Updated project metadata. Oligodendrocytes, the myelinating cells of the central nervous system, are essential for correct brain function. They originate from oligodendrocyte precursor cells (OPCs) through a differentiation process which is only incompletely understood and impaired in a variety of demyelinating diseases. Better knowledge of this differentiation holds the promise to develop novel therapies for these disorders. We investigated the differentiation of rat oligodendrocyte precursor cells to oligodendrocytes in vitro. After confirmation of differentiation by immunohistochemical analysis using cell type-specific marker proteins, we conducted a quantitative proteomics study using tandem mass tags (TMT). We investigated four time points of differentiation covering early, intermediate, and late stages. Data analysis was perfomed using Mascot and Maxquant.