Networking to segregate the endomesoderm Available to Purchase

Early in animal development, most of the endoderm and the mesoderm segregate from the endomesoderm. In sea urchin embryos, a gene regulatory circuit that includes the Delta/Notch signalling pathway (which is expressed in the micromeres, precursors of the skeletal mesoderm) and the transcription factors Gcm and FoxA (which are expressed in the mesoderm and the endoderm, respectively) controls endomesoderm segregation. Now, on p. 83, Jenifer Croce and David McClay describe how Delta, Gcm and FoxA interact temporally and spatially to control this important process. Their combined lineage and gene expression analyses indicate that, shortly before hatching, Gcm and FoxA are co-expressed in the most vegetal endomesoderm descendant cells (Veg2L cells). At hatching, Gcm expression continues in these cells, whereas FoxA expression is downregulated in the Veg2L cells and activated in the cells lying directly above. Delta/Notch signalling in the micromeres is needed for at least 2.5 hours to maintain...