Current understanding of genetics and epigenetics in pseudoexfoliation syndrome and glaucoma

Cellular senescence and glaucoma

Cellular senescence, a characteristic feature of the aging process, is induced by diverse stressors. In recent years, glaucoma has emerged as a blinding ocular disease intricately linked to cellular senescence. The principal pathways implicated are oxidative stress, mitochondrial dysfunction, DNA damage, autophagy impairment, and the secretion of various senescence- associated secretory phenotype factors. Research on glaucoma-associated cellular senescence predominantly centers around the increased resistance of the aqueous humor outflow pathway, which is attributed to the senescence of the trabecular meshwork and Schlemm's canal. Additionally, it focuses on the mechanisms underlying retinal ganglion cell senescence in glaucoma and the corresponding intervention measures. Given that cell senescence represents an irreversible phase preceding cell death, an in-depth investigation into its mechanisms in the pathogenesis and progression of glaucoma, particularly by specifically blocking the signal transduction of cell senescence, holds the potential to decrease the outflow resistance of aqueous humor. This, in turn, could provide a novel avenue for safeguarding the optic nerve in glaucoma.

Comprehensive Proteomic Profiling of Exfoliation Glaucoma Via Mass Spectrometry Reveals SVEP1 as a Potential Biomarker

Purpose

This study investigated the proteomic landscape of exfoliation glaucoma to find potential biomarkers.

Methods

The study enrolled 34 patients diagnosed with either exfoliation syndrome with/without glaucoma or age-related cataract. Plasma proteins were analyzed through mass spectrometry and Mendelian randomization (MR) based on data from deCODE, FinnGen, Atherosclerosis Risk in Communities (ARIC), eQTLGen, and UK Biobank (UKB) cohorts to infer relationships.

Results

Among 2025 plasma proteins analyzed, 130 were differentially expressed in the exfoliation glaucoma group, which exhibited elevated intraocular pressure. Our proteomics data suggested that infection, immune responses including intestinal immune network, endocrine hormones, and complement and coagulation cascades are involved in the development of exfoliation glaucoma. Notably, there was a significant correlation between SVEP1 and exfoliation glaucoma (odds ratio [OR] = 1.20, 95% confidence interval [CI] = 1.10 to 1.31, P = 0.0000428), with findings corroborated in an independent cohort. Further analysis predicted a protective role of LOXL1-AS1 in exfoliation glaucoma through its regulation of SVEP1 expression. In MR phenome-wide association studies, SVEP1 was associated with complications of exfoliation glaucoma. After multiple testing corrections, there was a tendency for SVEP1 to be associated with glaucoma (OR = 1.14, 95% CI = 1.11 to 1.16, P = 0.0000003) and type 2 diabetes (OR = 1.07, 95% CI = 1.05 to 1.08, P = 0.0000067).

Conclusions

Plasma proteomic analysis reveals that high expression of SVEP1 is a risk factor for exfoliation glaucoma, which potentially affects diabetes and is affected by estradiol or LOXL1-AS1. However, further research is needed to establish causality.

RNA methylation homeostasis in ocular diseases: All eyes on Me

RNA methylation is a pivotal epigenetic modification that adjusts various aspects of RNA biology, including nuclear transport, stability, and the efficiency of translation for specific RNA candidates. The methylation of RNA involves the addition of methyl groups to specific bases and can occur at different sites, resulting in distinct forms, such as N6-methyladenosine (m6A), N1-methyladenosine (m1A), 5-methylcytosine (m5C), and 7-methylguanosine (m7G). Maintaining an optimal equilibrium of RNA methylation is crucial for fundamental cellular activities such as cell survival, proliferation, and migration. The balance of RNA methylation is linked to various pathophysiological conditions, including senescence, cancer development, stress responses, and blood vessel formation, all of which are pivotal for comprehending a spectrum of eye diseases. Recent findings have highlighted the significant role of diverse RNA methylation patterns in ophthalmological conditions such as age-related macular degeneration, diabetic retinopathy, cataracts, glaucoma, uveitis, retinoblastoma, uveal melanoma, thyroid eye disease, and myopia, which are critical for vision health. This thorough review endeavors to dissect the influence of RNA methylation on common and vision-impairing ocular disorders. It explores the nuanced roles that RNA methylation plays in key pathophysiological mechanisms, such as oxidative stress and angiogenesis, which are integral to the onset and progression of these diseases. By synthesizing the latest research, this review offers valuable insights into how RNA methylation could be harnessed for therapeutic interventions in the field of ophthalmology.

