Fig. 6. FGF-8 (A-D) and BMP-2 (E-I) expression at stages 14 and 18. (A) FGF-8
expression in the lateral pharynx. Moderate expression in arches 1 and 2 with
pronounced expression in arches 3-6. FGF-8 expression persists in the
pharyngeal pouch/grooves after expression in the arches has diminished. (B)
Sectioned whole-mount embryo showing that FGF-8 expression in arch 3 is in the
ectoderm covering the pharyngeal arches and in the endoderm where it meets the
ectoderm in the pharyngeal pouches. (C) FGF-8 expression at stage 18 is
diminished in the caudal pharyngeal arches and completely absent in arches 1
and 2. Expression remains in the interval between the maxillary and mandibular
prominences and the second pouch/groove. (D) Sectioned stage 18 whole-mount
showing the greatly diminished FGF-8 expression in arches 2 and 3. (E) BMP-2
expression in the caudal outflow tract and splanchnic mesoderm that is
continuous with the outflow tract at stage 14. (F) BMP-2 expression at stage
14 stops abruptly caudal to the outflow tract in an oblique section. (G) The
splanchnic mesoderm between the inflow and outflow at stage 14 is devoid of
BMP-2 expression. (H) BMP-2 expression can be seen in the inflow myocardium
and dorsal mesocardium at stage 14. (I) By stage 18, BMP-2 is no longer
expressed by the splanchnic mesoderm or myocardium but can now be seen in the
endocardium. All scale bars are 100 µm.
