Abstract
Purpose:
The optic nerve is a white matter tract that conveys visual information to the brain. It is formed by retinal ganglion cell axons from the inner cell layer of the retina, and begins at the optic nerve head, which is present at the optic disk region of the retina. A detailed investigation of the proteome of the normal human optic nerve will facilitate studies of the biology and pathophysiology of the optic nerve.
Methods:
We created a resource by conducting an in-depth proteomic analysis of the optic nerve from five adults. Five human donor eyes were obtained from the Lions Eye Institute, Tampa, FL. Right eyes were selected from five adults (4 males, 1 female), age 51-76 y, with no history of eye disease or previous eye surgery<br /> <br /> The optic nerve was transected at the surface of the posterior sclera from freshly enucleated eyes. Each optic nerve sample was cut to exactly 5 mm. Optic nerve samples were immediately snap frozen and stored at -80°C until processing for mass spectrometry. Proteins were fractionated using SDS-PAGE. After in-gel digestion, peptides were analyzed using LC-MS/MS on an Orbitrap Elite mass spectrometer.
Results:
We identified 2,711 proteins in the human optic nerve, and twenty-one protein isoforms. Proteins included central nervous system proteins such as the astrocytic marker glial fibrillary acidic protein, several proteins expressed by oligodendrocytes (laminin, proteolipid protein, and fibronectin), and myelin proteins (myelin basic protein, myelin-associated glycoprotein). Structural proteins included those involved in neuronal protection and regeneration (α crytallins A and B, dedicator of cytokinesis proteins, ciliary neurotrophic factor) and paranodal structural proteins (neurofascin, contactin, α, β, and γ adducins, septin 2, endophilin, ankyrin β, spectrin). Proteins associated with disease included proteins seen in open-angle glaucoma (thioredoxin, heat shock protein-70), and proteins associated with optic neuritis (aquaporin-4).
Conclusions:
Our results provide the most comprehensive proteomic data set to date of the optic nerve. This catalogue of proteins of the optic nerve may help facilitate future studies regarding the biology of the optic nerve in health and disease.