Fig. 3. Phenotype of conditional mutants Nkx2.5^Cre/+;Tbx1^flox/–. (A,B) Thymic hypoplasia in a conditional mutant (B) compared with wild-type embryo (A) at E18.5. Asterisks indicate thymic lobes. (C-E) Intracardiac phenotype in wild-type (C), conditional (D) and Tbx1^–/– (E) mutants. Embryos in D and E have essentially identical phenotypes. C'-E' aortic arch and great artery patterning in wild-type (C'), conditional (D') and Tbx1^–/– (E') mutants at E18.5. (F,G) Lateral views of ink-injected Tbx1^+/– (F) and conditional mutant (G) embryos at E10.5. Note the absence of the 4th pharyngeal arch artery and reduced distance between the 3rd and 6th in the conditional mutant embryo. ao: aorta; rcc and lcc: right and left common carotid artery; rsa and lsa: right and left subclavian artery; pa: pulmonary arteries; pt: pulmonary trunk; RV: right ventricle; T: truncus arteriosus; VSD: ventricular septum defect. Scale bars: 1 mm in A-E and C'-E'; 200 µm in F,G.