MOLECULAR-CLONING OF ZCOE2, THE ZEBRAFISH HOMOLOG OF XENOPUS XCOE2 AND MOUSE EBF-2, AND ITS EXPRESSION DURING PRIMARY NEUROGENESIS

Xcoe2 is a recently identified HLH transcription factor of the Xenopus primary neurogenesis pathway, which is necessary downstream of Neurog enin to stabilize neuroblast determination (Dubois, L. et al., 1998. C urr. Biol. 8, 199-209). We report here the embryonic expression patter n of Zcoe2, its zebrafish homolog. As observed for Xcoe2, Zcoe2 is str ongly expressed in a subset of the neurogenin1- (ngn1-) positive prima ry neuroblasts of the spinal cord. In the anterior neural plate, in co ntrast, ZcoeZ is expressed earlier and more widely than ngn1. This pat tern is strongly maintained in the presumptive mesencephalon and rhomb omeres 1-4 until the 2-3-somite stage. This expression of ZcoeZ in the brain anlage calls for a re-analysis in zebrafish of the functional r elationship demonstrated in Xenopus between Coe2 and Neurogenin factor s. At later stages, ZcoeZ is expressed in early forming neurons of the anterior brain and is a marker of the olfactory placodes. (C) 1998 El sevier Science Ireland Ltd. All rights reserved.