Genetic screening & oxidative stress analysis in primary open angle glaucoma (POAG)

Abstract

Purpose: To evaluate the mutation spectrum in all candidate genes and perform whole mitochondrial DNA analysis in North Indian Primary Open Angle Glaucoma and correlate these with oxidative stress.

Methods: The study included 54 POAG patients & 50 controls. MYOC, NTF4 & WDR36 genes were amplified by PCR. Mitochondrial genome was screened in cases negative for any changes in the candidate genes. Reactive oxygen species (ROS) levels were measured by chemiluminescence method & total antioxidant capacity (TAC) was measured by ELISA. Microarray analysis was done by Agilent human whole genome oligo microarrays. Significantly differentially expressed genes were validated by real time PCR.

Results: Twenty six cases (48.2%) had a pathogenic nucleotide change in exon 1 of MYOC (G887A) corresponding to amino acid change p.R76K . None of the controls presented these changes. Total of 156 (in patients) & 79 (in controls) mtDNA nucleotide variations were found in this study. Five pathogenic changes (3 novel & 2 reported) were found. Complex I had highest number of non synonymous changes. Blood ROS levels were significantly higher (p=0.03) & TAC levels significantly lower (p<0.001) in patients as compared to controls. There was a positive correlation (r=0.79, p=0.0001) & a strong negative correlation (r=-0.89, p=0.0001) of total number of mtDNA nucleotide changes in coding region with ROS levels & TAC levels respectively. We found 380 dysregulated genes in POAG cases. Major pathways involved were cell adhesion-ECM remodeling, IL1 signaling & cytoskeletal remodelling.

Conclusions: Nearly half of POAG cases had mutations in exon 1 of MYOC. Mitochondrial nucleotide changes lead to oxidative stress in POAG. The pathways involving the dysregulated genes are the ones mainly involved in the maintainance of Trabecular Meshwork integrity & structure.

Keywords: 539 genetics