome (WMS), which is also caused by mutations in the fibrillin-1 gene (FBN1), suggesting functional linkage between ADAMTS10 and fibrillin-1, the principal component of microfibrils. Here, we established a mouse line with the G661R mutation of Adamts10 (Adamts10G661R/G661R) to determine if they develop features of WMS and alterations of ocular fibrillin microfibrils.

Methods

Intraocular pressure (IOP) was measured using a TonoLab rebound tonometer. Central cornea thickness (CCT), anterior chamber depth (ACD) and axial length (AL) of the eye were examined by spectral-domain optical coherence tomography. Sagittal eye sections from mice at postnatal day 10 (P10) and at 3 and 24 months of age were stained with antibodies against fibrillin-1, fibrillin-2, and ADAMTS10.

Results

IOP was not elevated in Adamts10G661R/G661R mice. Adamts10G661R/G661R mice had smaller bodies, thicker CCT, and shallower ACD compared to wild-type mice but normal AL. Adamts10G661R/G661R mice displayed persistent fibrillin-2 and enhanced fibrillin-1 immunofluorescence in the lens zonules and in the hyaloid vasculature and its remnants in the vitreous.

Conclusions

Adamts10G661R/G661R mice recapitulate the short stature and ocular phenotypes of WMS. The altered fibrillin-1 and fibrillin-2 immunoactivity in Adamts10G661R/G661R mice suggests that the G661R mutation of Adamts10 perturbs regulation of the fibrillin isotype composition of microfibrils in the mouse eye.

Glaucoma Heritability: Molecular Mechanisms of Disease

Glaucoma is one of the world’s leading causes of irreversible blindness. A complex, multifactorial disease, the underlying pathogenesis and reasons for disease progression are not fully understood. The most common form of glaucoma, primary open-angle glaucoma (POAG), was traditionally understood to be the result of elevated intraocular pressure (IOP), leading to optic nerve damage and functional vision loss. Recently, researchers have suggested that POAG may have an underlying genetic component. In fact, studies of genetic association and heritability have yielded encouraging results showing that glaucoma may be influenced by genetic factors, and estimates for the heritability of POAG and disease-related endophenotypes show encouraging results. However, the vast majority of the underlying genetic variants and their molecular mechanisms have not been elucidated. Several genes have been suggested to have molecular mechanisms contributing to alterations in key endophenotypes such as IOP (LMX1B, MADD, NR1H3, and SEPT9), and VCDR (ABCA1, ELN, ASAP1, and ATOH7). Still, genetic studies about glaucoma and its molecular mechanisms are limited by the multifactorial nature of the disease and the large number of genes that have been identified to have an association with glaucoma. Therefore, further study into the molecular mechanisms of the disease itself are required for the future development of therapies targeted at genes leading to POAG endophenotypes and, therefore, increased risk of disease.

Large-scale machine-learning-based phenotyping significantly improves genomic discovery for optic nerve head morphology

Genome-wide association studies (GWASs) require accurate cohort phenotyping, but expert labeling can be costly, time intensive, and variable. Here, we develop a machine learning (ML) model to predict glaucomatous optic nerve head features from color fundus photographs. We used the model to predict vertical cup-to-disc ratio (VCDR), a diagnostic parameter and cardinal endophenotype for glaucoma, in 65,680 Europeans in the UK Biobank (UKB). A GWAS of ML-based VCDR identified 299 independent genome-wide significant (GWS; p ≤ 5 × 10-8) hits in 156 loci. The ML-based GWAS replicated 62 of 65 GWS loci from a recent VCDR GWAS in the UKB for which two ophthalmologists manually labeled images for 67,040 Europeans. The ML-based GWAS also identified 93 novel loci, significantly expanding our understanding of the genetic etiologies of glaucoma and VCDR. Pathway analyses support the biological significance of the novel hits to VCDR: select loci near genes involved in neuronal and synaptic biology or harboring variants are known to cause severe Mendelian ophthalmic disease. Finally, the ML-based GWAS results significantly improve polygenic prediction of VCDR and primary open-angle glaucoma in the independent EPIC-Norfolk cohort.

