Hideaki Sato

Visualizing expression patterns of Shh and Foxf1 genes in the foregut and lung buds by optical projection tomography

Congenital malformations of the foregut are common in humans. The respiratory and digestive tubes are both derived by division of the foregut primordium. Sonic hedgehog (Shh) and Fork head box F1 (Foxf1) genes encode regulatory molecules that play a pivotal role in gut and lung morphogenesis and are therefore important candidate genes to be examined in models of foregut developmental disruption. Optical projection tomography (OPT) is a new, rapid and non-invasive technique for three-dimensional (3D) imaging of small biological tissue specimens that allows visualization of the tissue distribution of RNA in developing organs while also recording morphology. To explore the application of OPT in this context, we visualized Shh and Foxf1 gene expression patterns in the mouse foregut and lung buds at several stages of development. Time-mated CBA/Ca mice were harvested on embryonic days 9–12. The embryos were stained following whole mount in situ hybridization with labelled RNA probes to detect Shh and Foxf1 transcripts at each stage. The embryos were scanned by OPT to obtain 3D representations of gene expression domains in the context of the changing morphology of the embryo. OPT analysis of Shh and Foxf1 expression in the foregut and lung buds revealed extra details of the patterns not previously reported, particularly in the case of Foxf1 where gene expression was revealed in a changing pattern in the mesenchyme around the developing lung. Shh expression was also revealed in the epithelium of the lung bud itself. Both genes were detected in complementary patterns in the developing bronchi as late as E12, showing successful penetration of molecular probes and imaging at later stages. OPT is a valuable tool for revealing gene expression in an anatomical context even in internal tissues like the foregut and lung buds across stages of development, at least until E12. This provides the possibility of visualizing altered gene expression in an in vivo context in genetic or teratogenic models of congenital malformations.

Downregulation of GATA4 and GATA6 in the heart of rats with nitrofen-induced diaphragmatic hernia

PURPOSE The high incidence of cardiac malformations in humans and animal models with congenital diaphragmatic hernia (CDH) is well known. The precise molecular mechanisms underlying cardiac maldevelopment in CDH are still unclear. It has been reported that GATA4 and GATA6, members of the GATA transcription factor family, act cooperatively to regulate cardiovascular development, and the levels of cardiac GATA4 and GATA6 are important regulators of cardiomyocyte proliferation, cardiac morphogenesis, and embryo survival. In addition, the GATA4/GATA6 double heterozygous mutant embryo model displayed a spectrum of cardiovascular malformations similar to those seen in human CDH and nitrofen-induced animal models, including ventricular and aortopulmonary septal defects and thin ventricular myocardium. To test the hypothesis that expression of GATA4 and GATA6 is reduced in early stages of gestation in a CDH hypoplastic heart, we investigated the expression of GATA4 and GATA6 in the hearts of nitrofen-treated rats in early gestation. Wnt2, bone morphogenetic protein 4 (BMP4), and myocyte enhancer factor 2C (MEF2C) were also investigated as GATA4/6 target genes involved in cardiogenesis. MATERIALS AND METHODS Fetal rat hearts of normal (n = 7) and nitrofen-treated (n = 7) dams were harvested on embryonic day 13. The expression of GATA4, GATA6, Wnt2, BMP4, and MEF2C was analyzed in each heart by real-time reverse transcription-polymerase reaction. RESULTS The gene expression of GATA4, GATA6, Wnt2, BMP4, and MEF2C on embryonic day 13 were significantly reduced (P < .05) in the hearts of nitrofen-treated animals compared with normal hearts of equivalent age. CONCLUSION Decreased expression of GATA4 and GATA6 and their target genes in the developing fetal heart may perturb the delicate regulation of cardiovascular development, resulting in cardiovascular malformations in the nitrofen rat model.

Abnormal Notochord Branching Is Associated with Foregut Malformations in the Adriamycin Treated Mouse Model

Oesophageal atresia (OA) and tracheooesophageal fistula (TOF) are relatively common human congenital malformations of the foregut where the oesophagus does not connect with the stomach and there is an abnormal connection between the stomach and the respiratory tract. They require immediate corrective surgery and have an impact on the future health of the individual. These abnormalities are mimicked by exposure of rat and mouse embryos in utero to the drug adriamycin. The causes of OA/TOF during human development are not known, however a number of mouse mutants where different signalling pathways are directly affected, show similar abnormalities, implicating multiple and complex signalling mechanisms. The similarities in developmental outcome seen in human infants and in the adriamycin treated mouse model underline the potential of this model to unravel the early embryological events and further our understanding of the processes disturbed, leading to such abnormalities. Here we report a systematic study of the foregut and adjacent tissues in embryos treated with adriamycin at E7 and E8 and analysed between E9 and E12, comparing morphology in 3D in 149 specimens. We describe a spectrum of 8 defects, the most common of which is ventral displacement and branching of the notochord (in 94% of embryos at E10) and a close spatial correspondence between the site of notochord branching and defects of the foregut. In addition gene expression analysis shows altered dorso-ventral foregut patterning in the vicinity of notochord branches. This study shows a number of features of the adriamycin mouse model not previously reported, implicates the notochord as a primary site of disturbance in such abnormalities and underlines the importance of the model to further address the mechanistic basis of foregut congenital abnormalities.

Embryonic Wnt gene expression in the nitrofen-induced hypoplastic lung using 3-dimensional imaging

PURPOSE Wnts have been reported to play a key role in the lung morphogenesis. We have previously reported that pulmonary gene expression of Wnt2 and Wnt7b is downregulated on day 15 of gestation in the nitrofen-induced congenital diaphragmatic hernia (CDH) model. However, the distribution pattern of gene expression of Wnts in the very early lung development remains unclear. Optical projection tomography (OPT) is a new technique for 3-dimensional imaging of small developing organs and gene distribution combined with whole-mount in situ hybridization. We designed this study to investigate the distribution pattern of Wnts gene expression in lung buds of nitrofen-induced CDH model using OPT. METHODS Embryos from normal and nitrofen-treated dams were harvested on embryonic day 10 (E10), and divided into controls and nitrofen group, respectively. Whole-mount in situ hybridization to detect transcripts of Wnt2 and Wnt7b was performed, analyzed, and reconstructed using OPT. RESULTS The expression of Wnt2 transcripts was detected in the lung bud mesenchyme and markedly diminished in nitrofen group compared to controls, whereas Wnt7b transcripts were expressed in the mesoderm of bronchi and the lung bud with no detectable difference between 2 groups. CONCLUSION We provide evidence for the first time that Wnt2 expression is downregulated at lung bud stage in the nitrofen model. Optical projection tomography is potentially a useful approach to visualize both gene expression and morphology during very early stages of lung development.