Development of an AAV-CRISPR-Cas9-based treatment for dominant cone-rod dystrophy 6.

Abstract

Cone-rod dystrophy 6 (CORD6) is caused by gain-of-function mutations in the GUCY2D gene, which encodes retinal guanylate cyclase-1 (RetGC1). There are currently no treatments available for this autosomal dominant disease, which is characterized by severe, early-onset visual impairment. The purpose of our study was to develop an adeno-associated virus (AAV)-CRISPR-Cas9-based approach referred to as "ablate and replace" and evaluate its therapeutic potential in mouse models of CORD6. This two-vector system delivers (1) CRISPR-Cas9 targeted to the early coding sequence of the wild-type and mutant GUCY2D alleles and (2) a CRISPR-Cas9-resistant cDNA copy of GUCY2D ("hardened" GUCY2D). Together, these vectors knock out ("ablate") expression of endogenous RetGC1 in photoreceptors and supplement ("replace") a healthy copy of exogenous GUCY2D. First, we confirmed that ablation of mutant R838S GUCY2D was therapeutic in a transgenic mouse model of CORD6. Next, we established a proof of concept for "ablate and replace" and optimized vector doses in Gucy2e+/-:Gucy2f-/- and Gucy2f-/- mice, respectively. Finally, we confirmed that the "ablate and replace" approach stably preserved retinal structure and function in a novel knockin mouse model of CORD6, the RetGC1 (hR838S, hWT) mouse. Taken together, our results support further development of the "ablate and replace" approach for treatment of CORD6.

• Authors: Russell W Mellen, Kaitlyn R Calabro, K Tyler McCullough, Sean M Crosson, Alejandro de la Cova, Diego Fajardo, Emily Xu, Sanford L Boye, Shannon E Boye
• Journal: Molecular therapy. Methods & clinical development (Mol Ther Methods Clin Dev) Vol. 30 Pg. 48-64 (Sep 14 2023) ISSN: 2329-0501 [Print] United States
• PMID: 37361352 (Publication Type: Journal Article)
• Copyright: © 2023 The Author(s).