Figure 3

Tgfβ gene expression in the developing limb. (A-H) Gene expression of tgfβ2 analyzed by in situ hybridization. (A) Whole mount in situ hybridization of an embryo at stage HH18 showing transcripts of tgfβ2 at the level of the limb field in the somatic mesoderm on the flank of the embryos (arrow). (B) Transverse vibratome section at the level of the wing bud (W) of an embryo at stage HH19 showing intense labeling in the somatopleura and associated limb mesenchyme (black arrow). Note also tgfβ2 transcripts in the floor plate of the neural tube (NT) and notochord (white arrow). (C-E) Detailed views of the wing bud at stages HH20 (C), HH21 (D), and HH22 (E) showing the expression domain of tgfβ2 in the mesenchyme of the posterior margin of the bud (arrows). (F-H) Tgfβ2 expression domains at stage HH24 are present in the dorsal and ventral mesoderm and in the AER. (F) Longitudinal vibratome section of the wing bud showing the intense accumulation of transcripts in the dorsal and ventral mesoderm associated with the premuscle masses, and a more reduced expression in the distal undiferentiated mesoderm (arrows). (G and H) are whole mount specimens illustrating the dorsal expression domain (G) and the AER domain (H). (I) Longitudinal section of the embryonic wing bud at stage HH24 showing the expression of tgfβ3 in the dorsal and ventral regions outlining the territory that is occupied by the premuscle masses. Note lower levels of expression in the undifferentiated distal limb mesoderm (arrow).