Visual Function of Wild Type and Channelrhodopsin-2 Transgenic Rats

Abstract

Purpose: : We previously reported that the transduction of the channelrhodopsin-2 gene (ChR2) into the retinal ganglion cells (RGCs) could restore the visual function in the genetically blind rats. The purpose of this study is to investigate effects of ectopic expression of the ChR2 in the RGCs on normal visual function.

Methods: : The N-terminal fragment (residues 1-315) of the ChR2 was fused to a fluorescent protein, Venus, in frame at the end of the ChR2 coding fragment (ChR2V). The ChR2V was subcloned to the downstream of the Thy-I promoter. We investigated the expression of the ChR2V in six transgenic lines and chose a line 4 for later investigations. To identify the RGCs in the ganglion cell layer (GCL), the RGCs were retrogradely labeled with a fluorescent tracer, Fluorogold, by the injection of the dye into a superior colliculus. The expression of ChR2V in the retina was observed by the flat-mounted retinas and retinal slices under a fluorescence microscope. Visual function was evaluated by recording visually evoked potentials (VEPs) with various stimulus patterns, erectroretinogram (ERG) and optomotor responses.

Results: : The expression of ChR2V driven by the Thy I promoter was localized in RGCs. Histological analysis did not show any specific changes caused by the ectopic expression of ChR2V. Amplitudes and waveforms of VEPs and ERGs in the Thy I-ChR2V were almost same with wild type rats. In the behavior test, there were no significant differences in the spatial frequencies and contrast sensitivities between in wild type and Thy I-ChR2V rats.

Conclusions: : The ectopic expression of ChR2V in the retinal ganglion cells did not disturb normal visual function in wister rat.

Keywords: retinitis • gene transfer/gene therapy • regeneration