Complete canthi removal reveals that forces from the amnioserosa alone are sufficient to drive dorsal closure in Drosophila.
Bottom Line: Canthi maintain purse string curvature (necessary for their dorsalward forces), and zipping at the canthi shortens leading edges, ensuring a continuous epithelium at closure completion.Dissection of one or both canthi resulted in tissue recoil and flattening of each purse string.How the embryo coordinates multiple, large forces (each of which is orders of magnitude greater than the net force) during native closure and is also resilient to multiple perturbations are key extant questions.
Affiliation: Department of Biology, Duke University, Durham, NC 27708.Show MeSH
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Mentions: Finally, we investigated the position of the centroid of each tracked amnioserosa cell in cut embryos as a function of time after recoil and the observed pause in the dorsalward movement of the purse strings. Cells with the largest speeds were not localized to a specific region of the embryo or a specific window in time (Figure 9, A and A′, and Supplemental Movies S7 and S8). In Figure 9, cell trajectories are in false colors, with the color of this heat map indicating speed. We could not discern a pattern for the cells with the largest velocities in either laser-cut embryos or unperturbed native embryos. This suggests that after the initial recoil from canthus removal, external forces on the cell sheet rebalance, and each amnioserosa cell stabilizes by returning to native net movements over time.
Affiliation: Department of Biology, Duke University, Durham, NC 27708.