Fig. 7. Regulation of Fgf8 expression by Bmp signaling. Bmp2 beads placed in zone I, induced ectopic expression of Fgf8 (compare arrows in treated embryo in B with control in A), and induced ectopic Nkx2.5 expression (E). Note that while Nkx2.5 was induced only immediately surrounding the Bmp2 bead (E), Fgf8 was induced throughout zone I (B). Bmp2-soaked beads placed in zone III, lateral to the heart field, induced neither Fgf8 (C) nor Nkx-2.5 (F) in zone III, but, interestingly, did induce low levels of Fgf8 expression in zone I, some distance away (arrow in C). In contrast to the results in B, beads that were soaked in higher levels of Bmp2 (30 ng/µl), repressed Fgf8 expression (D). aip, anterior intestinal portal; b, Bmp2 bead, 5 ng/µl; bhi, Bmp2 bead, 30 ng/µl; c, control bead.
