The basic helix-loop-helix olig3 establishes the neural plate boundary of the trunk and is necessary for development of the dorsal spinal cord.

olig genes encode a previously unrecognized group of vertebrate-specific basic helix-loop-helix transcription factors. As shown in mice, chickens, and zebrafish, two members of this group, olig1 and olig2, are involved in the differentiation of motoneurons and oligodendrocytes, but nothing is known about the role of the third member, olig3. Here, we show that olig3 plays an essential role in the establishment of the neural crest-lateral neural plate boundary. In zebrafish embryos, morpholino-induced olig3 inactivation dramatically increases the number of neural crest cells, but lateral neural plate fates (interneurons and astrocytes) are missing. Zebrafish swirl mutants that have impaired bone morphogenetic protein signaling and lack neural crest cells display an expanded olig3 expression domain. Moreover, olig3 is up-regulated in mindbomb mutants lacking the neural crest because of an impaired notch signaling, and olig3 repression in such mutants rescues the neural crest. In addition, olig3 regulates ngn1 and deltaA expression in interneuron precursors. Our results indicate that olig3 has an essential proneural activity in the dorsal spinal cord and cooperates with the Delta/Notch regulatory loop to establish the boundary between the neural crest and the lateral neural plate. Thus, a proper regulation of the olig gene family is essential for the formation of three cell types (oligodendrocytes, astrocytes, and neural crest) that are unique to vertebrates.

[1]  F. Guillemot,et al.  The activity of neurogenin1 is controlled by local cues in the zebrafish embryo. , 1997, Development.

[2]  David J. Anderson,et al.  The bHLH Transcription Factors OLIG2 and OLIG1 Couple Neuronal and Glial Subtype Specification , 2002, Cell.

[3]  David J. Anderson,et al.  neurogenin1 Is Essential for the Determination of Neuronal Precursors for Proximal Cranial Sensory Ganglia , 1998, Neuron.

[4]  S. Wilson,et al.  Bmp activity establishes a gradient of positional information throughout the entire neural plate. , 1999, Development.

[5]  H. Kondoh,et al.  Wnt signaling plays an essential role in neuronal specification of the dorsal spinal cord. , 2002, Genes & development.

[6]  E. Agius,et al.  L'inducteur céphalique Cerberus est un inhibiteur multivalent extracellulaire , 1999 .

[7]  D. Melton,et al.  A molecular mechanism for the effect of lithium on development. , 1996, Proceedings of the National Academy of Sciences of the United States of America.

[8]  Andrew P. McMahon,et al.  The zebrafish organizer requires chordino , 1997, Nature.

[9]  T. Jessell,et al.  Coordinate Regulation of Motor Neuron Subtype Identity and Pan-Neuronal Properties by the bHLH Repressor Olig2 , 2001, Neuron.

[10]  Nancy Hopkins,et al.  Insertional mutagenesis in zebrafish rapidly identifies genes essential for early vertebrate development , 2002, Nature Genetics.

[11]  Cheol‐Hee Kim,et al.  Mind bomb is a ubiquitin ligase that is essential for efficient activation of Notch signaling by Delta. , 2003, Developmental cell.

[12]  M. Lardelli,et al.  The identity and distribution of neural cells expressing the mesodermal determinant spadetail , 2002, BMC Developmental Biology.

[13]  E. Weinberg,et al.  Dorsal and intermediate neuronal cell types of the spinal cord are established by a BMP signaling pathway. , 2000, Development.

[14]  L. Zon,et al.  Cloning and genetic mapping of zebrafish BMP-2. , 1998, Developmental genetics.

[15]  T. Jessell,et al.  Sonic hedgehog: a common signal for ventral patterning along the rostrocaudal axis of the neural tube. , 1995, The International journal of developmental biology.

[16]  J. Postlethwait,et al.  Structure of the zebrafish snail1 gene and its expression in wild-type, spadetail and no tail mutant embryos. , 1993, Development.

[17]  A. Amores,et al.  Zebrafish smoothened functions in ventral neural tube specification and axon tract formation. , 2001, Development.

[18]  C. Nüsslein-Volhard,et al.  Mutations affecting neurogenesis and brain morphology in the zebrafish, Danio rerio. , 1996, Development.

[19]  E. D. De Robertis,et al.  Chordin is required for the Spemann organizer transplantation phenomenon in Xenopus embryos. , 2003, Developmental cell.

[20]  M. Ekker,et al.  Ventral and lateral regions of the zebrafish gastrula, including the neural crest progenitors, are established by a bmp2b/swirl pathway of genes. , 1998, Developmental biology.

[21]  Manuel J. Aybar,et al.  Interplay between Notch signaling and the homeoprotein Xiro1 is required for neural crest induction in Xenopus embryos , 2003, Development.

[22]  A. Schier,et al.  Mutations affecting the development of the embryonic zebrafish brain. , 1996, Development.

[23]  C. Nüsslein-Volhard,et al.  fork head domain genes in zebrafish , 1998, Development Genes and Evolution.

[24]  C. Haass,et al.  A γ‐secretase inhibitor blocks Notch signaling in vivo and causes a severe neurogenic phenotype in zebrafish , 2002, EMBO reports.

[25]  A. Chitnis,et al.  Sensitivity of proneural genes to lateral inhibition affects the pattern of primary neurons in Xenopus embryos. , 1996, Development.

[26]  S. Ekker,et al.  Effective targeted gene ‘knockdown’ in zebrafish , 2000, Nature Genetics.

[27]  D. Grunwald,et al.  Lithium perturbation and goosecoid expression identify a dorsal specification pathway in the pregastrula zebrafish. , 1993, Development.

[28]  Uwe Strähle,et al.  Multiple regulatory elements with spatially and temporally distinct activities control neurogenin1 expression in primary neurons of the zebrafish embryo , 2003, Mechanisms of Development.

[29]  Hae-Chul Park,et al.  olig2 is required for zebrafish primary motor neuron and oligodendrocyte development. , 2002, Developmental biology.

[30]  T. Jessell,et al.  The specification of dorsal cell fates in the vertebrate central nervous system. , 1999, Annual review of neuroscience.

[31]  Joanne Chan,et al.  Sonic Hedgehog–Regulated Oligodendrocyte Lineage Genes Encoding bHLH Proteins in the Mammalian Central Nervous System , 2000, Neuron.

[32]  T. Jessell,et al.  Genetic ablation reveals that the roof plate is essential for dorsal interneuron specification , 2000, Nature.

[33]  R. Kelsh,et al.  Zebrafish colourless encodes sox10 and specifies non-ectomesenchymal neural crest fates. , 2001, Development.

[34]  M. Halpern,et al.  Genes dependent on zebrafish cyclops function identified by AFLP differential gene expression screen , 2000, Genesis.

[35]  J. Lewis,et al.  Delta-Notch signalling and the patterning of sensory cell differentiation in the zebrafish ear: evidence from the mind bomb mutant. , 1998, Development.

[36]  J. Eisen,et al.  Delta/Notch signaling promotes formation of zebrafish neural crest by repressing Neurogenin 1 function. , 2002, Development.

[37]  A. Nielsen,et al.  Structural and functional characterization of the zebrafish gene for glial fibrillary acidic protein, GFAP. , 2003, Gene.