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Dorsal closure occurs approximately 12 hours post-fertilization, and takes 2-3 hours to complete. Tension generated in the amnioserosa (central tissue), the lateral epidermis (surrounding tissue), and actomyosin purse string (bright fluorescent structure between the two tissues) drive closure to completion. This embryo is expressing sGMCA, the ubiquitously expressed GFP-labeled actin binding domain of moesin.
Time-lapse confocal images of the edge-cut protocol. Dorsal closure staged embryos expressing a GFP-tagged protein that labels the cytoskeleton are cut using a steered laser. The behavior of the tissues after cutting (i.e. recoiling away from the cut) indicates that they are under tension during dorsal closure.
This close-up view of the canthus, the region of the dorsal opening where seam formation occurs, highlights the dynamic cellular projections called filopodia. This embryo is expressing fluorescently labeled junctional proteins (green) and F-actin binding protein (red).