Formation of adherens junctions leads to the emergence of a tissue-level tension in epithelial monolayers.
Bottom Line: Adherens junctions and desmosomes integrate the cytoskeletons of adjacent cells into a mechanical syncitium.Though much is known about the biological mechanisms underlying junction formation, little is known about how tissue-scale mechanical properties are established.As a consequence, inhibition of any of the molecular mechanisms participating in adherens junction initiation, remodelling and maturation significantly impeded the emergence of tissue-level tension in monolayers.
Affiliation: London Centre for Nanotechnology, University College London, London WC1H 0AH, UK Department of Physics, University College London, London WC1E 6BT, UK Engineering Doctorate Program, Department of Chemistry, University College London, London WC1H 0AJ, UK.Show MeSH
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Mentions: Next, we examined the role of the biological mechanisms involved in adherens junction formation in the establishment of tissue-level tension. In the current consensus view of adherens junction formation (Harris and Tepass, 2010), lamellipodial crawling, powered by Arp2/3-complex-mediated F-actin polymerisation, allows cells to make initial contacts with their neighbours that can be subsequently broadened by further lamellipodial extension. Consistent with a central role for actin polymerisation, incubating the cells with latrunculin B to depolymerise actin filaments prevented the formation of intercellular junctions and the generation of traction stresses (Fig. 5A). Temporal increases in apparent stiffness following replating were severely diminished (Fig. 5B). Differential interference contrast imaging during monolayer formation (Fig. 5C; supplementary material Movie 3) and phalloidin staining of F-actin (Fig. 5D) confirmed the presence of lamellipodial crawling under our experimental conditions. To examine the role of Arp2/3 in the establishment of tissue tension, we treated reforming monolayers with the Arp2/3-complex inhibitor CK666 (Nolen et al., 2009), which has been shown to inhibit lamellipodial protrusion in neutrophils (Wilson et al., 2013) and aplysia growth cones (Yang et al., 2012). Treatment of mature monolayers with CK666 led to loss of junctional localisation of the Arp2/3 complex (supplementary material Fig. S4D), confirming the effectiveness of the inhibitor in MDCK cells, in agreement with previous work (Tang and Brieher, 2012). When we treated reforming monolayers with CK666, cells no longer formed lamellipodia and this resulted in poorly interconnected monolayers (Fig. 5E). Lack of junction formation and decreased traction stresses severely impeded the establishment of monolayer stiffness (Fig. 5F).
Affiliation: London Centre for Nanotechnology, University College London, London WC1H 0AH, UK Department of Physics, University College London, London WC1E 6BT, UK Engineering Doctorate Program, Department of Chemistry, University College London, London WC1H 0AJ, UK.