Background: Whereas Notch signalling is essential for somitogenesis, mice deficient for the basic helix-loop-helix (bHLH) genes Hes1 and Hes5, downstream Notch effectors, display normal somite formation, indicating that there may be an as-yet unidentified Hes1-related bHLH gene.
Results: We identified a novel bHLH gene, designated Hes7, from mouse embryos. Hes7 has a conserved bHLH domain in the amino-terminal region and the WRPW domain at the carboxy-terminal end, like Hes1. The mouse Hes7 gene is located next to Aloxe3, which is mapped to a position 37.0 cM from the centromere on chromosome 11. In a transfection analysis, Hes7 represses transcription from the N box- and E box-containing promoters. In addition, Hes7 suppresses the E47-induced transcriptional activation. Promoter analysis indicated that Hes7 expression is controlled by Notch signalling. Strikingly, Hes7 is specifically expressed in the presomitic mesoderm in a dynamic manner. We also identified two related bHLH genes from human: one is closely related to mouse Hes7 and therefore designated hHes7 and the other designated hHes4.
Conclusion: The structure, transcriptional activity and expression pattern in the presomitic mesoderm of Hes7 are very similar to those of Hes1, suggesting that Hes7, together with Hes1, may play a role in somite formation under the control of Notch signalling.