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Creation: the first seven days

Researchers at Ludwig Stockholm and Karolinska Institutet have conducted a detailed molecular analysis of the embryo’s first week of development by exploring the expression of the genome in individual cells. The study, led by Rickard Sandberg of Ludwig Cancer Research and Fredrik Lanner of Karolinska Institutet and published in the current issue of Cell, finds that there is considerable difference in embryonic development between humans and mice, the animal model most commonly used for study in the field.

The researchers also report that genes on the X chromosome are regulated very differently from those on other chromosomes in these early stages of development. During the first seven days of development, as the egg develops into a hollow ball of cells known as a blastocyst, three functionally distinct types of cells emerge. Each must mature properly for pregnancy to commence, but it has thus far been unclear exactly when, in what order and how the cell types form in humans. By detecting gene expression in individual cells from donated human embryos, the researchers identified which genes are used in the embryo’s cells at different times during the first week. They found that the first three cell types form later and seem to mature more simultaneously in the human than in the mouse. The study not only sheds light on a crucial stage of development but also adds to our knowledge of how stem cells are formed and regulated, information of importance to regenerative medicine. A more detailed report about the study is available here.


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