RNA Sequencing of Lens Capsular Epithelium Implicates Novel Pathways in Pseudoexfoliation Syndrome

Abstract

Purpose Pseudoexfoliation syndrome (PEX) is a common systemic disease that results in severe and often irreversible vision loss. Despite considerable research effort, PEX remains incompletely understood. This study sought to perform the first RNAseq study in elucidate the pathophysiology of PEX, and contribute a publicly available transcriptomic data resource for future research. Methods Human ocular lens capsular epithelium samples were collected from 25 patients with PEX and 39 non-PEX controls undergoing cataract surgery. RNA extracted from these specimens was subjected to polyadenylated (mRNA) selection and deep bulk RNA sequencing. Differential expression analysis investigated protein-coding gene transcripts. Exploratory analyses used pathway analysis tools, and curated class- and disease-specific gene sets. Results Differential expression analysis demonstrated that 2882 genes were differentially expressed according to PEX status. Genes associated with viral gene expression pathways were among the most upregulated, alongside genes encoding ribosomal and mitochondrial respiratory transport chain proteins. Cell adhesion protein transcripts including type 4 collagen subunits were downregulated. Conclusions This comparative transcriptomic dataset highlights novel and previously recognized pathogenic pathways in PEX and provides the first comprehensive transcriptomic resource, adding an additional layer to build further understanding of PEX pathophysiology.

Genome-Wide RNA Sequencing of Human Trabecular Meshwork Cells Treated with TGF-β1: Relevance to Pseudoexfoliation Glaucoma

“…Our analysis showed that several XFM components were upregulated in response to TGF-β1 in normal HTM tissue, see Figure 4 . A recently published summary of genes known to be expressed in XFM was used to create a gene list [ 4 ]. Genes that appeared to be upregulated with high significance (FDR < 0.05) were VCAN, ELN, LTBP2, ADAM19, LDHA, FBN1, while MYL6, MYH9 and LOXL1 were also upregulated based on their p -value.…”

“…Stimulation of normal HTM cells with TGF-β1 modulates pathways and biological processes that show much overlap with processes known to be associated with XFG such as ECM remodelling [ 38 , 39 ], modulation of oxidative stress [ 6 ], UPR [ 40 ] and changes in the expression of certain growth factors [ 14 , 41 , 42 ]. Based on these overlapping findings with XFG expression studies [ 4 , 18 , 43 ] the proposed cellular model could be a useful tool to gain more insight in the pathogenesis of XFG which is still poorly understood [ 1 , 2 , 3 , 44 ]. A comparison of relevant pathways and biological processes between this study and literature is discussed in more detail below.…”

“…To determine enrichment of relevant gene lists not found in common databases, such as exfoliation material (XFM) genes and XFS GWAS results, custom lists were created and gene expression for these gene lists was determined. For XFM genes, the list published in Supplementary Table S3 of [ 4 ] was used. A gene list of XFS GWAS genes was compiled from [ 36 ].…”

“…Pathognomonic XFM deposits are deposited on several structures in the anterior segment of the eye including the lens, ciliary body, iris and trabecular meshwork in XFG. This XFM consists of elastin, fibrillin, fibulins, latent TGF-β binding proteins, lysyl oxidase like 1 (LOXL1) and other components [ 4 , 5 ]. In XFG, the intraocular pressure (IOP) is elevated, presumably in part due to obstruction of the outflow facility by XFM [ 6 ] and changes in the outflow facility consisting of the trabecular meshwork (TM) and Schlemm’s canal (SC).…”

“…Despite advances in genetic basis of XFS/XFG [ 2 ] there is a need for the integration of multiomics data and further experimental work to fully elucidate the molecular mechanisms driving XFS/XFG [ 2 , 4 , 16 ]. Obtaining disease relevant tissue from human subjects with XFG is challenging [ 17 , 18 ] and researchers have used lens capsule and Tenon’s ocular fibroblasts as a surrogate for the trabecular meshwork [ 4 , 14 , 19 ]. However, molecular and cellular alterations in the trabecular meshwork drive the reduction in outflow facility and raised IOP seen in XFG.…”