Data Independent Acquisition Mass Spectrometry of the Human Lens Enhances Spatiotemporal Measurement of Fiber Cell Aging

Abstract

The ocular lens proteome undergoes post-translational and progressive degradation as fiber cells age. The oldest fiber cells and the proteins therein are present at birth and are retained through death. Transparency of the lens is maintained in part by the high abundance crystallin family proteins (up to 300 mg/mL), which establishes a high dynamic range of protein abundance. As a result, previous Data Dependent Analysis (DDA) measurements of the lens proteome are less equipped to identify the lowest abundance proteins. In an attempt to probe more deeply into the lens proteome, we measured the insoluble lens proteome of an 18-year-old human with DDA and newer Data Independent Analysis (DIA) methods. By applying library free DIA search methods, 4,564 protein groups, 48,474 peptides and 5,577 deamidation sites were detected: significantly outperforming the quantity of identifications in using DDA and Pan-Human DIA library searches. Finally, by segmenting the lens into multiple fiber cell-age related regions, we uncovered cell-age resolved changes in proteome composition and putative function.