Hardin, J. and Weliky, M. (2019). Cell rearrangement induced by filopodial tension accounts for the late phase of convergent extension in the sea urchin archenteron.
1Department of Integrative Biology, University of Wisconsin, Madison, WI 53706.
2Department of Brain and Cognitive Sciences, Center for Visual Science, University of Rochester, Rochester, NY 14627.
Supplemental material for the following paper:
Hardin, J. and Weliky, M. (2019). Cell rearrangement induced by filopodial tension accounts for the late phase of convergent extension in the sea urchin archenteron. Mol. Biol. Cell 30:1911-1919.. PubMed
George Oster was a pioneer in using mechanical models to interrogate morphogenesis in animal embryos. Convergent extension is a particularly important morphogenetic process to which George Oster gave significant attention. Late elongation of the sea urchin archenteron is a classic example of convergent extension in a monolayered tube, which has been proposed to be driven by extrinsic axial tension due to the activity of secondary mesenchyme cells. Using a vertex-based mechanical model, we show that key features of archenteron elongation can be accounted for by passive cell rearrangement due to applied tension. The model mimics the cell elongation and the Poisson effect (necking) that occur in actual archenterons. We also show that, as predicted by the model, ablation of secondary mesenchyme cells late in archenteron elongation does not result in extensive elastic recoil. Moreover, blocking the addition of cells to the base of the archenteron late in archenteron elongation leads to excessive cell rearrangement consistent with tension-induced rearrangement of a smaller cohort of cells. Our mechanical simulation suggests that responsive rearrangement can account for key features of archenteron elongation and provides a useful starting point for designing future experiments to examine the mechanical properties of the archenteron.
Combined supplementary table and images: Download (PDF; 4.2 Mb)
Video #1 (0.4 Mb) Archenteron elongation in L pictus.
Description: Time lapse movie of archenteron elongation in L. pictus. Time elapsed in minutes from the start of the movie is shown.
Download (0.4 Mb)
Video #2 (48 Mb): Vertex modeling of induced cell rearrangement under applied axial tension.
Description: Effects of externally applied tension on a two-dimensional vertex model of a rearranging epithelium corresponding to Figure 2A. See the text for further description of modeling procedures.
Download (48 Mb)