Automated AI labeling of optic nerve head enables insights into cross-ancestry glaucoma risk and genetic discovery in >280,000 images from UKB and CLSA

Cupping of the optic nerve head, a highly heritable trait, is a hallmark of glaucomatous optic neuropathy. Two key parameters are vertical cup-to-disc ratio (VCDR) and vertical disc diameter (VDD). However, manual assessment often suffers from poor accuracy and is time intensive. Here, we show convolutional neural network models can accurately estimate VCDR and VDD for 282,100 images from both UK Biobank and an independent study (Canadian Longitudinal Study on Aging), enabling cross-ancestry epidemiological studies and new genetic discovery for these optic nerve head parameters. Using the AI approach, we perform a systematic comparison of the distribution of VCDR and VDD and compare these with intraocular pressure and glaucoma diagnoses across various genetically determined ancestries, which provides an explanation for the high rates of normal tension glaucoma in East Asia. We then used the large number of AI gradings to conduct a more powerful genome-wide association study (GWAS) of optic nerve head parameters. Using the AI-based gradings increased estimates of heritability by ∼50% for VCDR and VDD. Our GWAS identified more than 200 loci associated with both VCDR and VDD (double the number of loci from previous studies) and uncovered dozens of biological pathways; many of the loci we discovered also confer risk for glaucoma.

Systemic Treatment with Nicotinamide Riboside Is Protective in Two Mouse Models of Retinal Ganglion Cell Damage

Glaucoma etiology often includes retinal ganglion cell (RGC) death associated with elevated intraocular pressure (IOP). However, even when IOP is managed well, disease can progress. It is thus important to develop therapeutic approaches that directly protect RGCs in an IOP-independent manner. Compromised nicotinamide adenine dinucleotide (NAD⁺) metabolism occurs in neurodegenerative diseases, including models of glaucoma. Here we report testing the protective effects of prophylactically systemically administered nicotinamide riboside (NR), a NAD⁺ precursor, in a mouse model of acute RGC damage (optic nerve crush (ONC)), and in a chronic model of RGC degeneration (ocular hypertension induced by intracameral injection of microbeads). For both models, treatment enhanced RGC survival, assessed by counting cells in retinal flatmounts immunostained for Brn3a+. In the ONC model, treatment preserved RGC function, as assessed by pattern electroretinogram, and suppressed retinal inflammation, as assessed by immunofluorescence staining of retinal fixed sections for glial fibrillary acidic protein (GFAP). This is the first study to demonstrate that systemic treatment with NR is protective in acute and chronic models of RGC damage. The protection is significant and, considering that NR is highly bioavailable in and well-tolerated by humans, may support the proposition of prospective human subject studies.

Commonalities of optic nerve injury and glaucoma-induced neurodegeneration: Insights from transcriptome-wide studies

Glaucoma is a collection of diseases that lead to an irreversible vision loss due to damage of retinal ganglion cells (RGCs). Although the underlying events leading to RGC death are not fully understood, recent research efforts are beginning to define the genetic changes that play a critical role in the initiation and progression of glaucomatous injury and RGC death. Several genetic and experimental animal models have been developed to mimic glaucomatous neurodegeneration. These models differ in many respects but all result in the loss of RGCs. Assessing transcriptional changes across different models could provide a more complete perspective on the molecular drivers of RGC degeneration. For the past several decades, changes in the retinal transcriptome during neurodegeneration process were defined using microarray methods, RNA sequencing and now single cell RNA sequencing. It is understood that these methods have strengths and weaknesses due to technical differences and variations in the analytical tools used. In this review, we focus on the use of transcriptome-wide expression profiling of the changes occurring as RGCs are lost across different glaucoma models. Commonalities of optic nerve crush and glaucoma-induced neurodegeneration are identified and discussed.

Risk Stratification and Clinical Utility of Polygenic Risk Scores in Ophthalmology

Translational Relevance

Common genetic variants can be used to effectively stratify the risk of disease development and progression and may be used to guide screening, triaging, monitoring, or treatment thresholds.

