Identification of essential sequence motifs in the node/notochord enhancerof Foxa2 (Hnf3 beta) gene that are conserved across vertebrate species

The expression of a winged-helix transcription factor, Foxa2/HNF3 beta, is essential for development of the node and the notochord. We examined the no de/notochord enhancer of mouse Foxa2 for sequence motifs conserved across v ertebrate species. We cloned Foxa2 genes from chicken and fish, and identif ied the respective node/notochord enhancers that were active in transgenic mouse embryos. Comparison of the sequences of the enhancers revealed three evolutionally conserved sequence motifs, CS1, CS2 and CS3. Mutational analy sis of the mouse enhancer indicated that CS3 is indispensable for gene expr ession in the node and the notochord, while CS1 and CS2 are required to aug ment enhancer activity. These motifs do not correspond to the consensus bin ding sequences of transcription factors known to be involved in node/notoch ord development. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved .