Figure 2. Noggin4 binds and antagonises Wnt8.

(a) Analysis of Noggin4 interactions with ActivinB, Xnr2, Xnr4 and XWnt8 by CoIP assay. (b) Frizzled8 competes with Noggin4 for Wnt8 binding in the CoIP assay. Embryos were injected at the 2-cell stage with Noggin4 and Wnt8 mRNA or with these mRNAs mixed with increasing amounts of Frizzled8 mRNA as indicated. CoIP was conducted using crude extracts of the mid-gastrula embryos as described by⁵². See Methods section for the method of WB quantification. (c) Induction of a secondary head with a cyclopic eye by co-injection of Noggin4 and tBR mRNA (60%, n = 70). tBR mRNA injected alone induces only a secondary trunk (80%, n = 70). No secondary axes were observed in the control embryos injected by EGFP mRNA (100%, n = 60). (c’) Location of co-injected Fluorescein-Lysin-Dextran (FLD) in tadpoles shown in (c).