Distinct expression patterns of different Enhancer of split bHLH genes during embryogenesis of Drosophila melanogaster

E(spl) bHLH genes are targets of the Notch pathway: they an transcriptional ly activated in response to the Notch signal. Yet, during imaginal developm ent, additional regulatory factors appear to modulate transcription resulti ng in different expression patterns. During early embryogenesis all E(spl) bHLH genes are expressed in roughly the same domain, namely the neurogenic ectoderm. Within this region these seven genes show a highly dynamic, yet d istinct transcriptional activity. Our analysis further detected tissue spec ific expression of some E(spl) genes at later embryonic stages. Prominent d ifferences were observed in the dorsolateral and procephalic neuroectoderma l regions as well as in the mesoderm. These observations indicate that othe r factors in addition to the Notch signal participate in the regulation of the individual E(spl) genes not only in imaginal tissues but also during ne uroblast specification and other cell fate determination events in the embr yo.