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Complete canthi removal reveals that forces from the amnioserosa alone are sufficient to drive dorsal closure in Drosophila.

Wells AR, Zou RS, Tulu US, Sokolow AC, Crawford JM, Edwards GS, Kiehart DP - Mol. Biol. Cell (2014)

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.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Duke University, Durham, NC 27708.

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No noticeable change in centroid trajectories of amnioserosa cells follow canthus removal. (A, A′, B, B′) Three-dimensional (3D) representation of embryos with position in the x- and y-axes and time in the z-axis. (A, A′) The 3D representation of an embryo with one canthus removed, showing two different orientations. (A) Top view of A′ (see Supplemental Movie S7 for its corresponding video). (B, B′) The 3D representation of a native embryo showing the same two orientations as in A and A′ (see Supplemental Movie S8 for its corresponding video). The thin, grayish-red curves indicate the position of the leading edge over time as dorsal closure progresses. The thin blue lines trace the dorsal midline. The thin green lines orthogonal to the dorsal midline trace the length of greatest height (H) in the embryo. The dark traces with colors ranging from dark blue to red indicate the centroid velocities. “Warmer” false colors indicate faster velocities. The cells with faster velocities do not appear to be localized to any region in the space or time domain for both the cut and the uncut embryo. The velocity at each time point is computed as a moving average with a window size of 50 s. The cell centroid traces in the first 30 min are bold to indicate higher confidence in the accuracy of the trace. Cell tracking after 30 min deteriorates, and thus the cell centroid traces may not be as accurate (not bold).
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Figure 9: No noticeable change in centroid trajectories of amnioserosa cells follow canthus removal. (A, A′, B, B′) Three-dimensional (3D) representation of embryos with position in the x- and y-axes and time in the z-axis. (A, A′) The 3D representation of an embryo with one canthus removed, showing two different orientations. (A) Top view of A′ (see Supplemental Movie S7 for its corresponding video). (B, B′) The 3D representation of a native embryo showing the same two orientations as in A and A′ (see Supplemental Movie S8 for its corresponding video). The thin, grayish-red curves indicate the position of the leading edge over time as dorsal closure progresses. The thin blue lines trace the dorsal midline. The thin green lines orthogonal to the dorsal midline trace the length of greatest height (H) in the embryo. The dark traces with colors ranging from dark blue to red indicate the centroid velocities. “Warmer” false colors indicate faster velocities. The cells with faster velocities do not appear to be localized to any region in the space or time domain for both the cut and the uncut embryo. The velocity at each time point is computed as a moving average with a window size of 50 s. The cell centroid traces in the first 30 min are bold to indicate higher confidence in the accuracy of the trace. Cell tracking after 30 min deteriorates, and thus the cell centroid traces may not be as accurate (not bold).

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.


Complete canthi removal reveals that forces from the amnioserosa alone are sufficient to drive dorsal closure in Drosophila.

Wells AR, Zou RS, Tulu US, Sokolow AC, Crawford JM, Edwards GS, Kiehart DP - Mol. Biol. Cell (2014)

No noticeable change in centroid trajectories of amnioserosa cells follow canthus removal. (A, A′, B, B′) Three-dimensional (3D) representation of embryos with position in the x- and y-axes and time in the z-axis. (A, A′) The 3D representation of an embryo with one canthus removed, showing two different orientations. (A) Top view of A′ (see Supplemental Movie S7 for its corresponding video). (B, B′) The 3D representation of a native embryo showing the same two orientations as in A and A′ (see Supplemental Movie S8 for its corresponding video). The thin, grayish-red curves indicate the position of the leading edge over time as dorsal closure progresses. The thin blue lines trace the dorsal midline. The thin green lines orthogonal to the dorsal midline trace the length of greatest height (H) in the embryo. The dark traces with colors ranging from dark blue to red indicate the centroid velocities. “Warmer” false colors indicate faster velocities. The cells with faster velocities do not appear to be localized to any region in the space or time domain for both the cut and the uncut embryo. The velocity at each time point is computed as a moving average with a window size of 50 s. The cell centroid traces in the first 30 min are bold to indicate higher confidence in the accuracy of the trace. Cell tracking after 30 min deteriorates, and thus the cell centroid traces may not be as accurate (not bold).
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Related In: Results  -  Collection

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Figure 9: No noticeable change in centroid trajectories of amnioserosa cells follow canthus removal. (A, A′, B, B′) Three-dimensional (3D) representation of embryos with position in the x- and y-axes and time in the z-axis. (A, A′) The 3D representation of an embryo with one canthus removed, showing two different orientations. (A) Top view of A′ (see Supplemental Movie S7 for its corresponding video). (B, B′) The 3D representation of a native embryo showing the same two orientations as in A and A′ (see Supplemental Movie S8 for its corresponding video). The thin, grayish-red curves indicate the position of the leading edge over time as dorsal closure progresses. The thin blue lines trace the dorsal midline. The thin green lines orthogonal to the dorsal midline trace the length of greatest height (H) in the embryo. The dark traces with colors ranging from dark blue to red indicate the centroid velocities. “Warmer” false colors indicate faster velocities. The cells with faster velocities do not appear to be localized to any region in the space or time domain for both the cut and the uncut embryo. The velocity at each time point is computed as a moving average with a window size of 50 s. The cell centroid traces in the first 30 min are bold to indicate higher confidence in the accuracy of the trace. Cell tracking after 30 min deteriorates, and thus the cell centroid traces may not be as accurate (not bold).
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.

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.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Duke University, Durham, NC 27708.

Show MeSH
Related in: MedlinePlus