GSE183117
Multi-omics analyses reveal early metabolic imbalance and mitochondrial stress in neonatal photoreceptors leading to cell death in Pde6b rd1/rd1 mouse model of retinal degeneration
Retinal diseases exhibit extensive genetic heterogeneity and complex etiology with varying onset and severity. Mutations in over 200 genes can lead to photoreceptor dysfunction and/or cell death in retinal neurodegeneration. To deduce molecular pathways that initiate and/or drive cell death, we adopted a temporal multi-omics approach and examined molecular and cellular events in newborn and developing photoreceptors before the onset of degeneration in a widely-used Pde6brd1/rd1 (rd1) mouse, a model of autosomal recessive retinitis pigmentosa caused by PDE6B mutations. Transcriptome profiling of neonatal and developing rods from the rd1 retina revealed early downregulation of genes associated with anabolic pathways and energy metabolism. Quantitative proteomics of rd1 retina showed early changes in calcium signaling and oxidative phosphorylation, with specific partial bypass of complex I electron transfer, which precede the onset of cell death. Concurrently, we detected alterations in central carbon metabolism, including dysregulation of components associated with glycolysis, pentose phosphate and purine biosynthesis. Ex vivo assays of oxygen consumption and transmission electron microscopy validated early and progressive mitochondrial stress and abnormalities in mitochondrial structure and function of rd1 rods. These data uncover mitochondrial over-activation and related metabolic alterations as determinants of early pathology and implicate aberrant calcium signaling as an initiator of higher mitochondrial stress. Our studies thus provide a mechanistic framework with mitochondrial damage and metabolic disruptions as early drivers of photoreceptor cell death in retinal degeneration. Overall design: We generated rd1-GFP mice by mating the Pde6brd1/rd1 mice to TgNrlp-EGFP (WT) (Akimoto et al., 2006) mice, used flow cytometry to purify GFP+ rods at P2, P4, P6, P8 and P10 and performed RNA-seq analysis. Isolated cells were lysis with TRIzol LS and the total RNA were isolated. RNAseq data were generated using TruSeq Stranded mRNA Sample Prep Kit (Illumina) and 125 base pair-end reads were generated on HiSeq 2500 platform (Illumina).