FIG. 5.

C1 and C2, but not Dkk1, synergize with LRP6 in axis induction. (A and B) C1 and C2 synergize with LRP6 in axis induction. Embryos were injected with LRP6 mRNA (3 ng) and either 10 pg of Dkk1 or C1 or 1 ng of Dkk2 or C2 mRNAs, as shown. (A) Representative embryos. (B) Combined results of three separate experiments. (C to E) Activation of the Siamois promoter by coexpression of LRP6 and the C-terminal Dkk constructs. Embryos were injected into two ventral-animal blastomeres with pSia-Luc DNA (20 pg) and the following RNAs: LRP6 at 2 ng; Dkk2, C2, or C3 at 50 pg; tBR at 20 pg; and Dkk1 or C1 at 10 pg, as shown. Luciferase activity was measured as described in Fig. 2. Each experiment was performed at least three times; representative experiments are shown.