The Ocular Surface and the Anterior Segment of the Eye in the Pseudoexfoliation Syndrome: A Comprehensive Review

Pseudoexfoliation syndrome (PXS) is an age-related fibrillopathy where fibrillar exfoliation material accumulates and deposits in ocular and extra-ocular tissue. Within the eye, this substance accumulates on the ocular surface and in the anterior segment of the eye, impacting ocular structures such as the conjunctiva, Tenon's capsule, sclera, cornea, iris, ciliary body, trabecular meshwork, and lens. This review aims to collate the current literature on how each anatomical part of the eye is affected by PXS, with a strong focus on molecular changes. We also summarise the current understanding of the key genetic factors influencing the development of PXS.

Exfoliation syndrome genetics in the era of post-GWAS

Exfoliation syndrome (XFS), or pseudoexfoliation syndrome, is considered a systemic disorder that leads to glaucoma with progressive visual field loss. A better insight into the underlying pathogenic mechanism will help diagnose the disease and prevent and slow progression. Here, we provide an overview of disease pathogenesis in the light of GWAS and multi-omics research. We discuss possible environmental interactions related to XFS. We investigate the potential interactions in differentially expressed genes from RNA-Seq by using Ingenuity Pathway Analysis. MAPK pathway was identified as the top network of these genes. Further investigation is needed to verify our results in vivo. It is necessary to establish an animal model mimicking exfoliation syndrome phenotypes.

Insights on the Genetic and Phenotypic Complexities of Optic Neuropathies

Background/Objectives: Optic neuropathies are a category of illnesses that ultimately cause damage to the optic nerve, leading to vision impairment and possible blindness. Disorders such as dominant optic atrophy (DOA), Leber hereditary optic neuropathy (LHON), and glaucoma demonstrate intricate genetic foundations and varied phenotypic manifestations. This narrative review study seeks to consolidate existing knowledge on the genetic and molecular mechanisms underlying ocular neuropathies, examine genotype-phenotype correlations, and assess novel therapeutic options to improve diagnostic and treatment methodologies. Methods: A systematic literature review was performed in October 2024, utilizing PubMed, Medline, the Cochrane Library, and ClinicalTrials.gov. Search terms encompassed "optic neuropathy", "genetic variants", "LHON", "DOA", "glaucoma", and "molecular therapies". Studies were chosen according to established inclusion criteria, concentrating on the genetic and molecular dimensions of optic neuropathies and their therapeutic ramifications. Results: The results indicate that DOA and LHON are mostly associated with the mitochondrial dysfunction resulting from pathogenic variants in nuclear genes, mainly OPA1, and mitochondrial DNA (mtDNA) genes, respectively. Glaucoma, especially its intricate variants, is linked to variants in genes like MYOC, OPTN, and TBK1. Molecular mechanisms, such as oxidative stress and inflammatory modulation, are pivotal in disease progression. Innovative therapeutics, including gene therapy, RNA-based treatments, and antioxidants such as idebenone, exhibit promise for alleviating optic nerve damage and safeguarding vision. Conclusions: Genetic and molecular investigations have markedly enhanced our comprehension of ocular neuropathies. The amalgamation of genetic and phenotypic data is essential for customized medical strategies. Additional research is required to enhance therapeutic strategies and fill the gaps in our understanding of the underlying pathophysiology. This interdisciplinary approach shows potential for enhancing patient outcomes in ocular neuropathies.

