Fig. 2. Inhibition of BMP signalling expands the expression of the pre-placodal genes Six4 and Eya2. Primitive streak stage embryos were electroporated with control GFP containing vector (A,D) or with SMAD6-IRES-GFP vector (B,C,E,F). Expression of Six4 (A-C; blue) and Eya2 (D-F, blue) was assessed by in situ hybridisation and the electroporated cells were visualised by staining with GFP antibody (brown in A,C,D,F). While Six4 and Eya2 expression is normal in control embryos (A,D), expression of both genes is expanded when BMP signalling is inhibited (B,C,E,F). Six4 expression is not observed in the trunk region (arrows in C) and ectopic expression of both Six4 (B,C, arrowheads) and Eya2 (E,F, arrowheads) is limited laterally.