Movie 1.

Active mitochondria in a dorsal marginal zone explant. Mitochondrial membrane potential detected using TMRE (green pseudocolor). TMRE is a cell permeable cationic dye that accumulates in active mitochondria based on their high membrane potential. Individual cell outlines are labeled by transgenic expression of membrane targeted GFP (pseudocolored gray). Note the high TMRE signal in leader row cells compared to follower row cells. Dorsal marginal zones were dissected from early gastrula stage Xenopus embryos and plated on fibronectin coated coverslips in the presence of TMRE. They were allowed to migrate for one hour before imaging. Each frame of the video is a maximum intensity projection of 5 z slices spaced 3.0 microns apart. Z stacks were captured 1 minute apart for a total of 5 minutes.