Minimal phenotypes in transgenic mice with the human LOXL1/LOXL1-AS1 locus associated with exfoliation glaucoma

Exfoliation syndrome is a leading cause of secondary glaucoma worldwide. Among the risk-factors for exfoliation syndrome and exfoliation glaucoma that have been investigated, a genetic association with 15q24.1 is among the most striking. The leading candidates for the causal gene at this locus are LOXL1 and/or LOXL1-AS1, but studies have not yet coalesced in establishing, or ruling out, either candidate. Here, we contribute to studies of the 15q24.1 locus by making a partially humanized mouse model in which 166 kb of human genomic DNA from the 15q24.1 locus was introduced into the mouse genome via BAC transgenesis (B6-Tg(RP11-71M11)Andm). Transgenic expression of human genes in the BAC was only detectable for LOXL1-AS1. One cohort of 34 mice (21 experimental hemizygotes and 13 non-carrier control littermates) was assessed by slit-lamp exams and SD-OCT imaging at early (1-2 months) and mid (4-5 months) time points; fundus exams were performed at 5 months of age. A second smaller cohort (3 hemizygotes) were aged extensively (>12 months) to screen for overt abnormalities. Across all genotypes and ages, 136 slit-lamp exams, 128 SD-OCT exams, and 42 fundus exams detected no overt indices of exfoliation syndrome. Quantitatively, small, but statistically significant, age-related declines in ganglion cell complex thickness and total retinal thickness were detected in the hemizygotes at 4 months of age. Overall, this study demonstrates complexity in gene regulation from the 15q24.1 locus and suggests that LOXL1-AS1 is unlikely to be a monogenic cause of exfoliation syndrome but may contribute to glaucomatous retinal damage.

Proteomic characteristics of the aqueous humor in Uyghur patients with pseudoexfoliation syndrome and pseudoexfoliative glaucoma

Pseudoexfoliation syndrome (PEX) is characterized by the deposition of fibrous pseudoexfoliation material (PEXM) in the eye, and secondary glaucoma associated with this syndrome has a faster and more severe clinical course. The incidence of PEX and pseudoexfoliative glaucoma (PEXG) exhibits ethnic clustering; however, few proteomic studies related to PEX and PEXG have been conducted in Asian populations. Therefore, we aimed to conduct proteomic analysis on the aqueous humor (AH) obtained from Uyghur patients with cataracts, those with PEX and cataracts, and those with PEXG and cataracts to better understand the molecular mechanisms of the disease and identify its potential biomarkers. To this end, AH was collected from patients with cataracts (n = 10, control group), PEX with cataracts (n = 10, PEX group), and PEXG with cataracts (n = 10, PEXG group) during phacoemulsification. Label-free quantitative proteomic techniques combined with bioinformatics were used to identify and analyze differentially expressed proteins (DEPs) in the AH of PEX and PEXG groups. Then, independent AH samples (n = 12, each group) were collected to validate DEPs by enzyme-linked immunosorbent assay (ELISA). The PEX group exhibited 25 DEPs, while the PEXG group showed 44 DEPs, both compared to the control group. Subsequently, we found three newly identified proteins in both PEX and PEXG groups, wherein FRAS1-related extracellular matrix protein 2 (FREM2) and osteoclast-associated receptor (OSCAR) exhibited downregulation, whereas coagulation Factor IX (F9) displayed upregulation. Bioinformatics analysis suggested that extracellular matrix interactions, abnormal blood-derived proteins, and lysosomes were mainly involved in the process of PEX and PEXG, and the PPI network further revealed F9 may serve as a potential biomarker for both PEX and PEXG. In conclusion, this study provides new information for understanding the proteomics of AH in PEX and PEXG.