Diabetic retinopathy (DR) is a leading cause of vision loss, yet its systemic proteomic mediators remain largely elusive. This study aimed to identify causal plasma proteins, map their cell-type-specific localization in the retina, and experimentally validate their expression under disease-relevant stress. We conducted a proteome-wide association study (PWAS) integrating UK Biobank plasma pQTL data (N = 53,022) with DR GWAS summary statistics. Causal relationships were inferred utilizing summary-data-based Mendelian randomization (SMR) and Bayesian colocalization. Prioritized candidates were mapped to the Human and Mouse Retina Cell Atlases via single-nucleus RNA sequencing (snRNA-seq). Finally, to substantiate the computational findings, in vitro validation of COL4A1 was performed in ARPE-19 cells cultured under hyperglycemic conditions utilizing quantitative real-time PCR (qPCR) and transcriptomic dataset re-analysis. The PWAS identified 26 proteins significantly associated with DR. Subsequent causal inference prioritized 12 high-confidence candidates, including GSTT2B, COL4A1, PAM, and GALNT3. Notably, GSTT2B emerged as a Tier-1 protective causal protein (Z = −3.609; P_SMR = 1.22 × 10⁻⁴). snRNA-seq mapping revealed that GSTT2B is robustly expressed in Müller glia and the retinal pigment epithelium (RPE), whereas COL4A1 is prominently enriched in vascular compartments. These specific expression signatures exhibited partial conservation across species with notable cell-type specific variations. Crucially, in vitro validation confirmed that COL4A1 mRNA expression is significantly upregulated under high-glucose stress. Furthermore, druggability analysis highlighted actionable targets, identifying GSTT2B as a highly probable causal mediator and COL4A1 as a prioritized candidate for structural intervention. This study provides robust genetic, single-cell, and experimental evidence implicating specific plasma proteins in DR pathogenesis. The identification of GSTT2B-mediated protective pathways and the hyperglycemia-induced upregulation of COL4A1 offer a high-resolution molecular atlas to guide drug repositioning and precision therapeutic strategies.

Primary open-angle glaucoma (POAG) is a leading cause of irreversible blindness driven by elevated intraocular pressure from compromised aqueous outflow. While genome-wide association studies have identified numerous risk loci, specific candidate proteins and their cellular mechanisms remain elusive. We employed a multi-omics framework integrating UK Biobank plasma proteomics (N = 53,022) and large-scale POAG GWAS summary statistics. We performed a Proteome-Wide Association Study, Mendelian Randomization, and Bayesian colocalization to infer causality. Identified candidates were mapped to human and mouse ocular scRNA-seq atlases to characterize cell-type specificity, followed by druggability assessments. We prioritized five putative causal proteins, with SEL1L and TFPI demonstrating the strongest evidence. Cross-species scRNA-seq revealed that SEL1L and SERPINF1 are robustly expressed in the trabecular meshwork (TM), particularly the juxtacanalicular tissue, implicating them in outflow resistance. Conversely, TFPI and SLC9A3R2 localize to Schlemm’s canal endothelium, suggesting a role in modulating barrier function. Pathway analyses highlighted endoplasmic reticulum protein processing and coagulation cascades. This study maps putative causal POAG proteins to conventional outflow pathway cells, highlighting SEL1L as a novel target for TM homeostasis and TFPI for drug repurposing, thereby providing data-driven hypotheses to facilitate precision glaucoma therapeutics.

Age-related macular degeneration (AMD) is a major cause of irreversible visual impairment, yet identifying effector proteins and tissue-specific mechanisms underlying genome-wide association study (GWAS) loci remains challenging. This study aimed to systematically prioritize candidate causal circulating proteins and delineate their cellular and transcriptional dynamics in AMD. We integrated plasma protein quantitative trait loci (pQTL) summary statistics from the UK Biobank Pharma Proteomics Project (UKB-PPP; $N=\mathrm{53,022}$) with FinnGen AMD GWAS data using proteome-wide association studies (PWAS), summary-data-based Mendelian randomization (SMR) with the HEIDI test, and Bayesian colocalization analysis. Prioritized candidates were mapped across human and murine retinal single-cell/single-nucleus RNA sequencing atlases. Transcriptional responsiveness was validated in an independent clinical microarray dataset (GSE103060) and in human retinal pigment epithelial cells (ARPE-19) via in vitro inflammatory stimulation and RT-qPCR. Target tractability was assessed using pharmacological databases. Multi-stage genetic screening prioritized five candidate proteins stratified into two confidence tiers: three Tier 1 causal drivers supported by colocalization (PP4 > 0.80)—including risk factors CSF2, IL20RB, and WARS1 (also known as WARS)—alongside two Tier 2 candidates supported by SMR and HEIDI, comprising risk factor PILRA and inversely associated metabolic factor ACADSB. Retinal transcriptomic mapping localized PILRA specifically to microglia, ACADSB to inner retinal neurons, and WARS1 to photoreceptors, RPE, and vascular compartments, while IL20RB and CSF2 exhibited low baseline expression. In independent validation cohorts, IL20RB and WARS1 were significantly up-regulated in choroidal neovascularization (CNV) membrane-derived RPE from patients with AMD ($p<0.01$). Exposure of ARPE-19 cells to TNF-$\alpha$ markedly induced mRNA levels of IL20RB ($P=0.0025$) and WARS1 ($p<0.0001$). Dual normalization against ACTB as a secondary internal reference yielded consistent significant induction. Pathway enrichment highlighted cytokine-driven receptor cascades (JAK-STAT signaling) and mitochondrial substrate catabolism (branched-chain amino acid and fatty acid metabolism). Drug–target profiling identified small molecules and nutraceuticals interacting with ACADSB, CSF2, and WARS1. By combining large-scale plasma proteomic genetics with single-cell mapping and experimental validation, this study identifies a prioritized set of candidate causal proteins linking neuroimmune activation, vascular remodeling, and mitochondrial bioenergetics in AMD, providing candidate entry points for mechanistic and therapeutic exploration.