
Tissue flow in epithelial convergent extension is driven by positive feedback on myosin-generated cytoskeletal tension, and the extent of this flow is limited by the initial cell packing order, as demonstrated through a geometric-tension-dynamics model.


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a-geometric-tension-dynamics-model-of-epithelial-convergent-extension-by-claussen-et-al-


A Geometric-Tension-Dynamics Model of Epithelial Convergent Extension by Claussen et al.


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Epithelial convergent extension results from the controlled transformation of internal force balance geometry.


Shape changes of epithelia during animal development, such as convergent extension, are achieved through concerted mechanical activity of individual cells. While much is known about the corresponding large scale tissue flow and its genetic drivers, key open questions regard the cell-scale mechanics, e.g. internal vs external driving forces, and coordination, e.g. bottom-up self-organization vs top-down genetic instruction. To address these questions, we develop a quantitative, model-based analysis framework to relate cell geometry to local tension in recently obtained timelapse imaging data of gastrulating Drosophila embryos. This analysis provides a systematic decomposition of cell shape changes and T1–rearrangements into internally driven, active, and externally driven, passive, contributions. Specifically, we find evidence that germ band extension is driven by active T1 processes that self-organize through positive feedback acting on tensions. More generally, our findings suggest that epithelial convergent extension results from controlled transformation of internal force balance geometry which we quantify with a novel quantification tool for local tension configurations.

### Competing Interest Statement

The authors have declared no competing interest.

The Geometric Basis of Epithelial Convergent Extension

epithelial-flow-and-force-balance-geometry-transformation


Epithelial Flow and Force-Balance Geometry Transformation
