Background: We developed an efficient in vitro method to differentiate mouse ES cells into the definitive endoderm (DE) and then Pdx1-expressing pancreatic lineages using mesodermal-derived supporting cells, M15. Using this method, resulting ES cell-derived DE and Pdx1-expressing cells were isolated by cell sorting, and their gene expression profiles were investigated with DNA microarray. Genes that were specifically expressed in DE and/or in Pdx1-expressing cells were extracted and their expression patterns in normal embryonic development were studied.
Results: Genes whose expression increased in DE and Pdx1 positive cells compared to the undifferentiated ES cells were chosen and in situ hybridizations were performed. Out of 54 genes examined, 27 were expressed in the DE of E8.5 mouse embryos and 15 genes were expressed in distinct domains in the pancreatic buds of E14.5 embryos. Among those genes expressed were Foxq1, CpM, Foxp4, Pcdh1, and Zmiz1, which were previously reported in other endodermal tissues. Genes, such as Parm1, Tmem184a, Hipk2 and Sox4 were reported to be expressed during early pancreatic development. Nptx2, C2cd4b, Tcf7l2 and Kiss1r were reported to be associated with beta cell or pancreatic functions in the adult. Akr1c19, Aebp2, Pbxip1 and Creb3l1, were novel and have not been described as being expressed either in DE or the pancreas.
Conclusions: We identified 27 genes, including 4 novel genes expressed in DE and pancreatic progenitor cells during normal development using an ES cell in vitro differentiation system. These results showed that DE cells and Pdx1/GFP-expressing cells obtained from our M15 based differentiation method mimic cells during the normal developmental processes. Additionally, ES cells are an excellent model for studies of early developmental processes.