Fig. 4. Fgf8, but not Bmp2, can rescue cardiac gene expression in embryos lacking endoderm. Endoderm was removed from embryos at stage 5-6 and either Bmp2-soaked beads (b) or Fgf8-soaked beads (f) or control beads (c) were placed on top of the now accessible mesoderm. The embryos were cultured until stage 8-9 and processed for in situ hybridization for Nkx2.5 (A-D). Bmp2-soaked beads had little effect in rescuing Nkx2.5 expression (A,B). By contrast, Fgf8 beads rescued expression of Nkx2.5 in the embryos that lack endoderm (C,D). An asterisk (*) marks experimental beads in sections. ecto, ectoderm; edge, edge of endoderm; endo, endoderm; meso, mesoderm; np, neural plate.