Polarization of Myosin II refines tissue material properties to buffer mechanical stress

Abstract

As tissues develop, they are subjected to a variety of mechanical forces. Some of these forces, such as those required for morphogenetic movements, are instrumental to the development and sculpting of tissues. However, mechanical forces can also lead to accumulation of substantial tensile stress, which if maintained, can result in tissue damage and impair tissue function.Despite our extensive understanding of force-guided morphogenesis, we have Results MyoII is essential for setting tissue stiffness and elasticity.Cell shape is defined by the balance of forces exerted on cells through the external environment (such as cell-cell and cell-ECM adhesion) and the forces exerted by intracellular cell components such as the actomyosin cortex (Mao and Baum, 2015). Therefore, the pathways controlling these processes are likely to be critical in responses to mechanical stress. We focused on the nonmuscle Myosin II (MyoII) contractility pathway, as MyoII had been shown to be recruited to the cell cortex in force-driven morphogenetic processes such as mesoderm invagination in gastrulation as well as by deformation applied through micropipette aspiration (Fernandez-Gonzalez et al., 2009;Pouille et We are grateful to Nic Tapon, in whose lab the development of the stretching device was initiated, for his support. We thank GREM (Griffon Gravure) for building the first prototype of stretching/compression device. We thank Duncan Farquharson, Simon Townsend, Piotr Sienkiewicz from Mechanical and Electronic Workshops at University College London for design and execution of final version of stretching/compression device. We thank Davide Heller for help with junctional myosin intensity measurements. We thank John Zhang for his help drawing the photo masks, and JDPhoto-Tools for printing.

Stress relaxation in epithelial monolayers is controlled by the actomyosin cortex

“…However, the amplitude was smaller than in cultured monolayers (~35%) and occurred over a longer duration (>100 s, Fig 1d,e, S5b). As ECM is known to turn over slowly 34 , these data indicate that larval epithelia bear at least a third of the total tissue stress and dynamically relax stress, consistent with previous qualitative observations 35 .…”

Radially patterned cell behaviours during tube budding from an epithelium

“…We also predicted that active circumferential junction contraction would be driven by myosin II accumulation at circumferential junctions ( Figure 6E ). Recent studies have indicated that in some tissues, as response to mechanical pulling, myosin II accumulates and becomes polarised at junctions parallel to the pulling force ( Duda et al, 2018 ; Fernandez-Gonzalez et al, 2009 ). Hence if intercalation occurred as a passive response, we would expect either no myosin II polarisation or mechanically induced localisation to radially oriented junctions ( Figure 6E’ ).…”

The devil is in the mesoscale: Mechanical and behavioural heterogeneity in collective cell movement

“…Self-organisation may in some tissues depend on mechanical feedback. For example, tension-or stretch-dependent recruitment of myosin II [58,72,73] could locally induce transient mini-cables. Alternatively, structures could self-organise in response to a pull from a neighbouring tissue.…”