Fig. 5. Phenotype of Chrd^-/- embryos at E14.5. (A,A') Skeletal preparation of wild-type (A) and (A') mutant littermates. Arrowheads in A' indicate underdeveloped vertebral neural arches. (B,B') Dorsal view of the base of the cranium. Arrows in B indicate the presence of the anterior notochord. Arrowheads in B' indicate the cartilaginous bridge that links the primordia of the basisphenoid (bs) and basioccipital bones (bo). oc, otic capsule; lc, laryngeal cartilages. (C,C') External view of wild-type (C) and mutant (C') animals. Note the severe oedema (arrowheads) and haemorrhage in the Chrd^-/- embryo. (D,D') Wild-type (D) and Chrd^-/- (D') mutant hearts. ao, aorta; pt, pulmonary trunk; ta, truncus arteriosus. (E-F') Coronal sections of wild-type (E,F) and mutant (E',F') embryos. In the thorax of the mutant (E') the undivided truncus arteriosus is clearly visible. In the mutant, an enlarged anterior spinal artery (asa, inset in F') is seen instead of a notochord (no). Note the striking reduction of the pharynx (ph) and the absence of the eustachian tube (eu) in the mutant. da, descending aorta.