GFP transgenic mice reveal active canonical Wnt signal in neonatal brain and in adult liver and spleen

In the past decades, the function of the Writ canonical pathway during embryogenesis has been intensively investigated; however, little survey of neonatal and adult tissues has been made, and the role of this pathway remains largely unknown. To investigate its role in mature tissues, we generated two new reporter trans genic mouse lines, ins-TOPEGFP and ins-TOPGAL, that drive EGFP and beta-galactosidase expression under TCF/ beta-catenin, respectively. To obtain the accurate expres sion pattern, we flanked these transgenes with the HS4 insulator to reduce chromosomal positional effects. Analysis of embryos showed that the reporter genes were activated in regions where canonical Writ activity has been implicated. Furthermore, their expression patterns were consistent in both lines, indicating the accuracy of the reporter signal. In the neonatal brain, the reporter signal was detected in the mesencephalon and hippocampus. In the adult mice, the reporter signal was found in the mature pericenteral hepatocytes in the normal liver. Furthermore, during inflammation the number of T cells expressing the reporter gene increased in the adult spleen. Thus, in this research, we identified two organs, i.e., the liver and spleen, as novel organs in which the Writ canonical signal is in motion in the adult. These transgenic lines will provide us broader opportunities to investigate the function of the Writ canonical pathway in vivo.