Tissue fusion over nonadhering surfaces

Significance

Tissue fusion is a frequent and important event in embryonic development during which two facing identical tissues meet and bridge collectively over a gap before merging into a continuous structure. Illustrations of tissue fusion include the formation of the palate or epithelial wound healing. In vivo fusion events, particularly in embryonic development, often involve the purse-string contraction of a pluricellular actomyosin cable present at the free edge. By studying the fusion of a monolayer over imprinted nonadherent domains, we provide evidence and characterize the purse-string mechanism in the situation where cells do not develop adhesions with their underlying substrate. A model that also involves active epithelial fluctuations describes well the experimental observations.