Fig. 2.

Differential inputs from cWnt and BMP2/4 signaling. (A) Effect of NvBMP2/4 knockdown and NvTcf knockdown on germ layer specification in Nematostella embryos. (A′) Control-MO–injected embryo at 48 hpf. (B′) NvBMP2/4-MO–injected embryo at 48 hpf. Embryos are stained with phalloidin (green) and propidium iodide (red). Note how disorganized the internal issue is and the lack of endomesodermal epithelialization. (B) Effects on gene expression after BMP MO injection (E′–H′ and M′–P′) compared with control embryos (A′–D′ and I′–L′) analyzed by in situ hybridization. Insets show oral views of the embryo. (C) Venn diagram depicting unique and shared sets of down-regulated and up-regulated genes between dnTCF-injected embryos vs. dextran-injected control embryos and BMP2/4 morpholino-injected embryos vs. dextran-injected control embryos at 24 hpf. (D) Model GRN circuit that would potentially result in separating the central ring domain into an inner and an outer ring. (E) At 24 hpf, the animal hemisphere contains at least four domains defined by differential gene expression as demonstrated by Röttinger et al. (25): the central domain, the central ring, the central ring + ring domain, and the external ring. Based on the model proposed in this study, integrated inputs from canonical Wnt signaling and BMP2/4 signaling splits the central ring domain into two: an outer central ring coexpressing NvTcf and NvBMP2/4 and an inner central ring expressing NvBra, NvFoxA, and NvWntA.