Association of Genetic Polymorphisms in Oxidative Stress and Inflammation Pathways with Glaucoma Risk and Phenotype

Oxidative stress and neuroinflammation are involved in the pathogenesis and progression of glaucoma. Our aim was to evaluate the impact of selected single-nucleotide polymorphisms in inflammation and oxidative stress genes on the risk of glaucoma, the patients’ clinical characteristics and the glaucoma phenotype. In total, 307 patients with primary open-angle glaucoma or ocular hypertension were enrolled. The control group included 339 healthy Slovenian blood donors. DNA was isolated from peripheral blood. Genotyping was performed for SOD2 rs4880, CAT rs1001179, GPX1 rs1050450, GSTP1 rs1695, GSTM1 gene deletion, GSTT1 gene deletion, IL1B rs1143623, IL1B rs16944, IL6 rs1800795 and TNF rs1800629. We found a nominally significant association of GSTM1 gene deletion with decreased risk of ocular hypertension and a protective role of IL1B rs16944 and IL6 rs1800629 in the risk of glaucoma. The CT and TT genotypes of GPX1 rs1050450 were significantly associated with advanced disease, lower intraocular pressure and a larger vertical cup–disc ratio. In conclusion, genetic variability in IL1B and IL6 may be associated with glaucoma risk, while GPX and TNF may be associated with the glaucoma phenotype. In the future, improved knowledge of these pathways has the potential for new strategies and personalised treatment of glaucoma.

Genome-wide meta-analysis identifies 127 open-angle glaucoma loci with consistent effect across ancestries

Primary open-angle glaucoma (POAG), is a heritable common cause of blindness world-wide. To identify risk loci, we conduct a large multi-ethnic meta-analysis of genome-wide association studies on a total of 34,179 cases and 349,321 controls, identifying 44 previously unreported risk loci and confirming 83 loci that were previously known. The majority of loci have broadly consistent effects across European, Asian and African ancestries. Cross-ancestry data improve fine-mapping of causal variants for several loci. Integration of multiple lines of genetic evidence support the functional relevance of the identified POAG risk loci and highlight potential contributions of several genes to POAG pathogenesis, including SVEP1, RERE, VCAM1, ZNF638, CLIC5, SLC2A12, YAP1, MXRA5, and SMAD6. Several drug compounds targeting POAG risk genes may be potential glaucoma therapeutic candidates.

The GGLEAM Study: Understanding Glaucoma in the Ohio Amish

Glaucoma leads to millions of cases of visual impairment and blindness around the world. Its susceptibility is shaped by both environmental and genetic risk factors. Although over 120 risk loci have been identified for glaucoma, a large portion of its heritability is still unexplained. Here we describe the foundation of the Genetics of GLaucoma Evaluation in the AMish (GGLEAM) study to investigate the genetic architecture of glaucoma in the Ohio Amish, which exhibits lower genetic and environmental heterogeneity compared to the general population. To date, we have enrolled 81 Amish individuals in our study from Holmes County, Ohio. As a part of our enrollment process, 62 GGLEAM study participants (42 glaucoma-affected and 20 unaffected individuals) received comprehensive eye examinations and glaucoma evaluations. Using the data from the Anabaptist Genealogy Database, we found that 80 of the GGLEAM study participants were related to one another through a large, multigenerational pedigree containing 1586 people. We plan to integrate the health and kinship data obtained for the GGLEAM study to interrogate glaucoma genetics and pathophysiology in this unique population.

Genetic pre-screening for glaucoma in population-based epidemiology: protocol for a double-blind prospective screening study within Lifelines (EyeLife)

Background

Early detection of glaucoma is paramount to maintain patients’ eyesight, however glaucomatous vision loss tends to begin in the periphery with up to 50% of patients unaware they are affected. Because glaucomatous vision loss is permanent, screening appears attractive, but currently is not cost-effective. Therefore we aim to investigate the utility of genetic pre-screening for glaucoma in a population-based setting, called EyeLife.

Methods

EyeLife adopts a double blind prospective design with contrasting groups. Selected participants (n = 1600) from the Lifelines cohort are 55 years of age or older, and of either the highest or lowest 20% of the genetic risk distribution for glaucoma. We obtained a highly curated list of genetic variants from the literature to obtain each participants’ genetic risk for glaucoma. Participants will undergo comprehensive ophthalmic screening. The primary outcome is the relative risk of glaucoma given a high genetic risk compared to a low genetic risk.

