ScRNAseq of Different Inherited Retinal Disease Mouse Models Identifies Common Cone Disease Mechanisms

Abstract

Purpose : Loss of cone photoreceptor function has the largest impact on the quality of life for people living with inherited retinal diseases (IRDs). However, the mechanisms of cone cell death in IRDs are yet to be fully elucidated. This project aims to investigate the common disease mechanisms of cone degeneration in different IRD mouse models, with the goal of identifying a novel therapeutic target independent of the gene-causing mutation.

Methods : This study used the Cnga3^-/-, and Pde6c^cpfl1 achromatopsia (ACHM) mouse models, and the retinal degeneration 1 (Rd1) retinitis pigmentosa (RP) mouse. Single-cell RNAseq (scRNAseq) was used to evaluate differential gene expression patterns between healthy and IRD cone cells at post-natal day 24 (P24). Flow cytometry was used to evaluate the temporal progression of cone degeneration in all models.

Results : ScRNAseq analysis showed increased oxidative phosphorylation and mitochondrial dysfunction in IRD models compared to healthy controls at P24. The mammalian target of rapamycin (mTOR) pathway was dysregulated in all disease models, with further in silico analysis predicting downregulation of rapamycin-insensitive companion of mTOR (RICTOR). Autophagy markers were prominent in the Rd1 retina; however, our data indicated less than expected dysregulation of classic cell death markers in ACHM mouse models at P24, a previously identified peak in cone death from previous literature. Furthermore, flow cytometry for cone quantification identified late disease-associated cone death at P70 in the Cnga3^-/- and P50 in the Pde6c^cpfl1, while significant cone loss was observed in the Rd1 retina at P24. Ongoing scRNAseq analysis has been extended to these later time points for Cnga3^-/- and Pde6c^cpfl1 to further examine cone disease mechanisms.

Conclusions : Similarities in cone disease mechanisms between ACHM and RP mouse model suggests the potential of identifying a therapeutic target for IRDs irrespective of the disease-causing mutation. As suggested in other studies for RP, modulation of the mTOR pathway may present a potential therapy to attenuate cone death in different IRD models. The lack of classic cell death markers in the ACHM models’ scRNAseq at P24 may be due to later peaks in cell death in the Cnga3^-/- and Pde6c^cpfl1 identified through our cone quantification, which warrants further scRNAseq investigation.

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