Mesp2 initiates somite segmentation through the Notch signalling pathway.
The Notch-signalling pathway is important in establishing metameric pattern during somitogenesis. In mice, the lack of either of two molecules involved in the Notch-signalling pathway, Mesp2 or presenilin-1 (Ps1), results in contrasting phenotypes: caudalized versus rostralized vertebra. Here we adopt a genetic approach to analyse the molecular mechanism underlying the establishment of rostro-caudal polarity in somites. By focusing on the fact that expression of a Notch ligand, Dll1, is important for prefiguring somite identity, we found that Mesp2 initiates establishment of rostro-caudal polarity by controlling two Notch-signalling pathways. Initially, Mesp2 activates a Ps1-independent Notch-signalling cascade to suppress Dll1 expression and specify the rostral half of the somite. Ps1-mediated Notch-signalling is required to induce Dll1 expression in the caudal half of the somite. Therefore, Mesp2- and Ps1-dependent activation of Notch-signalling pathways might differentially regulate Dll1 expression, resulting in the establishment of the rostro-caudal polarity of somites.
Pubmed ID: 10932180 RIS Download
Animals | Basic Helix-Loop-Helix Transcription Factors | Body Patterning | Embryo, Mammalian | Female | Gene Expression Regulation, Developmental | Humans | Ligands | Male | Membrane Proteins | Mice | Mice, Inbred C57BL | Mice, Inbred CBA | Mice, Transgenic | Mutation | Presenilin-1 | Receptors, Notch | Signal Transduction | Somites | Transcription Factors