In wild-type blastulae (Control), wnt1 is localized to endoderm precursors and is down-regulated in mesoderm precursors (indicated by the white arrow). When Notch is knocked down (Notch MASO), wnt1 is not down-regulated in mesoderm precursors, and wnt1 is expressed throughout the endomesoderm. Note. Adapted from “Sequential Signaling Crosstalk Regulates Endomesoderm Segregation in Sea Urchin Embryos,” by A. J. Sethi et al., 2012, Science, 335, p. 590-593. Copyright 2012 by AAAS.