Multi-omic analysis of photoreceptor alterations during early-onset retinal degeneration in Mfrp-/- mice

Abstract

Loss-of-function mutations in the membrane frizzled-related protein (MFRP) gene are associated with autosomal recessive ocular disorders such as nanophthalmos, posterior microphthalmia, and retinitis pigmentosa, yet the molecular mechanisms underlying MFRP-related retinal degeneration remain poorly defined. To investigate these mechanisms, we generated and characterized Mfrp-/- mice and conducted an integrated multi-omic analysis to map the onset and progression of transcriptional changes during retinal degeneration. Using longitudinal in vivo imaging, histological and immunohistochemical analysis, qRT-PCR, single-nucleus RNA sequencing (snRNA-seq), snATAC seq (single-nucleus Assay for Transposase-Accessible Chromatin using sequencing) and spatial transcriptomics (GeoMx DSP), we identified early and progressive photoreceptor loss in Mfrp-/- mice, beginning by 28d. Retinal thinning and autofluorescent deposits in Mfrp-/- mice were accompanied by decreased expression of rod and cone opsins. Transcriptomic profiling by snRNA-seq revealed distinct, photoreceptor-specific gene expression changes, including early upregulation of inflammatory and stress-related genes and later downregulation of genes involved in chromatin remodeling, synaptic function, and neurodevelopment. Spatial transcriptomic analysis of the outer nuclear layer (ONL) revealed disruptions in mitochondrial function, mTORC1 signaling, and G protein-coupled receptor pathways. These findings define a temporally and spatially coordinated program of degeneration triggered by Mfrp loss and demonstrate that Mfrp is required for the maintenance of photoreceptor integrity and gene regulatory homeostasis during retinal development. Our work establishes Mfrp-/- mice as a robust model for dissecting photoreceptor vulnerability and provides a transcriptomic atlas of disease progression with potential relevance for therapeutic development in MFRP-associated retinal dystrophies.