Fig. 3. Blocking FGF signal transduction with SU5402 (10 µM final) in wild-type limb buds (E10.5, 34-36 somites) phenocopies aspects of the disruption of Jag1 and Hoxd13 expression in Grem1-deficient limb buds. (A-D) Asterisks indicate the anterior margins when necessary. (A) Jag1 expression in a wild-type forelimb bud cultured for 16 hours. Left panel: dorsal view with posterior towards the bottom and distal towards the left. Right panel: view onto the distal part of the same limb bud to reveal the anterior expansion of Jag1 expression at this stage. (B) Jag1 distribution in a wild-type forelimb bud cultured with SU5402 for 16 hours. Left panel: top view onto the distal limb to allow direct comparison with the control. Right panel: dorsal view. (C) Hoxd13 expression in a wild-type forelimb bud cultured for 16 hours. Left panel: dorsal view. Right panel: top view. (D) Hoxd13 distribution in a wild-type forelimb bud cultured with SU5402 for 16 hours. Left panel: top view of the distal limb to reveal the downregulation of Hoxd13 expression and lack of anterior expansion in the distal mesenchyme. Right panel: dorsal view. (E,F) Jag1 (E) and Hoxd13 expression (F) in wild-type and Grem1 deficient (Grem1^In2/In2) forelimb buds at E11.0 (42 somites, not cultured), which corresponds to a stage similar to the limb buds shown in A-D.