Fig. 3. Chimeric embryos and single blastomere injections indicate that signaling restricting the size of the animal plate is indirectly dependent on vegetal signaling. (A) The scheme for chimeras with animal half derived from a -cadherin RNA-injected embryo and vegetal half uninjected. (B) Scheme for octomere injections. (C-E) Epifluorescence of chimera labeled with anti-serotonin and anti-myc. (C) A normal number and pattern of serotonergic neurons form in the chimera. Inset is DIC of chimera (72 hours) the animal plate is marked with an asterisk. Normal archenteron forms in chimeras (arrowhead). (D) The recombinant embryo has co-injected myc protein lineage marker in ectoderm. Arrowhead indicates the position of endoderm and the asterisk is beside the animal plate. (E) Merged image of C,D. (F-H) Recombined confocal stack of an embryo in which one cell of eight-cell embryo was co-injected with RNA encoding stabilized ß-catenin and myc as a lineage marker. (F) Normally patterned apical organ with four serotonergic neurons differentiates in an octomere injected chimera. Inset is DIC, an asterisk marks the animal plate. (G) The lineage marker Myc and -cadherin is in ectoderm from injected octomere. (H) Merge of F,G. (I-K) Epifluorescent images of octomere-injected embryo. (I) SpNk2.1 protein is like uninjected embryos, indicating no direct effect of -cadherin. Inset is DIC image, asterisk indicates the animal plate. (J) Myc immunoreactive cells. (K) Merge of I,J. Scale bar: 20 µm.