Using pluripotency cell markers to identify primordial germ cells in embryos of the laboratory opossum, Monodelphis domestica

The lineage which becomes primordial germ cells (PGCs), and later the gametes, in various animals is sequestered early during embryonic development. This population of pluripotent cells is first observed in the extra-embryonic portion of the mouse epiblast on day 7.25 of gestation. They then undergo mitosis and migrate, reaching the genital ridge on day 9.5 of gestation. Marsupial PGCs, by contrast, are poorly characterized. Meanwhile, the embryos of these mammals are larger and more accessible because implantation occurs late during pregnancy, and with only meager yolk-sac adhesivity to the endometrium. Moreover, the topology of the conceptus and the superficial position of the fetus itself on the yolk sac suggest that visualization of PGCs should be amenable to analysis by different microscopy approaches, including whole-mounts. We are using immunohistochemistry, fluorescence and confocal microscopy to determine the expression pattern of the pluripotency cell-marker proteins encoded by Oct-3/4, vasa, and Nanog. We anticipate our results to be useful in studying PGC differentiation and migration in the laboratory opossum