Cell–cell contact landscapes in Xenopus gastrula tissues

2021 ◽  
Vol 118 (39) ◽  
pp. e2107953118
Author(s):  
Debanjan Barua ◽  
Martina Nagel ◽  
Rudolf Winklbauer

Molecular and structural facets of cell–cell adhesion have been extensively studied in monolayered epithelia. Here, we perform a comprehensive analysis of cell–cell contacts in a series of multilayered tissues in the Xenopus gastrula model. We show that intercellular contact distances range from 10 to 1,000 nm. The contact width frequencies define tissue-specific contact spectra, and knockdown of adhesion factors modifies these spectra. This allows us to reconstruct the emergence of contact types from complex interactions of the factors. We find that the membrane proteoglycan Syndecan-4 plays a dominant role in all contacts, including narrow C-cadherin–mediated junctions. Glypican-4, hyaluronic acid, paraxial protocadherin, and fibronectin also control contact widths, and unexpectedly, C-cadherin functions in wide contacts. Using lanthanum staining, we identified three morphologically distinct forms of glycocalyx in contacts of the Xenopus gastrula, which are linked to the adhesion factors examined and mediate cell–cell attachment. Our study delineates a systematic approach to examine the varied contributions of adhesion factors individually or in combinations to nondiscrete and seemingly amorphous intercellular contacts.

2015 ◽  
Vol 210 (2) ◽  
pp. 333-346 ◽  
Author(s):  
Pierre-Olivier Strale ◽  
Laurence Duchesne ◽  
Grégoire Peyret ◽  
Lorraine Montel ◽  
Thao Nguyen ◽  
...  

Oligomerization of cadherins could provide the stability to ensure tissue cohesion. Cadherins mediate cell–cell adhesion by forming trans-interactions. They form cis-interactions whose role could be essential to stabilize intercellular junctions by shifting cadherin clusters from a fluid to an ordered phase. However, no evidence has been provided so far for cadherin oligomerization in cellulo and for its impact on cell–cell contact stability. Visualizing single cadherins within cell membrane at a nanometric resolution, we show that E-cadherins arrange in ordered clusters, providing the first demonstration of the existence of oligomeric cadherins at cell–cell contacts. Studying the consequences of the disruption of the cis-interface, we show that it is not essential for adherens junction formation. Its disruption, however, increased the mobility of junctional E-cadherin. This destabilization strongly affected E-cadherin anchoring to actin and cell–cell rearrangement during collective cell migration, indicating that the formation of oligomeric clusters controls the anchoring of cadherin to actin and cell–cell contact fluidity.


2009 ◽  
Vol 20 (7) ◽  
pp. 1949-1959 ◽  
Author(s):  
Koichi Miura ◽  
Jin-Min Nam ◽  
Chie Kojima ◽  
Naoki Mochizuki ◽  
Hisataka Sabe

ADP-ribosylation factor (Arf) 6 activity is crucially involved in the regulation of E-cadherin–based cell–cell adhesions. Erythropoietin-producing hepatocellular carcinoma (Eph)-family receptors recognize ligands, namely, ephrins, anchored to the membrane of apposing cells, and they mediate cell–cell contact-dependent events. Here, we found that Arf6 activity is down-regulated in Madin-Darby canine kidney cells, which is dependent on cell density and calcium ion concentration, and we provide evidence of a novel signaling pathway by which ligand-activated EphA2 suppresses Arf6 activity. This EphA2-mediated suppression of Arf6 activity was linked to the induction of cell compaction and polarization, but it was independent of the down-regulation of extracellular signal-regulated kinase 1/2 kinase activity. We show that G protein-coupled receptor kinase-interacting protein (Git) 1 and noncatalytic region of tyrosine kinase (Nck) 1 are involved in this pathway, in which ligand-activated EphA2, via its phosphorylated Tyr594, binds to the Src homology 2 domain of Nck1, and then via its Src homology 3 domain binds to the synaptic localizing domain of Git1 to suppress Arf6 activity. We propose a positive feedback loop in which E-cadherin–based cell–cell contacts enhance EphA-ephrinA signaling, which in turn down-regulates Arf6 activity to enhance E-cadherin–based cell–cell contacts as well as the apical-basal polarization of epithelial cells.


2001 ◽  
Vol 114 (24) ◽  
pp. 4349-4358 ◽  
Author(s):  
Juliet C. Coates ◽  
Adrian J. Harwood

The development of the non-metazoan eukaryote Dictyostelium discoideum displays many of the features of animal embryogenesis, including regulated cell-cell adhesion. During early development, two proteins, DdCAD-1 and csA, mediate cell-cell adhesion between amoebae as they form a loosely packed multicellular mass. The mechanism governing this process is similar to epithelial sheet sealing in animals. Although cell differentiation can occur in the absence of cell contact, regulated cell-cell adhesion is an important component of Dictyostelium morphogenesis, and a third adhesion molecule, gp150, is required for multicellular development past the aggregation stage.Cell-cell junctions that appear to be adherens junctions form during the late stages of Dictyostelium development. Although they are not essential to establish the basic multicellular body plan, these junctions are required to maintain the structural integrity of the fruiting body. The Dictyostelium β-catenin homologue Aardvark (Aar) is present in adherens junctions, which are lost in its absence. As in the case of its metazoan counterparts, Aar also has a function in cell signalling and regulates expression of the pre-spore gene psA.It is becoming clear that cell-cell adhesion is an integral part of Dictyostelium development. As in animals, cell adhesion molecules have a mechanical function and may also interact with the signal-transduction processes governing morphogenesis.


2021 ◽  
Author(s):  
Ivar Noordstra ◽  
Mario Diez Hermoso ◽  
Lilian Schimmel ◽  
Alexis Bonfim-Melo ◽  
Joseph Mathew Kalappurakkal ◽  
...  

Adherens junctions (AJs) fundamentally mediate cell-cell adhesion, yet the mechanisms that determine where or when AJs assemble are not understood. Here we reveal a mechanosensitive clutch that initiates AJ assembly. Before cell-cell contact, alpha-catenin couples surface E-cadherin complexes to retrograde flow of the actin cortex. Cortical flows with opposed orientations persist after contact, applying tension to alpha-catenin within trans-ligated cadherin complexes. Tension unfolds the alpha-catenin actin-binding domain (ABD), which is expected to mediate a catch bond with F-actin. However, catch bond behaviour is not sufficient for AJ assembly in a molecular clutch model. Instead, it is also necessary for the activated ABD to promote cis-clustering of E-cadherin molecules by bundling F-actin. Thus, this alpha-catenin clutch transduces the mechanical signal of cortical flow to assemble AJs.


Author(s):  
Phanish Puranam

In this chapter, my aim is describe the links between the formal and informal structure of organizations, and propose a systematic approach to analyzing these links. I first discuss how the two are related and influence each other. Next, revisiting the theme of organizations as “marvels but not miracles” I argue that formal design can be useful even when it not predicated on high levels of comprehension or intelligence. This is because it can compensate for aspects of the informal organization, as well as shape the emergence of the informal organization. I discuss an instance of a micro-structural approach to such issues in some detail, and conclude by offering a multiplex network formulation that can help us make progress in studying the complex interactions between formal and informal organizational structures.


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