Discussion

If genetic pre-screening is successful, it will increase the yield of a glaucoma screening program by focusing on high-risk individuals. This, in turn, may improve long-term visual health of middle-aged and elderly people.

Trial registration

Ethics approval was obtained on January 31, 2019, and the study was retrospectively registered with the Netherlands Trial Register (NL8718) on the 17th of June, 2020.

Increased Susceptibility to Glaucomatous Damage in Microfibril Deficient Mice

Purpose

To test whether mice with microfibril deficiency due to the Tsk mutation of fibrillin-1 (Fbn1Tsk/+) have increased susceptibility to pressure-induced retinal ganglion cell (RGC) degeneration.

Methods

Intraocular pressure (IOP) elevation was induced in Fbn1Tsk/+ and wild type (wt) mice by injecting microbeads into the anterior chamber. Mice were then followed up for four months, with IOP measurements every three to six days. Retinas were stained for Brn3a to determine RGC number. Optic nerve cross-sections were stained with p-phenylene diamine to determine nerve area, axon number, and caliber and thickness of the pia mater.

Results

Microbead injection induced significant IOP elevation that was significantly less for Fbn1Tsk/+ mice compared with wt. The optic nerves and optic nerve axons were larger, and the elastic fiber-rich pia mater was thinner in Fbn1Tsk/+ mice. Microbead injection resulted in reduced optic nerve size, thicker pia mater, and a slight decrease in axon size. Fbn1Tsk/+ mice had significantly greater loss of RGCs and optic nerve axons compared with wt (14.8% vs. 5.8%, P = 0.002, and 17.0% vs. 7.5%, P = 0.002, respectively).

Conclusions

Fbn1Tsk/+mice had altered optic nerve structure as indicated by larger optic nerves, larger optic nerve axons and thinner pia mater, consistent with our previous findings. Despite lower IOP elevation, Fbn1Tsk/+mice had greater loss of RGCs and optic nerve axons, suggesting increased susceptibility to IOP-induced optic nerve degeneration in microfibril-deficient mice.

Association of Glaucoma Risk Genes with Retinal Nerve Fiber Layer in a Multi-ethnic Asian Population: The Singapore Epidemiology of Eye Diseases Study

Purpose

Genome-wide association studies have identified several genes associated with glaucoma. However, their roles in the pathogenesis of glaucoma remain unclear, particularly their effects on retinal nerve fiber layer (RNFL) thickness. The aim of this study was to investigate the associations between the identified glaucoma risk genes and RNFL thickness.

Methods

A total of 3843 participants (7,020 healthy eyes) were enrolled from the Singapore Epidemiology of Eye Diseases (SEED) study, a population-based study composing of three major ethnic groups—Malay, Indian, and Chinese—in Singapore. Ocular examinations were performed, and spectral-domain optical coherence tomography (SD-OCT) was used to measure circumpapillary RNFL thickness. We selected 35 independent glaucoma-associated genetic loci for analysis. An linear regression model was conducted to determine the association of these variants with circumpapillary RNFL, assuming an additive genetic model. We conducted association analysis in each of the three ethnic groups, followed by a meta-analysis of them.

Results

The mean age of the included participants was 59.4 ± 8.9 years, and the mean RFNL thickesss is 92.3 ± 11.2 µm. In the meta-analyses, of the 35 glacuoma loci, we found that only SIX6 was significantly associated with reduction in global RNFL thickness (rs33912345; β = −1.116 um per risk allele, P = 1.64E-05), and the effect size was larger in the inferior RNFL quadrant (β = −2.015 µm, P = 2.9E-6), and superior RNFL quadrant (β = −1.646 µm, P = 6.54E-5). The SIX6 association were consistently observed across all three ethnic groups. Other than RNFL, we also found several genetic varaints associated with vertical cuo-to-disc ratio (ATOH7, CDKN2B-AS1, and TGFBR3-CDC7), rim area (SIX6 and CDKN2B-AS1), and disc area (SIX6, ATOH7, and TGFBR3-CDC7). The association of SIX6 rs33912345 with NRFL thickness remained similar after further adjusting for disc area and 3 other disc parameter associated SNPs (ATOH7, CDKN2B-AS1, and TGFBR3-CDC7).

