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Title: Ultrafast epithelial contractions provide insights into contraction speed limits and tissue integrity

By definition of multicellularity, all animals need to keep their cells attached and intact, despite internal and external forces. Cohesion between epithelial cells provides this key feature. To better understand fundamental limits of this cohesion, we study the epithelium mechanics of an ultrathin (∼25 μm) primitive marine animalTrichoplax adhaerens, composed essentially of two flat epithelial layers. With no known extracellular matrix and no nerves or muscles,T. adhaerenshas been claimed to be the “simplest known living animal,” yet is still capable of coordinated locomotion and behavior. Here we report the discovery of the fastest epithelial cellular contractions known in any metazoan, to be found inT. adhaerensdorsal epithelium (50% shrinkage of apical cell area within one second, at least an order of magnitude faster than other known examples). Live imaging reveals emergent contractile patterns that are mostly sporadic single-cell events, but also include propagating contraction waves across the tissue. We show that cell contraction speed can be explained by current models of nonmuscle actin–myosin bundles without load, while the tissue architecture and unique mechanical properties are softening the tissue, minimizing the load on a contracting cell. We propose a hypothesis, in which the physiological role of the contraction dynamics is to resist external stresses while avoiding tissue rupture (“active cohesion”), a concept that can be further applied to engineering of active materials.

 
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NSF-PAR ID:
10077151
Author(s) / Creator(s):
; ; ;
Publisher / Repository:
Proceedings of the National Academy of Sciences
Date Published:
Journal Name:
Proceedings of the National Academy of Sciences
Volume:
115
Issue:
44
ISSN:
0027-8424
Page Range / eLocation ID:
p. E10333-E10341
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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