(A) Distribution of the endogenous Sox7 protein during OFT development at mouse E10.5 (a–c), E11.5 (d–f) and E12.5 (g–i). Strong nuclear staining for Sox7 is seen in the ECs and mesenchymal cells of OFT. (B) Distribution of the endogenous SOX7 protein in OFT at human Carnegie Stage 13 (CS13). SOX7 expression in the OFT is limited to the ECs and mesenchymal cells. Representative sagittal sections are shown (n=3 embryos for each stage). Arrowheads, ECs; asterisks, mesenchymal cells. A, atrium; V, ventricle. Scale bars = 500 μm A (a,d,g) and B (a); Scale bars = 100 μm A (b,e,h) and B (b); Scale bars = 50 μm A (c,f,i) and B (c).