These phases were established based on the increasingly complex morphology and the expression pattern of well-defined markers. CNPase, 2′,3′-cyclic nucleotide 3′-phosphodiesterase; FABP, fatty-acid-binding proteins; GalC, galactocerebroside C; MAG, myelin associated glycoprotein; MBP, myelin basic protein; MOG, myelin OL glycoprotein;Olig1/2 two basic helix-loop-helix transcription factors; PDGF-Rα, platelet-derived growth factor; PLP, proteolipid protein; PSA-NCAM, polysialic acid-neural cell adhesion molecule.