Conclusions

Of the 35 glaucoma identified risk loci, only SIX6 is significantly and independently associated with thinner RNFL. Our study further supports the involvement of SIX6 with RNFL thickness and pathogensis of glaucoma.

Analyzing a putative enhancer of optic disc morphology

Background

Genome-wide association studies have identified the CDC7-TGFBR3 intergenic region on chromosome 1 to be strongly associated with optic disc area size. The mechanism of its function remained unclear until new data on eQTL markers emerged from the Genotype-Tissue Expression project. The target region was found to contain a strong silencer of the distal (800 kb) Transcription Factor (TF) gene GFI1 (Growth Factor Independent Transcription Repressor 1) specifically in neuroendocrine cells (pituitary gland). GFI1 has also been reported to be involved in the development of sensory neurons and hematopoiesis. Therefore, GFI1, being a developmental gene, is likely to affect optic disc area size by altering the expression of the associated genes via long-range interactions.

Results

Distribution of haplotypes in the putative enhancer region has been assessed using the data on four continental supergroups generated by the 1000 Genomes Project. The East Asian (EAS) populations were shown to manifest a highly homogenous unimodal haplotype distribution pattern within the region with the major haplotype occurring with the frequency of 0.9. Another European specific haplotype was observed with the frequency of 0.21. The major haplotype appears to be involved in silencing GFI1repressor gene expression, which might be the cause of increased optic disc area characteristic of the EAS populations.

The enhancer/eQTL region overlaps AluJo element, which implies that this particular regulatory element is primate-specific and confined to few tissues.

Conclusion

Population specific distribution of GFI1 enhancer alleles may predispose certain ethnic groups to glaucoma.

[Genome-wide studies of primary open-angle glaucoma]

The article reviews literature on developmental stages of genome-wide association studies (GWAS) of primary open-angle glaucoma (POAG). This problem is currently developing and one of the most complex in ophthalmology. The article considers main GWAS of POAG and established GWAS-significant polymorphisms associated with the disease. The topic of genome-wide studies of primary open-angle glaucoma will be of certain interest to ophthalmologists, materials on GWAS-significant loci can be used both in the selection of polymorphisms in replicative studies of POAG in various populations of Russia, and to expand ideas about the molecular genetic mechanisms of the development of the disease.

Prevalence of primary open-angle glaucoma in a Somalia population

PURPOSE

To determine the prevalence of primary open-angle glaucoma (POAG) in patients over 40 years that presented to our tertiary hospital in Somalia Mogadishu.

METHODS

This prospective cross-sectional study included 1550 patients older than 40 years that presented to the ophthalmology clinic of Somalia Mogadishu - Turkey Training and Research Hospital. The patients were evaluated in terms of age, gender, intraocular pressure, and optical cup/disk (C/D) ratio, and central corneal thickness measurements were taken.

RESULTS

The prevalence of glaucoma in the study population over the age of 40 years was 7%. The prevalence of glaucoma was 40% in the 40-50-year group, 6.8% in the 50-60-year group, 7% in the 60-70-year group, 9.9% in the 70-80-year group, and 12.3% in the 80-90-year group. The prevalence of glaucoma statistically significantly increased with advancing age (p < 0.001). The mean intraocular pressure was measured as 16.7 ± 3.3 mmHg for the overall patient population, 16.3 ± 2.9 mmHg for the female patients, and 17.1 ± 3.1 mmHg for the male patients. The mean intraocular pressure of the patients diagnosed with POAG was 27.3 ± 4.2 mmHg, and their mean corneal thickness was 507.9 µm, which was significantly lower than the value of the patients without POAG (545.8) (p < 0.001). The mean C/D ratio was calculated as 0.56 ± 0.21 for the patients with POAG and general 0.24 ± 0.16 for the overall patient population, indicating a statistically significant difference (p < 0.001).

