Ophthalmic Biology Laboratory Archives

Retinal pigment epithelium (RPE) located at the back of the eye is essential for vision. It supports the photoreceptors, providing molecules required for their function. One of the main proteins produced by the RPE and indispensable for vision is the RPE65 enzyme, which is responsible for chemical signaling at the initial step of visual processing. De novo nonsense mutations in the Rpe65 gene underlie inherited genetic disorders of the eyes, resulting in blindness. To address this problem, we have harnessed the power of adenine base editors (ABEs) with Cas9 – single-guide RNA machinery to target the mutations in the Rpe65 gene for their repair. We delivered genes coding for ABEs and the Cas9 system subretinally via a lentiviral vector. Our therapeutic manipulation corrected the pathogenic mutation in a mouse model with up to 29% efficiency and with minimal formation of indel and off-target mutations. The ABE-treated mice displayed restored RPE65 expression and its activity in the visual cycle. Moreover, we have observed near-normal levels of retinal and visual functions. Our findings motivate the further testing of ABEs for the treatment of inherited retinal diseases and for the correction of pathological mutations with non-canonical protospacer-adjacent motifs.

Authors:

dr Andrzej Foik, e-mail: afoik@ichf.edu.pl & dr Anna Posłuszny, e-mail: aposluszny@ichf.edu.pl

Pertinent published article:

Restoration of visual function in adult mice with an inherited retinal disease via adenine base editing

Susie Suh, Elliot H. Choi, Henri Leinonen, Andrzej T. Foik, Gregory A. Newby, Wei-Hsi Yeh, Zhiqian Dong, Philip D. Kiser, David C. Lyon, David R. Liu & Krzysztof Palczewski, Nat Biomed Eng. 2021 Feb;5(2):169-178.

https://doi.org/10.1038/s41551-020-00632-6

One of the methods for evoking plasticity in the visual system is repeated stimulation with appropriate visual stimuli. Repeated exposure to sensory stimuli can induce neuronal network changes in the cortical circuits and improve the perception of these stimuli in the primary visual cortex (V1). The aim of our studies was to investigate the effect of repetitive visual training on the magnitude of visual responses in the primary visual cortex and in the superior colliculus (SC), the subcortical structure of the extrageniculate visual pathway in rats. Our study showed that a three-hour, passive visual training with light flashes enhanced visual responses both at the cortical level and in the superior colliculus. The next part of our study focused on distinguishing which input projection is responsible for the observed training effect in the SC, especially whether the increase of collicular response depends on the enhancement in the V1. The SC receives information both from the retina and from layer 5 of the V1. The experiment with pharmacological blocking of V1 did not suppress training-related plasticity in the SC. These results for the first time identified the superior colliculus as a possible target for training strategies to improve the efficiency of the visual process; e.g., in the case of primary visual cortex injuries.

Author:

dr Katarzyna Kordecka, e-mail: kkordecka@ichf.edu.pl