Abstract
Purpose :
Loss of central vision constitutes the major underlying reason for visual handicap in western industrialized nations. Stargardt’s Disease 1 (STGD1) is an autosomal recessive disease of early onset and severe visual handicap, representing the most frequent inherited macular degeneration. The gene in which mutations are responsible for STGD1 has been identified, ABCA4, coding for a member of the ATP binding cassette super family, expressed specifically in retina.
The aim of this project is to compare the vulnerability of rod and cone photoreceptors to ABCA4 loss by a CRISPR-CAS9 strategy using a diurnal rodent. The animal model, Fat Sand Rat Psammomys obesus, is a diurnal cone-rich species in which cone photoreceptors are represented in large numbers (~30-40% total photoreceptors), more closely resembling the human macula, and allowing detailed structural, functional and biochemical analyses.
Methods :
We performed subretinal injections of Adeno-Associated Virus (AAV)-CRISPR-CAS9 constructs in Psammomys obesus, to obtain an ABCA4 - KO. RT-qPCR and immunofluorescence staining were performed to confirm the loss of ABCA4; to analyse the functional and morphological consequences to ABCA4 loss we performed non-invasive imaging (Electroretinography, Optical coherence tomography, Fundus imaging).
Results :
RT-qPCR and immunofluorescence staining show a loss of ABCA4 expression in photoreceptors transduced by AAV-CRISPR-CAS9 compared to control injections. CRISPR-CAS9-ABCA4 -/- treated eyes exhibit extensive and rapid retinal degeneration by 2 months post-injection, as seen by OCT, and ERG recording showed significant declines in photopic (cone) light responses.
Conclusions :
In conclusion, cone-rich rodents offer a unique scenario to explore molecular and cellular changes occurring in human maculopathies like STGD1, and should provide a valuable means to appraise potential therapeutic strategies.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.