CONCLUSIONS

A high rate of POAG is seen in patients over 40 years of age in Somalia. The mechanism underlying POAG needs to be investigated in this population.

The Pathophysiological Significance of Fibulin-3

Fibulin-3 (also known as EGF-containing fibulin extracellular matrix protein 1 (EFEMP1)) is a secreted extracellular matrix glycoprotein, encoded by the EFEMP1 gene that belongs to the eight-membered fibulin protein family. It has emerged as a functionally unique member of this family, with a diverse array of pathophysiological associations predominantly centered on its role as a modulator of extracellular matrix (ECM) biology. Fibulin-3 is widely expressed in the human body, especially in elastic-fibre-rich tissues and ocular structures, and interacts with enzymatic ECM regulators, including tissue inhibitor of metalloproteinase-3 (TIMP-3). A point mutation in EFEMP1 causes an inherited early-onset form of macular degeneration called Malattia Leventinese/Doyne honeycomb retinal dystrophy (ML/DHRD). EFEMP1 genetic variants have also been associated in genome-wide association studies with numerous complex inherited phenotypes, both physiological (namely, developmental anthropometric traits) and pathological (many of which involve abnormalities of connective tissue function). Furthermore, EFEMP1 expression changes are implicated in the progression of numerous types of cancer, an area in which fibulin-3 has putative significance as a therapeutic target. Here we discuss the potential mechanistic roles of fibulin-3 in these pathologies and highlight how it may contribute to the development, structural integrity, and emergent functionality of the ECM and connective tissues across a range of anatomical locations. Its myriad of aetiological roles positions fibulin-3 as a molecule of interest across numerous research fields and may inform our future understanding and therapeutic approach to many human diseases in clinical settings.

A mega-analysis of expression quantitative trait loci in retinal tissue

Significant association signals from genome-wide association studies (GWAS) point to genomic regions of interest. However, for most loci the causative genetic variant remains undefined. Determining expression quantitative trait loci (eQTL) in a disease relevant tissue is an excellent approach to zoom in on disease- or trait-associated association signals and hitherto on relevant disease mechanisms. To this end, we explored regulation of gene expression in healthy retina (n = 311) and generated the largest cis-eQTL data set available to date. Genotype- and RNA-Seq data underwent rigorous quality control protocols before FastQTL was applied to assess the influence of genetic markers on local (cis) gene expression. Our analysis identified 403,151 significant eQTL variants (eVariants) that regulate 3,007 genes (eGenes) (Q-Value < 0.05). A conditional analysis revealed 744 independent secondary eQTL signals for 598 of the 3,007 eGenes. Interestingly, 99,165 (24.71%) of all unique eVariants regulate the expression of more than one eGene. Filtering the dataset for eVariants regulating three or more eGenes revealed 96 potential regulatory clusters. Of these, 31 harbour 130 genes which are partially regulated by the same genetic signal. To correlate eQTL and association signals, GWAS data from twelve complex eye diseases or traits were included and resulted in identification of 80 eGenes with potential association. Remarkably, expression of 10 genes is regulated by eVariants associated with multiple eye diseases or traits. In conclusion, we generated a unique catalogue of gene expression regulation in healthy retinal tissue and applied this resource to identify potentially pleiotropic effects in highly prevalent human eye diseases. Our study provides an excellent basis to further explore mechanisms of various retinal disease etiologies.

The retina is a multilayered and highly specified neural tissue crucial for high-resolution visual perception and spatial orientation. Environmental and genetic insults to the retina result in many blinding diseases, such as age-related macular degeneration or glaucoma. Commonly, many of these diseases are age-related suggesting that minor changes are accumulating over a life-time, with little or no contribution of strong individual effects. Specifically, this is true for genetic factors known to underlie the etiology of complex diseases including the prevalent eye diseases. In our study, we searched for effects on gene expression due to genetic variation using 311 healthy post-mortem retinal tissue samples. We show that 3,007 of the 16,766 genes investigated are regulated in the retina by genetic variations. Of these, 80 genes are potentially associated to one or more of twelve complex eye diseases or retinal traits tested. Interestingly, 10 genes appear to be involved in the development of several eye traits suggesting that cellular mechanisms may act at a common point in the disease process. Consequently, our study provides the basis to further explore retinal disease pathways and is likely to highlight target molecules for future therapeutic applications.

