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Hello. My name is Janet Rossant. I'm a senior scientist at the Hospital for Sick Children in Toronto and Professor of Molecular Genetics at the University of Toronto. This talk is going to be about stem cells from the early mammalian embryo.
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Early mammalian development is the stage of development of which the zygote, a single fertilized egg, develops through to the blastocyst. The blastocyst is the stage of development from which we can derive embryonic stem cells. And as I'll show you later, in the mouse we can also derive other stem cells that represent some of the extra embryonic lineages that a mammalian embryo uses to survive in the uterus. If we look at the stages of mouse development shown here, these stages from a single cell to the blastocyst take four days. And we see that the embryo undergoes a process known as cleavage in which the cells continue to divide, but don't specialize until it begins to cavitate to form a blastocyst with three distinct cell types. The outer, trophectoderm, enclosing a group of cells at one end called the inner cell mass, which then go on to form epiblast and the primitive endoderm.