Fig. 4. Defective EMT in the Tie2^Cre; Bmpr1a n/f mutant embryos. (A,B) Histologic analysis of wild-type (A) and Tie2^Cre; Bmpr1a n/f mutant (B) embryos, showing lack of migrating mesenchymal cells in the AV cushion region at 9.5 dpc (arrows). (C,D) Immunohistochemistry of phospho-Smad1/5/8, showing Bmp-responsive endocardium in the control embryo (arrows in C). In the mutant, endocardium with no phospho-Smad1/5/8 (arrows in D) or reduced phospho-Smad1/5/8 is shown (D, arrowhead). (E-N) Whole-mount in-situ hybridization analysis with Twist1 (E,F), VE-cadherin (G-J), Notch1 (K,L) and Snai1 (M,N). Genotypes are shown, and arrows denote hybridization signal. a, atrium; ba1, first branchial arch; ba2, second branchial arch; v, ventricle.