Fig. 1.
En1-Cre inactivated Smad1 and Smad5 conditional null alleles in ventral ectoderm and ventral AER of forelimb buds. (A–D) Immunofluorescence detecting Smad1 (A, B) and Smad5 (C, D) in E10.5 control (A, C) (Smad1f/+; Smad5f/f) and Smad1/5 mutant (B, D) (En1Cre/+; Smad1f/f; Smad5f/f) forelimb buds respectively. Smad1 and Smad5 were detected in the dorsal ectoderm but not in the ventral ectoderm and ventral half of AER of Smad1/5 mutant. (E, F) Immunofluorescence detecting pSmad1/5/8 in the forelimb buds of E10.5 control (E) (En1Cre/+; Smad1f/+; Smad5f/f) and Smad1/5 mutant (F) (En1Cre/+; Smad1f/f; Smad5f/f). pSmad1/5/8 signal was detected throughout AER and ectoderm in both control and Smad1/5 mutant. The histological samples are sectioned saggitally along the dorsal–ventral axis of the limb buds. Arrows indicate the major axes: D, dorsal; V, ventral; Di, distal; Pr, proximal. Scale bar: 50 µm.