Author ORCID Identifier

https://orcid.org/0009-0002-4395-2135

Date of Award

27-3-2025

Document Type

Thesis

School

School of Chemical & Biotechnology

Programme

Ph.D.-Doctoral of Philosophy

First Advisor

Dr.S.Sripriya

Second Advisor

Dr.Suma Mohan

Keywords

Genetics, Complex Disease, Primary Glaucoma, Pseudoexfoliation Syndrome, Next Generation Sequencing, DNA Methylation Analysis, Epigenetics, Mitochondria DNA Analysis

Abstract

BACKGROUND: Glaucoma is the second most common cause of blindness globally typically diagnosed with a triad of clinical symptoms of increased intraocular pressure (IOP) with associated optic disc, optic nerve head (ONH) changes, and visual field defects. Genetic and environmental factors are some of the strong aetiology factors for glaucoma and identification of these factors has a potential implication in the management of the disease and its outcome. There is a paradigm shift towards understanding the genetics of glaucoma, wherein the variants in the nuclear, mitochondrial genome and other regulatory regions are being identified as contributing risk factors.

METHODOLOGY AND RESULTS: The current study is conducted in 3 distinct sample sets: large extended multiplex consanguineous families with primary open-angle glaucoma (POAG), primary angle-closure glaucoma (PACG) and pseudoexfoliation syndrome (XFS) patients. Whole exome sequencing (WES) and trios analysis was performed in PACG families and probable disease-causing rare variants were identified in ZFYVE19, SLC12A1, and COL1A1 genes in 2 of the three families screened.

These genes are implicated in IOP regulation and extracellular matrix (ECM) remodelling. Mitochondrial genes (MT-ND1, MT-ND2, MT-ND5, MT-ND6, MT-ATP6, MT-CYB) involved in lipid metabolism were analyzed in primary glaucoma patients and DNA variants in MT-ND5 (m.13469T>A), MT-CYB (m.15326A>G) and MT-ATP6 (m.8860A>G) genes associated with vertical cup-to-disc ratio (VCDR) and central corneal thickness (CCT) were identified. Screening the coding regions of in LOXL1, POMP and TMEM136 genes did not identify any rare variants for the disease but specific SNP haplotypes were correlated with susceptibility for XFS risk and UV exposure. The differential methylation patterns were assessed in POAG and XFS using whole genome bisulfite sequencing (WGBS) and the Infinium BeadChip array.

WGBS in POAG patients identified numerous differentially methylated genes (DMGs), including SIX6 and WNT7B, with significant correlations to elevated IOP. The hypermethylation of the SIX6 gene showed a significant correlation with elevated IOP in PACG patients and also found a 35.2% similarity in methylation profiles between cultured human tenon fibroblasts (HTFs) and matched blood samples. Decreased LOXL1 gene expression was observed in HTFs from patients, which correlated with differential methylation of the Sp-1 binding sites located at -253, -243bp upstream of the LOXL1 promoter's transcription start site.

CONCLUSION: The identified genetic variants and differential methylation in primary glaucoma play significant roles in IOP regulation, neuronal protection, and contributing to retinal ganglion cell (RGC) loss implicated in disease pathology. Although these rare variants account for a relatively small population-attributable risk for IOP and glaucoma, they may hold predictive value for specific patient subgroups. Future research on validating these findings through in vitro methods and larger cohorts to confirm their causal roles to elucidate underlying mechanisms is warranted. Overall, this study highlights the utility of NGS and pathway-based analyses in elucidating the genetic and epigenetic complexities of glaucoma, providing insights into disease mechanisms and identification of potential biomarkers that may enhance diagnosis and treatment strategies.

Download

Share

COinS