Purchase this article with an account.
Benjamin Gaub, Michael Berry, Joshua Levitz, John Flannery, Ehud Isacoff; Vision Restoration in Mouse Models of RP using Light-Gated G-Protein Coupled Receptors. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4688.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Retinitis pigmentosa (RP), an inherited eye disease that leads to blindness following progressive photoreceptor degeneration, affects 2 million people worldwide. Despite this significant impact on the entire population, there is no FDA approved treatment for RP to date. Recent experiments suggest that virus-mediated expression of light sensitive ion-channels can restore visual function in rd mice in-vitro and in-vivo. However, the sensitivity levels of these optogenetic actuators post major limitations to vision restoration. The illumination threshold is well above physiological light conditions and is potentially harmful to the retina. More worrying yet, the larger the eye, the more distance light has to travel until it reaches the retina, leading to a significant dop in light intensity. Moving to higher order animal models will require actuators that are more senisitive to light.
Realizing the significance of this problem, we sought to devise light-gated proteins that can utilize the intracellular G-proteins of retinal ON-bipolar cells (ON-BC). Employing the cell’s own amplification machinery, we reasoned, might lead to enhanced sensitivity. We chose to study both natural and engineered light-gated GPCRs. In order to mimic the ON-BC's native signalling cascade, we designed light-gated metabotropic glutamate receptors (Li-mGluRs) using tethered azobenzene-based photo-chromic ligands. We also explored whether ectopic expression of verterbrate rhodopsin in ON-BCs would depolarize cells in a light dependent fashion. We were able to target expression of light-gated GPCRs to ON-BCs selectively using Adeno Associated Viruses (AAVs) and cell specific promotor elements.
Currently, we are in the process of testing the ability of our light gated GPCRs to reanimate ON-BC signalling in rd-10 mice using in-vitro (MEA) and in-vivo (visually guided behavior) techniques. Preliminary in-vitro results suggest that vertebrate rhodopsin is up to 1,000x more light sensitive compared to channelrhodopsin under the same experimental parameters.
Light-gated GPCRs expressed upstream in the degenerating retinal circuit have the potential to enhance light sensitivity. Harnessing the cell's internal amplification machinery will help to lower the light intensity needed to "drive" the optogenetic actuators used as visual prosthetics.
This PDF is available to Subscribers Only