Abstract
Purpose: :
To determine whether laser–induced elevated IOP in a mouse glaucoma model alters electrophysiologic responses and retinal gene expression using microarray analysis.
Methods: :
Control and elevated IOP eyes were harvested 4 weeks after laser treatment, and total RNA was isolated from retina using the RNeasy mini protocol. Microarray analysis was performed using Affymetrix Mouse 430 2.0 gene chips at the Microarray Core Facility at Baylor College of Medicine. RGC function was assessed by using whole cell voltage–clamp and multielectrode recording techniques.
Results: :
Over 1000 genes showed a 1.5 fold or greater difference in expression between normal retina and retina with elevated IOP. Several genes linked to apoptosis were found to be altered. These include Aven, a caspase activation inhibitor, which is down–regulated, Hip1, which regulates glutamate receptor trafficking and was up–regulated, and the TNF family receptor gene Ltbr, which was up–regulated. Other genes not directly linked to apoptosis were altered as well. One of these, Cacna1a, is a voltage dependent calcium channel subunit that can affect the function of GABA receptors and adrenergic receptors, and has been linked to neurological deficits. Genes with altered expression levels that have also been shown to to be altered in other animal glaucoma models included Ptp4a3 (protein tyrosine phosphatase), Serpina3n (serine proteinase inhibitor) and Lyzs (lysozyme). Whole cell voltage clamp recording showed the sensitivity of α ganglion cells was approximately 2 log units lower in RGCs from retinas with elevated IOP compared to controls. The spatial distribution of RGC sensitivity and response was assessed using a multielectrode array.
Conclusions: :
Many retinal genes were found to be altered in the mouse glaucoma model that have not been identified in other animal glaucoma models. Further studies using quantitative RT–PCR and knockout mice will allow in–depth analysis of the roles of these altered genes. Sesitivity of RGCs was reduced in retinas from eyes with elevated IOP.
Keywords: intraocular pressure • gene microarray • electrophysiology: non-clinical