Fig. 4

The Wnt8a pathway is repressed but mechanistically intact in p18ahub embryos.

(A–J) In situ hybridization for Wnt8a pathway components or downstream genes. Animal pole views, dorsal at right, except (C, D) are lateral views, dorsal at right, insets show animal pole views. At an early gastrula stage in WT (A, n = 14) wnt8a was expressed around the margin but was absent from the axial mesoderm (arrows). In p18ahub embryos at a late blastula stage (B, n = 20) wnt8a expression was absent from the presumptive dorsal half of the embryo. The expression of vox was reduced in late blastula p18ahub embryos (D, 11/13 embryos) compared to WT embryos (C, n = 18). By early gastrulation, WT embryos (E, n = 20) showed prominent ventrolateral vox expression, while vox was nearly absent from equivalent stage p18ahub embryos (F, n = 12). ved was expressed similarly to vox in WT (G, n = 10) and was also nearly undetectable in p18ahub embryos (H, n = 10) at early gastrulation. eve1 in WT (I, n = 17) marks developing ventroposterior mesoderm and was nearly absent from p18ahub embryos by early gastrulation (J, n = 12). Splice blocking wnt8a MOs variably dorsalized WT embryos (K). (L) Injection of MO against chd ventralized both WT and p18ahub embryos (compare to p18ahub uninjected, K). (M) Simultaneous reduction of Chd and Wnt8a causes dorsalization in p18ahub embryos, indicating that endogenous Wnt8a signal transduction is intact and functional in p18ahub embryos that are depleted of Chd. Representative embryos at 1 dpf are shown in N–Q.