Figure 6

Sfrp1 _NTR rescue ability is observed also with Wnt1 , another canonical ligand. (a-e) Dorsal views of embryos at stage 19–20 injected with GFP mRNA (a), Wnt1 (b), or Wnt1 together with Sfrp1 (c), Sfrp1 _CRD (d), or Sfrp1 _NTR (e) mRNAs. (f-j) Lateral views of embryos processed for double in situ hybridization with rx3 (red) and foxA2 (blue) probes injected with the same mRNAs, respectively. The phenotype induced by Wnt1 mRNA injection is very similar to that observed with Wnt8: the optic vesicles fail to develop (b), with a reduction in rx3 expression (g). This defect is reverted by Sfrp1 (c,h) and Sfrp1 _NTR (e,j) but not by Sfrp1 _CRD (d,i) co-expression. (k) Percentage of embryos showing reduction in the size of the forebrain/optic vesicles upon injection of Wnt1 mRNA or together with equimolecular amounts of mRNAs encoding different variants of Sfrp1. Scale bar: 0.2 mm.