Fig. 8. Xcyr61 can antagonise the Wnt pathway. (A) Constructs used in these experiments. (B-H) Antagonism of Xwnt8-induced secondary axes (arrows) was obtained with full-length Xcyr61 and a construct comprising only domain 4 (CT), but inhibition was not observed with a construct comprising domains 1 and 2 (IGFBP and VWC). In all experiments Xwnt8 mRNA (20 pg) was injected ventrally either alone or together with RNA encoding Xcyr61 (500 pg), Xcyr61 (1,2; 500 pg), or Xcyr61 (4; 2 ng). (I,J) Xcyr61 blocks induction of the TOPFLASH reporter by Xwnt8 (I) but inhibits induction by Dishevelled (I) and ß-catenin (J) only weakly. Luciferase assays were performed on animal caps injected with the indicated RNAs (600 pg) together with 10 pg each of the TOPFLASH reporter and pRL-TK as a standardisation control.