In wild-type early mesenchyme blastulae (Control), endodermal transcripts brachyury (bra), foxa, and blimp1b are localized to endodermal precursors (C to E) (corresponding to the yellow cells of Figure 2 and visualized by the pink fluorescence), and are down-regulated in mesodermal precursors (indicated by the white arrow and corresponding to the green cells of Figure 2). When Hox11/13b is knocked down (Hox11/13b MASO), brachyury (bra), foxa, and blimp1b are down-regulated everywhere in the endomesoderm (G to I), suggesting that these genes are Hox11/13b target genes. When Notch is knocked down (Notch MASO), brachyury (bra), foxa, and blimp1b are not down-regulated in mesoderm precursors and thus are expressed everywhere in the endomesoderm (K to M), but wild-type expression is recovered when Hox11/13b is knocked out in addition to Notch (Notch + Hox11/13b MASOs) (O to Q). Hox11/13b mRNA is up-regulated in Hox11/13bmorphants (B, F and N) because Hox11/13b represses its own transcription. 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.