Fig. 6

Tak1{Delta}/{Delta} embryos have defects in vascular smooth muscle. To visualize smooth muscle, embryos were stained by immunohistochemistry using an antibody to SMA (purple staining in all panels). (A-C) E9.5 embryos. (D-F) E10.5 embryos. At E9.5 the Tak1+/{Delta} control embryo has a layer of SMA-expressing cells beginning along the dorsal aorta (A, arrowheads). The class II (B) and class I Tak1{Delta}/{Delta} (C) embryos have no SMA expression along their dorsal aorta (arrowheads). At E10.5, the Tak1+/{Delta} control embryo (D) shows a continuous layer of SMA expression all along the dorsal aorta (arrowheads). The more severely affected Tak1{Delta}/{Delta} embryo (F) has a complete absence of SMA expression in the dorsal aorta (arrowheads) and the less severely affected embryo (E) has only a few loosely associated expressing cells (arrowheads). All the embryos display staining of the somites and heart. S, somites; O, otic vesicle; H, heart.