Planar polarized actomyosin contractile flows control epithelial junction remodelling.
Force generation by Myosin-II motors on actin filaments drives cell and tissue morphogenesis. In epithelia, contractile forces are resisted at apical junctions by adhesive forces dependent on E-cadherin, which also transmits tension. During Drosophila embryonic germband extension, tissue elongation is driven by cell intercalation, which requires an irreversible and planar polarized remodelling of epithelial cell junctions. We investigate how cell deformations emerge from the interplay between force generation and cortical force transmission during this remodelling in Drosophila melanogaster. The shrinkage of dorsal-ventral-oriented ('vertical') junctions during this process is known to require planar polarized junctional contractility by Myosin II (refs 4, 5, 7, 12). Here we show that this shrinkage is not produced by junctional Myosin II itself, but by the polarized flow of medial actomyosin pulses towards 'vertical' junctions. This anisotropic flow is oriented by the planar polarized distribution of E-cadherin complexes, in that medial Myosin II flows towards 'vertical' junctions, which have relatively less E-cadherin than transverse junctions. Our evidence suggests that the medial flow pattern reflects equilibrium properties of force transmission and coupling to E-cadherin by α-Catenin. Thus, epithelial morphogenesis is not properly reflected by Myosin II steady state distribution but by polarized contractile actomyosin flows that emerge from interactions between E-cadherin and actomyosin networks.
IBDML, UMR6216 CNRS-Université de la Méditerranée, Campus de Luminy, case 907, 13288 Marseille Cedex 09, France.
Matteo
M
Rauzi
Pierre-François
PF
Lenne
Thomas
T
Lecuit
D000205:Actomyosin / Q000378:metabolism*; D000818:Animals; D015820:Cadherins / Q000378:metabolism; D016764:Cell Polarity; D029721:Drosophila Proteins / Q000378:metabolism; D004331:Drosophila melanogaster / Q000166:cytology* / Q000196:embryology*; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000196:embryology; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D007365:Intercellular Junctions / Q000378:metabolism; D024462:Myosin Type II / Q000378:metabolism; D021381:Protein Transport
D015820:Cadherins; D029721:Drosophila Proteins; D000205:Actomyosin; D024462:Myosin Type II