Clonal differentiation in the mouse embryo

A 3D reconstruction of an early mouse blastocyst. The blastocyst is formed three- four days post fertilization in the mouse and it is at this stage that the cells start to differentiate. Two types of cells form, those that will be part of the inner cell mass and ultimately form the fetus and the others become part of the trophectoderm and will act as the supporting cells forming structures like the placenta. In this embryo Cdx2 was over-expressed in half the embryo at the two-cell-stage. The Cdx2 gene is essential for correct organisation in the early embryo in mice and required for placenta formation. Without this gene the embryo would fail to form. The cells that resulted from the half of the embryo that over expressed this gene contributed disproportionally to the trophectoderm (shown in pink). The cells from the non-injected half of the embryo are shown in yellow.