Fig. 7.

Combinatorial activity of Bmp and Fgf signals promotes expression of different regional markers of the gastrula ectoderm. Lateral views of late gastrula stage embryos with dorsal towards the right. Genes analysed are indicated to the left of the rows: otx2, prospective head neural ectoderm; hoxb1b, prospective trunk neural ectoderm; eve1, prospective tail neural ectoderm and mesoderm; p63, prospective epidermis. Bmp activity was modulated by expression of exogenous chordin or bmp2b; Fgf activity was modulated by expression of a dominant-negative Fgf receptor (XFD) or fgf3. The presumed state of activation of the two pathways is indicated in red/green above each column. Note that overexpression of fgf3 (E) induces chordin (see Fig. 2Q) and therefore suppresses Bmp activity (Koshida et al., 2002).