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Genetic variants associated with development of pseudoexfoliation syndrome

ABSTRACT: Pseudoexfoliation syndrome (PEXS) is a late-onset disorder in which fibrillar material accumulates at abnormally high concentrations mainly in the anterior segment of the eye. PEXS is the most common cause of secondary glaucoma, which can ultimately lead to blindness and is associated with a higher risk of cataract and serious complications following different types of intraocular surgery. Although PEXS clearly has a genetic component, it remains poorly explored. In our genome-wide association study, we searched for an association of genetic variants with this disorder among older Poles with PEXS without glaucoma.

ORGANISM(S): Homo sapiens

PROVIDER: GSE93205 | GEO | 2018/01/31

REPOSITORIES: GEO

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Project description:Primary Open-Angle Glaucoma (POAG) and Pseudoexfoliation Glaucoma (PEXG) are forms of glaucoma with distinct etiologies, but they share a common type of optic neurodegeneration that leads to irreversible loss of retinal ganglion cells, visual field and blindness if left untreated. The main objective in the present study was to explore whether differential-proteomic analysis of blood serum from patients with POAG or PEXG could lead to the identification of candidate biomarkers of glaucoma and provide clues to pathogenic mechanisms. A total of 202 blood samples from medically treated patients with POAG (n=73), PEXG (n=59), and cataracts (control, n=70) were collected and analyzed following a proteomic workflow that involved two phases: discovery and validation. In the discovery phase, differential-proteomics (2D-DIGE) methodology led to the identification of a panel of 35 proteins that were altered (i.e., over- or under-expressed) in serum samples of glaucoma patients. Functional pathway analysis suggested a potential involvement of these proteins in immunological and inflammatory pathways. In the validation phase, ELISA assays of the top-17-ranked proteins confirmed that most of them were over-expressed in the glaucoma groups. Stepwise discriminant analysis of the ELISA data resulted in a six-protein panel (APOA4, TF, C3, APOL1, IGHG2, C4A) that was used to generate multivariate predictive models. These models achieved a diagnostic efficiency of 81% (correct assignment), specificity of 83%, and sensitivity of 92%. Specifically, 100% efficacy was reached in the discrimination of the POAG group from control, and 86% efficacy in the discrimination of POAG from PEXG. Overall, these data demonstrate the discovery of a panel of serum biomarkers that could be used in large-scale multiplexed screenings for the diagnosis of POAG and PEXG patients. Furthermore, these biomarkers may have a role in the pathogenesis, and association to immune-inflammatory processes with glaucoma.

Project description:Pseudoexfoliation syndrome (PEX) is a systemic disorder that manifests as a fluffy, proteinaceous fibrillar material throughout the body. In the eye, such deposits result in glaucoma (PEXG), due to impeding aqueous humor outflow. When a patient presents acute glaucoma, it is necessary to remove some of the aqueous fluid within the eye to relief pain and pressure. This label free proteomics dataset was collected from human donors during cataract surgery. The aqueous humor was collected during essential ophthalmic procedures that allowed paracentesis after obtaining informed consents from human subjects without collecting identifiers, but all disease and medication history were collected. The sample collection included non-glaucomatous controls (CTL-GC), those with pseudoexfoliation syndrome (PEX-GC), and synthesized GC-Globulin pure protein (GC-Pure). Approximately 50-120 ul volume of AH was collected by paracentesis and stored in -80C immediately upon acquisition until analysis. Protein extraction was carried out by homogenization of the tissue in extraction buffer (TEAB, NaCl and SDS). Protein amounts were estimated and normalized to 10 ug across experimental samples. Samples were reduced using TCEP, alkylated with iodoacetamide and digested overnight with trypsin. Untargeted liquid chromatography-mass spectrometry was performed on an Easy nLC 1000 liquid chromatograph coupled to a QExactive mass spectrometer (LC-MS/MS). Data analysis was performed using Proteome Discoverer 3.0 and Graph Pad Prism 10. Each sample was run three separate times. Raw mass spectrometry data files were analyzed using Proteome Discoverer 3.0. The human proteome was downloaded from UniProt and used as the target database for protein identification. Max missed cleavage site was set to 2 and minimum peptide length to 6. Precursor Mass Tolerance was set to 10ppm and Fragment Mass Tolerance to 0.02 Da. Post-translational modifications for experimental proteins included oxidation, acetylation, and carbamidomethylation. The normalization was set to total peptide amount and confidence to low.

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Genetic variants associated with development of pseudoexfoliation syndrome

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