Unipolar distributions of junctional Myosin II identify cell stripe boundaries that drive cell intercalation throughout Drosophila axis extension

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Abstract

Convergence and extension movements elongate tissues during development. Drosophila germ-band extension (GBE) is one example, which requires active cell rearrangements driven by Myosin II planar polarisation. A combinatorial code of Toll receptors downstream of pair-rule genes contributes to this polarization via local cell-cell interactions. We developed novel computational methods to analyse the spatiotemporal dynamics of Myosin II. We show that initial Myosin II bipolar cell polarization gives way to unipolar enrichment at parasegmental boundaries and two further boundaries within each parasegment, concomitant with a doubling of cell number as the tissue elongates. These boundaries are the primary sites of cell intercalation, behaving as mechanical barriers and providing a mechanism for how cells remain ordered during GBE. Enrichment at parasegment boundaries during GBE is independent of Wingless signaling, suggesting pair-rule gene control. We propose an updated cell-cell interaction model for Myosin II polarization that we tested in a vertex-based simulation.

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Robert J Tetley

Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom

Competing interests
The authors declare that no competing interests exist.
Guy B Blanchard

Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom

Competing interests
The authors declare that no competing interests exist.
Alexander G Fletcher

School of Mathematics and Statistics, University of Sheffield, Sheffield, United Kingdom

Competing interests
The authors declare that no competing interests exist.
Richard J Adams

Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom

Competing interests
The authors declare that no competing interests exist.
Bénédicte Sanson

Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom

For correspondence
bs251@cam.ac.uk

Competing interests
The authors declare that no competing interests exist.

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