Identification of differentiating neural progenitor cell markers using shotgun isobaric tagging mass spectrometry

The use of neural precursor cells (NPCs) represents a promising repair strategy for many neurological disorders. This requires an understanding of the molecular events and biological features that regulate the self-renewal of NPCs and their differentiation into neurons, astrocytes, and oligodendendrocytes. In this study, we have characterized the proteomic changes that occur upon differentiation of these cells using the novel iTRAQ labeling chemistry for quantitative mass spectrometry. In total, 55 distinct proteins underwent expression changes during NPC differentiation. This included 14 proteins that were identified by our previous two-dimensional difference gel electrophoresis (2D-DIGE) analysis of differentiating mouse neurospheres. The importance of the iTRAQ approach was demonstrated by the identification of additional proteins that were not resolved by the 2D-DIGE technology. The proteins identified by the iTRAQ approach included growth factors, signaling molecules, proliferating cell-specific proteins, heat shock proteins, and other proteins involved in the regulation of metabolism and the transcriptional and translational machinery. Further characterization of the identified proteins should provide greater insight into the mechanisms involved in regulation of neurogenesis in the adult central nervous system and potentially that of other proliferating cell types, including peripheral stem cells or cancer cells.