Fig. 2. Expression of the dominant-negative Tbx5 (EnTbx5) and Tbx4 (EnTbx4) induces repression of Wnt and Fgf genes, and Pea3. (A) When EnTbx5 was misexpressed in the prospective wing field by in ovo electroporation, Wnt2b expression was repressed 24 hours after electroporation (arrowheads), whereas this gene was normally expressed in the left side. (A') Robust fluorescent signals derived from the co-electroporated EGFP gene were evident where Wnt2b was repressed. (B) By contrast, Wnt8c expression was normal 14 hours after electroporation of EnTbx5 in the prospective leg field. (B') Robust GFP fluorescent signals were observed in the leg field. (C) Expression of Fgf8 was repressed in the hypoplastic right wing buds (red arrowheads). Normal expression of Fgf8 was evident in the left wing buds. (D) Robust Env expression indicated successful EnTbx5 misexpression in the prospective wing field 19 hours after electroporation (arrowheads). In such embryos, expression of Fgf10 (E) and Pea3 (F) was repressed, whereas the normal expression was evident on the opposite side of the embryo. (G) When EnTbx4 electroporation was performed in the prospective leg field, Wnt8c expression was repressed (arrowheads) where robust GFP signals were observed (G'). (H) When EnTbx4 was misexpressed in the prospective wing field, Wnt2b expression was unaffected, although this area showed strong GFP signals (H'). (I) Expression of Fgf10 was repressed in the hypoplastic leg buds (red arrowheads). Normal expression of this gene was evident in the left leg buds. (J) Thirty hours after electroporation, robust env expression was evident in the leg field (red arrowheads). In its serial sections, expression of Fgf8 (K) and Pea3 (L) was repressed (red arrowheads). (M-O) Top row shows wings and bottom row shows legs. Arrowheads indicate repression. (M) When a dominant-negative form of Lef1 (dnLef1) was misexpressed, expression of Fgf10 was weakly repressed in both dnLef1-misexpressed wing and leg fields 24 hours after electroporartion. At this stage, expression of Tbx5 and Tbx4 was normal. (N) Repression of Fgf10 became evident 30 hours after electroporation. At this stage, expression of Tbx5 and Tbx4 was also weakly repressed. (O) Repression of Tbx5 and Tbx4 became evident 36 hours after electroporation.