In the January 1 issue of G&D, Drs. Gustavo Leone and Michael Robinson (Ohio State University) and colleagues uncover a stem-cell specific role for the well-known tumor suppressor gene, Rb, in the developing mammalian embryo. Researchers had previously shown that mice deficient in Rb die as embryos. Using a combination of sophisticated mouse genetics and 3D computer modeling, OSU scientists have now determined why: Rb is required for the maintenance of the trophoblast stem cell population, which is essential for forming the placenta. Specific loss of Rb in trophoblast stem cells results in an overexpansion of trophoblast cells, aberrant placental formation, and embryonic death. These findings implicate a role for the Rb pathway in the development of the human placenta and may provide a link between Rb, and possibly other cell cycle regulators, and pregnancy-related complications such as miscarriages and pre-eclempsia. The demonstration that Rb tumor suppressor function is critical in trophoblast stem cells of the placenta will also certainly fuel the emerging hypothesis that stem-like cells may serve as a repository in which tumor suppressor function is critical to prevent cancer.
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