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Keywords:

  • olig1;
  • olig2;
  • myelin;
  • oligodendrocytes;
  • zebrafish;
  • hedgehog;
  • notch;
  • eGFP

Abstract

Myelin, the isolating sheath around large diameter axons, is formed in the central nervous system (CNS) by oligodendrocytes. We isolated the zebrafish ortholog of olig1, a bHLH transcription factor, and describe the origin and development of oligodendrocytes in the zebrafish brain. Olig1:mem-eGFP transgenic animals demonstrate the highly dynamic nature of oligodendrocyte membrane processes, providing a tool for studying in vivo oligodendrocyte development. Formation of oligodendrocytes and initiation of olig1 expression are under the control of long-range hedgehog and notch signaling while maintenance of olig1 expression only depends on hedgehog. Over-expression of olig1 did not affect myelin formation in the brain and combined over-expression of olig1 and olig2 could not rescue loss of hedgehog signaling, indicating that critical factors other than olig1 and olig2 are necessary. Lastly, knockdown of Olig1 in an Olig2-sensitized background did result in defects in CNS myelination, indicating a functional overlap between Olig1 and Olig2 proteins. Developmental Dynamics 238:887–898, 2009. © 2009 Wiley-Liss, Inc.