DNA Methylation of human trabecular meshwork: searching for biomarkers of glaucoma

Abstract

Purpose : To study the DNA methylation status of patients with primary open-angle glaucoma (POAG), and the expression of genes hypo- or hypermethylated and the concentration of the proteins coded by those genes in POAG.

Methods : A case-control study in POAG patients and control subjects was carried out. First, we performed the study of the DNA methylation in trabecular meshwork samples of POAG patients (n=15) and cadaver samples (n=15), combining bisulfite conversion of genomic DNA and whole-genome amplification. After that, we analyzed the relative expression of several hypo- and hypermethylated genes in blood samples of POAG patients (n=30) and healthy controls (n=30) by real time PCR (7900HT Fast Real-Time PCR System, Applied Biosystems, Foster City, CA, USA). Finally, we determined the concentration of the proteins coded by those genes by means of enzyme-linked immunosorbent assays.

Results : After sequencing the samples, we got the methylation status of thousand genes and loci. Among them, the TP53AIP1, VSX2 and CDH23 genes were hypomethylated and the GPX4, GDNF and PITX1 genes were hypermethylated in POAG samples compared to control samples. The hypomethylated genes showed a higher expression in the POAG group, but only the difference in expression of the TP53AIP1 gene was statistically significant (p=0.001). Regarding the hypermethylated genes, only the GPX4 gene had a significantly lower expression in POAG group (p=0.025). We observed statistically significant differences in the concentration of proteins encoded by the genes with differential expression between POAG and control groups (TP53AIP1 and GPX4).

Conclusions : The DNA methylation profile is different in trabecular meshwork of primary open-angle glaucoma compared to controls. Due to the different methylation status, the expression of the TP53AIP1 gene and the protein encoded by this gene is increased and GPX4 gene and its protein is decreased in POAG. Thus, apoptosis in trabecular meshwork is stimulated while the antioxidant capacity is inhibited in the glaucoma group. Further studies in larger sample sizes are needed to clarify the role of epigenetic alterations in the onset and / or progression of glaucomatous disease.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.