Fig. 7. TGFß2-treated whole mouse embryos in culture reveal outflow tract malformations that are similar to Rxra–/– embryos. Each group of four images represents serial sections 40 µm apart through the OFT of a representative embryo. (A-D) OFT of a wild-type embryo dissected at E12.5. The orifices of the aortic and pulmonary outlets are well separated. (E-H) OFT of a wild-type embryo dissected at E11.5 and cultured for 24 hours. Similar to the E12.5 wild type, the orifices of the aortic and pulmonary outlets are well separated. (I-L)) OFT of an Rxra–/– embryo dissected at E11.5 and cultured for 24 hours. Rxra–/– embryos in culture retained the malformed outflow tract phenotype. Thus, the AoP septum has not descended into the OFT to the same extent as in the wild type and, as a result, the beginning of an AoP septum defect is apparent (I, arrow). Note the cushions are also underdeveloped and malformed. (M-P) OFT of a wild-type embryo dissected at E11.5 and cultured for 24 hours in the presence of 10 ng/ml TGFß2. The phenotype is similar to the Rxra–/– in that the AoP septum has not formed properly (M, arrow) and the cushions are underdeveloped and malformed. ao, aortic outlet. p, pulmonary outlet.
