Mouse early embryogenesis is characterized by dynamic structural changes that are associated with cellular processes such as cell proliferation, apoptosis, differentiation, and migration. Early embryos adopt peculiar morphologies that are extremely different from the forms in which they are ultimately born; many of these morphological characteristics and processes are necessary in order for fertilized eggs to develop properly. Many important developmental events occur in early embryos. We are interested in identifying the molecular mechanisms that regulate early embryogenesis, and determining how the behavior of each cell is orchestrated within the context of the whole embryo.
In particular, we have studied axis formation in mouse embryos. Our interest in this topic originated with our discovery of a gene, Lefty, whose expression pattern is left–right asymmetric. The three body axes (antero–posterior, dorso–ventral and left–right) are established in early embryos. At embryonic day (E) 5.7, the distal visceral endoderm migrates to the future anterior side to form the anterior visceral endoderm (AVE). The opposite side of the AVE becomes the posterior, and the primitive streak appears in the posterior epiblast at E6.5. The node is then formed at the anterior tip of the primitive streak, and the leftward flow of extra-embryonic fluid is generated by rotation of primary cilia on the ventral surface of the node. These events trigger left–right axis formation, which leads to asymmetric gene expression in the lateral plate mesoderm. Lefty genes play fundamental roles in these processes. We have now extended our research interest to encompass a wide range of developmental events, as well as stem cells derived from mouse early embryos.