A new humanized ARMS2^A69S variant mouse model of age-related macular degeneration (AMD).

Abstract

Purpose : ARMS2 and HTRA1, two tightly linked genes on chromosome 10q26 – are significantly associated with AMD risk. To understand the contribution of ARMS2 to AMD risk, a humanized ARMS2^A69S (rs10490924, p.Ala69Ser) mouse model and its wild-type counterpart were generated on the C57BL/6J (B6J) background, using a CRISPR/Cas9 mediated approach. The human ARMS2 gene was inserted upstream of the mouse Htra1 gene into a non-coding site homologous between humans and mice, and a native promoter to preserve the normal regulatory regions was used. The aim of this study was to characterize and establish this new humanized ARMS2^A69S mouse model for AMD.

Methods : The ARMS2^A69S mutant mice were compared to the wild-type ARMS2^A69 WT and B6J controls. The phenotype of aging mice was characterized using fundus photography, optical coherence tomography (OCT), light and electron microscopy and immunohistochemistry. The transcriptome of ARMS2^A69S mice was compared to that of the B6J mice at an early age of P14.

Results : Fundus photography confirms significantly more spots in ARMS2^A69S mutant mice as compared to both ARMS2^A69 WT and B6J mice at 18 months of age. Sub-retinal deposits with hyper-reflective regions below the deposits were observed by OCT, corresponding to the observed fundus spots. Abnormalities in the RPE layer, including dysmorphology, multinucleation and duplication as well as sub-retinal ectopic nuclei and focal reduction or absence of basal infoldings were observed by light and electron microscopy. Abnormal lipid accumulation was confirmed in ARMS2^A69S mice by staining with lipid specific filipin stain at 12 months of age. Transcriptomic analysis confirmed significant upregulation of Htra1 expression and downregulation of multiple mitochondrial genes including Nd2, Nd4, Nd6 and Cytb in RPE enriched tissue fractions from ARMS2^A69S mice as compared to B6J mice.

Conclusions : The ARMS2^A69S mice faithfully recapitulate multiple AMD-associated phenotypes, confirming that these mice are a suitable model for AMD. This model will serve as a resource for further dissection and validation of common mechanisms that are altered due to ARMS2 variants that contribute to AMD pathology, and that can be utilized in interventional studies such as testing new therapeutics and targets.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

 

(A-B)Fundus photos showing spots in ARMS2^A69S mice (C-D) Sub-retinal deposits with hyperreflective regions (↑) corresponding to the spots (*) in B.