Primary open angle glaucoma genetics: The common variants and their clinical associations (Review)

Glaucoma is a group of progressive optic neuropathies that have in common characteristic optic nerve head changes, loss of retinal ganglion cells and visual field defects. Among the large family of glaucomas, primary open‑angle glaucoma (POAG) is the most common type, a complex and heterogeneous disorder with environmental and genetic factors contributing to its pathogenesis. Approximately 5% of POAG is currently attributed to single‑gene or Mendelian forms of glaucoma. Genetic linkage analysis and genome‑wide association studies have identified various genomic loci, paving the path to understanding the pathogenesis of this enigmatic, blinding disease. In this review we summarize the most common variants reported thus far and their possible clinical correlations.

Rare protein-altering variants in ANGPTL7 lower intraocular pressure and protect against glaucoma

Protein-altering variants that are protective against human disease provide in vivo validation of therapeutic targets. Here we use genotyping data from UK Biobank (n = 337,151 unrelated White British individuals) and FinnGen (n = 176,899) to conduct a search for protein-altering variants conferring lower intraocular pressure (IOP) and protection against glaucoma. Through rare protein-altering variant association analysis, we find a missense variant in ANGPTL7 in UK Biobank (rs28991009, p.Gln175His, MAF = 0.8%, genotyped in 82,253 individuals with measured IOP and an independent set of 4,238 glaucoma patients and 250,660 controls) that significantly lowers IOP (β = -0.53 and -0.67 mmHg for heterozygotes, -3.40 and -2.37 mmHg for homozygotes, P = 5.96 x 10-9 and 1.07 x 10-13 for corneal compensated and Goldman-correlated IOP, respectively) and is associated with 34% reduced risk of glaucoma (P = 0.0062). In FinnGen, we identify an ANGPTL7 missense variant at a greater than 50-fold increased frequency in Finland compared with other populations (rs147660927, p.Arg220Cys, MAF Finland = 4.3%), which was genotyped in 6,537 glaucoma patients and 170,362 controls and is associated with a 29% lower glaucoma risk (P = 1.9 x 10-12 for all glaucoma types and also protection against its subtypes including exfoliation, primary open-angle, and primary angle-closure). We further find three rarer variants in UK Biobank, including a protein-truncating variant, which confer a strong composite lowering of IOP (P = 0.0012 and 0.24 for Goldman-correlated and corneal compensated IOP, respectively), suggesting the protective mechanism likely resides in the loss of interaction or function. Our results support inhibition or down-regulation of ANGPTL7 as a therapeutic strategy for glaucoma.

Using BXD mouse strains in vision research: A systems genetics approach

We illustrate the growing power of the BXD family of mice (recombinant inbred strains from a cross of C57BL/6J and DBA/2J mice) and companion bioinformatic tools to study complex genome-phenome relations related to glaucoma. Over the past 16 years, our group has integrated powerful murine resources and web-accessible tools to identify networks modulating visual system traits-from photoreceptors to the visual cortex. Recent studies focused on retinal ganglion cells and glaucoma risk factors, including intraocular pressure (IOP), central corneal thickness (CCT), and susceptibility of cellular stress. The BXD family was exploited to define key gene variants and then establish linkage to glaucoma in human cohorts. The power of this experimental approach to precision medicine is highlighted by recent studies that defined cadherin 11 (Cdh11) and a calcium channel (Cacna2d1) as genes modulating IOP, Pou6f2 as a genetic link between CCT and retinal ganglion cell (RGC) death, and Aldh7a1 as a gene that modulates the susceptibility of RGCs to death after elevated IOP. The role of three of these gene variants in glaucoma is discussed, along with the pathways activated in the disease process.

