Proteomic analysis of autoimmune retinopathy implicates NrCAM as a potential biomarker

To identify vitreous molecular biomarkers associated with autoimmune retinopathy (AIR).

Case-control study.

We analyzed six eyes from four patients diagnosed with AIR and eight comparative controls diagnosed with idiopathic macular holes and epiretinal membranes.

Vitreous biopsies were collected from the participants and analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) or multiplex ELISA.

Protein expression changes were evaluated by 1-way ANOVA (significant p-value <0.05), hierarchical clustering, and pathway analysis to identify candidate protein biomarkers.

There were 16 significantly upregulated and 17 significantly downregulated proteins in the vitreous of three AIR patients compared to controls. The most significantly upregulated proteins included lysozyme C (LYSC), zinc-alpha-2-glycoprotein (ZA2G), complement factor D (CFAD), transforming growth factor-beta induced protein (BGH3), beta-crystallin B2, and alpha-crystallin A chain. The most significantly downregulated proteins included disco-interacting protein 2 homolog (DIP2C), retbindin (RTBDN), and amyloid beta precursor like protein 2 (APLP2). Pathway analysis revealed that vascular endothelial growth factor (VEGF) signaling was a top represented pathway in the vitreous of AIR patients compared to controls. In comparison to a different cohort of three AIR patients analyzed by multiplex ELISA, a commonly differentially expressed protein was neuronal cell adhesion molecule (NrCAM) with p-values of 0.027 in the LC-MS/MS dataset and 0.035 in the ELISA dataset.

Protein biomarkers such as NrCAM in the vitreous may eventually help diagnose AIR.