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: We evaluated the oscillations in the apical cross section of the amnioserosa cells after canthus removal by tracking the change in area as a function of time with an automated cell segmentation program (see Materials and Methods and Supplemental Movie S6). The segmentation algorithm effectively tracked cell boundaries 30 min (after a 1– to 2-min delay) after laser dissection. Previous studies (Sokolow et al., 2012) observed that individual amnioserosa cell oscillations in unperturbed embryos range from 4 to 10 mHz, which correspond to a 1.7- to 4.2-min period. Thus the 30-min window we specified can capture at least seven full cell oscillations. We observed no remarkable quantitative differences in frequencies or amplitudes of the area oscillations in amnioserosa cells adjacent to the site of laser dissection, far from that site, or in native embryos. This observation was consistent for all cut and native embryos (Figure 7).
Affiliation: Department of Biology, Duke University, Durham, NC 27708.