A CEP290 C-Terminal Domain Complements the Mutant CEP290 of Rd16 Mice In Trans and Rescues Retinal Degeneration

Abstract

SUMMARY Mutations in CEP290 cause ciliogenesis defects, leading to diverse clinical phenotypes, including Leber congenital amaurosis (LCA). Gene therapy for CEP290-associated diseases is hindered by the 7.4 kb CEP290 coding sequence, which is difficult to deliver in vivo. The multi-domain structure of the CEP290 protein suggests that a specific CEP290 domain may complement disease phenotypes. Thus, we constructed AAV vectors with overlapping CEP290 regions and evaluated their impact on photoreceptor degeneration in Cep290rd16/rd16 and Cep290rd16/rd16;Nrl—/— mice, two models of CEP290- LCA. One CEP290 fragment (the C-terminal 989 residues, including the domain deleted in mutant mice) reconstituted CEP290 function and resulted in cone preservation and delayed rod death. The CEP290 C-terminal domain also improved cilia phenotypes in mouse embryonic fibroblasts and iPSC-derived retinal organoids carrying the Cep290rd16 mutation. Our study strongly argues for in trans complementation of CEP290 mutations by a cognate fragment and suggests therapeutic avenues.

Delineating the role of eIF2α in retinal degeneration

“…However, knocking out GADD34 resulted in a delay in retinal degeneration but had no impact on retinal function as assessed by ERG. This could be due to the rd16 mouse model having a photoreceptor ciliopathy 22,23 , as these animals do not form normal outer segments 22,27 . This makes rd16 mice particularly challenging to rescue.…”

Clinical characteristics of individual organ system disease in non-motile ciliopathies

“…While malformations in the brain and skeletal system are determined prenatally, the disease process in the retina, liver, kidneys and the endocrine-metabolic system progresses as the patients get older, providing a window of opportunity for treatments that may ameliorate or reverse the course of disease. Targeted drugs and gene-based therapies such as gene replacement, exon skipping, readthrough and gene editing are being developed for specific aspects of ciliopathies including retinopathy [111,112], polycystic kidney disease [113,114], and obesity [115]. In this issue, "Retinal disease in ciliopathies: recent advances with a focus on stem cell-based therapies review" by Chen, H et al, "Novel Treatments for Polycystic Kidney Disease" by Patil, A et al, and "Using human urine-derived renal epithelial cells to model kidney disease in inherited ciliopathies" by Sayer, J and Molinari, E., focus on organ-specific targeted therapeutic approaches to ciliopathies.…”

Targeted exon skipping rescues ciliary protein composition defects in Joubert syndrome patient fibroblasts

“…However, due to the large gene size, gene replacement therapies may prove challenging in the case of CEP290 , although lentiviral transfer of CEP290 has been employed successfully in patient cells 27 and administration of multiple AAV intein vectors improves the retinal phenotype of LCA mice by reconstituting full-length CEP290 expression 28 . Another strategy that has been successfully explored in LCA models to overcome the limitations imposed by CEP290 large size is represented by the in trans complementation of the mutation using selected fragments of the gene 29,30 . On the other hand, mutations that affect transcript splicing would be ideal targets for ASO-mediated therapies, as shown in the case of the common mutation c.2991 + 1655A > G in CEP290 , which introduces a pseudo-exon and causes LCA 31–33 .…”