Ah-Young Chung, et al. the remodeling of the actin cyto-skeleton during myelination. A key effecter of Rho-GTPase is Rho-kinase (ROCK), a serine/ threonine kinase that regulates cell migration, proliferation and survival (Mueller et al., 2005). ROCK is expressed in Schwann cells at the onset of myelination, and pharmacological inhibition of ROCK activity causes Schwann cells form aberrant short myelin segments. However, after ROCK inhibition is removed, new myelin segments are formed normally (Melendez-Vasquez et al., 2004), indicating that ROCK plays an important role together with Rho- GTPase in the progression of the Schwann cell membrane encase- ment of the axon during myelination. Rho-associated coiled-coil containing protein kinase 2b (Rock2b) is a ROCK family protein and our microarray data showed that Rock2b expression was hi- ghly elevated in myelina-ting oligodendrocytes, suggesting the possibility that Rock2b function is involved in myelin formation in CNS oligodendrocytes. Selenoprotein P, plasma, 1a (Sepp1a) is a selenium binding protein. Selenium is an essential micronutrient necessary for normal growth and function of the brain, and sele- nium deficiency causes a CNS demyelinating disease. Selenium is required for the normal morphological development of oligo- dendrocytes and their survival in vitro (Eccleston and Silberberg, 1984), and is also required for the normal up-regulation of myelin genes in differentiating oligodendrocytes (Gu et al., 1997). Therefore, significant up-regulation of Sepp1a in mature oligodendrocytes indicates the possibility that Sepp1a is involved in selenium signa- ling in oligodendrocyte differentiation. We also examined the previously unannotated genes zgc:110191 and zgc:112160. These two novel factors are expressed at elevated levels in differentiated oligodendrocytes. ACKNOWLEDGEMENTS This work was supported by the Korea Research Foundation Grant funded by the Korean Govern-ment (KRF-2008-313-C00764). REFERENCES 1. Barres BA, Lazar MA and Raff MC (1994) A novel role for thyroid hormone, glucocorticoids and retinoic acid in timing oligodendrocyte development. Development 120:1097-1108. 2. Bolis A, Coviello S, Visigalli I, Taveggia C, Bachi A, Chishti AH, Hanada T, Quattrini A, Previtali SC, Biffi A and Bolino A (2009) Dlg1, Sec8, and Mtmr2 regulate membrane homeostasis in Schwann cell myelination. J Neurosci 29: 8858-8870. 3. Cahoy JD, Emery B, Kaushal A, Foo LC, Zamanian JL, Christopherson KS, Xing Y, Lubischer JL, Krieg PA, 90 www.enjournal.org Krupenko SA, Thompson WJ and Barres BA (2008) A transcriptome database for astrocytes, neurons, and oligo- dendrocytes: a new resource for understanding brain development and function. J Neurosci 28:264-278. 4. Carney TJ, Dutton KA, Greenhill E, Delfino-Machin M, Dufourcq P, Blader P and Kelsh RN (2006) A direct role for Sox10 in specification of neural crest-derived sensory neurons. Development 133:4619-4630. 5. Charles P, Hernandez MP, Stankoff B, Aigrot MS, Colin C, Rougon G, Zalc B and Lubetzki C (2000) Negative regulation of central nervous system myelination by poly-sialylated- neural cell adhesion molecule. Proc Natl Acad Sci USA 97:7585-7590. 6. Chen Y, Wu H, Wang S, Koito H, Li J, Ye F, Hoang J, Escobar SS, Gow A, Arnett HA, Trapp BD, Karandikar NJ, Hsieh J and Lu QR (2009) The oligodendrocyte-specific G protein-coupled receptor GPR17 is a cell- intrinsic timer of myelination. Nat Neurosci 12:1398-1406. 7. Cunliffe VT and Casaccia-Bonnefil P (2006) Histone de- acetylase 1 is essential for oligodendrocyte specification in the zebrafish CNS. Mech Dev 123:24-30. 8. Dugas JC, Tai YC, Speed TP, Ngai J and Barres BA (2006) Functional genomic analysis of oligodendrocyte differen- tiation. J Neurosci 26:10967-10983. 9. Eccleston PA and Silberberg DH (1984) The differentiation of oligodendrocytes in a serum-free hormone-supplemented medium. Brain Res 318:1-9. 10. Emery B (2010) Regulation of oligodendrocyte differentiation and myelination. Science 330:779-782. 11. Franklin RJ (2002) Why does remyelination fail in multiple sclerosis? Nat Rev Neurosci 3:705-714. 12. Gorczyca D, Ashley J, Speese S, Gherbesi N, Thomas U, Gundelfinger E, Gramates LS and Budnik V (2007) Post- synaptic membrane addition depends on the Discs-Large- interacting t-SNARE Gtaxin. J Neurosci 27:1033-1044. 13. Gu J, Royland JE, Wiggins RC and Konat GW (1997) Selenium is required for normal upregulation of myelin genes in differentiating oligodendrocytes. J Neurosci Res 47:626- 635. 14. Kess aris N, Pringle N and R ichards on WD (2008) Specification of CNS glia from neural stem cells in the embryonic neuroepithelium. Philos Trans R Soc Lond B Biol Sci 363:71-85. 15. Kimmel CB, Ballard WW, Kimmel SR, Ullmann B and Schilling TF (1995) Stages of embryonic development of the zebrafish. Dev Dyn 203:253-310. 16. Lee OK, Frese KK, James JS, Chadda D, Chen ZH, Javier http://dx.doi.org/10.5607/en.2011.20.2.85