Aberrant DNA methylation of miRNAs in Fuchs endothelial corneal dystrophy

Abstract

18Homeostatic maintenance of corneal endothelial cells is essential for maintenance of corneal 19 deturgescence and corneal transparency. In Fuchs endothelial corneal dystrophy (FECD), an 20 accelerated loss and dysfunction of endothelial cells leads to progressively severe visual 21impairment. An abnormal accumulation of extracellular matrix is a distinctive hallmark of the 22 disease, however the molecular pathogenic mechanisms underlying this phenomenon are not fully 23 understood. We recently reported characteristic patterns of DNA methylation changes in the 24 corneal endothelial cells of patients with FECD. Here, we investigate genome-wide and sequence-25 specific DNA methylation changes of miRNA genes in corneal endothelial samples derived from 26 patients with FECD. We show that the majority of miRNA genes are hypermethylated at their 27 promoter regions in FECD. More specifically, miR-199B is an extensively hypermethylated 28 miRNA gene at its promoter region and its mature transcript miR-199b-5p was previously found 29 to be almost completely silenced in FECD. Using a cell-based assay, we find that miR-199b-5p 30 directly inhibits the expression of two epithelial mesenchymal transition (EMT)-inducing genes, 31Snai1 and ZEB1. Taken together, these findings suggest a novel regulatory mechanism of matrix 32 protein production by corneal endothelial cells in which miR-199b-5p hypermethylation leads to 33 its down-regulated expression and thereby the decreased expression of miR-199b-5p target genes, 34including Snai1 and ZEB1. Our results support miR-199b-5p as a potential therapeutic target to 35 prevent or slow down the progression of FECD disease. 36 37 Author summary 38 Fuchs endothelial corneal dystrophy (FECD) due to corneal endothelial cell degeneration is one 39 of the most common heritable causes of corneal visual loss and a leading indication for corneal 40 3 transplantation. The progressive loss of corneal endothelial cells is accompanied by an abnormal 41 deposition of extracellular matrix in the form of guttae. Here we discover that miRNA gene 42 promoters are frequent targets of aberrant DNA methylation in FECD. In particular, we describe 43 a novel epigenetic mechanism used by corneal endothelial cells to regulate extracellular matrix 44 production. We find that miRNA-199b-5p functions as a negative regulator of Snai1 and ZEB1, 45 two zinc finger transcription factors that have been shown to lead to increased production of 46 extracellular matrix proteins. Furthermore, miR-199B was extensively hypermethylated in FECD 47 and its mature transcript miR-199b-5p directly binds to the 3′-UTRs of Snai1 and ZEB1 genes. 48Ultimately, this may negatively modulate Snai1-and ZEB1-mediated production of extracellular 49 matrix proteins. This work is the first to identify an important role of DNA methylation in the 50 epigenetic regulation of miRNA-target genes in FECD and to describe a potential epigenetic 51 biomarker for the treatment of FECD patients. 52 53

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

“…Different pathogenic mechanisms have been proposed for FECD such as the toxic role of RNA (Mootha et al 2015;Hu et al 2018), increased expression of extracellular matrix due to reduction of microRNA (Matthaei et al 2014;Okumura et al 2015;Pan et al 2019), repeat-associated non-ATG translation (Soragni et al 2018) and hypermethylation in the corneal endothelium (Khuc et al 2017;Pan et al 2019). The mechanisms causing the association between (CTG) n repeat expansion and FECD is beyond the grasp of this study and further research is required.…”