Fig. 2. E9.5 knockout (A, k/o) and hypomorphic (B, hy/hy) embryos, and E12.5 hypomorphic embryos (C, hy/hy) demonstrate retarded developmental size when compared with wild-type embryos (+/+). Arrows indicate blood vessel dilations in the region of the sinus venosus (A,B) or in the head (C). A blister in the hypomorphic embryo is marked with an arrowhead (C).