Humanized Kcnv2 E151X mouse captures hallmarks of KCNV2-associated retinal dystrophy

Abstract

Background KCNV2-associated retinopathy is a rare inherited retinal dystrophy caused by variants in the KCNV2 gene, leading to disrupted photoreceptor function and slowly progressive vision loss. Patients have characteristic electroretinography abnormalities, including reduced cone responses, delayed and reduced rod responses to low light flashes and paradoxally large rod-driven responses to bright flashes of light. To model this condition, we generated the Kcnv2 E151X mouse line and assessed its structural and functional retinal features.

Methods We have employed CRISPR/Cas 9 gene editing technology to generate a mouse line with an early stop mutation in position E151- orthologous to the commonly encountered E143X mutation in humans - and performed a combination of Iimmunohistochemistry and Western Blot to confirm the absence of the full-length KCNV2-encoded protein, Kv8.2. To assess how closely it models the human disease, we have characterised the KCNV2 mutant mouse line at histological and functional levels employing immunohistochemistry and electroretinography, respectiveley.

Results Kcnv2 mutant mice showed markedly reduced photopic responses and reproduced the supernormal rod phenotype as described in affected individuals. In the morphological context, mutant retinas demonstrated strong and early glial fibrillary acidic protein upregulation together with reduced counts of cone arrestin positive cells as well as photoreceptors in general. Power calculations based on the data obtained herein suggest therapeutic trials are feasible with small sample sizes.

Conclusions The Kcnv2 mutant mouse line replicates key functional and structural hallmarks of KCNV2– associated retinopathy. This model provides a relevant platform for mechanistic studies and preclinical evaluation of gene based or pharmacological therapies targeting cone and rod photoreceptor dysfunction.