Heritability of Inner Retinal Layer and Outer Retinal Layer Thickness: The Healthy Twin Study

The purpose of the study is to evaluate the heritability of inner retinal layer (IRL) and outer retinal layer (ORL) thicknesses in the healthy Korean population. This was a cross-sectional, twin and family study. We included 374 Korean adults with healthy eyes from 89 families. IRL thickness (from the internal limiting membrane to the external limiting membrane) and ORL thickness (from the external limiting membrane to the outer border of the retinal pigment epithelium layer) were measured in the nine macular subfields as defined by the Early Treatment of Diabetic Retinopathy Study using optical coherence tomography. The heritability on IRL and ORL thicknesses were investigated using a variance decomposition model. The heritability of IRL thickness was 0.87, 0.58, 0.85, 0.89, and 0.74 for the central, inner superior, inner inferior, inner temporal, inner nasal subfields, respectively; and 0.62, 0.83, 0.62, and 0.60 for the outer superior, outer inferior, outer temporal, outer nasal subfields, respectively. The heritability of ORL thickness was 0.56, 0.75, 0.66, 0.72, and 0.56 for the central, inner superior, inner inferior, inner temporal, inner nasal subfields, respectively; and 0.64, 0.63, 0.73, 0.54 for the outer superior, outer inferior, outer temporal, and outer nasal subfields, respectively. The heritability estimates of IRL thickness and ORL thickness ranged from moderate to high. The IRL thickness at the central, inner temporal, and inner inferior subfields had particularly high heritability.

Clinical implications of recent advances in primary open-angle glaucoma genetics

Over the last decade, genetic studies, including genome-wide association studies (GWAS), have accelerated the discovery of genes and genomic regions contributing to primary open-angle glaucoma (POAG), a leading cause of irreversible vision loss. Here, we review the findings of genetic studies of POAG published in English prior to September 2019. In total, 74 genomic regions have been associated at a genome-wide level of significance with POAG susceptibility. Recent POAG GWAS provide not only insight into global and ethnic-specific genetic risk factors for POAG susceptibility across populations of diverse ancestry, but also important functional insights underlying biological mechanisms of glaucoma pathogenesis. In this review, we also summarize the genetic overlap between POAG, glaucoma endophenotypes, such as intraocular pressure and vertical cup-disc ratio (VCDR), and other eye disorders. We also discuss approaches recently developed to increase power for POAG locus discovery and to predict POAG risk. Finally, we discuss the recent development of POAG gene-based therapies and future strategies to treat glaucoma effectively. Understanding the genetic architecture of POAG is essential for an earlier diagnosis of this common eye disorder, predictive testing of at-risk patients, and design of gene-based targeted medical therapies none of which are currently available.

Determining Possible Shared Genetic Architecture Between Myopia and Primary Open-Angle Glaucoma

Purpose

To determine genetic correlations between common myopia and primary open-angle glaucoma (POAG).

Methods

We tested the association of myopia polygenic risk scores (PRSs) with POAG and POAG endophenotypes using two studies: the Australian & New Zealand Registry of Advanced Glaucoma (ANZRAG) study comprising 798 POAG cases with 1992 controls, and the Rotterdam Study (RS), a population-based study with 11,097 participants, in which intraocular pressure (IOP) and optic disc parameter measurements were catalogued. PRSs were derived from genome-wide association study meta-analyses conducted by the Consortium for Refractive Error and Myopia (CREAM) and 23andMe. In total, 12 PRSs were constructed and tested. Further, we explored the genetic correlation between myopia, POAG, and POAG endophenotypes by using the linkage disequilibrium score regression (LDSC) method.

Results

We did not find significant evidence for an association between PRS of myopia with POAG (P = 0.81), IOP (P = 0.07), vertical cup-disc ratio (P = 0.42), or cup area (P = 0.25). We observed a nominal association with retinal nerve fiber layer (P = 7.7 × 10-3) and a significant association between PRS for myopia and disc area (P = 1.59 × 10-9). Using the LDSC method, we found a genetic correlation only between myopia and disc area (genetic correlation [RhoG] = -0.12, P = 1.8 × 10-3), supporting the findings of the PRS approach.

Conclusions

Using two complementary approaches we found no evidence to support a genetic overlap between myopia and POAG; our results suggest that the comorbidity of these diseases is not influenced by common variants. The association between myopia and optic disc size is well known and validates this methodology.