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Nature Cell Biology 9, 1127–1129 (1 October 2007) | doi:10.1038/ncb1007-1127

Cell fate in the Hand of Plk4

Marvin E. Tanenbaum & Ren|[eacute]| H. Medemao

An intriguing question in developmental biology is how distinct embryonic stem cells develop into a specific lineage with high spatial and temporal precision. For example, at embryonic day 4.5, roughly the time of implantation, trophoblast stem (TS) cells must make a choice: either continue to proliferate and become diploid trophoblast cells or exit the mitotic cell cycle and initiate an endoreplication cycle that produces polyploid trophoblast giant (TG) cells.