Rat and mouse epiblasts differ in their capacity to generate extraembryonic endoderm.

In this study we have compared the in vitro differentiation potential of epiblast tissue from mouse and rat embryos. Epiblasts were isolated from egg cylinder stage embryos by microdissection and placed in culture. Rat cultures were distinguished by the copious production of parietal endoderm cells. Mouse epiblasts, in contrast, did not produce parietal endoderm. This difference in capacity to regenerate extraembryonic endoderm marks a surprising distinction in development of the pluripotential lineage between these two closely related rodents.