A zebrafish Id homologue and its pattern of expression during embryogenesis

We describe the cloning, sequencing and pattern of transcript distribution during embryogenesis of a zebrafish Id homologue that we have called Id6. Transcription of the gene is spatially regulated, and its pattern of transcription shows considerable overlaps with those of other zebrafish genes with homology to Drosophila neurogenic genes, such as Notch and Delta. Since all these genes are coexpressed in particular cells, they may function together in a single genetic circuit in zebrafish as they do in Drosophila. A zebrafish homologue of Drosophila AS-C proteins can activate transcription of a CAT reporter gene by binding to an E-box in mouse 3T3 cells, either alone or in conjunction with ZfE12. The activation of transcription is inhibited in the presence of Id6. This indicates that the zebrafish gene described here is a genuine member of the Id family, and suggests that it may serve a function similar to that of the Drosophila gene emc and mammalian Ids during development.