Aberrant DNA methylation of miRNAs in Fuchs endothelial corneal dystrophy

Abstract

Homeostatic maintenance of corneal endothelial cells is essential for maintenance of corneal deturgescence and transparency. in fuchs endothelial corneal dystrophy (fecD), an accelerated loss and dysfunction of endothelial cells leads to progressively severe visual impairment. An abnormal accumulation of extracellular matrix (ecM) is a distinctive hallmark of the disease, however the molecular pathogenic mechanisms underlying this phenomenon are not fully understood. Here, we investigate genome-wide and sequence-specific DNA methylation changes of miRNA genes in corneal endothelial samples from fecD patients. We discover that miRnA gene promoters are frequent targets of aberrant DNA methylation in FECD. More specifically, miR-199B is extensively hypermethylated and its mature transcript miR-199b-5p was previously found to be almost completely silenced in FECD. Furthermore, we find that miR-199b-5p directly and negatively regulates Snai1 and ZEB1, two zinc finger transcription factors that lead to increased ECM deposition in FECD. Taken together, these findings suggest a novel epigenetic regulatory mechanism of matrix protein production by corneal endothelial cells in which miR-199B hypermethylation leads to miR-199b-5p downregulation and thereby the increased expression of its target genes, including Snai1 and ZEB1. our results support miR-199b-5p as a potential therapeutic target to prevent or slow down the progression of FECD disease. Corneal transparency is critical for good visual acuity. The corneal endothelium regulates the hydration status of the cornea and has an essential role in maintaining corneal deturgescence and preventing edema that can degrade corneal transparency. It is the innermost layer of the cornea and is composed of a single layer of cells that pump excess fluid out of the cornea through active ion-transport processes 1,2. Fuchs endothelial corneal dystrophy (FECD) is a bilateral, slowly progressive disorder in which the corneal endothelial cells are diseased and become less efficient at removing fluid. As a result, the highly ordered arrangement of collagen fibers in the corneal stromal layer become disrupted, leading to corneal opacification and vision loss 3. Other clinical phenotypic changes that occur in FECD include an excessive accumulation of extracellular matrix (ECM), formation of central excrescences (corneal guttae), thickening of Descemet's membrane, and corneal scarring 4. At earlier stages of FECD, the formation of corneal guttae can cause light scatter and optical aberrations that can impair vision, even in the absence of overt corneal edema. In later FECD, overt endothelial dysfunction and resultant corneal edema contribute significantly to visual loss. Corneal endothelial cells are largely non-regenerative in vivo and their loss is often irreversible 5. Medical management is often inadequate and corneal endothelial transplantation remains the main therapeutic option to restore vision in patients with advanced FECD. FECD is a leading indication for corneal transplantation i...

DNA methylation changes and increased mRNA expression of coagulation proteins, Factor V and Thrombomodulin in Fuchs endothelial corneal dystrophy

“…Lack of the TCF4 genotype and different filtering methods in previous FECD methylation studies could be one of the reasons why there is not much agreement in our results compared to Khuc et al [34] and Pan et al [25] who used Illumina 450K methylation array without genotyping TCF4. We used a different method to calculate significant changes between FECD and controls; β-values versus M-values and an absolute difference versus linear model, which could also bring the dissimilarities.…”

“…A well-known consequence of DNA methylation at gene promoter regions is gene silencing, whereas gene body methylation may be involved in the regulation of gene splicing [32,33]. DNA methylation patterns in CE tissue from FECD patients with unknown TCF4 status have been investigated earlier, revealing altered methylation of promoter regions in FECD patients compared to controls [25,34]. However, the effect of an expanded CTG18.1 locus on methylation in FECD remains unknown.…”

TCF4 trinucleotide repeat expansion in Swedish cases with Fuchs' endothelial corneal dystrophy

“…2015; Pan et al. 2019), repeat‐associated non‐ATG translation (Soragni et al. 2018) and hypermethylation in the corneal endothelium (Khuc et al.…”

Expression and Function of ZEB1 in the Cornea

“…Pan et al indicated that the high degree of miR-199b-5p methylation may be related to the pathogenesis of FECD. They confirmed that miR-199b-5p directly targets the 3′-UTR of SNAI1 and ZEB1 transcripts and represses their expression and link the downregulation of miR-199b-5p by its methylation to the upregulation of both SNAI1 and ZEB1 [ 48 ]. Riazuddin et al reported a pathogenic mutation of ZEB1 in FECD, but other studies have not shown a significant correlation between ZEB1 and the disease [ 49 ].…”