Sequential Signaling Crosstalk Regulates Endomesoderm Segregation in Sea Urchin Embryos

Abstract

Lineage Identity Segregation of endoderm and mesoderm lineages is a fundamental event in early embryogenesis. Using sea urchin embryos, Sethi et al. (p. 590 ) found that Notch and canonical Wnt pathways crosstalk progressively partitions the endomesoderm to discrete endoderm and mesoderm fates. This three-step signaling exchange demonstrates how the timing of signaling crosstalk is regulated in vivo through temporally and spatially staggered genetic circuits that intersect only at specific developmental stages.