When an epithelial cell divides, the constriction of the cytokinetic ring is associated with a local accumulation of myosin II in the neighbouring cells and detachment at E-cadherin contacts at the site of the ring. Such junction remodelling and myosin II reorganization is essential for morphogenesis, but how the events above are coordinated is unclear.

Bellaïche and colleagues now find that reduced E-cadherin concentration, caused by forces generated from contractile ring constriction, results in actomyosin flow to concentrate myosin II in neighbouring cells (Nature 545, 103–107; 2017).

Through imaging and laser ablation experiments in Drosophila notum epithelium, the authors initially demonstrate that cytokinesis generates pulling forces, which induces myosin II accumulation in neighbouring cells. They also note that the local decrease in E-cadherin is accompanied by junction elongation and occurs prior to detachment from the neighbours and myosin II accumulation. Simulations and analysis of E-cadherin dynamics suggest that elongation of the junction results in dilution of E-cadherin, and indeed, lowering E-cadherin levels can rescue myosin II accumulation in neighbours in mutants with perturbed constriction. Further modelling shows that a decrease in friction along the junction is sufficient to drive actomyosin flows in neighbouring cells, and time-lapse experiments reveal reduced actomyosin flow and a delay in myosin II accumulation in mutants with less cytokinetic contractility and E-cadherin decrease.

These findings demonstrate the importance of actomyosin flow in force sensing and transmission during cytokinesis.