Human Optic Nerve: An Enhanced Proteomic Expression Profile

Ophthalmology and visual health are new frontiers for postgenomic research and technologies such as proteomics. In this context, the optic nerve and retina extend as the outgrowth of the brain, wherein the latter receives the optical input and the former relays the information for processing. While efforts to understand the optic nerve proteome have been made earlier, there exists a lacuna in its biochemical composition and molecular functions. We report, in this study, a high-resolution mass spectrometry-based approach using an Orbitrap Fusion Tribrid mass spectrometer to elucidate the human optic nerve proteomic profile. Raw spectra were searched against NCBI Human RefSeq 75 database using SEQUEST HT and MASCOT algorithms. We identified nearly 35,000 peptides in human optic nerve samples, corresponding to 5682 proteins, of which 3222 proteins are being reported for the first time. Label-free quantification using spectral abundance pointed out to neuronal structural proteins such as myelin basic protein, glial fibrillary acidic protein, and proteolipid protein 1 as the most abundant proteins. We also identified several neurotransmitter receptors and postsynaptic density synaptosomal scaffold proteins. Pathway analysis revealed that a majority of the proteins are structural proteins and have catalytic and binding activity. This study is one of the largest proteomic profiles of the human optic nerve and offers the research community an initial baseline optic nerve proteome for further studies. This will also help understand the protein dynamics of the human optic nerve under normal conditions.