Alterations in mitochondrial morphology during trophoblast differentiation.

The overview picture shows the different areas of a typical E6.5 embryo outgrowth (outgrowth direction from left to right): the epiblast mountain (left), followed by the proximal zone of densely arranged undifferentiated trophoblast stem cells and finally the distal zone (right) of differentiated trophoblast cells. A–G The alteration of mitochondrial morphology during proximo-distal trophoblast differentiation in wildtype outgrowths is shown by co-immunostaining of the mitochondrial marker Atad3 (green) and the trophoblast differentiation marker Mash2 (red). Nuclei are visualized by DAPI staining (blue). In cells of the proximal trophoblast (A – C), the mitochondria are small and diffusely distributed (A), here Mash2 is localized to the cytoplasm (B). Instead in the distal region of the outgrowths (D – G), the cells contain enlarged, swollen mitochondria (D, F and arrowhead in G), and additionally small mitochondria arranged in arrays from the center to the periphery of the cell (D, arrow in F). In distal cells, Mash2 is localized to the nucleus and is also detected in the matrix of the swollen mitochondria (E, F and G). G is a magnified detail of F.