Proteomic identification of differentially expressed genes in neural stem cells and neurons differentiated from embryonic stem cells of cynomolgus monkey (Macaca fascicularis) in vitro

Understanding neurogenesis is valuable for the treatment of nervous system disorders. However, there is currently limited information about the molecular events associated with the transition from primate ES cells to neural cells. We therefore sought to identify the proteins involved in neurogenesis, from Macaca fascicularis ES cells (CMK6 cell line) to neural stem (NS) cells to neurons using two-dimensional gel electrophoresis (2-DE), peptide mass fingerprinting (PMF), and liquid chromatography-tandem mass spectrometry (LC-MS-MS). During the differentiation of highly homogeneous ES cells to NS cells, we identified 17 proteins with increased expression, including fatty acid binding protein 7 (FABP7), collapsin response mediator protein 2 (CRMP2), and cellular retinoic acid binding protein 1 (CRABP1), and seven proteins with decreased expression. In the differentiation of NS cells to neurons, we identified three proteins with increased expression, including CRMP2, and 10 proteins with decreased expression. Of these proteins, FABP7 is a marker of NS cells, CRMP2 is involved in axon guidance, and CRABP1 is thought to regulate retinoic acid access to its nuclear receptors. Western blot analysis confirmed the upregulation of FABP7 and CRABP1 in NS cells, and the upregulation of CRMP2 in NS cells and neurons. RT-PCR results showed that CRMP2 and FABP7 mRNAs were also upregulated in NS cells, while CRABP1 mRNA was unchanged. These results provide insight into the molecular basis of monkey neural differentiation.